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11.
This paper describes the hydrographic conditions observed during six surveys carried out during 2003 and 2004, in the framework of the “IDEA Project” (acronym for “Influence of oceanographic structure and dynamics on demersal populations in waters of the Balearic Islands”). The surveys were developed on the shelf and slope of Mallorca Island, in particular in two fishing grounds at the north and south of the Mallorca channel. Periodic movements of the fishing fleet between these two areas have been regularly reported, suggesting a seasonal variability of the resources which could be in turn associated with the hydrodynamic variability. With this motivation, water masses affecting these grounds have been identified and their seasonal variability has been studied. Different oceanographic and environmental conditions have been found between the two fishing grounds. These differences are related to the presence of mesoscale structures, associated with the Western Mediterranean Intermediate Water (WIW) at the north of the Ibiza channel and big gyres detached from the Algerian Current. The former has been shown to have influence on the regional oceanic circulation and the latter could affect the progress of fresh Atlantic Water (AW) towards the channels and make possible the presence of high salinity values at intermediate waters at the south of Mallorca Island. Historical data from other oceanographic cruises carried out in the region are finally used to discuss the interannual variability of these mesoscale structures. 相似文献
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基于现场取样和室内试验,分析了铣刨方式对RAP组成与性能的影响,分析了铣刨速度、破碎处理与否对RAP级配组成的影响。结果表明:分层铣刨回收显著降低了RAP组成变异性;铣刨速度宜控制在6~8 m/min;破碎处理工艺有利于提高RAP的再生利用率。 相似文献
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W. Fauriat C. Mattrand N. Gayton A. Beakou T. Cembrzynski 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2016,54(5):585-605
When assessing the statistical variability of fatigue loads acting throughout the life of a vehicle, the question of the variability of road roughness naturally arises, as both quantities are strongly related. For car manufacturers, gathering information on the environment in which vehicles evolve is a long and costly but necessary process to adapt their products to durability requirements. In the present paper, a data processing algorithm is proposed in order to estimate the road profiles covered by a given vehicle, from the dynamic responses measured on this vehicle. The algorithm based on Kalman filtering theory aims at solving a so-called inverse problem, in a stochastic framework. It is validated using experimental data obtained from simulations and real measurements. The proposed method is subsequently applied to extract valuable statistical information on road roughness from an existing load characterisation campaign carried out by Renault within one of its markets. 相似文献
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Travel time reliability, an essential factor in traveler route and departure time decisions, serves as an important quality of service measure for dynamic transportation systems. This article investigates a fundamental problem of quantifying travel time variability from its root sources: stochastic capacity and demand variations that follow commonly used log-normal distributions. A volume-to-capacity ratio-based travel time function and a point queue model are used to demonstrate how day-to-day travel time variability can be explained from the underlying demand and capacity variations. One important finding is that closed-form solutions can be derived to formulate travel time variations as a function of random demand/capacity distributions, but there are certain cases in which a closed-form expression does not exist and numerical approximation methods are required. This article also uses probabilistic capacity reduction information to estimate time-dependent travel time variability distributions under conditions of non-recurring traffic congestion. The proposed models provide theoretically rigorous and practically useful tools for understanding the causes of travel time unreliability and evaluating the system-wide benefit of reducing demand and capacity variability. 相似文献
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A mathematical model was used to simulate monthly responses of the Gulf of Mexico hypoxia to variations in climate and anthropogenic nutrient loading over a 45-year period. We examined six hypothetical future scenarios that are based on observed and projected changes in the Mississippi River discharge, Mississippi River nitrate concentrations, and ambient water temperatures. In particular, we investigated the implications of a 30% decrease in the Mississippi River nitrogen flux, which was recently proposed by the Mississippi River Watershed/Gulf of Mexico Hypoxia Task Force as a measure to reduce the size of the hypoxic zone. Model simulations suggest that the frequency of hypoxia in the northern Gulf of Mexico is highly sensitive to variations in riverine nitrate flux, but also to variations in freshwater discharge and ambient water temperatures. A 30% decrease in the Mississippi River nitrate flux, for example, would reduce the frequency of hypoxia by 37%. Nevertheless, a 20% increase the Mississippi River discharge, which may occur under some climate change scenarios, would produce an increase in the frequency of hypoxia of the same magnitude. Thus, if the potential climatic variations are taken into account, a 30% decrease in the nitrogen flux of the Mississippi River may not be sufficient to accomplish the proposed hypoxia management goal. 相似文献
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Exploring spatial variety in patterns of activity-travel behaviour: initial results from the Toronto Travel-Activity Panel Survey (TTAPS) 总被引:1,自引:0,他引:1
Studies of urban travel behaviour typically focus on weekday activities and commuting. This is surprising given the rising
contribution of discretionary activities to daily travel that has occurred during the last few decades. Moreover, current
understanding of the relationship between travel behaviour and land use remains incomplete, with little research carried out
to explore spatial properties of activity-travel behaviour during the off-peak and weekend time periods. Weekend behaviours,
for example, influenced by the availability of time and the spatiotemporal distribution of “weekend” destinations, likely
produce spatially and temporally distinct activity-travel patterns. Using data from the first wave of the Toronto Travel-Activity
Panel Survey (TTAPS), this paper examines an area of research that has received little attention; namely, the presence of
spatial variety in activity-travel behaviour. The paper begins by looking at the extent to which individuals engage in spatially
repetitive location choices during the course of a single week. Area-based measures of geographical extent and activity dispersion
are then used to expose differences in weekday-to-weekend and day-to-day activity-travel patterns. Examination of unclassified
activities carried out over a 1 week period reveals a level of spatial repetition that does not materialise across activities
classified by type, travel mode, and planning strategy. Despite the inherent spatial flexibility offered by the personal automobile,
spatial repetition is also found to be surprisingly similar across travel modes. The results also indicate weekday-to-weekend,
and day-to-day fluctuations in spatial properties of individual activity-travel behaviour. These findings challenge the utility
of the short-run survey as an instrument for capturing archetypal patterns of spatial behaviour. In addition, the presence
of a weekday-to-weekend differential in spatial behaviour suggests that policies targeting weekday travel reduction could
have little impact on travel associated with weekend activities.
相似文献
Tarmo K. RemmelEmail: |