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- Jiang, Junqiang, et al.
(author)
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VGWO: Variant Grey Wolf Optimizer with High Accuracy and Low Time Complexity
- 2023
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In: Computers, Materials and Continua. - : TECH SCIENCE PRESS. - 1546-2218 .- 1546-2226. ; 77:2, s. 1617-1644
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Journal article (peer-reviewed)abstract
- The grey wolf optimizer (GWO) is a swarm-based intelligence optimization algorithm by simulating the steps of searching, encircling, and attacking prey in the process of wolf hunting. Along with its advantages of simple principle and few parameters setting, GWO bears drawbacks such as low solution accuracy and slow convergence speed. A few recent advanced GWOs are proposed to try to overcome these disadvantages. However, they are either difficult to apply to large-scale problems due to high time complexity or easily lead to early convergence. To solve the abovementioned issues, a high-accuracy variable grey wolf optimizer (VGWO) with low time complexity is proposed in this study. VGWO first uses the symmetrical wolf strategy to generate an initial population of individuals to lay the foundation for the global seek of the algorithm, and then inspired by the simulated annealing algorithm and the differential evolution algorithm, a mutation operation for generating a new mutant individual is performed on three wolves which are randomly selected in the current wolf individuals while after each iteration. A vectorized Manhattan distance calculation method is specifically designed to evaluate the probability of selecting the mutant individual based on its status in the current wolf population for the purpose of dynamically balancing global search and fast convergence capability of VGWO. A series of experiments are conducted on 19 benchmark functions from CEC2014 and CEC2020 and three real-world engineering cases. For 19 benchmark functions, VGWO's optimization results place first in 80% of comparisons to the state-of-art GWOs and the CEC2020 competition winner. A further evaluation based on the Friedman test, VGWO also outperforms all other algorithms statistically in terms of robustness with a better average ranking value.
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| 2. |
- Xiong, Zhifang, et al.
(author)
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Intensified aridity over the Indo-Pacific Warm Pool controlled by ice-sheet expansion during the Last Glacial Maximum
- 2022
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In: Global and Planetary Change. - : Elsevier BV. - 0921-8181. ; 217
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Journal article (peer-reviewed)abstract
- The magnitude, direction and cause of precipitation changes across the Indo-Pacific Warm Pool (IPWP) during the Last Glacial Maximum (LGM) remain elusive. In particular, it is still inconclusive whether tropical or extra-tropical factors controlled such precipitation changes. Determining the spatio-temporal distribution of precipitation in the IPWP during the LGM is a valid strategy to address this issue, but the existing precipitation records are dominantly from maritime continents and marginal seas, with few data from pelagic oceans. In order to fill this gap, we analyzed the oxygen isotopic compositions of single Ethmodiscus rex diatom frustules (δ18OE. rex) from a sediment core (WPD-03) consisting of laminated diatom mats (LDMs) in the eastern Philippine Sea (EPS). δ18OE. rex was controlled mainly by sea-surface salinity variation and, thus, can reflect open-ocean precipitation changes across the IPWP. Our precipitation proxy records, in combination with existing published data, reveal spatial patterns of precipitation change that indicate overall drying across the IPWP during the LGM. Based on a comparison of paleoclimatic records with modeling results, we propose that extra-tropical factors (ice-sheet size) controlled precipitation variability in the IPWP during the LGM through a combination of zonal shifts of ENSO and meridional migration of the ITCZ. Strong aridity during the LGM prevented formation of a subsurface barrier layer and, hence, allowed accessing of sufficient nutrients to surface waters, stimulating blooms of E. rex and subsequent formation of LDMs in the IPWP. These findings suggest an important role for high-latitude climate in the tropical hydrological cycle during the LGM.
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