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2002 Vol. 28, No. 2

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Algorithms for Surface Smoothing in Reverse Engineering
XI Ping, LIU Yong
2002, 28(2): 125-128.
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Surface smoothing is one of the important technologies of reverse engineering. This paper introduces a set of simple and useful algorithms for surface smoothing, including disposing error points, step smoothing, hand smoothing and automation smoothing, relationships among these algorithms and skills of using these algorithms in engineering are discussed in detailed. The feasibility of these algorithms are verified by their application in automobile engineering.
Study on Availability Analysis for Repairable System
KONG De-liang, WANG Shao-ping
2002, 28(2): 129-132.
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An availability analysis method for repairable system i.e. Dynamic Fault Tree Analysis(DFTA) was presented .To achieve high reliability and availability, redundant hardware and fault-tolerant software associated with dynamic process, time sequence, backup and failure recovery were adopted in the computer control system. Combing DFTA method and Markov model for repairable system, the dynamic process of a fault-tolerant system and the repairable process can be easily described. To calculate the equivalent failure rate, recovery rate and availability of top event of a complicated system, it is necessary to divide the system into several subtrees which can treated with Markov model. Recurrent, the availability parametes from top to down can achieve the availability analysis for the complicated system.
Effectiveness of Weaving Maneuver Strategy of a Missile
JIANG Yu-xian, CUI Jing
2002, 28(2): 133-136.
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Effectiveness of weaving maneuver strategy of a missile when it passes through a Missile-Defence-System(MDS) is addressed. A linearized planar engagement model is used. Closed form solutions for the miss distance of interceptor are derived from the case where the interceptor's guidance system is modeled by a first-order lag and the maneuver acceleration is unlimited. The miss solutions consist of two components, one is the transient, the other is the steady. The effectiveness is measured in terms of the break-defence probability over a set of engagements in which the weaving-durations are normally distributed around its desired value. Comparisons are made between the effectiveness of the transient and the steady weaving maneuver strategy .
Diagnose of Noise Fatigue Sources of a Helicopter
XIONG Jun-jiang, SHANG Da-jing, GUO Ai-min
2002, 28(2): 137-140.
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According to the wavelet transformation theory, a diagnose method for helicopters is established, including the order number of the wavelet decomposition and reconstruction, the noise signal decomposition, the separate signal reconstruction and 1/3 times frequency calculation. Since this method is with the high distinguishability for the low frequency signal and easy to reconstruct, it is fit for the noise signal separation of helicopter. By this method, the simulating noise signals are separated, and the separated signals are compared with the original signals, then it is found that the error between the separated signal and the original signal is lower than 2.3 percent. Moreover, on the basis of this method, the noise signals of the main rotor and tail rotor recorded from an AS350 helicopter are separated. It is shown that this diagnose method can be used to treat the non-stationary noise signals and separate the noise signals of the main rotor and tail rotor of the helicopter.
On the Analysis and Design Method of System Safety
XIONG Jun-jiang, LIU Bao-cheng, GAO Hong
2002, 28(2): 141-143.
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Based on the logical relations among its four major contents and a qualitative approach of system safety analysis and design, a new method for the treatment of a secondary failure, multiple failure and hidden failure in FHA and FMEA were proposed. Moreover, a mean rank method for the quantitative analysis of the base events was given by which the distribution parameter estimation formulas of the incomplete life data were derived. Finally, a more appropriate and accurate technological package for system safety analysis and design was established and applied to the system safety engineering of some airplane flaps successfully.
Prediction of Output SNR of Analog Optic Receiver
NI Nan, SU Guo-bin, LI Zheng, LIU Jian-sheng
2002, 28(2): 144-148.
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The amplitude-frequency characteristic of transmission function of APD GaAsFET analog optic receiver is usually nonideal in stopband. For this reason, the output Signal Noise Ratio(SNR) is often lowered. A method is proposed to analyze and calculate the lowered output SNR caused by the nonideal stopband characteristic. A quantitative relation is established using a low-band filter, which helps to improve the output SNR. The output noise formula of this paper is universally applicable to APD-GaAsFET analog optic receiver.
Methods of Integrating and Constructing Distributed Service Objects on Web
LANG Bo, HUANG Rui, LI Wei-qin
2002, 28(2): 149-152.
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It is very important to realize distributed service objects sharing on Web. CORBA and Java are the two supporting technologies in achieving this aim. This paper first puts forward the integration framework of distributed objects, with the idea of integrating CORBA, Java and Web together. Then, it describes several methods for constructing distributed service objects. These methodologies have been implemented and verified in an Internet/Intranet based integrated product management information system-NetPDIS.
A Taylor Series Method in Nonlinear Structural Dynamics
ZHAO Li-bin, ZHANG Jian-yu, WANG Shou-mei
2002, 28(2): 153-156.
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A Taylor series method for solving nonlinear structural dynamics problems where nonlinear items can be expressed as a polynomial with multiple variables was established. Different from existing methods, the Taylor series method satisfies governing equations in continuous intervals rather than at discrete time instants or in an average form. It solves dynamics problems through a sequence of recursions of Taylor expansion coefficients, without the necessity of solving simultaneous equations. The method was compared with the Runge-Kutta method through solving classical equations of Duffing, Van der Pol and the free vibration equation of two DOFs with quadratic nonlinear items. Numerical results indicated that the proposed Taylor series method is an excellent alternative for solving the aforementioned nonlinear dynamics problems.
High-Speed Image Acquisition Technology in Vision Inspection
ZHOU Fu-qiang, ZHANG Guang-jun
2002, 28(2): 157-160.
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A hardware implementation solution to image acquisition in vision inspection based on special video decoder SAA7111 and FPGA (Field Programmable Gate Array) was proposed. Interfaces among the image acquisition system, the computer and the font-end hardware processing system were successfully completed. Real-time image capturing and real-time image processing can be carried out simultaneously by using two-frame memory to store image data in turn.
Modeling and Control of Attitude Dynamics of a Space Station with Changing Structure
ZHAO Chao, ZHOU Feng-qi, ZHOU Jun
2002, 28(2): 161-164.
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First, a quasi-coordinate Lagrange method was employed to derive a mathematical model for a space station with a fixed structure containing flexible appendages. Then, taking into account the characteristics of structure change, a mathematical model for a space station with changing structure was generated through some appropriate transformations. On the above basis, a new decentralized variable-structure control algorithm was adopted to control the attitude and the flexible vibrations of the space station. Finally, the validity of the proposed scheme was verified by simulation results.
Stable Dynamic Mode of Inverted Pendulum Systems
YANG Ya, ZHANG Ming
2002, 28(2): 165-168.
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A concept about the dynamic mode of an inverted pendulum system when it is stabilized was proposed.The main dynamic modes of single,double and triple inverted pendulum systems with a single motor were concluded through analyzing their physical structure.On the basis that these systems can be stabilized successfully,relations between the coefficients of control law and the main dynamic modes were given.Experiments showed that these dynamic modes do exist and can be changed from one to another on line while an inverted pendulum system is stabilized.
Realization of an Air Combat Simulation System Based on DIS
ZHANG Shan, WANG Xing-ren
2002, 28(2): 169-172.
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To meet the need of evaluating fight efficiency of modern aviation weapon systems, a scheme of air combat simulation system based on distributed interactive simulation (DIS) was presented. With describing the architecture, the function divisions and the critical technology points of the scheme, an experimental example of air combat simulation using this system in a virtual simulation environment was introduced. The simulation results showed that the new scheme can develop much better simulation content, scale, reality and reliability than traditional methods and so displayed broad application foreground.
Influence of Streamwise Vortex on Turbulence Characteristics of Endwall Flow in a Compressor Cascade
LIU Huo-xing, CHEN Mao-zhang, JIANG Hao-kang
2002, 28(2): 173-177.
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To understand the influence of streamwise vortex on turbulence characteristics, the turbulence characteristics of flow in the corner region of a compressor cascade passage were measured by using a three-dimensional Laser Doppler Velocimetry system. The result indicated that the turbulence kinetic has a maxima in the core regions of the streamwise vortex and regions that interacted between the vortex and boundary layer, and the vortex or motion of the vortex has strong influence on the distributions of the Reynolds normal stress and shear stress.
Planning of Conflict-Free Motion for Multiple Robots in Structured Environment
ZHAN Qiang, CHOU Wu-sheng
2002, 28(2): 178-180.
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A real-time conflict-free motion planning method, i.e. priority based rules method, was proposed for multiple mobile robots conducting individual tasks in one structured environment. By taking the advantages of rules method and priority method, the present method can not only make robots avoid collisions and conflicts with other objects in real time, but also resolve the inevitable conflicts on line by virtue of the priority of these robots. The method can make the motions of multiple robots more robust and time-saving.
Structure Characteristics of Phosphorus-Doped Hydrogenated Nano-Crystalline Silicon Films
WANG Jin-liang, XU Gang-yi, WANG Tian-min
2002, 28(2): 181-185.
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B-and P-doped hydrogenated nanocrystalline silicon films (nc-Si:H) were generated by plasma enhanced chemical vapor deposition (PECVD). Effects of technique parameters on the microstructure and physical properties of the films were examined. The microstructure of the nc-Si:H films were studied by means of high resolution electron microscopy (HREM) and Raman scattering. The growth characteristics of doped nc-Si:H films were discussed based on theory and experiments. It was conclude that both the growth and the doping mechanism of doped nc-Si:H films are different form those of μc-Si:H and a-Si:H. In the growing process of nc-Si:H films, most of the inclusion atoms are inactive and present at grain boundarics.
Automatic Testing of Radio Altimeters by VXI Bus Technology
HUANG Zhi, LIU Zhong
2002, 28(2): 186-189.
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A scheme to test air borne equipments automatically was proposed based on VXI bus technology. The function and structure of the scheme were described by taking two common types of radio altimeters as examples. With introducing the key techniques involved in the scheme, an idea to improve the poor measurability of older radio altimeters by testing in different layers aided with hand tests was stressed. Finally, simulation tests were carried out to demonstrate the feasibility of the scheme, at a trouble locating rate of 85 pct and a trouble shooting rate of 60 pct for the altimeters.
Characterization of 3-D Surface Topography by Root-Mean-Square Wavelengt
LI Cheng-gui, LI Xing-shan
2002, 28(2): 190-193.
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Based on fractal geometry theory, a root-mean-square(RMS) wavelength method was proposed to quantitatively evaluate a 3D stochastic surface topography, by means of the surface spectral moments. Through DFT of the profile measured by a Talysurf-10 contact stylus instrument, we obtained the power spectrum and thefractal dimension of the profile. Further, the zero and 2nd order spectral moments of the profile and the surface were obtained. Using these parameters, the evaluation of RMS wavelength was conducted. By experiments for ground samples, the validity of the present method was confirmed.
Study on Automatic Selection of Current Images
SU Hui-min, GAO Jian-hong, CHEN Zhe
2002, 28(2): 194-197.
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Automatic selection of Current Image (CI) is a key technology for automation of scene matching navigation system. An algorithm for automatic selection of CI based on 3-layers BP net integrated with Sobel template and on neural network was proposed. The simulation results indicated that the algorithm is simple in structure, short in time, and highly accurate in image classification. By analysis of testing samples, BP parallel structure was shown to be achievable in real time implementation. As tested by Least Square and Bayes Scene Matching algorithms, the current image could reach a final precision higher than 0.5 pixel by means of BP net automatic selection algorithm, simple Scene Matching and accurate Scene Matching.
A Method to Simplify Fuzzy Logic System Structure Based on Rule Sensitivity
SUN Duo-qing, HUO Wei
2002, 28(2): 198-201.
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A method to simplify fuzzy logic system (FLS) structure was presented based on rule sensitivity. With introducing the concept of rule sensitivity, a new function was constructed and added into objective function to get a penalty function.In this way, a new performance index was obtained. Then, fuzzy logic system parameters were modified by optimizing the performance index. On the above basis, as many as possible sensitivities can be approximated to zero, while keeping outputs of the fuzzy logic system approximate to the desire ones. Finally, the fuzzy logic system was simplified by eliminating those rules with approximately zero sensitivities. The efficiency of the method was verified by simulation results.
Probability Damage Tolerance Analysis for Structures with Multiple Fatigue Cracks under Corrosive Environment
ZHANG Jian-yu, FEI Bin-jun
2002, 28(2): 202-204.
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Analyzing damage tolerance capability of structures with multiple fatigue cracks is an important task for the current assessing of structural fatigue reliability of aging airplanes. Based on probability damage tolerance theory for structures with multiple fatigue cracks under normal environment, a probability damage tolerance analysis method was established for structures with multiple fatigue cracks under corrosive environment. Using the model of logarithmic normal random variables to describe crack propagation processes, a reliability-life curve is presented for the structures with multiple cracks under corrosive environment, by considering the influences of the air during corrosion flight and the randomicity of crack propagation. A numerical example is given to prove the validity of the proposed method.
Study on Reliability and Mean Safety Coefficient of Components
JIA Xing-lan, LIU Wen-ting
2002, 28(2): 205-207.
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Based on stress-strength interference model, calculation formula of reliability and mean safety coefficients and their relationships are derived, corresponding to different distributions of stress and strength. Through practical calculations it is shown that, when the distributions of stress and strength are subordinated to normal distribution or others, the value of mean safety coefficients is about the same, though the value of reliability is quite different. It is safer for common components to use normal distribution, and it is more exact for very important components to use logarithmic normal distribution or Weibull distribution.
A Real-Time Image Transmission Scheme for Pilotless Aircraft
LIU Rong-ke, ZHANG Xiao-lin
2002, 28(2): 208-212.
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In the present scheme, an integer wavelet transform algorithm with modified set partitioning in hierarchical trees(SPIHT) coder was introduced to compress images. RS, symbol interleaves and trellis coded modulation(TCM) with multi-level quadrature amplitude modulation(QAM) were used to get an excellent forward error correcting ability. Orthogonal frequency division multiplexing(OFDM) scheme was adopted to improve spectrum efficiency and to decrease the average power. Bit error probability of the scheme was analyzed. The scheme was shown to possess higher compression rate, stronger progressive transmission ability, better numeration efficiency and more excellent error-resilience. Together with a performance of multi-path resilience and echo resilience, the above advantages make the proposed scheme compliant with pilotless aircraft conditions and feasible in practice.
A Multi-Mode Self-Adaptive Compression System for Color Images Based on Low Pass Filter
A Multi-, YANG Bo
2002, 28(2): 213-216.
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To overcome the drawbacks of available techniques in rapid real-time processing of color images, a color image compression system with higher processing rate and higher PSNR was put forward. It was found that with the rotation of YUV space, the chromatogram of an original image can be changed and so the compression effect can be improved. By comparing the effects of available interpolation methods on the quality of the last image restored, a two-dimensional digital over lap low-pass filter was used, combined with a monochromatic multi-mode self-adaptive compression method. By the computer testes, it was demonstrated that the proposed system has an obviously higher processing rate and PSNR than JPEG method within a fixed range of compression ratio.
Aeroengine Multi-Rotors Dynamics Optimum Design——Model and Tool
MA Mei, LI Qiang-hua, WANG Rong-qiao
2002, 28(2): 217-220.
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Based on detail analyzed an optimization model of rotor dynamics of aeroengine multi-rotors system, the sum of weight of normal subjection function of fuzzy sets theory was used to describe the distribution of multi-order critical rotor speeds versus multi in common used operating speeds, and to formulate an optimal objective function. According to the design specification and criterion, design variables and constraints which markedly influence the critical rotor speeds were chosen. Finally, an optimization mathematics model for rotor dynamics of aeroengines was formulated successfully. The integrated tool of aeroengine rotor dynamics was set up with VC+ +6.0, where Windows' I/O interface and visual post processing were implemented. The optimization algorithm was encapsulated to the form of DLL, MSC/PATRAN/NASTRAN was also integrated in it to optimize and analyze the deformation and stress for the rotor dynamics of aeroengine multi-rotors. Multi-rotors of an aeroengine were optimized and analyzed with this tool to examine its validity.
Factors Affecting the Precision of Heterodyne Interferometer
ZHAO Hui-jie, ZHANG Guang-jun
2002, 28(2): 221-224.
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Non-linear errors resulted from mis-installation of common-path heterodyne interferometer affect the precision of its measurement system. Four factors which can lead to such non-linear errors were identified,they are the frequency mixing, the phase jump of different metals to be measured, the tilt of the measured surface and NA of the aperture. Based on heterodyne and vector analysis theories, origins and modes of the frequency mixing error and phase jump error were analyzed. On the above basis, procedures to improve the accuracy of the measurement system were suggested. It was demonstrated that the precision of the laser heterodyne measurement system can be improved to nanometer orders.
Decoupling Control of Aircraft Environmental Control System with High Pressure Water Separation
HE Jun, ZHAO Jing-quan, YUAN Xiu-gan
2002, 28(2): 225-227.
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Aircraft environmental control system(ECS) with high pressure water separation is a representative complex coupling control system of MIMO. Flight-tests proved that the controlling means with conventional PID control could not refrigerate the electronic equipment and the cabin satisfactorily. An attempt was made to use the controlling means of output feedback and static decoupling to improve the actual aircraft ECS. Through computer simulation, it was demonstrated that the improved aircraft ECS can satisfy the system design demands.
Electromagnetic Compatibility Analysis of Plane Antennas
SU Dong, WANG Dong, WANG Ming, SUN Cong
2002, 28(2): 228-230.
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On the assumption that a cabin and a horn antenna were under the bottom of an airplane, FDTD method was applied to analyze the antenna patterns which are generally affected by the body of the airplane. By adjusting the relative positions between the body and the antenna, some interesting results were obtained, which are suggested to be useful for a reasonable distribution of the plane antennas.
On the Convergence of Finite Element Method with Different Extension-Compression Elastic Modulus
LIU Xiang-bin, MENG Qing-chun
2002, 28(2): 231-234.
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For finite element method with different extension-compression modulus,this paper discusses the influence of modulus of elasticity in shear on the convergence of numerical calculation, and puts forward a method relating not only the sign but also the dimension of the principal stress to the modulus of elasticity in shear. On the above basis, a factor η is proposed to accelerate convergence. By using this η in the numerical calculations of different modulus problems, it is found that the convergence velocity can be obviously accelerated.
Design and Research of High-Lift Mild-Stall Airfoils
KONG Fan, HUA Jun, XIANG Jin, ZHANG Zhong
2002, 28(2): 235-237.
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Design research of high-lift, mild-stall airfoils (BUAA-K1/BUAA-K2) was conducted in order to investigate their design strategy, methods and technology for a long-endurance aircraft. Wind-tunnel experimental results indicated that, while keep satisfactory aerodynamical features of high lift and mild stall, the maximum lift coefficient and the maximum endurance factor of a wing with BUAA-K1/BUAA-K2 high-lift, mild-stall airfoils can be increased respectively by 15 percent and 25 percent, relative to that of a wing with the well known GAW-1/GAW-2 airfoils.
Numerical Simulations of the Combined Effects of Atomic Oxygen and Ultraviolet on Polyimide
GAO Shao-lun, SUN Bing, ZHU Cheng-min, ZHOU Ding
2002, 28(2): 238-241.
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Based on a mathematical mode proposed by the authors to describe the physical interactions of atomic oxygen and ultraviolet with polyimide, numerical simulations of their combined radiation effects on polyimide with and without coated layers in Low Earth Orbit (LEO) and ground experiment environment were conducted. The results are consistent with the Long Duration Exposure Facility (LDEF) results, providing a valuable reference for the design of spacecrafts.
An Approach-Search Algorithm Used in GPS Single Frequency Kinematic Relative Positioning
YU Wen-bo, GAO Guo-jiang, ZHAO Yan
2002, 28(2): 242-244.
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To compensate the low reliability of normal search algorithm of Real Time Kinematic positioning(RTK) technology, an approach-search algorithm is proposed. This algorithm is based on a set of double difference equation of each epoch. By decomposing these equations, this real-time algorithm can integrate the merits of approaching and searching methods, and so can be used to solve the problem of ambiguity resolution in difference kinematic relative positioning with GPS single frequency carrier phase. Real test shows that the ambiguity can be accurately determined in 2~3 minutes with the present algorithm.
A New Algorithm of Multi-Shadowed Projective Area and Its Application in Fighter Aircraft Vulnerability Analysis
XU Yuan-ming, LONG Wei, WANG Yong
2002, 28(2): 245-248.
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An accurate surface model for an aircraft and its components was constructed by using B-spline theory. The model can be discretilized into triangle surface elements, relationships among geometrical elements were represented with the improved winged-edge structure. Based on inclusion-exclusion principle of set theory,a new algorithm to calculate the whole projective area was put forward to those overlapped complex geometrical objects in any direction. The algorithm has been used successfully in fighter aircraft vulnerability analysis. Applications showed that the algorithm is stable,reliable and accurate.

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