JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

On a Class of Second Order Differential Inequality with Continuous Distributed Deviating Arguments 

Wang Peiguang, Ge Weigao

1999, 8(4): 337-341.

[Abstract](183)

Abstract:
Aim To study properties of solutions to a class of second order differential inequality with continuous distributed deviating arguments. Methods A direct analysis technique was used. Results and Conclusion Some sufficient conditions that ensure a class of second order delay differential inequality having no eventually positive solutions were obtained; which generalized some given results. Using the results; some oscillatory criteria for solutions of the hyperbolic equation with distributed deviating arguments can be established.

Existence of Periodic Solution for a Dirichlet Problem

Sun Yingfei, Zhou Meike, Fan Tianyou

1999, 8(4): 342-346.

[Abstract](148)

Abstract:
Aim To discuss the existence of periodic solutions for the first boundary problem of incompressible non Newtonian fluids; a problem arising from polymer processing and concerned with the first initial boundary value problem of nonstationary flow of the non Newtonian viscous incompressible fluids through slit dice. Methods The monotone operator theory and Schauders fixed point theorem were used. Results and Conclusion The existence theorem of periodic solutions of a Dirichlet problem is proved under reasonable conditions.

Periodic Boundary Value Problem for Functional Differential Equations with Impulses 

He Zhimin

1999, 8(4): 347-351.

[Abstract](176)

Abstract:
Aim To investigate the periodic boundary value problem for functional differential equations with impulses. Methods The method of upper and lower solutions and the monotone iterative technique were used to establish our results. Results and Conclusion The results of the existence of maximal and minimal solutions of the periodic boundary value problem for functional differential equations with impulses are obtained.

On the Existence of Positive Solutions for Impulsive Neutral Differential Equations 

He Zhimin, Ge Weigao

1999, 8(4): 352-356.

[Abstract](156)

Abstract:
Aim To investigate the existence of positive solutions for impulsive neutral differential equations. Methods The Banach contraction principle was used to establish our results. Results and Conclusion The results of the existence of positive solutions for impulsive neutral differential equations are obtained.

Quantitative Study on Characteristics of the Weibull Distribution

Zhang Tieling, Zheng Muqiao, Zhang Zuming

1999, 8(4): 357-363.

[Abstract](239)

Abstract:
Aim To quantitatively study three characteristics of the Weibull distribution. Methods Theoritical analysis of the three characteristics of parameters of the Weibull distribution was done and mathematics software was used to make some chart analysis. Results 17 equations and 7 figures were made. Conclusion Under the standard form; the class of the Weibull probable density founction(pdf) curves appear double peak shape. Under the standard form; the maximum value point curve of the Weibull pdf takes line t =0 and t=1 as asymptotes. When β = 3 30-3 40; the Weibull distribution is the most similar to the normal distribution.

New Formulation for Arbitrary Cracks Problem and Its Stress Intensity Factor of Plane Elasticity

Yang Xiaochun, Fan Tianyou, Liu Shiqiang

1999, 8(4): 364-369.

[Abstract](157)

Abstract:
Aim The general arbitrary cracked problem in an elastic plane was discussed. Methods For the purpose of acquiring the solution of the problem; a new formulation on the problem was proposed. Compared with the classical plane elastic crack model; only the known conditions were revised in the new formulation; which are greatly convenient to solve the problem; and no other new condition was given. Results and Conclusion The general exact analytic solution is given here based on the formulation though the problem is very complicated. Furthermore; the stress intensity factors K Ⅰ; K Ⅱ of the problem are also given.

Dynamic Behavior of Voltage Across Small Capacitance Josephson Junction

Shao Bin, Zou Jian, Su Wenyong, Li Qianshu

1999, 8(4): 370-373.

[Abstract](140)

Abstract:
Aim To study the dynamic behavior of voltage across small capacitance Josephson junction. Methods A model of the mesoscopic Josephson junction coupled with a single mode quantized radiation field was used. Results A Gaussian type envelope factor exhibiting quantum collapse and revival(CR) phenomenon was obtained. Conclusion It is shown that for the squeezed state the time evolution of the voltage can exhibit drastically quantum CR phenomenon.

Deposition of High Quality GaN Film Under High ECR Plasma Density 

Du Xiaolong, Chen Guangchao, Yao Xinzi, Zhu Hesun

1999, 8(4): 374-380.

[Abstract](176) [PDF 228KB](2)

Abstract:
Aim To investigate the influence of ion density(ni)on the deposition of wurtzite GaN films on the substrate of α Al 2O3(0001)by electron cyclotron resonance plasma. Methods Langmuir probe measurement; Double crystal X ray diffraction and Hall measurement were used. Results The quality of GaN film strongly depended on its growth condition. The higher ion density resulted in a higher amount ratio of N/Ga and a lower background electron concentration of GaN film. When the GaN was prepared in the ion density of 2 0×10 11cm -3; the amount ratio of N/Ga was close to 1; the electron background density was 3 7×10 18 cm -3 and its full width at half magnitude(FWHM) was 16?arcmin. Conclusion The quality of GaN film can be improved by raising the plasma density.

Frequency Response Computation and Error Analyses

Yao Xiaoxian, Lin Fan

1999, 8(4): 381-385.

[Abstract](194)

Abstract:
Aim To derive the error formulae for the algorithm of frequency response computation. Methods This algorithm was introduced theoretically; the error sources of the algorithm were analyzed and the formulae of the main error were derived. Results The repeatability and stability of the processing results of the algorithm are better than those measured by 1250 Frequency Analysor. Conclusion The error formulae derived are theoretically right and practically valid.

Finite Element Analysis of the Temperature Distribution in Orthogonal Metal Machining

Liu Defu, Yu Xiaoxia, Lou Pingyi

1999, 8(4): 386-391.

[Abstract](191)

Abstract:
Aim To Research the temperature distribution in orthogonal metal machining and to build a finite element analysis model about the temperature distribution. Methods With the finite element method of thermal conduction; the temperature distributions in various machining conditions were computed according to the experimental data such as cutting force; shear angle; etc. Results The computational results agree with some classic experimental results; and thermal effect due to process parameters was observed. Conclusion The finite element analysis model is reasonable; and it's a feasible scheme for studying the temperature distribution in orthogonal metal machining system.

Sinusoidal FM Fuze's Channel Leak and Its Jamming Mechanism 

Han Chuanzhao, Shi Jusheng, Cui Zhanzhong

1999, 8(4): 392-397.

[Abstract](219)

Abstract:
Aim To get the theory base of designing FM fuze's jamming signal; its jamming mechanism was studied. Methods A sinusoidal FM fuze was analyzed in time domain and frequency domain and the concept of channel leak was presented. Results It was proved that information channel leak exists in FM fuze because of the nonlinear property of the mixer. The jamming signal was designed based on the channel leak and the jamming mechanism was analyzed in detail. Conclusion This kind of jamming signal can jam the sinusoidal FM fuzes effectively just depending on the jamming signal's feature itself. It's different from the traditional jamming way of simulating echo. Though the sinusoidal FM fuze was just analyzed; the principle is applicable to all FM fuzes. At the same time; it may be used as the reference for FM radar and communication countermeasures.

Math Imitation of the Texture of Particle Cluster Emitted from Diesel Engine

Zheng Shiqin, Liu Shuyan, Huang Hongbin

1999, 8(4): 398-402.

[Abstract](147)

Abstract:
Aim The particle texture from diesel engine was imitated by use of computer. Methods The theory of fractal geometry and the diffusion limited aggregation model were used to simulate the micron texture. Results The fractal dimensions of granule distribution and corpuscle superficial area are quite conformed with those of measurement. Conclusion The texture parameters of engine particle cluster can be obtained precisely by use of fractal theory.

Night Vision Characteristics and Application of MTV-2821CB CCD Camera

Lin Jiaming, Wei Jianzhong, Chen Jing, Hao Qun, Zhang Xiang

1999, 8(4): 403-409.

[Abstract](168)

Abstract:
Aim To describe accumulating frames characteristics of CCD camera as a night vision detector. Methods Utilizing CCD external trigger; computer video capture card and image processing software; the image accumulation was made. Results The detection of the static object image whose illuminance on the CCD FPA(focal plane array) was less than 3.7×10^-5lx was realized and the image's resolution of 300?TV lines was achieved. Conclusion This experimental system can provide a kind of night vision device capable of detecting the static object at low light level and with low cost compared to an image intensifier.

Electrode Location Efficiency and Equivalent Circuit for Flexure Vibration of Piezoelectric Beam 

Jia Yubin, Sun Yunan, Qin Bingkun

1999, 8(4): 410-415.

[Abstract](215)

Abstract:
Aim To provide technical parameters for development of quartz gyro. Methods Theory of elastic beam was applied to piezoelectric beam. Based on the concept of equivalent volume force and energy conservation; the formula of electrode location efficiency was derived. And the electric system was compared with the dynamic one according to the principle of equivalent circuit for piezoelectric crystal; and the general formulae of the parameters for the equivalent circuit; R n L n C n ; were derived. Results and Conclusion Optimum electrode location is chosen; and the derived equivalent circuit parameters are the theoretical base of the circuit design for quartz gyro.

Structural Complexity Analysis of Information Systems Based on Petri Nets

Wang Jingguang, Gan Renchu

1999, 8(4): 416-423.

[Abstract](103)

Abstract:
Aim To present a quantitative method for structural complexity analysis and evaluation of information systems. Methods Based on Petri net modeling and analysis techniques and with the aid of mathematical tools in general net theory(GNT); a quantitative method for structure description and analysis of information systems was introduced. Results The structural complexity index and two related factors; i.e. element complexity factor and connection complexity factor were defined; and the relations between them and the parameters of the Petri net based model of the system were derived. Application example was presented. Conclusion The proposed method provides a theoretical basis for quantitative analysis and evaluation of the structural complexity and can be applied in the general planning and design processes of the information systems.

Visualization of Explosive Field

Zhang Wenyao, Ning Jianguo, Zheng Zuguo

1999, 8(4): 424-429.

[Abstract](252)

Abstract:
Aim To visualize the explosive field and design a useful and practicable software tool to analyze explosive field. Methods An ideal model of the explosive field with a protective wall; which was simulated by another program MMIC(multi material in cell); was brought forward. The physical data output by MMIC were changed into image data represented by DIB bitmaps through the following steps: normalizing; coding; mapping and displaying. The object oriented method was applied in programming. Results and Conclusion With the tool; the explosive field with a protective wall is visualized. The overview of explosive field and some details about the transmission of shock wave in the field; such as reflection; flow over an obstacle and Mach reflection; are shown.

Aerodynamic Interpolation for Flight Vehicles with Aerodynamic Axial Asymmetry

Xia Qunli, Qi Zaikang

1999, 8(4): 430-436.

[Abstract](283)

Abstract:
Aim To study wind tunnel test data interpolation methods for flight vehicle with aerodynamic axial asymmetry. Methods For different body aerodynamic roll angles; proper wind tunnel test schemes were selected and trigonometric series were used for aerodynamic interpolation. Results and Conclusion A simple and effective scheme for wind tunnel test and an accurate aerodynamic interpolation method are developed with satisfactory results.

Effect of Aerodynamically Stabilized Seeker Dynamics on System Analysis

Xia Qunli, Qi Zaikang

1999, 8(4): 437-442.

[Abstract](168)

Abstract:
Aim To study the effect of aerodynamically stabilized seeker dynamics on guided bomb system analysis. Methods A thorough analysis of aerodynamically stabilized seeker dynamics was made to show that because of the much smaller time constant; its dynamic model can be greatly simplified. Results and Conclusion In guided bomb guidance/control digital simulation; with the use of the simplified seeker model; simulation time can be reduced without the loss of simulation accuracy.

Microwave Attenuation of Solid Propellant Exhaust Plume in Oblique Orientation 

Liu Qingyun, An Dongmei, Zhang Ping

1999, 8(4): 443-448.

[Abstract](114)

Abstract:
Aim To investigate the effects of the incident orientation on the microwave attenuation. Methods Attenuation allowing microwave signal transmitting in an oblique or vertical direction through the solid propellant exhaust plume was computed; and the experiments were performed utilizing a lab scale solid rocket motor with a fully expanded nozzle. Results The predicted results accord well with the experimental results. Conclusion The microwave attenuation in the oblique path is greater than that in the vertical path.

1999 Vol. 8, No. 4