Relative Dielectric Permittivity Variations during Compaction as a Mean of Compaction Quality Control: Case Study on Laterite Samples from Senegal

This study explores an alternative to the classical use of direct methods, as water content and dry density measurements, for compaction quality control. For this purpose, the dielectric properties of lateritic materials are determined by radar method and are compared with the permittivity determined from the Topp formula and from the CRIM model. This approach allowed to establish a relationship between the geotechnical properties determined during compaction such as dry density, water content or porosity with dielectric permittivity. The obtained results made it possible to determine an optimum dielectric permittivity corresponding to the optimum dry density and the optimum water content that could be used for non-destructive in situ compaction testing. Such an approach should improve the implementation and effectiveness of in situ compaction quality control of geotechnical infrastructures.

Design of Broadband Metamaterial Absorbers for Permittivity Sensitivity and Solar Cell Application

A broadband and ultra-thin absorber for solar cell application is designed. The absorber consists of three layers,and the difference is that the four split ring resonators made of metal gold are encrusted in the gallium arsenide(GaAs) plane in the top layer. The simulated results show that a perfect absorption in the region from 481.2 to 684.0 THz can be obtained for either transverse electric or magnetic polarization wave due to the coupling effect between the material of GaAs and gold. The metamaterial is ultra-thin, having the total thickness of56 nm, which is less than one-tenth resonance wavelength, and the absorption coefflcients at the three resonance wavelengths are above 90%. Moreover, the effective medium theory, electric field and surface current distributions are adopted to explain the physical mechanism of the absorption, and the permittivity sensing applications are also discussed. As a result, the proposed structure can be used in many areas, such as solar cell, sensors, and integrated photodetectors.

Large Scale Analysis of Complex Permittivity of Breast Cancer in Microwave Band

To obtain some prior knowledge of breast cancer detection by microwave imaging, we have measured and analyzed the complex permittivity of tissues extracted from over 140 breast cancer surgeries. The relative permittivity and conductivity of tumor at 1.6 GHz were 17.5% and 16.2% higher than those of mammary gland tissue, respectively. In invasive ductal carcinoma of scirrhous type, 8 out of 64 had higher relative permittivity and conductivity of mammary gland than those of tumor. However, when evaluated by the Debye parameter considering the frequency dependence of the tissue, it is rare that ε∞ and Δε of cancer are simultaneously lower than those of mammary gland. The relative permittivity and conductivity of fibroadenoma are almost the same as those of mammary glands. The relative permittivity and conductivity of each tissue showed strong linearity. Microwave imaging requires accurate reconstruction of ε∞ and Δε to distinguish cancer from normal tissue.

Dielectric Permittivity of Various Cement-Based Materials during the First 24 Hours Hydration

The dielectric permittivity of cementitious materials during 24 hours hydration period at a frequency of 2.45 GHz using a network analyzer with open-ended probe technique was measured. Influences of water-to-cementitious ratios, cement types, pozzolans and aggregate types are taken into consideration. The results show that dielectric permittivity is strongly affected by initial water-to-cementitious ratio and the rate of hydration reaction which can be changed by fineness of cement (Types 1 and 3), pozzolan materials and aggregates (river sand with/without crushed limestone rock). Dielectric permittivity is relatively high and remains constant during the dormant period, after that it decreases rapidly when the hydration reaction resumes and continues to decrease during the acceleratory period.

The c-axis complex permittivity and electrical impedance in BaFe_2As_2: Experimental examination on transformation validity

Complex permittivity and electrical impedance have been measured along the c-axis in single crystals BaFe_2 As_2,which are the conductors known as the parent compound of 122-type iron superconductor. The resultant relative errors defined in the study indicate the existence of the transformation between complex permittivity and electrical impedance in the conductors, and these two physics quantities possibly reveal different aspects of the consistent superconductivityrelevant physics picture.

A New Numerical Method for Calculation of Complex Dielectric Permittivity

In this paper, a new numerical method-Kuhn algorithm with contour integral-is intrroduced and used to calculate the complex dielectric permittivities of materials from the short-circuitedwaveguide measurements. Some numerical results are given to verify the validity and efficiency ofthe new numerical method and the complex dielectric permittivities of materials calculated by thenew numerical method are quite identical with the results given by other works.

Modeling of high permittivity insulator structure with interface charge by charge compensation

An analytical model of the power metal–oxide–semiconductor field-effect transistor(MOSFET)with high permittivity insulator structure(HKMOS)with interface charge is established based on superposition and developed for optimization by charge compensation.In light of charge compensation,the disturbance aroused by interface charge is efficiently compromised by introducing extra charge for maximizing breakdown voltage(BV)and minimizing specific ON-resistance(R_(on,sp)).From this optimization method,it is very efficient to obtain the design parameters to overcome the difficulty in implementing the R_(on,sp)–BV trade-off for quick design.The analytical results prove that in the HKMOS with positive or negative interface charge at a given length of drift region,the extraction of the parameters is qualitatively and quantitatively optimized for trading off BV and Ron,sp with JFET effect taken into account.

THE MEASUREMENT OF COMPLEX PERMITTIVITY OF ANISOTROPIC DIELECTRICS BY MEANS OF AN ELECTROMAGNETIC OPEN RESONATOR

By applying the perturbation method and the complex-source-point theory, the theoretical research of measurement of complex permittivity of uniaxial anisotropic materials by means of an electromagnetic open resonator has been made, and the double refraction phenomenon due to anisotropy of measured dielectric materials has been quantitatively analyzed. Finally, measurements have been made on some single-crystal quartz specimens using an automated open resonator measurement system at 8mm band.

Dielectric Permittivity of Rigid Rapeseed Oil Polyol Polyurethane Biofoams and Petrochemical Foams at Low Frequencies

Early investigations of dielectric permittivity of rigid polyurethane foams at low frequencies were made on petrochemical-origin foams,mainly by means of parallel plate capacitors.In the present investigation biopolyol was synthesized from Latvia-grown rapeseeds’oil by the transesterification method with triethanolamine,in an environmentally friendly process,without emission of harmful substances,at temperatures 175℃±5℃.Rigid,closed-cell rapeseed oil polyol polyurethane biofoams and petrochemical foams were made ensuring content of the renewable rapeseed oil polyol in ready foams 27 wt.%–29 wt.%.Dielectric permittivity of the polyurethane foams and the underlying monolithic petrochemical-origin polyurethane and biopolyurethane was measured with a non-destructive dielectric spectrometer equipped with a capacitive sensor of one-side access type at 16 discrete frequencies distributed geometrically over the band 10 Hz,…,330 kHz.Permittivity value of the gaseous phase in the closed-cells was estimated to beεg≈1.001 that corresponds to the values,characteristic for the most of gases.Dielectric permittivity of petrochemical polyurethane foams and the mentioned biofoams was compared with permittivity of polyurethane foams from industrial producers Sika JSC and General Plastics Manufacturing Co.Polyurethane foams of the developed formulation exhibit competitive,low dielectric permittivity,not exceeding that of the foams from industrial producers:petrochemical foams up to 550 kg/m^(3) and the mentioned biofoams,comprising the renewable rapeseed oil polyol,up to densities 230–250 kg/m^(3).Considering petrochemical-origin polyurethane foams as a heterogeneous media“Polymer—gaseous phase”,the applicability of the rule of mixture and Maxwell–Garnett equation to model mathematically the dependence of effective dielectric permittivity on the volume fraction of phases was showed.

Permittivity of composites used for Luneburg lens antennas by drilling holes based on 3-D printing technique

Due to the attractive performances such as the ability of beam focus,broadband,multi-beam scanning and other features,Luneburg lens antennas are applied in multi-beam antenna,which overcomes the problem of gain loss produced by multi-beam parabolic antenna.Based on 3-D printing technique,Luneburg lens antennas by drilling holes are studied.Permittivity and loss tangent of the equivalent lens materials can be influenced by original materials,hole shapes,hole directions,and porosity.After tests,polystyrene with waxes may be the most appropriate materials for Luneburg lens with high strength.Permittivity with the shape of triangle is the lowest due to the homogeneity.Relative permittivities with the direction at a range of 15°-45°are lower while loss tangent at a range of 0°-30°.Radial directional holes are more appropriate for Luneburg lens.The relative permittivity is decreased with the increment of porosity.After calculations,the forecasts calculated by Looyenga and A-BG theory are more precise.Finally,Luneburg lens with two layers is fabricated by 3-D printing.

Wide-Temperature-Range Dielectric Permittivity Measurement under High Pressure

Two measurement systems are developed for in-situ dielectric property measurement under high pressure in a wide-temperature range from 77 K to 1273 K. The high-temperature system ranging from room temperature up to 1273 K is equipped with a hexahedron anvils press,while the low-temperature system ranging from liquid nitrogen temperature to normal condition is equipped using the piston cylinder setup with a specially designed sample chamber. Using these configurations, the dielectric property measurement of ferroelectric BaTiO_3 and multiferroic Tm_(0.5)Gd_(0.5)MnO_3 compounds are demonstrated, which proves the validity of the systems through the tuning of the polarization and phase transition boundary by high pressure. These two systems will be equally applicable to a wide variety of electronic and transport property measurements of insulators,semiconductors,as well as battery materials.

High-Temperature Permittivity and Data-Mining of Silicon Dioxide at GHz Band

The high-temperature permittivity of quartz fibre-reinforced silicon dioxide (SiO2/SiO2 ) nano-composites is studied on the basis of the multi-scale theoretical model.We obtain the permittivity of the SiO2/SiO2 at high temperature,which is dependent on the temperature by data-mining.The result shows that the permittivity and loss tangent obtained by data-mining are well consistent with the measured ones.The high-temperature permittivity can be well predicted for SiO2/SiO2 by the as-proposed model and the data-mining method.

Nonresonant Metamaterials with an Ultra-High Permittivity

A nonresonant structure composed of metal cut-wires for realization of metamaterials is proposed.This kind of metamaterial works at an ultra broad bandwidth with uniform permittivity.Theoretical analysis and numerical simulations are carried out to study this inclusion and expression for the effective permittivity is given.Several methods are studied to enhance the permittivity and a nonresonant metamaterial with an ultra-high permittivity is obtained.A demonstration shows that the permittivity of this metamaterial can be as high as 145.

Effect of ions on conductivity and permittivity in the Polar Mesosphere Summer Echoes region

For the first time,the effect of ions on complex conductivity and permittivity of dusty plasma at Polar Mesosphere Summer Echoes(PMSE)altitude is analyzed.Because of ions higher mass and smaller thermal velocity,generally,their effects are not considered in the study of electromagnetic properties of dusty plasmas.In this study,we modified the equations of conductivity and permittivity by adding the effect of ions.In the PMSE altitude region between 80 and 90 km,a local reduction in electron density(i.e.,an electron biteout),is produced by electron absorption onto dust particles.The bite-out condition contains high dust density and smaller electron density.From simulation results in comparatively strong bite-out conditions,we found that the ion effects on conductivity become significant with smaller dust size,lower electron temperature,and lower neutral density.For comparatively weak bite-out conditions,the ion effects on conductivity become significant with larger dust size,higher electron temperature,and higher neutral density.On the other hand,for different dust sizes,electron temperatures and neutral density,the ion effects on complex permittivity become significant only in very strong bite-out conditions.Based on these simulation results,we conclude that,in the absence of electron bite-out conditions,the effect of ions on complex conductivity and permittivity is not significant and can be ignored.However,during bite-out conditions,the effect of ions becomes significant and cannot be ignored because it significantly changes the conductivity and permittivity of dusty plasmas.

Dielectric permittivity of dusty plasma in the Earth's mesosphere

This paper deals with the dielectric permittivity of dusty plasma in the earth’s mesosphere.We give expressions for the complex dielectric permittivity of dusty plasma,taking into account the effects of the dust charging process and magnetic field.We discuss the dielectric permittivity of dusty plasma in several cases,such as high frequency approximation,parallel propagation in MF/HF band,and effects of plasma movement.Finally,the expressions are employed to study the phenomenon of radar echoes from the polar summer mesosphere.We report that dielectric permittivity caused by the dust charging process gives a radar cross section proportional to ω–4 and produces a number density of charged dust that agrees with measurements of mesopheric radar echoes.

A Broadband Complex Permittivity Probe Using Stepped Coaxial Line

This paper proposes the stepped coaxial line sensor using the reflection coefficient in microwave range for complex permittivity measuring. The proposed probe is adapted from the conventional SMA connector which is cheap and easy to fabricate. The analysis model of the probe has been done by using FDTD method with the reference material such as the distilled water. The stepped SMA probe presents the accurate result compared with the convention one. The permittivity values of the concentrated alcohols of 10%, 15% and 20% as DUTs at 24oC in a frequency range of 0.1 GHz to 6 GHz have been measured using the proposed probe. Also, the measurement of salted butter permittivity has been performed. The measured results are more accurate compared with the commercial probe.

Measurable Dielectric Permittivity Range for TE and TM Modes in a Shielded Dielectric Resonator

Dielectric resonator methods constitute one of the most useful techniques for the measurement of electromagnetic material properties in the microwave frequency range. Several geometric configurations are used for this purpose and, in the present paper, we consider the case of a dielectric rod enclosed in a cylindrical metallic enclosure. To carry out dielectric measurements in this system it is necessary to know the highest permittivity constant value for which the resonance condition still can be attained into the cavity. Using an approach based on magnetic and electric Hertzian potentials we have derived the set of TE and TM modes for the relevant geometry described and, then we have calculated the valid dielectric permittivity constant range of measurements for low-loss materials in a cylindrical cavity using a simple resonance frequency condition. Finally, we present a simple application of this method in order to determine the dielectric permittivity constant of heavy oil with 11 API.

Permittivity Measurement of Low-Loss Substrates Based on Split Ring Resonators

In this paper, we present the complex permittivity measurement of low-loss substrates based on a microstrip-line-excited split-ring resonator (SRR). Permittivity of an unknown substrate is calculated based on the change in oscillation frequency of SRR caused by the material-under-test (MUT) above the SRR. Theoretical analysis and results of the simulations and experiments demonstrate the microstrip-line-excited SRR can be used to effectively improve measurement sensitivity. Simple equations for measurement of low-loss substrates using SRR are proposed and experimentally verified.

Complex Permittivity and Permeability Studies Viewing Antenna Applications of NBR-Based Composites Comprising Conductive Fillers

The work presents studies on the complex permittivity and permeability of composites based on acrylonitrile butadiene rubber containing combinations of conductive fillers which include carbon black and nickel powder. The properties of those composites, containing each of the fillers at the same amount were compared. The permittivity and permeability values of the composites are influenced remarkably by their morphology and structure as well as by the morphological and structural specifics of both fillers. As electron scanning microscopy studies confirm, those parameters are predetermined by the nature of the composites studied—particle size, particles arrangement in the matrix and their tendency to clustering. Last but not least matrix-filler interface phenomena also impact the characteristics in question. The possibilities for applications of the composites in antennae have been studied, in particular, as substrates and insulating layers in flexible antennae for body centric communications (BCCs). The research results allow the conclusion that these materials can find such applications indeed. Composites of higher conductivity can be used where surface waves are generated to provide on-body communications, while composites of lower conductivity may be used for antennae that will be on the body of a person and will transmit to and receive from other antennas that are not on the body of the same person (off-body communications). It is clear that one can engineer the properties of antennae substrates at microwave frequencies by adjusting the filler content and the type of filler and thus control and tailor the antenna performance specific for a particular application.

Determination of Material Properties like Permittivity and Density with Microwaves

With the help of electromagnetic waves in deci-, centi- and millimeter-wave range (microwaves) it is possible to determine the properties of non-metallic objects like permittivity or density in a nondestructive and if necessary in a contactless way. Depending on the type of the test object the measurement can be carried out both with low-cost narrowband or more expensive wideband devices and sensors. To get the characteristic value in most cases it is necessary to calibrate the test device with the help of reference materials. It is recommendable to sustain a constant distance (lift-off or standoff) between the antenna of the sensor and the test object. The paper deals with the characterization of asphalt, especially the determination of its density.