JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Stability of Controlled Hamilton Systems Excited by Gaussian White Noise

2008, 17(1): 1-4.

[Abstract](155)

Abstract:
A new method is introduced in this paper. This method can be used to study the stability of controlled holonomic Hamilton systems under disturbance of Gaussian white noise. At first, the motion equation of controlled holonomic Hamilton systems excited by Gaussian noise is formulated. A theory to stabilize the system is provided. Finally, one example is given to illustrate the application procedures.

Fuzzy Control of Semi-Active Suspension Based on 7-DOF Tracked Vehicle

ZHANG Ming-ze, ZHANG Yong-fa

2008, 17(1): 5-9.

[Abstract](246)

Abstract:
On the basis of analyzing the system constitution of tracked vehicle semi-active suspension, which consists of electrorheological (ER) damper and shape memory alloy (SMA) spring, a seven degree of freedom (7-DOF) dynamic model is established. The change of the elasticity of SMA spring and the characteristics of the ER shock absorber are studied. In addition, the study about fuzzy control logic is also carried out. Simulation of a C grade road under random excitations and definite disturbances is performed. Simulation result shows the fuzzy control strategy, which is used in the control of semi-active suspension system with ER damper and SMA springs, is effective, stable and reliable.

Computer Stochastic Processing of Fuze Overload

WANG Ya-bin, LIU Ming-jie, TAN Hui-min

2008, 17(1): 10-13.

[Abstract](196)

Abstract:
The method which can simulate the stochastic process of the overload during the course of a projectile launching is discussed in detail. The calculated theory bases on the principle of information diffusion in fuzzy theory. To approach the actual launching overload, the calculated theoretical overload is disposed by the white noise. The dynamic test is used to calculate the fuze response of the launching overload. Finally, the launching overload of a projectile fuze is simulated to verify the validity of the method. The result is found basically to be in accord with the actual launching overload of the fuze, and the calculation accuracy is perfect.

Water Hammer Model of Shock Absorber Throttle Slice

CHEN Yi-jie, GU Liang, LEI Sheng-guang, GUAN Ji-fu

2008, 17(1): 14-19.

[Abstract](163)

Abstract:
In allusion to easy invalidation of damping valve in vehicle shock absorber caused by the impact from the road surface, the importance of the study of damping valve water hammer pressure is presented. The physical model of damping valve with the circle throttle slice is established. The time for the throttle slice deformation is studied by using the finite software, and the laws that how the structure parameters affect the deformation time are obtained. Combining the theory of water hammer, the water hammer initial and boundary condition of the damping valve is deduced, and the water hammer model of throttle slice is established. The analysis of simulation results indicates that the water hammer pressure amplitude and the amount of water hammer oscillation period can be reduced and the dependability of the valve can be enhanced by modifying the structure parameters and aperture width between slice and valve body.

Investigation of Surface Roughness in High-Speed Milling of Aeronautical Aluminum Alloy

PAN Yong-zhi, AI Xing, ZHAO Jun, WAN Yi

2008, 17(1): 20-24.

[Abstract](115)

Abstract:
An approach is presented to optimize the surface roughness in high-speed finish milling of 7050-T7451 aeronautical aluminum alloy. In view of this, the multi-linear regression model for surface roughness has been developed in terms of slenderness ratio, cutting speed, radial depth-of-cut and feed per tooth by means of orthogonal experimental design. Variance analyses were applied to check the adequacy of the predictive model and the significances of the independent input parameters. Response contours of surface roughness were generated by using response surface methodology (RSM). From these contours, it was possible to select an optimum combination of cutting parameters that improves machining efficiency without increasing the surface roughness.

Application of Machine Vision to Vehicle Automatic Collision Warning Algorithm

WANG Jiang-feng, GAO Feng, XU Guo-yan, YAO Sheng-zhuo

2008, 17(1): 25-29.

[Abstract](185)

Abstract:
Using the new technologies such as information technology, communication technology and electronic control technology, vehicle collision warning system(CWS) can acquire road condition, adjacent vehicle march condition as well as its dynamics performance continuously, then it can forecast the oncoming potential collision and give a warning. Based on the analysis of driver's driving behavior, algorithm's warning norms are determined. Based on warning norms adopting machine vision method, the cooperation collision warning algorithm(CWA) model with multi-input and multi-output is established which is used in supporting vehicle CWS. The CWA is tested using the actual data and the result shows that this algorithm can identify and carry out warning for vehicle collision efficiently, which has important meaning for improving the vehicle travel safety.

Simulation Research on an Active Anti-Roll System for an Air Spring Passenger Car

ZHANG Jun, LI Xi-zhao

2008, 17(1): 30-34.

[Abstract](180)

Abstract:
To reduce the roll movement of an air spring passenger car, an active anti-roll system is developed, which is constructed with hydraulic and pneumatic units to change spring rate during cornering. For the comparing research between the passive and active system, a two-track vehicle model and a co-simulation model of air spring system are built. For the simulation research on the linear movement of the actuator, a mathematical model is considered as dynamical subsystem in the co-simulation model. To active control the roll angle of vehicle body, a sliding-mode controller with optimized control parameters for the test vehicle is introduced into the model. The characteristics of sliding-mode controller is discussed and the validation of active antiroll control is proved by comparison with other control methods. The results show that the roll angle of air spring vehicle is reduced obviously with the active anti-roll actuator in comparison with that of the passive system. Compared with other control methods, sliding-mode controller has an advantage of shortest switching times, which leads to a longer lifetime of actuator and valves.

Stability, Convergence of Harmonious Particle Swarm Optimizer and Its Application

PAN Feng, CHEN Jie, CAI Tao, GAN Ming-gang, WANG Guang-hui

2008, 17(1): 35-40.

[Abstract](196)

Abstract:
Particle swarm optimizer (PSO), a new evolutionary computation algorithm, exhibits good performance for optimization problems, although PSO can not guarantee convergence of a global minimum, even a local minimum. However, there are some adjustable parameters and restrictive conditions which can affect performance of the algorithm. The sufficient conditions for asymptotic stability of an acceleration factor and inertia weight are deduced in this paper. The value of the inertia weight w is enhanced to (-1,1). Furthermore a new adaptive PSO algorithm-harmonious PSO (HPSO) is proposed and proved that HPSO is a global search algorithm. Finally it is focused on a design task of a servo system controller. Considering the existence of model uncertainty and noise from sensors, HPSO are applied to optimize the parameters of fuzzy PID controller. The experiment results demonstrate the efficiency of the methods.

Method of Dynamic Knowledge Representation and Learning Based on Fuzzy Petri Nets

WEI Sheng-jun, HU Chang-zhen, SUN Ming-qian

2008, 17(1): 41-45.

[Abstract](168)

Abstract:
A method of knowledge representation and learning based on fuzzy Petri nets was designed. In this way the parameters of weights, threshold value and certainty factor in knowledge model can be adjusted dynamically. The advantages of knowledge representation based on production rules and neural networks were integrated into this method. Just as production knowledge representation, this method has clear structure and specific parameters meaning. In addition, it has learning and parallel reasoning ability as neural networks knowledge representation does. The result of simulation shows that the learning algorithm can converge, and the parameters of weights, threshold value and certainty factor can reach the ideal level after training.

Robust Wavelet-Based Facial Image Watermarking Against Geometric Attacks Using Coordinate System Recovery

ZHAO Pei-dong, XIE Jian-ying

2008, 17(1): 46-50.

[Abstract](220)

Abstract:
A coordinate system of the original image is established using a facial feature point localization technique. After the original image transformed into a new image with the standard coordinate system, a redundant watermark is adaptively embedded in the discrete wavelet transform(DWT) domain based on the statistical characteristics of the wavelet coefficient block. The coordinate system of watermarked image is reestablished as a calibration system. Regardless of the host image rotated, scaled, or translated(RST), all the geometric attacks are eliminated while the watermarked image is transformed into the standard coordinate system. The proposed watermark detection is a blind detection. Experimental results demonstrate the proposed scheme is robust against common and geometric image processing attacks, particularly its robustness against joint geometric attacks.

Adaptive Modeling for Security Infrastructure Fault Response

CUI Zhong-jie, YAO Shu-ping, HU Chang-zhen

2008, 17(1): 51-57.

[Abstract](218)

Abstract:
Based on the analysis of inherent limitations in existing security response decision-making systems, a dynamic adaptive model of fault response is presented. Several security fault levels were founded, which comprise the basic level, equipment level and mechanism level. Fault damage cost is calculated using the analytic hierarchy process. Meanwhile, the model evaluates the impact of different responses upon fault repair and normal operation. Response operation cost and response negative cost are introduced through quantitative calculation. This model adopts a comprehensive response decision of security fault in three principles-the maximum and minimum principle, timeliness principle, acquiescence principle, which assure optimal response countermeasure is selected for different situations. Experimental results show that the proposed model has good self-adaptation ability, timeliness and cost-sensitiveness.

Design of Adaptive Fuzzy PID Altitude Control System for Unmanned Aerial Vehicle

SHI Gang, YANG Shu-xing, JING Ya-xing, XU Yong

2008, 17(1): 58-61.

[Abstract](170)

Abstract:
Based on Matlab/Simulink and Fuzzy Logic toolboxes, the altitude control system is designed and simulated. The validity of conventional PID control method and adaptive fuzzy PID control method is compared. It can be drawn out that the adaptive fuzzy PID control method is superior to the conventional PID in rising time and overshoot etc. The effectiveness of a fuzzy PID controller shows potential application in the future, especially in the presence of model uncertainty or changing dynamics and time-varying parameters.

Doppler Signal Simulation and Analytic System for Radio Fuze

PAN Xi, CUI Zhan-zhong

2008, 17(1): 62-66.

[Abstract](299)

Abstract:
A system for simulating and analyzing the Doppler signal of air-target fuse is established by constructing two parts: Doppler signal testing with simulation and Doppler signal analysis. The first part establishes the near-field target characteristic model where the Doppler spectrum in different encounter condition is obtained. The second part mainly deals with a general purpose hardware platform to obtain and process the Doppler signal as well as a software to estimate the Doppler spectrum. The model and the result of Doppler spectrum analysis were verified by experiments.

Novel Grouped Probability Data Association Algorithm for MIMO Detection

CHE Wen, ZHAO Hui, WANG Wen-bo

2008, 17(1): 67-70.

[Abstract](92)

Abstract:
To bridge the performance gap between original probability data association (PDA) algorithm and the optimum maximum a posterior (MAP) algorithm for multi-input multi-output (MIMO) detection, a grouped PDA (GP-PDA) detection algorithm is proposed. The proposed GP-PDA method divides all the transmit antennas into groups, and then updates the symbol probabilities group by group using PDA computations. In each group, joint a posterior probability (APP) is computed to obtain the APP of a single symbol in this group, like the MAP algorithm. Such new algorithm combines the characters of MAP and PDA. MAP and original PDA algorithm can be regarded as a special case of the proposed GP-PDA. Simulations show that the proposed GP-PDA provides a performance and complexity tradeoff between original PDA and MAP algorithm.

An Enhanced LDPC Coded Partial Incremental Redundancy HARQ Scheme

JIA Min-li, HE Zun-wen, KUANG Jing-ming

2008, 17(1): 71-75.

[Abstract](185)

Abstract:
An enhanced scheme is proposed for high code rate low density parity check (LDPC) coded partial incremental redundancy (PIR) hybrid automatic repeat request (HARQ). It employs the unequal error protection (UEP) technique for incremental redundancy bits and uses the constellation rearrangement (CoRe) technique for information bits in retransmissions so as to reduce the reliability variances of all encoded bits after soft combining. Simulation results show that the proposed scheme applies to both regular LDPC and irregular LDPC cases and can efficiently improve frame error rate (FER) performance and throughput performance.

FPGA Implementation of Wave Pipelining CORDIC Algorithms

CUI Wei

2008, 17(1): 76-80.

[Abstract](192)

Abstract:
The implementation of the coordinate rotational digital computer (CORDIC) algorithm with wave pipelining technique on field programmable gate array (FPGA) is described. All data in FPGA-based wave pipelining pass through a number of logic gates, in the same way that all data pass through the same number of registers in a conventional pipeline. Moreover, all paths are routed using identical routing resources. The manual placement, timing driven routing and timing analyzing techniques are applied to optimize the layout for achieving good path balance. Experimental results show that a 256-LUT logic depth circuit mapped on XC4VLX15-12 runs as high as 330MHz, which is a little lower than the speed of 336MHz based on the conventional 16-stage pipelining in the same chip. The latency of the wave pipelining circuit is 30.3ns, which is 36.4% shorter than the latency of 16-stage conventional pipelining circuit.

High Speed Versatile Reed-Solomon Decoder for Correcting Errors and Erasures

WANG Hua, FAN Guang-rong, WANG Ping-qin, KUANG Jing-ming

2008, 17(1): 81-86.

[Abstract](93)

Abstract:
A new Chien search method for shortened Reed-Solomon (RS) code is proposed, based on this, a versatile RS decoder for correcting both errors and erasures is designed. Compared with the traditional RS decoder, the weighted coefficient of the Chien search method is calculated sequentially through the three pipelined stages of the decoder. And therefore, the computation of the errata locator polynomial and errata evaluator polynomial needs to be modified. The versatile RS decoder with minimum distance 21 has been synthesized in the Xilinx Virtex-Ⅱ series field programmable gate array (FPGA) xc2v1000-5 and is used by concatenated coding system for satellite communication. Results show that the maximum data processing rate can be up to 1.3Gbit/s.

Facile Synthesis of 2PbCO3·Pb(OH)2 Microcrystals and Its Catalytic Behavior for Transesterification of Dimethyl Carbonate with Phenol

WANG Qiang, LUO Sheng-jun, CAO Min-hua, HU Chang-wen

2008, 17(1): 87-91.

[Abstract](254)

Abstract:
Polyhedron lead hydroxide carbonate (2PbCO3·Pb(OH)2) microcrystals have been prepared in solution phase via a facile method in the presence of surfactant cetyltrimethylammonium bromide (CTAB). All the samples were characterized by powder X-ray diffraction pattern (XRD), field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED). The possible growth mechanism was discussed. 2PbCO3·Pb(OH)2 microcrystals were found to be a novel and efficient catalyst for the synthesis of diphenyl carbonate (DPC) by transesterification of dimethyl carbonate (DMC) with phenol. Compared with some other catalysts, such as AlCl3, ZnCl2, and Mg5(CO3)4(OH)2, 2PbCO3·Pb(OH)2 microcrystals are stable and show relatively high activity at low catalyst amount. When the reaction was carried out at 180℃, with a molar ratio of phenol to DMC of 2:1, a reaction time 14h, and a catalyst amount 0.2% (molar ratio to phenol), the selectivity of DPC and methyl phenyl carbonate (MPC) was 14.7% and 78.8%, respectively.

Approach to the Synthesis of Dimeric Salen-Co(Ⅲ):A Recoverable Catalyst for Rac-Eprichlorohydrin HKR

ZHOU Zhi-ming, LI Lian-you, WEN Hong-liang, YU Cong-xuan

2008, 17(1): 92-95.

[Abstract](88)

Abstract:
The synthesis of chiral dimeric Salen ligand 5,5′-methylene-di-[(R,R)-{N-(3-tert-butylsalicylidine)-N′-(3′,5′-di-tert-butylsalicylidene)}-1,2-cyclohexanediamine] which using 2-tert-butylphenol as starting material is reported. This compound reacts with cobalt (Ⅱ) acetate and then oxidized by air to give dimeric Salen catalyst 5 in this paper, which catalyzes the hydrolytic kinetic resolution (HKR) of racemic epichlorohydrin to afford biologically important chiral epoxides and diols. Ee values of diol up to 97% were obtained, and the catalyst was recovered with no apparent loss.

Studies on the Fingerprint of Yubaizhi by High-Performance Liquid Chromato Graphy

YU Yu-hong, SUN Yan-ke, LI Xue-chun, DAI Rong-ji, MENG Wei-wei, DENG Yu-lin

2008, 17(1): 96-99.

[Abstract](101)

Abstract:
The investigation of fingerprint of Yubaizhi was performed by high-performance liquid chromatography (HPLC). Chromatographic conditions were: the mobile phase was the mixture of acetonitrile-water (43:57, v/v); the flow rate was 1mL/min; the column temperature was 40℃; the detection wavelength was 254nm. The stability, precision and reproducibility were performed according to "Specification of Fingerprint of Injection of Chinese Traditional Medicine (temporarily)" regulated by State Food and Drug Administration(SFDA). The HPLC fingerprints of Yubaizhi from various locations were well constant.

Novel Method of Hyperbranched Polymer Modified Nano-SiO2-Grafting Hyperbranched Poly (amide-ester) from Nano-SiO2 by One-Step Polycondensation

ZHAO Hui, LI Jie, SUN Rui-min, LUO Yun-jun

2008, 17(1): 100-103.

[Abstract](146)

Abstract:
A new method of surface chemical modification of nano-SiO2 is proposed in this paper. In the presence of catalyst, the active hydroxyl groups on the surface of nano-SiO2 reacted with AB2-type monomer (N, N-dihydroxyethyl-3-amino methyl propionate) by one-step polycondensation. And the product's Fourer transform infrared (FTIR) graphs and transmission electron microscopy(TEM) images proved that hyperbranched poly (amine-ester) was grafted on nano-SiO2 surface successfully. Results show that the modified nano-SiO2 exhibits excellent dispersion and stability in some solvents such as alcohol and chloroform.

Effect of Hyperbranched Poly(amine-ester) Grafted Nano-SiO2 on Reinforcement and Toughness of PVC

LI Jie, ZHAO Hui, SUN Rui-min, LUO Yun-jun

2008, 17(1): 104-108.

[Abstract](92)

Abstract:
Nano-SiO2 was modified using silane coupling agent (KH-550) and hyperbranched poly(amine-ester) respectively, and Poly(vinyl chloride) (PVC)/modified nano-SiO2 composites were made by melt-blending. The composites' structures andmechanical properties were characterized by transmission electron microscopy(TEM), sanning electronic microscopy(SEM) and electronic universal testing machine. The results show that nano-SiO2 grafted by hyperbranched poly (amine-ester) increases obviously in dispersion in PVC matrix, and mechanical properties of PVC are effectively improved. Moreover, it was found that mechanical properties of PVC/nano-SiO2 composites reach the best when weight percent of nano-SiO2 in PVC matrix is 1%. Compared with crude PVC, the tensile strength of hyperbranched poly (amine-ester) grafted nano-SiO2/PVC composite increases by 24.68% and its break elongation, flexural strength and impact strength increase by 15.73%, 4.07% and 1841.84%, respectively. Moreover, the processing of the composites is improved.

Testing of High-Strength Zr-Based Bulk Metallic Glass with the Split Hopkinson Pressure Bar

XUE Yun-fei, CAI Hong-nian, WANG Lu, ZHANG Hai-feng, CHENG Huan-wu

2008, 17(1): 109-114.

[Abstract](110)

Abstract:
The split Hopkinson pressure bar (SHPB) was used to determine the dynamic compressive strength of the high-strength Zr38Ti17Cu10.5Co12Be22.5 bulk metallic glass at strain rate on the order of 102s-1. It is shown that at high strain rates beyond about 1000s-1, uniform deformation within the metallic glass specimen could not be achieved and dispersion in the transmitted pulse can lead to discrepancies in measuring the dynamic failure strength of the present Zr-based bulk metallic glass. Based on these reasons, a copper insert was placed between the strike bar and the input bar to obtain reliable and consistent experimental data for testing of the Zr38Ti17Cu10.5Co12Be22.5 bulk metallic glass using the SHPB. Negative strain rate sensitivity was found in the present Zr-based bulk metallic glass.

Three-Dimensional Simulation of Plasma Jet and Particle Groups in Plasma Spraying

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

2008, 17(1): 115-121.

[Abstract](105)

Abstract:
The temperature field, velocity field, as well as species distribution in three-dimensional space are successfully calculated by establishing three-dimensional geometry model and solving plasma jet-substrate interaction equations, optimized particle trajecory models, as well as particle-particle heat transfer equations in three-dimensionalal space. Under typical working conditions, the flying trajectories and distribution of ZrO2 ceramic particles and Ni metal particles are also simulated. Results show that, the plasma jet becomes wider near the substrate, and the stochastic trajectory model is preferable to simulate the turbulent diffusion effect of particles. In addition, Ni metal particles penetrate relatively more deeply than ZrO2 ceramic particles due to larger density.

Synthesis of Caged Bicyclic Phosphate Derivatives

FANG Xiao-min, OU Yu-xiang, LUO Rui-bin, WANG Yong, LIAN Dan-jun, LI Xin

2008, 17(1): 122-126.

[Abstract](168)

Abstract:
Seven caged bicyclic phosphate compounds were synthesized by using 1-oxo-4-hydroxymethy1-2,6,7-trioxa-1-pho-sphabicyclo[2.2.2] octane (PEPA) as starting material. Within them were three PEPA derivatives containing single caged bicyclic phosphate structure(1a,2a,3a), another three PEPA deviratives containing two caged bicyclic phosphate structures(1b,2b,3b) and one devirative(1c) containing three caged bicyclic phosphate structures. Structures of the products were characterized by FTIR, 1H NMR, elemental analysis and TG analysis. The reaction conditions were also discussed. Thermal analysis showed they had high thermal stability and excellent char-forming ability. Besides, these compounds had pentaerythritol bone and flame retardant elements of phosphorus, bromine or nitrogen simultaneously in their molecules, endowed them with good fire retardancy, and made them can be used as intumescent flame retardant.

2008 Vol. 17, No. 1