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281.
Yann Ourmières Pierre Brasseur Marina Lévy Jean-Michel Brankart Jacques Verron 《Journal of Marine Systems》2009,75(1-2):100-115
A sequential assimilative system has been implemented into a coupled physical–biogeochemical model (CPBM) of the North Atlantic basin at eddy-permitting resolution (1/4°), with the long-term goal of estimating the basin scale patterns of the oceanic primary production and their seasonal variability. The assimilation system, which is based on the SEEK filter [Brasseur, P., Verron, J., 2006. The SEEK filter method for data assimilation in oceanography: a synthesis. Ocean Dynamics. doi: 10.1007/s10236-006-0080-3], has been adapted to this CPBM in order to control the physical and biogeochemical components of the coupled model separately or in combination. The assimilated data are the satellite Topex/Poseidon and ERS altimetric data, the AVHRR Sea Surface Temperature observations, and the Levitus climatology for salinity, temperature and nitrate.In the present study, different assimilation experiments are conducted to assess the relative usefulness of the assimilated data to improve the representation of the primary production by the CPBM. Consistently with the results obtained by Berline et al. [Berline, L., Brankart, J-M., Brasseur, P., Ourmières, Y., Verron, J., 2007. Improving the physics of a coupled physical–biogeochemical model of the North Atlantic through data assimilation: impact on the ecosystem. J. Mar. Syst. 64 (1–4), 153–172] with a comparable assimilative model, it is shown that the assimilation of physical data alone can improve the representation of the mixed layer depth, but the impact on the ecosystem is rather weak. In some situations, the physical data assimilation can even worsen the ecosystem response for areas where the prior nutrient distribution is significantly incorrect. However, these experiments also show that the combined assimilation of physical and nutrient data has a positive impact on the phytoplankton patterns by comparison with SeaWiFS ocean colour data, demonstrating the good complementarity between SST, altimetry and in situ nutrient data. These results suggest that more intensive in situ measurements of biogeochemical nutrients are urgently needed at basin scale to initiate a permanent monitoring of oceanic ecosystems. 相似文献
282.
While authorities consider transit as one of the solutions to enhance sustainable mobility, they do not provide a steady funding for its operation and growth. This inconsistency between political discourse and real intervention has motivated nine transit operators from six metropolitan areas of Quebec to conduct a study on the contribution of transit to sustainability. This article first presents the process of selecting indicators. For some of the indicators developed, the estimation method is detailed, which comprises of the following factors: resources, emission prevention, contribution to daily physical activity, accessibility to public transit and to activity locations, daily savings of using transit in comparison with car use, and the relative safety of transit use. Finally, the article explains the conceptual, methodological, and informational challenges that influenced the selection of indicators and their estimation methodologies. 相似文献
283.
William L. Garrison 《先进运输杂志》2000,34(1):31-63
I critique the innovation processes that yield transportation's technologies, and to aid my analysis I look back to take advantage of the accumulation of experiences and insights marked by the millennium. I identify supply, transport, and user systems. Transport systems move things; supply systems provide fuel, pavements, and other inputs to transport activities; and user systems combine transport with other activities for socially useful purposes. The discussion then shifts from structure to behavior, and a short review of the emergence of today's systems reminds us that technological advances may improve the provision of old services, offer new ways of doing old things, or induce qualitative changes that enable doing new things. With these structural and behavioral matters in mind, I challenge the reader to judge the present situation and the future. 相似文献
284.
杨进峰 《变流技术与电力牵引》2006,(5):26-30,39
论述了IGBT门极驱动器设计新方案,它具有先进的保护功能,如元件采用双电平开通以减小峰值电流,采用双电平关断以限制过电压,以及防止出现桥臂贯通的有源密勒箝位.此外还介绍一种包括双电平关断驱动器和有源密勒箝位功能的新电路,并对所述功能的试验及结果进行阐述,重点介绍双电平关断驱动器的中间电平对IGBT过电压的影响. 相似文献
285.
The key features of the western Galician shelf hydrography and dynamics are analyzed on a solid statistical and experimental basis. The results allowed us to gather together information dispersed in previous oceanographic works of the region. Empirical orthogonal functions analysis and a canonical correlation analysis were applied to a high-resolution dataset collected from 47 surveys done on a weekly frequency from May 2001 to May 2002. The main results of these analyses are summarized bellow. Salinity, temperature and the meridional component of the residual current are correlated with the relevant local forcings (the meridional coastal wind component and the continental run-off) and with a remote forcing (the meridional temperature gradient at latitude 37°N). About 80% of the salinity and temperature total variability over the shelf, and 37% of the residual meridional current total variability are explained by two EOFs for each variable. Up to 22% of the temperature total variability and 14% of the residual meridional current total variability is devoted to the set up of cross-shore gradients of the thermohaline properties caused by the wind-induced Ekman transport. Up to 11% and 10%, respectively, is related to the variability of the meridional temperature gradient at the Western Iberian Winter Front. About 30% of the temperature total variability can be explained by the development and erosion of the seasonal thermocline and by the seasonal variability of the thermohaline properties of the central waters. This thermocline presented unexpected low salinity values due to the trapping during spring and summer of the high continental inputs from the River Miño recorded in 2001. The low salinity plumes can be traced on the Galician shelf during almost all the annual cycle; they tend to be extended throughout the entire water column under downwelling conditions and concentrate in the surface layer when upwelling favourable winds blow. Our evidences point to the meridional temperature gradient acting as an important controlling factor of the central waters thermohaline properties and in the development and decay of the Iberian Poleward Current. 相似文献
286.
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288.
[目的]实战损伤条件下,舰艇进水是舱室进水漫延与舰员抗沉行为相对抗的过程。现有的不沉性理论无法客观、全面评估抗沉干预对战损舰艇进水过程的影响,缺少从全时域的角度对战损舰艇进水过程开展预测的手段。[方法]首先,分析抗沉干预下舰艇破损进水的耦合关系,构建进水过程时域模型,进而给出数值求解算法;其次,结合案例分析抗沉干预要素对不沉性的影响,并开发可视化、交互式的仿真系统。[结果]通过仿真系统实现了进水过程与多种抗沉干预方式的综合评估,是对现有不沉性理论的有效补充。[结论]该成果不仅可帮助设计人员掌握抗沉设计方案对干预进水过程的有效性,指导舰艇抗沉能力的设计;还可应用于抗沉指挥决策的态势预报,具有较高的军事应用价值。 相似文献
289.
Reggiani Giulia van Oijen Tim Hamedmoghadam Homayoun Daamen Winnie Vu Hai L. Hoogendoorn Serge 《Transportation》2022,49(3):897-925
Transportation - A fully separated bicycle network from vehicular traffic is not realistic even for the most bicycle-friendly cities. Thus, all around the world urban cycling entails switching... 相似文献
290.
The mass data of social media and social networks generated by users play an important role in tracking users’sentiments and opinions online.A good polarity lexicon which can effectively improve the classification results of sentiment analysis is indispensable to analyze the user’s sentiments.Inspired by social cognitive theories,we combine basic emotion value lexicon and social evidence lexicon to improve traditional polarity lexicon.The proposed method obtains significant improvement in Chinese text sentiment analysis by using the proposed lexicon and new syntactic analysis method. 相似文献