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11.
The paper presents a comprehensive multi-objective hydrodynamic optimisation procedure and its application to the early design of a floating liquefied natural gas (LNG) terminal for improved seakeeping and wave attenuation characteristics on its lee side. Genetic algorithms are used to find the Pareto optima designs followed by multi-objective decision making procedures to select the optimum design among them. The paper addresses the definition of the relevant optimisation problem and the set-up and interface of relevant software tools, presents results of systematic studies with respect to the minimisation of the motion responses and wave elevation on the leeward side of free-floating terminals and concludes with analysis and critical review of the obtained results and their impact on terminal design. 相似文献
12.
B. Miles T. Kalbacher O. Kolditz C. Chen J. Gronewold W. Wang A. Peter 《Environmental Geology》2007,52(7):1399-1412
Ongoing developments in geological and hydrogeological investigation techniques, especially direct-push methods, have led
to an increase in the quality, density and spatial resolution of data available from such investigations. This has created
new challenges in the development of numerical models in terms of accurately and efficiently translating detailed and complex
conceptual models into effective numerical models. Suitable geometrical and numerical modelling tools are essential in order
to meet these challenges. This paper describes the development of a three-dimensional hydrogeological flow model for a contaminated
site near Berlin, Germany, based on high-resolution geological data obtained principally using direct-push methods. The available
data were first interpreted to construct a detailed GIS-based geological model, which formed the basis of the conceptual site
model. The conceptual model was then translated into a geometrical model, which was used to create a finite element numerical
model. An innovative geometry object-based approach enabled the complex structural details of the conceptual model to be accurately
reproduced in the numerical model domain. The resulting three-dimensional steady-state unconfined flow model was successfully
calibrated using external automated calibration software, whereby parameter values for groundwater recharge and hydraulic
conductivity were determined. 相似文献
13.
Unexploded war-time bombs (UXB) can be found at the ground surface or buried at depths of up to 20 m, where surface-based detection methods become ineffective due to signal weakness and interference. A total-field borehole magnetometer can penetrate to such depths and collect relatively quiet data. However, conventional interpretation techniques suffer from the inherent non-uniqueness in the borehole dimension. In this paper, a constrained optimisation method is utilised for the interpretation of total-field borehole magnetometer data for the detection of deeply buried unexploded bombs. The major advantage over conventional techniques comes from the analytically-derived constraints imposed on the parameter vector by excluding non-geosensible results from consideration and hence reducing the non-uniqueness to a minimal level. A depth dependant objective function is defined to minimise the interference and measurement errors. A test site has been developed for evaluation using real world data. The interpretation results demonstrate its superior capability in handling real-world problems with high non-uniqueness. Furthermore, this method provides a way to estimate the moment strength without knowing the exact position. Together with the modelled signature data for different objects, characterisation of a particular bomb is possible from the inversion of a single total-field borehole profile. 相似文献
14.
15.
This paper focuses on an analysis by the boundary element method (BEM) of the pile-to-pile interaction for pile groups with dissimilar piles of different pile lengths embedded in saturated poroelastic soil. The behaviour of the poroelastic homogeneous soil is governed by Biot’s consolidation equations. The pile–soil system is decomposed into extended soil and fictitious piles. Considering the compatibility of vertical strain between fictitious piles and soil, the second kind of Fredholm integral equations were obtained to predict the axial force and settlement along pile shafts numerically. For the analysis of the interaction factor, two loading conditions for a two-dissimilar-pile system were proposed: (a) only one pile is loaded and (b) each pile is subjected to a load proportional to the pile length. Furthermore, the two-pile system was extended to pile groups with a rigid cap to capture the optimum design where each pile shares the same loading at the pile heads. The optimum results require shortening the peripheral piles and elongating internal piles, and the consolidation effect needs to be considered due to the adjustment of loading distribution among piles. 相似文献
16.
Creation of a geological fracture network model conditioned to in situ geometric measurements is of great importance to geoprofessionals, as fractures dominate pathways for fluid flow, a major concern for many engineering applications. This paper introduces and applies the Stochastic Nelder Mead simplex method to automatically calibrate stochastic parameters of geometric characterisations of a discrete fracture network model. This method can overcome the non-convergence of a previous exploratory approach on the classic Nelder Mead method by others, and is an effective substitution to the manual trial-and-error method and is complementary to existing conditional simulation approaches. The procedure to integrate the Stochastic Nelder Mead with a discrete fracture network is presented in detail, and a case study was conducted. Results show that the improved model can better handle the stochastic nature of the underlying system and effectively simulates the observed number and mean trace length of these fractures, although the model results underestimate its standard deviation. Simulated distributions of trace lengths and spacings are within acceptable ranges except for some small offsets, which can be adjusted during model runs. 相似文献
17.
《水文科学杂志》2013,58(6)
Abstract Abstract Various uncertainties are inherent in modelling any reservoir operation problem. Two of these are addressed in this study: uncertainty involved in the expression of reservoir penalty functions, and uncertainty in determining the target release value. Fuzzy set theory was used to model these uncertainties where the preferences of the decision maker for the fuzzified parameters are expressed as membership functions. Nonlinear penalty functions are used to determine the penalties due to deviations from targets. The optimization was performed using a genetic algorithm with the objectives to minimize the total penalty and to maximize the level of satisfaction of the decision maker with fuzzified input parameters. The proposed formulation was applied to the problem of finding the optimal release and storage values, taking Green reservoir in Kentucky, USA as a case study. The approach offers more flexibility to reservoir decision-making by demonstrating an efficient way to represent subjective uncertainties, and to deal with non-commensurate objectives under a fuzzy multi-objective environment. 相似文献
18.
Jan-Henrik Haunert Alexander Wolff 《International journal of geographical information science》2013,27(12):1871-1897
Topographic databases normally contain areas of different land cover classes, commonly defining a planar partition, that is, gaps and overlaps are not allowed. When reducing the scale of such a database, some areas become too small for representation and need to be aggregated. This unintentionally but unavoidably results in changes of classes. In this article we present an optimisation method for the aggregation problem. This method aims to minimise changes of classes and to create compact shapes, subject to hard constraints ensuring aggregates of sufficient size for the target scale. To quantify class changes we apply a semantic distance measure. We give a graph theoretical problem formulation and prove that the problem is NP-hard, meaning that we cannot hope to find an efficient algorithm. Instead, we present a solution by mixed-integer programming that can be used to optimally solve small instances with existing optimisation software. In order to process large datasets, we introduce specialised heuristics that allow certain variables to be eliminated in advance and a problem instance to be decomposed into independent sub-instances. We tested our method for a dataset of the official German topographic database ATKIS with input scale 1:50,000 and output scale 1:250,000. For small instances, we compare results of this approach with optimal solutions that were obtained without heuristics. We compare results for large instances with those of an existing iterative algorithm and an alternative optimisation approach by simulated annealing. These tests allow us to conclude that, with the defined heuristics, our optimisation method yields high-quality results for large datasets in modest time. 相似文献
19.
Seong-Yun Hong David O'Sullivan 《International journal of geographical information science》2013,27(8):1457-1477
To understand residential clustering of contemporary immigrants and other ethnic minorities in urban areas, it is important to first identify where they are clustered. In recent years, increasing attention has been given to the use of local statistics as a tool for finding the location of racial/ethnic residential clusters. However, since many existing local statistics are primarily developed for epidemiological studies where clustering is associated with relatively rare events, its application in studies of residential segregation may not always yield satisfactory results. This article proposes an optimisation clustering method for delineating the boundaries of ethnic residential clusters. The proposed approach uses a modified greedy algorithm to find the most likely extent of clusters and employs total within-group absolute deviations as a clustering criterion. To demonstrate the effectiveness of the method, we applied it to a set of synthetic landscapes and to two empirical data sets in Auckland, New Zealand. The results show that the proposed method can detect ethnic residential clusters effectively and that it has potential for use in other disciplines as it offers an ability to detect large, arbitrarily shaped clusters. 相似文献
20.
Bhardwaj Pandit G. L. Sivakumar Babu 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2018,12(2):152-168
Traditional reliability-based design methodologies often involve selection of design which is of lowest cost and satisfies safety requirements. But, this design is sensitive to variation in statistics of input parameters (noise parameters) and might become unsatisfactory if an underestimation of coefficient of variation of input parameters is made. A relatively new design methodology known as robust geotechnical design (RGD) is applied for the case of reinforcement of rock slope using end-anchored rock bolts. This ensures selection of a cost-effective and safe design for which probability of failure (Pf) of reinforced rock slope is least sensitive to the noise parameters. Reliability-based RGD approach involves evaluation of Pf for each design with different possible noise parameters. Finding Pf for the complex geotechnical structure is computationally expensive, and thus an augmented radial basis function-based response surface is used as a surrogate to the finite element model of rock slope. This response surface, being very efficient, also performs well for a range of values of noise parameters. Later, minimum distance algorithm is applied to obtain a cost-effective and robust design. Finally, a comparison is made in the costs between two robust designs obtained for different target probability of failure for the same rock slope. 相似文献