Internal Anisotropy Research Articles

Relation of internal gravity wave anisotropy with neutral wind characteristics in the upper atmosphere

AbstractThis paper studies the interaction of internal gravity waves (IGW) with neutral wind using the statistics of traveling ionospheric disturbances (TID) from the Radio Physical Complex of the Institute of Solar‐Terrestrial Physics. The complex includes the Irkutsk Incoherent Scatter Radar (IISR), Irkutsk Ionosonde (DPS‐4), and Ekaterinburg HF Radar (EKB). The aim of this study is to give a common explanation for the TID azimuth distributions obtained with the IISR‐ionosonde and HF coherent radar and show that the measurements of 3‐D TID characteristics put into the hands of researchers an important tool to study neutral wind in the thermosphere. The distinctive features of this study are the following: (1) using different TID statistics from independent tools and, correspondingly, independent methods for determining TID characteristics; (2) using the 3‐D TID characteristics for testing the wind‐filtering hypothesis, which allows us to separate the IGW‐induced TIDs from TIDs of other nature and identify three TID types depending on their elevation angles; and (3) using the local time‐azimuth distribution of the TID number for testing the wind‐filtering hypothesis. This study allowed us to conclude that the observed IGW azimuth anisotropy can be mainly explained by the wind filtration mechanism with considering winds at 90–250 km heights. Using the 3‐D IGW characteristics allows us to estimate neutral wind parameters. Proposed methods are applicable for any tool which can obtain TID 3‐D characteristics. Using the proposed methods will enable us to organize a worldwide campaign to improve the existing neutral wind models.

Sonic metamaterials: Reflection on the role of topology on dispersion surface morphology

Investigating dispersion surface morphology of sonic metamaterials is crucial in providing information on related phenomena as inertial coupling, acoustic transparency, polarisation, and absorption. In the present study, we look into frequency surface morphology of two-dimensional (2D) metamaterials of K3,3 and K6 topologies. The elastic structures under consideration consist of the same substratum lattice points and form a pair of sublattices with hexagonal symmetry. We show that, through introducing universal localised mass-in-mass phononic microstructures at lattice points, six single optical frequency-surfaces can be formed with required properties including negative group velocity. Splitting the frequency-surfaces is based on the classical analog of the quantum phenomenon of ‘energy-level repulsion’, which can be achieved only through internal anisotropy of the nodes and allows us to obtain different frequency band gaps.

The impact of sedimentary anisotropy on solute mixing in stacked scour‐pool structures

AbstractThe spatial variability of hydraulic conductivity is known to have a strong impact on solute spreading and mixing. In most investigations, its local anisotropy has been neglected. Recent studies have shown that spatially varying orientation in sedimentary anisotropy can lead to twisting flow enhancing transverse mixing, but most of these studies used geologically implausible geometries. We use an object‐based approach to generate stacked scour‐pool structures with either isotropic or anisotropic filling which are typically reported in glacial outwash deposits. We analyze how spatially variable isotropic conductivity and variation of internal anisotropy in these features impacts transverse plume deformation and both longitudinal and transverse spreading and mixing. In five test cases, either the scalar values of conductivity or the spatial orientation of its anisotropy is varied between the scour‐pool structures. Based on 100 random configurations, we compare the variability of velocity components, stretching and folding metrics, advective travel‐time distributions, one and two‐particle statistics in advective‐dispersive transport, and the flux‐related dilution indices for steady state advective‐dispersive transport among the five test cases. Variation in the orientation of internal anisotropy causes strong variability in the lateral velocity components, which leads to deformation in transverse directions and enhances transverse mixing, whereas it hardly affects the variability of the longitudinal velocity component and thus longitudinal spreading and mixing. The latter is controlled by the spatial variability in the scalar values of hydraulic conductivity. Our results demonstrate that sedimentary anisotropy is important for transverse mixing, whereas it may be neglected when considering longitudinal spreading and mixing.

Predictors and brain connectivity changes associated with arm motor function improvement from intensive practice in chronic stroke.

Background and Purpose: The brain changes that underlie therapy-induced improvement in motor function after stroke remain obscure. This study sought to demonstrate the feasibility and utility of measuring motor system physiology in a clinical trial of intensive upper extremity rehabilitation in chronic stroke-related hemiparesis. Methods: This was a substudy of two multi-center clinical trials of intensive robotic and intensive conventional therapy arm therapy in chronic, significantly hemiparetic, stroke patients. Transcranial magnetic stimulation was used to measure motor cortical output to the biceps and extensor digitorum communus muscles. Magnetic resonance imaging (MRI) was used to determine the cortical anatomy, as well as to measure fractional anisotropy, and blood oxygenation (BOLD) during an eyes-closed rest state. Region-of-interest time-series correlation analysis was performed on the BOLD signal to determine interregional connectivity. Functional status was measured with the upper extremity Fugl-Meyer and Wolf Motor Function Test. Results: Motor evoked potential (MEP) presence was associated with better functional outcomes, but the effect was not significant when considering baseline impairment. Affected side internal capsule fractional anisotropy was associated with better function at baseline. Affected side primary motor cortex (M1) activity became more correlated with other frontal motor regions after treatment. Resting state connectivity between affected hemisphere M1 and dorsal premotor area (PMAd) predicted recovery. Conclusions: Presence of motor evoked potentials in the affected motor cortex and its functional connectivity with PMAd may be useful in predicting recovery. Functional connectivity in the motor network shows a trends towards increasing after intensive robotic or non-robotic arm therapy. Clinical Trial Registration URL: http://www.clinicaltrials.gov. Unique identifiers: NCT00372411 \& NCT00333983.

Top-down, decoupled control of constitutive parameters in electromagnetic metamaterials with dielectric resonators of internal anisotropy

A meta-atom platform providing decoupled tuning for the constitutive wave parameters remains as a challenging problem, since the proposition of Pendry. Here we propose an electromagnetic meta-atom design of internal anisotropy (εr ≠ εθ), as a pathway for decoupling of the effective- permittivity εeff and permeability μeff. Deriving effective parameters for anisotropic meta-atom from the first principles, and then subsequent inverse-solving the obtained decoupled solution for a target set of εeff and μeff, we also achieve an analytic, top-down determination for the internal structure of a meta-atom. To realize the anisotropy from isotropic materials, a particle of spatial permittivity modulation in r or θ direction is proposed. As an application example, a matched zero index dielectric meta-atom is demonstrated, to enable the super-funneling of a 50λ-wide flux through a sub-λ slit; unharnessing the flux collection limit dictated by the λ-zone.

Anisotropic optical response of optically opaque elastomers with conductive fillers as revealed by terahertz polarization spectroscopy

Elastomers are one of the most important materials in modern society because of the inherent viscoelastic properties due to their cross-linked polymer chains. Their vibration-absorbing and adhesive properties are especially useful and thus utilized in various applications, for example, tires in automobiles and bicycles, seismic dampers in buildings, and seals in a space shuttle. Thus, the nondestructive inspection of their internal states such as the internal deformation is essential in safety. Generally, industrial elastomers include various kinds of additives, such as carbon blacks for reinforcing them. The additives make most of them opaque in a wide spectral range from visible to mid-infrared, resulting in that the nondestructive inspection of the internal deformation is quite difficult. Here, we demonstrate transmission terahertz polarization spectroscopy as a powerful technique for investigating the internal optical anisotropy in optically opaque elastomers with conductive additives, which are transparent only in the terahertz frequency region. The internal deformation can be probed through the polarization changes inside the material due to the anisotropic dielectric response of the conductive additives. Our study about the polarization-dependent terahertz response of elastomers with conductive additives provides novel knowledge for in situ, nondestructive evaluation of their internal deformation.

Magnetization dynamics in dilute Pd1-xFex thin films and patterned microstructures considered for superconducting electronics

Motivated by recent burst of applications of ferromagnetic layers in superconducting digital and quantum elements, we study the magnetism of thin films and patterned microstructures of Pd0.99Fe0.01. In this diluted ferromagnetic system, a high-sensitivity ferromagnetic resonance (FMR) experiment reveals spectroscopic signatures of re-magnetization and enables the estimation of the saturation magnetization, the anisotropy field, and the Gilbert damping constant. The detailed analysis of FMR spectra links the observed unexpectedly high reduced anisotropy field (0.06–0.14) with the internal anisotropy, points towards a cluster nature of the ferromagnetism, and allows estimating characteristic time scale for magnetization dynamics in Pd-Fe based cryogenic memory elements to (3−5)×10−9 s.

Predictors and brain connectivity changes associated with arm motor function improvement from intensive practice in chronic stroke

Background and Purpose: The brain changes that underlie therapy-induced improvement in motor function after stroke remain obscure. This study sought to demonstrate the feasibility and utility of measuring motor system physiology in a clinical trial of intensive upper extremity rehabilitation in chronic stroke-related hemiparesis. Methods: This was a substudy of two multi-center clinical trials of intensive robotic and intensive conventional therapy arm therapy in chronic, significantly hemiparetic, stroke patients. Transcranial magnetic stimulation was used to measure motor cortical output to the biceps and extensor digitorum communus muscles. Magnetic resonance imaging (MRI) was used to determine the cortical anatomy, as well as to measure fractional anisotropy, and blood oxygenation (BOLD) during an eyes-closed rest state. Region-of-interest time-series correlation analysis was performed on the BOLD signal to determine interregional connectivity. Functional status was measured with the upper extremity Fugl-Meyer and Wolf Motor Function Test. Results: Motor evoked potential (MEP) presence was associated with better functional outcomes, but the effect was not significant when considering baseline impairment. Affected side internal capsule fractional anisotropy was associated with better function at baseline. Affected side primary motor cortex (M1) activity became more correlated with other frontal motor regions after treatment. Resting state connectivity between affected hemisphere M1 and dorsal premotor area (PMAd) predicted recovery. Conclusions: Presence of motor evoked potentials in the affected motor cortex and its functional connectivity with PMAd may be useful in predicting recovery. Functional connectivity in the motor network shows a trends towards increasing after intensive robotic or non-robotic arm therapy. Clinical Trial Registration URL: http://www.clinicaltrials.gov. Unique identifiers: NCT00372411 \\& NCT00333983.

Predictors and brain connectivity changes associated with arm motor function improvement from intensive robotic practice in chronic stroke

Background and Purpose: The brain changes that underlie therapy-induced improvement in motor function after stroke remain obscure. This study sought to demonstrate the feasibility and utility of measuring motor system physiology in a clinical trial of intensive upper extremity rehabilitation in chronic stroke-related hemiparesis. Methods: This was a substudy of two multi-center clinical trials of intensive robotic arm therapy in chronic, significantly hemiparetic, stroke patients. Transcranial magnetic stimulation was used to measure motor cortical output to the biceps and extensor digitorum communus muscles. Magnetic resonance imaging (MRI) was used to determine the cortical anatomy, as well as to measure fractional anisotropy, and blood oxygenation (BOLD) during an eyes-closed rest state. Region-of-interest time-series correlation analysis was performed on the BOLD signal to determine interregional connectivity. Functional status was measured with the upper extremity Fugl-Meyer and Wolf Motor Function Test. Results: Motor evoked potential (MEP) presence was associated with better functional outcomes, but the effect was not significant when considering baseline impairment. Affected side internal capsule fractional anisotropy was associated with better function at baseline. Affected side primary motor cortex (M1) activity became more correlated with other frontal motor regions after treatment. Resting state connectivity between affected hemisphere M1 and dorsal premotor area (PMAd) predicted recovery. Conclusions: Presence of motor evoked potentials in the affected motor cortex and its functional connectivity with PMAd may be useful in predicting recovery. Functional connectivity in the motor network shows a trends towards increasing after intensive robotic or non-robotic arm therapy. Clinical Trial Registration URL: http://www.clinicaltrials.gov. Unique identifiers: CT00372411 & NCT00333983.

Transfer of spin reorientation in a NdCo5/Fe bilayer

A NdCo5 (37 nm)/Fe (22 nm) hard/soft bilayer was grown by pulsed laser deposition on a MgO (1 1 0) substrate, and investigated by vibrating sample magnetometry and ferromagnetic resonance (FMR). Due to the direct exchange coupling at the NdCo5/Fe interface, the spin reorientation transition (SRT) typical of NdCo5 is observed also in the bilayer by means of global magnetometry. Concerning the magnetization dynamics, the interlayer magnetic coupling is weak, thus allowing the identification of the FMR signals in the sample as those originating mainly from the individual responses of the Fe and NdCo5 layers. In the NdCo5 layer, the effective coupling field is negligible compared to the internal anisotropy, and the magnetization precession is similar to the one found in a NdCo5 single layer. In the magnetically soft Fe layer, however, the precession of the moments occurs in the exchange field stemming from the dynamically fixed NdCo5 layer, giving rise to a partial transfer of magnetic anisotropy from the latter and enabling us to follow the SRT of NdCo5 by measuring the Fe FMR peak field position. Controlling the anisotropy direction in the soft layer by making use of the SRT in the hard layer can find applications in future spintronic devices.

Non-Markovian Magnetization Dynamics for Uniaxial Nanomagnets

A stochastic approach for the description of the time evolution of the magnetization of nanomagnets is proposed, that interpolates between the Landau-Lifshitz-Gilbert and the Landau-Lifshitz-Bloch approximations, by varying the strength of the noise. Its finite autocorrelation time, i.e. when it may be described as colored, rather than white, is, also, taken into account and the consequences, on the scale of the response of the magnetization are investigated. It is shown that the hierarchy for the moments of the magnetization can be closed, by introducing a suitable truncation scheme, whose validity is tested by direct numerical solution of the moment equations and compared to the averages obtained from a numerical solution of the corresponding colored stochastic Langevin equation. This comparison is performed on magnetic systems subject to both an external uniform magnetic field and an internal one-site uniaxial anisotropy.

Macro deformation and micro structure of 3D granular assemblies subjected to rotation of principal stress axes

This paper presents a numerical investigation on the behavior of three dimensional granular materials during continuous rotation of principal stress axes using the discrete element method. A dense specimen has been prepared as a representative element using the deposition method and subjected to stress rotation at different deviatoric stress levels. Significant plastic deformation has been observed despite that the principal stresses are kept constant. This contradicts the classical plasticity theory, but is in agreement with previous laboratory observations on sand and glass beads. Typical deformation characteristics, including volume contraction, deformation non-coaxiality, have been successfully reproduced. After a larger number of rotational cycles, the sample approaches the ultimate state with constant void ratio and follows a periodic strain path. The internal structure anisotropy has been quantified in terms of the contact-based fabric tensor. Rotation of principal stress axes densifies the packing, and leads to the increase in coordination numbers. A cyclic rotation in material anisotropy has been observed. The larger the stress ratio, the structure becomes more anisotropic. A larger fabric trajectory suggests more significant structure re-organization when rotating and explains the occurrence of more significant strain rate. The trajectory of the contact-normal based fabric is not centered in the origin, due to the anisotropy in particle orientation generated during sample generation which is persistent throughout the shearing process. The sample sheared at a lower intermediate principal stress ratio $$(b=0.0)$$ has been observed to approach a smaller strain trajectory as compared to the case $$b=0.5$$ , consistent with a smaller fabric trajectory and less significant structural re-organisation. It also experiences less volume contraction with the out-of plane strain component being dilative.

Influence of composition, strain, and electric field anisotropy on different emission colors and recombination dynamics from InGaN nanodisks in pencil-like GaN nanowires

This work reports an experimental and theoretical insight into phenomena of two-color emission and different electron-hole recombination dynamics in InGaN nanodisks, incorporated into pencil-like GaN nanowires. The studied nanodisks consist of one polar (on $c$ facet) and six (nominally) identical semipolar (on $r$ facets) sections, as confirmed by transmission electron microscopy. The combination of cathodoluminescence with scanning electron microscopy spatially resolves the nanodisk two-color emission, the low-energy emission (\ensuremath{\sim}500 nm) originating from the polar section, and the high-energy emission (\ensuremath{\sim}400 nm) originating from the semipolar section. This result has been directly linked to a ``facet-dependent'' nanodisk composition, the In content being significantly higher in the polar ($\ensuremath{\sim}20%$) vs semipolar ($\ensuremath{\sim}10%$) section (as quantified by energy dispersive x-ray spectroscopy), further leading to a strong facet-dependent strain anisotropy. Time-resolved cathodoluminescence reveals significantly different electron-hole recombination times in the two sections, moderately fast (\ensuremath{\sim}1.3 ns) vs fast (\ensuremath{\sim}0.5 ns) in polar/semipolar sections, respectively, the difference being linked to a strong anisotropy in the nanodisk internal electric fields. To determine the influence of each of the three contributing ``facet-related'' anisotropies (composition, strain, and electric field) on the two-color emission, a proper simulation [relying on virtual crystal approximation and involving three-dimensional (3D) continuum mechanical modeling, a 3D Poisson equation, and a one-dimensional Schr\"odinger equation] has been performed. The theoretical simulations allow the three effects to be quantitatively disentangled, revealing a clear hierarchy among their contributing weights, the facet-dependent composition inhomogeneity being identified as the dominant one (and the strain inhomogeneity being identified as the least significant one). As for different recombination times, while it is mainly linked to the internal electric field anisotropy, we also suggest that it is, very likely, influenced by gradually increasing In content along the nanodisk growth direction (lattice-pulling effect); the latter mechanism keeps electrons and holes in (relative) proximity within the polar section, enabling their relatively fast and efficient radiative recombination.

Coldwellite, Pd3Ag2S, A New Mineral Species From the Marathon Deposit, Coldwell Complex, Ontario, Canada

Abstract Coldwellite, ideally Pd 3 Ag 2 S, is a new mineral species discovered in a heavy-mineral concentrate from the Marathon deposit, Coldwell Complex, Ontario Canada. It is cubic, crystallizing in space group P 4 3 32 (#212) with a 7.2470(8) A, V 380.61(1) A 3 , Z = 4. The five strongest lines of the X-ray powder-diffraction pattern [ d in A (I)( hkl )] are: 2.427(100)(221), 2.302(38)(310), 2.195(38)(311), 1.4280(44)(510,431), 0.9294(24)(650,643), and 0.9208(20)(732,651). Associated minerals in the discovery sample include Au-Ag alloy, hollingworthite, isoferroplatinum, keithconnite, kotulskite, mertieite-II, michenerite, palladoarsenide, sobolevskite, sperrylite, stillwaterite, vysotskite, Ti- and Cr-rich magnetite and ilmenite, pyrrhotite, chalcopyrite, and pentlandite, with trace amounts of bornite, cobaltite, and galena. Coldwellite is white with a light pinkish brown tint, and it has a metallic luster. No streak or microhardness could be measured. The mineral shows no internal reflections, pleochroism, bireflectance, or anisotropy. The reflectance values (%) in air for the standard COM wavelengths are: 41.9 (470 nm), 44.9 (546 nm), 44.0 (589 nm), and 45.0 (650 nm). The density, 9.90(1) g/cm 3 , was calculated using the empirical formula and the unit-cell parameters from the refined crystal-structure. The average result ( n = 23) of electron-microprobe analyses is: Pd 56.1, Fe 0.16, Ag 38.2, S 5.63, total 100.09 wt.%, which corresponds to (Pd 2.99 Fe 0.02 ) Σ3.01 Ag 2.00 S 0.99 , based on 6 apfu . The name recalls the type locality.

Direct observation by using Brewster angle microscopy of the diacetylene polimerization in mixed Langmuir film

Mixed Langmuir monolayers of 10,12-Pentacosadiynoic acid (DA) and amphiphilic hemicyanine (HSP) have been fabricated at the air–water interface. The mixed monolayer has been proved to be completely homogeneous. The DA molecules are arranged in a single monolayer within the mixed Langmuir monolayer, as opposed to the typical trilayer architecture for the pure DA film. Brewster angle microscopy has been used to reveal the mesoscopic structure of the mixed Langmuir monolayer. Flower shape domains with internal anisotropy due the ordered alignment of hemicyanine groups have been observed. Given the absorption features of the hemicyanine groups at the wavelength used in the BAM experiments, the enhancement of reflection provoked by the absorption process leads to the observed anisotropy. The ordering of such groups is promoted by their strong self-aggregation tendency. Under UV irradiation at the air–water interface, polydiacetylene (PDA) has been fabricated. In spite a significant increase in the domains reflectivity has been observed owing to the modification in the mentioned enhanced reflection, the texture of the domains remains equal. The PDA polymer chain therefore grows in the same direction in which the HSP molecules are aligned. This study is expected to enrich the understanding and design of fabrication of PDA at interfaces.

English

From the literature, it is found that two different criteria were followed for the prediction of transverse thermal conductivity (K2) of fiber reinforced plastic (FRP) composites. In the first criterion, the internal anisotropy of the lamina is assumed negligible and K2 is estimated using simple Fourier’s law of 1-D heat conduction applied to representative volume element (RVE). Whereas in the second approach, an electrical analogy method is followed. To estimate the effect of internal anisotropy, through thickness thermal conductivity (K3) of an FRP lamina is determined by both the approaches through finite element method for an RVE in the auxiliary plane. The problem is modeled in ANSYS 15 software. In the present paper studies are made for various volume fractions (0.1-0.75) and for various angles (20°-90°) made by the section plane with the fiber axis. It is observed that the through thickness thermal conductivity is consistent in the second approach, whereas in the first approach there is considerable variation (max 8.7%) with the orientation of the unit cell.    Key words: Through thickness thermal conductivity, finite element method (FEM), unit cell orientation.

Paleoflow directions of a subaqueous lahar deposit around the Miocene Keserűs Hill lava dome complex (North Hungary) as constrained by photo-statistics and anisotropy of magnetic susceptibility (AMS)

A twofold fabric analysis by using photo-statistics on rock surfaces and low-field anisotropy of magnetic susceptibility (AMS) is presented, making it possible to infer paleoflow directions, which in turn helps to constrain the primary volcanic geomorphology of a deeply eroded mid-Miocene field (Keserűs Hill lava dome group, Visegrád Mountains, North Hungary). The analyses were carried out on the Rám Hill Pumiceous Sandstone (RHPS) that, based on its petrographic features, is considered as a subaqueously emplaced laharic deposit.The observed anisotropic frequencies of clast a-axis azimuths, the good agreement of fabric directions obtained for all and most elongated samples (elongation>2.5), the good clustering of the declinations of the K1 susceptibilities largely corresponding with the result of image analysis, allow to infer reliable flow directions. The obtained large-scale paleoflow paths show a quasi-radial pattern around the central part of the Visegrád Mountains, which quantitatively confirms the previous hypothesis on the volcanic structure, namely a central edifice-topped syn-eruptive topography.The RHPS is characterized by a clast fabric (revealed by photostatistics on cutted rock surfaces considering the lapilli-sized fraction) as strong as in subaerial PDC deposits, but by a significantly weaker magnetic fabric. The weak magnetic fabric is supposed to be the result of rock heterogeneity, thus the weakening effect of abundant lithic clasts with strong internal magnetic susceptibility anisotropy, different from the shape anisotropy of the clasts and the flow-related magnetic fabric of the fine-grained matrix.

FLOW PATTERNS AROUND DARK MATTER HALOS: THE LINK BETWEEN HALO DYNAMICAL PROPERTIES AND LARGE-SCALE TIDAL FIELD

We study how halo intrinsic dynamical properties are linked to their formation processes for halos in two mass ranges, $10^{12}-10^{12.5}h^{-1}{\rm M_\odot}$ and $\ge 10^{13}h^{-1}{\rm M_\odot}$, and how both are correlated with the large scale tidal field within which the halos reside at present. Halo merger trees obtained from cosmological $N$-body simulations are used to identify infall halos that are about to merge with their hosts. We find that the tangential component of the infall velocity increases significantly with the strength of the local tidal field, but no strong correlation is found for the radial component. These results can be used to explain how the internal velocity anisotropy and spin of halos depend on environment. The position vectors and velocities of infall halos are aligned with the principal axes of the local tidal field, and the alignment depends on the strength of the tidal field. Opposite accretion patterns are found in weak and strong tidal fields, in the sense that in a weak field the accretion flow is dominated by radial motion within the local structure, while a large tangential component is present in a strong field. These findings can be used to understand the strong alignments we find between the principal axes of the internal velocity ellipsoids of halos and the local tidal field, and their dependence on the strength of tidal field. They also explain why halo spin increases with the strength of local tidal field, but only in weak tidal fields does the spin-tidal field alignment follow the prediction of the tidal torque theory. We discuss how our results may be used to understand the spins of disk galaxies and velocity structures of elliptical galaxies and their correlations with large-scale structure.

Consistency in Electrical Analogy Approach with Respect to Thermal Conductivity Mismatch in FRP Composites

From the literature it is found that, two different approaches were followed for the prediction of transverse thermal conductivity (K2) of FRP composites. In the first approach, the internal anisotropy of the lamina is assumed negligible and K2 is estimated using simple Fourier's law of 1-D heat conduction applied to Representative Volume Element (RVE). Whereas in the second approach, electrical analogy method is followed. To estimate the effect of internal anisotropy, through thickness thermal conductivity (K3) of an FRP lamina is determined by both the approaches using the Finite Element method for an RVE in the auxiliary plane. The problem is modelled in ANSYS 15 software. In the present paper studies are made for various Kf/Km values (1-50) and for various angles (200-900) made by the section plane with the fiber axis. It is observed that the through thickness thermal conductivity is consistent in the second approach, whereas in the first approach there is considerable variation (max. 8.6%) with the orientation of the unit cell.

Interplay of stress, temperature, and giant magnetoimpedance in amorphous soft magnets

Giant Magnetoimpedance (GMI)-based sensing devices have attracted attention from both academia and industry due to their low cost, flexibility, and excellent sensitivity. Potential applications range widely from current and stress sensors, navigation systems, magnetic recording, to more demanding ones such as field sensors for deep drilling and oil fracking at elevated temperature. To realize the latter, the temperature dependence of GMI effect must be well understood. Herein, we report a study on the GMI effect in a Cobalt-based amorphous microwire under temperature cycles between 20 °C–560 °C. The GMI ratio was observed to decrease from 126.1% at 20 °C to 68.5% at 230 °C, rapidly drop at ∼290 °C and reach a near zero value above 320 °C in the first half of the measurement where the temperature was increased. Upon cooling down from 560 °C to 20 °C, the GMI ratio exhibits little variation at ∼95% in the 260 °C–20 °C regime. Similarly, the anisotropy-temperature profile was also observed to change irreversibly during the temperature cycle. Previous work has found the correlation between internal stress, anisotropy, permeability, and GMI effect. We hypothesize that irreversibility in GMI-temperature and anisotropy-temperature profiles stem from internal relief in the amorphous structure, which is locked in during the rapid cooling. In the subsequent temperature cycles, the GMI-temperature and anisotropy-temperature profiles show little variation, thus supporting the notion that the internal stress relief is complete after the first temperature cycle.