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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.

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

Pyrite morphology and episodic euxinia of the Ediacaran Doushantuo Formation in South China

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Science China Earth Sciences 2017年第1期60卷 102-113页

作者： YE YunTao WU ChaoDong ZHAI LiNa AN ZhengZe Key Laboratory of Orogenic Belts and Crustal Evolution Ministry of Education School of Earth and Space Sciences Peking University Beijing 100871 China Institute of Oil & Gas Peking University Beijing 100871 China No. 103 Geological Team Guizhou Bureau of Geology and Mineral Exploration and Development Tongren 554300 China

The Ediacaran Doushantuo Formation with well-preserved fossil record in South China provides a rare window for our understanding of biological evolution,global carbon cycle,and oceanic redox *** negativeδ^(13)C anomalies(i.e.,the Shuram excursion)in Ediacaran successions worldwide fundamentally challenge the traditional models of isotopic mass ***,conflicting opinions of both oxic and anoxic conditions have been proposed for the deep waters during this ***,we present a detailed study of pyrite morphology and carbonate carbon isotope data documented from drill core samples at Songtao County,northeastern *** aggregates are the dominant pyrite form in black shale and they can transfer to euhedral crystals through continuous growth of the constituent microcrystals.A positive correlation between microcrystal sizes(d)and framboid diameters(D)is observed,while the different D/d ratios of framboids in argillaceous dolostone and black shale reflect different substrate *** microprobe analyses reveal no consistent compositional patterns between framboidal and euhedral *** size distributions of the investigated drill core,in combination with previously published redox data from the intra-shelf Jiulongwan section,shelf margin Zhongling section,and lower slope Wuhe section,suggest that three episodes of marine euxinia have been established throughout the deposition of the Doushantuo *** time lag between the uppermost euxinic interval and the Shuram excursion may arise from the depression of sulfate reduction maintained by other oxidants.

关键词： Ediacaran Doushantuo Formation Framboidal pyrite Carbon isotope Ocean anoxia Yangtze Platform

Instability of cylinder wake under open-loop active control

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Applied Mathematics and Mechanics(English Edition) 2017年第3期38卷 439-452页

作者： Yadong HUANG Benmou ZHOU Zhaolie TANG Science and Technology on Transient Physics Laboratory Nanjing University of Science and Technology Nanjing 210094 China

Instability of a wake controlled by a streamwise Lorentz force is investigated through a Floquet stability analysis. The streamwise Lorentz force, which is a two-dimensional control input created by an electromagnetic actuator located on the cylinder surface,adjusts the base flow to affect the three-dimensional wake instability and achieve wake stabilization and transition delay. The instability mode at a Reynolds number Re = 300 can be transformed from B to A with N = 1.0, where N is an interaction number representing the strength of the Lorentz force relative to the inertial force in the fluid. The wake flow is Floquet stable when N increases to 1.3. The spanwise perturbation wavelengths are 3.926 D and 0.822 D in the modes A and B, respectively, where D is the cylinder diameter. In addition, the oscillating amplitudes of drag and lift are reduced with the increase in the interaction number. Particle tracing is used to explore the essential physical mechanism for mode transformation. The path lines show that suppression of flow separation hinders the fluid deformation and rotation, leading to the decrease in elliptic and hyperbolic instability regions, which is the material cause of mode *** of the results indicate that wake stabilization and transition delay can be achieved under open-loop active control via the streamwise Lorentz force.

关键词： flow instability global stability analysis open-loop active control streamwise Lorentz force wake stabilization transition delay

Impact of Wake on Downstream Adjacent Rotor in Low-speed Axial Compressor

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Journal of Thermal Science 2004年第2期13卷 114-120页

作者： Xinqian Zheng Sheng Zhou Beijing Univ Aeronaut & Astronaut Sch Jet Prop Beijing 100083 Peoples R China

This paper investigates the effect of upstream wake on unsteady separated flow field of downstream adjacent vanes by solving 2D unsteady Reynolds-averaged Navier-Stokes equations discretized by a high-order scheme. The results indicated that the maximum relative reduction of loss coefficient was 27.2% when the relative passing frequency (the ratio of wake passing frequency to the characteristic frequency of trailing-vortex shedding of downstream adjacent rotor) is less than 2.5. The amplitude of wake defect exists a threshold value and the aerodynamic performance is enhanced monotonically with the amplitude of wake defect basically. The effective range of incidence must be greater than 8°, which is near the stall boundary.

关键词： unsteady flow separated flow rotor/stator interaction axial flow compressor.

Synthesis of vinylferrocene and the ligand-exchange reaction between its copolymer and carbon nanotubes

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Frontiers of Chemical Science and Engineering 2014年第2期8卷 171-178页

作者： Ran SHI Hai WANG Ping TANG Yuezhen BIN Department of Polymer Materials and Engineering Dalian University of Technology Dalian 116024 China Department of Future Industry-Oriented Basic Science and Materials Toyota Technological Institute Tempaku Nagoya 468-8511 Japan

To improve the dispersibility of carbon nanotubes （CNTs）, poly（vinylferrocene-co-styrene）（poly （Vf-co-St））, was grafted onto the surface of CNTs by a ligand-exchange reaction. Poly（Vf-co-St） was obtained by a radical copolymerization reaction using styrene and vinylferrocene as the monomers. The vinylferrocene was synthesized from ferrocene via a Friedel-Crafts acylation. The molecular weight, molecular weight distribution, and amount of Vf in the poly（Vf-co-St） were 1.32 × 104, 1.69 and 17.6% respectively. The degree of grafting of the copolymer onto the CNTs surface was calculated from thermogravimetric analysis and varied from 27.1% to 79.7%. The addition of the poly（Vf-co-St） greatly promoted the dispersibility of the modified CNTs in anhydrous alcohol. The electrical conductivity of compo- sites prepared from the polymer-grafted CNTs and copolymer （acrylonitrile, 1,3-butadiene and styrene, ABS） strongly depended on the degree of grafting. These results show that the amount of polymer grafted onto the surface of CNTs can be controlled and that the electrical properties of composites prepared with these grafted polymers can be tuned.

关键词： vinylferrocene poly (Vf-co-St) CNTs dis-persibility