Theses/Dissertations - Physics
http://hdl.handle.net/2104/4793
2018-06-22T01:48:42ZEnvironmental applications of plasma physics : aerosolized nanoparticle decontamination using an inductively heated plasma device.
http://hdl.handle.net/2104/10338
Environmental applications of plasma physics : aerosolized nanoparticle decontamination using an inductively heated plasma device.
Materials with sizes on the nanometer scale are highly desired for their unique size-dependent properties that prove beneficial in industrial and consumer processes. However, the increased use of nanomaterials could lead to an increased risk of exposure to materials that are detrimental to human health. The link between inhalation of nano-scale particles and diseases of the lungs are of particular concern. In an effort to reduce the risk of exposure to aerosolized nanometer sized particles, a new method is recommended to remove nanoparticles from the air using plasma. It is proposed that the test system subject SiO2 nanoparticles to plasma treatment in an inductively heated plasma generator to study the effectiveness and efficiency of plasma as an aerosolized nanoparticle decontamination mechanism. The treatment system is a multi-step process involving the generation and characterization of nanoparticles and plasma treatment, followed by the collection and disposal or distribution of remaining particles.
2018-04-17T00:00:00ZIR-improved DGLAP-CS parton shower effects in W + jets at √ s = 7, 8, and 13 TeV.
http://hdl.handle.net/2104/10198
IR-improved DGLAP-CS parton shower effects in W + jets at √ s = 7, 8, and 13 TeV.
The invention and development of collider physics in the twentieth century provides us with opportunities to determine which particles exist in nature, their properties, and the ways they interact with each other. The discovery of the Higgs boson, the last undetected particle predicted in the Standard Model (SM) of Particle Physics, brought a lot of excitement to the international physics community. The SM is based on the gauge group SU(3)QCD ×SU(2)weak ×U(1)hypercharge. Through a process called Spontaneous Symmetry Breaking (SSB), it is broken down to SU(3)QCD × U(1)EM at a scale around 247 GeV [1]. Since the SM is a renormalizable theory with 27 parameters, we can test it by performing enough experiments with enough precision. It is possible to improve the infrared aspects of the standard treatment of the DGLAP-CS evolution theory to take into account a large class of higher-order corrections that significantly improve the precision of the theory for any given level of fixed-order calculation of its respective kernels [2]. We use recently introduced MC realizations of IR-improved DGLAP-CS parton showers to study the attendant improvement effects in W + jets at the LHC in the MG5 aMC@NLO framework for exact O(αs) corrections. Implementation of the new IR-improved kernels in the framework of HERWIG6.5 yields the new IR-improved parton shower MC HERWIRI1.031 [3]. Events are showered by HERWIG6.5 and HERWIRI1.031 with PTRMS = 2.2 GeV and PTRMS = 0 GeV, respectively. We compare our results with the available LHC data and discuss the corresponding phenomenological implications. In Chapter Four we have used the latest results provided by CMS and ATLAS for 7 TeV. In Chapter Five we have used the CMS results published in 2017 for 8 TeV.
2017-11-27T00:00:00ZTwo-dimensional Hořava-Lifshitz theory of gravity.
http://hdl.handle.net/2104/10193
Two-dimensional Hořava-Lifshitz theory of gravity.
In this dissertation, two-dimensional Hařava theory of gravity has been studied on the classical and quantum mechanical levels. The classical solutions of the projectable and nonprojectable Hořava gravity have been found and their spacetime structures are investigated in terms of Penrose diagrams. When quantizing the theory in the canonical approach, the integral Hamiltonian constraint in the projectable case will generate the so-called Wheeler-DeWitt equation which can be exactly solved if the invariant length and its conjugate momentum are used as new variables. On the other hand, for the nonprojectable case, the lapse function is no longer a Lagrangian multiplier but one of the canonical variables. This results in a local and second-class Hamiltonian constraint which can be solved for the lapse function. The quantization of nonprojectable case is carried out by directly dropping the unphysical degrees of freedom, that is, replacing Poisson brackets with Dirac brackets. In the last part of the dissertation, the interactions between two-dimensional Hořava gravity and a non-relativistic scalar field are considered. In the projectable case, the minimal coulping is adopted and canonical quantization is carried out in the same way as we have done for the pure gravity case. In the non-projectable case, we turn to the non-minimal couplings and find both Killing and Universal horizons from classical solutions.
2017-11-03T00:00:00ZImaging surface reactions at molecular level on TiO₂ surfaces.
http://hdl.handle.net/2104/10178
Imaging surface reactions at molecular level on TiO₂ surfaces.
Understanding the structure and properties of TiO₂ surfaces is critical to achieve a better understanding of heterogeneous catalytic reactions on TiO₂. In this thesis, rutile TiO₂ (110) and anatase TiO₂ (001) surfaces have been investigated using scanning tunneling microscopy (STM). The approach of comparison of the same nanoscale area during reaction allows the site-specific molecular-level understanding of surface catalytic reactions. The rutile TiO₂(110) (1×1) surface prepared by cycles of Ar-ion sputtering and e-beam annealing was studied using acetone as a probe molecule. It was found that acetone molecules preferably adsorb on the oxygen vacancy sites at room temperature. The sequential isothermal STM images show acetone either diffuse along the bridge-bonded oxygen row or from the oxygen row to the titanium row and then moving along the titanium row. By exposing the reduced TiO₂(110) (1×1) surface to O₂, the surface became partially oxidized. The consecutive reaction steps of acetone molecules with the partially oxidized surface was studied. It was found that acetone molecules react with the oxygen adatoms and the bridge-bound oxygen vacancies. As a result of reactions, two different types of species were formed. With more cleaning cycles at higher temperatures, TiO₂(110) transformed from the reduced (1×1) phase to the cross-linked (1×2) phase. The structure of cross-linked (1×2) TiO₂(110) was studied through the interaction of trimethyl acetic acid (TMAA) with various sites on the surfaces. At low coverage, TMAA molecules mostly adsorb in troughs and on cross-links. With increasing coverage, they form a chain in the trough. At higher coverage, TMAA molecules adsorb on strands in both centered and off-centered configurations. Comparing three different models, the adsorption of TMAA strongly supports the Ti₂O model. The atomic structure of anatase TiO₂(001) expitaxial thin films has been studied. Three types of features were found on the bright rows of the (1×4) reconstructed surface from the high bias STM images. High resolution STM images taken at the same area at different bias voltages show that these features are originated from two basic atomic building blocks. Based on that, a modified added molecule model was proposed.
2017-11-01T00:00:00Z