JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Limit Cycles in the Stability Analysis of a Chemical System

Ge Weigao

1994, 3(1): 1-6.

[Abstract](162)

Abstract:
Aris and Amundson studied a chemical reactor and obtained the two equationsDaoud showed that at most one limit cycle may exist in the region of interest. Itis showed in this paper that other singular points exist and that a stable limitt cycle existsaround the singularity (1/2, 2) when K∈(9-δ, 9).

Interval Sampling Method for Steady-State Simulation Output Analysis

Zhang Hongduan, Bao Juwu, Feng Yuncheng

1994, 3(1): 8-17.

[Abstract](220)

Abstract:
A new algorithm namely the interval sampling method, applicable to the analysisof steady-state simulation output is proposed. This algorithm uses the time series analysisto carry out conrrelation analysis of the steady-state simulation output so as to obtain theobservation data which are actually uncorrelated in nature. On the basis of theseuncorrelated data gathered, some satisfactory deductions cam be made on the data under re search. A comparison between batch means method and the interval sampling method hasbeen performed by taking the M/M/l queuing system as an example. The results attestedthat the interval sampling method is mere accurate than the batch means method.

Stochastic Responses of a Shell of Rotational Symmetry Haing Physically Nonlinear Behavior

Gao Shiqiao

1994, 3(1): 19-25.

[Abstract](234)

Abstract:
Concrete is considered as an elastic body when subjected to compressive stress butas a brittle body when subjected to tensile stress. That is, after the elastic extremum it cannotcontinue to bear the stress. Based on this.'cracked' physical model, for stochastic extemalwind loads, nonlinear stochastic constitutive equations have been established. To solve equations of nonlinear stochastic vibration, an iterative statistic linearization method (ISLM) hasbeen developedb. Some statistic characteristics were foundd out.

Some New Results from the Electron Theory on the Elastical of Alkahoe Earth Metals and Rare Earth Elements

Cui Xiushan, Xing Shengdi

1994, 3(1): 26-32.

[Abstract](161)

Abstract:
With the introduction of Poisson's ratio in the expression of Young's modulus,nearly all the theoretical values of the various elastic moduli for the alkaline earth metals and rare earth elements can be greatly refined, with the single exception of the theoreticalvalue of Young's modulus for Pr which is slightly increased This points to the validityof the new theory, that the bulk modulus is independent of the Poisson's ratio, and further that the valency electron structures of solids as determined by Yu's theory are correct.

Multi-SPline Technique for the Extraction of Drag Coeffidents from Radar Data

Qi Zaikang

1994, 3(1): 33-42.

[Abstract](183)

Abstract:
In the preparation of firing tables, the determination of projectile drag coefficientsthrough firing test radar data reduction is very important. Many methods have been developed for this work but none of them appear to be satisfactory in one Way or another. Inthis paper a multi-spline model of drag coefficient (cd) curve is developed that can guaranteefirst derivative continuity of the cd curve and has good flexibility of fitting accurately to acd curve from subsonic up to supersonic range. Practical firing data reduction tests showboth fast convergence and accurate fitting results. Typical velocity fitting RMS errors are0.05-0.08 m/s.

An Analysis on the Mechanism Governing the Effect of Bomb Length upon the Sensitivity of Detection of a Capacitance Fuze

Deng Jiahao, Shi Jusheng

1994, 3(1): 43-50.

[Abstract](232)

Abstract:
For a detector in a capacitanee fuze working in an electrostatic field, the bomblength (effective length of the conductor part) is an important factor affecting the sensitivityof detection. For the two different kinds of detecting circuit models in general use (the frequency-sensitive and the amplitude-coupling ), mechanism of the effect of bomblength on the sensitvity of detection is analyzed. Through the analysis a conclusion in fullagreement with experimental results has been drawn, that is. the longer the bomb length,the higher the sensitivity, on the condition that the sizes and the sites of the detecting electrodes and bomb diameter remain unchanged.

A Laser-Diode-Pumped Nd:YAG Laser Q-Switched with a YAG Color Center Chip

Li Jiaze, Gao Chunqing

1994, 3(1): 52-58.

[Abstract](209)

Abstract:
A laser-diode-pumped Nd: YAG laser Q-switched Passively with a YAG colorcenter chip has been deveolped. The Q-switched pulse output has a duration of 25-70ns,an energy of about 7.9 μJ and a repetition frequency of 1.25-5.0kHz when the laser cavityparameters and pump power are changed. The Q-switched dynamics is analyzed with therate equation theorry. The theoretical and experimental results agree well.

Optimum Design of Impedance Simulator for Phased Array Antnnas

Lu Xin, Li Shizhi

1994, 3(1): 59-63.

[Abstract](154)

Abstract:
The impedance of a solid state active phased array antenna varing with frequency and beam scanning scanning angle be matched with the solid state active matching network (SSAMN). In order to adjust and measure the radar conveniently and Securely, it is necessary for the impedance of the simulator of the phased array antennas to be optimized.Having selected the PIN dilde controlling circuits and the circuit parameters optimized,the simulator circuit is determined through numerical computation The experiment is given in support of the simulation.

A Modeling-Based Radar Superresolution Approach

Liu Zhiwen, Ke Youan

1994, 3(1): 64-74.

[Abstract](189) [PDF 766KB](4)

Abstract:
On the basis of modeling of multiple targets and radar returning signals, a new method for radar range superresolution is introduced in this paper. This method tums the resolution of multiple closely spaced targets into an identification of the target impulse response functions. The least-square (LS) method is then used to estimate impulse resoonse functions of the targets. The concept of radar range resolution probability is also introduced.It is shown from the simulation results that the new superresolution method is much efficient, and has advantages such as having a simple structure, as well as high resolution.

A Study on the Static Characteristics of Typical Composite High Speed On-Off Valves

Chen Baojiang, Cao Fan

1994, 3(1): 75-81.

[Abstract](181)

Abstract:
Natural properties of high speed on-off valves can be described through their on-off behavior and spool movement (static and oscillating) characteristics. High speed on-off valves can be combined with actuators in systems into four typical types of composite valves whose static characteristics are related not only to the structures of the single valves and the composite ones, but also to the PWM control modes. It is proved that the composite valves have similar features as those of servo valves. The nonlinear specific properties of single valves composited can be completely compensated by the suitable PWM control modes.

Applicahon of a Simplified Model Reference Adaptive Algorithm

Wang Liyan, Gong Xiaodong, Jin Zhili, Cao Fan

1994, 3(1): 82-90.

[Abstract](244)

Abstract:
The application of a simplifed model reference adaptive control(SMRAC) on a typical Pump controlled motor electrohydraulic servo system is studied here. The algorithm of first-order scalar SMRAC ac second-order vector SMRAC are derived. Computer simulations of the algorithms are presented. Experimental results prove that the method of control adopted here perform satisfactorily over a wide range of operating conditions.

Electrorheological Fluid and Its Application in Vibration Control

Wei Chenguan, Fu Zhao

1994, 3(1): 91-98.

[Abstract](170)

Abstract:
This paper deals with the application of electrorheological fluid (ERF) in shock absorbers. Such shock absorbers (ERF shock absorbers) whose damping force is controlled Continuously and promptly through electric singnals, can be used in many kinds of mechanical equipment for vibration control. Typical structures of ERF shock absorbers are described and requirements for the ERF employed in shock absorbers are discussed. A new kind of shock absorber and its control system are presented and test results of the ERF shock absorber are given.

1994 Vol. 3, No. 1