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Search Results: 1 - 10 of 113260 matches for " ZHANG Hao "
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The Coupling of Voltage and Frequecncy Response in Splitting Island and Its Effects on Load-shedding Relays  [PDF]
Hao Yang, Baohui Zhang
Energy and Power Engineering (EPE) , 2013, DOI: 10.4236/epe.2013.54B128
Abstract:

The voltage and frequency dynamics interact with each other in the island after splitting. The current frequency response model without considering the voltage effect would bring remarkable errors when analyzing the frequency dynamic progress in the island with large-capacity active-power shortage. In this paper, coupling effects of voltage and frequency are studied to indicate that initial reactive-power deficit and load characteristics have strong effects on the coupling effects of the voltage and frequency. Moreover, control effects of currently used under frequency load-shedding relays (UFLS) and under voltage load-shedding relays (UVLS) which are installed and executed independently are examined to find that it would sometimes cause excessive or inadequate control without considering the coupling, suggesting that it is necessary to develop coordinate control methods for voltage and frequency problems.

Spatial-Spectral Boosting Analysis for Stroke Patients' Motor Imagery EEG in Rehabilitation Training
Hao Zhang,Liqing Zhang
Computer Science , 2013, DOI: 10.3233/978-1-61499-419-0-537
Abstract: Current studies about motor imagery based rehabilitation training systems for stroke subjects lack an appropriate analytic method, which can achieve a considerable classification accuracy, at the same time detects gradual changes of imagery patterns during rehabilitation process and disinters potential mechanisms about motor function recovery. In this study, we propose an adaptive boosting algorithm based on the cortex plasticity and spectral band shifts. This approach models the usually predetermined spatial-spectral configurations in EEG study into variable preconditions, and introduces a new heuristic of stochastic gradient boost for training base learners under these preconditions. We compare our proposed algorithm with commonly used methods on datasets collected from 2 months' clinical experiments. The simulation results demonstrate the effectiveness of the method in detecting the variations of stroke patients' EEG patterns. By chronologically reorganizing the weight parameters of the learned additive model, we verify the spatial compensatory mechanism on impaired cortex and detect the changes of accentuation bands in spectral domain, which may contribute important prior knowledge for rehabilitation practice.
Analysis of the Spectral Resolution of a TeO2 based Noncollinear Acousto-Optic Tunable Filter  [PDF]
Chunguang Zhang, Hao Wang, Yishen Qiu
Engineering (ENG) , 2011, DOI: 10.4236/eng.2011.33027
Abstract: The spectral resolution is a main index of evaluating the performance of the designed acousto-optic tunable filter (AOTF). In this letter, an accurate expression of the spectral resolution is presented by considering both the birefringence and the rotatory property of TeO2 crystal. The deduced expression is significant in improving the accuracy of the design of an AOTF and pushing the development of the high-performance AOTF.
Study of Ni/Al Interface Diffusion by Molecular Dynamics Simulation  [PDF]
Chunguang Zhang, Hao Wang, Yishen Qiu
Engineering (ENG) , 2011, DOI: 10.4236/eng.2011.33026
Abstract: Molecular dynamics simulation of Ni/Al interface diffusion is carried out by Embedded Atom Method (EAM) potential. The problem how the temperature affects Ni/Al interface diffusion is discussed. The initial dynamic behavior of Ni/Al interface diffusion at high temperature is shown. The study in this letter is helpful to understand the origin of diffusion phenomenon.
A Slacks-based Measure of Efficiency of Electric Arc Furnace Activity with Undesirable Outputs  [PDF]
Hao Zhang, Xiang Su, Shilun Ge
Journal of Service Science and Management (JSSM) , 2011, DOI: 10.4236/jssm.2011.42027
Abstract: Efficiency reflects a scenario of higher quality product with fewer resource inputs and less pollution discharge. In terms of a manufacturing firm, it means a win-win strategy in both economic and environmental categories. The paper ex-tends the Electric Arc Furnace (EAF) activity management by taking pollution discharge as undesirable outpust. After reviewing relative undesirable outputs DEA literatures and comparing their advantages and shortcomings, the current paper introduces SBM models to treat undesirable outputs and then measures the efficiency of each EAF activity. Based on resources input and activity quantity output and undesirable outputs, the DEA model can evaluate the efficiency of EAF activity. By the input-output combination, the sensitivity analysis is done. At last, the paper demonstrates the ap-plication of efficiency measurement in EAF activity of an iron&steel enterprise. The result implies objectivity, accuracy and practicability of the activity analysis and valuation method based on SBM-Undesirable model.
A Novel Real-Time Fault Diagnostic System for Steam Turbine Generator Set by Using Strata Hierarchical Artificial Neural Network  [PDF]
Changfeng YAN, Hao ZHANG, Lixiao WU
Energy and Power Engineering (EPE) , 2009, DOI: 10.4236/epe.2009.11002
Abstract: The real-time fault diagnosis system is very great important for steam turbine generator set due to a serious fault results in a reduced amount of electricity supply in power plant. A novel real-time fault diagnosis system is proposed by using strata hierarchical fuzzy CMAC neural network. A framework of the fault diagnosis system is described. Hierarchical fault diagnostic structure is discussed in detail. The model of a novel fault diagnosis system by using fuzzy CMAC are built and analyzed. A case of the diagnosis is simulated. The results show that the real-time fault diagnostic system is of high accuracy, quick convergence, and high noise rejection. It is also found that this model is feasible in real-time fault diagnosis.
Performance Analysis of a Threshold-Based Relay Selection Algorithm in Wireless Networks  [PDF]
Hao Niu, Taiyi Zhang, Li Sun
Communications and Network (CN) , 2010, DOI: 10.4236/cn.2010.22014
Abstract: Relay selection is an effective method to realize the cooperative diversity gain in wireless networks. In this paper, we study a threshold-based single relay selection algorithm. A reasonable threshold value is set at each relay node, and the first relay with the instantaneous channel gain larger than the threshold will be se-lected to cooperate with the source. The exact and closed form expression for its outage probability is de-rived over independent, non-identically distributed (i. n. i. d) Rayleigh channels. The complexity of the algo-rithm is also analyzed in detail. Simulation results are presented to verify our theoretical analysis.
Development of Used Car Market in China  [PDF]
Yali Yang, Hao Chen, Ruoping Zhang
Modern Economy (ME) , 2013, DOI: 10.4236/me.2013.46048
Abstract:

Although still in its early development phase, rapid growth of auto ownership has also injected new vitality for used car market in China. Under the support of series policy, the used car market reveals leaping development character with qualified changes. It is essential to understand the new changes in the used car market. This paper conducted research on the new features of used car market in China to promote its development. Environment analysis showed that used car market will be strongly enhanced by the blooming of auto market, rapid GDP growth and policy support, which experienced steady trade scale increase and structure optimization. The used car trade experienced steady trade scale increase and structure optimization. Along with the purchasing pattern changing, significant expansion of the secondhand car market is imminent, even with hinder issues such as lack of integrity, evaluation criteria and after-service system, and incomplete policy and regulation. Several new features were identified, strong policy support, enlarging market scale and irradiation loop, remarkable concentration increase, increased status of brand used car, and enhanced trading service platform establishment. It is indicated that China’s used car market is making the shift from subordinate position to one of the dominant positions in auto industry, which is expected into a high speed, up-going development passage in the future.

The New Approximate Calculation Method for the First Order Reliability  [PDF]
Gangli Hao, Xuli Liang, Shujian Zhang
Applied Mathematics (AM) , 2013, DOI: 10.4236/am.2013.43075
Abstract: The new method is presented for computing engineering structure reliability by direct searching the next checking point and accelerating convergence based on the analysis of errors in the center point method and borrowing ideas form the merits of the other First-Order Second Moment (FOSM) methods. The idea of the direct searching method is constructing a new explicit searching formula to make the new checking point being more closed to the failure surface based on the results of the center point method. The new checking point has steepest descent character because the searching path is the gradient of the approximate surface. An example shows that the method presented in this article has well precision. Although the direct searching formula may not reach the globally optimal point, the error can be controlled owing to the locally optimal plan at each searching step.
On the Modular Erd?s-Burgess Constant  [PDF]
Jun Hao, Haoli Wang, Lizhen Zhang
Open Journal of Discrete Mathematics (OJDM) , 2019, DOI: 10.4236/ojdm.2019.91003
Abstract: Let n be a positive integer. For any integer a, we say that is idempotent modulo n if a2≡a(mod n). The n-modular Erdös-Burgess constant is the smallest positive integer l such that any l integers contain one or more integers, whose product is idempotent modulo n. We gave a sharp lower bound of the n-modular Erdös-Burgess constant, in particular, we determined the n-modular Erdös-Burgess constant in the case when n was a prime power or a product of pairwise distinct primes.
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