JOURNAL OF BEIJING INSTITUTE OF TECHNOLOGY

YAN Ting, YAN Wei, SHEN Cheng-wu, LI Zhi-da

2007, 16(3): 253-255.

[Abstract](151)

Abstract:
There are many forms of tensor theory which are quite different.Discussions are put forward and their relationships are found.The differences between them depend on whether there is metric on the space and the basis is orthonormal.

Field Method for Integrating the First Order Differential Equation

JIA Li-qun, ZHENG Shi-wang, ZHANG Yao-yu

2007, 16(3): 256-258.

[Abstract](175)

Abstract:
An important modern method in analytical mechanics for finding the integral,which is called the field-method,is used to research the solution of a differential equation of the first order.First,by introducing an intermediate variable,a more complicated differential equation of the first order can be expressed by two simple differential equations of the first order,then the field-method in analytical mechanics is introduced for solving the two differential equations of the first order.The conclusion shows that the field-method in analytical mechanics can be fully used to find the solutions of a differential equation of the first order,thus a new method for finding the solutions of the first order is provided.

Lie Symmetry and Hojman Conserved Quantity of Maggi Equations

HU Chu-le, XIE Jia-fang

2007, 16(3): 259-261.

[Abstract](254)

Abstract:
Lie symmetry of Maggi equations is studied.Its determining equation and restriction equation of nonholonomic constraint are given.A Hojman conserved quantity can be deduced directly by using the Lie symmetry.An example is given to illustrate the application of the result.

Markov Chain for Reuse Strategies of Product Families

LUO Jia, JIANG Lan

2007, 16(3): 262-267.

[Abstract](95)

Abstract:
A methodology is presented to plan reuse strategies of common modules in a product family by using the concepts of function degradation,reliability,function requirement,cost and life time.Markov chain model is employed to predict function degradation and reliability.A utility model is used to evaluate the preference between used modules and new modules.An example of cascading-requirment product family illustrates the main ideas of our work.The Markov models are used effectively to predict function degradation and reliability.Utility theory is helpful to evaluate the reuse options of common modules.

Reliability Allocation and Optimization of Engine System by Using Genetic Algorithm and Monte Carlo Method

LIU Xing-hua, XU Gui-hong, MA Chao-chen, LI Shu-fen

2007, 16(3): 268-273.

[Abstract](201)

Abstract:
A new reliability allocation model has been built for engine system,which is a repairable system,and consists of a large number of mechanical components.The cost and reliability are taken as objective function and constraint condition respectively.The parameters of components lifetime distribution are given as decision variables,and the component lifetimes are assumed to follow that Weibull distribution.The allocation is separated into two steps to reduce calculated amount of one allocation.Genetic algorithm and Monte Carlo method are applied to solve distribution parameters and system cost separately.

Three-Dimensional Models for Analyzing the Cyclic Variations in a Lean Burn CNG Engine

LI Guo-xiu, YU Yu-song, LIU Jian-ying

2007, 16(3): 274-278.

[Abstract](97)

Abstract:
Three-dimensional models,consisting of the flame kernel formation model,flame kernel development model and natural gas single step reaction model,are used to analyze the contribution of cyclic equivalence ratio variations to cyclic variations in the compressed natural gas(CNG)lean burn spark ignition engine.Computational results including the contributions of equivalence ratio cyclic variations to each combustion stage and effects of engine speed to the extent of combustion variations are discussed.It is concluded that the equivalence ratio variations affect mostly the main stage of combustion and hardly influence initial kernel development stage.

Design and Trafficability Study of Flexible Wheel for Planetary Exploration Rover

LI Wen, GAO Feng, XU Guo-yan

2007, 16(3): 279-283.

[Abstract](133)

Abstract:
To reduce sending costs,a flexible wheel configuration is proposed.The wheel is made of titanium alloy(Ti-6Al-4V)in consideration of the planetary environment factors(i.e.strong radiation,big temperature differences,high vacuum),and mass constraint of launch vehicle.The advantages of the proposed wheel involves the potential for:① small sending volume and mass,② large deployed area and volume to reduce wheel loading,③ a damping effect to smooth motion on rough terrain.To study the trafficability and tractive performance of the wheel concept,the drawbar pull and driven torque were calculated based on simplified model of terramechanics formulations.The results show that the wheel possesses sufficient drawbar pull to negotiate all types of soil stratums listed in this contribution.

New Technique for Estimating and Suppressing Narrowband Interference in DSSS Systems

XIA Cai-jie, AN Jian-ping, WANG Ai-hua

2007, 16(3): 284-289.

[Abstract](148)

Abstract:
A generalized approach for narrowband interference(NBI)suppression in direct sequence spread spectrum(DSSS)communication systems using adaptive infinite impulse response(IIR)filter is presented.The excision filter coefficients depend on both the jammer power and its instantaneous frequency.The dependency of the filter construction on the jammer power is significant as it allows optimal tradeoff between interference removal and signal distortion by maximizing the receiver signal to noise ratio improvement(SNRI).Instead of traditional adaptive line enhancer(ALE)estimator,a preferable NBI estimator-Fourier interpolation estimator(FIE)is proposed.Closed-form expressions of the SNR improvement and theoretical bit error rate(BER)based on the assumption that the output of the correlator is Gaussian distributed are both derived.Performance results obtained by numerical simulation are also presented and compared with theoretical results.

Novel Channel Estimation Method in Broadband MIMO-OFDM Systems

JIAO Hui-ying, AN Jian-ping

2007, 16(3): 290-294.

[Abstract](193)

Abstract:
A least square(LS)parametric channel estimation method in broadband multiple input multiple output(MIMO)orthogonal frequency division multiplexing(OFDM)systems is proposed.The mean square error(MSE)performance using optimal training pilots is also given,which proves the method can improve the estimation precision greatly in sparse channel.Since such method needs the multi-path time delays information of the channel,the probabilistic data association(PDA)method is employed to estimate the time delay of each path.Simulation results show that both the bit error rate(BER)and the MSE performance of the proposed method are better than the traditional LS channel estimation method.

Heuristic Reduction Algorithm Based on Pairwise Positive Region

QI Li, LIU Yu-shu

2007, 16(3): 295-299.

[Abstract](204)

Abstract:
To guarantee the optimal reduct set,a heuristic reduction algorithm is proposed,which considers the distinguishing information between the members of each pair decision classes.Firstly the pairwise positive region is defined,based on which the pairwise significance measure is calculated between the members of each pair classes.Finally the weighted pairwise significance of attribute is used as the attribute reduction criterion,which indicates the necessity of attributes very well.By introducing the noise tolerance factor,the new algorithm can tolerate noise to some extent.Experimental results show the advantages of our novel heuristic reduction algorithm over the traditional attribute dependency based algorithm.

Improved Support Vector Machine Approach Based on Determining Thresholds Automatically

WANG Xiao-hua, YAN Xue-mei, WANG Xiao-guang

2007, 16(3): 300-304.

[Abstract](187)

Abstract:
To improve the training speed of support vector machine(SVM),a method called improved center distance ratio method(ICDRM)with determining thresholds automatically is presented here without reduce the identification rate.In this method border vectors are chosen from the given samples by comparing sample vectors with center distance ratio in advance.The number of training samples is reduced greatly and the training speed is improved.This method is used to the identification for license plate characters.Experimental results show that the improved SVM method—ICDRM does well at identification rate and training speed.

Performance Analysis of Distributed Neyman-Pearson Detection Systems

ZHAO Juan, TAO Ran, WANG Yue, ZHOU Si-yong

2007, 16(3): 305-309.

[Abstract](149)

Abstract:
The performance of a distributed Neyman-Pearson detection system is considered with the decision rules of the sensors given and the decisions from different sensors being mutually independent conditioned on both hypothese.To achieve the better performance at the fusion center for a general detection system of n>3 sensor configuration,the necessary and sufficient conditions are derived by comparing the probability of detection at the fusion center with that of each of the sensors,with the constraint that the probability of false alarm at the fusion center is equal to that of the sensor.The conditions are related with the performances of the sensors and using the results we can predict the performance at the fusion center of a distributed detection system and can choose appropriate sensors to construct efficient distributed detection systems.

Some Pathological Knowledge Discovered in Large Database of Type 2 Diabetes

LUO Sen-lin, GAO Juan, JIA Hong-bo, WANG Heng, ZHANG Tie-mei, HAN Yi-wen

2007, 16(3): 310-314.

[Abstract](97)

Abstract:
Taking the advantage of the nearly 14 000 items of multi-source,multi-dimension practical dataset of type 2 diabetes,and a series of data mining experiments are designed to seek for important type 2 diabetes risk factors and their relationships with blood glucose.The valuable pathological knowledge includes,the decision tree is almost identical with the list of clinical diabetic risk factors;9 items important risk factors of type 2 diabetes were found,and the relationship between the main risk factors and the blood glucose,and the feature of critical value of the risk factors were given too in this paper.These valuable results are good to the cure and macro-control type 2 diabetes.

EyeScreen:A Vision-Based Gesture Interaction System

LI Shan-qing, XU Yi-hua, JIA Yun-de

2007, 16(3): 315-320.

[Abstract](171)

Abstract:
EyeScreen is a vision-based interaction system which provides a natural gesture interface for human-computer interaction(HCI)by tracking human fingers and recognizing gestures.Multi-view video images are captured by two cameras facing a computer screen,which can be used to detect clicking actions of a fingertip and improve the recognition rate.The system enables users to directly interact with rendered objects on the screen.Robustness of the system has been verified by extensive experiments with different user scenarios.EyeScreen can be used in many applications such as intelligent interaction and digital entertainment.

Explosive Ferroelectric Power Supply of Flux Compression Generator

WANG De-wu, HE Yuan-ji, TAN Hui-min

2007, 16(3): 321-325.

[Abstract](189)

Abstract:
Useful electrical pulses of a few hundred kilowatts lasting for several microseconds can be obtained by the depolarization process of PZT95/5 ferroelectric ceramics.In this paper,taking account of the dielectric relaxation,and finite resistance,a new mathematical model of PZT95/5 ferroelectric ceramics subjected to normal-mode shock wave is suggested.Explosive shock wave techniques have also been used to investigate the response of PZT95/5 ferroelectric ceramics with inductive loads in experiments.The predictions from the model have a good agreement with observed results.In addition,an explosive ferroelectric generator composed of explosive shock wave generators,electric units,and additional capacitors is design to power small-size helical flux compression generators.The test results with the maximal output energy of up to 80 J are given and experimental results are also considered.

Fizeau Interferometery for THz-Waves' Frequency and Intensity Measurement

SIDDIQUE Muhammad, YANG Su-hui, LI Zhuo, LI Ping

2007, 16(3): 326-329.

[Abstract](272)

Abstract:
A terahertz-wave generator based on optical parametric oscillator principle,detection based on combination of Fizeau wedged interferometer and an electro-optical crystal ZnTe has been studied.The analytical solution based on the basic principle of operation of solid wedge Fizeau interferometer has been realized.The mathematical calculations for THz frequency and intensity measurement dependent on wedge angle and fringe spacing have been considered.The efficiency of THz wave detection depends upon optimized wedge angle has been also realized.The feasibility of detection of THz waves' frequency and intensity by solid Fizeau interferometer(THz-waves' range of 1-3 THz)has been studied.By optimization of other parameters like thickness of Fizeau film,refractive index,material of Fizeau film,we can proceed towards the design of Fizeau interferometer for required research plans as it is a simple and inexpensive interferometer.

FDTD Computation of Scattering by Buried Objects

ZHANG Xiao-yan, SHENG Xin-qing

2007, 16(3): 330-334.

[Abstract](165)

Abstract:
A computational approach of scattering by buried objects is presented by using finite-difference time-domain(FDTD)method,the uniaxial perfectly matched layer(UPML),and reciprocity theorem.The numerical performance of this approach is investigated by numerical experiments.The radar cross sections(RCS)of various buried objects with different electrical sizes,shapes,dielectric constants,are computed and analyzed.The results show that for the conducting cube,the RCS curves are fluctuant,but for the sphere shape one,the curves are smooth.Comparing with scattering in the free space,the ground greatly affects the RCS by dielectric targets,but little does by conducting targets.For the buried dielectric objects,iterative steps can be evaluated by four to five round-trip traversals of the Huygens box,but for the conducting ones,the time steps can be reduced to three round-trip traversals.When the ground is lossy,the run-time can be reduced more to two round-trip traversals.

Model and Emulation of the System for the Passive Electrostatic Detecting People Through the Medium

HAN Lei, CUI Zhan-zhong

2007, 16(3): 335-339.

[Abstract](209)

Abstract:
The plane medium and point charge are regarded as an integral system.The static field's distribution situation of the point charge is studied in the medium structure of plane division layers by using mirror image method,drawing the point charge's calculation expression of the electric potential in every medium space.The mathematics model of passive electrostatic detecting people through the medium(regular distance between the goal point charge and the medium)is established,using MATLAB software to carry out emulation of the model and analysing the result,establishing the theoretical foundation for studying the technology of the passive static detecting people through the wall.

Preparation and Property of Bisphenol A Bis (diphenyl phosphate) Oligomer

LI Bing-hai, OU Yu-xiang, XIN Fei

2007, 16(3): 340-345.

[Abstract](137)

Abstract:
Bisphenol A bis(diphenyl phosphate)oligomer(BDP)is prepared successfully from the reactants consisting of phosphorus oxychloride(POCl3),bisphenol A and phenol with a Friedel-Crafts catalyst.The resultant products were examined with thermo-gravimetric analysis(TGA)and high performance liquid chromatography(HPLC).Thermogravimetry data shows that BDP decomposes at 375 ℃ when 5% weight lost.Experiments results show that catalyst is preferably AlCl3 and the amount of it is preferably 1% relative to bisphenol A by mole.POCl3/bisphenol A mole ratio is preferably about 5∶1 to 6∶1.Experiments unclosed that a seal apparatus is very important to the properties of product.

Synthesis and Aqueous Solution Viscosity of Hydrophobically Modified Xanthan Gum

QIAN Xiao-lin, WU Wen-hui, YU Pei-zhi, WANG Jian-quan

2007, 16(3): 346-351.

[Abstract](179)

Abstract:
Two xanthan gum derivatives hydrophobically modified by 4 or 8 tetradecyl chains per 100 xanthan gum structure units were synthesized.The derivatives were studied by scanning electron microscope and pyrene fluorescence spectrometry.And the aqueous solution apparent viscosity of the derivatives was investigated.The results indicate that the network of the derivatives with more hydrophobic groups is closer and tighter.With increasing of alkyl chain substitution degree,the hydrophobically associating interactions enhance in aqueous solution.Aqueous solution apparent viscosity of the derivatives increases with increasing of polymer concentration and alkyl substitution degree,and decreases with the increase of temperature.In the brine solution,the strong viscosity enhancement phenomenon appears.The interaction between the derivatives and surfactant sodium dodecylbenzene sulfonate is strong.

Organomontmorillonites Modified with 2-Methacryloyloxy Ethyl Alkyl Dimethyl Ammonium Bromide

WANG Jian-quan, WU Wen-hui

2007, 16(3): 352-357.

[Abstract](108)

Abstract:
Organomontmorillonites(organo-MMT)were synthesized by means of montmorillonites(MMT)modified with a series of 2-methacryloyloxy ethyl alkyl dimethyl ammonium bromide(MAAB)having different alkyl chain lengths as cationic surfactants through a cationic exchanging reaction,and were characterized by FTIR,TG,elemental analysis,and XRD.The microenvironment of the organic interlayer such as the orientation and arrangement of the alkyl chains of MAAB,as well as the properties of nanocomposite hydrogels,were also investigated.The amount of organic components absorbed on interlayer and the basal spacing of organo-MMT both increase with the increasing of alkyl length of MAAB.When carbon number of alkyl chain is in the region of 8 to 14,the alkyl chains between layers would adopt a disordered gauche conformation;while the carbon number is 16,an ordered all-trans conformation with a vertical orientation would be found together with the disordered gauche conformation according to the results of XRD and FTIR.Due to the difference of microenvironment of organic interlayer,the Young's moduli of the nanocomposite hydrogels increased as the alkyl chains of MAAB became longer.

Photoinduced DNA Cleavage of Fullerols,Water-Soluble Polyhydroxylated [C₆₀] Fullerene Derivatives

QIAO Xin-ge, YANG Xin-lin, HUANG Cheng, TAN Xin, ZHANG Yu-fei, ZHAO Dong-xu, LI Wei-jing, YU Qun

2007, 16(3): 358-362.

[Abstract](99)

Abstract:
The effects of polyhydroxylated [C60] fullerene derivatives fullerols on DNA was studied,using the plasmid pXJ41-neo DNA as the experimental model.The cleaved DNA products were detected by agarose gel electrophoresis.The results showed that fullerols could stimulate DNA cleavage in dose and irradiation dependent manners.0.4 mmol/L fullerols together with 1.5 h exposure to a 500 W tungsten halogen lamp at a distance of 20 cm could convert most of plasmid DNA from the intact form into the nicked and linear forms.Scavengers of various reactive oxygen species(ROS)including sodium azide,mannitol and superoxide dismutase(SOD)could inhibit the photoinduced DNA cleavage of fullerols.These data presented for the first time the photoinduced biological activities of fullerols,and implied a possible use of these fullerene derivatives as the candidates for novel photosensitizers in the biomedical therapy.

New Advanced Technology on Waste Resourcelization of the Black Pulping Liquor

ZHOU Yi, HAN Yuan-yuan, ZHANG Dong-xiang

2007, 16(3): 363-368.

[Abstract](65)

Abstract:
Combining the characteristics of the black pulping liquor that contains a lot of lignin and other biomass resources,the technology of comprehensive waste utilization is employed.The reconstructive preparation of modified urea-formaldehyde glue by adding black pulping liquor and the application in extruding the medium density fibre board using this modified urea-formaldehyde glue is researched.Results show that when applying the preparation technology that alkaline reaction and then weak acid reaction,the appropriate preparation process is as follows:the adding urea process is divided into three stages(proportion 2∶1∶1);the pH value is 8.0,and the reaction time is 40 min in the addition reaction stage;the pH value will be naturally reduced to 3.5-5.0,and the reaction time is 45 min in the aggregation reaction stage;the pH value is 8.0 in the urea complement stage.And the optimal condition of the reconstructive preparation the modified urea-formaldehyde glue is adding the condensed black pulping liquor after hydroxymethylation in the beginning of polycondensation reaction by 5% proportion.The application in extruding medium density fibre board with this modified urea-fosmaldehyde glue is proved feasible.

Enhanced Nutrient Removal with Upflow Biological Aerated Filter for Reclaimed Water

WANG Hai-dong, PENG Yong-zhen, WANG Shu-ying, ZHANG Yan-ping

2007, 16(3): 369-374.

[Abstract](162)

Abstract:
A two-stage upflow biological aerated filter was designed as an advanced treatment process to optimize the operating parameters and study the correlative factors influencing the efficiency of nitrification,denitrification and phosphorus removal.The experimental results showed that the final effluent of the two-stage upflow biofilter process operated in series could meet the stringent limits of the reclaimed water for the total nitrogen of 2 mg/L,and total phosphorus of 0.3 mg/L.The high treatment efficiency allowed the reactor operating at very high hydraulic loadings and reaching nearly complete nitrification and denitrification.

Fast Diagnosis of Transient Plasma by Langmuir Probe

TANG En-ling, ZHANG Qing-ming, OUYANG Ji-ting

2007, 16(3): 375-378.

[Abstract](101)

Abstract:
A method for the fast measurement of electron temperature and density with temporal resolution in transient plasma has been implemented by Langmuir probe.The diagnostic system consists of a single Langmuir probe driven by a high frequency sinusoidal voltage.The current and voltage spectrum on the probe were detected synchronously by an oscilloscope with sampling rate being at least 5 times higher than the frequency of sweep voltage.The system has been used to diagnose the transient plasma generated by hypervelocity-impact of LY12 aluminum projectile into LY12 aluminum target.

2007 Vol. 16, No. 3