JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

A Boundary Value Problem for Second Order Functional Differential Equations with Impulses

He Zhinmin, Ge Weigao

1998, 7(4): 323-329.

[Abstract](192)

Abstract:
Aim To investigate the boundary value problem for second order functional differentiai equations with impulses. Methods The fixed point principle was used to establish our results. Results and Conclusion The results of the esistence, the uniqueness and the continuous dependence on aprameter of soiutions of the boundary value problems for second order functional differential equations with impulses are obtained.

Singular Points, Closed Orbits, Stable Manifolds and Unstable Manifolds of Second Order Autonomous Birkhoff Systems

Chen Xiangwei, Mei Fengxiang

1998, 7(4): 330-336.

[Abstract](209) [PDF 165KB](4)

Abstract:
Aim To study singular points, closed orbits, stable manifolds and unstable manifolds of a second order autonomous Birkhoff system. Methods Qualitative methods of ordinary differential equation were used. Results and Conclusion The criteria for singular points, closed orbits and hyperbolic equilibrium points of a second order autonomous Birkhoff system are given. Moreover the stability of equilibria, stable manifolds and unstable manifolds are obtained.

Research on Transient Response of Motorcycle with One Tire Colliding on Ground

Gu Liang, Qn Jinli, Zhang Zhenhua, Song Yujie, Niu Tongbin

1998, 7(4): 337-344.

[Abstract](249)

Abstract:
Aim To study the transient response of motorcycle with one tire colliding on ground. Methods Taking the colliding velocity as an independent variable, the changing law of the biggest collision inertia load of motorcycle′s sprung mass, unsprung mass and driver was studied, while its front and rear tire colliding on ground respectively.Results and Conclusion According to the working conditions of motorcycle shock absorbers and the characteristic of response curve, the transient response of the acceleration, the velocity and the displacement were discussed section by section. And the result of simulating the actual JH125 motorcycle was given.

The Effect of Silane Grafted Polypropylente on the Property of Different Filler/Polypropylene Composites

Qiu Wulin, Luo Yunjun, Luo Shanguo, Tan Huimin

1998, 7(4): 345-350.

[Abstract](204)

Abstract:
Aim To determine the effect of silane grafted polypropylene on the property of different filler/polypropylene composites. Methods Polypropylene (PP) composites filled with talc(Ta), baryta sulfate and calcium carbonate coupled with silane grafted polypropylene (PP-g-Si) were made, their mechanical properties and thermal properties were investigated, respectively. Results As compared with the non-coupled composites, the mechanical properties of PP/Ta/PP-g-Si composites were improved to some extent, though the values of tensile modulus and the strain at peak were decreased. But for PP/BaSO4 and PP/CaCO3 composites, the values of their mechanical properties varied slightly or even decreased with increasing PP-g-Si content within the experimental component. Meanwhile, PP-g-Si also affected the melting and crystallization behavior of PP in the composites. Conclusion PP-g-Si offers compatibilization in PP/Ta composites, but offers no-compatibilization in PP/BaSO4 and PP/CaCO3 composites within the extent of the present range of PP-g-Si, which shows that PP-g-Si can be used as the macromolecular coupling agent of PP and Ta composite.

Thermal Cyclic Effects of Metal Matrix Composites

Wu Xiaobai, Liao Li, Hu Gengkai

1998, 7(4): 351-358.

[Abstract](334)

Abstract:
Aim To simulate the thermal cyclic effects of metal matrix compeithe. Methods Based on Eshelby′s inclusion theory, a constitutive model for metal matrix composites and an elastic constraint method were formulated to predict the cyclic isothermal and cyclic thermomechanical behaviors of metal matrix composites. Results and Conclusion A SiC reinforced A1 2xxx-T4 composite was studied theoretically with the model. With the constitutive relation of the matrix, the mechanical behaviors of the composite under different loading condition, such as different loading rates, mechanical and thermal mechanical cyclic loading, can be quantitatively predicted. The thermal ratchetting effect of the composite can be predicted by the model.

New Design Method for Engine Cooling Fan

Huang Hongbin, Zheng Shiqin, Liu Shuyan, Yan Weige

1998, 7(4): 359-365.

[Abstract](295)

Abstract:
Aim To put forward a type of math model for optimizing fan′s twisting law.Methods This math model wu based on turbo-machinery Euler equations and calculus of variation, it was conducted for optimizing the aerodynamic parameters along the blade height of the fan, and the math method was produced for the optimization of fan's twisting law. Results The type 6102Q engine cooling fan was optimized by use of this model, and the calculation on data were contrasted with those of iso-reaction coefficiency flow type and free vortex flow type. Some probleme existing in long blade can be solved by use of above method. Conclusion The design parameters needn't be determined artificially, so calculating results are more rational to a high degree than that from other mehods.

New Algorithm for Real-Time CAC Decisions

Zhang Ying, Tao Ran, Zhou Siyong, Wang Yue

1998, 7(4): 366-372.

[Abstract](356)

Abstract:
Aim To Put forward an improve algorithm for real-time connection admission control (CAC) decision. Methods converted equations of Cell loss ratio (CLR) upper bound were derived based on typical approaches to reduce computing load. Moreover, the effects of usage parameter control (UPC) policing and bandwidth allocation functions were combined to deduce improver equations. computing load and admission region of the new algorithm were analyzed, while numerical examples and comparisons with classical non-parametic method were also included. Results Computing burden was reduced. More accurate estimation of CLR was obtained. The admission region of new algorithm was larger than typical non-parametric approach and was variable according to the burst length.Conclusion The calculation burden of new algorithm for CLR estimation is lighter than classical non-parametric approach. In addition to that, just as many information as what we can get in connection setup process are used for CAC decision. So it is not only a practicable but also an effective method that can be used in real-time processing.

Exploring on Hierarchical Kalman Filtering Fusion Accuracy

Luo Senlin, Zhang Hefei, Pan Limin

1998, 7(4): 373-379.

[Abstract](185)

Abstract:
Aim To analyze the traditional hierarchical Kalman filtering fusion algorithm theoretically and point out that the traditional Kalman filtering fusion algorithm is complex and can not improve the tracking precision well, even it is impractical, and to propose the weighting average fusion algorithm. Methods The theoretical analysis and Monte Carlo simulation methods were ed to compare the traditional fusion algorithm with the new one, and the comparison of the root mean square error statistics values of the two algorithms was made. Results The hierarchical fusion algorithm is not better than the weighting average fusion and feedback weighting average algorithm The weighting filtering fusion algorithm is simple in principle, less in data, faster in processing and better in tolerance.Conclusion The weighting hierarchical fusion algorithm is suitable for the defective sensors.The feedback of the fusion result to the single sersor can enhance the single sensorr's precision. especially once one sensor has great deviation and low accuracy or has some deviation of sample period and is asynchronous to other sensors.

Compensation for the Influence of Radar-Target Relative Speed on Step Frequency MMW Target Identification

Yang Jun, Qi Zaikang

1998, 7(4): 380-387.

[Abstract](202)

Abstract:
Aim To study the influence of radar-target relative speed on frequency MMW high-resolution ore-dimension distance profile and the compensation for it. Methods Based on the distance travelled by the electromagnetic wave, analyses were made for the compensation algorithm and the expression of the inverse FFT base distance was given.The relative importance of different compensation terms was studied in great detail. The concept of searching compensation was put forward. Results and Condclusion Dcm-△Dvimis the be distance of inverse FFT transformation, the effect caused by the distance △Dim on one-dimension profile is negligible, and the effect caused by the distance Dvim should not be neglected and must be compensated.

A Modelling Scheme for Flexible Robot Manipulators

Guo Qiao, Wu Yue, Lu Jilian

1998, 7(4): 388-394.

[Abstract](354)

Abstract:
Aim To propose a modelling method for flexible manipulators. Methods The improved algorithm and structure of the ANN (artificial neural networks) were used. All of the data used in the process of modelling came from experiments based on a very flexible link which was fixed on a FANUC Robot S-Model 300 in our lab.Results and Conclusion The theoretical analysis and experiment results showed that this modelling scheme is more suitable for flexible systems with characteristics of fast changing dynamics, and also it can be more accurate than others and is more convenient for real-time use.

Application of Composite Ultrafine Particles in ER Fluids

Zhang Shaohua, Xia Guodong, Wei Chenguan

1998, 7(4): 395-399.

[Abstract](255)

Abstract:
Aim To obtain a kind of electrorheological (ER) flind with high comprehensive properties in order to satisfy the needs of engineering application. Methods A new type of dispersed phase── composite ultrafine particles (UFP) was obtained by the method of microemulsion, which was used to mix with silicon oil. aam electroinduced stress and apparent viscosity of the ER fluids with three different volume fractions were tested under the conditions of different temperatures, electric fields and shear rates. Results A series of systematic tests show that the new type of ER fluids with volume fraction of 30% possesses obvious ER effect. Conclusion The double layers polarization plays an important role in ER effect.

Improvement of CORDIC Algorithm

Shi Jinglin, Li Tao, Yu Bo, Zhang Qunying, Han Yueqiu

1998, 7(4): 400-405.

[Abstract](269)

Abstract:
Aim To discuss the basic CORDIC algorithm that can be applied to digital signal processing and its applying condition called convergence range.Methods In addition to the original basic equation, another group iterative equation was used to evaluate the correspondent values of input data that did not lie within the convergence range. Results and Conclusion The improved CORDIC algorithm removes the limits of the range of convergence and can adapt itself to the variations of input values. The correctness of improved CORDIC algorithms has been proved by calculating examples.

A Blackboard-Based Multi-Agent Cooperative Expert System Tool

Cao Yuanda, Jiang Nutao

1998, 7(4): 406-411.

[Abstract](248)

Abstract:
Aim To design and implement a multi-agent cooperative problem solving expert system tool. Methods A blackboard system was adopted in the system as a data sharing and information exchanging center, to coordinate the complex cooperative problem solving. The system was developed in UNIX and MSWindows 95 mixed TCP/IP network environment. Results and Conclusion A prototype system of a multi-agent cooperative expert systems tool is implemented.The experiment demonstrates that the fundamental functions of a cooperative expert systems is realized.

Application of Image Fusion Methods to Cell Imaging Processing

Li Qin, Dai Caihong, Yu Xin, Wang Susheng, Zhang Tongcun, Cao Enhua, Li Jingfu

1998, 7(4): 412-417.

[Abstract](203)

Abstract:
Aim To fuse the fluorescence image and transmission image of a cell into a single image containing more information than any of the individual image. Methods Image fusion technology was applied to biological cell imaging processing. It could match the images and improve the confidence and spatial resolution of the images. Using two algorithms, double thresholds algorithm and denoising algorithm based on wavelet transform, the fluorescence image and transmission image of a Cell were merged into a composite image. Results and Conclusion The position of fluorescence and the structure of cell can be displyed in the composite image. The signal-to-noise ratio of the exultant image is improved to a large extent. The algorithms are not only useful to investigate the fluorescence and transmission images, but also suitable to observing two or more fluoascent label proes in a single cell.

Development and Application of the Professional Software for Formulation Optimization Design

Li Dinghua, Zhang Chang, Zhang Liang, Wang Jianqi

1998, 7(4): 418-424.

[Abstract](248)

Abstract:
Aim To research the computer optimization design in material formulation. Methods The professional software including experimental design, mathematical modeling and optimization of single and multiple purposes was developed and applied to the formulation design for the flame retardant ethylenepropylene-diene mischpolymer (EPDM) insulation composites. With the aid of equipartition design, the mathematical models were established based on the optimization of the four properties (limiting oxygen index, volume resistance, tensile strength and elongation). Results The models from limited experiments had good significance, and the modeling analysis conclusions were in good agreement with later experiments. The optimization formulation was practically excellent. Conclusion The software enables practically a comprehensive multi-purpose use of material formulation research.

1998 Vol. 7, No. 4