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131.
Sara Y. Kenno Sreekanta Das John B. Kennedy Ronald B. Rogge Michael Gharghouri 《Marine Structures》2010,23(3):263-273
This paper provides an in-depth study of residual stress distributions found in stiffened steel plate structures, such as those typically used in ship hulls. The effect of stiffener spacing on the distribution of residual stress components was studied. The welding heat input was also varied between high and moderate to study the effect of heat input level on residual stress distributions. Four specimens, resembling typical stiffened steel plate structures used in ship hulls were built and tested. Steel plates of 9.5 mm thickness were stiffened by welding L127 × 76 × 9.5 steel angles. The test was completed using the neutron diffraction method. The three normal components of residual stress were obtained in this study. It was found that a lower heat input results in higher tensile residual stress and that there exists a critical stiffener spacing somewhere beyond 250 mm that creates a maximum tensile residual stress value near the welded connection. 相似文献
132.
Michael K. Adjemian C.-Y. Cynthia Lin Jeffrey Williams 《Transportation Research Part A: Policy and Practice》2010,44(9):661-675
In this article, we show that vehicle type ownership is spatially dependent at both the regional and household-level even after controlling for income and population density. We discuss reasons for the existence of spatial effects in vehicle ownership, and note potential implications for policymakers. Our results point to the importance of spatial relationships in transportation research and highlight the hazards of ignoring their role in affecting transportation outcomes. For example, if vehicle type choice is affected by neighborhood spillovers, agencies that regulate traffic flow and road safety could tailor their choice projections and policy tools to account for such interdependence. 相似文献
133.
Wojciech Walkusz Joclyn E. Paulic William J. Williams Slawomir Kwasniewski Michael H. Papst 《Journal of Marine Systems》2011,84(3-4):78-84
The distribution and diet of larval and juvenile Arctic cod (Boreogadus saida) were studied during summer 2005 in the coastal Canadian Beaufort Sea. A total of 275 individuals were captured and the highest abundance was observed at station depths of 20–30 m. This corresponds well with the location of the frontal zone where the Mackenzie River plume water and open sea water meet. Diet examinations were performed on 220 Arctic cod, which were found undamaged from sampling. We observed a gradual decrease in prey number per fish and increase in prey size as larvae grew which corresponded to a shift from Rotifera and nauplii towards larger copepodid stages. However, at all sizes, the larvae remain generalists and feed on a broad range of organisms. Environmental changes due to climate warming could have a two-fold impact on fish larvae feeding in the studied region. First, the potential for increased primary production may lead to increased zooplankton production that may impact the feeding and nutrition positively. On the other hand, greater discharge of turbid water from the Mackenzie River may reduce light penetration in the water column that may negatively influence the ability of visual predators to successively forage. 相似文献
134.
Michael C. Poulton 《运输规划与技术》2013,36(2):75-80
In recent years a great deal of time and effort has been expended on the development of new modes of transport for cities. It is argued in this paper that this work is unlikely to be very productive because the major remaining flaw in the provision of transportation services—the inability of one mode to provide a good service to concentrated and dispersed trip ends—seems unavoidable. To make the required breakthrough a new mode must be frugal in its demands for space, flexible in its operation and fast. But an analysis of the performance of existing and prototype modes suggest that there is a fundamental technological barrier that precludes any one mode from performing well in more than two out of these three ways. This implies that any further improvements in travel for the urbanite must be made through existing modes and their derivatives and will be quite limited. It also suggests that the only possible way of substantially improving urban transportation is to build or rebuild towns so that one of the important mode attributes mentioned above is rendered superfluous. 相似文献
135.
Reiner Onken Horst Garbe Stefan Schröder Michael Janik 《Journal of Marine Science and Technology》2010,15(4):427-433
A novel self-contained probe is presented which measures the sediment temperature of tidal flats between the surface and 40-cm
depth, and indicates whether the flats are flooded or dry. Depending on the selected acquisition interval, the endurance of
the probe is more than 6 months. It can be applied for the investigation of thermodynamic properties of the tidal flats impacting
physical and biological processes. Intensive tests have shown that the probe is robust and reliable and can be easily operated
by a single person. In case of rough weather conditions, the usage of scour protectors is recommended. 相似文献
136.
This paper examines the current situation in the largest of the Baltic States - Lithuania - with respect to the development of international transport and logistics in the context of the severe political, economic and social changes that have taken place since 1991. Utilizing statistics previously unavailable for the region, the paper examines the impact of transition and the competitive role of East European carriers upon a specific international movement of electronic goods between Frankfurt/Main in Germany and Vilnius in Lithuania, developing a detailed cost model for the alternative modal choices that are available - road and ship/road. Rail transport is excluded as no international rail services between the two countries are available and there are no plans for such services in the near future. From this, a series of issues for the future in the context of potential EU membership, transport infrastructure developments and logistical trends is analysed. 相似文献
137.
Transportation - This study examines changes in activity-travel patterns of employed people during a recession by using a tour-based representation of the activity-based approach. The term tour is... 相似文献
138.
New Zealand (NZ) has developed a coastal management framework that includes large watersheds and territorial waters (out to 12 nautical miles). The article describes the developing conflicts associated with the biophysical and epistemological dimensions of expanding coastal marine space for aquaculture. We first review aquaculture policy in NZ, and recent evidence of the biophysical impacts from increasing terrestrial inputs on marine ecosystems. We provide a case study of conflict over a recent proposal to expand salmon aquaculture in the Marlborough Sounds, which covers some 4,000 km2 of sounds, islands, and peninsulas. Based on information and data from interviews of stakeholders involved in the aquaculture planning, we describe three diverse epistemologies of science—client-based science, civic science, and Māori traditional ecological knowledge. We conclude the article with a critical review of how to better resolve spatial conflicts that often emerge in coastal management and planning. 相似文献
139.
Statistical inference on transit route‐level origin–destination flows using automatic passenger counter data 下载免费PDF全文
We consider inferring transit route‐level origin–destination (OD) flows using large amounts of automatic passenger counter (APC) boarding and alighting data based on a statistical formulation. One critical problem is that we need to enumerate the OD flow matrices that are consistent with the APC data for each bus trip to evaluate the model likelihood function. The OD enumeration problem has not been addressed satisfactorily in the literature. Thus, we propose a novel sampler to avoid the need to enumerate OD flow matrices by generating them recursively from the first alighting stop to the last stop of the bus route of interest. A Markov chain Monte Carlo (MCMC) method that incorporates the proposed sampler is developed to simulate the posterior distributions of the OD flows. Numerical investigations on an operational bus route under a realistic OD structure demonstrate the superiority of the proposed MCMC method over an existing MCMC method and a state‐of‐the‐practice method. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
140.
Michael J. Clay 《运输规划与技术》2013,36(3):181-209
Traveler behavior plays a role in the effectiveness of travel demand management (TDM) policies. Personal travel management is explored in this paper by analyzing individuals' adoption and consideration of 17 travel‐related alternatives in relation to socio‐demographic, mobility, travel‐related attitude, personality and lifestyle preference variables. The sample comprises 1282 commuters living in urban and suburban neighborhoods of the San Francisco Bay Area. Among the findings: females were more likely to have adopted/considered the more ‘costly’ strategies; those with higher mobility were more likely to have adopted/considered travel‐maintaining as well as travel‐reducing strategies; and those who like travel and want to do more are less likely to consider travel‐reducing strategies. These findings, when combined with those of earlier work on this subject, present a compelling argument for the need to further understand traveler behavior – particularly in response to congestion and TDM policies. 相似文献