JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

SHEN Da wei

2001, 10(2): 113-118.

[Abstract](226)

Abstract:
Let Q n denote the class of all polynomials p(z) nonvanishing in the unit disk with deg p≤n and p (0)=1, and let W n denote the class of all polynomials s(z) satisfying deg s≤n and for all p∈Q n, sp∈Q n , where denotes the Hadamard product. Some properties for W n and Q n are obtained.

Injective Envelopes of a Hilbert C^*Module

XU Tian zhou, CAI Tao, LI Bing zhao

2001, 10(2): 119-124.

[Abstract](100)

Abstract:
As in homology, the notion of injectivity is introduced in the category whose objects are Hilbert C module over a C algebra and whose morphism are bounded module operators. The definition of injective envelopes of an extension of a Hilbert C modules over a C algebra is introduced, and is characterized in terms of the injectivity and essence. It is shown that every Hilbert C module has a unique (up to H isometrics) injective envelope if it exists. It is also shown that an extension of a Hilbert C module is an injective envelope if and only if it is an injective and essential extension. Moreover, every Hilbert C module over a W algebra has a unique (up to H isometrics) injective envelope and the injective envelope of a Hilbert C module H is maximal essential extension of H .

Invariance of Numerical Character of Matrix Products and Their Statistical Applications

ZHANG Bao xue, ZHANG Dan song

2001, 10(2): 125-130.

[Abstract](173)

Abstract:
To study the invariance of numerical character of matrix products and their statistical applications by matrix theory and linear model theory. Necessary and sufficient conditions are established for the product AB -C to have its numerical characters invariant with respect to every minimum norm g inverse, respectively. The algebraic results derived are then applied to investigate relationships among BLUE, WLSE and OLSE under the general Gauss? Markoff model.

Exact Invariants and Adiabatic Invariants of Nonholonomic Variable Mass Systems

CHEN Xiang wei, MEI Feng xiang

2001, 10(2): 131-137.

[Abstract](100)

Abstract:
By the theory of symmetries and conserved quantities, the exact invariants and adiabatic invariants of nonholonomic variable mass systems are studied. The perturbation problem of symmetries for the nonholonomic variable mass systems under small excitation is discussed. The concept of high order adiabatic invariant is presented, and the form of exact invariants and adiabatic invariants as well as the conditions for their existence are given. Then the corresponding inverse problem is studied.

Form Invariance of Birkhoffian Systems

MEI Feng xiang, CHEN Xiang wei

2001, 10(2): 138-142.

[Abstract](176) [PDF 162KB](5)

Abstract:
The form invariance of Birkhoffian systems is a kind of invariance of the Birkhoffian equations under the infinitesimal transformations. The definition and criteria of the form invariance are given, and the relation between the form invariance and the Noether symmetry is studied.

Active Control of Initial Disturbances for Rockets and Missiles

BI Shi hua, LI Hai bin, LI Ji hong, FANG Yuan qiao

2001, 10(2): 143-148.

[Abstract](211)

Abstract:
The active control theory and methods of initial disturbances for rockets and missiles are investigated. The rocket or missile/launcher is simplified as a flexible beam excited by a moving varying velocity rigid body which has two points in contact with the beam. The control force is applied at the supporting point on the beam. Active control strategies based on optimal control theory are proposed and computer simulation is carried out. Simulation results are consistent with the theoretical results, and show that the active control strategies proposed can accomplish the purpose to control the initial disturbances actively. The results show that active control of initial disturbances for rockets and missiles is feasible for application.

New Color-Difference Formula Based on CIECAM97s

HUAN Hui, LI Wei, ZHAO Da zun

2001, 10(2): 149-152.

[Abstract](117)

Abstract:
To deduce a new color difference formula based on CIE 1997 Color Appearance Model(CIECAM97s), a color space Jab is first constructed with color appearance descriptors J,a,b in CIECAM97s. The new formula is then deduced in the space and named CDF CIECAM97s. The factors for lightness, chroma and hue correction in the formula are derived by linear regression according to BFD? CP data sets. It is found by statistical analysis that CDF CIECAM97s is in closer accordance with the visual assessments when compared with CMC(1∶1), CIE94 and CIE L a b color difference formulae. Based on color appearance model, the new color difference formula can be used to predict color difference perception in a varity of different viewing conditions.

Selective Erasure of Multiplexed Holograms in Fe:LiNbO₃by Complementary Holography

XIE Jing hui, ZHANG Ze ming, HE Qing sheng, WU Min xian, JIN Guo fan

2001, 10(2): 153-156.

[Abstract](185)

Abstract:
To study the selective erasure and rewriting of the multiplexed holographic storage in photorefractive crystals. According to the mechanism on forming of phase hologram in photorefractive crystal, by incoherently addition of the complementary hologram and the original hologram, the selective erasure and rewriting were accomplished. The complementary holography is an effective and convenient technique for selective erasure and rewriting of multiplexed holographic storage in photorefractive crystals.

Process Environment Oriented Concurrent Tolerance Analysis

YAN Yan, NING Ru xin

2001, 10(2): 157-162.

[Abstract](188)

Abstract:
Tolerance analysis is investigated under an environment of concurrent design in order to lead to optimized tolerance, as traditional tolerance analysis is often inefficient and liable to mistakes. Making full use of knowledge in manufacturing tolerance analysis combined with the beta distribution model is introduced and applied. The use of beta distribution reflects fully actual capabilities in manufacture. Concurrent tolerance design is a manufacturing environment oriented design process paying more attention to influences or restraints on product design caused by such factors as the manufacturing process, machine capabilities, economy in manufacturing, etc. Process environment oriented tolerance analysis is more flexible making the designed results more practical and effective.

Intelligent Examination Monitoring and Maintenance for the Safety of Operation of Flexible Manufacturing Systems

ZHANG Jian min, LI Shi jian, HAO Juan

2001, 10(2): 163-168.

[Abstract](200)

Abstract:
Based on the system of electric power supply for flexible manufacturing systems (FMS), a study has been carried out on the intelligent safety examination, monitoring and maintenance of its running environment. On the basis of the specific feature of the power supply network of an FMS, real time monitoring system of the power supply network and the fault diagnostic expert system for the power equipment have been designed. This system can diagnose not only definite fault phenomena, but also fuzzy, uncertain fault phenomena as well. Fault diagnostic knowledge base for the power equipment has been founded hierarchy architecture model and the method of fault tree analysis. Feasibility of this system has been proved by computer simulation.

Computation of the Fatigue Life of Road Wheel with Double-Layer Rubber Flange

ZHENG Mu qiao, SUN Feng chun, JIANG Xuan, ZHANG Jun

2001, 10(2): 169-174.

[Abstract](222)

Abstract:
In order to increase the fatigue life (FL) of road wheels (RW), a kind of double layer rubber flange (DLRF) is put forward. It consists of two layers of rubber, where metal wires are laid in the inner layer and the outer layer has no inlaid metal wires. Stress, strain and temperature field of DLRF were calculated with ANSYS finite element analysis (FEA) software, FL of DLRF RW was also computed with fracture mechanics fatigue theory. The results of computation indicate that the heat generated in RW's rubber flange (RF) can be reduced by the use of DLRF, and the FL of RW can be increased without affecting the mechanical intensity of RW.

Diode Pumped Monolithic Unidirectional Nonplanar Single-Frequency Ring Laser

WU Ke ying, ZHAO Chang ming, SHI Jun feng, WEI Guang hui, LIU An han, CUI Lian rong, ZHU Zhen, HONG Dong mei

2001, 10(2): 175-179.

[Abstract](202)

Abstract:
Diode pumped monolithic nonplanar ring laser has been developed, yielding single frequency laser and has the advantages of compactness, reliability and high efficiency. Its principles are given in detail and a monolithic nonplanar ring laser is designed. As a result, a laser of hundreds milliwatts cw single frequency output was built up, placed in a magnetic field and pumped by LD. The optical conversion efficiency was more than 15% and the slope efficiency more than 30%. The laser beam had a good quality, with M 2 about 1 2.

Improved Design and SOVA Algorithm for Serial Concatenated Convolutional Code

WAN Lei, KUANG Jing ming

2001, 10(2): 180-185.

[Abstract](125)

Abstract:
To improve the performance of the short interleaved serial concatenated convolutional code(SCCC) with low decoding iterative times, the structure of Log MAP algorithm is introduced into the conventional SOVA decoder to improve its performance at short interleaving delay. The combination of Log MAP and SOVA avoids updating the matrices of the maximum path, and also makes a contribution to the requirement of short delay. The simulation results of several SCCCs show that the improved decoder can obtain satisfied performance with short frame interleaver and it is suitable to the high bit rate low delay communication systems.

Simulation of Quantum Noise in the Low-Light-Level Imaging System

ZOU Zheng feng, LU Han sheng, BAI Ting zhu, GAO Zhi yun

2001, 10(2): 186-190.

[Abstract](195)

Abstract:
A mathematical model of quantum noise having much effect on the low light imaging system is set up. To simulate the quantum noise, the random numbers obeying noise distribution must be formed and are weighted on the basis of the model created. Three uniform random sequences are built by the linear congruential method, of which two are used to form integer number and decimal fraction parts of the new random sequence respectively and the third to shuffle the new sequence. And then a Gauss sequence is formed out of uniform distribution by a function transforming method. It actualizes the simulation in real time of quantum noise in the low light imaging system, where video flow is extracted in real time, the noise summed up and played back side by side with the original video signs by a simulation software.

Simulation Study of the Workspace of the Parallel Machine Tool

ZHANG Jian min, HAO Juan, WANG Zeng ping

2001, 10(2): 191-196.

[Abstract](323)

Abstract:
A new three dimensional simulation method is introduced to study the workspace of a 6 PSS (P denotes a prismatic kinematic pair, S denotes a spherical kinematic pair) parallel machine tool. This algorithm adopts the method of numerical analysis to investigate the boundary points in a series of sections which form the surface of the workspace. That is, to study such points that have the largest polar radius on a certain section in a system of polar coordinates according to conditions of constraint. The constraint conditions considered in the article include the maximum and minimum displacements of each dieblock, the maximum and minimum angles of oscillation in each hinge. By converting the constraint inequalities into constraint equations, the largest polar radius corresponding to every constraint condition can be evaluated and the minimum one is used to decide the boundary point. This algorithm greatly simplifies the computational process and can be used to analyze any section of the workspace. It provides a theoretical basis for the structural design of such a machine tool.

Method of Growth in Finding the Test Cube of Industrial Robots

LU Ji lian, ZHAO Zhan fang, ZHANG Qiang

2001, 10(2): 197-203.

[Abstract](234)

Abstract:
In order to find the test cube for industrial robots as specified by ISO 9283, a seed cube is grown up in an irregular working space of the robot, provided that the corners of the cube do not exceed the boundary of the working space. All possible cubes are searched, and the cube with the maximum volume is selected. The calculation examples show that the method of growth can be used for a variety of industrial robots. The method of growth can determine the test cube and test points of irregular working space according to ISO 9283, and can avoid blindness and randomness in the selection of test points.

Fault Diagnosis of Vehicle Transmission System Based on Rough Set Theory

LI Xiao lei, ZHANG Zhen hua, WU Xiao bing, TIAN Chun shu

2001, 10(2): 204-208.

[Abstract](240)

Abstract:
Rough set theory is used to treat the data of vehicle transmission system faults. The minimum fault feature vector can be obtained by calculating the importance and dependency of each attribute. Real time diagnosis, as a result, can be actualized. Ultimate decision making can be done by analyzing the consistency of decision information. The result shows that rough set theory is useful and possesses its unique merits in this field.

Data Conversion Among Different Databases Under an Integrated Network Environment

LIANG Yun rong, GAO Wei ling, YANG Qian

2001, 10(2): 209-214.

[Abstract](193)

Abstract:
Method for data conversion of heterogeneous DBMS's in the integrated network environment is introduced. The technical approach used can perform data conversion of heterogeneous databases located on different nodes of the network, such as Oracle, Sybase, Informix, MS SQL Server, SQL Anywhere and Foxpro. The conversion system adopts the Client/Server architecture and provides visual integrated interface for users.

New Wavefront Handshaking Circuits

LIU Zhen yu, CHEN He, HAN Yue qiu

2001, 10(2): 215-219.

[Abstract](123)

Abstract:
Two types of handshaking circuits are proposed to implement the asynchronous communication between two processing elements in the wavefront array processors. After correcting the flaws in the original design, these circuits make the system more robust and flexible. These circuits have compact architectures and are of higher performance. Besides, compared with other handshaking circuits, these designs are more suitable for FPGA.

Powertrain Torque Control Based on Torque Observer

GAN Hai yun, ZHAO Chang lu, SUN Ye bao, GE Yun shan, ZHANG Fu jun

2001, 10(2): 220-224.

[Abstract](194)

Abstract:
To reduce shock during transmission gear shift, a transmission torque feedback closed loop control system is proposed based on the powertrain system model and a torque observer. The ignition time of engine was delayed to reduce transmission output shaft torque during gear shift. In contrast to traditional control method, the closed loop control system based on torque observer can obviously reduce the transmission output shaft torque during gear shift. It can be concluded that by way of torque feedback closed loop control, transmission shift shock can be reduced.

2001 Vol. 10, No. 2