Variation Of Dielectric Research Articles

Microwave Characterization of Hydrophilic and Hydrophobic Plant Pathogenic Fungi Using Open-Ended Coaxial Probe

Plant diseases have a direct impact on agricultural food production. The time required to detect the pathogen plays a crucial role to minimize the fungal-induced disease damage in crops. Current microbial detection techniques take several days to identify the disease. Microwave detection techniques have proven to be a good candidate in identifying pathogens. Microwave dielectric characterization based on an open-ended coax technique is proposed to electrically characterize pathogens having potential applications in plant diseases. Seven common fungi growing on major crops in the United Arab Emirates were isolated and cultured in the lab. A microwave dielectric assessment kit, based on the open-ended coax technology, was used to obtain the dielectric properties of samples. Our data demonstrated a distinct variability between soil- and air-borne pathogenic fungi. Thus, individual fungi can be identified based on their specific microwave dielectric signature. Factors such as conidial sporulation and hyphal growth and polarization of these fungi may attribute to these electric discrepancies. Dielectric spectroscopy modeling based on the Havriliak–Negami model was used to help to understand the molecular structure interaction with the high-frequency signal. This paper revealed a significant dielectric contrast behavior variation among all seven fungi. This paper also supported previous results obtained by other researchers, which classified fungi into two main groups, namely hydrophilic and hydrophobic. Nonetheless, the fungus Alternaria solani has different behavior from this classification. This research is the first to demonstrate the ability of dielectric microwave characterizations tests to facilitate rapid diagnosis and appropriate treatments of plant diseases.

A Metamaterial-Inspired Dual-Band High-Sensitivity Microwave Sensor Based on Multiple Split Ring Resonators for Sensing Applications

This paper introduces the design, manufacture, and evaluation of a compact metamaterial-inspired sensor, aiming at detecting dielectric properties of small liquids in a microwave measurement system. The proposed sensor is based on a microwave-coupled multiple split ring resonators (MSRR). The sensing principle is based on field perturbation theory. Then the sensor's resonance characteristics will change when the sensor is loaded with the materials under test (MUT). We have demonstrated that the sensor has a very high sensitivity to sensing the dielectric variations of its surroundings. When the resonance occurs, the strongest electric field intensity of the sensor is better than 105 V/m. The proposed sensor is simulated and optimized using ANSYS high frequency structure simulator (HFSS) to ensure its operating frequency is near 3 GHz and 4.5 GHz. Measurement results agree well with the simulation results. Some experiments show that this sensor can detect the dielectric property of liquids with very small volumes (∼12.56 mm3).

Characterisation of breast tissue using compact microstrip antenna

This paper presents a more improved method to characterise the breast tissue by employing a unique microstrip antenna. The pattern of the proposed antenna consists of a radiating patch with a rectangular slot, three stubs, a feed-line and a partial ground plane. Several parameters are used to analyse the microstrip antenna. The antenna designed provides a wide usable frequency band range from 2.4-4.76 GHz. In order to observe the interaction between the antenna and breast tissue, a heterogeneous breast model having dielectric characteristics similar to the human tissue is used. The tumour in the breast tissue is analysed by measuring the resonant frequency of the reflected signal. The results show that the shift in resonant frequency decreases as the size of tumour increases due to dielectric variation in the breast tissue.

Higher permittivity of Ni-doped lead zirconate titanate, Pb[(Zr0.52Ti0.48)(1-x) Nix]O3, ceramics

The paper reports highest obtained dielectric constant for Ni-doped Lead Zirconate Titanate [PZT, Pb(Zr0.52Ti0.48)O3] ceramics. The Ni-doped PZT ceramic pellets were prepared via conventional solid-state reaction method with Ni content chosen in the range 0–20 at%. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were employed to investigate the crystal structure of the prepared ceramics. The X-ray diffraction analysis indicated that the ceramic pellets had crystallized into tetragonal perovskite structure. A minute displacement of XRD peaks was detected in the diffraction spectra of Ni-doped PZT ceramic samples which when examined by size-strain plot (SSP) method revealed presence of homogenous strain that decreased with increase in concentration of Ni. In FTIR the maximum absorption at 597 cm−1, 608 cm−1, 611 cm−1, 605 and 613 cm−1 for Ni = 0, 5, 10, 15 and 20 at%, respectively, confirmed the formation of perovskite structure in all the compositions and the slight shift suggests decrease in cell size on doping. The values of dielectric constant (ε′) & tanδ as a function of frequency and temperature were measured for the prepared ceramics and it revealed highest ever reported dielectric constant for Ni - doped PZT with Ni = 5 at%. The dielectric variation with temperature exhibited a diffused type ferroelectric–paraelectric phase transition for the doped samples. Also, the maximum dielectric constant value (ε′max) decreased while the phase transition temperature increased with increase in doping concentration of Ni. The estimated activation energy of different compositions was found to increase from 0.057 to 0.068 eV for x = 0.00 to x = 0.20 in ferroelectric phase. The piezoelectric, ferroelectric and magnetic properties were also investigated.

Monitoring the residual capacity of activated carbon in an emission abatement system using a non-contact, high resolution microwave resonator sensor

The accumulation of non-desorbed species or heel buildup reduces the capacity and lifetime of adsorbents used in cyclic adsorption/desorption processes. This study investigates the changes in the physical, chemical, and dielectric properties of beaded activated carbon (BAC) and their relation to the adsorbent residual capacity (i.e., residual lifetime) during cyclic adsorption/desorption using a non-contact, high-resolution microwave resonator sensor. The resonant frequency of the sensor responds to changes in the dielectric properties of the medium surrounding the sensor. BAC samples with different degrees of capacity reduction as indicated by the apparent density, BET surface area, total pore and micropore volumes were tested. A linear correlation (R2 = 0.93) between the apparent density of the BAC samples and the resonant frequency shift of the sensor was observed, irrespective of heel composition indicating that the effect of adsorbent porosity on dielectric property variation is more important than heel composition. The sensor’s ability for fast and continuous measurement makes it an ideal candidate for real-time monitoring of adsorbent capacity status in cyclic adsorption/desorption processes.

Parallel-Plate Luneburg Lens Antenna for Broadband Multibeam Radiation at Millimeter-Wave Frequencies With Design Optimization

This paper presents the implementation of Luneburg lens antenna based on a 2-D parallel-plate structure for broadband multibeam radiation at millimeter-wave frequencies. In particular, each beam pattern of this 2-D Luneburg lens antenna has a narrow beamwidth along the multibeam dimension, and exhibits a broad beamwidth along the other cross section, analogous to the radiation from a 1-D array of antennas embedded inside the parallel-plate structure. Furthermore, the isolation to external structures by the top and bottom metal parallel plates may reduce the beam distortion from external interferences, and therefore enhance its compatibility to integrate with other radio frequency (RF) components to form an RF subsystem module. In addition, a theoretic model to realize the dielectric variation of Luneburg lens is developed by using stacked multiple planar layered dielectric materials for a cheap manufacture. In this paper, numerical simulation to validate the developed model of 2-D Luneburg lens design is first presented. Afterward, simulation and experimental measurement results of a practical design are both presented to validate the design concept.

Research on dielectric characterization of laterite ores under microwave radiation

Dielectric property of laterite ores plays a key role in the determination of its treatment effect by microwave. However, till date, to our knowledge, there is no article reported on the dielectric property of laterite ores up to the nickel–iron alloy extraction temperature of around 1200 °C, which impedes the efficient application of microwave power in the nickel–iron alloy extraction. This paper, in view of this, aims to provide the dielectric property variation of laterite ores treated by microwave radiation from room temperature up to 1250 °C. A custom-designed ridge waveguide-based system is applied to perform the measurement. To verify the reliability of the measured results and explain the experimental phenomenon, X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis are employed to conduct a thorough understanding on the variation of dielectric properties of laterite ores under different temperatures. The measured data are qualitatively verified by its temperature change tendency, SEM and XRD analysis. This work may be helpful to avoid thermal runaway, design more efficient microwave devices and optimize the existing production line of microwave treating laterite ores.

Enhanced Model for Continuous Dielectric-Based Asphalt Compaction Evaluation

The compaction of asphalt concrete significantly affects long-term pavement performance. Although coring provides a relatively accurate way of assessing in-place density at specific locations, the coverage of the assessment is limited, especially at longitudinal joint locations. This can be particularly problematic because it is difficult to identify problematic locations that are likely to fail prematurely using current compaction assessment methods. Ground penetrating radar (GPR) provides an attractive nondestructive testing alternative for evaluation of compaction quality, especially with recent significant improvements in the GPR technology for this specific application. However, assessment of the air void content of the asphalt mix from the GPR-measured dielectric constant of the surface requires conversion of dielectric variation to air void content variation, which is the subject of this paper. An alternative to the commonly used model is proposed, leading to more justifiable predictions for low values of dielectric constants. The proposed model was used to interpret data from a 7-mi long asphalt overlay construction project. The results of the interpretation as compared with the results obtained with the conventional model show an improvement on the stability of the prediction at low air void contents, especially when core calibration data are limited and uncertainty is considered. These results are promising in the direction of reducing field cores necessary to have a stable model providing continuous compaction assessment of new asphalt pavement construction.

An Energy-Efficient Wirelessly Powered Millimeter-Scale Neurostimulator Implant Based on Systematic Codesign of an Inductive Loop Antenna and a Custom Rectifier.

In this work, a switched-capacitor-based stimulator circuit that enables efficient energy harvesting for neurostimulation applications is presented, followed by the discussion on the optimization of the inductive coupling front-end through a codesign approach. The stimulator salvages input energy and stores it in a storage capacitor, and, when the voltage reaches a threshold, releases the energy as an output stimulus. The dynamics of the circuit are automatically enabled by a positive feedback, eliminating any stimulation control circuit blocks. The IC is fabricated in a 180nm CMOS process and achieves a quiescent current consumption of 1.8 μA. The inductive coupling front-end is optimized as a loaded resonator, in which the input impedance of the custom rectifier directly loads the inductive loop antenna. The loaded quality factor and the rectifier's efficiency determine the reception sensitivity of the stimulator, while a balance should be achieved for the robustness of the system against dielectric medium variations by increasing the reception bandwidth. The finalized stimulator adopts a 4.9mm × 4.9mm inductive loop antenna and achieves an overall assembly dimension of 5mm × 7.5mm. Operating at the resonant frequency of 198MHz, the stimulator works at a 14cm distance from the transmitter in the air. An animal experiment was performed, in which a fully implanted stimulator excited the sciatic nerve of a rat that consequently triggered the movement of the limb.

Ab initio calculation of stressed cesium iodide lattices and resulting surface plasmon resonance peak shifts

Alkali halides have received attention due to their potential application as detector coating. This is due to the appearance of Surface Plasmon Resonance (SPR) absorption peaks in their absorption spectrum. The formation of SPR peaks is due to the formation of cesium metal clusters within the cesium halide matrix. Experimental work on cesium iodide explained the formation of cesium clusters in cesium iodide films. It was experimentally seen that when iodine atom escapes from the cesium iodide unit cell, then the newly created cubic unit cell of cesium exerts force on neighboring cesium iodide unit cells. This force results in cesium iodide taking up a tetragonal lattice structure. The aim of this paper is to theoretically investigate the tetragonal cesium iodide’s band structure and dielectric constant using ab initio calculations. The results indicate that both the band structure and the dielectric constant of cesium iodide in tetragonal phase show a systematic variation with changes in the lattice constant. This alteration in dielectric constant or variation in refractive index of cesium iodide, which acts as the surrounding media for the cesium metal clusters, induces a shift in the SPR peak position. The calculated dielectric constants were used for Gan model calculations of the extinction coefficient and evaluation of SPR peak position ([Formula: see text]). A redshift in [Formula: see text] was seen with increasing dielectric constant that appears with stress acting on cesium iodide’s lattice. These results were found to be in agreement with experimental results reported earlier by us.

Effect of tumor properties on energy absorption, temperature mapping, and thermal dose in 13.56-MHz radiofrequency hyperthermia

Computational techniques can enhance personalized hyperthermia-treatment planning by calculating tissue energy absorption and temperature distribution. This study determined the effect of tumor properties on energy absorption, temperature mapping, and thermal dose distribution in mild radiofrequency hyperthermia using a mouse xenograft model. We used a capacitive-heating radiofrequency hyperthermia system with an operating frequency of 13.56 MHz for in vivo mouse experiments and performed simulations on a computed tomography mouse model. Additionally, we measured the dielectric properties of the tumors and considered temperature dependence for thermal properties, metabolic heat generation, and perfusion. Our results showed that dielectric property variations were more dominant than thermal properties and other parameters, and that the measured dielectric properties provided improved temperature-mapping results relative to the property values taken from previous study. Furthermore, consideration of temperature dependency in the bio heat-transfer model allowed elucidation of precise thermal-dose calculations. These results suggested that this method might contribute to effective thermoradiotherapy planning in clinics.

Evaluating the dielectric strength of helium-nitrogen gas mixtures by plasma parameter measurements

Plasma diagnostic experiments are used for understanding the dielectric strength of gaseous cooling media. Plasma measurements on helium-nitrogen gas mixtures with varying composition were conducted with a single-tip Langmuir probe. The data from the measurements were used to derive the electron temperature and electron density. The results suggest that the measured electron temperature is suitable for assessing the dielectric strength variation of the gaseous media as a function of gas composition. However, the results also confirmed that the measured electron density is substantially influenced by the effective wall area of the plasma chamber and thus is inappropriate for being used as the indicator of dielectric strength variation.

Structural and Electrical Studies of MnGdxFe2-xO4 Nanoparticles

Manganese ferrite, belonging to the class of the mixed spinel ferrites substituted with various transition metals had been extensively explored because of its desirable properties in a vast area of applications. In recent years, there has been growing interest towards the incorporation of lanthanide ions to the spinel ferrites. As lanthanide ions possess larger ionic radii than ionic radii of iron ions, their substitution may give rise to lattice strain and hence solubility limit. Nevertheless, traces of lanthanide ions substitution in the spinel structures were reported to bring appreciable changes in their properties. Consequently, in the present work, the effect of gadolinium substitution on structural and electrical properties of manganese ferrite was investigated.Gadolinium doped manganese ferrite with the chemical formula MnGdxFe2-xO4 (where x = 0.02, 0.04, 0.06, 0.08 and 0.10) had been synthesized by co-precipitation method. XRD studies confirm the spinel structure and the variation in the size and the lattice constant with the gadolinium concentration was studied. SEM studies give the morphological structure of the prepared samples.The electrical properties namely frequency dependence of dielectric constant, dielectric loss tangent and variation of dc-resistivity with gadolinium concentration were investigated and the observed behaviors were discussed.

Tailoring of surface plasmon resonances in TiN/(Al0.72Sc0.28)N multilayers by dielectric layer thickness variation

Alternative designs of plasmonic metamaterials for applications in solar energy-harvesting devices are necessary due to pure noble metal-based nanostructures’ incompatibility with CMOS technology, limited thermal and chemical stability, and high losses in the visible spectrum. In the present study, we demonstrate the design of a material based on a multilayer architecture with systematically varying dielectric interlayer thicknesses that result in a continuous shift of surface plasmon energy. Plasmon resonance characteristics of metal/semiconductor TiN/(Al,Sc)N multilayer thin films with constant TiN and increasing (Al,Sc)N interlayer thicknesses were analyzed using aberration-corrected and monochromated scanning transmission electron microscopy-based electron energy loss spectroscopy (EELS). EEL spectrum images and line scans were systematically taken across layer interfaces and compared to spectra from the centers of the respective adjacent TiN layer. While a constant value for the TiN bulk plasmon resonance of about 2.50 eV was found, the surface plasmon resonance energy was detected to continuously decrease with increasing (Al,Sc)N interlayer thickness until 2.16 eV is reached. This effect can be understood to be the result of resonant coupling between the TiN bulk and surface plasmons across the dielectric interlayers at very low (Al,Sc)N thicknesses. That energy interval between bulk and decreasing surface plasmon resonances corresponds to wavelengths in the visible spectrum. This shows the potential of tailoring the material’s plasmonic response by controlling the (Al,Sc)N interlayer thickness, making TiN-based multilayers good prospects for plasmonic metamaterials in energy devices.

Simulation of thin-TFETs using transition metal dichalcogenides: effect of material parameters, gate dielectric on electrostatic device performance

In recent years, a lot of scientific research effort has been put forth for the investigation of Transition Metal Dichalcogenides (TMDC) and other Two Dimensional (2D) materials like Graphene, Boron Nitride. Theoretical investigation on the physical aspects of these materials has revealed a whole new range of exciting applications due to wide tunability in electronic and optoelectronic properties. Besides theoretical exploration, these materials have been successfully implemented in electronic and optoelectronic devices with promising results. In this work, we have investigated the effect of monolayer TMDC materials and monolayer TMDC alloys on the performance of a promising electronic device that can achieve steep switching characteristics- thin Tunneling Filed Effect Transistor or thin-TFET, using self-consistent determination of conduction, valance band levels in the device and a simplified model of interlayer tunneling current that treats scattering semi-classically and incorporates the energy broadening effect using a Gaussian approximation. We have also explored the effect of gate dielectric material variation, interlayer material variation on the performance of the device.

Empirical models to correlate the basic physical and chemical indices of modified rice bran and mustard oil

ABSTRACTModified rice bran oil (RBO) and modified mustard oil (MO) were prepared by adding oleic acid and oxidized oil separately. The physical and chemical indices like dielectric constant, viscosity, peroxide value (PV), acid value (AV), free fatty acids (FFA), iodine value (IV), and saponification value (SV) of pure and modified RO and MO were determined and correlated. Dielectric constant and viscosity were found to decrease in a non-linear fashion with increase in temperature (30°C–75°C). The dependence of dielectric constant and viscosity with temperature was investigated using model empirical equations. The dielectric variation was studied using Akerlof and Oshry’s model equations, which exhibited high dependency of R2 ranges from 0.99 to 0.997. The behaviour of viscosity with temperature was studied with Wright’s equation and the correlation coefficient (R2) was found to be 0.998. Model equations were developed, which relates dielectric constant with IV, SV, and PV with the regression coefficients R2 = 0.955, 0.936, and 0.994, respectively. The developed equations can be used in processing, pipelining, and to predict the parameters at a desired temperature. On comparing the correlations between the physical and chemical properties of the oil samples, RBO and its modified forms exhibited more oxidative stability than modified MO.

Magnetic-control-electric and reversal behavior of ZnO/NiFe/ZnO multilayer films

The magnetic-control-electric and corresponding dielectric behavior of the ZnO/NiFe/ZnO multilayer films have been demonstrated by applying an ultrathin bimetallic NiFe inserting layer into ZnO films, and fabricated by radio-frequency magnetron sputtering at room temperature without introducing any oxygen gas during deposition process. At first, a high quality crystalline ZnO(002) textured film was deposited and exhibited a dielectric constant value of around 10 confirmed at room temperature with the Agilent 42941B probe and 4294A impedance meters ranged from 40 Hz to 20 MHz. Once ZnO inserted with a 5 nm-thick NiFe inserting layer, the value of dielectric constant was dramatically increased from 10 to 12.5. This phenomenon can be attributed to redistribute the strongly interface charges between ZnO and NiFe layers and accompany with the relaxation of internal stress of ZnO. On the other hand, the external magnetic field induced dielectric variation can also be clearly observed, and the ZnO film with NiFe inserting layer demonstrates a 0.05%-0.10% dielectric tunability. The magnetic-control-electric and corresponding dielectric behavior of ZnO/NiFe/ZnO multilayers with a single inserting NiFe layer compared with that of pure ZnO film also conclude the magnetoelectric effect in present multilayered structures. Moreover, the grain size of the ZnO films was gradually increased from 32.5 nm to 40.5 nm while inserting with an ultrathin NiFe bimetallic layer. This grain structure transition can be attributed to the lattice misfit between ZnO and NiFe. This research work demonstrates that a single NiFe insering layer can effectively control the dielectric and magnetic characters in the ZnO/NiFe/ZnO multilayered structures and provide valuable multifunctional behaviors for potential novel applications design such as ferroic sensor.

High-sensitive dual-band sensor based on microsize circular ring complementary terahertz metamaterial

Recently, resonance sensing based on the terahertz metamaterials has attracted considerable attentions due to the enhancement and confinement of local fields in microsize gap of resonant structures. Here, a high-sensitive dual-band sensor based on the complementary terahertz metamaterial composed of microsize circular ring gap array is proposed to detect the thickness and refractive index of thin film. The structure of this sensor is polarization insensitive dual-band operating mode and can be easily filled by the biomolecules. Simulation results demonstrate that the dual-band resonances are very sensitive to the dielectric variation, and the sensitivity levels of 99 GHz/refractive index unit (RIU) for mode f1 and 242 GHz/RIU for mode f2 are obtained and further enhanced by optimizing structures. Therefore, this structure can exhibit promising application for monitoring thin film thickness.

Dielectric variations of potato induced by irreversible electroporation under different pulses based on the cole-cole model

To investigate dielectric property variations induced by electric pulses, equivalent doses of conventional irreversible electroporation (IRE) and high-frequency IRE were used to treat potato slices. The dielectric property of the potatoes were measured before and after treatment in the frequency band of 0.1 Hz-10 MHz, and then the Cole-Cole model was used to fit the experimental data in the frequency band of 1 kHz-10 MHz to explain the β dispersion mechanism. The Cole-Cole model parameters showed that under an equivalent dose, the conventional IRE pulses were more efficient than the high-frequency IRE pulses for electroporation. After treatment with conventional IRE pulses, the DC conductivity greatly increased at time 0 after the pulses and showed little recovery over time. The electroporation effect of the high-frequency IRE pulses improved with increasing pulse duration. This study presents a potential new method for evaluating the effects of IRE during and immediately after the treatment process.

Method to Determine the Root Cause of Low- $\kappa$ SiCOH Dielectric Failure Distributions

Low- $\kappa $ SiCOH reliability is a growing concern for integrated circuit reliability. An important consideration for product qualification involves the accurate extrapolation to the low percentile failures based on the results from a group of samples. A method is presented to determine the root cause of failure distributions amongst a group of dielectric samples using voltage ramp data. Samples’ leakage current traces and breakdown voltages are compared with each other. Using this method, it was determined that the dielectric spacing variation dominates across-wafer failure, while variation of local breakdown strength affects in-chip failure.