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 ...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-Ⅱis prevented from premature convergence and refine the performance of NSGA-Ⅱat each step.In the distribution problem of a distribution center in Michigan,US,the GNSGA-Ⅱis compared with NSGA-Ⅱ.As a result,the GNSGA-Ⅱis 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
【背景】黄瓜绿斑驳花叶病毒(cucumber green mottle mosaic virus,CGMMV)是我国重要的检疫性植物病毒之一,主要侵染葫芦科作物,造成世界范围内葫芦科作物的严重减产。PsbQ(oxygen-evolving enhancer protein 3)蛋白是组成PSⅡ复合物(O...【背景】黄瓜绿斑驳花叶病毒(cucumber green mottle mosaic virus,CGMMV)是我国重要的检疫性植物病毒之一,主要侵染葫芦科作物,造成世界范围内葫芦科作物的严重减产。PsbQ(oxygen-evolving enhancer protein 3)蛋白是组成PSⅡ复合物(OEC)的相关蛋白之一,参与PSⅡ组装、稳定PSⅡ功能,并对植物应对生物和非生物胁迫反应起调控作用。前期研究显示CGMMV侵染后可以显著下调寄主叶绿体调控基因NbPsbQ1的表达。【目的】明确NbPsbQ1参与CGMMV侵染的机制,为CGMMV病害防控提供理论依据。【方法】通过构建NbPsbQ1及CGMMV CP的荧光表达载体,转化GV3101农杆菌后浸润本氏烟叶片,激光共聚焦显微镜观察其亚细胞定位;利用qRT-PCR技术分析NbPsbQ1在CGMMV侵染不同时期和CP过表达后的转录水平;利用双分子荧光互补、免疫共沉淀和酵母双杂交试验分别验证NbPsbQ1与CP在体内及体外的互作;通过TRV沉默技术分析NbPsbQ1在CGMMV侵染过程中的作用;瞬时过表达NbPsbQ1进一步验证NbPsbQ1对CGMMV蛋白水平及转录水平的影响;测定NbPsbQ1沉默以及CGMMV侵染不同时间植株的光合效率指标,从而分析NbPsbQ1以及CGMMV对植株光合作用的影响。【结果】亚细胞定位结果显示NbPsbQ1定位于叶绿体,而CP定位于细胞质和细胞核;在CGMMV侵染以及CP过表达后,与对照相比,NbPsbQ1的转录水平均明显下调;双分子荧光互补和免疫共沉淀试验结果均证明NbPsbQ1与CP在体内互作,且两者互作使NbPsbQ1的定位从叶绿体迁移至细胞质,但酵母双杂交试验证明两者在植物体外不互作;在沉默植株上接种CGMMV,4 d后观察到处理组和对照组均有部分植株系统叶开始出现斑驳、卷曲症状,而TRV:NbPsbQ1组的发病植株数量始终多于对照组;同时检测mRNA水平和蛋白水平表达结果也表明NbPsbQ1的沉默有效促进了CGMMV的积累;NbPsbQ1瞬时过表达抑制CGMMV CP积累进一步证实NbPsbQ1抑制CGMMV侵染;测定NbPsbQ1沉默植株的光合效率指标,发现与对照组相比,NbPsbQ1沉默后显著降低植株叶片的净光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr),胞间CO_(2)浓度(Ci)明显升高,表明NbPsbQ1参与植株光合作用;同时,发现在CGMMV侵染9 d时,Gs、Tr明显下降而Ci升高。【结论】CGMMV CP与NbPsbQ1在体内互作,并改变其叶绿体定位;随着CGMMV不断侵染,光合作用系统Ⅱ相关基因NbPsbQ1表达水平下调,光合效率受到抑制,从而促进病毒后期的积累。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-Ⅱis prevented from premature convergence and refine the performance of NSGA-Ⅱat each step.In the distribution problem of a distribution center in Michigan,US,the GNSGA-Ⅱis compared with NSGA-Ⅱ.As a result,the GNSGA-Ⅱis 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.
