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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.
11

Design of a 5 Degree of Freedom Kinematic Stage for the Dual Crystal Backlighter Imager Diagnostic

Nguyen, Nicholas 01 June 2020 (has links)
The National Ignition Facility (NIF) is home to the world’s most energetic laser. The facility is one of the leading centers in inertial confinement fusion (ICF) experiments to research and understand sustainable fusion energy. To fully document and understand the physics occurring during experiments, precise diagnostics are used for a wide range of purposes. One diagnostic, the crystal backlighter imager (CBI), allows for X-ray imaging of the target at late stages of its implosion. The aim of this project was to increase the current capabilities of the CBI diagnostic with the addition of a second crystal. This thesis focuses on the design development of the 5 degrees of freedom precision stages used to align each of the crystals. The motivations for the addition of a second crystal are covered in the introduction. A ray tracing model was generated to explore the required range of travel for both crystals, as well as explore potential effects of transitioning to a two-crystal system. The requirements of the precision stage are outlined based on the flaws of the current stage and areas with desired improvements. A dynamic analysis was performed on modified supporting hardware for CBI, to determine areas of interest in redesigning components for the two-crystal system. Further research is performed on commercial and literature methods used to design precision optomechanical stages. Finally, the design development is documented outlining the considered options, modifications to the existing system, and the proposed design solution. A design is proposed that meets the project requirements set at the beginning of design development.
12

Caractérisation et optimisation d'une étape statique d'hydrolyse des ordures ménagères résiduelles en vue de leur méthanisation hors-sol / Characterization and optimization of a static process hydrolyzing residual municipal solid waste for their anaerobic digestion

Carlei, Hugues 01 July 2013 (has links)
Dans le cadre des législations européennes relatives au traitement des déchets et aux énergies renouvelables, la méthanisation apparaît comme une alternative prometteuse pour la stabilisation et la valorisation des Ordures Ménagères Résiduelles (OMR). D'un point de vue opérationnel l'hétérogénéité et les difficultés de mise en mouvement d'une matrice aussi complexe que les OMR sont à l'origine de pertes de rendement voire de l'arrêt d'installations de méthanisation. Les performances de méthanisation sont en particulier limitées par l'étape d'hydrolyse des fractions lignocellulosiques qui représentent la majorité du potentiel méthanogène des OMR. Dans ce contexte, l'objectif principal du travail de thèse, était l'étude d'un procédé de percolation dans lequel le déchet n'est pas mis en mouvement. Au travers de ce travail nous avions également pour ambition de produire des connaissances à caractère plus générique sur l'hydrolyse afin d'en améliorer les performances. Des expériences préliminaires ont d'abord permis la définition d'un système expérimental adéquat pour l'étude à l'échelle laboratoire de l'hydrolyse des OMR. La représentativité d'un déchet reconstitué, reproductible et d'utilisation aisée, a notamment été vérifiée en termes de potentiel méthanogène, de profil hydrolytique et de flore microbienne. Suite à la définition de ce système expérimental, son comportement hydrolytique a été comparé à celui d'un test de lixiviation de référence (NF EN 12457-4) afin de valider l'intérêt opérationnel de la percolation pour l'hydrolyse des OMR. De façon inattendue, l'extraction de 38,90% de la matière carbonée initiale du déchet a ainsi été mise en évidence lors de l'hydrolyse par percolation contre 17,84% lors de l'hydrolyse par lixiviation, renforçant l'intérêt suscité par la percolation pour l'hydrolyse des OMR. L'optimisation des performances d'hydrolyse par percolation a ensuite été réalisée par le criblage de huit paramètres opérationnels afin de déterminer leur influence sur les performances d'hydrolyse des OMR, au travers de deux plans d'expérience. L'ajout d'alcalinité (12 gHCO3-.L-1) et la recirculation du percolat pendant 6 h par jour ont ainsi permis d'augmenter significativement les performances d'hydrolyse, passant de 17 à 43% d'extraction de la matière organique (DCO) initiale du déchet (autrement dit de 26 à 69% de la matière biodégradable initiale). L'étude des communautés microbiennes et de leur activité a également été réalisée. Le séquençage des pyrotags d'ADNr 16S a ainsi permis de mettre en évidence le caractère dominant des Classes Clostridia et Bacteroidia au sein des communautés hydrolytiques. Le couplage de cette démarche qualitative à une approche quantitative par qPCR sur une série de biomarqueurs taxonomiques et fonctionnels a permis de montrer qu'il existe une corrélation positive entre l'ajout de carbonates, la neutralisation du pH, la quantité de matière hydrolysée à 14 jours et soit l'abondance de la Classe Bacteroidia soit celle des gènes de la famille hydA, impliqués dans la fermentation. Finalement, l'analyse microbiologique a été approfondie au jour 4, c'est-à-dire durant la phase d'hydrolyse intense, grâce à une approche de métatranscriptomique. L'analyse des transcrits fonctionnels indique que l'alcalinité influence l'activité des microorganismes de la Classe Clostridia dès le jour 4 des essais d'hydrolyse. Plus spécifiquement, l'ajout de carbonates semble corrélé à une modification du métabolisme des sucres chez des microorganismes non cultivables apparentés à Clostridium cellulolyticum et à l'augmentation de l'expression de l'opéron nif, impliqué dans la fixation de l'azote, chez différents groupes de microorganismes. / In the framework of the European green policy, anaerobic digestion appears as a promising technology for stabilization and valorization of Municipal Solid Waste (MSW). In practice, mechanical mixing of a complex and heterogeneous matrix such as MSW induces major operational constraints. Anaerobic digestion performances are especially limited by hydrolysis of lignocellulosic fractions which represent the main part of MSW methanogenic potential. In this context, this PhD project was aiming to characterize and optimize of a percolation process in which MSW stands still. Preliminary experiments were conducted in order to define an experimental system suitable for lab-scale study of MSW hydrolysis. Therefore, the representativeness of an easy-to-use and reproducible reconstituted waste was verified in terms of methanogenic potential, hydrolytic profiles and associated microbial communities. Following system definition, hydrolysis behavior by percolation was compared to a reference lixiviation test (NF EN 12457-4). Surprisingly, hydrolysis by percolation permitted the extraction of 39% of carbonated matter initially contained in waste whereas 18% were extracted during hydrolysis by lixiviation, thus validating operational benefit of percolation for MSW hydrolysis. Optimization of hydrolysis performance was then conducted through the screening of eight operational parameters for their influence on MSW hydrolysis performances thanks to two Designs Of Experiment (DOE). Cumulative effect of alkalinity addition (12 gHCO3-.L-1) and percolate recirculation (6 hour.day-1) significantly improved hydrolysis yield, from 17 to 43% of extracted organic matter compared to the initial content of waste (corresponding to an extraction of 26 and 69% of biodegradable matter). Structure and activity of hydrolytic microbial communities were also studied. 16S rDNA-pyrotags sequencing brought out the dominance of classes Clostridia and Bacteroidia. Additionally, a quantitative approach led by qPCR revealed a correlation between carbonates addition, pH neutralization, amounts of hydrolyzed matter at day 14 and either class Bacteroidia or genes from hydA family, involved in fermentation. Finally, metatranscriptomic approach was conducted at day 4 in order to further study microbial activity during the intense hydrolysis phase. According to functional analysis, alkalinity seems have positive influence on class Clostridia activity. More specifically, carbonates addition seems correlated to a modification of carbohydrates metabolism of organisms affiliated to Clostridium cellulolyticum and to transcriptional up-regulation of nif operon, involved in nitrogen fixation, among various types of microorganisms.
13

Feasibility of Nuclear Plasma Interaction studies with the Activation Technique

Nogwanya, Thembalethu January 2018 (has links)
>Magister Scientiae - MSc / Electron-mediated nuclear plasma interactions (NPIs), such as Nuclear Excitation by Electron Capture (NEEC) or Transition (NEET), can have a signi cant impact on nuclear cross sections in High Energy Density Plasmas (HEDPs). HEDP environments are found in nuclear weapons tests, National Ignition Facility (NIF) shots and in the cosmos where nucleosynthesis takes place. This thesis explores the impact of NPIs on highly excited nuclei. This impact is understood to be more intense in highly-excited nuclei states in the quasi-contiuum which is populated by nuclear reactions prior to their decay by spontaneous -ray emission. Attempts thus far have failed in measuring the NEEC process [1, 2], while NEET process has been observed experimentally [3, 4]. Direct observation of NPIs is hindered by the lack of a clear signature of their effect in HEDP environments. Hence this should test a new signature [5] for NPIs for highly-excited nuclei by investigating isomeric to ground state feeding from the isomeric state. An experiment was performed using the reactions 197Au(13C, 12C)198Au and 197Au(13C, 12C2n)196Au at Lawrence Berkeley National Laboratory in inverse kinematics with an 197Au beam of 8.5 MeV/u energy. Several measurements were performed with different target configurations. The activated foils were counted at the low-background counting facility of Lawrence Livermore National Laboratory. From these data, the double isomeric to ground state ratio (DIGS) were extracted with the assistance of the decay equations that were included in the experiment. As the NPIs effects are rather small the lines for analysis had to be chosen carefully so that the extracted ratios would not contain significant errors. The measured DIGS ratios were then compared with the result of the theoretical DIGS ratios. The results showed that the calculated DIGS ratios deviated substantially from unity although this was with large uncertainties. Because of the large errors obtained, the DIGS ratios were found to be inconclusive as a signature for detecting the effects of NPIs such as angular momentum distribution changes in HEDP environmen
14

Tidseffektivitet vid ljumskbråcksoperationer : - Jämförelse mellan privat- och offentlig vårdgivare / Time Efficiency in Inguinal Hernia Surgery : Comparison of Private- and Public Healthcare Provider

Karlsson, Louise, Olofsson, John January 2015 (has links)
Bakgrund: Ljumskbråck är den vanligaste operationen inom allmänkirurgin, varje år utförs nästan 20 000 operationer i Sverige. I Östergötland utförs ljumskbråcksoperationer på tre ställen inom ramen för dagkirurgi; vid Aleris Specialistvård i Motala (ASM), Närsjukvården i Finspång (NiF) samt Medicinskt Centrum i Linköping (MCL). Det finns en teori om att privata vårdgivare är mer tidseffektiva än offentliga vårdgivare. De privata anses kunna utföra fler operationer under en given tid, men ingen studie har gjorts på tidseffektiviteten kring operationerna hos respektive vårdgivare. Denna studie har genomförts för att detektera om det finns en skillnad i hur lång tid olika moment tar att utföra och vad denna skillnad i sådana fall beror på, samt om patientunderlaget skiljer sig mellan klinikerna. Metod: Studien omfattade 70 patienter fördelade på tre kliniker; ASM, MCL och NiF. Ljumskbråcksoperationerna delades upp i flertalet moment som mättes med digital klocka. Dessutom samlades uppgifter in om patientens ålder, ASA-klass, BMI samt information om vilka som närvarade i operationssalen. Statistisk analys gjordes enligt Kruskal-Wallis. Programvaran som användes var SPSS version 22. Resultat: Studien fann ingen signifikant skillnad i BMI, ASA-klass eller ålder mellan klinikernas patienter (p > 0,05 för samtliga). Däremot fanns stora skillnader vad gäller hur lång tid ett flertal av momenten under ljumskbråcksoperationen tog. Slutsats: Studien påvisar att det finns stora skillnader i olika moment vid ljumskbråcksoperationer. De privata klinikerna var alltid snabbare än den offentliga kliniken. Då det saknas studier inom området vore det intressant att se om det finns liknande skillnader vid andra ingrepp som utförs av olika aktörer. / Background: Inguinal hernia surgery is one of the most common surgeries within general surgery, with approximately 20 000 surgeries per year in Sweden. There are three places in Östergötland County where inguinal hernias are executed within outpatient surgery; at Aleris Specialistvård in Motala (ASM), Närsjukvården in Finspång (NiF) and at Medicinskt Centrum in Linköping (MCL). There is a theory that private health care providers are more time-efficient than public health care providers. The private health care providers are considered to perform more operations over a given time though no studies has been done on time efficiency. This study was performed to detect if there is a difference in time in the various steps during the surgery between the clinics, what causes these differences and if the patients differ. Methods: The study includes 70 patients distributed on three outpatient surgery clinics; ASM, MCL and NiF. The inguinal hernia operations were divided into shorter steps measured with a digital watch.  Furthermore, data were noted about the patients’ age, ASA-score, BMI and who were present in the operating room. Statistical analyses were performed with the Kruskal-Wallis one-way analysis of variance. The software used was SPSS version 22. Results: The study found no significant difference in BMI, ASA-score and age between the health care providers (p > 0,05). However, regarding the time efficiency, there were significant differences between the clinics. Conclusions: The study concludes that there are big differences in time, within the various steps in the inguinal hernia surgeries, between the clinics. The private health care providers were always faster than the public health care provider. Since no earlier studies have been made in this area, it would be interesting to see if there are similar differences in other types of surgeries.

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