北部湾单站海流旋转谱分析

本文对北部湾内一个连续7d的海流观测站的资料进行旋转谱分析。结果表明,该海区潮流属于不正规全日潮,全日周期分量的谱能量与半日周期分量的谱能量的比值为1.7。全日周期分量的椭圆主轴方向为341°,且椭圆主轴方向较稳定。整个流场基本上受顺时针旋转流所控制。总的趋势,在低频段海流的北分量自谱能量远比东分量自谱大。东分量谱相对北分量有一个较短的时间滞后,且北分量与东分量相关性较好。分析结果与以往对测站所在海区观测的潮流准调和分析结果相吻合。     

Stability of Temperature and Conductivity Sensors of Argo Profiling Floats

After recalibration of the temperature and conductivity sensors of three Argo profiling floats recovered after operations for four to nine months, the results indicate that the floats basically showed no significant drift, either in temperature or salinity, and adequately fulfilled the accuracy requirement of the Argo project (0.005°C for temperature and 0.01 psu for salinity). Only the third float showed a significant offset in salinity of about −0.02 psu, as expected from comparison between the float data and the shipboard conductivity-temperature-depth data. This offset was caused by the operational error of the PROVOR-type float, in which the surface water was pumped immediately after the launch, fouling the conductivity sensor cell. This revised version was published online in July 2006 with corrections to the Cover Date.     

Experimental Study on Stability of Breakwaters with Penetrating Box Foundations

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A time-dependent numerical model of the mild-slope equation

On the basis of the previous studies, the simplest hyperbolic mild-slope equation has been gained and the linear time-dependent numerical model for the water wave propagation has been established combined with different boundary conditions. Through computing the effective surface displacement and transforming into the real transient wave motion, related wave factors will be calculated. Compared with Lin’s model, analysis shows that calculation stability of the present model is enhanced efficiently, because the truncation errors of this model are only contributed by the dissipation terms, but those of Lin’s model are induced by the convection terms, dissipation terms and source terms. The tests show that the present model succeeds the merit in Lin’s model and the computational program is simpler, the computational time is shorter, and the computational stability is enhanced efficiently. The present model has the capability of simulating transient wave motion by correctly predicting at the speed of wave propagation, which is important for the real-time forecast of the arrival time of surface waves generated in the deep sea. The model is validated against analytical solution for wave diffraction and experimental data for combined wave refraction and diffraction over a submerged elliptic shoal on a slope. Good agreements are obtained. The model can be applied to the theory research an d engineering applications about the wave propagation in a biggish area.     

地震作用对琼州海峡海缆路由区海底稳定性影向的分析

以琼州海峡的北海—临高段海缆路由为例,利用计算对比的方法,分析了地震作用下,路由区3m以浅海底土液化或滑移的可能性,评价了路由区海底的稳定性。结果发现,在地震烈度为Ⅶ度的地震作用下,砂性土海底的地震剪应力平均值(0.86kPa,1.72kPa和2.57kPa)小于砂性土的液化剪应力(1.60kPa,3.20kPa和4.81kPa);粘性土海底的地震剪应力平均值(1.25kPa,2.49kPa和3.74kPa)小于粘性土的抗滑剪应力平均值(4.07kPa,4.61kPa和4.49kPa),路由区海底稳定性良好;在地震烈度为Ⅷ度的地震作用下,砂性土海底的地震剪应力平均值(1.73kPa,3.45kPa和5.12kPa)大于砂性土的液化剪应力;粘性土海底的地震剪应力平均值(2.49kPa,4.98kPa和7.47kPa)除表层外,大于粘性土的抗滑剪应力,路由区海底会发生失稳破坏。     

边坡整体稳定的可靠性分析方法

边坡整体滑动稳定性的可靠性分析是建立在土体具有的抗力大于荷载效应的概率基础上进行设计和校验的。在条分法的基础上推导出了进行边坡稳定可靠性分析的统一极限状态方程 ,将土的容重γ、内摩擦角φ、粘聚力 c作为随机变量 ,当其为非正态分布时 ,进行当量正态化 ,考虑变量相关的情况 ,用简化相关法对随机变量进行统计分析 ,并以 Bishop圆弧滑动法为例 ,用 JC法求解边坡的可靠性指标及失效概率 ,给出计算安全系数和可靠性指标的算法程序。并就影响可靠性指标的因素如抗剪强度指标、变量分布形式、土性参数的变异性等进行了讨论。     

Bowen数和东中国海Bowen数分布

本文讨论Bowen数的意义、功能和计算法。同时,依据多年水文气象实测资料作统计,计算出东中国海的Bo值。其结果绘制成1月至12月的月平均分布图,从而对本海域的Bo分布特点作详细分析介绍。     

On the instability of “folded” equilibria of a flexible nonstretchable thread attached to the satellite in a circular orbit

The author considers a problem of Lyapunov's stability of relative equilibria of a flexible nonstretchable thread attached to the satellite moving in a circular Keplerian orbit in the first approximation. When it is in the position of relative equilibrium, the thread is known to be situated either along the radius vector of the orbit (the radial equilibrium) or along the circular orbit (the tangential equilibrium) and in each case the thread can be in a folded state. The author shows that folded radial equilibria of the thread are always unstable while tangential ones are unstable if the thread is sufficiently short in comparison with the radius of the orbit. The generalized Chetaev functional has been constructed to prove the instability.     

思林水电站通航建筑物高边坡稳定分析和评价

应用ANSYS结构分析软件,模拟了思林水电站通航建筑物高边坡的地形、地质条件以及开挖的过程,建立边坡开挖的有限元计算分析模型,分析边坡在自然状态、分级开挖以及锚杆支护加固等工况下的应力、变形及其整体稳定性.定义单元的局部安全系数,得到了边坡开挖加固后稳定安全系数的分布.根据计算成果,指出现设计加固措施可以保证边坡稳定,无需增加其他工程措施.     

非饱和膨胀土边坡的稳定性分析

为了提高非饱和膨胀土边坡的稳定,采用了土工膜覆盖边坡表面的方法.基于非饱和渗流理论,采用有限元程序对用膜覆盖和不覆盖的边坡分别进行了降雨蒸发干湿循环条件下的数值分析.在计算结果基础上,采用极限平衡法分析了边坡的稳定性.结果表明,用膜覆盖后边坡能长期保持非饱和状态,土体吸力较高,其稳定安全系数明显高于无膜保护的边坡,用复合土工膜覆盖边坡有利于提高非饱和膨胀土边坡的稳定.