We have studied the transformation process from primary instabilities to secondary instabilities with direct numerical simulations and stability theories(Spatial Biglobal and plane-marching parabolized stability equat...We have studied the transformation process from primary instabilities to secondary instabilities with direct numerical simulations and stability theories(Spatial Biglobal and plane-marching parabolized stability equations)in detail.First Mack mode and second Mack mode are shown to be able to evolve into the sinuous mode and the varicose mode of secondary instability,respectively.Although the characteristics of second Mack mode eventually lose in the downstream due to the synchronization with the continuous spectrum,second Mack mode is found to be able to trigger a sequence of mode resonations which in turn give birth to highly unstable secondary instabilities.In contrast,first Mack mode does not involve in any mode synchronization.Nevertheless,it can still“jump”to a sinuous mode of secondary instability with a much larger growth rate than that of the first Mack mode.Therefore,secondary instabilities of Görtler vortices are highly receptive to the primary instabilities in the upstream,so that one should consider the primary instability in the upstream and the secondary instability in the downstream as a whole in order to get an accurate prediction of the boundary layer transition.展开更多
<正> For Bose-Einstein condensation of neutral atoms in anisotropic traps at zero temperature,we presentsimple analytical methods for computing the properties of ground state and single vortex of Bose-Einstein c...<正> For Bose-Einstein condensation of neutral atoms in anisotropic traps at zero temperature,we presentsimple analytical methods for computing the properties of ground state and single vortex of Bose-Einstein condensates,and compare those results to extensive numerical simulations.The critical angular velocity for production of vortices iscalculated for both positive and negative scattering lengths a,and find an analytical expression for the large-N limit ofthe vortex critical angular velocity for a>0,and the critical number for condensate population approaches the point ofcollapse for a<0,by using approximate variational method.展开更多
This paper presents a flexible and wearable textile array antenna designed to generate Orbital Angular Momentum(OAM)waves with Mode+2 at 3.5 GHz(3.4 to 3.6 GHz)of the sub-6 GHz fifth-generation(5G)New Radio(NR)band.Th...This paper presents a flexible and wearable textile array antenna designed to generate Orbital Angular Momentum(OAM)waves with Mode+2 at 3.5 GHz(3.4 to 3.6 GHz)of the sub-6 GHz fifth-generation(5G)New Radio(NR)band.The proposed antenna is based on a uniform circular array of eight microstrip patch antennas on a felt textile substrate.In contrast to previous works involving the use of rigid substrates to generate OAM waves,this work explored the use of flexible substrates to generate OAM waves for the first time.Other than that,the proposed antenna was simulated,analyzed,fabricated,and tested to confirm the generation of OAMMode+2.With the same design,OAM Mode−2 can be generated readily simply by mirror imaging the feed network.Note that the proposed antenna operated at the desired frequency of 3.5 GHz with an overall bandwidth of 400 MHz in free space.Moreover,mode purity analysis is carried out to verify the generation of OAM Mode+2,and the purity obtained was 41.78%at free space flat condition.Furthermore,the effect of antenna bending on the purity of the generated OAM mode is also investigated.Lastly,the influence of textile properties on OAM modes is examined to assist future researchers in choosing suitable fabrics to design flexible OAM-based antennas.After a comprehensive analysis considering different factors related to wearable applications,this paper demonstrates the feasibility of generating OAMwaves using textile antennas.Furthermore,as per the obtained Specific Absorption Rate(SAR),it is found that the proposed antenna is safe to be deployed.The findings of this work have a significant implication for body-centric communications.展开更多
Gravitation is still the least understood interaction among the fundamental forces of Nature. A new theory that explains the mechanism of gravitation and the origin Newton’s laws of gravitation and general relativity...Gravitation is still the least understood interaction among the fundamental forces of Nature. A new theory that explains the mechanism of gravitation and the origin Newton’s laws of gravitation and general relativity and distinguishes between two of the Newton’s laws has been proposed. It is shown that the vortex formation created during the Big Bang event is the origin of the gravitational force. The vortex curves the vacuum (space-time) around it, attract and condense energy and dust to its center to form the mass. The gradient pressure in the vortex creates a flow that upon interaction with an object transfers a part of its momentum to the object and pushes it toward the center. The force exercised on the object is equivalent to Newton’s second law. The force of attraction between two vortices is equivalent to Newton’s third law. The drag force between the energy flow of the vortex and the static vacuum diminishes the gravitational force and is equivalent to the G constant. The proposed theory could provide new interesting insights for a comprehensive understanding of gravitation and represents a theoretical starting point for the engineering of anti-gravitation technology.展开更多
Spin is an intrinsic form of angular momentum carried by elementary particles, composite particles, and atomic nuclei. It is wildly believed that spin is a purely quantum mechanical concept and has no classical analog...Spin is an intrinsic form of angular momentum carried by elementary particles, composite particles, and atomic nuclei. It is wildly believed that spin is a purely quantum mechanical concept and has no classical analogue. In fact, elementary particles are conceived as point objects which have no axis to “spin” around. Therefore, there is no explaining how spin arises at the fundamental level, why particles have the values they do, and what underpins the Pauli Exclusion principle and Bose-Einstein behavior. However, spin is like a vector quantity;it has a definite magnitude, and it has a “direction”, in order to spin should be composite. In this paper we propose a physical explanation for spin of the electron at the sub-particle level, relying on the vortex model of the electron. The electron is described as a superfluid frictionless vortex which has a mass, angular momentum and spin to provide a complete explanation of all properties of the electron: it composite, spinning around its own axis, produces a tiny magnetic fields independent of those from its orbital motions. The classical hydrodynamic laws are used to describe the quantum properties of the electron, such as spin, angular momentum, magnetic momentum and a magnetic dipole. The circulation in the vortex is constant, and the angular momentum of the vortex is conserved and has the same value of Planck constant. The direction of the angular momentum of a spinning electron vortex is along the axis of rotation and determined by the direction of spin. The spin quantum number 1/2 has a fixed value which represents the gap between the circulation rate of the core of the vortex and the boundaries of the vortex. The changeable values +1/2 “spin-up” or -1/2 “spin-down” indicate the direction of the magnetic dipole of the vortex. The relation between spin and Planck constant is discussed and the origin h/4pi angular momentum units are revealed.展开更多
We investigates the effect of Taylor-Grtler vortex on the Reynolds stress transport in the rotating turbulent channel flow by direct numerical simulation. The Taylor-Grtler vortex is detected by longitudinal avera...We investigates the effect of Taylor-Grtler vortex on the Reynolds stress transport in the rotating turbulent channel flow by direct numerical simulation. The Taylor-Grtler vortex is detected by longitudinal average of velocity fluctuation in the channel and defined as TG fluctuation. It has been found that turbulent diffusion is significant in the Reynolds stress transportation at the suction side of rotating turbulent channel in contrast with the turbulent channel flow without rotation and Taylor-Grtler vortex plays an important role in the turbulent diffusion in Reynolds stress transport. The paper focuses on the low and moderate rotation number, but the effect of the rotation number on the Reynolds stress transport is also reported.展开更多
Solitons are stable solitary waves.In 1834,Scott Russel first observed such a solitary water wave in a narrow channel near Edinburgh.In 1895,D.Korteweg and G.de Vries had derived the Korteweg-de Vries (KdV)equations f...Solitons are stable solitary waves.In 1834,Scott Russel first observed such a solitary water wave in a narrow channel near Edinburgh.In 1895,D.Korteweg and G.de Vries had derived the Korteweg-de Vries (KdV)equations for waves on shallow water surfaces.In 1965,N.Zabusky and M.Kruskal had demonstrated the stability of the solitary waves in the Korteweg-de Vries equation using numerical simulations,and coined the term "soliton".In 1967,Gardner, Greene,Kruskal,and Miura had discovered the mathematical technique of the inverse scattering transform to find analytical solutions to the KdV equation in a systematic manner,and the KdV equation was thus recognized as a paradigmatic integrable partial differential equation.展开更多
基金This work is funded by National Key Research and Development Project(2016YFA0401200).
文摘We have studied the transformation process from primary instabilities to secondary instabilities with direct numerical simulations and stability theories(Spatial Biglobal and plane-marching parabolized stability equations)in detail.First Mack mode and second Mack mode are shown to be able to evolve into the sinuous mode and the varicose mode of secondary instability,respectively.Although the characteristics of second Mack mode eventually lose in the downstream due to the synchronization with the continuous spectrum,second Mack mode is found to be able to trigger a sequence of mode resonations which in turn give birth to highly unstable secondary instabilities.In contrast,first Mack mode does not involve in any mode synchronization.Nevertheless,it can still“jump”to a sinuous mode of secondary instability with a much larger growth rate than that of the first Mack mode.Therefore,secondary instabilities of Görtler vortices are highly receptive to the primary instabilities in the upstream,so that one should consider the primary instability in the upstream and the secondary instability in the downstream as a whole in order to get an accurate prediction of the boundary layer transition.
基金The project supported by the State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Foundation under Grant No. T152501 and the Foundation of Education Commission of Zhejiang Province of China under Grant No. 20040599
文摘<正> For Bose-Einstein condensation of neutral atoms in anisotropic traps at zero temperature,we presentsimple analytical methods for computing the properties of ground state and single vortex of Bose-Einstein condensates,and compare those results to extensive numerical simulations.The critical angular velocity for production of vortices iscalculated for both positive and negative scattering lengths a,and find an analytical expression for the large-N limit ofthe vortex critical angular velocity for a>0,and the critical number for condensate population approaches the point ofcollapse for a<0,by using approximate variational method.
基金This work was supported by Ministry of Higher Education through the Fundamental Research Grant Scheme(FRGS)under a grant number of FRGS/1/2020/ICT09/UNIMAP/02/2.
文摘This paper presents a flexible and wearable textile array antenna designed to generate Orbital Angular Momentum(OAM)waves with Mode+2 at 3.5 GHz(3.4 to 3.6 GHz)of the sub-6 GHz fifth-generation(5G)New Radio(NR)band.The proposed antenna is based on a uniform circular array of eight microstrip patch antennas on a felt textile substrate.In contrast to previous works involving the use of rigid substrates to generate OAM waves,this work explored the use of flexible substrates to generate OAM waves for the first time.Other than that,the proposed antenna was simulated,analyzed,fabricated,and tested to confirm the generation of OAMMode+2.With the same design,OAM Mode−2 can be generated readily simply by mirror imaging the feed network.Note that the proposed antenna operated at the desired frequency of 3.5 GHz with an overall bandwidth of 400 MHz in free space.Moreover,mode purity analysis is carried out to verify the generation of OAM Mode+2,and the purity obtained was 41.78%at free space flat condition.Furthermore,the effect of antenna bending on the purity of the generated OAM mode is also investigated.Lastly,the influence of textile properties on OAM modes is examined to assist future researchers in choosing suitable fabrics to design flexible OAM-based antennas.After a comprehensive analysis considering different factors related to wearable applications,this paper demonstrates the feasibility of generating OAMwaves using textile antennas.Furthermore,as per the obtained Specific Absorption Rate(SAR),it is found that the proposed antenna is safe to be deployed.The findings of this work have a significant implication for body-centric communications.
文摘Gravitation is still the least understood interaction among the fundamental forces of Nature. A new theory that explains the mechanism of gravitation and the origin Newton’s laws of gravitation and general relativity and distinguishes between two of the Newton’s laws has been proposed. It is shown that the vortex formation created during the Big Bang event is the origin of the gravitational force. The vortex curves the vacuum (space-time) around it, attract and condense energy and dust to its center to form the mass. The gradient pressure in the vortex creates a flow that upon interaction with an object transfers a part of its momentum to the object and pushes it toward the center. The force exercised on the object is equivalent to Newton’s second law. The force of attraction between two vortices is equivalent to Newton’s third law. The drag force between the energy flow of the vortex and the static vacuum diminishes the gravitational force and is equivalent to the G constant. The proposed theory could provide new interesting insights for a comprehensive understanding of gravitation and represents a theoretical starting point for the engineering of anti-gravitation technology.
文摘Spin is an intrinsic form of angular momentum carried by elementary particles, composite particles, and atomic nuclei. It is wildly believed that spin is a purely quantum mechanical concept and has no classical analogue. In fact, elementary particles are conceived as point objects which have no axis to “spin” around. Therefore, there is no explaining how spin arises at the fundamental level, why particles have the values they do, and what underpins the Pauli Exclusion principle and Bose-Einstein behavior. However, spin is like a vector quantity;it has a definite magnitude, and it has a “direction”, in order to spin should be composite. In this paper we propose a physical explanation for spin of the electron at the sub-particle level, relying on the vortex model of the electron. The electron is described as a superfluid frictionless vortex which has a mass, angular momentum and spin to provide a complete explanation of all properties of the electron: it composite, spinning around its own axis, produces a tiny magnetic fields independent of those from its orbital motions. The classical hydrodynamic laws are used to describe the quantum properties of the electron, such as spin, angular momentum, magnetic momentum and a magnetic dipole. The circulation in the vortex is constant, and the angular momentum of the vortex is conserved and has the same value of Planck constant. The direction of the angular momentum of a spinning electron vortex is along the axis of rotation and determined by the direction of spin. The spin quantum number 1/2 has a fixed value which represents the gap between the circulation rate of the core of the vortex and the boundaries of the vortex. The changeable values +1/2 “spin-up” or -1/2 “spin-down” indicate the direction of the magnetic dipole of the vortex. The relation between spin and Planck constant is discussed and the origin h/4pi angular momentum units are revealed.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10872109, 10828204 and 10925210)the sponsor from the Sino-French Laboratory LIAMA (97-03)
文摘We investigates the effect of Taylor-Grtler vortex on the Reynolds stress transport in the rotating turbulent channel flow by direct numerical simulation. The Taylor-Grtler vortex is detected by longitudinal average of velocity fluctuation in the channel and defined as TG fluctuation. It has been found that turbulent diffusion is significant in the Reynolds stress transportation at the suction side of rotating turbulent channel in contrast with the turbulent channel flow without rotation and Taylor-Grtler vortex plays an important role in the turbulent diffusion in Reynolds stress transport. The paper focuses on the low and moderate rotation number, but the effect of the rotation number on the Reynolds stress transport is also reported.
文摘Solitons are stable solitary waves.In 1834,Scott Russel first observed such a solitary water wave in a narrow channel near Edinburgh.In 1895,D.Korteweg and G.de Vries had derived the Korteweg-de Vries (KdV)equations for waves on shallow water surfaces.In 1965,N.Zabusky and M.Kruskal had demonstrated the stability of the solitary waves in the Korteweg-de Vries equation using numerical simulations,and coined the term "soliton".In 1967,Gardner, Greene,Kruskal,and Miura had discovered the mathematical technique of the inverse scattering transform to find analytical solutions to the KdV equation in a systematic manner,and the KdV equation was thus recognized as a paradigmatic integrable partial differential equation.
