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Appl. Sci., Volume 7, Issue 6 (June 2017)

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Editorial

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Open AccessEditorial Special Issue on Advancing Grid-Connected Renewable Generation Systems
Appl. Sci. 2017, 7(6), 577; doi:10.3390/app7060577
Received: 18 May 2017 / Revised: 31 May 2017 / Accepted: 31 May 2017 / Published: 3 June 2017
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(This article belongs to the Special Issue Advancing Grid-Connected Renewable Generation Systems)

Research

Jump to: Editorial, Review, Other

Open AccessArticle Endoscopic Laser-Based 3D Imaging for Functional Voice Diagnostics
Appl. Sci. 2017, 7(6), 600; doi:10.3390/app7060600
Received: 28 April 2017 / Revised: 29 May 2017 / Accepted: 6 June 2017 / Published: 9 June 2017
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Abstract
Recently, we reported on the in vivo application of a miniaturized measuring device for 3D visualization of the superior vocal fold vibrations from high-speed recordings in combination with a laser projection unit (LPU). As a long-term vision for this proof of principle, we
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Recently, we reported on the in vivo application of a miniaturized measuring device for 3D visualization of the superior vocal fold vibrations from high-speed recordings in combination with a laser projection unit (LPU). As a long-term vision for this proof of principle, we strive to integrate the further developed laserendoscopy as a diagnostic method in daily clinical routine. The new LPU mainly comprises a Nd:YAG laser source (532 nm/CW/2 ω ) and a diffractive optical element (DOE) generating a regular laser grid (31 × 31 laser points) that is projected on the vocal folds. By means of stereo triangulation, the 3D coordinates of the laser points are reconstructed from the endoscopic high-speed footage. The new design of the laserendoscope constitutes a compromise between robust image processing and laser safety regulations. The algorithms for calibration and analysis are now optimized with respect to their overall duration and the number of required interactions, which is objectively assessed using binary classifiers. The sensitivity and specificity of the calibration procedure are increased by 40.1% and 22.3%, which is statistically significant. The overall duration for the laser point detection is reduced by 41.9%. The suggested semi-automatic reconstruction software represents an important stepping-stone towards potential real time processing and a comprehensive, objective diagnostic tool of evidence-based medicine. Full article
(This article belongs to the Special Issue Laser Processing for Bioengineering Applications)
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Open AccessArticle Separation Control on a Bridge Box Girder Using a Bypass Passive Jet Flow
Appl. Sci. 2017, 7(6), 501; doi:10.3390/app7060501
Received: 2 March 2017 / Revised: 6 May 2017 / Accepted: 9 May 2017 / Published: 24 May 2017
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Abstract
In the present study, a bypass passive jet flow control method was proposed to mitigate unsteady wind loads and to manipulate the flow field around a single box girder of a bridge. With a geometric ratio of 1:125, the single box girder model
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In the present study, a bypass passive jet flow control method was proposed to mitigate unsteady wind loads and to manipulate the flow field around a single box girder of a bridge. With a geometric ratio of 1:125, the single box girder model was determined using the cross-section of the Great Belt East Bridge. During the experiments, one test model without control was adopted, while five different test models with different suction/jet configurations were employed to analyze the effects of the control method and to reveal the underlying mechanism of different control schemes. The incoming wind speed was fixed to 12 m/s and the wind attack angles were changed from −20° to 20°, resulting in a corresponding Reynolds number of Re = 0.28 × 105–0.74 × 105 based on the different attack angles. A six-component force balance, a set of digital sensor array (DSA) pressure transducers, and a particle image velocimetry (PIV) system was used to measure the aerodynamic forces, pressure distributions, and flow fields around the test models to evaluate the control effectiveness of different control cases. Detailed flow structures are presented and discussed for two test cases when the angles of attack are +15° and −20°. The effects of control on the aerodynamic forces were first investigated to determine and select the best one out of five control cases. The pressure distributions on the surface of the test model without control and the best control case were then compared to evaluate the control effectiveness of the pressure gradient and the fluctuating pressure coefficients. The flow fields around the test models demonstrate that the bypass passive jet flow control could decrease vortex strength, delay flow separation, and change recirculation region and size. The results of the aerodynamic forces, pressure distributions, and flow fields indicate that the bypass passive jet flow control method results in effective control. Full article
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Open AccessArticle A Statistical Model Updating Method of Beam Structures with Random Parameters under Static Load
Appl. Sci. 2017, 7(6), 601; doi:10.3390/app7060601
Received: 8 April 2017 / Revised: 31 May 2017 / Accepted: 5 June 2017 / Published: 9 June 2017
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Abstract
This paper presents a new statistical model updating method of beam structures with random parameters under static load. The new updating method considers structural parameters and measurement errors to be random. To reduce the unmeasured degrees of freedom in the finite element model,
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This paper presents a new statistical model updating method of beam structures with random parameters under static load. The new updating method considers structural parameters and measurement errors to be random. To reduce the unmeasured degrees of freedom in the finite element model, a static condensation technique is used in this method. A statistical model updating equation with respect to element updated factors is established afterwards. The element updated factors are expanded as random multivariate power series. Using a high-order perturbation technique, the statistical model updating equation can be solved to obtain the coefficients of the power series expansions of the element updated factors. The results of two numerical examples show that for the solution of the statistical model updating equation, the accuracy of the proposed method agrees with that of the Monte Carlo simulation method very well. The static responses obtained by the updated finite element model coincide with the measured results very well. Finally, a series of static load tests of the concrete beam are conducted to testify the effectiveness of the proposed method. Full article
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Open AccessArticle A Multi-Year Study on Rice Morphological Parameter Estimation with X-Band Polsar Data
Appl. Sci. 2017, 7(6), 602; doi:10.3390/app7060602
Received: 29 March 2017 / Revised: 24 May 2017 / Accepted: 8 June 2017 / Published: 9 June 2017
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Abstract
Rice fields have been monitored with spaceborne Synthetic Aperture Radar (SAR) systems for decades. SAR is an essential source of data and allows for the estimation of plant properties such as canopy height, leaf area index, phenological phase, and yield. However, the information
[...] Read more.
Rice fields have been monitored with spaceborne Synthetic Aperture Radar (SAR) systems for decades. SAR is an essential source of data and allows for the estimation of plant properties such as canopy height, leaf area index, phenological phase, and yield. However, the information on detailed plant morphology in meter-scale resolution is necessary for the development of better management practices. This letter presents the results of the procedure that estimates the stalk height, leaf length and leaf width of rice fields from a copolar X-band TerraSAR-X time series data based on a priori phenological phase. The methodology includes a computationally efficient stochastic inversion algorithm of a metamodel that mimics a radiative transfer theory-driven electromagnetic scattering (EM) model. The EM model and its metamodel are employed to simulate the backscattering intensities from flooded rice fields based on their simplified physical structures. The results of the inversion procedure are found to be accurate for cultivation seasons from 2013 to 2015 with root mean square errors less than 13.5 cm for stalk height, 7 cm for leaf length, and 4 mm for leaf width parameters. The results of this research provided new perspectives on the use of EM models and computationally efficient metamodels for agriculture management practices. Full article
(This article belongs to the Special Issue Polarimetric SAR Techniques and Applications)
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Open AccessArticle A New Life for Cross-Linked Plastic Waste as Aggregates and Binder Modifier for Asphalt Mixtures
Appl. Sci. 2017, 7(6), 603; doi:10.3390/app7060603
Received: 26 May 2017 / Revised: 5 June 2017 / Accepted: 6 June 2017 / Published: 10 June 2017
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Abstract
Every year, millions of tons of plastic waste, with potential to be reused, are wasted in landfills. Based on a literature review and in a local market analysis, cross-linked polyethylene (PEX) waste arose as the material with the greatest potential to be tested
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Every year, millions of tons of plastic waste, with potential to be reused, are wasted in landfills. Based on a literature review and in a local market analysis, cross-linked polyethylene (PEX) waste arose as the material with the greatest potential to be tested for incorporation in asphalt mixtures due to the difficulty in its recycling and the lack of solutions for its reuse. Thus, in the present work, mixtures produced with and without PEX were tested in order to compare their performance, aiming at understanding if this waste could successfully be used as an alternative material for this type of application. Thus, water sensitivity, rutting resistance, stiffness modulus and fatigue cracking resistance tests were carried out on asphalt mixtures with up to 5% PEX. Based on the results obtained, it can be concluded that the incorporation of PEX in asphalt mixtures is a viable solution for paving works, especially when high service temperatures are expected. It also decreases the density of the mixture, which can be attractive to lighten structures. Thus, this technology contributes to give new life to cross-linked polyethylene plastic waste. Full article
(This article belongs to the Special Issue Advanced Asphalt Materials and Paving Technologies)
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Open AccessArticle Effect of Seasonal Temperature on the Performance and on the Microbial Community of a Novel AWFR for Decentralized Domestic Wastewater Pretreatment
Appl. Sci. 2017, 7(6), 605; doi:10.3390/app7060605
Received: 27 February 2017 / Revised: 5 June 2017 / Accepted: 5 June 2017 / Published: 11 June 2017
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Abstract
Due to environmental burden and human health risks in developing countries, the treatment of decentralized domestic wastewater has been a matter of great concern in recent years. A novel pilot-scale three-stage anaerobic wool-felt filter reactor (AWFR) was designed to treat real decentralized domestic
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Due to environmental burden and human health risks in developing countries, the treatment of decentralized domestic wastewater has been a matter of great concern in recent years. A novel pilot-scale three-stage anaerobic wool-felt filter reactor (AWFR) was designed to treat real decentralized domestic wastewater at seasonal temperature variations of 8 to 35 °C for 364 days. The results showed that the average chemical oxygen demand (COD) removal efficiencies of AWFR in summer and winter were 76 ± 7.2% and 52 ± 5.9% at one day and three days Hydraulic Retention Time (HRT), respectively. COD mass balance analysis demonstrated that even though COD removal was lower in winter, approximately 43.5% of influent COD was still converted to methane. High-throughput MiSeq sequencing analyses indicated that Methanosaeta, Methanobacterium, and Methanolinea were the predominant methanogens, whereas the genus Bacillus probably played important roles in fermentation processes throughout the whole operation period. The performance and microbial community composition study suggested the application potential of the AWFR system for the pretreatment of decentralized domestic wastewater. Full article
(This article belongs to the Special Issue Wastewater Treatment and Reuse Technologies)
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Open AccessArticle Effects of Nozzle Configuration on Rock Erosion Under a Supercritical Carbon Dioxide Jet at Various Pressures and Temperatures
Appl. Sci. 2017, 7(6), 606; doi:10.3390/app7060606
Received: 18 May 2017 / Revised: 7 June 2017 / Accepted: 9 June 2017 / Published: 12 June 2017
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Abstract
The supercritical carbon dioxide (SC-CO2) jet offers many advantages over water jets in the field of oil and gas exploration and development. To take better advantage of the SC-CO2 jet, effects of nozzle configuration on rock erosion characteristics were experimentally
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The supercritical carbon dioxide (SC-CO2) jet offers many advantages over water jets in the field of oil and gas exploration and development. To take better advantage of the SC-CO2 jet, effects of nozzle configuration on rock erosion characteristics were experimentally investigated with respect to the erosion volume. A convergent nozzle and two Laval nozzles, as well as artificial cores were employed in the experiments. It was found that the Laval nozzle can enhance rock erosion ability, which largely depends on the pressure and temperature conditions. The enhancement increases with rising inlet pressure. Compared with the convergent nozzle, the Laval-1 nozzle maximally enhances the erosion volume by 10%, 21.2% and 30.3% at inlet pressures of 30, 40 and 50 MPa, respectively; while the Laval-2 nozzle maximally increases the erosion volume by 32.5%, 49.2% and 60%. Moreover, the enhancement decreases with increasing ambient pressure under constant inlet pressure or constant pressure drop. The growth of fluid temperature above the critical value can increase the enhancement. In addition, the jet from the Laval-2 nozzle with a smooth inner profile always has a greater erosion ability than that from the Laval-1 nozzle. Full article
(This article belongs to the Special Issue The Applications of Supercritical Carbon Dioxide)
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Open AccessArticle Improved Performance of High-Voltage Vertical GaN LEDs via Modification of Micro-Cell Geometry
Appl. Sci. 2017, 7(6), 506; doi:10.3390/app7060506
Received: 24 March 2017 / Revised: 7 May 2017 / Accepted: 9 May 2017 / Published: 24 May 2017
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Abstract
Vertical-type high-voltage light-emitting diodes (HV-LEDs) with 2 × 2 micro-cells were fabricated on Cu substrates, and the micro-cell geometry was modified to enhance the optoelectronic performance. The current spreading in micro-cell is most dominantly affected by the distance between electrode and edge of
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Vertical-type high-voltage light-emitting diodes (HV-LEDs) with 2 × 2 micro-cells were fabricated on Cu substrates, and the micro-cell geometry was modified to enhance the optoelectronic performance. The current spreading in micro-cell is most dominantly affected by the distance between electrode and edge of chip. When square cells were combined in a HV-LED, the device performance was poor due to an obvious current-crowding phenomenon that occurred near the electrodes. This was attributed that the electrodes in these four square micro-cells were all far away from the edges, resulting in the severe current-crowding phenomenon. On the contrary, as the HV-LED was prepared with four rectangle, triangle, or L-shaped micro-cells, the electrodes were close to the edges of micro-cells and the current spreading effect can be easily improved. Although a HV-LED connected with L-shaped cells possessed a better current spreading effect and a lower surface temperature, the light extraction was relatively low because of an electrode-shading loss effect. When triangular cells were used to prepare the HV-LED, the device achieved a superior optoelectronic performance compared with that of other cells because of a lower current-crowding effect and a more uniform light emission. After an epoxy package process, a lower forward voltage of 14.9 V and a higher output power of 353.2 mW were obtained using this HV-LED at an injection current of 80 mA. Additionally, the wall-plug efficiencies of this device at 20 and 80 mA were 41.1% and 29.7%, respectively. The results confirm that the design of triangular cell is beneficial for enhancing the optoelectronic performance of HV-LEDs. Furthermore, the fabrication processes of vertical LEDs have high potential for HV-LED applications. Full article
(This article belongs to the Section Optics and Lasers)
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Open AccessArticle The Influences of Assisting Gas Type and Process Parameters on the Fiber Laser Microprofiling of Thin CoCr Tubes for Vascular Stents
Appl. Sci. 2017, 7(6), 608; doi:10.3390/app7060608
Received: 24 March 2017 / Revised: 4 June 2017 / Accepted: 7 June 2017 / Published: 12 June 2017
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Abstract
Cobalt chromium (CoCr) alloy tubes have been widely used in manufacturing of vascular stents, due to their excellent bio-mechanical properties, especially their high strength. In recent years, fiber lasers have been used in the micro-machining of vascular stents, given their better cutting quality
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Cobalt chromium (CoCr) alloy tubes have been widely used in manufacturing of vascular stents, due to their excellent bio-mechanical properties, especially their high strength. In recent years, fiber lasers have been used in the micro-machining of vascular stents, given their better cutting quality than neodymium-doped yttrium aluminum garnet (Nd:YAG) lasers. A comparison study of CoCr fiber laser cutting with oxygen and argon is presented, and the differences, such as surface topography, chemical composition, and kerfs geometry, between the oxygen cuts and argon cuts are studied. Three types of topographies are obtained for the oxygen cuts, and the underlying reason for the different topographies are discussed. The influences of key parameters including power, repetition rate, pulse width, and cutting speed on the cutting quality are analyzed. The present research can also provide an optimization guideline for the micro-profiling of CoCr vascular stents. Full article
(This article belongs to the Section Optics and Lasers)
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Open AccessArticle Kinetics Study of Gas Pollutant Adsorption and Thermal Desorption on Silica Gel
Appl. Sci. 2017, 7(6), 609; doi:10.3390/app7060609
Received: 6 April 2017 / Revised: 7 June 2017 / Accepted: 8 June 2017 / Published: 12 June 2017
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Abstract
Silica gel is a typical porous desiccant material. Its adsorption performance for gaseous air pollutants was investigated to determine its potential contribution to reducing such pollutants. Three gaseous air pollutants, toluene, carbon dioxide, and methane, were investigated in this paper. A thermogravimetric analyzer
[...] Read more.
Silica gel is a typical porous desiccant material. Its adsorption performance for gaseous air pollutants was investigated to determine its potential contribution to reducing such pollutants. Three gaseous air pollutants, toluene, carbon dioxide, and methane, were investigated in this paper. A thermogravimetric analyzer was used to obtain the equilibrium adsorption capacity of gases on single silica gel particles. The silica gel adsorption capacity for toluene is much higher than that for carbon dioxide and methane. To understand gas pollutant thermal desorption from silica gel, the thermogravimetric analysis of toluene desorption was conducted with 609 ppm toluene vapor at 313 K, 323 K, and 333 K. The overall regeneration rate of silica gel was strongly dependent on temperature and the enthalpy of desorption. The gas pollutant adsorption performance and thermal desorption on silica gel material may be used to estimate the operating and design parameters for gas pollutant adsorption by desiccant wheels. Full article
(This article belongs to the Section Chemistry)
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Open AccessArticle Passive Vibration Control of a Semi-Submersible Floating Offshore Wind Turbine
Appl. Sci. 2017, 7(6), 509; doi:10.3390/app7060509
Received: 20 March 2017 / Revised: 8 May 2017 / Accepted: 9 May 2017 / Published: 26 May 2017
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Abstract
Floating offshore wind turbines have the potential to commercially convert the vast wind resource in deep-water area. Compared with fixed-bottom wind turbines, motions of the floating foundation complicate vibrations and loads of the wind turbine in offshore environment. To alleviate the responses of
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Floating offshore wind turbines have the potential to commercially convert the vast wind resource in deep-water area. Compared with fixed-bottom wind turbines, motions of the floating foundation complicate vibrations and loads of the wind turbine in offshore environment. To alleviate the responses of the wind turbine, this study investigates the use of fore–aft tuned mass damper (TMD) in nacelle/tower for passive control of a semi-submersible offshore wind turbine. A simplified structural model, considering the degree-of-freedom of platform pitch and surge, tower tilt and TMD translation, is proposed in the light of motion features of semi-submersible platform. After identifying ten unknown parameters, the correctness of the deterministic model is validated by pitch free decay responses. The mass, stiffness and damping of TMD are optimized using both method of exhaustion and genetic algorithm to avoid local minimum. Six optimized TMD devices are evaluated under three kinds of realistic environment conditions. The control effectiveness is assessed by the extreme and fatigue response reduction ratios. It is found that the high stiffness TMDs that directly dissipate the energy of tower oscillation exhibit an overall stable performance. Similar to the spar-type foundation, the TMDs in the nacelle/tower are capable of extending the service life of floating wind turbines. Full article
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Open AccessFeature PaperArticle Vibro-Acoustic Numerical Analysis for the Chain Cover of a Car Engine
Appl. Sci. 2017, 7(6), 610; doi:10.3390/app7060610
Received: 20 January 2017 / Revised: 18 May 2017 / Accepted: 8 June 2017 / Published: 12 June 2017
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Abstract
In this work, a vibro-acoustic numerical and experimental analysis was carried out for the chain cover of a low powered four-cylinder four-stroke diesel engine, belonging to the FPT (FCA Power Train) family called SDE (Small Diesel Engine). By applying a methodology used in
[...] Read more.
In this work, a vibro-acoustic numerical and experimental analysis was carried out for the chain cover of a low powered four-cylinder four-stroke diesel engine, belonging to the FPT (FCA Power Train) family called SDE (Small Diesel Engine). By applying a methodology used in the acoustic optimization of new FPT engine components, firstly a finite element model (FEM) of the engine was defined, then a vibration analysis was performed for the whole engine (modal analysis), and finally a forced response analysis was developed for the only chain cover (separated from the overall engine). The boundary conditions applied to the chain cover were the accelerations experimentally measured by accelerometers located at the points of connection among chain cover, head cover, and crankcase. Subsequently, a boundary element (BE) model of the only chain cover was realized to determine the chain cover noise emission, starting from the previously calculated structural vibrations. The numerical vibro-acoustic outcomes were compared with those experimentally observed, obtaining a good correlation. All the information thus obtained allowed the identification of those critical areas, in terms of noise generation, in which to undertake necessary improvements. Full article
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Open AccessArticle Application of Finite Layer Method in Pavement Structural Analysis
Appl. Sci. 2017, 7(6), 611; doi:10.3390/app7060611
Received: 25 April 2017 / Revised: 2 June 2017 / Accepted: 7 June 2017 / Published: 13 June 2017
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Abstract
The finite element (FE) method has been widely used in predicting the structural responses of asphalt pavements. However, the three-dimensional (3D) modeling in general-purpose FE software systems such as ABAQUS requires extensive computations and is relatively time-consuming. To address this issue, a specific
[...] Read more.
The finite element (FE) method has been widely used in predicting the structural responses of asphalt pavements. However, the three-dimensional (3D) modeling in general-purpose FE software systems such as ABAQUS requires extensive computations and is relatively time-consuming. To address this issue, a specific computational code EasyFEM was developed based on the finite layer method (FLM) for analyzing structural responses of asphalt pavements under a static load. Basically, it is a 3D FE code that requires only a one-dimensional (1D) mesh by incorporating analytical methods and using Fourier series in the other two dimensions, which can significantly reduce the computational time and required resources due to the easy implementation of parallel computing technology. Moreover, a newly-developed Element Energy Projection (EEP) method for super-convergent calculations was implemented in EasyFEM to improve the accuracy of solutions for strains and stresses over the whole pavement model. The accuracy of the program is verified by comparing it with results from BISAR and ABAQUS for a typical asphalt pavement structure. The results show that the predicted responses from ABAQUS and EasyFEM are in good agreement with each other. The EasyFEM with the EEP post-processing technique converges faster compared with the results derived from ordinary EasyFEM applications, which proves that the EEP technique can improve the accuracy of strains and stresses from EasyFEM. In summary, the EasyFEM has a potential to provide a flexible and robust platform for the numerical simulation of asphalt pavements and can easily be post-processed with the EEP technique to enhance its advantages. Full article
(This article belongs to the Special Issue Advanced Asphalt Materials and Paving Technologies)
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Open AccessArticle Composite Kernel Method for PolSAR Image Classification Based on Polarimetric-Spatial Information
Appl. Sci. 2017, 7(6), 612; doi:10.3390/app7060612
Received: 14 April 2017 / Revised: 31 May 2017 / Accepted: 9 June 2017 / Published: 13 June 2017
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Abstract
The composite kernel feature fusion proposed in this paper attempts to solve the problem of classifying polarimetric synthetic aperture radar (PolSAR) images. Here, PolSAR images take into account both polarimetric and spatial information. Various polarimetric signatures are collected to form the polarimetric feature
[...] Read more.
The composite kernel feature fusion proposed in this paper attempts to solve the problem of classifying polarimetric synthetic aperture radar (PolSAR) images. Here, PolSAR images take into account both polarimetric and spatial information. Various polarimetric signatures are collected to form the polarimetric feature space, and the morphological profile (MP) is used for capturing spatial information and constructing the spatial feature space. The main idea is that the composite kernel method encodes diverse information within a new kernel matrix and tunes the contribution of different types of features. A support vector machine (SVM) is used as the classifier for PolSAR images. The proposed approach is tested on a Flevoland PolSAR data set and a San Francisco Bay data set, which are in fine quad-pol mode. For the Flevoland PolSAR data set, the overall accuracy and kappa coefficient of the proposed method, compared with the traditional method, increased from 95.7% to 96.1% and from 0.920 to 0.942, respectively. For the San Francisco Bay data set, the overall accuracy and kappa coefficient of the proposed method increased from 92.6% to 94.4% and from 0.879 to 0.909, respectively. Experimental results verify the benefits of using both polarimetric and spatial information via composite kernel feature fusion for the classification of PolSAR images. Full article
(This article belongs to the Special Issue Polarimetric SAR Techniques and Applications)
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Open AccessArticle Direct-Current Forced Interruption and Breaking Performance of Spiral-Type Contacts in Aero Applications
Appl. Sci. 2017, 7(6), 512; doi:10.3390/app7060512
Received: 21 March 2017 / Revised: 3 May 2017 / Accepted: 10 May 2017 / Published: 26 May 2017
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Abstract
This paper analyses the transient characteristics and breaking performance of direct-current (DC) forced-interruption vacuum interrupters in 270 V power-supply systems. Three stages are identified in forced interruption: the DC-arcing stage, current-commutation stage, and voltage-recovery stage. During the current-commutation stage, the reverse peak-current coefficient
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This paper analyses the transient characteristics and breaking performance of direct-current (DC) forced-interruption vacuum interrupters in 270 V power-supply systems. Three stages are identified in forced interruption: the DC-arcing stage, current-commutation stage, and voltage-recovery stage. During the current-commutation stage, the reverse peak-current coefficient k, which is a key design factor, is used to calculate the rate of current at zero-crossing (di/dt). MATLAB/Simulink simulation models are established to obtain the transient characteristics influenced by the forced-commutation branch parameters and the coefficient k. To study the breaking performance of spiral-type contacts, experiments are conducted for different contact materials and arcing times for currents less than 3.5 kA. During the DC-arcing stage, a locally intensive burning arc is observed in the CuW80 contact; however, it is not observed in the CuCr50 contact. On examining the re-ignition interruption results of the CuW80 contact, the intensive burning arc is found to be positioned within a possible re-ignition region. When the arcing time is longer than 1 ms, the intensive burning arc occurs and affects the breaking performance of the spiral-type contacts. If the DC-arcing stage is prolonged, the total arcing energy increases, which leads to a lower breaking capacity. Full article
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Open AccessArticle Equivalence between Fuzzy PID Controllers and Conventional PID Controllers
Appl. Sci. 2017, 7(6), 513; doi:10.3390/app7060513
Received: 25 March 2017 / Revised: 3 May 2017 / Accepted: 6 May 2017 / Published: 2 June 2017
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Abstract
This paper proposes the equivalence between fuzzy Proportional-Integral-Derivative (PID) controllers and conventional PID controllers. A well-designed conventional PID controller, with the help of the proposed method, can be rapidly transformed to an equivalent fuzzy logic controller (FLC) by observing and defining the operating
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This paper proposes the equivalence between fuzzy Proportional-Integral-Derivative (PID) controllers and conventional PID controllers. A well-designed conventional PID controller, with the help of the proposed method, can be rapidly transformed to an equivalent fuzzy logic controller (FLC) by observing and defining the operating ranges of the input/output of the controller. Furthermore, the knowledge base of the proposed equivalent fuzzy PID controller is represented as a cube fuzzy associative memory (FAM), instead of a combination of PD-type and PI-type FLCs in most research. Simulation results show the feasibility of the proposed technique, both in continuous and discrete time. Since the design techniques of conventional linear PID controllers have matured, they can act as preliminary expert knowledge for nonlinear FLCs designs. Based on the proposed equivalence relationship, the designer can further tune the membership functions of fuzzy variables in the control rules to exhibit the nonlinearity of a FLC and yield more satisfactory system responses in an efficient way. Full article
(This article belongs to the Section Computer Science and Electrical Engineering)
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Open AccessArticle Energy Regeneration Hydraulic System via a Relief Valve with Energy Regeneration Unit
Appl. Sci. 2017, 7(6), 613; doi:10.3390/app7060613
Received: 21 April 2017 / Revised: 9 June 2017 / Accepted: 9 June 2017 / Published: 13 June 2017
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Abstract
Relief valves are widely used in industrial machinery. Due to the outlet of the relief valve being connected to the tank, the pressure drop of the relief valve is frequently equal to the inlet pressure. Accordingly, the energy loss of the relief valve
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Relief valves are widely used in industrial machinery. Due to the outlet of the relief valve being connected to the tank, the pressure drop of the relief valve is frequently equal to the inlet pressure. Accordingly, the energy loss of the relief valve is very high in some cases and this will worsen with an increase in the rated pressure of the hydraulic system. In order to overcome the disadvantage of overflow energy loss in a relief valve, a hydraulic energy regeneration unit (HERU) is connected to the outlet of the relief valve to decrease the pressure drop between the inlet and outlet of the relief valve. The overflow loss, which is characterized by the pressure drop, can be reduced accordingly. The approach is to convert the overflow energy loss in hydraulic form and allow for release when needed. The configuration and working principle of the relief valve with HERU is introduced in this present study. The mathematical model is established to obtain the factors influencing the stability of the relief valve. The working pressure of the hydraulic accumulator (HA) is explored. Furthermore, the control process of the operating state of the HA is scheduled to decide whether to regenerate the energy via the HERU. The software AMESim is utilized to analyze the performance and characteristics of the relief valve with HERU. Following this, the test rig is built and used to verify the effectiveness of the proposed relief valve with HERU. The experimental results show that the relief valve with the HERU connected to its outlet can still achieve better pressure-regulating characteristics. The energy regeneration efficiency saved by the HA is up to 83.6%, with a higher pre-charge pressure of the HA. This indicates that the proposed structure of the relief valve with HERU can achieve a better performance and higher regeneration efficiency. Full article
(This article belongs to the Special Issue Power Transmission and Control in Power and Vehicle Machineries)
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Open AccessArticle Terawatt-Isolated Attosecond X-ray Pulse Using a Tapered X-ray Free Electron Laser
Appl. Sci. 2017, 7(6), 614; doi:10.3390/app7060614
Received: 30 March 2017 / Revised: 29 May 2017 / Accepted: 8 June 2017 / Published: 13 June 2017
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Abstract
High power attosecond (as) X-ray pulses are in great demand for ultrafast dynamics and high resolution microscopy. We numerically demonstrate the generation of a ~230 attosecond, 1.5 terawatt (TW) pulse at a photon energy of 1 keV, and a 115 attosecond, 1.2 TW
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High power attosecond (as) X-ray pulses are in great demand for ultrafast dynamics and high resolution microscopy. We numerically demonstrate the generation of a ~230 attosecond, 1.5 terawatt (TW) pulse at a photon energy of 1 keV, and a 115 attosecond, 1.2 TW pulse at a photon energy of 12.4 keV, using the realistic electron beam parameters such as those of Korean X-ray free electron laser (XFEL) in a tapered undulator configuration. To compensate the energy loss of the electron beam and maximize its radiation power, a tapering is introduced in the downstream section of the undulator. It is found that the tapering helps in not only amplifying a target radiation pulse but also suppressing the growth of satellite radiation pulses. Tapering allows one to achieve a terawatt-attosecond pulse only with a 60 m long undulator. Such an attosecond X-ray pulse is inherently synchronized to a driving optical laser pulse; hence, it is well suited for the pump-probe experiments for studying the electron dynamics in atoms, molecules, and solids on the attosecond time-scale. For the realization of these experiments, a high level of synchronization up to attosecond precision between optical laser and X-ray pulse is demanded, which can be possible by using an interferometric feedback loop. Full article
(This article belongs to the Special Issue X-Ray Free-Electron Laser)
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Open AccessArticle Non-Pulse-Leakage 100-kHz Level, High Beam Quality Industrial Grade Nd:YVO4 Picosecond Amplifier
Appl. Sci. 2017, 7(6), 615; doi:10.3390/app7060615
Received: 27 April 2017 / Revised: 22 May 2017 / Accepted: 26 May 2017 / Published: 14 June 2017
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Abstract
A non-pulse-leakage optical fiber pumped 100-kHz level high beam quality Nd:YVO4 picosecond amplifier has been developed. An 80 MHz, 11.5 ps mode-locked picosecond laser is used as the seed with single pulse energy of 1 nJ. By harnessing the double β-BaB2
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A non-pulse-leakage optical fiber pumped 100-kHz level high beam quality Nd:YVO4 picosecond amplifier has been developed. An 80 MHz, 11.5 ps mode-locked picosecond laser is used as the seed with single pulse energy of 1 nJ. By harnessing the double β-BaB2O4 (BBO) crystal Pockels cells in both the pulse picker and regenerative amplifier, the seed pulse leakage of the output is suppressed effectively with an adjustable repetition rate from 200 to 500 kHz. Through one stage traveling-wave amplifier, a maximum output power of 24.5 W is generated corresponding to the injected regenerative amplified power of 9.73 W at 500 kHz. The output pulse duration is 16.9 ps, and the beam quality factor M2 is measured to be 1.25 with near-field roundness higher than 99% at the full output power. Full article
(This article belongs to the Special Issue Solid State Lasers Materials, Technologies and Applications)
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Open AccessArticle Smartphones as a Light Measurement Tool: Case of Study
Appl. Sci. 2017, 7(6), 616; doi:10.3390/app7060616
Received: 25 April 2017 / Revised: 29 May 2017 / Accepted: 7 June 2017 / Published: 14 June 2017
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Abstract
In recent years, smartphones have become the main computing tool for most of the population, making them an ideal tool in many areas. Most of these smartphones are equipped with cutting-edge hardware on their digital cameras, sensors and processors. For this reason, this
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In recent years, smartphones have become the main computing tool for most of the population, making them an ideal tool in many areas. Most of these smartphones are equipped with cutting-edge hardware on their digital cameras, sensors and processors. For this reason, this paper discusses the possibility of using smartphones as an accessible and accurate tool, focusing on the measurement of light, which is an element that has a high impact on human behavior, which promotes conformance and safety, or alters human physiology when it is inappropriate. To carry out this study, three different ways to measure light through smartphones have been checked: the ambient light sensor, the digital camera and an external Bluetooth luxmeter connected with the smartphone. As a result, the accuracy of these methods has been compared to check if they can be used as accurate measurement tools. Full article
(This article belongs to the Section Computer Science and Electrical Engineering)
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Open AccessArticle An Automatic Measurement Method for Absolute Depth of Objects in Two Monocular Images Based on SIFT Feature
Appl. Sci. 2017, 7(6), 517; doi:10.3390/app7060517
Received: 12 March 2017 / Revised: 2 May 2017 / Accepted: 9 May 2017 / Published: 25 May 2017
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Abstract
Recovering depth information of objects from two-dimensional images is one of the very important and basic problems in the field of computer vision. In view of the shortcomings of existing methods of depth estimation, a novel approach based on SIFT (the Scale Invariant
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Recovering depth information of objects from two-dimensional images is one of the very important and basic problems in the field of computer vision. In view of the shortcomings of existing methods of depth estimation, a novel approach based on SIFT (the Scale Invariant Feature Transform) is presented in this paper. The approach can estimate the depths of objects in two images which are captured by an un-calibrated ordinary monocular camera. In this approach, above all, the first image is captured. All of the camera parameters remain unchanged, and the second image is acquired after moving the camera a distance d along the optical axis. Then image segmentation and SIFT feature extraction are implemented on the two images separately, and objects in the images are matched. Lastly, an object’s depth can be computed by the lengths of a pair of straight line segments. In order to ensure that the most appropriate pair of straight line segments are chosen, and also reduce computation, convex hull theory and knowledge of triangle similarity are employed. The experimental results show our approach is effective and practical. Full article
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Open AccessArticle Synthesis and Biophysical Insights into the Binding of a Potent Anti-Proliferative Non-symmetric Bis-isatin Derivative with Bovine Serum Albumin: Spectroscopic and Molecular Docking Approaches
Appl. Sci. 2017, 7(6), 617; doi:10.3390/app7060617
Received: 21 May 2017 / Revised: 11 June 2017 / Accepted: 12 June 2017 / Published: 14 June 2017
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Abstract
As part of the research endeavors to combat cancer, a non-symmetric bis-isatin derivative (compound 3) was synthesized and showed a significant anti-proliferative potency. The current study provides a comprehensive characterization of the interaction of compound 3 with the drug-transporting protein bovine serum
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As part of the research endeavors to combat cancer, a non-symmetric bis-isatin derivative (compound 3) was synthesized and showed a significant anti-proliferative potency. The current study provides a comprehensive characterization of the interaction of compound 3 with the drug-transporting protein bovine serum albumin (BSA) via the use of spectroscopic tools along with molecular docking studies. Fluorescence spectral measurements showed that the BSA intrinsic fluorescence can be significantly quenched by the addition of compound 3 and the formation of a non-fluorescent complex. Further measurements revealed a static type of quenching with Stern–Volmer and Linweaver–Burk constants of 105. The thermodynamic parameters of the binding were calculated to be ΔS° 105.09 ± 5.32 with ΔH° of −0.72 ± 0.71 and negative ΔG° values. In addition, synchronous fluorescence and 3D fluorescence spectroscopy suggested that compound 3 did not induce conformational changes in BSA. Site competition experiments revealed that compound 3 competes with warfarin within the BSA binding domain (Sudlow site I). This was further confirmed by the molecular docking results showing a binding energy of −25.93 kJ/mol for compound 3-BSA. Hence, the observed results in the present study assumed that the compound 3-BSA binding is spontaneous, involving electrostatic forces and hydrogen bonding. Full article
(This article belongs to the Section Chemistry)
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Open AccessFeature PaperArticle Iridescent Perfect Absorption in Critically-Coupled Acoustic Metamaterials Using the Transfer Matrix Method
Appl. Sci. 2017, 7(6), 618; doi:10.3390/app7060618
Received: 31 May 2017 / Revised: 7 June 2017 / Accepted: 12 June 2017 / Published: 14 June 2017
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Abstract
The absorption performance of a locally-reacting acoustic metamaterial under oblique incidence is studied. The metamaterial is composed of a slotted panel, each slit being loaded by an array of Helmholtz resonators. The system is analytically studied using the transfer matrix method, accounting for
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The absorption performance of a locally-reacting acoustic metamaterial under oblique incidence is studied. The metamaterial is composed of a slotted panel, each slit being loaded by an array of Helmholtz resonators. The system is analytically studied using the transfer matrix method, accounting for the viscothermal losses both in the resonator elements and in the slits, allowing the representation of the reflection coefficient in the complex frequency plane. We show that by tuning the geometry of the metamaterial, perfect absorption peaks can be obtained on demand at selected frequencies and different angles of incidence. When tilting the incidence angle, the peaks of perfect absorption are shifted in frequency, producing an acoustic iridescence effect similar to the optic iridescence achieved by incomplete band gap. Effectively, we show that in this kind of locally-reacting metamaterial, perfect and omnidirectional absorption for a given frequency is impossible to achieve because the metamaterial impedance does not depend on the incidence angle (i.e., the impedance is a locally reacting one). The system is interpreted in the complex frequency plane by analysing the trajectories of the zeros of the reflection coefficient. We show that the trajectories of the zeros do not overlap under oblique incidence, preventing the observation of perfect and omnidirectional absorption in locally reacting metamaterials. Moreover, we show that for any locally resonant material, the absorption in diffuse field takes a maximal value of 0.951, which is achieved by a material showing perfect absorption for an incidence angle of 50.34 degrees. Full article
(This article belongs to the Section Acoustics)
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Open AccessArticle Simulation Investigation on Combustion Characteristics in a Four-Point Lean Direct Injection Combustor with Hydrogen/Air
Appl. Sci. 2017, 7(6), 619; doi:10.3390/app7060619
Received: 5 May 2017 / Revised: 5 June 2017 / Accepted: 12 June 2017 / Published: 14 June 2017
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Abstract
To investigate the combustion characteristics in multi-point lean direct injection (LDI) combustors with hydrogen/air, two swirl–venturi 2 × 2 array four-point LDI combustors were designed. The four-point LDI combustor consists of injector assembly, swirl–venturi array and combustion chamber. The injector, swirler and venturi
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To investigate the combustion characteristics in multi-point lean direct injection (LDI) combustors with hydrogen/air, two swirl–venturi 2 × 2 array four-point LDI combustors were designed. The four-point LDI combustor consists of injector assembly, swirl–venturi array and combustion chamber. The injector, swirler and venturi together govern the rapid mixing of hydrogen and air to form the mixture for combustion. Using clockwise swirlers and anticlockwise swirlers, the co-swirling and count-swirling swirler arrays LDI combustors were achieved. Using Reynolds-Averaged Navier–Stokes (RANS) code for steady-state reacting flow computations, the four-point LDI combustors with hydrogen/air were simulated with an 11 species and 23 lumped reaction steps H2/Air reaction mechanism. The axial velocity, turbulence kinetic energy, total pressure drop coefficient, outlet temperature, mass fraction of OH and emission of pollutant NO of four-point LDI combustors, with different equivalence ratios, are here presented and discussed. As the equivalence ratios increased, the total pressure drop coefficient became higher because of increasing heat loss. Increasing equivalence ratios also corresponded with the rise in outlet temperature of the four-point LDI combustors, as well as an increase in the emission index of NO EINO in the four-point LDI combustors. Along the axial distance, the EINO always increased and was at maximum at the exit of the dump. Along the chamber, the EINO gradually increased, maximizing at the exit of chamber. The total temperature of four-point LDI combustors with different equivalence ratios was identical to the theoretical equilibrium temperature. The EINO was an exponential function of the equivalence ratio. Full article
(This article belongs to the Special Issue Clean Energy and Fuel (Hydrogen) Storage)
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Open AccessArticle Experimental Investigations of Composite Adsorbent 13X/CaCl2 on an Adsorption Cooling System
Appl. Sci. 2017, 7(6), 620; doi:10.3390/app7060620
Received: 7 April 2017 / Revised: 23 May 2017 / Accepted: 12 June 2017 / Published: 14 June 2017
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Abstract
A new experimental device which tests the adsorption performance of the 13X/CaCl2 composite adsorbent under vacuum conditions was established. In this device, heat transfer characteristics in the adsorbent bed have a great influence on the adsorbent performance, the temperature of the bottom
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A new experimental device which tests the adsorption performance of the 13X/CaCl2 composite adsorbent under vacuum conditions was established. In this device, heat transfer characteristics in the adsorbent bed have a great influence on the adsorbent performance, the temperature of the bottom outside bed is very close to the temperature of the bottom inside bed and the temperature difference between them at the end of heating and cooling are 5.66 °C and 0.303 °C, respectively. The following conclusions could be drawn: the equilibrium water uptake of composite adsorbent CA10X (zeolite 13X impregnated with 10 wt % CaCl2 solution) was increased 5.7% compared with that of 13X, and the water uptake was 0.37 g/g. The composite adsorbent CA10X has a better performance in the adsorption refrigeration system. Full article
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Open AccessArticle Application of Matched-Filter Concepts to Unbiased Selection of Data in Pump-Probe Experiments with Free Electron Lasers
Appl. Sci. 2017, 7(6), 621; doi:10.3390/app7060621
Received: 27 April 2017 / Revised: 6 June 2017 / Accepted: 9 June 2017 / Published: 16 June 2017
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Abstract
Pump-probe experiments are commonly used at Free Electron Lasers (FEL) to elucidate the femtosecond dynamics of atoms, molecules, clusters, liquids and solids. Maximizing the signal-to-noise ratio of the measurements is often a primary need of the experiment, and the aggregation of repeated, rapid,
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Pump-probe experiments are commonly used at Free Electron Lasers (FEL) to elucidate the femtosecond dynamics of atoms, molecules, clusters, liquids and solids. Maximizing the signal-to-noise ratio of the measurements is often a primary need of the experiment, and the aggregation of repeated, rapid, scans of the pump-probe delay is preferable to a single long-lasting scan. The limited availability of beamtime makes it impractical to repeat measurements indiscriminately, and the large, rapid flow of single-shot data that need to be processed and aggregated into a dataset, makes it difficult to assess the quality of a measurement in real time. In post-analysis it is then necessary to devise unbiased criteria to select or reject datasets, and to assign the weight with which they enter the analysis. One such case was the measurement of the lifetime of Intermolecular Coulombic Decay in the weakly-bound neon dimer. We report on the method we used to accomplish this goal for the pump-probe delay scans that constitute the core of the measurement; namely we report on the use of simple auto- and cross-correlation techniques based on the general concept of “matched filter”. We are able to unambiguously assess the signal-to-noise ratio (SNR) of each scan, which then becomes the weight with which a scan enters the average of multiple scans. We also observe a clear gap in the values of SNR, and we discard all the scans below a SNR of 0.45. We are able to generate an average delay scan profile, suitable for further analysis: in our previous work we used it for comparison with theory. Here we argue that the method is sufficiently simple and devoid of human action to be applicable not only in post-analysis, but also for the real-time assessment of the quality of a dataset. Full article
(This article belongs to the Special Issue X-Ray Free-Electron Laser)
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Open AccessArticle ANN Sizing Procedure for the Day-Ahead Output Power Forecast of a PV Plant
Appl. Sci. 2017, 7(6), 622; doi:10.3390/app7060622
Received: 4 May 2017 / Revised: 5 June 2017 / Accepted: 12 June 2017 / Published: 15 June 2017
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Abstract
Since the beginning of this century, the share of renewables in Europe’s total power capacity has almost doubled, becoming the largest source of its electricity production. In 2015 alone, photovoltaic (PV) energy generation rose with a rate of more than 5%; nowadays, Germany,
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Since the beginning of this century, the share of renewables in Europe’s total power capacity has almost doubled, becoming the largest source of its electricity production. In 2015 alone, photovoltaic (PV) energy generation rose with a rate of more than 5%; nowadays, Germany, Italy, and Spain account together for almost 70% of total European PV generation. In this context, the so-called day-ahead electricity market represents a key trading platform, where prices and exchanged hourly quantities of energy are defined 24 h in advance. Thus, PV power forecasting in an open energy market can greatly benefit from machine learning techniques. In this study, the authors propose a general procedure to set up the main parameters of hybrid artificial neural networks (ANNs) in terms of the number of neurons, layout, and multiple trials. Numerical simulations on real PV plant data are performed, to assess the effectiveness of the proposed methodology on the basis of statistical indexes, and to optimize the forecasting network performance. Full article
(This article belongs to the Special Issue Computational Intelligence in Photovoltaic Systems)
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Open AccessArticle Analysis of Preparation and Properties on Shape Memory Hydrogenated Epoxy Resin Used for Asphalt Mixtures
Appl. Sci. 2017, 7(6), 523; doi:10.3390/app7060523
Received: 18 April 2017 / Revised: 11 May 2017 / Accepted: 15 May 2017 / Published: 23 May 2017
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Abstract
The objective of this investigation is to prepare the shape memory hydrogenated epoxy resin used for asphalt mixtures (SM-HEP-AM) and study its properties. The shape memory hydrogenated epoxy resin (SM-HEP) is prepared using hydrogenated bisphenol A epoxy resin (AL-3040), polypropylene glycol diglycidylether diacrylate
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The objective of this investigation is to prepare the shape memory hydrogenated epoxy resin used for asphalt mixtures (SM-HEP-AM) and study its properties. The shape memory hydrogenated epoxy resin (SM-HEP) is prepared using hydrogenated bisphenol A epoxy resin (AL-3040), polypropylene glycol diglycidylether diacrylate (JH-230), and isophorone diamine (IPDA). The formulations of the SM-HEP-AM are obtained by the linearly fitted method. The thermo-mechanical property, molecular structure, and shape-memory performance of the SM-HEP-AM are studied. The glass-transition temperature (Tg) is determined using the differential scanning calorimeter (DSC). The results proved that the Tg level increased when the JH-230 content decreased. The thermo-mechanical property of the SM-HEP-AM is measured by dynamical mechanical analysis (DMA). The storage modulus of the SM-HEP-AM decreased with the increase in the JH-230 content. The above phenomena are attributed to the change in the JH-230 content. The shape memory performance results of the SM-HEP-AM indicate that specimen deformation can completely recover after only several minutes at Tg + 10 °C and Tg + 20 °C. The shape recovery time of the SM-HEP-AM increases with increased JH-230 content, and the change between the shape recovery time and JH-230 content gradually decreased as the temperature increased. The deformation recovery performance of asphalt mixture with and without the SM-HEP-AM (Tg = 40 °C) was tested by the deformation recovery test. This was used to prove that the SM-HEP-AM helps to improve the deformation recovery performance of the asphalt mixture. Full article
(This article belongs to the Section Mechanical Engineering)
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Open AccessFeature PaperArticle Combined CFD-Stochastic Analysis of an Active Fluidic Injection System for Jet Noise Reduction
Appl. Sci. 2017, 7(6), 623; doi:10.3390/app7060623
Received: 3 May 2017 / Revised: 13 June 2017 / Accepted: 14 June 2017 / Published: 16 June 2017
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Abstract
In the framework of DANTE project (Development of Aero-Vibroacoustics Numerical and Technical Expertise), funded under the Italian Aerospace Research Program (PRORA), the prediction and reduction of noise from subsonic jets through the reconstruction of turbulent fields from Reynolds Averaged Navier Stokes (RANS) calculations
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In the framework of DANTE project (Development of Aero-Vibroacoustics Numerical and Technical Expertise), funded under the Italian Aerospace Research Program (PRORA), the prediction and reduction of noise from subsonic jets through the reconstruction of turbulent fields from Reynolds Averaged Navier Stokes (RANS) calculations are addressed. This approach, known as Stochastic Noise Generation and Radiation (SNGR), reconstructs the turbulent velocity fluctuations by RANS fields and calculates the source terms of Vortex Sound acoustic analogy. In the first part of this work, numerical and experimental jet-noise test cases have been reproduced by means RANS simulations and with different turbulence models in order to validate the approach for its subsequent use as a design tool. The noise spectra, predicted with SNGR, are in good agreement with both the experimental data and the results of Large-Eddy Simulations (LES). In the last part of this work, an active fluid injection technique, based on extractions from turbine and injections of high-pressure gas into the main stream of exhausts, has been proposed and finally assessed with the aim of reducing the jet-noise through the mixing and breaking of the turbulent eddies. Some tests have been carried out in order to set the best design parameters in terms of mass flow rate and injection velocity and to design the system functionalities. The SNGR method is, therefore, suitable to be used for the early design phase of jet-noise reduction technologies and a right combination of the fluid injection design parameters allows for a reduction of the jet-noise to 3.5 dB, as compared to the baseline case without injections. Full article
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Open AccessArticle Efficiency Evaluation of Operation Analysis Systems Based on Dynamic Data Envelope Analysis Models from a Big Data Perspective
Appl. Sci. 2017, 7(6), 624; doi:10.3390/app7060624
Received: 14 April 2017 / Revised: 12 June 2017 / Accepted: 12 June 2017 / Published: 16 June 2017
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Abstract
The operating environment of power grid enterprises is complex with a range of monitoring indicators. To grasp the overall operational status in time and find the key affecting factors, Balanced Scorecard Card (BSC), Interpretive Structural Model (ISM), Principal component analysis (PCA) should be
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The operating environment of power grid enterprises is complex with a range of monitoring indicators. To grasp the overall operational status in time and find the key affecting factors, Balanced Scorecard Card (BSC), Interpretive Structural Model (ISM), Principal component analysis (PCA) should be applied. This paper proposed several grid enterprise operators and monitoring indicator systems (which include achievement indicators and driver indicators), and applied PCA for verification and evaluation. The achievement indicators mainly reflected the effectiveness of business operations, which included corporate value, social value, customer value, and so on. Driver indicators mainly reflected the core resources and operations process management of business operations, which have a direct impact on the achievement indicators. The driver and achievement indicators were used as input and output indicators for the provinces to assess the efficiency of operations, and appropriate measures were proposed for improvement. The results showed that the dynamic data envelopment analysis (DEA) model could reflect the time lag of the grid enterprises operating investment and income much better than the other two methods, and the static changes compared to assess efficiency had an average around 4%. Full article
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Open AccessArticle Large Earthquake Magnitude Prediction in Chile with Imbalanced Classifiers and Ensemble Learning
Appl. Sci. 2017, 7(6), 625; doi:10.3390/app7060625
Received: 19 April 2017 / Revised: 31 May 2017 / Accepted: 13 June 2017 / Published: 16 June 2017
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Abstract
This work presents a novel methodology to predict large magnitude earthquakes with horizon of prediction of five days. For the first time, imbalanced classification techniques are applied in this field by attempting to deal with the infrequent occurrence of such events. So far,
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This work presents a novel methodology to predict large magnitude earthquakes with horizon of prediction of five days. For the first time, imbalanced classification techniques are applied in this field by attempting to deal with the infrequent occurrence of such events. So far, classical classifiers were not able to properly mine these kind of datasets and, for this reason, most of the methods reported in the literature were only focused on moderate magnitude prediction. As an additional step, outputs from different algorithms are combined by applying ensemble learning. Since false positives are quite undesirable in this field, due to the social impact that they might cause, ensembles have been designed in order to reduce these situations. The methodology has been tested on different cities of Chile, showing very promising results in terms of accuracy. Full article
(This article belongs to the Section Computer Science and Electrical Engineering)
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Open AccessArticle A Wireless Sensor Network Using GNSS Receivers for a Short-Term Assessment of the Modal Properties of the Neckartal Bridge
Appl. Sci. 2017, 7(6), 626; doi:10.3390/app7060626
Received: 31 March 2017 / Revised: 30 May 2017 / Accepted: 8 June 2017 / Published: 16 June 2017
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Abstract
In this article, we present a novel structural health monitoring system based on a wireless sensor network for GNSS (global navigation satellite system) receivers. The GNSS network presented here consists of three GNSS rover stations and one base station that are deployed at
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In this article, we present a novel structural health monitoring system based on a wireless sensor network for GNSS (global navigation satellite system) receivers. The GNSS network presented here consists of three GNSS rover stations and one base station that are deployed at the Neckartal bridge on the Autobahn A81 in southwest Germany. The newly-developed GNSS sensor nodes support satellite data logging up to a sampling rate of 20 Hz. Due to the ultra-low-power consumption achieved by the wake-up receiver during inactive periods, the nodes offer a lifetime from 20 to almost 200 days, without energy harvesting and depending on the satellite data logging period. By performing differential post-processing, precise positioning information in the millimeter range could be achieved. Using the GNSS sensors, we determined resonant frequencies at 0.33 Hz and 1.31 Hz, mainly in the lateral direction of the bridge. To verify the GNSS results, we placed an accelerometer on the bridge. The frequencies detected by the acceleration sensor correspond well to the frequencies found by the GNSS sensors, although the accelerometer measured further higher frequencies as it is probably more sensitive to small amplitudes. Full article
(This article belongs to the Special Issue Structural Health Monitoring (SHM) of Civil Structures)
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Open AccessArticle Stereoscopic Image Super-Resolution Method with View Incorporation and Convolutional Neural Networks
Appl. Sci. 2017, 7(6), 526; doi:10.3390/app7060526
Received: 6 March 2017 / Revised: 10 May 2017 / Accepted: 12 May 2017 / Published: 26 May 2017
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Abstract
Super-resolution (SR) plays an important role in the processing and display of mixed-resolution (MR) stereoscopic images. Therefore, a stereoscopic image SR method based on view incorporation and convolutional neural networks (CNN) is proposed. For a given MR stereoscopic image, the left view of
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Super-resolution (SR) plays an important role in the processing and display of mixed-resolution (MR) stereoscopic images. Therefore, a stereoscopic image SR method based on view incorporation and convolutional neural networks (CNN) is proposed. For a given MR stereoscopic image, the left view of which is observed in full resolution, while the right view is viewed in low resolution, the SR method is implemented in two stages. In the first stage, a view difference image is defined to represent the correlation between views. It is estimated by using the full-resolution left view and the interpolated right view as input to the modified CNN. Accordingly, a high-precision view difference image is obtained. In the second stage, to incorporate the estimated right view in the first stage, a global reconstruction constraint is presented to make the estimated right view consistent with the low-resolution right view in terms of the MR stereoscopic image observation model. Experimental results demonstrated that, compared with the SR convolutional neural network (SRCNN) method and depth map based SR method, the proposed method improved the reconstructed right view quality by 0.54 dB and 1.14 dB, respectively, in the Peak Signal to Noise Ratio (PSNR), and subjective evaluation also implied that the proposed method produced better reconstructed stereoscopic images. Full article
(This article belongs to the Special Issue Holography and 3D Imaging: Tomorrows Ultimate Experience)
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Open AccessArticle Entropy Analysis for Damage Quantification of Hysteretic Dampers Used as Seismic Protection of Buildings
Appl. Sci. 2017, 7(6), 628; doi:10.3390/app7060628
Received: 7 May 2017 / Revised: 1 June 2017 / Accepted: 13 June 2017 / Published: 17 June 2017
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Abstract
Relative wavelet energy entropy (RWEE) is proposed to detect and quantify damage to hysteretic dampers used for the passive seismic control of building structures. Hysteretic dampers have the role of dissipating most of the energy input of an earthquake. Minor or moderate earthquakes
[...] Read more.
Relative wavelet energy entropy (RWEE) is proposed to detect and quantify damage to hysteretic dampers used for the passive seismic control of building structures. Hysteretic dampers have the role of dissipating most of the energy input of an earthquake. Minor or moderate earthquakes do not exhaust the energy dissipation capacity of the dampers, yet they damage them. For this reason, continuous or periodic damper-health evaluation is required to decide if they need to be replaced. Such evaluation calls for the application of efficient structural health monitoring techniques (SHM). This paper focuses on the well-known vibration technique, which is applied to a particular type of hysteretic damper called Web Plastifying Damper (WPD), patented by the University of Granada. Vibration signals, properly recorded by piezoelectric sensors attached around the damaged area of the dampers, are decomposed by means of wavelet packet analysis. Then, the relative wavelet energy entropy of these decompositions is used to calculate the proposed index. Validation of RWEE for this particular application involved dampers installed in two different specimens of reinforced concrete structures subjected to earthquake sequences of increasing intensity. When compared with a well-established mechanical energy-based damage index, results demonstrate that RWEE is a successful and low-cost technique for reliable in-situ monitoring of dampers. Full article
(This article belongs to the Section Mechanical Engineering)
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Open AccessArticle Experimental Study and Numerical Simulation of a Laminated Reinforced Concrete Shear Wall with a Vertical Seam
Appl. Sci. 2017, 7(6), 629; doi:10.3390/app7060629
Received: 10 April 2017 / Revised: 2 June 2017 / Accepted: 13 June 2017 / Published: 17 June 2017
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Abstract
In this paper, 12 laminated reinforced concrete shear walls are designed for cyclic loading tests. Seismic performance of laminated reinforced concrete shear walls with vertical seams are evaluated by the failure mode, deformability, hysteresis curve, stiffness degradation, and energy dissipation capacity. In addition,
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In this paper, 12 laminated reinforced concrete shear walls are designed for cyclic loading tests. Seismic performance of laminated reinforced concrete shear walls with vertical seams are evaluated by the failure mode, deformability, hysteresis curve, stiffness degradation, and energy dissipation capacity. In addition, two different construction measures and construction techniques are designed to study their influence on the wall behavior, which provides a reference for the construction of laminated reinforced concrete shear walls. The numerical simulation of the specimen is carried out with ABAQUS, which is in good agreement with the experimental results. These results provide a technical basis for the design, application, and construction of the laminated reinforced concrete shear wall structure. Full article
(This article belongs to the Special Issue The Industrialization of the Building Construction Process)
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Open AccessArticle Comparative Study of Stator Configurations of a Permanent Magnet Linear Oscillating Actuator for Orbital Friction Vibration Actuator
Appl. Sci. 2017, 7(6), 630; doi:10.3390/app7060630
Received: 8 April 2017 / Revised: 20 May 2017 / Accepted: 5 June 2017 / Published: 17 June 2017
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Abstract
A PM orbital friction vibration actuator (OFVA) which composes four linear oscillating actuators (LOA) is proposed in this paper. This paper presents the design, analysis, and experimental validation of stator configuration of a permanent magnet LOA to improve its thrust force characteristics. First,
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A PM orbital friction vibration actuator (OFVA) which composes four linear oscillating actuators (LOA) is proposed in this paper. This paper presents the design, analysis, and experimental validation of stator configuration of a permanent magnet LOA to improve its thrust force characteristics. First, the magnetized topology and the coil configuration are interpreted. The optimization design goal of the LOA was established and the end effects of the actuator are illustrated. The influences of stator design parameters on the performance of LOA were investigated and the optimal parameters have been identified with reference to the thrust force density and thrust force ripple. Results showed that a quasi‐Halbach magnetized E‐cored LOA with obtrapezoid teeth has the best electromagnetic performances of all the LOAs examined here. Finally, the predicted thrust force characteristics were validated by measurements on a prototype actuator. Full article
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Open AccessArticle Demonstration of High-Speed Optical Transmission at 2 µm in Titanium Dioxide Waveguides
Appl. Sci. 2017, 7(6), 631; doi:10.3390/app7060631
Received: 16 May 2017 / Revised: 12 June 2017 / Accepted: 15 June 2017 / Published: 17 June 2017
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Abstract We demonstrate the transmission of a 10-Gbit/s optical data signal in the 2 µm waveband into titanium dioxide waveguides. Error-free transmissions have been experimentally achieved taking advantage of a 23-dB insertion loss fiber-to-fiber grating-based injection test-bed platform. Full article
(This article belongs to the Special Issue Guided-Wave Optics)
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Open AccessArticle Supercritical Transesterification of Waste Vegetable Oil: Characteristic Comparison of Ethanol and Methanol as Solvents
Appl. Sci. 2017, 7(6), 632; doi:10.3390/app7060632
Received: 15 May 2017 / Revised: 9 June 2017 / Accepted: 12 June 2017 / Published: 17 June 2017
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Abstract
Transesterification of waste vegetable oil is one of the promising partial substitutes for fossil fuels. The degradation characteristics of waste vegetable oil using supercritical alcohols (ethanol and methanol) have been studied in this research. The elementary target was to conduct comparative analysis of
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Transesterification of waste vegetable oil is one of the promising partial substitutes for fossil fuels. The degradation characteristics of waste vegetable oil using supercritical alcohols (ethanol and methanol) have been studied in this research. The elementary target was to conduct comparative analysis of the effect of supercritical methanol and supercritical ethanol as solvents on the transesterification along with the analysis of product obtained in terms of carbon number. The experiments were carried out at transesterification temperatures of 250, 270 and 290 °C, retention time of 0 to 60 min at an interval of 15 min and oil to alcohol molar ratios of 1:6, 1:12 and 1:18 for both alcohols. The conversion increased with increase in transesterification temperature and retention time. At 290 °C, almost 99% conversion was achieved for 60-min holding time for both alcohols. Increase in conversion of waste vegetable oil was observed as the molar ratio increased. Supercritical transesterification resulted into ester yield higher than 95% with non-ester composition and glycerol collectively less than 5%. Full article
(This article belongs to the Section Energy)
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Open AccessArticle Experimental Investigation on the Effects of DBD Plasma on the Film Cooling Effectiveness of a 30-Degree Slot
Appl. Sci. 2017, 7(6), 633; doi:10.3390/app7060633
Received: 22 March 2017 / Revised: 22 May 2017 / Accepted: 15 June 2017 / Published: 19 June 2017
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Abstract
The effects of dielectric barrier discharge (DBD) plasma on the film cooling effectiveness of a 30-degree slot was experimentally investigated in a low-speed wind tunnel. The pressure sensitive paint (PSP) technique was used to measure the film cooling effectiveness, and two blowing ratios
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The effects of dielectric barrier discharge (DBD) plasma on the film cooling effectiveness of a 30-degree slot was experimentally investigated in a low-speed wind tunnel. The pressure sensitive paint (PSP) technique was used to measure the film cooling effectiveness, and two blowing ratios (0.5 and 1.0) were tested. A sinusoidal waveform with a 1-kHz frequency was supplied to the exposed electrode. Two input voltages (6 and 7 kV) and two exposed electrode locations were considered. The results showed that the film cooling effectiveness of the slot was higher for the blowing ratio of the 1.0 case than that for the blowing ratio of the 0.5 case regardless of plasma operation. The higher input voltage case (7 kV) showed higher film cooling effectiveness than the lower input voltage case (6 kV). The improvement in film cooling effectiveness facilitated by the DBD plasma was more significant when the coolant had less momentum. The maximum improvement of the area averaged film cooling effectiveness was 2.3% for the case with the exposed electrode located at the slot exit and a blowing ratio of 0.5. Full article
(This article belongs to the Special Issue Advances in Thermal System Analysis and Optimization)
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Open AccessArticle Optimized Design of Thermoelectric Energy Harvesting Systems for Waste Heat Recovery from Exhaust Pipes
Appl. Sci. 2017, 7(6), 634; doi:10.3390/app7060634
Received: 1 June 2017 / Revised: 14 June 2017 / Accepted: 15 June 2017 / Published: 19 June 2017
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Abstract
With the increasing interest in energy efficiency and resource protection, waste heat recovery processes have gained importance. Thereby, one possibility is the conversion of the heat energy into electrical energy by thermoelectric generators. Here, a thermoelectric energy harvesting system is developed to convert
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With the increasing interest in energy efficiency and resource protection, waste heat recovery processes have gained importance. Thereby, one possibility is the conversion of the heat energy into electrical energy by thermoelectric generators. Here, a thermoelectric energy harvesting system is developed to convert the waste heat from exhaust pipes, which are very often used to transport the heat, e.g., in automobiles, in industrial facilities or in heating systems. That is why a mockup of a heating is built-up, and the developed energy harvesting system is attached. To build-up this system, a model-based development process is used. The setup of the developed energy harvesting system is very flexible to test different variants and an optimized system can be found in order to increase the energy yield for concrete application examples. A corresponding simulation model is also presented, based on previously developed libraries in Modelica®/Dymola®. In the end, it can be shown—with measurement and simulation results—that a thermoelectric energy harvesting system on the exhaust pipe of a heating system delivers extra energy and thus delivers a contribution for a more efficient usage of the inserted primary energy carrier. Full article
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Open AccessArticle Fundamental Limits on Spatial Resolution in Ultrafast X-ray Diffraction
Appl. Sci. 2017, 7(6), 534; doi:10.3390/app7060534
Received: 7 April 2017 / Revised: 16 May 2017 / Accepted: 17 May 2017 / Published: 23 May 2017
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Abstract
X-ray Free-Electron Lasers have made it possible to record time-sequences of diffraction images to determine changes in molecular geometry during ultrafast photochemical processes. Using state-of-the-art simulations in three molecules (deuterium, ethylene, and 1,3-cyclohexadiene), we demonstrate that the nature of the nuclear wavepacket initially
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X-ray Free-Electron Lasers have made it possible to record time-sequences of diffraction images to determine changes in molecular geometry during ultrafast photochemical processes. Using state-of-the-art simulations in three molecules (deuterium, ethylene, and 1,3-cyclohexadiene), we demonstrate that the nature of the nuclear wavepacket initially prepared by the pump laser, and its subsequent dispersion as it propagates along the reaction path, limits the spatial resolution attainable in a structural dynamics experiment. The delocalization of the wavepacket leads to a pronounced damping of the diffraction signal at large values of the momentum transfer vector q, an observation supported by a simple analytical model. This suggests that high-q measurements, beyond 10–15 Å 1 , provide scant experimental payback, and that it may be advantageous to prioritize the signal-to-noise ratio and the time-resolution of the experiment as determined by parameters such as the repetition-rate, the photon flux, and the pulse durations. We expect these considerations to influence future experimental designs, including source development and detection schemes. Full article
(This article belongs to the Special Issue X-Ray Free-Electron Laser)
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Open AccessArticle Use of Rolling Piston Expanders for Energy Regeneration in Natural Gas Pressure Reduction Stations—Selected Thermodynamic Issues
Appl. Sci. 2017, 7(6), 535; doi:10.3390/app7060535
Received: 18 January 2017 / Revised: 18 May 2017 / Accepted: 20 May 2017 / Published: 23 May 2017
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Abstract
Gas pressure reduction stations are commonly applied to decrease the pressure of natural gas in the transmission pipelines. In such stations, natural gas is expanded in throttling valves without producing any energy. Through the use of expander in natural gas pressure reduction stations,
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Gas pressure reduction stations are commonly applied to decrease the pressure of natural gas in the transmission pipelines. In such stations, natural gas is expanded in throttling valves without producing any energy. Through the use of expander in natural gas pressure reduction stations, it is possible to recover the pressure energy of the natural gas during expansion, and drive the electrical generator. Possible solutions include turbines and volumetric expanders. However, turbines are complicated and expensive, while volumetric expanders are simple and cheap. This paper presents an analytical modeling of rolling piston expander work conditions when adopted to natural gas expansion. The main objective of this research was therefore a comprehensive analysis of influence of varied sizes of the expander components and natural gas thermal properties at the inlet and at the outlet of the expander, on the expander output power. The analysis presented in this paper indicates that the rolling piston expander is a good alternative to the turbines proposed for energy recovery in natural gas pressure reduction stations. Full article
(This article belongs to the Section Energy)
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Open AccessArticle Random Forest Prediction of IPO Underpricing
Appl. Sci. 2017, 7(6), 636; doi:10.3390/app7060636
Received: 2 May 2017 / Revised: 12 June 2017 / Accepted: 15 June 2017 / Published: 20 June 2017
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Abstract
The prediction of initial returns on initial public offerings (IPOs) is a complex matter. The independent variables identified in the literature mix strong and weak predictors, their explanatory power is limited, and samples include a sizable number of outliers. In this context, we
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The prediction of initial returns on initial public offerings (IPOs) is a complex matter. The independent variables identified in the literature mix strong and weak predictors, their explanatory power is limited, and samples include a sizable number of outliers. In this context, we suggest that random forests are a potentially powerful tool. In this paper, we benchmark this algorithm against a set of eight classic machine learning algorithms. The results of this comparison show that random forests outperform the alternatives in terms of mean and median predictive accuracy. The technique also provided the second smallest error variance among the stochastic algorithms. The experimental work also supports the potential of random forests for two practical applications: IPO pricing and IPO trading. Full article
(This article belongs to the Section Computer Science and Electrical Engineering)
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Open AccessArticle Microtab Design and Implementation on a 5 MW Wind Turbine
Appl. Sci. 2017, 7(6), 536; doi:10.3390/app7060536
Received: 27 March 2017 / Revised: 12 May 2017 / Accepted: 18 May 2017 / Published: 24 May 2017
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Abstract
Microtabs (MT) consist of a small tab placed on the airfoil surface close to the trailing edge and perpendicular to the surface. A study to find the optimal position to improve airfoil aerodynamic performance is presented. Therefore, a parametric study of a MT
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Microtabs (MT) consist of a small tab placed on the airfoil surface close to the trailing edge and perpendicular to the surface. A study to find the optimal position to improve airfoil aerodynamic performance is presented. Therefore, a parametric study of a MT mounted on the pressure surface of an airfoil has been carried out. The aim of the current study is to find the optimal MT size and location to increase airfoil aerodynamic performance and to investigate its influence on the power output of a 5 MW wind turbine. Firstly, a computational study of a MT mounted on the pressure surface of the airfoil DU91W(2)250 has been carried out and the best case has been found according to the largest lift-to-drag ratio. This airfoil has been selected because it is typically used on wind turbine, such as the 5 MW reference wind turbine of the National Renewable Energy Laboratory (NREL). Second, Blade Element Momentum (BEM) based computations have been performed to investigate the effect of the MT on the wind turbine power output with different wind speed realizations. The results show that, due to the implementation of MTs, a considerable increase in the turbine average power is achieved. Full article
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Open AccessArticle Path Loss Measurements of Indoor LTE System for the Internet of Things
Appl. Sci. 2017, 7(6), 537; doi:10.3390/app7060537
Received: 23 January 2017 / Revised: 2 May 2017 / Accepted: 8 May 2017 / Published: 23 May 2017
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Abstract
The Internet of Things (IoT) provides communication service for future smart manufacturing, which is capable of independently exchanging and responding to information to manage industrial production processes. For the purpose of connecting machines, devices, sensors, and people with each other in a factory,
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The Internet of Things (IoT) provides communication service for future smart manufacturing, which is capable of independently exchanging and responding to information to manage industrial production processes. For the purpose of connecting machines, devices, sensors, and people with each other in a factory, reliable and scalable communication networks used in the cellular IoT are of great importance. This paper aims at channel parameter measurements of indoor Long Term Evolution systems in order to achieve good coverage and service reliability (SR) for the IoT. For the purpose of determining the path loss exponent and the standard deviation of the received shadow fading signal, we use software defined radio techniques to build a small cell experimental platform which contains an evolved node B and user equipment. Received power measurements were performed on this platform. Finally, based on the experimental results, the modified path loss model and the calculated fade margin (FM) for 90% SR are exploited to predict the coverage range of the small cell base station deployed in the factory. The measured path loss channel models are compared with International Telecommunication Union (ITU) path loss channel model. Full article
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Open AccessArticle Functionalization of a Hydrophilic Commercial Membrane Using Inorganic-Organic Polymers Coatings for Membrane Distillation
Appl. Sci. 2017, 7(6), 637; doi:10.3390/app7060637
Received: 3 May 2017 / Revised: 13 June 2017 / Accepted: 16 June 2017 / Published: 20 June 2017
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Abstract
Membrane distillation is a thermal separation technique using a microporous hydrophobic membrane. One of the concerns with respect to the industrialization of the technique is the development of novel membranes. In this paper, a commercially available hydrophilic polyethersulfone membrane with a suitable structure
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Membrane distillation is a thermal separation technique using a microporous hydrophobic membrane. One of the concerns with respect to the industrialization of the technique is the development of novel membranes. In this paper, a commercially available hydrophilic polyethersulfone membrane with a suitable structure for membrane distillation was modified using available hydrophobic coatings using ORMOCER® technology to obtain a hydrophobic membrane that can be applied in membrane distillation. The surface modification was performed using a selection of different components, concentrations, and application methods. The resulting membranes can have two hydrophobic surfaces or a hydrophobic and hydrophilic surface depending on the application method. An extensive characterization procedure confirmed the suitability of the coating technique and the obtained membranes for membrane distillation. The surface contact angle of water could be increased from 27° up to 110°, and fluxes comparable to membranes commonly used for membrane distillation were achieved under similar process conditions. A 100 h test demonstrated the stability of the coating and the importance of using sufficiently stable base membranes. Full article
(This article belongs to the Special Issue Wastewater Treatment and Reuse Technologies)
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Open AccessArticle Investigation on Eddy Current Sensor in Tension Measurement at a Resonant Frequency
Appl. Sci. 2017, 7(6), 538; doi:10.3390/app7060538
Received: 29 March 2017 / Revised: 3 May 2017 / Accepted: 9 May 2017 / Published: 24 May 2017
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Abstract
For resolving deficiencies of conventional tension measurement methods, this paper proposes a novel eddy current sensor with a single-coil structure based on the inverse magnetostrictive effect. An inductor–resistor–capacitor (LRC) model of eddy current sensor, which considers more parameters than the traditional inductor–resistor (LR)
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For resolving deficiencies of conventional tension measurement methods, this paper proposes a novel eddy current sensor with a single-coil structure based on the inverse magnetostrictive effect. An inductor–resistor–capacitor (LRC) model of eddy current sensor, which considers more parameters than the traditional inductor–resistor (LR) model, was established. The eddy current sensor was operated by a swept frequency signal that ranged from 0.1 MHz to 1.6 MHz, encompassing the sensor resonant frequency. At the resonant frequency, the data of impedance magnitude and phase were extracted and linear relations between the impedance parameters and the external tension were ascertained. The experimental results show that the resonant frequency and impedance magnitude of eddy current sensor will decrease linearly with the increase of the external tension, which is consistent with the theoretical model. In addition, to improve sensor performance, the sleeve structure was designed to reduce the loss of magnetic field. Both finite element simulations and experimental results demonstrate that the sleeve structure provides a higher permeability path to the magnetic field lines than the non-sleeve structure and effectively improves sensor sensitivity and correlation coefficient. Full article
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Open AccessArticle Levels of Organic Pollution Indicators in Groundwater at the Old Landfill and Waste Management Site
Appl. Sci. 2017, 7(6), 638; doi:10.3390/app7060638
Received: 19 May 2017 / Revised: 15 June 2017 / Accepted: 16 June 2017 / Published: 20 June 2017
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Abstract
The aim of this paper was to assess groundwater quality in a landfill and waste management site, with special regard to levels of organic pollution indicators: chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total organic carbon (TOC). Analysis of specific indicators
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The aim of this paper was to assess groundwater quality in a landfill and waste management site, with special regard to levels of organic pollution indicators: chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total organic carbon (TOC). Analysis of specific indicators was conducted for piezometers located in the area of the Radiowo landfill, the composting plant and the facilities adjacent to the landfill. The article discusses the temporal and spatial changes of selected organic pollution indicators. Based on the results of groundwater monitoring, several maps of COD, BOD and TOC areal distribution were provided. Statistical distribution of monitoring data was presented using box-and-whisker plots. Pearson’s correlation coefficients between selected pollution indicators were measured with a significance level set at p < 0.01 and p < 0.05. The strongest correlation was observed between BOD and COD. The maximum BOD/COD ratio was observed at the level of 1.561 before the closure of the vertical barrier, whereas, at present, average values of this ratio are below 0.18. The results indicate significant improvement of groundwater quality in the landfill site after the closure of the vertical barrier. In particular, this refers to BOD values, which decreased even 160 times in the 1998–2016 monitoring period. Full article
(This article belongs to the Section Chemistry)
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Open AccessArticle Multidisciplinary Aerodynamic Design of a Rotor Blade for an Optimum Rotor Speed Helicopter
Appl. Sci. 2017, 7(6), 639; doi:10.3390/app7060639
Received: 16 May 2017 / Revised: 9 June 2017 / Accepted: 13 June 2017 / Published: 20 June 2017
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Abstract
The aerodynamic design of rotor blades is challenging, and is crucial for the development of helicopter technology. Previous aerodynamic optimizations that focused only on limited design points find it difficult to balance flight performance across the entire flight envelope. This study develops a
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The aerodynamic design of rotor blades is challenging, and is crucial for the development of helicopter technology. Previous aerodynamic optimizations that focused only on limited design points find it difficult to balance flight performance across the entire flight envelope. This study develops a global optimum envelope (GOE) method for determining blade parameters—blade twist, taper ratio, tip sweep—for optimum rotor speed helicopters (ORS-helicopters), balancing performance improvements in hover and various freestream velocities. The GOE method implements aerodynamic blade design by a bi-level optimization, composed of a global optimization step and a secondary optimization step. Power loss as a measure of rotor performance is chosen as the objective function, referred to as direct power loss (DPL) in this study. A rotorcraft comprehensive code for trim simulation with a prescribed wake method is developed. With the application of the GOE method, a DPL reduction of as high as 16.7% can be achieved in hover, and 24% at high freestream velocity. Full article
(This article belongs to the Section Mechanical Engineering)
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Open AccessArticle Coordination of EVs Participation for Load Frequency Control in Isolated Microgrids
Appl. Sci. 2017, 7(6), 539; doi:10.3390/app7060539
Received: 30 April 2017 / Revised: 19 May 2017 / Accepted: 19 May 2017 / Published: 24 May 2017
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Abstract
Increasing the penetration levels of renewable energy sources (RESs) in microgrids (MGs) may lead to frequency instability issues due to intermittent nature of RESs and low inertia of MG generating units. On the other hand, presence of electric vehicles (EVs), as new high-electricity-
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Increasing the penetration levels of renewable energy sources (RESs) in microgrids (MGs) may lead to frequency instability issues due to intermittent nature of RESs and low inertia of MG generating units. On the other hand, presence of electric vehicles (EVs), as new high-electricity- consuming appliances, can be a good opportunity to contribute in mitigating the frequency deviations and help the system stability. This paper proposes an optimal charging/discharging scheduling of EVs with the goal of improving frequency stability of MG during autonomous operating condition. To this end, an efficient approach is applied to reschedule the generating units considering the EVs owners’ behaviors. An EV power controller (EVPC) is also designed to determine charge and discharge process of EVs based on the forecasted day-ahead load and renewable generation profiles. The performance of the proposed strategy is tested in different operating scenarios and compared to those from non-optimized methodologies. Numerical simulations indicate that the MG performance improves considerably in terms of economy and stability using the proposed strategy. Full article
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Open AccessArticle Application of FBG Based Sensor in Pipeline Safety Monitoring
Appl. Sci. 2017, 7(6), 540; doi:10.3390/app7060540
Received: 29 March 2017 / Revised: 24 April 2017 / Accepted: 12 May 2017 / Published: 24 May 2017
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Abstract
Pipeline leakage and corrosion are two serious threats to pipeline safety operation. Therefore, to ensure the safety operation of long-distance pipeline, it is of great significance to conduct pipeline monitoring. Since hoop strain is an effective indicator to reflect the inner pressure fluctuation
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Pipeline leakage and corrosion are two serious threats to pipeline safety operation. Therefore, to ensure the safety operation of long-distance pipeline, it is of great significance to conduct pipeline monitoring. Since hoop strain is an effective indicator to reflect the inner pressure fluctuation and the wall thickness reduction of the pipeline, a method of monitoring leakage and corrosion simultaneously was proposed based on hoop strain measurement. In order to test the hoop strain variation, this paper introduces a fiber Bragg grating (FBG) strain hoop sensor. To verify the monitoring method and the performance of this FBG strain sensor, a pipeline leakage simulation experiment and corrosion simulation experiment were conducted on an actual pipeline and a polyvinyl chloride (PVC) pipe model, respectively. The experimental results demonstrate that the pipeline leakage and corrosion can be detected by the FBG hoop strain sensor. The FBG strain hoop sensor is a promising device in pipeline safety monitoring. Full article
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Open AccessArticle FERMI: Present and Future Challenges
Appl. Sci. 2017, 7(6), 640; doi:10.3390/app7060640
Received: 12 May 2017 / Revised: 12 June 2017 / Accepted: 12 June 2017 / Published: 21 June 2017
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Abstract
We present an overview of the FERMI (acronym of Free Electron laser Radiation for Multidisciplinary Investigations) seeded free electron laser (FEL) facility located at the Elettra laboratory in Trieste. FERMI is now in user operation with both the FEL lines FEL-1 and FEL-2,
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We present an overview of the FERMI (acronym of Free Electron laser Radiation for Multidisciplinary Investigations) seeded free electron laser (FEL) facility located at the Elettra laboratory in Trieste. FERMI is now in user operation with both the FEL lines FEL-1 and FEL-2, covering the wavelength range between 100 nm and 4 nm. The seeding scheme adopted for photon pulse production makes FERMI unique worldwide and allows the extension of table top laser experiments in the extreme ultraviolet/soft X-ray region. In this paper, we discuss how advances in the performance of the FELs, with respect to coherent control and multi-colour pulse production, may push the development of original experimental strategies to study non-equilibrium behaviour of matter at the attosecond-nanometer time-length scales. This will have a tremendous impact as an experimental tool to investigate a large array of phenomena ranging from nano-dynamics in complex materials to phenomena that are at the heart of the conversion of light into other forms of energy. Full article
(This article belongs to the Special Issue X-Ray Free-Electron Laser)
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Open AccessArticle Design and Implementation of an Interactive Interface for Demand Response and Home Energy Management Applications
Appl. Sci. 2017, 7(6), 641; doi:10.3390/app7060641
Received: 24 April 2017 / Revised: 1 June 2017 / Accepted: 16 June 2017 / Published: 21 June 2017
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Abstract
Demand response (DR) implementations have recently found wide application areas in the context of smart grids. The effectiveness of these implementations is primarily based on the willingness of end-users to be involved in such programs. In this paper, an interactive and user-friendly interface
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Demand response (DR) implementations have recently found wide application areas in the context of smart grids. The effectiveness of these implementations is primarily based on the willingness of end-users to be involved in such programs. In this paper, an interactive and user-friendly interface is presented in order to facilitate and accordingly to increase the participation of end-users in DR programs. The proposed interface has the capability of providing the targeted information about the DR events to end-users and system operators, as well as allowing end-users to interactively monitor and control the progress of their appliances. In addition to its benefits to system operators and thus to the improved operation of power systems, the proposed interface particularly aims to exploit the potential energy-related cost savings by providing the required information and resources to end-users via mobile phone. A separate interface apart from the mentioned end-user oriented interface has also been developed for the system operator to more effectively check the status of DR applications in detail. The capabilities of the proposed concept are evaluated in a real smart home in terms of various aspects. Full article
(This article belongs to the Special Issue Smart Home and Energy Management Systems)
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Open AccessArticle Stereophonic Microphone Array for the Recording of the Direct Sound Field in a Reverberant Environment
Appl. Sci. 2017, 7(6), 541; doi:10.3390/app7060541
Received: 15 March 2017 / Revised: 15 May 2017 / Accepted: 17 May 2017 / Published: 24 May 2017
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Abstract
State-of-the-art stereo recording techniques using two microphones have two main disadvantages: first, a limited reduction of the reverberation in the direct sound component, and second, compression or expansion of the angular position of sound sources. To address these disadvantages, the aim of this
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State-of-the-art stereo recording techniques using two microphones have two main disadvantages: first, a limited reduction of the reverberation in the direct sound component, and second, compression or expansion of the angular position of sound sources. To address these disadvantages, the aim of this study is the development of a true stereo recording microphone array that aims to record the direct and reverberant sound field separately. This array can be used within the recording and playback configuration developed in Grosse and van de Par, 2015. Instead of using only two microphones, the proposed method combines two logarithmically-spaced microphone arrays, whose directivity patterns are optimized with a superdirective beamforming algorithm. The optimization allows us to have a better control of the overall beam pattern and of interchannel level differences. A comparison between the newly-proposed system and existing microphone techniques shows a lower percentage of the recorded reverberance within the sound field. Full article
(This article belongs to the Special Issue Spatial Audio)
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Open AccessArticle Computational Analysis and Artificial Neural Network Optimization of Dry Turning Parameters—AA2024-T351
Appl. Sci. 2017, 7(6), 642; doi:10.3390/app7060642
Received: 26 April 2017 / Revised: 8 June 2017 / Accepted: 9 June 2017 / Published: 21 June 2017
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Abstract
In dry turning operation, various parameters influence the cutting force and contribute in machining precision. Generally, the numerical cutting models are adopted to establish the optimum cutting parameters and results are substantiated with the experimental findings. In this paper, the optimal turning parameters
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In dry turning operation, various parameters influence the cutting force and contribute in machining precision. Generally, the numerical cutting models are adopted to establish the optimum cutting parameters and results are substantiated with the experimental findings. In this paper, the optimal turning parameters of AA2024-T351 alloy are determined through Abaqus/Explicit numerical cutting simulations by employing the Johnson-Cook thermo-viscoplastic-damage material model. Turning simulations were verified with published experimental data. Considering the constrained and nonlinear optimization problem, the artificial neural networks (ANN) were executed for training, testing, and performance evaluation of the numerical simulations data. Two feedforward backpropagation neural networks were developed with ten hidden neutrons in each hidden layer. The Log-Sigmoid transfer function and the Levenberg-Marquardt algorithm were applied in the model. The ANN models were studied with four input parameters: the cutting speed (200, 400, and 800 m/min), tool rake angle (5°, 10°, 14.8°, and 17.5°), cutting feed (0.3 and 0.4 mm), and the contact friction coefficients (0.1 and 0.15).The two target parameters include the tool-chip interface temperature and the cutting reaction force. The performance of the trained data was evaluated using root-mean-square error and correlation coefficients. The ANN predicted values were compared both with the Abaqus simulations and the published experimental findings. All of the results are found in good approximation to each other. The performance of the ANN models demonstrated the fidelity of solving and predicting the optimum process parameters. Full article
(This article belongs to the Section Mechanical Engineering)
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Open AccessArticle Near-Field Coupling and Mode Competition in Multiple Anapole Systems
Appl. Sci. 2017, 7(6), 542; doi:10.3390/app7060542
Received: 17 April 2017 / Revised: 9 May 2017 / Accepted: 11 May 2017 / Published: 24 May 2017
PDF Full-text (1088 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
All-dielectric metamaterials are a promising platform for the development of integrated photonics applications. In this work, we investigate the mutual coupling and interaction of an ensemble of anapole states in silicon nanoparticles. Anapoles are intriguing non-radiating states originated by the superposition of internal
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All-dielectric metamaterials are a promising platform for the development of integrated photonics applications. In this work, we investigate the mutual coupling and interaction of an ensemble of anapole states in silicon nanoparticles. Anapoles are intriguing non-radiating states originated by the superposition of internal multipole components which cancel each other in the far-field. While the properties of anapole states in single nanoparticles have been extensively studied, the mutual interaction and coupling of several anapole states have not been characterized. By combining first-principles simulations and analytical results, we demonstrate the transferring of anapole states across an ensemble of nanoparticles, opening to the development of advanced integrated devices and robust waveguides relying on non-radiating modes. Full article
(This article belongs to the Special Issue Guided-Wave Optics)
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Open AccessArticle DegoViz: An Interactive Visualization Tool for a Differentially Expressed Genes Heatmap and Gene Ontology Graph
Appl. Sci. 2017, 7(6), 543; doi:10.3390/app7060543
Received: 27 March 2017 / Revised: 2 May 2017 / Accepted: 25 May 2017 / Published: 25 May 2017
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Abstract
Microarray is a general scheme to identify differentially expressed genes for a target concept and can be used for biology. The output is presented utilizing a heatmap that biologists analyze in related terms of gene ontology to determine the characteristics of differentially expressed
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Microarray is a general scheme to identify differentially expressed genes for a target concept and can be used for biology. The output is presented utilizing a heatmap that biologists analyze in related terms of gene ontology to determine the characteristics of differentially expressed genes. In this paper, we propose an integrated visualization tool for a heatmap and gene ontology graph. Most of the previous methods used were static and none of them were combined. The proposed visualization tool integrates these and provides users with an interactive management ability. Users can easily identify and confirm related terms of gene ontology for given differentially expressed genes. Further, the proposed tool visualizes the connections between genes on the heatmap and gene ontology graph. Therefore, the proposed tool can be used for precision healthcare. Full article
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Open AccessFeature PaperArticle Arginine-Mediated Self-Assembly of Porphyrin on Graphene: A Photocatalyst for Degradation of Dyes
Appl. Sci. 2017, 7(6), 643; doi:10.3390/app7060643
Received: 17 May 2017 / Revised: 9 June 2017 / Accepted: 13 June 2017 / Published: 21 June 2017
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Abstract
Porphyrin nanostructures with well-controlled size, shape and functionality can be used for visible-light photocatalysis. In this work, a graphene@porphyrin nanofibre composite was successfully fabricated via arginine-mediated self-assembly of tetrakis (4-carboxyphenyl) porphyrin (TCPP) on graphene nanoplates (GNPs). The formation and crystallisation of the graphene@porphyrin
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Porphyrin nanostructures with well-controlled size, shape and functionality can be used for visible-light photocatalysis. In this work, a graphene@porphyrin nanofibre composite was successfully fabricated via arginine-mediated self-assembly of tetrakis (4-carboxyphenyl) porphyrin (TCPP) on graphene nanoplates (GNPs). The formation and crystallisation of the graphene@porphyrin nanofibre composite was fully characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), fourier transform infrared (FTIR), ultraviolet-visible (UV-vis) and fluorescence spectroscopy. The assembled TCPP nanofibers were 50–200 nm in diameter with length in micrometers long, which were densely and uniformly distributed on the surface of graphene. The GNPs@TCPP nanofibers showed enhanced visible-light photocatalytic activity in comparison with free-standing TCPP nanorods for the degradation of Rhodamine B (RhB) and methyl orange (MO). The possible photodegradation mechanism of these dyes by the GNPs@TCPP nanofiber photocatalyst was proposed. Full article
(This article belongs to the Section Nanotechnology and Applied Nanosciences)
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Open AccessArticle Split-And-Delay Unit for FEL Interferometry in the XUV Spectral Range
Appl. Sci. 2017, 7(6), 544; doi:10.3390/app7060544
Received: 29 March 2017 / Revised: 5 May 2017 / Accepted: 22 May 2017 / Published: 25 May 2017
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Abstract
In this work we present a reflective split-and-delay unit (SDU) developed for interferometric time-resolved experiments utilizing an (extreme ultraviolet) XUV pump–XUV probe scheme with focused free-electron laser beams. The developed SDU overcomes limitations for phase-resolved measurements inherent to conventional two-element split mirrors by
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In this work we present a reflective split-and-delay unit (SDU) developed for interferometric time-resolved experiments utilizing an (extreme ultraviolet) XUV pump–XUV probe scheme with focused free-electron laser beams. The developed SDU overcomes limitations for phase-resolved measurements inherent to conventional two-element split mirrors by a special design using two reflective lamellar gratings. The gratings produce a high-contrast interference signal controlled by the grating displacement in every diffraction order. The orders are separated in the focal plane of the focusing optics, which enables one to avoid phase averaging by spatially selective detection of a single interference state of the two light fields. Interferometry requires a precise relative phase control of the light fields, which presents a challenge at short wavelengths. In our setup the phase delay is determined by an in-vacuum white light interferometer (WLI) that monitors the surface profile of the SDU in real time and thus measures the delay for each laser shot. The precision of the WLI is 1 nm as determined by optical laser interferometry. In the presented experimental geometry it corresponds to a time delay accuracy of 3 as, which enables phase-resolved XUV pump–XUV probe experiments at free-electron laser (FEL) repetition rates up to 60 Hz. Full article
(This article belongs to the Special Issue X-Ray Free-Electron Laser)
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Open AccessArticle Effects of Three Different Additives and Two Different Bulk Densities on Maize Silage Characteristics, Temperature Profiles, CO2 and O2–Dynamics in Small Scale Silos during Aerobic Exposure
Appl. Sci. 2017, 7(6), 545; doi:10.3390/app7060545
Received: 3 April 2017 / Revised: 16 May 2017 / Accepted: 16 May 2017 / Published: 25 May 2017
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Abstract
Silage quality and aerobic stability are sometimes insufficient. If management requirements are not met, or to improve silage quality, additives are often used. The objective of this study is to investigate the effects of different factors on silage during aerobic conditions. Whole-crop forage
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Silage quality and aerobic stability are sometimes insufficient. If management requirements are not met, or to improve silage quality, additives are often used. The objective of this study is to investigate the effects of different factors on silage during aerobic conditions. Whole-crop forage maize was harvested and 24 buckets (65 L) were filled and assigned to one of four treatment groups: (1) control (no treatment); (2) chemical additive (sodium benzoate, potassium sorbate, sodium acetate); (3) a mixed biological inoculant containing Lactobacillus buchneri, L. plantarum, and Pediococcus acidilacti; and (4) a mixed biological inoculant containing L. buchneri, L. plantarum, and L. rhamnosus. An untreated variation was also ensiled. Two different densities were adjusted during ensiling. After opening, the temperature was measured for seven days and O2 and CO2 concentrations were analysed. The findings show that the chemical additive very effectively prevented silage from reheating and deteriorating. Aerobic reheating of silage was also successfully inhibited through biological additives and high density. Full article
(This article belongs to the Section Chemistry)
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Open AccessArticle Control of the Polymorphism of Calcium Carbonate Produced by Self-Healing in the Cracked Part of Cementitious Materials
Appl. Sci. 2017, 7(6), 546; doi:10.3390/app7060546
Received: 14 April 2017 / Revised: 11 May 2017 / Accepted: 23 May 2017 / Published: 25 May 2017
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Abstract
Cracking is an inherent development in reinforced concrete structures and can lead to serious damages during their service period. The repeated occurrence of such damages can enlarge the cracks, thereby allowing other deteriorating elements such as CO2 and Cl to further
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Cracking is an inherent development in reinforced concrete structures and can lead to serious damages during their service period. The repeated occurrence of such damages can enlarge the cracks, thereby allowing other deteriorating elements such as CO2 and Cl to further infiltrate the concrete, which can seriously compromise the concrete structure. This study focuses on the type of calcium carbonate (CaCO3) crystals generated by the self-healing phenomenon. Owing to polymorphism, CaCO3 has three types of crystal forms—calcite, vaterite, and aragonite—whose formation can be controlled by the temperature and pH. Vaterite has the highest density among these crystals, and it is expected to be capable of self-healing. Therefore, experiments were conducted to establish the conditions required to promote the generation of vaterite. A saturated Ca(OH)2 solution with CO2 nanobubbles (CN) was employed for effective self-healing. The temperature was controlled at 20, 40, and 60 °C, and the pH was controlled at 9.0, 10.5, and 12.0. The results showed that the self-healing of cracks occurred both on the surface and internally, and the main product of the self-healing phenomenon was vaterite in CaCO3 crystals at a pH of 9.0 and a temperature of 40 °C. Furthermore, the addition of a saturated Ca(OH)2 solution with CO2 nanobubbles (CN) resulted in the most effective self-healing of the surface and internal cracks. Full article
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Open AccessArticle Modular and Offsite Construction of Piping: Current Barriers and Route
Appl. Sci. 2017, 7(6), 547; doi:10.3390/app7060547
Received: 12 April 2017 / Revised: 6 May 2017 / Accepted: 19 May 2017 / Published: 26 May 2017
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Abstract
To investigate current practices and identify challenges of piping prefabrication, this paper conducts a comprehensive survey to mechanical, electrical, and plumbing (MEP) contractors. This paper is performed in three main steps. First, the current state of piping prefabrication, the attitude of MEP contractors
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To investigate current practices and identify challenges of piping prefabrication, this paper conducts a comprehensive survey to mechanical, electrical, and plumbing (MEP) contractors. This paper is performed in three main steps. First, the current state of piping prefabrication, the attitude of MEP contractors to piping prefabrication, and the challenges of piping prefabrication are identified through a comprehensive data collection process that included semi-structured interviews, case studies, site visits, and questionnaires. The second step included suggesting a pattern and roadway of piping prefabrication. The results showed that: (1) The attitudes to feasibility of piping prefabrication differ in piping systems, piping connector modes, and types of project; and (2) building information modelling (BIM) promotes the adoption of piping prefabrication. Integrated project delivery (IPD), and distributor’s early involvement into projects have significant effects on the successful implementation of piping prefabrication. (3) The main barriers and challenges were identified including the low level of standardization of design, lack of preferential policy, economies of scale, low-skilled workers, as well as the availability of fittings and valves. In the final step, a four-phase route of piping prefabrication is suggested for MEP contractors to expand the prefabrication capacity incrementally. The main contributions of this paper include: (1) This paper proposes a route for MEP contractors to improve their piping construction through the Modular and offsite construction (MOC) method. (2) This paper finds that the level of feasibility of piping prefabrication differs in piping systems, connection modes, and types of project. Challenges and barriers of piping prefabrication are firstly identified. Full article
(This article belongs to the Special Issue The Industrialization of the Building Construction Process)
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Open AccessFeature PaperArticle Bioimaging Using Full Field and Contact EUV and SXR Microscopes with Nanometer Spatial Resolution
Appl. Sci. 2017, 7(6), 548; doi:10.3390/app7060548
Received: 18 April 2017 / Revised: 12 May 2017 / Accepted: 23 May 2017 / Published: 26 May 2017
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Abstract
We present our recent results, related to nanoscale imaging in the extreme ultraviolet (EUV) and soft X-ray (SXR) spectral ranges and demonstrate three novel imaging systems recently developed for the purpose of obtaining high spatial resolution images of nanoscale objects with the EUV
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We present our recent results, related to nanoscale imaging in the extreme ultraviolet (EUV) and soft X-ray (SXR) spectral ranges and demonstrate three novel imaging systems recently developed for the purpose of obtaining high spatial resolution images of nanoscale objects with the EUV and SXR radiations. All the systems are based on laser-plasma EUV and SXR sources, employing a double stream gas puff target. The EUV and SXR full field microscopes—operating at 13.8 nm and 2.88 nm wavelengths, respectively—are currently capable of imaging nanostructures with a sub-50 nm spatial resolution with relatively short (seconds) exposure times. The third system is a SXR contact microscope, operating in the “water-window” spectral range (2.3–4.4 nm wavelength), to produce an imprint of the internal structure of the investigated object in a thin surface layer of SXR light sensitive poly(methyl methacrylate) photoresist. The development of such compact imaging systems is essential to the new research related to biological science, material science, and nanotechnology applications in the near future. Applications of all the microscopes for studies of biological samples including carcinoma cells, diatoms, and neurons are presented. Details about the sources, the microscopes, as well as the imaging results for various objects will be shown and discussed. Full article
(This article belongs to the Special Issue Laser Processing for Bioengineering Applications)
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Open AccessArticle Effect of Load Transfer Section to Toughness for Steel Fiber-Reinforced Concrete
Appl. Sci. 2017, 7(6), 549; doi:10.3390/app7060549
Received: 12 April 2017 / Revised: 16 May 2017 / Accepted: 16 May 2017 / Published: 26 May 2017
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Abstract
This study analyzed the correlation between the load transfer properties and the overall toughness in the flexural behavior of steel fiber-reinforced concrete after concrete matrix cracking. Beam specimens with identical aspect ratios were made with three different types of steel fiber, each of
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This study analyzed the correlation between the load transfer properties and the overall toughness in the flexural behavior of steel fiber-reinforced concrete after concrete matrix cracking. Beam specimens with identical aspect ratios were made with three different types of steel fiber, each of which had different properties, and were used for the flexural test. The load displacement graph from the test was divided into sections by behavioral properties, and the regression model by mix was analyzed to extract the correlation between the load transfer section (concrete-fiber) and the overall toughness. The analysis results showed three types of load displacement curve based on the fiber type and fiber content, and confirmed that the load reduction section towards fiber after concrete cracking and the slope and area of the load reascension section had a huge impact on the overall toughness. The regression model of the whole toughness (Tb) was then acquired by proposing the resulting correlation as the load transfer factor (LTF). Full article
(This article belongs to the Section Materials)
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Open AccessArticle Pore Characteristics and Their Effects on the Material Properties of Foamed Concrete Evaluated Using Micro-CT Images and Numerical Approaches
Appl. Sci. 2017, 7(6), 550; doi:10.3390/app7060550
Received: 2 May 2017 / Revised: 12 May 2017 / Accepted: 22 May 2017 / Published: 26 May 2017
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Abstract
Foamed concrete contains numerous pores inside the material, and these pores are a significant factor determining the material characteristics. In particular, the pore distribution characteristics of foamed concrete significantly affect its thermal and mechanical properties. Therefore, an appropriate investigation is necessary for a
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Foamed concrete contains numerous pores inside the material, and these pores are a significant factor determining the material characteristics. In particular, the pore distribution characteristics of foamed concrete significantly affect its thermal and mechanical properties. Therefore, an appropriate investigation is necessary for a more detailed understanding of foamed concrete. Here, a set of foamed concrete samples with different densities is used in order to investigate the density effects on the pore characteristics, as well as the physical properties of the materials. The pore distribution characteristics of these samples are investigated using an X-ray micro-computed tomography (micro-CT) imaging technique with probabilistic and quantitative methods. Using these methods, the anisotropy, the pore circularity factor and the relative density of cell thickness are examined. The thermal (thermal conductivity) and mechanical (directional modulus and strength) properties of each foamed specimen are computed using numerical simulations and compared with experimental results. From the obtained results, the effects of the pore sizes and shapes on the local and global properties of the foamed concrete are examined for developing advanced foamed concrete with lower thermal conductivity by minimizing the strength reduction. Full article
(This article belongs to the Section Materials)
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Open AccessArticle The Aerodynamic Analysis of a Rotating Wind Turbine by Viscous-Coupled 3D Panel Method
Appl. Sci. 2017, 7(6), 551; doi:10.3390/app7060551
Received: 11 March 2017 / Revised: 18 May 2017 / Accepted: 22 May 2017 / Published: 26 May 2017
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Abstract
In addition to the many typical failure mechanisms that afflict wind turbines, units in Taiwan are also susceptible to catastrophic failure from typhoon-induced extreme loads. A key component of the strategy to prevent such failures is a fast, accurate aerodynamic analysis tool through
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In addition to the many typical failure mechanisms that afflict wind turbines, units in Taiwan are also susceptible to catastrophic failure from typhoon-induced extreme loads. A key component of the strategy to prevent such failures is a fast, accurate aerodynamic analysis tool through which a fuller understanding of aerodynamic loads acting on the units may be derived. To this end, a viscous-coupled 3D panel method is herewith proposed, which introduces a novel approach to simulating the severe flow separation so prevalent around wind turbine rotors. The validity of the current method’s results was assessed by code-to-code comparison with RANS data for a commercial 2 MW wind turbine rotor. Along the outboard and inboard regions of the rotor, pressure distributions predicted by the current method showed excellent agreement with the RANS data, while pressure data along the midspan region were slightly more conservative. The power curve predicted by the current method was also more conservative than that predicted by the RANS solver, but correlated very well with that provided by the turbine manufacturer. Taking into account the high degree of comparability with the more sophisticated RANS solver, the excellent agreement with the official data, and the considerably reduced computational expense, the author believes the proposed method could be a powerful standalone tool for the design and analysis of wind turbine blades, or could be applied to the emerging field of wind farm layout design by providing accurate body force input to actuator line rotors within full Navier-Stokes models of multi-unit wind farms. Full article
(This article belongs to the Section Energy)
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Open AccessArticle Effects of Temperature Variations during Sintering of Metal Ceramic Tooth Prostheses Investigated Non-Destructively with Optical Coherence Tomography
Appl. Sci. 2017, 7(6), 552; doi:10.3390/app7060552
Received: 23 March 2017 / Revised: 23 May 2017 / Accepted: 24 May 2017 / Published: 26 May 2017
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Abstract
Calibration loss of ovens used in sintering metal ceramic prostheses leads to stress and cracks in the material of the prostheses fabricated, and ultimately to failure of the dental treatment. Periodic calibration may not be sufficient to prevent such consequences. Evaluation methods based
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Calibration loss of ovens used in sintering metal ceramic prostheses leads to stress and cracks in the material of the prostheses fabricated, and ultimately to failure of the dental treatment. Periodic calibration may not be sufficient to prevent such consequences. Evaluation methods based on firing supplemental control samples are subjective, time-consuming, and rely entirely on the technician’s skills. The aim of this study was to propose an alternative procedure for such evaluations. Fifty prostheses were sintered in a ceramic oven at a temperature lower, equal to or larger than the temperature prescribed by the manufacturer. A non-destructive imaging method, swept source (SS) optical coherence tomography (OCT) was used to evaluate comparatively the internal structure of prostheses so fabricated. A quantitative assessment procedure is proposed, based on en-face OCT images acquired at similar depths inside the samples. Differences in granulation and reflectivity depending on the oven temperature are used to establish rules-of-thumb on judging the correct calibration of the oven. OCT evaluations made on a regular basis allow an easy and objective monitoring of correct settings in the sintering process. This method can serve rapid identification of the need to recalibrate the oven and avoid producing prostheses with defects. Full article
(This article belongs to the Special Issue Development and Application of Optical Coherence Tomography (OCT))
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Open AccessArticle Modeling of Heat Transfer and Oscillating Flow in the Regenerator of a Pulse Tube Cryocooler Operating at 50 Hz
Appl. Sci. 2017, 7(6), 553; doi:10.3390/app7060553
Received: 4 April 2017 / Revised: 19 May 2017 / Accepted: 22 May 2017 / Published: 5 June 2017
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Abstract
The regenerator of the pulse tube refrigerator (PTR) operates with oscillating pressure and mass flow, so a proper description of the heat transfer characteristics of the oscillating flow in the regenerator is crucial. In this paper, a one-dimensional model based on Lagrangian representation
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The regenerator of the pulse tube refrigerator (PTR) operates with oscillating pressure and mass flow, so a proper description of the heat transfer characteristics of the oscillating flow in the regenerator is crucial. In this paper, a one-dimensional model based on Lagrangian representation is developed to simulate the oscillating flow in the regenerator of the PTR. The continuity equation, momentum equation and energy equation are solved iteratively using the SIMPLER algorithm. The Darcy-Brinkman-Forchheimer model is used in the momentum equation, and a thermal non-equilibrium model is implemented in the energy equation. Lagrangian representation is employed to describe the thermodynamics of fluid parcels while the Eulerian representation (control volume method) is adopted for the energy equation of the solid matrix. The boundary conditions are set as the periodic flow of the sine function. The thermodynamic parameters of the gas parcels are obtained, which reveal the critical processes of the heat transfer in the regenerator under oscillating flow. The performance of the regenerator with different geometries is evaluated based on the numerical results. The present study provides insight for better understanding the physical process in the regenerator of the PTR, and the proposed model serves as a useful tool for the design and optimization of the cryogenic regenerator. Full article
(This article belongs to the Special Issue Heat Transfer Processes in Oscillatory Flow Conditions)
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Open AccessArticle Optimal Design of an Air-to-Air Heat Exchanger with Cross-Corrugated Triangular Ducts by Using a Particle Swarm Optimization Algorithm
Appl. Sci. 2017, 7(6), 554; doi:10.3390/app7060554
Received: 22 March 2017 / Revised: 8 May 2017 / Accepted: 17 May 2017 / Published: 26 May 2017
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Abstract
Air-to-air heat exchangers with cross-corrugated triangular ducts are widely used in various industrial fields to recover waste heat. The geometric parameters of the heat exchangers greatly affect the performance and total annual cost of these systems. In this study, the effectiveness-number of transfer
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Air-to-air heat exchangers with cross-corrugated triangular ducts are widely used in various industrial fields to recover waste heat. The geometric parameters of the heat exchangers greatly affect the performance and total annual cost of these systems. In this study, the effectiveness-number of transfer units (ε-NTU) method was utilized to develop the thermal mathematical model, which was verified by comparing it with previous research. The configuration parameters of the heat exchanger were optimized in this study. The particle swarm optimization (PSO) algorithm was applied using both single and multi-objective algorithm. The colburn factor (j factor), friction factor (f factor), and comprehensive thermal hydraulic performance index (JF factor) were considered as objective functions to be optimized using a single objective and multi-objective algorithm. Then, the entropy generation rate and total annual cost were optimized by using a multi-objective PSO algorithm. In addition, to identify the influential geometric parameters, a global sensitivity analysis was performed. The sensitivity analysis showed that the apex angle θ, channel height H, and heat exchanger height Lh influenced the performance and annual total cost of these systems. Full article
(This article belongs to the Special Issue Sciences in Heat Pump and Refrigeration)
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Open AccessArticle Construction of Nonblocking Wavelength/Space Switches with AWGs and WSSes
Appl. Sci. 2017, 7(6), 555; doi:10.3390/app7060555
Received: 25 March 2017 / Revised: 7 May 2017 / Accepted: 22 May 2017 / Published: 26 May 2017
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Abstract
In this paper, we how to use two technologies, AWG (arrayed-waveguide grating) and WSS (wavelength selective switches), to design nonblocking wavelength/space optical cross connects. An AWG is a passive device and can route multiple wavelengths simultaneously. However, to apply AWGs, there are several
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In this paper, we how to use two technologies, AWG (arrayed-waveguide grating) and WSS (wavelength selective switches), to design nonblocking wavelength/space optical cross connects. An AWG is a passive device and can route multiple wavelengths simultaneously. However, to apply AWGs, there are several issues to consider, including the wavelength conversion range, crosstalk, and switch size constraint. We show a decomposition technique for designing an AWG-based nonblocking wavelength/space switch. The decomposition is carried out in a transformed space network. The new technique is simpler in concept and more flexible in setting switch sizes. We also study another class of wavelength/space switches that are based on WSSes and compare the two approaches in terms of the scalability, switch size constraint, and number of WCs (wavelength converters) required. Full article
(This article belongs to the Special Issue Optical Interconnects)
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Open AccessArticle Energy-Efficient Caching for Mobile Edge Computing in 5G Networks
Appl. Sci. 2017, 7(6), 557; doi:10.3390/app7060557
Received: 31 March 2017 / Revised: 20 May 2017 / Accepted: 23 May 2017 / Published: 27 May 2017
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Abstract
Mobile Edge Computing (MEC), which is considered a promising and emerging paradigm to provide caching capabilities in proximity to mobile devices in 5G networks, enables fast, popular content delivery of delay-sensitive applications at the backhaul capacity of limited mobile networks. Most existing studies
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Mobile Edge Computing (MEC), which is considered a promising and emerging paradigm to provide caching capabilities in proximity to mobile devices in 5G networks, enables fast, popular content delivery of delay-sensitive applications at the backhaul capacity of limited mobile networks. Most existing studies focus on cache allocation, mechanism design and coding design for caching. However, grid power supply with fixed power uninterruptedly in support of a MEC server (MECS) is costly and even infeasible, especially when the load changes dynamically over time. In this paper, we investigate the energy consumption of the MECS problem in cellular networks. Given the average download latency constraints, we take the MECS’s energy consumption, backhaul capacities and content popularity distributions into account and formulate a joint optimization framework to minimize the energy consumption of the system. As a complicated joint optimization problem, we apply a genetic algorithm to solve it. Simulation results show that the proposed solution can effectively determine the near-optimal caching placement to obtain better performance in terms of energy efficiency gains compared with conventional caching placement strategies. In particular, it is shown that the proposed scheme can significantly reduce the joint cost when backhaul capacity is low. Full article
(This article belongs to the Special Issue Green Wireless Networks)
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Open AccessArticle Low Frequency Interactive Auralization Based on a Plane Wave Expansion
Appl. Sci. 2017, 7(6), 558; doi:10.3390/app7060558
Received: 2 March 2017 / Revised: 12 May 2017 / Accepted: 23 May 2017 / Published: 27 May 2017
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Abstract
This paper addresses the problem of interactive auralization of enclosures based on a finite superposition of plane waves. For this, room acoustic simulations are performed using the Finite Element (FE) method. From the FE solution, a virtual microphone array is created and an
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This paper addresses the problem of interactive auralization of enclosures based on a finite superposition of plane waves. For this, room acoustic simulations are performed using the Finite Element (FE) method. From the FE solution, a virtual microphone array is created and an inverse method is implemented to estimate the complex amplitudes of the plane waves. The effects of Tikhonov regularization are also considered in the formulation of the inverse problem, which leads to a more efficient solution in terms of the energy used to reconstruct the acoustic field. Based on this sound field representation, translation and rotation operators are derived enabling the listener to move within the enclosure and listen to the changes in the acoustic field. An implementation of an auralization system based on the proposed methodology is presented. The results suggest that the plane wave expansion is a suitable approach to synthesize sound fields. Its advantage lies in the possibility that it offers to implement several sound reproduction techniques for auralization applications. Furthermore, features such as translation and rotation of the acoustic field make it convenient for interactive acoustic renderings. Full article
(This article belongs to the Special Issue Spatial Audio)
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Open AccessArticle Rogue Wave Modes for the Coupled Nonlinear Schrödinger System with Three Components: A Computational Study
Appl. Sci. 2017, 7(6), 559; doi:10.3390/app7060559
Received: 13 April 2017 / Revised: 9 May 2017 / Accepted: 16 May 2017 / Published: 29 May 2017
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Abstract
The system of “integrable” coupled nonlinear Schrödinger equations (Manakov system) with three components in the defocusing regime is considered. Rogue wave solutions exist for a restricted range of group velocity mismatch, and the existence condition correlates precisely with the onset of baseband modulation
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The system of “integrable” coupled nonlinear Schrödinger equations (Manakov system) with three components in the defocusing regime is considered. Rogue wave solutions exist for a restricted range of group velocity mismatch, and the existence condition correlates precisely with the onset of baseband modulation instability. This assertion is further elucidated numerically by evidence based on the generation of rogue waves by a single mode disturbance with a small frequency. This same computational approach can be adopted to study coupled nonlinear Schrödinger equations for the “non‐integrable” regime, where the coefficients of self‐phase modulation and cross‐phase modulation are different from each other. Starting with a wavy disturbance of a finite frequency corresponding to the large modulation instability growth rate, a breather can be generated. The breather can be symmetric or asymmetric depending on the magnitude of the growth rate. Under the presence of a third mode, rogue wave can exist under a larger group velocity mismatch between the components as compared to the two‐component system. Furthermore, the nonlinear coupling can enhance the maximum amplitude of the rogue wave modes and bright four‐petal configuration can be observed. Full article
(This article belongs to the Special Issue Guided-Wave Optics)
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Open AccessArticle Evaluation of a Novel Controlled Cutting Fluid Impinging Supply System When Machining Titanium Alloys
Appl. Sci. 2017, 7(6), 560; doi:10.3390/app7060560
Received: 11 April 2017 / Revised: 17 May 2017 / Accepted: 25 May 2017 / Published: 29 May 2017
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Abstract
Following a comprehensive review on titanium machining and methods of cutting fluid application, this paper presents a new Controlled cutting fluid impinging supply system (Cut‐list) developed to deliver an accurate amount of cutting fluid into the machining zone via wellpositioned coherent nozzles based
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Following a comprehensive review on titanium machining and methods of cutting fluid application, this paper presents a new Controlled cutting fluid impinging supply system (Cut‐list) developed to deliver an accurate amount of cutting fluid into the machining zone via wellpositioned coherent nozzles based on the calculation of the heat generated. The performance of the new system was evaluated against a conventional flood cutting fluid supply system during step shoulder milling of Ti‐6Al‐4V using vegetable oil‐based cutting fluid. The comparison was performed at different cutting speeds and feed rates. Comparison measures/indicators were cutting force, workpiece temperature, tool flank wear, burr formation and average surface roughness (Ra). The new system provided significant reductions in cutting fluid consumption of up to 42%. Additionally, reductions in cutting force, tool flank wear and burr height of 16.41%, 46.77%, and 31.70% were recorded, respectively. Smaller Ra values were also found with the use of the new system. Full article
(This article belongs to the Section Mechanical Engineering)