Search results for " set"
showing 10 items of 2095 documents
Partial data inverse problems for Maxwell equations via Carleman estimates
2015
In this article we consider an inverse boundary value problem for the time-harmonic Maxwell equations. We show that the electromagnetic material parameters are determined by boundary measurements where part of the boundary data is measured on a possibly very small set. This is an extension of earlier scalar results of Bukhgeim-Uhlmann and Kenig-Sj\"ostrand-Uhlmann to the Maxwell system. The main contribution is to show that the Carleman estimate approach to scalar partial data inverse problems introduced in those works can be carried over to the Maxwell system.
Linearized Calderón problem and exponentially accurate quasimodes for analytic manifolds
2022
In this article we study the linearized anisotropic Calderon problem on a compact Riemannian manifold with boundary. This problem amounts to showing that products of pairs of harmonic functions of the manifold form a complete set. We assume that the manifold is transversally anisotropic and that the transversal manifold is real analytic and satisfies a geometric condition related to the geometry of pairs of intersecting geodesics. In this case, we solve the linearized anisotropic Calderon problem. The geometric condition does not involve the injectivity of the geodesic X-ray transform. Crucial ingredients in the proof of our result are the construction of Gaussian beam quasimodes on the tra…
From the banks of Upper Tigris River to the Zagros Highlands. The Tübingen Eastern Ḫabur Archaeological Survey. Trial season 2013
2016
After decades of strife and unrest, during which Northern Iraq remained closed to the outside world, a new era of international scientific enterprise has begun in this region thanks to the recent democratic and civil upturn and its subsequent economic resurgence. In the last few years, together with the restoration and refurbishment of historical monuments, there has also been a spread of new archaeological undertakings in the form of surveys and excavations, the quality and quantity of which is fully shown in the present volume. A Tübingen University research project was initiated in the northernmost part of Iraqi-Kurdistan, in the province of Dohuk. The research area is located at the foo…
Disentangling Isoetes setacea and removing threats to Isoetes echinospora
2015
The name Isoetes setacea has been applied to two different species, causing nomenclatural and taxonomic confusion. Some authors have rejected it on that account, yet it is currently used in a sense that is incompatible with its type. That type represents one of two similar species, I. echinospora and I. lacustris, which still today grow together at the type locality. An epitype is designated here, ensuring that I. setacea is sunk in synonymy under I. lacustris. A second name potentially threatening I. echinospora is I. tenella. It is currently regarded as a synonym of I. lacustris, but its type, a plate in Flora Danica, cannot be confidently identified, nor are there any specimens associate…
A conspectus of and key to GreekIsoetes(Isoetaceae), based on a reassessment of Haussknecht's gatherings of 1885
2015
The three Isoetes species recorded from Thessalia (Thessaly) in N Greece by Haussknecht, in 1899, under the names I. setacea, I. heldreichii, and I. phrygia, were reassessed using megaspore and microspore ornamentation in addition to macromorphological features. “Isoetes setacea” is not the SW European I. delilei to which the name I. setacea was generally misapplied, nor “I. echinospora” as it has been called due to a misunderstanding, but a so far undescribed species here named I. haussknechtii; it has not been found again in Haussknecht’s locality but has recently turned up in Peloponnisos and the E Aegean Islands. I. heldreichii, described from Haussknecht’s gathering, is apparently exti…
Reducing the Human Effort in Text Line Segmentation for Historical Documents
2021
Labeling the layout in historical documents for preparing training data for machine learning techniques is an arduous task that requires great human effort. A draft of the layout can be obtained by using a document layout analysis (DLA) system that later can be corrected by the user with less effort than doing it from scratch. We research in this paper an iterative process in which the user only supervises and corrects the given draft for the pages automatically selected by the DLA system with the aim of reducing the required human effort. The results obtained show that similar DLA quality can be achieved by reducing the number of pages that the user has to annote and that the accumulated h…
A relevance feedback CBIR algorithm based on fuzzy sets
2008
CBIR (content-based image retrieval) systems attempt to allow users to perform searches in large picture repositories. In most existing CBIR systems, images are represented by vectors of low level features. Searches in these systems are usually based on distance measurements defined in terms of weighted combinations of the low level features. This paper presents a novel approach to combining features when using multi-image queries consisting of positive and negative selections. A fuzzy set is defined so that the degree of membership of each image in the repository to this fuzzy set is related to the user's interest in that image. Positive and negative selections are then used to determine t…
Searches for small-scale anisotropies from neutrino point sources with three years of IceCube data
2015
Recently, IceCube found evidence for a diffuse signal of astrophysical neutrinos in an energy range of $60\,\mathrm{TeV}$ to the $\mathrm{PeV}$-scale. The origin of those events, being a key to understanding the origin of cosmic rays, is still an unsolved question. So far, analyses have not succeeded to resolve the diffuse signal into point-like sources. Searches including a maximum-likelihood-ratio test, based on the reconstructed directions and energies of the detected down- and up-going neutrino candidates, were also performed on IceCube data leading to the exclusion of bright point sources. In this paper, we present two methods to search for faint neutrino point sources in three years o…
Horizontal competition in multilevel governmental settings
2013
28 pages; Governments situated on the same level of a multi-level governmental system compete with each other as well as with governments placed higher or lower. This paper is concerned with horizontal competition only. It discusses both competition based on the mobility of agents and competition based on comparisons of performance across jurisdictions - i.e., yardstick competition. With regard to the first kind, the focus is on the capacity of governments and voters to decide policies in spite of the mobility of agents. Some attention is also given to non-standard mechanisms in which mobility is manipulated so as to change the structure of the electorate. The paper considers two forms of h…
Khovanov homology for signed divides
2009
The purpose of this paper is to interpret polynomial invariants of strongly invertible links in terms of Khovanov homology theory. To a divide, that is a proper generic immersion of a finite number of copies of the unit interval and circles in a [math] –disc, one can associate a strongly invertible link in the [math] –sphere. This can be generalized to signed divides: divides with [math] or [math] sign assignment to each crossing point. Conversely, to any link [math] that is strongly invertible for an involution [math] , one can associate a signed divide. Two strongly invertible links that are isotopic through an isotopy respecting the involution are called strongly equivalent. Such isotopi…