A mathematical framework for inverse wave problems in heterogeneous media

This paper provides a theoretical foundation for some common formulations of inverse problems in wave propagation, based on hyperbolic systems of linear integro-differential equations with bounded and measurable coefficients. The coefficients of these time-dependent partial differential equations respresent parametrically the spatially varying mechanical properties of materials. Rocks, manufactured materials, and other wave propagation environments often exhibit spatial heterogeneity in mechanical properties at a wide variety of scales, and coefficient functions representing these properties must mimic this heterogeneity. We show how to choose domains (classes of nonsmooth coefficient functions) and data definitions (traces of weak solutions) so that optimization formulations of inverse wave problems satisfy some of the prerequisites for application of Newton's method and its relatives. These results follow from the properties of a class of abstract first-order evolution systems, of which various physical wave systems appear as concrete instances. Finite speed of propagation for linear waves with bounded, measurable mechanical parameter fields is one of the by-products of this theory

Recipients\u27 Attitudes Toward Welfare

While the general plight of welfare recipients has long been recognized, little or nothing to date has been ascertained concerning their views toward the system that largely determines their lives. Many recipients find themselves manipulated by a less than personalized bureaucracy but few researchers have sought to examine the experiences and attitudes of these recipients toward that system. Given the recent figures which indicate a welfare explosion (Piven and Cloward, 1971), and the vast expenditures for public assistance programs (Skolnick and Dales, 1969:5), the lack of systematic empirical research in this area is disconcerting. Such information should be of considerable value to the practioner within the social welfare context. Differing policy orientations frequently are implemented without the guidance of relevant baseline information. Further inquiry into the strains inherent in the system would certainly lend itself to a more efficient and workable model. Our purpose here is to carry out such an analysis

Sky Variability in the y Band at the LSST Site

We have measured spatial and temporal variability in the y band sky brightness over the course of four nights above Cerro Tololo near Cerro Pachon, Chile, the planned site for the Large Synoptic Survey Telescope (LSST). Our wide-angle camera lens provided a 41 deg field of view and a 145 arcsec pixel scale. We minimized potential system throughput differences by deploying a deep depletion CCD and a filter that matches the proposed LSST y_3 band (970 nm-1030 nm). Images of the sky exhibited coherent wave structure, attributable to atmospheric gravity waves at 90 km altitude, creating 3%-4% rms spatial sky flux variability on scales of about 2 degrees and larger. Over the course of a full night the y_3 band additionally showed highly coherent temporal variability of up to a factor of 2 in flux. We estimate the mean absolute sky level to be approximately y_3 = 17.8 mag (Vega), or y_3 = 18.3 mag (AB). While our observations were made through a y_3 filter, the relative sky brightness variability should hold for all proposed y bands, whereas the absolute levels should more strongly depend on spectral response. The spatial variability presents a challenge to wide-field cameras that require illumination correction strategies that make use of stacked sky flats. The temporal variability may warrant an adaptive y band imaging strategy for LSST, to take advantage of times when the sky is darkest.Comment: 8 pages, 5 figures, accepted to PASP. Minor changes from referee report and editor's revisions

Indigenous and Non-Indigenous Paraprofessionals: An Empirical Comparison

This paper provides a comparative description of indigenous and nonindigenous paraprofessionals who were employed in a social service capacity in a large urban setting. Personal interviews were conducted with 88 paraprofessionals employed by the Fulton County Department of Family and Children Servives (Atlanta, Ga.). The primary variables discussed include an assessment of the respondent\u27s background, their present employment situation, experience with and attitudes toward welfare and general attitudinal measures. The results provide a basic demographic profile of the indigenous and non-indigenous paraprofessional and indicate their differing characteristics. Briefly, the indigenous respondents were less anomic, felt more efficacious in terms of helping clients, had a less favorable stance toward welfare, had less training and were considerably more more satisfied with their job than were their non-indigenous counterparts. Additionally, the implications of these findings and considerations which need to be explored in future research are discussed

Rich Intercultural Music Engagement Enhances Cultural Understanding: The Impact of Learning a Musical Instrument Outside of One’s Lived Experience

Rich intercultural music engagement (RIME) is an embodied form of engagement whereby individuals immerse themselves in foreign musical practice, for example, by learning a traditional instrument from that culture. The present investigation evaluated whether RIME with Chinese or Middle Eastern music can nurture intercultural understanding. White Australian participants were randomly assigned to one of two plucked-string groups: Chinese pipa (n = 29) or Middle Eastern oud (n = 29). Before and after the RIME intervention, participants completed measures of ethnocultural empathy, tolerance, social connectedness, explicit and implicit attitudes towards ethnocultural groups, and open-ended questions about their experience. Following RIME, White Australian participants reported a significant increase in ethnocultural empathy, tolerance, feelings of social connection, and improved explicit and implicit attitudes towards Chinese and Middle Eastern people. However, these benefits differed between groups. Participants who learned Chinese pipa reported reduced bias and increased social connectedness towards Chinese people, but not towards Middle Eastern people. Conversely, participants who learned Middle Eastern oud reported a significant increase in social connectedness towards Middle Eastern people, but not towards Chinese people. This is the first experimental evidence that participatory RIME is an effective tool for understanding a culture other than one’s own, with the added potential to reduce cultural bias.</p

Mode Selection and Target Classification in Cognitive Radar Networks

Cognitive Radar Networks were proposed by Simon Haykin in 2006 to address problems with large legacy radar implementations - primarily, single-point vulnerabilities and lack of adaptability. This work proposes to leverage the adaptability of cognitive radar networks to trade between active radar observation, which uses high power and risks interception, and passive signal parameter estimation, which uses target emissions to gain side information and lower the power necessary to accurately track multiple targets. The goal of the network is to learn over many target tracks both the characteristics of the targets as well as the optimal action choices for each type of target. In order to select between the available actions, we utilize a multi-armed bandit model, using current class information as prior information. When the active radar action is selected, the node estimates the physical behavior of targets through the radar emissions. When the passive action is selected, the node estimates the radio behavior of targets through passive sensing. Over many target tracks, the network collects the observed behavior of targets and forms clusters of similarly-behaved targets. In this way, the network meta-learns the target class distributions while learning the optimal mode selections for each target class.Comment: 6 pages, 5 figure

Experimental Demonstration of Time-Delay Interferometry for the Laser Interferometer Space Antenna

We report on the first demonstration of time-delay interferometry (TDI) for LISA, the Laser Interferometer Space Antenna. TDI was implemented in a laboratory experiment designed to mimic the noise couplings that will occur in LISA. TDI suppressed laser frequency noise by approximately 10^9 and clock phase noise by 6x10^4, recovering the intrinsic displacement noise floor of our laboratory test bed. This removal of laser frequency noise and clock phase noise in post-processing marks the first experimental validation of the LISA measurement scheme.Comment: 4 pages, 4 figures, to appear in Physical Review Letters end of May 201