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Results from four different methods for stochastic dynamic response analysis of a proposed jack-up platform are compared. This structure exhibits both significant dynamic amplification and non-linear transfer of sea elevation into load effects. Both estimation of extreme response and fatigue damage are considered. The most complex procedure based on time-domain simulation and step-by-step integration is employed as a benchmark for assessment of three simplified methods. The simplifications consist of various types of linearization in conjunction with transfer function approximations. Applicability of the methods to structures with increasingly non-linear behaviour and dynamic amplification is briefly discussed. 相似文献
843.
The implications of increased competition among ports for port policy and management 总被引:1,自引:0,他引:1
Trevor D. Heaver 《Maritime Policy and Management》1995,22(2):125-133
The increased competition faced by ports is more focused than previously on the performance of logistics systems of which the individual terminals in ports are critical hubs. The changes in competitive conditions raise issues about appropriate public port policies and strategies of port managements. This paper argucs that the port industry should (and is) moving in the direction of more harmonized policies based on economic principles. Port policies based on cost recovery from users of port facilities and services need to be adopted as the international standard. The competitive environment favours considerable local autonomy. Port management, in addition to possible direct responsibility for terminal management, needs to focus on activities with economies of scale or scope. Such activities, which span the requirements of terminals and may even warrant inter-port cooperation, enhance the services available for many port users. 相似文献
844.
M. Masson A. W. van Weers R. E. J. Groothuis H. Dahlgaard R. D. Ibbett K. S. Leonard 《Journal of Marine Systems》1995,6(5-6)
99Tc and 125Sb have been released in low level liquid waste at the reprocessing plant at La Hague (Fr). Over a number of years data have been obtained on the concentration of 99Tc in sea water and in seaweed from sampling locations close to and at increasing distances north and east of the point of release into the English Channel.In addition such data have been obtained on 125Sb for a small number of sampling points. These time series, and the information derived from their intercomparison and from comparison with the release data, are presented in this paper.Time series on 99Tc as well as 125Sb in sea water and seaweed clearly confirm a considerable decrease in release rates at La Hague over the years 1986–1993. Transit times and transfer factors derived from the series are generally in good agreement with the results of modelling efforts. The data do not provide evidence for a time lag between levels of the radionuclides in sea water and those in seaweed longer than a few months.The very high concentration factors for 99Tc in brown seaweeds make these seaweeds very useful for environmental monitoring the radionuclide at low release rates and to trace releases in areas remote from the point of release. 相似文献
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Examination of the phylogenetic structure of the family Candaciidae shows the genus Paracandacia to comprise a strongly modified branch emerging from the clade commonly denoted as Candacia. This has been confirmed by studying selected character phylogenies. It is argued that the resulting paraphyletic nature of Candacia auct., though in a cladistic context undesirable on theoretical grounds, has to be accepted as inevitable. Recent studies on molluscs and arthropods, viz., have demonstrated that the continuous origin of paraphyletic taxa from previously monophyletic ones is nothing but a naturally occurring process, intrinsically embodied in the course of evolution. 相似文献