Table of Content

30 June 2008, Volume 14 Issue 3

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Articles

Wideband Ceramics Cylindrical Dielectric Resonator Antennas

ZHANG Li-na;ZHONG Shun-shi;XU Sai-qing;ZHU Yu-xiao

2008, 14(3):  221-224 . 

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A wideband cylindrical dielectric resonator antenna with high dielectric constant is proposed, analyzed and designed. The ceramics cylindrical dielectric resonator antenna with an air gap excited by an H-shaped slot is adopted to overcome the narrow bandwidth under the condition of high dielectric constant. An impedance bandwidth of 12.6% has been achieved with a smaller size of the dielectric resonator and better radiation performance.


Improved Frequency Offset Estimation for OFDM with High Performance

ZHOU Sheng;CHEN Hui-min;JIN Yan-liang

2008, 14(3):  225-229 . 

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An improved frequency offset estimation method used in high speed wireless environment is proposed. A training sequence frame is made of Zadoff-Chu sequences with four times repetition. First, the received signal is correlated with local training sequences to eliminate the influence of training sequence. Fine frequency synchronization is achieved by taking two times of frequency offset estimation. The proposed method has good estimation accuracy and large estimation span. All processes of the frequency offset estimation are taken before FFT, leading to a saving of the system synchronization time and reduction of the system complexity. Simulations in AWGN and Rayleigh channels verify validity of the technique.

Speech Enhancement Based on Wavelet Thresholding Multi-taper Estimators

JIAO Ren-jie;HOU Li-min

2008, 14(3):  230-235 . 

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An effective method to smooth prior SNR is proposed. Based on the definition of prior SNR, this method smoothes prior SNR by using wavelet thresholding multi-taper estimators to reduce variance of speech and noise power spectrum.The method for smoothing prior SNR can avoid delay in the estimated prior SNR when energy level at the beginning of speech is high by using the decisiondirected method. It can also enhance estimation accuracy of prior SNR. Speech enhancement combined with this method can effectively suppress “music noise”, especially at low input SNR

Design of Band-Pass Filter with Novel OpenLoop Resonators

JIANG Xin-hua;LI Guo-hui

2008, 14(3):  236-238 . 

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In this paper, several square open-loop resonators with transmission lines are proposed to design optimized bandpass filters. In comparison with conventional open-loop resonator bandpass filters, the proposed filter can achieve size reduction. A compact microstrip filter using one of these open-loop resonators is fabricated and measured. Simulation and measurement on the fabricated filter show highfrequency selectivity and good stop-band characteristic with small dimensions. Compared with conventional filters using coupled square openloop resonators, the proposed filter has a size reduction of 30%.


Design and Implementation of a Remote Control System

HE Xiao;ZHANG Xue-fan;LI Hui-min;OU Chi-yun

2008, 14(3):  239-243 . 

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A general description of a remote control system based on serial communication equipment is given. It uses centralized control and nagement based on effective protocol of MCUs and PC,I²C and windows networks programming. Tests show that the system is robust, expandable, flexible and reliable. The design of software and hardware, and test results are given.


Semi Cover-Avoiding Property and Structure of Finite Groups

GUO Xiu-yun;CUI Ya-qiong

2008, 14(3):  244-247 . 

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In this paper, several sufficient conditions for a finite group to be supersolvable are given by means of maximal subgroups of Sylow subgroups having either semi cover-avoiding property or seminormal property, and several known results are generalized.

Matrix Form of the van der Waerden Number Problem on Circle

ZHANG Yan-fei;CHEN Fang;HUANG Yi-ru

2008, 14(3):  248-252 . 

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In this paper we seek a good way to improve the up-bound of the van der Waerden number. We translate the problem of van der Waerden number on circle into a linear system of inequalities in a matrix form. We study the matrix form to find a good up-bound of the van der Waerden number on circle, and find two particular results. When p=nr±1, we obtain an expression of x and b_k.

Perfect Codes with Respect to Lee Metric

JIN Qing-fang;YANG Jian-sheng;WANG De-xiu

2008, 14(3):  253-255 . 

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This paper obtain a necessary condition for the existence of Lee weight perfect codes over Z_q , q∈Z,q≥4 and show that the Lee weight perfect codes do not exist over Z₄. This paper also show that perfect codes do not exist over Z_4k with respect to a new distance, which is related to Lee metric.


Wronskian Solutions of the KP Equation via a Modified Bilinear Bäcklund Transformation


XUAN Qi-fei;ZHANG Da-jun

2008, 14(3):  256-259 . 

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In this paper Wronskian solutions of the KP equation are discussed via a modified bilinear Bäcklund transformation. The conditions that the Wronskian entries satisfy are obtained and the Wronskian verification is achieved by means of the Wronskian technique. Finally, some explicit Wronskian entries are given.

Isotropic Constant of B_pⁿ and Its Asymptotic Properties

XUE Lian;CHEN Qiao-yun;HE Bin-wu

2008, 14(3):  260-264 . 

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Let B_pⁿ={x∈Rⁿ | ‖x‖_p≤1} be a unit ball of n-dimension normed space l_pⁿ. It is shown that B_pⁿ is isotropic convex body if 1≤p≤∞, and the isotropic constant formula of B_pⁿ is given.Moreover, asymptotic properties of isotropic constant of B_pⁿ is obtained as n→∞ and p→∞

Stochastic Level-Value Approximation for Global Optimization


YANG Yi;PENG Zheng;YAN Kan;WU Dong-hua

2008, 14(3):  265-270 . 

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We propose a stochastic level-value approximating method (SLVAM) for
global optimization problem that is defined in an entire box. We discuss and establish a sufficient condition for the global optimality in probability measure
, and prove that the SLVAM algorithm is convergent in probability. Numerical results show its effectiveness.

Numerical Inversion of Abel Transform

ZHAO Zhen-yu;HE Guo-qiang;LIU Wei

2008, 14(3):  271-275 . 

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This paper discusses a problem of numerical inversion of Abel transform. A new method for numerical differentiation is introduced. A reasonable method to deal with singular integral is given. The theoretical results and numerical examples show that the proposed method is effective.

Refined Sensitive Driving Traffic Flow Model with Slow-to-Start During Dcceleration

HUANG Xue-feng;DONG Li-yun

2008, 14(3):  276-280 . 

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In order to get better description of real traffic, an improved cellular automaton (CA) model is proposed on the basis of a sensitive driving CA model. The slow-to-start effect is introduced during the acceleration process, which is dependent on acceleration probability. It is found that the maximum flow decreases with decreasing acceleration probability. Furthermore, a refined sensitivedriving model is proposed. The corresponding simulation indicates that, with the density lower than 0.24, the flow is independent of acceleration probability, while with the density higher than 0.24, the flow reduces with decreasing acceleration probability for the same density. Phase separation between free phase and congested phase is clearly worked out in a temporalspatial pattern. Moreover,the meta-stability phenomena are reproduced under different initial conditions.Finally, the simulated fundamental diagram shows a pretty good agreement with that based on experimental data.
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Numerical Simulation of Trajectories and Diffusion of Fluid Particles and Brownian Particles in a Rayleigh-Bénard Convection Flow


DONG Hai-ming;LU Zhi-ming

2008, 14(3):  281-285 . 

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The trajectories of fluid particles and Brownian particles in a twodimensional
periodic RayleighBénard convection are investigated by assuming a streamfunc
tion with freestress boundary conditions. It is shown that fluid particles ori
ginally located in the central of the cell move periodically, whereas those orig
inally located at the edge of the cell move in a chaotic way. The length of cent
ral region of the cell decreases with the increasing oscillation amplitude and S
trouhal number. The movement of Brownian particles can be either periodic or cha
otic from whichever region the particles originate. The diffusion for both fluid
particles and Brownian particles is standard diffusion at large time of particl
es being released.


Thermodynamics Research of Martensitic Phase Transition in Ni-Mn-Ga Heusler Alloys


LI Zhe;JING Chao;CHEN Ji-ping;LU Yu-ming;CAO Shi-xun;ZHANG Jin-cang

2008, 14(3):  286-289 . 

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The martensitic transition temperature and thermal hysteresis temperature in Ni_51.5Mn₂₄Ga_24.5singlecrystalline and Ni_47.5Mn_27.5Ga₂₅ polycrystal were investigated by means of AC magnetic susceptibility. According to the boundary frication phenomenological theory, the energy was calculated consumed for phase boundary motion in these free samples during martensitic transformation. It has been found that the energy consumed for phase boundary motion is 19.96 J/mol and 34.93 J/mol, respectively, which is only a small part of the latent heat of martensitic transformation. Furthermore, omparative thermodynamic parameter indicated that thermal hyseresis of martensitic transformation originates from the friction of phase boundary motion, which in turn accounts for the thermal hysteresis during transformation in Ni-Mn-Ga alloys quite well.

Synthesis of Ultrafine HMS Mesoporous Molecular Sieve (Ⅰ)—Effect of Synthesis Conditions

LI Hao;LIU Hong;HE Shi-qiang

2008, 14(3):  290-294 . 

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HMS mesoporous molecular sieve was synthesized using dodecylamine (DDA) as a template and tetethylorthosilicalite (TEOS) as a silicon source. The effects of synthesis parameters such as pH, synthesis temperature and time, DDA/SiO₂, H₂O/SiO₂and EtOH/SiO₂molar ratio on the structure and particle size of HMS were investigated systematically. It is shown that the synthesis parameters have great influence on the structure and particle size of HMS. The ultrafine HMS mesoporous molecular sieve of 100～300 nm can be obtained under the condition of pH=7, DDA/SiO₂=0.27, H₂O/SiO₂=66.7, EtOH/SiO₂=6.5, reaction temperature 20 °C, and reaction time 18 h.

QoS of Content Service Platform in Ubiquitous Computing


YUAN Jie;WANG Ming-hui;BI De-chuang

2008, 14(3):  295-298 . 

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Building a contents service platform (CSP) is an effective approach to improve t
he quality of service (QoS) in the ubiquitous computing environment. CSP built following the symmetrical and active service model can provide personalized initiative services, and upgrade QoS on the user level. However QoS is damaged indirectly due to the cost for execution of the service capability, especially the aggravation of the server performance bottleneck resulted from rapidly increasing users attracted by the capability. Dynamic server cluster is proposed to solve the problem, implementing QoS assurance on the end-system level. For the dynamic server cluster, simulation is carried out, with its performance evaluated, selection of parameters analyzed, and a prototype implemented.

Experimental Study on Desulfurization Performance of Hot Gas at Medium and High Temperature


BAO Guo-hang;GUO Shu-qiang;-ZHANG Yi-fan;DING Wei-zhong

2008, 14(3):  299-305 . 

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Desulfurization at medium and high temperature is a key technique for improving utilization factor of cleaning coal. Mnbased sorbent used for hot gas was investigated in this experimental study. The performance of Mn-based sorbent was studied from sintering temperature, sulfidation temperature, sulfidation gas and initial H₂S concentration in the fixed-bed reactor. The experimental results show that H₂S could be removed to 2×10^-6 by the sorbents sintered at 1 100 ℃,also showing good mechanical strength. Desulfurization of the sorbent performed at 700 ℃ was shown to have the best performance, and sulfur capacity was 31.8%. H₂S concentration in the outlet gas from reactor increased with the presence of CO₂ that increased the oxygen potential. The concentration of H2S in the outlet increased from 2×10^-6 to 20×10^-6 when CO² content increased from 0% to 4.53%. The desulfurization precision did not vary with the increase of initial H₂S concentration, while the duration of the breakthrough period was cut shorter.

Nonlinear Finite Element Analysis of Temperature Field of Reinforced Concrete Members


ZHANG Zhi-mei;YE Zhi-ming;LIU Tao;

2008, 14(3):  306-312 . 

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In fires, determination of the temperature field of reinforced concret
e members is not only a basis for analyzing mechanical properties of the members at high temperature, but also a basis of constituting rehabilitation schemes of the structures after fires. In this paper, a set of finite element equations for temperature field analysis of reinforced concrete members are established by using methods of Galerkin weighted residual and backward difference. In the analysis, the temperaturedependent thermal properties of concrete are considered, and the iterative process of heat flow equilibrium is used for improving precision of the temperature field solution. Based on the theoretical research, a computer program TFARC (Temperature Field Analysis of RC) is developed with Matlab. The program can be used to analyze steady state thermal problems, linear transient thermal problems and nonlinear transient thermal problems. Comparison between numerical results with test data and the exact solutions shows that the program developed for temperature field analysis of reinforced concrete members is reliable.

Nonlinear Dynamic Stiffness for Lateral Vibration of Floating Pile


ZHANG Yu-zhu;YANG Xiao;LIU Xin

2008, 14(3):  313-318 . 

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Dynamic stiffness for lateral vibration of a viscoelastic floating pile in a nonlinear viscoelastic soil layer is investigated. We make the soil portion below the floating pile end equivalent to a virtual soil-pile and divide the whole soil layer into a nonlinear viscoelastic inner zone and a linear viscoelastic outer zone. This way, a semi-analytical solution for dynamic behavior in the frequency domain of the composed pile is obtained using the equivalent linearization method and variable separation method. Expressions of dynamic stiffness on top of the floating pile are given. Dynamic stiffness of the pile are then analyzed numerically for different vibration frequencies. Effects of the physical and geometrical parameters are examined. It is revealed that the dynamic lateral stiffness of the floating pile depends heavily on the amplitude of the vibration, nonlinear soil property, pile length, etc. Generally, stiffnesses of the pile are significantly decreased due to soil nonlinearity. Furthermore, the increment of stiffness cannot be achieved only by increasing length of the floating pile. There exists an optimization pile length. The results obtained are useful in pile design.

Mutual Affection Analysis for Variable Stiffness Tall Structures


JIA Yuan;ZHU Jie-jiang

2008, 14(3):  319-322 . 

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To analyze tall structures with aseismic optimal, we present a mutual affection analysis of tall structures with variable stiffness. Using the equivalent column model, the whole structure is divided into levels. There are only two degrees of freedom. So analysis of tall structures is simplified. Using this method, the freedoms of degrees of the whole structure are greatly reduced. The method can be applies to analysis of tall structures with variable stiffness. The
method is simple and reasonable.

Expression of Sc1754CP and Preparation of Anti-Sc1754CP Antibody


LI Rong;SONG Ren-tao;XU Zheng-kai;LI Ping

2008, 14(3):  323-327 . 

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The recombinant coat protein of TMVSc1754 can induce hypersensitive reaction in susceptible tobacco. However this protein hardly is accumulated in the inoculated plants. In order to clarify the role of Sc1754CP in this hypersensitive reaction, we overexpressed Sc1754CP in E.coli. Polyclonal AntiSc1754CP rabbit polyclonal antibody has been successfully prepared. The Sc1754CP protein and the antibody against Sc1754CP can help us further study this unknown incompatible reaction between pathogen and host.

Extraction of Fagopyrum Dibotrys (D.Don) Hara through CO₂ Supercritical Fluid


LUAN Mei;LU Jing-ci;YONG Ke-lan;CHEN Xu;GU Hui-juan;LI Chang-yun

2008, 14(3):  328-330 . 

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The experiment was focused on the extraction of Fagopyrum dibotrys (D.Don) Hara through supercritical fluid. Factors such as pressure, temperature, time, CO₂ fluid velocity, and material size are taken to optimize the processes. Extraction from the supercritical fluid shows better result compared to Fagopyrum dibotrys (D.Don) Hara treated by petroleum ether in Soxhlet apparatus with Allihn condenser. The inhibitory activity of α-glucosidase experiment on the residua part after the extraction from 60% ethanol indicates that Fagopyrum dibotrys (D.Don) Hara after the CO₂ supercritical fluid extraction has better effect on inhibitory activity than Soxhlet extraction and saturation method.