Carbon dioxide reduction, as a sustainable and versatile strategy for the access of chemical fuels, has attracted increasing attention and enormous efforts have been devoted to it in recent years. However, employing c...Carbon dioxide reduction, as a sustainable and versatile strategy for the access of chemical fuels, has attracted increasing attention and enormous efforts have been devoted to it in recent years. However, employing carbon dioxide as double synthons via bimolecular reduction remains challenging. Here, by leveraging the bimolecular reduction of carbon dioxide to carbonyl and methyl respectively, we describe a Pd-catalyzed trifunctionalization of alkynes with aryl iodide for the first time and showcase its advantages on the formation of various β-diketones and their application in the constructing of heterocyclic compounds with important biological activity, including pyrimidine, oxazole, pyrazole.展开更多
Dynamic adaptive streaming over HTTP(DASH)can adaptively select the appropriate video bitrate for mobile users.Mobile edge computing(MEC)scenario is of great benefit to improve the performance of mobile networks by pr...Dynamic adaptive streaming over HTTP(DASH)can adaptively select the appropriate video bitrate for mobile users.Mobile edge computing(MEC)scenario is of great benefit to improve the performance of mobile networks by providing computing and storage capabilities.And the utilization of spectrum resources can be improved by multicast transmission,but the performance of the multicast transmission will be directly affected by the selected grouping algorithm and resource allocation algorithm.In order to improve the quality of experience(QoE)of video users in the 5G MEC scenario,this paper proposes a QoE-driven DASH multicast scheme,which mainly covers the grouping algorithm and the adaptive bitrate(ABR)algorithm.First of all,we take the optimized target QoE as the basis for grouping and propose an adaptive grouping algorithm that can dynamically adjust the grouping results.Besides,we design a joint optimization ABR algorithm based on the prediction of QoE,which comprehensively considers the process of resource allocation and bitrate decision-making based on the prediction of QoE of video segments in a certain forward-looking field of view.The simulation results show that the proposed DASH multicast scheme performs well in QoE and fairness.展开更多
Nowadays,video streaming counts for the major part of network traffic over the Internet.However,on account of the host-to-host mechanism of the traditional IP network,video distribution over IP-based Internet encounte...Nowadays,video streaming counts for the major part of network traffic over the Internet.However,on account of the host-to-host mechanism of the traditional IP network,video distribution over IP-based Internet encounters bottlenecks.Fortunately,a new proposed future Internet architecture,named data networking(NDN)can improve the performance of video distribution by its features such as in-network storage,multi-path forwarding,etc.In this paper,we design an adaptive bitrate algorithm based on Lyapunov optimization theory over NDN to optimize the long-term quality-of-experience(QoE)of video distribution while ensuring the stability of the whole system.When the network condition is abundant and stable,the problem can be simplified by approximating to a fixed-slot queuing model,but the theoretical performance will degrade when the network status is poor and fluctuate fiercely.Therefore,we divide the problem into two models of fixed time slot and non-fixed time slot and design two Lyapunov optimization algorithms to adapt different network scenarios.The proposed algorithms do not require prior knowledge of the network bandwidth and are capable of running online with the client’s available information.Simulation and realistic experiment results demonstrate that our algorithms perform better than others in NDN.展开更多
基金supported by the National Natural Science Foundation of China(21971073,22001075,22231002)the Natural Science Foundation of Guangdong Province(2019A1515011468)+2 种基金the Discipline Construction Project of Guangdong Medical University(4SG23231G,4SG23249G)the Ordinary University Characteristic Innovation Project of Guangdong Province(2022KTSCX047)the Key-Area Research and Development Program of Guangdong Province(2020B010188001)。
文摘Carbon dioxide reduction, as a sustainable and versatile strategy for the access of chemical fuels, has attracted increasing attention and enormous efforts have been devoted to it in recent years. However, employing carbon dioxide as double synthons via bimolecular reduction remains challenging. Here, by leveraging the bimolecular reduction of carbon dioxide to carbonyl and methyl respectively, we describe a Pd-catalyzed trifunctionalization of alkynes with aryl iodide for the first time and showcase its advantages on the formation of various β-diketones and their application in the constructing of heterocyclic compounds with important biological activity, including pyrimidine, oxazole, pyrazole.
基金the National Key R&D Program of China under Grant 2020YFA0711400the National Science Foundation of China under Grant 61673360the CETC Joint Advanced Research Foundation under Grant 6141B08080101.
文摘Dynamic adaptive streaming over HTTP(DASH)can adaptively select the appropriate video bitrate for mobile users.Mobile edge computing(MEC)scenario is of great benefit to improve the performance of mobile networks by providing computing and storage capabilities.And the utilization of spectrum resources can be improved by multicast transmission,but the performance of the multicast transmission will be directly affected by the selected grouping algorithm and resource allocation algorithm.In order to improve the quality of experience(QoE)of video users in the 5G MEC scenario,this paper proposes a QoE-driven DASH multicast scheme,which mainly covers the grouping algorithm and the adaptive bitrate(ABR)algorithm.First of all,we take the optimized target QoE as the basis for grouping and propose an adaptive grouping algorithm that can dynamically adjust the grouping results.Besides,we design a joint optimization ABR algorithm based on the prediction of QoE,which comprehensively considers the process of resource allocation and bitrate decision-making based on the prediction of QoE of video segments in a certain forward-looking field of view.The simulation results show that the proposed DASH multicast scheme performs well in QoE and fairness.
基金supported by the National Key R&D Program of China under Grant 2020YFA0711400the National Science Foundation of China under Grant 61673360the CETC Joint Advanced Research Foundation under Grant 6141B08080101.
文摘Nowadays,video streaming counts for the major part of network traffic over the Internet.However,on account of the host-to-host mechanism of the traditional IP network,video distribution over IP-based Internet encounters bottlenecks.Fortunately,a new proposed future Internet architecture,named data networking(NDN)can improve the performance of video distribution by its features such as in-network storage,multi-path forwarding,etc.In this paper,we design an adaptive bitrate algorithm based on Lyapunov optimization theory over NDN to optimize the long-term quality-of-experience(QoE)of video distribution while ensuring the stability of the whole system.When the network condition is abundant and stable,the problem can be simplified by approximating to a fixed-slot queuing model,but the theoretical performance will degrade when the network status is poor and fluctuate fiercely.Therefore,we divide the problem into two models of fixed time slot and non-fixed time slot and design two Lyapunov optimization algorithms to adapt different network scenarios.The proposed algorithms do not require prior knowledge of the network bandwidth and are capable of running online with the client’s available information.Simulation and realistic experiment results demonstrate that our algorithms perform better than others in NDN.
