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本文以水面驳船的升沉和横荡运动作为立管上端的激励条件,选用“皮尔逊-莫斯科维奇”海浪谱,立管上的流体动力用Morison方程估算。立管上端与驳船连接处允许任意弹性旋转固定。用有限元法进行空间域离散,并用中心差分法进行了系统时域模拟。 相似文献
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Based on a typical one-free-degree ship roll motion equation, the cusp catastrophe model is built including the bifurca- tion set equation, splitting factor 'u' and regular factor 'v', where both 'u' and 'v' are further expressed with typical flooded ship parameters. Then, the roll catastrophe mechanism is analyzed mainly by means of 'u', under the given parameters of a typical trawler boat. The aim of this research is to reveal the mutagenic mechanism of the roll stability and provide a reference for improving ship roll stability. 相似文献
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Suppression of Chaos in a Bose-Einstein Condensate Loaded into a Moving Optical Superlattice Potential
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We have shown that the application of modulating the secondary lattice is an efficient route to suppressing the generation of chaotic traveling waves of a Bose-Einstein Condensate with attractive interatomic interaction loaded into a moving optical superlattiee consisting of two lattices. With the Melnikov method, we obtain the optimal value of the relative phase between the two lattice harmonics for the control of chaos. We also find that the regularization route as the potential depth of the secondary lattice is varied and fairly rich, including the period-doubling bifurcations. 相似文献
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黄振华 《应用数学和力学(英文版)》2007,28(9):1153-1162
The interactions between regular surface waves and a surface-pitching slotted barrier are investigated both analytically and experimentally.A quasi-linear theory is developed using the eigenfunction expansion method.The energy dissipation within the barriers is modeled by a quadratic friction factor,and an equivalent linear dissipation coefficient,which is depth-varying,wave-height dependent,is introduced to linearize the matching condition at the surface-pitching barrier.By comparing the theoretical results with laboratory experiments,it is shown that the present method can satisfactorily predict the variation of the reflection and transmission coefficients with wave height. 相似文献
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针对从高频地波雷达海洋回波多普勒谱反演海浪参数的非线性积分方程,采用线性化近似可以转化为线性积分方程,类似于第一类Fredholm积分方程.文中采用数值方法将线性积分方程转化为二次型最优化问题,并采用共轭梯度法来求解.针对海浪参数的非负先验特性,在迭代过程中,加入非负约束项对共轭梯度法进行了改进.在单部雷达和双部雷达情况下进行正演数值模拟,然后用模拟数据添加不同信噪比的随机噪声进行海浪参数反演,无论是单峰海浪谱还是有两个传播方向的双峰谱反演结果均表明了本文提出的算法在不同信噪比下的有效性. 相似文献
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为了研究随机起伏海面的散射对水声信道特性的影响,以及不同信道估计算法在该信道条件下的性能问题,该文从利用Monte Carlo方法模拟的基于PM海浪谱的二维随机起伏海面出发,提取了与风向不同夹角的一维随机起伏海面,并利用Kirchhoff近似法计算了其散射强度。将得到的声散射特性和海面环境信息融入到信道模型中,建立了基于PM海浪谱的随机信道模型。通过仿真分析了不同风速、传播距离条件下,声波的传播损失和信道冲激响应变化,并利用l_0-最小均方误差法、匹配追踪算法和正交匹配追踪算法进行了信道估计。给出了不同环境条件下,三种算法估计性能的综合比较结果,验证了算法针对该信道模型的有效性。 相似文献
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海面波浪对光线的扰动以及海水对光的吸收和散射对水下对空成像有重大影响。建立了水下对空成像的光学计算模型,采用基于PM谱的海浪模型和基于小角度散射理论的水下辐射场传输模型,利用光线追迹分析波浪对光线的扰动,得到了像面照度的分布。仿真结果的分析表明,像面上的照度由视场中心向边缘递减,并随成像深度增加按指数衰减,海浪对图像的破坏程度在消光边界附近最大。 相似文献