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排序方式: 共有75条查询结果,搜索用时 31 毫秒
1.
Brian J. Thomas 《Maritime Policy and Management》1995,22(3):239-253
Overmanning and restrictive labour practices are major causes of low productivity in Indian ports. Proposals are put forward for a programme of reforms to support investment in modern cargo handling systems. 相似文献
2.
This paper explains the theory in support of total cost analysis (TCA) to compare transportation system alternatives. The full costs of each alternative are first aggregated, including travel time costs and monetizable environmental and social costs. Many costs which are considered on the benefits side of the equation in benefit-cost analysis (BCA) as "cost savings" are brought over to the costs side. Total cost differences among alternatives are then traded off against their estimated non-monetized benefits or impacts, just as a consumer trades off product quality against cost before deciding which product he or she will buy. One advantage of TCA over traditional BCA is that the concept of "total cost" is more easily understood by the public and by political decision-makers than BCA concepts such as "net present worth", "benefit-cost ratio" and "internal rate of return". A second advantage is that there is no suggestion that all "benefits" have been considered; decision-makers are free to use their own value judgements to trade off total cost against non-monetizable social, environmental and economic impacts, just as they trade off quality and convenience against cost when purchasing goods and services in their roles as consumers. The TCA approach is demonstrated in this paper through a case study of two systemwide alternatives for the Baltimore, MD urban area. 相似文献
3.
Brian J. Thomas 《Maritime Policy and Management》2013,40(3):239-240
Overmanning and restrictive labour practices are major causes of low productivity in Indian ports. Proposals are put forward for a programme of reforms to support investment in modern cargo handling systems. 相似文献
4.
Fearghal Ryan Brian Caulfield 《Transportation Research Part D: Transport and Environment》2010,15(6):362-365
Public service fleets offer an attractive option for introducing new renewable fuels on a large scale, which allow for the reduction of both greenhouse gas emissions and exhaust air pollutants. This study examines the use of biomethane (bio-CNG) and compressed natural gas for part of the bus fleet in Dublin, Ireland. The emissions produced from the 2008 fleet based at one of the city’s seven bus depots are compared to use of new diesel and bio-CNG buses. The optimum feedstock for bio-CNG production in Ireland was then investigated, as well as the quantity of feedstock needed to produce the required bio-CNG to fuel the bus fleet examined. As expected the results showed a substantial decrease in all exhaust emissions from the use of bio-CNG buses compared the 2008 fleet. Grass silage was chosen as the optimum feedstock for production of bio-CNG in Ireland. 相似文献
5.
Rajiv Ganguly Brian M. Broderick 《Transportation Research Part D: Transport and Environment》2010,15(8):513-521
Atmospheric dispersion models based on the Gaussian line source formulation tend to give poor results for low wind speed and parallel wind directions. Certain dispersion models like HIWAY-2 have an inbuilt dispersion algorithm to adjust in such situations but no correction exists for mathematical based Gaussian dispersion models. We evaluate the performance of a hybrid model a mathematical model, to assess its suitability as an alternative to the Gaussian based models. 相似文献
6.
Atiela Incecik John Bowers Gill Mould Oguz Yilmaz 《Journal of Marine Science and Technology》1998,3(3):145-150
Floating moored offshore structures have a significant future in offshore operations as an attractive economic alternative
to fixed structures in deep waters and/or in areas where there is no existing infrastructure. This paper describes an analysis
procedure based on the structure variable approach to estimate load and response values of a moored offshore platform at a
given return period by taking into account the joint occurrence of wave, wind, and current. The results show that the most
severe mooring loads may not occur when wind, wave, and current are collinear and are at their maximum design values, i.e.,
the 50- or 100-year case. It is recommended that the extreme mooring design loads for moored offshore systems should be determined
through a range of physical or numerical simulations where wave, wind, and current are noncollinear and act with less severe
magnitudes than the 50- or 100-year case. This recommendation has also been adopted in the ITTC/Ocean Engineering Committee
recommendations to the ITTC Conference held in September 1996. 相似文献
7.
Rajiv Ganguly Brian M. Broderick 《Transportation Research Part D: Transport and Environment》2009,14(4):231-239
Different methods for predicting levels of roadside NO2 from NOx concentrations have been proposed. Prior work suggests that either a linear or a logarithmic relationship exists among the roadside NO2 and NOx concentrations. We modify and compare those methods with new formulations based on the principles of the original methods for datasets pertaining to Dublin. A new relationship based on the power law is developed to better model the decay of the ratio of (NO2/NOx)road ratio with increasing NOx concentration. These formulations are compared and examined at two study sites: at an intermittently congested urban street canyon and a free-flowing motorway. 相似文献
8.
通过对交通拥堵进行反思,认为交通拥堵是充满活力的成功城市的伴生品,应从不同角度考虑拥堵问题.提出了十项有别于传统观点的提议,主要包括:机动性至关重要,交通拥堵是社会、经济活力的象征;道路扩容效果短暂,并会诱发潜在需求,但仍可带来一定的社会、经济效益;土地使用对出行行为的改变需要长期的努力;紧凑型发展会加剧交通拥堵;降低... 相似文献
9.
Circuit net list bipartitioning using simulated annealing technique has been proposed in the paper. The method converges asymptotically
and probabilistically to global optimization. The circuit net list is partitioned into two partitions such that the number
of interconnections between the partitions is minimized. The proposed method begins with an innovative clustering technique
to obtain a good initial solution. Results obtained show the versatility of the proposed method in solving non polynomial
hard problems of circuit net list partitioning and show an improvement over those available in literature. 相似文献
10.
Brian Gaylord Daniel C. Reed Libe Washburn Peter T. Raimondi 《Journal of Marine Systems》2004,49(1-4):19
The physical–biological linkages controlling the dispersal of spores produced by macroalgae that reside in kelp forests are complicated and laced with feedbacks. Here we discuss the fundamental elements of these interactions. Biological considerations include spore swimming and sinking speeds, their periods of viability in the plankton, and the height of spore release above the seafloor, which together determine the durations over which spores can be swept by horizontal currents before they contact the seafloor. Morphologies and material properties of canopy forming kelps may also influence the drag exerted on passing waters by the kelps, the plants' ability to persist in the face of rapid flows, and thereby the degree to which impinging currents are redirected around, or slowed within, kelp forests. Macroalgal life histories, and the size of spore sources as controlled by the dimensions of kelp forests and the density and fecundity of individuals within them, influence effective dispersal distances as well. Physical considerations encompass the mean speed, direction, and timescales of variability of currents relative to spore suspension times, the interaction of surface gravity waves with currents in producing turbulence in the benthic boundary layer, wind-driven surface mixing, water stratification, and shoreline bathymetry and substratum roughness, all of which can affect the interplay of vertical and horizontal transport of macroalgal spores. Intricate within-forest processes may induce attenuation of current speeds and consequent reductions in seabed shear, along with simultaneous production of small-scale turbulence in kelp wakes. Slower mean currents and smaller eddy scales in turn may attenuate vertical mixing within forests, thus extending spore suspension times. Further complexities likely arise due to changes in the relative rates of horizontal and vertical dispersion, modifications to the overall profiles of vertical mixing, and the creation of fine-scale secondary flows around kelp individuals and substratum features. Under conditions of more rapid currents, submergence of the surface canopy and the establishment of skimming flows at the canopy–fluid interface may introduce additional coherent flow structures that alter rates of fluid exchange to and from the forest. Many of these coupled physical–biological processes are just beginning to be examined in a rigorous fashion in kelp forests, but their potential importance is clear. 相似文献