In order to evaluate recycle economy of end-of-life vehicles quantitatively,an economy model based on a recycle model of end-of-life vehicles and recycle cost analysis. With a practical example of recycling engines of...In order to evaluate recycle economy of end-of-life vehicles quantitatively,an economy model based on a recycle model of end-of-life vehicles and recycle cost analysis. With a practical example of recycling engines of end-of-life vehicles ,the validity of the recycle economy model and good recycle economy of the end-of-life vehicle engine were justified. It is concluded that ① remanufacture-ability of the part or component of the vehicles; ② the organization and management level of a recycle corporation; ③ policies and regulations of the government are crucial factors to raise the recycle economy of the end-of-life vehicle.展开更多
In traditional urban geography, city contact research is a classic study element in city research. In general, researchers use the traditional gravity model to characterize the contacts that exist between two cities. ...In traditional urban geography, city contact research is a classic study element in city research. In general, researchers use the traditional gravity model to characterize the contacts that exist between two cities. The traditional gravity model assumes ideal conditions, but these preconditions and their results often do not exist in realistic conditions. Thus, we used a modified gravity model to characterize the city contacts within a specific region. This model considers factors such as intercity complementarities, government intervention, and the diversity of the transportation infrastructure which is characterized as the transportation distance instead of the traditional Euclidean distance. We applied this model to an empirical study of city contact in the Zhujiang(Pearl) River Delta(PRD) of China. The regression results indicated that the modified gravity model could measure city contact more accurately and comprehensively than the traditional gravity model, i.e., it yielded a higher adjusted R2 value(0.379) than the traditional gravity model result(0.259). Our study also suggests that, in addition to urban-regional and metropolitan development, the complementarities of the basic functions of cities at the administrative and market levels, as well as the corporeal and immaterial levels, play very significant roles in the characterization of city contact. Given the complexity of city contact, it will be necessary to consider more relevant influential factors in the modified gravity model to characterize the features of city contact in the future.展开更多
Network calculus provides new tools for performance analysis of networks, but analyzing networks with complex topologies is a challenging research issue using statistical network calculus. A service model is proposed ...Network calculus provides new tools for performance analysis of networks, but analyzing networks with complex topologies is a challenging research issue using statistical network calculus. A service model is proposed to characterize a service process of network with complex topologies. To obtain closed-form expression of statistical end-to-end performance bounds for a wide range of traffic source models, the traffic model and service model are expanded according to error function. Based on the proposed models, the explicit end-to-end delay bound of Fractional Brownian Motion（FBM） traffic is derived, the factors that affect the delay bound are analyzed, and a comparison between theoretical and simulation results is performed. The results illustrate that the proposed models not only fit the network behaviors well, but also facilitate the network performance analysis.展开更多
Effects of the speed relaxation time on the optimal velocity car-following model (OVM) with delay time due to driver reaction time proposed by Bando et al.(1995) were studied by numerical methods. Results showed that ...Effects of the speed relaxation time on the optimal velocity car-following model (OVM) with delay time due to driver reaction time proposed by Bando et al.(1995) were studied by numerical methods. Results showed that the OVM including the delay is not physically sensitive to the speed relaxation times. A modified car-following model is proposed to overcome the deficiency. Analyses of the linear stability of the modified model were conducted. It is shown that coexisting flows appear if the initial homogeneous headway of the traffic flow is between critical values. In addition, phase transitions occur on varying the initially homogeneous headway.展开更多
This paper summarizes the approach, findings and evaluation methodology for a study that investigated the feasibility and potential impacts of street conversion options on traffic operations in downtown Birmingham, A...This paper summarizes the approach, findings and evaluation methodology for a study that investigated the feasibility and potential impacts of street conversion options on traffic operations in downtown Birmingham, Alabama. Of particular interest were issues related to conversion of grid systems from one-way to two-way operations. Recommendations on the most promising design and control configurations for implementation are also provided. A literature review was performed that threw light on the issues and challenges associated with implementation of street conversions, and the available best practices. A comprehensive traffic impact analysis that ensued employed the SYNCHRO computer simulation model to represent current and future operations so as to assess the implications of two-way conversions at and around the test sites. Detailed realistic two-way operations scenarios were developed that considered geometric and right-of-way restrictions, the location of land uses that generate and/or attract vehicular and pedestrian traffic, connectivity with the street grid, and accessibility to nearby freeway facilities, as well as practical concerns.展开更多
基金National Natural Science Foundation ofChina(No.50235030)
文摘In order to evaluate recycle economy of end-of-life vehicles quantitatively,an economy model based on a recycle model of end-of-life vehicles and recycle cost analysis. With a practical example of recycling engines of end-of-life vehicles ,the validity of the recycle economy model and good recycle economy of the end-of-life vehicle engine were justified. It is concluded that ① remanufacture-ability of the part or component of the vehicles; ② the organization and management level of a recycle corporation; ③ policies and regulations of the government are crucial factors to raise the recycle economy of the end-of-life vehicle.
基金Under the auspices of National Natural Science Foundation of China(No.41271177)Guangdong Natural Science Foundation(No.S2012010008902)
文摘In traditional urban geography, city contact research is a classic study element in city research. In general, researchers use the traditional gravity model to characterize the contacts that exist between two cities. The traditional gravity model assumes ideal conditions, but these preconditions and their results often do not exist in realistic conditions. Thus, we used a modified gravity model to characterize the city contacts within a specific region. This model considers factors such as intercity complementarities, government intervention, and the diversity of the transportation infrastructure which is characterized as the transportation distance instead of the traditional Euclidean distance. We applied this model to an empirical study of city contact in the Zhujiang(Pearl) River Delta(PRD) of China. The regression results indicated that the modified gravity model could measure city contact more accurately and comprehensively than the traditional gravity model, i.e., it yielded a higher adjusted R2 value(0.379) than the traditional gravity model result(0.259). Our study also suggests that, in addition to urban-regional and metropolitan development, the complementarities of the basic functions of cities at the administrative and market levels, as well as the corporeal and immaterial levels, play very significant roles in the characterization of city contact. Given the complexity of city contact, it will be necessary to consider more relevant influential factors in the modified gravity model to characterize the features of city contact in the future.
基金Supported by the National Natural Science Foundation Major Research Plan of China （No. 90718003）, the National Natural Science Foundation of China （No. 60973027）, and the National High Technology Research and Development Program of China （No. 2007AA01Z401 ）.
文摘Network calculus provides new tools for performance analysis of networks, but analyzing networks with complex topologies is a challenging research issue using statistical network calculus. A service model is proposed to characterize a service process of network with complex topologies. To obtain closed-form expression of statistical end-to-end performance bounds for a wide range of traffic source models, the traffic model and service model are expanded according to error function. Based on the proposed models, the explicit end-to-end delay bound of Fractional Brownian Motion（FBM） traffic is derived, the factors that affect the delay bound are analyzed, and a comparison between theoretical and simulation results is performed. The results illustrate that the proposed models not only fit the network behaviors well, but also facilitate the network performance analysis.
基金Project (No. G1998030408) supported by the National Basic Re-search Program (973) of China
文摘Effects of the speed relaxation time on the optimal velocity car-following model (OVM) with delay time due to driver reaction time proposed by Bando et al.(1995) were studied by numerical methods. Results showed that the OVM including the delay is not physically sensitive to the speed relaxation times. A modified car-following model is proposed to overcome the deficiency. Analyses of the linear stability of the modified model were conducted. It is shown that coexisting flows appear if the initial homogeneous headway of the traffic flow is between critical values. In addition, phase transitions occur on varying the initially homogeneous headway.
文摘This paper summarizes the approach, findings and evaluation methodology for a study that investigated the feasibility and potential impacts of street conversion options on traffic operations in downtown Birmingham, Alabama. Of particular interest were issues related to conversion of grid systems from one-way to two-way operations. Recommendations on the most promising design and control configurations for implementation are also provided. A literature review was performed that threw light on the issues and challenges associated with implementation of street conversions, and the available best practices. A comprehensive traffic impact analysis that ensued employed the SYNCHRO computer simulation model to represent current and future operations so as to assess the implications of two-way conversions at and around the test sites. Detailed realistic two-way operations scenarios were developed that considered geometric and right-of-way restrictions, the location of land uses that generate and/or attract vehicular and pedestrian traffic, connectivity with the street grid, and accessibility to nearby freeway facilities, as well as practical concerns.
