西南交通大学学报

Development Strategy and Single-Layer User-Data Switching Platform Architecture for Next Generation Internet

ZENG Hua-Shen, CHEN Xi

2011, 24(6): 889-899. doi: 10.3969/j.issn.0258-2724.2011.06.001

[Abstract](1155)

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Abstract:
Based on researches on NGI (next generation internet) architecture and its related techniques carried out by Sichuan Network Communication Technology Key Laboratory, NGI development strategy and its architecture were discussed comprehensively. The emphasis was given to NGI framework at the laboratory, including NGI development strategy BSF-OES (backbone substrate first, outwards extension second), SUPA (single-layer user-data switching platform architecture), EPFTS (Ethernet-oriented physical frame timeslot switching), and future ONASM (open network and application service model). In addition, it was discussed how to meet the challenges such as high-speed switching, QoS insurance, security, and mobility with the framework of SUPANET (single-layer user-data switching platform architecture network) and how to realize the goal of NGI.

Optimization of Kernel Parameters Based on Third-Order Rényi Entropy

FENG Chao, YUAN Chao-Wei

2011, 24(6): 899-903. doi: 10.3969/j.issn.0258-2724.2011.06.002

[Abstract](946)

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In order to obtain an optimal tradeoff between cross-term reduction and high time-frequency concentration in time-frequency distribution of Cohen's class, an optimization algorithm of kernel parameters based on third-order Rényi entropy was proposed. From the asymptotic cross term invariance of third-order Rényi entropy, the optimal kernel parameters can be obtained by searching the transition of the curve of third-order Rényi entropy versus kernel parameters. The theoretical analysis and simulation results show that the optimization of kernel parameters based on third-order Rényi entropy can match the kernel function best with signals to yield a high-performance time-frequency distribution.

Blind Estimation of Symbol Rates of Multi-component Phase-Shift Keying Signals

YU Ning-Yu, MA Gong-Guang, , SHI , Rong

2011, 24(6): 904-909. doi: 10.3969/j.issn.0258-2724.2011.06.003

[Abstract](947)

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Abstract:
To solve the parameter estimation problem of multi-component phase-shift keying (PSK) signals intercepted simultaneously by a single-channel receiver in the same bandwidth, a new blind estimation algorithm was proposed. With this algorithm, blind signal separation is avoided and the symbol rate of each independent signal can be estimated directly. The linearity of the 2nd-order conjugated cyclic correlation for a multi-component PSK signal was derived theoretically, so that the symbol rate of each independent signal can be extracted without interference. In addition, a simple and effective method was proposed to enhance spectrum peaks. Compared with spectrum peaks obtained based on the 2nd-order conjugated cyclic correlation, spectrum peaks obtained by the proposed method are legible. The simulation results indicate that with the proposed algorithm the correct probability of symbol rates can reach 98% when the power ratio of a two-component signal is 1 to 1 and the signal-to-noise ratio (SNR) is -5 dB. Especially in a single-component signal case, the proposed algorithm can bring more than 4 dB performance improvement compared with the existing algorithm

Face Recognition Method Combining 2DLPP with 2DPCA

JI Yong-Feng, HUO Yuan-Lian

2011, 24(6): 910-916. doi: 10.3969/j.issn.0258-2724.2011.06.004

[Abstract](1215)

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In order to overcome the limitation that two-dimensional locality preserving projection (2DLPP) needs more data to represent face features, a new method, named two-dimensional locality preserving projection-principal component analysis (2DLPP-PCA), was proposed. By simultaneously considering 2DLPP and 2DPCA, the 2DLPP-PCA can not only reduce the data needed in preserving face features, but also effectively extract the local structure information from 2DLPP and the global structure information from 2DPCA. The experiments on the ORL, Yale and CAS-PEAL-R1 face databases indicate that the 2DLPP-PCA is a high-performance method for face feature extraction, with the best average recognition rate higher than 99% when the number of training samples on the ORL face database is 6.

Interval Type-2 Fuzzy Logic System Based on Multi-resolution Analysis

DING Wei, HUANG Jing-Chun

2011, 24(6) doi: 10.3969/j.issn.0258-2724.2011.06.005

[Abstract](2135)

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Abstract:
In order to effectively express and deal with the uncertainty of systems, an interval type-2 fuzzy logic system based on multi-resolution analysis was proposed, and a multi-resolution interval type-2 membership function was constructed. In addition, its structure and learning algorithm were given based on scaling function decomposition. The antecedent of the multi-resolution interval type-2 fuzzy system is a multi-resolution membership function, and the consequent is a linear function of inputs. As a result, the multi-resolution interval type-2 fuzzy system can divide the input universe adaptively and optimize system architecture. Finally, a noisy time series was predicted using the multi-resolution interval type-2 fuzzy system. The complexity of the prediction result is small, and the root-mean-square error is 0.105 2.

Improved Arc-Length Method for Solving Buckling Problem

ZHOU Ling-Yuan, LI Jiao, LI Tong-Mei

2011, 24(6): 922-925. doi: 10.3969/j.issn.0258-2724.2011.06.005

[Abstract](1296)

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Abstract:
A modified arc-length method was proposed to solve the problem that the traditional Newton-Raphson method fails in nonlinear finite element analysis on structures with buckling in the structure or softening in the material. The unbalanced load vector in the nonlinear equations is decomposed into two orthogonal vectors. A new constraint equation was derived, and solved to obtain the current load step factor. Complex roots are avoided by modifying the arc length. Two examples of nonlinear analyses on arch structures with geometric and material nonlinearity were presented, respectively. The snap-through in the post-bulking period was also revealed in the examples. The results demonstrate that solutions can be obtained with the proposed method when buckling in the structure or softening in the material occurs.

Two-StageDamageDetectionMethodBasedon ImprovedParticleSwarm OptimizationAlgorithm

GUO Hui-Yong, WANG Lei, LI Zheng-Liang

2011, 24(6): 926-932.

[Abstract](1391)

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In orderto solvestructural multi-damageidentification problem,atwo-stage identificationmethodbasedontheparticleswarm optimization (PSO)algorithm andthe Bayesiantheorywasproposed.Inthismethod,structuralmodalstrainenergy (MSE)and frequencyareconsideredastwoinformationsources,andthe methodsbasedonfrequency changeand MSE dissipationratioareutilizedtoextractdamageinformation.Then,the Bayesiantheoryisutilizedtointegratethetwoinformationsourcesandpreliminarilydetect structuraldamagelocations.Finally,the PSO algorithm isadoptedto preciselyidentify structuraldamagelocationsandextents.Inordertoimprovetheidentificationresultsofa simplePSOalgorithm,threeimprovedstrategies,particleposition mutation,elitistmicro- searchanddoubleconvergencecriterion,werepresented.Thesimulationresultsforatwo- dimensionaltrussstructureshowthattheBayesiantheorycanidentifythesuspecteddamage locations,theimproved PSO algorithm can preciselydetectthedamageextent,andthe identificationprecisionofthePSOalgorithm withthethreeimprovedstrategiesisobviously betterthanthoseoftheotherPSOalgorithmsandthegeneticalgorithm.

Experimental Research on Load-Bearing Capacity of Fire-Damaged Reinforced Concrete Continuous T-Beams

XIANG Kai, WANG Guo-Hui

2011, 24(6): 933-939. doi: 10.3969/j.issn.0258-2724.2011.06.008

[Abstract](1440)

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In order to research the effects of heating and cooling on the load-bearing capacity of fire-damaged reinforced concrete (RC) continuous beams, loading tests of three RC continuous T-beams were conducted. A parametric analysis for the load-bearing capacity of fire-damaged RC continuous beams were carried out with the finite element method. A simplified method for evaluating the ultimate load of RC continuous beams after fire was presented. The research results show that a fire-damaged RC continuous T-beam exhibits a low midspan yield load, ultimate load and stiffness compared with a control T-beam, and the decrease of stiffness is greater than that of the load-bearing capacity. Within heating time of 120 min, ratio of reinforcement has a significant effect on the load-bearing capacity of a fire-damaged RC continuous T-beams, while heating time and concrete strength have a finite influence. The simplified method is capable of predicting the ultimate load of fire-damaged continuous RC beams exactly.

Fatigue Performance of Anchorage Zone for Long-Span Single Pylon Cable-Stayed Bridge

WEI Xing, JIANG Shi-Zhong

2011, 24(6): 940-945. doi: 10.3969/j.issn.0258-2724.2011.06.009

[Abstract](1501)

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In order to investigate the fatigue performance of a new cable-to-girder anchorage in a cable-stayed bridge with steel box girder, different force transfer paths and mechanic behaviors of two types of anchorages connecting anchor-plate with web of box girder or anchor-plate with top plate of box girder were analyzed for different joint structures between anchor-plate and main girder. Software ANSYS was used to the simulation of anchorage zone to obtain the distribution and concentration degree of stresses. Fatigue test of a full-scale model for the anchorage zone was designed and carried out. By combining simulation analysis with experiment results, fatigue performance of connect welds in the new anchorage system under cyclic load was investigated. Theoretical and experimental results show that fatigue strength of the new anchorage system can meet the need of design. Connecting anchor-plate with web of box girder makes stress concentration reduce, the allowable fatigue stress of weld details increase and the fatigue performance of anchorage zone be improved.

Hysteresis Characteristics of Shear Friction Damper with Two Resistances and Displacements

ZHANG Peng-Bo, BO Yi, DIAO Shi-Chun

2011, 24(6): 946-952. doi: 10.3969/j.issn.0258-2724.2011.06.010

[Abstract](1004)

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A shear friction damper with two resistances and displacements was designed to improve the safety and comfort of a building under different horizontal loads. Pseudo-dynamic loading experiment was conducted on 4 full-scale damper assemblies with different loading procedures. The resistances of the dampers were set by adjusting the fastening forces of connecting bolts. The experimental results indicated that the damper provided adjustable low and high frictional resistances, respectively, in small and large displacements, and the transition speed between low and high frictional resistances depended on loading procedure and the clearances in kinematic pairs. The combination of steel and Al alloy plates as a frictional pair showed a stable frictional coefficient.

WebGIS-Based Safety Risk Management System of Underground Engineering

CHOU Wen-Ge, LI Jun-Song, HU Lan

2011, 24(6): 953-960. doi: 10.3969/j.issn.0258-2724.2011.06.011

[Abstract](1080)

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To solve the problem of dynamical safety risk assessment and management during the construction period of an underground project, a risk index system was developed based on the analysis of safety risks at this stage. By considering close-spaced impact, a method to assess the safety risks was given, and the risk acceptance criteria for underground engineering was proposed. A risk management system based on WebGIS was built for a tunnel project along the Beijing-Shijiazhuang passenger railway line. This system has functions such as the real-time collections of information on monitoring data, expert assessment and access control system, the dynamic assessment and alerting of the safety risks and the raising of corresponding suggestions. Practical application and monitoring result indicates that the system can lower safety risk at the construction stage of an underground project and reduce the possibility of accidents happening efficiently.

SHPB Experiment of Dynamic Mechanical Behaviorof Compacted Clay

LIU Dun-Xin, CHEN Zhong-Fu, XU Wei-Fang

2011, 24(6): 960-965. doi: 10.3969/j.issn.0258-2724.2011.06.012

[Abstract](1092)

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Abstract:
Because of soils' low wave velocity and impedance and large deformation, it is unable to obtain their reliable and accurate dynamic stress-strain curves with a conventional SHPB (split Hopkinson pressure bar) experimental device. To investigate the compressive mechanic properties of compacted clays under strain rates varying from 600 to 2 500 s-1, compacted clay specimens were subjected to axial impact with different projectile speeds by using the improved SHPB with a diameter of 25 mm made of polycarbonate and a small pellet of vacuum seal cement as pulse shaper, and the validity of the experiment was discussed by considering the stress equilibrium and constant strain rate. The results show that the polycarbonate SHPB device can be used to the dynamic experiment of compacted clays, the dynamic stress and strain of a compacted clay are sensitive to strain rate, and the relationship between dynamic stress and strain rate may be expressed by an exponential function.

Application Condition of Point Safety Factor Method for Stability Analysis of Landslide

YANG Tao, MA Hui-Min, DAI Jie

2011, 24(6): 966-972. doi: 10.3969/j.issn.0258-2724.2011.06.013

[Abstract](1157)

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To determine the landslide stage for suitable application of the point safety factor method, calculational results obtained using this method and the rigid-body limit equilibrium method were analyzed and compared, and factors influencing point safety factor were analyzed. The results show that the beginning stage of the plastic flow state of sliding zone is suitable to the use of point safety factor, so the applicable condition of the point safety factor method is the critical state of sliding beginning. At the stage, in a two-dimension condition the whole safety factor based on the point safety factor method shows a good agreement with that based on the rigid-body limit equilibrium method; in a three-dimension condition, the calculated results are accorded with the reserving strength concept, i.e., the safety factor of sliding decreases K times when its shear strength decreases K times.

Three-Dimensional Visualization of Arsenic Aggregates in Porous Media

BANG Dao-Beng, HUANG Chao, Aaron PACKMAN

2011, 24(6): 973-978. doi: 10.3969/j.issn.0258-2724.2011.06.014

[Abstract](1034)

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In order to investigate the change of internal structure of porous media caused by arsenic deposition, the X-ray difference micro-tomography was used to characterize the distribution of arsenic aggregates in porous media by scanning arsenic samples prepared in the laboratory and arsenic-rich fluvial sediments from Río Loa in Chile. After image processing, background noise in the tomograms was reduced and arsenic information was enhanced. Then the processed images were used to generate 3D spatial distribution datasets of arsenic in the media. Tools like Avizo 6 and Blob3D were used to reconstruct and visualize these 3D datasets. 3D visualization showed that arsenic accumulated in the pore space and grain surface, arsenic aggregates with different sizes had distinctly different morphologies, that is small aggregates tended to be spherical while big aggregates were relatively flat. The research results show that the X-ray difference micro-tomography can be used to observe the pre- and post-deposition structures of porous media and has no any destruction to the samples.

Influence of Additional Stiffness of Traction Bar on Vertical Dynamic Performance of Subway Vehicles

MA Wei-Hua, LUO Shi-Hui, SONG Rong-Rong

2011, 24(6): 979-982. doi: 10.3969/j.issn.0258-2724.2011.06.015

[Abstract](1256)

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Abstract:
To solve the wheel wear problems of the subway vehicles such as wheel tread wear, spalling, wheel out of round, and the problem that the vertical vibration of car body and the vertical ride index exceed the standard values, the additional stiffness function of the traction bar was studied through theoretical structure analysis and dynamic simulation. The results show that the vehicle braking system was not the main cause of the above problems, and that the additional stiffness function caused by the short length of the traction bar and the bigger connection stiffness on the ends are the main reason why the car body is sensitive to vertical impact. For the vehicle in braking condition or running on curve, the damping function of the secondary suspension decreases due to the additional stiffness of the traction bar system. The response of the car body to the vertical impact increases significantly if the additional stiffness function of the traction bar system is taken into account. The vertical dynamic response and vertical dynamic performance of the subway vehicle can be improved efficiently by decreasing the connection stiffness of the traction bar to 25%.

Fast Intersection Algorithm between Spatial Triangle Pairs

ZHOU Yi-Sheng, DING Guo-Fu, HE Yong

2011, 24(6): 984-988. doi: 10.3969/j.issn.0258-2724.2011.06.016

[Abstract](1084)

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To improve the collision detection efficiency, a fast triangle-triangle intersection detection algorithm was proposed, which is based on the principle of accurate intersection calculation between edges of different triangles. In the algorithm, the linear dependence of edge vectors of triangles, projection character of segment, and intermediate calculation results are used to improve the performance of intersection detection. Many types of samples were used to test the accuracy and efficiency of the proposed algorithm in comparison with the typical algorithms proposed by Guigue, Shen, Mller, and Tropp. The experimental results show that the detection precision of the proposed algorithm was the same as the typical algorithms, but its detection speed of the former was over 3.5% faster than them in the case that triangles intersection rate was greater than 0.2, and the performance in detection speed increased with the intersection rate and the amounts of triangles increasing.

Wind-Induced Security of High-Speed Trains on the Ground

XU Meng-Ge, ZHANG Ji-Ye, ZHANG Wei-Hua

2011, 24(6): 989-995. doi: 10.3969/j.issn.0258-2724.2011.06.017

[Abstract](1375)

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In order to study the running security of high-speed trains under strong crosswinds, an aerodynamic model and a vehicle system dynamic model for computing the wind-induced vibration of the high-speed trains were established based on the theories of aerodynamics and multi-body system dynamics. With the models, the characteristics of crosswind aerodynamic loads acting on the train body under different wind angles, different wind speeds, and different running speeds were calculated. Then, according to the standard of Testing of High-Speed Electric Multiple Unit on Completion of Construction, the operational safety of the head car, middle car, and tail car of the train were analyzed using the operational safety indicators of the derailment coefficient, the load reduction rate, the axle lateral force, and the wheel-rail vertical force. The results show that the security of the head car is lower than the other two cars in all cases; and when the wind angle is 90° in a cross-wind situation, the security of the head car is the worst. The maximum safe wind speed decreases sharply as the train speed increases: when the train speed is 200 km/h, the maximum safe wind speed is 29.61 m/s, and when the train speed is 400 km/h, the maximum wind speed is 18.87 m/s.

Numerical Analysis of Aerodynamic Dipole Source on High-Speed Train Surface

ZHENG Zheng-Yu, LI Ren-Xian

2011, 24(6): 996-1002. doi: 10.3969/j.issn.0258-2724.2011.06.018

[Abstract](1229)

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Based on the Lighthill's acoustic equation, the boundary element method (BEM) combined with the computational fluid dynamics (CFD) was utilized to achieve the distribution of aerodynamic dipole source on high-speed train surface. The strength and distribution of the aerodynamic dipole source under different train speeds were investigated, and train's external aerodynamic acoustic field based on the aerodynamic dipole source was analyzed by a numerical simulation. The research results show that when a train runs at 270 km/h and the frequency is 2.5 kHz, main aerodynamics noise source with a sound pressure level over 90 dB is located near its bogies, and the maximal sound pressure level is approximately 97 dB.

Rapid Collision Detection Based on OBB Algorithm and Penetration Avoidance Mechanism

WANG Pei-Dun, WANG Wen-Jing, CHEN Feng

2011, 24(6): 1003-1008. doi: 10.3969/j.issn.0258-2724.2011.06.019

[Abstract](1131)

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A new penetration avoidance mechanism based on forward prevention was proposed to improve the real time performance and reality of collision detection in virtual assembly systems. In virtual assembly manipulation, grasp and release of virtual objects and penetration avoidance were implemented using an OBB algorithm and a hierarchical detection method to avoid artifact caused by a traditional penetration avoidance algorithm. The proposed algorithm, with the help of a data glove and a tracker with 6 DOF, was applied to a simulation experiment on the virtual assembly of a set of motor shell moulds that had a large virtual scene in a semi-immersive virtual environment. The simulation result demonstrated that the virtual assembly system provided realistic assembly operation for the millisecond collision response without penetration.

Experimental Research on Tail Rudder Efficiency of Super-Cavitaion Vehicle

FEI Xuan, ZHANG Yu-Wen, DENG Fei

2011, 24(6): 1008-1013. doi: 10.3969/j.issn.0258-2724.2011.06.020

[Abstract](1135)

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In order to acquire the input conditions of super-cavitaion vehicle control trajectory and overall design, a scaled model experiment on tail rudder was carried out to investigate the generation of ventilated supercavity and the dynamics characteristics of tail rudder angle of an underwater vehicle. The effects of ventilation air amount and tail rudder angle upon the configuration and hydrodynamics characteristics of a model supercavity were analyzed to obtain the influence regularities of tail rudder angle on lift force and angle of attack (AOA) and ventilation air amount on tail rudder efficiency. In addition, compensation measures for the supercavity tail floating-up caused by gravity were discussed. The experiment results show that in a wet state, the lift curve slope of tail rudder surfaces of an underwater super-cavitaion vehicle is a positive constant to be projected to the global area as the same as a common underwater vehicle under the same condition; when the super-cavitaion occurs and the AOA is 0.4°, the rudder effect will be reduced because of coupling lift force loss of main cavity, and it is insensitive to ventilation air amount; when the AOA is bigger than 1.2°, the characteristics of the rudder effect will be gradually restored, at the moment the main cavity has been away from the wing and the rudder surfaces are in a wet state.

Distribution Characteristics of Falling Film Thickness around Horizontal Tube and Its Influences on Heat Transfer

HOU Hao, BI Qi-Cheng, MA Gong

2011, 24(6): 1013-1018. doi: 10.3969/j.issn.0258-2724.2011.06.021

[Abstract](998)

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According to the physical characteristics of gas-liquid interfaces, the film thickness on the perimeter of a horizontal tube was experimentally studied by a conductance probe method to understand the flow behavior of a falling film. Measurements were conducted under the following conditions: outside diameter D=20—32 mm, intertube spacing S=10—40 mm, and film Reynolds number Re=150—800. Falling film distributions over a range of circumferential angles from 10° to 170° were obtained and their effects on heat transfer were examined and analyzed. The results indicate that the values predicted by Nusselt's theory are larger than the measured values on the lower perimeter of the tube. The minimal values of the film thickness tend to locate at different circumferential angles in the range of 90° to 115° under different operating conditions. The film thickness decreases with the intertube spacing increasing and increases with Re. Moreover, the changes in tube diameter have little influence on the film distribution. The rough outer wall of the tubes can make the film thinner. In addition, the film free-surface is disrupted in the region of scale formation, which facilitates the formation of dry patches on the heat transfer surface.

Occlusion and Duplicate Setting of Roadside Traffic Signs for Ordinary Multilane Highways

LIU Jian, JIANG Jun, XIE Hai-Fei

2011, 24(6): 1019-1024. doi: 10.3969/j.issn.0258-2724.2011.06.022

[Abstract](1214)

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Heavy vehicles account for a large proportion on ordinary highways. In order to solve the occlusion problem that heavy vehicles shelter roadside traffic signs, an analysis was made for the sign recognition process of car drivers at the median lane being occluded by heavy vehicles at the outside lane on an ordinary bidirectional highway with 2 lanes in each direction, and the calculation formulas for occlusion length and occlusion probability in the sign recognition process was derived. Then, the calculation flow to determine the duplicate setting times of roadside traffic signs was designed, and a model for calculating the space between the duplicated traffic signs was established. The proposed method was verified by an example. The results show that, when the speed limit sign is duplicated once, the probability that the two speed limit signs are both occluded by heavy vehicles is 0.023, and the best space between duplicated traffic signs is 155 m.

Regional Emergency Logistics Network Design Based on Reliability Analysis

CHEN Jian, YAN Qi-Peng, HE Ya-Min

2011, 24(6): 1025-1031. doi: 10.3969/j.issn.0258-2724.2011.06.023

[Abstract](1659)

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A bi-level programming model for network design of regional emergency logistics was formulated for the network to survive in natural disasters and to meet the needs of emergency supplies. There are two objectives in the upper programming model: a shortest total logistics time and maximum connectivity reliability under emergency. The upper model was solved by transforming it into a single objective model. The lower model was a user equilibrium assignment model with a fixed demand. An improved simulated annealing optimization algorithm was used to solve the whole bi-level programming model. Results of a numerical example indicated that adding the objective function of maximum connectivity reliability under emergency into the upper model decreased the system maximum criticality from 821.55 to 32.66, and total logistics cost by 0.22%, with the same total investment and logistics time.

Conflict Avoidance Oriented Airport Surface Aircraft Taxiing Guidance Method

SHANG Xin-Min, AN Hong-Feng, WANG Chong

2011, 24(6): 1032-1039. doi: 10.3969/j.issn.0258-2724.2011.06.024

[Abstract](988)

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To avoid confliction troubles between aircrafts at high density airports, an aircraft taxiing guidance framework based on hybrid system is proposed. Firstly, an aircraft taxiing dynamic model in continuous space and discrete event dynamic system models for the taxiing operation on straightaway and intersection are built, and a surface operation observer that maps the continuous dynamic state into discrete observation is proposed. Secondly, the forbidden state avoidance-based regulations described by linear inequality constraints and logical mutex constraints are introduced to express surface traffic control rules, and the discrete controller design method are proposed. Finally，the mapping from the enabling state of controllable transition in the straightaway and intersection operation models to control strategies is built. The validation by control system of an airfield lighting sand table shows that the taxiing guidance method can issue feasible control strategies in time and generate taxi manoeuvring instructions for aircrafts to avoid potential taxiing conflicts effectively.

Simulation of Aircraft Flight Track by BéZier and B-spline Curve

LI Xin-Qing, LAN Shi-Yong, LI Gang

2011, 24(6): 1040-1045. doi: 10.3969/j.issn.0258-2724.2011.06.025

[Abstract](1385)

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To overcome the limitations of motion equation which can not control the curve shape of aircraft tracks, a method of track simulation by Bézier and B-spline curves was proposed since the civil aircrafts have regular flying rules and its motion follows the beacons in flight plan defined before flight. In this method, lengths of the Bézier and open uniform B-spline curves are approximated by sum of line segments subdivided from the curves; then, Bézier control points of the track curve are calculated with the beacon positions in flight plan and the real-time status such as flying speed, position, etc. of the aircraft. The B-spline method needs not to create new control points for generation of aircraft flight track curve because it can create a rational track curve using beacons. Furthermore, the position of the next point in flight track is calculated by the interpolation equation of Bézier or B-spline curve. The simulation result shows that the Bézier and B-spline track curve are basically the same as the real track curve. The proposed methods are superior to the method of motion equation, for it can create all kinds of track curves. Under the condition of 18 beacons, the calculating time of the Bézier method is 0.13 s and can satisfy the real-time requirement.

Modeling and Simulation of Fleet Planning for Liner Shipping

YANG Qiu-Beng, XIE Xin-Lian, FEI Guang-Dan

2011, 24(6): 1046-1054. doi: 10.3969/j.issn.0258-2724.2011.06.026

[Abstract](1282)

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In order to improve and optimize a liner shipping system and to meet the requirements of liner service with fixed schedules, a mixed-integer nonlinear model for fleet planning was established based on the multi-call liner route pattern. The objective of the model is to maximize the discounted cash flow of fleet operation during the planning period. Based on the characteristics of the model, a Lagrangian relaxation heuristic algorithm was developed to solve it. A liner fleet of shipping company was taken as an example to demonstrate the model, and the optimal solution including ship allocation, sail frequency and fleet development for multi-route, multi-ship, large-scale fleet planning is obtained by using the proposed heuristic algorithm. The simulation results indicate that the model is able to synthetically take into account many factors such as the forecasted flow of commodity, deadweight utilization and chartering in and out of vessels during fleet planning. Therefore, the model can be applied to the typical liner operation pattern with the same type of ships deployed on the same route, providing decision support for liner fleet planning.

Supply Chain Postponement Strategy Model for Mass Customization

ZHANG Min, CHENG Wen-Meng, ZHANG Ze-Jiang

2011, 24(6): 1055-1059. doi: 10.3969/j.issn.0258-2724.2011.06.027

[Abstract](828)

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In order to bring the overall efficiency of supply chain into full play and provide the best production strategy for manufacturers, the cost relationships in general stage and customized stage are analyzed, and a supply chain postponement strategy model aimed at the minimum total cost of manufacturer is established by using queuing theory according to the characteristics of supply chain delay manufacturing activities for mass customization, and customers' personalized requirements and waiting time. The proposed strategy model mainly studies the relationships between production costs and parameters of component commonality differentiation point and inventory level for the manufacturers in mass customization production. It obtains the minimum total cost of manufacturers by using the heuristic algorithm to determine the optimal ratio of differentiation and the best inventory level of component commonality, and provides an effective decision-making tool for manufacturers. The results of a case study show that the ratio of differentiation differs with the inventory level of component commonality, and the optimal ratio of differentiation is in between 0.45-0.65; when the inventory level and differentiation point of component commonality are 19 and 0.60, respectively, the minimum total cost (155.857 yuan) of manufacturer is achieved.

Effect of Diameter of Leachate Drainage Pipeline on Operation of Simulated Semi-aerobic Landfill with Leachate Recirculation

YANG Hong-Wei, YANG Xiao-Dong, LIU Dan

2011, 24(6): 1060-1066. doi: 10.3969/j.issn.0258-2724.2011.06.028

[Abstract](1019)

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In order to study the effect of the diameter of leachate drainage pipeline on operational characteristics of semi-aerobic landfills, three simulated semi-aerobic landfills with leachate recirculation were constructed in laboratory using different diameters (80, 50, and 25 mm) of leachate drainage pipelines, and the variations in temperature of the waste, quantity of the leachate, quality of the leachate, etc., during 344 days were analyzed. The results show that the diameter had an obvious influence on the operational characteristics. With the increase of the diameter, the quantity of leachate decreased, the pH of leachate rose quickly, and the leachate quality indexes such as the chemical oxygen demand, NH3-N concentration, and total nitrogen concentration improved rapidly. Under this experimental condition, the organic in the waste could be degraded completely when the diameter ratio of leachate pipeline to waste heap was no less than 1∶32. On the other hand, when the diameter ratio reached 1∶16, the organic could be degraded completely, and the nitrogen compounds could be reduced efficiently.

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2011 Vol. 24, No. 6