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2000 Vol. 26, No. 4

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Radiolocation Technology in LA-CDMA Wireless Cellular Network
GAO Yan, LI Yong-hui, ZHANG Qi-shan
2000, 26(4): 373-376.
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Applications by the radiolocation technology in a code-division multiple access (CDMA) wireless cellular network are discussed, especially was used to manage fleet and vehicles in an Intelligent Traffic System (ITS) . In the LA-CDMA wireless communication system, a third generation communication system, which was invented by Chinese and has Independent Intelligent Property (IIP), the principle and methods for an additional radiolocation service are given. We propose two ways to implement it ,one is by the forward link, the other is by the reverse link, the advantages and disadvantages are also compared for each other in this article. We also analyze the problems that are encountered when using LA-CDMA cellular networks for position.
Modeling and Implementing for Mobile Radio Fading Channel in IF Based on FPGA
GAO Yan, LI Yong-hui, ZHANG Qi-shan
2000, 26(4): 377-380.
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A device based in Field Programmable Logic Array(FPGA)to simulate the channel propagation characteristics of the ground mobile environment at Inter Frequency (IF) has been designed and implemented.This device allows the performance of a mobile radio unit to be evaluated in laboratory under controlled conditions. The adjustable fading bandwidths and additional long delays were implemented by using the relative new signal processing technologies of FPGA device. A typical model to simulate the multi-path effects up to three different propagation paths was introduced , more paths' simulation can be implemented by increasing the number of same units. The channel simulator was designed to simulate mobile platform speeds up to 120km/h and multi-path components, having calculated time delay spreads of up to 9 μs.
Optimal Period Interleaver for Turbo Codes
QI Feng, WANG Mu-zhong, SHAO Ding-rong, ZHANG Yan-zhong
2000, 26(4): 381-384.
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By analyzing the relation between input sequences and feedback polynomials, we find the reason why low-weight codewords for Turbo code are generated.The concept of optimal period interleavers for Turbo codes is introduced. A novel design scheme for interleavers used for Turbo codes is presented. The main idea of this method is to design the interleaver based on an optimal period interleaver. Simulation results are presented for Turbo codes using our interleavers. A magnitude improvement in bit error rate performance is obtained at high signal-noise ratio compared to Turbo codes using other conventional interleavers. According to simulations results, it is significant to apply the optimal period interleaver in the practical interleaver design. This is particularly of interest to Turbo coding applications in mobile communications where short frames are typical.
Public Traffic Information Management System in Intelligent Transport Systems
ZHANG Fei-zhou, YANG Dong-kai, FAN Yue-zu, SUN Xian-fang
2000, 26(4): 385-388.
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The contents of study and development in intelligent transport systems(ITS) in our country is introduced, and then the main ideas of public traffic information management system and its dynamic management are expatiated upon. The study and development of public traffic information management system in ITS can enhance to contact with roads, vehicles, drivers and managers one another, so that managers could know the public traffic situation well. Thus traffic congestion can be effectively solved and road traffic faculties can be improved, and so the public traffic intelligent management can be realized. Therefore the efficiency of road transportation and travelling safety will be enhanced, the public traffic information management system has wider prospect in the future.
Study of Redundant Tasks Allocation for Distributed System
CHEN Xian-feng, QIU Li-hua, WANG Zhan-lin
2000, 26(4): 389-392.
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A tasks assignment algorithm for the distributed fault-tolerance system is presented, we considered the periodicity, redundancy,adaptability and importance degree of the simulation system tasks and the load balancing of the processors in the algorithm. The algorithm achieved the redundant distribution of the system tasks by three steps of static tasks assignment and distributed the active, passive and sleeping copies of one task to different processors. The system would change the task's state and realize system reconfiguration by dynamic awakening algorithm of redundant tasks in case of the processor failure. The redundant tasks assignment algorithm can achieve the dependability requirement of the simulation system, at the same time, it can ensure the system real-time performance.
Optimization of In-Flight Shutdown Rate of Aero-Engine
BAI Guang-chen, WANG Yan-rong
2000, 26(4): 393-395.
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Optimization methods to control the in-flight shutdown rate and the maintenance cost of civil aero-engines are presented in this paper. The mathematical planing approach to determine the optimal in-flight shutdown rate of an aero-engine is developed, in which the lost expectation of in-flight shutdown is taken as the index of indirect operating cost and the minimum sum of maintenance cost and indirect operating cost is treated as the optimization objective. On the basis of the mathematical planing, a simple optimization method to control in-flight shutdown rate and maintenance cost is provided. The methodologies have reference value for an airline company to make decisions to control task reliability level and maintenance cost of an aero-engine in the wing.
Random Model of Fatigue Multi-Crack Propagation
ZHANG Jian-yu, FEI Bin-jun, ZHAO Li-bin
2000, 26(4): 396-399.
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Stochastic damage tolerance method based on the stochastic fracture mechanics is one of the most important aspects of design and evaluation technique of aircraft structure. Stochastic damage tolerance analysis model is constituted with random crack propagation model and reliability analysis model. The random model of crack propagation corresponding to interactive multi-crack has been presented in this paper. Some basic concepts are discussed, for instance: far cracks, near cracks, stochastic-life camber. A unified differential equation of multi-crack propagation is established. Basing on some engineering hypothesis, the calculation of crack propagation has been abbreviated. The damage tolerance technique has been developed in the paper. A large progress has been made on stochastic damage tolerance analysis of multi-cracked structure.
Research on Support Decision System(SDS) of Optimum Matching of Man-Machine Interface in Mechanical Systems
LIU Zhong-bao, DONG Su-jun, YAO Hong-wei
2000, 26(4): 400-403.
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Support decision system(SDS) of the optimum matching of man-machine interface in mechanical systems is made by using the theory of SDS. The multi-dimension adjustable simulator stand for the optimum matching of man-machine interface in mechanical system has been structured with the use of Computer aided design (CAD) technology. This stand is made mainly up of frame, instrument panel, stage surface, pedestal and other components. It is able to simulate the man-machine interface in various mechanical systems. The experiment evaluation for the degree of optimal matching of man-machine interface in mechanical system can be realized by this stand. Method and model databases have been structured with the Analyses of hierarchy process (AHP) and Fuzzy comprehensive evaluation (FCE).According to this system ,the optimization of the initial choices can be well completed for its saving time ,man and source.
Nonlinear Flight Control Design for Supermaneuverable Aircraft
FAN Zi-qiang, FANG Zhen-ping
2000, 26(4): 404-407.
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The design of a flight control system for a supermaneuverable aircraft by means of nonlinear dynamic inversion was discussed in detail. First, the dynamics to be controlled are separated into fast and slow variables in terms of singular perturbation theory. The fast variables are the three angular rates and the slow variables are the angle of attack, sideslip angle, and bank angle. Then two dynamic inversion control laws are designed for the fast and slow variables respectively, the outputs of outer loops are used as the inputs of inner loops. The resulting control system is demonstrated using post-stall maneuver simulation, the simulation results show that the dynamic inversion control law achieves a high level performance in post-stall maneuver conditions.
Investigation on Heat Transfer between Gas and Rubber Particles in Fixed Bed and Vibrated Fluidized Bed
WANG Xiao-xin, YUAN Xiu-gan
2000, 26(4): 408-411.
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The effect of parameters on radial heat conductive coefficient is analyzed by researching into radial heat conductivity of rubber particles in fixed bed. The fluidized bed should be applied to enhance the process of heat transfer between gas and solids in order to minimize the effect of lower heat conductivity of rubber. It is indicated that vibration strengthen more than gas velocity affects heat transfer in vibrated fluidized bed (VFB) from the analysis of the correlations. In the case of reaching the same heat transfer results, the VFB can decrease gas velocity more than common fluidized bed can do, and energy conservation may be realized by using VFB technology.
Vibrations of Stepped One-Way Rectangular Plates
ZHANG Ying-shi
2000, 26(4): 412-415.
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Vibrations of non-unitary materials n-step one-way rectangular plates are researched. Differential equations of free/forced vibrations for such plates are established by using singular functions, their general solutions solved with method of initial parameter. The traditional solvent of static and dynamic problems for stepped prismatic beams is to set up ordinary differential equation in each step and answer it respectively. That is so troublesome. With W operator, resolution of the former may be expressed with one equation only, and expression of vibration mode function/frequency equations of plate on usual supports derived. Forced responses of like that plates stated here under different-type loads discussed with generalized functions. Influence functions given here are strong tools to settle ordinary differential equations which described in the text. It can also be to deal with problems of static buckling and steadiness of stepped beams or one-way rectangular plates.
Steric Effects in Rate Constants for Bimolecular Dissociation
ZHANG Jing-bai, LI Chun-xuan
2000, 26(4): 416-419.
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The steric effects for bimolecular dissociation were investigated via the collision theory, and a sterically dependent bimolecular dissociation model was established. In order to validate the developed model, the rate constants of typical reactions taken place in air under thermal equilibrium condition were then calculated based on the new model, and were compared with the results obtained by the classical collision theory, as well as the available experimental data. As shown by the Arrhenius plots presented in this paper that the new model would provide more accurate results than the classical collision theory, when compared with the experimental data. The plots also depict some exceptional cases in the reactions of N2+N and O2+O, where there are discrepancies among the theoretical and experimental data. These discrepancies are also discussed in the present paper.
Confidence Level Analysis Method of Incomplete Fatigue Life
XIONG Jun-jiang, LIU Bao-cheng, ZOU Shang-wu, Shang Da-jing
2000, 26(4): 420-423.
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By means of the rank statistical method and the mean ranks of the incomplete fatigue life data, the distribution parameter estimation formulas are derived. After the mean and the standard deviation of the population distribution are deduced, the confidence limit of the incomplete fatigue life is presented according to t-distribution theory. Two application examples of this method for the fatigue life prediction of the composite rotor and the rotor component in engine are given. In these examples, the results determined respectively by this method and the supposed complete life method are compared, and it is found that the safe life determined by this method is longer since the information of the incomplete life data is more fully used in this method.
Determination of Non-Linear Buckling Load for Simple Supported Beam with Bounded Initial Imperfection
TONG Zong-kai, WANG Shou-mei, QIU Zhi-ping
2000, 26(4): 424-427.
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A method to obtain non-linear buckling loads of simple supported beam with initial imperfection is presented,Which avoids differential equation sets initial value problems resulting from another definition of buckling load,and the proposed method save computational cost. Fourier series to describe initial imperfection is viewed bounded variables followed a certain probability distribution,the range of buckling load under a certain reliability is obtained via statistical method,and a non-stochastic interval method to determine the range of buckling load is presented to describe a situation when only limited information is available on initial imperfection. Finally,the results from both approaches are critically contrasted,the scope of application is given qualitatively for each approach.
Data Treatment Expert System for Median Stochastic Load-Spectrum
YAN Chu-liang, ZHANG Shu-ming, YE Ge, GAO Zhen-tong
2000, 26(4): 428-431.
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The precondition of solving life prediction and life extension for airplane structures is to work out a typical load-time history, i.e. load-spectrum, which can simulate airplane's real service situation. This is the basis of theory analysis and whole-size structure fatigue test. In view of this, the data treatment and the compilation procedure of median stochastic load-spectrum are discussed. The data treatment expert system for median stochastic load-spectrum is created. It includes system framework design, data description and parameter configuration, implementation process and database design, etc. The research achievement has been used for load-spectrum data treatment and compilation for airplane, aeroengine, airplane landing gear and main fighting tank, etc.
Rules of Inference for Quantifiers in Discrete Mathematics
HE Zi-qiang
2000, 26(4): 432-434.
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The conditions satisfied for the existential instantiation and the universal generalization in the natural deduction system are described clear, whereas they are described rather vaguely in many textbooks on discrete mathematics. Contrasting with that the existential instantiation in some textbooks is used only for formulas without free variables, according to the condition we given, it may be also used for formulas with free variables and the ability to reason has increased. Introducing the equivalence between interpretations and the equivalence between assignments with respect to a set of formulas, it is proved that the system is sound, that is, in a proof, the conclusion is a logical consequence of the premises.
Walkthrough and Interaction Technology for Virtual BUAA
HAO Ai-min, ZHANG Bei, ZHAO Qin-ping
2000, 26(4): 435-438.
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A layer construction of scene database for virtual BUAA(Beijing University of Aeronautics and Astronautics) campus has been put forward, a paging algorithm based on model control planes has been provided, three scene complexity simplification strategies of redundant modeling data simplification, texture mapping and multiple LOD(Level of Detail) models have been realized. Much attention has been paid to discussing the picking approaches of virtual entity based on the standard two dimension input device and manipulation of restricted moving entity has been realized. And finally a brief introduction has been made to the realization of general walkthrough engine frame work which has nothing to do with models.
Study on Seal of Gas Along Cylindrical Spiral Groove
CHEN Jian-ping, ZHAO Pi-zhi, WANG Zhi-shan
2000, 26(4): 439-442.
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The governing equation of gas cylindrical spiral groove is solved theoretically by the coordinate transformation from non-rectangle grid in computational area with complex shape to rectangle grid. The purpose of the transformation is to avoid re-forming grid while the structural parameters being changed. The design parameters that affect the seal performance are proposed. The relationship of these major parameters such as groove numbers and spiral angle to seal pressure is revealed and the optimized result is obtained. Mass experiments are conducted in designed test rig. Experimental results have a good agreement with the calculated ones. In the end, the selecting domain of structural parameters to design gas cylindrical spiral groove seal is concluded for engineering application.
Mesh Model Simplification Method Based on Volume Criterion
CHENG Ji-hua, FAN Yu-qing
2000, 26(4): 443-446.
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Model simplification is used in a variety of disciplines, such as virtual reality, CAD/CAM, dynamic simulation and so forth. This paper presents a new method to delete vertex of the mesh model, which is based on volume criterion. To decide whether certain vertex can be removed, the method uses the variety value of volume when the vertex is removed as criterion. By the method, the simplified model can approximate original model very well. Because the volume criterion has distinct geometry and engineering meaning, the simplified model can be used as both displaying model and designing model. In order to improve the mesh quality, the paper introduces an optimal method based on swapping diagonal for re-triangulating the local mesh. The paper also gives an example to illustrate efficiency of the method.
Magnetic Field Numerical Calculation of Rectangular Poled Magnetic Fluid Sealing Device
ZHAO Guo-wei, CHI Chang-qing, WANG Zhi-shan
2000, 26(4): 447-450.
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Magnetic leakage is described accurately by magnetic propagation equation on the boundary of magnetic dielectric and non-linear magnetization characteristic of different magnetic dielectric is considered, the distribution of steady, non-linear and forced axial symmetry magnetic field in magnetic fluid sealing device with different number of the poles is calculated by solving the partial difference equation described by magnetic vector potential, and unequally spaced net finite difference is adopted in the numerical calculation. This method overcomes the error caused by ideal estimation on magnetic leakage and work point of different place in magnetic dielectric in magnetic circuit method, the results are accurate, reasonable, reliable, and provide useful basis for structural design.
Experimental Study on a New Type of Combined Seal System
WANG Zhi-shan, CHEN Jian-ping, ZHAO Pi-zhi
2000, 26(4): 451-453.
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A new type of combined seal system with ferromagnetic flow and gas along cylindrical spiral groove is proposed in this paper. Based on the study of the two seals respectively, experiments on the combined seal system are carried out. Results show that the seal system has enough seal ability to fulfil the speed limit from zero to designed value. At high speed, gas seal can prevent the splash of ferromagnetic flow effectively and restore the seal ability when the seal film of ferromagnetic flow breaks up, so it is a pollution-free and reliable seal. It is also revealed that the combined seal is characterized by being adapted to diverse seal occasion by adjusting structural design parameters. The performances are beyond the reach of other kind of non-contact seals.
Two Improvements to an Algorithm of Feature Recognition
XU Shi-xin
2000, 26(4): 454-456.
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Two improvements are discussed with regard to an important type of feature recognition algorithm, which is Falcidieno's algorithm. Firstly, when extracting the explicit features, the original algorithm cannot handle the case when protrusion features and depression features are adjacent. But the improved algorithm can do. It deals with the mixed loop, which is composed of convex edges and concave edges, and then classifies the features into protrusion ones and depression ones. Secondly, a property to extract the implicit protrusion features is discovered. And the method to treat with the implicit features is modified. Hence more kinds of implicit protrusion features can be recognized. These improvements extend remarkably the application range of the algorithm.
Partial Least-Squares Regressive Analysis and Modeling for Tool Wear
LIU Qiang
2000, 26(4): 457-460.
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The algorithm of partial least-squares regression(PLSR) is briefed firstly. The PLSR analysis is applied to the sample data sets of cutting tool wear under different machining conditions. Six independent variables for modeling including cutting speed V, cutting force components Fx, Fy and Fz, as well as force ratios Fy/Fx and Fz/Fx, are screened from eight original variables based upon the variable important projection and the factor loading. The model with the six independent variables and the flank wear of cutting tool as the dependent variable is built up by using PLSR approach. Two sample data sets, one under the cutting conditions covered in the modeling data and the other under new different cutting conditions, are used to verify the model respectively. The results demonstrate that the variable screening is reasonable and the satisfied values of the flank wear of cutting tools can be obtained from the PLSR model.
Neural Network Approach to R&D Project Termination
LIU Quan, GUAN Jian-cheng
2000, 26(4): 461-464.
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In order to help manager to make termination decision for the ongoing R&D project timely and correctly, the authors review and compare the theory and methodology of termination decision from the literature. Furthermore, we discuss the considerable importance to identify attributes of an ongoing R&D project. To identify attributes of an ongoing R&D project, the authors examine characteristics and scopes of neural network. Thus, the feasibility of neural network, which is possibly used in R&D project termination decisions, is further explored. On the basis of the theory and methodology of neural network, this study attempts to develop a mode identification method to make R&D project termination decisions in an effective manner. Finally, the validity of the proposed method is verified by an example. The result shows that the method is both simple and practical.
Evaluations of Interface Management by Gray Cluster and Empirical Study
GUAN Jian-cheng, ZHANG Hua-sheng
2000, 26(4): 465-469.
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The interface management between R&D/Marketing and R&D/Production is essential to commercialization of S&T achievements and success of technological innovation. It is, however, very difficult to evaluate levels of the interface management for an enterprise during its innovative process. The paper presents a gray cluster analysis with intervals, in order to assess the integration of interface management for the concerned firms. The proposed method, which can address the critical problems faced, has several advantages. First, it can quantify the impact factors on the interface and identify different perceptions of importance about the same factor between the two sides of the interface, too. It is also more facilitating to decide the evaluating standards by using the analysis technique than before. The interface between R&D and marketing in some typical firms is then empirically assessed to test the validity of the method. The results indicate the proposed analytic tool is indeed effective.
Identification of Optimal Subspace from PLS Regression
WANG Hui-ping, LIU Qiang, TU Yong-ping
2000, 26(4): 473-476.
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Partial least-squares regression, a novel approach for multivariate analysis, is widely used for modeling a multi-collinear variable data set, with improved model accuracy and reliability based on building a subspace with most explanatory ability to the data set. In this paper the factor analysis method is presented to transform orthogonally the optimal subspace, which is obtained from partial least-squares regression. The transformation can identify each factor in a meaningful way but does not change the results of partial least-squares regression model. Therefore, the physical meaning of the optimal subspace of partial least-squares regression can be illustrated. A case study demonstrates that the original variable set is divided into several variable groups after the orthogonal transform, each of which is corresponding to a new factor in the subspace such that its explanatory ability is improved.
Optimization Model for Production Planning with Information Feedback
LIU Chen-yong, ZHOU Hong
2000, 26(4): 477-480.
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The concepts of feedback parameters and feedback constraints are brought forward.The optimization model for production planning with information feedback is proposed and compared with two traditional approaches,liner programming and heuristic method.The results show that the production planning obtained with the optimization model for production planning with information feedback can assure the production on process in balance , make full use of the production capacities and resource in the enterprise ,reduce the cost and improve the profit. Hence it is superior to the others.The model has been used in decision support system for production management,and can be applied to MRP-Ⅱand ERP as well.
Parameter Estimation Based on LMI with Bounded Data Uncertainties
YANG Zhi-hui, MAO Jian-qin, WEI Ke-hui
2000, 26(4): 481-484.
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A class of parameter estimation problem is put forth with bounded data uncertainties, and solved it based on linear matrix inequalities (LMI). The uncertainties are expressed by a priori bounds on perturbations of coefficient matrix and its elements, which covers some situations explored in [3] and [4] and is a more general one. Thus, the proposed method, which based on LMI, is simple, practical, and general. We analyzed the solution, and discussed several special cases, such as selected columns are subject to perturbations. Simulation results give more details of the proposed method.
Structure Characteristics and Piezo-Resistance Effect in Hydrogenated Nanocrystalline Silicon Films
CHEN Chen, HE Yu-liang, QI Xiang-lin
2000, 26(4): 485-489.
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A study of electrical properties of P doped hydrogenated nanocrystalline silicon films (nc-Si:H) indicate that the room temperature dark conductivity σ is in the range of 10-1-101S·cm-1,two magnitudes higher than that of undoped nc-Si:H films. We also found the relationship between doping concentration Np and σ, that is strikingly similar to the pc-Si films. The conductivity activation energy ΔE of P-doped nc-Si:H is (1-3)×10-2eV, lower than the undoped nc-Si:H films. Otherwise, we investigated the piezo-resistance effect of P doped samples. Compared with undoped nc-Si:H samples, the piezo-resistance coefficient K is lower. We discussed the effect of hydrogen content to the K values.
Study on Reliability Simulation Testing System for Embedded Software
LIU Bin, GAO Xiao-peng, LU Min-yan, RUAN Lian
2000, 26(4): 490-493.
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The reliability simulation test method and the test environment for embedded software is researched. The architecture of the reliability simulation testing system for embedded software is given. Based on the architecture,the paper analyzes the characteristics of the reliability simulation test method for embedded software , and discusses the following subjects such as simulation test method,test environment configuration, key technique , and feasible solutions. Especially, the paper proposes a new idea to create the test cases for embedded software reliability testing.
Study of Shock Response Spectrum Control
YUAN Hong-jie, LI Chuan-ri
2000, 26(4): 494-496.
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At present, The technique of the control of the shock response spectrum is popular on shock test.The method of sums of exponentially decaying sinusoid components to match acceleration shock response spectrum is described by this paper. The acceleration,velocity,and displacement characteristics of the resulting shock waveforms can meet limitations imposed by the physical capabilities of vibration exciters, And hence The resulting shock waveforms can be reproduced on a shaker using shock vibration control techniques,The principle of reproducing shock waveforms on the shaker is discussed, The estimation and update of transfer function is discussed, The effect of duration of the drive waveform is also analyzed.

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