JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Sun Liang, Zhao Jun, Yang Gang

1998, 7(1): 1-5.

[Abstract](323) [PDF 223KB](30)

Abstract:
Aim To research new characterization and circuit property of binary matroid. Methods Constract the modular pairs of hyperplanes of a a matroid. Results and Conclusion It is proved that a matroid M on finite set S is binary if and only if for any two distinct hyper-planes H1 and H2, if H1H2S ,and H1 and H2 are modular pair, then S-(H1H2) is a hyperplande .And a necessary and sufficient condition for a binary matroid to have a k-circuit is obtained.

Uniqueness of the Viscosity Solutions for the Initial Value Problem of One Type of Second Order Partial Differential Equation

Liu Changhe, Huan Zhongdan, Tong Mingsheng

1998, 7(1): 6-11.

[Abstract](261) [PDF 260KB](28)

Abstract:
Aim To prove the uniqueness of the viscosity solutions for the initial value problems of one type of second order parabolic partial differential equations: Methods Using comparison theorem. Results and Conclusion If u0 is uniform continuousfunction in RN , F is continuous function in RNx(N) and F is degenerate elliptic, then thisequation has the sole viscosity solution.

Algebraic Structure of the Dynamical Equations of Holonomic Mechanical System in Relative Motion

Zhang Yi, Mei Fengxiang

1998, 7(1): 12-18.

[Abstract](333) [PDF 331KB](28)

Abstract:
Aim To study an algebraic of the dynamical equations of holonomic mechanical systems in relative motion. Methods The equations of motion were presented in a contravariant algebraic form and an algebraic product was determined. Results and Conclusion The equations a Lie algebraic structure if any nonpotential generalized force doesn't exist while while the equations possess a Lie-admissible algebraic structure if nonpotential generalized forces exist .

Differential Variational Principles and Equations of Motion of Mechanical Systems with Unilateral Constraints

Zhang Yi, Mei Fengxiang

1998, 7(1): 19-25.

[Abstract](256) [PDF 340KB](30)

Abstract:

Lie Symmetries and Conserved Quantities of Holonomic Systems with Remainder Coordinates

Mei Fengxiaing

1998, 7(1): 26-31.

[Abstract](179) [PDF 290KB](27)

Abstract:
Aim To study the Lie symmetries and the consered quantities of the holonomic systems with remainder coordinates. Methods Using the invariance of the ordinary differential equations under the infinitesimal transformations to establish the determining equations and the restriction equations of the Lie symmetries of the systems. Results and Conclusion the structure equation and the form of conserved quantities were obtained. An example was given to illustrate the application of the result.

Research of the Phase Sensitive Detection Property of Magnetic Sensor Based on Hall Effect

Chen Jinyue, Zhou Liwei, Ding Shouqian, Li Wenshen

1998, 7(1): 32-38.

[Abstract](388) [PDF 182KB](27)

Abstract:
Aim to detect the characteristic weak magnetic field signal against the strong noises background. Methods In combination with a low-pass-filter, the correlation output of magne-* tic sensors between the magnetic field and reference current was utilized to provide a DC output voltage proportional to the applied magnetic induction, computer simulation was* done to investigate the correlation output of the Hall-effect sensors. Results Some analysis results concerning the noise property, harmonic supppression and the sensitivity were given. Conclsion The minimum detection signal of the equipment evolved from the mentioned cor-* relation theory can be 10-6 T. In addition to the DC output, such sensors can also measure the phase of the detected magnetic induction and has good harmonic suppression as well as* noise elimination.

Relationships Between Average Molecular Mass and Intrinsic viscosity of Three Typical Polyanhydrides

Shuai Xintao, Tan Huimin, Wang Xiaoqing

1998, 7(1): 39-42.

[Abstract](295) [PDF 189KB](29)

Abstract:
Aim To study the relationships between average molecular mass and intrinsic viscosity of polyanhydrides. Methods With chloroform as solvent and petroleum ether as the precipitating agent polyanhydride was separated into a series of grades with different average molecular mass. The absolute average molecular mass (M) and intrinsic viscosity ([]) of every grade were measured. Results and Conclusion The relationships between [] and M of three typical polyanhydrides were obtained from bi-logarithm coordinate plotting of [] versus M.

Capillary Zone Electrophoresis of Native Amino Acids with Indirect Ultraviolet Detection

Wang Hong, Gu Junling, Fu Ruonong, Hu Hanfang, Ding Tianhui

1998, 7(1): 43-48.

[Abstract](239) [PDF 317KB](26)

Abstract:
Aim To strdy the separation of native amino acids using capillary zone electro- pboresis (CZE) with indirect ultraviolet detecition. Methods 13 native amino acids were sepa- rated by capillary electrophoresis with indirect detection . The experiments were carried out with homemade CE apparatus under the following operating conditior conditions: a fused-silica capillary col- umn of 50.0cm effect length and of 75m i.d. was used. 7 organic acids were used as BGAE, and a positive potential of separation in CZE with indirect detection. After optimizing for l3 native amino acids were established. Conclusion The choice of BGAe is an important factor influencing the efficiency of separation in CZE with indiect detection .After optimizing the separation conditions a baseline separation for 13 native amino acids is obtained.

Stability of Three-Dimensional Trunk Motion

Gun Qiao

1998, 7(1): 49-54.

[Abstract](332) [PDF 306KB](28)

Abstract:
Aim To analyse stability of the three-dimensional rotational movements of a human torso system under perturbations using anatomical data of muscles (McGill, 1992). Methods To use the linearized analysis methods and a special model in which the effect of ligamentous and passive resitance by discs and fibers is included. Results The model is capable of predicting the muscle forces,and joint reaction forces at the L5/Sl which are the biomechani- cal factors used to asses the risk of the discs and annulus fibers. Conclusions It can also be used to analyze and neural excitation levels for a diverse Set of trunk movement.

Dynamic Rangefinding Device Using Amplitude-Modulated Continuous UltrasonicWave+

Hua Hong, Wang Yongtian, Xu Tong

1998, 7(1): 55-61.

[Abstract](248) [PDF 352KB](26)

Abstract:
Aim To develop a high speed and high resolution dynamic rangefinding device for the measurement of large distances.Methods The device was comprised of an ultrasonic transmitter and a receiver,and a receiver , and a continuous ultrasonic wave amplitude-modulated by a low- frequency acoustic signal was used. The rangefinding was achieved by detecting the phase difference between the transmitted and received ultrasonic signals. The design principle. hard- ware implementation , experimental results and performance analysis of the device are included. Results and Conclusion Experiments show that the accuracy of the device are included. within 1.5m while its dynamic data update rate can be up to 40kHz.

Piecewise Curve-Fitting Method for Measured Profile

Xia Fujie.

1998, 7(1): 62-66.

[Abstract](262) [PDF 235KB](28)

Abstract:
Aim To determine the measured profile of a wheel in railway vehicle.Methods So- called piecewise curve-fitting method of the third derivative continuity is employed . Results The formulas of the piecewise curve fitting method were derived the curve-fitting profile of a wheel looks very fine and its first to third derivatives are also smooth.Conclusion The new piecewise curve fitting method is fine enough to fit the measured profile data of a wheel for the purpose of vehicle system dynamic analysis.

The Development and Realization Mechaismof Concurrent Engineering

Ning Ruxin, Zhang Xu

1998, 7(1): 67-72.

[Abstract](277) [PDF 290KB](26)

Abstract:
Aim To study the development and realization mechanism of concurrent engineering(CE).Methods The realization mechanism based on multi-agent and micro-circulation were dis-cussed.Results The specialties of micro-circulation are wholly adaptable to the circulationtheory and information exchange requirement in CE,which can explain the nature of CEsuccessfully.Conclusion The micro-circulation theory can be adopted as a new realizationmechanism of CE.

New System to Measure the Yaw and PitchAngles of Rocket in Launch Phase

Wang Zhijun, Wang Ruichen, Wang Hui, Cai Hanwen

1998, 7(1): 73-77.

[Abstract](265) [PDF 273KB](28)

Abstract:
Aim To describe a news system for measuring the and pitch angles of rocket during the launch phase Methods Optical system was to reflect the spot that represents the angular movement of rocket to the position sensitive detector that can convert analogue signal into digital one.Results Compared with conventional optical lever test system which had been applied to measure rocket attitude angle,the new system used the position sensitive detector to replace the screen and high-speed photographic instrumentation as grapher,which can avert photointerpretive data reduction and apply to field experiment more easily and pre- cisely .Conclusion Experimental results show that the test system can be used in measuring the yaw and pitch angles of rocket effectively.

Design and Experimental Study of an 80C196KC-Based SRD System Controller

Sun Guofu, Feng Shuhua, Gao Chao

1998, 7(1): 78-83.

[Abstract](269) [PDF 304KB](28)

Abstract:
Aim To design and experimentally study an 80C196KC-based SRD (switched re- luctance motor drive drive sytem) controller,Methods with the guidelines of the digitized SRD system controller,the circuit design and software programming were completed,and a relevantexperimental system was PUT forward to test the newly designed controller.Result The experi-mental study showed that the newlydesigned controller had good speed-adjusting characteristicfor a switched reluctance motor ,its stable error was less than 5% and its full-load startingtime was shorter than 1.8s .Conclusion The new controller has reasonable circuit design and suitable controlling algorithm,and it is a feasible SRD system controller design scheme.

Criteria Selecting Knowledge Base in the FuzzyController of the Electrohydraulic Position Control System

Gao Jianchen, Wu Pingdong

1998, 7(1): 84-91.

[Abstract](271) [PDF 405KB](29)

Abstract:
Aim To analyse the influence of knowledge base on the performance of the fuzzy controller of the electrohydraulic position control system,and to determine their selection cri- teria. Methods Experiments based on different membership functions,scaling factors and con-trol rules were done separately.The experiment results and the influence of different know- ledge base on the control performance were analysed in theory so that criteria of selcting knowledge base can be summarized correctly.Results Knowledge base,including membershipfunctions, scaling factors and control rules,has a crucial effect on the fuzzy control system.Suitably selected knowledge base can lead to good control performance of fuzzy control sys-tem. Conclusion Being symmetric,having an intersection ratio of 1 and satisfying width con- dition are three necessities for selecting membership functions.Selecting scaling factors dependson both the system requirement and a comprehensive analysis in the overshoot,oscillation, rising time and stability. Integrity and continuity must be guaranteed when determining control rules.

Design and Implementation of a Heterogeneous Database System over the Intranet

Yao Lingzhong, Xing Yanhui, Song Hantao, Yang NanGuo, Guo Guisuo, Sun Dan

1998, 7(1): 92-99.

[Abstract](333) [PDF 388KB](27)

Abstract:
Aim To develop a heterogeneous database united system(HDBUS)that combines the local database of Oracle, Sybase and SQL server distributed on different server into a global database,and supports the global transaction management and parallel query over the Intranet Methods In the designing and implementation of HDBUS two important concepts heterogeneous tables join. Results and Conclu- tion The first concept can be used to process the parallel query of multiple database server, the second one is the key technology of heterogeneous is the key technology of heterogeneous distribute database.

The Design and Implementation of IPCMechanism in Mach Operating System

Zhao Xiaohui, Wang Jianguo, Shu Hua

1998, 7(1): 100-106.

[Abstract](328) [PDF 350KB](25)

Abstract:
Aim To design the home -made embedded real time operating system COSIX V2.O/RT developing platform,the Mach operating system interprocess communication mech- anism based on object-oriented technique was analyzed. Methods Not only being the trans-mission channel,but also being the abstract of all the entity in the Mach operating system.ports play the most important role in Mach IPC(interprocess communication).Ports were de-vided into 4 types: system ports, privileged ports user ports and kernel ports.All these ports'creation,run and kill processes and the message transmission in IPC were analyzed.ResultsMach IPC has been widely used in Client/Server run environment.Packing and unpacking inmessage transmission must restrict the run efficiency of IPC Conclusion To enhance IPC runefficiency and at the same time enhance the operating system's run efficiency,some of thesystem calls should be rewritten and implemented with trapped mode in kernel.In the end the aim of designing real time operating system is achieved.

A Model of Steady-State Convective Combustion of Micropore Propellants

Wang Boxi

1998, 7(1): 107-112.

[Abstract](247) [PDF 317KB](27)

Abstract:
Aim To develop a physical and mathematical model related to micropore para- meters of steady-state convective combustion of micropore propellants(MPP). Methods The micropore parameters were measured by WXT-88 mage analysis apparatus and the convective combustion characteristic of MPP was measured by a large volume closed bomb, respectively. Rasults Statistical physical model of burning in the micropore and granular burning were developed. The burning rate equation of steady-state convective combustion of MPP was obtained. Conclusions This model correlates the convective burning rate with micropores para- meters for the first time,and the calculating values of convective burning rate are in agreement with test results.The model also can be used to estimate the effects of microporous parame- ters, basic mass burning rate, MPP density and pressure in combustion chamber on the convective combustion characteristics of MPP.

1998 Vol. 7, No. 1