Frequency Dependence

Partial discharge (PD) spectral response to variations in the supply voltage frequency was experimentally investigated through laboratory-based tests. The PD spectral content of each defect type responded uniquely to variations in the sinusoidal supply voltage frequency in the range 20 to 400 Hz. The findings are interpreted using the theory of space charge dynamics in PD mechanisms. Prospective diagnostic applications

The electrical properties of double perovskite Ho2NiTiO6 (HNT) are investigated by impedance spectroscopy in the temperature range 30–420 °C and frequency range 100 Hz to 1 MHz. The X-ray diffraction analysis reveals that the compound crystallizes in monoclinic phase. The imaginary part of impedance (Z″) as a function of frequency shows Debye type relaxation. The frequency dependence of Z″ peak is found to obey an Arrhenius law with an activation energy of 0.129 eV. Impedance data presented in the Nyquist plot (Z″ vs. Z′) are used to identify an equivalent circuit and to know the bulk and interface contributions. The complex impedance analysis of HNT exhibits the appearance of both the grain and grain-boundary contribution. The results of bulk ac conductivity as a function of temperature and frequency are presented. The activation energy (0.129 eV), calculated from the slope of log τ versus 103/T plot, is found to be the nearly same as calculated (0.130 eV) from dc conductivity. The frequency dependent conductivity spectra obey the power law.

Magnetic soils can seriously hamper the performance of electromagnetic sensors for the detection of buried land mines and unexploded ordnance (UXO). Soils formed on basaltic substrates commonly have large concentrations of ferrimagnetic iron oxide minerals, which are the main cause of soil magnetic behavior. Previous work has shown that viscous remanent magnetism (VRM) in particular, which is caused by the presence of ferrimagnetic minerals of different sizes and shapes, poses a large problem for electromagnetic surveys. The causes of the variability in magnetic soil properties in general and VRM in particular are not well understood. In this paper we present the results of laboratory studies of soil magnetic properties on three Hawaiian Islands: O"ahu, Kaho"olawe, and Hawaii. The data show a strong negative correlation between mean annual precipitation and induced magnetization, and a positive correlation between mean annual precipitation and the frequency dependent magnetic behavior. Soil erosion, which reduces the thickness of the soil cover, also influences the magnetic properties.

We report the structural and magnetic properties of the La1−xTbxMn1/2Sc1/2O3 series. LaMn1/2Sc1/2O3 shows a long range ferromagnetic ordering in agreement with a fully polarized Mn-sublattice. The substitution of La with Tb produces structural changes which affect the magnetic properties. This substitution leads to a contraction in the unit cell volume that mainly reduces the M–O–M bond angle (M = Mn,

Both small amplitude oscillatory and steady shear measurements were carried out at 25 °C, 50 °C, and 75 °C in order to determine the rheological properties of the mixtures of flaxseed gum (0.1–0.5%) and native maize starch (3%). It was found that the apparent viscosities of the samples increased with the increasing of flaxseed gum concentration. The apparent viscosities of the samples were fitted well to the power law model (the values of R2 were between 0.954 and 0.999). The consistency index (K) of the gum–starch mixtures increased with the increasing of flaxseed gum concentration. The gum–starch mixtures showed gel-like behavior since the storage modulus (G′) was much larger than the loss modulus (G″) and the frequency dependence of both modulus was not significant. The G′ and G″ of the gum–starch mixtures was increased with the increasing of flaxseed gum concentration. The influence of temperature was more significant for the flaxseed gum–maize starch mixtures compared to maize starch gel.