Rotation Gradient Research Articles

On the dynamics and resonance frequency of an electro-elastic rotary non-classical piezoelectric microdisk

In this research, frequency and resonance area information of a size-dependent electro-elastic rotary non-classical piezoelectric microdisk via modified couple stress theory (MCST) is presented. The computational formulation of the electrically microdisk, non-classical governing equations of electrically annular microdisk are derived by adding the symmetric rotation gradient and higher-order stress tensors to the strain energy. The current non-classical approach is capable for capturing the size-dependency in the electrically annular microdisk by using single material length scale factor. Finally, the non-classical governing equations are solved using generalized differential quadrature method (GDQM). Afterward, a parametric study is carried out to investigate the effects of applied ampere, length scale factor, applied voltage, and radius ratio on the resonance area and frequency responses of the electrically microdisk by considering MCST. The meaningful of resonance area in the current research is that, all designers should have attention to the lower values of natural frequency for obtaining the accurate results. Afterward, a parametric study is done to present the impacts of the radius ratio, length scale parameter, circumferential and radial mode number, geometry of piezoelectric material, applied voltage, and boundary conditions on the frequency responses of the piezoelectric microdisk by considering MCST. The results show that, when the foundation is considered, the effect of the radius ratio on the critical voltage of a piezoelectric microdisk reduces.

Flexure mechanics of nonlocal modified gradient nano-beams

Abstract Two frameworks of the nonlocal integral elasticity and the modified strain gradient theory are consistently merged to conceive the nonlocal modified gradient theory. The established augmented continuum theory is applied to a Timoshenko–Ehrenfest beam model. Nanoscopic effects of the dilatation, the deviatoric stretch, and the symmetric rotation gradients together with the nonlocality are suitably accommodated. The integral convolutions of the constitutive law are restored with the equivalent differential model subject to the nonclassical boundary conditions. Both the elastostatic and elastodynamic flexural responses of the nano-sized beam are rigorously investigated and the well posedness of the nonlocal modified gradient problems on bounded structural domains is confirmed. The analytical solution of the phase velocity of flexural waves and the deflection and the rotation fields of the nano-beam is detected and numerically illustrated. The transverse wave propagation in carbon nanotubes is furthermore reconstructed and validated by the molecular dynamics simulation data. Being accomplished in revealing both the stiffening and softening structural responses at nano-scale, the proposed nonlocal modified gradient theory can be beneficially implemented for nanoscopic examination of the static and dynamic behaviors of stubby nano-sized elastic beams.

A kinematic analysis of ionized extraplanar gas in the spiral galaxies NGC 3982 and NGC 4152

ABSTRACT We present a kinematic study of ionized extraplanar gas in two low-inclination late-type galaxies (NGC 3982 and NGC 4152) using integral field spectroscopy data from the DiskMass H α sample. We first isolate the extraplanar gas emission by masking the H α flux from the regularly rotating disc. The extraplanar gas emission is then modelled in the 3D position–velocity domain using a parametric model described by three structural and four kinematic parameters. Best-fitting values for the model are determined via a Bayesian MCMC approach. The reliability and accuracy of our modelling method are carefully determined via tests using mock data. We detect ionized extraplanar gas in both galaxies, with scale heights $0.83^{+0.27}_{-0.40}\, \mathrm{kpc}$ (NGC 3982) and $1.87^{+0.43}_{-0.56}\, \mathrm{kpc}$ (NGC 4152) and flux fraction between the extraplanar gas and the regularly rotating gas within the disc of 27 and 15 per cent, respectively, consistent with previous determinations in other systems. We find lagging rotation of the ionized extraplanar gas in both galaxies, with vertical rotational gradients $-22.24^{+6.60}_{-13.13} \, \mathrm{km\, s^{-1}\, kpc^{-1}}$ and $-11.18^{+3.49}_{-4.06}\, \mathrm{km\, s^{-1}\, kpc^{-1}}$, respectively, and weak evidence for vertical and radial inflow in both galaxies. The above results are similar to the kinematics of the neutral extraplanar gas found in several galaxies, though this is the first time that 3D kinematic modelling of ionized extraplanar gas has been carried out. Our results are broadly consistent with a galactic fountain origin combined with gas accretion. However, a dynamical model is required to better understand the formation of ionized extraplanar gas.

Study of double-diffusive convection in a rotating couple-stress ferromagnetic fluid in the presence of varying gravitational field and horizontal magnetic field saturating in a porous medium

The results of double-diffusive convection on the liquid coatings of ferromagnetic liquids is studied by researchers by various theoretical and hydrodynamics concepts of hydrodynamics. However this study is done in presence of varying gravitational field. The study of such couple-stress ferromagnetic fluids in presence of fluctuating gravitational field is still not explored. As we know that gravitational field varies on different points on the earth; for this reason the study of couple-stress ferromagnetic liquids in presence of variable gravity fields is highly required. In this paper we studied the impact of medium permeability, stable solute gradient, couple-stress, rotation, magnetic field, and magnetization of a couple-stress ferromagnetic fluid in presence of variable gravitational field. For this study a coating of couple-stress ferromagnetic fluid saturating in a porous medium when fluid layer is heated and soluted. We examined the results of the magnetic field on couple-stress ferromagnetic fluids, its thermosolutal instability during rotation. A linearized concept and normal mode technique are used to acquire the dispersion relation. For the case of stationary convection, medium permeability, couple-stress, and magnetic field have both stabilizing and destabilizing results under certain conditions. A stable solute gradient has a stabilizing result on the system. Also, the rotation has a stabilizing result for λ>0 and destabilizing result for λ 0 and λ<0. The critical Rayleigh number for the onset of instability is decided numerically and graphically also. The principle of exchange of stabilities is observed to keep genuine in the absence of rotation, magnetic field, and stable solute gradient under certain conditions.

Особенности сложных колебаний гибких микрополярных сетчатых панелей

In this paper, a mathematical model of complex oscillations of a flexible micropolar cylindrical mesh structure is constructed. Equations are written in displacements. Geometric nonlinearity is taken into account according to the Theodore von Karman model. A non-classical continual model of a panel based on a Cosserat medium with constrained particle rotation (pseudocontinuum) is considered. It is assumed that the fields of displacements and rotations are not independent. An additional independent material parameter of length associated with a symmetric tensor by a rotation gradient is introduced into consideration. The equations of motion of a panel element, the boundary and initial conditions are obtained from the Ostrogradsky – Hamilton variational principle based on the Kirchhoff – Love’s kinematic hypotheses. It is assumed that the cylindrical panel consists of n families of edges of the same material, each of which is characterized by an inclination angle relative to the positive direction of the axis directed along the length of the panel and the distance between adjacent edges. The material is isotropic, elastic and obeys Hooke’s law. To homogenize the rib system over the panel surface, the G. I. Pshenichnov continuous model is used. The dissipative mechanical system is considered. The differential problem in partial derivatives is reduced to an ordinary differential problem with respect to spatial coordinates by the Bubnov – Galerkin method in higher approximations. The Cauchy problem is solved by the Runge – Kutta method of the 4th order of accuracy. Using the establishment method, a study of grid geometry influence and taking account of micropolar theory on the behavior of a grid plate consisting of two families of mutually perpendicular edges was conducted.

A numerical study on the thermal capillary-buoyancy convection of a binary mixture driven by rotation and surface-tension gradient in a shallow annular pool

The thermal capillary-buoyancy convection with the Soret effect in a rotating annular pool was investigated by a series of three-dimensional numerical simulations. The annular pool is heated at the outer cylinder, cooled at the inner cylinder and filled with the n-decane/n-hexane binary mixture with an initial mass fraction of 50%. The present investigation focuses on the effects of the Taylor number and aspect ratio on the flow stability and flow patterns of the thermal capillary-buoyancy convection. The results show that the critical thermal capillary Reynolds number increases with the increase of the Taylor number, while decreases with the increase of the aspect ratio. Once the thermal capillary Reynolds number exceeds the critical value, the basic flow bifurcates to the flow pattern composed by the slender spiral waves and hydrothermal waves at a relatively small aspect ratio. In addition, the slender spiral waves are gradually suppressed with the increase of the aspect ratio. The basic flow transits to the hydrothermal waves at a relatively large aspect ratio. With the increasing Taylor number, the hydrothermal waves usually develop to the coexistence of the hydrothermal waves and internal oscillatory flow, which is created by the rotating vortex contained in the basic flow. Moreover, the Soret effect creates the concentration gradient opposite to temperature gradient, which enhances the thermal capillary-buoyancy convection in the binary mixture.

Amplitude motion and frequency simulation of a composite viscoelastic microsystem within modified couple stress elasticity

In this research, amplitude motion and frequency simulation of a thick annular microsystem with graphene nanoplatelets (GPL) reinforcement in the framework of the modified couple stress theory (MCST) is undertaken. For obtaining the effective Poisson ratio, and mass density, the role of mixture is employed. As well as this, the Halpin–Tsai micromechanics model is presented for modeling the effective Young module of the current composite microstructure. The mathematical formulations of the current microstructure, size-dependent governing equations and boundary conditions are obtained by considering the MCST’s terms such as higher-order stress tensors, and symmetric rotation gradient into strain energy of the size-dependent GPL reinforced composite (GPLRC) microstructure. Finally, the generalized differential quadrature method (GDQM) is employed to obtain eigenvalue and eigenvectors of the GPLRC microsystem. Afterward, a parametric study is conducted to present the impacts of the radios ratio, length scale parameter, viscoelastic parameter, radial and circumferential mode number, and GPL’s geometry, on the amplitude motion, and frequency characteristics of the GPLRC annular microsystem. The results demonstrate that in the higher value of the radius ratio and time-dependent parameter, we can ignore the influence of length scale parameter on the amplitude and frequency of the annular microsystem. The useful suggestion of this study is that as the thickness of the GPLs increases, the impact of length scale parameter on the frequency of the annular microsystem decreases.

Comparison of EBSD, DIC, AFM, and ECCI for active slip system identification in deformed Ti-7Al

The use of SEM-DIC, AFM, ECCI, and HR-EBSD to characterize slip-system activity was assessed on the same material volume of Ti7Al. This study presents a robust comparison of the various methods for the first time, including an assessment of their advantages and disadvantages, and how they can be used effectively in a complementary fashion. The analysis of the different approaches was carried out in a blind, round-robin manner at three different universities. A Ti7Al specimen was deformed in uniaxial tension to approximately 3% axial strain, and the active slip systems were independently identified using (i) trace analysis; (ii) in-SEM digital image correlation, (iii) observations of residual dislocations from ECCI, and (iv) long-range rotation gradients through HR-EBSD, with consistent trace identification in all cases. Displacement data from AFM was used to augment SEM-DIC displacement data by providing complementary out-of-plane displacement information. Furthermore, short-range dislocation gradients (measured by DIC) provided insight into the residual geometrically necessary dislocation (GND) content, and was consistent with the GND content extracted from EBSD data and ECCI images, confirming the presence of residual GNDs on the dominant slip systems resulting in visible slip bands. These approaches can be used in tandem to provide multi-modal information on slip band identification, strain and orientation gradients, out-of-plane displacements, and the presence of GNDs and SSDs, all of which can be used to inform and validate the development of dislocation-based crystal plasticity and strain gradient models.

Numerical modelling for elastic wave equations including rotational deformation and strain gradient

In this work, through introducing the first and second derivatives of strain gradient into the strain energy density function that depends only on the classical strain in conventional continuum mechanics theory to describe the microscopic interactions, the elastic wave equations including rotational deformation and strain gradient based on the Aifantis’s strain gradient theory is derived. The elastic wave equations including rotational deformation and strain gradient with consideration of the scale effects caused by the microscopic interactions will make seismograms appear obvious changes, which are reflected in amplitude attenuation and dispersion, especially P-wave and S-wave propagate in a dispersive manner based on this theory. The results of numerical modelling and theoretical analysis verify this conclusion. The closer the wavelength is to the characteristic scale of the media (lattice size and interparticle distance), the macroscopic response which results from the microscopic interactions becomes more prominent. To further study the effects of microstructure interactions, we compare the results of numerical modelling with the real data when high-speed train passed the piers in Dingxing County in both time and frequency domains, some conclusions are drawn from the comparison.

Effect of Magnetic Field on Thermosolutal Instability of Rotating Ferromagnetic Fluid Under Varying Gravity Field

This paper deals with the theoretical investigation of the effect of a magnetic field, rotation and magnetization on a ferromagnetic fluid under varying gravity field. To find the exact solution for a ferromagnetic fluid layer contained between two free boundaries, we have used a linear stability analysis and normal mode analysis method. For the case of stationary convection, a stable solute gradient has a stabilizing effect, while rotation has a stabilizing effect if λ&gt;&lt;i&gt;0&lt;/i&gt; and destabilizing effect if λ&lt;&lt;i&gt;0&lt;/i&gt;. Further, the magnetic field is discovered to have both a stabilizing and destabilizing effect for both λ&gt;&lt;i&gt;0&lt;/i&gt; and λ&lt;&lt;i&gt;0&lt;/i&gt;. It is likewise discovered that magnetization has a stabilizing effect for both λ&gt;&lt;i&gt;0&lt;/i&gt; and λ&lt;&lt;i&gt;0&lt;/i&gt; in the absence of the stable solute gradient. Graphs have been plotted by giving numerical values of various parameters. In the absence of rotation, magnetic field and stable solute gradient, the principle of exchange of stabilities is found to hold true for certain conditions.

Study of double-diffusive convection in a rotating couple-stress ferromagnetic fluid in the presence of varying gravitational field and horizontal magnetic field saturating in a porous medium

The results of double-diffusive convection on the liquid coatings of ferromagnetic liquids is studied by researchers by various theoretical and hydrodynamics concepts of hydrodynamics. However this study is done in presence of varying gravitational field. The study of such couple-stress ferromagnetic fluids in presence of fluctuating gravitational field is still not explored. As we know that gravitational field varies on different points on the earth; for this reason the study of couple-stress ferromagnetic liquids in presence of variable gravity fields is highly required. In this paper we studied the impact of medium permeability, stable solute gradient, couple-stress, rotation, magnetic field, and magnetization of a couple-stress ferromagnetic fluid in presence of variable gravitational field. For this study a coating of couple-stress ferromagnetic fluid saturating in a porous medium when fluid layer is heated and soluted. We examined the results of the magnetic field on couple-stress ferromagnetic fluids, its thermosolutal instability during rotation. A linearized concept and normal mode technique are used to acquire the dispersion relation. For the case of stationary convection, medium permeability, couple-stress, and magnetic field have both stabilizing and destabilizing results under certain conditions. A stable solute gradient has a stabilizing result on the system. Also, the rotation has a stabilizing result for λ&gt;0 and destabilizing result for λ&lt;0 the system. It is likewise observed that in the absence of a stable solute gradient, magnetization has a stabilizing result on the system for both λ&gt;0 and λ&lt;0. The critical Rayleigh number for the onset of instability is decided numerically and graphically also. The principle of exchange of stabilities is observed to keep genuine in the absence of rotation, magnetic field, and stable solute gradient under certain conditions.

On the dynamics of a laminated annular piezoelectric microsystem on a viscoelastic substrate within modified couple stress elasticity

This article deals with the vibrational characteristics of a laminated composite annular microplate using a non-classical continuum theory called modified couple stress theory (MCST). Also, the structure is patched with the piezoelectric layer and covered with a viscoelastic foundation that simulated via the Kelvin-Voight model. The non-classical governing equations and boundary conditions of the size-dependent annular microplate are derived by adding the symmetric rotation gradient and higher-order stress tensors to the strain energy. The current non-classical model is capable of capturing the size-dependency in the annular microplate by using only one material length scale parameter. Moreover, the mathematical formulation of annular microplate based on the classical model can be recovered from the present model by neglecting the material length scale parameter. Finally, the non-classical governing equations are solved using the generalized differential quadrature method (GDQM) for various boundary conditions. Afterward, a parametric study is carried out to investigate the effects of the length scale parameter, piezoelectric layer, radius ratio, circumferential and radial mode number, geometry of laminated layer, and boundary conditions on the frequency responses of the annular microplate by considering MCST. The results show that in the grater elastic properties ratio () factor, increasing the damping parameter () cannot make any changes in the frequency of the disk.

Thermodynamically consistent thermoelastic plate and shell formulations for small deformation and small strain using non-classical continuum mechanics incorporating internal rotations

The work presented in a recent paper by the authors [35] for a thermodynamically consistent and kinematic assumption free plate and shell formulation for small deformation and small strain based on the conservation and balance laws of classical continuum mechanics (CCM) is extended here for non-classical continuum mechanics (NCCM). This formulation incorporates additional physics due to internal rotations that arise due to the deformation gradient tensor. This physics is neglected in CCM, hence is absent in the plate and shell formulation of reference [35]. Consideration of this new physics requires modifications of the current balance laws as well as consideration of a new balance law “balance of moment of moments” (BMM) [2, 3]. Cauchy stress tensor becomes non-symmetric. Cauchy moment tensor is conjugate to the symmetric part of the rotation gradient tensor which exists now due to new physics. Balance of angular momenta yields additional three differential equations as part of the mathematical model. The new balance law (BMM) establishes symmetry of the Cauchy moment tensor. The new physics considered here exists in all deforming solid continua as it is due to the deformation gradient tensor, but is ignored in CCM. The consequence of this new physics is additional stiffness, hence additional strain energy storage and change in the time history of displacements and stress field compared to formulations based on CCM. The basic mathematical model for the plate and shell deformation consists of conservation and balance laws in $$\mathbb {R}^3$$ based on NCCM incorporating internal rotations. The associated finite element formulations for obtaining the solution of the mathematical model consists of : (i) geometry of the plate or shell described by the flat or curved middle surface (as done conventionally) and nodal vectors locating the top and bottom faces of the plate/shell (ii) the displacement field approximation that is p-version hierarchical in the plane as well as in the transverse direction (iii) integral form is constructed using Galerkin Method with Weak Form (GM/WF) and the corresponding element equations. The formulation presented here remains valid and accurate for thin as well as thick plate/shell and naturally reduces to the formulation of reference [35] based on classical continuum mechanics. Model problem studies and comparisons with the studies based on CCM formulation [35] will be presented in a follow up paper.

A comprehensive parametric study for hygro-thermal-vibration characteristics of the rotary composite microdisk system

Mechanical systems especially annular microdisks have many applications in different fields such as engineering, agriculture, and medicine. Addressed in this article, as the first attempt, is frequency and displacement analysis of a size-dependent thick rotary microsystem reinforced with graphene nanoplatelets (GPL) under hygro-thermal environment via modified couple stress theory (MCST) as the higher-order elasticity theory. The Coriolis and centrifugal effects due to the rotation are considered. The computational formulation of the microsystem, nonclassical governing equations, and corresponding boundary conditions of size-dependent thick graphene nanoplatelets reinforced composite (GPLRC) annular microsystem are derived by adding the symmetric rotation gradient and higher-order stress tensors to the strain energy. The nonclassical governing equations are solved using generalized differential quadrature method (GDQM) for various boundary conditions. The results show that the impact of radius ratio on the frequency of the system is considerable than the effect of length scale factor and the mentioned issue is more clear at higher value of rotating speed. As a good suggestion for some relevant industries, for the radius ratio (r0/ri ) less than 5.5 we can use the displacement filed of the microdisk and for more than 5.5 should use displacement filed of microring for modeling the microstructure. The presented outputs can be used in the structural health monitoring.

Vibrational characteristics of a higher-order laminated composite viscoelastic annular microplate via modified couple stress theory

This article deals with the vibrational characteristics of a laminated composite annular microplate using a non-classical continuum theory called modified couple stress theory (MCST). The structure is covered with a viscoelastic foundation that is simulated via the Kelvin-Voight model. The non-classical governing equations and boundary conditions of the size-dependent annular microplate are derived by adding the symmetric rotation gradient and higher-order stress tensors to the strain energy. The current non-classical model is capable of capturing the size-dependency in the annular microplate by using only one material length scale parameter; moreover, the mathematical formulation of annular microplate via the classical model can be recovered from the present model by neglecting the material length scale parameter. Finally, the non-classical governing equations are solved using the generalized differential quadrature method (GDQM) for various boundary conditions. Afterward, a parametric study is carried out to investigate the effects of the length scale parameter, radius ratio, circumferential and radial mode number, geometry of the laminated layer, and boundary conditions on the frequency responses of the annular microplate by considering MCST. The results show that in the grater elastic properties ratio (E1/E2) factor, increasing the viscoelastic parameter cannot make any changes in the frequency of the disk.

Nonlinear axisymmetric bending analysis of strain gradient thin circular plate

A size-dependent nonlinear bending theory for axisymmetric thin circular plate is proposed by using the principle of minimum potential energy. The formulation is based on the strain gradient theory of Zhou et al. and the von Kármán geometric nonlinearity. The governing equations and boundary conditions are obtained and further reduced to that based on the couple stress theory, modified couple stress theory and even classical theory by neglecting some or all strain gradient components, respectively. Besides, the corresponding linear theory is also obtained by excluding the nonlinear terms from the present theory. The bending problems for both simply supported and fully clamped circular plate subjected to uniformly distributed load are solved by using the differential quadrature method (DQM) and iteration method. The comparison between theoretical and numerical results of linear bending deflection shows good agreement. The numerical results of nonlinear bending deflection based on these different theories reveal the size-dependency of circular plate bending rigidity. The effect of strain gradients enhances the bending rigidity of circular plate, in which rotation gradient plays a dominant role in controlling the stiffening effect of bending rigidity. When the thickness of circular plate is close to the higher-order material constant, the strain gradient effects are comparable or even dominant in comparison with the traditional bending rigidity. When the thickness of circular plate is much greater than the higher-order material constant, all strain gradient effects can be ignorable and the differences of deflections among these theories are negligible.

Ordered Rate Constitutive Theories for Non-Classical Thermofluids Based on Convected Time Derivatives of the Strain and Higher Order Rotation Rate Tensors Using Entropy Inequality.

This paper considers non-classical continuum theory for thermoviscous fluids without memory incorporating internal rotation rates resulting from the antisymmetric part of the velocity gradient tensor to derive ordered rate constitutive theories for the Cauchy stress and the Cauchy moment tensor based on entropy inequality and representation theorem. Using the generalization of the conjugate pairs in the entropy inequality, the ordered rate constitutive theory for Cauchy stress tensor considers convected time derivatives of the Green’s strain tensor (or Almansi strain tensor) of up to orders as its argument tensors and the ordered rate constitutive theory for the Cauchy moment tensor considers convected time derivatives of the symmetric part of the rotation gradient tensor up to orders . While the convected time derivatives of the strain tensors are well known the convected time derivatives of higher orders of the symmetric part of the rotation gradient tensor need to be derived and are presented in this paper. Complete and general constitutive theories based on integrity using conjugate pairs in the entropy inequality and the generalization of the argument tensors of the constitutive variables and the representation theorem are derived and the material coefficients are established. It is shown that for the type of non-classical thermofluids considered in this paper the dissipation mechanism is an ordered rate mechanism due to convected time derivatives of the strain tensor as well as the convected time derivatives of the symmetric part of the rotation gradient tensor. The derivations of the constitutive theories presented in the paper is basis independent but can be made basis specific depending upon the choice of the specific basis for the constitutive variables and the argument tensors. Simplified linear theories are also presented as subset of the general constitutive theories and are compared with published works.

Compatibility conditions from a Gram–Schmidt decomposition of deformation gradient in two dimensions

Planar deformations are analyzed in the context of a Gram-Schmidt decomposition of deformation gradient into a rotation and upper triangular stretch, where the latter consists of up to three possibly nonzero terms. Necessary—and sufficient under suitable restrictions—conditions for integrability of deformation gradient and stretch (geometrically, vanishing torsion and curvature of a certain affine connection) reduce to a system of three partial differential equations (PDEs). This system appears more convenient than corresponding compatibility conditions from polar decompositions, especially for motions involving simple shear. Admissible families of triangular stretch corresponding to simple shear, pure shear, dilation, and uniaxial strain are analyzed. Also considered are simultaneous simple shear and axial stretch, for which a non-trivial solution with non-vanishing rotation gradient is constructed.

Characteristics and vertical structure of oceanic mesoscale eddies in the Bay of Bengal

The signatures of mesoscale eddies induced surface and subsurface changes have not been comprehensively quantified for the Bay of Bengal (BoB) region. This study quantifies the statistical properties and three-dimensional (3D) eddy structures in the BoB. To accomplish this, the satellite altimetry data combined with automated eddy detection and tracking algorithm is used. Horizontal distribution of surface characteristics of eddies is analyzed by using 24 years (1993–2016) of AVHRR infrared satellite sea surface temperature (SST) and 7 years (2010–2016) of sea surface salinity (SSS) of SMOS satellite data. Surface eddy centric composite analysis reveals the existence of warm (cold) and diverse SSS anomalies for anticyclonic (cyclonic) eddies. During winter, it is important to note that the eddy induced SST and SSS anomalies show the dipole patterns show opposite phases for the cyclonic and anticyclonic eddies. Observed diploe structures are consistent with the eddy rotation and background large-scale meridional gradient of temperature and salinity fields. The 3D structure of eddies is investigated by using the ARMOR3D and Argo float profiles. The horizontal distribution of temperature and salinity anomalies from ARMOR3D signify the monopole structure of eddies in the subsurface layers. Further, the analysis of composite averages of 241 (200) Argo temperature profiles indicates the core of anticyclonic (cyclonic) eddies centered at about ∼140 m (∼100 m). However, salinity profiles depict the existence of core at ∼65 m (∼50 m). This study have practical relevance to a variety of stakeholders and finds profound importance in the validation of eddy-resolving ocean models for the BoB region.

Bayesian optimization for a high- and uniform-crystal growth rate in the top-seeded solution growth process of silicon carbide under applied magnetic field and seed rotation

Abstract The Top-Seeded Solution Growth (TSSG) method is a promising technique for the production of high-quality SiC single crystal. To achieve a high- and uniform-growth rate in the TSSG process of SiC, the fluid flows developing in the growth solution (melt), due to the applied and induced electromagnetic fields, buoyancy, seed rotation, and free surface tension gradient, need to be controlled. Previous numerical analysis has shown that such complex flows in the TSSG melt can be controlled by the applications of a static magnetic field and seed rotation. However, the requirement of significant computational resources prevented us from carrying out the needed optimization for the process parameters involved. In order to resolve the computational demand issue, in this study, we utilized the Bayesian optimization algorithm for an efficient optimization of the associated control parameters of the TSSG process of SiC. It was shown that the Bayesian algorithm determines the optimal state at about roughly 1/4 of the computational cost of a conventional optimization, and accurately predicts the growth-rate evaluation function around the optimal state. The optimal state obtained by the present optimization process predicts a high- and uniform-growth rate in the TSSG system of SiC considered in this work.