Tangent Measurements Research Articles

High temperature dielectric constant and loss tangent measurements [advertisement

High temperature dielectric constant and loss tangent measurements [advertisement

Computation of Strain State in a ${\rm Nb}_{3}{\rm Sn}$ Strand Using Nonlinear Hierarchical Models

The large range of length scales present within accelerator magnets suggests the incorporation of a hierarchical structure into computational models. Evaluation of the strain state present within the superconducting filaments is necessary in order to determine the critical current of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn based magnets. As part of an ongoing investigation at LBNL, a three-dimensional nonlinear multiscale model is developed to investigate the behavior of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands. The strain state in the superconducting filaments is examined by simulating a cool down from reaction to 4.2 K. The effects of strand geometry on the final strain state are also explored. The validity of the model is tested through the comparison of the predicted moduli to experimental tangent measurements.

High temperature dielectric constant and loss tangent measurements [advertisement

High temperature dielectric constant and loss tangent measurements [advertisement

Loss tangent imaging: Theory and simulations of repulsive-mode tapping atomic force microscopy

An expression for loss tangent measurement of a surface in amplitude modulation atomic force microscopy is derived using only the cantilever phase and the normalized cantilever amplitude. This provides a direct measurement of substrate compositional information that only requires tuning of the cantilever resonance to provide quantitative information. Furthermore, the loss tangent expression incorporates both the lost and stored energy into one term that represents a fundamental interpretation of the phase signal in amplitude modulation imaging. Numerical solutions of a cantilever tip interacting with a simple Voigt modeled surface agree with the derived loss tangent to within a few percent.

High temperature dielectric constant and loss tangent measurements [advertisement

High temperature dielectric constant and loss tangent measurements [advertisement

Dielectric Anomaly in La0.7Sr0.3Fe0.05Mn0.95O3/BaTiO3 Composite

La0.7Sr0.3Fe0.05Mn0.95O3/BaTiO3 composite was synthesized and characterized by X-ray diffraction (XRD), transmission electron microscopic (TEM), ac conductivity (σac) and dielectric measurements (ϵr). The crystal structure of this composite have been determined by the Rietveld refinement powder XRD data at room temperature which confirmed by TEM. The dielectric constant (ϵr), dielectric loss (tan δ) and ac conductivity (σac) was investigated in the frequency (0.120–100 kHz) and temperature (293–401 K) The ac conductivity and loss tangent (tan δ) measurements conclude that the conduction mechanism in this sample is due to small polaron hopping. The composite sample exhibited broad dielectric anomalies in the vicinity of the ferroelectric-to-paraelectric transition temperature. The Curie-Weiss law was found to be valid at a temperature above the transition temperature.

UNCERTAINTY ESTIMATION IN COMPLEX PERMITTIVITY MEASUREMENTS BY SHIELDED DIELECTRIC RESONATOR TECHNIQUE USING THE MONTE CARLO METHOD

In this paper, we estimate the uncertainty in complex per- mittivity measurements performed in a shielded dielectric resonator, by using the Monte Carlo Method. We selected this approach since the theoretical expressions required to interpret the experimental results are highly non-linear. Furthermore the resonant frequency of the sys- tem and its quality factor are highly correlated. Thus we propose a model for the measurement process which considers the major sources of uncertainty previously reported in published experimental results. The proposed model combined with the Monte Carlo method was used to propagate the probability distributions of each uncertainty contri- bution, obtaining a) the approximate probability density function for the measured complex permittivity, and b) the estimated expanded uncertainty for the mode TE011. The results show that this procedure leads to small uncertainty intervals for the real part of the dielectric permittivity, while it is not very reliable in the loss tangent measure- ment. Additionally, for each input quantity, we calculated the standard deviation in the experimental results produced independently by each uncertainty contribution.

Tangent measures of non-doubling measures

AbstractWe construct a non-doubling measure on the real line, all tangent measures of which are equivalent to Lebesgue measure.

Harmonic polynomials and tangent measures of harmonic measure

We show that on an NTA domain if each tangent measure to harmonic measure at a point is a polynomial harmonic measure then the associated polynomials are homogeneous. Geometric information for solutions of a two-phase free boundary problem studied by Kenig and Toro is derived.

Concentrated monotone measures with non-unique tangential behavior in ℝ3

We show that for every ɛ > 0 there is a set A ⊂ ℝ3 such that H1 ⌞A is a monotone measure, the corresponding tangent measures at the origin are non-conical and non-unique and H1 ⌞A has the 1-dimensional density between 1 and 2+ɛ everywhere in the support.

Phase pure synthesis of BiFeO 3 nanopowders using diverse precursor via co-precipitation method

Amorphous powder of BiFeO 3 (BFO) was synthesized at low-temperature (80 °C) by co-precipitation method. Optimal synthesis conditions for phase pure BFO were obtained. Powders were calcined in the temperature range from 400 to 600 °C for 1 h. Iso-statically pressed powder was sintered at 500 °C for 2 h. Differential scanning calorimetric thermo-gram guided for phase transition, crystallization and melting temperatures. X-ray diffraction confirmed the amorphous nature of as synthesized powder and phase formation of calcined powders. Calcination at temperature ≥400 °C resulted in nano crystalline powders with perovskite structure. Average crystallite size increased with the increase in calcination temperature. Scanning electron microscopic studies revealed dense granular microstructure of the sintered samples. The sintered samples exhibited high dc resistivity at room temperature which decreased with the increase in temperature. Dielectric constant, dielectric loss tangent and ac conductivity measurements were carried out in the frequency range (10 Hz to 2 MHz). The samples responded weak electric and magnetic polarization at room temperature with unsaturated and hysteresis free loops, respectively.

Structural, Dielectric, and Magnetic Characterization of Nanocrystalline Ni–Co Ferrites

Spinel ferrites containing Nickel and Cobalt of composition with nominal formula Ni(1−x)Co(x)Fe2O4 (x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5) prepared by the coprecipitation method are reported. The single phase spinel formation of ferrites was confirmed by X-ray diffraction techniques. The lattice constants (ath) were calculated based on the ionic radii of the constituents. The calculated lattice constants are smaller than the measured, because for calculations ideal ionic radii are used. The particle size calculated from the Scherrer formula varied within 15 to 33 nm. The dielectric constant and dielectric loss tangent measurement were carried out at room temperature as a function of frequency from 100 Hz to 3 MHz. Both the dielectric constant and dielectric loss tangent increased with increase in cobalt concentration. Ferrimagnetic transition temperature as a function of Co concentration was measured with the low field ac susceptibility apparatus. The ferrimagnetic transition (Tc) was observed in the temperature range 573 to 720 K. The Tc decreased with the addition of Co concentration. The effect of Co concentration on the magnetic properties was investigated using a vibrating sample magnetometer (VSM). It was found that both magnetic saturation (Ms) and coercivity (Hc) increase with Co concentration.

Dielectric loss and magnetic behavior of combustion synthesized ferrite-ferroelectric composites

Spinel-type nickel cadmium ferrite and perovskite-type barium strontium titanate ferroelectric and their composites have been grown by combustion route. The variation of loss tangent with frequency in the range 100 Hz to 1 MHz was studied. The ac conductivity was derived from dielectric constant (e′) and loss tangent (tanδ) measurements. The nature of conduction is discussed on the basis of small polaron hopping model. The dependence of saturation magnetization (Ms) and remanent magnetization (Mr) of the composites is also reported.

Characterizations of intrinsic rectifiability in Heisenberg groups

We define rectifiable sets in the Heisenberg groups as countable unions of Lipschitz images of subsets of a Euclidean space, in the case of low-dimensional sets, or as countable unions of subsets of intrinsic C 1 surfaces, in the case of low-codimensional sets. We characterize both low-dimensional rectifiable sets and low codimensional rectifiable sets with positive lower density, in terms of almost everywhere existence of approximate tangent subgroups or of tangent measures.

English

The effect of aging on Sr 2+ modified Lead Zirconate Titanate (PSZT) ceramics have been studied. Aging was assessed by the measurement of dielectric constant and dielectric loss tangent as a function of time and temperature. Dielectric constant and dielectric loss tangent measured at different temperature range. Absolute rate of aging and relative rate of aging was determined. The PSZT ceramic showed sharp dielectric peak at temperature 300 o C. The result showed that with increased temperature both the dielectric constant and rate of aging increased. Defence Science Journal, 2010, 60(6), pp.683-686 , DOI:http://dx.doi.org/10.14429/dsj.60.55

Influence of copper substitution on magnetic and electrical properties of MgCuZn ferrite prepared by microwave sintering method

Polycrystalline MgCuZn ferrites with chemical formula Mg 0.50-xCu xZn 0.50Fe 2O 4 ( x = 0.00, 0.05, 0.10, 0.15, 0.20, 0.25 and 0.30) were prepared by microwave sintering method. These powders were calcined, compacted and sintered at 950 °C for 30 min. Structural, microstructural and elemental analyses were carried out using X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray spectrometry (EDS), respectively. The lattice parameter is found to increase with increasing copper content. A remarkable densification is observed with the addition of Cu ions in the ferrites. The sintered ferrite was characterized for initial permeability, dielectric constant and dielectric loss tangent and ac conductivity measurements. The temperature variation of the initial permeability of these samples was carried out from 30 °C to 200 °C. The dielectric constant, dielectric loss tangent and ac conductivity have been measured in the frequency range of 100 Hz to 1 MHz. Initial permeability and dielectric constant were found to increase and dielectric loss decreased with Cu substitution for Mg, up to x = 0.20. The ferrite powder prepared is suitable for the application in multilayer chip inductor due to its low-temperature sinterability, good magnetic properties and low loss at high frequency.

Condition Assessment of Power Transformers Using Loss Tangent Measurements

Mineral oil, cellulose paper and pressboard are the main insulation materials in a power Transformer. During service, increase of moisture, as the by -products ageing and increases the risk of insulation failure. This paper presents the possibility to use loss tangent (or power factor) and capacitance (tanδ and C) measurements as an estimate of the 'wetness' of aged transformer insulation. Firstly, oil, paper and pressboard samples were aged under laboratory conditions and their tan S and dielectric constant (er) values were measured. Applying the tanδ and er obtained onto a transformer insulation model, the tanδ and C of transformer were calculated and the effects of insulation geometry, moisture content (MC) of pressboard, oil conductivity (σ oil) and insulation temperature under test were established. It was found that tanδ and C values of a transformer strongly dep ended on its insulation geometry and the temperature. If the temperature is fixed, the change of tanδ value of a transformer can be a direct measure of moisture in pressboard for 'wet' and 'extremely wet' conditions. For a 'dry ' transformer, the σoil oil value is needed as an additional known parameter in order to estimate accurately the moisture in pressboard.

Tape Casting and Dielectric Properties of Zn2Te3O8‐Based Ceramics with an Ultra‐Low Sintering Temperature

The suitability of dielectric ceramics made of zinc tellurate (Zn2Te3O8) and titanium dioxide (TiO2) with an ultra‐low sintering temperature (650°C) for tape casting and thus for the multimodule technique with Al electrodes was investigated. The properties of the tape before and after sintering as well as the amount of organic additives for the casting process and a thermal analysis of the tape up to 1000°C are reported. In addition, electrodes on a multilayer module made on stacked tapes were prepared using Al paste and postfiring, followed by relative permittivity and loss tangent measurements to verify the electrical performance of the whole structure. The dielectric properties of the stacked module without any electrodes were also measured. The results show that the composition is well suited for the tape process but extra care should be taken especially with the proper sintering temperature for optimized electrical performance.

Anomalously high capacitance of β-rhombohedral boron induced by structural defects

Capacitance and dielectric loss tangent measurements have been carried out for β-rhombohedral boron within the frequency range 102 – 104 Hz and temperature interval 77 – 373 K. Different specimens were studied: high-purity macrocrystals, vapor-liquid-grown faceted crystals, zone-melted single crystals, and crucible-melted polycrystals. Within the whole ranges of measurements, the capacitance of all samples was 10–60 times larger than their geometric capacitance. Temperature dependences of the capacitance reveal two-level step-like behavior. Location of levels is independent from the applied electric field frequency, but at higher frequencies, the capacitance steps shift to lower temperatures. For all frequencies, an abrupt rise in capacitance takes place at one and same temperature ∼ 290 K. At low temperature, dielectric losses are negligible, but they increase towards the room temperature. At ∼ 290 K (i.e., simultaneously with the abrupt rise in capacitance) their value abruptly falls down. Dielectric properties of β-rhombohedral boron are discussed on the basis of generalized barrier model of the heterogeneous semiconductor within its three-layer version. Planar defects like twins and stacking faults characteristic for real crystals are assumed to produce local elastic stresses sufficient for the local lowering in conductivity due to the piezoresistive effect. Consequently, layers adjacent to the planar defects should represent low-conducting inclusions in the relatively high-conducting matrix. In addition, the lesser-conducting barrier layers should appear at their boundaries. Effect at ∼ 290 K seems to be related with a symmetry-restoring phase transition driven by the occupation patterns of certain atomic sites in β-rhombohedral crystalline boron lattice.

Comparison of QTinno, a fully automated electrocardiographic analysis program, to semiautomated electrocardiographic analysis methods in a drug safety study in healthy subjects

Background Improved automated methods for electrocardiographic (ECG) analysis are needed, particularly for drug development purposes. Objectives This study compared a novel fully automated method for ECG analysis (QTinno; NewCardio, Santa Clara, CA) to 2 semiautomated digital methods: global measurement from the earliest QRS onset to the latest T-wave offset on representative superimposed beats (global) and tangent measurement on 3 consecutive beats in one lead (tangent). Methods All 3 methods were used to determine uncorrected and rate-corrected QT interval duration (QT and QTcF) and related metrics in 1422 digital 12-lead ECGs from a phase 1 drug study. Global and tangent annotations were manually adjusted by the same 3 cardiologists wherever necessary. No adjustments were made in QTinno determinations. Results QTinno returned QTcF change from time-matched baseline (ΔQTcF) that differed minimally from both global and tangent methods (mean pairwise difference: 0.1 millisecond between QTinno and global, 1.1 milliseconds between QTinno and tangent). The average absolute QT and QTcF intervals by QTinno were approximately 5 milliseconds longer than global and 25 milliseconds longer than by tangent. QTinno had lower intrinsic variability for ΔQTcF than either global or tangent (between-subject SD: QTinno 4.0 milliseconds, global 5.6 milliseconds, tangent 6.4 milliseconds; within-subject SD: QTinno 4.8 milliseconds, global 7.4 milliseconds, tangent 10.6 milliseconds). All methods were robust in detecting the largest placebo-adjusted mean time-matched ΔQTcF (15-25 milliseconds) induced by study drug. Conclusions The methods show good agreement for drug-induced QTc prolongation. Lower intrinsic variability of ΔQTcF by QTinno could facilitate smaller sample sizes or increase study power in thorough QTc studies.