Showing papers in "Ieej Transactions on Electrical and Electronic Engineering in 2013"

Multiobjective particle swarm optimization for a novel fuzzy portfolio selection problem

Abstract: On the basis of the portfolio selection theory, this paper proposes a novel fuzzy multiobjective model that can evaluate investment risk properly and increase the probability of obtaining an expected return. In building this model, fuzzy value-at-risk (VaR) is used to evaluate the exact future risk in terms of loss. The VaR can directly reflect the greatest loss of a selection case under a given confidence level. Conversely, variance, the measure of the spread of a distribution around its expected value, is utilized to make the selection more stable. This model can provide investors with more significant information for decision making. To solve this model, an improved Pareto-optimal-set-based multiobjective particle swarm optimization (IMOPSO) algorithm is designed to obtain better solutions in the Pareto front. The proposed model and algorithm are exemplified by specific numerical examples. Furthermore, comparisons are made between IMOPSO and other existing approaches. Experiments show that the model and algorithm are effective in solving the multiobjective portfolio selection problem. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Intelligent combinatorial auctions of decentralized task assignment for AGV with multiple loading capacity

Abstract: The need to have an efficient transportation system has attracted worldwide attention. Although there is increasing demand to implement distributed control system for industrial applications, there is still an unexplored potential of deploying distributed transportation system. This paper focuses on dynamic assignment of transportation requests to a fleet of vehicles in real time. We introduce an improved combinatorial auction methodology to accommodate the distributed task assignment procedure. Based on a multiagent architecture, each vehicle is represented by an intelligent agent that bids for task and plans its own schedule. On the other hand, the auctioneer has the objective of minimizing transportation tardiness. An automated guided vehicle (AGV) has been selected as the case study, and numerical experiments have been carried out. The result obtained shows that the improved task assignment approach is able to produce performance competitive to a conventional task assignment. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Sputtering condition optimization of sputtered IrOx and TiN stimulus electrodes for retinal prosthesis

Abstract: We have optimized the sputtering conditions for sputtered IrOx and TiN electrodes for retinal prosthesis. The basic electrochemical characteristics were evaluated by cyclic voltammetry, and the surface morphology was inspected by atomic force microscopy. To measure the charge delivery capacity (CDC), a 300-µm diameter electrode was formed, a balanced biphasic current pulse was applied, and the voltage response was measured. From the experimental results, the CDCs of IrOx and TiN in the best sputtering conditions were improved by more than 8 and 4 times compared to that of Pt, respectively. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Dual-Camera Acquisition for Accurate Measurement of Three-Dimensional Eye Movements

Abstract: In this paper, we suggest a new approach for accurate measurement of three-dimensional eye movements employing dualcamera acquisition. Two calibrated mini CCD cameras are used to capture two simultaneous images of one eye. Center of mass and template matching algorithms are utilized to obtain two-dimensional coordinates of the center of pupil and iris striation. Instead of asking each patient to fulfill intricate calibration steps, a novel and simpler technique to solve geometric distortion is presented by utilizing Direct Linear Transformation (DLT) algorithm that requires only one preliminary calibration procedure for each camera without changing any camera installation. The DLT algorithm is then used to extract three-dimensional coordinates of the center of pupil and iris striation from prior two-dimensional coordinates data, allowing the three-dimensional angular positions of the eye to be computed. Real-time eyeball visualization based on tracking results is incorporated to help clinicians diagnose the eye movements. Experimental results show that our system has high accuracy as the average errors in horizontal, vertical, and torsional angular positions were confined to 0:15 , 0:14 , and 0:20 , respectively. Real-time implementation demonstrates that our system can be used in clinical routine to observe either voluntary or involuntary human eye movements. c 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Fault current calculation in distribution systems with inverter‐based distributed generations

Abstract: Fault current calculation in distribution systems faces the problem with participation of inverter-based distributed generation (IBDG). This paper analyzes the fault response of IBDG in order to model it under fault condition. An adaptive algorithm based on an iterative technique is then proposed to calculate the fault current in a system with the installation of IBDG. This algorithm is first validated by the conventional fault calculation technique in case of a system without IBDG. Then, a time-variant simulation is performed to validate the proposed algorithm for the system with IBDG. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Research on influencing factors of corrosive sulfur attacking copper in insulating oil and prevention

Abstract: The influencing factors (temperature, electric field, and oxygen) of sulfur attack in transformer oil are studied through comparative tests on new oil, oil in service, and these two oils with the deactivator additive BTA (benzotriazole, C6H4N3H). The influence of these factors on the chemical reaction between copper and corrosive sulfur is analyzed in further. The results show that temperature, electric field, and oxygen can promote the reaction between copper and corrosive sulfur. Moreover, oxygen also accelerates the aging of the insulating oil. On the contrary, recharging nitrogen can remove oxygen and reduce sulfur's corrosive activity. Adding the BTA deactivator can also prevent corrosion, even during the accelerated aging of oil with oxygen. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Recent progress of SiC power devices and applications

Abstract: Devices made of the wide-bandgap semiconductor silicon carbide are capable of not only providing excellent performance for higher voltages, higher switching frequencies, higher junction temperatures, and higher power than silicon devices, but also leading to drastic reduction in system complexity, volume, and weight, as well as higher efficiency and better reliability of power electronics systems. The newly emerged technology has made rapid progress during the past decade, and we can expect even greater advantages and potential for energy savings and emission reduction in the coming years. In this paper, the research on SiC material and device technologies, the benefits, and some remaining issues are discussed. Recent progress (since 2007) in applications such as DC–DC, AC–DC, DC–AC, and AC–AC converters is discussed. Also, future applications and perspectives are analyzed. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Economic Load Dispatch with Nonsmooth Cost Functions Using Evolutionary Particle Swarm Optimization

Abstract: This paper presents an evolutionary particle swarm optimization (EPSO) method for solving the nonconvex economic load dispatch (ELD) problem. In practice, the nonconvex and the discontinuous cost function should be considered when optimizing ELD problem with constraints such as valve point effects, prohibited operating zones, ramp-rate limits, and transmission loss of the system. In view of these constraints, the ELD problem is difficult to solve by any mathematical method. In EPSO, the evolutionary programming concept (combination, tournament competition, sorting, and selection) is employed in the classical PSO method in order to find the best individual and best group position based on the survival particle. The effectiveness of the EPSO is tested on 3-, 6-, 15-, and 38-unit systems. The results obtained by EPSO are also compared with classical PSO and other results reported in the literature. It is concluded that the EPSO method can produce lower generation cost compared to the existing methods. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

An extended probabilistic model building genetic network programming using both of good and bad individuals

Abstract: Classical estimation of distribution algorithms (EDAs) generally use truncation selection to estimate the distribution of the good individuals while ignoring the bad ones However, various researches in evolutionary algorithms (EAs) have reported that the bad individuals may affect and help solving the problem This paper proposes a new method to use the bad individuals by studying the substructures rather than the entire individual structures to solve reinforcement learning (RL) problems, which generally factorize their entire solutions to the sequences of state–action pairs This work was studied in a recent graph-based EDA named probabilistic model building genetic network programming (PMBGNP), which could solve RL problems successfully, to propose an extended PMBGNP The effectiveness of this work is verified in an RL problem, namely robot control Compared to other related work, results show that the proposed method can significantly speed up the evolution efficiency © 2013 Institute of Electrical Engineers of Japan Published by John Wiley & Sons, Inc

An efficient class association rule-pruning method for unified intrusion detection system using genetic algorithm

Abstract: Genetic network programming (GNP)-based class association rule mining has been demonstrated to be efficient for misuse and anomaly detection. However, misuse detection is weak in detecting brand new attacks, while anomaly detection has a defect of high positive false rate. In this paper, a unified detection method is proposed to integrate misuse detection and anomaly detection to overcome their disadvantages. In addition, GNP-based class association rule mining method extracts an overwhelming number of rules which contain much redundant and irrelevant information. Therefore, in this paper, an efficient class association rule-pruning method is proposed based on matching degree and genetic algorithm (GA). In the first stage, a matching degree-based method is applied to preprune the rules in order to improve the efficiency of the GA. In the second stage, the GA is implemented to pick up the effective rules among the rules remaining in the first stage. Simulations on KDDCup99 show the high performance of the proposed method. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Signal injection method without torque ripple based on maximum torque control frame

Abstract: This paper presents a new signal injection method without torque ripple for sensorless controls of salient-pole synchronous motors at low speeds. At low speeds, since the back electromotive force (EMF) including position information decreases, additional signals are injected to estimate position information of saliency. The torque ripple caused by the injections of signal currents can be represented by a cross product of a virtual flux and a differential current vector. An f-axis of maximum torque control frame is defined to the direction of the virtual flux. Therefore, signal injection without torque ripple is realized by using the f-axis current. In this paper, a signal injection method with f-axis current is proposed, and the effects of the estimation error are discussed to apply the method for position-sensor-less controls. The proposed injection method allows us to flexibly design frequencies of the signal current. The validity of the proposed method and applicability to position estimation are confirmed by experimental tests. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Damping of low-frequency oscillations using an SVC-based supplementary controller

Abstract: In this paper, the optimal tunning problem of parameters of a conventional lead–lag controller (LLC) and a fuzzy logic controller (FLC) based on the static Var compensator (SVC) is considered. The solution is obtained using an improved particle swarm optimization (IPSO) algorithm. The membership functions and scaling factors of the FLC and LLC parameters are optimized using the above-mentioned technique. The proposed controllers are settled down to an SVC that is installed at the middle of a transmission line connecting a single machine to an infinite bus system. Simulation results show the superiority of the optimized FLC compared to the optimized LLC and also when the SVC is without the supplementary controller under different disturbances and loading conditions. The simulations and analyses are implemented in MATLAB environment. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Improving transparency of bilateral control system by sliding mode assist disturbance observer

Abstract: Transparency is an important indicator to evaluate the performance of a bilateral control system. Uncompensated disturbances in high frequency degrade the transparency in the traditional disturbance observer (DOB) based bilateral control. This paper analyzes the influence of the uncompensated disturbances, and proposes a sliding mode assist disturbance observer (SMADO) to solve the problem. The sliding mode technique helps the original DOB to estimate the disturbances in high frequency by making use of a rapid switching control value. The required switching gain is small in the proposal, which is good for alleviating the chattering. Moreover, to avoid conservative and arbitrary design of the switching gain, a reasonable benchmark is proposed by employing the estimation error between the original DOB and another parallel DOB with a different cutoff frequency. The validity of the proposal is confirmed by experiments. 2013 Institute of Electrical Engineers of Japan.

Experiments on lightning protection for automatic weather stations using artificially triggered lightning

Abstract: This paper focuses on the voltages electromagnetically induced by the multiple return strokes involved in a triggered lightning on an overhead power line and a vertical signal line of an automatic weather station (AWS), and the backflow currents and residual voltages in a surge protection device (SPD) embedded in the power line. Pulses of voltage on the overhead power line corresponding to the return strokes with the peak currents ranging from −6.67 to −26.47 kA showed bipolar features. Subpeaks and main peaks ranged from 0.99 to 4.47 kV and from −4.98 to −10.31 kV, respectively. The voltage waveforms corresponding to the return strokes on the vertical signal line of wind speed were of two types: with and without a subpeak after the main peak. All the main peaks, with the peak value from −0.41 to −3.10 kV, were ‘V’ shaped. A significant relationship exists between the peak currents of the return strokes and the 10–90% average gradients of the voltages. The peaks of currents through the SPD ranged from −0.22 to −1.64 kA. The durations of residual voltages ranged from 0.6 to 5.9 ms, average value being 2.1 ms. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Comprehensive comparison of FACTS devices for exclusive loadability enhancement

Abstract: A complete comparison of a number of well-known flexible alternating current transmission system (FACTS) devices for static voltage stability enhancement is presented. Various performance measures including power–voltage (P–V) curves, voltage profiles, and power losses are compared under normal and contingency conditions. The importance of proper modeling of FACTS devices, including the DC side, is emphasized because, at their limits, most of these devices behave like a fixed capacitor or inductor. A simple placement technique of series FACTS devices and unified power flow controller (UPFC) is proposed considering exclusive loading margin enhancement. A new idea of loading margin increase per cost is proposed to find the appropriate FACTS devices for investment. The paper provides a guide for utilities to have an appropriate choice of FACTS device for enhancing static voltage stability and loading margin by comparing technical merits and demerits of each of these devices in terms of system performance.

PVDF actuator for high-frequency fatigue test of thin-film metals

Abstract: This paper suggests a poly(vinylidene fluoride) (PVDF) piezoelectric diaphragm actuator used in a novel fatigue test method for thin metal films. A thin-film metal specimen is stamped on top of the actuator using a stamping epoxy. As the actuator vibrates, the stress in the specimen increases until it fails under fatigue. A finite element model of the actuator is built, and its vibration amplitude is confirmed to be in a good agreement with experiment. Then, a model of the specimen is added to this model to simulate the vibration of the specimen for fatigue test. Stress analysis of the specimen at a driving voltage of 200 V0−p confirms that this actuator can increase the stress in the specimen to near 1 GPa, which is high enough for the fatigue test of metals such as titanium. In the experiment, a thin-film titanium specimen is stamped on top of the actuator which is then vibrated. The stress in the fatigue gauge on thin-film specimen increased until the specimen failed under fatigue. This shows that the proposed PVDF actuator is suitable for the fatigue test of thin-film metals such as titanium. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Force-Based Disturbance Observer for Dynamic Force Control and a Position/Force Hybrid Controller

Abstract: In this paper, a force-based disturbance observer (DOB) and a force control system using the DOB are proposed to obtain dynamic force control under disturbances. A DOB can reduce the effect of disturbances and modeling errors on robots. In a conventional DOB, an acceleration response is fed back to a reference, enabling highly precise position control. In other words, the effect of disturbances is decreased by emphasizing the effect of inertial forces. When a force controller is implemented, however, inertial forces are regarded as disturbances respect to a force response. Because inertial forces increase according to the acceleration, conventional DOBs are not suitable for dynamic force control. In the proposed DOB, a force response is fed back instead of an acceleration response. The effect of inertial forces is thus eliminated, thereby improving the tracking performance of force controllers. The proposed method's validity is verified analytically and experimentally. A position/force hybrid controller and a DOB for the controller are proposed as an extension of the proposed DOB. A bilateral controller is given as an example of the proposed hybrid controller, and its tracking performance is demonstrated experimentally. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

An accurate forearm EMG signal classification method using two‐channel electrode

Abstract: An accurate electromyography (EMG) classification algorithm to control a virtual hand prosthesis with 12 degrees of freedom using two surface EMG electrodes is presented in this paper. We propose the application of independent component analysis (ICA) for blind-source separation of the EMG signals obtained from two electrodes. One of the problems affecting the EMG classification accuracy is the location dependence of the EMG signal due to the superposition of signals from multiple sources. ICA is used to separate the two signals obtained from two surface electrodes into two independent EMG signals prior to the feature extraction and classification processes. We demonstrate that the EMG classification accuracy can be improved using the ICA algorithm. We also propose a novel eigen-based feature that is extracted from the short-time Fourier transform (STFT) magnitude spectrum. Our new feature not only decreases feature dimensions but also performs better than other well-known features. We also implement the EMG classification scheme on the virtual robot arm. The performance shows promising result as indicated by a decrease in the Davies–Bolden (DB) index after applying the ICA © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Design of freely configurable safety light curtain using hemispherical mirrors

Abstract: Safety light curtains provide reliable and cost-effective protection against access into hazardous points or areas. However, in practice, peopl still need to adjust the light detection element accurately in order to receive the safe amount of irradiating laser light. In our proposed system, we utilized light emitting diodes (LEDs) as the light source, and designed two hemispherical mirrors to receive the LED light, and used PSoC microcomputer to determine the threshold voltage value. Compared with recent market products, the proposed system is freely configurable, and with no dead zone detection. In addition, compared to the laser light, the LED light has the advantages of no radiation, small electropult, low-cost, and high efficiency. After conducting sufficient experiments, the proposed system has been found to successfully detect the intruder with 100% recognition rate, which can meet the needs of industrialization. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Multi‐SVM classifier system with piecewise interpolation

Abstract: Several researchers have shown that multiple classifier systems can result in effective solutions to difficult real-world classification tasks. However, most of these approaches are easily influenced by noise, and the training datasets for local classifiers get easily imbalanced. One of the main reasons for this is that it is hard to guarantee that the centers of the subsets are close to the separation hyperplane, so that it is difficult to evenly distribute the samples in the two sides of the hyperplane. In order to solve this problem, we redefine the description of classifier modeling problem as a task of piecewise approximation of the separation hyperplane. On the basis of this description, we propose a novel multiple support vector machine (SVM) classifier system. Its main contribution is a novel construction approach to the subtraining datasets. The proposed approach partitions the area close to the separation hyperplane into some subsets to construct the subtraining datasets. The subtraining datasets describe the subtasks for identifying segments of the separation hyperplane. Local SVMs are trained to solve the respective subtasks. Finally, the decisions of these local SVMs are appropriately combined on the basis of a probabilistic interpretation to obtain the final classification decision. The effectiveness of this approach is demonstrated through comparisons with some well-known approaches on both synthetic and real-world datasets. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Fast SVM training using edge detection on very large datasets

Abstract: In a standard support vector machine (SVM), the training process has O(n3) time and O(n2) space complexities, where n is the size of the training dataset. For very large datasets, it is thus computationally infeasible. Reducing the size of training dataset is naturally considered as a method to solve this problem. SVM classifiers are constructed by using the training samples called support vectors (SVs) that lie close to the separation boundary. Thus, removing the other samples that are not relevant to SVs might have no effect on building the separation boundary. In other words, we need to reserve the samples that are likely to be SVs. Therefore, a method based on edge detection techniques is proposed to extract such samples near the separation boundary. In order to avoid overfitting, we also use a clustering algorithm to keep the distribution properties of the training dataset. The samples selected by the edge detector and the centroids of clusters are used to reconstruct the training dataset. In the proposed approach, the edge detection technique helps us to extract the local properties around the separation boundary and the clustering algorithm preserves the properties of the entire data. The reconstructed training dataset with a smaller number of samples can make the training process very fast without degrading the classification accuracy. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Improvement of saturation property of iron powder core by flux homogenizing structure

Abstract: A new core structure is proposed to improve the saturation property of an inductor made of iron powder core. In the conventional structure made of a single core material, converging flux lines cause local magnetic saturation at the inner side of the corners of the magnetic path. Therefore, the conventional inductor shows worse saturation property than expected from its core material. This degradation mechanism is solved in the proposed core structure through homogenization of the flux distribution at the corners. Experiments are performed to evaluate the flux homogenization and improvement of the saturation property. Results show a homogenized flux distribution in the proposed core structure. Furthermore, the flux level improved by 28% while the inductance decreased by 40% of its initial value. Both these results are consistent with theoretical expectations, except that a larger improvement is found in the experiment compared to the 16% improvement predicted by numerical calculation. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Stochastic unit commitment problem considering risk constraints and its improved GA-based solution method

Abstract: This paper proposes a model of the stochastic unit commitment (SUC) problem, which takes account of the uncertainty of electric power demand and its resulting risk, and its solution method based on an improved genetic algorithm (IGA). The uncertainty of electric power demand is modeled using a set of scenarios which are introduced by scenario analysis. The variance, which measures the dispersion of generation costs of unit commitment schedule under each scenario around the expected generation cost, is used as a measure of risk. Based on the expected returns–variance of returns (E–V) rule in the theory of portfolio analysis, a utility function is devised by appending the variance of the expected generation cost into the original expected generation cost function, with consideration of the risk attitude of the generation companies and power exchange centers. The objective of this optimization problem is to minimize the utility function. The proposed IGA is used to solve this NP-hard optimization problem. Based on numerical examples, the superiority of the IGA-based solution method is verified through comparison with a traditional GA-based solution method. Optimal schedules of SUC, as well as the expected costs and variances, are compared with/without risk constraints, and with different risk attitudes. Test results show that, in solving the SUC problem, it is necessary to consider the electric power demand uncertainty and its resulting risk, as well as the risk attitude of the decision maker. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

WLAV state estimation for power system containing multitype FACTS devices

Abstract: This paper presents the state estimation of power system in which not only the bus voltages but also the states of the flexible AC transmission system (FACTS) are considered as the state variables. By using the rectangular form of state variables and equivalent measurement techniques, a linear measurement model with constraints of FACTS device is obtained. The predictor–corrector interior point method based on the weighted least absolute value criterion is developed for solving the optimization problem. Simulation results on the modified IEEE 14-bus and 118-bus test systems are provided. The numerical results indicate the effectiveness of the proposed approach. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Application of Kalman filter to hot‐spot temperature monitoring in oil‐immersed power transformer

Abstract: Winding hot-spot temperature (HST) is an important factor that affects the insulation life of an oil-immersed power transformer. Thus, precise prediction and close monitoring of HSTs are necessary to avoid thermal damage. In this paper, a differential equation for HST prediction is presented, which takes into consideration the effects of the top-oil temperature variations and thermal dynamics of the load. A discrete form of this equation based on the framework of the Kalman filter (KF) algorithm was used to establish a real-time estimation model for the HST. The KF-based model was validated by a sample heat-run test involving a transformer setup in the laboratory. Moreover, the proposed model was applied to a real, large power transformer and compared with the classical IEEE-Annex G method. Results show that the HSTs estimated by the KF-based model are closer to the measured values. The exhibited potential applicability and generality in real-time prediction for HST demonstrate that the proposed model can be employed for online monitoring of HSTs for large power transformers. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

A generalized fault location method based on voltage sags for distribution network

Abstract: An enhanced fault location method based on voltage sag profiles for distribution networks is presented in this paper In other previous methods, only a single measurement has been used The proposed method can be used with any number of measurements in the network, making it more general A new ranking approach that addresses multiple possibilities of the faulted section is proposed Different case studies with various numbers of measurements are performed on a large 11-kV network with the main feeder consisting of 42 buses to validate the method The test results show that there is an improvement in terms of accuracy in detecting the faulted section in the first attempt for each additional measurement Therefore, by utilizing the average value of each measurement, a better accuracy of fault location can be achieved © 2013 Institute of Electrical Engineers of Japan Published by John Wiley & Sons, Inc

Identifying the distribution difference between two populations of fuzzy data based on a nonparametric statistical method

Abstract: Nonparametric statistical tests are a distribution-free method without any assumption that data are drawn from a particular probability distribution. In this paper, to identify the distribution difference between two populations of fuzzy data, we derive a function that can describe continuous fuzzy data. In particular, the Kolmogorov–Smirnov two-sample test is used for distinguishing two populations of fuzzy data. Empirical studies illustrate that the Kolmogorov–Smirnov two-sample test enables us to judge whether two independent samples of continuous fuzzy data are derived from the same population. The results show that the proposed function is successful in distinguishing two populations of continuous fuzzy data and useful in various applications. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

High-efficiency current-doubler rectifier with low output current ripple and high step-down voltage ratio

Abstract: This paper presents a current-doubler rectifier with low output current ripple and high step-down voltage ratio. In the proposed rectifier, two extra inductors are introduced to extend the duty ratio of the switches, which in turn reduces the peak current through the isolation transformer as well as the output current ripple; two extra diodes are used to provide discharge paths for the two extra inductors. To highlight the merits of the proposed rectifier, its performance indexes, such as voltage gain function, secondary winding peak current of the isolation transformer, and output current ripple, are analyzed and compared with the conventional current-doubler rectifier. In this paper, a zero-voltage-switching phase-shift full-bridge converter with the proposed rectifier with an input voltage of 400 V, output voltage of 12 V, and full load power of 500 W has been implemented and verified, and experimental results have shown that 90% conversion efficiency could be achieved at full load. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Water quality analysis in Lake Hachiroko, Japan, using ALOS AVNIR‐2 data

Abstract: In recent years, remote sensing has been used to assessing water pollution distribution. In this study, water quality is analyzed using data collected by the Advanced Visible and Near Infrared Radiometer type-2 (AVNIR-2) of the Advanced Land Observing Satellite (ALOS) at various points in time. We carried out fuzzy regression analysis of the AVNIR-2 data and direct measurements of local water quality. The relationship between the water quality data and the AVNIR-2 data was analyzed by solving both the min and max problems. By comparing the maps of estimated water quality with actual distributions of water quality in the study area, we found that the method used in this study allows effective derivation of water quality conditions from AVNIR-2 data, which provides 10-m spatial resolution. Furthermore, by comparing the maps created using AVNIR-2 data collected at different times, we obtained results suggesting temporal changes in water quality. We also compared the results obtained using data collected by the optical sensor of the Landsat thematic mapper (TM) with 30-m resolution and those obtained using data collected by the active sensor of JERS-1 synthetic aperture radar (SAR), and examined the differences in classification results resulting from differences in resolution and sensors. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

A compact descriptor CHOG3D and its application in human action recognition

Abstract: In this paper, we propose a new method to calculate local features. We extend the FAST corner detector to the spatiotemporal space to extract the shape and motion information of human actions. And a compact peak-kept histogram of oriented spatiotemporal gradients (CHOG3D) is proposed to calculate local features. CHOG3D is calculated in a small support region of a feature point, and it employs the simplest gradient, the first-order gradient, for descriptor calculation. Through parameter training, the proper length of the CHOG3D is determined to be 80 elements, which is 1/12.5 times the dimension of HOG3D in the KTH dataset. In addition, it keeps the peak value of quantized gradient to represent human actions more exactly and distinguish them more correctly. CHOG3D overcomes the disadvantages of the complex calculation and huge length of the descriptor HOG3D. From a comparison of the computation cost, CHOG3D is 7.56 times faster than HOG3D in the KTH dataset. We apply the algorithm for human action recognition with support vector machine. The results show that our method outperforms HOG3D and some other currently used algorithms. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.