65 research outputs found
A p.c.f. self-similar set with no self-similar energy
No full textAn example of a p.c.f. (post-critically finite) self-similar set without eigenform for any set of weights, is provided. The existence of an eigenform on such sets was an important, long-standing open problem in analysis on fractals.This problem is related to that of existence of self-similar energies on fractals, because self-similar energies on p.c.f. self-similar sets are obtained by using eigenforms (and only in this way). A general existence result of self-similar energies was previously established by the present author with respect to a weaker version of self-similarity
Vectoriseren van rasterlijnen
No full textThis thesis deals with the vectorisation of gridlines extracted from greyvalue-images. After a general introduction with, a.o. the problems that come up for discussion, a survey is presented of the material on which the problems bear, namely digital images. To extract the gridline-structures from these images, some operations are necessary to apply. They are edge-detection and line-following. After discussion of both these operations, the artificially created test-image is described on which the final vectorising-algorithm will be tested. Next the polygonal approximation is being discussed by showing some methods with their approximating criteria and other characteristics. Because of some disadvantages of these methods compared with the minimax polygonal approximation method, the latter is chosen. This minimax-method contains the following. Given a certain, polygon (here, the gridline) find a a less segmented polygon (vectorline) which approximates the former as well as possible. Last criterium means that the original polygonvertices (pixelcentra) may not have a bigger distance to the final polygon(side) than a certain a priori value 'E'. This method is optimal in that way, that it always finds the longest straight line (polygonside) that satisfies the discussed distance-criterium. Not optimal is that this method is a so-called sequential method. This means that the calculation of each polygonside is extended by one point every time. Fact is namely that non-sequential methods might give better results. That's why the non-sequential least squares method is described for comparison and the differences with the minimax method are discussed. Finally the test of the algorithm on the testdata takes place and the results are submitted to precision-analyses in particular. The report ends with some conclusions concerning the applicated method and some recommendations for further researchCivil Engineering and Geoscience
Winter body mass and over-ocean flocking as components of danger management by Pacific dunlins
No full textAbstract Background We compared records of the body mass and roosting behavior of Pacific dunlins (Calidris alpina pacifica) wintering on the Fraser River estuary in southwest British Columbia between the 1970s and the 1990s. 'Over-ocean flocking' is a relatively safe but energetically-expensive alternative to roosting during the high tide period. Fat stores offer protection against starvation, but are a liability in escape performance, and increase flight costs. Peregrine falcons (Falco peregrinus) were scarce on the Fraser River estuary in the 1970s, but their numbers have since recovered, and they prey heavily on dunlins. The increase has altered the balance between predation and starvation risks for dunlins, and thus how dunlins regulate roosting behavior and body mass to manage the danger. We therefore predicted an increase in the frequency of over-ocean flocking as well as a decrease in the amount of fat carried by dunlins over these decades. Results Historical observations indicate that over-ocean flocking of dunlins was rare prior to the mid-1990s and became common thereafter. Residual body masses of dunlins were higher in the 1970s, with the greatest difference between the decades coinciding with peak peregrine abundance in October, and shrinking over the course of winter as falcon seasonal abundance declines. Whole-body fat content of dunlins was lower in the 1990s, and accounted for most of the change in body mass. Conclusions Pacific dunlins appear to manage danger in a complex manner that involves adjustments both in fat reserves and roosting behavior. We discuss reasons why over-ocean flocking has apparently become more common on the Fraser estuary than at other dunlin wintering sites.</p
Instability of time-dependent wind-driven ocean gyres
No full textThe wind-driven ocean circulation at midlatitudes is susceptible to several types of instabilities. One of the simplest models of these flows is the quasigeostrophic barotropic potential vorticity equation in an idealized ocean basin. In this model, the route to complex spatio/temporal flows is through successive bifurcations. The aim of this study is to describe the physics of the destabilization process of a periodic wind-driven flow associated with a secondary bifurcation. Although bifurcation theory has proven to be a valuable tool to determine the physical mechanisms of destabilization of fluid flows, the analysis of the stability of time-dependent (for example, periodic) flows, using this methodology, is computationally unpractical, due to the large number of degrees-of-freedom involved. The approach followed here is to construct a low-order model using numerical Galerkin projection of the full model equations onto the dynamically active eigenmodes. The resulting reduced model is shown to capture the local dynamics of the full model. The physical mechanism of the destabilization of the periodic wind-driven flow is deduced from the reduced model. While there are several stabilizing processes, notably rectification, the destabilization occurs due to time-dependent increase of the background horizontal shear in the flow.Civil Engineering and Geoscience
A Meta-Analysis of Genome-Wide Association Scans Identifies IL18RAP, PTPN2, TAGAP, and PUS10 As Shared Risk Loci for Crohn's Disease and Celiac Disease
No full textThis is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Measurement of the production cross-section of psi(2S) -> J/psi(-> mu(+)mu(-))pi(+) pi(-) in pp collisions at root s=7 TeV at ATLAS
No full text© 2014, The Author(s). Abstract: The prompt and non-prompt production cross-sections for ψ(2S) mesons are measured using 2.1 fb−1 of pp collision data at a centre-of-mass energy of 7 TeV recorded by the ATLAS experiment at the LHC. The measurement exploits the ψ(2S) → J/ψ(→ μ+μ−)π+π− decay mode, and probes ψ(2S) mesons with transverse momenta in the range 10 ≤ pT< 100 GeV and rapidity |y| < 2.0. The results are compared to other measurements of ψ(2S) production at the LHC and to various theoretical models for prompt and non-prompt quarkonium production.[Figure not available: see fulltext.]
Measurement of the cross section for inclusive isolated-photon production in collisions at TeV using the ATLAS detector
No full textSee paper for full list of authors - 36 pages in total, author list starting page 20, 3 figures, 2 tables, submitted to Physics Letters B, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2016-08/International audienceInclusive isolated-photon production in collisions at a centre-of-mass energy of 13 TeV is studied with the ATLAS detector at the LHC using a data set with an integrated luminosity of 3.2 fb. The cross section is measured as a function of the photon transverse energy above 125 GeV in different regions of photon pseudorapidity. Next-to-leading-order perturbative QCD and Monte Carlo event-generator predictions are compared to the cross-section measurements and provide an adequate description of the data
Search for a new resonance decaying to a or boson and a Higgs boson in the final states with the ATLAS Detector
No full textSee paper for full list of authors – 14 pages plus author list + cover pages (30 pages total), 4 figures, 1 tables, submitted to EPJC, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2013-23/International audienceA search for a new resonance decaying to a or boson and a Higgs boson in the final states is performed using 20.3 fb of collision data recorded at 8 TeV with the ATLAS detector at the Large Hadron Collider. The search is conducted by examining the invariant mass distribution for a localized excess. No significant deviation from the Standard Model background prediction is observed. The results are interpreted in terms of constraints on the Minimal Walking Technicolor model and on a simplified approach based on a phenomenological Lagrangian of Heavy Vector Triplets
Higgs boson production cross-section measurements and their EFT interpretation in the 4 ℓ decay channel at √s= 13 TeV with the ATLAS detector
No full textHiggs boson properties are studied in the four-lepton decay channel (where lepton = e, μ) using 139 fb - 1 of proton–proton collision data recorded at s=13 TeV by the ATLAS experiment at the Large Hadron Collider. The inclusive cross-section times branching ratio for H→ ZZ∗ decay is measured to be 1.34 ± 0.12 pb for a Higgs boson with absolute rapidity below 2.5, in good agreement with the Standard Model prediction of 1.33 ± 0.08 pb. Cross-sections times branching ratio are measured for the main Higgs boson production modes in several exclusive phase-space regions. The measurements are interpreted in terms of coupling modifiers and of the tensor structure of Higgs boson interactions using an effective field theory approach. Exclusion limits are set on the CP-even and CP-odd ‘beyond the Standard Model’ couplings of the Higgs boson to vector bosons, gluons and top quarks. © 2020, The Author(s)
Measurement of the splitting scales in events in collisions at TeV with the ATLAS detector
No full textSee paper for full list of authors - 42 pages in total, author list starting page 26, 8 figures, 1 table, submitted to JHEP, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2015-14/International audienceA measurement of the splitting scales occuring in the jet-clustering algorithm is presented for final states containing a boson. The measurement is done using 20.2 fb of proton-proton collision data collected at a centre-of-mass energy of TeV by the ATLAS experiment at the LHC in 2012. The measurement is based on charged-particle track information, which is measured with excellent precision in the region relevant for the transition between the perturbative and the non-perturbative regimes. The data distributions are corrected for detector effects, and are found to deviate from state-of-the-art predictions in various regions of the observables
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