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Dissertations / Theses on the topic 'Permittivity'
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Okubo, Hitoshi, Hideki Shumiya, Masahiro Ito, and Katsumi Kato. "Optimization Techniques on Permittivity Distribution in Permittivity Graded Solid Insulators." IEEE, 2006. http://hdl.handle.net/2237/9498.
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Lam, Kim. "Non-linear inversion for relative permittivity." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/14708.
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The gradient method, Levenberg-Marquardt (LM) method, L₂ cooled roughness (CRL2)
method and L₁ cooled roughness (CRL1) method are applied to the problem of recovering the relative permittivity structure of a dielectric object. The CRL1 method is a novel technique for the recovery of the relative permittivity structure of a dielectric object introduced in this work. The frequencies used in this work range from 0.80Hz to 1.2 GHz. The size of the permittivity structure is approximately 1 wavelength, which is approximately 30cm at 10Hz. The gradient method and LM method were unable to recover the relative permittivity structure unless the starting model is very close to the target. Both methods require a starting model that is close to the target model for them to be successful. The CRL2 method was able to recover a blurry approximation to the target relative permittivity structure. The blurriness is due to the L₂ norm. The CRL1 method is able to recover “blocky” structure. In the absence of noise, the CRL1 method was able to recover structure that was approximately one third wavelength in size. The recovery of structure at a fraction of a wavelength is highly sensitive to noise. Even at 0.0 1% noise, the CRL1 algorithm had difficulty recovering the exact structure.
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Lienstromberg, Christina. "On Microelectromechanical Systems with General Permittivity." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLN007/document.
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Dans le cadre de la thèse des modèles physico-mathématiques pour des microsystèmes électromécaniques avec une permittivité générale sont développés et analysés par des méthodes mathématiques modernes du domaine des équations aux dérivées partielles. En particulier ces systèmes sont à frontière libre et pour conséquence difficiles à traiter. Des méthodes numériques ont été développées pour valider les résultats analytiques obtenus<br>In the framework of this thesis physical/mathematical models for microelectromechanical systems with general permittivity have been developed and analysed with modern mathematical methods from the domain of partial differential equations. In particular these systems are moving boundary problems and thus difficult to handle. Numerical methods have been developed in order to validate the obtained analytical results
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Scholte, John W. "The complex permittivity of compacted Halton till." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0006/MQ42199.pdf.
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Kokan, Julie Runyan. "Processing of low permittivity silica thin films." Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/20032.
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Nicholls, Simon J. "High permittivity ceramics for dielectrically loaded applications." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/16354/.
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A temperature-stable, ultra-high permittivity dielectric ceramic, based on CTLNT, has been successfully fabricated at significantly reduced sintering temperatures with no deterioration of microwave properties, through the addition of a Bi_4B_2O_9 (BBO) sintering aid. This work has been an extension of previous findings where it was shown that 0.2CaTiO_3-0.8(Li_0.5Nd_0.5)TiO_3 (CTLNT) with 4wt% BBO as a liquid-phase sintering aid gives rise to exceptional microwave (MW) dielectric properties, (relative permittivity, ε_r = 127, quality factor, Qf_0 = 2700 GHz, and temperature coefficient of the resonant frequency, τ_f = +4 ppm/°C) at reduced sintering temperatures (1200°C). Prior to this, it has been exceptionally difficult to produce a large ε_r dielectric material, with both a low sintering temperature and near-zero temperature stability, without dramatic deterioration of the dielectric properties of the material. This contribution set out to investigate and understand the sintering mechanism between the CTLNT + xwt% BBO system, to aid in the development of designer sintering aids in the development of other microwave dielectric ceramic materials and devices. CTLNT + 1, 3, 4 and 5wt% BBO compositions were fabricated and a variety of analysis techniques were used, such as density, XRD, SEM, TEM, EDS and MW characterisation. Density increased with increasing BBO concentration and sintering temperature, and the MW results reflected the changes in density. The 1wt% BBO composition showed the greatest variation between the sintering temperatures, and 4wt% composition demonstrated optimum MW results of: ε_r=125, Qf_0=2518 GHz and τ_f=4 ppm/°C, at a sintering temperature of 1200°C. The variation of τ_f with changes in BBO concentration was non-linear, which suggested a chemical reaction was taking place. XRD results revealed no secondary phases, regardless of BBO concentration. SEM results showed increased crystal grain size as BBO concentration and sintering temperatures increased, as well as increased contrast variation on the polished surface and darker-contrast amorphous phase in the fracture surface. The contrast variation in the polished surfaces were also indicative of a chemical reaction. Using a combination of XRD, TEM and SEM it was demonstrated that highly polarisable Bi3+ ions entered the CTLNT perovskite lattice and locally increasing ε_r. The accompanying ex-solution of TiO2 precipitates, observed and analysed under SEM and TEM, as the BBO concentration increased implied the formation of Ti vacancies (V_Ti^'''') in the perovskite matrix to compensate for the extra positive charge of the Bi3+. The ex-solution of Ti indicates Bi3+ ions substitute onto the A-site of the perovskite crystal system for lower valence ionic elements, after the following generic defect equation: 4(A)_A^x+(Ti)_Ti^x⇒4(Bi)_A^∙+V_Ti^'''' The residual phase was found to be a boron-rich liquid-phase, which acted as the sintering aid, with a large negative τ_f which compensates for the positive τ_f of the CTLNT. The CTLST + xwt% BBO system (S = Sm) was then investigated to determine if a similar mechanism would occur. CTLST + 1, 2, 3 and 4wt% BBO compositions were fabricated and underwent the same analysis techniques. Density increased with increasing BBO concentration up to 1250°C, after which density fell for all samples; the 4wt% BBO composition exhibited the largest density, at 1250°C. The MW results reflected this trend, which saw a general increase in ε_r as BBO concentration and sintering temperature increased, which fell universally at 1300°C. 〖Qf〗_0 would generally increase with increased BBO concentration, across all sintering temperatures, while a dip was observed at 1250°C, and the 4wt% BBO composition demonstrated optimum properties of: ε_r = 105.7, Qf_0 = 3295 GHz and τ_f = -4 ppm/°C, sintered at 1200°C. Contrary to the CTLNT system, the variation of τ_f with BBO content and sintering temperature was linear. SEM reflected density changes, where crystal grain increased with increasing BBO concentration, up to 1250°C. At 1300°C, samples suffered from dissolution into the liquid-phase, increasing pore sizes, decreasing density and, thus, impacting on the MW properties of the samples. Similar to the CTLNT system, contrast variation was observed, in addition to darker B-rich liquid phase in the fracture surface. EDS from both SEM and TEM revealed that Bi was present within the CTLST matrix, however no TiO2 precipitates were observed. Large Zr contamination within CTLST is the likely cause of the difference in defect chemistry, as excess of Zr substitution onto the perovskite B-site compensates for Bi substitution onto the A-site, negating the need for TiO_2 precipitates to ex-solve. Multi-layer ceramic capacitors (MLCCs) of the CTLNT + 4wt% BBO composition were fabricated to determine whether the temperature stabilities of the material in conjunction with a large ε_r would allow the material to be a suitable candidate as a Class 1 C0G/NP0 MLCC device. Fabrication of the devices followed the conventional method, but required modification due to delamination. These modifications included: longer firing times to allow for binders and plasticisers to burn-out fully; calcined alumina powder base to fire and sinter samples upon, to avoid sticking issues; and solvent wetting of individual layers to adequately fuse layers together pre-firing and sintering. Successful MLCC devices had case sizes of EIA ‘2928’ and IEC ‘7472’. SEM and EDS revealed no mixing or exchange of materials between the dielectric and the platinum internal electrode, and generally good adhesion between both materials. Electrical tests revealed that, despite the temperature stability observed at 1-3 GHz in the MW study, that the MLCC devices would be classed as EIA “M8J” and IEC “P1000”, however maximum available test frequency of 1 MHZ is much lower than the average operating frequencies of class 1 devices, which lie between 100 MHz – 30 GHz.
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Herve, Yann. "Le radar WISDOM à bord du Rover de la mission ExoMars : Caractérisation et préparation du retour scientifique." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLV071/document.
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La recherche de trace de vie, passée ou présente, sur Mars est l’objectif principal de la mission martienne européenne ExoMars (ESA-Roscosmos), dont le lancement est prévu pour l’été 2020. Cette mission déposera à la surface de Mars un Rover équipé d'instruments dédiés notamment à l’étude du sous-sol de la planète dont une foreuse collectera des échantillons. Le travail de thèse présenté dans ce manuscrit porte sur la préparation du retour scientifique de l’expérience du radar WISDOM (Water Ice and Subsurface Deposits Observation on Mars) embarqué à bord du Rover d’ExoMars 2020 et dont l’objectif principal est la caractérisation, avant forage, du sous-sol proche de Mars.Les données recueillies par WISDOM permettront d’identifier les formations géologiques du sous-sol et de comprendre les processus qui en sont à l’origine. Elles guideront également les opérations de prélèvement d'échantillons en profondeur. L'objectif de cette thèse était de préparer les outils de traitements et d'interprétation de ces données. Les résultats obtenus doivent permettre d'exploiter au mieux les possibilités de l'instrument et d’atteindre les ambitieux objectifs technologiques (en termes notamment de résolution et de sensibilité) et scientifiques fixés. Plus précisément, il s’agissait de mettre en place des outils pour aboutir à une description des premiers mètres du sous-sol via l’interprétation des radargrammes de WISDOM en termes d’épaisseur de couche(s), de rugosité des interfaces, de distribution en taille d’éventuelles roches enfouies, d’orientation des strates et de constantes géo-électriques pour les unités géologiques détectées.Ce travail de thèse a permis la mise en place d’une chaîne de traitement de données ainsi que d’outils d’interprétation (traitement automatique et modélisation du radar).L’approche a été d’aborder le problème à la fois du point de vue théorique et du point de vue pratique. En conséquence, ce travail s’est appuyé sur deux aspects indissociables que sont, d’une part, la modélisation (analytique et numérique) du fonctionnement de l’instrument dans son environnement et, d’autre part, le traitement des données simulées et/ou expérimentales obtenues en milieu contrôlé ou lors de campagnes de mesures organisées dans le cadre de cette thèse<br>The main objective of European ExoMars (ESA-Roscosmos) mission is to search for signs of past or present life on Mars. The mission, to be launched in summer 2020, will deliver a rover on the surface of Mars. This rover accommodates instruments designed to investigate the close subsurface and, in particular, a drill that will collect samples at depth ranging from 0.5 m to 2 m. This thesis manuscript relates the preparation of the scientific return of the WISDOM (Water Ice and Subsurface Deposits Observation on Mars) radar experiment whose main objective is to characterize, before drilling, the shallow subsurface of Mars.Data obtained by WISDOM will shed the light on geological structures in the subsurface and therefore help trace back the history of the investigated Martian sites. Furthermore, they will help to identify the most promising locations to collect samples without jeopardizing the drill. The objective of this thesis was to efficiently pave the way to data interpretation and appraise WISDOM’s potentiality.In order to reach the ambitious scientific and technologic objectives (especially in terms of resolution and sensitivity) of WISDOM, we have developed tools that rely on a deep understanding of the instrument. The ultimate goal of these tools is to provide a reliable representation of the shallow subsurface and quantitative interpretation in terms of thickness and orientation of underground layers, roughness at interfaces, distribution of buried rocks and geoelectrical constant for each geological unit detected.This thesis manuscript describes the signal processing chain and tools developed in order to prepare WISDOM’s scientific return. When possible, approaches based on automatic detection were preferred. This work relies both on theoretical and practical investigations, including an accurate (analytical and numerical) modeling of the instrument operations and test on experimental data acquired during field campaigns on potential Martian analogs
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Akhtar, Jaleel. "Controlled resolution reconstruction of one-dimensional permittivity profiles." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=971682518.
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Lienstromberg, Christina [Verfasser]. "On microelectromechanical systems with general permittivity / Christina Lienstromberg." Hannover : Technische Informationsbibliothek (TIB), 2016. http://d-nb.info/1099105137/34.
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Umaña, Juan Antonio. "Measurement of complex dielectric permittivity of pavement materials." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0004/MQ32519.pdf.
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Marais, Johannes Izak Frederik. "A permittivity measurement system for high frequency laboratories." Thesis, Link to the online version, 2006. http://hdl.handle.net/10019/580.
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Weinberg, Shari. "In-plane permittivity of spin-coated polymer films." Thesis, Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/9363.
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Zhang, Maomao. "Permittivity and conductivity imaging in electrical capacitance tomography." Thesis, University of Bath, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.687378.
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Electrical capacitance tomography (ECT) is a technology that images the dielectric permittivity distribution of materials under test. ECT has been used as a tool for process monitoring in particular for two-phase flow measurement. These applications mainly focus on the dielectric samples, whose conductivity is negligibly small. This thesis studies ECT imaging with conductivity considerations. The conductive materials will affect the capacitance measurements and introduce difficulties in the ECT image reconstruction. This thesis presents solutions based on ECT to image material of different values of conductivity in different practical process or monitoring scenarios: the conductivity within materials under test is considered to be higher than 10^6 S/m, or less than 10 S/m. This work consists of the following innovative steps. (i) Through an ECT monitoring, floating (i.e., electrically non-grounded) metallic samples are imaged as dielectric illusions and the analysis of capacitance measurements over the conductors is delivered. (ii) Magnetic induction tomography (MIT) is firstly used for locating grounded metallic samples, thereafter as an assistant method to guide ECT to image the dielectric components. (iii) In low conductivity case MIT, as an indicator of conductive material again, helps ECT to solve multiphase flow problems. (iv) The multi-frequency complex ECT measurement provides a potential method to improve the ECT imaging ability for both conductive and dielectric materials. The first three ideas have been testified by both simulated and experimental results, while the fourth part is simulation-based results only on current stage.
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Pring, Philip Charles Jarrett. "A wideband spectrometer for the measurement of permittivity." Thesis, University of Warwick, 1989. http://wrap.warwick.ac.uk/106480/.
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Measurements of dielectric relaxations below 1 GHz, and over a wide temperature range, can yield important information on the dynamics of dipoles at both the microscopic and macroscopic levels. Complete characterisations of materials over this region are rare and normally require the integration of several measuring techniques. Although advances in electronics have extended the range of existing techniques, there remains, however, a need for an instrument of superior bandwidth. The present work addresses this problem and is concerned specifically with the methodology and implementation of an automated spectrometer designed to measure the complex permittivity of solids over 13 decades of frequency (between 10−5 Hz and 108 Hz) and at temperatures between -185 °C and +600 °C. Following reviews of current theory and experimental methods, the design and operational criteria of the spectrometer are discussed in principle and in detail. The structure of the operating software is described and examples of algorithms are given. The successful operation of the spectrometer is demonstrated by experiment, including isothermal investigations of the dielectric behaviour of poly(methylmethacrylate) at 35 °C and low density poly(ethylene) at 30 °C.
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González, López Giselle. "Wireless sensors embedded in high permittivity lossy media." Doctoral thesis, Universitat Politècnica de Catalunya, 2021. http://hdl.handle.net/10803/672242.
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The design of wireless sensors for operation embedded in a medium with high losses creates a series of additional constraints that should be taken into consideration at design stage to enhance sensor performance. In such a medium, both the real and the imaginary part of the relative permittivity will have a high value. In this thesis, the effect of the imaginary part (which basically accounts for medium losses) on sensor performance and signal propagation will be analysed in detail.
Although the attenuating effect the losses of this surrounding medium will have on a propagating microwave signal can be foreseen, there is still much to be learned with respect to how these dielectric properties impact the actual performance of the sensor, and how this effect may be prevented or mitigated at design stage. Furthermore, currently available set-ups to measure the performance of radiating devices have not been conceived to measure devices that do not operate in air.
Bearing this in mind, this thesis intends to shed some light on the specific challenges encountered when designing devices for embedded operation in high permittivity lossy materials. This is done by means of two specific embedded application scenarios. In the first one a wireless RFID temperature sensor is placed inside a concrete structure to monitor the evolution of the setting process of concrete. Whereas in the second scenario a microwave bodyscope is used to monitor metallic implants inside the human body. Finally, in-field results are presented for both scenarios.
High accuracy measurements of the evolution of concrete's relative permittivity over time and frequency are presented, which are then used as reference at sensor design stage. A specific analysis of the correlation between antenna performance and surrounding medium's dielectric properties is conducted and some preliminary design guidelines are provided. Furthermore, a novel miniaturized anechoic chamber for X-wave and embedded measurement is presented.<br>El diseño de sensores inalámbricos para operación dentro de medios con muchas pérdidas, genera una serie de limitaciones adicionales que han de ser tenidas en consideración durante la etapa de diseño para mejorar el rendimiento del sensor. En tal medio, tanto la parte real como la imaginaia de la permitividad relativa tendrán un valor elevado. En esta tesis, el efecto de la parte imaginaria (la cual está asociada a las pérdidas del medio) en el rendimiento del sensor y en la propagación de la señal serán analizados en detalle. Aunque el efecto atenuante que las pérdidas del medio tienen en una señal de microondas al propagarse a lo largo del mismo resulta previsible, hay aun mucho que aprender con respecto a cómo estas propiedades dieléctricas impactan en el rendimiento del sensor, y cómo este efecto puede ser evitado o mitigado durante la etapa de diseño. Adicionalmente, los sistemas de medida de dispositivos radiantes disponibles actualmente no han sido concebidos para llevar a cabo medidas de dispositivos que no operan en aire. Con esto en mente, esta tesis tiene la intención de arrojar algo de luz sobre los desafíos específicos asociados al diseño de dispositivos para operación embedida en medios con pérdidas. Para ello, serán utilizados dos escenarios de aplicación específicos. En el primero, un sensor RFID de temperatura es colocado dentro de una estructura de hormigón para monitorizar la evolución del proceso de fraguado del hormigón. Mientras que en el segundo caso un "bodyscope" de microondas es utilizado para monitorizar implantes metálicos dentro del cuerpo humano. Finalmente, resultados de medidas de campo son presentados para ambos escenarios. Medidas de alta precision de la evolución de la permitividad relativa del hormigón a lo largo del tiempo y en un cierto ancho de banda, son también presentadas. Estos valores son utilizados como referencia durante la etapa de diseño del sensor. Un análisis específico de la correlación entre el rendimiento de la antena y las propiedades dieléctricas del medio es llevado a cabo, y proveyendo algunas recomendaciones preliminares a tener en cuenta durante la etapa de diseño. Finalmente, se presenta un nuevo diseño de una cámara anecoica miniaturizada para medidas de sensores embebidos.
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Rai, Sheila. "Complex permittivity measurements by multi-mode microwave resonant cavity." Thesis, Imperial College London, 1992. http://hdl.handle.net/10044/1/11517.
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Amiet, Andrew. "Free space permittivity and permeability measurements at microwave frequencies." Monash University, Dept. of Electrical and Computer Systems Engineering, 2003. http://arrow.monash.edu.au/hdl/1959.1/9529.
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Sloma, A. "Complex dielectric permittivity of water, inorganic and organic solutions." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0019/MQ58086.pdf.
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Meda, Venkatesh. "Integrated dual frequency permittivity analyzer using cavity perturbation concept." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38236.
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Optimal utilization of microwave energy requires more basic knowledge of the dielectric properties of the material under investigation. The dielectric properties of materials subjected to microwaves are known to depend on moisture content, temperature and density of the material as well as the frequency of the applied microwave field. This thesis is focussed on the development and evaluation of the new Permittivity Analyser to measure the dielectric properties of agri-food materials at 915 and 2450 MHz using cavity perturbation concept.<br>In this study, the dielectric properties measuring system was designed and developed using cavity perturbation concept to measure the essential and fundamental parameters of microwave-material interaction; dielectric constant and dielectric loss factor of selected agri-food substances and organic solvents. The TM010 mode of electromagnetic energy was selected and configured to operate at the peakresonant condition for both ISM (Industrial, Scientific and Medical) approved frequencies of .915 and 2450 MHz frequencies. The resonant perturbation cavities were designed, fabricated and tested using the network analyser and the permittivity analyser. High Q (ratio of energy supplied to absorbed) values were reported for both frequencies. Basic calibration of the measurement system was performed using standard media such as air, water and alcohol. Necessary mathematical steps and algorithms were written and integrated into a user-friendly software program (Visual basic 6.0) to carry out the entire measurement.<br>The dielectric properties (epsilon' & epsilon ″) of materials such as; edible oils---canola, soya and sunflower oils, neem oil/pulp, homogenized milk (1, 2 and 3.25% fat), organic solvents such as ethanol, hexane and their mixtures were determined at various temperatures and frequency (915, 2450 MHz) combinations, using cavity perturbation technique. Linear relationships between the dielectric properties and temperature found in the literature were confirmed to be valid for certain ranges in case of edible oils, organic solvents and milk samples tested with the cavity perturbation method. Repeatibility and variability aspects of the permittivity analyzer at both the frequencies are presented.
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Waldron, Isaac James. "Ring Resonator Method for Dielectric Permittivity Measurements of Foams." Digital WPI, 2006. https://digitalcommons.wpi.edu/etd-theses/666.
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Dielectric permittivity measurements provide important input to engineering and scientific disciplines due to the effects of permittivity on the interactions between electromagnetic energy and materials. A novel ring resonator design is presented for the measurement of permittivity of low dielectric constant foams. A review of dielectric material properties and currently available measurement methods is included. Measurements of expanded polystyrene are reported and compared with results from the literature; good agreement between measurements and published results is shown.
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Ware, Brenton R. "Frequency response based permittivity sensors for measuring air contaminants." Thesis, Kansas State University, 2012. http://hdl.handle.net/2097/14190.
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Master of Science<br>Department of Biological and Agricultural Engineering<br>Naiqian Zhang<br>Permittivity, displayed when a dielectric material is exposed to an electric field, is a useful property for measuring impurities in a dielectric medium. These impurities often have a dipole moment different from the pure material, and the dipoles align through polarization and impede electric current. By measuring the resulting impedance in a known geometry, the permittivity can be determined.
Four permittivity sensors were utilized to measure contaminants that are associated with biofuels, specifically glycerol, ethanol, and ammonia. These sensors were based around either stainless steel or aluminum plates to ensure durability and reliability. By connecting each of these sensors to a signal generating control box, the gain and phase can be measured at 609 frequencies, from 10 kHz up to 120 MHz.
Data from each of the three contaminants were run through a method for detection. Measurements for ambient air and air with the contaminants were compared with a statistical analysis. Glycerol, ethanol, and ammonia each had significantly different measurements in the gain and phase data at a unique set of frequencies. Using a neural network analysis for detection resulted in a 95.8%, 93.9%, and 97.1% success rate for detecting glycerol, ethanol, and ammonia, respectively.
For ethanol and ammonia, where multiple concentrations were measured, regression methods were used to relate the frequency response data to the contaminant concentration. Stepwise regression, wavelet transformation followed by stepwise regression, partial least squares regression, and neural network regression were the four methods used to establish these relationships. Several regressions over-fit the data, showing coefficient of determination (R[superscript]2) values of 1.000 for training data, yet very low R[superscript]2 values for validation data. However, the best R[superscript]2 values of all the regressions were 1.000 and 0.996 for the training and validation data, respectively, from measuring ammonia.
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Jackson, Mitchell L. "Modeling the microwave frequency permittivity of thermoplastic composite materials." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06232009-063055/.
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Ravindran, Ramasamy. "Deposition and characterization of high permittivity thin-film dielectrics." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4530.
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Thesis (M.S.)--University of Missouri-Columbia, 2006.<br>The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 17, 2009) Includes bibliographical references.
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Croizer, Mathieu. "Applicateurs destinés aux études d’effets biologiques des ondes électromagnétiques sub-nanosecondes." Thesis, Limoges, 2015. http://www.theses.fr/2015LIMO0127/document.
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Depuis les années 1960, les scientifiques se sont intéressés à l’étude d’effets biologiques provoqués par des champs électromagnétiques impulsionnels. Les premiers effets ont été observés avec des impulsions dont la durée va de quelques microsecondes à quelques millisecondes. Ce phénomène, appelé électroporation, est de nos jours utilisé dans des thérapies anticancéreuses appelées électrochimiothérapies. Les études en laboratoires avec des impulsions ont continuées, mais avec des impulsions de plus en plus courtes, notamment des impulsions pouvant atteindre une durée de quelques centaines de picosecondes avec des amplitudes de forts niveaux (100MV/m). Ces études sont encore émergentes et nécessitent d’être poursuivies, mais pour cela, il est nécessaire de concevoir des moyens d’expérimentations électromagnétiques fiables. Ce travail de thèse consistait à concevoir deux applicateurs de champ électrique : un applicateur in vitro, dans le but d’illuminer des cellules contenues dans des éprouvettes et un applicateur in vivo dans le but de prévoir de futures thérapies non invasives pour le patient. Pour l’applicateur in vitro, les différents résultats obtenus en simulations et expérimentalement sont très encourageant et montrent qu’il est déjà possible d’effectuer des expérimentations biologiques avec. Pour l’applicateur in vivo, qui s’agit de l’antenne PSIRA initialement développée par C. E. Baum, plusieurs problématiques ont été soulevées. Tout d’abord, il a été montré que les tissus biologiques tels que la peau où les muscles ont des permittivités relatives élevées et de fortes pertes pour des fréquences de l’ordre de quelques GHz et au-delà. Afin de maximiser la pénétration de champ électrique à l’intérieur de ces tissus, il a été décidé d’immerger l’antenne dans un milieu de forte permittivité, tels que la glycérine et l’eau. Ces liquides possèdent également des pertes diélectriques non négligeables. Ces pertes ont un fort impact négatif sur les performances de l’antenne. Pour rendre ce système opérationnel plusieurs modifications doivent être opérées, notamment en changeant le milieu d’immersion par un milieu sans pertes<br>Since the years 1960, scientists have been interested to the study of biologic effects caused by pulsed electrical fields. The first effects were obtained with microseconds pulses and milliseconds pulses. This phenomenon has been called electroporation and it’s used in anticancerous therapies called electrochimiotherapies. Laboratory studies are continuing, but with shorter pulses like high level subnanoseconds pulses (100MV/m). These studies are emerging and must be pursued, but it’s necessary to design reliable electromagnetic systems. The goal of this thesis was to design two electrical field applicators: an in vitro applicator, to illuminate biologic cells contained in test tube and an in vivo applicator to predict future non invasive therapies. For the in vitro applicator, simulations and experimental results are very encouraging and biological experimentations would be possible with this system. For the applicator in vivo, which is the PSIRA antenna designed par C. E. Baum, many problems are highlighted. First, biological tissues like skin and muscle have high permittivity and high dielectric losses with frequencies in the order of GHz and behind. To maximize electric field penetration in these backgrounds it was decided to submerge the antenna in high permittivity background too, like glycerin and water. These liquids have high dielectric losses which have a strong negative impact on the antenna performances. To make this system operational, some modifications must be done, like changing the actual background with a no losses background
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Li, Ming. "Composition-structure-property relationships in high permittivity oxide-bassed perovskites." Thesis, University of Sheffield, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489139.
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The composition-structure-property relationships of several important oxides are reported. The effect of sintering atmosphere, cooling rate and post annealing in N2 on the composition, B-site cation ordering, electrical conductivity and microwave dielectric loss of BCN ceramics have been investigated. X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Raman Spectroscopy (RS) results confirm that a slow cooling rate from the sintering temperature and/or post annealing below the order-disorder phase transition temperature increases the degree of B-site cation 1:2 ordering regardless of the oxygen partial pressure (pOj) of the sintering and/or annealing atmosphere.
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Pendock, Graeme. "An investigation of minerals using microwave measurement of complex permittivity." Master's thesis, University of Cape Town, 1990. http://hdl.handle.net/11427/8339.
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Includes bibliography.<br>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 various forms of mineral analysis. Simple, low cost, on-line mineral analysis techniques are of interest to the mining industry. The objectives of this research project were to cover the background theory of microwave interaction with minerals and to investigate different microwave measurement techniques that could possibly be applied to mineral measurement. Measurements were then to be performed on selected minerals in order to observe any differences between them. Finally, to comment on the feasibility of using microwave measurement techniques for the differentiation, identification and analysis of minerals.
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Xie, Yuzhen. "Complex permittivity of a clayey soil permeated by aqueous ionic solution." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0005/MQ42227.pdf.
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Anderson, Christopher Jean B. Randall. "Determining the complex permittivity of materials with the Waveguide-Cutoff method." Waco, Tex. : Baylor University, 2006. http://hdl.handle.net/2104/4206.
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Lee, Kyeonghwan. "A dielectric permittivity sensor for simultaneous measurement of multiple soil properties /." Search for this dissertation online, 2005. http://www.lib.umi.com/cr/ksu/main.
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SOUZA, JORGE ANGELO MITRIONE. "EFFECTS OF HIGH PERMITTIVITY DIELECTRIC SUBSTRATES APPLIED OVER MICROWAVE PRINTED CIRCUITS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2014. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=24716@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO<br>A presente tese descreve e analisa a utilização de substratos e superstratos dielétricos para a otimização do desempenho de antenas impressas configuradas através de microlinhas. São avaliadas as características de casamento de impedância, geração de ondas de superfície, ganho, diretividade, facilidade de montagem, facilidade de medição, diagrama de radiação e possibilidade de miniaturização. São avaliadas também as antenas configuradas através de guias dielétricos para aplicações na banda milimétrica e no domínio do Terahertz. Um procedimento inicial para seleção do substrato, do superstrato e do modelo de antena é sugerido. Várias antenas utilizando microlinhas são simuladas, realizadas e caracterizadas.<br>This work presents the research, design and optimization of the fundamental effects of dielectric substrate and superstrate over printed antennas performance. Impedance matching, surface waves generation, gain, directivity, assembling, pattern diagram and miniaturization are investigated. A new dielectric waveguide antenna is also investigated for millimetric and Terahertz applications. A initial criteria for choosing a more efficient substrate, superstrate for a specific antenna model is suggested. Several antennas models are simulated, realized and measured.
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Lim, Teck-Guan. "Millimetre-wave tapered slot antennas on thick and high permittivity substrates." Thesis, University of Surrey, 2005. http://epubs.surrey.ac.uk/844576/.
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A simple and novel solution is proposed to overcome the main beam splitting of the tapered slot antenna (TSA) fabricated on a thick substrate with high dielectric constant. It utilised arrays of metal strip gratings to reduce the undesirable surface waves. Measured result of a 10lambda0 long 35GHz linear taper slot antenna (LTSA), shows a dramatic improvement in the radiation pattern and a measured front-to-back ratio of 20dB for both the planes. Further analysis shows that the metal strip gratings help to improve the directivity and return loss of shorter LTSAs. Comparing with a basic LTSA without modification, the 4lambda0 LTSA has a 4.3dB and 14.8dB improvement on its directivity and return loss, respectively, which is 13.2dB and 22.3dB. In addition, the side lobe level is also suppressed from -5.2dB to -14.4dB. A new stepped profile formed by multiple constant slot width sections, to match the impedance between the feed and the aperture, is developed. This novel step-tapered profile increases the directivity of the antenna without increasing its length. A step-tapered slot antenna (STSA) is demonstrated at 28GHz. It has a directivity of 7.9dB, a 2.5dB improvement over a LTSA with the same physical design, and shows no sign of main beam splitting. With the incorporation of the metal strip gratings, the directivity of the STSA further increases to 11.0dB with a return loss of 17.2dB. Finally, an improved CPW-to-slotline transition is developed for the STSA. The above work helps to open up the TSA for commercial millimetre-wave applications, such as radio-over-fibre, satellite communications and remote sensing, which previously were not feasible due to the requirements of fragile and costly ultra thin substrate or micromachining.
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健司, 堺. "Design of composite electromagnetic wave absorber by controlling permeability and permittivity." Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB10354136/?lang=0, 2010. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB10354136/?lang=0.
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Chai, Francis Kang-liang 1968. "Domain switching and spatial dependence of permittivity in ferroelectric thin films." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/282219.
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A domain model consistent with the measured capacitance-voltage ( CV) characteristic of PZT (Pb( Zr,Ti)O₃) capacitors is proposed. The model is introduced using a macroscopic electric field that is spatially uniform through the depth of the film. Then this multiple-domain model is generalized, and a spatially varying electric field model with a domain structure varying through the depth of the film is proposed. The spatial variation of the electric field is caused by dopant-ion charges in this work. A position-dependent permittivity is then deduced. Based upon this permittivity, the extraction of doping profiles in ferroelectric thin film capacitors using ferroelectric capacitance-voltage (CV) measurements is studied. The doping profile relation to measured CV curves for ferroelectric thin film capacitors is found to be analogous to the well-known result of metal-semiconductor Schottky junctions with an easily determined effective dielectric constant. Computer simulation shows the electrical doping concentration of ferroelectric thin film capacitors can be profiled accurately with the proposed model. The profiling shows compensation of the p-type PZT samples by the n-type niobium doping. Limitations of the Schottky profiling on ferroelectrics are investigated. Based on the approximate doping profiles extracted from CV measurement and the deduced permittivity, the measured CV characteristics are reconstructed through computer simulations. It is found that there is a minimum doping level below which it is not possible to obtain the doping profile from CV measurements. This minimum level depends on the shape of the CV curve, and a method to determine this minimum level from the CV curve is presented. For the films measured in this work, the minimum level is about 10¹⁸ cm⁻³. It is also found using the model that niobium doping slightly slows the volume growth of polarization with the electric field and has a tendency to increase the coercive field.
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Legras, Benoit. "Adsorptions et désorptions compétitives sous irradiation micro-ondes : étude de la conversion d’énergie électromagnétique couplée aux transferts de matière et de chaleur." Thesis, Rouen, INSA, 2011. http://www.theses.fr/2011ISAM0017/document.
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Dans cette thèse, nous nous sommes particulièrement intéressés au cas d'adsorptions compétitives sur des zéolithes, de molécules polaires en phase gaz, sous irradiation micro-ondes. Dans un premier temps, nous avons étudié de façon approfondie les mécanismes d'interactions onde-matière sur des systèmes adsorbant-adsorbant à l'aide de mesures de permittivités. Dans un second temps, des adsorptions ont été effectuées à l'échelle pilote et ont permis d'analyser les possibilités réelles, offertes par les micro-ondes. Le procédé de régénération adsorbant sous micro-ondes a été décrit à l'aide d'un modèle multi-physique et validé expérimentalement. Un procédé de purification d'un courant gazeux humide chargé en COV apolaire a été proposé. Ce procédé permet une récupération sélective et efficace des molécules d'eau et de toluène. Ce procédé s'appuie sur les différences de sélectivités d'adsorption de plusieurs zéolithes, ainsi que sur leurs pertes diélectriques contrastées<br>In this thesis, we particularly focused on competitive sorption of polar/apolar gaseous mixtures on zeolites under microwave irradiations. In a first step, we precisely studied wave-material mechanisms occuring between an electromagnetic wave and an adsorbat-adsorbent couple by studying thier dieclectric properties. In a second step, co-sorptions under microwave on a bench test have been realised and analysed. They showed the real advantages that microwave can bring to tjis process. Then, a regeneration process have benn described with a pmutiphysic modelling and experimentally validated. A purification process of a humide gas flow loaded with an apolar VOC have been proposed. The case of toluene, as an apolar compound, has been experimentally treated. This process allows an efficient and selective recovery of water and toluene molecules. This process uses the sorption selectivity properties of several zeolites and their contrasted dielectric losses
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Letertre, Thibaut. "Etude des comportements électromagnétiques des matériaux en fonction de la température pour modéliser l'impact des échauffements générés par les frottements de l'air sur un aéronef lors d'un vol à vitesse élevée." Thesis, Aix-Marseille, 2019. http://www.theses.fr/2019AIXM0388.
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En aéronautique, la variation en fonction de la température des caractéristiques électromagnétiques dans le domaine spectral des fréquences radar, de certains matériaux peut générer des problèmes importants comme une modification du fonctionnement des antennes radar, ou encore une modification de la signature radar de l'aéronef, ce qui peut engendrer une dégradation importante des niveaux de furtivité nominaux d'avions d'arme. En effet, les matériaux utilisés dans la conception d’aéronefs discrets vis-à-vis des ondes électromagnétiques sont souvent soumis à des échauffements liés d’une part, aux frottements avec l’air dans le cadre de vols à hautes vitesses (par exemple pour les bords d’attaques des ailes) et d’autre part à des échauffement liés à la proximité de sources de chaleurs directes comme des tuyères de moteurs à réactions ou sorties d’échappements. Les objectifs principaux de ce projet sont de concevoir un système large bande de caractérisations électromagnétiques de matériaux en fonction de la température et de proposer des modèles électromagnétiques relatifs à certains matériaux en incluant le paramètre d’intérêt, à savoir la température. Au-delà de ce travail de recherches de cette thèse, les résultats seront transposables à d’autres cas soit à températures modérées comme des températures biologique pour suivre des processus d’évolutions des permittivités de certains tissus en fonction d’une variation de température locale soit à températures plus élevées comme pour le suivi RFiD de dispositifs soumis à des températures élevées<br>In the field of aeronautics, the temperature-dependent variation of electromagnetic characteristics in the spectral range of radar frequencies of certain materials can generate significant problems such as changes in the operation of radar antennas or changes in the aircraft's radar signature, which can lead to a significant deterioration in the nominal stealth levels of weapon aircraft. Indeed, the materials used in the design of aircraft that are discreet with respect to electromagnetic waves are often subjected to heating due to friction with the air during high-speed flights (for example, for the leading edges of wings) and to heating due to the proximity of direct heat sources such as reaction engine nozzles or exhaust outlets. The main objectives of this project are to design a broadband system for the electromagnetic characterization of materials as a function of temperature and to propose electromagnetic models for certain materials, including the parameter of interest, temperature. Beyond this research work of this thesis, the results will be transposable to other cases either at moderate temperatures such as biological temperatures to follow processes of evolution of permittivities of certain tissues according to a local temperature variation or at higher temperatures as for RFiD monitoring of devices subjected to high temperatures
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Thomas, John Rhodes. "Investigation of properties of materials with negative permittivity and permeability : negative refraction /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/6113.
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Jenkins, Sharon. "Measurements of the complex permittivity of dielectric reference liquids and human tissues." Thesis, University of Bristol, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241174.
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Utley, Barbra Crompton. "Evaluation of a Permittivity Sensor for Continuous Monitoring of Suspended Sediment Concentration." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/29570.
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According to the US Environmental Protection Agency (USEPA) sediment is a leading cause of water quality impairment (US EPA, 2002). The annual costs of sediment pollution in North America alone are estimated to range between $20 and $50 billion (Pimentel et al., 1995; Osterkamp et al, 1998, 2004). Due to the large spatial and temporal variations inherent in sediment transport, suspended sediment measurement is challenging.
The overall goal of this research was to develop and test an inexpensive sensor for continuous suspended sediment monitoring in streams. This study was designed 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 within the system. This study developed prediction models for SSC with input variables of temperature, specific conductivity, and gain and/or phase at multiple frequencies. The permittivity sensor is comprised of an electrode, power source, and a control box or frequency generator.
Fixed and mixed effect, multiple, linear regression models were created and compared for target frequencies. However, it was not possible to meet the normality requirements for prediction accuracy. Partial Least Squares (PLS) regression techniques were also applied to gain and phase data for 127 of the 635 frequencies. The three models with the lowest error between predicted and actual values of SSC for validation were further tested with nine levels of independent validation data. The largest model error (error>50%) occurred for the top three models at 0 and 500 mg/L. At the higher concentrations error varied from 1-40%.
Once the treatment levels, of the independent validation data set, were near 1000 mg/L the prediction accuracy increased for the top three models. Model 3A, a phase based model, preformed the best. Model 3A was able to predict six of the nine independent validation treatment levels within 300 mg/L. Future research will provide additional laboratory and field testing of the prototype sensor.<br>Ph. D.
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Tang, Ning. "A real-time control system for a frequency response-based permittivity sensor." Thesis, Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/1434.
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Boltaev, A. P., F. A. Pudonin, and I. A. Sherstnev. "Electrical and Dielectric Properties of Nanoisland Systems Below Percolation Threshold." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34818.
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Electric and dielectric properties of nanoisland metal films were studied in this work. Permittivity of
these films was determined from the analysis of the dependences of the susceptance of the films. It is found
that the effective permittivity of the researched structures has abnormally high positive value (107-108). The
temperature dependence of the permittivity of the films practically does not differ from the temperature
dependence of the conductivity of these films. Such behavior of these dependences is possible, if the reasons
for the change of permittivity and conductivity of the films with the temperature are of the same nature. With
the growth of the electric field effective permittivity of the films decreases and the conductivity increases. The
cause behind the high effective permittivity of the films is the island nature of these metal films, and it is
associated with the polarization of the dipoles, formed by couples negatively and positively charged metal
islands.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34818
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Naseem, Abbasali. "Computation and Analysis of Effective Permittivity of Thin Film Nanostructures: An Effective Medium Perspective." University of Toledo / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1279298769.
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Boujamaa, Rachid. "Caractérisations physico-chimiques et électriques d’empilements de couches d’oxyde à forte permittivité (high-k) / grille métallique pour l’ajustement du travail effectif de la grille : application aux nouvelles générations de transistors." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENT100.
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Cette thèse s'inscrit dans le cadre du développement des technologies CMOS 32/28nm chez STMicroelectronics. Elle porte sur l'étude d'empilements de grille métal/diélectrique high-k élaborés selon une stratégie d'intégration Gate First, où le couple TiN/HfSiON est introduit avec une couche interfaciale SiON et une encapsulation de la grille TiN par du polysilicium. Cette étude s'est principalement focalisée sur l'analyse des interactions entre les différentes couches constituant les empilements, en particulier des additifs lanthane et aluminium, employés pour moduler la tension de seuil Vth des transistors NMOS et PMOS respectivement. Les analyses physico-chimiques réalisées au cours de ces travaux ont permis de mettre en évidence la diffusion en profondeur des éléments La et Al à travers le diélectrique de grille HfSiON sous l'effet du recuit d'activation des dopants à 1065°C. Les résultats obtenus ont montré que ce processus de diffusion entraine une réaction du lanthane et de l'aluminium avec la couche interfaciale de SiON pour former un silicate stable La(ou Al)SiO au profit de la couche de SiON. L'analyse des propriétés électrique des structures MOS a permis de révéler que la présence d'atomes La ou Al proximité de l'interface HfSiON/SiON conduit à la présence d'un dipôle généré à cette interface, qui a pour effet de décaler le travail de sortie effectif de la grille métallique<br>This thesis is part of the development of CMOS technologies 32/28nm STMicroelectronics. It focuses on the study of stacks of metal / high-k dielectric prepared by an integration strategy Gate First , where the couple TiN / HfSiON gate is introduced with an interfacial layer SiON and encapsulation of TiN gate polysilicon by . The study was mainly focused on the analysis of interactions between the various layers forming the stacks , in particular lanthanum and aluminum additives , used for modulating the threshold voltage Vth of the PMOS and NMOS transistors respectively . The physico-chemical analyzes in this work helped to highlight the depth distribution of the elements La and Al through the HfSiON gate dielectric under the influence of dopant activation annealing at 1065 ° C. The results obtained showed that this diffusion process causes a reaction of lanthanum and aluminum with the interfacial layer of SiON to form a stable silicate La ( or Al ) SiO benefit of the SiON layer . The analysis of electrical properties of MOS structures revealed that the presence of the atoms near the Al or HfSiON / SiON interface leads to the presence of a dipole generated at this interface , which has the effect of shifting actual output work of the metal gate
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Azzolina, Jury Federico. "Préparation et caractérisation de zéolithes dopées par des métaux de transition : Mesure de propriétés diélectriques et magnétiques et leur application à la synthèse de composés chimiques sous irradiation microondes." Thesis, Rouen, INSA, 2013. http://www.theses.fr/2013ISAM0025.
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Cette étude est centrée sur la synthèse et la préparation de zéolithes modifiées par des métaux de transition avec leurs applications en catalyse sous irradiation microondes. Des travaux précédents ont montré l’intérêt de modifier des zéolithes avec des métaux de transition pour leur application sur des réactions d’oxydation et d’utiliser les microondes afin d’augmenter les vitesses de réaction. Dans cette thèse, nous avons étudié deux types de structure zéolithique (MEL et FAU) dopés par des métaux de transition (Co, Mn, Fe, Zn, Ni, Cr) à différentes concentrations. Une étude classique de caractérisation a permis d’augmenter la connaissance sur la préparation de zéolithes modifiées et de comprendre leur influence sur l’activité catalytique. La réaction d’oxydation partielle du styrène pour la production du benzaldéhyde a été choisie comme réaction modèle. La zéolithe Co-ZSM-11 a présenté la meilleure activité catalytique dans cette étude ainsi que par rapport à d’autres catalyseurs présentés dans la littérature.Les réactions d’oxydation du styrène ont été étudiées sous irradiation microondes et sous chauffage conventionnel. Aucune différence sur l’activité des zéolithes dopées n’a été observée pour les deux types de chauffage. Les faibles valeurs de permittivités et perméabilités des zéolithes dopées par des métaux de transition rendent difficile l’intensification du procédé d’obtention de benzaldéhyde à partir de l’oxydation du styrène sous microondes. Les paramètres de la réaction modèle ont été optimisés et une étude cinétique a été menée avec la zéolithe Co-ZSM-11. Enfin, le chauffage par hystérésis diélectrique a été utilisé dans la synthèse de zéolithes ZSM-11. Le temps de synthèse a été considérablement réduit (80%) par rapport au temps nécessaire sous chauffage conventionnel<br>This study focuses on the synthesis and preparation of modified zeolites with transition metals and theirs applications in catalysis under microwave irradiation. Previous works have shown interest in modifying zeolites with transition metals for their application to oxidation reactions and in using microwave irradiation in order to increase the reaction rates. In this thesis, we studied two types of zeolite structure (MEL and FAU) doped with transitionmetals (Co, Mn, Fe, Zn, Ni, Cr) at different concentrations. A classic characterization study has increased the knowledge on the preparation of modified zeolites and the understanding of their influence on thecatalytic activity. The styrene partial oxidation reaction for benzaldehyde production was chosen as amodel reaction. Co-ZSM-11 zeolite presented the best catalytic activity in this study and also compared to other catalysts found in the literature. The styrene oxidation reactions were studied under microwave irradiation and under conventional heating. No difference in the activity of doped zeolites was observed for both types of heating. The low values of permittivity and permeability of zeolites doped with transition metals make difficult the intensification of the benzaldehyde production process from styrene oxidation under microwave. The parameters of the model reaction have been optimized and a reaction kinetic study was carried out by using the Co-ZSM-11 zeolite. Finally, the hysteresis dielectric heating was used in the synthesis of ZSM-11. The synthesis time was significantly reduced (80%) under microwave irradiation compared to conventional heating
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Couderc, Orian. "Inversion de permittivités d’une structure dièdrique au moyen de la polarimétrie radar." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLC009/document.
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Dans la situation d’un radar monostatique la configuration diédrique présente l’avantage de renvoyer un signal fort grâce au mécanisme de double rebond. De plus, il s’agit d’une configuration omniprésente par exemple en zone urbaine, avec des structures rue-bâtiment, ou en forêt, avec des structures de type sol-arbre. Les signaux rétrodiffusés sont donc liés à ces structures, plus précisément aux matériaux les composant, via leurs permittivités diélectriques. Retrouver ces permittivités depuis la mesure des champs rétrodiffusés permettrait l’identification des matériaux de la structure diédrique. Ceci mène à des applications telles que la détection de défauts dans la structure, l’estimation de la teneur en eau des sols ou du béton, ou in fine à des thématiques de classification, pour des objets dans des images radar par exemple, ou de détection de changement. En modélisant le mécanisme de double rebond lié à la structure de dièdre par deux réflexions successives via les coefficients de Fresnel, trois méthodes d’inversion des permittivités ont été mises en place au cours de la thèse. La première, analytique, utilise à un angle d’incidence donné la mesure des champs copolarisés. Les deux autres méthodes, alliant une partie analytique et une partie numérique, nécessitent la mesure, du ratio polarimétrique pour l’une, du champ horizontal pour l’autre, effectuée à deux angles d’incidence différents. Ces méthodes ont été validées numériquement à l’aide de la méthode d’Optique Géométrique fournie par le logiciel FEKO. Des mesures en chambre anéchoique ont été effectuées afin de valider ces méthodes. De même une mesure in-situ a été effectuée sur un dièdre en béton formé par un angle entre deux murs<br>For a monostatic radar, the dihedral arrangementexhibits a strong response compare tobare surface. This phenomenon can be seen in radarimages of urban areas or forestry as building andstreets and trunks and ground are forming such structures.This signature can be modelled with the doublebounce equation as a cascade of Fresnel reflectioncoefficients. These coefficients depend on the permittivitiesof the structures. Finding these permittivitiesfrom the backscattered fields may allowed to identifythe materials involved in the dihedral. Thereforethiscan be applied for default detection, moisture retrievaland classification topics for instance.By modelling the double bounce scattering with Fresnelcoefficients, three methods have been developedto retrieve these permittivities. The first one uses asingle incidence angle and the measurements of copolarisedfields. The last two methods need the measurementof the copolarised fields ratio or of the horizontalelectric field alone at two different incidenceangles. All these methods have been validated, firstnumerically using FEKO RL-GO method, then experimentally,with measurements in anechoic chamber. Atlast, in-situ measurements have been performed on awall corner made of concrete to assess the methodon a real case
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Apedjinou, Anoumou. "Cavité de type klystron pour des dispositifs microondes." Thesis, Limoges, 2019. http://www.theses.fr/2019LIMO0017/document.
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Les propriétés électriques des matériaux sont des données indispensables dans les phases de conception de circuits micro-ondes. Ainsi, de nombreuses méthodes ont été mises au point en s’appuyant sur des mesures de paramètres «S», pour les systèmes de transmission-réflexion, ou de fréquences de résonance, pour les méthodes résonantes. Chacune d’entre elles présente des caractéristiques adaptées à un type de géométrie d’échantillon, à une bande de fréquence d’analyse, à une précision des résultats souhaitée... Dans tous les cas, les dimensions de l’échantillon doivent être au moins de l’ordre de grandeur de la longueur d’onde et donc, les caractérisations deviennent impossibles aux basses fréquences pour des échantillons de petites tailles. Un autre inconvénient de ces méthodes est qu’il est obligatoire de connaître parfaitement l’épaisseur de l’échantillon pour déterminer avec précision les caractéristiques électriques du matériau. L’objectif de ce travail de thèse a donc consisté à mettre au point une nouvelle méthode de caractérisation en s’appuyant sur une cavité de géométrie particulière. Celle-ci permet des mesures basses fréquences pour des dimensions très inférieures à la longueur d’onde. Avec un système de couplage original, nous avons pu également obtenir une réponse en transmission particulière, caractérisée par une fréquence de résonance et une fréquence d’antirésonance. Par rapport aux méthodes classiques qui ne travaillent que sur la fréquence de résonance, cette double information permet de déterminer à la fois la permittivité du milieu mais également l’épaisseur de l’échantillon<br>The electrical properties of the materials are essential data in the design phases of microwave circuits. Thus, many methods have been developed based on "S" parameter measurements, for transmission-reflection systems, or resonance frequencies, for resonant methods. Each of them has characteristics adapted to a type of the samplegeometry, to the frequency band of analysis, to a desired precision of the results... In all the cases, the dimensions of the sample must be at least of the order of the wavelength and therefore the characterizations become impossible at low frequencies for samples of small sizes. Another disadvantage of these methods is that it is mandatory to know perfectly the thickness of the sample to accurately determine the electrical characteristics of the material. The objective of this thesis work was therefore to develop a new method of characterization based on a cavity of particular geometry. This allows low frequency measurements for dimensions much smaller than the wavelength. With an original coupling system, we have also been able to obtain a particular transmission response, characterized by a resonance frequency and an antiresonance frequency. Compared to conventional methods that only work on the resonant frequency, this double information makes it possible to determine both the permittivity of the medium but also the thickness of the sample
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Tkachov, Igor Ivanovich. "Millimeter wave complex dielectric permittivity and complex magnetic permeability measurements of absorbing materials /." Thesis, Connect to Dissertations & Theses @ Tufts University, 2000.
Find full textAbstract:
Thesis (Ph.D.)--Tufts University, 2000.<br>Adviser: Mohammed Nurul Afsar. Submitted to the Dept. of Electrical Engineering. Includes bibliographical references (leaves 183-192). Access restricted to members of the Tufts University community. Also available via the World Wide Web;
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Rahtu, Antti. "Atomic layer deposition of high permittivity oxides : film growth and in situ studies." Helsinki : University of Helsinki, 2002. http://ethesis.helsinki.fi/julkaisut/mat/kemia/vk/rahtu/.
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Shultz, Sarah. "Calibration of permittivity sensors to measure contaminants in water and in biodiesel fuel." Thesis, Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/2339.
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Alabaster, C. M. "The Microwave properties of tissue and other lossy dielectrics." Thesis, Cranfield University, 2004. http://hdl.handle.net/1826/251.
Full textAbstract:
This thesis describes work on the theoretical modelling and experimental measurement
of the complex permittivity of dielectrics. The main focus of research has been into the
characterisation of permittivity of planar and layered samples within the millimetre
wave band. The measurement method is based on the free-space measurement of the
transmission and reflection coefficients of samples. A novel analytical method of
determining the transmission and reflection coefficients as functions of frequency
arising from a generalised structure of planar dielectric layers is also described and
validated. The analytical method is based on signal flow techniques. The measurement
and analytical techniques have been applied in two main areas: firstly, the acquisition of
new data on human skin in the band 57 to 100GHz and secondly, the detection and
location of defects in composite materials for which a band of 90 to 100GHz was used.
Measurements have been made on the complex permittivity of a single sample of
excised human skin fixed in formaldehyde. The experimental results have been
corrected to account for the fixing process in formaldehyde and are projected to body
temperature. This data is, to the best of the author’s knowledge, the first of its kind to be
published. Predicted skin permittivity based on various relaxation models varies widely
and only partially fits the measured data. The experimental results have been used to
determine the parameters of a Cole-Cole function which gives the best fit to the
measured data. The measured skin data has also been used to calculate power deposition
in skin exposed to millimetre wave radiation. This work concludes that a skin surface
temperature rise of only 0.20C results from a thirty second exposure to signals of
100W/m2.
Experimental work with fibreglass composite samples has shown that defects such as
delaminations, voids, matrix cracks and improper cure result in resolvable differences in
the dielectric properties of the samples at 90 – 100GHz. The measurement technique is
particularly sensitive to the detection of cracks and its spatial resolution is 20mm or
better. Whilst confirming the general conclusions of previously published work, the
specific findings of this study are novel.
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Флюнт, О. Є. "Зміна параметрів діелектричного спектра системи зі стрибковою провідністю під дією одновісного тиску". Thesis, Сумський державний університет, 2014. http://essuir.sumdu.edu.ua/handle/123456789/39552.
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Для пояснення сильної залежності діелектричного відгуку від одновісного тиску запропоновано модель системи, у якій виникають певні утворення елементарних диполів. Тому експериментальні діелектричні спектри відображають властивості утворень диполів, характерні частоти яких розподілені за степеневим законом. Відповідно до моделі, одновісний тиск приводить до однакової відносної зміни характер-
них частот ефективних диполів. Модель пояснює як підвищення діелектричної проникності, так і зменшення показника степеня n у разі підвищення одновісного тиску.