Micro electrical discharge machining(EDM) deposition process is a new micro machining method for fabrication of metal micro structures. In this process, the high level of tool electrode wear is used to achieve the m...Micro electrical discharge machining(EDM) deposition process is a new micro machining method for fabrication of metal micro structures. In this process, the high level of tool electrode wear is used to achieve the metal material deposition. Up to now, the studies of micro EDM deposition process focused mainly on the researches of deposition process, namely the effects of discharge parameters in deposition process on the deposition rate or deposition quality. The research of the formation of micro structures with different discharge energy density still lacks. With proper conditions and only by the z-axis feeding in vertical direction, a novel shape of micro spiral structure can be deposited, with 0.11 mm in wire diameter, 0.20 mm in outside diameter, and 3.78 mm in height. Then some new deposition strategies including angular deposition and against the gravity deposition were also successful. In order to find the forming mechanism of the spiral structures, the numerical simulation of the transient temperature distribution on the discharge point was conducted by using the finite-element method(FEM). The results show that there are two major factors lead to the forming of the spiral structures. One is the different material removal form of tool electrode according with the discharge energy density, the other is the influenced degree of the movement of the removed material particles in the discharge gap. The more the energy density in single discharge is, the smaller the mass of the removed material particles is, and the easier the movements of which will be changed to form an order tendency. The fine texture characteristics of the deposited micro spiral structures were analyzed by the energy spectrum analysis and the metallographic analysis. It shows that the components of the deposited material are almost the same as those of the tool electrode. Moreover the deposited material has the brass metallic luster in the longitudinal profile and has compact bonding with the base material. This research is useful to understand the micro-process of micro EDM deposition better and helpful to increase the controllability of the new EDM method for fabrication of micro structures.展开更多
The steady axis-symmetrical atmosphere dynamical equations are used for describing spiral structure of tropical cyclones under four-force (pressure gradient force, Coriolis force, centrifugal force, and friction forc...The steady axis-symmetrical atmosphere dynamical equations are used for describing spiral structure of tropical cyclones under four-force (pressure gradient force, Coriolis force, centrifugal force, and friction force) balance, and the dynamical systems of three-dimensional (3D) velocity field are introduced. The qualitative analysis of the dynamical system shows that there are down 3D spiral structures in eye of tropical cyclone and tropical cyclone is 3D counterclockwise up spiral structure. These results are consistent with the observed tropical cyclone on the weather map.展开更多
On the basis of Poisson's equation for the logarithmic perturbation of matter density, we provide improved estimates of scale heights and spiral structures for non-edge-on spiral galaxies by subtracting the surface b...On the basis of Poisson's equation for the logarithmic perturbation of matter density, we provide improved estimates of scale heights and spiral structures for non-edge-on spiral galaxies by subtracting the surface brightness distributions from observed images. As examples, the non-edge-on spiral galaxies PGC 24996, which is face-on, and M31, which is inclined, are studied. The scale height, pitch angle and inclination angle of M31, our nearest neighbor, that are presented in this work, agree well with previous research.展开更多
The 3-D spiral structure resulting from the balance between the pressure gradient force, Coriolis force, and viscous force is a common atmospheric motion pattern. If the nonlinear advective terms are considered, this ...The 3-D spiral structure resulting from the balance between the pressure gradient force, Coriolis force, and viscous force is a common atmospheric motion pattern. If the nonlinear advective terms are considered, this typical pattern can be bifurcated. It is shown that the surface low pressure with convergent cyclonic vorticity and surface high pressure with divergent anticyclonic vorticity are all stable under certain conditions. The anomalous structure with convergent anticyclonic vorticity is always unstable. But the anomalous weak high pressure structure with convergent cyclonic vorticity can exist, and this denotes the cyclone’s dying out.展开更多
The nonlinear stellar response to the growing spiral gravitational disturbance is calculated. The result shows that this nonlinear response leads to the increase of Q, and the decrease of the growth rate. This self-re...The nonlinear stellar response to the growing spiral gravitational disturbance is calculated. The result shows that this nonlinear response leads to the increase of Q, and the decrease of the growth rate. This self-regulation mechanism is an important reason for the growing spiral mode to reach a quasi-stationary state eventually.展开更多
We have studied some properties including surface brightness in the u, g, r, i, and z bands of the nearly face-on galaxy PGC 35105. By subtracting a model surface brightness distribution from the observed image we obt...We have studied some properties including surface brightness in the u, g, r, i, and z bands of the nearly face-on galaxy PGC 35105. By subtracting a model surface brightness distribution from the observed image we obtain the residual image that shows only the spiral arms freed from the contamination by the bulge. From this we measured the the inclination, pitch angle, and forbidden radius (identified with the innermost point of the arm) for each of the two arms; and that for each of the five observing bands. We found these three parameters are largely independent of the observing band.展开更多
We present a method of calculating the scale height of non-edge-on spiral galaxies, together with a formula for errors. The method is based on solving Poisson's equation for a logarithmic disturbance of matter densit...We present a method of calculating the scale height of non-edge-on spiral galaxies, together with a formula for errors. The method is based on solving Poisson's equation for a logarithmic disturbance of matter density in spiral galaxies. We show that the spiral arms can not extend to inside the "forbidden radius" r0, due to the effect of the finite thickness of the disk. The method is tested by re-calculating the scale heights of 71 northern spiral galaxies previously calculated by Ma, Peng & Gu. Our results differ from theirs by less than 9%. We also present the scale heights of a further 23 non-edge-on spiral galaxies.展开更多
We present disk thicknesses, some other parameters and their statistics of 108 nonedge-on spiral galaxies. The method for determining the disk thickness is based on solving Poisson's equation for a disturbance of mat...We present disk thicknesses, some other parameters and their statistics of 108 nonedge-on spiral galaxies. The method for determining the disk thickness is based on solving Poisson's equation for a disturbance of matter density in three-dimensional spiral galaxies. From the spiral arms found we could obtain the pitch angles, the inclination of the galactic disk, and the position of the innermost point (the forbidden region with radius r0 to the galactic center) of the spiral arm, and finally the thickness.展开更多
Researches on nonlinear atmospheric dynamics in China (1999-2002) are briefly surveyed. This review includes the major achievements in the following branches of nonlinear dynamics: nonlinear stability theory, nonlinea...Researches on nonlinear atmospheric dynamics in China (1999-2002) are briefly surveyed. This review includes the major achievements in the following branches of nonlinear dynamics: nonlinear stability theory, nonlinear blocking dynamics, 3D spiral structure in the atmosphere, traveling wave solution of the nonlinear evolution equation, numerical predictability in a chaotic system, and global analysis of climate dynamics. Some applications of nonlinear methods such as hierarchy structure of climate and scaling invariance, the spatial-temporal series predictive method, the nonlinear inverse problem, and a new difference scheme with multi-time Ievels are also introduced.展开更多
Based on nonlinear wave mixing, we experimentally propose a scheme for directly generating optical orbital angular momentum(OAM) by a spirally structured fundamental wave interacting with a nonlinear medium, in which ...Based on nonlinear wave mixing, we experimentally propose a scheme for directly generating optical orbital angular momentum(OAM) by a spirally structured fundamental wave interacting with a nonlinear medium, in which the nonlinear susceptibilities are homogenous. In the experiment, the second-harmonic generation of a fundamental wave carrying positive(negative) integers and fractional OAM states was investigated. This study presents a convenient approach for dynamic control of OAM of vortex beams, which may feature their applications in optical manipulation and optical communication.展开更多
For a composite system of gravitationally coupled stellar and gaseous discs, we have carried out a linear stability analysis for axisyrnmetric coplanar perturbations using the two-fluid formalism. The background stell...For a composite system of gravitationally coupled stellar and gaseous discs, we have carried out a linear stability analysis for axisyrnmetric coplanar perturbations using the two-fluid formalism. The background stellar and gaseous discs are taken to be scale-free with all physical variables varying as powers of the cylindrical radius r with compatible exponents. The unstable modes set in as neutral modes or stationary perturbation configurations with angular frequency f33 = 0. The axisyrnmetric stable range is bounded by two marginal stability curves derived from stationary perturbation configurations. Because of the gravitational coupling between the stellar arid the gaseous discs, one only needs to consider the parameter regime of the stellar disc. There exist two unstable regimes in general: a collapse regime corresponding to large-scale perturbations and a ring-fragmentation regime corresponding to short-wavelength perturbations. The composite system will collapse if it rotates too slowly and will succumb to ring-fragmentation instabilities if it rotates sufficiently fast. The overall stable range against axisyrnmetric perturbations is determined by a necessary D-criterion involving the effective Mach number squared Ds2 (the squared ratio of the stellar disc rotation speed to the stellar velocity dispersion up to a numerical factor). Different mass ratio S and sound speed ratio η of the gaseous and stellar disc components will alter the overall stability. For spiral galaxies or circumnuclear discs, we further include the dynamical effect of a massive dark matter halo. Astrophysical applications to disc galaxies, proto-stellar discs and circumnuclear discs are given as examples.展开更多
We report the discovery of 64 luminous infrared galaxies, based on new observations of 20 square degrees from the LAMOST Complete Spectroscopic Survey of Pointing Area at the Southern Galactic Cap and the WISE 22 μm ...We report the discovery of 64 luminous infrared galaxies, based on new observations of 20 square degrees from the LAMOST Complete Spectroscopic Survey of Pointing Area at the Southern Galactic Cap and the WISE 22 μm catalog from the AllW ISE Data Release. Half of them are classified as late-type spirals and the others are classified as peculiar/compact galaxies. The peculiar/compact galaxies tend to exhibit higher luminosities and lower stellar masses. We also separate AGNs from HII galaxies in a simple way by examining LAMOST spectra. Those cases show that host AGNs are easily distinguished from others in the mid-infrared color-color diagrams.展开更多
Regeneration of severe bone defects remains an enormous challenge in clinic.Developing regenerative scaffolds to directionally guide bone growth is a potential strategy to overcome this hurdle.Conch,an interesting cre...Regeneration of severe bone defects remains an enormous challenge in clinic.Developing regenerative scaffolds to directionally guide bone growth is a potential strategy to overcome this hurdle.Conch,an interesting creature widely spreading in ocean,has tough spiral shell that can continuously grow along the spiral direction.Herein,inspired by the physiological features of conches,a conch-like(CL)scaffold based onβ-TCP bioceramic material was successfully prepared for guiding directional bone growth via digital light processing(DLP)-based 3D printing.Benefiting from the spiral structure,the CL scaffolds significantly improved cell adhesion,proliferation and osteogenic differentiation in vitro compared to the conventional 3D scaffolds.Particularly,the spiral structure in the scaffolds could efficiently induce cells to migrate from the bottom to the top of the scaffolds,which was like“cells climbing stairs”.Furthermore,the capability of guiding directional bone growth for the CL scaffolds was demonstrated by a special half-embedded femoral defects model in rabbits.The new bone tissue could consecutively grow into the protruded part of the scaffolds along the spiral cavities.This work provides a promising strategy to construct biomimetic biomaterials for guiding directional bone tissue growth,which offers a new treatment concept for severe bone defects,and even limb regeneration.展开更多
A re-buncher with spiral arms for a heavy ion linear accelerator named as SSC-LINAC at HIRFL (the heavy ion research facility of Lanzhou) has been constructed. The re-buncher, which is used for beam longitudinal mod...A re-buncher with spiral arms for a heavy ion linear accelerator named as SSC-LINAC at HIRFL (the heavy ion research facility of Lanzhou) has been constructed. The re-buncher, which is used for beam longitudinal modulation and matching between the RFQ and DTL, is designed to be operated in continuous wave (CW) mode at the Medium-Energy Beam-Transport (MEBT) line to maintain the beam intensity and quality. Because of the longitudinal space limitation, the re-buncher has to be very compact and will be built with four gaps. We determined the key parameters of the re-buncher cavity from the simulations using Microwave Studio software, such as the resonant frequency, the quality factor Q and the shunt impedance. The detailed design of a 53.667 MHz spiral cavity and measurement results of its prototype will be presented.展开更多
基金supported by National Natural Science Foundation of China(Grant No.50675049)
文摘Micro electrical discharge machining(EDM) deposition process is a new micro machining method for fabrication of metal micro structures. In this process, the high level of tool electrode wear is used to achieve the metal material deposition. Up to now, the studies of micro EDM deposition process focused mainly on the researches of deposition process, namely the effects of discharge parameters in deposition process on the deposition rate or deposition quality. The research of the formation of micro structures with different discharge energy density still lacks. With proper conditions and only by the z-axis feeding in vertical direction, a novel shape of micro spiral structure can be deposited, with 0.11 mm in wire diameter, 0.20 mm in outside diameter, and 3.78 mm in height. Then some new deposition strategies including angular deposition and against the gravity deposition were also successful. In order to find the forming mechanism of the spiral structures, the numerical simulation of the transient temperature distribution on the discharge point was conducted by using the finite-element method(FEM). The results show that there are two major factors lead to the forming of the spiral structures. One is the different material removal form of tool electrode according with the discharge energy density, the other is the influenced degree of the movement of the removed material particles in the discharge gap. The more the energy density in single discharge is, the smaller the mass of the removed material particles is, and the easier the movements of which will be changed to form an order tendency. The fine texture characteristics of the deposited micro spiral structures were analyzed by the energy spectrum analysis and the metallographic analysis. It shows that the components of the deposited material are almost the same as those of the tool electrode. Moreover the deposited material has the brass metallic luster in the longitudinal profile and has compact bonding with the base material. This research is useful to understand the micro-process of micro EDM deposition better and helpful to increase the controllability of the new EDM method for fabrication of micro structures.
基金supported by the National Natural Science Foundation of China(Granted No.40975027)
文摘The steady axis-symmetrical atmosphere dynamical equations are used for describing spiral structure of tropical cyclones under four-force (pressure gradient force, Coriolis force, centrifugal force, and friction force) balance, and the dynamical systems of three-dimensional (3D) velocity field are introduced. The qualitative analysis of the dynamical system shows that there are down 3D spiral structures in eye of tropical cyclone and tropical cyclone is 3D counterclockwise up spiral structure. These results are consistent with the observed tropical cyclone on the weather map.
基金Supported by the National Natural Science Foundation of China
文摘On the basis of Poisson's equation for the logarithmic perturbation of matter density, we provide improved estimates of scale heights and spiral structures for non-edge-on spiral galaxies by subtracting the surface brightness distributions from observed images. As examples, the non-edge-on spiral galaxies PGC 24996, which is face-on, and M31, which is inclined, are studied. The scale height, pitch angle and inclination angle of M31, our nearest neighbor, that are presented in this work, agree well with previous research.
基金Many thanks are due to sup-port from the Ministry of Science and Technology of China through a special public welfare project under Grant No.2002DIB20070from the National Natural Science Foundation of China(Grant No.40305006).
文摘The 3-D spiral structure resulting from the balance between the pressure gradient force, Coriolis force, and viscous force is a common atmospheric motion pattern. If the nonlinear advective terms are considered, this typical pattern can be bifurcated. It is shown that the surface low pressure with convergent cyclonic vorticity and surface high pressure with divergent anticyclonic vorticity are all stable under certain conditions. The anomalous structure with convergent anticyclonic vorticity is always unstable. But the anomalous weak high pressure structure with convergent cyclonic vorticity can exist, and this denotes the cyclone’s dying out.
文摘The nonlinear stellar response to the growing spiral gravitational disturbance is calculated. The result shows that this nonlinear response leads to the increase of Q, and the decrease of the growth rate. This self-regulation mechanism is an important reason for the growing spiral mode to reach a quasi-stationary state eventually.
基金Supported by the National Natural Science Foundation of China.
文摘We have studied some properties including surface brightness in the u, g, r, i, and z bands of the nearly face-on galaxy PGC 35105. By subtracting a model surface brightness distribution from the observed image we obtain the residual image that shows only the spiral arms freed from the contamination by the bulge. From this we measured the the inclination, pitch angle, and forbidden radius (identified with the innermost point of the arm) for each of the two arms; and that for each of the five observing bands. We found these three parameters are largely independent of the observing band.
基金Supported by the National Natural Science Foundation of China
文摘We present a method of calculating the scale height of non-edge-on spiral galaxies, together with a formula for errors. The method is based on solving Poisson's equation for a logarithmic disturbance of matter density in spiral galaxies. We show that the spiral arms can not extend to inside the "forbidden radius" r0, due to the effect of the finite thickness of the disk. The method is tested by re-calculating the scale heights of 71 northern spiral galaxies previously calculated by Ma, Peng & Gu. Our results differ from theirs by less than 9%. We also present the scale heights of a further 23 non-edge-on spiral galaxies.
基金the National Natural Science Foundation of China.
文摘We present disk thicknesses, some other parameters and their statistics of 108 nonedge-on spiral galaxies. The method for determining the disk thickness is based on solving Poisson's equation for a disturbance of matter density in three-dimensional spiral galaxies. From the spiral arms found we could obtain the pitch angles, the inclination of the galactic disk, and the position of the innermost point (the forbidden region with radius r0 to the galactic center) of the spiral arm, and finally the thickness.
基金supported by the National Natural Science Foundation of China(Grant Nos.40221503,40275025,40023001)the Chinese Academy of Sciences(No.KZCX2-SW-210).
文摘Researches on nonlinear atmospheric dynamics in China (1999-2002) are briefly surveyed. This review includes the major achievements in the following branches of nonlinear dynamics: nonlinear stability theory, nonlinear blocking dynamics, 3D spiral structure in the atmosphere, traveling wave solution of the nonlinear evolution equation, numerical predictability in a chaotic system, and global analysis of climate dynamics. Some applications of nonlinear methods such as hierarchy structure of climate and scaling invariance, the spatial-temporal series predictive method, the nonlinear inverse problem, and a new difference scheme with multi-time Ievels are also introduced.
基金supported by the National Natural Science Foundation of China(Nos.11864017,61765008,and 12064017)the Scientific and Technology Project of Jiangxi Provincial Education Department(No.GJJ161539)+3 种基金the Open Project of Key Laboratory of Photoelectronics and Communication of Jiangxi Province(No.2015005)the Open Project of Jiangxi Key Laboratory of Nanomaterials and Sensors(No.2017007)the Open Fund by State Key Laboratory of Advanced Optical Communication Systems and Networks(No.2017GZKF18)the Young Talent Development Plan of Jiangxi Normal University 2019。
文摘Based on nonlinear wave mixing, we experimentally propose a scheme for directly generating optical orbital angular momentum(OAM) by a spirally structured fundamental wave interacting with a nonlinear medium, in which the nonlinear susceptibilities are homogenous. In the experiment, the second-harmonic generation of a fundamental wave carrying positive(negative) integers and fractional OAM states was investigated. This study presents a convenient approach for dynamic control of OAM of vortex beams, which may feature their applications in optical manipulation and optical communication.
基金the National Natural Science Foundation of China.
文摘For a composite system of gravitationally coupled stellar and gaseous discs, we have carried out a linear stability analysis for axisyrnmetric coplanar perturbations using the two-fluid formalism. The background stellar and gaseous discs are taken to be scale-free with all physical variables varying as powers of the cylindrical radius r with compatible exponents. The unstable modes set in as neutral modes or stationary perturbation configurations with angular frequency f33 = 0. The axisyrnmetric stable range is bounded by two marginal stability curves derived from stationary perturbation configurations. Because of the gravitational coupling between the stellar arid the gaseous discs, one only needs to consider the parameter regime of the stellar disc. There exist two unstable regimes in general: a collapse regime corresponding to large-scale perturbations and a ring-fragmentation regime corresponding to short-wavelength perturbations. The composite system will collapse if it rotates too slowly and will succumb to ring-fragmentation instabilities if it rotates sufficiently fast. The overall stable range against axisyrnmetric perturbations is determined by a necessary D-criterion involving the effective Mach number squared Ds2 (the squared ratio of the stellar disc rotation speed to the stellar velocity dispersion up to a numerical factor). Different mass ratio S and sound speed ratio η of the gaseous and stellar disc components will alter the overall stability. For spiral galaxies or circumnuclear discs, we further include the dynamical effect of a massive dark matter halo. Astrophysical applications to disc galaxies, proto-stellar discs and circumnuclear discs are given as examples.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11173030, 11225316, 11078017, 11303038, 10833006, 10978014 and 10773014)the National Basic Research Program of China (973 program, 2014CB845705 and 2012CB821800)+1 种基金the Key Laboratory of Optical Astronomy, National Astronomical Observatories,Chinese Academy of Sciencessupported by the Strategic Priority Research Program "The Emergence of Cosmological Structures" of the Chinese Academy of Sciences (Grant No. XDB09000000)
文摘We report the discovery of 64 luminous infrared galaxies, based on new observations of 20 square degrees from the LAMOST Complete Spectroscopic Survey of Pointing Area at the Southern Galactic Cap and the WISE 22 μm catalog from the AllW ISE Data Release. Half of them are classified as late-type spirals and the others are classified as peculiar/compact galaxies. The peculiar/compact galaxies tend to exhibit higher luminosities and lower stellar masses. We also separate AGNs from HII galaxies in a simple way by examining LAMOST spectra. Those cases show that host AGNs are easily distinguished from others in the mid-infrared color-color diagrams.
基金This work was supported by the National Key Research and Development Program of China(grant number 2021YFB3800800)the Natural Science Foundation of China(grant numbers 32225028,32130062)+1 种基金Science and Technology Commission of Shanghai Municipality(grant number 21DZ1205600)Shanghai Pilot Program for Basic Research-Chinese Academy of Science,Shanghai Branch(grant number JCYJ-SHFY-2022-003).
文摘Regeneration of severe bone defects remains an enormous challenge in clinic.Developing regenerative scaffolds to directionally guide bone growth is a potential strategy to overcome this hurdle.Conch,an interesting creature widely spreading in ocean,has tough spiral shell that can continuously grow along the spiral direction.Herein,inspired by the physiological features of conches,a conch-like(CL)scaffold based onβ-TCP bioceramic material was successfully prepared for guiding directional bone growth via digital light processing(DLP)-based 3D printing.Benefiting from the spiral structure,the CL scaffolds significantly improved cell adhesion,proliferation and osteogenic differentiation in vitro compared to the conventional 3D scaffolds.Particularly,the spiral structure in the scaffolds could efficiently induce cells to migrate from the bottom to the top of the scaffolds,which was like“cells climbing stairs”.Furthermore,the capability of guiding directional bone growth for the CL scaffolds was demonstrated by a special half-embedded femoral defects model in rabbits.The new bone tissue could consecutively grow into the protruded part of the scaffolds along the spiral cavities.This work provides a promising strategy to construct biomimetic biomaterials for guiding directional bone tissue growth,which offers a new treatment concept for severe bone defects,and even limb regeneration.
基金Supported by Pioneering and Interdisciplinary Research of Big Sciences (Y115210YQ0)
文摘A re-buncher with spiral arms for a heavy ion linear accelerator named as SSC-LINAC at HIRFL (the heavy ion research facility of Lanzhou) has been constructed. The re-buncher, which is used for beam longitudinal modulation and matching between the RFQ and DTL, is designed to be operated in continuous wave (CW) mode at the Medium-Energy Beam-Transport (MEBT) line to maintain the beam intensity and quality. Because of the longitudinal space limitation, the re-buncher has to be very compact and will be built with four gaps. We determined the key parameters of the re-buncher cavity from the simulations using Microwave Studio software, such as the resonant frequency, the quality factor Q and the shunt impedance. The detailed design of a 53.667 MHz spiral cavity and measurement results of its prototype will be presented.