Search results for "database."
showing 10 items of 2119 documents
Analysis of the Relationship Between Context and Solution Plan in Modelling Tasks Involving Estimations
2021
In this chapter we analyse students’ written solution plan of a sequence of modelling tasks involving estimations. Our research objective is to statistically analyse whether there is a relation between the solution plan and the characteristics of the context of the real estimation task. From previous work, we have identified some task variables that are directly related to the context. In this study we have designed a sequence of modelling tasks and we have analysed the productions of N = 224 Spanish pre-service primary school teachers. The results show that there is a relationship between the variables of the task and the solution plan used by the students in each case. From the results of…
Past price “memory” in the housing market: testing the performance of different spatio-temporal specifications.
2017
ABSTRACTRecent methodological developments provide a way to incorporate the temporal dimension when accounting for spatial effects in hedonic pricing. Weight matrices should decompose the spatial effects into two distinct components: bidirectional contemporaneous spatial connections; and unidirectional spatio-temporal effects from past transactions. Our iterative estimation approach explicitly analyses the role of time in price determination. The results show that both spatio-temporal components should be included in model specification; past transaction information stops contributing to price determination after eight months; and limited temporal friction is exhibited within this period. T…
Scientific production in bioethics in Spain through MEDLINE
2007
Fundamento: Describir la producción científica española en bioética entre 1966 y 2003. Métodos: Se seleccionaron los documentos publicados por autores españoles y recogidos en la base de datos MEDLINE, mediante el cruce de las palabras bioética con otras diversas del mismo ámbito. Resultados: Se estudiaron 858 documentos, de los cuales 78 (9,1%) se publicaron entre 1966 y 1983, 163 (19%) entre 1984 y 1993, y 617 (71,9%) entre 1994 y 2003. Los principales temas publicados fueron: legislación y derechos (15,4%) e investigación y comités de ética (13,1%). En el último período se ha observado un aumento significativo de las publicaciones sobre genética y clonación y un descenso sobre las de abo…
First search for point sources of high-energy cosmic neutrinos with the ANTARES neutrino telescope
2011
Results are presented of a search for cosmic sources of high-energy neutrinos with the ANTARES neutrino telescope. The data were collected during 2007 and 2008 using detector configurations containing between 5 and 12 detection lines. The integrated live time of the analyzed data is 304 days. Muon tracks are reconstructed using a likelihood-based algorithm. Studies of the detector timing indicate a median angular resolution of 0.5 0.1deg. The neutrino flux sensitivity is 7.5 ¿ 10 -8(E ¿/ GeV) -2 GeV -1 s -1 cm -2 for the part of the sky that is always visible (¿ < -48deg), which is better than limits obtained by previous experiments. No cosmic neutrino sources have been observed.
Scientific collaborations: Principles of wikibridge design
2010
Semantic wikis, wikis enhanced with Semantic Web technologies, are appropriate systems for community-authored knowledge models. They are particularly suitable for scientific collaboration. This paper details the design principles ofWikiBridge, a semantic wiki.
Tandem repeats lead to sequence assembly errors and impose multi-level challenges for genome and protein databases
2019
AbstractThe widespread occurrence of repetitive stretches of DNA in genomes of organisms across the tree of life imposes fundamental challenges for sequencing, genome assembly, and automated annotation of genes and proteins. This multi-level problem can lead to errors in genome and protein databases that are often not recognized or acknowledged. As a consequence, end users working with sequences with repetitive regions are faced with ‘ready-to-use’ deposited data whose trustworthiness is difficult to determine, let alone to quantify. Here, we provide a review of the problems associated with tandem repeat sequences that originate from different stages during the sequencing-assembly-annotatio…
Adaptive learning of compressible strings
2020
Suppose an oracle knows a string $S$ that is unknown to us and that we want to determine. The oracle can answer queries of the form "Is $s$ a substring of $S$?". In 1995, Skiena and Sundaram showed that, in the worst case, any algorithm needs to ask the oracle $\sigma n/4 -O(n)$ queries in order to be able to reconstruct the hidden string, where $\sigma$ is the size of the alphabet of $S$ and $n$ its length, and gave an algorithm that spends $(\sigma-1)n+O(\sigma \sqrt{n})$ queries to reconstruct $S$. The main contribution of our paper is to improve the above upper-bound in the context where the string is compressible. We first present a universal algorithm that, given a (computable) compre…
Zero-Error Affine, Unitary, and Probabilistic OBDDs
2017
We introduce the affine OBDD model and show that zero-error affine OBDDs can be exponentially narrower than bounded-error unitary and probabilistic OBDDs on certain problems. Moreover, we show that Las Vegas unitary and probabilistic OBDDs can be quadratically narrower than deterministic OBDDs. We also obtain the same results by considering the automata versions of these models.
Parallel In-Memory Evaluation of Spatial Joins
2019
The spatial join is a popular operation in spatial database systems and its evaluation is a well-studied problem. As main memories become bigger and faster and commodity hardware supports parallel processing, there is a need to revamp classic join algorithms which have been designed for I/O-bound processing. In view of this, we study the in-memory and parallel evaluation of spatial joins, by re-designing a classic partitioning-based algorithm to consider alternative approaches for space partitioning. Our study shows that, compared to a straightforward implementation of the algorithm, our tuning can improve performance significantly. We also show how to select appropriate partitioning parame…
A Two-level Spatial In-Memory Index
2020
Very large volumes of spatial data increasingly become available and demand effective management. While there has been decades of research on spatial data management, few works consider the current state of commodity hardware, having relatively large memory and the ability of parallel multi-core processing. In this work, we re-consider the design of spatial indexing under this new reality. Specifically, we propose a main-memory indexing approach for objects with spatial extent, which is based on a classic regular space partitioning into disjoint tiles. The novelty of our index is that the contents of each tile are further partitioned into four classes. This second-level partitioning not onl…