2000 Vol. 26, No. 6

Display Method:
Study on Stability of PolymerBased PTC Composites
WANG Ji-e, LI Xiao-bing, JI Xiao-qiang, XIE You-hua
2000, 26(6): 621-623.
Abstract:
The objective in studying and using polymer-based PTC (Positive Temperature Coefficient) materials is to increase PTC intensity of conductive composites and stabilize the reproducibility of the room temperature resistivity. On repeated heating cycling through the switch temperature or above it, the room temperature resistivity rises and the PTC intensity decreases. The effects of radiation cross-linking and continuous thermal aging in various atmospheres for a long time on the properties of the polymer-based PTC materials, such as the room temperature resistivity, PTC intensity, crystallinity and switch temperature, were studied. The results indicated that radiation cross-linking and nitrogen atmosphere were both favor of improving the electricity stability of PTC materials, the variety ratios of the room temperature resistivity and PTC intensity were relatively small.
Novel Inhibitors of Microbiologically Inducing Corrosion of A3 Steel in Anaerobic Environment
LIU Jian-hua, LI Song-mei, YANG Ying-guang
2000, 26(6): 624-627.
Abstract:
The effect of sterilization of four inhibitors(BHA-1,BHA-2,BHA-3,1227)and the behaviors of microbiologically inducing corrosion of A3 steel in 3.5%NaCl solutions with and without sulfate-reducing bacteria(SRB) in anaerobic conditions were investigated by using microbiologic method, weight-loss method and surface analysis. It was found that the pitting corrosion attack of A3 steel was accelerated by SRB. And the inhibitors could affect the growth process of SRB and inhibit the corrosion attack of SRB and Cl-, hence, the corrosion rate of A3 steel was decreased. It was demonstrated that the inhibitors had the double function of inhibition-sterilization. One of four inhibitors, BHA-2 gave the best result of inhibition and sterilization, and its efficiency of inhibition-sterilization was better than 1227 bactericide which was usually used to inhibit the corrosion caused by SRB.
Electron Beam Curing and Its Application in Processing Field of Advanced Composites
MAO Shu-li, SUI Gang, ZHONG Wei-hong, ZHANG Zuo-guang
2000, 26(6): 628-632.
Abstract:
In this paper,radiation curing and photo curing are compared.The fundamental process of electron beam (EB) curing is elaborated,and the features of EB cured composites are discussed.Furthermore,the development of EB cured composites technology is summarized,which includes the selection of the resins suitable for EB curing,photoinitiators,active diluents and the curing mechanism.Finally,a kind of low-energy EB curing technology is introduced and some innovative resins are exploited.
Influence Analysis of Differential Corrections Transmitting Cycle on Positioning Precision
YANG Dong-kai, ZHANG Qi-shan
2000, 26(6): 633-635.
Abstract:
The positioning error elements of GPS are described and the differential means are proposed in detail. The mathematics models of pseudo-range position and pseudo-range differential position are also introduced. The relationship between the corrected user pseudo-range residue and SA signal is analyzed. Based on the temporal correlation of SA signal, a suitable transmitting cycle of correction is then acquired in the local differential method. The correction contains pseudo-range correction and pseudo-range rate correction, which are included in the RTCM SC-104 telegraphese 1. In final, the practical conclusion is provided via many pseudo-range differential position experiments in a fixed point and many different correction-transmitting cycles.
Performance Evaluation of Optical Burst-Mode Receiver Based on Peak-Detector in Adaptive Threshold Control Circuit
HUANG Jing-yu, LI Zheng, SU Guo-bin
2000, 26(6): 636-639.
Abstract:
This paper purposes a theoretical analysis of the BER performance of burst-mode receiver. Considering two inherent factors, decay time constant and noise characteristic of the adaptive decision threshold, a comprehensive model to analyse the performance of burst-mode receiver is proposed. The theoretical model explains the burst-mode receiver's sensitivity penalty and agrees with the experiment result. The power penalty is about 2.3 dB at a BER of 10-9 compared with convention receiver in the condition of continue mode when n=23,Kf=0.05,Kr=10. Even if the Kf=0, because of the noise of decision threshold, there is a BER penalty when work in the burst mode.
SAR Bayesian SuperResolution Algorithm with a Correction of Perturbed Point Spread Function
WANG Guo-dong, ZHOU Yin-qing, LI Chun-sheng
2000, 26(6): 640-643.
Abstract:
According to Bayesian formulation,an estimate-maximise (EM) algorithm of SAR super-resolution is presented for reconstructing radar cross sections from SAR images.The algorithm incorporates successfully the prior knowledge about the image scene into image reconstruction,which can effectively improve classical resolution of SAR image.Furthermore,the algorithm can limit the effects of perturbed point spread function (PSF) by using a parameterized model and estimating model parameters.Combining two methods,the algorithm can realize SAR super-resolution with effect.The key of the algorithm is to construct a reasonable PSF model,which can fit SAR image data and collateral SAR imaging system parameters information simultaneously.
Radiation Performances of a Incline Rectangular Aperture Antenna
Lü Shan-wei, ZHANG Jiang-lin
2000, 26(6): 644-646.
Abstract:
The incline rectangular aperture antenna is one whose opening is tapered only on both narrow sides of a rectangular waveguide, placed on a perfectly infinite conducting plane, excited by the dominant H10 mode in the rectangular waveguide. The electric and magnetic field components over the aperture and radiated field formula are simply analyzed. The main beam pointing lies off broadside, namely the major lobe pointing deviates from the perpendicular of the aperture and the axis of the excited waveguide. The principal plane patterns have been calculated and the input voltage standing wave ratio (VSWR) versus measured frequencies is given. It is found that the VSWR is related to the incline angle of the aperture, and can be improved using different incline angles.
RCS of Metal Dielectric Joint on the Aircraft Cabin
JIANG Xin, NIU Bao-qiang, WANG Bao-fa
2000, 26(6): 647-649.
Abstract:
An analysis is presented which of the diffraction due to a material discontinuity formed by the junction of a thick dielectric half-plane with a metallic one having the same thickness.This is accomplished by considering the solution of several subproblems, including the direct diffraction and the coupling field due to a plane wave incident on a loaded open-ended parallel plate waveguide and their radiation and reflection.To take advantage of this idea for calculating the metal-dielectric joint on the aircraft cabin,the final result is in accord with the document-s.
Brown Motion Diffusion Model for Chaff Clouds
YANG Xue-bin, Lü Shan-wei
2000, 26(6): 650-652.
Abstract:
The diffusion model and numerical simulation model for chaff clouds are modeled on the assumption that the speed of air where chaff locates is a Winner random process and the mass of chaff is zero so it can trace the atmosphere speed very well. For the diffusion model and numerical simulation model, the numerical character of chaff clouds during diffusion is obtained. Comparing numerical character of above two models, it shows that the variance of atmosphere motion must be modified so the time step used in numeric simulation has no effect on numerical character of chaff clouds. The numerical simulation result agreed with this analysis.
Resonant Coriolis Massflow Meter
FAN Shang-chun, LIU Guang-jian, SONG Zhi-sheng
2000, 26(6): 653-655.
Abstract:
The essential sensing mechanism was investigated for the resonant Coriolis direct massflow meter in detail.The mathematical model of the resonant direct massflow meter was established,based on a typical U-type tube resonant sensing structure.The output signal calculating model was provided for the above massflow meter based on measuring the amplitude ratio.A signal processing circuit prototype was designed and developed by making use of MCS-51 type micro-processor,based on the above output signal calculating model.The testing results show that measuring error is less than 0.1%F.S.for the above developed processing circuit prototype.The theoretical and experimental results obtained here are of practical significance for developing the Coriolis resonant direct massflow meter.
Design and Practice of Power Consumption Management for ZH2518 Portable Pressure Calibrator
FAN Shang-chun, WU Dong-sheng
2000, 26(6): 656-659.
Abstract:
Design scheme and engineering practice project of power consumption were proposed for ZH2518 portable pressure calibrator, based on its actual operation. The minimum power consumption management was discussed from the device and system in operation scope, firstly. Second, The above management was investigated from the following three aspects: intrinsically, operating and powering lower consumption. The theoretical design and testing research were carried out from the master computer and pressure measuring modules, respectively. Finally, the testing results show that the design scheme is reasonable and the actual operation effect of the power management system is obvious.
Theoretical Analysis on ElectroHydraulic Load Simulator
PEI Zhong-cai, WANG Zhan-lin, WANG Li-guo
2000, 26(6): 660-662.
Abstract:
The thesis gives a thorough theoretical analysis on electro-hydraulic load simulator,builds up loading system mathematical model, shows all the factors which affect the performance of load simulator,analyzes the effects of structure parameters to the frequency characteristics of the loading system by simulation.The results prove that the enlargement of load stiffness and leakage coefficient of loading system and the decrease of motor displacement and the total compressed volume can enhance the response velocity.So rational selection of structure parameter of loading system becomes the key to enhance the load simulator performance.The analysis results can provide the theoretical bases for developing the load simulator with high performance.
Hybrid Method of Computer Aided FMECA and FTA
TAO Jian-feng, WANG Shao-ping, YAO Yi-ping
2000, 26(6): 663-665.
Abstract:
Fault Tree Analysis (FTA) is an affective method from top to bottom, which can evaluate system reliability and safety. Failure Mode Effect and Criticality Analysis (FMECA) is a quantity reliability analysis from down to top. This paper combines the disadvantage between FTA and FMECA, finds the joints between FMECA and FTA of complex system. Before the joints, this paper presented the automatic transform algebra between the FMECA and FTA of sub fault tree, otherwise the computer aided dynamic fault tree method is established after the joints. The application of tree redundancy actuator of this method is content.
Application of Neural Networks in Differential Game
ZHOU Rui, LI Hui-feng
2000, 26(6): 666-668.
Abstract:
The existing problems of application of differential game in practice are analyzed.Considering the processes of practical dynamic conflicts,neural networks combined with the theory of multilayer intelligence control are introduced to modeling the problem of differential game.It turns the problem of differential game into the problem of maneuver identification and optimization control based on neural networks.This process of solving differential games is more conformity with practice,and provides an efficient method for adding human experience and combining the qualitative analysis with quantitative analysis of differential game.The adaptive distributed learning rate of neural networks is developed to increase the learning speed and performance greatly.
Exploring the Means of Raising Pressure and Stable Range of ContraRotating Axial Compressor System
LI Qiu-shi, LU Ya-jun, YU Qing
2000, 26(6): 669-672.
Abstract:
Through experiments on a contra-rotating fan, the performance base line and stall margin have been analyzed at varies rotate speed matching and varies axial gap between two rotors. Used global five-hole pressure probe, the steadyflow field between contra-rotating rotors has been also measured, and the especial aerodynamic characteristic of contra-rotating fan has been analyzed more deeply when its rotate speed and axial gap changed. At last, basing on the experiment results and the same research in the world, this paper conclude some viewpoints on the means of raising pressure and stable range of a contra-rotating axial compressor system.
Boundary Element Analysis of Temperature Field of Body
DING Li, YUAN Xiu-gan
2000, 26(6): 673-675.
Abstract:
Due to intricacy of tissues and boundaries of body, it is very difficult to get a precise three-dimension temperature field about studied model of body. Boundary element methods was utilized to understand the meanings of equations of model effortlessly, to make calculation simply and to get a three-dimension temperature field easily, since it has one characteristic, which approximate calculation is only based on unknown functions on the dots of boundary fulfilling integral calculus equations. The result proved that boundary element methods has well advantages compare with other numerical methods in dealing with complicated boundary, programming and the time of computation, and tallied with experiment and other methods.
Experiment of Silver Interconnects of Photovoltaic Solar Array in IFM GroundBased AO Effect Simulation Facility
SHEN Zhi-gang, WANG Zhong-tao, ZHAO Xiao-hu, JIN Hai-wen
2000, 26(6): 676-679.
Abstract:
Photovoltaic solar array systems are being considered as potential power sources for spacecraft applications. But the AO effect on silver solar cell interconnects would limit the useful life of the solar array. So the experiments were constructed to investigate the interaction between silver interconnects of photovoltaic solar array which are to be used on spacecraft and atomic oxygen environment in the ground-based AO effect simulation facility. After the experiment, different degradation effects of the Ag films and the other plated protective coatings due to atomic oxygen were obtained. This would be of much value in selecting and determining the suitable protective coatings that would keep the silver interconnects from AO degradation while in LEO.
Euler Solution of a 3D WingBody Configuration with Aileron
LI Jin, ZHU Zi-qiang, WU Zong-cheng, CHEN Ze-min
2000, 26(6): 680-683.
Abstract:
A Euler method for solving the flow around a wing-body configuration with deflection of control surface (aileron) is presented. Using the combination of patched grid and domain decomposition techniques, the complex flow around this kind of configuration is effectively solved. An internal coupling condition is given to make the conservation of flux satisfied. In the computation Van Leer-s scheme is used to discretize the inviscid flux terms and a new Limiter function is constructed to realize TVD character. Numerical results show that present method is an effective one for solving the flow around wing-body configuration with control surface deflection .
Flow Visualization of Swept Wing/Body Junctions
ZHANG Hua, Lü Zhi-yong, YUAN Hui-jing
2000, 26(6): 684-687.
Abstract:
Flow visualization test of swept wing/body junctions has been performed with laser light sheet technique and sodium-fluorescence dyed liquid method in the water channel of BUAA. The results show that in addition to Reynolds number, the angle of attack and the swept angle are also very important parameters that influence the horseshoe vortex characteristics in the juncture zone. It is found that there exists a new kind of 3-D steady vortex system——back vortex, which is different from the horseshoe vortex and the Karman vortex. The back vortex exists for both swept cylinder and swept wing conditions. It comes from the rear part of the junctions and extends into space. The back vortexes will breakdown under certain angle of attack and the swept angle. The characteristic of swept wing back vortex is different from that of swept cylinder back vortex. The forming mechanism of this back vortex system and its relationship with horseshoe vortex system are also discussed. Finally, some typical sections of the junctions have been measured using PIV technique.
Determination of the Effective Modulus of the Syntactic Foam Containing Hollow Spheres by Differential Scheme and MoriTanaka Method
YAN Han-bing
2000, 26(6): 688-690.
Abstract:
On the basis of differential scheme and Mori-Tanaka method,two methods are developed to determine the effective modulus of composite reinforced by hollow spheres with changing contents and changing ratio of inside and outside radii.Then,Multi-step homogenization technique is adopted to determine the effective modulus of multi-phase composite.By the two approaches mentioned above,the effective modulus of the syntactic foam containing hollow glass spheres are calculated. The results show that the theoretical prediction of the Young-s modulus is precise enough.The factors of hollow spheres that influence the composite modulus are analyzed.
Research on Improved Crack Initiation Approach of Durability Analysis
LIU Wen-ting, LIU Tong
2000, 26(6): 691-693.
Abstract:
There are three important shortages having influence on engineering application in crack initiation approach of durability analysis established.They are researched and improved in this paper.Durability test for a group of analogous specimens is carried out under service load spectrum of the structure.On the basis of test data of crack initial life,the factors cp in three-parameter formula of crack initial p-s-N curves for structural details are determined by backward compute method. After analyzing big influence of standard deviation of logarithm crack initial life on economic life,this standard deviation is made as 0.176~0.2 that is general value for logarithm fatigue life of aircraft structures. Then an improved crack initiation approach of durability analysis is developed and is successfully applied for the durability evaluation of aircraft structures.
Reliability Methods to Determine Fracture Toughness K1C and Fracture Threshold Value ΔKth
XIONG Jun-jiang, PENG Jun-hua, GAO Zhen-tong
2000, 26(6): 694-696.
Abstract:
According to the randomization method of deterministic equation,fracture p-JR-Δa curve equation is established.From this fracture p-JR-Δa curve and fracture passivation curve,fracture critical value (J1C) p with the reliability level of p may be obtained.By means of fracture testing principle,fracture (K1C)p can be derived from (J1C)p.Then the reliability method to determine fracture threshold value ΔKth is presented.After the treatment of test data,some important results are obtained.From the statistical test,it is validated that fracture threshold value ΔKth follows the normal distribution.
Inverse Simulation for Helicopter Maneuvering Flight
YANG Chao, XIONG Liang-yu, ZHANG Xiao-gu
2000, 26(6): 697-700.
Abstract:
Inverse simulation and analysis of the representative maneuvering flight for the current helicopter are presented.The more sophisticated nonlinear model of flight dynamics,which include non-uniform inflow model,nonlinear aerodynamics of fuselage,rotor flap motion and forces coupling with the motion of helicopter body,is considered in inverse simulation.The algorithm of inverse simulation is proper to the above nonlinear model,and the assembled iteration method is used to solve generalized nonlinear algebraic equations.The representative maneuvering flight of pop-up and 180 degrees lever turn are described into mathematical expressions.For a sample current helicopter,the inverse simulation is calculated and analyzed for the maneuvers of pop-up and 180 degrees lever turn.
Study on Local Buckling of Stitched Composite Laminates with an Elliptical Delamination
GUI Liang-jin, YE Ning, LI Zheng-neng, KOU Chang-he
2000, 26(6): 701-704.
Abstract:
Delamination buckling of stitched laminates can cause high interlaminar stresses which, in turn, lead to delamination growth. This study presents a three-dimensional model to analysis local buckling of stitched composite laminates with an embedded elliptic delamination near the surface. The effects of geometry parameters of ellipse and stitching thread on buckling loads are investigated by Rayleigh-Ritz energy method. The results show that stitching significantly improves critical buckling loads, the buckling loads increase rapidly with increase in equivalent elastic coefficient of stitching thread. The buckling loads are relatively large when the long axis of ellipse is vertical to the loading direction. With the increase in length of long axis, the buckling loads decrease and converge gradually.
Effective Wove Algorithm for Software Structure Graph
SUN Chang-ai, LIU Chao, JIN Mao-zhong
2000, 26(6): 705-709.
Abstract:
Visualization of information is an important approach of understanding the structure of software and complex calls between modules of structural software hinder to analysis and understanding of software structure.A wove algorithm called generalized tensility balance algorithm, which is characterized by link dimension of modules, that is total of fan in and fan out, is present. And the idea of the paper is to represent the complex call relative of modules by intuitive graph.The principle and rules of the algorithm are discussed. It is proved by practice that the program graph produced by the algorithm of this paper is high symmetrical and high coupling, with least cross line, meets esthetics principle, graphical semantic limit and harmony principle.
Performance Analysis and Visualization for DSM-Based Parallel Programs
LONG Xiang, LI Wei
2000, 26(6): 710-713.
Abstract:
According to the architecture of the shared memory based network of stations and the implementation of its memory coherence protocol,using experimental methodology to characterized the shared memory access,process schedule,and synchronize overhead. Several parameters which primarily affect the performance of a parallel application are analyzed.Then gave a method of how to analyze the performance of an application running on the system by using our performance method and characteristic parameters.Applying this method to performance visualization of parallel application and system,implemented a performance visualization tool to display and analyze the behavior and performance of a parallel application running on a distributed shared memory based network of workstations.
Research about Non-Manifold Modeling System and It's Boolean Operation
ZHANG Xue-ming, SHI Fa-zhong
2000, 26(6): 714-717.
Abstract:
At first, describes the basic principal of non-manifold geometric modeling , the data structure,and some basic operations of the system used,then describes the basic theory of Boolean operation in non-manifold geometric modeling which consists of extended EULER formula, set ownship classification function, regular set and regular set operation. Finally, the five basic operation steps of Boolean operation are described,that is,①intersection, include the intersection of edge with edge, edge with face, edge with volume, face with face, face with volume. ②the formation of new loops and their partition into new sub-loops and sub-faces . ③the topology elements classification. ④linking the face into shells and linking shells into volumes. ⑤the formation of lamina elements which include lamina vertex, lamina edges, lamina faces.
Java SDAI Study and Implementation
CHEN Ji-bing, YANG Jun, ZHAO You-zhen, DENG Jia-ti
2000, 26(6): 718-721.
Abstract:
For integrating product data on the Internet, the STEP SDAI(Standard Data Access Interface) based on Java language is implemented. This system includes these models: mapping of EXPRESS model to Java Language, application program interface according with SDAI session schema,and two converters, one is JOS to Part 21 file, the other is JOS to STEP Database. Base on this Java SDAI interface,STEP application can adopt Browser/Server architecture, using a current Browser(IE or Netscape), users can access the STEP data on Internet. Optionally, this Java SDAI interface support STEP Part 21 file or RDBMS. At last, a demo based on Java SDAI is developed.
Robust Reduced-Order Controller Design Based on LMI
SUN Xiu-xia, MAO Jian-qin
2000, 26(6): 722-725.
Abstract:
A non-convex problem has to be solved in the designing of reduced-order H controller based on linear matrix inequality(LMI), which is so far an open problem. In this paper, a new method is presented to design reduced-order H contrller with convex optimization. It guarantees H performance, but some conservation may be introduced. In order to decrease the conservation, the projection principle is used. Thus, a lower order robust controller can be obtained but the H performance may not be guaranteed. It is a trade-off between the order of controller and the H performance in practice. Generally, if the projection error is small enough, the design result could be satisfied. The simulation results illustrate the advantages of this method.
Research on FaultTolerant Control of Dynamically Redundant Manipulators
CHEN Wei-hai, WU Zhen, DING Xi-lun, ZHANG Qi-xian
2000, 26(6): 726-730.
Abstract:
This paper is focused on the fault-tolerant control of dynamically redundant manipulators. Through optimizing the ellipsoidal sphere of joint torque, the dynamic fault-tolerant ability will be improved because the product of the principal axis length of the sphere can be increased. Based on this method, a joint torque redistribution algorithm for online fault-tolerant control of dynamically redundant manipulators has been presented. In order to reduce the error of trajectory tracing, the effects of PID and SMC control laws have also been compared. The effectiveness of the proposed algorithms has been demonstrated by simulation.
Input Variable Description Method for Real-Time Software Test Case Auto-Generation
CHEN Xue-song, LU Min-yan, RUAN Lian
2000, 26(6): 731-734.
Abstract:
In order to solve the problem of describing the input space for generating software reliability test cases automatically, the concept of promissory functions is presented. The input variables are classified according to their real time and valuing characteristics. The description of the valuing property for those input variables with random valuing characteristic are studied based on stochastic process theory. A model for describing the input variables is established. An example is given to illustrate the method of analyzing the input variables discussed above.