Physics Commons^™

Effect Of Cdcl_2/Annealing On The Crystalline Transformation Of Cdte Thin Films Grown By Evaporation At A Low Substrate Temperature, İsmai̇l Polat, Sali̇h Yilmaz, Emi̇n Bacaksiz, Mustafa Altunbaş, Murat Tomaki̇n

Turkish Journal of Physics

The structural and optical properties of CdTe thin films prepared at a low substrate temperature were investigated before and after the CdCl_2/annealing. The crystal structure of CdTe film was cubic with a strong (111) preferential orientation. Annealing at 400 °C without CdCl_2 treatment results in a decrease in the (111) peak intensity while the intensities of the (220), (311) and (331) peaks appeared, indicating that the texture is significantly changed. However, after the CdCl_2/annealing, the film exhibited a hexagonal phase as a dominant structure. The scanning electron microscopy patterns showed that the as-deposited and annealed samples had almost the same …

Electronic Structure Of The Ge And Se Vacancies In Gese Layered Semiconductor, Zakir Jahangirli

Turkish Journal of Physics

We report the results of a theoretical investigation of electronic properties of ideal cation and anion vacancies in GeSe. The calculations have been performed using self-consistent Green's function method. The bulk electronic structure is described by a tight-binding Hamiltonian in the bases sets of Linear Combinations of Atomic Orbitals (LCAO). The Green's function of the perfect crystal evaluated using an eigenfunction expansion employing wave functions and band structures obtained from a self-consistent, pseudopotential, local-density-functional calculation. The defect potential is calculated using occupied electron states of the perturbed system. Results are obtained in terms of vacancy bound states, vacancy resonances, and …

Exotic Localized Structures Based On The Symmetrical Lucas Function Of The (2+1)-Dimensional Generalized Nizhnik-Novikov-Veselov System, Emad A-B. Abdel-Salam, Zeid I. A. Al-Muhiameed

Turkish Journal of Physics

Based on the Lucas Riccati method and a linear variable separation method, new variable separation solutions of the (2+1)-dimensional generalized Nizhnik-Novikov-Veselov system are derived. Then, we give a positive answer for the following question: Are there any localized excitations derived by the use of another functions? For this purpose, some attention will be paid to dromion, peakon, multi dromion-solitoff excitations, regular fractal dromions, stochastic fractal dromion structure and combined structures including bell-like compactons, peakon-like compactons and compacton-like semi-foldons based on the golden main. With the help of the modified Weierstrass function, we discuss the stochastic fractal dromion structure both analytically …

A High Luminosity Erl On Ring E^-E^+ Collider For A Super Charm Factory, Erdal Recepoglu, Saleh Sultansoy

Turkish Journal of Physics

A high luminosity energy recovery linac-on-ring type electron-positron collider operating as super charm factory is proposed. It is shown that a luminosity above L = 10^{35}cm^{-2}s^{-1} can be achieved for center of mass energy \sqrt{s}=3.77 GeV. The physics goals of this machine in investigation for charmed particles properties are briefly discussed.

A 3d Model For Thickness And Diffusion Capacitance Of Emitter-Base Junction Determination In A Bifacial Polycrystalline Solar Cell Under Real Operating Condition, Senghane Mbodji, Babacar Mbow, Fabe Idrissa Barro, Gregoire Sissoko

Turkish Journal of Physics

This paper aims at presenting the behaviour of the space charge region for an n^+-p-p^+ bifacial solar cell under monochromatic illumination. It also deals with mathematical relations in the describing and the use of new approach that involves both junction and back surface recombination velocities with a 3D modelling study. Based on the normalized carriers' density, versus base depth, the space-charge layer thickness (Z_{0,u}) is studied for various parameters such as grain size g, grain boundaries recombination velocity S_{gb}, wavelength \lambda and for different operating conditions. Therefore, the relationship between Z_{0,u} and the diffusion capacitance C_u show that junction in …

Hall Effect On Mhd Forced Convection From An Infinite Porous Plate With Dissipative Heat In A Rotating System, Nazibuddin Ahmed, Jiwan Krishna Goswami

Turkish Journal of Physics

An attempt has been made to study the Hall effect on MHD forced convection from an infinite horizontal porous plate with dissipative heat in a rotating system with uniform free stream when the temperature at the plate varies periodically with time. The entire system rotates with a constant angular velocity about the normal to the plate. A uniform magnetic field is assumed to be applied along the normal to the plate directed into the fluid region. The governing equations are solved analytically. The expressions for the velocity and temperature field are obtained in non-dimensional form. The skin friction due to …

Stress-Strain Characteristics, Dynamic Recrystallization, Grain Growth, And Melting Point Of The Binary And Ternary Solder Alloys, Shakib Moqbel Ali Mohammed Alsowidy, Mohammed Ali Shukri

Turkish Journal of Physics

An advanced solder alloy, Pb-10wt%Sn-3wt%Zn, has been developed to improve the mechanical properties of the Pb-10wt%Sn based solders. Deformation behavior of Pb-10wt%Sn and Pb-10wt%Sn-3wt%Zn alloys was investigated in tension at strain rates from 0.005% to 0.25% s^{-1} in the temperature range 383--433 K. The stress-strain characteristics curves showed two deformation modes: (i) continuous work softening and fracture following a sharp stress in Pb-10wt%Sn, (ii) work hardening with steady-state flow and fracture just after yielding in Pb-10wt%Sn-3wt%Zn. In the work softening type, relatively coarse grains ranging from 30 to 60 \mu m are produced by dynamic recrystallization (DRX). In the work …

Anharmonic Properties Of Potassium Halide Crystals, Krishna Murti Raju

Turkish Journal of Physics

An effort has been made to obtain the anharmonic properties of potassium halides starting from primary physical parameters viz. nearest neighbor distance and hardness parameters assuming long- and short- range potentials at elevated temperatures. The elastic energy density for a deformed crystal can be expanded as power series of strains for obtaining coefficients of quadratic, cubic and quartic terms which are known as the second, third and fourth order elastic constants respectively. When the values of the higher order elastic constants are known for a crystal, many of the anharmonic properties of the crystal can be treated within the limit …

Optical Characterization Of Fe^{3+} Doped Cds Nanoparticles Synthesized By Wet-Chemical Route, Seyed Mohammad Taheri Otaqsara, Mohammad Hassan Yousefi, Ali Azam Khosravi

Turkish Journal of Physics

Fe^{3+} doped CdS nanoparticles using Mercaptoethanol as a capping agent were prepared by colloidal wet-chemical method. UV-VIS spectra show that Fe-doping can effectively tune energy band structure, i.e. a large blue shift (\sim 30 nm) with increasing Fe concentration. PL measurement of doped CdS nanoparticles shows an additional emission band at \sim 532 nm, which can be due to radiative transition of dopant level to ground state. X-ray diffraction patterns studies revealed cubic crystal phase. TEM micrographs show a spherical shape and nearly well distribution with an average particle size of \sim 4 nm.

Numerics Of The Lattice Boltzmann Method: Effects Of Collision Models On The Lattice Boltzmann Simulations, Li-Shi Luo, Wei Liao, Xingwang Chen, Yan Peng, Wei Zhang

Mathematics & Statistics Faculty Publications

We conduct a comparative study to evaluate several lattice Boltzmann (LB) models for solving the near incompressible Navier-Stokes equations, including the lattice Boltzmann equation with the multiple-relaxation-time (MRT), the two-relaxation-time (TRT), the single-relaxation-time (SRT) collision models, and the entropic lattice Boltzmann equation (ELBE). The lid-driven square cavity flow in two dimensions is used as a benchmark test. Our results demonstrate that the ELBE does not improve the numerical stability of the SRT or the lattice Bhatnagar-Gross-Krook (LBGK) model. Our results also show that the MRT and TRT LB models are superior to the ELBE and LBGK models in terms of …

Gauge-Gravity Duality And Its Applications To Cosmology And Fluid Dynamics, Jae-Hyuk Oh

University of Kentucky Doctoral Dissertations

This thesis is devoted to the study of two important applications of gauge-gravity duality: the cosmological singularity problem and conformal fluid dynamics. Gauge-gravity duality is a concrete dual relationship between a gauge theory (such as electromagnetism, the theories of weak and strong interactions), and a theory of strings which contains gravity. The most concrete application of this duality is the AdS/CFT correspondence, where the theory containing gravity lives in the bulk of an asymptotically anti-de-Sitter space-time, while the dual gauge theory is a deformation of a conformal field theory which lives on the boundary of anti-de-Sitter space-time(AdS).

Our first application …

Comparative Imaging Study In Ultrasound Mri, Ct And Dsa Using A Multi-Modality Renal Artery Phantom, Deirdre King, Andrew Fagan, Carmel Moran, Jacinta Browne

Articles

A range of anatomically-realistic multi-modality renal artery phantoms consisting of vessels with varying degrees of stenosis was developed and evaluated using four imaging techniques currently used to detect renal artery stenosis (RAS). The spatial resolution required to visualize vascular geometry and the velocity detection performance required to adequately characterize blood flow in patients suffering from RAS is currently ill-defined, with the result that no one imaging modality has emerged as a gold standard technique for screening for this disease.

Methods: The phantoms, which contained a range of stenosis values (0, 30, 50, 70 and 85%), were designed for use with …

Photoassociative Spectroscopy Of Ultracold Metastable Argon, M. K. Shaffer, G. Ranjit, C. I. Sukenik, M. Walhout

Physics Faculty Publications

We present results of photoassociative spectroscopy performed on ultracold metastable argonatoms in a magneto-optical trap. Ion spectra are obtained with laser detuning up to a few gigahertz below the 4s[3/2]₂ → 4p[5/2]₃ trapping transition at 811 nm and with intensities in a range of ~(10²-10⁵)I_Sat. We also compute dipole-dipole potentials for both singly and doubly excited diatomic molecules and use a Leroy-Bernstein analysis to determine the approximate vibrational spacings in the (s+p) and (p+p) manifolds. Based on this theoretical framework, we explain a broad background feature in our data and suggest that …

Cell Count Moments In The Halo Model, J. N. Fry, S. Colombi, Pablo Fosalba, Anand Balaraman, István Szapudi, R. Teyssier

Physics & Astronomy: Faculty Publications

We study cell count moments up to fifth order of the distributions of haloes, of halo substructures as a proxy for galaxies, and of mass in the context of the halo model and compare theoretical predictions to the results of numerical simulations. On scales larger than the size of the largest cluster, we present a simple point cluster model in which results depend only on cluster–cluster correlations and on the distribution of the number of objects within a cluster, or cluster occupancy. The point cluster model leads to expressions for moments of galaxy counts in which the volume-averaged moments on …

Predicted Ultrafast Dynamic Metallization Of Dielectric Nanofilms By Strong Single-Cycle Optical Fields, Maxim Durach, Anastasia Rusina, Matthias F. Kling, Mark I. Stockman

Physics & Astronomy: Faculty Publications

We predict a dynamic metallization effect where an ultrafast (single-cycle) optical pulse with a ≲1  V/Åfield causes plasmonic metal-like behavior of a dielectric film with a few-nm thickness. This manifests itself in plasmonic oscillations of polarization and a significant population of the conduction band evolving on a ∼1  fs time scale. These phenomena are due to a combination of both adiabatic (reversible) and diabatic (for practical purposes irreversible) pathways.

Generation Of Mid-Ir Wavelengths, Deborah Robinson, Robert Hartsock, Kelly Gaffney

STAR Program Research Presentations

Generation of mid-IR wavelengths

Deborah Robinson, Robert Hartsock, and Kelly Gaffney

Abstract

Research to determine basic molecular properties utilizing pump/probe experiments is an on going effort at SLAC. Here we have been given the task to generate mid-IR laser pulses and commission a mid-IR detector for said experiments and research. The mid-IR pulses will be used to probe the changes in molecular properties induced by exciting the electrons in molecules with visible pump pulses. In order to accomplish this, an optical parametric amplifier (OPA) has been set-up and aligned. The pump beam for the OPA is a 40 femtosecond 800nm …

Development Of A Vessel Mimicking Material For Use In Anatomically Realistic Doppler Flow Phantoms, Deirdre King, Carmel Moran, John Mcnamara, Andrew Fagan, Jacinta Browne

Articles

Polyvinyl alcohol cryogel, (PVA-C) is presented as a vessel mimicking material for use in anatomically realistic Doppler flow phantoms. Three different batches of 10 % wt PVA-C containing (i) PVA-C alone, (ii) PVA-C with anti-bacterial agent and (iii) PVA-C with silicon carbide particles were produced, each with 1 to 6 freeze-thaw cycles. The resulting PVA-C samples were characterized acoustically (over a range 2.65 - 10.5 MHz) and mechanically in order to determine the optimum mixture and preparation for mimicking the properties of healthy and diseased arteries found in vivo. This optimum mix was reached with the PVA-C with anti-bacterial agent …

The Influence Of Taking High School Physics As [A] Junior On Act Science Scores, Bartholomew T. Frey

Masters Theses

In recent years, policymakers, parents, and business leaders have expressed concern about the lack of student success on standardized tests in science. While the consensus is that the problem needs to be addressed, there is little agreement about how to achieve the increased test scores. This study examines the role of the specific science sequencing of biology, chemistry and physics completed by the junior year and increased ACT science test scores. This study compared the achievement of students who took physics as a junior with students who took physics as a senior on the ACT science test. This study continued …

High Pressure And Micro-Spectroscopic Studies Of Single Living Erythrocytes And The Intraerythrocytic Multplication Cycle Of Plasmodium Falciparum, Silki Arora

Electronic Theses and Dissertations

A novel experimental approach for micro-absorption spectroscopy and high-pressure microscopy of single cells is developed and applied to the investigation of morphological, volume, and spectroscopic changes in healthy red blood cells (RBCs) and erythrocytes infected with the malaria parasite Plasmodium falciparum. Through real-time optical imaging of individual erythrocytes (size ~ 7[micrometer]) we determine the change in volume over the pressure range from 0.1 to 210 MPa. The lateral diameter of healthy RBCs decreases reversibly with pressure with an approximate slope of 0.015 [micrometer] / MPa. In infected cells, clear differences in the deformability and between the compression and decompression curves …

Characterization Of The Nonlinear Refractive Index Of Carbon Disulfide Over An Extended Spectral And Temporal Range, Marcus Seidel

Electronic Theses and Dissertations

The intensity dependent refractive index change of a medium is frequently described in terms of the product n₂ · I where n₂ is the nonlinear refractive index and I the light intensity. The nonlinear refractive index is often treated as constant which is a reasonable assumption if the light interacts only with bound electrons. In the case of carbon disulfide (CS₂) however, nuclear motions contribute to n₂. These motions occur on the sub picosecond time scale and thus become especially relevant for ultrashort laser pulses. The neat liquid CS₂ is studied because it exhibits a large nonlinear refractive index in …

An Approach To Improve The Failure Rate Model Of A Solid State Laser By Utalizing The Physics Of Failure Methodology, Omar L. Thompson

Electronic Theses and Dissertations

The ability to predict the failure rate of any military laser is very critical. In-field laser usage does not support the troubleshooting and repairing of a complex electro optical system. The only published laser failure rate model was last updated by the Department of Defense in 1975. Consequently, the failure rate predicted is inaccurate due to model deficiencies. This dissertation has developed a laser failure rate model for diode pumped lasers with improved failure rate prediction accuracy. The model has surpassed the capabilities of the Department of Defense model by the inclusion of key performance attributes that are currently not …

Magnetization Precession And Domainwall Structure In Cobalt-Ruthenium-Cobalt Trilayers, Zhen Li, Ralph Skomski, Sy-Hwang Liou, Steven Michalski, Mircea Chipara, Roger D. Kirby

Physics & Astronomy Faculty Publications

The magnetization dynamics of Co(5 nm)/Ru/Co(5 nm) trilayers with Ru thicknesses from 0.3–0.6 nm is experimentally and theoretically investigated. The coupling between the Co layers is antiferromagnetic (AFM) and yields a stable AFM domain structure with frozen domain walls. Comparing high-resolution magnetic force microscopy (MFM) and pump-probe measurements, we analyze the behavior of the films for different field-strength regimes. For moderate magnetic fields, pump-probe measurements provide dynamic characterization of the coupled precessional modes in the GHz range. The dynamics at small fields is realized by the pinning of AFM domain walls at inhomogeneities. The MFM images yield a domain-wall width …

Low Noise And Low Repetition Rate Semiconductor-Based Mode-Locked Lasers, Dimitrios Mandridis

Electronic Theses and Dissertations

The topic of this dissertation is the development of low repetition rate and low noise semiconductor-based laser sources with a focus on linearly chirped pulse laser sources. In the past decade chirped optical pulses have found a plethora of applications such as photonic analogto-digital conversion, optical coherence tomography, laser ranging, etc. This dissertation analyzes the aforementioned applications of linearly chirped pulses and their technical requirements, as well as the performance of previously demonstrated chirped pulse laser sources. Moreover, the focus is shifted to a specific application of the linearly chirped pulses, timestretched photonic analog-to-digital conversion (TS ADC). The challenges of …

Metal Blacks As Scattering Centers To Increase The Efficiency Of Thin Film Solar Cells, Deep R. Panjwani

Electronic Theses and Dissertations

Metal nano particles are investigated as scattering centers on front surface of thin-film solar cells to improve efficiency. The principle is that scattering, which is enhanced near the plasmon resonance frequency of the particle and depends on particle size, increases the effective optical path length of incident light, leading to more light absorption in active layer of thin film solar cell. The particular types of particles investigated here are known as "metal-black", well known as an IR absorber for bolometric infrared detectors. Gold-black was deposited on commercial thin-film solar cells using a thermal evaporator in a nitrogen ambient at pressures …

Fine-Scale Structures In Saturn's Rings Waves, Wakes And Ghosts, Kevin Baille

Electronic Theses and Dissertations

The Cassini mission provided wonderful tools to explore Saturn, its satellites and its rings system. The UVIS instrument allowed stellar occultation observations of structures in the rings with the best resolution available (around 10 meters depending on geometry and navigation), bringing our understanding of the physics of the rings to the next level. In particular, we have been able to observe, dissect, model and test the interactions between the satellites and the rings. We first looked at kilometer-wide structures generated by resonances with satellites orbiting outside the main rings. The observation of structures in the C ring and their association …

Laser Induced Breakdown Spectroscopy For Detection Of Organic Residues Impact Of Ambient Atmosphere And Laser Parameters, Christopher G. Brown

Electronic Theses and Dissertations

Laser Induced Breakdown Spectroscopy (LIBS) is showing great potential as an atomic analytical technique. With its ability to rapidly analyze all forms of matter, with little-to-no sample preparation, LIBS has many advantages over conventional atomic emission spectroscopy techniques. With the maturation of the technologies that make LIBS possible, there has been a growing movement to implement LIBS in portable analyzers for field applications. In particular, LIBS has long been considered the front-runner in the drive for stand-off detection of trace deposits of explosives. Thus there is a need for a better understanding of the relevant processes that are responsible for …

The Effectiveness Of Teaching Methods Designed To Improve Student Engagement And Retention Of Physics Subject Matter For Both Science And Non-Science Majors, Dan Maronde

Electronic Theses and Dissertations

The necessity of students’ engagement with the subject matter for successful learning is welldocumented in education research in general, and in physics education research in particular. This study examines the merits of two different programs designed to improve student learning through enhanced student engagement with the material. The target populations of the two programs are different: One is the group of students taking a physical science class as part of the general curriculum required of non-science, non-engineering majors; the other is the group of students, mostly in engineering disciplines, who must take the calculus-based introductory physics sequence as part of …

Design, Fabrication, And Testing Of High-Transparency Deep Ultra-Violet Contacts Using Surface Plasmon Coupling In Subwavelength Aluminum Meshes, Clarisse Mazuir

Electronic Theses and Dissertations

The present work aims at enhancing the external quantum efficiencies of ultra-violet (UV) sensitive photodetectors (PDs) and light emitting diodes (LEDs)for any light polarization. Deep UV solid state devices are made out of AlGaN or MgZnO and their performances suffer from the high resistivity of their p-doped regions. They require transparent p-contacts; yet the most commonly used transparent contacts have low transmission in the UV: indium tin oxide (ITO) and nickel-gold (Ni/Au 5/5 nms) transmit less than 50% and 30% respectively at 300 nm. Here we investigate the use of surface plasmons (SPs) to design transparent p-contacts for AlGaN devices …

Relativistic R-Matrix Theory, Janina Grineviciute

Dissertations

We have developed a relativistic coupled{channel reaction theory in which binary break-up channels satisfy a relative Dirac equation. This theory is developed by extending the R-matrix formalism of Lane and Thomas to the relativistic case and implementing the Dirac oscillator basis. The motivation for this project is testing po- tentials for the dense matter calculations and generating relativistic wave functions for the nal states in the knockout reactions. As an example of the formalism we have calculated observables for the proton scattering on light-to-medium weight nuclei in the relativistic impulse approximation using the relativistic Love-Franey amplitudes of Horowitz. The R-matrix …

Commissioning Of The Helical Orbit Spectrometer: A New Device For Measuring Nuclear Reactions In Inverse Kinematics, Jonathan C. Lighthall

Dissertations

The Helical Orbit Spectrometer (HELIOS) at Argonne National Laboratory is the first implementation of a radical new concept for measuring nuclear reactions. Direct nuclear transfer reactions are powerful tools for studying the properties of the atomic nucleus. A traditional example is the neutron-transfer reaction (d ,p), wherein an accelerated beam of deuterons d bombards a heavy target. The incoming deuteron transfers a neutron to the target nucleus and the outgoing proton p is detected to study the properties of the residual heavy nucleus. A new frontier of nuclear reaction studies involving short-lived exotic nuclei—which are unsuitable for use …