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181.
Trip generation of vulnerable populations in three Canadian cities: a spatial ordered probit approach 总被引:1,自引:0,他引:1
Matthew J. Roorda Antonio Páez Catherine Morency Ruben Mercado Steven Farber 《Transportation》2010,37(3):525-548
This paper provides an analysis of trip generation of three vulnerable groups: single-parent families, low income households,
and the elderly. It compares the mobility of these groups to that of the general population in three Canadian urban areas
of Hamilton, Montreal and Toronto, based on data from large-sample metropolitan transport surveys. An ordered probit model
with spatially expanded coefficients is used for the analysis. Spatial expansion shows that there are spatial mobility trends
for elderly populations and low-income populations even after socio-economic attributes are accounted for. Such spatial differences
are not generally found for single parent families. This novel spatial analysis provides clues as to where vulnerable populations
may experience greater degrees of social exclusion. It provides information to help prioritize transportation infrastructure
projects or other social programs to take into account the needs of vulnerable populations with the lowest levels of mobility. 相似文献
182.
F. Payri A. J. Torregrosa A. Broatch L. Monelletta 《International Journal of Automotive Technology》2009,10(6):761-769
Combustion noise in passenger cars powered with direct injection (DI) diesel engines is frequently the main reason why end-users
are reluctant to drive this type of vehicle. Thus, the great potential of diesel engines for environment preservation — due
to their lower CO2 emissions — could be missed. This situation worsens with the current design trends (engine downsizing) and the emerging new
diesel combustion concepts (Homogeneous Charge Compression Ignition-HCCI, Premixed Charge Compression Ignition-PCCI, etc.),
which are intrinsically noisy. This negative feature can be even more critical in transient operation due to the contribution
of the temporal changes of both source and transmission path on engine noise. Therefore, combustion noise must be considered
as an additional essential factor in engine development, together with performance, emissions and driveability. Thus, suitable
evaluation procedures that can be integrated into the global engine development process in a timely and cost-effective manner
are imperative. Regarding the evaluation procedures, most of the work available in the literature addressed combustion noise
at steady operation. To surpass this limitation, two possible approaches — adapted from the classical and multiple regression
methods — for the overall level assessment of combustion noise in transient conditions are evaluated in this paper. 相似文献
183.
Several authors have reported a strong linear relationship between daily phytoplankton production and the product of chlorophyll biomass, photic depth, and incident irradiance for a variety of estuaries. This “light · biomass” (BZpIo) formulation has been proposed as an alternative to traditional mechanistic approaches for computing phytoplankton production in numerical estuarine models. One limitation to their application in shallow systems is that the BZpIo models have been developed in relatively deep estuaries where light does not reach the bottom. We propose a nonlinear correction factor to adapt the BZpIo relationship to shallow systems where light does reach the bottom. Our function takes into account variations in incident irradiance, attenuation coefficient for light, photosynthetic efficiency, and maximum rate of photosynthesis. A series of correction polynomials are proposed for various ranges of incident irradiance, and are integrated into a single multiple polynomial which applies across all irradiance levels. Our new correction factor was tested against a 14C-based productivity dataset from shallow stations in Narragansett Bay, RI and an O2-based dataset from shallow (1.1 m) lagoon mesocosms at the University of Rhode Island. Results showed that our polynomials accurately correct BZpIo-predicted rates of production in shallow water columns. Application of our correction factor to a series of shallow water productivity datasets from the literature together with theoretical calculations show how significant the shallow water correction can be, especially in very shallow water columns with low turbidity. 相似文献
184.
T.J. Andersen L.C. Lund-Hansen M. Pejrup K.T. Jensen K.N. Mouritsen 《Journal of Marine Systems》2005,55(3-4):123-138
This study was carried out to describe the difference in erodibility and aggregation in a tidal basin including both subtidal and intertidal study sites and to use these results to explain the shifting erosion/deposition cycles at the sites. Erosion thresholds, erosion rates and settling velocities of the eroded material were measured at a mudflat transect and at sediment cores taken from a nearby tidal channel during surveys made in May 2000 and March 2002. Surface samples were analysed for grain-size, chl. a content, faecal pellet content, dry bulk density and organic content. Additionally, surface samples were taken at eight occasions in the period January 2002 to May 2003 from shallow tidal channels in the area. These samples were analysed for mud content and showed that major shifts in sediment distribution occurred in the period. The erodibility of the mudflat was generally high due to pelletization by the mudsnail Hydrobia ulvae but close to the salt marsh much lower erodibility was found, probably due to stabilisation by microphytobenthos. In contrast, the erodibility of the channel bed seemed to be very little influenced by biological activity and the relatively low erodibility found here was caused by physical characteristics of the sediment. The sediment eroded from the mudflat was generally strongly pelletized and showed high settling velocities whereas less aggregation and lower settling velocities were found for the channel bed sediments. Temporal variations of the mudflat stability and hydrodynamics resulted in temporal variations of deposition and erosion and the changing stability at the mudflat is likely to be one of the main reasons for a general transport of fine-grained sediment from the mudflat to the channel in the cold seasons and vice versa during the rest of the year. 相似文献
185.
Craig J. Forsyth 《Maritime Policy and Management》1999,26(1):61-68
This paper examines the meaning of four common maritime and admiralty terms: found, cargo, ballast and voyage . These terms are problematic because their definitions are elastic which makes application of the terms difficult. The four terms are important because significant legal consequences are attached to each of them, particularly for seamen on flags of convenience (FOC) and crews of convenience (COC) vessels in US ports. The findings of the author are based on personal experience as well as research conducted in preparation as an expert witness in several maritime cases in both the US District Courts and in Louisiana State Courts, personal interviews with seamen on FOC/COC vessels, interviews with legal and economic experts on the international maritime industry and officials of national and international labour organizations. 相似文献
186.
J. J. Kalker 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1986,15(5):255-269
In the present paper the theories of the railway wheel and the automotive tyre are discussed. After an introduction the paper opens with a discussion of the common ground, viz. the rolling motion of deformable bodies. Then the railway wheel is discussed, and it is shown that all aspects may be calculated numerically from the material constants Poisson's ratio, Young's modulus, and the coefficient of friction, and from the geometry of wheel and rail. Next the automotive wheel is considered. Such a wheel is very anisotropic, to the extent that the theory of the lateral motion (out-of-plane dynamics) is radically different from the longitudinal, or in-plane motion. Moreover, the analysis of the automotive wheel heavily relies on experiments. In the conclusion, the theories are compared. 相似文献
187.
Spatial fisheries ecology: Recent progress and future prospects 总被引:1,自引:0,他引:1
L. Ciannelli P. Fauchald K.S. Chan V.N. Agostini G.E. Dingsr 《Journal of Marine Systems》2008,71(3-4):223
We review recent progresses made in the study of fish distribution and survival over space — i.e., fisheries spatial ecology. This is achieved by first surveying the most common statistical approaches and relative challenges associated with the analysis of fisheries spatial data, loosely grouped in geostatistical and regression approaches. Then we review a selected number of case-studies implementing the discussed techniques. We conclude by proposing new areas of statistical and ecological research to further our understanding of how fish distribute and survive in space. This review serves a dual purpose by emphasizing the scientific importance of studying spatial interactions to better understand the temporal dynamics of fish abundance, and by promoting the development of new analytical and ecological approaches for the analysis of spatial data. Through our survey we cover different statistical techniques, marine ecosystems and life stages. This analytical, geographic and ontogenetic variety is also purposely selected to highlight the importance of comparative and multidisciplinary studies across diverging ecological disciplines, ecosystems and life stages. Besides having a general ecological relevance this review also bears a more applied significance, owing to the increasing need for protecting renewable marine resources along with their primary habitat. 相似文献
188.
189.
A survey of U.S. and European responses to the energy crises engendered by the Arab boycott of October 1973–April 1974 is presented. U.S. Government policy actions with respect to allocation, rationing, price, and conservation measures are reviewed and contrasted with those of affected European governments. The results of those policies and their effects on transportation energy supply and demand behavior with respect to both commodity and passenger movement are described.Based on short- and long-term impact assessments of the policies considered, the authors identify significant research requirements.The authors were heavily engaged in U.S. responses to the energy emergency, and were asked to undertake study missions to those European nations significantly affected by the crisis to seek out avenues for mutual aid, and joint research, in resolving common energy problems. This paper is one product of those study missions. 相似文献
190.