JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Adaptive Simulated Annealing Based Protein Loop Modeling of Neurotoxins

HUANG Li-na, CHEN Jie

2003, 12(4): 337-341.

[Abstract](76)

Abstract:
A loop modeling method, adaptive simulated annealing, for ab initio prediction of protein loop structures, as an optimization problem of searching the global minimum of a given energy function, is proposed. An interface-friendly toolbox—LoopModeller in Windows and Linux systems, VC++ and OpenGL environments is developed for analysis and visualization. Simulation results of three short-chain neurotoxins modeled by LoopModeller show that the method proposed is fast and efficient.

The Model Reference Adaptive Fuzzy Control for the Vehicle Semi-Active Suspension

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

2003, 12(4): 342-346.

[Abstract](183)

Abstract:
The LQG control system is employed as vehicle suspension's optimal target system, which has an adaptive ability to the road conditions and vehicle speed in a limited bandwidth. In order to keep the optimal performances when the suspension parameters change, a model reference adaptive fuzzy control (MRAFC) strategy is presented. The LQG control system serves as the reference model in the MRAFC system. The simulation results indicate that the presented MRAFC system can adapt to the parameters variation of vehicle suspension and track the optimality of the LQG control system, the presented vehicle suspension MRAFC system has the ability to adapt to road conditions and suspension parameters change.

Tank Fire Control Systems Accuracy Assignment Based on Fuzzy Comprehensive Judgment Method

LIU Wen-guo, CHEN Jie, DOU Li-hua

2003, 12(4): 347-351.

[Abstract](174) [PDF 175KB](3)

Abstract:
A method of accuracy assignment based on fuzzy comprehensive judgment method (FCJM) in tank fire control system is proposed. From the flowing route of the error sources and their respective correlative signals, the transfer functions of several sources are analysed by means of mathematic simulation, and FCJM is applied to obtain the cost comprehensive factor for each part of system, combining its error sensitivity factor the mathematical model is built to solve the accuracy assignment problem. Simulation result shows the proposed method can help designer of tank fire control system work out an optimal system more efficiently and more economically.

Multi-Valued Associative Memory Neural Network

XIU Chun-bo, LIU Xiang-dong, ZHANG Yu-he

2003, 12(4): 352-356.

[Abstract](164)

Abstract:
A novel learning method for multi-valued associative memory network is introduced, which is based on Hebb rule, but utilizes more information. According to the current probe vector, the connection weights matrix could be chosen dynamically. Double-valued and multi-valued associative memory are all realized in our simulation experiment. The experimental results show that the method could enhance the associative success rate.

Research on Digital Dynamic Testing Technique for Electrohydraulic Servovalve

WANG Shou-kun, WANG Jun-zheng, ZHAO Jiang-bo, ZHANG Yu-he

2003, 12(4): 357-361.

[Abstract](130)

Abstract:
The digital testing technique based on computers for dynamic characteristics of electrohydraulic servovalves via frequency scan method is researched. The no-load piston which measures the servo's transient output flow is designed properly. The velocity testing method by which the speed signal can be obtained indirectly by means of a piezoelectral accelerometer is given. High speed sampling has been realized in Windows OS. Wavelet denoising and Fourier transform are adopted in data processing and analyses. The testing technique discussed has been applied to actual testing systems and the experimental results have proved it to be correct.

Pneumatic Rotary Actuator Angle Control System

WANG Peng, PENG Guang-zheng, WU Qing-he

2003, 12(4): 362-365.

[Abstract](185)

Abstract:
Based on the adaptive control method, a kind of parameter adjustor was used to control pneumatic rotary actuator to track the expected output. The system uses electropneumatic proportional valve as control device, which adjusts the gas flow of actuator 's two cavities, then changes the pressure of cavity and pushes the piston of actuator to move, so the rotary actuator 's axis can be made to revolve to the required angle at last. According to the characteristic of pneumatic system, the control system was described with a fourth-order mathematic model. The control rule is deduced by model reference adaptive control method. By the result of experiment, it was proved that by using the adaptive control method, the output of rotary actuator could track the expected value timely and accurately.

Design and Implementation of Bidirectional Dijkstra Algorithm

FU Meng-yin, LI Jie, ZHOU Pei-de

2003, 12(4): 366-370.

[Abstract](180)

Abstract:
Bidirectional Dijkstra algorithm whose time complexity is 8O（n²） is proposed. The theory foundation is that the classical Dijkstra algorithm has not any directional feature during searching the shortest path. The algorithm takes advantage of the adjacent link and the mechanism of bidirectional search, that is, the algorithm processes the positive search from start point to destination point and the negative search from destination point to start point at the same time. Finally, combining with the practical application of route-planning algorithm in embedded real-time vehicle navigation system （ERTVNS）, one example of its practical applications is given, analysis in theory and the experimental results show that compared with the Dijkstra algorithm, the new algorithm can reduce time complexity, and guarantee the searching precision, it satisfies the needs of ERTVNS.

Adaptive Federal Kalman Filtering for SINS/GPS Integrated System

YANG Yong, MIAO Ling-juan

2003, 12(4): 371-375.

[Abstract](222)

Abstract:
A new adaptive federal Kalman filter for a strapdown integrated navigation system/global positioning system (SINS/GPS) is given. The developed federal Kalman filter is based on the trace operation of parameters estimation's error covariance matrix and the spectral radius of update measurement noise variance-covariance matrix for the proper choice of the filter weight and hence the filter gain factors. Theoretical analysis and results from simulation in which the SINS/GPS was compared to conventional Kalman filter are presented. Results show that the algorithm of this adaptive federal Kalman filter is simpler than that of the conventional one. Furthermore, it outperforms the conventional Kalman filter when the system is undertaken measurement malfunctions because of its possession of adaptive ability. This filter can be used in the vehicle integrated navigation system.

Color Reproduction on CRT Displays via BP Neural Networks Under Office Environment

YANG Wei-ping, LIAO Ning-fang, CHAI Bing-hua, HU Zhong-ping, BAI Li, LI Zhao-jian

2003, 12(4): 376-380.

[Abstract](153)

Abstract:
A CRT characterization method based on color appearance matching is presented. A matching between Munsell color chips and CRT charts was obtained in vision perceiver in typical office environment and viewing condition by recommending. And neural networks were utilized to accomplish the color space conversion from CIE standard color space to CRT device color space. The neural networks related the color space conversion and color reproduction of soft/hard-copy directly to the influence of the illuminance and viewing condition in vision perceiver. The average color difference of training samples is 3.06 and that of testing samples is 5.17. The experiment results indicated that the neural networks can satisfy the requirements for the color appearance of hard-copy reproduction in CRT.

Temporal Characteristics of GaAs NEA and Alkali Metal Photocathodes

LI Xiang-min, ZHOU Li-wei

2003, 12(4): 381-384.

[Abstract](126)

Abstract:
The temporal characteristics of GaAs NEA and alkali metal photocathodes are studied using Monte Carlo simulation method. The electron transit time and its distribution functions in the photocathodes are calculated. Based on the results, the time modulation transfer functions and temporal resolutions of the photocathodes are obtained. The results show that the response time and temporal resolution of alkali metal photocathode is in femitosecond order and those of GaAs NEA photocathode are in picosecond order.

Novel Mapping Design Criterion for BICM-ID with Square QAM Constellations

LIU Lin-nan, FEI Ze-song, ZHAO Sheng-hui, KUANG Jing-ming

2003, 12(4): 385-389.

[Abstract](120)

Abstract:
Mapping design criteria of bit-interleaved coded modulation with iterative decoding (BICM-ID) with square 16QAM are analyzed. Three of the existing criteria are analyzed and compared with each other. Through the comparison, two main characters of the mapping design criteria are found. They are the harmonic mean of the minimum squared Euclidean distance and the average of Hamming distances with the nearest Euclidean distance. Based on these two characters, a novel mapping design criterion is proposed and a label mapping named mixed mapping is searched according to it. Simulation results show that mixed mapping performs better than the other mappings in BICM-ID system.

Novel Spatially Adaptive Image Denoising Algorithm Based on Covariance Estimation in Wavelet Domain

XIE Zhi-hong, SHEN Ting-zhi, WANG Hai

2003, 12(4): 390-394.

[Abstract](153)

Abstract:
A new method for image denoising is proposed. By analyzing image's statistical properties in wavelet domain, it is shown that the natural image has a strong and spatial variable covariance structure relationship in local space of sub-band. A non-direct estimation method is suggested to make an adaptive estimate of spatial variable covariance by estimating the correlation coefficient and variance of subband image separately. It can be used to estimate adaptive filtering of subband image. The experiment shows that this method can improve the image's SNR, and has strong ability to preserve edges.

Blind Image Quality Assessment Based on Hybrid Fuzzy-Genetic Technique

WANG Hai, SHEN Ting-zhi, XIE Zhi-hong

2003, 12(4): 395-398.

[Abstract](183)

Abstract:
A new method for no-reference image quality assessment based on hybrid fuzzy-genetic technique is proposed. Noise variance and edge sharpness level of the restored image are two basic metrics for assessing the performance of the restoration algorithm, then a fuzzy if-then inference system is developed to combine the two metrics to get a final quality score, and the parameters of the fuzzy membership function are trained with genetic algorithms. Experiments results show that the image quality score correlates well with mean opinion score and the proposed approach is robust and effective.

Novel Extended Phonemic Set for Mandarin Continuous Speech Recognition

XIE Xiang, KUANG Jing-ming

2003, 12(4): 399-402.

[Abstract](210)

Abstract:
An extended phonemic set of mandarin from the view of speech recognition is proposed. This set absorbs most principles of some other existing phonemic sets for mandarin, like Worldbet and SAMPA-C, and also takes advantage of some practical experiences from speech recognition research for increasing the discriminability between word models. And the experiments in speaker independent continuous speech recognition show that hidden Markov models defined by this phonemic set have a better performance than those based on initial/final units of mandarin and have a very compact size.

Comparative Study on Channel Compensation for Robust Speech Recognition

ZHAO Jun-hui, KUANG Jing-ming, HUANG Shi-lei

2003, 12(4): 403-406.

[Abstract](196)

Abstract:
Some channel compensation techniques integrated into front-end of speech recognizer for improving channel robustness are described. These techniques include cepstral mean normalization, rasta processing and blind equalization. Two standard channel frequency characteristics, G.712 and MIRS, are introduced as channel distortion references and a mandarin digit string recognition task is performed for evaluating and comparing the performance of these different methods. The recognition results show that in G.712 case blind equalization can achieve the best recognition performance while cepstral mean normalization outperforms the other methods in MIRS case which is capable of reaching a word error rate of 3.96%.

MCS Selection Criteria Based on Performance Simulation for HSDPA

YANG Xiao-qian, ZHAO Sheng-hui, FEI Ze-song, KUANG Jing-ming

2003, 12(4): 407-411.

[Abstract](123)

Abstract:
An adaptive modulation and coding (AMC) scheme integrated with multi-code transmission for high speed downlink packet access is presented and some modulation and coding scheme (MCS) selection criteria are proposed to maximize single user data rates. Based on link-level performance analysis, the MCS selection criteria are proposed with the constraints of QoS requirement, modulation level, channel coding rate and the number of available channelization codes. By allowing multiple transmission parameters changing, these criteria make the scheme more flexible to time-varying mobile channel with comparatively low complexity through a look-up table method. The AMC scheme is sensitive to the changes of channel condition and can save the channelization codes in an applicable way by applying these criteria.

New Channel Simulator for Adaptive HF Communication Systems

ZHANG Yu-bing, KUANG Jing-ming, LIU Jia-kang

2003, 12(4): 412-415.

[Abstract](196)

Abstract:
The high frequency (HF) channel simulators with time-varying parameters based on the Watterson model are analyzed. The methods of simulating the HF channel with time-varying parameters are proposed. The linearly time-varying delay spread is introduced into the channel simulators to simulate the transition states between two channel modes of CCIR520-1. Two signals, including a 500 Hz and a 1 000 Hz bandwidth signal are respectively input into the standard Watterson HF channel model and the proposed channel model with time-varying parameters. Some simulation results prove that the proposed HF channel model with time-varying parameters can reflect the time-varying characteristics of frequency selected fading of HF channel.

The Real Time Mixing Module Design for HDTV Data of SMPTE 274M and PC Video Data

WEI Jiang-li, ZHAO Bao-jun, HAN Yue-qiu

2003, 12(4): 416-419.

[Abstract](69)

Abstract:
A real time mixing module for high definition television (HDTV) data of SMPTE 274M and PC video data is designed. The hardware implementation, algorithm and simulation of the mixing module are given. In order to improve the capability of data processing, an anti-fuse FPGA chip and a mechanism of pipelining and modularization are adopted. With 6 parallel LUTs and a fast algorithm, it can mix 4∶2∶2 component signals in luminance and chrominance space respectively in real time. According to the simulation, the module has the ability to mix the uncompressed HDTV data with PC video data in real time, which can not be fulfilled by current ASIC chips. Furthermore, it can be extended to multi-stage mixing with the thoughts implied by the design. The mixing module can be widely used in HDTV production systems.

Novel Way to Suppress Reverberation Based on Fractional Fourier Transform

DENG Bing, TAO Ran, QI Lin, LIU Feng

2003, 12(4): 420-424.

[Abstract](181)

Abstract:
A novel method of anti-reverberation based on the fractional Fourier transformation is presented. By virtue of the fact that it has a good focus property in the fractional Fourier domain, the linearly frequency modulation (LFM) signal can be seperated from the reverberation through a swept-frequency filter. With the actual reverberation data and the LFM pulse for seperation, the good results are obtained: the reverbareation is largely removed, and relatively the better performance is shown under the lower signal reverberation ratio (SRR). Based on the theorical analyses and simulation results, two schemes for detecting targets are provided: one is the detection of the LFM echo from the target with a threshold by means of this method directly; the other is to detect the target by means of other methods, with this method performing pre-process to increase SRR, which need enough large SRR.

Using LMS Adaptive Filter in Direct Wave Cancellation

XU Yuan-jun, TAO Ran, WANG Yue, SHAN Tao

2003, 12(4): 425-427.

[Abstract](226)

Abstract:
The way to use the least-mean-square (LMS) arithmetic to cancel the direct wave for a passive radar system is introduced. The model of the direct wave is deduced. By using the LMS adaptive FIR filter, the software solution for FM passive radar system is developed instead of the hardware consumption of the existent experiment system of passive radar. Further more some simulative results are given. The simulative results indicate that using LMS arithmetic to cancel the direct wave is effective.

Rough Set Based Fuzzy Neural Network for Pattern Classification

LI Kan, LIU Yu-shu

2003, 12(4): 428-431.

[Abstract](216)

Abstract:
A rough set based fuzzy neural network algorithm is proposed to solve the problem of pattern recognition. The least square algorithm (LSA) is used in the learning process of fuzzy neural network to obtain the performance of global convergence. In addition, the numbers of rules and the initial weights and structure of fuzzy neural networks are difficult to determine. Here rough sets are introduced to decide the numbers of rules and original weights. Finally, experiment results show the algorithm may get better effect than the BP algorithm.

New E-Commerce Model Based on Multi-Agent Automated Negotiation

XIANG Chuan-jie, JIA Yun-de

2003, 12(4): 432-435.

[Abstract](207)

Abstract:
A new multi-agent automated negotiation model is developed and evaluated, in which two competitive agents, such as the buyer and seller, have firm deadlines and incomplete information about each other. The negotiation is multi-dimensional in different cases. The model is discussed in 6 kinds of cases with different price strategies, warrantee strategies and time strategies. The model improves the model of Wooldridge and that of Sycara to a certain extent. In all possible situations, the optimal negotiation strategy is analyzed and presented, and an e-commerce model based on multi-agent automated negotiation model is also illustrated for the e-commerce application in the future.

Load Balancing Algorithm for Cache Cluster

LIU Mei-hua, GU Zhi-min, CAO Yuan-da

2003, 12(4): 436-440.

[Abstract](171)

Abstract:
By the load definition of cluster, the request is regarded as granularity to compute load and implement the load balancing in cache cluster. First, the processing power of cache-node is studied from four aspects: network bandwidth, memory capacity, disk access rate and CPU usage. Then, the weighted load of cache-node is customized. Based on this, a load-balancing algorithm that can be applied to the cache cluster is proposed. Finally, Polygraph is used as a benchmarking tool to test the cache cluster possessing the load-balancing algorithm and the cache cluster with cache array routing protocol respectively. The results show the load-balancing algorithm can improve the performance of the cache cluster.

Statistical Language Model for Chinese Text Proofreading

ZHANG Yang-sen, CAO Yuan-da

2003, 12(4): 441-445.

[Abstract](210)

Abstract:
Statistical language modeling techniques are investigated so as to construct a language model for Chinese text proofreading. After the defects of n-gram model are analyzed, a novel statistical language model for Chinese text proofreading is proposed. This model takes full account of the information located before and after the target word wi, and the relationship between un-neighboring words w_iand w_jin linguistic environment（LE）. First, the word association degree between w_iand w_jis defined by using the distance-weighted factor, w_jis l words apart from w_iin the LE, then Bayes formula is used to calculate the LE related degree of word w_i, and lastly, the LE related degree is taken as criterion to predict the reasonability of word w_ithat appears in context. Comparing the proposed model with the traditional n-gram in a Chinese text automatic error detection system, the experiments results show that the error detection recall rate and precision rate of the system have been improved.

Markov Model for Packet Scheduling in the Transmission of Streaming Media

PAN Hao, SONG Han-tao, WANG Da-zhen

2003, 12(4): 446-449.

[Abstract](199)

Abstract:
The difficulties in the transmission of streaming media are analyzed, the packet scheduling on the streaming media server is studied. A Markov model is proposed under the effect of the complex dependency among the streaming media packets and the parameters of the transmission channel. On the basis of the Markov model, a policy is made to queue the streaming media packets in the sending buffer by using the iteration method, which can optimize the playback quality under the lack of the channel bandwidth.

Intelligent Agent-Based System for Digital Library Information Retrieval

SHI Xue-lin, NIU Zhen-dong, SONG Han-tao, SONG Li-zhe

2003, 12(4): 450-454.

[Abstract](224)

Abstract:
A new information search model is reported and the design and implementation of a system based on intelligent agent is presented. The system is an assistant information retrieval system which helps users to search what they need. The system consists of four main components: interface agent, information retrieval agent, broker agent and learning agent. They collaborate to implement system functions. The agents apply learning mechanisms based on an improved ID3 algorithm.

2003 Vol. 12, No. 4