scholarly journals Numerical differentiation methods for the logarithmic derivative technique used in dielectric spectroscopy

2010 ◽  
Vol 4 (2) ◽  
pp. 87-93
Author(s):  
Henrik Haspel ◽  
Ákos Kukovecz ◽  
Zoltán Kónya ◽  
Imre Kiricsi
Keyword(s):  
Logarithmic Derivative ◽  
Low Frequency ◽  
Numerical Differentiation ◽  
Dielectric Measurement ◽  
Dielectric Relaxation Spectroscopy ◽  
Derivative Analysis ◽  
Dielectric Data ◽  
Frequency Regime ◽  
Influential Parameters ◽  
Convolution Method

In dielectric relaxation spectroscopy the conduction contribution often hampers the evaluation of dielectric spectra, especially in the low-frequency regime. In order to overcome this the logarithmic derivative technique could be used, where the calculation of the logarithmic derivative of the real part of the complex permittivity function is needed. Since broadband dielectric measurement provides discrete permittivity function, numerical differentiation has to be used. Applicability of the Savitzky-Golay convolution method in the derivative analysis is examined, and a detailed investigation of the influential parameters (frequency, spectrum resolution, peak shape) is presented on synthetic dielectric data.

scholarly journals Master curve generation and modeling of ac conductivity for Mn0.7+xZn0.3SixFe2–2xO4 spinel ferrite system

2017 ◽  
Vol 07 (03) ◽  
pp. 1750022 ◽  
Author(s):  
N. H. Vasoya ◽  
Prafulla K. Jha ◽  
K. G. Saija ◽  
J. A. Bhalodia ◽  
K. B. Modi
Keyword(s):  
Grain Boundaries ◽  
Ac Conductivity ◽  
Spinel Ferrite ◽  
Low Frequency ◽  
Compositional Dependence ◽  
Dielectric Data ◽  
Frequency Regime ◽  
Scaling Process ◽  
And Diffusion ◽  
Ferrite System

The compositional dependence of ac conductivity ([Formula: see text]), real ([Formula: see text]′) and imaginary ([Formula: see text]′′) parts of complex electric conductivity ([Formula: see text]*) was investigated as a function of temperature ([Formula: see text]) and frequency ([Formula: see text] for Mn[Formula: see text]Zn[Formula: see text]SixFe[Formula: see text]O4, [Formula: see text], 0.1, 0.2 and 0.3 spinel ferrite system. The compositional dependence of lattice constant values suggested that the most of the substituted Si[Formula: see text]-ions reside at grain boundaries and only a few Si-ions are inside grains. The variation of [Formula: see text], [Formula: see text], [Formula: see text] is explained on the basis of segregation and diffusion of Si[Formula: see text] ions at grain boundaries and grains, respectively, and the electrode effect. Thermal variation of ac conductivity at fixed frequency suggested two different mechanisms which could be responsible for conduction in the system. It is found that [Formula: see text]* is not the preferred presentation for dielectric data and the scaling process of real part of conductivity by normalized frequency and the scaled frequency were found unsuccessful. The fitting results of ac conductivity data with path percolation approximation were found suitable in low-frequency regime while in high-frequency regime, effective medium approximation (EMA) was found successful.

scholarly journals Influence of Li2CO3 addition on electrical and magnetic properties of Ni0.6Mg0.4Fe2O4

2020 ◽  
Vol 10 (03) ◽  
pp. 2050003
Author(s):  
M. R. Hassan ◽  
M. T. Islam ◽  
M. N. I. Khan
Keyword(s):  
Magnetic Properties ◽  
Single Phase ◽  
Low Frequency ◽  
Solid State Reaction Method ◽  
Charge Carriers ◽  
X Ray Diffraction ◽  
X Ray ◽  
Electrical And Magnetic Properties ◽  
Frequency Regime ◽  
Xrd Patterns

In this research, influence of adding Li2CO3 (at 0%, 2%, 4%, 6%) on electrical and magnetic properties of [Formula: see text][Formula: see text]Fe2O4 (with 60% Ni and 40% Mg) ferrite has been studied. The samples are prepared by solid state reaction method and sintered at 1300∘C for 6[Formula: see text]h. X-ray diffraction (XRD) patterns show the samples belong to single-phase cubic structure without any impurity phase. The magnetic properties (saturation magnetization and coercivity) of the samples have been investigated by VSM and found that the higher concentration of Li2CO3 reduces the hysteresis loss. DC resistivity increases with Li2CO3 contents whereas it decreases initially and then becomes constant at lower value with temperature which indicates that the studied samples are semiconductor. The dielectric dispersion occurs at a low-frequency regime and the loss peaks are formed in a higher frequency regime, which are due to the presence of resonance between applied frequency and hopping frequency of charge carriers. Notably, the loss peaks are shifted to the lower frequency with Li2CO3 additions.

MACROSCOPICALLY QUANTIZED HOLE STATES IN La2-χSrχCuO4-δ FILM CRYSTAL OBSERVABLE UP TO ROOM TEMPERATURE

2001 ◽  
Vol 15 (09) ◽  
pp. 1239-1252 ◽  
Author(s):  
M. SUGAHARA ◽  
S. OGI ◽  
K. ARAKI ◽  
R. SUGIURA
Keyword(s):  
Doping Level ◽  
Low Frequency ◽  
Side Surface ◽  
Life Time ◽  
Cell Number ◽  
Polarization Property ◽  
Dielectric Measurement ◽  
Charge Motion ◽  
Macroscopic Quantum ◽  
Macroscopic Quantum Effects

Theoretical study of multi-layered CuO 2 surfaces with localization potential shows that (i) special stable macroscopic quantum states appear when [Formula: see text], where χ is the doping level and G is the unit-cell number, and that (ii) the physical phenomena related to ‖c charge motion takes place just as expected in the fictitious situation where whole uniformly doped holes concentrate in one-side surface. In the dielectric measurement of doping-level dependence and film-thickness dependence on c-oriented La 2-χ Sr χ CuO 4-δ film, we find that (a) anomalous low-frequency polarization is enhanced when a scaling parameter χG is near to [Formula: see text], that (b) quasi-static measurement of the polarization property in low doped film shows two typical characteristics explicable by the fictitious charge concentrations, and that (c) ‖c small-voltage conduction measurement on low doped film also shows two types of characteristic which are switched each other triggered by laser irradiation. Since these macroscopic quantum effects with plural levels with very long life time are observable even up to room temperatures, they may be useful in quantum computing application.

Design and optimization of acoustic liners with a shear grazing flow: OPAL software platform applications

2021 ◽  
Vol 263 (6) ◽  
pp. 152-163
Author(s):  
Remi Roncen ◽  
Pierre Vuillemin ◽  
Patricia Klotz ◽  
Frank Simon ◽  
Fabien Méry ◽  
...  
Keyword(s):  
Noise Reduction ◽  
Low Frequency ◽  
Small Scale ◽  
Software Platform ◽  
Total Size ◽  
Linearized Euler Equations ◽  
Design And Optimization ◽  
Acoustic Liners ◽  
Frequency Regime ◽  
Grazing Flow

In the context of noise reduction in diverse applications where a shear grazing flow is present (i.e., engine nacelle, jet pump, landing gear), improved acoustic liner solutions are being sought. This is particularly true in the low-frequency regime, where space constraints currently limit the efficiency of classic liner technology. To perform the required multi-objective optimization of complex meta-surface liner candidates, a software platform called OPAL was developed. Its first goal is to allow the user to assemble a large panel of parallel/serial assembly of unit acoustic elements, including the recent concept of LEONAR materials. Then, the physical properties of this liner can be optimized, relatively to given weighted objectives (noise reduction, total size of the sample, weight), for a given configuration. Alternatively, properties such as the different impedances of liner unit surfaces can be optimized. To accelerate the process, different nested levels of optimization are considered, from 0D analytical coarse designs in order to reduce the parameter space, up to 2D plan or axisymmetric high-order Discontinuous Galerkin resolution of the Linearized Euler Equations. The presentation will focus on the different aspects of liner design considered in OPAL, and present an application on different samples made for a small scale aeroacoustic bench.

scholarly journals Spacecraft and interplanetary contributions to the magnetic environment on-board LISA Pathfinder

2020 ◽  
Vol 494 (2) ◽  
pp. 3014-3027
Author(s):  
M Armano ◽  
H Audley ◽  
J Baird ◽  
P Binetruy ◽  
M Born ◽  
...  
Keyword(s):  
Magnetic Field ◽  
New Technologies ◽  
Magnetic Measurements ◽  
Magnetic Measurement ◽  
Low Frequency ◽  
Lisa Pathfinder ◽  
Frequency Regime ◽  
The Magnetic Field ◽  
Instrument Sensitivity ◽  
Stationary Component

ABSTRACT LISA Pathfinder (LPF) has been a space-based mission designed to test new technologies that will be required for a gravitational wave observatory in space. Magnetically driven forces play a key role in the instrument sensitivity in the low-frequency regime (mHz and below), the measurement band of interest for a space-based observatory. The magnetic field can couple to the magnetic susceptibility and remanent magnetic moment from the test masses and disturb them from their geodesic movement. LPF carried on-board a dedicated magnetic measurement subsystem with noise levels of 10 $\rm nT \ Hz^{-1/2}$ from 1 Hz down to 1 mHz. In this paper we report on the magnetic measurements throughout LPF operations. We characterize the magnetic environment within the spacecraft, study the time evolution of the magnetic field and its stability down to 20 μHz, where we measure values around 200 $\rm nT \ Hz^{-1/2}$, and identify two different frequency regimes, one related to the interplanetary magnetic field and the other to the magnetic field originating inside the spacecraft. Finally, we characterize the non-stationary component of the fluctuations of the magnetic field below the mHz and relate them to the dynamics of the solar wind.

scholarly journals Sub-wavelength focusing of acoustic waves in bubbly media

2017 ◽  
Vol 473 (2208) ◽  
pp. 20170469 ◽  
Author(s):  
Habib Ammari ◽  
Brian Fitzpatrick ◽  
David Gontier ◽  
Hyundae Lee ◽  
Hai Zhang
Keyword(s):  
Acoustic Waves ◽  
Wave Scattering ◽  
Low Frequency ◽  
Scattering Function ◽  
Point Scatterer ◽  
Layer Potential ◽  
Spherical Bubble ◽  
Acoustic Wave Scattering ◽  
Frequency Regime ◽  
Sub Wavelength

The purpose of this paper is to investigate acoustic wave scattering by a large number of bubbles in a liquid at frequencies near the Minnaert resonance frequency. This bubbly media has been exploited in practice to obtain super-focusing of acoustic waves. Using layer potential techniques, we derive the scattering function for a single spherical bubble excited by an incident wave in the low frequency regime. We then propose a point scatterer approximation for N bubbles, and describe several numerical simulations based on this approximation, that demonstrate the possibility of achieving super-focusing using bubbly media.

Magnetoimpedance of Epitaxial Y3Fe5O12 (001) Thin Film in Low-Frequency Regime

2020 ◽  
Vol 12 (37) ◽  
pp. 41802-41809
Author(s):  
Rohit Medwal ◽  
Ushnish Chaudhuri ◽  
Joseph Vimal Vas ◽  
Angshuman Deka ◽  
Surbhi Gupta ◽  
...  
Keyword(s):  
Thin Film ◽  
Low Frequency ◽  
Frequency Regime

scholarly journals Greybody Factors for Schwarzschild Black Holes: Path-Ordered Exponentials and Product Integrals

Universe ◽  
2018 ◽  
Vol 4 (9) ◽  
pp. 93 ◽  
Author(s):  
Finnian Gray ◽  
Matt Visser
Keyword(s):  
Black Holes ◽  
High Frequency ◽  
Low Frequency ◽  
Intermediate Frequency ◽  
General Context ◽  
Matrix Formalism ◽  
Barrier Penetration ◽  
Frequency Regime ◽  
Transfer Matrix Formalism ◽  
Numerical Approaches

In earlier work concerning the sparsity of the Hawking flux, we found it necessary to re-examine what is known regarding the greybody factors of black holes, with a view to extending and expanding on some old results from the 1970s. Focusing specifically on Schwarzschild black holes, we have re-calculated and re-assessed the greybody factors using a path-ordered-exponential approach, a technique which has the virtue of providing a pedagogically useful semi-explicit formula for the relevant Bogoliubov coefficients. These path-ordered-exponentials, being based on a variant of the “transfer matrix” formalism, are closely related to so-called “product integrals”, leading to quite straightforward and direct numerical evaluation, while side-stepping any need for numerically solving the relevant ordinary differential equations. Furthermore, while considerable analytic information is already available regarding both the high-frequency and low-frequency asymptotics of these greybody factors, numerical approaches seem better adapted to finding suitable “global models” for these greybody factors in the intermediate frequency regime, where most of the Hawking flux is actually concentrated. Working in a more general context, these path-ordered-exponential techniques are also likely to be of interest for generic barrier-penetration problems.

scholarly journals Period spacing of gravity modes strongly affected by rotation

2017 ◽  
Vol 598 ◽  
pp. A105 ◽  
Author(s):  
V. Prat ◽  
S. Mathis ◽  
F. Lignières ◽  
J. Ballot ◽  
P.-M. Culpin
Keyword(s):  
Internal Rotation ◽  
Low Frequency ◽  
Rotation Vector ◽  
Mathematical Form ◽  
Be Stars ◽  
Rotating Stars ◽  
Perturbative Methods ◽  
Frequency Regime ◽  
Spectral Patterns ◽  
Rapidly Rotating Stars

Context. As of today, asteroseismology mainly allows us to probe the internal rotation of stars when modes are only weakly affected by rotation using perturbative methods. Such methods cannot be applied to rapidly rotating stars, which exhibit complex oscillation spectra. In this context, the so-called traditional approximation, which neglects the terms associated with the latitudinal component of the rotation vector, describes modes that are strongly affected by rotation. This approximation is sometimes used for interpreting asteroseismic data, however, its domain of validity is not established yet. Aims. We aim at deriving analytical prescriptions for period spacings of low-frequency gravity modes strongly affected by rotation through the full Coriolis acceleration (i.e. without neglecting any component of the rotation vector), which can be used to probe stellar internal structure and rotation. Methods. We approximated the asymptotic theory of gravito-inertial waves in uniformly rotating stars using ray theory described in a previous paper in the low-frequency regime, where waves are trapped near the equatorial plane. We put the equations of ray dynamics into a separable form and used the Einstein-Brillouin-Keller (EBK) quantisation method to compute modes frequencies from rays. Results. Two spectral patterns that depend on stratification and rotation are predicted within this new approximation: one for axisymmetric modes and one for non-axisymmetric modes. Conclusions. The detection of the predicted patterns in observed oscillation spectra would give constraints on internal rotation and chemical stratification of rapidly rotating stars exhibiting gravity modes, such as γ Doradus, SPB, or Be stars. The obtained results have a mathematical form that is similar to that of the traditional approximation, but the new approximation takes the full Coriolis, which allows for propagation near the centre, and centrifugal accelerations into account.

Sign in / Sign up

Export Citation Format

Share Document