Dissertations / Theses: 'Surface impedance'

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Aude, Diana Prado Lopes. "Modeling superconductors using surface impedance techniques." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61254.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 53-54).
This thesis develops a simulation tool that can be used in conjunction with commercially available electromagnetic simulators to model the behavior of superconductors over a wide range of frequencies. This simulation method can be applied to metals both in the normal and superconducting state and is based on calculating surface impedance as a function of temperature, frequency and material parameters (such as the coherence length and the normal state conductivity). The surface impedance calculations apply the Mattis Bardeen and Zimmermann formulations of conductivity for superconductors to classical transmission line theory. When the tool is used with the Zimmermann formulation, it can model the behavior of superconductors with arbitrary purity, including very clean superconductors, which cannot be handled correctly by the Mattis Bardeen conductivity approach used in current simulators such as SuperMix [1]. Simulations were performed using the developed tool with Ansoft's HFSS EM simulator. The results for a copper printed circuit board resonator showed very good agreement with measured data, attesting to the soundness of the transmission line theory used to develop this tool. A microfabricated niobium coplanar waveguide resonator - for use in quantum computing applications - was also modeled and simulations gave the expected results for the electric field distributions and the variation of Q with temperature and capacitive coupling. The tool developed here can therefore be used to predict the electromagnetic behavior of a superconducting device as function of the material parameters, operating temperature and frequency. With measurements of the device's Q at a recorded frequency and temperature, this tool can also be used to determine the mean free path of the material (assuming other material parameters such as coherence length, transition temperature (Tc) and the ratio of the energy gap to kBTc are known). Equivalently, if all material parameters are known, comparison of Q measurements with simulation results can be used to determine the operating temperature, which may otherwise be difficult to measure in cryogenic environments.
by Diana Prado Lopes Aude.
S.B.

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Porch, Adrian. "Microwave surface impedance of YBa₂Cu₃O₇." Thesis, University of Cambridge, 1992. https://www.repository.cam.ac.uk/handle/1810/283677.

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Syropoulou, Stella. "AC Impedance Testing of Surface Treatments on Concrete." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511869.

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Xiao, Binping. "Surface Impedance of Superconducting Radio Frequency (SRF) Materials." W&M ScholarWorks, 2012. https://scholarworks.wm.edu/etd/1539623605.

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Superconducting radio frequency (SRF) technology is widely adopted in particle accelerators. There remain many open questions, however, in developing a systematic understanding of the fundamental behavior of SRF materials, including niobium treated in different ways and various other bulk/thin film materials that are fabricated with different methods under assorted conditions. A facility that can measure the SRF properties of small samples in a range of 2∼40 K temperature is needed in order to fully answer these questions. The Jefferson Lab surface impedance characterization (SIC) system has been designed to attempt to meet this requirement. It consists of a sapphire-loaded cylindrical Nb TE011 cavity at 7.4 GHz with a 50 mm diameter flat sample placed on a non-contacting end plate and uses a calorimetric technique to measure the radio frequency (RF) induced heat on the sample. Driving the resonance to a known field on this surface enables one to derive the surface resistance of a relatively small localized area. TE011 mode identification has been done at room temperature and 4 K, and has been compared with Microwave StudioRTM and SuperFish simulation results. RF loss mechanisms in the SIC system are under investigation. A VCO phase lock loop system has been used in both CW and pulsed mode. Two calorimeters, with stainless steel and Cu as the thermal path material for high precision and high power versions, respectively, have been designed and commissioned for the SIC system to provide low temperature control and measurement. A power compensation method has been developed to measure the RF induced power on the sample. Simulation and experimental results show that with these two calorimeters, the whole thermal range of interest for SRF materials has been covered, The power measurement error in the interested power range is within 1.2% and 2.7% for the high precision and high power versions, respectively. Temperature distributions on the sample surface for both versions have been simulated and the accuracy of sample temperature measurements have been analysed. Both versions have the ability to accept bulk superconductors and thin film superconducting samples with a variety of substrate materials such as Al, A12O3, Cu, MgO, Nb and Si. Tests with polycrystalline and large grain bulk Nb samples have been done at impedance, least-squares fittings have been done using SuperFit2.0, a code developed by G. Ciovati and the author.;Microstructure analyses and SRF measurements of large scale epitaxial MgB2 films have been reported. MgB2 films on 5 cm dia. sapphire disks were fabricated by a Hybrid Physical Chemical Vapor Deposition (HPCVD) technique. The electron-beam backscattering diffraction (EBSD) results suggest that the film is a single crystal complying with a MgB2(0001)//A1 2O3(0001) epitaxial relationship. The SRF properties of different film thicknesses (200 nm and 350 nm) were evaluated using SIC system under different temperatures and applied fields at 7.4 GHz. A surface resistance of 9+/-2 muO has been observed at 2.2 K.;Based on BCS theory with moving Cooper pairs, the electron states distribution at 0K and the probability of electron occupation with finite temperature have been derived and applied to anomalous skin effect theory to obtain the surface impedance of a superconductor with moving Cooper pairs. We present the numerical results for Nb.

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Motta, Marcelo Jorge de Assis. "Equivalent impedance of rough surface at low grazing angles." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA369420.

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Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, September 1999.
"September 1999". Thesis advisor(s): R. Janaswamy. Includes bibliographical references (p. 77). Also avaliable online.

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Chen, Quan, and 陳全. "Efficient numerical modeling of random surface roughness for interconnect internal impedance extraction." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B3955708X.

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Tonkin, Bryan Anthony. "Microwave properties of bulk and thick film YBaâ†2Cuâ†3Oâ†7â†-â†x superconductors." Thesis, University of Portsmouth, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282543.

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Abu, Bakar Mizarina. "Microwave properties of high temperature superconducting thin films." Thesis, University of Birmingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289384.

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One of the most exciting studies of contemporary physics is that of high temperature superconductor (HTS). Since its discovery, a large body of experimental and theoretical work by various groups has attempted to achieve a common understanding of this phenomenon. One of the main driving forces for applications centres on the possibility of new and improved microwave devices based on HTS materials, mainly due to the large reduction in the surface resistance that HTS has to offer. However, various problems need to be addressed before the use of HTS materials can be justified, for example fundamental issues such as the nonlinearity of these materials with respect to microwave power, which form the basis of this work. Microwave measurements were conducted on four magnetron sputtered and three laser ablated, Icm2 YBCO thin films, grown on LaAI03 and MgO substrates, respectively, employing the dielectric (rutile) resonator and coplanar resonator techniques. The low power response of the films was initially analysed, looking for clues to the underlying pairing mechanisms in these films. Power dependence and microwave intennodulation distortion (lMD) measurements were conducted between 12 K to 60 K to investigate the nonlinear response of the films, both in zero and finite dc (10 mT) fields. The effect of patterning on the microwave response of the films was also studied. From these measurements, it was observed that the microwave losses of these films are extrinsic in nature, probably a consequence of weak links/defects, and the results also show that films fabricated from the same technique can have significantly varying quality.

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Morgan, Benjamin. "Microwave surface impedance of YBa₂Cu₃O₆.₉₅ in the mixed state." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615118.

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Baumeister, Carl Robert. "Electrochemical impedance spectroscopy and surface plasmon resonance for diagnostic antibody detection." Diss., University of Pretoria, 2012. http://hdl.handle.net/2263/31495.

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The successful use of biomarker antibody detection for disease diagnosis is currently restricted to cases where the antibody affinity and specificity of interaction with antigen is high. Evanescent field biosensing, e.g. Surface Plasmon Resonance (SPR), and electrochemical detection, in particular Electrochemical Impedance Spectroscopy (EIS), have been shown viable for detection of lower affinity antibodies, based on the principle that these technologies allow the measurement of antibody binding to immobilized antigen, i.e. without the need to wash away excess, non-bound antibodies or using labelled antibodies. Proof of principle for this in the case of detection of biomarker anti-mycolic acid antibodies for TB diagnosis has been provided in the Mycolic acid Antibody Real-Time Inhibition assay (MARTI) by our research group. Although already patented and published, MARTI is not yet a feasible diagnostic test due to slow sample turn-around time, affordability and technical vulnerability associated with unstable lipid antigen surface chemistry and the difficulty of standardization of liposome carriers of mycolic acids used for measuring the binding inhibition of serum antibodies to immobilized antigen. Here, these challenges were addressed by investigating the use of a magnetic field for more stable lipid antigen immobilization, new phospholipid compositions to generate more stable liposome carriers for lipid antigen in solution and the use of screen-printed electrodes (SPE) in EIS to address affordability of diagnosis and improve sample turn-around time. The latter approach appeared quite promising in distinguishing a TB positive and a TB negative patient serum and is amenable to automation by means of a flow injection system.
Dissertation (MSc)--University of Pretoria, 2012.
Biochemistry
MSc
Unrestricted

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Delaunay, Guy. "Modelisation d'objets de revolution multicouches par impedance de surface. Application au calcul de surface equivalente radar." Paris 11, 1990. http://www.theses.fr/1990PA112269.

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Ce document presente une contribution apportee a la simulation numerique de diffraction electromagnetique et au calcul de ser d'objets de revolution, formes d'un noyau conducteur revetu de couches minces. La faisabilite du remplacement de la cible par une impedance de surface est ici etudiee, pour eviter des limitations en cout ou en fiabilite des calculs lors de la resolution des equations integrales surfaciques usuelles pour des revetements a couches fines ou nombreuses. Les modelisations les plus courantes sont rappelees (modele de leontovich, solutions analytiques sur une geometrie plane ou cylindrique), les limitations analysees, et une formulation avec correction de courbure developpee. Une nouvelle determination d'impedance de surface est proposee pour traiter des revetements minces de cibles variees; elle fait appel a une formulation integrale allegee et a une technique de differences finies; les caracteristiques exactes de l'objet sont prises en compte, sans restriction d'incidence. Cette methode hybride est testee sur des formes simples telles que sphere, cone-sphere, cylindre tronque. Elle est susceptible de reduire sensiblement le cout des calculs, surtout lorsque l'on s'interesse a la synthese de revetements complexes

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Cepek, Tomáš. "Planární anténa na EBG substrátu." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-221013.

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The aim of the thesis is to describe EBG substrate and exminate his influence on some types of antennas and choose one of them for realization. In first part this thesis describes the paramaeters of antenna in generall, in the second part is dedicated to introduction with EBG substrate mainly on the surface with the high impedance (HIES). The third part deals with the simulations of microstrip patch antennas with EBG substrate and without EBG substrate. In the last parts was designed and optimized antenna using superstrate.

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Chen, Quan. "Efficient numerical modeling of random surface roughness for interconnect internal impedance extraction." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/HKUTO/record/B3955708X.

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Bashir, Shahid. "Design and synthesis of non uniform high impedance surface based wearable antennas." Thesis, Loughborough University, 2009. https://dspace.lboro.ac.uk/2134/5919.

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This thesis is concerned with the design and fabrication of flexible textile wearable antennas integrated with the newly introduced artificial materials known as high impedance surfaces (HIS). With the rapid growth and use of wireless communication systems more and more people are taking advantage of portable computing systems on daily basis. Also with the advancement in electronic industry new and sophisticated wireless devices have been introduced which are being used closed to human body. For user convenience there is an increasing need for integrating antennas on or in the clothing. The conventional antennas being rigid and obtrusive to user movements have limitations. There is a need of antennas made of flexible textile materials that can be part of user clothing defined as wearable antennas. Also with the miniaturisation trend in electronic industry, antenna designers are facing a challenge to come up with a compact, low profile,multi function efficient antenna designs occupying a small physical space. By integrating antennas in user clothing this limited space problem can also be resolved. With the easy availability of electro textile materials it is now possible to manufacture complete fabric antennas. The entire design cycle of wearable fabric antennas starting from material selection to prototype fabrication and antenna testing was carried out in this thesis. A novel technique for antenna fabrication using electro textile material is proposed that will have major implications on wearable computing industry. The use of HIS for antenna performance enhancement is growing at a rapid pace. In this thesis a modified wearable form of HIS defined as non uniform HIS is presented and successfully integrated with antenna for improved performance under low profile limitation. The HIS was also integrated with normal patch antenna to reduce its size and improve its gain and impedance bandwidth. These wearable antennas were then tested under real operating conditions. The measured results validated the design idea and showed that there are many possibilities for these unique artificial materials to be exploited for future wearable on body communication antennas.

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Dai, Chenyun. "Studies of the relationship between the surface electromyogram, joint torque and impedance." Digital WPI, 2016. https://digitalcommons.wpi.edu/etd-dissertations/433.

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"This compendium-format dissertation (i.e., comprised mostly of published and in-process articles) primarily reports on system identification methods that relate the surface electromyogram (EMG)—the electrical activity of skeletal muscles—to mechanical kinetics. The methods focus on activities of the elbow and hand-wrist. The relationship between the surface EMG and joint impedance was initially studied. My work provided a complete second-order EMG-based impedance characterization of stiffness, viscosity and inertia over a complete range of nominal torques, from a single perturbation trial with slowly varied torque. A single perturbation trial provides a more convenient method for impedance evaluation. The RMS errors of the EMG-based method were 20.01% for stiffness and 7.05% for viscosity, compared with the traditional mechanical measurement. Three projects studied the relationship between EMG and force/torque, a topic that has been studied for a number of years. Optimal models use whitened EMG amplitude, combining multiple EMG channels and a polynomial equation to describe this relationship. First, we used three techniques to improve current models at the elbow joint. Three more features were extracted from the EMG (waveform length, slope sign change rate and zero crossing rate), in addition to EMG amplitude. Each EMG channel was used separately, compared to previous studies which combined multiple channels from biceps and, separately, from triceps muscles. Finally, an exponential power law model was used. Each of these improvement techniques showed better performance (P<0.05 and ~0.7 percent maximum voluntary contraction (%MVC) error reduction from a nominal error of 5.5%MVC) than the current “optimal” model. However, the combination of pairs of these techniques did not further improve results. Second, traditional prostheses only control 1 degree of freedom (DoF) at a time. My work provided evidence for the feasibility of controlling 2-DoF wrist movements simultaneously, with a minimum number of electrodes. Results suggested that as few as four conventional electrodes, optimally located about the forearm, could provide 2-DoF simultaneous, independent and proportional control with error ranging from 9.0–10.4 %MVC, which is similar to the 1-DoF approach (error from 8.8–9.8 %MVC) currently used for commercial prosthesis control. The third project was similar to the second, except that this project studied controlling a 1-DoF wrist with one hand DoF simultaneously. It also demonstrated good performance with the error ranging from 7.8-8.7 %MVC, compared with 1-DoF control. Additionally, I participated in two team projects—EMG decomposition and static wrist EMG to torque—which are described herein. "

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Cure, David. "Reconfigurable Low Profile Antennas Using Tunable High Impedance Surfaces." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4659.

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This dissertation shows a detailed investigation on reconfigurable low profile antennas using tunable high impedance surfaces (HIS). The specific class of HIS used in this dissertation is called a frequency selective surface (FSS). This type of periodic structure is fabricated to create artificial magnetic conductors (AMCs) that exhibit properties similar to perfect magnetic conductors (PMCs). The antennas are intended for radiometric sensing applications in the biomedical field. For the particular sensing application of interest in this dissertation, the performance of the antenna sub-system is the most critical aspect of the radiometer design where characteristics such as small size, light weight, conformability, simple integration, adjustment in response to adverse environmental loading, and the ability to block external radio frequency interference to maximize the detection sensitivity are desirable. The antenna designs in this dissertation are based on broadband dipole antennas over a tunable FSS to extend the usable frequency range. The main features of these antennas are the use of an FSS that does not include via connections to ground, their low profile and potentially conformal nature, high front-to-back radiation pattern ratio, and the ability to dynamically adjust the center frequency. The reduction of interlayer wiring on the tunable FSS minimizes the fabrication complexity and facilitates the use of flexible substrates. This dissertation aims to advance the state of the art in low profile tunable planar antennas. It shows a qualitative comparison between antennas backed with different unit cell geometries. It demonstrates the feasibility to use either semiconductor or ferroelectric thin film varactor-based tunable FSS to allow adjustment in the antenna frequency in response to environment loading in the near-field. Additionally, it illustrates how the coupling between antenna and HIS, and the impact of the varactor losses affect the antenna performance and it shows solutions to compensate these adverse effects. Novel hybrid manufacturing approaches to achieve flexibility on electrically thick antennas that could be transitioned to thin-film microelectronics are also presented. The semiconductor and ferroelectric varactor-based tunable low profile antennas demonstrated tunability from 2.2 GHz to 2.65 GHz with instantaneous bandwidths greater than 50 MHz within the tuning range. The antennas had maximum thicknesses of λ/45 at the central frequency and front to back-lobe radiation ratios of approximately 15dB. They also showed impedance match improvement in the presence of a Human Core Model (HCM) phantom at close proximity distances of the order of 10-20 mm. In addition, the use of thin film ferroelectric Barium Strontium Titanate (BST) varactors in the FSS layer enabled an antenna that had smaller size, lower cost and less weight compared to the commercially available options. The challenging problems of fabricating robust flexible antennas are also addressed and novel solutions are proposed. Two different types of flexible antennas were designed and built. A series of flexible microstrip antennas with slotted grounds which demonstrated to be robust and have 42% less mass than typically used technologies (e.g., microstrip antennas fabricated on Rogers® RT6010, RT/duroid® 5880, etc.); and flexible ferroelectric based tunable low profile antennas that showed tunability from 2.42 GHz to 2.66 GHz using overlapping metallic plates instead of a continuous ground plane. The bending test results demonstrated that, by placing cuts on the ground plane or using overlapping metallic layers that resemble fish scales, it was possible to create highly conductive surfaces that were extremely flexible even when attached to other solid materials. These new approaches were used to overcome limitations commonly encountered in the design of antennas that are intended for use on non-flat surfaces. The material presented in this dissertation represents the first investigation of reconfigurable low profile antennas using tunable high impedance surfaces where the desired electromagnetic performance as well as additional relevant features such as robustness, low weight, low cost and low complexity were demonstrated.

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Wang, Junfeng 1971. "A new surface integral formation of EMQS impedance extraction for 3-D structures." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80210.

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Remillard, Stephen Keith. "The effects of granularity on the microwave surface impedance of high kappa superconductors." W&M ScholarWorks, 1993. https://scholarworks.wm.edu/etd/1539623844.

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The microwave surface impedance of granular high temperature superconductors is an important figure of merit for technological applications. Because the behavior of the granular materials deviates significantly from that of the ideal defect free superconductors, the loss mechanisms are not fully understood. This dissertation seeks to quantify the contribution of granularity to centimeter wave and millimeter wave losses. By understanding these losses, the superconductive coupling between neighboring grains can also be understood.;The weakly coupled grain model is used as a phenomenological description of the microwave surface impedance. The granular superconducting surface is modelled as an effective resistively shunted Josephson junction. The measured surface impedance is compared to the model by plotting the normalized surface resistance versus the normalized surface reactance.;The model offers a quantitative explanation of many features observed in the surface impedance data including a local maximum in the surface reactance versus static magnetic field. The model also predicts the weaker than quadratic BCS frequency dependence of the surface resistance. The surface impedance of granular superconductors is always observed to saturate in high static magnetic fields. From analysis with the weakly coupled grain model it is concluded that the saturation is due to superconducting microshorts with properties which are independent of magnetic field.;Finally, measurement of surface resistance with an open Fabry-Perot resonator is treated within as a mini-dissertation. The loss mechanisms in the open resonator geometry are considered. The ohmic losses are computed numerically from a vector theory, and Bethe diffraction theory is used to compute a lower limit for losses arising from mode mixing.

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De, Cliff Steve V. "Electrochemical Quartz Crystal Microbalance and Impedance Analysis investigations of surface processes at platinum electrodes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq20996.pdf.

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Husain, Adel Abdulmajeed. "Paint coated steel in Kuwaiti corrosion environment : surface corrosion mapping & electrochemical impedance spectroscopy." Thesis, Imperial College London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336601.

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Wen, Xuejin. "Design, Fabrication, and Characterization of Field-Effect and Impedance Based Biosensors." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1308312352.

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Kearns, James A. "An investigation of the diffraction of an acoustic plane wave by a curved surface of finite impedance." Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/16749.

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Martin, James Stephen. "An experimental study of the scattered near field of submerged objects with surface impedance discontinuities." Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/16095.

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Hu, Xin 1979. "The use of conduction mode basis functions in surface integral formulation for wideband impedance extraction." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/87356.

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Ma, Mingxian. "A Feasibility Study of Particle Sorter Using Impedance Detection and Traveling Surface Acoustic Wave Sorting." University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1436206839.

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YOSHIKAWA, DANIEL S. "Efeito de tratamentos de modificação da superfície na resistência à corrosão do alumínio 1050." reponame:Repositório Institucional do IPEN, 2011. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9970.

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Made available in DSpace on 2014-10-09T14:06:31Z (GMT). No. of bitstreams: 0
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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Pires, Carneiro Leonardo [Verfasser]. "Development of an Electrochemical Biosensor Platform and a Suitable Low-Impedance Surface Modification Strategy / Leonardo Pires Carneiro." Karlsruhe : KIT Scientific Publishing, 2014. http://www.ksp.kit.edu.

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Zhu, Yu. "Modélisation de structures à haute impédance." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00621152/en/.

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Les Surfaces à Haute Impédance (SHI) ont été largement étudiées pour améliorer toutes sortes de performances des antennes, comme le gain, le facteur de qualité, les formes et dimensions. L'objectif de cette thèse est de modéliser les structures de SHI et de caractériser leurs performances en vue de futures applications aux antennes.Après une brève introduction aux structures SHI et une étude de quelques modèles analytiques fréquemment traités dans la littérature, deux nouvelles méthodes numériques sont proposées pour calculer l'impédance de surface de structures SHI. Ces deux méthodes (dites " méthode du flux de Poynting " et " méthode / ") sont validées sur des structures symétriques, puis mises en service sur des structures de SHI asymétriques. Elles sont également validées par comparaison de résultats analytiques, numériques et expérimentaux.Nous présentons ensuite un modèle équivalent basé sur l'idée de remplacer les structures hétérogènes de SHI par une surface homogène, caractérisée par son impédance surfacique. Ce modèle nous permet d'avoir une prédiction avec un temps de calcul et une occupation de mémoire PC largement réduits.

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Mogensen, Gavin. "Instrumentation for Impedance Measurements in the ELF/VLF Band for Geophysical Investigations." Thesis, Griffith University, 2015. http://hdl.handle.net/10072/367343.

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Electromagnetic investigations of the upper layers of the earth are of particular interest to earth scientists and mining geophysics companies. This thesis outlines a novel hand-held electronic instrument that performs shallow earth surface impedance measurements to depths of 100 m or less. The device named “TranSIM” (Transient Surface Impedance Meter) operates in the ELF/VLF frequency band and utilises both remote single frequency military transmitter signals and naturally occurring sferics to perform broad band surface impedance measurements. The device incorporates high precision GPS which provides survey point co-ordinates and accurate date-time stamping, enabling data synchronisation and cooperative surveying across multiple devices. A wireless communications link to a host computer was implemented, enabling high speed data transfer with the host computer for data logging and post-processing. A Windows@ based software application was developed to provide software control of on-board electronics and for advanced data processing and data logging. The application incorporates satellite map imagery with live up-dates of GPS tracking data. Pseudo real-time data analysis is presented through a rich graphical user interface.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
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Park, Young-Jin [Verfasser]. "Applications of photonic bandgap structures with arbitrary surface impedance to Luneburg lenses for automotive radar / Young-Jin Park." Karlsruhe : IHE, 2002. http://d-nb.info/1005498512/34.

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Li, Qin. "The study of DNA dynamics at carbon electrode surface toward DNA sensors by fluorescence and electrochemical impedance spectroscopy." Thesis, Kansas State University, 2011. http://hdl.handle.net/2097/9159.

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Master of Science
Department of Chemistry
Jun Li
This study is focused on exploring the mechanisms of DNA dynamics at carbon electrode surfaces under a strong electric field for the development of novel DNA hybridization sensors. Oligonucleotides with FAM6 attached at the distal end are covalently tethered on the carbon electrode surface. The fluorescence emission from the FAM6 is strongly quenched in close proximity to the electrode surface. The modulation to the fluorescence intensity is correlated with the reversible reorientation of the negatively charged DNA molecules under the electric field within the electric double layer. The orientation dynamics are apparently determined by the interplay of the electropotential, salt concentration, and stiffness of the DNA molecules. We have observed that dsDNAs switch with fast dynamics (in < 0.05 second) followed by relaxation at a slower rate (in > 0.1 second) when the electric field is altered by stepping the electropotential to a more positive or negative value. The DNA reorientation exhibits strong dependence on the PBS buffer concentration and electric double layer thickness. A preliminary calculation based on dipole-surface energy transfer theory indicates that the critical distance between FAM6 and glassy carbon surface is 10.95 nm. In connection with the fluorescence study, the effect of DNA hybridization on electrochemical impedance spectroscopy (EIS) has also been investigated by two methods in an attempt to develop a fast electronic detection method. First, EIS at high AC amplitude (141 mV rms) with DNA-modified glassy carbon electrodes before and after target DNA hybridization have shown notable change at high frequencies, likely related to the DNA reorientation processes. Second, reversible EIS detection of DNA hybridization has been demonstrated with patterned regular carbon nanofiber arrays at normal AC amplitude (10 mV rms). The combination of these two methods will be explored in future studies. The effects of the electric field on surface-tethered molecular beacons (MBs) have also been studied with fluorescence spectroscopy. An increase in fluorescence at negative bias is observed accompanying the opening of the MB stem, which leads to larger separation between fluorophore and quencher. At positive bias, the rehybridization of the MB stem leads to a decrease in fluorescence intensity.

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TokgÃ¶z, CaÄŸatay. "Asymptotic high frequency analysis of the surface fields of a source excited circular cylinder with an impedance boundary condition /." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1486402544591534.

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Wilson, Glenn Andrew, and glenn wilson@griffith edu au. "Plane Wave Propagation Problems in Electrically Anisotropic and Inhomogeneous Media with Geophysical Applications." Griffith University. School of Microelectronic Engineering, 2003. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20030325.210206.

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Boundary value problems required for modelling plane wave propagation in electrically anisotropic and inhomogeneous media relevant to the surface impedance methods in electromagnetic geophysics are formally posed and treated. For a homogeneous TM-type wave propagating in a half space with both vertical and horizontal inhomogeneities where the TM-type wave is aligned with one of the elements of the conductivity tensor, it is shown using exact solutions that the shearing term in the homogeneous Helmholtz equation for inclined anisotropic media: [Equation 1], unequivocally vanishes and solutions need only be sought to the homogeneous Helmholtz equation for biaxial media: [Equation 2]. This implies that those problems posed with an inclined uniaxial conductivity tensor can be identically stated with a fundamental biaxial conductivity tensor, provided that the conductivity values are the reciprocal of the diagonal terms from the Euler rotated resistivity tensor: [Equation 3], [Equation 4], [Equation 5]. The applications of this consequence for numerical methods of solving arbitrary two-dimensional problems for a homogeneous TM-type wave is that they need only to approximate the homogeneous Helmholtz equation and neglect the corresponding shearing term. The self-consistent impedance method, a two-dimensional finite-difference approximation based on a network analogy, is demonstrated to accurately solve for problems with inclined uniaxial anisotropy using the fundamental biaxial anisotropy equivalence. The problem of a homogeneous plane wave at skew incidence upon an inclined anisotropic half space is then formally treated. In the half space, both TM- and TE-type waves are coupled and the linearly polarised incident TM- and TE-type waves reflect TE- and TM-type components. Equations for all elements of the impedance tensor are derived for both TM- and TE-type incidence. This offers potential as a method of predicting the direction of anisotropic strike from tensor impedance measurements in sedimentary environments.

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34

Wilson, Glenn Andrew. "Plane Wave Propagation Problems in Electrically Anisotropic and Inhomogeneous Media with Geophysical Applications." Thesis, Griffith University, 2003. http://hdl.handle.net/10072/365776.

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Boundary value problems required for modelling plane wave propagation in electrically anisotropic and inhomogeneous media relevant to the surface impedance methods in electromagnetic geophysics are formally posed and treated. For a homogeneous TM-type wave propagating in a half space with both vertical and horizontal inhomogeneities where the TM-type wave is aligned with one of the elements of the conductivity tensor, it is shown using exact solutions that the shearing term in the homogeneous Helmholtz equation for inclined anisotropic media: [Equation 1], unequivocally vanishes and solutions need only be sought to the homogeneous Helmholtz equation for biaxial media: [Equation 2]. This implies that those problems posed with an inclined uniaxial conductivity tensor can be identically stated with a fundamental biaxial conductivity tensor, provided that the conductivity values are the reciprocal of the diagonal terms from the Euler rotated resistivity tensor: [Equation 3], [Equation 4], [Equation 5]. The applications of this consequence for numerical methods of solving arbitrary two-dimensional problems for a homogeneous TM-type wave is that they need only to approximate the homogeneous Helmholtz equation and neglect the corresponding shearing term. The self-consistent impedance method, a two-dimensional finite-difference approximation based on a network analogy, is demonstrated to accurately solve for problems with inclined uniaxial anisotropy using the fundamental biaxial anisotropy equivalence. The problem of a homogeneous plane wave at skew incidence upon an inclined anisotropic half space is then formally treated. In the half space, both TM- and TE-type waves are coupled and the linearly polarised incident TM- and TE-type waves reflect TE- and TM-type components. Equations for all elements of the impedance tensor are derived for both TM- and TE-type incidence. This offers potential as a method of predicting the direction of anisotropic strike from tensor impedance measurements in sedimentary environments.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Microelectronic Engineering
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35

Sjödin, Mattias. "Investigating Particle Cracking in Single- and Polycrystalline Nickel-Rich Cathodes using In Situ Impedance Spectroscopy." Thesis, Uppsala universitet, Strukturkemi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-449968.

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State-of-the-art Li-ion cathode materials are based on LiMO2 (M=Ni, Mn, Co) layered transition metal oxides (denoted NMC) with Ni-rich composition because of their high specific capacity. Yet, these materials suffer from poor capacity retention due to crack formation during de-/lithiation cycling. Particle cracking leads to exposure of new electrode surface which leads to Li-inventory loss, increased side reactions, and electric disconnection. Quantification of the extent of cracking is therefore desirable, especially during in situ whilst cycling of the Li-ion cell. Herein, we evaluate and improve an analytical methodology based on electrochemical impedance spectroscopy (EIS) in order to estimate the changes in electrochemically active surface area of both poly- and single-crystalline Ni0.8Mn0.1Co0.1(NMC811) active materials. A transmission-line model (TLM) applied to both non-blocking and blocking electrode condition was utilized in order to deconvolute and interpret the acquired experimental data. Fits of the complex TLM equivalent-circuits to the impedance spectra was facilitated by developing a global stochastic iterative function based on local multivariate optimization. Impedance analysis during short- term cycling showed that the single-crystalline NMC811 suffered from less particle cracking and side reactions compared to polycrystalline NMC811, which was also confirmed from post-mortem gas adsorption analysis. A novel approach to estimate the extent of particle cracking in commercial Li-ion cells by utilizing an empirically strong positive correlation between the charge-transfer capacitance and resistance was proposed. The work presented herein demonstrates the unique prospects of the EIS methodology in the development and research of future rechargeable batteries

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36

Melais, Sergio E. "A quasi Yagi antenna with end fire radiation over a metal ground." [Tampa, Fla] : University of South Florida, 2009. http://purl.fcla.edu/usf/dc/et/SFE0003246.

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37

SAVINO, UMBERTO. "Physical properties of metal-oxide surfaces for CO2 valorisation." Doctoral thesis, Politecnico di Torino, 2020. http://hdl.handle.net/11583/2823956.

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38

Forslund, Ola. "Scattering and propagation of electromagnetic waves in planar and curved periodic structures - applications to plane wave filters, plane wave absorbers and impedance surfaces." Doctoral thesis, KTH, Alfvén Laboratory, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3825.

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The subject of this thesis is scattering of electromagneticwaves from planar and curved periodic structures. The problemspresented are solved in the frequency domain.

Scattering from planar structures with two-dimensionalperiodic dependence of constitutive parameters is treated. Theconstitutive parameters are assumed to vary continuously orstepwise in a cross section of a periodically repeating cell.The variation along a longitudinal coordinate z is arbitrary. Ageneral skew lattice is assumed. In the numerical examples, lowloss and high loss dielectric materials are considered. Theproblem is solved by expanding the .elds and constitutiveparameters in quasi-periodic and periodic functionsrespectively, which are inserted into Maxwells equations.Through various inner products de.ned with respect to the cell,and elimination of the longitudinal vector components, a linearsystem of ordinary di.erential equations for the transversecomponents of the .elds is obtained. After introducing apropagator, which maps the .elds from one transverse plane toanother, the system is solved by backward integration.Conventional thin metallic FSS screens of patch or aperturetype are included by obtaining generalised transmission andre.ection matrices for these surfaces. The transmission andre.ection matrices are obtained by solving spectral domainintegral equations. Comparisons of the obtained results aremade with experimental results (in one particular case), andwith results obtained using a computer code based on afundamentally di.erent time domain approach.

Scattering from thin singly curved structures consisting ofdielectric materials periodic in one dimension is alsoconsidered. Both the thickness and the period are assumed to besmall. The .elds are expanded in an asymptotic power series inthe thickness of the structure, and a scaled wave equation issolved. A propagator mapping the tangential .elds from one sideto the other of the structure is derived. An impedance boundarycondition for the structure coated on a perfect electricconductor is obtained.

Keywords:electromagnetic scattering, periodicstructure, frequency selective structure, frequency selectivesurface, grating, coupled wave analysis, electromagneticbandgap, photonic bandgap, asymptotic boundary condition,impedance boundary condition, spectral domain method,homogenisation

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39

CAPPELLO, BARBARA. "Analysis and Reduction of the Scattering by Cloaked Metallic Cylinders Beyond the Quasi-static Limit." Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2915197.

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40

Ulrich, Christian. "Electric Fields for Surface Design and Chemical Analysis." Doctoral thesis, Linköpings universitet, Tillämpad Fysik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-12485.

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This thesis deals with the use of electric fields for evaluation and control of chemical systems. An electric field can result in the flow of charge across an interface between a metal and a solution, by means of chemical reactions. This interplay between electricity and chemistry, i.e. electrochemistry, is a field of crucial importance both within research and industry. Applications based on electrochemical principles encompass such diverse areas as batteries and fuel cells, pH electrodes, and the glucose monitor used by people suffering from diabetes.A major part of the present work concerns the use of static electric fields in solutions containing a non-contacted metal surface. In such a setup it is possible to control the extent of electrochemical reactions at different positions on the metal. This allows the formation and evaluation of various types of gradients on electrodes, via indirectly induced electrochemical reactions. This approach is a new and simple way of forming for instance molecular gradients on conducting surfaces. These are very advantageous in biomimetic research, because a gradient contains a huge amount of discrete combinations of for example two molecules. The basis for the technique is the use of bipolar electrochemistry. Briefly, a surface can become a bipolar electrode (an electrode that acts as both anode and cathode) when the electric field in the solution exceeds a certain threshold value, thereby inducing redox reactions at both ends. In our experiments, the driving force for these reactions will vary along the electrode surface. Since the result of an electrochemical reaction can be the deposition or removal of material from an electrode, bipolar electrochemistry can be used to create gradients of that material on a surface. In order to gain a deeper understanding of these processes, the potential and current density distributions at bipolar electrodes were investigated with different methods. Especially the use of imaging techniques was important for the visualization and analysis of the gradients. Using this knowledge, the formation of more complex gradients was facilitated, and the results were further compared to simulations based on simple conductivity models. These simulations also provided us with means to predict the behavior of new and interesting setup geometries for pattering applications.The other major part is more application driven and deals with the use of alternating electric fields for chemical analysis, a technique known as electrochemical impedance spectroscopy (EIS). In this work, EIS has been applied for the analysis of engine oils and industrial cutting fluids. Emphasis was placed on practical aspects of the measurement procedure, and on the evaluation of the results using statistical methods. It was for example shown that it was possible to simultaneously determine the amount of different contaminants in low conducting solutions. Generally, EIS is used to measure the impedance of a solution or a solid, often as a function of the frequency of the alternating electric field. The impedance of a system is closely correlated to its complex dielectric constant, and EIS can therefor be used to examine many chemical and physical processes. It is further well suited for characterizing low conducting media with little or no redox-active species. The evaluation of impedance data is often a quite complex task, which is why we have made use of statistical methods that drastically reduce the effort and quickly reveal significant intrinsic parameters.

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41

Yang, Yaqin. "Surface treated cp-titanium for biomedical applications : a combined corrosion, tribocorrosion and biological approach." Thesis, Châtenay-Malabry, Ecole centrale de Paris, 2014. http://www.theses.fr/2014ECAP0050/document.

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La tribocorrosion peut être définie comme l’ étude de l’influence des facteurs environnementaux (chimiques et/ou électrochimiques) et mécanique (frottement) sur le comportement tribologique de surfaces en mouvement relatifs. En raison de leurs caractéristiques particulières: performances mécaniques, associées à une faible densité, bonne tenue à la corrosion, biocompatibilité, le titane et ses alliages sont souvent utilisés dans le domaine médical comme implants dentaires et orthopédiques. Cependant, leur faible résistance vis-À-Vis du frottement en milieu agressif et plus spécifiquement biologique reste un frein à leur usage courant dans le domaine prothétique. Pour améliorer la résistance à la corrosion et à l'usure du titane et de ses alliages, différentes méthodes de modification de la surface ont été proposées durant ces dernières décennies. Dans ce cadre, le but de ce travail est de comparer les comportements en corrosion et tribocorrosion du titane commercialement pur (cp Ti), avec ce même matériau ayant subi au préalable les traitements suivants :- soit une étape d'oxydation thermique à 650 °C à l’air durant 48 h (formation d’un film d'oxyde de titane (TiO2) en surface),- soit un dépôt électrochimique de calcium phosphate (CaP) en surface,- soit un dépôt électrochimique de calcium phosphate (CaP) suivi d’une tape d’oxydation thermique à 650 °C à l’air durant 6 h (formation d’un dépôt de type CaP/TiO2 en surface). Les phases cristallines des films modifiés ont été identifiées par diffraction des rayons X (XRD). La microscopie électronique à balayage (MEB) en combinaison avec la spectroscopie à dispersion d'énergie (EDS) a été utilisée pour caractériser la morphologie et la composition de ces films.Le comportement en corrosion pure des échantillons cp Ti avec ou sans modifications de surface à été étudié in situ à partir des mesures électrochimiques de suivi du potentiel en circuit ouvert (OCP), de la spectroscopie d'impédance électrochimique (EIS) et du tracé de courbes de polarisation potentio-Dynamiques.Le comportement en tribocorrosion à été étudié quant à lui à l'aide d'un tribomètre de type pion-Disque apte à travailler en milieu aqueux et permettant outre l’enregistrement des paramètres tribologiques classiques, la mise en œuvre in situ des techniques électrochimiques utilisées lors de l’étude en corrosion pure. Caractérisation et analyses de la surface(composition, morphologie, rugosité …) sont effectuées avant et après chaque étude de comportement (corrosion et tribocorrosion). Un protocole pour la culture des cellules sur la surface de titane a été validé, en se basant sur les résultats expérimentaux préliminaires
Tribocorrosion is defined as the study of the interplay between chemical, electrochemical and mechanical processes that leads to a degradation of passivating materials in a corrosive environment. Due to the low density, excellent mechanical properties, high corrosion resistance and good biocompatibility, titanium and its alloys are widely used as dental and orthopedic implants. However, the poor wear resistant and bio-Inert properties limit their further development as more efficient and economic biomedical implants. To improve the corrosion-Wear resistance and even bioactivity of metallic implants, different surface modification methods are imposed in the past decades.The aim of this work is to provide a deep insight in the area of corrosion and tribocorrosion behavior of commercially pure titanium (cp Ti) under the guidance of a tribocorrosion protocol for passivating materials. And then three different surface modification treatments, as:- one-Step thermal oxidation at 650 °C for 48 h in air atmosphere to form a titania (TiO2) film on the surface of cp Ti.- one-Step electrochemical deposition of calcium phosphate (CaP) bioactive film on the surface of cp Ti.- electrochemical deposition of CaP bioactive film followed by thermal oxidation at 650 °C for 6 h in air atmosphere to form a CaP/TiO2 bioceramic film on cp Ti surface.The crystalline phases of the modified films were identified by X-Ray diffraction (XRD). Scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS) was used to characterize the morphology and composition of these films on cp Ti surface. In situ electrochemical measurements, like open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization are used to characterize the corrosion behavior of cp Ti samples without or with surface modification. The tribocorrosion behavior was investigated in an aqueous environment by combining a pin-On-Disc tribometer with the in situ electrochemical equipment. The classical tribological parameters could be also recorded under mechanical loaded condition. Surface characterization and analysis (like chemical composition, morphology, roughness...) are carried out before and after each corrosion and tribocorrosion test. A protocol for the culture of cells on the surface of titanium was validated, basing on the preliminary experimental results

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42

Sanders, Wesley Crowell. "Examining the Effects of Applied Potential on the Surface Charge of Functionalized Monolayers for Site-Directed Ionic Self Assembly." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/29523.

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The focus of this dissertation research involves surface charge manipulation of functionalized monolayers. Application of potential to acid or base terminated organic films immobilized on electrodes results in the ionization of the terminal groups. The ionization of these groups using applied potential provides conditions favorable the control of polyelectrolyte deposition to the monolayer surface. Research is presented that asserts that the interfacial pH of acid or base terminated monolayers responds to applied potential as a result of the accumulation of phosphate counterions to the monolayer-solution interface. Results obtained from applied potential modulation of surface charge endeavors strongly suggest that manipulation of terminal group ionization with applied potential “turns on“ or “turns off“ the charge of the monolayer. Switching on the surface charge of functionalized monolayers using applied potential yields conditions that make it possible for the promotion or inhibition of electrostatic attachment of polyelectrolyte to the monolayer surface. Electrostatic interactions between immobilized polyelectrolytes and redox probes result in changes in electron transfer that can be monitored with electrochemical impedance measurements. Impedance measurements provide a qualitative assessment of the degree of potential-driven polyelectrolyte self assembly. The electrostatic interactions between the redox probe in solution and the terminal region of monolayers directly affects the extent of charge-transfer between the electrode and the redox probe in solution. For this reason, impedance measurements are able to provide an indication of whether or not potential drives to electrostatic deposition to the terminal region of a functionalized monolayer. Unlike impedance measurements, quartz crystal microbalance measurements provide quantitative mass assessments that confirm polyelectrolyte deposition of inhibition under the direction of applied potential. Application of appropriate potentials is shown to induce variations in the electrostatic interactions between redox probes in solution and terminal groups of monolayers. Variations in the electrostatic interactions between the modified electrode and the redox probe modulate electron transfer that produces varying current. Since scanning electrochemical microscopy (SECM) relies on modulation of feedback current underneath a ten-micrometer platinum tip, SECM provides a means for monitoring of potential-driven surface charge modulation. Experiments presented in this dissertation will show that in addition to monitoring the effect of applied potential on the charge of ionizable surface groups, SECM can also be used to selectively deposit a polyelectrolyte to the surface of a carboxylic acid terminated monolayer. The SECM tip was rastered over the surface of a functionalized monolayer in the form of a simple pattern while the electrode was immersed in a dilute polyelectrolyte solution. As the SECM tip was moved and potential stepped more positive than the PZC, ionization was confined ionization to one spot encouraging localized ionic self assembly.
Ph. D.

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43

Saleh, Gameel [Verfasser], Klaus [Akademischer Betreuer] Solbach, and Daniel [Akademischer Betreuer] Erni. "High Impedance Surface – Electromagnetic Band Gap (HIS-EBG) Structures for Magnetic Resonance Imaging (MRI) Applications / Gameel Saleh. Gutachter: Daniel Erni. Betreuer: Klaus Solbach." Duisburg, 2013. http://d-nb.info/104601157X/34.

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44

AZZOUZ, FOUAD. "Contribution a la modelisation de toles ferromagnetiques par impedance de surface et elements finis application au calcul des puissances du chauffage par induction." Nantes, 2000. http://www.theses.fr/2000NANT2107.

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Le chauffage par induction de materiaux ferromagnetiques en couches minces (toles) necessite l'emploi de frequences elevees ; ce qui complique aussi bien la modelisation des systemes que les mesures electromagnetiques ou thermiques. Les modeles physiques et mathematiques bases sur les equations de maxwell restent toujours d'actualite et le recours aux methodes numeriques est indispensable. La methode des elements finis (mef) a ete choisie comme outil de base de resolution et son couplage a une impedance de surface en non-lineaire permet de prendre en compte l'effet de peau. Des outils elements finis ont ainsi ete developpes dans le cadre de cette these sous environnement matlab en 1d, 2d, axisymetrie et en 3d, utilisant les elements nodaux, d'aretes et les elements mixtes. La validation des outils en 2d a ete effectuee par comparaison avec des calculs obtenus au sein de notre laboratoire en utilisant le logiciel fluxexpert, et avec des donnees experimentales. La validation des outils en 3d a ete effectuee par comparaison avec des mesures et des solutions de problemes proposees par la communaute scientifique internationale (ieee team workshops, ieej workshop) en magnetostatique et en magnetodynamique. D'autre part, nous avons propose une definition d'impedance de surface non-lineaire. Cette definition est obtenue a partir de l'energie electromagnetique et d'une identification en 1d utilisant une formulation en champ magnetique h. L'application de ce modele en 2d, utilisant une formulation en potentiel vecteur magnetique a a un cas reel (dispositif d'edf de chauffage par induction a inducteur monospire) a donne des resultats tres satisfaisants avec un faible cout tant en place memoire qu'en temps de calcul sur micro-ordinateur. Le modele a ensuite ete applique avec succes a un cas 3d, utilisant la formulation av-a, v etant le potentiel scalaire electrique. En vue d'un couplage du probleme electromagnetique avec le probleme thermique, nous avons etendu la definition de l'impedance de surface a la prise en compte des effets de la temperature.

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45

Leonardi, Ornella. "Circularly polarized antennas." Doctoral thesis, Università di Catania, 2014. http://hdl.handle.net/10761/1496.

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In recent years low profile, lightness, compactness, easy manufacturing and integrability with solid-state devices on a circuit board have become a priority in the antenna design. Microstrip antennas are a possible answer to these new requirements in several areas, such as remote sensing, mobile satellite and cellular communications, direct broadcast satellite (DBS) system and global positioning system (GPS). Many of the above mentioned applications make use of circularly polarized antennas. However, such requirement in planar microstrip antenna is not a trivial task since many factors have to be considered including fabrication tolerance and systematic errors in the manufacturing process. In the present thesis we address the task to achieve circular polarization with very compact planar antennas in two ways: 1) a more conventional one dealing with two innovative designs; 2) a less conventional one through of artificial materials, such as High Impedance Surface (HIS). As far as the first point is concerned, two standard designs have been developed for a Dedicated Short Range Communication (DSRC) system. In particular, we have proposed two innovative compact antennas that represent a step forward with respect to other available DSRC solution. The two proposed antenna prototypes have been optimized, fabricated and experimentally tested. They represent an answer to the need of achieving good circular polarization antennas in a small mobile On-Board Unit (OBU) of a DSRC system. As a further study, we have considered to improve performance such as the radiated power, the gain and the directivity, or to reduce the global antenna thickness. For this reason we have developed a full-wave model for periodic surface and considered their employment to achieve circular polarization. As a proof of concept, we have tested a simple arrangement that allows circular polarization of the radiated field. The thesis is organized as follows. In the first part, we briefly introduce some relevant technical features of microstrip antenna s. Then the properties of circular polarized waves are discussed, with particular interest in wireless communications. The circular polarization quality factors and antenna measurement setup are briefly introduced and discussed. In the second part, we address the design and the experimental characterization of two circularly polarized microstrip patch antenna prototypes. In the last part of the thesis, High Impedance Surfaces (HIS) are briefly introduced. Then, a simple FEM-model is presented and compared with the standard FTDT-model used in literature. In this respect, a rectangular-array-patch working as HIS surface is considered and tested to achieve circular polarization with a printed dipole.

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46

Cleveland, Jerika Dawn. "The Design and Analysis of a Microstrip Line Which Utilizes Capacitive Gaps and Magnetic Responsive Particles to Vary the Reactance of the Surface Impedance." Thesis, North Dakota State University, 2019. https://hdl.handle.net/10365/31552.

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This thesis presents the work of using magnetic responsive particles as a method to manipulate the surface impedance reactance of a microstrip line containing uniform capacitive gaps and cavities containing the particles. In order to determine the transmission line?s surface impedances created by each gap and particle containing cavities, a sub-unit cell that centers the gap and cavities was used. Shown in simulation, the magnetic responsive particles can then be manipulated to increase or decrease the reactance of the surface impedance based on the strength of the magnetic field present. The sub-unit cell with the greatest reactance change was then implemented into a unit cell, which is a cascade of sub-unit cells. This unit cell design was simulated, milled and tested to determine the response a unit cell should see based on extreme states of the particles represented by copper vias and open air cavities.

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SZURKALO, MARGARIDA. "Investigacao do efeito de moleculas auto-organizaveis na resistencia a corrosao da liga de aluminio 1050." reponame:Repositório Institucional do IPEN, 2009. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9488.

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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

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48

Nilebäck, Erik. "A novel biotinylated surface designed for QCM-D applications." Thesis, Linköping University, Department of Physics, Chemistry and Biology, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-19250.

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Control of protein immobilization at sensor surfaces is of great interest within various scientific fields, since it enables studies of specific biomolecular interactions. To achieve this, one must be able to immobilize proteins with retained native structure, while minimizing non-specific protein binding. The high affinity interaction between streptavidin (SA) and biotin is extensively used as a linker between a surface, where SA is immobilized, and the (biotinylated) molecule of interest. Self- assembled monolayers (SAMs) of poly- and oligo ethylene glycol (PEG and OEG) derivatives have been proven in literature to minimize non-specific protein binding, and biotin-exposing SAMs have been shown efficient for immobilization of SA.

The aim of this master's thesis project was to develop biotinylated gold surfaces for quartz crystal microbalance with dissipation monitoring (QCM-D) applications through the self-assembly of mixed monolayers of thiolated OEG (or PEG) derivatives with or without a terminal biotin head group. For this, different thiol compounds were to be compared and evaluated. For the systems under study, the required biotin density for maximum specific SA immobilization was to be established, while keeping the non-specific serum adsorption at a minimum. Model experiments with biotinylated proteins immobilized to the SA-functionalized surfaces were to be performed to evaluate the possibilities for commercialization.

A protocol for the preparation of a novel biotinylated surface was developed based on the immersion of gold substrates in an ethanolic incubation solution of dithiols with OEG chains (SS-OEG and SS-OEG-biotin, 99:1) and found to give reproducible results with respect to low non-specific protein binding and immobilization of a monolayer of SA. The modified surfaces allowed for subsequent immobilization of biotinylated bovine serum albumin (bBSA) and biotinylated plasminogen (bPLG). PLG was the subject of a challenging case study, using a combination of QCM-D and surface plasmon resonance (SPR), where the immobilized protein was subjected to low molecular weight ligands that were believed to induce conformational changes. The high control of the surface chemistry allowed for the interpretation of the increased dissipation shift upon ligand binding in terms of conformational changes.

An obstacle before commercialization of the described biotinylated surfaces is that they do not seem stable for storage > 7 days. The reasons for this have to be investigated further.

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49

Volpati, Diogo [UNESP]. "Fabricação e caracterização de filmes finos de perileno: arquitetura molecular e aplicações sensoriais." Universidade Estadual Paulista (UNESP), 2008. http://hdl.handle.net/11449/94501.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Filmes finos do bis benzimidazo perileno (AzoPTCD) foram fabricados usando as técnicas de Langmuir, Langmuir-Blodgett (LB) e evaporação a vácuo (PVD). A estabilidade térmica durante a fabricação dos filmes PVD ('DA ORDEM DE' '400 GRAUS' a '10 POT. -6' Torr) e a integridade da estrutura molecular pela dissolução do AzoPTCD em ácidos fortes para a fabricação dos filmes de Langmuir e LB foram monitoradas pelo espalhamento Raman. Complementarmente a análise termogravimétrica revelou que a degradação térmica do AzoPTCD ocorre a '675 GRAUS'. Os filmes de Langmuir revelaram um alto empacotamento molecular do AzoPTCD sobre a subfase aquosa, onde as moléculas estão apoiadas sobre seu eixo maior ou menor. A adição de íons metálicos na subface aquosa revelou uma sensibilidade do AzoPTCD a presença destes íons, deslocando as isotermas para maiores valores de área molecular média. O crescimento dos filmes LB e PVD sobre substratos sólidos foi monitorado através da espectroscopia de absorção UV-Vis, e a morfologia dos filmes PVD foi estudada via microscopia de força atômica (AFM) em função da espessura em massa. A organização molecular dos filmes PVD foi determinada usando as regras de seleção de superfície aplicadas na espectroscopia de absorção no infravermelho (modos de transmissão e reflexão). Apesar da organização molecular, a difração de raios-x revelou que os filmes PVD são amorfos. Cálculos teóricos (Density functional theory -B3LYP) foram usados para atribuição dos modos vibracionais nos espectros de absorção no infravermelho e espalhamento Raman ressoante Nanoestruturas metálicas, capazes de ativar os fenômenos de amplificação em superfície foram usadas para estudos de espalhamento Raman ressonante amplificado em superfície (SERRS) e fluorescência amplificada em superfície (SEF) nos filmes LB e PVD. Através...
Thin solid films of bis benzimidazo perylene (AzoPTCD) were fabricated using Langmuir, Langmuir-Blodgett (LB) and physical vapor deposition (PVD) techniques. Thermal stability during the fabrication of PVD films ('DA ORDEM DE' '400 GRAUS' a '10 POT. -6' Torr) and chemical structure integrity by dissolution of the AzoPTCD in a strong acid were monitored by Raman scattering. Complementary thermogravimetric results showed that thermal degradation of AzoPTCD occurs at '675 GRAUS'. Langmuir films showed a high molecular packing with the molecules tilted onto the aqueous subphase. Besides, the AzoPTCD л-A isotherms were shifted to larger areas due to the addition of metallic ions in the subphase. The growth of the LB and PVD films were established through UV-Vis absorption spectroscopy, and the surface morphology in PVD films was probed by atomic force microscopy (AFM) as function of the mass thickness. The AzoPTCD molecular organization in the PVD films was determined using the selection rules of infrared absorption spectroscopy (transmission and reflection-absorption modes). Despite the molecular organization, X-ray diffraction revealed that the PVD films are amorphous. Theoretical calculations (Density Functional Theory, B3LYP) were used to assign the vibrational modes in the infrared and Raman spectra. Metallic nanostructures, able to sustain localized surface plasmons (LSP) were used to achieve surface-enhanced resonance Raman scattering (SERRS) and surface-enhanced fluirescence (SEF) in the LB and PVD films. The conductivity and rectifier character of the PVD films of AzoPTCD were determined by current as function of tension curves (I(V)) in dc measurements. The impedance spectroscopy in ac measurements was used to study the performance of PVD films of the AzoPTCD as transductor elements in sensing units applied to discriminate... (Complete abstract click electronic access below)

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Dorosh, Anastasiia. "Design of Microstrip Microwave Devices with Lumped Elements by Means of Modern CADs." Thesis, Linnéuniversitetet, Institutionen för fysik och elektroteknik (IFE), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-30365.

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Abstract:

In this report the analysis of microstrip electrodynamic structures on basis of high-temperature superconductors is carried out and a mathematical model of microstrip devices with lumped and distributed nonlinear properties is created. For this purpose nonlinear integral equations method and method of moments are used. In the issue of the work a SHF filter based on the equivalent circuit of elements with lumped parameters is also studied. It is ascertained that the received mathematical model allows to achieve more proper results of modeling on compensation of variation of current-density distribution nearby the edges of conductor break.

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Dissertations / Theses on the topic 'Surface impedance'

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