Moments of inertia and the Chandlerian period for two-and three-layer models of the Galilean satellite Io     

V. N. Zharkov  A. L. Sobisevich 《Astronomy Letters》2005,31(3):205-212

We consider two-layer (Fe-FeS core+silicate mantle) and three-layer (Fe-FeS core+silicate mantle+crust) models of the Galilean satellite Io. Two parameters are known from observations for the equilibrium figure of the satellite, the mean density ρ₀ and the Love number k₂. Previously, the Radau-Darwin formula was used to determine the mean moment of inertia. Using formulas of the Figure Theory, we calculated the principal moments of inertia A, B, and C and the mean moment of inertia I for the two-and three-layer models of Io using ρ₀ and k₂ as the boundary conditions. We concluded that when modeling the internal structure of Io, it is better to use the observed value of k₂ than the moment of inertia I derived from k₂ using the Radau-Darwin formula. For the models under consideration, we calculated the Chandlerian wobble periods of Io. For the three-layer model, this period is approximately 460 days.  相似文献   

Potential impact of climate change on aquatic insects: A sensitivity analysis for European caddisflies (Trichoptera) based on distribution patterns and ecological preferences   总被引：1，自引：1，他引：0  

Daniel Hering  Astrid Schmidt-Kloiber  John Murphy  Sofie Lücke  Carmen Zamora-Muñoz  Manuel Jesús López-Rodríguez  Thomas Huber  Wolfram Graf 《Aquatic Sciences - Research Across Boundaries》2009,71(1):3-14

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荆江三口分流变化及三峡水库蓄水影响          下载免费PDF全文

朱玲玲  许全喜  戴明龙 《水科学进展》2016,27(6):822-831

长江中游荆江的水沙通过三口洪道分流入洞庭湖,三口分流是荆江-洞庭湖关系调整的驱动因子,为揭示其变化特征及三峡工程运用的影响,基于大量的原观数据,系统研究了近60年三口分流比的变化过程,提出其显著调整特征及诱发因素,引入径流还原计算方法,量化了三峡水库不同运用方式对三口分流量的影响幅度。结果表明:①特大洪水及重大人类活动等诱发因素作用下,三口分流比出现4~5年持续性减小的趋势调整期,之后进入分流比稳定恢复的平衡调整期;②2003-2014年,三峡水库汛前枯水补偿调度使得三口分流量年均增加8.000亿m3,汛后蓄水使得三口分流量年均减小29.00亿m3,对三口分流综合影响量为年均减少21.00亿m3,占同期三口年均分流量的4.29%。  相似文献   

A spatial cross‐correlation model of spectral accelerations at multiple periods     

Christophe Loth  Jack W. Baker 《地震工程与结构动力学》2013,42(3):397-417

Many seismic loss problems (such as disruption of distributed infrastructure and losses to portfolios of structures) are dependent upon the regional distribution of ground‐motion intensity, rather than intensity at only a single site. Quantifying ground‐motion over a spatially‐distributed region therefore requires information on the correlation between the ground‐motion intensities at different sites during a single event. The focus of the present study is to assess the spatial correlation between ground‐motion spectral accelerations at different periods. Ground motions from eight well‐recorded earthquakes were used to study the spatial correlations. On the basis of obtained empirical correlation estimates, we propose a geostatistics‐based method to formulate a predictive model that is suitable for simulation of spectral accelerations at multiple sites and multiple periods, in the case of crustal earthquakes in active seismic regions. While the calibration of this model and investigation of its implications were somewhat complex, the model itself is very simple to use for making correlation predictions. A user only needs to evaluate a simple equation relying on three sets of coefficients provided here to compute a correlation coefficient for spectral values at two periods and at a specified separation distance. These results may then be used in evaluating the seismic risk of portfolios of structures with differing fundamental periods. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

半封闭海湾固有振动周期的数值计算     

王钟Jun  龙宝森 《海岸工程》1998,17(4):1-4

用二维数值模式,根据芝罘湾的实测水深和形状,计算了该湾的固有振动周期,与实测资料吻合较好。计算结果同时给出了当节点N=1,2,...,6时,湾内的振幅分布（合波长、波节线分布）,以及纵振动和横振动分布情况。  相似文献   

极值波高与历时联合分布的重现水平分析     

陈子燊  位帅 《海洋通报》2020,39(5):530-535

使用美国北卡罗来纳州的 FRF 1985—2016 年的极值波高及其持续时间数据，采用最优的 Gumbel-Hougaard copula函数和 Kendall 分布函数构建极值波高和相应历时不同组合的联合概率分布模式，分析各个组合的遭遇概率、“或”重现期、“且”重现期和 Kendall 重现期，以出现最大可能概率的方法推算各组合联合设计值。结果表明：Kendall 重现期所对应的累积频率更准确地代表了特定设计频率下的风险率；重现期分别为 5 年、10 年、20 年、50 年、100 年、200 年推算的 Kendall重现期设计值介于“或”重现期和“且”重现期设计值之间，小于相应的边缘分布设计值；基于 Kendall 重现期的极值波高及其持续时间不同重现期组合推算的结果可为海洋工程构筑物设计与风险管理提供新的选择与参考。  相似文献   

重现期高潮位在广西全日潮岸段警戒潮位核定等应用中的局限性分析     

姜绍材  黄子眉 《海洋预报》2020,37(1):28-32

对广西沿海各验潮站重现期高潮位进行了计算,通过分析传统重现期高潮位计算方法发现该局限性主要为广西全日潮潮汐性质下天文潮与风暴增水叠加概率过低和广西沿海堤防标准普遍偏低所致。根据不同岸线类型,结合海堤实际防御能力、海洋灾害承灾体和风险区划,提出适用于广西的红色警戒潮位核定新方法,对其它全日潮岸段警戒潮位核定和防潮应急管理等提供新的思路。  相似文献   

基于多元分布函数的区域洪水频率分析          下载免费PDF全文

卢韦伟  陈璐  周建中  陈华 《水文》2015,35(5):6-10

极端洪水事件的频率分析往往局限于单个站点,当研究区域内包含多个水文站点时,单变量频率分析方法,会导致低估或高估洪灾风险率。因此,需要进行区域频率分析。传统区域重现期计算方法,同一重现期对应多种设计洪水组合,而基于Kendall分布函数的重现期计算方法(KRP)有效的解决了这一问题。故本文引入三维非对称Copula分布函数拟合区域内各个站点年最大流量的相关关系,利用半参数法估计Copula函数的参数,并采用KRP推求区域洪水发生的重现期。结果表明:区域发生T年一遇的洪水概率远远大于单个站点发生T年一遇的洪水概率;KRP克服了实测序列较短的问题,且能准确估算洪水重现期。本研究为防洪部门制定防洪措施提供一定的科学依据。  相似文献   

历史时期伊犁河谷文化遗址时空特征及驱动力分析   总被引：3，自引：2，他引：1  

王芳  张小雷  杨兆萍  栾福明  熊黑钢  王昭国  时卉 《地理学报》2015,70(5)

运用Arc GIS软件对伊犁河谷文化遗址时空分布进行分析,探讨了遗址时空演变特征与人文历史、自然环境的关系。结果表明:1从夏—西周到清—近现代6个时期中,遗址数量及在总数中的比重、出现频率呈倒"V"型变化,从萌芽阶段到巅峰阶段,至衰落阶段。2遗址的空间分布格局由前3个时期的"东高西低"转变为后3个时期的"西高东低",人类活动空间重心发生了转移。3遗址主要分布在1~5级坡度上,其比重由春秋—秦时期的75%增至清—近现代时期的93.75%;而遗址集中分布高程则由春秋—秦和西汉—南北朝时期的4~8级转移到后3个时期的1~4级,且其数量表现出明显的从高海拔的山地丘陵向低海拔平原、从高坡度向低坡度转移。4研究区遗址演变模式与典型干旱区遗址迁移模式相反,表现为特殊的"中上游→下游"迁移的"湿润模式"。5研究区文化遗址分布、时空演变受政治、经济、生产力等人文因素和地貌、海拔、坡度、气候等自然因素的综合影响。由于其气候湿润,水资源丰富,虽然遗址分布和演变表现出一定的河谷谷地、阶地、平原、水资源等"自然因素"指向性规律,但更突出表现为生产力水平、政治稳定、经济发展、商贸交通等"人文力量"指向性规律,这一点在中后期表现得更为明显。  相似文献   

Changes to flood peaks of a mountain river: implications for analysis of the 2013 flood in the Upper Bow River,Canada          下载免费PDF全文

Paul H. Whitfield  John W. Pomeroy 《水文研究》2016,30(25):4657-4673

The mountain headwater Bow River at Banff, Alberta, Canada, was subject to a large flood in June 2013, over which considerable debate has ensued regarding its probability of occurrence. It is therefore instructive to consider what information long‐term streamflow discharge records provide about environmental change in the Upper Bow River basin above Banff. Though protected as part of Banff National Park, since 1885, the basin has experienced considerable climate and land cover changes, each of which has the potential to impact observations, and hence the interpretations of flood probability. The Bow River at Banff hydrometric station is one of Canada's longest‐operating reference hydrological basin network stations and so has great value for assessing changes in flow regime over time. Furthermore, the station measures a river that provides an extremely important water supply for Calgary and irrigation district downstream and so is of great interest for assessing regional water security. These records were examined for changes in several flood attributes and to determine whether flow changes may have been related to landscape change within the basin as caused by forest fires, conversion from grasslands to forest with fire suppression, and regional climate variations and/or trends. Floods in the Upper Bow River are generated by both snowmelt and rain‐on‐snow (ROS) events, the latter type which include flood events generated by spatially and temporally large storms such as occurred in 2013. The two types of floods also have different frequency characteristics. Snowmelt and ROS flood attributes were not correlated significantly with any climate index or with burned area except that snowmelt event duration correlated negatively to the Pacific Decadal Oscillation. While there is a significant negative trend in all floods over the past 100 years, when separated based on generating process, neither snowmelt floods nor large ROS floods associated with mesoscale storms show any trends over time. Despite extensive changes to the landscape of the basin and in within the climate system, the flood regime remains unchanged, something identified at smaller scales in the region but never at larger scales. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献