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University of Nebraska at Omaha

2003

Series

Articles 1 - 8 of 8

Full-Text Articles in Physical Sciences and Mathematics

Dielectric Permittivity And Electric Modulus In Bi2ti4o11, Jianjun Liu, Chun-Gang Duan, Wei-Guo Yin, Wai-Ning Mei, Robert W. Smith, John R. Hardy Aug 2003

Dielectric Permittivity And Electric Modulus In Bi2ti4o11, Jianjun Liu, Chun-Gang Duan, Wei-Guo Yin, Wai-Ning Mei, Robert W. Smith, John R. Hardy

Physics Faculty Publications

Frequency and temperature dependences of dielectric permittivity and electric modulus of pure and Ba-doped Bi2Ti4O11 were studied in the ranges of 1021–106 Hz and 2150–350 °C, respectively. We found that the antiferroelectric phase transition temperature of Bi2Ti4O11 decreases with Ba doping. In the permittivity studies, we also observed dielectric relaxation peaks shift to higher temperature with increasing frequency. Furthermore, in the electric modulus formalism, conducting peaks were uncovered above 150 °C in addition to the dielectric relaxation peak. We discussed the mechanisms for the dielectric relaxation and conduction processes based on TiO6 octahedra distortion and a space-charge model.

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Computing Answer Sets Of A Logic Program Via-Enumeration Of Sat Certificates, Yuliya Lierler, Marco Maratea Jan 2003

Computing Answer Sets Of A Logic Program Via-Enumeration Of Sat Certificates, Yuliya Lierler, Marco Maratea

Computer Science Faculty Proceedings & Presentations

Answer set programming is a new programming paradigm proposed based on the answer set semantics of Prolog. It is well known that an answer set for a logic program is also a model of the program's completion. The converse is true when the logic program is "tight". Lin and Zhao showed that for non-tight programs the models of completion which do not correspond to answer sets can be eliminated by adding to the completion what they called "loop formulas". Nevertheless, their solver ASSAT 1 has some disadvantages: it can work only with basic rules, and it can compute only one …

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Goal-Converging Behavior Networks And Self-Solving Planning Domains, Bernhard Nebel, Yuliya Lierler Jan 2003

Goal-Converging Behavior Networks And Self-Solving Planning Domains, Bernhard Nebel, Yuliya Lierler

Computer Science Faculty Proceedings & Presentations

Agents operating in the real world have to deal with a constantly changing and only partially predictable environment and are nevertheless expected to choose reasonable actions quickly. One way to address this problem is to use behavior networks as proposed by Maes, which support real-time decision making. Robotic soccer appears to be one domain where behavior networks have been proven to be particularly successful. In this paper, we analyze the reason for the success by identifying conditions that make behavior networks goal converging, i.e., allow them to reach the goals regardless of which particular action selection scheme is used. In …

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Introducing The Global Diffusion Of The Internet Series, Peter Wolcott, Seymour E. Goodman Jan 2003

Introducing The Global Diffusion Of The Internet Series, Peter Wolcott, Seymour E. Goodman

Information Systems and Quantitative Analysis Faculty Publications

Many genes can play a role in multiple biological processes or molecular functions. Identifying multifunctional genes at the genome-wide level and studying their properties can shed light upon the complexity of molecular events that underpin cellular functioning, thereby leading to a better understanding of the functional landscape of the cell. However, to date, genome-wide analysis of multifunctional genes (and the proteins they encode) has been limited. Here we introduce a computational approach that uses known functional annotations to extract genes playing a role in at least two distinct biological processes. We leverage functional genomics data sets for three organisms—H. sapiens, …

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Molecular Dynamics Simulation Of The Order- Disorder Phase Transition In Solid Nano2, Wei-Guo Yin, Chun-Gang Duan, Wai-Ning Mei, Jianjun Liu, Robert W. Smith, John R. Hardy Jan 2003

Molecular Dynamics Simulation Of The Order- Disorder Phase Transition In Solid Nano2, Wei-Guo Yin, Chun-Gang Duan, Wai-Ning Mei, Jianjun Liu, Robert W. Smith, John R. Hardy

Physics Faculty Publications

We present molecular dynamics simulations of solid NaNO2 using pair potentials with the rigid-ion model. The crystal potential surface is calculated by using an a priori method which integrates the ab initio calculations with the Gordon-Kim electron gas theory. This approach is carefully examined by using different population analysis methods and comparing the intermolecular interactions resulting from this approach with those from the ab initio Hartree-Fock calculations. Our numerics show that the ferroelectric-paraelectric phase transition in solid NaNO2 is triggered by rotation of the nitrite ions around the crystallographical c axis, in agreement with recent x-ray experiments @Gohda et al., …

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Comparison Of The Theoretical And Experimental Band Structure Of Poly (Vinylidene Fluoride) Crystal, Chun-Gang Duan, Wai-Ning Mei, John R. Hardy, Stephen Ducharme, Jaewu Choi, Peter A. Dowben Jan 2003

Comparison Of The Theoretical And Experimental Band Structure Of Poly (Vinylidene Fluoride) Crystal, Chun-Gang Duan, Wai-Ning Mei, John R. Hardy, Stephen Ducharme, Jaewu Choi, Peter A. Dowben

Physics Faculty Publications

The electronic structure and band symmetries of the ferroelectric phase of poly (vinylidene fluoride) (PVDF) are studied by using the first-principles density-functional method. Our calculated results agree well with the angle-resolved photoemission experiments. We find that the PVDF crystal has an energy gap of about 6 eV at the Γ-point. Large dispersion of the valence band is found only along the chain direction, which is consistent with the quasi-one-dimensional nature of PVDF. In particular, the band symmetries of the valence states deduced theoretically are in good agreement with experiment. Finally, further investigations on the electronic structure of poly(trifluoroethylene) (PTrFE) …

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Utilizing Structure Property Correlations To Predict And Analyze Two Derivatives Of An Ampicillin Homologous Series, C. Malesa, J. Stoddard, Ronald Bartzatt Jan 2003

Utilizing Structure Property Correlations To Predict And Analyze Two Derivatives Of An Ampicillin Homologous Series, C. Malesa, J. Stoddard, Ronald Bartzatt

Chemistry Faculty Publications

Structure Property Correlation methods such as regression analysis and pattern recognition are applied to predict the molecular properties of two members of an ampicillin homologous series. The pentyl and hexyl esters of ampicillin are also evaluated for their similarity to other penicillins by use of multiple regression, contingency tables, cluster analysis, correspondence analysis, self organizing tree algorithms, factor analysis, principal component analysis, box plots, and other graphing methods. Other members of the homologous series include methyl, ethyl, propyl, and butyl esters of ampicillin which have been previously synthesized and tested in tissue culture against Escherichia coli. All of the tested …

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Spectral Functions Of The Falicov-Kimball Model With Electronic Ferroelectricity, Wei-Guo Yin, Wai-Ning Mei, Chun-Gang Duan, Hai-Qing Lin, John R. Hardy Jan 2003

Spectral Functions Of The Falicov-Kimball Model With Electronic Ferroelectricity, Wei-Guo Yin, Wai-Ning Mei, Chun-Gang Duan, Hai-Qing Lin, John R. Hardy

Physics Faculty Publications

We calculate the angular resolved photoemission spectrum of the Falicov-Kimball model with electronic ferroelectricity where d- and f-electrons have different hoppings. In mix-valence regimes, the presence of strong scattering processes between d – f excitons and a hole, created by emission of an electron, leads to the formation of pseudospin polarons and novel electronic structures with bandwidth scaling with that of d – f excitons. Especially, in the two-dimensional case, we find that flat regions exist near the bottom of the quasiparticle band in a wide range of the d- and f-level energy difference.

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