Search

Abstract Functionally graded beams (FGBs) have been studied extensively in literature to predict their static stability and dynamic behavior. In typical FGBs, each of material variation has significant influence on overall beams’ strength. This research utilized single and multi-objective optimization approaches to optimize the volume fraction distribution in the Timoshenko FGBs in order to maximize the fundamental frequency while minimizing mass and axial stresses. The FGBs with different ratios of material properties are considered. Several metaheuristic optimization techniques are utilized to address single and multi-objective problems. For validating purpose, computational optimization results are compared with those available in the literature. [ABSTRACT FROM AUTHOR]

Currently, population aging has aroused much concern in many countries since the elderly occupy a lot of social public resources in hospitals and nursing homes. Home health care (HHC) is treated as an alternative solution to serve the elderly community. In recent years, managing and organizing the operation of HHCs receive a great deal of attention. The HHC routing and scheduling problems attract huge amounts of interest from modeling and optimization areas. Nevertheless, there are rarely studies focusing on the cooperation of multiple HHC centers in such problems. This work addresses a multi-center, multi-objective and stochastic HHC routing and scheduling problem for minimizing the total operation cost and penalty cost incurred by earliness and delay service, where the caregivers' working time, customers' requirements and resource constraints are considered. Firstly, a multi-objective chance-constrained programming model is developed to formulate the studied problem. Secondly, a multi-objective cooperation evolutionary algorithm by using stochastic simulation is specially developed, in which two populations respectively perform global and local searches, and the cooperation of two populations is designed. The stochastic simulation approach is employed to evaluate the quality and feasibility of the obtained solutions. Finally, extensive experiments are performed on a set of test instances and three multi-objective optimization algorithms are compared to verify the performance of the proposed algorithm. The comparisons and discussions validate the competitiveness of the designed approach. [ABSTRACT FROM AUTHOR]

Minimum cost of energy is the main goal of a wind farm layout optimization. This is achieved by maximizing the total energy while minimizing the total costs of the farm. In this study, two sizes of commercial turbines were considered to investigate the effect of a non-homogenous farm on the layout optimization process. A cost model consisting of turbines, cable, transformers, foundation, and service vehicle routes was developed. Using Genetic Algorithm and Artificial Neural Network, first the superiority of the new algorithm in turbines and cable layout was verified versus previous studies. Next, two cases were investigated, i.e. (1) a farm populated with identical turbines and (2) a farm with a random mixture of both sizes of turbines. The layouts of both cases were optimized by both single and multi-objective optimizations. In the single objective optimization, only the larger turbines remained in the optimal layout of the second case and reduced the Levelized Cost of Energy (LCOE) into half of the first case. Multi-objective optimization clarified the reason for selecting larger size turbines in the layouts when the goal of the optimization was to minimize the cost of energy. As reported in literature, non-homogenous farms produce higher output. However, they impose a higher LCOE which makes them less appealing to developers. • Single objective (cost) and multi-objective (cost & power output) optimization result in different layout. • Non-homogenous farms produce higher power output. • Non-homogenous farms impose a higher LCOE which makes them less appealing to developers. [ABSTRACT FROM AUTHOR]