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The Global ETD Search service is a free service for researchers
to find electronic theses and dissertations. This service is
provided by the
Networked Digital Library of Theses and Dissertations.
Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
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A SPECTROSCOPIC INVESTIGATION OF A SURFACE-DISCHARGE-MODE, DIELECTRIC BARRIER DISCHARGEStanfield, Scott Alan, II 30 December 2009 (has links)
No description available.
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Modelling and Applications of the Hollow Cathode PlasmaSöderström, Daniel January 2008 (has links)
This thesis presents experimental and modelling research on atmospheric pressure hollow cathodes and hollow electrodes. Experiments with the hybrid hollow electrode activated discharge (H-HEAD), which is a combination of a hollow cathode and a microwave plasma source, is presented. The experiments show that this source is able to produce long plasma columns in air and nitrogen at atmospheric pressure and at very low gas flow rates. Measurements of the vibrational temperature of the nitrogen molecules are also presented in this thesis. The vibrational temperature is an indication of the electron temperature in the plasma, an important characteristic of the plasma. Modelling work on the hollow cathode at atmospheric pressure with fluid equations is also presented. It is shown that the inclusion of fast and secondary electrons, characteristic of the hollow cathode plasmas, increases the sheath width. The sheath width was found to be of the order of 100 μm. By modelling the plasma as highly collisional by using the drift-diffusion approximation, it was shown that the increase in sheath thickness was larger at lower pressures than at higher pressures. Still, the sheath width can be of the order of 100 μm. A pulsed atmospheric plasma in a hollow electrode geometry was also modelled by the drift-diffusion fluid equations, with the addition of the energy equation for electrons. Rate and transport coefficients for the electrons were calculated from the solution to the Boltzmann equation as functions of mean electron energy. The dynamics of the plasma at pulse rise time showed large electron density and mean energy peaks at the cathode ends, but also that these quantities were enhanced at the centre of the discharge, between the cathode plates.
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Vergleich dielektrisch behinderter Entladungen bezüglich der physikalischen Eigenschaften und der Wirkung auf Holz und Holzwerkstoffe / Comparison of dielectric barrier discharges regarding their physical properties and the influence on wood and wooden materialsPeters, Frauke 22 October 2018 (has links)
No description available.
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Étude expérimentale de micro-plasmas froids à la pression atmosphérique générés par des hautes tensions de formes différentes / Experimental study of atmospheric pressure cold micro-plasmas generated by high voltages of different waveformsGazeli, Kristaq 26 October 2015 (has links)
Cette thèse porte sur l'étude de micro-plasmas froids à la pression atmosphérique générés à partir de différents réacteurs des configurations basées sur le principe des Décharges à Barrière Diélectrique (DBD) et alimentés par des générateurs de tension impulsionnelle et sinusoïdale. Les plasmas sont formés dans des gaz nobles tels que l'hélium et l'argon (gaz vecteurs), et également dans des mélanges réalisés avec des gaz moléculaires tels que l'azote et l'oxygène afin de produire des Espèces Réactives de l’Azote et de l’Oxygène (ERA, ERO). La (ré)activité chimique du plasma est ainsi supposée être accrue, permettant le traitement de matériaux inertes ou vivants pour diverses applications (fonctionnalisation de surfaces, inactivation de cellules, régénération de tissus vivants, etc.). La caractérisation des plasmas étudiés est réalisée en enregistrant les aspects électriques et optiques en fonction des paramètres élémentaires, comme l’amplitude et la fréquence de la tension, le débit du gaz, la configuration des électrodes, et le rapport cyclique dans le cas du régime pulsé. Ainsi, la (ré)activité chimique des plasmas est évaluée tandis que au même temps les mécanismes de la génération des plasmas et les façons de l’optimisation de la chimie sont dévoilées. Finalement, nous examinons l'efficacité du plasma dans le domaine biomédical en traitant divers systèmes biologiques (bactéries, liposomes, cellules) sans effets thermiques. / The present PhD thesis is devoted to the study of atmospheric pressure cold micro-plasmas produced in different Dielectric Barrier Discharge (DBD) reactors which are driven by pulsed or sinusoidal high voltages. Noble gases such as helium and argon are used as carrier gases, whereas admixtures with nitrogen and oxygen are studied as well. The formation of Reactive Nitrogen and Oxygen Species (RNS, ROS) is thus achieved, and the possibility of improving the chemical (re)activity of the plasmas is demonstrated. This is of interest in the treatment of inert or living materials (e.g. surface functionalization, cell inactivation, living tissue regeneration, etc.). Plasmas are characterized by recording electrical and optical features as a function of principal operational parameters, including voltage amplitude and frequency, gas flow rate, electrode configuration, and voltage duty cycle in the case of pulsed waveform. The physico-chemical (re)activity of the plasmas is thus evaluated, while at the same time mechanisms on the plasma generation and paths for chemistry optimization are unveiled. Finally, the efficiency of the plasma in relation to biomedical applications is tested by treating different biological systems (bacteria, liposomes, cells) while preventing any thermal effect.
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