A dynamic virtual machine scheduling is the discrete optimization problem that schedules virtual machines over the set of physical servers at each discrete scheduling interval. As this problem is NP-complete, heuristi...
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A dynamic virtual machine scheduling is the discrete optimization problem that schedules virtual machines over the set of physical servers at each discrete scheduling interval. As this problem is NP-complete, heuristic and greedy approaches may get stuck at the local minima and produce the suboptimal solution. Therefore, we proposed server residual efficiency-aware particle swarm optimization (SR-PSO) algorithm for dynamic virtual machine scheduling in this work. The classical PSO operators are tuned to suit dynamic virtual machine scheduling. The proposed bi-objective fitness function guides the proposed algorithm during the exploration of global solution space and schedules virtual machines over the physical servers operating at optimum energy efficiency or near it with minimum virtual machine migrations. A virtual machine selection algorithm is proposed that selects the virtual machines whose migration results in servers' optimum energy efficiency. The server underload detection algorithm is proposed that categorizes servers as underloaded if they operate with energy inefficiency. The SR-PSO algorithm is aware of discrete scheduling intervals, and at each scheduling interval, only those VMs are rescheduled that are prone to service level agreement SLA violation or lower server utilization. We have used a cloudsim simulator to simulate our proposed work, and the results show significant improvement in energy consumption for the dynamic VM scheduling. More specifically, our proposed approach is 45.4% and 50% more energy efficient than the previous dynamic virtual machine scheduling approaches.
The exploration and trade-off analysis of different aerodynamic design configurations requires solving optimization problems. The major bottleneck to assess the optimal design is the large number of time-consuming eva...
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The exploration and trade-off analysis of different aerodynamic design configurations requires solving optimization problems. The major bottleneck to assess the optimal design is the large number of time-consuming evaluations of high-fidelity computational fluid dynamics (CFD) models, necessary to capture the non-linear phenomena and discontinuities that occur at higher Mach number regimes. To address this limitation, we introduce an original non-myopic multifidelity Bayesian framework aimed at including expensive high-fidelity CFD simulations for the optimization of the aerodynamic design. Our scheme proposes a novel two-step lookahead policy to maximize the improvement of the solution quality considering the rewards of future steps, and combines it with utility functions informed by the fluid dynamic regime and the information extracted from data, to wisely select the aerodynamic model to interrogate. We validate the proposed framework for the case of a constrained drag coefficient optimization problem of a NACA 0012 airfoil, and compare the results to other popular multifidelity and single-fidelity optimization frameworks. The results suggest that our strategy outperforms the other approaches, allowing to significantly reduce the drag coefficient through a principled selection of limited evaluations of the high-fidelity CFD model.
Efficient management of water distribution systems (WDSs) is critical to ensuring sustainable access to safe and reliable water. This study addresses the dual challenge of optimizing hydraulic performance and water qu...
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This paper presents a set of benchmark topology optimization problems that are used to evaluate the performance of optimization software. The topology optimization formulations considered in this benchmark set include...
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ISBN:
(数字)9781624106095
ISBN:
(纸本)9781624106095
This paper presents a set of benchmark topology optimization problems that are used to evaluate the performance of optimization software. The topology optimization formulations considered in this benchmark set include mass-constrained compliance minimization, stress-constrained mass minimization, mass and stress-constrained compliance minimization, and mass and frequency-constrained compliance minimization. Both structured and unstructured quadrilateral and hexahedral meshes are used with conventional and non-conventional topology optimization design domains. In total, the benchmark set contains 108 2D and 72 3D domain and mesh combinations. In this preliminary work, the performance of the optimizers SNOPT, IPOPT and ParOpt are evaluated. Performance profiles are used to assess the performance of an optimizer across the full benchmark set. We find that SNOPT performs the best overall among all optimizers. Furthermore, a modification of the quasi-Newton Hessian update provides a considerable performance benefit in both objective function value and discreteness measure.
The design of complex system architectures brings with it a number of challenging issues, among others large combinatorial design spaces. optimization can be applied to explore the design space, however gradient-based...
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ISBN:
(数字)9781624106101
ISBN:
(纸本)9781624106101
The design of complex system architectures brings with it a number of challenging issues, among others large combinatorial design spaces. optimization can be applied to explore the design space, however gradient-based optimization algorithms cannot be applied due to the mixed-discrete nature of the design variables. It is investigated how effective surrogate-based optimization algorithms are for solving the black-box, hierarchical, mixed-discrete, multiobjective system architecture optimization problems. Performance is compared to the NSGAII multi-objective evolutionary algorithm. An analytical benchmark problem that exhibits most important characteristics of architecture optimization is defined. First, an investigation into algorithm effectiveness is performed by measuring how accurately a known Pareto-front can be approximated for a fixed number of function evaluations. Then, algorithm efficiency is investigated by applying various multi-objective convergence criteria to the algorithms and establishing the possible trade-off between result quality and function evaluations needed. Finally, the impact of hidden constraints on algorithm performance is investigated. The code used for this paper has been published.
The Mars Oxygen ISRU Experiment (MOXIE) is an instrument onboard NASA's Perseverance rover. On April 20th, 2021, MOXIE generated oxygen on Mars from the carbon dioxide present in the Martian atmosphere, demonstrat...
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The Mars Oxygen ISRU Experiment (MOXIE) is an instrument onboard NASA's Perseverance rover. On April 20th, 2021, MOXIE generated oxygen on Mars from the carbon dioxide present in the Martian atmosphere, demonstrating, for the first time, in-situ resource utilization (ISRU) on the surface of another celestial body. Learnings from MOXIE on Mars have aided in the design of a scaled-up version of MOXIE. Oxygen generated from this scaled-up system would be used as propellant in a Mars Ascent Vehicle that would enable the crew to return to Earth once their mission was complete, as well as in life support systems. Failure of any of its subsystems would result in a loss of mission due to the inability of the crew to return to Earth. Accordingly, risk analysis is one of the most crucial steps in the design of the scaled-up MOXIE that must be completed and understood before building and launching the system to Mars. The intent of this paper is to present a comprehensive, quantitative analysis of the operational risks associated with this Mars ISRU plant. We then present an approach to optimize the reliability of each subsystem using a modified probabilistic risk assessment and heuristics-based optimization algorithm.
Reconstructions of genome-scale metabolic networks from different organisms have become popular in recent years. Metabolic engineering can simulate the reconstruction process to obtain desirable phenotypes. In previou...
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Reconstructions of genome-scale metabolic networks from different organisms have become popular in recent years. Metabolic engineering can simulate the reconstruction process to obtain desirable phenotypes. In previous studies, optimization algorithms have been implemented to identify the near-optimal sets of knockout genes for improving metabolite production. However, previous works contained premature convergence and the stop criteria were not clear for each case. Therefore, this study proposes an algorithm that is a hybrid of the ant colony optimization algorithm and flux balance analysis (ACOFBA) to predict near optimal sets of gene knockouts in an effort to maximize growth rates and the production of certain metabolites. Here, we present a case study that uses Baker's yeast, also known as Saccharomyces cerevisiae, as the model organism and target the rate of vanillin production for optimization. The results of this study are the growth rate of the model organism after gene deletion and a list of knockout genes. The ACOFBA algorithm was found to improve the yield of vanillin in terms of growth rate and production compared with the previous algorithms. (C) 2014 Elsevier Ltd. All rights reserved.
Swarm intelligence is a research field that models the collective behavior in swarms of insects or animals. Recently, a kind of Drosophila (fruit fly) inspired optimization algorithm, called fruit fly optimization alg...
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Swarm intelligence is a research field that models the collective behavior in swarms of insects or animals. Recently, a kind of Drosophila (fruit fly) inspired optimization algorithm, called fruit fly optimization algorithm (FOA), has been developed. This paper presents a variation on original FOA technique, named multi-swarm fruit fly optimization algorithm (MFOA), employing multi-swarm behavior to significantly improve the performance. In the MFOA approach, several sub-swarms moving independently in the search space with the aim of simultaneously exploring global optimal at the same time, and local behavior between sub-swarms are also considered. In addition, several other improvements for original FOA technique is also considered, such as: shrunk exploring radius using osphresis, and a new distance function. Application of the proposed MFOA approach on several benchmark functions and parameter identification of synchronous generator shows an effective improvement in its performance over original FOA technique. (C) 2014 Elsevier Inc. All rights reserved.
A numerical method for determining the five-parameter model of photovoltaic cells is presented in the paper. Explicit equations are applied to analyze the relations between parameters which are solved by an optimizati...
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A numerical method for determining the five-parameter model of photovoltaic cells is presented in the paper. Explicit equations are applied to analyze the relations between parameters which are solved by an optimization algorithm. Lambert W function is implemented to convert the I-V characteristic implicit equation to an explicit one, so the output current and voltage of photovoltaic cells can be obtained by substituting the five parameters into the explicit I-V equation. Several cells are used to verify the accuracy of the proposed method from different aspects. It is found that the proposed method gives precise results and can be applicable to various types of photovoltaic cells. (C) 2014 Elsevier Ltd. All rights reserved.
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