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1998 Vol. 24, No. 3

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Research of Modificating Unsaturated Polyester Resinby Copolymerizing Bismaleimide
Zhang Fusheng, Zhuang Yan
1998, 24(3): 249-252.
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The modification of an unsaturated polyester(UP) resin by copolymering a second co-reactive monomer as thermosetting bismaleimide(BMI) was studied. The resulting inter-crosslinked network showed an obvious enchancement of the glass transition temperature ,elastic modulus and strength. FTIR is used to investigate the c=c double bond conversion of the various reactive species in the copolymerization.The conversions are 70.83%,95.64% and 97.69%for UP resin ,styrene and BMI respectively.It was shown that BMI is strongly accelerated in the curing reaction of the UP resin. SEM analysis performed on the fracture surface of the various investigated resin system showed that there was no evidence of phase seperation.
Study on Microstructure and Aabrasive Resistance of Laser Cladding TiN Surface Alloyed TC9
Chen Chinan, Su Mei
1998, 24(3): 253-255.
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Laser surface cladding with TiN is utilized to improve the wear resistance of TC9 titanium alloy. Microstructure and phase constitution are studied by using SEM, EDX and XRD. Microhardness measurements and wear experiments without lubrication are performed to test the properties. The experimental results show that there is a strong bonding between the laser surface cladded layer and the substrate. TiN dentrites of different size and unmelted TiN particles exist in the laser surface cladded layer. Unlubricated sliding wear test shows that wear resistance of TC9 alloy laser surface cladded with TiN is improved noticeably compared with that of the substrate.
Computation of Electromagnetic Scattering Character fromComplicated Object Partially Coated with RAM
Li Jianhui, Su Donglin, Li Qing, Lü Shanwei
1998, 24(3): 256-259.
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The general formulas of the scattering field when the parallel and vertical polarization plane wave incident on the objects are given.The method of determining the strong scattering source of complex objects,and the effective method of selecting region coated with radar absorbing material(RAM) are presented.At the same time,the electromagnetic field scattered from three dimension complex objects partially coated with RAM is analyzed.At last,the calculated results are given,and the validity was tested.The method improves the calculation accuracy of complex RCS,and is fit for the engineering application.
Scattering Character from Perfectly Conducting Cylinder Coated with Plasma
Huang Xingzhong, Lü Shanwei
1998, 24(3): 260-262.
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The general formulas of the scattering field and scattering parameter definition when the parallel and vertical polarization plane wave respectively incident on the cylinder are given.The radar scattering cross section(RCS) of the metal cylinder coated with undensed plasma,densed plasma and loss material are numerically analyzed.Bistatic RCS of conduction cylinder is analyzed comprehensively and each factor affecting its RCS is also analyzed.Some numeric result and useful conclusion obtained are given,which offers useful reference for studying scattering mechanism furtherly from reentry.
GPS Positioning Algorithm Based on Least Square Recurrence Estimate
Chang Qing, Liu Zhongkan, Zhang Qishan
1998, 24(3): 263-266.
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This paper proves,in theory,that GDOP decreases as the number of satellite increases.Then the recurrence algorithm of GDOP and positioning solution is proposed based on the existing positioning software.This algorithm chooses the fifth satellite which enables GDOP5 to be minimized from the surplus visible satellites and make use of the positioning information provided by this satellite to correct the four-satellite positioning solution.Finally,the method for choosing the fifth satellite is given.The purpose of the algorithm is to exchange the least amount calculation for the effective improvement of the positioning precision.
Method to Improve Performance of Estimation of DOA Using Toeplitz Characteristic
Si Deyi, Le Qiang, Shen Shituan
1998, 24(3): 267-269.
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A method is proposed to make the estimation of the covariance become Toeplitz matrix using the Toeplitz characteristic of covariance matrix . It can improve the performance of estimation of DOA in the low SNR and shot snapshot , and dose not add complex multiplication. It is used in the MUSIC algorithm and the PRO-ESPRIT algorithm . The numerical simulation results show that the spatial spectrum and the depth between wave crest and trough are increased in the MUSIC algorithm , and the standard deviations of the estimation of DOA are decreased in the MUSIC algorithm and the PRO-ESPRIT algorithm in the low SNR .The method can be used in other DOA estimation algorithm .
CGF Terrain Representation and Reasoning with Contour Map
Wang Changjin, Le Ningning, Wang Xingren
1998, 24(3): 270-273.
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A digital contour map is used for terrain representation of Computer Generated Forces(CGF) in Distributed Interactive Simulation(DIS).The method of contourline terrain representation and reasoning is presented.After discussing the determination of terrain and intervisibility,and etc.,it is shown that this approach is practical and it's reasoning is simple.This approach has an advantage in easily acquiring and editing the map data.This CGF contourline terrain representation and reasoning is better than the polyonal,especially in the simulation of navy or air combat in wide range.
Calculation of Mission Reliability of Fault-Tolerant Standby Storage System
Jin Hong, Zhang Hongyue, Li Peiqiong
1998, 24(3): 274-276.
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The calculation of the mission reliability of a fault-tolerant standby storage system is discussed.Whether the fault detector,switch and the standby component are reliable or not affect the reliability of the fault-tolerant system directly.In order to evaluate its mission reliability correctly,the detector and switch which have a certain false detection probability and false switching probability are considered in this paper.To our knowledge,Markov model is the main tool to deal with this problem which is seldom discussed in China.Here Markov theory is applied to determine the system states and their corresponding state transfer matrix,by which the problem of calculating fault-tolerant reliability can be solved.Moreover,the calculation models of some relative error probabilities are discussed.
Method of Conditional Filtering for Stochastic System with Distributed Parameters
Wu Sentang
1998, 24(3): 277-278.
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In the case of the stochastic system with distributed parameters exist observation noise in its control input and its control output, the conditional filtering method of the stochastie system with distributed parameters is presented.While the optimum estimation of system state is obtained, the optimum estimation value of unknown control input can be obtained at the same time, the algorithm with the structure's similarity of system state and control input estimated device, the algorithm provides a new approach to reduce value computatioonal complexity of filtering algorithm of distributed parameters system, and has a wide application prospect in enginerring practice.
Design and Simulation of Integrated Flight/Vectored Thrust Control System
Shen Gongzhang, Hao Jiankang, Peng Kemao, Zhang Minglian
1998, 24(3): 279-282.
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The design of the flight control system with the vectored thrust is discussed. The flight state variables are separated into the fast and the slow state variables based on their transient responses. Nonlinear dynamic inversion is adopted to design them separately. The simulations of the flight of the fighter at high angle-of-attack and the attacking process of the designed flight control law combined with the integrated flight/fire control system on the 6-DOF aircraft equation are made. The results prove that the integrated flight/vectored thrust control system can implement the flight at high angle-of-attack and meet the requirement of the integrated flight/fire control system. The adopted method is promising in the engineering application.
Design of Integrated Flight/Vectored Nozzle Control System at Take-Off
Peng Kemao, Shen Gongzhang, Wen Chuanyuan
1998, 24(3): 283-286.
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Four kind of configurations are adopted to analyze the improvement of the vectored nozzle control on the flight performances at take-off,where the baseline aircraft is modified to add the horizontal canard or/and vectored nozzle. The models of the aircraft longitudinal motion at the different progresses of the take-off are established. The system controllers of the integrated flight/vectored nozzle control system at take-off are respectively designed according to the configurations. The simulations of the aircraft at take-off are made on the established models and nonlinear propulsion system model. The results prove that the designed system controllers are available to implement the take-off mission. The major specifications prove that the vectored nozzle control can significantly improve the flight performances at take-off when appropriately coordinated with the aerodynamic control effectors.
DR Algorithms and Parameter Estimating in DIS System
Gong Guanghong, Wang Xingren
1998, 24(3): 287-290.
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A method of position/orientation estimation called dead reckoning methodology has been playing an important role in DIS system,which is employed to simulate synthetic warfare environment simulation and military training exercise containing multi-force and multi-platform. First,common DR algorithms and their characteristics are introduced,and then a new valid DR algorithm is presented in this paper. This algorithm is based on two-order transfer function idea and has two feature parameters,which are natural frequency and damper coefficient. The two feature parameters can be real-time calculated by previous state values of last three frames. Last of all,the comparison between the new DR algorithm and common DR algorithms is described and the simulation result is given at the end of this paper.
Fuzzy Adaptive Controller Based on BP Algorithm
Zhou Changyu, Wang Wenshun
1998, 24(3): 291-294.
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When we apply fuzzy control to a unknow process,we can't find good control rule because of we don't know it's characteristics.This paper based on an analytic structure of fuzzy controller put forward a method,which combines fuzzy controller and neural network.Use neural network to make identification of system and provide necessary message for LS.Regard control object as an output part of network.Based on message provided by neural network adopt BP algorithm to modify experience rule.Thus,improve dynamic process of fuzzy control system.Simulation results indicate:this controller has better adaptability for variety of model parameters and can modify original system control rule,makes a output follow system input tracks faster.
Analysis Failures on Attenuating Vibration of Squeeze Film Damper
Liu Fangjie
1998, 24(3): 295-300.
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The meaning of study the failure of attenuating vibration of the squeeze film damper is detailed.First,the achievement in scientific research accomplished by J.W.Lund,E.J.Hahn,R.Holmes,R.A.Cookson and E.J.Gunter five academic groups for study the squeeze film damper in international is compendiously reviewed．The talks about the failure on attenuating vibration of squeeze film damper for them are concluded．Specially the reasons of failure of squeeze film damper caused by its not proper design are emphalically point out．The phenomena of failure are not going across the critical speed of a rotor,and causing the rotor bearing system to produce a bistable characteristic.The methods to avoid the failure have:to adjust the relationship between the radial clearance and the unbalance,applied the full film,to use flexible bearing housing and limited the unbalance.The conclusion of this paper is if the design parameters are not properly selected is not only unable to attenuate vibration but also cause the operation of rotor system unstable or unable to stride over critical state.
Mathematical Analysis on Combat Efficiency of Military Aircraft
Wang Yinsheng, Wu Zhe
1998, 24(3): 301-303.
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The mathematical methods of theoretical analysis to determine some unknown or omitted parameters in combat efficiency theory of military aircraft based on the present models of combat efficiency of airforce equipment and the actual data of military operation are introduced in order to develop or improve the theory with practical work and some new concepts, such as combat efficiency and actual efficiency among airforce mission.For example,the combat efficiency usually comes from academic research and could be also called appraisal efficiency or static efficiency.After modified with actual data of military operation of past records which also could be seen like actual combat efficiency,confrontation efficiency and dynamic efficiency.Through calculation and analysis it must be noted that the numerical value of actual combat efficiency is larger or much larger than the value of combat efficiency.
Optimization Aerodynamic Design for Transonic Airfoil
Yan Chao, Xie Lei, Li Yunxiao
1998, 24(3): 304-307.
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Computational Fluid Dynamics(CFD) and optimization technique are combined in this paper for the purpose of optimal aerodynamic design of transonic airfoil. In this method, 2-D Euler equations are numerically solved to simulate the flow around airfoil using finite volume method, then geometric conditions, optimization equations are implemented to modify the airfoil through shape functions. The two steps are iterated until optimal aerodynamic performance of airfoil is achieved under certain conditions. Two cases, both based on the original airfoil of NACA0012, are presented to show the efficiency of this method.
Correlative Parameter Estimated Method in Random Process of Fatigue Crack Propagation
Zhang Jianyu, Fei Binjun
1998, 24(3): 308-310.
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Lognormal random process model of fatigue crack propagation is usually used in the reliability and damage tolerance analysis.Basing on the model, a new method of evaluating the auto correlative parameter in usual stationary normal random process by the experimental data is established.By using this method, the value of the correlative parameter can be evaluated directly on the basis of the experimental data.At the same time, the confidence interval of the parameters is obtained by using Monte-Carlo method.At the end of the paper, a numerical example is given.In this example, a group experimental data of the specimens with fastening holes under pseudorandom spectrum loading, that obtained 237 data points, is used to determine the value of this correlative parameter.
Effects of Vortex Generators on Maximum Lift and StallAngle of Attack over Wings
Shen Xialing, Gao Ge, Liu Baojie, Yang Xiaoning
1998, 24(3): 311-314.
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The effects of locations and various cambers of small delta vortex generators on the maximum lift and stall angle of attack of wings are studied in the wind tunnel.The small delta vortex generators varied in cambers and locations are fixed on the wing model which has NACA 0012 of span 500 mm chord 250 mm.The test results show that when the delta generator is the optimum position on the wing,the maximum increase of the maximum lift coefficient and stall angle of attack of the wing may be obtained and that when the position of the delta generator is fixed,delta vortex generators of various cambers may be used to increase the maximum lift coefficient and stall angle of attack of the wing and their increments are not much difference.
Numerical Simulation and Optimization for Contraction Flow of Water Tunnel
Wu Zongcheng, Chen Yanqing, Wan Xi
1998, 24(3): 315-318.
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A numerical method and computer program for non-symmetrical contraction flow of a water tunnel are described in this paper, which use the finite volume approach to solve the unsteady Euler equation, the basic algorithm is the explicit predictor-corrector scheme of MacCormack. For several typical contraction curve, the three-dimensional flow field calculation is made, the wall pressures along the centerlines or corner lines at top or bottom and velocity distributions of exit section are obtained, the results are compared to choose the optimal contraction curve to meet the design needs. It is shown that this approach and program are valid for the three-dimensional contraction design.
Analytical Method of Solution on Delamination in Symmetrical Orthogonal Composite Laminated Beams
Wang Qizhi, Meng Qingchun, Zhang Xing
1998, 24(3): 319-322.
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Using the principle of superposition, the transverse loading state of a laminated beam with delaminations is divided into symmetric and antisymmetric states. Furthermore, the antisymmetric loading state is subdivided into the antisymmetric transverse loading state acting on a beam without delamination and the additional shear loading state which is applied along the delamination surfaces of the laminated beam. Therefore, the problem of delamination can be reduced to the analysis about the additional displacements and stresses which are caused by the additional shear loading. Then, a simple mechanics model about delamination is established. Finally, the analytical solutions of displacement and stress are determined by the theory of engineering beam. The stress intensity factor is obtained by the energy release rate method.
Research on Design Principles to CAD/CAM Geometric Platform Based on STEP/AP203
Ren Aihua, Wei Juxia
1998, 24(3): 323-326.
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The approaches and the design principles to the CAD/CAM geometric platform based on shared standard semantic models of STEP/AP203 in the CIMS environment are expounded in this paper. STEP gives the possibility of developing software component architecture in terms of object-oriented technology. Therefore, the more flexible and open properties can be provided by the CAD/CAM integrated system to meet requirement oriented changes. These properties are the key elements to support the future integrated manufacturing business and concurrent engineering ect.. A general purpose geometric platform frame which is independent of specific graphics systems is given in this paper. The frame is fit for different kinds of specific graphics systems. The advantage for the approaches shows that the software design of CAD/CAM is independent from specific graphics systems. Within the scope of some powerful graphics system, the CAD software can be run on these graphics systems by plugging the systems' APIs in the correspondent API (Applicatin Programme Interface) sockets.
Performance Gradient Estimation for M/G/1 Queueing System Using Nonstandard Analysis
Huang Hongxuan, Han Limin, Feng Yuncheng
1998, 24(3): 327-330.
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Estimating performance gradient is an important issue in the study of Discrete Event Dynamic Systems(DEDS). Because of discontinuous sample path, it is difficult to estimate performance gradient with respect to probability parameters by traditional perturbation analysis.A new kind of algorithm, which is based on Dirac δ-Function, is established by Nonstandard Analysis for M/G/1 queueing system performance gradient estimation with respect to a kind of probability parameter.Strongly consistency and asymptotically unbiasedness of new estimators are proved by means of integrating finite increment with infinitesimal one. New method uses special spline functions to approximate δ-Function in its implementation. It can estimate simultaneously sojourn time and busy period length gradient w.r.t probability parameter. Numerical results indicate that new estimators have lower relative errors and t-test value of unbiasedness.
Some Issues about Information System Integration
Liu Lu, Zhang Zhaohui, Yao Zhong
1998, 24(3): 331-335.
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Several issues in the information system integration are discussed,such as information integration,function integration,platform integration and human integration etc..A multiphase-based methodology for information system integration is presented,in which the integration is the goal of the system integration,functions integration is the base framework of the system integration,platforms integration is the technological basis of the system integration,and the human integration is the guarantee of the system integration.Based upon the practice of an airline integration information system,a multiphase-based methodology proposed in the paper has illustrated which possesses a theoretical guide for the system integration development.
Effective Measurement in Project Cost and Schedule Control
Wang Liwen
1998, 24(3): 336-338.
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Earned Value is the most important measurement in the project cost and schedule control. This paper describes the concept and methods of earned value,and its application in the project cost and schedule control. Then, this paper tells how to forecast the likely cost to complete the project,and intruduces the concept of S-curve. Using S-curve, it's easy to present that whether the project is under-or overspent as it progress, and if the project is ahead or behind schedule. At last,this paper describes the difference between the baseline complete cost and the budget. The baseline complete cost is one of the measurement of project control, while the budget is the expected cost which the owner of the project wants to pay. The difference between the two is the contingency.
Kinematic Inverse Problem and Stability of Wheeled Mobile Robots
Lu Zhen, Yan Biao
1998, 24(3): 339-341.
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Mobile robot can be regarded as the combination of a manipulator and a walking machine.It has more manoeuvrable and larger working-space.Thus,it is suitable for long-range operation both in the space and the ground.The most common used mobile robots are wheeled mobile robots(WMR).The wheeles lead to the non-holomotic constraints.In this paper,the non-holomotic constraints and kinematics geometry are analysed to formulate two solutions of the inverse-kinematic problems of WMR.Secondly,a method on controlling the self-motion of WMR is proposed to resolve the stability of the moving platform,which is verify by simulation.
Accuracy Analysis of Micromanipulator
Bi Shusheng, Zong Guanghua
1998, 24(3): 342-345.
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Two types mechanism of micromanipulator appeared in recent years. It is the serial mechanism and the parallel mechanism. They possess their respective strong and weak points. Based on the complementary law, one new type which is called Serial-parallel Mechanism is presented in this paper. In order to evaluate the effects of the structural parameter errors upon the pose accuracy, a vector arithmetic method is applied to establish the relations between the pose accuracy and manufacturing tolerances, actuation errors, and connection errors of two stages. The sensitivity parameters affecting the micromanipulator pose are discussed. And some results which are very useful to the design and manufacture of the micromanipulator are derived. The analysis method can also be used on the accuracy analysis of other type parallel or serial-parallel mechanisms.
Coordinate Transformation and Effective Velocity for One Class of Hydrodynamic Sliding Bearing
Yan Deyuan, Guo Jingjing, Zhang Xiaohong
1998, 24(3): 346-349.
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The differential equations of pressure for two moving surfaces hydrodynamic sliding bearing are deduced by transforming coordinate transformation method, and the concept of effective velocity is introduced. Then a simple and convenient method for engineering design of this bearing is presented. In case that other parameters keeping constant, improving effective velocity is an efficiency way to improve the bearing capacity of two moving surfaces hydrodynamic sliding bearing. As for two moving surfaces hydrodynamic sliding thrust bearing,carefully composing the directions of wedge and rotating direction of two moving surfaces is the key to improve the effective velocity.
Active Back-propagation Algorithm Based on Adjusting Error for Multilayer Feed-forward Neural Network
Luo Dehan, Chen Weihai
1998, 24(3): 350-353.
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The back-propagation (BP) algorithm was used as a learning algorithm in training multilayer feed-forward neural networks (MLFNN) in past years, and some improved BP algorithms have recently been developed to speed up MLFNN learning. However, the effeciency of these improved BP algorithms are limited due to ignoring the activity of adjusting error during training MLFNN. In this paper, an active back propagation (ABP) algorithm based on improved BP algorithm is developed for MLFNN trained. The ABP algorithm alters the adjusting errors of MLFNN during the network trained, according to the error tendency of the network, and aimed to enhance rapidity of the network trained. The paper describes experiments that compare the performance of ABP algorithm with improved BP algorithms. The experiment results have shown that the ABP algorithm gives more efficient than improved BP algorithm for MLFNN trained.
Structure Design for 7-DOF BUAA-RR Manipulator
Qian Xikang
1998, 24(3): 354-357.
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In order to avoid obstacles in task space, overcome interior singularities and improve the performance of manipulators, redundant manipulators have been thoroughly researched and developed. In the process of designing BUAA-RR 7 degrees of freedom, a complete set of principles and methods are proposed on design of mechanical structure, joint and parts. BUAA-RR 7-DOF manipulator is characterized by self-motion and overcoming joint limitations, which has a feasible and compact structure. BUAA-RR operates dexterously and reliably, and is able to avoid obstacles and overcome singularity. Practice verifies the feasibility of above principles and methods.
General Development Shell for Fault Diagnostic Expert System
Zhao Tingdi
1998, 24(3): 358-361.
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FDEST—The general development shell for non-real Fault Diagnostic Expert Systems(FDES) based on the reliability analysis methods is introduced in this paper,there are strong inference and good openness,it can apply to establish FDES for varied military materiel and civilian products.At first,the structure and functions of the FDEST is described,and then,the reasoning method based on reliability analysis method-Fault Tree Analysis(FTA):forwards and backwards inference logic,supporting three imprecise arithmetic about Bayes,Mycin,Fuzzy and four relationship of fault logic;object-oriented and rule representation of knowledge,the supporting multimedia interpretation engine and fault process model(text,image,voice and video);Applying object-oriented technique to design and implement the software:dividing objects(FDEST object,knowledge object and FDFS object),object communications and system interface etc.key technique is discussed.
Research on Comprehensive Application of System Engineering with Quality Function Deployment
Yang Duoming, Ruan Lian
1998, 24(3): 362-364.
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It is presented here that the idea on comprehensive application of System Engineering and Quality Function Deployment. A standardizing and programmable method is developed for determining requirements, making trade-off and finally, implementing these requirements, by means of System Engineering's fundamentals and process, and the frame of Quality Function Deployment. According to the process of practical work, the aim of "Customer the First" is reflected throughout the process, i. e. customer requirements basically drive the decision-making of the top policy-making team, determine the development and production of products. It provides scientific and measurable methods for decisions of the top-down managers by introducing the fundamentals and process of System Engineering to Quality Function Deployment. It is mainly introduced that the process and methods for the comprehensive trade-off of alternatives.
Preliminary Study on Arcjet
Liu Yu, Zhang Zhenpeng, Wu Hanji, Feng Xuezhang
1998, 24(3): 365-368.
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The two-dimensional axisymmetric subsonic-transonic-supersonic flow in an experimental arcjet thruster is simulated numerically using flux vector splitting method.The profiles of density,velocity,temperature,pressure and Mach number can be obtained by the computation.The computation grid and some computed results are given here.The test equipment such as power supply system,ignition system,propellant supply system,arcjet thruster,thrust measuring device and vacuum system are introduced briefly.Some working phenomena of the arcjet are observed and discussed.Three different kinds of instability appeared in the process of the experiments.Except some important parameters are measured,it is found that the operating stability of Argon is better than that of Nitrogen.
Numerical Simulation of Gas Mixing in Cross-flow
Xu Xu, Zhang Zhenpeng
1998, 24(3): 369-372.
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A time-split explicit TVD MacCormack algorithm is used to solve the two-dimensional N-S equations coupled with species diffusion equations.Both molecular and turbulent properties of viscosity,thermal conductivity and mass conductivity are calculated.In order to deal with the near wall separation of boundary layer,the low Reynolds number ｋ-ε turbulence model of Lam and Bremhorst is used in this procedure.A sample of plane cross-flow is used to test the reliability and accuracy of this method and the results show that this scheme can be applied to solve the problem of supersonic flow fields with gas mixing,the solutions are satisfactory.

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