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991.
992.
Assessing the technical efficiency, service effectiveness, and technical effectiveness of the world’s railways through NDEA analysis 总被引:1,自引:0,他引:1
This paper presents an approach to include both the unstorable feature of transportation service and the technological differences within railway companies in efficiency and effectiveness measurements. We explore efficiency and effectiveness for a group of 40 global railways in the year 2002, using traditional data development analysis (TDEA) and network data development analysis (NDEA). Comparing the results obtained from the NDEA model with those from the TDEA indicate that performance measures are quite different in terms of the magnitude, and even using different DEA type models to evaluate railway system performance does not distort the ranking of their performance. We also analyze the inter-related effects among three performance measures, finding that transportation service characteristics have positive effects on the evaluation of performance. Generally speaking, the NDEA model provides deeper insight regarding the sources of inefficiency and process-specific guidance to railway managers so as to help them improve their railway’s performance. 相似文献
993.
Understanding of the activity-travel patterns of children is becoming increasingly important to various policy makers. Further,
there is also a growing recognition that intra-household interactions need to be explicitly accommodated in travel models
for realistic forecasts and policy evaluation. In the light of these issues, this paper contributes towards an overall understanding
of the school-travel behavior of children and the related interdependencies among the travel patterns of parents and children.
An econometric model is formulated to simultaneously determine the choice of mode and the escorting person for children’s
travel to and from school. The 2000 San Francisco Bay Area Travel Survey (BATS) data are used in the model estimation process.
Empirical results indicate that the characteristics of child like age, gender, and ethnicity, and employment and work flexibility
characteristics of the parents have strong impacts on the mode choice decisions. In addition, the impacts of some of these
attributes on the choice of mode to school are different from the corresponding impacts on the choice of mode from school. The distance between home and school is found to strongly and negatively impact the choice of walking to and from
school, with the impact being stronger for walking to school. Several land-use and built-environment variables were explored,
but were found not to be statistically significant predictors.
相似文献
Sivaramakrishnan Srinivasan (Corresponding author)Email: |
994.
Konstantinos G. Zografos Konstantinos N. Androutsopoulos Teemu Sihvola 《Transportation》2008,35(6):777-795
Flexible transport services include a wide range of demand responsive transport systems that provide non-conventional passenger
and freight transportation services. Several alternative business models varying according to the local market conditions,
the socio-economic, legal, and institutional framework may be developed for the provision of Flexible Transport Systems (FTS).
The objective of this paper is twofold: first to present an integrated methodological framework for developing and assessing
alternative FTS business models and second to demonstrate its applicability to a case study regarding the prioritization of
alternative FTS business models for the provision of flexible passenger transport services in Helsinki.
相似文献
Teemu SihvolaEmail: |
995.
The aim of this work is to test the application of a method for making a qualitative evaluation of pedestrian crossings, based on the methodology of Khisty (Transportation Research Record 1438:45–50, 1994). The study identifies the Performance Measures (Comfort, Safety, System Continuity), with their respective attributes (waiting time, space available while waiting to cross, number of pedestrians, one-way or two-way street, state of the road surface, road width, vehicle speed, visibility, lighting conditions, guardrails, absence of obstacles in vicinity, state of sidewalks, lowered kerb, pedestrian signals, central island), which may be utilized in the evaluation. The first step was to ascertain the relative importance, from the point of view of the pedestrian, of the Performance Measures employed. Then the level-of-service (LOS), as perceived by the users, was determined for each of the pedestrian crossings in the survey, on the basis of the users’ level of satisfaction with each attribute. Khisty’s methodology makes it possible to relate the overall level of satisfaction with a qualitative LOS for the pedestrian facility under analysis. The chosen methodology was adapted to the Brazilian context, in a case study carried out in the city of São Paulo (Brazil), in collaboration with the local Traffic Engineering Corporation (Companhia de Engenharia de Tráfego, CET-SP). To this end, four pedestrian crossings at road junctions with traffic lights were analysed. The qualitative LOS obtained were compared to the quantitative LOS, calculated according to the Highway Capacity Manual (TRB 2000). 相似文献
996.
997.
The wind pressure distribution and wind-induced vibration responses of long-span spatial groined latticed vaults (SGLVs) were numerically simulated, which always are ones of the most important problems in the structural wind resistance design. Incompressible visco-fluid model was introduced, and the standard k-εtwo equation model and semi-implicit method for pressure linked equation (SIMPLE) were used to describe the flow turbulence. Furthermore, the structural dynamic equation was set up, which is solved by Newmark-β method. And several sort of wind-induced vibration coefficients such as the wind-induced vibration coefficient corresponding to the nodal displacement responses and wind loads were suggested. In the numerical simulation where the SGLV consisting of the cylindrical sectors with different curved surface was chosen as the example,the influence on the relative wind pressure distribution and structural wind-induced vibration responses of the closed or open SGLV caused by such parameters as the number of cylindrical sectors, structural curvature and the ratio of rise to span was investigated. Finally, some useful conclusions on the local wind pressure distribution on the structural surface and the wind-induced vibration coefficients of SGLV were developed. 相似文献
998.
The smoothed particle hydrodynamics (SPH), as a fully Lagrangian particle method, has been successfully applied to astrophysical problems and extended to elastic dynamics and computational fluid dynamics.High order derivatives have to be approximated when elastic dynamics problems are modeled. However, the approximation errors in SPH could lead to computational failure in the case that the order of derivative is high.A novel method was proposed in order to improve the accuracy of SPH method, which shows the relationship between the selected functions and their SPH approximations. The entire involved system was represented by a finite number of particles that carry individual mass and occupy individual space, and the integral interpolation was approximated by a summation interpolation. In addition, error comparison was made between SPH method with and without the present improvement. 相似文献
999.
Sacrificial multi-piece molds can be used for producing complex parts. To obtain the optimal design of molds automatically, a multi-objective optimal approach is proposed. Mold pieces number, material utilization and partitioning area are taken as the objective functions, and the machinability of each mold piece is taken as constraint condition. Genetic algorithm (GA) is adopted to realize global optimization of partitioning process. Each mold piece in optimal scheme can be manufactured by milling and drilling operations, which reduce the tooling cost and shorten product cycle obviously. Using the proposed approach, mold design can be significantly automated for making complex parts. 相似文献
1000.
A multi-try counter-meshing gears (CMG) discrimination device based on micro electromechani-cal system (MEMS) technology was designed for some specified information fields. The discrimination deviceconsists of two groups of metal CMG, two pawl/ratchet mechanisms, two driving micromotors and two re-setting micromotors, which make the CMG withdraw by raising the pawls. The energy-coupling element isa photoelectric sensor with a circular plate which is notched. Micromotor is fabricated using the ultravioletLiGA (UV-LiGA) fabrication process and precision mechanical engineering. The discrimination device has thefunction which can automatically reset, with the correct resetting code, it can be tried another times. 相似文献