JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

The Reputation Model of Multi Stage Dynamic Game

1999, 8(1): 1-6.

[Abstract](214)

Abstract:
Aim To study the implicit restriction mechanism for hidden action in multi stage dynamic game. Methods A reputation model for restriction on repeated principal agent relationship was established by using the theory on principal agent problem in information economics and the method of game theory to study the implicit restriction mechanism for hidden action. Results and Conclusion It is proved that there exists implicit restriction mechanism for the multi stage principal agent relationship, some conditions for effective restriction are derived, the design methods of implicit restriction mechanism are presented.

ESPRIT Based Feature Extraction of Helicopter Acoustic Signal

ZHOU Zhong-lai, LI Ping, ZHENG Lian, SHI Ju-sheng

1999, 8(1): 7-13.

[Abstract](217)

Abstract:
Aim To extract harmonic frequencies of helicopter acoustic signal as features for hel icopter identification. Methods Estimation of signal parameters via rotational invariance techniques(ESPRIT) was selected to extract harmonic frequencies from really measured helicopter acoustic signal and an algorithm based on the SVD TLS was used. Results ESPRIT correctly extracted harmonic frequencies of helicopter using the data of limited length under the variousflight conditions. Conclusion ESPRIT is an effective method of extracting harmonic frequencies and using harmonic frequencies of helicopter acoustic signal to recognize helicopter is feasible.

The Deficiency and Nevanlinna Direction of the Meromorphic Functions

ZHANG Xue-lian

1999, 8(1): 14-18.

[Abstract](326)

Abstract:
Aim To study the value distribution of meromorphic functions in angular domains, the deficiency, the deficient value, the Nevanlinna direction and other singular directions. Methods A fundamental inequality of Nevanlinna characteristic functions in the angular domain was used, which is similar with the Nevanlinna secondary fundamental theorem. Results The deficiency and deficient value of meromorphic functions about an angular domain and a direction were defined. The definition of Nevanlinna direction was improved. Conclusion For a family of meromorphic functions, it is proved that the number of deficient values is at most countable and the sum of deficiencies isnt greater than 2. The existence of the Nevanlinna direction is obtained. The existence of Borel and Julia directions and the relation between them are found.

Oscillatory Criteria for a Class of Boundary Value Problem of Nonlinear Hyperbolic Equations

WANG Pei-guang, GE Wei-gao

1999, 8(1): 19-23.

[Abstract](197)

Abstract:
Aim To study a class of boundary value problem of hyperbolic partial functional differential equations with continuous deviating arguments. Methods An averaging technique was used. The multi dimensional problem was reduced to a one dimensional oscillation problem for ordinary differential equations or inequalities. Results and Conclusion The known results of oscillation of solutions for a class of boundary value problem of hyperbolic partial functional differential equations with discrete deviating arguments are generalized, and the oscillatory criteria of solutions for such equation with two kinds of boundary value conditions are obtained.

Asymptotic Behavior and Nonexistence of Positive Solutions of Delay Difference Equations

PENG Ming-shu

1999, 8(1): 24-29.

[Abstract](179) [PDF 209KB](2)

Abstract:
Aim To obtain new criteria for asymptotic behavior and nonexistence of positive solutions of nonlinear neutral delay difference equations. Methods By means of Hlder inequality and a method of direct analysis, some interesting Lemmas were offered. Results and Conclusion New criteria for asymptotic behavior and nonexistence of positive solutions of nonlinear neutral delay difference equations are established, which extend and improve the results obtained in the literature. Some interesting examples illustrating the importance of our results are also included.

Third Order Upwind Schemes for Convection Equations

DING Li-juan

1999, 8(1): 30-35.

[Abstract](319) [PDF 197KB](13)

Abstract:
Aim To construct a third order upwind scheme for convection equation. Methods Upwind Lagrange interpolation was used. Results and Conclusion The schemes L p stability for p∈ is proved. Numerical examples show that performance of the third order upwind scheme is better than that of most second order schemes.

Analysis of Dynamic Failure of Plastic Spherical Shells Under Local Impact

NING Jian-guo, LIU Hai-yan, WANG Yun-yan, YANG Gui-tong

1999, 8(1): 36-41.

[Abstract](209)

Abstract:
Aim To study the dynamic failure of the plastic spherical shell impacted by a missile. Methods The deformation mode of spherical shells was given by introducing isometric transformation. The governing equation of motion of the rigid plastic spherical shell was given by energy balance. This equation was solved by using Runge Kutta method. Results The relationships between the impact force, dimple radius, central point deflection and time were obtained. The response time initial velocity, the maximal impact force permanent initial velocity, the central point deflection initial velocity and the dimple radius initial velocity characteristics were respectively plotted. Conclusion A comparison made between the theoretical results and the experimental ones indicates that the two groups of results are in conformity with each other.

A Model on the Void Fraction in Liquid Slugs for Vertical Slug Flow

XIA Guo-dong, ZHANG Shao-hua, WEI Chen-guan, ZHOU Fang-dei, HU Ming-sheng

1999, 8(1): 42-47.

[Abstract](146)

Abstract:
Aim To develop a hydrodynamic model on the void fraction in liquid slugs for gas liquid slug flow in vertical tubes. Methods Developing the model by considering the gas exchange between the Taylor bubble and the following liquid slug. Results Some experimental data are obtained to check the model. In comparison with previous published results, the predictions from this model are better and in good agreement with the experimental data. The error is within ±20%. Conclusion The proposed model can correctly predict the void fraction in liquid slugs for gas liquid two phase slug flow in vertical tubes.

Femtosecond Induced Absorption of PbS Nanoparticles Modified by AOT

GUO Lin, WANG Hao, AI Xi-cheng, YANG Qing-lin, ZOU Ying-hua, LI Qian-shu, ZHU He-sun

1999, 8(1): 48-54.

[Abstract](222)

Abstract:
Aim To prepare PbS nanoparticles modified by manoxol OT (AOT) and determine its transient nonlinear optical properties. Methods The PbS nanoparticles were prepared by using microemulsion method and the transient nonlinear optical properties were investigated with standard time resolved pump probe techniques. Results A very rapid induced absorption was investigated. The decay time of the PbS nanoparticles modified is about 100 fs. Conclusion The transient induced absorption in PbS nanoparticles modified by AOT arises from the biexciton effect and the trapped carrier induced Stark effect. The surface chemical modification environment has significant effects on the transient nonlinear optical properties.

Melting Behavior of PA6 and PA6/PE Blends Crystallized from Amorphous State

QIU Wu-lin, LUO Yun-jun, LUO Shan-guo, TAN Hui-min, LI Zheng-jun, MAI Kan-jun, ZENG Han-jun

1999, 8(1): 55-59.

[Abstract](206)

Abstract:
Aim To investigate the melting behavior of polyamide 6 in polyamide 6/polyethy lene blends crystallized from amorphous state. Methods DSC was used to test effects of annealing temperature, annealing time, DSC scan rate, and the step wise annealing on the melting peaks of the ice water quenched specimens. Results and Conclusion Varied melting peaks of PA6 component were obtained. The degree of perfection and the crystallization degree of PA6 crystals decreased in the blends, and the crystallization degree of PA6 increased with the increasing of the annealing time. The height of the upper melting peak of reference PA6 is higher than that in blends.

Chiral Separation of Chlorpheniramine by Capillary Electrophoresis

LU Guang-ju, GU Jun-ling, ZHANG Jian, FU Ruo-nong

1999, 8(1): 60-64.

[Abstract](171)

Abstract:
Aim To study the chiral separation of chlorpheniramine(Chp) by using a mixture of β CD and glutamate β CD as the chiral additive in CE. Methods Mixture of β cyclodextrin and glutamate β cyclodextrin was used as a chiral selector to the separation of chlorpheniramine. The effects of the concentrations of β cyclodextrin and glutamate β cyclodextrin, the voltage and the pH of buffers on the separation of chlorpheniramine were studied. Results The chiral recognization of the mixed chiral selector was better than that of a single selector. At pH below 4, the pH of buffers did not affect the separation and the separation of chlorpheniramine had good reproducibility. Conclusion Using a mixture of β CD and Glu β CD as chiral selector is useful for the enantioseparation of Chp in CE.

Elastic Field of a Straight Dislocation in One Dimensional Hexagonal Quasicrystals

Li Xian-fang, SUN Ying-fei, FAn Tian-you

1999, 8(1): 65-70.

[Abstract](176)

Abstract:
Aim To study dislocation elasticity theory in quasicrystals. Methods A dislocation was separated into pure edge part and pure screw part and their superposition was used to find the elastic field. Results and Conclusion The elastic solution of a straight dislocation parallel to the quasiperiodic axis in 1D hexagonal quasicrystals was obtained and the generalized Peach Koehler force on a dislocation in quasicrystals was given.

Research and Development of Cemented Carbide Multifacet Drill for Drilling High Strength Steel

PANG Si-qin, YU Qi-xun, JI Guang-zhen

1999, 8(1): 71-75.

[Abstract](191)

Abstract:
Aim To research on a solid cemented carbide multi facet drill for drilling high strength steel. Methods Assimilating some features of multi facet drill edge structures, through systematic drilling experiments, a new type of solid cemented carbide drill was developed and the drill geometry was optimized. Results With the new type drill,the drilling force decreases by 10%-20%, the drilling productivity (drilled holes per hour) increases by 2-3 times, and the drilling precision and surface finish increase by one level. Conclusion The new type drill possesses excellent drilling performance.

Dynamic Spherical Cavity Expansion in Concrete

LIN Jian-xun, JIANG Hao-zheng, JIANG Jian-wei, WANG Xiu-lan

1999, 8(1): 76-82.

[Abstract](215)

Abstract:
Aim To determine the stress on wall of the spherical cavity while the spherical cavity expanding in concrete. Methods In Eulerian coordinate, the dimensionless radial stress equations were derived for the spherically symmetric, cavity expansion problem in plastic and elastic region of concrete by means of the similarity transformation. In the equations, Mohr Coulomb yield criterion was used.Results The dimensionless radial stress profiles were obtained. The relation between the dimensionless radial stress and the locked volumetric strain was analysed.Conclusion The test results show that the relative error between the model, which is applied in the closed form penetration equations that are developed, and the test data is less than 15.8%.

Design of a Kind of Model Reference Adaptive Missile Control System

WANG Jun, ZHANG Tian-qiao, WANG Zheng-jie

1999, 8(1): 83-87.

[Abstract](354) [PDF 175KB](14)

Abstract:
Aim To present an adaptive missile control system adaped to the external disturbance and the mobility of target movement. Methods Model reference adaptive control (MRAC) was applied and modified in the light of the traits of the anti tank missile. Results Simulation results demonstrated this control system satisfied the requirement of anti tank missile of dive overhead attack. Conclusion It is successful to use MRAC in missile control system design, the quality is better than that designed by classical control theory.

New Architecture of Pipeline CORDIC

LI Tao, HAN Yue-qiu

1999, 8(1): 88-93.

[Abstract](173)

Abstract:
Aim To design an ASIC based on CORDIC(coordinate rotations digital computer) to meet the requirement of coordinate conversion in high speed radar signal processing. Methods A new pipeline CORDIC architecture easily realized in VLSI was introduced. Results and Conclusion The results of hardware simulation with FPGA show that the pipeline CORDIC architecture meets the requirement.

SAR Moving Target Detection and Imaging Based on WVH Transform

DONG Yong-qiang, TAO Ran, ZHOU Si-yong, WANG Yue

1999, 8(1): 94-100.

[Abstract](336)

Abstract:
Aim To propose a generalized and closed representation of the Wigner Ville Hough transform(WVHT), for the moving target detection and imaging in the design of synthetic aperture radar(SAR). Methods Based on the line integral, the WVH transform was derived by combining the Wigner Ville distribution (WVD) and the Hough transform (HT) together. The new transform was then verified with computer by the simulated SAR echoes. Results and Conclusion The correctness and the validity of the WVH transform were proved by the computer simulation. Compared with the conventional WVD HT method, the new approach based on the WVHT can simplify the processing procedure, it can translate the chirp echoes of multi targets of SAR from the time domain into the parameter space directly, while suppressing the cross terms of WVD and estimating the motion coefficients for the final imaging. It is obvious that the WVH transform can be also used in other cases for the chirp signal detection.

The Method for Separating Texts from Mechanical Engineering Drawings

WU Lin-rui, CHEN Jiong-bai, YUAN Zeng-feng

1999, 8(1): 101-107.

[Abstract](267)

Abstract:
Aim To separate texts from graphics on mechanical engineering drawings. Methods By improved labeling run, the size of circumscribed rectangle and pixel density about the connected graphs on a drawing were gained, according to these value, texts not sticking to graphics could be separated from a drawing. The concept of appendant block was introduced, using the appendant block, texts sticking to graphics could be determined and cut. Results Texts and symbols on mechanical engineering drawings can be separated well. Conclusion This method is simple and fast, it does not destroy the shape of texts and symbols, it can be used for separating texts and symbols from all linear graphics.

Master Curve Method of Cumulative Damage for Prediction of Service Life

SHEN Ting-fang

1999, 8(1): 108-112.

[Abstract](189) [PDF 174KB](6)

Abstract:
Aim To study the theory and method for the prediction of service life of solid rocket propellant grain. Methods With the aid of discontiguous diagnostic technology and method of accumulated damage using accelerated aging or heat air oven, the aging isotherms for void content versus aging time were determined. According to the principle of time temperature equivalence the viscoelastic master curve for the prediction of service life were obtained. Results and Conclusion The service life of HMX CMDB solid rocket propellant grain were obtained. Because the critical storage life is measured, the accuracy of predicting the service life of the grain has been increased greatly.

1999 Vol. 8, No. 1