排序方式： 共有55条查询结果，搜索用时 406 毫秒
31.
基于人工沙坝影响波浪破碎的理论分析,采用极端高水位、设计高水位和0.00m水位下的极限波高作为入射波,对近岸人工沙坝进行了模拟试验,研究波浪动力对人工沙坝剖面的变形及其对岸滩养护的影响。结果表明:坝顶水深和沙坝高度之比h/d决定沙坝的稳定性,h/d较小时,沙坝能接近稳定;沙坝的变形与坝前波浪破碎有关,可用坝顶水深和临界水深之比h/hb判定波浪在沙坝上的破碎;近岸人工沙坝使波浪提前破碎,滩肩拓宽,使泥沙向岸输移大于向海输移,减小岸滩侵蚀区域,增大淤积范围。 相似文献
32.
近年来北部湾沿岸产业的快速发展对海湾特别是潮间带的生态环境造成一定的污染压力。双壳类动物对重金属有极强的富集能力,其体内的重金属含量是海洋污染监测的重要指标。根据2011年春季北部湾潮间带的波纹巴非蛤(Paphia undulata)软组织中7种重金属(Hg、Cd、Pb、Cr、Cu、Zn、As)的测定结果,分析该区域蛤体内重金属的空间分布特征。通过计算单因子标准指数(Pi)、金属污染指数(MPI)、生物-沉积物积累因子(BSAF)、重金属周最大理论摄入量(TMWI),评价波纹巴非蛤对沉积物中重金属的积累特征、生物质量及食用风险。研究表明,波纹巴非蛤体软组织中重金属污染总体水平不高,但站位间差异明显;该生物对沉积物中不同种类重金属的积累能力不同,对Cd、Hg、Zn的积累能力高于Pb、Cr、Cu、As;计算得到的各种重金属周最大理论摄入量(TMWI)均远低于食品添加剂联合专家委员会(JECFA)规定的相应限值,造成食用风险的可能性较低。 相似文献
33.
后弯管式波力发电装置作为一种漂浮式振荡水柱式装置,具有可靠性强、安装维护方便、工作地点灵活的特点。本文在前人研究基础上,以10kW级后弯管式漂浮型发电装置为研究对象,以装置的水动力学性能为主要研究内容,以气室内相对波高作为主要表征参数,通过断面水槽水工物理模型试验,考察了气室内水柱振荡幅度与入射波波高和入射波周期之间的关系,分析了气室完全开敞、输气管添加负载以及弯管横管长度对气室内水柱振荡的影响,为进一步的大功率装置设计与试验提供了理论依据。 相似文献
34.
烟台市地热资源主要分布在北纬37°15′以北的花岗岩地区断裂构造带交会部位,多属断裂构造控制的对流型中低温地热田。烟台市现有地热井24口,均属热水型,其温度范围26～87℃,主要用于洗浴、养殖、采暖、娱乐4个方面。通过对地热资源的勘查开发利用现状和开发中存在的问题分析研究,进而提出地热资源勘查开发利用的远景规划。 相似文献
35.
Interdecadal changes in the storm track activity over the North Pacific and North Atlantic 总被引：4，自引：1，他引：3
Sun-Seon Lee June-Yi Lee Bin Wang Kyung-Ja Ha Ki-Young Heo Fei-Fei Jin David M. Straus Jagadish Shukla 《Climate Dynamics》2012,39(1-2):313-327
Analysis of NCEP-NCAR I reanalysis data of 1948–2009 and ECMWF ERA-40 reanalysis data of 1958–2001 reveals several significant interdecadal changes in the storm track activity and mean flow-transient eddy interaction in the extratropics of Northern Hemisphere. First, the most remarkable transition in the North Pacific storm track (PST) and the North Atlantic storm track (AST) activities during the boreal cold season (from November to March) occurred around early-to-mid 1970s with the characteristics of global intensification that has been noticed in previous studies. Second, the PST activity in midwinter underwent decadal change from a weak regime in the early 1980s to a strong regime in the late 1980s. Third, during recent decade, the PST intensity has been enhanced in early spring whereas the AST intensity has been weakened in midwinter. Finally, interdecadal change has been also noted in the relationship between the PST and AST activities and between the storm track activity and climate indices. The variability of storm track activity is well correlated with the Pacific Decadal Oscillation and North Atlantic Oscillation prior to the early 1980s, but this relationship has disappeared afterward and a significant linkage between the PST and AST activity has also been decoupled. For a better understanding of the mid-1970s’ shift in storm track activity and mean flow-transient eddy interaction, further investigation is made by analyzing local barotropic and baroclinic energetics. The intensification of global storm track activity after the mid-1970s is mainly associated with the enhancement of mean meridional temperature gradient resulting in favorable condition for baroclinic eddy growth. Consistent with the change in storm track activity, the baroclinic energy conversion is significantly increased in the North Pacific and North Atlantic. The intensification of the PST and AST activity, in turn, helps to reinforce the changes in the middle-to-upper tropospheric circulation but acts to interfere with the changes in the low-tropospheric temperature field. 相似文献
36.
A numerical ensemble-mean approach was employed to solve a nonlinear barotropic model with stochastic basic flows to analyze the nonlinear effects in the formation of the North Atlantic Oscillation (NAO). The nonlinear response to external forcing was more similar to the NAO mode than the linear response was, indicating the importance of nonlinearity. With increasing external forcing and enhanced low-frequency anomalies, the effect of nonlinearity increased. Therefore, for strong NAO events, nonlinearity should be considered. 相似文献
37.
Simulation of state-dependent high-frequency atmospheric variability associated with ENSO 总被引：1，自引：1，他引：0
Jong-Seong Kug K. P. Sooraj Daehyun Kim In-Sik Kang Fei-Fei Jin Yukari N. Takayabu Masahide Kimoto 《Climate Dynamics》2009,32(5):635-648
High-frequency atmospheric variability depends on the phase of El Nino/Southern Oscillation (ENSO). Recently, there is increasing
evidence that state-dependent high-frequency atmospheric variability significantly modulates ENSO characteristics. Hence,
in this study, we examine the model simulations of high-frequency atmospheric variability and, further, its dependency on
the El Nino phase, using atmospheric and coupled GCMs (AGCM and CGCM). We use two versions of physical packages here—with
and without convective momentum transport (CMT)—in both models. We found that the CMT simulation gives rise to a large climatological
zonal wind difference over the Pacific. Also, both the climate models show a significantly improved performance in simulating
the state-dependent noise when the CMT parameterization is implemented. We demonstrate that the better simulation of the state-dependent
noise results from a better representation of anomalous, as well as climatological, zonal wind. Our further comparisons between
the simulations, demonstrates that low-frequency wind is a crucial factor in determining the state-dependency of high-frequency
wind variability. Therefore, it is suggested that the so-called state-dependent noise is directly induced by the low-frequency
wind anomaly, which is caused by SST associated with ENSO. 相似文献
38.
Jong-Seong Kug Fei-Fei Jin Juhyun Park Hong-Li Ren In-Sik Kang 《Climate Dynamics》2010,35(6):1011-1026
In this study, scale interaction between synoptic eddies and low-frequency flow is investigated. It is demonstrated here that
there is a general rule, the “left-hand rule”, that describes synoptic eddy feedback onto low-frequency flow. The rule is
that low-frequency anomalies systematically stir and deform the transient eddies in such a way that the irrotational eddy-vorticity
fluxes are directed preferentially about 90° toward the left-hand side of the low-frequency flow; thus this eddy feedback
plays a positive role in maintaining and prolonging low-frequency flow under the stormy atmosphere. Similarly, we show that
the irrotational eddy-temperature and moisture fluxes are also directed preferentially about 90° toward the left-hand side
of the low-frequency flow in the northern hemisphere. The eddy-temperature fluxes and their vertical structure play a positive
role in reinforcing the low-frequency flow in the low levels. The moisture fluxes play a role in enhancing low-frequency flow
by providing eddy-induced moisture convergence and divergence. 相似文献
39.
海底输油管线是海洋油气田开发的生命线工程,在复杂的海洋环境中易发生破坏.为使管线实现自埋防护,提出用柔性材料代替刚性导流板安装在管线顶部,不仅可以增加阻水面积,加大冲刷深度和范围,而且可以减缓刚性导流板对管线上部水流的扰动强度和尾流涡旋的扰动强度,减小管线的振动.利用力学关系由变形方程推导出海底管线与海底间距离为零以及不为零情况下柔性导流板变形的二次曲面方程和自由端最大挠度.在单向流条件下将不同材料不同长度的柔性导流板安装在管线中轴上方开展试验研究,测量柔性导流板在水流作用下的变形曲面.对比分析利用公式计算柔性导流板的自由端最大挠度和曲面变形数据与试验结果,发现两者吻合较好. 相似文献
40.
针对管线绕流剪切层区的水流特征,利用射流分析的类似方法,通过简化控制方程,从理论上探讨了剪切层区的时均速度分布规律。物理试验中采用ADV测速仪对回流区流场进行了测量,对各流区流速和紊动强度变化趋势进行了讨论,并将试验结果与理论推导进行对比,二者基本吻合,为进一步研究海底管线防护措施提供了理论依据。 相似文献