Using the SKAGEX dataset for evaluation of ocean model skills

Numerical ocean models are now being applied in numerous oceanographic studies. However, the qualities of the model results are often uncertain and there is a great need for standards and procedures for evaluation of the skills of numerical general circulation models. In this paper measurements from repeated hydrographical sections across Skagerrak taken in 1990, the SKAGEX dataset, are used to evaluate the skills of two σ-coordinate ocean models and to study the sensitivity of these models to model parameters. A methodology for quantification of model skills based on observations from repeated hydrographical sections in general is suggested. Area averages of absolute differences are for Skagerrak completely dominated by the discrepancies in the upper few meters of the ocean and may not be used to assess models' abilities to reproduce the fields in the larger and deeper part of the ocean. Therefore, discrepancies between average values in time from the observed fields and time averaged values from model outputs are related to the natural variability of the fields. The numbers produced with the suggested measure are relative numbers that will be specific for each section and for each series of observation. Ideally we would therefore like to see the measures computed for a number of sections for various models and choices of model parameters in order to assess model skills. The value of the SKAGEX dataset as a tool for model improvements is demonstrated. Evidence to support the importance of applying non-oscillatory, gradient preserving advection schemes in areas with sharp density fronts is given. The method is used to identify that the forcing/initial values/boundary values for the temperature field are inferior to the corresponding values for the salinity field. With the present coarse resolution, 11 layers in the vertical, it is shown that it is far from obvious that the quality of the model results improve when replacing simple Richardson number formulations for vertical mixing processes with higher order turbulence closure in the Skagerrak area.     

Interactions of wind and density driven currents in North Sea ROFIs—a model study

Three different versions of a baroclinic three-dimensional circulation model of the North Sea are used to obtain information on the wind and density interactions in the North Sea ROFIs (Regions Of Freshwater Influence): the standard version with fully prognostic treatment of salinity and temperature is compared to a barotropic model run on the same grid on the one hand and to an also fully prognostic model run on a four times coarser grid on the other hand. In order to gain knowledge on the wind and density interactions, two opposing wind directions are chosen for investigation, namely a time of strong north wind, 21st–28th April 1982, and a time of strong southwest wind, 22nd–24th May 1982. In the April case the effect of the salinity gradients on the border of the ROFIs of Rhine, Weser, Ems and Elbe, i.e. along the continental shore, is shown to lead to a clear enhancement of the mean surface currents. In May this result is partly disguised by the additional effect of the thermocline in the deeper parts of the North Sea, i.e. in the classical shelf sea regime region. Nevertheless, the same pattern of enhanced mean surface currents along the coast is detected and is of the same order of magnitude as in the April case. It is thus concluded that although the circulation in the North Sea is reversed by the wind, the density induced component of the general circulation is modified only slightly.     

第三方物流及发展的新趋势

浅析了第三方物流及发展的新趋势.     

砂卵石地层泥水盾构施工技术难点及控制措施分析——以兰州地铁穿黄隧道工程为例

为解决泥水盾构在砂卵石地层掘进过程中所面临的刀盘结构磨损严重、刀盘开口率调节不便、刀具磨损严重、泥水环流系统堵塞以及泥浆管路磨损严重等工程技术难题,针对兰州地铁穿黄隧道工程富水砂卵石地层条件,提出刀盘结构适应性改进措施、刀具磨损控制措施、环流系统改进措施以及泥浆管路磨损控制措施。研究表明： 1）对刀盘结构进行适应性改进,可有效解决砂卵石地层刀盘结构磨损严重和刀盘开口率调节等问题; 2）将边缘单刃滚刀改为双刃滚刀,导流刀改为撕裂刀,可有效增强盾构刀具的耐磨性能,提高盾构的掘进效率; 3）从碎石系统改进和大漂石、卵石处理2个方面对盾构环流系统进行改进,可有效解决盾构环流系统堵塞的问题; 4）将整体泥浆管路分为3段,相邻管路之间用法兰盘连接,可有效解决泥浆管路局部磨损严重的难题。     

基于层次分析法的张家港木材流通中心选址

利用层次分析法,建立了张家港木材流通中心选址问题的结构模型,对流通中心的各备选地址进行了评估,选出最为合适的中心地址,为张家港的木材流通中心选址决策提供了科学依据.     

Hydrological changes in the Mediterranean Sea in relation to changes in the freshwater budget: A numerical modelling study

The response of the Mediterranean Sea and the various sub-basins to changes in the freshwater budget are investigated in a process-oriented study, using the POM model. The model is first integrated using values of the Nile and Ebro rivers runoff, as well as of the Dardanelles freshwater input, typical of the fifties. The model reaches a steady state representative of that existing in the Mediterranean prior to the major damming period after 90 years of integration. Then the model is integrated using the reduced river runoff values typical of the after-damming period. The additional impact of decadal scale trends in the precipitation rate as well as of intense surface cooling periods/events on the thermohaline circulation during the last 40 years were also examined. The model results show that the dramatic reduction of the Nile freshwater input and to a lesser extent the reduction of the freshwater input from the Dardanelles Straits induced a large increase in the sea surface salinity in the Aegean and Levantine basins in the late sixties/early seventies, in agreement with observations. Furthermore, the Ebro runoff reduction during the same period further enhanced the salinity increase in the Levantine basin as higher salinity surface waters of the western basin reached the eastern basin via the Atlantic Water circulation. This saltier surface layer in the vicinity of the Rhodes Gyre favoured the preconditioning for the formation of the Levantine Intermediate Water, resulting in about 40% increase of its formation rate. This in turn resulted in the production of saltier and larger amounts of deep waters in the various deep-water formation sites. According to the model, the river damming and decreased precipitation since the eighties explain about 95% of the observed salinity increase in the Western Mediterranean Deep Water over the last 40 years. The major contributor to this increase was proved to be the Nile damming. The salt increase in the surface layer is proved to be insufficient to produce alone the two climatic transient events in the deep waters of the Eastern Mediterranean in the late sixties and early nineties, respectively. Surface cooling was found to be important, resulting in large deep water formation and thus allowing the propagation of the increased surface salinity signal to the deep layers. However, model results demonstrate that the river damming played an important role in the long-term salt preconditioning of the surface/intermediate layers, thus contributing in triggering the two events.     

温里健脾外敷药袋对家兔血液流变学的影响

将３０只健康家兔随机分为３组：模型组，以高脂饲料喂养；用药组，以相似高脂饲料喂养，同时神阙穴敷以温里健脾药袋；正常组，以常规饲料喂养。３０ｄ后，用旋转筒式粘度计，体外血栓形成仪及酶法测定以上实验动物血液的高切变率（２００ｓ－１）粘度，低切变率（４０ｓ－１）粘度，体外血栓及血清血脂等血液流变学指标。结果表明，温里健脾药袋能降低血液粘度（Ｐ＜０．０５）；减低体外血栓指数（Ｐ＜０．０１）；降低血清总胆固醇量（Ｐ＜０．０１）．提示温里健脾药袋具有活血化瘀功能。     

应用国产心肺机进行犬无肝期静脉转流的可行性研究

本实验阻断肝十二指肠韧带及肝上和肝下下腔静脉,制造犬无肝期模型,在SWAN-GANZ导管的监护下,使用国产心肺机单泵进行门、下腔静脉向颈外静脉的转流,取得了良好的效果。整个转流期间血液动力学指标维持在正常低水平,转流量39ml/kg·min左右,90min的转流对血液成份影响不大,本转流方式可用于临床原位肝移植。     

哈尔滨松花江斜拉桥9#主墩桩基础钻孔施工工艺

主要介绍哈尔滨绕城公路西段松花江特大桥主桥9#主塔桩径2.0m、桩长70m的钻孔桩成孔施工技术。     

钻孔灌注桩反循环工艺探讨

介绍了钻孔灌注桩反循环成孔作业的原理,指出反循环成孔工艺与正循环成孔工艺相比,具有钻进速度和成桩效率提高、孔壁稳定、成孔质量好、混凝土浇筑质量能够得到有效保障等优点。最后介绍了工程实例。