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881.
Wave effect on the ocean circulations through mass transport and wave-induced pumping 总被引:2,自引:0,他引:2
The wave Coriolis-Stokes-Force-modified ocean momentum equations are reviewed in this paper and the wave Stokes transport is pointed out to be part of the ocean circulations. Using the European Centre for Medium-Range Weather Forecasts 40-year reanalysis data (ERA-40 data) and the Simple Ocean Data Assimilation (SODA) version 2.2.4 data, the magnitude of this transport is compared with that of wind-driven Sverdrup transport and a 5-to-10-precent contribution by the wave Stokes transport is found. Both transports are stronger in boreal winter than in summers. The wave effect can be either contribution or cancellation in different seasons. Examination with Kuroshio transport verifies similar seasonal variations. The clarification of the efficient wave boundary condition helps to understand the role of waves in mass transport. It acts as surface wind stress and can be functional down to the bottom of the ageostrophic layer. The pumping velocities resulting from wave-induced stress are zonally distributed and are significant in relatively high latitudes. Further work will focus on the model performance of the wave-stress-changed-boundary and the role of swells in the eastern part of the oceans. 相似文献
882.
Dynamic response analysis of a floating mooring system 总被引:1,自引:0,他引:1
An innovative floating mooring system with two or more independent floating mooring platforms in the middle and one rigid platform on each side is proposed for improving efficiency and safety in shallow water. For this new system, most of collision energy is absorbed through the displacement of floating platforms. In order to illustrate the validity of the system, a series of model tests were conducted at a scale of 1:40. The coupled motion characteristics of the floating mooring platforms were discussed under regular and irregular waves, and the influences of wave direction and other characteristics on dynamic response of the system were analyzed. The results show that the mooring system is safest at 0° of wave incident angle, whereas the most dangerous mooring state occurs at 90° of wave incident angle. Motion responses increase with the increase of wave height, but are not linearly related to changes in wave height. 相似文献
883.
Improvement of pseudo-static method for slope stability analysis 总被引:2,自引:0,他引:2
traditional In this paper, two drawbacks pseudo-static method (vertical of the slice method) in the slope stability evaluation have been studied. First, the sliding mass is divided into vertical slices according to this method, which is irrational to some extent in the seismic design of slope. Second, only peak ground acceleration (PGA) is considered, and the effects of shaking frequency and duration on slope stability are neglected. And then, based on the theory of elastic wave and the summarized geological model, this paper put forwards an improved method of pseudo-method by using the theory of elastic wave and Hilbert-Huang transform. The improved pseudostatic method gives reasonable considerations to the time-frequency effects of seismic wave and its rationality has been verified by the shaking table test. This method can evaluate the safety of a slope, the happening time and the scale of landslides. At the same time, this method also can improve the high accuracy of the evaluation of the safety of the slope. 相似文献
884.
随着世界经济的发展,全球城镇化进程正在以前所未有的速度进行。城镇化带来的耕地占用、生态环境破坏、水资源短缺等问题日益受到关注。快速获取和共享城镇变化信息对于人地关系研究及可持续发展意义重大。借助遥感手段监测城镇变化信息,已经普遍得到应用,目前,多光谱遥感数据是最经济和可行的遥感监测数据源。本文基于多光谱卫星数据,有效利用城镇地区特有的地物光谱特征,建立不同类别城镇信息的提取模式和技术流程。这些可以通过多光谱遥感数据提取的信息包括城镇建成区、水体和绿地等。选择我国东部沿海区域内城镇化进程明显的江苏盐城主城区作为试验点,基于地物光谱特征分析,依据本文建立的城镇化信息提取流程,采用阈值分析和二值化处理方法,实现了盐城市亭湖区主要城镇区2000、2002、2006年三期城镇信息快速提取,使在更大范围内,促进此类信息的快速获取和共享,具有现实意义。 相似文献
885.
Min Wang Wei Wang Benlin He Mingliang Sun Yansheng Yin Lan Liu Wuyuan Zou Xuefei Xu 《中国海洋大学学报(英文版)》2010,9(4):376-380
TiO2 films were formed on metallic titanium substrates by the anodic oxidation method in H2SO4 solution under the 80V D.C.. Phase component and microstructure were characterized by X-ray diffraction (XRD) and scanning
electron microscopy (SEM). Water contact angles on titanium oxide film surface were measured under both dark and sunlight
illumination conditions. Corrosion tests were carried out in seawater under different illumination conditions by electrochemistry
impedance spectrum (EIS) and polarization curves. The result showed that the TiO2 film prepared by the anodic oxidation method was anatase with a uniform structure and without obvious pores or cracks on
its surface. The average water contact angle of the film was 116.4° in dark, in contrast to an angle of 42.7° under the UV
illumination for 2 hours, which demonstrates good hydrophobic property. The anti-corrosion behavior of the TiO2 film was declining with the extended immersion time. Under dark conditions, however, the hydrophobic TiO2 film retarded the water infiltrating into the substrate. The impedance changed slowly and the corrosion current density was
2 orders of magnitude lower than that with the film illuminated by sunlight. All of those mentioned above indicate that the
TiO2 film possesses much better performance under dark condition, and it can be applied as an engineering material under dark
seawater environment. 相似文献
886.
电台中波转播站多建于城市近郊区,由于天线高耸落雷几率高,因而易受雷击干扰。针对建站时原已通过防雷验收的转播站设施在投入使用后依然频遭雷击受损的状况,分析了其防雷系统的内在布设技术问题,认为广播中波转播站原有防雷系统的一些关键技术缺漏是遭雷击受损的主要原因,并从转播站的实际情况出发,提出了转播站防雷设计的几个关键技术问题的解决方法:接地网逐级分流、屏蔽馈线再加设外屏蔽环群技术以及不同的线路、不同系统保护的配合方法等,从而形成广播转播站完整的防雷保护系统框架。 相似文献
887.
888.
利用四川省双流县1965~2008年春季降水、温度资料,分析双流县44年的春季气候变化特征。结果表明:①双流县3~5月降水的变化有1.52年、6.96年、18.36年的主要时间尺度;双流县3~5月温度的变化有10.56年时间尺度。②双流县春季降水的突变发生在20世纪80年代中期,自此以后降水逐渐由多变少;温度的突变发生在20世纪90年代中期,自此以后温度逐渐由偏低变为偏高;降水的突变早于温度的突变。③根据春季降水量和温度的主要时间尺度,估计近期春季降水量可能偏少;近期春季温度总体趋势可能偏高。 相似文献
889.
890.
对大气非线性惯笥重力内波方程组,利用相平面分析法导出了相应的KdV方程。采用直接积分法求出两类有意义的孤立波解,讨论了波解的基本特征,并着重分析了一类奇异孤立波与某些天气系统(如青藏高原500hPa低涡)的可能联系。 相似文献