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931.
932.
A study of the Alboran sea mesoscale system by means of empirical orthogonal function decomposition of satellite data 总被引:1,自引:0,他引:1
A. Baldacci G. Corsini R. Grasso G. Manzella J. T. Allen P. Cipollini T. H. Guymer H. M. Snaith 《Journal of Marine Systems》2001,29(1-4)
This paper presents the results of a combined empirical orthogonal function (EOF) analysis of Advanced Very High Resolution Radiometer (AVHRR) sea surface temperature (SST) data and sea-viewing wide field-of-view sensor (SeaWiFS) chlorophyll concentration data over the Alboran Sea (Western Mediterranean), covering a period of 1 year (November 1997–October 1998). The aim of this study is to go beyond the limited temporal extent of available in situ measurements by inferring the temporal and spatial variability of the Alboran Gyre system from long temporal series of satellite observations, in order to gain insight on the interactions between the circulation and the biological activity in the system. In this context, EOF decomposition permits concise and synoptic representation of the effects of physical and biological phenomena traced by SST and chlorophyll concentration. Thus, it is possible to focus the analysis on the most significant phenomena and to understand better the complex interactions between physics and biology at the mesoscale. The results of the EOF analysis of AVHRR-SST and SeaWiFS-chlorophyll concentration data are presented and discussed in detail. These improve and complement the knowledge acquired during the in situ observational campaigns of the MAST-III Observations and Modelling of Eddy scale Geostrophic and Ageostrophic motion (OMEGA) Project. 相似文献
933.
Juan-Antonio Carrasco Eric J. Miller 《Transportation Research Part A: Policy and Practice》2009,43(1):90-104
This paper presents a social activity-travel generation model, which explicitly incorporates the individual’s social dimension through the concept of personal networks, modeling the multilevel structure of social relations defined by these networks. The objective of the analysis is to study the relevance of the social dimension as a source of explanation of social activity-travel generation behavior between an individual and each relevant person of their social life. The paper uses a disaggregated perspective of personal networks, explicitly incorporating the characteristics of each network member as well as the characteristics of the overall social structure. Using an ordinal multilevel specification that accounts for the social network in which individuals are embedded, four dimensions are studied: personal characteristics, “with whom” activities are performed, social network composition and structure, and ICT (information and communication technology) interaction. The results show that a proper and complete understanding of social activity generation requires going beyond the individualistic paradigm, explicitly incorporating the role of the social dimension in the study of this decision-making process. 相似文献
934.
J. Edward Anderson 《先进运输杂志》2000,34(1):3-29
The paper begins with a review of the rational for development of personal rapid transit, the reasons it has taken so long to develop, and the process needed to develop it. Next I show how the PRT concept can be derived from a system‐significant equation for life‐cycle cost per passenger‐mile as the system that minimizes this quantity. In the bulk of the paper I discuss the state‐of‐the‐art of a series of technical issues that had to be resolved during the development of an optimum PRT design. These include capacity, switching, the issue of hanging vs. supported vehicles, guideways, vehicles, control, station operations, system operations, reliability, availability, dependability, safety, the calculation of curved guideways, operational simulation, power and energy. The paper concludes with a listing of the implications for a city that deploys an optimized PRT system. 相似文献
935.
在运输系统相互间的竞争和铁路内部竞争中,现代化的机车车辆是起决定性作用的因素.从用户的角度讨论了现代化机车车辆的功能特征,并深入研究了相互间的竞争以及铁路内部竞争和制造厂之间的竞争对机车车辆现代化的作用以及对今后的影响. 相似文献
936.
Regional governance of port development in China: a case study of Shanghai International Shipping Center 总被引:3,自引:0,他引:3
When China enters the World Trade Organisation (WTO) and becomes more involved in the global economy, her major seaports will be pivotal places where the international shipping and terminal operators interact, conflict and co-operate with the local and the central governments. To demonstrate and understand these interactions, this article analyzes the case of the Yangtze River Delta (YRD), where the competition, co-operation and governance of Shanghai and Ningbo, the two largest ports on Chinese mainland, concern all stakeholders from the central and local governments of China to the container terminal operators and shipping lines overseas.
This paper first develops a conceptual framework for analyzing port development in a regional context. The article then introduces the case of the Shanghai International Shipping Center with a focus on the efforts of the Shanghai Government to establish a regional hub port, which also involves two nearby provinces. This case study reveals the course of the decision-making processes and the power networks currently governing the port development in the YRD. Two domains of port governance are discussed: the role of port authorities in port internal governance, and the crucial influences of local and central governments on the port external governance. It provides evidence that the power of shipping lines and international terminal operators are not as prevalent as in many ports in western countries. It is suggested that the lack of good regional port governance in the region is due to structural problems in administration. 相似文献
This paper first develops a conceptual framework for analyzing port development in a regional context. The article then introduces the case of the Shanghai International Shipping Center with a focus on the efforts of the Shanghai Government to establish a regional hub port, which also involves two nearby provinces. This case study reveals the course of the decision-making processes and the power networks currently governing the port development in the YRD. Two domains of port governance are discussed: the role of port authorities in port internal governance, and the crucial influences of local and central governments on the port external governance. It provides evidence that the power of shipping lines and international terminal operators are not as prevalent as in many ports in western countries. It is suggested that the lack of good regional port governance in the region is due to structural problems in administration. 相似文献
937.
Dissolved and particulate phases of carbon (DIC, DOC, POC) and nutrients (DIN, DIP, DSi, DON, DOP, PN) were investigated bimonthly from August 1999 to August 2000 to study biogeochemical dynamics of carbon and nutrients in Tapong Bay, a small semi-enclosed and hypertrophic lagoon in southwestern Taiwan. The lagoon has only a tidal inlet for exchanging water between Tapong Bay and Taiwan Strait, which may result in low water exchange rates and various oxygen-deficient conditions in bottom water of the inner bay during warm seasons. The water exchange time of Tapong Bay ranges from 7 days (summer) to 13 days (winter) with a mean of 10 days. Nutrient dynamics were largely ascribed to allochthonous inputs, biological and exported removals in the lagoon. Diffusion fluxes from sediments to overlying water accounted for only about 7.6% of annual DIN inputs and 1.0% of annual DIP inputs. High primary productivity (89 mol C m−2 year−1) supported by abundant nutrients primarily drove the lagoon into a hypertrophic condition as particulate organic matter was derived mainly from biological production. Excess of DIP appeared to occur throughout the study period in the lagoon. Temperature, solar radiation and turbidity, rather than nutrients, perhaps controlled seasonal variations of primary productivity. The net ecosystem production (NEP) derived from daily changes of DOC and POC inventories was about 6.3 mmol C m−2 day−1 that was close to 6.7 mmol C m−2 day−1 simulated from the biogeochemical modeling. Therefore, the net ecosystem production (NEP) rate of organic carbon estimated from the biogeochemical model was reliable, and the NEP was temporally variable with an annual mean of 5.8 mol C m−2 year−1, implying that Tapong Bay was an autotrophic system. Although calcification proceeded pronouncedly in warm seasons, an invasion of CO2 was significant in this system. In terms of nitrogen budget, the annual nitrogen fixation exceeded the annual denitrification with a magnitude of 1.30 mol N m−2 year−1, which may be supported by the abundance of nitrogen fixation microplanktons in the lagoon. 相似文献
938.
Nonlinear Dynamics of Vehicle Traction 总被引:3,自引:0,他引:3
B. J. Olson S. W. Shaw G. St p n 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2003,40(6):377-399
Summary The purpose of this study is to understand the nonlinear dynamics of longitudinal ground vehicle traction. Specifically, single-wheel models of rubber-tired automobiles under straight-ahead braking and acceleration conditions are investigated in detail. Customarily, the forward vehicle speed and the rotational rate of the tire/wheel are taken as dynamic states. This paper motivates an alternative formulation in which wheel slip, a dimensionless measure of the difference between the vehicle speed and the circumferential speed of the tire relative to the wheel center, replaces the angular velocity of the tire/wheel as a dynamic state. This formulation offers new insight into the dynamic behavior of vehicle traction. The unique features of the modeling approach allow one to capture the full range of dynamic responses of the single-wheel traction models in a relatively simple geometric manner. The models developed here may also be useful for developing and implementing anti-lock brake and traction control control schemes. 相似文献
939.
S. Mü ller M. Uchanski J. K. Hedrick 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2003,39(2):121-133
Summary Each vehicle on a section of highway is potentially a driving condition 'sensor.' For example, a vehicle's speed give can give a clue about the traffic conditions in its section of roadway. By 'cooperative estimation,' we mean a system that uses a communication network to combine the experience of many vehicles into parameter estimates that are more useful than the estimates that any individual vehicle could generate by itself. This paper demonstrates the cooperative estimation concept by showing how it can be used to estimate traffic conditions and road friction without using roadside sensors. 相似文献
940.