Electron-positron colliders operating in the GeV center-of-mass range,or tau-charm energy region,have been proved to enable competitive frontier research due to several unique features.With the progress of high-energy...Electron-positron colliders operating in the GeV center-of-mass range,or tau-charm energy region,have been proved to enable competitive frontier research due to several unique features.With the progress of high-energy physics in the last two decades,a new-generation Tau-Charm factory,called the Super Tau-Charm Facility(STCF),has been actively promoted by the particle physics community in China.STCF has the potential to address fundamental questions such as the essence of color confinement and the matter-antimatter asymmetry within the next decades.The main design goals of the STCF are a center-of-mass energy ranging from 2 to 7 GeV and a luminosity surpassing 5×10^(34)cm^(−2)s^(−1)that is optimized at a center-of-mass energy of 4 GeV,which is approximately 50 times that of the currently operating Tau-Charm factory-BEPCII.The STCF accelerator has two main parts:a double-ring collider with a crab-waist collision scheme and an injector that provides top-up injections for both electron and positron beams.As a typical third-generation electron-positron circular collider,the STCF accelerator faces many challenges in both accelerator physics and technology.In this paper,the conceptual design of the STCF accelerator complex is presented,including the ongoing efforts and plans for technological research and develop-ment,as well as the required infrastructure.The STCF project aims to secure support from the Chinese central government for its construction during the 15th Five-Year Plan(2026-2030).展开更多
Efficient elastic wave focusing is crucial in materials and physical engineering.Elastic coding metasurfaces,which are innovative planar artificial structures,show great potential for use in the field of wave focusing...Efficient elastic wave focusing is crucial in materials and physical engineering.Elastic coding metasurfaces,which are innovative planar artificial structures,show great potential for use in the field of wave focusing.However,elastic coding lenses(ECLs)still suffer from low focusing performance,thickness comparable to wavelength,and frequency sensitivity.Here,we consider both the structural and material properties of the coding unit,thus realizing further compression of the thickness of the ECL.We chose the simplest ECL,which consists of only two encoding units.The coding unit 0 is a straight structure constructed using a carbon fiber reinforced composite material,and the coding unit 1 is a zigzag structure constructed using an aluminum material,and the thickness of the ECL constructed using them is only 1/8 of the wavelength.Based on the theoretical design,the arrangement of coding units is further optimized using genetic algorithms,which significantly improves the focusing performance of the lens at different focus and frequencies.This study provides a more effective way to control vibration and noise in advanced structures.展开更多
Electrorheological（ER） fluid is a type of smart fluid whose shear yield stress relies on the external electrical field strength. The transition of ER fluid microstructure driven by the electrical field is the reason...Electrorheological（ER） fluid is a type of smart fluid whose shear yield stress relies on the external electrical field strength. The transition of ER fluid microstructure driven by the electrical field is the reason why viscosity changes.Experimentally, the transparent electrodes are used to investigate the column size distribution where an external electric field is applied to a colloidal suspension, i.e., ER fluid is increased. The coarsening profile of ER suspensions is strongly related to electrical field strength, but it is insensitive to particle size. In addition, in a low field range the shear stress corresponding to the mean column diameter is studied and they are found to satisfy a power law. However, this dependence is invalid when the field strength surpasses a threshold value.展开更多
The Qinghai-Xizang Plateau(abbreviated as Q-X Plateau)is the world’s highest plateau,characterized by a Holarctic flora.The plateau and its surrounding mountainous areas cover two of the 34 world’s biodiversity hots...The Qinghai-Xizang Plateau(abbreviated as Q-X Plateau)is the world’s highest plateau,characterized by a Holarctic flora.The plateau and its surrounding mountainous areas cover two of the 34 world’s biodiversity hotspots.Former studies have shown that the diversity of fungal species on the plateau,especially that in the east-southeastern part,is remarkably high.In 2017,the Chinese government initiated the second scientific expedition to the Q-X Plateau.Supported by this comprehensive project,we conducted intensive fungal sampling on the Q-X Plateau and its surrounding areas,including the middle and southern parts of the Gaoligong Mountains,the Ailao Mountains,and the Yunnan-Guizhou Plateau.Ninety-two new and notable species of Basidiomycota are reported in this paper,based on 501 specimens and 1706 newly generated DNA sequences.These taxa involve 37 genera of seven orders,i.e.,Agaricales,Auriculariales,Boletales,Cantharellales,Phallales,Polyporales,and Russulales,covering both Heterobasidiomycetes and Homobasidiomycetes.One new section,64 new species,one new subspecies,two new varieties,one new combination,five new synonyms,and 11 new records to China,were documented.Ectomycorrhizal fungi account for two-thirds of the species,while the remaining ones are saprotrophic.Most specimens studied are from altitudes 2000-3700 m,in broad-leaved fagaceous forests,mixed forests with pines and fagaceous trees,and subalpine coniferous forests.Among the 92 species documented,30 species are exclusive to the subalpine region,and 12 species cover both the subalpine and subtropical zones.Most of these subalpine species are either formerly described temperate species or close relatives of north temperate taxa,which suggests a strong temperate affinity of the funga on the Q-X Plateau.In obvious contrast to the subalpine elements,species from the adjacent subtropical zone often sit on long branches with an isolated position or have a close relationship with species from other subtropical and tropical parts of the world.In the surrounding areas with lower altitude of the Q-X Plateau,the endemic species apparently have evolved for a longer time,some relict species found their refuge,and the funga received more immigrants from the tropics.By comparing the species reported from the western Himalayas,through the Hengduan Mountains and central China to Taiwan Island,we found that altitude matters more than geographical distance in the development of the funga.The sharp altitude gradient on the Q-X Plateau and its surrounding mountains acts as a biodiversity hotspot to further test such speculation.In future studies,more efforts should be focused on other representative groups(Gomphalales,Hymenochaetales,Thelephorales,and Tremellales)and on the southern slope of the western Himalayas and the Pamir-Kunlun regions.展开更多
Dark photons have been well motivated as strong candidates for dark force carriers and light dark matter in the sub-GeV mass range.Compared with collider experiments,fixed-target experiments provide a complementary ap...Dark photons have been well motivated as strong candidates for dark force carriers and light dark matter in the sub-GeV mass range.Compared with collider experiments,fixed-target experiments provide a complementary approach to searching for dark photons,particularly in the lower mass range.We have studied the physics potential of the electron-on-target experiment based on the Shanghai SHINE facility,which provides 10 MHz single electron beam at 8 GeV energy.This analysis focuses on dark photons being produced via electron and nucleon interaction and then decays to dark matter candidates,which escape detection as missing momentum in the detector.This experiment takes advantage of using missing momentum to enhance signal versus background separation power.In this study,signal samples as a function of dark photon mass and an inclusive background sample with 2.5 billion events are simulated with GEANT4.For better background estimates,major rare background processes have also been simulated.This paper presents the experiment and detector design,signal and background simulations,analysis strategy,and the prospective study of the experiment sensitivity.With 9×10^(14) electron-on-target events(about three years running),this experiment is expected to rule out most of the sensitive regions predicted by popular dark photon models.展开更多
基金supported by the National Key Research and Development Program of China(No.2022YFA1602200)the National Natural Science Foundation of China(Nos.12341501 and 12405174)the Hefei Comprehensive National Science Center for the strong support on the STCF key technology research project.
文摘Electron-positron colliders operating in the GeV center-of-mass range,or tau-charm energy region,have been proved to enable competitive frontier research due to several unique features.With the progress of high-energy physics in the last two decades,a new-generation Tau-Charm factory,called the Super Tau-Charm Facility(STCF),has been actively promoted by the particle physics community in China.STCF has the potential to address fundamental questions such as the essence of color confinement and the matter-antimatter asymmetry within the next decades.The main design goals of the STCF are a center-of-mass energy ranging from 2 to 7 GeV and a luminosity surpassing 5×10^(34)cm^(−2)s^(−1)that is optimized at a center-of-mass energy of 4 GeV,which is approximately 50 times that of the currently operating Tau-Charm factory-BEPCII.The STCF accelerator has two main parts:a double-ring collider with a crab-waist collision scheme and an injector that provides top-up injections for both electron and positron beams.As a typical third-generation electron-positron circular collider,the STCF accelerator faces many challenges in both accelerator physics and technology.In this paper,the conceptual design of the STCF accelerator complex is presented,including the ongoing efforts and plans for technological research and develop-ment,as well as the required infrastructure.The STCF project aims to secure support from the Chinese central government for its construction during the 15th Five-Year Plan(2026-2030).
基金Project supported by the National Natural Science Foundation of China(Grant No.12404531)the Natural Science Foundation of the Higher Education Institutions of Jiangsu Province,China(Grant No.23KJB140011)。
文摘Efficient elastic wave focusing is crucial in materials and physical engineering.Elastic coding metasurfaces,which are innovative planar artificial structures,show great potential for use in the field of wave focusing.However,elastic coding lenses(ECLs)still suffer from low focusing performance,thickness comparable to wavelength,and frequency sensitivity.Here,we consider both the structural and material properties of the coding unit,thus realizing further compression of the thickness of the ECL.We chose the simplest ECL,which consists of only two encoding units.The coding unit 0 is a straight structure constructed using a carbon fiber reinforced composite material,and the coding unit 1 is a zigzag structure constructed using an aluminum material,and the thickness of the ECL constructed using them is only 1/8 of the wavelength.Based on the theoretical design,the arrangement of coding units is further optimized using genetic algorithms,which significantly improves the focusing performance of the lens at different focus and frequencies.This study provides a more effective way to control vibration and noise in advanced structures.
基金supported by the National Natural Science Foundation of China(Grant Nos.11474345 and 11674043)
文摘Electrorheological（ER） fluid is a type of smart fluid whose shear yield stress relies on the external electrical field strength. The transition of ER fluid microstructure driven by the electrical field is the reason why viscosity changes.Experimentally, the transparent electrodes are used to investigate the column size distribution where an external electric field is applied to a colloidal suspension, i.e., ER fluid is increased. The coarsening profile of ER suspensions is strongly related to electrical field strength, but it is insensitive to particle size. In addition, in a low field range the shear stress corresponding to the mean column diameter is studied and they are found to satisfy a power law. However, this dependence is invalid when the field strength surpasses a threshold value.
基金funded by the Second Tibetan Plateau Scientific Expedition and Research Program(No.2024QZKK02010303)the Second Qinghai-Tibet Plateau Scientific Expedition and Research(STEP)Program(No.2019QZKK0503)+13 种基金the Major science and technology projects and key R&D plans/programs,Yunnan Province(No.202202AE090001)the Innovation Guidance and Technology-Based Enterprise Cultivation Program of Yunnan Province Science and Technology Department(No.202504BI090008)to QZthe Joint Funds of the National Natural Science Foundation of China and Yunnan Provincial Government(No.U2202205)the Yunnan Revitalization Talent Support Program:Science&Technology Champion Project(No.202305AB350004)to ZLYNational Natural Science Foundation of China(Nos.32170022,30970020,31093440,31770031)the Biodiversity Survey and Assessment Project(No.2019HJ2096001006)“Investigation of Macrofungi of Maguan County”issued by Ministry of Ecology and Environment of the People’s Republic of China to XHWthe National Natural Science Foundation of China(No.32270025)CAS“Light of West China”Program,Natural Science Foundation of Yunnan Province for Excellent Young Scholars(No.202301AW070011)Biological Resources Programme,CAS(No.CAS-TAX-24-063)Natural Science Foundation of Yunnan Province(No.202201AT070128)Yunnan Revitalization Talent Support Program‘Young Talent’Project(No.YNWRQNBJ-2018-266)to GWNational Natural Science Foundation of China(No.31970023)to QCthe Postdoctoral Fellowship Program of CPSF(No.GZB20240769)to FMY.
文摘The Qinghai-Xizang Plateau(abbreviated as Q-X Plateau)is the world’s highest plateau,characterized by a Holarctic flora.The plateau and its surrounding mountainous areas cover two of the 34 world’s biodiversity hotspots.Former studies have shown that the diversity of fungal species on the plateau,especially that in the east-southeastern part,is remarkably high.In 2017,the Chinese government initiated the second scientific expedition to the Q-X Plateau.Supported by this comprehensive project,we conducted intensive fungal sampling on the Q-X Plateau and its surrounding areas,including the middle and southern parts of the Gaoligong Mountains,the Ailao Mountains,and the Yunnan-Guizhou Plateau.Ninety-two new and notable species of Basidiomycota are reported in this paper,based on 501 specimens and 1706 newly generated DNA sequences.These taxa involve 37 genera of seven orders,i.e.,Agaricales,Auriculariales,Boletales,Cantharellales,Phallales,Polyporales,and Russulales,covering both Heterobasidiomycetes and Homobasidiomycetes.One new section,64 new species,one new subspecies,two new varieties,one new combination,five new synonyms,and 11 new records to China,were documented.Ectomycorrhizal fungi account for two-thirds of the species,while the remaining ones are saprotrophic.Most specimens studied are from altitudes 2000-3700 m,in broad-leaved fagaceous forests,mixed forests with pines and fagaceous trees,and subalpine coniferous forests.Among the 92 species documented,30 species are exclusive to the subalpine region,and 12 species cover both the subalpine and subtropical zones.Most of these subalpine species are either formerly described temperate species or close relatives of north temperate taxa,which suggests a strong temperate affinity of the funga on the Q-X Plateau.In obvious contrast to the subalpine elements,species from the adjacent subtropical zone often sit on long branches with an isolated position or have a close relationship with species from other subtropical and tropical parts of the world.In the surrounding areas with lower altitude of the Q-X Plateau,the endemic species apparently have evolved for a longer time,some relict species found their refuge,and the funga received more immigrants from the tropics.By comparing the species reported from the western Himalayas,through the Hengduan Mountains and central China to Taiwan Island,we found that altitude matters more than geographical distance in the development of the funga.The sharp altitude gradient on the Q-X Plateau and its surrounding mountains acts as a biodiversity hotspot to further test such speculation.In future studies,more efforts should be focused on other representative groups(Gomphalales,Hymenochaetales,Thelephorales,and Tremellales)and on the southern slope of the western Himalayas and the Pamir-Kunlun regions.
基金supported by the National Natural Science Foundation of China(Grant No.12150006)Shanghai Pilot Program for Basic Research—Shanghai Jiao Tong University(Grant No.21TQ1400209)。
文摘Dark photons have been well motivated as strong candidates for dark force carriers and light dark matter in the sub-GeV mass range.Compared with collider experiments,fixed-target experiments provide a complementary approach to searching for dark photons,particularly in the lower mass range.We have studied the physics potential of the electron-on-target experiment based on the Shanghai SHINE facility,which provides 10 MHz single electron beam at 8 GeV energy.This analysis focuses on dark photons being produced via electron and nucleon interaction and then decays to dark matter candidates,which escape detection as missing momentum in the detector.This experiment takes advantage of using missing momentum to enhance signal versus background separation power.In this study,signal samples as a function of dark photon mass and an inclusive background sample with 2.5 billion events are simulated with GEANT4.For better background estimates,major rare background processes have also been simulated.This paper presents the experiment and detector design,signal and background simulations,analysis strategy,and the prospective study of the experiment sensitivity.With 9×10^(14) electron-on-target events(about three years running),this experiment is expected to rule out most of the sensitive regions predicted by popular dark photon models.
