Motion Of Core Research Articles

On the Origin of Geostrophic Liquid Cylinders in Rotating Sphere with Oscillating Inner Core

The effect of non-axisymmetric inertial waves on the zonal flow structure in a rotating spherical shell is studied experimentally. The wave source is the inner core, which performs circular oscillations in the equatorial plane. The case of positive frequencies that corresponds to the advanced core motion is considered. As a result of non-linear effects, a quasi-two-dimensional axisymmetric steady flow with a complex distribution of angular velocity is generated. The extrema in the velocity profile are equivalent to the nested liquid geostrophic cylinders, which appearance is due to the interaction of the inertial waves within a viscous boundary layer. One of the extrema is associated with the critical latitude at the core boundary, where the inertial waves are excited. With an increase in the oscillation frequency, the position of this extremum gradually shifts to the rotation axis. Additional geostrophic circulation occurs close to the points where the inertial wave reflects from the cavity boundary.

Magnetic vortex near the extended linear magnetic inhomogeneity

In this paper, the problem of a magnetic vortex motion in a field of extended linear inhomogeneity is solved theoretically. The motion parameters are calculated by the method of collective variables (Thiel’s equation) with the vortex effective mass and the third-order gyrovector. On the basis of the equation of motion, the influence of the core mass and the third-order gyrovector on the character of the vortex motion as a quasiparticle is analyzed. Using the method of magnetostatic charges, analytical expressions are obtained for the effective potentials where the vortex core is located: (a) near the edge of the magnet or at the boundary of different magnetic phases, (b) near the linear inhomogeneity of local anisotropy (bidirectional and unidirectional). The solution of the equation of motion made it possible to obtain the trajectories of the core in various physical situations. In addition, the paper discusses the features of the Hall effect for vortices/skyrmions, which are provided by the inertial properties and a third-order gyrovector. It is shown that when the core of a linear inhomogeneity crosses a unidirectional anisotropy or the boundary of magnetic phases, a curvature of the trajectory is observed, which is similar to the refraction of light at the boundary of optically dissimilar environment. It is important to note that the introduction of the mass and gyroscopic effect of the third order in the equation of motion showed that the motion of the vortex, even in a homogeneous potential, is not translational. In this case, the trajectory is an overlay of cycloids of different rotation frequencies (analytical expressions are obtained for the frequencies). It is shown that, the introduction of the mass and the gyroscopic term of the third order, the motion of the vortex core cannot be considered translational at least during the time of the transition mode until the stationary mode of motion takes place.

Anomalous dislocation core structure in shock compressed bcc high-entropy alloys

Recent studies of complex concentrated alloys suggest unusual dislocation core structure and motion, thanks to a collective concentration/structural inhomogeneity. Less is known whether these effects also work in extreme conditions where the solid solution effect is overwhelmed by the large driving force. Here, we investigate the dislocation structure behind a shock-wave front in bcc high-entropy alloys (HEAs) using large-scale molecular dynamics (MD) simulations. In contrast to bcc elemental metals, we find anomalous “extended“ edge dislocation structure (6 ~ 8 Burgers vector) with high stability in shock compressed TiZrNb and NiCoFeTi HEAs. The unique dislocation structures can facilitate faster dislocation motion, thus deterring the early nucleation of deformation twins. Combined with continuum elasticity theory, we show that the “extended“ dislocation structure can be attributed to the presence of local structures with low elastic stability that are imparted by the nanoscale chemical heterogeneities in HEAs. We also show how the dislocation structures are affected by the interatomic potentials.

Flicker and random telegraph noise between gyrotropic and dynamic C-state of a vortex based spin torque nano oscillator

Vortex based spin torque nano oscillators (STVOs) can present more complex dynamics than the spin torque induced gyrotropic (G) motion of the vortex core. The respective dynamic modes and the transition between them can be controlled by experimental parameters such as the applied dc current. An interesting behavior is the stochastic transition from the G-to a dynamic C-state occurring for large current densities. Moreover, the C-state oscillations exhibit a constant active magnetic volume. We present noise measurements in the different dynamic states that allow accessing specific properties of the stochastic transition, such as the characteristic state transition frequency. Furthermore, we confirm, as theoretically predicted, an increase of flicker noise with Idc2 when the oscillation volume remains constant with the current. These results bring insight into the potential optimization of noise properties sought for many potential rf applications with spin torque oscillators. Furthermore, the investigated stochastic characteristics open up new potentialities, for instance in the emerging field of neuromorphic computing schemes.

Luminescent Amphiphilic Aminoglycoside Probes to Study Transfection.

We report the characterization of amphiphilic aminoglycoside conjugates containing luminophores with aggregation‐induced emission properties as transfection reagents. These inherently luminescent transfection vectors are capable of binding plasmid DNA through electrostatic interactions; this binding results in an emission “on” signal due to restriction of intramolecular motion of the luminophore core. The luminescent cationic amphiphiles effectively transferred plasmid DNA into mammalian cells (HeLa, HEK 293T), as proven by expression of a red fluorescent protein marker. The morphologies of the aggregates were investigated by microscopy as well as ζ‐potential and dynamic light‐scattering measurements. The transfection efficiencies using luminescent cationic amphiphiles were similar to that of the gold‐standard transfection reagent Lipofectamine® 2000.

New Evidence for the Fluctuation Characteristics of Intradecadal Periodic Signals in Length‐Of‐Day Variation

AbstractThe intradecadal fluctuations in the length‐of‐day variation (∆LOD) are considered likely to play an important role in core motions. Two intradecadal oscillations, with ∼5.9 and ∼8.5 years periods (referred to as SYO and EYO, respectively), have been detected in previous studies. However, whether the SYO and the EYO have exhibited stable damping trends since 1962 and whether geomagnetic jerks are possible excitation sources for the SYO/EYO are still debated. In this study, based on different methods and different ∆LOD records with different time spans, we showed robust evidence to prove that the SYO and the EYO have had no stable damping trends since 1962. We also found that there may be a ∼7.6 years signal, but given that its average amplitude is too small, further confirmations are needed in the future. After confirming that the jerks have no special consistency with the peaks/valleys of the EYO/SYO, we further used a deconvolution process and confirmed that the geomagnetic jerks seem to be related to sudden changes in the SYO/EYO time series and their excitation series. Thus we finally suggest that jerks are possible excitation sources of the SYO/EYO. After using a deconvolution process, we estimate that the period P and quality factor Q of the SYO and the EYO are [P = 5.85 ± 0.06 years, Q ≥ 180] and [P = 8.45 ± 0.17 years, Q ≥ 350], respectively.

Unidirectional switching of magnetic vortex core in a nanocavity mediated nanodisk: Looking for a reliable low-power-driven and fast switching in terms of geometric parameters

Reliable unidirectional switching of magnetic vortex core driven by continuous rotating magnetic field is investigated using a permalloy nanodisk with a nanocavity inserted in the center in combination with micromagnetic simulations. It is reported that once the vortex core is confined in a nanocavity of diameter is comparable to the core size, the modes of the core motion (divergence/convergence modes) are modulated differently by the nanocavity: the threshold field amplitude required for vortex core switching is reduced for convergence mode, but not for divergence mode. We found that the confinement of the nanocavity to the core is mediated by the cavity height as well. Low-power-driven fast unidirectional switching is found to be achievable by carefully choosing the value of the nanocavity height.

Beyond the gyrotropic motion: Dynamic C-state in vortex spin torque oscillators

In the present study, we investigate a dynamical mode beyond the gyrotropic (G) motion of a magnetic vortex core in a confined magnetic disk of a nano-pillar spin torque nano-oscillator (STNO). It is characterized by the in-plane circular precession associated with a C-shaped magnetization distribution. We show a transition between G- and C-state modes, which is found to be stochastic in a current-controllable range. Supporting our experimental findings with micromagnetic simulations, we believe that the results provide further opportunities for the dynamic and stochastic control of STNOs, which could be interesting to be implemented, for example, in neuromorphic networks.

FG and viscoelastic models combination for vibroacoustic modeling of sandwich structures made of open and closed cell foam materials

This paper presents a new method based on a functionally graded viscoelastic model for examining the acoustic vibrations of a submerged sandwich shell in the fluid. The structure consists of two isotropic shells that the space between them is filled with open-cell and closed-cell foams. A laminate model is used to get the equations of motion of the foam core. It is assumed that the core is composed of an infinite number of viscoelastic layers, while the properties of the adjacent layers are different. Consequently, complex Young’s and shear moduli are dependent on the frequency of excitation. Density and Young modulus vary according to a distribution function through the thickness. Because of the effective roles of rotary inertia and shear deformation, the governing equations of the sandwich structure are obtained by the three-dimensional theory of elasticity. The Zener model is used for describing the viscoelastic behavior of foam. Next, the solution procedure of the vibroacoustic behavior is derived by the transfer matrix method. Finally, the effects of mechanical parameters of foam such as relative density, edge material fraction, relaxation time, volume fraction, and power index are examined. The results exhibit that open-cell foam is better sound insulation than closed-cell foam.

Observation and Simulation of a Bifurcating Thunderstorm over Beijing

AbstractThe aim of this study was the analysis and simulation of the life cycle of a bifurcating thunderstorm that passed over Beijing, China, on 22 July 2015. Data from 150 surface weather sites and an S-band radar were used in conjunction with WRF simulations that used its multilevel Building Environment Parameterization (BEP) urbanization option. The Urban-case simulation used Beijing land-use information, and the NoUrban one replaced all urban areas by croplands. The Urban case correctly simulated both the observed weak 10-m winds over Beijing (<1.0 m s−1) and the weak 2-m urban heat island (<0.5°C). Observed radar and rain gauge data, as well as the Urban-case results, all showed precipitation bifurcation around Beijing, with maximum accumulations in convergent flow areas on either side of the city. The Urban case also reproduced the observed precipitation minima over the urban area and in a downwind rain shadow. The observations and Urban-case results both also showed bifurcated flow, even when the storm was still upwind of Beijing. The subsequent bifurcated precipitation areas thus each moved along a preexisting flow branch. Urban-case vertical sections showed downward motion in the divergence areas over the urban core and upward motions over the lateral convergence zones, both up to 6 km. Given that the NoUrban case showed none of these features, these differences demonstrate how the impact of cities can extend upward into deep local convection. Additional case-study simulations are needed to more fully understand urban storm bifurcation mechanisms in this and other storms for cities in a variety of climates.

Impact of Boundary Layer Physics on Tropical Cyclone Simulations in the Bay of Bengal Using the WRF Model

In this work, the sensitivity of tropical cyclone (TC) simulations over the Bay of Bengal to planetary boundary layer (PBL) physics in the WRF model is investigated. Numerical simulations are performed with WRF-ARW model using NCEP GFS data for five very severe cyclonic storms (Vardha, Hudhud, Phailin, Lehar and Thane). Five conceptually different PBL schemes (YSU, MYJ, QNSE, MYNN and BouLac) are evaluated. Results of 25 sensitivity experiments showed that PBL physics mainly affected the intensity while producing small variations in track prediction. The QNSE, followed by MYJ and BouLac, produced highly intensified storms, and MYNN produced weakly intensified storms. The YSU scheme showed better comparisons with IMD best track estimates. From the analysis of five cyclones, it is found that the YSU produced minimum errors for central pressure (−5.4, −0.8, −2.6, −5.25 hPa), maximum wind (19, 7.6, −0.96, −0.77 m/s) and track (66, 146, 182, 217 km) at 24-, 48-, 72- and 96-h forecast intervals. Analysis of various thermodynamical and dynamical parameters clearly showed that the PBL physics impacts the predictions by variation of (1) surface energy fluxes, (2) convergence, (3) inflow/outflow, (4) tangential winds, (5) vertical motion and (6) strength of the warm core and associated storm structure. A detailed analysis conducted in the case of Hudhud indicated that the PBL schemes influenced the intensity predictions through a WISHE type of feedback by the variation of convergence, radial inflow, vertical motion, and surface fluxes. While the YSU and MYNN schemes produced moderate values of radial inflow, the QNSE, MYJ and BouLac schemes produced stronger inflow. The stronger inflow, spin-up and stronger wind-induced transport of energy fluxes in the QNSE, MYJ and BouLac schemes led to a stronger convection and a higher intensification of TCs in these simulations.

Chirality-dependent asymmetric vortex core structures in a harmonic excitation mode

Chirality of the magnetic vortex plays an essential role in dynamic excitations of the magnetic vortex structure. In a harmonic excitation of the vortex gyrotropic motion, it has been known that the chirality determines its phase to the driving force. From our micromagnetic simulations, we find an additional role of chirality in the harmonic excitation of the vortex gyration. The shear deformation of the three-dimensional structure of the vortex core is determined by the chirality of the vortex. We confirm that this is due to the gyrotropic field. For the same vortex core motion with the same polarization but with opposite chirality, it turns out that the opposite gyrotropic field is formed at the spiral magnetization in the vicinity of the vortex core structure.

Activation Loop Dynamics Are Coupled to Core Motions in Extracellular Signal-Regulated Kinase-2.

The activation loop segment in protein kinases is a common site for regulatory phosphorylation. In extracellular signal-regulated kinase 2 (ERK2), dual phosphorylation and conformational rearrangement of the activation loop accompany enzyme activation. X-ray structures show the active conformation to be stabilized by multiple ion pair interactions between phosphorylated threonine and tyrosine residues in the loop and six arginine residues in the kinase core. Despite the extensive salt bridge network, nuclear magnetic resonance Carr-Purcell-Meiboom-Gill relaxation dispersion experiments show that the phosphorylated activation loop is conformationally mobile on a microsecond to millisecond time scale. The dynamics of the loop match those of previously reported global exchange within the kinase core region and surrounding the catalytic site that have been found to facilitate productive nucleotide binding. Mutations in the core region that alter these global motions also alter the dynamics of the activation loop. Conversely, mutations in the activation loop perturb the global exchange within the kinase core. Together, these findings provide evidence for coupling between motions in the activation loop and those surrounding the catalytic site in the active state of the kinase. Thus, the activation loop segment in dual-phosphorylated ERK2 is not held statically in the active X-ray conformation but instead undergoes exchange between conformers separated by a small energetic barrier, serving as part of a dynamic allosteric network controlling nucleotide binding and catalytic function.

Photon-induced molecular implementation of a quantized magnetic flux photoelectron

A fundamental magnetic flux quantum can be implemented into a free rotating molecule when the interacting molecular electron experiences the maximum possible intrinsic energy uncertainty of a gaussian, transform-limited half-cycle optical photon wavepacket. A magnetic flux resonance condition can be defined at this limit, with photoionization quenching, and the excited molecular electron is drawn into a Rydberg-like spherical surface where a 3D-diffraction pattern is oscillating at the minimum of a bound potential around a primary formed closed electronic loop. The induced rotational motion of the molecular ion core is initiated at the threshold of a robust inertial effect and the dissipated information entropy is the lowest allowed. The integrated quantum possibilities occur in the process as structural properties of a quantized magnetic flux implementation threshold.

Investigating fatigue failure of core motion mechanism for a small oil-free wobble-plate compressor

Abstract The study is driven by a recent experimental test for a small-size high-speed oil-free wobble-plate compressor, in which abrupt local fatigue failure of the wobble plate is encountered. To explore the causes, a fatigue prediction method is proposed, which involves the dynamic force calculation, stress prediction, and fatigue analysis. The dynamic forces is obtained by solving the coupled dynamic, thermodynamic and kinematic models. The dynamic stress with thermal effect is predicted, where the temperature field is calculated by solving the thermal conduction equation with the experimentally measured solid-surface temperature acting as boundary conditions, and the obtained temperature distribution is incorporated into the FEM (finite element method) prediction for thermal-dynamic stress. It is found that intensive friction heating causes the wobble plate significant local temperature rise and it is largely responsible for the structural failure. The Goodman mean stress correction method and wobble plate material S–N (Stress amplitude versus cycle Number) curves are incorporated to predict the fatigue life of wobble plate. The predicted fatigue life is comparable to the experimentally measured, which has verified the developed method. The wobble plates of 7075-T6 aluminum alloy and H62 brass alloy are compared, and the former produces a smaller dynamic stress for its smaller elasticity modulus and larger specific heat but a shorter fatigue life due to its S–N curve smaller stress amplitude.

The influence of leading-edge deflection on the stability of the leading-edge vortices

To examine the effect of leading-edge deflected angle [Formula: see text] on the stability of the leading-edge vortex, the three-dimensional flow field of a flapping wing is simulated by a numerical method. The multi domain mesh generation, dynamic mesh and large eddy simulation technology are employed to capture the finer flowfield structure. The wings perform pure periodic oscillations, and the Reynolds number ( Re) is 4527 based on the chord length c. The folding line formed after the deflection coincides with the pitch axis and is located at the 1/4 c from the leading edge. The results show that the increase of [Formula: see text] maintains the strength of the leading-edge vortex for longer time, and weakens the influence of the motion of the wing on the leading-edge vortex intensity. The flowfield topological analysis shows that the increase of [Formula: see text] also prevents the formation of secondary vortices between the wing surface and the leading-edge vortices, which indirectly contributes to the attachment of the leading-edge vortices to the wing. Moreover, the vortex dynamics equations have been analyzed, and the results indicate that the increase of [Formula: see text] will delay the occurrence of spanwise convection of vorticity and weaken its intensity. In addition, it can also suppress the spanwise flow behind the leading-edge vortices toward the symmetric plane. As a result, increasing [Formula: see text] stabilizes the boundary layer in this region and thereby stabilizes the leading-edge vortices indirectly. Finally, a new parameter is introduced to quantitatively evaluate the proximity of the leading-edge vortex to the surface of the plate. Our method comprehensively considers the influence of the leading-edge vortex scale and the core motion on the approaching of the leading-edge vortex to the wing, and some important conclusions on the developing law of the leading-edge vortex, which are agreement with the experimental measurement, are obtained.

The Research of the Swirling Flow of the Power Fluid during its Passing through the Hydrodynamic Cavitator

The article presents the theoretical research of the use of swirling flows with reverse jets and with developed precessing vortex core in cavitators and other devices. While describing the motion of the vortex core in the free swirling jet of the fluid it is necessary to take into account that according to the experimental data the vortex core can swirl along the length of the jet and moves around the jet axis in the zone between the area of reverse flows and the boundary outer layer. In this case, it is the vortex core which is under the influence of the basic swirling flow. Herewith, it is necessary to take into account that due to commensurate sizes of the vortex core and the jet, the impact on the core will be different owing to non-uniform distribution of speeds in the jet itself. On the basis of the known formulas, the authors have deduced the improved theoretical dependence of the degree of flow swirl on the flow rate, the vortex core vibration frequency and structural parameters under the conditions of the consistency of swirling flow itself. The theoretical dependence shows that the degree of flow swirl is directly proportional to the precessing vortex core vibration frequency and inversely proportional to the square of mass flow rate. Thus, ensuring the consistency of the swirling flow with varying flow-rate requires the corresponding change of the swirl degree or the influence on the frequency of vibrations of the precessing vortex core. On the basis of the deduced theoretical dependences, the authors have developed and implemented in the computer programs the following calculations: the dependence of the coefficient of the flow swirl on the vortex core vibration frequency; the simulation of the precession of the vortex core in the swirling flow; the research of speed fluctuation in the swirling flow; speed fluctuation during the interaction of swirling jets.

A Time‐Varying 3‐D Displacement Model of the ~5.9‐Year Westward Motion and its Applications for the Global Navigation Satellite System Positions and Velocities

AbstractTo advance geodynamics and geophysical research, high precision Global Navigation Satellite System (GNSS) observations of velocity and position are needed. In this study, we construct a 3‐D model of a ~5.9‐year periodic signal for the Earth surface displacements. This model is mainly based on the determined time sequences and the Y22 spatial pattern of this ~5.9‐year periodic signal from the global Global Positioning System (GPS) observations. Based on the constructed model, we calculate synthetic temporal 3‐D displacements on the Earth surface and the velocity changes, and we compare them to observed GPS displacements. Our results reveal that the ~5.9‐year signal contributes to surface displacements and velocity fields. Maximum displacements for the N, E, and U components can reach up to 0.28, 0.55, and 1.69 mm, respectively; maximum velocity effects can up to 1.69 mm/year for the U component (depending on record length). For those studies which need millimeter or even submillimeter accuracy (e.g., tectonic deformations, glacial isostatic adjustment, and deformations caused by core motions), these effects cannot be simply ignored. Our results also confirm that the model we present here can heavily reduce the ~5.9‐year signal in the original GPS time series. We suggest that our model should be used to pretreatment the GPS data at the observation level, which could improve signals used for geophysical or geodynamic interpretations.

Coaxial Electrospinning: Jet Motion, Core–Shell Fiber Morphology, and Structure as a Function of Material Parameters

Two core–shell-structured polystyrene/poly(vinyl pyrrolidone) (PS/PVP) and PVP/PS composite fibers were prepared via coaxial electrospinning in this study. Different concentrations of PVP solutions with a variety of viscosities and conductivities were adopted in the experiment. The influences of both viscosity and conductivity on the Taylor cone, jet motion, morphology, and internal structure of the resultant core–shell fiber were investigated in a comprehensive and systematic manner. As shown in the images of Taylor cone and jet motion, which were captured by a high-speed camera, different PVP concentrations in the core and shell would result in different core and shell thicknesses as well as distinct jet motion patterns including straight jet length, envelop angle, and frequency of whipping process, thus obtaining the core–shell fibers with different diameters. Not only jet motion and Taylor cone but also the polymer solution concentration and the role of PVP in core and shell have a tremendous influence on the morphology and the internal structure of the resultant core–shell fiber. Additionally, the formation mechanisms of PS/PVP and PVP/PS fibers were studied by means of Fourier transform infrared (FTIR). The experimental results provide a basis for further design and optimization of processing conditions, so as to control the nanostructure of core–shell composite fibers.

Nano-oscillator based on radial vortex by overcoming the switching of core

The spin torque nano-oscillators (STNOs) have garnered significant interest as a potential nanosized microwave signal generator. However, the core of magnetic radial vortex may be annihilated at the edge with the large spin polarized current density, which leads to unstable STNOs. In this work, we propose new STNOs based on a magnetic radial vortex by overcoming the annihilation of core at the edge, which was realized by adding high magnetic crystal anisotropy materials on the boundary of the nanodisk. It is found that the oscillation frequency reaches up to 2.8 GHz through a circular motion of core of magnetic radial vortex, and the radial vortex-based STNOs have advantages of small size, lower driving current. Our result has important significance to design new STNOs and provide a possible candidate for designing of spintronic devices based on magnetic radial vortex.