Physics Commons^™

Self-Assembled Nano-Structures On The Icosahedral Al-Pd-Mn Quasicrystal, Mehmet Erbudak, Jean-Nicolas Longchamp, Yves Weisskopf

Turkish Journal of Physics

A quasicrystal is a solid with an aperiodic atomic distribution, but displaying discrete diffraction pattern. At an interface where an ordinary crystal and a quasicrystal intersect, the lack of commensurability between the structures leads to misfits on atomic scale resulting in a wealth of novelties. Here, we present experimental observations on three essentially different cases: Al, Fe, and Si ultra-thin layers grown in vacuum on the pentagonal surface of an icosahedral Al-Pd-Mn quasicrystal. In all three cases, the growing layer decays into nm-size islands. Al is the major alloy component of the substrate material and provides a natural tool to …

Computational Studies On Mechanical Properties Of Carbon Nanotori, Tahi̇r Çağin, Guanghua Gao, William A. Goddard Iii

Turkish Journal of Physics

Carbon has diverse structures, especially (0-dimensional) fullerenes, (1-dimensional) tubes have generated great interest among scientists and technologists. Studies of the structures and properties of these low dimensional carbon molecules show tremendous potential for use in nanoscale device applications. Motivated by these exciting possibilities in finding new forms of carbon materials and their potential applications, we have designed hypothetical single wall carbon nano-toroids. Carbon toroids are also ideal in studying the elastic and plastic deformation behavior of nanotubes under bending loads. We can accurately correlate the behavior of the tubes to its uniform curvature. In this particular work we focused on …

Relativistic Density Functional Theory Method: Applications To Autoionization States Of Atoms, Şaki̇r Erkoç

Turkish Journal of Physics

A brief introductory information about the accurate atomic calculations using Density Functional Theory has been reviewed. How relativistic effects can be considered in atomic calculations through the density functional theory has been discussed. Some sample calculation results for the autoionization states of the neutral and cationic atoms have been presented.

Tkachenko Modes Of The Square Vortex Lattice In A Two-Component Bose-Einstein Condensate, M. Keçeli̇, M. Ö. Oktel

Turkish Journal of Physics

We study Tkachenko modes of the square vortex lattice of a two-component Bose-Einstein condensate (BEC) in the mean-field quantum Hall regime, considering the coupling of these modes with density excitations. We derive the hydrodynamic equations and obtain the dispersion relations of the excitation modes. We find that there are two types of excitations, gapped inertial modes and gapless Tkachenko modes. These modes have two branches which we call acoustic and optical modes in analogy with phonons. The former has quadratic while the latter has linear wave-number dependence in both inertial and Tkachenko modes. Acoustic Tkachenko mode is found to be …

Pseudopotential-Based Full Zone K . P Technique For Indirect Bandgap Semiconductors: Si, Ge, Diamond And Sic, Ceyhun Bulutay

Turkish Journal of Physics

The k . p is a versatile technique that describes the semiconductor band structure in the vicinity of the bandgap. The technique can be extended to full Brillouin zone by including more coupled bands into consideration. For completeness, a detailed formulation is provided where the associated k . p parameters are extracted from the local empirical pseudopotential method in the form of band edge energies and generalized momentum matrix elements. We demonstrate the systematic improvement of the technique with the proper choice of the band edge states for the group-IV indirect bandgap semiconductors: Si, Ge, diamond and SiC of the …

A Molecular Dynamics Study Of The Static Structure, Thermodynamic And Transport Properties Of Liquid Iron Using The Modified Analytic Embedded Atom Method, Serap Şentürk Dalgiç, İbrahi̇m Koçoğlu

Turkish Journal of Physics

Using the modified analytic embedded atom method (MAEAM), we have carried out molecular dynamics (MD) simulation to compute structure,thermodynamic and transport properties of liquid iron. The Foiles type effective pair potential based on the MAEAM potential functions proposed by Quyang and co-workers are shown to predict the pair distribution function well near its melting. The calculated thermodynamic properties such as, the internal energy, Helmholtz free energy and entropy are in a good agreement with experimental data. The results for the computed self-diffusion coefficients are in reasonable agreement with experiments and other works.

Self-Diffusion Coefficients In Liquid Ag Using The Embedded Atom Model Based Effective Pair Potentials, Seyfetti̇n Dalgiç, Mutlu Çolakoğullari

Turkish Journal of Physics

We present the dynamical properties of liquid Ag at different temperatures, using the Mishin and Doyoma-Kagure version of the Embedded Atom Model (EAM) potentials. They have been evaluated within the framework of the mode-coupling theory, using a self-consistent scheme that uses as input data only the static structure functions and the interatomic pair potentials of the liquid Ag. We have computed single-particle and collective time dependent properties of liquid Ag, and thereby calculated its self-diffusion constants. We have also discussed our results comparing with both experimental data and results of molecular dynamic simulation.

Molecular Dynamics Study Of Thermal Properties Of Intermetallic Alloys, H. H. Kart, Mehmet Tomak, Tahi̇r Çağin

Turkish Journal of Physics

Molecular dynamics simulations of bulk copper, gold pure metals and their ordered intermetallics alloys of Cu_3Au(L1_2) and CuAu_3(L1_2) have been carried out between above 0 K and below the their melting points of the materials for predicting their temperature-dependent thermophysical properties. The effects of temperature and concentration on the physical properties such as enthalpy, volume, heat capacity, thermal expansion and density of Cu_xAu_{1-x} are studied. Especially, temperature-dependent polynomial functions of enthalpy, volume and density are obtained. Sutton-Chen (SC) and Quantum Sutton-Chen (Q-SC) many-body potentials are used in the constant enthalpy-constant pressure ensemble (HPN) and constant pressure-constant temperature ensemble (TPN). Three …

A Detailed Ensemble Monte Carlo Study Of The Effect Of Quantum Well Width On Quantum Well Infrared Photodetector Characteristics, Sema Memi̇ş, Oray Orkun Cellek, Umut Bostanci, Mehmet Tomak, Cengi̇z Beşi̇kçi̇

Turkish Journal of Physics

We present a simulation based investigation of the dependence of the device characteristics on the quantum well width in AlGaAs/GaAs quantum well infrared photodetectors (QWIPs) through the ensemble Monte Carlo technique. The simulations on two different standard Al_{0.3}Ga_{0.7}As/GaAs QWIPs with quantum well widths of 36 and 44 Å have shown that the gain in the former is considerably higher, which is due to much longer lifetime of the photoexcited electrons as a result of lower capture probability in the device. We discuss this observation by the investigation of the electron scattering rates in these structures through realistically evaluated scattering mechanisms …

Casimir Energies For Some Single Cavities, Haci Ahmedov, İsmai̇l Hakki Duru

Turkish Journal of Physics

Casimir energies are discussed for some cavities.

The Symmetric Teleparallel Gravity, Muzaffer Adak

Turkish Journal of Physics

We study symmetric teleparallel (STP) gravity model, in which only spacetime non-metricity is nonzero. First we obtain STP equivalent Einstein-Hilbert Lagrangian and give an approach for a generic solution in terms of only metric tensor. Then we obtain a spherically symmetric static solution to the Einstein's equation in STP space-time and discuss the singularities. Finally, we study a model given by a Lagrangian 4-form quadratic in non-metricity. Thus, we seek Schwarzschild-type solutions because of its observational success and obtain some sets of solutions. Finally, we discuss physical relevance of the solutions.

Degenerate Spin Structures And The Lévy-Leblond Equation, Teki̇n Dereli̇, Şahi̇n Koçak, Murat Li̇moncu

Turkish Journal of Physics

Newton-Cartan manifolds and the Galilei group are defined by the use of co-rank one degenerate metric tensor. Newton-Cartan connection is lifted to the degenerate spinor bundle over a Newton-Cartan 4-manifold by the aid of degenerate spin group. Levy-Leblond equation is constructed with the lifted connection.

Explicit Realization Of Pseudo-Hermitian And Quasi-Hermitian Quantum Mechanics For Two-Level Systems, Ali̇ Mostafazadeh, Seher Özçeli̇k

Turkish Journal of Physics

We give an explicit characterization of the most general quasi-Hermitian operator H, the associated metric operators \eta_+, and \eta_+-pseudo-Hermitian operators acting in C^2. The latter represent the physical observables of a model whose Hamiltonian and Hilbert space are respectively H and \C^2 endowed with the inner product defined by \eta_+. Our calculations allows for a direct demonstration of the fact that the choice of an irreducible family of observables fixes the metric operator up to a multiplicative factor.

Infinite-Hamiltonian Structures Of The Riemann Equation, Refi̇k Turhan

Turkish Journal of Physics

We give two distinct infinite-Hamiltonian representations for the Riemann equation. One with first order Hamiltonian operators and another with third order-first order Hamiltonian operators. Both representations contain an arbitrary function of the dynamical variable. We prove that all the Hamiltonian operators of the Riemann equation are mutually compatible.

Non-Commutative And Non-Anticommutative Supersymmetric U(1) Gauge Theories, Kayhan Ülker

Turkish Journal of Physics

We introduce a parent action for component fields of N=1 supersymmetric U(1) gauge theory in four dimensions which generates both the original and the (s-) dual supersymmetric actions. By using the noncommutative and nonanticommutative deformations of this theory we propose the corresponding parent actions as generalizations of the ordinary case. We then show that duality symmetry under the interchange of fields with duals accompanied by the replacement of the noncommutativity and nonanticommutativity parameters in a suitable way.

Hamilton-Jacobi Formulation Of Siegel Superparticle, N. I. Farahat, Hanaa A. Elegla

Turkish Journal of Physics

The Hamilton-Jacobi formalism of constrained systems is used to study Siegel superparticles moving in R^{4 mid 4} flat superspace. The equations of motion for a singular system are obtained as total differential equations in many variables. These equations of motion are in exact agreement with those obtained by Dirac's method.

Ibm-2 Calculations Of Selected Even-Even Ruthenium Nuclei, İlyas İnci̇, Nuretti̇n Türkan

Turkish Journal of Physics

In this study, we have employed the Interacting Boson Model-2 (IBM-2) to determine the most appropriate Hamiltonian for the study of ruthenium nuclei in the region A \cong 100. Using the best fit values of parameters to construct the Hamiltonian, we have estimated energy levels and multipole mixing ratios (\delta (E2/M1)) for some doubly-even Ru nuclei. The results are compared with previous experimental and theoretical data and it is observed that they are in good agreement.

Ibm-2 Calculations Of Selected Even-Even Palladium Nuclei, İlyas İnci̇, Nuretti̇n Türkan

Turkish Journal of Physics

In this study, we have employed the Interacting Boson Model-2 (IBM-2) to determine the most appropriate Hamiltonian for the study of palladium nuclei. Using the best fit values of parameters to construct the Hamiltonian, we have estimated energy levels and multipole mixing ratios (\delta (E2/M1)) for some doubly-even Pd nuclei. The results are compared with previous experimental and theoretical data and it is observed that they are in good agreement.

Band Gap Of Cubic Aln, Gan And Inn Compounds Under Pressure, S. Berrah, Hamza Abid, A. Boukortt, Mohamed Sehil

Turkish Journal of Physics

Numerical simulation based on FP-LAPW calculations is applied to study the lattice parameters, bulk modulus and band gap energy of zinc blende binaries AlN, GaN and InN under hydrostatic pressure. The results obtained are in a good agreement with experimental and theoretical values.

Influence Of Thickness On Optical Properties Of A: As_2se_3 Thin Films, Dinesh C. Sati, Rajendra Kumar, Ram Mohan Mehra

Turkish Journal of Physics

This paper reports optical properties of amorphous chalcogenide thin films of As_2Se_3 of different thicknesses 2000-6800 Å. The transmittance and reflectance of thin films were measured in the wavelength range 500-1000 nm. It was found that the optical band gap increases with film thickness. Variation of refractive index n and extinction coefficient k with thickness have been studied to analyze optical efficiency of the As_2Se_3 thin films. The dielectric behavior of the films has also been studied and high frequency dielectric constants \varepsilon_{\infty} has been estimated as a function of thickness of films.

Comment On "Characterization Of In_4te_3 Single Crystals", M. Cankurtaran, H. Çeli̇k

Turkish Journal of Physics

No abstract provided.

Monodomain Dynamics For Rigid Rod And Platelet Suspensions In Strongly Coupled Coplanar Linear Flow And Magnetic Fields. Ii. Kinetic Theory, M. Gregory Forest, Sarthok Sircar, Qi Wang, Ruhai Zhou

Mathematics & Statistics Faculty Publications

We establish reciprocity relations of the Doi-Hess kinetic theory for rigid rod macromolecular suspensions governed by the strong coupling among an excluded volume potential, linear flow, and a magnetic field. The relation provides a reduction of the flow and field driven Smoluchowski equation: from five parameters for coplanar linear flows and magnetic field, to two field parameters. The reduced model distinguishes flows with a rotational component, which map to simple shear (with rate parameter) subject to a transverse magnetic field (with strength parameter), and irrotational flows, for which the reduced model consists of a triaxial extensional flow (with two extensional …

Noise Characerization For Proposed Ucf Phyiscal Science Building Sites., Jorge Martinez

Electronic Theses and Dissertations

Today's Advance Technology Facilities require low noise levels and increased noise monitoring. Ambient noise can interfere with the accuracy and precision of experiments and manufacturing processes. Therefore preconstruction site surveys are needed to develop strategies for mitigating noise. Vibration and low frequency electromagnetic fields are particularly detrimental for sensitive instruments, and they are also difficult to mitigate. However a large part of these costs can be avoided or minimized if a quiet building site is selected in the first place. Accelerometers and gauss meters combined with a computer for acquisition and analysis provide a low cost method of evaluating noise …

Potential Of Vibrational Spectroscopy In The Diagnosis Of Human Tumours., Eoghan O'Faolain

Doctoral

Just fewer than 20,000 people are annually diagnosed with some form of cancer in Ireland and one in three people are likely to contract some form of cancer by age 74. With the number of cases increasing at an annual rate of 2%, the early detection and treatment of cancer is becoming increasingly important. Both IR and Raman spectroscopy offer the potential for real time, quantitative detection of cancer and even precancer. This study investigates the potential of Raman and Fourier transform infrared, both benchtop and synchrotron spectroscopies for the detection of cervical cancer. The tissue was classified and its …

Dissolution, Reactor, And Environmental Behavior Of Zro2-Mgo Inert Fuel Matrix: Neutronic Evaluation Of Zro2-Mgo Inert Fuels, E. Fridman, A. Galperin, E. Shwageraus

Fuels Campaign (TRP)

Various fuel cycle concepts for plutonium incineration in existing PWR loaded with Inert Matrix Fuel (IMF), in which uranium is replaced by neutron-transparent inert matrix material, are currently under investigation at BGU. Some of the studied designs include ZrO₂-based IMF with annular fuel geometry and ZrO₂-MgO based IMF with the relative amount of MgO varied from 30v/o to 70v/o. These concepts are analyzed via detailed three-dimensional full core simulation of existing PWR including thermal-hydraulic feedback. The whole core simulations are carried out with the SILWER code. The SILWER code, which is a part of the ELCOS …

University Of Nevada, Las Vegas Transmutation Research Program Annual Report Academic Year 2005-2006, Anthony Hechanova, Rebecca Arbour

Transmutation Research Program Reports (TRP)

It is my pleasure to present the UNLV Transmutation Research Program’s fifth annual report that highlights the academic year 2005 – 2006. Supporting this document are the many technical reports and scientific papers that have been generated over the past five years.

In the fifth year of our program, we saw amazing growth in the Radiochemistry Ph.D. program with a total of 12 students in the second year of the program (twice the number we anticipated in the program proposal). In the back of this issue, under Infrastructure Augmentation, you will find some news about the new academic programs sponsored …

Investigation Of Optical Spectroscopy Techniques For On-Line Materials Accountability In The Solvent Extraction Process, Gary Cerefice, Kenneth Czerwinski

Safeguards Campaign (TRP)

The long-term goal of this project is the evaluation of optical spectroscopy-based techniques for the on-line, real-time determination of actinide element concentrations in fuel recycling plant process streams. To generate the information necessary to evaluate the potential of these systems, initial experiments will focus on determining the detection limits for UV/Vis and LFS will be measured for the actinide elements under chemical conditions representative of the process streams for the UREX+ process. The system will then be systematically explored to examine the impact of acid concentration, nitrate concentration, redox potential, diluent concentration, ligand concentration, and contaminant/ fission product concentration on …

Optical Spectroscopy: Quarterly Report: 01/01/06 – 03/31/06, Harry Reid Center For Environmental Studies. Nuclear Science And Technology Division

Safeguards Campaign (TRP)

Progress report for the quarter: laser system alignment finished, site visit scheduled for final spectrometer configuration; initial studies on UO2 2+/NO3 -/H+ completed; preliminary data regression in progress; preliminary work on uranyl/AHA and organic/aqueous interface systems started.

Combined Radiation Detection Methods For Assay Of Higher Actinides In Separation Processes (Afci), Denis Beller, Warnick Kernan

Safeguards Campaign (TRP)

The ultimate objective of this project is to develop technology to detect and accurately measure quantities of higher actinides in processing systems without taking frequent samples. These systems include used fuel receipt, separations batches, and pipelines. A variety of measurements may be combined to calculate flow rates of actinide elements with a to-be-determined precision. Nuclear and decay characteristics of materials during processing will be acquired, conceptual designs of monitoring systems will be developed, radiation transport studies will be conducted to develop an understanding of operational regimes, and experiments will be performed to confirm performance. Radiation transport and scoping studies will …

Neutron Multiplicity Measurements Of Target/Blanket Materials, Denis Beller

Transmutation Sciences Physics (TRP)

The U.S. Advanced Fuel Cycle Initiative (AFCI) is a program to develop economic and environmental methods to reduce the impact of waste from commercial nuclear fuel cycles. One concept for near-complete destruction of waste isotopes from used nuclear fuel is accelerator-driven transmutation. High-power accelerators would be used to produce high-energy charged particles, which then collide with heavy metal targets to create a cascade of neutrons. These neutrons then cause nuclear reactions in subcritical systems.

To design these systems, complex reactor physics computer codes and highly detailed data libraries are used to compute the reactivity of systems, reaction rates, destruction rates, …