JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Coupling Frequency of the Liquid Sloshing in a Cylindrical Tank with a Flexible Baffle

YUE Bao-zeng

2006, 15(1): 1-4.

[Abstract](196)

Abstract:
The coupling oscillation of a liquid in a cylindrical tank with an elastic slosh baffle is investigated. Free surface conditions are considered in the study. The complexity of the coupled boundary-value problem for the liquid and elastic damping spacer results in significant analytical difficulties. Two different velocity potential functions are respectively used in the liquid domain above, or below the damping spacer. A coupled frequency equation is obtained by using the pair of velocity potential functions. The numerical and theoretical analysis show that the natural frequency changes according to the location and stiffness of the spacer. Results indicate that the frequency coupling between damping spacer and sloshing liquid is obvious near the free liquid surface. It is shown that the coupling frequency increases with the increase of damping baffle rigidity.

ALE Fractional Step Finite Element Method for Fluid-Structure Nonlinear Interaction Problem

YUE Bao-zeng

2006, 15(1): 5-8.

[Abstract](198)

Abstract:
A computational procedure is developed to solve the problems of coupled motion of a structure and a viscous incompressible fluid. In order to incorporate the effect of the moving surface of the structure as well as the free surface motion, the arbitrary Lagrangian-Eulerian formulation is employed as the basis of the finite element spatial discretization. For numerical integration in time, the fraction step method is used. This method is useful because one can use the same linear interpolation function for both velocity and pressure. The method is applied to the nonlinear interaction of a structure and a tuned liquid damper. All computations are performed with a personal computer.

Estimation of Initial Disturbances for Rockets Based on Interactions of Rockets and Directional Tubes

CHEN Zhen, BI Shi-hua

2006, 15(1): 9-12.

[Abstract](66)

Abstract:
In the range of the rockets/launcher system itself, the dynamic equations for rocket and directional tube during semi-constraint period have been constructed by using Newton-Euler method. Considering the interaction of rockets and directional tubes when clearances exist, the method of estimating initial disturbances for the rocket by using vibration data of the directional tube has been given. The estimated results have been compared with the simulation results computed by the dynamic simulating software ADAMS. Results computed by the two methods are basically consistent and the computing errors do not increase with the variation of the clearance. The validity of the proposed method has been proved.

Short Range Top Attack Trajectory Optimum Design Based on Genetic Algorithm

TANG Sheng-jing, XU Xiao-xia, DAI Bin

2006, 15(1): 13-16.

[Abstract](176)

Abstract:
A flying-body is considered as the reference model, the optimized mathematical model is established. The genetic operators are designed and algorithm parameters are selected reasonably. The scheme control signal in short range top attack flight trajectory is optimized by using genetic algorithm. The short range top attack trajectory designed meets the design requirements, with the increase of the falling angle and the decrease of the minimum range. The application of genetic algorithm to top attack trajectory optimization is proved to be feasibly and effectively according to the analyses of results.

Research on Spray, Combustion and Emission Characteristics for DI Diesel Engine

GE Yun-shan, ZHANG Shi-ying, ZHOU Lei, ZHANG Fu-jun

2006, 15(1): 17-21.

[Abstract](237)

Abstract:
To improve the combustion chamber shape that can decrease the directed injection (DI) diesel emission, the theories of DI diesel spray, combustion and pollutant formation model are analysed and implemented based on the CFD code FIRE. Results show that the chamber with contracting orifice can get stronger squish swirl intensity. The results of the verification studies show a good accordance with the measurements and reveal that the individual processes of spray evolution, combustion and pollutant formation are well captured in FIRE. Finally, based on the analyzing and comparing of the calculation results of different chambers, a combustion chamber of contracting orifice geometry with lower emission is proposed.

Research on Vehicle Control Technology Using Four-Wheel Independent Steering System

CHEN Si-zhong, SHU Jin, YANG Lin

2006, 15(1): 22-26.

[Abstract](259)

Abstract:
The enhancement of vehicle handling stability and maneuverability through active and independent rear wheels control is presented. Firstly, the configuration of four-wheel independent steering prototype vehicle is introduced briefly. Then the concrete overall design of the electronic controllers of four wheel independent steering system (4WIS) is formulated in details. Under the control strategy of zero sideslip angle at mass center, the mathematical model of 4WIS is established to deduce the equations of separated rear wheel steering angles. According to these equations, simulation analysis for 4WIS vehicle performances is finished to show that 4WIS vehicle can improve the maneuverability greatly at low speed and increase the handling stability at high speed. Finally, the road test of 4WIS vehicle has performed to verify the correctness of simulation and show that compared with the conventional four wheel steering (4WS) vehicle, the 4WIS vehicle not only improves the kinematical harmony but also decreases steering resistance and lighten abrasion of tires.

Functional Virtual Prototyping in Vehicle Chassis Reform Analysis and Improvement Design

CHEN Xiao-kai, LIN Yi, WANG Jun

2006, 15(1): 27-30.

[Abstract](164)

Abstract:
The contribution of functional virtual prototyping to vehicle chassis development is presented. The different topics that we took into consideration were reform analysis and improvement design during the vehicle chassis development. A frame of coordinates based on the digital-model was established, the main CAE analysis methods, multi-body system dynamics and finite element analysis were applied to the digital-model build by CAD/CAM software. The method was applied in the vehicle chassis reform analysis and improvement design, all the analysis and design projects were implemented in the uniform digital-model, and the development was carried through effectively.

New Adaptive Approach for Road Condition Identification in ASR Control System

ZHANG Jing-bo, MA Yue-feng, LIU Zhao-du, QI Zhi-quan

2006, 15(1): 31-35.

[Abstract](168)

Abstract:
A novel tire-road adaptive model in longitude direction to formulate the dynamic characteristic between tire and road is proposed in this paper, based on this model, a new adaptive approach of road condition identification is presented to identify the model's parameters on-line in order to improve the performance of anti-slip regulation system(ASR). The optimal slip is determined by using the drive wheel's slip and longitude traction force in ASR before the slipping of the drive wheel. Co-simulation is done based on the model for JETTA GTX building with ADAMS/CAR and Matlab, and results show that the adaptive model accords with Pacejka model very well. This adaptive model has simpler form, less number of parameters and higher adaptability than usual, and the new identification approach has a small amounts of operation, which is very suitful for ASR.

Rolling Control Characteristic Experimental Investigation of a Canard Missile with Free-Spinning Tail

LEI Juan-mian, WU Jia-sheng, MENG Ling-tao

2006, 15(1): 36-38.

[Abstract](253)

Abstract:
To study the rolling control characteristics of a canard-controlled missile, a series of wind tunnel experiment is conducted. The experimental method, the structure features of wind tunnel model and the experimental results are introduced in this paper. The experimental data show that the canard is an inefficient rolling control device for canard-controlled missile with fixed tail fins; but for the free-spinning tail fin configuration, the canard can conduct rolling control of the missile, and even have higher controlling efficiency under larger canard deflection angle.

Investigation on the Sediment Characteristics of the Electrostatic Cyclonic Precipitator

LI Ming-hua, MA Chao-chen, WEI Ming-shan, WU Qian-li

2006, 15(1): 39-42.

[Abstract](103)

Abstract:
In order to find out the relationship between the sediment characteristics and collecting efficiency of the electrostatic cyclonic precipitator, an online study for the sediment characteristics of electrostatic cyclonic precipitator had been done with Kompton back scatter method, with the collecting efficiency tested at the same time. And the relationship between the sediment characteristics and the collecting efficiency was gotten. The sediment thickness increased with time extended and the concentration increased when the inlet velocity was fixed. The collecting efficiency increased with the inlet velocity increased, but dropped with the concentration increased. When the concentration and inlet velocity were fixed, the collecting efficiency drop a little with the increase of sediment thickness. The sediment would decrease the corona current in the collecting filed, which would make the electrostatic effect fall, then made the collecting efficiency drop a little.

Strapdown Homing Guidance System Design for Some Ammunition

SONG Jian-mei, LI Quan-yun

2006, 15(1): 43-47.

[Abstract](94) [PDF 187KB](4)

Abstract:
The strapdown homing guidance system for some ammunition was mainly studied. A strong tracking Kalman filter was designed for the strapdown homing guidance system using the information measured by the strapdown homing seeker to estimate relative movement variables between the ammunition and target. Then the optimal proportional law, which using the estimated information, guided the ammunition. Simulation results show that the designed strapdown homing guidance system with strong tracking Kalman filter can attack the maneuvering target effectively, and satisfy the performance index for the guided ammunition system.

Grid-Based Pseudo-Parallel Genetic Algorithm and Its Application

CHEN Hai-ying, GUO Qiao, XU Li

2006, 15(1): 48-52.

[Abstract](183)

Abstract:
Aimed at the problems of premature and lower convergence of simple genetic algorithms (SGA), three ideas——partition the whole search uniformly, multi-genetic operators and multi-populations evolving independently are introduced, and a grid-based pseudo-parallel genetic algorithms (GPPGA) is put forward. Thereafter, the analysis of premature and convergence of GPPGA is made. In the end, GPPGA is tested by both six-peak camel back function, Rosenbrock function and BP network. The result shows the feasibility and effectiveness of GPPGA in overcoming premature and improving convergence speed and accuracy.

Analysis of Deviations in an Agent and Ontology-Based Dialogue Management System

HU Si-kang, CAO Yuan-da

2006, 15(1): 53-56.

[Abstract](213)

Abstract:
Algorithms of detecting dialogue deviations from a dialogue topic in an agent and ontology-based dialogue management system(AODMS) are proposed. In AODMS, agents and ontologies are introduced to represent domain knowledge. And general algorithms that model dialogue phenomena in different domains can be realized in that complex relationships between knowledge in different domains can be described by ontologies. An evaluation of the dialogue management system with deviation-judging algorithms on 736 utterances shows that the AODMS is able to talk about the given topic consistently and answer 86.6% of the utterances, while only 72.1% of the utterances can be responded correctly without deviation-judging module.

LMI Approach to Robust H_∞/H₂Controller Design with Regional Poles Constraint of a Pump-Motor System

GUO Chu-sheng, WANG Xiang-zhou, WANG Yu

2006, 15(1): 57-61.

[Abstract](194)

Abstract:
The time domain guideposts requirements of a pump-motor system is transfered into a series of constraints which express the robust performance upper bound and regional poles limits of the closed loop system. Then the servo system control problem is transferred into the problem of robust performance optimizing under regional poles constrains described by linear matrix inequality （LMI）. These LMIs are easy to solve through the Matlab LMI-toolbox. Simulations indicate that the controller has excellent dynamic, static and disturbance rejection performance, and the control system is robust and has perfect H₂performance to the bounded external torque disturbance.

Adaptive Track Predicting Control for Target Tracking Control Systems

ZHAO Jiang-bo, WANG Jun-zheng, ZHONG Qiu-hai

2006, 15(1): 62-65.

[Abstract](177)

Abstract:
According to the characteristic of maneuvering targets tracking system, adaptive track predicting control is proposed from the point of predicting the motion track of the maneuvering target. For this method, least mean square(LMS) adaptive filter is applied to estimate the future track of the target. The structure of this filter is simple and the calculation amount is small. It is therefore suitable to being used in real-time control system. Testing results have proved that the control method can improve the tracking precision for maneuvering targets obviously.

Cluster-Based Distributed Algorithms for Very Large Linear Equations

GU Zhi-min, MARTA Kwiatkowska, FU Yin-xia

2006, 15(1): 66-70.

[Abstract](100)

Abstract:
In many applications such as computational fluid dynamics and weather prediction, as well as image processing and state of Markov chain etc., the grade of matrix n is often very large, and any serial algorithm cannot solve the problems. A distributed cluster-based solution for very large linear equations is discussed, it includes the definitions of notations, partition of matrix, communication mechanism, and a master-slaver algorithm etc., the computing cost is O(n3/N), the memory cost is O(n2/N), the I/O cost is O(n2/N), and the communication cost is O(Nn), here, N is the number of computing nodes or processes. Some tests show that the solution could solve the double type of matrix under 106×106 effectively.

Image-Moment Based Affine Invariant Watermarking Scheme Utilizing Neural Networks

WU Jian-zhen, XIE Jian-ying, YANG Yu-pu

2006, 15(1): 71-75.

[Abstract](167)

Abstract:
A new image watermarking scheme is proposed to resist rotation, scaling and translation (RST) attacks. Six combined low order image moments are utilized to represent image information on rotation, scaling and translation. Affine transform parameters are registered by feedforward neural networks. Watermark is adaptively embedded in discrete wavelet transform (DWT) domain while watermark extraction is carried out without original image after attacked watermarked image has been synchronized by making inverse transform through parameters learned by neural networks. Experimental results show that the proposed scheme can effectively register affine transform parameters, embed watermark more robustly and resist geometric attacks as well as JPEG2000 compression.

Visibility Culling Algorithm with Hierarchical Adaptive Bounding Setting

ZHENG Fu-ren, LI Feng-xia, ZHAN Shou-yi, YANG Bing

2006, 15(1): 76-80.

[Abstract](178)

Abstract:
Hierarchical adaptive bounding setting (HABS), a novel algorithm to reduce potentially visible set, is designed to be used for various geometry shape character in complex simulation scene to greatly improve geometry spatial storage precision. A spatial hierarchy tree is used to represent the topology of the model, and then the visibility geometry set from the viewpoint is determined by processing the hierarchy tree and frustum detection. In this process, HABS improves the viewpoint-to-region visibility detection efficiently. The algorithm is well-suited for complex models whose shape characters are various.

Remote Control Guidance Law Design Using Variable Structure Control

MENG Xiu-yun, WANG Qi

2006, 15(1): 81-84.

[Abstract](152) [PDF 144KB](2)

Abstract:
A method of sliding mode variable structure control for the missile body being a time varying system is presented. A remote control guidance law is designed. The method has strong robustness to target's maneuver. To reduce the chattering phenomena, quasi-sliding mode variable structure control method is used. Simulation results show that the proposed method has small miss distance for any kind of maneuvering targets and requires small control energy.

Research of Crossbar Switch of High Performance Network of Signal Processing System

HE Bin, HAN Yue-qiu

2006, 15(1): 85-90.

[Abstract](173)

Abstract:
The new type of embedded signal processing system based on the packet switched network is achieved. According to the application field and the characteristics of signal processing system, the RapidIO protocol is used to solve the high-speed interconnection of multi-digital signal processor (DSP). Based on this protocol, a kind of crossbar switch module which is used to interconnect multi-DSP in the system is introduced. A route strategy, some flow control rules and error control rules, which adapt to different RapidIO network topology are also introduced. Crossbar switch performance is analyzed in detail by the probability module. By researching the technique of crossbar switch and analyzing the system performance, it has a significant meaning for building the general signal processing system.

Novel Frame Shift and Integral Technique for Enhancing Low-Light-Level Moving Images

SONG Yong, HAO Qun, WANG Yong-tian

2006, 15(1): 91-96.

[Abstract](183)

Abstract:
A novel frame shift and integral technique for the enhancement of low light level moving image sequence is introduced. According to the technique, motion parameters of target are measured by algorithm based on difference processing. To obtain spatial relativity, images are shifted according to the motion parameters. As a result, the processing of integral and average can be applied to images that have been shifted. The technique of frame shift and integral that includes the algorithm of motion parameter determination is discussed, experiments with low light level moving image sequences are also described. The experiment results show the effectiveness and the robustness of the parameter determination algorithm, and the improvement in the signal-to-noise ratio (SNR) of low light level moving images.

Joint Power Control with Inter-Link Interference Prediction for Wireless Ad Hoc CDMA Networks

ZHANG Shu, RONG Meng-tian, LI Zhe-feng

2006, 15(1): 97-101.

[Abstract](166)

Abstract:
A joint power control algorithm for ad hoc networks based on code division multiple access (CDMA) was studied. Firstly, the new algorithm was deduced in theory. Then, the system model was developed. In the proposed algorithm, all transmitting nodes assigned in the same time slot adjust their transmitter power based on current information, which takes into account the adjustments of transmitter power of other transmitting nodes in next step and the prediction of inter-link interference power level at the receive node. Simulation results indicate that the proposed algorithm outperforms the conventional algorithms in terms of smaller standard deviation of receiver signal-to-interference-ratio, lower system interference and higher energy efficiency.

Joint Estimation of 2-D DOA and Polarization by Using the Linear Array with Diverse Polarizations

XU You-gen, LIU Zhi-wen

2006, 15(1): 102-105.

[Abstract](194)

Abstract:
A linear array of diversely polarized antennas with one pair of identical sensors is used to obtain closed-form unambiguous estimation of 2-D direction of arrival (DOA) and polarization. Spatial phase information together with weighted 3-D polarization-angular coherence structure (PACS) are first recovered with fourth-order cumulants manipulation via a new 2-D ESPRIT variant. Spatial filtering is performed to obtain the scaled PACS, from which the closed-form 2-D DOA and polarization estimates can be derived with only quadrant ambiguity involved. The undesired quadrant ambiguity can be further resolved by using the acquired estimate of spatial phase factor.

Design of a Radar Signal Simulator Based on Virtex-Ⅱ Series FPGA

ZHENG Zhe, LI Jia-qi, WU Si-liang

2006, 15(1): 106-110.

[Abstract](222)

Abstract:
A simulation method to simulate the pseudorandom code P.M PP radar's echo signal is proposed that makes use of the pre-generated Doppler simulation data, according to the relative movement parameter of the radar and the target. It resolves the problem of the high precision distance simulation and the high speed digital shift phase. At the same time, the radar dynamic digital video frequency target signal simulator is designed. Simulation results of the critical unit and the output waveform are given. The result of the test satisfies the system's request.

Nitration of Wood Cellulose in HNO₃/Organic Solvent Medium

SHAO Zi-qiang, WANG Wen-jun, WANG Fei-jun, WANG Ji-xun, TAN Hui-min

2006, 15(1): 111-114.

[Abstract](201)

Abstract:
A steam explosion pretreatment at various severities was applied to pure wood cellulose; the influences of steam pretreatment on the morphological structure, the hydrophilic property and viscosity-average molecular weight of cellulose were evaluated. The nitration of steam-exploded cellulose was carried out in the nitrating agent medium （HNO₃/organic solvent）. The performance indexes of nitrocellulose, prepared from original and steam exploded samples, were determined by using the polarized optical microscope. The results show that after pretreatment the reactivity of the three hydroxyl groups in anhydroglucose unit of cellulose is improved, and the nitrogen content and the uniformity of NC from steam exploded cellulose observably increas.

Quantum Entropy of a Single Cooper-Pair Box Interacting with Two Electromagnetic Fields

LI Jun-gang, ZOU Jian, SHAO Bin

2006, 15(1): 115-118.

[Abstract](177)

Abstract:
A Hamiltonian which represents the interaction between a single Cooper-pair box and two quantized electromagnetic fields is considered in order to find new ways for quantum information. The wave function in Schrdinger picture is obtained. The evolution of the entropy of the box as a function of the scaled time is ploted to measure the entanglement between the box and the fields. It is found that the entanglement is sensitive to the detuning between the Josephson energy and the fields frequency, increasing the detuning can decrease the entanglement.

On the Center of Generic Hecke Algebra

WEI Feng, BAO Gang

2006, 15(1): 119-122.

[Abstract](187)

Abstract:
The concept of norm and cellular algebra are introduced and then the cellular basis is used to replace the Kazhdan-Lusztig basis. So a new base for the center of generic Hecke algebra associated with finite Coxeter group is found. The new base is described by using the notion of cell datum of Graham and Lehrer and the notion of norm.

Better Hausdorff Dimension Estimations of Quadratic and Cubic Functions' Julia Sets

FANG Li-ping, ZHANG Chun-hong

2006, 15(1): 123-126.

[Abstract](74)

Abstract:
More accurate Hausdorff dimension estimations of Julia sets for two simple functions are given by the methods of composition mapping and invariant set of contraction mapping. For quadratic function f_c（z）= z2+ c（c∈AC^U）, the range of parameter c is expanded largely and a result on the Hausdorff dimension of its Julia set is gained. Similarly, a better result is obtained for cubic function f_c（z）=z3+c（c∈AC^U）.

2006 Vol. 15, No. 1