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Power SiC MOSFET Model with Simplified Description of Linear and Saturation Operating Regions
Ruiyun Fu,Enrico Santi,Yucheng Zhang 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
The goal of this work is to develop a physicsbased SiC MOSFET model with a simplified description of linear and saturation operation mechanism in the channel and JFET region. Finite element simulations show that most of the increased voltage drop at saturation occurs at the end of the channel and in the JFET region close to the channel, which is the region where the current spreads out from the channel. A simplified model is proposed to simply describe the mechanism of current saturation of power SiC MOSFET using a nonlinear voltage source at the end of the channel. The model is validated both statically and under resistive and inductive switching conditions for SiC MOSFET.
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Image Encryption Research based on Key Extracted from Iris Feature
RuiYun Xie,MingFei Wang,BenZhai Hai 보안공학연구지원센터 2015 International Journal of Security and Its Applicat Vol.9 No.6
The encryption algorithm has disadvantages like the long key making memory difficult and uneasy safekeeping, which causes a potential threat to the information security. Therefore, a new direction of the encryption method research is to combine the biometric information with the traditional encryption algorithm. The key extracted from the iris and AES encryption algorithm are used in the image encryption algorithm. The db2 wavelet decomposition to the iris region is performed, and the third level high frequency coefficient is extracted as the iris feature codes, from which a 192 bit key is generated by using the stochastic mapping function. The randomness of the key extraction is analyzed. The proposed algorithm is employed to do the encryption test to the image. The encryption effect is compared with the scrambling encryption effect of the classic Arnold method. The experiment results show that security of the encryption image gained by using the proposed algorithm is higher, achieving the purpose of protecting image information.
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The Practice of Remote Sensing in Monitoring Land Use
Jicheng, Zhao,Ruiyun, Zhao 대한원격탐사학회 2001 International Symposium on Remote Sensing Vol.17 No.1
This paper introduces the practice of remote sensing to monitor the land usage. Moreover, 66 cities with a population of 500,000 each in China have successfully applied this technology to review the change in land, especial the cultivated land for construction. In order to find the change information in land usage, two or three scenes of remote sensing images , which were received in different time , are processed and analyzed by comparing with each other. Then, fieldwork is developed to verify the above change information. As a result, this technology has provided valuable technical guarantee for the government to enforce the land management effectively and promptly.
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An Applied Research on Improved Watershed Algorithm in Medical Image Segmentation
BenZhai Hai,RuiYun Xie,PeiYan Yuan 보안공학연구지원센터 2016 International Journal of Signal Processing, Image Vol.9 No.11
The image segmentation technology is of great significance to the target identification. The watershed segmentation algorithm has wide application in image segmentation. The traditional watershed segmentation often causes the problems of over segmentation and noise sensitivity. Therefore, a medical image segmentation algorithm is proposed based on K-means clustering algorithm and improved watershed algorithm. First, K - means clustering algorithm is used for initial segmentation, and then the concept of similarity is put forward to improve the original watershed algorithm. Finally, the adjacent tiles of the initial segmentation is merged. The magnetic resonance image is regarded as the segmentation object. The experimental result shows that the proposed algorithm effectively solves the problem of the over-segmentation of traditional watershed algorithm, and achieves a satisfactory effect for the image segmentation.
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An Iris Localization Algorithm based on Geometric Features of the Circle
Ming Fei Wang,RuiYun Xie,BenZhai Hai 보안공학연구지원센터 2015 International Journal of Signal Processing, Image Vol.8 No.7
An iris localization algorithm with the fast speed is proposed based on geometric features of the circle combing coarse localization with fine localization to avoid the problem of the slow speed of the classical iris localization algorithm. First, the row and column scanning method is employed to find four strings in the pupil. Four couples of tangency points are located by using the perpendicular bisector of strings and the threshold of the pupil boundary. The mean value of the coordinate parameters of the tangency points is regarded as the parameters for inner edge rough localization parameters. Then the calculus method is used for precise localization of the inner edge. The priori knowledge of the close distance between inner and outer edge centers of the circle is used to narrow the search range of the calculus method localizing outside edge, to significantly improving the speed of iris localization. The experimental results show that the proposed algorithm can improve the speed of iris localization with the high localizing accuracy.
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Yucheng Zhang,Roshan Shrestha,Ruiyun Fu 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
In this paper, two beneficial features are enabled in uncontrolled rectifiers by controlling virtual-airgap variable reactor (VAG-VR): 1) fail-safe function - the VAG-VR can automatically isolate the faulty rectifier from power source, to ensure the power quality of other devices connected to the power source and protect the faulty rectifier from large fault current and thus overheating; 2) initial charge limitation - the VAG-VR provides a large reactance initially to suppress high current to a specified level in the uncontrolled rectifier. Then the reactance of VAG-VR decreases to the minimum value gradually, which does not affect the steady-state operation of rectifiers. Compared with other existing approaches of initial charge limitation, the VAG-VR demonstrates controllable reactance rather than resistance. Moreover, the fail-safe function is a novel feature brought into the uncontrolled rectifiers. In the test, the transient voltage sag is reduced from 84 V to 23 V and the inrush current into the faulty rectifier is limited from 125 A to 34 A. These two beneficial features are verified by simulation tests as well as experiments.
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Fault Detection for a Class of Closed-loop Hypersonic Vehicle System via Hypothesis Test Method
Xunhong Lv,Yifan Fang,Zehui Mao,Bin Jiang,Ruiyun Qi 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.1
This paper studies the fault detection problem for a class of hypersonic vehicle with actuator faults,disturbances and random noises. To handle the unknown disturbances, an unknown input Kalman filter (UIKF) ispresented to estimate the unknown system states and disturbances, simultaneously. Considering that the closed-loopstructure brings the robustness to the hypersonic vehicle, which could cover some faults, the Total Measurable FaultInformation Residual (ToMFIR) is employed as the fault detection residual. Moreover, to deal with the randomnoises, the hypothesis testing method is utilized to obtain the thresholds under some fault detection performances(false alarm rate and missing alarm rate). The fault detectability condition is also derived. Finally, the simulationsverify the effectiveness of the proposed fault detection method
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