7,336 research outputs found

    Tracking Vector Magnetograms with the Magnetic Induction Equation

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    The differential affine velocity estimator (DAVE) developed in Schuck (2006) for estimating velocities from line-of-sight magnetograms is modified to directly incorporate horizontal magnetic fields to produce a differential affine velocity estimator for vector magnetograms (DAVE4VM). The DAVE4VM's performance is demonstrated on the synthetic data from the anelastic pseudospectral ANMHD simulations that were used in the recent comparison of velocity inversion techniques by Welsch (2007). The DAVE4VM predicts roughly 95% of the helicity rate and 75% of the power transmitted through the simulation slice. Inter-comparison between DAVE4VM and DAVE and further analysis of the DAVE method demonstrates that line-of-sight tracking methods capture the shearing motion of magnetic footpoints but are insensitive to flux emergence -- the velocities determined from line-of-sight methods are more consistent with horizontal plasma velocities than with flux transport velocities. These results suggest that previous studies that rely on velocities determined from line-of-sight methods such as the DAVE or local correlation tracking may substantially misrepresent the total helicity rates and power through the photosphere.Comment: 30 pages, 13 figure

    Fanchette : Tambourine Dance

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    https://digitalcommons.library.umaine.edu/mmb-ps/2073/thumbnail.jp

    Deer-Activated Bio-Acoustic Frightening Device Deters White-Tailed Deer

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    White-tailed deer (Odocoileus virginianus) damage urban and suburban plantings as well as crops and stored feed. Public demand for non-lethal control methods is high. Several frightening devices are available for deer, but problems exist with most, including: ease of application, cost, acclimation by animals, and public acceptance. Frightening devices that have the greatest likelihood of being effective incorporate mechanisms triggered by animal activation or bioacoustic alarm or distress calls. We tested the efficacy of a frightening device that played pre-recorded distress calls of adult female white-tailed deer when activated by an infrared motion sensor. Potential benefits of the device are that deer are less likely to acclimate to animal-activated and infrequently projected calls and that distress calls may elicit a stronger and longer lasting response. We tested the product in DeSoto National Wildlife Refuge (DNWR) in eastern Nebraska and western Iowa during late winter 2010. We established 3 treatment sites and 3 control sites, each being 0.004 ha and located \u3e0.6 km apart to reduce the likelihood of dependence among treatments and associated controls. At each treatment site, we deployed deeractivated bioacoustics devices and motion-activated cameras to record deer responses to the devices. We maintained 1 13-day pretreatment period (10 Mar– 22 Mar) and 1 13-day treatment period (23 Mar– 4 Apr) and recorded breaches and consumption of feed by deer. The deer-activated bio-acoustic frightening device reduced deer entry into protected sites by 99.3% (δ = -558.00, P = 0.089) and bait consumption by 100% (δ = -75.20, P = 0.064). Unfortunately, small sample size (n = 3) and a natural decline in motivation of deer to access bait due to spring green-up diminished the statistical significance of results. The deer-activated bioacoustics device was effective, deer did not acclimate to the device, and the device was not invasive. The frightening device we evaluated demonstrated potential for reducing damage in disturbed environments and agricultural settings. The device currently is being marked as DeerShield by BirdGuard (http://www.deershieldpro.com/). We thank Greg Clements, Scott Groepper, Greg Phillips, and Dave Baasch for assistance. We thank Tom Cox, Mindy Sheets, and the staff at DNWR for access and assistance. Funding was provided by the United States Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services, National Wildlife Research Center and the University of Nebraska-Lincoln School of Natural Resources

    On Synergies Between Information Retrieval and Digital Libraries

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    In this paper we present the results of a longitudinal analysis of ACM SIGIR papers from 2003 to 2017. ACM SIGIR is the main venue where Information Retrieval (IR) research and innovative results are presented yearly; it is a highly competitive venue and only the best and most relevant works are accepted for publication. The analysis of ACM SIGIR papers gives us a unique opportunity to understand where the field is going and what are the most trending topics in information access and search. In particular, we conduct this analysis with a focus on Digital Library (DL) topics to understand what is the relation between these two fields that we know to be closely linked. We see that DL provide document collections and challenging tasks to be addressed by the IR community and in turn exploit the latest advancements in IR to improve the offered services. We also point to the role of public investments in the DL field as one of the core drivers of DL research which in turn may also have a positive effect on information accessing and searching in general

    A Path Algorithm for Constrained Estimation

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    Many least squares problems involve affine equality and inequality constraints. Although there are variety of methods for solving such problems, most statisticians find constrained estimation challenging. The current paper proposes a new path following algorithm for quadratic programming based on exact penalization. Similar penalties arise in l1l_1 regularization in model selection. Classical penalty methods solve a sequence of unconstrained problems that put greater and greater stress on meeting the constraints. In the limit as the penalty constant tends to ∞\infty, one recovers the constrained solution. In the exact penalty method, squared penalties are replaced by absolute value penalties, and the solution is recovered for a finite value of the penalty constant. The exact path following method starts at the unconstrained solution and follows the solution path as the penalty constant increases. In the process, the solution path hits, slides along, and exits from the various constraints. Path following in lasso penalized regression, in contrast, starts with a large value of the penalty constant and works its way downward. In both settings, inspection of the entire solution path is revealing. Just as with the lasso and generalized lasso, it is possible to plot the effective degrees of freedom along the solution path. For a strictly convex quadratic program, the exact penalty algorithm can be framed entirely in terms of the sweep operator of regression analysis. A few well chosen examples illustrate the mechanics and potential of path following.Comment: 26 pages, 5 figure

    Testing the Higgs boson gluonic couplings at LHC

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    We study Higgs + jet production at hadron colliders in order to look for new physics residual effects possibly described by the dim=6dim=6 operators {\O}_{GG} and {\widetilde\O}_{GG} which induce anomalous HggHgg and HgggHggg couplings. Two ways for constraining these operators at LHC may be ~useful. The first is based on the total Higgs boson production rate induced by gluon-gluon fusion, in which the main cause of limitations are due to theoretical uncertainties leading to sensitivities of ∣dG∣≃3.×10−4|d_G|\simeq 3.\times 10^{-4} and ∣d~G∣≃1.4×10−3|\widetilde{d}_G|\simeq 1.4\times 10^{-3} for the corresponding anomalous couplings, in the mass range 100 GeV \lsim \mh \lsim 2~00 GeV. These results imply sensitivity to new physics scales of 51 and 24 TeV respectively. The second way investigated here concerns the shape of the Higgs transverse momentum; for which the theoretical uncertainties are less severe and the limitations are mainly induced by statistics. A simple analysis, based on the ratio of the number of events at large and low pTp_T at LHC, leads to similar sensitivities, if only the H→γγH\to \gamma \gamma decay mode is used. But the sensitivities can now be improved by a factor 2 to 10, depending on the Higgs mass, if the Higgs decay modes to WW∗WW^*, ZZ∗ZZ^*, WWWW, ZZZZ are also used.Comment: 23 pages and 7 figures, version to appear in Phys.ReV.D. e-mail: [email protected]

    A Search for Jet Handedness in Hadronic Z0Z^0 Decays

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    We have searched for signatures of polarization in hadronic jets from Z0→qqˉZ^0 \to q \bar{q} decays using the ``jet handedness'' method. The polar angle asymmetry induced by the high SLC electron-beam polarization was used to separate quark jets from antiquark jets, expected to be left- and right-polarized, respectively. We find no evidence for jet handedness in our global sample or in a sample of light quark jets and we set upper limits at the 95% C.L. of 0.063 and 0.099 respectively on the magnitude of the analyzing power of the method proposed by Efremov {\it et al.}Comment: Revtex, 8 pages, 2 figure
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