西南交通大学学报

Numerical Analysis of Ground Vibrations of Viaduct Induced by High-Speed Maglev Vehicle

ZHAO Chunfa, JIA Xiaohong, ZHAI Wanming

2010, 23(6): 825-829. doi: 10.3969/j.issn.0258-2724.2010.06.001

[Abstract](2286)

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Abstract:
An interaction model of maglev vehicle-bridge system was built to calculate dynamic magnetic forces of maglev vehicles, and the calculated forces were input into a finite element model of the pier foundation of a viaduct to obtain ground vibration responses. Numerical results show that the attenuation law of ground vibrations induced by maglev vehicles are similar to that induced by wheel-rail vehicles, except that there is not a rebound zone about 25 m away from the track centerline. The effect of vehicle speed on ground vibrations is significant: the ground vibration at the same point increases by about 10 dB as the vehicle speed increases from 125 km/h to 430 km/h.

Design and Realization of On-Board Communication Platform for High-Speed Maglev Train Based on RTLinux

LIU Zhigang, HAN Zhiwei, PENG Quanwei, ZHOU Zhiguo

2010, 23(6): 830-836. doi: 10.3969/j.issn.0258-2724.2010.06.002

[Abstract](1300)

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For the demand of an on-board communication platform for high-speed maglev trains, a plan based on RTLinux (real-time linux) was proposed, including the architecture design of the communication platform based on RTLinux, the designs and realizations of real-time and non-real-time processing modules. The driver program of RTLinux for CPCI-CAN (compact peripheral component interconnect-control area network) board was given and realized through the discussion of program development. In addition, the real-time performance of the communication platform of the diagnosis system was analyzed by virtue of the dispatch time model and the transmission delay model. The real-time simulation results show that the mean update time of all network nodes in the communication platform is 290 ms to meet the real-time demand (the response time should be less than 500 ms) for a high-speed maglev train.

Efficiency Analysis and Parameter Optimization of CPT System

SUN Yue, XIA Chenyang, DAI Xin, SU Yugang

2010, 23(6): 836-842. doi: 10.3969/j.issn.0258-2724.2010.06.003

[Abstract](1524)

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In order to solve the problem that the efficiency computing methods for CPT systems with different resonant coupling topological structures are different, a general method for efficiency computing of CPT systems with different resonant coupling topological structures was proposed through analyzing CPT systems with four typical resonant coupling topological structures. To raise the efficiency of CPT systems, the parameters of the resonant coupling topological structure of a current-fed CPT system were optimized through mathematical modeling to achieve a high efficiency of energy output. In addition, by taking the current-fed CPT system as an experimental model, the effectiveness of the proposed computing method and the optimization of parameters were discussed. The result shows that the maximum efficiency of the resonant coupling topological structure of the current-fed CPT system is 92%, while its theoretical optimization value is 93%.

Novel FB-ZVZCS-PWM Converter Based on Phase-Shift Control

CHEN Tefang, FU Qiang, CHEN Chunyang, YU Mingyang

2010, 23(6): 843-849. doi: 10.3969/j.issn.0258-2724.2010.06.004

[Abstract](1595)

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A novel topological structure for full-bridge (FB) zero-voltage and zero-current switching (ZVZCS) converter based on phase-shifted pulse-width modulation (PS-PWM) was proposed to overcome the shortcomings of the existing topological structures, such as high current stress, complex control and narrow load range. This topological structure can not only realize soft switching steadily to both leading and lagging legs when the load rate is higher than 15%, but also make current stress decrease largely. In addition, a small signal model for the topological structure was established, and its dynamic performance was simulated numerically using software Matlab. Finally, a converter prototype with a capacity of 8 kW and an output voltage of 110 V was developed to prove the correctness of the theoretical analysis and the rationality of the parameter design.

Theoretical Study on Magnetism of Fe-Based Superconductor SmOFeAs

PAN Min, 2, HUANG Zheng, CHENG Cuihua, ZHAO Yong, 4

2010, 23(6): 850-854. doi: 10.3969/j.issn.0258-2724.2010.06.005

[Abstract](1188)

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To investigate the superconductivity induced by 5d element doping in and physical pressure on Fe-based superconductor, the crystal structure of SmFeAsO was calculated, and the effects of pressure and Ir doping at Fe site on the lattices, electronic and magnetic properties of SmFeAsO were analyzed using SGGA+U(the spin generalized gradient approximation plus Hubbard model) method. The results show that the coulomb interaction between Fe-3d electrons is about 4 eV. The decreased magnetism indicates that the antiferromagnetic spin density wave (SDW) of the Fe-based compound SmOFeAs will be suppressed by physical pressure and chemical doping, which is in agreement with experimental results. Electron doping with Ir cause the SmFe1-xIrxAsO system to change from an antiferromagnetic SDW state into a nonmagnetic one, with superconductivity coexisting with antiferromagnetism and occurring in the vicinity of a magnetic quantum critical point.

Dynamic Characteristics of Soil Subgrade Bed for Ballastless Track

JIANG Guanlu, KONG Xianghui, MENG Liji, WANG Zhimeng

2010, 23(6): 855-862. doi: 10.3969/j.issn.0258-2724.2010.06.006

[Abstract](1646)

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In order to study the nonlinear elastic properties of the deformation modulus and reaction coefficient of soil subgrade bed, a large-scale test model of ballastless track subgrade and a comprehensive field test were used to analyze the static and dynamic characteristics of the ballastless track subgrade before and after rainfall under step static and dynamic loading. The result indicates that along the transverse direction in the subgrade cross section, both the static response and dynamic response have a saddle-shaped distribution. The largest static response and dynamic response measured are under the concrete base slab at the track position, while the responses under the centre-line and two ends of the concrete slab are small. The most intense dynamic responses are measured in the surface layer of subgrade bed （graded gravel area）, and they reduce sharply with depth. Compared with before rainfall, the subgrade static stress, dynamic stress, acceleration, and dynamic deformation increased about 12%, 3%, 35%, and 13%, respectively, at most after rainfall. Therefore, sufficient emphasis should be placed on the waterproofing and drainage measures.

Investigation on Application of Gabion Structure to Railway Bridge Embankment in Mining Subsidence Area

YU Guangyun, 2, LIU Can, ZHANG Yan

2010, 23(6): 863-867. doi: 10.3969/j.issn.0258-2724.2010.06.007

[Abstract](1124)

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In order to provide a reference for the application of Gabion structures in mine railway, their mechanical behavior and stress-strain relationship under uniaxial compression were obtained through the uniaxial compressive tests of Gabion structures filled with gravels or coal gangues. The experimental results show that under uniaxial compression, the mechanical behavior and stress-strain characteristics of Gabion structures with different grain compositions have no obvious regularities. The compressive strength of a Gabion structure filled with gravels is larger than that filled with coal gangues. And Gabion structures filled with gravels can meet the requirements of the load-bearing capacity of railway bridge embankment.

Spatial Stability Analysis of Butterfly-Shape Arch Bridges Based on Unified Theory

PU Qianhui, HUO Xuejin, YANG Yongqing

2010, 23(6): 868-874. doi: 10.3969/j.issn.0258-2724.2010.06.008

[Abstract](1459)

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In order to investigate the stability of bridges, based on the unified theory considering the confining action of steel tube, the first- and second-class stabilities of butterfly-shape concrete-filled steel tube arch bridges were analyzed. The first-class stability safety factor was obtained from the calculation of eigenvalue. By considering the effects of the geometry nonlinearity and material nonlinearity on the ultimate bearing capacity, the second-class stability safety factor was gained by the load incremental iteration method. By taking the main bridge on south-central ring district of Taiyuan City as the research object, the spatial stabilities of this bridge at the construction and finished stages were analyzed. The research results show that the stability safety factors obtained by the transformed section method and the composite element method are less than those obtained by the unified theory, so the unified theory can be applied to the stability analysis of concrete-filled steel tube arch bridges. The lateral torsional deformation is the primary buckling form of a butterfly-shape arch bridge, and the structure stability is influenced by the initial imperfection, the distribution of live load, cross wind and so on. The second-class stability safety factor is lower than the first-class stability safety factor.

Wake Effect of Bridge Tower on Coupling Vibration of Wind-Vehicle-Bridge System

LI Yongle, CHEN Ning, CAI Xiantang, 2, QIANG Shizhong

2010, 23(6): 875-882. doi: 10.3969/j.issn.0258-2724.2010.06.009

[Abstract](1283)

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With the action of cross wind, the existence of bridge tower results in a significant change in the distribution of wind field above bridge deck. In order to investigate the adverse influence of the change of wind field on the running safety and comfortability of a train, the CFD (computational fluid dynamics) numerical method was used to simulate the wind field above the bridge deck nearby the towers of a long-span suspension bridge. By a wind tunnel test with section model for deck and vehicles, the aerodynamic coefficients of vehicles running along rails with different positions and the bridge were measured respectively. Based on the wind field distribution and the measured aerodynamic coefficients, a self-developed analysis software BANSYS was adopted to conduct a contrast analysis for the dynamic responses of vehicles running through a bridge tower along different rail positions. The research results indicate that the changes of wind field nearby the bridge tower are dramatic to result in a local acceleration effect. And the sudden change of wind field nearby the bridge tower has an obvious influence on the lateral responses of vehicles.

Effects of 3D Wind Flow on Drag Coefficients of Stay Cables

SUO Qifeng, LI Mingshui, HE Xiangdong

2010, 23(6): 882-887. doi: 10.3969/j.issn.0258-2724.2010.06.010

[Abstract](1464)

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Models of stay cable sections and a corresponding drag coefficient testing system were designed to investigate the effects of cable surface pattern, inclination and yaw angles, and wind turbulence intensity on drag coefficient of the stay cables under 3D wind flows. Wind tunnel test indicates that the drag coefficient increases with an increase in the inclination angle when the yaw angle is about 0°, but it has a little change when the yaw angle is about 90°. The drag coefficient of dimpled cables or cable with helical strakes increases about twice compared with that of smooth cables, and the greater the ratio of dimpled area to the whole surface area and the higher the helical strakes, the larger the drag coefficient. The turbulence intensity has significant effect on the drag coefficient for a smooth cable.

Characteristics of Restoring Force of High Strength Reinforced Concrete Frame Columns

LI Zhengliang, FENG Hong, CHEN Yongqing

2010, 23(6): 888-892. doi: 10.3969/j.issn.0258-2724.2010.06.011

[Abstract](1257)

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A restoring force model was necessary for dynamic analysis of members under seismic action. In this paper, by analysis of the test results of low cyclic reversed loading experiments conducted on totally 19 steel reinforced high-strength concrete (HSRC) columns with different parameters (the slenderness ratio λ≥3), the dimensionless skeleton curves, dimensionless hysteresis loops, and stiffness degradation rules of the HSRC columns were simulated using the experimental fitting method. Based on these simulations, a restoring force model was established for the HSRC columns. The results show that the dimensionless skeleton curves can be expressed by a four-segment polygonal line; the dimensionless hysteresis loops can be expressed by a three-segment polygonal line; after each cycle, the stiffness degradation become more serious, and the curve returns but overshoots the original unloading point; the stiffness degradation between the yield point and limit point increases with an increase in the absolute horizontal displacement.

Co-Rotational Formulation-Based Analysis of Shell Buckling

ZHOU Lingyuan, LI Tongmei, LI Qiao

2010, 23(6): 893-897. doi: 10.3969/j.issn.0258-2724.2010.06.012

[Abstract](1124)

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In order to solve the nonlinear problem in analyzing the bulking of thin-walled structures, an updated Lagrangian co-rotational method for the nonlinear analysis of shell structures was presented. A program based on this method was developed, and 2 numerical examples of the buckling analysis of shell structures were given. In this method, an updated Lagrangian formulation is adopted to build the equilibrium equation of shell elements under large displacements, and then the tangent stiffness matrix is get with the energy theory. The polar decomposition theory is applied in the computations of the new co-rotational coordinates of elements and the rigid body rotations of nodes, and the finite rotation theory is introduced to separate rigid displacements from total displacements to get deformations of the nodes. As a result, stresses of an element can be calculated based on the deformations by using the small-strain theory to obtain the element state for the current load step. The numerical examples indicate that the nonlinear analysis method based on co-rotational (CR) formulation is efficient and accuracy in solving the buckling of shell structures.

Influencing Factors of Shear Capacity of Concrete Beam Reinforced with GFRP

SHI Xiao-Quan, ZHANG Zhi-Jiang, LI Zhi-Ye, LOU Xi-Hui

2010, 23(6): 898-904. doi: 10.3969/j.issn.0258-2724.2010.06.013

[Abstract](1551)

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To deeply study the shear behavior of concrete beams reinforced with glass fiber reinforce plastic (GFRP), factors influencing the shear capacity of a GFRP-reinforced concrete beam were investigated through tests of 57 concrete beams. The investigation mainly concerns the influences of stirrup and shear-span ratio on the shear capacity. In addition, a comparative analysis of concrete beams reinforced respectively with GFRP and steel on the shear capacity was carried out under the same parameters, such as reinforcement ratio, geometry size, concrete strength and shear-span ratio. The relationship between the influence coefficient of GFRP on concrete shear capacity and the shear-span ratio was researched. The results show that stirrups make the initial cracking shear strength of a GFRP-reinforced concrete beam increase about 7.4% to 30.0%, and the maximum stirrup stress is much less than its tensile strength when the concrete beam reaches its ultimate load-bearing capacity to indicate that the effective strain of stirrup controls its shear strength. The shear capacity of a GFRP-reinforced concrete beam increases firstly with the reduction of shear-span ratio, and then decreases. The influence coefficient of GFRP on concrete shear capacity increases with shear-span ratio reducing.

Mechanical Analysis of Ballastless Track with Damaged Cracks under Train Load

LIN Hongsong, LI Peigang, YAN Hua, LIU Xueyi

2010, 23(6): 904-908. doi: 10.3969/j.issn.0258-2724.2010.06.014

[Abstract](1604)

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In order to study the effect of cracks on the mechanics of ballastless track, a spatial finite element model of ballastless track with a crack was established based on the cracking characteristics of in-situ concrete layer, in which the singularity of the crack tip was simulated by 20-node hexahedron isoparametric singular element using the theory of elastic fracture mechanics. The mechanics of ballastless track under train load was then analyzed. The results show that the effect of the roadbed slab crack on the vertical displacements of rail and roadbed slab is small, and on the stresses of the top bar and concrete of the roadbed slab is not remarkable. Besides, the stress of the bottom bar has a sudden increase at the crack tip; the static and dynamic crack widths are almost the same. Under train load，for the roadbed slab with a 60 mm deep bottom crack, the crack width increases to 0.017 mm, and the bar stress at the crack tip is two times that without cracks.

Numerical Simulation of Radial Fretting Behaviors Using Ball-Plate Model

SHEN Huoming, LIU Juan, ZHU Minhao, HUANG Qian

2010, 23(6): 909-913. doi: 10.3969/j.issn.0258-2724.2010.06.015

[Abstract](1390)

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A ball-plate model and the Hertz theory were used to determine the relation between distributed forces and the contact radii on a Si3N4 ball and a Vita Mark II ceramic block. A finite element model was derived to determine the distribution of stress, strain and sliding. The simulation results are practically consistent with test results reported by somebody else. The friction coefficient in the sliding area has a little effect on stress and strain in the stick zone, but its effects on stress, strain and sliding are not neglectable in the sliding zone. Friction pair materials with similar elastic modulus and Poisson's ratios are desirable for reducing relative sliding and wear. Significant sliding appears in the sliding area, and the largest sliding appears near the outer edge of the contact zone.

Experimental Investigation on Tensile Mechanical Properties of BFRP Bars

GU Xingyu, SHEN Xin, LU Jiaying

2010, 23(6): 914-919. doi: 10.3969/j.issn.0258-2724.2010

[Abstract](1506)

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In order to probe into the mechanical properties of basalt fiber reinforced polymer (BFRP) bars, basic mechanical properties of BFRP bars were investigated by two strain test methods: the extensometer and optical fiber detection techniques. A new type of bar, called as basalt fiber-steel wires composite (BFSWC) bar with high elastic modulus was developed by adding steel wires into BFRP bars for low tensile elastic modulus of BFRP bars. The experimental result indicates that the stress-strain curve of a BFRP bar is linear, its elastic modulus is only about 23% elastic modulus of a steel bar, and the elastic modulus tested by the optical fiber detection technique is 12.3% higher than that obtained by the extensometer. BFRP bar's elastic modulus becomes low as its diameter gets big, and adding steel wires into a BFRP bar can significantly improve its elastic modulus.

Effect of Implantation Dose and Energy on Structure of Titanium Oxide Films

WANG Jinbiao, YANG Ping, LI Guicai, CHEN Jiang, SUN Hong, HUANG Nan

2010, 23(6): 920-925. doi: 10.3969/j.issn.0258-2724.2010.06.017

[Abstract](1136)

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In order to investigate the influences of ion implantation and vacuum annealing on the structure and properties of titanium oxide (TiO2) film, rutile titanium oxide film was synthesized on Si wafer using the unbalance reactive magnetron sputtering method, and then modified by phosphorus ion implantation and succeeding vacuum annealing. The experimental results show that an increase in implantation dose and energy will aggravate the damage to the crystalline structure of the film. After vacuum annealing, a broadening and red shift occurred to Raman peaks for both the implanted and unimplanted titanium oxide films, and the sheet resistance of the film decreased to 100—200 Ω/cm2, because of the energy band structure change caused by oxygen defects and low-valent titanium.

Double Layer Genetic Algorithm for Integrated Scheduling Optimization of Part and Tool Flows

ZHAO Dan, ZHANG Jiatai, SHU Haisheng, ZHAO Gang

2010, 23(6): 926-931. doi: 10.3969/j.issn.0258-2724.2010.06.018

[Abstract](1582)

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To solve the schedule optimization problem involving both part flow and tool flow in an FMS (flexible manufacturing system), a mathematical model of integrated scheduling for part and tool flows was presented, in which the objective was to minimize system make-span. A double-layer GA (genetic algorithm) was proposed for global optimization of the model. The outer and the inner layers of the GA were to search optimal and feasible operation sequences and tool assignment, respectively, and the fitness of the tool assignment was used to evaluate the outer layer optimization. A case study shown that the system make-span and waiting the time for tools were reduced by 19.7% and 20.4%, respectively, using the proposed double-layer GA compared with those obtained using heuristic rules.

Optimization Algorithm for Wagon-Flow Allocation in Marshalling Station

XUE Feng, WANG Ciguang, ZHANG Zhanjie, 2

2010, 23(6): 932-937. doi: 10.3969/j.issn.0258-2724.2010.06.019

[Abstract](1764)

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To improve the convergence performance of optimization algorithms for static and dynamic wagon-flow allocation, a genetic-ant algorithm was proposed, in which unnecessary search was avoided by limiting the solution space and coding schemes with their sequence number matrix following the rules of scheme tree in a marshalling station. An optimization algorithm based on GAAA (genetic and ant algorithm) was designed, which takes the characteristic of wagon-flow allocation problems into consideration and makes use of advantages of genetic and ant algorithms. It uses a genetic algorithm to obtain optimized break-up schemes and generate initial pheromones, and an ant algorithm to select the most optimum break-up scheme to produce a wagon-flow allocation scheme. Results of examples show that the proposed algorithm converges within 30 s for a wagon-flow allocation problem, in which the number of arrival and departure trains does not exceed 25 during an operation period.

Application of Random Number in Driving Cycle Model

SHI Qin, LI Youwen, Zheng Yubo

2010, 23(6): 938-945. doi: 10.3969/j.issn.0258-2724.2010.06.020

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Vehicle driving states that vary with time were taken as a Markov process to reduce the influences of uncertainty and small variations in driving speed on the driving cycle model. Collected data were classified into model events of idling, acceleration, deceleration, and constant velocity using maximum likelihood estimation. The model events with similar average speeds were categorized into six states, and their transition probabilities were calculated. Pseudo-random numbers satisfying distribution of the state transition probabilities were generated to extend the length of driving cycle. The application of the driving cycle model to the roads in Hefei (a city in China) shows that the average error in obtained typical driving cycles was 7.81% compared with the experimental data in terms of main driving characteristic parameters of a typical driving cycle，decreasing by 14.72% compared with that by principal component analysis.

Traffic Flow Time Series Periodicity Based on Recurrence Quantitative Analysis

HE Zhaocheng, LI Zhitao, ZHAO Jianming

2010, 23(6): 946-951. doi: 10.3969/j.issn.0258-2724.2010.06.021

[Abstract](1359)

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In order to improve traffic flow prediction accuracy, recurrence plot and recurrence quantitative analysis were introduced to analyze the traffic flow time series periodicity. Further more, the prediction methods BPNN(back propagation neural network) and K-NN(nearest neighbor) were employed to predict the short-term traffic flows with different periodicity. The result of an empirical study indicates that the traffic flow time series periodicity differs with the length of statistical time interval and the time period in a day. The traffic flow time series with a statistical time interval of 5 min show a good real-time performance and a strong periodicity. The periodicity has a positive correlation with the prediction accuracy of short-term traffic flow: The traffic flow in night time has a weak periodicity for which the prediction accuracy is 87.41%, while the traffic flow in day time has a strong periodicity for which the prediction accuracy is 92.16%.

Semi-actuated Signal Control Algorithm for Two-Phase Signalized Intersections

YU Quan, LIU Peihua, LIU Xiaoming, 2

2010, 23(6): 952-957. doi: 10.3969/j.issn.0258-2724.2010.06.022

[Abstract](1104)

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In order to study the influence of pedestrian and bicycle groups on the semi-actuated signal timing algorithm, an analysis was made of the characteristics of left-turn vehicles crossing pedestrian and bicycle groups at two-phase intersections first. Then, based on the HCM 2000(highway capacity manual 2000) queue service time model, a new model for calculating the initial green signal time in the semi-actuated signal control algorithm was built using the critical gap theory and the principle of balance between the arriving and departing left-turn vehicles. Semi-actuated signal timing plan was computed with the proposed model using the data collected in Huairou District of Beijing, and was validated by evaluation of the level of service (LOS) using the index of signal control delay in the field experiment. The numerical test results show that the total control delay of the whole intersection decreases 37.8%, and the LOS improves from grade C to grade B, so the proposed model can make the signal timing plan more adapted to intersections with many pedestrian and bicycle groups.

Evaluation Method for Time-Slot Availability of Crossing Air Route

ZHANG Jin, HU Minghua, ZHANG Chen

2010, 23(6): 958-964. doi: 10.3969/j.issn.0258-2724.2010.06.023

[Abstract](1635)

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To increase the efficiency of airspace use, an entry clearance strategy of the crossing air route was proposed and a mathematical model was established. Then, a new method for evaluating the airspace time-slot availability, with different combinations of various crossing route structure patterns and entry clearance strategies, was provided. The influence on the time-slot availability of the crossing air route imposed by the structural constraints, such as route length and crossing angle, and the deviation angle were analyzed by simulation. The results show that extending the route length under the fixed deviation angles could enhance the airspace time-slot available rate to a maximum level as high as 82%, 90%, and 97% when the deviation angle is 10°, 20°, and 30°, respectively. However, the approach of extending route length has a marginal effect; that is, there is no more promotion effect in the time-slot availability when the route length exceeds a threshold. Under the same route length and deviation angle, increasing the crossing angle would also enhance the airspace time-slot availability.

Model of Train Residence Time within GSM-R Cell in Section of Passenger Dedicated Line

LI Ye, YAN Yusong

2010, 23(6): 965-972. doi: 10.3969/j.issn.0258-2724.2010.06.024

[Abstract](1385)

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In order to investigate the essential parameters in a GSM-R (global system for mobile communication for railway) system, such as train channel occupation time and train handover rate, a new distribution model of train residence time within a GSM-R cell in SPDL (section of passenger dedicated line) was established. This model is based on the hypotheses that path length and train's average speed within the GSM-R cell in SPDL follow uniform distributions, the former is deduced from the hypothesis that the GSM-R cell coverage submits a uniform distribution. From the above hypotheses, the theoretical and simulation results were obtained. The research results show that when the radius of a GSM-R cell in SPDL is between 3 to 8 km, the theoretical and simulation results of the distribution of train residence time within the GSM-R cell agree well.

Connectivity Enhancement Based on Network Coding for Wireless Multi-hop Ad Hoc Networks

ZHU Xiping, 2, FANG Xuming

2010, 23(6): 972-976. doi: 10.3969/j.issn.0258-2724.2010.06.025

[Abstract](1156)

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To provide a reference for planning and designing wireless multi-hop ad hoc networks, the influences of physical-layer network coding and network coding diversity on the connectivity of wireless multi-hop ad hoc networks were analyzed. The theoretical and numerical analyses of the network sustained routing hop were carried out. The reserach result shows that compared with a physical-layer network coding cooperative transmission, the network coding diversity cooperative transmission can improve the sustained routing hops in wireless multi-hop ad hoc networks greatly, and the gain can be up to above 3 to greatly improve network connectivity to enhance network throughput.

Quick Discretization Algorithm for Rough Set Based on Dynamic Clustering

HU Feng, 2, WANG Guoyin, DAI Jin

2010, 23(6): 977-983. doi: 10.3969/j.issn.0258-2724.201

[Abstract](1287)

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In order to process the discretization of a decision table with large quantity objects, it is necessary to develop a high efficient discretization algorithm. The distribution of the importance values of candidate cuts on single attribute in a decision table was analyzed, and based on the distribution, a two-step solution procedure and a high efficient discretizaiton algorithm based on the rough set theory were proposed. Firstly, the candidate cuts are dynamically clustered in the light of their importance, so the number of the candidate cuts will decrease. Secondly, the final result cuts will be selected quickly from the clustered cuts using the heuristic method, as a result, the discretizaion of the decision table can be implemented by the final result cuts. The experiment results show that after dynamic clustering, the number of candidate cuts in most of data sets can be decreased by more than 80% to raise the efficiency of next cut selection greatly. To seven UCI data sets, Iris, Wine, Glass, Ecoli, Breast_w, Pima and Letter, in the experiments, their recognition rates are about 92.0％, 92.1％, 69.3％, 65.7％, 95.3％, 67.1％ and 76.5％ respectively using the proposed algorithm.

Algorithm for Multiple Sources Angle Tracking

AI Ming-Shun, MA Hong-Guang, LIU Gang

2010, 23(6): 984-989. doi: 10.3969/j.issn.0258-2724.2010.06.027

[Abstract](1139)

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In order to solve the problem of multiple sources angle-only tracking, a novel algorithm was proposed by combining the rooting orthogonal propagator method (OPM) and the zero-tracking. As a result, the iterative angle estimation and automatic association were carried out. Two parameters, the forgetting factor and the order of polynomial equation, are involved in the proposed algorithm, and they can be tuned respectively to change the performance of the algorithm, so it is adaptive to the condition that the signal-noise ratio (SNR) and the angular velocity of the sources are changing. The simulation results show that the proposed algorithm possesses a better performance and flexibility than the conventional ones do, and its root mean square error (RMSE) is lower than 0.15° when the SNR is above 0 dB.

WRF/CALMET-Based Wind Field Simulation of Mountain Regions

WANG Wenyong, CHEN Nan

2010, 23(6): 990-996. doi: 10.3969/j.issn.0258-2724.2010.06.028

[Abstract](1154)

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To more accurately simulate the local wind field caused by the terrain thermal of mountains, the atmospheric flow field of a valley industrial park was simulated by using the mesoscale weather model WRF (weather research and forecasting model) proposed by the United States NCAR (National Center for Atmospheric Research), and the simulated result was amended in a small scale (with a grid distance of 0.1 km ) by using the diagnostic wind field model CALMET. In the simulation, a triple-nested grid program is used in the WRF model, and the distance between two grids in the inner layer of the network is 1.0 km. The research result shows that there is a great difference between WRF-based simulated results and measured values, while WRF/CALMET-based simulated results are close to the measured values. The conclusion is that the WRF/CALMET coupled model should be used to simulate the atmospheric flow field of mountain regions.

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2010 Vol. 23, No. 6