2008 Vol. 8, No. 3

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Impacting experiment and numerical simulation of energy-absorbing component of vehicles
Xie Su-chao, Tian Hong-qi, Yao Song
Abstract: In order to design the crashworthy car-body of one train and to realize its passive safety, an impacting experiment fo trolley was carried out to study the energy-absorbing property of energy-absorbing component for the car-body. During the impacting experiment process of trolley, the plastic deformation of the component is steady and ordered beginning with the anticipative part, and the absorbed energy is proportional to the maximum deformation, so the component has good energy-absorbing property. Based on experiment result, a finite element impacting model was set up by using explicit dynamic finite element theory, and numerical simulation was carried out. Relativity analysis result shows that simulation result accords well with experiment result, the curves of impacting forces are consistent well, and the maximum peak values of impacting forces are 2486.3 and 2423.1 kN respectively, the differences of the maximum deformations and the first peak values of impacting forces are less than 3%, and the difference of rebound velocities is less than 4%. So the validity and reliability of numerical simulation are verified by impacting experiment, and it is feasible to design and optimize the energy-absorbing components through numerical calculation.More>
2008, 8(3): 1-5.
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Influence of wheel-rail impact on fatigue of bogie frame
Xiao Shou-ne, Li Hua-li, Yang Guang-wu, Deng Rui
Abstract: In order to analyze the effect of wheel-rail impact on the fatigue life of bogie frame, a bogie frame of a three-axle locomotive was taken as an example, the differential equation of wheel-rail impact was established, and the load history of wheel-rail impact was obtained by using Runge-Kutta formula. A finite element model consisting of wheelsets, bogie frame and carbody was established by using finite element method, the stress histories of different dangerous points on the frame were derived by using transient dynamics analysis technology, the S-N relations of 16 Mn material and fatigue damage cumulative rule were analyzed, and the fatigue life of the frame was calculated under the impact of wheel-rail tie-in. Analysis result shows that the stress response of the frame is not accordant with wheel-rail impact force to achieve the maximum value, but there is a longer response process after impacting; the influence of wheel-rail impact on the fatigue of bogie frame is great, especially, on the cover board of side-girder near axle box spring block, and the fatigue life of the frame is 5.15×106 km under its malocclusion joint for 25.0 m long track.More>
2008, 8(3): 6-9.
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Prediction of interior aerodynamic noise of high-speed train cab
Xiao You-gang, Tian Hong-qi, Zhang Hong
Abstract: In order to decrease the noise in train cab, the fluctuation pressures of head curved surface of high-speed train were calculated by using large eddy simulation method, which were exerted on the finite element model of train cab as excitement load, the vibration speeds of cab plates were obtained by using harmonic response analysis, and were taken as the excitement condition of acoustic boundary element model of train cab, and the interior aerodynamic noises at different frequencies were attained by using acoustic analysis. Computation result shows that the aerodynamic noises levels in cab change from 52.3 to 58.8 dB (A), at the transitional place from cab windowpane to train roof and near the largest outline of head longitudinal section, the noise press level (SPL) of field points are greater, the noises are dominant ranging from 50 to 315 Hz; the aerodynamic noises in cab are low frequency noises mainly, if the largest outline of head longitudinal section is smoother, the noises will be reduced.More>
2008, 8(3): 10-14.
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Design of shock absorber matching to optimal damping of vehicle suspension
Zhou Zhang-cheng, Meng Jie
Abstract: In order to design optimum shock absorber for vehicle, its optimal damping coefficients were studied according to the optimization damping ratio of suspension, a mathematic model of its velocity characteristic was built, an optimal design method of its valves parameters was put forward, its performance and whole vehicle vibration tests were carried out, and its performances were compared with that of original shock absorber. Computation result shows that the maximum warp between testing values and optimal requiring values is 9%, the transfer function values of whole vehicle vibration with designed shock absorbers are lower than that with original shock absorbers in the scope of low frequency, the resonance hereabout 13 Hz is depressed, so the model and method are feasible.More>
2008, 8(3): 15-19.
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Sensitivity analysis method of vehicle steering system under braking condition
Liu Xi-dong, Ma Jian, Guo Rong-qing
Abstract: In order to determine the effect of the sensitivity of steering system on the shimmy of front wheel under braking condition, wheel, front axle and leaf springs were considered as a whole, the changes of dimensional states of leaf spring and steering system were analyzed, a mathematic method of the shimmy angle of front wheel was proposed, and the sensitivity of steering system was evaluated with the shimmy angle resulted from the change of dimensional state of steering system. Computation result indicates that the maximum of the shimmy angle is 0.5° when braking force is 35 kN. Obviously, the sensitivity of vehicle steering system is lower, the evaluation result accords with its real state, so the method is feasible.More>
2008, 8(3): 20-23.
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Industry standard composition principles and general technology features of vehicle gas-fuel heater
Shen Fu-lin, Tan Rong-ke, Liu Dong
Abstract: In order to promote the product development of vehicle gas-fuel heater and standardize the product performance and quality supervising management, the theories of gas characteristic, burning theory, noise testing principle and modern control technology were referred, and the indices and testing methods of vehicle emission, noise, safety in domestic and foreign similar standards were studied. It is pointed that the emissions of vehicle gas-fuel heater can be controlled effectively when the volume contents of CO, NOx and HC in vehicle emissions are taken as emission indices and excess air coefficient is 1, the product noise can be tested objectively and accurately when GB/T 3767—1996 is adopted, and the product work safety can be effectively controlled when ignition security time and flameout security time are taken as control indices. According to prototype test result and the latest domestic and foreign standards, the technical indices and testing methods in Chinese automobile industry standard of vehicle gas-fuel heater (QC/T 769—2006) are established, so that the standard can synthetically standardize the product quality in safety, electric characteristics, stability and reliability and so on.More>
2008, 8(3): 24-27.
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Control method of time on wing for civil aeroengine
Rong Xiang, Zuo Hong-fu, Zhang Hai-jun
Abstract: In order to apply condition based maintenance (CBM) to control civil aeroengine time on wing (TOW), the features of aeroengine CBM and TOW were discussed, and the proportional intensity model was established to describe the relation among TOW, condition monitoring variables and failure intensity. TOW control limit due to performance deterioration and optimal preventive maintenance (PM) interval under minimizing expected total maintenance cost per unit time were implemented. The operation data of a CF6-80C2A5 engine were studied. It is pointed that the less failure intensity is, the lower TOW control limit is; moreover, the cost rate between PM and corrective maintenance can affect optimal PM interval; sufficient engine operation data are the keys of accurate TOW control, such as engine removal and on wing history records, maintenance cost, requirements of airworthiness and manufacturer, and time limits of life limited parts etc.More>
2008, 8(3): 28-32.
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Digital signal processing method of fluxgate compass
Yang Xiao-dong, Chen Li-min
Abstract: In order to improve the pointing precision and stability of fluxgate compass, a digital signal processing method was put forward. Driving signal was generated by micro processor, magnetic field digital signal from fluxgate sensor was collected by convert analog, even harmonics were obtained by Fourier transform from original signal, and the orientation of fluxgate compass was calculated according to even harmonics. Computation result shows that the amplitude of quadratic harmonic is biggest, its extraction precision is improved by five times at least, the noise of original signal is reduced, its using efficiency is enhanced and the sensitivity of fluxgate sensor is improved because of the computed orientation from multiple even harmonics, so the method is feasible.More>
2008, 8(3): 33-36.
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Research on design indices of perpetual asphalt pavement
Cui Peng, Shao Min-hua, Sun Li-jun
Abstract: In order to investigate the design method of perpetual asphalt pavement, the indices about tensile strain at the bottom of asphalt layer and the compressive strain at the top of subgrade were validated with SHELL design method, AI design method and so on, the strain indices were statistically analyzed according to the structure combination of representative perpetual asphalt pavement in foreign countries, and the design indices were modified based on the pavement design parameters in China, the two foreign design indices of perpetual pavement were approved to be reasonable, the control indices of structure design for perpetual pavement in China were put forward as follows: the tensile strain at the bottom of asphalt layer should be not more than 120×10-6, and the compressive strain at the top of subgrade should be not more than 280×10-6, the mechanical analyses of test road structures were carried out. Study result shows that the tensile strains at the bottom of asphalt layers are less than 120×10-6, and the compressive strains at the top of subgrades are less than 280×10-6, so the test road sections satisfy the indices of perpetual pavement.More>
2008, 8(3): 37-42.
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Durability of synthetic fiber reinforced concrete for airport pavement
Cen Guo-ping, Ma Guo-qiang, Wang Shuo-tai, Zhang Leng-jing
Abstract: In order to improve the durability of airport pavement concrete, the impermeabilities, frost resistances and abrasion resistances of three kinds of fiber(single polypropylene, reticular polypropylene and polyacrylonitrile) reinforced concretes were tested in laboratory. Hydrostatic pressure method and chloride penetration method were used in impermeability test, fast freeze-thaw method was used in frost resistance test, and ball bearing method was used in abrasion resistance test. Test result indicates that when the volume fraction of fiber is 0.10%, the levels of the impermeabilities and frost resistances for fiber reinforced concretes increase by 40%~160% compared with normal pavement concrete, their abrasion resistances increase by 23%~50%; when the fraction is within 0.15%~0.18%, their impermeabilities and frost resistances are best.More>
2008, 8(3): 43-45.
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Thermoelectric field model of microwave hot in-place recycling for asphalt pavements
Sun Tong-sheng, Shi Jin-fei, Zhu Song-qing, Wang Hong-xiang, Zhang Zhi-sheng
Abstract: In order to improve the efficiency of radiation electric field and the distribution uniformity of temperature field in microwave heating for asphalt mixtures, the radiation field integrals of basic surface elements were computed, a mathematic model of radiation electric field for microwave heating device was built by using Huygens' principle, a mathematic model of temperature field for asphalt mixtures in front of radiation surface was established by using the law of energy conservation, and the influences of structure parameters and media physical properties on thermoelectric field were analyzed. The lengths of antennas in E-plane and H-plane were optimized by using the theories of antenna near-field radiation, microwave heating experiments were made for two kinds of antennas with different lengths in E-plane and H-plane, and the temperature fields were simulated. Simulation result indicates that the temperatures of asphalt mixtures in most regions are from 75 ℃ to 90 ℃ and decline slightly around the periphery when using the antenna in accordance with the length principle; however, the temperatures are over 130 ℃ in local regions and under 70 ℃ in most regions when using the other antenna. Obviously, the temperature field is more homogeneously and the heating efficiency is improved by using the former antenna, which demonstrates the accuracy of thermoelectric field model and the availability of structure optimization.More>
2008, 8(3): 46-51.
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Influence factor analysis of deformation behaviors for reinforced backfills behind abutment
Liu Meng-cheng, Wang Juan, Huang Xiao-ming
Abstract: In order to analyze the mechanics mechanism of reducing differential settlement at the transition section between abutment and embankment by means of reinforced backfills, the field sizes of centrifugal modeling tests were referenced, a plane-strain numerical analysis model of reinforced backfills behind abutment was established by ABAQUS finite element method, the influence factors of different reinforced design parameters such as spaces, lengths and rigidities of geogrids, strength of backfill material and stiffness of subsoil were analyzed, and the deformation behaviors of reinforced backfills behind abutment were studied. Analysis result indicates that the surface settlement of backfills behind abutment can be reduced effectively by reducing the spaces of geogrids, or increasing the elastic moduluses of geogrids, the inner friction angles of backfill material and stiffness of subsoil, or adopting the inverse-triangle variable-lengths reinforced layout of geogrids; however, the influence of subsoil stiffness on the deformation behaviors of reinforced backfills depends on the interaction characters between subsoil and reinforced backfills.More>
2008, 8(3): 52-57.
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Permanent deformation prediction model of sandy soil under repeated load
Zhang Hong-liang, Guo Zhong-yin, Gao Qi-ju, Cong Lin
Abstract: In order to predict the permanent deformation of subgrade, a dynamic triaxial test of sandy soil under repeated load was made by using universal testing machine(UTM), the development curves of the deformation were got, the relationship formula between plastic strain and load acting time was found, the regression formulas among the coefficients of the relationship formula, water content and resilient modulus were fitted by using least square method, and their reliability was analyzed. Analysis result shows that when load acting time reaches 10 000, the minimum and maximum relative errors between permanent deformation prediction result and measured result are 52% and 376% respectively; the minimum and average correlative coefficients of the regression formulas are 0.31 and 0.41 respectively, which are greater than the critical value of 0.28, and the correlative coefficient between theoretical curve and measured one is more than 0.99. So the reliability of the proposed prediction formulas of permanent deformation for sandy soil is higher, but existing prediction model is not suitable for sandy soil.More>
2008, 8(3): 58-62.
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Numerical simulation and field test at the cut to fill location of subgrade treated with geogrids
Zhang Yong-qing, Wang Xuan-cang, Wang Chao-hui, Chen Xi-mei
Abstract: The compression deformations and interaction of the subgrade and groundsill were considered at the cut to fill location, a finite element model of subgrade deformation was established by using ANSYS software, the influence rules of the vertical space and length of geogrids at cut location on subgrade were simulated, the field test and subsidence track observation at different test sections were carried out, and the influence of geogrids layer number on the unequal settlement of subgrade was studied. The result indicates that when the vertical space of geogrids is 0.8~1.0 m, the change of vertical displacement for pavement is slower, the unequal settlement of subgrade is less, so it is recommended that the rational vertical space of geogrids is not bigger than 1.0 m; the smallest chose length of geogrids at reinforcing end in cut section is 2 m for economy because the influence of the length change on the vertical displacement of pavement is less; the unequal settlement of subgrade can be reduced effectively by burying a layer of geogrid at the bottom of 96 area and 94 area respectively.More>
2008, 8(3): 63-67.
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Mixed artificial fish school algorithm of aircraft sequencing in terminal area
Wang Fei, Xu Xiao-hao, Zhang Jing
Abstract: In order to ensure flight safety and effectively sequence landing aircrafts in terminal area, an object model with minimum total delay was developed, the ideas of selection operation in genetic algorithm (GA) and the acceptance according to probability in simulated annealing (SA) algorithm were considered, a mixed algorithm was proposed based on artificial fish school algorithm (AFSA), the sequence problem of landing aircraft was solved, and its computational result was compared with the ones computed by first-come-first-serve (FCFS) algorithm, SA algorithm and ant colony optimization (ACO) algorithm. Simulation result shows that the total delays are respectively reduced by 9.3% and 48.0% for single and double runways compared with FCFS algorithm, computational time is less than 3 s, while the delay and computational time are least compared with SA algorithm and ant colony optimization algorithm, so the mixed algorithm (MA) is feasible.More>
2008, 8(3): 68-72.
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Computational method of longitudinal safety separation based on flight following theory
Zhang Zhao-ning, Li Xin-hua, Wang Li-li
Abstract: In order to accurately compute longitudinal safety separation between airplanes, the effect factors of the separation were analyzed, the effect degrees of human factors on the separation were measured according to the reaction times of controllers and pilots, a flight following model was built according to the times, the influences of the times on the separation were quantitated, and a computational method of the separation was put forward. Simulation result indicates that in flight period, the adjacency is dangerous when the separation is less than 3.0 km, whenas, the minimum computation separation is 3.6 km for flight safety, so the model and method are feasible, and are important theories to constitute flight separation standards.More>
2008, 8(3): 73-76.
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Optimization model and algorithm of port cluster system
Feng Xue-jun, Wang Wei, Jiang Liu-peng
Abstract: In order to roundly optimize the scale, structure and layout of port cluster system, improve their dynamic harmony, a double planning model was built by using multi-agent simulation method based on complex system theory, and a multi-agent(MA) genetic algorithm(GA) was proposed. Global optimization agent was established to achieve the synergic optimization among the agents of port cluster system, the scale effect factor of port was introduced, an allocation model of freight volume in the hinterland of port was constructed and applied in the switching rules of port agents. Computation result shows that the model tends to the optimal solution after the 60th iteration, the total benefit of the system increases by 48%, its structure and size become rational, so the model and algorithm are feasible.More>
2008, 8(3): 77-81.
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Computation model of network scale for urban rail transit based on traffic demand overflow
An Xue-wu, Du Dian-hu, Ma Chao-qun, Zhou Wei
Abstract: In order to compute the network scale of urban rail transit based on the development degree of roads, the computation methods were analyzed at present, and a new computation model based on traffic demand overflow was built. With the precondition that road network could afford taffic service at certain service level in the future, the overflow of total traffic demand contrasted with road network capacity was computed, the overflow was transformed to passenger transport demand and was transported by rail transit, the rational scale of rail transit network could be confirmed by using its load intensity, the network scale of Xi'an rail transit in 2020 was computed by using different methods, and the computation results were compared. The result from travel demand model is 103.68 km, the result from financial strength analysis is 66.32~94.74 km, the result from the new model is 95.89 km, the results are basically accordant, so the new model is feasible.More>
2008, 8(3): 82-85.
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Combined layout mode of metropolitan highway-railway transport hubs based on integration of traffic resources
Zhu Yan-dong, Dan Jin, Li Xu-hong
Abstract: In order to optimize the layout of highway-railway transport hubs and the allocation of distribution traffic resources, the layout relationships of highway-railway hubs at different levels were analyzed, a distribution evaluation model of hub passenger flow was built, and a combined layout mode of highway-railway hubs was presented. Analysis result indicates that the independent layout mode of suburban railway hub is appropriate to the downtown area of megacity, "suburban railway + general highway hub" mode, "general railway + metropolitan-area highway hub" mode and "general railway+general highway hub" mode are appropriate to middle-circle layer area, "suburban railway + general highway hub" mode, "suburban railway + rapid highway hub" mode, "high-speed railway+general highway hub" mode, and "high-speed railway + rapid highway hub" mode are appropriate to outer-circle layer area; for the different distribution modes of combined highway-railway hubs, competition-dominated mode or complete competition mode is appropriate to "different station-different yard" layout or "different station-same yard" layout, and cooperation-dominated mode or complete cooperation mode is appropriate to "same station-same yard" layout or "different station-same yard" layout. The layout modes can reduce traffic burden, satisfy traffic demand and show great applicability in typical megacities.More>
2008, 8(3): 86-90.
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Transportation analysis of Chinese expressway network in 2006
Chen Yin-san, Xiao Run-mou, Ma Jian, Qin Hua-rong
Abstract: To understand passenger and freight transport in Chinese expressway network, the database of toll-by-weight system was introduced, a method of complete investigation and sampling survey was applied, the transport statistics of expressway network was carried out, and the transport actuality was analyzed. Analysis result shows that truck traffic volume accounts for 36.09% of total traffic volume, 57.23% of freight turnover volume is completed by tractor-trailer combinations; the percentage of empty to loaded truck kilometers is about 20.13%, it is higher of short distance intra-province transportation than long distance inter-province transportation; 30.12% of passenger turnover volume is completed by passenger cars and minitype buses, the seat amount of every bus is less than 13, average passengers carried by per car are 2.55, but major passenger turnover volume is completed by buses; 43.80% of passengers and 53.92% of cargoes are from counties and rural areas. Obviously, Chinese expressway network is the artery in multimodal transportation system, and it improves the equitable improvement of society.More>
2008, 8(3): 91-96.
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Identifying method of geometry parameters for oversize vehicle
Zhang Wen-hui, Guan Qiang, Deng Hong-xing, Li Sheng-qin
Abstract: In order to improve the precision of inspecting oversize transportation, identifying method of geometry parameters for oversize vehicle was proposed. Vehicle was scanned by using two laser measurement sensors respectively to acquire the half outlines of vehicle and the coordinates of all inspecting points, the height and width of vehicle were computed according to the minimum abscissa of left outline, the maximal abscissa of right outline and the minimum ordinate of two outlines, the whole outline of vehicle was gained by using outline synthetic method, vehicle length was identified according to the datum marks consisted of light curtain and light-electricity switch and was compared with the standard of oversize transportation. Computation result shows that inspecting error is within ±3%, vehicle license is stored in time, so the precision of the method is higher, and inspecting result is intuitionistic.More>
2008, 8(3): 97-100.
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Cross-platform application technologies in ITS
Jin Ling, Chen Qi-mei, Wang Wei
Abstract: To adapt the development of diversified business in integrative transportation network and realize the compatibility, standardization and adaptability of traffic information transmission, Web, CORBA and QT cross-platform technologies in heterogeneous information system and H.264 video trans-coding principle were studied, the basic transmission requirements on data and images of ITS were analyzed, a traffic information surveillance technology was proposed, and the Web browser interface of scalable SVG map based on B/S mode and the ViewBox window based on C/S mode and H.264 video trans-coding technology were taken as its base. Application result shows that the new technologies can satisfy the requirements of wide area and real time of ITS, and can improve the cross-platform transmission quality of ITS images and system robustness.More>
2008, 8(3): 101-107.
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Research status and prospect of emergency transportation evacuation
Liu Xiao-ming, Hu Hong
Abstract: In order to actualize a well-ordered transportation organization and improve the efficiency of emergency evacuation, the characters of some natural disasters, such as hurricane, flood ect, which could be early warned, observed and treated were analyzed, the mechanisms of emergency evacuation, the methods of traffic organization and the technical application of traffic simulation at home and abroad were studied, and with regard to prepare the emergency evacuation contingency plan for 2008 Olympic Games in Beijing, the research orientation and systematic planning method of emergency evacuation which were fit for Chinese situation and traffic environment were proposed.Analysis result indicates that bus transit should be used as the main transportation evacuation mode in China, transportation evacuation efficiency and organization levels can be improved by perfecting the planning system of emergency evacuation, integrating the key traffic technologies such as route selection, traffic control and evacuation time calculation, and a decision and evaluation system of emergency transportation evacuation is established by applying traffic simulation and ITS technologies.More>
2008, 8(3): 108-115.
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Multilevel-fuzzy comprehensive evaluation method of airline's competitiveness
Yu Jian, Li Yan-wei
Abstract: In order to evaluate airline's competitiveness exactly, a multilevel-fuzzy comprehensive evaluation method was proposed, the denotation of airline's competitiveness and its effect factors were analyzed, and a competitiveness evaluation index system of network airline was built, in which the weights of evaluation indices were determined by analytic hierarchy process(AHP). The membership grades of qualitative indices were determined with statistical method of fuzziness, positive index, neutral index and negative index were applied to define the membership grades of quantitative indices. Analysis result indicates that the system is reasonable, the method can resolve the fuzzinesses of evaluation indices and rating levels appropriately, the evaluation result can reflect the general level of airline's competitiveness objectively, and the airline can cultivate its competitiveness exactly according to the result.More>
2008, 8(3): 116-121.
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Profit model and algorithm of distribution system for vendor managed inventory
Liu Cheng, Yang Yong-sheng
Abstract: In order to increase the profit of distribution system, the distribution network was studied whose topology structure was one distributor or supplier and many retailers, the system optimization was analyzed when the product demand had stochastic price elasticity, retailer inventory control policy of cycle check and vendor managed inventory (VMI)mode were adopted, the profit optimization model and solving algorithm of distribution system were established. Calculation result shows that the ratio between supplying goods price and normal wholesale price doesn't affect the model optimal solution, total sales and suppliers' profits decrease with the increase of goods retail prices, but the retailers' profits increase. So the ratio between supplying goods price and normal wholesale price can be determined through the negotiation when total system profit is maximal, and suppliers' enthusiasm can be aroused when a certain proportion profit is transferred from retailers to suppliers.More>
2008, 8(3): 122-126.
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