1,930 research outputs found

    An improved geometric inequality via vanishing moments, with applications to singular Liouville equations

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    We consider a class of singular Liouville equations on compact surfaces motivated by the study of Electroweak and Self-Dual Chern-Simons theories, the Gaussian curvature prescription with conical singularities and Onsager's description of turbulence. We analyse the problem of existence variationally, and show how the angular distribution of the conformal volume near the singularities may lead to improvements in the Moser-Trudinger inequality, and in turn to lower bounds on the Euler-Lagrange functional. We then discuss existence and non-existence results.Comment: some references adde

    Snow cover monitoring by machine processing of multitemporal LANDSAT MSS data

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    LANDSAT frames were geometrically corrected and data sets from six different dates were overlaid to produce a 24 channel (six dates and four wavelength bands) data tape. Changes in the extent of the snowpack could be accurately and easily determined using a change detection technique on data which had previously been classified by the LARSYS software system. A second phase of the analysis involved determination of the relationship between spatial resolution or data sampling frequency and accuracy of measuring the area of the snowpack

    A nonparametric multidimensional latent class IRT model in a Bayesian framework

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    We propose a nonparametric Item Response Theory model for dichotomously scored items in a Bayesian framework. Partitions of the items are defined on the basis of inequality constraints among the latent class success probabilities. A Reversible Jump type algorithm is described for sampling from the posterior distribution. A consequence is the possibility to make inference on the number of dimensions (i.e., number of groups of items measuring the same latent trait) and to cluster items when unidimensionality is violated

    LANDSAT-4/5 image data quality analysis

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    A LANDSAT Thematic Mapper (TM) quality evaluation study was conducted to identify geometric and radiometric sensor errors in the post-launch environment. The study began with the launch of LANDSAT-4. Several error conditions were found, including band-to-band misregistration and detector-to detector radiometric calibration errors. Similar analysis was made for the LANDSAT-5 Thematic Mapper and compared with results for LANDSAT-4. Remaining band-to-band misregistration was found to be within tolerances and detector-to-detector calibration errors were not severe. More coherent noise signals were observed in TM-5 than in TM-4, although the amplitude was generally less. The scan direction differences observed in TM-4 were still evident in TM-5. The largest effect was in Band 4 where nearly a one digital count difference was observed. Resolution estimation was carried out using roads in TM-5 for the primary focal plane bands rather than field edges as in TM-4. Estimates using roads gave better resolution. Thermal IR band calibration studies were conducted and new nonlinear calibration procedures were defined for TM-5. The overall conclusion is that there are no first order errors in TM-5 and any remaining problems are second or third order

    Semilinear equations with exponential nonlinearity and measure data

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    We study the existence and non-existence of solutions of the problem [GRAPHICS] where Omega is a bounded domain in R-N, N >=, 3, and it is a Radon measure. We prove that if it 4 pi HN-2, then (0.1) has a unique solution. We also show that the constant 4 pi in this condition cannot be improved. (c) 2005 Elsevier SAS. All rights reserved

    Microwave broadband characterization of aging of SU-8 polymer as CPW substrate

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    In this paper we present the methodology and the numerical results related to the analysis of aging of the SU- 8 polymer when used as a primary layer for the realization of Coplanar Waveguide (CPW) structures. As test devices, we used a set of transmission lines with different lengths and T-shaped open stubs shunt resonators; by using these geometries, we are able to acquire the data in a broadband range, in principle between 1 GHz and 40 GHz. We conduct the analysis by comparing two different technology run: the first wafer with a deposited layer by a 12-year-old SU-8 and the second wafer, with the same photolithographed metallic geometries, with a brand-new processed SU-8 photoresist
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