JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Integrated Systemfor Tube Bending Digital Manufacturing

LU Bo, TANG Cheng-tong, NING Ru-xin, SONG Yue-ying

2006, 15(2): 127-132.

[Abstract](71)

Abstract:
An integrated CAD/CAPP/CAM system of tube manufacturing based on integration frame is presented. In this system, two kinds of data conventions describing tube shape are presented in tube CAD subsystem, the object-oriented concept and the goal-driven inference mechanism have been applied in the development of the knowledge-based CAPP subsystem and simulation of tube processing under tube bending simulation subsystem is performed based on the tube model's piecewise representation. A tube product case is considered to give the application of the integrated system, and the advantages of the system in the use of tube bending are revealed.

Multi-Agent Reinforcement Learning Algorithm Based on Action Prediction

TONG Liang, LU Ji-lian

2006, 15(2): 133-137.

[Abstract](174)

Abstract:
Multi-agent reinforcement learning algorithms are studied.A prediction-based multi-agent reinforcement learning algorithm is presented for multi-robot cooperation task.The multi-robot cooperation experiment based on multi-agent inverted pendulum is made to test the efficency of the new algorithm,and the experiment results show that the new algorithm can achieve the cooperation strategy much faster than the primitive multi-agent reinforcement learning algorithm.

Calculating Model of Interference Amount for Miniaturized Gear and Shaft Shrink Fit

JIN Xin, ZHANG Zhi-jing, YE Xin, LI Zhong-xin

2006, 15(2): 138-143.

[Abstract](118)

Abstract:
Based on miniaturized components' characteristics, the method of assembling miniaturized gear and shaft together with corresponding calculating model of the interference amount are proposed. On the basis of main effecting factors analysis on the gear and shaft assembling interference amount, calculating formula including all factors effective on the interference amount necessary for reliable system running was built up. The methods of reverse calculating theoretical model was used to build up the equivalent simulation model of the theoretical one, together with simulation verification and case study for calculating formula. The results show that the cold assembling method is applicable for miniaturized gear and shaft, but in the assembling process, the interference amount compensating the shape error of contacting surfaces takes a large proportion, which is the main cause of stress variance on contacting surfaces.

Adaptive Noise Cancellation Method Used for Wheel Speed Signal of Integrate ABS/ASR System

MA Yue-feng, LIU Zhao-du, QI Zhi-quan, CUI Hai-feng

2006, 15(2): 144-147.

[Abstract](113)

Abstract:
A novel adaptive noise cancellation method for wheel speed signal of the anti-lock braking system/anti-slip regulation(ABS/ASR) control system is proposed. Based on the spectrum distribution of vehicle's wheel speed signal got from fast Fourier transform under various conditions, the high-pass filter is used to deal with original wheel speed signals sampled to get reference noise signal and the original wheel speed signals are used as adaptive filter's desired outputs. The difference between original signals and reference noise signals is used as the error signal for the adaptive FIR filter and also used as the whole adaptive noise cancellation system's final output. This method can obtain the noise signal on-line and is easy to use for real control system, which is useful to improve the performance of integrate system ABS/ASR.

Vibration Control of Vehicle Suspension System by Electrorheological Damper

ZHAO Xia, ZHANG Yong-fa

2006, 15(2): 148-151.

[Abstract](179)

Abstract:
An overview of electrorheological (ER) fluid characteristics is given. Based on the Bingham plasticity model and a simple parallel-plate model, the operation principle of ER damper is presented and a four-DOF dynamic model of a vehicle suspension is constructed. Then a semi-active control of vehicle suspension system by ER damper is obtained. According to the semi-active control theory, the acceleration frequency characteristic is achieved with Matlab toolbox. Simulation results show that the vibration of the suspension system is well controlled.

Method of Designing Missile Controller Based on Multi-Objective Opti mization

LIN Bo, MENG Xiu-yun, LIU Zao-zhen

2006, 15(2): 152-155.

[Abstract](103)

Abstract:
A method of designing robust controller based on genetic algorithm is presented in order to overcome the drawback of manual modification and trial in designing the control system of missile. Specification functions which reflect the dynamic performance in time domain and robustness in frequency domain are presented, then dynamic/static performance, control cost and robust stability are incorporated into a multi-objective optimization problem. Genetic algorithm is used to solve the problem and achieve the optimal controller directly. Simulation results show that the controller provides a good stability and offers a good dynamic performance in a large flight envelope. The results also validate the effectiveness of the method.

New Clustering Method in High-Di mensional Space Based on Hypergraph-Models

CHEN Jian-bin, WANG Shu-jing, SONG Han-tao

2006, 15(2): 156-161.

[Abstract](79)

Abstract:
To overcome the limitation of the traditional clustering algorithms which fail to produce meaningful clusters in high-dimensional, sparseness and binary value data sets, a new method based on hypergraph model is proposed. The hypergraph model maps the relationship present in the original data in high dimensional space into a hypergraph. A hyperedge represents the similarity of attribute-value distribution between two points. A hypergraph partitioning algorithm is used to find a partitioning of the vertices such that the corresponding data items in each partition are highly related and the weight of the hyperedges cut by the partitioning is minimized. The quality of the clustering result can be evaluated by applying the intra-cluster singularity value. Analysis and experimental results have demonstrated that this approach is applicable and effective in wide ranging scheme.

Chinese Term Extraction Based on PAT Tree

ZHANG Feng, FAN Xiao-zhong, XU Yun

2006, 15(2): 162-166.

[Abstract](217)

Abstract:
A new method of automatic Chinese term extraction is proposed based on Patricia (PAT) tree. Mutual information is calculated based on prefix searching in PAT tree of domain corpus to estimate the internal associative strength between Chinese characters in a string. It can improve the speed of term candidate extraction largely compared with methods based on domain corpus directly. Common collocation suffix, prefix bank are constructed and term part of speech (POS) composing rules are summarized to improve the precision of term extraction. Experiment results show that the F-measure is 74.97%.

Using Pure Translation to Get Euclidean Reconstruction

PEI Ming-tao, JIA Yun-de

2006, 15(2): 167-171.

[Abstract](119)

Abstract:
A technique for getting Euclidean reconstruction from two images of the same scene taken by a single moving camera, which undergoes a pure translation, is presented. Euclidean reconstruction of the scene up to three scale factors can be obtained by using this special but still realistic motion when the skew factor of the camera is zero; otherwise Euclidean reconstruction of the depth up to one scale factor can be achieved. The only assumption is that the camera intrinsic parameters are constant. Using this special but still realistic motion to do the reconstruction has the advantage that no projective reconstruction is needed and the Euclidean reconstruction is computed directly from the point correspondences in the two images.

Multilayer Multidi mensional Extension Set Theory

CAO Shao-zhong, YANG Guo-wei, TU Xu-yan

2006, 15(2): 172-176.

[Abstract](189)

Abstract:
In order to study the contradiction problem of multilayer multidimensional complex systems, the concepts of extension field and stable field of intersection and union of multilayer multidimensional extension set are given. Then the related operations and properties are discussed. The results of study expand the concepts of intersection and union of extension set to a general situation, and provide the theoretical basis for production of the concepts of intersection and union of multilayer multidimensional matter element system extension set. In this way, it will be possible that matter element system theory is used to creative designs of complex systems.

Clustering with Weighted Hyperlink and Sub Similarity Matrix

WU Ping, SONG Han-tao, ZHANG Li-ping, WU Zheng-yu

2006, 15(2): 177-180.

[Abstract](211)

Abstract:
A web page clustering algorithm called PageCluster and the improved algorithm ImPageCluster solving overlapping are proposed. These methods not only take the web structure and page hyperlink into account, but also consider the importance of each page which is described as in-weight and out-weight. Compared with the traditional clustering methods, the experiments show that the runtimes of the proposed algorithms are less with the improved accuracies.

User’s Relevance of PIR System Based on Cloud Models

KANG Hai-yan, FAN Xiao-zhong

2006, 15(2): 181-185.

[Abstract](93)

Abstract:
A new method to evaluate fuzzily user's relevance on the basis of cloud models has been proposed. All factors of personalized information retrieval system are taken into account in this method. So using this method for personalized information retrieval (PIR) system can efficiently judge multi-value relevance, such as quite relevant, comparatively relevant, commonly relevant, basically relevant and completely non-relevant, and realize a kind of transform of qualitative concepts and quantity and improve accuracy of relevance judgements in PIR system. Experimental data showed that the method is practical and valid. Evaluation results are more accurate and approach to the fact better.

Authenticated Key Agreement in Group Settings

LI Ming, WANG Yong, GU Da-wu, BAI Ying-cai

2006, 15(2): 186-189.

[Abstract](279)

Abstract:
An enhanced definition of implicit key authentication and a secure group key agreement scheme from pairings are presented. This scheme combines the merits of group public key and key trees to achieve a communication-efficient and authenticated group key agreement protocol. Besides, it avoids dependence on signature or MAC by involving member's long-term keys and short-term keys in the group key. Furthermore, the idea behind this design can be employed as a general approach to extend the authenticated two-party Diffie-Hellman protocols to group settings.

Method to Improve the Tracking Speed of the Early-Late Synchronizer

AN Jian-ping, WANG Jun

2006, 15(2): 190-194.

[Abstract](105)

Abstract:
A new early-late synchronizer is proposed to improve tracking speed. The performance of the traditional early-late synchronizer is analyzed in detail, the result shows that the different location and length of integral period can influence the discriminator characteristic, an improved integral structure is provided which can tracking the synchronization error better. According to the good tracking performance of Kalman filter, a new loop filter is designed. The new early-late synchronizer adopts both the new integral structure and the new loop filter. The analysis with loop theory and simulation results in Simulink show that the new bit synchronizer possesses higher tracking speed than the traditional early-late synchronizer.

Data-Driven Temporal Filtering on Teager Energy Time Trajectory for Robust Speech Recognition

ZHAO Jun-hui, XIE Xiang, KUANG Jing-ming

2006, 15(2): 195-200.

[Abstract](165)

Abstract:
Data-driven temporal filtering technique is integrated into the time trajectory of Teager energy operation (TEO) based feature parameter for improving the robustness of speech recognition system against noise. Three kinds of data-driven temporal filters are investigated for the motivation of alleviating the harmful effects that the environmental factors have on the speech. The filters include: principle component analysis (PCA) based filters, linear discriminant analysis (LDA) based filters and minimum classification error (MCE) based filters. Detailed comparative analysis among these temporal filtering approaches applied in Teager energy domain is presented. It is shown that while all of them can improve the recognition performance of the original TEO based feature parameter in adverse environment, MCE based temporal filtering can provide the lowest error rate as SNR decreases than any other algorithms.

Study on Unequal Error Protection for Distributed Speech Recognition System

XIE Xiang, WANG Si-yao, LIU Jia-kang

2006, 15(2): 201-205.

[Abstract](172)

Abstract:
The unequal error protection (UEP) is applied in distributed speech recognition (DSR) system and three schemes are proposed. All of these three schemes are evaluated on the GSM simulating platform for recognizing mandarin digit strings and compared with the equal error protection (EEP) scheme. Experiments show that UEP can protect the data transmitted in DSR system more effectively, which results in a higher word accurate rate of DSR system.

Adaptive Bit Loading Scheme with Semi-Blind Channel Estimation for OFDMSystems

LI Ying, SU Guang-chuan

2006, 15(2): 206-210.

[Abstract](180)

Abstract:
An adaptive bit loading and power-allocation scheme is proposed in order to augment the performance of the system based on orthogonal frequency division multiplexing (OFDM), which is based on the maximum power margin. Coinciding with the adaptive loading scheme, a semi-blind channel estimation algorithm using subspace decomposition method is proposed, which uses the information in the cyclic prefix. An initial channel state information is estimated by using the training sequences with the method of interpolation filtering. The proposed adaptive scheme is simulated on an OFDM wireless local area network(WLAN) system in a time-varying channel. The performance is compared to the constant loading scheme.

Design and Fabrication of 2-DOF Micromirror Array Based on Electro-Thermal Actuators

JIANG Jian-liang, HILLERINGMANN Ulrich

2006, 15(2): 211-215.

[Abstract](255)

Abstract:
With surface- and bulk-micromachining, an 8×8 mirrors array is designed, fabricated and tested, which is based on electro-thermal actuators and can be addressed individually. The micromirror is square-shaped, 4-corner-actuated. Its dimension is 200μm×200μm. The substrate below it is caved away to ensure a tilt at an angle as large as possible. To protect the etch-sensitive features on the front side of the wafer undamaged during wet deep silicon etch on the backside, the wax protective coating process is used. Mirror actuated by powering an alternative pair of heaters will tilt in 2-DOF. If its 4 cantilevers/heaters are powered synchronously, it will move in a piston mode. The effective arrays are more than 80% out of the three finished wafers. When the ramp voltage frequency applied to a pair of neighboring cantilevers is 5Hz at 10V, the average tilting angle can be ±8°.

Digital Image Scrambling Technology Based on the Symmetry of Arnold Transform

YANG Ya-li, CAI Na, NI Guo-qiang

2006, 15(2): 216-220.

[Abstract](212)

Abstract:
An improved digital image scrambling method based on Arnold transform is proposed. The method can be used for the rectangle image by splitting rectangle image into several square images. Furthermore,a pretreatment is added to speeding up the process and enhancing the scrambling effect. The recovering of the scrambled image depends on the reverse Arnold transform that has the same cycle times with the Arnold transform. The recovering is lossless and need not calculating the period of the Arnold transform. Finally, experimental results show the robustness of the method.

Synthesis and Structural Characterization of [Co（Q）₂（H₂O）₂]（Q=8-Hydroxyquinoline Ion）

HU Chang-wen, WANG Chun-xiu, LI Hui, NIU Xue-li, PAN Wan-long, GONG Yun

2006, 15(2): 221-224.

[Abstract](89)

Abstract:
The single crystal of bi（8-hydroxyquinoline） bihydrated cobalt（Ⅱ） complex, [Co（Q）₂（H₂O）₂] （Q=8-hydroxyquinoline ion）, has been synthesized by general method and structurally characterized by single crystal X-ray diffraction. Crystal data: C₁₈H₁₆CoN₂O₄, monoclinic, C2/c, a=1.3362（4） nm, b= 0.9412（3） nm, c=1.3543（4） nm, β=109.672（4）°, Z=4. In the complex, Co（Ⅱ） ion is six-coordinated, forming a distorted octahedron. H-bonding and π-π stacking interaction play a significant role to form and stabilize the three-dimensional structure.

Investigation on Hydrogenolysis of Hexabenzylhexaazaisowurtzitane

HAN Wei-rong, OU Yu-xiang, CHEN Bo-ren

2006, 15(2): 225-228.

[Abstract](143)

Abstract:
The compound of tetraacetyldibenzylhexaazaisowurtzitane (TADBIW) is the precursor of synthesizing the high energy density caged compound hexanitrohexaazaisowurtzitane (HNIW). TADBIW was obtained by hydrogenolysis of hexabenzylhexaazaisowurtzitane (HBIW). The hydrogenolysis product TADBIW contains a little amount of triacetyltribenzylhexaazaisowurzitane (TATBIW). It was proposed that the hydrogenolysis of HBIW would occur in a stepwise manner. Two compounds, diacetyltetrabenzylhexaazaisowurtzitance (DATBIW) and TATBIW, were synthesized by controlling the volumes of hydrogen that consumed during the hydrogenolysis debenzylation of HBIW. They are the intermediates of the hydrogenolysis of HBIW. The success of synthesizing these intermediates would be useful for researching the mechanism of the hydrogenolysis of HBIW. This is also useful for improving the hydrogenolysis process: increasing the amount of catalyst and prolonging the hours of reaction would produce high yields and enhance the purity of TADBIW.

Hydrothermal Synthesis of [ Mn₅（H₂PO₄）₂（PO₄）₂（H₂O）₄]Templated by Calixarene Under Mild Conditions

GONG Yun, LI Hui, HU Chang-wen

2006, 15(2): 229-232.

[Abstract](118)

Abstract:
The title compound [Mn₅（H₂PO₄）₂（PO₄）₂（H₂O）₄] was hydrothermally synthesized in the presence of calix[4]arene-p-tetrasulfonate. The title compound was structurally characterized by X-ray single crystal diffraction. It crystallizes in the monoclinic space group C2/c with a=1.7629（4）nm, b= 0.91344（18）nm, c=0.94977（19）nm, β=96.52（3）°, V=1.5195（5）nm³, Z=4 and R₁=0.0283, and exhibits a three-dimensional framework and channel structure. It was proposed that calixarene can act as template during the formation of the title compound because calixarene can bind Mn2+ through second-sphere coordination.

Novel Epoxy Resin/Si O₂Nanocomposites Preparation Method Based on Di minutive Bubbles Explosion

NIE Peng, ZHAO Xue-zeng, CHEN Fang, WANG Wei-jie, BAI Yong-ping

2006, 15(2): 233-238.

[Abstract](194)

Abstract:
To obtain suspended dispersion of nano-particles in liquid without any dispersant, a novel epoxy resin/SiO₂nanocomposites preparation method based on diminutive bubbles explosion is presented. And, corresponding nanocomposites preparation system was designed. The preparation system applies compressed gas as transmission medium to carry nanomaterials into epoxy resin solution. The compressed gas with nanomaterials turns into diminutive bubbles distributing in epoxy resin/SiO₂. The great pressure difference between inner and outer-bubbles led to bubbles inflation and explosion. During the bubble inflation, bubble oscillation may generate. The stretching rate may reach 10⁶s^-1, which favors more homogeneous dispersion of nano- particles. During the bubbles explosion the released energy and the explosion shock waves disperse the nano- particles into epoxy resin solution. By using the preparation system, epoxy resin/SiO₂nanocomposites were prepared. The SiO₂dispersed into epoxy as the configuration of 15nm-30nm particles.

Two Qubits Entanglement Dynamics in1D Heisenberg Chain with Intrinsic Decoherence

SHAO Bin, ZHANG Li-li, ZOU Jian

2006, 15(2): 239-241.

[Abstract](171)

Abstract:
To reveal how the decoherence modifies the time evolution of the entanglement of quantum system, the intrinsic decoherence approach and the entanglement of formation are used, and the time evolution of entanglement for two-qubit 1D quantum Heisenberg model in an external uniform magnetic field is derived. It is shown that the external magnetic field can strengthen the effects of the intrinsic decoherence on the entanglement of the system.

Structure of the Bifurcation Solutions for a Predator-Prey Model

WANG Yi-fu, MENG Yi-jie

2006, 15(2): 242-246.

[Abstract](114)

Abstract:
A system of reaction diffusion equations modeling the predator-prey interaction in an unstirred chemostat is considered. After transforming the model, the global bifurcation theorem is used to investigate the global structure of solutions of the system with b as the bifurcation parameter.

Inevitability and Emergent Problems of Science &Technology Innovation Access to Integration

LIU Li-jun, LU Xin-mei

2006, 15(2): 247-252.

[Abstract](119)

Abstract:
The causes and the problems of integration of scientific & technical innovation (ISTI) and inevitability are proposed. The status of domestic scientific & technical innovation is analysed. A series of emergent managerial problems caused by the system ISTI (SISTI) are pointed out. Because of Hall three dimensions structure's enlightenment, a three dimensional logical net diagram in which the system integration of innovation based on problem in real world but not on disciplinary logic is drawn. The intelligent group's need span is greater under the conditions of relatively low material level than common groups who have lower degree of education. The SISTI is composed by multi-rule and intelligent multi-agent behavior. It is concluded that the logical relationships of integrated technology which based on the author's experience and observation must be considerded for a valid management of SISTI.

2006 Vol. 15, No. 2