西南交通大学学报

The Development and Prospect of Application of Light Rail Vehicles

LI Fu, ZHANG Li-ping, HUANG Yun-hua

2002, 15(2): 111-116.

[Abstract](1386)

Abstract:
Light rail traffic is becoming a favored city traffic system because of its less pollution to environment, saving energy, less investment, quick benefit and big freight volume. The technologies of urban light rail vehicles are developing quickly. In this paper, the development of urban light rail vehicles is discussed in detail from the aspects of car-body, running gear and electric drive system, which involves the technologies of low floor, independent wheels and IGBT,etc. Meanwhile, the present application of light rail vehicles overseas is briefly introduced, and the future developing trend of light rail vehicles in cities is analyzed.

Dynamic Response of the Axially Moving Cable with Small Sag

LI Ying-hui, GAO Qing

2002, 15(2): 117-120.

[Abstract](1159)

Abstract:
Based on a mathematical model that describes the three-dimensional response of the axially moving cable with small sag and on the concept of wave propagation, an exact solution for the linear, in plane transverse vibration of the axially moving cable with general boundary conditions is obtained. The expression of the solution is derived in frequency domain and interpreted in terms of wave propagation functions. The physical interpretations of the vibrational response will play an important role in the design of active vibration wave controllers. The axially moving cable with fixed boundary conditions in two ends is used as an example to investigate the effect of equilibrium curvature on the dynamic responses and wave propagation.

Numerical Simulation of Velocity Field of Flow Around Square Cylinder

TONG Bing, ZHU Bing, ZHOU Ben-kuan

2002, 15(2): 121-124.

[Abstract](1587)

Abstract:
Using the large eddy simulation (LES) and the finite difference method, a three- dimensional simulation of the velocity field of flow around a square cylinder at a Reynolds number of 22 000 is conducted. The N-S equation is split into advection step, diffusion step and propagation step with the time split-operator. The near-wall effect is treated by using two-layer model, rather than the usually employed wall damping function. The convection term is discretized with upwind- central difference scheme, and the pressure equation is solved by successive over-relaxation (SOR) method. The computed mean velocity along the symmetry line is compared with experimental results reported in literatures. They are in good agreement with each other.

The Analysis of Delamination and Fracture in IC Packages

WANG Jun, YANG Fan, CHEN Da-peng

2002, 15(2): 125-128.

[Abstract](1508)

Abstract:
Micro-electronic components encapsulated with the high-polymer matrix composites are easy to be affected with damp. In the process of welding, the temperature and moisture often cause delamination and fracture in electronic components. For moisture and heat-sensitive high polymer materials, when considering the problem of elastic breakdown induced by moisture and heat, the strain energy release rate at the crack tip can be expressed as an integral form. With FEM and by using the expression of energy release rate, the curves for the relationship of energy release rate versus the ratios of crack length to the thickness of the package are obtained at different welding temperature. The fracture of the electronic components is predicted through Comparing the experimental data of strain energy release rate.

Evolution Equation of Viscoelastic Medium and Exact Solutions for Generalized Thermodynamic Forces

DAI Guang-ze, XIA Yan, ARAKI Shigetoshi

2002, 15(2): 129-133.

[Abstract](1173)

Abstract:
It is obvious that the exact solutions of the evolution equation, which is derived by regarding the deformation process of viscoelastic materials as an irreversible thermodynamic process, depend very much on the properties of their coefficient matrices. These matrices are usually affected by the nature of the generalized thermodynamic coordinates, which leads the solutions for the generalized thermodynamic coordinates to that: (1) under the condition that no neutrally stable equilibrium coordinates exist or they are only in the observed ones, the exact explicit solutions are in the same forms, furthermore the accelerative term will arise in the explicit solutions when parts of the coordinates participate in the entropy production; (2) under the condition that all the generalized thermodynamic coordinates participate in the entropy production, the term proportional to time will arise when only one neutrally stable equilibrium coordinate exists in the hidden ones and the generalized thermodynamic coordinates are given in the form of step function; (3) under the condition that the neutrally stable equilibrium coordinate exists in the hidden ones which participate in the entropy production, the accelerative term will arise in the explicit solutions when all of the observed coordinates and parts of the hidden ones participate in the entropy production regardless of the number of the neutrally stable equilibrium coordinates.

Experimental Study on Welding of D6AC Ultra-high Strength Steel with Thin-Wire Tandem Sequence Submerged Arc Welding

ZHOU You-long, WANG Yuan-liang, HUJiu-fu

2002, 15(2): 134-147.

[Abstract](1421)

Abstract:
The weldability of D6AC ultra-high strength steel is analyzed, and the fundamental of tandem sequence submerged arc welding with thin-wire is introduced. Welding tests are carried out to study the procedure of D6AC ultra-high strength steel welding with the tandem sequence submerged arc welding technology, and the character of welding ultra-high strength steels by use of this method is analyzed. With the thin-wire tandem sequence submerged arc welding technology, the cracking problem existing in the welding of D6AC ultra-high strength steel can be solved, the welding automation can be realized at low cost, and the low efficiency of TIG pulse welding and the high cost of high-energy density welding are avoided.

Diagnosing the Power Distribution among Cylinders by Crankshaft Torsional Vibration

DONG Da-wei, YAN Bing, TAN Da-ming

2002, 15(2): 138-141.

[Abstract](1399)

Abstract:
A new approach using the average effective pressure of each cylinder to diagnose the power distribution of a multi-cylinder engine is developed, in which the average effective pressure of each cylinder is calculated from measured crankshaft torsional vibrations. Specifically, the transfer function between the average effective pressure among cylinders and the measured crankshaft torsional vibrations is obtained by the sub-space method of dynamic condensation, and then the average effective pressures are obtained by solving contradiction equations with the least square method. The suggested diagnosis method is confirmed through experiments on 6135 type diesel engine.

The Parallel Computation of Steady Navier-Stokes Equations with Bi-CG Iterative Method Based on EBE Technique

YANG Zhong-chao

2002, 15(2): 142-145.

[Abstract](1669)

Abstract:
The parallel Bi-CG iterative method based on the element-by-element (EBE) technique is described, which is used in the solution of Navier-Stokes equation using finite element method. This algorithm is implemented with MPI on the Shuguang 2000 parallel system in the National High Capable Computation Center, Chengdu. The three-dimension cavity steady flow field is simulated, and a high speedup ratio is achieved. Because this method need not store the global matrix and save a lot of memory, the scale of flow field problems that can be solved with FEM is increased greatly.

Research and Application of Wigner-Ville Distribution Algorithm

CHEN Chun-jun, XIAO Heng

2002, 15(2): 146-149.

[Abstract](1094)

Abstract:
An algorithm using FFT to calculate Wignev-Ville Distribution (WVD) is introduced. In view of the complexity of time frequency distribution numerical calculation of Wigner-Ville quadratic function, and the large amount of calculation by the algorithm, a sampling algorithm is put forward, by which the length of data that can be handled gets increased in the condition of not changing the sampling frequency. Or, when dealing with the same data length, the calculation time is shortened greatly. The algorithm is applied to analyze the time frequency distributions of a simulated time varying sinusoidal signal and of the fast changing noise signal produced by closing a steel window, and satisfactory results are obtained.

Simplification Method for Triangulation Net in Surface Reconstruction

TIANHuai-wen, WANG Jin-nuo

2002, 15(2): 150-153.

[Abstract](1171)

Abstract:
The simplification scheme for triangulation net formed by a lot of 3-D scattered data points is discussed. Removing faces plan is employed for the mesh simplification algorithm. Some simplification criterions of triangulation net are introduced, with the emphasis on the calculation method for the simplification weight based on the normal vector of triangles. Meanwhile, the criteria of re-triangulation during the simplification of triangulation net are put forward, and the re- triangulation method based on the side expanding is presented.

Environmental Control Effect of Screen Doors in Subway

FENG Lian

2002, 15(2): 154-157.

[Abstract](1537)

Abstract:
Based on one-dimensional unsteady flow model, the velocity field of airflow and the temperature field in subway are simulated by use of the continuity equation, the motion equation and the convection-diffusion equation. For subway stations with screen doors and those without screen doors, analog computation and comparisons concerning the energy consumption rates of air conditioners and the temperature fields of the wind in tunnels are also made. The station with screen door is analyzed, and some rational suggestions are put forward

A Management Information System for Engineering Machinery

FENG Jian, JINHong-yun

2002, 15(2): 158-162.

[Abstract](1285)

Abstract:
The prototype of a management information system is built on VISUAL FOXPRO platform using the ActiveX technology for database. The prototype can be modified and improved by iteration according to requirements until a satisfactory and feasible system is formed. The developed system aims at the machinery management of medium and small-sized enterprises, involving the selection, utilization, repair, modification and replacement of mechanical engineering equipment.

Multi-Level Interest Management for Distributed Virtual Environment

SUN Li-xin, ZHU Chang-qian, SUN Ge-wei

2002, 15(2): 163-166.

[Abstract](1370)

Abstract:
The multi-level interest management for distributed virtual environment can reduce network loads greatly, but it also increases the volume of data transmitted. Therefore, a novel network communication method is put forward. With the method, a dispatcher only need transmit a data package from the multicast address to which the whole interest entity listens when it need synchronously send the data package to the high and the low interest entity sets. Simulation results show that compared with the traditional multi-level interest management, the method proposed in this paper not only can reduce the volume of data transmitted but also is easy to realize.

An Integrated Delivery Tracking System for E-Commerce

HE Rong, FANG Xu-ming

2002, 15(2): 167-171.

[Abstract](1283)

Abstract:
Based on the state-of-art of the e-commerce and logistics business in China, the design scheme of an integrated delivery tracking and inquiry system implemented by 3-level developing model is put forward. The key technologies such as design of database tables, information presentation and procession among applicationsystems, design of network structure based on dial Virtual Private Network with Layer Two Tunneling Protocol, and inquiry feedback implementation are elaborated.

Real-Time Video Technologies for MS-Windows

YANG Tian-wu, LIU Rong, PENG Qiang

2002, 15(2): 172-176.

[Abstract](1343)

Abstract:
The features of three video technologies for Windows system,i. e., GDI, DrawDib function set and DirectDraw, are briefly introduced. The theory and implementation methods of image zoom through sampling rate conversion are also introduced. The executive efficiencies of the three video technologies are compared, and the effect of the up-conversion images produced by these technologies for Windows is compared to that by software interpolation algorithm. And some experimental conclusions are presented

Analysis of Earth Temperature Field Character and Prediction of Rock Temperature at Qinling Railway Tunnel

XIE Qiang, CHEN Yong-ping

2002, 15(2): 177-179.

[Abstract](1787)

Abstract:
Qinling railway tunnel is a long and deep-burying mountain tunnel with a length of 18 448 m and a maximum depth of 1.645 km. In this paper, considering the problems of high temperature that may probably exist in tunnel construction, the earth temperature field of the tunnel is simulated with FEM. The character of the earth temperature field is analyzed, and the temperature of the surrounding rocks of the tunnel is predicted. Base on the earth temperature, the tunnel is divided into five regions. Field measurement shows that the prediction method has a high practicability.

Analysis of the Stability of Underwater Slope

ZHOU Shun-hua, LIUJian-guo, LI Yao-chen

2002, 15(2): 180-185.

[Abstract](1608)

Abstract:
For the underwater foundation ditch of the immersed tunnel excavated according to the plan of Nanjing immersed tunnel of high-speed railway crossing Yantze River, the head loss of the flow across the foundation ditch section is analyzed, and a high pressure district is obtained with the flow in the foundation ditch being neglected. Centrifugal model tests of soil were performed on several typical sections of the immersed tunnel under the condition of still water, namely, on the silty sand slope and the silty-fine sandy slope. The results show that the limit slope gradients of the silty sand layer and the fine sand layer is 1∶1 and is close to 1∶2 respectively, and that the damage of the underwater slope occurs at the bottom of the slope first. In addition, an elastic-plastic FEM analysis of the problem was made, with a result also supporting the conclusion that the damage of the underwater slope occurs at the bottom of the slope first.

Research on Fractal Characteristics of the Size-Distribution of Concrete Aggregates

XIA Chun, LIUHao-wu

2002, 15(2): 186-189.

[Abstract](1355)

Abstract:
The size-distribution of concrete aggregates is analyzed by using the principle of fractal geometry theory. The results indicate that the composition materials of concrete have many obvious fractal phenomena, and hence the fractal theory can become a new effective approach to researches on concrete. The relationships of fractal dimensionDversus the size-distribution of aggregates, the volume fractal dimensionV, and the porosity fractal dimensionPare established.

Discussion on Methods for Calculating Bearing Capacity of Tension Piles Set into Rock

WUXing-xu, YUZhi-qiang, ZHUANG Wei-lin

2002, 15(2): 190-194.

[Abstract](1346)

Abstract:
Based on the results of model tests and analysis of the failure-modes of tension piles set into rock, the existing formulas for calculating the bearing capacity of tension piles are researched. An improved formula is put forward, and the relative parameters in the new formula are also proposed. Finally, the improved formula is validated by the results of the model tests and is used to predict the ultimate uplift bearing capacity of the in situ tension piles at the Second Luzhou Changjiang Bridge.

Research on the Length of Plastic Hinge of Partially Prestressed Beams

PU Qian-hui, YANG Yong-qing

2002, 15(2): 195-198.

[Abstract](1385)

Abstract:
In order to study the length of the plastic zone in a PPC beam, a series of simply supported beam and continuous beam models were tested. The test results showed that the occurrence of the plastic hinge is postponed by the increase inRPPCat the middle span and between the intermediate supports, and that the reinforcement ratio had significant influence on the shape of M-φcurve. A formula proposed to calculate the length of the plastic hinge zone in PPC continuous beams with varied sections and differentRPPC. The simplicity and practicability of the formula was validated with the test results.

Research on Scaling Properties of the Variation of Flood Volume with Duration

CHANG Fu-xuan, DING Jing, WANG Wen-sheng

2002, 15(2): 199-203.

[Abstract](1055)

Abstract:
Using the flood data from three hydrologic stations in the Yangtze river, the temporal scaling properties of flood volume is studied with scaling theory. The results demonstrate that the variation of annual maximum flood volume with duration has a simple scaling property in a certain period of time. Based on the scaling property, the formula describing the relationship between flood intensity and duration is established. The annual maximum flood volumes are computed by use of this formula. The computed result approximates to the one obtained by the conventional method.

Iterative Algorithm for Fluid-Structure Coupling System Based on Improved Wilson-θMethod

YAN Qi-xiang, LIUHao-wu, XIA Chun

2002, 15(2): 204-208.

[Abstract](1638)

Abstract:
An improved Wilson-θmethod is obtained on the basis of the traditional Wilson-θmethod and its stability is analyzed. From the improved Wilson-θmethod, an iterative algorithm for solving the dynamic coupling equation is derived. The algorithm can be used to solve the dynamic reaction of fluid-structure coupling systems with ease. A computation example shows that the iterative algorithm is feasible and can enhance calculation efficiency

A New Kind of Minus-Pressure Air Flotation Equipment

OUYANG Feng, LI Gang, FU Yong-sheng

2002, 15(2): 209-211.

[Abstract](1204)

Abstract:
The mechanism of a new air flotation equipment with an air-water mixing chamber is explained. The removal efficiency of the equipment is determined under experimental conditions. For substances such as petroleum and suspended solids(SS), the removal efficiency is more than 95%. The experimental data are analyzed, and the relationship between the removal efficiency of the equipment and the rotational velocity is discussed. It is found that the removal efficiency increases with the rotational velocity before arriving at an optimal rotational velocity, and decreases over the optimal rotational velocity. Meanwhile, an empirical formula for evaluating the optimal rotational velocity is obtained.

The Second-Order Nonlinear Susceptibility in Semiconductor Asymmetric Step Quantum Well Structure

WEN Cheng-zhong, DOU Yu-huan

2002, 15(2): 212-214.

[Abstract](1118)

Abstract:
The characters of asymmetrical step wells are studied. The resonantly enhanced second- order susceptibilityχ(2)2ωis calculated, and the changes ofχ(2)2ωwith the width of the wells, the width and height of the step, the barrier width and the wave length of incident light are given. The obtained results provide a certain basis for optimizing the properties of second-harmonic producer, and developing new nonlinear optical materials.

Reducing Technique for Two Dimensional EM Scattering Problem with Single Axis Symmetric Structure

GUAN Zhen-hong, ZHU Feng

2002, 15(2): 215-217.

[Abstract](1362)

Abstract:
Big storage and long calculation time requirements are main obstacles for the development of moment method. Therefore, how to efficiently use geometric symmetric feature of scattering structures to reduce computer storage and calculation time for solving the scattering problems is significant in theory and application. In this paper, for the scattering structure with single axial symmetry, a new approach based on moment method is proposed by introducing imaginary decomposition. With this approach, the dimensions of matrix can be reduced to half of the ones in direct calculation, and three-quarter calculation time can be saved. Meanwhile, the formula for decomposition and the decomposition theory are also presented.

A Game Model for Joining in Supply Chain

CHEN Yan-ru, JIANG Yang-sheng, PU Yun

2002, 15(2): 218-222.

[Abstract](1489)

Abstract:
Supply Chain (SC) is a new relationship pattern among enterprises, and Supply Chain Management (SCM) is for this relationship essentially. Only after the research of this relationship is deeply done can the problems existing in the development of SCM be well solved. In this paper, a model for joining in SC is established with the knowledge of game theory for the first time. The correctness and applicability of the proposed model are proved through computation and validation, and many fundamental questions and characteristics of SCM are scientifically explained based on the model. The work of this paper is to provide a new way for the research of SC and SCM.

Solving Flight Conflict Problem with Network Flow Model

SUNHong

2002, 15(2): 223-226.

[Abstract](1345)

Abstract:
Flight-connecting schedule is the basis of making routine production plan of airline operation for airline companies. In this paper, according to the structural characteristics of single hub and spoke flight network, a bipartite graphic model and its optimization algorithm are developed for flight connecting in a hub and spoke network system to minimize the number of aircraft required. First, the flight-connecting problem is converted into the flight pairing connecting problem, and a bipartite graphic model describing the flight pairing connecting problem is built. Thus, an optimal flight-connecting problem is transformed to the maximum matching problem of the bipartite graphic model. Then, an assistant graph with single source and sink is created based on the bipartite graphic model. The maximum matching of the bipartite graph is obtained by calculating the maximum inflow with the Ford-Fulkerson algorithm, and a flight-connecting schedule with minimum craft number is accordingly produced. This provides a feasible method to computerize the work of making and optimizing a flight-connecting schedule. Moreover, through adjusting the upper limit of the time of passing depots, different flight-connecting schedules can be obtained. This brings flexibility to the making of production plans

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2002 Vol. 15, No. 2