特种回转面刀具成形理论的研究包括合理选择磨削该种刀具的工艺系统的形式(调整与运动),并确定系统中各运动应满足的函数关系。本文从微分几何和啮合原理的角度详细证明了磨削轮廓回转面与刀具轴线无交点的回转面刀具可以采用[x yφ]或[...特种回转面刀具成形理论的研究包括合理选择磨削该种刀具的工艺系统的形式(调整与运动),并确定系统中各运动应满足的函数关系。本文从微分几何和啮合原理的角度详细证明了磨削轮廓回转面与刀具轴线无交点的回转面刀具可以采用[x yφ]或[x y zφ]两种工艺系统,并严格地导出了系统中各运动之间应满足的函数关系。展开更多
The density wave theory of galactic spirals is a semi empirical theory consisting of the analysis of physically plausible mathematical models, the synthesis of extensive observational data, and an examination of the ...The density wave theory of galactic spirals is a semi empirical theory consisting of the analysis of physically plausible mathematical models, the synthesis of extensive observational data, and an examination of the applicability of the theoretical predictions of particular models for the interpretation of observational data. In this paper, the theory is reviewed from the general perception of order and chaos in dynamical systems. Prominent among the observational data is the well established morphological classification of galaxies according to Edwin Hubble, the luminosity class of Sidney van den Bergh, and the coexistence of regular and irregular global structures in many galaxies, as was first discovered in the whirlpool galaxy M51 by Fritz Zwicky. The regular structure is prominently observed in red and in infrared, and the irregular in blue and at 21 cm radio frequency. These and other data led to the concept of the existence of an essentially standing wave pattern in the older evolved stars, which in turn acts as a backbone for the global structure of the galaxy as a whole. Dynamically, the existence of irregular structures in the interstellar medium reflects the natural state of turbulent motion in gaseous motion at high speeds. In contrast, the essentially collisionless stellar system has a substantial 'microscale' of epicyclic motion that prevents, or smoothes out, irregularities on scales. It is pointed out that the spiral structure in galaxies is but one class of interesting phenomena that crucially relates to universal gravitation. Astronomical phenomena on all scales, from planets and satellites to protostars, stars and galaxies and the whole universe present other challenges to both theorists and observers, representing a wide field of opportunities for fruitful research. At the present time, they are being successfully met in individual cases through the development of new observational techniques to cover all frequencies of electromagnetic radiation and through the development of new analytica展开更多
Ⅰ. INTRODUCTION Neodymium yttrium aluminium tetraborate [Nd<sub>x</sub>Y<sub>1-x</sub>AL （BO<sub>3</sub>）<sub>4</sub>, （NYAB）] is a functional material which is sel...Ⅰ. INTRODUCTION Neodymium yttrium aluminium tetraborate [Nd<sub>x</sub>Y<sub>1-x</sub>AL （BO<sub>3</sub>）<sub>4</sub>, （NYAB）] is a functional material which is self-activated and self-frequent doubling. It belongs to an incongruent compound in the phase diagram, so the flux method is used for its crystal growth.展开更多
A conservation equation for topological charges of phase singularities （scroll and spiral waves） in excitable media is given. It provides some topological properties of scroll （spiral） waves： for example, the top...A conservation equation for topological charges of phase singularities （scroll and spiral waves） in excitable media is given. It provides some topological properties of scroll （spiral） waves： for example, the topological charge of the generated or annihilated spiral pair must be opposite. Additionally, we obtain another equation on scroll waves, which shows that singular filaments of scroll waves occur on a set of one-dimensional curves which may be either closed loops or infinite lines.展开更多
Horizontal velocity spirals with a clockwise rotation(downward looking) rate of 1.7?m^(-1), on average, were observed in the western and northern Yellow Sea from December 2006 to February 2007. With the observed therm...Horizontal velocity spirals with a clockwise rotation(downward looking) rate of 1.7?m^(-1), on average, were observed in the western and northern Yellow Sea from December 2006 to February 2007. With the observed thermal wind relation,the beta-spiral theory was used to explain the dynamics of spirals. It was found that the horizontal diffusion of geostrophic vortex stretching is likely to be a major mechanism for generating geostrophic spirals. Vertical advection associated with surface/bottom Ekman pumping and topography-induced upwelling is too weak to support these spirals. Strong wind stirring and large heat loss in wintertime lead to weak stratification and diminish the effects of vertical advection. The cooling effect and vertical diffusion are offset by an overwhelming contribution of horizontal diffusion in connection with vortex stretching. The Richardson number-dependent vertical eddy diffusivity reaches a magnitude of 10^(-4) m^2 s^(-1) on average. An eddy diffusivity of 2870 m^2 s^(-1) is required for dynamic balance by estimating the residual term. This obtained value of 10-4 m^2 s^(-1) is in good agreement with the estimation in terms of observed eddy activities. The suppressed and unsuppressed diffusivities in the observation region are 2752 and 2881 m^2 s^(-1), respectively, which supports a closed budget for velocity rotation.展开更多
The steady analytical solution of the perturbation equations describing the mesoscale vortex in the atmosphere is obtained. By analyzing the 3D wind field, the 3D spiral structure in physical space for unstable strati...The steady analytical solution of the perturbation equations describing the mesoscale vortex in the atmosphere is obtained. By analyzing the 3D wind field, the 3D spiral structure in physical space for unstable stratification is found. In many respects such as the 3D distribution of pressure and vorticity fields, the mesoscale spiral vortex is very similar to typically real cyclones. Key words Spirals tructure - Cyclones - 3D dynamical system Supported by the State Key Research Project on the Nonlinear Science and the Fund for Doctoral Station of the Ministry of Education, China.展开更多
文摘特种回转面刀具成形理论的研究包括合理选择磨削该种刀具的工艺系统的形式(调整与运动),并确定系统中各运动应满足的函数关系。本文从微分几何和啮合原理的角度详细证明了磨削轮廓回转面与刀具轴线无交点的回转面刀具可以采用[x yφ]或[x y zφ]两种工艺系统,并严格地导出了系统中各运动之间应满足的函数关系。
文摘The density wave theory of galactic spirals is a semi empirical theory consisting of the analysis of physically plausible mathematical models, the synthesis of extensive observational data, and an examination of the applicability of the theoretical predictions of particular models for the interpretation of observational data. In this paper, the theory is reviewed from the general perception of order and chaos in dynamical systems. Prominent among the observational data is the well established morphological classification of galaxies according to Edwin Hubble, the luminosity class of Sidney van den Bergh, and the coexistence of regular and irregular global structures in many galaxies, as was first discovered in the whirlpool galaxy M51 by Fritz Zwicky. The regular structure is prominently observed in red and in infrared, and the irregular in blue and at 21 cm radio frequency. These and other data led to the concept of the existence of an essentially standing wave pattern in the older evolved stars, which in turn acts as a backbone for the global structure of the galaxy as a whole. Dynamically, the existence of irregular structures in the interstellar medium reflects the natural state of turbulent motion in gaseous motion at high speeds. In contrast, the essentially collisionless stellar system has a substantial 'microscale' of epicyclic motion that prevents, or smoothes out, irregularities on scales. It is pointed out that the spiral structure in galaxies is but one class of interesting phenomena that crucially relates to universal gravitation. Astronomical phenomena on all scales, from planets and satellites to protostars, stars and galaxies and the whole universe present other challenges to both theorists and observers, representing a wide field of opportunities for fruitful research. At the present time, they are being successfully met in individual cases through the development of new observational techniques to cover all frequencies of electromagnetic radiation and through the development of new analytica
文摘Ⅰ. INTRODUCTION Neodymium yttrium aluminium tetraborate [Nd<sub>x</sub>Y<sub>1-x</sub>AL （BO<sub>3</sub>）<sub>4</sub>, （NYAB）] is a functional material which is self-activated and self-frequent doubling. It belongs to an incongruent compound in the phase diagram, so the flux method is used for its crystal growth.
基金Supported by the National Natural Science Foundation of China under Grant No 10675099, the Hong Kong Research Council （RGC）, and the Hong Kong Baptist University Faculty Research Fund （FRG）.
文摘A conservation equation for topological charges of phase singularities （scroll and spiral waves） in excitable media is given. It provides some topological properties of scroll （spiral） waves： for example, the topological charge of the generated or annihilated spiral pair must be opposite. Additionally, we obtain another equation on scroll waves, which shows that singular filaments of scroll waves occur on a set of one-dimensional curves which may be either closed loops or infinite lines.
基金funded by the National Natural Science Foundation of China (Grant Nos.41306003 and 41430963)the Fundamental Research Funds for Central Universities (Grant Nos.0905-841313038,1100-841262028 and 0905-201462003)+1 种基金the China Postdoctoral Science Foundation (Grant No.2013M531647)the Natural Science Foundation of Shandong (Grant No.BS2013HZ015)
文摘Horizontal velocity spirals with a clockwise rotation(downward looking) rate of 1.7?m^(-1), on average, were observed in the western and northern Yellow Sea from December 2006 to February 2007. With the observed thermal wind relation,the beta-spiral theory was used to explain the dynamics of spirals. It was found that the horizontal diffusion of geostrophic vortex stretching is likely to be a major mechanism for generating geostrophic spirals. Vertical advection associated with surface/bottom Ekman pumping and topography-induced upwelling is too weak to support these spirals. Strong wind stirring and large heat loss in wintertime lead to weak stratification and diminish the effects of vertical advection. The cooling effect and vertical diffusion are offset by an overwhelming contribution of horizontal diffusion in connection with vortex stretching. The Richardson number-dependent vertical eddy diffusivity reaches a magnitude of 10^(-4) m^2 s^(-1) on average. An eddy diffusivity of 2870 m^2 s^(-1) is required for dynamic balance by estimating the residual term. This obtained value of 10-4 m^2 s^(-1) is in good agreement with the estimation in terms of observed eddy activities. The suppressed and unsuppressed diffusivities in the observation region are 2752 and 2881 m^2 s^(-1), respectively, which supports a closed budget for velocity rotation.
基金Supported by the State Key Research Project on the Nonlinear Science the Fund for Doctoral Station of the Ministry of Educat
文摘The steady analytical solution of the perturbation equations describing the mesoscale vortex in the atmosphere is obtained. By analyzing the 3D wind field, the 3D spiral structure in physical space for unstable stratification is found. In many respects such as the 3D distribution of pressure and vorticity fields, the mesoscale spiral vortex is very similar to typically real cyclones. Key words Spirals tructure - Cyclones - 3D dynamical system Supported by the State Key Research Project on the Nonlinear Science and the Fund for Doctoral Station of the Ministry of Education, China.
