行经非平坦底面浅水孤立波演化的数值模拟

本文研究浅水孤立波行经非平坦底面的演化问题.将变底问题的Boussinesq方程进行改写后,直接应用三次样条理论离散,建立了一种简单且稳定的差分格式,对感兴趣的问题进行了多种数值模拟,对孤立波爬越过斜台阶后的分裂现象的数值结果与文献〔1—3〕的结果十分吻合,说明本文方法的可靠性.除此之外,本文对孤立波越过楔形以及孤立波形凸突底面的情况进行了多种参数的计算,显示出主波后逐渐衰弱的二次波列现象.     

似海底反射的地震速度和AVO效应

我们将浓度和压力作为一个函数得到冰和含气体水合物的地震波速度。同以往以简单的慢度和平均模量及双相模型为基础的理论不同，我们使用了Biot类型的三相理论，这一理论考虑了二种固体（颗粒和冰或笼形物）和一种液体（水）的存在，以及一个含气和水的多孔隙基质。对于固体的Berea砂岩，低于0℃时的纵波理论估计值过低，在含有冰－颗粒相互作用和颗粒胶结时与实验数据产生了好的吻合。严格地讲，水的比例与温度紧密相关。假定已知孔隙的平均半径和标准偏差，那么在一给定温度下的波速拟合就能对整个温度范围的速度进行预测。通过一个粘弹性的单相结构模型来计算反射系数。本文的分析是针对游离气带的顶部（位于含气体水合物的沉积层下）和底部（上履于饱含水的沉积层）进行的。如果似海底反射仅仅是由于胶结气体水合物与含游离气沉积层的分界面造成，我们可以得出结论：（1）在一定的气体饱和度下，很难估算低浓度情况下气体水合物数量。然而，水合物的高、低浓度还是可以区分的，因为它们分别呈现正和负的异常；（2）游离气和饱和度可以从反射振幅中而不是从异常类型中获取；（3）P波转化为S波的反射系数是指示高含量的气体水合物和游离气一个较好指示。另一方面，对于未胶结的沉积物，振幅随偏移距变化曲线总是为正。     

三传感器波浪水槽二次反射主动吸收方法

三传感器波浪水槽二次反射主动吸收方法是加拿大科学院水力中心最近开发的一种水槽反射波控制技术。该法在造波板前 1～ 2倍波长处布置 3个传感器 ,通过入反射波分离方法得到准确的入反射波参数 ,以此调整造波信号 ,有效地吸收由建筑物反射回到造波板的二次反射波。文中在分析波浪水槽二次反射吸收方法研究现状的基础上 ,介绍了加拿大水力中心对现有方法的改进及其效果     

渤、黄海假潮的气象学成因

对渤、黄海14个主要海湾的原始验潮记录进行了分析，从中筛选出水位变化幅度大于或等于50cm的54个假潮个例，着重分析了伴随假潮过程的天气形势，把可能引发假潮的天气形势归纳为4种基本类型。分析结果显示：绝大多数（92％）引发假潮的天气个例都与锋面活动有关；所有个例中低层大气基本上都是弱静力稳定，且都具有较强的垂直风速切变。根据观测事实和稳定度理论分析认为，低层大气的弱静力稳定层结构以及由垂直风速切变引起的剪切不稳定性，是假潮气象学成因的一种必要条件和物理机制。     

南海罗斯贝变形半径的地理及季节变化

根据南海 1°× 1°网格的标准层季节平均温、盐度资料 ,在未引入Boussinesq近似条件下 ,采用改进的Thompson Haskell算法求解线性化斜压海洋水平大尺度波的垂直结构方程 (重力内波方程 ) ,从而得到了南海各网格点的第一斜压重力波相速度和相应的罗斯贝变形半径 ,并探讨其地理分布和季节变化特征 ,以期有助于南海环流和中尺度涡旋以及有关海洋侧边界效应的研究。     

A General Linear Wave Theory for Water Waves Propagating over Uneven Porous Bottoms

Starting from the widespread phenomena of porous bottoms in the near shore region, considering fully the diversity of bottom topography and wave number variation, and including the effect of evanescent modes, a general linear wave theory for water waves propagating over uneven porous bottoms in the near shore region is established by use of Green‘s scond identity. This theory can be reduced to a number of the most typical mild-slope equations curreutly in use and provide a reliable research basis for follow-up development of nonlinear water wave theory involving porous bottoms.     

Mach Effect of Oblique Nonlinear Irregular Waves Interacting with Vertical Walls

Based on Hong‘s theory, previous random models, and a generalized expression suitable for FIT calculation, the interaction between irregular waves and vertical walls is numerically simulated. The results of simulation demonstrate that the wave energy changes with the incidence angle and the distance from the wall. Particularly, the Mach effect and the combined wave spectrum characteristics are analyzed in detail, which are significant in both theory and practice.     

Probabilistic Models for the Probability of Wave Breaking and Whitecap Coverage Based on Kinematic Breaking Criterion

More and more researches show that neither the critical downward acceleration nor the critical slope of water waves is a universal constant. On the contrary, they vary with particular wave conditions. This fact moders the models either for the probability of wave breaking B or for the whitecap coverage W based on these criteria difficult to apply. In this paper and the one which follows we seek to develop models for the prediction of both B and W based on the kinematical criterion. First, several joint probabihstic distribution functions (PDFs) of wave characteristics are derived, based on which the breaking properties B and W are estimated. The estimation is made on the assumption that a wave breaks ff the horizontal velocity of water particles at its crest exceeds the local wave celerity, and whitecapping occurs in regions of fluid where water particles travel faster than the waves. The consequent B and W depend on wave spectral moments of orders 0 to 4.Then the JONSWAP spectrum is used to represent the fetch-limited sea waves in deep water, so as to relate the probahility of wave breaking and the whitecap coverage with wind parameters. To this end, the time-averaging technique proposed by Glazman (1986) is applied to the estimation of the spectral moments involved, and furthermore, the theoretical models are compared with available observations collected from published literature. From the comparison, the averaging time scale is determined. The final models show that the probability of wave breaking as well as the whitecap coverage depends on the dimensionless fetch. The agreement between these models and the database is reasonable.     

城市建设中的地震小区划与浅层地震探测

简要阐述地震小区划在现代城市建设中的重要性以及在实施地震小区划的研究中浅层地震探测的重要作用及其方法原理,并给出应用浅层地震探测在城市地震小区划中的实例。     

一种稳定的AVO分析方法

振幅随偏移距变化（ＡＶＯ）的分析对时左校正非常敏感。用时间穿估计ＡＶ涌减少时差校正的误差，在每个时窗内，在每个时窗内，使用块ＮＭＯ能避免ＮＭＯ拉伸，剩余ＮＭＯ校正通过迭代互相关技术实现，时关 正后，时窗内的数据用偏移距坐标为变量表示的多项式乘常数脉冲来模拟。从而避免了数据从偏移琶角度呈慢度域的转换。用最小平方法求解地震脉冲和多项式系数。这种可分离最小平方问题的多项式系数和脉冲能力分别估计。简化的非