JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Elimination of the Background Noise of the Decoded Image in Fresnel Zone Plate Scanning Holography

SUN Ping, XIE Jing-hui

2005, 14(3): 225-228.

[Abstract](199)

Abstract:
A method of digitally high pass filtering in frequency domain is proposed to eliminate the background noise of the decoded image in Fresnel zone plate scanning holography. The high pass filter is designed as a circular stop, which should be suitable to suppressing the background noise significantly and remain much low frequency information of the object. The principle of high pass filtering is that the Fourier transform of the decoded image is multiplied with the high pass filter. Thus the frequency spectrum of the decoded image without the background noise is achieved. By inverse Fourier transform of the spectrum of the decoded image after multiplying operation, the decoded image without the background noise is obtained. Both of the computer simulations and the experimental results show that the contrast and the signal-to-noise ratio of the decoded image are significantly improved with digital filtering.

Linear Quadratic Integral Control for the Active Suspension of Vehicle

GUAN Ji-fu, GU Liang, HOU Chao-zhen, WU Yun-peng

2005, 14(3): 229-233.

[Abstract](180)

Abstract:
The quarter model of an active suspension is established in the form of controllable autoregressive moving average (CARMA) model. An accelerometer can be mounted on the wheel hub for measuring road disturbance; this signal is used to identify the CARMA model parameters by recursive forgetting factors least square method. The linear quadratic integral (LQI) control method for the active suspension is presented. The LQI control algorithm is fit for vehicle suspension control, for the control performance index can comprise multi controlled variables. The simulation results show that the vertical acceleration and suspension travel both are decreased with the LQI control in the low frequency band, and the suspension travel is increased with the LQI control in the middle or high frequency band. The suspension travel is very small in the middle or high frequency band, the suspension bottoming stop will not happen, so the vehicle ride quality can be improved apparently by the LQI control.

Comparison of ISFs and LSFs in Speech/Music Discrimination System

HONG Ying, ZHAO Sheng-hui, KUANG Jing-ming

2005, 14(3): 234-237.

[Abstract](151)

Abstract:
The immittance spectral frequencies (ISFs) is proposed as a new set of classification features and compared with the linear spectral frequencies (LSFs) applied in a frame-level wideband speech/music discrimination system. These two sets of features can be shared by the classifier and coding module to reduce the total computational complexity, making our classification system suitable for multi-mode audio coding applications. A performance assessment and comparison of the features are made. The experiment results show that the ISFs and LSFs have similar good performance when using full covariance matrices in classification models and the ISFs perform slightly better when using diagonal matrices. Their statistical differences for speech and music signals are also revealed.

Comparison of Three Schemes for Intermediate Data Rate Frame Synchronization

WANG Zhan-he, XING Mao-teng, WANG Hua, KUANG Jing-ming

2005, 14(3): 238-243.

[Abstract](212)

Abstract:
Based on the frame structure of intermediate data rate (IDR) modem for satellite communication, a new method for searching frame synchronization called group frame synchronization is proposed. At the same time, a candidate scheme in the classical frame synchronization and two candidate schemes in the group frame synchronization are presented, and the circuits for each scheme are designed in order to abstract the frame alignment signals from received data. Their implementation complexity and performances are also computed and given. Based on the analysis and performance comparison, a reasonable scheme is chosen and then verified through software simulation and hardware impletentation.

Ants-Based On-Demand Routing Algorithm for Mobile Ad Hoc Networks

WU Dong-ya, HOU Chao-zhen, HOU Zi-feng, WANG Zai-yue

2005, 14(3): 244-249.

[Abstract](75)

Abstract:
An ants-based on-demand routing algorithm (AORA) specialized for mobile ad hoc networks is proposed. AORA measures the network's traffic information including delivery time,route energy etc. by the continuous delivery of data packets,then calculates the compositive parameter for each route which can be seen as the stigmity and uses it to choose the comparatively optimal route in real time.To adjust the weight of each traffic information,the algorithm can meet the different demand of the network's user. Multipath source self repair routing (MSSRR) algorithm and dynamic source routing (DSR) can be seen as the special samples of AORA. The routing overhead is not increased in this algorithm. By using simulation, it can be seen that the performance of AORA is better than that of DSR in all scenarios obviously,especially the delivery fraction is increased by more than 100%.

Correcting Non-Word Errors Using a Combined Method

CAO Yuan-da, ZHOU Jie-long

2005, 14(3): 250-254.

[Abstract](189)

Abstract:
The weighted edit distance and metaphone+ algorithm are combined to correct the non-word errors. The speed is also optimized based on the observation that people rarely make mistakes in the initial letter of a word. A spelling checker is designed for an automatic detection and correction system for student essays. To evaluate the algorithm it is compared to some famous systems (MS Word2000, Aspell, winEdt). The results show that our approach is superior to the alternative approaches.

Method of Preventing Buffer Overflow Attacks by Intercepting DLL Functions

TAN Yu-an, CAO Yuan-da

2005, 14(3): 255-259.

[Abstract](94) [PDF 175KB](3)

Abstract:
The way of intercepting Windows DLL functions against buffer overflow attacks is evaluated. It's produced at the expense of hooking vulnerable DLL functions by addition of check code. If the return address in the stack belongs to a heap or stack page, the call is from illicit code and the program is terminated. The signature of malicious code is recorded, so it is possible for the next attack to be filtered out. The return-into-libc attacks are detected by comparing the entry address of DLL functions with the overwritten return address in the stack. The presented method interrupts the execution of malicious code and prevents the system from being hijacked when these intercepted DLL functions are invoked in the context of buffer overflow.

Classification Model with High Deviation for Intrusion Detection on System Call Traces

PENG Xin-guang, LIU Yu-shu, WU Yu-shu, YANG Yong

2005, 14(3): 260-263.

[Abstract](176)

Abstract:
A new classification model for host intrusion detection based on the unidentified short sequences and RIPPER algorithm is proposed. The concepts of different short sequences on the system call traces are strictly defined on the basis of in-depth analysis of completeness and correctness of pattern databases. Labels of short sequences are predicted by learned RIPPER rule set and the nature of the unidentified short sequences is confirmed by statistical method. Experiment results indicate that the classification model increases clearly the deviation between the attack and the normal traces and improves detection capability against known and unknown attacks.

Mobile Agent Based Framework for Integrating Digital Library System

ZHANG Fu-zhi, LIU Ming-ye, KONG Ling-fu

2005, 14(3): 264-268.

[Abstract](83)

Abstract:
Few of the current approaches to achieve the integration of digital library system have considered the influence of network factors on quality of service for the integration system of digital libraries. For this reason, a mobile agent based framework for integrating digital library system is proposed. Based on this framework, a prototype system is implemented and the key technique for it are described. Compared with the current approaches, using mobile agent technique to achieve the integration of digital library system can not only avoid transmitting a lot of data on the network, lower the dependence on network bandwidth for the system, but also improve the quality of service for the integration system of digital libraries in intermitted or unreliable network connection settings.

Observability of Inertial Navigation System

ZHANG Ting, WANG Bo, SHI Yong-sheng

2005, 14(3): 269-272.

[Abstract](143)

Abstract:
To improve the observability of strapdown inertial navigation system and the effectiveness of Kalman filter in the navigation system, the method of estimating the observability is analyzed based on eigenvalues and eigenvectors which are proved to be availabe, on this basis two-position alignment technigue is applied. The simulation shows that two-position alignment really makes the system's observability change from being incomplete to being complete, and the test method based on eigenvalues and eigenvectors is available to determine the observability of every state vector.

Present State of Explosion Seismic Wave Research and Primary Investigation on Its Characteristics

SUN Qing-yun, ZHANG Qi

2005, 14(3): 273-278.

[Abstract](201)

Abstract:
The present state and the significance of research on explosion seismic waves are discussed, and meanwhile the main contents and the basic problems to be solved in the study of explosion seismic waves are analyzed. The spectra characteristics of explosion seismic waves, functions of the isolated-seismic grooves and influences of the detonating methods on explosion seismic waves are investigated by experiments. The experimental method is introduced. Some experimental results are presented which are concerned with the influences of topographical conditions, explosive charges, ignition patterns, isolated-seismic grooves and the other related factors on the characteristics of seismic waves.

Characteristic Research on Evaporated Explosive Film

WANG Xiao-li, JIAO Qing-jie, CHEN Ming-hua, LI Guo-xin

2005, 14(3): 279-283.

[Abstract](87) [PDF 184KB](3)

Abstract:
The evaporation source of evaporated explosive was designed and improved based on the inherent specialties of explosive. The compatibility of explosives and addition agent with evaporation vessels was analyzed. The influence of substrate temperature on explosive was analyzed, the control method of substrate temperature was suggested. The influences of evaporation rate on formation of explosive film and mixed explosive film were confirmed. Optimum evaporation rate for evaporation explosive and the better method for evaporating mixed explosive were presented. The necessary characteristics of the evaporated explosive film were obtained by the research of the differences between the evaporated explosive and other materials.

Theoretical Analysis of Noise of Piston Knocking Cylinder Wall in Automotive Engines

XIAO Yun-kui, LI Shi-yi, CAO Ya-juan, YANG Wan-cheng, FENG Han-sheng

2005, 14(3): 284-288.

[Abstract](166)

Abstract:
Based on the loading conditions of engine, applying difference method to solve the hydrodynamic lubrication equation of piston skirt movement, the force acting on piston skirt and the moment on wrist pin were obtained. A computer program for simulating the piston second order motion was conducted to calculate the lateral motion of the upper part and the bottom part of piston skirts of the engine of automotive model CA1091. From the simulated result, the maximal impacting phase and the maximal impacting region of the piston were obtained. The result can be used for designing engine, diagnosing the noise of piston knocking cylinder wall and explaining many practical fault phenomena in theory.

Study of Piezoresistive Micro Electro-Mechanical Accelerometer Design Platform

ZHANG Jing-hua, SHI Geng-chen

2005, 14(3): 289-292.

[Abstract](83)

Abstract:
According to the inland micro electro-mechanical system (MEMS) process technique level, a design platform of piezoresistive micro electro-mechanical accelerometer is given. This platform is much more adaptable to the inland designer compared with the current MEMS CAD software. The design flow is presented in detail, and the key techique in the platform is analyzed amply. The structure design methodology is exemplified in the design of a piezoresistive accelerometer, and the accelerometer is the optimized structure for the given performance requirements. The accelerometer is now being manufactured.

Wind Tunnel Experimental Investigation on the Aerodynamic Characteristics of the Multifin Rockets and Missiles

HAO Lu, WU Jia-sheng

2005, 14(3): 293-296.

[Abstract](216)

Abstract:
The transonic-supersonic wind tunnel experiment on the aerodynamics of the rockets and missiles that have four, six, eight flat or wrap-around fins is introduced. The experimental results show, while M_∞<2.0, with the increase of the fins' number, the derivative of lift coefficient is increasing, the pressure center is shifting backwards, and the longitudinal static stability is augmenting. On the contrary, while the Mach number exceeds a certain supersonic value, the aerodynamic effectiveness of the eight-fin missiles would be lower than that of the six-fin missiles. For the low speed short-range missiles, by adopting six, eight or ten flat fins configuration, the lift effectiveness can be greatly increased, the pressure center can be shifted backwards, the static and dynamic stability can be obviously enhanced. For the high speed long-range large rockets and missiles launched from multi-tube launcher, the configuration adopting more than six fins can not be useful for increasing the stability but would make the rolling rate instable during the flight.

Extended Range Guided Munition Parameter Optimization Based on Genetic Algorithms

WANG Jin-zhu, LIU Zao-zhen, LIU Min

2005, 14(3): 297-301.

[Abstract](231)

Abstract:
Many factors influencing range of extended range guided munition (ERGM) are analyzed. The definition domain of the most important three parameters are ascertained by preparatory mathematical simulation, the optimized mathematical model of ERGM maximum range with boundary conditions is created, and parameter optimization based on genetic algorithm (GA) is adopted. In the GA design, three-point crossover is used and the best chromosome is kept so that the convergence speed becomes rapid. Simulation result shows that GA is feasible, the result is good and it can be easy to attain global optimization solution, especially when the objective function is not the convex one for independent variables and it is a multi-parameter problem.

Dynamic Analysis of Flexible Multibody Systems for High-Rise Building Window Cleaning Gondola

CHENG Ying, SUN Shan-chao, LONG Kai

2005, 14(3): 302-305.

[Abstract](186)

Abstract:
A virtual prototype of high-rise building window cleaning gondola based on multibody system dynamics software MSC.ADAMS is presented. The rigid bodies are modeled by CAD software and flexible bodies are modeled by discrete beam method. The whole machine's natural characteristics are analyzed and changed to frequency field. According to the results, the dangerous frequencies are avoided and the design can be optimized and the performance can be improved.

Energy Transferring Dynamic Equalization for Battery Packs

LI Hong-lin, ZHANG Cheng-ning, PENG Lian-yun, LI Jun-qiu, SUN Feng-chun

2005, 14(3): 306-309.

[Abstract](170)

Abstract:
The equivalent circuit model of battery and the analytic model of series battery uniformities are setup. The analysis shows that it is the key to maintain small voltage difference between cells in order to improve uniformities. Therefore a new technique combining low voltage difference, big current charging and bi-directional charge equalizer system is put forward and designed. The test shows that the energy transferring dynamic equalization system betters the series battery uniformities and protection during charging and discharging, improves the battery performance and extends the use life of series battery.

Steering Control of Wheeled Armored Vehicle with Brushless DC Motor

CHEN Hui-yan, WANG Jing-qi, ZHENG Pei

2005, 14(3): 310-313.

[Abstract](166)

Abstract:
Considering the steering characters of one type of wheeled armored vehicle, a brushless direct current (DC) motor is adapted as the actuator for steering control. After investigating the known algorithms, one kind of algorithm, which combines the fuzzy logic control with the self-adapting PID control and the startup and pre-brake control, is put forward. Then a test-bed is constructed, and an experiment is conducted. The result of experiment confirms the validity of this algorithm in steering control of wheeled armored vehicle with brushless DC motor.

Study on Ultracapacitors Parameter Design and Control Strategy of Electric Bus

LI Jun-qiu, SUN Feng-chun, ZHANG Cheng-ning, HE Hong-wen, SUN Li-qing

2005, 14(3): 314-318.

[Abstract](133)

Abstract:
Based on the analysis of ultracapacitors efficiency and vehicle driving character, three conditions restricting the ultracapacitors charge/discharge time are derived. The study focuses on ultracapacitors specific design rules decided by charge/discharge time and how to integrate with battery packs and converter through ultracapacitors' voltage and current double regulators. Through BFC6100-EV electric bus test, it is shown that the proposed method and control strategy are feasible and the system can effectively improve the bus dynamic performance and ability to receive braking energy effectively.

Syntheses of Ferrocenyl Schiff Bases Using Molecular Sieves and AlCl₃as Catalysts

ZHANG Hui-qing, ZHOU Zhi-ming, YU Cong-xuan

2005, 14(3): 319-322.

[Abstract](175)

Abstract:
In order to study the donor ability of ferrocenylimines as directing ortho metalation group（DMG） to lithium alkylide to prepare planar chiral ferrocene, a series of ferrocenyl schiff bases were synthesized by new methods using molecular sieves（0.4?nm） and AlCl₃as catalysts. The reaction periods were reduced using these two catalysts in contrast with Al₂O₃, which was a traditional method used in the literature. In addition, as an important feature of these schiff bases, we found that they were unstable as oils in air or when filtrated through silica gel, but were stable as solids. The structures of the new compounds were confirmed by IR, 1H NMR and HRMS.

Anti-Hyperglycemic Activity of Shan Tang Ping an Ethanol Extract from Yew Tree in Diabetic Rats

DENG Yu-lin, SHENG Ling-hui, DAI Rong-ji, XU Xiao-yu

2005, 14(3): 323-327.

[Abstract](203)

Abstract:
The extracts of yew tree have showed unique anti-tumor and anti-leakematic activities. Taxol extracted from it is effective against a variety of cancers, such as ovarian cancer and breast cancer. However the hypoglycemic efficacy of the extract has not been reported yet, so the effects of oral administration of yew tree extracts on streptozotocin-induced diabetic rats were examined. Administration of shan tang ping(STP), a fraction from the column separation of extract (450?mg/kg body weight), for 14 days reduced the serum glucose concentrations of fasted diabetic rats by 52.4%. In addition, it also decreased the concentrations of triglyceride (TG), total cholesterol (TC), and low density lipoprotein cholesterol (LDL-C). An oral glucose tolerance test (OGTT) was performed, a significant improvement in glucose tolerance was observed in rats treated with STP. These results suggest that STP has hypoglycemic properties and hypolipidemic action on streptozotocin-induced diabetic rats.

C^*-Structure of Quantum Double for Finite Hopf C^*-Algebra

JIANG Li-ning, WANG Li-guang

2005, 14(3): 328-331.

[Abstract](179) [PDF 145KB](2)

Abstract:
Let H be a finite Hopf C*-algebra and H′ be its dual Hopf algebra. Drinfeld's quantum double D（H） of H is a Hopf *-algebra. There is a faithful positive linear functional θ on D（H）. Through the associated Gelfand-Naimark-Segal （GNS） representation, D（H） has a faithful *-representation so that it becomes a Hopf C^*-algebra. The canonical embedding map of H into D（H） is isometric.

Optimal Orientations of the Generalized Cycles

SUN Liang, BU Qing

2005, 14(3): 332-335.

[Abstract](90)

Abstract:
Optimal orientations of the generalized cycles are studied. For a graph G, let D（G） be the family of the strong orientations of G,d（G）=min{d（D）|D∈D（G）} and ρ（G）=d（G）-d（G）, where d（G） and d（D） are the diameters of G and D respectively. Evaluate the value of ρ（G） is evaluated by reduction to absurdity when G is a generalized cycle C_n[K_m], and a complete result is obtained.

Translation Surfaces with Zero Mean Curvature in （2+p）-Dimensional Pseudo-Euclidean Space E₂^2+por E_p^2+p

SUN Hua-fei, WANG Xiao-hua, TANG Li

2005, 14(3): 336-339.

[Abstract](215)

Abstract:
Let E 2+p_p（resp.E 2+p₂） be a （2+p）-dimensional pseudo-Euclidean space with the index p （resp.2）. The maximal spacelike or minimal timelike translation surfaces M2 in E 2+p_por E 2+p₂are considered and a complete classification is given.

An Inexact Halley's Method

YAN Gui-feng, TIAN Xiang

2005, 14(3): 340-343.

[Abstract](191)

Abstract:
An inexact Halley's method—Halley-PCG(preconditioned conjugate gradient) method is proposed for solving the systems of linear equations for improved Halley method either by Cholesky factorization exactly or by preconditioned conjugate gradient method approximately. The convergence result is given and the efficiency of the method compared to the improved Halley's method is shown.

Adaptive Fuzzy Control for CVT Vehicle

FANG Zhi-qiang, WANG Hong-yan, WANG Liang-xi

2005, 14(3): 344-348.

[Abstract](211)

Abstract:
On the simple continuously variable transmission (CVT) driveline model, the design of adaptive fuzzy control system for CVT vehicle is presented. The adaptive fuzzy control system consists of a scaling factor self-tuning fuzzy-PI throttle controller, and a hybrid fuzzy-PID CVT ratio and brake controller. The presented adaptive fuzzy control strategy is vehicle model independent, which depends only on the instantaneous vehicle states, but does not depend on vehicle parameters. So it has good robustness against uncertain vehicle parameters and exogenous load disturbance. Simulation results show that the proposed adaptive fuzzy strategy has good adaptability and practicality value.

Method of Measuring Fixture Automatic Design and Assembly for Auto-Body Part

HU Cai-qi, LIN Zhong-qin, LAI Xin-min

2005, 14(3): 349-352.

[Abstract](77)

Abstract:
A method of 3-D measuring fixture automatic assembly for auto-body part is presented. Locating constraint mapping technique and assembly rule-based reasoning are applied. Calculating algorithm of the position and pose for the part model, fixture configuration and fixture elements in virtual auto-body assembly space are given. Transforming fixture element from itself coordinate system space to assembly space with homogeneous transformation matrix is realized. Based on the second development technique of unigraphics(UG), the automated assembly is implemented with application program interface (API) function. Lastly the automated assembly of measuring fixture for rear longeron as a case is implemented.

2005 Vol. 14, No. 3