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651.
T. Rossby Vladimir Ozhigin Victor Ivshin Sheldon Bacon 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(11):1955-1971
Few basins in the world exhibit such a wide range of water properties as those of the Nordic Seas with cold freshwaters from the Arctic in the western basins and warm saline waters from the Atlantic in the eastern basins. In this study we present a 50-year hydrographic climatology of the Nordic Seas in terms of depth and temperature patterns on four upper ocean specific volume anomaly surfaces. This approach allows us to better distinguish between change due to variations along such surfaces and change due to depth variations of the stratified water column. Depth variations indicate changes in the mass field while property variations along isopycnals give insight into isopycnal advection and mixing, as well as diapycnal processes. We find that the warmest waters on each surface are found in the north, close to where the isopycnal outcrops, a clear indication of downward mixing of the warmer, more saline waters on shallower isopycnals due to convective cooling at the surface. These saline waters come from the Norwegian Atlantic Slope Current by means of a very high level of eddy activity in the Lofoten Basin.The isopycnal analyses further show that the principal water mass boundary between the waters of Arctic origin in the west and Atlantic waters in the east aligns quite tightly with the Jan Mayen, Mohn, Knipovich Ridge system suggesting little cross-ridge exchange. Instead, the main routes of exchange between the eastern and western basins appear to be limited to the northern and southern ends of ridge system: Atlantic waters into the Greenland Sea in the Fram St and Artic waters into the southern Norwegian Sea just north of the Iceland-Faroe Ridge.Analysis of a representative isopycnal in the main pycnocline shows it to be stable over time with only small variations with season (except where it outcrops in winter in the Greenland and Iceland Seas). However, two very cold winters, 1968–1969, led to greater than average heat losses across the entire Lofoten Basin that eroded away much of the Lofoten eddy and induced the greatest temperature anomaly in the entire 50-year record. Interannual variations in isopycnal layer temperature correlate with the NAO index such that waters in the Iceland Sea become warmer than average with warming air temperatures and conversely in the Lofoten Basin. 相似文献
652.
The determination of costs and benefits experienced by crustaceans as a result of occupation by their symbionts has received increased attention from marine ecologists. However, the interactions between some important species and their associates remain unclear. We examined the distribution of amphipods in the genus Ischyrocerus on the red king crab Paralithodes camtschaticus, a commercially important species, in two areas of the Barents Sea. Ischyrocerus commensalis was found on 30.5% of crabs in Dalnezelenetskaya Bay (DZB) with the mean number per crab being 55.1, in Dolgaya Bay (DLB) these rates were 28.6% with 19.3 specimens per crab. Sympatric species Ischyrocerus anguipes was found on 13.5% of crabs in DZB with a mean of 7.3 individuals per host, in DLB it had much lower occurrence (1.3% and 1.5 specimens per host). There were no significant differences between proportions of male and female crabs infested by amphipods in both areas examined. Prevalence of amphipods was similar among years examined except for I. commensalis on small crabs (carapace length CL <90 mm) and I. anguipes on large crabs (CL >90 mm) in DZB. We found that I. commensalis and I. anguipes are not egg predators of P. camtschaticus in the Barents Sea, at least in summer. High numbers of I. commensalis occur in crab gills, and both mean intensity of the amphipods and their empty tubes increased with crab size. In the gills, I. commensalis predominated in the section nearest the mouth parts. Possible negative impacts for the hosts due to gills infestation are discussed. In contrast, I. anguipes were predominately found on the carapace and limbs of crabs and appears to be a less specific symbiont of P. camtschaticus. Both amphipod species seem to be commensals, however possible negative impacts for the host could not be excluded. 相似文献
653.
654.
Mai Tong Vladimir Rzhevskyt Dai Junwu George C Lee Qi Jincheng Qi Xiaozhai 《地震工程与工程振动(英文版)》2007,6(3):215-223
Major earthquakes of last 15 years (e.g., Northridge 1994, Kobe 1995 and Chi-Chi 1999) have shown that many near-fault ground motions possess prominent acceleration pulses. Some of the prominent ground acceleration pulses are related to large ground velocity pulses, others are caused by mechanisms that are totally different from those causing the velocity pulses or fling steps. Various efforts to model acceleration pulses have been reported in the literature. In this paper, research results from a recent study of acceleration pulse prominent ground motions and an analysis of structural damage induced by acceleration pulses are summarized. The main results of the study include: (1) temporal characteristics of acceleration pulses; (2) ductility demand spectrum of simple acceleration pulses with respect to equivalent classes of dynamic systems and pulse characteristic parameters; and (3) estimation of fundamental period change under the excitation of strong acceleration pulses. By using the acceleration pulse induced linear acceleration spectrum and the ductility demand spectrum, a simple procedure has been developed to estimate the ductility demand and the fundamental period change of a reinforced concrete (RC) structure under the impact of a strong acceleration pulse. 相似文献
655.
Sergey Polyansky Mikhail Sykhanov Vladimir Tikunov 《地球信息科学学报》2007,9(1):73-77
综合数字区域模型在区域可持续发展的任何模型实现中都是不可或缺的,而空间数据基础设施为综合数字区域模型提供了一个可靠的基础。其可以很方便地在地图信息或者直接在地理信息系统(GIS)内形成。这种GIS系统具有开发良好的模型函数,能够集成专家系统,也能被设计全尺度多媒体产品。GIS允许集成不同的信息资源、模型、可视化和分析、各种假设的详尽细节和为诸如自然-社会-经济等的复杂系统提供可选开发方案。一个综合辅助信息系统的结构包括紧密相关的社会-政治、经济(或生产)、自然资源和环境模块。它提供了对于不同区域范围社会生态系统的全面描述,显示了自然和人类资源的重要性。人们在这个研究领域将会谈及自然和社会管理。根据它们的变化层次体系(从全局范围到局部范围)可以描述所有专题,并且考虑在不同尺度上描述的现象的专业特征。超媒体系统原理可以通过链接集成主题来实现。这种系统的日益复杂性使得系统的智能化成为必要,专家系统和神经元网络可以从很复杂并且非常模糊的问题中得出可行的解决方案。现代GIS配有很多设备,对用户来说,这使得用基础地图和互联网获取必要的数据来编制专题图成为可能。数学建模的专业方法具有特殊的重要性,特别是那些旨在追求在区域变换到可持续发展模型时设想的详尽细节的方法。最高级的AIS能作为全尺度的决策支持系统使用。莫斯科国立大学试图实现上述思想,开发了俄罗斯可持续发展信息系统框架,特以俄罗斯南部地区为一案例。该示例一方面作为更大区域即国家的一部分进行描述,另一方面作为一个或多或少、基于资源发展的单元进行描述。也能对区域发展战略和改革措施提出建议。我们已经对所有俄罗斯地区进行了分类,并且指出了不同组(工业、农业等)的最典型代表。将精心设计几个系统的区域分支来描述整个国家的不同地域类型。计算机辅助信息系统提供用户以各种各样传统地图集的计算机的模拟,为决策者对未来的设计和区域发展变量评估等创造了条件。我们正在开发一个大范围有机废弃产品处理的测试GIS系统。其主要目标是为在废弃物储存和掩埋场所的生物降解进行方法研究。其应用包括:存放生活和工业废品的场所的使用和改进(包括工业和农业的场所和废品产生的地方);污水处理设备的建设和重建等。 相似文献