75 research outputs found
Rank-Based Learning and Local Model Based Evolutionary Algorithm for High-Dimensional Expensive Multi-Objective Problems
Surrogate-assisted evolutionary algorithms have been widely developed to
solve complex and computationally expensive multi-objective optimization
problems in recent years. However, when dealing with high-dimensional
optimization problems, the performance of these surrogate-assisted
multi-objective evolutionary algorithms deteriorate drastically. In this work,
a novel Classifier-assisted rank-based learning and Local Model based
multi-objective Evolutionary Algorithm (CLMEA) is proposed for high-dimensional
expensive multi-objective optimization problems. The proposed algorithm
consists of three parts: classifier-assisted rank-based learning,
hypervolume-based non-dominated search, and local search in the relatively
sparse objective space. Specifically, a probabilistic neural network is built
as classifier to divide the offspring into a number of ranks. The offspring in
different ranks uses rank-based learning strategy to generate more promising
and informative candidates for real function evaluations. Then, radial basis
function networks are built as surrogates to approximate the objective
functions. After searching non-dominated solutions assisted by the surrogate
model, the candidates with higher hypervolume improvement are selected for real
evaluations. Subsequently, in order to maintain the diversity of solutions, the
most uncertain sample point from the non-dominated solutions measured by the
crowding distance is selected as the guided parent to further infill in the
uncertain region of the front. The experimental results of benchmark problems
and a real-world application on geothermal reservoir heat extraction
optimization demonstrate that the proposed algorithm shows superior performance
compared with the state-of-the-art surrogate-assisted multi-objective
evolutionary algorithms. The source code for this work is available at
https://github.com/JellyChen7/CLMEA
Submarine fresh groundwater discharge into Laizhou Bay comparable to the Yellow River flux
Near- and off-shore fresh groundwater resources become increasingly important with the social and economic development in coastal areas. Although large scale (hundreds of km) submarine groundwater discharge (SGD) to the ocean has been shown to be of the same magnitude order as river discharge, submarine fresh groundwater discharge (SFGD) with magnitude comparable to large river discharge is never reported. Here, we proposed a method coupling mass-balance models of water, salt and radium isotopes based on field data of 223Ra, 226Ra and salinity to estimate the SFGD, SGD. By applying the method in Laizhou Bay (a water area of 6000 km2), we showed that the SFGD and SGD are 0.57 - 0.88 times and 7.35 - 8.57 times the annual Yellow River flux in August 2012, respectively. The estimate of SFGD ranges from 4.12 x 10^7 m3/d to 6.36 x 10^7 m3/d, while SGD ranges from 5.32 x 10^8 m3/d to 6.20 x 10^8 m3/d. The proportion of the Yellow River input into Laizhou Bay was less than 14% of the total in August 2012. Our method can be used to estimate SFGD in various coastal waters
An analytical solution of groundwater response to tidal fluctuation in a leaky confined aquifer
Abstract. An analytical solution is derived to investigate the influence of leakage on tidal response in a coastal leaky confined aquifer system. The analytical solution developed here is more general than the traditional solution obtained by Ferris [1951], which can be regarded as a special case of the solution presented in this paper. This solution is based on a conceptual model under the assumption that the groundwater level in the confined aquifer fluctuates in response to sea tide while that of the overlying unconfined aquifer remains constant. This conceptual model is supported by numerous field studies by previous researchers which have demonstrated that the tidal response in an unconfined aquifer may be negligible compared to that in a confined aquifer. The leakage has a significant impact on the tidal behavior of the confined aquifer. Hypothetical studies indicate that both tidal amplitude of groundwater head in the aquifer and the distance over which the aquifer can be disturbed by the sea tide will be considerably reduced because of the existence of leakage. This analytical solution is used to investigate the tidal and piezometer data at the Chek Lap Kok airport, Hong Kong Special Administrative Region, People’s Republic of China. 1
Tidal groundwater level fluctuations in L-shaped leaky coastal aquifer system
This paper presents an analytical solution to describe tidal groundwater level fluctuations in a coastal leaky aquifer system bounded by water -- land boundaries that form a right angle (referred to as L-shaped coastlines). The system consists of an unconfined aquifer, a confined aquifer and a leaky layer between them. Previously published analytical solutions that discuss only single aquifer constitute a special case of the new solution when the permeability of leaky layer approaches zero. A simple approximate solution without integral is presented. Error analysis and hypothetical example show that the approximate solution has adequate accuracy for both groundwater level prediction and parameter estimation for an L-shaped leaky aquifer system. q 2002 Elsevier Science B.V. All rights reserved
86 Water Resources and the Urban Environment Review of Analytical Studies of Tidal Groundwater Flow in Coastal Aquifer Systems
Abstract: Since the 1950s, numerous publications of analytical studies of tidal wave propagations in coastal aquifers have been appeared. This paper reviews the following aspects: importance of tidal effects in studies of coastal areas, analytical studies of tide-induced groundwater flow and related case studies. Finally several important open problems in analytical studies of tide-induced groundwater flow are proposed
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