西南交通大学学报

Organization Methods of Overnight Operation for Chinese High-Speed Railways

PENG Qiyuan, YANG Kui, WEN Chao, TAO Siyu

2015, 28(4): 569-576. doi: 10.3969/j.issn.0258-2724.2015.04.001

[Abstract](1439)

Abstract:
In current network operation mode, Chinese high-speed railways have been qualified for overnight operation to serve rail passenger better and improve rail company performance. Waiting, transferring, operation and maintenance in bidirectional lines meanwhile, and demand-based periodic operation are the overnight operation mode alternatives. The technical conditions, operation features, applicability and coordination with maintenance curfew, were presented. In contrast, waiting mode owns the priority with long travelling distance and short maintenance duration, and transferring mode is preferable with long maintenance duration. Demand-based periodic overnight operation and maintenance curfew satisfy daily maintenance demand, and provide better operation conditions in the case of large travelling demand.

Driving Speed Decision-Making on Complex Highways Based on Strategy of Trajectory-Speed Coupling

XU Jin, ZHAO Jun, LUO Qing, SHAO Yiming

2015, 28(4): 577-589. doi: 10.3969/j.issn.0258-2724.2015.04.002

[Abstract](984)

Abstract:
To provide the target speed profile for automatic driving of cars, a speed determination algorithm was presented based on the curvature of pre-view trajectory. Firstly, the position of trajectory on several preview cross-sections was determined and the curvature of each trajectory point was calculated and used as the input data of speed optimization. Secondly, selecting an objective function from minimum traveling time, driving comfort, minimum deviation from the cruise speed and a mixed mode, a speed decision was made under constraints of the lateral/longitudinal driving comfort and the maximum/minimum speed limit using a moving horizon algorithm. With the rolling of preview cross-sections with the forward movement of cars, the desired speed profiles along the distance traveled can be obtained. Finally, a field test was carried out on a complex mountainous highway to validate the proposed model, and examples of trajectory and speed decision of two mountainous highways and an F1 track was illustrated. The results show that: (1) speed profiles of different driving patterns were obtained though the combination of different modes of trajectory control and speed control, which could simulate the various driver behaviors; (2) as the simulated trajectory is generated within the road geometry, factors used for determining the edge of the roadway, such as radius, deflection angle, spirals, pavement width, deflecting direction can all affect the trajectory and then affect the driving speed, therefore the model is applicable to the highways with complex geometrical shapes.

Multi-scale Extraction of Road Network Incremental Information in Navigation Electronic Map

WANG Yanhui, YIN Chuan, DING Yuhong

2015, 28(4): 590-596. doi: 10.3969/j.issn.0258-2724.2015.04.03

[Abstract](776)

Abstract:
To overcome the disadvantage in matching old and new targets by use of usual experienced threshold value for incremental information extraction, a multi-scale extraction method is proposed for the road network incremental information in navigation electronic map. In this method, an Otsu-based adaptive threshold is adopted to determine the geometric matching criterion so as to detect incremental information; further, a progressive selection algorithm based on the mesh density of road network is improved to extract the incremental change information at a smaller scale in map generalization. Incremental updating test results show that: (1) by use of the Otsu-based adaptive threshold, the matching accuracy between the old-version road objects and new-version ones approximately reaches 90%, which is superior to that by use of the experienced threshold; (2) the improved progressive selection algorithm for incremental updating objects can meet the need of structural selection in road network incremental updating.

Evaluation of Guide Sign Layout in Rail Transit Hubs Based on Human Environment Interaction

GUO Fanliang, YU Dandan, DONG Baotian

2015, 28(4): 597-603. doi: 10.3969/j.issn.0258-2724.2015.04.004

[Abstract](989)

Abstract:
In order to optimize the guide sign layout of rail transit hubs and improve their operation efficiency and service level, a simulation model of passenger way-finding behavior was established using the cellular automat based on the interactive features between passenger way-finding behaviors and guide signs, and an evaluation index system of guide sign layout was developed. Then, a quantitative evaluation method on the basis of the dynamic simulation model was proposed, in which the passenger way-finding effect is analyzed using the GSign system by inputting such parameters as passenger flow, facilities and equipment. Finally, a case study was conducted for some typical scenarios of Beijing South Station. The results show that passengers' average walking speeds in typical inflow route, outflow route and transfer route are respectively increased by 4.0%, 3.2% and 13.3% by optimizing their guide signs, and the average relative error between simulating results and actual results is about 7%.

Vehicle-Turnout Coupled Dynamics and Improvement Measures for Heavy Haul Lines

HOU Bowen, GAO Liang, LIU Qibin

2015, 28(4): 604-609. doi: 10.3969/j.issn.0258-2724.2015.04.005

[Abstract](883)

Abstract:
To ensure that heavy-haul vehicle safely passes the turnout zone and increase turnout service life, a refined vehicle-turnout dynamic model was established based on the rigid-flexible coupling modeling method. The effects of the directions of vehicle passing turnout and vehicle speed on the dynamic characteristics of the vehicle-turnout system were analyzed. The performance of three improvement measures including setting track gauge bars, changing rail cant and increasing the widths of switch rail and nose rail were evaluated. Results show that setting track gauge bars in turnout zone decreases 43% wheel-rail lateral force and 5.1% wheel-rail vertical force respectively; changing the rail cant from 1:40 to 1:20 reduces 10.7% wheel-rail lateral force and 4.0% wheel-rail vertical force in the main route, and reduce 16.7% wheel-rail lateral force and 14.8% wheel-rail vertical force in the divergent route; increasing the width of the switch rail and nose rail with 2mm enlarges the wheel-rail interaction by 8.3%, but reduces18.8% rail dynamic bending stress.

Response Analysis of Long-Span Suspension Bridge under Mountainous Winds

HUANG Guoqing, SU Yanwen, PENG Liuliu, MA Cunming, LIAO Haili, LI Mingshui

2015, 28(4): 610-616. doi: 10.3969/j.issn.0258-2724.2015.04.006

[Abstract](1257)

Abstract:
This study investigates static wind and buffeting responses of long-span suspension bridges under non-stationary winds in the mountainous area, where a suspension bridge located in Yunnan province was taken as an example. Firstly, a scheme to reasonably determine the mean wind speed and accurately estimate the power spectrum density of wind fluctuation based on measured wind samples at the bridge site was introduced. Then, the nonlinear static wind response was calculated by considering the initial internal force state under dead load. Finally, based on the measured wind spectrum and the specification spectrum that is derived from the bridge design code, buffeting responses of the bridge were analyzed by the pseudo excitation method. The results show that the displacement of girder is dominated by the vertical vibration, and the dynamic displacement is larger than its static counterpart significantly. In addition, the static displacement is underestimated if an interval of 10 min is used to derive the mean wind speed; the wind spectrum based on the specification wind spectrum may lead to underestimated girder buffeting response,and threaten the bridge safety. These findings can provide useful references for the static and buffeting analyses of other long-span bridges constructed in mountainous terrains.

Influence of Wind Sensor Location on Bridge Tower on Measurement Results

ZHANG Mingjin, LI Yongle, YU Xianquan, LIU Dejing, ZHANG Li

2015, 28(4): 617-622. doi: 10.3969/j.issn.0258-2724.2015.04.007

[Abstract](1085)

Abstract:
In order to investigate the effect of wind sensor location on measurement results, finite volume method (FVM) was adopted to discretize the computational domain by taking the commercial computational fluid dynamics (CFD) software Fluent as a platform, and the k- turbulence model was used to calculate the wind environment. The variation laws of wind speeds and wind directions at wind observation points near bridge tower under different inflow wind speeds and directions were analyzed, and the correction values of wind speed and wind angle were given. The research results indicate that bridge tower affects the measurement results of wind sensors obviously, and the locations of wind sensors should be optimized. Wind speed ratio fluctuates from 0.45 to 1.30 when wind sensors are located in the upstream, and it changes from 0.05 to 1.25 when they are located in the downstream. The optimum locations of wind sensors should be where they have more than 1.0 time the characteristic size away from bridge tower and the angle between their locations and inflow is in the range of (45.0 to 56.5).

Model Updating Method for Prefabricated Multi-girder Bridges

ZHOU Zhengmao, YUAN Guifang, TIAN Qingyong

2015, 28(4): 623-629. doi: 10.3969/j.issn.0258-2724.2015.04.008

[Abstract](819)

Abstract:
In order to reflect the real status of an existing bridge, a new model updating method for multi-girder bridges was presented. In this method, the relative displacement in a hinge joint is supposed to be proportional to the shear force; the stiffness of hinge joint, flexural and torsional rigidity of girders are simultaneously taken as unknown parameters to be modified. The displacement equations are established with measured displacements on both sides of girders, and the optimal solution for the over-determined equations is obtained by the QR algorithm. The characters of multi-load cases, multi-loads and eccentric loads are considered in the proposed model, so that it can be used to bridge load tests. Numerical simulations for a multi-girder bridge with crash barriers and damages were carried out. The simulation results show that the proposed method can produce accurate corrected factors for girders with large damage or complex affiliated structures; load cases should be adopted as many as possible, and the loads should be arranged near the hinge joints or girders to be tested.

Stochastic Analysis of Bending Deflection for Reinforced Concrete Beam in Loading Process

XU Tengfei, BAI Xuemeng, ZHAO Renda

2015, 28(4): 630-634,647. doi: 10.3969/j.issn.0258-2724.2015.04.009

[Abstract](959)

Abstract:
Combining Monte Carlo sampling with nonlinear finite element method, the random analysis model for nonlinear deflection of reinforced concrete beams was established to assess the random deflection of in-service reinforced concrete beams. Based on this model, the stochastic deflection of the classic concrete beam in loading process was simulated. Meanwhile, the parametric analysis of reinforcement ratio of concrete section was performed. The results show that the variability of deflection changes in loading process. Under the loads of high probability of cracking, the variability of deflection reaches the maximum value. Moreover, the variability of deflection is affected by the reinforcement ratio. The lower reinforcement ratio leads to the higher variability of deflection. However, with the increment of the load, the variability of deflection is reduced. Finally, when the load is close to the serviceability limit state, the variability of deflection for different reinforcement ratios becomes stable and similar.

Construction Control of 500 m Scale Concrete- Filled Steel Tubular Arch Bridge

HAO Niebing, GU Anbang

2015, 28(4): 635-640. doi: 10.3969/j.issn.0258-2724.2015.04.010

[Abstract](932)

Abstract:
In order to solve the problems in construction control of 500 m scale concrete-filled steel tubular (CFST) arch bridges, the limitations of the existing construction control methods were analyzed. Based on the mechanical characteristics of the structure in construction process, an adjustable domain method for construction control was proposed, and the corresponding calculation formulas were deduced. From the preponderances of this method and the requirements of arch rib assembling, a line shape control measure for assembling was given. By controlling the line shape, stress and cable force to a certain range and adjusting them only in key construction stages, the adjustable domain method can reduce cable tension adjustment. The proposed method was applied to the Bosideng bridge, the errors of line shape and stress after closure were both within the allowable ranges of JTG/T F502011. The practice shows that the adjustable domain method is reliable for the construction control of 500 m scale CFST arch bridges.

Axial Compression Stress-Strain Model for UHPC Cylinders Confined by FRP

DENG Zongcai, WANG Yichao

2015, 28(4): 641-647. doi: 10.3969/j.issn.0258-2724.2015.04.011

[Abstract](1019)

Abstract:
In order to investigate the axial compression behaviors of FRP (fiber-reinforced polymer) confined UHPC (ultra-high performance concrete) specimens under axial compression, 30 FRP confined UHPC specimens and 3 unconfined UHPC cylindrical specimens were tested. The effects of FRP types, layers of fiber sheets, and confinement methods (FRP tube or FRP sheet) on the compression behaviors of confined UHPC were analyzed. Based the test results and considering the confinement ratio and lateral restraint stiffness, new models for predicting the compressive strength and ultimate strain were proposed. In addition, the Lam-Teng model was improved by revising its a parameter. The research results indicate that confinement ratio and lateral restraint stiffness are the major influencing factors of the compressive strength and ultimate strain of confined UHPC, and the stress-strain curve of a confined specimen is consisted of a parabola and a straight line segment. The improved Lam-Teng model has a goodness of fit of 0.96, so it can predict the stress-strain relationship of confined specimens more accurately.

Experimental Study on Shear Bearing Behavior of Continuous Steel-Concrete Composite Beams with Web Openings

LI Longqi, ZHOU Donghua, LIAO Wenyuan, CHEN Xu, YAO Kaicheng

2015, 28(4): 648-655. doi: 10.3969/j.issn.0258-2724.2015.04.012

[Abstract](1099)

Abstract:
In order to investigate the shear bearing behavior of continuous steel-concrete composite beams with web openings, five continuous composite beams with web openings under two monotonic symmetric concentrated loads were tested using the thickness and reinforcement ratio of slabs as variables. The shear separation method was introduced to calculate the shear stress borne by concrete slabs and steel beams of composite beams. The test results show that web openings not only decrease the stiffness and ultimate load-carrying capacity but also give rise to the redistribution of vertical shear force of steel beams and concrete slabs; that is, the concrete slab bears 85%-90% of the total cross-section shear at the web opening region. The plane hypothesis is not valid in the web opening area. The failure mode is the shear failure of concrete slab in the region near the opening. In addition, the ultimate load-carrying capacity and deformability of continuous composite beams can be increased by increasing the thickness and reinforcement ratio of a concrete slab, which can be used for enhancement of the web opening area.

Experimental Investigation on Anisotropic Creep Characteristics of Quartz Mica Schist

LIU Huaizhong, XIE Hongqiang, HE Jiangda, XIAO Mingli, ZHUO Li, LIU Jianfeng

2015, 28(4): 656-661,697. doi: 10.3969/j.issn.0258-2724.2015.04.013

[Abstract](776)

Abstract:
To investigate the anisotropic rheological properties of quartz mica schist in the underground chamber of Danba hydropower station, two groups of uniaxial compression creep tests were conducted on quartz mica schist samples. Based on the creep characteristics of quartz mica schist, the damage Nishihara model was improved by adding a nonlinear viscous component in series, the creep equation was derived in the light of the Lemaitre strain equivalence principle, and one-dimensional rheological mechanical parameters were obtained. Furthermore, the effects of schistosity and stress level on transient creep, decelerating creep, steady-state creep, accelerating creep and other creep characteristics were analyzed. The research results show that with the increase of stress, the instantaneous elastic modulus of quartz mica schist remains a constant roughly, but its hysteretic elastic modulus, stable viscous coefficient and creep failure time decrease. Quartz mica schist exhibits a strong visco-plasticity and high strength when loading direction is perpendicular to schistosity, while quartz mica schist shows strong instantaneous elasticity, visco-elasticity, viscosity and ductility when the loading direction is parallel to schistosity.

Revision of Additional Stress in Soils Based on Centrifuge Model Tests

WU Lijun, JIANG Guanlu, LI Anhong

2015, 28(4): 662-668. doi: 10.3969/j.issn.0258-2724.2015.04.014

[Abstract](829)

Abstract:
To improve the accuracy of embankment settlement control of high-speed railway, centrifuge model tests with different loading methods were conducted to investigate the distribution of additional stress in two medium-compression soils under subgrade load. In addition, numerical computations with PLAXIS2D finite element program and field tests were performed to verify the experimental distribution of additional stress. On the test results, a modified calculation method for additional stress considering the effect of width-to-height ratio was proposed. The research results show that additional stress decreases more quickly near the foundation surface, but its attenuation is gradually decelerated with depth increasing. There exist a significant difference between the distribution of additional stress based on the Boussinesq solution and that acquired from the centrifuge model tests. Furthermore, the additional stress calculated by the modified method approaches the calculation result based on the field test data.

Differential-Pressure Type Precision Measuring System of High-Speed Railway Substructure Settlement

ZHANG Wenchao, SU Qian, HUANG Junjie, WANG Wubin, JIANG Wei

2015, 28(4): 669-675. doi: 10.3969/j.issn.0258-2724.2015.04.015

[Abstract](986)

Abstract:
A differential-pressure type settlement measuring method based on pressure transmitter was proposed for precision measurement of high-speed railway substructure settlement and deformation. First, the settlement measuring principle was introduced based on Euler differential equation of static fluid. Then, the measurement system error caused by temperature change was solved by differential-pressure treatment and temperature correction of fluid density. Typical technical parameters of the pressure sensor, such as the thermal sensor drift and sensor range, were analyzed; and a high-precision integrated system for automatic settlement measurement, namely HSMS-1, was designed and used in practice to measure the settlement of a high-speed railway bridge. The results showed that the measured values by HSMS-1 were consistent with those by an electronic level in the temperature range of -18 to 42 ℃, and the maximum error was only 0.44 mm. With a measurement range of 300 mm, the accuracy class of system could reach 0.2. Therefore, this system is applicable to long-term automatic monitoring of high-speed railway substructure settlement in complex natural environments.

Extracting Fault Features of High-Speed Train Bogies Using Copula Function

JIN Weidong, LÜ, Qianyong, SUN Yongkui

2015, 28(4): 676-682. doi: 10.3969/j.issn.0258-2724.2015.04.016

[Abstract](1226)

Abstract:
To monitor the working condition of key components of high-speed train bogies in real time, an approach using Copula function to extract features is proposed. Vibration signals of a certain high-speed train are obtained under four typical working conditions, including normal condition, yaw damper fault, air spring fault, and lateral damper fault. The vibration signal is decomposed by ensemble empirical mode decomposition first. Then, the joint probability distribution of intrinsic mode functions is computed by Gaussian Copula function. The Kullback-Leibler distance of two marginal distribution functions, and the mean and variance of the joint probability density function are extracted as the features. The support vector machine is used to classify the working conditions. The experimental result shows that the average recognition rate is above 95% at the speed of 200 km/h, which verifies the effectiveness of the proposed feature extraction method.

Bi-level Imperfect Maintenance Strategy and Optimization for Single Component of Electric Multiple Unit

WANG Hong, DU Weixin, LIU Zhilong, JIANG Zuhua

2015, 28(4): 683-690. doi: 10.3969/j.issn.0258-2724.2015.04.017

[Abstract](795)

Abstract:
The maintenance of EMU (electric multiple unit) components is an important measure to ensure the operation reliability of vehicles. In addition, the determination of maintenance interval has direct influence on the safety of rail transport. Therefore, based on the multi-level maintenance rule of EMU in China, a multi-level imperfect maintenance policy was proposed. A component replaced in the 4-class repair of EMU was selected as an objective, and a bi-level imperfect maintenance model was established on the basis of the Weibull distribution of mileage fault. By utilizing the current maintenance rule of EMU as a template, two maintenance plans for the component were structured with maintenance cost and maintenance time as the optimal goals. The maintenance intervals and maintenance levels for each section of interest were optimized by using multi-objective genetic algorithm. Comparison with the optimization results of single maintenance mode shows that maintenance schedules based on the bi-level imperfect maintenance model can meet the reliability requirement at low cost. And maintenance schedules derived from case which does not exactly match vehicle repair levels can get higher component reliability with less maintenance costs and low requency.

Numerical Simulation of Residual Stress Field and Surface Roughness for Steel Plate Subjected to Shot Peening

QIANG Bin, LI Yadong, GU Ying, YANG Yuanlu

2015, 28(4): 691-697. doi: 10.3969/j.issn.0258-2724.2015.04.018

[Abstract](1112)

Abstract:
In order to study the distribution of residual stress field and surface roughness of a steel plate after shot peening treatment, finite element models of shot peening with multiple shots are established using ABAQUS. Through the models, the dynamic process of cast shot peening of Q345 steel plates used for bridge is simulated. Moreover, the effect of impact velocity, impact times, and shot diameter on the horizontal residual stress along the depth and on the surface roughness are analyzed. The results show that as the impact velocity, impact times, and shot diameter increase, the residual compressive stress has a trend of homogenization, the stress distribution range develops gradually in the direction of thickness, and the surface roughness increases gradually. According to the law of surface roughness changing with the impact times, a logarithmic function is proposed to represent the relationship between surface roughness and impact times. In addition, given a shot diameter of 1.4 mm, the relationship between surface roughness, impact velocity and impact times is presented.

Influence of Triethanolamine Content on CuS Thin Films Prepared by Chemical Bath Deposition

FAN Ximei, ZHANG Fengzhang, LI Xiangqi, WU Xiaofeng, FAN Jian, HUANG Yaohan, LI Guangli

2015, 28(4): 698-702. doi: 10.3969/j.issn.0258-2724.2015.04.019

[Abstract](723)

Abstract:
In order to study the effect of triethanolamine (TEA) on chemical bath deposition process, CuS thin films were successfully deposited onto glass substrates by chemical bath deposition using copper chloride, thiourea, ammonium and TEA as raw materials. The effects of TEA content on thickness, structure, morphology and optical properties of the obtained films and the deposition mechanism were investigated. The results showed that the TEA could act as a complexing agent to maintain the reaction stability. As the TEA content increased, the induction time of reaction increased to 23 min, the films exhibited bigger particles sizes after the same deposition time, and the film thickness increased to 240 nm. In addition, the transmittance of the films decreased with TEA increasing.

Microsphere Agglomeration Technique for Drug Release from Porous-Coated Ti

WANG Dongwei, XIAO Dongqin, DUAN Ke, LU Xiong, FENG Bo, WENG Jie

2015, 28(4): 703-709. doi: 10.3969/j.issn.0258-2724.2015.04.020

[Abstract](766)

Abstract:
A microsphere agglomeration technique incorporating gentamicin in porous-coated Ti was used to overcome technical disadvantages associated with available drug-release techniques for bone implants. Chitosan microspheres containing various concentrations of gentamicin were prepared by a water-in-oil emulsion method and lyophilized to dry powders. The powders were then spread on porous-coated Ti, and wetted with water to promote their agglomeration after they enter into the pores by gently tapping the samples. Microscopical analyses revealed that, the microspheres formed submilllimeter-sized agglomerates and entrapped in the pores. After immersion in shaking water bath (100 r/min, 37 ℃) for 7 d, 80%-83% of the agglomerates were retained in the coating, suggesting a reasonable entrapment stability. The microsphere-porous Ti complexes showed a rapid drug release in 24 h followed by a prolonged slow release. After coculture with Staphylococcus aureus for 48 h, the porous Ti carrying gentamicin-loaded microspheres produced clear inhibition zones, confirming its In vitro antibacterial activity.

Assessment Method of Gear Wear Condition Based on Data Mining

ZHANG Huailiang, LIU Sen, ZOU Baiwen

2015, 28(4): 710-716. doi: 10.3969/j.issn.0258-2724.2015.04.021

[Abstract](854)

Abstract:
To improve the accuracy of gear wear condition assessment, a novel gear wear condition assessment method based on data mining technology was proposed. In this method, a spur gear pair wear test was designed to extract oil parameters and vibration parameters within the whole life cycle of the gear pair first. Then, a clustering division of gear pair wear conditions was made, based on which, the association rules set between the monitoring parameters and gear pair wear conditions was obtained. Finally, a matching algorithm of association rules was developed to recognize the gear pair wear condition, and verified using the test data extracted from the wear test. The results show that the proposed gear wear assessment method based on data mining can effectively assess the wear condition of gear pairs, and the recognition rate is about 90%.

Modal Control Model and Vibration Control of SCLD Plate

WANG Pan, LU Jun, DENG Zhaoxiang, YANG Xiaoguang, WANG Zhengya, LIAO Haichen

2015, 28(4): 717-724. doi: 10.3969/j.issn.0258-2724.2015.04.022

[Abstract](858)

Abstract:
To effectively suppress the low frequency vibration of thin plate, the active vibration control of smart constrained layer damping (SCLD) structure was studied. Firstly, the damping characteristics of viscoelastic material varying with temperature and frequency were considered, and coupling finite element model for dynamics analysis was established based on GHM damping model. To address the large numbers of degrees of freedom of dynamics analysis model, model reduction was conducted through dynamic condensation in physical coordinate and complex modal truncation in state equation, and low-dimensional real modal control model was obtained from the conversion of complex modal space to the real modal space. Finally, the theoretical model was verified by modal experiment, and vibration controller was designed based on low-dimensional control model to validate the proposed method. The results show that the proposed combination reduction method is effective for SCLD structure. For the modal control model, the vibration control effect is desirable: the decay time of vibration response is shortened from 0.20 s to 0.08 s under unit step excitation, and the root mean square values of vibration response decreases 39.65% under gauss white noise excitation.

Performance Testing of Planar Internal Gear Primary-Enveloping Crown Worm Drive

CHEN Yonghong, CHEN Yan, WANG Jinge, ZHANG Guanghui

2015, 28(4): 725-731. doi: 10.3969/j.issn.0258-2724.2015.04.023

[Abstract](833)

Abstract:
In order to obtain the transmission performance parameters of the planar internal gear primary-enveloping crown worm drive (hereinafter referred to as crown worm drive), an electrically enclosed transmission performance test rig was built based on the meshing geometry and meshing performance to test the transmission performance of a prototype crown worm drive in various working conditions. The test results show that the actual contact areas are only two thirds of the theoretic contact area because of the manufacture error and assembly error. The transmission efficiency of the crown worm drive increases with the rotational speed increasing: as the load increases, the transmission efficiency decreases significantly at low speed, and presents a slight rise at high speed. In various working conditions, the maximum transmission efficiency is 69.05%, and the maximum temperature rise of box oil is no more than 89.8 ℃. Therefore, the crown worm drive has an excellent transmission performance, and is suitable for heavy power transmission.

Dynamic Performance of Anti-climber Device for Trains in Crash

DING Sansan, LI Qiang, LU Yujiang, XIAO Shoune

2015, 28(4): 732-739. doi: 10.3969/j.issn.0258-2724.2015.04.024

[Abstract](865)

Abstract:
In order to investigate the influential factors of a vehicle's overriding condition in a crash, a 2D collision dynamics model that considers the dynamic coupling relationship between anti-climbers was set up. Based on this model, a geometric searching algorithm for anti-climber contact was presented, and a method for calculating the anti-climber's longitudinal resistant force based on energy conservation law was developed. Expressions of the anti-climber resistant force and torque were derived taking into account the influence of the large plastic deformation and dynamic factors. In addition, a numerical example was provided to simulate the dynamic characteristics of the anti-climber. The results show that the meshing degree between ant-climber teeth has a close relation with the maximum absolute and relative rotation angles of the anti-climber. The maximum absolute rotation angle of anti-climber teeth can be reduced by decreasing the longitudinal resistant force and the energy absorption length and increasing the bending rigidity of the anti-climber device. The maximum relative rotation angle of anti-climber teeth increases with the energy absorption length. With the bending rigidity of the anti-climber increasing, the maximum relative rotation angle shows a trend of first increase and then decrease, but the longitudinal resistant force of the anti-climber has no significant effect on the relative rotation angle. Compared with the traditional finite element method, the proposed method can reduce the calculation time by 10% .

Multidisciplinary Multi-objective Optimization Design of Hollow End Mill Based on Response Surface Method

ZHAO Hongfeng, SHAN Zhongde, LIU Feng, ZANG Yong

2015, 28(4): 740-746. doi: 10.3969/j.issn.0258-2724.2015.04.025

[Abstract](851)

Abstract:
In order to deal with the difficulty of removing sand chips in digitally machining sand molds without pattern with dry cutting, a hollow end mill was designed that can remove sand chips by pneumatic conveying. First, combined with simulation analysis and response surface method, a multidisciplinary multi-objective optimal model of hollow end mill was established to achieve good static and dynamic performance and good removing chips performance. Then, the Pareto optimal solutions were obtained using non-dominated Sorting Genetic Algorithm II (NSGA-II). Finally, the reliability of optimization results was verified by the simulation and experiments. The Pareto optimal results, compared with the initial design, show that the total deformation of tool nose relative to work piece reduces 0.1% on average, the first-order natural frequency increases averagely 0.8%, and the average wind velocity at the outlet of sand mold cavity increases averagely 10.2%, improving the overall performance of hollow end mill.

Integrated Optimization of Cargo Distribution and Ship Speed for Heavy-Cargo Transportation

LI Xiaojun, XIE Xinlian

2015, 28(4): 747-754. doi: 10.3969/j.issn.0258-2724.2015.04.026

[Abstract](850)

Abstract:
In order to study the influence of different fuel consumption of semi-submersible vessels with full-load and no-load on heavy cargo distribution and optimal speed, a integrated optimization model of cargo distribution and ship speed was built, and a global search method based on an insertion method and an improved recursive smoothing algorithm (IRSA) was designed. In this method, the insertion method was used to solve the cargo distribution problem, and the IRSA was used to calculate the optimal speed of full-load and no-load ships. The results of an application example show that compared with the traditional recursive smoothing algorithm (RSA), the global search method can reduce the transportation cost 2.403 million Yuan; compared with the time based discretization approach with the time window divided into six and nine parts, the global search method can decrease the CUP time by 71.1 and 767.3 s, respectively.

Document Semantic Compression Algorithm Based on Phrase Topic Model

WANG Lidong, ZHANG Yin, LÜ, Mingqi

2015, 28(4): 755-763. doi: 10.3969/j.issn.0258-2724.2015.04.027

[Abstract](843)

Abstract:
To extract representative semantic terms, a document SCPTM (semantic compression based on phrase topic modeling) algorithm was proposed. Firstly, SCPTM converts semantic terms extraction to the optimization model of maximization, and uses a greedy search algorithm to generate approximate solution. Then, in order to compute input parameters for SCPTM, phrase discovery model LDACOL was employed to extract important topics in phrase pattern. Meanwhile, the instability of topic allocation in LDACOL model was improved, so that the extracted semantic terms can satisfy the demand of human cognition. Finally, to evaluate the performance of topic discovery, the improved LDACOL was compared with LDA, LDACOL and TNG, and SCPTM was used for semantic compression on different corpora. Then the effectiveness of the algorithm was evaluated by clustering results. Empirical experimental results show that the preformance of topic discovery of improved LDACOL is superior over other three models in most cases. The accuracy of extracting the representative semantic terms by the proposed algorithm can reach 70%-100%, and can achieve better results for document clustering compared with other dimension-reduction algorithms, such as PCA, MDS and ISOMAP.

Quantitative Indices of Streetscape Visual Evaluation and Their Validity Analyses

HAN Junwei, DONG Liang

2015, 28(4): 764-769. doi: 10.3969/j.issn.0258-2724.2015.04.028

[Abstract](928)

Abstract:
In order to establish an effective index system of streetscape visual evaluation, 6 quantitative indices were proposed to reflect the objective visual attributes of streetscape based on the idea of image processing, and their validity was verified by digital images of 10 walking streets. The mathematical analyses of subjective and objective indices show that street width-to-height ratio, street width, sky openness index, visual entropy, and color complexity can reflect the streetscape's objective visual attributes effectively (correlation coefficient is above 0.633, significance is smaller than 0.05); the complexity of sight is the most important factor in the streetscape visual evaluation because of its high weight of 22.6%.

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2015 Vol. 28, No. 4