近年来随着学术交流的不断深入,美国芝加哥菲尔德自然历史博物馆(Field Museum of Natural History)收藏的中国碑帖拓本日益为人们所关注,《宋拓赵侍郎不流本游相〈兰亭〉》就是其中之一。该本为游相《兰亭》"己之二"(第五十...近年来随着学术交流的不断深入,美国芝加哥菲尔德自然历史博物馆(Field Museum of Natural History)收藏的中国碑帖拓本日益为人们所关注,《宋拓赵侍郎不流本游相〈兰亭〉》就是其中之一。该本为游相《兰亭》"己之二"(第五十二种),翻刻于一"九字已损"、"五字未损"的定武古本。由于卷改册装,其上"赵氏孟林"骑缝印被一分为二,十分罕见。在目前关于"赵氏孟林"的文献记载尚不充分、明确的情况下,可以从已知的游相《兰亭》拓本装潢钤印定式本身入手,对其进行分析。检览统计若干游相《兰亭》相关信息,笔者认为,赵孟林是明初晋藩朱棡装潢人的可能性较大。作为游相《兰亭》标志要素之一的蓝纸隔水,则是经朱氏收藏后重新进行装裱的一个显著特征。而同一取材、或有或无的蓝纸小签上所标注的"天干编次帖本名称",亦是游相《兰亭》标志要素之一,或许正是出自赵孟林之手,当然也不排除朱棡亲笔的可能。展开更多
Secondary electron emission(SEE)has emerged as a critical issue in next-generation accelerators.Mitigating SEE on metal surfaces is crucial for enhancing the stability and emittance of particle accelerators while exte...Secondary electron emission(SEE)has emerged as a critical issue in next-generation accelerators.Mitigating SEE on metal surfaces is crucial for enhancing the stability and emittance of particle accelerators while extending their lifespan.This paper explores the application of laser-assisted water jet technology in constructing high-quality micro-trap structures on 316L stainless steel,a key material in accelerator manufacturing.The study systematically analyzes the impact of various parameters such as laser repetition frequency,pulse duration,average power,water jet pressure,repeat times,nozzle offset,focal position,offset distance between grooves,and processing speed on the surface morphology of stainless steel.The findings reveal that micro-groove depth increases with higher laser power but decreases with increasing water jet pressure and processing speed.Interestingly,repeat times have minimal effect on depth.On the other hand,micro-groove width increases with higher laser power and repeat times but decreases with processing speed.By optimizing these parameters,the researchers achieved high-quality pound sign-shaped trap structure with consistent dimensions.We tested the secondary electron emission coefficient of the"well"structure.The coefficient is reduced by 0.5 at most compared to before processing,effectively suppressing secondary electron emission.These results offer indispensable insights for the fabrication of micro-trap structures on material surfaces.Laser-assisted water jet technology demonstrates considerable potential in mitigating SEE on metal surfaces.展开更多
The hot compression tests of 7Mo super austenitic stainless(SASS)were conducted to obtain flow curves at the temperature of 1000-1200℃and strain rate of 0.001 s^(-1)to 1 s^(-1).To predict the non-linear hot deformati...The hot compression tests of 7Mo super austenitic stainless(SASS)were conducted to obtain flow curves at the temperature of 1000-1200℃and strain rate of 0.001 s^(-1)to 1 s^(-1).To predict the non-linear hot deformation behaviors of the steel,back propagation-artificial neural network(BP-ANN)with 16×8×8 hidden layer neurons was proposed.The predictability of the ANN model is evaluated according to the distribution of mean absolute error(MAE)and relative error.The relative error of 85%data for the BP-ANN model is among±5%while only 42.5%data predicted by the Arrhenius constitutive equation is in this range.Especially,at high strain rate and low temperature,the MAE of the ANN model is 2.49%,which has decreases for 18.78%,compared with conventional Arrhenius constitutive equation.展开更多
Aim To study singular points, closed orbits, stable manifolds and unstable manifolds of a second order autonomous Birkhoff system. Methods Qualitative methods of ordinary differential equation were used. Results and ...Aim To study singular points, closed orbits, stable manifolds and unstable manifolds of a second order autonomous Birkhoff system. Methods Qualitative methods of ordinary differential equation were used. Results and Conclusion The criteria for singular points, closed orbits and hyperbolic equilibrium points of a second order autonomous Birkhoff system are given. Moreover the stability of equilibria, stable manifolds and unstable manifolds are obtained.展开更多
文摘近年来随着学术交流的不断深入,美国芝加哥菲尔德自然历史博物馆(Field Museum of Natural History)收藏的中国碑帖拓本日益为人们所关注,《宋拓赵侍郎不流本游相〈兰亭〉》就是其中之一。该本为游相《兰亭》"己之二"(第五十二种),翻刻于一"九字已损"、"五字未损"的定武古本。由于卷改册装,其上"赵氏孟林"骑缝印被一分为二,十分罕见。在目前关于"赵氏孟林"的文献记载尚不充分、明确的情况下,可以从已知的游相《兰亭》拓本装潢钤印定式本身入手,对其进行分析。检览统计若干游相《兰亭》相关信息,笔者认为,赵孟林是明初晋藩朱棡装潢人的可能性较大。作为游相《兰亭》标志要素之一的蓝纸隔水,则是经朱氏收藏后重新进行装裱的一个显著特征。而同一取材、或有或无的蓝纸小签上所标注的"天干编次帖本名称",亦是游相《兰亭》标志要素之一,或许正是出自赵孟林之手,当然也不排除朱棡亲笔的可能。
文摘Secondary electron emission(SEE)has emerged as a critical issue in next-generation accelerators.Mitigating SEE on metal surfaces is crucial for enhancing the stability and emittance of particle accelerators while extending their lifespan.This paper explores the application of laser-assisted water jet technology in constructing high-quality micro-trap structures on 316L stainless steel,a key material in accelerator manufacturing.The study systematically analyzes the impact of various parameters such as laser repetition frequency,pulse duration,average power,water jet pressure,repeat times,nozzle offset,focal position,offset distance between grooves,and processing speed on the surface morphology of stainless steel.The findings reveal that micro-groove depth increases with higher laser power but decreases with increasing water jet pressure and processing speed.Interestingly,repeat times have minimal effect on depth.On the other hand,micro-groove width increases with higher laser power and repeat times but decreases with processing speed.By optimizing these parameters,the researchers achieved high-quality pound sign-shaped trap structure with consistent dimensions.We tested the secondary electron emission coefficient of the"well"structure.The coefficient is reduced by 0.5 at most compared to before processing,effectively suppressing secondary electron emission.These results offer indispensable insights for the fabrication of micro-trap structures on material surfaces.Laser-assisted water jet technology demonstrates considerable potential in mitigating SEE on metal surfaces.
文摘The hot compression tests of 7Mo super austenitic stainless(SASS)were conducted to obtain flow curves at the temperature of 1000-1200℃and strain rate of 0.001 s^(-1)to 1 s^(-1).To predict the non-linear hot deformation behaviors of the steel,back propagation-artificial neural network(BP-ANN)with 16×8×8 hidden layer neurons was proposed.The predictability of the ANN model is evaluated according to the distribution of mean absolute error(MAE)and relative error.The relative error of 85%data for the BP-ANN model is among±5%while only 42.5%data predicted by the Arrhenius constitutive equation is in this range.Especially,at high strain rate and low temperature,the MAE of the ANN model is 2.49%,which has decreases for 18.78%,compared with conventional Arrhenius constitutive equation.
文摘Aim To study singular points, closed orbits, stable manifolds and unstable manifolds of a second order autonomous Birkhoff system. Methods Qualitative methods of ordinary differential equation were used. Results and Conclusion The criteria for singular points, closed orbits and hyperbolic equilibrium points of a second order autonomous Birkhoff system are given. Moreover the stability of equilibria, stable manifolds and unstable manifolds are obtained.
