JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Drive Signal Frequency-Lock Method Based on 90° Phase Shift for Quartz Angular-Rate Sensor

LIAO Xing-cai, SUN Yu-nan, TANG Qiong, CUI Fang

2005, 14(1): 1-3.

[Abstract](184)

Abstract:
A drive signal frequency-lock method for quartz angular-rate sensor is presented. The calculation result obtained by the equivalent volume force analytic method indicated that when taking the inherent frequency of the drive tines as the drive signal frequency the phase of the reference vibration is 90° behind that of the drive signal, and the square of amplitude is less than that of the maximal amplitude by 1/（4Q²_d） merely. The curves derived from the finite element analytic method proved that near the inherent frequency the phase shift of the feedback voltage is identical to that of the reference vibration, and the amplitude is proportional to that of the reference vibration, and the phase shift is linear approximatively with the frequency shift. The frequency shift could be calculated according to the phase shift obtained by quadrature correlation detection, so the drive signal frequency could be locked at the inherent frequency of the drive tines by means of iteration.

FPGA-Based Efficient Programmable Polyphase FIR Filter

CHEN He, XIONG Cheng-huan, ZHONG Shun-an, WANG Hua

2005, 14(1): 4-8.

[Abstract](190)

Abstract:
The modelling, design and implementation of a high-speed programmable polyphase finite impulse response(FIR) filter with field programmable gate array(FPGA) technology are described. This FIR filter can run automatically according to the programmable configuration word including symmetry/asymmetry, odd/even taps, from 32 taps up to 256 taps. The filter with 12 bit signal and 12 bit coefficient word-length has been realized on a Xilinx VirtexⅡ-v1500 device and operates at the maximum sampling frequency of(160 MHz).

Mandarin Digits Speech Recognition Using Support Vector Machines

XIE Xiang, KUANG Jing-ming

2005, 14(1): 9-12.

[Abstract](148) [PDF 151KB](2)

Abstract:
A method of applying support vector machine(SVM) in speech recognition was proposed, and a speech recognition system for mandarin digits was built up by SVMs. In the system, vectors were linearly extracted from speech feature sequence to make up time-aligned input patterns for SVM, and the decisions of several 2-class SVM classifiers were employed for constructing an N-class classifier. Four kinds of SVM kernel functions were compared in the experiments of speaker-independent speech recognition of mandarin digits. And the kernel of radial basis function has the highest accurate rate of 99. 33%, which is better than that of the baseline system based on hidden Markov models(HMM)(97. 08%). And the experiments also show that SVM can outperform HMM especially when the samples for learning were very limited.

Predicting Reliability of Tactical Network Using RBFNN

WANG Xiao-kai, HOU Chao-zhen

2005, 14(1): 13-17.

[Abstract](162)

Abstract:
A description of the reliability evaluation of tactical network is given, which reflects not only the non-reliable factors of nodes and links but also the factors of network topological structure. On the basis of this description, a reliability prediction model and its algorithms are put forward based on the radial basis function neural network(RBFNN) for the tactical network. This model can carry out the non-linear mapping relationship between the network topological structure, the nodes reliabilities, the links reliabilities and the reliability of network. The results of simulation prove the effectiveness of this method in the reliability and the connectivity prediction for tactical network.

Optimization of Mapping Rule of Bit-Interleaved Turbo Coded Modulation with 16QAM

FEI Ze-song, YANG Yu, LIU Lin-nan, KUANG Jing-ming

2005, 14(1): 18-21.

[Abstract](149) [PDF 256KB](6)

Abstract:
Optimization of mapping rule of bit-interleaved Turbo coded modulation with 16 quadrature amplitude modulation(QAM) is investigated based on different impacts of various encoded bits sequence on Turbo decoding performance. Furthermore, bit-interleaved in-phase and quadrature phase(I-Q) Turbo coded modulation scheme are designed similarly with I-Q trellis coded modulation(TCM). Through performance evaluation and analysis, it can be seen that the novel mapping rule outperforms traditional one and the I-Q Turbo coded modulation can not achieve good performance as expected. Therefore, there is not obvious advantage in using I-Q method in bit-interleaved Turbo coded modulation.

Multi-Sensor Data Fusion Technologies for Blanket Jamming Localization

WANG Ju, WU Si-liang, ZENG Tao

2005, 14(1): 22-26.

[Abstract](200)

Abstract:
The localization of the blanket jamming is studied and a new method of solving the localization ambiguity is proposed. Radars only can acquire angle information without range information when encountering the blanket jamming. Netted radars could get position information of the blanket jamming by make use of radars' relative position and the angle information, when there is one blanket jamming. In the presence of error, the localization method and the accuracy analysis of one blanket jamming are given. However, if there are more than one blanket jamming, and the two blanket jamming and two radars are coplanar, the localization of jamming could be error due to localization ambiguity. To solve this confusion, the Kalman filter model is established for all intersections, and through the initiation and association algorithm of multi-target, the false intersection can be eliminated. Simulations show that the presented method is valid.

New Iterated Decoding Algorithm Based on Differential Frequency Hopping System

LIANG Fu-lin, LUO Wei-xiong

2005, 14(1): 27-31.

[Abstract](177)

Abstract:
A new iterated decoding algorithm is proposed for differential frequency hopping(DFH) encoder concatenated with multi-frequency shift-key(MFSK) modulator. According to the character of the frequency hopping(FH) pattern trellis produced by DFH function, maximum a posteriori(MAP) probability theory is applied to realize the iterate decoding of it. Further, the initial conditions for the new iterate algorithm based on MAP algorithm are modified for better performance. Finally, the simulation result compared with that from traditional algorithms shows good anti-interference performance.

Dimensionality Reduction by Mutual Information for Text Classification

LIU Li-zhen, SONG Han-tao, LU Yu-chang

2005, 14(1): 32-36.

[Abstract](201)

Abstract:
The frame of text classification system was presented. The high dimensionality in feature space for text classification was studied. The mutual information is a widely used information theoretic measure, in a descriptive way, to measure the stochastic dependency of discrete random variables. The measure method was used as a criterion to reduce high dimensionality of feature vectors in text classification on Web. Feature selections or conversions were performed by using maximum mutual information including linear and non-linear feature conversions. Entropy was used and extended to find right features commendably in pattern recognition systems. Favorable foundation would be established for text classification mining.

Dynamic Multicast Grouping Approach in HLA-Based Distributed Interactive Simulation

DAI Zhong-jian, HOU Chao-zhen

2005, 14(1): 37-40.

[Abstract](205)

Abstract:
In order to improve the efficiency of data distributed management service in distributed interactive simulation based on high level architecture(HLA) and to reduce the network traffic and save the system resource, the approaches of multicast grouping in HLA-based distributed interactive simulation are discussed. Then a new dynamic multicast grouping approach is proposed. This approach is based on the current publication and subscription region in the process of simulation. The results of simulation experiment show that this approach can significantly reduce the message overhead and use fewer multicast groups.

Application of Bayesian Dynamic Forecast in Anomaly Detection

YAN Hui, CAO Yuan-da

2005, 14(1): 41-44.

[Abstract](186)

Abstract:
A macroscopical anomaly detection method based on intrusion statistic and Bayesian dynamic forecast is presented. A large number of alert data that cannot be dealt with in time are always aggregated in control centers of large-scale intrusion detection systems. In order to improve the efficiency and veracity of intrusion analysis, the intrusion intensity values are picked from alert data and Bayesian dynamic forecast method is used to detect anomaly. The experiments show that the new method is effective on detecting macroscopical anomaly in large-scale intrusion detection systems.

Method of Improving the Navigation Accuracy of SINS by Continuous Rotation

YANG Yong, MIAO Ling-juan, SHEN Jun

2005, 14(1): 45-49.

[Abstract](168)

Abstract:
A method of improving the navigation accuracy of strapdown inertial navigation system(SINS) is studied. The particular technique discussed involves the continuous rotation of gyros and accelerometers cluster about the vertical axis of the vehicle. Then the errors of these sensors will have periodic variation corresponding to components along the body frame. Under this condition, the modulated sensor errors produce reduced system errors. Theoretical analysis based on a new coordinate system defined as sensing frame and test results are presented, and they indicate the method attenuates the navigation errors brought by the gyros' random constant drift and the accelerometer's bias and their white noise compared to the conventional method.

Adaptive Fuzzy Attitude Control of Flexible Satellite

GUAN Ping, LIU Xiang-dong, CHEN Jia-bin

2005, 14(1): 50-54.

[Abstract](229) [PDF 189KB](12)

Abstract:
The adaptive fuzzy control is applied in the attitude stabilization of flexible satellite. The detailed design procedure of the adaptive fuzzy control system is presented. Two T-S models are used as both controller and identifier. The parameters of the controller could be modified according to the information of the identifier. Simulation results show that the method can effectively cope with the uncertainty of flexible satellite by on-line learning and thus posses the good robustness. With the proposed method, the precise attitude control is accomplished.

Directional Dispensing of KE-Rod

LU Yong-gang, JIANG Jian-wei, SUI Shu-yuan, MEN Jian-bing

2005, 14(1): 55-58.

[Abstract](97)

Abstract:
With the numerical simulation and high-speed camera, a series of images of dispensing of rod from different devices were obtained. The process of dispensing of rods driven by aiming explosive charge and the influence of different structures on dispensing velocity and angle of KE-rod were studied through analyzing the images. All these can be helpful for the design of new concept anti tactical ballistic missile(ATBM) KE-rod warheads.

Discussion on Failure Sensitive Parameters of an EED Life Performance in Storage

YAN Nan, JIANG Min-rong

2005, 14(1): 59-62.

[Abstract](142)

Abstract:
An issue to distinguish sensitive parameters of storage life prior to the failure of a bridgewire electro-(explosive) device(EED) is studied. The degradations of bridgewire resistance, 50% firing current, ignition delay time, bridgewire molten time and powder color with the storage time were measured under a simulating accelerated life test of high-temperature and high-humidity. The most sensitive parameter suitable to evaluate the EED storage life is discussed. It is concluded that the standard deviation of resistance change is the most sensitive degradation variable, and the next is bridgewire molten time, 50% firing current and ignition delay time. The mean of resistance is an insensitive degradation parameter.

Position Control of Single Pneumatic Muscle Actuator

FAN Wei, PENG Guang-zheng, NING Ru-xin

2005, 14(1): 63-66.

[Abstract](163)

Abstract:
The PID, fuzzy, self-organized fuzzy and self-organized fuzzy-PID controllers are adopted in the position control of single pneumatic muscle actuator. Experiments show that the self-organized fuzzy-PID is obviously effective for the position control of single pneumatic muscle actuator, which can realize precision within 0. 3 mm and withstand 18?N variable load plus about 36?N fixed load. It is relatively precise and robust.

New Method of Road Surface Identification in Anti-Lock Braking System

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

2005, 14(1): 67-70.

[Abstract](176)

Abstract:
Based on the vehicle-road dynamic model, the road characteristic parameter, which depends on different types of road surfaces, is introduced and a new method of road surface identification for automotive anti-lock braking system(ABS) is proposed. According to the characteristics of vehicle-road dynamic model, a simple math resolution method of the model's factors is established. Only using the information of wheel speed, the vehicle reference velocity and the wheel slip ratio are estimated real-timely. And based on the wheel dynamic model, the road characteristic parameter is determined to identify the road surface for the determination of thresholds of ABS regulative parameters. With this new method, the road surface identification can be accurately obtained and calculation time is short that it can meet the ABS real time control need, and it also improves the performance of ABS.

Electronic Unit Pump Diesel Engine Control Unit Design for Integrated Powertrain System

LIU Bo-lan, ZHAO Chang-lu, ZHANG Fu-jun, HUANG Ying

2005, 14(1): 71-74.

[Abstract](184)

Abstract:
The performance of the electronic unit pump(EUP) diesel engine is studied, it will be used in the integrated powertrain and its multi parameters are controllable. Both the theoretical analysis and experiment research are taken. A control unit for the fuel quantity and timing in crankshaft domain is designed on this basis and the engine experiment test has been done. For the constant speed camshaft driving EUP system, the fuel quantity will increase as the supply angle goes up and injection timing has no effect. The control precision can reach 1°CA. The full injection timing MAP and engine peak performance curves are made successfully.

Surface Modification for Metal Hydride Electrode of Ni/MH Battery

YANG Kai, WU Feng, LI Li, CHEN Shi

2005, 14(1): 75-78.

[Abstract](93)

Abstract:
A novel method was applied to the surface modification of the metal hydride(MH) electrode of the Ni/MH battery. The electrode was plated with a thin silver film by using plasma technology and its effect on the performance of the Ni/MH battery was examined. Charge-discharge test proved that the battery with modified electrode exhibits a better high-rate dischargeability and chargeability than the battery with untreated electrode. The battery with modified electrode exhibits satisfactory durability. After 500 cycles, the capacities of the batteries with modified and unmodified electrode are 90. 1% and 82. 3% of their original capacities. The inner pressure test shows that the battery with modified electrode displays a much lower inner gas pressure on charging. The experimental results demonstrate that this method is an effective way for the surface modification of the electrode of the Ni/MH battery.

Number of Negative Entries in A²≤0

SHAO Yan-ling, SUN Liang

2005, 14(1): 79-82.

[Abstract](157)

Abstract:
Let A be a real matrix or a sign pattern of order n. N_-（A） denotes the number of negative entries in A. In 1972 R DeMarr and A Steger conjectured: If A is a real matrix of order n such that A²≤0, then(N_-（A²）≤）（n-1）²+1. Now the conjecture is proved to be true when A is reducible or a matrix of order n≤3 and some sufficient conditions for N_-（A²）≤（n-1）²+1 are given. It is also proved that N_-（A²）≤n²-（4n+）5 when A is a reducible combinatorially symmetric sign pattern such that A²≤0, and the extreme sign patterns are characterized.

General Expression of Elastic Tensor for Anisotropic Materials

HUANG Bo

2005, 14(1): 83-86.

[Abstract](96)

Abstract:
In order to formulate a general expression of elastic tensor for anisotropic materials, a method of tensor derivative is used for determining relationship between fourth-order elastic tensor and second-order structure tensor that has satisfied material symmetrical conditions. From this general expression of elastic tensor, specific expressions of elastic tensor for different anisotropic materials, such as isotropic materials, transverse isotropic materials and orthogonal-anisotropic materials, can be deduced. This expression underlies the scalar description of anisotropic factors, which are used for classifying and analyzing anisotropic materials. Cubic crystals are analyzed macroscopically by means of the general expression and anisotropic factor.

Plane Elasticity and Dislocation of One-Dimensional Hexagonal Quasicrystals with Point Group 6

LIU Guan-ting, GUO Rui-ping, FAN Tian-you

2005, 14(1): 87-91.

[Abstract](119)

Abstract:
Plane elasticity theory of one-dimensional hexagonal quasicrystals with point group 6 is proposed and established. As an application of this theory, one typical example of dislocation problem in the quasicrystals is investigated and its exact analytic solution is presented. The result obtained indicates that the stress components of(elastic) fields of a straight dislocation in the quasicrystals still first order singularity, which is the same as the(general crystals,) but are related with the Burgers vector of phason fields, which is different from the general(crystals. )

Quantum Dynamics of a Charge Qubit in a Squeezed Field

ZOU Jian, CHEN Zhuo, SHAO Bin

2005, 14(1): 92-95.

[Abstract](253)

Abstract:
The quantum dynamics of a charge qubit, which makes up of a single-Cooper-pair box, are explored. The Cooper-pair box is irradiated by a squeezed field in an ideal one-mode cavity. By the result of the Schrodinger equation, the Cooper pairs number 〈N〉 is conveniently obtained. Then it is proved that the oscillations of the Cooper-pair number 〈N〉 are decreasing with the increasing squeezing parameter of the squeezed field.

Demonstration Analysis of Relationship Between R&D Investment and GDP

HAN Bo-tang, LIU Bai-shan, CHEN Keng

2005, 14(1): 96-99.

[Abstract](75)

Abstract:
To reveal the quantitative relationship between research and development(R&D) investment and gross domestic product(GDP) in China, we have demonstrated and analyzed the relationship between R&D investment and science and technology(S&T) progress, and based on a mount of S&T statistical data, have proceeded demonstration research of the relationship between R&D investment and GDP in China with Solow and vector auto regression(VAR) models. Cubic curve fitting and cross-correlation analysis of them with SPSS have shown that there is a strong synchronic relationship between R&D investment and GDP.

Transient Air-Fuel Ratio Control in a CNG Engine Using Fuzzy Neural Networks

LI Guo-xiu, ZHANG Xin

2005, 14(1): 100-103.

[Abstract](170)

Abstract:
The fuzzy neural networks has been used as means of precisely controlling the air-fuel ratio of a lean-burn compressed natural gas(CNG) engine. A control algorithm, without based on engine model, has been(utilized) to construct a feedforward/feedback control scheme to regulate the air-fuel ratio. Using fuzzy neural networks, a fuzzy neural hybrid controller is obtained based on PI controller. The new controller, which can adjust parameters online, has been tested in transient air-fuel ratio control of a CNG engine.

Simultaneous Nitrogen and Phosphorus Removal by Denitrifying Dephosphatation in a(AO）₂Sequencing Batch Reactor

ZHANG Yan-ping, PENG Yong-zhen, WANG Shu-ying, WANG Shao-po

2005, 14(1): 104-108.

[Abstract](188)

Abstract:
A 24 L working volume reactor was used for the research on simultaneous phosphorus(P） and nitrogen(N） removal by denitrifying dephosphatation in an anaerobic-oxid-anoxic-oxid sequencing batch reactor(（AO）₂SBR） system. The durations of each phase are: anaerobic 1. 5 h, aerobic 2. 5 h, anoxic 1. 5 h, post-aerobic 0. 5 h, settling 1. 0 h, fill 0. 5 h. The successful removal of nitrogen and phosphorus is achieved in a stable(AO）₂SBR. The effluent P concentrations is below 1 mg/L, and the COD,TN and P average removal efficiency is 88. 9%, 77. 5% and 88. 7%, respectively. The batch experiment results show that the durations of aerobic and anoxic phase influence the P removal efficiency. Some feature points are found on the DO, ORP and pH curves to demonstrate the complete of phosphate release and phosphate uptake. These feature points can be used for the control of(AO）₂SBR.

Equivalence of Chetaev Model and Vacco Model in Ideal Nonholonomic System and Active Realization Nonideal Nonholonomic System

ZHAO Yue-yu, JIN Bo, XU Wen-xi

2005, 14(1): 109-112.

[Abstract](76)

Abstract:
The Chetaev model and Vacco model in nonholonomic system are studied. The equivalence of the Chetaev model and Vacco model in ideal nonholonomic system and nonideal nonholonomic system realized actively is testified. If nonholonomic constraint is nonideal, the Vacco model is usable from the aspect of mathematics. A general method is given that can be utilized to deal with the ideal nonholonomic system and nonideal nonholonomic system realized actively.

2005 Vol. 14, No. 1