Thesis (Ph. D.)--University of Chicago, Department of Physics, June 2000. / Includes bibliographical references. Also available on the Internet.

Effective field theory (EFT) provides a framework to exploit separation of scales in the physical system in order to perform systematic model-independent calculations. There has been significant interest in applying the methods of EFT to halo nuclei. Using halo effective field theory, I provide a model-independent calculation of the radiative neutron capture on lithium-7 over an energy range where the contribution from the 3+ resonance becomes important. This reaction initiate the sequence in the carbon-nitrogen-oxygen (CNO) cycle in the inhomogeneous BBN models, and determine the amount of heavy element production from its reaction rate. One finds that a satisfactory description of the capture reaction, in the present single-particle approximation, suggests the use of a resonance width about three times larger than the experimental value. Power counting arguments that establish a hierarchy for the electromagnetic one- and two-body currents is also presented. The neutron capture of Lithium7 calculation has direct impact on the proton capture on beryllium7 which plays an important role in the neutrino experiments studying physics beyond the Standard Model of particle physics. As a further study of halo nuclei interactions, the cross section of radiative capture of a neutron by carbon-14 is calculated by considering the dominant contribution from electric dipole transition. This is also a part of the CNO cycle and as the slowest reaction in the chain it limits the flow of the production of heavier nuclei A > 14. The cross section is expressed in terms of the elastic scattering parameters of an effective range expansion. Contributions from both the resonant and non-resonant interactions are calculated. Significant interferences between these leads to a capture contribution that deviates from a simple Breit-Wigner resonance form. Using EFT, I present electromagnetic form factors of several halo nuclei. The magnetic dipole moment and the charge radii of carbon-15, beryllium-11, and carbon-19 halo systems are considered. Prediction is made for the magnetic moment in the leading order. I can only provide some estimates for the form factors in next-to-leading order where two-body currents appear. The estimates are based on power counting unless the effective range and the magnetic moment are known. Charge radii for three systems have also been estimated at LO and NLO.

The proton is described by the electric G_E and magnetic G_M form factors which characterise its internal structure. The way to measure the proton form factors consists in measuring the angular distribution of the e-p elastic scattering accessing the so-called Space-Like region where q^2<0. Using the crossed channel pbar p<-->e+e-, one accesses another kinematical region, the so-called Time-Like region where q^2>0. However, due to the pbar p<-->e+e- threshold q^2_{th}, only the kinematical domain q^2>q^2_{th}>0 is available. To access the unphysical region, one may use the pbar p --> pi0e+e- reaction where the pi0 takes away a part of the system energy allowing q^2 to be varied between q^2_{th} and almost 0. This thesis aims to show the feasibility of such measurements with the PANDA detector which will be installed on the antiproton ring at the FAIR facility at Darmstadt. To describe the pbar p --> pi0e+e- reaction, a Lagrangian based approach is developed. The 5-fold differential cross section is determined and related to linear combinations of hadronic tensors. Under the assumption of one nucleon exchange, the hadronic tensors are expressed in terms of the 2 complex proton electromagnetic form factors. An extraction method which provides an access to the proton electromagnetic form factor ratio R=|G_E|/|G_M| and for the first time in an unpolarized experiment to the cosine of the phase difference is developed. Such measurements have never been performed in the unphysical region. Extended simulations were performed to show how the ratio R and the cosine can be extracted from the positron angular distribution. Furthermore, a model is developed for the pbar p-->pi0pi+pi- background reaction considered as the most dangerous one. The background contribution can be reduced to the percent level or even less. The corresponding signal efficiency ranges from a few % to 30%. The precision on the determination of the ratio R and of the cosine is determined using the expected counting rates via Monte Carlo method. A part of this thesis is also dedicated to more technical work with the study of the prototype of the electromagnetic calorimeter and the determination of its resolution.

In this study, cooling of small form factor computer is numerically investigated. The numerical model is analyzed using a commercial computational fluid dynamics software Icepak&trade / . The effects of grid selection, discretization schemes and turbulence models are discussed and presented. In addition, physical phenomena like recirculation and relaminarization are addressed briefly. For a comparison with the computational fluid dynamics results, an experiment is conducted and some temperature measurements are obtained from critical locations inside the chassis.The computational results were found to be in good agreement with the experimental ones.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (p. 139-148).

The widespread deployment of wireless sensors in our homes, offices, factories and infrastructure has opened the door for system designers to create novel approaches for powering wireless sensor nodes. In recent years, energy harvesting has emerged as the power supply of choice for embedded system designers, enabling wireless sensors to be used in applications that previously were not feasible with conventional battery-powered designs. This report details the design and development of an energy harvesting wireless sensor from concept to production. Design constraints included the requirement to operate reliably in a wide variety of environments, the use of commercially available components, and a visually appealing form factor. The result is a very power-efficient, solar-powered wireless sensor that measures temperature, voltage, and illumination level at the solar cell and has an ultra slim form factor. / text

This research project searches for new physics in the τ sector that would resolve the tension between BABAR measurement for the pion-photon transition form factor Fπ0(Q^2)and the standard model asymptotic prediction. This behaviour could be explained by a new light pseudo-scalar state that mixes with the π 0 and enhances its coupling to the c and b quarks or the τ lepton, or by a new spin-0 particle with mass very close to the π 0 . We examine one channel to test for existence of such objects: their creation in association with τ pairs in e+ e− collisions. The analysis uses a typical cut-based approach as the large predicted cross-sections and the kinematics of the final states allow for a direct selection of signal events and background suppression. Current simulation studies predict a 90% CL limit on the production cross-section on the order of 100 fb in case of no signal, while the theory predicts production cross-sections on the order of 1 pb to 100 pb depending on the model. / Graduate / 0798 / beaa@uvic.ca

The x-ray atomic form-factor determines the x-ray optical properties of materials and is a fundamental parameter for critical x-ray investigations. However, despite uncertainty estimates of order 1%, differences of 2-10% between x-ray mass attenuation measurements render comparison with the various theoretical tabulations meaningless. Moreover, such uncertainties impose limits on the accuracy of various quantitative investigations. We determine the imaginary component of the atomic form-factor from measurements of the x-ray mass attenuation coefficient. With the exception of the measurements of Tran et.al. [Phys. Rev. A 64, (062506); 67, (042716); J. Phys. B 38, (89)] with a 0.3% accuracy, previous work has been unable to achieve accuracies below 1%, and differences between results claiming this accuracy often exceed 6%.We have developed a full-foil mapping technique which has improved the measurement accuracy by an order of magnitude. This technique overcomes limitations arising from absorber thickness variations, using the average integrated column density and attenuation measurements across the entire surface of the absorber. We have examined measurements obtained over a wide range of parameter space for systematic deviations indicative of experimental error. Among others, this has led to the identification and correction of a 1% discrepancy arising from the x-ray bandwidth. Resulting measurement accuracies for molybdenum are 0.02-0.15%. Preliminary results for tin suggest a final accuracy of 0.1-1%. We compare these measurements with several commonly-used tabulations and identify a number of systematic discrepancies whose causes are discussed.

BARRETO, Isaac Moreira. Cálculo do fator-de-forma exato entre áreas diferencial e finita usando CSG. 2008. 62 f. Dissertação (Mestrado em ciência da computação)- Universidade Federal do Ceará, Fortaleza-CE, 2008. / Submitted by Elineudson Ribeiro (elineudsonr@gmail.com) on 2016-07-11T16:45:40Z No. of bitstreams: 1 2008_dis_imbarreto.pdf: 752627 bytes, checksum: 2c1a97d41785e527e97633cc6c7e9756 (MD5) / Approved for entry into archive by Rocilda Sales (rocilda@ufc.br) on 2016-07-18T13:45:29Z (GMT) No. of bitstreams: 1 2008_dis_imbarreto.pdf: 752627 bytes, checksum: 2c1a97d41785e527e97633cc6c7e9756 (MD5) / Made available in DSpace on 2016-07-18T13:45:29Z (GMT). No. of bitstreams: 1 2008_dis_imbarreto.pdf: 752627 bytes, checksum: 2c1a97d41785e527e97633cc6c7e9756 (MD5) Previous issue date: 2008 / The Ray-Tracing and Radiosity methods are the main representatives of the method that solve the global illumination problem. In both mthods it is necessary to know the energy tranfer ratio between two areas. This ratio, called form factor, is one of the key concepts in Radiosity methods and is being more frequently used in Ray-Tracing methods with finite area light sources. There are many methods for the computation of the form factor, most of them are approximative due to a matter of performance, but, in some specific cases, the extra computational effort needed to compute the exact value of the form factor can improve the overall performance of the illumination method. In general, in these cases, the computational effort needed to obtain an acceptable approximation of the form factor outweighs the effort necessary to compute the exact value. Furthermore there are situation, for example, shadow boundary shading, in which a high precision is far more important than a performance gain. In this work we present a method to compute the exact form factor between a finite area and a differential area which uses CSG techniques to identify the ooccluded areas of the source. / Os métodos de Ray-Tracing e Radiosidade são os principais representantes dos métodos existentes para resolver o problema de iluminação global. Em ambos os métodos se faz necessário saber a taxa de transferência de energia luminosa entre duas áreas. Essa taxa de transferência, chamada de fator-de-forma, é um dos pontos principais no método de Radiosidade e vem sendo usado cada vez com mais frequência em métodos de Ray-Tracing com fontes luminosas de área finita. Existem vários métodos para o cálculo do fator-de-forma, a maioria deles são aproximativos por uma questão de desempenho. Porém, em casos específicos, o trabalho extra para calcular o valor exato do fator-de-forma pode melhorar o desempenho global do método. Em geral, nesses casos, o esforço necessário para se obter uma aproximação aceitável do valor do fator-de-forma supera o esforço necessário para calcular o valor exato em si. Além disso, existem situações, tais como a renderização nas áreas de fronteiras de sombras, em que uma alta precisão é mais importante do que um ganho no desempenho. Nessas situações, é desejável que o método tenha ao seu dispor uma maneira de calcular o valor exato do fator-de-forma. Neste trabalho é apresentado um método para calcular o fator-de-forma exato entre uma área finita e uma área diferencial que utiliza de técnicas CSG para identificar as áreas ocluídas do polígono emissor.

abstract: The OLYMPUS experiment measured the two-photon exchange contribution to elastic electron-proton scattering, over a range of four-momentum transfer from \(0.6 < Q^2 < 2.2\) \((\mathrm{GeV/c})^2\). The motivation for the experiment stemmed from measurements of the electric-to-magnetic form factor ratio of the proton \(\mu G_E/G_M\) extracted from polarization observables in polarized electron-proton scattering. Polarized electron-proton scattering experiments have revealed a significant decrease in \(\mu G_E/G_M\) at large \(Q^2\), in contrast to previous measurements from unpolarized electron-proton scattering. The commonly accepted hypothesis is that the discrepancy in the form factor ratio is due to neglected higher-order terms in the elastic electron-proton scattering cross section, in particular the two-photon exchange amplitude. The goal of OLYMPUS was to measure the two-photon exchange contribution by measuring the positron-proton to electron-proton elastic scattering cross section ratio, \(\sigma_{e^+p}/\sigma_{e^-p}\). The two-photon exchange contribution is correlated to the deviation of the cross section ratio from unity. In 2012, the OLYMPUS experiment collected over 4 fb\(^{-1}\) of \(e^+p\) and \(e^-p\) scattering data using electron and positron beams incident on a hydrogen gas target. The scattered leptons and protons were measured exclusively with a large acceptance spectrometer. OLYMPUS observed a slight rise in \(\sigma_{e^+p}/\sigma_{e^-p}\) of at most 1-2\% over a \(Q^2\) range of \(0.6 < Q^2 < 2.2\) \((\mathrm{GeV/c})^2\). This work discusses the motivations, experiment, analysis method, and the preliminary results for the cross section ratio as measured by OLYMPUS. / Dissertation/Thesis / Doctoral Dissertation Physics 2016