JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

Service Model for Multi-Provider IP Service Management

YU Cheng-zhi, SONG Han-tao, LIU Li

2005, 14(4): 353-358.

[Abstract](101)

Abstract:
In order to solve the problems associated with Internet IP services management, a generic service model for multi-provider IP service management is proposed, which is based on a generalization of the bandwidth broker idea introduced in the differentiated services (DiffServ) environment. This model consists of a hierarchy of service brokers, which makes it fit into providing end-to-end Internet services with QoS support. A simple and scalable mechanism is used to communicate with other cooperative domains to enable customers to dynamically setup services connections over multiple DiffServ domains. The simulation results show that the proposed model is real-time, which can deal with many flow requests in a short period of time, so that it is fit for the service management in a reasonably large network.

Improving Reactive Ad Hoc Routing Performance by Geographic Route Length

CAO Yuan-da, YU Yan-bing, LU Di

2005, 14(4): 359-364.

[Abstract](154)

Abstract:
In order to help reactive ad hoc routing protocols select better-performance routes, a novel metric named geographic route length (GRL) is proposed. The relationship between GRL metric and routing performance is analyzed in detail. Combined with hop metric, GRL is applied into the original ad hoc on-demand distance vector (AODV) to demonstrate its effectiveness. Simulation experiments have shown that GRL can effectively reduce packet delay and route discovery frequency, thus can improve reactive ad hoc routing performance.

Practical Algorithm for Real-Time Panorama Mosaic

PENG Qi-min, JIA Yun-de, LIU Yang

2005, 14(4): 365-368.

[Abstract](215)

Abstract:
A real-time algorithm for cylindrical panorama mosaic from un-calibrated images is presented. A novel scheme based on feature matching is proposed to align the images. Feature candidates are extracted with Plessy's corner detector and then are matched between consecutive frames based on FFT. Overlays between consecutive frames are detected with an improved two-step feature matching. Finally, the images are stitched by fusing in accordance with the found seam linked matched features. This method can be implemented efficiently and show robustness to varying illumination and perspective distortion.

Theoretical Calculation of Ultrashort-Pulse Optical Parametric Generation

LI Xu, ZHU Zhen-he, GU Tao, SUN Yu-nan

2005, 14(4): 369-372.

[Abstract](116)

Abstract:
A general theory of optical parametric generation that accounts for pump depletion, loss, phase mismatch, group-velocity mismatch among the pump, signal and idler pulses, and intrapulse group- velocity dispersion is proposed for coherent ultrashort pulses with arbitrary shapes and carrier chirps. The coupled differential equations are numerically solved using a symmetric split-step beam-propagation method. The general solutions of these equations are obtained and the optical parametric generation process is theoretically investigated. Results show that the major factors, which remarkably affect the optical parametric conversion efficiency and durations of the pulses in phase-matched structure, are the group velocity mismatch and the intrapulse group velocity dispersion.

Study on Burn-In and Screening Method for 1 310 nm InGaAsP Laser Diodes

SU Mei-kai, GAO Zhi-yun, LIU Bing-qi, ZUO Fang

2005, 14(4): 373-377.

[Abstract](78)

Abstract:
The accelerating burn-in and screening method of processing 1 310 nm InGaAsP of laser diodes (LDs) is introduced. It is confirmed that the theory of burn-in and screening is based on the second derivative minimum of burn-in curve, and the new testing method has been given, that is automatic current control (ACC) burn-in and automatic power control (APC) testing. This avoidably bring the errors of testing in only ACC or APC method, which need to monitor and control or test LDs power change by photo-detector (PD) at high temperature, and LDs or PDs must be into the same environment (PD will be burn-in at the same time). Through the experiment, the accelerating burn-in and screening condition of the devices has been confirmed: ACC, 200 mA,100 ℃, 8 h. This raise work efficiency 12 times than Bellcore standard and save testing fee.

Improved Approach Based on SVM for License Plate Character Recognition

WANG Xiao-hua, WANG Xiao-guang

2005, 14(4): 378-381.

[Abstract](202) [PDF 162KB](2)

Abstract:
An improved approach based on support vector machine (SVM) called the center distance ratio method is presented for license plate character recognition. First the support vectors are pre-extracted. A minimal set called the margin vector set, which contains all support vectors, is extracted. These margin vectors compose new training data and construct the classifier by using the general SVM optimized. The experimental results show that the improved SVM method does well at correct rate and training speed.

Realizable Hardware-Based Method for Digital Modulation Classification

HAN Li, WAN Jin-bo

2005, 14(4): 382-385.

[Abstract](185)

Abstract:
A new method suited for hardware implementation is developed to classify 8 different digital modulation types with raised cosine base-band impulse without knowing the carrier frequency and symbol timing. The normalized histogram of stagnation points for instantaneous parameters is used to recognize both ideal rectangular and raised cosine base-band digital signals. Carrier frequency estimation is used to enhance the recognition rate of phase-modulated signals. In the condition of 10 dB signal noise ratio (SNR), the recognizing rate is over 80%. The new algorithm is suited for hardware implementation.

Characteristic-Based Time Domain Method for Cylindrically Conformal Microstrip Patch Antennas

XU Xiao-wen, XIN Li

2005, 14(4): 386-390.

[Abstract](188)

Abstract:
The characteristics of a cylindrical conformal microstrip patch antenna are analyzed by using the characteristic-based time domain (CBTD) method. A governing equation in the cylindrical coordinate system is formulated directly to facilitate the analysis of cylindrically conformal microstrip patch antennas. The algorithm has second-order accuracy both in time and space domain and has the potential to eliminate the spurious wave reflection from the numerical boundaries of the computational domain. Numerical results demonstrate the important merits and accuracy of the proposed technique in computational electromagnetics.

Study on the Technique of Passive Millimeter Wave Detector

ZHANG Yan-mei

2005, 14(4): 391-395.

[Abstract](188)

Abstract:
In order to initiate the flight immediately when it reaches the top of the pedrail vehicle, technical parameters of radiometer have been designed and speedy effective signal processing method has been adopted.After analyzing the difference of signal characteristic between the main jam and the target, a method of identifying target in time domain is given. The target distinguishing rules are set up by extracting the magnitude, the slope and the width of the signal, combining with distinguishing the dimension of the target. The result of the theoretic analysis shows that the detecting scheme adopted can ensure the detector to identify and orientate the pedrail vehicle's top armour, as well as control the detonation precisely.

Design of Guided Air Ammunition's Optimal Guidance Law

LIU Min, LIU Zao-zhen, WANG Bao-cheng

2005, 14(4): 396-399.

[Abstract](182) [PDF 242KB](3)

Abstract:
Some long distance air ammunition can be used to attack large still target. According to this character and according to the mathematical description of target-missile relative motion built by the message supplied by the strapdown inertial navigation system/global position system (SINS/GPS) of air ammunition, optimal guidance law is designed by applying optimal control theory. The simulation is provided to indicate that when the air ammunition reaches the target, its line-of-sight (LOS) and LOS angular rate can nearly equal zero. So the air ammunition can get good terminal attitude, and the air ammunition reaches the target at the expected velocity and heading.

Realization Techniques of Virtual Assembly Process Planning System

LIU Jian-hua, NING Ru-xin, TANG Cheng-tong

2005, 14(4): 400-405.

[Abstract](185) [PDF 424KB](2)

Abstract:
The key realization techniques of virtual assembly process planning (VAPP) system are analyzed, including virtual assembly model, real-time collision detection, automatic constraint recognition algorithm, cable harness assembly process planning and visual assembly process plan at the workshop. A virtual assembly model based on hierarchical assembly task list (HATL) is put forward, in which assembly tasks are defined to express component assembling operations and are sequentially and hierarchically organized according to different subassemblies, which can perfectly model the construction process of product. And a multi-layer automatic geometry constraint recognition algorithm of how to identify assembly constraint relations in the virtual environment is proposed, then a four-layer collision detection algorithm is discussed. A VAPP system is built and some simple mechanical assemblies are used to illustrate the feasibility of the proposed method and algorithms.

Optimizing Spray and Combustion in Diesel Engine by Multidimensional Numerical Simulation

ZHOU Lei, ZHAO Chang-lu, ZHANG Fu-jun

2005, 14(4): 406-410.

[Abstract](158) [PDF 467KB](2)

Abstract:
The calculation of spray and combustion in diesel engines is described by using the softwares FIRE and BOOST. The application of the resulting computational method to the simulation of fuel spray and breakup, mixture formation and combustion in a heavy duty diesel is presented. According to detailed insight into the governing processes provided by the simulation results, various aspects of the dependence of the spray propagation and combustion on the chamber geometry and spray angle are discussed. Then, global cylinder- averaged pressure traces are extracted from the space and time resolved field quantities and compared to in-cylinder pressure measurements. Finally, an optimized configuration of the chamber geometry and spray angle with a new injection rate of higher injection pressure is proposed.

Characteristics of Vibration Induced by Cavitation

WANG Guo-yu, TAO Lei, LIU Shu-yan, QIAN Jian-jun

2005, 14(4): 411-415.

[Abstract](179)

Abstract:
Cavitation-induced vibration characteristics and the relations between the vibration and cavitation are studied. Cavitation vibrations are measured around a model hollow-jet valve by an accelerometer under cavitating and non-cavitating conditions. The measurement data is analyzed by FFT method. The corresponding cavitating flow patterns are photographed by a high-speed camera with an xenon flash lamp. The frequency band of the vibration induced by cavitation is determined. To compare the vibration intensities under different cavitation conditions, a definition of vibration acceleration level is introduced based on power spectral density of the vibration. By the analysis of vibration, the definitions of characteristic cavitation number are suggested. According to these cavitation numbers, the cavitation process is divided into three stages, that is, incipient cavitation, subcavitation and supercavitation.

Combined Reconstructive and Displacive Mechanisms Involved in Bainitic Transformation

SU Tie-jian, LI Shu-kui, WANG Fu-chi

2005, 14(4): 416-419.

[Abstract](267)

Abstract:
TEM observation and analysis have been conducted on bainitic transformation with and without the influence of externally applied tensile stress for alloyed steel 35MV7. Recrystallization was found to occur within the bainitic structures transformed at 450 ℃ in cases of both with and without the application of external stress, and coupling between the reconstructive and displacive mechanisms is expected, due to the relatively high holding temperature and high dislocation density yielded with the displacive mechanism. Recrystallization was not observed within the bainitic structures transformed at lower temperature of 350 ℃, both with and without the application of stress; However, for the stressed specimen, the structure with very fine subgrains was found to be preserved and not reconstructed thermically, due to the low temperature and short holding time.

Determination of 9-Deoxo-9a-Aza-9a-Homoerythromycin A and Related Substances by High-Performance Liquid Chromatography

SHI Ying, YAO Guo-wei, OU Yu-xiang, MA Min

2005, 14(4): 420-424.

[Abstract](132)

Abstract:
A high-performance liquid chromatography(HPLC) method was developed and validated for the assay of 9-deoxo-9a-aza-9a-homoerythromycin A and related substances that might coexist in products as impurities that originate from the synthesis processes. A chromatographic system comprising an ODS 150 mm× 4.6 mm I.D. column, a mobile phase of cetonitrile monobasic potassium phosphate buffer (25/75), a flow rate of 1.2 mL/min, a temperature of 30 ℃ and a UV detector set at 205 nm has shown good chromatographic separation for 9-deoxo-9a-aza-9a-homoerythromycin A and other related substances. The linearity of the calibration curves, the precision, expressed as relative standard deviations, of the HPLC method have been studied. The HPLC method under study was found to be specific, precise, accurate and reproducible, indicating stability.

Crystal Structure and Spectrum Character of Bis[1-(4-Methoxyphenyl)-3-(1H-1,2,4-Triazol-1-yl)-1-Propanone] dichorozinc(Ⅱ) Complex

CAO Ke-guang, WANG Zhong-wei, SUN Cheng-hui, ZHAO Xin-qi

2005, 14(4): 425-428.

[Abstract](58)

Abstract:
The titled new complex was synthesized and determined by X-ray diffraction. The crystal belongs to monoclinic, P-1 group, a=1.899 7（4） nm, b=0.581 07（12） nm, c=2.420 9（5） nm, β=90.65（3）°, V=2.672 2（9） nm³, Z=4, D_c=1.488 g/cm³. It has C₂symmetry with the axis through the Zn atom, and the zinc atom is coordinated by two N atoms of the 1-（4-methoxyphenyl）-3-（1H-1,2,4-triazol-1-yl）-1-propanone ligands and two Cl^-atoms, forming a slightly distorted tetrahedron. Intermolecular hydrogen bonds make the complex stable. IR and electronic spectra study of the target complex were also carried.

New Approach to Synthesis of Naftidrofuryl

ZHOU Zhi-ming, LIANG Yin, YU Cong-xuan

2005, 14(4): 428-432.

[Abstract](259) [PDF 147KB](186)

Abstract:
A new method of synthesizing N, N-(diethylamino)ethyl-2-(1-naphthylmethyl)-3-tetrahydrofurfuryl propionate was proposed. The key intermediate diethyl tetrahydrofurfuryl propionate was synthesized by acylation of p-toluenesulfo-chloride with tetrahydrofurfuryl alcohol,then by alkylation of tetrahydro-furfuryl p-toluenesulfonate with diethyl malonate. The yield of N,N-(diethylamino)ethyl-2-(1-naphthyl-methyl)-3-tetrahydrofurfuryl propionate was raised from 34.0% to 46.4%; the reaction time was greatly shortened. The method described is feasible with higher yield, and has industrial prospects.

Improved Electrochemical Performance of Surface-Modified Metal Hydride Electrodes

YANG Kai, WU Feng, CHEN Shi, ZHANG Cun-zhong

2005, 14(4): 433-437.

[Abstract](59)

Abstract:
A novel plating process was applied to the surface modification of the metal hydride (MH) electrode of the MH/Ni batteries. The electrode was plated with a thin nickel film about 0.1 μm thick by using multi-arc ion plating technique. The X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) were used to analyze the electrodes. Influence of the surface modification on the performance of the MH/Ni batteries was studied. It is shown that the surface modification could enhance the electrode conductivity and decrease the batteries ohimic resistance by 28.2%. After surface modification, the discharge capacity of the batteries at 5C (8.5 A) is increased by 212 mA·h and discharge voltage is increased by 0.09 V. The surface modification also improves the cyclic durability of the batteries. The inner pressure of the batteries with modified electrode during overcharging is much lower than that with unmodified electrode. The experimental results demonstrate that this process is an effective way for the surface modification of the electrode of MH/Ni batteries.

Effect of Overcharge on Electrochemical Performance of Sealed-Type Nickel/Metal Hydride Batteries

LI Li, WU Feng, CHEN Ren-jie, CHEN Shi

2005, 14(4): 438-441.

[Abstract](74)

Abstract:
The effects of overcharge on electrochemical performance of AA size sealed-type nickel/metal hydride(Ni/MH) batteries and its degradation mechanism were investigated. The results indicated that the relationship between the effects of different overcharge currents on the increasing velocity of inner pressure and the degradation velocity of cycle life and discharge voltage remains in almost direct proportion. After overcharge cycles, the positive electrode materials remain the original structure, but there occur some breaks because of the irreversible expand of crystal lattice. And the negative electrode alloy particles have inconspicuous pulverization, but are covered with lots of corrosive products and its main component is rare earth hydroxide or oxide. These are all the main reasons leading to the degradation behavior of the discharge capacity and cycle life of Ni/MH batteries.

Quantum Entropy of a Cooper-Pair Box in a Single-Mode Cavity Field

ZHANG Chun-yu, ZOU Jian, SHAO Bin

2005, 14(4): 442-444.

[Abstract](181)

Abstract:
A Cooper-pair box biased by a classical voltage and also irradiated by a squeezed state field is considered in order to find new ways to quantum communication and calculation. The quantum dynamics of the Cooper-pair box and the entanglement which is the core theoretics of quantum communication and calculation is investigated in this system, which is related to the squeezing parameter of the squeezed state. A model of Hamiltonian which represents the interaction between box and quantum field is introduced. Finally, the relationship between the entanglement and the squeezing parameter of the squeezed state is demonstrated.

On the ｛P₂,P₃｝-Factor of Cubic Graphs

GOU Kui-xiang, SUN Liang

2005, 14(4): 445-448.

[Abstract](121)

Abstract:
Let G=（V,E） be a finite simple graph and P_ndenote the path of order n. A spanning subgraph F is called a ｛P₂,P₃｝-factor of G if each component of F is isomorphic to P₂or P₃. With the path-covering method, it is proved that any connected cubic graph with at least 5 vertices has a ｛P₂,P₃｝-factor F such that |P₃（F）|≥|P₂（F）|, where P₂（F） and P₃（F） denote the set of components of P₂and P₃in F, respectively.

Existence Results of Third Order Multi-Point Boundary Value Problem at Resonance

DU Zeng-ji, BAI Zhan-bing, GE Wei-gao

2005, 14(4): 449-452.

[Abstract](181)

Abstract:
A kind of third order multi-point boundary value problems, x（t）=f（t,x（t）,x′（t）,x″（t））+ e（t）, t∈（0,1）,x（0）=αx（ξ）,x′（0）=0,x（1）=∑m-2j=1β_jx（η_j）, f∈C[0,1]×R³,e（t）∈L¹[0,1],α≥0, is considered, all the β_j's have not the same sign, 0 <ξ<1,0<η_{1
<η_{2<…
<η_{m-2 <1. By using the coincidence degree theory, some existence theorems for the problems at resonance are obtained.}}}

On the Supereulerian Index of a Graph

XIONG Li-ming, YAN Hui-ya

2005, 14(4): 453-457.

[Abstract](192)

Abstract:
Two methods for determining the supereulerian index of a graph G are given. A sharp upper bound and a sharp lower bound on the supereulerian index by studying the branch-bonds of G are got.

Ranking Method for Complementary Judgment Matrixes with Fuzzy Numbers Based on Hausdorff Metric Distance

HOU Fu-jun, WU Qi-zong

2005, 14(4): 458-461.

[Abstract](346)

Abstract:
A method for ranking complementary judgment matrixes with traspezoidal fuzzy numbers based on Hausdorff metric distance and fuzzy compromise decision approach is proposed. With regard to fuzzy number complementary judgment matrixes given by a decider group whose members have various weights, the experts information was aggregated first by means of simple weight average(SWA) method and Bonissone calculational method. Hence a matrix including all the experts' preference information was got. Then the matrix' column members were added up and the fuzzy evaluation values of the alternatives were got. Lastly, the Hausdorff metric distance and fuzzy compromise decision approach were used to rank the fuzzy evaluation values and then the ranking values of all the alternatives were got. Because exact numbers and triangular fuzzy numbers could all be transformed into trapezoidal fuzzy numbers, the method developed can rank complementary judgment matrixes with trapezoidal fuzzy numbers, triangular fuzzy numbers and exact numbers as well. An illustrative example is also given to verify the developed method and to demonstrate its feasibility and practicality.

Measuring Marketing Performance: Investigation into Practice and Certification

WANG Xiu-cun, LU Bin-bin

2005, 14(4): 462-466.

[Abstract](177)

Abstract:
The content validity of marketing performance measurement metrics in China is reported. Based on the respondents in the research, the statistic analysis of relative importance, and the frequencies of use of marketing metrics are given. It is shown that the marketing metrics are consistent with market orientation, sectors and the role of managers, that affect the way in measuring marketing performance. The investigation results provide certified basis for developing marketing performance assessment systems in Chinese enterprises.

Intrusion Detection Approach Using Connectionist Expert System

MA Rui, LIU Yu-shu, DU Yan-hui

2005, 14(4): 467-470.

[Abstract](162)

Abstract:
In order to improve the detection efficiency of rule-based expert systems, an intrusion detection approach using connectionist expert system is proposed. The approach converts the AND/OR nodes into the corresponding neurons, adopts the three-layered feed forward network with full interconnection between layers, translates the feature values into the continuous values belong to the interval [0,1], shows the confidence degree about intrusion detection rules using the weight values of the neural networks and makes uncertain inference with sigmoid function. Compared with the rule-based expert system, the neural network expert system improves the inference efficiency.

New Regional Satellite Positioning Constellation Scheme Discussion

CHU Hai-bin, ZHANG Nai-tong, GU Xue-mai

2005, 14(4): 471-476.

[Abstract](110)

Abstract:
The characteristics of present “Beidou” satellite positioning system are analyzed. In order to perfect our country regional satellite positioning system, the idea of “Beidou” geosychronous earth orbit (GEO) satellites combined with some middle earth orbit (MEO) satellites constellation is put forward. The details of general satellite constellation optimized method are described, using this method the multiple positioning constellation design results are gained. And those results belong to two type of schems, one is 2 GEO plus some MEO satellites and the other is 3 GEO plus some MEO satellites. Through simulation and comparison, among those multiple design results, final optimized regional positioning constellation is given. In order to check the chosen constellation cover performance, the position dilution of precision(PDOP) is calculated, and with satellite constellation simulation software Satlab many coverage performances of the chosen constellation substellar point track, elevation, azimuth and visible satellites number changing situation are also simulated.

Experimental Study on Single Ignition Characteristics of Mixed Solid and Liquid Fuel

WANG De-run, SHEN Zhao-wu, ZHOU Ting-qing

2005, 14(4): 477-480.

[Abstract](207)

Abstract:
In order to probe into the single ignition characteristics of mixed solid and liquid fuel, optical and electrical experiments on unconfined volume dispersion and single ignition of few dosage of ternary fuel mixture are successfully done. Experimental results show that cloud detonation is distinguished from explosion of trinitrotoluene charge. The single ignition process of mixed fuel containing aluminum powder(Al), propylene oxide(PO) and explosive (TNT) can be divided into four stages, the overpressure within its explosion field first increases, then decays with increase of distance. Explosion effects can be enhanced with adding proper trinitrotoluene into fuel mixture, the optimized ratio is m(Al)∶m(PO)∶m(TNT)=55∶35∶10. The overpressure of binary mixed fuel containing Al and TNT decays like trinitrotoluene charge with increase of distance, but its value is higher than the trinitrotoluene charge's in the same mass at longer distance. The continual action time of plus overpressure during cloud detonation reaches magnitude of 10 ms and is about 100 times longer than the trinitrotoluene charge's.

2005 Vol. 14, No. 4