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Microstructure and properties of in situ synthesized TiB_2+WC reinforced composite coatings

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Rare Metals 2008年第5期27卷 451-456页

作者： li jun zhang Huiying li Wenge zhang Guangjun School of Materials Engineering Shanghai University of Engineering Science Shanghai 201620 China

Nickel-based composite coatings reinforced by in situ synthesized TiB2 and WC particles were deposited on stainless steel by laser cladding, and their microstmcture and mechanical properties were investigated. The results show that the coatings are mainly composed of 7-Ni cellular dendrites and dispersed spherical/strip/network shaped TiB2 and equiaxial WC particles. The initial WC particles are dissolved to become fine and mostly dispersed within Y-Ni cellular dendrites. The coating prepared at a special laser energy of 0.225 kJ@mm^-2 is uniform, continuous, and free of pores and cracks. With the decrease in special energy density, TiB2 phase changes from fine spherical particles which cluster together to strip shape with different morphologies and further crystallizes to form network structure, and the dispersion zone also gradually changes from intragranular to intergranular phase. The coating possesses a higher microhardness compared with the substrate, and it has a good metallurgical bond with the substrate and excellent cracking resistance.

关键词： laser cladding in situ synthesis composite coating microstructure

Research on optimizing the noise figure of low noise amplifier method via bias and frequency

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The Journal of China Universities of Posts and Telecommunications 2011年第4期18卷 118-122页

作者： zhang li-jun li li-nan The School of Urban Rail Transportation Soochow University Suzhou 215021 China School of Electronic and Information Engineering Beijing Jiaotong University Beijing 100044 China

In this paper, we present the design of an integrated low noise amplifier （LNA） for wireless local area network （WLAN） applications in the 5.15-5.825 GHz range using a SiGe BiCMOS technology. A novel method that can determine both the optimum bias point and the frequency point for achieving the minimum noise figure is put forward. The method can be used to determine the optimum impedance over a relevant wider operating frequency range. The results show that this kind of optimizing method is more suitable for the WLAN circuits design. The LNA gain is optimized and the noise figure （NF） is reduced. This method can also achieve the noise match and power match simultaneously. This proposal is applied on designing a LNA for IEEE 802.1 la WLAN. The LNA exhibits a power gain large than 16 dB from 5.15 to 5.825 GHz range. The noise figure is lower than 2 dB. The OIP3 is -8 dBm. Also the LNA is matched to 50 Ω input impedance with 6 mA DC current for differential design.

关键词： LNA SiGe BiCMOS noise figure WLAN

Adaptive Iterative Learning Control for Nonlinear Time-delay Systems with Periodic Disturbances Using FSE-neural Network

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International Journal of Automation and computing 2011年第4期8卷 403-410页

作者： Chun-li zhang jun-Min li Department of Applied Mathematics Xidian University Xi＇an 710071 PRC

An adaptive iterative learning control scheme is presented for a class of strict-feedback nonlinear time-delay systems, with unknown nonlinearly parameterised and time-varying disturbed functions of known periods. Radial basis function neural network and Fourier series expansion （FSE） are combined into a new function approximator to model each suitable disturbed function in systems. The requirement of the traditional iterative learning control algorithm on the nonlinear functions （such as global lipschitz condition） is relaxed. Furthermore, by using appropriate Lyapunov-Krasovskii functionals, all signs in the closed loop system are guaranteed to be semiglobally uniformly ultimately bounded, and the output of the system is proved to converge to the desired trajectory. A simulation example is provided to illustrate the effectiveness of the control scheme.

关键词： Adaptive control iterative learning control (ILC) time-delay systems Fourier series expansion-neural network periodic disturbances.

A time-dependent numerical model of the mild-slope equation

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Acta Oceanologica Sinica 2007年第2期26卷 106-114页

作者： SONG Zhiyao zhang Honggui KONG jun li Ruijie zhang Wei State Key Laboratory of Hydrology - Water Resources and Hydraulic Engineering Ocean College Hohai University Nanjing 210098 China

On the basis of the previous studies, the simplest hyperbolic mild-slope equation has been gained and the linear time - dependent numerical model for the water wave propagation has been established combined with different boundary conditions. Through computing the effective surface displacement and transforming into the real transient wave motion, related wave factors will be calculated. Compared with lin＇s model, analysis shows that calculation stability of the present model is enhanced efficiently, because the truncation errors of this model are only contributed by the dissipation terms, but those of lin＇s model are induced by the convection terms, dissipation terms and source terms. The tests show that the present model succeeds the merit in lin＇ s model and the computational program is simpler, the computational time is shorter, and the computational stability is enhanced efficiently. The present model has the capability of simulating transient wave motion by correctly predicting at the speed of wave propagation, which is important for the real - time forecast of the arrival time of surface waves generated in the deep sea. The model is validated against analytical solution for wave diffraction and experimental data for combined wave refraction and diffraction over a submerged elliptic shoal on a slope. Good agreements are obtained. The model can be applied to the theory research an d engineering applications about the wave propagation in a biggish area.

关键词： effective wave number effective surface displacement function numerical error stability analysis

Performance Analysis of Anti-Interference UWB-OFDM System

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The Journal of China Universities of Posts and Telecommunications 2006年第2期13卷 6-9,38页

作者： zhang Shi-bing CAO Shi-ke zhang li-jun Communication and Information Engineering Institute Nanjing University of Posts and Telecommunications Nanjing 210003 P.R. China School of Electronics and Information Nantong University Nantong 226007 P.R. China

This paper examines the robustness of anti-interference Ultra-Wide-Band UWB-OFDM （AI-UWB） systems in presence of narrow-band interference. It analyzes the bit error rate performance of the systems in both the single-user and multi-user modes, and compares its robustness in different code matrixes. By encoding transmitted symbols and spreading their power over all sub-bands, AI-UWB systems can make full use of the frequency diversity across the sub-bands and have more robustness to the narrowband interference. Simulating results show that different codes have almost the same robustness to the narrowband interference. The encoding and spreading could suppress the narrowband interference effectively. Compared with the IS-UWB systems, our approach has more than 5 dB interference margin.

关键词： UWB anti-interference bit error rate coding spreading

Efficient channel blind estimator for multiuser system with conjugate cyclostationarity

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The Journal of China Universities of Posts and Telecommunications 2008年第4期15卷 1-6页

作者： ZHOU Ke CAO Shi-ke zhang li-jun Communication and Information Engineering College Nanjing University of Posts and Telecommunications Nanjing 210003 China

The problem of blind channel identification in a multiuser system is considered in this article. For this purpose, a blind identification algorithm is proposed based on the conjugate cyclostationarity of the received signal. The new approach contains a two-stage identification procedure. First, the separation technique in the cyclic domain is used to separate the second-order cyclic statistics for each user. Second, a subspace algorithm based on the rational subspace theory is exploited to estimate the desired channel. Theoretical analysis and simulation results show that this algorithm is suitable for a multiuser system. Compared with other methods, the algorithm shows good performance even in a bad situation when the number of users is large and the diversity condition is unavailable.

关键词： conjugate cyclostationarity rational subspace theory subspace algorithm

High performance liquid chromatography with immobilized Ru(bpy)_3^(2+)-KMnO_4 chemiluminescence detection and its application in metabolism of repaglinide in pig liver microsomes

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Chinese Chemical Letters 2011年第10期22卷 1245-1248页

作者： Ai Hua Fu Zhu jun zhang li li Chen Xiao Ming zhang Pan Xue Key Laboratory of Analytical Chemistry for life Science of Shaanxi Province School of Chemistry and Materials Science Shaanxi Normal University Xi＇ an 710062 China

A novel high performance liquid chromatography-chemiluminescence（HPLC-CL） method for investigation of in vitro metabolism of repaglinide in pig liver microsomes with microdialysis sampling technique was *** chromatographic separation was performed on a Hypersil BDS-C18 column with an isocratic mobile phase consisting of methanol and 0.01 mol/L KH_2PO_4（pH 3.0）（volume ratio 75：25） at a flow rate of 1.0 mL/*** detection was based on the chemiluminescence reaction of repaglinide with acidic potassium permanganate（KMnO_4） and tris（2,2＇-bipyridyl）ruthenium（Ⅲ）（Ru（bpy）_3^（3＋））,which was immobilized on the cationic ion-exchange resin for obtaining high sensitivity and reducing consumption of expensive reagent.

关键词： High performance liquid chromatography Chemiluminescence Microdialysis Repaglinide Immobilized Ru(bpy)_3^(2+)

The Substitution Secant/Finite Difference Method for Large Scale Sparse Unconstrained Optimization

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Acta Mathematicae Applicatae Sinica 2005年第4期21卷 581-596页

作者： Hong-wei zhang jun-xiang li Department of Applied Mathematics Dalian University of Technology Dalian 116024 China

This paper studies a substitution secant/finite difference （SSFD） method for solving large scale sparse unconstrained optimization problems. This method is a combination of a secant method and a finite difference method, which depends on a consistent partition of the columns of the lower triangular part of the Hessian matrix. A q-superlinear convergence result and an r-convergence rate estimate show that this method has good local convergence properties. The numerical results show that this method may be competitive with some currently used algorithms.

关键词： Unconstrained optimization substitution Hessian sparsity secant method

Synthesis of 2H-3,1-pyrazolo[3,4-e]oxazines via a new conversion of Friedlander reaction

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Chinese Chemical Letters 2007年第6期18卷 636-638页

作者： li, Jia Rong zhang, li jun Chen, Jin Nan Yang, Xi Quan Wang, li jun Zhao, Xiao Fan Qiu, jun Xia Beijing Inst Technol Sch Chem Engn & Environm Beijing 100081 Peoples R China

2H-3,l-Pyrazolo[3,4-e]oxazines (5a-c) and tacrine analogies (6a-c) were designed and prepared using 5-amino-4-cyanopyrazole (7) and cycloketones (2a-c) as reactants. The study demonstrated that the new conversion existed in the Friedlander reaction of o-aminocyanopyrazole with cycloketones. (C) 2007 Jia Rong li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

关键词： pyrazole oxazines tacrine cyclocondensation synthesis