Table of Content

30 September 2001, Volume 19 Issue 3

Previous Issue    Next Issue

Articles

Applications of Depth Distribution to the Study of Period Distribution in Error-correcting Codes

YUE Dian-wu, E. Shwedyk

2001, 19(3):  189-192. 

Asbtract ( 269 )   PDF (168KB) ( 101 )  

Related Articles | Metrics

In this paper, we find a relationship between the depth distribution and the period distribution in error-correcting codes. With the help of the depth distribution, we propose a new method for finding the period distribution of a linear code with a length to the power of 2. We can thus determine the period distribution of some classes of linear codes with a length to the power of 2, such as the extended Hamming code and the extended cyclic code.

Enlarging the Capacities of Bidirectional WDM Star Single-hop Networks by Wavelength Reuse

GAN Chao-qin, SUN Xiao-han, ZHANG Ming-de

2001, 19(3):  193-197. 

Asbtract ( 261 )   PDF (208KB) ( 88 )  

Related Articles | Metrics

To cope with the restriction placed on the capacities of bidirectional WDM star single-hop networks by the limited number of wavelengths, a scheme of wavelength reuse is proposed in this paper. Though the network structure proposed is simple, the scheme can be easy implemented in practice. In the scheme, the number of nodes can be increased by reusing wavelengths, the delay of network can be reduced, the throughput can be increased under the same number of nodes, and the properties of network are improved. Besides, the scheme can be applied to interconnections between two bidirectional WDM star single-hop networks. In this paper, the network's structure is discussed and the properties of wavelength reuse in the network are analyzed. Furthermore, the required gain and output power of optical amplifier in it are computed. Finally, the maximum number of wavelengths utilized by the network and the maximum number of nodes supported by the network are computed.

Blind Separation for Post-nonlinear Mixture of Sub-and Super-Gaussian Signals

CHEN Yang, HE Zhen-ya

2001, 19(3):  198-201. 

Asbtract ( 230 )   PDF (196KB) ( 82 )  

Related Articles | Metrics

The problem of blind separation of signals in post-nonlinear mixture is addressed. The learning rules for the general post-nonlinear separation structure are derived by a maximum likelihood approach. An algorithm for blind separation of post-nonlinearly mixed sub-and super-Gaussian signals based on the results of previous work is proposed. The effectiveness of the algorithm is verified by experiments on artificial and natural signals.

The Symble Error Rate over HFC Baseband Digital Reverse Channel

MAO Hui-min, YE Jia-jun, LI Ying-chun

2001, 19(3):  202-205. 

Asbtract ( 282 )   PDF (176KB) ( 87 )  

Related Articles | Metrics

This paper analyzes the impact of doubleside clipping noise and quantization noise on HFC baseband digital channel caused by A/D converter. The formula of symble error rate and some useful conclusions are derived.

A Fast Frequency Sweeping Method for RCS Computation Based on AWE Technique

TONG Chuang-ming, HONG Wei, WANG Jie

2001, 19(3):  206-209. 

Asbtract ( 322 )   PDF (177KB) ( 102 )  

Related Articles | Metrics

The method of moments (MOM) in conjunction with the asymptotic waveform evaluation (AWE) technique is applied to predict the radar cross-section (RCS) of an arbitrarily shaped twodimensional (2-D) perfect electric conductor (PEC) cylinder over a frequency band. The electric field integral equation (EFIE) of a 2-D PEC cylinder is solved by using MOM to obtain the equivalent surface current on the PEC cylinder. In the AWE technique, the equivalent surface current at a given frequency is expanded in the desired frequency band in a Taylor's series. The Taylor's series coefficients are then matched via the Pade approximation to a rational function. By using the rational function, the surface current is obtained at any frequency within the frequency range, which is in turn used to calculate RCS of the 2-D PEC cylinder. It was observed that AWE could result in considerable CPU time saving.

Blind Extraction of Independent Signals from Their Linear Mixtures

LIU Ju, NIE Kai-bao, HE Zhen-ya

2001, 19(3):  210-213. 

Asbtract ( 272 )   PDF (180KB) ( 90 )  

Related Articles | Metrics

Observed signals are always the linear mixture of some independent components. Independent component analysis (ICA) is a novel technique for dealing with such a problem. Most of the existing algorithms separate individual independent sources simultaneously. In this paper, basing on the independence assumption of the original sources, we propose a new blind separating criterion, where the square of fourth-order cumulants of the sources are employed. We next develop an ICA approach which can sequentially extract independent components blindly one by one. A new deflation technique is used in this approach for removing the previously extracted signals from the mixture. Computer simulations show the validity of the proposed approach.

Application of IIR Filter Feedback Differential Detection in π/4 DQPSK

HJGUO Dao-sheng, GAN Zhong-min, ZHANG Bang-ning, LIU Ai-jun

2001, 19(3):  214-217. 

Asbtract ( 323 )   PDF (178KB) ( 76 )  

Related Articles | Metrics

In this paper, we emphasize on analyzing the application of ⅡR filter feedback differential detection in differential demodulation of π/4DQPSK. The practical implementation scheme is presented. The BER performance and its correction capability are investigated by computer simulation in AWGN channel. The simulation results show that the improved performance of proposed algorithm is superior to conventional differential demodulation by 1.2dB at a BER of 10-4 in AWGN channel. Considering that the loss of implementation and the test result of practical system agree with the simulation result, the algorithm can be widely applied in practical satellite communication system, thereby improving the system's traditional differential detection and the capacity and communication quality of a satellite communication system with limited power.

Hyperchaotic Systems with Coupled-feedback and Its Application to Cryptography Communications

YAN Sen-lin, WU Shi-bao, PANG Huan-gang, SUN Xiao-han, ZHANG Ming-de

2001, 19(3):  218-223. 

Asbtract ( 274 )   PDF (267KB) ( 250 )  

Related Articles | Metrics

In this paper, chau's circuit hyperchaotic systems with coupled-feedback are investigated and proved. Four pairs of double-scroll attractors have been produced by its hyprtchaotic dynamic behavior. The chaos masking of the hyperchaotic phenomena in the cryptography communications schemes and the application of chaos shift keying technology have been proposed and studied through numerical simulations

Influences of Nonlinear Gain Compression on Switching Characteristics of TOAD

PANG Huan-gang, ZHANG Zhi-yuan, YAN Sen-lin, SUN Xiao-han, ZHANG Ming-de

2001, 19(3):  224-227. 

Asbtract ( 283 )   PDF (187KB) ( 88 )  

Related Articles | Metrics

In this paper, the influences of nonlinear gain compression (NGC) on switching characteristics of a terahertz optical asymmetric demultiplexer (TOAD) are investigated thoroughly by taking into account the gain saturation and NGC effects of semiconductor optical amplifier (SOA). And a concept of effective switching window width is presented for the first time. It is shown that the switching window shape is influenced dramatically by the NGC. The bigger NGC is, the more sensitive is the TOAD output to the position of the SOA. If the NGC is small, however, the control pulse energies will have great effects on the effective switching window width. Only when the control pulse is narrow, will the effective switching window width be influenced by the NGC. The effective switching window width will be small if the NGC and the distance between the SOA and the midpoint of the loop are small.

Fault Detection for Linear Analog IC: The Method of Short Circuit Admittance Parameters

LI Feng, SHANG Hui-liang, KONG Qing-sheng

2001, 19(3):  228-232. 

Asbtract ( 360 )   PDF (203KB) ( 82 )  

Related Articles | Metrics

A fault detection method, i.e, the method of short-circuit admittance parameters, for linear analog IC is proposed in this paper. Only two time voltage measurements at the ports of the circuit are suggested to decide whether the circuit is working normally. This method can be used to design a circuit automatic detecting equipment for technicians to decide whether there is any fault in the linear analog circuits. The attractive merits of this method are the component parameter tolerance and the error reduction in measurement and calculation.

A Calibration Method for Measuring Data in Dynamic Balancing of Crankshafts

Yu Li-zhen

2001, 19(3):  233-236. 

Asbtract ( 407 )   PDF (165KB) ( 130 )  

Related Articles | Metrics

A multiple variations linear regression calibration method for measuring data in dynamic balancing of crankshafts is discussed. It can obtain satisfactory results from calibrating and has been used in the production-line of crankshafts.

H^∞ Control of Discrete Time-delay Systems Based on LMI

LI Zhi-hu, SHAO Hui-he, WANG Jing-cheng

2001, 19(3):  237-240. 

Asbtract ( 319 )   PDF (160KB) ( 82 )  

Related Articles | Metrics

This paper deals with the problem of H^∞ control for linear discrete systems with multiple state delays. Based on-linear matrix inequalities, a sufficient condition is presented for the systems to be H^∞ state feedback stabilizable. By solving a certain linear matrix inequality, the H^∞ controllers are obtained. A numeric example is given to demonstrate the effectiveness and superiority of the design method.

A Neural Network Based Approach for Concurrent Activities Scheduling

YAN Ji-hong, WU Cheng

2001, 19(3):  241-244. 

Asbtract ( 350 )   PDF (173KB) ( 85 )  

Related Articles | Metrics

Scheduling activities in concurrent product development process is of great significance to shorten development lead time and minimize the cost; moreover, it can eliminate the unnecessary redesign periods and guarantee that serial activities can be executed as concurrently as possible. This paper presents a constraint satisfaction neural network and heuristic combined approach for concurrent activities scheduling. In the combined approach, the neural network is used to obtain feasible starting time of all the activities based on sequence constraints, the heuristic algorithm is used to obtain feasible solution of the scheduling problem based on resource constraints. The feasible scheduling solution is obtained by a gradient optimization function. Applications have shown that the proposed combined approach is efficient and feasible with respect to concurrent activities scheduling.

Reliable H_∞ State Feedback Control for Uncertain Nonlinear Systems with Duplicated Actuators

FU Yu-sun, TIAN Zuo-hua, SHI Song-jiao

2001, 19(3):  245-248. 

Asbtract ( 307 )   PDF (172KB) ( 74 )  

Related Articles | Metrics

This paper is concerned with the reliable state feedback controller design problem for a class of uncertain nonlinear systems with duplicated actuators. By using dissipative theory, a procedure of designing reliable nonlinear controller is presented on the basis of solutions of the Hamilton-Jacobi inequality. The resulting closed-loop system is reliable in the sense that the performance(i.e., internal stability and H_∞ attenuation) of the closed-loop system is guaranteed not only when all actuators are operational, but also when some actuator outages occur.

A Fuzzy Self-tuning Controller Based on Fuzzy Competitive Learning

WANG Hong-wei, HE Han-gen, ZHAN Rong-kai, HUANG Ke-di

2001, 19(3):  249-252. 

Asbtract ( 309 )   PDF (175KB) ( 82 )  

Related Articles | Metrics

A fuzzy self-tuning controller based on fuzzy competitive learning is proposed in this paper. First of all, an on-line fuzzy identifying algorithm is confirmed by means of fuzzy competitive learning, and the convergence about a recursive algorithm of fuzzy competitive learning is proved. On the basis of on-line identification of subjects with the aid of the proposed method, the parameters of the adjuster are automatically adjusted. The proposed method is used to control a non-linear system to demonstrate its advantages, and the result is shown at the end of the paper.

The Visualizing of the Dynamic Running of Petri Net

YE Zhi-bao, JIANG Chang-jun, ZHANG Zhao-qing, QIAO Ru-liang

2001, 19(3):  253-256. 

Asbtract ( 367 )   PDF (167KB) ( 72 )  

Related Articles | Metrics

This paper mainly discusses the method for designing the visual running of Petri net. The key technology of performance of visual running is described and the method of designing the visual running of Petri net is presented.

Non-Fick Effect of Abnormal Mass Transfer Within Porous Media

WANG Xin, WANG Hai, SHI Ming-heng, YU Wei-ping

2001, 19(3):  257-260. 

Asbtract ( 269 )   PDF (177KB) ( 63 )  

Related Articles | Metrics

Because mass propagation velocity has a finite value for porous media in an unsteady mass transfer process, the hypothesis that mass propagation velocity in a mass transfer process is infinite is inconsistent with the real situation in the case of wet porous materials in a highly intense drying process. In this paper, a description of an unsteady humidity profile in the form of the hyperbolic equation is made. From the equation, wave characteristic can be seen in the mass transfer field of the inner material. One-dimensional hyperbolic equation of mass transfer within wet porous materials in a highly intense drying process is developed. The non-Fick phenomena in a highly intense drying process are analyzed by the comparison of the solutions between the Fick equation and the non-Fick equation. The calculation results show that when mass flux or mass transfer coefficient is high, the non-Fick effect is noticiable and it is not negligible in an intense drying process.

Oriental Shift at CdTe/Cd_1-y Zn_yTe, Hg_1-x Cd_xTe/CdTe and CdTe/GaAs Heterojunctions Grown on (112) plane

LIU Yi-zu, YU Fu-ju

2001, 19(3):  261-264. 

Asbtract ( 273 )   PDF (180KB) ( 86 )  

Related Articles | Metrics

A tilt in the[111] crystallographic direction, and a tilt angle of 0.21850° were determined by XDRD (X-ray double crystal diffraction) in a CdTe/Cd 0.959 Zn 0.041 Te (112) B heterojunction grown by means of MBE (molecular beam epitaxy), and a quasi-Sine function between the rotation angle Δφ around sample surface normal and the diffraction angle difference Δθ was drawn in order to obtain optimal data. A special oriented cross-section of Hg_0.535 Cd_0.465 Te/CdTe/GaAs (112) B multilayer grown by MBE was prepared for HRTEM (high resolution transmission electron microscopy) determination, and the HRTEM images show that the buffer layer CdTe (112) relative to the substrate GaAs (112) is inclined by about 3° towards the[111] orientation at the CdTe/GaAs heterojunction, and that the epilayer Hg_0.535 Cd_0.465 Te (112) relative to the buffer layer CdTe (112) is inclined by about 1° towards the[111] orientation, in the opposite direction of[111] at the Hg_0.535 Cd_0.465 Te/CdTe heterojunction. The relationship of the tilt angles at the Hg_0.535 Cd_0.465 Te/CdTe/GaAs multilayer was also analyzed.

Under-groundwater Detecting Effect of the Nuclear Magnetic Resonance Method in the Water-poor Area

YUAN Zhao-ling, WAN Le, LI Zhen-yu

2001, 19(3):  265-267. 

Asbtract ( 467 )   PDF (133KB) ( 151 )  

Related Articles | Metrics

The nuclear magnetic resonance (NMR) method has an advantage over other geophysical methods in under groundwater detecting. But it is apt to be disturbed by electromagnetic in terference. This paper illustrates the under groundwater detecting effect of the NMR method with an example:searching for under-groundwater on the site of a large-scale transformer substation located in Hubei Province.

Power Density Optimization of a Real Regenerated Brayton Cycle Coupled to Variable-temperature Heat Reservoirs

CHEN Lin-gen, ZHENG Jun-lin, SUN Feng-rui

2001, 19(3):  268-272. 

Asbtract ( 307 )   PDF (215KB) ( 66 )  

Related Articles | Metrics

The analytical formulas for the relations between power density and pressure ratio of a real regenerated Brayton cycle coupled to variable-temperature heat reservoirs are derived by using finite-time thermodynamics. In the analysis, the irreversibilities involve the heat resistance losses in the hot-and cold-side heat exchangers and regenerator, the irreversible compression and expansion losses in the compressor and turbine, and the pressure losses in the piping. The effects of the thermal conductance distribution of hot-and cold-side heat exchangers and of the thermal capacity rate matching between the working fluid and the heat reservoirs on the power density are studied by detail numerical examples.

A Nonlinear Discriminant Analysis Method: The Globes Piling Method and Its Application

LIU Zheng-shi, ZHOU Yi-fang

2001, 19(3):  273-276. 

Asbtract ( 321 )   PDF (171KB) ( 64 )  

Related Articles | Metrics

A new non-linear discriminant method is proposed. It can be applied in failure diagnosis and quality control. The algorithm is presented, and basic properties are investigated. The method is simple. It can be easily programmed and widely used. The effectiveness and engineering practicability of the method is shown in diagnosing ball bearing skidding defect.

Fretting Fatigue Characteristics of Titanium JZAlloy at Elevated Temperature JZUnder Complex Loads

DAI Zhen-dong, WANG Min, ZHU Ru-peng, PAN Sheng-cai

2001, 19(3):  277-282. 

Asbtract ( 267 )   PDF (272KB) ( 89 )  

Related Articles | Metrics

The effects of the various parameters on the fretting fatigue life and the fretting friction coefficient for a contact pair of titanium alloy and stainless steel are experimentally studied at the room and elevated temperature. The test results show that fretting fatigue life heavily declines at low tensile stresses, and its greatest decrease corresponds to the contact pressure at which the dissipated friction work is the maximum. It changes with temperature nonlinearly:it decreases first when the temperature is between 20 to 200℃, increases up to 300℃ and then reduces to several cycles between 400 to 500℃. The fretting fatigue life under complex loads monotonously decreases with the increase of the high cycle load while the low cycle loads keep constant. The friction coefficient (FC) increases with the number of cycles at the beginning, then reduces, and finally keeps a stable value. FC reduces greatly with the increase of the temperature due to the formation of the lubricious oxide film. FC increases linearly with the amplitude when it is less than the critical value and then keeps constant, the value of the coefficient can be regressed as f=2.691-0.409 ln_N^e. The coefficient increases from 0.2 to 0.8 with the increase of amplitudes from 5 to 45 micrometers.