With the explosive growth and need for high-speed wireless communications, more and more energy is consumed to support the required quality of service. Therefore, energy efficient or green communication has become a v...With the explosive growth and need for high-speed wireless communications, more and more energy is consumed to support the required quality of service. Therefore, energy efficient or green communication has become a very hot topic under the ground of limited energy resource and environmentally friendly transmission schemes. MIMO technique is capable of reducing the transmission power thanks to its diversity and multiplexing gain. Moreover, antenna selection(AS) is an alternative to extract many of the benefits in MIMO systems with a reduced cost of complexity and power. Although many works including several survey papers have investigated AS in MIMO systems, the goal of these works is only the capacity maximization or error rate minimization, which fails to guarantee the optimality of the energy efficiency in MIMO systems. In this paper, we overview the state of the art in the AS schemes in energy efficient MIMO systems, the goal of which is to optimize the energy efficiency of the whole system. Specifically, we introduce energy efficient AS in point-to-point MIMO, cooperative MIMO, multiuser MIMO and largescale MIMO systems, respectively. Several challenging and practical issues in this area are also addressed.展开更多
In the 1940s, KIRKENDALL showed that diffusion in binary solid solutions cannot be described by only one diffusion coefficient. Rather, one has to consider the diffusivity of both species. His findings changed the tre...In the 1940s, KIRKENDALL showed that diffusion in binary solid solutions cannot be described by only one diffusion coefficient. Rather, one has to consider the diffusivity of both species. His findings changed the treatment of diffusion data and the theory of diffusion itself. A diffusion-based framework was successfully employed to explain the behaviour of the Kirkendall plane. Nonetheless, the complexity of a multiphase diffusion zone and the morphological evolution during interdiffusion requires a physico-chemical approach. The interactions in binary and more complex systems are key issues from both the fundamental and technological points of view. This paper reviews the Kirkendall effect from the circumstances of its discovery to recent developments in its understanding, with broad applicability in materials science and engineering.展开更多
The characteristics of single and multiple tandem jets(n=2,3,4) in crossflow have been investigated using the realizable k-ε model.The results of this model agree well with experimental measurements using PIV(Particl...The characteristics of single and multiple tandem jets(n=2,3,4) in crossflow have been investigated using the realizable k-ε model.The results of this model agree well with experimental measurements using PIV(Particle Image Velocimetry) or LIF(Laser Induced Fluorescence).We analyzed the calculated results and obtained detailed properties of velocity and concentration of the multiple jets in the pre-merging and post-merging regions.When the velocity ratio is identical,the bending degree of the leading jet is greater than that of the rear jets.The last jet penetrates deeper as the jet number increases,and the shielding effect of the front jet declines with jet spacing increase.Interaction of the jet and crossflow induces formation and development of a counter-rotating vortex pair(CVP).CVP makes the distribution of concentration appear kidney-shaped(except in the merging region),and maximum concentration is at the center of the counter-rotating vortex.Concentration at the CVP center is 1.03-1.4 times that of the local jet trajectory.Post-merging velocity and concentration characteristics differ from those of the single jet because of the shielding effect and mixing of all jets.This paper presents a unified formula of trajectory,concentration half-width and trajectory dilution,by introducing a reduction factor.展开更多
基金supported by NSFC under grant No. 61322111 and No. 61401249the National Basic Research Program of China (973 Program) No. 2013CB336600+1 种基金Specialized Research Fund for the Doctoral Program of Higher Education (SRFDP) under Grant No. 20130002120001Chuanxin Funding, and Beijing nova program No.Z121101002512051
文摘With the explosive growth and need for high-speed wireless communications, more and more energy is consumed to support the required quality of service. Therefore, energy efficient or green communication has become a very hot topic under the ground of limited energy resource and environmentally friendly transmission schemes. MIMO technique is capable of reducing the transmission power thanks to its diversity and multiplexing gain. Moreover, antenna selection(AS) is an alternative to extract many of the benefits in MIMO systems with a reduced cost of complexity and power. Although many works including several survey papers have investigated AS in MIMO systems, the goal of these works is only the capacity maximization or error rate minimization, which fails to guarantee the optimality of the energy efficiency in MIMO systems. In this paper, we overview the state of the art in the AS schemes in energy efficient MIMO systems, the goal of which is to optimize the energy efficiency of the whole system. Specifically, we introduce energy efficient AS in point-to-point MIMO, cooperative MIMO, multiuser MIMO and largescale MIMO systems, respectively. Several challenging and practical issues in this area are also addressed.
文摘In the 1940s, KIRKENDALL showed that diffusion in binary solid solutions cannot be described by only one diffusion coefficient. Rather, one has to consider the diffusivity of both species. His findings changed the treatment of diffusion data and the theory of diffusion itself. A diffusion-based framework was successfully employed to explain the behaviour of the Kirkendall plane. Nonetheless, the complexity of a multiphase diffusion zone and the morphological evolution during interdiffusion requires a physico-chemical approach. The interactions in binary and more complex systems are key issues from both the fundamental and technological points of view. This paper reviews the Kirkendall effect from the circumstances of its discovery to recent developments in its understanding, with broad applicability in materials science and engineering.
基金supported by the National Natural Science Foundation of China (Grant No. 11172218)academic award for excellent Ph.D.Candidates funded by the Ministry of Education of China
文摘The characteristics of single and multiple tandem jets(n=2,3,4) in crossflow have been investigated using the realizable k-ε model.The results of this model agree well with experimental measurements using PIV(Particle Image Velocimetry) or LIF(Laser Induced Fluorescence).We analyzed the calculated results and obtained detailed properties of velocity and concentration of the multiple jets in the pre-merging and post-merging regions.When the velocity ratio is identical,the bending degree of the leading jet is greater than that of the rear jets.The last jet penetrates deeper as the jet number increases,and the shielding effect of the front jet declines with jet spacing increase.Interaction of the jet and crossflow induces formation and development of a counter-rotating vortex pair(CVP).CVP makes the distribution of concentration appear kidney-shaped(except in the merging region),and maximum concentration is at the center of the counter-rotating vortex.Concentration at the CVP center is 1.03-1.4 times that of the local jet trajectory.Post-merging velocity and concentration characteristics differ from those of the single jet because of the shielding effect and mixing of all jets.This paper presents a unified formula of trajectory,concentration half-width and trajectory dilution,by introducing a reduction factor.
