The effects of atomic number Z on the energy distribution of hot electrons generated by the interaction of 60fs, 130mJ, 800nm, and 7×10^17W/cm^2 laser pulses with metallic targets have been studied experimentally...The effects of atomic number Z on the energy distribution of hot electrons generated by the interaction of 60fs, 130mJ, 800nm, and 7×10^17W/cm^2 laser pulses with metallic targets have been studied experimentally. The results show that the number and the effective temperature of hot electrons increase with the atomic number Z of metallic targets, and the temperature of hot electrons are in the range of 190-230keV, which is consistent with a scaling law of hot electrons temperature.展开更多
High entropy alloys(HEAs)have been the star materials in electrocatalysis research in recent years.One of their key features is the greatly increased multiplicity of active sites compared to conventional catalytic mat...High entropy alloys(HEAs)have been the star materials in electrocatalysis research in recent years.One of their key features is the greatly increased multiplicity of active sites compared to conventional catalytic materials.This increased multiplicity stimulates a cocktail effect and a scaling-relation breaking effect,and results in improved activity.However,the multiplicity of active sites in HEAs also poses new problems for mechanistic studies.One apparent problem is the inapplicability to HEA catalysts of the currently most popular mechanistic study method,which uses the electrocatalytic theoretical framework(ETF)based on the computational hydrogen electrode(CHE).The ETF uses a single adsorption energy to represent the catalyst,i.e.,a catalyst is represented by a'point'in the volcanic relationship.It naturally does not involve the multiplicity of active sites of a catalyst,and hence loses brevity in expressing the cocktail effect and scaling-relation breaking effect in HEA catalysis.This paper attempts to solve this inapplicability.Based on the fact that the adsorption energy distribution of HEAs is close to a normal distribution,the mean and variance of the adsorption energy distribution are introduced as descriptors of the ETF,replacing the original single adsorption energy.A quantitative relationship between the variance and the cocktail and scaling-relation braking effects is established.We believe the method described in this work will make the ETF more effective in mechanistic studies of HEA electrocatalysis.展开更多
In geostationary orbits and other quasi-vacuum environments,relativistic electron beams are affected by the initial emittance and space charge effects during the propagation process,resulting in beam quality degradati...In geostationary orbits and other quasi-vacuum environments,relativistic electron beams are affected by the initial emittance and space charge effects during the propagation process,resulting in beam quality degradation.Furthermore,axial energy distribution change in the beam and the axial transient electromagnetic effect caused by current changes in the head and tail regions of the beam also cause the beam to expand and affect its quality.In this study,the particle-in-cell method was used to construct a long-range propagation model of a relativistic electron beam in a vacuum environment.By calculating and simulating the axial energy distribution of the beam and the changes in the transient electromagnetic field,the axial effect during the propagation process was analyzed,and the parameter change law of the effective propagation of the beam was explored.This provided a theoretical reference for a more accurate assessment of the beam quality during propagation.展开更多
In order to clarify the edge and interface effect on the adhesion energy between graphene(Gr)and its substrate,a theoretical model is proposed to study the interaction and strain distribution of Gr/Si system in terms ...In order to clarify the edge and interface effect on the adhesion energy between graphene(Gr)and its substrate,a theoretical model is proposed to study the interaction and strain distribution of Gr/Si system in terms of continuum medium mechanics and nanothermodynamics.We find that the interface separation and adhesion energy are determined by the thickness of Gr and substrate.The disturbed interaction and redistributed strain in the Gr/Si system induced by the effect of surface and interface can make the interface adhesion energy decrease with increasing thickness of Gr and diminishing thickness of Si.Moreover,our results show that the smaller area of Gr is more likely to adhere to the substrate since the edge effect improves the active energy and strain energy.Our predictions can be expected to be a guide for designing high performance of Grbased electronic devices.展开更多
The vacuum energy density of free scalar quantum field in a Rindler distributional space-time with distributional Levi-Cività connection is considered. It has been widely believed that, except in very extreme sit...The vacuum energy density of free scalar quantum field in a Rindler distributional space-time with distributional Levi-Cività connection is considered. It has been widely believed that, except in very extreme situations, the influence of acceleration on quantum fields should amount to just small, sub-dominant contributions. Here we argue that this belief is wrong by showing that in a Rindler distributional background space-time with distributional Levi-Cività connection the vacuum energy of free quantum fields is forced, by the very same background distributional space-time such a Rindler distributional background space-time, to become dominant over any classical energy density component. This semiclassical gravity effect finds its roots in the singular behavior of quantum fields on a Rindler distributional space-times with distributional Levi-Cività connection. In particular we obtain that the vacuum fluctuations have a singular behavior at a Rindler horizon . Therefore sufficiently strongly accelerated observer burns up near the Rindler horizon. Thus Polchinski’s account doesn’t violate the Einstein equivalence principle.展开更多
The report of Chinese Communist Party's 18th National Congress clearly stated that the construction of ecological civilization needs to join hands with the overall layout of the construction of socialism with Chin...The report of Chinese Communist Party's 18th National Congress clearly stated that the construction of ecological civilization needs to join hands with the overall layout of the construction of socialism with Chinese characteristics,and the greatest obstacle to achieving ecological civilization is the energy structure in China.Currently,the third industrial revolution—marked by green technology and cloud computing technology—is happening,and it will have a huge impact on future energy development.The fundamental way to solve the problem of energy resource constraints is developing the renewable energy,and the fundamental approach for renewable energy is developing distributed energy and services.The important factors to achieving China's energy production and consumption revolution are accelerating the construction of distributed energy system and overall energy structure adjustment in China.展开更多
基金Project supported by the National Natural Science Foundation of China （Grant No 10275056） and the Science and Technology 0ffice of Sichuan, China （Grant 04JY029-097）.
文摘The effects of atomic number Z on the energy distribution of hot electrons generated by the interaction of 60fs, 130mJ, 800nm, and 7×10^17W/cm^2 laser pulses with metallic targets have been studied experimentally. The results show that the number and the effective temperature of hot electrons increase with the atomic number Z of metallic targets, and the temperature of hot electrons are in the range of 190-230keV, which is consistent with a scaling law of hot electrons temperature.
文摘High entropy alloys(HEAs)have been the star materials in electrocatalysis research in recent years.One of their key features is the greatly increased multiplicity of active sites compared to conventional catalytic materials.This increased multiplicity stimulates a cocktail effect and a scaling-relation breaking effect,and results in improved activity.However,the multiplicity of active sites in HEAs also poses new problems for mechanistic studies.One apparent problem is the inapplicability to HEA catalysts of the currently most popular mechanistic study method,which uses the electrocatalytic theoretical framework(ETF)based on the computational hydrogen electrode(CHE).The ETF uses a single adsorption energy to represent the catalyst,i.e.,a catalyst is represented by a'point'in the volcanic relationship.It naturally does not involve the multiplicity of active sites of a catalyst,and hence loses brevity in expressing the cocktail effect and scaling-relation breaking effect in HEA catalysis.This paper attempts to solve this inapplicability.Based on the fact that the adsorption energy distribution of HEAs is close to a normal distribution,the mean and variance of the adsorption energy distribution are introduced as descriptors of the ETF,replacing the original single adsorption energy.A quantitative relationship between the variance and the cocktail and scaling-relation braking effects is established.We believe the method described in this work will make the ETF more effective in mechanistic studies of HEA electrocatalysis.
基金National Natural Science Foundation of China(Nos.61372050,U1730247)the HighPower Microwave Key Laboratory Foundation Program(No.6142605200301)。
文摘In geostationary orbits and other quasi-vacuum environments,relativistic electron beams are affected by the initial emittance and space charge effects during the propagation process,resulting in beam quality degradation.Furthermore,axial energy distribution change in the beam and the axial transient electromagnetic effect caused by current changes in the head and tail regions of the beam also cause the beam to expand and affect its quality.In this study,the particle-in-cell method was used to construct a long-range propagation model of a relativistic electron beam in a vacuum environment.By calculating and simulating the axial energy distribution of the beam and the changes in the transient electromagnetic field,the axial effect during the propagation process was analyzed,and the parameter change law of the effective propagation of the beam was explored.This provided a theoretical reference for a more accurate assessment of the beam quality during propagation.
基金This work was supported by the Natural Science Foundation of Guangdong Province(Grant Nos.2019A1515010916 and 2018A030307028)the Featured Innovation Project of Guangdong Education Department(2018KTSCX150)+1 种基金the Maoming Natural Science Foundation of Guangdong,China,(Grant No.2019018001)the Guangdong Province Major Foundation of Fundamental Research(Grant No.517042).
文摘In order to clarify the edge and interface effect on the adhesion energy between graphene(Gr)and its substrate,a theoretical model is proposed to study the interaction and strain distribution of Gr/Si system in terms of continuum medium mechanics and nanothermodynamics.We find that the interface separation and adhesion energy are determined by the thickness of Gr and substrate.The disturbed interaction and redistributed strain in the Gr/Si system induced by the effect of surface and interface can make the interface adhesion energy decrease with increasing thickness of Gr and diminishing thickness of Si.Moreover,our results show that the smaller area of Gr is more likely to adhere to the substrate since the edge effect improves the active energy and strain energy.Our predictions can be expected to be a guide for designing high performance of Grbased electronic devices.
文摘The vacuum energy density of free scalar quantum field in a Rindler distributional space-time with distributional Levi-Cività connection is considered. It has been widely believed that, except in very extreme situations, the influence of acceleration on quantum fields should amount to just small, sub-dominant contributions. Here we argue that this belief is wrong by showing that in a Rindler distributional background space-time with distributional Levi-Cività connection the vacuum energy of free quantum fields is forced, by the very same background distributional space-time such a Rindler distributional background space-time, to become dominant over any classical energy density component. This semiclassical gravity effect finds its roots in the singular behavior of quantum fields on a Rindler distributional space-times with distributional Levi-Cività connection. In particular we obtain that the vacuum fluctuations have a singular behavior at a Rindler horizon . Therefore sufficiently strongly accelerated observer burns up near the Rindler horizon. Thus Polchinski’s account doesn’t violate the Einstein equivalence principle.
文摘The report of Chinese Communist Party's 18th National Congress clearly stated that the construction of ecological civilization needs to join hands with the overall layout of the construction of socialism with Chinese characteristics,and the greatest obstacle to achieving ecological civilization is the energy structure in China.Currently,the third industrial revolution—marked by green technology and cloud computing technology—is happening,and it will have a huge impact on future energy development.The fundamental way to solve the problem of energy resource constraints is developing the renewable energy,and the fundamental approach for renewable energy is developing distributed energy and services.The important factors to achieving China's energy production and consumption revolution are accelerating the construction of distributed energy system and overall energy structure adjustment in China.
