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Interruption Phenomenon in Intermediate-Frequency Vacuum Arc

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Plasma Science and Technology 2016年第3期18卷 311-318页

作者：蒋原武建文 School of Automation Science and Electrical Beihang University

In the condition of the 3 mm gap, experiments for 360 Hz intermediate-frequency vacuum arc are carried out in interrupters with the diameters being 41 mm and with the contact materials being CuCr50 and Cu-W-WC alloy respectively. The results indicate that the contacts material is closely related to the breaking capacity of the vacuum interrupters and characteristics of an intermediate-frequency vacuum arc. For contacts with the same diameter, the breaking capacity of CuCr50 is better than that of Cu-W-WC. When the current fails to be interrupted, the arcs overflow the gap and present irregular performances in the first half wave. Consequently a voltage spike appears. More macroscopic metal droplets can be seen in the arc column between CuCr50 contacts because of the lower melting point. It is observed that the droplet emission is much more severe during arc reignition than that in the first half wave. It is much more conspicuous that the high frequency arc voltage noises appear in Cu-W-WC contacts when the vacuum arcs reignite, for higher temperature and stronger electronic emission ability of Cu-W-WC contacts.

关键词： intermediate-frequency vacuum arc axial magnetic field (AMF) arc voltage,arc reignition droplet emission

ON ALMOST PRECOVERS AND ALMOST PREENVELOPES

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Acta Mathematica Scientia 2006年第3期26卷 395-400页

作者：毛立新丁南庆佟文廷 Department of Basic Courses Nanjing Institute of Technology Nanjing 211167China Department of Mathematics Nanjing University Nanjing 210093China

Let C be a class of R-modules closed under isomorphisms and finite direct sums. It is first shown that the finite direct sum of almost C-precovers is an almost C-precover and the direct sum of an almost C-cover and a ... 详细信息

关键词： Almost precover almost preenvelope

Numerical Simulation of Gas Holdup Distribution in a Standard Rushton Stirred Tank Using Discrete Particle Method

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Chinese Journal of Chemical Engineering 2007年第6期15卷 808-813页

作者：韩路长刘跃进罗和安 College of Chemical Engineering Xiangtan UniversityXiangtan 411105China

The discrete particle method was used to simulate the distribution of gas holdup in a gas-liquid standard Rushton stirred tank. The gas phase was treated as a large number of bubbles and their trajectories were tracked with the results of motion equations. The two-way approach was performed to couple the interphase momentum exchange. The turbulent dispersion of bubbles with a size distribution was modeled using a stochastic tracking model, and the added mass force was involved to account for the effect of bubble acceleration on the surrounding fluid. The predicted gas holdup distribution showed that this method could give reasonable prediction comparable to the reported experimental data when the effect of turbulence was took into account in modification for drag coefficient.

关键词： numerical simulation gas holdup stirred tank discrete particle

Low complexity method for spreading sequence estimation of DSSS signal in non-cooperative communication systems

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Journal of Systems Engineering and Electronics 2009年第1期20卷 41-49页

作者： Chang Liang Wang Fuping Wang Zanji Dept. of Electrical Engineering Tsinghua Univ. Beijing 100084 P. R. China

It is a necessary step to estimate the spreading sequence of direct sequence spread spectrum （DSSS） signal for blind despreading and demodulation in non-cooperative communications. Two innovative and effective detection statistics are proposed to implement the synchronization and spreading sequence estimation procedure. The proposed algorithm also has a low computational complexity with only linear additions and modifications. Theoretical analysis and simulation results show that the algorithm performs quite well in low SNR environment, and is much better than all the existing typical algorithms with a comprehensive consideration both in performance and computational complexity.

关键词： direct sequence spread spectrum detection statistic low complexity.

Adaptive adjustment of iterative learning control gain matrix in harsh noise environment

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Journal of Systems Engineering and Electronics 2013年第1期24卷 128-134页

作者： Bingqiang Li Hui Lin Hualing Xing School of Automation Northwestern Polytechnical University School of Water Resources and Architectural Engineering Northwest A&F University

For the robustness problem of open-loop P-type iterative learning control under the influence of measurement noise which is inevitable in actual systems, an adaptive adjustment algorithm of iterative learning nonlinear gain matrix based on error amplitude is proposed and two nonlinear gain functions are given. Then with the help of Bellman-Gronwall lemma, the robustness proof is derived. At last, an example is simulated and analyzed. The results show that when there exists measurement noise, the proposed learning law adjusts the learning gain matrix on line based on error amplitude, thus can make a compromise between learning convergence rate and convergence accuracy to some extent： the fast convergence rate is achieved with high gain in initial learning stage, the strong robustness and high convergence accuracy are achieved at the same time with small gain in the end learning stage, thus better learning results are obtained.

关键词： iterative learning control open-loop P-type learninglaw nonlinear gain measurement noise robustness.

Analytic Extension of Functions from Analytic Hilbert Spaces

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Chinese Annals of Mathematics,Series B 2007年第3期28卷 321-326页

作者： Kai WANG School of-Mathematical Sciences Fudan University Shanghai 200433 China.

Let M be an invariant subspace of H^2 v,It is shown that for each f∈ M^⊥,f can be analytically extended across эBd/σ（Sz1,…Szd）.

关键词： Analytic Hilbert space Spectrum Analytic extension

Investigation on Centrifugal Impeller in an Axial-radial Combined Compressor with Inlet Distortion

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Journal of Thermal Science 2011年第6期20卷 486-494页

作者： Du Li Ce Yang Ben Zhao Mi Zhou Mingxu Qi Jizhong Zhang School of Mechanical Engineering Beijing Institute of Technology Beijing China Basic Subject Department Bohai Shipbuilding Vocational College Huludao China National Key Laboratory of Diesel Engine Turbocharging Technology Datong China

Assembling an axial rotor and a stator at centrifugal compressor upstream to build an axial-radial combined compressor could achieve high pressure ratio and efficiency by appropriate size *** upstream potential flow and wake effect appear at centrifugal impeller *** this paper,the axial-radial compressor is unsteadily simulated by three-dimensional Reynolds averaged Navier-Stokes equations with uniform and circumferential distorted total pressure inlet condition to investigate upstream effect on radial *** results show that spanwise nonuniform total pressure distribution is generated and radial and circumferential combined distortion is formed at centrifugal rotor *** upstream stator wake deflects to rotor rotation direction and decreases with blade span *** distortion causes different separated flow formations at different pitch *** tip leakage vortex is suppressed in centrifugal blade *** distorted inlet condition,flow direction of centrifugal impeller leading edge upstream varies evidently near hub and shroud but varies slightly at *** addition,compressor stage inlet distortion produces remarkable effect on blade loading of centrifugal blade both along chordwise and pitchwise.

关键词： axial-radial combined compressor centrifugal impeller wake inlet distortion

Simultaneous hybrid modeling of a nosiheptide fermentation process using particle swarm optimization

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Chinese Journal of Chemical Engineering 2016年第11期24卷 1631-1639页

作者： Qiangda Yang Hongbo Gao Weijun Zhang Huimin Li School of Metallurgy Northeastern University Shenyang 110819 China Department of Electromechanical Engineering Liaoning Provincial College of Communications Shenyang 110122 China

Hybrid modeling approaches have recently been investigated as an attractive alternative to model fermentation processes. Normally, these approaches require estimation data to train the empirical model part of a hybrid model. This may result in decreasing the generalization ability of the derived hybrid model. Therefore, a simultaneous hybrid modeling approach is presented in this paper. It transforms the training of the empirical model part into a dynamic system parameter identification problem, and thus allows training the empirical model part with only measured data. An adaptive escaping particle swarm optimization(AEPSO) algorithm with escaping and adaptive inertia weight adjustment strategies is constructed to solve the resulting parameter identification problem, and thereby accomplish the training of the empirical model part. The uniform design method is used to determine the empirical model structure. The proposed simultaneous hybrid modeling approach has been used in a lab-scale nosiheptide batch fermentation process. The results show that it is effective and leads to a more consistent model with better generalization ability when compared to existing ones. The performance of AEPSO is also demonstrated.

关键词： Bioprocess Dynamic modeling Neural networks Optimization

Changes in endogenous hormone levels and redox status during enhanced adventitious rooting by rare earth element neodymium of Dendrobium densiflorum shoot cuttings

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Journal of Rare Earths 2008年第6期26卷 869-874页

作者：罗建平张竞成王瑛 School of Biotechnology and Food Engineering Hefei University of Technology

The effects of neodymium nitrate （Nd^3＋） on the adventitious rooting of Dendrobium densiflorum shoot cuttings were studied. The addition of Nd^3＋（5 μmol/L） to culture medium significantly increased rooting frequency. Histological investigation showed that Nd^3＋ did not change the process of root initiation. Nd^3＋ did not influence total endogenous cytokinin levels, but significantly increased the level of endogenous indole-3-acetic acid （IAA） in the base of shoot cuttings. Compared to the control, the ratio of IAA/cytokinins was very high in the Nd^3＋ treatment. These results suggested that the enhanced rooting frequency may be related to the increase in endogenous IAA level in Nd^3＋ treatment. Analysis of enzyme activities showed that the enhanced accumulation of the endogenous IAA by Nd^3＋ should not be attributed to inhibition of IAA decomposition by IAA oxidase or promotion of cytokinin decomposition by cytokinin oxidase. Besides, Nd^3＋ increased the ratio of reduced glutathione （GSH） and oxidized glutathione （GSSG） in the process of adventitious rooting while the ratio of ascorbate （ASC） to dehydroascorbate （DHA） was not affected.

关键词： Dendrobium densiflorum neodymium nitrate adventitious rooting indole-3-acetic acid cytokinins rare earths