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Zhe Wei,Li Li,Fang Zhao 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.7
Aero-engine blades often fracture failed due to resonance. In order to analyze the vibration characteristics of high-speed rotating blades of aero-engine more accurately, not only the out-of-plane deformation and in-plane deformation, but also the in-plane deformation caused by out-of-plane deformation are taken into account in the process of research on the rigid-flexible coupling dynamics of blade. The study using the hypothetical modal method to describe the deformation of the blade and using the Lagrangian dynamics equation to establish the first-order approximation coupled dynamics equation of the flexible blade with threedimensional large displacement motion. The simulation results show that the theoretical results of the first approximation coupling model are consistent with the actual results, but the zeroorder approximation coupling model is flawed when the blade speed is high. Based on the firstorder approximation coupling model, the vibration frequency, frequency-steering and modeswitching problems of the blade are analyzed, and the feasibility of the proposed method is verified.
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Binomial Distribution Based Reputation for WSNs: A Comprehensive Survey
( Zhe Wei ),( Shuyan Yu ) 한국인터넷정보학회 2021 KSII Transactions on Internet and Information Syst Vol.15 No.10
Most secure solutions like cryptography are software based and they are designed to mainly deal with the outside attacks for traditional networks, but such soft security is hard to be implemented in wireless sensor networks to counter the inside attacks from internal malicious nodes. To address this issue, reputation has been introduced to tackle the inside malicious nodes. Reputation is essentially a stimulating mechanism for nodes’ cooperation and is employed to detect node misbehaviors and improve the trust-worthiness between individual nodes. Among the reputation models, binomial distribution based reputation has many advantages such as light weight and ease of implementation in resource-constraint sensor nodes, and accordingly researchers have proposed many insightful related methods. However, some of them either directly use the modelling results, apply the models through simple modifications, or only use the required components while ignoring the others as an integral part of the whole model, this topic still lacks a comprehensive and systematical review. Thus the motivation of this study is to provide a thorough survey concerning each detailed functional components of binomial distribution based reputation for wireless sensor networks. In addition, based on the survey results, we also argue some open research problems and suggest the directions that are worth future efforts. We believe that this study is helpful to better understanding the reputation modeling mechanism and its components for wireless sensor networks, and can further attract more related future studies.
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Cross-Correlation Measurements of Phase Noise Induced by Relative Intensity Noise in Photodetectors
Zhewei Cao,Chun Yang,Zhenghua Zhou 한국광학회 2016 Current Optics and Photonics Vol.20 No.6
Up-converted phase noise, which is induced by the low-frequency relative intensity noise (RIN) of alaser through AM-PM conversion within a photodetector (PD), is first measured here by means of across-correlation method. Our proposed measurement system can isolate the RIN-induced phase noise fromnoise contributions of other components, such as amplifiers, modulators, and mixers. In particular, shotnoise and thermal noise generated from the PD are also suppressed by this method, so that standalonecharacteristics of the RIN-induced phase noise can be obtained. Experimental results clearly show thequantitative relationship between the RIN-induced phase noise and the incident optical power of the PD. Our findings indicate that the least RIN-induced phase noise appeared at the saturation point of the PD,which is about -162 dBc/Hz at 10 kHz offset.
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Zhu Dezhao,Cao Zhewei,Li Xianghua,Yang Chun 한국광학회 2014 Current Optics and Photonics Vol.18 No.5
We propose a novel approach to measure the residual phase noise (RPN) of a photodiode (PD) based on a two-tone correlation method. Compared with the previous measurements of the RPNs of PDs, this method is more convenient in practical application. In this method, two microwave sources and other components were placed in two isolated links sharing the same PD, so the noises of them were uncorrelated. With an FFT analyzer, the uncorrelated noises could be mostly suppressed while only the RPN of the PD was preserved. Voltage-dependent nonlinearities of PDs were studied previously. In this letter, we investigate the relationship between the RPN of the PD and the bias voltage on the PD. By changing the bias voltage, the difference of the RPN can be up to 10 dB.
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An Empirical Study of Qualities of Association Rules from a Statistical View Point
Dorn, Maryann,Hou, Wen-Chi,Che, Dunren,Jiang, Zhewei Korea Information Processing Society 2008 Journal of information processing systems Vol.4 No.1
Minimum support and confidence have been used as criteria for generating association rules in all association rule mining algorithms. These criteria have their natural appeals, such as simplicity; few researchers have suspected the quality of generated rules. In this paper, we examine the rules from a more rigorous point of view by conducting statistical tests. Specifically, we use contingency tables and chi-square test to analyze the data. Experimental results show that one third of the association rules derived based on the support and confidence criteria are not significant, that is, the antecedent and consequent of the rules are not correlated. It indicates that minimum support and minimum confidence do not provide adequate discovery of meaningful associations. The chi-square test can be considered as an enhancement or an alternative solution.
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