As two independent problems,scheduling for parts fabrication line and sequencing for mixed-model assembly line have been addressed respectively by many researchers.However,these two problems should be considered simul...As two independent problems,scheduling for parts fabrication line and sequencing for mixed-model assembly line have been addressed respectively by many researchers.However,these two problems should be considered simultaneously to improve the efficiency of the whole fabrication/assembly systems.By far,little research effort is devoted to sequencing problems for mixed-model fabrication/assembly systems.This paper is concerned about the sequencing problems in pull production systems which are composed of one mixed-model assembly line with limited intermediate buffers and two flexible parts fabrication flow lines with identical parallel machines and limited intermediate buffers.Two objectives are considered simultaneously：minimizing the total variation in parts consumption in the assembly line and minimizing the total makespan cost in the fabrication/assembly system.The integrated optimization framework,mathematical models and the method to construct the complete schedules for the fabrication lines according to the production sequences for the first stage in fabrication lines are presented.Since the above problems are non-deterministic polynomial-hard（NP-hard）,a modified multi-objective genetic algorithm is proposed for solving the models,in which a method to generate the production sequences for the fabrication lines from the production sequences for the assembly line and a method to generate the initial population are put forward,new selection,crossover and mutation operators are designed,and Pareto ranking method and sharing function method are employed to evaluate the individuals＇ fitness.The feasibility and efficiency of the multi-objective genetic algorithm is shown by computational comparison with a multi-objective simulated annealing algorithm.The sequencing problems for mixed-model production systems can be solved effectively by the proposed modified multi-objective genetic algorithm.展开更多
目的通过Meta分析评估氨甲环酸(tranexamic acid,TXA)用于内侧开放楔形胫骨高位截骨术(medial open wedge high tibial osteotomy,OWHTO)的临床疗效。方法计算机检索PubMed、谷歌学术搜索(Google scholar)、考克兰图书馆(The Cochrane L...目的通过Meta分析评估氨甲环酸(tranexamic acid,TXA)用于内侧开放楔形胫骨高位截骨术(medial open wedge high tibial osteotomy,OWHTO)的临床疗效。方法计算机检索PubMed、谷歌学术搜索(Google scholar)、考克兰图书馆(The Cochrane Library)循证医学数据库、荷兰医学文摘数据库(The Excerpta Medica ExcerptaMedica Database,Database,EMBASE)、科学引文数据库(Web of Science,WOS)中关于TXA应用于OWHTO的临床研究,截止日期为2021-01月。采用R语言进行统计分析。结果纳入5篇临床研究文献,共计532例患者,TXA组258例,对照组274例。Meta分析结果显示,总失血量TXA组与对照组差异有统计学意义(SMD=-2.25,95%CI:-3.91~0.59,P=0.008),总引流量两组之间差异有统计学意义(SMD=-0.79,95%CI:-1.17~-0.42,P<0.001);术后1天血红蛋白下降值两组之间差异有统计学意义(SMD=-1.00,95%CI:-1.25~-0.75,P<0.001);术后2天血红蛋白下降值两组之间差异有统计学意义(SMD=-1.15,95%CI:-2.14~-0.16,P=0.023);并发症发生率两组之间差异有统计学意义(OR=0.21,95%CI:0.04~0.98,P=0.047)。除并发症发生率外,其他4项指标的敏感性分析显示整体结果具有稳定性,结论可靠。结论TXA应用于OWHTO手术可有效减少患者失血,降低并发症发生率。展开更多
基金supported by National Natural Science Foundation of China (Grant No.50875101)National Hi-tech Research and Development Program of China (863 Program,Grant No.2007AA04Z186)
文摘As two independent problems,scheduling for parts fabrication line and sequencing for mixed-model assembly line have been addressed respectively by many researchers.However,these two problems should be considered simultaneously to improve the efficiency of the whole fabrication/assembly systems.By far,little research effort is devoted to sequencing problems for mixed-model fabrication/assembly systems.This paper is concerned about the sequencing problems in pull production systems which are composed of one mixed-model assembly line with limited intermediate buffers and two flexible parts fabrication flow lines with identical parallel machines and limited intermediate buffers.Two objectives are considered simultaneously：minimizing the total variation in parts consumption in the assembly line and minimizing the total makespan cost in the fabrication/assembly system.The integrated optimization framework,mathematical models and the method to construct the complete schedules for the fabrication lines according to the production sequences for the first stage in fabrication lines are presented.Since the above problems are non-deterministic polynomial-hard（NP-hard）,a modified multi-objective genetic algorithm is proposed for solving the models,in which a method to generate the production sequences for the fabrication lines from the production sequences for the assembly line and a method to generate the initial population are put forward,new selection,crossover and mutation operators are designed,and Pareto ranking method and sharing function method are employed to evaluate the individuals＇ fitness.The feasibility and efficiency of the multi-objective genetic algorithm is shown by computational comparison with a multi-objective simulated annealing algorithm.The sequencing problems for mixed-model production systems can be solved effectively by the proposed modified multi-objective genetic algorithm.
