68 Matching Results

Search Results

Results: 1 - 24 next
open access

Determination of the spin-flip time in ferromagnetic SrRuO3 from time-resolved Kerr measurements

Description: We report time-resolved Kerr effect measurements of magnetization dynamics in ferromagnetic SrRuO{sub 3}. We observe that the demagnetization time slows substantially at temperatures within 15K of the Curie temperature, which is {approx} 150K. We analyze the data with a phenomenological model that relates the demagnetization time to the spin flip time. In agreement with our observations the model yields a demagnetization time that is inversely proportional to T-T{sub c}. We also make a direct c… more
Date: July 30, 2010
Creator: Kantner, C. L. S.; Langner, M. C.; Siemons, W.; Blok, J. L.; Koster, G.; Rijnders, A.J. H. M. et al.
Partner: UNT Libraries Government Documents Department
open access

Holey Silicon as an Efficient Thermoelectric Material

Description: This work investigated the thermoelectric properties of thin silicon membranes that have been decorated with high density of nanoscopic holes. These ?holey silicon? (HS) structures were fabricated by either nanosphere or block-copolymer lithography, both of which are scalable for practical device application. By reducing the pitch of the hexagonal holey pattern down to 55 nm with 35percent porosity, the thermal conductivity of HS is consistently reduced by 2 orders of magnitude and approaches t… more
Date: September 30, 2010
Creator: Tang, Jinyao; Wang, Hung-Ta; Hyun Lee, Dong; Fardy, Melissa; Huo, Ziyang; Russell, Thomas P. et al.
Partner: UNT Libraries Government Documents Department
open access

2010 Thin Film & Small Scale Mechanical Behavior Gordon Research Conference

Description: Over the past decades, it has been well established that the mechanical behavior of materials changes when they are confined geometrically at least in one dimension to small scale. It is the aim of the 2010 Gordon Conference on 'Thin Film and Small Scale Mechanical Behavior' to discuss cutting-edge research on elastic, plastic and time-dependent deformation as well as degradation mechanisms like fracture, fatigue and wear at small scales. As in the past, the conference will benefit from contrib… more
Date: July 30, 2010
Creator: Balk, Dr. Thomas
Partner: UNT Libraries Government Documents Department
open access

Bottom Production from Fixed-Target to Large Hadron Collider Energies

Description: We present a state-of-the-art compilation of the existing bottom production cross sections in elementary collisions, from fixed-target to collider experiments. We then discuss the theoretical uncertainties on the total and differential bottom cross sections in the FONLL approach. In particular, we show total cross sections and kinematical distributions of the bottom hadrons and their decays: B {yields} e/{mu}X, B {yields} D {yields} e/{mu}, and B {yields} J/{psi}X. After seeing that the calcula… more
Date: November 30, 2010
Creator: Nelson, R. E.; Vogt, R.; Lourenco, C. & Wohri, H. K.
Partner: UNT Libraries Government Documents Department
open access

J/psi production and absorption in p + A and d+Au collisions

Description: The level of 'anomalous' charmonium suppression in high-energy heavy-ion collisions and its interpretation as a signal of quark-gluon plasma formation requires a robust understanding of charmonium production and absorption in proton-nucleus collisions. In a previous study we have shown that, contrary to common belief, the so-called J/{psi} 'absorption cross section', {sigma}{sub abs}{sup J/{psi}}, is not a 'universal constant' but, rather, an effective parameter that depends very significantly … more
Date: November 30, 2010
Creator: Vogt, R; Lourenco, C & Woehri, H
Partner: UNT Libraries Government Documents Department
open access

Determination of Natural Beryllium (Be) in Soil and Swipe Samples Utilizing Yttrium/Beryllium Ratio

Description: 1. Objective: A method to determine whether beryllium (Be) components in surface swipe samples are from a natural source is needed. 2. Methods: Soil samples and surface swipes from area facilities were analyzed for marker elements to identify source pathways for beryllium (Be). To be useful, the natural marker element must be present at reasonably consistent levels across the site, must correlate with the Be concentration, and not have the potential to be present from non-natural sources. 3. Re… more
Date: September 30, 2010
Partner: UNT Libraries Government Documents Department
open access

OVERVIEW OF IMPACTS OF TECHNOLOGY DEPLOYMENT ON THE MISSION OF THE DEPARTMENT OF ENERGY OFFICE OF ENVIRONMENTAL MANAGEMENT

Description: The Environmental Management (EM) mission is to complete the safe cleanup of the environmental legacy brought about from five decades of nuclear weapons development and government-sponsored nuclear energy research. The EM program has embraced a mission completion philosophy based on reducing risk and environmental liability over a 40-50 year lifecycle. The Department has made great progress toward safely disposing of its legacy nuclear waste. EM Research and Development (R&D) program manage… more
Date: November 30, 2010
Creator: McCabe, D.; Chamberlain, G.; Looney, B. & Gladden, J.
Partner: UNT Libraries Government Documents Department
open access

2010 Membranes: Materials & Processes Gordon Research Conference

Description: The GRC series on Membranes: Materials and Processes have gained significant international recognition, attracting leading experts on membranes and other related areas from around the world. It is now known for being an interdisciplinary and synergistic meeting. The next summer's edition will keep with the past tradition and include new, exciting aspects of material science, chemistry, chemical engineering, computer simulation with participants from academia, industry and national laboratories.… more
Date: July 30, 2010
Creator: Lin, Jerry
Partner: UNT Libraries Government Documents Department
open access

ASPH modeling of Material Damage and Failure

Description: We describe our new methodology for Adaptive Smoothed Particle Hydrodynamics (ASPH) and its application to problems in modeling material failure. We find that ASPH is often crucial for properly modeling such experiments, since in most cases the strain placed on materials is non-isotropic (such as a stretching rod), and without the directional adaptability of ASPH numerical failure due to SPH nodes losing contact in the straining direction can compete with or exceed the physical process of failu… more
Date: April 30, 2010
Creator: Owen, J M
Partner: UNT Libraries Government Documents Department
open access

TIMELY DELIVERY OF LASER INERTIAL FUSION ENERGY (LIFE)

Description: The National Ignition Facility (NIF), the world's largest and most energetic laser system, is now operational at Lawrence Livermore National Laboratory. A key goal of the NIF is to demonstrate fusion ignition for the first time in the laboratory. Its flexibility allows multiple target designs (both indirect and direct drive) to be fielded, offering substantial scope for optimization of a robust target design. In this paper we discuss an approach to generating gigawatt levels of electrical power… more
Date: November 30, 2010
Creator: Dunne, A M
Partner: UNT Libraries Government Documents Department
open access

Analysis of NSTX Upgrade OH Magnet and Center Stack

Description: The new ohmic heating (OH) coil and center stack for the National Spherical Torus Experiment (NSTX) upgrade are required to meet cooling and structural requirements for operation at the enhanced 1 Tesla toroidal field and 2 MA plasma current. The OH coil is designed to be cooled in the time between discharges by water flowing in the center of the coil conductor. We performed resistive heating and thermal hydraulic analyses to optimize coolant channel size to keep the coil temperature below 100 … more
Date: November 30, 2010
Creator: A. Zolfaghari, P. Titus, J. Chrzanowski, A. Salehzadeh, F. Dahlgren
Partner: UNT Libraries Government Documents Department
open access

Coarse Spaces by Algebraic Multigrid: Multigrid Convergence and Upscaled Error Estimates

Description: We give an overview of a number of algebraic multigrid methods targeting finite element discretization problems. The focus is on the properties of the constructed hierarchy of coarse spaces that guarantee (two-grid) convergence. In particular, a necessary condition known as 'weak approximation property', and a sufficient one, referred to as 'strong approximation property' are discussed. Their role in proving convergence of the TG method (as iterative method) and also on the approximation proper… more
Date: April 30, 2010
Creator: Vassilevski, P S
Partner: UNT Libraries Government Documents Department
open access

A Plasma Lens for Magnetron Sputtering

Description: A plasma lens, consisting of a solenoid and potential-defining ring electrodes, has been placed between a magnetron and substrates to be coated. Photography reveals qualitative information on excitation, ionization, and the transport of plasma to the substrate.
Date: November 30, 2010
Creator: Anders, Andre & Brown, Jeff
Partner: UNT Libraries Government Documents Department
open access

GyPSuM: A Detailed Tomographic Model of Mantle Density and Seismic Wave Speeds

Description: GyPSuM is a tomographic model fo mantle seismic shear wave (S) speeds, compressional wave (P) speeds and detailed density anomalies that drive mantle flow. the model is developed through simultaneous inversion of seismic body wave travel times (P and S) and geodynamic observations while considering realistic mineral physics parameters linking the relative behavior of mantle properties (wave speeds and density). Geodynamic observations include the (up to degree 16) global free-air gravity field,… more
Date: March 30, 2010
Creator: Simmons, N A; Forte, A M; Boschi, L & Grand, S P
Partner: UNT Libraries Government Documents Department
open access

DEVELOPMENT OF CERAMIC WASTE FORMS FOR AN ADVANCED NUCLEAR FUEL CYCLE

Description: A series of ceramic waste forms were developed and characterized for the immobilization of a Cesium/Lanthanide (CS/LN) waste stream anticipated to result from nuclear fuel reprocessing. Simple raw materials, including Al{sub 2}O{sub 3} and TiO{sub 2} were combined with simulated waste components to produce multiphase ceramics containing hollandite-type phases, perovskites (particularly BaTiO{sub 3}), pyrochlores and other minor metal titanate phases. Three fabrication methodologies were used, i… more
Date: November 30, 2010
Creator: Marra, J.; Billings, A.; Brinkman, K. & Fox, K.
Partner: UNT Libraries Government Documents Department
open access

Doping evolution of the electronic structure in the single-layer cuprates Bi2Sr2&#8722xLaxCuO6 delta: Comparison with other single-layer cuprates

Description: We have performed angle-resolved photoemission and core-level x-ray photoemission studies of the single-layer cuprate Bi{sub 2}Sr{sub 2-x}La{sub x}CuO{sub 6+{delta}} (Bi2201) and revealed the doping evolution of the electronic structure from the lightly-doped to optimally-doped regions. We have observed the formation of the dispersive quasi-particle band, evolution of the Fermi 'arc' into the Fermi surface and the shift of the chemical potential with hole doping as in other cuprates. The doping… more
Date: April 30, 2010
Creator: Hashimoto, M.
Partner: UNT Libraries Government Documents Department
open access

Normal State Spectral Lineshapes of Nodal Quasiparticles in Single Layer Bi2201 Superconductor

Description: A detailed study of the normal state photoemission lineshapes and quasiparticle dispersion for the single layer Bi{sub 2}Sr{sub 2-x}La{sub x}CuO{sub 6+{delta}}(Bi2201) superconductor is presented. We report the first experimental evidence of a double peak structure and a dip of spectral intensity in the energy distribution curves (EDCs) along the nodal direction. The double peak structure is well identified in the normal state, up to ten times the critical temperature. As a result of the same s… more
Date: April 30, 2010
Creator: Lanzara, A.
Partner: UNT Libraries Government Documents Department
open access

Angle-Resolved Photoemission Spectroscopy on Electronic Structure and Electron-Phonon Coupling in Cuprate Superconductors

Description: In addition to the record high superconducting transition temperature (T{sub c}), high temperature cuprate superconductors are characterized by their unusual superconducting properties below T{sub c}, and anomalous normal state properties above T{sub c}. In the superconducting state, although it has long been realized that superconductivity still involves Cooper pairs, as in the traditional BCS theory, the experimentally determined d-wave pairing is different from the usual s-wave pairing found… more
Date: April 30, 2010
Creator: Zhou, X.J.
Partner: UNT Libraries Government Documents Department
open access

Dense Metal Plasma in a Solenoid for Ion Beam Neutralization

Description: Space-charge neutralization is required to compress and focus a pulsed, high-current ion beam on a target for warm dense matter physics or heavy ion fusion experiments. We described approaches to produce dense plasma in and near the final focusing solenoid through which the ion beam travels, thereby providing an opportunity for the beam to acquire the necessary space-charge compensating electrons. Among the options are plasma injection from pulsed vacuum arc sources located outside the solenoid… more
Date: October 30, 2010
Creator: Anders, Andre; Kauffeldt, Marina; Oks, Efim M. & Roy, Prabir K.
Partner: UNT Libraries Government Documents Department
open access

Initial and Final State Interaction Effects in Small-x Quark Distributions

Description: We study the initial and final state interaction effects in the transverse momentum dependent parton distributions in the small-x saturation region. In particular, we discuss the quark distributions in the semi-inclusive deep inelastic scattering, Drell-Yan lepton pair production and dijet-correlation processes in pA collisions. We calculate the quark distributions in the scalar-QED model and then extend to the color glass condensate formalism in QCD. The quark distributions are found universal… more
Date: August 30, 2010
Creator: Xiao, Bo-Wen & Yuan, Feng
Partner: UNT Libraries Government Documents Department
open access

Robust Computation of Morse-Smale Complexes of Bilinear Functions

Description: The Morse-Smale (MS) complex has proven to be a useful tool in extracting and visualizing features from scalar-valued data. However, existing algorithms to compute the MS complex are restricted to either piecewise linear or discrete scalar fields. This paper presents a new combinatorial algorithm to compute MS complexes for two dimensional piecewise bilinear functions defined on quadrilateral meshes. We derive a new invariant of the gradient flow within a bilinear cell and use it to develop a p… more
Date: November 30, 2010
Creator: Norgard, G. & Bremer, P. T.
Partner: UNT Libraries Government Documents Department
open access

Towards improved characterization of high-risk releases using heterogeneous indoor sensor systems

Description: The sudden release of toxic contaminants that reach indoor spaces can be hazardous to building occupants. For an acutely toxic contaminant, the speed of the emergency response strongly influences the consequences to occupants. The design of a real time sensor system is made challenging both by the urgency and complex nature of the event, and by the imperfect sensors and models available to describe it. In this research, we use Bayesian modeling to combine information from multiple types of sens… more
Date: June 30, 2010
Creator: Sreedharan, Priya; Sohn, Michael D.; Nazaroff, William W. & J. Gadgil, Ashok
Partner: UNT Libraries Government Documents Department
open access

Hollow Plasma in a Solenoid

Description: A ring cathode for a pulsed, high-current, multi-spot cathodic arc discharge was placed inside a pulsed magnetic solenoid. Photography is used to evaluate the plasma distribution. The plasma appears hollow for cathode positions close the center of the solenoid, and it is guided closer to the axis when the cathode is away from the center.
Date: November 30, 2010
Creator: Anders, Andre; Kauffeldt, Marina; Oks, Efim M. & Roy, Prabir K.
Partner: UNT Libraries Government Documents Department
Back to Top of Screen