Validation of the communications link analysis and simulation system (CLASS)

CLASS (Communication Link Analysis and Simulation System) is a software package developed for NASA to predict the communication and tracking performance of the Tracking and Data Relay Satellite System (TDRSS) services. The methods used to verify CLASS are described. The usefulness of a software tool such as CLASS depends strongly on the reliability and accuracy of the results it produces. For this reason, considerable attention was paid to validation throughout the CLASS development

Analysis methodology for flow-level evaluation of a hybrid mobile-sensor network

Our society uses a large diversity of co-existing wired and wireless networks in order to satisfy its communication needs. A cooper- ation between these networks can benefit performance, service availabil- ity and deployment ease, and leads to the emergence of hybrid networks. This position paper focuses on a hybrid mobile-sensor network identify- ing potential advantages and challenges of its use and defining feasible applications. The main value of the paper, however, is in the proposed analysis approach to evaluate the performance at the mobile network side given the mixed mobile-sensor traffic. The approach combines packet- level analysis with modelling of flow-level behaviour and can be applied for the study of various application scenarios. In this paper we consider two applications with distinct traffic models namely multimedia traffic and best-effort traffic

Directly Determined Linear Radii and Effective Temperatures of Exoplanet Host Stars

We present interferometric angular sizes for 12 stars with known planetary companions, for comparison with 28 additional main-sequence stars not known to host planets. For all objects we estimate bolometric fluxes and reddenings through spectral energy distribution fits, and in conjunction with the angular sizes, measurements of effective temperature. The angular sizes of these stars are sufficiently small that the fundamental resolution limits of our primary instrument, the Palomar Testbed Interferometer, are investigated at the sub-milliarcsecond level and empirically established based upon known performance limits. We demonstrate that the effective temperature scale as a function of dereddened $(V-K)_0$ color is statistically identical for stars with and without planets. A useful byproduct of this investigation is a direct calibration of the $T_{\rm EFF}$ scale for solar-like stars, as a function of both spectral type and $(V-K)_0$ color, with an precision of $\bar{\Delta T}_{\rm {(V-K)}_0} = 138$K over the range $(V-K)_0=0.0-4.0$ and $\bar{\Delta T}_{\rm {SpType}} = 105$K for the range F6V -- G5V. Additionally, we provide in an appendix spectral energy distribution fits for the 166 stars with known planets which have sufficient photometry available in the literature for such fits; this derived "{\tt XO-Rad}" database includes homogenous estimates of bolometric flux, reddening, and angular size.Comment: Accepted for publication in Ap

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

Two-gap superconductivity in single crystal Lu2_2Fe3_3Si5_5 from penetration depth measurements

Single crystal of Lu$_2$Fe$_3$Si$_5$ was studied with the tunnel-diode resonator technique in Meissner and mixed states. Temperature dependence of the superfluid density provides strong evidence for the two-gap superconductivity with almost equal contributions from each gap of magnitudes $\Delta_1/k_BT_c=1.86$ and $\Delta_1/k_BT_c=0.54$. In the vortex state, pinning strength shows unusually strong temperature dependence and is non-monotonic with the magnetic field (peak effect). The irreversibility line is sharply defined and is quite distant from the $H_{c2}(T)$, which hints on to enhanced vortex fluctuations in this two-gap system. Altogether our findings provide strong electromagnetic - measurements support to the two-gap superconductivity in Lu$_2$Fe$_3$Si$_5$ previously suggested from specific heat measurements