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Search Results: 1 - 10 of 434210 matches for " D. J. Dean "
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Computational Science and Innovation
D. J. Dean
Physics , 2010, DOI: 10.1088/1742-6596/312/6/062001
Abstract: Simulations - utilizing computers to solve complicated science and engineering problems - are a key ingredient of modern science. The U.S. Department of Energy (DOE) is a world leader in the development of high-performance computing (HPC), the development of applied math and algorithms that utilize the full potential of HPC platforms, and the application of computing to science and engineering problems. An interesting general question is whether the DOE can strategically utilize its capability in simulations to advance innovation more broadly. In this article, I will argue that this is certainly possible.
Progress and challenges in the theory of nuclei
D. J. Dean
Physics , 2007, DOI: 10.1016/j.nuclphysa.2008.02.235
Abstract: Nuclear theory today aims for a comprehensive theoretical framework that can describe all nuclei. I discuss recent progress in this pursuit and the associated challenges as we move forward.
Effect of nuclear structure on Type Ia supernova nucleosynthesis
D. J. Dean
Physics , 2000, DOI: 10.1016/S0375-9474(01)00695-9
Abstract: The relationship among nuclear structure, the weak processes in nuclei, and astrophysics becomes quite apparent in supernova explosion and nucleosynthesis studies. In this brief article, I report on progress made in the last few years on calculating electron capture and beta-decay rates in iron-group nuclei. I also report on applications of these rates to Type-Ia nucleosynthesis studies.
Factorization of shell-model ground-states
T. Papenbrock,D. J. Dean
Physics , 2003, DOI: 10.1103/PhysRevC.67.051303
Abstract: We present a new method that accurately approximates the shell-model ground-state by products of suitable states. The optimal factors are determined by a variational principle and result from the solution of rather low-dimensional eigenvalue problems. The power of this method is demonstrated by computations of ground-states and low-lying excitations in sd-shell and pf-shell nuclei.
Shell Model Monte Carlo method in the $pn$-formalism and applications to the Zr and Mo isotopes
C. Ozen,D. J. Dean
Physics , 2005, DOI: 10.1103/PhysRevC.73.014302
Abstract: We report on the development of a new shell-model Monte Carlo algorithm which uses the proton-neutron formalism. Shell model Monte Carlo methods, within the isospin formulation, have been successfully used in large-scale shell-model calculations. Motivation for this work is to extend the feasibility of these methods to shell-model studies involving non-identical proton and neutron valence spaces. We show the viability of the new approach with some test results. Finally, we use a realistic nucleon-nucleon interaction in the model space described by (1p_1/2,0g_9/2) proton and (1d_5/2,2s_1/2,1d_3/2,0g_7/2,0h_11/2) neutron orbitals above the Sr-88 core to calculate ground-state energies, binding energies, B(E2) strengths, and to study pairing properties of the even-even 90-104 Zr and 92-106 Mo isotope chains.
On phases in weakly interacting finite Bose systems
D. J. Dean,T. Papenbrock
Physics , 2001, DOI: 10.1103/PhysRevA.65.043603
Abstract: We study precursors of thermal phase transitions in finite systems of interacting Bose gases. For weakly repulsive interactions there is a phase transition to the one-vortex state. The distribution of zeros of the partition function indicates that this transition is first order, and the precursors of the phase transition are already displayed in systems of a few dozen bosons. Systems of this size do not exhibit new phases as more vortices are added to the system.
Gamow-Teller GT+ distributions in nuclei with mass A=90-97
A. Juodagalvis,D. J. Dean
Physics , 2004, DOI: 10.1103/PhysRevC.72.024306
Abstract: We investigate the Gamow-Teller strength distributions in the electron-capture direction in nuclei having mass A=90-97, assuming a 88Sr core and using a realistic interaction that reasonably reproduces nuclear spectroscopy for a wide range of nuclei in the region as well as experimental data on Gamow-Teller strength distributions. We discuss the systematics of the distributions and their centroids. We also predict the strength distributions for several nuclei involving stable isotopes that should be experimentally accessible for one-particle exchange reactions in the near future.
Density matrix renormalization group and wave function factorization for nuclei
T. Papenbrock,D. J. Dean
Physics , 2004, DOI: 10.1088/0954-3899/31/8/016
Abstract: We employ the density matrix renormalization group (DMRG) and the wave function factorization method for the numerical solution of large scale nuclear structure problems. The DMRG exhibits an improved convergence for problems with realistic interactions due to the implementation of the finite algorithm. The wave function factorization of fpg-shell nuclei yields rapidly converging approximations that are at the present frontier for large-scale shell model calculations.
Monte Carlo methods and applications for the nuclear shell model
D. J. Dean,J. A. White
Physics , 1998, DOI: 10.1063/1.59542
Abstract: The shell-model Monte Carlo (SMMC) technique transforms the traditional nuclear shell-model problem into a path-integral over auxiliary fields. We describe below the method and its applications to four physics issues: calculations of sdpf- shell nuclei, a discussion of electron-capture rates in pf-shell nuclei, exploration of pairing correlations in unstable nuclei, and level densities in rare earth systems.
Explaining First-Year Seedling Survival from Quality Distributions of Bare-Root Seedlings and Microsites in Industrial Plantations  [PDF]
Puskar N. Khanal, Thomas J. Dean, Scott D. Roberts, Donald L. Grebner, Thomas J. Straka
Open Journal of Forestry (OJF) , 2018, DOI: 10.4236/ojf.2018.83023
Abstract: First-year seedling survival impacts all subsequent management planning in plantation forestry. Descriptive statistics of first-year seedling survival data from the Louisiana Department of Agriculture and Forestry (LDAF) indicated that survival success reaches a plateau at between 79% - 85% under normal weather conditions. We provide an explanation for this plateau based on an analysis of seedling and microsite qualities involved in operational pine plantations by: 1) using a conceptual model demonstrating how variation in seedling quality and microsite quality interact to determine plantation survival, 2) presenting an example to characterize quality distributions of seedling and microsite qualities, and 3) comparing model outcomes based on measured distributions to realistic values of first-year survival. Simulation results indicated that consistent survival could result from random pairings of initial seedling and site quality distributions. LDAF data analysis indicated that 72% of seedlings were associated with the most frequent quality class that comprised seedlings with stem caliper between 3.2 to 4.7 mm and average stem height and volume of 25.75 cm and 3.43 cm3, respectively. Similarly, assessment of microsites at planting sites in Southeast Louisiana indicated that 48% of planted seedlings were associated with the most frequent microsite quality class which supported first-year height increment between 9 to 29 cm. Modelling of current operational practice indicated that using seedlings with larger caliper size would increase first year survival, but would result in higher establishment costs. The conceptual model could be modified to for use in other regions regardless of species types involved.
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