JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Optimal Boundary Control Method for Domain Decomposition Algorithm

2000, 9(2): 113-119.

[Abstract](270)

Abstract:
To study the domain decomposition algorithms for the equations of elliptic type, the method of optimal boundary control was used to advance a new procedure for domain decomposition algorithms and regularization method to deal with the ill posedness of the control problem. The determination of the value of the solution of the partial differential equation on the interface——the key of the domain decomposition algorithms——was transformed into a boundary control problem and the ill posedness of the control problem was overcome by regularization. The convergence of the regularizing control solution was proven and the equations which characterize the optimal control were given therefore the value of the unknown solution on the interface of the domain would be obtained by solving a series of coupling equations. Using the boundary control method the domain decomposion algorithm can be carried out.

Form Invariance of Lagrange System

MEI Feng-xiang

2000, 9(2): 120-124.

[Abstract](443) [PDF 161KB](27)

Abstract:
To study a form invariance of Lagrange system, the form invariance of Lagrange equations under the infinitesimal transformations was used. The definition and criterion for the form invariance are given. The relation between the form invariance and the Noether symmetry was established.

Existence of Periodic Solutions for Higher Order Autonomous Birkhoff Systems

CHEN Xiang-wei, MEI Feng-xiang

2000, 9(2): 125-130.

[Abstract](173) [PDF 194KB](165)

Abstract:
Qualitative methods of ordinary differential equation and Liapunov center theorem were used to study the existence of periodic solutions for higher order autonomous Birkhoff systems. For higher order autonomous Birkhoff systems, the character of the characteristic roots of the Fréchet derivative C was obtained. Furthermore the existence theorem of periodic solutions was obtained by using Liapunov center theorem, and an example was presented to illustrate the results.

Lie Symmetries and Conserved Quantities of Arbitrary Order Nonholonomic Systems

ZHAO Shu-xin, SHANG Mei, MEI Feng-xiang

2000, 9(2): 131-137.

[Abstract](208)

Abstract:
The invariance of the differential equations under the infinitesimal transformations was used to study the Lie symmetries and conserved quantities of arbitrary order nonholonomic systems. The determining equations, the restriction equations, the structure equation and the form of the conserved quantities were obtained.

Representation Theory of Three-Dimensional Elliptical Crack Under Dynamic Loading

FAN Tian-you

2000, 9(2): 138-141.

[Abstract](229)

Abstract:
The relation between the normal displacement on the surface of a dynamical elliptical crack and the normal stress over the crack surface was studied. The three dimensional elastody-namic equations and Fourier Laplace transforms are used. Based on the influence function and the inversion of integral transforms, one can find that if the distribution of normal displacement on the surface of a dynamic elliptical crack is a polynomial of degreenin x₁and x₂, then the normal pressure acting over the ellipse is also a polynomial P_n(x₁,x₂) of the same degree in x₁and x₂.

Zero-Point Energy and Fluctuation in a Field-Josephson Junction-Coupled System

SHAO Bin, ZOU Jian, LI Qian-shu

2000, 9(2): 142-147.

[Abstract](190)

Abstract:
To investigate the interaction of a mesoscopic Josephson junction with a single mode quantized electromagnetic field, the diagnonalizing process of the coupled system Hamiltonian was performed by using an unitary transformation. Zero- point energy and zero- point fluctuation of the coupled system were shown. For the ground state of the coupled system, the quantum fluctuations of the flux and charge operators in the field and junction subsystems can exhibit smaller quantum noise than the zero point fluctuations of the individual subsystems. Thus, when the coupled system is in its lowest energy state, which means that no radiation appear, the two subsystems exhibit nonclassical behavior.

Resource Allocation Using Timed Petri Nets and Heuristic Search

ZHANG Zhi-ming, WANG Yue, TAO Ran, YAN Fei, ZHOU Si-yong

2000, 9(2): 148-154.

[Abstract](217)

Abstract:
Traditional models for project management have not adequately incorporated a number of factors that are important for resource allocation. This paper proposed a unified timed Petri net model in which scheduling and planning were collectively carried out to take full advantages of the flexibility of the FMS. Through the lens of system theory, two types of resources were distinguished: major role and auxiliary role, and the major role was used to construct the FMS' Petri net. The method simplified the Petri net's construction and gave a clear flow chart for scheduling. Hence, the auxiliary resource allocation could be easily carried out according to the schedule, which was proposed by heuristic search algorithm. At last, the efficacy of the Petri net model for online scheduling in a resource constrained environment was discussed.

Material Design and Experimental Analysis of a New Type of Semiconductor ER Fluids

ZHU Shi-sha, WEI Chen-guan

2000, 9(2): 155-159.

[Abstract](267)

Abstract:
To improve the electrorheological effect of electrorheological fluid (ERF), a new type of the electrosensitive particle material, polynaphthalene quinone was prepared, whose molecules contain blended atoms of nitrogen, oxygen, sulphur and big π bond conjugate system. In both DC and AC electric fields, the ERF material showed a distinct ER effect. Especially, in the alternating electric field, the shear stress of this material versus AC voltage has a better quadratic relation than that of the other materials. The experimental data showed that organic semiconductor polymers with big π bond conjugate system are a new type of electrosensitive particle materials which are worth well developing.

Optimum Design of the Control System for a Laser Beam Riding Guidance Anti-Tank Missile

WENG Yan, WANG Zheng-jie, ZHANG Tian-qiao

2000, 9(2): 160-165.

[Abstract](176) [PDF 191KB](15)

Abstract:
The optimum theory and methods were adopted to design the laser beam riding guidance anti tank missile's control system in the short run. Through building the mathematical model of system, selecting a proper method and taking advantage of computer's high speed calculation and logic traits, an optimal controller was designed. Simulation results showed that the designed control system has fair performance and it satisfies the tactical and technical requirements. The results also demonstrate that by the combination of the optimizing methods and the computer the control system could be designed as soon as possible.

Feasibility Research on the High Speed Rotary Positive Air Filter

YAN Wei-ge, LIU Shu-yan

2000, 9(2): 166-170.

[Abstract](198)

Abstract:
The structure, separation principle and feasibility research for a new type of vehicle air filter called the high speed rotary positive air filter were described. The analysis of the experimental data showed that the principle and structure of it were feasible and it possessed high separation efficiency and great self cleaning ability. Compared with the conventional air filter it also has lower air intake loss. So it is worth further practical research.

Experimental Research on the Filtering Efficiency for a New Style of Air Filter

LIU Shu-yan, LIU Ying, LI Fu-qing, HUANG Hong-bin, YAN Wei-ge

2000, 9(2): 171-175.

[Abstract](305)

Abstract:
The primarily designed high speed rotary self cleaning air filter adopted axial outlet and tangential inlet, the filtering efficiency of the filter was relative low and couldn't reach the lowest efficiency limit. In order to enhance the filtering efficiency, the inlet and outlet structure of this new style of air filter were improved and the experimental research was carried out. The results showed that the filtering efficiency of the filter exceeded the lowest limit, this new style air filter can be practically developed further.

MWI in Cylindrical Coordinates and Its Application

XIE Yuan-chun, GAO Ben-qing, DENG Ci-ping

2000, 9(2): 176-182.

[Abstract](314)

Abstract:
Based on FDTD difference expressions and eigenfunctions of Maxwell functions in cylindrical coordinates, mesh wave impedances (MWIs) in 2D and 3D cylindrical coordinates were introduced. Combined with the concept of perfectly matched layer (PML), MWI-PML absorbing boundary condition (ABC) algorithm was deduced in 2D cylindrical coordinates. Numerical experiments were done to investigate the validity of MWI and its application in cylindrical coordinates FDTD algorithm. The results showed that MWI in cylindrical coordinates can be used to accurately calculate the nu-merical reflection error caused by different mesh increments in non uniform FDTD. MWI can also provide theoretical criterion to define the permitted variable range of mesh dimension. MWI-PML ABC is easy to be applied and reduces low numerical reflection, which only causes a little higher re-flection error compared with Teixeira's PML.

High-SpeedReal-TimeDataAcquisitionSystem Realized by Interleaving/Multiplexing Technique

Lü Jie, MO Yi-qun, LUO Wei-xiong

2000, 9(2): 183-188.

[Abstract](216)

Abstract:
The interleaving/multiplexing technique was used to realize a 200 MHz real-time data acquisition system. Two 100 MHz ADC modules worked parallelly and every ADC plays out data in ping pang fashion. The design improved the system conversion rata to 200 MHz and reduced the speed of data transporting and storing to 50 MHz. The high speed HDPLD and ECL logic parts were used to control system timing and the memory address. The multi layer print board and the shield were used to decrease interference produced by the high speed circuit. The sys-tem timing was designed carefully. The interleaving/multiplexing technique could improve the system conversion rata greatly while reducing the speed of external digital interfaces greatly. The design resolved the difficulties in high speed system effectively. The experiment proved the data acquisition system is stable and accurate.

Application of TMS320C80 in Image Processing

DENG Feng, DAI Qing-yu, YANG Zhan-xin, HE Pei-kun, MAO Er-ke

2000, 9(2): 189-194.

[Abstract](277)

Abstract:
To study the application of TMS320C80 in image processing, an image processing system was designed based on this device, and the task of real-time image processing was well accomplished on the hardware platform. TMS320C80 architecture's high degree of on chip in-tegration and software flexibility will make it widely used in image processing that requires high processing speeds.

Adaptive Nonlinear PID Control and Rule-Based Compensation for Systems with Backlash

REN Xue-mei, LI Yan, GONG Zhi-hao

2000, 9(2): 195-200.

[Abstract](183)

Abstract:
The control of dynamic nonlinear systems with unknown backlash was considered. By using an efficient approach to estimate the unknown backlash parameters, a rule-based backlash compensator was presented for canceling the effect of backlash. Adaptive nonlinear PID controller together with rule-based backlash compensator was developed and a satisfactory tracking performance was achieved. Simulation results demonstrated the effectiveness of the proposed method.

Application of Artificial Neural Network to Battlefield Target Classification

LI Fang, ZHANG Zhong-min, LI Ke-jie

2000, 9(2): 201-204.

[Abstract](255)

Abstract:
To study the capacity of artificial neural network (ANN) applying to battlefield target classification and result of classification, according to the characteristics of battlefield target acoustic and seismic signals, an on the spot experiment was carried out to derive acoustic and seismic signals of a tank and jeep by special experiment system. Experiment data processed by fast Fourier transform(FFT) were used to train the ANN to distinguish the two battlefield targets. The ANN classifier was performed by the special program based on the modified back propagation (BP) algorithm. The ANN classifier has high correct identification rates for acoustic and seismic signals of battlefield targets, and is suitable for the classification of battlefield targets. The modified BP algorithm eliminates oscillations and local minimum of the standard BP algorithm, and enhances the convergence rate of the ANN.

Application of the Computer Simulation Technique to Developing EFI Engine

ZHANG Fu-jun, ZHAO Chang-lu, HUANG Ying, GE Yun-shan, SUN Ye-bao

2000, 9(2): 205-210.

[Abstract](149)

Abstract:
The application of computer simulation technique to electronic controlled fuel injection(EFI) engine was studied to increase the development speed and improve the overall performance of the engine and car. On the basis of an EFI system developed by ourselves, the simulation model of the initial control data and engine operation points during a driving cycle and the car performance pridiction model were established. This method was applied to a mini car. The experiment showed that the simulated control data has good accuracy; and the engine test points and car performances obtained by simulation are useful for the matching of EFI system with gasoline engine and the development speed is increased.

Research on the Nickel Metal Hydride Battery Quick Charger

ZHANG Cheng-ning, ZHAO Hong-jie, SUN Feng-chun, ZHANG Wang

2000, 9(2): 211-216.

[Abstract](209)

Abstract:
In order to design a new type of quick charger for NiMH battery, the new method of pulse charge discharge was adopted after studying the charge process and analyzing the NiMH battery charge characteristics. The charge and discharge experiments were carried out to check feasibility and superiority of the new method. The results indicated that with the discharge pulse added the charger can charge quickly, the battery voltage and temperature can be properly controlled to prevent the battery being destroyed, and the capacity of the NiMH battery is greater than that of the battery without the discharge pulse added.

Computation of Electromagnetic Properties of Mildly Overexpanded and Underexpanded Rocket Exhaust Plume

LIU Qing-yun, HUANG Zhen-yu, ZHANG Ping, XU Wen-can

2000, 9(2): 217-224.

[Abstract](161)

Abstract:
An improved near far field divided coupled method was established to investigate the electromagnetic properties of mildly overexpanded and underexpanded rocket exhaust plumes. Firstly, axisymmetric Navier Stokes equations incorporated with k ε two equation turbulence models were solved using time dependent approach to calculate the pressure of the near filed. Secondly, parabolized axisymmetric Navier Stokes equations incorporated with finite rate chemical kinetics models were marching on the detailed pressure map of the near field. The termination of the near field would yield the initial line for the far field. In addition, in the far field, the spatial marching method was directly used under the constant pressure condition, but considering more complicated chemically reacting process. Finally, the electromagnetic parameters of the whole plume were calculated with the electron conductive model. The calculated results of the overexpanded and underexpanded rocket exhaust plume were discussed. The predicted microwave attenuation accorded with the experimental results. This improved method is feasible for calculating the microwave attenuation characteristics of mildly non fully expanded rocket exhaust plumes.

2000 Vol. 9, No. 2