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101.
???Ч????????????????????????????????????????Baarda??????д???????????????????????Baarda??????????????????????????????????????÷????????Ч?????????????е?????????????????? 相似文献
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Sardine Sardinops sagax distributed off the west and south coasts of South Africa have traditionally been assumed to comprise a single well-mixed stock for assessment and management purposes. New research, however, lends weight to the possibility of two stocks in this region. A precautionary management approach thus needs to consider the impact of management decisions on the hypothesised two individual stocks as well as on the resource as a whole. As a first step in this process, Bayesian assessments of South African sardine are presented, which compare results for the traditional single-stock hypothesis with those that follow from a new two-mixing-stock hypothesis. Recruits from the west stock are assumed to move to and remain part of the south stock in annual pulses of varying size. This movement is estimated to be appreciable, and to take place from a substantially more productive west stock to the south stock. This immigration makes a greater contribution to the south-stock biomass than do years of above-average south-stock recruitment. Importantly, this two-mixing-stock hypothesis is shown to be consistent with the data available. Further alternative sardine stock-structure hypotheses suggested by the most recent data are discussed. 相似文献
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The Phoenix Lander landed on Mars on 25 May 2008. It has instruments on board to explore the geology and climate of subpolar Mars and to explore if life ever arose on Mars. Although the Phoenix mission is not a life detection mission per se, it will look for the presence of organic compounds and other evidence to support or discredit the notion of past or present life.The possibility of extant life on Mars has been raised by a reinterpretation of the Viking biology experiments [Houtkooper, J. M., Schulze-Makuch, D., 2007. A possible biogenic origin for hydrogen peroxide on Mars: the Viking results reinterpreted. International Journal of Astrobiology 6, 147-152]. The results of these experiments are in accordance with life based on a mixture of water and hydrogen peroxide instead of water. The near-surface conditions on Mars would give an evolutionary advantage to organisms employing a mixture of H2O2 and H2O in their intracellular fluid: the mixture has a low freezing point, is hygroscopic and provides a source of oxygen. The H2O2-H2O hypothesis also explains the Viking results in a logically consistent way. With regard to its compatibility with cellular contents, H2O2 is used for a variety of purposes in terran biochemistry. The ability of the anticipated organisms to withstand low temperatures and the relatively high water vapor content of the atmosphere in the Martian arctic, means that Phoenix will land in an area not inimical to H2O2-H2O-based life. Phoenix has a suite of instruments which may be able to detect the signatures of such putative organisms. 相似文献
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SMS在新一代天气雷达运行状态监视报警中的应用 总被引:3,自引:2,他引:1
引言
新一代天气雷达具有观测时空分辨率高、连续工作等一系列特点,决定了它在现代气象观测业务中的重要地位。由于新一代天气雷达观测时间密度大,处于24h工作状态,不可避免会出现故障,依靠人工对其运行状态进行完全监视不可能实现,很多突如其来的故障不是马上就会引起雷达值班人员的注意,所以有必要建立新一代天气雷达运行状态监视和报警系统。 相似文献
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卡尔曼滤波模型误差的识别 总被引:3,自引:1,他引:2
陶本藻 《大地测量与地球动力学》1999,19(4):15-20
本文在简述卡尔曼滤波模型基础上讨论了模型误差的检验和估计问题,提出了检验卡尔曼滤波模型误差显著性的几种统计假设检验方法,探讨并给出了估计模型误差的方法和公式。 相似文献
107.
ABSTRACT“Panta Rhei – Everything Flows” is the science plan for the International Association of Hydrological Sciences scientific decade 2013–2023. It is founded on the need for improved understanding of the mutual, two-way interactions occurring at the interface of hydrology and society, and their role in influencing future hydrologic system change. It calls for strategic research effort focused on the delivery of coupled, socio-hydrologic models. In this paper we explore and synthesize opportunities and challenges that socio-hydrology presents for data-driven modelling. We highlight the potential for a new era of collaboration between data-driven and more physically-based modellers that should improve our ability to model and manage socio-hydrologic systems. Crucially, we approach data-driven, conceptual and physical modelling paradigms as being complementary rather than competing, positioning them along a continuum of modelling approaches that reflects the relative extent to which hypotheses and/or data are available to inform the model development process.
EDITOR D. Koutsoyiannis; ASSOCIATE EDITOR not assigned 相似文献
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Based on the theory of dynamic wheel–rail interactions, a dynamic model of coupled train–bridge system subjected to earthquakes is established, in which the non‐uniform characteristics of the seismic wave input from different foundations are considered. The bridge model is based on the modal comprehension analysis technique. Each vehicle is modelled with 31 degrees of freedom. The seismic loads are imposed on the bridge by using the influence matrix and exerted on the vehicles through the dynamic wheel–rail interaction relationships. The normal wheel–rail interaction is tackled by using the Hertzian contact theory, and the tangent wheel–rail interaction by the Kalker linear theory and the Shen–Hedrick–Elkins theory. A computer code is developed. A case study is performed to a continuous bridge on the planned Beijing–Shanghai high‐speed railway in China. Through input of typical seismic waves with different propagation velocities to the train–bridge system, the histories of the train running through the bridge are simulated and the dynamic responses of the bridge and the vehicles are calculated. The influences of train speed and seismic wave propagation velocity on the dynamic responses of the bridge–vehicle system are studied. The critical train speeds are proposed for running safety on high‐speed railway bridges under earthquakes of various intensities. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献