37,466 research outputs found

    Improving an inequality for the divisor function

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    We improve using elementary means an explicit bound on the divisor function due to Friedlander and Iwaniec. Consequently we modestly improve a result regarding a sieving inequality for Gaussian sequences.Comment: 8 pages, to appear in Bull. AustM

    The Coherence Problem: Mapping the Theory and Delivery of Infrastructure Resilience Across Concept, Form, Function, and Experienced Value

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    In this contribution we explore the interface between the functional characteristics of infrastructures as artefacts and social need supplier. Specifically we are concerned with the ways in which infrastructure performance measures are articulated and assessed and whether there are incongruities between the technical and broader, social goals which infrastructure systems are intended to aspire to. Our analysis involves comparing and contrasting system design and performance metrics across the technical — social boundary, generating new insights for those tasked with the design and operation of networked infrastructures. The assessment delivered in the following sections is inherently interdisciplinary and cross-sectoral in nature, bringing thinking from the social and environmental sciences together with contributions from mathematics and engineering to offer a commentary which is relevant to all types of physical infrastructure

    NiH2 capacity fade during early cycling

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    Tests were conducted on nickel hydrogen batteries to determine the charge efficiency of the nickel electrode as a function of rate and temperature, cell discharge capacity, and capacity fade. Test procedures and results are presented in outline and graphic form

    Slew maneuvers on the SCOLE Laboratory Facility

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    The Spacecraft Control Laboratory Experiment (SCOLE) was conceived to provide a physical test bed for the investigation of control techniques for large flexible spacecraft. The control problems studied are slewing maneuvers and pointing operations. The slew is defined as a minimum time maneuver to bring the antenna line-of-sight (LOS) pointing to within an error limit of the pointing target. The second objective is to rotate about the LOS within the 0.02 degree error limit. The SCOLE problem is defined as two design challenges: control laws for a mathematical model of a large antenna attached to the Space Shuttle by a long flexible mast; and a control scheme on a laboratory representation of the structure modelled on the control laws. Control sensors and actuators are typical of those which the control designer would have to deal with on an actual spacecraft. Computational facilities consist of microcomputer based central processing units with appropriate analog interfaces for implementation of the primary control system, and the attitude estimation algorithm. Preliminary results of some slewing control experiments are given

    What is Driving Immigrants from El Salvador to Las Vegas? (2000-2010)

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    The purpose of this study is to examine if death rates due to crime or unemployment drove immigrants from El Salvador to migrate to Las Vegas between the years of 2000 to 2010. This study will be most directly based on the research conducted in the study Unauthorized Immigrant Population: National and State Trends, 2010, conducted by the Pew Research Center. Pew Research Center’s study focuses on finding an estimation on the number of undocumented immigrants that have entered the United States, the number of immigrants that are in the United States workforce, and the trends regarding what states and what cities immigrants are deciding to reside. The importance of my research proposal is that immigration as a topic tends to be biased based on the political climate. Research should be unbiased and should allow a platform where all of the facts surrounding a particular topic can be found. This will allow a deeper discussion surrounding the topic of Salvadoran immigrants in Las Vegas, Nevada, instead of discussing whether immigration is right or wrong based upon an individual’s moral reasoning. It is crucial that we focus on facts and that researchers are committed to unbiased research for the betterment of understanding the necessity of immigration policy reform. Through my research, I hypothesize that there will be a direct correlation to the number of immigrants in Las Vegas from El Salvador due to high unemployment and high homicide rates

    Two-Locus Likelihoods under Variable Population Size and Fine-Scale Recombination Rate Estimation

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    Two-locus sampling probabilities have played a central role in devising an efficient composite likelihood method for estimating fine-scale recombination rates. Due to mathematical and computational challenges, these sampling probabilities are typically computed under the unrealistic assumption of a constant population size, and simulation studies have shown that resulting recombination rate estimates can be severely biased in certain cases of historical population size changes. To alleviate this problem, we develop here new methods to compute the sampling probability for variable population size functions that are piecewise constant. Our main theoretical result, implemented in a new software package called LDpop, is a novel formula for the sampling probability that can be evaluated by numerically exponentiating a large but sparse matrix. This formula can handle moderate sample sizes (n≤50n \leq 50) and demographic size histories with a large number of epochs (D≥64\mathcal{D} \geq 64). In addition, LDpop implements an approximate formula for the sampling probability that is reasonably accurate and scales to hundreds in sample size (n≥256n \geq 256). Finally, LDpop includes an importance sampler for the posterior distribution of two-locus genealogies, based on a new result for the optimal proposal distribution in the variable-size setting. Using our methods, we study how a sharp population bottleneck followed by rapid growth affects the correlation between partially linked sites. Then, through an extensive simulation study, we show that accounting for population size changes under such a demographic model leads to substantial improvements in fine-scale recombination rate estimation. LDpop is freely available for download at https://github.com/popgenmethods/ldpopComment: 32 pages, 13 figure
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