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2000 Vol. 26, No. 3

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Numerical Simulation of Temperature Field for Investment Casting Solidification Process
WANG Gui, YANG Li, ZHOU Tie-tao
2000, 26(3): 249-251.
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After studying the specific property of the investment casting , the 3-D numerical simulation of temperature field based on the finite difference method (FDM) for the solidification process of investment casting has been developed by dealing mold/environment boundary and riser/ environment boundary condition with convection and radiation to improve old modeling. The numerical simulation of temperature field and shrinkage defect prediction for a valve casting, which was involved in 4 kinds of casting processes, were carried out. The good agreement has been obtained between the numerical simulation and the experimental result verification. Based on the numerical simulation result, the casting process of the valve for practical mass production has been set up.
Lossless SAR Image Compression Using Integer to Integer Wavelet Transform
WANG Zu-lin, ZHOU Yin-qing
2000, 26(3): 252-255.
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Three advantages of wavelet transform constructed with lifting scheme are introduced and then invertible wavelet transform pairs of several integer to integer have been given. After discussed the features of SAR image, a method for lossless compression of SAR image by means of integer to integer wavelet transform has been presented. The advantages of the method are fast in-place calculation and progressive transfer. The experimental results for ERS-1 single-look SAR images and IEEE standard images show that the method is slightly better than DPCM, and only one decomposition level is needed to compress SAR image and more levels are not necessary.
Multifractal Spectrum and Calculation
WANG Zu-lin, ZHOU Yin-qing
2000, 26(3): 256-258.
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Multifractal theory is an effective tool for the singularity processing of signal, but only a few special sets have analytic multifractal spectrum expression. The calculation of multifractal spectrum is important and difficult. This paper introduces one of the formal system of multifractal theory in brief and presents an approach to calculate the multifractal spectrum of general sets. The approach makes use of the dynamic link data structure and decreases greatly the demand for memory. By means of the approach , the multifractal spectrum of Cantor set is calculated. The result is in accordance with the theory analysis and shows that the presented algorithm is valid.
Designing Simulation of RF Low Noise Amplifier
LIU Jiu-wen
2000, 26(3): 259-262.
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A design approach of low noise amplifiers (LNA), which are employed in the receiving terminals of radio frequency integrated circuits (RFIC), based on HP's EESOF simulation software is studied. In this design example, a HP's GaAs FET (HP ATF21186) is applied. The required satisfactions are: entire gain of LNA should be larger than 33dB, noise figure should be less than 2.0, and input and output standing wave should be smaller than 2.0. Since the stability of ATF-21186 is not good enough and also the above design satisfactions must be required, the study is focused on an optimized design scheme to obtain a high stability, lower noise figure and better input/output matching. The design is done first in a equivalent lumped circuit model and then all lumped elements are implemented by planer circuit, which is required by integrated circuit. The simulation results of EESOF software show that the approach in this paper is accurate and efficient.
Study of Multipul-Target Telemetring System Scheme
CHENG Ji-kuan, CHEN Ling
2000, 26(3): 263-266.
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This paper firstly proposes the multipul-target telemetring scheme using DS/CDMA system on the basis of the requirement of the system ,then detailedly presents the operating principle and the key technology of the multipul-target telemetring system .In addition ,the block diagram of the system is shown .The capability of simultaneous measuring parameters of multipul-target is characteristic of the system , and the capability of anti-interference of the system isstronger than that of systems using FDMA or TDMA technology .Furthermore ,it can combine with the GPS technology to complete the tasks of telemetring and telecontrol simultaneously. In a word , the scheme of the multipul-target telemetring system is economical and practicable.
Study of the Channel Access Parameters for VHF Air-to-Ground Datalink
ZHANG Jun, FANG Xin, ZHANG Qi-shan
2000, 26(3): 267-269.
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The system throughput and the message transmission delay influenced by the channel access parameters under various channel access rules is studied in this paper. The analysis is based on the model of channel access state transition for VHF air-to-ground data-link and CSMA matrix analysis method. The channel access parameters include the updating rate of report, the message length, the detecting density, the date rate of data-link, the coverage of remote ground stations, the number of aircrafts operated by remote ground station. The simulation results show that these parameters have significant effects on the performance of VHF air-to-ground data-link. At the same time, valuable conclusion is obtained from the simulation results.
Intelligent Transport System and Its Informatics Model
YANG Dong-kai, WU Jin-pei, ZHANG Qi-shan
2000, 26(3): 270-273.
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ITS(Intelligent Transport System) is a new transport system evolved from the traditional traffic engineering. The research object of ITS is the spatial and time relationship of people, vehicle, road and environment which are named four transport elements together, and it is called transport information in broad sense. Firstly, the system frame is presented on the basis of introduction of international ITS research, and then it is proposed in the aspectof information technology that ITS is an information system where transport information is collected, transferred, processed and exploited. Informatics model is given too. Finally, the four basic elements about information technology in ITS are described.
Research on the Relation Between the Seeker's Handover and the Geometrical Position of the Missile and the Target
QU Jian-ming, MAO Shi-yi, LI Shao-hong
2000, 26(3): 274-277.
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A single error angle model of seeker’s pointing angle is proposed first, which is different from two error angle model in that it’s easy to analyzed the beam pointing error by just analyzing the single error angle. The optimal geomet rical position between the missile and the target at handover is derived in order to minimizes the pointing error by applying linear transformation, and the optimal geomet rical position at handover which minimize the Doppler frequency error is also obtained. The performance of handover is benchmarked by the probability of interception, which includes three parts, the probability of detection, the probability of the Doppler frequency falling in the bandwidth of Doppler filter and the probability of the target falling in the main lobe of the beam. The probability of interception is influenced by geomet rical position between target and missile, including the range and the line of sight. Finally asimple but typical situation is analyzed to illust rate the relation between the geomet rical position and the probability of interception.
Studies on Several Key-Problems of the Swift Target Acquisition in Array Radars
XU Bin, YANG Chen-yang, QU Jian-ming, LI Shao-hong
2000, 26(3): 278-281.
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Two key-problems,angle measurement and angle prediction, of the swift target acquisition in array radar are studied. Firstly, from the respect of required beam arrangement, discrimination feature and the performance of angle measurement, the two algorithms named amplitude-comparison monopulse-like algorithm and average weighted with amplitude algorithm, for measuring the target-s angle with array radars are studied. The method for nonlinear adjustment when the average weighted with amplitude algorithm is applied is posed. Then, the algorithms for predicting the target-s angle with tracking filters are analysed. A simple decoupled filter named SDF is presented. At last, these algorithms are tested in a simulation system for array radar.
Effects of Stability of Antenna Pointing on Spaceborne SAR Imaging Quality
HUANG Yan, LI Chun-sheng, CHEN Jie, ZHOU Yin-qing
2000, 26(3): 282-285.
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The stability of antenna pointing is researched from the viewpoint of the effects of antenna pointing instability of spaceborne synthetic aperture radar(SAR) on image quality. Based on uniformity weighting antenna, the location and amplitude of the paired-echo resulting from instability of antenna pointing are derived in detail. And the effects of paired-echo on peak sidelobe ratio and integrated sidelobe ratio of impulse response function are analyzed. Moreover the Doppler center frequency error due to instability of antenna pointing is studied. According to the offsets of SAR imaging dependant on the Doppler center frequency error, the required stability of antenna pointing is given. At last the computer simulation is made to verify the analysis.
Modal Technique in Time Domain for the FDTD-Diakoptics
SU Dong-lin, Lü Shan-wei, ZHANG Qi-shan
2000, 26(3): 286-289.
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A modal technique in time domain for the FDTD-Diakoptics is proposed. Based on modal functions in time domain, which are formed according to geometries of structures, a microwave circuit is equivalent to a multi-mode circuit. Full-wave analysis method is used to get the time domain responses ofthe multi-mode circuit. Then Fourier transfer technique is employed to obtain the impulse responses. The multi-mode circuit is equivalent to a multi-port circuit and the FDTD-Diakoptics is applied to analyze whole circuit. In this paper, some rules about the excitation of full-wave analysis are given and also the bandwidth for inverse Fourier transfer in calculating impulse responses of time-domain modes are discussed. Finally the approach is verified by a waveguide bandpass filter. The results show good agreements with FDTD results.
S-Band MMIC Amplifier Design Using HEMT
YANG Xue-bin, Lü Shan-wei, SU Dong-lin, WANG Liang-chen
2000, 26(3): 290-292.
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The design procedure of S-Band microwave monolithic integrated circuits (MMIC's) amplifier using high electron mobility transistors (HEMT's) is proposed. The topology of the circuit designed is taken into account in order to guarantee the stability. A 200Ω resistance is parallel with the drain port of HEMT. It lowers the gain and enlarges the noise of amplifier but ensures that the amplifier is absolutely stable. Simulation results by Libra2.1 show that the gain in 2~3GHz is 14.2dB, gain ripple is smaller than 0.4dB and the noise figure is 2.7dB. These parameters satisfy the practical requirement.
Analysis of Mutual Coupling of Superstrate-Loaded Cylindrical-Rectanular Microstrip Antennas
LIU Zhang-fa, Lü Shan-wei
2000, 26(3): 293-295.
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The mutual coupling between microstrip antenna elements has affected the performances of microstrip arrays, on the other hand, substrate cover or superstrate-loaded on microstrip arrays is necessary to prevent the damage of nature or man made. The effect of substrate cover should be considered when we design conformal microstrip antenna and arrays. This paper proposes an analysis and computation of mutual coupling of superstrate-loaded cylindrical-rectangular microstrip antennas fed by coaxial probe by using rigorous full-wave method. The calculation results about mutual coupling of E- and H-plane are given. The variations of the mutual coupling with curvature of cylinder, the spacing between microstrip elements and frequency are discussed. The coupling with different grounded dielectric substrate and superstrate are analyzed simultaneously.
Two-Dimensional Angles Estimation of Wide-Band Signals with Spatial-Temporal DFT Projection
SI De-yi, SHEN Shi-tuan, LIU Rong-ke
2000, 26(3): 296-298.
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A new method of estimation two-dimensional angles of wide-band arrival signals is presented with spatial-temporal DFT projection. The sensor array is consisted of three coplanar uniform linear arrays (ULA). For every ULA, the wide-band signals are sampled in spatial and temporal, then 2-D discrete Fourier transform is carried out. A projection operation on 2-D representation of wide-band signals is applied in the spatial-temporal frequency domain. The direction cosine relative to the ULA axes is estimated by MUSIC algorithm. Using the direction cosines relative to three ULA axes, the correct pair is obtained, then the azimuth and elevation are estimated. The method has the advantages of projection method that does not require any a prior information about sources and does not require transformation matrices and has good performance at low SNR, and does not require 2-D spectrum searching. Simulation experimental results are presented demonstrating the capabilities of the method.
Application of GPS/INU/GIS Integrated Location and Navigation Technologies in Intelligent Transport Systems
ZHANG Fei-zhou, FAN Yue-zu, SUN Xian-fang
2000, 26(3): 299-302.
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The basic idea of intelligent transport systems(ITS) is introduced in this paper. GPS/INU/DM integrated navigation & location technology and its application in ITS are described. In addition, several technical measures to increase integrated navigation & location precision and reliability are presented. This technology combines satellite navigation, inertial navigation with information technologies, and has all-direction, 24 hours standby and non-shadowed characteristics. The ‘automation’ of transportation management and the ‘intelligence’ of vehicular driving will be realized through using of integrated navigation & location technology. Integrated navigation & location technology has better practicing value and widely prospect.
Research on Coding of Road Information in ITS
SHI Yan-shan, WANG Ke, FAN Yue-zu
2000, 26(3): 303-306.
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The code of road information is analyzed, based on the data provided by a model of the traffic volume. The method to compress data is equivalent conversion of the initial source, so the probability distribution of the equivalent conversed source becomes more sequential with less entropy value and greater compression ratio than those of initial one. When being transmitted, the instantaneously decodable code could be coded via huffman-algorithm in order that the average length of variable length prefix code (VLPC) is closed to the entropy value of the source. The result shows that the correlation of traffic volume at a cross is more than that in a street as well as in whole a city. Its achievements can be applied in ITS to communicate the road information.
Consideration in the Electromagnetic Design of Brushless DC Motor for Flight Control
ZHU Yao-zhong, WANG Zi-qiang
2000, 26(3): 307-310.
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Development of the electromechanical actuation system for use in primary flight controls is one of the major technologies in the path to an all-electric airplane. Brushless DC motor(BLDCM) is the key in this system. In BLDCM designs, the use of samarium cobalt magnet can significantly reduce motor mass and increase efficiency. Such motor output of a high torque has a low rotor inertia, and quick responsibility.The machine volume is mainly limited by heating and a rise in temperature which results from the losses in the stator, it is independent of magnetic energy of PM materials. On the other hand, the use of pulse width modulation(PWM) inverter for BLDCM leads to a high increase of core loss. This paper presents the major electromagnetic factors of BLDCM, taking into account PWM inverter source, specification, power/mass and peak torque/rotor inertia etc.
Stabilizing Triple-Inverted Pendulum Using Computer
YANG Ya-wei, ZHANG Ming-lian
2000, 26(3): 311-314.
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Personified intelligent control idea based on the physical model of system is proposed in this paper.Qualitative control law is acquired through the qualitative analysis of system model.The personified intelligent idea is applied to adjusting the control law by observing the dynamic behavior of system on line.The mechanical properties of system and the physical properties of motor are considered synthetically in designing feedback control law.An intelligent damp term is added to the control law due to the system behavior and all feedback gain coefficients are given.A nonlinear control law is established and the triple inverted pendulum with a single motor is controlled steadily using computer.Another triple inverted pendulum with different structure is also stabilized successfully by the same way.The experimental datum curves are attached.
Neural-Network Control of Agile Missile
JING Shao-guang, WANG Qing, SONG Zi-shan
2000, 26(3): 315-317.
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A neural network based controller of agile missile capable of high angle of attack flight is presented. Super agility is needed in close-in combat. For the missile to possess super agility (high angle of attack capability) some form of alternate control is needed, vectoring the thrust (or using reaction jets) can provide this capability. With super agility requirements, missiles expected to maneuver in extreme flight conditions where there is a considerable amount of nonlinearity. The objective of this paper is to examine the use of neural network (NN) as an integral part of nonlinear dynamic inverse control. A fuzzy learning gain is adopted to enhance the stability of neural network. The NN are used to generate feedback control to force the plant toward desirable responses. A reference model is used to represent the ordered index of the closed-loop system performance. A benefit in the case is that the control system tends to be more robust. A simulation is presented and the results show the perfect tracking performance.
Study of Digital Control in Electrohydraulic Sero Loading System
JIANG Jia-he, YU Tong-wu, SONG Zi-shan
2000, 26(3): 318-320.
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This paper discusses the application of digital control in electro-hydraulic Servo loading system.With a microcomputer and a A/D and D/A module,applying a open-closed loop optimized design method, the control in electro-hydraulic servo system is realized. Besides, some PID algorithm is studied. It interprets the system hardware,software,and experiment.On the basis of full throretical design,a lot of experimental researches are made.Experimental results of the two algorithm are analysed by comparison and in effect,the indexes of open-closed loop algorithm are higher than those of PID algorithm.Finally,this paper studied the extraneous force's elimination.Experimental results proved that the method of eliminating extraneous force is successful and effective.
Flight Simulation System of Large Civil Aircraft Based on Network
LIU Li, PENG Xiao-yuan, WANG Xing-ren
2000, 26(3): 321-324.
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With a flight simulation system of large civil aircraft developed by the Simulation Research Division at the Beijing University of Aeronautics and Astronautics, this paper introduces its hardware composing and network topology. The distribution of the simulator cockpit, the functions and distribution in the network system of some subsystems including modeling and managing computer, visual system, instrument system, acoustic system, interface system, instructor control computer, and flight management computer have been introduced. The software structure of the modeling and managing computer has been described. Then some key techniques in net communication and real-time property of the system have been discussed.
Study on Missile-s RCS Calculation
ZHANG Yun-fei, WU Zhe, LU Zhu-hui
2000, 26(3): 325-328.
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High frequency scattering theory, including physical optics, physical theory of diffraction and equivalent electric current theory, were used to calculate the radar cross section of various scattering resources of missiles, such as flat plate, circular cylinder, quadric surface, edge and so on. Combined with the equation of traveling wave and dihedral reflector, the RCS of total missile was calculated. The measurements and calculations agreed with well. It has been proved that the analysis to missile scattering resources is right, and the modulation to missile scattering resources is quite exact. So high frequency method can satisfied the engineering analysis need for the RCS calculation of missiles. The major scattering resource in top direction is radar antenna or infrared head, in side direction is dihedral reflector formed by missile wings, missile body and wings.
Numerical Modeling of the Explosive Decompression Process with MSOGS
YANG Feng, LIN Gui-ping, XIAO Hua-jun
2000, 26(3): 329-332.
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A simple mathematical model about the dynamic variation of alveolar oxygen partial pressure during explosive decompression is established in this paper. With this model the process of alveolar oxygen pressure change during explosive decompression process is simulated with molecular sieve oxygen generating system(MSOGS). The effects of concentration of supplying oxygen and the flight altitude is analyzed. The predicting and experimental results are in good agreement. This model provides an easy approach to calculate the critical time for the explosive decompression process. It is helpful for design of life-support equipment and medical watch of high altitude flight.
General Scheme of Aircraft Intelligent Hydraulic Pump System
CHEN Bin, WANG Zhan-lin, QIU Li-hua, FEI Bin-jun
2000, 26(3): 333-336.
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High-pressure, high-power, and so on are the main development trends of aircraft hydraulic system. Based on the traditional constant pressure variable flow pump system, the high-pressure and high-power of the system will surely lead to an increase of non-effective power, then it's temperature will increase urgently. This is a very difficult problem on the development of future aircraft. High pressure, variable flow and variable pressure intelligent pump system is the best solution to this problem. A general scheme of a high pressure, variable flow and variable pressure aircraft intelligent hydraulic pump system is proposed in this paper. It is initiatively controlled by a microcomputer, and has four working modes: flow, pressure, power and integration. Also, it has a malfunction working mode and a state monitoring ability.
Technology of Modeling for Shape Memory Alloy Reinforced Composites
SU Zhong-qing, MAI Han-chao, LU Meng
2000, 26(3): 337-339.
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Based on a lot of experiments on the thermo-mechanical properties of shape memory alloy reinforced composites, which have already been applied in some intelligent structures, the quadrangular and triangular models are established in this paper, and the corresponding formulae of Finite Element Method are developed accordingly. As the result of these work above, the analytical software for SMARC, including the static and dynamic analysis, is programmed and applied for computing a cantilever structure, which is embedded with the SMA, as an example. The result is quite reasonable. With the development of smart and intelligent materials and structures, it is no doubt the SMARC will play an important role in the future.
Research on the Numerical Simulation of Aircraft Carrier Air Wake
PENG Jing, JIN Chang-jiang
2000, 26(3): 340-343.
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A model of carrier air wake is selected to simulate the spatial distribution of velocity of air wake in MATLAB on a PC for study of environmental effects on approaching and landing of the carrier base aircraft. The air wake can be divided into four components according to their causes: the power spectra of the component of free random turbulence is simulated by means of shape filter; the steady component is acquired by linear interpolating; the periodic component is directly calculated; and the random turbulence induced by carrier is realized with SIMULINK Toolbox in MATLAB. The simulation shows that the periodic component is the dominant component of the air wake. The further validation of this model needs supports of more experimental data and data obtained aboard.
Structure Optimization Design Study of Fuselage Main Frame
XIE Yong-he, WU Wen-zheng
2000, 26(3): 344-347.
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The method of optimization theory based on dual method was transplanted to design fuselage main frame, and the optimizing model of fuselage main frame was established. The target function is the weight of fuselage main frame. There are three kinds of constraints: dimension, strength and flexural rigidity constraint. The program(SAAOP) based on optimization theory was designed. The numerical results show that the structural strength after fuselage main frame was optimized is fit, all so the flexural rigidity of wing juncture. So this program can be used to design the main strength frame of large-scale leptodermous fuselage in predesign.
FE Contact Search Model Research in Sheet Metal Forming
WANG Xiao-lin, ZHOU Xian-bin
2000, 26(3): 348-351.
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On the basis of the parametric curved-surface tool description and finite element meshing tool description, a curved-surface & element description method for the tool geometric shape model is established. An updated global & local contact search algorithm is introduced. An optimized selection for intersected iterative initial value and a contact judgement rule based on the no-penetration theory is deduced. Then a finite element contact search model for numerical simulation in sheet metal forming processes is set up. The model not only improves the astringency of the finite element numerical simulation, but also enhances the efficiency & stability of the numerical simulation of contact processes. The astringency, efficiency & stability of this model are verified well by calculation and experiment.
Research and Practice of PPOR Model of Product Data Management System
ZHOU Chang-sheng, WANG Xu-hai, ZHAO Yong-shun, DENG Jia
2000, 26(3): 352-356.
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Due to sharply increase on quantity and volume of product data in product design processes,enterprise must improve management on those product data. In spite of depend on different point of view of product data management,various product data management system is developed,but still some basic characteristics they have is similar,it is proposed that several principles would be satisfied in developing product data management system. Because PDM (Product Data Management) is to integrate and management data information which relate developing product,it is crucial to studying the model of information management in PDM for realizing a PDM system. This paper proposes PPOR model,respectively reference product information management model,process information management model,organization information management model and resource information management model. These models correlate each other. They are all described by EXPRESS-G language,and applied in a prototype system based on STEP.
Pilot Study of Aircraft Configurations Control
YANG Xi, FAN Yu-qing
2000, 26(3): 357-360.
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In order to effectively manage the complicated aircraft configurations in modern aircraft manufacture industry and to resolve the difficult problems on aircraft configurations control in product data management, the characteristics of modern aircraft manufacture and the questions brought forward to aircraft manufacture industry nowadays by them are analyzed. The importance of configurations control is also emphasized. After some correlative primary conceptions about aircraft configurations control techniques are explicitly defined, the successful experiences on these techniques within Boeing Aircraft Company Group are used for reference to specially indicated the four key contents of aircraft configurations control. Aiming at the actuality and future of Chinese aircraft manufacture industry, the tasks to realize the aircraft configurations control techniques which should be accomplished at present time are also elucidated.
Study on Evaluating Arithmetic of Network Solving for Product Conceptual Design
HAN Xiao-jian, DENG Jia
2000, 26(3): 361-364.
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product conceptual design is a complicated process of reasoning solution and its workload of reasoning、verdict of design process often is very huge.Using a expression method of knowledge of "And/Or" tree, a embedded study of principle solution of product conceptual design process and its evaluation of combined principle project is made, a arithmetic of evaluation of decomposed and integrated network is presented, a well base of enhanced efficiency of design and optimized process of product conceptual design is founded, as a result, a evaluation method of formalization for more developed support implement of computer software for intelligent product design is provided.
Robust Control of Interval Discrete Systems
ZHANG Yuan, JIA Ying-min
2000, 26(3): 365-368.
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The edge check results of the continuous interval systems are first extended to the interval discrete systems by employing the convex analysis way of value set. Further, in order to obtain some vertex check results, the discussion is limited to such a case when only lower-order coefficients of transfer function of the discrete system are disturbed. It is shown that the closed-loop stability of an interval discrete system with a first-order controller can be guaranteed by that of its vertex plants provide that the pole of the controller satisfies the corresponding inequality conditions on the highest order of the disturbed coefficients. Here, the argument growing principle plays an important role in the proof of the main conclusion. An example is also included for illustrating the obtained results.
Imperfect Bifurcation of One-Dimensional Vector Field with a Time-Dependent Parameter
HUA Cun-cai, LU Qi-shao, WANG Qi
2000, 26(3): 369-372.
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A new and simple method is proposed for studying an imperfect bifurcation problem of one-dimensional vector field with a time-dependent parameter. A basic method of scaling balance is established. By combining this method with the continuity of the solutions of ordinary differential equations with respect to time and parameters, the delayed bifurcation transition and the influences on the bifurcation diagrams are discussed. Three different types of model bifurcation equations are analyzed concretely, the scaling relations and the intervals of bifurcation transition are given. The qualitative analysis results coincide with the numerical ones. Our studies imply that there exists a critical value of imperfect parameter such that if the imperfect parameter is respectively smaller than, equal to and larger than the critical value, the corresponding time dependent bifurcation is delayed, almost the same as and advanced the steady one respectively.

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