JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Application of Improved Genetic Algorithm in Network Fault Diagnosis Expert System

SU Li min, HOU Chao zhen, DAI Zhong jian, ZHANG Ya jing

2003, 12(3): 225-229.

[Abstract](148)

Abstract:
Knowledge acquisition is the “bottleneck” of building an expert system. Based on the optimization model, an improved genetic algorithm applied to knowledge acquisition of a network fault diagnostic expert system is proposed. The algorithm applies operators such as selection, crossover and mutation to evolve an initial population of diagnostic rules. Especially, a self adaptive method is put forward to regulate the crossover rate and mutation rate. In the end, a knowledge acquisition problem of a simple network fault diagnostic system is simulated, the results of simulation show that the improved approach can solve the problem of convergence better.

Filtering and Estimation of Vehicular Dead Reckoning System Based on Hopfield Neural Network

BI Jun, FU Meng yin, ZHANG Qi hong

2003, 12(3): 230-235.

[Abstract](197)

Abstract:
The algorithm of Hopfield neural network filtering and estimation is studied. The model of vehicular dead reckoning system fitting for the algorithm is constructed, and the design scheme of system filtering and estimation based on Hopfield network is proposed. Compared with Kalman filter, the algorithm does not require very precise system model and the prior knowledge of noise statistics and does not diverge easily. The simulation results show that the vehicular dead reckoning system based on Hopfield network filtering and estimation has the good position precision, and needn't require the inertial sensors with high precision. Therefore, the algorithm has the good practicability.

Threshold Determination and Analysis of Laser Pulse Range Finder

YIN Cong, HAN Shao kun, LIU Xun liang, ZHANG Hua peng, ZHAO Yue jin

2003, 12(3): 236-239.

[Abstract](178)

Abstract:
Under different conditions, the highest detection probability should be acquired while receiving laser echo during laser pulse range finding. The threshold voltage of the signal detection can be set corresponding to different conditions by using resistor network. As a feedback loop, automatic noise threshold circuit could change the threshold voltage following the noise level. The threshold can track the noise closely, rapidly and accurately by adopting this combination. Therefore, the receiving capability of laser echo receiving system will be maximized, and it can detect weaker laser pulse from noise.

Detection of Petroleum Pollutants by Using Laser Induced Fluorescence Imaging

HE Fei, YAN Ji xiang, LI Jia ze

2003, 12(3): 240-242.

[Abstract](199)

Abstract:
A new laser induced fluorescence imaging system used for detecting and locating the petroleum pollutants is presented. A unique feature of the system was using a combination of a frequency tripled Nd:YAG pulse laser and an image intensified CCD camera as imaging detector. The delay time of the system and the exposure time of the CCD are controlled by a delay generator. Petroleum pollutants on various backgrounds had been detected and located by this system. This imaging technique provides a useful noninvasive approach for the detection of petroleum pollutants, which can be used in remote sensing.

Two Efficient Techniques to Simplify the Excitation Setting Problem in R-FDTD Algorithm

LIU Bo, GAO Ben qing, YANG Shi ming, XUE Zheng hui

2003, 12(3): 243-246.

[Abstract](93)

Abstract:
As a lately developed technique for FDTD, R FDTD (reduced FDTD) algorithm is complicated for dealing with the problem of excitation setting. In order to get rid of such difficulty, two simple techniques are proposed. One technique is to classify field points into two types according to the value of electric divergence equation. The other technique is subregion connection. The corresponding modified R FDTD can not only inherit the memory efficient character, but also eliminate the complexity aroused by the existence of excitation and conductors. Simulation results are compared between those obtained from traditional FDTD and those from R FDTD. Good agreement is observed.

Adaptive Dual-Threshold Edge Detection Based on Wavelet Transform

HOU Shu juan, MEI Wen bo, ZHANG Zhi ming

2003, 12(3): 247-250.

[Abstract](78) [PDF 174KB](2)

Abstract:
In order to solve the problems of local maximum modulus extraction and threshold selection in the edge detection of finite resolution digital images, a new wavelet transform based adaptive dual threshold edge detection algorithm is proposed. The local maximum modulus is extracted by linear interpolation in wavelet domain. With the analysis on histogram, the image is filtered with an adaptive dual threshold method, which effectively detects the contours of small structures as well as the boundaries of large objects. A wavelet domain's propagation function is used to further select weak edges. Experimental results have shown the self adaptivity of the threshold to images having the same kind of histogram, and the efficiency even in noise tampered images.

Image Combination Analysis in SPECAN Algorithm of Spaceborne SAR

ZANG Tie fei, LI Fang hui, LONG Teng

2003, 12(3): 251-254.

[Abstract](169)

Abstract:
An analysis of image combination in SPECAN algorithm is delivered in time frequency domain in detail and a new image combination method is proposed. For four multi looks processing one sub aperture data in every three sub apertures is processed in this combination method. The continual sub aperture processing in SPECAN algorithm is realized and the processing efficiency can be dramatically increased. A new parameter is also put forward to measure the processing efficient of SAR image processing. Finally, the raw data of RADARSAT are used to test the method and the result proves that this method is feasible to be used in SPECAN algorithm of spaceborne SAR and can improve processing efficiently. SPECAN algorithm with this method can be used in quick look imaging.

New Image Recognition Method Based on Rough-Sets and Fuzzy Theory

ZHANG Yan, LI Feng xia, ZHAN Shou yi

2003, 12(3): 255-259.

[Abstract](194)

Abstract:
A new image recognition method based on fuzzy rough sets theory is proposed, and its implementation discussed. The performance of this method as applied to ferrography image recognition is evaluated. It is shown that the new method gives better results than fuzzy or rough sets method when used alone.

Design and Implementation of an RDP Device Driver for Windows 2000

TAN Yu an, CAO Yuan da

2003, 12(3): 260-264.

[Abstract](155)

Abstract:
A redundant data path(RDP) device driver for Windows 2000 is proposed and implemented to provide automatic transparent failover and load balancing across multiple SCSI or fibre paths between the hosts and the storage subsystems. RDP driver is implemented as a filter driver on top of the traditional disk device driver, it is completely transparent to the upper file system and the lower level physical device. I/O requests bound for the disk device are routed first to the RDP driver, then RDP driver calls the disk driver to perform these I/O requests. RDP detects the path failure and reroutes all subsequent I/O traffic through survival paths. I/O requests are distributed to different physical paths to achieve the maximum throughput. The multi layered device driver approach significantly reduces the implementation overhead and improves portability, and does not require any changes to the OS or the on disk data layout. RDP driver keeps applications running under path fault conditions and improves disk I/O performance.

Model of Trust Management in Open Network Environment

CAO Yuan da, NING Yu peng

2003, 12(3): 265-268.

[Abstract](164)

Abstract:
To keep open network more efficacious and secure, it is necessary that a nice trust model and method of trust management must be developed. The reason why traditional trust models are incomplete in their function to manage trust is explained, and a general model based on hybrid trust model and introducer protocol is provided. The hybrid model is more flexible and efficacious to manage trust compared with hierarchy model and Web model. The introducer protocol is a better solution to build, maintain and refresh the trust relationship in open network environment.

On the Elastic Vibration Model for High Length-Diameter Ratio Rocket with Attitude Control System

ZHU Bo li, YANG Shu xing

2003, 12(3): 269-272.

[Abstract](274) [PDF 158KB](14)

Abstract:
An elastic vibration model for high length diameter ratio spinning rocket with attitude control system which can be used for trajectory simulation is established. The basic theory of elastic dynamics and vibration dynamics were both used to set up the elastic vibration model of rocket body. In order to study the problem more conveniently, the rocket's body was simplified to be an even beam with two free ends. The model was validated by simulation results and the test data.

Experimental Study of the Impact Damage of Composition B and Plastic Bonded Explosive

CHEN Peng wan, HUANG Feng lei, DING Yan sheng

2003, 12(3): 273-277.

[Abstract](207)

Abstract:
A long pulse low velocity gas gun with a gas buffer is used to induce impact damage in cast Composition B and hot pressed PBXN 5. To obtain different damage states, a range of projectile velocities are used by controlling the launching pressure of gas gun. The stress history during impact loading is recorded. Various methods are used to characterize the damage state of impacted explosive samples. The microstructure is examined by use of scanning electronic microscopy (SEM) and polarized light microscopy (PLM). The densities and ultrasonic attenuation are also measured. The results show that both Composition B and PBXN 5 exhibit some damage characteristics of brittle materials. However, due to the difference in compositions, PBXN 5 exhibits better resistance to impact loading than Composition B.

Direct Monte Carlo Method Simulation of the Synthesis of Carbon Particle Through Coagulation in the Detonation of Explosives

MA Feng, YUN Shou rong, HUANG Feng lei

2003, 12(3): 278-281.

[Abstract](217)

Abstract:
A model is constructed and used in computing the coagulation probability of free carbon during the detonation of explosives. A direct simulation Monte Carlo (DSMC) program is constructed to simulate the coagulation of free carbon particles. The evaluation of the distribution spectrum of particles in the system is obtained. The simulation result is consistent with the experimental curve.

Heat Transfer Between a Missile's Combustion Chamber and the Warhead

ZHAO Yong tao, ZHANG Qi, BAI Chun hua, YAN Hua

2003, 12(3): 282-285.

[Abstract](131)

Abstract:
Under higher temperatures the charge within a warhead will be subjected to physical and chemical changes, which will influence the security of the warhead launching process. In this paper the problem is studied adopting finite difference method for the case of a rocket powered missile. Temperature distribution tables are given through quadrature experiments, and the results fit the actual measured values very well. The results also show that to ensure the launching security of rocket powered missiles having warhead charge critical temperature close to about 60?℃, the designer can select appropriate heat insulation structural parameters.

Simulation Analysis of Indoor Gas Explosion Damage

QIAN Xin ming, CHEN Lin shun, FENG Chang gen

2003, 12(3): 286-289.

[Abstract](199)

Abstract:
The influence factors and process of indoor gas explosion are studied with AutoReaGas explosion simulator. The result shows that venting pressure has great influence on the indoor gas explosion damage. The higher the venting pressure is, the more serious the hazard consequence will be. The ignition location has also evident effect on the gas explosion damage. The explosion static overpressure would not cause major injury to person and serious damage to structure in the case of low venting pressure (lower than 2 kPa). The high temperature combustion after the explosion is the major factor to person injury in indoor gas explosion accidents.

Design and Development of a Vector Control System of Induction Motor Based on Dual CPU for Electric Vehicle

SUN Feng chun, ZHAI Li, ZHANG Cheng ning, PENG Lian yun

2003, 12(3): 290-295.

[Abstract](147)

Abstract:
A vector control system for electric vehicle (EV) induction motor drive system is designed and developed. Its hardware system based on dual CPU(microcomputer 80C196KC and DSP TMS320F2407) is implemented. The fundamental mathematics equations of induction motor in the general synchronously rotating reference frame ( M T frame) used for vector control are achieved by coordinate transformation. Rotor flux equation and torque equation are deduced. According to these equations, an induction motor mathematical model and rotor flux observer model are built separately. The rotor flux field oriented vector control method is implemented based on these models in system software, some of the simulation results with Matab/Simulink are given. The simulation results show that the vector control system for EV induction motor drive system has better static and dynamic performance, and the rotor flux field oriented vector control method was practically verified.

Study on a Closed-Loop Air-Fuel Control System of Gasoline Engines by Simulation

ZHANG Fu jun, ZHAO Chang lu, HUANG Ying, HAO Li jun

2003, 12(3): 296-301.

[Abstract](167)

Abstract:
In order to study the factors that influence the air fuel ratio(A/F), the amplitude and frequency of A/F fluctuation, to reform the control strategy, and to improve the efficiency of three way catalyst(TWC), a model of closed loop control system including the engine, air fuel mixing and transportation, oxygen sensor and controller, etc., is developed. Various factors that influence the A/F control are studied by simulation. The simulation results show that the reference voltage of oxygen sensor will influence the mean value of A/F ratio, the controller parameters will influence the amplitude of A/F fluctuation, and the operating conditions of the engine determine the frequency of A/F fluctuations, the amplitude of A/F fluctuation can be reduced to within demanded values by logical selection of the signal acquisition method and controller parameters. Higher A/F fluctuation frequency under high speed and load can be reduced through software delay in the controller. The A/F closed loop control system based on the simulation results, accompanied with a rare earth element TWC, gives a better efficiency of conversion against harmful emissions.

Analysis of Control Characteristic for the Drive System of Electric Transit Bus

ZHANG Cheng ning, LI Hong lin, SUN Feng chun, ZHANG Wang

2003, 12(3): 302-306.

[Abstract](143)

Abstract:
The drive control system of the permanent magnetic direct current motor with the enhanced magnetism windings used in the electric transit bus is developed. The mathematics model of the drive control system for this motor is established. The new mode that the added exiting magnetism field could be weakened and the speed of the motor could be controlled automatically is proposed and realized. The method of root locus design is applied to analyze the acceleration control characteristic. The results of simulation show that the new drive motor control system has extraordinary response characteristic and adjustable performance. Experiments of vehicle running show that the drive control system's antijamming ability is strong and the adjustable performance is fast and smooth, it can meet the demand of power characteristic very well.

New Image Operator and Its Application in the Inner Surface Detection of Artillery Pipe

ZHENG Jun, XU Chun guang, XIAO Ding guo, HANG Jian min

2003, 12(3): 307-311.

[Abstract](89)

Abstract:
Aimed at the image detection on the ablation wearing, scrape wearing and rifling angle of the artillery body pipe, the character of the inner surface image of the pipe is discussed, the model for rifling, ablation wearing and scrape wearing is brought up, and a new image operator is proposed for these detection. This operator can detect the rifling angle in a high precision, and tell the ablation wearing from scrape wearing in the image, therefore the degree of ablation wearing and scrape wearing can be detected efficiently. This is useful for the artillery body pipe's producing process and life evaluation.

Preparation and Characterization of Super Absorbent Resin from Natural Cellulose

LI Jie, MA Feng guo, TAN Hui min

2003, 12(3): 312-315.

[Abstract](225)

Abstract:
The grafting polyacrylamide onto wood pulp cellulose (cell g PAM) was performed with cerous ammonium nitrate as the initiator and hydrolyzed to produce the super absorbent resin. The FTIR shows that the polyacrylamide is grafted on the cellulose. After hydrolyzation, part of acrylamino groups are transformed into carboxyl groups. The XRD analysis shows that the graft polymerization occurred at the amorphous section and the surface of the crystal section of cellulose. The SEM graph reveals that there is a layer of polymer on the surface of cellulose fiber and the fibril structure of the cellulose surface is covered. After hydrolyzation, the surface of the product is different from that of cell g PAM's and the surface is scraggy. The technical conditions to prepare high water absorbent resin were confirmed. Through the radical graft copolymerization, the high water absorbent resin can be produced from wood pulp cellulose.

Sign Patterns That Allow the Given Matrix

SHAO Yan ling, SUN Liang

2003, 12(3): 316-318.

[Abstract](217)

Abstract:
Let P be a property referring to a real matrix. For a sign pattern A, if there exists a real matrix B in the qualitative class of A such that B has property P, then we say A allows P. Three cases that A allows an M matrix, an inverse M matrix and a P 0 matrix are considered. The complete characterizations are obtained.

Signed Total Domination in Graphs

XING Hua ming, SUN Liang, CHEN Xue gang

2003, 12(3): 319-321.

[Abstract](203)

Abstract:
Let G=(V,E) be a simple graph. For any real valued function f:V →R, the weight of f is f(V) = ∑f(v) over all vertices v∈V . A signed total dominating function is a function f:V→{-1,1} such that f(N(v)) ≥1 for every vertex v∈V . The signed total domination number of a graph G equals the minimum weight of a signed total dominating function on G . In this paper, some properties of the signed total domination number of a graph G are discussed.

On Translation Hypersurfaces with Constant Mean Curvature in (n+1)-Dimensional Spaces

CHEN Chun, SUN Hua fei, TANG Li

2003, 12(3): 322-325.

[Abstract](223)

Abstract:
The translation hypersurfaces with nonzero constant mean curvature in (n+1) dimensional spaces are studied. It is the generalization of the classical Scherk theorem. The classification of translation hypersurfaces with nonzero constant mean curvature in Euclidean and Lorentz spaces is completely given.

Enhancing the Security of He-Kiesler Signature Schemes

LI Chun hui, CHEN Yi hong

2003, 12(3): 326-328.

[Abstract](94)

Abstract:
Although the He Kiesler signature is said to be proposed based on the discrete logarithm problem and the factorization problem, it has been proved that the signature is not as secure as it was stated to be. A new signature scheme is here proposed based on the discrete logarithm problem and the factorization problem to enhance the security of the He Kiesler signature.

Study on Game Theory of Social Law Enforcement

ZHANG Guo chen, LI Zhi cheng

2003, 12(3): 329-331.

[Abstract](95)

Abstract:
Based on the basis of the two stage dynamic game of complete information and purely tactful perfect equilibrium theory, the non cooperative gaming between the police department and the criminals is analyzed. Dynamic game can be proved to forecast and explain potential tactful choices of the police department and the criminals at various stages, so as to analyze the essence of the law enforcement by the theoretical models.

Dynamic Damage Model of Brittle Rock and Its Application

GAO Wen xue, LIU Yun tong, YANG Jun, HUANG Feng lei

2003, 12(3): 332-336.

[Abstract](196)

Abstract:
On the basis of shock induced experiments and the ultrasonic tests of the damaged rocks, the damage evolution relation between the attenuation coefficient of sound wave and the damage dissipated energy is described. Based on the TCK and RDA models, a damage model which connects the shock compression and tensile damage is established. And then the damage model is implemented in LS DYNA3D dynamic nonlinear program. Numerical simulation of deep hole blasting of groove is studied by use of the damage model proposed. The rock damage evolution process and the distributing rules of stress field under the explosion load are described well fairly, which provides the theory basis for the engineering blasting design.

2003 Vol. 12, No. 3