# Physical Sciences and Mathematics Commons™

Articles 1 - 30 of 74910

## Full-Text Articles in Physical Sciences and Mathematics

Jan 2016

#### Matrix Multiplication, Trilinear Decompositions, Apa Algorithms, And Summation, Victor Pan

##### Faculty Works

Matrix multiplication (hereafter we use the acronym MM) is among the most

fundamental operations of modern computations. The efficiency of its

performance depends on various factors, in particular vectorization, data

movement and arithmetic complexity of the computations, but here we focus

just on the study of the arithmetic cost and the impact of this study on

other areas of modern computing. In the early 1970s it was expected that

the straightforward cubic time algorithm for MM will soon be accelerated

to enable MM in nearly quadratic arithmetic time, with some far fetched

implications. While pursuing this goal the mainstream research ...

An Optimal Threshold Strategy In The Two-Envelope Problem With Partial Information, Martin Egozcue, Luis Fuentes García Oct 2015

#### An Optimal Threshold Strategy In The Two-Envelope Problem With Partial Information, Martin Egozcue, Luis Fuentes García

##### Martin Egozcue

No abstract provided.

Castelnuovo–Mumford Regularity And Arithmetic Cohen–Macaulayness Of Complete Bipartite Subspace Arrangements, Zach Teitler, Douglas A. Torrence Jun 2015

#### Castelnuovo–Mumford Regularity And Arithmetic Cohen–Macaulayness Of Complete Bipartite Subspace Arrangements, Zach Teitler, Douglas A. Torrence

##### Mathematics Faculty Publications and Presentations

We give the Castelnuovo–Mumford regularity of arrangements of (n−2)-planes in Pn whose incidence graph is a sufficiently large complete bipartite graph, and determine when such arrangements are arithmetically Cohen–Macaulay.

#### Gal: A Stepwise Model For Automated Cloud Shadow Detection In Hico Oceanic Imagery Utilizing Guided Filter, Pixel Assignment, And Geometric Linking, Jennerpher Renee Meyers

##### Dissertations

Detection of cloud shadow pixels is an important step in image processing in several remote sensing ocean-color application domains, such as obtaining chlorophyll content. While shadow detection algorithms do exist, the vast majority are for over land which leaves few options for detection over water.

The detection of cloud shadow over water in HICO imagery is a unique problem. As its name implies, HICO (Hyperspectral Imager for the Coastal Ocean) imagery is produced for coastal and oceanic regions. Since land based algorithms remove water before processing, these approaches would not be applicable. The only currently published HICO shadow pixel detection ...

#### Video Event Recognition And Prediction Based On Temporal Structure Analysis, Kang Li

##### Computer Engineering Dissertations

The increasing ubiquitousness of multimedia information in today's world has positioned video as a favored information vehicle, and given rise to an astonishing generation of social media and surveillance footage. Consumer-grade video is becoming abundant on the Internet, and it is now easier than ever to download multimedia material of any kind and quality. This raises a series of technological demands for automatic video understanding, which has motivated the research community to guide its steps towards a better attainment of such capabilities. As a result, current trends on cognitive vision promise to recognize complex events and self-adapt to different ...

Apr 2015

#### A Right To Cyber Counter Strikes - The Risks Of Legalizing Hack Back, Jan Kallberg

##### Jan Kallberg

The idea to legalize hacking back has gained traction the last years and received several influential corporate and political proponents in the United States and Europe. The growing frustration with repeated cyberattacks and lack of credible law enforcement pushes for alternative ways to prevent future cyberattacks. As of today, counter cyberattacks are illegal in a majority of the nations because it constitutes another cybercrime independent from the initial attack. If cyber counter attacks were legalized it raises a set of questions. The first line of questions are linked to the underlying assumptions that the proposal to legalize counter cyberattacks are ...

Apr 2015

#### Random Multipliers Numerically Stabilize Gaussian And Block Gaussian Elimination: Proofs And An Extension To Low-Rank Approximation, Victor Pan, Xiaodong Yan

##### Faculty Works

We study two applications of standard Gaussian random multipliers. At first we prove that with a probability close to 1 such a multiplier is expected to numerically stabilize Gaussian elimination with no pivoting as well as block Gaussian elimination. Then, by extending our analysis, we prove that such a multiplier is also expected to support low-rank approximation of a matrix without customary oversampling. Our test results are in good accordance with this formal study. The results remain similar when we replace Gaussian multipliers with random circulant or Toeplitz multipliers, which involve fewer random parameters and enable faster multiplication. We formally ...

Dust Devils And Dustless Vortices On A Desert Playa Observed With Surface Pressure And Solar Flux Logging, Ralph D. Lorenz, Brian K. Jackson Mar 2015

#### Dust Devils And Dustless Vortices On A Desert Playa Observed With Surface Pressure And Solar Flux Logging, Ralph D. Lorenz, Brian K. Jackson

##### Physics Faculty Publications and Presentations

Dust devils are convective vortices rendered visible by lofted dust, and may be a significant means of injecting dust into the atmosphere, on both Earth and Mars. The fraction of vortices that are dust-laden is not well-understood, however. Here we report a May/June 2013 survey on a Nevada desert playa using small stations that record pressure and solar flux with high time resolution (2 Hz): these data allow detection of vortices and an estimate of the dust opacity of the subset of vortices that geometrically occult the sun. The encounter rate of vortex pressure drops of 0.3 hPa ...

Validated Automatic Brain Extraction Of Head Ct Images, John Muschelli Iii, Natalie L. Ullman, Daniel F. Hanley, Paul Vespa, Ciprian M. Crainiceanu Mar 2015

#### Validated Automatic Brain Extraction Of Head Ct Images, John Muschelli Iii, Natalie L. Ullman, Daniel F. Hanley, Paul Vespa, Ciprian M. Crainiceanu

##### John Muschelli III

Background

X-ray Computed Tomography (CT) imaging of the brain is commonly used in diagnostic settings. Al- though CT scans are primarily used in clinical practice, they are increasingly used in research. A fundamental processing step in brain imaging research is brain extraction – the process of separating the brain tissue from all other tissues. Methods for brain extraction have either been validated but not fully automated, or have been fully automated and informally proposed, but never formally validated.

Aim

To systematically analyze and validate the performance of FSL’s brain extraction tool (BET) on head CT images of patients with intracranial ...

Slides: Practicing Sustainability In Natural Resource Industries, Gary D. Libecap Feb 2015

#### Slides: Practicing Sustainability In Natural Resource Industries, Gary D. Libecap

##### Natural Resource Industries and the Sustainability Challenge (Martz Winter Symposium, February 27-28)

Presenter: Gary D. Libecap, Bren School of Environmental Science and Management and Economics Department, University of California, Santa Barbara, National Bureau of Economic Research (NBER)

10 slides

Tectono-Metamorphic History Of The Eastern Taureau Shear Zone, Mauricie Area, Québec: Implications For The Exhumation Of The Mid-Crust In The Grenville Province, Renaud Soucy La Roche, Félix Gervais, Alain Tremblay, James L. Crowley, Gilles Ruffet Feb 2015

#### Tectono-Metamorphic History Of The Eastern Taureau Shear Zone, Mauricie Area, Québec: Implications For The Exhumation Of The Mid-Crust In The Grenville Province, Renaud Soucy La Roche, Félix Gervais, Alain Tremblay, James L. Crowley, Gilles Ruffet

##### Geosciences Faculty Publications and Presentations

This study investigates the tectono-metamorphic history and exhumation mechanisms of the mid-crustal Mékinac-Taureau domain of the Mauricie area, central Grenville Province. Macro- and micro-structural analyses reveal the top-down-to-the-ESE sense of shear on the eastern Taureau shear zone, a major extensional structure that exhumed the mid-crustal Mékinac-Taureau domain and juxtaposed it against the lower grade rocks of the Shawinigan domain. Peak metamorphism in the Mékinac-Taureau domain, inferred to be the result of northwestward thrusting and regional crustal thickening, took place under PT conditions of 1000–1100 MPa and 820–880 °C prior to 1082 ± 20 Ma. Retrograde conditions varying from ...

Jan 2015

#### Negative Binomial Regerssion, 2nd Ed, 2nd Print, Errata And Comments, Joseph Hilbe

##### Joseph M Hilbe

Errata and Comments for 2nd printing of NBR2, 2nd edition. Previous errata from first printing all corrected. Some added and new text as well.

Torsion Free Biconformal Spaces: Reducing The Torsion Field Equations, James Thomas Wheeler Jan 2015

#### Torsion Free Biconformal Spaces: Reducing The Torsion Field Equations, James Thomas Wheeler

##### James Thomas Wheeler

Our goal is to solve the full set of torsion and co-torsion field equations of Euclidean biconformal space, with only the assumption of vanishing torsion. Here we begin by resolving the involution constraints, symmetry conditions and torsion field equation into a single equation for further study.

Jan 2015

#### Grafalgo - A Library Of Graph Algorithms And Supporting Data Structures, Jonathan Turner

##### All Computer Science and Engineering Research

This report provides an overview of Grafalgo, an open-source library of graph algorithms and the data structures used to implement them. The programs in this library were originally written to support a graduate class in advanced data structures and algorithms at Washington University. Because the code's primary purpose was pedagogical, it was written to be as straightforward as possible, while still being highly efficient. Grafalgo is implemented in C++ and incorporates some features of C++11.

The library is available on an open-source basis and may be downloaded from https://code.google.com/p/grafalgo/. Source code documentation is ...

#### Statistical Variation Of Diverse Light Emission Measurements From Bisphenol/Amine Epoxy Under Energetic Electron Bombardment, Justin Christensen

##### Physics Capstone Project

Dielectric materials subjected to energetic electron fluxes can emit light in several forms. We have observed three distinct types of emissions: (i) short-duration (<1 ms), high-intensity electrostatic discharge (ESD) or “arc” events; (ii) intermediate-duration, high-intensity events which begin with a bright arc followed by an exponential decay of intensity (~10 to 100 s decay constant), termed “flares”; and (iii) long-duration, low-intensity emission, or cathodoluminescence, that continues as long as the electron flux is on. These events were studied for bulk samples of bisphenol/amine epoxy, using an electron gun with varying current densities (0.3 to 5 nA/cm2) and energies (12 to 40 keV) in a high vacuum chamber. Light emitted from the samples was measured with a high-sensitivity visible to near-infrared video camera. Results of the spatial and temporal extent for each type of event are presented as well as a discussion of how absolute spectral radiance and rates for each type of event are dependent on incident electron current density, energy, and power density and on material type, temperature, and thickness. Applications of this research to spacecraft charging and light emissions are discussed.

Minimum Rank Of Graphs With Loops, Chassidy Bozeman, Annavictoria Ellsworth, Leslie Hogben, Jephian Chin-Hung Lin, Gabi Maurer, Kathleen Nowak, Aaron Rodriguez, James Strickland Jan 2015

#### Minimum Rank Of Graphs With Loops, Chassidy Bozeman, Annavictoria Ellsworth, Leslie Hogben, Jephian Chin-Hung Lin, Gabi Maurer, Kathleen Nowak, Aaron Rodriguez, James Strickland

##### Electronic Journal of Linear Algebra

A loop graph $\mf G$ is a finite undirected graph that allows loops but does not allow multiple edges. The set $\sym(\lG)$ of real symmetric matrices associated with a loop graph $\lG$ of order $n$ is the set of symmetric matrices $A=[a_{ij}]\in\Rnn$ such that $a_{ij}\ne 0$ if and only if $ij\in E(\lG)$. The minimum (maximum) rank of a loop graph is the minimum (maximum) of the ranks of the matrices in $\sym(\lG)$. We characterize loop graphs having minimum rank at most two (by forbidden induced subgraphs and graph complements) and ...

Modeling Count Data; Errata And Comments, Joseph M. Hilbe Jan 2015

#### Modeling Count Data; Errata And Comments, Joseph M. Hilbe

##### Joseph M Hilbe

Modeling Count Data: Errata and Comments PDF. Will be updated on a continuing basis.

A Comparative Study Of The Oxidation Characteristics Of Two Gasoline Fuels And An N-Heptane/Iso-Octane Surrogate Mixture, Tamour Javed, Ehson F. Nasir, Et-Touhami Es-Sebbar, Aamir Farooq Jan 2015

#### A Comparative Study Of The Oxidation Characteristics Of Two Gasoline Fuels And An N-Heptane/Iso-Octane Surrogate Mixture, Tamour Javed, Ehson F. Nasir, Et-Touhami Es-Sebbar, Aamir Farooq

##### Dr. Et-touhami Es-sebbar

Ignition delay times and CO, H2O, OH and CO2 time-histories were measured behind reflected shock waves for two FACE (Fuels for Advanced Combustion Engines) gasolines and one PRF (Primary Reference Fuel) blend. The FACE gasolines chosen for this work are primarily paraffinic and have the same octane rating (∼RON = 84) as the PRF blend, but contain varying amounts of iso- and n-paraffins. Species time-histories and ignition delay times were measured using laser absorption methods over a temperature range of 1350–1550 K and pressures near 2 atm. Measured species time-histories and ignition delay times of the PRF blend and the ...

Peat Formation Concentrates Arsenic Within Sediment Deposits Of The Mekong Delta, Jason W. Stuckey, Michael V. Schaefer, Benjamin D. Kocar, Jessica Dittmar, Juan Lezama Pacheco, Shawn G. Benner, Scott Fendorf Jan 2015

#### Peat Formation Concentrates Arsenic Within Sediment Deposits Of The Mekong Delta, Jason W. Stuckey, Michael V. Schaefer, Benjamin D. Kocar, Jessica Dittmar, Juan Lezama Pacheco, Shawn G. Benner, Scott Fendorf

##### Geosciences Faculty Publications and Presentations

Mekong River Delta sediment bears arsenic that is released to groundwater under anaerobic conditions over the past several thousand years. The oxidation state, speciation, and distribution of arsenic and the associated iron bearing phases are crucial determinants of As reactivity in sediments. Peat from buried mangrove swamps in particular may be an important host, source, or sink of arsenic in the Mekong Delta. The total concentration, speciation, and reactivity of arsenic and iron were examined in sediments in a Mekong Delta wetland by X-ray fluorescence spectrometry (XRF), X-ray absorption spectroscopy (XAS), and selective chemical extractions. Total solid-phase arsenic concentrations in ...

#### Some Covariance Inequalities For Non-Monotonic Functions With Applications To Mean-Variance Indiference Curves And Bank Hedging, Martin Egozcue

##### Martin Egozcue

No abstract provided.

Applying Multiple Imputation For External Calibration To Propensty Score Analysis, Yenny Webb-Vargas, Kara E. Rudolph, D. Lenis, Peter Murakami, Elizabeth A. Stuart Jan 2015

#### Applying Multiple Imputation For External Calibration To Propensty Score Analysis, Yenny Webb-Vargas, Kara E. Rudolph, D. Lenis, Peter Murakami, Elizabeth A. Stuart

##### Johns Hopkins University, Dept. of Biostatistics Working Papers

Although covariate measurement error is likely the norm rather than the exception, methods for handling covariate measurement error in propensity score methods have not been widely investigated. We consider a multiple imputation-based approach that uses an external calibration sample with information on the true and mismeasured covariates, Multiple Imputation for External Calibration (MI-EC), to correct for the measurement error, and investigate its performance using simulation studies. As expected, using the covariate measured with error leads to bias in the treatment effect estimate. In contrast, the MI-EC method can eliminate almost all the bias. We confirm that the outcome must be ...

Gathering The Requirements For A Mobile Device Tutorial For Older Adults, Michele A. Washington Jan 2015

#### Gathering The Requirements For A Mobile Device Tutorial For Older Adults, Michele A. Washington

##### GSCIS ETDs

The United States, as well as other nations, is experiencing an increase in the older adult population. As a result of older adults living longer, mobile devices can be a major component in improving older adults' quality of life. However, older adults may encounter difficulties when using the mobile devices. This research examined the requirements in addressing the needs of older adults when using a mobile device. Specifically, the research focused on gathering the task and feature requirements for a mobile device tutorial for older adults. The approach was accomplished by the development of a mobile device questionnaire, which was ...

#### Rationality Of The Spectral Action For Robertson-Walker Metrics And The Geometry Of The Determinant Line Bundle For The Noncommutative Two Torus, Asghar Ghorbanpour

##### University of Western Ontario - Electronic Thesis and Dissertation Repository

In noncommutative geometry, the geometry of a space is given via a spectral triple $(\mathcal{A,H},D)$. Geometric information, in this approach, is encoded in the spectrum of $D$ and to extract them, one should study spectral functions such as the heat trace $\Tr (e^{-tD^2})$, the spectral zeta function $\Tr(|D|^{-s})$ and the spectral action functional, $\Tr f(D/\Lambda)$.

The main focus of this thesis is on the methods and tools that can be used to extract the spectral information. Applying the pseudodifferential calculus and the heat trace techniques, in addition to computing the newer ...

Adaptive, Group Sequential Designs That Balance The Benefits And Risks Of Wider Inclusion Criteria, Michael Rosenblum, Brandon S. Luber, Richard E. Thompson, Daniel F. Hanley Jan 2015

#### Adaptive, Group Sequential Designs That Balance The Benefits And Risks Of Wider Inclusion Criteria, Michael Rosenblum, Brandon S. Luber, Richard E. Thompson, Daniel F. Hanley

##### Johns Hopkins University, Dept. of Biostatistics Working Papers

We propose a new class of adaptive randomized trial designs aimed at gaining the advantages of wider generalizability and faster recruitment, while mitigating the risks of including a population for which there is greater a priori uncertainty. Our designs use adaptive enrichment, i.e., they have preplanned decision rules for modifying enrollment criteria based on data accrued at interim analyses. For example, enrollment can be restricted if the participants from predefined subpopulations are not benefiting from the new treatment. To the best of our knowledge, our designs are the first adaptive enrichment designs to have all of the following features ...

Advantages Of A Finite Extensible Nonlinear Elastic Potential In Lattice Boltzmann Simulations, Tai-Hsien Wu, Dewei Qi Jan 2015

#### Advantages Of A Finite Extensible Nonlinear Elastic Potential In Lattice Boltzmann Simulations, Tai-Hsien Wu, Dewei Qi

##### The Hilltop Review

A new structure, generalized lattice nonlinear spring model (GLNSM), which adopts non-linear FENE-LJ potential instead of harmonic potential, has been coupled with lattice Boltzmann simulation for solving fluid-solid interaction problem. In this article, a significant work is the relationship between the GLNSM (FENE-LJ potential) and Young’s modulus has been described in detail. A validation has also been presented to prove that GLNSM is reliable.

Wi-Fi Location Determination For Semantic Locations, Keith J. Kelley Jan 2015

#### Wi-Fi Location Determination For Semantic Locations, Keith J. Kelley

##### The Hilltop Review

In Wi-Fi location determination literature, little attention is paid to locations that do not have numeric, geometric coordinates, though many users prefer the convenience of non-coordinate locations (consider the ease of giving a street address as opposed to giving latitude and longitude). It is not often easy to tell from the title or abstract of a Wi-Fi location determination article whether or not it has applicability to semantic locations such as room-level names. This article surveys the literature through 2011 on Wi-Fi localization for symbolic locations.

Review Of Naked Statistics: Stripping The Dread From Data By Charles Wheelan, Michael T. Catalano Jan 2015

#### Review Of Naked Statistics: Stripping The Dread From Data By Charles Wheelan, Michael T. Catalano

##### Numeracy

Wheelan, Charles. Naked Statistics: Stripping the Dread from Data (New York, NY, W. W. Norton & Company, 2014). 282 pp. ISBN 978-0-393-07195-5

In his review of What Numbers Say and The Numbers Game, Rob Root (Numeracy 3(1): 9) writes “Popular books on quantitative literacy need to be easy to read, reasonably comprehensive in scope, and include examples that are thought-provoking and memorable.” Wheelan’s book certainly meets this description, and should be of interest to both the general public and those with a professional interest in numeracy. A moderately diligent learner can get a decent understanding of basic statistics from ...

Improving University Students' Perception Of Mathematics And Mathematics Ability, Shelly L. Wismath, Alyson Worrall Jan 2015

#### Improving University Students' Perception Of Mathematics And Mathematics Ability, Shelly L. Wismath, Alyson Worrall

##### Numeracy

Although mathematical and quantitative reasoning skills are an essential part of adult life in our society, many students arrive at post-secondary education without such skills. Taking a standard mathematics course such as calculus may do little to improve those skills. Using a modification of the Tapia & Marsh questionnaire, we surveyed 62 students taking a broad quantitative reasoning course designed to develop quantitative skills, with respect to two broad attitudinal areas: students’ perception of their own ability, confidence and anxiety, and their perception of the value of mathematics in their studies and their lives. Pre- to post-course comparisons were done by ...

Leveraging Prognostic Baseline Variables To Gain Precision In Randomized Trials, Elizabeth Colantuoni, Michael Rosenblum Jan 2015

#### Leveraging Prognostic Baseline Variables To Gain Precision In Randomized Trials, Elizabeth Colantuoni, Michael Rosenblum

##### Johns Hopkins University, Dept. of Biostatistics Working Papers

We focus on estimating the average treatment effect in a randomized trial. If baseline variables are correlated with the outcome, then appropriately adjusting for these variables can improve precision. An example is the analysis of covariance (ANCOVA) estimator, which applies when the outcome is continuous, the quantity of interest is the difference in mean outcomes comparing treatment versus control, and a linear model with only main effects is used. ANCOVA is guaranteed to be at least as precise as the standard unadjusted estimator, asymptotically, under no parametric model assumptions, and also is locally, semiparametric efficient. Recently, several estimators have been ...

On The Detection Of Exoplanets Via Radial Velocity Doppler Spectroscopy, Joseph P. Glaser Jan 2015

#### On The Detection Of Exoplanets Via Radial Velocity Doppler Spectroscopy, Joseph P. Glaser

##### The Downtown Review

Since the discovery of the first exoplanet occurred in the late 1980s, physicists and astronomers have confirmed the existence of over 1783 planets orbiting other stars. Over the years, several methods have been developed for detecting these celestial systems, but none has thus far been more successful than the use of Radial Velocity Doppler Spectroscopy. As such, this paper attempts to break down the barriers placed before new entries into the field by detailing the theoretical premise and experimental process of this most successful technique. The content enclosed is geared for the senior undergraduate student with some knowledge of vector-based ...