分类: 工程与技术科学 >> 工程数学 提交时间: 2024-05-10
摘要: Aiming at the distributed flexible job shop scheduling problem under dual resource constraints considering the influence of workpiece transportation time between factories and machines, a distributed flexible job shop scheduling problem (DFJSP) model with the optimization goal of minimizing completion time is established, and an improved mayfly algorithm (IMA) is proposed to solve it. Firstly, the mayfly position vector is discrete mapped to make it applicable to the scheduling problem. Secondly, three-layer coding rules of process, worker and machine is adopted, in which the factory selection is reflected by machine number, according to the characteristics of the model, a hybrid initialization strategy is designed to improve the population quality and diversity; Thirdly, an active time window decoding strategy considering transportation time is designed for the worker-machine idle time window to improve the local optimization performance of the algorithm; In addition, The improved crossover and mutation operators is designed to expand the global search range of the algorithm. Finally, through simulation experiments, the results of various algorithms are compared to verify the effectiveness of the proposed algorithm for isomorphism and isomerism factories instances.
分类: 工程与技术科学 >> 工程通用技术 提交时间: 2024-05-10
摘要: Due to the complexity of the production shop in discrete manufacturing industry, traditional genetic algorithm (GA) cannot solve the production scheduling problem well. In order to enhance the GA-based method to solve the production scheduling problem, the simulated annealing algorithm (SAA) is used to develop an improved hybrid genetic algorithm. Firstly, the crossover probability and mutation probability of the genetic operation are adjusted, and the elite replacement operation is adopted for simulated annealing operator. Then, a mutation method is used for the comparison and replacement of the genetic operations to obtain the optimal value of the current state. Lastly, the proposed hybrid genetic algorithm is compared with several scheduling algorithms, and the superiority and efficiency of the proposed method are verified in solving the production scheduling.
分类: 能源科学 >> 能源(综合) 提交时间: 2024-04-02
摘要: In this article, a numerical analysis is done on the temperature of 4 plate-shaped battery cells with phase change material (PCM) chambers around each one in a rectangular shape. The batteries are placed in a channel with air flow. The study is done transiently in a time of ten minutes. The batteries are of lithium ion type and the analysis is provided in two dimensions. The battery cells are arranged in the form of two single battery cells at the beginning, and end of the channel and two battery cells in the middle of the channel. These two middle batteries are placed in parallel. By changing the distance between the two middle batteries from two to three cm, this study is conducted to investigate the temperature of each of the four battery cells and changes in the amount of frozen PCM. Finally, the results showed that the temperature of the two batteries at the beginning and the end, increased continuously during the ten minutes of the study. At a distance of three cm from the middle batteries, the lowest temperature occurred on the first and last batteries, while at the same distance, the highest temperature occurred on the middle ones. At a distance of two cm from the middle batteries, the lowest amount of frozen PCM was observed, while at a distance of three cm from the middle batteries, the highest amount of frozen PCM was found on the first and last batteries.
分类: 机械工程 >> 机械工程其他学科 提交时间: 2024-04-02
摘要: In this study, first, an orthopedic plate was 3D printed with Polylactic acid (PLA) and coated with polycaprolactone (PCL)/Akermanite (AKT) nano-fibers. The composition included 8 wt.% of PCL and 3 wt.% of nAKT, while diameter of the PCL/AKT nano-fibers was approximately 253 nm ± 33 nm. Thermomechanical properties such as pressure, three-point bending flexural, and thermal conductivity of coated and non-coated specimens were examined and compared. In the next step, the bioactivity of the coated samples was evaluated following a 28-day immersion in simulated body fluid (SBF). Further, scanning electron microscope (SEM) images were taken to assess morphology of nanofibers and apatite formation on samples. By adding PCL to PLA, the maximum pressure force is enhanced by 16.83%. Further by adding nAKT to PLA+PCL sample, the maximum pressure force is enhanced by 4.72%. Further, by adding PCL to PLA, the maximum bending flexural force is enhanced by 21.06%. Further by adding nAKT to PLA+PCL sample, the maximum bending flexural force is enhanced by 21.39%. The results of this study are used to improve modeling of the orthopedic plates.
分类: 水利工程 >> 水利工程其他学科 提交时间: 2024-04-01
摘要: A new digital twin (DT) framework with optimal sensor placement (OSP) is proposed to accurately calculate the modal responses and identify the damage ratios of the offshore jacket platforms. The proposed damage identification framework consists of two models (namely one OSP model and one damage identification model). The OSP model adopts the multi-objective Lichtenberg algorithm (MOLA) to perform the sensor number/location optimization to make a good balance between the sensor cost and the modal calculation accuracy. In the damage identification model, the Markov Chain Monte Carlo (MCMC)-Bayesian method is developed to calculate the structural damage ratios based on the modal information obtained from the sensory measurements, where the uncertainties of the structural parameters are quantified. The proposed method is validated using an offshore jacket platform, and the analysis results demonstrate efficient identification of the structural damage location and severity.