Isotropy Parameters Research Articles

Reynolds number dependency of small scale structures in steady anisotropic turbulence produced by implicit large-eddy simulation

This study presents small-scale fluctuation characteristics of anisotropic steady turbulence reproduced by implicit large eddy simulation (LES). The Reynolds number dependence of this small-scale fluctuation characteristic is approached in this study. This study focuses on that, a small scale turbulence field is not needed to be isotropic if the Reynolds number is sufficiently high. The anisotropic steady turbulence is maintained steady by using the forcing terms in the governing equations. The results of the implicit LES are compared with those obtained by direct numerical simulation (DNS) and LES based on the Smagorinsky model. Spatial derivatives are discretized using a fourth-order central difference scheme that conserves the kinetic energy of the turbulence field. The governing equations are integrated for the temporal direction using the fourth-order Runge-Kutta method. The results of enstrophy and small-scale turbulence characteristics quantified by the isotropy parameter are found to be consistent between the implicit LES and DNS.

Three-dimensional structure of polarization singularities of a light field near a dielectric spherical nanoparticle.

We numerically study the structure of polarization singularity lines in a near-field of the sub-wavelength dielectric particle when it is irradiated by a monochromatic elliptically polarized plane wave. For the various values of the ellipticity degree of the incident radiation, we trace the CT and LT-lines on which the polarization ellipse turns into a circle or a line, respectively. The continuous variation of the isotropy parameters of the singularities is visualized along the lines. The main rules of CT and LT-lines deformation, emergence, and vanishing are revealed.

Fine characteristics of polarization singularities in a three-dimensional electromagnetic field and their properties in the near field of a metallic nanospheroid

Isotropy parameters of truly linear (${L}^{T}$) and truly circular (${C}^{T}$) polarization singularities in a three-dimensional monochromatic electromagnetic field are defined. It is demonstrated that these parameters characterize the distribution of polarization ellipses near the singular points in a more detailed way than a topological index. A numerical algorithm which tracks ${C}^{T}$ and ${L}^{T}$ lines and visualizes the changes of isotropy parameters along the lines is proposed. The algorithm is applied to visualize the polarization singularity lines and their properties in the vicinity of a metallic nanospheroid that is irradiated by a plane elliptically polarized wave. It is shown that both ${C}^{T}$ and ${L}^{T}$ lines appear close to the surface of the nanoparticle and they are three-dimensional closed loops or arcs that start and end at the surface of the nanospheroid. In most cases the singular lines of different types are topologically linked.

Geometric Factor as the Characteristics of the Three-Dimensional Process of Volume Changes of Heavy Soils

During simulation of a water regime of heavy soils, it is necessary to know the isotropy parameters of any volume changes. Volume changes appear in both vertical and horizontal directions. In vertical directions, they appear as a topsoil movement, and in horizontal directions as the formation of a crack network. The ratio between horizontal and vertical change is described using the geometric factor, rs. In the present paper, the distribution of volume changes to horizontal and vertical components is characterized by the geometric factor, in selected soil profiles, in the East Slovakian Lowland. In this work the effect of soil texture on the value of the geometric factor and thus, on the distribution of volume changes to vertical and horizontal components was studied. Within the hypothesis, the greatest influence of the clay soil component was shown by the geometric factor value. New information is obtained on the basis of field and laboratory measurements. Results will be used as inputs for numerical simulation of a water regime for heavy soils in the East Slovakian Lowland.

Doped-SiCNT as a promising sensor for detection of CS2 molecule

ABSTRACTIn order to explore the novel sensors for detection of carbon disulfide (CS2) molecule, the electronic sensitivity of Pd or Ni–SiCNT to CS2 molecule is investigated using density functional theory and dispersion-corrected density functional theory methods. The adsorption energy, charge transfer, density of states and molecular frontier orbital of all systems are also analyzed. The adsorption energy values reveal that PdSi or NiSi–SiCNT weakly adsorbed the CS2 molecule and their electronic properties do not change by adsorbing a gas molecule. While replacing C atom with Ni and Pd atoms can enhance the adsorption energy. Moreover, it is found that the electronic properties of PdC or NiC–SiCNT are changed upon exposure to the CS2 molecule. And NiC–SiCNT has more sensitivity to CS2 when compared to other considered nanotubes. Therefore, NiC–SiCNT is more suitable for detection and CS2 adsorption than other investigated nanotubes. NBO analysis reveals that electrons transfer from the CS2 molecule to the nanotube. 13C and 29Si chemical shielding tensors are computed using the gauge-independent atomic orbital method. Nuclear magnetic resonance calculations reveal that the isotropy parameters at the sites of Si nuclei which are directly bonded to the impurity atoms undergo significant changes.

The projected gravitational potential of the galaxy cluster MACS J1206 derived from galaxy kinematics

We reconstruct the radial profile of the projected gravitational potential of the galaxy cluster MACS-J1206 from 592 spectroscopic measurements of velocities of cluster members. For doing so, we use a method we have developed recently based on the Richardson-Lucy deprojection algorithm and an inversion of the spherically-symmetric Jeans equation. We find that, within the uncertainties, our reconstruction agrees very well with a potential reconstruction from weak and strong gravitational lensing as well as with a potential obtained from X-ray measurements. In addition, our reconstruction is in good agreement with several common analytic profiles of the lensing potential. Varying the anisotropy parameter in the Jeans equation, we find that isotropy parameters which are either small, $\beta\lesssim0.2$, or decrease with radius yield potential profiles which strongly disagree with that obtained from gravitational lensing. We achieve the best agreement between our potential profile and the profile from gravitational lensing if the anisotropy parameter rises quite steeply to $\beta\approx0. 6$ within $\approx0.5\,\mathrm{Mpc}$ and stays constant further out.

Microcantilever suspension using hard masks and a two phase RIE method

This study presents the application of simple and efficient Reactive Ion Etching (RIE) methods to suspend microcantilevers using a two electrode plasma reactor. The process consists of two steps and poses a viable, robust, and cost effective alternative to other methods such as XeF2 vapor etching. Aluminum hard mask was employed for general purpose use in processes where materials other than silicon are used to form the microcantilever. Successive etching steps of silicon substrate with SF6/O2 and CF4/O2 plasmas were applied sequentially in a two phase configuration where the first phase is relatively anisotropic and the second phase is more isotropic. This allowed for suspension of microcantilevers while maintaining well-defined undercut characteristics. Etch characteristics were measured for different process parameters, and the effect of O2 concentration, power, and pressure on etch rate and isotropy was presented. The selectivity to aluminum mask was measured to be larger than 250:1 in the used recipes. It was also shown on the test structures that the amount of undercut is observable as contrast differentials using simple SEM imaging techniques on metal film hard mask. During individual characterization of etch profiles, isotropy parameters varying between approximately 0.4–0.95 were obtained under different etch conditions. The maximum etch rates of SF6 based and CF4 based etch recipes were found to be 30.5μm/min and 3.2μm/min, respectively, for varying conditions. Aluminum microcantilevers with dimensions of 100μm×300μm were successfully released after 90min of processing with 30μm of travel distance to the underlying notch.

Applications of deterministic and stochastic rock physics modelling to anisotropic velocity model building

ABSTRACTModern anisotropic depth imaging requires transverse isotropy velocity models. Because the surface seismic experiment alone cannot uniquely determine all transverse isotropy parameters, additional information is required. Traditional methods that use checkshots can only constrain anisotropy locally near the well and thus model building requires 3D extrapolation of well data. We propose to use rock physics. Rock physics compaction modelling of shales and sandy shales can be used to constrain and predict anisotropic parameters of sediments whose depositional environment is governed by compaction. In this study, we present several applications of rock physics modelling to anisotropic velocity model building. We show how both deterministic and stochastic rock physics modelling can be used for initial anisotropic velocity model building and as a constraint for anisotropic parameter estimation. In all cases, all predicted anisotropy models are physical and realizable in terms of effective medium theory and do not violate elasticity theory.

Entanglement transfer via XXZ Heisenberg chain with DM interaction

The role of spin-orbit interaction, arises from the Dzyaloshinski-Moriya anisotropic antisymmetric interaction, on the entanglement transfer via an antiferromagnetic XXZ Heisenberg chain is investigated. From symmetrical point of view, the XXZ Hamiltonian with Dzyaloshinski-Moriya interaction can be replaced by a modified XXZ Hamiltonian which is defined by a new exchange coupling constant and rotated Pauli operators. The modified coupling constant and the angle of rotations are depend on the strength of Dzyaloshinski-Moriya interaction. In this paper we study the dynamical behavior of the entanglement propagation through a system which is consist of a pair of maximally entangled spins coupled to one end of the chain. The calculations are performed for the ground state and the thermal state of the chain, separately. In both cases the presence of this anisotropic interaction make our channel more efficient, such that the speed of transmission and the amount of the entanglement are improved as this interaction is switched on. We show that for large values of the strength of this interaction a large family of XXZ chains becomes efficient quantum channels, for whole values of an isotropy parameter in the region $-2 \leq \Delta \leq 2$.

Development of Micro-Force Sensor Based on 3-RRR Parallel Mechanism

A new style micro-force sensor based on a 3-RRR parallel micro-motion stage which had been researching recent years was introduced in this paper. The sensor can be used in micro-force and micro-torque detection in precision engineering. The result and experience from 3-RRR micro-motion stage research bring this new idea. In the first place, the branched chain structure in motion stage needs to be simplified and improved to adapt to the requirement of sensor. Secondly, a mechanics model is constructed according to the sense organ structure. The Jacobin Matrix which is the most important matrix on parallel structure is analyzed and deduced. The relationship among key dimension is worked out through isotropy parameters. With the theory analysis, the final structure of sense organ is determined. The elastomeric sensor body was pasted with electrical-resistance strain gauges, after it was manufactured by Wire-EDM. Strain gauges employed Wheatstone bridge and amplifier AD620 to produce measuring data. Experiment has indicated that the new sensor is competent for micro-force detecting in X, Y direction and micro-moment around Z direction with high stability and reliability.

Improved test of Lorentz invariance in electrodynamics using rotating cryogenic sapphire oscillators

We present new results from our test of Lorentz invariance, which compares two orthogonal cryogenic sapphire microwave oscillators rotating in the lab. We have now acquired over 1 year of data, allowing us to avoid the short data set approximation (less than 1 year) that assumes no cancellation occurs between the ${\stackrel{\texttildelow{}}{\ensuremath{\kappa}}}_{e\ensuremath{-}}$ and ${\stackrel{\texttildelow{}}{\ensuremath{\kappa}}}_{o+}$ parameters from the photon sector of the standard model extension. Thus, we are able to place independent limits on all eight ${\stackrel{\texttildelow{}}{\ensuremath{\kappa}}}_{e\ensuremath{-}}$ and ${\stackrel{\texttildelow{}}{\ensuremath{\kappa}}}_{o+}$ parameters. Our result represents up to a factor of 10 improvement over previous nonrotating measurements (which independently constrained seven parameters) and is a slight improvement (except for ${\stackrel{\texttildelow{}}{\ensuremath{\kappa}}}_{e\ensuremath{-}}^{ZZ}$) over results from previous rotating experiments that assumed the short data set approximation. Also, an analysis in the Robertson-Mansouri-Sexl framework allows us to place a new limit on the isotropy parameter ${P}_{MM}=\ensuremath{\delta}\ensuremath{-}\ensuremath{\beta}+\frac{1}{2}$ of $9.4(8.1)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$, an improvement of a factor of 2.

Test of Lorentz Invariance in Electrodynamics Using Rotating Cryogenic Sapphire Microwave Oscillators

We present the first results from a rotating Michelson-Morley experiment that uses two orthogonally orientated cryogenic sapphire resonator oscillators operating in whispering gallery modes near 10 GHz. The experiment is used to test for violations of Lorentz invariance in the framework of the photon sector of the standard model extension (SME), as well as the isotropy term of the Robertson-Mansouri-Sexl (RMS) framework. In the SME we set a new bound on the previously unmeasured kappa(ZZ)(e-) component of 2.1(5.7) x 10(-14), and set more stringent bounds by up to a factor of 7 on seven other components. In the RMS a more stringent bound of -0.9(2.0) x 10(-10) on the isotropy parameter, P(MM) = delta-beta + 1 / 2 is set, which is more than a factor of 7 improvement.

Thermal and mechanical stresses in transversely isotropic coatings

Three-dimensional sliding contact and thermal contact stress analysis of transversely isotropic coatings on isotropic or transversely isotropic substrate is presented. Fourier transforms are used to obtain solutions for temperature rise and stresses. The solutions are illustrated with temperature rise and stresses in a single layered half-space induced by moving Hertz pressure. The effects of coating thickness, friction coefficient and Peclet number (dimensionless heat source velocity) on temperature rise and stresses in coated bodies are discussed. It is found that the effect of the isotropy parameter of coating (ratio of lateral thermal conductivity to normal thermal conductivity) on dimensionless surface temperature rise is not significant at higher Peclet numbers. It is also found that frictional heating can lower the maximum surface tensile stress. In low friction contacts, the thermal effects on Von Mises stress in the coating and the substrate are not particularly significant.

Empirical relationships between transverse isotropy parameters and Vp/Vs: Implications for AVO

The transverse isotropy (TI) parameters ε and δ control amplitude variation with offset (AVO) response at most angles of incidence used in exploration, although the value of δ is not usually known and is difficult to measure. Published measurements on TI materials show that there is a useful empirical correlation between [Formula: see text] and δ. The relationship between δ and [Formula: see text] can be simplified by assuming a linear relationship between [Formula: see text] and [Formula: see text]. Anellipticity parameter η also shows a useful empirical correlation with [Formula: see text]. The correlations imply that knowledge of [Formula: see text] is sufficient to make an estimate of the anellipticity of the P‐ and S‐wavefronts in a rock, regardless of the lithology. In this way, the effect of TI on the AVO response of a particular interface may be estimated in the absence of any more accurate data. The empirical relationships indicate that rocks tend to become more anelliptic with increasing [Formula: see text]. Rocks with [Formula: see text] smaller than about 1.8 tend to have zero to small positive values of δ, while rocks with [Formula: see text] larger than around 2 tend to have zero to medium negative δ values. Most previous work has assumed a positive value of δ in shales, but this is not necessarily true. If in fact the δ of a shale is negative ([Formula: see text] is around 2 or higher), and overlies a sandstone, the positive change in δ across the interface could cause a false negative AVO gas indicator. If shale with [Formula: see text] less than 1.8, as measured in organic‐rich and overpressured shales, overlies a water‐filled sandstone, this could cause a false positive AVO gas indicator. However, if the effect of TI can be estimated, then the chances of success for AVO analysis in correctly predicting the presence of hydrocarbons can be increased.

Determination of the gas-dynamic isotropy parameter for gas-particle scattering on a solid surface by laser-induced fluorescence in a cell

Determination of the gas-dynamic isotropy parameter for gas-particle scattering on a solid surface by laser-induced fluorescence in a cell

A quasi-2D nonlinear spin wave theory for the insulating undoped cuprates

We propose a nonlinear spin wave theory of anisotropic 3D (quasi-2D) quantum Heisenberg antiferromagnets, which is equivalent to or reduces to known spin wave theories of isotropy parameter δ takes the values 0 or 1, respectively. With δ increasing from zero also the Néel temperature T N increases from zero. Applied to the antiferromagnetism of the layer-like cuprate La 2CuO 4 it describes quite satisfactorily the existing experimental data of the Néel temperature, correlation length, and staggered magnetization of the material if J = 1034 K and δ = 4×10 −5.