Parameter identification of a compliant nonlinear SDOF system in random ocean waves by reverse MISO method

The determination of the drag and inertia coefficients, which enter into the wave force model given by Morison's equation, is particularly uncertain and difficult when a linear spectral model is used for ocean waves, and the structure is compliant and has nonlinear dynamic response. In this paper, a nonlinear System Identification method, called Reverse Multiple Inputs–Single Output (R–MISO) is applied to identify the hydrodynamic coefficients as well as the nonlinear stiffness parameter for a compliant single-degree-of-freedom system. Four different types of problems have been identified for use in various situations and the R–MISO has been applied to all of them. One of the problems requires iterative solution strategy to identify the parameters. The method has been found to be efficient in predicting the parameters with reasonable accuracy and has the potential for use in the laboratory experiments on compliant nonlinear offshore systems.     

湍流数值模拟中封闭模式应用的局限性

通过对琼州海峡的潮流场特征进行数值模拟，指出了选择不同的特征混合长度表达式对数值模拟结果的影响，表明了基于特征混合长度理论的流封闭模式在近海湍流数值模拟中应用的局限性。     

旋转谱理论探讨

本文应用向量随机过程分解模型对旋转谱作出物理解释;此外,还修改了线性振荡度的定义,导出了极化度、线性振荡度和旋转系数之间的关系式,并讨论了它们与总相干、同相相干、异相相干之间的关系。     

南沙群岛海域水体漫衰减系数Kd(490)的特性研究

对南沙群岛海区水体Kd(490）的特性进行了深入分析和探讨,研究结果表明：Kd（490）的垂直分布与同步测量的海水叶绿素a浓度的垂直分布有很强的相关性;Kd（490）的垂直分布反映出该区域海水存在较强的分层现象,研究中还发现上行辐亮度漫衰减系数KL（490）与Kd（490）垂直变化趋势相当一致,但是以二者达到最大值的深度为界,上层水体的KL（490）值稍大于Kd(490）值,在这一深度以下则相反。     

均匀土质边坡稳定性计算的一种新方法

根据土力学原理 ,推导出一种在不考虑渗流力的情况下 ,确定斜坡临界滑动面和计算斜坡稳定系数的新方法。介绍了该方法在若干土石方工程中的应用实例。     

西太平洋暖池区海—气通量计算分析

用J.Launiaimen和T.Vihma提出的近地面层湍流通量计算方法,对我国在1992年11月至1993年2月TOGA—COARE—IOP实验中所获资料计算处理。得出所在站位的海一气间显效、潜热及动量通量。指出西大平洋暖池海区游热通量与显效通量之比为10.14:1;风速大于8m/s后各通量随风速的变化率明显增加;动量与热量的块体通量系数Cd和Ce,h随风速变化有相似的规律;Monin—Obukhov大气稳定度参数Z/L与△T/U_(10)之间有较好的统计关系。     

Validation and Improvement of Satellite-Derived Surface Solar Radiation over the Northwestern Pacific Ocean

The purpose of this study is to validate and improve satellite-derived downward surface shortwave radiation (DSSR) over the northwestern Pacific Ocean using abundant in situ data. The DSSR derivation model used here assumes that the reduction of solar radiation by clouds is proportional to the product of satellite-measured albedo and a cloud attenuation coefficient. DSSR is calculated from Geostationary Meteorological Satellite-5/Visible Infrared Spin-Scan Radiometer data in 0.05° × 0.05° grids. The authors first compare the satellite DSSR derived with a cloud attenuation coefficient table determined in past research with in situ values. Although the hourly satellite DSSR agrees well with land in situ values in Japan, it has a bias of +13∼+34 W/m² over the ocean and the bias is especially large in the low latitudes. The authors then improve the coefficient table using the ocean in situ data. Usage of the new table successfully reduces the bias of the satellite DSSR over the ocean. The cloud attenuation coefficient for low-albedo cases over the ocean needs to be larger in the low latitudes than past research has indicated. Daily and hourly DSSR can be evaluated from the satellite data with RMS errors of 11–14% and 30–33%, respectively, over a wide region of the ocean by this model. It is also shown that the cloud attenuation coefficient over land needs to be smaller than over the ocean because the effect of the radiation reflected by the land surface cannot be ignored.     

广西沿岸海平面变化的关联维数研究

采用相空间重构和关联维数方法，研究了广西沿岸月平均海平面变化的分形特征，结果表明，相空间重构的延迟时间τ为3△t，当关联维数趋于饱和时，石头埠，北海和龙尾的相空间维数为7，而涠洲岛为9，它们的关联维数平均值平均值分别为6.6507,6.5414,6.7059.     

两参量的海面阻力系数模式的探讨

从风浪的能量平衡方程出发，引进若干风要素与波要素以及波要素之间的定性关系，经演算可导出海面阻力系数（Ｃｐ）或是风速（Ｕ）和波龄（β）或是Ｕ和波高（Ｈ）的函数，然后沿用最小二乘法，终将得出４组１２个回归方程。当β（或β）或Ｈ为某一给定值，惟有Ｕ为唯一参量时，所提各式均可简化为非线性方程：ＣＤ＝ａ＋ｂ，Ｕ＋ｃ．Ｕ＾２；式中ａ，ｂ和ｃ为三个经验系数，就所检验的例子而言，本文的结果与实际的符合前人的为好。