JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

ASIC Design and Implementation for Digital Pulse Compression Chip

2004, 13(1): 1-4.

[Abstract](113) [PDF 166KB](2)

Abstract:
A novel ASIC design of changeable-point digital pulse compression (DPC) chip is presented. System hardware resource is reduced to one third of the traditional design method through operations sharing hardware, (i.e.) let FFT, complex multiplication and IFFT be fulfilled with the same hardware structure. Block-floating-point scaling is used to enhance the dynamic range and computation accuracy. This design applies parallel pipeline structure and the radix-4 butterfly operation to improve the processing speed. In addition, a triple-memory-space(TMS) configuration is used that allows input, computation and output operations to be overlapped, so that the dual-butterfly unit is never left in an idle state waiting for I/O operation. The whole design is implemented with only one chip of XC2V500-5 FPGA. It can implement 1 024-point DPC within 91 6 μs.The output data is converted to floating-point formation to achieve seamless interface with TMS320C6701. The validity of the design is verified by simulation and measurement results.

Research on Estimator and Testing Acquisition Schemes in Direct Sequence Spectrum Spreading Systems

CHEN Yan, HUANG Qi-hua, AN Jian-ping, LUO Wei-xiong

2004, 13(1): 5-9.

[Abstract](146)

Abstract:
Serveral methods for the pararrel acquisition of a PN sequence in a baseband direct sequence spread spectrum system are investigated. Four different kinds of schemes are considered: the optimal estimation scheme, the locally optimal estimation scheme, the optimal testing searches and the locally optimal testing scheme. In the four kinds of parallel acquisition schemes, the expressions for the probability of error are given and compared with the actual error probabilities obtained via Monte Carlo simulation. We also outline a technique that can be suboptimal because of a large amount of hardware and computation when using the parallel acquisition schemes.

Performance Analysis of Wireless Mobile Radio Hybrid(DS/FH) Spread Spectrum Network

YU Xiao-gang, WANG Hua, KUANG Jing-ming

2004, 13(1): 10-14.

[Abstract](177)

Abstract:
By the flexible redefinition of frequency-occupation and frequency-collision event, the frequency-(collision) probability of hybrid(DS/FH) spread spectrum network is analyzed. This probability is based on the simultaneous transmission number threshold and is discussed in synchronous and asynchronous circumstances respectively. And then, the network throughput based on the packet correct reception probability is analyzed. Two models which have finite and infinite population respectively is discussed. At last, the numerical results are given.

Randomized Algorithms for Probabilistic Optimal Robust Performance Controller Design

SONG Chun-lei, XIE Ling

2004, 13(1): 15-19.

[Abstract](110)

Abstract:
Polynomial-time randomized algorithms were constructed to approximately solve optimal robust performance controller design problems in probabilistic sense and the rigorous mathematical justification of the approach was given. The randomized algorithms here were based on a property from statistical learning theory known as (uniform) convergence of empirical means (UCEM). It is argued that in order to assess the performance of a controller as the plant varies over a pre-specified family, it is better to use the average performance of the controller as the objective function to be optimized, rather than its worst-case performance. The approach is illustrated to be efficient through an example.

Agent Belief with Credibility and Its Revision Mechanism

LIU Qiong-xin, LIU Yu-shu, ZHENG Jian-jun, ZHU Juan

2004, 13(1): 20-23.

[Abstract](166)

Abstract:
An approach to characterize the credibility of beliefs of an agent is proposed in this paper, which can define the uncertainty of beliefs, calculation rules and inference rules about credibility and a method for belief revision based on abductive reasoning is also given. When an agent receives some new information, if the new information is consistent with the current belief set, then incorporate this new information with an appropriate credibility, otherwise the choice will be different depending on the characters of agents, and the deliberated agents will choose the belief with a better explanation under the current belief set. Removing one belief may cause the removal of those beliefs that, together with others, logically entail the formula to be removed. A method based on abduction is proposed to solve these problems.

New Algorithm to Evaluate the Unreliability of Flow Networks Based on Minimal Cutsets

WANG Fang, HOU Chao-zhen

2004, 13(1): 24-28.

[Abstract](69)

Abstract:
Several conclusions on minimal cutset are proposed, from which a new algorithm is deduced to evaluate the unreliability of flow networks. Beginning with one unreliability product of the network, disjointed unreliability products are branched out one by one, every of which is selected from the network minimal cutsets. Finally the unreliability of the network is obtained by adding all these unreliability products up.

New Asymmetric Fuzzy PID Control for Pneumatic Position Control System

XUE Yang, PENG Guang-zheng, FAN Meng, WU Qing-he

2004, 13(1): 29-33.

[Abstract](265) [PDF 184KB](6)

Abstract:
A fuzzy control algorithm of asymmetric fuzzy strategy is introduced for a servo-pneumatic position system. It can effectively solve the difficult problems of single rod low friction cylinders, which are mainly caused by asymmetric structures and different friction characteristics in two directions. On the basis of this algorithm, a traditional PID control is used to improve dynamic performance. Furthermore, a new asymmetric fuzzy PID control with α factor is advanced to improve the self-adaptability and robustness of the system. Both the theoretical analyses and experimental results prove that, with this control strategy, the dynamic performance of the system can be greatly improved. The system using this control algorithm has strong robustness and it obtains desired overshoot and repeatability in both transient and steady-state responses.

Local Optimization and Adversarial Consideration: Agent Skills in Everest Simulation Team

GU Yang, CUI Li-hui, LIU Jun-feng, WANG Qing-lin

2004, 13(1): 34-38.

[Abstract](108)

Abstract:
Skilled individual agents are firm basis of a strong soccer team. The skills available to Everest 2002 (agents) include kicking, dribbling, forwarding, ball interception and tackling. These intermediate sub goals are implemented by a combination of local optimization which hopes to determine the optimal primitive action from a local perspective and adversarial consideration which takes into account opponents and limitations imposed by simulation environment. Everest 2002 RoboCup simulation teams, building on 11 skilled agents and an on-line coach, won the 2nd place in RoboCup 2002 simulation league.

Dynamic Region Updating Strategy in HLA-Based Distributed Interactive Simulation

DAI Zhong-jian, HOU Chao-zhen, SU Li-min

2004, 13(1): 39-42.

[Abstract](177)

Abstract:
The HLA(high level architecture)-based distributed interactive simulation uses interest management mechanism to reduce the traffic on network and improve the system scalability. Making region updating occur only when needed can improve the interest management. Typically a static threshold is defined before simulation to trigger the region updating. Now a dynamic threshold is used to trigger region updating , the threshold is adapted by the real-time massage in simulation, named as update lifetime. The result of experiment shows that this policy can overcome the weak point of static threshold and can meet the requirements of bandwidth and simulation correctness.

Deformation and Failure of Polymer Bonded Explosives

CHEN Peng-wan, HUANG Feng-lei, DING Yan-sheng

2004, 13(1): 43-47.

[Abstract](198) [PDF 246KB](3)

Abstract:
The deformation and failure of pressed polymer bonded explosives under different types of loads including tension, compression and low velocity impact are presented. Brazilian test is used to study the tensile properties. The microstructure of polymer bonded explosives and its evolution are studied by use of scanning electronic microscopy and polarized light microscopy. Polishing techniques have been developed to prepare samples for microscopic examination. The failure mechanisms of polymer bonded explosives under different loads are analyzed. The results show that interfacial debonding is the predominant failure mode in quasi-static tension, while extensive crystal fractures are induced in compression. With the increase of strain rate, more crystal fractures occur. Low velocity impact also induces extensive crystal fractures.

Optimal Structural Modifications of a Gun Tripod for Desired Natural Frequencies

WANG Jian-zhong, ZHOU Ya-ming, DUO Ying-xian

2004, 13(1): 48-53.

[Abstract](206) [PDF 208KB](4)

Abstract:
Sensitivity analysis and structural modification techniques are used to investigate the structural modifications of a machine gun tripod which suffers from severe vibration during firing due to the resonance. The finite element analysis and modal test techniques are used to determine the natural frequencies of the machine gun. The sensitivities of natural frequencies with respect to the structural parameters of the tripod are obtained by the method of sensitivity analysis, and they can be used as an indication for the structural modification of the tripod so as to shift the natural frequencies effectively. By the structural modification techniques, finally, the optimal structural modifications of the tripod for desired natural frequencies are made to avoid the resonance, and this optimal structural modification is verified by re-analysis of the modified structure and the vibration contrast between original structure and modified structure. The research resulted in a successful structural modification for desired natural frequencies, which can avoid the resonance and thereby greatly improve the shooting precision of the machine gun during firing.

Engineering Model for Detecting Sensitivity of the Coupling Capacitance Detector

WANG Wei, DENG Jia-hao, YIN Jun, HUANG Yan

2004, 13(1): 54-57.

[Abstract](179)

Abstract:
The sensitivity engineering model of the coupling capacitance detector is built to provide the theoretic foundation for designing its circuits and electrodes scientifically. The sensitivity concept model of the capacitance proximity detector is discussed, and the detecting sensitivity of the coupling capacitance detector is analyzed theoretically. Then the sensitivity engineering model, which can reflect the main parameters relationship of the detecting circuit is set up based on the foregoing analyses. It is concluded that: ① the sensitivity is mainly correlative with some parameters including the voltage transmission factor of the demodulator, the oscillating voltage amplitude and the amplitude variation constant of the oscillator; ② the sensitivity is also influenced by the areas of electrodes and the distance between electrodes of the detector.

Modal Test/Calculation Correlation Study on the Lower Crankcase of High-Duty Diesel Engine

FENG Hui-hua, ZUO Zheng-xing, LIAO Ri-dong, ZHANG Ru-hua

2004, 13(1): 58-62.

[Abstract](190)

Abstract:
To set up the dynamic FEM model of a high-duty diesel's lower crankcase with sufficient precision, modal correlation research on tested and calculated modes have been fulfilled. MACs between each mode pairs, CoMACs and ECoMACs on each node of modal testing model have been calculated. On the assistant of modal shape comparison, MACs could afford information about correlating relations between tested and calculated mode groups. CoMACs and ECoMACs have pointed out the direction of structure modification to FEM model. The results of the study show that the analytic model built has a certain degree of accuracy.

Structure and Control Strategies of Fuel Cell Vehicle

SONG Jian-guo, ZHANG Cheng-ning, SUN Feng-chun, ZHONG Qiu-hai

2004, 13(1): 63-66.

[Abstract](168)

Abstract:
The structure and kinds of the fuel cell vehicle (FCV) and the mathematical model of the fuel cell processor are discussed in detail. FCV includes many parts: the fuel cell thermal and water management, fuel supply, air supply and distribution, AC motor drive, main and auxiliary power management, and overall vehicle control system. So it requires different kinds of control strategies, such as the PID method, zero-pole method, optimal control method, fuzzy control and neural network control. Along with the progress of control method, the fuel cell vehicle's stability and reliability is up-and-up. Experiment results show FCV has high energy efficiency.

Dynamic Characteristics of Supercavitating Flow Around a Hydrofoil

WANG Guo-yu, ZHANG Mei-hong, LIU Shu-yan, Ikohagi Toshiaki

2004, 13(1): 67-70.

[Abstract](160)

Abstract:
Supercavitation dynamic characteristics around a hydrofoil are studied with both high-speed visualization and drag and lift measurements. In the supercavitation condition, the cavitation area covers the entire surface of the foil. There is a distinct interface between the main flow and the supercavitating flow regions. The cavitating region is filled with cavitation bubble and water mixture. Small fluctuations of the interface are observed, which indicates that even a relative smooth surface is formed in this state, the interface is unsteady. The minimum drag is to be obtained in the supercavitation condition.

Computer-Based Simulation and Test System for the Calibration of EFI Engine

ZHAO Chang-lu, ZHANG Fu-jun, HUANG Ying, GE Yun-shan, LIU Fu-shui

2004, 13(1): 71-75.

[Abstract](159) [PDF 201KB](3)

Abstract:
A computer-based simulation and test system is developed. This system has the following functions: producing the initial control MAP with good accuracy, calibrating the electronic control unit (ECU) on-line, (identifying) the dynamic transfer functions for air/fuel ratio, idle speed and ignition timing control. So the experiment work is reduced and the calibration is accelerated. In order to increase the simulation accuracy of the initial control MAP, the mathematical models are not only based on theoretical equations, but also on the control data of reference working points, which is obtained by the on-line calibration of special engines. The application of this system on a mini-car shows that the simulated control MAP has good accuracy, the interface of the system is friendly, the integrated simulation and test system is a powerful aid for EFI engine calibration and the development speed is accelerated.

Comparative Process for the Preparation of 9-Oxime Erythromycin A

SUN Jing-guo, YAO Guo-wei, OU Yu-xiang

2004, 13(1): 76-79.

[Abstract](261)

Abstract:
The comparative process for preparing 9-oxime erythromycin A (EMAO) is investigated. EMAO was synthesized and compared by the reaction of erythromycin and hydroxylamine hydrochloride with various bases such as sodium acetate, triethylamine, etc. A new synthetic method is established. The oximation is performed under dynamic buffer system; less degradation impurities are formed. The yield of EMAO reaches more than 95%, HPLC analysis shows that the purity of EMAO is more than 90%, and the E/Z isomeric ratio preponderates over 7∶1.

Numerical Simulation of Basic Parameters in Plasma Spray

FAN Qun-bo, WANG Lu, WANG Fu-chi

2004, 13(1): 80-84.

[Abstract](182)

Abstract:
On the basis of energy balance in the plasma gas, a new, simplified but effective mathematical model is developed to predict the temperature, velocity and ionization degrees of different species at the torch exit, which can be directly calculated just by inputting the general spraying parameters, such as current, voltage, flow rates of gases, etc. Based on this method, the effects of plasma current and the flow rate of Ar on the basic parameters at the torch exit are discussed. The results show that the temperature, velocity and ionization degrees of gas species will increase with increasing the plasma current; while increasing Ar flow rate can increase the velocity at the exit but decrease the temperature and ionization degrees of plasma species. The method would be helpful to predict the temperature and velocity fields in a plasma jet in future, and direct the practical plasma spray operations.

Numerical Simulation of Twin-Screw Extrusion with Wall Slip

HU Dong-dong, CHEN Jin-nan

2004, 13(1): 85-89.

[Abstract](185)

Abstract:
Wall slip boundary condition is first introduced into twin-screw extrusion with the Navier slip law. Three-dimensional isothermal flow in the twin-screw extruder is simulated by using the finite element package POLYFLOW. Profiles of velocity contours in the screw channel and shear rate distributions in the intermeshing region are presented for different slip coefficients. Curves of axial pressure difference, average shear rate and dispersive mixing index vs. the slip coefficient are plotted and discussed. Comparisons are also made between the wall slip conditions and the non-slip condition. The simulation results indicate that, as the level of wall slip decreases, the axial pressure difference rises, the shear effect is intensified and the axial mixing is also enhanced. All these flow characteristics seem to level off with the increase of the slip coefficient. However, because of the inherent limitation of the Navier slip law, use of an overestimated slip coefficient would predict an over-sticky state between the screw surface and the polymer melt.

Bounds on Fractional Domination of Some Products of Graphs

CHEN Xue-gang, SUN Liang, XING Hua-ming

2004, 13(1): 90-93.

[Abstract](203) [PDF 186KB](13)

Abstract:
Let γ f（G） and γ^tf（G） be the fractional domination number and fractional total domination number of a graph G respectively. Hare and Stewart gave some exact fractional domination number of P n×P m （grid graph） with small n and m . But for large n and m , it is difficult to decide the exact fractional domination number. Motivated by this, nearly sharp upper and lower bounds are given to the fractional domination number of grid graphs. Furthermore, upper and lower bounds on the fractional total domination number of strong direct product of graphs are given.

Lie Symmetry and Non-Noether Conserved Quantity for Hamiltonian Systems

WU Hui-bin

2004, 13(1): 94-95.

[Abstract](193)

Abstract:
A non-Noether conserved quantity for the Hamiltonian system is studied. A particular infinitesimal transformation is given and the determining equations of Lie symmetry are established. An existence theorem of the non-Noether conserved quantity is obtained. An example is given to illustrate the application of the result.

Quantum Fluctuation Properties of Polariton System in Thermal Vacuum State Field

SHAO Bin, YU Tian-sheng, ZOU Jian, ZENG Tian-hai

2004, 13(1): 96-99.

[Abstract](75)

Abstract:
Using the theory of thermal field dynamics (TFD), a model polariton system is investigated and the squeezing properties of the polariton system at finite temperature is discussed. It is shown that when the photon field is initially in a thermal vacuum state and the phonon initially in its lowest energy level state (the vacuum state), the phonon, photon and also the polariton system can exhibit nonclassical behaviour.

Collapse-Revival and Entanglement in a Single-Cooper-Pair Box with a Single-Mode Cavity Field

ZHANG Meng, ZOU Jian, SHAO Bin

2004, 13(1): 100-102.

[Abstract](88)

Abstract:
A single-Cooper-pair box biased by a classical voltage and also irradiated by a single-mode quantized field is considered. The degree of entanglement between the quantized field and the single-Cooper-pair box is examined by using the field entropy. It is found that the collapse and revival phenomenon can exist in this system, the entropy reaches its local minimum at one-half of the quiescent period, and the larger the entropy, the greater the entanglement is.

Analysis on Dynamic Dielectric Recovery and Statistical Property of Vacuum Circuit-Breakers with Multi-Breaks

LIAO Min-fu, DUAN Xiong-ying, ZOU Ji-yan

2004, 13(1): 103-108.

[Abstract](192)

Abstract:
Based on the dynamic dielectric recovery process in the vacuum gaps in series, investigations were made on post-arc insulation state in double and multi-breaks operation in high voltage power system. From the research on the breakdown weak points in high voltage vacuum gaps, their turnout and distribution, some theoretic work were made to set up the models for describing the statistical property of multi-breaks vacuum circuit-breakers' breakdown and post-arc re-strike, which can be used for explaining the mechanism of the improvement in the breaking capacity of multi-breaks units compared with that of single-break ones which have the same equivalent gap length. The advantages of vacuum breakers with multi-breaks are proposed.

Motion Analysis of an Electric Vehicle with Two Independent Drive Motors

CHEN Yong, CHEN Quan-shi, SUN Feng-chun

2004, 13(1): 109-112.

[Abstract](169)

Abstract:
Motion analyses are performed with the help of stability and simulation analysis, which can provide theoretical bases for applications of an electric vehicle with two independent drive motors. Compared with one-motor drive electric vehicle, the two-motor drive electric vehicle has the advantage of easy layout, simple power train and good drivability and handling characteristics. Analysis shows the method connecting armatures of two DC motors in parallel can function as mechanical differential without a steering sensor, which can simplify structure and increase reliability of the controller. Computer simulations and experiment are carried out to verify conclusions.

2004 Vol. 13, No. 1