A classification of scalar field potentials with cosmological scaling solutions

An attractive method of obtaining an effective cosmological constant at the present epoch is through the potential energy of a scalar field. Considering models with a perfect fluid and a scalar field, we classify all potentials for which the scalar field energy density scales as a power-law of the scale factor when the perfect fluid density dominates. There are three possibilities. The first two are well known; the much-investigated exponential potentials have the scalar field mimicking the evolution of the perfect fluid, while for negative power-laws, introduced by Ratra and Peebles, the scalar field density grows relative to that of the fluid. The third possibility is a new one, where the potential is a positive power-law and the scalar field energy density decays relative to the perfect fluid. We provide a complete analysis of exact solutions and their stability properties, and investigate a range of possible cosmological applications.Comment: 8 pages RevTeX file with four figures incorporated (uses RevTeX and epsf

On Intercept Probability Minimization under Sparse Random Linear Network Coding

This paper considers a network where a node wishes to transmit a source message to a legitimate receiver in the presence of an eavesdropper. The transmitter secures its transmissions employing a sparse implementation of Random Linear Network Coding (RLNC). A tight approximation to the probability of the eavesdropper recovering the source message is provided. The proposed approximation applies to both the cases where transmissions occur without feedback or where the reliability of the feedback channel is impaired by an eavesdropper jamming the feedback channel. An optimization framework for minimizing the intercept probability by optimizing the sparsity of the RLNC is also presented. Results validate the proposed approximation and quantify the gain provided by our optimization over solutions where non-sparse RLNC is used.Comment: To appear on IEEE Transactions on Vehicular Technolog

High-Speed Data Dissemination over Device-to-Device Millimeter-Wave Networks for Highway Vehicular Communication

Gigabit-per-second connectivity among vehicles is expected to be a key enabling technology for sensor information sharing, in turn, resulting in safer Intelligent Transportation Systems (ITSs). Recently proposed millimeter-wave (mmWave) systems appear to be the only solution capable of meeting the data rate demand imposed by future ITS services. In this poster, we assess the performance of a mmWave device-to-device (D2D) vehicular network by investigating the impact of system and communication parameters on end-users.Comment: To appear in IEEE VNC 2017, Torino, I

\u27\u27Shots from the Pulpit:\u27\u27 An Ethnographic Content Analysis of United States Anti-Gambling Social Movement Documents from 1816-2010

The history of anti-gambling impulses is perhaps as old as the gambling impulse itself, but academic research has thus far neglected the topic of anti-gambling social movements. Using social movement literature as a theoretical guide and ethnographic content analysis as a methodological tool, this paper examines anti-gambling documents produced in the United States over nearly two hundred years. During this period, three distinct periods emerge: first, an early ( 1816-1915) period framed the gambling act on strict religious grounds as an individual sin. This religious framing was then challenged by the rise of more rational and scientifically-based medical discourses on problem gambling (1915-1980). From 1980 through the present, gambling opponents have modified (and in some cases reversed) their arguments- and now incorporate both moral and scientific rhetoric into their claims. Drawing from sociological research and theory, we identify a process of frame inversion in which problem gamblers were once cast as villains to be scorned, but now are characterized as sympathetic victims of the gaming industry. In this first academic study of anti-gambling social movement rhetoric, we develop an illustrative example of how social movements\u27 rhetorical tactics can change over time, and of the kinds of opponents the global gaming industry has faced - and might still face in the future

The macroeconomics of happiness

We show that macroeconomic movements have strong effects on the happiness of nations. First, we find that there are clear microeconomic patterns in the psychological well-being levels of a quarter of a million randomly sampled Europeans and Americans from the 1970's to the 1990's. Happiness equations are monotonically increasing in income, and have a similar structure in different countries. Second, movements in reported well-being are correlated with changes in macroeconomic variables such as Gross Domestic Product. This holds true after controlling for the personal characteristics of respondents, country fixed-effects, year dummies, and country-specific time trends. Third, the paper establishes that recessions create psychic losses that extend beyond the fall in GDP and rise in the number of people unemployed. These losses are large. Fourth, the welfare state appears to be a compensating force: higher unemployment benefits are associated with higher national well-being

Preferences over inflation and unemployment : evidence from surveys of happiness

This paper has two aims. The first is to show that citizens care about these two variables. We present evidence that inflation and unemployment belong in a well-being function. The second is to calculate the costs of inflation in terms of unemployment. We measure the relative size of the weights attached to these variables in social well-being. Policy implications emerg

Evolution in the Clustering of Galaxies for Z < 1

Measuring the evolution in the clustering of galaxies over a large redshift range is a challenging problem. For a two-dimensional galaxy catalog, however, we can measure the galaxy-galaxy angular correlation function which provides information on the density distribution of galaxies. By utilizing photometric redshifts, we can measure the angular correlation function in redshift shells (Brunner 1997, Connolly et al. 1998) which minimizes the galaxy projection effect, and allows for a measurement of the evolution in the correlation strength with redshift. In this proceedings, we present some preliminary results which extend our previous work using more accurate photometric redshifts, and also incorporate absolute magnitudes, so that we can measure the evolution of clustering with either redshift or intrinsic luminosity.Comment: 6 pages, 6 figures requires paspconf.sty. To be published in "Photometric Redshifts and High Redshift Galaxies", eds. R. Weymann, L. Storrie-Lombardi, M. Sawicki & R. Brunner, (San Francisco: ASP Conference Series

Investigation of advanced counterrotation blade configuration concepts for high speed turboprop systems. Task 4: Advanced fan section aerodynamic analysis

The purpose of this study is the development of a three-dimensional Euler/Navier-Stokes flow analysis for fan section/engine geometries containing multiple blade rows and multiple spanwise flow splitters. An existing procedure developed by Dr. J. J. Adamczyk and associates and the NASA Lewis Research Center was modified to accept multiple spanwise splitter geometries and simulate engine core conditions. The procedure was also modified to allow coarse parallelization of the solution algorithm. This document is a final report outlining the development and techniques used in the procedure. The numerical solution is based upon a finite volume technique with a four stage Runge-Kutta time marching procedure. Numerical dissipation is used to gain solution stability but is reduced in viscous dominated flow regions. Local time stepping and implicit residual smoothing are used to increase the rate of convergence. Multiple blade row solutions are based upon the average-passage system of equations. The numerical solutions are performed on an H-type grid system, with meshes being generated by the system (TIGG3D) developed earlier under this contract. The grid generation scheme meets the average-passage requirement of maintaining a common axisymmetric mesh for each blade row grid. The analysis was run on several geometry configurations ranging from one to five blade rows and from one to four radial flow splitters. Pure internal flow solutions were obtained as well as solutions with flow about the cowl/nacelle and various engine core flow conditions. The efficiency of the solution procedure was shown to be the same as the original analysis

Investigation of Advanced Counterrotation Blade Configuration Concepts for High Speed Turboprop Systems. Task 3: Advanced Fan Section Grid Generator Final Report and Computer Program User's Manual

A procedure is studied for generating three-dimensional grids for advanced turbofan engine fan section geometries. The procedure constructs a discrete mesh about engine sections containing the fan stage, an arbitrary number of axisymmetric radial flow splitters, a booster stage, and a bifurcated core/bypass flow duct with guide vanes. The mesh is an h-type grid system, the points being distributed with a transfinite interpolation scheme with axial and radial spacing being user specified. Elliptic smoothing of the grid in the meridional plane is a post-process option. The grid generation scheme is consistent with aerodynamic analyses utilizing the average-passage equation system developed by Dr. John Adamczyk of NASA Lewis. This flow solution scheme requires a series of blade specific grids each having a common axisymmetric mesh, but varying in the circumferential direction according to the geometry of the specific blade row

Tobacco Use and Health Insurance Literacy Among Vulnerable Populations: Implications for Health Reform

Background: Under the Affordable Care Act (ACA), millions of Americans have been enrolling in the health insurance marketplaces. Nearly 20% of them are tobacco users. As part of the ACA, tobacco users may face up to 50% higher premiums that are not eligible for tax credits. Tobacco users, along with the uninsured and racial/ethnic minorities targeted by ACA coverage expansions, are among those most likely to suffer from low health literacy – a key ingredient in the ability to understand, compare, choose, and use coverage, referred to as health insurance literacy. Whether tobacco users choose enough coverage in the marketplaces given their expected health care needs and are able to access health care services effectively is fundamentally related to understanding health insurance. However, no studies to date have examined this important relationship.Methods: Data were collected from 631 lower-income, minority, rural residents of Virginia. Health insurance literacy was assessed by asking four factual questions about the coverage options presented to them. Adjusted associations between tobacco use and health insurance literacy were tested using multivariate linear regression, controlling for numeracy, risk-taking, discount rates, health status, experiences with the health care system, and demographics.Results: Nearly one third (31%) of participants were current tobacco users, 80% were African American and 27% were uninsured. Average health insurance literacy across all participants was 2.0 (SD 1.1) out of a total possible score of 4. Current tobacco users had significantly lower HIL compared to non-users (−0.22, p \u3c 0.05) after adjustment. Participants who were less educated, African American, and less numerate reported more difficulty understanding health insurance (p \u3c 0.05 each.)Conclusions: Tobacco users face higher premiums for health coverage than non-users in the individual insurance marketplace. Our results suggest they may be less equipped to shop for plans that provide them with adequate out-of-pocket risk protection, thus placing greater financial burdens on them and potentially limiting access to tobacco cessation and treatment programs and other needed health services