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771.
Entering the 21st century, one of the most significant demographic changes in developed countries is the aging of the population. Travel is an important aspect of older people's economic well-being, so with the aging of the population, improving transport for older people is increasingly important. This article presents the results of a study of older people's travel behaviour based largely but not exclusively on LATS (London Area Travel Survey) 2001 data. The focus is on older people's trip chaining behaviour, including trip chain complexity, trip purpose sequence and mode choice in a chain. After identifying the policy implications it looks at the role of Special Transport Services in improving the supply of transport for older people, taking the London Borough of Camden as a case study. 相似文献
772.
公路工程单价合同中变更单价的确定方法 总被引:1,自引:0,他引:1
随着政府对基建项目尤其是国家重点工程的监督力度加大,工程变更问题已成为项目审计的核心问题之一,科学、合理、规范地确定变更工程的单价具有深远的意义,值得深入研究. 相似文献
773.
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775.
强夯法加固饱和粉土地基的效果 总被引:2,自引:0,他引:2
该文通过一工程实例,介绍通过合理确定施工参数,并采用严格的工艺控制,强夯法在饱和粉土地基处理中取得了良好的加固效果。 相似文献
776.
The methodology for modeling no-frost refrigerator is described based on the component models developed in Part I, and then,
system simulation is applied to a BCD-235W refrigerator-freezer (RF). Experiments are carried out to study “pull-down” and
steady-state performance of the RF, and to determine how the experiment and simulation temperature stack up against each other.
Good match is found between simulated and measured results for the “pull-down” period. For the steady-state period, the simulation
results are also found to agree well with experiment ones except for the temperature profiles of the refrigerator compartment
(RC) and freezer compartment (FC). The average temperature and the energy consumption errors between measurement and simulation
are less than 10%. Although the model can not reflect the non-uniform air temperature fields in the RC and FC, the variation
range and periodicities of the temperature correlate well between the simulation and experiment. We conclude that such a model
is valid for investigating the performance of no-frost refrigerator.
相似文献
777.
Dynamic simulation and performance investigation of no-frost refrigerator: Part I mathematical model
A dynamic approach for the modeling, simulation and analysis of no-frost Refrigerator (RF) is discussed. In Part I, the complex
interactions among the components in the cooling system are analyzed in detail, based on which the modeling simplifications
are proposed. Then, the mathematical models for the evaporator, cabinet and duct-fan are presented. The whole system is divided
into two subsystems—refrigerant cycling system and air cycling system. In order to simplify the model, two closed-loop systems
are broken into the compressor component and the evaporator component, respectively. A general distributed parameter model
is employed for evaporator with homogeneous flow to simplify the two-phase evaporating flow region. The z-transfer function model is used to describe the cabinet load. Computational fluid dynamics (CFD) method is employed to obtain
the pressure drop and flow rate curve of the duct-fan model.
相似文献
相似文献
778.
Fish are able to make good use of vortices. In a complex flow field, many fish continue to maintain both efficient cruising
and maneuverability. Traditional man-made propulsion systems perform poorly in complex flow fields. With fish-like propulsion
systems, it is important to pay more attention to complex flow fields. In this paper, the influence of vortices on the hydrodynamic
performance of 2-D flapping-foils was investigated. The flapping-foil heaved and pitched under the influence of inflow vortices
generated by an oscillating D-section cylinder. A numerical simulation was run based the finite volume method, using the computational
fluid dynamics (CFD) software FLUENT with Reynolds-averaged Navier-Stokes (RANS) equations applied. In addition, dynamic mesh
technology and post processing systems were also fully used. The calculations showed four modes of interaction. The hydrodynamic
performance of flapping-foils was analyzed and the results compared with experimental data. This validated the numerical simulation,
confirming that flapping-foils can increase efficiency by absorbing energy from inflow vortices. 相似文献
779.
780.