JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

A Hybrid Neural Network for Spatiotemporal Pattern Recognition

Cao Yuanda, Chen Yifeng

1996, 5(1): 1-6.

[Abstract](330) [PDF 317KB](24)

Abstract:
A hybrid network is presented for spatio-temporal feature detecting, which is called TS-LM-SOFM. Its top layer is a novel single layer temporal sequence recognizer called TS which can transform sparse temporal sequential pattern into abstract spatial feature representations. The bottom layer of TS-LM-SOFM, a modified self-organizing feature map, is used as a spatial feature detector. A learning matrix connects the two layers. Experiments show that the hybrid network can well capture the spatio-temporal features of input signals.

The Effect of Cutout on Natural Frequencies of Thin Plate

Yang Guoshu

1996, 5(1): 7-12.

[Abstract](252) [PDF 304KB](25)

Abstract:
The laws that natural frequencies of rectangular plate with a cutout will change with size and position of cutout are obtained by analytic, numerical and experimental methods.

Nonequilibrium Statistical Theory of Fracture

Xing Xiusan

1996, 5(1): 13-18.

[Abstract](386) [PDF 329KB](26)

Abstract:
Nonequilibrium statistical theory of fracture is a theory of fracture that macromechanical quantities can be derived from the microscopic atomic mechanism of microcrack(or microvoid)evolution kinetcs by means of nonequilibrium statistical physical concepts and methods. The microcrack evolution equation is the central equation in the theory.The coefficents of the equation, the microcrack growth rate and the microcrack nucleation rate,come from microscopic atomic mechanism.The solution of the equation connects with macromechanical quantities by the model of the weakest chain. All the other formulas and quantities, for instance, distribution function,fracture probability, reliability, failure rate and macromechanical quantities such as strength, toughness, life etc. and their statistical distribution function and statistical fluctuation are derived in a unified fashion and expressed by a few physical parameters. This theory can be widely applied to various kinds of fracture, such as the brittle, fatigue, delayed and environmental fracture of metals and structural ceramics. The theoretical framework of this theory is given in this paper.

Analysis of a Cavity Used for Medical Purposes with the Dyadic Green's Functions and the Moment method

Xue Zhenghui, Liu Yongshan, Li Desheng, Wang Kun

1996, 5(1): 19-26.

[Abstract](393) [PDF 384KB](27)

Abstract:
The structure of a microwave radiator used for medical purposes is described. The dyadic Green's function and the method are used to analyze this Kind of multimode rectangular medium-filled cavity. The distribution of electromagnetic field intensity and the power density,as well as the temperature effect in the biological sample load are obtained.OPtimization of the size of cavity and the position of the input aperture have been performed with the computer to optimize the uniformity or microwave effect and the input VSWR.Necessary experiments were performed to compare the data obtained with theoretical analysis.

Crystal Growth and Structure of Novel Tolane Nonlinear Optical Materials

Wang Chaoguo, Feng Jinseng, Yu Congxuan

1996, 5(1): 27-34.

[Abstract](288) [PDF 402KB](25)

Abstract:
A novel tolane 4-methoxy-4'-nitro-diphenyl-acetylene (MONA) has been prepared quantitatively by reacting cuprous p-methoxy phenyl-acetylene with p-iodonitrobenzene. A single crystal of the Moan was grown by solution growth method. The crystal was then characterized by X-ray diffraction structure analysis and second-harmonic generation(SHG)investigation. Polymorphous crystal forms of the MONA were grown from different solvents having different nonlinear optical properties depending on their different crystal structures. The relationship between the crystal growth and crystal structure is discusse.

A Peptides Migration Model in capillary Zone Electrophoresis

Liang Heng, Wang Zhenggang, Gu Junling, Fu Ruonong, Lin Bingcheng

1996, 5(1): 35-39.

[Abstract](256) [PDF 264KB](26)

Abstract:
A peptides migration model based on the principle of mechanics is presented in capillary zone electrophoresis (CZE). It is shown that the migration that the (tr) is a function of electric (Q), relative molecular mass (Mr), conformation parameter (Rc) of peptides and electrophoretic condition parameter(A). The conformation parameter is introduced to characterize multifarious shapes owing to the complex conlormation and the various kinds of macromolecules, where Rc≥1/3. The parameters A and Rc can be obtained from experimental data. The times of migration of the nine standard peptides were measured in pH 2.5buffer on different electrophoretic conditions in CZE. The experimental results agreed well with the theoretical prediction.

Study on Longitudinal Load Distribution on Gear Tooth

Ge Beijing, Zhao Guoshan

1996, 5(1): 40-48.

[Abstract](450) [PDF 437KB](34)

Abstract:
Regularity of longitudinal load distribution on gear tooth when tooth faces are contacted uniformly and when only tooth ends are contacted, and influence on distribution exerted by longitudinal correction and flexible gear structure, are studied in the paper with method of finite element calculation combined with experiment. Research shows that load concentration exists on the conditions of uniform contact or one-end contact, and in the later case the stress nonuniformity factor on root is 1.5 to 2.0 times larger than in the former case. It also verifies that longitudinal correction and increased flexibility of gear structure are effective to improve longitudinal load distribution.

Hardware-in-loop Simulation(HLS) of Homing Anti-tank Missile

Song Jianmei, Zhang Tianqiao

1996, 5(1): 49-54.

[Abstract](296) [PDF 281KB](27)

Abstract:
The simulation techniques of hardware-in-loop simulation(HLS) of homing antitank missile based on the personal computer (PC) are discussed. The PC and MCS-96 chip controller employ A/D and D/A boards (with photoelectricity isolation) to transfer measur ment and control information about homing head, gyro and rudder and utilize the digital hand shaking board to build correct communication communication protocol. In order to satisfy the real-time requirement of HLS, this paper first simplifies the aerodynamic data file reasonably, then builds a PC software with C language. The program of the controller part is made with PL/M language. The simulation of HLS based on PC is done with the same sampling period of 10ms as that of YH-F1 and the experiment results are identical to those of digital simulation of the homing anti-tank guided missile.

A Kinetic Model of Dielectric Ageing

Ding Hongzhi, Zhao Rubao, Xing Xiusan, Zhu Hesun

1996, 5(1): 55-62.

[Abstract](302) [PDF 409KB](26)

Abstract:
A kinetic model of dielectric ageing is presented. The central finding of this investigation is that there is a power-law relationship between the local electric field concentration and the rate of defect-tip initiated conducting crack growth. By applying such a power-law conducting crack growth rate expression to the evaluation of the life of solid dielectrics, the empirical classical ageing law of insulation materials can be derived theoretically as a lobical result. All the results are universal and agree with the experimental data of oxide films.

Infrared Absorption and [CuO₅] Pyramid of High T_cSuperconductor Bi-Sb-Sr-Ca-Cu-O System

Song Guilan, Zhu Zhengfang, Bai Peiguang

1996, 5(1): 63-67.

[Abstract](361) [PDF 266KB](26)

Abstract:
The infrared absorption spectra of different superconducting phase of high Tc super conductor Bi-Sb-Sr-Ca-Cu-O have been measured . The results show that only in the range of 400cm-1 -700cm-1,there is a group of peaks which changes with different superconducting phases.According to group theory and infrared spectra of CuO, this group of peaks could be assigned to be the [CuO6]octahedron, the [CuO5] pyramid and the [CuO4]plane quadrilateral,but not CU-O plane or CU-O chain. Furthermore, the quasi-three dimensional Cu-O layers consisting of [CuO5] pyramids and proper coupling between them are essential factor for high Tc. It seems that the weaker compling of layers, the higher Tc

Multimedia Engineering Database Management Systems

Liang Yunrong, Guo Guisuo, Song Hantao;Feng Xi, Feng Xi, Gao Chunlei, Guo Sheng

1996, 5(1): 68-73.

[Abstract](282) [PDF 316KB](25)

Abstract:
In the Engine CAD application system engineering database management system (ECAD-EDBMS) is the kernel. ECAD-EDBMS can manage and process the multimedia such as graphics, data, text, sound, image and video. It provides the integrated environment and more functions for many subsystems of ECAD and engine designers. So it improves the design efficiency.

An Analysis of the Structure of Carbide-tool Utilization Expert System

Pang Siqin, Zhang Qiyuan, Yu Qixun

1996, 5(1): 74-79.

[Abstract](246) [PDF 323KB](26)

Abstract:
The necessity and feasibility of an expert system for carbide-tool utilization are analyzed and a practical system named CUES(carbide-tool utilization expert system ) is developed and realized. The system concept, module structure, data management, inference strategy and the interface design of the system are discussed in.detail. The system would be useful not only for the preparation of tool bank of FMS or CIMS, but the for the proper application of cemented carbide tools in conventional machining Processes.

Cross Spectral Estimation and Its Application in Missile Systems

Wei Hualiang, Liu Zaozhen, Zhang Tianqiao

1996, 5(1): 80-84.

[Abstract](296) [PDF 263KB](28)

Abstract:
A new method based on cross-spectrum estimation for the verification and validation of computer simulation models is expounded in accordance with the characteristics of missile systems. The new method can expose the differences between two time processes in several aspects and can also give quantitative analysis results about the statistical consistence between them. An application to an actual anti-tank missile system simulation is presented and the calculated results confirm the effectiveness of the method. The approach can also be employed to verify the simulation models of other dynamic systems.

Theoretical Study and Structural Design of ERF Shock Absorbers

Wei Chenguan, Fu Zhao

1996, 5(1): 85-94.

[Abstract](328) [PDF 499KB](26)

Abstract:
Electrorheologica (ER) technique is a developing technology. In a wide range of engineering applications of ER fluid, shock absorbers employing ER fluids, whose damping force can be controlled continuously and promptly through electric signals, is one of the most prospective applications of ER fluid. In this paper, the theoretical midel and method to predict the damping force of ERF shock absorbers are established.

1996 Vol. 5, No. 1