Table of Content

10 June 2003, Volume 21 Issue 2

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Articles

A Study of the Sound Absorption Property of Grain

GUO Min, SHANG Zhi-yuan, SHI Huan-wen

2003, 21(2):  111-116. 

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By using the method of standing wave tube, we studied the sound absorption coefficient of grain for the first time. The sound absorption property of the grain piled in different thickness was researched. We found the relationship between the sound absorption property of a pile of grain and its shape, size and thickness within the frequency range of 100~5000Hz. It was shown that grain is a highly sound-absorbing medium. The sound absorption property of a pile of grain has something to do with its shape, size and thickness. This study provides a theoretical base and helps to accumulate data for detecting sound signals of the pests in grain.

A Multiple Time Scales Analysis of the Runoff Variation Along the Upper Reaches of the Yellow River

LIU Jim-ping, TIAN Feng-wei, HUANG Qiang

2003, 21(2):  117-121. 

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By applying the theory of wavelet transformation and the 1919-1996 natural runoff records of Lanzhou hydrometric station, the runoff variation along the upper reaches of the Yellow River is studied. The periods of runoff and points of abrupt change at different time scales are analyzed. The wavelet variance verification indicates that the main periods of the runoff variation along the upper reaches of the Yellow River are 22, 15, 4 and 37 years respectively in order of importance. Basing on the main period of 22 years, we predict that runoff will be in the dry period from about 1996 to about 2007.

The Characteristics of Type V Intermittency Displayed in a Kind of Two-Dimensional Maps with a Background of Impact Oscillators

ZHAO Jin-gang, CHAO Xiao-gang, WANG Wen-xiu, WANG Ying-mei, ZHANG Kai, WANG Xu-ming, HE Da-ren

2003, 21(2):  122-126. 

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Type V intermittency is found to exist widely in a kind of two-dimensional maps with a background of impact oscillators. It has two characteristics. Firstly, the prelude phase-locking staircase to type V intermittency before entering chaos includes the traditional-like and multiple-like devil's staircase structures; secondly, the chaotic attractor appearing after the staircase is always the end-results of the image set of the discontinuous borderline.

Computing the Largest Lyapunov Exponent from Time Series

LI Guo-hui, ZHOU Shi-ping, XU De-ming

2003, 21(2):  127-131. 

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A method to calculate the largest Lyapunov exponent from the observed time series based on its definition is proposed. We have tested it on several known systems, such as the Logistic model, the Henon mapping and the Lorenz system. It is found that the estimated largest Lyapunov exponent from time series has a reasonable good accuracy. More remarkably, the simulation result is independent of the embedding dimension and the delay time to a certain extent. The shorter data and the lower dimension of phase space simplify the computation without significant loss of precision.

The Triple I Algorithm for the Implication I(x,y) Operator Based on Vague Sets

XU Zhang-yan, LI Fan, FENG Jia-li

2003, 21(2):  132-136. 

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The definition of the implication operator of the interval set and a concrete implication operator are given. The calculation formulas of the triple IVMP algorithm for the implication I(x,y) operator based on Vague sets are obtained. The reversible properties of the triple IVMP algorithm are analyzed, and the essential conditions of the reversible properties of the triple IVMP algorithm for implication I(x,y) operator based on Vague sets are obtained. Because the Vague set is better than the Fuzzy set in expressing the uncertain knowledge, the triple I thinking is more believable and the triple IVMP algorithm is more satisfying in the uncertain reasoning.

A Research on the High Performance DCA-Tree Cube in the Multidimensional Data Warehouse System

HU Kong-fa, DONG Yi-sheng, XU Li-zhen, ZHUANG Xiao-qing, YANG Ke-hua

2003, 21(2):  137-140. 

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In this paper, the authors propose using the DCA-tree (a modified version of the R^*-tree) to create the high performance data cube aggregate-tree cube (DCA-tree cube). The authors also describe the key techniques such as DCA-tree cube creating, MOLAP rapid querying, DCA-tree cube incremental updating, etc. The analytical result of the algorithm shows that the performance of the DCA-tree cube in querying and updating is better than that of the cube created by the aggregate techniques such as dynamic data cube (DDC), etc. The DCA-tree cube can update incrementally while new data of some dimensions are inserted.

Minimizing the Range of Lateness on a Single Machine with the Workpieces Processed in Batches

CHENG Ming-bao, SUN Shi-jie, HE Long-min

2003, 21(2):  141-145. 

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There are n workpieces to be processed at time zero. The length of time needed for processing them varies with each workpiece. The workpieces are divided into b batches, and all the workpieces in the same batch must be processed together, successively or at same time. The problem under consideration is to minimize the range of lateness. To solve such a scheduling problem, this paper determines some properties and constructs corresponding pseudopolynomial algorithms.

The Strategy of Integrated Study of “Bluetooth” and the Intelligent Machine

YIN Yue-hong, SHENG Xin-jun

2003, 21(2):  146-150. 

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In this paper the strategy and key problems of integrated study on "Bluetooth" and the intelligent machine are illustrated in detail. A project-a recent study on Bluetooth-based Service Robot-is presented as an example.

The Design of Fuzzy Adaptive Robust Control Algorithm via the Dissipative System Theory Approach

YANG Yan-sheng

2003, 21(2):  151-156. 

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A new fuzzy adaptive robust control algorithm is presented for a class of uncertain nonlinear systems. In the algorithm, Takagi-Sugeno-type fuzzy logic systems are used to approximate unknown functions in the systems, and the adaptive mechanism with minimal learning pa-rameterizations can be achieved by using the dissipative system theory. An example illustrating the method of ship roll stabilization by the fin control system is included. It is shown that the designed system can guarantee the performance of the global asymptotic stability.

The Power Spectrum Estimation Method Based on Continuous Wavelet Transformation

XU Ke-jun, LI Yong-san

2003, 21(2):  157-160. 

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According to the idea of the power spectrum analog analysis method, the power spectrum of signal is estimated by using the continuous wavelet transformation. The basic principle of the power spectrum estimation is presented and the program flow given. The simulation results which are compared with the power spectrum estimation method based on FFT are presented in this paper.

A Parametric Integration to Solve Axisymmetric Indentation of Semi-Infinite Medium by a Flat-Round Punch

ZHAO De-wen, WANG Xiao-wen, LIU Xiang-hua, WANG Guo-dong

2003, 21(2):  161-164. 

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A parametric equation to establish velocity field for the indentation of semi-infinite medium by a flat-round punch was proposed, and corresponding parametric integration to deformation power was performed as a new method in this paper. A minimal analytical upper-bound solution of stress state factor for the indentation was obtained. The result is shown to be lower than that of triangle velocity field for the plane-strain indentation.

A Research on Interpart Feature Modeling

HUANG Xiang, YAN Chong-jing

2003, 21(2):  165-167. 

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A new method, virtual-part-based interpart feature modeling, and its mathematical representation are proposed in this paper. It extends the single part feature-based modeling to interpart feature modeling. In this way, local modification of the solid model of base parts is done by Boolean operation between base parts and the virtual part. Assemblying and part modeling are conducted simultaneously. So it greatly increases modeling efficiency, assures interpart associativity, and the design knowledge can be encapsulated conveniently through the virtual part. etc.. A rapid design system of mechanical connecting elements is thus developed in UG.

The Exergoeconomical Optimal Performances of a Three-Heat-Source Refrigerator

YANG Hui-shan

2003, 21(2):  168-172. 

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An optimal analysis based on the rate of profit objective function is carried out on a class of three-heat-source refrigerators working under the operation of the Newton' heat transfer law. The exergoeconomical optimal performance of refrigerator is derived, and the internal relation between it and the ecological optimal performance is revealed. The conclusions obtained here may provide some new theoretical guidance for the manufacture and the optimal design of three-heat-source refrigerators.

Size Effect in Ferroelectric Switching

XU Rong-qing, ZHOU Qing-chun, WANG Mao-xiang

2003, 21(2):  173-176. 

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The Orihara-Ishibashi theory of finite ferroelectric system is applied to the cubic ferro-electrics. The expressions of the ratio of the reversed domain volume to the system volume Q(t) and the reversal rate dQ/dt which is closely related to the switching current, are given for cubic domain reversals. Computations indicate that the switching current drops with the size of the ferroelectric system, and in a certain range of l(l<0. 75), the switching time also decreases with l.

The Performance of the DCF Transmission System

WANG Chen, RAO Min, TANG Rong, LI Lei, ZHANG Ming-de, SUN Xiao-han

2003, 21(2):  177-181. 

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The effects of nonlinear effects on the WDM system are presented here. Through the simulation of the DCF transmission system with different schemes, the optimized scheme of transmission link and input power is obtained. The results show that the transmission performance of mix-compensation is better than that of pre-compensation and post-compensation. The transmission performances of the various channels are compared.

A Low-Complexity Modulation Scheme for DAMB

SHU Feng, LI Chong-yi, ZHAO Guang-ling, WU Le-Nan

2003, 21(2):  182-186. 

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The time-domain DAPSK+OFDM is proposed for digital amplitude modulation broadcast (DAMB), which offers a low-complexity uncoded modulation scheme. First, the AM channel model below 30MHz is described, and the baseband model based on the OFDM system is shown. Next, the modulation, demodulation and BER performance of 32DAPSK4-OFDM are investigated in AWGN channel. Finally, the BER performance of 32DAPSK + OFDM is simulated in all the AM channels.

The Design and Approach for PDF Data Driver IC

WU Jian-hui, SUN Wei-feng, LU Sheng-li

2003, 21(2):  187-192. 

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A new structure of HV-NDMOS (high voltage N-channel lateral double-diffused MOSFET) for PDF data driver IC is presented, and the advantage of avoiding punch-through is discussed. The processes and the basic parameters for PDF date drive IC are proposed. At the same time, a novel technique, polycrystalline silicon self-aligned etching used to etch the thick gate oxide of HV-PMOS (high voltage P-channel MOSFET) is also demonstrated. Finally, the test and analyses for the IC are carried out, and this proves that the designed IC can meet practical needs.

A Security Analysis of the IPSec Based WLAN Solution and a Study of Its Algorithm

WU Yue, SHI Xiao-hong, CAO Xiu-ying, BI Guang-guo

2003, 21(2):  193-198. 

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This paper describes the vulnerability of the wired equivalent privacy(WEP) protocol in current IEEE802. 11 WLAN standard, such as key sequence reuse, key management and refreshment, message authentication and integrity, etc. It also presents a security solution for WLAN based on IP Security (IPSec) and discusses the fundamental principles of data origin authentication, integrity protection, anti-replay protection and key exchange, Finally it describes their software implementations, makes a security analysis of the solution and looks into the future research.

A Cumulant -Based DOA Estimation Algorithm for CDMA System in Spatial Colored Noise

YANG Wei, CHENG Shi-xin

2003, 21(2):  199-204. 

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The conventional direction of arrival (DOA) detection algorithm is generally based on the second-order spectrum estimation while assuming that the noise is additive white Gaussian noise (AWGN). Concentrating on spatial colored noise of unknown spectrum quality, which is more realistic in any scenario, a novel high-order cumulant MUSIC DOA estimation algorithm for synchronous CDMA system with decorrelator has been proposed. The proposed algorithm not only has the advantages that the DOA of multipath signals can be estimated independently by eliminating all the other resolvable multipath signal interference but while on spatial colored noise case the proposed algorithm estimates DOAs of the decoupled multipath signal more effectively and accurately than the conventional second-order MUSIC algorithm.

The Application of the Finite Difference Frequency Domain Method in Two Dimension Periodic Guided Waves Structures

XU Feng, HONG Wei, ZHOU Hou-xing

2003, 21(2):  205-208. 

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A novel finite-difference freqency-domain method is presented for the analysis of electromagnetic wave propagation in periodic structures. The boundary conditions are set according to Floquet's theorem for periodic structures. Floquet's theorem is used both on the electric field boundary and the magnetic field boundary. Thus, the computational domain is restricted to a single period, and the absorbing boundary conditions can be used on the other boundaries. The propagation constant can be obtained by means of calculating matrix eigenvalues, and there is no need to solve the high-order equation. In this way, the calculation time is greatly saved.

A Method Based on the Rough Neural Network for Analysing Deception Risks

SHENG Zhao-han, LIU Bing-xiang

2003, 21(2):  209-213. 

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This paper states the basic concept of deception and analyses the causes that give rise to the risk of deception. The methods of identification, analyzing and estimation of deception risks are discussed. The shortcomings of the traditional models for evaluating deception are also discussed. A method based on the rough neural network for analyzing deception risks is suggested and an example is given to validate the algorithm. The results show the feasibility and validity of the method. The research work furnishes a basis for further study of applying rough neural network to the analysis and prediction of deception risks.

The Theoretical Formula of Wood's Radial Thermal Conductivity

CHEN Tong-ying, YANG Qing-xian

2003, 21(2):  214-216. 

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The theoretical formula of wood's radial thermal conductivity was derived through anal-ogism in accordance with the cell structure and thermal conductivity of the wood. With the formula derived, the theoretical values of thermal conductivity of 20 species of trees were calculated and comparison was also made with the experimental values under the same conditions. The resultsand average error 4.9%.

A Study on the Influence of the Geometrical Parameter on the Thermal Expansion of Mechanical Parts

MIAO En-ming, FEI Ye-tai

2003, 21(2):  217-220. 

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This paper briefly describes the significance of thermal deformation in scientific research and production. It points out the limitations of the traditional method for calculating the thermal expansion and the important effect of geometrical parameter on the thermal expansion deformation of mechanical parts. The relationship between the geometrifcal body parameter and the thermal expansion coefficient is analyzed through theoretical discussion and experiments. A preliminary investigation into the relationship between the value of thermal expansion due to the geometrical parameter and the value of traditional thermal expansion has been curried out through experiments.