Digital Commons Network^™

Oscillation Criteria For First-Order Forced Nonlinear Difference Equations, Ravi P. Agarwal, Said R. Grace, Tim Smith

Publications

Some new criteria for the oscillation of first-order forced nonlinear difference equations are established.

Robust Control Techniques Enabling Duty Cycle Experiments Utilizing A 6-Dof Crewstation Motion Base, A Full Scale Combat Hybrid Electric Power System, And Long Distance Internet Communications, Marc Compere, Jarrett Goodell, Miguel Simon, Wilford Smith, Mark Brudnak

Publications

The RemoteLink effort supports the U.S. Army's objective for developing and fielding next generation hybrid-electric combat vehicles. It is a distributed soldierin- the-Ioop and hardware-in-the-Ioop environment with a 6-DOF motion base for operator realism, a full-scale combat hybrid electric power system, and an operational context provided by OneSAF. The driver/gunner crewstations rest on one of two 6-DOF motion bases at the U.S. Army TARDEC Simulation Laboratory (TSL). The hybrid power system is located 2,450 miles away at the TARDEC Power and Energy System Integration Laboratory (P&E SIL). The primary technical challenge in the RemoteLink is to operate both laboratories together …

Developing A Methodology For Assessing Safety Programs Targeting Human Error In Aviation, Scott Shappell, Douglas Wiegmann

Publications

There is a need to develop an effective methodology for generating comprehensive intervention strategies that map current and proposed safety programs onto well-established types of human error. Two separate studies were conducted using recommendations from NTSB accident investigations and several joint FAA and industry working groups. The goal of the studies was to validate a proposed framework for developing and examining safety initiatives that target human error in aviation. The results suggest five approaches to reducing human factors associated with aviation accidents. When combined with the Human Factors Analysis and Classification System, the resulting Human Factors Intervention Matrix will provide …

Spitzer White Dwarf Planet Limits, F. Mullally, Ted Von Hippel, D. E. Winget

Publications

We present preliminary limits on the presence of planets around white dwarf stars using the IRAC photometer on the Spitzer space telescope. Planets emit strongly in the mid-infrared which allows their presence to be detected as an excess at these wavelengths. We place limits of 5 MJ for 8 stars assuming ages of 1 Gyr, and 10 MJ for 23 stars.We describe our survey, present our results and comment on approaches to improve our methodology.

Cluster Observations Of Reconnection Due To The Kelvin-Helmholtz Instability At The Dawnside Magnetospheric Flank, K. Nykyri, A. Otto, B. Lavraud, C. Mouikis, L. M. Kistler, A. Balogh, H. Rème

Publications

On 3 July 2001, the four Cluster satellites traversed along the dawnside magnetospheric flank and observed large variations in all plasma parameters. The estimated magnetopause boundary normals were oscillating in the z-direction and the normal component of the magnetic field showed systematic ~2–3 min bipolar variations for 1 h when the IMF had a small positive bz-component and a Parker-spiral orientation in the x, y-plane. Brief ~33 s intervals with excellent deHoffman Teller frames were observed satisfying the Wal´en relation. Detailed comparisons with 2- D MHD simulations indicate that Cluster encountered rotational discontinuities generated by Kelvin-Helmholtz instability. We estimate a …

The Effect Of Auditory And Visual Distracters On The Useful Field Of View: Implications For The Driving Task, Joanne Wood, Alex Chaparro, Louise Hickson, Nick Thyer, Philippa Carter, Julie Hancock, Adrene Hoe, Ivy Le, Louisa Sahetapy, Floravel Ybarzabal

Publications

PURPOSE. The driving environment is becoming increasingly complex, including both visual and auditory distractions within the in-vehicle and external driving environments. This study was designed to investigate the effect of visual and auditory distractions on a performance measure that has been shown to be related to driving safety, the useful field of view.

METHODS. A laboratory study recorded the useful field of view in 28 young visually normal adults (mean 22.6 +- 2.2 years). The useful field of view was measured in the presence and absence of visual distracters (of the same angular subtense as the target) and with three …

Efficacy Of Virtual Models In A Production Systems Course, Lawrence Whitman, Barbara Chaparro

Publications

Wichita State University has developed an integrated set of virtual reality models of an aircraft assembly line. These models are intended to provide students an ‘artifact’ of industrial and manufacturing engineering by providing a realistic environment for initial learning and application. By utilizing a virtual model of the line, students are able to view the process and interrogate the process details, make changes and observe the effects, and gain a better understanding of the concepts and their interrelationships. This paper presents the method used to assess if virtual models (computer models of a real factory) lead to: improved perception of …

Signals For Lorentz Violation In Post-Newtonian Gravity, Quentin G. Bailey, V. Alan Kostelecký

Publications

The pure-gravity sector of the minimal standard-model extension is studied in the limit of Riemann spacetime. A method is developed to extract the modified Einstein field equations in the limit of small metric fluctuations about the Minkowski vacuum, while allowing for the dynamics of the 20 independent coefficients for Lorentz violation. The linearized effective equations are solved to obtain the post-Newtonian metric. The corresponding post-Newtonian behavior of a perfect fluid is studied and applied to the gravitating many-body system. Illustrative examples of the methodology are provided using bumblebee models. The implications of the general theoretical results are studied for a …

Debris Disks Around White Dwarfs: The Daz Connection, Mukremin Kilic, Ted Von Hippel, Et Al.

Publications

We present near-infrared spectroscopic observations of 20 previously known DAZ white dwarfs obtained at the NASA Infrared Telescope Facility. Two of these white dwarfs (G29-38 and GD 362) are known to display significant K-band excesses due to circumstellar debris disks. Here we report the discovery of excess K-band radiation from another DAZ white dwarf WD0408041 (GD56). Using spectroscopic observations, we show that the excess radiation cannot be explained by a stellar or substellar companion, and is likely to be caused by a warm debris disk. Our observations strengthen the connection between the debris disk phenomena and the observed …

Innovative Schematic Concept Analysis For A Space Suit Portable Life Support Subsystem, M. Schuller, R. Kobrick, T. Lalk, L. Wiseman, F. Little, Et Al.

Publications

Conceptual designs for a space suit Personal Life Support Subsystem (PLSS) were developed and assessed to determine if upgrading the system using new, emerging, or projected technologies to fulfill basic functions would result in mass, volume, or performance improvements. Technologies were identified to satisfy each of the functions of the PLSS in three environments (zero-g, Lunar, and Martian) and in three time frames (2006, 2010, and 2020). The viability of candidate technologies was evaluated using evaluation criteria such as safety, technology readiness, and reliability. System concepts (schematics) were developed for combinations of time frame and environment by assigning specific technologies …

Inverting Color-Magnitude Diagrams To Access Precise Star Cluster Parameters: A Bayesian Approach, Ted Von Hippel, Et Al.

Publications

We demonstrate a new Bayesian technique to invert color-magnitude diagrams of main-sequence and white dwarf stars to reveal the underlying cluster properties of age, distance, metallicity, and line-of-sight absorption, as well as individual stellar masses. The advantages our technique has over traditional analyses of color-magnitude diagrams are objectivity, precision, and explicit dependence on prior knowledge of cluster parameters. Within the confines of a given set of often-used models of stellar evolution, a single mapping of initial to final masses, and white dwarf cooling, and assuming photometric errors that one could reasonably achieve with the Hubble Space Telescope, our technique …

Reweighting At-Sat To Mitigate Group Score Differences, Andrew R. Dattel, Raymond E. King

Publications

The Air Traffic Selection and Training (AT-SAT) test battery is the selection tool for applicants for Air Traffic Control Specialist (ATCS) positions within the Federal Aviation Administration (FAA) who have not previously been employed as an air traffic controller. AT-SAT is an aptitude test developed to predict the likelihood of successfully learning ATCS skills. Before operational use, however, concerns were raised about the low passing rate of incumbent (who are fully trained and certified) ATCS personnel (who participated in the initial research) and score differences between groups, which could result in adverse impact (possible unfair discrimination). To address these concerns, …

Book Review: Evolution Of Stars And Stellar Populations, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Evolution of Stars and Stellar Populations by Maurizio Salaris and Santi Cassisi Wiley, 2005 374p, 047009219X $150.00, 047009219X $60.00

Human Error And Commercial Aviation Accidents: A Comprehensive, Fine-Grained Analysis Using Hfacs, Scott Shappell, Cristy Detwiler, Kali Holcomb, Carla Hackworth, Albert Boquet, Douglas Wiegmann

Publications

The Human Factors Analysis and Classification System (HFACS) is a theoretically based tool for investigating and analyzing human error associated with accidents and incidents. Previous research has shown that HFACS can be reliably used to identify general trends in the human factors associated with military and general aviation accidents. The aim of this study was to extend previous examinations of aviation accidents to include specific aircrew, environmental, supervisory, and organizational factors associated with 14 CFR Part 121 (Air Carrier) and 14 CFR Part 135 (Commuter) accidents using HFACS. The majority of causal factors were attributed to the aircrew and the …

Lp 400-22, A Very Low Mass And High-Velocity White Dwarf, Adela Kawka, Stephane Vennes, Terry D. Oswalt, J. Allyn Smith, Nicole M. Silvestri

Publications

We report the identification of LP 400-22 (WD 2234 + 222) as a very low mass and high-velocity white dwarf. The ultraviolet GALEX and optical photometric colors and a spectral line analysis of LP 400-22 show this star to have an effective temperature of 11,080 ± 140 K and a surface gravity of log g p 6.32 ± 0.08. Therefore, this is a helium-core white dwarf with a mass of 0.17 M_Ꙩ. The tangential velocity of this white dwarf is 414 ± 43 km s^-1, making it one of the fastest moving white dwarfs known. We …

The Mystery Deepens: Spitzer Observations Of Cool White Dwarfs, Mukremin Kilic, Ted Von Hippel, Et Al.

Publications

We present 4.5 and 8 µm photometric observations of 18 cool white dwarfs obtained with the Spitzer Space Telescope. Our observations demonstrate that four white dwarfs with Teᶠᶠ < 6000 K show slightly depressed mid-infrared fluxes relative to white dwarf models. In addition, another white dwarf with a peculiar optical and near-infrared spectral energy distribution (LHS 1126) is found to display significant flux deficits in Spitzer observations. These mid-infrared flux deficits are not predicted by the current white dwarf models including collision-induced absorption due to molecular hydrogen. We postulate that either the collision-induced absorption calculations are incomplete or there are other unrecognized physical processes occurring in cool white dwarf atmospheres. The spectral energy distribution of LHS 1126 surprisingly fits a Rayleigh-Jeans spectrum in the infrared, mimicking a hot white dwarf with effective temperature well in excess of 105 K. This implies that the source of this flux deficit is probably not molecular absorption but some other process.

Traveling Wavetrains In The Complex Cubic-Quintic Ginzburg-Laundau Equation, S.C. Mancas, S. Roy Choudhury

Publications

In this paper we use a traveling wave reduction or a so–called spatial approximation to comprehensively investigate the periodic solutions of the complex cubic–quintic Ginzburg–Landau equation. The primary tools used here are Hopf bifurcation theory and perturbation theory. Explicit results are obtained for the post–bifurcation periodic orbits and their stability. Generalized and degenerate Hopf bifurcations are also briefly considered to track the emergence of global structure such as homoclinic orbits.

Origin Of The Turbulent Spectra In The High-Altitude Cusp: Cluster Spacecraft Observations, K. Nykyri, B. Grison, P. J. Cargill, B. Lavraud, E. Lucek, I. Dandouras, A. Balogh, N. Cornilleau-Wehrlin, H. Reme

Publications

High-resolution magnetic field data from Cluster Flux GateMagnetometer (FGM) and the Spatio-Temporal Analysis of Field Fluctuations (STAFF) instruments are used to study turbulent magnetic field fluctuations during the highaltitude cusp crossing on 17 March 2001. Despite the quiet solar wind conditions, the cusp was filled with magnetic field turbulence whose power correlates with the field-aligned ion plasma flux. The magnetic field wave spectra shows power law behavior with both double and single slopes with break in the spectra usually occurring in the vicinity of the local ion cyclotron frequency. Strong peaks in the wave power close to local ion cyclotron …

Bifurcations And Competing Coherent Structures In The Cubic-Quintic Ginzburg-Landau Equation I: Plane Wave (Cw) Solutions, S.C. Mancas, S. Roy Choudhury

Publications

Singularity Theory is used to comprehensively investigate the bifurcations of the steady-states of the traveling wave ODEs of the cubic-quintic Ginzburg-Landau equa- tion (CGLE). These correspond to plane waves of the PDE. In addition to the most general situation, we also derive the degeneracy conditions on the eight coefficients of the CGLE under which the equation for the steady states assumes each of the possible quartic (the quartic fold and an unnamed form), cubic (the pitchfork and the winged cusp), and quadratic (four possible cases) normal forms for singularities of codimension up to three. Since the actual governing equations are …

Book Review: Fred Hoyle's Universe, T. D. Oswalt

Publications

This document is Dr. Oswalt’s review of Fred Hoyle's Universe by Jane Gregory. Oxford, 2005 406p, 0198507917 $29.95

Beneath The Tip Of The Iceberg: A Human Factors Analysis Of General Aviation Accidents In Alaska Versus The Rest Of The United States, Cristy Detwiler, Carla Hackworth, Kali Holcomb, Albert Boquet, Elaine Pfleiderer, Douglas Wiegmann, Scott Shappell

Publications

Historically, general aviation (GA) accidents have been overlooked and their impact under-appreciated when compared with those in the commercial or military sector. Recently however, the Federal Aviation Administration and other governmental and civilian organizations have focused their attention on one piece of this proverbial “iceberg,” that being GA accidents occurring in Alaska. This study examines more than 17,000 GA accidents using the Human Factors Analysis and Classification System. Comparisons of Alaska to the rest of the U.S. (RoUS) included traditional demographic and environmental variables, as well as the human errors committed by aircrews. Overall, categorical differences among unsafe acts (decision …

The Clock Paradox In A Static Homogeneous Gravitational Field, Preston Jones, Lucas F. Wanex

Publications

The gedanken experiment of the clock paradox is solved exactly using the general relativistic equations for a static homogeneous gravitational field. We demonstrate that the general and special relativistic clock paradox solutions are identical and in particular that they are identical for finite acceleration. Practical expressions are obtained for proper time and coordinate time by using the destination distance as the key observable parameter. This solution provides a formal demonstration of the identity between the special and general relativistic clock paradox with finite acceleration and where proper time is assumed to be the same in both formalisms. By solving the …

Numerical Simulation Of Nonlinear Elastic Wave Propagation In Piecewise Homogeneous Media, Arkadi Berezovski, Mihhail Berezovski, Juri Engelbrecht

Publications

Systematic experimental work [S. Zhuang, G. Ravichandran, D. Grady, J. Mech. Phys. Solids 51 (2003) 245–265] on laminated composites subjected to high velocity impact loading exhibits the dispersed wave field and the oscillatory behavior of waves with respect to a mean value. Such a behavior is absent in homogeneous solids. An approximate solution to the plate impact in layered heterogeneous solids has been developed in [X. Chen, N. Chandra, A.M. Rajendran, Int. J. Solids Struct. 41 (2004) 4635–4659]. The influence of the particle velocity on many process characteristics was demonstrated. Based on earlier results [A. Berezovski, J. Engelbrecht, G.A. Maugin, …

Intra-Industry Specialization And Trade Expansion In U.S. Trade With The Free Trade Areas Of The Americas (Ftaa), John R. Ledgerwood, E. M. Ekanayake, Mihalis Halkides

Publications

This paper aims to explain the extent of vertical and horizontal intra-industry trade (IIT) in United State's foreign trade with the other 33 members of the Free Trade Areas of the Americas (FTAA). It also attempts to identify the country- and industry-specific determinants of vertical and horizontal IIT. This study uses detailed trade data at the 10-digit Harmonized System (HS) industry level and covers a longer and more recent period, 1990 through 2005. The Grubel-Lloyd intra-industry trade index is used to calculate the intensity of these two types of intra-industry trade. One of the main findings is that, with the …

Cognitive Engineering Research Methodology: A Proposed Study Of Visualization Analysis Techniques, Cristin M. Hall, Sonya A.H. Mcmullen, David L. Hall

Publications

The rapid development of new sensors and wide-band communications provides the capability to collect enormous amounts of data. An increasing challenge involves how to understand and interpret the data to yield knowledge about evolving situations or threats (e.g., of military situations, state of complex systems, etc.). New visualization tools and techniques are becoming available to support advanced visualization including three-dimensional, full immersion display environments and tools to support novel visualizations. Examples include network system display tools and evolving multi-sensory situation environments. Despite the emergence of such tools, there has been limited systematic test and evaluations to determine the efficacy of …

On Doubly Periodic Solutions Of Quasilinear Hyperbolic Equations Of The Fourth Order, T. Kiguradze, T. Smith

Publications

The problem on doubly periodic solutions is considered for a class of quasilinear hyperbolic equations. Effective sufficient conditions of solvability and unique solvability of this problem are established.

Rocket And Radar Investigation Of Background Electrodynamics And Bottom-Type Scattering Layers At The Onset Of Equatorial Spread F, D. L. Hysell, M. F. Larsen, C. M. Swenson, Aroh Barjatya, Et. Al

Publications

Sounding rocket experiments were conducted during the NASA EQUIS II campaign on Kwajalein Atoll designed to elucidate the electrodynamics and layer structure of the postsunset equatorial F region ionosphere prior to the onset of equatorial spread F (ESF). Experiments took place on 7 and 15 August 2004, each comprised of the launch of an instrumented and two chemical release sounding rockets. The instrumented rockets measured plasma number density, vector electric fields, and other parameters to an apogee of about 450 km. The chemical release rockets deployed trails of trimethyl aluminum (TMA) which yielded wind profile measurements. The Altair radar was …

Which Theory Applies: An Analysis Of Information Systems Research, Leila Halawi, Richard Mccarthy

Publications

Research in information systems has rapidly expanded during its relatively brief existence. IT offers organizations a fundamental decision-enhancing environment that extends new opportunities, therefore producing thriving, competitive firms, adding business value and offering valuable products and services to customers. Research within the IT domain has produced several new theories, some of which have been used to help explain and predict end-user use of technologies. We provide a comprehensive overview of the major IT theories and review their theoretical fundamentals.

Observations Of Triboelectric Charging Effects On Langmuir-Type Probes In Dusty Plasma, Aroh Barjatya, C. M. Swenson

Publications

Investigation of Earth’s mesosphere using sounding rockets equipped with a myriad of instruments has been a highly active field in the last 2 decades. This paper presents data from three separate instruments: an RF impedance probe, a DC fixed bias Langmuir probe, and an electric field probe, that were flown on a mesospheric sounding rocket flight investigating the presence of charged dust within and/or around a sporadic metal layer. The combined data set indicates a case of payload surface charging, the causes of which are investigated within this paper. A generic circuit model is developed to analyze payload charging and …

Book Review: Digital Crime And Forensic Science In Cyberspace, Gary C. Kessler

Publications

This document is Dr. Kessler's review of Digital Crime and Forensic Science in Cyberspace, by P. Kanellis, E. Kiountouzis, N. Kolokotronis, and D. Martakos. Idea Group Publishing, 2006. ISBN: 1-59140-873-3.