Large-eddy simulation（LES） was originally proposed for simulating atmospheric flows in the 1960 s and has become one of the most promising and successful methodology for simulating turbulent flows with the improveme...Large-eddy simulation（LES） was originally proposed for simulating atmospheric flows in the 1960 s and has become one of the most promising and successful methodology for simulating turbulent flows with the improvement of computing power. It is now feasible to simulate complex engineering flows using LES. However, apart from the computing power, significant challenges still remain for LES to reach a level of maturity that brings this approach to the mainstream of engineering and industrial computations. This paper will describe briefly LES formalism first, present a quick glance at its history, review its current state focusing mainly on its applications in transitional flows and gas turbine combustor flows, discuss some major modelling and numerical challenges/issues that we are facing now and in the near future, and finish with the concluding remarks.展开更多
In early September 2023,when its market cap jumped to 428 billion USD,a valuation topping the estimated 2022 gross domestic product of its Scandinavian home country,the drugmaker Novo Nordisk(Bagsværd,Denmark)bri...In early September 2023,when its market cap jumped to 428 billion USD,a valuation topping the estimated 2022 gross domestic product of its Scandinavian home country,the drugmaker Novo Nordisk(Bagsværd,Denmark)briefly eclipsed the French luxury brand conglomerateLMVH(Paris,France)as Europe's most valuable company[1].The reason for the company's soaring worth?Its already best-selling weight loss drug Wegovy was being released to patients in the United Kingdom.展开更多
The Oxford English Dictionary(OED)was originally published between 1884 and 1928,but even today we are only scratching the surface of its full potential as a major searchable online resource.This article looks briefly...The Oxford English Dictionary(OED)was originally published between 1884 and 1928,but even today we are only scratching the surface of its full potential as a major searchable online resource.This article looks briefly at how and why the dictionary was originally established in the second half of the nineteenth century,before examining how today's editors are updating its content in the first comprehensive revision programme the dictionary has ever undergone.The remainder of the article investigates the current online site and looks into the future—to see what strategies the dictionary is employing and imagining as it moves away from being a book on computer to becoming a fully-fledged online language resource.展开更多
On the basis of eight atmospheric reanalyses, we analyzed the spatial-temporal characteristics of global evaporation and also briefly evaluated the eight reanalyses. The results indicate that the long-term mean annual...On the basis of eight atmospheric reanalyses, we analyzed the spatial-temporal characteristics of global evaporation and also briefly evaluated the eight reanalyses. The results indicate that the long-term mean annual evaporation obtained from different reanalyses are consistent over most regions, with significant maritime-continental contrasts, as well as differences in meridional directions, and the land evaporation generally decreases with the increase of altitude. In addition, the temporal evolution of global evaporation varies significantly among the datasets, MERRA, ERA-Interim, NCEP-NCRA, and NCEP-DOE are very similar, whereas CFSR agrees best with ERA-40. Comparison of the inter-annual to inter-decadal variability of land evaporation reveals large differences among the reanalyses, whereas MERRA, CFSR, and NCEP-DOE are exactly similar. The temporal variation of evaporation over the oceans showed a relatively high consistency, which indicates that the quality of the reconstructed evaporation values over the oceans is higher, and even greater uncertainties lie in the estimates of evaporation over the land. In general, MERRA and NCEP-DOE may appropriately reflect the spatial-temporal characteristics of global evaporation, showing strong representativeness. The CFSR and ERA-40 are capable of revealing the characteristics of land evaporation, whereas ERA-Interim, NCEP-NCAR, OAFlux, and HOAPS are relatively applicable for research focused on the evaporation over the oceans. According to ERA-40, NCEP-NCAR, and OAFlux, global evaporation significantly decreased for the period of 1958–1978. In contrast, most of the eight reanalyses show a significant linear increase for the period of 1979–2011, and evaporation over the oceans was even more pronounced. Furthermore, the results are presented for the mean annual cycle of global evaporation, the changes at the low latitudes in the Northern Hemisphere are most distinct, and the monthly variation amplitude of the land evaporation was higher than that of the evaporati展开更多
The cryostat is a vacuum tight container enveloping the entire basic systems of the ITER tokamak machine,including a vacuum vessel,a superconducting magnet and thermal shield etc.It is evacuated to a pressure of 10^-4...The cryostat is a vacuum tight container enveloping the entire basic systems of the ITER tokamak machine,including a vacuum vessel,a superconducting magnet and thermal shield etc.It is evacuated to a pressure of 10^-4Pa to limit the heat transfer via gas conduction and convection to the cryogenically cooled components.Another important function of cryostat is to support all the loads from the tokamak to the concrete floor of the pit by its support system during different operational regimes and accident scenarios.This paper briefly presents the design evolution and associated analysis of the cryostat support system and the structural interface with the building.展开更多
Central RF frequency is a key parameter of storage rings. This paper presents the measurement of central RF frequency of the HLS-Ⅱ storage ring with the sextupole modulation method. Firstly, the basis of central RF f...Central RF frequency is a key parameter of storage rings. This paper presents the measurement of central RF frequency of the HLS-Ⅱ storage ring with the sextupole modulation method. Firstly, the basis of central RF frequency measurement of the electron storage ring is briefly introduced. Then, the error sources and the optimized measurement method for the HLS-Ⅱ storage ring are discussed. The workflow of a self-compiled Matlab script used in central RF frequency measurement is also described. Finally, the results achieved by using two data processing methods to cross-check each other are shown. The measured value of the central RF frequency demonstrates that the circumference deviation of the HLS-Ⅱ storage ring is less than 1 mm.展开更多
Uniaxial strain induced ferroelectric phase transitions in rutile TiO2 are investigated by first-principles calculations. The calculated results show that the in-plane tensile strain induces rutile TiO2, paraelectric ...Uniaxial strain induced ferroelectric phase transitions in rutile TiO2 are investigated by first-principles calculations. The calculated results show that the in-plane tensile strain induces rutile TiO2, paraelectric phase with P4-2/mnm （D4h） space group, to a ferroelectric phase with Pm（Cs） space group, driven by the softening behaviour of the Eul mode. In addition, the out-of-plane tensile strain, vertical to the ab plane, leads to a ferroelectric phase with P42nm （C4v） space group, driven by the softening behaviour of the A2u mode. The critical tensile strains are 3.7% in-plane and 4.0% out-of-plane, respectively. In addition, the in-plane compression strain, which has the same structure variation as out- of-plane tensile strain due to Poisson effect, leads the paraelectric rutile TiO2 to a paraelectric phase with Pnnm （D2h） space group driven by the softening behaviour of the B1g mode. These results indicate that the sequence ferroelectric （or paraelectric） phase depends on the strain applied. The origin of ferroelectric stabilization in rutile TiO2 is also discussed briefly in terms of strain induced Born effective charge transfer.展开更多
The discovery of the three-dimensional Dirac semimetals have expanded the family of topological materials,and attracted massive attentions in recent few years.In this short review,we briefly overview the quantum trans...The discovery of the three-dimensional Dirac semimetals have expanded the family of topological materials,and attracted massive attentions in recent few years.In this short review,we briefly overview the quantum transport properties of a well-studied three-dimensional Dirac semimetal,Cd3As2.These unusual transport phenomena include the unexpected ultra-high charge mobility,large linear magnetoresistivity,remarkable Shubnikov-de Hass oscillations,and the evolution of the nontrivial Berry＇s phase.These quantum transport properties not only reflect the novel electronic structure of Dirac semimetals,but also give the possibilities for their future device applications.展开更多
The recent discovery of three-dimensional（3D） topological insulators（TIs） has provided a fertile ground for obtaining further insights into electron localization in condensed matter systems.In the past few years,a...The recent discovery of three-dimensional（3D） topological insulators（TIs） has provided a fertile ground for obtaining further insights into electron localization in condensed matter systems.In the past few years,a tremendous amount of research effort has been devoted to investigate electron transport properties of 3D TIs and their low dimensional structures in a wide range of disorder strength,covering transport regimes from weak antilocalization to strong localization.The knowledge gained from these studies not only offers sensitive means to probe the surface states of 3D TIs but also forms a basis for exploring novel topological phases.In this article,we briefly review the main experimental progress in the study of the localization in 3D TIs,with a focus on the latest results on ultrathin TI films.Some new transport data will also be presented in order to complement those reported previously in the literature.展开更多
Multiple sclerosis（MS） is an autoimmune mediated neurodegenerative disease characterized by demyelination and oligodendrocyte（OL） loss in the central nervous system and accompanied by local inflammation and infilt...Multiple sclerosis（MS） is an autoimmune mediated neurodegenerative disease characterized by demyelination and oligodendrocyte（OL） loss in the central nervous system and accompanied by local inflammation and infiltration of peripheral immune cells. Although many risk factors and symptoms have been identified in MS, the pathology is complicated and the cause remains unknown. It is also unclear whether OL apoptosis precedes the inflammation or whether the local inflammation is the cause of OL death and demyelination. This review briefly discusses several models that have been developed to specifically ablate oligodendrocytes in an effort to separate the effects of demyelination from inflammation.展开更多
There is no available theoretical description of electron transfer from negative projectiles at a velocity below 0.1 a.u.during grazing scattering on insulating surfaces.In this low-velocity range,electron-capture and...There is no available theoretical description of electron transfer from negative projectiles at a velocity below 0.1 a.u.during grazing scattering on insulating surfaces.In this low-velocity range,electron-capture and electron-loss processes coexist.For electron capture,the Demkov model has been successfully used to explain the velocity dependence of the negative-ion fraction formed from fast atoms during grazing scattering on insulating surfaces.For electron loss,we consider that an electron may be transferred from the formed ionic diabatic quasi-molecular state to the formed covalent diabatic quasi-molecular state by the crossing of the potential curves of negative projectiles approaching the surface cations,which can be described by the Landau-Zener two-energy-level crossing model.Combining these two models,we obtain good agreement between the experimental and calculated data for the F-LiF（OOl） collision system,which is briefly discussed.展开更多
Two-dimensional（2D） topological insulators（TTs,or quantum spin Hall insulators） are special insulators that possess bulk 2D electronic energy gap and time-reversal symmetry protected one-dimensional（1D） edge sta...Two-dimensional（2D） topological insulators（TTs,or quantum spin Hall insulators） are special insulators that possess bulk 2D electronic energy gap and time-reversal symmetry protected one-dimensional（1D） edge state.Carriers in the edge state have the property of spin-momentum locking,enabling dissipation-free conduction along the 1D edge.The existence of 2D TIs was confirmed by experiments in semiconductor quantum wells.However,the 2D bulk gaps in those quantum wells are extremely small,greatly limiting potential application in future electronics and spintronics.Despite this limitation,2D TIs with a large bulk gap attracted plenty of interest.In this paper,recent progress in searching for TIs with a large bulk gap is reviewed briefly.We start by introducing some theoretical predictions of these new materials and then discuss some recent important achievements in crystal growth and characterization.展开更多
Regarding climate change in China, ordinary people, even meteorologists, would think the cold waves from Siberia dominate winter temperature in southeast China. As oceanographers, however, we must know the role of oce...Regarding climate change in China, ordinary people, even meteorologists, would think the cold waves from Siberia dominate winter temperature in southeast China. As oceanographers, however, we must know the role of ocean circulation in climate change. This text briefly discusses how important is the role of the Western Pacific Ocean circulation in climate change in southeast China on the basis of CTD data gathered by the R/V Science 1 in the western Pacific in September and October, 1986 and 1987 respectively , and statistical air temperature data in southeast China.展开更多
One of the most prominent changes during stress is the increased outpouring of glucocorticoids (GC), which has been subjected to extensive studies by many authors.
One of the efficient approaches used on calculating the generation and dissipation of seismic pore pres-sure in saturated soil mass is based on coupling the formulations of Terzaghi’s theory wity a seismic porepressu...One of the efficient approaches used on calculating the generation and dissipation of seismic pore pres-sure in saturated soil mass is based on coupling the formulations of Terzaghi’s theory wity a seismic porepressure generation model in undrained condition. To solve this coupled equation for practical problems,most researchers employ essentially numerical methods such as finite elements. While these methods are in-dispensable for arbitrary geometries and soil inhomogeneities, analytical solutions are still desirable whichenhance physical understanding of the essentials and halp the development of efficient and accurate numeri-cal methods [1-4].展开更多
Barefoot running has been around for millions of years,and it is safe to presume that for most of that time,the practice occasioned little interest.Our ancestors ran barefoot because they had no shoes.When footwear wa...Barefoot running has been around for millions of years,and it is safe to presume that for most of that time,the practice occasioned little interest.Our ancestors ran barefoot because they had no shoes.When footwear was first invented during the last 40,000 years (no doubt at different times and in different places),shoes were by necessity minimal-essentially sandals and moccasins-designed to protect the sole of the foot but lacking any of the sophisticated features and materials present in modem running shoes such as elevated cushioned heels,arch supports,and toe springs.Most of these features were invented in the 1970s,and they quickly became more popular and sophisticated as running underwent a worldwide boom.Today,the vast majority of runners think it is normal to wear cushioned running shoes,and would never dream of running without them.展开更多
文摘Large-eddy simulation（LES） was originally proposed for simulating atmospheric flows in the 1960 s and has become one of the most promising and successful methodology for simulating turbulent flows with the improvement of computing power. It is now feasible to simulate complex engineering flows using LES. However, apart from the computing power, significant challenges still remain for LES to reach a level of maturity that brings this approach to the mainstream of engineering and industrial computations. This paper will describe briefly LES formalism first, present a quick glance at its history, review its current state focusing mainly on its applications in transitional flows and gas turbine combustor flows, discuss some major modelling and numerical challenges/issues that we are facing now and in the near future, and finish with the concluding remarks.
文摘In early September 2023,when its market cap jumped to 428 billion USD,a valuation topping the estimated 2022 gross domestic product of its Scandinavian home country,the drugmaker Novo Nordisk(Bagsværd,Denmark)briefly eclipsed the French luxury brand conglomerateLMVH(Paris,France)as Europe's most valuable company[1].The reason for the company's soaring worth?Its already best-selling weight loss drug Wegovy was being released to patients in the United Kingdom.
文摘The Oxford English Dictionary(OED)was originally published between 1884 and 1928,but even today we are only scratching the surface of its full potential as a major searchable online resource.This article looks briefly at how and why the dictionary was originally established in the second half of the nineteenth century,before examining how today's editors are updating its content in the first comprehensive revision programme the dictionary has ever undergone.The remainder of the article investigates the current online site and looks into the future—to see what strategies the dictionary is employing and imagining as it moves away from being a book on computer to becoming a fully-fledged online language resource.
基金supported by the National Basic Research Program of China(Grant Nos.2013CB430204,2012CB955900)the National Natural Science Foundation of China(Grant Nos.41375078,41175084)the Special Scientific Research Fund of Meteorological Public Welfare Profession of China(Grant No.GYHY201106016)
文摘On the basis of eight atmospheric reanalyses, we analyzed the spatial-temporal characteristics of global evaporation and also briefly evaluated the eight reanalyses. The results indicate that the long-term mean annual evaporation obtained from different reanalyses are consistent over most regions, with significant maritime-continental contrasts, as well as differences in meridional directions, and the land evaporation generally decreases with the increase of altitude. In addition, the temporal evolution of global evaporation varies significantly among the datasets, MERRA, ERA-Interim, NCEP-NCRA, and NCEP-DOE are very similar, whereas CFSR agrees best with ERA-40. Comparison of the inter-annual to inter-decadal variability of land evaporation reveals large differences among the reanalyses, whereas MERRA, CFSR, and NCEP-DOE are exactly similar. The temporal variation of evaporation over the oceans showed a relatively high consistency, which indicates that the quality of the reconstructed evaporation values over the oceans is higher, and even greater uncertainties lie in the estimates of evaporation over the land. In general, MERRA and NCEP-DOE may appropriately reflect the spatial-temporal characteristics of global evaporation, showing strong representativeness. The CFSR and ERA-40 are capable of revealing the characteristics of land evaporation, whereas ERA-Interim, NCEP-NCAR, OAFlux, and HOAPS are relatively applicable for research focused on the evaporation over the oceans. According to ERA-40, NCEP-NCAR, and OAFlux, global evaporation significantly decreased for the period of 1958–1978. In contrast, most of the eight reanalyses show a significant linear increase for the period of 1979–2011, and evaporation over the oceans was even more pronounced. Furthermore, the results are presented for the mean annual cycle of global evaporation, the changes at the low latitudes in the Northern Hemisphere are most distinct, and the monthly variation amplitude of the land evaporation was higher than that of the evaporati
文摘The cryostat is a vacuum tight container enveloping the entire basic systems of the ITER tokamak machine,including a vacuum vessel,a superconducting magnet and thermal shield etc.It is evacuated to a pressure of 10^-4Pa to limit the heat transfer via gas conduction and convection to the cryogenically cooled components.Another important function of cryostat is to support all the loads from the tokamak to the concrete floor of the pit by its support system during different operational regimes and accident scenarios.This paper briefly presents the design evolution and associated analysis of the cryostat support system and the structural interface with the building.
基金Supported by National Natural Science Foundation of China(11105141,11175173)the upgrade project of Hefei Light Source
文摘Central RF frequency is a key parameter of storage rings. This paper presents the measurement of central RF frequency of the HLS-Ⅱ storage ring with the sextupole modulation method. Firstly, the basis of central RF frequency measurement of the electron storage ring is briefly introduced. Then, the error sources and the optimized measurement method for the HLS-Ⅱ storage ring are discussed. The workflow of a self-compiled Matlab script used in central RF frequency measurement is also described. Finally, the results achieved by using two data processing methods to cross-check each other are shown. The measured value of the central RF frequency demonstrates that the circumference deviation of the HLS-Ⅱ storage ring is less than 1 mm.
基金supported by the Scientific Research Foundation of the Education Department of Zhejiang Province, China (Grant No. Y200805750)
文摘Uniaxial strain induced ferroelectric phase transitions in rutile TiO2 are investigated by first-principles calculations. The calculated results show that the in-plane tensile strain induces rutile TiO2, paraelectric phase with P4-2/mnm （D4h） space group, to a ferroelectric phase with Pm（Cs） space group, driven by the softening behaviour of the Eul mode. In addition, the out-of-plane tensile strain, vertical to the ab plane, leads to a ferroelectric phase with P42nm （C4v） space group, driven by the softening behaviour of the A2u mode. The critical tensile strains are 3.7% in-plane and 4.0% out-of-plane, respectively. In addition, the in-plane compression strain, which has the same structure variation as out- of-plane tensile strain due to Poisson effect, leads the paraelectric rutile TiO2 to a paraelectric phase with Pnnm （D2h） space group driven by the softening behaviour of the B1g mode. These results indicate that the sequence ferroelectric （or paraelectric） phase depends on the strain applied. The origin of ferroelectric stabilization in rutile TiO2 is also discussed briefly in terms of strain induced Born effective charge transfer.
基金Project supported by the National Basic Research Program or China(Grant Nos.2012CB821402 and 2015CB921401)the National Natural Science Foundation of Chinathe Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learning,and STCSM of China(Grant No.15XD1500200)
文摘The discovery of the three-dimensional Dirac semimetals have expanded the family of topological materials,and attracted massive attentions in recent few years.In this short review,we briefly overview the quantum transport properties of a well-studied three-dimensional Dirac semimetal,Cd3As2.These unusual transport phenomena include the unexpected ultra-high charge mobility,large linear magnetoresistivity,remarkable Shubnikov-de Hass oscillations,and the evolution of the nontrivial Berry＇s phase.These quantum transport properties not only reflect the novel electronic structure of Dirac semimetals,but also give the possibilities for their future device applications.
基金Project supported by the National Basic Research Program of China(Grant Nos.2012CB921703 and 2015CB921102)the National Natural Science Foundation of China(Grant Nos.61425015,11374337,and 91121003)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB070202)
文摘The recent discovery of three-dimensional（3D） topological insulators（TIs） has provided a fertile ground for obtaining further insights into electron localization in condensed matter systems.In the past few years,a tremendous amount of research effort has been devoted to investigate electron transport properties of 3D TIs and their low dimensional structures in a wide range of disorder strength,covering transport regimes from weak antilocalization to strong localization.The knowledge gained from these studies not only offers sensitive means to probe the surface states of 3D TIs but also forms a basis for exploring novel topological phases.In this article,we briefly review the main experimental progress in the study of the localization in 3D TIs,with a focus on the latest results on ultrathin TI films.Some new transport data will also be presented in order to complement those reported previously in the literature.
文摘Multiple sclerosis（MS） is an autoimmune mediated neurodegenerative disease characterized by demyelination and oligodendrocyte（OL） loss in the central nervous system and accompanied by local inflammation and infiltration of peripheral immune cells. Although many risk factors and symptoms have been identified in MS, the pathology is complicated and the cause remains unknown. It is also unclear whether OL apoptosis precedes the inflammation or whether the local inflammation is the cause of OL death and demyelination. This review briefly discusses several models that have been developed to specifically ablate oligodendrocytes in an effort to separate the effects of demyelination from inflammation.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11175075,11405078,11474140,11404152,and 11305083)
文摘There is no available theoretical description of electron transfer from negative projectiles at a velocity below 0.1 a.u.during grazing scattering on insulating surfaces.In this low-velocity range,electron-capture and electron-loss processes coexist.For electron capture,the Demkov model has been successfully used to explain the velocity dependence of the negative-ion fraction formed from fast atoms during grazing scattering on insulating surfaces.For electron loss,we consider that an electron may be transferred from the formed ionic diabatic quasi-molecular state to the formed covalent diabatic quasi-molecular state by the crossing of the potential curves of negative projectiles approaching the surface cations,which can be described by the Landau-Zener two-energy-level crossing model.Combining these two models,we obtain good agreement between the experimental and calculated data for the F-LiF（OOl） collision system,which is briefly discussed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.U1632272,11574201,and 11521404)support from the Changjiang Scholars Program,Chinathe Program for Professor of Special Appointment(Eastern Scholar),China
文摘Two-dimensional（2D） topological insulators（TTs,or quantum spin Hall insulators） are special insulators that possess bulk 2D electronic energy gap and time-reversal symmetry protected one-dimensional（1D） edge state.Carriers in the edge state have the property of spin-momentum locking,enabling dissipation-free conduction along the 1D edge.The existence of 2D TIs was confirmed by experiments in semiconductor quantum wells.However,the 2D bulk gaps in those quantum wells are extremely small,greatly limiting potential application in future electronics and spintronics.Despite this limitation,2D TIs with a large bulk gap attracted plenty of interest.In this paper,recent progress in searching for TIs with a large bulk gap is reviewed briefly.We start by introducing some theoretical predictions of these new materials and then discuss some recent important achievements in crystal growth and characterization.
文摘Regarding climate change in China, ordinary people, even meteorologists, would think the cold waves from Siberia dominate winter temperature in southeast China. As oceanographers, however, we must know the role of ocean circulation in climate change. This text briefly discusses how important is the role of the Western Pacific Ocean circulation in climate change in southeast China on the basis of CTD data gathered by the R/V Science 1 in the western Pacific in September and October, 1986 and 1987 respectively , and statistical air temperature data in southeast China.
文摘One of the most prominent changes during stress is the increased outpouring of glucocorticoids (GC), which has been subjected to extensive studies by many authors.
文摘One of the efficient approaches used on calculating the generation and dissipation of seismic pore pres-sure in saturated soil mass is based on coupling the formulations of Terzaghi’s theory wity a seismic porepressure generation model in undrained condition. To solve this coupled equation for practical problems,most researchers employ essentially numerical methods such as finite elements. While these methods are in-dispensable for arbitrary geometries and soil inhomogeneities, analytical solutions are still desirable whichenhance physical understanding of the essentials and halp the development of efficient and accurate numeri-cal methods [1-4].
文摘Barefoot running has been around for millions of years,and it is safe to presume that for most of that time,the practice occasioned little interest.Our ancestors ran barefoot because they had no shoes.When footwear was first invented during the last 40,000 years (no doubt at different times and in different places),shoes were by necessity minimal-essentially sandals and moccasins-designed to protect the sole of the foot but lacking any of the sophisticated features and materials present in modem running shoes such as elevated cushioned heels,arch supports,and toe springs.Most of these features were invented in the 1970s,and they quickly became more popular and sophisticated as running underwent a worldwide boom.Today,the vast majority of runners think it is normal to wear cushioned running shoes,and would never dream of running without them.
