西南交通大学学报

Aerodynamic Analysis on Entrance Hood of High Speed railway Tunnels

LI Renxian, GUAN Yongjiu, ZHAO Jing, ZHAO Jiwei

2012, 25(2): 175-180. doi: 10.3969/j.issn.0258-2724.2012.02.001

[Abstract](1773)

Abstract:
Based on computational fluid dynamics method, the effects of tunnel entrance hood structure to aerodynamic influence in tunnel were analyzed by numerical simulation as high speed train running into tunnels. The influences of some structure factors were calculated, such as length of transition section, length of bumper section, rate of open hole on entrance hood, entrance structure of entrance hood and so on. Simulation results show that the effects of length of transition section and entrance structure of entrance hood to the aerodynamic influence are very small; length of bumper section is by no mean the longer the batter, there is an optimum length for bumper section as other structure parameters fixed; opening holes on entrance hood will assist reduce the peak of pressure gradient in tunnel, but will make the peak air pressure increase; and entrance hood installed at tunnel entrance will reduce the peak pressure of pressure pulse as two trains passing through each other in tunnel.

Calculation Method for Embedded Continuous Pile-Board Structure under Thermal Stresses

SU Qian, BAI Hao, HUANG Junjie, LI Xing

2012, 25(2): 181-186. doi: 10.3969/j.issn.0258-2724.2012.02.002

[Abstract](1614)

Abstract:
In order to probe into the method to calculate the temperature effect of an embedded continuous pile-board structure, a concept of temperature effect-based zoning was put forward and a model for the temperature effect was established after analyzing the calculation method for the temperature effect of over-long frame structures. Based on the deformation compatibility principle and considering slab-filler and pile-soil interactions and the elastic-plastic properties of reinforced concrete piles, a calculation formula for temperature force was induced. The method was used in a specific engineering case. The result shows that the calculated value of longitudinal displacement is 1.2 times of the measured value, indicating this method of analyzing the temperature effect of an embedded continuous pile-board structure is effective.

DEM Simulation of Ballast Degradation and Breakage under Cyclic Loading

, JING Guoqing, , FENG Kun, GAO Liang, WANG Jun

2012, 25(2): 187-191. doi: 10.3969/j.issn.0258-2724.2012.02.003

[Abstract](1451)

Abstract:
In order to reflect the micro-mechanism of ballast-sleeper interaction and the process of ballast breakage, a 3-D ballast-sleeper model based on the discrete element method (DEM) was established, and ballast degradation and breakage under cyclic loading were simulated. In this model, irregular ballast particles are modeled by clusters, they are divided into two kinds, i.e., unbreakable and breakable, and ballast is respectively subjected to monotonic and cyclic loads. The research results show that under the same load, contact force between ballast and sleeper is larger when the ballast is loaded than that when it is unloaded. The crushed clusters mainly appear underneath the sleeper, particle crushing is a major factor for sleeper settlement, and the sleeper settlement increases when ballast strength reduces.

Damping Characteristics of Ballast Mat on Culvert

LI Peigang, LIU Xueyi, HAO Yuanxing

2012, 25(2): 192-197. doi: 10.3969/j.issn.0258-2724.2012.02.004

[Abstract](1400)

Abstract:
In order to provide a theoretical basis for the design and optimization of ballast mat on railway culvert, a vertical coupling dynamical model for a vehicle-track-culvert system was established based on the wheel-rail coupling dynamics theory and the finite element method. LS-DYNA, a large-scale dynamical analyzing program, was used to analyze the time-frequency characteristics of dynamic responses of vehicle, track and culvert with and without using the vibration mitigation measure of ballast mat. In addition, the proper rigidity of the ballast mat was investigated. The results show that the adoption of the vibration mitigation measure does not aggravate wheel-rail dynamic interaction and affect the running safety of trains. Furthermore, the measure can evidently decrease the dynamic response of culvert, while rarely influence rail vibration. It has a certain damping effect on the vibration of sleeper, but has a negative influence on ballast vibration. The proper rigidity of ballast mat is suggested to be from 50 to 100 MPa/m.

Influencing Factors of Adjustment Quantity of Vertical Track Profile Irregularity

WEI Xiankui, QUAN Shunxi, WANG Ping

2012, 25(2): 198-203. doi: 10.3969/j.issn.0258-2724.2012.02.005

[Abstract](1760)

Abstract:
In order to probe into the relationship between practical adjustment quantity and calculated adjustment quantity of vertical track profile irregularity, a calculation method for adjustment quantity of vertical track profile irregularity was put forward, and a coupling calculation model of rail-fastener-rail-pad was established. The influencing factors, including vertical rail-pad stiffness, sleeper span and numbers of loosened fasteners and adjustment sleepers were analyzed. The research results show that vertical rail-pad stiffness has a large influence on the adjustment quantity when there is only one adjustment sleeper, while sleeper span and the number of loosen fasteners have a little influence on the adjustment quantity. Under the condition of continuous multiple adjustment sleepers with the same calculated adjustment quantity, the adjustment quantity of in-between sleepers can reach the calculated adjustment quantity.

Field Tests of Soft Marine Clay Foundation Reinforced by T-shaped Bidirectional Dry Jet Mixing Piles

XIE Shenghua, 2, LIU Songyu, DU Guangyin

2012, 25(2): 204-209. doi: 10.3969/j.issn.0258-2724.2012.02.006

[Abstract](1452)

Abstract:
In order to overcome disadvantages of the marine soft soil foundation treated by the conventional dry jet mixing(DJM) piles, such as mixing non-uniformity of soil cement and low strength of pile body, a technique of using T-shaped bidirectional DJM piles was proposed to reinforce the soft marine clay foundation in Lianyungang area of China. Single pile tests were conducted in a field site of the Lianyungang-Linyi Expressway (Jiangsu Section). Disturbance effects of DJM during installation and static load test after the construction of the T-shaped bidirectional DJM were analyzed. The dissipation process of the excess pore water pressure after installation, load, and settlement parameters were monitored during the static load test. The results indicate that the excess pore water pressure exceeded the effective overburden stress of the soil during installation, probably due to the larger diameter of upper head of the T-shaped DJM pile and the repeated mixing process. However, excess pore water pressure dissipated quickly just after installation. Single pile installation had an influence scope of 510 times the pile radius. The single pile static load test results indicate that, compared to bidirectional and conventional DJM piles with the same diameter, the ultimate bearing capacity of the T-shaped bidirectional DJM pile increased 36% and 76%, respectively. Therefore, T-shaped bidirectional DJM is characterized by high pile strength and high single pile bearing capacity.

Aerodynamic Characteristics of Vehicle-Bridge System under Cross Wind: Parameter Studies Based on Wind Tunnel Test

LI Yongle, HU Peng, ZHANG Mingjin, 2, XU Youlin

2012, 25(2): 210-217. doi: 10.3969/j.issn.0258-2724.2012.02.007

[Abstract](1617)

Abstract:
In order to investigate the effects of vehicle motion on the aerodynamic characteristics of a vehicle-bridge system, a three-vehicle model and a single-vehicle model respectively for full-scale rail transit vehicles and road transit vehicles were designed to measure the aerodynamic forces acting on the vehicles and bridge deck under different testing cases by a self-developed wind tunnel test system with a moving vehicle model. The effects of vehicle speed, yaw angle, rail position of vehicle on bridge deck and vehicle type on the aerodynamic characteristics of vehicles and bridge deck were researched. The results show that vehicle drag and lift coefficients tend to increase with the increase of vehicle speed and the decrease of resultant yaw angle, and vehicle speed has a significant effect on the aerodynamic forces in the single-vehicle model. The effect of rail position on vehicle and bridge aerodynamic coefficients is notable, and bridge aerodynamic coefficients are insensitive to vehicle speed and resultant yaw angle.

Mitigation Measures of Vortex-Induced Vibration of Suspension Bridge Based on Section Model Test

SUN Yanguo, LIAO Haili, LI Mingshui

2012, 25(2): 218-223. doi: 10.3969/j.issn.0258-2724.2012.02.008

[Abstract](1738)

Abstract:
In order to investigate the vortex-induced vibration performance of long-span suspension bridges and propose effective mitigation measures, a long-span suspension bridge with steel-box girder was taken as an engineering example. By a section model wind tunnel test with a scale of 1∶20, the effects of railings, maintenance rail and guide vane on the vortex-induced vibration performance of main girder at a low damping were investigated, and the mitigation measure of setting guide vane inside the maintenance rail was applied in bridge engineering. In addition, the mechanism of the vortex-induced vibration was discussed based on the test phenomenon. The research results show that the vortex-induced vibration can be effectively mitigated by the above measure, and the mitigation measure makes the aerodynamic shape of the main girder be more reasonable. Furthermore, the structure for this measure is relatively simple to be convenient for engineering application.

Numerical Simulation for Diffraction around Large-Diameter Circular Cylinder Subjected to Three-Dimension Wave

, ZHU Bing, SONG Suidi, TAN Changjian

2012, 25(2): 224-229. doi: 10.3969/j.issn.0258-2724.2012.02.009

[Abstract](1293)

Abstract:
In order to research interaction between three-dimensional waves and structures, a numerical model for the interaction of three-dimensional waves and a structure was established based on the concept of two-phase flow, the volume of fluid (VOF) method and incompressible viscous fluid equations in large eddy simulation (LES). Interaction between three-dimensional waves and a large-diameter circular cylinder was simulated numerically. The virtual boundary force method (VBFM) and two-step boundary-pinpoint method were adopted to determine the boundaries of the structure. The research show that the numerical simulation result of the circumfluence factor for a large-diameter circular cylinder has a good agreement with the analytical solution. The established numerical model can successfully simulate the interaction between three-dimensional waves and structures.

THE DAMAGE-COUPLED TIME-DEPENDENT MULTIAXIAL THEORETICAL MODEL: II. THE ENGINEERING APPLICABILITY OF FINITE ELEMENT IMPLEMENTATION

, GAO Qing

2012, 25(2): 230-235. doi: 10.3969/j.issn.0258-2724.2012.02.010

[Abstract](1758)

Abstract:
A damaged-coupled time-dependent fatigue failure model was implemented into the finite element code ABAQUS via user material subroutine UMAT, and typical numerical examples were used to simulate the low cycle fatigue (LCF) failure behavior of 63Sn-37Pb solder alloy structural specimen under nonproportional loading paths. The comparison with the experimental results under the same loading paths shows that the implemented constitutive model can simulate the load response and the load decaying with cyclic number, and predict LCF life of the solder structural specimen well. Therefore, the finite element implementation of fatigue failure model is reasonable and effective.

Melting Behaviors of Capric Acid in Rectangular Enclosure

YUAN Yanping, CAO Xiaoling, BAI Li, YANG Xiaojiao

2012, 25(2): 236-240. doi: 10.3969/j.issn.0258-2724.2012.02.011

[Abstract](1537)

Abstract:
An enthalpy-porous model was used to simulate the melting behaviors of capric acid in a rectangular enclosure with a heated wall on one side. The simulation accuracy was verified by comparing the simulated results with those by experiment. The simulation results showed that average Nusselt number and its decreasing rate reduced gradually with an increase in Fourier number. An exponential function for melting volume fraction was regressed, the exponents of which for Stefan number, Rayleigh number and Fourier number were 0.663 5, 0.190 6, and 0.853 5, respectively.

Robust Multi-objective Optimization Design of Two-Tooth Difference Rolling Movable Teeth Transmission

LIANG Shangming, SUN Qiang, YAO Jin

2012, 25(2): 241-245. doi: 10.3969/j.issn.0258-2724.2012.02.012

[Abstract](1626)

Abstract:
To improve the design of two-tooth difference rolling movable teeth transmission, a mathematical model of multi-objective robust optimization design for the transmission was established by optimization design theory and robust design method, taking account of the effect on the feasible region caused by deviations of design variables and design constants. Then, a solution method of the model was proposed based on the simulated annealing algorithm, and a numerical example was given for illustration. The numerical results show that the robust optimization design based on the simulated annealing algorithm, compared with the ordinary optimization design, can reduce the volume of two-tooth difference rolling movable teeth transmission by 24.1%.

Transformation Effect During Controlled Cooling of X65 Heavy Pipeline Plate

, LU Jiansheng, SONG Peng, Lu Jianguo,

2012, 25(2): 245-251. doi: 10.3969/j.issn.0258-2724.2012.02.013

[Abstract](1639)

Abstract:
To study the phase transformation effect during the controlled cooling of X65 heavy pipeline plate, a thermomechanical coupled finite element model was established, where the developed linear mixture thermal expansion model, the modified Avrami transformation dynamics model, and the Leblond model were combined. Using the model, the influence of transformation effect on temperature, residual stress, and strain was studied during the asymmetric controlled cooling of X65 heavy pipeline plates with 3 kW/(m2K) laminar cooling coefficient on top surface and 1 kW/(m2K) on bottom surface. The result shows that latent heat slowed the cooling speed of inner and bottom surface by 50％and 25％, respectively, during the phase transformation. Peak stresses, 89 MPa and -89 MPa, were induced due to latent heat, and 130 MPa and -170 MPa from TRIP (transformation induced plasticity) effect. Because of the coexistence of tensile and compressive stresses caused by latent heat and TRIP effect, the overall residual stresses were reduced. Moreover, the magnitude and distribution of the overall residual stresses were dependent significantly on the structural stress with peak values of 723 MPa and -479 MPa from transformation dilatation. 　　

Effects of Particle Shape on Friction Mechanism Based on Discrete Element Method

DU Xin, ZENG Yawu, GAO Rui, YAN Jing, CAO Yuan

2012, 25(2): 252-257. doi: 10.3969/j.issn.0258-2724.2012.02.014

[Abstract](1328)

Abstract:
In order to reveal the effects of particle shape on friction mechanism, frictions among non-viscous particles were decomposed into the macro biting-force and the mesoscopic biting-force. Impact and angle-of-repose (AOR) numerical tests were conducted to study the effects of particle shape on macro biting-force and mesoscopic biting-force by modeling irregular shape particles using discrete element method. The results of numerical tests show that the friction coefficient of irregularly shaped particles is nearly two times its interface friction coefficient, while the friction coefficient of ellipsoid particles is approximately equal to the interface friction coefficient. Meanwhile, different particle shapes endowed the particles with rolling or slipping characteristics, and influence the macro biting-force and the granular friction behavior.

Synchronization Control of Electro-hydraulic Servo System Based on Single Neuron

JIANG Xiaoxia

2012, 25(2): 258-264. doi: 10.3969/j.issn.0258-2724.2012.02.015

[Abstract](1604)

Abstract:
In order to probe into the synchronization control of an electro-hydraulic servo system, a large platform with four hydraulic cylinders was taken as the research object, and the four hydraulic cylinders were identified mathematically with experiment data, and the adaptive neuron technique was employed to realize the synchronization control. Two strategies of virtual master cylinder and hybrid neural synchronization control were proposed. The simulation results show that the strategy of virtual master cylinder can achieve a desirable synchronization performance, the maximum synchronization error is 0.260 6 mm, but it needs to build the mathematical model of one hydraulic cylinder. The strategy of hybrid neural synchronization control does not need to build the mathematical model and can achieve a relative good synchronization control performance by adjusting parameters to minimize synchronization error, and the maximum synchronization error is 0.431 3 and 0.382 5 mm respectively under the sinusoidal input signals of 3 and 8 Hz.

Energy-Saving Optimal Control of Following Trains Based on Genetic Algorithm

LU Qiheng, FENG Xiaoyun, WANG Qingyuan

2012, 25(2): 265-270. doi: 10.3969/j.issn.0258-2724.2012.02.016

[Abstract](1672)

Abstract:
In order to study the optimum operating strategy for energy saving of the following train in a following operation, the static speed constraints of the trains and the dynamic speed constraints of the following train were put forward under a four-aspect fixed autoblock system. On this basis, an energy-saving optimal operation model of the following train was created taking the train control notch and the corresponding train position as control variables. With the help of the external punishment function, the model was solved by the changeable chromosome length multi-objective genetic algorithm (GA). The shifting strategy of the train control notch was optimized using the chromosome length mutation operator of GA to determine the change times of the train control notch during the whole trip. The simulation result from a four-aspect fixed autoblock system simulation platform shows that the method can reduce the energy consumption and trip time error of the following train by 4.3% and 1.7%, respectively, on the premise of safety and punctuality.

Robust Rudder Roll Stabilization of Guaranteed Attractor

TU Jianjun, 2, HE Hanlin

2012, 25(2): 271-278. doi: 10.3969/j.issn.0258-2724.2012.02.017

[Abstract](1436)

Abstract:
In order to meet the requirements of single input in designing the stabilizing controller for ships with single rudder or linked twin rudders and make the controller robust to ocean wave disturbance, a concept of guaranteed attractor disturbance rejection was presented for a class of system with persistent disturbance. Using back-stepping design, Barbalat lemma and Lyapunov theory, a scalar adaptive robust controller for this system was designed by solving an algebraic Riccati equation to restrain the system states into a bounded attractor. Furthermore, a criterion of the attractor minimization was brought forward in the form of linear matrix inequalities to optimize the effect of disturbance rejection control. Taking as an example the weak chaos phenomenon in the roll motion of the fishery administration ship 1500HP under weak wave, the designed disturbance rejection controller was used as rudder moment to control the chaos in its roll motion, and a numerical simulation was made to verify the disturbance rejection effect of the controller. The results show that the states of the ship roll model converge rapidly and stay in the presupposed attractor under the guaranteed attractor controller, while the attractor can be further compressed through optimization of the attractor controller.

Building Modes of Integrative Passenger Rail Transit System

HE Dong, ZHU Jianmei

2012, 25(2): 279-284. doi: 10.3969/j.issn.0258-2724.2012.02.018

[Abstract](1303)

Abstract:
To meet the increasing demand for passenger rail transit system from city development and passenger travel, a concept of integrative passenger rail transit system (IPRTS) was defined for the generalized system including railway and urban rail transit, and the disadvantages of the traditional stopping mode of railway trains were analyzed. Then, fundamental principles for IPRTS constructing was presented, i.e., the people foremost, maximum whole benefit, and coordinated development with city. According to different connection forms between railway and urban rail transit, three building modes of the IPRTS were put forward, including dual-purpose mode, common-rail mode, and station transfer mode. The building modes for 23 situations with different characteristics were determined by judgment of 7 conditions, namely, traditional mode adaptability, city position, railway conditions, railway route, urban rail transit conditions and planning, engineering factors, and transportation organization. This can provide a decision support for the IPRTS building.

Spot Speed Prediction Model Based on Grey Neural Network

WU Zhizhou, FAN Yujie, MA Wanjing

2012, 25(2): 285-290. doi: 10.3969/j.issn.0258-2724.2012.02.019

[Abstract](1353)

Abstract:
To overcome the detecting data error due to the temporal and spatial instability of traffic condition and improve the accuracy of spot speed prediction, a spot speed prediction model based on grey neural network was developed on the basis of grey prediction model and BP(back propagation) neutral network. The model combines the characters of low data demand of grey prediction model and the self-learning and self-adaptive abilities of BP neutral network. It uses field data as output to build different grey prediction models, and then the predicted results are used as inputs to train the BP neural network to obtain the optimized model. Case study shows that compared with those of the traditional grey theory and BP neural network models, the average relative deviation between predicted and field data at 20，40，60 s sampling intervals can decrease 32% on average using the proposed model. Therefore, the proposed model can be used as a basis for traffic condition estimation and travel time prediction.

Path Optimization in Stochastic and Time-Dependent Networks with Multi-attributes

CHEN Jingrong, YU Jianning, LI Yinzhen

2012, 25(2): 291-298. doi: 10.3969/j.issn.0258-2724.2012.02.020

[Abstract](2792)

Abstract:
In order to improve the real-time traffic guidance, all the attributes for each section were defined as discrete random variables with respect to time in the light of the stochastic and time-dependent properties of attributes of sections in traffic networks. Based on the above, a model of path optimization was built for stochastic and time-dependent networks with multi-attributes. The multiple attribute decision making based on the information entropy theory was used to get the algorithm for the model. In this model, by adjusting the search order of nodes the information of each node can be obtained through only one computational step, the results of path selection can be achieved from all nodes to a specified destination in multi-attributes, then a traveler can get his ways by the arrival time. In the end, an example was given to illustrate the concrete steps of the algorithm and prove that stochastic and time-dependent networks do not follow first in, first out condition.

Safety Analysis of Car Drivers' Fixation Characteristics on Freeways

HU Jiangbi, WANG Weili, ZHANG Shouran

2012, 25(2): 299-305. doi: 10.3969/j.issn.0258-2724.2012.02.021

[Abstract](1307)

Abstract:
In order to provide a theoretical basis for the design and operational safety evaluation of freeways, 453 combined alignment sections of a four-lane two-way freeway were selected to study the dynamic visual fixation points on pavements of 13 drivers according to drivers' fixation characteristics in processes of driver-vehicle-road cooperation. The distribution of drivers' fixation points on pavements and the characteristics of the fixation concentration region were analyzed under different running speeds and various combined alignment sections. In addition, a concept of driver expectation sight distance was proposed, and a computational model of the driver expectation sight distance was built for different running speeds. The results show that the driver expectation sight distance is related to the running speed and horizontal radius. When the horizontal radius is less than or equal to 800 m, drivers' visual field will be restricted as the running speed increases, and some speed limit measures should be taken to ensure the driving safety.

Formalization and Goodness-of-Fit Analysis of Web Quality Model

ZHU Yan, ZHAO Bo

2012, 25(2): 306-312. doi: 10.3969/j.issn.0258-2724.2012.02.022

[Abstract](1259)

Abstract:
In order to rationally standardize the proposed web quality model (WebQM) and verify the feasibility and effectiveness of the model in actual web quality assessment, WebQM was formalized in the ISO/IEC Z language and studied empirically based on the structural equation model (SEM) approach. By building a sample data set and constructing an SEM for WebQM, the goodness-of-fit of WebQM was analyzed based on the generalized least square method. Calculated GFI (goodness-of-fit index), AGFI (adjusted goodness-of-fit index) and CFI (comparative fit index) for actual sample data are 0.944, 0.911 and 0.981, respectively. The result shows that WebQM highly conforms to the actual web source quality status and is feasible and effective.

Fast Search of Multi-channel Mass Data Based on Optimal Entropy Matching

ZHANG Limei, LIU Lu

2012, 25(2): 313-317. doi: 10.3969/j.issn.0258-2724.2012.02.023

[Abstract](1272)

Abstract:
In order to obtain the data corresponding to certain condition or status from mass test data quickly and accurately, the problems existing in conventional time-sequence search methods were analyzed, and a fast search approach for multi-channel mass data was proposed based on optimal entropic matching. In this approach, the conventional time matching is replaced by status matching. The approach depends mainly on entropy testing to need few parameters, have less reliance on neighborhood time and largely reduce the error caused by time synchronization between different channels. Furthermore, it has a big search scale and a fast search speed. The result shows that in certain condition, the search speed can be increased by thousands of times with an improved matching precision, and the relative error of every main parameter is less than 0.05.

Optimization of Time Parameters in Static Segment in FlexRay Network

WANG Gang, RONG Jian, DING Tianbao

2012, 25(2): 318-324. doi: 10.3969/j.issn.0258-2724.2012.02.024

[Abstract](1552)

Abstract:
In order to achieve the maximum network bandwidth utilization of FlexRay bus, the payload length in a FlexRay static frame was optimized. Based on a present optimization model for the static segment in a FlexRay network and by simplifying a nonlinear operator to a linear one, an analytical expression of the optimal static slot length was derived. The correctness of the expression was validated through numerical experiments and its applicable range was obtained. The research result shows that the optimal value of the payload length of a FlexRay static frame is proportional to the square root of the average length of all the static signals in a FlexRay network, and compared with a numerical method, the analytical expression increases calculation efficiency by 99%.

Dynamic Characteristics of Typical Hydraulic Notches

CHEN Jinshi, LIU Xinhui, YUAN Wanrong, WANG Tongjian, ZHAO Feng

2012, 25(2): 325-332. doi: 10.3969/j.issn.0258-2724.2012.02.025

[Abstract](1698)

Abstract:
In order to improve the performance of a hydraulic system and select proper notches of a hydraulic control valve, mathematical models for flow areas of five typical hydraulic notches were established, and corresponding simulation models were set up based on software AMESim. The effects of input signal, load and notch dimension on the systematic dynamic characteristics of the five notches were analyzed numerically. The results show that under the same dimension, L-shaped notches are applicable under the circumstances of heavy load and rapid pressure establishing, and triangle notches are suited for the conditions of pressure stability and high sensitive response. To increase the apparent dimensions of notches appropriately can improve the dynamic characteristic of the system.

Location-Allocation Model of Logistics Distribution Network of Fast Fashion Products in Mature Period

LIU Sijing, ZHANG Jin, LI Guoqi

2012, 25(2): 333-340. doi: 10.3969/j.issn.0258-2724.2012.02.026

[Abstract](1784)

Abstract:
In order to solve the logistics network location-allocation problem of fast fashion products in mature period of e-commerce retailing, a multi-period non-liner mixed integer programming model was proposed for the fast fashion products' logistics distribution network consisting of four parties and four layers. In this model, the maximization of profit is taken as the optimization objective, sales strategy and controllable lead time are taken into account, and the genetic algorithm is adopted to achieve the discount rate and the locations, allocations and service plans of warehouses, third party logistics enterprises and pickup spots. The case study results illustrate that when the discount rate is 0.687, the total profit of a logistics distribution network reaches the maximum value, and when the gathering time is not less than 2 d, the growth rate of the total profit decreases rapidly.

Integrated Evaluation for Operation Performance of Air Traffic Control in Terminal Area

HU Minghua, LIU Weidong

2012, 25(2): 341-347. doi: 10.3969/j.issn.0258-2724.2012.02.027

[Abstract](1633)

Abstract:
An evaluation method for operation performance of terminal control at a single-runway airport was proposed by integrating principal component analysis and K-means cluster analysis. The Chengdu terminal area with a single runway was taken as an example of application of the proposed method. According to expert questionnaires, a three-layer index system was prepared, from which 20 indexes as independent as possible were chosen as raw data for principal component analysis, and 84 sets of samples, one for the period of an hour, were collected from everyday peak periods (10:0022:00) of a week. The evaluation results were in fairly good consistency with those by experts. They also fed back for optimization of operation performance of terminal control, and desired results were achieved.

Optimization Model for Area Traffic Flow Management under Constraint of Deterministic Airspace Capacity

p style, ZHANG Ying, XIE Hua, HU Minghua

2012, 25(2): 348-354. doi: 10.3969/j.issn.0258-2724.2012.02.028

[Abstract](1370)

Abstract:
To solve area air traffic congestion problems, an integer programming model based on time-based metering for area traffic flow management was built. The optimization objectives of the model are minimizing the total weighted delay and minimizing the weighted delay out of the area, and the two objectives are correlated through a decision preference parameter. In addition to the deterministic sector capacity constraint, two new constraints, including the miles-in-trail restriction for the traffic flow and the maximum allowable delay time for flights in the sector, are added to the model to satisfy the practical operation constraints of area traffic flow management. The model was then solved with the software CPLEX through a numerical example using the real operational airspace data and flight data from the Middle South Area Control Center. The results show that the decision preference parameter can adjust the two objectives, and that the newly added constraints can satisfy the practical needs and ensure the feasibility of the strategy implementation, that is produce additional workload for the controllers when implementing the resulting strategy.

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2012 Vol. 25, No. 2