JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

The Existence of Generalized Solutions for a Nonhomogeneous Boundary Value Problem

1998, 7(3): 210-214.

[Abstract](222)

Abstract:
Aim The existence of generalized solution for a class of nonlinear partial differential equations with nonhanogeneous boundary condition was investigated. This problem arises from polymer processing concerned with the first initial-boundary value problem or the nonstationary floW of non-Newtonian viscous incompressiblee fluid through the slit dice. MethodsThe monotone operator theory and the Schauder's fixal point theorem were used. Results and Conclusion The existence theorem of generalized solutions for a the of nonlinear partial differential equations with nonhormogeneous boundary condition is proved under reasonable conditions

Lie Symmetries and Conserved Quantities of Holonomic Mechanical Systems in Terms of Quasi-Coordinatee

Fu Jingli, Liu Rongwan, Mei Fengxiang

1998, 7(3): 215-220.

[Abstract](146)

Abstract:
Aim To study the Lie symmetries and conserved quantities of holonomic mechanical systems in terms of qnasi-coordinates. Methods The definition of an infinitesimal generator for the holonomic mechanical systems in terms of quasi-coordinates was given. Lie's method of the invariance of ordinary differential equations under infinitesimal transformations was used. Results and Conclusion The determining equations of the Lie symmetries of holonomic mechanical systems in terms of quassi-coordinates are established. The structure equation and the form of conserved quantities are obtained. An example to illustrate the applicaiton of the result is given.

Lie Symmetries and Conserved Quantities of Systems of Relative Motion Dynamics

Liu Rongwan, Fu Jingli, Mei Fengxiang

1998, 7(3): 221-225.

[Abstract](181) [PDF 233KB](2)

Abstract:
Aim To study the Lie symmetries and conserved quantities of the dynamical equationsof relative motion for holonomic mechanical systems. Methods Lie's method of the invariance of ordinary differential equations under infinitesimal transformations was used. Results and Conclusion The determining equaiton of the Lie symmetries for the dynamical equationS of relative motion is established.The structure quation and the form conserved quantities are obtained. An example iD illustrate the application of the result is given.

Several Fundamental Theorems and Conservative Integrals in Quasicrystal Elasticity Theory

Li Xianfang, Sun Yingfei, Fan Tianyou

1998, 7(3): 226-232.

[Abstract](150)

Abstract:
Aim To extend several fundamental theorems of conventional elasticity theory to quasicrystalelasticity theory. Methods The basic governing equations of quasicrystal elasticity theory and Gauss's theorem were applied in the derivation. Results and Conclusion The principle of virtual work, Betti's reciprocal theorem and the uniqueness theorem of quasicrystal elasticity theory are proud, and some conservative integrals in quasicrystal elasticty theory are obtained.

Dynamic Response of Stepped Beams Under Impulsive Loading

Sun Tao, Feng Shunshan

1998, 7(3): 233-239.

[Abstract](149)

Abstract:
Aim To analyze dynamic failure of aerospace strutures subjected lateral impulsive loading. Methods Structures were modeled as rigid-perfectly plastic free-free stepped beams. Basic equations of motion un set up for analysis. Results Final pat deformation and rigid motion solutions were determined for a uniform impulsive loading. The critical rupture conditions for a space shuttle and a missile were obtained. Conclusion Failure is possible for aerospace structures under a uniform impulsive loading, but it is mere difficult in space.

Nonequilibrium Statistical Nature of Intergranular Brittle Fracture in Polycrystal

Shao Bin, Xing Xiusan

1998, 7(3): 240-246.

[Abstract](158)

Abstract:
Aim To study intergranular brittle fracture behaviors in polycrystal. Methods Nonequilibrium statistical theory of fracture was made and the blocking influence of triple junctions on crack growth was considered . Results The intergranular crack growth rate was given, the fracture probability, reliability, statistical distribution function of fracture strength, fracture toughness and their statistical average values changing with grain size, interface energy and other physical parameters were derived. Conclusion Nonequilibrium statistical theory of the intergranular brittle fracture is build-up.

Finite Element Analysis on Plane Stress Crack Growth in a Power-Law Hardening Material

Wu Xiangfa, Fan Tianyou

1998, 7(3): 247-251.

[Abstract](241)

Abstract:
Aim To determine numerically the field characteristics in the vied at the tip of a place crack growing steadily in a power-law hardening material. Meteods. Methods on the Euler mode and small-scale yield assumption, the numerical results were given by nonlinear finite element analysis. Results The numerical results of the shape of the active plastic sone, the angular distribution of stresseses and Clack tip opening displacement (CTOD) in the vicinity at the hp of the steadily groWing CraCk are determined. Conclusion The comparison between the numerical results given by the present wort and those given by analytic asymptotic analysis shows that the present work reached a very high accuracy.

Analytic Study on a Plane Stress Tensile Crack in a Power-Law Hardening Material

Wang Wenxin, Zhang Liangxin, Fan Tianyou

1998, 7(3): 252-256.

[Abstract](174)

Abstract:
Aim To construct an analytic solution for the asymptotic field near a tensile cracktip of power-law hardening material under Plane stress condition. Methods Constructing funtion method was used. Results The exact asymptotic field was found. Conclusion The exact analytic solution for the problem is available.

Scaling Rules for the Percolation Model of Dielectric Breakdown

Zou Jian, Ding Hongzhi, Xing Xiusan

1998, 7(3): 257-261.

[Abstract](141)

Abstract:
Aim To study the dIelectric breakdown phenomenon in the materials with quenched disorder. Methods Renormolization group methods were used. Results The percolation limit for breakdown pc , the breakdown field Ec～(Pc-p)v, and the fractal dimension of the structure of dielectric breakdown df were obtained. Conclusion The breakdown properties of the materials with quenched disorder are characterized by universal power laws, where the exponents are universal.

Three Cinnamyl β-Cyclodextrins Used as GC Stationary Phases

Xiao Deqing, Ling Yun, Fu Ruonong, Zhao Zhengtong, Gu Juuling, Wen Yuxiu

1998, 7(3): 262-267.

[Abstract](172)

Abstract:
Aim To study the chromatographis beheviors of three new cinnamyl cyclodextrin derivative stationary phases. Mehtods Three new cinnamyl β-cyclodextrins, heptakis-(2, 6-di-O-cinnamyl-3-O-methyl)-β-CD, heptakis-(2, 6-di-O-cinnamyl-3-O-acetyl-)-β-CD and heptakis-2, 6-di-O-cirinamyl-3-O-trifluoroacetyl)-β-CD were synthesized and coatal on fused-silica capillary columns . Results The new stationary phases have better thermal stability, good column efficiency and excellent mpaxation power for some sutstituted benzene positional isomers. It was found that the introduction of cinnamyl groups has a significant effect on these stationary phases. Conclusion There new subetituted β-CD compounds are very suitable to be ed as gas chromatographic stationary phases.

Investigation on Two Novel Substituted β-Cyclodextrins Used as GC Stationary

Xiao Deqing, Ling Yun, Fu Ruonong, Gu Junling, Zhao Zhengtong, Dai Rongji

1998, 7(3): 268-273.

[Abstract](151)

Abstract:
Aim To study the chromatographic behaviors of two dipentyl cyclodextrin derivative stationary phases. Methods Two new β-cyclodextrin derivatives, heptakis-[2, 6-di-O-pentyl-3-O-(4-nitrobenzyl)] -β-CD and heptakis-[2, 6-di-O-pentyl-3 -O-(5 -hexenyl)]-β-CD, were synthesized and coatal on fed-silica capillary columns. The chromatographic behaviors of the columns were characterized . Results It was found that the she, polarity, and aromatic property of the substituted group at the 3-position of heptakis-(2, 6 - di - O - pentyl) - β - cyclodextrins greatly influenced their chromatographic properties and separation ability. The introduction of aromatic group or a group containing a double-bond may bring π-π interactions between the host and guest molecules, and therefore increases the separation ability of the β-CDs for substituted benzene isomers. Conclusion The new substituted β-CD compounds are very suitable for being used as gas chromatogaphic stationary phases.

Study on the Dielectric Properties of Chemical Vapor Deposited Diamond Film

Wang Hao, Wang Xiufen, Guo Lin, Zhu Hesun

1998, 7(3): 274-279.

[Abstract](168) [PDF 396KB](2)

Abstract:
Aim To study the dielectric properties of diamond film. Methods Dielectric properties (the frequency dependenCe of conductance, permittivity, and loss factor) of diamond film preped by DC are plasma jet chemical vapor deposition (CVD) were studied. Resuls Dielectric properties of CVD diamond fAn depend mainly on its polycrystalline nature, and the presence of non-diamond disordered graphitic regions and impurities between diamond grains of the film. Annealing at 500℃ leads to the removal of greater part of disordered graphitic regions, but am not remove all disordered graphitic regions and impurities. Conclusion Much work nab to be done tO prepare or post-treat diamond films before using CVD diamond as a substrate for electronic devices.

Study of Diesel Engine Management System

Zhang Yotong, Cheng Changqi, Liu Xinghua

1998, 7(3): 280-285.

[Abstract](176)

Abstract:
Aim To study the diesel engine management spstem (DEMS). The DEMS can consider many engine parameters and so it can acquire the optimum system performance. Methods On the basis of analyzing the characteristics of diesel engine electronic system, the real-time, multi-tasks system design methods were used for the heavy duty vehicular diesel engine electronic control system . The hardware and software of DEMS were developed. Results and Conalusion By the test on dieSel engine bed, the system was verified and the foundation of the fully developed DEMS was laid.

Calculation and Analysis of Near Field of Airborne Short Wave Antenna

Xue Zhenghui, Gao Benqing, Liu Ruixiang, Lu Xin, Yang Li

1998, 7(3): 286-292.

[Abstract](214)

Abstract:
Aim To calculate and analyze the near field distribution of ariborne short wave antenna. Methods B-spline method was used to get the mathermatital model of a Boeing 707320Baircraft and simulate its short wave antenna . FDTD (finite-difference time-domain) method are ed tO complete the calculation and analysis. Results The near field distributions on aircraft's surface were obtained, the curve and gray figures of the normalized near field value were shown. Conclusion These modeling and calculating methods can provide data foraircraft's EMC analysis and design.

Model Identification of Water Purification Systems Using RBF Neural Network

Xu Lixin

1998, 7(3): 293-298.

[Abstract](204)

Abstract:
Aim The RFB (radial hats function) netal network was studied for the model indentificaiton of an ozonation/BAC system. Methods The optimal ozone's dosage and the remain time in carbon tower were analyzed to build the neural network model by which the expected outflow CODM can be acquired under the inflow CODM condition. Results The improved self-organized learning algorithm can assign the centers into appropriate places , and the RBF network's outputs at the sample points fit the experimental data very well. Conclusion The model of ozonation /BAC system based on the RBF network am describe the relationshipamong various factors correctly, a new prouding approach tO the wate purification process is provided.

Target Tracking Using the Interactive Multiple Model Method

Zhang Jinsong, Yang Weiqin, Hu Shiqiang

1998, 7(3): 299-304.

[Abstract](365)

Abstract:
Aim To develop a practical target tracking algorithm for different motion modes. Methods After creation of the new model, it was implemented by computer simulation to prove its performance and compared with the often-used current statistical model. Results The simulation results show that the new IMM (interactive multiple model) have low tracking error in both maneuVering segment and non^Inaneuwi segment while the current statistical model bas muCh higher tracking error in non-maneuvering segment. Conclusion In the point of trackintaccuracy, the new IMM method is much better than the current acceleration method. It can develop into a practical target hacking method.

Kalman Fliter Approach to Multisensor Registration of Moving Platform

Hu Shiqiang, Tang Weiqin, Wei Wuzhong

1998, 7(3): 305-310.

[Abstract](222)

Abstract:
Aim To find an effective method to remove the registration error in multi-sensor systems. Methods A Kalman filtering technique was proposed to estimate and remove sensor bias and sensor fare tilt errors in multisensor systems with a moving platform. Results Simulation results are presented to demonstrate the performance of the approach. Conclusion The Kalman filter algorithm am detect registration errors and use this information to converge tracks from independent sensors. This is particularly important if the data from the sensors are to fused.

Multitask Data Processing in a Wireless Alarm System

Liu Jie, Han Yueqiu, Song Wenxia

1998, 7(3): 311-315.

[Abstract](175) [PDF 258KB](6)

Abstract:
Aim To achieve multitask data procssing in a wireless alarm system by computer. Methods The alarm system was composed of hardware and software. The hardware was composed of a master master computer and slave transmitters. On urgent ugent occasion, one or more of the transmitters transmitted alarm signals and the master computer received the signals; interruption, residence, graph and word processing were utilized in software to achieve multitiask data processing . Results The main computer can conduct precise and quick multitask data procesing in any condition so long as alarm signals are received. The processing speed is higher than ordinary alarm System. Conclusion The master computer can conduct safe and quick multitask data processing by way of reliable design of software and hardware , so there is no need of special processor.

A New Adaptive Image Segmentation Method

Shen Tingzhi, Fang Ziwen, Wu Lingyan, Wang Fei

1998, 7(3): 316-321.

[Abstract](328) [PDF 282KB](17)

Abstract:
Aim Researching the optimal thieshold of image segmentation. M^ethods An adaptiveimages segmentation method based on the entropy of histogram of gray-level picture and genetic. algorithm (GA) was presental. Results In our approach, the segmentation problem was formulated as an optimization problem and the fitness of GA which can efficiently search the segmentation parameter space was regarded as the quality criterion. Conclusion The methodcan be adapted for optimal behold segmentation.

1998 Vol. 7, No. 3