Shortest Path Problems on a Polyhedral Surface

We develop algorithms to compute shortest path edge sequences, Voronoi diagrams, the Fréchet distance, and the diameter for a polyhedral surface

Minimizing the stabbing number of matchings, trees, and triangulations

The (axis-parallel) stabbing number of a given set of line segments is the maximum number of segments that can be intersected by any one (axis-parallel) line. This paper deals with finding perfect matchings, spanning trees, or triangulations of minimum stabbing number for a given set of points. The complexity of these problems has been a long-standing open question; in fact, it is one of the original 30 outstanding open problems in computational geometry on the list by Demaine, Mitchell, and O'Rourke. The answer we provide is negative for a number of minimum stabbing problems by showing them NP-hard by means of a general proof technique. It implies non-trivial lower bounds on the approximability. On the positive side we propose a cut-based integer programming formulation for minimizing the stabbing number of matchings and spanning trees. We obtain lower bounds (in polynomial time) from the corresponding linear programming relaxations, and show that an optimal fractional solution always contains an edge of at least constant weight. This result constitutes a crucial step towards a constant-factor approximation via an iterated rounding scheme. In computational experiments we demonstrate that our approach allows for actually solving problems with up to several hundred points optimally or near-optimally.Comment: 25 pages, 12 figures, Latex. To appear in "Discrete and Computational Geometry". Previous version (extended abstract) appears in SODA 2004, pp. 430-43

Novos processos de realiza??o e circula??o no longa-metragem brasileiro Castanha

Submitted by Caroline Xavier ([email protected]) on 2017-06-30T14:25:25Z No. of bitstreams: 1 DIS_CRISTIANE_SCHEFFER_REQUE_COMPLETO.pdf: 7431317 bytes, checksum: 7594c1fa99a067fd069012681a6a13dd (MD5)Made available in DSpace on 2017-06-30T14:25:25Z (GMT). No. of bitstreams: 1 DIS_CRISTIANE_SCHEFFER_REQUE_COMPLETO.pdf: 7431317 bytes, checksum: 7594c1fa99a067fd069012681a6a13dd (MD5) Previous issue date: 2017-03-29Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPESThis dissertation studies the Brazilian audiovisual marketplace between 2012 and 2015 based on the relationship between different modes of production and distribution of domestic films. The main focus is on the production process behind the film Castanha (Davi Pretto, Rio Grande do Sul, 2014), analyzing each phase of production by comparing it to another contemporary film with different characteristics, such as the director's experience, budget size, screenplay development, and its regional location within Brazil. The references follow the guidelines of the triad method (BARONE, 2009), which defines the audiovisual field through its three main activities: production, distribution and exhibition. The analysis is constructed through the perspective of the cinematic fact (COHEN-S?AT, 1946; METZ, 1980), considering aspects related to what happened before, during and after the film and its encounter with the public. The main objective is to look at certain production aspects of Castanha in comparison to the production of the film Reaching for the moon (Bruno Barreto, Rio de Janeiro, 2013), its distribution in comparison to Rat Fever (Cl?udio Assis, Pernambuco, 2012), and its exhibition in comparison to the path taken by The second mother (Anna Muylaert, S?o Paulo, 2015), and through this analysis noting asymmetries and similarities in the production and distribution of recent domestic feature films. Based on data made available by Ancine and Filme B, it is possible to look beyond the market figures, questioning the validity of box office rankings as the only parameter for measuring a film?s success. This study considers concepts that vary from Chris Anderson?s long tail to the Latin American scenario of Canclini and Mart?n-Barbero, including studies of the Brazilian marketplace by Butcher, Gatti, Chalupe, R?gio, as well as Barone. Finally, this dissertation offers elements that contribute to the discussion around the exhibition paths taken by Brazilian films with niche qualities, both in traditional movie theaters and outside of them.Esta disserta??o estuda o mercado audiovisual brasileiro de 2012 a 2015, a partir de rela??es estabelecidas entre diferentes formas de realiza??o e circula??o de filmes nacionais. Tomando como objeto principal o processo para realiza??o da obra Castanha (Davi Pretto, RS, 2014), a proposta ? analisar cada uma de suas fases ao lado de outro filme contempor?neo, por?m com caracter?sticas origin?rias diversas tais como experi?ncia do diretor, dimens?o do or?amento, constru??o do roteiro e localiza??o regional no Brasil. As refer?ncias seguem diretrizes a partir do m?todo da tr?ade (BARONE, 2009), que define o ambiente audiovisual atrav?s de suas principais atividades: produ??o, distribui??o e exibi??o. A constru??o da an?lise ocorre a partir da perspectiva do fato cinematogr?fico (COHEN-S?AT, 1946; METZ, 1980), observando aspectos relacionados ao que acontece antes, durante e depois do filme, de seu encontro com o p?blico. O objetivo principal ? observar elementos da produ??o de Castanha junto ? produ??o do filme Flores raras (Bruno Barreto, RJ, 2013), seu trabalho de distribui??o junto ao de Febre do rato (Cl?udio Assis, PE, 2012), e sua exibi??o alinhada ao percurso realizado por Que horas ela volta? (Anna Muylaert, SP, 2015), e desta an?lise perceber assimetrias e semelhan?as na realiza??o e circula??o de longas-metragens nacionais recentes. Com base em dados fornecidos atrav?s da Ancine e Filme B, ? poss?vel lan?ar um olhar al?m dos n?meros do mercado, questionando a validade dos rankings de bilheteria como ?nico par?metro para verificar o sucesso de um filme. O trabalho traz conceitos de autores que variam da cauda longa de Chris Anderson ? realidade latino-americana de Canclini e Mart?n-Barbero, passando pelos estudos do mercado brasileiro a partir de Butcher, Gatti, Chalupe, R?gio, al?m do pr?prio Barone. Por fim, esta disserta??o traz elementos que contribuem para a discuss?o sobre a trajet?ria dos filmes brasileiros com vi?s de nicho, tanto nas tradicionais salas de cinema como al?m destas telas

The geodesic diameter of polygonal domains

This paper studies the geodesic diameter of polygonal domains having h holes and n corners. For simple polygons (i.e. h = 0), it is known that the geodesic diameter is determined by a pair of corners of a given polygon and can be computed in linear time. For general polygonal domains with h ≥ 1, however, no algorithm for computing the geodesic diameter was known prior to this paper. In this paper, we present the first algorithm that computes the geodesic diameter of a given polygonal domain in worst-case time O(n 7.73) or O(n 7 (logn + h)). Among other results, we show the following geometric observation: the geodesic diameter can be determined by two points in its interior. In such a case, there are at least five shortest paths between the points. © 2010 Springer-Verlag.Proc. of the 18th European Symposium on AlgorithmsSCOPUS: cp.kinfo:eu-repo/semantics/publishe

Distributed Regression For Heterogeneous Data Sets

Existing meta-learning based distributed data mining approaches do not explicitly address context heterogeneity across individual sites. This limitation constrains their applications where distributed data are not identically and independently distributed. Modeling heterogeneously distributed data with hierarchical models, this paper extends the traditional meta-learning techniques so that they can be successfully used in distributed scenarios with context heterogeneity

Adaptive spatial partitioning for multidimensional data streams

We propose a space-efficient scheme for summarizing multidimensional data streams. Our sketch can be used to solve spatial versions of several classical data stream queries efficiently. For instance, we can track ε-hotspots, which are congruent boxes containing at least an ε fraction of the stream, and maintain hierarchical heavy hitters in d dimensions. Our sketch can also be viewed as a multidimensional generalization of the ε-approximate quantile summary. The space complexity of our scheme is O ( 1 ε log R) if the points lie in the domain [0, R]d, where d is assumed to be a constant. The scheme extends to the sliding window model with a log(εn) factor increase in space, where n is the size of the sliding window. Our sketch can also be used to answer ε-approximate rectangular range queries over a stream of d-dimensional points.