Hydrodynamic numerical modelling of storm surges — Application to the Bay of Bengal

A hydrodynamic numerical model and a tide-surge interaction model are described for the evaluation of storm surges and their interaction with the tides in the Bay of Bengal. Numerical experiments are performed with the help of these models to simulate the surges generated by three recent severe cyclonic storms which struck the east coast of India and Bangladesh. The predicted peak sea-surface elevations compare well with the limited observed values.     

Storm surges in the Bay of Bengal

In this paper, the scaling of the shallow water equations in terms of the speed of a cyclone moving over a basin, and another velocity related to basin characteristics is reported. The zero-order equations for which numerical solutions were obtained earlier are described. For a basin of uniform depth, an analytical solution has been obtained for the zero-order equations. The solution suggests that, in the initial stages, the divergence of the wind stress is more important than the curl of the wind stress. In subsequent stages, the curl becomes more important. It is also shown that the basin does not respond to a cyclone until a certain time has elapsed. The adjustment time depends on the storm speed, and is inversely proportional to the square-root of the basin depth.     

杭州湾、浙江沿海一带风暴潮数值预报研究

分析了风暴潮的特点、成灾、危害,介绍了杭州湾风暴潮的重大影响,在Visual Studio 2010平台下,采用C++编程语言开发了二维并行数值预报的可视化软件.通过输入计算域的水深数据及每6h变化的台风参数实现风暴潮数值计算,在界面上直观地显示台风的移动路径和伴随着台风移动整个计算域的增水时历过程,同时同步显示所选验潮站的风暴潮增水时历曲线和移行台风风速大小、方向时历曲线.结合杭州湾的实际地形,将计算域进行了粗网格、二分之一网格细化和四分之一网格细化三种划分,选取5612号、7708号台风和2012年的Damrey、Haikui台风,分别对粗网格和两种细网格区域进行计算.还将5612号、7708号台风的计算结果与验潮站的实测数据进行比对.结果表明,网格的粗细对计算结果的影响不大,但对比实测数据后发现网格越粗计算结果与实测潮位数据的吻合性就越好.     

A Transformed Coordinates Shallow Water Model for the Head of the Bay of Bengal Using Boundary-Fitted Curvilinear Grids

The Bay of Bengal is surrounded by coastline except to the south, where there is open sea. The coastline bends most sharply along the coast of Bangladesh, and there are many small and large islands in the offshore region there. In order to incorporate the island boundaries and the curved coastline properly, in any numerical scheme it is often necessary to consider a very fine grid resolution along the coastal belts whereas this is unnecessary away from the coasts. However, a very fine resolution involves more memory and more CPU time in the numerical solution process, and invites numerical instability. On the other hand, boundary-fitted curvilinear grids in hydrodynamic models for coastal seas, bays and estuaries not only fit to the coastline but also render the finite difference schemes simpler and more accurate. In this article, the boundary-fitted curvilinear grids for the model represent the complete boundary of the area considered by four curves defined by four functions, and the four boundaries of two of the larger islands are then represented approximately by two general functions. An appropriate independent coordinate transformation maps the curvilinear physical area to a square domain, and each island boundary is transformed to a rectangle within this square domain. The vertically integrated shallow water equations are transformed to the new space domain, and solved by a regular explicit finite difference scheme. The model is applied to compute the water levels due to astronomical tides, and also the water levels due to surges associated with tropical storms that hit the coast of Bangladesh.     

The effects of climate change on storm surges around the United Kingdom

Coastal flooding is often caused by extreme events, such as storm surges. In this study, improved physical models have been used to simulate the climate system and storm surges, and to predict the effect of increased atmospheric concentrations of greenhouse gases on the surges. In agreement with previous studies, this work indicates that the changes in atmospheric storminess and the higher time-average sea-level predicted for the end of the twenty-first century will lead to changes in the height of water levels measured relative to the present day tide. However, the details of these projections differ somewhat from earlier assessments.Uncertainty in projections of future extreme water levels arise from uncertainty in the amount and timing of future greenhouse gas emissions, uncertainty in the physical models used to simulate the climate system and from the natural variability of the system. The total uncertainty has not yet been reliably quantified and achieving this should be a priority for future research.     

诺模图法预报风暴潮的高精度数值实现

介绍了用诺模图法预报登陆台风引起最大风暴潮增水的基本思路,给出了较为详尽的诺模图建立过程和方法,提供了进行诺模图法预报计算所必需的图表.选用二元三点插值和二元全区间插值法进行诺模图/表的插值计算,并用C++语言编写了计算机程序,选用一个算例进行了校验计算.结果表明,这一计算机程序能获得精度较高的预报结果.     

On Bayesian interval prediction of future records

Based on the one-sample scheme, Bayesian prediction bounds for the s ^th future record value are obtained. All of the informative and future observations are assumed to be obtained from a general class of distributions which includes the Weibull, compound Weibull, Pareto, beta, Gompertz, compound Gompertz among other distributions. The prior belief of the experimenter is measured by a proper general conjugate prior which was suggested by AL-Hussaini (1999b).     

SPLASH诺模图的修正及应用

介绍了采用SPLASH模式诺模图法预报登陆台风引起最大风暴潮增水的基本思路和方法,并对SPLASH模式诺模图作了一定的修正和完善,使对其的编程计算更加易于实现且结果更精确.在此基础上对SPLASH模式诺模图法进行二元插值计算编程,并用若干个算例验证,获得了较为精确的预报结果.     

多级漏孔泄漏分析及其漏率预测方法研究

为了评估气体介质经多级漏孔的泄漏量,指导多道密封结构的安全设计,有必要研究气体经多级漏孔的泄漏特性。通过建立双级与多级漏孔的数学模型,在不同的初始条件下对多级漏孔的泄漏特性进行了计算分析。结果表明:多级漏孔的稳定漏率仅与各级独立漏孔漏率有关,与中间空腔体积无关,其倒数等于各级漏孔漏率的倒数之和。影响稳定时间的因素包括末级漏孔的漏率、其余各级漏孔组成的多级漏孔漏率以及中间空腔的容积。利用分析结果,提出了多级漏孔漏率的预测方法。     

On the nature of over-dispersion in motor vehicle crash prediction models

Statistical modeling of traffic crashes has been of interest to researchers for decades. Over the most recent decade many crash models have accounted for extra-variation in crash counts--variation over and above that accounted for by the Poisson density. The extra--variation--or dispersion--is theorized to capture unaccounted for variation in crashes across sites. The majority of studies have assumed fixed dispersion parameters in over-dispersed crash models--tantamount to assuming that unaccounted for variation is proportional to the expected crash count. Miaou and Lord [Miaou, S.P., Lord, D., 2003. Modeling traffic crash-flow relationships for intersections: dispersion parameter, functional form, and Bayes versus empirical Bayes methods. Transport. Res. Rec. 1840, 31-40] challenged the fixed dispersion parameter assumption, and examined various dispersion parameter relationships when modeling urban signalized intersection accidents in Toronto. They suggested that further work is needed to determine the appropriateness of the findings for rural as well as other intersection types, to corroborate their findings, and to explore alternative dispersion functions. This study builds upon the work of Miaou and Lord, with exploration of additional dispersion functions, the use of an independent data set, and presents an opportunity to corroborate their findings. Data from Georgia are used in this study. A Bayesian modeling approach with non-informative priors is adopted, using sampling-based estimation via Markov Chain Monte Carlo (MCMC) and the Gibbs sampler. A total of eight model specifications were developed; four of them employed traffic flows as explanatory factors in mean structure while the remainder of them included geometric factors in addition to major and minor road traffic flows. The models were compared and contrasted using the significance of coefficients, standard deviance, chi-square goodness-of-fit, and deviance information criteria (DIC) statistics. The findings indicate that the modeling of the dispersion parameter, which essentially explains the extra-variance structure, depends greatly on how the mean structure is modeled. In the presence of a well-defined mean function, the extra-variance structure generally becomes insignificant, i.e. the variance structure is a simple function of the mean. It appears that extra-variation is a function of covariates when the mean structure (expected crash count) is poorly specified and suffers from omitted variables. In contrast, when sufficient explanatory variables are used to model the mean (expected crash count), extra-Poisson variation is not significantly related to these variables. If these results are generalizable, they suggest that model specification may be improved by testing extra-variation functions for significance. They also suggest that known influences of expected crash counts are likely to be different than factors that might help to explain unaccounted for variation in crashes across sites.     

Windstorm and storm surges in Europe: loss trends and possible counter-actions from the viewpoint of an international reinsurer

Windstorm disasters (including storm surges) account for about one-third of all natural disasters throughout the world (by number, fatalities and economic losses), but for more than two-thirds of the corresponding insured losses. Trend analyses reveal that major windstorm disasters and the losses generated by them have increased drastically in recent decades. Risk partnership between the state, the affected population and the insurance industry assumes a key role with regard to the windstorm hazard. Scientists, engineers and insurers must work together in formulating their requirements and shaping them in such a way that politicians can derive clearly recognizable policy options (e.g. land-use, restrictions, design-code adjustments) from them. Another important aspect is stepping up the efforts being made towards curbing climate change, which will, otherwise, exacerbate the risk in the future.     

基于VOF法的风暴潮洪水演进三维数值模拟

为了提高风暴潮灾害应急处置能力,确保防潮安全,文章建立了耦合流体体积函数(VOF)法的三维非稳态水气两相流k-ε模型,采用等效糙率的方法处理城市密集建筑群,既考虑了其阻水作用,又考虑了其蓄水作用。针对天津市滨海新区海河与永定新河之间区域的风暴潮洪水演进数值模拟与分析,对100年一遇风暴潮洪水淹没情况进行分析,并对不同频率的风暴潮洪水的严重性进行了比较。结果表明,随着风暴潮发生频率的增加,风暴潮淹没范围逐渐减小,水深随着频率的增加是逐渐减少的,该研究为海堤安全管理、风暴潮灾害的快速科学评估提供了理论依据和技术支持。     

The rationale of reliability prediction

This paper is the first of what is intended to be a series of papers which investigate the foundations of reliability theory, particularly when applied to the prediction process. It will contrast current reliability practice against those practices common in normal science and engineering. The claim will be made that in general the prediction process as used in reliability, when stripped of the mathematical embellishments, is no more than simple enumeration: a method long held by the philosophers of science to be unreliable and in general a poor basis on which to make predictions. This initial paper rejects the statistical method as being an insufficient basis for making predictions and claims that it is incapable of logically supporting its conclusions. Although no evidence is provided to substantiate this claim, a number of scientific methods, both of historical and present day importance, are briefly reviewed with which one can contrast the statistical method.     

基于GRNN的粘弹材料阻尼性能的预测

考虑到粘弹性材料阻尼性能随环境的非线性变化，运用GRNN（广义回归网络）对粘弹阻尼材料动态力学性能函数进行逼近，并构建预测模型。结果证明，该模型具有良好的函数逼近效果，能够较准确的预测材料的动态力学性能，为阻尼材料的研究、开发和性能评定提出了一些指导性的建议。     

The success of the prediction of Haicheng earthquake and the negligence of the Tangshan earthquake

The success of the prediction of Haicheng earthquake and the failure of the prediction of Tangshan earthquake were both well known in the world. What happened, why such a strong earthquake as occurred in Haicheng had been predicted successfully and with a small loss of lives and property? Why a successively strong earthquake about a year later in a region not so further was failure in the imminent stage of prediction and there were so many fatalities and a great degree of property? The author addresses these points based on these true experiences including the first hand experiences leading up to, during, and following these two earthquarter. In addition, he also introduced some seimic phenomena which he had seen after Chichi earthquake in Taiwan.     

Evaluating the Impact of Prediction Techniques: Software Reliability Perspective

Maintaining software reliability is the key idea for conducting quality research. This can be done by having less complex applications. While developers and other experts have made significant efforts in this context, the level of reliability is not the same as it should be. Therefore, further research into the most detailed mechanisms for evaluating and increasing software reliability is essential. A significant aspect of growing the degree of reliable applications is the quantitative assessment of reliability. There are multiple statistical as well as soft computing methods available in literature for predicting reliability of software. However, none of these mechanisms are useful for all kinds of failure datasets and applications. Hence finding the most optimal model for reliability prediction is an important concern. This paper suggests a novel method to substantially pick the best model of reliability prediction. This method is the combination of analytic hierarchy method (AHP), hesitant fuzzy (HF) sets and technique for order of preference by similarity to ideal solution (TOPSIS). In addition, using the different iterations of the process, procedural sensitivity was also performed to validate the findings. The findings of the software reliability prediction models prioritization will help the developers to estimate reliability prediction based on the software type.     

直流换流站噪声计算软件开发与预测水平研究

随着环保意识的不断加强,直流换流站的噪声问题正越来越受到重视.目前直流换流站的环境预测软件几乎都是国外进口的通用预测软件,该文对一款由国内自主开发的直流换流站环境噪声计算软件的软件结构、功能模块、程序编制及基本算法等方面进行了阐述,并对其预测水平进行了研究,结果表明:与国外预测软件SoundPlan与Cadna/A相比...     

Strength prediction of sheet to tube single sided resistance spot welding

Single-Sided Spot Welding (SSSW) procedure is considered as a feasible method to join hydroformed or closed section parts to others in vehicle productions. A ‘doughnut’ shaped or ring nugget can be formed between the two workpieces during this process. The strengths of conventional button spot welds can be determined by the attributes of weldments and many functions that link weld diameter, sheet thickness and material properties to weld strength have been established. For welds of sheet to tube joining, the strength prediction model is greatly different from that of conventional welds for the completely different nugget form. In this study, computer experiments were conduced using the concept of design of experiments (DOE) and the method of finite element used to simulate the tensile-shear tests. The stress and strain distribution contour clouds during tensile-shear process were analyzed and quantitative relationship models were established to link a weld’s geometric and material properties to its tensile-shear strength. The results can give a simple judgment whether a ring spot weld was good only by its appearance.     

A framework for the prediction and management of environmental cracking problems

The complexity of engineering systems is growing steadily with the introduction of advanced materials and modern protective methods. This increasing technical complexity is paralleled by an increasing awareness of the risks, hazards and liabilities related to the operation of engineering systems. Environmental cracking (EC) is, in the context of lifetime prediction, one of the most important forms of damage because of its insidious and catastrophic character. EC and particularly stress corrosion cracking (SCC) can affect a wide variety of metals and alloys exposed to specific environments. After briefly reviewing some of the tests and simple models used to evaluate and represent the susceptibility of materials to SCC, this paper proposes the adoption of a top-down approach, used in the aircraft industry for the development of its maintenance programmes, as an information model for the integration of lifetime data. Such an approach can provide the ability to accommodate different sources of information into a single information system while keeping the specific details in a managerial context.