土壤非饱和带确定性数值模型研究进展

土壤非饱和带确定性数值模型在农业、环境、工程等领域有着广泛的应用。本文结合土壤非饱和带的单重介质理论、双重介质理论和多相流理论，以及这些理论在实际应用中存在的一些问题，介绍了国外最近十几年来土壤非饱和带确定性数值模型取得的最新进展，并且这些模型中的大部分已经进入了商业应用阶段。     

地磁场模型及在海洋环境中的应用需求研究

地磁场是地球固有的基本物理场,地磁场模型是海洋环境保障的重要信息。分析了对地磁场建模理论、现今具有代表性的主磁场模型、地壳异常模型及其他磁场模型最新研究成果,对照地磁场模型在海洋环境中的应用现状,认为现今地磁场模型的分辨率和精度等技术指标尚未能满足地磁匹配导航和水下目标探测等保障需求。提出要深化海域磁场模型应用需求论证,加强现有海域磁力测量资料的整编,积极开展海域地磁场观测的理论创新、技术创新和方法研究,研发出我国海域高精度高分辨率的地磁场模型。     

海岸带边坡防浪林消浪理论与实验研究

在海岸边坡上种植防浪林是一种新的护岸形式,应用理论分析和模型实验对其进行了初步研究.建立波浪在斜坡上传播的控制方程及边界条件,应用摄动理论求解非线性解,得到了一阶精确解和二阶近似解.在模型实验中,确定几何比尺为 1∶10,选取桧柏树枝作为防浪林模型,根据量纲分析,确定的主要影响因素是海岸边坡坡度、波高、波周期、水深与防浪林树宽.实验结果表明,防浪林宽度与岸坡坡度对消浪效果影响较大.     

赤潮监测网络的数据库建模和系统实现

介绍一个典型的赤潮监测网络的数据库建模和系统实现，重点是数据库的逻辑建模，以及ERA模型在逻辑建模中的应用。在建模过程中，应用了数据库规范化理论，减少了冗余数据，提高了系统的可维护性。最后，简要说明了建立在数据库建模基础上的赤潮监测网络的系统实现。     

最大熵模型在海洋生物适生区预测中的应用

最大熵模型是以最大熵理论为基础的一种物种分布模型。经过十几年的发展,最大熵模型的计算方法不断迭代并趋于稳定,并在陆地生物适生区预测中开展了系统的、成熟的应用。而在海洋环境中,最大熵模型的应用也已经进入到了快速发展的阶段。但是受限于数据量的匮乏,最大熵模型在海洋环境中的应用仍旧需要不断的探索。最大熵模型具有小样本量预测的优势,其相关应用成果为单一物种、生物群落、生物多样性的保护,生物入侵事件的管控和预警,渔业养殖的减耗增效等提供了关键性的数据支撑,同时在海洋古生态学研究、海洋基因资源获取、海洋极端环境生物多样性保护等方面极具发展前景。     

东海带鱼种群动态管理与最优化开发策略

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。     

一类生化反应动力系统极限环的存在唯一性

研究微分方程定性理论的应用,利用定性分析的方法,讨论了一类在生化反应中的动力系统,证明了其极限环的存在性、不存在性及极限环的存在唯一性,从而得到了完整的结果。     

水深可见光遥感方法研究进展

水深测量对于水利、航运、近海工程等具有重要作用。在总结国内外水体遥感测深主要方法和研究进展的基础上,对水深遥感反演中各类模型存在的问题进行了讨论。结果表明:理论解译模型模拟了光在水体内的辐射传输过程,水深反演精度较高,但模型计算需要大量的水体光学参数且计算过程烦琐;半理论半经验模型对理论解译模型进行了简化,所需水体光学参数少且具有较好的精度而被广为应用;统计相关模型通过直接建立遥感图像光谱值和实测水深之间的相关关系而获得水深数据,且计算相对简单,但由于实测水深值与遥感图像光谱值的事实相关性无法保证,使采用该类模型反演的水深结果有时并不理想。提高水深遥感反演精度,必须进一步加强遥感器研究,充分考虑水体中的溶解、悬浮物质等信息干扰,科学构建水深模型和大气校正模型。     

回声模型视角下的蓝色经济系统自适应机制研究

为了深入研究海洋经济的发展问题,结合可持续发展理念,引入蓝色经济系统的概念并对其内涵进行了阐述。在此基础之上,论证了蓝色经济系统具备复杂适应系统的基本特征,应用复杂适应系统理论中的Echo模型,构建了蓝色经济系统的运行模式并分析了其自适应机制,得出了"蓝色经济系统及其子系统可以通过创新机制、学习机制、协调机制及进化机制来实现自适应行为"的结论,为蓝色经济系统的运行构建了理论基础。     

天然气水合物生成数值模拟的DAVIE模型和意义

天然气水合物生成数值模拟是以水合物热力学理论为基础,结合计算机方法来模拟水合物在海底环境下生成和分解、分布和富集的热力学、动力学过程。Davie模型是首个能够预测海洋沉积物中天然气水合物体积和分布的定量模型,它系统地模拟了海底天然气水合物的海洋环境和质量平衡,并将其应用到已知水合物分布地区进行对比,取得了很好的效果。     

A new method for determining threshold in using PGCEVD to calculate return values of typhoon wave height

In using the PGCEVD (Poisson-Gumbel Compound Extreme Value Distribution) model to calculate return values of typhoon wave height, the quantitative selection of the threshold has blocked its application. By analyzing the principle of the threshold selection of PGCEVD model and in combination of the change point statistical methods, this paper proposes a new method for quantitative calculation of the threshold in PGCEVD model. Eleven samples from five engineering points in several coastal waters of Guangdong and Hainan, China, are calculated and analyzed by using PGCEVD model and the traditional Pearson type III distribution (P-Ⅲ) model, respectively. By comparing the results of the two models, it is shown that the new method of selecting the optimal threshold is feasible. PGCEVD model has more stable results than that of P-Ⅲ model and can be used for the return wave height in every direction.     

Estimation of extreme wave heights using GEOSAT measurements

Satellite technology has yielded a large database of global ocean wave heights which may be used for engineering applications. However, the sampling protocol used by the satellite leads to some difficulties in making use of these data for practical applications. These difficulties and techniques to estimate extreme wave heights using satellite measurements are discussed. Significant wave heights for a 50-year return period are estimated using GEOSAT measurements for several regions around North America. Techniques described here may be used for estimation of wave heights associated with any specified return interval in regions where buoy data are not readily available.     

Kinematics of extreme waves in deep water

The velocity profiles under crest of a total of 62 different steep wave events in deep water are measured in laboratory using particle image velocimetry. The waves take place in the leading unsteady part of a wave train, focusing wave fields and random wave series. Complementary fully nonlinear theoretical/numerical wave computations are performed. The experimental velocities have been put on a nondimensional form in the following way: from the wave record (at a fixed point) the (local) trough-to-trough period, T_TT and the maximal elevation above mean water level, η_m of an individual steep wave event are identified. The local wavenumber, k and an estimate of the wave slope, ε are evaluated from ω²/(gk)=1+ε², where ω=2π/T_TT and g denotes the acceleration of gravity. A reference fluid velocity, is then defined. Deep water waves with a fluid velocity up to 75% of the estimated wave speed are measured. The corresponding kη_m is 0.62. A strong collapse of the nondimensional experimental velocity profiles is found. This is also true with the fully nonlinear computations of transient waves. There is excellent agreement between the present measurements and previously published Laser Doppler Anemometry data. A surprising result, obtained by comparison, is that the nondimensional experimental velocities fit with the exponential profile, i.e. e^ky, y the vertical coordinate, with y=0 in the mean water level.     

波高的长期极值统计分布

通过对国内外常用的４种极值波高分布模式的拟合与比较,得到了以下结论：（１）由于地区差异,港口工程技术规范给出的一单一模式并非具有普遍性,对同一工程应该采用多种理论分布进行计算比较,从中选择最佳模式。（２）应用麦奎尔特法拟合Ｗｅｉｂｕｌｌ分布实现了对未知参数的一举寻优,解的收敛速度快,结果稳定且精度高。同时对其它几种分布实现了资料的微机化处理;（３）本文算例用４种极值分布对不同重视值波高进行了比较,     

双峰谱型海浪的波高和周期分布

本文利用收集到的实测双峰谱型海浪过程资料，把这些资料以波高和周期的相关系数为参数分成５组，讨论每组双峰谱型下被高、周期的统计分布．并探讨了相关系数对波高分布和周期分布的影响。     

Numerical Simulation of Extreme Sea Levels Using Location Specific High Resolution Model for Gujarat Coast of India

Although the frequency of tropical cyclones is less in the Arabian sea compared to that of the Bay of Bengal, there are several severe tropical cyclones which caused extensive damage along the Gujarat coast. In view of the high tidal range in the funnel-shaped gulfs of the Khambhat and the Kachch, it is very useful to study the surge response in these regions. There is always a possibility of abnormal rise of sea level when the occurrence of surge coincides with high tide, which may eventually cause inundation of vast stretches of shallow coastal areas. In view of this, a location specific fine resolution model is developed for the Gujarat coast. The east-west and north-south grid distances for the model are 5.1 km and 5.2 km, respectively. Several numerical experiments are carried out to compute the extreme sea levels using the wind stress forcings representative of 1982, 1996, and 1998 cyclones, which crossed this region. The model-computed extreme sea levels are in good agreement with the available observations.     

Analysis of the extreme wave elevation due to second-order diffraction around a vertical cylinder

Statistical analysis of nonlinear random waves is important in coastal and ocean engineering. One approach for modeling nonlinear waves is second-order random wave theory, which involves sum- and difference-frequency interactions between wave components. The probability distribution of the non-Gaussian surface elevation can be solved using a technique developed by Kac and Siegert [21]. The wave field can be significantly modified by wave diffraction due to a structure, and the nonlinear diffracted wave elevation can be of interest in certain applications, such as the airgap prediction for an offshore structure. This paper investigates the wave statistics due to second-order diffraction, motivated by the scarcity of prior research. The crossing rate approach is used to evaluate the extreme wave elevation over a specified duration. The application is a bottom-supported cylindrical structure, for which semi-analytical solutions for the second-order transfer functions are available. A new efficient statistical method is developed to allow the distribution of the diffracted wave elevation to be obtained exactly, accounting for the statistical dependency between the linear, sum-frequency and difference-frequency components. Moreover, refinements are proposed to improve the efficiency for computing the free surface integral. The case study yields insights into the problem. In particular, the second-order nonlinearity is found to significantly amplify the extreme wave elevation, especially in the upstream region; conversely, the extreme elevation at an oblique location downstream is attenuated due to sheltering effects. The statistical dependency between the linear and sum-frequency components is also shown to be important for the extreme wave statistics.     

Extreme Sea Levels Associated With Severe Tropical Cyclones Hitting Orissa Coast of India

Extreme sea levels associated with severe cyclonic storms are common occurrences along the east coast of India. The coastal districts of Orissa have experienced major surges in the past. The recent Paradip super cyclone is one of the most severe cyclones, causing extensive damage to property and loss of lives. Extreme sea levels are major causes for coastal flooding in this region. Damages can be minimized if the extreme sea levels are forecast well in advance. In the present study, we develop a location specific, fine resolution model for the Orissa coast on the lines similar to that of IIT-D storm surge model (Dube et al. 1994). The model runs on a personal computer. The bathymetry for the model is extracted from very fine resolution naval hydrographic charts for the region extending from the south of Orissa to south of West Bengal. A simple drying scheme has also been included in the model in order to avoid the exposure of land near the coast due to strong negative sea surface elevations. An attempt was made in this study to simulate extreme sea levels along the Orissa coast using the data of past severe cyclones. The model results reported in the present study are in good agreement with available observations or estimates.     

海湾区海水中的溶存甲烷 Ⅰ.分布特征及成因

本文基于日本东京湾、伊势湾和浜名湖的调查资料，详细地讨论了海湾区海水中溶存甲烷的分布特征、成因及其来源。溶存甲烷在海湾中的分布主要受物理混合过程所控制；由河流携入和沉积物中产生是海湾区海水中溶存甲烷的两个主要来源。     

On the parametric resonance of container ships

This work deals with parametric resonance which poses a great danger especially for container ships sailing in following or head seas. Important parameters that are effective in roll resonance are pointed out. For this purpose, a containership is taken as an example to analyze its stability in longitudinal waves based on the method worked out by American Bureau of Shipping (ABS). Unfavorable sailing conditions such as heading and speed, which directly depend on the environmental conditions, have been determined for this particular ship. These conditions may be reported to the master to guide him to keep his ship out of parametric resonance zones. Numerical details of the procedure have been worked out and provided as well.