网络功能虚拟化(network function virtualization,NFV)旨在以软件的方式实现网络功能从而替代传统网络中的专有硬件设备.为了应对日益增长的资源密集型需求,面向软件的网络功能虚拟化带来了如虚拟网络功能的管理、低延迟的调度和虚拟...网络功能虚拟化(network function virtualization,NFV)旨在以软件的方式实现网络功能从而替代传统网络中的专有硬件设备.为了应对日益增长的资源密集型需求,面向软件的网络功能虚拟化带来了如虚拟网络功能的管理、低延迟的调度和虚拟网络资源分配等问题.虚拟网络功能调度问题本身为NP-hard,在虚拟网络功能资源调度延迟的特定问题上,为保证良好的用户体验,需要确保网络资源被合理地分配和协调以防止资源的过度供应和保持端到端低延迟.针对网络资源调度的延时问题建立了以最小化资源调度总体服务延迟为目标的整数线性规划模型.此外,为了满足网络动态性较高的特性,设计了一种基于贪婪的启发式算法,此算法首先构建辅助图,然后根据考虑到网络传播时延影响的不同业务链之间的时延影响分析来选择资源调度方案,并且对很多点处理功能采用了多路传输的方式.最终的实验结果表明:所提算法可以有效地指导模型的求解,在降低网络总体服务延时方面比之前相关研究有5%～15%的性能提升.展开更多
The highly mobility of vehicles, intermittent communication between the vehicles and the requirements of real time applications are some of the main challenges of multi-hop message delivery in Vehicular Ad Hoc Networ...The highly mobility of vehicles, intermittent communication between the vehicles and the requirements of real time applications are some of the main challenges of multi-hop message delivery in Vehicular Ad Hoc Networks （ VANETs ）. There are also additional challenges, especially when the destination for the message delivery is a moving vehicle. In this paper, we propose a novel multihop message delivery method, called the Coverage Area-based oPportunistic message forwarding algorithm （CAP）. The main idea of CAP is to cover the potential area of a moving target vehicle as much as possible with the reachable area of the required delivery messages, so that the message can be delivered successfully. Because the success ratio and overhead of the multi-hop message delivery are two important but incompatible parameters in CAP, two tunings are discussed in the algorithm in order to maintain the balance of the two parameters. The simulation results show that compared with other reference approaches, CAP provides an efficient message delivery with a higher success ratio and a shorter message deNNy.展开更多
目的探讨定量CT测量的腹内脂肪与心血管代谢风险(cardiometabolic risk,CMR)的相关性。方法本研究选取中国健康定量CT大数据项目中符合入组标准的研究对象76226例。腹内脂肪面积的测量采用Mindways的定量CT(QCT)Pro Model 4系统。本研...目的探讨定量CT测量的腹内脂肪与心血管代谢风险(cardiometabolic risk,CMR)的相关性。方法本研究选取中国健康定量CT大数据项目中符合入组标准的研究对象76226例。腹内脂肪面积的测量采用Mindways的定量CT(QCT)Pro Model 4系统。本研究收集的心血管代谢指标包括收缩压、舒张压、空腹血糖、总胆固醇、三酰甘油、低密度脂蛋白胆固醇和高密度脂蛋白胆固醇。CMR得分定义为血压、血糖、三酰甘油和高密度脂蛋白胆固醇水平异常得分之和。采用限制性立方样条模型和有序多分类Logistic回归模型分析腹内脂肪面积与心血管代谢风险的相关性。结果研究对象年龄为(50±13)岁,男性占58.8%。男性腹内脂肪面积平均值显著高于女性[(191.7±77.1)cm^(2)比(116.4±56.2)cm^(2),P<0.001]。随着腹内脂肪面积的增加,年龄校正后的心血管代谢指标水平(高密度脂蛋白胆固醇除外)均呈上升趋势。当腹内脂肪面积为300 cm^(2)时,CMR得分≥1的年龄校正后比值比[OR值(95%CI)]男性为14.61(13.31~16.04),女性为5.46(4.06~7.36);CMR得分≥3的年龄校正后可能性男性为31.7%,女性为31.3%。结论基于CT扫描的QCT测量的腹内脂肪面积与心血管代谢风险密切相关。在接受低剂量CT扫描筛查肺癌的健康体检人群中可考虑同时测量腹内脂肪,有助于控制和管理腹型肥胖(特别是内脏脂肪)。展开更多
Software Defined Networking （SDN） is an emerging networking paradigm that assumes a logically centralized control plane separated from the data plane. Despite all its advantages, separating the control and data plan...Software Defined Networking （SDN） is an emerging networking paradigm that assumes a logically centralized control plane separated from the data plane. Despite all its advantages, separating the control and data planes introduces new challenges regarding resilient communications between the two. That is, disconnec- tions between switches and their controllers could result in substantial packet loss and performance degradation. This paper addresses this challenge by studying the issue of control traffic protection in SDNs with arbitrary numbers of controllers. Specifically, we propose a control traffic protection scheme that combines both local rerouting and constrained reverse path forwarding protections, through which switches can locally react to fail- ures and redirect the control traffic using standby backup forwarding options. Our goal is then to find a set of primary routes for control traffic, called protected control network, where as many switches as possible can benefit from the proposed protection scheme. We formulate the protected control network problem, prove its NP-hardness, and develop an algorithm that reconciles proteetability and performance （e.g., switch-to-control latency）. Through extensive simulations based on real topologies, we show that our approach significantly im- proves protectability of control traffic. The results should help further the process of deploying SDN in real-world networks.展开更多
Background Subdural hematoma （SDH） is a common complication of spontaneous intracranial hypotension （SIH）.To date,the management of SDH caused by SIH remains controversial.In this paper,we reviewed the clinical co...Background Subdural hematoma （SDH） is a common complication of spontaneous intracranial hypotension （SIH）.To date,the management of SDH caused by SIH remains controversial.In this paper,we reviewed the clinical course of SDH in patients with SIH,and discuss the underlying mechanism and attributing factors for rapid resolution of subdural hematomas after epidural blood patch （EBP） surgery.Methods We retrospectively reviewed a cohort of seventy-eight SIH patients diagnosed and treated with targeted EBP in our neurology center.Patients who received early CT/MRI follow-up after EBP operation were included.Results A series of four cases of SIH complicated with SDHs were evaluated.Early follow-up neuroimages of these patients revealed that SDHs could be partially or totally absorbed just two to four days after targeted epidural blood patch treatment.Conclusion Targeted epidural blood patch can result in rapid hematoma regression and good recovery in some patients with a combination of SDH and SIH.展开更多
Network virtualization provides a powerful way of sharing substrate networks. Efficient allocation of network resources for multiple virtual networks( VNs) has always been a challenging task. Especially under the ever...Network virtualization provides a powerful way of sharing substrate networks. Efficient allocation of network resources for multiple virtual networks( VNs) has always been a challenging task. Especially under the everincreasing demand of customized VN requests,many problems arise as network conditions change constantly.Particularly with the emergance of resource conflict alongside the development of VNs,service provider( SP) needs to provide a faster and more effective solution. Recently,software defined network( SDN) has emerged as a new networking paradigm,SDN’s centralized control and customizable routing features present new opportunities for convenient and flexible embedding VNs in the network. However,due to the limitations of SDN,replacing all legacy devices in current operational networks by SDN-enabled switches in a short span of time is impractical.Thus,in our study,we focus on the scenario of VN embedding( VNE) in software-defined hybrid networks. In this work,first of all,we propose partially deploying SDN nodes; and then,we use the characteristics of SDN to allocate resources for VN requests,and redirect the path for requests conflict in hybrid SDN network. We formulate the problems and provide simple algorithms to solve them. Simulation results show that our scheme has high ratio in responsiveness and acceptance.展开更多
文摘网络功能虚拟化(network function virtualization,NFV)旨在以软件的方式实现网络功能从而替代传统网络中的专有硬件设备.为了应对日益增长的资源密集型需求,面向软件的网络功能虚拟化带来了如虚拟网络功能的管理、低延迟的调度和虚拟网络资源分配等问题.虚拟网络功能调度问题本身为NP-hard,在虚拟网络功能资源调度延迟的特定问题上,为保证良好的用户体验,需要确保网络资源被合理地分配和协调以防止资源的过度供应和保持端到端低延迟.针对网络资源调度的延时问题建立了以最小化资源调度总体服务延迟为目标的整数线性规划模型.此外,为了满足网络动态性较高的特性,设计了一种基于贪婪的启发式算法,此算法首先构建辅助图,然后根据考虑到网络传播时延影响的不同业务链之间的时延影响分析来选择资源调度方案,并且对很多点处理功能采用了多路传输的方式.最终的实验结果表明:所提算法可以有效地指导模型的求解,在降低网络总体服务延时方面比之前相关研究有5%～15%的性能提升.
基金The research was supported partially by the Major State Basic Research Development Program (973 Program) of China under Grant No.2009CB320504，the National High-tech Research and Development Program (863 Program) of China under Grant No.2011AA01A101，the National Natural Science Foundation of China under Grant No.61271041
文摘The highly mobility of vehicles, intermittent communication between the vehicles and the requirements of real time applications are some of the main challenges of multi-hop message delivery in Vehicular Ad Hoc Networks （ VANETs ）. There are also additional challenges, especially when the destination for the message delivery is a moving vehicle. In this paper, we propose a novel multihop message delivery method, called the Coverage Area-based oPportunistic message forwarding algorithm （CAP）. The main idea of CAP is to cover the potential area of a moving target vehicle as much as possible with the reachable area of the required delivery messages, so that the message can be delivered successfully. Because the success ratio and overhead of the multi-hop message delivery are two important but incompatible parameters in CAP, two tunings are discussed in the algorithm in order to maintain the balance of the two parameters. The simulation results show that compared with other reference approaches, CAP provides an efficient message delivery with a higher success ratio and a shorter message deNNy.
文摘目的探讨定量CT测量的腹内脂肪与心血管代谢风险(cardiometabolic risk,CMR)的相关性。方法本研究选取中国健康定量CT大数据项目中符合入组标准的研究对象76226例。腹内脂肪面积的测量采用Mindways的定量CT(QCT)Pro Model 4系统。本研究收集的心血管代谢指标包括收缩压、舒张压、空腹血糖、总胆固醇、三酰甘油、低密度脂蛋白胆固醇和高密度脂蛋白胆固醇。CMR得分定义为血压、血糖、三酰甘油和高密度脂蛋白胆固醇水平异常得分之和。采用限制性立方样条模型和有序多分类Logistic回归模型分析腹内脂肪面积与心血管代谢风险的相关性。结果研究对象年龄为(50±13)岁,男性占58.8%。男性腹内脂肪面积平均值显著高于女性[(191.7±77.1)cm^(2)比(116.4±56.2)cm^(2),P<0.001]。随着腹内脂肪面积的增加,年龄校正后的心血管代谢指标水平(高密度脂蛋白胆固醇除外)均呈上升趋势。当腹内脂肪面积为300 cm^(2)时,CMR得分≥1的年龄校正后比值比[OR值(95%CI)]男性为14.61(13.31~16.04),女性为5.46(4.06~7.36);CMR得分≥3的年龄校正后可能性男性为31.7%,女性为31.3%。结论基于CT扫描的QCT测量的腹内脂肪面积与心血管代谢风险密切相关。在接受低剂量CT扫描筛查肺癌的健康体检人群中可考虑同时测量腹内脂肪,有助于控制和管理腹型肥胖(特别是内脏脂肪)。
基金supported in part by National High-tech R&D Program of China(863 Program)(Grant Nos.2013AA0133012015AA016101)
文摘Software Defined Networking （SDN） is an emerging networking paradigm that assumes a logically centralized control plane separated from the data plane. Despite all its advantages, separating the control and data planes introduces new challenges regarding resilient communications between the two. That is, disconnec- tions between switches and their controllers could result in substantial packet loss and performance degradation. This paper addresses this challenge by studying the issue of control traffic protection in SDNs with arbitrary numbers of controllers. Specifically, we propose a control traffic protection scheme that combines both local rerouting and constrained reverse path forwarding protections, through which switches can locally react to fail- ures and redirect the control traffic using standby backup forwarding options. Our goal is then to find a set of primary routes for control traffic, called protected control network, where as many switches as possible can benefit from the proposed protection scheme. We formulate the protected control network problem, prove its NP-hardness, and develop an algorithm that reconciles proteetability and performance （e.g., switch-to-control latency）. Through extensive simulations based on real topologies, we show that our approach significantly im- proves protectability of control traffic. The results should help further the process of deploying SDN in real-world networks.
文摘Background Subdural hematoma （SDH） is a common complication of spontaneous intracranial hypotension （SIH）.To date,the management of SDH caused by SIH remains controversial.In this paper,we reviewed the clinical course of SDH in patients with SIH,and discuss the underlying mechanism and attributing factors for rapid resolution of subdural hematomas after epidural blood patch （EBP） surgery.Methods We retrospectively reviewed a cohort of seventy-eight SIH patients diagnosed and treated with targeted EBP in our neurology center.Patients who received early CT/MRI follow-up after EBP operation were included.Results A series of four cases of SIH complicated with SDHs were evaluated.Early follow-up neuroimages of these patients revealed that SDHs could be partially or totally absorbed just two to four days after targeted epidural blood patch treatment.Conclusion Targeted epidural blood patch can result in rapid hematoma regression and good recovery in some patients with a combination of SDH and SIH.
基金supported by the National Natural Science Foundation of China ( 61602051)the Fundamental Research Funds for the Central Universities ( 2017RC11)
文摘Network virtualization provides a powerful way of sharing substrate networks. Efficient allocation of network resources for multiple virtual networks( VNs) has always been a challenging task. Especially under the everincreasing demand of customized VN requests,many problems arise as network conditions change constantly.Particularly with the emergance of resource conflict alongside the development of VNs,service provider( SP) needs to provide a faster and more effective solution. Recently,software defined network( SDN) has emerged as a new networking paradigm,SDN’s centralized control and customizable routing features present new opportunities for convenient and flexible embedding VNs in the network. However,due to the limitations of SDN,replacing all legacy devices in current operational networks by SDN-enabled switches in a short span of time is impractical.Thus,in our study,we focus on the scenario of VN embedding( VNE) in software-defined hybrid networks. In this work,first of all,we propose partially deploying SDN nodes; and then,we use the characteristics of SDN to allocate resources for VN requests,and redirect the path for requests conflict in hybrid SDN network. We formulate the problems and provide simple algorithms to solve them. Simulation results show that our scheme has high ratio in responsiveness and acceptance.
