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Appl. Sci., Volume 8, Issue 12 (December 2018)

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Open AccessArticle Statistical Analysis of Table-Tennis Ball Trajectories
Appl. Sci. 2018, 8(12), 2595; https://doi.org/10.3390/app8122595 (registering DOI)
Received: 12 November 2018 / Revised: 7 December 2018 / Accepted: 10 December 2018 / Published: 12 December 2018
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Abstract
In this work, the equations of motion for table-tennis balls were numerically solved on graphics processing units (GPUs) using Compute Unified Device Architecture (CUDA) for systematical statistical studies of the impact of ball size and weight, as well as of net height, on
[...] Read more.
In this work, the equations of motion for table-tennis balls were numerically solved on graphics processing units (GPUs) using Compute Unified Device Architecture (CUDA) for systematical statistical studies of the impact of ball size and weight, as well as of net height, on the distribution functions of successful strokes. Half a billion different initial conditions involving hitting location, initial spin, and velocities were analyzed to reach sufficient statistical significance for the different cases. In this paper, an advanced statistical analysis of the database generated by the simulation is presented. Full article
(This article belongs to the Special Issue Computer Science in Sport)
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Open AccessArticle Modeling of Positive Switching Impulse Discharge of UHV Transmission Line Air Gaps
Appl. Sci. 2018, 8(12), 2594; https://doi.org/10.3390/app8122594 (registering DOI)
Received: 19 November 2018 / Revised: 6 December 2018 / Accepted: 10 December 2018 / Published: 12 December 2018
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Abstract
Positive switching impulse discharge characteristics are an important basis for the external insulation design of transmission line towers. At present, the characteristics are obtained mainly by real tower discharge tests. Since the existing research on the discharge model is not perfect, test designs
[...] Read more.
Positive switching impulse discharge characteristics are an important basis for the external insulation design of transmission line towers. At present, the characteristics are obtained mainly by real tower discharge tests. Since the existing research on the discharge model is not perfect, test designs are not reasonable, which results in high costs. The influence of line height and tower width on the discharge characteristics of Ultra High Voltage (UHV) transmission lines air gaps is studied in this paper. The results show that the line height had little influence on the breakdown voltage of air gaps in UHV transmission lines. A tower-width discharge model was obtained by fitting the breakdown voltage of air gaps with different gap lengths and tower widths. By analyzing the gap characteristic factors of different transmission lines, a discharge model of different tower air gaps in UHV transmission lines was presented. The breakdown voltage calculated by the models was in good agreement with the test results, and the errors were not more than 5%. Full article
(This article belongs to the Section Energy)
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Open AccessArticle A 20 W, Less-Than-1-kHz Linewidth Linearly Polarized All-Fiber Laser
Appl. Sci. 2018, 8(12), 2593; https://doi.org/10.3390/app8122593 (registering DOI)
Received: 12 November 2018 / Revised: 8 December 2018 / Accepted: 8 December 2018 / Published: 12 December 2018
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Abstract
We report a continuous-wave high-output power and narrow-linewidth all-fiber laser at 1550 nm with the master oscillator power amplifier (MOPA) configuration. An all-fiber distributed feedback seed laser was boosted by three cascaded fiber amplifiers. In the experiment, we adopted a large-mode-area (LMA) Er
[...] Read more.
We report a continuous-wave high-output power and narrow-linewidth all-fiber laser at 1550 nm with the master oscillator power amplifier (MOPA) configuration. An all-fiber distributed feedback seed laser was boosted by three cascaded fiber amplifiers. In the experiment, we adopted a large-mode-area (LMA) Er3+:Yb3+-co-doped polarization-maintaining fiber to increase nonlinear thresholds and avoided the broadening of the laser linewidth. A linear-polarization fiber laser with average output power of 20 W, linewidth of 0.88 kHz, and power jitter less than 2% was finally achieved. Full article
(This article belongs to the Section Optics and Lasers)
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Open AccessArticle Fast Path Planning for Autonomous Ships in Restricted Waters
Appl. Sci. 2018, 8(12), 2592; https://doi.org/10.3390/app8122592 (registering DOI)
Received: 7 November 2018 / Revised: 4 December 2018 / Accepted: 7 December 2018 / Published: 12 December 2018
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Abstract
Presently, there is increasing interest in autonomous ships to reduce human errors and support intelligent navigation, where automatic collision avoidance and path planning is a key problem, especially in restricted waters. To solve this problem, a path-guided hybrid artificial potential field (PGHAPF) method
[...] Read more.
Presently, there is increasing interest in autonomous ships to reduce human errors and support intelligent navigation, where automatic collision avoidance and path planning is a key problem, especially in restricted waters. To solve this problem, a path-guided hybrid artificial potential field (PGHAPF) method is first proposed in this paper. It is essentially a reactive path-planning algorithm that provides fast feedback in a changeable environment, including dynamic target ships (TSs) and static obstacles, for steering an autonomous ship safely. The proposed strategy, which is a fusion of the potential field and gradient methods, consists of potential-based path planning for arbitrary static obstacles, gradient-based decision-making for dynamic TSs, and their combination with consideration of the prior path and waypoint selection optimization. A three-degree-of-freedom dynamic model of a Mariner class vessel and a low-level controller have been incorporated together in this method to ensure that the vessel’s positions are updated at each time step in order to acquire a more applicable and reliable trajectory. Simulations show that the PGHAPF method has the potential to rapidly generate adaptive, collision-free and International Regulations for Preventing Collisions at Sea (COLREGS)-constrained trajectories in restricted waters by deterministic calculations. Furthermore, this method has the potential to perform path planning on an electronic chart platform and to overcome some drawbacks of traditional artificial potential field (APF) methods. Full article
(This article belongs to the Section Energy)
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Open AccessArticle Issue-Based Clustering of Scholarly Articles
Appl. Sci. 2018, 8(12), 2591; https://doi.org/10.3390/app8122591 (registering DOI)
Received: 13 November 2018 / Revised: 3 December 2018 / Accepted: 10 December 2018 / Published: 12 December 2018
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Abstract
A scholarly article often discusses multiple research issues. The clustering of scholarly articles based on research issues can facilitate analyses of related articles on specific issues in scientific literature. It is a task of overlapping clustering, as an article may discuss multiple issues,
[...] Read more.
A scholarly article often discusses multiple research issues. The clustering of scholarly articles based on research issues can facilitate analyses of related articles on specific issues in scientific literature. It is a task of overlapping clustering, as an article may discuss multiple issues, and hence, be clustered into multiple clusters. Clustering is challenging, as it is difficult to identify the research issues with which to cluster the articles. In this paper, we propose the use of the titles of the references cited by the articles to tackle the challenge, based on the hypothesis that such information may indicate the research issues discussed in the article. A technique referred to as ICRT (Issue-based Clustering with Reference Titles) was thus developed. ICRT works as a post-processor for various clustering systems. In experiments on those articles that domain experts have selected to annotate research issues about specific entity associations, ICRT works with various clustering systems that employ state-of-the-art similarity measures for scholarly articles. ICRT successfully improves these systems by identifying clusters of articles with the same research focuses on specific entity associations. The contribution is of technical and practical significance to the exploration of research issues reported in scientific literature (supporting the curation of entity associations found in the literature). Full article
(This article belongs to the Section Computer Science and Electrical Engineering)
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Open AccessArticle Deep Learning Applied to Scenario Classification for Lane-Keep-Assist Systems
Appl. Sci. 2018, 8(12), 2590; https://doi.org/10.3390/app8122590 (registering DOI)
Received: 8 November 2018 / Revised: 26 November 2018 / Accepted: 29 November 2018 / Published: 12 December 2018
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Abstract
Test, verification, and development activities of vehicles with ADAS (Advanced Driver Assistance Systems) and ADF (Automated Driving Functions) generate large amounts of measurement data. To efficiently evaluate and use this data, a generic understanding and classification of the relevant driving scenarios is necessary.
[...] Read more.
Test, verification, and development activities of vehicles with ADAS (Advanced Driver Assistance Systems) and ADF (Automated Driving Functions) generate large amounts of measurement data. To efficiently evaluate and use this data, a generic understanding and classification of the relevant driving scenarios is necessary. Currently, such understanding is obtained by using heuristic algorithms or even by manual inspection of sensor signals. In this paper, we apply deep learning on sensor time series data to automatically extract relevant features for classification of driving scenarios relevant for a Lane-Keep-Assist System. We compare the performance of convolutional and recurrent neural networks and propose two classification models. The first one is an online model for scenario classification during driving. The second one is an offline model for post-processing, providing higher accuracy. Full article
(This article belongs to the Special Issue Multi-Actuated Ground Vehicles: Recent Advances and Future Challenges)
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Open AccessArticle Study of the Stability of Functionalized Gold Nanoparticles for the Colorimetric Detection of Dipeptidyl Peptidase IV
Appl. Sci. 2018, 8(12), 2589; https://doi.org/10.3390/app8122589 (registering DOI)
Received: 24 November 2018 / Accepted: 7 December 2018 / Published: 12 December 2018
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Abstract
In this report, we investigated three stabilization strategies of gold nanoparticles and their practical application for the visual detection of dipeptidyl peptidase IV (DPP-IV). Citrate-capped gold nanoparticles (Au NPs) are generally unstable in high-ionic-strength samples. Au NPs are easily tagged with various proteins
[...] Read more.
In this report, we investigated three stabilization strategies of gold nanoparticles and their practical application for the visual detection of dipeptidyl peptidase IV (DPP-IV). Citrate-capped gold nanoparticles (Au NPs) are generally unstable in high-ionic-strength samples. Au NPs are easily tagged with various proteins and biomolecules rich in amino acids, leading to important biomedical applications including targeted drug delivery, cellular imaging, and biosensing. The investigated assays were based on different modes of stabilization, such as the incorporation of polyethylene glycol (PEG) groups, stabilizer peptide, and bifunctionalization. Although all approaches provided highly stable Au NP platforms demonstrated by zeta potential measurements and resistance to aggregation in a high-ionic-strength saline solution, we found that the Au NPs modified with a separate stabilizer ligand provided the highest stability and was the only platform that demonstrated sensitivity to the addition of DPP-IV, whilst PEGylated and peptide-stabilized Au NPs showed no significant response. Full article
(This article belongs to the Special Issue Nano-Biointerface for Biosensing)
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Open AccessArticle Entropy Generation in MHD Eyring–Powell Fluid Flow over an Unsteady Oscillatory Porous Stretching Surface under the Impact of Thermal Radiation and Heat Source/Sink
Appl. Sci. 2018, 8(12), 2588; https://doi.org/10.3390/app8122588 (registering DOI)
Received: 11 November 2018 / Revised: 25 November 2018 / Accepted: 4 December 2018 / Published: 12 December 2018
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Abstract
In this article, we have briefly examined the entropy generation in magnetohydrodynamic (MHD) Eyring–Powell fluid over an unsteady oscillating porous stretching sheet. The impact of thermal radiation and heat source/sink are taken in this investigation. The impact of embedded parameters on velocity function,
[...] Read more.
In this article, we have briefly examined the entropy generation in magnetohydrodynamic (MHD) Eyring–Powell fluid over an unsteady oscillating porous stretching sheet. The impact of thermal radiation and heat source/sink are taken in this investigation. The impact of embedded parameters on velocity function, temperature function, entropy generation rate, and Bejan number are deliberated through graphs, and discussed as well. By studying the entropy generation in magnetohydrodynamic Eyring–Powell fluid over an unsteady oscillating porous stretching sheet, the entropy generation rate is reduced with escalation in porosity, thermal radiation, and magnetic parameters, while increased with the escalation in Reynolds number. Also, the Bejan number is increased with the escalation in porosity and magnetic parameter, while increased with the escalation in thermal radiation parameter. The impact of skin fraction coefficient and local Nusselt number are discussed through tables. The partial differential equations are converted to ordinary differential equation with the help of similarity variables. The homotopy analysis method (HAM) is used for the solution of the problem. The results of this investigation agree, satisfactorily, with past studies. Full article
(This article belongs to the Section Nanotechnology and Applied Nanosciences)
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Open AccessArticle The Effect of Different Mixed Organic Solvents on the Properties of p(OPal-MMA) Gel Electrolyte Membrane for Lithium Ion Batteries
Appl. Sci. 2018, 8(12), 2587; https://doi.org/10.3390/app8122587 (registering DOI)
Received: 16 November 2018 / Revised: 6 December 2018 / Accepted: 10 December 2018 / Published: 12 December 2018
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Abstract
A solvent is a key factor during polymer membrane preparation, and it is directly related to application performance as a separator for lithium ion battery (LIB). In this study, different mixed solvents were employed to prepare polymer (p(OPal-MMA)) membranes by the phase inversion
[...] Read more.
A solvent is a key factor during polymer membrane preparation, and it is directly related to application performance as a separator for lithium ion battery (LIB). In this study, different mixed solvents were employed to prepare polymer (p(OPal-MMA)) membranes by the phase inversion technique. The polymer membrane then absorbed liquid electrolytes to obtain gel electrolytes (GPEs). The surface morphologies and porosities of these membranes were investigated, and lithium ion transferences and electrochemical performances of these GPEs were also measured. The membrane displayed an interconnected three-dimensional framework structure with uniformly distributed pores when using DMF as a porogen. When combined with acetone as the component solvent, the prepared GPE displayed the largest lithium ion transference number (0.706), the highest porosity (42.6%) and ion conductivity (3.99 × 10−3 S/cm). Even when assembled as Li/GPE/LiFePO4 cell, it exhibited the highest initial specific capacity of 167 mAh/g and retained most capacity (162 mAh/g) after 50 cycles. The results presented here probably provide reference for choosing an appropriate mixed solvent in fabricating polymer membranes. Full article
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Open AccessArticle Between-Limb Symmetry during Double-Leg Vertical Hop Landing in Males an Average of Two Years after ACL Reconstruction is Highly Correlated with Postoperative Physiotherapy Supervision Duration
Appl. Sci. 2018, 8(12), 2586; https://doi.org/10.3390/app8122586 (registering DOI)
Received: 16 October 2018 / Revised: 8 December 2018 / Accepted: 10 December 2018 / Published: 12 December 2018
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Abstract
This study investigates whether double-leg and single-leg vertical hops (VH) landing between-limb symmetry in males, an average of two years after anterior cruciate ligament (ACL) reconstruction (ACLR), is associated with postoperative physiotherapy supervision duration. Thirty-eight healthy controls and thirty-eight males after primary unilateral
[...] Read more.
This study investigates whether double-leg and single-leg vertical hops (VH) landing between-limb symmetry in males, an average of two years after anterior cruciate ligament (ACL) reconstruction (ACLR), is associated with postoperative physiotherapy supervision duration. Thirty-eight healthy controls and thirty-eight males after primary unilateral ACLR, with the use of ipsilateral semitendinosus and gracilis tendon autograft, on average two years before, underwent bilateral peak vertical ground reaction force (vGRF) measurements during double-leg and single-leg VH landing, using two force plates. The vGRF was normalized to the body mass (vGRF BM). The vGRF BM limb symmetry index (LSI) was calculated. Tests for dependent and independent samples and linear Pearson’s correlation coefficient (r) calculations were performed. There were significant between-leg differences in the double-leg (p < 0.001) vGRF BM values. The longer the postoperative physiotherapy supervision duration was, the higher the double-leg VH LSI values (r = 0.727; p < 0.001). There was also a significant but weak positive association between the single-leg VH landing LSI value and the physiotherapy supervision duration (r = 0.333; p = 0.041). Between-limb symmetry during double-leg VH landing in males, an average of two years after ACLR, was correlated with postoperative physiotherapy supervision duration. Fully supervised postoperative physiotherapy for a minimum of six months is more effective for improving VH landing limb symmetry in patients after ACLR. Full article
(This article belongs to the Section Applied Biosciences and Bioengineering)
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Open AccessArticle A Measurement System for Time Constant of Thermocouple Sensor Based on High Temperature Furnace
Appl. Sci. 2018, 8(12), 2585; https://doi.org/10.3390/app8122585 (registering DOI)
Received: 25 October 2018 / Revised: 8 December 2018 / Accepted: 10 December 2018 / Published: 12 December 2018
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Abstract
In dynamic temperature measurement, thermocouple sensors are widely used, and their dynamic characteristics directly affect the accuracy of the test results. So before applying thermocouple sensors to dynamic temperature measurement, their dynamic characteristics should be obtained, and their dynamic performance parameters should be
[...] Read more.
In dynamic temperature measurement, thermocouple sensors are widely used, and their dynamic characteristics directly affect the accuracy of the test results. So before applying thermocouple sensors to dynamic temperature measurement, their dynamic characteristics should be obtained, and their dynamic performance parameters should be analyzed. The time constant is the most important dynamic parameter, which reflects the response speed of a thermocouple sensor. Therefore, it is necessary to measure the time constant. The time constant is closely related to the heat transfer mode, so the heat transfer environment of the time constant measurement system should be similar to the application environment of thermocouple sensor. When using the thermocouple to measure the temperature in various kilns, the heat transfer is mainly through the radiative mode, and existing equipment, such as constant temperature water/oil tank, shock wave tube and other devices, cannot be used to measure the time constant to reflect scenarios in actual measurement applications. Therefore, this paper proposed a new method to measure the time constant of the thermocouple by improved high temperature furnace. In the system, the high temperature furnace was used to generate the stable temperature field, and the fast feed device was used to insert the thermocouple into the high temperature furnace and generates the ramp temperature excitation. The temperature can reach 1500 °C in the furnace, and the temperature error in uniform temperature field is ±1 °C. Finally, the time constant of a K-type thermocouple was measured, and the uncertainty of the measurement result was analyzed. Full article
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Open AccessArticle Compaction Characteristics and Minimum Void Ratio Prediction Model for Gap-Graded Soil-Rock Mixture
Appl. Sci. 2018, 8(12), 2584; https://doi.org/10.3390/app8122584 (registering DOI)
Received: 6 November 2018 / Revised: 5 December 2018 / Accepted: 9 December 2018 / Published: 12 December 2018
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Abstract
Gap-graded soil-rock mixtures (SRMs), composed of coarse-grained rocks and fine-grained soils particles, are very inhomogeneous materials and widely encountered in geoengineering. In geoengineering applications, it is necessary to know the compaction characteristics in order to estimate the minimum void ratio of gap-graded SRMs.
[...] Read more.
Gap-graded soil-rock mixtures (SRMs), composed of coarse-grained rocks and fine-grained soils particles, are very inhomogeneous materials and widely encountered in geoengineering. In geoengineering applications, it is necessary to know the compaction characteristics in order to estimate the minimum void ratio of gap-graded SRMs. In this paper, the void ratios of compacted SRMs as well as the particle breakage during vibrating compaction were investigated through a series of vibrating compaction tests. The test results show that gap-graded SRMs may reach a smaller void ratio than the SRM with a continuous gradation under some circumstances. When the particles in a gap interval play the role of filling components, the absence of them will increase the void ratio of the SRM. The particle breakage of gap-graded SRMs is more prominent than the SRM with continuous gradation on the whole, especially at the gap interval of 5–20 mm. Based on the test results, a minimum void ratio prediction model incorporating particle breakage during compaction is proposed. The developed model is evaluated by the compaction test results and its validation is discussed. Full article
(This article belongs to the Special Issue Emerging Construction Materials and Sustainable Infrastructure)
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Open AccessArticle Metrology of Nanostructures by Tomographic Mueller-Matrix Scatterometry
Appl. Sci. 2018, 8(12), 2583; https://doi.org/10.3390/app8122583 (registering DOI)
Received: 16 November 2018 / Revised: 7 December 2018 / Accepted: 10 December 2018 / Published: 12 December 2018
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Abstract
The development of necessary instrumentation and metrology at the nanoscale, especially fast, low-cost, and nondestructive metrology techniques, is of great significance for the realization of reliable and repeatable nanomanufacturing. In this work, we present the application of a homemade novel optical scatterometer called
[...] Read more.
The development of necessary instrumentation and metrology at the nanoscale, especially fast, low-cost, and nondestructive metrology techniques, is of great significance for the realization of reliable and repeatable nanomanufacturing. In this work, we present the application of a homemade novel optical scatterometer called the tomographic Mueller-matrix scatterometer (TMS), for the measurement of photoresist gratings. The TMS adopts a dual rotating-compensator configuration and illuminates the nanostructure sequentially under test conditions by a plane wave, with varying illumination directions and records. For each illumination direction, the polarized scattered field along various directions of observation can be seen in the form of scattering Mueller matrices. That more scattering information is collected by TMS than conventional optical scatterometry ensures that it achieves better measurement sensitivity and accuracy. We also show the capability of TMS for determining both grating pitch and other structural parameters, which is incapable by current zeroth-order methods such as reflectometry- or ellipsometry-based scatterometry. Full article
(This article belongs to the Special Issue Precision Dimensional Measurements)
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Open AccessArticle Multi-Channel Electrical Impedance-Based Crack Localization of Fiber-Reinforced Cementitious Composites under Bending Conditions
Appl. Sci. 2018, 8(12), 2582; https://doi.org/10.3390/app8122582 (registering DOI)
Received: 30 September 2018 / Revised: 4 December 2018 / Accepted: 6 December 2018 / Published: 12 December 2018
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Abstract
This study proposes a multi-channel electrical impedance-based crack localization technique of fiber-reinforced cementitious composites (FRCCs) under bending conditions. FRCCs have a self-sensing capability by adding conductive steel fibers into nonconductive cementitious composites, making it possible to measure electrical impedance without sensor installation. Moreover,
[...] Read more.
This study proposes a multi-channel electrical impedance-based crack localization technique of fiber-reinforced cementitious composites (FRCCs) under bending conditions. FRCCs have a self-sensing capability by adding conductive steel fibers into nonconductive cementitious composites, making it possible to measure electrical impedance without sensor installation. Moreover, FRCCs materials can be used as a structural member thanks to its own enhanced structural ductility as well as stiffness. In a structural health monitoring point of view, these characteristics make FRCCs suitable for monitoring structural hot spots, particularly where the crack is most likely to be initiated. Since the electrical impedance obtained from FRCCs is typically sensitive to environmental and operational conditions, false alarms are often triggered. The proposed technique can minimize the false alarms by using currently measured multi-path data as well as localize a crack within the sensing range. To examine the feasibility of crack localization in FRCCs, an instantaneous multi-channel electrical impedance acquisition system and a crack localization algorithm are developed. Subsequently, three-point bending tests are carried out under various temperature conditions. The validation test results reveal that cracks are successfully identified and localized even under varying temperature conditions. Full article
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Open AccessArticle Pavement Performance Investigation of Nano-TiO2/CaCO3 and Basalt Fiber Composite Modified Asphalt Mixture under Freeze‒Thaw Cycles
Appl. Sci. 2018, 8(12), 2581; https://doi.org/10.3390/app8122581 (registering DOI)
Received: 12 November 2018 / Revised: 5 December 2018 / Accepted: 7 December 2018 / Published: 12 December 2018
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Abstract
The objective of this research is to evaluate the pavement performance degradation of nano-TiO2/CaCO3 and basalt fiber composite modified asphalt mixtures under freeze‒thaw cycles. The freeze‒thaw resistance of composite modified asphalt mixture was studied by measuring the mesoscopic void volume,
[...] Read more.
The objective of this research is to evaluate the pavement performance degradation of nano-TiO2/CaCO3 and basalt fiber composite modified asphalt mixtures under freeze‒thaw cycles. The freeze‒thaw resistance of composite modified asphalt mixture was studied by measuring the mesoscopic void volume, stability, indirect tensile stiffness modulus, splitting strength, uniaxial compression static, and dynamic creep rate. The equal-pitch gray prediction model GM (1, 3) was also established to predict the pavement performance of the asphalt mixture. It was concluded that the high- and low-temperature performance and water stability of nano-TiO2/CaCO3 and basalt fiber composite modified asphalt mixture were better than those of an ordinary asphalt mixture before and after freeze‒thaw cycles. The test results of uniaxial compressive static and dynamic creep after freeze‒thaw cycles showed that the high-temperature stability of the nano-TiO2/CaCO3 and basalt fiber composite modified asphalt mixture after freeze‒thaw was obviously improved compared with an ordinary asphalt mixture. Full article
(This article belongs to the Special Issue Asphalt Materials)
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Open AccessArticle Visible Measurement of Terahertz Power Based on Capsulized Cholesteric Liquid Crystal Film
Appl. Sci. 2018, 8(12), 2580; https://doi.org/10.3390/app8122580 (registering DOI)
Received: 27 October 2018 / Revised: 4 December 2018 / Accepted: 10 December 2018 / Published: 12 December 2018
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Abstract
We demonstrate a new method to detect terahertz (THz) power using a temperature-supersensitive capsulized cholesteric liquid crystal film based on the thermochromic and thermodiffusion effect, which is clearly observed. A quantitative visualization of the THz intensity up to 4.0 × 103 mW/cm
[...] Read more.
We demonstrate a new method to detect terahertz (THz) power using a temperature-supersensitive capsulized cholesteric liquid crystal film based on the thermochromic and thermodiffusion effect, which is clearly observed. A quantitative visualization of the THz intensity up to 4.0 × 103 mW/cm2 is presented. The diameter of the color change area is linearly dependent on the THz radiation power above 0.07 mW in the steady state. Moreover, the THz power can be detected for 1 sec of radiation with a parabolic relation to the color change area. The THz power meter is robust, cost-effective, portable, and even flexible, and can be used in applications such as THz imaging, biological sensing, and inspection. Full article
(This article belongs to the Special Issue Liquid Crystal THz Photonics: Materials, Devices and Applications)
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Open AccessArticle Real-Time Tunnel Deformation Monitoring Technology Based on Laser and Machine Vision
Appl. Sci. 2018, 8(12), 2579; https://doi.org/10.3390/app8122579 (registering DOI)
Received: 23 October 2018 / Revised: 7 December 2018 / Accepted: 7 December 2018 / Published: 11 December 2018
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Abstract
Structural health monitoring is a topic of great concern in the world, and tunnel deformation monitoring is one of the important tasks. With the rapid developments in tunnel traffic infrastructure construction, engineers need a portable and real-time system to obtain the tunnel deformation
[...] Read more.
Structural health monitoring is a topic of great concern in the world, and tunnel deformation monitoring is one of the important tasks. With the rapid developments in tunnel traffic infrastructure construction, engineers need a portable and real-time system to obtain the tunnel deformation during construction. This paper reports a novel method based on laser and machine vision to automatically measure tunnel deformation of multiple interest points in real time and effectively compensate for the environment vibration, and moreover it can overcome the influence of a dusty and dark tunnel environment in low visibility. An automatic and wireless real-time tunnel deformation monitoring system, which is based on laser and machine vision and can give early warnings for tunnel collapse accidents, is proposed. The proposed system uses a fixed laser beam as a monitoring reference. The image acquisition modules mounted on the measured points receive the laser spots and measure the tunnel accumulative deformation and instantaneous deformation velocity. Compensation methods are proposed to reduce measurement errors caused by laser beam feasibility, temperature, air refraction index, and wireless antenna attitude. The feasibility of the system is verified through tunnel tests. The accuracy of the detection system is better than 0.12 mm, the repeatability is less than 0.11 mm, and the minimum resolution is 10 μm; therefore, the proposed system is very suitable for real-time and automatic detection of tunnel deformation in low visibility during construction. Full article
(This article belongs to the Special Issue Precision Dimensional Measurements)
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Open AccessArticle Hybrid Modulation Strategy to Eliminate Current Distortion for PV Grid-Tied H6 Inverter
Appl. Sci. 2018, 8(12), 2578; https://doi.org/10.3390/app8122578
Received: 20 November 2018 / Revised: 5 December 2018 / Accepted: 6 December 2018 / Published: 11 December 2018
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Abstract
This paper proposes a new hybrid modulation mode (HMM) to eliminate the zero-crossing distortion of grid current and enable reactive power provision for a H6 configuration PV (photovoltaic) grid-tied inverter. The common mode voltage, leakage current, and efficiency for the proposed approach are
[...] Read more.
This paper proposes a new hybrid modulation mode (HMM) to eliminate the zero-crossing distortion of grid current and enable reactive power provision for a H6 configuration PV (photovoltaic) grid-tied inverter. The common mode voltage, leakage current, and efficiency for the proposed approach are also analyzed. In order to improve grid frequency tracking a novel frequency self-adaptive proportional-integral-resonant (FSAPIR) controller is implemented which reduces error for changes in grid frequency. The proposed approach provides the basis for accurately adjusting the active and reactive current without error to improve the grid support capability of the inverter. Theoretical analysis, simulation, and experiment verify the newly proposed modulation mode and controller. Full article
(This article belongs to the Special Issue Control and Protection Issues of Grid-Tied Photovoltaic System)
Open AccessArticle Design, Synthesis and Antifungal Activity of Novel Benzoylcarbamates Bearing a Pyridine Moiety
Appl. Sci. 2018, 8(12), 2577; https://doi.org/10.3390/app8122577
Received: 1 November 2018 / Revised: 5 December 2018 / Accepted: 8 December 2018 / Published: 11 December 2018
PDF Full-text (316 KB)
Abstract
Many natural and synthetic pyridine derivatives have good biological activity, and are widely used in the fields of pesticides and medicines. On the other hand, carbamate fungicides possess some unique properties, such as high efficiency, strong selectivity, low toxicity, and environmental friendliness, and
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Many natural and synthetic pyridine derivatives have good biological activity, and are widely used in the fields of pesticides and medicines. On the other hand, carbamate fungicides possess some unique properties, such as high efficiency, strong selectivity, low toxicity, and environmental friendliness, and are often used to control many plant diseases. Therefore, discovering novel pyridine-based carbamates is of great significance. In this paper, we chose the excellent fungicides tolprocarb and picarbutrazox as lead compounds, integrating benzoyl, carbamate, and pyridinyl moieties into a molecule. Thus, we designed and synthesized a series of substituted benzoyl carbamates containing a pyridine ring, and evaluated the in vitro antifungal activity. The target compounds exhibited moderate to strong bioactivity against Botrytis cinerea, among which the compounds 4d, 4f, 4g, and 4h exhibited significant activity with EC50 values (the concentration resulting in a 50% inhibition) of 6.45–6.98 μg/mL, and their activities were near or superior to that of chlorothalonil. Additionally, 4h exhibited moderate activity against Sclerotinia sclerotiorumwith an EC50 value of 10.85 μg/mL. Full article
(This article belongs to the Section Chemistry)
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Open AccessArticle An Image Segmentation Method Using an Active Contour Model Based on Improved SPF and LIF
Appl. Sci. 2018, 8(12), 2576; https://doi.org/10.3390/app8122576
Received: 14 October 2018 / Revised: 28 November 2018 / Accepted: 8 December 2018 / Published: 11 December 2018
PDF Full-text (1526 KB) | Supplementary Files
Abstract
Inhomogeneous images cannot be segmented quickly or accurately using local or global image information. To solve this problem, an image segmentation method using a novel active contour model that is based on an improved signed pressure force (SPF) function and a local image
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Inhomogeneous images cannot be segmented quickly or accurately using local or global image information. To solve this problem, an image segmentation method using a novel active contour model that is based on an improved signed pressure force (SPF) function and a local image fitting (LIF) model is proposed in this paper, which is based on local and global image information. First, a weight function of the global grayscale means of the inside and outside of a contour curve is presented by combining the internal gray mean value with the external gray mean value, based on which a new SPF function is defined. The SPF function can segment blurred images and weak gradient images. Then, the LIF model is introduced by using local image information to segment intensity-inhomogeneous images. Subsequently, a weight function is established based on the local and global image information, and then the weight function is used to adjust the weights between the local information term and the global information term. Thus, a novel active contour model is presented, and an improved SPF- and LIF-based image segmentation (SPFLIF-IS) algorithm is developed based on that model. Experimental results show that the proposed method not only exhibits high robustness to the initial contour and noise but also effectively segments multiobjective images and images with intensity inhomogeneity and can analyze real images well. Full article
(This article belongs to the Special Issue Intelligent Imaging and Analysis)
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Open AccessArticle Chemical Composition of Lipophilic Bark Extracts from Pinus pinaster and Pinus pinea Cultivated in Portugal
Appl. Sci. 2018, 8(12), 2575; https://doi.org/10.3390/app8122575
Received: 25 November 2018 / Revised: 6 December 2018 / Accepted: 8 December 2018 / Published: 11 December 2018
PDF Full-text (352 KB)
Abstract
The chemical composition of lipophilic bark extracts from Pinus pinaster and Pinus pinea cultivated in Portugal was evaluated using gas chromatography-mass spectrometry. Diterpenic resin acids were found to be the main components of these lipophilic extracts, ranging from 0.96 g kg−1 dw
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The chemical composition of lipophilic bark extracts from Pinus pinaster and Pinus pinea cultivated in Portugal was evaluated using gas chromatography-mass spectrometry. Diterpenic resin acids were found to be the main components of these lipophilic extracts, ranging from 0.96 g kg−1 dw in P. pinea bark to 2.35 g kg−1 dw in P. pinaster bark. In particular, dehydroabietic acid (DHAA) is the major constituent of both P. pinea and P. pinaster lipophilic fractions, accounting for 0.45 g kg−1 dw and 0.95 g kg−1 dw, respectively. Interestingly, many oxidized compounds were identified in the studied lipophilic extracts, including DHAA-oxidized derivatives (7-oxo-DHAA, 7α/β-hydroxy-DHAA, and 15-hydroxy-DHAA, among others) and also terpin (an oxidized monoterpene). These compounds are not naturally occurring compounds, and their formation might occur by the exposure of the bark to light and oxygen from the air, and the action of micro-organisms. Some of these compounds have not been previously reported as lipophilic constituents of the bark of the referred pine species. Other constituents, such as aromatic compounds, fatty acids, fatty alcohols, and sterols, are also present in the studied extracts. These results can represent an opportunity to valorize P. pinaster and P. pinea by-products as a primary source of the bioactive resin acids that are integrated into the current uses of these species. Full article
(This article belongs to the Section Chemistry)
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Open AccessArticle An Improved Skewness Decision Tree SVM Algorithm for the Classification of Steel Cord Conveyor Belt Defects
Appl. Sci. 2018, 8(12), 2574; https://doi.org/10.3390/app8122574
Received: 13 November 2018 / Revised: 4 December 2018 / Accepted: 7 December 2018 / Published: 11 December 2018
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Abstract
Skewness Decision Tree Support Vector Machine (SDTSVM) algorithm is widely known as a supervised learning model for multi-class classification problems. However, the classification accuracy of the SDTSVM algorithm depends on the perfect selection of its parameters and the classification order. Therefore, an improved
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Skewness Decision Tree Support Vector Machine (SDTSVM) algorithm is widely known as a supervised learning model for multi-class classification problems. However, the classification accuracy of the SDTSVM algorithm depends on the perfect selection of its parameters and the classification order. Therefore, an improved SDTSVM (ISDTSVM) algorithm is proposed in order to improve the classification accuracy of steel cord conveyor belt defects. In the proposed model, the classification order is determined by the sum of the Euclidean distances between multi-class sample centers and the parameters are optimized by the inertia weight Particle Swarm Optimization (PSO) algorithm. In order to verify the effectiveness of the ISDTSVM algorithm with different feature space, experiments were conducted on multiple UCI (University of California Irvine) data sets and steel cord conveyor belt defects using the proposed ISDTSVM algorithm and the conventional SDTSVM algorithm respectively. The average classification accuracies of five-fold cross-validation were obtained, based on two kinds of kernel functions respectively. For the Vowel, Zoo, and Wine data sets of the UCI data sets, as well as the steel cord conveyor belt defects, the ISDTSVM algorithm improved the classification accuracy by 3%, 3%, 1% and 4% respectively, compared to the SDTSVM algorithm. The classification accuracy of the radial basis function kernel were higher than the polynomial kernel. The results indicated that the proposed ISDTSVM algorithm improved the classification accuracy significantly, compared to the conventional SDTSVM algorithm. Full article
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Open AccessArticle Control of Porosity in Parts Produced by a Direct Laser Melting Process
Appl. Sci. 2018, 8(12), 2573; https://doi.org/10.3390/app8122573
Received: 27 November 2018 / Revised: 8 December 2018 / Accepted: 10 December 2018 / Published: 11 December 2018
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Abstract
Recent advances in direct laser melting (DLM) have demonstrated its great potential for manufacturing three-dimensional porous metal parts. Various combinations of powder layering and processing parameters can be set to adjust the porous properties of the final parts. This study presents the effects
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Recent advances in direct laser melting (DLM) have demonstrated its great potential for manufacturing three-dimensional porous metal parts. Various combinations of powder layering and processing parameters can be set to adjust the porous properties of the final parts. This study presents the effects of powder morphologies and process parameters on porosity formation during DLM. Four types of Fe-powders composed of spherical or non-spherical particles with different sizes were experimentally investigated. Furthermore, the laser processing parameters, such as laser energy density, laser focus, and line spacing, which have a significant effect on the results, were characterized. In the case of a mixed powder composed of spherical and non-spherical powders, the packing density decreases as the non-spherical powder size increases. The porosity of the laser-melted layer increases with the degree of size misfit between the non-spherical and spherical powders. Decreased laser absorption and enlargement of the powder-depleted zone as a result of decreased packing density increases the porosity during DLM. The overall results show that the porosity of DLM parts could be actively controlled by adjusting the process parameters and powder morphologies. Full article
(This article belongs to the Section Optics and Lasers)
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Open AccessReview High Resolution Brillouin Sensing of Micro-Scale Structures
Appl. Sci. 2018, 8(12), 2572; https://doi.org/10.3390/app8122572
Received: 24 October 2018 / Revised: 23 November 2018 / Accepted: 25 November 2018 / Published: 11 December 2018
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Abstract
Brillouin distributed measurement techniques have been extensively developed for structural health monitoring using fibre optic nerve systems. The recent advancement in the spatial resolution capabilities of correlation-based Brillouin distributed technique have reached the sub-mm regime, making this approach a suitable candidate for monitoring
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Brillouin distributed measurement techniques have been extensively developed for structural health monitoring using fibre optic nerve systems. The recent advancement in the spatial resolution capabilities of correlation-based Brillouin distributed technique have reached the sub-mm regime, making this approach a suitable candidate for monitoring and characterizing integrated photonic devices. The small dimension associated with the short length of these devices—on the order of the cm- and mm-scale—requires high sensitivity detection techniques and sub-mm spatial resolution. In this paper, we provide an overview of the different Brillouin sensing techniques in various micro-scale structures such as photonic crystal fibres, microfibres, and on-chip waveguides. We show how Brillouin sensing is capable of detecting fine transverse geometrical features with the sensitivity of a few nm and also extremely small longitudinal features on the order of a few hundreds of μ m . We focus on the technique of Brillouin optical correlation domain analysis (BOCDA), which enables such high spatial resolution for mapping the opto-acoustic responses of micro-scale waveguides. Full article
(This article belongs to the Special Issue Optical Correlation-domain Distributed Fiber Sensors)
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Open AccessArticle Methodology for Optical Engine Characterization by Means of the Combination of Experimental and Modeling Techniques
Appl. Sci. 2018, 8(12), 2571; https://doi.org/10.3390/app8122571
Received: 19 November 2018 / Revised: 3 December 2018 / Accepted: 7 December 2018 / Published: 11 December 2018
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Abstract
Optical engines allow for the direct visualization of the phenomena taking place in the combustion chamber and the application of optical techniques for combustion analysis, which makes them invaluable tools for the study of advanced combustion modes aimed at reducing pollutant emissions and
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Optical engines allow for the direct visualization of the phenomena taking place in the combustion chamber and the application of optical techniques for combustion analysis, which makes them invaluable tools for the study of advanced combustion modes aimed at reducing pollutant emissions and increasing efficiency. An accurate thermodynamic analysis of the engine performance based on the in-cylinder pressure provides key information regarding the gas properties, the heat release, and the mixing conditions. If, in addition, optical access to the combustion process is provided, a deeper understanding of the phenomena can be derived, allowing the complete assessment of new injection-combustion strategies to be depicted. However, the optical engine is only useful for this purpose if the geometry, heat transfer, and thermodynamic conditions of the optical engine can mimic those of a real engine. Consequently, a reliable thermodynamic analysis of the optical engine itself is mandatory to accurately determine a number of uncertain parameters among which the effective compression ratio and heat transfer coefficient are of special importance. In the case of optical engines, the determination of such uncertainties is especially challenging due to their intrinsic features regarding the large mechanical deformations of the elongated piston caused by the pressure, and the specific thermal characteristics that affect the in-cylinder conditions. In this work, a specific methodology for optical engine characterization based on the combination of experimental measurements and in-cylinder 0D modeling is presented. On one hand, the method takes into account the experimental deformations measured with a high-speed camera in order to determine the effective compression ratio; on the other hand, the 0D thermodynamic analysis is used to calibrate the heat transfer model and to determine the rest of the uncertainties based on the minimization of the heat release rate residual in motored conditions. The method has been demonstrated to be reliable to characterize the optical engine, providing an accurate in-cylinder volume trace with a maximum deformation of 0.5 mm at 80 bar of peak pressure and good experimental vs. simulated in-cylinder pressure fitting. Full article
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Open AccessReview Machine Learning Approaches for Outdoor Air Quality Modelling: A Systematic Review
Appl. Sci. 2018, 8(12), 2570; https://doi.org/10.3390/app8122570
Received: 15 November 2018 / Revised: 6 December 2018 / Accepted: 8 December 2018 / Published: 11 December 2018
PDF Full-text (2100 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Current studies show that traditional deterministic models tend to struggle to capture the non-linear relationship between the concentration of air pollutants and their sources of emission and dispersion. To tackle such a limitation, the most promising approach is to use statistical models based
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Current studies show that traditional deterministic models tend to struggle to capture the non-linear relationship between the concentration of air pollutants and their sources of emission and dispersion. To tackle such a limitation, the most promising approach is to use statistical models based on machine learning techniques. Nevertheless, it is puzzling why a certain algorithm is chosen over another for a given task. This systematic review intends to clarify this question by providing the reader with a comprehensive description of the principles underlying these algorithms and how they are applied to enhance prediction accuracy. A rigorous search that conforms to the PRISMA guideline is performed and results in the selection of the 46 most relevant journal papers in the area. Through a factorial analysis method these studies are synthetized and linked to each other. The main findings of this literature review show that: (i) machine learning is mainly applied in Eurasian and North American continents and (ii) estimation problems tend to implement Ensemble Learning and Regressions, whereas forecasting make use of Neural Networks and Support Vector Machines. The next challenges of this approach are to improve the prediction of pollution peaks and contaminants recently put in the spotlights (e.g., nanoparticles). Full article
(This article belongs to the Special Issue Monitoring and Modeling: Air Quality Evaluation Studies)
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Open AccessArticle An Efficient Method to Learn Overcomplete Multi-Scale Dictionaries of ECG Signals
Appl. Sci. 2018, 8(12), 2569; https://doi.org/10.3390/app8122569
Received: 7 November 2018 / Revised: 21 November 2018 / Accepted: 22 November 2018 / Published: 11 December 2018
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Abstract
The electrocardiogram (ECG) was the first biomedical signal for which digital signal processing techniques were extensively applied. By its own nature, the ECG is typically a sparse signal, composed of regular activations (QRS complexes and other waveforms, such as the P and T
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The electrocardiogram (ECG) was the first biomedical signal for which digital signal processing techniques were extensively applied. By its own nature, the ECG is typically a sparse signal, composed of regular activations (QRS complexes and other waveforms, such as the P and T waves) and periods of inactivity (corresponding to isoelectric intervals, such as the PQ or ST segments), plus noise and interferences. In this work, we describe an efficient method to construct an overcomplete and multi-scale dictionary for sparse ECG representation using waveforms recorded from real-world patients. Unlike most existing methods (which require multiple alternative iterations of the dictionary learning and sparse representation stages), the proposed approach learns the dictionary first, and then applies a fast sparse inference algorithm to model the signal using the constructed dictionary. As a result, our method is much more efficient from a computational point of view than other existing algorithms, thus becoming amenable to dealing with long recordings from multiple patients. Regarding the dictionary construction, we located first all the QRS complexes in the training database, then we computed a single average waveform per patient, and finally we selected the most representative waveforms (using a correlation-based approach) as the basic atoms that were resampled to construct the multi-scale dictionary. Simulations on real-world records from Physionet’s PTB database show the good performance of the proposed approach. Full article
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Open AccessArticle An Observer-Based Active Fault Tolerant Controller for Vehicle Suspension System
Appl. Sci. 2018, 8(12), 2568; https://doi.org/10.3390/app8122568
Received: 24 October 2018 / Revised: 30 November 2018 / Accepted: 5 December 2018 / Published: 11 December 2018
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Abstract
This paper proposes an observer-based active fault-tolerant controller for a half-vehicle active suspension system subjected to the actuator fault as the nonzero offset fault. By constructing the augmented fault suspension system model, an H weighted output feedback controller was developed to improve
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This paper proposes an observer-based active fault-tolerant controller for a half-vehicle active suspension system subjected to the actuator fault as the nonzero offset fault. By constructing the augmented fault suspension system model, an H weighted output feedback controller was developed to improve the vehicle dynamics performances under a fault-free condition. Moreover, a robust observer was designed to make an accurate estimation of the fault information with the auxiliary diagnosis system and further to develop an H fault compensation controller, such that the closed-loop control system can eliminate the negative effects of the actuator faults on vehicle suspension performances. Finally, a numerical simulation investigation was provided to verify the effectiveness of the proposed controller under the random and bump road disturbances. Full article
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Open AccessArticle A Thermomechanical Analysis of Conformal Cooling Channels in 3D Printed Plastic Injection Molds
Appl. Sci. 2018, 8(12), 2567; https://doi.org/10.3390/app8122567
Received: 1 November 2018 / Revised: 4 December 2018 / Accepted: 7 December 2018 / Published: 11 December 2018
PDF Full-text (5123 KB) | HTML Full-text | XML Full-text
Abstract
Plastic injection molding is a versatile process, and a major part of the present plastic manufacturing industry. The traditional die design is limited to straight (drilled) cooling channels, which don’t impart optimal thermal (or thermomechanical) performance. With the advent of additive manufacturing technology,
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Plastic injection molding is a versatile process, and a major part of the present plastic manufacturing industry. The traditional die design is limited to straight (drilled) cooling channels, which don’t impart optimal thermal (or thermomechanical) performance. With the advent of additive manufacturing technology, injection molding tools with conformal cooling channels are now possible. However, optimum conformal channels based on thermomechanical performance are not found in the literature. This paper proposes a design methodology to generate optimized design configurations of such channels in plastic injection molds. The design of experiments (DOEs) technique is used to study the effect of the critical design parameters of conformal channels, as well as their cross-section geometries. In addition, designs for the “best” thermomechanical performance are identified. Finally, guidelines for selecting optimum design solutions given the plastic part thickness are provided. Full article
(This article belongs to the Special Issue 3D Printing of Metals)
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Open AccessArticle Identification and Monitoring of Parkinson’s Disease Dysgraphia Based on Fractional-Order Derivatives of Online Handwriting
Appl. Sci. 2018, 8(12), 2566; https://doi.org/10.3390/app8122566
Received: 30 October 2018 / Revised: 3 December 2018 / Accepted: 6 December 2018 / Published: 11 December 2018
PDF Full-text (443 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Parkinson’s disease dysgraphia affects the majority of Parkinson’s disease (PD) patients and is the result of handwriting abnormalities mainly caused by motor dysfunctions. Several effective approaches to quantitative PD dysgraphia analysis, such as online handwriting processing, have been utilized. In this study, we
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Parkinson’s disease dysgraphia affects the majority of Parkinson’s disease (PD) patients and is the result of handwriting abnormalities mainly caused by motor dysfunctions. Several effective approaches to quantitative PD dysgraphia analysis, such as online handwriting processing, have been utilized. In this study, we aim to deeply explore the impact of advanced online handwriting parameterization based on fractional-order derivatives (FD) on the PD dysgraphia diagnosis and its monitoring. For this purpose, we used 33 PD patients and 36 healthy controls from the PaHaW (PD handwriting database). Partial correlation analysis (Spearman’s and Pearson’s) was performed to investigate the relationship between the newly designed features and patients’ clinical data. Next, the discrimination power of the FD features was evaluated by a binary classification analysis. Finally, regression models were trained to explore the new features’ ability to assess the progress and severity of PD. These results were compared to a baseline, which is based on conventional online handwriting features. In comparison with the conventional parameters, the FD handwriting features correlated more significantly with the patients’ clinical characteristics and provided a more accurate assessment of PD severity (error around 12%). On the other hand, the highest classification accuracy (ACC = 97.14%) was obtained by the conventional parameters. The results of this study suggest that utilization of FD in combination with properly selected tasks (continuous and/or repetitive, such as the Archimedean spiral) could improve computerized PD severity assessment. Full article
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