Increase In Rotation Frequency Research Articles

The Study of Three-Dimensional Granular Stream Flowing through the Test Hopper-Shaped Target

The experiments are carried out in a three-dimensional channel with a screw conveyor, which plays the role of granular drives for the granular flow system and determines the injection of granular in the test target section. The jam-to-dense transition of granular flow is studied with the different inclination angle. The results show that, with a fixed diameter of hopper orifice and initial filling position, there is a change from jam to dense when the inclination angle larger than 22°. Variation of the flow rate with elevated frequency of the screw conveyor is further studied. The flow pattern is changed from dilute to dense with increasing rotation frequency of the screw rod. When the rotation frequency is larger than 5 Hz, the flow is dense. The dynamic balance of the interface between dilute to dense granular is observed in the main target section. We further research the dynamic interface by measuring the highest and lowest location with time and also simulate the gravity flow rate and screw conveyor flow rate with EDEM. From the results, we find that the interface between dilute flow and dense flow is influenced by the combined action of crew conveyor flow and dense gravity flow.

Dust-induced instability with dust charge fluctuations in a rotating dusty plasma

The dust-induced instability involving charge fluctuations is studied in rotating dusty plasma. Due to dust charging dynamics, the dust-induced instability mode which was first put forward by Mikhailovskii et al. [A.B. Mikhailovskii, S.V. Vladimirov, J.G. Lominadze, V.S. Tsypin, A.P. Churikov, N.N. Erokhin, R.M.O. Galvao, Phys. Plasmas 15, 014504 (2008)] will be replaced by dust-charging-rotational instability (DCRI) mode. Comparing to the dust-induced instability, the new instability mode also exists in an increasing rotation frequency profile, but always with a greater growth rate. The analysis indicates that the rotational instability mode induced by dust charge is always unstable. The present results may be used to investigate the rotating dusty plasma experiments and observations.

Rotational tuning of the dipole-dipole interaction in a Bose gas of magnetic atoms

We investigate the dynamics of a Bose-Einstein condensate of magnetic atoms in which the dipoles are rotated by an external magnetic field. The time-averaged dipole-dipole interaction between the atoms is effectively tuned by this rotation, however recent experimental and theoretical developments show that dynamic instabilities emerge that may cause heating. We present simulations of a realistic tuning sequence in this system, and characterize the system behavior and the emergence of instabilities. Our results indicate that the instabilities develop more slowly as the rotation frequency increases, and indicate that experiments with tuned dipole-dipole interactions should be feasible.

Ground state of spin-orbit coupled rotating ferromagnetic Bose-Einstein condensate in toroidal trap

Realization of spinor Bose-Einstein condensate in an optical trap has made it possible to create a variety of topological nontrivial structures, due to the vector character of the order parameter. Recently, artificial spin-orbit coupling in the spinor Bose-Einstein condensate, owing to coupling between the spin and the center-of-mass motion of the atom, provides an unprecedented opportunity to search for novel quantum states. As is well known, the potential well in the Bose-Einstein condensate is adjustable. The toroidal trap is an important model potential because of its simplicity and richness in physics. In particular, the spinor Bose-Einstein condensate under the toroidal trap has brought an ideal platform for studying fascinating properties of a superfluid, such as persistent flow and symmetry-breaking localization. For the case of the spin-orbit-coupled Bose-Einstein condensate, the previous studies of the toroidal trap mainly focused on the two-component or antiferromagnetic case. However, in the presence of a toroidal trap, there remains an open question whether the combined effects of the spin-orbit coupling and rotation can produce previously unknown types of topological excitations in the ferromagnetic Bose-Einstein condensate. In this work, by using quasi two-dimensional Gross-Pitaevskii equations, we study the ground state structure of spin-orbit coupled rotating ferromagnetic Bose-Einstein condensate in the toroidal trap. We concentrate on the effects of the spin-orbit coupling and the rotation on the ground states. The numerical results show that in the presence of a toroidal trap, the ground state structure is displayed as half-skyrmion chain with circular distribution. Adjusting the strength of spin-orbit coupling not only changes the number of half-skyrmion in the system, but also controls the symmetry of half-skyrmion with circular distribution. As the rotation frequency increases, the system undergoes the transitions from the plane wave to the half-skyrmion chain with circular distribution, and eventually developing the half-skyrmion phase of triangular lattice. Next, we examine the effect of spin-independent interaction on spin-orbit coupled rotating spinor Bose-Einstein condensate. As the spin-independent interaction increases, the topological defects in the condensate increase due to the variation of the local magnetic order. We also discuss the influence of well shape on the ground state structure. These topological structures can be detected via the time-of-flight absorption imaging technique. The spin-orbit coupled spinor Bose-Einstein condensate in the toroidal trap is an important quantum platform, which not only opens up a new avenue for exploring the exotic topological structures, but also is crucial for realizing the transitions among different ground states. This work paves the way for futureexploring the topological defects and the corresponding dynamical stability in quantum system subjected to the toroidal trap.

ПРОБЛЕМЫ РАЗВИТИЯ ТЯГОВЫХ ПРИВОДОВ ПАССАЖИРСКИХ ЭЛЕКТРОВОЗОВ С БЕСКОЛЛЕКТОРНЫМИ ТЭД

The paper considers a problem of creation of new traction drives with brushless electric traction motors (ETM) for passenger locomotives. Analysis of drive designs revealed that the increase of power of induction motors through the increase of rotation frequency leads to the contradiction between requirements for the design reliability, on the one hand, and requirements for technological simplicity, on the other hand. In order to solve the contradiction it is necessary to use ETM designs that have enhanced torque and minimal dimensions in axial direction. It is established that ETM with disk rotor (axial magnetic flux) satisfy such requirements. The authors proposed an aggregate scheme of support-frame traction drives that include ETM with disk rotor, which allows significantly increasing the adaptability to manufacture and repairability of drive at preservation of reliability. As a result, the authors made a conclusion about the reasonability of conducting research and development work on creation of locomotive ETM with axial magnetic flux. The authors have submitted an application for a patent on the proposed design of traction drive.

Thermal Damage of Intake Valves in ICE with Variable Timing

The article provides the study on causes of damage to ICE intake valves, in the course of which the intake valve heads have been overheated and deformed as a result of material creep. On the example of the failure detected in the analysed engine, it has been established that the traditionally known reasons such as the combustion process failure cannot cause the damage described. For the purpose of determining the real causes of damage to the intake valves the authors simulated the thermal state of the intake valve in the heatingcooling conditions with the impact of gas in the cylinder and the impact of air in the intake pipe as well as the contact heat exchange with the seat with regard to thermal conductivity along the stem. The calculations have shown that with the increase of rotation frequency the failure of the control system that causes the engine to run at high rotation frequencies with a small intake valve lift leads to the temperature increase higher than it is recommended for the materials used, which causes the described overheating. Based on the conducted research the authors have developed recommendations for improving the reliability of the intake valves performance in the ICEs with variable valve timing.

Topological excitations in rotating Bose-Einstein condensates with Rashba-Dresselhaus spin-orbit coupling in a two-dimensional optical lattice

We study the ground-state configurations and spin textures of rotating two-component Bose-Einstein condensates (BECs) with Rashba-Dresselhaus spin-orbit coupling (RD-SOC), which are confined in a two-dimensional (2D) optical lattice plus a 2D harmonic trap. In the absence of rotation, a relatively small isotropic 2D RD-SOC leads to the generation of ghost vortices for initially miscible BECs, while it gives rise to the creation of rectangular vortex-antivortex lattices for initially immiscible BECs. As the strength of the 2D RD-SOC enhances, the visible vortices or the 2D vortex-antivortex chains are created for the former case, whereas the rectangular vortex-antivortex lattices are transformed into vortex-antivortex rings for the later case. For the initially immiscible BECs with fixed 2D RD-SOC strength, the increase of rotation frequency can result in the structural phase transition from square vortex lattice to irregular triangular vortex lattice and the system transition from initial phase separation to phase mixing. In addition, we analyze the combined effects of 1D RD-SOC and rotation on the vortex configurations of the ground states for the case of initial phase separation. The increase of 1D SOC strength, rotation frequency or both of them may result in the formation of vortex chain and phase mixing. Furthermore, the typical spin textures for both the cases of 2D RD-SOC and 1D RD-SOC are discussed. It is shown that the system favors novel spin textures and skyrmion configurations including an exotic skyrmion-half-skyrmion lattice (skyrmion-meron lattice), a complicated meron lattice, a skyrmion chain, and a Bloch domain wall.

Enhanced diffusion and magnetophoresis of paramagnetic colloidal particles in rotating magnetic fields.

Dispersions of paramagnetic colloids can be manipulated with external magnetic fields to assemble structures via dipolar assembly and control transport via magnetophoresis. For fields held steady in time, the dispersion structure and dynamic properties are coupled. This coupling can be problematic when designing processes involving field-induced forces, as particle aggregation competes against and hinders particle transport. Time-varying fields drive dispersions out-of-equilibrium, allowing the structure and dynamics to be tuned independently. Rotating the magnetic field direction using two biaxial fields is a particularly effective mode of time-variation and has been used experimentally to enhance particle transport. Fundamental transport properties, like the diffusivity and magnetophoretic mobility, dictate dispersions' out-of-equilibrium responses to such time-varying fields, and are therefore crucial to understand to effectively design processes utilizing rotating fields. However, a systematic study of these dynamic quantities in rotating fields has not been performed. Here, we investigate the transport properties of dispersions of paramagnetic colloids in rotating magnetic fields using dynamic simulations. We find that self-diffusion of particles is enhanced in rotating fields compared to steady fields, and that the self-diffusivity in the plane of rotation reaches a maximum value at intermediate rotation frequencies that is larger than the Stokes-Einstein diffusivity of an isolated particle. We also show that, while the magnetophoretic velocity of particles through the bulk in a field gradient decreases with increasing rotation frequency, the enhanced in-plane diffusion allows for faster magnetophoretic transport through porous materials in rotating fields. We examine the effect of porous confinement on the transport properties in rotating fields and find enhanced diffusion at all pore sizes. The confined and bulk values of the transport properties are leveraged in simple models of magnetophoresis through tortuous porous media.

Topological Defects of Spin–Orbit Coupled Bose–Einstein Condensates in a Rotating Anharmonic Trap

We investigate the topological defects and spin structures of binary Bose-Einstein condensates (BECs) with Dresselhaus spin-orbit coupling (D-SOC) in a rotating anharmonic trap. Our results show that for initially mixed BECs without SOC the increasing rotation frequency can lead to the structural phase transition of the system. In the presence of isotropic D-SOC, the system sustains vortex pair,Anderson--Toulouse coreless vortices, circular vortex sheets, and combined vortex structures. In particular, when the rotation frequency is fixed above the radial trapping frequency the strong D-SOC results in a peculiar topological structure which is comprised of multi-layer visible vortex necklaces, hidden vortex necklaces and a hidden giant vortex. In addition, the system exhibits rich spin textures including basic skyrmion, meron cluster, skyrmion string and various skyrmion lattices. The skyrmions will be destroyed in the limit of large D-SOC or rotation frequency. Furthermore, the effects of anisotropic D-SOC and Rashba-Dresselhaus SOC on the topological structures of the system are discussed.

Механические свойства сварных соединений плит алюминиевого сплава АД0, выполненных сваркой плавлением и трением с перемешиванием

Optimum parameters are defined for friction stir welding modes of aluminum AD0 plates of 28mm thick. It is shown that at friction stir welding with mixing (FSW) aluminum AD0 plates a qualitative joint formation can be ensured at the expense of bilateral welding (alternatively on the right and root side of the joint). At the intensive plastic deformation impact and metal heating at the expense of friction the structure of welded AD0 alloy plates is formed by means of the narrow bands ("onion rings" successive interchange) having an ultra-dispersion grain structure. At heat application increase at the expense of the increase of tool rotation frequency and a tool pressure force a temperature-time mode of welding supporting a partial recrystallization of deformed grains in a joint center is changed. At the application of maximum tensile stresses a welded joint destruction occurs along a division border of media with a different structure in consequence of the incompatibility of their deformation.

Properties of the Shannon Information Entropy in Rotating Bose-Einstein Condensate

Motivated by recent develpoment in the field of quantum information, we study the Shannon information entropy \((S)\) formation in a rotating Bose-Einstein condensate. We obtain numerical solutions of the three-dimensional Gross-Pitaevskii equation. We conclude that with the increase of rotational frequency \(({\Omega })\), the vortex number (Nv) increases, and the system shows more disordered configurations. At the same time, the Landsberg’s order parameter \((\delta )\) exhibits quick decay. We also investigate the dynamics behavior, numerical results show that the total entropy S gradually increases as a function of time t. The order parameter \(\delta \) becomes vanishing even for the upper limit of the rotational frequency \({\Omega }\).

Ground-state phases of spin–orbit coupled spin-1 Bose–Einstein condensate in a plane quadrupole field

We study the ground-state phases of two-dimensional spin–orbit coupled spin-1 Bose–Einstein condensate loaded in a plane quadrupole field. In the absence of rotation, for the fixed spin-orbit coupling strength, the ordinary stripe phase is found when the strength of the magnetic field gradient is small. As the strength of magnetic field gradient enhances, the system realizes the phases with three layer vortices along the radial direction. The number of vortices in the second layer is successively increased and the vortices in the outermost layer disappear when the strength of magnetic field gradient surpass the critical value. For the large strength of magnetic field gradient, the system only has the inner layer vortices. The magnetic field inhibits the region of vortices. For the fixed magnetic field gradient strength, the vortices of the system elongate along the radial direction and form a series of vortex lines, the number of the vortex line increases as the strength of spin-orbit coupling enhances. By adding the rotation, for the fixed strengths of spin-orbit coupling and magnetic field gradient, the number of second layer vortices also successively increases as the rotational frequency increases. The number of vortices in the certain layer of the ground-state density can be regularly changed under the effects of the magnetic field and spin–orbit coupling.

The effect of parametric excitation on a dynamic system of cutting process

The problem of ensuring stability of movements of the tool about workpiece taking into account parametric self-excitation is considered. The factors causing periodic changes of parameters in dynamic system when cutting are analyzed. They are connected with spatial anisotropy of properties of elasticity in a subsystem of the processed workpiece with allowance variations on workpiece rotation perimeter, with kinematic perturbation from mechanical part of drives of executive elements of the machine, with periodic processes in a cutting zone. The generalized dynamic model of system with periodically changing parameters is given. Influence of periodically changing parameters on stability of trajectories is studied. The features of loss of stability specific to dynamic systems of cutting are disclosed. In particular, it is shown that due to parametrical effects with increasing cutting speed at increase of rotational frequency of spindle there is always a critical frequency at which the system loses stability.

Vortex states and spin textures of rotating spin–orbit-coupled Bose–Einstein condensates in a toroidal trap

We consider the ground-state properties of Rashba spin–orbit-coupled pseudo-spin-1/2 Bose–Einstein condensates (BECs) in a rotating two-dimensional (2D) toroidal trap. In the absence of spin–orbit coupling (SOC), the increasing rotation frequency enhances the creation of giant vortices for the initially miscible BECs, while it can lead to the formation of semiring density patterns with irregular hidden vortex structures for the initially immiscible BECs. Without rotation, strong 2D isotropic SOC yields a heliciform-stripe phase for the initially immiscible BECs. Combined effects of rotation, SOC, and interatomic interactions on the vortex structures and typical spin textures of the ground state of the system are discussed systematically. In particular, for a fixed rotation frequency above the critical value, the increasing isotropic SOC favors a visible vortex necklace in each component which is accompanied by a hidden giant vortex plus a (several) hidden vortex necklace(s) in the central region. In the case of one-dimensional anisotropic SOC, large SOC strength results in the generation of hidden linear vortex string and the transition from initial component separation (component mixing) to component mixing (component separation). Furthermore, the peculiar spin textures including skyrmion lattice, skyrmion pair and skyrmion string are revealed in this system.

Energy Taxis in Escherichia Coli on the Single-Cell Level

Energy taxis allows bacteria to respond to external stresses that affect its electron transport system, and to navigate to the environment optimal for energy generation. For example, in an oxygen gradient bacteria accumulate in a sharply defined band at the oxygen concentration that maximizes their proton motive force (PMF) which is coupled to electron transport (Zhulin, 1996). Examples of energy taxis include aerotaxis, taxis to alternative electron acceptors, and taxis to respiratory substrates. In E. coli, energy sensing is mediated by Tar and Aer receptors: Tar senses changes in PMF, while Aer is likely a redox sensor (Edwards, 2007). It is therefore expected that in the spatial gradient of oxygen or alternative electron acceptors changes in bacterial swimming behavior, e.g. tumble bias, will be correlated with PMF, but this has never been demonstrated directly.We study taxis to nitrate - an alternative electron acceptor for E. coli - in bacteria under anaerobic conditions at the single cell level, using an optical trap (Min, 2009). We move bacteria in a defined gradient of nitrate inside the flow chamber, and measure resulting changes in both tumble bias and flagella rotation frequency, which is proportional to PMF under low viscous load that corresponds to free swimming bacteria (Gabel, 2003).Our preliminary results show that under anaerobic conditions E. coli respond to changes in nitrate concentration, which is reflected in both tumble bias and flagella rotation. Thus running response or decrease in tumble bias corresponds to the increase in flagella rotation frequency and vice versa. While changes in tumble bias are transient and are followed by adaptation, nitrate concentration change have long-lasting effect on flagella rotation which is expected if PMF depends on the absolute concentration of nitrate.Using our method we can measure preferred concentration of nitrate for individual bacteria at which their PMF is maximized and how it depends on other factors such as concentration of electron donor, energetic state of the bacteria and mode of metabolism.References J. C. Edwards et al. Mol Microbiol (2007). I. B. Zhulin et al. J Bacteriol (1996). T. L. Min et al. Nature Methods (2009). C. V Gabel & H. C. Berg. PNAS (2003).

Thermodynamic properties of a rotating ideal Bose gas in an anisotropic harmonic trap

In this paper, the thermodynamic properties of a rotating Bose gas in an anisotropic harmonic trap are investigated. Using the density of states method, the thermodynamic potential, transition temperature, condensate fraction and heat capacity are analytically calculated. Consequently, the change of these thermodynamic quantities with reduced temperature, particle number and the rotation frequency are studied. It is found that, unlike the previous studied cases where the trapping potential is planar isotropic, due to the fact that the system has two stable regions as the rotation frequency increases, the thermodynamic quantities behave quite differently in these two stable regions. The validity of our results are also discussed.

Surface void suppression for pure copper by high-speed laser scanner welding

Welding of copper was conducted using a single-mode fiber laser rotated at a high speed by a galvano scanner. The rotation diameter and frequency were changed to investigate the effect of the beam rotation on the welding quality. The rotation diameter changed from 0.3 to 1.0mm and the rotation frequency changed from 77 to 285Hz. The weld depth obtained with scanning is smaller than that obtained without scanning. The weld depth decreases as rotation frequency increases, regardless of the rotation diameter. The bead width obtained with scanning is larger than that obtained without scanning because of the larger laser radiation area. In the welding there is an unscanned area, based on the relationship between laser scanning conditions and welding speed, that makes the weld depth periodic. It was found that welding geometry can be controlled by adjusting scanning parameters. Spatter and surface voids decrease as rotation frequency and diameter increase. It was confirmed a scanning speed over 500mm/s suppressed large spatter and surface voids.

Measurement of the torque on diluted ferrofluid samples in rotating magnetic fields

We study magnetic suspensions with different concentrations of ferromagnetic nanoparticles in a spherical container under the action of a rotating magnetic field. Experimental data on the concentration dependence of the rotational effect, viz. the torque exerted by the magnetic field, are presented. We explain the observed torque characteristics using a model that takes into account field-driven aggregation of the magnetic nanoparticles in stationary or slowly rotating fields. At sufficiently high rotation rates, the rotating magnetic field obviously destroys these aggregates, which results in a decreasing torque with increasing rotation frequency of the field.

Band structure inSn113

The structure of collective bands in $^{113}\mathrm{Sn}$, populated in the reaction $^{100}\mathrm{Mo}(^{19}\mathrm{F},\phantom{\rule{0.16em}{0ex}}p5n)$ at a beam energy of 105 MeV, has been studied. A new positive-parity sequence of eight states extending up to 7764.9 keV and spin $(39/{2}^{+})$ has been observed. The band is explained as arising from the coupling of the odd valence neutron in the ${g}_{7/2}$ or the ${d}_{5/2}$ orbital to the deformed 2p-2h proton configuration of the neighboring even-$A$ Sn isotope. Lifetimes of six states up to an excitation energy of 9934.9 keV and spin $47/{2}^{\ensuremath{-}}\mathrm{belonging}$ to a $\mathrm{\ensuremath{\Delta}}I=2$ intruder band have been measured for the first time, including an upper limit for the last state, from Doppler-shift-attenuation data. A moderate average quadrupole deformation ${\ensuremath{\beta}}_{2}=0.22\ifmmode\pm\else\textpm\fi{}0.02$ is deduced from these results for the five states up to spin $43/{2}^{\ensuremath{-}}$. The transition quadrupole moments decrease with increase in rotational frequency, indicating a reduction of collectivity with spin, a feature common for terminating bands. The behavior of the kinematic and dynamic moments of inertia as a function of rotational frequency has been studied and total Routhian surface calculations have been performed in an attempt to obtain an insight into the nature of the states near termination.

Catastrophic instabilities of modified DA-DC hybrid surface waves in a semi-bounded plasma system

We find the catastrophic instabilities and derive the growth rates for the dust-cyclotron resonance (DCR) and dust-rotation resonance (DRR) modes of the modified dust-acoustic and dust-cyclotron (DA-DC) hybrid surface waves propagating at the plasma–vacuum interface where the plasma is semi-bounded and composed of electrons and rotating dust grains. The effects of magnetic field and dust rotation frequency on the DCR- and DDR-modes are also investigated. We find that the dust rotation frequency enhances the growth rate of DCR-mode and the effect of dust rotation on this resonance mode decreases with an increase of the wave number. We also find that an increase of magnetic field strength enhances the DCR growth rate, especially, for the short wavelength regime. In the case of DRR-mode, the growth rate is found to be decreased less sensitively with an increase of the wave number compared with the case of DCR, but much significantly enhanced by an increase of dust rotation frequency. The DRR growth rate also decreases with an increase of the magnetic field strength, especially in the long wavelength regime. Interestingly, we find that catastrophic instabilities occur for both DCR- and DRR-modes of the modified DA-DC hybrid surface waves when the rotational frequency is close to the dust-cyclotron frequency. Both modes can also be excited catastrophically due to the cooperative interaction between the DCR-mode and the DRR-mode.