西南交通大学学报

Algorithm for Power Flow of Electric Traction Network Based on Equivalent Circuit of AT-Fed System

HE Zhengyou, FANG Lei, GUO Dong, YANG Jianwei

2008, 21(1): 1-7.

[Abstract](1578)

Abstract:
An improved algorithm based on equivalent circuit of autotransformer-fed(AT-fed) systems was proposed to calculate power flows of electric traction networks.In the proposed algorithm,locomotives are treated as a constant power model,and the leakage impedance of ATs is considered.Power flows when there are multiple trains are calculated by the principle of superposition and iteration.The influence of leakage impedance ATs on the performances of electric traction networks can be simulated with the proposed algorithm.Results of simulation show that the algorithm converges after about 5 iterations for single train,and about 10 iterations for 4 trains;it can solve the power flow problem of AT-fed efficiently regardless of the number and positions of trains;and it is more accurate than the commonly used algorithms based on equivalent circuit of AT-fed system.

Partial DC Variable Elimination Method for Calculation of AC/DC Power Flow

ZHUANG Huimin, XIAO Jian, HUANG Yanquan

2008, 21(1): 8-13.

[Abstract](1355)

Abstract:
A partial DC variable elimination method for calculation of AC/DC power flow was proposed to overcome the main disadvantages of the existing unified iterative methods.In its computational model,the converters are treated as PQ-loads that depend on the control angles and the voltages on the AC side.The DC reactive power is the only parameter to be specified in calculation,and the partial differential formulas in Jacobian matrix do not change when the DC control model changes.A numerical example shows that the proposed method has good feasibility,and its computational efficiency is raised by about 5% compared with the existing variable elimination method.

Effects of Typical Defects on Electrical Fields in High-Voltage (Storage) Capacitors

ZHANG Xueqin, WU Guangning, LI Xiaohua, BIAN Shanshan

2008, 21(1): 14-18.

[Abstract](1576)

Abstract:
Four typical defects,that is,inner,contact,overlap and oil defects,were modeled based on the insulation structure and its working environment in high-voltage storage capacitors.Two dimensional axisymmetric electrical fields were analyzed with finite element method.The results show that the electrical field around an inner defect may be higher than the rated value of the dielectric,and distorts more significantly with a greater space charge density under reverse pulse voltages;contact defects(burrs and oxidized spots) cause electrical concentration;the electric field on the corner at an overlap defect is higher than the rated value of the dielectric;and oil defect does not cause high electrical field and basically unaffected by space charges.

Random Early Detection Algorithm of Self-similar Traffic

TAN Xianhai, HUANG Yuanhui, JIN Weidong

2008, 21(1): 19-24.

[Abstract](1347)

Abstract:
A random early detection(RED) algorithm of self-similar traffic with self-similar traffic input can improve the effectiveness of network congestion control by taking the characteristic of traffic into account.Setting of parameters for the RED algorithm was investigated.Based on the characteristic of self-similar traffic,a parameter setting scheme for the RED algorithm of self-similar traffic was proposed,and the structure and implementation process of this algorithm were given.Based on fractional Brownian motion(FBM) and its envelope process,formulas of calculating the upper queue threshold and the packet drop rate in the RED algorithm were derived.The simulation results indicate that the proposed RED algorithm can well control the queue size and improve the performance of active queue management.Compared with the standard RED algorithm,the proposed RED algorithm can admit more connections under the condition of the same packet loss probability.

Optimized Design and Implementation of HDB3 Encoder and Decoder

ZHANG Qiaowen, ZHU Zhongjie, LIANG Feng, DAI Yingjun

2008, 21(1): 25-28,76.

[Abstract](1374)

Abstract:
To solve the drawbacks of the existing HDB3(high density bipolar 3) encoders, such as high encoding complexity and long output delay,a fast design method for HDB3 encoders based on block encoding,unified polarity judgment and position polarity judgment was proposed.As a result,a fast design method for decoding was proposed based on polarity judgment to avoid checking substitute nodes in the process of decoding.Simulation results in QuartusⅡ 5.1 show that the proposed encoding and decoding methods have advantages over the existing methods in resource consumption and operation speed.Compared with the existing methods,with the proposed encoding and decoding methods the number of logic elements is dropped by 25% for encoding and 40% for decoding,and the fan-out numbers for encoding and decoding are decreased by 29.4% and 50.9% respectively.The test result indicates that the new encoder and decoder have a right function and can be applied to actual circuits.

Algorithm for Implicit Surface Reconstruction from Point Cloud Data with Noises

YANG Jun, ZHU Changqian

2008, 21(1): 29-34.

[Abstract](1399)

Abstract:
An algorithm for reconstructing surfaces from point clouds with noises and outliers acquired with a 3D scanner was presented.In the algorithm,each point is shifted using a filtering operator based on mean shift scheme to the local maximum of kernel density function to suppress noises and remove the outliers.The filtered data are divided into subdomains using an adaptive octree subdivision method.A local shape function is computed on each subdomain,and all the local shape functions with their weights are summed up using the method of partition of unity to approximate the global domain.Numerical experiments demonstrate that the proposed method is robust and accurate and convenient in implementing multi-resolution 3D reconstruction from point clouds data containing noises and outliers.

Improvement on CK Metrics Suite for Object-Oriented Software

LI Xiaohang, HU Xiaopeng

2008, 21(1): 35-39.

[Abstract](1135)

Abstract:
To overcome the shortcomings of CK suite in terms of its metrics,such as WMC(weighted methods per class),DIT(depth of inheritance tree),and LCOM(lack of cohesion in methods) for object-oriented software,an improved CK(ICK) suite was proposed.In the ICK suite,weighted method argument complexity per class(WMACC),weighted attribute complexity per class(WACC),relative DIT(RDIT),cohesion in methods(CM),and encapsulation ratio(ER) were defined.The ICK suite was evaluated and compared with the CK suite using the classes in the Util package of Java,and the results show that WMACC and CM describe the complexity and cohesion of methods better,and RDIT is more suitable for object-oriented software.WACC and ER provide metrics for attribute complexity and performance in encapsulation,respectively.

Factors Influencing Porformances of Hydraulic Anti-sway System for Container Cranes

CHENG Wenming, ZHONG Bin, MA Lili, WU Xiao

2008, 21(1): 40-44.

[Abstract](1645)

Abstract:
To analyze the main factors and key parameters affecting the performances of the hydraulic anti-sway system for container cranes,simplified system dynamic equations were derived to meet practical requirements on the basis of structural characteristic of the anti-sway system and its trolley-load system.Simulation results show that structural parameters and hoist load are the main factors affecting the performances of the anti-sway system for a certain length of hoist rope;the performances depend also on structural parameters(or hoist mass) when the hoist load(or structural parameters) is/are known;and the optimal ratio of a generalized structure parameter to the hoist mass is in a range of 1.6-2.0 s-1.

Design of Dispatching Platform for Development of Virtual Prototype of Rolling Stocks

ZOU Yisheng, DING Guofu, ZHANG Weihua, LIU Jia

2008, 21(1): 45-50.

[Abstract](1636)

Abstract:
To coordinate members and tasks in a team,and manage different types of data for development of virtual prototype of rolling stocks,a dispatching platform was designed and implemented.Two-level protections,systematic and project-based,were used to ensure safety of the system.The principle of PDM(product data management) was used to manage data in terms of data storage structure and data flow.A system message engine was designed for collaboration among multi-tasks.An implementation case of the dispatching platform was presented to show the feasibility of the design.

Thermoelastic Stresses Due to Wheel-Rail Contact in Pure Sliding State

ZHAO Xin, JIN Xuesong, WEN Zefeng, WU Lei

2008, 21(1): 51-56.

[Abstract](1590)

Abstract:
A finite element method was applied to establish a thermal-mechanical coupling model for wheel-rail contact in pure sliding state.The non-steady heat conduction between the contacting surfaces of wheel-rail,heat-convection and radiation between the wheel-rail and the ambient were considered.Analysis emphases were put on thermal and stress fields in the expansion process of contact patch due to wear of pure sliding,the effect of expansion rate of contact patch on thermoelastic stresses,and on failure locations of wheel-rail under the thermal-mechanical loads.Calculation results show the expansion of the contact patch significantly affects temperature and stress distributions,and the planes of maximum shear stress and shear strain are at angles about 50° and 140° with respect to the sliding direction.

Globally Exponential Stability of Dynamic Neural Networks with Distributed Delays

ZHANG Keyue, REN Dianbo, ZHANG Jiye

2008, 21(1): 57-61.

[Abstract](1705)

Abstract:
The existence,uniqueness and globally exponential stability of the equilibrium point of a dynamic neural network with distributed delays were studied without assumption of boundedness and differentiability of activation functions.Sufficient criteria for existence,uniqueness and global exponential stability of the equilibrium point of such neural networks were obtained based on the knowledge of M-matrix,topology and Liapunov stability theory.A test matrix was constructed by the weight matrix and the conditions satisfying activation functions of the neural networks.A neural network has a unique equilibrium point and is globally exponential stable if the test matrix is an M-matrix.

Flutter of Delta Wing under Aerodynamic Heating

YE Xianhui, YANG Yiren

2008, 21(1): 62-66.

[Abstract](1252)

Abstract:
From the characteristics of aerothermoelasticity,the effects of temperature in aerodynamic heating on the mode of a delta wing and the characteristic of its flutter were researched.The temperature distribution of the delta wing under aerodynamic heating was investigated with flux balance equation,and the influences of temperature on the natural dynamic characteristics of two typical supersonic delta wing models were analyzed with FEM(finite element method).The aerodynamic load was calculated with the second order piston theory of supersonic aerodynamics,and the flutter equations were solved with the P-K method.The research results show that aerodynamic heating will result in changes in the natural dynamic characteristics of the models,so the flutter velocity of the delta wing will decline sharply.

Simulation of SHPB Test on Concrete and Uniformity of Stresses

CAO Jixing, CHEN Qiu, ZHANG Jiping

2008, 21(1): 67-70.

[Abstract](1912)

Abstract:
Split Hopkinson pressure bar(SHPB) tests on C100 and C80 concrete specimens were simulated with explicit dynamic finite element software LS-DYNA.The concrete specimens were simulated with the Johnson-Holmquist-concrete constitutive model.The stress-strain curves obtained by simulation are in good agreement with the experimental results reported in literature.Stress uniformity in the C100 specimen was analyzed.Result shows that the stresses in the specimen are not uniform in a short period before failure,which brings error to test result.

Experimental Investigation on Flexural Behavior of Prestressed Concrete-Filled Steel Box Beam

ZHAN Yulin, ZHAO Renda, XIE Bangzhu, MOU Tingmin, FAN Bikun

2008, 21(1): 71-76.

[Abstract](1500)

Abstract:
An experiment was conducted on 8 prestressed concrete-filled steel box beams to investigate the flexural behavior of prestressed concrete-filled steel box beams.The test parameters include concrete strength,steel strength,prestressing degree,steel ratio and loading pattern.The strain distribution of steel and concrete and the stress increment of prestressed tendons were obtained.The effect of local buckling of steel plate on the flexural behavior of prestressed concrete-filled steel box beams was investigated.By considering the confined effect of compression core concrete,load-deflection curves were gained with the fiber analysis method.The predicted results based on the fiber analysis method were compared with the experimental ones to show an accordance.The research results show that prestressed concrete-filled steel box beams have a good flexural behavior to have a vast application prospect.

Modification of Tension Field Theory on I-girder Web

KANG Xiaoxian, QIANG Shizhong

2008, 21(1): 77-81.

[Abstract](1536)

Abstract:
To take the restraint provided to I-girder webs by the flange and the initial imperfection of structure into account,the advantages and disadvantages of the Basler tension field theory and the Rockey tension field theory were discussed based on a comparison between the nonlinear FEM(finite element method) analysis and test results,and the applicable range of these tension field theories was pointed out,i.e.,depth-thickness ratio of web hw/tw≥160.A formula was proposed for the shear buckling coefficient to describe the restraint of the flange,and the proposed formula was used to modify the Basler tension field theory.The modified tension field theory considering the contribution of the flange was applied to predict the shear resistance of webs,showing an excellent accuracy.The research provides a reference for the designs of steel bridges and other steel structures and the emendation of the related norms.

FEM Simulation of Straightening Tongue Rail of High-Speed Turnout

ZHOU Wen, LIU Xueyi

2008, 21(1): 82-85,95.

[Abstract](1676)

Abstract:
To provide a theoretic reference for straightening the tongue rail of high-speed turnouts,a finite element model for tongue rail was proposed using three dimensional solid finite elements.The effects of loading distance,loading mode and loading value on the plastic deformation,stress and lineshape of tongue rail were analyzed.The research results show that to a given loading value,the plastic deformation of tongue rail decreases with the increase of loading distance,and the straightening value changes gradually from excess to insufficiency;and to a given loading distance,the plastic deformation of tongue rail rises with the increase of loading value,and the straightening value changes gradually from insufficiency to excess.The straightening mode of vertical loading and lateral constraints on rail foot can improve the lineshape of tongue rail.As a result, a great loading distance,a small loading value and lateral constraints on rail foot should be adopted in the straightening of tongue rail.

Wheel/Rail Contact Irregularity in Crossing Zone of High-Speed Turnout

CAI Xiaopei, LI Chenghui

2008, 21(1): 86-90.

[Abstract](1429)

Abstract:
To identify the characteristics of wheel/rail contact irregularity in crossing zone of high-speed turnouts,a numerical model was set up based on the least distance searching method and analyzing the structures of point rail and wing rail. The law of wheel/rail contact irregularity induced by different point hiding structures and wheel treads was investigated by taking a No.42 high-speed turnout for 350 km/h passenger dedicated line as an example.The research results show that the biggest irregularity is located at the gauge measure and wheel/rail contact points transferring from wing rail to point rail.Under the condition of the same point hiding structure and wheel tread,lateral irregularity plays a greater role than vertical irregularity.By adopting a horizontal point hiding structure and respectively reducing the high of point rail by 10.0,3.0 and 0.0 mm in the sections with a top width of 10.0,15.0 or 35.0 mm,wheel/rail contact irregularity can be controlled effectively.Along with the running of trains and the wearing of wheels,lateral irregularity will increase,while vertical irregularity will decrease.

Model and Algorithm for Estimation of Wagon Flow of Stage Operating Plan Based on Break-up and Make-up Sequences

WANG Zhengbin, DU Wen, WU Baiqing, YANG Yan

2008, 21(1): 91-95.

[Abstract](1588)

Abstract:
In order to realize automational dispatch,an estimation model for wagon flow of a stage operating plan for a technical station was established based on the close relationship between the make-up content and source of outbound trains and the sequences of break-up and make-up operations of trains and by taking the operation of shunting locomotive as the core factor.Based on the optimal break-up and make-up sequences of trains and by combining with the tabular method in solving transportation problems,a hybrid-genetic algorithm for this model was designed,and the relevant program software was developed.An axample shows that the running time of the designed algorithm does not exceed 10 min on an ordinary P4 computer.

Forecast of Railway Freight Ton-Kilometers Based on Semi-parametric Regression

WANG Ruyi, WANG Ciguang, GUO Zizheng, TANG Jianqiao

2008, 21(1): 96-100.

[Abstract](1750)

Abstract:
To raise the forecast precision of railway freight ton-kilometers(RFTK),seven factors reflecting the supply capacity of railway transportation were selected out based on a qualitative analysis and the grey relevancy degree theory,and a semi-parametric regression model was established.The partial least-squares regression method was used to process the multicollinearity of variables,i.e.,the seven factors,and the non-parameter method was applied to express qualitative factors.The research result shows that with the established semi-parametric regression model,the least relative error of the forecast result for RFTK is only 1.7%,and compared with the linear regression model and the grey forecast model,the semi-parametric regression model has a better effect and higher precision for the forecast of railway freight ton-kilometers.

Early-Warning Model of Irregular Flight Management Based on Correlation Function in Extension Theory

YAO Yun, ZHU Jinfu

2008, 21(1): 101-106.

[Abstract](1510)

Abstract:
To solve the problem that there is no early-warning technique for conflict management of irregular flight services,the matter element analysis in extension theory was used to build an early-warning model with 5 indices(anticipated delay time,margin of resources,affected passenger number,service ability and event status),each of which has 5 grades(normal,attensional,precautious,danger and crisis).Due to the complicated relation among factors in conflict,a simple correlation function in extension theory was used to determine the evaluation weights in the model.The early-warning grades are expressed quantitatively.A case study shows that the model is suitable for evaluation of irregular flight services qualitatively,and for assisting early-warning decision quantitatively.

Insertion Heuristic Algorithm for Dynamic Vehicle Routing Problem with Fuzzy Due-Time

ZHANG Jianyong, LI Jun, GUO Yaohuang

2008, 21(1): 107-113.

[Abstract](1542)

Abstract:
In order to effectively solve the dynamic vehicle routing problem with considering the preferences of customers,the traditional static vehicle routing problem with time windows(VRPTW) was expanded to a new situation with dynamic customers,and the time windows were replaced by fuzzy due-time representing the preferences of customers.After a simple description of the fuzzy due-time and the dynamic vehicle routing problem with fuzzy due-time,an insertion heuristic algorithm was proposed.In this algorithm,a two-directional push-bump procedure is employed to decide the optimal time to serve customers,and the average satisfaction degree of customers and the traveling distance and waiting time of vehicles are considered synthetically to optimize the increase of total cost caused by new customers.Finally,an example was presented to show the validity of the proposed algorithm.

Variational Inequality Equilibrium Model for Multiclass and Multicriteria Stochastic Traffic Networks with Elastic Demands

XU Bing, ZHU Daoli

2008, 21(1): 114-119.

[Abstract](1580)

Abstract:
An equilibrium model for multiclass and multicriteria stochastic traffic networks with elastic demands was established using variational inequality method under assumptions that the weights of criteria are dependent of classes of travelers, and that cost functions are unsymmetrical.The model generalizes the equilibrium model for stochastic traffic networks of single class of travelers.It was proved that the continuity and strict monotonicity of mappings in the variational model ensure the existence and uniqueness of equilibrium flows,respectively.Generalized travel cost for a road section is affected by demands and traffic flows on other related road sections,and is a function of flows on all roads.This variational inequality is solved with a diagonal algorithm.An example was presented to show the feasibility of the proposed model and the algorithm.

Division of Transportation Corridor in Wide Area Network Based on OD Table

LI Degang, BIAN lili, LUO Xia, HUO Yamin

2008, 21(1): 120-124.

[Abstract](1586)

Abstract:
A theory for division of transportation corridor in a WAN(wide area network) was proposed based on the relationship between the whole and a part of the network,and the characteristic that the correlation degree between two regions connected by the corridor decreases as the distance between them increases.Calculation complexity of correlation degree was analyzed.A correlation degree between two regions is calculated from OD(origin to destination) tables,and is represented by the OD flows of passengers and cargo.A method for division of a corridor based on OD tables was presented,and the procedure of application of OD tables was discussed.The feasibility of the proposed method was verified by division of the southwest corridor in China.

Coordinative and Incentive Mechanisms of One-Shot Cooperation in Supply Chain

LIN Qiang, GU Peiliang

2008, 21(1): 125-130.

[Abstract](1431)

Abstract:
The coordination in a supply chain was analyzed.A cooperation model for the balance of one-shot cooperation was derived following the principal-agents mechanism with the factors influencing profit distribution being known.The results of analyses show that the effort level and the total net profit are lower when a noncooperative strategy is adopted than when a cooperative strategy is adopted;the distribution coefficient of a member in the supply chain is proportional to its contributive coefficient,but is inversely proportional to its innovation cost and opportunity cost coefficients;a member gets more profit as it utilizes resources efficiently,and gets a larger proportion of total profit if the possibility of its cooperation with the non-supply chain members is high.

Research on Syntheses of PU Microcapsule for Gene Engineering Cell

ZHANG Zhibin, PENG Xuelin, CHEN Huiqing, SHAN Lianhai

2008, 21(1): 131-135.

[Abstract](1297)

Abstract:
Polyurethane(PU) water solutions were synthesized by combining the prepolymerization,chain-extension,neutralization and dispersion-diffluence methods in one step.And PU microcapsules were synthesized with the coacervation phase separation method.The synthetic conditions of PU water solutions and PU microcapsules were investigated,including the effects of the kinds of diisocyanate,the feed ratios of toluene-2,4-diisocyanate(TDI) and polyethylene glycol(PEG),reaction temperature,reaction time and stirred velocity on the morphology of PU microcapsules.The PU microcapsules were synthesized with TDI,PEG,dimethylol propionic acid(DMPA) and triethylamine(TEA).The structure and morphology of the PU microcapsules were measured with infrared spectrum(IR),differential scanning calorimetry(DSC) and scanning electron microscope(SEM).The diameter of the globose PU microcapsules is 2 mm or so,the cavity diameter in the PU microcapsules is 50 to 500 μm,and the membrane orifice diameter of the PU microcapsules is 20 to 100 nm.Furtheremore,the optimal conditions of synthesizing the stable, good morphology and microphase separation structural PU microcapsules were given.These conditions are as follows: the prepolymerization,chain-extension and neutralization temperatures are 60,50 and 30℃ respectively,both the times of prepolymerization and chain-extension are 2 h,the stirring velocities of prepolymerization and chain-extension are 500 to 600 r/min,and the stirring velocity of dissolution is 700 to 800 r/min.

Fisher Discrimination Method and Its Application

ZHONG Chong, GUO Qiang

2008, 21(1): 136-141.

[Abstract](1426)

Abstract:
The Fisher discrimination method is a multiple logical probabilistic discrimination method with a wide application and strong discrimination ability to financial risks.Based on the Fisher discrimination method and actual data,a system of discrimination indexes for the financial risks of Chinese universities and colleges was proposed,and a linear Fisher discrimination model was established.In addition,an empirical test was carried out on the basis of actual financial data from 72 universities and colleges in China in recent years.The test result shows that the Fisher discrimination model established has a high accuracy and reliability.

Experimental Investigation on Removal of Organics in Leachate Using Semi-aerobic Aged Refuse

ZHANG Aiping, LIU Dan, SU Yanping, LIU Yong

2008, 21(1): 142-146.

[Abstract](1382)

Abstract:
In order to investigate the removal characteristics and efficiency,semi-aerobic refuse with an age of 3 a in the laboratory was used to remove organics in leachate by filling in bioreactors by perfusion under the conditions of natural ventilation and closed landfilling.The experimental investigation shows that the most of organics with a molecular weight of less than 2×103 are removed by the aged refuse.Under natural ventilation and closed landfilling conditions,the removal efficiency of total dissolved organics is respectively 92% and 87% when hydraulic load is 40 L/(m3·d),and that of total dissolved refractory organics is respectively 34% and 21% when the hydraulic load is 50 L/(m3·d).Under a natural ventilation condition,the removal efficiency of chemical oxygen demand(COD) increases from 85% up to 93% as the hydraulic load decreases from 50 to 25 L/(m3·d),and the relative volume load decreases from 600 to 300 g/(m3·d).After continuous operation of 40 d,the mass concentration of COD in effluent ranges from 400 to 900 mg/L.

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2008 Vol. 21, No. 1