By using the equations describing typhoons in the atmosphere, the steady three-dimensional stream fieldand the corresponding pressure and temperature fields are obtained. The three-dimensional velocity fields construc...By using the equations describing typhoons in the atmosphere, the steady three-dimensional stream fieldand the corresponding pressure and temperature fields are obtained. The three-dimensional velocity fields construct anonlinear autonomuos system in the physical space. It is shown that the center of typhoon is a local minimum pressurewith positive vertical vorticity and horizontal convergence in lower levels and a local maximum pressure with negativevertical vorticity and horizontal divergence in the upper levels. Because there exits two saddle-focus points in the autnomous system, there exist the spiral patterns, in which the winds blow spirally in and out of the center in the lowerand upper levels in the Northern Hemisphere and cause the ascending motion near the center and dascending motionnear the edge, respectively . All these are in fair conformity with the observations. It implies that the rotation of earthand the viscosity of air play an important role in the spiral structure of typhoons.展开更多
In this paper, the evolution of the pattern transition induced by the vortical electric field （VEF） is investigated. Firstly, a scheme is suggested to generate the VEF by changing the spatial magnetic field. Secondl...In this paper, the evolution of the pattern transition induced by the vortical electric field （VEF） is investigated. Firstly, a scheme is suggested to generate the VEF by changing the spatial magnetic field. Secondly, the VEF is imposed on the whole medium, and the evolutions of the spiral wave and the spatiotemporal chaos are investigated by using the numerical simulation. The result confirms that the drift and the breakup of the spiral wave and the new net-like pattern are observed when different polarized fields are imposed on the whole medium respectively. Finally, the pattern transition induced by the polarized field is discussed theoretically.展开更多
Flasher origami pattern has been widely utilized to improve the stowage efficiency of deployable structures.Nevertheless,flasher origami cannot be folded fully flat,and they still have great potential for optimization...Flasher origami pattern has been widely utilized to improve the stowage efficiency of deployable structures.Nevertheless,flasher origami cannot be folded fully flat,and they still have great potential for optimization in terms of storage volume and folding creases.In this paper,a flat foldable equiangular spiral folding pattern inspired by the sunflower disk is introduced.Then,a parametric design method for this equiangular spiral crease diagram is introduced in detail.Subsequently,a kinematic model of the equiangular spiral folding pattern is established based on the kinematic equivalence between rigid origami and spherical linkages.A simulation of the developed model demonstrates that the equiangular spiral folding pattern can be folded flat.Using the folded ratio as an evaluation index,the calculated results and experiments show that the equiangular spiral crease pattern can yield fewer creases and improve stowage efficiency in comparison to flasher origami pattern.Equiangular spiral folding pattern can save a considerable amount of space and provide a new approach to spatially deployable structures.展开更多
文摘By using the equations describing typhoons in the atmosphere, the steady three-dimensional stream fieldand the corresponding pressure and temperature fields are obtained. The three-dimensional velocity fields construct anonlinear autonomuos system in the physical space. It is shown that the center of typhoon is a local minimum pressurewith positive vertical vorticity and horizontal convergence in lower levels and a local maximum pressure with negativevertical vorticity and horizontal divergence in the upper levels. Because there exits two saddle-focus points in the autnomous system, there exist the spiral patterns, in which the winds blow spirally in and out of the center in the lowerand upper levels in the Northern Hemisphere and cause the ascending motion near the center and dascending motionnear the edge, respectively . All these are in fair conformity with the observations. It implies that the rotation of earthand the viscosity of air play an important role in the spiral structure of typhoons.
基金supported by the National Natural Science Foundation of China (Grant Nos 10747005,10572056 and30670529)the Fund of Lanzhou University of Technology of China (Grant No Q200706)
文摘In this paper, the evolution of the pattern transition induced by the vortical electric field （VEF） is investigated. Firstly, a scheme is suggested to generate the VEF by changing the spatial magnetic field. Secondly, the VEF is imposed on the whole medium, and the evolutions of the spiral wave and the spatiotemporal chaos are investigated by using the numerical simulation. The result confirms that the drift and the breakup of the spiral wave and the new net-like pattern are observed when different polarized fields are imposed on the whole medium respectively. Finally, the pattern transition induced by the polarized field is discussed theoretically.
基金supported in part by National Key R&D Program of China(Grant No.2018YFB1304600)CAS Interdisciplinary Innovation Team(Grant No.JCTD-2018-11)the Natural Science Foundation of China(Grant No.51775541).
文摘Flasher origami pattern has been widely utilized to improve the stowage efficiency of deployable structures.Nevertheless,flasher origami cannot be folded fully flat,and they still have great potential for optimization in terms of storage volume and folding creases.In this paper,a flat foldable equiangular spiral folding pattern inspired by the sunflower disk is introduced.Then,a parametric design method for this equiangular spiral crease diagram is introduced in detail.Subsequently,a kinematic model of the equiangular spiral folding pattern is established based on the kinematic equivalence between rigid origami and spherical linkages.A simulation of the developed model demonstrates that the equiangular spiral folding pattern can be folded flat.Using the folded ratio as an evaluation index,the calculated results and experiments show that the equiangular spiral crease pattern can yield fewer creases and improve stowage efficiency in comparison to flasher origami pattern.Equiangular spiral folding pattern can save a considerable amount of space and provide a new approach to spatially deployable structures.
