JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Numerical Simulations of Tungsten Alloy Rods Penetration into Alumina Ceramic/Armor Steel Composite Target

LI Jin-zhu, HUANG Feng-lei, ZHANG Lian-sheng

2008, 17(3): 253-258.

[Abstract](164)

Abstract:
The Johnson-Holmquist constitutive ceramic model is re-implemented into the LS-DYNA3D program to simulate the penetration of long rod projectile into ceramic/armor steel composite targets.The damage evolution,fracture propagation,and spall damage in the ceramic/armor targets is represented during the simulation procedure and the accuracy of the penetration depth comparing between the simulating and experimental results is reliable with an error less than 8%.The relationship between the mass efficiency factor.differential factor and ceramic tiles thickness is given out for the penetration results with/without a cover plate.

Modeling and Simulation of a Bonding Process for Space Solar Cells

ZHAO Hui, LI Pei-bo, FU Zhuang, ZHAO Yan-zheng

2008, 17(3): 259-263.

[Abstract](209)

Abstract:
A bonding process for space solar cells implemented by an automated coating and bonding system was theoretically investigated for future parametric studies to achieve better bonding quality.First,the mechanical pmpetries of sillcone adhesive and the vacuum.suction cup were experimentally analyzed.Based on the constitutive relationship of four parts in the bonding process,the dynamic bonding process was modeled systematically,and numerically simulated by a commercial finite element analysis code,Adina.The final bonding edge-alignment error and the thickness and uniformity of the adhesive layer were obtained from simulation and validated by experiments.A simulation platform was created for predicting the final bonding quality via adjusting bonding parameters when dimensions of the solar cells and adhesive were changed.

State Dependent Regenerative Delay Model for High-Speed Milling Processes

SONG Qing-hua, AI Xing, WAN Yi, ZHAO Jun, PAN Yong-zhi

2008, 17(3): 264-269.

[Abstract](177)

Abstract:
A 2 DOF dynamic model of regenerative chatter model with state-dependent time delay is developed in milling proceSses.Regenerative effects,"ploughing"or"rubbing"effects between the flank of the cutting edge and the machined surface,and feed effects are considered.It is shown that the regenerative delay is detemined bv the combination of the cutter rotation and the tool vibrations resulting in a state-dependent time delay.The governing equation is a delay-differential equation with state-dependent delay(SD-DDE),as opposed to the standard models with constant time delay.Based on Frechet derivative theory,the linearization of periodic state-dePendent delay differential equation is also investigated.For a system with practical milling parameters.the incorporation of the state.dependent delay into the model does not essentially affect the linear stability properties of the system.

Design Method for the Magnetic Bearing Control System with Fuzzy-PID Approach

XU Chun-guang, LV Dong-ming, HAO Juan

2008, 17(3): 270-273.

[Abstract](209)

Abstract:
The five degree freedom magnetic bearing is researched and its structure and working principles are introduced also.Based on the fuzzy control technology,combining fuzzy algorithm and PID control method,identifying the transition process mode of the online system to get the PID parameters'self-adjusting,the magnetic bearing system's Fuzzy-PID nonlinear controller is designed by analyzing the system control demands.The Fuzzy-PID nonlinear controller can deal with the magnetic bearing system's open loop instability and strong nonlinearity,and the approach could improve the system's rapidity,adaptability,stability and dynamic characteristics.Comparative analysis and experiments are conducted between linear PID and nonlinear fuzzyPID control methods,the results show that the fuzzy-PID controller is better,and the five-freedom magnetic bearing's rotary precision experiments are conducted by the fuzzy-PID controller,it satisfies the control rotary precision demands and realizes the bearing's steady floating and rotating.

Experimental Observations of Cavitating Flows Around a Hydrofoil

ZHANG Min-di, WANG Guo-yu, DONG Zi-qiao, LI Xiang-bin, GAO De-ming

2008, 17(3): 274-279.

[Abstract](121)

Abstract:
The cavitation around a hydrofoil is studied experimentally tO shed light on the multiphase fluid dynamies.Different cavitation regimes are studied by using high speed visualization and particle image velocimetry(PIV).As decreasing the cavitation number,four cavitating flow regimes are observed:incipient cavitation,sheet cavitation,cloud cavitation,and supercavitation.From the incipient cavitation to the cloud cavitation,bubbles become more and more.Phenomena with large-scale vortex structure and rear re-entrant jet associated with the cloud cavitation,and subsequent development in the supercavitation are described.The velocity in the cavitation regions in the different cavitation conditions is low compared to that of the free stream.The large velocity gradient is also observed in the cavitating flow region near the suHace of the hydrofoil.

Development of a Composite Suspension with a Coil and Hydro-Pneumatic Spring

YANG Bo, CHEN Si-zhong, WU Zhi-cheng, YANG Lin

2008, 17(3): 280-284.

[Abstract](185)

Abstract:
A new composite suspension is developed,where a coil spring and a hydro-pneumatic spring are used in order to improve the poor reliability of off-road vehicle with pure hydro-pneumatic suspension.According to road conditions,the two springs play different roles.The method for matching the composite suspension stiffness and distributing the load is proposed.The working pressure of hydro-pneumatic spring as well as the load and stiffness characteristics of composite suspension is compared with a pure hydro-pneumatic suspension.In addition,the ISO weighted vehicle body acceleration,suspension travel and relative dynamic load of the wheels between two kinds of suspension are analyzed with a quarter vehicle mode.The simulation result shows that the developed composite suspension is more suitable for off-road vehicle than the one hydro-pneumatic suspension,because the composite suspension can reduce the working pressure, improve the reliability and keep a similar ride cornfort with hydro-pneumatic suspension.

Initiation Style Optimization of Aimed Warhead by Numerical Simulation

WEI Ji-feng, LI Na, WEN Yu-quan, WANG Wen-jie

2008, 17(3): 285-289.

[Abstract](188)

Abstract:
The kill characteristics of aimed warhead were studied.Emphasis on the improvement of initiation system,experiments and three dimensional numerical investigations were carried out.Simulation results of side three initiation points fit experiments well.Optimal initiation style is obtained through further simulation.It shows that the effective fragments and the effective kill energy of the optimal scheme increase 12.8%and 10.1%respectively.

EFP Warhead Missile Fuze Analysis and Simulation

LI Wei, FAN Ning-jun, WANG Zheng-jie

2008, 17(3): 290-293.

[Abstract](269)

Abstract:
The explosive formed penetrator(EFP)warhead missile projects the blast fragments in one direction normal to the missile longitudinal axis.Through analyzing on the two restrictions of EFP warhead explosion:trajectory restriction and attitude requirement,the concept of fuse time-delay tolerance is presented to be the measurement of the time of the EFP warhead explosion.The calculation models of fuze time-delaY tolerance under two restrictions are provided.Some crucial parameters playing important roles in calculation under attitude requirements are simulated.The simulation results show that the engagement plane angle,roll rate and warhead attack standoff influence the tolerance dramatically.

Locality Aware Optimal Task Scheduling Algorithm for TriBA——A Novel Scalable Architecture

KHAN Haroon-Ur-Rashid, SHI Feng

2008, 17(3): 294-299.

[Abstract](124)

Abstract:
An optimal algorithmic approach to task scheduling for,triplet based architecture(TriBA),is proposed in this paper.TriBA is considered to be a high performance,distributed parallel computing architecture.TriBA consists of a 2D grid of small,programmable processing units,each physically connected to its three neighbors.In parallel or distributed environment an efficient assignment of tasks to the processing elements is imperatire to achieve fast job turnaround time.Moreover,the sojourn time experienced by each individual job should be minimized.The arriving jobs are comprised of parallel applications,each consisting of multiple-independent tasks that must be instantaneously assigned to processor queues,as they arrive.The processors indeDendently and concurrently service these tasks.The key scheduling issues is,when some queue backlogs are small,an incoming job should first spread its tasks to those lightly loaded queues in order to take advantage of the parallel processing gain.Our algorithmic approach achieves optimality in task scheduling by assigning consecutive tasks to a triplet of processors exploiting locality in tasks.The experimental results show that tasks allocatian to triplets of processing elements is efficient and optimal.Comparison to well accepted interconnection strategy,2D mesh,is shown to prove the effectiveness of our algorithmic approach for TriBA.Finally we conclude that TriBA can be an efficient interconnection strategy for computations intensive applications,if tasks assignment is carried out optimally using algorithmic approach.

Feature Selection via Analysis of Relevance and Redundancy

WANG Sa, WANG Ke-yong, ZHENG Lian

2008, 17(3): 300-304.

[Abstract](204)

Abstract:
Feature selection is an important problem in pattern classification systems.High dimension fisher criterion(HDF)is a good indicator of class separability.However,calculating the high dimension fisher ratio is difficult.A new feature selection method,called fisher-and-correlation(FC),is proposed.The proposed method is combining fisher criterion and correlation criterion based on the analysis of feature relevance and redundancy.The proposed methodology is tested in five different classification applications.The presented resuits confirm that FC performs as well as HDF does at much lower computational complexity.

Dynamic Routing Algorithm for Increasing Robustness in Satellite Networks

LI Dong-ni, ZHANG Da-kun

2008, 17(3): 305-310.

[Abstract](112)

Abstract:
In low earth orbit(LEO)and medium earth orbit(MEO)satellite networks,the network topology changes rapidly because of the high relative speed movement of satellites.When some inter-satellite links (ISLs)fail,they can not be repaired in a short time.In order to increase the robustness for LEO/MEO satellite networks,an effective dynamic routing algorithm is proposed.All the routes to a certain node are found by constructing a destination oriented acyclic directed graph(DOADG)with the node as the destination.In this algorithm,multiple routes are provided,loop-free is guaranteed,and as long as the DOADG maintains,it is not necessary to reroute even if some ISLs fail.Simulation results show that comparing to the conventional routing algorithms,it is more efficient and reliable,costs less transmission overhead and converges faster.

Development of a High Power Programmable Precise Time-Delay Trigger/Ignition System for MFCG

WU Bi, HE Yuan-hang, ZHANG Qing-ming, MA Yue-fen

2008, 17(3): 311-315.

[Abstract](162)

Abstract:
High-power precise delay trigger/ignition system is a programmable pulse generator developed for experiment controlling in explosively driven magnetic flux compression generators.Precise delay pulses are generated by the digital circuit,after being magnified and sharpened through multistage isolated amplifiers and rising edge sharpening device,high-voltage steep delay pulses with precision less than us level are obtained.This system has been used in our compact magnetic flux compression generator experiments in place of the traditional primaeord delay device.

Non-overshooting and Non-undershooting Cubic Spline Interpolation for Empirical Mode Decomposition

YUAN Ye, MEI Wen-bo, WU Si-liang, YUAN Qi

2008, 17(3): 316-321.

[Abstract](222)

Abstract:
To suppress the overshoots and undershoots in the envelope fitting for empirical mode decomposition (EMD),an alternative cubic spline interpolation method without overshooting and undershooting is proposed.On the basis of the derived slope constraints of knots of a non-overshooting and non-undershooting cubic interpolant,together with"not-a-knot"conditions the cubic spline interpolants are constructed by replacing the requirement for equal second order derivatives at every knot with Brodlie's derivative formula.Analysis and simulation experiments shoW that this approach can effectively avoid generating new extrema,shifting or exaggerating the exiting ones in a signal,and thus significantly improve the decomposition performance of EMD.

Temporal Shape Error Concealment for Video Objects

YU Ye, XIE Xu-dong, LU Jian-hua, ZHENG Jun-li, CHEN Chang-wen

2008, 17(3): 322-329.

[Abstract](180)

Abstract:
A novel temporal shape error concealment technique is proposed,which can be used in the context of object-based video coding schemes.In order to reduce the effect of the shape variations of a video object,the curvature scale space(CSS)technique is adopted to extract features,and then these features are used for boundary matching between the current frame and the previous frame.Because the temporal,spatial and statistical video contour information are all considered,the proposed method can find the optimal matching,which is used to replace the damaged contours.The simulation results show that the proposed algorithm achieves better subjective,objective qualities and higher efficiency than those previously developed methods.

Channel Pre-emphasis Equalization for a 270 km 40×40 Gbit/s WDM System with Cascaded EDFAs/Raman Amplifiers

YANG Ai-ying, SUN Yu-nan

2008, 17(3): 330-334.

[Abstract](97)

Abstract:
Optical channel pre-emphasis equalization is experimentally researched for a 270 km 40×40 Gbit/s wavdength division multiplexing(WDM) transmission system with three Erbium-doped fiber amplifiers(EDFAs)and Raman amplifiers concatenated as booster amplifier.The channel imbalance of the overall system changes with different sets of power launched into EDFAs.By appropriately choosing the power input to concatenated EDFAs.the output spectrum of 40 channel signal can be equalized to the most extent.The merit of benefit can be around 5.5 dB by this pre-emphasis equalization.The requirement for the gain equalizer is therefore greatly released.Then the gain imbalance of the overall system and the power imbalance of 40 channels are compared and the two almost matches,but the significant difference lies on some channels.Finally,the pump power into Raman amplifier is also optimized,and another 1.3 dB improvement of channel equalization can be further achieved.

New Precision Guidance Method Based on Bistatic Synthetic Apterture Radar

YANG Chun, ZENG Tao

2008, 17(3): 335-340.

[Abstract](187)

Abstract:
A new method is presented to improve guidance precision.This method is based on histatic synthetic aperture radar.The illuminator works in side looking mode,providing the synthetic aperture and the receiver is disposed on the seeker which operates in the forward looking mode.The receiving antenna is composed of four sub-antennas and so four synthetic aperture radar(SAR)images are to be generated.Target is positioned in SAR images by image matching.The bearing and elevation of image element of target are measured by the principle of monopulse angular measurement.Theory of the proposed method is derived and simulation on bearing measurement is done.Simulation shows that the method is valid and if SNR of target's image is above 30 dB.the angular measuring difference is witbin the confines of 0.04 degree.

Minimal-Length Interoperability Test Sequences Generation via Genetic Algorithm

ZHONG Ning, KUANG Jing-ming, HE Zun-wen

2008, 17(3): 341-345.

[Abstract](195)

Abstract:
A novel interoperability test sequences optimization scheme is proposed in which the genetic algo-rithm(GA)is used to obtain the minimal-length interoperability test sequences.During our work,the basicin teroperability test sequences are generated based on the minimal-complete-coverage criterion,which removes the redundancy from conformance test sequences.Then interoperability sequences minimization problem can be considered as an instance of the set covering problem,and the GA is applied to remove redundancy in interoperability transitions.The results show that compared to conventional algorithm,the proposed algorithm is more practical to avoid the state space explosion problem,for it can reduce the length of the test sequences and maintain the same transition coverage.

Edge Detection Algorithm of SAR Images with Wedgelet Filter

REN Chao, WU Si-liang, JIAO Li-cheng

2008, 17(3): 346-350.

[Abstract](177)

Abstract:
Based on the analysis of the characteristics of synthetic aperture radar(SAR)images,a new edge detection method is proposed.The wedgelet transform is introduced into the area of SAR image speckle reduction for it can provide a nearly optimal representation for images in the horizon class.The wedgelet filter has good ability in keeping edge and speckle reduction.Then,a ratio edge detector is applied after a process of speckle reduction.The experimental results show that the method outperforms substantially others visually.

Effects of Forming Pressure on the Porosity of Polyimide Porous Materials

PU Yu-ping, LV Guang-shu, ZHAO Peng, XIAO Han-cheng

2008, 17(3): 351-354.

[Abstract](108)

Abstract:
Based on a series of experiments,the theory of relationship between normal pressure and pores' characters fit for polymer was set up for the first time.On the study of relation between normal pressure and porosity,experience model of polyimide porous materials was proposed which is similar to the traditional experience model of the metal porous material.While being pressed.polyimide was found soon to come into elastoplastic deformation progress in this paper,so the theory model of metal porous material based on Hooker's law Was not fit for the polymer any more.A new elasto-plastic deformation and exhausting model is proposed which shows better agreement with polymer material's pressing process.

Exact Solution of a Cylinder Tube Made of Metallic Foam Under Inner Pressure

ZHU Ai-yu, FAN Tian-you

2008, 17(3): 355-360.

[Abstract](223)

Abstract:
Exact solution of the stress and velocity fields of a cylinder tube of metallic foams under inner Pressure is given in which the Triantafillou and Gibson constitutive law(TG model)for the material is taken as a basis of the calculation.The nonlinear equation is turned linear equation by introducing a kinematics parameter.The differences between the full condensed materials and the effect of the relative densitv are also discussed.

Giant Magnetostrictive Material Exciter for Panel Loudspeaker

WANG Rui, ZHANG Yong-fa

2008, 17(3): 361-364.

[Abstract](211)

Abstract:
The exciter component in a panel loudspeaker has a profound effect on the overall performance of the system.The equivalent circuit analysis of the combination of giant magnetostrictive material exciter and distributed mode panel is introduced and how exciter parameters influence panel lffudspeaker's performance is discussed.NumericaI predictions are given in order to show how these influences are manifested.

Entanglement Transfer in a Four-Qubit Dimerized Heisenberg System

SHAO Bin, HUANG Min, WANG Zhao-ming, ZOU Jian

2008, 17(3): 365-367.

[Abstract](86)

Abstract:
Entanglement transfer is investigated in a dimerized Heisenberg system.Coneurrence as the measure of entanglement is calculated by the time-evolved state starting from an initially entangled state of spin pair.It is shown that perfect entanglement transfer can be realized at 80me special time and suitable interacting.

Geometrical Structures of Certain Class of Statistical Manifolds

ZHANG Zhen-ning, SUN Hua-fei, ZHONG Feng-wei

2008, 17(3): 368-371.

[Abstract](71)

Abstract:
The geometrical structures of the certain class of statistical manifolds are investigated.The geometrical metrics of such statistical manifolds are obtained,which includes the original geometrical metrics of S.Amari.

Simulation About the Growth of Chinese Firm's Safety Management Capability

LIU Tie-zhong, LI Zhi-xiang

2008, 17(3): 372-378.

[Abstract](101)

Abstract:
Aiming at the deficiency of exterminating measures of Chinese firm safety management,a simulation model of Chinese firm's safety management capability based on the organizational learning theory,in which the simulation method of system dynamics is utilized.The level variable and rate vailable are designed based on the practical situation and change situation of corresponding variables of firm's safety management capability.Simulation firms are built with accident ease groups of the oil industry,chemieal industry,machine industry,coal mining industry,and weapon industry.Through analyzing the simulation result,the growth law of Chinese firm's safety management capability is obtained as follows:the accumulating and the coupling of safety knowledge should be emphasized at the same time;the balance of learning behavior of individual,group and organization should be considered together;different types of Chinese firm should take different safety policies according to their practical situations.

2008 Vol. 17, No. 3