西南交通大学学报

Description and Smoothing of Die Surfaces in Plate Deforming Simulation

LI Bai-lin, LINJian-guo

2003, 16(2): 119-201.

[Abstract](1243)

Abstract:
To describe and smooth curves and curved surfaces in finite element simulation, a method for modifying die surfaces in plate deforming simulation is proposed. The description of the surfaces is based on point representation, and the fairness of a surface is represented with the difference between the original points and those after modification. A simulation system is implemented by use of finite element software ABAQUS. An example of simulation is presented, showing that the proposed method and the simulation system is applicable in die surface modification assisted with finite element method.

Calculation of Displacements of Vehicle Suspension on Tangent and Curved Tracks

WANG Kai-yun, ZHAI Wan-ming

2003, 16(2): 122-126.

[Abstract](1458)

Abstract:
A method is introduced in this paper to calculate the displacements of vehicle suspension when the train is running on tangent and curved tracks. This method makes use of the analysis of the displacement a point on a rigid body relative to reference coordinates, and calculates the displacement through coordinate transform. The reference coordinates are built on both the tangent and curved tracks. This method is accurate and simple.

Dynamic Behaviors and Parameters of Freight Cars with Frame-Bogies

WANG Yong, L Ke-wei, GUO Xiao-feng, CHEN Bao-shun

2003, 16(2): 127-131.

[Abstract](1698)

Abstract:
Based on dynamics theory of multi-body systems, a nonlinear mathematical model of frame-bogies with Lenoir damper for freight cars is established. A tank car is taken as an example to study the effects of main parameters on hunting stability, dynamic curving behaviors and running responses of vehicle systems. It is shown that the dynamic behaviors of a freight vehicle can be improved greatly by optimization and balancing of the parameters of the bogies. For the bogies concerned, the critical hunting speed can be raised, without deteriorating the performances on curved lines, by properly increasing the stiffness of the axle-box suspension and the friction torque of side bearing, as well as reducing the longitudinal clearance of side bearings.

Algorithm for Wheel Rail Contact Geometry

WANG Jue, LI Zhi

2003, 16(2): 132-137.

[Abstract](1736)

Abstract:
An algorithm for wheel rail contact geometry is proposed, which can detect single and multi-contact rigid patches, or loss of contact of wheels with rails in dynamic simulation of railway vehicles. The rigid contact patches are the bases to determine the penetration and curvatures for the Hertz theory, the normal gap of the contact zones for non-Hertz theory, and the center and normal direction for dynamic simulations. The validity of the proposed algorithm is verified with 3D OpenGL graphs, and the algorithm has been applied to the development of simulation software for full 3D vehicle system dynamics.

Contact Pressure and Deformation between Two Cylindrical Beams of Finite Lengths

CHENJie, WANG Wei

2003, 16(2): 138-141.

[Abstract](1215)

Abstract:
An approximate analytical formula is derived based on the two theories of generalized displacements of beams to calculate contact pressure and deformation between two cylindrical beams of finite lengths. With an example of calculation, the results obtained by the new method are compared with those by the traditional method and with some experimental observations, showing that the new method is more accurate.

Characters of Noises from Mechanical Car Retarders in Railway Marshalling Yards

WANG Feng-qin, WANG Zhong-shi, XIONG Li

2003, 16(2): 142-145.

[Abstract](1565)

Abstract:
To study the characters of noises from railway marshalling yards, noises are recorded in Kunming Eastern Railway Station. The noises created by mechanical car retarders are the major noise resources in railway marshalling yards, and are the results of vertical and horizontal responses to vertical excitation. The noises from mechanical car retarders in railway marshalling yards are continuous and of multi-peak pulses and scattering spectrum.

Application of Genetic Algorithms in Structural Optimization Design with Discrete Variables

ZHANG Si-cai, ZHANG Fang-xiao

2003, 16(2): 146-150.

[Abstract](1685)

Abstract:
The application of genetic algorithm in optimization design of structures with discrete variables is presented with an example of optimization design for three-bar hyper static truss structures with discrete variables. The comparison between the result obtained by traditional method and that by genetic algorithm indicates that genetic algorithm is more effective for structural optimization with discrete variables. Genetic algorithm is also used to solve a ten-bar truss structure with discrete variables. The effect of population on convergence of the algorithm is analyzed for the three-and ten-bar truss structures. The result reveals that the rational selection of the population is closely related with the chrome length.

Data Processing System for Large Structure Test

DAN Dan-hui, ZHENG Yu, WANG Xu

2003, 16(2): 151-153.

[Abstract](1552)

Abstract:
To deal with a great amount of data acquired in a large structure test efficiently, a data processing system is established. The database model to store the original experimental data is abstracted according to the test of civil engineering structures and in-site inspection. A database management program is designed based on the processing procedures and as the preprocessing program for the data to be used in MATLAB that has strong calculating functions. This system has the full functions of data acquisition, processing and visualization.

Design of Catwalk of Tongtian Bridge

LIAO Li-kun

2003, 16(2): 154-158.

[Abstract](1781)

Abstract:
Tongtian bridge is a foot bridge in Jiulonghsan tourism region, Zhejiang province. Its main span is 208 m. It is light in weight and has good anti-wind properties. A special cable truss structure is adopted. The bridge span consists of the supporting cables, the backward pulling cables, the cables for road surface, the anti-wind cables, and so on. To increase the structural stiffness and stability, all the cables are prestressed. The construction is difficult, because of the spatial structure of the bridge tower, the main cables and those for road surface. The design scheme and nonlinear calculation applied in the design are presented in this paper. The curves and stresses of the cables are calculated under the static and dynamic loads.

Identification of Aerodynamic Derivatives of Ideal Thin Plates with Artificial Neural Network

LI Lin, LI Qiao

2003, 16(2): 159-163.

[Abstract](1584)

Abstract:
A BP artificial neural network (ANN) method is introduced to identify aerodynamic derivatives of ideal thin plates. An artificial neural network is constructed followed by the comparison between the prediction results influenced by some factors. The mothods of data processing have strong effects on training results, and the effects of other factors are relatively weak. The training results show that this approach is feasible with satisfactory accuracy.

Analysis of Pile-Subsoil Interaction with Sand-Box Model Test and Calculation

LOU Yi-hong, PENG Jun-sheng

2003, 16(2): 164-168.

[Abstract](1498)

Abstract:
A coupling finite-infinite element method is proposed to calculate the stress and deformation of pile-subsoil coupling systems under large deflection. A new kind of interface elements with thickness is inserted in the interface between the soil and pile, which can dovetail with elastoplastic models of soil and reflect the deformation in the interface and its nearby shear failure area reasonably. The result of an example is reasonably in accord with data of on-site observation, verifying the feasibility of the proposed method.

Time-History Reliability Analysis of Reinforced Concrete Frames under Frequent Earthquakes

CHEN Ying, ZHANG Xin-pei, ZHU Chang-chun

2003, 16(2): 169-172.

[Abstract](1430)

Abstract:
By taking earthquake motions as a random process and through time dispersion, a method combining improved pseudo variable method, matrix displacement method and time-history method is proposed to analyze the time-history reliability of reinforced concrete frames that are under frequent earthquakes. This method takes the randomicity of earthquake motions and structural parameters into account, and can be used for reliability analysis of the whole process of an earthquake. An example shows the validity of the method.

Design of Prestressed Anchor-Cable with Reinforced Slab for Strengthening Existing Retaining Walls

XIA Xiong, ZHOU De-pei

2003, 16(2): 173-177.

[Abstract](1490)

Abstract:
Based on elastoplastic theory and a practical project case of prestressed anchor-cable with reinforced slab for strengthening the retaining walls of railway subgrade shoulders, a method is proposed to calculate the anchor-cable length under the condition that cohesion shearing stress is non-uniformly distributed. The stability of the project is analyzed by taking the slab as a beam, and the slabs are designed according to the stresses in the interfaces between the wall, the cement and the reinforcement. The proposed method has been applied in engineering practice with satisfactory outputs.

Vertical Bearing Capacity of Rock-Socketed Piles Influenced by Batholith Strength

YUAN Wen-zhong, YUZhi-qiang, XIE Tao

2003, 16(2): 178-182.

[Abstract](1677)

Abstract:
The influence of batholith on the vertical pulling bearing capacity of rock-socketed piles is studied. The test results show that the extension of stress and the angle between fracture-sections depend on the strength and integrality of batholith. The higher is the strength ratio of piles to batholith, the more uniform is the shear stress distribution on their interfaces. The displacement is the control index of pile design if the strength of batholith is much less than those of the piles. Failure of a pile depends mainly on the distribution and characteristics of rock discontinuities, and under this condition, the anchorage section should be placed at middle or lower parts of the piles.

Tunnel Ventilation Network Calculation

ZENG Yan-hua, LI Yong-lin, HE Chuan, GUAN Bao-shu

2003, 16(2): 183-187.

[Abstract](1532)

Abstract:
Based on the structure of a tunnel ventilation network and the principles of airflow in it, simulation computation is done for the ventilation of two long highway tunnels using the Scott- Hosley method and the ventilation path method to investigate the effects of the placement and adjustment of jet fans. The results show that a long tunnel with longitudinal and sectional ventilation forms a network and its computation can be carried out by natural airflow distribution to determine the site of jet fans, the amount of airflow and the mode of airflow regulation.

Optimization of Regional Traffic and Transportation Structures

ZHUJian-mei, YANHai-feng, WANG Bo

2003, 16(2): 188-191.

[Abstract](1625)

Abstract:
The necessity and feasibility of optimization of regional traffic and transportation structures are analyzed. An optimization indexing system is proposed, and then an optimization model for describing regional traffic and transportation structures is derived that is a combination of qualitative and quantitative analyses. This study is to provide a clew to optimize regional traffic and transportation systems that are usually very complicated.

Deduction Coefficient of Passenger Train on Speed-up Single-Track Lines

NI Shao-quan, L Hong-xia, MA Si

2003, 16(2): 192-195.

[Abstract](1459)

Abstract:
Raising the speed of passenger trains will change the speed difference between passenger and freight trains, resulting in changes in the removal coefficient of the passenger trains and the passing capacity on a non-paralleled train diagram. The variation range of removal coefficients of raising-speed passenger trains in semi-automatic block zones on a single railway line is determined through theoretical study and simulation. The variation range is large when the number of passenger trains is small, and vice versa, and tends to decrease with the increase in the speeds of passenger trains. When the number of passenger trains is over 10 pairs, the removal coefficient is in the range of 0.8 to 1.1, being most likely between 0.9 to 1.0. It is suggested to take the removal coefficient in the range of 0.85 to 1.15.

Influence of V Form Skylight on Carrying Capacity of Railways

WANG Jin-yongYANHai-fengXU Shao-xing

2003, 16(2): 196-200.

[Abstract](1355)

Abstract:
Based on the analysis of the structures of train diagrams, the features of V form skylights on busy trunk lines are studied, and a mathematical model is proposed to analyze the key factors in a V form skylight, which influence the carrying capacity of railways. Sensitivity analysis on the factors in a V form skylight shows that the deduction of carrying capacity of a railway line is directly proportional to the time spans and the lengths of V form skylights and inversely proportional to the speed of freight trains and the intervals between trains.

Analysis of Removal Coefficient of Speed-up Passenger Trains in Hankou-Danjiangkou Railway Line

JIAHua-qiang, WANG Jian-jun, XIONG Wei

2003, 16(2): 201-203.

[Abstract](1859)

Abstract:
The basic removal coefficient and additional removal coefficient of speed-up passenger trains on single railway lines are analyzed by taking Hankou-Danjiangkou railway line as the background. When the speed of freight trains is as it is and that of passenger trains is about 120 km/ h, the removal coefficient is between -0.045 and -0.136, the speed-up of passenger trains results in a rise in removal coefficient by 0.2 to 0.7, and a speed-up train passing over another causes an increase in removal coefficient by 0.05 to 0.10. Generally, the removal coefficient of speed-up of passenger trains is about 1.6.

Taming Bullwhip Effect in a Supply Chain by Information Sharing

MA Zu-jun, DAI Ying, WUZhen-ye

2003, 16(2): 204-207.

[Abstract](1506)

Abstract:
The bullwhip effect in a supply chain seriously decreases the operation efficiency of the supply chain. The bullwhip effect can be understood in terms of amplification of information distortion and time lag. The causes are analyzed systemically. Information sharing is an effective countermeasure to depress the bullwhip effect.

Selection of Control Policy for Lean Manufacture Systems

KANG Jie, RENXin-xin

2003, 16(2): 208-211.

[Abstract](1527)

Abstract:
There are three control policies, namely Kanban, CONWIP (constant work in process) and hybrid controls, for lean manufacture that is one of the dominant concepts of management. A difficulty in practice of lean manufacture is how to select the control policy, and it is the concern of this study. Based on the quantitative analysis of the tree control policies, a general model and eigenfunctions are derived for lean manufacture systems. The general model is solved with genetic algorithm and simulation. The comparison of the three control strategies shows that the hybrid control strategy is superior to the others.

Fractal Structure of China Stock Market

SHUJian-ping, TAN De-qing, WUJiong

2003, 16(2): 212-214.

[Abstract](1242)

Abstract:
To understand the essence of the market is the base of investment. In this paper, we used Shang Hai Stock Market Index to study the price behavior. The result indicate that China market has a fractal structure; furthermore, we study the part structure of China market fractal with general dimensions and the scaling behavior of different range return in time axis, the results show that China market has obvious multi-fractal characteristi

Effect of Investment in Higher Education on Economy Growth of China

WANG Chong, LIUJian-feng, ZHOUHe-fang

2003, 16(2): 216-219.

[Abstract](1183)

Abstract:
Based on the standpoint that investment of higher education is a producible investment has been acknowledged by societies in China, the relationship between higher education and the increase of economy expressed by producible function is analyzed with regressive analysis with the data from 1990 to 2000. The analysis shows that, compared with capital, the investment in higher education has had much less contribution to the economic growth of China, which is closely related to inadequate investment in higher education and implying the necessity to increase investment in higher education and enrollment of students.

Key Technology and Schemes of Optical Communication between GEO and LEO

RONG Jian, HU Yu

2003, 16(2): 220-223.

[Abstract](1271)

Abstract:
Optical space communication is the best way to overcome the bottle-neck in the high speed communication between low earth orbit (LEO) and geostationary earth orbit (GEO) satellites. The key techniques and difficulties in optical space communication are high date rates and high power lamphouse technology. Two schemes are proposed for the communication, one using 1 550 nm band and the other taking 800 nm band. It is suggested that the scheme using 1 550 nm band be preferable with the available technologies.

Correlation of Variable-Length Spreading Sequences and Its Application in Performance Evaluation of DS-CDMA

XIEJun-song

2003, 16(2): 223-226.

[Abstract](1237)

Abstract:
Based on the analysis of the correlation properties of variable-length spreading sequences, the performance of the asynchronous multi-rate DS-CDMA system employing orthogonal variable spreading factor (OVSF) sequences is studied. Analytical results of multiple access interference (MAI) are derived in terms of aperiodic partial correlation of the spreading sequences. The numerical results demonstrate that the sequence lengths of interfering users have significant effects on BER performance of desired users, while the effect of sequence length of desired users is negligible.

Multivalue Coded Genetic Algorithm

QIUXiao-ping, TANG Yong-chuan, MENG Dan, XU Yang

2003, 16(2): 227-130.

[Abstract](1625)

Abstract:
A multivalue coded genetic algorithm (MVCGA), adoptingk-order extend binary coding, is proposed for solving the problem of classic genetic algorithm (CGA), such as premature convergence and lack of diversity in the population. The new genetic algorithm can reserve the diversity of the population and reach the global optimum easily. An example verifies that MVCGA has better optimization capability than CGA.

Development of Semantic Collation System in a Special Field

ZHENG Feng-bin, XIA Bao-sheng, JIANG Bao-qing, QIAO Bao-jun

2003, 16(2): 231-234.

[Abstract](1628)

Abstract:
This paper presents the design principle and implementation of a semantic collation system to automatically detect political errors in newspapers and magazines before their publication. The sentences are cut into words, followed by detecting sensitive words and terms. The errors of some words and terms are picked up easily by their meanings; and that of the others are determined by fuzzy matching of the whole sentence where the words or terms locate with the knowledge database.

A Multitype Watermark Scheme

MA Miao, TIANHong-peng, HAO Chong-yang

2003, 16(2): 235-239.

[Abstract](1140)

Abstract:
The characteristic and the difficulties in the implementation of multitype watermarks are discussed. Based on the discussion, a multitype watermark scheme is proposed, in which wavelet coefficients are split into blocks. With every type of watermarks normalized, the approach customizes embedding respectively for each type of watermarks. Seven watermarks of 3 types are embedded at one time. Finally, simulations prove the feasibility of the proposed scheme.

Three-Dimensional Terrain Visualization Based on VRML

PENG Yi-pu, LIU Wen-xi

2003, 16(2): 240-244.

[Abstract](1406)

Abstract:
The methods to realize three-dimensional terrain visualization are discussed, and the proto node definition suitable for three-dimensional terrain visualization extended according to virtual reality modeling language (VRML). The method solves the problem of the use of large-scale data directly in the VRML environment, calculation with high precision and real-time wandering.

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2003 Vol. 16, No. 2