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1998 Vol. 24, No. 2

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Study of Surface Characteristic with Microwave Plasma Treated Amorphous Alloy Coating
Zhu Liqun, Zhong Qunpeng, Kazuo Sugiyama
1998, 24(2): 125-128.
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Ni-W,Ni-W-B amorphous alloy coating is modified by means of microwave plasma treatment and the effect of the modification on the structure,surface component ,corrosion and oxidation resistance of Ni-W,Ni-W-B amorphous alloy coating is studied. The results show the corrosion-resistance (in H2SO4,HNO3 solution) and the high temperature oxidation-resistance (700℃) of the modified amorphous alloy coating are improved .The contents of tungsten and oxygen element in the modified amorphous alloy coating are increased and the structure of plasma modified Ni-W,Ni-W-B alloy coating is still amorphous.
Study of Electropolymerization of Diacetone Acrylamide on Carbon Fiber Surface
Zhang Fusheng Wu Yu, Zhuang Yan
1998, 24(2): 129-132.
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The electropolymerization (EP) of diacetong acrylamide (DAA) and acrylic acid/DAA on Carbon fiber Surface and the effects of EP coating upon performance of Epoxy unidirectional CFRP were studied . The shear strength of CFRP was significantly improved from 45.57 MPa to 70.36 MPa and 81.24 MPa respectively . The mechanism of EP and bridge function of EP coating as an intermediate between carbon fiber and epoxy matrix were discussed . When radical capturer was added into the monomer solution , the formation of EP coating was strongly retarded . This phenomenon implicated DAA EP mechanism may be free radical polymerization.
Design of Slotted Linear Array in a Camrectangular Waveguide
Lü Shanwei, Gao Wenjun, Li Sichao, Diao Hainan
1998, 24(2): 133-136.
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A new waveguide which can change the wide wall of a rectangular waveguide into a symmetric arc wall is named as a camrectangular waveguide.Comparing to sectoral waveguide,the new waveguide has the same voltage characteristics and is easier to be produced and fixed.An approximate formula of the dominant mode fields and the normalized conductance of a longitudinal resonant slot cut in the curved wall of a camrectangular waveguide are given.A resonant slot linear array in C & X band is designed,in which the slot voltage distribution is equiphase and the input is matched.The input voltage stationary ware ratio and the H plane pattern of the antenna are measured.The experimental results show the conformance with theoretical results.
Theory and Development of Electrical Impedance Tomography Technology
Cheng Jikuan, Sun Jinping, Du Yan, Liu Zhongkan
1998, 24(2): 137-140.
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Electrical Impedance Tomography(EIT) is a new technique that forms images of electric resistivity or conductivity within the body through measuring the current or the voltage of the surface. As a mathematical physics inverse problem,EIT is a developing technique on its own feature and difficulty.This paper gives an introduction of the EIT technology in details.It includes the primary theory,technical difficulty,system analysis as well as the recent research background and trend all over the world.It introduces ACT3 to give a simple analysis realizing the EIT system.
Numerical Calculation of Scattering Characteristics from PerfectlyConducting Cylinder Coated with Dielectric Material
Huang Xingzhong, Lü Shanwei
1998, 24(2): 141-144.
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The general scattering field expressions are given when the plane wave propagates to a perfectly conducting cylinder coated with radar absorbing material and its scattering fields are calculated comprehensively.The method to calculate Bessel function and Hankel function with imaginary argument is discussed.The various curves of bistatic RCS are given when the incident electric field is parallel and vertical to the cylinder axis,respectively.The variations of bistatic RCS with the material thickness,incident frequency,and the dielectric constant and permeability of the material are obtained,respectively.The results can be used as useful references.
Data Link Design for Automatic Vehicle Location Systemwith High Capacity and Precision
Wu Shaochun, Li Xianliang, Zhang Qishan
1998, 24(2): 145-148.
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The present automatic vehicle location system (AVLS) has some defaults such as smaller capacity,alarm collision and lower precision etc.Based on the characteristic analysis of AVLS and slot ALOHA (SALOHA),a new method of data link design,which is called Broadcast Reserved ALOHA (BRALOHA),is proposed in this paper,consequently the base station broadcasts differential GPS(DGPS) information,and mobile users transmit their location information reservely,and smooth GPS receiver's noise.It has been shown that BRALOHA is satisfied with the design for AVLS with high capacity and precision by its centralized communication scheme,the throughput versus offered load and throughput versus delay performance .
Capacity and Channel Design of Small Telemetry System
Li Sanzhong, Li Xianliang, Zhang Qishan
1998, 24(2): 149-152.
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Some problems about overall design of a small unmanned air vehicle telemetry system are presented in this paper.The construction and fundamental principle of the telemetry system is simply introduced.According to the telemetry task requirement,the key problems which should be solved at first are demonstrated mainly by system's capacity design and channel design.The needed data transmission rate is carefully calculated with the telemetry parameter table provided by user and on this basis the frame structure is decided.The bit error rate in factual telemetry channel is grossly estimated in theory and a channel encoding scheme is provided to improve data transmission quality to meet with the requirement for extremely low bit error rate.
Analysis of the Terminal Seeker Presetting Accuracy due to the Guidance Radar Errors
Zhao Hongliang, Mao Shiyi, Li Shaohong
1998, 24(2): 153-156.
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The tactical missile seeker handover accuracy from midcourse to terminal guidance is researched.The small perturbation method is proposed to analyse error sensitivity of the seeker presetting parameters from error sources.Firstly,the terminal guidance seeker presetting parameters are computed,based on the equations of a surfacetoair missile movement and a target movement.Then the seeker presetting unaccuracy due to the command guidance radar measurement errors is also computed.It can be seen that the seeker presetting errors increase rapidly when the missile is close to the target,which leads to an important conclusion that the late seeker handover from midcourse to teminal guidance should be avoided.
Reseanloop Model for the Scattering Field of the Target
Yu Yang, Wang Baofa, Zhou Yinqing
1998, 24(2): 157-160.
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The resean loop mothed for solving the scattering field of complex targets in resonance region is presented.The idea of wire grid is using the induction current flowing on the three dimensional wire grids to simulate the continuous conduct surface excited by the incident electromagnetic wave.Unlike the single wire grid model published before,we use the resean loop model to simulate every continuous conduct facet,so the Kirhoff Law is automatically satisfied on each junction.Based on analyzing the geometric model of the targets,the RCS of complex aircrafts are obtained by using corresponding EM model and CGFFT in resonance region.Numerical results verify the correctness and usability of the resean loop electromagnetic model presented by this paper.
Weighted NewtonRaphson Algorithm for Electrical Impedance Tomography
Du Yan, Liu Zhongkan, Cheng Jikuan
1998, 24(2): 161-164.
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A proper weight matrix is used to improve the NewtonRaphson algorithm for the electrical impedance tomography image reconstruction,and a weighted NewtonRaphson algorithm is proposed.The new weighted algorithm can overcome the defect of baddistributed resolution for reconstructed image by using original NewtonRaphson method.This kind of defect is from illcondition of inverse problem and some mathemetical and physical factors such as injecteds current,electrodes disposition,geometrical position of pixel etc.Compared with the simple NewtonRaphson algorithm,the image reconstructed by the weighted one is much better while the computation amount is almost not increased.The algorithm for computation of the weight matrix is also discussed in detail.
Application of Fuzzy Inference Compound Method to Resistance Furnace Temperature Control System
Wang Wenshun, Wan Rui
1998, 24(2): 165-169.
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According to the characterestic of resistance furnace temperature control,temperature rising oneway control,large time delay and timevariation of parameter,using method of fuzzy compositional rule of inference establish fuzzy model and design fuzzy cntroler.In order to increase control system precision,it gives a fuzzy variable K,and sets parameter selfadjusting fuzzy control system.This system can on line selfadjusting controller parameters according to the error and variations of the error.It makes the system steady precision improved.
Study on Grid Generation of Gas Turbine Combustor
Xu Hang, Yang Rong
1998, 24(2): 170-173.
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The interactive grid generation method has been studied.The 3D bodyfitted grid for whole combustor,which is composed of diffuser,outer and inner annular combustor,has been generated.The better density and orthogonality of grid could be achieved,The primary,dilution and film cooling holes on the liner of combustor could be treated properly.The type of grid on the boundary surface was exported for the numerical calculation of combustion flow.The boundary curves and distributions of grid points on them could be determined interactively.By use of the VISUAL BASIC language,all parts of grid generation were integrated into a set of software.
Effects of 3D Flow on Aerodynamic Stability of Axial Flow Compressor
Cao Renjing, Zhou Sheng
1998, 24(2): 174-177.
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Concerning the models for discribing aerodynamic stability of axial flow compressor,the original model is onedimensional,and it is reasonable for the onset of surge only.For the onset of rotating stall,there are just some twodimensional models at published literatures.A threedimensional aerodynamic of compressor has been presented in this paper.An aerodynamic stability model concerning radial disturbance of compressor is presented.The calculated results show that the occurrence of radial disturbance is related to the axial velocity disturbance,which has important effect on aerodynamic stability of compressor.The position of onset of stall,in blade tip or hub,is dependent upon the characteristics of blade element.The comparisons of calculated results predicted by 2D and 3D aerodynamic stability model have also been made in this paper.
Turbulent Intensities Distributions over a Riblets Surface
Wang Jinjun, Lan Shilong
1998, 24(2): 178-180.
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The LDV technique has been used to measure the turbulent intensity distribution of turbulent boundary layer flow over a riblets surface.The experimental results indicate that,in comparision with the smooth surface results,the maximum value of turbulent intensity is smaller,but its occurrence position is farther.Moreover,in the region very near the riblets surface,i.e. y++<4,there exists greater value of turbulent intensities,which means that where the riblets surface enhances the flow turbulence.For y/δ≥0.06,the distribution of turbulent intensity can be described as u′/u=2.3exp(-0.9y/δ),otherwise,u′/u=36.4y/δ.
Correlative Analysis between Pressure Distributions and VortexPattern of DoubleDelta Wings at High Angles of Attack
Feng Yanan, Zheng Bo, Quan Shaoping
1998, 24(2): 181-184.
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The pressure distributions on two models of doubledelta wing were measured in the low speed wind tunnel in BUAA.They are 75°/45° and 75°/60° doubledelta wings with sharp or round outboard leadingedge.The analysis indicates that two peaks of the pressure distributions on some typical cross sections of the doubledelta wing characterize the double vortices while the one peak of those characterize the single or merged vortex patterns.The position of the vortex core can be marked by the location of the spanwise pressure peak.The vortex breakdown can be displayed by the decrease of the pressure peak and flat pressure distribution with increasing angle of attack.The outboard leadingedge of the doubledelta wing being blunted causes inboard and outboard vortices close each other and stronger interaction.The pressure distributions and vortex breakdown positions will be unsymmetric about the centreline of the wing due to a side slip.All of the unsymmetric vortex flow characteristics that can be found on the correlative pressure distributions.
Unsteady Flow Behaviour of a Slender Delta Wing Rock
Xia Xuejian, Liu Rizhi, Yang Xiaofeng
1998, 24(2): 185-188.
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The flow visualization of vortex behaviour for the two conditions of static and dynamic during wing rock motion was conducted and photograph records were taken for a slender delta wing in a various roll angle at α=30 ° and 40°.Results indicated that the vortex behaviour was quite different at the same roll angle between static and dynamic conditions.The time lag effects of vortex behaviour during wing rock comparing with static condition was observed.The time lag of vertical positions of vortices was apparent during wing rock motion,whereas the time lag was not significant for spanwise positions of vortices.The effect of starting angle of wing rock on the vortex behaviour was considerable.
Calculating Method of Aerodynamic Heating for Space Shuttles
Shen Xialing
1998, 24(2): 189-192.
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Approximate methods for calculating aerodynamic heating rates on space shuttles are discussed.Various methods are given for predicting the heating rate at axisymmetric stagnation points,general three dimensional stagnationpoints and the leading edge stagnation point of wings.Numerous laminar and turbulent heating techniques for flat plates and cones are analyzed and compared.A brief review of some methods is presented to predict heating rate for winward centerline and lateral direction off the symmetry plane.The results show that the methods are simpler and can guarantee enought precision for predicting aerodynamic heating environment of space shuttles.
Calculation of the Electromagnetic Scattered Field and Radar Cross Section
Xue Xiaochun, Li Zongrui, Zhu Ziqiang, Dong Jinming
1998, 24(2): 193-196.
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The paper focus on the description of the dimensional distribution of the timedomain scattered electromagnetic field around a 2D body and Radar Cross Section ( RCS ).The calculation of electromagnetic field usually conforms with the frequencydomain.A high frequency calculation method is mainly adopted,the calculation of fluid field agrees with timedomain.For the purpose of optimization design computation combining of the fluid field and the electromagnetic field,an integrated timedomain scheme is required.By separating the representative value into positive and negative value,allowance errors can be hold down respectively,the timedomain fluxsplitting method is applied to calculation of RCS in comparison with LaxWendroff Scheme.Therefore,the final results of the two methods were consistent.
Effects of Airfoil Geometric Parameters on Wing's Scattering Characteristics
Ma Dongli
1998, 24(2): 197-199.
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The effects of airfoil geometric parameters on wing's spacial and polarized scattering characteristics have been systematically revealed.The results of the study indicated that the calculating value of diffraction from trailing edge by using the formula of the straight wedge is very far from experimental results for vertical polarization,and the contribution of thickness of the trailing edge to scattering must be considered in the calculation.The scattering peak of leading edge depends only on radius of airfoil for horizontal polarization.But for vertical polarization,it depends on maximum thickness and the location of maximum thickness.Engineering formulas for evaluating all scattering peaks were given in the paper.It is important for the design of low RCS wing.
Experimental Studies of Impact Protection Performance of Aircrew Helmet Typical Component
Chen Zuorong, Yang Yiqian, Ma Hezhong
1998, 24(2): 200-202.
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The impact protections provided by several aircrew helmet components are investigated in using the SHPB apparatus.The energy absorption rates of these components are examined.The impact process and energy absorption process are discussed.Further,the way in which the material mechanical properties of helmet shell and the density of helmet foam liner affecting the energy absorption capacity of helmet is analyzed,showing that the mechanical properties of shell and the density of foam liner play an important role in the energy absorption process to a certain extent.The experimental method used by this paper is original.This work provides reliable experimental basis for designing a new generation aircrew helmet.
High Cycle Fatigue Model Based on Brittle Damage Mechanism
Xiao Yingchun, Li Songnian, Gao Zhentong
1998, 24(2): 203-206.
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An isotropic continuum damage mechanics model for high cycle fatigue derived from irreversible thermodynamic dissipative theory is presented.The model is different from Lemaitre model in damage mechanisms.The former is based on a brittle mechanism,and the later is ductile.The model incorporates successfully the high cycle fatigue into a unified thermodynamic framework.The effect of stress ratio R is considered in its damage evolution law.According to the high cycle fatigue SN curve under symmetrical loading,a Log S Log N curve for an arbitrary stress ratio R can be derived by using this model.The model has been applied to the smooth specimen of LC9 high strengthen aluminum alloy.A good agreement between theoretical Log S Log N curves and experimental ones is obtained.
State DecompositionEnergy Method for Analysis of Debonding Problem of Honeycomb Sandwich Plates
Miao Changqing, Meng Qingchun, Zhang Xing
1998, 24(2): 207-211.
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A sandwich plate with debonding between the face plates and honeycomb core is considered.A mechanical analysis model is built to study a honeycomb sandwich plate with debonding by state decomposition method.Analysis for debonding of honeycomb sandwich plates is carried out the by method of additional displacements and additional stresses produced by debonding between the face and core.The additional displacements of honeycomb sandwich plates containing rectangular debonding are analyzed by double trigonometric series and RayleighRitz method.The convergence of displacements shown by computation is satisfactory well.The result of displacements provides a simple and reasonable model for solving buckling load and fracture mechanics parameters of the honeycomb sandwich plate with debonding.
Advanced Technology in the Design of Environmental Control System for Avionics Pods
Yu Jianzu, Qian Yiji, Gao Zexi, Gao Cheng
1998, 24(2): 212-215.
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To ensure the reliability of equiments mounted in the avionics pods, an environmental control system (ECS) should be equipped in the pod independently. There are two difficulties in designing pod ECS: one is that the aircraft has no enough electrical power to drive the pod ECS; another is that some elements and devices can't suffer higher temperature, which requires a good environmental condition. This paper introduces a new ram air driven ECS for the avionics pods, which adopts the design concept of cool thermal storage for saving energy. The system operates on a reverse bootstrap air cycle and with a regenerative heat exchanger as well as an intelligent control subsystem. To overcome the difficulty of low ram air pressure head, by use of aerodynamic theory, the total pressure recovery σ of the ram air inlet is raised and the differential pressure between the inlet and outlet air of the ECS is increased, therefore, the greater expansion ratio ε of the cooling turbine is acquired. Test results demonstrate that the designed system has good performance.
High Speed Machining of Grey Cast Iron Using CBN Tools
Chen Wuyi, D.K.Aspinwall
1998, 24(2): 216-219.
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The cutting performance of CBN tools when machining grey cast iron with different pearlite/ferrite ratio at high cutting speed up to 1100 m/min was investigated concerning tool flank and crater wear,tool life and the influence of oxygen rich atmosphere.It was found that nose wear of Amborite was slightly greater than that of BZN6000 and craters were more likely to occur on the tools machining high ferrite iron at low cutting speed.BZN6000 achieved longest tool life at the cutting speed of 700 m/min when machining workpieces with high ferrite content,while the tool life of Amborite increased consistently with the increase of cutting speed when machining high pearlite cast iron.Cutting in the oxygen rich atmosphere could reduce tool wear and the effect was more significant with BZN6000 tools.The explanations for the phenomena were discussed.
Mathematic Model of Process Dimension Parameter Planning
Chen Zhitong, Du Pei
1998, 24(2): 220-223.
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Since nearly all of the dimension parameters in technological process planning are coupled together,manual method in the process dimension parameter planning(PDPP) is not always efficient and effective.In order to increase design efficiency and effect, an essential mathematic model about PDPP is established,and two basic constraint sets are given.This model is not only helpful to realize the automation and optimization of PDPP,but also useful to verify the correctness of existing PDPP methods and to find better PDPP methods.
Study on Weibull Distribution for Large Scale Complex System's R&D Budge Expense Estimation
Xu Zhe, Feng Yuncheng
1998, 24(2): 224-227.
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Study on budget of expense for large complex systems is the primary problem in the filed of cost analysis.Weibull timedependent expense model is an econometric model about manpower and finance for large complex systems,and also called life cycle model.In this paper Weibull distribution characteristics,parameter estimation methods and several models are studied,Weibull theoretical explanation are given.Finally,a case is analyzed,by making use of experience estimation method to estimate characteristic parameter,then gain R&D expense budget distribution.It provides that the distribution can well accord with the practical system in project budget stage.
Competitive Strategy of Enterprises and Manufacturing Systems' Dynamic Development
Zheng Yun, Wei Fajie
1998, 24(2): 228-232.
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In today's world manufacturing system has to meet new challenges for the market needs changing day by day. In order to meet the changes of the market, to form self-competition superiority, and to have great ability to deal with the changes, manufacturing system must have the character istic of continuing dynamic development.Manufacturing management need new thinking from the point of strategy. Now to many manufacturing managers' views, to apply flexibility to manufacturing is played an increasingly important role. As a consequence, no matter what kind of industrial enterprises, traditional or new are, there is an ever-increasing demand for application of flexibility. The application of flexibility for enterprises to reduce or redefine market uncertainties is introduced in this paper.
Numerical Simulation of Vortical Flows over Fighter Configuration with Euler Equations
Zhang Zhengke, Zhu Ziqiang, Zhuang Fenggan
1998, 24(2): 233-236.
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A three-stage explicit scheme is used for time-stepping solutions of Euler equations discretized in physical curvilinear grid cell of finite volume simulating vortical flows over a generic fighter configuration. The predicted pressure distribution on wing surface is in good agreement with experiments. The primary vortex from leading edge of wing as well as the secondary vortex on upper wing surface is captured. The secondary vortex in the solution of Euler equations is attributed to the combined effect of adverse pressure gradient, sharp edge and artificial viscosity, and the flow picture of the secondary vortex is qualitatively similar to that of experimental observation.
Computation of Near Sea Flight Vehicle Reflection from Sea and Sky Background Radiation
Xu Nanrong, Lei Jianchang
1998, 24(2): 237-240.
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The reflective characteristics of sea and sky background radiation,which have important effect on the infrared signature from flight vehicle above sea,are studied in the paper.The statistical distribution of wave facet directions is discussed,the effects of randomly riging and falling sea wave on the sea surface radiation and on the sun light reflection are also discussed.Calculation methods of irradiance from sea surface radiation and reflected sun light on observation point are derived in the paper.Finally a computation example is given,which shows the sea and sky background radiation has important effect on infrared characteristic especially in the front area of a flight vehicle.
Design and Investigation of Pulse Combustors
Cheng Xianchen
1998, 24(2): 241-244.
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It presents results obtained in an ongoing project at BUAA,stemming from the need to develop more ratinoal design methods.It discusses the effect of parameters of main elements of pulse combustors,including combustor chamber,tail pipe,injector and reactant supply system upon its performance,in the aspect of satisfying Rayleigh's criterion,the basical law of pulsating combustion.It was found that,a limit of minimum length of the tail pipe exists for a certain pulse combustor to keep an indispensable acoustic impedance.The characteristic and geometry of the reactant supply system and injector are very critical.It is proposed that an engineering design approach could be developed based on a velocity similarity concept.A series of pulse heaters rating 10 kW~300 kW were developed successfully using this concept.
Application of Multivariate Analysis in Studying the GraduateSchools' Scales of Universities in China
Xu Huijuan, Wang Huiwen
1998, 24(2): 245-248.
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Using part of the graduate schools' data in 1994 from 18 Chinese polytechnic universities with the State Council approved graduate schools,and by means of factor analysis and cluster analysis,two factors are extracted from the eight variables standing for the graduate schools' scales of the 18 Chinese polytechnic universities.One is related to the doctoral scales,the other is related to the master's scales.The graduate schools' scales of the 18 Chinese polytechnic universities in 1994 are rated and classified according to the two comprehensive factors' scores.The study method can be a reference for educational assessment on the graduate schools' scales of polytechnic universities.

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