Vehicle routing problem in distribution （VRPD） is a widely used type of vehicle routing problem （VRP）, which has been proved as NP-Hard, and it is usually modeled as single objective optimization problem when mode...Vehicle routing problem in distribution （VRPD） is a widely used type of vehicle routing problem （VRP）, which has been proved as NP-Hard, and it is usually modeled as single objective optimization problem when modeling. For multi-objective optimization model, most researches consider two objectives. A multi-objective mathematical model for VRP is proposed, which considers the number of vehicles used, the length of route and the time arrived at each client. Genetic algorithm is one of the most widely used algorithms to solve VRP. As a type of genetic algorithm （GA）, non-dominated sorting in genetic algorithm-Ⅱ （NSGA-Ⅱ） also suffers from premature convergence and enclosure competition. In order to avoid these kinds of shortage, a greedy NSGA-Ⅱ （GNSGA-Ⅱ） is proposed for VRP problem. Greedy algorithm is implemented in generating the initial population, cross-over and mutation. All these procedures ensure that NSGA-Ⅱ is prevented from premature convergence and refine the performance of NSGA-Ⅱ at each step. In the distribution problem of a distribution center in Michigan, US, the GNSGA-Ⅱ is compared with NSGA-Ⅱ. As a result, the GNSGA-Ⅱ is the most efficient one and can get the most optimized solution to VRP problem. Also, in GNSGA-Ⅱ, premature convergence is better avoided and search efficiency has been improved sharply.展开更多
目的分析影响ICU脓毒症患者预后的危险因素及血镁水平联合急性生理与慢性健康Ⅱ(acute physiology and chronic health evaluationⅡ,APACHE-Ⅱ)评分对ICU脓毒症患者预后的预测价值。方法对2020年1月—2022年1月期间收治的185例ICU脓毒...目的分析影响ICU脓毒症患者预后的危险因素及血镁水平联合急性生理与慢性健康Ⅱ(acute physiology and chronic health evaluationⅡ,APACHE-Ⅱ)评分对ICU脓毒症患者预后的预测价值。方法对2020年1月—2022年1月期间收治的185例ICU脓毒症患者展开回顾性研究,依据患者28 d生存情况将其分为死亡组(n=94)和存活组(n=91),单因素和logistic多因素分析脓毒症患者28 d死亡的危险因素。Pearson分析血镁水平、APACHE-Ⅱ评分与各项危险因素的相关性,受试者工作特征曲线(receiver operating characteristic,ROC)分析血镁联合APACHE-Ⅱ评分对ICU脓毒症患者预后的预测价值。结果APACHE-Ⅱ评分、序贯器官衰竭评分(sequential organ failure assessment,SOFA)、降钙素原(procalcitonin,PCT)、低镁血症、血小板计数为ICU脓毒症患者28d死亡的危险因素(P<0.05)。APACHE-Ⅱ评分与SOFA评分、PCT水平、低镁血症均呈现正相关(P<0.05),与血小板计数呈现负相关(P<0.05)。低镁血症与APACHE-Ⅱ评分、SOFA评分、PCT水平均呈现正相关(P<0.05),与血小板计数呈现负相关(P<0.05)。低镁血症(AUC=0.697)、APACHE-Ⅱ评分(AUC=0.745)对ICU脓毒症患者预后均有较好的预测价值,且二者联合(AUC=0.866)预测效果更佳。结论低镁血症联合APACHE-Ⅱ评分ICU脓毒症患者28 d死亡有较好的预测价值,临床中可将血镁水平和APACHE-Ⅱ评分作为判断预后的指标。展开更多
The need to transport goods across countries and islands has resulted in a high demand for commercial vessels.Owing to such trends,shipyards must efficiently produce ships to reduce production costs.Layout and materia...The need to transport goods across countries and islands has resulted in a high demand for commercial vessels.Owing to such trends,shipyards must efficiently produce ships to reduce production costs.Layout and material flow are among the crucial aspects determining the efficiency of the production at a shipyard.This paper presents the initial design optimization of a shipyard layout using Nondominated Sorting Algorithm-Ⅱ(NSGA-Ⅱ)to find the optimal configuration of workstations in a shipyard layout.The proposed method focuses on simultaneously minimizing two material handling costs,namely work-based material handling and duration-based material handling.NSGA-Ⅱ determines the order of workstations in the shipyard layout.The semiflexible bay structure is then used in the workstation placement process from the sequence formed in NSGA-Ⅱ into a complete design.Considering that this study is a case of multiobjective optimization,the performance for both objectives at each iteration is presented in a 3D graph.Results indicate that after 500 iterations,the optimal configuration yields a work-based MHC of 163670.0 WBM-units and a duration-based MHC of 34750 DBM-units.Starting from a random solution,the efficiency of NSGA-Ⅱ demonstrates significant improvements,achieving a 50.19%reduction in work-based MHC and a 48.58%reduction in duration-based MHC.展开更多
横波可控震源振动器平板作为页岩气勘探中的关键部件,其疲劳寿命直接影响可控震源的使用寿命和勘探精度。然而,传统的振动器平板疲劳寿命优化方法未考虑平板与平板齿间焊接残余应力的影响,导致平板结构在抗疲劳优化设计方面效果不佳。为...横波可控震源振动器平板作为页岩气勘探中的关键部件,其疲劳寿命直接影响可控震源的使用寿命和勘探精度。然而,传统的振动器平板疲劳寿命优化方法未考虑平板与平板齿间焊接残余应力的影响,导致平板结构在抗疲劳优化设计方面效果不佳。为此,使用局部灵敏度法对平板疲劳寿命进行敏感性分析,确定了焊接残余应力为影响疲劳寿命的关键因素。随后,建立了平板的各向最大焊接残余应力与焊接速度和焊接层间温度之间的数学模型,并以各向最大焊接残余应力为约束,以疲劳寿命为优化目标,建立相应的优化模型。最后,利用NSGA-Ⅱ(nondominated sorting genetic algorithm-Ⅱ,非支配排序遗传算法-Ⅱ)获取Pareto解集,并结合熵权法和TOPSIS(technique for order preference by similarity to ideal solution,逼近理想解排序)法确定最佳优化方案:焊接速度为10.23 mm/s,焊接层间温度为105℃。结果表明,优化后平板的疲劳寿命为10.23年,相比优化前提高了17.72%。研究结果可为横波可控震源振动器平板的疲劳寿命优化提供科学有效的理论方法和工程指导。展开更多
基金supported by National Natural Science Foundation of China (No.60474059)Hi-tech Research and Development Program of China (863 Program,No.2006AA04Z160).
文摘Vehicle routing problem in distribution （VRPD） is a widely used type of vehicle routing problem （VRP）, which has been proved as NP-Hard, and it is usually modeled as single objective optimization problem when modeling. For multi-objective optimization model, most researches consider two objectives. A multi-objective mathematical model for VRP is proposed, which considers the number of vehicles used, the length of route and the time arrived at each client. Genetic algorithm is one of the most widely used algorithms to solve VRP. As a type of genetic algorithm （GA）, non-dominated sorting in genetic algorithm-Ⅱ （NSGA-Ⅱ） also suffers from premature convergence and enclosure competition. In order to avoid these kinds of shortage, a greedy NSGA-Ⅱ （GNSGA-Ⅱ） is proposed for VRP problem. Greedy algorithm is implemented in generating the initial population, cross-over and mutation. All these procedures ensure that NSGA-Ⅱ is prevented from premature convergence and refine the performance of NSGA-Ⅱ at each step. In the distribution problem of a distribution center in Michigan, US, the GNSGA-Ⅱ is compared with NSGA-Ⅱ. As a result, the GNSGA-Ⅱ is the most efficient one and can get the most optimized solution to VRP problem. Also, in GNSGA-Ⅱ, premature convergence is better avoided and search efficiency has been improved sharply.
文摘目的分析影响ICU脓毒症患者预后的危险因素及血镁水平联合急性生理与慢性健康Ⅱ(acute physiology and chronic health evaluationⅡ,APACHE-Ⅱ)评分对ICU脓毒症患者预后的预测价值。方法对2020年1月—2022年1月期间收治的185例ICU脓毒症患者展开回顾性研究,依据患者28 d生存情况将其分为死亡组(n=94)和存活组(n=91),单因素和logistic多因素分析脓毒症患者28 d死亡的危险因素。Pearson分析血镁水平、APACHE-Ⅱ评分与各项危险因素的相关性,受试者工作特征曲线(receiver operating characteristic,ROC)分析血镁联合APACHE-Ⅱ评分对ICU脓毒症患者预后的预测价值。结果APACHE-Ⅱ评分、序贯器官衰竭评分(sequential organ failure assessment,SOFA)、降钙素原(procalcitonin,PCT)、低镁血症、血小板计数为ICU脓毒症患者28d死亡的危险因素(P<0.05)。APACHE-Ⅱ评分与SOFA评分、PCT水平、低镁血症均呈现正相关(P<0.05),与血小板计数呈现负相关(P<0.05)。低镁血症与APACHE-Ⅱ评分、SOFA评分、PCT水平均呈现正相关(P<0.05),与血小板计数呈现负相关(P<0.05)。低镁血症(AUC=0.697)、APACHE-Ⅱ评分(AUC=0.745)对ICU脓毒症患者预后均有较好的预测价值,且二者联合(AUC=0.866)预测效果更佳。结论低镁血症联合APACHE-Ⅱ评分ICU脓毒症患者28 d死亡有较好的预测价值,临床中可将血镁水平和APACHE-Ⅱ评分作为判断预后的指标。
基金Supported by Direktorat Riset dan Pengembangan(Directorate of Research and Development)Universitas Indonesia(NKB-690/UN2.RST/HKP.05.00/2022).
文摘The need to transport goods across countries and islands has resulted in a high demand for commercial vessels.Owing to such trends,shipyards must efficiently produce ships to reduce production costs.Layout and material flow are among the crucial aspects determining the efficiency of the production at a shipyard.This paper presents the initial design optimization of a shipyard layout using Nondominated Sorting Algorithm-Ⅱ(NSGA-Ⅱ)to find the optimal configuration of workstations in a shipyard layout.The proposed method focuses on simultaneously minimizing two material handling costs,namely work-based material handling and duration-based material handling.NSGA-Ⅱ determines the order of workstations in the shipyard layout.The semiflexible bay structure is then used in the workstation placement process from the sequence formed in NSGA-Ⅱ into a complete design.Considering that this study is a case of multiobjective optimization,the performance for both objectives at each iteration is presented in a 3D graph.Results indicate that after 500 iterations,the optimal configuration yields a work-based MHC of 163670.0 WBM-units and a duration-based MHC of 34750 DBM-units.Starting from a random solution,the efficiency of NSGA-Ⅱ demonstrates significant improvements,achieving a 50.19%reduction in work-based MHC and a 48.58%reduction in duration-based MHC.
文摘横波可控震源振动器平板作为页岩气勘探中的关键部件,其疲劳寿命直接影响可控震源的使用寿命和勘探精度。然而,传统的振动器平板疲劳寿命优化方法未考虑平板与平板齿间焊接残余应力的影响,导致平板结构在抗疲劳优化设计方面效果不佳。为此,使用局部灵敏度法对平板疲劳寿命进行敏感性分析,确定了焊接残余应力为影响疲劳寿命的关键因素。随后,建立了平板的各向最大焊接残余应力与焊接速度和焊接层间温度之间的数学模型,并以各向最大焊接残余应力为约束,以疲劳寿命为优化目标,建立相应的优化模型。最后,利用NSGA-Ⅱ(nondominated sorting genetic algorithm-Ⅱ,非支配排序遗传算法-Ⅱ)获取Pareto解集,并结合熵权法和TOPSIS(technique for order preference by similarity to ideal solution,逼近理想解排序)法确定最佳优化方案:焊接速度为10.23 mm/s,焊接层间温度为105℃。结果表明,优化后平板的疲劳寿命为10.23年,相比优化前提高了17.72%。研究结果可为横波可控震源振动器平板的疲劳寿命优化提供科学有效的理论方法和工程指导。
