On the growth of disturbances to forced and dissipated barotropic flows     

Jieping Zou  John Fyfe 《地球物理与天体物理流体动力学》2013,107(1-4):41-56

Abstract

We consider the growth of disturbances to large-scale zonally-asymmetric steady states in a truncated spectral model for forced and dissipated barotropic flow. A variant of the energy method is developed to optimize the instantaneous disturbance energy growth rate. The method involves solving a matrix eigenvalue problem amenable to standard numerical techniques. Two applications are discussed. (1) The global stability of a family of steady states is assessed in terms of the Ekman damping coefficient r. It is shown that monotonic global stability (i.e., every disturbances energy monotonically decays to zero) prevails when r≥r_c . (2) Initially fastest-growing disturbances are constructed in the r<r_c regime. Particular attention is paid to a subregion of the r<r_c regime where initially-growing disturbances exist despite stability with respect to normal modes. Nonlinear time-dependent simulations are performed in order to appraise the time evolution of various disturbances.  相似文献   

Optimum design of stone column-improved soft soil using multiobjective optimization technique     

Kousik Deb  Anirban Dhar 《Computers and Geotechnics》2011

A combined simulation–optimization-based methodology is proposed to identify the optimal design parameters for granular bed–stone column-improved soft soil. The methodology combines a finite difference-based simulation model and an evolutionary multiobjective optimization model. A combined simulation–optimization methodology is developed for two different formulations: (a) the minimization of maximum settlement and the minimization of differential settlement subject to stress constraints; (b) the minimization of maximum settlement, the minimization of differential settlement and the maximization of the degree of consolidation subject to stress constraints. The developed methodology is applied to an illustrative system. Different scenarios are evaluated to examine critical field conditions. The solution results show that the modular ratio and the ultimate stress carrying capacity of the stone column are the most important parameters for optimal design. The obtained results also show the potential applicability of the developed methodology.  相似文献   

Optimal design of pumping tests in leaky aquifers for stream depletion analysis     

Steen Christensen  Vitaly A. Zlotnik  Daniel M. Tartakovsky 《Journal of Hydrology》2009,375(3-4):554-565

We analyze the optimal design of a pumping test for estimating hydrogeologic parameters that are subsequently used to predict stream depletion caused by groundwater pumping in a leaky aquifer. A global optimization method is used to identify the test’s optimal duration and the number and locations of observation wells. The objective is to minimize predictive uncertainty (variance) of the estimated stream depletion, which depends on the sensitivities of depletion and drawdown to relevant hydrogeologic parameters. The sensitivities are computed analytically from the solutions of Zlotnik and Tartakovsky [Zlotnik, V.A., Tartakovsky, D.M., 2008. Stream depletion by groundwater pumping in leaky aquifers. ASCE Journal of Hydrologic Engineering 13, 43–50] and the results are presented in a dimensionless form, facilitating their use for planning of pumping test at a variety of sites with similar hydrogeological settings. We show that stream depletion is generally very sensitive to aquitard’s leakage coefficient and stream-bed’s conductance. The optimal number of observation wells is two, their optimal locations are one close to the stream and the other close to the pumping well. We also provide guidelines on the test’s optimal duration and demonstrate that under certain conditions estimation of aquitard’s leakage coefficient and stream-bed’s conductance requires unrealistic test duration and/or signal-to-noise ratio.  相似文献   

Optimizing fixed observational assets in a coastal observatory     

Sergey Frolov  António Baptista  Michael Wilkin 《Continental Shelf Research》2008

Proliferation of coastal observatories necessitates an objective approach to managing of observational assets. In this article, we used our experience in the coastal observatory for the Columbia River estuary and plume to identify and address common problems in managing of fixed observational assets, such as salinity, temperature, and water level sensors attached to pilings and moorings. Specifically, we addressed the following problems: assessing the quality of an existing array, adding stations to an existing array, removing stations from an existing array, validating an array design, and targeting of an array toward data assimilation or monitoring.  相似文献   

雹云成雹机制及最佳催化方案的数值研究     

黄毅梅  李子华等 《河南气象》2001,(3):35-37

应用中科院大气物理研究所建立的三维雹云模式，对河南南阳1999年5月9日一次降雹过程进行了数值模拟，模拟结果表明：云内存在过冷水累积区，冰雹在过冷水累积区长大；使用不同催化方案催化后，均能起到减少地面降雹的作用，但是在雹云形成的不同时间、不同的催化部位和使用不同的催化剂量，其消雹效果不一样，在冰雹形成前于过冷水累积区催化效果最好。  相似文献   

鄂尔多斯周缘地震带地震活动的分期和相关分析   总被引：3，自引：0，他引：3  

杜兴信  张春生 《地震研究》1992,15(2):135-144

利用最优分割法对鄂尔多斯周缘地震带(区)的地震活动进行了分期,并作了相关分析。结果表明,1000年以来汾渭地震带北段可划为4个活跃期,每个活跃期的中心间距约300年,最大地震为7级,天水—陕南地震带(区)近一、二百年的地震活动可分为持续约10年左右的几个地震簇。所有分期中,海原地震带能量释放最大,且最近仍很活跃。汾渭地震带和海原—银川地震带活跃期存在相关现象,且其南段往往先于北段活跃,目前活动水平较低。该带1900年以来地震还有与河套地震带地震相呼应的现象和沿构造带南北迁移的规律。根据分期和相关结果推测,鄂尔多斯周缘各地震带都存在中强地震背景。其中海原—银川地震带近期发生5—6级或更大地震的可能性较大,天水—陕南地震带近期也有发生中强地震的可能。汾渭地震带虽然存在孕育6级以上大震的背景,但近年还不会发生强震。  相似文献   

东海带鱼种群动态管理与最优化开发策略          下载免费PDF全文

薛频  罗秉征 《海洋与湖沼》1993,24(1):72-78

根据1960—1986年东海带鱼春夏汛和冬汛资料,提出了均匀渔捞死亡假设,推导出种群状态更新方程式,并应用状态变量法建立了东海带鱼的随机动态系统模型;在此基础上以随机动态规划理论计算了东海带鱼资源在不稳定补充条件下的最优化开发率和限额捕捞量,并模拟预测了带鱼最优化策略的效应。  相似文献   

北部湾沿岸海区设计波浪的确定     

滕学春  吴秀杰  刘丽惠 《海洋科学进展》1995,(3)

本文基于北部湾沿岸海区多年的实测资料，于不同海区主浪向和次主浪向分别取年极值波高为样本资料．采用Ｐ－Ⅲ型和短期测波资料频率分析方法，分别估算了各海区不同重现期的设计波高，并依据式（１）计算出相应的平均周期。尽管样本资料和估算方法不变，但每次估算的结果互不相同，其差异甚至很大．利用Ｋｏｌｍｏｇｏｒｏｆｆ等适合度方法检验所得的结果，能够准确地判断出沿岸各海区不同重现期的最佳设计波浪。  相似文献   

无氧功实验适宜负荷确定方法的研究     

洪涛  杨善君  郑根发  徐鑫明  范跃 《中国海洋大学学报(自然科学版)》1995,(3)

为更准确的确定自行车无氧实验的适宜负荷，对４３名（１５岁～２１岁）受试者进行了Ｗｉｎｇａｔｅ法无氧功复实验，并对三种间接推算无氧功率适宜负荷的方法进行了比较。结果显示：用直接筛选法确定的适宜负荷与体重、腿围、腿力均高度相关。但与腿力的相关程度最高，与腿围的相关程度次之，与体重的相关程度最低。作者认为，体重、大腿围只能间接的反映腿部力量。用形态系数法和Ｗｉｎｇａｔｅ法确定无氧功率实验适宜负荷时，其准确性易受肌肉质量、训练水平等个体差异的影响。腿力百分比法确定的适宜负有适合于各个项目不同层次的受试者。腿力百分比法会成为一种新的更为准确的无氧功率实验适宜负荷间接确定法。  相似文献   

Ocean wave energy harvesting with a piezoelectric coupled buoy structure     

《Applied Ocean Research》2015

An expedient piezoelectric coupled buoy energy harvester from ocean waves is developed. The harvester is made of several piezoelectric coupled cantilevers attached to a floating buoy structure, which can be easily suspended in the intermediate and deep ocean for energy harvesting. In the buoy structure, a slender cylindrical floater is attached on a large sinker. The energy harvesting process is realized by converting the transverse ocean wave energy to the electrical energy via the piezoelectric patches mounted on the cantilevers fixed on the buoy. A smart design of the buoy structure is developed to increase the energy harvesting efficiency by investigation of the effects of the sizes of the floater and the sinker. A numerical model is presented to calculate the generated electric power from buoy energy harvester. The research findings show that up to 24 W electric power can be generated by the proposed expedient buoy harvester with the length of the piezoelectric cantilevers of 1 m and the length of the buoy of 20 m. The technique proposed in this research can provide an expedient, feasible and stable energy supply from the floating buoy structure.  相似文献