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
This study aims to gain insight into the DNA-specific recognition mechanism of c-Myb transcription factor during the regulation of cell early differentiation and proliferation.Therefore,we chose the chicken myeloid ge...This study aims to gain insight into the DNA-specific recognition mechanism of c-Myb transcription factor during the regulation of cell early differentiation and proliferation.Therefore,we chose the chicken myeloid gene,mitochondrial import protein 1(mim-1),as a target to study the binding specificity between potential dual-Myb-binding sites.The c-Myb-binding site in mim-1 is a pseudo-palindromic sequence AACGGTT,which contains two AACNG consensuses.Simulation studies in different biological scenarios revealed that c-Myb binding with mim-1 in the forward strand(complex F)is more stable than that in the reverse strand(complex R).The principal component analysis(PCA)dynamics trajectory analyses suggested an opening motion of the recognition helices of R2 and R3(R2R3),resulting in the dissociation of DNA from c-Myb in complex R at 330 K,triggered by the reduced electrostatic potential on the surface of R2R3.Furthermore,the DNA confirmation and hydrogen-bond interaction analyses indicated that the major groove width of DNA increased in complex R,which affected on the hydrogenbond formation ability between R2R3 and DNA,and directly resulted in the dissociation of DNA from R2R3.The steered molecular dynamics(SMD)simulation studies also suggested that the electrostatic potential,major groove width,and hydrogen bonds made major contribution to the DNA-specific recognition.In vitro trials confirmed the simulation results that c-Myb specifically bound to mim-1 in the forward strand.This study indicates that the three-dimensional(3D)structure features play an important role in the DNA-specific recognition mechanism by c-Myb besides the AACNG consensuses,which is beneficial to understanding the cell early differentiation and proliferation regulated by c-Myb,as well as the prediction of novel c-Myb-binding motifs in tumorigenesis.展开更多
The elastic-plastic transition regime and brittle-ductile transition regime in scratch process for optical glass BK7 were analyzed based on the Hertzian equation and the stress ratio theory which was proposed by Wei. ...The elastic-plastic transition regime and brittle-ductile transition regime in scratch process for optical glass BK7 were analyzed based on the Hertzian equation and the stress ratio theory which was proposed by Wei. The interacting scratch process for optical glass BK7 with the grit interval distance as the variable was simulated by the ABAQUS software of finite element simulation based on the energy fracture theory. Double grits interacting scratch test for optical glass BK7 was carried out on the DMG ULTRASONIC 70-5 linear, by which the reliability of finite element simulation was verified. The surface morphology of the workpiece was analyzed by scanning electron microscopy（SEM）, which showed that the width of groove increased obviously with the increase of scratch depth and the grit interval distance. Results of the width of groove were consistent with the simulation results. The subsurface damage layer was analyzed by the method of HF acid etching, which showed that there was an area of cracks intersecting. The scratching force was measured by the threedimensional dynamometer of KISTLER, which showed that the second scratching force increased with the increase of scratching depth and the grit interval distance. The force in the second scratch was smaller than that in the first time, which was consistent with the Griffith fracture theory.展开更多
At present the bored construction method is one of the main construction methods of metro and tunnel construction in China. The empirical estimated formulas of tunnel ground surface settlement using the bored construc...At present the bored construction method is one of the main construction methods of metro and tunnel construction in China. The empirical estimated formulas of tunnel ground surface settlement using the bored construction method were obtained, combining the mechanical stimulant calculated result of tunnel model of different embedded depth, different cross section and different construction method and the actual measurement data of Beijing metro construction. According to the regressed analysis of calculated data, the calculated equations of ground surface settlement value and settlement range of tunnel section under the condition of different embedded depth, different cross section and different construction method were gained. Among them there are some empirical formulas can apply to the construction design of metro tunnel directly.展开更多
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.
基金supported by the National Key Research and Development Program of China(Nos.2022YFC2402900 and 2022YFC2402901)the Fundamental Research Funds for the Central Universities(No.226-2022-00213)the Joint Funds of the Zhejiang Provincial Natural Science Foundation of China(No.LHDMD23H300001).
文摘This study aims to gain insight into the DNA-specific recognition mechanism of c-Myb transcription factor during the regulation of cell early differentiation and proliferation.Therefore,we chose the chicken myeloid gene,mitochondrial import protein 1(mim-1),as a target to study the binding specificity between potential dual-Myb-binding sites.The c-Myb-binding site in mim-1 is a pseudo-palindromic sequence AACGGTT,which contains two AACNG consensuses.Simulation studies in different biological scenarios revealed that c-Myb binding with mim-1 in the forward strand(complex F)is more stable than that in the reverse strand(complex R).The principal component analysis(PCA)dynamics trajectory analyses suggested an opening motion of the recognition helices of R2 and R3(R2R3),resulting in the dissociation of DNA from c-Myb in complex R at 330 K,triggered by the reduced electrostatic potential on the surface of R2R3.Furthermore,the DNA confirmation and hydrogen-bond interaction analyses indicated that the major groove width of DNA increased in complex R,which affected on the hydrogenbond formation ability between R2R3 and DNA,and directly resulted in the dissociation of DNA from R2R3.The steered molecular dynamics(SMD)simulation studies also suggested that the electrostatic potential,major groove width,and hydrogen bonds made major contribution to the DNA-specific recognition.In vitro trials confirmed the simulation results that c-Myb specifically bound to mim-1 in the forward strand.This study indicates that the three-dimensional(3D)structure features play an important role in the DNA-specific recognition mechanism by c-Myb besides the AACNG consensuses,which is beneficial to understanding the cell early differentiation and proliferation regulated by c-Myb,as well as the prediction of novel c-Myb-binding motifs in tumorigenesis.
基金Funded by the National Key Research and Development Program of China(No.2016YFB1102204)the Major State Basic Research Development Program of China(973 Program)(No.2011CB013202)the National Natural Science Foundation of China(No.51175126)
文摘The elastic-plastic transition regime and brittle-ductile transition regime in scratch process for optical glass BK7 were analyzed based on the Hertzian equation and the stress ratio theory which was proposed by Wei. The interacting scratch process for optical glass BK7 with the grit interval distance as the variable was simulated by the ABAQUS software of finite element simulation based on the energy fracture theory. Double grits interacting scratch test for optical glass BK7 was carried out on the DMG ULTRASONIC 70-5 linear, by which the reliability of finite element simulation was verified. The surface morphology of the workpiece was analyzed by scanning electron microscopy（SEM）, which showed that the width of groove increased obviously with the increase of scratch depth and the grit interval distance. Results of the width of groove were consistent with the simulation results. The subsurface damage layer was analyzed by the method of HF acid etching, which showed that there was an area of cracks intersecting. The scratching force was measured by the threedimensional dynamometer of KISTLER, which showed that the second scratching force increased with the increase of scratching depth and the grit interval distance. The force in the second scratch was smaller than that in the first time, which was consistent with the Griffith fracture theory.
文摘At present the bored construction method is one of the main construction methods of metro and tunnel construction in China. The empirical estimated formulas of tunnel ground surface settlement using the bored construction method were obtained, combining the mechanical stimulant calculated result of tunnel model of different embedded depth, different cross section and different construction method and the actual measurement data of Beijing metro construction. According to the regressed analysis of calculated data, the calculated equations of ground surface settlement value and settlement range of tunnel section under the condition of different embedded depth, different cross section and different construction method were gained. Among them there are some empirical formulas can apply to the construction design of metro tunnel directly.
