西南交通大学学报

Mechanical Properties of Steel-Concrete Composite Section in Space Rigid Frame

LI Xiaozhen, XIAO Lin, SU Xiaobo, WEI Xing

2012, 25(6): 907-914. doi: 10.3969/j.issn.0258-2724.2012.06.001

[Abstract](1258)

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Abstract:
In order to investigate the mechanical properties and load transfer mechanism of steel-concrete composite section in a space rigid frame structure for high-speed railway, a section model test with a scale of 1 to 2 and nonlinear finite element analysis were carried out. The test model was loaded respectively under a serviceability limit state and an ultimate limit state to obtain the distributions and variations of stresses and deformation of main members in loading process. In addition, the relationship of load distribution between load transfer members in the composite section was investigated by a nonlinear finite element analysis. The research results show that the stresses of steel plate, concrete and perforated rebar in a shear connector are on a low level. The relative slip between steel box and concrete is small, and both of them can collaboratively bear force. Besides, concrete, steel plate and shear connectors in the composite section are all in an elastic stage, and their stress distributions are uniform, indicating that the structure has a high safety margin. The steel-concrete composite section can effectively transfer load, and load distribution is reasonable as bearing plate and shear connectors share half of the load respectively.

Simplified CQC Method for Resonant Response of Long-Span Roof Structure

LUO Nan, LIAO Haili, LI Mingshui

2012, 25(6): 915-921. doi: 10.3969/j.issn.0258-2724.2012.06.002

[Abstract](1072)

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Abstract:
In order to improve the calculation efficiency of the traditional CQC (complete quadratic combination) method, a simplified CQC method to calculate the resonant responses of a long-span roof structure, called SCQC method for short, was proposed based on the analyses of modal frequency response function and modal force spectrum. With considering structural dynamic characteristics and wind characteristics, the contributions of real and imaginary parts of the modal frequency response function and the modal force spectrum to response variance are considered in the SCQC method. In addition, the method considers modal coupling effect so as to assure the calculation accuracy. The SCQC method was applied to the analysis of the resonant responses of a swimming pool roof structure, and the analysis results were compared with ones based on the traditional CQC method. The results show that compared with the traditional CQC method, the proposed method has a small error, and the maximum error is only 2.73%to verify its feasibility and effectiveness.

Human-Induced Vibration Analysis and Measurement of Long-Span Composite Floors

CAO Lilin, LI Aiqun, ZHANG Zhiqiang, ZHOU Deliang, ZHOU Chaoyang

2012, 25(6): 922-928. doi: 10.3969/j.issn.0258-2724.2012.06.003

[Abstract](1237)

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Abstract:
In order to investigate the human-induced vibration performance of large-span composite floors, crowd excitation was simulated by the random method based on a normal footfall force curve and other individual factors such as crowd distribution and step frequency. Human-induced vibration responses of a large-span composite floor were analyzed with the help of the multi-support excitation and the time history analysis method, and multiple tuned mass dampers with different parameters were designed to control the vibration responses of the large-span floor. The actual dynamic properties of the composite floor under two distinct construction phases were tested, and vertical vibration responses of the composite floor with and without multiple tuned mass dampers under different crowd-induced excitations were measured. The research results show that the types and walking routes of human-induced excitations have significant effects on the floor responses and the large-span composite floor has very closely-spaced modes of vibration. The vertical acceleration responses induced by crowd excitation are relatively great under certain condition, and the human-induced responses of a structure with multiple tuned mass dampers decrease dramatically to meet the requirement of body serviceability.

Effects Analysis of Cracking of CRTSⅡ Slab Track on Subgrade

WANG Ping, XU Hao, CHEN Rong, XU Jingmang

2012, 25(6): 929-934. doi: 10.3969/j.issn.0258-2724.2012.06.004

[Abstract](1427)

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In order to analyze the influences of cracking of CRTS (China railway track system) Ⅱ slab track on subgrade on a vehicle and ballastless track, a finite element model for beam body on an elastic foundation and a vertical coupling dynamical model for a vehicle-track-subgrade system were established on the basis of the elastic foundation beam theory, the finite element method and the wheel-rail coupling dynamics theory. ANSYS/LS-DYNA, a large finite element software, was used to analyze the static and dynamic properties of track and the stability of a train under track slab cracking. The analysis results show that track slab cracking has less effect on the stress of track and has no effect on the stability and security of a train. With increase of train speed and cracking of track slab, the wheel-rail force and the dynamic responses of track become bigger, so vibration reduction or vibration isolation and control measures of the track geometric irregularity should be adopted to reduce the dynamic responses of track in the crack area. The cracking of track slab has effects on the durability and lifetime of ballastless track, so it should be repaired in time.

Mechanical Characteristics of Main Structure of Mining Tunnel under Water Pressure

ZHANG Zhiqiang, HE Benguo, MA Tengfei

2012, 25(6): 935-941. doi: 10.3969/j.issn.0258-2724.2012.06.005

[Abstract](1530)

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Abstract:
In order to probe into the mechanical characteristics of main structure of a mining tunnel under the action of water pressure, model tests were carried out for investigating the mechanical characteristics of tunnel, the interaction between lining and strata and the failure modes of the structure were researched. Non-uniform water pressure-soil pressure device for a horseshoe-shaped tunnel section was designed. The mechanical characteristics of main structure subjected to water pressure and soil pressure were simulated experimentally. The reserach result demonstrates that moment has a butterfly-shaped distribution along lining perimeter, and the distribution of axial force appears as an ellipse. With the raise of soil pressure, bending moment, axial force, deformation, and eccentricity of lining increase. The increase of lateral pressure coefficient will lead to the reductions of bending moment and axial force. In addition, water pressure will influence the axial force of lining sharply and bending moment gradually. Consequently, limited water pressure is less than 500 kPa.

Rational Seismic Protective Length for Portal of Railway Tunnel

GENG Ping, CAO Dongjie, TANG Jinliang, QUAN Qianlong, CHENG Bangfu

2012, 25(6): 942-948,954. doi: 10.3969/j.issn.0258-2724.2012.06.006

[Abstract](1922)

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In order to determine the rational seismic protective length for tunnel portal and achieve the optimal earthquake-resistant performance, a dynamic analysis model for tunnel portal was set up to a 140 km/h single-line railway tunnel with a width of 6.4 m, the influences of surrounding rock conditions and physical and mechanical parameters of lining on the internal force responses of lining at tunnel portal under seismic action were analyzed. The acceleration response of surrounding rock and the distribution of lining internal force responses were discussed. The numerical simulation results show that lining internal forces will obviously reduce beyond 3 times the tunnel width far from the portal. The shaking table test carried out with 3 times tunnel width as seismic protective length at tunnel portal indicates that shock absorption effect is remarkable to verify the rationality of the seismic protective length.

Measurement Method of Strata Attitude Based on Google Earth

PU Hao, YANG Xinlin, ZHAO Haifeng, LI Jian

2012, 25(6): 949-954. doi: 10.3969/j.issn.0258-2724.2012.06.007

[Abstract](1108)

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Abstract:
In order to solve the problems of high difficulty and low efficiency in measuring strata attitude in harsh natural condition areas, a method to fulfill the fast batch calculation of shallow strata attitude in any area of the globe through C# programming was proposed by using the digital terrain and image data provided by the Google Earth. This method takes the Google Earth as its basic 3D geographic information platform and uses Google Earth COM API to interact with the Google Earth, and it can dynamically get the coordinates of strata boundary points. Geodetic coordinates of the WGS84 ellipsoid are converted into plane coordinates through the Gauss projection transform, and a fitted plane equation for strata is obtained through the least-square fitting method. Based on the fitted plane equation, strata attitude can be obtained through calculation, and the 3D visualization of measurement results are realized through KML. An application experiment shows that this proposed method is effective and efficient for data acquisition and real-time adjustment of strata boundary points. Moreover, the calculation results can be presented visually and vividly through visualization.

Registration Method for Unmanned Aerial Vehicle Images Based on Point Feature and Edge Feature

HE Jing, LI Yongshu, LI Xin, TANG Min

2012, 25(6): 955-961. doi: 10.3969/j.issn.0258-2724.2012.06.008

[Abstract](1196)

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Abstract:
To solve the problem of registration of unmanned aerial vehicle (UAV) images with a large distortion, an improved method based on the combination of point and line features was proposed. With this method, preparatory registration is completed by extracting point features with the scale invariant feature transform (SIFT) algorithm, and a polynomial function is used to correct an image coarsely. On the basis of the above, the edge features of the image are extracted, and the registration of the edge features is carried out based on the distance similarity. The registration results of point and edge features are filtered by utilizing the color energy difference. A small-bin based differential correction method is used for finally accurate correction. The experimental results show that the proposed method can overcome the drawbacks of the point feature registration and the edge feature registration, the registration robustness is improved by 10%, and it can effectively complete the registration of UAV images with a large distortion.

Modified Algorithm for Simulation of Injection Molding Process

SHI Jianjun, CHENG Zhiqiang, LIU Baosheng

2012, 25(6): 962-967. doi: 10.3969/j.issn.0258-2724.2012.06.009

[Abstract](1364)

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Abstract:
In order to improve the accuracy of numerical simulation for injection molding process, a notion similar to upwind method was introduced. As the governing equation of the filling state takes the form of an advection equation, distorted simulation result may be induced by the flow of air in the mold cavity. To solve the problem, a numerical correction method was proposed. This method weakens the adverse effect of air flow velocity field on the filling process, by modifying the fluid velocity field through systematic operations based on an efficient explicit algorithm and finite element software. Thus, the advection of filling state mainly depends on the flow field behind the filling front. In addition, a numerical simulation was made in mold cavities of shapes ⊥ and L to verify the effectiveness of the method. The result shows that the proposed method can suppress the distortion phenomenon of filling flow effectively, and ensure a correct filling process in complex channels, in which the flow directions have large-angel changes.

A New Time-Domain Method for Force Identification

ZHU Tao, XIAO Shoune, YANG Guangwu

2012, 25(6): 968-973. doi: 10.3969/j.issn.0258-2724.2012.06.010

[Abstract](1176)

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Abstract:
In order to identify unknown load accurately and reduce the influence of measurement noise on identification results, a new time-domain method for dynamic load identification was proposed based on dynamic programming and Bellman optimization principle. First, the objective function between measured and identified system responses was established using the state-space formulation and the least square error method. Then, discrete equations of motion based on the system displacement, velocity, and acceleration responses were obtained by Newmark integration method. Finally, the dynamic programming method and Bellman optimization principle were used for minimization of the objective function to estimate the excitation forces, and identification formulations of optimal dynamic load were deduced. In addition, the numerical example was provided to verify the proposed mathematical model. The results show that the proposed method has a strong adaptability in dynamic load identification; under 10% noise disturbance, the error of measured response is always less than 25%.

μ-Synthesis Control for Self-powered Active Suspension of Vehicles

CHEN Yanqiu, SONG Pengyun, ZHANG Jiye, ZHANG Keyue

2012, 25(6): 974-981. doi: 10.3969/j.issn.0258-2724.2012.06.011

[Abstract](1071)

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Abstract:
In order to improve the stability, vibration isolation, and energy feedback performance of a self-powered active suspension of vehicles, a self-powered active suspension model with parametric perturbation for 1/4 car body was built, and a dynamics analysis was made using the model. Then, a robust controller was designed based on μ-synthesis approach. A simulation was conducted in the MATLAB/SIMULINK environment to verify the controller performance. The result indicates that in the condition of parameter perturbation and surface irregularity disturbance, the μ-synthesis controller designed for the self-powered active suspension system was robust and stable: the peak structured singular value of the closed-loop system with parametric uncertainty was 0.580 9. With this controller, the vibration isolation performance of the suspension system was improved, and the gain of vertical acceleration of the car body was reduced by about 9 dB at the natural frequency.

Markov Decision Process for the Energy Management of Parallel Hybrid Vehicles

XIAO Renxin, LI Tao, QIN Ying, ZOU Gan

2012, 25(6): 982-988. doi: 10.3969/j.issn.0258-2724.2012.06.012

[Abstract](1141)

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In order to study the energy management strategy of single-shaft parallel hybrid electric vehicles, dynamic equations of the power-train system were set up to analyze the non-aftereffect property of the required torque. To achieve the optimization objective of minimizing the oil consumption under a fixed battery capacity, Markov decision process was carried out to implement the torque allocation strategy, and the policy iteration algorithm was used to solve the Markov decision model for energy management. In addition, the Markov decision process for energy management was simulated under the condition of J1015 driving cycles and Kunming driving cycles, and executed on line. The results show that compared to the strategy based on dynamic programming, the energy management strategy based on Markov decision process, which can be implemented on line, can make the battery capacity change more smoothly, but is globally sub-optimal in oil consumption: with the new strategy, the oil consumption is increased by 1.32 L per 100 km in case of J1015 driving cycles and 1.59 L per 100 km in case of Kuming driving cycles.

Driving Cycle Construction of City Road Based on Vehicles Energy Consumption in Jinan

HUANG Wanyou, CHENG Yong, LI Chuang

2012, 25(6): 989-995,1026. doi: 10.3969/j.issn.0258-2724.2012.06.013

[Abstract](1075)

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Abstract:
A driving cycle was constructed to guide new vehicle development and power-train optimization. Key factors that affect vehicle energy consumption, such as road slope, vehicle transient specific power, and vehicle speed, were analyzed. Taking vehicle energy consumption and road slope into consideration, characteristic values of kinematic sequences were proposed. Then, candidate driving cycles were constructed according to the analysis result of kinematic sequences by using tools such as principal composition analysis and clustering analysis. Finally, the actual driving cycle for Jinan was selected from candidate driving cycles by comprehensive consideration of the correlation coefficient, relative error, and key parameters probability distribution. Results indicate that the average error between characteristic values related to vehicle speed and total samples is within 2.82%, and the average error between other characteristic values and total samples is within 3.40%. Therefore, the characteristic values of driving cycle calculated from the presented method can characterize the driving cycle of the real roads in Jinan.

Changing Rule of Driver's Recognition Distance in Daytime and Nighttime on Freeway

CHENG Guozhu, XUE Changlong, HAN Juan

2012, 25(6): 996-1002. doi: 10.3969/j.issn.0258-2724.2012.06.014

[Abstract](1079)

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In order to set the speed limit standard on freeway in daytime and nighttime and to ensure enough time for drivers to acquire information, the data of driver's recognition distance in daytime and nighttime were compared and analyzed using mathematical statistics and regression analysis methods. By studying the quantitative impacts of driving speed, horizontal curve radius, and longitudinal slope on driver's recognition distance in daytime and nighttime, models were established for the relationship among driver's recognition distance, driving speed, horizontal curve radius, and longitudinal slope. The results show that the driver's recognition distance in nighttime decreases by 8.5% averagely and 30.4% maximally compared with that in daytime. The decreasing rate is affected by driving speed and highway alignment. The relationship between driver's recognition distance in daytime and driving speed, horizontal curve radius, and longitudinal slope are negative logarithmic, positive linear,and negative exponential, respectively; and model's R-square is 0.852. In contrast, the relationship between driver's recognition distance in nighttime and driving speed, horizontal curve radius, longitudinal slope are negative linear, positive logarithmic, and negative exponential, respectively; and model's R-square is 0.983.

Comprehensive Dynamic Model Analysis of Proton Exchange Membrane Fuel Cell

CHEN Weirong, ZHANG Hanyue, LI Qi

2012, 25(6): 1003-1008. doi: 10.3969/j.issn.0258-2724.2012.06.015

[Abstract](1259)

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Abstract:
For a further study on PEMFC (proton exchange membrane fuel cell) operation characteristics, a synthetic dynamic model with the use of MATLAB/SIMULINK was built on the basis of the combination of the experimental model and the mechanistic model of PEMFC, containing a voltage dynamic model, a hydrogen and air supply dynamic model and a thermal dynamic model. The dynamic characteristics of PEMFC at different loads and temperature conditions were analyzed. A testing platform based on the Ballard's 1.2 kW NEXA system was set up, and with the platform the simulation model was verified by experiments. The research result show that the proposed model can reflect the dynamic characteristics of PEMFC, and the deviations between experimental data and simulation results are 2.06% to stack voltage and 0.36% to power to validate the correctness of the proposed model.

Insulation Life Model and Partial Discharge Characteristic of Magnet Wires under Square Pulse Voltage

CAO Kaijiang, XU Yue, WU Guangning, XU Huihui, ZHANG Yiqiang, LUO Yang

2012, 25(6): 1009-1014. doi: 10.3969/j.issn.0258-2724.2012.06.016

[Abstract](1002)

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Abstract:
In order to investigate the aging and failure mechanism of insulation under square pulse voltage, an insulation life characteristic device for high frequency and high impulse voltage and a partial discharge (PD) test system were adopted. PD activity and its impact factors as well as life characteristic of magnet wires under different frequencies and rise times were investigated, and insulation aging life models for different frequencies and rise times under square pulse voltage were obtained. The research result indicates that with increasing of frequency and shortening of square pulse rise time, the PD activity becomes severe and the life of magnet wires decreases. Correlation coefficients for the life models of different rise times and frequencies are 0.93 and 0.95, respectively.

Design and Implementation of Boost Type Active Power Factor Correction Controller IC

DAI Guoding, MA Xiaohui, OU Jian, XUE Chaoyao, MA Renyue, LU Jing

2012, 25(6): 1015-1020. doi: 10.3969/j.issn.0258-2724.2012.06.017

[Abstract](1053)

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Abstract:
A boost type active power factor correction controller based on the critical mode control technology was proposed to restrain harmonic currents and improve the efficiency of electrical power. A total harmonic distortion optimizer circuit was specially integrated to solve the crossover distortion problem that input current is zero. And a voltage feedback circuit with two over-voltage detection modes was designed to achieve fast instantaneous response and unexpected protection. A chip, with an area of only 1.36 mm2, was fabricated by the CSMC 0.5 μm BCD process. A 80 W APFC circuit was constituted based on the chip. The test results under a full load show that the measured power factor is 0.997, the total harmonic distortion of input current is 3.1% and the efficiency is 96.8% to prove that the chip achieves the function of power factor correction.

Series Resonance Analysis Based on Branch-Circuit Method

WANG Bin, JIANG Xiaofeng, GAO Shibin, QIU Zhongcai

2012, 25(6): 1021-1026. doi: 10.3969/j.issn.0258-2724.2012.06.018

[Abstract](972)

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A frequency spectrum analysis technology based on the branch-circuit method was proposed to effectively analyze the branch harmonic over-current caused by series resonance in power systems. The proposed method was tested on the three-bus and IEEE 14-node systems and compared with the modal analysis method, which analyzes the resonance mechanism by utilizing the eigenvalue of the singular admittance matrix. The series frequencies determined by the peak admittance obtained by the branch-circuit method are be close to the resonance frequencies obtained by the modal analysis, showing the effect of the proposed method in analyzing series resonance.

Algorithm of Distributed Frequent Closed Patterns Mining

YANG Junrui, ZHANG Min, HE Hongde

2012, 25(6): 1027-1033. doi: 10.3969/j.issn.0258-2724.2012.06.019

[Abstract](1045)

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In order to improve the mining efficiency, an algorithm, PFCI-Miner, based on distributed frequent closed patterns mining was proposed. This algorithm adopts a master-slave structure to implement task distribution. The master processor assigns a task efficiently by sending a proposed prefix path table (PrePthx), and the slave processors mine local frequent closed patterns with the help of a proposed store tree (Trac-tree). Finally the master processor mines the global frequent closed patterns. The algorithm uses star-like topology in order to make all data communications only between the master processor and the slave processors, there being no communication and no synchronization among all slave processors. Computer simulation on synthesis and mushroom data sets under the distribution of 3 PC computers shows that compared with the DP-FP algorithm, the AFCIM (adaptive frequent closed itemsets mining model) algorithm and the DFCIM (distributed frequent closed itemsets mining) algorithm, the PFCI-Miner algorithm has, on average, 43.66%, 42.17%, 53.48% and 51.86%, 47.62%, 62.78% improvements in the efficiency respectively.

Two-Step Hybrid PSO-Based Clustering Algorithm

WANG Zonghu, LIU Zhijing, CHEN Donghui

2012, 25(6): 1034-1040,1063. doi: 10.3969/j.issn.0258-2724.2012.06.020

[Abstract](1154)

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In order to solve the problems of the existing PSO (particle swarm optimization) K-means algorithms, i.e., their calculation speeds are slow and the clustering results are unstable when samples have a high dimension, some high-quality sub-clusters were generated by hierarchical agglomerative clustering. These sub-clusters were used as the search space of candidate centroids of the PSO K-means. In order to reduce the computational complexity when the dimension of a sample is high, a simplified particle encoding method was proposed. In addition, chaotic idea was introduced to keep the diversity of particle swarm to avoid premature. By two-step hybrid clustering the advantages of the hierarchical clustering, the partitioning clustering and the PSO were combined. The experimental results on several UCI data sets show that compared with the best results of several contrastive algorithms, the purity of its clustering result increases by 1% to 8% and the consuming time reduces by 50% at least.

Product Remanufacturing and Pricing Decisions and Supply Chain Coordination of Closed-Loop Supply Chain with Dual Sale Channels

XU Bing, WU Ming

2012, 25(6): 1041-1048. doi: 10.3969/j.issn.0258-2724.2012.06.021

[Abstract](1288)

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In order to analyze the impact of direct-sale channel on retail-sale channel and the effect of product remanufacturing on cost control, a Stackelberg game model between one manufacturer and one retailer under decentralized control, and a decision model of closed-loop supply chain (CLSC) under centralized control were established using the game theory. The decisions and profits of each agent and supply chain are obtained by solving the models. Based on contract theory, a wholesale price contract with transfer payment for the CLSC with dual sale channels was put forward to coordinate the decisions of the two agents and supply chain. The result reveals that under decentralized control mode, the direct-sale price and retail price are higher than their counterpart under centralized control model, except the product remanufacturing rate and profit of CLSC. The wholesale price contract with transfer payment can coordinate the decision behaviors of manufacturer and retailer, increase their profits and the profit of CLSC, and realize supply chain coordination and win-win between producer and seller. The direct-sale channel in CLSC can attract potential demand and improve total demand, yet the risk of channel operation will be augmented along with the transfer of demand from retail-sale channel to direct-sale channel. Therefore, the impact of direct-sale channel on retail-sale channel should be lessened as possible. In addition, a numeric example demonstrates the reasonability of the proposed models and the feasibility of the wholesale price contract with transfer payment.

Joint Purchasing Policy for Perishable Products Based on Cooperative Game Theory

LI Jun, YUE Qing, FENG Hairong

2012, 25(6): 1049-1056. doi: 10.3969/j.issn.0258-2724.2012.06.022

[Abstract](1016)

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In order to reduce purchasing cost, and maintain long competitiveness, enterprises often adopt joint purchasing policy. A cost allocation model for retailers' joint purchasing perishable items was established based on the characteristics of perishable products. In this model, the cost allocation problem of jointly purchasing perishable products among retailers was converted into a cost allocation game based on the cooperation game theory. Analysis of retailer's behaviors proves that the cost allocation game is concave, and there exists an optimal joint purchasing policy. The results show that joint purchasing saves the fixed ordering cost and the total cost per unit time for every retailer, and the cost saving increases with the decay rate. In addition, when considering the coordination cost, if the ratio of the fixed ordering cost to the sum of inventory cost and purchasing cost is decreasing, the corresponding cost allocation game satisfies subadditivity and has nonempty core.

Optimization of Railcar Flow Combination Scheme for Strategic Loading Domain Based on Heavy Haul Transportation

HAN Xuesong, ZHAO Jun, PENG Qiyuan

2012, 25(6): 1057-1063. doi: 10.3969/j.issn.0258-2724.2012.06.023

[Abstract](1121)

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In order to investigate the railcar flow operation optimization of heavy haul transportation loading side, the railcar organization process in the strategic loading domain of heavy haul transportation was analyzed. According to the supply level of goods resource and transportation operation mode, the stations in the strategic loading area were classified into three levels, including strategic loading point, strategic loading area, and strategic loading domain. Then, a railcar flow combination scheme optimization model was established, which is based on the characteristics that car flows are organized in the way of unit heavy haul train and combined heavy haul train. In this model, minimization of the total combined time of the combined heavy haul train was the objective, the yearly target traffic volume, line capacity, loading capacity of loading point (area), etc. were constraints, and combination mapping was adopted to deal with the railcar flow delivery relationship in the combination station. In addition, an effective heuristic method was designed to solve the model. The results of a case study show that three equivalent combination schemes can be obtained by the proposed optimization method. Among them, optimization scheme 2 is consistent with the real railcar flow organization scheme, and the other two equivalent schemes, although with different combination contents, have the same time consumption.

Low Noise Design of Cylinder Head Cover Based on Multi-objective Topography Optimization

WANG Liansheng, HAO Zhiyong, JING Guoxi

2012, 25(6): 1064-1068. doi: 10.3969/j.issn.0258-2724.2012.06.024

[Abstract](991)

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In order to reduce the structural radiation noise of a diesel engine cylinder head cover, the finite element method (FEM) and boundary element method (BEM) were used for its virtual prediction and obtained the critical modal with dominant contribution to the structural radiation noise. Considering the static stiffness and several critical dynamic frequencies as Euclidean distance's multi-objective function, weighted compromise programming approach was applied to multi-objective topography optimization of the cylinder head cover. With the optimization result, the CAD model of the cover was redesigned taking manufacturing and assembling process into account. Finally, the radiation noise of the optimized cylinder head cover was analyzed under the same boundary conditions. The results show that the integral stiffness is improved, the critical frequencies avoid the original resonance frequency range that radiates noise most and the total acoustic power level has dropped by 3.5 dB (A).

Conflict-Free 4D Trajectory Prediction Based on Hybrid System Theory

HAN Yunxiang, TANG Xinmin, HAN Songchen

2012, 25(6): 1069-1074. doi: 10.3969/j.issn.0258-2724.2012.06.025

[Abstract](1366)

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In order to increase airspace capacity, the hybrid system theory was used to build a state switch model of aircraft between different segments that is based on the aircraft aerodynamics models by setting three flight status including climb, decent, and level flight as well as seven parameters of height and speed during the process of aircraft trajectory strategic planning. Then, a state evolution model was also built for an aircraft with parameters such as aircraft weight, airspeed, altitude, and ground distance continuously changing during the same segment. In order to plan multi-aircraft trajectories, a conflict-free trajectory planning method was proposed by adjusting the aircraft arrival time and flight speed. The simulation of a case study shows that using the hybrid recursive method, the aircraft take-off 4D trajectory with aircraft performance constraints can be obtained within 3 s, the two models proposed in this paper can reflect the aircraft horizontal and vertical trajectory profiles precisely, and the conflict-free trajectory planning method is effective.

Lateral Collision Risk Model on Parallel Routes Based on Communication, Navigation and Surveillance Performances

HUANG Baojun

2012, 25(6): 1075-1080,1091. doi: 10.3969/j.issn.0258-2724.2012.06.026

[Abstract](1270)

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In order to assess the parallel route spacing safety in radar control environment, air traffic controller (ATC) intervention processes for aircraft lateral deviation were analyzed. Then based on analysis of the traditional collision risk models, two lateral collision risk models on parallel routes including and excluding human cognitive reliability were established taking into consideration the communication, navigation, and surveillance (CNS) performances and ATC intervention processes. The impacts of ATC intervention and CNS performances on minimum safety route spacing were discussed through numerical examples. The results show that compared with communication and surveillance performances, navigation performance has a larger impact on collision risk; therefore, RNAV 2 navigation specification is recommended to be adopted for reducing route spacing. In addition, improving human cognitive reliability can also effectively reduce the parallel route spacing.

Effect of Intermediate Heat Treatment on Microstructure and Properties of FGH4095 Superalloy

XU Yi, WEI Kuan, SHU Qin

2012, 25(6): 1081-1085. doi: 10.3969/j.issn.0258-2724.2012.06.027

[Abstract](1015)

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Abstract:
In order to study the effect of heat treatment on the distribution characteristics of γ' strengthening phase in powder metallurgy superalloy FGH4095, the FGH4095 superalloy powders were prepared by argon gas atomization. After powder screening and inclusion removal, compacts were formed by hot isostatic pressing (HIP) sintering. Then the size, morphology, and distribution of the γ' strengthening phases were analyzed for the superalloy specimens subjected to different heat treatments; the tensile properties at 20℃ and 650℃ were tested; and the instant fracture microstructures at 650 ℃ were compared. The results show that intermediate heat treatment processes could improve the distribution and shape of the γ' phase. After the intermediate heat treatment, the high-temperature (650 ℃) tensile performances improved obviously: the yield strength σ0.2 increased from 1 150 to 1 210 MPa, and the tensile strength σb increased from 1 230 to 1 460 MPa. The intermediate heat treatment increased the total number of the middle γ' phase, optimized grain boundaries, and improved the high temperature plastic property of the alloy.

Grey Target Optimization of Waterproof Adhesive Material for Concrete Bridge Deck Pavement Based on Mechanical Analysis

YU Xin, LI Yingtao, LIU Yun

2012, 25(6): 1086-1091. doi: 10.3969/j.issn.0258-2724.2012.06.028

[Abstract](1347)

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Abstract:
In order to select the optimal waterproof adhesive material that meets the stress needs of concrete box girder bridge deck pavement, taking the viaduct in widening project of the Shanghai-Hangzhou Expressway as an example, a composite structure model of the whole bridge was established using the finite element method, and the influence of braking, overloading, random dynamic loading on the mechanical response of the waterproof adhesive layer was analyzed. The technique parameters of some typical materials for waterproof adhesive layer were tested in lab, and then analyzed by the grey target theory. The result shows that braking plus overloading has a larger effect on the shear stress of adhesive layer than the random dynamic loading caused by bridge deck roughness, and may produce a maximum shear stress of 0.397 MPa. The rubber asphalt and SBS modified asphalt both have good performance, and can be used as the material of waterproof adhesive layer.

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2012 Vol. 25, No. 6