scholarly journals Comments on frequency dependent AC conductivity in polymeric materials at low frequency regime

2019 ◽  
Vol 19 (4) ◽  
pp. 491-497 ◽  
Author(s):  
Christos Tsonos
Keyword(s):  
Ac Conductivity ◽  
Low Frequency ◽  
Polymeric Materials ◽  
Frequency Dependent ◽  
Frequency Regime

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.

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 Estimating the frequency dependent behavior of marine sediment sound speeds using low frequency aircraft sound

2008 ◽  
Vol 123 (5) ◽  
pp. 3349-3349
Author(s):  
Alireza Amiri‐Simkooei ◽  
Mirjam Snellen ◽  
Dick G. Simons ◽  
Michael Buckingham
Keyword(s):  
Marine Sediment ◽  
Low Frequency ◽  
Frequency Dependent ◽  
Sound Speeds ◽  
Dependent Behavior

scholarly journals A TEST FOR RARE MALE MATING ADVANTAGE WITH DROSOPHILA PSEUDOOBSCURA KARYOTYPES

Genetics ◽  
1984 ◽  
Vol 107 (4) ◽  
pp. 577-589
Author(s):  
Wyatt W Anderson ◽  
Celeste J Brown
Keyword(s):  
Mating Success ◽  
Low Frequency ◽  
Behavioral Observation ◽  
Drosophila Pseudoobscura ◽  
Male Mating ◽  
Frequency Dependent ◽  
Mating Advantage ◽  
Large Numbers ◽  
Laboratory Populations ◽  
Statistical Artifact

ABSTRACT Recent work has called into question the reality of the rare male mating advantage, pointing out that it could be a statistical artifact of marking flies for behavioral observation or of experimental bias in collecting males. We designed an experiment to test for rare male mating advantage that avoids these sources of bias. Large numbers of males of three Drosophila pseudoobscura karyotypes were allowed to mate with females of one karyotype in population cages. The females were then isolated before multiple mating occurred and their progeny used to diagnose the males that mated them. Populations were studied at five sets of male karyotypic frequencies. The mating success of the male homokaryotypes ST/ST and CH/CH, relative to that of the heterokaryotype ST/CH, was frequency dependent. Both ST/ST and CH/CH males displayed a statistically significant mating advantage at low frequency by comparision with their mating success in the midrange of karyotypic frequencies. Both male homokaryotypes also showed a significantly greater mating success at high homokaryotypic frequency than at intermediate frequencies, which is the same as saying that the heterokaryotype not only failed to show a rare male advantage but actually suffered a mating disadvantage at low frequency. We conclude that rare male mating advantage is not always an experimental or methodological artifact but does occur in laboratory populations of D. pseudoobscura. It may occur for some genotypes and not for others, however, and it may be only one of several forms of frequency-dependent mating behavior operating in a population.

scholarly journals Reproducibility of frequency-dependent low frequency fluctuations in reaction time over time and across tasks

PLoS ONE ◽  
2017 ◽  
Vol 12 (9) ◽  
pp. e0184476 ◽  
Author(s):  
Zan-Zan Liu ◽  
Hui-Jie Qu ◽  
Zhuo-Ling Tian ◽  
Meng-Jian Han ◽  
Yi Fan ◽  
...  
Keyword(s):  
Reaction Time ◽  
Low Frequency ◽  
Frequency Dependent ◽  
Frequency Fluctuations ◽  
Over Time
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