Prediction of local scour around circular piles under waves using a novel artificial intelligence approach

Abstract

The scour phenomena around vertical piles in oceans and under waves may influence the structure stability. Therefore, accurately predicting the scour depth is an important task in the design of piles. Empirical approaches often do not provide the required accuracy compared with data mining methods for modeling such complex processes. The main objective of this study is to develop three data-driven methods, locally weighted linear regression (LWLR), support vector machine (SVR), and multivariate linear regression (MLR) to predict the scour depth around vertical piles due to waves in a sand bed. It is the first effort to develop the LWLR to predict scour depth around vertical piles. The models simulate the scour depth mainly based on Shields parameter, pile Reynolds number, grain Reynolds number, Keulegan–Carpenter number, and sediment number. 111 laboratory datasets, derived from several experimental studies, were used for the modeling. The results indicated that the LWLR provided highly accurate predictions of the scour depths around piles (R?=?0.939 and RMSE = 0.075). Overall, this study demonstrated that the LWLR can be used as a valuable tool to predict the wave-induced scour around piles.     

Characteristics of Scour and Deposition in Front of Breakwaters Under Irregular Broken Clapotis

First the scour and deposition patterns of the sandy seabed in front of a vertical breakwater under the action of irregular broken clapotis are investigated experimentally and classified into five types: scour type Ⅰ , scour type Ⅱ, scour type Ⅲ, deposition type Ⅰ, and deposition type Ⅱ . Secondly, the processes of formation of scour and deposition patterns are probed in comparison with those induced by regular broken clapotis and standing waves. Thirdly, the criteria for distinguishing scour and deposition patterns under irregular broken clapotis are presented.     

新建水坝对下游已建水工建筑物的影响分析

分析了新建水坝及社会经济发展因素对坝下游水流及泥沙的影响，用一个简易河床模型来说明新建大坝后下游河床的演变规律，通过坝下游河床一般演变分析来阐述局部冲刷对已建水工建筑物基础的影响及对已建水工建筑基础的防护措施。     

The effect of tidal inlets on open coast storm surge hydrographs

Bridge scour modeling requires storm surge hydrographs as open ocean boundary conditions for coastal waters surrounding tidal inlets. These open coast storm surge hydrographs are used to accurately determine both horizontal and vertical circulation patterns, and thus scour, within the inlet and bay for an extreme event. At present, very little information is available on the effect that tidal inlets have on these open coast storm surge hydrographs. Furthermore, current modeling practice enforces a single design hydrograph along the open coast boundary for bridge scour models. This study expands on these concepts and provides a more fundamental understanding on both of these modeling areas.     

Learning to trade ethically: Knowledgeable capitalism, retailers and contested commodity chains

This paper explores what happens when corporations engage explicitly in practices of organisational learning not only to become better capitalists by generating ever more innovative ways of maintaining profitability, improving competitiveness and maximising shareholder value, but also to become more responsible corporate citizens in their business practices. In particular, I evaluate the ways in which UK food and clothing retailers are learning to develop their ethical trading programmes in response to political calls for more responsible trading. Thrift’s [Thrift, N., 2005. Knowing Capitalism. Sage, London] notion of ‘knowledgeable, or soft, capitalism’ is adopted to understand the creative and experimental ways in which retailers and their mentors (ethical consultancies, social auditors and multi-stakeholder organisations) are learning to trade ethically. Two specific examples of formal learning spaces experienced by UK food and clothing retailers are examined: (i) training courses on social auditing and (ii) corporate awareness-raising courses on ethical trade. These courses are shown to encompass various participative and affective practices of learning. And while particular limits to the success of these courses are argued to exist, ethical learning practices discussed in this paper are nonetheless suggested to play a role in the making of new, albeit moderate, forms of responsible capitalism.     

水库下游河流再造床过程中的河岸侵蚀

根据实测河道地形资料,分析了水库下游河床演变中的河岸侵蚀现象,包括不同横向边界约束条件、不同床沙组成和不同河型河段的河岸侵蚀的特征及规律。结果表明:①水库下游均会有河岸侵蚀发生,但初期一般以下切为主,后期以展宽为主。②对于横向边界约束较强的河段,河岸侵蚀相对较弱;相反,则河岸坍塌严重,河岸侵蚀强烈;③对不同的河床组成和边滩组成的河段:河床较粗特别是形成抗冲粗化层,且边滩组成较细的河段,河岸侵蚀现象非常剧烈;河床组成较细的河段,如果边滩抗冲性较强,则河岸侵蚀现象相对较弱,如果滩地组成较细、容易坍塌,河岸侵蚀也会较强;④不同的河型有着不同的河岸侵蚀现象。分汊河段以主汊为主;游荡段的游荡特性在初期受到抑制;弯曲河段的撇弯切滩现象较普遍。     

葛洲坝水利枢纽运行后泥沙冲淤变化分析

对葛洲坝水利枢纽及其运行情况和河段特性进行了介绍。分析认为葛洲坝水利枢纽运行前后的入库水沙特性基本一致。探讨了库区冲淤变化特点、淤积量及其分布,冲淤过程及达到冲淤平衡的时间。对坝下游河床的冲淤过程、冲淤量、达到冲淤平衡的时间以及河床粗化,河底高程历年变化及同流量水位降低的原因、降低量及变化过程进行了分析总结。研究结果可为进一步探讨三峡水利枢纽与葛洲坝水利枢纽联合调度运用后水库泥沙淤积变化规律提供参考。     

Competitive Adjustment and Advancement in Global Commodity Chains II: The Case of the Singapore Garment Industry

This is the second part of a contribution to the debate on the possibilities of leveraging economic globalisation — through incorporation in international production networks and global commodity chains (GCCs) — as a strategy for developing countries to industrialise and advance their position in the world economy. In the first part, we analysed the experience of the East Asian apparel industry and addressed the issues of sustaining positions, upgrading to more rewarding roles, and advancing to less dependent positions within production networks and GCCs. We developed an analytical framework at both the firm and industry levels, and subsequently identified alternative firm- and industry-level strategies and trajectories. The present paper deals with these issues in the context of the Singapore apparel industry. Based on extensive empirical research, we demonstrate that although the East Asian experience of upgrading and repositioning within the GCC is to some extent emulated in the case of the Singapore apparel industry, the outcomes have been less favourable in terms of the depth, extent and strength of these trajectories. The differing outcomes can be explained in terms of different (systemic) conditions in the Singapore business environment, including the agency of local players, the geography of sourcing networks, and the role of the state and prevailing business attitudes. Our conclusions merit continued attention in both research and policy circles on the development of capabilities at the firm level, and the role of local business and institutional environments in local industry development processes under globalisation.     

Crisis, coincidences and strategic market behaviour: the internationalization of Indonesian clothing brand-owners

Despite the fact that most Indonesian brand-owners continue to emphasize their marketing activities in the domestic market, several brand-owners have started to export clothing under their own label. This has been particularly the result of the economic crisis in the late 1990s, which affected companies serving the domestic market. Companies were trying to compensate for the loss of sales on the domestic market by redirecting their marketing activities to foreign countries. This export strategy has been driven largely by the sole aim to survive. However, in addition to these export activities, some companies have rather sophisticated, long-standing business relations to their distributors in overseas markets. This paper explores these export activities in the context of the global commodity chain framework.     

A simulation model of morphological,vegetation and sediment changes in ephemeral streams

A model to simulate channel changes in ephemeral river channels and to test the effects of hydrological changes due to climate change and[sol ]or land use change was developed under the auspices of the EU funded MEDALUS programme (Mediterranean Desertification and Land Use). The model, CHANGISM (Channel Change GIS Simulation Model), is designed to simulate the effect of channel flow events and of climate conditions on morphology, sediment and vegetation, through sequences of events and conditions, over periods of up to several decades. The modelling is based on cellular automata but with calculations for water and sediment continuity. Process rules have both deterministic and stochastic elements. An important feature of the model is that it incorporates feedback elements between each event. The main aim of the model is to indicate the likely outcomes of events and combinations of conditions. It is linked to GIS for both input and output. The modelling is based on a channel reach and state is input as GIS layers of morphology (DEM), sediment and vegetation cover and state. Other initial conditions of soil moisture, groundwater level, and overall gradient are input. Parameters for processes are read from tables and can be easily changed for successive runs of the model. The bases for decisions on process specifications are discussed in this paper. Initial tests of the operation and sensitivity of the model were made on idealized reaches. The model was then tested using data from monitored sites in SE Spain. Simulations using clearwater flow worked well but initial simulations using events with sediment loads showed some tendency for excess deposition. Further tests and modifications are taking place. Overall, the model is one of the most sophisticated that simulates the interaction of flows with sediment and vegetation and the outcomes in terms of erosion, deposition, morphology, sediment cover, vegetation cover and plant survival over periods of up to 30 years for the scale of a channel reach. Copyright © 2005 John Wiley & Sons, Ltd.