Search results for "RAV"
showing 10 items of 5866 documents
Improving table compression with combinatorial optimization
2002
We study the problem of compressing massive tables within the partition-training paradigm introduced by Buchsbaum et al. [SODA'00], in which a table is partitioned by an off-line training procedure into disjoint intervals of columns, each of which is compressed separately by a standard, on-line compressor like gzip. We provide a new theory that unifies previous experimental observations on partitioning and heuristic observations on column permutation, all of which are used to improve compression rates. Based on the theory, we devise the first on-line training algorithms for table compression, which can be applied to individual files, not just continuously operating sources; and also a new, …
Multi-scale analysis of the European airspace using network community detection
2014
We show that the European airspace can be represented as a multi-scale traffic network whose nodes are airports, sectors, or navigation points and links are defined and weighted according to the traffic of flights between the nodes. By using a unique database of the air traffic in the European airspace, we investigate the architecture of these networks with a special emphasis on their community structure. We propose that unsupervised network community detection algorithms can be used to monitor the current use of the airspaces and improve it by guiding the design of new ones. Specifically, we compare the performance of three community detection algorithms, also by using a null model which t…
Fast MATLAB assembly of FEM matrices in 2D and 3D: Edge elements
2014
We propose an effective and flexible way to assemble finite element stiffness and mass matrices in MATLAB. We apply this for problems discretized by edge finite elements. Typical edge finite elements are Raviart-Thomas elements used in discretizations of H(div) spaces and Nedelec elements in discretizations of H(curl) spaces. We explain vectorization ideas and comment on a freely available MATLAB code which is fast and scalable with respect to time.
Simulation-based marginal likelihood for cluster strong lensing cosmology
2015
Comparisons between observed and predicted strong lensing properties of galaxy clusters have been routinely used to claim either tension or consistency with $\Lambda$CDM cosmology. However, standard approaches to such cosmological tests are unable to quantify the preference for one cosmology over another. We advocate approximating the relevant Bayes factor using a marginal likelihood that is based on the following summary statistic: the posterior probability distribution function for the parameters of the scaling relation between Einstein radii and cluster mass, $\alpha$ and $\beta$. We demonstrate, for the first time, a method of estimating the marginal likelihood using the X-ray selected …
Depletion in Bose-Einstein condensates using quantum field theory in curved space
2007
5 pages.-- PACS nrs.: 03.75.Kk; 05.30.Jp; 04.62.+v; 04.70.Dy.-- ISI Article Identifier: 000246074600122.-- ArXiv pre-print available at: http://arxiv.org/abs/cond-mat/0610367
Features of the Energy Spectrum of Cosmic Rays above 2.5×10$^{18}$ eV Using the Pierre Auger Observatory
2020
We report a measurement of the energy spectrum of cosmic rays above $2.5{\times} 10^{18}$ eV based on $215,030$ events. New results are presented: at about $1.3{\times} 10^{19}$ eV, the spectral index changes from $2.51 \pm 0.03 \textrm{ (stat.)} \pm 0.05 \textrm{ (sys.)}$ to $3.05 \pm 0.05 \textrm{ (stat.)}\pm 0.10\textrm{ (sys.)}$, evolving to $5.1\pm0.3\textrm{ (stat.)} \pm 0.1\textrm{ (sys.)}$ beyond $5{\times} 10^{19}$ eV, while no significant dependence of spectral features on the declination is seen in the accessible range. These features of the spectrum can be reproduced in models with energy-dependent mass composition. The energy density in cosmic rays above $5{\times} 10^{18}$ eV …
Ar ceļošanas vajadzībām saistītās informācijas sociālā tīklā FaceBook novērtējums
2019
Maģistra darba „Ar ceļošanas vajadzībām saistītās informācijas sociālā tīklā FaceBook novērtējums” ietvaros tika analizēta tūrisma informācijas satura sociālajā tīklā FaceBook atbilstība patērētāju vēlmēm un vajadzībām. Darba teorētiskā bāze balstās uz tūrisma nozares, patērētāju uzvedības un informācijas laikmeta komunikācijas teorijām, īpaši izceļot sociālo mediju teorijas, savukārt pētījuma veikšanai izmantotā metodoloģija ir kontentanalīze, aptaujas un eksperta intervija. Pētījuma gaitā tika analizēti 2091 FaceBook publikācijas, 300 aptaujas un viens eksperta viedoklis. Rezultātā tika izprastas ceļotāju vēlmes un vajadzības par tūrisma informācijas saturu sociālajā tīklā FaceBook, kuras…
The General Routing Problem polyhedron: Facets from the RPP and GTSP polyhedra
1998
[EN] In this paper we study the polyhedron associated with the General Routing Problem (GRP). This problem, first introduced by Orloff in 1974, is a generalization of both the Rural Postman Problem (RPP) and the Graphical Traveling Salesman Problem (GTSP) and, thus, is NP -hard. We describe a formulation of the problem such that from every non-trivial facet-inducing inequality for the RPP and GTSP polyhedra, we obtain facet-inducing inequalities for the GRP polyhedron, We describe a new family of facet-inducing inequalities for the GRP, the honeycomb constraints, which seem to be very useful for solving GRP and RPP instances. Finally, new classes of facets obtained by composition of facet-i…
Natural light in the architectural interior: Fake news on the Caravaggio of Palermo
2022
The paper investigates the mystery of a painting, Caravaggio’s The Nativity, and the scope of certain design devices implied in the interior/exterior relationship and described as a function of recognisable physical elements. For a long time, it was believed that this painting, placed on the altar of the oratory of San Lorenzo, was made in Palermo. It is a piece of fake news detected by interpreting and examining an architectural interior. Here, the value of natural light emerges, and we glimpse an irrefutable truth and therefore achieve an understanding of what happens when observing The Nativity and the oratory. What is the difference between recognising and identifying the arche, that is…