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Nomenclatura Unesco > (33) Ciencias Tecnológicas

Mostrando recursos 21 - 40 de 2,178

21. Structural anisotropy by static compaction
Induced anisotropy can be applied to soils in different ways, in natural or in laboratory conditions. The aim of this work was to study the effect of load compaction in a specific remoulded residual soil from granite, especially in terms of its effect on the critical state behaviour and isotropic compression. For that purpose, isotropic compression tests and triaxial compression tests were performed up to high pressures in specimens compacted in two different ways: by moist tamping or by multi-layer heavy static compaction imposed by a load frame. The results indicated that isotropic consolidation to high pressures can minimize the...

22. Stiffness and strength governing the static liquefaction of tailings - Fernando Schnaid; Jucélia Bedin; António Joaquim Pereira Viana Da Fonseca; Leandro Costa-Filho
In this study, the behavior of gold tailings is evaluated by a series of drained and undrained triaxial tests carried out in compression and extension and sheared under monotonic loading, allowing the critical state line (CSL) to be established. The observed highly nonlinear shape of the CSL under undrained loading was used to investigate the mechanics of tailings that were dictated by state transitions captured by both the state parameter and the measured values of shear-wave velocities. The definition of a zone is where state conditions may develop strain hardening (stable zone) or strain softening with high compressibility while maintaining...

23. Influence of grain size and mineralogy on the porosity/cement ratio - Sara Silva; António Joaquim Pereira Viana Da Fonseca; Nilo Consoli; Márcio Floss; Nuno Cristelo
The porosity/cement ratio is defined as the ratio between porosity and the volumetric cement content (volume of cement over the total volume) and it is often adjusted by an exponent (#958;) to the volumetric cement content (n/Civ#958;) which seems to depend on the type of soil. This ratio is very useful to analyse artificially cemented soils and it depends on easily calculated moulding properties. Although there are already some results regarding the correlation of this ratio with the mechanical behaviour of different soils, a theory explaining the variation of its exponent (#958;) has yet to be established. In thispaper the...

24. Indexation of dynamic and static geomechanical properties of a cemented aggregate for transportation engineering - António Joaquim Pereira Viana Da Fonseca; Miguel Amaral; Antonio Fabrizio Panico; Sara Silva
This paper presents an extensive experimental program aiming to the mechanical characterisation of an aggregate stabilised with cement. This geomaterial is the product of a quarry of limestone located in north region of Portugal. The aggregate is often used in current subgrading of infrastructures for transportation, namely in railway lines. Complementary, aggregatecement admixtures are used for transition zones, such as in between deformable embankments on soft grounds lining on rigid structures, such as bridgesfounded on deep foundations, such as piles or similar. The demand for smooth transition between diverse stiffness zones implies an optimization of the composition of the enriched...

25. Fatigue cyclic tests on artificially cemented soil
Artificially cemented soils are frequently used in the infrastructural layers of road or railway platforms but the durability of these structures is often questioned when subjected to cyclic loads. In order to evaluate the fatigue behavior, this paper presents long cyclic triaxial tests over several soil cement mixtures using a very well graded silty sand and Portland cement. In undrained cemented tests, pore pressure decreased as a sign of plastic degradation, resulting that the effective stresses rose during the tests. For that reason, the resilient moduli were normalized to the effective stress, revealing a clear drop on the normalized resilient...

26. Isotropic yielding of unsaturated cemented silty sand - Marcos Arroyo; Miguel Amaral; Enrique Romero; António Joaquim Pereira Viana Da Fonseca
Unsaturated cemented soils are frequent both as designed materials and as naturally occurring layers. Both desiccation and cementation act separately as hardening mechanisms, but it is not clear how exactly their effects combine. Do they enhance one another? Are they mutually reinforcing? This study presents results from an experimental campaign aimed at answering these questions. Five different mixtures of soil (a granite saprolite) and cement (with cement contents in the range 0% to 7% on a dry weight basis) are tested in isotropic compression at four different water content levels. Initial void ratio is also controlled, using two initial compaction...

27. Numerical Methodology to Minimize Resolution and Sensitivity Effects in P-Wave Measurements
Artificially cemented soils are frequently used in the infrastructural layers of road or railway platforms but the durability of these structures is often questioned when subjected to cyclic loads. In order to evaluate the fatigue behavior, this paper presents long cyclic triaxial tests over several soil cement mixtures using a very well graded silty sand and Portland cement. In undrained cemented tests, pore pressure decreased as a sign of plastic degradation, resulting that the effective stresses rose during the tests. For that reason, the resilient moduli were normalized to the effective stress, revealing a clear drop on the normalized resilient...

28. Parameters controlling stiffness and strength of artificially cemented soils - N. C. Consoli; A. Viana da Fonseca; Rios Silva, S.; R. C. Cruz; A. Fonini
The treatment of soils with cement is an attractive technique when a project requires improvement of the local soil for the construction of subgrades for rail tracks, for roads, as a support layer for shallow foundations, and to prevent sand liquefaction. This paper advances understanding of the key parameters for the control of strength and stiffness of cemented soils by testing two soils with different gradings and quantifying the influence of porosity/cement ratio on both initial shear modulus (G0) and unconfined compressive strength (qu). It is shown that the porosity/cement ratio is an appropriate parameter toassess both the initial stiffness...

29. On the Training of Artificial Neural Networks with Radial Basis Function Using Optimum-Path Forest Clustering - Gustavo H. Rosa; Kelton A. P. Costa; Leandro A. Passos Júnior; João P. Papa; Alexandre X. Falcão; João Manuel R. S. Tavares
In this paper, we show how to improve the Radial Basis Function Neural Networks effectiveness by using the Optimum-Path Forest clustering algorithm, since it computes the number of clusters on-the-fly, which can be very interesting for finding the Gaussians that cover the feature space. Some commonly used approaches for this task, such as the well known k-means, require the number of classes/clusters previous its performance. Although the number of classes is known in supervised applications, the real number of clusters is extremely hard to figure out, since one class may be represented by more than one cluster. Experiments over 9...

30. Toward hemodynamic diagnosis of carotid artery stenosis based on ultrasound image data and computational modeling - Luísa C. Sousa; Catarina F. Castro; Carlos C. António; André Miguel F. Santos; Rosa Maria dos Santos; Pedro Miguel A. C. Castro; Elsa Azevedo; João Manuel R. S. Tavares
The ability of using non-expensive ultrasound (US) image data together with computer fluid simulation to access various severities of carotid stenosis was inquired in this study. Subject- specific hemodynamic conditions were simulated using a developed finite element solver. Individual structured meshing of the common carotid artery (CCA) bifurcation was built from segmented longitudinal and cross-sectional US images; imposed boundary velocities were based on Doppler US measurements. Simulated hemodynamic parameters such as velocities, wall shear stress (WSS) and derived descriptors were able to predict disturbed flow conditions which play an important role in the development of local atherosclerotic plaques. Hemodynamic features...

31. Desarrollo local basado en la articulación del sector de la ciencia y tecnología y las PyMIs: las estrategias de parques tecnológicos en Argentina - Del Giorgio Solfa, Federico
Las PyMIs que se hallan fuera de una red productiva o alejadas de las organizaciones (estatales; ONGs) del Sistema Nacional de Innovación, se encuentran en una situación desventajosa respecto de las grandes empresas o de otras industrias que están integradas a un cluster productivo. Una de las instituciones consideradas para este tipo de estrategia, es el parque tecnológico. Para que el modelo funcione según este enfoque, es fundamental valorizar las capacidades endógenas del tejido productivo y los elementos de la mesoeconomía vinculados al capital social y a la fortaleza de las instituciones. Este trabajo de tesis doctoral, retomará el debate...

32. La investigación en España: realidad, problemas y esperanzas - Fernández Rañada, Antonio
El profesor Fernández-Rañada comenzó su disertación con un resumen selecto de los hechos más significativo de la historia de la ciencia en España, desde el siglo XVI al XX. Explicó los orígenes de situaciones y tópicos frecuentes relativos a la ciencia en España. Comenta que, lamentablemente, ha predominado hasta nuestro siglo la concepción utilitarista de la investigación que se vienen arrastrando desde el reinado de Felipe II. En la denominada "transición política" que tuvo lugar hace a finales de la década de los años setenta se plantearon varios problemas básicos para la modernización de nuestra nación como fueron: � La denominada "cuestión social". � La cuestión de la forma del...

33. Definição de Critérios de Salvaguarda e Valorização da Fábrica de Cerâmica das Devesas - Mariana Silva; Joaquim Teixeira; Luís Ferreira
The present article is extracted from an ongoing investigation that aims to define an architectural intervention strategy for the Devesas#8217; Ceramic Factory, leading to its protection and enhancement. The proposed methodology consists on the development of a study focused in four main lines: i) characterization of the it preservation status of the existing, including its historical context; ii) discussion of the definition criteria of the value elements existing in the Portuguese legislation and its application in the context of industrial heritage and in particular to the case study, including the identification of elements of tangible and intangible value; iii) analysis...

34. Flexibilidade do Design como resposta à variaçãode condicionantes tecnológicas durante o projecto - CAFAP; FGA
Pretende-se realçar a importância da capacidade de adaptação dos conceitosformais propostos pelo Design, potenciando a competitividade das soluçõesimpostas pelos condicionalismos técnicos (características dos materiais eprocessos de fabrico), no contexto de projectos de desenvolvimento deproduto. Esta característica, implícita nos projectos onde o Design intervém,permite obter soluções mais adequadas às necessidades dos utilizadores,quer do ponto de vista do produto acabado quer do ponto de vista doprocesso produtivo (melhor relação custo-utilidade). No presente artigo sãoapresentados diferentes conceitos de design para uma carroçaria emmaterial compósito, do tipo sanduíche, de um autocarro que circulará emserviço de shuttle, no Polo Universitário da Asprela (Porto), no âmbito...

35. Utilização de XML numa plataforma de Data Mining distribuído - Ruy Ramos; Carlos Gonçalves; Rui Camacho
O processo de Extracção de Conhecimento em Bases de Dados(Knowledge Discovery in Databases - KDD) envolve a análise deextensas bases de dados e recurso a complexos algoritmos de análise dedados (Data Mining). Este processo requer, geralmente, recursos computacionaisdedicados e de elevado custo o que reduz signicativamenteo número de utilizadores capazes de efectuar tais análises. Neste artigoapresentamos uma arquitectura baseada em computadores pessoais distribuídos numa rede de computadores de uma organização e que permitea realização de tarefas de KDD sem recursos computacionais dedicadose sem perturbar o funcionamento da organização. A arquitectura é denominadaHarvard - HARVesting Architecture of idle machines foRData mining....

36. Proceedings CLME 2008 - 5º Congresso Luso-Moçambicano de Engenharia, IICEM - 2º Congresso de Engenharia de Moçambique.

37. An Evolutionary Particle Swarm Optimization, EPSO, Approach to Optimize the Operation of Hydro Stations in Market Environment - André Pacheco; João Tomé Saraiva
This paper describes the application of Evolutionary Particle Swarm Optimization, EPSO, to the optimization of the short term operation of hydro stations in market environment. The maximization of the revenues of hydro stations, namely pumping stations, is gaining increasing attention by generation companies. However, this is typically a complex problem given the non linear relation between the power, the flow and the head, the temporal coupling between stations in cascade and the increasing number of pumping stations. The EPSO based algorithm displayed a very good performance in terms of the quality of the final operation plan as well as regarding...

38. RobTech - Task 1.3 - Survey in Architectural Design and Construction - José Pedro Sousa; João Pedro Xavier; Rui Póvoas
This report is part of the research project quot;Robotic Technologies for a Non-Standard Design and Construction in Architecturequot;, supported by the FCT - Fundação para a Ciência e a Tecnologia. In the scope of the introductory activities of the project (T1.1, T.1.2 and T1.3), the present task surveys architectural projects showing pertinent issues regarding material, formal (geometry) or construction. These projects has the potential to inspire interesting challenges to be tackled by means of robotic fabrication technologies.

39. Hybrid Simulation-Optimization Methods: A Taxonomy and Discussion - Gonçalo Figueira; Bernardo Almada Lobo
The possibilities of combining simulation and optimization are vast and the appropriate design highly depends on the problem characteristics. Therefore, it is very important to have a good overview of the different approaches. The taxonomies and classifications proposed in the literature do not cover the complete range of methods and overlook some important criteria. We provide a taxonomy that aims at giving an overview of the full spectrum of current simulation-optimization approaches. Our study may guide researchers who want to use one of the existing methods, give insights into the cross-fertilization of the ideas applied in those methods and create...

40. Improving the efficiency of ILP systems using an Incremental Language Level Search - Rui Camacho
We propose and evaluate a technique to improve the eciency of an ILP system. The technique avoids the generation of useless hypotheses.It denes a language bias coupled with a search strategy and is called Incremental Language Level Search (ILLS). The techniques havebeen encoded in the ILP system IndLog. The proposal leads to substantial eciency improvements in a set of ILP datasets referenced on theliterature.

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