842 research outputs found
Computing many faces in arrangements of lines and segments
No full textWe present randomized algorithms for computing many faces in an arrangement of lines or of segments in the plane, which are considerably simpler and slightly faster than the previously known ones. pn The main new idea is a simple randomized O(n log n) expected time algorithm for computing root n cells in an arrangement of n lines.A part of this work was done while the first and third authors were visiting Charles University and while the first author was visiting Utrecht University. The first author has been supported by National Science Foundation Grant CCR-93-01259 and an NYI aword. The second author has been supported by Charles University grant No. 351 and Czech Republic Grant GACR 201/93/2167. The third author has been supported by the Netherlands' Organization for Scientific Research (NWO) and partially supported by ESPRIT Basic Research Action No. 7141 (project ALCOM 2:Algorithms and Complexity)
A deterministic algorithm for the three-dimensional diameter problem
No full textWe give a deterministic algorithm for computing the diameter of an n-point set in three dimensions with O(n log(c)n) running time, where c is a constant.This research was supported by the Netherlands' Organization for Scientific Research (NWO) and partially by the ESPRIT Basic Research Action No. 7141 (project ALCOM II). J.M. acknowledges support by Humboldt Research Fellowship. Part of this research was done while he visited Utrecht University
ON RAY SHOOTING IN CONVEX POLYTOPES
No full textLet P be a convex polytope with n facets in the Euclidean space of a (small) fixed dimension d. We consider the membership problem for P (given a query point, decide whether it lies in P) and the ray shooting problem in P (given a query ray originating inside P, determine the first facet of P hit by it). It was shown in [AM2] that a data structure for the membership problem satisfying certain mild assumptions can also be used for the ray shooting problem, with a logarithmic overhead in query time, Here we show that some specific data structures for the membership problem can be used for ray shooting in a more direct way, reducing the overhead in the query time and eliminating the use of parametric search. We also describe an improved static solution for the membership problem, approaching the conjectured lower bounds more tightly
No Helly theorem for stabbing translates by lines in R-3
No full textFor each n > 2 we construct a convex body K subset of R-3 and a finite family F of disjoint translates of K such that any n - 1 members F admit a line transversal, but F has no line transversal
Monetary policy and the banking sector in Turkey
No full textWe find that monetary policy influenced Turkish bank lending between 1991 and 2007 through the money and bank lending channels. While capital and GDP growth have positive and significant long-run effects on bank loan growth, inflation, bank size and efficiency are not significant determinants. The latter is despite our finding that all Turkish banks' efficiency improved over the period. Domestic banks are unexpectedly found to be more efficient than foreign banks. With no evident dynamics or fixed-effects in loan growth we prefer the pooled-OLS estimator. We caution against assuming fixed-effects and dynamics are present as this may adversely affect inference. © 2013 Elsevier B.V
From Disruption to Post-pandemic Scenario
No full textFollowing the previous Chapter 18, this concluding this chapter (Part 2 of two) puts forward options for regulators triggered by COVID-19, bringing to the conclusion that the pandemic is an unprecedented opportunity to redefining boundaries and refocusing the priority on innovation for transparency. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
Nucleon spin structure studies in Drell–Yan process at COMPASS
No full textThe nucleon structure is presently described by Transverse Momentum Dependent (TMD) Parton Distribution Functions (PDFs), which generalise the collinear PDFs, adding partonic spin and transverse momentum degrees of freedom. The recent HERMES and COMPASS data on hadron production in deep inelastic scattering (SIDIS) of leptons off transversely polarised nucleons have provided a decisive validation of this framework. Nevertheless, the TMD PDFs should be studied in complementary reactions, like pp hard scattering and Drell-Yan processes. In particular the Sivers TMD PDF, which encodes the correlation between the nucleon spin and quark transverse momentum and appears in the Sivers Transverse Spin Asymmetry (TSA), is expected to have opposite sign in DY and SIDIS. In 2015 COMPASS measured for the first time the Drell-Yan reaction pi- p↑ → mu- mu X to test this prediction and the results have been recently published. The main topic of the thesis is the first measurement of the TSAs weighted with the dimuon transverse momentum in this data. These asymmetries complement the conventional TSAs and their advantage is that they do not contain convolutions over intrinsic transverse momenta. My analysis work is described in detail and the results are compared with calculations based on the extraction of the Sivers function from the recently measured weighted Sivers asymmetry in SIDIS. The thesis also contains a theoretical introduction, the description of the apparatus focused on the polarised target and its monitoring system to which I contributed. Finally, a chapter dedicated to the first original analysis in my PhD, the measurement of a Sivers-like asymmetry in the J/psit production in SIDIS, which is related to the gluon Sivers function, is included as well
Flow Mechanism of Sand-Water Mixtures in Pipelines
No full textMechanical Maritime and Materials Engineerin
Constructing levels in arrangements and higher order Voronoi diagrams
No full textWe give simple randomized incremental algorithms for computing the Amk-level in an arrangement of n lines in the plane or in an arrangement of n planes in . The expected running time of our algorithms is for the planarcase and O(nk2 + n log3n) for the three-dimensional case. Both bounds are optimal unless k is very small. The algorithm generalizes to computing the Amk-level in an arrangement of discs or x-monotone Jordan curves in the plane. Our approach can also compute the k-level; this yields a randomized algorithm for computing the order-k Voronoi diagram of n points in the plane in expected time O(k(n-k)log n + n log3n)
Quantum sign permutation polytopes
No full textConvex polytopes are convex hulls of point sets in the n-dimensional space E n that generalize 2-dimensional convex polygons and 3-dimensional convex polyhedra. We concentrate on the class of n-dimensional polytopes in E n called sign permutation polytopes. We characterize sign permutation polytopes before relating their construction to constructions over the space of quantum density matrices. Finally, we consider the problem of state identication and show how sign permutation polytopes may be useful in addressing issues of robustness
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