Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

2019

Discipline
Institution
Keyword
Publication
Publication Type
File Type

Articles 12991 - 13000 of 13000

Full-Text Articles in Physical Sciences and Mathematics

Ads₄/Cft₃ Holography From Four-Dimensional Gauged Supergravity, Khem Upathambhakul Jan 2019

Ads₄/Cft₃ Holography From Four-Dimensional Gauged Supergravity, Khem Upathambhakul

Chulalongkorn University Theses and Dissertations (Chula ETD)

We study holographic RG flows from N = 3 and N = 4 gauged supergravities in four dimensions. The scalar manifold of N = 3 gauged supergravity is in the form of the coset space G/H = SU(3, n)/SU(3) × SU(n) × U(1). Possible gauge groups, in this study, are given by SO(3) × SO(3), SO(3, 1), SO(2, 2), SO(2, 1) × SO(2, 2), and SL(3, R). We then study N = 4 gauged supergravity from type II compactification on T⁶/Z₂ × Z₂ with non-semisimple gaugings. The scalar manifold of N = 4 gauged supergravity is in the form of …

Go to article

Multipole Resonance Probe Measurement In Plasma, Natthapong Jampaiboon Jan 2019

Multipole Resonance Probe Measurement In Plasma, Natthapong Jampaiboon

Chulalongkorn University Theses and Dissertations (Chula ETD)

Active plasma resonance spectroscopy (APRS) is one of the interesting methods which could avoid plasma contamination problem occurs in a conventional Langmuir probe measurement. It is because the probe conductors are covered by a dielectric material. The APRS probe can be of any shape. A multipole resonance probe is a hemisphere APRS probe since a sphere imposes the simplest way to find an analytical solution by solving the Laplace equation in the spherical coordinates with the azimuthal symmetry. In this study, the APRS probes in the hemisphere, microstrip, and parallel rod shapes were constructed. Plasma density was obtained by using …

Go to article

Effects Of Magnesium Substitution On Electronic Properties Of Calcium Difluoride, Natthasart Chintananon Jan 2019

Effects Of Magnesium Substitution On Electronic Properties Of Calcium Difluoride, Natthasart Chintananon

Chulalongkorn University Theses and Dissertations (Chula ETD)

We use density functional theory to find the phase transitions of CaF2. The results show that CaF2 adopts the fluorite structure, with the space group Fm-3m, in the range 0f 0-8 GPa and transforms into the cotunnite structure, with the space group Pnma, above 8 GPa. The electronic band structure of the Pnma-CaF2 structure expresses an insulating phase, and the bandgap collapses under pressure above 70 GPa. In this work, we proposed a new decoration of Ca/Mg-substituted fluorides MgxCa1-xF2, using the cluster expansion technique which is commonly used to study alloys. We found that the Mg0.25Ca0.75F2, with a Pm structure, …

Go to article

Effect Of Hydrogen Exposure On The Electronic And Optical Properties Of Insulating Titanates, John G. Connell Jan 2019

Effect Of Hydrogen Exposure On The Electronic And Optical Properties Of Insulating Titanates, John G. Connell

Theses and Dissertations--Physics and Astronomy

Hydrogen exposure of insulating d0-titanates, such as SrTiO3 (STO), has displayed the formation of intriguing conducting states. These conducting states form through the use of forming gas (N2/H2) annealing or hydrogen plasma exposure, where hydrogen gas is exposed to high energy microwaves. The exposure of STO to hydrogen causes metallic conductivity due to the introduction of hydrogen cations on some of the oxygen sites. However, the optical properties of this hydrogen-exposed STO have not been well-studied. Further, Ba0.5Sr0.5TiO3 (BST), an insulating dielectric, also shows changes in its conductivity …

Go to article

The Role Of Angular Momentum In The Interplay Between Disk Galaxies And Their Host Dark Matter Halos: Corollaries For The Hubble Fork Diagram, Angela Collier Jan 2019

The Role Of Angular Momentum In The Interplay Between Disk Galaxies And Their Host Dark Matter Halos: Corollaries For The Hubble Fork Diagram, Angela Collier

Theses and Dissertations--Physics and Astronomy

A majority of disk galaxies host stellar bars that regulate and amplify the flow of angular momentum, J, between disks and their parent dark matter (DM) halos. These bars constitute the prime factor driving internal galaxy evolution. Yet, a non-negligible fraction of disks lack this morphological feature, which led to adoption of the Hubble Fork Diagram. The complex evolution of barred galaxies has been studied by means of numerical simulations, complemented by observations. Despite prolonged efforts, many fundamental questions remain, in part because cosmological simulations still lack the necessary resolution to account for resonant interactions and simulations of isolated …

Go to article

Electronic Properties Of Atomically Thin Material Heterostructures, M. Javad Farrokhi Jan 2019

Electronic Properties Of Atomically Thin Material Heterostructures, M. Javad Farrokhi

Theses and Dissertations--Physics and Astronomy

There is a movement in the electronic industry toward building electronic devices with dimensions smaller than is currently possible. Atomically thin 2D material, such as graphene, bilayer graphene, hBN and MoS2 are great candidate for this goal and they have a potential set of novel electronic properties compare to their bulk counterparts due to the exhibition of quantum confinement effects. To this goal, we have investigated the electric field screening of multilayer 2D materials due to the presence of impurity charge in the interface and vertical electric fifield from back gate. Our result shows a dramatic difference of screening behavior …

Go to article

Magnetic Field Monitoring In The Sns Neutron Edm Experiment, Alina Aleksandrova Jan 2019

Magnetic Field Monitoring In The Sns Neutron Edm Experiment, Alina Aleksandrova

Theses and Dissertations--Physics and Astronomy

It is a well known fact that the visible universe is made almost entirely of baryonic matter. Yet, this is also one of the greatest puzzles that physicists are trying to solve: Where did all of this matter come from in the first place? The Standard Model (SM) of particle physics predicts a baryon asymmetry that is much smaller than what is observed in nature. In order to try and explain this discrepancy, Sakharov (1967) postulated three necessary conditions for baryogenesis in the early universe. One of these is the requirement that charge conjugation (C) and the product of C …

Go to article

Exploring The Molecular Origin Of Jet Fuel Thermal Oxidative Deposition Through Statistical Analysis Of Mass Spectral Data And Pyrolysis Gas Chromatography/Mass Spectrometry Of Deposits, Krege Matthew Christison Jan 2019

Exploring The Molecular Origin Of Jet Fuel Thermal Oxidative Deposition Through Statistical Analysis Of Mass Spectral Data And Pyrolysis Gas Chromatography/Mass Spectrometry Of Deposits, Krege Matthew Christison

University of the Pacific Theses and Dissertations

ASTM D3241 (Standard Test Method for Thermal Oxidation Stability of Aviation Turbine Fuels) measures the thermal oxidative stability of jet fuels under elevated temperature and pressure conditions. When jet fuels fail ASTM D3241, either at the refinery or in the distribution system, there can be supply disruptions and financial losses. Understanding the causes of poor thermal oxidative stability in jet fuels could help prevent or mitigate issues. In order to develop a deeper understanding of the molecular precursors that lead to ASTM D3241 failures, a number of analytical methodologies and data treatment techniques have been developed, applied, and reported here. …

Go to article

Novel Adsorbent For Industrial Wastewater Treatment Applications, Islam M. Al-Akraa, Ahmed Y. Zakaria Eng, Dalia A. Ali Eng, Hany A. Elazab Dr, Hoda A. Elsawy Dr Jan 2019

Novel Adsorbent For Industrial Wastewater Treatment Applications, Islam M. Al-Akraa, Ahmed Y. Zakaria Eng, Dalia A. Ali Eng, Hany A. Elazab Dr, Hoda A. Elsawy Dr

Chemical Engineering

In this study, the hydroxyapatite powder is investigated for both of methylene blue and thymol blue in aqueous solution. The physical and chemical properties of the adsorbent were evaluated systematically using the different techniques including Microsoft Excel programming, linear regression model and also the coefficient of determination. Batch adsorption experiments were conducted to determine the effect of contact time, solution pH, initial dye concentrations, and also the adsorbent dosage on adsorption. The adsorption kinetic parameters confirmed the better fitting of pseudo-second order kinetic model for both of methylene blue and thymol blue. The isotherm data of methylene blue and thymol …

Go to article

Agent-Based Modeling And Simulation Approaches In Stem Education Research, Shanna R. Simpson-Singleton, Xiangdong Che Jan 2019

Agent-Based Modeling And Simulation Approaches In Stem Education Research, Shanna R. Simpson-Singleton, Xiangdong Che

Journal of International Technology and Information Management

The development of best practices that deliver quality STEM education to all students, while minimizing achievement gaps, have been solicited by several national agencies. ABMS is a feasible approach to provide insight into global behavior based upon the interactions amongst agents and environments. In this review, we systematically surveyed several modeling and simulation approaches and discussed their applications to the evaluation of relevant theories in STEM education. It was found that ABMS is optimal to simulate STEM education hypotheses, as ABMS will sensibly present emergent theories and causation in STEM education phenomena if the model is properly validated and calibrated.

Go to article

First Prev