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Fundamental study of crack initiation and propagation. [Computer model of ductile fracture]

Description: Objective is to determine the fracture toughness of A533B-1 steel by computer modeling Charpy V-notch tests. A computer model of ductile fracture was developed that predicts fracture initiation. The model contains a set of material-dependent parameters obtained by computer simulations of small specimen tests. The computer calculations give detailed stress and strain histories up to the time of fracture, which are used to determine the model parameter values. The calibrated fracture model, that … more
Date: December 21, 1977
Creator: Norris, D.M. Jr.; Reaugh, J.E.; Moran, B.; Quinones, D.F. & Wilkins, M.L.
Partner: UNT Libraries Government Documents Department
open access

Absolute instrumental neutron activation analysis at Lawrence Livermore Laboratory

Description: The Environmental Science Division at Lawrence Livermore Laboratory has in use a system of absolute Instrumental Neutron Activation Analysis (INAA). Basically, absolute INAA is dependent upon the absolute measurement of the disintegration rates of the nuclides produced by neutron capture. From such disintegration rate data, the amount of the target element present in the irradiated sample is calculated by dividing the observed disintegration rate for each nuclide by the expected value for the d… more
Date: December 21, 1977
Creator: Heft, R.E.
Partner: UNT Libraries Government Documents Department
open access

Dissociative electron attachment to the H2O molecule II: nucleardynamics on coupled electronic surfaces within the local complexpotential model

Description: We report the results of a first-principles study of dissociative electron attachment (DEA) to H{sub 2}O. The cross sections were obtained from nuclear dynamics calculations carried out in full dimensionality within the local complex potential model by using the multi-configuration time-dependent Hartree method. The calculations employ our previously obtained global, complex-valued, potential energy surfaces for the three ({sup 2}B{sub 1}, {sup 2}A{sub 1}, and {sup 2}B{sub 2}) electronic Feshba… more
Date: December 21, 2006
Creator: Haxton, Daniel J.; Rescigno, Thomas N. & McCurdy, C. William
Partner: UNT Libraries Government Documents Department
open access

Charm Spectroscopy at BaBar

Description: We present a mini-review on charm spectroscopy at the BABAR experiment. We first report on the c{bar s} meson spectrum, and present precise measurements of the D{sub s1}(2536) meson as well as the properties of the many new states discovered since 2003 (D*{sub s0}(2317), D{sub s1}(2460), D*{sub sJ}(2860), and D{sub sJ}(2700) mesons). We then discuss about charmed baryons observed recently in the BABAR experiment: {Omega}{sub c}{sup 0} and {Omega}*{sub c}{sup 0} css baryons, {Lambda}{sub c}(2940… more
Date: December 21, 2007
Creator: Poireau, Vincent
Partner: UNT Libraries Government Documents Department
open access

Hierarchy of multiple many-body interaction scales in high-temperature superconductors

Description: To date, angle-resolved photoemission spectroscopy has been successful in identifying energy scales of the many-body interactions in correlated materials, focused on binding energies of up to a few hundred meV below the Fermi energy. Here, at higher energy scale, we present improved experimental data from four families of high-T{sub c} superconductors over a wide doping range that reveal a hierarchy of many-body interaction scales focused on: the low energy anomaly ('kink') of 0.03-0.09eV, a hi… more
Date: December 21, 2006
Creator: Hussain, Zahid; Meevasana, W.; Zhou, X. J.; Sahrakorpi, S.; Lee, W. S.; Yang, W. L. et al.
Partner: UNT Libraries Government Documents Department
open access

Scaling, Microstructure and Dynamic Fracture

Description: The relationship between pullback velocity and impact velocity is studied for different microstructures in Cu. A size distribution of potential nucleation sites is derived under the conditions of an applied stochastic stress field. The size distribution depends on flow stress leading to a connection between the plastic flow appropriate to a given microstructure and nucleation rate. The pullback velocity in turn depends on the nucleation rate resulting in a prediction for the relationship betwee… more
Date: December 21, 2005
Creator: Minich, R W; Kumar, M; Schwarz, A & Cazamias, J
Partner: UNT Libraries Government Documents Department
open access

Object Classification at the Nearby Supernova Factory

Description: We present the results of applying new object classification techniques to the supernova search of the Nearby Supernova Factory. In comparison to simple threshold cuts, more sophisticated methods such as boosted decision trees, random forests, and support vector machines provide dramatically better object discrimination: we reduced the number of nonsupernova candidates by a factor of 10 while increasing our supernova identification efficiency. Methods such as these will be crucial for maintaini… more
Date: December 21, 2007
Creator: Aragon, Cecilia R.; Bailey, Stephen; Aragon, Cecilia R.; Romano, Raquel; Thomas, Rollin C.; Weaver, B. A. et al.
Partner: UNT Libraries Government Documents Department
open access

Portable, Low-cost NMR with Laser-Lathe Lithography Produced

Description: Nuclear Magnetic Resonance (NMR) is unsurpassed in its ability to non-destructively probe chemical identity. Portable, low-cost NMR sensors would enable on-site identification of potentially hazardous substances, as well as the study of samples in a variety of industrial applications. Recent developments in RF microcoil construction (i.e. coils much smaller than the standard 5 mm NMR RF coils), have dramatically increased NMR sensitivity and decreased the limits-of-detection (LOD). We are using… more
Date: December 21, 2006
Creator: Herberg, J. L.; Demas, V.; Malba, V.; Bernhardt, A.; Evans, L.; Harvey, C. et al.
Partner: UNT Libraries Government Documents Department
open access

Evidence for p-type doping of InN

Description: No Description Available.
Date: December 21, 2005
Creator: Jones, R. E.; Yu, K. M.; Li, S. X.; Walukiewicz, W.; Ager, J. W., III; Haller, E. E. et al.
Partner: UNT Libraries Government Documents Department
open access

Limitations and Failures of the Layzer Model

Description: We report several limitations and failure modes of the recently expanded Layzer model for hydrodynamic instabilities. The failures occur for large initial amplitudes, for stable accelerations, and for spikes in two-fluid systems.
Date: December 21, 2007
Creator: Mikaelian, K O
Partner: UNT Libraries Government Documents Department
open access

Photonic Equation of Motion With Application to the Lamb Shift

Description: A photonic equation of motion is proposed which is the scalar product of four-vectors and therefore a Lorentz invariant. A photonic equation of motion, which has not been heretofore established in quantum electrodynamics (QED), would capture the quantum nature of light but yet not have the standard field-operator form, thereby making practical calculations easier to perform. The equation of motion proposed here is applied to the Lamb shift. No divergences exist, and the result agrees with the o… more
Date: December 21, 2006
Creator: Ritchie, A. B.
Partner: UNT Libraries Government Documents Department
open access

Readout of TPC Tracking Chambers with GEMs and Pixel Chip

Description: Two layers of GEMs and the ATLAS Pixel Chip, FEI3, have been combined and tested as a prototype for Time Projection Chamber (TPC) readout at the International Linear Collider (ILC). The double-layer GEM system amplifies charge with gain sufficient to detect all track ionization. The suitability of three gas mixtures for this application was investigated, and gain measurements are presented. A large sample of cosmic ray tracks was reconstructed in 3D by using the simultaneous timing and 2D spati… more
Date: December 21, 2007
Creator: Kadyk, John; Kim, T.; Freytsis, M.; Button-Shafer, J.; Kadyk, J.; Vahsen, S.E. et al.
Partner: UNT Libraries Government Documents Department
open access

Cavity BPM System Tests for the ILC Spectrometer

Description: The main physics program of the International Linear Collider (ILC) requires a measurement of the beam energy at the interaction point with an accuracy of 10{sup -4} or better. To achieve this goal a magnetic spectrometer using high resolution beam position monitors (BPMs) has been proposed. This paper reports on the cavity BPM system that was deployed to test this proposal. We demonstrate sub-micron resolution and micron level stability over 20 hours for a 1 m long BPM triplet. We find micron-… more
Date: December 21, 2007
Creator: Slater, M.
Partner: UNT Libraries Government Documents Department
open access

Synchrotron Facilities and Free Electron Lasers

Description: Synchrotron radiation (SR) is electromagnetic radiation emitted when a charged particle travels along a curved trajectory. Initially encountered as a nuisance around orbits of high energy synchrotron accelerators, it gradually became an indispensable research tool in many applications: crystallography, X-ray lithography, micromechanics, structural biology, microprobe X-ray experiments, etc. So-called first generation SR sources were exploiting SR in parasitic mode at electron accelerators built… more
Date: December 21, 2007
Creator: Vaclav, Vylet; U., /Duke & Liu, James
Partner: UNT Libraries Government Documents Department
open access

An Innovative Method for Dynamic Characterization of Fan FilterUnit Operation.

Description: Fan filter units (FFU) are widely used to deliver re-circulated air while providing filtration control of particle concentration in controlled environments such as cleanrooms, minienvironments, and operating rooms in hospitals. The objective of this paper is to document an innovative method for characterizing operation and control of an individual fan filter unit within its operable conditions. Built upon the draft laboratory method previously published [1] , this paper presents an updated meth… more
Date: December 21, 2006
Creator: Xu, Tengfang
Partner: UNT Libraries Government Documents Department
open access

An LTCC 94 GHz Antenna Array

Description: An antenna array is designed in low-temperature cofired ceramic (LTCC) Ferro A6M{trademark} for a mm-wave application. The antenna is designed to operate at 94 GHz with a few percent bandwidth. A key manufacturing technology is the use of 3 mil diameter vias on a 6 mil pitch to construct the laminated waveguides that form the beamforming network and radiating elements. Measurements for loss in the laminated waveguide are presented. The slot-fed cavity-radiating element is designed to account fo… more
Date: December 21, 2007
Creator: Aguirre, J; Pao, H; Lin, H; Garland, P; O'Neill, D & Horton, K
Partner: UNT Libraries Government Documents Department
open access

Photofragment Translational Spectroscopy of Propargyl Radicals at 248 nm

Description: The photodissociation of propargyl radical, C{sub 3}H{sub 3}, and its perdeuterated isotopolog was investigated using photofragment translational spectroscopy. Propargyl radicals were produced by 193 nm photolysis of allene entrained in a molecular beam expansion, and then photodissociated at 248 nm. photofragment time-of-flight spectra were measured at a series of laboratory angles using electron impact ionization coupled to a mass spectrometer. Data for ion masses corresponding to C{sub 3}H{s… more
Date: December 21, 2007
Creator: Goncher, S. J.; Moore, D. T.; Sveum, N. E. & Neumark, D. M.
Partner: UNT Libraries Government Documents Department
open access

Comparisons of hydrodynamic beam models with kinetic treatments. Revision 1

Description: Hydrodynamic models have been derived by Mark and Yu and by others to described energetic self-pinch beams, such as those used in ion-beam fusion. The closure of the Mark-Yu model is obtained with adiabatic assumptions mathematically analogous to those of Chew, Goldberger, and Low for MHD. The other models treated here use an ideal gas closure and a closure by Newcomb based on an expansion in V/sub th//V/sub z/. Features of these hydrodynamic beam models are compared with a kinetic treatment.
Date: December 21, 1983
Creator: Boyd, J. K.; Mark, J. W.; Sharp, W. M. & Yu, S. S.
Partner: UNT Libraries Government Documents Department
open access

Atomic processes in high-density plasmas

Description: This review covers dense atomic plasmas such as that produced in inertial confinement fusion. The target implosion physics along with the associated atomic physics, i.e., free electron collision phenomena, electron states I, electron states II, and nonequilibrium plasma states are described. (MOW)
Date: December 21, 1982
Creator: More, R.M.
Partner: UNT Libraries Government Documents Department
open access

Sol-gel coatings for high power laser optics-past, present and future

Description: An investigation into the preparation of sol-gel coatings for high power lasers was started at LLNL in 1983 and AR coatings were successfully developed for use in the Nova laser in 1984. Several other large lasers now use these coatings. Subsequent work on HR coatings resulted in AlOOH/SiO{sub 2} and later ZrO{sub 2} or HfO{sub 2}/SiO{sub 2} systems of good optical performance. The use of organic polymer binders gave increased damage threshold and enhanced optical performance. We are in the pro… more
Date: December 21, 1993
Creator: Thomas, I. M.
Partner: UNT Libraries Government Documents Department
open access

A Task Adaptive parallel graphics renderer

Description: This paper presents a graphics renderer which incorporates new partitioning methodologies of memory and work for efficient execution on a parallel computer. The Task Adaptive domain decomposition scheme is an image space method involving dynamic partitioning of rectangular pixel area tasks. The author shows that this method requires little overhead, allows coherence within a parallel context, handles worst case scenarios effectively, and executes efficiently with little processor synchronizatio… more
Date: December 21, 1992
Creator: Whitman, S.
Partner: UNT Libraries Government Documents Department
open access

Coarse-Grained Molecular Dynamics and Multiscale Modeling of NEMS Resonators

Description: We review concurrent multiscale simulations of dynamic and temperature-dependent processes found in nanomechanical systems coupled to larger scale surroundings. We focus on the behavior of sub-micron Micro-Electro-Mechanical Systems (MEMS), especially microresonators. These systems are often called NEMS, for Nano-Electro-Mechanical Systems. The coupling of length scales methodology we have developed for MEMS employs an atomistic description of small but key regions of the system, consisting of … more
Date: December 21, 2001
Creator: Rudd, R E
Partner: UNT Libraries Government Documents Department
open access

The status of open heavy flavor production at RHIC

Description: We discuss the calculation of open heavy flavor cross sections at RHIC and describe how the semileptonic decays of charm and bottom quarks can be separated.
Date: December 21, 2010
Creator: Vogt, R
Partner: UNT Libraries Government Documents Department
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