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  • About
  • 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.
1

A dynamic rate theory for the response of metals during steady state and pulsed irradiation

Ghoniem, Nasr Mostafa. January 1900 (has links)
Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 322-329).
2

Effect of electron beam irradiation on quality and shelf-life of Tommy Atkins mango (Mangifera indica l.) and blueberry (Vaccinium corymbsum l.)

Moreno Tinjaca, Maria Alexandra 25 April 2007 (has links)
The main goal of this research was to determine the feasibility of using electron beam irradiation as an alternative disinfestation technology while preserving the overall quality of mangoes, and to verify its suitability for the preservation shelf life of blueberries. Physicochemical and sensory characteristics of the fruits were evaluated. Mangoes were irradiated at 1.0, 1.5 and 3.1 kGy using a 10MeV (10 kW) linear accelerator (LINAC) with double beam fixture. Samples were stored at 12ºC and 62.7% RH for 21 days. Blueberries packed in plastic clamshell containers were irradiated at 1.1, 1.6 and 3.2 kGy doses using the same linear accelerator with a single beam. The shelf life of the berries stored at 5ºC and 70.4% RH was evaluated for 14 days. The firmness of mangoes irradiated at 1.5 and 3.1 kGy significantly (p > 0.05) decreased during storage. There was a reduction of total sugars (8.1% and 14.1%) in samples irradiated at 1.0 kGy and 1.5 kGy, respectively. All irradiated mangoes had significantly lower (50- 70 %) ascorbic acid content throughout storage. The phenolic compounds increased in samples irradiated at 1.5 kGy (27.4%) and 3.1 kGy) (18.3%). Sensory evaluation of the fruits irradiated with 3.1 kGy showed significantly less acceptability for overall quality, color, texture and aroma. Irradiation of blueberries at 1.1 kGy had no significant (p > 0.05) effect on the fruits' physicochemical characteristics with the exception of ascorbic acid which decreased by 17% after 14 days. A significant decrease in texture (firmness) of irradiated berries was observed during storage time. Total sugars decreased in all irradiated fruits while total phenolics and tannins increased (10 -20%). Sensory attributes of samples irradiated with 1.1 kGy and 1.6 kGy were found acceptable by the panelists. The high dose-treated fruits were considered unacceptable. The results from this research suggest that a 1.5 kGy is the best treatment to maintain the quality attributes of mangoes and increase the shelf life by three days. The electron beam irradiation of packed blueberries at doses of 1.1 and 1.6 kGy ensures and enhances the quality and the shelf life of blueberries up to 14 days.
3

An investigation of electron irradiated type IIa and N-doped CVD diamonds by microscopic photoluminescence (PL) spectroscopy

Wotherspoon, Alex January 2003 (has links)
No description available.
4

Characterization of an in-core irradiator for testing of microelectronics in a mixed radiation environment

Aghara, Sukesh K. January 2003 (has links) (PDF)
Thesis (Ph. D.)--University of Texas at Austin, 2003. / Vita. Includes bibliographical references. Available also from UMI Company.
5

Optical emission from irradiated thin metallic foils

Frank, Allen Lee. January 1962 (has links)
Thesis (M.S. in Physics)--Vanderbilt University. / Typescript. Bibliography: l. 83-84.
6

The effects of implanted hydrogen and helium on cavity formation in self-ion irradiated nickel

Bullen, Daniel Bernard. January 1900 (has links)
Thesis (Ph. D.)--University of Wisconsin--Masison, 1984. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
7

Irradiation of Food

Misner, Scottie, Curtis, Carol, Whitmer, Evelyn 05 1900 (has links)
2 pp. / Revised version of 1999 title by Meer and Misner / Food irradiation is the treatment of food by a certain type of intense energy known as ionizing radiation. This involves exposing bulk or packaged food to carefully controlled amounts of energy. Food does not come in contact with radioactive material. The publication discusses the technology of food irradiation including; the energy source, effect on foods, identifying treated foods, environmental concerns and approved uses in the U.S.
8

Propriétés électro-optiques et diélectriques de cristaux liquides photo-ferroélectriques / Electro-optical and dielectric properties of photo-ferroelectrics liquid crystals

Boussoualem, Yahia 29 June 2010 (has links)
Ce travail concerne l’étude des effets de la lumière sur les propriétés optiques, électro-optiques et diélectriques d’un cristal liquide pur de la famille azobenzène. Ces études ont été réalisées, en fonction de la température et de l’intensité de la lumière UV, en phase smectique C hélicoïdale (SmC*) qui est photo-ferroélectrique. Les études optiques ont montré que les modifications observées, sous irradiation UV, sont dues à la photo-isomérisation des molécules azobenzène. Le passage de la forme Trans à la forme Cis se traduit par des changements des propriétés physico-chimiques du composé et une diminution de la température de transition haute température SmC*-TGBA. Les études électro-optiques révèlent une forte diminution de la polarisation spontanée Ps et une baisse modérée de l’angle d’inclinaison q. La spectroscopie diélectrique montre que l’amplitude du mode de Goldstone augmente et sa fréquence de relaxation diminue sous irradiation lumineuse. L’exploitation des résultats montre que les évolutions photo-induites des amplitudes et fréquences de relaxation du mode Goldstone sont étroitement liées aux variations de Ps, de µ, de la viscosité rotationnelle °G et de la constante élastique de flexion K3. Dans la seconde partie de ce travail, nous avons quantifié les populations des deux isomères ainsi que les paramètres caractéristiques de leur dynamique sous irradiation à l’aide d’un modèle théorique. D’autre part nous avons montré que les variations des propriétés optiques, électro-optiques et diélectriques sont étroitement liées à la profondeur de pénétration de la lumière incidente dans la cellule. Ces comportements obéissent à une loi de type Beer-Lambert-Bouguer. / This work concerns the study of the light effects on the optical, electro-optical and dielectric properties of a pure azobenzene liquid crystal. These studies were carried out, according to temperature and the UV light intensity, in the helicoidal SmC phase which is photo-ferroelectric.The optical studies show that the observed modifications, under UV irradiation, are due to the photo-isomerization of the azobenzene molecules. The transformation from the Trans to Cis form results in changes of the physico-chemical properties and a reduction of the SmC*-TGBA transition temperature Tc.The electro-optical studies reveal a strong decrease of the spontaneous polarization Ps and a moderate one of the tilt angle q. The dielectric spectroscopy studies show that the amplitude of the Goldstone mode increases and the relaxation frequency decreases under irradiation.We show that these variations of the dielectric strength and relaxation frequencies, under UV illumination, are related, at the same time, of the variations of Ps, q , rotational viscosity g G and elastic constant K3. Using a theoretical model, we determine in the second part of this work the populations of the Trans and Cis isomers as well as the characteristic dynamic parameters under irradiation. Finally we show that the variations of the optical, electro-optical and dielectric properties are closely related to the light penetration depth in the cell. Finally we show that the variations of the optical, electro-optical and dielectric properties are closely related to the light penetration depth in the cell. These behaviors obey to a Beer-Lambert law.
9

Theory of compositional effects in irradiation damage

Murphy, Susan Mary January 1987 (has links)
No description available.
10

Irradiation aux ions des carbures ZrC et TiC. Effets des pertes d'énergie électronique et nucléaire. / Ion irradiation of carbides ZrC and TiC. Effects of electronic and nuclear energy losses

Pellegrino, Stéphanie 01 October 2015 (has links)
Cette étude est orientée sur les céramiques réfractaires des métaux de transition, comme le carbure de titane et de zirconium, envisagées pour leurs caractéristiques de résistance en conditions extrêmes. Ces céramiques seraient soumises à différentes sources d'irradiation (les neutrons, les produits de fission, les désintégrations alpha) dans les futurs réacteurs de génération IV. Les rayonnements rencontrés en réacteur peuvent être simulés par des irradiations externes à l'aide d'accélérateurs de particules, en utilisant des ions variés dans une large gamme d'énergie. Ces instruments permettent de reproduire en conditions contrôlées l'endommagement subi par des les matériaux internes aux centrales nucléaires.Dans un tel contexte radiatif, deux processus majeurs gouvernent l'endommagement des matériaux: les collisions nucléaires induites par les irradiations avec des ions de faible énergie (comme les noyaux de recul) et les excitations électroniques intervenant dans les irradiations avec des ions de grande énergie (comme les produits de fission). La prédominance de l'un ou de l'autre de ces processus est reliée à la masse et à l'énergie de la particule accélérée. Pour comprendre la contribution de chaque effet dans les mécanismes d'endommagement des structures cristallines soumises à des irradiations, nous avons simulé des rayonnements impliquant, d'une part, des ions de basse énergie, i.e. de quelques MeV et, d'autre part, des ions de grande énergie, i.e. de quelques centaines de MeV. Les principaux objectifs de ce travail ont été: (i) d'étudier le comportement de ces deux carbures sous irradiation, (ii) de déterminer les modifications structurales, chimiques et mécaniques induites par les effets nucléaires et électroniques, (iii) de comprendre les mécanismes d'endommagement dans ces carbures dans le régime nucléaire et (iv) d'essayer d'expliquer les résultats expérimentaux par les calculs obtenus en simulation.Pour cela, différentes techniques de caractérisation ont été combinées afin d'expliquer le scénario de ces carbures sous irradiation avec comme référence, le carbure de silicium SiC très étudié par le passé. Ces techniques complémentaires sont: la spectrométrie de rétrodiffusion de Rutherford en mode canalisé (RBS-C), la diffraction des rayons X (DRX), la spectroscopie Raman, la microscopie électronique en transmission (MET) et la nanoindentation. La combinaison de ces techniques expérimentales ainsi que la simulation a permis de conforter nos résultats et les différentes hypothèses formulées. Nous avons pu établir ainsi un scénario pour ces deux types de carbures TiC et ZrC sous irradiation aux ions. / This study is focused on the ceramic refractory transition metals, such as titanium carbide and zirconium envisaged to their strength characteristics under extreme conditions. These ceramics are subject to various sources of radiation (neutrons, fission products, the alpha decays) in future generation reactors IV. Radiation encountered in the reactor can be simulated by external irradiation with particle accelerators, using various ions in a wide energy range. These instruments can reproduce in controlled conditions damage suffered by nuclear materials.In such radiative context, two major processes govern damages into the materials: nuclear collisions induced by irradiation with low energy ions (like the recoil nuclei) and electronic excitations involved in irradiation with high-energy ions (such as fission products). The predominance of one of these processes is connected to the mass and energy of the accelerated particle. To understand the contribution of each effect in the damage mechanisms of crystal structures subjected to irradiation, we simulated radiation involving, on the one hand, low energy ions, i.e. a few MeV and, secondly, high energy ions, i.e. a few hundred MeV. The main objectives of this work were: (i) to study the behavior of these two carbides under irradiation, (ii) determine the structural, chemical and mechanical changes induced by nuclear and electronic effects, (iii) understand the damage mechanisms in these carbides in the nuclear regime and (iv) to try to explain the experimental results obtained by simulation calculations.For this, various characterization techniques were combined to explain the scenario of these carbides under irradiation as a reference, the silicon carbide SiC extensively studied in the past. These additional techniques are: Rutherford Backscattering Spectrometry in channeling mode (RBS-C), the X-ray diffraction (XRD), Raman spectroscopy, Transmission Electron Microscopy (TEM) and nanoindentation. The combination of these experimental techniques and simulation helped to consolidate our results and various assumptions. We were able to establish a scenario for these two types of carbides TiC and ZrC under ion irradiation.

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