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Appl. Sci., Volume 7, Issue 1 (January 2017)

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Cover Story Composites having hydroxyapatite (HAp) nanoparticles are widely employed in biomedical applications [...] Read more.
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Editorial

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Open AccessEditorial Acknowledgement to Reviewers of Applied Sciences in 2016
Appl. Sci. 2017, 7(1), 75; doi:10.3390/app7010075
Received: 12 January 2017 / Accepted: 12 January 2017 / Published: 12 January 2017
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Abstract
The editors of Applied Sciences would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2016.[...] Full article

Research

Jump to: Editorial, Review

Open AccessArticle Identification and Evaluation of Composition in Food Powder Using Point-Scan Raman Spectral Imaging
Appl. Sci. 2017, 7(1), 1; doi:10.3390/app7010001
Received: 20 October 2016 / Revised: 13 December 2016 / Accepted: 15 December 2016 / Published: 22 December 2016
Cited by 1 | PDF Full-text (3531 KB) | HTML Full-text | XML Full-text
Abstract
This study used Raman spectral imaging coupled with self-modeling mixture analysis (SMA) for identification of three components mixed into a complex food powder mixture. Vanillin, melamine, and sugar were mixed together at 10 different concentration level (1% to 10%, w/w) into powdered non-dairy
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This study used Raman spectral imaging coupled with self-modeling mixture analysis (SMA) for identification of three components mixed into a complex food powder mixture. Vanillin, melamine, and sugar were mixed together at 10 different concentration level (1% to 10%, w/w) into powdered non-dairy creamer. SMA was used to decompose the complex multi-component spectra and extract the pure component spectra and corresponding contribution images. Spectral information divergence (SID) values of the extracted pure component spectra and reference component spectra were computed to identify the components corresponding to the extracted spectra. The contribution images obtained via SMA were used to create Raman chemical images of the mixtures samples, to which threshold values were applied to obtain binary detection images of the components at all concentration levels. The detected numbers of pixels of each component in the binary images was found to be strongly correlated with the actual sample concentrations (correlation coefficient of 0.99 for all components). The results show that this method can be used for simultaneous identification of different components and estimation of their concentrations for authentication or quantitative inspection purposes. Full article
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Open AccessArticle Leak Detection in Water-Filled Small-Diameter Polyethylene Pipes by Means of Acoustic Emission Measurements
Appl. Sci. 2017, 7(1), 2; doi:10.3390/app7010002
Received: 24 November 2016 / Revised: 13 December 2016 / Accepted: 16 December 2016 / Published: 22 December 2016
Cited by 5 | PDF Full-text (4388 KB) | HTML Full-text | XML Full-text
Abstract
The implementation of effective strategies to manage leaks represents an essential goal for all utilities involved with drinking water supply in order to reduce water losses affecting urban distribution networks. This study concerns the early detection of leaks occurring in small-diameter customers’ connections
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The implementation of effective strategies to manage leaks represents an essential goal for all utilities involved with drinking water supply in order to reduce water losses affecting urban distribution networks. This study concerns the early detection of leaks occurring in small-diameter customers’ connections to water supply networks. An experimental campaign was carried out in a test bed to investigate the sensitivity of Acoustic Emission (AE) monitoring to water leaks. Damages were artificially induced on a polyethylene pipe (length 28 m, outer diameter 32 mm) at different distances from an AE transducer. Measurements were performed in both unburied and buried pipe conditions. The analysis permitted the identification of a clear correlation between three monitored parameters (namely total Hits, Cumulative Counts and Cumulative Amplitude) and the characteristics of the examined leaks. Full article
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Open AccessArticle Automated Cart with VIS/NIR Hyperspectral Reflectance and Fluorescence Imaging Capabilities
Appl. Sci. 2017, 7(1), 3; doi:10.3390/app7010003
Received: 29 September 2016 / Revised: 18 November 2016 / Accepted: 30 November 2016 / Published: 22 December 2016
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Abstract
A system to take high-resolution Visible/Near Infra-Red (VIS/NIR) hyperspectral reflectance and fluorescence images in outdoor fields using ambient lighting or a pulsed laser (355 nm), respectively, for illumination purposes was designed, built, and tested. Components of the system include a semi-autonomous cart, a
[...] Read more.
A system to take high-resolution Visible/Near Infra-Red (VIS/NIR) hyperspectral reflectance and fluorescence images in outdoor fields using ambient lighting or a pulsed laser (355 nm), respectively, for illumination purposes was designed, built, and tested. Components of the system include a semi-autonomous cart, a gated-intensified camera, a spectral adapter, a frequency-triple Nd:YAG (Neodymium-doped Yttrium Aluminium Garnet) laser, and optics to convert the Gaussian laser beam into a line-illumination source. The front wheels of the cart are independently powered by stepper motors that support stepping or continuous motion. When stepping, a spreadsheet is used to program parameters of image sets to be acquired at each step. For example, the spreadsheet can be used to set delays before the start of image acquisitions, acquisition times, and laser attenuation. One possible use of this functionality would be to establish acquisition parameters to facilitate the measurement of fluorescence decay-curve characteristics. The laser and camera are mounted on an aluminum plate that allows the optics to be calibrated in a laboratory setting and then moved to the cart. The system was validated by acquiring images of fluorescence responses of spinach leaves and dairy manure. Full article
(This article belongs to the Special Issue Applications of Hyperspectral Imaging for Food and Agriculture)
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Open AccessArticle Numerical Simulation and Experimental Validation for the Thermal Analysis of a Compact LED Recessed Downlight with Heat Sink Design
Appl. Sci. 2017, 7(1), 4; doi:10.3390/app7010004
Received: 15 October 2016 / Revised: 13 December 2016 / Accepted: 13 December 2016 / Published: 22 December 2016
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Abstract
Light emitting diode (LED)-recessed downlighting is currently mainly used for indoor lighting of residential and commercial buildings. Maintaining a low junction temperature and increasing the lifetime and reliability of LED lighting is desirable. This study investigated designed heat sinks’ heat dissipation and capability
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Light emitting diode (LED)-recessed downlighting is currently mainly used for indoor lighting of residential and commercial buildings. Maintaining a low junction temperature and increasing the lifetime and reliability of LED lighting is desirable. This study investigated designed heat sinks’ heat dissipation and capability of maintaining a low junction temperature, as well as increases in the lifetime and reliability of the lighting. This paper presents a designed traditional trapezoidal aluminum finned heat sink (ALFHS) and annular open cell copper foam heat sink (CUFHS) mounted to a 10 W compact LED-recessed downlight (CLRDL) and individually installed in a simulation 105 mm × 105 mm × 100 mm (L × W × H) test box. The purpose was to evaluate the temperature performance by testing the downlight in a small enclosed space with high ambient temperature while the LED is in operation. The downlight exhibited a long lifetime at normal use temperature and functioned according to Arrhenius’ law. Numerical simulation was performed first and followed by experimental validation. The heat sink design was the main factor in the heat management of the CLRDL. The heat sinks height was determined using numerical simulation and experimental validation before and after installation (INST) of the ALFHS and CUFHS. The CUFHS height was initially selected based on a larger heat dissipation capacity, and then by determining the ALFHS height. Both the ALFHS and CUFHS with the same height of 17 mm exhibited a similar capacity of heat dissipation before INST. Subsequent to INST, the temperature of the solder point of the ALFHS was higher than that of the CUFHS with an identical height of 17 mm. To compare the heat dissipation behavior of the two heat sinks, the ALFHS height was increased to 23 mm, which is 6 mm higher than that of the CUFHS. The results of a stationary simulation study for junction temperature coincides with the experimental results tested obtained using J-type thermocouples and a data acquisition system. The temperature of the solder point of the CLRDL with both the ALFHS and CUFHS was 91.7 °C after INST, corresponding to an LED junction temperature of 121.7 °C, which is lower than specified 135 °C LED limit temperature. The temperature distributions of specified points under natural convection were evaluated. The CLRDL installed in a small enclosed space withstood the lifetime requirements according to the results of an accelerated life test prediction. The CLRDL lumen maintenance was tested to be more than 25,000 h. The experimental results demonstrate compliance with the Energy Star® requirements for indoor LED lighting fixtures. Full article
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Open AccessArticle Reverse Circulation Drilling Method Based on a Supersonic Nozzle for Dust Control
Appl. Sci. 2017, 7(1), 5; doi:10.3390/app7010005
Received: 5 November 2016 / Revised: 13 December 2016 / Accepted: 19 December 2016 / Published: 27 December 2016
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Abstract
To reduce dust generated from drilling processes, a reverse circulation drilling method based on a supersonic nozzle is proposed. The suction performance is evaluated by the entrainment ratio. A series of preliminary laboratory experiments based on orthogonal experimental design were conducted to test
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To reduce dust generated from drilling processes, a reverse circulation drilling method based on a supersonic nozzle is proposed. The suction performance is evaluated by the entrainment ratio. A series of preliminary laboratory experiments based on orthogonal experimental design were conducted to test the suction performance and reveal the main factors. Computational fluid dynamics (CFD) were conducted to thoroughly understand the interaction mechanism of the flows. The Schlieren technique was further carried out to reveal the flow characteristic of the nozzle. The results show that the supersonic nozzle can significantly improve the reverse circulation effect. A high entrainment ratio up to 0.76 was achieved, which implied strong suction performance. The CFD results agreed well with experimental data with a maximum difference of 17%. This work presents the great potential for supersonic nozzles and reverse circulation in dust control, which is significant to protect the envrionment and people’s health. Full article
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Open AccessArticle Modeling of Temperature Field during Multi-Pass GMAW Surfacing or Rebuilding of Steel Elements Taking into Account the Heat of the Deposit Metal
Appl. Sci. 2017, 7(1), 6; doi:10.3390/app7010006
Received: 3 November 2016 / Revised: 8 December 2016 / Accepted: 15 December 2016 / Published: 22 December 2016
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Abstract
This paper proposed an analytical model for describing the temperature field of multi-pass arc weld surfacing. The temperature field is described analytically assuming a bimodal volumetric model of the heat source and a semi-infinite body model of the (rebuilt) workpiece. The suggested analytical
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This paper proposed an analytical model for describing the temperature field of multi-pass arc weld surfacing. The temperature field is described analytically assuming a bimodal volumetric model of the heat source and a semi-infinite body model of the (rebuilt) workpiece. The suggested analytical solution takes into account the temperature changes caused not only by the direct heat of an electric arc, but also by the heat of the applied weld (melted metal of electrode). The solution considers temperature increments caused by overlaying consecutive welding sequences and by self-cooling of areas previously heated. Computations of the temperature field are carried out during the multi-pass gas metal arc welding (GMAW) surfacing of a steel plate. The results are presented in the form of transient and maximum (achieved in whole welding process) temperature distributions in the element’s cross-section, as well as thermal cycles at the selected point. Full article
(This article belongs to the Special Issue Gas Metal Arc Welding)
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Open AccessArticle Design and Optimization of a Lorentz-Force-Driven Planar Motor
Appl. Sci. 2017, 7(1), 7; doi:10.3390/app7010007
Received: 5 October 2016 / Accepted: 16 December 2016 / Published: 22 December 2016
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Abstract
This paper describes a short-stroke Lorentz-force-driven planar motor which can realize three-degree-of-freedom motions in high-precision positioning systems. It is an extended version of our previous publication. Based on the analytical model, the force expression concerning the main dimensional parameters is derived. Compared with
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This paper describes a short-stroke Lorentz-force-driven planar motor which can realize three-degree-of-freedom motions in high-precision positioning systems. It is an extended version of our previous publication. Based on the analytical model, the force expression concerning the main dimensional parameters is derived. Compared with the finite element simulation, the optimization method in this paper is completely based on the mathematical model, which saves considerable time and has clear physical meaning. The effect of the main parameters on the motor performances such as force, force density, and acceleration are analyzed. This information can provide important design references for researchers. Finally, one prototype is tested. The testing values for the resistance and inductance of the square coil agree well with the analytical values. Additionally, the measured forces show a good agreement with the analytical force expression, and the force characteristics show a good symmetry in the x and y directions. Full article
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Open AccessArticle Connectivity Maintenance Based on Multiple Relay UAVs Selection Scheme in Cooperative Surveillance
Appl. Sci. 2017, 7(1), 8; doi:10.3390/app7010008
Received: 4 November 2016 / Revised: 8 December 2016 / Accepted: 15 December 2016 / Published: 22 December 2016
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Abstract
For the purpose of remote command and situation awareness, multiple unmanned aerial vehicles (UAVs) cooperative surveillance with a ground station via multihop communications is presented in this paper. Considering limited communication capacities, a reliable UAV-to-UAV communication relay chain is dynamically established for connectivity
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For the purpose of remote command and situation awareness, multiple unmanned aerial vehicles (UAVs) cooperative surveillance with a ground station via multihop communications is presented in this paper. Considering limited communication capacities, a reliable UAV-to-UAV communication relay chain is dynamically established for connectivity maintenance and real-time surveillance information transmission. Firstly, a multiple UAVs cooperative surveillance framework is constructed with history detection information and surveillance payoff estimation. Secondly, four attributes are proposed to characterize differences among UAV alternatives in communication network containing a ground station, and a novel multiple relay UAVs selection scheme based on fuzzy optimum selection is developed to achieve tradeoff between surveillance mission and connectivity maintenance. Furthermore, satisfied with collision avoidance, limited communication and UAV kinematic constraints, the optimal UAV motion plan is obtained by decentralized receding horizon control, which is solved by particle swarm optimization with elite mechanism. Simulations demonstrate the effectiveness of the proposed methods in multi UAVs cooperative surveillance. Full article
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Open AccessArticle Estimation of Noise Magnitude for Speech Denoising Using Minima-Controlled-Recursive-Averaging Algorithm Adapted by Harmonic Properties
Appl. Sci. 2017, 7(1), 9; doi:10.3390/app7010009
Received: 16 October 2016 / Revised: 6 December 2016 / Accepted: 15 December 2016 / Published: 22 December 2016
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Abstract
The accuracy of noise estimation is important for the performance of a speech denoising system. Most noise estimators suffer from either overestimation or underestimation on the noise level. An overestimate on noise magnitude will cause serious speech distortion for speech denoising. Conversely, a
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The accuracy of noise estimation is important for the performance of a speech denoising system. Most noise estimators suffer from either overestimation or underestimation on the noise level. An overestimate on noise magnitude will cause serious speech distortion for speech denoising. Conversely, a great quantity of residual noise will occur when the noise magnitude is underestimated. Accurately estimating noise magnitude is important for speech denoising. This study proposes employing variable segment length for noise tracking and variable thresholds for the determination of speech presence probability, resulting in the performance improvement for a minima-controlled-recursive-averaging (MCRA) algorithm in noise estimation. Initially, the fundamental frequency was estimated to determine whether a frame is a vowel. In the case of a vowel frame, the increment of segment lengths and the decrement of threshold for speech presence were performed which resulted in underestimating the level of noise magnitude. Accordingly, the speech distortion is reduced in denoised speech. On the contrary, the segment length decreases rapidly in noise-dominant regions. This enables the noise estimate to update quickly and the noise variation to track well, yielding interference noise being removed effectively through the process of speech denoising. Experimental results show that the proposed approach has been effective in improving the performance of the MCRA algorithm by preserving the weak vowels and consonants. The denoising performance is therefore improved. Full article
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Open AccessArticle Physicochemical Properties and In Vitro Dissolution of Spiramycin Microparticles Using the Homogenate-Antisolvent Precipitation Process
Appl. Sci. 2017, 7(1), 10; doi:10.3390/app7010010
Received: 5 November 2016 / Revised: 14 December 2016 / Accepted: 19 December 2016 / Published: 22 December 2016
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Abstract
Due to its low bioavailability and slow dissolution rate, the micronized spiramycin powder was thus prepared by the homogenate-antisolvent precipitation (HAP) process. The optimum micronization conditions of the HAP process were found to be as follows: precipitation temperature of 4.6 °C, precipitation time
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Due to its low bioavailability and slow dissolution rate, the micronized spiramycin powder was thus prepared by the homogenate-antisolvent precipitation (HAP) process. The optimum micronization conditions of the HAP process were found to be as follows: precipitation temperature of 4.6 °C, precipitation time of 10 min, spiramycin concentration of 20 mg/mL, dripping speed of the added solvent into the antisolvent of 44 mL/h, antisolvent (water) to solvent (dimethyl sulfide (DMSO)) volume ratio of 7:1, and shear rate of 5000 rpm. With this HAP process, the mean particle size was 228.36 ± 3.99 nm. The micronized spiramycin was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, high-performance liquid chromatography, and gas chromatograph analyses. In comparison with the raw drug, the chemical structure of micronized spiramycin was not changed. The dissolution rate experiments showed that the dissolution rate of the spiramycin was significantly increased after micronization. Full article
(This article belongs to the Special Issue Nanomanufacturing of Biomedical Systems and Devices)
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Open AccessArticle Decentralized Integral-Based Event-Triggered Stabilization for Linear Plant with Actuator Saturation and Output Feedback
Appl. Sci. 2017, 7(1), 11; doi:10.3390/app7010011
Received: 28 October 2016 / Revised: 9 December 2016 / Accepted: 16 December 2016 / Published: 22 December 2016
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Abstract
This paper studies the integral-based event-triggered asymptotic stabilization for a continuous-time linear plant. Both actuator saturation and observer-based output feedback are considered. The sensors and actuators are implemented in a decentralized manner and a type of Zeno-free decentralized integral-based event condition is designed
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This paper studies the integral-based event-triggered asymptotic stabilization for a continuous-time linear plant. Both actuator saturation and observer-based output feedback are considered. The sensors and actuators are implemented in a decentralized manner and a type of Zeno-free decentralized integral-based event condition is designed to guarantee the asymptotic stability of the closed-loop systems. The positive lower bound of inter-event times is guaranteed by enforcing the event conditions not to be triggered until some fixed intervals. A linear optimization problem is introduced to find the largest stability region. Moreover, the co-design of the parameters in event conditions and the controller gain matrices is proposed in terms of linear matrix inequalities. Finally, two numerical examples are given to illustrate the efficiency and the feasibility of the proposed results. Full article
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Open AccessArticle Biotransformation of Lactones with Methylcyclohexane Ring and Their Biological Activity
Appl. Sci. 2017, 7(1), 12; doi:10.3390/app7010012
Received: 14 November 2016 / Revised: 12 December 2016 / Accepted: 19 December 2016 / Published: 24 December 2016
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Abstract
The aim of the study was to obtain biological active compounds during biotransformation. Three bicyclic halolactones with methylcyclohexane ring (2-chloro-4-methyl-9-oxabicyclo-[4.3.0]nonan-8-one, 2-bromo-4-methyl-9-oxabicyclo[4.3.0]nona- -8-one and 2-iodo-4-methyl-9-oxabicyclo[4.3.0]nonan-8-one) obtained from the corresponding γ,δ-unsaturated acid were subjected to a screening biotransformation using 22 fungal strains. Two of these
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The aim of the study was to obtain biological active compounds during biotransformation. Three bicyclic halolactones with methylcyclohexane ring (2-chloro-4-methyl-9-oxabicyclo-[4.3.0]nonan-8-one, 2-bromo-4-methyl-9-oxabicyclo[4.3.0]nona- -8-one and 2-iodo-4-methyl-9-oxabicyclo[4.3.0]nonan-8-one) obtained from the corresponding γ,δ-unsaturated acid were subjected to a screening biotransformation using 22 fungal strains. Two of these strains (Cunninghamella japonica AM472 and Fusarium culmorum AM10) were able to transform halolactones into 2-hydroxy-4-methyl-9-oxabicyclo[4.3.0]nonan-8-one by hydrolytic dehalogenation with good yield. The biotransformation product was structurally different from its synthetically prepared analog. All halolactones and hydroxylactones were tested for their biological activity. The chlorolactone inhibited growth of Staphylococcus aureus (max ΔOD = 0), Escherichia coli (max ΔOD = 0.3) and Candida albicans (max ΔOD = 0) strains. Bromolactone caused inhibition of growth of Staphylococcus aureus (max ΔOD = 0) and Fusarium linii (max ΔOD = 0) strains. Iodolactone limited growth of Staphylococcus aureus (max ΔOD = 0), Escherichia coli (max ΔOD = 0.25), Candida albicans (max ΔOD = 0.45) and Pseudomonas fluorescens (max ΔOD = 0.42) strains. Hydroxylactone caused inhibition of growth of Staphylococcus aureus (max ΔOD = 0.36) and Pseudomonas fluorescens (max ΔOD = 0.39) strains only. The test performed on aphids Myzus persicae (Sulz.) showed that chloro- and bromolactone exhibited deterrent activity after 24 h (ID = 0.5 and 0.4, respectively), while hydroxylactone was a weak attractant (ID = −0.3). Full article
(This article belongs to the Section Chemistry)
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Open AccessArticle Passivity-Based Control for a Micro Air Vehicle Using Unit Quaternions
Appl. Sci. 2017, 7(1), 13; doi:10.3390/app7010013
Received: 31 October 2016 / Revised: 6 December 2016 / Accepted: 13 December 2016 / Published: 23 December 2016
Cited by 1 | PDF Full-text (1232 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this paper the development and practical implementation of a Passivity-Based Control (PBC) algorithm to stabilize an Unmanned Aerial Vehicle (UAV) described with unit quaternions are presented. First, a mathematical model based on Euler-Lagrange formulation using a logarithmic mapping in the quaternion space
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In this paper the development and practical implementation of a Passivity-Based Control (PBC) algorithm to stabilize an Unmanned Aerial Vehicle (UAV) described with unit quaternions are presented. First, a mathematical model based on Euler-Lagrange formulation using a logarithmic mapping in the quaternion space is introduced. Then, a new methodology: a quaternion-passivity-based control is derived, which does not compute excessive and complex Partial Differential Equations (PDEs) for synthesizing the control law, making a significant advantage in comparison with other methodologies. Therefore, the control design to a system as the quad-rotor is easily solved by the proposed methodology. Another advantage is the possibility to stabilize quad-rotor full dynamics which may not be possible with classical PBC techniques. Experimental results and numerical simulations to validate our proposed scheme are presented. Full article
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Open AccessArticle A Novel Method for Sensorless Speed Detection of Brushed DC Motors
Appl. Sci. 2017, 7(1), 14; doi:10.3390/app7010014
Received: 7 October 2016 / Revised: 17 November 2016 / Accepted: 6 December 2016 / Published: 24 December 2016
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Abstract
Many motor applications require accurate speed measurement. For brushed dc motors, speed can be measured with conventional observers or sensorless observers. Sensorless observers have the advantage of not requiring any external devices to be attached to the motor. Instead, voltage and/or current are
[...] Read more.
Many motor applications require accurate speed measurement. For brushed dc motors, speed can be measured with conventional observers or sensorless observers. Sensorless observers have the advantage of not requiring any external devices to be attached to the motor. Instead, voltage and/or current are measured and used to estimate the speed. The sensorless observers are usually divided into two groups: those based on the dynamic model, and those based on the ripple component. This paper proposes a method that measures the current of brushed dc motors and analyses the position of its spectral components. From these spectral components, the method estimates the motor speed. Three tests, performed each with the speeds ranging from 2000 to 3000 rpm either at constant-speed, at slowly changing speeds, or at rapidly changing speeds, showed that the average error was below 1 rpm and that the deviation error was below 1.5 rpm. The proposed method: (i) is a novel method that is not based on either the dynamic model or on the ripple component; (ii) requires only the measurement of the current for the speed estimation; (iii) can be used for brushed dc (direct current) motors with a large number of coils; and (iv) achieves a low error in the speed estimation. Full article
(This article belongs to the Section Energy)
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Open AccessCommunication Impedance-Based Non-Destructive Testing Method Combined with Unmanned Aerial Vehicle for Structural Health Monitoring of Civil Infrastructures
Appl. Sci. 2017, 7(1), 15; doi:10.3390/app7010015
Received: 15 November 2016 / Revised: 13 December 2016 / Accepted: 20 December 2016 / Published: 22 December 2016
Cited by 5 | PDF Full-text (2684 KB) | HTML Full-text | XML Full-text
Abstract
Unmanned aerial vehicles (UAVs), commonly known as drones, are a rising topic in remote sensing technologies for structural health monitoring. With technology advancement in cameras, the visual inspection method using drones is gaining much attention in the field of civil engineering. However, although
[...] Read more.
Unmanned aerial vehicles (UAVs), commonly known as drones, are a rising topic in remote sensing technologies for structural health monitoring. With technology advancement in cameras, the visual inspection method using drones is gaining much attention in the field of civil engineering. However, although visual inspection methods are feasible for finding cracks in structures, the limitations of image processing for finding internal damage or small defects cannot be ignored. To overcome this problem, a possible application concept of UAV, combined with a vibration-based non-destructive health monitoring method, is proposed. The idea is for the drone to temporarily attach the piezoelectric transducer onto a specific region where excitation and data acquisition occurs simultaneously. This eliminates the need for a structure to be covered with hundreds of sensors for monitoring, as this concept uses a single piezoelectric transducer for monitoring a structure. The proposed work offers new areas of research by converging UAV with a vibration-based method, as associated problems are required to be solved. Full article
(This article belongs to the Special Issue Structural Health Monitoring (SHM) of Civil Structures)
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Open AccessArticle Comparison of Cooling Different Parts in a High Pressure Ratio Centrifugal Compressor
Appl. Sci. 2017, 7(1), 16; doi:10.3390/app7010016
Received: 5 October 2016 / Revised: 18 November 2016 / Accepted: 12 December 2016 / Published: 22 December 2016
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Abstract
Cooling in a centrifugal compressor can improve the performance and reduce the impeller temperature. In a centrifugal compressor, external walls can be cool down, which is known as the shell cooling. This method avoids undesirable effects induced by other cooling methods. Cooling can
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Cooling in a centrifugal compressor can improve the performance and reduce the impeller temperature. In a centrifugal compressor, external walls can be cool down, which is known as the shell cooling. This method avoids undesirable effects induced by other cooling methods. Cooling can be applied on different external walls, such as the shroud, diffuser or the back plate. This paper focuses on seeking the most effective cooling place to increase the performance and reduce the impeller temperature. It is found that shroud cooling improves the compressor performance the most. Shroud cooling with 2400 W of cooling power increases the pressure ratio by 4.6% and efficiency by 1.49%. Each 500 W increase in the shroud cooling power, increases the efficiency by 0.3%. Diffuser cooling and back plate cooling have an identical effect on the polytropic efficiency. However, back plate cooling increases the pressure ratio more than diffuser cooling. Furthermore, only back plate cooling reduces the impeller temperature, and with 2400 W of cooling power, the impeller temperature reduces by 45 K. Full article
(This article belongs to the Section Energy)
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Open AccessFeature PaperArticle An Equivalent Layer-Wise Approach for the Free Vibration Analysis of Thick and Thin Laminated and Sandwich Shells
Appl. Sci. 2017, 7(1), 17; doi:10.3390/app7010017
Received: 24 November 2016 / Revised: 10 December 2016 / Accepted: 14 December 2016 / Published: 22 December 2016
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Abstract
The main purpose of the paper is to present an innovative higher-order structural theory to accurately evaluate the natural frequencies of laminated composite shells. A new kinematic model is developed starting from the theoretical framework given by a unified formulation. The kinematic expansion
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The main purpose of the paper is to present an innovative higher-order structural theory to accurately evaluate the natural frequencies of laminated composite shells. A new kinematic model is developed starting from the theoretical framework given by a unified formulation. The kinematic expansion is taken as a free parameter, and the three-dimensional displacement field is described by using alternatively the Legendre or Lagrange polynomials, following the key points of the most typical Layer-wise (LW) approaches. The structure is considered as a unique body and all the geometric and mechanical properties are evaluated on the shell middle surface, following the idea of the well-known Equivalent Single Layer (ESL) models. For this purpose, the name Equivalent Layer-Wise (ELW) is introduced to define the present approach. The governing equations are solved numerically by means of the Generalized Differential Quadrature (GDQ) method and the solutions are compared with the results available in the literature or obtained through a commercial finite element program. Due to the generality of the current method, several boundary conditions and various mechanical and geometric configurations are considered. Finally, it should be underlined that different doubly-curved surfaces may be considered following the mathematical framework given by the differential geometry. Full article
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Open AccessArticle Rheological Properties with Temperature Response Characteristics and a Mechanism of Solid-Free Polymer Drilling Fluid at Low Temperatures
Appl. Sci. 2017, 7(1), 18; doi:10.3390/app7010018
Received: 6 October 2016 / Revised: 19 December 2016 / Accepted: 20 December 2016 / Published: 23 December 2016
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Abstract
The rheological properties of drilling fluid have important effects during drilling in natural gas hydrate at low temperatures. The present study was performed using theoretical analysis. Experiments and micro-analyses were carried out to determine the rheological properties with temperature response characteristics and the
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The rheological properties of drilling fluid have important effects during drilling in natural gas hydrate at low temperatures. The present study was performed using theoretical analysis. Experiments and micro-analyses were carried out to determine the rheological properties with temperature response characteristics and the mechanism involved in solid-free polymer drilling fluid (SFPDF) at low temperatures when drilling in permafrost with natural gas hydrates (NGH). The curves of shear stress with the shear rates of three kinds of polymer drilling fluids, Semen Lepidii natural vegetable gum, polyacrylamide, and xanthan gum, were drawn. Then, statistical and related analyses of test data were performed using Matlab ver. 8.0. Through regression analysis, the Herschel–Bulkley model was used to characterize the rheological characteristics of SFPDF. On this basis, the laws regarding the rheological properties of the three kinds of SFPDF under changing temperatures were analyzed and rheological properties with temperature response state equations were established. Next, the findings of previous studies on rheological properties with temperature response characteristics of the SFPDF were reviewed. Finally, the rheological properties with temperature response mechanisms were assessed using scanning electron microscopy and infrared spectrum analysis. Full article
(This article belongs to the Section Materials)
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Open AccessArticle Characterization of Reduced Graphene Oxide (rGO)-Loaded SnO2 Nanocomposite and Applications in C2H2 Gas Detection
Appl. Sci. 2017, 7(1), 19; doi:10.3390/app7010019
Received: 31 October 2016 / Revised: 4 December 2016 / Accepted: 17 December 2016 / Published: 23 December 2016
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Abstract
Acetylene (C2H2) gas sensors were developed by synthesizing a reduced graphene oxide (rGO)-loaded SnO2 hybrid nanocomposite via a facile two-step hydrothermal method. Morphological characterizations showed the formation of well-dispersed SnO2 nanoparticles loaded on the rGO sheets with
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Acetylene (C2H2) gas sensors were developed by synthesizing a reduced graphene oxide (rGO)-loaded SnO2 hybrid nanocomposite via a facile two-step hydrothermal method. Morphological characterizations showed the formation of well-dispersed SnO2 nanoparticles loaded on the rGO sheets with excellent transparency and obvious fold boundary. Structural analysis revealed good agreement with the standard crystalline phases of SnO2 and rGO. Gas sensing characteristics of the synthesized materials were carried out in a temperature range of 100–300 °C with various concentrations of C2H2 gas. At 180 °C, the SnO2–rGO hybrid showed preferable detection of C2H2 with high sensor response (12.4 toward 50 ppm), fast response-recovery time (54 s and 23 s), limit of detection (LOD) of 1.3 ppm and good linearity, with good selectivity and long-term stability. Furthermore, the possible gas sensing mechanism of the SnO2–rGO nanocomposites for C2H2 gas were summarized and discussed in detail. Our work indicates that the addition of rGO would be effective in enhancing the sensing properties of metal oxide-based gas sensors for C2H2 and may make a contribution to the development of an excellent ppm-level gas sensor for on-line monitoring of dissolved C2H2 gas in transformer oil. Full article
(This article belongs to the Special Issue Metal Oxide Nanostructures)
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Open AccessArticle Resistivity and Its Anisotropy Characterization of 3D-Printed Acrylonitrile Butadiene Styrene Copolymer (ABS)/Carbon Black (CB) Composites
Appl. Sci. 2017, 7(1), 20; doi:10.3390/app7010020
Received: 17 October 2016 / Revised: 14 December 2016 / Accepted: 19 December 2016 / Published: 4 January 2017
Cited by 1 | PDF Full-text (2193 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The rapid printing of 3D parts with desired electrical properties enables numerous applications. Fused deposition modeling (FDM) using conductive thermoplastic composites has been a valuable approach for such fabrication. The parts produced by FDM possess various controllable structural features, but the effects of
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The rapid printing of 3D parts with desired electrical properties enables numerous applications. Fused deposition modeling (FDM) using conductive thermoplastic composites has been a valuable approach for such fabrication. The parts produced by FDM possess various controllable structural features, but the effects of the structural features on the electrical properties remain to be determined. This study investigated the effects of these features on the electrical resistivity and resistivity anisotropy of 3D-printed ABS/CB composites. The effects of the process parameters of FDM, including the layer thickness, raster width, and air gap, on the resistivity in both the vertical and horizontal directions for cubic samples were studied because the internal structure of the printed parts depended on those process parameters. The resistivities of printed parts in different parameter combinations were measured by an impedance analyzer and finite element models were created to investigate the relationship between the resistivity and the internal structure. The results indicated that the parameters remarkably affected the resistivity due to the influence of voids and the bonding condition between adjacent fibers. The resistivity in the vertical direction ranged from 70.40 ± 2.88 Ω·m to 180.33 ± 8.21 Ω·m, and the resistivity in the horizontal direction ranged from 41.91 ± 2.29 Ω·m to 58.35 ± 0.61 Ω·m at the frequency of 1 kHz. Moreover, by adjusting the resistivities in different directions, the resistivity anisotropy of the printed parts can be manipulated from 1.01 to 3.59. This research may serve as a reference to fabricate parts with sophisticated geometry with desired electrical resistivity and resistivity anisotropy. Full article
(This article belongs to the Section Materials)
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Open AccessArticle Numerical Simulation of Multi-Crystalline Silicon Crystal Growth Using a Macro–Micro Coupled Method during the Directional Solidification Process
Appl. Sci. 2017, 7(1), 21; doi:10.3390/app7010021
Received: 30 September 2016 / Revised: 20 November 2016 / Accepted: 15 December 2016 / Published: 26 December 2016
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Abstract
In this work, the crystal growth of multi-crystalline silicon (mc-Si) during the directional solidification process was studied using the cellular automaton method. The boundary heat transfer coefficient was adjusted to get a suitable temperature field and a high-quality mc-Si ingot. Under the conditions
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In this work, the crystal growth of multi-crystalline silicon (mc-Si) during the directional solidification process was studied using the cellular automaton method. The boundary heat transfer coefficient was adjusted to get a suitable temperature field and a high-quality mc-Si ingot. Under the conditions of top adiabatic and bottom constant heat flux, the shape of the crystal-melt interface changes from concave to convex with the decrease of the heat transfer coefficient on the side boundaries. In addition, the nuclei form at the bottom boundary while columnar crystals develop into silicon melt with amzigzag-faceted interface. The higher-energy silicon grains were merged into lower energy ones. In the end, the number of silicon grains decreases with the increase of crystal length. Full article
(This article belongs to the Special Issue Silicon Photonics Components and Applications)
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Open AccessArticle Effect of the Impact of Chemical and Environmental Factors on the Durability of the High Density Polyethylene (HDPE) Geogrid in a Sanitary Landfill
Appl. Sci. 2017, 7(1), 22; doi:10.3390/app7010022
Received: 12 October 2016 / Revised: 6 December 2016 / Accepted: 15 December 2016 / Published: 23 December 2016
Cited by 1 | PDF Full-text (4149 KB) | HTML Full-text | XML Full-text
Abstract
A high density polyethylene (HDPE) uniaxial geogrid was exhumed after twenty years of service in a sanitary landfill, and its properties were examined. A geogrid installed in a landfill is exposed to mechanical and chemical factors (e.g., a wide pH range and high
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A high density polyethylene (HDPE) uniaxial geogrid was exhumed after twenty years of service in a sanitary landfill, and its properties were examined. A geogrid installed in a landfill is exposed to mechanical and chemical factors (e.g., a wide pH range and high temperatures), as well as different weather conditions. This paper presents the results of physical and mechanical analyses of virgin and aged HDPE geogrid samples. Structural changes observed by differential scanning calorimetry and Fourier transform infrared spectroscopy (FT-IR) spectroscopy correlate with the mechanical properties of the aged geogrid. The mechanical properties were found to have changed only slightly. In the FT-IR spectrum of the topmost layer of the aged geogrid samples, no significant changes were observed compared to the spectrum of the top layer of the virgin samples. This indicates the strong chemical resistance of the HDPE material, which is able to withstand environmental conditions for at least 20 years of service in a landfill. Full article
(This article belongs to the Section Materials)
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Open AccessArticle A Genetic Regulatory Network-Based Method for Dynamic Hybrid Flow Shop Scheduling with Uncertain Processing Times
Appl. Sci. 2017, 7(1), 23; doi:10.3390/app7010023
Received: 2 November 2016 / Revised: 6 December 2016 / Accepted: 19 December 2016 / Published: 4 January 2017
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Abstract
The hybrid flow shop is a typical discrete manufacturing system. A novel method is proposed to solve the shop scheduling problem featured with uncertain processing times. The rolling horizon strategy is adopted to evaluate the difference between a predictive plan and the actual
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The hybrid flow shop is a typical discrete manufacturing system. A novel method is proposed to solve the shop scheduling problem featured with uncertain processing times. The rolling horizon strategy is adopted to evaluate the difference between a predictive plan and the actual production process in terms of job delivery time. The genetic regulatory network-based rescheduling algorithm revises the remaining plan if the difference is beyond a specific tolerance. In this algorithm, decision variables within the rolling horizon are represented by genes in the network. The constraints and certain rescheduling rules are described by regulation equations between genes. The rescheduling solutions are generated from expression procedures of gene states, in which the regulation equations convert some genes to the expressed state and determine decision variable values according to gene states. Based on above representations, the objective of minimizing makespan is realized by optimizing regulatory parameters in regulation equations. The effectiveness of this network-based method over other ones is demonstrated through a series of benchmark tests and an application case collected from a printed circuit board assembly shop. Full article
(This article belongs to the Special Issue Modeling, Simulation, Operation and Control of Discrete Event Systems)
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Open AccessArticle The Preparation and Characterization of Immobilized TiO2/PEG by Using DSAT as a Support Binder
Appl. Sci. 2017, 7(1), 24; doi:10.3390/app7010024
Received: 30 September 2016 / Revised: 6 December 2016 / Accepted: 13 December 2016 / Published: 23 December 2016
Cited by 1 | PDF Full-text (4233 KB) | HTML Full-text | XML Full-text
Abstract
Immobilized TiO2 was prepared by adding a small composition of polyethylene glycol (PEG) as a binder, and this paper reported for the very first time the formation of C=O from oxidized PEG, which acted as an electron injector in enhancing photoactivity. Water-based
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Immobilized TiO2 was prepared by adding a small composition of polyethylene glycol (PEG) as a binder, and this paper reported for the very first time the formation of C=O from oxidized PEG, which acted as an electron injector in enhancing photoactivity. Water-based TiO2 with PEG formulation was deposited by using a brush technique onto double-sided adhesive tape (DSAT) as a support binder to increase the adhesiveness of immobilized TiO2. The photocatalytic activity of immobilized TiO2-PEG was measured by photodegradation of 12 mg·L−1 methylene blue (MB) dye. The optimum condition of immobilized TiO2-PEG was observed at TiO2/PEG-2 (TP2) with 10:0.1 for the TiO2/PEG ratio, which resulted in a 1.8-times higher photodegradation rate as compared to the suspension mode of pristine TiO2. The high photodegradation rate was due to the formation of the active C=O bond from oxidized PEG binder in immobilized TiO2-PEG as observed by Fourier transform infrared and X-ray photoelectron spectroscopy analyses. The presence of C=O has escalated the photoactivity by forming an electron injector to a conduction band of TiO2 as proven by higher photoluminescence intensity obtained for TP2 as compared to pristine TiO2. The TP2 sample has also increased its adhesiveness when DSAT is applied as a support binder where it can be recycled up to eight times and comparable to recent photocatalysis cycle developments. Full article
(This article belongs to the Section Chemistry)
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Open AccessArticle Size Control of Carbon Encapsulated Iron Nanoparticles by Arc Discharge Plasma Method
Appl. Sci. 2017, 7(1), 26; doi:10.3390/app7010026
Received: 15 November 2016 / Revised: 16 December 2016 / Accepted: 20 December 2016 / Published: 26 December 2016
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Abstract
Size control of core@shell nanostructures is still a challenge. Carbon encapsulated iron nanoparticles (CEINPs) were synthesized by arc discharge plasma method in this study. CEINPs size can be controlled by varying gas composition, due to change in plasma properties. The morphology and structural
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Size control of core@shell nanostructures is still a challenge. Carbon encapsulated iron nanoparticles (CEINPs) were synthesized by arc discharge plasma method in this study. CEINPs size can be controlled by varying gas composition, due to change in plasma properties. The morphology and structural features were investigated using scanning electron microscopy, transmission electron microscopy (TEM) and high-resolution TEM. Magnetic properties were studied to confirm the changes in CEINPs size by using superconducting quantum interference device. In order to evaluate the carbon shell protection and ensure the absence of iron oxide, selected area electron diffraction technique, energy-dispersive x-ray spectroscopy and electron energy loss spectroscopy were employed. Moreover, the degree of carbon order–disorder was studied by Raman Spectroscopy. It was concluded that arc discharge method is a suitable technique for precise size control of CEINPs. Full article
(This article belongs to the Special Issue Biodegradable and Biocompatible Nanoparticles)
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Open AccessArticle In Situ Test Study on Freezing Scheme of Freeze-Sealing Pipe Roof Applied to the Gongbei Tunnel in the Hong Kong-Zhuhai-Macau Bridge
Appl. Sci. 2017, 7(1), 27; doi:10.3390/app7010027
Received: 30 October 2016 / Revised: 9 December 2016 / Accepted: 19 December 2016 / Published: 27 December 2016
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Abstract
In order to solve the water sealing problem of soil between pipes of long distance curved pipe-jacked technology, Freeze-Sealing Pipe Roof (FSPR) as an innovative pre-supporting method in tunnel engineering is being applied to the Gongbei Tunnel in the Hong Kong-Zhuhai-Macau Bridge. The
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In order to solve the water sealing problem of soil between pipes of long distance curved pipe-jacked technology, Freeze-Sealing Pipe Roof (FSPR) as an innovative pre-supporting method in tunnel engineering is being applied to the Gongbei Tunnel in the Hong Kong-Zhuhai-Macau Bridge. The definition of FSPR is that large diameter steel pipes are laid out in a circle around the cross section of tunnel in advance, then the artificial ground freezing method is adopted to freeze soil between steel pipes to form water-sealing curtain. An effective freeze control system, which contains master freezing tubes, enhancing freezing tubes and limiting freezing tubes, is established for building up the frozen soil curtain, maintaining its stability during excavation and controlling the volume of frozen soil to limit frost heave dynamically. An in-situ test was carried out to explore the optimal freezing scheme and control mode. The results of the test show that the principal freezing scheme of the solid pipe with hollow pipe as a complement is the most optimal scheme in active freezing phase of the real construction. Meanwhile, cold control mode is suggested to control frost heave in maintained freezing phase. The conclusions have important guiding significance for this kind of engineering construction. Full article
(This article belongs to the Special Issue Advances in Thermal System Analysis and Optimization)
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Open AccessArticle Experimental Evaluation of Lubrication Characteristics of a New Type Oil-Film Bearing Oil Using Multi-Sensor System
Appl. Sci. 2017, 7(1), 28; doi:10.3390/app7010028
Received: 4 November 2016 / Revised: 12 December 2016 / Accepted: 13 December 2016 / Published: 26 December 2016
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Abstract
In order to evaluate the operating performance of a new type oil-film bearing oil S220, a new test bearing was designed based on oil-film bearing test rig. The operating temperature of S220 was tested through the thermocouples installed on a test bearing; the
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In order to evaluate the operating performance of a new type oil-film bearing oil S220, a new test bearing was designed based on oil-film bearing test rig. The operating temperature of S220 was tested through the thermocouples installed on a test bearing; the operating oil-film pressure was tested through pressure transducers; and the operating oil-film thickness was tested through displacement transducers. Meanwhile, M220 was also tested as a comparison, and both oils are based on mineral oil. The results showed that all property indexes of the test rig can meet the specified requirements and can guarantee the performance test of oil-film bearing oil; the operating temperature of S220 is generally equal to that of M220, and both have the same operating stability. The temperature property conforms to Formula (1) and the operating temperature under different load cases can be predicted. Although oil-film pressure of M220 is a little more stable, the oil-film pressure of S220 is similar to that of M220. Moreover, both have the similar oil-film thickness, and the oil-film thickness of S220 is slightly smaller than that of M220, especially at the beginning of operation. Ultimately, oil S220 is evaluated to be suitable for actual engineering application. Full article
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Open AccessArticle Rapid Synthesis of Gold Nanoparticles from Quercus incana and Their Antimicrobial Potential against Human Pathogens
Appl. Sci. 2017, 7(1), 29; doi:10.3390/app7010029
Received: 5 October 2016 / Revised: 7 December 2016 / Accepted: 9 December 2016 / Published: 16 January 2017
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Abstract
In current study, bioreduction of tetrachloroauric acid (HAuCl4·3H2O) was carried out using leaves extract of Quercus incana for nanoparticle synthesis. The nanoparticles were characterized by ultraviolet visible spectrum (UV), Fourier-transform infrared (FT-IR), and transmission electron microscopy (TEM) analysis. The
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In current study, bioreduction of tetrachloroauric acid (HAuCl4·3H2O) was carried out using leaves extract of Quercus incana for nanoparticle synthesis. The nanoparticles were characterized by ultraviolet visible spectrum (UV), Fourier-transform infrared (FT-IR), and transmission electron microscopy (TEM) analysis. The gold nanoparticles (GNPs) were generally clumpy agglomerates of polydispersed particles, with an average size in the range 5.5–10 nm. The Gas chromatography–mass spectrometry (GC–MS) qualitative analysis and FT-IR data supported the presence of bioactive compounds, which are responsible for the metal reduction and nanoparticles stabilization. The biocompatibility of synthesized GNPs was evaluated via antibacterial activity by using human bacterial pathogens. The results showed that synthesized GNPs showed enhanced antibacterial activity against all bacterial pathogens. Full article
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Open AccessArticle Effects of the Concentration of Eu3+ Ions and Synthesizing Temperature on the Luminescence Properties of Sr2−xEuxZnMoO6 Phosphors
Appl. Sci. 2017, 7(1), 30; doi:10.3390/app7010030
Received: 13 September 2016 / Revised: 5 December 2016 / Accepted: 22 December 2016 / Published: 27 December 2016
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Abstract
The effect of Eu2O3 concentration on the luminescence properties of double perovskite (cubic) Sr2−xEuxZnMoO6 phosphors was thoroughly investigated using different synthesizing temperatures. Phosphors with the composition Sr2−xEuxZnMoO6,
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The effect of Eu2O3 concentration on the luminescence properties of double perovskite (cubic) Sr2−xEuxZnMoO6 phosphors was thoroughly investigated using different synthesizing temperatures. Phosphors with the composition Sr2−xEuxZnMoO6, where Eu2O3 was substituted for SrO and x was changed from 0 to 0.12, were synthesized by the solid-state method at temperatures of 900–1200 °C, respectively. Analysis of the X-ray diffraction (XRD) patterns showed that even when the synthesizing temperature was 1100 °C, secondary or unknown phases were observed in Sr2−xEuxZnMoO6 ceramic powders. The effect of the concentration of Eu3+ ions on the luminescence properties of the Sr2−xEuxZnMoO6 phosphors was readily observable because no characteristic emission peak was observed in the Sr2ZnMoO6 phosphor. Two characteristic emission peaks at 597 and 616 nm were observed, which correspond to the 5D07F1 and 5D07F2 transitions of Eu3+ ions, respectively. The two characteristic emission peaks of the Sr2−xEuxZnMoO6 phosphors were apparently influenced by the synthesizing temperature and the concentration of Eu3+ ions. When x was larger than 0.08, a concentration quenching effect of Eu3+ ions in the Sr2−xEuxZnMoO6 phosphors could be observed. The lifetime of the Sr2−xEuxZnMoO6 phosphors decreased as the synthesizing temperature increased. A linear relation between temperature and lifetime was obtained by using a fitting curve of t = −0.0016 × T + 3.543, where t was lifetime and T was synthesizing temperature. Full article
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Open AccessArticle Implementation of a Motor Diagnosis System for Rotor Failure Using Genetic Algorithm and Fuzzy Classification
Appl. Sci. 2017, 7(1), 31; doi:10.3390/app7010031
Received: 26 September 2016 / Revised: 15 December 2016 / Accepted: 21 December 2016 / Published: 27 December 2016
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In this paper, the diagnosis of induction motor rotor failure with fuzzy theory and genetic algorithm is presented. The proposed method can evaluate the status of an operating motor. According to the measurement of electrical data, this research establishes the relationship of rotor
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In this paper, the diagnosis of induction motor rotor failure with fuzzy theory and genetic algorithm is presented. The proposed method can evaluate the status of an operating motor. According to the measurement of electrical data, this research establishes the relationship of rotor failures with spectrum features. Through the learning of genetic algorithm, membership parameters can be adjusted to optimal positions. The simulation that combines fuzzy theory and a genetic algorithm has preferable diagnostic results for the rotor failures. The designed processes will be applied as a reference for building the diagnostic methods of other motor failures. Full article
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Open AccessArticle Autofluorescence Imaging and Spectroscopy of Human Lung Cancer
Appl. Sci. 2017, 7(1), 32; doi:10.3390/app7010032
Received: 16 November 2016 / Revised: 23 December 2016 / Accepted: 23 December 2016 / Published: 28 December 2016
PDF Full-text (3403 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Lung cancer is one of the most common cancers, with high mortality rate worldwide. Autofluorescence imaging and spectroscopy is a non-invasive, label-free, real-time technique for cancer detection. In this study, lung tissue sections excised from patients were detected by laser scan confocal microscopy
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Lung cancer is one of the most common cancers, with high mortality rate worldwide. Autofluorescence imaging and spectroscopy is a non-invasive, label-free, real-time technique for cancer detection. In this study, lung tissue sections excised from patients were detected by laser scan confocal microscopy and spectroscopy. The autofluorescence images demonstrated the cellular morphology and tissue structure, as well as the pathology of stained images. Based on the spectra study, it was found that the majority of the patients showed discriminating fluorescence in tumor tissues from normal tissues. Therefore, autofluorescence imaging and spectroscopy may be a potential method for aiding the diagnosis of lung cancer. Full article
(This article belongs to the Special Issue Dimensional Micro and Nanometrology)
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Open AccessArticle Improving Corrosion Resistance and Biocompatibility of Magnesium Alloy by Sodium Hydroxide and Hydrofluoric Acid Treatments
Appl. Sci. 2017, 7(1), 33; doi:10.3390/app7010033
Received: 21 November 2016 / Revised: 21 December 2016 / Accepted: 22 December 2016 / Published: 28 December 2016
Cited by 1 | PDF Full-text (3000 KB) | HTML Full-text | XML Full-text
Abstract
Owing to excellent mechanical property and biodegradation, magnesium-based alloys have been widely investigated for temporary implants such as cardiovascular stent and bone graft; however, the fast biodegradation in physiological environment and the limited surface biocompatibility hinder their clinical applications. In the present study,
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Owing to excellent mechanical property and biodegradation, magnesium-based alloys have been widely investigated for temporary implants such as cardiovascular stent and bone graft; however, the fast biodegradation in physiological environment and the limited surface biocompatibility hinder their clinical applications. In the present study, magnesium alloy was treated by sodium hydroxide (NaOH) and hydrogen fluoride (HF) solutions, respectively, to produce the chemical conversion layers with the aim of improving the corrosion resistance and biocompatibility. The results of attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) indicated that the chemical conversion layers of magnesium hydroxide or magnesium fluoride were obtained successfully. Sodium hydroxide treatment can significantly enhance the surface hydrophilicity while hydrogen fluoride treatment improved the surface hydrophobicity. Both the chemical conversion layers can obviously improve the corrosion resistance of the pristine magnesium alloy. Due to the hydrophobicity of magnesium fluoride, HF-treated magnesium alloy showed the relative better corrosion resistance than that of NaOH-treated substrate. According to the results of hemolysis assay and platelet adhesion, the chemical surface modified samples exhibited improved blood compatibility as compared to the pristine magnesium alloy. Furthermore, the chemical surface modified samples improved cytocompatibility to endothelial cells, the cells had better cell adhesion and proliferative profiles on the modified surfaces. Due to the excellent hydrophilicity, the NaOH-treated substrate displayed better blood compatibility and cytocompatibility to endothelial cells than that of HF-treated sample. It was considered that the method of the present study can be used for the surface modification of the magnesium alloy to enhance the corrosion resistance and biocompatibility. Full article
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Open AccessArticle Application of Canola Oil Biodiesel/Diesel Blends in a Common Rail Diesel Engine
Appl. Sci. 2017, 7(1), 34; doi:10.3390/app7010034
Received: 23 November 2016 / Revised: 15 December 2016 / Accepted: 23 December 2016 / Published: 28 December 2016
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Abstract
In this study, the application effects of canola oil biodiesel/diesel blends in a common rail diesel engine was experimentally investigated. The test fuels were denoted as ULSD (ultra low sulfur diesel), BD20 (20% canola oil blended with 80% ULSD by volume), and PCO
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In this study, the application effects of canola oil biodiesel/diesel blends in a common rail diesel engine was experimentally investigated. The test fuels were denoted as ULSD (ultra low sulfur diesel), BD20 (20% canola oil blended with 80% ULSD by volume), and PCO (pure canola oil), respectively. These three fuels were tested under an engine speed of 1500 rpm with various brake mean effective pressures (BMEPs). The results indicated that PCO can be used well in the diesel engine without engine modification, and that BD20 can be used as a good alternative fuel to reduce the exhaust pollution. In addition, at low engine loads (0.13 MPa and 0.26 MPa), the combustion pressure of PCO is the smallest, compared with BD20 and ULSD, because the lower calorific value of PCO is lower than that of ULSD. However, at high engine loads (0.39 MPa and 0.52 MPa), the rate of heat release (ROHR) of BD20 is the highest because the canola oil biodiesel is an oxygenated fuel that promotes combustion, shortening the ignition delay period. For exhaust emissions, by using canola oil biodiesel, the particulate matter (PM) and carbon monoxide (CO) emissions were considerably reduced with increased BMEP. The nitrogen oxide (NOx) emissions increased only slightly due to the inherent presence of oxygen in biodiesel. Full article
(This article belongs to the Section Energy)
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Open AccessArticle Strength Correlation and Prediction of Engineered Cementitious Composites with Microwave Properties
Appl. Sci. 2017, 7(1), 35; doi:10.3390/app7010035
Received: 10 November 2016 / Revised: 7 December 2016 / Accepted: 14 December 2016 / Published: 27 December 2016
Cited by 2 | PDF Full-text (3342 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the results of microwave and mechanical measurements of engineered cementitious composites (ECCs) using a nondestructive microwave near-field detecting technique. The objective of this research is to investigate the correlations between effective conductance and compressive strength of ECCs at various curing
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This paper presents the results of microwave and mechanical measurements of engineered cementitious composites (ECCs) using a nondestructive microwave near-field detecting technique. The objective of this research is to investigate the correlations between effective conductance and compressive strength of ECCs at various curing ages under the influence of different initial water contents. Parallel measurements and regression analysis on compressive strength and microwave conductance were undertaken. It is shown that the strength evolution of ECCs can be accurately modeled and predicted by using microwave conductance at the early ages using bi-exponential functions. Compressive strength grows as a function of decreasing effective conductance, whereas the regression coefficients of the correlation models have a linear variation with water-to-binder ratios. These findings have highlighted the effectiveness of the microwave technique in detecting the variation of liquid phase morphology and pore structure. Full article
(This article belongs to the Special Issue Structural Health Monitoring (SHM) of Civil Structures)
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Open AccessArticle Dual-Fuel Combustion for Future Clean and Efficient Compression Ignition Engines
Appl. Sci. 2017, 7(1), 36; doi:10.3390/app7010036
Received: 24 November 2016 / Revised: 20 December 2016 / Accepted: 23 December 2016 / Published: 29 December 2016
Cited by 3 | PDF Full-text (2599 KB) | HTML Full-text | XML Full-text
Abstract
Stringent emissions limits introduced for internal combustion engines impose a major challenge for the research community. The technological solution adopted by the manufactures of diesel engines to meet the NOx and particle matter values imposed in the EURO VI regulation relies on using
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Stringent emissions limits introduced for internal combustion engines impose a major challenge for the research community. The technological solution adopted by the manufactures of diesel engines to meet the NOx and particle matter values imposed in the EURO VI regulation relies on using selective catalytic reduction and particulate filter systems, which increases the complexity and cost of the engine. Alternatively, several new combustion modes aimed at avoiding the formation of these two pollutants by promoting low temperature combustion reactions, are the focus of study nowadays. Among these new concepts, the dual-fuel combustion mode known as reactivity controlled compression ignition (RCCI) seems more promising because it allows better control of the combustion process by means of modulating the fuel reactivity depending on the engine operating conditions. The present experimental work explores the potential of different strategies for reducing the energy losses with RCCI in a single-cylinder research engine, with the final goal of providing the guidelines to define an efficient dual-fuel combustion system. The results demonstrate that the engine settings combination, piston geometry modification, and fuel properties variation are good methods to increase the RCCI efficiency while maintaining ultra-low NOx and soot emissions for a wide range of operating conditions. Full article
(This article belongs to the Special Issue Internal Combustion Engines (ICE) for Ground Transport)
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Open AccessArticle Systematic Evaluation on Speckle Suppression Methods in Examination of Ultrasound Breast Images
Appl. Sci. 2017, 7(1), 37; doi:10.3390/app7010037
Received: 18 September 2016 / Revised: 5 December 2016 / Accepted: 8 December 2016 / Published: 28 December 2016
Cited by 3 | PDF Full-text (3017 KB) | HTML Full-text | XML Full-text
Abstract
Breast ultrasound is an important tool used in the medical treatment and diagnosis of breast tumor. However, noise defined as speckles are generated inevitably. Although the existence of speckle may be beneficial to diagnosis if used by a well-trained observer, it often causes
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Breast ultrasound is an important tool used in the medical treatment and diagnosis of breast tumor. However, noise defined as speckles are generated inevitably. Although the existence of speckle may be beneficial to diagnosis if used by a well-trained observer, it often causes disturbance which negatively affects clinical diagnosis, not only by reducing resolution and contrast of ultrasound images, but also by adding difficulties to recognize tumor region accurately. In this paper, we investigate a number of popular de-speckling algorithms, including filters based on frequency domain, filters based on local statistical properties, filters based on minimum mean square error (MMSE), and filters based on Partial Differential Equation (PDE). Two visual measurement evaluation criteria, i.e., Mean to Variance Ratio (VMR) and Laplace Response of Domain (LRD), are chosen for the performance comparison of those filters in the application of ultrasound breast image filtering. Moreover, the filtering effect is further evaluated with respect to the segmentation accuracy of tumor regions. According to the evaluation results, we conclude that Bilateral Filter (BF) achieves the best visual effect. Although Weickert J Diffusion (WJD) and Total Variation (TV) can also obtain good visual effect and segmentation accuracy, they are very time-consuming. Full article
(This article belongs to the Special Issue Biomedical Ultrasound)
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Open AccessArticle An Experimental Validated Control Strategy of Maglev Vehicle-Bridge Self-Excited Vibration
Appl. Sci. 2017, 7(1), 38; doi:10.3390/app7010038
Received: 12 October 2016 / Revised: 23 December 2016 / Accepted: 23 December 2016 / Published: 4 January 2017
Cited by 1 | PDF Full-text (3122 KB) | HTML Full-text | XML Full-text
Abstract
This study discusses an experimentally validated control strategy of maglev vehicle-bridge vibration, which degrades the stability of the suspension control, deteriorates the ride comfort, and limits the cost of the magnetic levitation system. First, a comparison between the current-loop and magnetic flux feedback
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This study discusses an experimentally validated control strategy of maglev vehicle-bridge vibration, which degrades the stability of the suspension control, deteriorates the ride comfort, and limits the cost of the magnetic levitation system. First, a comparison between the current-loop and magnetic flux feedback is carried out and a minimum model including flexible bridge and electromagnetic levitation system is proposed. Then, advantages and disadvantages of the traditional feedback architecture with the displacement feedback of electromagnet yE and bridge yB in pairs are explored. The results indicate that removing the feedback of the bridge’s displacement yB from the pairs (yEyB) measured by the eddy-current sensor is beneficial for the passivity of the levitation system and the control of the self-excited vibration. In this situation, the signal acquisition of the electromagnet’s displacement yE is discussed for the engineering application. Finally, to validate the effectiveness of the aforementioned control strategy, numerical validations are carried out and the experimental data are provided and analyzed. Full article
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Open AccessArticle Spin-Related Micro-Photoluminescence in Fe3+ Doped ZnSe Nanoribbons
Appl. Sci. 2017, 7(1), 39; doi:10.3390/app7010039
Received: 19 October 2016 / Revised: 7 December 2016 / Accepted: 22 December 2016 / Published: 29 December 2016
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Abstract
Spin-related emission properties have important applications in the future information technology; however, they involve microscopic ferromagnetic coupling, antiferromagnetic or ferrimagnetic coupling between transition metal ions and excitons, or d state coupling with phonons is not well understood in these diluted magnetic semiconductors (DMS).
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Spin-related emission properties have important applications in the future information technology; however, they involve microscopic ferromagnetic coupling, antiferromagnetic or ferrimagnetic coupling between transition metal ions and excitons, or d state coupling with phonons is not well understood in these diluted magnetic semiconductors (DMS). Fe3+ doped ZnSe nanoribbons, as a DMS example, have been successfully prepared by a thermal evaporation method. Their power-dependent micro-photoluminescence (PL) spectra and temperature-dependent PL spectra of a single ZnSe:Fe nanoribbon have been obtained and demonstrated that alio-valence ion doping diminishes the exciton magnetic polaron (EMP) effect by introducing exceeded charges. The d-d transition emission peaks of Fe3+ assigned to the 4T2 (G) → 6A1 (S) transition at 553 nm and 4T1 (G) → 6A1 (S) transition at 630 nm in the ZnSe lattice have been observed. The emission lifetimes and their temperature dependences have been obtained, which reflected different spin–phonon interactions. There exists a sharp decrease of PL lifetime at about 60 K, which hints at a magnetic phase transition. These spin–spin and spin–phonon interaction related PL phenomena are applicable in the future spin-related photonic nanodevices. Full article
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Open AccessArticle Unstable and Multiple Pulsing Can Be Invisible to Ultrashort Pulse Measurement Techniques
Appl. Sci. 2017, 7(1), 40; doi:10.3390/app7010040
Received: 1 November 2016 / Revised: 15 December 2016 / Accepted: 20 December 2016 / Published: 29 December 2016
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Abstract
Multiple pulsing occurs in most ultrashort-pulse laser systems when pumped at excessively high powers, and small fluctuations in pump power in certain regimes can cause unusual variations in the temporal separations of sub-pulses. Unfortunately, the ability of modern intensity-and-phase pulse measurement techniques to
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Multiple pulsing occurs in most ultrashort-pulse laser systems when pumped at excessively high powers, and small fluctuations in pump power in certain regimes can cause unusual variations in the temporal separations of sub-pulses. Unfortunately, the ability of modern intensity-and-phase pulse measurement techniques to measure such unstable multi-pulsing has not been studied. Here we report calculations and simulations finding that allowing variations in just the relative phase of a satellite pulse causes the second pulse to completely disappear from a spectral interferometry for direct electric field reconstruction (SPIDER) measurement. We find that, although neither frequency-resolved optical gating (FROG) nor autocorrelation can determine the precise properties of satellite pulses due to the presence of instability, they always succeed in, at least, seeing the satellite pulses. Also, additional post-processing of the measured FROG trace can determine the correct approximate relative height of the satellite pulse and definitively indicate the presence of unstable multiple-pulsing. Full article
(This article belongs to the Special Issue Ultrashort Optical Pulses)
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Open AccessArticle Deep Fault Recognizer: An Integrated Model to Denoise and Extract Features for Fault Diagnosis in Rotating Machinery
Appl. Sci. 2017, 7(1), 41; doi:10.3390/app7010041
Received: 17 October 2016 / Revised: 12 December 2016 / Accepted: 27 December 2016 / Published: 30 December 2016
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Abstract
Fault diagnosis in rotating machinery is significant to avoid serious accidents; thus, an accurate and timely diagnosis method is necessary. With the breakthrough in deep learning algorithm, some intelligent methods, such as deep belief network (DBN) and deep convolution neural network (DCNN), have
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Fault diagnosis in rotating machinery is significant to avoid serious accidents; thus, an accurate and timely diagnosis method is necessary. With the breakthrough in deep learning algorithm, some intelligent methods, such as deep belief network (DBN) and deep convolution neural network (DCNN), have been developed with satisfactory performances to conduct machinery fault diagnosis. However, only a few of these methods consider properly dealing with noises that exist in practical situations and the denoising methods are in need of extensive professional experiences. Accordingly, rethinking the fault diagnosis method based on deep architectures is essential. Hence, this study proposes an automatic denoising and feature extraction method that inherently considers spatial and temporal correlations. In this study, an integrated deep fault recognizer model based on the stacked denoising autoencoder (SDAE) is applied to both denoise random noises in the raw signals and represent fault features in fault pattern diagnosis for both bearing rolling fault and gearbox fault, and trained in a greedy layer-wise fashion. Finally, the experimental validation demonstrates that the proposed method has better diagnosis accuracy than DBN, particularly in the existing situation of noises with superiority of approximately 7% in fault diagnosis accuracy. Full article
(This article belongs to the Special Issue Deep Learning Based Machine Fault Diagnosis and Prognosis)
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Open AccessArticle Groundwater Mixing Process Identification in Deep Mines Based on Hydrogeochemical Property Analysis
Appl. Sci. 2017, 7(1), 42; doi:10.3390/app7010042
Received: 16 September 2016 / Revised: 21 December 2016 / Accepted: 26 December 2016 / Published: 31 December 2016
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Abstract
Karst collapse columns, as a potential water passageway for mine water inrush, are always considered a critical problem for the development of deep mining techniques. This study aims to identify the mixing process of groundwater deriving two different limestone karst-fissure aquifer systems. Based
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Karst collapse columns, as a potential water passageway for mine water inrush, are always considered a critical problem for the development of deep mining techniques. This study aims to identify the mixing process of groundwater deriving two different limestone karst-fissure aquifer systems. Based on analysis of mining groundwater hydrogeochemical properties, hydraulic connection between the karst-fissure objective aquifer systems was revealed. In this paper, piper diagram was used to calculate the mixing ratios at different sampling points in the aquifer systems, and PHREEQC Interactive model (Version 2.5, USGS, Reston, VA, USA, 2001) was applied to modify the mixing ratios and model the water–rock interactions during the mixing processes. The analysis results show that the highest mixing ratio is 0.905 in the C12 borehole that is located nearest to the #2 karst collapse column, and the mixing ratio decreases with the increase of the distance from the #2 karst collapse column. It demonstrated that groundwater of the two aquifers mixed through the passage of #2 karst collapse column. As a result, the proposed Piper-PHREEQC based method can provide accurate identification of karst collapse columns’ water conductivity, and can be applied to practical applications. Full article
(This article belongs to the Section Chemistry)
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Open AccessFeature PaperArticle Property Analysis of Exfoliated Graphite Nanoplatelets Modified Asphalt Model Using Molecular Dynamics (MD) Method
Appl. Sci. 2017, 7(1), 43; doi:10.3390/app7010043
Received: 18 November 2016 / Revised: 12 December 2016 / Accepted: 18 December 2016 / Published: 3 January 2017
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Abstract
This Molecular Dynamics (MD) simulation paper presents a physical property comparison study between exfoliated graphite nanoplatelets (xGNP) modified and control asphalt models, including density, glass transition temperature, viscosity and thermal conductivity. The three-component control asphalt model consists of asphaltenes, aromatics, and saturates based
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This Molecular Dynamics (MD) simulation paper presents a physical property comparison study between exfoliated graphite nanoplatelets (xGNP) modified and control asphalt models, including density, glass transition temperature, viscosity and thermal conductivity. The three-component control asphalt model consists of asphaltenes, aromatics, and saturates based on previous references. The xGNP asphalt model was built by incorporating an xGNP and control asphalt model and controlling mass ratios to represent the laboratory prepared samples. The Amber Cornell Extension Force Field (ACEFF) was used with assigned molecular electro-static potential (ESP) charge from NWChem analysis. After optimization and ensemble relaxation, the properties of the control and xGNP modified asphalt models were computed and analyzed using the MD method. The MD simulated results have a similar trend as the test results. The property analysis showed that: (1) the density of the xGNP modified model is higher than that of the control model; (2) the glass transition temperature of the xGNP modified model is closer to the laboratory data of the Strategic Highway Research Program (SHRP) asphalt binders than that of the control model; (3) the viscosities of the xGNP modified model at different temperatures are higher than those of the control model, and it coincides with the trend in the laboratory data; (4) the thermal conductivities of the xGNP modified asphalt model are higher than those of the control asphalt model at different temperatures, and it is consistent with the trend in the laboratory data. Full article
(This article belongs to the Special Issue Advanced Asphalt Materials and Paving Technologies)
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Open AccessArticle Designing a Novel High-Performance FBG-OADM Based on Finite Element and Eigenmode Expansion Methods
Appl. Sci. 2017, 7(1), 44; doi:10.3390/app7010044
Received: 6 December 2016 / Revised: 27 December 2016 / Accepted: 28 December 2016 / Published: 30 December 2016
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Abstract
This study designed a novel high-performance fiber Bragg grating (FBG) optical add/drop multiplexers (OADMs) by referring to current numerical simulation methods. The proposed FBG-OADM comprises two single-mode fibers placed side by side. Both optical fibers contained an FBG featuring identical parameters and the
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This study designed a novel high-performance fiber Bragg grating (FBG) optical add/drop multiplexers (OADMs) by referring to current numerical simulation methods. The proposed FBG-OADM comprises two single-mode fibers placed side by side. Both optical fibers contained an FBG featuring identical parameters and the same geometric structure. Furthermore, it fulfills the full width at half maximum (FWHM) requirement for dense wavelength-division multiplexers (DWDMs) according to the International Telecommunication Union (i.e., FWHM < 0.4 nm). Of all related numerical calculation methods, the combination of the finite element method (FEM) and eigenmode expansion method (EEM), as a focus in this study, is the only one suitable for researching and designing large-scale components. To enhance the accuracy and computational performance, this study used numerical methods—namely, the object meshing method, the boundary meshing method, the perfectly matched layer, and the perfectly reflecting boundary—to simulate the proposed FBG-OADM. The simulation results showed that the novel FBG-OADM exhibited a −3 dB bandwidth of 0.0375 nm. In addition, analysis of the spectrum revealed that the drop port achieved the power output of 0 dB at an operating wavelength of 1550 nm. Full article
(This article belongs to the Special Issue Guided-Wave Optics)
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Open AccessArticle Arc Shape Characteristics with Ultra-High-Frequency Pulsed Arc Welding
Appl. Sci. 2017, 7(1), 45; doi:10.3390/app7010045
Received: 17 October 2016 / Revised: 2 December 2016 / Accepted: 7 December 2016 / Published: 3 January 2017
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Abstract
Arc plasma possesses a constriction phenomenon with a pulsed current. The constriction is created by the Lorentz force, the radial electromagnetic force during arc welding, which determines the energy distribution of the arc plasma. Welding experiments were carried out with ultra-high-frequency pulsed arc
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Arc plasma possesses a constriction phenomenon with a pulsed current. The constriction is created by the Lorentz force, the radial electromagnetic force during arc welding, which determines the energy distribution of the arc plasma. Welding experiments were carried out with ultra-high-frequency pulsed arc welding (UHFP-AW). Ultra-high-speed camera observations were produced for arc surveillance. Hue-saturation-intensity (HSI) image analysis was used to distinguish the regions of the arc plasma that represented the heat energy distribution. The measurement of arc regions indicated that, with an ultra-high-frequency pulsed arc, the constriction was not only within the decreased arc geometry, but also within the constricted arc core region. This can be checked by the ratio of the core region to the total area. The arc core region expanded significantly at 40 kHz at 60 A. A current level of 80 A caused a decrease in the total region of the arc. Meanwhile, the ratio of the core region to the total increased. It can be concluded that arc constriction depends on the increased area of the core region with the pulsed current (>20 kHz). Full article
(This article belongs to the Special Issue Gas Tungsten Arc Welding)
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Open AccessArticle Ultrafast Optical Heating Induced Polarization-Dependent Optical Switching in Gold Nanowires
Appl. Sci. 2017, 7(1), 46; doi:10.3390/app7010046
Received: 9 October 2016 / Revised: 24 December 2016 / Accepted: 27 December 2016 / Published: 12 January 2017
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Abstract
Excitation using femtosecond laser pulses induced ultrafast heating of discontinuous gold nanowires, resulting in transient thermal expansion of the gold nanostructures that constitute the nanowires. The cross-plasmon resulting from the closely arranged gold nanostructures along the nanowires was modified by the change in
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Excitation using femtosecond laser pulses induced ultrafast heating of discontinuous gold nanowires, resulting in transient thermal expansion of the gold nanostructures that constitute the nanowires. The cross-plasmon resulting from the closely arranged gold nanostructures along the nanowires was modified by the change in the small gaps due to the thermal effect. This led to the spectral shift of the cross-plasmon resonance and laid the photophysical basis for the optical switching. A femtosecond pump-probe scheme was used to investigate the ultrafast optical switching dynamics. The most efficient optical switching effect was observed when the pump and probe laser pulses were polarized perpendicular and parallel to the discontinuous gold nanowires, respectively. Full article
(This article belongs to the Special Issue Ultrashort Optical Pulses)
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Open AccessArticle Development of a Simulation Framework for Analyzing Security of Supply in Integrated Gas and Electric Power Systems
Appl. Sci. 2017, 7(1), 47; doi:10.3390/app7010047
Received: 22 November 2016 / Revised: 21 December 2016 / Accepted: 23 December 2016 / Published: 5 January 2017
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Abstract
Gas and power networks are tightly coupled and interact with each other due to physically interconnected facilities. In an integrated gas and power network, a contingency observed in one system may cause iterative cascading failures, resulting in network wide disruptions. Therefore, understanding the
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Gas and power networks are tightly coupled and interact with each other due to physically interconnected facilities. In an integrated gas and power network, a contingency observed in one system may cause iterative cascading failures, resulting in network wide disruptions. Therefore, understanding the impacts of the interactions in both systems is crucial for governments, system operators, regulators and operational planners, particularly, to ensure security of supply for the overall energy system. Although simulation has been widely used in the assessment of gas systems as well as power systems, there is a significant gap in simulation models that are able to address the coupling of both systems. In this paper, a simulation framework that models and simulates the gas and power network in an integrated manner is proposed. The framework consists of a transient model for the gas system and a steady state model for the power system based on AC-Optimal Power Flow. The gas and power system model are coupled through an interface which uses the coupling equations to establish the data exchange and coordination between the individual models. The bidirectional interlink between both systems considered in this studies are the fuel gas offtake of gas fired power plants for power generation and the power supply to liquefied natural gas (LNG) terminals and electric drivers installed in gas compressor stations and underground gas storage facilities. The simulation framework is implemented into an innovative simulation tool named SAInt (Scenario Analysis Interface for Energy Systems) and the capabilities of the tool are demonstrated by performing a contingency analysis for a real world example. Results indicate how a disruption triggered in one system propagates to the other system and affects the operation of critical facilities. In addition, the studies show the importance of using transient gas models for security of supply studies instead of successions of steady state models, where the time evolution of the line pack is not captured correctly. Full article
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Open AccessArticle Experimental and Numerical Investigation on Non-Newtonian Nanofluids Flowing in Shell Side of Helical Baffled Heat Exchanger Combined with Elliptic Tubes
Appl. Sci. 2017, 7(1), 48; doi:10.3390/app7010048
Received: 25 October 2016 / Revised: 26 December 2016 / Accepted: 28 December 2016 / Published: 4 January 2017
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Abstract
In this paper, an aqueous solution of xanthan gum (XG) at a weight fraction as high as 0.2% was elected as the non-Newtonian base liquid, the multi-walled carbon nanotubes (MWCNTs) dispersed into non-Newtonian XG aqueous at different weight factions of MWCNTs was prepared.
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In this paper, an aqueous solution of xanthan gum (XG) at a weight fraction as high as 0.2% was elected as the non-Newtonian base liquid, the multi-walled carbon nanotubes (MWCNTs) dispersed into non-Newtonian XG aqueous at different weight factions of MWCNTs was prepared. Convection heat transfer of non-Newtonian nanofluids in the shell side of helical baffled heat exchanger combined with elliptic tubes has been investigated experimentally and numerically using single-phase flow model. Results showed that the enhancement of the convective heat transfer coefficient increases with an increase in the Reynolds number and the nanoparticle concentration. For nanofluids with 0.2 wt %, 0.5 wt % and 1.0 wt % MWCNTs, the Nusselt number, respectively, increases by 11%, 21% and 35% on average at the same Reynolds number, while the comprehensive thermal performance factors are 3%–5%, 15%–17% and 24%–26% higher than that of base fluid at the same volume rate. A remarkable heat transfer enhancement can be obtained by adding MWCNTs into XG aqueous solution based on thermal resistance analysis. Correlations have been suggested for the shell-side Nusselt number and friction factor of non-Newtonian nanofluids in the helical baffled heat exchanger with elliptic tubes. Good agreements existed between corrections and experimental data. Full article
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Open AccessArticle FTIR and Raman Characterization of TiO2 Nanoparticles Coated with Polyethylene Glycol as Carrier for 2-Methoxyestradiol
Appl. Sci. 2017, 7(1), 49; doi:10.3390/app7010049
Received: 16 September 2016 / Revised: 29 October 2016 / Accepted: 11 November 2016 / Published: 4 January 2017
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Abstract
The aim of this study was to prepare a novel targeting drug delivery system for 2-Methoxyestradiol (2ME) in order to improve the clinical application of this antitumor drug. It is based in nanoparticles (NPs) of titanium dioxide (TiO2) coated with polyethylene
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The aim of this study was to prepare a novel targeting drug delivery system for 2-Methoxyestradiol (2ME) in order to improve the clinical application of this antitumor drug. It is based in nanoparticles (NPs) of titanium dioxide (TiO2) coated with polyethylene glycol (PEG) and loaded with 2ME. A complete IR and Raman characterization have been made to confirm the formation of TiO2–PEG–2ME composite. Vibrational modes have been assigned for TiO2, PEG, and 2ME and functionalized TiO2–PEG and TiO2–PEG–2ME. The observed variation in peak position of FTIR and Raman of each for these composites has been elucidated in terms of intermolecular interactions between PEG–2ME and TiO2, obtaining step-by-step the modification processes that were attributed to the conjugation of PEG and 2ME to TiO2 NPs. Modifying TiO2 NPs with PEG loaded with the 2ME drug revealed that the titanium dioxide nanocarrier possesses an effective adsorption capability, and we discuss their potential application as a system of drug delivery. Full article
(This article belongs to the Special Issue Biodegradable and Biocompatible Nanoparticles)
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Open AccessArticle Measurements and Modeling of the Nonlinear Behavior of a Guitar Pickup at Low Frequencies †
Appl. Sci. 2017, 7(1), 50; doi:10.3390/app7010050
Received: 24 October 2016 / Revised: 16 December 2016 / Accepted: 27 December 2016 / Published: 4 January 2017
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Abstract
Description of the physical behavior of electric guitars is still not very widespread in the scientific literature. In particular, the physical models describing a nonlinear behavior of pickups still requires some refinements. The study presented in this paper is focused on nonlinear modeling
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Description of the physical behavior of electric guitars is still not very widespread in the scientific literature. In particular, the physical models describing a nonlinear behavior of pickups still requires some refinements. The study presented in this paper is focused on nonlinear modeling of the pickups. Two main issues are raised. First, is the currently most used nonlinear model (a Hammerstein model) sufficient for the complex nonlinear behavior of the pickup? In other words, would a more complex model, such as a Generalized Hammerstein that can deal better with the nonlinear memory, yield better results? The second troublesome issue is how to measure the nonlinear behavior of a pickup correctly. A specific experimental set-up allowing for driving the pickup in a controlled way (string displacement perpendicular to the pickup) and to separate the nonlinear model of the pickup from other nonlinearities in the measurement chain is proposed. Thanks to this experimental set-up, a Generalized Hammerstein model of the pickup is estimated for frequency range 15–500 Hz and the results are compared with a simple Hammerstein model. A comparison with experimental results shows that both models succeed in describing the pickup when used in realistic conditions. Full article
(This article belongs to the Section Acoustics)
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Open AccessArticle Vision-Based Perception and Classification of Mosquitoes Using Support Vector Machine
Appl. Sci. 2017, 7(1), 51; doi:10.3390/app7010051
Received: 3 October 2016 / Revised: 14 December 2016 / Accepted: 27 December 2016 / Published: 5 January 2017
Cited by 3 | PDF Full-text (3320 KB) | HTML Full-text | XML Full-text
Abstract
The need for a novel automated mosquito perception and classification method is becoming increasingly essential in recent years, with steeply increasing number of mosquito-borne diseases and associated casualties. There exist remote sensing and GIS-based methods for mapping potential mosquito inhabitants and locations that
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The need for a novel automated mosquito perception and classification method is becoming increasingly essential in recent years, with steeply increasing number of mosquito-borne diseases and associated casualties. There exist remote sensing and GIS-based methods for mapping potential mosquito inhabitants and locations that are prone to mosquito-borne diseases, but these methods generally do not account for species-wise identification of mosquitoes in closed-perimeter regions. Traditional methods for mosquito classification involve highly manual processes requiring tedious sample collection and supervised laboratory analysis. In this research work, we present the design and experimental validation of an automated vision-based mosquito classification module that can deploy in closed-perimeter mosquito inhabitants. The module is capable of identifying mosquitoes from other bugs such as bees and flies by extracting the morphological features, followed by support vector machine-based classification. In addition, this paper presents the results of three variants of support vector machine classifier in the context of mosquito classification problem. This vision-based approach to the mosquito classification problem presents an efficient alternative to the conventional methods for mosquito surveillance, mapping and sample image collection. Experimental results involving classification between mosquitoes and a predefined set of other bugs using multiple classification strategies demonstrate the efficacy and validity of the proposed approach with a maximum recall of 98%. Full article
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Open AccessArticle High-Resolution Digital-to-Time Converter Implemented in an FPGA Chip
Appl. Sci. 2017, 7(1), 52; doi:10.3390/app7010052
Received: 9 November 2016 / Revised: 24 December 2016 / Accepted: 27 December 2016 / Published: 4 January 2017
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Abstract
This paper presents the design and implementation of a new digital-to-time converter (DTC). The obtained resolution is 1.02 ps, and the dynamic range is about 590 ns. The experimental results indicate that the measured differential nonlinearity (DNL) and integral nonlinearity (INL) are −0.17~+0.13
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This paper presents the design and implementation of a new digital-to-time converter (DTC). The obtained resolution is 1.02 ps, and the dynamic range is about 590 ns. The experimental results indicate that the measured differential nonlinearity (DNL) and integral nonlinearity (INL) are −0.17~+0.13 LSB and −0.35~+0.62 LSB, respectively. This DTC builds coarse and fine Vernier delay lines constructed by programmable delay lines (PDLs) to ensure high performance delay. Benefited by the close-loop feedback mechanism of the PDLs’ control module, the presented DTC has excellent voltage and temperature stability. What is more, the proposed DTC can be implemented in a single field programmable gate array (FPGA) chip. Full article
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Open AccessArticle Thin-Walled CFST Columns for Enhancing Seismic Collapse Performance of High-Rise Steel Frames
Appl. Sci. 2017, 7(1), 53; doi:10.3390/app7010053
Received: 30 November 2016 / Revised: 21 December 2016 / Accepted: 24 December 2016 / Published: 5 January 2017
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Abstract
This paper numerically studied the collapse capacity of high-rise steel moment-resisting frames (SMRFs) using various width-to-thickness members subjected to successive earthquakes. It was found that the long-period component of earthquakes obviously correlates with the first-mode period of high-rises controlled by the total number
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This paper numerically studied the collapse capacity of high-rise steel moment-resisting frames (SMRFs) using various width-to-thickness members subjected to successive earthquakes. It was found that the long-period component of earthquakes obviously correlates with the first-mode period of high-rises controlled by the total number of stories. A higher building tends to produce more significant component deterioration to enlarge the maximum story drift angle at lower stories. The width-to-thickness ratio of beam and column components overtly affects the collapse capacity when the plastic deformation extensively develops. The ratio of residual to maximum story drift angle is significantly sensitive to the collapse capacity of various building models. A thin-walled concrete filled steel tubular (CFST) column is proposed as one efficient alternative to enhance the overall stiffness and deformation capacity of the high-rise SMRFs with fragile collapse performance. With the equivalent flexural stiffness, CFST-MRF buildings with thin-walled members demonstrate higher capacity to avoid collapse, and the greater collapse margin indicates that CFST-MRFs are a reasonable system for high-rises in seismic prone regions. Full article
(This article belongs to the Special Issue Applications of Thin-Walled Structures)
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Open AccessArticle The Meaning and Measure of Vertical Resolution in Optical Surface Topography Measurement
Appl. Sci. 2017, 7(1), 54; doi:10.3390/app7010054
Received: 2 December 2016 / Revised: 28 December 2016 / Accepted: 30 December 2016 / Published: 5 January 2017
Cited by 1 | PDF Full-text (781 KB) | HTML Full-text | XML Full-text
Abstract
Vertical resolution is the most widely quoted and most frequently misunderstood performance specification for equipment that measures surface topography. Here I propose to use internationally standardized terms and definitions for measurement noise and surface topography repeatability as more meaningful quantifiers for measurement performance.
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Vertical resolution is the most widely quoted and most frequently misunderstood performance specification for equipment that measures surface topography. Here I propose to use internationally standardized terms and definitions for measurement noise and surface topography repeatability as more meaningful quantifiers for measurement performance. A specific example is an interference microscope operating with a 100 Hz, 1 k × 1 k pixel camera, and a sinusoidal phase modulation to convert intensity data to a height map. The measurement noise is found experimentally to be 0.072 nm for a 1 s data acquisition using a surface topography repeatability test, which determines the random height-equivalent noise level for an individual pixel in the areal surface topography map. Under ideal conditions, the measured noise is equivalent to the instrument noise that may be published in a performance specification in place of the more common, but poorly defined, vertical resolution specification. Full article
(This article belongs to the Special Issue Dimensional Micro and Nanometrology)
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Open AccessArticle Thermal Stability, Combustion Behavior, and Mechanical Property in a Flame-Retardant Polypropylene System
Appl. Sci. 2017, 7(1), 55; doi:10.3390/app7010055
Received: 5 November 2016 / Revised: 20 December 2016 / Accepted: 27 December 2016 / Published: 10 January 2017
Cited by 1 | PDF Full-text (7406 KB) | HTML Full-text | XML Full-text
Abstract
In order to comprehensively improve the strength, toughness, flame retardancy, smoke suppression, and thermal stability of polypropylene (PP), layered double hydroxide (LDH) Ni0.2Mg2.8Al–LDH was synthesized by a coprecipitation method coupled with the microwave-hydrothermal treatment. The X-ray diffraction (XRD), morphology,
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In order to comprehensively improve the strength, toughness, flame retardancy, smoke suppression, and thermal stability of polypropylene (PP), layered double hydroxide (LDH) Ni0.2Mg2.8Al–LDH was synthesized by a coprecipitation method coupled with the microwave-hydrothermal treatment. The X-ray diffraction (XRD), morphology, mechanical, thermal, and fire properties for PP composites containing 1 wt %–20 wt % Ni0.2Mg2.8Al–LDH were investigated. The cone calorimeter tests confirm that the peak heat release rate (pk–HRR) of PP–20%LDH was decreased to 500 kW/m2 from the 1057 kW/m2 of PP. The pk–HRR, average mass loss rate (AMLR) and effective heat of combustion (EHC) analysis indicates that the condensed phase fire retardant mechanism of Ni0.2Mg2.8Al–LDH in the composites. The production rate and mean release yield of CO for composites gradually decrease as Ni0.2Mg2.8Al–LDH increases in the PP matrix. Thermal analysis indicates that the decomposition temperature for PP–5%LDH and PP–10%LDH is 34 °C higher than that of the pure PP. The mechanical tests reveal that the tensile strength of PP–1%LDH is 7.9 MPa higher than that of the pure PP. Furthermore, the elongation at break of PP–10%LDH is 361% higher than PP. In this work, the synthetic LDH Ni0.2Mg2.8Al–LDH can be used as a flame retardant, smoke suppressant, thermal stabilizer, reinforcing, and toughening agent of PP products. Full article
(This article belongs to the Section Chemistry)
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Open AccessArticle Impact on the Gas Barrier Property of Silicon Oxide Films Prepared by Tetramethylsilane-Based PECVD Incorporating with Ammonia
Appl. Sci. 2017, 7(1), 56; doi:10.3390/app7010056
Received: 27 October 2016 / Revised: 13 December 2016 / Accepted: 28 December 2016 / Published: 5 January 2017
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Abstract
The gas barrier property of a silicon oxide (SiOx) film synthesized from plasma-enhanced chemical vapor deposition using the tetramethysilane (TMS)-oxygen gas mixture was modified by introducing ammonia gas in the glow discharge. The change in the glow discharge with the ammonia
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The gas barrier property of a silicon oxide (SiOx) film synthesized from plasma-enhanced chemical vapor deposition using the tetramethysilane (TMS)-oxygen gas mixture was modified by introducing ammonia gas in the glow discharge. The change in the glow discharge with the ammonia gas incorporation was monitored by an optical emission spectrometer (OES). Structures, chemical bond configurations, and material properties of the resulting films were investigated. The introduced ammonia gas in the TMS-oxygen plasma resulted in emission lines dominated by the N2 and CN species with the suppression of the OH and oxygen-related radicals, thereby introducing nitrogen and carbon atoms in the deposited film. A silicon oxynitride (SiOxNy) film had the best surface morphology and the lowest residual internal stress was achievable by controlling the reactant gas flow ratio of the ammonia and oxygen. The barrier property to the water vapor permeation of the silicon oxide film (~1.65 g/m2/day) deposited onto the polyethylene terephthalate (PET) substrate was thus greatly improved to 0.06 g/m2/day for the film synthesized from an adequate TMS-oxygen-ammonia gas mixture. Full article
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Open AccessArticle Flexural Capacity of a New Composite Beam with Concrete-Infilled Tubular Lower Flange
Appl. Sci. 2017, 7(1), 57; doi:10.3390/app7010057
Received: 11 October 2016 / Revised: 16 November 2016 / Accepted: 18 November 2016 / Published: 6 January 2017
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Abstract
This paper proposes a new steel concrete composite beam that has a similar shape to the conventional steel wide flange beam, but whose lower flange has a tubular shape with infilled concrete. It has openings in the web for perfect integration between concrete
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This paper proposes a new steel concrete composite beam that has a similar shape to the conventional steel wide flange beam, but whose lower flange has a tubular shape with infilled concrete. It has openings in the web for perfect integration between concrete and steel materials, and the tubular lower flange is reinforced with steel rebars to enhance its flexural strength. The bending capacity of the new composite beam was investigated by performing a two-point loading test on seven specimens, which can be categorized mainly into two types, non-composite and fully composite specimens. The load versus displacement curves were plotted for all the specimens and their failure modes were identified. Theoretical equations were proposed to estimate the flexural strength of the new composite beam members, and their accuracy was examined by comparing the predictions of the equations with the test results. Full article
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Open AccessArticle Feasibility Assessments of the Use of Recycled Fibers in Nonwoven Fabrics
Appl. Sci. 2017, 7(1), 58; doi:10.3390/app7010058
Received: 20 October 2016 / Revised: 30 November 2016 / Accepted: 23 December 2016 / Published: 5 January 2017
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Abstract
Environmental protection has become an increasing concern, which makes recycling and reclaiming highly important. In addition to governmental campaigns and promotion, enterprises should examine each perspective thoroughly in order to prevent excessive resource consumption. In this study, recycled materials, including recycled far-infrared polyester
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Environmental protection has become an increasing concern, which makes recycling and reclaiming highly important. In addition to governmental campaigns and promotion, enterprises should examine each perspective thoroughly in order to prevent excessive resource consumption. In this study, recycled materials, including recycled far-infrared polyester (FPET) fiber, three-dimensional crimped hollow flame-retarding (TPET) fiber, and low-melting-point polyester (LPET) fiber, are used to form nonwoven fabrics. The influence of different amounts of FPET fiber, 0–80 wt %, on the properties of nonwoven fabrics was examined. The sheath of LPET fibers can be melted as a result of hot pressing, which provides cohesion between fibers that mechanically improves the nonwoven fabrics. The tensile strength, tearing strength, air permeability, and far infrared (FIR) emissivity of the nonwoven fabrics were examined, thereby determining the optimal parameters. The test results show that the thermally treated nonwoven fabrics have better mechanical properties and FIR emissivity, compared to those of non-thermally treated nonwoven fabrics. Moreover, more FPET fibers cause the mechanical properties along the cross machine direction (CD) to decrease by 9% and that along the machine direction (MD) to decrease by 5%. In particular, all the thermally treated samples exhibit a FIR emissivity of 0.8, which is health-promoting. Full article
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Open AccessArticle Aligned Nanofiber Topography Directs the Tenogenic Differentiation of Mesenchymal Stem Cells
Appl. Sci. 2017, 7(1), 59; doi:10.3390/app7010059
Received: 15 December 2016 / Revised: 21 December 2016 / Accepted: 23 December 2016 / Published: 6 January 2017
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Abstract
Tendon is commonly injured, heals slowly and poorly, and often suffers re-injury after healing. This is due to failure of tenocytes to effectively remodel tendon after injury to recapitulate normal architecture, resulting in poor mechanical properties. One strategy for improving the outcome is
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Tendon is commonly injured, heals slowly and poorly, and often suffers re-injury after healing. This is due to failure of tenocytes to effectively remodel tendon after injury to recapitulate normal architecture, resulting in poor mechanical properties. One strategy for improving the outcome is to use nanofiber scaffolds and mesenchymal stem cells (MSCs) to regenerate tendon. Various scaffold parameters are known to influence tenogenesis. We designed suspended and aligned nanofiber scaffolds with the hypothesis that this would promote tenogenesis when seeded with MSCs. Our aligned nanofibers were manufactured using the previously reported non-electrospinning Spinneret-based Tunable Engineered Parameters (STEP) technique. We compared parallel versus perpendicular nanofiber scaffolds with traditional flat monolayers and used cellular morphology, tendon marker gene expression, and collagen and glycosaminoglycan deposition as determinants for tendon differentiation. We report that compared with traditional control monolayers, MSCs grown on nanofibers were morphologically elongated with higher gene expression of tendon marker scleraxis and collagen type I, along with increased production of extracellular matrix components collagen (p = 0.0293) and glycosaminoglycan (p = 0.0038). Further study of MSCs in different topographical environments is needed to elucidate the complex molecular mechanisms involved in stem cell differentiation. Full article
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Open AccessArticle Investigations on the Effects of Vortex-Induced Vibration with Different Distributions of Lorentz Forces
Appl. Sci. 2017, 7(1), 61; doi:10.3390/app7010061
Received: 31 October 2016 / Revised: 2 December 2016 / Accepted: 3 January 2017 / Published: 7 January 2017
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Abstract
The control of vortex-induced vibration (VIV) in shear flow with different distributions of Lorentz force is numerically investigated based on the stream function–vorticity equations in the exponential-polar coordinates exerted on moving cylinder for Re = 150. The cylinder motion equation coupled with the
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The control of vortex-induced vibration (VIV) in shear flow with different distributions of Lorentz force is numerically investigated based on the stream function–vorticity equations in the exponential-polar coordinates exerted on moving cylinder for Re = 150. The cylinder motion equation coupled with the fluid, including the mathematical expressions of the lift force coefficient C l , is derived. The initial and boundary conditions as well as the hydrodynamic forces on the surface of cylinder are also formulated. The Lorentz force applied to suppress the VIV has no relationship with the flow field, and involves two categories, i.e., the field Lorentz force and the wall Lorentz force. With the application of symmetrical Lorentz forces, the symmetric field Lorentz force can amplify the drag, suppress the flow separation, decrease the lift fluctuation, and then suppress the VIV while the wall Lorentz force decreases the drag only. With the application of asymmetrical Lorentz forces, besides the above-mentioned effects, the field Lorentz force can increase additional lift induced by shear flow, whereas the wall Lorentz force can counteract the additional lift, which is dominated on the total effect. Full article
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Open AccessArticle Massive-MIMO Sparse Uplink Channel Estimation Using Implicit Training and Compressed Sensing
Appl. Sci. 2017, 7(1), 63; doi:10.3390/app7010063
Received: 15 October 2016 / Revised: 21 December 2016 / Accepted: 4 January 2017 / Published: 9 January 2017
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Abstract
Massive multiple-input multiple-output (massive-MIMO) is foreseen as a potential technology for future 5G cellular communication networks due to its substantial benefits in terms of increased spectral and energy efficiency. These advantages of massive-MIMO are a consequence of equipping the base station (BS) with
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Massive multiple-input multiple-output (massive-MIMO) is foreseen as a potential technology for future 5G cellular communication networks due to its substantial benefits in terms of increased spectral and energy efficiency. These advantages of massive-MIMO are a consequence of equipping the base station (BS) with quite a large number of antenna elements, thus resulting in an aggressive spatial multiplexing. In order to effectively reap the benefits of massive-MIMO, an adequate estimate of the channel impulse response (CIR) between each transmit–receive link is of utmost importance. It has been established in the literature that certain specific multipath propagation environments lead to a sparse structured CIR in spatial and/or delay domains. In this paper, implicit training and compressed sensing based CIR estimation techniques are proposed for the case of massive-MIMO sparse uplink channels. In the proposed superimposed training (SiT) based techniques, a periodic and low power training sequence is superimposed (arithmetically added) over the information sequence, thus avoiding any dedicated time/frequency slots for the training sequence. For the estimation of such massive-MIMO sparse uplink channels, two greedy pursuits based compressed sensing approaches are proposed, viz: SiT based stage-wise orthogonal matching pursuit (SiT-StOMP) and gradient pursuit (SiT-GP). In order to demonstrate the validity of proposed techniques, a performance comparison in terms of normalized mean square error (NCMSE) and bit error rate (BER) is performed with a notable SiT based least squares (SiT-LS) channel estimation technique. The effect of channels’ sparsity, training-to-information power ratio (TIR) and signal-to-noise ratio (SNR) on BER and NCMSE performance of proposed schemes is thoroughly studied. For a simulation scenario of: 4 × 64 massive-MIMO with a channel sparsity level of 80 % and signal-to-noise ratio (SNR) of 10 dB , a performance gain of 18 dB and 13 dB in terms of NCMSE over SiT-LS is observed for the proposed SiT-StOMP and SiT-GP techniques, respectively. Moreover, a performance gain of about 3 dB and 2.5 dB in SNR is achieved by the proposed SiT-StOMP and SiT-GP, respectively, for a BER of 10 2 , as compared to SiT-LS. This performance gain NCME and BER is observed to further increase with an increase in channels’ sparsity. Full article
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Open AccessArticle High Electrocatalytic Performance of CuCoNi@CNTs Modified Glassy Carbon Electrode towards Methanol Oxidation in Alkaline Medium
Appl. Sci. 2017, 7(1), 64; doi:10.3390/app7010064
Received: 4 November 2016 / Revised: 26 December 2016 / Accepted: 4 January 2017 / Published: 10 January 2017
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Abstract
A novel non-precious multiwalled carbon nanotubes (CNTs)—supported metal oxide electrocatalyst was developed for methanol electrooxidation in alkaline medium. The catalyst was fabricated by simultaneous electrodeposition of copper-cobalt-nickel ternary nanostructures (CuCoNi) on a glassy carbon electrode (GCE) modified with CNTs. The proposed electrode was
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A novel non-precious multiwalled carbon nanotubes (CNTs)—supported metal oxide electrocatalyst was developed for methanol electrooxidation in alkaline medium. The catalyst was fabricated by simultaneous electrodeposition of copper-cobalt-nickel ternary nanostructures (CuCoNi) on a glassy carbon electrode (GCE) modified with CNTs. The proposed electrode was characterized using X-ray diffraction (XRD), energy dispersive X-ray (EDX), and scanning electron microscopy (SEM). The electrochemical behavior and the electrocatalytic performance of the suggested electrode towards the oxidation of methanol were evaluated by cyclic voltammetry (CV), linear sweep voltammetry (LSV), and chronoamperometry (CA) in alkaline medium. Several parameters were investigated, e.g., deposition time, potential scan rate, etc. Compared to Cu, Co, or Ni mono electrocatalysts, the electrode based on ternary-metals exhibited superior electrocatalytic activity and stability towards methanol electrooxidation. For instance, CuCoNi@CNTs/GCE has shown at least 2.5 times electrocatalytic activity and stability compared to the mono eletrocatalysts. Moreover, the present study found that the optimized loading level is 1500 s of simultaneous electrodeposition. At this loading level, it was found that the relation between the Ip1/2 function and scan rate gives the characteristic features of a catalytic process. The enhanced activity and stability of CuCoNi@CNTs/GCE was attributed to (i) a synergism between three metal oxides coexisting in the same structure; (ii) the presence of CNTs as a support for the metal oxides, that offers high surface area for the deposited tertiary alloy and suppresses the aggregation and sintering of the metals oxide with time; as well as (iii) the increase of the conductivity of the deposited semiconducting metal oxides. Full article
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Open AccessArticle Optimal Control to Increase Energy Production of Wind Farm Considering Wake Effect and Lifetime Estimation
Appl. Sci. 2017, 7(1), 65; doi:10.3390/app7010065
Received: 1 November 2016 / Revised: 22 December 2016 / Accepted: 4 January 2017 / Published: 11 January 2017
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Abstract
In a wind farm, the upstream wind turbine may cause power loss to the downstream wind turbines due to the wake effect. Meanwhile, the energy production is determined by the power generation and the lifetime of the wind turbine. In this paper, an
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In a wind farm, the upstream wind turbine may cause power loss to the downstream wind turbines due to the wake effect. Meanwhile, the energy production is determined by the power generation and the lifetime of the wind turbine. In this paper, an optimal active power control method is proposed to maximize the energy production of wind farms by considering the wake effect and the lifetime of wind turbine. It starts with the analysis of the pitch angle curve and active power curve seen from the Maximum Power Point Tracking (MPPT) of individual wind turbines. Taking the wake effect into account, the pitch angle curve and active power curve are optimized with the aim of Maximum Power Generation (MPG) of the wind farm. Afterwards, considering the lifetime of wind turbines, a comparison is offered between the MPPT method and the MPG method for energy production using a simplified two-turbine wind farm as an example. Due to the small range of the effective wake area, it is found that the energy production is almost the same. Finally, the pitch angle curve and active power curve are optimized according to the Maximum Energy Production (MEP) of a wind farm. Upon considering and contrasting the MPPT method and the MEP method, it can be seen that the energy production of wind farms can be increased even in the case of there not being an effective wake area. Full article
(This article belongs to the Special Issue Advancing Grid-Connected Renewable Generation Systems)
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Open AccessArticle A Modified Bio-Ecological Process for Rural Wastewater Treatment
Appl. Sci. 2017, 7(1), 66; doi:10.3390/app7010066
Received: 20 October 2016 / Revised: 5 January 2017 / Accepted: 5 January 2017 / Published: 10 January 2017
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Abstract
Limited water resources and ensuring access to clean water are critical environmental challenges, especially for the developing world. In particular, rural domestic wastewater has become a significant source for the pollution of freshwater bodies. A modified bio-ecological A2O-wetland system for rural wastewater treatment
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Limited water resources and ensuring access to clean water are critical environmental challenges, especially for the developing world. In particular, rural domestic wastewater has become a significant source for the pollution of freshwater bodies. A modified bio-ecological A2O-wetland system for rural wastewater treatment consisting of a biological unit (anaerobic baffled reactor, anoxic tank and oxic unit, A2O) and an ecological unit (horizontal flow constructed wetland) was developed, and key performance indicators were identified. The bio-ecological treatment system showed high removal efficiency for pollutants, successfully achieving 91%, 85%, 78%, and 92% removal efficiencies for chemical oxygen demand (COD), ammonium (NH4–N), total nitrogen (TN), and total phosphorus (TP), respectively. The concentrations of pollutants in the effluent from the system were lower than the Class 1 A regulated values of the Chinese National Standard GB18918-2002. The system offered high removal efficiency, simple operation, and low energy consumption. The A2O-wetland is a good alternative for rural wastewater treatment systems. Full article
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Open AccessArticle Nonlinear Integral Type Observer Design for State Estimation and Unknown Input Reconstruction
Appl. Sci. 2017, 7(1), 67; doi:10.3390/app7010067
Received: 12 November 2016 / Revised: 2 January 2017 / Accepted: 4 January 2017 / Published: 14 January 2017
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Abstract
This paper is concerned with model-based robust observer designs for state observation and its application for unknown input reconstruction. Firstly, a sliding mode observer (SMO), which provides exponential convergence of estimation error, is designed for a class of multivariable perturbed systems. Observer gain
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This paper is concerned with model-based robust observer designs for state observation and its application for unknown input reconstruction. Firstly, a sliding mode observer (SMO), which provides exponential convergence of estimation error, is designed for a class of multivariable perturbed systems. Observer gain matrices subject to specific structures are going to be imposed such that the unknown perturbation will not affect estimate precision during the sliding modes; Secondly, to improve discontinuous control induced in the SMO as well as pursue asymptotic estimate precision, a proportional-integral type observer (PIO) is further developed. Both the design procedures of the SMO and PIO algorithms are characterized as feasibility issues of linear matrix inequality (LMI) and thus the computations of the control parameters can be efficiently solved. Compared with the SMO, it will be demonstrated that the PIO is capable of achieving better estimation precision as long as the unknown inputs are continuous. Finally, a servo-drive flexible robot arm is selected as an example to demonstrate the applications of the robust observer designs. Full article
(This article belongs to the Special Issue Selected Papers from the 2016 International Conference on Inventions)
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Open AccessArticle Arbuscular Mycorrhizal Fungi Regulate the Growth and Phyto-Active Compound of Salvia miltiorrhiza Seedlings
Appl. Sci. 2017, 7(1), 68; doi:10.3390/app7010068
Received: 25 September 2016 / Revised: 19 December 2016 / Accepted: 4 January 2017 / Published: 13 January 2017
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Abstract
Roots and rhizomes of Salvia miltiorrhiza (S. miltiorrhiza) are widely used for the treatment of cardiovascular diseases. Arbuscular mycorrhizal fungi (AMFs) have been shown to enhance plant growth and increase secondary metabolites concentration in many plant species. However, effects of AMFs
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Roots and rhizomes of Salvia miltiorrhiza (S. miltiorrhiza) are widely used for the treatment of cardiovascular diseases. Arbuscular mycorrhizal fungi (AMFs) have been shown to enhance plant growth and increase secondary metabolites concentration in many plant species. However, effects of AMFs on S. miltiorrhiza have not been explored. A pot culture was designed as one control (non-AMF) treatment and four AMFs (G.m, Glomus mosseae; G.a, Glomus aggregatum; G.v, Glomus versiforme; G.i, Glomus intraradices) treatments were performed in order to evaluate the effects of AMFs on plant growth, as well as phyto-active compounds’ concentration of S. miltiorrhiza seedlings. Plants were harvested after 90 days: agronomic traits and concentration; and an accumulation of mineral elements, as well as phyto-active compounds were detected. All AMFs inoculated plants formed mycorrhizal structures, and an infection ratio; also, the intensity of inoculated roots was higher than 84.61% and 23.86%, respectively. Mycorrhizal dependency was above 144.62%. Seedlings with AMFs inoculation had significantly higher plant height, leather leaf length, top leaflet size, base leaflet length, taproot length, taproot diameter and biomass than those with non-AMF inoculation. In addition, inoculation with AMFs increased N, P, and K accumulation significantly, but barely had any effect on mineral elements’ concentrations. AMFs inoculation also significantly improved tanshinones concentrations and stimulation in order to accumulate salvianolic acid B. G.v and G.i were effective for seedlings growth; G.m and G.i were also effective for phyto-active compounds. In total, S. miltiorrhiza inoculation with AMFs had positive effects on growth and active components, especially inoculation with G.v. Full article
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Open AccessArticle Analysis of Thermo-Elastic Fracture Problem during Aluminium Alloy MIG Welding Using the Extended Finite Element Method
Appl. Sci. 2017, 7(1), 69; doi:10.3390/app7010069
Received: 21 November 2016 / Revised: 1 January 2017 / Accepted: 4 January 2017 / Published: 12 January 2017
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Abstract
The thermo-elastic fracture problem and equations are established for aluminium alloy Metal Inert Gas (MIG) welding, which include a moving heat source and a thermoelasticity equation with the initial and boundary conditions for a plate structure with a crack. The extended finite element
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The thermo-elastic fracture problem and equations are established for aluminium alloy Metal Inert Gas (MIG) welding, which include a moving heat source and a thermoelasticity equation with the initial and boundary conditions for a plate structure with a crack. The extended finite element method (XFEM) is implemented to solve the thermo-elastic fracture problem of a plate structure with a crack under the effect of a moving heat source. The combination of the experimental measurement and simulation of the welding temperature field is done to verify the model and solution method. The numerical cases of the thermomechanical parameters and stress intensity factors (SIFs) of the plate structure in the welding heating and cooling processes are investigated. The research results provide reference data and an approach for the analysis of the thermomechanical characteristics of the welding process. Full article
(This article belongs to the Special Issue Gas Metal Arc Welding)
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Open AccessArticle Online Monitoring of Laser-Generated XUV Radiation Spectra by Surface Reflectivity Measurements with Particle Detectors
Appl. Sci. 2017, 7(1), 70; doi:10.3390/app7010070
Received: 24 November 2016 / Revised: 3 January 2017 / Accepted: 4 January 2017 / Published: 10 January 2017
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Abstract
In this contribution, we present a wavelength-sensitive method for the detection of extreme ultraviolet (XUV) photon energies between 30 eV and 120 eV. The method is based on 45° reflectivity from either a cesium iodide-coated or an uncoated metal surface, which directs the
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In this contribution, we present a wavelength-sensitive method for the detection of extreme ultraviolet (XUV) photon energies between 30 eV and 120 eV. The method is based on 45° reflectivity from either a cesium iodide-coated or an uncoated metal surface, which directs the XUV beam onto an electron or ion detector and its signal is used to monitor the XUV beam. The benefits of our approach are a spectrally sensitive diagnosis of the XUV radiation at the interaction place of time-resolved XUV experiments and the detection of infrared leak light though metal filters in high-harmonic generation (HHG) experiments. Both features were tested using spectrally shaped XUV pulses from HHG in a capillary, and we have achieved excellent agreement with XUV spectrometer measurements and reflectivity calculations. Our obtained results are of interest for time-resolved XUV experiments presenting an additional diagnostic directly in the interaction region and for small footprint XUV beamline diagnostics. Full article
(This article belongs to the Section Optics and Lasers)
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Open AccessArticle Wind-Induced Fatigue Analysis of High-Rise Steel Structures Using Equivalent Structural Stress Method
Appl. Sci. 2017, 7(1), 71; doi:10.3390/app7010071
Received: 24 November 2016 / Revised: 26 December 2016 / Accepted: 5 January 2017 / Published: 20 January 2017
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Abstract
Welded beam-to-column connections of high-rise steel structures are susceptive to fatigue damage under wind loading. However, most fatigue assessments in the field of civil engineering are mainly based on nominal stress or hot spot stress theories, which has the disadvantage of dependence on
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Welded beam-to-column connections of high-rise steel structures are susceptive to fatigue damage under wind loading. However, most fatigue assessments in the field of civil engineering are mainly based on nominal stress or hot spot stress theories, which has the disadvantage of dependence on the meshing styles and massive curves selected. To address this problem, in this paper, the equivalent structural stress method with advantages of mesh-insensitive quality and capability of unifying different stress-life curves (S-N curves) into one is introduced to the wind-induced fatigue assessment of a large-scale complicated high-rise steel structure. The multi-scale finite element model is established and the corresponding wind loading is simulated. Fatigue life assessments using equivalent structural stress method, hot spot stress method and nominal stress method are performed, and the results are verified and comparisons are made. The mesh-insensitive quality is also verified. The results show that the lateral weld toe of the butt weld connecting the beam flange plate and the column is the location where fatigue damage most likely happens. Nominal stress method considers fatigue assessment of welds in a more global way by averaging all the stress on the weld section while in equivalent structural stress method and hot spot method local stress concentration can be taken into account more precisely. Full article
(This article belongs to the Special Issue Structural Health Monitoring (SHM) of Civil Structures)
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Open AccessArticle Luminescent Properties of Silicon Nanocrystals:Spin on Glass Hybrid Materials
Appl. Sci. 2017, 7(1), 72; doi:10.3390/app7010072
Received: 15 October 2016 / Revised: 5 December 2016 / Accepted: 8 December 2016 / Published: 13 January 2017
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Abstract
The photoluminescence characteristics of films consisting of Si nanocrystals either coated with or embedded into Spin on Glass (SOG) were studied. Si nanocrystals showing red or blue luminescence when suspended in alcohol solution were obtained from porous silicon films. These were then either
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The photoluminescence characteristics of films consisting of Si nanocrystals either coated with or embedded into Spin on Glass (SOG) were studied. Si nanocrystals showing red or blue luminescence when suspended in alcohol solution were obtained from porous silicon films. These were then either deposited in Si substrates and coated with SOG, or mixed in an SOG solution that was later spun on Si substrates. Both types of films were thermally annealed at 1100 °C for three hours in N2 atmosphere. Transmission electron microscopy measurements showed a mean diameter of 2.5 nm for the Si nanocrystals, as well as the presence of polycrystalline Si nanoagglomerates. These results were confirmed by X-ray diffraction studies, which revealed the (111), (220) and (311) Bragg peaks in Si nanocrystals. Fourier transform infrared spectroscopy studies showed that the coated films present higher chemical reactivity, promoting the formation of non-stoichiometric SiO2, while the embedded films behave as a stoichiometric SiO2 after the thermal annealing. The PL (photoluminescence) characterization showed that both embedded and coated films present emission dominated by the Quantum Confinement Effect before undergoing any thermal treatment. After annealing, the spectra were found to be modified only in the case of the coated films, due to the formation of defects in the nanocrystals/SiO2 interface. Full article
(This article belongs to the Special Issue Silicon Photonics Components and Applications)
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Open AccessArticle Development of a Robotic Arm Based Hydrogel Additive Manufacturing System for In-Situ Printing
Appl. Sci. 2017, 7(1), 73; doi:10.3390/app7010073
Received: 24 November 2016 / Revised: 6 January 2017 / Accepted: 9 January 2017 / Published: 11 January 2017
PDF Full-text (3273 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In-situ printing is a promising injury repair technique that can be directly applied during surgical operations. This paper features a potential in-situ printing platform based on a small-scale robotic arm with a micro-sized dispenser valve. A double-light-source curing method was applied to print
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In-situ printing is a promising injury repair technique that can be directly applied during surgical operations. This paper features a potential in-situ printing platform based on a small-scale robotic arm with a micro-sized dispenser valve. A double-light-source curing method was applied to print poly(ethylene glycol) diacrylate (PEGDA) with a 20% (weight/volume) ratio and the entire process was controlled automatically by a computer interface where droplet diameter, curing time, mechanical properties were measured and essential printing parameters (e.g., nozzle velocity, nozzle frequency) were determined. Three different two-dimensional (2D) plane models (namely, square, circular, and heart-shaped) were printed during initial printing trials. The feasibility study of in-situ printing on curved surfaces was tested using a three-dimensional (3D) printed defect model. The defect was successfully filled using both parallel and ring printing paths. In conclusion, the robotic arm printing platform and its forming method can achieve a rapid curing of PEGDA hydrogel on a curved surface and has the potential to be applied to in-situ printing. Full article
(This article belongs to the Special Issue Materials for 3D Printing)
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Open AccessArticle A Study on the Control Performance of Electronic Differential System for Four-Wheel Drive Electric Vehicles
Appl. Sci. 2017, 7(1), 74; doi:10.3390/app7010074
Received: 29 September 2016 / Revised: 7 January 2017 / Accepted: 9 January 2017 / Published: 12 January 2017
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Abstract
The electronic differential system (EDS) is an important issue for four-wheel drive electric vehicles. This paper delineates an advanced EDS steering strategy and carries out a careful study of its control performance by numerical simulations that comply with the requirements of ISO4238:2012. The
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The electronic differential system (EDS) is an important issue for four-wheel drive electric vehicles. This paper delineates an advanced EDS steering strategy and carries out a careful study of its control performance by numerical simulations that comply with the requirements of ISO4238:2012. The results demonstrate that the EDS feedback gain plays an important role to its control performance, particularly to its steering characteristics. Moreover, the analysis and discussion disclose the mechanism of the relationship between the feedback gain and the steering characteristics, which will contribute to further research and EDS development. Full article
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Open AccessArticle Theoretical Analysis of Effective Thermal Conductivity for the Chinese HTR-PM Heat Transfer Test Facility
Appl. Sci. 2017, 7(1), 76; doi:10.3390/app7010076
Received: 26 September 2016 / Revised: 6 January 2017 / Accepted: 9 January 2017 / Published: 12 January 2017
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Abstract
The Chinese high temperature gas-cooled reactor pebble bed module (HTR-PM) demonstration project has attracted increasing attention. In order to support the project, a large-scale heat transfer test facility has been constructed for pebble bed effective thermal conductivity measurement over the whole temperature range
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The Chinese high temperature gas-cooled reactor pebble bed module (HTR-PM) demonstration project has attracted increasing attention. In order to support the project, a large-scale heat transfer test facility has been constructed for pebble bed effective thermal conductivity measurement over the whole temperature range (0~1600 °C). Based on different heat transfer mechanisms in the randomly packed pebble bed, three different types of effective thermal conductivity have been theoretically evaluated. A prediction of the total effective thermal conductivity of the pebble bed over the whole temperature range is provided for the optimization of the test facility and guidance of further experiments. Full article
(This article belongs to the Section Energy)
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Open AccessArticle Application of Near-Infrared Hyperspectral Imaging to Detect Sulfur Dioxide Residual in the Fritillaria thunbergii Bulbus Treated by Sulfur Fumigation
Appl. Sci. 2017, 7(1), 77; doi:10.3390/app7010077
Received: 8 November 2016 / Revised: 22 December 2016 / Accepted: 6 January 2017 / Published: 12 January 2017
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Abstract
Sulfur-fumigated Chinese medicine is a common issue in the process of Chinese medicines. Detection of sulfur dioxide (SO2) residual content in Fritillaria thunbergii Bulbus is important to evaluate the degree of sulfur fumigation and its harms. It helps to control the
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Sulfur-fumigated Chinese medicine is a common issue in the process of Chinese medicines. Detection of sulfur dioxide (SO2) residual content in Fritillaria thunbergii Bulbus is important to evaluate the degree of sulfur fumigation and its harms. It helps to control the use of sulfur fumigation in Fritillaria thunbergii Bulbus. Near-infrared hyperspectral imaging (NIR-HSI) was explored as a rapid, non-destructive, and accurate technique to detect SO2 residual contents in Fritillaria thunbergii Bulbus. An HSI system covering the spectral range of 874–1734 nm was used. Partial least squares regression (PLSR) was applied to build calibration models for SO2 residual content detection. Successive projections algorithm (SPA), weighted regression coefficients (Bw), random frog (RF), and competitive adaptive reweighted sampling (CARS) were used to select optimal wavelengths. PLSR models using the full spectrum and the selected optimal wavelengths obtained good performance. The Bw-PLSR model was applied on a hyperspectral image to form a prediction map, and the results were satisfactory. The overall results in this study indicated that HSI could be used as a promising technique for on-line visualization and monitoring of SO2 residual content in Fritillaria thunbergii Bulbus. Detection and visualization of Chinese medicine quality by HSI provided a new rapid and visual method for Chinese medicine monitoring, showing great potential for real-world application. Full article
(This article belongs to the Special Issue Applications of Hyperspectral Imaging for Food and Agriculture)
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Open AccessFeature PaperArticle Improving Nanofiber Membrane Characteristics and Membrane Distillation Performance of Heat-Pressed Membranes via Annealing Post-Treatment
Appl. Sci. 2017, 7(1), 78; doi:10.3390/app7010078
Received: 16 December 2016 / Revised: 23 December 2016 / Accepted: 5 January 2017 / Published: 12 January 2017
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Abstract
Electrospun membranes are gaining interest for use in membrane distillation (MD) due to their high porosity and interconnected pore structure; however, they are still susceptible to wetting during MD operation because of their relatively low liquid entry pressure (LEP). In this study, post-treatment
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Electrospun membranes are gaining interest for use in membrane distillation (MD) due to their high porosity and interconnected pore structure; however, they are still susceptible to wetting during MD operation because of their relatively low liquid entry pressure (LEP). In this study, post-treatment had been applied to improve the LEP, as well as its permeation and salt rejection efficiency. The post-treatment included two continuous procedures: heat-pressing and annealing. In this study, annealing was applied on the membranes that had been heat-pressed. It was found that annealing improved the MD performance as the average flux reached 35 L/m2·h or LMH (>10% improvement of the ones without annealing) while still maintaining 99.99% salt rejection. Further tests on LEP, contact angle, and pore size distribution explain the improvement due to annealing well. Fourier transform infrared spectroscopy and X-ray diffraction analyses of the membranes showed that there was an increase in the crystallinity of the polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) membrane; also, peaks indicating the α phase of polyvinylidene fluoride (PVDF) became noticeable after annealing, indicating some β and amorphous states of polymer were converted into the α phase. The changes were favorable for membrane distillation as the non-polar α phase of PVDF reduces the dipolar attraction force between the membrane and water molecules, and the increase in crystallinity would result in higher thermal stability. The present results indicate the positive effect of the heat-press followed by an annealing post-treatment on the membrane characteristics and MD performance. Full article
(This article belongs to the Special Issue Membrane Distillation) Printed Edition available
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Open AccessArticle Molecular Dynamics Study on the Resonance Properties of a Nano Resonator Based on a Graphene Sheet with Two Types of Vacancy Defects
Appl. Sci. 2017, 7(1), 79; doi:10.3390/app7010079
Received: 2 December 2016 / Revised: 4 January 2017 / Accepted: 5 January 2017 / Published: 12 January 2017
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Abstract
Due to the excellent electronic, optical, thermal, chemical, and mechanical properties of graphene, it has been applied in microdevices and nanodevices. However, there are some structural defects in graphene limiting its application in micro electromechanical systems (MEMS). These structural defects are inevitable during
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Due to the excellent electronic, optical, thermal, chemical, and mechanical properties of graphene, it has been applied in microdevices and nanodevices. However, there are some structural defects in graphene limiting its application in micro electromechanical systems (MEMS). These structural defects are inevitable during processing, and it is difficult to assess their effect on the micro/nano devices. Therefore, this communication used molecular dynamics to study the resonance properties of a nanoelectromechanical systems (NMES) resonator based on a graphene sheet with a single vacancy defect and edge defects. This communication focuses on three factors: vacancy types, external force, and temperature. The resonance frequencies of both types of graphene increased with external stress loading, and the resonance frequency of the graphene showed a clear step-shaped variation. Nonlinear deformation of the sheet occurred between resonant processes. When the external force was less than 15.91 nN, the resonance frequencies of the two types of graphene showed a consistent trend. The maximum frequency was up to 132.90 GHz. When the external force was less than 90 nN, the resonance frequencies of graphene with edge defects were greater and changed more rapidly. Temperature did not have a huge influence on the resonance frequencies of either type of graphene structure. The resonance frequencies of graphene with two different vacancy defects showed a consistent trend. Full article
(This article belongs to the Special Issue Graphene and Graphene Oxide in Biomedical Application)
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Open AccessArticle Tribological Properties of Aluminum Nanoparticles as Additives in an Aqueous Glycerol Solution
Appl. Sci. 2017, 7(1), 80; doi:10.3390/app7010080
Received: 13 October 2016 / Revised: 30 December 2016 / Accepted: 9 January 2017 / Published: 13 January 2017
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