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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.
41

Investigating thermally assisted controlof magnetization using plasmons

Chettouh, Louiza January 2019 (has links)
No description available.
42

A Monte Carlo simulation study of collimators for a high-spatial-resolution Gamma Emission Tomography instrument

Anastasiadis, Anastasios January 2019 (has links)
The present master thesis concerns a study of collimator designs for a high-spatial-resolution Gamma Emission Tomography (GET) instrument for used fuels utilizing Monte Carlo simulation codes. Designing a collimator for this purpose is a multilateral process that requires many interconnected and conflicting objectives to be taken into consideration. The purpose is to design a high-spatial-resolution GET system that combines in the best way the properties of a high detector count-rate, high photopeak to total spectrum ratio, low detector dead time and low leaking background radiation through the collimator material. As to achieve the best trade-off among these objectives, the GEANT4 and the Serpent 2 simulation codes were implemented. Used fuel contains various γ-ray emitting radionuclides and depending on the burnup history and cooling time their absolute intensities vary (i.e. for higher γ-ray intensity from the fuel, bigger collimator length is demanded). For this reason, Serpent 2 was used to produce long- and short-cooled fuel gamma emission spectra of low and high burnup. According to the obtained spectra, the collimator slit dimensions and material were determined. As far as the collimator length and material is concerned, the GEANT4 simulation toolkit was used to deal with shielding problems by applying the geometry splitting/Russian roulette variance reduction techniques. Serpent 2 simulations were performed in order to determine the transmitted signal intensity through the slit for various slit height and width dimensions. Finally, it was investigated the peak-to-total ratio change for different slit sizes and when a cavity structure was added along the slit length. / Denna uppsats handlar om kollimatordesign för hög rumsupplösning i gammaemissionstomografi (GET) av använt kärnbränsle genom att använda Monte Carlo-simuleringskoder. Att konstruera en kollimator för detta syfte är en process som kräver hänsyn till sammankopplande och ibland konflikterande målsättningar. Målet är att designa en GET-system som på bästa sätt kombinerar följande specifikationer: hög räknehastighet i detektorn, hög peak-to-total ratio, låg detektors dödtid och låg bakgrund från läckage genom skärmingsmaterialet. För att uppnå bästa möjliga resultat mellan dessa punkter användes simuleringskoderna GEANT4 och Serpent 2. Använt kärnbränsle innehåller varierande radionuklider och beroende på deras utbränning och nedkylningstid deras emissioner (absolutintensitet) varierar (t.ex större kollimatorers längd krävs vid högre intensitet från bränslet). Serpent 2 har använts för att beräkna gammaemisionsspektra för lång- och kort-kylda bränslen med låga och höga utbränningar. Med dessa hypotetiska bränslen, har spaltdimensioner och material undersökts. Beträffande spaltlängden och materialval användes GEANT4 genom att tillämpa variansreduktionsteknikerna geometry splitting/Russian roulette. Spaltbredden och spalthöjden hittades med Serpent 2 genom att beräkna transmissionssignal genom spalter av varierande dimensioner. Slutligen, undersöktes hur peak-to-total ratio ändras för olika spaltmått och även när en kavitet introduceras i kollimatorn.
43

Local PT-Symmetry preserves the no-signaling principle

Pokhrel, Dipendra 01 July 2016 (has links)
Bender and Boettcher explored a quantum theory based on a non-Hermitian PT­ symmetric Hamiltonian , where PT is the operator of the space-time reflection and demonstrated that the PT-symmetric Hamiltonian can possess entirely real spectra. In this thesis, we point out that in the framework of PT-symmetric quantum mechanics; the calculation of matrix elements in the Hilbert space is ill-defined. We point out the importance of using CPT inner product in PT-symmetric systems. We manifested our assessment using the CPT inner product prescription for the entangled wave function of the composite system. We show that for a composite system with a local PT-symmetry, it preserves the no-signaling condition and the orthogonality of the states.The reduced density matrix is diagonal and independent of the non-Hermitian parameter . We reaffirm the consistency of PT-symmetric quantum mechanics as a candidate for a fundamental theory .
44

Selection and categorization of reconstructed objects in boosted hh → bbτ−τ+ events

Dimitriadi, Christina January 2019 (has links)
No description available.
45

Development of Fingerprint Traceability in a Modern Sawmill

Möller, Carl-Johan January 2019 (has links)
No description available.
46

A problem related to an oblique cone

Reynolds, James Milton 01 January 1932 (has links)
No description available.
47

A mitochondrial DNA and Y-STR study of the Iraqi population

Lazim, Hayder H. January 2018 (has links)
No description available.
48

Extraction and Determination of a Selected Polyphenol from Selected Red and Black Grapes By High Performance Liquid Chromatography.

Niles, Summer Nicole 18 December 2010 (has links)
Polyphenols are a group of compounds found naturally in plants and they provide much of the flavor, color, and taste to fruits, vegetables, seeds, and other parts of the plants They also act as antioxidants which provide numerous health benefits by protecting cells against damage caused by free radicals. Their antibacterial, anti-inflammatory and anti-allergenic properties have also contributed to the prevention of degenerative diseases, such as cardiovascular diseases and cancers by slowing the rate of oxidative stress on cells. This study was aimed at the identification and quantitation of a specific polyphenol, quercetin, found in grapes commonly purchased at grocery stores to show their benefits toward human health. Samples of red and black grapes were collected and their polyphenolic compounds were extracted from the pulp using an organic solvent extraction method. High pressure liquid chromatography (hplc) was then used for the determination and quantitation of quercetin in each of samples. Quercetin was identified in both the red and black grape samples at retention times around five minutes. Due to technical problems with the HPLC instrument, only estimates of the amount of quercetin in each of the analyzed samples could be calculated with the highest estimated yield being 8.29 mg/mL of quercetin in black grape extract #4.
49

Synthesis and Characterization of Complexes of [Rh2(NPhCOCH3)4] and Nitriles.

Tan, Jennie 15 December 2012 (has links)
The rhodium carboxamide [Rh2(NPhCOCH3)4]L (L=axial ligand), has applications as a catalyst for carbenoid transformations. To explore the nature of the rhodium-carbene bond, studies between Rh2(NPhCOCH3)4 and nitriles were proposed. Trials of the benzonitrile, o-tolunitrile, and m-tolunitrile have been performed and characterized on the 2,2-trans [Rh2(NPhCOCH3)4] complex via NMR spectroscopy, IR spectroscopy, and X-ray crystallography.
50

Soliton Solutions of the Nonlinear Schrödinger Equation.

Middlemas, Erin 11 May 2013 (has links)
The nonlinear Schrödinger equation is a classical field equation that describes weakly nonlinear wave-packets in one-dimensional physical systems. It is in a class of nonlinear partial differential equations that pertain to several physical and biological systems. In this project we apply a pseudo-spectral solution-estimation method to a modified version of the nonlinear Schrödinger equation as a means of searching for solutions that are solitons, where a soliton is a self-reinforcing solitary wave that maintains its shape over time. The pseudo-spectral method estimates solutions by utilizing the Fourier transform to evaluate the spatial derivative within the nonlinear Schrödinger equation. An ode solver is then applied to the resulting ordinary differential equation. We use this method to determine whether cardiac action potential states, which are perturbed solutions to the Fitzhugh-Nagumo nonlinear partial differential equation, create soliton-like solutions. After finding soliton-like solutions, we then use symmetry group properties of the nonlinear Schrödinger equation to explore these solutions. We also use a Lie algebra related to the symmetries to look for more solutions to our modified nonlinear Schrödinger equation.

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