Low-frequency dielectric dispersion and microwave dielectric properties of dry and water-saturated limestones of Jodhpur region

Geophysics ◽  
2006 ◽  
Vol 71 (5) ◽  
pp. G269-G277 ◽  
Author(s):  
R. J. Sengwa ◽  
A. Soni
Keyword(s):  
Dielectric Constant ◽  
Chemical Composition ◽  
Bulk Density ◽  
Low Frequency ◽  
Dielectric Dispersion ◽  
Complex Dielectric Constant ◽  
Frequency Limit ◽  
Microwave Dielectric ◽  
Limestone Sample ◽  
Water Saturated

We investigated the complex dielectric constant of 17 different grades of dry and water-saturated limestone samples from the Jodhpur region in the frequency range of [Formula: see text] to [Formula: see text] and also at [Formula: see text] at room temperature. The Cole-Cole dielectric dispersion model was used to compute the values of low-frequency-limit dielectric constant, high-frequency-limit dielectric constant, dielectric strength, and principal value of the relaxation time for each dry limestone sample. The chemical composition, sample bulk density, and porosity of each sample studied were determined to learn which of these factors govern their dielectric parameters. Analysis of the low-frequency dielectric constant confirms that chemical composition and bulk density are the ma-jor factors governing the dielectric constant values; but for water-saturated samples, the frequency-dependent dielectric constant values are also sensitive to porosity and grain size. The ac conductivity of all of the dry samples increases with the increase in frequency from [Formula: see text] to [Formula: see text], but water-saturated samples have comparatively high conductivity; some samples have values independent of the frequency. The microwave dielectric constant of dry samples depends mainly on the amount of the constituents of the oxide, their chemical composition, and sample bulk density. The contribution of the measured dielectric-constant values of each oxide present in the sample is identified by using their density-reduced values of the dielectric constant. The porosity-dependent mixing equations for solid and fluid components of the system were also found suitable for determining the dielectric constant of water-saturated limestone samples at microwave frequency.

scholarly journals The Effect of Bulk Density on Emission Behavior of Soil at Microwave Frequencies

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
V. K. Gupta ◽  
R. A. Jangid
Keyword(s):  
Dielectric Constant ◽  
Bulk Density ◽  
Soil Surface ◽  
Microwave Remote Sensing ◽  
Microwave Frequency ◽  
Soil Samples ◽  
Microwave Emission ◽  
Complex Dielectric Constant ◽  
Semiempirical Model ◽  
Surface Boundary

Dielectric constant and dielectric loss (ε′ and ε″) of different soil samples with bulk densities varying from 1.3 to 2.0 gm/cm3 are determined at a single microwave frequency 9.78 GHz and at temperature 37.0°C. Different bulk densities of same soil are achieved by filling the wave guide cell with an equal volume but a different mass of soil. Further, ε′ and ε″ of these soil samples are also estimated by semiempirical model and compared with the experimental results. The values of ε′ and ε″ increase as bulk density of the soil increases. In view of microwave remote sensing, the Fresnel reflectivity of soil is computed from the knowledge of the complex dielectric constant and the surface boundary condition. Using Kirchhoff’s reciprocity theorem the microwave emissivity is estimated from Fresnel reflectivity of the surface. It is observed that the microwave emission from the soil surface inhibits as bulk density of soil increases. Further, the roughness of soil surface has been taken into consideration in the emissivity computation and observed that the emissivity increases with increasing roughness of the soil surface.

Sintering, Microstructure and Dielectric Properties of Ca-Al-B-Si-O Glass/Al2O3 Composites with Various SiO2 Content

2011 ◽  
Vol 130-134 ◽  
pp. 1516-1519
Author(s):  
Ming Liu ◽  
Hong Qing Zhou ◽  
Hai Kui Zhu ◽  
Min Liu ◽  
Jian Xin Zhao
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Silicon Dioxide ◽  
Bulk Density ◽  
Microwave Dielectric Properties ◽  
Microwave Dielectric ◽  
Tan Δ ◽  
Silicon Dioxide Content

The effects of silicon dioxide addition on the sintering, microstructure and microwave dielectric properties of Ca-Al-B-Si-O glass/Al2O3 composites were investigated. Results show that: Increasing the silicon dioxide content in the glass leads to the corresponding rise of bulk density, dielectric constant of the LTCC materials and the decrease of its dielectric loss and porosity. A bulk density of 2.92 g·cm-3, a porosity of 0.2%, aεr value of 7.11 and a tan δ value of 0.00096(measured at 10 MHz) are obtained for 68 wt% silicon dioxide of the samples sintered at 875°C for 30 min.

scholarly journals Microwave dielectric properties of Na+-substituted CaMg0.9Li0.2Si2O6 ceramics

2022 ◽  
Vol 355 ◽  
pp. 01024
Author(s):  
Fangyi Huang ◽  
Hua Su ◽  
Xiaoli Tang
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Bulk Density ◽  
Microwave Dielectric Properties ◽  
Solid State Reaction Method ◽  
Low Dielectric Constant ◽  
Second Phase ◽  
Experimental Sample ◽  
Low Dielectric ◽  
Microwave Dielectric

Ceramics with low dielectric constant are widely used in high frequency substrates. The low temperature sintered CaMg0.9-xNa2xLi0.2Si2O6(x = 0–0.05 and 0.1) ceramics with low dielectric constant and dielectric loss were prepared by the traditional solid-state reaction method, with 0.5wt%LBSCA additive. The XRD patterns of the samples were obtained by X-ray diffraction and it was found that there were three ceramic components, CaMgSi2O6, CaSiO3 and Na2MgSiO4, which indicated that the experimental sample was a multiphase ceramic system. Through the trend of bulk density as functions of the content of substitution and the change of SEM morphology, it could be found that appropriate amount of Na+ substitution can promote the grain growing and the densification of ceramics. Results demonstrated that both the Q × f and εr were relevant to bulk density and the second phase. The τf was also affected by the second phase to some extent. In particular, the ceramics sintered at 925 °C for 3h possessed the desirable microwave dielectric properties for LTCC application: εr = 7.03, Q × f = 17,956 GHz, and τf= −79 ppm/°C.

scholarly journals Влияние химического состава кристаллов TlIn-=SUB=-1-x-=/SUB=-Er-=SUB=-x-=/SUB=-S-=SUB=-2-=/SUB=- (0≤ x≤0.01) на их диэлектрические характеристики и параметры локализованных состояний

2019 ◽  
Vol 61 (11) ◽  
pp. 2030
Author(s):  
С.Н. Мустафаева ◽  
М.М. Асадов
Keyword(s):  
Dielectric Constant ◽  
Charge Transfer ◽  
Chemical Composition ◽  
High Frequency ◽  
Ac Conductivity ◽  
Relaxation Dispersion ◽  
Complex Dielectric Constant ◽  
High Frequency Range ◽  
Frequency Range ◽  
Frequency Dependences

The frequency dependences of the real (ε) and imaginary (ε ″) components of the complex dielectric constant, tangent of dielectric loss (tan) and ac conductivity (σac) of the obtained TlIn1-хErхS2 (0  x  0.01) crystals have been studied in the frequency range f = 5104–3.5107 Hz. It is established that in TlIn1-хErхS2 a relaxation dispersion of ε and ε″ takes place. The effect of erbium concentration (Er) in TlIn1-хErхS2 crystals on their dielectric coefficients was studied. In the high frequency range, the ac conductivity of TlIn1-хErхS2 crystals obeyed the σac ~ f 0.8 law, which is characteristic of a hopping charge transfer mechanism at states localized near the Fermi level. The parameters of states localized in the band gap and the influence of the chemical composition of the TlIn1-хErхS2 crystals on these parameters are estimated.

Dielectric Relaxation and Microwave Dielectric Properties of Bi2O3–ZnO–Ta2O5 Ceramics

2002 ◽  
Vol 17 (6) ◽  
pp. 1502-1506 ◽  
Author(s):  
Hyuk-Joon Youn ◽  
Clive Randall ◽  
Ang Chen ◽  
Tom Shrout ◽  
Michael T. Lanagan
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Low Frequency ◽  
Microwave Dielectric Properties ◽  
Β Phase ◽  
Microwave Dielectric ◽  
Α Phase ◽  
Frequency Independent ◽  
Temperature Relaxation ◽  
Two Phases

The permittivity of two primary phases within the Bi2O3–ZnO–Ta2O5 system was measured from 100 Hz to approximately 8.7 GHz. A cubic pyrochlore (Bi3/2Zn1/2)(Zn1/2Ta3/2)O7 phase (a phase) exhibited a dielectric constant of 71 at low frequency which decreased to 64 at approximately 10 GHz. A lower symmetry zirconolite Bi2(Zn1/3Ta2/3)2O7 phase (β phase) was also measured and had a frequency independent dielectric constant of 60. The temperature dependence of the capacitance (τC), measured from −55 to 120 °C, was 78 ppm/°C for the β phase and nonlinear for the α phase having no unique slope. The primary difference in dielectric properties between these two phases was a low-temperature relaxation of the α phase, which is modeled as a basic Debye-type relaxation.

Evaluation of Special Hearing Aids for Deaf Children

1971 ◽  
Vol 36 (4) ◽  
pp. 527-537 ◽  
Author(s):  
Norman P. Erber
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Hearing Aid ◽  
Low Frequency ◽  
Acoustic Stimulation ◽  
Deaf Children ◽  
Frequency Range ◽  
Frequency Limit ◽  
Unpublished Studies ◽  
Published Research

Two types of special hearing aid have been developed recently to improve the reception of speech by profoundly deaf children. In a different way, each special system provides greater low-frequency acoustic stimulation to deaf ears than does a conventional hearing aid. One of the devices extends the low-frequency limit of amplification; the other shifts high-frequency energy to a lower frequency range. In general, previous evaluations of these special hearing aids have obtained inconsistent or inconclusive results. This paper reviews most of the published research on the use of special hearing aids by deaf children, summarizes several unpublished studies, and suggests a set of guidelines for future evaluations of special and conventional amplification systems.

Development of a Capacitor Probe to Detect Subsurface Deterioration in Concrete

1997 ◽  
Vol 503 ◽  
Author(s):  
B. K. Diefenderfer ◽  
I. L. Al-Qadi ◽  
J. J. Yoho ◽  
S. M. Riad ◽  
A. Loulizi
Keyword(s):  
Dielectric Constant ◽  
Portland Cement ◽  
Electromagnetic Waves ◽  
Low Cost ◽  
Complex Dielectric Constant ◽  
Life Cycle Costs ◽  
Parallel Plates ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Set Up

ABSTRACTPortland cement concrete (PCC) structures deteriorate with age and need to be maintained or replaced. Early detection of deterioration in PCC (e.g., alkali-silica reaction, freeze/thaw damage, or chloride presence) can lead to significant reductions in maintenance costs. However, it is often too late to perform low-cost preventative maintenance by the time deterioration becomes evident. By developing techniques that would enable civil engineers to evaluate PCC structures and detect deterioration at early stages (without causing further damage), optimization of life-cycle costs of the constructed facility and minimization of disturbance to the facility users can be achieved.Nondestructive evaluation (NDE) methods are potentially one of the most useful techniques ever developed for assessing constructed facilities. They are noninvasive and can be performed rapidly. Portland cement concrete can be nondestructively evaluated by electrically characterizing its complex dielectric constant. The real part of the dielectric constant depicts the velocity of electromagnetic waves in PCC. The imaginary part, termed the “loss factor,” describes the conductivity of PCC and the attenuation of electromagnetic waves.Dielectric properties of PCC have been investigated in a laboratory setting using a parallel plate capacitor operating in the frequency range of 0.1 to 40.1MIHz. This capacitor set-up consists of two horizontal-parallel plates with an adjustable separation for insertion of a dielectric specimen (PCC). While useful in research, this approach is not practical for field implementation. A new capacitor probe has been developed which consists of two plates, located within the same horizontal plane, for placement upon the specimen to be tested. Preliminary results show that this technique is feasible and results are promising; further testing and evaluation is currently underway.

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