By Mobile Edge Computing(MEC), computation-intensive tasks are offloaded from mobile devices to cloud servers, and thus the energy consumption of mobile devices can be notably reduced. In this paper, we study task off...By Mobile Edge Computing(MEC), computation-intensive tasks are offloaded from mobile devices to cloud servers, and thus the energy consumption of mobile devices can be notably reduced. In this paper, we study task offloading in multi-user MEC systems with heterogeneous clouds, including edge clouds and remote clouds. Tasks are forwarded from mobile devices to edge clouds via wireless channels, and they can be further forwarded to remote clouds via the Internet. Our objective is to minimize the total energy consumption of multiple mobile devices, subject to bounded-delay requirements of tasks. Based on dynamic programming, we propose an algorithm that minimizes the energy consumption, by jointly allocating bandwidth and computational resources to mobile devices. The algorithm is of pseudo-polynomial complexity. To further reduce the complexity, we propose an approximation algorithm with energy discretization, and its total energy consumption is proved to be within a bounded gap from the optimum. Simulation results show that, nearly 82.7% energy of mobile devices can be saved by task offloading compared with mobile device execution.展开更多
With the emerging connected autonomous driving paradigm,more advanced applications leveraging vehicular communications are drawing tremendous attentions.In order to analyze the feasibility and performance of these app...With the emerging connected autonomous driving paradigm,more advanced applications leveraging vehicular communications are drawing tremendous attentions.In order to analyze the feasibility and performance of these applications,it is necessary to build an evaluation platform that jointly considers vehicular communication,road traffic and vehicle dynamics.This article describes our recent progress on network-level autonomous driving simulator based on the Cellular-Vehicle-to-Everything(C-V2X)protocol,and a joint platform combined with SUMO and CARLA simulators for evaluating road traffic and vehicle dynamics.To demonstrate its effectiveness,this article implements a hybrid multi-intersection scheduling scheme on the platform,and shows the advantages of the scheme in terms of traffic efficiency and fault tolerance.A remote driving application based on CARLA,wherein the interplay between communication and computation is also investigated.展开更多
Microwave absorbing materials(MAMs)are playing an increasingly essential role in the development of wireless communications,high-power electronic devices,and advanced target detection technology.MAMs with a broad-band...Microwave absorbing materials(MAMs)are playing an increasingly essential role in the development of wireless communications,high-power electronic devices,and advanced target detection technology.MAMs with a broad-bandwidth response are particularly important in the area of communication security,radiation prevention,electronic reliability,and military stealth.Although considerable progress has been made in the design and preparation of MAMs with a broad-bandwidth response,a number of challenges still remain,and the structure–function relationship of MAMs is still far from being completely understood.Herein,the advances in the design and research of MAMs with a broad-bandwidth response are outlined.The main strategies for expanding the effective absorption bandwidth of MAMs are comprehensively summarized considering three perspectives:the chemical combination strategy,morphological control strategy,and macrostructure control strategy.Several important results as well as design principles and absorption mechanisms are highlighted.A coherent explanation detailing the influence of the chemical composition and structure of various materials on the microwave absorption properties of MAMs is provided.The main challenges,new opportunities,and future perspectives in this promising field are also presented.展开更多
Metallic iron particles are of great potential for microwave absorption materials due to their strong magnetic loss ability.However,the oxidation susceptibility of metallic iron particles in the atmospheric environmen...Metallic iron particles are of great potential for microwave absorption materials due to their strong magnetic loss ability.However,the oxidation susceptibility of metallic iron particles in the atmospheric environment is regarded as a major factor causing performance degradation.Although many efforts have been developed to avoid their oxidation,whether partial surface oxidized iron particles can improve the microwave absorbing performance is rarely concerned.In order to explore the effect of partial surface oxidation of iron on its properties,the designed yolk–shelled(Fe/FeO_(x))@C composites with multiple heterointerfaces were synthesized via an in-situ polymerization and a finite reduction–oxidation process of Fe_(2)O_(3)ellipsoids.The performance enhancement mechanisms of Fe/FeO_(x)heterointerfaces were also elaborated.It is demonstrated that the introduction of Fe-based heterogeneous interfaces can not only enhance the dielectric loss,but also increase the imaginary part of the permeability in the higher frequency range to strengthen the magnetic loss ability.Meanwhile,the yolk–shell structure can effectively improve impedance matching and enhance microwave absorption performances via increasing multiple reflection and scattering behaviors of incident microwaves.Compared to Fe@C composite,the effective absorption(reflection loss(RL)<−10 dB)bandwidth of the optimized(Fe/FeO_(x))@C-2 increases from 5.7 to 7.3 GHz(10.7–18.0 GHz)at a same matching thickness of 2 mm,which can completely cover Ku-band.This work offers a good perspective for the enhancement of magnetic loss ability and microwave absorption performance of Fe-based microwave absorption materials with promising practical applications.展开更多
Seed-mediated growth is the most general way to controllably synthesize bimetal nano-heterostructures.Despite successful instances through trial and error were reported, the way for second metal depositing on the seed...Seed-mediated growth is the most general way to controllably synthesize bimetal nano-heterostructures.Despite successful instances through trial and error were reported, the way for second metal depositing on the seed, namely whether the symmetry of resulted nano-heterostructure follows the original crystal symmetry of seed metal, remains an unpredictable issue to date. In this work, we propose that the thermodynamic factor, i.e., the difference of equilibrium electrochemical potentials(corresponding to their Fermi levels) of two metals in the growth solution, plays a key role for the symmetry breaking of bimetal nano-heterostructures during the seed-mediated growth. As a proof-of-principle experiment, by reversing the relative position of Fermi levels of the Pd nanocube seeds and the second metal Au with changing the concentration of reductant(L-ascorbic acid) in the growth solution, the structure of as-prepared products successfully evolved from centrosymmetric Pd@Au core-shell trisoctahedra to asymmetric Pd-Au hetero-dimers. The idea was further demonstrated by the growth of Ag on the Pd seeds. The present work intends to reveal the origin of symmetry breaking in the seed-mediated growth of nano-heterostructures from the viewpoint of thermodynamics, and these new insights will in turn help to achieve rational construction of bimetal nano-heterostructures with specific functions.展开更多
The reaction of a metallo-organic ligand(LA)in which two"V"-shaped bisterpyridines attaching to metaposition of"X"-shaped tetraterpyridine via connectivity and Zn^(2+)ions gave rise to 3D supramole...The reaction of a metallo-organic ligand(LA)in which two"V"-shaped bisterpyridines attaching to metaposition of"X"-shaped tetraterpyridine via connectivity and Zn^(2+)ions gave rise to 3D supramolecular architectures:octagram(Zn_(8)LA_(4)).However,a position varied ligand(LB)in which two"V"-shaped bisterpyridines locating at the ortho-position of"X"-shaped tetraterpyridine afforded a different 3D hexagram(Zn_(6)LB_(3)).Full characterizations included NMR(^(1)H,^(13)C,^(2)D COSY,NOESY and DOSY),ESI-MS,TWIM-MS,TEM and AFM.The resulted structures were directly determined by the position of two"V"-shaped bisterpyridines attaching to"X"-shaped tetraterpyridine.展开更多
基金the National Key R&D Program of China 2018YFB1800804the Nature Science Foundation of China (No. 61871254,No. 61861136003,No. 91638204)Hitachi Ltd.
文摘By Mobile Edge Computing(MEC), computation-intensive tasks are offloaded from mobile devices to cloud servers, and thus the energy consumption of mobile devices can be notably reduced. In this paper, we study task offloading in multi-user MEC systems with heterogeneous clouds, including edge clouds and remote clouds. Tasks are forwarded from mobile devices to edge clouds via wireless channels, and they can be further forwarded to remote clouds via the Internet. Our objective is to minimize the total energy consumption of multiple mobile devices, subject to bounded-delay requirements of tasks. Based on dynamic programming, we propose an algorithm that minimizes the energy consumption, by jointly allocating bandwidth and computational resources to mobile devices. The algorithm is of pseudo-polynomial complexity. To further reduce the complexity, we propose an approximation algorithm with energy discretization, and its total energy consumption is proved to be within a bounded gap from the optimum. Simulation results show that, nearly 82.7% energy of mobile devices can be saved by task offloading compared with mobile device execution.
基金This work was supported by the National Key R&D Program of China(Grant No.2019YFE0196600)the Nature Science Foundation of China(No.61871254,No.91638204,No.61861136003)the program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning,and research funds from the Shanghai Institute for Advanced Communication and Data Science(SICS).
文摘With the emerging connected autonomous driving paradigm,more advanced applications leveraging vehicular communications are drawing tremendous attentions.In order to analyze the feasibility and performance of these applications,it is necessary to build an evaluation platform that jointly considers vehicular communication,road traffic and vehicle dynamics.This article describes our recent progress on network-level autonomous driving simulator based on the Cellular-Vehicle-to-Everything(C-V2X)protocol,and a joint platform combined with SUMO and CARLA simulators for evaluating road traffic and vehicle dynamics.To demonstrate its effectiveness,this article implements a hybrid multi-intersection scheduling scheme on the platform,and shows the advantages of the scheme in terms of traffic efficiency and fault tolerance.A remote driving application based on CARLA,wherein the interplay between communication and computation is also investigated.
基金supported by the National Natural Science Foundation of China(Nos.21771151 and 21931009).
文摘Microwave absorbing materials(MAMs)are playing an increasingly essential role in the development of wireless communications,high-power electronic devices,and advanced target detection technology.MAMs with a broad-bandwidth response are particularly important in the area of communication security,radiation prevention,electronic reliability,and military stealth.Although considerable progress has been made in the design and preparation of MAMs with a broad-bandwidth response,a number of challenges still remain,and the structure–function relationship of MAMs is still far from being completely understood.Herein,the advances in the design and research of MAMs with a broad-bandwidth response are outlined.The main strategies for expanding the effective absorption bandwidth of MAMs are comprehensively summarized considering three perspectives:the chemical combination strategy,morphological control strategy,and macrostructure control strategy.Several important results as well as design principles and absorption mechanisms are highlighted.A coherent explanation detailing the influence of the chemical composition and structure of various materials on the microwave absorption properties of MAMs is provided.The main challenges,new opportunities,and future perspectives in this promising field are also presented.
基金supported by the National Natural Science Foundation of China(Nos.21771151 and 21931009)the Natural Science Foundation of Fujian Province of China(No.2022J01042).
文摘Metallic iron particles are of great potential for microwave absorption materials due to their strong magnetic loss ability.However,the oxidation susceptibility of metallic iron particles in the atmospheric environment is regarded as a major factor causing performance degradation.Although many efforts have been developed to avoid their oxidation,whether partial surface oxidized iron particles can improve the microwave absorbing performance is rarely concerned.In order to explore the effect of partial surface oxidation of iron on its properties,the designed yolk–shelled(Fe/FeO_(x))@C composites with multiple heterointerfaces were synthesized via an in-situ polymerization and a finite reduction–oxidation process of Fe_(2)O_(3)ellipsoids.The performance enhancement mechanisms of Fe/FeO_(x)heterointerfaces were also elaborated.It is demonstrated that the introduction of Fe-based heterogeneous interfaces can not only enhance the dielectric loss,but also increase the imaginary part of the permeability in the higher frequency range to strengthen the magnetic loss ability.Meanwhile,the yolk–shell structure can effectively improve impedance matching and enhance microwave absorption performances via increasing multiple reflection and scattering behaviors of incident microwaves.Compared to Fe@C composite,the effective absorption(reflection loss(RL)<−10 dB)bandwidth of the optimized(Fe/FeO_(x))@C-2 increases from 5.7 to 7.3 GHz(10.7–18.0 GHz)at a same matching thickness of 2 mm,which can completely cover Ku-band.This work offers a good perspective for the enhancement of magnetic loss ability and microwave absorption performance of Fe-based microwave absorption materials with promising practical applications.
基金supported by the National Basic Research Program of China(2015CB93230)the National Key Research and Development Program of China(2017YFA0206801)+1 种基金the National Natural Science Foundation of China(21333008,21671163,21721001,and 21773190)the Fundamental Research Funds for the Central Universities(20720160026)
文摘Seed-mediated growth is the most general way to controllably synthesize bimetal nano-heterostructures.Despite successful instances through trial and error were reported, the way for second metal depositing on the seed, namely whether the symmetry of resulted nano-heterostructure follows the original crystal symmetry of seed metal, remains an unpredictable issue to date. In this work, we propose that the thermodynamic factor, i.e., the difference of equilibrium electrochemical potentials(corresponding to their Fermi levels) of two metals in the growth solution, plays a key role for the symmetry breaking of bimetal nano-heterostructures during the seed-mediated growth. As a proof-of-principle experiment, by reversing the relative position of Fermi levels of the Pd nanocube seeds and the second metal Au with changing the concentration of reductant(L-ascorbic acid) in the growth solution, the structure of as-prepared products successfully evolved from centrosymmetric Pd@Au core-shell trisoctahedra to asymmetric Pd-Au hetero-dimers. The idea was further demonstrated by the growth of Ag on the Pd seeds. The present work intends to reveal the origin of symmetry breaking in the seed-mediated growth of nano-heterostructures from the viewpoint of thermodynamics, and these new insights will in turn help to achieve rational construction of bimetal nano-heterostructures with specific functions.
基金supported by the National Natural Science Foundation of China(No.21971257 for P.Wang)support from the Ministry of Science and Technology of Taiwan(No.MOST106-2628-M-002-007-MY3)。
文摘The reaction of a metallo-organic ligand(LA)in which two"V"-shaped bisterpyridines attaching to metaposition of"X"-shaped tetraterpyridine via connectivity and Zn^(2+)ions gave rise to 3D supramolecular architectures:octagram(Zn_(8)LA_(4)).However,a position varied ligand(LB)in which two"V"-shaped bisterpyridines locating at the ortho-position of"X"-shaped tetraterpyridine afforded a different 3D hexagram(Zn_(6)LB_(3)).Full characterizations included NMR(^(1)H,^(13)C,^(2)D COSY,NOESY and DOSY),ESI-MS,TWIM-MS,TEM and AFM.The resulted structures were directly determined by the position of two"V"-shaped bisterpyridines attaching to"X"-shaped tetraterpyridine.