Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 243 for “"permittivity"”.
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Variable permittivity dielectric material loaded stepped-horn antenna
… loaded with dielectric material of variable permittivity is proposed to improve radiation characteristics and/or to increase the electrical dimensions of the radiating structure compared to unloaded empty one. A hybrid numerical technique is used to analyze such an antenna. The tapered …
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Modeling the microwave frequency permittivity of thermoplastic composite materials
… the mixture model and experimental results for permittivity as a function of temperature at 9.4 GHz.
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An investigation of minerals using microwave measurement of complex permittivity
Microwave measurement techniques have found many industrial and commercial applications. This measurement potential of microwaves, together with observations that different minerals show different microwave heating characteristics, suggests the possibility of applying microwave techniques to …
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Evaluation of a Permittivity Sensor for Continuous Monitoring of Suspended Sediment Concentration
… to determine if the gain and phase components of permittivity could be used to predict suspended sediment concentrations (SSC). A bench-scale suspension system was designed and tested to guarantee that there were no significant differences in the sediment suspension vertically or horizontally …
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A Study of Acoustic Velocity and Dielectric Permittivity Anisotropy in Relation to Finite Strain in Deformed Rock
… of propagation of acoustic waves and dielectric permittivity were measured for samples from the quarry and then compared with strain determined by preferred orientation for the same samples. Further measurements of acoustic velocity were done on samples from locations along the axis of the Welsh …
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Experimental investigation of carrier mobility degradation in metal oxide semiconductor field effect transistors of high permittivity gate dielectrics
Scaling of electronic devices is driven, from the consumption side, by the need for compact electrical products, increase in device speed and from the production side, by lowering of production cost. However, aggressive scaling gives rise, among others, to high gate tunnelling currents in …
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Influence of antenna pattern on synthetic aperture radar (SAR) imaging and complex permittivity extraction from images of multilayered media
… methodology is proposed to extract the permittivity distribution for a multilayered composite medium from its produced SAR image.
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Non-invasive electromagnetic wave sensor for flow measurement and biphase application
… occur inside a cavity and the differences in the permittivity of the measures phases. By measuring this response over the range of discrete frequencies the sample can be characterised. Polar material like water has relatively high permittivity (ε_r= 81), while non-polar material such as oil and …
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Extracting material constitutive parameters from scattering parameters
… can be described electrically by their complex permittivity and permeability. These constitutive parameters determine the response of the material to electromagnetic (EM) radiation. The precise knowledge of complex permittivity and permeability is required not only for scientific but also for …
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Identifying shallow subsurface stratigraphy and voids using dispersive characteristics of electromagnetic and surface waves
… signals to identify the thickness and dielectric permittivity of thin soil layers using Ground Penetrating Radar (GPR) techniques. Data for this experiment were acquired in a large experimental tank, where the permittivity and thickness of each soil layer was controlled. Six different experiments …
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Technology assessment and market analysis of solid state ultracapacitors
… to possess high breakdown voltage and/or DC permittivity. Among the available SSU models, Electrical Energy Storage Units (EESUs) have been reported to possess energy density as high as 280 Wh/kg with the permittivity and breakdown voltage enhancements achieved through engineering composition …
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Electrochemical Impedance Spectroscopy using adjustable nanometer-gap electrodes
… analysis technique for measuring the electrical permittivity and conductivity of liquids and gases. Presently, the limiting factor for using EIS as a portable chemical detection technology is the lack of absolute accuracy stemming from uncertainties in the geometrical factor used to convert …
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Modeling and simulations of diphasic composites for development of high energy density dielectrics
… because they can synergistically combine high permittivity with high breakdown strength of the individual phases. Energy density, which captures permittivity and dielectric breakdown strength as vital material parameters, dominates this research challenge. Avenues for increasing the effective …
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Soft nanocomposites with enhanced electromechanical response for dielectric elastomer actuators
… their properties are increasing the relative permittivity of the active material, while maintaining high electric breakdown strength and low stiffness, which would lead to enhanced electrostatic storage ability and hence, reduced operating voltage. Improvement of the functional properties is …
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Novel applications of the Josephson Effect: Ferroelectric Characterisation and Capacitively Shunted Grain Boundary Junctions
… junction capacitance was poorly understood. The permittivity of SrTiO3 is 24000 at 4.2K. A series of YBa2Cu3O7-d Josephson junctions of lengths from 2mm to 20mm was patterned on a SrTiO3 bicrystal and the Fiske resonance dispersion relation was measured. The dispersion relation consisted of two …
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Microwave sensing of bulk electrical properties of tank track pad rubber
A complex permittivity measurement system composed of a network analyzer and a open-ended coaxial waveguide has been used to evaluate the permittivity of rubber samples. The conductivity of rubber provides an indication of the dispersion of carbon black throughout the rubber matrix. The technique …
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Non-invasive microwave and millimeter wave reflectometry and imaging for human skin diagnosis and materials characterization
… and skin, the proper knowledge of the complex permittivity of healthy skin is critically important. To this end, the common used measurement methods for <i>in vivo</i> skin complex permittivity are reviewed and analyzed in this study, subsequent to which a more accurate method is proposed and …
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Experimental and theoretical investigations into the switching of liquid crystal devices
… crystal cells. While static measurements of the permittivity liquid crystal cells are well established, here a novel transient permittivity technique is developed and applied to several liquid crystalline substances in a variety of geometries. This technique utilises A.C. waveforms to measure the …
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Simulation of Simultaneously Negative Medium Metamaterials
… documentation, the metamaterials have relative permittivity and/or relative permeability of values less than 1, including negative values. If the material has negative permittivity and permeability at the same time, the material is also referred to as simultaneously negative medium (DNG medium). …
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