Improved Bounds on Information Dissemination by Manhattan Random Waypoint Model

With the popularity of portable wireless devices it is important to model and predict how information or contagions spread by natural human mobility -- for understanding the spreading of deadly infectious diseases and for improving delay tolerant communication schemes. Formally, we model this problem by considering $M$ moving agents, where each agent initially carries a \emph{distinct} bit of information. When two agents are at the same location or in close proximity to one another, they share all their information with each other. We would like to know the time it takes until all bits of information reach all agents, called the \textit{flood time}, and how it depends on the way agents move, the size and shape of the network and the number of agents moving in the network. We provide rigorous analysis for the \MRWP model (which takes paths with minimum number of turns), a convenient model used previously to analyze mobile agents, and find that with high probability the flood time is bounded by $O\big(N\log M\lceil(N/M) \log(NM)\rceil\big)$, where $M$ agents move on an $N\times N$ grid. In addition to extensive simulations, we use a data set of taxi trajectories to show that our method can successfully predict flood times in both experimental settings and the real world.Comment: 10 pages, ACM SIGSPATIAL 2018, Seattle, U

Activity: UD Building Block

https://ecommons.udayton.edu/mktg_images/1007/thumbnail.jp

Activity: UD Building Block-HOME

https://ecommons.udayton.edu/mktg_images/1006/thumbnail.jp

Picking a way forward: valuing and managing traditional shellfish gathering for Littorina littorea

Littorina littorea (periwinkles) have been harvested by hand picking from the shore since prehistoric times. Harvests are generally unregulated, catches are not linked to particular shores and fisheries statistics are considered to be unreliable. The absence of key data has made it difficult to develop harvesting recommendations. Surveys around Strangford Lough, Northern Ireland were used to investigate the size structure and relationships among densities in different size classes. Three size classes were identified in surveyed L. littorea, with mean shell lengths of 0.81, 1.56 and 2.48 cm. Assuming that the age classes represent year classes, data across different shores suggested that the ratio between densities in successive year classes was not constant. Proportionally fewer individuals were found in the larger, older, size class as the density of the smaller size class on a shore increased. This density-dependent relationship was modelled with a Ricker curve for the year 1 to year 2 and the year 2 to year 3 transitions. The predicted transition rates from Ricker curves were used in a size-structured model to describe L. littorea dynamics. An emergent property of the size-structured model is a decline in mean shell length with overall density of a population. This prediction was supported by the survey data from Strangford Lough and by an independent survey of Irish shores. The size-structured model predicts potential harvests of individuals above 2.06 cm as a function of recruitment rate. Maximum harvest was predicted for a density of 5 year 1 individuals m−2, leading to 13.8 year 3 individuals m−2 or an estimated annual harvest weight of 67 g m−2. Modelled estimates of production provide a means to value shores and develop harvest predictions for management purposes

Iterative Solutions to the Inverse Geometric Problem for Manipulators with no Closed Form Solution

A set of new iterative solutions to the inverse geometric problem is presented. The approach is general and does not depend on intersecting axes or calculation of the Jacobian. The solution can be applied to any manipulator and is well suited for manipulators for which convergence is poor for conventional Jacobian-based iterative algorithms. For kinematically redundant manipulators, weights can be applied to each joint to introduce stiffness and for collision avoidance. The algorithm uses the unit quaternion to represent the position of each joint and calculates analytically the optimal position of the joint when only the respective joint is considered. This sub-problem is computationally very efficient due to the analytical solution. Several algorithms based on the solution of this sub-problem are presented. For difficult problems, for which the initial condition is far from a solution or the geometry of the manipulator makes the solution hard to reach, it is shown that the algorithm finds a solution fairly close to the solution in only a few iterations

Book Reviews

Book reviews of: Grant at Vicksburg: The General and the Siege. By Michael B. Ballard. Carbondale: Southern Illinois University Press, 2013. Illustrations, maps, notes, index. Pp. xiii, 232. $32.95 cloth,$32.95 e-book. ISBN: 9780809332403. A Voice That Could Stir an Army: Fannie Lou Hamer and the Rhetoric of the Black Freedom Movement. By Maegan Parker Brooks (Jackson: University Press of Mississippi, 2014. Index, bibliography. Pp. 314. $60 cloth,$60 e-book. ISBN 978- 1-628646-004-9.) A New Southern Woman: T he Correspondence of Eliza Lucy Irion Neilson, 1871-1883. Edited by Giselle Roberts. (Columbia: University of South Carolina Press, 2013. Acknowledgements, illustrations, notes, index. Pp. viii, 306. $49.95 cloth. ISBN: 9781611171037.) Pageants, Parlors, and Pretty Women: Race and Beauty in the Twentieth-Century South. By Blain Roberts. (Chapel Hill: University of North Carolina Press, 2014). Acknowledgments, illustrations, notes, bibliography, index. Pp. ix, 363.$39.95 hardcover, $29.99 e-book. ISBN: 978-1-4696-1420-5.) Black Freedom, White Resistance, and Red Menace: Civil Rights and Anticommunism in the Jim Crow South. By Yasuhiro Katagiri. (Baton Rouge: Louisiana State University Press, 2014. Acknowledgements, illustrations, notes, index. Pp.xi, 392.$47.50 hardcover. ISBN 9780807153130.) Natchez Country: Indians, Colonists, and the Landscapes of Race in French Louisiana. By George Edward Milne. (Athens: The University of Georgia Press, 2015. List of figures, acknowledgments, notes, bibliography, index. Pp. xi, 293. $84.95 cloth,$26.95 paper. ISBN: 9780820347509.) In Remembrance of Emmett Till: Regional Stories and Media Responses to the Black Freedom Struggle. By Darryl Mace. (Lexington: University Press of Kentucky, 2014. Preface, introduction, illustrations, acknowledgements, notes, bibliography, index. Pp. xi, 212. $40 cloth. ISBN: 978- 0-8131-4536-5.) The Edible South: The Power of Food and the Making of an American Region. By Marcie Cohen Ferris. (Chapel Hill: The University of North Carolina Press, 2014. 496 pp., 7x10, 50 halftones, notes, bibl., index.$35 cloth, $34.99 e-book. ISBN: 978- 1-4696-1768-8.) Down to the Crossroads: Civil Rights, Black Power, and the Meredith March Against Fear. By Aram Goudsouzian. (New York: Farrar, Straus and Giroux, 2014. Map, notes, acknowledgements, index. Pp. ix, 351.$30 cloth, $18 paper. ISBN: 0374192200.) After Slavery: Race, Labor, and Citizenship in the Reconstruction South. Edited by Bruce Baker and Brian Kelly. Afterword by Eric Foner. (Gainesville: University Press of Florida, 2013. Acknowledgments, images, maps, notes, bibliography, index. Pp. vii, 279.$74.95 cloth. $24.95 paper. ISBN 978- 0-8130-4477-4.) George Ohr: Sophisticate and Rube. By Ellen J. Lippert. (Jackson: University Press of Mississippi, 2013. Acknowledgements, illustrations, notes, bibliography, index, Pp. x, 163.$40 cloth. ISBN: 9781617039010.

Mental, social, and physical well-being in New Hampshire, Oregon, and Washington, 2010 Behavioral Risk Factor Surveillance System: implications for public health research and practice related to Healthy People 2020 foundation health measures on well-being

BACKGROUND: Well-being is now accepted as one of four cross-cutting measures in gauging progress for Healthy People 2020. This shift to population indicators of well-being redresses notions of health that have focused on absence of illness (negative health) as a primary or sufficient indicator of positive functioning. The purpose of this study was to estimate mental, social, and physical well-being in three US states using new measures piloted on the 2010 Behavioral Risk Factor Surveillance Survey System (BRFSS). Baseline estimates were provided for states overall, and within states for demographic subgroups, those with chronic health conditions or disabilities, and those with behavioral risk factors. METHODS: Ten validated questions designed to assess mental (e.g., satisfaction with life, satisfaction with life domains, happiness), physical (e.g., satisfaction with energy level), and social dimensions (e.g., frequency of social support) of well-being were selected with state input for inclusion on BRFSS. 18,622 individuals responded to the BRFSS surveys administered by New Hampshire (N = 3,139), Oregon (N = 2,289), and Washington (N = 13,194). Multivariate adjusted proportions of positive responses to well-being items were examined. RESULTS: After adjustment for confounders, about 67% of adults in these states had high levels of well-being, including >80% reporting experiencing happiness. Most adults were satisfied with their work, neighborhood, and education, but significant differences were seen in subgroups. Well-being differed by demographic characteristics such as marital status, health behaviors, chronic conditions, and disability status, with those who reported a disability and smokers consistently experiencing the worst well-being. CONCLUSIONS: Well-being is accepted as one of four cross-cutting measures in gauging progress for Healthy People 2020. Well-being differs by important sociodemographic factors and health conditions (e.g., age, employment, smoking, disability status). These findings provide baseline estimates for the three states to use in gauging improvements in well-being and can serve as a model for other state-level or national surveillance systems. These findings also assist states in identifying vulnerable subgroups who may benefit from potential interventions such as those in the National Prevention Strategy that focus on enhancing well-being where such disparities exist

A Critical Assessment of Stellar Mass Measurement Methods

In this paper we perform a comprehensive study of the main sources of random and systematic errors in stellar mass measurement for galaxies using their Spectral Energy Distributions (SEDs). We use mock galaxy catalogs with simulated multi-waveband photometry (from U-band to mid-infrared) and known redshift, stellar mass, age and extinction for individual galaxies. Given different parameters affecting stellar mass measurement (photometric S/N ratios, SED fitting errors, systematic effects, the inherent degeneracies and correlated errors), we formulated different simulated galaxy catalogs to quantify these effects individually. We studied the sensitivity of stellar mass estimates to the codes/methods used, population synthesis models, star formation histories, nebular emission line contributions, photometric uncertainties, extinction and age. For each simulated galaxy, the difference between the input stellar masses and those estimated using different simulation catalogs, $\Delta\log(M)$, was calculated and used to identify the most fundamental parameters affecting stellar masses. We measured different components of the error budget, with the results listed as follows: (1). no significant bias was found among different codes/methods, with all having comparable scatter; (2). A source of error is found to be due to photometric uncertainties and low resolution in age and extinction grids; (3). The median of stellar masses among different methods provides a stable measure of the mass associated with any given galaxy; (4). The deviations in stellar mass strongly correlate with those in age, with a weaker correlation with extinction; (5). the scatter in the stellar masses due to free parameters are quantified, with the sensitivity of the stellar mass to both the population synthesis codes and inclusion of nebular emission lines studied.Comment: 33 pages, 20 Figures, Accepted for publication in Astrophysical Journa