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High-spin states in {sup 71}As, {sup 72}Se, and {sup 72}Br. (open access)

High-spin states in {sup 71}As, {sup 72}Se, and {sup 72}Br.

The {sup 16}O + {sup 58}Ni reaction was used to study yrast and non-yrast excitations in {sup 71}As, {sup 72}Se, and {sup 72}Br. High-spin yrast and negative-parity non-yrast bands were observed in {sup 72}Se. The F{sub 7/2} proton extruder orbital was identified in {sup 71}As. The odd-even staggering in the {pi}g{sub 9/2}{nu}g{sub 9/2} decoupled band in {sup 72}Br is compared with similar structures in heavier Br isotopes.
Date: August 25, 1998
Creator: Fotiades, N.
System: The UNT Digital Library
Quantum Monte Carlo calculations of light nuclei. (open access)

Quantum Monte Carlo calculations of light nuclei.

Quantum Monte Carlo calculations using realistic two- and three-nucleon interactions are presented for nuclei with up to eight nucleons. We have computed the ground and a few excited states of all such nuclei with Greens function Monte Carlo (GFMC) and all of the experimentally known excited states using variational Monte Carlo (VMC). The GFMC calculations show that for a given Hamiltonian, the VMC calculations of excitation spectra are reliable, but the VMC ground-state energies are significantly above the exact values. We find that the Hamiltonian we are using (which was developed based on {sup 3}H, {sup 4}He, and nuclear matter calculations) underpredicts the binding energy of p-shell nuclei. However our results for excitation spectra are very good and one can see both shell-model and collective spectra resulting from fundamental many-nucleon calculations. Possible improvements in the three-nucleon potential are also be discussed.
Date: August 25, 1998
Creator: Pieper, S. C.
System: The UNT Digital Library
A numerical study of short residence time FCC riser flows with a new flow/kinetics modeling technique. (open access)

A numerical study of short residence time FCC riser flows with a new flow/kinetics modeling technique.

Fluid Catalytic Cracking (FCC) technology is the most important process used by the refinery industry to convert crude oil to valuable lighter products such as gasoline. New and modified processes are constantly developed by refinery companies to improve their global competitiveness and meet more stringent environmental regulations. Short residence time FCC riser reactor is one of the advanced processes that the refining industry is actively pursuing because it can improve the yield selectivity and efficiency of an FCC unit. However, as the residence time becomes shorter, the impact of the mixing between catalyst and feed oil at the feed injection region on the product yield becomes more significant. Currently, most FCC computer models used by the refineries perform sophisticated kinetic calculations on simplified flow field and can not be used to evaluate the impact of fluid mixing on the performance of an FCC unit. Argonne National Laboratory (AFL) is developing a computational fluid dynamic (CFD) code ICRKFLO for FCC riser flow modeling. The code, employing hybrid hydrodynamic-chemical kinetic coupling techniques, is used to investigate the effect of operating and design conditions on the product yields of FCC riser reactors. Numerical calculations were made using the code to examine the impacts …
Date: August 25, 1998
Creator: Chang, S. L.
System: The UNT Digital Library
The measurement of the mass of the W boson from the Tevatron. (open access)

The measurement of the mass of the W boson from the Tevatron.

This paper presents measurements of the mass of the W vector boson from the CDF and D0 experiments using data collected at {radical}s = 1.8 TeV during the 1994-1995 data taking run. CDF finds a preliminary mass of M{sub W} = 80.43 {+-} 0.16 GeV and D0 measures a mass of M{sub W} = 80.44 {+-} 0.12 GeV.
Date: August 25, 1998
Creator: Thurman-Keup, R.
System: The UNT Digital Library
A numerical investigation of the scale-up effects on flow, heat transfer, and kinetics processes of FCC units. (open access)

A numerical investigation of the scale-up effects on flow, heat transfer, and kinetics processes of FCC units.

Fluid Catalytic Cracking (FCC) technology is the most important process used by the refinery industry to convert crude oil to valuable lighter products such as gasoline. Process development is generally very time consuming especially when a small pilot unit is being scaled-up to a large commercial unit because of the lack of information to aide in the design of scaled-up units. Such information can now be obtained by analysis based on the pilot scale measurements and computer simulation that includes controlling physics of the FCC system. A Computational fluid dynamic (CFD) code, ICRKFLO, has been developed at Argonne National Laboratory (ANL) and has been successfully applied to the simulation of catalytic petroleum cracking risers. It employs hybrid hydrodynamic-chemical kinetic coupling techniques, enabling the analysis of an FCC unit with complex chemical reaction sets containing tens or hundreds of subspecies. The code has been continuously validated based on pilot-scale experimental data. It is now being used to investigate the effects of scaled-up FCC units. Among FCC operating conditions, the feed injection conditions are found to have a strong impact on the product yields of scaled-up FCC units. The feed injection conditions appear to affect flow and heat transfer patterns and the …
Date: August 25, 1998
Creator: Chang, S. L.
System: The UNT Digital Library