Engineering topics
Miller, D
Publications and source records attributed to Miller, D.
Fission Barriers of Super-Heavy Nuclei and Search for Element 120
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Direct reaction experimental studies with beams of radioactive tin ions
The tin chain of isotopes provides a unique region in which to investigate the evolution of single-particle structure, spreading from N = 50 at {sup 100}Sn, through 10 stable isotopes and the N = 82 shell closure at {sup 132}Sn out into the r-process path. Direct reactions performed on radioactive ion beams are sensitive spectroscopic tools for studying exotic nuclei. Here we present one experiment knocking out neutrons from tin isotopes that are already neutron deficient and two reactions that add a neutron to neutron-rich {sup 130}Sn. Both techniques rely on selective particle identification and the measurement of γ rays in coincidence with charged ions. We present the goals of the two experiments and the particle identification for the channels of interest. The final results will be presented in future publications.
New Half-lives of r -process Zn and Ga Isotopes Measured with Electromagnetic Separation
Not Available
Low-energy structure of 27 66 Co 39 and 27 68 Co 41 populated through β decay
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Studies of 48 Ni Using the Optical Time Projection Chamber
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Optimization of water use and cost of electricity for an MEA carbon capture process, January 26, 2012
DOE goals are: 90% CO{sub 2} capture, Less than 30% increase in COE, and to reduce water use by 70% at 50% cost of dry cooling. Objectives are: (1) Develop detailed models of supercritical power plant, MEA carbon capture process, CO{sub 2} compression; and (2) Optimize process for conflicting goals of minimizing water use and COE CO{sub 2} capture greatly increases COE and water use, power gen. 1/3 of fresh water use, and water scarcity is increasing.
Production and decay of the heaviest nuclei 293,294117 and 294118
No abstract prepared.
Enforcing elemental mass and energy balances for reduced order models
Development of economically feasible gasification and carbon capture, utilization and storage (CCUS) technologies requires a variety of software tools to optimize the designs of not only the key devices involved (e., g., gasifier, CO{sub 2} adsorber) but also the entire power generation system. High-fidelity models such as Computational Fluid Dynamics (CFD) models are capable of accurately simulating the detailed flow dynamics, heat transfer, and chemistry inside the key devices. However, the integration of CFD models within steady-state process simulators, and subsequent optimization of the integrated system, still presents significant challenges due to the scale differences in both time and length, as well the high computational cost. A reduced order model (ROM) generated from a high-fidelity model can serve as a bridge between the models of different scales. While high-fidelity models are built upon the principles of mass, momentum, and energy conservations, ROMs are usually developed based on regression-type equations and hence their predictions may violate the mass and energy conservation laws. A high-fidelity model may also have the mass and energy balance problem if it is not tightly converged. Conservations of mass and energy are important when a ROM is integrated to a flowsheet for the process simulation of the entire chemical or power generation system, especially when recycle streams are connected to the modeled device. As a part of the Carbon Capture Simulation Initiative (CCSI) project supported by the U.S. Department of Energy, we developed a software framework for generating ROMs from CFD simulations and integrating them with Process Modeling Environments (PMEs) for system-wide optimization. This paper presents a method to correct the results of a high-fidelity model or a ROM such that the elemental mass and energy are conserved perfectly. Correction factors for the flow rates of individual species in the product streams are solved using a minimization algorithm based on Lagrangian multiplier method. Enthalpies of product streams are also modified to enforce the energy balance. The approach is illustrated for two ROMs, one based on a CFD model of an entrained-flow gasifier and the other based on the CFD model of a multiphase CO{sub 2} adsorber.
Characterizing the Effects of Etch-induced Material Modification on the Crystallization Properties of Nitron Doped Ge2Sb2Te5
The chemical and structural effects of processing on the crystallization of nitrogen doped Ge{sub 2}Sb{sub 2}Te{sub 5} is examined via x-ray photoelectron spectroscopy (XPS), x-ray absorption spectroscopy (XAS), time resolved laser reflectivity, and time resolved x-ray diffraction (XRD). Time resolved laser reflectivity and XRD show that exposure to various etch and ash chemistries significantly reduces the crystallization speed while the transition temperature from the rocksalt to the hexagonal phase is increased. XPS and XAS attribute this to the selective removal and oxidization of N, Ge, Sb, and Te, thus altering the local bonding environment to the detriment of device performance.
Digital signal processing for radioactive decay studies
The use of digital acquisition system has been instrumental in the investigation of proton and alpha emitting nuclei. Recent developments extend the sensitivity and breadth of the application. The digital signal processing capabilities, used predominately by UT/ORNL for decay studies, include digitizers with decreased dead time, increased sampling rates, and new innovative firmware. Digital techniques and these improvements are furthermore applicable to a range of detector systems. Improvements in experimental sensitivity for alpha and beta-delayed neutron emitters measurements as well as the next generation of superheavy experiments are discussed.
Lifetime Measurement of the 2{sub 1}{sup +} State in {sup 20}C
Establishing how and when large N/Z values require modified or new theoretical tools is a major quest in nuclear physics. Here we report the first measurement of the lifetime of the 2{sub 1}{sup +} state in the near-dripline nucleus {sup 20}C. The deduced value of {tau}{sub 2{sub 1}{sup +}}=9.8{+-}2.8(stat){sub -1.1}{sup +0.5}(syst) ps gives a reduced transition probability of B(E2;2{sub 1}{sup +}{yields}0{sub g.s.}{sup +})=7.5{sub -1.7}{sup +3.0}(stat){sub -0.4}{sup +1.0}(syst) e{sup 2} fm{sup 4} in good agreement with a shell model calculation using isospin-dependent effective charges.