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Articles 1 - 29 of 29
Full-Text Articles in Physical Sciences and Mathematics
On The Existence Of Multiple Periodic Solutions For The Vector P-Laplacian Via Critical Point Theory, Haishen Lu, Donal O'Regan, Ravi P. Agarwal
On The Existence Of Multiple Periodic Solutions For The Vector P-Laplacian Via Critical Point Theory, Haishen Lu, Donal O'Regan, Ravi P. Agarwal
Mathematics and System Engineering Faculty Publications
We study the vector p-Laplacian (∗){−(|u′|p−2u′)′=∇F(t,u)a.e.t∈[0,T],u(0)=u(T),u′(0)=u′(T),1
Investigation Of Egocentric And Exocentric Distance Perception In Virtual Environments: Application To Enhance Transfer Of Training In Multi-Model Ves, Cali Fidopiastis
Investigation Of Egocentric And Exocentric Distance Perception In Virtual Environments: Application To Enhance Transfer Of Training In Multi-Model Ves, Cali Fidopiastis
Link Foundation Modeling, Simulation and Training Fellowship Reports
In this report we summarize the results for three experiments completed during the Link Fellowship period. The aim of the first and second experiments were to test the efficacy of a novel assessment procedure for determining visual acuity and quantifying depth errors of observers wearing an optical see-t1u·ough prototype head-mounted display. If successful, the assessments could provide an optimization procedure capable of discerning limitations attributed to separate components of the VE system or to the system as a whole. The second experiment explored the feasibility of utilizing mixed reality (a mix of real and virtual items) environments for the study …
Correlogram Method For Comparing Bio-Sequences, Gandhali P. Samant
Correlogram Method For Comparing Bio-Sequences, Gandhali P. Samant
Theses and Dissertations
Sequence comparison is one of the most primitive operations used in bio-informatics. It is used as a basis for many other complex manipulations in the field of Computational Molecular Biology. Many methods and algorithms were developed to compare and align sequences effectively. Most of these methods use linear comparison and some standard scoring schemes to calculate the similarity between sequences. We described an alternative approach to compare sequences based on the correlogram method. This method has already been used in the past for comparing images. By using the correlogram method, a sequence is projected on a 3-D space and the …
Galactic Cosmic-Ray Modulation Using A Solar Minimum Mhd Heliosphere: A Stochastic Particle Approach, Bryan M. Ball, Ming Zhang, Hamid K. Rassoul, Timur J. Linde
Galactic Cosmic-Ray Modulation Using A Solar Minimum Mhd Heliosphere: A Stochastic Particle Approach, Bryan M. Ball, Ming Zhang, Hamid K. Rassoul, Timur J. Linde
Aerospace, Physics, and Space Science Faculty Publications
An example of Galactic cosmic-ray modulation in a fully three-dimensional heliosphere is presented here. We use a stochastic particle method to solve for modulation without requiring symmetric boundaries or fields. We include all typical modulation terms, including full three-dimensional drift. We have applied this to an MHD heliosphere appropriate for solar minimum conditions. This field includes nonradial solar wind velocity components, as well as a built-in nonspherical termination shock. Parameters that are of interest in modulation can be analyzed in detail, particularly the momentum change of cosmic rays during their transport through the heliosphere. We show radial profiles of modulation …
Dq Herculis In Profile: Whole Earth Telescope Observations And Smoothed Particle Hydrodynamics Simulations Of An Edge-On Cataclysmic Variable System, Matt A. Wood
Aerospace, Physics, and Space Science Faculty Publications
The old nova DQ Herculis was the Whole Earth Telescope Northern Hemisphere target for the 1997 July campaign and was observed on four nights with the SARA 0.9 m telescope during 2003 June. We present updated ephemerides for the eclipse and 71 s timings. The Fourier transform displays power at the presumed white dwarf spin period of 71.0655 s, but no significant power at either 142 or 35.5 s. The mean pulsed light curve is obtained by folding on the orbital period modulus the mean ephemeris of the 71 s period, and from this we calculate an O - C …
On Some Inequalities For Beta And Gamma Functions Via Some Classical Inequalities, Ravi P. Agarwal, Neven Elezović, Josip Pecaric
On Some Inequalities For Beta And Gamma Functions Via Some Classical Inequalities, Ravi P. Agarwal, Neven Elezović, Josip Pecaric
Mathematics and System Engineering Faculty Publications
We improve several results recently established by Dragomir et al. in (2000) for the Gamma and Beta functions. All we need is some clever applications of classical inequalities. Copyright © 2005 Hindawi Publishing Corporation.
Abundance Of Elements Beyond The Iron Group In Cool Do White Dwarfs, Pierre Chayer, Stéphane Vennes, Jean Jean François, Jeffrey W. Kruk
Abundance Of Elements Beyond The Iron Group In Cool Do White Dwarfs, Pierre Chayer, Stéphane Vennes, Jean Jean François, Jeffrey W. Kruk
Aerospace, Physics, and Space Science Faculty Publications
We report the presence of elements beyond the iron group in the atmospheres of the cool DO white dwarfs HD 149499 B and HZ 21. Photospheric lines of germanium (Z = 32), arsenic (33), selenium (34), tin (50), tellurium (52), iodine (53), and perhaps bromine (35) are observed in ultraviolet spectra of HD 149499 B obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE), the Goddard High Resolution Spectrograph (GHRS), and the International Ultraviolet Explorer. Germanium, arsenic, and tellurium are also observed in FUSE and GHRS spectra of HZ 21. Light elements such as carbon, silicon, phosphorus, and sulfur are present …
Cosmic Rays From Gamma-Ray Bursts In The Galaxy, Charles Dennison Dermer, Jeremy M. Holmes
Cosmic Rays From Gamma-Ray Bursts In The Galaxy, Charles Dennison Dermer, Jeremy M. Holmes
Aerospace, Physics, and Space Science Faculty Publications
The rate of terrestrial irradiation events by Galactic gamma-ray bursts (GRBs) is estimated using recent standard-energy results. We assume that GRBs accelerate high-energy cosmic rays, and we present results of three-dimensional simulations of cosmic rays moving in the Galactic magnetic field and diffusing through pitch-angle scattering. An on-axis GRB extinction event begins with a powerful prompt γ-ray and neutron pulse, followed by a longer lived phase from cosmic-ray protons and neutron-decay protons that diffuse toward Earth. Our results force a reinterpretation of reported ∼10¹⁸ eV cosmic-ray anisotropies and offer a rigorous test of the model in which high-energy cosmic rays …
The Model Dependence Of Solar Energetic Particle Mean Free Paths Under Weak Scattering, Gang Qin, Joseph R. Dwyer, Hamid K. Rassoul, Glenn M. Mason
The Model Dependence Of Solar Energetic Particle Mean Free Paths Under Weak Scattering, Gang Qin, Joseph R. Dwyer, Hamid K. Rassoul, Glenn M. Mason
Aerospace, Physics, and Space Science Faculty Publications
The mean free path is widely used to measure the level of solar energetic particles' diffusive transport. We model a solar energetic particle event observed by Wind STEP at 0.31-0.62 MeV nucleonˉ¹, by solving the focused transport equation using the Markov stochastic process theory. With different functions of the pitch angle diffusion coefficient D μμ, we obtain different parallel mean free paths for the same event. We show that the different values of the mean free path are due to the high anisotropy of the solar energetic particles. This makes it problematic to use just the mean free path to …
Singular Positone And Semipositone Boundary Value Problems Of Second Order Delay Differential Equations, Daqing Jiang, Xiaojie Xu, Donal O'Regan, Ravi P. Agarwal
Singular Positone And Semipositone Boundary Value Problems Of Second Order Delay Differential Equations, Daqing Jiang, Xiaojie Xu, Donal O'Regan, Ravi P. Agarwal
Mathematics and System Engineering Faculty Publications
In this paper we present some new existence results for singular positone and semipositone boundary value problems of second order delay differential equations. Throughout our nonlinearity may be singular in its dependent variable.
Hyperspectral Simulation And Recovery Of Submerged Targets In Turbid Waters, Charles R. Bostater
Hyperspectral Simulation And Recovery Of Submerged Targets In Turbid Waters, Charles R. Bostater
Ocean Engineering and Marine Sciences Faculty Publications
Modeled hyperspectral reflectance signatures just above the water surface are obtained from radiative transfer models to create synthetic images of targets below the water surface. Images are displayed as 24 bit RGB images of the water surface using selected channels. Example model outputs are presented in this paper for a hyperspectral Monte Carlo and a hyperspectral layered analytical iterative model of radiative transport within turbid shallow water types. Images at the selected wavelengths or channels centered at 490, 530 and 680 nm suggests the two models provide quite similar results when displayed as RGB images. The techniques are demonstrated to …
General Existence Principles For Nonlocal Boundary Value Problems With Ø-Laplacian And Their Applications, Ravi P. Agarwal, Donal O'Regan, Svatoslav Staněk
General Existence Principles For Nonlocal Boundary Value Problems With Ø-Laplacian And Their Applications, Ravi P. Agarwal, Donal O'Regan, Svatoslav Staněk
Mathematics and System Engineering Faculty Publications
The paper presents general existence principles which can be used for a large class of nonlocal boundary value problems of the form (ø(x′)) ′ = f1(t,x,x′) + f2(t,x,x′)F 1X + f3(t,x,x′)f2x,α(x) = 0, β(x) = 0, where fj satisfy local Carathéodory conditions on some [0,T] × Dj ⊂ ℝ, fj are either regular or have singularities in their phase variables (j = 1,2,3), f i, : C1[0.T] → C0[0,T] (i = 1,2), and α,β : C1[0.T] → ℝ are continuous. The proofs are based on the Leray-Schauder degree theory and use regularization and sequential techniques. Applications of general existence principles …
The Ccompton-Getting Effect Of Energetic Particles With An Anisotropic Pitch-Angle Distribution: An Application To Voyager 1 Results At ∼85 Au, Ming Zhang
Aerospace, Physics, and Space Science Faculty Publications
This paper provides a theoretical simulation of anisotropy measurements by the Low-Energy Charged Particle (LECP) experiment on Voyager. The model starts with an anisotropic pitch-angle distribution function in the solar wind plasma reference frame. It includes the effects of both Compton-Getting anisotropy and a perpendicular diffusion anisotropy that possibly exists in the upstream region of the termination shock. The calculation is directly applied to the measurements during the late 2002 particle event seen by Voyager 1. It is shown that the data cannot rule out either the model with zero solar wind speed or the one with a finite speed …
The Chromospheric Activity And Ages Of M Dwarf Stars In Wide Binary Systems, Nicole M. Silvestri, Suzanne L. Hawley, Terry D. Oswalt
The Chromospheric Activity And Ages Of M Dwarf Stars In Wide Binary Systems, Nicole M. Silvestri, Suzanne L. Hawley, Terry D. Oswalt
Aerospace, Physics, and Space Science Faculty Publications
We investigate the relationship between age and chromospheric activity for 139 M dwarf stars in wide binary systems with white dwarf companions. The age of each system is determined from the cooling age of its white dwarf component. The current limit for activity-age relations found for M dwarfs in open clusters is 4 Gyr. Our unique approach to finding ages for M stars allows for the exploration of this relationship at ages older than 4 Gyr. The general trend of stars remaining active for a longer time at a later spectral type is confirmed. However, our larger sample and greater …
Where Are The Magnetic White Dwarfs With Detached, Nondegenerate Companions?, James Liebert, Terry D. Oswalt
Where Are The Magnetic White Dwarfs With Detached, Nondegenerate Companions?, James Liebert, Terry D. Oswalt
Aerospace, Physics, and Space Science Faculty Publications
The Sloan Digital Sky Survey has already more than doubled the sample of white dwarfs with spectral classi- fications, the subset with detached M dwarf companions, and the subset of magnetic white dwarfs. In the course of assessing these new discoveries, we have noticed a curious, unexpected property of the total lists of magnetic white dwarfs and of white dwarf plus main-sequence binaries: there appears to be virtually zero overlap between the two samples! No confirmed magnetic white dwarf has yet been found in such a pairing with a main-sequence star. The same statement can be made for the samples …
Learning Implicit User Interest Hierarchy For Web Personalization, Hyoung-Rae Kim
Learning Implicit User Interest Hierarchy For Web Personalization, Hyoung-Rae Kim
Theses and Dissertations
Most web search engines are designed to serve all users in a general way, without considering the interests of individual users. In contrast, personalized web search engines incorporate an individual user's interests when choosing relevant web pages to return. In order to provide a more robust context for personalization, a user interest hierarchy (UIH) is presented. The UIH extracts a continuum of general to specific user interests from web pages and generates a uniquely personalized order to search results. This dissertation consists of five main parts. First, a divisive hierarchical clustering (DHC) algorithm is proposed to group words (topics) into …
Mindshare: A Collaborative Peer-To-Peer System For Small Groups, Gareth Charles Farrington
Mindshare: A Collaborative Peer-To-Peer System For Small Groups, Gareth Charles Farrington
Theses and Dissertations
We present Mindshare, a system for small group collaboration using Peer to Peer networking technology. This paper details the motivation behind its design, how it benefits users and details of its construction and operation. The solution focuses on the needs of small collaborating groups with limited computing experience and resources. Mindshare allows the group to share an unlimited number of files and visualize them in unified hierarchical file system. Mindshare synchronizes the files between users without user input. Its robust design allows files to be shared even when the owner is offline and allows users to work with files from …
Set Differential Equations With Causal Operators, Zahia Drici
Set Differential Equations With Causal Operators, Zahia Drici
Mathematics and System Engineering Faculty Publications
We obtain some basic results on existence, uniqueness, and continuous dependence of solutions with respect to initial values for set differential equations with causal operators.
Local Adjustment Of The Background Error Correlation For Surface Analyses Over Complex Terrain, David T. Myrick, John D. Horel, Steven M. Lazarus
Local Adjustment Of The Background Error Correlation For Surface Analyses Over Complex Terrain, David T. Myrick, John D. Horel, Steven M. Lazarus
Aeronautics Faculty Publications
The terrain between grid points is used to modify locally the background error correlation matrix in an objective analysis system. This modification helps to reduce the influence across mountain barriers of corrections to the background field that are derived from surface observations. This change to the background error correlation matrix is tested using an analytic case of surface temperature that encapsulates the significant features of nocturnal radiation inversions in mountain basins, which can be difficult to analyze because of locally sharp gradients in temperature. Bratseth successive corrections, optimal interpolation, and three-dimensional variational approaches are shown to yield exactly the same …
Keyword Spotting Using Normalization Of Posterior Probability Confidence Measures, Rachna Vijay Vargiya
Keyword Spotting Using Normalization Of Posterior Probability Confidence Measures, Rachna Vijay Vargiya
Theses and Dissertations
Keyword spotting techniques deal with recognition of predefined vocabulary keywords from a voice stream. This research uses HMM based keyword spotting algorithms for this purpose. The three most important components of a keyword detection system are confidence measure, pruning technique and evaluation of results. We suggest that best match for a keyword would be an alignment in which all constituent states have high emission probabilities. Therefore score of even the worst subsequence must also be better than a threshold and a path can be represented by the score of its worst subsequence match. This confidence measure is called Real Fitting. …
Evaluation Of A Wind Power Parameterization Using Tower Observations, Steven M. Lazarus, Jennifer Bewley
Evaluation Of A Wind Power Parameterization Using Tower Observations, Steven M. Lazarus, Jennifer Bewley
Ocean Engineering and Marine Sciences Faculty Publications
The spatial and temporal components of a published wind power parameterization method are evaluated using observed winds (9 m to 90 m) from 7 years of data collected at four towers in the Kennedy Space Center/Cape Canaveral Air Force Station network. The temporal component is governed by two parameterization inputs which represent the amplitude and mean of an assumed sinusoidal diurnal variation of the ratio of the 80 m to 10 m winds, respectively. Comparison with tower observations shows that the estimates of the mean ratio are robust but biased high, indicating that the temporal variation of the observations can …
Multidimensional Kolmogorov-Petrovsky Test For The Boundary Regularity And Irregularity Of Solutions To The Heat Equation, Ugur G. Abdulla
Multidimensional Kolmogorov-Petrovsky Test For The Boundary Regularity And Irregularity Of Solutions To The Heat Equation, Ugur G. Abdulla
Mathematics and System Engineering Faculty Publications
This paper establishes necessary and sufficient condition for the regularity of a characteristic top boundary point of an arbitrary open subset of ( ) for the diffusion (or heat) equation. The result implies asymptotic probability law for the standard -dimensional Brownian motion.
X-Ray Bursts Associated With Leader Steps In Cloud-To-Ground Lightning, Joseph R. Dwyer, Hamid K. Rassoul, M. Al-Dayeh, Lee Caraway, A. Chrest, Brian F. Wright, E. Kozak
X-Ray Bursts Associated With Leader Steps In Cloud-To-Ground Lightning, Joseph R. Dwyer, Hamid K. Rassoul, M. Al-Dayeh, Lee Caraway, A. Chrest, Brian F. Wright, E. Kozak
Aerospace, Physics, and Space Science Faculty Publications
X-ray and electric field measurements were made during five nearby negative natural lightning strikes in north central Florida during the summer of 2004. The observed X-ray emission typically was detected ∼1 ms before the first return stroke, during the stepped-leader phase, and had energies extending up to a few hundred keV. The X rays were produced in discrete, intense bursts emitted in coincidence with the formation of the leader steps, demonstrating unambiguously that the source of lightning X rays is closely related to the stepping process. The X-ray emission from lightning stepped leaders is found to be remarkably similar to …
Fixed Point Theory For Mönch-Type Maps Defined On Closed Subsets Of Fréchet Spaces: The Projective Limit Approach, Ravi P. Agarwal, Donal O'Regan, Jewgeni H. Dshalalow
Fixed Point Theory For Mönch-Type Maps Defined On Closed Subsets Of Fréchet Spaces: The Projective Limit Approach, Ravi P. Agarwal, Donal O'Regan, Jewgeni H. Dshalalow
Mathematics and System Engineering Faculty Publications
New Leray-Schauder alternatives are presented for Mönch-type maps defined between Fréchet spaces. The proof relies on viewing a Fréchet space as the projective limit of a sequence of Banach spaces.
Multiple Positive Solutions Of Singular Discrete P-Laplacian Problems Via Variational Methods, Ravi P. Agarwal
Multiple Positive Solutions Of Singular Discrete P-Laplacian Problems Via Variational Methods, Ravi P. Agarwal
Mathematics and System Engineering Faculty Publications
We obtain multiple positive solutions of singular discrete p-Laplacian problems using variational methods.
Pre-Computation Approach To Nonlinear Simulations Of Deformable Objects, Jernej Barbic
Pre-Computation Approach To Nonlinear Simulations Of Deformable Objects, Jernej Barbic
Link Foundation Modeling, Simulation and Training Fellowship Reports
My research area involves building real-time interactive simulations of solid deformable objects. For example, liver tissue should defo1m realistically during a vi1tual surgery simulation. A virtual assembly simulation can catch airplane construction design flaws early on during the manufacturing process. Deformable objects are also useful in computer games, for example to model the motion of trees in the wind. Researchers in computational physics, mechanics, and applied mathematics have been developing algorithms for simulations of deformable objects for the past 40 years. However, the partial differential equations of solid continuum mechanics that govern deformations of physical objects are very involved and …
A Comparison Between Monte Carlo Simulations Of Runaway Breakdown And Terrestrial Gamma-Ray Flash Observations, Joseph R. Dwyer, David M. Smith
A Comparison Between Monte Carlo Simulations Of Runaway Breakdown And Terrestrial Gamma-Ray Flash Observations, Joseph R. Dwyer, David M. Smith
Aerospace, Physics, and Space Science Faculty Publications
Monte Carlo simulations of the runaway breakdown of air are used to calculate the spectra of terrestrial gamma-ray flashes (TGFs), which are then compared with RHESSI and CGRO/BATSE observations. It is found that the recent RHESSI spectrum is not consistent with a source altitude above 24 km but can be well fit by a source in the range of 15-21 km, depending upon the electric field geometry of the source. Because 15 km is not unusual for the tops of thunderstorms, especially at low latitudes, and is lower than typical minimum sprite altitudes, the RHESSI data imply that thunderstorms and …
The Initiation Of Lightning By Runaway Air Breakdown, Joseph R. Dwyer
The Initiation Of Lightning By Runaway Air Breakdown, Joseph R. Dwyer
Aerospace, Physics, and Space Science Faculty Publications
A mechanism for lightning initiation by the sustained runaway breakdown of air is presented. Unlike earlior models that rely upon large cosmic-ray air showers, this mechanism uses the runaway electrons produced by the steady background of atmospheric cosmic-rays to amplify non-uniformities in the electric field. The ionization of air from the runaway electrons creates a region of discharge that propagates in the opposite direction of the electrons, enhancing the electric field in front of it to the point where a conventional breakdown can occur. As the discharged region grows, positron feedback can become important, dramatically increasing the flux of runaway …
X-Ray Bursts Produced By Laboratory Sparks In Air, Joseph R. Dwyer, Hamid K. Rassoul, Ziad H. Saleh, Martin A. Uman, J. Jerauld, J. Anderson Plumer
X-Ray Bursts Produced By Laboratory Sparks In Air, Joseph R. Dwyer, Hamid K. Rassoul, Ziad H. Saleh, Martin A. Uman, J. Jerauld, J. Anderson Plumer
Aerospace, Physics, and Space Science Faculty Publications
X-ray observations were made during fourteen 1.5 to 2.0 m high-voltage discharges in air produced by a 1.5 MV Marx circuit. All 14 discharges generated x-rays in the ∼30 to 150 keV range. The x-rays, which arrived in discrete bursts, less than 0.5 microseconds in duration, occurred from both positive and negative polarity rod-to-plane discharges as well as from small, 5-10 cm series spark gaps within the Marx generator. The x-ray bursts usually occurred when either the voltages across the gaps were the largest or were in the process of collapsing. The bursts are remarkably similar to the x-ray bursts …