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11,805 Matching Results
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INTERACTIONS OF DETONATION WAVES IN CONDENSED EXPLOSIVES
None
Date:
January 1, 1965
Creator:
Gardner, S.D. & Wackerle, J.
Object Type:
Report
System:
The UNT Digital Library
Parallel algorithm for transient solid dynamics simulations using finite elements and smoothed particle hydrodynamics
An efficient, scalable, parallel algorithm for treating contacts in solid mechanics has been applied to interactions between particles in smooth particle hydrodynamics (SPH). The algorithm uses three different decompositions within a single timestep: (1) a static FE-decomposition of mesh elements; (2) a dynamic SPH-decomposition of SPH particles; (3) and a dynamic contact-decomposition of contact nodes and SPH particles. The overhead cost of such a scheme is the cost of moving mesh and particle data between the decompositions. This cost turns out to be small in practice, leading to a highly load-balanced decomposition in which to perform each of the three major computational states within a timestep.
Date:
May 1, 1997
Creator:
Attaway, S. W.; Hendrickson, B. A.; Plimpton, S. J.; Swegle, J. W.; Gardner, D. R. & Vaughan, C. T.
Object Type:
Article
System:
The UNT Digital Library
Reaction cross-section calculations using new experimental and theoretical level structure data for deformed nuclei
A technique for modeling quasiparticle excitation energies and rotational parameters in odd-odd deformed nuclei has been used to construct sets of discrete states with energy 0 to 1.5 MeV in /sup 176/Lu and /sup 236/Np. These data were used as part of the input for calculation of isomer production cross-section ratios in the /sup 175/Lu(n,..gamma..)/sup 176/Lu and /sup 237/Np(n,2n)/sup 236/Np reactions. In order to achieve agreement with experiment, it has been found necessary to include in the modeled set many rotational bands (35 to 95), which are comprised of hundreds of levels with their gamma-ray branching ratios. It is essential that enough bands be included to produce a representative selection of K quantum numbers in the de-excitation cascade. 20 refs., 3 figs., 3 tabs.
Date:
October 5, 1984
Creator:
Hoff, R. W.; Gardner, D. G. & Gardner, M. A.
Object Type:
Article
System:
The UNT Digital Library
Detailed photonuclear cross-section calculations and astrophysical applications
We have investigated the role of an isomeric state and its coupling to the ground state (g.s.) via photons and neutron inelastic scattering in a stellar environment by making detailed photonuclear and neutron cross-section calculations for /sup 176/Lu and /sup 210/Bi. In the case of /sup 176/Lu, the g.s. would function as an excellent galactic slow- (s-) process chronometer were it not for the 3.7-h isomer at 123 keV. Our calculations predicted much larger photon cross sections for production of the isomer, as well as a lower threshold, than had been assumed based on earlier measurements. These two factors combine to indicate that an enormous correction, a factor of 10/sup 7/, must be applied to shorten the current estimate of the half-life against photoexcitation of /sup 176/Lu as a function of temperature. This severely limits the use of /sup 176/Lu as a stellar chronometer and indicates a significantly lower temperature at which the two states reach thermal equilibrium. For /sup 210/Bi, our preliminary calculations of the production and destruction of the 3 /times/ 10/sup 6/ y isomeric state by neutrons and photons suggest that the /sup 210/Bi isomer may not be destroyed by photons as rapidly as assumed in certain …
Date:
June 15, 1989
Creator:
Gardner, D. G.; Gardner, M. A. & Hoff, R. W.
Object Type:
Article
System:
The UNT Digital Library
Absolute dipole gamma-ray strength functions for /sup 176/Lu
We have derived absolute dipole strength-function information for /sup 176/Lu from an average resonance capture study of /sup 175/Lu with 2-keV neutrons, and from neutron capture cross-section measurements with neutrons from 30 keV to about 1 MeV. We found that we needed to increase our previous estimate of the relative M1/E1 strengths near 5 MeV by a factor of 3, and to revise downward the absolute magnitude of our E1 strength function. We accomplished the latter, while still maintaining continuity with the photonuclear data, by adjusting the one free parameter in our line shape. The present E1 and M1 strengths now seem correct both near the neutron separation energy and also around 1 MeV.
Date:
August 29, 1984
Creator:
Gardner, D. G.; Gardner, M. A. & Hoff, R. W.
Object Type:
Article
System:
The UNT Digital Library
Reaction cross-section calculations using new experimental and theoretical level structure data for deformed nuclei
A technique for modeling level structures of odd-odd nuclei has been used to construct sets of discrete states with energies in the range 0 to 1.5 MeV for several nuclei in the rare-earth and actinide regions. The accuracy of the modeling technique was determined by comparison with experimental data. Examination was made of what effect the use of these new, more complete sets of discrete states has on the calculation of level densities, total reaction cross sections, and isomer ratios. 9 refs.
Date:
May 1, 1985
Creator:
Hoff, R. W.; Gardner, D. G. & Gardner, M. A.
Object Type:
Article
System:
The UNT Digital Library
Isomer ratio calculations using modeled discrete levels
Isomer ratio calculations were made for the reactions: /sup 175/Lu(n,..gamma..)/sup 176m,g/Lu, /sup 175/Lu(n,2n)/sup 174m,g/Lu, /sup 237/Np(n,2n)/sup 236m,g/Np, /sup 241/Am(n,..gamma..)/sup 242m,g/Am, and /sup 243/Am(n,..gamma..)/sup 244m,g/Am using modeled level structures in the deformed, odd-odd product nuclei. The hundreds of discrete levels and their gamma-ray branching ratios provided by the modeling are necessary to achieve agreement with experiment. Many rotational bands must be included in order to obtain a sufficiently representative selection of K quantum numbers. The levels of each band must be extended to appropriately high values of angular momentum.
Date:
October 16, 1984
Creator:
Gardner, M. A.; Gardner, D. G. & Hoff, R. W.
Object Type:
Article
System:
The UNT Digital Library
Absolute dipole gamma-ray strength functions for /sup 176/Lu. Supplement
We have derived absolute dipole strength-function information for /sup 176/Lu from an average resonance capture study of /sup 175/Lu with 2-keV neutrons and from neutron capture cross-section measurements with neutrons from 30 keV to about 1 MeV. We found that we needed to increase our previous estimate of the relative M1/E1 strengths near 5 MeV by a factor of 3 and to revise downward the absolute magnitude of our E1 strength function. We accomplished the latter, while still maintaining continuity with the photonuclear data, by adjusting the one free parameter in our line shape. The present E1 and M1 strengths now seem correct both near the neutron separation energy and also around 1 MeV.
Date:
October 16, 1984
Creator:
Gardner, D. G.; Gardner, M. A. & Hoff, R. W.
Object Type:
Article
System:
The UNT Digital Library
Dipole strength functions in the actinide mass region
We have calculated a number of neutron- and photon-induced reactions for the actinide nuclei /sup 232/Th, /sup 238/U, and /sup 237/Np. By fitting average resonance capture (ARC) measurements and total neutron capture data, we deduced absolute dipole strength functions for /sup 233/Th and /sup 239/U. We have found that the M1/E1 ratio is the same as in the /sup 176/Lu case, but the total transition strength was larger by about 27%. 17 refs., 4 figs., 1 tab.
Date:
July 15, 1987
Creator:
Gardner, D. G.; Gardner, M. A. & Hoff, R. W.
Object Type:
Article
System:
The UNT Digital Library
Isomer ratio calculations using modeled discrete levels
We have calculated isomer ratios for the /sup 175/Lu(n,..gamma..), /sup 175/Lu(n,2n), /sup 237/Np(n,2n), /sup 241/Am(n,..gamma..), and /sup 243/Am(n,..gamma..) reactions using modeled level structures in the deformed, odd-odd product nuclei. We find: that the hundreds of discrete levels and their gamma-ray branching ratios provided by the modeling are necessary to achieve agreement with experiment, that many rotational bands must be included in order to obtain a sufficiently representative selection of K quantum numbers, and that the levels of each band must be extended to appropriately high values of angular momentum. 8 references.
Date:
August 29, 1984
Creator:
Gardner, M. A.; Gardner, D. G. & Hoff, R. W.
Object Type:
Article
System:
The UNT Digital Library
Experimental database and design concept for a 1-MW, 200-keV neutral-beam line based on a SITEX negative ion source
Scaling studies for a SITEX negative ion source to produce 200-keV, 10-A, long pulse D/sup -/ beams are under way at Oak Ridge National Laboratory (ORNL). Designs have been restricted to the use of established techniques and reasonably well-demonstrated scaling. The results show that the 1-A SITEX source can be directly scaled to produce 200-keV, 10-A long pulse ion beams with a source power efficiency of less than or equal to 5 kW of total plasma generator power per ampere of D/sup -/ beam generated. Extracted electron-to-D/sup -/ ratios should be less than or equal to 0.06, with all extracted electrons recovered at less than or equal to 10% of the first gap potential energy difference. The close-coupled accelerating structure will be 5 cm long and have five electrodes with 21 slits each, with a 50-kV/cm field in each gap.
Date:
January 1, 1983
Creator:
Dagenhart, W. K.; Gardner, W. L.; Stirling, W. L. & Whealton, J. H.
Object Type:
Article
System:
The UNT Digital Library
Electrode design and performance of the ORNL positive ion sources
The neutral beam development group at ORNL has designed, constructed, and shipped four 50-kV, 100-A sources to PPPL to be used for neutral beam heating of the confined plasma on the PDX tokamak. These sources have higher current capability than scaled-down sources, and they are required to run for 0.5 s as opposed to the 0.3-s requirement for PLT and ISX-B sources. Due to an innovative electrode design, these higher power sources met these requirements and achieved a higher transmission efficiency - 76% of the total input power on target vs 60% for the original ISX-B and modified PLT sources or 40% for the original PLT sources. As a consequence, a power of 2 MW of neutrals to the torus target was achieved; this is a record for measured neutral power and exceeds that of any other power source expected to be used on such advanced tokamaks as TFTR and D-III. A theoretical consideration of the relevant Poisson-Vlasov equations for ions extracted from a plasma was used to optimize the ion optics. Using the same electrode design with a tetraode accelerating structure and a new, indirectly heated cathode, repeatable long pulse, high energy conditions of 70 kV, 7 A, 8 …
Date:
January 1, 1980
Creator:
Whealton, J.H.; Gardner, W.L. & Haselton, H.H.
Object Type:
Article
System:
The UNT Digital Library
Effects of Some 3d and 4d Solutes on the Superconductivity of Technetium
None
Date:
January 1, 1972
Creator:
Koch, C. C.; Gardner, W. E. & Mortimer, M. J.
Object Type:
Report
System:
The UNT Digital Library
Micromechanical modeling of damage and inelasticity of composite materials in macroscopic structural analysis
The method of cells has been extended to include damage or debonding between all adjacent subcells using a finite element formulation for the original cells assembly. Damage is implemented by placing a nonlinear three-dimensional spring between adjacent subcells. With this arrangement the damage is inherently anisotropic. The ``nonlinear substructure`` cells finite element model is incorporated as a user defined material routine in a general purpose finite element code. The primary motivation for casting the method of cells as a finite element assemblage is to provide a composite constitutive model that facilitates the incorporation of various constituent material models, as well as any level of detail desired in the microstructure geometry. At present, the constituent material models may be anisotropic elastic or isotropic viscoelastic-plastic, while damage evolution is based on the macroscopic strain. The capability of the model is demonstrated through analyses of some simple structures loaded to failure.
Date:
December 1, 1994
Creator:
Macek, R. W.; Gardner, J. P. & Hackett, R. M.
Object Type:
Article
System:
The UNT Digital Library
Low-Cost Organic Moderator-Coolants for Nuclear Reactors
None
Date:
December 23, 1963
Creator:
Gardner, L. E.; Hutchinson, W. M. & Hillyer, J. C.
Object Type:
Report
System:
The UNT Digital Library
Technologies for the oil and gas industry
This is the final report of a five-month, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). The authors performed a preliminary design study to explore the plausibility of using pulse-tube refrigeration to cool instruments in a hot down-hole environment for the oil and gas industry or geothermal industry. They prepared and distributed a report showing that this appears to be a viable technology.
Date:
December 31, 1998
Creator:
Goff, S.J.; Swift, G.W. & Gardner, D.L.
Object Type:
Report
System:
The UNT Digital Library
Random and systematic field errors in the SNS ring: A study of their effects and compensation
The Accumulator Ring for the proposed Spallation Neutron Source (SNS) is to accept a 1 ms beam pulse from a 1 GeV Proton Linac at a repetition rate of 60 Hz. For each beam pulse, 10{sup 14} protons (some 1,000 turns) are to be accumulated via charge-exchange injection and then promptly extracted to an external target for the production of neutrons by spallation. At this very high intensity, stringent limits (less than two parts in 10,000 per pulse) on beam loss during accumulation must be imposed in order to keep activation of ring components at an acceptable level. To stay within the desired limit, the effects of random and systematic field errors in the ring require careful attention. This paper describes the studies of these effects and the magnetic corrector schemes for their compensation.
Date:
August 1998
Creator:
Gardner, C. J.; Lee, Y. Y. & Weng, W. T.
Object Type:
Article
System:
The UNT Digital Library
RANDOM AND SYSTEMATIC FIELD ERRORS IN THE SNS RING: A STUDY OF THEIR EFFECTS AND COMPENSATION
The Accumulator Ring for the proposed Spallation Neutron Source (SNS) [l] is to accept a 1 ms beam pulse from a 1 GeV Proton Linac at a repetition rate of 60 Hz. For each beam pulse, 10{sup 14} protons (some 1,000 turns) are to be accumulated via charge-exchange injection and then promptly extracted to an external target for the production of neutrons by spallation. At this very high intensity, stringent limits (less than two parts in 10,000 per pulse) on beam loss during accumulation must be imposed in order to keep activation of ring components at an acceptable level. To stay within the desired limit, the effects of random and systematic field errors in the ring require careful attention. This paper describes the authors studies of these effects and the magnetic corrector schemes for their compensation.
Date:
June 22, 1998
Creator:
Gardner, C. J.; Lee, Y. Y. & Weng, W. T.
Object Type:
Article
System:
The UNT Digital Library
Color Transparency and the Energy Evolution of Final-State Interactions in Charmonium Photoproduction
None
Date:
January 1, 1991
Creator:
Gardner, A. & Gardner, Susan
Object Type:
Report
System:
The UNT Digital Library
Indium dopant/defect complexes in lightly-doped ceria
Four well-defined indium-dopant/lattice-defect complexes and the non-complexed substitutional indium dopant have been observed by perturbed angular correlation (PAC) spectroscopy in cerium oxide. PAC is a nuclear hyperfine experimental method that detects interactions between a radioactive probe nucleus and nearby atoms. The magnitude and symmetry of those interactions provide a signature for the electromagnetic fields at the probe nucleus. These fields are produced by the arrangement of charges and magnetic moments in the near environment of the probe, so they provide a means of identifying defect structures.
Date:
December 31, 1991
Creator:
Wang, Ruiping; Gardner, J. A.; Evenson, W. E. & Sommers, J. A.
Object Type:
Article
System:
The UNT Digital Library
Bioinformatics for Microbial Genotyping of Equine Encephalitis Viruses, Orthopox Viruses, and Hantaviruses
None
Date:
August 8, 2011
Creator:
Gardner, S N & Jaing, C J
Object Type:
Article
System:
The UNT Digital Library
Pair Production Constraints on Superluminal Neutrinos Revisited
We revisit the pair creation constraint on superluminal neutrinos considered by Cohen and Glashow in order to clarify which types of superluminal models are constrained. We show that a model in which the superluminal neutrino is effectively light-like can evade the Cohen-Glashow constraint. In summary, any model for which the CG pair production process operates is excluded because such timelike neutrinos would not be detected by OPERA or other experiments. However, a superluminal neutrino which is effectively lightlike with fixed p{sup 2} can evade the Cohen-Glashow constraint because of energy-momentum conservation. The coincidence involved in explaining the SN1987A constraint certainly makes such a picture improbable - but it is still intrinsically possible. The lightlike model is appealing in that it does not violate Lorentz symmetry in particle interactions, although one would expect Hughes-Drever tests to turn up a violation eventually. Other evasions of the CG constraints are also possible; perhaps, e.g., the neutrino takes a 'short cut' through extra dimensions or suffers anomalous acceleration in matter. Irrespective of the OPERA result, Lorentz-violating interactions remain possible, and ongoing experimental investigation of such possibilities should continue.
Date:
February 16, 2012
Creator:
Brodsky, Stanley J. & Gardner, Susan
Object Type:
Article
System:
The UNT Digital Library
Evidence for the Absence of Gluon Orbital Angular Momentum in the Nucleon
The Sivers mechanism for the single-spin asymmetry in unpolarized lepton scattering from a transversely polarized nucleon is driven by the orbital angular momentum carried by its quark and gluon constituents, combined with QCD final-state interactions. Both quark and gluon mechanisms can generate such a single-spin asymmetry, though only the quark mechanism can explain the small single-spin asymmetry measured by the COMPASS collaboration on the deuteron, suggesting the gluon mechanism is small relative to the quark mechanism. We detail empirical studies through which the gluon and quark orbital angular momentum contributions, quark-flavor by quark-flavor, can be elucidated.
Date:
August 23, 2006
Creator:
Brodsky, S. J. & Gardner, S.
Object Type:
Article
System:
The UNT Digital Library
Calculation of the Mean Energy Loss in the BTA Stripping Foils and Comparison with Measurement
N/A
Date:
July 1, 2002
Creator:
Ahrens, L. & Gardner, C. J.
Object Type:
Report
System:
The UNT Digital Library