9,946 research outputs found
Analytical querying with typed linear algebra: integration with MonetDB
Dissertação de mestrado integrado em Informatics EngineeringCurrent digital transformations in society heavily rely on safe, easy-to-use, high-performance data storage and
analysis for smart decision taking. This triggered the need for efficient analytical querying solutions and the
columnar database model is increasingly regarded as the most efficient model for data organization in large
data banks. MonetDB is a pioneer in the column-wise database model and is currently at the forefront of high
performance DBMS engine.
A Linear Algebra Querying (LAQ) engine, using a columnar database paradigm and strongly inspired on Typed
Linear Algebra (TLA), was developed in a former MSc. dissertation, with a prototype Web interface. Performance
benchmarking of this engine showed it outperformed conventional referenced DBMS but it failed to beat MonetDB’s
performance.
This dissertation aims to improve the performance of the LAQ engine by following a different path: instead of a
standalone engine, the new approach implements the engine on top of MonetDB extended with RMA (Relational
Matrix Algebra) and inspired by the TLA approach. This enables the use of LAQ scripting to replace the main
stream relational algebra query language approach given by SQL.
Matrix operations commonly used in LAQ/TLA, such as matrix-matrix multiplication, Khatri-Rao product or
Hadamard-Schur product, had to be implemented in RMA to shift from the relational algebra paradigm to TLA.
A thorough analysis of the MonetDB/RMA showed the need to implement key TLA operators that are not
available at the frontend. Such operators were implemented and successfully tested and validated, paving the
way to future benchmarking its performance with TPC-H/OLAP queries and consequent fine tuning of the engine.Atualmente, as transformações digitais na sociedade confiam fortemente no armazenamento e na análise
de dados seguros, fáceis de usar e de alto desempenho para tomadas de decisão inteligentes. Este facto
desencadeou a necessidade de soluções de consultas analíticas eficientes, em que o modelo de bases de dados
colunar é cada vez mais considerado o modelo mais eficiente para organização de dados em grandes bancos de
dados. MonetDB é um sistema pioneiro no modelo de bases de dados colunar e atualmente está na vanguarda
de DBMS’s de alto desempenho.
Um motor Linear Algebra Querying (LAQ), que usa o paradigma de bases de dados colunar e fortemente
inspirado em Álgebra Linear Tipada (TLA), foi desenvolvido numa antiga dissertação de mestrado em Engenharia
Informática. O benchmarking do desempenho deste motor mostrou que supera DBMS tradicionais, mas não
conseguiu superar o desempenho do MonetDB.
Esta dissertação visa melhorar o desempenho do motor LAQ seguindo um caminho diferente: em vez de
um motor autónomo, a nova abordagem implementa o motor sobre o motor do MonetDB estendido com RMA
(Álgebra Relacional Matricial) e inspirado na abordagem de TLA. Isto permite o uso de scripts LAQ para substituir
a abordagem da linguagem de consulta de álgebra relacional fornecida pelo SQL.
Operações de matrizes comumente usadas em LAQ / TLA, como multiplicação de matrizes, produto Khatri-Rao
ou produto Hadamard-Schur, tiveram de ser implementadas em RMA para mudar do paradigma da álgebra
relacional para TLA.
Uma análise completa do MonetDB / RMA mostrou a necessidade de implementar os principais operadores
de TLA que não estão disponíveis no front-end. Esses operadores foram implementados, testados e validados
com sucesso, abrindo caminho para um futuro benchmarking do seu desempenho com queries TPC-H / OLAP e
consequente, ajuste do motor
The Effects of 3D Printing Parameters and Surface Treatments on Convective Heat Transfer Performance
Additive manufacturing technology and applications have quickly expanded in many industries over the last five years. As additive manufacturing is studied and refined, improvements in resolution and strength have helped propel further growth of the industry. This study focuses on an additive manufacturing technology called fused filament fabrication (FFF). FFF involves the extrusion and layer-by-layer deposition of a molten thermoplastic material to create the desired part. One potential new application of fused filament fabrication is the manufacture of heat exchangers and heat sinks. This study focuses on developing baseline experimental data related to convective heat transfer coefficients over surfaces of commonly used polymers in FFF 3d printing while varying printing parameters and surface treatments of the samples. A copper pipe containing two cartridge heaters was placed inside the ABS test samples with two thermocouples placed at the surface of the 3d printed material to measure the surface temperature of the cylinder. The samples were tested inside a wind tunnel to measure the effects of surface roughness and printing parameters on heat transfer over a range of velocities. Samples with different printing parameters were tested first. Parts with layer heights (LH) of 0.1 mm, 0.2 mm and 0.3 mm were printed. As the layer height increases the roughness also increased. Sample 1 of LH = 0.1 mm had a roughness of 9.72 μm and a heat transfer coefficient of 72 W/m2-K and sample 1 of LH = 0.3 mm had a roughness of 28.83 μm and a heat transfer coefficient of 85 W/m2-K, with fans operating at 12V. Surface treatment, such as acetone smoothing, sanding and sanding/acetone-smoothing were performed in other to reduce surface roughness. The acetone smoothing process affected more the samples with smaller layer heights. Sample 1 of LH = 0.2 mm had a roughness reduced to 11.43 μm and a heat transfer coefficient of 71 W/m2-K. Sanding and sanding/acetone-smoothing process recorded the smallest values for roughness, while recording the highest values for heat transfer coefficient. Sanded sample 2 of LH = 0.3 had a heat transfer coefficient of 101 W/m2-K and roughness of 4.35 μm
Routing cost optimization in Multi Overlay Robust Networks
In the present work we solve the problem of data flow routing in Multi-Overlay Robust
Networks (MORN) while aiming to minimize its routing cost. This kind of networks are typically
IP/MPLS Data Network deployed over an SDH/DWDM transport infrastructure.
Through the IP/MPLSMulti-Layer Data Network different kinds of services having a wide
variety of quality of service requirements are delivered. Those services are being transported by
an SDH/DWDM Transport Network which has different transport capacities. In this network,
routing cost depends not only on the assigned transport capacity but also in the technology that
it uses.
Our problem seeks not only to route data flows through Data and Transport Networks but
also to optimize routing costs and the reliability of the network. The inputs of our problem
are the topology of the Data and Transport networks as well as the budget that the network
operator has in order to improve its network routing costs and reliability. We will assume that
the operator can only use that budget for installing new links between existing transport nodes.
The output of the problem is the data flow routing in the Data and Transport Networks and
its associated cost. Routing in the Transport Network is calculated not only in the nominal
scenario - when all the Transport Network links are up and running - but also in each single
transport link failure case.En el presente trabajo se resuelve el problema de rutear flujos de datos en una Red Multi-
Capa Robusta (MORN por sus siglas en inglés), mientras que se trata de minimizar el costo
asociado a su ruteo. Este tipo de redes son generalmente redes de datos IP/MPLS desplegadas
sobre una infraestructura de transporte SDH/DWDM.
Sobre la red de datos IP/MPLS se cursan distintos servicios con diferentes requerimientos
de calidad de servicio (QoS). Los servicios de la Red de Datos son transportados por la red
SDH/DWDM la cual tiene distintas capacidades de transporte. En éste tipo de redes el costo
asociado al transporte depende no solo de la capacidad asignada para el transporte sino que
también depende de la tecncología utilizada para transportar dicha capacidad.
En el problema no sólo se busca enrutar flujos de datos a través de las Redes de Datos y
Transporte sino que también se busca optimizar los costos de ruteo y la confiabilidad de la red.
Como punto de partida, el problema toma como información la topología de las Redes de Datos
y Transporte así como cierto presupuesto que el operador de la red posee para poder mejorar
los costos de ruteo y la confiabilidad de su red. Asumiremos que dicho presupuesto solo puede
ser utilizado para instalar nuevos enlaces entre los nodos existentes en la Red de Transporte.
La salida del problema es el ruteo de los flujos de datos tanto en la Red de Datos como en la
de Transporte, así como el costo asociado a dicho ruteo. El ruteo en la Red de Transporte se
calcula no solo en el escenario nominal - cuando todos los enlaces de la Red de Transporte
están funcionales - sino que también en cada escenario de falla simple en sus enlaces
Consistent Gravitationally-Coupled Spin-2 Field Theory
Inspired by the translational gauge structure of teleparallel gravity, the
theory for a fundamental massless spin-2 field is constructed. Accordingly,
instead of being represented by a symmetric second-rank tensor, the fundamental
spin-2 field is assumed to be represented by a spacetime (world) vector field
assuming values in the Lie algebra of the translation group. The flat-space
theory naturally emerges in the Fierz formalism and is found to be equivalent
to the usual metric-based theory. However, the gravitationally coupled theory,
with gravitation itself described by teleparallel gravity, is shown not to
present the consistency problems of the spin-2 theory constructed on the basis
of general relativity.Comment: 16 pages, no figures. V2: Presentation changes, including addition of
a new sub-section, aiming at clarifying the text; version accepted for
publication in Class. Quantum Grav
Diluted planar ferromagnets: nonlinear excitations on a non-simply connected manifold
We study the behavior of magnetic vortices on a two-dimensional support
manifold being not simply connected. It is done by considering the continuum
approach of the XY-model on a plane with two disks removed from it. We argue
that an effective attractive interaction between the two disks may exist due to
the presence of a vortex. The results can be applied to diluted planar
ferromagnets with easy-plane anisotropy, where the disks can be seen as
nonmagnetic impurities. Simulations are also used to test the predictions of
the continuum limit.Comment: 5 pages, 6 figure
Earning the Keys to the Kingdom: Students’ Language Awareness, Identity and Representations of English-Speaking Others
The present linguistic reality involves finding ways of communication in the globalized environment, where people move all around the world in order to find work, learn, or share experiences. One issue arising from English language teaching is that it has mainly overlooked teaching culture across the curriculum, thus allowing the increase of negative attitudes and stereotypes.
This paper is set out to determine to what extent English language teaching (ELT) materials demonstrate the traits of the English-speaking Other, it what ways children are accessing the target ‘Kingdom’, and which are the best teaching strategies to provide them with the keys to the target world. Anchoring our perspective in CLIL and the 4 Cs, this study looks at ways of developing cutting-edge syllabi to develop intercultural awareness and preventing stereotypes. Findings from the application of the syllabi and resulting from an analysis of the cultural content of two internationally distributed ELT textbooks are reported. The present research put in evidence that cultural aspects are practically absent from the analyzed textbooks, thus lacking a key dimension in English Language Teaching and Education. Therefore, some recommendations for future textbook writers and EFL classroom practice are suggested
Analysis of cyanotoxins in water samples: method validation and application to monitoring and assessment of water quality
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