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941.
Most airlines across Asia are struggling to cope with an unprecedented economic crisis which they have very little control over, and the survival of some remains in doubt. The continuing uncertainty generated by the crisis has accelerated the process of change in the aviation industry and has highlighted the need for adaptability, and its effects have been deeper and longer lasting than previously anticipated. After a year-long slump in the Asian travel market, airlines are now considering a range of options and rehabilitation programmes including a series of cost-cutting measures. There appears to be a trend towards the extension and consolidation of strategic alliances, structural and operational reorganization, and the application of new technologies. The success of these measures will become apparent over time, but action is necessary to minimize the adverse consequences of the crisis which has dominated the region since 1997. 相似文献
942.
In this work a methodology is presented for the computation of the intersection of parametric surfaces, namely Non Uniform
Rational B-Splines (NURBS), with special attention to some specific requirements for applications to ship hull modeling. The
algorithm adopted and the steps of the proposed method are described, namely checking whether the surfaces intersect, preprocessing
of linear surfaces with strong discontinuities, computation of starting points, marching along intersection curves, and approximation
of the intersections with NURBS curves. Finally, the results of some intersection tests are presented and discussed. The results
are validated by comparison with results of commercial codes. 相似文献
943.
C. Adrián Saldarriaga-Isaza Carlos Vergara 《Transportation Research Part A: Policy and Practice》2009,43(5):572-579
Air pollution from mobile sources is an important environmental problem in larger cities. In 2001, a program was implemented to encourage the use of natural gas in vehicles in the Aburrá Valley in Colombia, with incentives to convert small cars from gasoline and diesel to hybrid engines with natural gas, most notably a cash subsidy. Using a survey administered to both commercial and private car owners we study the determinants of conversion under this fuel conversion program. We thus obtain information about the reasons for adoption of new technologies in vehicles. This allows us to discuss the possible outcomes of this type of policy. Results show that a large part of owners who switched would have done it anyway without the subsidy. Based on the findings, commercial vehicles are most likely to be converted to natural gas vehicles. 相似文献
944.
Sheldon H. Jacobson Douglas M. King Kevin C. Ryan Matthew J. Robbins 《Transportation Research Part A: Policy and Practice》2012,46(10):1586-1593
An increasing number of legislative efforts have been undertaken to prohibit the use of hand-held wireless devices while driving. As of July 2012, ten states and the District of Columbia enforce laws banning the use of hand-held cell phones while driving. Thirty-nine states and the District of Columbia have banned text messaging while driving. Recent studies of driver behavior suggest that hand-held wireless device usage negatively impacts driver performance. However few studies at the aggregate level address the plausible link between the use of hand-held wireless devices while driving, increased risk of automobile accidents, and government legislative efforts to reduce such risk. This paper analyzes data at the aggregate level and builds a regression model to estimate the long term accident rate reduction due to a hand-held ban. This model differs from previous studies, which consider short term accident rate reduction, by considering time trends in the accident rate due to the ban. Additionally, counties considered in this analysis are placed into groups based on driver density, defined by the number of licensed drivers per centerline mile of roadway, and a separate analysis is performed within these groups. This approach allows one to better quantify the effect of hand-held bans in counties of different driver densities. Results from this paper suggest that bans on hand-held wireless device use while driving reduce the rate of personal injury accidents in counties with high levels of driver density, but may increase accident rates in counties with low driver density levels. These results can inform transportation policymakers interested in reducing automobile-accident-risk attributable to the use of hand-held wireless devices while driving. 相似文献
945.
W. Perret R. Thater U. Alber C. Schwenk M. Rethmeier 《International Journal of Automotive Technology》2011,12(6):895-901
Fusion welding processes are widely used for joining metal structures, such as pipes, ships, and cars. In general, these joining
processes offer a very good compromise between reliability, safety, cost and maintenance which are important issues in the
current economical context. The negative heat effects of welding, i.e. distortions and residual stresses of the welded parts,
are well known and many researches in this field have already been done in the last decades in order to minimize them. On
the experimental side, many sophisticated procedures have become state of the art to deal with this problem. On the computational
side, the improvement of the simulation algorithms and the computing power enables the simulations of many physical phenomena
occurring during the welding process. The implementation of welding simulation techniques is nevertheless not an easy task
and often associated with expert knowledge which hinders their global application in an industrial environment. This paper
is focused on the industrial requirements of a welding simulation software with special respect to the needs of the automotive
industry. The necessary information to run a welding simulation and the expectations of a weld specialist without deep knowledge
in numerical methods are investigated. These expectations are tested on an automotive welded assembly with a commercially
available welding simulation software designed especially for the needs of the automotive industry. A welding experiment is
done and the measured temperature distributions and distortions serve as reference to validate the simulation results. The
result quality of the simulations of temperature fields and distortions is in best agreement with experimental data. The workflow
is well adapted for the considered industrial requirements and the time-tosolution as well as the computational costs are
acceptable, whereas the efficient calibration of the heat input model is still a point which will be further investigated
in current and future research works. 相似文献
946.
William C. Brewer Jr. 《Coastal management》2013,41(4):315-325
Abstract The requirement in the Coastal Zone Management Act of 1972 that federal projects be consistent with approved state coastal zone management programs is an important incentive for states to complete their programs. As a condition of program approval, states must first consult with the federal agencies concerned and provide opportunities for comment, with the hope of avoiding conflicts. The consistency requirement is also subject to various exceptions whose scope remains to be determined. One such exception of uncertain extent is the exclusion from the coastal zone of federal lands “the use of which is subject solely to the sole discretion ... of the Federal Government....”; Despite these uncertainties, however, the consistency provision represents a major change in federal policy, which has traditionally allowed federal agencies to operate largely without concern for state land or water use requirements. 相似文献
947.
948.
Jagadish C. Guria 《运输评论》2013,33(1):49-66
Road freight transport in New Zealand has operated under government regulations since 1936, primarily to protect the freight revenue of the New Zealand Railways. In 1983 an Act was passed to deregulate the freight transport industry and to switch over to a qualitative licensing system. This is expected to have some impact on competition within the road freight industry as well as between road and rail. This paper analyses the institutional structure of the road freight industry at the pre‐deregulation phase. The trend over the last few years, shows that the number of single vehicle owners (mostly owner‐drivers) and their share in the industry is growing at a faster rate than others. The vehicle authority distribution varies widely from one region to another in the country. Economic factors like employment, population, urbanization etc. could not explain this variation. The segregation of demand by existing government regulations appears to be the main reason for such diversity in vehicle authority distribution. Apparently there is no monopoly trend in the aggregate nor in the regional distribution. However, many owner drivers work closely with large firms, which may change the concentration observed in the distribution of vehicle authorities. Productivity is relatively high for one person operations, i.e., mainly owner drivers. It then goes down and then rises to a certain limit. This gives an indication of the possibility of economies of scale, the single vehicle firms being an exception. 相似文献
949.
The scattering problem involving water waves by small undulation on the porous ocean-bed in a two-layer fluid,is investigated within the framework of the two-dimensional linear water wave theory where the upper layer is covered by a thin uniform sheet of ice modeled as a thin elastic plate.In such a two-layer fluid there exist waves with two different modes,one with a lower wave number propagate along the ice-cover whilst those with a higher wave number propagate along the interface.An incident wave of a particular wave number gets reflected and transmitted over the bottom undulation into waves of both modes.Perturbation analysis in conjunction with the Fourier transform technique is used to derive the first-order corrections of reflection and transmission coefficients for both the modes due to incident waves of two different modes.One special type of bottom topography is considered as an example to evaluate the related coefficients in detail.These coefficients are depicted in graphical forms to demonstrate the transformation of wave energy between the two modes and also to illustrate the effects of the ice sheet and the porosity of the undulating bed. 相似文献
950.
Optimal ship tracking on a navigation route between two ports: a hydrodynamics approach 总被引:1,自引:0,他引:1
J. K. Panigrahi C. P. Padhy D. Sen J. Swain O. Larsen 《Journal of Marine Science and Technology》2012,17(1):59-67
The optimal trajectory from Calcutta port to Mumbai port is charted for a tanker transshipping from the East coast to the
West coast of India during rough weather. Rough weather is simulated over Indian seas using the state-of-the-art WAM numerical
wave model (WAMDI Group in J Phys Oceanogr 18:1775–1810, 1988), assimilating satellite (IRS-P4) wind fields. These simulated wave fields and two-dimensional (2D) directional wave spectrum
are an absolute representation of the irregular seaway. Hence, the same for the monsoon month of August 2000 formed the input
basis for this study. Loss of ship speed due to the wave field (i.e., nonlinear motion of the tanker in waves) and associated
sea-keeping characteristics in the seaway are estimated (Bhattacharya in Dynamics of marine vehicles, Wiley, New York, 1978). The approach adopted in this paper is unique in that it takes into account both voluntary and involuntary speed reductions
of the ship. It helps in ship tracking by the optimum route using inverse velocity as the weight function for the path in
an efficient way. Dijkstra’s algorithm [Numer Math 1(3):269–271, 1959] is applied in an iterative manner for determining the optimum track. The optimum track information has broad scope for use
in modern shipping industry for obtaining safe and least-time routing by avoiding schedule delays with economic fuel consumption. 相似文献