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• • 1998, Vol. 21 No. 2 Published date:10 March 1998 Last issue Next issue

  Original articles

  • Topology Optimization of CCS7 Network
  • Xin Zhanhong, Xu Tao
  • Journal of Beijing University of Posts and Telecommunications. 1998, 21(2): 1-5.
  • Abstract ( 380 )     HTML     　　
  • The topology optimization of CCS7 network in China is studied, several mathematical models are built in light of the decomposition of the problem, and correspondent algorithms are provided. The computing resultswith the network of 123 nodes show that the models and algorithms are quite satisfied, the partition of 9 to 12 signaling regions is suitable and economical inChina, and the location and matching of HTSPs are reasonable.
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  • The Autocorrelation Function of Generalized m-Sequence over GF(q^m)
  • Li Zhongxian, Yang Yixian
  • Journal of Beijing University of Posts and Telecommunications. 1998, 21(2): 6-9.
  • Abstract ( 297 )     HTML     　　
  • The autocorrelation function of generalized m-sequence over GF(q^m) is proved to be two-valued, and it is pointed out that one conjecture of Golomb's can't be generalized to GF(q^m) .
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  • Robust Noise Suppression Methods in Speech Recognition
  • Cui Yi, Zhang Dong, Shi Liangping, Chen Liyuan
  • Journal of Beijing University of Posts and Telecommunications. 1998, 21(2): 10-14.
  • Abstract ( 249 )     HTML     　　
  • Experiment shows that speech recognition system withhigh recognition rate in laboratory environment will greatly decreased in practical field. This severally restricted the use of speech recognition techniques.We carried out a serials of experiments and studies in the parcel sorting workstation, and proposed robust noise suppression methods which revealed encouragingresults in the practical field. The experimental data are given.
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  • Priority Traffic Policing Mechanisms and Their#br# Perfomance Simulations
  • Pang Qixiang, Cheng Shiduan
  • Journal of Beijing University of Posts and Telecommunications. 1998, 21(2): 15-18.
  • Abstract ( 352 )     HTML     　　
  • Six mechanisms for policing traffic with different priorities of cells are presented. They are different from each other in the following aspects: cell buffer sharing, token grabbing, FIFO and HOL effect. Their performance evaluations are obtained through simulations. Simulaiton results showthat the sixth mechanism which uses buffer sharing, token grabbing and jump-ahead policies reaches the best comprehensive performance.
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  • Control Algorithm of Active Vibration Control
  • Liu Xiaoping, Zhang Yanling, Li Qi
  • Journal of Beijing University of Posts and Telecommunications. 1998, 21(2): 19-27.
  • Abstract ( 296 )     HTML     　　
  • The coupled modal control of structural vibration isstudied, and a new control algorithm is presented, in which the physical meaningofthe performance index of the linear Quadratic Regulator(LQR) is very clear.Simulations for the active vibration control of a structural model are carried out.The results show that thepositions of the control points and measure points have great influence on the control.
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  • Modeling on Cutting and Feed Driving Force#br# in Noncircular Sectional Turning
  • Deng Zhongliang
  • Journal of Beijing University of Posts and Telecommunications. 1998, 21(2): 28-32.
  • Abstract ( 307 )     HTML     　　
  • A discussion on turning force, working angle and radial feeding movement during the turning procedure of noncircular sectional elements, a model on the turning force is presented.Based on the analyses and calculation on turning force of elliptical, quadrilateral and octagon elements, a driving force model of feeding mechanism is built.
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  • Forward Displacement Analysis of the 6-5 Stewart Platform
  • Han Lin, Wen Fuan, Liang Chonggao
  • Journal of Beijing University of Posts and Telecommunications. 1998, 21(2): 33-42.
  • Abstract ( 268 )     HTML     　　
  • A closed-form solution to the forward displacement analysis of 6-5 Stewart platform mechanism is presented. The problem is reducedto a 20th degree polynomial equation in a single unknown, from which 40 different locations of the platform can be derived. Numerical example confirms these theoretical results.
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  • Magnetic Properties of NdFe_10.5V_1.5N_x
  • Wang Yonggang, Ge Senlin
  • Journal of Beijing University of Posts and Telecommunications. 1998, 21(2): 43-45.
  • Abstract ( 267 )     HTML     　　

  • High performance powders of NdFe_10.5V_1.5N_x with B_r=1.08 T, H_cj=342 kA/m,(BH)_max=137 kJ/m, and T_c＞820 K were successfully prepared by optimizing the homogenizing treatment of parent alloys, nitrogenation temperature and time, and particle size before and after nitrogenation.Therelationship of the crystallographic structure and the intrinsic magnetic properties to the nitrogen content is investigated.It is found that the nitrogen content is vital to obtaining high performance magnetic powders based on NdFe_10.5V_1.5N_x. In comparison with quenching Nd-Fe-B powders, NdFe_10.5V_1.5N_x powders are characteristics of a larger maximum energy product and a lower cost.Obviously, it is of significant in permanentmagnet applications.

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  • Decoding a Kind of Linear Block Codes Using Neural Network
  • Ma Xiaomin, Yang Yixian, Zhang Zhaozhi
  • Journal of Beijing University of Posts and Telecommunications. 1998, 21(2): 46-50.
  • Abstract ( 274 )     HTML     　　
  • After characteristics and decomposition of complementary codes are discussed, A decomposition decoding strategy for complementary codes based on neural network is presented. The attractors of neural network are introduced to implement error correction decoding. The complementary codes are decomposed into a subcode and several cosets of the subcode, which can further decrease complexityof decoding using neural networks, carrying out high efficiency decoding in realtime. The paper demonstrates the principle and the procedure of the decoding structure, and analysis the performance of the decoding.
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  • The Serial MLSE Multi-User Detection#br# of the Multi-Path Asynchronous DS/CDMA Signals
  • Zhang Wurong, Wu Weiling
  • Journal of Beijing University of Posts and Telecommunications. 1998, 21(2): 51-55.
  • Abstract ( 293 )     HTML     　　
  • The Maximum Likelihood Sequential Estimation (MLSE)algorithm of a asynchronous DS/CDMA system over time invariant channel is investigated firstly, then the MLSE detector over multi-path fading channel is detailed.Analyses show the computational complexity of a MLSE detector over multi-path fading channel is determined by the delay spread.If the delay spread is within one information bit, the multi-path MLSE has a complexity of O(2^k) which is the same of a MLSE algorithm over time invariant channel, while K is the number of users.The detector can be implemented by a dynamicprogramming algorithm such as Viterbi algorithm with variable state number.
  • References | Supplementary Material | Related Articles

  • Dynamic Characteristices of a Wavelength Converter#br# Based on XGM in SOA
  • Zheng Xueyan, Guan Kejian, Ye Peida
  • Journal of Beijing University of Posts and Telecommunications. 1998, 21(2): 56-60.
  • Abstract ( 337 )     HTML     　　
  • The dynamic characteristics of a wavelength converter based on cross-gain modulation in semiconductor optical amplifiers is analyzed theoretically.For first time, the dynamic carrier recovery time is used to equivalent the high frequency saturation filtering effect of the signal channel during the calculation and it is proved by comparing the outputting waveform gottenthrough this way and the experiment results reported in other papers.Ways to reduce the influence of the chirping on the converted signal and ISI of the converted signal are discussed.
  • References | Supplementary Material | Related Articles

  • Performance of a Multicode M-ary/CDMA#br# over Rayleigh Fading Channel
  • Sun Wenjiang, Zhang Ping, Hu Jiandong
  • Journal of Beijing University of Posts and Telecommunications. 1998, 21(2): 61-65.
  • Abstract ( 321 )     HTML     　　
  • The performance of a multicode M-ary/CDMA system over Rayleigh fading channel is analyzed and the numerical result is calculated analyzed.The result is found that the high rate data of users' can be transmitted,but the complexity of the system is higher.
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  • Sub-Channels Pilot Frequency Synchronization Method#br# of DMT System on the Frequency Domain
  • Li Xiangming, Yue Guangxin
  • Journal of Beijing University of Posts and Telecommunications. 1998, 21(2): 66-70.
  • Abstract ( 301 )     HTML     　　
  • The frequency domain sub-channels pilot frequency synchronization method of DMT system is studied.It is demonstrated that both blocks and samples timing recovery can be realized with this method.The relations between the circular shift interpolation sequence and discrete Fourier transform is found .Such a relation is successfully applied in the DMT system to realize the samples timing recovery.
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  • The Research and Design of V5.2 Interface in the Access Network
  • Leng Tao, Sun Shuhe
  • Journal of Beijing University of Posts and Telecommunications. 1998, 21(2): 71-75.
  • Abstract ( 257 )     HTML     　　
  • ITU-T had drawn out an interface standard named V5.2 years.It is an open interface between user equipment and local exchange and will bring out an important reform in the access network.This paper discussed thetechnique of V5.2 interface and give out an implementation design of AN equipment.
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  • An Efficient Multisignature Scheme Based on the One-Way#br# Algebraic Homomorphism
  • Li Xiaojie, Yang Yixian
  • Journal of Beijing University of Posts and Telecommunications. 1998, 21(2): 76-80.
  • Abstract ( 262 )     HTML     　　
  • A weakness in a multisignature scheme designed by E.Chida is pointed out here, this scheme is not strong enough to resist the internal attack. And an improved multisignature scheme based on the one-way algebraic homomorphism is presented and its security level is as same as DSAsignature scheme at least.
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