Rotational Dependence Research Articles

Measurements of CO2-broadening and -shift parameters of the ethylene spectral lines near 3.3 µm

The absorption spectra of the mixtures of ethylene and carbon dioxide at seven different partial pressures of both gasses have been recorded using the Bruker IFS 125 HR FTIR spectrometer at room temperature in the 3.3 µm region. The multispectrum fitting procedure has been applied to these spectra to recover the spectral line parameters. The broadening and shift coefficients induced in ethylene by carbon dioxide pressure have been obtained for almost 2000 lines in the region of the ν11 absorption band between 2928 and 3056 cm−1. The rotational dependence of the broadening parameters was analyzed. The similarity of the CO2-broadening coefficient to the self-broadening coefficient was revealed and discussed.

Convection and Dynamo in Newly Born Neutron Stars

Abstract To study properties of magnetohydrodynamic (MHD) convection and resultant dynamo activities in proto-neutron stars (PNSs), we construct a “PNS in a box” simulation model and solve the compressible MHD equation coupled with a nuclear equation of state (EOS) and simplified leptonic transport. As a demonstration, we apply it to two types of PNS model with different internal structures: a fully convective model and a spherical-shell convection model. By varying the spin rate of the models, the rotational dependence of convection and the dynamo that operate inside the PNS is investigated. We find that, as a consequence of turbulent transport by rotating stratified convection, large-scale structures of flow and thermodynamic fields are developed in all models. Depending on the spin rate and the depth of the convection zone, various profiles of the large-scale structures are obtained, which can be physically understood as steady-state solutions to the “mean-field” equation of motion. Additionally to those hydrodynamic structures, a large-scale magnetic component of  ( 10 15 ) G is also spontaneously organized in disordered tangled magnetic fields in all models. The higher the spin rate, the stronger the large-scale magnetic component grows. Intriguingly, as an overall trend, the fully convective models have a stronger large-scale magnetic component than that in the spherical-shell convection models. The deeper the convection zone extends, the larger the size of the convective eddies becomes. As a result, rotationally constrained convection seems to be more easily achieved in the fully convective model, resulting in a higher efficiency of the large-scale dynamo there. To gain a better understanding of the origin of the diversity of a neutron star’s magnetic field, we need to study the PNS dynamo in a wider parameter range.

Generation of mean flows in rotating anisotropic turbulence: The case of solar near-surface shear layer

Context.Results from helioseismology indicate that the radial gradient of the rotation rate in the near-surface shear layer (NSSL) of the Sun is independent of latitude and radius. Theoretical models using the mean-field approach have been successful in explaining this property of the NSSL, while global direct or large-eddy magnetoconvection models have so far been unable to reproduce this.Aims.We investigate the reason for this discrepancy by measuring the mean flows, Reynolds stress, and turbulent transport coefficients under conditions mimicking those in the solar NSSL.Methods.Simulations with as few ingredients as possible to generate mean flows were studied. These ingredients are inhomogeneity due to boundaries, anisotropic turbulence, and rotation. The parameters of the simulations were chosen such that they matched the weakly rotationally constrained NSSL. The simulations probe locally Cartesian patches of the star at a given depth and latitude. The depth of the patch was varied by changing the rotation rate such that the resulting Coriolis numbers covered the same range as in the NSSL. We measured the turbulent transport coefficient relevant for the nondiffusive (Λ-effect) and diffusive (turbulent viscosity) parts of the Reynolds stress and compared them with predictions of current mean-field theories.Results.A negative radial gradient of the mean flow is generated only at the equator where meridional flows are absent. At other latitudes, the meridional flow is comparable to the mean flow corresponding to differential rotation. We also find that the meridional components of the Reynolds stress cannot be ignored. Additionally, we find that the turbulent viscosity is quenched by rotation by about 50% from the surface to the bottom of the NSSL.Conclusions.Our local simulations do not validate the explanation for the generation of the NSSL from mean-field theory where meridional flows and stresses are neglected. However, the rotational dependence of the turbulent viscosity in our simulations agrees well with theoretical predictions. Moreover, our results agree qualitatively with global convection simulations in that an NSSL can only be obtained near the equator.

Microstructural characteristics governing the lattice rotation in Al-Mg alloy using in-situ EBSD

The lattice rotation behavior of Al-4%Mg alloy subjected to tensile deformation is studied through in-situ electron backscatter diffraction (EBSD). The emphasis is laid on the effect of the orientation of neighbors, second phase particles, and the local deformation state on the lattice rotation characteristics. The results obtained show that the lattice rotation response of grains with similar initial orientation is largely different characterized by differences in the magnitude of rotation, rotation rate, rotation path, and activation of slip systems. The rotation path of grains towards reaching the stable end orientations is found to be governed by the microstructural relationships such as the misorientation and fraction of grain boundary segment shared with the immediate neighbors. Also, the local reorientations associated with the second phase particles, slip plane kinking, and triple junctions due to disruption of the slip activity and deformation heterogeneity of the neighbors significantly affect the average rotation of the grains and the rate of rotation. The rotation path of such local lattice rotations in grains is not strictly bound by the microstructural relationship with the neighbors. Further, when the shape change of grains introduced by local deformation mechanisms is significant, lattice rotations accompanying slip deviate from the rotation tendency based on the microstructural relationship with the neighbors. The observed dependence of lattice rotation of grains with simple slip activity on the misorientation and fraction of grain boundary segment shared with the immediate neighbors is also validated through full-field crystal plasticity simulation using DAMASK software. Simulation results also reveal the state of stress in grains that favor the initiation of local deformation mechanisms and the associated lattice reorientations observed experimentally. Altogether, this study renders gainful insights on the dependence of the lattice rotation of polycrystalline Al-4%Mg alloy on the microstructural characteristics which are of significant considerations to the development of constitutive description of crystal plasticity models in improving the accuracy of predicting the bulk engineering properties and texture development.

Lithium depletion and angular momentum transport in F-type and G-type stars in Galactic open clusters

Context. Open clusters provide unambiguous clues to understand the evolution of 7Li at the surface of low-mass stars and its possible correlation with stellar rotation, which is a challenge for both stellar hydrodynamics and Galactic chemical evolution. Aims. We aim to quantify the efficiency of the transport processes for both angular momentum and chemicals that are required to explain simultaneously the observed behaviour of surface 7Li (and 9Be) and rotation as well as the internal rotation profiles inferred from helio- and asteroseismology in F- and G-type main sequence stars. Methods. We apply the model for the transport of angular momentum and chemicals that we tailored in a previous work for solar-type stars to an extended range of initial masses and metallicities corresponding to F- an G-type stars in a sample of 20 Galactic open clusters. We evaluate its ability to explain the 7Li, 9Be, and rotation periods observations. This model includes atomic diffusion, rotation-induced processes (for which we tested different prescriptions for shear turbulence), penetrative convection with a rotational dependence, parametric viscosity and turbulence, and magnetic braking. Results. Over the entire range of masses, metallicities, and ages explored, we reproduce the evolution of the surface rotation rates and predict, for the first time, the observed anti-correlation between the surface rotation rate and 7Li depletion as a consequence of the penetrative convection prescription. The 7Li behaviour and its evolution with time is well reproduced for G-type stars. However, the ability of the model to reproduce the so-called 7Li dip centred around ∼6600 K strongly depends on the adopted prescriptions for shear turbulence. It also requires a stellar mass dependence for the parametric viscosity adopted for the transport of angular momentum, similar to the behaviour predicted for the generation and luminosity of internal gravity waves generated by stellar convective envelopes. Finally, the model predicts internal rotation profiles in good agreement with asteroseismic constraints in main sequence stars. Conclusions. We provide an efficient way to model G-type stars of different ages and metallicities successfully. However, the 7Li and 9Be dip constraints urgently call for further hydrodynamical studies to better model turbulence in stars, and for the exploration of physical processes such as tachocline mixing for the transport of chemicals and internal gravity waves for the transport of angular momentum. Finally, additional data for the internal rotation and for 9Be in main sequence low-mass stars are definitively needed.

Review of the strain-based formulation for analysis of plane structures Part I: Formulation of basics and the existing elements

Since the introduction of the finite element approach, as a numerical solution scheme for structural and solid mechanics applications, various for mulation methodologies have been proposed. These ways offer different advantages and shortcomings. Among these techniques, the standard displacement-based approach has attracted more interest due to its straightforward scheme and generality. Investigators have proved that the other strategies, such as the force-based, hybrid, assumed stress, and as sumed strain provides special advantages in comparison with the classicfinite elements. For instance, the mentioned techniques are able to solve difficulties, like shear locking, shear parasitic error, mesh sensitivity, poor convergence, and rotational dependency. The main goal of this two-part study is to present a brief yet clear portrait of the basics and advantages of the direct strain-based method for development of high-performance plane finite elements. In this article, which is the first part of this study, assump tions and the basics of this method are introduced. Then, a detailed review of all the existing strain-based membrane elements is presented. Although the strain formulation is applicable for different types of structures, most of the existing elements pertain to the plane structures. The second part of this study deals with the application and performance of the reviewed elements in the analysis of plane stress/strain problems.

Line intensities and self-broadening coefficients of CH3I in the region of ν5 and ν3+ν6 bands

Systematic measurements of self-broadening coefficients for 992 transitions in the ν5 and ν3+ν6 perpendicular bands of CH3I up to the quantum numbers 3 ≤ J ≤ 52 and 0 ≤ K ≤ 12 have been performed for the first time using a mono-spectrum fitting technique utilizing a Voigt profile. Our previous line intensity measurements [Boughdiri, et al., JQSRT 221 (2018) 147-154] are also extended using new spectra recorded at room temperature at five pressures from 1.15 to 9.98 mbar using the Bruker IFS125HR Fourier Transform spectrometer at the AILES beamline of the SOLEIL Synchrotron facility. The measured absolute intensities were used to derive the transition dipole moment squared for each line, the band intensities as well as the Herman–Wallis coefficients. The rotational dependences of the self-broadening coefficients have been clearly observed and modeled. The data were compared with previous works. The results are given as supplementary data table for a possible use in atmospheric and industrial applications.

Anisotropic electron-nuclear interactions in a rotating quantum spin bath

The interaction between a central qubit spin and a surrounding bath of spins is critical to spin-based solid-state quantum sensing and quantum information processing. Spin-bath interactions are typically strongly anisotropic, and rapid physical rotation has long been used in solid-state nuclear magnetic resonance to simulate motional averaging of anisotropic interactions, such as dipolar coupling between nuclear spins. Here, we show that the interaction between electron spins of nitrogen-vacancy centers and a bath of $^{13}\mathrm{C}$ nuclear spins in a diamond rotated at up to 300 000 rpm introduces decoherence into the system via frequency modulation of the nuclear spin Larmor precession. The presence of an off-axis magnetic field necessary for averaging of the dipolar coupling leads to a rotational dependence of the electron-nuclear hyperfine interaction, which cannot be averaged out with experimentally achievable rotation speeds. Our findings offer new insights into the use of physical rotation for quantum control with implications for quantum systems having motional and rotational degrees of freedom that are not fixed.

Effect Magneto – Optic on Ferromagnetic Nanoparticle Polymer Composite Films

Optical properties of a composite material made of ferromagnetic matel nanoparticles embedded in dielectric host are studied. A nonlinear dependence of the optical rotation on magnetic field resulting from the reorientation of nanoparticles is demonstrated. The data of optical properties finding were applied to the magneto – optic experimental data of nickel ferrite (NiFe2 O4) ferromagnetic nanoparticles embedded in polymer (PMMA) host. The magneto – optic is applied at wavelength (540 nm) and magnetic field intensity (450 m T), from result we found the affect magneto – optical on samples.

Ориентационные характеристики возбуждения прецессии намагниченности на интерференционной решетке, создаваемой фемтосекундным лазером.

The subject of investigation in this work is the excitation of magnetization precession in magnetic film on the surface of which is formed the temperature relief which is formed by interference picture formatted by preliminary divided ray from femtosecond laser. It is mentioned the discovered in experiment the dependence of excitation efficiency from the orientation of magnetic field applied in the plane of film. The main aim of this work is the theoretical interpretation of observed orientation dependence. The realized in experiment scheme “pump-probe” is described. The whole geometry of task is proposed. This geometry includes in oneself the magnetic film with formed in its surface interference picture and applied in the plane of film the constant field. It is shown that by the thermal expansion in the film the elastic waves two types are excited; the surface Rayleigh waves and leaky longitudinal waves. The projections of wave-vectors of propagating waves to plane of film are normal to the strips of interference picture. The orientation of field may change from to longitudinal to transverse from the same strips. The components of deformation tensor of Rayleigh and leaky waves are determined. The precession of magnetization in the coordinate system connected with field is investigated. By using the apparatus of crossing matrixes it is found the components of deformation tensor are determined. In the frame of linear approach in this system the task about excitation of magnetization precession by elastic deformations by Rayleigh and leaky waves is solved. The dynamical component of magnetization precession which ensures the light polarization rotation which passes along the normal to the plane of film is found. It is shown that the angle of rotation is straight proportional to the tensor deformation components with the summarization with the resonance character of precession magnetization dependence from the value of magnetic field. The dependence of polarization rotation from orientation of field which is applied in the plane of film is found. It is shown that by the orientation of field along and across the interference stripes the rotation of polarization plane is absent. Between these extreme orientations the dependence has appearance as two maxima divided by deep minimum. The received results are compared with data of experiment. It is found the quality and in some cases quantity correlation. The recommendations for further development of work are proposed.

Molecular architecture dependence of mesogen rotation during uniaxial elongation of liquid crystal elastomers

Macroscopic deformation of liquid crystal elastomers (LCEs) has been assumed to result from the coupling dynamics of the elastic polymer network and liquid-crystalline mesogenic units. However, the microscopic dynamics of LCE molecules are extremely difficult to directly observe from experiments. In this work, in silico experiments of uniaxial elongation of LCEs were performed by molecular dynamics simulations. The molecular systems of main- and side-chain-type LCEs were constructed using coarse-graining techniques. The stress–strain curves as the response to an external force were obtained, and the orientational order parameter of the mesogens along the elongation axis was observed as evidence of symmetry breaking. For the main-chain LCEs, soft elasticity was clearly observed regardless of the details of the molecular architecture. A plateau region of the stress–strain curves appeared, corresponding to drastic symmetry breaking of the orientational order. In contrast, for the side-chain LCEs, the presence/absence of soft elasticity was highly dependent on the details of the molecular architecture. In some cases, rotation of the mesogens was inhibited by a local steric constraint by the main chain and crosslinked particles, which prevented the onset of soft elasticity.

On the polarization rotation by means of electromagnetically induced transparency

The limitations on the effect of electromagnetically induced transparency (EIT) imposed by the degeneracy of atomic levels are considered. The dependence of the EIT-induced polarization rotation of the weak probe field on the characteristics of the resonant transitions and that of the control field is studied. The conditions for the 90∘-rotation without absorption are discussed.

Exploring Nanoscale Lubrication Mechanisms of Multilayer MoS2 During Sliding: The Effect of Humidity.

Solid lubricants have received substantial attention due to their excellent frictional properties. Among others, molybdenum disulfide (MoS2) is one of the most studied lubricants. Humidity results in a deterioration of the frictional properties of MoS2. The actual mechanism at the nanoscale is still under debate, although there are indications that chemical reactions are not likely to occur in defect-free structures. In this study, we performed nonequilibrium molecular dynamics simulations to study the frictional properties of multilayer MoS2 during sliding in the presence of water. Moreover, we also investigated the effect of sliding speed and normal load. We confirmed earlier results that a thin layer of water organizes as a solidified, ice-like network of hydrogen bonds as a result of being confined in a two-dimensional fashion between MoS2. Moreover, we found that there exists an energy-driven, rotational dependence of the water network atop/beneath MoS2. This orientational anisotropy is directly related to the dissipative character of MoS2 during sliding. Finally, three distinct frictional regimes were identified, two for a thin layer of water and one for bulk water. In the case of a thin layer and low coverage, water represents a solid-like contaminant, causing high energy dissipation. For a thin layer and high coverage, water starts to act as a solid-like lubricant, reducing dissipation during sliding. Finally, a regime where water acts as a liquid lubricant, characterized by a clear velocity dependence was found.

Equivariant Wavelets: Fast Rotation and Translation Invariant Wavelet Scattering Transforms

Wavelet scattering networks, which are convolutional neural networks (CNNs) with fixed filters and weights, are promising tools for image analysis. Imposing symmetry on image statistics can improve human interpretability, aid in generalization, and provide dimension reduction. In this work, we introduce a fast-to-compute, translationally invariant and rotationally equivariant wavelet scattering network (EqWS) and filter bank of wavelets (triglets). We demonstrate the interpretability and quantify the invariance/equivariance of the coefficients, briefly commenting on difficulties with implementing scale equivariance. On MNIST, we show that training on a rotationally invariant reduction of the coefficients maintains rotational invariance when generalized to test data and visualize residual symmetry breaking terms. Rotation equivariance is leveraged to estimate the rotation angle of digits and reconstruct the full rotation dependence of each coefficient from a single angle. We benchmark EqWS with linear classifiers on EMNIST and CIFAR-10/100, introducing a new second-order, cross-color channel coupling for the color images. We conclude by comparing the performance of an isotropic reduction of the scattering coefficients and RWST, a previous coefficient reduction, on an isotropic classification of magnetohydrodynamic simulations with astrophysical relevance.

Shape-driven optofluidic rotational actuation

In the present work, we report light-induced rotation of millimeter-sized objects driven by their non-symmetric shape. The light-induced torque is originated by the thermal gradient on different sides of the teeth of star-shaped objects floating on liquid surfaces that leads to unbalanced surface tension due to the Marangoni effect. The dependence of the angular rotation on the number of teeth is demonstrated. The angular velocity is linearly dependent on the light intensity and follows a simple time behavior typical of objects moving under fluid friction.Graphic abstract

Lithium depletion and angular momentum transport in solar-type stars

Context. Transport processes occurring in the radiative interior of solar-type stars are evidenced by the surface variation of light elements, in particular 7Li, and the evolution of their rotation rates. For the Sun, inversions of helioseismic data indicate that the radial profile of angular velocity in its radiative zone is nearly uniform, which implies the existence of angular momentum transport mechanisms that are efficient over evolutionary timescales. While there are many independent transport models for angular momentum and chemical species, there is a lack of self-consistent theories that permit stellar evolution models to simultaneously match the present-day observations of solar lithium abundances and radial rotation profiles. Aims. We explore how additional transport processes can improve the agreement between evolutionary models of rotating stars and observations for 7Li depletion, the rotation evolution of solar-type stars, and the solar rotation profile. Methods. Models of solar-type stars are computed including atomic diffusion and rotation-induced mixing with the code STAREVOL. We explore different additional transport processes for chemicals and for angular momentum such as penetrative convection, tachocline mixing, and additional turbulence. We constrain the resulting models by simultaneously using the evolution of the surface rotation rate and 7Li abundance in the solar-type stars of open clusters with different ages, and the solar surface and internal rotation profile as inverted from helioseismology when our models reach the age of the Sun. Results. We show the relevance of penetrative convection for the depletion of 7Li in pre-main sequence and early main sequence stars. The rotational dependence of the depth of penetrative convection yields an anti-correlation between the initial rotation rate and 7Li depletion in our models of solar-type stars that is in agreement with the observed trend. Simultaneously, the addition of an ad hoc vertical viscosity νadd leads to efficient transport of angular momentum between the core and the envelope during the main sequence evolution and to solar-type models that match the observed profile of the Sun. We also self-consistently compute for the first time the thickness of the tachocline and find that it is compatible with helioseismic estimations at the age of the Sun, but we highlight that the associated turbulence does not allow the observed 7Li depletion to be reproduced. The main sequence depletion of 7Li in solar-type stars is only reproduced when adding a parametric turbulent mixing below the convective envelope. Conclusions. The need for additional transport processes in stellar evolution models for both chemicals and angular momentum in addition to atomic diffusion, meridional circulation, and turbulent shear is confirmed. We identify the rotational dependence of the penetrative convection as a key process. Two additional and distinct parametric turbulent mixing processes (one for angular momentum and one for chemicals) are required to simultaneously explain the observed surface 7Li depletion and the solar internal rotation profile. We highlight the need of additional constraints for the internal rotation of young solar-type stars and also for the beryllium abundances of open clusters in order to test our predictions.

N2-, O2- and Air-broadened half-widths and line shifts of methyl chloride in the 10 µm region

N2- and O2-broadening coefficients were measured at room temperature for 2914 ro-vibrational lines of methyl chloride in the region from 920 to 1140 cm−1 corresponding to the ν6 band, using a high-resolution Fourier transform spectrometer and a mono-spectrum non-linear least squares fitting of Voigt profiles. The spectra were recorded at the AILES beamline of the SOLEIL Synchrotron facility at various mixtures of CH3Cl with N2 or O2 gas. Broadening coefficients were retrieved for the two isotopes of CH3Cl from which we derived the air-broadenings. The rotational dependences of these coefficients were analyzed and modeled first using an empirical model, which reproduces the measurements within of about 5%. Pressure-induced shifts are also measured for about 375 and 418 transitions for O2- and N2-perturbers respectively with no obvious rotational dependence. The average absolute accuracies of the measurements are estimated to be about 7 and 17% for broadening and shift coefficients respectively. Comparisons are performed with previous measurements and next with semi-classical predictions achieved in this work. The entire set of results is given as Supplementary data Table for a use in spectroscopic databases and atmospheric detection.

Measurements of Line Intensities and Self-broadening Coefficients in the ν2 Band of CH3I

The line intensities and pressure broadening coefficients for transitions in the three branches of the ν2 parallel band of CH3I are measured for the first time for about 1317 lines with rotational quantum numbers 2 ≤ J ≤ 70 and 0 ≤ K ≤ 13 using a mono-spectrum fitting technique utilizing a Voigt profile. Five spectra have been recorded at room temperature (T = 297.6 K) with a high resolution Fourier transform spectrometer at pressures between 1.15 and 9.98 mbar. The measured intensities were used to derive the transition dipole moment squared for each line, the band intensity as well as the Herman–Wallis coefficients. These parameters were used to predict the values of line intensities. The band intensity was compared with previous works performed at medium resolution. The rotational dependencies of the self-broadening coefficients have been clearly observed and modeled using an empirical model. The average accuracies were estimated to be around 5 % for line intensities and self-broadening coefficients.The whole set of results is given as supplementary material for a possible use in atmospheric and industrial applications.

Розробка методу визначення параметрів поступального й обертального руху оптичного джерела реєстрації безпілотного літального апарата

В статі розглядається метод визначення параметрів поступального й обертального руху оптичного джерела реєстрації безпілотного літального апарата (БПЛА), заснованого на аналізі потоку, отриманого від оптичного датчика, що знаходиться на борту БПЛА, з наступним використанням отриманих даних для уточнення навігаційної інформації та у якості автономного джерела даних для навігації апарату на місцевості. Автономне управління польотом є відкритою науковою проблемою, особливо там, де немає можливості застосувати зовнішні системи позиціонування. Головним завданням, що необхідно вирішити в рамках даної проблеми, є складність якісного позиціонування з використанням лише вбудованих сенсорів. В роботі проведено аналіз працездатності методу на чистих і на зашумлених зображеннях поверхні землі. Проаналізована залежність визначення позиції, та повороту апарата в залежності від характеру поверхні та відстані до неї оптичного датчику. Отримані результати дозволяють використовувати запропонований метод для уточнення даних щодо траєкторії руху апарата отриманих з інших джерел так і для автономної навігації БПЛА.

Retroreflection and Wettability Controlled Smart Indicator Based on Responsive Bilayer Photonic Crystals for Traffic Warning

AbstractDue to the increasing human mortality caused by natural disasters and traffic accidents, the development of smart traffic warning systems is urgent. The first smart indicator for traffic warning based on bilayer photonic crystals with both selective retroreflection and response reflection optical properties is developed. The wettability‐controlled reflection evaluates the risk of landslides and warns drivers to slow down, while the retroreflection simultaneously displays iridescent vivid structural colors to observers at different viewing directions relative to the illumination direction and informs drivers the approaching of the accident blackspot. The mechanism involves diffractions in the periodic nanostructures and uses the wettability of vertical surfaces to realize the spectral diversity of reflectance. Moreover, colorful flickering structural colors based on the rotational periodic diffraction and angle dependence of the retroreflection are designed for speed limits warning. It demonstrates an energy‐efficient, smart, and tunable multi‐functionalized bilayer photonic crystal that is especially suitable for nighttime traffic warning, advertisement, and periodic warning display applications.