西南交通大学学报

Using Free-Station Linear-Angular Intersection Network in Tunnel Horizontal Survey of High-Speed Railway

LIU Chenglong, JIN Guoqing, YANG Xuefeng, WANG Changjin, XU Xiaozuo

2014, 27(1): 1-7. doi: 10.3969/j.issn.0258-2724.2014.01.001

[Abstract](1356)

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Abstract:
To deal with the defects of loop traverse networks for the tunnel of high-speed railway, such as less redundant observations, great sensitivity to lateral refraction, difficult usage of control points and large lateral error, a new method using free-station linear-angular intersection network for the horizontal control survey inside tunnel was proposed. The calculation models for the two indexes,relative mean square error of distance and the lateral breakthrough error,were established for the free-station linear-angular intersection network. The simulation results show that the errors of two indexes can meet the accuracy requirements of the high-speed rail survey specifications. The tunnel breakthrough accuracy is increased by 20%, and also the efficiency of measurement is improved. Qualitative and qualitative analysis proved that the free-station linear-angular intersection network can substitute the loop traverse network.

Strapdown Inertial Measurement Method Based on Data Fusion Technique and Its Application to Railway Track

WANG Xuemei, NI Wenbo

2014, 27(1): 8-14,51. doi: 10.3969/j.issn.0258-2724.2014.01.002

[Abstract](1069)

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Abstract:
To further increase the accuracy of strapdown inertial measurement system, based on Kalman data fusion technique, a novel strapdown inertial measuring method for railway track geometrical parameters was proposed. By analyzing major error factors that affect the strapdown inertial system, the error state space equations were constructed. The selection of external observations and their influences on the observability and the degree of observability of the Kalman filter were also analyzed. The velocity and roll angle were used as external observations, and the random vibration interference was modeled with second-order auto-regression equations. The simulation results show that compared with the common Kalman filtering algorithm, the proposed method can greatly increase the estimation accuracy of Kalman filtering state variables, and the standard deviation of pitch angle and azimuth angle is decreased by 1.5° to 2.5°.

Dynamics Interaction between Heavy-Haul Locomotive and Track under Driving Conditions

LIU Pengfei, WANG Kaiyun, ZHAI Wanming

2014, 27(1): 15-20. doi: 10.3969/j.issn.0258-2724.2014.01.003

[Abstract](1306)

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Abstract:
In order to investigate the characteristics of the dynamic interaction between locomotive and elastic track, a locomotive-track coupled dynamics model for the heavy-haul locomotive driven by axle hung traction motor was built, taking the electric motor drive system and traction into account. Then, the wheel/rail contact tangential force under large slip conditions and the adhesion utilization rate for the heavy-haul locomotive with a traction of 450 kN were calculated using the Polach nonlinear creep force model. As the traction varied between 150 and 450 kN, the wheel/rail dynamic interaction of the locomotive passing through a curved track was analyzed. The results show that the utilization factor of adhesive weight reaches 91.2% when the traction is 450 kN; and an increase in traction is favorable to improve the lateral wheel/rail dynamic interaction, but will worsen the wheel/rail wear.

Modeling of Coupler and Draft Gear Systems and Their Compressive Behaviors for Heavy-Haul Locomotives

XU Ziqiang, WU Qing, MA Weihua, LUO Shihui

2014, 27(1): 21-26. doi: 10.3969/j.issn.0258-2724.2014.01.004

[Abstract](1558)

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Abstract:
To study the compressive behavior of the coupler and draft gear system for heavy-haul locomotives, a typical cylindrical-pin coupler with coupler shoulder alignment control module and a long-flat pin coupler with tail friction surface were built, and a mathematical model for the coupler and draft gear system of heavy-haul locomotives were presented based on the resilient rubber draft gear model with nonlinear hysteresis characteristic. Using a train model composed of 4 locomotives and 1 simplified freight wagon, the compressive behaviors of the coupler and draft gear system and its effect on the wheelset lateral force and wheel/rail wear were investigated when the heavy-haul train was running on the straight track. The results show that, the compressive behaviors of the cylindrical-pin coupler and the long-flat pin coupler can be simulated accurately using the interactive coupler shoulder alignment control module and tail friction surface module. With the two stabilized functions, the coupler can constrain its rotation angle within 4.0°, thus decreasing the lateral component of coupler force and improving the running safety of the locomotive.

Feature Extraction of High Speed Train Bogie Based on Ensemble Empirical Mode Decomposition and Sample Entropy

QIN Na, JIN Weidong, HUANG Jin, LI Zhimin, LIU Jingbo

2014, 27(1): 27-32. doi: 10.3969/j.issn.0258-2724.2014.01.005

[Abstract](1314)

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Abstract:
To monitor the working condition of key components of high speed train bogie in time, a novel method for feature extraction is proposed by combination of ensemble empirical mode decomposition (EEMD) and sample entropy theory. Vibration signals are obtained from train body and bogie under four typical working conditions, such as normal condition, air spring fault, lateral damper fault, and yaw damper fault. After EEMD, signals have been decomposed into a series of intrinsic mode functions (IMFs), and the sample entropies of these IMFs constitute a high dimensional characteristic vector. Finally, the support vector machine is used to identify the fault conditions based on the characteristic vector. The experimental result shows that the recognition rate is 88% at the speed of 200 km/h. Therefore, this feature extraction method is effective for high speed train bogie fault signals.

Dynamic Reliability of Novel Damped Outrigger System

TAN Ping, FANG Chuangjie, WANG Lei, ZHOU Fulin

2014, 27(1): 33-38,65. doi: 10.3969/j.issn.0258-2724.2014.01.006

[Abstract](1082)

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Abstract:
Two novel damped outrigger systems, viscous type (VD) and buckling restrained brace type (BRB), were presented for high rise buildings with outriggers. The probability density evolution method (PDEM) was introduced into the analysis of such systems. Random sources from site excitation and damper parameters were considered, respectively. The Kanai-Tajimi model was used to generate artificial ground motion. The 2.5-times mean square error method with 15 discrete representative points from random normal variables was proposed. The total variation diminishing finite differential scheme (TVD) was applied to provide the probability density evolution of maximal story drift angle, and the equivalent extreme value method (EVEM) was utilized to analyze the relationship between dynamic reliability and targeted story drift angle limit. The research results show that both proposed novel damped outrigger systems can reach higher reliability than traditional aseismatic structures. The VD type outrigger system possesses a high reliability under random site excitation, while the BRB type outrigger system is more reliable in the case of random damper parameters. Therefore, the design of redundant outriggers as damped outriggers is capable of increasing the safety of high-rise buildings and it is worthwhile to popularize and apply them in real engineering.

Seismic Reliability Analysis of Continuous Rigid Frame Bridge Using Probability Density Evolution Method

LIU Zhangjun, XIONG Min, WAN Yong

2014, 27(1): 39-44. doi: 10.3969/j.issn.0258-2724.2014.01.007

[Abstract](1211)

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Abstract:
In engineering practice, ground motion has strong randomness in time and spatial distributions. In order to capture accurately the seismic response behavior of long-span bridge structures, the randomness of earthquake excitation should be considered in dynamic response and reliability analyses. By using the orthogonal expansion model for non-stationary ground motion processes and combining the probability density evolution theory, the random seismic response and reliability analyses of a continuous rigid frame bridge are researched under uniform excitation and non-uniform excitation. The research results show that the seismic reliability of long-span bridge structures under uniform excitation and non-uniform excitation are obviously different. When pier top displacement control is used as failure criteria of the seismic reliabilities under uniform excitation and non-uniform excitation, their relative error is up to 50%, and when pier top moment control as failure criteria, their relative error is up to 200%.

Relability of van der Pol-Duffing Oscillator with Fractional Derivative under Wide-Band Noise Excitations

CHEN Lincong, LI Haifeng, MEI Zhen, ZHU Weiqiu

2014, 27(1): 45-51. doi: 10.3969/j.issn.0258-2724.2014.01.008

[Abstract](1338)

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Abstract:
To investigate the first-passage time of van der Pol-Duffing oscillator with fractional derivative under wide-band noise excitations, the restoring force described by a fractional derivative was firstly separated into the equivalent quasi-linear dissipative force and quasi-linear restoring force by using the generalized harmonic balance technique, which yields an equivalent nonlinear stochastic system without fractional derivative. Then, the equivalent nonlinear stochastic system was approximated as one-dimensional diffusive process by using the stochastic averaging method, and the backward Kolmogorov equation associated with the averaged equation was then established and solved to yield the conditional reliability function and mean first-passage time of system. Finally, the numerical simulation demonstrates that the analytical results agree well with those derived by the Monte Carlo simulation; the system reliability improves with the fractional order; and the restoring force described by the fractional derivative can not be regarded as a special damping force.

Full-Scale Model Test of Pre-stressed Cable-Pylon Anchorage for Single-Oblique-Pylon Cable-Stayed Bridges

YE Huawen, LI Cuijuan, XU Xun, XIAO Lin, QIANG Shizhong

2014, 27(1): 52-58. doi: 10.3969/j.issn.0258-2724.2014.01.009

[Abstract](1068)

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Abstract:
In order to ensure the safety of cable-pylon anchorage of Maxin Bridge in Xiamen, a full-scale model test under oblique loading and spatial finite element analysis were conducted to analyze the mechanical behavior of the prestressed cable pylon installed with asymmetric cables and embedded with small-radius U shape prestressed system. The complicated anchorage zone was investigated under different service phrases, including prestressing, service, asymmetric cable action, and overloading. The results show that numerical and experimental results have a good agreement, the effective prestress has a significant effect on the behavior of the zone, and the effect of asymmetric cable loading is slight. In addition, the ultimate bearing capacity of the cable-pylon anchorage with hooped prestress system exceeds 1.7 times the design cable load, which verifies its reliability.

Short-Term Temperature Characteristics of H-Shaped Section Concrete Pylon of Cable-Stayed Bridge

DAI Pu, QIAN Yongjiu

2014, 27(1): 59-65. doi: 10.3969/j.issn.0258-2724.2014.01.010

[Abstract](1215)

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Abstract:
In order to research the effects of temperature load acting on solid concrete pylon, a calculation method was put forward based on the fundamental principles of the heat transfer theory. In this method, initial conditions are determined by means of applying periodic load, and boundary conditions are ascertained from the thermal equilibrium on the surface. By taking a certain bridge as an example, the short-term temperature characteristics of H-shaped section concrete pylon were analyzed by using indirect temperature-stress coupling finite element method, and the distribution features of temperature field and thermal stress were obtained. The analysis result indicates that under the most unfavorable short-term temperature load, temperature cracks may appear on the surface of H-shaped section concrete pylon, so a special attention should be paid to design.

Experimental Investigation of Temperature Effects on Dynamic Characteristics of Reinforced Concrete Slab

CHEN Bo, SUN Yuzhou, GUO Weihua

2014, 27(1): 66-71. doi: 10.3969/j.issn.0258-2724.2014.01.011

[Abstract](1021)

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Abstract:
Concrete structures are prone to solar radiation and environmental air changes, which may cause non-uniform temperature distribution and thereby induce changes in structural dynamic properties. An experimental model was constructed to conduct the measurement on time-varying temperature distribution and structural dynamic properties during a whole day. The temperature gradient and ambient temperature were tested by thermal sensors. A program package was developed on the basis of the modal analysis theory to identify the natural frequencies, mode shapes and damping ratios of the slab. The experimental results indicate that the structural natural frequencies were affected by temperature. If the temperature was increased by 1 ℃, the first-and second-order natural frequencies were decreased by 0.074 and 0.228 Hz, respectively.

Bending Performances of High-Strength Steel-Encased Composite Beams

CAO Lilin, SHI Qiyin, WANG Zhen, GE Yitao, LI Aiqun

2014, 27(1): 72-78. doi: 10.3969/j.issn.0258-2724.2014.01.012

[Abstract](989)

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Abstract:
In order to investigate the bending behavior of high-strength steel-encased composite beams under static load, bending performances of three simply-supported beam specimens with full-interaction and different strengths of steel and concrete were investigated experimentally. The load-defection relationship, strain distribution, steel-concrete interface slippage, crack development and failure mode of these beams were discussed. Based on the test results, the calculation formulas of normal section bearing capacity of high-strength steel-encased composite beam were presented. The research results show that compared with an ordinary composite beam, the bending capacity of a high-strength steel-encased composite beams under static load increases by over 60%, and the displacement ductility coefficients for the three beams are 2.16, 2.76 and 2.34, respectively, indicating that a high strength steel-encased composite beam has a good bending performance.

Dimension-Reduction Method for Structural Reliability Analysis

LI Jinping, JIAO Shengjie, CHEN Jianjun, LIU Guoliang, XU Xinxin

2014, 27(1): 79-85. doi: 10.3969/j.issn.0258-2724.2014.01.013

[Abstract](1152)

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Abstract:
To predict the reliability of implicit and nonliear performance function for complex structures, a dimension-reduction method was presented. The multi-dimensional integration applied to calculate statistical moments of performance function is transformed into multiple low dimensional integrations using the bivariate dimension-reduction method, and the low dimensional integrations are then numerically calculated by the Gauss-Hermite integration. After obtaining the statistical moments, the maximum entropy principle (MEP) is used to determine the best probability density function of performance function for reliability analysis. The proposed method has the merit that the reliabilities at different limit-state values can be obtained readily by determining the probability density function of performance function simultaneously. The results of two examples show that the relative error of failure probability obtained by the proposed method is less than 0.5% compared with that derived by one million times simulations of the Monte Carlo method.

Synthetic Displacement of Steady-State Vibration under Random-Phase Harmonic Excitation

WANG Baisheng

2014, 27(1): 86-92. doi: 10.3969/j.issn.0258-2724.2014.01.014

[Abstract](892)

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Abstract:
The superstructure members of multi-story factories directly sustain the dynamic loads of power machines. Accurate displacement calculation of such members is considered as a key problem that remains to be solved. Based on the theories of probability and vibration, the distribution function of synthetic displacement of two random-phase harmonic vibrations in the form of analytic expression, as well as the distribution function of three random-phase harmonic vibrations in the form of single variable integral was deduced. The distribution fitting tests of numerical simulation results show significant difference between the actual distribution of synthetic displacement and normal distribution. Moreover, with amplitude separated from random phase and linear transformation, a new approximation of synthetic displacement was established, which is superior to the square root sum of square method. On the basis of reciprocal-displacement theorem, an example of a multistory loom factory building was used to illustrate the approximation procedures in the finite element modeling and calculation.

Computational Modeling of Flows in Random Porous Media using Lattice Boltzmann Method

LUO Zhongxian, QIU Yanjun, YU Huaqian

2014, 27(1): 93-96,118. doi: 10.3969/j.issn.0258-2724.2014.01.015

[Abstract](929)

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Abstract:
In order to capture the relation between permeability and porosity, fluid flowing through two-dimensional random porous media was simulated at pore level by enforcing the no-slip condition on the fluid-solid interface. Fluid flow in two dimensional randomly generated porous media was simulated at the pore-scale using the lattice Boltzmann method (LBM). Random media were constructed by placing solid points with a random distribution. The Darcy's law was verified. The research result shows that the permeability varies exponentially with the porosity at low porosity less than about 0.3, being close agreement with the present result.

Experimental Study on Acoustic Emission Features of Marbles during Unloading Failure Process

CONG Yu, WANG Zaiquan, ZHENG Yingren, ZHANG Liming

2014, 27(1): 97-104. doi: 10.3969/j.issn.0258-2724.2014.01.016

[Abstract](908)

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Abstract:
To explore the relationship between stress path and emission characteristics during failure process, the conventional triaxial compression test, and constant axial stress and unloading confining pressure test were performed on marbles. The results show that acoustic emission features differ with stress paths. In the conventional triaxial compression experiment, the maximum of acoustic emission count rate takes place at the sudden drop point of stress, behind the stress peak, while the acoustic count rate maximizes at the stress peak during the experiments of unloading confining pressure. Before the conventional triaxial compression failure, the acoustic emission of the rock sample is alternated between the fluctuating and quiet period, and the paths of constant axial stress and unloading compression are characterized by burstiness. Under a low confining pressure, the experiment of unloading confining pressure reveals that the acoustic emission count rate falls evidently at the unloading position, and a higher confining pressure will result in a rock failure lasting longer and a higher acoustic count rate at the time of failure. In addition, a higher rate of unloading pressure will bring a shorter quiet period to the sample unloaded, and hence a higher maximum acoustic count rate during the whole failure process. When unloading occurs at the plastic stage, there will be a small amount of acoustic emission occurring with a relatively high count rate, but comparatively lower than the rate in the rock failure process.

Accuracy of Settlement Prediction of Composite Foundation by Centrifuge Model Tests

FENG Yan, JIANG Guanlu, CHEN Weizhi, LI Anhong

2014, 27(1): 105-110. doi: 10.3969/j.issn.0258-2724.2014.01.017

[Abstract](1064)

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To quantitatively assess the prediction ability of geotechnical centrifuge model test for composite foundation, centrifugal model tests were carried out on two kinds of composite foundation. Through the comparison of experimental and field filling results, the factors affecting the prediction accuracy, including the type of composite foundation, test method, soil types and others, were analyzed. The results show that: the prediction accuracy of the similar grading method model is low, and the prediction accuracy of the similar mechanical parameters method can improve the prediction accuracy effectively. Furthermore, the prediction accuracy is influenced by soil characteristics and reinforcing methods.

Statistical Damage Constitutive Model of Cement and Asphalt Mortar

FU Qiang, XIE Youjun, ZHENG Keren, ZENG Xiaohui

2014, 27(1): 111-118. doi: 10.3969/j.issn.0258-2724.2014.01.018

[Abstract](975)

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In order to investigate the constitutive relationship for cement and asphalt mortar (CA mortar) under different strain rates, a statistical damage constitutive model considering the strain rate effect of CA mortar was established by using the method of statistical damage mechanics. In addition, the variation of damage properties of CA mortar with strain rate was discussed. The research results show that correlation coefficients between fitting results based on the constitutive model and experimental ones are all above 0.978 1, and the constitutive model can effectively reflect the transformation of toughness to brittleness of CA mortar with the increase of strain rate. A great strain rate will result in a small damage rate of CA mortar before the peak damage rate and a big damage rate after the peak damage rate.

Model and Algorithm of Multi-objective Discrete Transportation Network Design under Stochastic Demand among OD Pairs

YANG Ming, SU Biao, SUN Zhijie, XU Yi

2014, 27(1): 119-125. doi: 10.3969/j.issn.0258-2724.2014.01.019

[Abstract](1227)

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Abstract:
In order to solve the multi-objective optimization problem under uncertain traffic demand among practical OD pairs, a bi-level programming model was proposed to optimize the traffic management, environment protection, investment cost, and user behavior for stochastic multi-objective discrete transportation network design. The upper-level programming model was constructed using the chance constrained model and the ideal point model for multi-objective optimization, and the lower-level programming model was constructed using the user equilibrium assignment model under a fixed traffic demand. To ensure the solution accuracy of the proposed model, a genetic algorithm based on Frank-Wolfe algorithm, Monte-Carlo simulation, and adaptive niche technology was designed, and its corresponding program was developed using Matlab. In addition, the model and algorithm were tested in the Nguyen-Dupuis network. The result indicates that the model can reflect the objectives and constrains of practical network planning, and the algorithm is global convergent, hence providing a reference for the practical transportation planning.

Platoon Flow Dispersion Model Based on Truncated Normal Distribution of Speed

WU Weitiao, SHEN L, JIN Wenzhou

2014, 27(1): 126-133. doi: 10.3969/j.issn.0258-2724.2014.01.020

[Abstract](1002)

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Abstract:
In order to overcome the defect in Pacey's platoon dispersion model that the speed distribution assumption does not conform to the field situation, a platoon dispersion model based on flow patterns was established to study the relationship between the arriving flow distribution at the downstream intersection and the departing flow distribution at the upstream intersection. In this model, vehicle speeds are assumed to follow a truncated normal distribution, ranging from minimum to maximum speed; and a piecewise function was used to construct the arriving flow distribution function at downstream intersections. The platoon flow distribution mode was investigated using the field collected data between two adjacent intersections. The results show that compared with the Robertson model, the proposed truncated normal distribution of speed is more consistent with the actual situation, and that the proposed model can precisely describe the change trend of the platoon flow passing the downstream intersection and ensure the flow conservation.

Relationships between Crash Rate and Traffic Density at Urban Expressway Diverge Segments

WU Yong, LIU Xinrong, LI Rui

2014, 27(1): 134-140. doi: 10.3969/j.issn.0258-2724.2014.01.021

[Abstract](948)

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In order to seek safer methods of geometric design and traffic control strategies, the characteristics of crash rate (CR) varying with traffic flow conditions at diverge segments was studied based on Nagoya Urban Expressway network. Diverge segments were generally defined from 450 m upstream to 300 m downstream of ramp junctions. The relationships between CR and traffic flow density, as well as the tendencies of CR at diverge segments of different geometric features were analyzed. The results show that the CR in uncongested flow is convex downward to the traffic density. By contrast, the CR increases with the traffic density in congested flow and its value is much higher than in uncongested flow. In addition, in uncongested flow, multi-vehicle crash is the main crash mode and its RC is increasing with the traffic density. Compared to straight alignments, downstream sections of diverging area, and right-hand structures, significantly higher RC exist in curve alignments, upstream sections, and left-hand structures, respectively.

Computer-Assisted Determination of Out-of-Gauge Grade of Goods Based on Space Geometry

TAN Zhengmin, PENG Qiyuan, CHEN Si, GONG Xue

2014, 27(1): 141-146. doi: 10.3969/j.issn.0258-2724.2014.01.022

[Abstract](870)

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Due to the complex shape and huge bulk of out-of-gauge goods, it is difficult and error-prone to determine the level of out-of-gauge just by manual calculation with a large workload. In order to solve this problem, quantitative partition of the outer contour of goods was performed according to space geometry and spatial relative position, and a screening and optimization algorithm was used to find the calculation points and to judge the out-of-gauge grade of the goods automatically. An application example show that the out-of-gauge grade of the cargo is reduced to the second level from the supper level that is originally judged by the conventional method using simple and regular outer contours. The outer contour of goods obtained by this algorithm is more close to the actuality, and the errors of out-of-gauge grade caused by overevaluation of the practical contour using simple and regular outer contours is reduced. In addition, through computer-assisted calculation of the out-of-gauge grade of big cargoes, this algorithm can reduce the calculating time to less than 10 min, with a 66% improvement in the calculation speed over the traditional algorithm.

Sorting Decision Model for Dynamic Fault Tolerance Based on Dominance Relation Rough Set

GOU Guanglei, WANG Guoyin, LI Hong

2014, 27(1): 147-152. doi: 10.3969/j.issn.0258-2724.2014.01.023

[Abstract](896)

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To enhance the fault-tolerant capacity of the dominance relation rough set model in solving sorting decision problems, three efficient sorting decision algorithms are proposed by regarding the fault-tolerant processing as a dynamic adjusting process according to the fault tolerance direction of the user's preference, i.e., upward, downward, or synthesis of the both. The boundary objects are initially ranked by the proposed algorithms, and the obtained results are adjusted using the coverage information as the heuristic criteria to achieve a accurate or near accurate sorting of the object finally. In contrast to the variable-consistency dominance-based rough set approach (VC-DRSA), the proposed algorithms do not need prior domain knowledge to determine and adjust a threshold. Application of the algorithms to wine quality dataset show that the proposed methods can achieve a 21.34% improvement in average sorting accuracy and a 50.91% reduction in average mis-sorting cost, compared with the existing methods.

K-Multiple Constrained Shortest Paths Problem for Connecting Path Search in International Flight Path Network

XU Tao, DING Xiaolu, LI Jianfu

2014, 27(1): 153-159. doi: 10.3969/j.issn.0258-2724.2014.01.024

[Abstract](853)

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In order to solve the problem that the connecting path search method takes long time in international flight path network, according to the features of the connecting path search in the network, a constrained Yen* algorithm, which adopts the heuristic strategy of A* algorithm and is based on the Yen algorithm, is proposed to solve the K-multiple constrained shortest paths (KMCSP) problem. The proposed algorithm is tested in the international flight path network under the constraints of transfer times and a given transferring node. The results show that compared with the constrained Yen algorithm, the constrained Yen* algorithm improves the searching efficiency by 2.98 times, reduces the average running time by 78.3%, and decrease the search space by 86% with a small fluctuation range. Therefore, the constrained Yen* algorithm can be used to quickly solve the multiple constrained connecting path problem in international flight path network.

Robust Design of Sheet Forming Process Based on Dynamic Kriging Model

XIE Yanmin

2014, 27(1): 160-164. doi: 10.3969/j.issn.0258-2724.2014.01.025

[Abstract](959)

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In order to decrease the quality fluctuation in stamping caused by uncertain factors, and to increase the global approximation accuracy of the traditional static metamodel, a robust design approach for stamping forming process based on dynamic Kriging model was proposed, which combined the robust design with the finite element method. The controllable factors of forming were initially designed. Then, the objective values and their variance were obtained by finite element method, and the roust Kriging model was constructed for the stamping forming. In addition, the global optimization algorithm was employed to optimize the current metamodel to find the potential global optimum. During the optimization process, the design of experiment and corresponding metamodel were updated for improving the approximation accuracy around the global optimum until the global optimum was found under the convergence conditions. The optimization strategy was applied into cup forming in NUMISHEET' 93, and the results show that the standard deviation was reduced from 0.012 2 to 0.008 1 after robust optimization. Application of the robust method based on dynamic Kriging model to sheet forming can obtain satisfactory results.

POI Classfication Based Sweep Coverage Scheme in Wireless Sensor Networks

SHU Li, LIN Feng, LIU Zhonghao, YOU Jian, ZHOU Jiliu

2014, 27(1): 165-172. doi: 10.3969/j.issn.0258-2724.2014.01.026

[Abstract](1001)

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A sweep coverage model for wireless sensor network which satisfies both POI (point of interest) coverage and data delivery was proposed. The sweep coverage problem was proved to be a NP-hard after translating it to a vehicle routing problem which is a classic combinatorial optimization problem. Based on this model, a novel sweep coverage scheme FCSC (FDBSCAN_clustering_based sweep coverage) was proposed by introducing clustering algorithm to classify POIs in accordance with their locations. FCSC was operated with two steps. In the first step, all the POIs in monitoring area were classified using FDBSCAN algorithm. Then, in the second step, an insertion heuristic algorithm was applied for the POIs in the same cluster to generate the trajectory of mobile sensor nodes. The simulation results show that compared with traditional sweep coverage approaches, FCSC effectively reduces the computational complexity and decreases overall execution time by more than 50% while achieving the similar performance in the same network scenarioes.

Substructure Normal Modes Selection Method for Component Mode Synthesis

LI Xingquan, DENG Zhaoxiang, LI Chuanbing, ZHANG Jingcheng, LI Yingqiang

2014, 27(1): 173-178. doi: 10.3969/j.issn.0258-2724.2014.01.027

[Abstract](1547)

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In order to reduce the normal mode number of retained substructures in the fixed interface component mode synthesis method, both frequency truncation and effective mode mass truncation methods were used for selection of component normal modes. By comparative analysis of the applicability of the two methods, the suitable normal mode truncation method for calculating structural low frequency dynamic characteristics was obtained. The computation results show that the normal modes of substructures retained by the frequency truncation method was 1/2 less than that by the effective mode mass truncation method. When computing complex structure low frequency vibration characteristics, setting the normal mode cutoff frequency to 2-3 times the upper frequency limit is sufficient to ensure high accuracy and efficiency, and the normal modes retained by the frequency truncation method can reflect better the substructure deformation caused by system low-frequency vibration. In contrast, the effective mode mass method cannot estimate the relative contribution of normal modes between substructures to the system low-frequency vibration characteristics; therefore, its truncation results may contain many redundant modes from substructures of small size and large stiffness.

Analysis on Influence of Train Interior Design on User Satisfaction and Visual Perception

LI Juan, XU Bochu, ZHI Jinyi, DONG Shiyu, WANG Chao

2014, 27(1): 179-184. doi: 10.3969/j.issn.0258-2724.2014.01.028

[Abstract](1160)

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To analyze the influence of train interior design factors on customer satisfaction and visual perception,9 sets of interior design plans for EMU second-class carriage were used as experimental stimulus with different tones and figure-ground relations, and the eye-movement characters of 19 subjects were recorded by the remote eye-tracking device (RED). The satisfactory degree of the stimulus was evaluated by the subjects. The analyzed results show that the subjects paid high attentions on the seat area, and the percentage of average fixation time was 39%. The influence of tonal relations on the satisfaction evaluation was remarkable,and the experimental stimulus with contrastive tone had high evaluation of satisfaction. The influence of figure-ground relations on the evaluation of satisfaction was not remarkable,and the visual fixation of the subjects focused on the area with apparent pattern. Moreover, visual perception had contrast tendentiousness and symbol aggregation effect.

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2014 Vol. 27, No. 1