Textured surfaces with certain micro/nano structures have been proven to possess some advanced functions,such as reducing friction,improving wear and increasing wettability.Accurate prediction of micro/nano surface te...Textured surfaces with certain micro/nano structures have been proven to possess some advanced functions,such as reducing friction,improving wear and increasing wettability.Accurate prediction of micro/nano surface textures is of great significance for the design,fabrication and application of functional textured surfaces.In this paper,based on the kinematic analysis of cutter teeth,the discretization of ultrasonic machining process,transformation method of coordinate systems and the cubic spline data interpolation,an integrated theoretical model was established to characterize the distribution and geometric features of micro textures on the surfaces machined by different types of ultrasonic vibration-assisted milling(UVAM).Based on the theoretical model,the effect of key process parameters(vibration directions,vibration dimensions,cutting parameters and vibration parameters)on tool trajectories and microtextured surface morphology in UVAM is investigated.Besides,the effect of phase difference on the elliptical shape in 2D/3D ultrasonic elliptical vibration-assisted milling(UEVAM)was analyzed.Compared to conventional numerical models,the method of the cubic spline data interpolation is applied to the simulation of microtextured surface morphology in UVAM,which is more suitable for characterizing the morphological features of microtextured surfaces than traditional methods due to the presence of numerous micro textures.The prediction of surface roughness indicates that the magnitude of ultrasonic amplitude in z-direction should be strictly limited in 1D rotary UVAM,2D and 3D UEVAM due to the unfavorable effect of axial ultrasonic vibration on the surface quality.This study can provide theoretical guidance for the design and fabrication of microtextured surfaces in UVAM.展开更多
The next generation of very long baseline interferometry(VLBI)is stepping into the era of microarcsecond(μas)astronomy,and pushing astronomy,especially astrometry,to new heights.VLBI with the Square Kilometre Array(S...The next generation of very long baseline interferometry(VLBI)is stepping into the era of microarcsecond(μas)astronomy,and pushing astronomy,especially astrometry,to new heights.VLBI with the Square Kilometre Array(SKA),SKA-VLBI,will increase current sensitivity by an order of magnitude,and reach astrometric precision routinely below 10μas,even challenging 1μas.This advancement allows precise parallax and proper motion measurements of various celestial objects.Such improvements can be used to study objects(including isolated objects,and binary or multiple systems)in different stellar stages(such as star formation,main-sequence stars,asymptotic giant branch stars,pulsars,black holes,white dwarfs,etc.),unveil the structure and evolution of complex systems(such as the Milky Way),benchmark the international celestial reference frame,and reveal cosmic expansion.Furthermore,the theory of general relativity can also be tested with SKA-VLBI using precise measurements of light deflection under the gravitational fields of different solar system objects and the perihelion precession of solar system objects.展开更多
Antibiotic resistance or tolerance of pathogens is one of the most serious global public health threats.Bacteria in biofilms show extreme tolerance to almost all antibiotic classes.Thus,use of antibiofilm drugs withou...Antibiotic resistance or tolerance of pathogens is one of the most serious global public health threats.Bacteria in biofilms show extreme tolerance to almost all antibiotic classes.Thus,use of antibiofilm drugs without bacterial-killing effects is one of the strategies to combat antibiotic tolerance.In this study,we discovered a coumarin–chalcone conjugate C9,which can inhibit the biofilm formation of three common pathogens that cause nosocomial infections,namely,Pseudomonas aeruginosa,Staph-ylococcus aureus,and Escherichia coli,with the best antibiofilm activity against P.aeruginosa.Further investigations indicate that C9 decreases the synthesis of the key biofilm matrix exopolysaccharide Psl and bacterial second messenger cyclic-di-GMP.Meanwhile,C9 can interfere with the regulation of the quorum sensing(QS)system to reduce the virulence of P.aeruginosa.C9 treatment enhances the sensitivity of biofilm to several antibiotics and reduces the survival rate of P.aeruginosa under starvation or oxidative stress conditions,indicating its excellent potential for use as an antibiofilm-forming and anti-QS drug.展开更多
基金Supported by Shandong Provincial Natural Science Foundation of China(Grant No.ZR2023QE041)China Postdoctoral Science Foundation(Grant No.2023M731862)National Natural Science Foundation of China(Grant No.51975112).
文摘Textured surfaces with certain micro/nano structures have been proven to possess some advanced functions,such as reducing friction,improving wear and increasing wettability.Accurate prediction of micro/nano surface textures is of great significance for the design,fabrication and application of functional textured surfaces.In this paper,based on the kinematic analysis of cutter teeth,the discretization of ultrasonic machining process,transformation method of coordinate systems and the cubic spline data interpolation,an integrated theoretical model was established to characterize the distribution and geometric features of micro textures on the surfaces machined by different types of ultrasonic vibration-assisted milling(UVAM).Based on the theoretical model,the effect of key process parameters(vibration directions,vibration dimensions,cutting parameters and vibration parameters)on tool trajectories and microtextured surface morphology in UVAM is investigated.Besides,the effect of phase difference on the elliptical shape in 2D/3D ultrasonic elliptical vibration-assisted milling(UEVAM)was analyzed.Compared to conventional numerical models,the method of the cubic spline data interpolation is applied to the simulation of microtextured surface morphology in UVAM,which is more suitable for characterizing the morphological features of microtextured surfaces than traditional methods due to the presence of numerous micro textures.The prediction of surface roughness indicates that the magnitude of ultrasonic amplitude in z-direction should be strictly limited in 1D rotary UVAM,2D and 3D UEVAM due to the unfavorable effect of axial ultrasonic vibration on the surface quality.This study can provide theoretical guidance for the design and fabrication of microtextured surfaces in UVAM.
基金funded by the National Natural Science Foundation of China(NSFC,Grant Nos.12203104 and 11933011)the Natural Science Foundation of Jiangsu Province(grants No.BK20210999)+2 种基金the National SKA Program of China(grant No.2022SKA0120103)the Entrepreneurship and Innovation Program of Jiangsu Provincethe Key Laboratory for Radio Astronomy,CAS。
文摘The next generation of very long baseline interferometry(VLBI)is stepping into the era of microarcsecond(μas)astronomy,and pushing astronomy,especially astrometry,to new heights.VLBI with the Square Kilometre Array(SKA),SKA-VLBI,will increase current sensitivity by an order of magnitude,and reach astrometric precision routinely below 10μas,even challenging 1μas.This advancement allows precise parallax and proper motion measurements of various celestial objects.Such improvements can be used to study objects(including isolated objects,and binary or multiple systems)in different stellar stages(such as star formation,main-sequence stars,asymptotic giant branch stars,pulsars,black holes,white dwarfs,etc.),unveil the structure and evolution of complex systems(such as the Milky Way),benchmark the international celestial reference frame,and reveal cosmic expansion.Furthermore,the theory of general relativity can also be tested with SKA-VLBI using precise measurements of light deflection under the gravitational fields of different solar system objects and the perihelion precession of solar system objects.
基金the National Natural Science Foundation of China(91951204,32200149)the National Key R&D Program of China(2021YFA0909500,2021YFC2301004,2019YFC804104),and the CAS‐TWAS PhD Fellowship for Pramod Bhasme.
文摘Antibiotic resistance or tolerance of pathogens is one of the most serious global public health threats.Bacteria in biofilms show extreme tolerance to almost all antibiotic classes.Thus,use of antibiofilm drugs without bacterial-killing effects is one of the strategies to combat antibiotic tolerance.In this study,we discovered a coumarin–chalcone conjugate C9,which can inhibit the biofilm formation of three common pathogens that cause nosocomial infections,namely,Pseudomonas aeruginosa,Staph-ylococcus aureus,and Escherichia coli,with the best antibiofilm activity against P.aeruginosa.Further investigations indicate that C9 decreases the synthesis of the key biofilm matrix exopolysaccharide Psl and bacterial second messenger cyclic-di-GMP.Meanwhile,C9 can interfere with the regulation of the quorum sensing(QS)system to reduce the virulence of P.aeruginosa.C9 treatment enhances the sensitivity of biofilm to several antibiotics and reduces the survival rate of P.aeruginosa under starvation or oxidative stress conditions,indicating its excellent potential for use as an antibiofilm-forming and anti-QS drug.
