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991.
992.
Urbanization and demands for mobility have spurred the development of mass rapid transit infrastructure in industrializing
Asia. Differences between the character of pre-existing urban structure in these localities and worldwide precedents suggest
a need for studies examining how new rapid transit systems function locally. This study of Bangkok’s elevated and underground
rail systems identifies relationships between the built environment and pedestrian behavior surrounding stations. Based on
details of 1,520 pedestrian egress trips from three elevated and three underground stations in 2006, multiple regression and
analysis of variance (ANOVA) revealed that types of pedestrian destinations, reflecting land uses, were related to length
of walking egress trips. Trips to shopping centers and office buildings were longer, while trips to eating places were shorter.
The most common type of pedestrian trip recorded was to another vehicle, and trips to automobile taxis and motorcycle taxis
figured prominently. Policy implications of the findings are considered. 相似文献
993.
The collapse of the ventilated cavitation occurring on a cylindrical vehicle during the water-exit is numerically researched. The numerical model employs the finite volume method to solve the multiphase Reynoldsaveraged Navier-Stokes (RNNS) equations and uses the volume of fluid (VOF) method to capture the free surface. A practical water wave environment that the vehicle usually encounters is reproduced in a numerical wave flume, so that the water wave’s effect on the cavity collapse flow regime is investigated. The main feature of the waterexit collapse of a ventilated cavity is studied under the wave-free condition. The result indicates that a collapsing ventilated cavity experiences two stages, in which the pattern of cavity evolution is different. In the early stage, the cavity undergoes a rapid shrinkage as a closed body. In the late stage, the cavity releases gas from the front due to the increase of the cavity pressure. The water wave effect is investigated at three typical wave phases: the wave crest, the wave trough and the wave node. Results show that when the vehicle is launched under the wave node, the cavity collapse regime remains fairly axisymmetric and is similar to the wave-free case. However, when the vehicle is launched under the wave crest and trough, the cavity evolution presents highly three-dimensional (3D) features. The results of predicted cavity size, pressure distributions and hydrodynamic forces at different wave phases show that the wave effect is relatively weak at the wave node but becomes apparent at the wave crest and trough. 相似文献
994.
This paper presents theoretical analysis of unconventional forging process of hollowed shaft from Ti-6Al-4V alloy in a three-slide
forging press. This method in comparison with other metal forming methods allows for obtaining of hollowed products. The designed
process is verified theoretically by means of numerical simulations based on finite element method with assumption of 3D state
of strain. The following factors are considered in the analysis: material flow kinematics, strain distribution, temperature
distribution and force of process. On the basis of results, it is stated that the application of designed technology allows
for obtaining of a product of assumed quality. A comparison is made between material consumption in analyzed process and material
consumption in typical metal forming methods, also in used at present technology of shaft manufacturing by machining only.
It is stated that the application of forging in the three-slide forging press allows for a considerable decrease of manufacturing
costs due to material savings and decrease of labor consumption of operations at finishing. 相似文献
995.
A 2D finite element model was established for inertia friction welding of GH4169 nickel-base superalloy based on the ABAQUS
environment. The remeshing and map solution techniques were adopted to solve the problem of element distortion. The effect
of rotation speed on the temperature field and axial shortening of joints was investigated. The results show that the interface
temperature increases rapidly to higher than 900°C within 1 s. And then, it increases slowly to a quasi-stable value. The
axial shortening begins to augment quickly when a uniform interface temperature field has formed and the plasticized material
is extruded from the interface to form an obvious flash. The rotation speed of the flywheel controls the welding process and
has a significant influence on the temperature evolution and axial shortening of joints. 相似文献
996.
Bayes risk (BR) decoding methods have been widely investigated in the speech recognition area due to its flexibility and complexity
compared with the maximum a posteriori (MAP) method regarding to minimum word error (MWE) optimization. This paper investigates
two improved approaches to the BR decoding, aiming at minimizing word error. The novelty of the proposed methods is shown
in the explicit optimization of the objective function, the value of which is calculated by an improved forward algorithm
on the lattice. However, the result of the first method is obtained by an expectation maximization (EM) like iteration, while
the result of the second one is achieved by traversing the confusion network (CN), both of which lead to an optimized objective
function value with distinct approaches. Experimental results indicate that the proposed methods result in an error reduction
for lattice rescoring, compared with the traditional CN method for lattice rescoring. 相似文献
997.
The presence of wrinkles in the membrane is the main factor to induce the reflector surface inaccuracy of the space inflatable
antenna. Based on the commercial finite element package ABAQUS, a numerical procedure for membrane wrinkle analysis was set
up and used to analyze a space inflatable antenna which was under inner pressure to evaluate its wrinkle characteristics.
First, the inner pressure effect on the reflector’s wrinkle pattern was studied thoroughly. As inner pressure increases, both
the number and the amplitude of the wrinkles decrease, but the total deformation of the whole reflector surface increases
much. Second, the influence of the interactions between antenna’s parts was investigated comprehensively. Any kind of unwanted
interaction deteriorates reflector’s wrinkle characteristics. The works are valuable to the development and research of the
space inflatable antenna. 相似文献
998.
Paul S. Szwed 《WMU Journal of Maritime Affairs》2011,10(2):183-208
Given the inherent complexity of the maritime transportation system, developing effective policy can be challenging. Using
risk factors identified by an elicitation and aggregation of expert judgment, a relative-risk rating scheme was developed
in the theory-building tradition of the social sciences. The model was empirically evaluated using 18 months of data from
the US small passenger vessel sector. The model identified that the top 10% of relatively highest risk vessels accounted for
50% of all marine casualties during the period of examination. A policy for deploying the model nationally is proposed. 相似文献
999.
A generalized collaborative optimization (CO) framework is proposed to the optimization design of the lines of an underwater vehicle. The resistance and maneuvering performances are concerned about and taken as the optimization objectives in the optimization framework. The resistance, lateral force and yaw moment are calculated by RANS method. To improve the optimization efficiency, an automatic integration optimization platform is constructed in which a surrogate model is adopted. A SUBOFF model is taken as the verification model. The optimal results demonstrate the validity of the optimization strategy proposed. 相似文献
1000.
It is widely recognized that individual decision-making is subject to the evaluation of gains and losses around a reference
point. The estimation of discrete choice models increasingly use data from stated choice experiments which are pivoted around
a reference alternative. However, to date, the specification of a reference alternative in transport studies has been fixed,
whereas it is common to observe individuals adjusting their preferences according to a change in their reference point. This
paper focuses on individual reactions, in a freight choice context, to a negative change in the reference alternative values,
identifying the behavioural implications in terms of loss aversion and diminishing sensitivity. The results show a significant
adjustment in the valuation of gains and losses around a shifted reference alternative. In particular, we find an average
increase in loss aversion for cost and time attributes, and a substantial decrease for punctuality. These findings are translated
to significant differences in the willingness to pay and willingness to accept measures, providing supporting evidence of
respondents’ behavioural reaction. 相似文献