JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Boundary Value Problems of p-Laplace Equations with Finite Time Delay

2001, 10(1): 1-6.

[Abstract](258) [PDF 194KB](28)

Abstract:
By establishing equivalent fixed point theorem, the boundary value problems of p Laplace equations with finite time delay are studied. It's the first time that the functional differential equation is discussed with p Laplacian. The topological degree and fixed point theorem on cone are used to prove the existence of solution and positive solution. The conditions are all easy to check.

L_loc^∞-Estimates for Local Solutions of Nonlinear Parabolic Equations

WANG Yi fu

2001, 10(1): 7-11.

[Abstract](448) [PDF 167KB](34)

Abstract:
To obtain L ∞ loc estimates for the local solution of nonlinear parabolic equations, local energy estimates and Moser iteration are used. Under some structural conditions, a local sup estimates of the local solution is established in terms of some integral normal of the solution in a larger domain, which is independent of initial and boundary data.

Oscillation of Systems of Parabolic Differential Equations with Deviating Arguments

DENG Li hu, WANG Hong zhou, GE Wei gao

2001, 10(1): 12-16.

[Abstract](284) [PDF 162KB](28)

Abstract:
To study a class of boundary value problems of parabolic differential equations with deviating arguments, averaging technique, Green's formula and symbol function sign(·) are used. The multi dimensional problem was reduced to a one dimensional oscillation problem for ordinary differential equations or inequalities. Two oscillatory criteria of solutions for systems of parabolic differential equations with deviating arguments are obtained.

First Integrals and Reduction of the Birkhoffian System

ZHENG Gai hua, CHEN Xiang wei, MEI Feng xiang

2001, 10(1): 17-22.

[Abstract](258) [PDF 190KB](30)

Abstract:
Refer to the Hamiltonian system, first integrals of the Birkhoffian system can be found by using of the perfect differential method. Through these first integrals, the order of the Birkhoffian system can be reduced. Then according to the alternate of the coordinate, a kind of new partial differential operator was defined in order to hold the Birkhoff form. The result shows that the Birkhoffian system has generalized energy integrals and cyclic integrals. Furthermore, each integral can reduce the order of equations two degrees.

Effect of Nonlinear Geometric Behavior on Random Response of Rotational Shell

GAO Shi qiao, Niemann H J

2001, 10(1): 23-28.

[Abstract](182) [PDF 196KB](28)

Abstract:
Aimed at the large deformation problem of industry cooling tower shell, the mathematical model for the random response of rotational shell under the external random excitation is established by statistic perturbation method. The effect of nonlinear geometric behavior on the response of rotational shell is analyzed.

Nonlinear Stochastic Response of Rotational Shell Under the Action of Stationary Strong Wind Loads

GAO Shi qiao, Niemann H J

2001, 10(1): 29-33.

[Abstract](322) [PDF 162KB](33)

Abstract:
Based on the theoretical analysis of nonlinear random response of structure, for the engineering practical problem, that is, the large deformation of industry cooling tower shell structure under the action of strong wind loads, the statistic perturbation method is also used to analyze some statistic characteristics of the nonlinear random response of rotational shell with geometric nonlinearity and stationary strong wind load considered. Through computation, some average values of nornal displacements and the nonlinear effect factor of the cooling tower shell are given.

Post-Buckling Analysis for Elastic Thin Plate Under Unilateral Frictionless Restraint

ZHANG Yun, CHENG Zhao xiong

2001, 10(1): 34-38.

[Abstract](221) [PDF 175KB](30)

Abstract:
To investigate the buckling and post buckling behaviors of elastic thin plate under frictionless unilateral restraint, enduring the coupling action of lognitudinal and transverse loads, the principle of minimum potential energy and variational method are used and series functions with unknown coefficients are taken as trial functions of functional to solve the large deflection and non linear bending problem of a thin plate and find relation curves between deflection of plate and loads. The proposed method can capture the buckling and post buckling behaviors of a thin plate in different geometrical and load boundary conditions. The analysis confirms that there occur snap and bifurcation behaviors in the post buckling stage of the plate. And these results show the validity of the variational method for solving buckling problems of thin plate.

Numerical Simulation of the 2-D Explosive Field for the Effect of Protective Wall's Shape

SHEN Yu ling, NING Jian guo

2001, 10(1): 39-44.

[Abstract](386) [PDF 189KB](36)

Abstract:
The effect of the protective wall's shape on the shock wave of 2 D explosive field is studied. Under the condition that the outside force, the outside resources and the heat exchange are ignored, the partial differential conservation equations of the compressible fluid are given by adopting the fluid model. The “and” splitting scheme to calculate the transport step by using the multi material in cell(MMIC) method is adopted. At the same time, for the detonation products, the JWL state equation is adopted, and the air is approximately regarded as the ideal gas. Accordingly the effects of the shapes of the protective wall's both sides on the shock wave are obtained, and the relations between them are listed in the paper. So it can be obtained that the shape of the edge near to the explosive center of the protective wall affects the shock wave more obviously.

Pyrolysis-Gas Chromatography/Mass Spectrometry for Microstructure and Pyrolysis Pathway of Polyester-Polyether Multiblock Copolymer

LUO Ai qin, YE Ling, FU Ruo nong, XIE Gui yang, WANG Xian lun

2001, 10(1): 45-50.

[Abstract](235) [PDF 149KB](27)

Abstract:
The composition and sequence distribution of monomeric units in polyester polyether multiblock copolymer were studied by pyrolysis? gas chromatography (PGC) and pyrolysis gas chromatography/mass spectrometry (PGC/MS). PGC was applied to study the F t curve of the multiblock copolymer and PGC/MS was used to separate and identify the pyrolyzates. DTA experiment was used to study the decomposition temperature. The results show that the beginning point of elastomer's decomposition was about 300?℃ and the decomposition temperature of most of the sample was 550?℃. Many pyrolyzates were produced because of the breaking of weak bonds in the sample. The possible microstructure was verified and the pyrolysis pathway of the copolymer was investigated.

Contact Problem in Decagonal Two-Dimensional Quasicrystal

ZHOU Wang min, FAN Tian you

2001, 10(1): 51-55.

[Abstract](391) [PDF 107KB](29)

Abstract:
As a new structure of solid matter quasicrystal brings profound new ideas to the traditional condensed matter physics, its elastic equations are more complicated than that of traditional crystal. A contact problem of decagonal two? dimensional quasicrystal material under the action of a rigid flat die is solved satisfactorily by introducing displacement function and using Fourier analysis and dual integral equations theory, and the analytical expressions of stress and displacement fields of the contact problem are achieved. The results show that if the contact displacement is a constant in the contact zone, the vertical contact stress has order -1/2 singularity on the edge of contact zone, which provides the important mechanics parameter for contact deformation of the quasicrystal.

New LCA Approach with Fuzzy Evaluation

ZHANG Zhi jing, WANG Xin yi, CAO Mo

2001, 10(1): 56-62.

[Abstract](325) [PDF 219KB](38)

Abstract:
A quantitative and comprehensive method of product life cycle assessment(LCA) with fuzzy theory is developed, which will help designers to select the optimum design scheme for product life cycle design(LCD). Based on the theory of multiple attribute decision making, an algorithm of comprehensive and comparative evaluation for product environmental adaptability is presented. A program is built and used in an example of design improvement. The result shows that the proposed method and algorithm are practical and effective to the development of green products.

Numerical Simulation of Extrusion Pressure in the Process of Hydrostatic Extrusion

ZHANG Zhao hui, WANG Fu chi, CHENG Jing wei, LI Shu kui

2001, 10(1): 63-68.

[Abstract](290) [PDF 188KB](29)

Abstract:
In order to study the laws of the extrusion pressure changing with the extrusion parameters in the process of hydrostatic extrusion for the tungsten alloys, the large deformation elasto plastic theory and the software of ANSYS 5 5 are used to carry out the numerical simulation research. The laws of the extrusion pressure changing with the extrusion parameters, such as the die angle, extrusion ratio, and friction coefficient, are obtained. The simulation results are in good agreement with the experimental ones, and the simulated results are believable.

Typical Explosive Trains Analyzing and Computer Simulating

DU Zhi ming, WANG Cheng, ZHANG Jian guang

2001, 10(1): 69-74.

[Abstract](292) [PDF 242KB](34)

Abstract:
Through system analysis of typical explosive trains in various fuses, physical and correspondent mathematical models of typical explosive trains are established, based on mass conservation, momentum conservation, energy conservation and so on. MAZE and DYNA2D program is used to dispose these models and results of the simulating of elements of explosive trains in a typical fuse are obtained. It is helpful for designing fuses.

Simulation Study on the Feasibility of Gun-Launched Missile Against Attack Helicopters

WANG Kuang biao, ZHANG Tian qiao

2001, 10(1): 75-80.

[Abstract](249) [PDF 233KB](26)

Abstract:
The feasibility of providing the tank a limited anti helicopter ability with gun launched missile is studied. A type of simulation model of gun launched missile against attack helicopters is established. The simulation and the parameter optimization of missile control system under various circumstances are done. The gun launched missile can directly hit the helicopters in the typical tracks, all the missdistances are less than 1?m and the maximum overload is less than available overload. Gun launched missile is a feasible choice for tanks against attack helicopters.

Research on Software Radio Fuze

HUANG Zhong hua, CUI Zhan zhong, LIN Sen, LI Ping

2001, 10(1): 81-85.

[Abstract](396) [PDF 204KB](29)

Abstract:
The functions and characteristics of software radio are discussed. Using techniques and method of software radio, the concept and advantages of a new kind of radio fuze, software radio fuze, are analysed. Several kinds of hardware platform structures of the software radio fuze are studied and the key techniques are analysed. The software radio fuze will become the most promising radio fuze techniques in 21st century.

Suppression of Speckle in SAR Images Using Wavelet-Based HMM

ZHANG Zhi ming, WANG Yue, TAO Ran, ZHOU Si yong

2001, 10(1): 86-92.

[Abstract](373) [PDF 245KB](35)

Abstract:
In order to suppress the speckle appearing in synthesis aperture radar (SAR) images, a novel speckle reduction method based on wavelet domain hidden Markov tree (HMT) was proposed. First, the image was logarithmic transformed to change the statistical property of the speckles. Then an HMT was constructed in the correspondent wavelet domain. Based on this model, the image signal was restored by maximum likelihood estimation and speckle noise was suppressed. Simulating SAR images had shown that the performance of the filter is satisfactory for both speckle smoothing and edges presentation, and for generating visually natural images as well.

Herrmann Method of Analyzing Structure Design Velocity Field

ZOU Wen sheng, ZUO Zheng xing, FENG Hui hua, LIAO Ri dong, ZHANG Hong guang

2001, 10(1): 93-100.

[Abstract](303) [PDF 242KB](30)

Abstract:
The shape optimization is studied by adopting the domain integrated method which is based on the calculus of variations during the shape design sensitivity analysis. A new method of improving the efficiency of the design velocity field analysis and the quality of the finite element method (FEM) mesh is put forward. The sensitivity analysis which is based on the calculus of variations is used in the shape optimization. The design velocity field is solved by Herrmann method. An example shows that both the quality of the FEM mesh and the efficiency of the computing of the design velocity field are improved by Herrmann method. So the effect and the efficiency of the shape optimization are guaranteed. If using sensitivity analysis which is based on the calculus of variations in the shape optimization, the sensitivity analysis can be a relatively independent module. The efficiency of computing the design velocity field and the quality of mesh will be improved by using Herrmann method.

Monitoring Tool Wear States in Turning Based on Wavelet Analysis

WANG Zhong min, WANG Xin yi, CHEN Ai di, JIA Yu ping

2001, 10(1): 101-107.

[Abstract](325) [PDF 372KB](31)

Abstract:
To monitor the tool wear states in turning, a new way based on the wavelet transformation to get the signal characters, which can reflect the tool wear states, was proposed. Using discrete dyadic wavelet transform, the acoustic emission(AE) signal of cutting process was decomposed; the root mean square(RMS) values of the decomposed signals at different scales were taken as the feature vector; the technique of fuzzy pattern identification was used to real time monitor the tool wear states. Based on choosing the suitable standard samples, this method can correctly identify the tool wear states. Experiments showed that the technique based on wavelet analysis is suitable for real time implementation in manufacturing application.

Theoretical Calculation of Nitrogen Q-Branch CARS Spectra

YAN Jun, XU Geng guang

2001, 10(1): 108-112.

[Abstract](207) [PDF 165KB](30)

Abstract:
The coherent anti Stokes Raman spectrum (CARS) technology, as a new temperature measurement method, is paid more and more attention to recently. The theoretical CARS spectra of nitrogen Q branch are calculated, the spectra at different temperatures are obtained and the effect on the CARS spectra of Raman line width is also discussed. The results show that CARS spectra are sensitive to temperature and spectrum solution is good when the Raman line width is narrow enough. The accuracy of detonation temperature measurement with this technology will reach high level.

2001 Vol. 10, No. 1