Going Further with Point Pair Features

Point Pair Features is a widely used method to detect 3D objects in point clouds, however they are prone to fail in presence of sensor noise and background clutter. We introduce novel sampling and voting schemes that significantly reduces the influence of clutter and sensor noise. Our experiments show that with our improvements, PPFs become competitive against state-of-the-art methods as it outperforms them on several objects from challenging benchmarks, at a low computational cost.Comment: Corrected post-print of manuscript accepted to the European Conference on Computer Vision (ECCV) 2016; https://link.springer.com/chapter/10.1007/978-3-319-46487-9_5

The galactic center black hole as a possible retro-lens for the S2 orbiting star

Holz & Wheeler (\cite{hw}) have recently proposed that a Schwarzschild black hole may act as a retro-lens which, if illuminated by a powerful light source, deflects light ray paths to large bending angles and a series of luminous arcs (or rings in the case of aligned objects) centered on the black hole may form. Obviously, the most convenient geometry to get retro-lensing images would be that of a very bright star close to a massive black hole, say the putative $\sim 4\times 10^6$ M$_{\odot}$ black hole at the galactic center. Recent observations of the galactic center region in the $K$-band have revealed the presence of a very bright main sequence star (labelled S2) with mass $\sim 15$ M$_{\odot}$ orbiting at close distance (130-1900 AU) from Sgr A$^*$. The relatively vicinity of S2 to the central massive black hole may offer a unique laboratory to test the formation of retro-lensing images. The next generation of space-based telescopes in the $K$-band (like NGST) may have high enough limiting magnitude necessary to observe such retro-lensing images.Comment: 4 pages, 2 Postscript figures, accepted for pubblications on Astronomy and Astrophysic

Light Propagation in Nonlinear Waveguide and Classical Two-Dimensional Oscillator

The quantum optical problem of the propagation of electromagnetic waves in a nonlinear waveguide is related to the solutions of the classical nonstationary harmonic oscillator using the method of linear integrals of motion [ Malkin et.al., Phys Rev. 2D (1970) p.1371 ]. An explicit solution of the classical oscillator with a varying frequency, corresponding to the light propagation in an anisotropic waveguide is obtained using the expressions for the quantum field fluctuations. Substitutions have been found which allow to establish connections of the linear and quadratic invariants of Malkin et.al. to several types of invariants of quadratic systems, considered in later papers. These substitutions give the opportunity to relate the corresponding quantum problem to that of the classical two-dimensional nonstationary oscillator, which is physically more informative.Comment: 14 pages, including one Table, 29 bibliographic references; E-mail: [email protected]

Scattering on Dislocations and Cosmic Strings in the Geometric Theory of Defects

We consider scattering of elastic waves on parallel wedge dislocations in the geometric theory of defects or, equivalently, scattering of point particles and light rays on cosmic strings. Dislocations are described as torsion singularities located on parallel lines, and trajectories of phonons are assumed to be the corresponding extremals. Extremals are found for arbitrary distribution of the dislocations in the monopole, dipole, and quadrupole approximation and the scattering angle is obtained. Examples of continuous distribution of wedge and edge dislocations are considered. We have found that for deficit angles close to -2\pi a star located behind a cosmic string may have any even number of images, 2,4,6,... The close relationship between dislocations and conformal maps is elucidated in detail.Comment: 30 pages, 14 figures, minor change

Financing Quality Education for All

In OECD countries the average expenditure on primary and secondary education institutions is about 3.5% of GDP. The investment in education has large implications for economic development and the proper functioning of democratic institutions, as well as overall well-being. However, clear consensus and guidance on which system leads to the best educational outcomes is lacking. This volume describes the resource allocation for compulsory and special needs education for a selection of well-performing countries and regions on PISA tests. By studying the funding systems in well-performing countries and regions the authors identify the elements in the respective funding systems that are associated with best outcomes and have the ideal characteristics to pursue particular goals of education systems such as equity and efficiency. The funding methods of primary and secondary education as well as special needs education are covered

Geodesics around line defects in elastic solids

Topological defects in solids, usually described by complicated boundary conditions in elastic theory, may be described more simply as sources of a gravity- like deformation field in the geometric approach of Katanaev and Volovich. This way, the deformation field is described by non-Euclidean metric that incorporates the boundary imposed by the defects. A possible way of gaining some insight into the motion of particles in a medium with topological defects (e.g., electrons in a dislocated metal) is to look at the geodesics of the medium around the defect. In this work, we find the exact solution for the geodesic equation for elastic medium with a generic line defect, the dispiration, that can either be a screw dislocation or a wedge disclination for particular choices of its parameters.Comment: 10 pages, Latex, 4 figures, accepted for publication in Phys. Lett.

Aparecida

O presente Trabalho de Conclusão de Curso de Bacharelado em Artes Visuais - Bacharelado, do Instituto de Artes da universidade Federal do Rio Grande do Sul - UFRGS, apresenta uma pesquisa acerca da trajetória artística e processo criativo da graduanda Evelyn Holz, assim como as questões latentes destes e como se desdobraram ao longo deste percurso. A pesquisa visa esmiuçar estes trabalhos organizados em três capítulos: Florescer, que trata principalmente das questões de representação de transtornos mentais. Busto, que perpassa as questões de artes feministas. E Aparecida que aborda a criação de uma personagem em formato de vulva, dando continuidade às temáticas feministas. Investigando suas questões estéticas e conceituais e como estas se articulam, buscando assim, compreender melhor o papel de artista da autora e como essas questões se relacionam com ela e com a sociedade. Para enriquecer a pesquisa, são utilizadas como fortes referências Heloísa Buarque de Holanda (2018) e Hèléne Cixous (2022)