Networking plays a crucial role in cloud computing especially in an inter-cloud environment, where data communications among data centers located at different geographical sites form the foundation of inter-cloud fede...Networking plays a crucial role in cloud computing especially in an inter-cloud environment, where data communications among data centers located at different geographical sites form the foundation of inter-cloud federation. Data transmissions required for inter-cloud federation in the complex inter-cloud networking system are often point-to-multi points, which calls for a more effective and efficient multicast routing algorithm in complex networking systems. In this paper, we investigate the multicast routing problem in the inter-cloud context with K constraints where K ≥ 2. Unlike most of existing algorithms that are too complex to be applied in practical scenarios, a novel and fast algorithm for establishing multicast routing tree for interclouds is proposed. The proposed algorithm leverages an entropybased process to aggregate all weights into a comprehensive metric, and then uses it to search a multicast tree(MT) on the basis of the shortest path tree(SPT). We conduct complexity analysis and extensive simulations for the proposed algorithm from the approximation perspective. Both analytical and experimental results demonstrate that the algorithm is more efficient than a representative multi-constrained multicast routing algorithm in terms of both speed and accuracy, and thus we believe that the proposed algorithm is applicable to the inter-cloud environment.展开更多
为了识别地铁站点与常规公交线路衔接换乘存在的换乘效率低等问题,提高城市公共交通系统运行效率和服务水平,促进城市公共交通可持续发展以及响应公众需求和监督,需要对地铁站点与常规公交衔接换乘进行全面系统评价.基于便利性、可靠性...为了识别地铁站点与常规公交线路衔接换乘存在的换乘效率低等问题,提高城市公共交通系统运行效率和服务水平,促进城市公共交通可持续发展以及响应公众需求和监督,需要对地铁站点与常规公交衔接换乘进行全面系统评价.基于便利性、可靠性、可达性、通畅性及舒适度等5个维度15个指标,建立地铁站点与常规公交的衔接换乘评价指标体系;选取CRITIC(criteria importance through inter-criteria correlation)方法对指标进行客观赋权,采用云模型生成基于基本算法的评价标准云和结果云,评价结果通过云的数字特征和云图直观展现,进而对识别出的问题和不足采取相应改进措施.以中国青岛市主城区45个地铁站点与常规公交衔接换乘为案例进行评价,结果表明,衔接换乘综合评价等级为“中等”,准则层(便利性、可靠性、可达性、通畅性和舒适度)的衔接换乘评价等级均为“中等”以上,基本符合青岛市主城区地铁站点与常规公交衔接换乘的特点,验证了评价模型的有效性和合理性.评价结果有助于优化公共交通资源配置,提高城市交通系统的整体运行效率,缓解城市交通拥堵.展开更多
基于视频的点云压缩(Video based point cloud compression, V-PCC)为压缩动态点云提供了高效的解决方案,但V-PCC从三维到二维的投影使得三维帧间运动的相关性被破坏,降低了帧间编码性能.针对这一问题,提出一种基于V-PCC改进的自适应分...基于视频的点云压缩(Video based point cloud compression, V-PCC)为压缩动态点云提供了高效的解决方案,但V-PCC从三维到二维的投影使得三维帧间运动的相关性被破坏,降低了帧间编码性能.针对这一问题,提出一种基于V-PCC改进的自适应分割的视频点云多模式帧间编码方法,并依此设计了一种新型动态点云帧间编码框架.首先,为实现更精准的块预测,提出区域自适应分割的块匹配方法以寻找最佳匹配块;其次,为进一步提高帧间编码性能,提出基于联合属性率失真优化(Rate distortion optimization, RDO)的多模式帧间编码方法,以更好地提高预测精度和降低码率消耗.实验结果表明,提出的改进算法相较于V-PCC实现了-22.57%的BD-BR (Bjontegaard delta bit rate)增益.该算法特别适用于视频监控和视频会议等帧间变化不大的动态点云场景.展开更多
为了直观细致了解乘客在乘坐轨道交通时的体验感受,从乘客感知角度构建了满意度评价指标体系,采用CRITIC(criteria importance through inter-criteria correlation)法来实现指标的客观赋权,并用基于云模型的基本算法生成评价云和结果云...为了直观细致了解乘客在乘坐轨道交通时的体验感受,从乘客感知角度构建了满意度评价指标体系,采用CRITIC(criteria importance through inter-criteria correlation)法来实现指标的客观赋权,并用基于云模型的基本算法生成评价云和结果云,通过云的数字特征和云图的比较直观展现评价结果.以上海市轨道交通2号线的乘客满意度评价为例,验证了评价方法的有效性和合理性,同时该评价结果除了反映乘客的满意程度,也提供了对乘客认知差异和共识度的衡量,使得其具备了更大的使用价值.展开更多
基金supported by the National Natural Science Foundation of China(61309031)
文摘Networking plays a crucial role in cloud computing especially in an inter-cloud environment, where data communications among data centers located at different geographical sites form the foundation of inter-cloud federation. Data transmissions required for inter-cloud federation in the complex inter-cloud networking system are often point-to-multi points, which calls for a more effective and efficient multicast routing algorithm in complex networking systems. In this paper, we investigate the multicast routing problem in the inter-cloud context with K constraints where K ≥ 2. Unlike most of existing algorithms that are too complex to be applied in practical scenarios, a novel and fast algorithm for establishing multicast routing tree for interclouds is proposed. The proposed algorithm leverages an entropybased process to aggregate all weights into a comprehensive metric, and then uses it to search a multicast tree(MT) on the basis of the shortest path tree(SPT). We conduct complexity analysis and extensive simulations for the proposed algorithm from the approximation perspective. Both analytical and experimental results demonstrate that the algorithm is more efficient than a representative multi-constrained multicast routing algorithm in terms of both speed and accuracy, and thus we believe that the proposed algorithm is applicable to the inter-cloud environment.
文摘为了识别地铁站点与常规公交线路衔接换乘存在的换乘效率低等问题,提高城市公共交通系统运行效率和服务水平,促进城市公共交通可持续发展以及响应公众需求和监督,需要对地铁站点与常规公交衔接换乘进行全面系统评价.基于便利性、可靠性、可达性、通畅性及舒适度等5个维度15个指标,建立地铁站点与常规公交的衔接换乘评价指标体系;选取CRITIC(criteria importance through inter-criteria correlation)方法对指标进行客观赋权,采用云模型生成基于基本算法的评价标准云和结果云,评价结果通过云的数字特征和云图直观展现,进而对识别出的问题和不足采取相应改进措施.以中国青岛市主城区45个地铁站点与常规公交衔接换乘为案例进行评价,结果表明,衔接换乘综合评价等级为“中等”,准则层(便利性、可靠性、可达性、通畅性和舒适度)的衔接换乘评价等级均为“中等”以上,基本符合青岛市主城区地铁站点与常规公交衔接换乘的特点,验证了评价模型的有效性和合理性.评价结果有助于优化公共交通资源配置,提高城市交通系统的整体运行效率,缓解城市交通拥堵.
文摘基于视频的点云压缩(Video based point cloud compression, V-PCC)为压缩动态点云提供了高效的解决方案,但V-PCC从三维到二维的投影使得三维帧间运动的相关性被破坏,降低了帧间编码性能.针对这一问题,提出一种基于V-PCC改进的自适应分割的视频点云多模式帧间编码方法,并依此设计了一种新型动态点云帧间编码框架.首先,为实现更精准的块预测,提出区域自适应分割的块匹配方法以寻找最佳匹配块;其次,为进一步提高帧间编码性能,提出基于联合属性率失真优化(Rate distortion optimization, RDO)的多模式帧间编码方法,以更好地提高预测精度和降低码率消耗.实验结果表明,提出的改进算法相较于V-PCC实现了-22.57%的BD-BR (Bjontegaard delta bit rate)增益.该算法特别适用于视频监控和视频会议等帧间变化不大的动态点云场景.
文摘为了直观细致了解乘客在乘坐轨道交通时的体验感受,从乘客感知角度构建了满意度评价指标体系,采用CRITIC(criteria importance through inter-criteria correlation)法来实现指标的客观赋权,并用基于云模型的基本算法生成评价云和结果云,通过云的数字特征和云图的比较直观展现评价结果.以上海市轨道交通2号线的乘客满意度评价为例,验证了评价方法的有效性和合理性,同时该评价结果除了反映乘客的满意程度,也提供了对乘客认知差异和共识度的衡量,使得其具备了更大的使用价值.
