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581.
Philip J. Zwart Philippe G. Godin Justin Penrose Shin Hyung Rhee 《Journal of Marine Science and Technology》2008,13(4):346-355
An accurate, efficient algorithm for solving free surface flows around ship hulls is described. Accuracy is achieved using
a compressive advection discretization which maintains a sharp free surface interface representation without relying on a
small time step. Efficiency is obtained using a solution algorithm which implicitly couples velocity, pressure, and volume
fractions. The algorithm has been implemented in a computational fluid dynamics code called CFX and is validated by means
of a comparisonwith experimental data of benchmark cases in both steady and transient conditions. 相似文献
582.
C. Asensio J.M. López R. Pagán I. Pavón M. Ausejo 《Transportation Research Part D: Transport and Environment》2009,14(5):360-366
One of the most difficult and expensive tasks in making noise pollution maps is the collection and processing of the data needed to create acoustic models. In the case of road traffic noise maps, obtaining speed data for light and heavy vehicles a problem that has usually been avoided by using a road’s speed limit or by making assumptions based on experience from similar road types. Here global positioning systems-based techniques are applied for acquiring vehicle speed data and adapted to fulfill the requirements of noise prediction models. 相似文献
583.
Marlene Calderon Veiga 《WMU Journal of Maritime Affairs》2004,3(2):171-192
Background
The question of what should be the right level of preparedness to react to a major oil spill (i.e. the EXXON VALDEZ spill, the ERIKA spill, and the PRESTIGE spill) is highly debated, especially in the aftermath of such spills. Little research, however, has been conducted with the aim to identify and compare governments’ best practices not only to fund preparedness measures but also to assess the countries’ ability to respond effectively to catastrophic oil spills. It is the author’s belief that important lessons can be learnt from a comparative analysis of countries’ best practices. 相似文献584.
A 3D displacement discontinuity method is applied to solve the fracture mechanics problems of the mixed mode crack under compression.
Friction between the surface of the closed crack is considered by establishing a simple and efficient iterative algorithm
based on method of contact resistance mitigation. On the surfaces of the closed crack, the Mohr-coulomb rule is satisfied
by iteration when the crack is in condition of sliding. The stress intensity factors are obtained using displacement fitting
method. It is shown that the numerical results agree with the experimental results well and that friction plays an important
role in resisting crack propagation. 相似文献
585.
An experimental study was carried out to understand the phenomena of the boiling flow of liquid nitrogen in inclined tubes with closed bottom by using a high speed motion analyzer.The experimental tubes are 0.018 and 0.014 m inner diameter(ID) and 1.0 m in length.The range of the inclination angle is 45°-90° from the horizontal.The experimental observation on the liquid slug was carried out along the tubes.Statistical method was employed to analyze the experimental data.The experiment analyzed the influences of the inclination angle and the tube diameter on the liquid slug length and velocity.The results show the liquid slug propagation velocity increases with the decrease of inclination angle θ.For all cases,the maximum values of the mean liquid slug lengths were obtained at θ = 60°.The mean liquid slug lengths were greater for large tube at higher tube position.These conclusions provide a basis for further study liquid slug of cryogenic two-phase undeveloped slug flow. 相似文献
586.
Carlton Basmajian 《Transportation》2010,37(1):59-84
Though driving to and from work has become a prevalent experience in the lives of individuals in every metropolitan region
in the US, much remains to be learned about the activity from the perspective of the drivers. To increase our understanding
of the motivation for certain travel behaviors, we must first know something about what those drivers experience. The existing
literature explains much, but the application of new methodologies could improve our ability to explain the willingness of
individuals to choose to drive through increasingly congested road networks. The results of this study of oral histories of
12 women commuters underscore the idea that commute should be seen as a set of subjective behaviors that contradict some existing
assumptions about why individuals commute. 相似文献
587.
Since Tian Jun proposed the difference expansion embedding technique, based on which, many reversible watermarking techniques
were proposed. However, these methods do not perform well when the payload is high. In this paper, we proposed an expandable
difference threshold controlled scheme for these three methods. Experiments show that our scheme improves the performance
of these three methods for heavy payload. 相似文献
588.
Reliable research synthesis is of high significance for a transport policy which tries to base its decisions on available
empirical evidence. There is growing doubt whether the frequently used narrative approach provides a scientifically defensible
way of synthesising a body of quantitative research results. The present paper demonstrates meta-analysis as a more objective
and powerful alternative for this task. For this purpose evaluation data synthesised in two earlier narrative reviews on the
effectiveness of work travel plans [Cairns et al. Making travel plans work: research report (former), Department for Transport,
Local Government and the Regions (DTLR), London, 2002; Smarter choices—changing the way we travel. (Final report of the research project: The influence of soft factor interventions
on travel demand. Research report for the Department for Transport.) London. Retrieved 1 December 2005, from , 2004] are meta-analytically re-analysed and compared with the conclusions drawn from the narrative synthesis of these data. Our
meta-analyis provides only limited support for the conclusion that addressing parking is the hallmark of successful work travel
plans. Our meta-analysis indicates that site and organisational factors as well as characteristics of the monitoring process
are significant predictors of effective work travel plans, whereas Cairns et al. view little evidence for the impact of these
factors. 相似文献
589.
This paper addresses the issue of using before and after surveys to evaluate behavioural changes in response to transport
policies and investments, a procedure that, we argue is done far too rarely in this profession. Further, it demonstrates very
clearly that, in almost all conceivable cases, there are considerable economies to be obtained by using a panel (again, under-utilised
in our profession) to undertake evaluation, rather than successive independent cross-sectional surveys. The paper also addresses
the critical issue of sample size requirements for measuring changes of a relatively small magnitude in travel behaviour;
i.e., to state, with 95% confidence, that if there is a ∂ percent change in behaviour for the sample, there is a ∂ percent ± e
percent change in the behaviour of the population, where e is the sampling error. In this paper, we present a method for calculating such sample size requirements from first principles
and demonstrate the applicability both hypothetically and then empirically using data from the Puget Sound Transportation
Panel. The formulation enables designers of before and after surveys to investigate the trade-offs between the statistical
accuracy of their predictions and the sample size requirements systematically, without the need to specify ∂ a priori. This
latter point is crucial, we argue, because we have limited information on ∂, yet, as we explain here, it drives the sample
size requirements using alternative, well-cited approaches for calculating sample sizes to assess behavioural change. The
results have important ramifications both for those implementing transport policies intended to produce behavioural change,
especially when a cost-benefit evaluation of the policy is desired, and for those interpreting the results reported in previous
studies. 相似文献
590.
Martin F. Diez-Picazo 《WMU Journal of Maritime Affairs》2007,6(2):241-247
A cross-cutting Maritime Policy can ensure that climate change threats and challenges in regards to seas and oceans are dealt
with in a wide policy framework that takes into account the impacts that climate change may have on other sectors and vice
versa. 相似文献