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University of Arkansas, Fayetteville

Journal of the Arkansas Academy of Science

2006

Articles 1 - 9 of 9

Full-Text Articles in Physical Sciences and Mathematics

Study Of Causal Component Placement In An Active Sound Cancellation System, Eileen Anderson, Andrew B. Wright Jan 2006

Study Of Causal Component Placement In An Active Sound Cancellation System, Eileen Anderson, Andrew B. Wright

Journal of the Arkansas Academy of Science

In a feedforward Active Sound Cancellation (ASC) system, the acoustic delay between a primary source and an error microphone must be greater than the delay between the measurement of that source by the reference microphone and the arrival of the secondary source's wave at the error microphone. Such a configuration is called a causal configuration. For periodic disturbances, cancellation can still be achieved in non-causal configuration. Since the waveform is periodic, each cycle of the waveform is identical, and the cycle being canceled is not the measured part of the waveform, but a subsequent cycle in the waveform. Non-periodic sources …

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Density Functional Studies Of The Structure And Bonding In Piano Stool Carbene Complexes, John P. Graham, Robbie Davis Jan 2006

Density Functional Studies Of The Structure And Bonding In Piano Stool Carbene Complexes, John P. Graham, Robbie Davis

Journal of the Arkansas Academy of Science

No abstract provided.

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Density Functional Studies Of The Structure And Bonding Of Nitrosyl Metalloporphyrin Complexes, John P. Graham, Robbie Davis Jan 2006

Density Functional Studies Of The Structure And Bonding Of Nitrosyl Metalloporphyrin Complexes, John P. Graham, Robbie Davis

Journal of the Arkansas Academy of Science

Density functional calculations were used to determine optimized geometries fornitrosyl-metalloporphyrin complexes of Fe(II),Co(II)and Mn(II).The optimized structures were found to be consistent with experimental data and previous computational predictions using single point density functional calculations. Vibrational frequencies for the N-0stretching mode were also calculated and shown to be consistent with experimental data. The nature of the bonding between the metal center and nitrosyl ligand is discussed in relation to the structure of the M-N-0 linkage. The results were found to be consistent with previous descriptions derived from the Fenske-Hall approximate molecular orbital method. Other interesting structural features in the optimized geometries …

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Aquatic Macroinvertebrates Of The Strawberry River System In North-Central Arkansas, George L. Harp, Henry W. Robison Jan 2006

Aquatic Macroinvertebrates Of The Strawberry River System In North-Central Arkansas, George L. Harp, Henry W. Robison

Journal of the Arkansas Academy of Science

The Strav/berry River has been designated an Extraordinary Resource Water, an Ecologically Sensitive Water Body, and a Natural and Scenic Waterway. As such, it is particularly important that the biodiversity of this river system be documented thoroughly. The purpose of this research was to develop a comprehensive list of the aquatic macroinvertebrates of the Strawberry River and its major tributaries. The information was developed from a thorough literature review and by examining specimens housed in various collections of the Arkansas State University Museum of Zoology and collections of the authors. The latter included 9 collections at 4 sites along the …

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Variational Symmetries And Conservation Laws In Linearized Gravity, Balraj Menon Jan 2006

Variational Symmetries And Conservation Laws In Linearized Gravity, Balraj Menon

Journal of the Arkansas Academy of Science

The methods of symmetry group analysis are applied to the action functional of linearized gravity to derive necessary conditions for the existence of variational symmetries. Two classes of variational symmetries of linearized gravity are discussed, and the local conservation laws associated with these variational symmetries are presented by applying Noether's theorem

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Parallel Algorithms For Multicriteria Shortest Path Problems, David L. Sonnier Jan 2006

Parallel Algorithms For Multicriteria Shortest Path Problems, David L. Sonnier

Journal of the Arkansas Academy of Science

This paper presents two strategies for solving multicriteria shortest path problems with more than two criteria. Given an undirected graph within vertices, medges, and a set of K weights associated with each edge, we define a path as a sequence of edges from vertex s to vertex t. We want to find the Pareto-optimal set of paths from s to t. The solutions proposed herein are based on cluster computing using the Message-Passing Interface (MPI) extensions to the C programming language. We solve problems with 3 and 4 criteria, using up to 8 processors in parallel and using solutions based …

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Perkin Reaction: Rapid And Efficient Process Optimization Through A Microwave/Design Of Experiments Couple, R. David Pace, Laura Mcwilliams Jan 2006

Perkin Reaction: Rapid And Efficient Process Optimization Through A Microwave/Design Of Experiments Couple, R. David Pace, Laura Mcwilliams

Journal of the Arkansas Academy of Science

Microwave chemistry and a Design of Experiments (DOE) protocol were employed together in order to rapidly and efficiently optimize a modified Perkin reaction. Microwave heating significantly reduced the reaction time, and the DOE provided a statistically significant understanding of underlying process relationships in a minimum number of experimental runs. In all, the reaction time was reduced from1hour to 2 minutes, factors important to yield were identified, an interesting cross-term interaction was discovered, and it was demonstrated that the more economical sodium acetate trihydrate catalyst was a viable alternative to the more costly anhydrous sodium acetate.

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Ichthyofaunal Assemblages In Three Approximate But Ecologically Diverse Streams In Clark County, Arkansas, C. Renn Tumlison, Scott Jordan, Lesley Self, Henry W. Robison Jan 2006

Ichthyofaunal Assemblages In Three Approximate But Ecologically Diverse Streams In Clark County, Arkansas, C. Renn Tumlison, Scott Jordan, Lesley Self, Henry W. Robison

Journal of the Arkansas Academy of Science

Three tributaries to the Ouachita River in eastern Clark County, Arkansas, empty into the river within a collective distance of about 9 km. The streams drain basins derived from the Wilcox formation, partially overlain by terrace and alluvial deposits. Despite their proximity, the streams are very different: L'Eau Frais has a gravel substrate and was recognized by the French as a cool water stream, Tupelo Creek is a bottomland stream from which numerous Water Tupelo (Nyssa aquatica) emerge, and Saline Bayou was named due to its marked salinity. We studied the assemblages of fishes in these 3 very different drainages …

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Electron Shock Waves, Mostafa Hemmati, Michael Weller, Taylor Duncan Jan 2006

Electron Shock Waves, Mostafa Hemmati, Michael Weller, Taylor Duncan

Journal of the Arkansas Academy of Science

In this paper we describe numerical investigations of breakdown waves concentrating on antiforce waves. We employed one-dimensional electron fluid dynamical equations for a luminous pulse wave propagating into a neutral gas region and subjected to an applied electric field. We assumed that the electrons were the main element in the propagation of the wave and that the electron gas partial pressure provided the driving force. These waves are considered to be shock fronted and are composed of two regions: the thin sheath region behind the shock front and the thicker quasi-neutral region following the sheath region. Our set of equations, …

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