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Appl. Sci., Volume 6, Issue 11 (November 2016)

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Open AccessArticle
Digital Controller Design Based on Active Damping Method of Capacitor Current Feedback for Auxiliary Resonant Snubber Inverter with LC Filter
Appl. Sci. 2016, 6(11), 377; https://doi.org/10.3390/app6110377 - 22 Nov 2016
Cited by 2 | Viewed by 2674
Abstract
In some high-performance applications, an LC filter must be added to the auxiliary resonant snubber inverter (ARSI) to reduce the output current ripple. However, resonance occurs due to the additional LC filter, which makes the traditional closed-loop control not suitable to be used [...] Read more.
In some high-performance applications, an LC filter must be added to the auxiliary resonant snubber inverter (ARSI) to reduce the output current ripple. However, resonance occurs due to the additional LC filter, which makes the traditional closed-loop control not suitable to be used directly. Therefore, this paper presents a double-loop digital control based on the active damping method of capacitor current feedback to stabilize the system. Most of the studies on active damping methods are focused on the grid in consideration of zero resistance. However, the load resistance should not be neglected in the drive system. Therefore, the load resistance and digital control delays are considered in this paper. Moreover, an improved loading method is proposed to improve the duty ratio range. In order to verify the effectiveness of the controller, a prototype was developed. The simulation and experimental results demonstrate that soft-switching can be realized for the entire load range. The maximum duty ratio is improved by 0.01 by using the proposed loading method. The resonance can be eliminated by using the proposed control method. Full article
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Open AccessArticle
Ammonium Removal from Landfill Leachate by Means of Multiple Recycling of Struvite Residues Obtained through Acid Decomposition
Appl. Sci. 2016, 6(11), 375; https://doi.org/10.3390/app6110375 - 22 Nov 2016
Cited by 4 | Viewed by 1432
Abstract
The treatment of landfill leachate, due to its great polluting load, is a very difficult task. In particular, the abatement of high ammonium concentrations represents one of the main issues. Among the available techniques, struvite precipitation is an effective method for the removal [...] Read more.
The treatment of landfill leachate, due to its great polluting load, is a very difficult task. In particular, the abatement of high ammonium concentrations represents one of the main issues. Among the available techniques, struvite precipitation is an effective method for the removal and recovery of NH4+ load. However, due to the lack of phosphorus and magnesium amounts, the struvite formation results in an expensive process in the leachate treatment. To overcome this issue, in the present work, we developed a simple and suitable method for ammonium removal by the multiple recycling of struvite decomposition residues. In this regard, a procedure for acid dissolution of struvite, produced by using industrial grade reagents, was initially defined. The effect of pH, temperature, and acid type was investigated. The experimental results proved the effectiveness of both hydrochloric and acetic acid, which allow a high and selective release of ammonium at T = 50 °C and pH = 5.5. The multiple reuse of decomposition products, combined with the supplementation of a small quantity of phosphorus and magnesium at molar ratios of n(N):n(Mg):n(P) = 1:0.05:0.05, guarantees stable NH4+ abatement of about 82%. The proposed process allows a cost saving of around to 74% and can be easily applied in industrial treatment plants. Full article
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Open AccessArticle
Field Measurements of Water Supply and Drainage Noise in the Bathrooms of Korea’s Multi-Residential Buildings
Appl. Sci. 2016, 6(11), 372; https://doi.org/10.3390/app6110372 - 22 Nov 2016
Cited by 3 | Viewed by 2460
Abstract
In Korea, water supply and drainage noises result in one of the main noise complaints because more than 50% of people reside in multi-residential buildings. In this study, a series of field measurements were therefore carried out to examine the current noise situation. [...] Read more.
In Korea, water supply and drainage noises result in one of the main noise complaints because more than 50% of people reside in multi-residential buildings. In this study, a series of field measurements were therefore carried out to examine the current noise situation. The noise levels were measured in the bathrooms of the upper and lower floors, as well as in habitable rooms. The measurement results for the bathrooms of the lower floor (N = 113) are 47.8 dBA (water closet), 42.7 dBA (basin), and 33.9 dBA (bathtub) for water drainage, while values vary between 33.7 dBA and 37.0 dBA for the water supply. The results suggest that the water drainage noise needs to be controlled first. The system bathroom (42.8 dBA) produced lower noise levels than the wet construction method (48.2 dBA) for all of the sanitary wares. The highest noise levels in the living rooms (N = 11) and bedrooms (N = 8) of the lower floor are 34.3 dBA and 39.1 dBA, respectively. The average noise level in the rooms (N = 19) is 37.8 dBA. The overall result suggests that it is necessary to develop an acoustic guideline to satisfy the higher Class of the 2nd ISO/CD 19488, although the current noise level satisfies Class C (living room) and Class D (bedroom). Full article
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Open AccessArticle
The Machining of Hard Mold Steel by Ultrasonic Assisted End Milling
Appl. Sci. 2016, 6(11), 373; https://doi.org/10.3390/app6110373 - 21 Nov 2016
Cited by 5 | Viewed by 2680
Abstract
This study describes the use of ultrasonic-assisted end milling to improve the quality of the machined surface of hard Stavax (modified AISI 420) mold steel and to reduce the amount of work involved in the final polishing process. The effects of input voltage, [...] Read more.
This study describes the use of ultrasonic-assisted end milling to improve the quality of the machined surface of hard Stavax (modified AISI 420) mold steel and to reduce the amount of work involved in the final polishing process. The effects of input voltage, the stretch length and cutter holding force on the amplitude of the ultrasonic vibration used were measured. The effect of ultrasonic frequency (25 and 50 kHz) and amplitude (0, 2.20 and 3.68 μm) as well as the effect of the rake angle (6° and −6°) and the cutter helix angle (25°, 35° and 45°) on tool wear and quality of the workpiece surface finish were also investigated. It was found that the ultrasonic amplitude increased with cutter stretch length and input voltage, as expected. The amplitude remained constant when the cutter holding force exceeded 15 N. The experimental results showed that the ultrasonic amplitude had an optimum value with respect to surface finish. However, large amplitude ultrasonics did not necessarily improve quality. Furthermore, the cutters used for ultrasonic-assisted milling show less wear than those used for normal milling. It was also found that a positive rake angle and cutters with a large helix angle gave a better surface finish. Full article
(This article belongs to the Special Issue Selected Papers from the 2016 International Conference on Inventions)
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Open AccessArticle
Land Cover Classification Using a KOMPSAT-3A Multi-Spectral Satellite Image
Appl. Sci. 2016, 6(11), 371; https://doi.org/10.3390/app6110371 - 21 Nov 2016
Cited by 4 | Viewed by 2529
Abstract
New sets of satellite sensors are frequently being added to the constellation of remote sensing satellites. These new sets offer improved specification to collect imagery on-demand over specific locations and for specific purposes. The Korea Multi-Purpose Satellite (KOMPSAT) series of satellites is a [...] Read more.
New sets of satellite sensors are frequently being added to the constellation of remote sensing satellites. These new sets offer improved specification to collect imagery on-demand over specific locations and for specific purposes. The Korea Multi-Purpose Satellite (KOMPSAT) series of satellites is a multi-purposed satellite system developed by Korea Aerospace Research Institute (KARI). The recent satellite of the KOMPSAT series, KOMPSAT-3A, demonstrates high resolution multi-spectral imagery with infrared and high resolution electro-optical bands for geographical information systems applications in environmental, agricultural and oceanographic sciences as well as natural disasters. In this study, land cover classification of multispectral data was performed using four supervised classification methods: Mahalanobis Distance (MahD), Minimum Distance (MinD), Maximum Likelihood (ML) and Support Vector Machine (SVM), using a KOMPSAT-3A multi-spectral imagery with 2.2 m spatial resolution. The study area for this study was selected from southwestern region of South Korea, around Buan city. The training data for supervised classification was carefully selected by visual interpretation of KOMPSAT-3A imagery and field investigation. After classification, the results were then analyzed for the validation of classification accuracy by comparison with those of field investigation. For the validation, we calculated the User’s Accuracy (UA), Producer’s Accuracy (PA), Overall Accuracy (OA) and Kappa statistics from the error matrix to check the classification accuracy for each class obtained individually from different methods. Finally, the comparative analysis was done for the study area for various results of land cover classification using a KOMPSAT-3A multi-spectral imagery. Full article
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Open AccessReview
Advanced Microbubbles as a Multifunctional Platform Combining Imaging and Therapy
Appl. Sci. 2016, 6(11), 365; https://doi.org/10.3390/app6110365 - 21 Nov 2016
Cited by 2 | Viewed by 1958
Abstract
Microbubbles as traditional ultrasound contrast agents have seen tremendous developments and bio-applications in the past decades. Due to their outstanding performance, advanced microbubbles as a multifunctional platform combining both imaging and therapy have been increasingly attracting attention. Associated with ultrasound-mediated stimuli, targeting drug [...] Read more.
Microbubbles as traditional ultrasound contrast agents have seen tremendous developments and bio-applications in the past decades. Due to their outstanding performance, advanced microbubbles as a multifunctional platform combining both imaging and therapy have been increasingly attracting attention. Associated with ultrasound-mediated stimuli, targeting drug transportation with high precision can be established and, as a consequence, a synergistic treatment strategy may prevail, which implies a bright perspective for this brand-new technology. This perspective article will summarize the latest developments on the advanced microbubbles, and review their emerging biomedical applications for the vast community of both applied ultrasound and functional ultrasound-based materials. Full article
(This article belongs to the Special Issue Biomedical Ultrasound)
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Open AccessArticle
Design and Implementation of an Optimal Energy Control System for Fixed-Wing Unmanned Aerial Vehicles
Appl. Sci. 2016, 6(11), 369; https://doi.org/10.3390/app6110369 - 19 Nov 2016
Cited by 3 | Viewed by 2714
Abstract
In conventional flight control design, the autopilot and the autothrottle systems are usually considered separately, resulting in a complex system and inefficient integration of functions. Therefore, the concept of aircraft energy control is brought up to solve the problem of coordinated control using [...] Read more.
In conventional flight control design, the autopilot and the autothrottle systems are usually considered separately, resulting in a complex system and inefficient integration of functions. Therefore, the concept of aircraft energy control is brought up to solve the problem of coordinated control using elevator and throttle. The goal of this study is to develop an optimal energy control system (OECS), based on the concept of optimal energy for fixed-wing unmanned aerial vehicles (UAVs). The energy of an aircraft is characterized by two parameters, which are specific energy distribution rate, driven by elevator, and total specific energy rate, driven by throttle. In this study, a system identification method was employed to obtain the energy model of a small UAV. The proposed approach consists of energy distribution loop and total energy loop. Energy distribution loop is designed based on linear-quadratic-Gaussian (LQG) regulator and is responsible for regulating specific energy distribution rate to zero. On the other hand, the total energy loop, based on simple gain scheduling method, is responsible for driving the error of total specific energy rate to zero. The implementation of OECS was successfully validated in the hard-in-the-loop (HIL) simulation of the applied UAV. Full article
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Open AccessArticle
Spectral Envelope Transformation in Singing Voice for Advanced Pitch Shifting
Appl. Sci. 2016, 6(11), 368; https://doi.org/10.3390/app6110368 - 19 Nov 2016
Cited by 2 | Viewed by 1769
Abstract
The aim of the present work is to perform a step towards more natural pitch shifting techniques in singing voice for its application in music production and entertainment systems. In this paper, we present an advanced method to achieve natural modifications when applying [...] Read more.
The aim of the present work is to perform a step towards more natural pitch shifting techniques in singing voice for its application in music production and entertainment systems. In this paper, we present an advanced method to achieve natural modifications when applying a pitch shifting process to singing voice by modifying the spectral envelope of the audio excerpt. To this end, an all-pole model has been selected to model the spectral envelope, which is estimated using a constrained non-linear optimization. The analysis of the global variations of the spectral envelope was carried out by identifying changes of the parameters of the model along with the changes of the pitch. With the obtained spectral envelope transformation functions, we applied our pitch shifting scheme to some sustained vowels in order to compare results with the same transformation made by using the Flex Pitch plugin of Logic Pro X and pitch synchronous overlap and add technique (PSOLA). This comparison has been carried out by means of both an objective and a subjective evaluation. The latter was done with a survey open to volunteers on our website. Full article
(This article belongs to the Section Acoustics and Vibrations)
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Open AccessArticle
Longitudinal Jitter Analysis of a Linear Accelerator Electron Gun
Appl. Sci. 2016, 6(11), 350; https://doi.org/10.3390/app6110350 - 19 Nov 2016
Cited by 1 | Viewed by 1361
Abstract
We present measurements and analysis of the longitudinal timing jitter of a Beijing Electron Positron Collider (BEPCII) linear accelerator electron gun. We simulated the longitudinal jitter effect of the gun using PARMELA to evaluate beam performance, including: beam profile, average energy, energy spread, [...] Read more.
We present measurements and analysis of the longitudinal timing jitter of a Beijing Electron Positron Collider (BEPCII) linear accelerator electron gun. We simulated the longitudinal jitter effect of the gun using PARMELA to evaluate beam performance, including: beam profile, average energy, energy spread, and XY emittances. The maximum percentage difference of the beam parameters is calculated to be 100%, 13.27%, 42.24% and 65.01%, 86.81%, respectively. Due to this, the bunching efficiency is reduced to 54%. However, the longitudinal phase difference of the reference particle was 9.89°. The simulation results are in agreement with tests and are helpful to optimize the beam parameters by tuning the trigger timing of the gun during the bunching process. Full article
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Open AccessCommunication
Feasibility Study of a Gripper with Thermally Controlled Stiffness of Compliant Jaws
Appl. Sci. 2016, 6(11), 367; https://doi.org/10.3390/app6110367 - 18 Nov 2016
Cited by 4 | Viewed by 1578
Abstract
This paper proposes a simple and compact compliant gripper, whose gripping stiffness can be thermally controlled to accommodate the actuation inaccuracy to avoid or reduce the risk of breaking objects. The principle of reducing jaw stiffness is that thermal change can cause an [...] Read more.
This paper proposes a simple and compact compliant gripper, whose gripping stiffness can be thermally controlled to accommodate the actuation inaccuracy to avoid or reduce the risk of breaking objects. The principle of reducing jaw stiffness is that thermal change can cause an initial internal compressive force along each compliant beam. A prototype is fabricated with physical testing to verify the feasibility. It has been shown that when a voltage is applied, the gripping stiffness effectively reduces to accommodate more inaccuracy of actuation, which allows delicate or small-scale objects to be gripped. Full article
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Open AccessArticle
Validation of a Numerical Model for the Prediction of the Annoyance Condition at the Operator Station of Construction Machines
Appl. Sci. 2016, 6(11), 363; https://doi.org/10.3390/app6110363 - 18 Nov 2016
Cited by 3 | Viewed by 1134
Abstract
It is well-known that the reduction of noise levels is not strictly linked to the reduction of noise annoyance. Even earthmoving machine manufacturers are facing the problem of customer complaints concerning the noise quality of their machines with increasing frequency. Unfortunately, all the [...] Read more.
It is well-known that the reduction of noise levels is not strictly linked to the reduction of noise annoyance. Even earthmoving machine manufacturers are facing the problem of customer complaints concerning the noise quality of their machines with increasing frequency. Unfortunately, all the studies geared to the understanding of the relationship between multidimensional characteristics of noise signals and the auditory perception of annoyance require repeated sessions of jury listening tests, which are time-consuming. In this respect, an annoyance prediction model was developed for compact loaders to assess the annoyance sensation perceived by operators at their workplaces without repeating the full sound quality assessment but using objective parameters only. This paper aims at verifying the feasibility of the developed annoyance prediction model when applied to other kinds of earthmoving machines. For this purpose, an experimental investigation was performed on five earthmoving machines, different in type, dimension, and engine mechanical power, and the annoyance predicted by the numerical model was compared to the annoyance given by subjective listening tests. The results were evaluated by means of the squared value of the correlation coefficient, R2, and they confirm the possible applicability of the model to other kinds of machines. Full article
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Open AccessArticle
A Calibration Method for Nonlinear Mismatches in M-Channel Time-Interleaved Analog-to-Digital Converters Based on Hadamard Sequences
Appl. Sci. 2016, 6(11), 362; https://doi.org/10.3390/app6110362 - 18 Nov 2016
Cited by 3 | Viewed by 1673
Abstract
The time-interleaved analog-to-digital converter (TIADC) is an architecture used to achieve a high sampling rate and high dynamic performance. However, estimation and compensation methods are required to maintain the dynamic performance of the constituent analog-to-digital converters (ADCs) due to channel mismatches. This paper [...] Read more.
The time-interleaved analog-to-digital converter (TIADC) is an architecture used to achieve a high sampling rate and high dynamic performance. However, estimation and compensation methods are required to maintain the dynamic performance of the constituent analog-to-digital converters (ADCs) due to channel mismatches. This paper proposes a blind adaptive method to calibrate the nonlinear mismatches in M-channel TIADCs (M-TIADCs). The nonlinearity-induced error signal is reconstructed by the proposed multiplier Hadamard transform (MHT) structure, and the nonlinear parameters are estimated by the filtered-X least-mean square (FxLMS) algorithm. The performance of cascade calibration is also analyzed. The numerical simulation results show that the proposed method consumes much less hardware resources while maintaining the calibration performance. Full article
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Open AccessFeature PaperArticle
Harmonic Differential Quadrature Analysis of Soft-Core Sandwich Panels under Locally Distributed Loads
Appl. Sci. 2016, 6(11), 361; https://doi.org/10.3390/app6110361 - 18 Nov 2016
Cited by 4 | Viewed by 1622
Abstract
Sandwich structures are widely used in practice and thus various engineering theories adopting simplifying assumptions are available. However, most engineering theories of beams, plates and shells cannot recover all stresses accurately through their constitutive equations. Therefore, the soft-core is directly modeled by two-dimensional [...] Read more.
Sandwich structures are widely used in practice and thus various engineering theories adopting simplifying assumptions are available. However, most engineering theories of beams, plates and shells cannot recover all stresses accurately through their constitutive equations. Therefore, the soft-core is directly modeled by two-dimensional (2D) elasticity theory without any pre-assumption on the displacement field. The top and bottom faces act like the elastic supports on the top and bottom edges of the core. The differential equations of the 2D core are then solved by the harmonic differential quadrature method (HDQM). To circumvent the difficulties in dealing with the locally distributed load by point discrete methods such as the HDQM, a general and rigorous way is proposed to treat the locally distributed load. Detailed formulations are provided. The static behavior of sandwich panels under different locally distributed loads is investigated. For verification, results are compared with data obtained by ABAQUS with very fine meshes. A high degree of accuracy on both displacement and stress has been observed. Full article
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Open AccessArticle
Extending the Effective Ranging Depth of Spectral Domain Optical Coherence Tomography by Spatial Frequency Domain Multiplexing
Appl. Sci. 2016, 6(11), 360; https://doi.org/10.3390/app6110360 - 17 Nov 2016
Cited by 2 | Viewed by 2546
Abstract
We present a spatial frequency domain multiplexing method for extending the imaging depth range of a spectral domain optical coherence tomography (SDOCT) system without any expensive device. This method uses two galvo scanners with different pivot-offset distances in two independent reference arms for [...] Read more.
We present a spatial frequency domain multiplexing method for extending the imaging depth range of a spectral domain optical coherence tomography (SDOCT) system without any expensive device. This method uses two galvo scanners with different pivot-offset distances in two independent reference arms for spatial frequency modulation and multiplexing. The spatial frequency contents corresponding to different depth regions of the sample can be shifted to different frequency bands. The spatial frequency domain multiplexing SDOCT system provides an approximately 1.9-fold increase in the effective ranging depth compared with that of a conventional full-range SDOCT system. The reconstructed images of phantom and biological tissue demonstrate the expected increase in ranging depth. The parameters choice criterion for this method is discussed. Full article
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Open AccessArticle
A Sibelobe Suppressing Beamformer for Coherent Plane Wave Compounding
Appl. Sci. 2016, 6(11), 359; https://doi.org/10.3390/app6110359 - 17 Nov 2016
Cited by 4 | Viewed by 1493
Abstract
Contrast degradation is a critical problem in ultrasound plane wave imaging (PWI) resulting from signals leakage from the sidelobes. An ideal sidelobe reduction method may enhance the contrast without remarkably increasing computational load. To this end, we introduce a new singular value decomposition [...] Read more.
Contrast degradation is a critical problem in ultrasound plane wave imaging (PWI) resulting from signals leakage from the sidelobes. An ideal sidelobe reduction method may enhance the contrast without remarkably increasing computational load. To this end, we introduce a new singular value decomposition (SVD) sidelobe reduction beamformer for coherent plane wave compounding (CPWC) based on a previous work. The SVD takes advantage of the benefits of the different features of the mainlobe and sibelobe in terms of spatio-angular coherence and removes the sidelobes before the final coherent summation. This SVD-based method provides a three-dimensional approach (2D in the space and 1D in the angle) while the computation load is kept satisfactory by a dimension-reduced operation before the SVD. To directly observe the sidelobe level, we demonstrate the performance of our SVD method with a point spread function (PSF) simulation. Compared to CPWC, our method shows a 6.2 dB reduction in the peak sidelobe level (PSL). We also applied our method to the anechoic cyst inside the speckle for the imaging contrast. Both in the simulation and phantom studies, our method enhances the contrast-to-noise ratio (CNR) by more than 10%. Therefore, this new beamformer can be an efficient way to suppress sidelobes in PWI. Full article
(This article belongs to the Special Issue Biomedical Ultrasound)
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Open AccessArticle
TRAP: A Three-Way Handshake Server for TCP Connection Establishment
Appl. Sci. 2016, 6(11), 358; https://doi.org/10.3390/app6110358 - 16 Nov 2016
Cited by 1 | Viewed by 3155
Abstract
Distributed denial of service attacks have become more and more frequent nowadays. In 2013, a massive distributed denial of service (DDoS) attack was launched against Spamhaus causing the service to shut down. In this paper, we present a three-way handshaking server for Transmission [...] Read more.
Distributed denial of service attacks have become more and more frequent nowadays. In 2013, a massive distributed denial of service (DDoS) attack was launched against Spamhaus causing the service to shut down. In this paper, we present a three-way handshaking server for Transmission Control Protocol (TCP) connection redirection utilizing TCP header options. When a legitimate client attempted to connect to a server undergoing an SYN-flood DDoS attack, it will try to initiate a three-way handshake. After it has successfully established a connection, the server will reply with a reset (RST) packet, in which a new server address and a secret is embedded. The client can, thus, connect to the new server that only accepts SYN packets with the corrected secret using the supplied secret. Full article
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Open AccessArticle
Energy-Efficient On–Off Power Control of Femto-Cell Base Stations for Cooperative Cellular Networks
Appl. Sci. 2016, 6(11), 356; https://doi.org/10.3390/app6110356 - 16 Nov 2016
Cited by 2 | Viewed by 1374
Abstract
Improving energy efficiency (EE) of mobile communication systems (MCSs) has been considered a key aim in recent years, and has been the subject of intense research interest. One of the simplest yet most powerful ways to increase the EE is to turn off [...] Read more.
Improving energy efficiency (EE) of mobile communication systems (MCSs) has been considered a key aim in recent years, and has been the subject of intense research interest. One of the simplest yet most powerful ways to increase the EE is to turn off redundant communication entities whose operation does not greatly affect the overall performance of the MCS. In this paper, we propose a novel on–off power control scheme for femto-cell base stations (FBSs) considering cooperative transmission in which multiple FBSs collaborate on the same data transmission. In the proposed scheme, the operation of the redundant FBSs is halted in an adaptive manner. For the proper determination of redundant FBSs with low computational complexity, we propose using the level of contribution (LOC), which specifies the importance of a given FBS in the cooperative transmission. Redundant FBSs are chosen based on their LOC value, and these FBSs are turned off in order to reduce the power consumption of MCSs while minimizing the degradation of the overall throughput of cooperative transmissions. The performance of the proposed scheme is verified through extensive simulations, which shows that near-optimal performance can be achieved without excessive computations. Full article
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Open AccessArticle
Compact Aberration-Free Relay-Imaging Multi-Pass Layouts for High-Energy Laser Amplifiers
Appl. Sci. 2016, 6(11), 353; https://doi.org/10.3390/app6110353 - 16 Nov 2016
Cited by 3 | Viewed by 1747
Abstract
We present the results from a theoretical investigation of laser beam propagation in relay imaging multi-pass layouts, which recently found application in high-energy laser amplifiers. Using a method based on the well-known ABCD-matrix formalism and proven by ray tracing, it was possible to [...] Read more.
We present the results from a theoretical investigation of laser beam propagation in relay imaging multi-pass layouts, which recently found application in high-energy laser amplifiers. Using a method based on the well-known ABCD-matrix formalism and proven by ray tracing, it was possible to derive a categorization of such systems. Furthermore, basic rules for the setup of such systems and the compensation for low order aberrations are derived. Due to the introduced generalization and parametrization, the presented results can immediately be applied to any system of the investigated kinds for a wide range of parameters, such as number of round-trips, focal lengths and optics sizes. It is shown that appropriate setups allow a close-to-perfect compensation of defocus caused by a thermal lens and astigmatism caused by non-normal incidence on the imaging optics, as well. Both are important to avoid intensity spikes leading to damages of optics in multi-pass laser amplifiers. Full article
(This article belongs to the Section Optics and Lasers)
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Open AccessArticle
Mathematical Models of Androgen Resistance in Prostate Cancer Patients under Intermittent Androgen Suppression Therapy
Appl. Sci. 2016, 6(11), 352; https://doi.org/10.3390/app6110352 - 16 Nov 2016
Cited by 5 | Viewed by 1989
Abstract
Predicting the timing of a castrate resistant prostate cancer is critical to lowering medical costs and improving the quality of life of advanced prostate cancer patients. We formulate, compare and analyze two mathematical models that aim to forecast future levels of prostate-specific antigen [...] Read more.
Predicting the timing of a castrate resistant prostate cancer is critical to lowering medical costs and improving the quality of life of advanced prostate cancer patients. We formulate, compare and analyze two mathematical models that aim to forecast future levels of prostate-specific antigen (PSA). We accomplish these tasks by employing clinical data of locally advanced prostate cancer patients undergoing androgen deprivation therapy (ADT). While these models are simplifications of a previously published model, they fit data with similar accuracy and improve forecasting results. Both models describe the progression of androgen resistance. Although Model 1 is simpler than the more realistic Model 2, it can fit clinical data to a greater precision. However, we found that Model 2 can forecast future PSA levels more accurately. These findings suggest that including more realistic mechanisms of androgen dynamics in a two population model may help androgen resistance timing prediction. Full article
(This article belongs to the Special Issue Dynamical Models of Biology and Medicine) Printed Edition available
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Open AccessArticle
Investigating the Influence of Plasma-Treated SiO2 Nanofillers on the Electrical Treeing Performance of Silicone-Rubber
Appl. Sci. 2016, 6(11), 348; https://doi.org/10.3390/app6110348 - 16 Nov 2016
Cited by 4 | Viewed by 1468
Abstract
This study presents an investigation of electrical tree performance as well as the effect of filler concentration of silicone rubber (SiR) filled with atmospheric-pressure plasma-treated silicon dioxide (SiO2) nanofiller. Atmospheric-pressure plasma was used to treat the SiO2 nanofiller surfaces to [...] Read more.
This study presents an investigation of electrical tree performance as well as the effect of filler concentration of silicone rubber (SiR) filled with atmospheric-pressure plasma-treated silicon dioxide (SiO2) nanofiller. Atmospheric-pressure plasma was used to treat the SiO2 nanofiller surfaces to enhance compatibility with SiR matrices. A fixed AC voltage of 10 kV, 50 Hz was applied to untreated, silane-treated, and plasma-treated nanocomposites with filler concentrations of 1, 3, and 5 wt % to investigate their electrical performance during electrical treeing. The result showed that plasma-treated SiO2 nanoparticles were uniformly well dispersed and formed strong covalent bonds with the molecules of the SiR polymer matrix. The plasma-treated nanocomposites were able to resist the electrical treeing better than the untreated or silane-treated nanocomposites. The increase in filler concentration enhanced the electrical tree performances of the nanocomposites. The result from this study reveals that the plasma-treated nanocomposites exhibited the best result in inhibiting the growth of electrical treeing compared to the existing surface treatment methods used in this study. Full article
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Open AccessArticle
Numerical Study of Photoacoustic Pressure for Cancer Therapy
Appl. Sci. 2016, 6(11), 357; https://doi.org/10.3390/app6110357 - 15 Nov 2016
Cited by 4 | Viewed by 1152
Abstract
A commonly used therapy for cancer is based on the necrosis of cells induced by heating through the illumination of nanoparticles embedded in cells. Recently, the photoacoustic pressure shock induced by the illumination pulse was proved and this points to another means of [...] Read more.
A commonly used therapy for cancer is based on the necrosis of cells induced by heating through the illumination of nanoparticles embedded in cells. Recently, the photoacoustic pressure shock induced by the illumination pulse was proved and this points to another means of cell destruction. The purpose of this study is to propose a model of the photoacoustic pressure in cells. The numerical resolution of the problem requires the accurate computation of the electromagnetism, the temperature and the pressure around the nanostructures embedded in a cell. Here, the problem of the interaction between an electromagnetic excitation and a gold nanoparticle embedded in a cell domain is solved. The variations of the thermal and photoacoustic pressures are studied in order to analyze the pressure shock wave inducing the collapse of the cell’s membrane in cancer therapy. Full article
(This article belongs to the Section Nanotechnology and Applied Nanosciences)
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Open AccessArticle
Analysis of the Numerical Diffusion in Anisotropic Mediums: Benchmarks for Magnetic Field Aligned Meshes in Space Propulsion Simulations
Appl. Sci. 2016, 6(11), 354; https://doi.org/10.3390/app6110354 - 15 Nov 2016
Viewed by 2509
Abstract
This manuscript explores numerical errors in highly anisotropic diffusion problems. First, the paper addresses the use of regular structured meshes in numerical solutions versus meshes aligned with the preferential directions of the problem. Numerical diffusion in structured meshes is quantified by solving the [...] Read more.
This manuscript explores numerical errors in highly anisotropic diffusion problems. First, the paper addresses the use of regular structured meshes in numerical solutions versus meshes aligned with the preferential directions of the problem. Numerical diffusion in structured meshes is quantified by solving the classical anisotropic diffusion problem; the analysis is exemplified with the application to a numerical model of conducting fluids under magnetic confinement, where rates of transport in directions parallel and perpendicular to a magnetic field are quite different. Numerical diffusion errors in this problem promote the use of magnetic field aligned meshes (MFAM). The generation of this type of meshes presents some challenges; several meshing strategies are implemented and analyzed in order to provide insight into achieving acceptable mesh regularity. Second, Gradient Reconstruction methods for magnetically aligned meshes are addressed and numerical errors are compared for the structured and magnetically aligned meshes. It is concluded that using the latter provides a more correct and straightforward approach to solving problems where anisotropicity is present, especially, if the anisotropicity level is high or difficult to quantify. The conclusions of the study may be extrapolated to the study of anisotropic flows different from conducting fluids. Full article
(This article belongs to the Special Issue Applications of Complex Fluids)
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Open AccessArticle
Quantum Control of Population Transfer and Vibrational States via Chirped Pulses in Four Level Density Matrix Equations
Appl. Sci. 2016, 6(11), 351; https://doi.org/10.3390/app6110351 - 15 Nov 2016
Cited by 2 | Viewed by 1941
Abstract
We investigate the effect of chirped excitation and the excitation detuning on the coherent control of population transfer and vibrational states in a four-level system. Density matrix equations are studied for optimally enhanced processes by considering specific parameters typical of oxazine systems. Our [...] Read more.
We investigate the effect of chirped excitation and the excitation detuning on the coherent control of population transfer and vibrational states in a four-level system. Density matrix equations are studied for optimally enhanced processes by considering specific parameters typical of oxazine systems. Our simulations show a strong dependence on the interplay between chirp and excitation detuning and predict enhancement factors up to 3.2 for population transfer and up to 38.5 for vibrational coherences of electronic excited states. The study of the dynamics of the populations and vibrational coherences involved in the four-level system allows an interpretation of the different enhancement/suppression processes observed. Full article
(This article belongs to the Special Issue Ultrashort Optical Pulses)
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Open AccessArticle
Thin Film Williamson Nanofluid Flow with Varying Viscosity and Thermal Conductivity on a Time-Dependent Stretching Sheet
Appl. Sci. 2016, 6(11), 334; https://doi.org/10.3390/app6110334 - 15 Nov 2016
Cited by 22 | Viewed by 1999
Abstract
This article describes the effect of thermal radiation on the thin film nanofluid flow of a Williamson fluid over an unsteady stretching surface with variable fluid properties. The basic governing equations of continuity, momentum, energy, and concentration are incorporated. The effect of thermal [...] Read more.
This article describes the effect of thermal radiation on the thin film nanofluid flow of a Williamson fluid over an unsteady stretching surface with variable fluid properties. The basic governing equations of continuity, momentum, energy, and concentration are incorporated. The effect of thermal radiation and viscous dissipation terms are included in the energy equation. The energy and concentration fields are also coupled with the effect of Dufour and Soret. The transformations are used to reduce the unsteady equations of velocity, temperature and concentration in the set of nonlinear differential equations and these equations are tackled through the Homotopy Analysis Method (HAM). For the sake of comparison, numerical (ND-Solve Method) solutions are also obtained. Special attention has been given to the variable fluid properties’ effects on the flow of a Williamson nanofluid. Finally, the effect of non-dimensional physical parameters like thermal conductivity, Schmidt number, Williamson parameter, Brinkman number, radiation parameter, and Prandtl number has been thoroughly demonstrated and discussed. Full article
(This article belongs to the Special Issue Recent Developments of Nanofluids) Printed Edition available
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Open AccessArticle
Moving Object Tracking and Its Application to an Indoor Dual-Robot Patrol
Appl. Sci. 2016, 6(11), 349; https://doi.org/10.3390/app6110349 - 12 Nov 2016
Cited by 4 | Viewed by 1981
Abstract
This paper presents an application of image tracking using an omnidirectional wheeled mobile robot (WMR). The objective of this study is to integrate image processing of hue, saturation, and lightness (HSL) for fuzzy color space, and use mean shift tracking for object detection [...] Read more.
This paper presents an application of image tracking using an omnidirectional wheeled mobile robot (WMR). The objective of this study is to integrate image processing of hue, saturation, and lightness (HSL) for fuzzy color space, and use mean shift tracking for object detection and a Radio Frequency Identification (RFID) reader for confirming destination. Fuzzy control is applied to omnidirectional WMR for indoor patrol and intruder detection. Experimental results show that the proposed control scheme can make the WMRs perform indoor security service. Full article
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Open AccessArticle
Oxygen Carrier Aided Combustion (OCAC) of Wood Chips in a Semi-Commercial Circulating Fluidized Bed Boiler Using Manganese Ore as Bed Material
Appl. Sci. 2016, 6(11), 347; https://doi.org/10.3390/app6110347 - 12 Nov 2016
Cited by 15 | Viewed by 2573
Abstract
Oxygen Carrier Aided Combustion (OCAC) is realized by using an active oxygen-carrying bed material in fluidized bed boilers. The active material is reduced in fuel rich parts of the boiler and oxidized in air rich parts. Advantages could be achieved such as new [...] Read more.
Oxygen Carrier Aided Combustion (OCAC) is realized by using an active oxygen-carrying bed material in fluidized bed boilers. The active material is reduced in fuel rich parts of the boiler and oxidized in air rich parts. Advantages could be achieved such as new mechanisms for oxygen transport in space and time. Here calcined manganese ore has been used as active bed material in a 12 MWth circulating fluidized bed boiler. The fuel was wood chips and the campaign lasted more than two weeks. From an operational point of view, manganese ore worked excellently. From the temperature profile of the boiler it can be concluded that fuel conversion was facilitated, especially in the dense bottom bed. The effect did not always translate to reduced emissions, which suggests that final combustion in the cyclone outlet was also influenced. Substituting 10% of the sand bed with manganese ore made it possible to reduce the air to fuel ratio without generating large amounts of CO. The use of 100% manganese ore resulted in higher emissions of CO than the sand reference, but, when combined sulphur feeding, dramatic reductions in CO emissions, up to 90% compared to sand reference, was achieved. Full article
(This article belongs to the Section Energy)
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Open AccessArticle
On Squeezed Flow of Jeffrey Nanofluid between Two Parallel Disks
Appl. Sci. 2016, 6(11), 346; https://doi.org/10.3390/app6110346 - 11 Nov 2016
Cited by 34 | Viewed by 1876
Abstract
The present communication examines the magnetohydrodynamic (MHD) squeezing flow of Jeffrey nanofluid between two parallel disks. Constitutive relations of Jeffrey fluid are employed in the problem development. Heat and mass transfer aspects are examined in the presence of thermophoresis and Brownian motion. Jeffrey [...] Read more.
The present communication examines the magnetohydrodynamic (MHD) squeezing flow of Jeffrey nanofluid between two parallel disks. Constitutive relations of Jeffrey fluid are employed in the problem development. Heat and mass transfer aspects are examined in the presence of thermophoresis and Brownian motion. Jeffrey fluid subject to time dependent applied magnetic field is conducted. Suitable variables lead to a strong nonlinear system. The resulting systems are computed via homotopic approach. The behaviors of several pertinent parameters are analyzed through graphs and numerical data. Skin friction coefficient and heat and mass transfer rates are numerically examined. Full article
(This article belongs to the Special Issue Recent Developments of Nanofluids) Printed Edition available
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Open AccessArticle
Experimental Study on the Force-Bearing Performance of Masonry Structures with a Marble-Graphite Slide Seismic Isolator at the Foundation
Appl. Sci. 2016, 6(11), 345; https://doi.org/10.3390/app6110345 - 10 Nov 2016
Viewed by 1414
Abstract
As part of the search for a seismic isolator for low-rise buildings, this paper proposes a marble-graphite slide seismic isolation system composed of marble-graphite slides, an upper foundation beam, the lower counterpart of the upper beam, and the corresponding stop blocks, with the [...] Read more.
As part of the search for a seismic isolator for low-rise buildings, this paper proposes a marble-graphite slide seismic isolation system composed of marble-graphite slides, an upper foundation beam, the lower counterpart of the upper beam, and the corresponding stop blocks, with the stop blocks consisting of restrictive screws, positioning plates, nut connectors and stop holes linking the two foundation beams. To provide the desired isolation performance, plain mortar bars can be included at the beam interface to better control the initiating loads for foundation slippage. Tests of low-reversed cyclic loading were performed on four different masonry specimens: a recycled brick wall, a clay brick wall, an integrated recycled brick wall with flay ash blocks sandwiched between, and its clay brick counterpart. The four specimens were provided with marble-graphite slide isolators placed at the foundations. The isolator thickness was 20 mm, and the graphite and the marble served as a lubricant and a bearing, respectively. This paper then analyses all of the specimens in terms of the damage that occurred, the initiating load for slippage, the hysteretic performance, the bearing capacity and the performance of the stop blocks. The results indicate that mortar bars embedded in the marble-graphite slide isolator offer effective control of the initiating load, and the isolation system delivers good hysteretic performance. The stop blocks are capable of withstanding a large-magnitude earthquake and are a good choice for constraining the slippage displacement. Damage or failure of the specimens occurs only when the low-reversed cyclic loading continues after slippage takes place. The design is shown to be an outstanding and flexible seismic scheme for use in low-rise buildings. Full article
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Open AccessArticle
Analysis and Compensation of Dead-Time Effect of a ZVT PWM Inverter Considering the Rise- and Fall-Times
Appl. Sci. 2016, 6(11), 344; https://doi.org/10.3390/app6110344 - 09 Nov 2016
Cited by 2 | Viewed by 2465
Abstract
The dead-time effect, as an intrinsic problem of the converters based on the half-bridge unit, leads to distortions in the converter output. Although several dead-time effect compensation or elimination methods have been proposed, they cannot fully remove the dead-time effect of blanking delay [...] Read more.
The dead-time effect, as an intrinsic problem of the converters based on the half-bridge unit, leads to distortions in the converter output. Although several dead-time effect compensation or elimination methods have been proposed, they cannot fully remove the dead-time effect of blanking delay error, because the output current polarity is difficult detect accurately. This paper utilizes the zero-voltage-switching (ZVT) technique to eliminate the blanking delay error, which is the main drawback of the hard-switching inverter, although the technique initially aims to improve the efficiency. A typical ZVT inverter—the auxiliary resonant snubber inverter (ARSI) is analyzed. The blanking delay error is completely eliminated in the ARSI. Another error source caused by the finite rise- and fall-times of the voltage is analyzed, which was not considered in the hard-switching inverter. A compensation method based on the voltage error estimation is proposed to compensate the rise- and fall-error. A prototype was developed to verify the effectiveness of the proposed control. Both the simulation and experimental results demonstrate that the qualities of the output current and voltage in the ARSI are better than that in the hard-switching inverter due to the elimination of the blanking delay error. The total harmonic distortion (THD) of the output is further reduced by using the proposed compensation method in the ARSI. Full article
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Open AccessArticle
Optimization of One-Step In Situ Transesterification Method for Accurate Quantification of EPA in Nannochloropsis gaditana
Appl. Sci. 2016, 6(11), 343; https://doi.org/10.3390/app6110343 - 08 Nov 2016
Cited by 5 | Viewed by 1631
Abstract
Microalgae are a valuable source of lipid feedstocks for biodiesel and valuable omega-3 fatty acids. Nannochloropsis gaditana has emerged as a promising producer of eicosapentaenoic acid (EPA) due to its fast growth rate and high EPA content. In the present study, the fatty [...] Read more.
Microalgae are a valuable source of lipid feedstocks for biodiesel and valuable omega-3 fatty acids. Nannochloropsis gaditana has emerged as a promising producer of eicosapentaenoic acid (EPA) due to its fast growth rate and high EPA content. In the present study, the fatty acid profile of Nannochloropsis gaditana was found to be naturally high in EPA and devoid of docosahexaenoic acid (DHA), thereby providing an opportunity to maximize the efficacy of EPA production. Using an optimized one-step in situ transesterification method (methanol:biomass = 90 mL/g; HCl 5% by vol.; 70 °C; 1.5 h), the maximum fatty acid methyl ester (FAME) yield of Nannochloropsis gaditana cultivated under rich condition was quantified as 10.04% ± 0.08% by weight with EPA-yields as high as 4.02% ± 0.17% based on dry biomass. The total FAME and EPA yields were 1.58- and 1.23-fold higher separately than that obtained using conventional two-step method (solvent system: methanol and chloroform). This one-step in situ method provides a fast and simple method to measure fatty acid methyl ester (FAME) yields and could serve as a promising method to generate eicosapentaenoic acid methyl ester from microalgae. Full article
(This article belongs to the Section Chemistry)
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