North Carolina Agricultural and Technical State University (NCA&T) has established a master's degree program in computationalscience and Engineering (CSE). The CSE master's program would have three tracks...
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North Carolina Agricultural and Technical State University (NCA&T) has established a master's degree program in computationalscience and Engineering (CSE). The CSE master's program would have three tracks with a focus on computationalscience, but distinguish across the domain areas of specialization. The goal of the track is to produce biological and life scientists, business professionals and economists and agricultural scientists with focus and expertise in computationalsciences and the primary domain areas.
We present a theoretical method to study atomic photoabsorption processes in a temporally periodic external field. The time development of the atomic dipole moment is propagated by numerical time propagation, and the ...
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We present a theoretical method to study atomic photoabsorption processes in a temporally periodic external field. The time development of the atomic dipole moment is propagated by numerical time propagation, and the photoabsorption cross sections is obtained directly from the Fourier transform of the autocorrelation function without summing up over the Floquet-Fourier components. As an example, we study the photoabsorption spectra of hydrogen atoms exposed in a mixture of static and periodically oscillating magnetic fields for the transition from 1s→2p. The atomic energy structure and photoabsorption spectra show interesting dependence on the strength of the oscillating magnetic field. Tuning the combination of the magnetic field strengths, we can control the photoabsorption process. The proposed method is general and can be applied to processes in which the number of relevant high harmonic components of the Fourier expansion is so large that the conventional Floquet method is intractable.
Asymmetric profiles have been observed in the recombination cross section of Be-like Bi obtained by measuring the electron energy dependence of the ion abundance ratio in an electron-beam ion trap. In contrast to the ...
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Asymmetric profiles have been observed in the recombination cross section of Be-like Bi obtained by measuring the electron energy dependence of the ion abundance ratio in an electron-beam ion trap. In contrast to the previous x-ray measurements, the present measurement gives the integrated recombination cross section with higher statistical quality, which provides a benchmark to test the relativistic theory involving the interference between the resonant and continuum states. The comparison with our theoretical study shows that the Breit interaction plays an important role in this case.
A simple an effective algorithm for performing distance queries between a large number of points stored in quadtrees and octrees. The algorithm is developed and tested for the construction of diffusion-limited aggrega...
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A simple an effective algorithm for performing distance queries between a large number of points stored in quadtrees and octrees. The algorithm is developed and tested for the construction of diffusion-limited aggregates. To achieve an enhancement on the searching time we accept approximate distance values with low precision at the first levels of the hierarchical structure, and accurate ones at the last level. The structure of the trees is the only feature used for the determination of approximate distances at any stage. These techniques allowed us to build DLA clusters with up to 109 particles for the two-dimensional case and up to 108 particles for the three-dimensional case. We also worked with the PDLA model obtaining fractal clusters with up to 1010 and 109 particles for two and three dimension clusters respectively. We worked on a supercomputer to run the PDLA simulations, as well as a high performance server for DLA simulations. We employed POSIX threads to provide parallelization and mutexes as control mechanisms to achieve synchronization between groups of 4 processors, hence simulating PDLA clusters with early convergence to the DLA model.
We investigated the space distribution of the rescattering electron wavepacket created in the laser-atom interaction by a full quantum simulation and a semiclassical calculation. Both the quantum simulation and the se...
We investigated the space distribution of the rescattering electron wavepacket created in the laser-atom interaction by a full quantum simulation and a semiclassical calculation. Both the quantum simulation and the semiclassical calculation showed that the rescattering electron beam current intensity can reach the order of 109 A/cm2, much intense than the conventional electron beam. Different from the convention electron beam, the rescattering electron beam is of a non-uniform distribution both in energy and space. The simulated information is important for analyzing the molecular structure in the rescattering imaging experiments.
We presented a theoretical method to study the capture of the antiprotrons by atoms solving a Chew-Goldberger-type integral equation directly. The scattering boundary conditions are automatically satisfied by adiabati...
We presented a theoretical method to study the capture of the antiprotrons by atoms solving a Chew-Goldberger-type integral equation directly. The scattering boundary conditions are automatically satisfied by adiabatically switching on the interaction between the antiprotons and targets. Hence the outgoing wave function is obtained without the tedious procedure of adjusting the total wave function in the asymptotic region. All the dynamical information can be derived from the scattering wave function obtained on pseudo-spectral grids numerically. Using this method, we obtained the state-specified capture cross sections when antiprotons collide with helium atoms. Differing from the capture processes of antiprotons by hydrogen atoms, the anomalous bumpy structures are revealed in the angular momentum dependent capture cross sections by helium atoms. Further analysis shows that the bumps arise from the partial channel closing due to the removal of the energy degeneracy in the antiprotonic helium atoms.
The interdisciplinary master's degree program in computationalscience and Engineering (CSE) at North Carolina A&T State University, Greensboro, NC is now more than 3 years old, and provides graduate education...
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The interdisciplinary master's degree program in computationalscience and Engineering (CSE) at North Carolina A&T State University, Greensboro, NC is now more than 3 years old, and provides graduate education in several computational areas and the associated primary field disciplines. The CSE program since its inception has presently graduated more than 12 students who are currently placed in several major industries. Our CSE graduateprogram offers an interdisciplinary curriculum combining computational core areas along with various domain areas. The students enrolled in the program begin with diversified backgrounds (prior undergraduate studies in various fields such as engineering, physical sciences, life sciences, mathematics, business, etc), and are required to take four core courses relevant to CSE for their graduation in the areas of applied probability and statistics, comprehensive numerical analysis, Data structures and parallel programming, computational and scientific visualization irrespective of their prior background. The preparation level for the diversified group of students in these courses depends on their undergraduate major. This poses significant challenges to graduate faculty teaching these courses and mentoring these students with diversified backgrounds. Our experiences and observations with the course content and structure, teaching methods, evaluation and student performances in these courses with diversified graduate students and their mentoring for the past 3 years are presented. The performances of the students in these core courses are correlated to their background and analyzed. Our experiences indicate students with a lesser preparation level seem to get geared quickly via peer guidance from the stronger students. In several cases, the performances were not related to an individual's prior background, but on their motivation and willingness to strive and succeed. The experiences indicate that the students can benefit well with additi
A collaborative research project established between the University of Tennessee (UT) computational fluid dynamics (CFD) lab and the Federal Aviation Administration (FAA) Civil Aerospace Medical Institute (CAMI) sough...
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A collaborative research project established between the University of Tennessee (UT) computational fluid dynamics (CFD) lab and the Federal Aviation Administration (FAA) Civil Aerospace Medical Institute (CAMI) sought to validate CFD prediction of the environmental control system (ECS)-generated ventilation velocity vector field with induced mass transport. The results of the velocity field validation exercise were published previously. An FAA Cooperative Research and Development Agreement (CRADA) project generated an experimental database of time-dependent inserted mass distributions in the CAMI Aircraft Environmental Research Facility (AERF). The companion CFD mass transport simulations were conducted at the UT CFD Lab using both commercial and proprietary computer codes. This paper reports the qualified results of the mass transport validation exercise.
We investigate the state-specified capture process of antiprotons by helium. Freezing one of the two electrons, we reduce this four-body rearrangement problem into a three-body problem. The capture cross sections are ...
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We investigate the state-specified capture process of antiprotons by helium. Freezing one of the two electrons, we reduce this four-body rearrangement problem into a three-body problem. The capture cross sections are calculated by solving the Chew-Goldberger-type integral equation. Differing from the capture of antiprotons by hydrogen atoms, the bumpy structures are revealed in the total angular momentum dependent capture cross sections. Further analysis shows that the bumps arise from the partial channel closing due to the removal of the energy degeneracy in the antiprotonic helium.
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