In order to improve the energy efficiency of large-scale data centers, a virtual machine(VM) deployment algorithm called three-threshold energy saving algorithm(TESA), which is based on the linear relation between the...In order to improve the energy efficiency of large-scale data centers, a virtual machine(VM) deployment algorithm called three-threshold energy saving algorithm(TESA), which is based on the linear relation between the energy consumption and(processor) resource utilization, is proposed. In TESA, according to load, hosts in data centers are divided into four classes, that is,host with light load, host with proper load, host with middle load and host with heavy load. By defining TESA, VMs on lightly loaded host or VMs on heavily loaded host are migrated to another host with proper load; VMs on properly loaded host or VMs on middling loaded host are kept constant. Then, based on the TESA, five kinds of VM selection policies(minimization of migrations policy based on TESA(MIMT), maximization of migrations policy based on TESA(MAMT), highest potential growth policy based on TESA(HPGT), lowest potential growth policy based on TESA(LPGT) and random choice policy based on TESA(RCT)) are presented, and MIMT is chosen as the representative policy through experimental comparison. Finally, five research directions are put forward on future energy management. The results of simulation indicate that, as compared with single threshold(ST) algorithm and minimization of migrations(MM) algorithm, MIMT significantly improves the energy efficiency in data centers.展开更多
The hottest topic now among Europe's automotive industry is CO2. The European Union has set the goal. By 2012, all Europe-based car makers would have to reduce the per car CO2 level to as low as 120-130g/km from t...The hottest topic now among Europe's automotive industry is CO2. The European Union has set the goal. By 2012, all Europe-based car makers would have to reduce the per car CO2 level to as low as 120-130g/km from the current 160g/km.展开更多
Cooperative adaptive cruise control(CACC)is acknowledged as an efficient solution to relieve traffic congestion while ensuring traffic safety.This paper aims to improve traffic efficiency via both the effective follow...Cooperative adaptive cruise control(CACC)is acknowledged as an efficient solution to relieve traffic congestion while ensuring traffic safety.This paper aims to improve traffic efficiency via both the effective following spacing policy and the CACC with platoon kinematics.Firstly,the correlation mechanism of safety spacing policy and time headway policy is analyzed,a versatile generic spacing model is established,and an efficient spacing policy is proposed by leveraging the concept of safety redundancy.Secondly,based on the“virtual centroid”of the platoon,the CACC upper control strategy with platoon kinematics is proposed to improve traffic efficiency.The strategy is complemented by the design of a sliding mode controller,which precisely allocates longitudinal acceleration.Additionally,a lower controller is developed to track the desired acceleration accurately and rapidly under various driving and braking conditions.Thirdly,eight typical scenarios for urban traffic are reconstructed via three-layer decompositions,and the index named synchronization is proposed to evaluate the performance of CACC with platoon kinematics.Finally,a simulation test is conducted,demonstrating that the proposed CACC strategy synchronously responds to the kinematics of the preceding platoon,reducing the accumulation of response delay,ensuring both vehicle following safety and efficiency.展开更多
基金Project(61272148) supported by the National Natural Science Foundation of ChinaProject(20120162110061) supported by the Doctoral Programs of Ministry of Education of China+1 种基金Project(CX2014B066) supported by the Hunan Provincial Innovation Foundation for Postgraduate,ChinaProject(2014zzts044) supported by the Fundamental Research Funds for the Central Universities,China
文摘In order to improve the energy efficiency of large-scale data centers, a virtual machine(VM) deployment algorithm called three-threshold energy saving algorithm(TESA), which is based on the linear relation between the energy consumption and(processor) resource utilization, is proposed. In TESA, according to load, hosts in data centers are divided into four classes, that is,host with light load, host with proper load, host with middle load and host with heavy load. By defining TESA, VMs on lightly loaded host or VMs on heavily loaded host are migrated to another host with proper load; VMs on properly loaded host or VMs on middling loaded host are kept constant. Then, based on the TESA, five kinds of VM selection policies(minimization of migrations policy based on TESA(MIMT), maximization of migrations policy based on TESA(MAMT), highest potential growth policy based on TESA(HPGT), lowest potential growth policy based on TESA(LPGT) and random choice policy based on TESA(RCT)) are presented, and MIMT is chosen as the representative policy through experimental comparison. Finally, five research directions are put forward on future energy management. The results of simulation indicate that, as compared with single threshold(ST) algorithm and minimization of migrations(MM) algorithm, MIMT significantly improves the energy efficiency in data centers.
文摘The hottest topic now among Europe's automotive industry is CO2. The European Union has set the goal. By 2012, all Europe-based car makers would have to reduce the per car CO2 level to as low as 120-130g/km from the current 160g/km.
基金the National Natural Science Foundation of China(52072144,52122216,51675217)the Opening Founding of State Key Laboratory of Automotive Simulation and Control(20201101)for supporting authors'research.
文摘Cooperative adaptive cruise control(CACC)is acknowledged as an efficient solution to relieve traffic congestion while ensuring traffic safety.This paper aims to improve traffic efficiency via both the effective following spacing policy and the CACC with platoon kinematics.Firstly,the correlation mechanism of safety spacing policy and time headway policy is analyzed,a versatile generic spacing model is established,and an efficient spacing policy is proposed by leveraging the concept of safety redundancy.Secondly,based on the“virtual centroid”of the platoon,the CACC upper control strategy with platoon kinematics is proposed to improve traffic efficiency.The strategy is complemented by the design of a sliding mode controller,which precisely allocates longitudinal acceleration.Additionally,a lower controller is developed to track the desired acceleration accurately and rapidly under various driving and braking conditions.Thirdly,eight typical scenarios for urban traffic are reconstructed via three-layer decompositions,and the index named synchronization is proposed to evaluate the performance of CACC with platoon kinematics.Finally,a simulation test is conducted,demonstrating that the proposed CACC strategy synchronously responds to the kinematics of the preceding platoon,reducing the accumulation of response delay,ensuring both vehicle following safety and efficiency.
