基于限时免费换乘的公交线网优化模型与求解算法

针对"限时免费换乘"政策的提出,为了使轨道交通与地面常规公共交通线网构成的综合公共交通网络更加合理,以公交线网系统总费用最小为目标,将"限时免费换乘"条件作为乘客乘车成本因子,以公交单条线路长度、线路非直线系数、线路重叠系数、换乘次数为约束条件,建立了城市轨道交通与地面常规公共交通线网优化模型。考虑"限时免费换乘"条件,从信息素的累积与惩罚机理着手改进了蚁群算法,并给出了将该算法求解城市轨道交通与地面常规公共交通线网优化模型的算法流程。所建立的模型与改进的蚁群算法为优化轨道交通与常规公共交通系统构成的综合公共交通网络提供了一种新方法。     

Expression of the intact C<Subscript>4</Subscript> type<Emphasis Type="Italic">pepc</Emphasis> gene cloned from maize in transgenic winter wheat

Maize intact C4-pepc gene was amplified through LA-PCR and successfully sub-cloned into modified vector pGreen0029 to form a stable expression construct named as pBAC214 (12 kb), which contains CaMV 35S promoter driven bar gene as selection marker. Comparing the cloned DNA sequences (6.7 kb) with published maize C4-pepc gene (GenBank accession E17154) sequences, the identity of DNA sequence alignment is 98.96%. There are only 49 differences between these two intact DNA sequences, of which 13 occur in the region of promoter, 18 in introns, and 18 in exons. The homology of mRNA sequence alignment is 99.38%, and the putative amino acids sequence identity is 99.38%. There are only 15 differences between these two mRNA, and these differences bring 4 sites mutant on the putative amino acids of PEPC protein. Through biolistic bombardment of PDS1000/He system, expression vector pBAC214 has been transformed into winter wheat. Southern blotting results show that the intact C4-pepc gene has been integrated into genome of winter wheat. SDS-PAGE analysis of leaf soluble protein in transgenic wheat showed that the intact C4opepc gene was well transcribed, spliced and translated as in maize. The enzyme activity of leaf PEPC in transgenic wheat has been detected. The activities of leaf PEPC increased over 3-5 times in some transgenic plants. The data of photosynthesis rate and transpiration rate of transgenic wheat flag leaves showed that the C4-pepc gene can increase the photosynthesis rate and transpiration rate of transgenic wheat.     

喷涂聚脲弹性防水涂料：防水防腐、耐磨耐冲击

近期。由广州市地下铁道总公司、广州地铁设计研究院有限公司等七个单位共同完成的“广州市轨道交通线网资源共享应用研究”通过了广东省科技厅科技成果鉴定。该项目以广州轨道交通网络化建设和运营为背景,在充分总结了广州轨道交通建设发展经验的基础上,     

基于四维消耗的公交线网优化模型及蚁群算法

针对城市公交线网的优化问题,应用四维消耗概念进行了综合研究,给出了公交线网优化的多目标线性规划模型及蚁群算法.在定义时间、空间、环境、能源等四维消耗概念的基础上,从点、线、面3个方面对公交线网优化问题进行研究.在考虑效益最大化、成本最小化、发展可持续化的情况下,利用效用函数建立了公交线网优化的多目标线性规划模型.并用蚁群算法对多目标线性规划模型求解,得到最佳的公交线路网络布局结构和公交线网运营效率.实例表明,利用蚁群算法优化后公交线网利用率增大、可达性良好、乘客出行时间减少,优化结果符合城市交通的实际情况,该方法合理可行.