Dissertations / Theses on the topic 'Gay bears'

Thesis (M.F.A.)--University of New Orleans, 2003.
Title from PDF title page (viewed on Apr. 5, 2005). "A thesis ... in partial fulfillment of the requirements for the degree of Master of Fine Arts in the Department of Drama and Communications." Vita. Includes bibliographical references (p. 72-93).

Despite the vast research regarding non-conformative bodies, there is little material on the gay bear representation in fashion modelling. This thesis investigates the bear embodiment in the runway shows of Walter Van Beirendonck, respectively W&LT Autumn/Winter 1995–1996 Paradise Pleasure Productions, W&LT Autumn/Winter 1996-1997 Wonderland, Walter Van Beirendonck Spring/Summer 2010 Wonder, and Walter Van Beirendonck Spring/Summer 2011 Read My Skin. Critical visual analysis follows the gay bear symbolism in the video recordings of the runways, revealing how it challenges the fashion industry’s body standards and, in a broader frame, the dictates of hegemonic masculinity. The concepts of gender performativity and biopower provide the theoretical frame of the study, while Madison Moore’s theory of ‘fabulousness’ and José Esteban Muñoz’s understanding of ‘utopia’ lead to the articulation of performances both masculine and queer.  The findings lead to the discovery of non-dual and body-inclusive gay bear embodiments that challenge the relationship between body and dress and can extends beyond the limits of the runway.

This thesis details the production process of a video documentary that describes the coming out processes of gay men who identify with the Bear subculture of the gay community and some of the conflicts and consequences that they face due to this action. The aim of this production was to portray with dignity and compassion the recorded feelings and personal histories of the subjects interviewed. Chapters are devoted to the development, pre-production, production and post-production phased of this documentary. A detailed script, transcripts, shot list, and other examples and illustrations are included to give a better understanding of the entire production. This thesis also includes other necessary documentation such as a detailed budget and copies of performance releas

学位授与年月日: 1999-03-23 ; 学位の種類: 新制・課程博士 ; 学位記番号: 1823
In this thesis, fundamental properties of gas cluster ion beams and their non-linear irradiation effects are studied. Applications in the fabrication of nano-structures (nano-processes) are demonstrated, as based on knowledge of the interactions between clusters and solid surfaces. In chapter 2, a cluster source which provides an intense neutral cluster beam by supersonic expansion from a Laval nozzle is described, and the high current cluster ion beam equipment is explained. By optimization of both ionization and transport conditions of the cluster beam, a high cluster ion current density of a few μA/cm2 was achieved. The detailed cluster size distribution following a supersonic expansion and the characteristics of the cluster beams are discussed in chapter 3 based on data obtained with a high resolution time of flight mass spectrometer. The formation of inert, reactive and complex gas clusters was verified, and their average cluster size was 2000atoms/cluster. With increasing cluster size, the ionization and collision cross-section increased, however, the kinetic energy of the impact was compensated by the cohesive energy of a large cluster. In chapter 4, interactions of cluster and target atoms in an energetic cluster ion impact are discussed. Most of the kinetic energy of cluster ions was deposited with high density on the surface regions of the targets, and subsequently, multiple collisions between targets and clusters occurred. This dense energy deposition resulted in intrinsic non-linear sputtering effects, such as high yield sputtering and crater formation, which could not be explained by the summation of the irradiation effects induced by the same number of monomer ions. The lateral sputtering effect, which is explained in that many sputtered atoms with cluster ions are emitted in the horizontal direction on the surface plane, was clarified experimentally for the first time, and this was verified by STM observations of single traces of cluster ion impacts. In chapter 5, an enhancement of the sputtering effects with reactive cluster ion beams and their applications are discussed. Since the impact area of the target by a cluster ion occurred under high temperature and high pressure conditions, chemical reactions on the target surface were enhanced. In the case of reactive cluster ion irradiation, dissociation of reactive molecules and clusters occurred simultaneously, and subsequently, enhancement of the etching rate was observed as a consequence of the production of volatile materials. Reactive cluster ion etching could be applied for Si fine pattern etching, and it provided solutions for charging up, isotropic etching, microloading and radiation damage problems. In chapter 6, the surface smoothing effect and mechanisms with cluster ions are discussed. The cluster ion exhibited marked surface smoothing effects and it was made clear from both experimental and simulation results that the lateral sputtering effect was significant for surface smoothing. Very smooth surfaces of CVD diamond films and SiC single crystal substrates were obtained using the gas cluster ion beam processing; these materials are difficult to etch using conventional processes. From these results, it can be summarized that gas cluster ion beam processing is effective in the fabrication of nano-structures and applications in the industrial field are expected.
Kyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第7843号
工博第1823号
新制||工||1140(附属図書館)
UT51-99-G437
京都大学大学院工学研究科電子物性工学専攻
(主査)教授 山田 公, 教授 橘 邦英, 教授 今西 信嗣
学位規則第4条第1項該当

Depuis l’invention de la chambre proportionnelle multifilaire en 1968, les détecteurs gazeux ont transformés les expériences de physique des hautes énergies. Les performances des chambres à fils ont beaucoup amélioré la précision des mesures jusqu’à ce que le flux de particules atteigne 104 Hz/mm2, la limite pour les détecteurs à lecture par fil. Pour dépasser cette limite, de nouveaux concepts de détecteurs gazeux sont apparus dans les années 1990, les Détecteurs Gazeux à Micro Motifs ou MPGD pour “Micro-Pattern Gas Detectors” en anglais. Avec l’avènement d’une nouvelle génération d’expériences, ces technologies connaissent un regain d’intérêt. En particulier les dé- tecteurs GEM et Micromegas ont prouvé qu’ils pouvaient atteindre une résolution spatiale meilleure que 100 μm, une résolution temporelle de 10 ns à un flux de particules supérieur à 106 Hz/mm2. Cette thèse est consacrée au développement, à la conception et à la caractérisation de ces détecteurs. La première partie de cette thèse porte sur le développement d’une chambre à projection temporelle, TPC pour “Time Projection Chamber” en anglais, destinée aux haut flux de particules. Traditionnellement lue par des chambres à fils, ces détecteurs sont limités par la charge d’espace crée par les ions qui remontent dans le volume de dérive. Il est donc nécessaire de neutraliser ces ions à l’aide d’une grille dont l’utilisation limite la fréquence de déclenchement à ∼ 1 kHz. Grâce à leur suppres- sion intrinsèque des ions, une lecture à base de GEM est envisagée pour lire une TPC sans avoir à recourir à une grille. Un prototype de 7 cm d’espace de dérive équipé de pads hexagonaux a été as- semblé à Munich. Munie de l’électronique AFTER dédié aux MPGDs, le détecteur a été testé à l’aide du faisceau d’électrons de l’accélérateur ELSA à Bonn, en Allemagne. Une seconde période de test à l’aide de muons de haute énergie a permis de démontrer les bonnes performances de la GEM-TPC. La seconde partie de cette thèse décrit le développement de la prochaine génération de détecteurs Micromegas pour l’expérience COMPASS-II. Les nouveaux Pixels Micromegas devront supporter un flux de hadrons de 5 × 106 Hz/mm2. Des tests avec les détecteurs actuels ont montré leur limitation en termes de flux de particules et de probabilité de décharge. Une réduction de cette probabilité d’un facteur de 10 à 100 est nécessaire. Ceci est à l’origine d’un programme de R&D qui a conduit à deux solutions : la pré-amplification par feuille de GEM et la protection des pistes par une structure resis- tive à base de résistances enterrées. Chacune de ces technologies a été testées avec des prototypes de 40×40 cm2, lus par l’électronique APV dans l’environnement de l’expérience COMPASS. Des résultats prometteurs en terme d’efficacité, de résolutions spatiale et temporelle sont présentés
Since the invention of Multi-Wire Proportional Chambers (MWPC) in 1968, gaseous detectors have transformed the field of high-energy physics experiments. The performances of MWPCs have greatly improved the precision of measurements up to a the particle rate of 104 Hz/mm2, which is the limit for wire detectors. To overcome this limitation, new concepts of gaseous detectors, the Micro-Pattern Gas Detectors, appeared in the late 90’s. Nowadays, a renewed interest in these technologies is brought about by the design of the next generation of experiments. Specifically GEM and Micromegas track- ing detectors have proved to reach spatial resolutions better than 100 μm and time resolutions below 10 ns at a rate above 106 Hz/mm2. This work is dedicated to the development of these concepts and to the design and characterization of new detectors. The first part of this thesis reports on the development of a Time Projection Chamber (TPC) for high rate environments. Traditionally read out by wire-chambers, these detectors suffer from the space charge created by back-drifting ions. This implies the use of an ion gate that limits the rate to ∼ 1 kHz. Thanks to their intrinsic ion back-flow suppression, GEMs have been considered to operate TPCs in an un-gated mode. A prototype with 7 cm drift length and hexagonal pad readout has been assem- bled and connected to the low noise AFTER front-end electronic readout dedicated to MPGDs. The chamber has been commissioned with an external tracking telescope using an electron beam at the ELSA facility. A second test beam period for precision measurements using high-energy muons has demonstrated the great performances of the GEM-TPC. The second part of this dissertation describes the development of the next generation of Micromegas for the future COMPASS-II experiment. The new Pixel Micromegas will have to sustain a hadron beam of 5 × 106 Hz/mm2. Tests with current COMPASS Micromegas detectors have shown their limitations in term of maximal particle rate and discharge probabilities. A factor 10 to 100 in discharges rate reduction is required. This triggered a R&D project that concluded on the selection of GEM pre- amplification and buried resistors structure as realistic options. Both these technologies have been tested with 40×40 cm2 prototypes, read by the fast APV25 front-end electronics, in COMPASS environ- ment; promising results on efficiency, spatial and time residuals are reported

Atomic beam experiments are limited by intensity. Intensity limitations are specially critical in the measurements of metastable atoms, since their relative population is several order of magnitude smaller than the beam population. This thesis provides a method for increasing the intensity of metastable argon and neon beams effusing from a hot cathode, glow discharge by use of a longitudinal magnetic field. The argon and neon metastable atom intensities have been measured for a range of discharge pressure, voltage, and current for a magnetic field strengths from 0 to 31 mT. For both argon and neon, the metastable atom beam intensity rises to a maximum value about one order of magnitude above the zero field case. A qualitative discussion of the theory of this phenomenon is also presented.

This thesis describes the design, construction, operation, and characterisation of an experimental apparatus that produces a source of internally cold, slow molecules that can be used for studying ion-molecule reactions at low temperatures. The apparatus combines buffer-gas cooling with a bent quadrupole velocity selector to cool both the translational and rotational degrees of freedom of the molecules. A cold cell (6 K) is filled with a buffer gas, such as helium, that exhibits sufficiently high vapour pressure for cryogenic applications. Hot molecules (150 to 300 K) enter the cell and thermalise with the buffer gas through collisions. Molecules are subsequently loaded into an electrostatic quadrupole guide, which acts as a velocity filter; only translationally cold polar molecules are guided around the bend. Using a buffer-gas-cooled source of molecules for electrostatic velocity selection, rather than a 300 K effusive source, yields a rotationally cold sample, with J ≤ 3. This rotational selectivity will enable the dependence of reaction cross sections on the reactant rotational state to be examined. Mass spectrometry is used to characterise cold molecular beams of ND3 and CH3F, while (2+1) REMPI spectra are recorded for the ammonia isotopologues. The peak velocity of guided ND3 is 75.86(0.70) ms-1 for standard conditions in a 6 K helium buffer gas cell (1.0 sccm ND3 flow rate, 0.6 mbar helium inlet pressure, ± 5 kV voltage). This corresponds to a peak kinetic energy of 6.92(0.13) K. (2+1) REMPI spectroscopy of the B1E''(v2'=5) ← X(1) transition enabled the rotational state distribution of guided ammonia molecules to be established. PGOPHER simulations of the experimental spectra suggest a rotational temperature of 10 K for ND3 molecules (from a 6 K helium buffer gas cell). The extent of translational and rotational cooling can be controlled by varying the molecular and buffer gas densities within the cell, by changing the temperature of the buffer gas cell (we can operate at 6 K or 17 K), or by changing the buffer gas. The translational temperature of guided ND3 is similar in a 6 K helium and 17 K neon buffer gas cell (peak kinetic energies of 6.92(0.13) K and 5.90(0.01) K, respectively) because the heavier neon gas has a slightly lower thermal velocity at 17 K than helium does at 6 K. Despite similar translational temperatures, the rotational temperature of guided ND3 is lower for molecules exiting the 6 K helium cell compared to the 17 K neon buffer gas cell (10 K and 15 K, respectively). The 6 K helium and 17 K neon buffer gas cells provide an excellent opportunity to investigate the effect of rotational cooling on branching ratios and reaction rates in low temperature ion-molecule reactions. The buffer gas cell and velocity guide described in this work will be combined with a linear Paul ion trap, to facilitate the study of cold ion-molecule reactions.

In this thesis, Gallium Nitride (GaN) micro- and nanostructures were fabricated based on focused ion beam (FIB) milling. The starting wafer is an epitaxial structure containing InGaN/GaN multi-quantum wells. High crystal quality structures such as the nano-cone, nanopillar array and single pillar were fabricated based on the FIB method. During the fabrication process, various approaches were designed to minimize FIB damage caused by Gallium ion bombardment. The fabrication process for nano-cone is a combination of mask preparation by FIB with subsequent reactive ion etching (RIE). For fabricating nanopillar arrays, the nanopillars were patterned directly using FIB with an optimized beam current followed by wet etching process to remove the damage. On the other hand, the single pillar is achieved by gradually decreasing the ion beam current as the diameter of the pillar becomes smaller. The first order Raman spectra for the nanopillar array reveal a strong additional peak when the diameter of the nanopillars is less than 220 nm. This peak can also be observed in GaN pillars without MQW and is clearly assigned to the surface optical (SO) mode originated from the A1 phonon in wurtzite GaN. The frequency of this SO mode is found to be sensitive with the diameter and surface roughness of the nanopillars. Temperature-variable photoluminescence (PL) measurements show that a broadband emission in the as-grown sample split into the two well-resolved bands for nanopillars and the emission band at the higher energy side quickly thermally quenched. Room temperature PL measurements on the single pillars exhibit an increasing blue-shift of the peak emission with the decreasing of the pillar diameter. Additional simulation data and excitation power dependent PL studies confirm the observation of strain relaxation in the pillar’s MQW due to FIB fabrication. The temperature variable PL on the single pillar shows a monotonous blue shift as the temperature arises to 300 K.
published_or_final_version
Electrical and Electronic Engineering
Master
Master of Philosophy

Made available in DSpace on 2014-10-09T12:55:26Z (GMT). No. of bitstreams: 0
Made available in DSpace on 2014-10-09T14:06:01Z (GMT). No. of bitstreams: 0
Dissertação (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

An analytical model of cracked composite beams vibrating in coupled bending-torsion is developed. The beam is made of fiber-reinforced composite with fiber angles in each ply aligned in the same direction. The crack is assumed open. The local flexibility concept is implemented to model the open crack and the associated compliance matrix is derived. The crack introduces additional boundary conditions at the crack location and these effects in conjunction with those of material properties are investigated. Free vibration analysis of the cracked composite beam is presented. The results indicate that variation of natural frequencies in the presence of a crack is affected by the crack ratio and location, as well as the fiber orientation. In particular, the variation pattern is different as the magnitude of bending-torsion coupling changes due to different fiber angles. When bending and torsional modes are essentially decoupled at a certain fiber angle if there is no crack, the crack introduces coupling to the initially uncoupled bending and torsion. Based on the crack model, aeroelastic characteristics of an unswept composite wing with an edge crack are investigated. The cracked composite wing is modeled by a cracked composite cantilever and the inertia coupling terms are included in the model. An approximate solution on critical flutter and divergence speeds is obtained by Galerkin's method in which the fundamental mode shapes of the cracked wing model in free vibration are used. It is shown that the critical divergence/flutter speed is affected by the elastic axis location, the inertia axis location, fiber angles, and the crack ratio and location. Moreover, model-based crack detection (size and location) by changes in natural frequencies is addressed. The Cawley-Adams criterion is implemented and a new strategy in grouping frequencies is proposed to reduce the probability of measurement errors. Finally, sensitivity of natural frequencies to model parameter uncertainties is investigated. Uncertainties are modeled by information-gap theory and represented with a collection of nested sets. Five model parameters that may have larger uncertainties are selected in the analysis, and the frequency sensitivities to uncertainties in the five model parameters are compared in terms of two immunity functions.
Ph. D.

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-08-07T14:21:56Z No. of bitstreams: 0
Made available in DSpace on 2015-08-07T14:21:56Z (GMT). No. of bitstreams: 0
Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Proposed are novel sensors for extreme environment power plants, laser beam analysis and biomedicine. A hybrid wireless-wired extreme environment temperature sensor using a thick single-crystal Silicon Carbide (SiC) chip embedded inside a sintered SiC probe design is investigated and experimentally demonstrated. The sensor probe employs the SiC chip as a Fabry-Perot (FP) interferometer to measure the change in refractive index and thickness of SiC with temperature. A novel temperature sensing method that combines wavelength-tuned signal processing for coarse measurements and classical FP etalon peak shift for fine measurements is proposed and demonstrated. This method gives direct unambiguous temperature measurements with a high temperature resolution over a wide temperature range. An alternative method using blackbody radiation from a SiC chip in a two-color pyrometer configuration for coarse temperature measurement and classical FP laser interferometry via the same chip for fine temperature measurement is also proposed and demonstrated. The sensor design is successfully deployed in an industrial test rig environment with gas temperatures exceeding 1200 C. This sensor is proposed as an alternate to all-electrical thermocouples that are susceptible to severe reliability and lifetime issues in such extreme environments. A few components non-contact thickness measurement system for optical quality semi-transparent samples such as Silicon (Si) and 6H SiC optical chips such as the one used in the design of this sensor is proposed and demonstrated. The proposed system is self-calibrating and ensures a true thickness measurement by taking into account material dispersion in the wavelength band of operation. For the first time, a 100% repeatable all-digital electronically-controlled pinhole laser beam profiling system using a Texas Instruments (TI) Digital Micro-mirror Device (DMD) commonly used in projectors is experimentally demonstrated using a unique liquid crystal image generation system with non-invasive qualities. Also proposed and demonstrated is the first motion-free electronically-controlled beam propagation analyzer system using a TI DMD and a variable focus liquid lens. The system can be used to find all the parameters of a laser beam including minimum waist size, minimum waist location and the beam propagation parameter M2. Given the all-digital nature of DMD-based profiling and all-analog motion-free nature of the Electronically Controlled Variable Focus Lens (ECVFL) beam focus control, the proposed analyzer versus prior-art promises better repeatability, speed and reliability. For the first time, Three Dimensional (3-D) imaging is demonstrated using an electronically controlled Liquid Crystal (LC) optical lens to accomplish a no-moving parts depth section scanning in a modified commercial 3-D confocal microscope. The proposed microscopy system within aberration limits has the potential to eliminate the sample or objective motion-caused mechanical forces that can distort the original sample structure and lead to imaging errors. A signal processing method for realizing high resolution three dimensional (3-D) optical imaging using diffraction limited low resolution optical signals is also proposed.
Ph.D.
Optics and Photonics
Optics and Photonics
Optics PhD

Dissertação de Mestrado em Segurança Alimentar
O furano tem sido detectado em diversos alimentos em particular nos que são sujeitos a tratamento térmico durante o processo de preparação industrial. É considerado um composto potencialmente cancerígeno para seres humanos, pelo que a sua presença nos alimentos se tornou uma questão de segurança alimentar. Desde 2007 que a Autoridade Europeia para a Segurança Alimentar tem procurado recolher o maior número de informação possível, relativa à presença de furano nos alimentos. Neste trabalho utilizou-se a técnica de Cromatografia Gasosa de Espaço de Cabeça acoplada a um espectrómetro de massa (HS-GC/MS) para avaliar os teores de furano em feijões enlatados. Foram analisadas 10 amostras (latas) independentes, seleccionadas aleatoriamente no mercado, de três marcas comercializadas em Portugal. A concentração média obtida foi de 3,27 ng/g, numa gama que variou entre 2,61 e 4,45 ng/g. Os limites de detecção calculados foram de 0,80 ng/g para as amostras PD, 1,26 ng/g para as amostras C e de 0,58 ng/g para as amostras F. Os limites de quantificação foram, respectivamente, de 2,44, 3,82 e 1,77 ng/g. Os coeficientes de variação do método foram inferiores a 10% e a percentagem de recuperação foi de 95%. Para estudar o efeito do tratamento térmico doméstico, foram também, analisadas amostras aquecidas à temperatura de 80°C, tendo-se verificado um aumento significativo na concentração do furano detectada. Comparou-se ainda a concentração média do furano obtido nos feijões em lata com a concentração média para o mesmo tipo de feijão conservado em frascos de vidro, tendose constatado não existirem diferenças significativas.
ABSTRACT - Furan has been detected in various foods in particular in those that suffer heat-treatment during industrial preparation. It is considered a potentially carcinogenic compound to humans, so its presence in foods has become a matter of food security. Since 2007, the European Food Safety Authority has thought to collect as much information as possible on the presence of furan in food. In this work we used the technique of head space gas chromatography coupled with mass spectrometry HS-GC/MS to assess the levels of furan in canned beans. We analyzed 10 independent samples (cans), randomly selected on the market, and from three brands sold in Portugal. The average concentration obtained was 3.27 ng/g, with a range that varied between 2.61 and 4.45 ng/g. The detection limits calculated were 0.80 ng/g for samples PD, 1.26 ng/g for samples C and 0,58 ng/g for samples F. The limits of quantification were, respectively, 2.44, 3.82 and 1,77 ng/g. The coefficients of variation of the method were less than 10% and the recovery was 95%. To study the effect of house heat treatment, samples heated at 80°C were also analyzed, and there have been a significant increase in the concentration of detected furan. It is also compared the average concentrations of furan obtained from canned beans with the average concentrations for the same type of beans stored in glass bottles. No significant differences were found.

Made available in DSpace on 2014-10-09T12:44:55Z (GMT). No. of bitstreams: 0
Made available in DSpace on 2014-10-09T13:59:48Z (GMT). No. of bitstreams: 1 07173.pdf: 11277724 bytes, checksum: 5b5dfb2b888fca36e76b5cf99fdb18ab (MD5)
Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares, Sao Paulo

L'objectif de cette these est de caracteriser l'endommagement de miroirs soumis a un rayonnement continu issu de lasers de hautes puissances a gaz carbonique. Il ressort de ce travail que la temperature de destruction est la grandeur physique qui qualifie la resistance des miroirs vis-a-vis de l'emission continue des lasers a gaz carbonique. Deux processus d'endommagement, le seuil et le vieillissement, sont associes a cette temperature de destruction. Le seuil represente la traversee de cette temperature de destruction lors de la mise en equilibre thermique du miroir. Ce mecanisme d'endommagement depend essentiellement de la conductivite thermique du substrat. Lors du vieillissement, la temperature de destruction est traversee en raison d'une evolution de l'absorbance du miroir. Ce processus de destruction, qui depend essentiellement de la qualite des couches minces, intervient apres le seuil avec une cinetique plus lente que celle associee a l'inertie thermique du miroir. Les consequences de l'existence d'une temperature de destruction sont etudiees experimentalement. Elles sont analysees a l'aide de modelisations thermiques, qui prennent en compte les non-linearites de l'absorbance et de la conductivite thermique du substrat. Ainsi, nous demontrons qu'en test, avec de petits faisceaux, le seuil de destruction est represente par le rapport entre la puissance et le rayon du faisceau laser. Avec la mesure de ce seuil de destruction, determine en test, il est possible, a l'aide de la loi d'echelle spatiale proposee, de connaitre le seuil de destruction du miroir en utilisation reelle avec de grands faisceaux. Un protocole de vieillissement des miroirs, utilise pour determiner la duree de vie des miroirs sous des irradiations continues de lasers a gaz carbonique, est egalement etabli

Orientadores: Antonio J. Ramirez, Maria Clara F. Ierardi
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
Made available in DSpace on 2018-08-09T21:56:05Z (GMT). No. of bitstreams: 1 Seraphim_RafaelMolena_M.pdf: 6485115 bytes, checksum: 380cfffee5fa982ec74a9cdc78c88e3a (MD5) Previous issue date: 2007
Resumo: O avanço cientifico no estudo de átomos, moléculas e proteínas tem recebido uma contribuição significativa dos aceleradores de partículas, que em sua grande maioria são utilizados para a geração de radiação síncrotron. Por isso, o aprimoramento destas máquinas mostra-se de extrema importância para manter a ciência em seu contínuo avanço. O sistema de vácuo destas máquinas apresenta-se como um importante parâmetro para o seu bom funcionamento e melhorias neste promovem diretamente melhorias na qualidade da radiação síncrotron gerada. Logo, o desenvolvimento deste trabalho teve como principal objetivo o estudo das juntas soldadas das câmaras de vácuo que compõem o acelerador do Laboratório Nacional de Luz Síncrotron (LNLS). As juntas foram preparadas com o processo de soldagem GTAW (Gás Tungsten Arc Welding) mediante a utilização de diferentes gases de proteção, como Argônio, Hélio e Nitrogênio, e misturas entre estes. Os estudos concentraram-se na análise da influência dos gases de proteção na dessorção de gases das juntas soldadas. Para a caracterização destas utilizaram-se as técnicas de análise de superfícies Dessorção Estimulada por Elétrons (DEE) e Dessorção Estimulada por Fótons (DEF). Adicionalmente, realizou-se um estudo comparativo entre as duas técnicas buscando-se estabelecer relações entre os resultados fornecidos pelas mesmas. Os resultados mostraram que a dessorção de gases independe do gás de proteção de soldagem, mas depende sim do nível de oxidação das juntas soldadas, as quais podem apresentar altas taxas de dessorção caso estejam muito oxidadas e os óxidos não sejam camadas contínuas. Em conclusão pode-se dizer que as juntas soldadas para câmaras de vácuo de aceleradores de partículas devem apresentar baixos níveis de oxidação, e apesar das semelhanças encontradas entre a DEE e a DEF é aconselhável utilizar a DEF para a caracterização de superfícies para trabalharem com radiação síncrotron
Abstract: The scientific advance of atoms, molecules and proteins studies has received an important contribution from particle accelerators, which are mainly used to generate synchrotron radiation. Hence, the improvement of these machines is necessary to maintain the continuous advance of science. One of the key components for the adequate operation of these accelerators is the vacuum system. Thus, its improvement directly impacts on the quality of the generated synchrotron radiation. Therefore, the principal purpose of this work is to study the gas desorption from the welding joints on the particle accelerators vacuum chambers. The welds were prepared using the GTAW (Gas Tungsten Arc Welding) process with different shielding gases, as argon, helium and nitrogen, and some mixtures of them. The study concentrated on the analysis of the shielding gas influence on the gas desorption from the welded joints. The gas desorption of the joints was evaluated using Electron Stimulated Desorption (ESD) and Photon Stimulated Desorption (PSD). In addition, it was carried out a comparative study between both desorption techniques to establish relationships between the results provided by them. The results showed that the gas desorption from the welding joints does not depend on the welding shielding gas, but on the oxidation level of the joint, which can present high desorption yield if it is highly oxidized and these oxides are not a continuous film. Therefore, it is advisable to minimize the oxidation during welding of vacuum chambers for particle accelerators. Regarding the comparison between ESD and PSD they were found some similarities. However, PSD will have better performance characterizing surfaces that will be exposed to synchrotron radiation
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica

Les instabilités de type Weibel naissent si la distribution des vitesses du plasma présente une anisotropie. Elles entraînent la génération d’un champ magnétique dû à la formation de filaments de courant ainsi qu’une activité électrostatique importante. Ces phénomènes de base apparaissent dans de nombreuses situations, naturelles (vent solaire, jets relativistes) ou expérimentales (interaction laser-plasma) : les plasmas dans lesquels ils naissent peuvent être relativistes ou non, magnétisés ou non, collisionnels ou non, ce qui pose la question du choix du modèle à utiliser pour les décrire. La théorie cinétique est le cadre le plus complexe dans lequel nous travaillerons. De par sa complexité, il est intéressant de développer des modèles réduits. Un premier travail mené au cours de cette thèse est l’utilisation d’un modèle fluide incluant la dynamique du tenseur de pression pour modéliser la phase linéaire des instabilités de type Weibel. On discute le rôle essentiel joué par les composantes hors diagonale du tenseur dans la génération du champ magnétique, puis la capacité du modèle à reproduire quantitativement ou qualitativement les résultats cinétiques en introduisant la notion de limite hydrodynamique. La seconde partie de la thèse est ciblée sur le développement du code semi-lagrangien relativiste VLEM utilisant une méthode de décomposition de domaine : on présente les principales méthodes mathématiques utilisées dans le code, puis on aborde la problématique de la conservation de la charge à laquelle on apporte une réponse reposant sur une adaptation de la méthode d’Esirkepov. Le code est enfin validé grâce à plusieurs simulations d’instabilités de type Weibel
Weibel-type instabilities occurs when the velocity distribution function of the charged particles displays a pronounced anisotropy. A long-lasting magnetic field is generated due to the formation of current filaments, and it is accompanied by an important electrostatic activity. These ``basic’’ phenomena have been greatly investigated because of their involvement in many physical problems, natural (solar wind, relativistic jets) or experimental (laser-plasma interaction) : they occurs in plasmas which can be collisional or not, magnetised or not, relativistic or not. One needs to choose a suitable model for their description. The kinetic theory is the most complete and somewhat complex theoretical framework which we will consider. Due to its complexity, it may be interesting to develop reduced models. The first work realised during this thesis is the utilisation of a non-relativistic fluid description, including the dynamics of the pressure tensor, in order to model the linear Weibel-type instabilities. We put in evidence the effect of the non-diagonal components of the tensor on the magnetic field generation. We discuss the ability of the model to reproduce quantitatively or qualitatively the kinetic results by introducing the hydrodynamics limit. The second part of this thesis work is dedicated to the development of the relativistic semi-lagrangian code VLEM, using a domain decomposition scheme : we present the main mathematical tools used in the code, then we deal with the problem of the charge conservation and propose a solution for VLEM, based on an adaptation of the Esirkepov method. Finally, we validate the code through simulations of Weibel-type

Le projet piafe consiste a produire des noyaux riches en neutrons par fission au sein d'une cible d'uranium placee pres du cur du reacteur de l'institut laue langevin, puis de transporter les produits de fission sous forme monochargee et a basse energie (inferieure a 30 kev) sur une distance de 400 m jusqu'au complexe accelerateur sara de l'institut des sciences nucleaires de grenoble. Une solution originale de guidage ayant ete proposee, l'objectif de cette these est de prouver la faisabilite d'un tel transport. Pour ceci, on s'est attache a etudier les effets sur le faisceau des defauts d'alignement des elements optiques (et de leur support) et du champ magnetique terrestre afin de determiner un systeme periodique de correction de la trajectoire centrale du faisceau. Puis, la realisation d'une ligne experimentale de 18 m a permis de faire une etude detaillee de l'interaction du faisceau avec le gaz residuel. Cette interaction se caracterise par les pertes de particules par echange de charge et l'augmentation d'emittance par diffusion coulombienne. La validation des modeles theoriques permet une extrapolation des phenomenes sur une distance de 400 m. Il est ainsi possible de conclure sur la faisabilite d'un tel transport

L'intégration de semiconducteurs III-V à gap direct sur silicium est un enjeu de taille pour le développement de l'optoélectronique. En effet, si le silicium est aujourd'hui à la base de la microélectronique, la nature indirecte de son gap en fait un très mauvais émetteur de lumière. Parmi les matériaux candidats à l'intégration, l'In(Ga)As présente l'avantage d'un gap direct plus faible que le silicium, favorisant un comportement de puits de potentiel pour les paires électrons-trous. En revanche, le fort désaccord paramétrique entre les deux matériaux fait de la croissance épitaxiale d'In(Ga)As sur silicium un sérieux défi pour le physicien. Cette thèse est focalisée sur l'étude par faisceaux d'ions de boîtes quantiques (BQs) d'In(Ga)As épitaxiées sur silicium et de leur encapsulation ultérieure par du silicium. L'analyse par rétrodiffusion élastique à haute énergie (RBS) a permis de quantifier la composition des îlots d'In(Ga)As et de la couche cap de Si. Des phénomènes d'exo-diffusion d'indium et la présence d'espèces en excès ont été mis en évidence. En pratiquant l'analyse en géométrie de canalisation (RBS-C), nous avons pu caractériser l'épitaxie des BQs sur le substrat ainsi que celle de la couche cap. La deuxième technique utilisée dans ce travail est l'analyse par rétrodiffusion élastique à moyenne énergie (MEIS), qui permet de profiler composition, défauts cristallins, et déformation avec une résolution sub-nanométrique au voisinage de la surface de la cible. Les spectres MEIS en modes aléatoire et canalisé ont permis d'obtenir le profil de composition et de défauts du plan de BQs. Enfin, la déformation du cristal d'In(Ga)As par rapport au monocristal de silicium du substrat a été étudiée grâce à l'effet de blocage du flux d'ions rétrodiffusés qui permet d'observer les ombres des axes et des plans cristallographiques.

Etude experimentale avec résolution temporelle à l'échelle de la nanoseconde des valeurs absolues des séctions efficaces pour les transferts partiels d'énergie électronique entre Na(4d) et He, Ar, N(2), O(2), N(2)o et SF(6). Développement quantitatif de deux modèles à intermediaire ionique : réseau de multicroisement et diffusion résonnants atome excité-molecule. Emploi de l'approximation d'impact avec correction d'effet de coeur pour la transfert de moment orbital na(4d -> 4f)

Doutoramento em Bioquímica
Os polissacarídeos são os componentes maioritários dos grãos de café verde e torrado e da bebida de café. Os mais abundantes são as galactomananas, seguindo-se as arabinogalactanas. Durante o processo de torra, as galactomananas e arabinogalactanas sofrem modificações estruturais, as quais estão longe de estar completamente elucidadas devido à sua diversidade e à complexidade estrutural dos compostos formados. Durante o processo de torra, as galactomananas e arabinogalactanas reagem com proteínas, ácidos clorogénicos e sacarose, originando compostos castanhos de alto peso molecular contendo nitrogénio, designados de melanoidinas. As melanoidinas do café apresentam diversas atividades biológicas e efeitos benéficos para a saúde. No entanto, a sua estrutura exata e os mecanismos envolvidos na sua formação permanecem desconhecidos, bem como a relação estrutura-atividade biológica. A utilização de sistemas modelo e a análise por espectrometria de massa permitem obter uma visão global e, simultaneamente, detalhada das modificações estruturais nos polissacarídeos do café promovidas pela torra, contribuindo para a elucidação das estruturas e mecanismos de formação das melanoidinas. Com base nesta tese, oligossacarídeos estruturalmente relacionados com a cadeia principal das galactomananas, (β1→4)-Dmanotriose (Man3), e as cadeias laterais das arabinogalactanas, (α1→5)-Larabinotriose (Ara3), isoladamente ou em misturas com ácido 5-Ocafeoilquínico (5-CQA), o ácido clorogénico mais abundante nos grãos de café verde, e péptidos compostos por tirosina e leucina, usados como modelos das proteínas, foram sujeitos a tratamento térmico a seco, mimetizando o processo de torra. A oxidação induzida por radicais hidroxilo (HO•) foi também estudada, uma vez que estes radicais parecem estar envolvidos na modificação dos polissacarídeos durante a torra. A identificação das modificações estruturais induzidas por tratamento térmico e oxidativo dos compostos modelo foi feita por estratégias analíticas baseadas principalmente em espectrometria de massa, mas também em cromatografia líquida. A cromatografia de gás foi usada na análise de açúcares neutros e ligações glicosídicas. Para validar as conclusões obtidas com os compostos modelo, foram também analisadas amostras de polissacarídeos do café obtidas a partir de resíduo de café e café instantâneo. Os resultados obtidos a partir dos oligossacarídeos modelo quando submetidos a tratamento térmico (seco), assim como à oxidação induzida por HO• (em solução), indicam a ocorrência de despolimerização, o que está de acordo com estudos anteriores que reportam a despolimerização das galactomananas e arabinogalactanas do café durante a torra. Foram ainda identificados outros compostos resultantes da quebra do anel de açúcares formados durante o tratamento térmico e oxidativo da Ara3. Por outro lado, o tratamento térmico a seco dos oligossacarídeos modelo (individualmente ou quando misturados) promoveu a formação de oligossacarídeos com um maior grau de polimerização, e também polissacarídeos com novos tipos de ligações glicosídicas, evidenciando a ocorrência de polimerização através reações de transglicosilação não enzimática induzidas por tratamento térmico a seco. As reações de transglicosilação induzidas por tratamento térmico a seco podem ocorrer entre resíduos de açúcares provenientes da mesma origem, mas também de origens diferentes com formação de estruturas híbridas, contendo arabinose e manose como observado nos casos dos compostos modelo usados. Os resultados obtidos a partir de amostras do resíduo de café e de café instantâneo sugerem a presença de polissacarídeos híbridos nestas amostras de café processado, corroborando a ocorrência de transglicosilação durante o processo de torra. Além disso, o estudo de misturas contendo diferentes proporções de cada oligossacarídeo modelo, mimetizando regiões do grão de café com composição distinta em polissacarídeos, sujeitos a diferentes períodos de tratamento térmico, permitiu inferir que diferentes estruturas híbridas e não híbridas podem ser formadas a partir das arabinogalactanas e galactomananas, dependendo da sua distribuição nas paredes celulares do grão e das condições de torra. Estes resultados podem explicar a heterogeneidade de estruturas de melanoidinas formadas durante a torra do café. Os resultados obtidos a partir de misturas modelo contendo um oligossacarídeo (Ara3 ou Man3) e 5-CQA sujeitas a tratamento térmico a seco, assim como de amostras provenientes do resíduo de café, mostraram a formação de compostos híbridos compostos por moléculas de CQA ligadas covalentemente a um número variável de resíduos de açúcar. Além disso, os resultados obtidos a partir da mistura contendo Man3 e 5-CQA mostraram que o CQA atua como catalisador das reações de transglicosilação. Por outro lado, nas misturas modelo contendo um péptido, mesmo contendo também 5-CQA e sujeitas ao mesmo tratamento, observou-se uma diminuição na extensão das reações transglicosilação. Este resultado pode explicar a baixa extensão das reações de transglicosilação não enzimáticas durante a torra nas regiões do grão de café mais ricas em proteínas, apesar dos polissacarídeos serem os componentes maioritários dos grãos de café. A diminuição das reações de transglicosilação na presença de péptidos/proteínas pode dever-se ao facto de os resíduos de açúcares redutores reagirem preferencialmente com os grupos amina de péptidos/proteínas por reação de Maillard, diminuindo o número de resíduos de açúcares redutores disponíveis para as reações de transglicosilação. Além dos compostos já descritos, uma diversidade de outros compostos foram formados a partir dos sistemas modelo, nomeadamente derivados de desidratação formados durante o tratamento térmico a seco. Em conclusão, a tipificação das modificações estruturais promovidas pela torra nos polissacarídeos do café abre o caminho para a compreensão dos mecanismos de formação das melanoidinas e da relação estrutura-atividade destes compostos.
Polysaccharides are the major components of green and roasted coffee beans, and coffee brew. The most abundant ones are galactomannans, followed by arabinogalactans. During the roasting process, galactomannans and arabinogalactans undergo structural modifications that are far to be completely elucidated due to their diversity and complexity of the compounds formed. During the roasting process, galactomannans and arabinogalactans react with proteins, chlorogenic acids, and sucrose, originating high molecular weight brown compounds containing nitrogen, known as melanoidins. Several biological activities and beneficial health effects have been attributed to coffee melanoidins. However, their exact structures and the mechanisms involved in their formation remain unknown, as well as the structure-biological activity relationship. The use of model systems and mass spectrometry analysis allow to obtain an overall view and, simultaneously, detailed, of the structural modifications in coffee polysaccharides promoted by roasting, contributing to the elucidation of the structures and formation mechanisms of melanoidins. Based on this thesis, oligosaccharides structurally related to the backbone of galactomannans, (β1→4)-D-mannotriose, and the side chains of arabinogalactans, (α1→5)-Larabinotriose, alone or in mixtures with 5-O-caffeoylquinic acid, the most abundant chlorogenic acid in green coffee beans, and dipeptides composed by tyrosine and leucine, used as models of proteins, were submitted to dry thermal treatments, mimicking the coffee roasting process. The oxidation induced by hydroxyl radicals (HO•) was also studied, since these radicals seem to be involved in the modification of the polysaccharides during roasting. The identification of the structural modifications induced by thermal and oxidative treatment of the model compounds was performed mostly by mass spectrometry-based analytical strategies, but also using liquid chromatography. Gas chromatography was used in the analysis of neutral sugars and glycosidic linkages. To validate the conclusions achieved with the model compounds, coffee polysaccharide samples obtained from spent coffee grounds and instant coffee were also analysed. The results obtained from the model oligosaccharides when submitted to thermal treatment (dry) or oxidation induced by HO• (in solution) indicate the occurrence of depolymerization, which is in line with previous studies reporting the depolymerization of coffee galactomannans and arabinogalactans during roasting. Compounds resulting from sugar ring cleavage were also formed during thermal treatment and oxidative treatment of Ara3. On the other hand, the dry thermal treatment of the model oligosaccharides (alone or when mixed) promoted the formation of oligosaccharides with a higher degree of polymerization, and also polysaccharides with new type of glycosidic linkages, evidencing the occurrence of polymerization via non-enzymatic transglycosylation reactions induced by dry thermal treatment. The transglycosylation reactions induced by dry thermal treatment can occur between sugar residues from the same origin, but also of different origins, with formation of hybrid structures, containing arabinose and mannose in the case of the model compounds used. The results obtained from spent coffee grounds and instant coffee samples suggest the presence of hybrid polysaccharides in these processed coffee samples, corroborating the occurrence of transglycosylation during the roasting process. Furthermore, the study of mixtures containing different proportions of each model oligosaccharide, mimicking coffee bean regions with distinct polysaccharide composition, subjected to different periods of thermal treatment, allowed to infer that different hybrid and non-hybrid structures may be formed from arabinogalactans and galactomannans, depending on their distribution in the bean cell walls and on roasting conditions. These results may explain the heterogeneity of melanoidins structures formed during coffee roasting. The results obtained from model mixtures containing an oligosaccharide (Ara3 or Man3) and 5-CQA and subjected to dry thermal treatment, as well as samples derived from spent coffee grounds, showed the formation of hybrid compounds composed by CQA molecules covalently linked to a variable number of sugar residues. Moreover, the results obtained from the mixture containing Man3 and 5-CQA showed that CQA acts as catalyst of transglycosylation reactions. On the other hand, in the model mixtures containing a peptide, even if containing 5-CQA and subjected to the same treatment, it was observed a decrease in the extent of transglycosylation reactions. This outcome can explain the low extent of non-enzymatic transglycosylation reactions during roasting in coffee bean regions enriched in proteins, although polysaccharides are the major components of the coffee beans. The decrease of transglycosylation reactions in the presence of peptides/proteins can be related with the preferential reactivity of reducing residues with the amino groups of peptides/proteins by Maillard reaction, decreasing the number of reducing residues available to be directly involved in the transglycosylation reactions. In addition to the compounds already described, a diversity of other compounds were formed from model systems, namely dehydrated derivatives formed during dry thermal treatment. In conclusion, the identification of the structural modifications in coffee polysaccharides promoted by roasting pave the way to the understanding of the mechanisms of formation of melanoidins and structure-activity relationship of these compounds.

碩士
世新大學
性別研究所
101
The aim of this study is to discuss fat male bodies in Taiwan gay community: “Bear” is represented as one of the classifications of gay body types. The definition of “bear” differs; what’s the decisive point when we discuss the sameness and differences of bear bodies? What these fat gay males may undergo as they embrace various definitions of “bear”? Through making and performing a “bear” body, how do fat gay males construct their masculinity? What’s the particularity of it? How do fat gay male bodies become a desirable category with gay community? How are the desires toward meaty and fat bodies closed off and represented? What’s the scenario of “meaty sexiness” of fat gay male bodies? This thesis adopted qualitative research methods conducting 5 focused interviews in Taiwan and enlisting 35 gays to demonstrate the plural answers to the question: “What is bear?” Boundary images of bears’ body types are drawn by informants on the body type triangle to outline two tendencies: “fat-including” and “fat-excluding”, and analyze the differences between the two. In addition, I also notice that there is the “bear clone” phenomenon based on a hegemony of body aesthetics, which makes “original bears” who have lower body and masculine capital, evolve into “transformed bears”, who have higher body capital so that higher social capital in gay community. Following this body aesthetics, this study further indicates the particular position of bears’ masculinity in gay communities. Finally, this thesis narrates how meaty body of gay males is being sexy and how desire toward meaty bodies is represented, and tries to liberate meaty sexualities which is long being peripheral in mainstream gay culture.

This thesis begins with an introduction to the interaction and refraction of light in continuous media. It is shown how these properties can be exploited to achieve focusing of parallel light rays in such a medium. Past work on Gas Lenses is reviewed, highlighting the progress in design of gas lenses, leading to a justification for the research described in the rest of the chapter. Original work by the author on the subject of continuous gas lenses at low and high pressure is then presented. Experiments show that gas lenses at low pressure have stable foci, but long focal lengths, while at high pressure two foci are produced, both of unstable character. These results are explained by a simple theory, and future applications of such lensing properties are presented. Chapter two introduces the concept of the Colliding Shock Lens (CSL), and presents shallow water wave simulations, conducted by the author, as a useful analogy to the interaction of shocks in the CSL. All the properties of the CSL lensing action are reproduced in the water simulations, yielding useful insight, by means of a simple experiment, into the physics of interacting shock waves. Chapter three presents original work by the author on the subject of multiple pulse thermal lensing. A theory is developed which predicts the behaviour of thermal lenses seen in an industrial laser chain. Experiments on thermallensing, as well as some solutions, are presented and discussed. Chapter four revises the theory of Zernike Polynomials and their application to the study of aberrations. Thermal aberrations are studied, including the aberrations introduced by thermal lensing and thermal blooming. The relationship between aberrations and subsequent beam quality and beam propagation is explored. Chapter five looks at the use of adaptive mirrors for mode matching. Although the theory of adaptive systems is well known, no-one has as yet tackled the problem of correcting for mode matching changes. A new way of thinking about mode matching is proposed, and the merits of this system, called characterisation space, are explained. Chapter six comprises the theory and design of a novel vacuum chamber which has applications in gas lens designs. All the gas lenses used in pressure experiments were housed in compressional vacuum chambers. The idea of a Tensional Vacuum Vessel (TVV) is introduced, and experiments show that such chambers are very successful low vacuum chambers. The advantages and applications of TVVs are discussed, specifically those relating to gas lens applications. At the end of this thesis it was apparent that more questions had been generated than answers. This is probably true of any study. Chapter seven therefore outlines some as yet unanswered questions, and gives some suggestions for starting points. Some of this work is presently being undertaken by the author.
Thesis (Ph.D.)-University of Natal, 1997.

重離子核聚變是一種能源技術，它有可能為人類未來提供無限的潔淨能源。通過高能粒子撞擊含高濃度氘和氚的目標，從而產生強大的壓縮衝擊波，最終引發氘和氚核子聚變並釋放出巨大核能。在過去的幾十年裡，從離子注入到核反應控制技術，以至於整個重離子核聚變的基本概念都得到迅速的發展。其中一個重要的核聚變條件就是要求非常低的離子束的縱向發射度。
在論文的第一部分，我們研發了一種TSC 技術，它可以減少因粒子加速器的電壓變化而引起的縱向發射度增長。通過數值模擬，結果表明離子束的縱向發射度得到了約89% 的降低。如果把TSC 技術應用於重離子核聚變，離子束的縱向發射度就可以有效地被降低，從而促進更高效的核聚變反應。在論文的第二部分，我們以離子束的電流信號分析為基礎，研發了一種非干擾性的離子束能量測量方法。對於傳統干擾性的離子束能量測量，這種強調非干擾性的測量方法對未來重離子核聚變實驗以及高能粒子加速器研發都有實質的應用價值。在論文的第三部分，我們從NDCX 實驗數據分析中，證實離子束的電流信號能夠有效地揭示離子束微弱的能量變化。這個實驗結果相應肯定了論文第二部分的電流信號分析處理方法。在論文的第四部分，我們模擬在真實的NDCX 環境下測試TSC 技術。模擬結果表明TSC 技術可有效地把離子束的縱向發射度減少近89% ，從而證明了TSC 技術在實際應用中的能力。在論文的最後部分，我們在強電流離子束的一維波動行為中引入橫縱向稱合分析，解釋了一維波動行為與數值模擬結果之間的細小偏差。
Heavy Ion Fusion (HIF) is a technology that has the potential to provide an unlimited source of clean energy for human future. HIF works by shooting at a capsule containing Deuterium and Tritium with energetic heavy ion beams such that the huge amount of kinetic energy carried by the ions is converted into strong compression shock waves. DT fuel is then compressed to form a high temperature and high density hotspot at the center of the capsule, thus igniting nuclear fusion between Deuterium and Tritium. Over the past few decades, the fundamental concepts of HIF had been tested in scaled ex¬periments from the source injection to the reaction chamber. To achieve the highest performance of ignition, ion beams with low longitudinal emittance is demanded.
In the first part of the thesis, we developed a novel Two-Step Correction (TSC) technique to reduce the growth of longitudinal emittance in an induc¬tion linac driver caused by variations in acceleration gap voltages. Through numerical studies, we achieved a reduction of longitudinal emittance by about 89% for high perveance ion beams. As a spinoff from the formalism developed in this study, we developed in the second part of the thesis a new non-invasive approach for the measurement of ion beam energy. The proposed diagnostics may have practical utility for future HIF experiments, particularly as higher energy accelerators are developed. It works by a generalized time-of-flight method, using two adjacent beam current signals to reconstruct the beam velocity profile. In the third part of the thesis, we verified that beam current signals are capable to reveal small beam energy variations by an NDCX-I experiment performed at Lawrence Berkeley National Laboratory. The result of this experiment confirms the formalism of the new non-invasive approach for the ion beam energy determination based on beam current signal analysis. In order to verify the effectiveness of TSC in real drivers, we proposed a new NDCX-I experiment in the fourth part of the thesis to test the limitations and performance of the correction technique in real environment. Through simulations with real driver features considered, a reduction of 89% of longitudinal emittance was observed, which confirms the ability of TSC in real applications. In the last part of the thesis, we revealed the limitation of the 1-D cold fluid model deployed in our analysis of space-charge waves for high perveance ion beams. We showed that inaccuracies are caused by transverse-longitudinal coupling which could be included in the wave equation for space-charge dominated beams.
Detailed summary in vernacular field only.
Detailed summary in vernacular field only.
Woo, Ka Ming = 抑制由粒子加速器的電壓變化所引起的縱向發射度 / 胡家明.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2012.
Includes bibliographical references (leaves 153-156).
Abstracts also in Chinese.
Woo, Ka Ming = Yi zhi you li zi jia su qi de dian ya bian hua suo yin qi de zong xiang fa she du / Hu Jiaming.
Abstract --- p.ii
概論 --- p.iv
Acknowledgement --- p.v
Chapter 1 --- Introduction --- p.1
Chapter 2 --- Background --- p.4
Chapter 2.1 --- Highlight --- p.4
Chapter 2.2 --- Introduction to fusion energy --- p.4
Chapter 2.3 --- Fusion technology --- p.5
Chapter 2.3.1 --- Magnetic confinement fusions --- p.5
Chapter 2.3.2 --- Inertial confinement fusions --- p.7
Chapter 2.4 --- Inertia confinement fusion --- p.9
Chapter 2.4.1 --- Principle of ICF --- p.9
Chapter 2.4.2 --- Implosion dynamics --- p.11
Chapter 2.4.3 --- Rayleigh-Taylor instability --- p.13
Chapter 2.4.4 --- Fast ignition --- p.14
Chapter 2.5 --- Heavy Ion Fusion --- p.16
Chapter 2.5.1 --- Comparison between laser and heavy ion driven fusions --- p.16
Chapter 2.5.2 --- Linear Induction Accelerator --- p.18
Chapter 2.6 --- Operation of a HIF driver --- p.20
Chapter 2.6.1 --- Source injection --- p.20
Chapter 2.6.2 --- Transport of ion beams --- p.21
Chapter 2.6.3 --- Acceleration of ion beams --- p.22
Chapter 2.6.4 --- Neutralized drift longitudinal compression --- p.24
Chapter 2.6.5 --- Target chamber --- p.25
Chapter 2.7 --- Transverse beam dynamics --- p.26
Chapter 2.7.1 --- Beam envelope equation --- p.26
Chapter 2.7.2 --- Matched beams solutions --- p.29
Chapter 2.8 --- Longitudinal beam dynamics --- p.30
Chapter 2.8.1 --- Cold plasma model --- p.30
Chapter 2.8.2 --- Self longitudinal electric field --- p.32
Chapter 2.8.3 --- Longitudinal emittance --- p.34
Chapter 2.9 --- Intense ion beam simulation --- p.35
Chapter 2.9.1 --- Particle-In-Cell method --- p.35
Chapter 2.9.2 --- WARP code --- p.36
Chapter 2.10 --- Conclusion --- p.37
Chapter 3 --- Techniques for correcting velocity and density fluctuations of ion beams --- p.39
Chapter 3.1 --- Highlight --- p.39
Chapter 3.2 --- The quest for short-pulse length ion beams --- p.40
Chapter 3.2.1 --- Applications of short-pulse ion beams --- p.40
Chapter 3.2.2 --- Consequence of the growth of longitudinal emittance --- p.41
Chapter 3.3 --- Effect of gap voltage variation on εzn --- p.42
Chapter 3.3.1 --- Description of simulation scenario --- p.42
Chapter 3.3.2 --- The coasting of an unperturbed ion beam and a velocitytilt beam --- p.43
Chapter 3.3.3 --- Effect of many constant voltage gaps --- p.44
Chapter 3.3.4 --- Effect of non-uniform voltage gap --- p.46
Chapter 3.4 --- One-step correction --- p.48
Chapter 3.4.1 --- Criteria for the one-step correction --- p.52
Chapter 3.4.2 --- Space-charge dominated beams --- p.55
Chapter 3.5 --- Two-step correction --- p.56
Chapter 3.5.1 --- Principle of two-step correction --- p.56
Chapter 3.5.2 --- Result of two-step correction --- p.59
Chapter 3.6 --- Conclusion --- p.62
Chapter 4 --- A new non-invasive approach for the measurement of ion beam energy --- p.63
Chapter 4.1 --- Highlight --- p.63
Chapter 4.2 --- Introduction --- p.64
Chapter 4.3 --- Derivation of the ion beam energy based on two current signals --- p.65
Chapter 4.3.1 --- Obtaining the time evolution of the beam current --- p.65
Chapter 4.3.2 --- Deriving the beam energy profile --- p.67
Chapter 4.3.3 --- Obtaining the average velocity --- p.70
Chapter 4.4 --- Checking the beam energy profile with 3-D PIC simulations --- p.72
Chapter 4.4.1 --- Determination of the average velocity --- p.73
Chapter 4.4.2 --- Computation of the beam energy profile --- p.74
Chapter 4.5 --- Signal magnification --- p.74
Chapter 4.6 --- Error propagations --- p.77
Chapter 4.7 --- Conclusion --- p.81
Chapter 5 --- Experimental verification of the beam current signal amplification --- p.83
Chapter 5.1 --- Highlight --- p.83
Chapter 5.2 --- Introduction to NDCX-I --- p.84
Chapter 5.3 --- Design of the NDCX-I experiment --- p.88
Chapter 5.4 --- Voltage profiles applied at the source plate --- p.90
Chapter 5.4.1 --- Marx voltage profile --- p.90
Chapter 5.4.2 --- Voltage modulation --- p.91
Chapter 5.5 --- Signal amplification of beam currents measured at the Faraday cup --- p.92
Chapter 5.6 --- Modeling of the space-charge wave propagation --- p.94
Chapter 5.6.1 --- Solving for the line-charge density profile at the source plate --- p.94
Chapter 5.6.2 --- Procedure of space-charge wave modeling --- p.99
Chapter 5.7 --- Conclusion --- p.101
Chapter 6 --- Implementation of Two-Step Correction in NDCX-I --- p.103
Chapter 6.1 --- Highlight --- p.103
Chapter 6.2 --- Application of the current signal analysis to the Two-Step Correction --- p.104
Chapter 6.3 --- Proposal of the new NDCX-I experiment --- p.107
Chapter 6.3.1 --- Design of the beamline --- p.107
Chapter 6.3.2 --- Description of the simulation scenario --- p.110
Chapter 6.3.3 --- Result of the Two-Step Correction simulation --- p.114
Chapter 6.4 --- Conclusion --- p.126
Chapter 7 --- Transverse-Longitudinal coupling in the wave equation --- p.128
Chapter 7.1 --- Highlight --- p.128
Chapter 7.2 --- Phenomenological study of residue --- p.129
Chapter 7.2.1 --- Description of the simulation scenario --- p.129
Chapter 7.2.2 --- Modeling of the velocity wave --- p.131
Chapter 7.2.3 --- Phenomenon of residue --- p.133
Chapter 7.3 --- Review of the space-charge wave equation --- p.141
Chapter 7.3.1 --- Fluid description of ion beams --- p.141
Chapter 7.3.2 --- Beam envelope perturbation --- p.145
Chapter 7.4 --- Conclusion --- p.149
Chapter 8 --- Conclusion --- p.150
Bibliography --- p.153

碩士
國立清華大學
奈米工程與微系統研究所
102
This research was to demonstrate the TD-GC-MS system and realize the idea of gas measurement and analysis, roasted coffee beans were chosen as our study target. Tenax-TA adsorbent tubes and a low flow rate pump were used to collect the coffee beans aroma. Then the adsorbent tube was submitted to TD-GC-MS for analysis. Different roasting conditions would give the coffee beans aroma various smells and taste characteristics. This is due to the complex chemical reactions occurred during the roasting process. 17 major components have been identified by GC-MS. Results showed that most components in coffee beans aroma increased with roast levels, while furfurals family had a downward tendency. A mechanism of the formation of furfural was proposed to explain the decrease in furfural. Storage time and monitoring intervals were also two factors that can affect the measurement results. Components had their own specific trends of change in their intensity over the storage period. This can be due to the molar mass, boiling points, and chemical structures. As the monitoring intervals prolonged, which means less sampling frequency, we found that the intensity of 2-methyl-furan significantly decayed at a slower rate.

Thesis (Ph.D.)--State University of New York at Buffalo, 2007.
Title from PDF title page (viewed on Nov. 08, 2007) Available through UMI ProQuest Digital Dissertations. Thesis adviser: Garvey, James F. Includes bibliographical references.

碩士
國立高雄應用科技大學
精密模具與機械產研碩士外國專班
99
A computational fluid dynamics model used to understand the hydrodynamics of three phase fluidized bed is presented in this paper. In the present investigation, an attempt has been made to study the complex hydrodynamics of three phase fluidized bed; bed expansion, holdup of two phases, bed pressure drop, fluidized bed voidage and velocity profile. The model is developed by using the commercial CFD code Fluent 6.2. The drag model for simulating is used Gidaspow model. The main focus on for analyzing the results is on the column with 1.5m height and diameter 0.1m. Euler-Euler multiphase flow approach is capable of predicting the overall performance of gas-liquid-solid fluidzed bed. The results obtained show that the liquid holdup increased with the inlet liquid velocity, gas holdup increased with the flow rate of gas and decreased with an increase in the liquid flow rate.

The effect of the refraction of a laser beam propagating through three different phase objects, i.e. a laser produced plasma and two different gas media, is investigated in this thesis. It is shown that these effects have useful applications. As an introduction to the work performed, a basic discussion of the theory of light is given. In the first experimental study, the accuracy of using the Refractive Fringe Diagnostic, as a tool to determine the electron density profiles of laser produced plasmas, is investigated [Buccellato et al. (1992)]. A comparative study is performed between an established method of determining the electron density profiles of laser produced plasmas, i.e. Nomarski interferometry, and the Refractive Fringe Diagnostic, by comparing experimental data obtained from the same laser shot. For the electron density profiles investigated, it is shown that the Refractive Fringe Diagnostic over-estimates the electron density by an order of magnitude. It is suggested that the electron density errors are due to the inherent assumptions of the Refractive Fringe Diagnostic. To verify this, a numerical simulation into the accuracy of the RFD is performed on a mathematically modelled plasma. The discrepancy in the numerical results are consistent with those of the experimental results and these can be attributed to the assumptions made by the Refractive Fringe Diagnostic. Laser light refracted by a gas medium, with a specific density profile, may produce a near diffraction limited focal spot. The remaining two experimental investigations deal with two novel gas lenses: the Pulsed Gas Lens and the Colliding Shock Lens. A radially expanding cylinder of gas produces a suitable density structure to focus laser light. A design of a gas lens, the Pulsed Gas Lens, using this principle is proposed as a final focusing lens for a laser fusion power station [Buccellato et al. (1993a)]. To establish the feasibility of such a lens a proof-of- principle design for the lens is given. A numerical simulation of this lens is performed by modelling the gas flow from the lens and raytracing through the determined density profiles inside the lens. It is found that this lens can be used as a focusing element. To establish certain practical aspects of the proof-of- principle design, a beam deflection device was constructed and tested. This beam deflection device models the lensing principle of the proposed lens. The laser beam deflection observed did not match the computed deflection. The opening mechanism for the proof-of-principle design did not produce an instantaneous opening of the chamber as was assumed in the simulation. The opening mechanism must be modified to decrease the opening time. Diverging spherical shock waves, produced by pairs of opposing electrodes evenly spaced on a circumference, produce a converging cylindrically symmetric shock wave. After convergence a suitable density structure exists for near diffraction li.mited focusing to occur. It is found that the Colliding Shock Lens is a varifocal lens: the focal length and lens diameter increase with time [Buccellato et al. (1993b)]. A numerical simulation is performed to model the operation of the Colliding Shock Lens. The numerical results compare favourably with the experimental results. From the simulation it is established that the lens diameter can be scaled up by increasing the physical size of the lens and the input energy to the lens. Potential applications of the colliding shock lens are discussed. To conclude this thesis, the results of the separate investigations are summarised.
Thesis (Ph.D.)-University of Natal, 1994.

LIDAR, an acronym for LIght Detection And Ranging, is a system used for studying the scattering of laser light incident on a parcel of air. This thesis investigates the atmosphere above the Durban region using two atmospheric LIDARs, referred to, in this study, as the "old LIDAR" and the "new LIDAR". The old LIDAR was used in a campaign of observation from July to October 1997 in a study of aerosol concentrations over Durban. This thesis will focus on, among other things, the local aerosol profiles for low altitude (0 to 10 km) and high altitude (10 to 35 km). In particular, the focus will shift on any long persistence in this region (it was found that the aerosol layer observed by M. Kuppen (1996) on June 1994 at 25 km may have moved to the higher altitude of 28 km in October 1997. This may be explained by stratospheric upwelling, carrying the layer to higher altitude. These aerosols are known to influence the local climate). This investigation will give some useful insight into the local atmospheric dynamics. The new LIDAR system (Rayleigh-Mie LIDAR) has been used to measure atmospheric temperatures from 20 to 60 km as well as aerosol extinction coefficients from 15 to 40 km. Height profiles of temperature have been measured by assuming that the LIDAR returns are solely due to Rayleigh scattering by molecular species and that the atmosphere obeys the perfect gas law and is in hydrostatic equilibrium (Hauchecorne and Chanin 1980). Since its installation in April 1999, the new LIDAR has been used to monitor stratospheric temperatures and aerosol concentrations from 10 to 40 km. In this study, we discuss in chapter 7 the results of a validation campaign conducted during the period of April 1999 to December 2000. Average monthly LIDAR temperatures are computed from April 1999 to December 1999 and compared with radiosonde temperatures obtained from the South African Weather Service (SAWS) at Durban. The monthly LIDAR temperature profiles over two years (1999 and 2000) were also computed and compared with the climatological model Cospar International Reference Atmosphere (CIRA)-1986 and with the average monthly European Centre for Medium Range Weather Forecast (ECMWF) temperatures . The results show that there is good agreement between LIDAR and SAWS radiosonde temperatures in the 20 and 30 km altitude range. Between 20 and 40 km, the monthly LIDAR temperatures agree closely with the CIRA-86 and ECMWF profiles. However, during winter, in the altitude range 40 to 60 km, LIDAR temperatures are warmer than CIRA-1986 and ECMWF temperatures, and they show large variability. These variations could be due to relatively fast transient phenomena like gravity waves or planetary waves propagating vertically in the stratosphere. As part of the validation process, the aerosol extinction coefficients retrieved from the LIDAR data have also been compared with the extinction coefficients measured by Stratospheric Aerosol and Gas Experiment (SAGE) II close to the LIDAR location and on coincident days. Appendix E of this thesis also investigates the concept of refraction by atmospheric gases as applied to gas lenses. A simple spinning pipe gas lens (SPGL) has been used as the objective lens of a camera to take pictures of the moon and sun spots. The SPGL is a varifocal length lens which depends on the temperature of the pipe and the angular velocity at which it spins. For our purpose a focal length of 8 m has been used. The moon pictures are compared with a lunar map so as to identify the maria.
Thesis (Ph.D.)-University of Natal, Durban, 2002.