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Appl. Sci., Volume 7, Issue 4 (April 2017)

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Cover Story (view full-size image) Membrane distillation (MD) is an emerging non-isothermal membrane separation process having broad [...] Read more.
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Open AccessArticle Investigation on Unsteady Flow Characteristics of a SCO2 Centrifugal Compressor
Appl. Sci. 2017, 7(4), 310; https://doi.org/10.3390/app7040310
Received: 31 December 2016 / Revised: 23 February 2017 / Accepted: 17 March 2017 / Published: 23 March 2017
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Abstract
Supercritical carbon dioxide (SCO2) is a vital working fluid in the application of power units and its high density helps to achieve a compact mechanical structure. Centrifugal compressors are of vital use in various kinds of equipment. In this paper, a
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Supercritical carbon dioxide (SCO2) is a vital working fluid in the application of power units and its high density helps to achieve a compact mechanical structure. Centrifugal compressors are of vital use in various kinds of equipment. In this paper, a SCO2 centrifugal compressor of large input power and mass flow rate is designed and numerically investigated. A thorough numerical analysis of the unsteady flow field in the centrifugal compressor is performed in ANSYS-CFX. The computation adopts hexahedral mesh, finite volume method, and the RNG k-ε two-equation turbulence model. Streamlines, temperature, pressure, and Mach number distributions at different time steps in one revolution period are covered to present the unsteady effect of turbomachinery. Meanwhile, the force on a single rotor blade is monitored to investigate the frequency components of exciting force, thus providing the foundation for vibration analysis. Moreover, the torque, output power, pressure ratio, and isentropic efficiency in the steady and the unsteady time-averaged condition are calculated and compared with the design condition to measure the validity of the design. In summary, the unsteady computation result reveals that the unsteady flow characteristics are prominent in the designed compressor and the design of impeller and diffuser meet the requirement. Full article
(This article belongs to the Special Issue The Applications of Supercritical Carbon Dioxide)
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Open AccessArticle An Encoder-Decoder Based Convolution Neural Network (CNN) for Future Advanced Driver Assistance System (ADAS)
Appl. Sci. 2017, 7(4), 312; https://doi.org/10.3390/app7040312
Received: 23 January 2017 / Revised: 28 February 2017 / Accepted: 17 March 2017 / Published: 23 March 2017
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Abstract
We propose a practical Convolution Neural Network (CNN) model termed the CNN for Semantic Segmentation for driver Assistance system (CSSA). It is a novel semantic segmentation model for probabilistic pixel-wise segmentation, which is able to predict pixel-wise class labels of a given input
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We propose a practical Convolution Neural Network (CNN) model termed the CNN for Semantic Segmentation for driver Assistance system (CSSA). It is a novel semantic segmentation model for probabilistic pixel-wise segmentation, which is able to predict pixel-wise class labels of a given input image. Recently, scene understanding has turned out to be one of the emerging areas of research, and pixel-wise semantic segmentation is a key tool for visual scene understanding. Among future intelligent systems, the Advanced Driver Assistance System (ADAS) is one of the most favorite research topic. The CSSA is a road scene understanding CNN that could be a useful constituent of the ADAS toolkit. The proposed CNN network is an encoder-decoder model, which is built on convolutional encoder layers adopted from the Visual Geometry Group’s VGG-16 net, whereas the decoder is inspired by segmentation network (SegNet). The proposed architecture mitigates the limitations of the existing methods based on state-of-the-art encoder-decoder design. The encoder performs convolution, while the decoder is responsible for deconvolution and un-pooling/up-sampling to predict pixel-wise class labels. The key idea is to apply the up-sampling decoder network, which maps the low-resolution encoder feature maps. This architecture substantially reduces the number of trainable parameters and reuses the encoder’s pooling indices to up-sample to map pixel-wise classification and segmentation. We have experimented with different activation functions, pooling methods, dropout units and architectures to design an efficient CNN architecture. The proposed network offers a significant improvement in performance in segmentation results while reducing the number of trainable parameters. Moreover, there is a considerable improvement in performance in comparison to the benchmark results over PASCAL VOC-12 and the CamVid. Full article
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Open AccessArticle Influence Analysis of a Higher-Order CSI Effect on AMD Systems and Its Time-Varying Delay Compensation Using a Guaranteed Cost Control Algorithm
Appl. Sci. 2017, 7(4), 313; https://doi.org/10.3390/app7040313
Received: 12 February 2017 / Revised: 16 March 2017 / Accepted: 20 March 2017 / Published: 23 March 2017
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Abstract
A control-structure interaction (CSI) effect commonly exists between an active mass damper/driver (AMD) system with a DC motor and a controlled building. Additionally, its higher-order component leads to the fact that the actual control force acts behind its theoretical time; i.e., time delay.
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A control-structure interaction (CSI) effect commonly exists between an active mass damper/driver (AMD) system with a DC motor and a controlled building. Additionally, its higher-order component leads to the fact that the actual control force acts behind its theoretical time; i.e., time delay. In this paper, the main influencing factors of a higher-order CSI effect are analyzed, including the input frequency of the control voltage, the structural parametric uncertainties, and the control gains. In addition, a new time-delay compensation controller based on a guaranteed cost control (GCC) algorithm is designed, to consider the higher-order CSI effect for multi-level steel frame structures. Experiments on a typical four-storey frame are conducted, to verify the performances of the proposed method. The results show that the proposed controller has an excellent control effect and stable control parameters, even under the situation of large parametric uncertainties and long time-varying delays. Full article
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Open AccessArticle Seismic Damage Evaluation of Concrete-Encased Steel Frame-Reinforced Concrete Core Tube Buildings Based on Dynamic Characteristics
Appl. Sci. 2017, 7(4), 314; https://doi.org/10.3390/app7040314
Received: 8 December 2016 / Revised: 5 February 2017 / Accepted: 16 March 2017 / Published: 23 March 2017
Cited by 2 | PDF Full-text (8322 KB) | HTML Full-text | XML Full-text
Abstract
To evaluate damage state and residual resistance of concrete-encased steel frame-reinforced concrete core tube buildings under earthquake actions, a criterion of damage assessment based on dynamic characteristics is proposed in this paper. Dynamic characterization experiments were conducted on a 10-story and 1/5 scaled
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To evaluate damage state and residual resistance of concrete-encased steel frame-reinforced concrete core tube buildings under earthquake actions, a criterion of damage assessment based on dynamic characteristics is proposed in this paper. Dynamic characterization experiments were conducted on a 10-story and 1/5 scaled building model using velocity sensors on each floor, and natural frequencies were obtained based on the measured data. Modal analysis was carried out using a nonlinear finite element program, and the simulation results of the dynamic characteristics agreed well with experimental ones. Then, the damage processes under different seismic wave inputs were revealed based on finite element analysis, and the max story drift angle was chosen to reflect the damage state and to quantify the degree of damage. A criterion of seismic damage assessment is proposed based on the relationship between the quantitative damage value and the dynamic characteristics, in which the higher order modes were considered. Moreover, influencing factors, including earthquake intensity and structural stiffness ratio, were analyzed, and the results indicated that the proposed damage index based on dynamic characteristics can account for the higher-order modes and provides an innovative approach to evaluate the seismic damage. Full article
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Open AccessArticle Zero-Voltage Ride-Through Capability of Single-Phase Grid-Connected Photovoltaic Systems
Appl. Sci. 2017, 7(4), 315; https://doi.org/10.3390/app7040315
Received: 10 December 2016 / Revised: 13 March 2017 / Accepted: 20 March 2017 / Published: 24 March 2017
Cited by 2 | PDF Full-text (3565 KB) | HTML Full-text | XML Full-text
Abstract
Distributed renewable energy systems play an increasing role in today’s energy paradigm. Thus, intensive research activities have been centered on improving the performance of renewable energy systems, including photovoltaic (PV) systems, which should be of multiple-functionality. That is, the PV systems should be
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Distributed renewable energy systems play an increasing role in today’s energy paradigm. Thus, intensive research activities have been centered on improving the performance of renewable energy systems, including photovoltaic (PV) systems, which should be of multiple-functionality. That is, the PV systems should be more intelligent in the consideration of grid stability, reliability, and fault protection. Therefore, in this paper, the performance of single-phase grid-connected PV systems under an extreme grid fault (i.e., when the grid voltage dips to zero) is explored. It has been revealed that combining a fast and accurate synchronization mechanism with appropriate control strategies for the zero-voltage ride-through (ZVRT) operation is mandatory. Accordingly, the representative synchronization techniques (i.e., the phase-locked loop (PLL) methods) in the ZVRT operation are compared in terms of detection precision and dynamic response. It shows that the second-order generalized integrator (SOGI-PLL) is a promising solution for single-phase systems in the case of fault ride-through. A control strategy by modifying the SOGI-PLL scheme is then introduced to single-phase grid-connected PV systems for ZVRT operation. Simulations are performed to verify the discussions. The results have demonstrated that the proposed method can help single-phase PV systems to temporarily ride through zero-voltage faults with good dynamics. Full article
(This article belongs to the Special Issue Advancing Grid-Connected Renewable Generation Systems)
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Open AccessArticle Fall Detection for Elderly from Partially Observed Depth-Map Video Sequences Based on View-Invariant Human Activity Representation
Appl. Sci. 2017, 7(4), 316; https://doi.org/10.3390/app7040316
Received: 1 February 2017 / Revised: 17 March 2017 / Accepted: 22 March 2017 / Published: 24 March 2017
Cited by 5 | PDF Full-text (1426 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents a new approach for fall detection from partially-observed depth-map video sequences. The proposed approach utilizes the 3D skeletal joint positions obtained from the Microsoft Kinect sensor to build a view-invariant descriptor for human activity representation, called the motion-pose geometric descriptor
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This paper presents a new approach for fall detection from partially-observed depth-map video sequences. The proposed approach utilizes the 3D skeletal joint positions obtained from the Microsoft Kinect sensor to build a view-invariant descriptor for human activity representation, called the motion-pose geometric descriptor (MPGD). Furthermore, we have developed a histogram-based representation (HBR) based on the MPGD to construct a length-independent representation of the observed video subsequences. Using the constructed HBR, we formulate the fall detection problem as a posterior-maximization problem in which the posteriori probability for each observed video subsequence is estimated using a multi-class SVM (support vector machine) classifier. Then, we combine the computed posteriori probabilities from all of the observed subsequences to obtain an overall class posteriori probability of the entire partially-observed depth-map video sequence. To evaluate the performance of the proposed approach, we have utilized the Kinect sensor to record a dataset of depth-map video sequences that simulates four fall-related activities of elderly people, including: walking, sitting, falling form standing and falling from sitting. Then, using the collected dataset, we have developed three evaluation scenarios based on the number of unobserved video subsequences in the testing videos, including: fully-observed video sequence scenario, single unobserved video subsequence of random lengths scenarios and two unobserved video subsequences of random lengths scenarios. Experimental results show that the proposed approach achieved an average recognition accuracy of 93 . 6 % , 77 . 6 % and 65 . 1 % , in recognizing the activities during the first, second and third evaluation scenario, respectively. These results demonstrate the feasibility of the proposed approach to detect falls from partially-observed videos. Full article
(This article belongs to the Special Issue Human Activity Recognition)
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Open AccessArticle Sensing Performance of a Vibrotactile Glove for Deaf-Blind People
Appl. Sci. 2017, 7(4), 317; https://doi.org/10.3390/app7040317
Received: 19 December 2016 / Revised: 17 March 2017 / Accepted: 20 March 2017 / Published: 24 March 2017
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Abstract
This paper presents a glove designed to assess the viability of communication between a deaf-blind user and his/her interlocutor through a vibrotactile device. This glove is part of the TactileCom system, where communication is bidirectional through a wireless link, so no contact is
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This paper presents a glove designed to assess the viability of communication between a deaf-blind user and his/her interlocutor through a vibrotactile device. This glove is part of the TactileCom system, where communication is bidirectional through a wireless link, so no contact is required between the interlocutors. Responsiveness is higher than with letter by letter wording. The learning of a small set of concepts is simpler and the amount learned can be increased at the user’s convenience. The number of stimulated fingers, the keying frequencies and finger response were studied. Message identification rate was 97% for deaf-blind individuals and 81% for control subjects. Identification by single-finger stimulation was better than by multiple-finger stimulation. The interface proved suitable for communication with deaf-blind individuals and can also be used in other conditions, such as multilingual or noisy environments. Full article
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Open AccessArticle Investigation of Interactive Strategies Used in Undertaking Collaborative Tasks
Appl. Sci. 2017, 7(4), 318; https://doi.org/10.3390/app7040318
Received: 14 January 2017 / Revised: 14 March 2017 / Accepted: 21 March 2017 / Published: 24 March 2017
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Abstract
Collaborative virtual environments (CVEs) present ways for human users to work together on a task. Research efforts of CVEs have mainly focused on the factors that affect the task performance of the users, such as awareness, communication, and presence. Furthermore, the users involved
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Collaborative virtual environments (CVEs) present ways for human users to work together on a task. Research efforts of CVEs have mainly focused on the factors that affect the task performance of the users, such as awareness, communication, and presence. Furthermore, the users involved normally have the same task experience or knowledge background. In this paper, we examined the effect of interactive strategies for human/human interaction, which involves human users with different levels of expertise. Within a CVE for an expert and a novice, we deployed three interactive strategies—Tele-Operation, Tele-Assistance3, and Tele-Assistance7—to give the three degrees of autonomy to the novice. Focusing on the performance of the novice, our findings revealed that each interactive strategy has a different effect on the task performance of the novice. These findings could aid in choosing an optimal interactive strategy for performing a collaborative task between an expert and a novice. Full article
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Open AccessArticle Analyses of the Effect of Cycle Inlet Temperature on the Precooler and Plant Efficiency of the Simple and Intercooled Helium Gas Turbine Cycles for Generation IV Nuclear Power Plants
Appl. Sci. 2017, 7(4), 319; https://doi.org/10.3390/app7040319
Received: 22 January 2017 / Revised: 16 March 2017 / Accepted: 20 March 2017 / Published: 24 March 2017
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Abstract
Nuclear Power Plant (NPP) precooler coolant temperature is critical to performance because it impacts the work required to increase the coolant pressure. Variation of the coolant temperature results in varied precooler hot gas temperatures, which are cooled before re-entry. For recirculation, the heat
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Nuclear Power Plant (NPP) precooler coolant temperature is critical to performance because it impacts the work required to increase the coolant pressure. Variation of the coolant temperature results in varied precooler hot gas temperatures, which are cooled before re-entry. For recirculation, the heat sink (usually sea water), could exit the precooler at unfavourable temperatures and impact the re-entering coolant, if not recirculated properly at the source. The study objective is to analyse the effects of coolant inlet temperature on the heat sink and cycle efficiency. The cycles are Simple Cycle Recuperated (SCR), Intercooler Cycle Recuperated (ICR), and Intercooled Cycle without Recuperation (IC). Results show that the co-current precooler provides favourable outlet heat sink temperatures but compromises compactness. For a similar technology level, the counter-current precooler yields excessive heat sink outlet temperatures due to a compact, robust, and efficient heat transfer design, but could be detrimental to precooler integrity due to corrosion, including the cycle performance, if not recirculated back into the sea effectively. For the counter-current, the ICR has the best heat sink average temperature ratio of 1.4; the SCR has 2.7 and IC has 3.3. The analyses aid the development of Gas Cooled Fast Reactors (GFRs) and Very High Temperature Reactors (VHTRs), where helium is used as the coolant. Full article
(This article belongs to the Special Issue Gas Turbines Propulsion and Power)
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Open AccessArticle A Study on the Optimal Actuation Structure Design of a Direct Needle-Driven Piezo Injector for a CRDi Engine
Appl. Sci. 2017, 7(4), 320; https://doi.org/10.3390/app7040320
Received: 13 January 2017 / Revised: 13 March 2017 / Accepted: 14 March 2017 / Published: 24 March 2017
Cited by 1 | PDF Full-text (8902 KB) | HTML Full-text | XML Full-text
Abstract
Recently, the high-pressure fuel injection performance of common-rail direct injection (CRDi) engines has become more important, due to the need to improve the multi-injection strategy. A multiple injection strategy provides better emission and fuel economy characteristics than a normal single injection scheme. The
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Recently, the high-pressure fuel injection performance of common-rail direct injection (CRDi) engines has become more important, due to the need to improve the multi-injection strategy. A multiple injection strategy provides better emission and fuel economy characteristics than a normal single injection scheme. The CRDi engine performance changes with the type of high-pressure electro-mechanical injector that is used and its injection response in a multi-injection scheme. In this study, a direct needle-driven piezo injector (DPI) was investigated, to optimize its actuation components, including the plate length, number of springs, and the elasticity of the spring between the injector needle and the piezo stack. Three prototype DPIs were proposed by this research. They were classified as Type 1, 2, and 3, depending on whether the injector needle was hydraulic or mechanical. Then, the optimal prototype was determined by conducting four evaluation experiments analyzing the maximum injection pressure, injection rate, spray visualization, and real engine combustion application. As a result, it was found that the Type 3 DPI prototype, with several pan-springs and plates, had the highest injection pressure, a steady injection rate, and the fastest spray speed. It also demonstrated the most effective emission reduction for a two-stage rapid spray injection in a single-cylinder CRDi engine. The Type 3 DPI displays an increased elasticity from its hydraulic needle that provides a synergy effect for improving DPI actuation. Full article
(This article belongs to the Special Issue Internal Combustion Engines (ICE) for Ground Transport)
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Open AccessArticle Optimization of Subcritical Water Extraction of Resveratrol from Grape Seeds by Response Surface Methodology
Appl. Sci. 2017, 7(4), 321; https://doi.org/10.3390/app7040321
Received: 15 January 2017 / Revised: 16 March 2017 / Accepted: 21 March 2017 / Published: 24 March 2017
Cited by 1 | PDF Full-text (1733 KB) | HTML Full-text | XML Full-text
Abstract
The subcritical water extraction (SWE) is a high-efficiency and environment-friendly extraction method. The extraction of resveratrol (RES) of grape seeds obtained from the wine production process was proposed using subcritical water extraction (SWE). The effects of different extraction process parameters on RES yield
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The subcritical water extraction (SWE) is a high-efficiency and environment-friendly extraction method. The extraction of resveratrol (RES) of grape seeds obtained from the wine production process was proposed using subcritical water extraction (SWE). The effects of different extraction process parameters on RES yield were investigated by single factors. Extraction optimization was conducted using response surface methodology (RSM). Extraction temperature was proven to be the most significant factor influencing RES yield. The optimal conditions was as follows: extraction pressure of 1.02 MPa, temperature of 152.32 °C, time of 24.89 min, and a solid/solvent ratio of 1:15 g/mL. Under these optimal conditions, the predicted extraction RES yield was 6.90 μg/g and the recoveries was up to 91.98%. Compared to other previous studies, this method required less pollution and less treatment time to extract RES from grape seeds. From these results, added economic value to this agroindustrial residue is proposed using environmentally friendly extraction techniques. Full article
(This article belongs to the Section Chemistry)
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Open AccessArticle The Application of Supercritical Carbon Dioxide and Ethanol for the Extraction of Phenolic Compounds from Chokeberry Pomace
Appl. Sci. 2017, 7(4), 322; https://doi.org/10.3390/app7040322
Received: 22 December 2016 / Revised: 20 March 2017 / Accepted: 21 March 2017 / Published: 25 March 2017
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Abstract
Chokeberry (Aronia melanocarpa (Michx.) Elliot) is a fruit with exceptionally high levels of phenolic compounds which are accumulated mainly in the peel; hence, the majority remains in the leftovers after juice production. Extraction with the use of carbon dioxide in supercritical conditions
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Chokeberry (Aronia melanocarpa (Michx.) Elliot) is a fruit with exceptionally high levels of phenolic compounds which are accumulated mainly in the peel; hence, the majority remains in the leftovers after juice production. Extraction with the use of carbon dioxide in supercritical conditions was used to isolate phenolic compounds from the pomace. The effect of the process parameters (temperature; pressure; and the addition of ethanol) on the extraction yields and properties of the extracts was investigated. The anthocyanin and total phenolic compound content, as well as the scavenging activity against five selected radicals, were evaluated. The best results were acquired for 35 °C, 10 MPa, and 80% m/m ethanol addition, the yield of phenolic compounds was 1.52 g per 100 g of pomace. The amount of extracted phenolics and the antioxidative attributes of the extracts were highly correlated. The impact of supercritical carbon dioxide density on the amount of recovered compounds was confirmed. The use of supercritical CO2 led to a significant reduction in the volume of organic solvent required for extraction. Full article
(This article belongs to the Special Issue The Applications of Supercritical Carbon Dioxide)
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Open AccessArticle Integrated Design of Hybrid Interstory-Interbuilding Multi-Actuation Schemes for Vibration Control of Adjacent Buildings under Seismic Excitations
Appl. Sci. 2017, 7(4), 323; https://doi.org/10.3390/app7040323
Received: 30 January 2017 / Revised: 15 March 2017 / Accepted: 22 March 2017 / Published: 25 March 2017
Cited by 1 | PDF Full-text (1038 KB) | HTML Full-text | XML Full-text
Abstract
The design of vibration control systems for the seismic protection of closely adjacent buildings is a complex and challenging problem. In this paper, we consider distributed multi-actuation schemes that combine interbuilding linking elements and interstory actuation devices. Using an advanced static output-feedback H
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The design of vibration control systems for the seismic protection of closely adjacent buildings is a complex and challenging problem. In this paper, we consider distributed multi-actuation schemes that combine interbuilding linking elements and interstory actuation devices. Using an advanced static output-feedback H approach, active and passive vibration control systems are designed for a multi-story two-building structure equipped with a selected set of linked and unlinked actuation schemes. To validate the effectiveness of the obtained controllers, the corresponding frequency responses are investigated and a proper set of numerical simulations is conducted using the full scale North–South El Centro 1940 seismic record as ground acceleration disturbance. The observed results indicate that using combined interstory-interbuilding multi-actuation schemes is an effective means of mitigating the vibrational response of the individual buildings and, simultaneously, reducing the risk of interbuilding pounding. These results also point out that passive control systems with high-performance characteristics can be designed using damping elements. Full article
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Open AccessArticle Empirical Mode Decomposition of Ultrasound Imagingfor Gain-Independent Measurement on Tissue Echogenicity: A Feasibility Study
Appl. Sci. 2017, 7(4), 324; https://doi.org/10.3390/app7040324
Received: 11 February 2017 / Revised: 25 February 2017 / Accepted: 22 March 2017 / Published: 25 March 2017
Cited by 1 | PDF Full-text (4820 KB) | HTML Full-text | XML Full-text
Abstract
Empirical mode decomposition (EMD) is an adaptive method for decomposing a signal into intrinsic mode functions (IMFs).This study explored using EMD of ultrasound imaging for gain-independent measurements on tissue echogenicity. The IMF-based echogenicity ratio (IER) was proposed using the first (C1
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Empirical mode decomposition (EMD) is an adaptive method for decomposing a signal into intrinsic mode functions (IMFs).This study explored using EMD of ultrasound imaging for gain-independent measurements on tissue echogenicity. The IMF-based echogenicity ratio (IER) was proposed using the first (C1) and second IMFs (C2) of ultrasound radiofrequency data. Experiments on lipid phantoms were conducted to investigate the practical performance of IER. Phantoms with lipid concentrations 0%–30% (n = 36) were scanned using a clinical ultrasound scanner to acquire the radiofrequency data under different gains (12–33 dB) for EMD and IER calculations. Experiments on a tissue-mimicking phantom were further performed using the same ultrasound system and data acquisition procedure to investigate the effect of ultrasound frequency on the IER at5–8 MHz.Experimental results showed that the IER measured under 33-dB gain decreased from 6.65 ± 0.23 to 3.97 ± 0.10 when the lipid concentrations were increased from 0% to 30%. When 12-dB gain was used, the IER decreased from 6.21 ± 0.29 to 3.39 ± 0.07. However, whenincreasing the frequency, the IER had a mean decreasing rate of −8.67% per MHz, which was lower than those of the C1 and C2 intensities.The proposed IER may allow gain-independent measurement on tissue echogenicity. Full article
(This article belongs to the Section Acoustics)
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Open AccessArticle A Substrate-Reclamation Technology for GaN-Based Lighting-Emitting Diodes Wafer
Appl. Sci. 2017, 7(4), 325; https://doi.org/10.3390/app7040325
Received: 20 February 2017 / Revised: 22 March 2017 / Accepted: 23 March 2017 / Published: 27 March 2017
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Abstract
This study reports on the use of a substrate-reclamation technology for a gallium nitride (GaN)-based lighting-emitting diode (LED) wafer. There are many ways to reclaim sapphire substrates of scrap LED wafers. Compared with a common substrate-reclamation method based on chemical mechanical polishing, this
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This study reports on the use of a substrate-reclamation technology for a gallium nitride (GaN)-based lighting-emitting diode (LED) wafer. There are many ways to reclaim sapphire substrates of scrap LED wafers. Compared with a common substrate-reclamation method based on chemical mechanical polishing, this research technology exhibits simple process procedures, without impairing the surface morphology and thickness of the sapphire substrate, as well as the capability of an almost unlimited reclamation cycle. The optical performances of LEDs on non-reclaimed and reclaimed substrates were consistent for 28.37 and 27.69 mcd, respectively. Full article
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Open AccessArticle An Improvement of a Fuzzy Logic-Controlled Maximum Power Point Tracking Algorithm for Photovoltic Applications
Appl. Sci. 2017, 7(4), 326; https://doi.org/10.3390/app7040326
Received: 31 December 2016 / Revised: 13 March 2017 / Accepted: 14 March 2017 / Published: 29 March 2017
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Abstract
This paper presents an improved maximum power point tracking (MPPT) algorithm using a fuzzy logic controller (FLC) in order to extract potential maximum power from photovoltaic cells. The objectives of the proposed algorithm are to improve the tracking speed, and to simultaneously solve
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This paper presents an improved maximum power point tracking (MPPT) algorithm using a fuzzy logic controller (FLC) in order to extract potential maximum power from photovoltaic cells. The objectives of the proposed algorithm are to improve the tracking speed, and to simultaneously solve the inherent drawbacks such as slow tracking in the conventional perturb and observe (P and O) algorithm. The performances of the conventional P and O algorithm and the proposed algorithm are compared by using MATLAB/Simulink in terms of the tracking speed and steady-state oscillations. Additionally, both algorithms were experimentally validated through a digital signal processor (DSP)-based controlled-boost DC-DC converter. The experimental results show that the proposed algorithm performs with a shorter tracking time, smaller output power oscillation, and higher efficiency, compared with the conventional P and O algorithm. Full article
(This article belongs to the Special Issue Energy Saving)
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Open AccessArticle The Experimental Study of the Temperature Effect on the Interfacial Properties of Fully Grouted Rock Bolt
Appl. Sci. 2017, 7(4), 327; https://doi.org/10.3390/app7040327
Received: 9 January 2017 / Revised: 11 March 2017 / Accepted: 24 March 2017 / Published: 27 March 2017
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Abstract
This study analyzes the phenomenon of performance deterioration in fully grouted rock bolts in tunnels with a dry, hot environment and high geothermal activity with a focus on temperature effects on interfacial bond performance. Three groups of fully grouted rock bolt specimens were
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This study analyzes the phenomenon of performance deterioration in fully grouted rock bolts in tunnels with a dry, hot environment and high geothermal activity with a focus on temperature effects on interfacial bond performance. Three groups of fully grouted rock bolt specimens were designed based on similar mechanical principles. They were produced and maintained at 20 °C, 35 °C, and 50 °C. Through the indoor gradual loading tensile test of specimens, variations of axial force and shear stress between the rock bolt and mortar adhesive interface were obtained under different environmental temperatures. Distribution of the axial force and shear stress on the anchorage section were found under different tensile forces. Results showed that, with an increase in specimen environmental temperature, maximum shear stress of the rock bolt section became smaller, while shear stress distribution along the rock bolt segment became more uniform. In addition, the axial force value at the same position along the pull end was greater, while axial stress along the anchorage’s length decayed faster. With an increase in tensile force under different temperatures, the axial force and maximum shear stress of rock bolt specimens along the anchorage section has a corresponding increase. Full article
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Open AccessArticle Simulation Analysis and Experiment of Variable-Displacement Asymmetric Axial Piston Pump
Appl. Sci. 2017, 7(4), 328; https://doi.org/10.3390/app7040328
Received: 1 December 2016 / Revised: 22 March 2017 / Accepted: 22 March 2017 / Published: 27 March 2017
Cited by 1 | PDF Full-text (6947 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The variable displacement pump control system has greater energy-saving advantages and application prospects than the valve control system. However, the variable displacement pump control of differential cylinder is not concurrent with the existing technologies. The asymmetric pump-controlled cylinder is, therefore, used to balance
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The variable displacement pump control system has greater energy-saving advantages and application prospects than the valve control system. However, the variable displacement pump control of differential cylinder is not concurrent with the existing technologies. The asymmetric pump-controlled cylinder is, therefore, used to balance the unequal volume flow through a single rod cylinder in closed-circuit system. This is considered to be an effective method. Nevertheless, the asymmetric axial piston pump (AAPP) is a constant displacement pump. In this study, variable-displacement asymmetric axial piston pump (VAPP) is investigated according to the same principle used in investigating AAPP. This study, therefore, aims at investigating the characteristics of VAPP. The variable-displacement output of VAPP is implemented by controlling the swash plate angle with angle feedback control circuit, which is composed of a servo proportional valve and an angular displacement sensor. The angular displacement sensor is connected to the swash plate. The simulation model of VAPP, which is set up through the ITI-SimulationX simulation platform, is used to predict VAPP’s characteristics. The purpose of implementing the experiment is to verify the theoretical results. Both the simulation and the experiment results demonstrated that the swash plate angle is controlled by a variable mechanism; when the swash plate angle increases, the flow of Port B and Port T increases while the response speed of Port B and Port T also accelerates. When the swash plate angle is constant, the flow of Port B and Port T increases along with the increase of pump speed, although the pressure-response speed of Port B is faster than that of Port T. Consequently, the flow pulsation of Port B and Port T tends to decrease gradually along with the increase of pump speed. When the pressure loaded on Port B equals to that of Port T, the flow ripple cycle of Port B is longer than that of Port T, whereas the peak flow of Port B is higher than that of Port T. Since the flow ripple of Port T is bigger than that of Port B, Port T should be connected to the low pressure sides or the oil tank so that it does not affect VAPP’s performance. Further, to avoid the backflow of VAPP from Port T to Port B, Port T cannot be loaded alone, and the loading pressure of Port T also cannot exceed that of Port B. Full article
(This article belongs to the Section Energy)
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Open AccessArticle Collision Avoidance for Cooperative UAVs with Rolling Optimization Algorithm Based on Predictive State Space
Appl. Sci. 2017, 7(4), 329; https://doi.org/10.3390/app7040329
Received: 23 December 2016 / Revised: 17 March 2017 / Accepted: 20 March 2017 / Published: 28 March 2017
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Abstract
Unmanned Aerial Vehicles (UAVs) have recently received notable attention because of their wide range of applications in urban civilian use and in warfare. With air traffic densities increasing, it is more and more important for UAVs to be able to predict and avoid
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Unmanned Aerial Vehicles (UAVs) have recently received notable attention because of their wide range of applications in urban civilian use and in warfare. With air traffic densities increasing, it is more and more important for UAVs to be able to predict and avoid collisions. The main goal of this research effort is to adjust real-time trajectories for cooperative UAVs to avoid collisions in three-dimensional airspace. To explore potential collisions, predictive state space is utilized to present the waypoints of UAVs in the upcoming situations, which makes the proposed method generate the initial collision-free trajectories satisfying the necessary constraints in a short time. Further, a rolling optimization algorithm (ROA) can improve the initial waypoints, minimizing its total distance. Several scenarios are illustrated to verify the proposed algorithm, and the results show that our algorithm can generate initial collision-free trajectories more efficiently than other methods in the common airspace. Full article
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Open AccessArticle Large-Scale Permanent Slide Imaging and Image Analysis for Diatom Morphometrics
Appl. Sci. 2017, 7(4), 330; https://doi.org/10.3390/app7040330
Received: 1 February 2017 / Revised: 16 March 2017 / Accepted: 23 March 2017 / Published: 28 March 2017
PDF Full-text (3490 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Light microscopy analysis of diatom frustules is widely used in basic and applied research, notably taxonomy, morphometrics, water quality monitoring and paleo-environmental studies. Although there is a need for automation in these applications, various developments in image processing and analysis methodology supporting these
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Light microscopy analysis of diatom frustules is widely used in basic and applied research, notably taxonomy, morphometrics, water quality monitoring and paleo-environmental studies. Although there is a need for automation in these applications, various developments in image processing and analysis methodology supporting these tasks have not become widespread in diatom-based analyses. We have addressed this issue by combining our automated diatom image analysis software SHERPA with a commercial slide-scanning microscope. The resulting workflow enables mass-analyses of a broad range of morphometric features from individual frustules mounted on permanent slides. Extensive automation and internal quality control of the results helps to minimize user intervention, but care was taken to allow the user to stay in control of the most critical steps (exact segmentation of valve outlines and selection of objects of interest) using interactive functions for reviewing and revising results. In this contribution, we describe our workflow and give an overview of factors critical for success, ranging from preparation and mounting through slide scanning and autofocus finding to final morphometric data extraction. To demonstrate the usability of our methods we finally provide an example application by analysing Fragilariopsis kerguelensis valves originating from a sediment core, which substantially extends the size range reported in the literature. Full article
(This article belongs to the Special Issue Automated Analysis and Identification of Phytoplankton Images)
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Open AccessArticle Simulation of Permanent Deformation in High-Modulus Asphalt Pavement with Sloped and Horizontally Curved Alignment
Appl. Sci. 2017, 7(4), 331; https://doi.org/10.3390/app7040331
Received: 30 December 2016 / Revised: 20 March 2017 / Accepted: 24 March 2017 / Published: 28 March 2017
Cited by 2 | PDF Full-text (2317 KB) | HTML Full-text | XML Full-text
Abstract
This study aims to evaluate the permanent deformation of high-modulus asphalt pavement in special road using viscoelastic theory. Based on the creep test, the Prony series representation of Burgers model parameters for different asphalt mixtures were obtained and used in the deformation simulation
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This study aims to evaluate the permanent deformation of high-modulus asphalt pavement in special road using viscoelastic theory. Based on the creep test, the Prony series representation of Burgers model parameters for different asphalt mixtures were obtained and used in the deformation simulation of a high-modulus asphalt pavement situated in a horizontally curved ramp. The orthogonal design method was used to show the effect of different factors on the deformation. Results reveal that rutting in curved ramp was greater than in straightaway. Further, evident upheaval was found on the downhill pavement surface and outer pavement parts of the curve due to longitudinal friction force and sideway force. In addition, the upper and middle asphalt courses in such road seemed more crucial to pavement anti-rutting performance, since inclusion of shear force changed pavement deformation characteristic and the potential rutting area tended to move up. Finally, a preliminary equation to predict rutting in sloped and curved road with widely accepted pavement structure in China was proposed. Full article
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Open AccessArticle An Independent Internal Cooling System for Promoting Heat Dissipation during Dry Cutting with Numerical and Experimental Verification
Appl. Sci. 2017, 7(4), 332; https://doi.org/10.3390/app7040332
Received: 26 December 2016 / Revised: 6 March 2017 / Accepted: 23 March 2017 / Published: 28 March 2017
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Abstract
The cooling system has emerged as an effective way to alleviate the excessive heat generation during dry cutting processes. In this paper, we investigated a novel type of internal cooling system, independent of additional mechanical accessories, as a promising cooling alternative. The proposed
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The cooling system has emerged as an effective way to alleviate the excessive heat generation during dry cutting processes. In this paper, we investigated a novel type of internal cooling system, independent of additional mechanical accessories, as a promising cooling alternative. The proposed system is devised as connected internal fluid channels of a-“V” shape created according to the geometric shape of the tool-holder. Enabling quantitative evaluation of the effectiveness of the proposed system, a new numerical approach is established. Within the approach, heat transfer equations are deduced according to thermodynamics; parameters of the equations are specified via analytical modeling. As a result, cutting temperatures can be estimated with high precision according to the outlet temperature. Moreover, a cutting experiment was carried out to verify the effectiveness of the proposed numerical approach. Tool-chip interface temperatures were measured using an infrared thermal imager. Smooth measurements with suppressed noises are derived based on a new adaptive mean filter originated by empirical mode decomposition (EMD). The experimental results demonstrate the proposed system can reduce the temperature substantially (almost 30% at the measuring point) and the results are highly consistent with those of numerical simulation. The proposed cooling system is a prospective enhancement for development of smart cutting tools. Full article
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Open AccessArticle Target Tracking Based on a Nonsingular Fast Terminal Sliding Mode Guidance Law by Fixed-Wing UAV
Appl. Sci. 2017, 7(4), 333; https://doi.org/10.3390/app7040333
Received: 10 January 2017 / Revised: 10 March 2017 / Accepted: 24 March 2017 / Published: 29 March 2017
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Abstract
This paper proposes a modified nonsingular fast terminal sliding mode (NFTSM) guidance law to solve the problem of ground moving target tracking for fixed-wing unmanned aerial vehicle (UAV) in a planar environment. Firstly, the loitering algorithm is analysed, which can steer the UAV
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This paper proposes a modified nonsingular fast terminal sliding mode (NFTSM) guidance law to solve the problem of ground moving target tracking for fixed-wing unmanned aerial vehicle (UAV) in a planar environment. Firstly, the loitering algorithm is analysed, which can steer the UAV to follow and circle around a ground moving target with the desired distance by heading angle control. Secondly, the effects of different parameters on the convergence time of sliding manifold is presented which is helpful for the designing of sliding manifold. Singularity can be avoided by using a modified saturation function which is obtained through a small range around the null point. Moreover, the NFTSM sliding manifold is used in the loitering algorithm. By using the Lyapunov theory, the finite-time convergence of the proposed method has been proved in the the reaching phase and the sliding phase. In order to verify the approach’s feasibility and benefits, numerical simulations are performed by using a moving target with three different motion states in comparison with the conventional sliding model control method. Simulation results indicate that, under the proposed NFTSM guidance law, the UAV can reach the desired distance in a short time. Full article
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Open AccessArticle Piecewise-Linear Frequency Shifting Algorithm for Frequency Resolution Enhancement in Digital Hearing Aids
Appl. Sci. 2017, 7(4), 335; https://doi.org/10.3390/app7040335
Received: 6 December 2016 / Revised: 22 March 2017 / Accepted: 25 March 2017 / Published: 29 March 2017
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Abstract
In human hearing, frequency resolution is a term used to determine how well the ear can separate and distinguish two sounds that are close in frequency. This capability of breaking speech sounds into various frequency components plays a key role in processing and
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In human hearing, frequency resolution is a term used to determine how well the ear can separate and distinguish two sounds that are close in frequency. This capability of breaking speech sounds into various frequency components plays a key role in processing and understanding speech information. In this paper, a piecewise-linear frequency shifting algorithm for digital hearing aids is proposed. The algorithm specifically aims at improving the frequency resolution capability. In the first step, frequency discrimination thresholds are processed by a computer testing software. Then, the input signal is parsed through the proposed piecewise-linear frequency shifting algorithm, which comprises of linearly stretching and compressing the frequency content at different frequency ranges. Experimental results showed that by using the proposed frequency shifting algorithm, the separation of formant tracks was increased in the stretching region and slightly squeezed in the adjacent compression region. Subjective assessment on six hearing-impaired persons with V-shaped audiograms demonstrated that nearly a 10% improvement of speech discrimination score was achieved for monosyllabic word lists tested in a quiet acoustic setting. In addition, the speech reception threshold was also improved by 2~8 dB when disyllabic word listswere tested in a noisy acoustic scenario. Full article
(This article belongs to the Section Acoustics)
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Open AccessArticle Reel-to-Reel Atmospheric Pressure Dielectric Barrier Discharge (DBD) Plasma Treatment of Polypropylene Films
Appl. Sci. 2017, 7(4), 337; https://doi.org/10.3390/app7040337
Received: 6 March 2017 / Revised: 24 March 2017 / Accepted: 25 March 2017 / Published: 29 March 2017
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Abstract
Atmospheric pressure plasma treatment of the surface of a polypropylene film can significantly increase its surface energy and, thereby improve the printability of the film. A laboratory-scale dielectric barrier discharge (DBD) system has therefore been developed, which simulates the electrode configuration and reel-to-reel
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Atmospheric pressure plasma treatment of the surface of a polypropylene film can significantly increase its surface energy and, thereby improve the printability of the film. A laboratory-scale dielectric barrier discharge (DBD) system has therefore been developed, which simulates the electrode configuration and reel-to-reel web transport mechanism used in a typical industrial-scale system. By treating the polypropylene in a nitrogen discharge, we have shown that the water contact angle could be reduced by as much as 40° compared to the untreated film, corresponding to an increase in surface energy of 14 mNm−1. Ink pull-off tests showed that the DBD plasma treatment resulted in excellent adhesion of solvent-based inks to the polypropylene film. Full article
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Open AccessArticle Fatigue Life Estimation of Medium-Carbon Steel with Different Surface Roughness
Appl. Sci. 2017, 7(4), 338; https://doi.org/10.3390/app7040338
Received: 2 March 2017 / Revised: 24 March 2017 / Accepted: 24 March 2017 / Published: 29 March 2017
Cited by 3 | PDF Full-text (2437 KB) | HTML Full-text | XML Full-text
Abstract
Medium-carbon steel is commonly used for the rail, wire ropes, tire cord, cold heading, forging steels, cold finished steel bars, machinable steel and so on. Its fatigue behavior analysis and fatigue life estimation play an important role in the machinery industry. In this
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Medium-carbon steel is commonly used for the rail, wire ropes, tire cord, cold heading, forging steels, cold finished steel bars, machinable steel and so on. Its fatigue behavior analysis and fatigue life estimation play an important role in the machinery industry. In this paper, the estimation of fatigue life of medium-carbon steel with different surface roughness using established S-N and P-S-N curves is presented. To estimate the fatigue life, the effect of the average surface roughness on the fatigue life of medium-carbon steel has been investigated using 75 fatigue tests in three groups with average surface roughness (Ra): 0.4 μm, 0.8 μm, and 1.6 μm, respectively. S-N curves and P-S-N curves have been established based on the fatigue tests. The fatigue life of medium-carbon steel is then estimated based on Tanaka-Mura crack initiation life model, the crack propagation life model using Paris law, and material constants of the S-N curves. Six more fatigue tests have been conducted to validate the presented fatigue life estimation formulation. The experimental results have shown that the presented model could estimate well the mean fatigue life of medium-carbon steel with different surface roughness. Full article
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Open AccessFeature PaperArticle Acoustic Emission and Modal Frequency Variation in Concrete Specimens under Four-Point Bending
Appl. Sci. 2017, 7(4), 339; https://doi.org/10.3390/app7040339
Received: 23 January 2017 / Revised: 20 March 2017 / Accepted: 22 March 2017 / Published: 30 March 2017
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Abstract
The Acoustic Emission (AE) and Dynamic Identification (DI) techniques were applied simultaneously, in an original way, to examine the stress dependent damage progress in pre-notched concrete beams tested in four-point bending. The damage mechanisms were characterized by analyzing the AE signals registered during
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The Acoustic Emission (AE) and Dynamic Identification (DI) techniques were applied simultaneously, in an original way, to examine the stress dependent damage progress in pre-notched concrete beams tested in four-point bending. The damage mechanisms were characterized by analyzing the AE signals registered during the tests, conducted by increasing the specimen’s vertical deflection. In particular, the dominant fracture mode was identified, and correlations between dissipated and emitted energies were investigated. Moreover, variations in the natural bending frequencies, produced by the crack advancement under loading, were detected and put in relation with the cumulated AE energy. Two different types of piezoelectric (PZT) sensors, operating in well distinct frequency ranges, were used to measure AE and modal signals. This study may be of interest with an outlook on possible correlations between a multi-parameter structural monitoring and the solution of inverse problems by numerical models. Full article
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Open AccessArticle Pulse Propagation Models with Bands of Forbidden Frequencies or Forbidden Wavenumbers: A Consequence of Abandoning the Slowly Varying Envelope Approximation and Taking into Account Higher-Order Dispersion
Appl. Sci. 2017, 7(4), 340; https://doi.org/10.3390/app7040340
Received: 23 December 2016 / Revised: 25 March 2017 / Accepted: 26 March 2017 / Published: 30 March 2017
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Abstract
We study linear and nonlinear pulse propagation models whose linear dispersion relations present bands of forbidden frequencies or forbidden wavenumbers. These bands are due to the interplay between higher-order dispersion and one of the terms (a second-order derivative with respect to the propagation
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We study linear and nonlinear pulse propagation models whose linear dispersion relations present bands of forbidden frequencies or forbidden wavenumbers. These bands are due to the interplay between higher-order dispersion and one of the terms (a second-order derivative with respect to the propagation direction) which appears when we abandon the slowly varying envelope approximation. We show that as a consequence of these forbidden bands, narrow pulses radiate in a novel and peculiar way. We also show that the nonlinear equations studied in this paper have exact soliton-like solutions of different forms, some of them being embedded solitons. The solutions obtained (of the linear as well as the nonlinear equations) are interesting since several arguments suggest that the Cauchy problems for these equations are ill-posed, and therefore the specification of the initial conditions is a delicate issue. It is also shown that some of these equations are related to elliptic curves, thus suggesting that these equations might be related to other fields where these curves appear, such as the theory of modular forms and Weierstrass ℘ functions, or the design of cryptographic protocols. Full article
(This article belongs to the Special Issue Guided-Wave Optics) Printed Edition available
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Open AccessArticle Design and Implementation of a Shape Shifting Rolling–Crawling–Wall-Climbing Robot
Appl. Sci. 2017, 7(4), 342; https://doi.org/10.3390/app7040342
Received: 28 November 2016 / Revised: 5 March 2017 / Accepted: 22 March 2017 / Published: 30 March 2017
Cited by 2 | PDF Full-text (4278 KB) | HTML Full-text | XML Full-text
Abstract
Designing an urban reconnaissance robot is highly challenging work given the nature of the terrain in which these robots are required to operate. In this work, we attempt to extend the locomotion capabilities of these robots beyond what is currently feasible. The design
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Designing an urban reconnaissance robot is highly challenging work given the nature of the terrain in which these robots are required to operate. In this work, we attempt to extend the locomotion capabilities of these robots beyond what is currently feasible. The design and unique features of our bio-inspired reconfigurable robot, called Scorpio, with rolling, crawling, and wall-climbing locomotion abilities are presented in this paper. The design of the Scorpio platform is inspired by Cebrennus rechenbergi, a rare spider species that has rolling, crawling and wall-climbing locomotion attributes. This work also presents the kinematic and dynamic model of Scorpio. The mechanical design and system architecture are introduced in detail, followed by a detailed description on the locomotion modes. The conducted experiments validated the proposed approach and the ability of the Scorpio platform to synthesise crawling, rolling and wall-climbing behaviours. Future work is envisioned for using these robots as active, unattended, mobile ground sensors in urban reconnaissance missions. The accompanying video demonstrates the shape shifting locomotion capabilities of the Scorpio robot. Full article
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Open AccessArticle Using Thermal Shock to Inhibit Biofilm Formation in the Treated Sewage Source Heat Pump Systems
Appl. Sci. 2017, 7(4), 343; https://doi.org/10.3390/app7040343
Received: 30 December 2016 / Revised: 16 March 2017 / Accepted: 24 March 2017 / Published: 30 March 2017
PDF Full-text (4015 KB) | HTML Full-text | XML Full-text
Abstract
Treated sewage source heat pump systems can reuse the waste energy in the treated sewage. However, biofilms in the heat exchangers decrease the system efficiency. This work investigates the feasibility of thermal shock at accessible temperatures in heat exchangers for biofilm inhibition. Bacillus
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Treated sewage source heat pump systems can reuse the waste energy in the treated sewage. However, biofilms in the heat exchangers decrease the system efficiency. This work investigates the feasibility of thermal shock at accessible temperatures in heat exchangers for biofilm inhibition. Bacillus subtilis biofilms were formed on coupons and in a miniaturized plate heat exchanger. Thermal shocks at different temperatures (50–80 °C) for different exposure times (1–60 min) were used to treat the biofilms. The results showed that thermal shock had a significant bactericidal and biofilm inhibition effect, and the effect was enhanced as the temperature and the exposure time increased. Data fitting of the biomass showed that temperature had a more significant influence on the biofilm inhibition effect than exposure time. The results of the heat exchanging experiments showed that high temperature thermal shock could significantly mitigate the heat transfer deterioration caused by the biofilms, indicating that thermal shock could be used as a viable biofilm inhibition approach for heat exchangers. Full article
(This article belongs to the Special Issue Sciences in Heat Pump and Refrigeration)
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Open AccessArticle Experimental Investigation of a Base Isolation System Incorporating MR Dampers with the High-Order Single Step Control Algorithm
Appl. Sci. 2017, 7(4), 344; https://doi.org/10.3390/app7040344
Received: 19 December 2016 / Revised: 7 March 2017 / Accepted: 25 March 2017 / Published: 30 March 2017
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Abstract
The conventional isolation structure with rubber bearings exhibits large deformation characteristics when subjected to infrequent earthquakes, which may lead to failure of the isolation layer. Although passive dampers can be used to reduce the layer displacement, the layer deformation and superstructure acceleration responses
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The conventional isolation structure with rubber bearings exhibits large deformation characteristics when subjected to infrequent earthquakes, which may lead to failure of the isolation layer. Although passive dampers can be used to reduce the layer displacement, the layer deformation and superstructure acceleration responses will increase in cases of fortification earthquakes or frequently occurring earthquakes. In addition to secondary damages and loss of life, such excessive displacement results in damages to the facilities in the structure. In order to overcome these shortcomings, this paper presents a structural vibration control system where the base isolation system is composed of rubber bearings with magnetorheological (MR) damper and are regulated using the innovative control strategy. The high-order single-step algorithm with continuity and switch control strategies are applied to the control system. Shaking table test results under various earthquake conditions indicate that the proposed isolation method, compared with passive isolation technique, can effectively suppress earthquake responses for acceleration of superstructure and deformation within the isolation layer. As a result, this structural control method exhibits excellent performance, such as fast computation, generic real-time control, acceleration reduction and high seismic energy dissipation etc. The relative merits of the continuity and switch control strategies are also compared and discussed. Full article
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Open AccessArticle Pet Fiber Reinforced Wet-Mix Shotcrete with Walnut Shell as Replaced Aggregate
Appl. Sci. 2017, 7(4), 345; https://doi.org/10.3390/app7040345
Received: 1 February 2017 / Revised: 19 March 2017 / Accepted: 29 March 2017 / Published: 31 March 2017
Cited by 1 | PDF Full-text (12403 KB) | HTML Full-text | XML Full-text
Abstract
In the rapidly developing modern society, many raw materials, such as crushed limestone and river sand, which are limited, are consumed by the concrete industry. Naturally, the usage of waste materials in concrete have become an interesting research area in recent years, which
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In the rapidly developing modern society, many raw materials, such as crushed limestone and river sand, which are limited, are consumed by the concrete industry. Naturally, the usage of waste materials in concrete have become an interesting research area in recent years, which is used to reduce the negative influence of concrete on the environment. Hence, this paper presents the development of a sustainable lightweight wet-mix shotcrete by replacing natural coarse gravel with a kind of byproduct, nut shell (walnut). Fibers made from dumped polyethylene terephthalate (PET) bottles were mixed in the composite to improve the properties of the lightweight wet-mix shotcrete. The initial evaluation of the fresh concrete mixed with different volume fraction of walnut shell was carried out in terms of its performance capacities of mechanical properties (i.e., tensile and compressive strength), pumpability and shootability (i.e., slump, pressure drop per meter and rebound rate) and the results were compared with plain concrete. With increase of walnut shell, compressive and splitting tensile strength of casting concrete decreased, while slump and pressure drop reduced slightly. Additionally, appropriate dosage of walnut shell can improve the shootability of fresh concrete with low rebound rate and larger build-up thickness. In the second series tests, polypropylene (PP) fiber and multi-dimension fiber were also mixed in composite for comparative analysis. After mixing fibers, the splitting tensile strength had obtained marked improvement with slight reduction of compressive strength, along with acceptable fluctuation in terms of pumpability and shootability. Furthermore, relation of density and compressive strength, relation of rebound and density, build-up thickness and relation of compressive and splitting tensile strength were discussed. This study found wet-mix shotcrete incorporating PET fiber with walnut shell of about 35% coarse aggregate replacement could be used for roadway support as lightweight shotcrete per requirements of mine support. Full article
(This article belongs to the Section Materials)
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Open AccessArticle Numerical Control Machine Tool Fault Diagnosis Using Hybrid Stationary Subspace Analysis and Least Squares Support Vector Machine with a Single Sensor
Appl. Sci. 2017, 7(4), 346; https://doi.org/10.3390/app7040346
Received: 25 February 2017 / Revised: 23 March 2017 / Accepted: 28 March 2017 / Published: 31 March 2017
Cited by 1 | PDF Full-text (3459 KB) | HTML Full-text | XML Full-text
Abstract
Tool fault diagnosis in numerical control (NC) machines plays a significant role in ensuring manufacturing quality. However, current methods of tool fault diagnosis lack accuracy. Therefore, in the present paper, a fault diagnosis method was proposed based on stationary subspace analysis (SSA) and
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Tool fault diagnosis in numerical control (NC) machines plays a significant role in ensuring manufacturing quality. However, current methods of tool fault diagnosis lack accuracy. Therefore, in the present paper, a fault diagnosis method was proposed based on stationary subspace analysis (SSA) and least squares support vector machine (LS-SVM) using only a single sensor. First, SSA was used to extract stationary and non-stationary sources from multi-dimensional signals without the need for independency and without prior information of the source signals, after the dimensionality of the vibration signal observed by a single sensor was expanded by phase space reconstruction technique. Subsequently, 10 dimensionless parameters in the time-frequency domain for non-stationary sources were calculated to generate samples to train the LS-SVM. Finally, the measured vibration signals from tools of an unknown state and their non-stationary sources were separated by SSA to serve as test samples for the trained SVM. The experimental validation demonstrated that the proposed method has better diagnosis accuracy than three previous methods based on LS-SVM alone, Principal component analysis and LS-SVM or on SSA and Linear discriminant analysis. Full article
(This article belongs to the Special Issue Deep Learning Based Machine Fault Diagnosis and Prognosis)
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Open AccessArticle Tangible User Interface and Mu Rhythm Suppression: The Effect of User Interface on the Brain Activity in Its Operator and Observer
Appl. Sci. 2017, 7(4), 347; https://doi.org/10.3390/app7040347
Received: 20 February 2017 / Revised: 20 March 2017 / Accepted: 28 March 2017 / Published: 31 March 2017
PDF Full-text (1248 KB) | HTML Full-text | XML Full-text
Abstract
The intuitiveness of tangible user interface (TUI) is not only for its operator. It is quite possible that this type of user interface (UI) can also have an effect on the experience and learning of observers who are just watching the operator using
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The intuitiveness of tangible user interface (TUI) is not only for its operator. It is quite possible that this type of user interface (UI) can also have an effect on the experience and learning of observers who are just watching the operator using it. To understand the possible effect of TUI, the present study focused on the mu rhythm suppression in the sensorimotor area reflecting execution and observation of action, and investigated the brain activity both in its operator and observer. In the observer experiment, the effect of TUI on its observers was demonstrated through the brain activity. Although the effect of the grasping action itself was uncertain, the unpredictability of the result of the action seemed to have some effect on the mirror neuron system (MNS)-related brain activity. In the operator experiment, in spite of the same grasping action, the brain activity was activated in the sensorimotor area when UI functions were included (TUI). Such activation of the brain activity was not found with a graphical user interface (GUI) that has UI functions without grasping action. These results suggest that the MNS-related brain activity is involved in the effect of TUI, indicating the possibility of UI evaluation based on brain activity. Full article
(This article belongs to the Special Issue Human Activity Recognition)
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Open AccessArticle Improved Gender Recognition during Stepping Activity for Rehab Application Using the Combinatorial Fusion Approach of EMG and HRV
Appl. Sci. 2017, 7(4), 348; https://doi.org/10.3390/app7040348
Received: 18 January 2017 / Revised: 27 March 2017 / Accepted: 27 March 2017 / Published: 31 March 2017
Cited by 2 | PDF Full-text (4304 KB) | HTML Full-text | XML Full-text
Abstract
Gender recognition is trivial for a physiotherapist, but it is considered a challenge for computers. The electromyography (EMG) and heart rate variability (HRV) were utilized in this work for gender recognition during exercise using a stepper. The relevant features were extracted and selected.
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Gender recognition is trivial for a physiotherapist, but it is considered a challenge for computers. The electromyography (EMG) and heart rate variability (HRV) were utilized in this work for gender recognition during exercise using a stepper. The relevant features were extracted and selected. The selected features were then fused to automatically predict gender recognition. However, the feature selection for gender classification became a challenge to ensure better accuracy. Thus, in this paper, a feature selection approach based on both the performance and the diversity between the two features from the rank-score characteristic (RSC) function in a combinatorial fusion approach (CFA) (Hsu et al.) was employed. Then, the features from the selected feature sets were fused using a CFA. The results were then compared with other fusion techniques such as naive bayes (NB), decision tree (J48), k-nearest neighbor (KNN) and support vector machine (SVM). Besides, the results were also compared with previous researches in gender recognition. The experimental results showed that the CFA was efficient and effective for feature selection. The fusion method was also able to improve the accuracy of the gender recognition rate. The CFA provides much better gender classification results which is 94.51% compared to Barani’s work (90.34%), Nazarloo’s work (92.50%), and other classifiers. Full article
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Open AccessArticle Electric Turbocharging for Energy Regeneration and Increased Efficiency at Real Driving Conditions
Appl. Sci. 2017, 7(4), 350; https://doi.org/10.3390/app7040350
Received: 23 January 2017 / Revised: 8 March 2017 / Accepted: 14 March 2017 / Published: 1 April 2017
Cited by 2 | PDF Full-text (13440 KB) | HTML Full-text | XML Full-text
Abstract
Modern downsized internal combustion engines benefit from high-efficiency turbocharging systems for increasing their volumetric efficiency. However, despite the efficiency increase, turbochargers often lack fast transient response due to the nature of the energy exchange with the engine, which deteriorates the vehicle’s drivability. An
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Modern downsized internal combustion engines benefit from high-efficiency turbocharging systems for increasing their volumetric efficiency. However, despite the efficiency increase, turbochargers often lack fast transient response due to the nature of the energy exchange with the engine, which deteriorates the vehicle’s drivability. An electrically-assisted turbocharger can be used for improving the transient response without any parasitic losses to the engine while providing energy recovery for increasing overall system efficiency. The present study provides a detailed numerical investigation on the potential of e-turbocharging to control load and if possible replace the wastegate valve. A parametric study of the optimum compressor/turbine sizing and wastegate area was performed for maximum torque, fast response time and energy regeneration across the real driving conditions speed/load area of the engine. The results showed that the implementation of a motor-generator could contribute to reducing the response time of the engine by up to 90% while improving its thermal efficiency and generating up to 6.6 kWh of energy. Suppressing the wastegate can only be achieved when a larger turbine is implemented, which as a result deteriorates the engine’s response and leads to energy provision demands at low engine speeds. Full article
(This article belongs to the Special Issue Internal Combustion Engines (ICE) for Ground Transport)
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Open AccessFeature PaperArticle Scan-Less Line Field Optical Coherence Tomography, with Automatic Image Segmentation, as a Measurement Tool for Automotive Coatings
Appl. Sci. 2017, 7(4), 351; https://doi.org/10.3390/app7040351
Received: 3 February 2017 / Revised: 28 March 2017 / Accepted: 29 March 2017 / Published: 1 April 2017
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Abstract
The measurement of the thicknesses of layers is important for the quality assurance of industrial coating systems. Current measurement techniques only provide a limited amount of information. Here, we show that spectral domain Line Field (LF) Optical Coherence Tomography (OCT) is able to
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The measurement of the thicknesses of layers is important for the quality assurance of industrial coating systems. Current measurement techniques only provide a limited amount of information. Here, we show that spectral domain Line Field (LF) Optical Coherence Tomography (OCT) is able to return to the user a cross sectional B-Scan image in a single shot with no mechanical moving parts. To reliably extract layer thicknesses from such images of automotive paint systems, we present an automatic graph search image segmentation algorithm. To show that the algorithm works independently of the OCT device, the measurements are repeated with a separate time domain Full Field (FF) OCT system. This gives matching mean thickness values within the standard deviations of the measured thicknesses across each B-Scan image. The combination of an LF-OCT with graph search segmentation is potentially a powerful technique for the quality assurance of non-opaque industrial coating layers. Full article
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Open AccessArticle Thermal Optimization of Horizontal Tubes with Tilted Rectangular Fins under Free Convection for the Cooling of Electronic Devices
Appl. Sci. 2017, 7(4), 352; https://doi.org/10.3390/app7040352
Received: 24 February 2017 / Revised: 24 March 2017 / Accepted: 28 March 2017 / Published: 2 April 2017
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Abstract
In the present work, the horizontal tubes with tilted rectangular fins under free convection are experimentally investigated for the cooling of electronic devices. The temperature differences of horizontal tubes with tilted rectangular fins are measured for several heat inputs, tilt angles, and numbers
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In the present work, the horizontal tubes with tilted rectangular fins under free convection are experimentally investigated for the cooling of electronic devices. The temperature differences of horizontal tubes with tilted rectangular fins are measured for several heat inputs, tilt angles, and numbers of fins. Using the measurement results, a correlation for the prediction of the Nusselt number is suggested. This correlation is suitable for the situation for Rayleigh numbers of 200,000–1,100,000, tilt angles of 0°–90°, and numbers of fins of 9–36. On the basis of the correlation, the cooling performances are presented for various numbers of fins and thicknesses of fins, and the value of the optimal cooling performance is found. Finally, the optimal cooling performances of tubes with tilted rectangular fins and conventional radial rectangular fins are compared. The comparison results show that the optimal cooling performance of the tube with tilted fins is 6% greater than that of the tube with radial rectangular fins. Full article
(This article belongs to the Special Issue Advances in Thermal System Analysis and Optimization)
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Open AccessArticle Algorithm and Implementation of Distributed ESN Using Spark Framework and Parallel PSO
Appl. Sci. 2017, 7(4), 353; https://doi.org/10.3390/app7040353
Received: 10 February 2017 / Revised: 20 March 2017 / Accepted: 30 March 2017 / Published: 2 April 2017
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Abstract
The echo state network (ESN) employs a huge reservoir with sparsely and randomly connected internal nodes and only trains the output weights, which avoids the suboptimal problem, exploding and vanishing gradients, high complexity and other disadvantages faced by traditional recurrent neural network (RNN)
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The echo state network (ESN) employs a huge reservoir with sparsely and randomly connected internal nodes and only trains the output weights, which avoids the suboptimal problem, exploding and vanishing gradients, high complexity and other disadvantages faced by traditional recurrent neural network (RNN) training. In light of the outstanding adaption to nonlinear dynamical systems, ESN has been applied into a wide range of applications. However, in the era of Big Data, with an enormous amount of data being generated continuously every day, the data are often distributed and stored in real applications, and thus the centralized ESN training process is prone to being technologically unsuitable. In order to achieve the requirement of Big Data applications in the real world, in this study we propose an algorithm and its implementation for distributed ESN training. The mentioned algorithm is based on the parallel particle swarm optimization (P-PSO) technique and the implementation uses Spark, a famous large-scale data processing framework. Four extremely large-scale datasets, including artificial benchmarks, real-world data and image data, are adopted to verify our framework on a stretchable platform. Experimental results indicate that the proposed work is accurate in the era of Big Data, regarding speed, accuracy and generalization capabilities. Full article
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Open AccessArticle A Wideband High-Voltage Power Amplifier Post-Linearizer for Medical Ultrasound Transducers
Appl. Sci. 2017, 7(4), 354; https://doi.org/10.3390/app7040354
Received: 21 January 2017 / Revised: 16 March 2017 / Accepted: 23 March 2017 / Published: 4 April 2017
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Abstract
The medical ultrasound transducer is a principal component in ultrasound systems, as it significantly influences system performance. The high-voltage power amplifier (HVPA) is the key ultrasound transmitter component and interfaces with the medical ultrasound transducer. Therefore, the performance of the HVPA critically affects
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The medical ultrasound transducer is a principal component in ultrasound systems, as it significantly influences system performance. The high-voltage power amplifier (HVPA) is the key ultrasound transmitter component and interfaces with the medical ultrasound transducer. Therefore, the performance of the HVPA critically affects the echo signal quality of the ultrasound transducer. As they are inherently non-linear devices, harmonic distortion of echo signals generated by the ultrasound transducers would critically deteriorate the echo signal quality in ultrasound systems. The primary aim of this research is to integrate a novel post-linearizer into the HVPA to suppress harmonic distortion in medical ultrasound transducers. Moreover, this study is based on the assumption that linearizing the HVPA could reduce the harmonic distortion components of the echo signals. The developed HVPA with post-linearizer was tested in an ultrasound microscopy system in order to demonstrate the harmonic suppression capability on the echo signal generated by the ultrasound transducer. When 10 MHz, 5-cycle, 26 dBm input power was sent to the HVPA with and without the post-linearizer circuits, the measured second-, third-, fourth- and fifth- harmonic distortions of a 10 MHz transducer with the post-linearizer (−13.11 dB, −10.81 dB, −16.33 dB, and −22.78 dB) were suppressed to a greater degree than those of the same transducer without the post-linearizer (−4.58 dB, −8.87 dB, −10.51 dB, and −15.31 dB).. Therefore, we conclude that the addition of the post-linearizer to the HVPA is a potentially useful electronic technique for improving echo signal quality in medical ultrasound transducers. Full article
(This article belongs to the Section Acoustics)
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Open AccessArticle Self-Organized Nanoscale Roughness Engineering for Broadband Light Trapping in Thin Film Solar Cells
Appl. Sci. 2017, 7(4), 355; https://doi.org/10.3390/app7040355
Received: 3 March 2017 / Revised: 24 March 2017 / Accepted: 28 March 2017 / Published: 4 April 2017
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Abstract
We present a self-organized method based on defocused ion beam sputtering for nanostructuring glass substrates which feature antireflective and light trapping effects. By irradiating the substrate, capped with a thin gold (Au) film, a self-organized Au nanowire stencil mask is firstly created. The
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We present a self-organized method based on defocused ion beam sputtering for nanostructuring glass substrates which feature antireflective and light trapping effects. By irradiating the substrate, capped with a thin gold (Au) film, a self-organized Au nanowire stencil mask is firstly created. The morphology of the mask is then transferred to the glass surface by further irradiating the substrate, finally producing high aspect ratio, uniaxial ripple-like nanostructures whose morphological parameters can be tailored by varying the ion fluence. The effect of a Ti adhesion layer, interposed between glass and Au with the role of inhibiting nanowire dewetting, has also been investigated in order to achieve an improved morphological tunability of the templates. Morphological and optical characterization have been carried out, revealing remarkable light trapping performance for the largest ion fluences. The photon harvesting capability of the nanostructured glass has been tested for different preparation conditions by fabricating thin film amorphous Si solar cells. The comparison of devices grown on textured and flat substrates reveals a relative increase of the short circuit current up to 25%. However, a detrimental impact on the electrical performance is observed with the rougher morphologies endowed with steep v-shaped grooves. We finally demonstrate that post-growth ion beam restructuring of the glass template represents a viable approach toward improved electrical performance. Full article
(This article belongs to the Special Issue Light Management for Optoelectronics)
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Open AccessArticle A New High-Efficiency Double-Stator Split-Pole Permanent-Magnet Vernier Machine with Flux-Focusing Topology
Appl. Sci. 2017, 7(4), 356; https://doi.org/10.3390/app7040356
Received: 23 December 2016 / Revised: 27 March 2017 / Accepted: 29 March 2017 / Published: 4 April 2017
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Abstract
Permanent-magnet vernier machines (PMVMs) have attracted much attention for their high efficiency and output torque in low-speed application. However, the conventional PMVM suffers from the problems of low power factor and high cogging torque. In this paper, a double-stator flux-focusing split-pole permanent-magnet vernier
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Permanent-magnet vernier machines (PMVMs) have attracted much attention for their high efficiency and output torque in low-speed application. However, the conventional PMVM suffers from the problems of low power factor and high cogging torque. In this paper, a double-stator flux-focusing split-pole permanent-magnet vernier machine (SP-PMVM) with low cogging torque and high power factor has been proposed. The split-pole topology in the vernier motor has been used mainly to modulate the magnetic flux in this paper, although the stator teeth are used for this purpose in some cases. The newly-proposed SP-PMVM topology is characterized by reduced flux leakage through using a flux-focusing topology and staggering approximately half of the pitch angularly between the inner stator and outer stator. Firstly, the vernier principle of the proposed SP-PMVM has been investigated by analytical methods. Secondly, a 12-slot-stator and 22-pole-pair-rotor SP-PMVM has been optimized with the goal of maximum average steady-state torque and the minimum cogging torque and ripple. Thirdly, the overall performance of the newly-proposed SP-PMVM has been analyzed as compared with the conventional PMVM. The results verify that the SP-PMVM can provide higher power factor, higher output torque and lower cogging torque than that of the conventional PMVM in low-speed application. Full article
(This article belongs to the Section Materials)
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Open AccessArticle Increasing the Performance of Vacuum Membrane Distillation Using Micro-Structured Hydrophobic Aluminum Hollow Fiber Membranes
Appl. Sci. 2017, 7(4), 357; https://doi.org/10.3390/app7040357
Received: 29 January 2017 / Accepted: 1 April 2017 / Published: 4 April 2017
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Abstract
This study develops a micro-structured hydrophobic alumina hollow fiber with a high permeate flux of 60 Lm−2h−1 and salt rejection over 99.9% in a vacuum membrane distillation process. The fiber is fabricated by phase inversion and sintering, and then modified
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This study develops a micro-structured hydrophobic alumina hollow fiber with a high permeate flux of 60 Lm−2h−1 and salt rejection over 99.9% in a vacuum membrane distillation process. The fiber is fabricated by phase inversion and sintering, and then modified with fluoroalkylsilanes to render it hydrophobic. The influence of the sintering temperature and feeding temperature in membrane distillation (MD) on the characteristics of the fiber and MD performance are investigated. The vacuum membrane distillation uses 3.5 wt % NaCl aqueous solution at 70 °C at 0.03 bar. The permeate flux of 60 Lm−2h−1 is the highest, compared with reported data and is higher than that for polymeric hollow fiber membranes. Full article
(This article belongs to the Special Issue Membrane Distillation) Printed Edition available
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Open AccessArticle Multiple Sensors Based Hand Motion Recognition Using Adaptive Directed Acyclic Graph
Appl. Sci. 2017, 7(4), 358; https://doi.org/10.3390/app7040358
Received: 19 February 2017 / Revised: 28 March 2017 / Accepted: 30 March 2017 / Published: 5 April 2017
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Abstract
The use of human hand motions as an effective way to interact with computers/robots, robot manipulation learning and prosthetic hand control is being researched in-depth. This paper proposes a novel and effective multiple sensor based hand motion capture and recognition system. Ten common
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The use of human hand motions as an effective way to interact with computers/robots, robot manipulation learning and prosthetic hand control is being researched in-depth. This paper proposes a novel and effective multiple sensor based hand motion capture and recognition system. Ten common predefined object grasp and manipulation tasks demonstrated by different subjects are recorded from both the human hand and object points of view. Three types of sensors, including electromyography, data glove and FingerTPS are applied to simultaneously capture the EMG signals, the finger angle trajectories, and the contact force. Recognising different grasp and manipulation tasks based on the combined signals is investigated by using an adaptive directed acyclic graph algorithm, and results of comparative experiments show the proposed system with a higher recognition rate compared with individual sensing technology, as well as other algorithms. The proposed framework contains abundant information from multimodal human hand motions with the multiple sensor techniques, and it is potentially applicable to applications in prosthetic hand control and artificial systems performing autonomous dexterous manipulation. Full article
(This article belongs to the Special Issue Human Activity Recognition)
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Open AccessArticle Mode Coupling Properties of the Plasmonic Dimers Composed of Graphene Nanodisks
Appl. Sci. 2017, 7(4), 359; https://doi.org/10.3390/app7040359
Received: 16 January 2017 / Revised: 28 March 2017 / Accepted: 30 March 2017 / Published: 5 April 2017
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Abstract
The electromagnetic properties of the plasmonic dimer composed of coupled graphene nanodisks are numerically investigated in this paper. The results demonstrate that the degeneracy of the plasmonic modes of the dimer is lifted when the coupling is introduced. The evolution of the plasmonic
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The electromagnetic properties of the plasmonic dimer composed of coupled graphene nanodisks are numerically investigated in this paper. The results demonstrate that the degeneracy of the plasmonic modes of the dimer is lifted when the coupling is introduced. The evolution of the plasmonic mode, with the variation of inter-disk distance and the chemical potential of one of the nanodisks, is studied. The proposed structure might find broad areas of application including light–matter interaction, optical switching, directional emission of the plasmonic emitter, etc. Full article
(This article belongs to the Section Optics and Lasers)
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Open AccessArticle Performance Analysis of a Fluidic Axial Oscillation Tool for Friction Reduction with the Absence of a Throttling Plate
Appl. Sci. 2017, 7(4), 360; https://doi.org/10.3390/app7040360
Received: 13 January 2017 / Revised: 29 March 2017 / Accepted: 30 March 2017 / Published: 5 April 2017
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Abstract
An axial oscillation tool is proved to be effective in solving problems associated with high friction and torque in the sliding drilling of a complex well. The fluidic axial oscillation tool, based on an output-fed bistable fluidic oscillator, is a type of axial
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An axial oscillation tool is proved to be effective in solving problems associated with high friction and torque in the sliding drilling of a complex well. The fluidic axial oscillation tool, based on an output-fed bistable fluidic oscillator, is a type of axial oscillation tool which has become increasingly popular in recent years. The aim of this paper is to analyze the dynamic flow behavior of a fluidic axial oscillation tool with the absence of a throttling plate in order to evaluate its overall performance. In particular, the differences between the original design with a throttling plate and the current default design are profoundly analyzed, and an improvement is expected to be recorded for the latter. A commercial computational fluid dynamics code, Fluent, was used to predict the pressure drop and oscillation frequency of a fluidic axial oscillation tool. The results of the numerical simulations agree well with corresponding experimental results. A sufficient pressure pulse amplitude with a low pressure drop is desired in this study. Therefore, a relative pulse amplitude of pressure drop and displacement are introduced in our study. A comparison analysis between the two designs with and without a throttling plate indicates that when the supply flow rate is relatively low or higher than a certain value, the fluidic axial oscillation tool with a throttling plate exhibits a better performance; otherwise, the fluidic axial oscillation tool without a throttling plate seems to be a preferred alternative. In most of the operating circumstances in terms of the supply flow rate and pressure drop, the fluidic axial oscillation tool performs better than the original design. Full article
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Open AccessArticle A Simplified Method to Estimate Sc-CO2 Extraction of Bioactive Compounds from Different Matrices: Chili Pepper vs. Tomato By-Products
Appl. Sci. 2017, 7(4), 361; https://doi.org/10.3390/app7040361
Received: 23 January 2017 / Revised: 22 March 2017 / Accepted: 31 March 2017 / Published: 5 April 2017
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Abstract
In the last few decades, the search for bioactive compounds or “target molecules” from natural sources or their by-products has become the most important application of the supercritical fluid extraction (SFE) process. In this context, the present research had two main objectives: (i)
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In the last few decades, the search for bioactive compounds or “target molecules” from natural sources or their by-products has become the most important application of the supercritical fluid extraction (SFE) process. In this context, the present research had two main objectives: (i) to verify the effectiveness of a two-step SFE process (namely, a preliminary Sc-CO2 extraction of carotenoids followed by the recovery of polyphenols by ethanol coupled with Sc-CO2) in order to obtain bioactive extracts from two widespread different matrices (chili pepper and tomato by-products), and (ii) to test the validity of the mathematical model proposed to describe the kinetics of SFE of carotenoids from different matrices, the knowledge of which is required also for the definition of the role played in the extraction process by the characteristics of the sample matrix. On the basis of the results obtained, it was possible to introduce a simplified kinetic model that was able to describe the time evolution of the extraction of bioactive compounds (mainly carotenoids and phenols) from different substrates. In particular, while both chili pepper and tomato were confirmed to be good sources of bioactive antioxidant compounds, the extraction process from chili pepper was faster than from tomato under identical operating conditions. Full article
(This article belongs to the Special Issue The Applications of Supercritical Carbon Dioxide)
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Open AccessArticle Experimental Damage Identification of a Model Reticulated Shell
Appl. Sci. 2017, 7(4), 362; https://doi.org/10.3390/app7040362
Received: 17 February 2017 / Revised: 29 March 2017 / Accepted: 29 March 2017 / Published: 6 April 2017
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Abstract
The damage identification of a reticulated shell is a challenging task, facing various difficulties, such as the large number of degrees of freedom (DOFs), the phenomenon of modal localization and transition, and low modeling accuracy. Based on structural vibration responses, the damage identification
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The damage identification of a reticulated shell is a challenging task, facing various difficulties, such as the large number of degrees of freedom (DOFs), the phenomenon of modal localization and transition, and low modeling accuracy. Based on structural vibration responses, the damage identification of a reticulated shell was studied. At first, the auto-regressive (AR) time series model was established based on the acceleration responses of the reticulated shell. According to the changes in the coefficients of the AR model between the damaged conditions and the undamaged condition, the damage of the reticulated shell can be detected. In addition, the damage sensitive factors were determined based on the coefficients of the AR model. With the damage sensitive factors as the inputs and the damage positions as the outputs, back-propagation neural networks (BPNNs) were then established and were trained using the Levenberg–Marquardt algorithm (L–M algorithm). The locations of the damages can be predicted by the back-propagation neural networks. At last, according to the experimental scheme of single-point excitation and multi-point responses, the impact experiments on a K6 shell model with a scale of 1/10 were conducted. The experimental results verified the efficiency of the proposed damage identification method based on the AR time series model and back-propagation neural networks. The proposed damage identification method can ensure the safety of the practical engineering to some extent. Full article
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Open AccessArticle Predictive Modelling and Analysis of Process Parameters on Material Removal Characteristics in Abrasive Belt Grinding Process
Appl. Sci. 2017, 7(4), 363; https://doi.org/10.3390/app7040363
Received: 28 February 2017 / Revised: 29 March 2017 / Accepted: 31 March 2017 / Published: 6 April 2017
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Abstract
The surface finishing and stock removal of complicated geometries is the principal objective for grinding with compliant abrasive tools. To understand and achieve optimum material removal in a tertiary finishing process such as Abrasive Belt Grinding, it is essential to look in more
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The surface finishing and stock removal of complicated geometries is the principal objective for grinding with compliant abrasive tools. To understand and achieve optimum material removal in a tertiary finishing process such as Abrasive Belt Grinding, it is essential to look in more detail at the process parameters/variables that affect the stock removal rate. The process variables involved in a belt grinding process include the grit and abrasive type of grinding belt, belt speed, contact wheel hardness, serration, and grinding force. Changing these process variables will affect the performance of the process. The literature survey on belt grinding shows certain limited understanding of material removal on the process variables. Experimental trials were conducted based on the Taguchi Method to evaluate the influence of individual and interactive process variables. Analysis of variance (ANOVA) was employed to investigate the belt grinding characteristics on material removal. This research work describes a systematic approach to optimise process parameters to achieve the desired stock removal in a compliant Abrasive Belt Grinding process. Experimental study showed that the removed material from a surface due to the belt grinding process has a non-linear relationship with the process variables. In this paper, the Adaptive Neuro-Fuzzy Inference System (ANFIS) model is used to determine material removal. Compared with the experimental results, the model accurately predicts the stock removal. With further verification of the empirical model, a better understanding of the grinding parameters involved in material removal, particularly the influence of the individual process variables and their interaction, can be obtained. Full article
(This article belongs to the Section Materials)
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Open AccessArticle Spectral Domain Optical Coherence Tomography for Non-Destructive Testing of Protection Coatings on Metal Substrates
Appl. Sci. 2017, 7(4), 364; https://doi.org/10.3390/app7040364
Received: 1 March 2017 / Revised: 29 March 2017 / Accepted: 31 March 2017 / Published: 6 April 2017
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Abstract
In this paper we demonstrate that optical coherence tomography (OCT) is a powerful tool for the non-destructive investiga