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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.
311

Measurement Of Sm Electro-weak Parameters In Reactor Antineutrino-electron Scattering In Texono Experiment

Deniz, Muhammed 01 May 2007 (has links) (PDF)
In this thesis a search for electron type neutrino-electron scattering cross-section and Weinberg Angle measurements were performed at KS Nuclear Power Station with 200 kg CsI(Tl) scintillating crystal detector located at a distance of 28 m from the 2.9 GW reactor core giving total flux of 6:52X10^12 cm^-2s^-1 in average at the experimental site. New analysis techniques and background suppression methods were developed. In the region of 3-8 MeV a measurement of SM cross section of (1:235+-0.577) XR_SM and Weinberg Angle of 0:264 +-0.075 which is quite consistent with the SM value of 0.23120(15)were obtained. These are the best results with wold wide level sensitivities at untested low energy region by using reactor anti-neutrinos.
312

Light Cone Qcd Sum Rules And Meson Physics

Kanik, Inanc 01 September 2008 (has links) (PDF)
In this thesis, we applied Light Cone QCD sum rules (LCSR) to several problems in meson physics. Semileptonic B-&gt / eta l v decays are important to get information on Cabibbo-Kobayashi-Maskawa (CKM) matrix elements. We calculated form factors of this decay in LCSR frame. Our results are confirmed by later studies and these similar studies had been used for enhancing result on b to u quark transition matrix element of CKM matrix by BaBar collaboration. We used LCSR method also for calculating coupling constant of radiative rho -&gt / eta photon decay since the analysis of the vector particle to pseudoscalar particle radiative decay with eta and eta&#039 / mesons in final state can provide insights to the long standing issue of the eta and eta&#039 / mixing. Our result g_{rho eta photon}=(1.4 &plusmn / 0.2) is very close to experimental value g_{ rho eta photon} = (1.42 &plusmn / 0.12). We also calculated magnetic moment of the rho meson in LCSR frame which is an important parameter since it is strongly related to internal structure of hadron. Our result 2.3 &plusmn / 0.5 in units of (e/2m_rho), is in better agreement with lattice QCD results than traditional QCD sum rules. Quark contents of light scalar mesons are still under debate and we analyzed phi -&gt / K K decays which is important for understanding the quark content of the f0 meson. Our final result is g_{phi KK} = 4.9 &plusmn / 0.8 which is in well agreement with existing experimental result g_{phi KK} = 4.8.
313

Entanglement In The Relativistic Quantum Mechanics

Yakaboylu, Enderalp 01 February 2010 (has links) (PDF)
In this thesis, entanglement under fully relativistic settings are discussed. The thesis starts with a brief review of the relativistic quantum mechanics. In order to describe the effects of Lorentz transformations on the entangled states, quantum mechanics and special relativity are merged by construction of the unitary irreducible representations of Poincar&eacute / group on the infinite dimensional Hilbert space of state vectors. In this framework, the issue of finding the unitary irreducible representations of Poincar&eacute / group is reduced to that of the little group. Wigner rotation for the massive particles plays a crucial role due to its effect on the spin polarization directions. Furthermore, the physical requirements for constructing the correct relativistic spin operator is also studied. Then, the entanglement and Bell type inequalities are reviewed. The special attention has been devoted to two historical papers, by EPR in 1935 and by J.S. Bell in 1964. The main part of the thesis is based on the Lorentz transformation of the Bell states and the Bell inequalities on these transformed states. It is shown that entanglement is a Lorentz invariant quantity. That is, no inertial observer can see the entangled state as a separable one. However, it was shown that the Bell inequality may be satisfied for the Wigner angle dependent transformed entangled states. Since the Wigner rotation changes the spin polarization direction with the increased velocity, initial dichotomous operators can satisfy the Bell inequality for those states. By choosing the dichotomous operators taking into consideration the Wigner angle, it is always possible to show that Bell type inequalities can be violated for the transformed entangled states.
314

Spinodal Instabilities In Symmetric Nuclear Matter Within A Nonlinear Relativistic Mean-field Approach

Acar, Fatma 01 August 2011 (has links) (PDF)
Spinodal instability mechanism and early development of density fluctuations for symmetric nuclear matter at finite temperature are studied. A stochastic extension of Walecka-type relativistic mean-field model including non-linear self-interactions of scalar mesons with NL3 parameter set is employed in the semi-classical approximation. The growth rates of unstable collective modes are investigated below the normal density and at low temperatures. The system exhibits most unstable behavior in longer wave lengths at baryon densities &rho / B = 0.4 &rho / 0 , while most unstable behavior occurs in shorter wavelengths at lower baryon densities &rho / B = 0.2 &rho / 0 . The unstable response of the system shifts towards longer wavelengths with the increasing temperature at both densities. The early growth of the density correlation functions are calculated, which provide valuable information about the initial size of the condensation and the average speed of condensing fragments. Furthermore, the relativistic results are compared with Skyrme type non-relativistic calculations. Qualitatively similar results are found in both non-relativistic and relativistic descriptions.
315

Discovery Potential Of Quantum Black Holes In Add Model With The Cms Detector

Gamsizkan, Halil 01 September 2011 (has links) (PDF)
With the long awaited start-up of the LHC, TeV scale physics is now in reach of the particles physicists to explore. There are many questions about the nature to be answered, and many more theories to be tested trying to answer them. The ADD model of extra dimensions is one such model, written to address the large mass hi- erarchy between the two fundamental energy scales in nature, the electroweak and the Planck scales. ADD model predicts stronger gravity at sub-millimeter distance scales, which would then lead to an interesting physical object to be produced at proton collusions at the LHC: Tiny quantum black holes. In this thesis we study the discovery potential of CMS for quantum black hole events for proton-proton collusions at sqrt(s) = 14 TeV. Our study details the trigger response of CMS, various criteria and methods for background rejection, affect of experimental uncertainties on measurements, for different model parameter values.
316

Application of rigorous coupled-wave analysis for studying radiative properties of micro/nanostructures and silver nanorods on gratings

Haider, Ahmad 08 July 2011 (has links)
Tailoring the radiative properties of periodic micro/nanostructures can be used as an efficient way to create devices which have applications in energy harvesting, bioengineering and optical sensing. These structures are analyzed by a rigorous solution of the electromagnetic wave phenomena at the interfaces. The thesis explores the application of rigorous coupled-wave analysis (RCWA) method to study the optical responses of microstructure arrays. First section of the thesis elucidates the various mechanisms which are responsible for causing enhanced light absorption in inclined parallel plate grating arrays. Illustrative evidences of surface plasmon and magnetic resonances are provided by one and two-dimensional plots prepared by RCWA. Analytical agreement with visual data is obtained through use of LC circuit models. Finally, the effects of different geometric parameters on the resonance conditions are investigated. The second part of the thesis deals with application of RCWA to study the effect of light scattering on inclined silver nanorod (AgNR) arrays grown on compact disc (CD) gratings. Depending on the manner in which AgNRs are oriented with respect to CD gratings, they exhibit different optical behavior to incoming light. Effects of both incident light polarization and AgNR orientation with respect to the grating have been studied through the use of RCWA and effective medium theory. Calculated results are compared with experimental values and good agreements are observed for total reflection as well as trends of individual diffraction orders.
317

Modeling and characterization of polycrystalline mercuric iodide radiation detectors. [electronic resource] / by Unmesh Khadilkar.

Khadilkar, Unmesh. January 2003 (has links)
Title from PDF of title page. / Document formatted into pages; contains 64 pages. / Thesis (M.E.E.)--University of South Florida, 2003. / Includes bibliographical references. / Text (Electronic thesis) in PDF format. / ABSTRACT: The ability of Mercuric Iodide (HgI2) to function as a highly efficient radiation detector at room temperature has generated great interest and has triggered further studies on this difficult material. This property is expected to enable significant enhancements to a far-ranging variety of applications and systems. HgI2 devices have shown superior performance at room temperature compared to elemental Si or Ge devices, which require to be cooled down to liquid nitrogen temperature when used as nuclear radiation detectors. While substantial studies have been conducted on single crystal HgI2, polycrystalline HgI2 remains a comparatively less studied form of this material. The primary use of HgI2 is as a direct radiation detector. It can also be used in applications with a scintillator intermediate to generate visible light from incident nuclear radiation. Hence its response to visible light can be used to study the electronic properties of HgI2 polycrystalline films. / ABSTRACT: The films are deposited on TEC-15 LOF glass with a Tin Oxide(Sn02) coating which acts as the growth surface. It also acts as the front contact with Palladium (Pd) being the back contact. Wire leads are attached to the palladium for electrical contact. The deposited films are circular in shape with a diameter of 2.5cm with thickness ranging from 50 to 600ìm. A maximum of 7 devices are contacted at various points on every film. For the measurements documented in this thesis, a tungsten-halogen lamp and an Oriel 1/4m grating monochromator are used as a light source. The incident flux on the sample is determined using a Si photodiode as reference. Device performance for both single crystal as well as polycrystalline films is documented. We have attempted to identify a set of optimum growth parameters using these measurements. / ABSTRACT: For a film to be considered favorably, not only should the individual devices show high quantum efficiencies and low dark currents, but the response of all devices on the same film should be uniform. A number of films are studied and the optimum film deposition conditions are commented upon. A powerful semiconductor device simulation tool, MEDICItm, is used to simulate the photoresponse of these films. The simulations are compared to the measurements and the transport and light absorption parameters of the polycrystalline films are determined. / System requirements: World Wide Web browser and PDF reader. / Mode of access: World Wide Web.
318

Radioaktive Stoffe bei Baumaßnahmen

Herrmann, Ralf, Ohlendorf, Frank 02 October 2013 (has links) (PDF)
Die Rückstände des Uranbergbaus in Sachsen wurden in der Vergangenheit bewusst oder unbewusst als Baumaterial im Straßen- und Wegebau, zum Planumsausgleich für Flächen und beim Hausbau verwendet. Die Broschüre richtet sich an Planungsbüros, Antragsteller sowie Ausführende im Bau- und Straßenbau und liefert umfassende Informationen für eine strahlenschutzgerechte, sichere und kostengünstige Verwertung oder Beseitigung dieser Stoffe. Enthalten sind Hinweise zu Planung, Antragstellung, Voruntersuchung, strahlen-schutzfachlicher Baubegleitung und Dokumentation von Baumaßnahmen, bei denen mit radioaktiven Stoffen zu rechnen ist.
319

Radiometric study of beach sand deposits along the Coast of Western Cape Province, South Africa.

Mbatha, Nkanyiso Bongumusa. January 2007 (has links)
<p><font face="TimesNewRomanPSMT"> <p align="left">Natural radioactivity studies have been carried out to study the textural characteristics, heavy mineral composition, provenance, sediment transport, and depositional environment of beach placer deposits. The naturally occurring radionuclides such as properties of beach sands, which reflect the geological characteristics such as transport and sorting processes and the depositional environment. The present work focuses on the radiometric characteristics of beach sand deposits along the west coastof South Africa. Beach sands samples were collected at the Melkbosstrand (MBS) and Ouskip (OSK) beach. The activity concentrations of these radionuclides were determined by high-resolution gamma-ray spectrometry using a high-purity germanium (HPGe) detector in a low-background configuration.</p> </font></p>
320

Festlegung und Mobilisierung von Uran und seinen radioaktiven Zerfallsprodukten in kohlenstoffreichen Gewässersedimenten / Fixation and mobilisation of uranium and its radioactive decay products in C-richwater sediments

Nassour, Mohammad 19 September 2014 (has links) (PDF)
The main aim of this work was to investigate the extent of uranium and radium -fixation and mobilization at the interface of mining influenced surface water and sub-hydric soils, sediment and plant detritus. A freshwater ecosystem (stream channels in an alder swamp forest – Alno-Lemnetum with low residence time shallow ponds) developed directly below a mining site (Neuensalz) and influenced by uranium containing water served as investigation site for the identification of possible fixation and mobilization mechanisms. In addition, investigations were carried out on sediments in a water reservoir downstream of the examined abandoned mining site. It could be shown, that radium concentrations of the examined surface water (2001 – 2004) are only slightly higher compared to the range of geogenic levels for German surface waters, and that its activity concentrations decreased along the investigated flow path. In contrast, uranium concentrations are well above geogenic levels and the concentration level stays high along the whole water pathway through the study area. The U-238:Ra-226 ratio of the examined surface water from the spring to a pond outflow significantly increased. The uranium chain activity concentrations in the sediments determined in this study partly exceeded considerably the regional geogenic level. For the sediment water the 238U: 226Ra ratio in the first part of the flow path is significantly shifted in favor of radium while in the second part the ratio is shifted in favor of uranium. There were indications that the dissolved uranium is transported in the form of soluble carbonate complexes. Radium however is rather fixed under dominantly oxidizing conditions along the mainly turbulent mixed shallow water pathway. The fixation of uranium and radium in the upper section of the pathway (direct below the spring) was found to be inorganically, whereas in the second part organic bonds are more indicated. The influence of allochthonous organic carbon as main metabolic energy source for low order lotic ecosystems on the fixation of uranium was investigated by analyzing, the effects of leaves (coarse particulate organic matter: CPOM) and their degradation products (mainly fine particulate organic matter: FPOM and biofilms etc.). It was found that the highly mobile fraction of uranium in the water pathway, preferably present under the given conditions in the form different uranyl-carbonato-complexes, is efficiently fixed on fresh organic plant material (plant litter, leaves) in the first steps of organic matter decomposition within a few days. But it also can be immobilized relatively stable. It was also found that CPOM is a temporary sink for uranium, which may be sedimented depending on the turbulence flow and discharge. This may contribute to the directional removal of uranium from the water into the sediment. Finally this work analyzed the conditions in the pelagic and benthic zone of the Neuensalz pre dam of the Pöhl reservoir, which is located downstream of the mining site. It presents a periodically stagnant water body with seasonally continuous sedimentation, a possible stable sink of uranium and products of radioactive decay in early diagenesis. Water samples of the pelagic zone and undisturbed sediment cores were taken and analyzed during winter stagnation. The results are discussed in front of seasonal changes in water chemistry and load data. U-238 and Ra-226 showed a culmination of activity concentrations in the sediment horizons from 25 to 35 cm depth, in particular at a centrally located sampling point (K3). At this point highest activity concentrations of 238U were found with a median value of 770 Bq*kg-1 at a depth of 30 cm. At the same location 226Ra shows activity concentrations of 250 Bq*kg-1(median). Based on the Cs-137 dating method a sedimentation rate of 1.5 cm*yr-1 was calculated for the pre-dam Neuensalz sediment. On average sedimentation rates for 238U of 3,7 ± 1,1 kBq*m-2*yr-1 and for 226Ra of 3,5 ± 0,5 kBq*m-2*yr-1 were calculated. Furthermore, a total uranium stock of 68 ± 6 kg per hectare in the sediment was estimated. In connection with a sedimentation period of 23 years, the uranium inventory in the sediments would correspond to a portion of approx. 18 % of the uranium feed by the water influx estimated for the same period. This estimation did not take into account a geogenic portion and other sources like fertilizer. For radium, the situation is reversed. An extrapolation of the cumulative load for the same period results in a lower value by almost a factor of 100 compared to uranium. This compares with a radium inventory in the sediment, which is about 15 times higher than the projected load. This leads to the conclusion that in addition to the supply from the mining legacy also the geogenic background and/or discontinuous particulate import (via storm water stream runoff etc.) has to be considered. The analysis of the bonding stability and related potential mobilization of the sedimentary uranium using sequential chemical extraction shows that most of the uranium is found in the organic fraction over the entire sediment layer, which may be identified as organically bound or as uraninite. In conclusion not only radium is immobilized near to the source but also a relevant share of uranium is permanently fixed even in/on durably deposited organic matter despite eu-trophic conditions with high nitrate load, traceable in deeper sediment layers due to e.g intensive land use. / Hauptziel der vorliegenden Arbeit war die Untersuchung des Umfangs der Festlegung bzw. Mobilisierung von Uran und Radium an der Grenzfläche von Bergbau beeinflußtem Oberflächenwasser und subhydrischen Böden, Sedimenten sowie Bestandsabfall (Detritus). Als Untersuchungsgebiet zur Identifizierung entsprechender Fixierungs- und Mobilisierungsmechanismen diente ein Süßwasser - Ökosystem (Bach in einem Erlenbruchwald – Alno-Lemnetum – und integrierte flache Teiche mit geringer Verweilzeit) unterhalb eines ehemaligen Uranerzbergbau-Gebietes (Neuensalz), das von uranhaltigem Wasser durchströmt ist. Darüber hinaus Sedimentanalysen eines periodisch stagnierenden Wasserkörpers (Vorsperre der Talsperre Pöhl) im Abstrombereich der untersuchten Bergbaualtlast vorgenommen. Es konnte gezeigt werden, dass die Radiumkonzentration des Oberflächenwassers (2001-2004) geringfügig über der des geogenen Niveaus für deutsche Oberflächenwässer liegt und dass die entsprechende Aktivitätskonzentration von Radium entlang der untersuchten Fließstrecke beginnend mit einer Quelle an einem Tailingdamm deutlich abnimmt. Dagegen liegen die Urankonzentrationen des Oberflächenwassers deutlich über dem geogenen Hintergrund. Seine Aktivitätskonzentrationen bleiben entlang der Fließstrecke weitgehend stabil. Das 238U:226Ra-Verhältnis des Oberflächenwassers wird sich entlang der Fließstrecke von der Quelle unterhalb des Tailingdammes bis zum Abfluss aus der ersten, schwächer durchflossenen kleinen Senke (Forellenteich) erhöht. Die in dieser Arbeit ermittelten Aktivitätskonzentrationen der untersuchten Nuklide der Sedimente lagen zum Teil erheblich über dem geogenen Niveau der Region. Das 238U:226Ra-Verhältnis des Bachsediments ist im ersten Teil der Fließstrecke deutlich zugunsten des Radiums verschoben, während es im zweiten Teil zugunsten von Uran verschoben ist. Dies weist darauf hin, dass das gelöste Uran in Form carbonatischer Komplexe transportiert wird. Radium wird dagegen unter den vorherrschenden oxidierenden Bedingungen entlangder Fließstrecke eher fixiert. Für die Festlegung von Uran und Radium wurde im oberen Teil der Fließstrecke (direkt unterhalb der Quelle) eher auf anorganische Bindungen geschlossen, während die Fixierung im zweiten Teil der Fließstrecke eher organischer Natur ist. Da im Oberlauf von Fließgewässern allochthoner organischer Kohlenstoff die wesentliche die Energiequelle für alle Ökosystemfunktionen bildet und eine besondere Funktion mit Blick auf Untersuchungsziel vermutet werden kann, wurde die Wirkung von Laub (grob- organisches Material: CPOM) und seinen Abbauprodukten (fein-partikuläres organisches Material: FPOM, Biofilm usw.) auf die Fixierung von Uran analysiert. Es wurde festgestellt, dass das im Wasserpfad sehr mobile Uran, welches unter den gegebenen Bedingungen vorzugsweise in verschiedenen Uranyl-Carbonato-Komplexen vorliegt, nicht nur an frischer organischer Substanz pflanzlichen Ursprungs (Bestandesabfall, Laub) im Verlauf biologischen Abbaus effizient gebunden und festgelegt wird, sondern auch sehr stabil immobilisiert werden kann. Es wurde auch ermittelt, dass CPOM ein temporärer Speicher für Uran ist, welcher je nach Fließgeschwindigkeit sedimentieren und damit zum gerichteten Transfer von Uran aus dem Wasser in das Sediment beitragen kann. Der anteilige Austrag über das verstärkt gebildete DOC über den Laubeintrag ist relativ gering. Schließlich wurden die Verhältnisse mit Bezug zur Fragestellung in der pelagischen und benthischen Zone der Vorsperre Neuensalz der Talsperre Pöhl analysiert, die stromabwärts des Bergbaugebietes anschießt. Die Vorsperre stellt einen periodisch stagnierenden Wasserkörper mit saisonaler kontinuierlicher Sedimentation dar und damit eine mögliche stabile Senke für Uran und seine radioaktiven Zerfallsprodukte in der Frühdiagenese. Wasserproben der pelagischen Zone und ungestörte Sedimentkerne wurden in der Phase der Winterstagnation entnommen, analysiert und unter Berücksichtigung saisonaler Unterschiede bezüglich Wasserchemie und Frachtdaten disskutiert. Für U-238 und Ra-226 zeigt sich eine Kulmination der Aktivitätskonzentration in den mittleren Sediment- Horizonten von 25-35 cm Tiefe, insbesondere an der Probenahmestelle K3. Dort fanden sich auch die höchsten Aktivitätskonzentrationen der Vorsperre für 238U mit einem Medianwert von 770 Bq*kg-1 in einer Tiefe von 30 cm. Für Ra-226 fand sich am selben Ort eine Aktivität von 250 Bq*kg-1 (Median). Anhand der Datierung mithilfe der Cs-137 Methode wurde für das Sediment der Vorsperre Neuensalz eine Sedimentationsrate von 1,5 cm*a-1 errechnet. Für Uran ergab sich eine Sedimentationsrate von 3,7 ± 1,1 kBq*m-2*a-1 und für Ra-226 eine solche von 3,50 ± 0,5 kBq*m-2*a-1. Darüber hinaus wurde die im Schnitt ca. 40 cm mächtigen Sedimente ein Uranvorrat von 68 ± 6 kg pro Hektar bilanziert. In Verbindung mit der Dauer des Bilanzzeitraumes der Sedimentation (23 Jahre) entspräche das in der Vorsperre vorgefundene Uraninventar einem Anteil von ca. 18 % der für diesen Zeitraum abgeschätzten Uranfracht im Wasserzufluss, wobei der geogene Anteil des Urans und die Ausbringung von Phosphatdüngemitteln in den Sedimenten noch nicht berücksichtigt ist. Für Radium sind die Verhältnisse umgekehrt. Wenn aus den gegenwärtigen Aktivitätskonzentrationen im Zufluss auf eine kumulative Fracht für den 23-jährigen Bilanzierungs- bzw. Betrachtungszeitraum hochgerechnet wird, ergibt sich ein fast um den Faktor 100 geringerer Wert, verglichen mit Uran. Dem steht ein Radiuminventar im Sediment gegenüber, welches etwa 15-mal größer als diese hochgerechnete Fracht ist. Daraus ist abzuleiten, dass neben der relativ geringen wassergelösten Zufuhr aus der Bergbaualtlast dem gegogenen Hintergrund im sedimentierenden Substrat sowie diskontinuierlich Partikel (über Regenwasserabfluss) Bedeutung beizumessen ist. Bei der Analyse der Bindungsverhältnisse des sedimentären Urans (sequentielle Extraktion) wurde der größte Anteil des Urans im Sediment als Uraninit bzw. als organisch gebunden identifiziert. Insgesamt ist zu schließen, dass nicht nur Radium in der Nähe von Quellen immobilisiert wird, sondern auch Uran eine dauerhafte Fixierung in ständig abgelagertem organischem Material erfährt. Diese Fixierung ist trotz eutropher Bedingungen mit hoher Niratbelastung stabil und in tieferen Sedimentschichten nachweisbar.

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