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UPCommons, el portal d'accés obert al coneixement de la UPC, està format pel conjunt de dipòsits institucionals oberts de la UPC i té com a missió garantir la preservació de la producció docent i de recerca cientificotècnica de la Universitat, maximitzant-ne la visibilitat i, conseqüentment, incrementant-ne l’impacte en la docència i la recerca de tot el món.
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Memòria: curs 2007-2008. Facultat de Matemàtiques i Estadística (FME)

dl., 02/05/2018 - 13:36
Memòria: curs 2007-2008. Facultat de Matemàtiques i Estadística (FME)
Categories: Novetats

L'FME en xifres: curs 2006-2007. Facultat de Matemàtiques i Estadística (FME)

dl., 02/05/2018 - 13:35
L'FME en xifres: curs 2006-2007. Facultat de Matemàtiques i Estadística (FME)
Categories: Novetats

Memòria, dades acadèmiques i de gestió: curs 2005-2006. Facultat de Matemàtiques i Estadística (FME)

dl., 02/05/2018 - 13:32
Memòria, dades acadèmiques i de gestió: curs 2005-2006. Facultat de Matemàtiques i Estadística (FME)
Categories: Novetats

Memòria: curs 2004-2005. Facultat de Matemàtiques i Estadística (FME)

dl., 02/05/2018 - 13:29
Memòria: curs 2004-2005. Facultat de Matemàtiques i Estadística (FME)
Categories: Novetats

Memòria: curs 2003-2004. Facultat de Matemàtiques i Estadística (FME)

dl., 02/05/2018 - 13:28
Memòria: curs 2003-2004. Facultat de Matemàtiques i Estadística (FME)
Categories: Novetats

Guidelines for seismic vulnerability reduction in the urban environment: LESSLOSS report no. 2007/04

dv., 02/02/2018 - 21:11
Guidelines for seismic vulnerability reduction in the urban environment: LESSLOSS report no. 2007/04 Oller Martínez, Sergio Horacio; Barbat Barbat, Horia Alejandro; Mata Almonacid, Pablo; Martínez García, Javier
Categories: Novetats

Analysis of the discharge capacity of radial gated-spillways using CFD and ANN: Oliana Dam case study

dv., 02/02/2018 - 21:05
Analysis of the discharge capacity of radial gated-spillways using CFD and ANN: Oliana Dam case study Salazar González, Fernando; Morán Moya, Rafael; Rossi, Riccardo; Oñate Ibáñez de Navarra, Eugenio The paper focuses on the analysis of radial-gated spillways, which is carried out by the solution of a numerical model based on the finite element method (FEM). The Oliana Dam is considered as a case study and the discharge capacity is predicted both by the application of a level-set-based free-surface solver and by the use of traditional empirical formulations. The results of the analysis are then used for training an artificial neural network to allow real-time predictions of the discharge in any situation of energy head and gate opening within the operation range of the reservoir. The comparison of the results obtained with the different methods shows that numerical models such as the FEM can be useful as a predictive tool for the analysis of the hydraulic performance of radial-gated spillways.
Categories: Novetats

A compressible Lagrangian framework for the simulation of the underwater implosion of large air bubbles

dv., 02/02/2018 - 21:02
A compressible Lagrangian framework for the simulation of the underwater implosion of large air bubbles Kamran, Kamran; Rossi, Riccardo; Oñate Ibáñez de Navarra, Eugenio; Idelsohn Barg, Sergio Rodolfo A fully Lagrangian compressible numerical framework for the simulation of underwater implosion of a large air bubble is presented. Both air and water are considered compressible and the equations for the Lagrangian shock hydrodynamics are stabilized via a variationally consistent multiscale method. A nodally perfect matched definition of the interface is used and then the kinetic variables, pressure and density, are duplicated at the interface level. An adaptive mesh generation procedure, which respects the interface connectivities, is applied to provide enough refinement at the interface level. This framework is verified by several benchmarks which evaluate the behavior of the numerical scheme for severe compression and expansion cases. This model is then used to simulate the underwater implosion of a large cylindrical bubble, with a size in the order of cm. We observe that the conditions within the bubble are nearly uniform until the converging pressure wave is strong enough to create very large pressures near the center of the bubble. These bubble dynamics occur on very small spatial (0.3 mm), and time (0.1 ms) scales. During the final stage of the collapse Rayleigh–Taylor instabilities appear at the interface and then disappear when the rebounce starts. At the end of the rebounce phase the bubble radius reaches 50% of its initial value and the bubble recover its circular shape. It is when the second collapse starts, with higher mode shape instabilities excited at the bubble interface, that leads to the rupture of the bubble. Several graphs are presented and the pressure pulse detected in the water is compared by experiment.
Categories: Novetats

A fast and accurate method to solve the incompressible Navier-Stokes equations

dv., 02/02/2018 - 20:57
A fast and accurate method to solve the incompressible Navier-Stokes equations Idelsohn Barg, Sergio Rodolfo; Nigro, Norberto; Gimenez, Juan; Rossi, Riccardo; Martí, Julio Marcelo Purpose: The purpose of this paper is to highlight the possibilities of a novel Lagrangian formulation in dealing with the solution of the incompressible Navier-Stokes equations with very large time steps. Design/methodology/approach: The design of the paper is based on introducing the origin of this novel numerical method, originally inspired on the Particle Finite Element Method (PFEM), summarizing the previously published theory in its moving mesh version. Afterwards its extension to fixed mesh version is introduced, showing some details about the implementation. Findings: The authors have found that even though this method was originally designed to deal with heterogeneous or free-surface flows, it can be competitive with Eulerian alternatives, even in their range of optimal application in terms of accuracy, with an interesting robustness allowing to use large time steps in a stable way. Originality/value: With this objective in mind, the authors have chosen a number of benchmark examples and have proved that the proposed algorithm provides results which compare favourably, both in terms of solution time and accuracy achieved, with alternative approaches, implemented in in-house and commercial codes.
Categories: Novetats

A contact algorithm for shell problems via Delaunay-based meshing of the contact domain

dv., 02/02/2018 - 20:52
A contact algorithm for shell problems via Delaunay-based meshing of the contact domain Kamran, Kamran; Rossi, Riccardo; Oñate Ibáñez de Navarra, Eugenio The simulation of the contact within shells, with all of its different facets, represents still an open challenge in Computational Mechanics. Despite the effort spent in the development of techniques for the simulation of general contact problems, an all-seasons algorithm applicable to complex shell contact problems is yet to be developed. This work focuses on the solution of the contact between thin shells by using a technique derived from the particle finite element method together with a rotation-free shell triangle. The key concept is to define a discretization of the contact domain (CD) by constructing a finite element mesh of four-noded tetrahedra that describes the potential contact volume. The problem is completed by using an assumed-strain approach to define an elastic contact strain over the CD.
Categories: Novetats

Collapse of the Pilcomayo River

dv., 02/02/2018 - 20:44
Collapse of the Pilcomayo River Martín Vide, Juan Pedro; Amarilla, Mabel; Zárate, Fernando José The Pilcomayo River flows south-eastwards from the Bolivian Andes across the Chaco Plains, setting the border between Argentina and Paraguay. It flows down along 1000km, in principle, to finally join the Paraguay River. It spills over the plains during the rainy season from January to March. The sediment load of the Pilcomayo is one of the largest in the world: 140milliontons per year, which is mostly wash load from the upland Andes. The mean concentration of suspended sediment is 15g/l. The maximum recorded concentration is as high as 60g/l. The river has built a large fan covering a surface of 210,000km2, with many abandoned channels. Today, it is a river prone to avulsion, raising border disputes between the two lowland countries, Argentina and Paraguay. Moreover, the very special feature of Pilcomayo River is that it does not actually flow into the Paraguay River. Very far upstream of the mouth in the Paraguay the channel blocks itself with sediment and wood debris forcing water and sediment to spread across the plains. Moreover, the point of blockage has moved hundreds of kilometers upstream throughout the 20th century. Many environmental issues arise because of this collapse (channel discontinuity), not the least of them is the migration of fish. The future of the river concerns Bolivia and the two lowland countries. © 2012 Elsevier B.V.
Categories: Novetats

Is it better to use gate opening as control variable than discharge to control irrigation canals?

dv., 02/02/2018 - 20:40
Is it better to use gate opening as control variable than discharge to control irrigation canals? Horváth, Klaudia; Galvis Restrepo, Eduard; Gómez Valentín, Manuel; Rodellar Benedé, José Centralized model predictive controllers are common in water systems. The control action variable can be the discharge, and the subsystems (canal pools) are modeled separately. This paper focuses on short canal pools where the interactions are stronger between canal pools. Could this procedure be better if gate openings were used as control action variables and the interconnected system were modeled for the controller? Model predictive controllers (MPCs) were developed using the discharge and the gate opening as control action variable and tested experimentally using the laboratory canal of the Technical University of Catalonia. It was found that for centralized MPCs for short canal pools, the use of gate opening as control action variable is more beneficial than discharge. Another additional advantage is that in this way it is possible to put constraints on the gate opening and the change of gate opening, which are important to the limitations of the physical system. (C) 2014 American Society of Civil Engineers.
Categories: Novetats

Environmental assessment of earth retaining wall structures

dv., 02/02/2018 - 20:34
Environmental assessment of earth retaining wall structures Puig Damians, Ivan; Bathurst, Richard; García Adroguer, Eduard; Josa Garcia-Tornel, Alejandro; Lloret Morancho, Antonio Life cycle assessment (LCA) is recognised as a powerful technique to determine the environmental impact component of sustainability assessments of structures in civil engineering projects at the time of design. This paper explains the principal parts and stages in an LCA methodology and demonstrates the approach using the examples of two conventional retaining wall types (gravity and cantilever type) and two mechanically stabilised earth (MSE) wall solutions using steel and polymeric soil reinforcement. The analyses include structures built to four different heights. The LCA methodology was able to quantitatively distinguish between the component environmental impacts of different wall solutions and thus provide a practical numerical score-based tool for designers to choose between candidate solutions. The MSE wall solutions resulted in lower environmental impacts than gravity and cantilever wall solutions as measured by global warming potential, cumulative energy demand, six major midpoint environmental indicator categories, three endpoint damage categories and in terms of overall endpoint scores. The target audiences for this paper are geotechnical and structural engineers engaged in the design of earth retaining wall structures but are less familiar with recent developments in LCA and how LCA can be linked to the design of these systems.
Categories: Novetats

La ciutat efímera de la nit

dv., 02/02/2018 - 20:13
La ciutat efímera de la nit Puigvert i Flotats, Mima Ponència presentada a: Session 7: Redes sociofísicas en el planeamiento urbano / Urban social and physical networks
Categories: Novetats

Substrate melting during laser heating of nanoscale metal films

dv., 02/02/2018 - 19:37
Substrate melting during laser heating of nanoscale metal films Font Martinez, Francesc We investigate heat transfer mechanisms relevant to metal films of nanoscale thickness deposited on a silicon (Si) substrate coated by a silicon oxide (SiO2) layer and exposed to laser irradiation. Such a setup is commonly used in the experiments exploring self and directed assembly of metal films that melt when irradiated by laser and then evolve on time scale measured in nanoseconds. We show that in a common experimental setting, not only the metal but also the SiO2 layer may melt. Our study of the effect of the laser parameters, including energy density and pulse duration, shows that melting of the substrate occurs on spatial and temporal scales that are of experimental relevance. Furthermore, we discuss how the thicknesses of metal and of the substrate itself influence the maximum depth and liquid lifetime of the melted SiO2 layer. In particular, we find that there is a minimum thickness of SiO2 layer for whichthis layer melts and furthermore, the melting occurs only for metal films of thickness in a specified range. In the experiments, substrate melting is of practical importance since it may significantly modify the evo-lution of the deposited nanoscale metal films or other geometries on nanoscale.
Categories: Novetats

La mirada crítica. Conversaciones con Germán Téllez

dj., 02/01/2018 - 14:33
La mirada crítica. Conversaciones con Germán Téllez Mayorga Cárdenas, Miguel Yuri; Fontana, Maria Pia; Roa, Margarita
Categories: Novetats

Mechanochemical pattern formation in simple models of active viscoelastic fluids and solids

dj., 02/01/2018 - 14:19
Mechanochemical pattern formation in simple models of active viscoelastic fluids and solids Alonso Muñoz, Sergio; Radszuweit, Markus; Engel, Harald; Baer, Markus The cytoskeleton of the organism Physarum polycephalum is a prominent example of a complex active viscoelastic material wherein stresses induce flows along the organism as a result of the action of molecular motors and their regulation by calcium ions. Experiments in Physarum polycephalum have revealed a rich variety of mechanochemical patterns including standing, traveling and rotating waves that arise from instabilities of spatially homogeneous states without gradients in stresses and resulting flows. Herein, we investigate simple models where an active stress induced by molecular motors is coupled to a model describing the passive viscoelastic properties of the cellular material. Specifically, two models for viscoelastic fluids (Maxwell and Jeffrey model) and two models for viscoelastic solids (Kelvin–Voigt and Standard model) are investigated. Our focus is on the analysis of the conditions that cause destabilization of spatially homogeneous states and the related onset of mechano-chemical waves and patterns. We carry out linear stability analyses and numerical simulations in one spatial dimension for different models. In general, sufficiently strong activity leads to waves and patterns. The primary instability is stationary for all active fluids considered, whereas all active solids have an oscillatory primary instability. All instabilities found are of long-wavelength nature reflecting the conservation of the total calcium concentration in the models studied.
Categories: Novetats

Elaboración de un programa de control del coste de construcción de utillajes en matricería y metalurgia

dj., 02/01/2018 - 14:12
Elaboración de un programa de control del coste de construcción de utillajes en matricería y metalurgia Fernández Cruz, Marc La exactitud en el desarrollo de ofertas de troqueles en matriceria tiene un efecto directo sobre las ganancias / perdidas tanto del fabricante cómo del comprador de las matrices. Para poder evaluar el precio de los troqueles es necesario el uso de la experiencia técnica con un éxito variable. Cuando los proyectos se basan en otros ya realizados la exactitud sobre el coste real puede ser del 30% [1] si no se usan programas de apoyo. Por la experiencia empresarial de Gestamp se tiene muy presente que los precios ofertados a cliente pueden diferir mucho de lo finalmente pagado al matricero que construye la matriz, además que en otros muchos casos los problemas intangibles, mantenimientos, no calidad de las piezas, complicaciones en los procesos productivos, etc. Pueden hacer retrasar la homologación de las piezas, con el consiguiente retraso en el pago del troquel por parte de cliente. Debido al sistema cada vez más competitivo en el sector automovilístico, las firmas cada día están más auditadas y exigen mejor calidad y precios ajustados a sus proveedores, cómo Gestamp, los cuales a su vez se ven obligados a pedir estas demandas recíprocamente a las empresas que fabrican los medios de producción. La dualidad de competir con las otras empresas proveedoras de piezas en la automoción, con cotizaciones cada vez más ajustadas y a la vez poder cubrir los costes de la forma más optimizada posible es el problemática que se le presenta a la empresa [Figura 1]. Es básico pues, intentar reducir la incertidumbre en el cálculo de las cotizaciones de los troqueles mediante el uso de programas algorítmicos que tengan en cuenta materiales, tiempos de fabricación, puestas a punto según las características determinadas por el proceso de fabricación de las piezas metálicas: tipo de proceso, tonelaje, número de operaciones. Detalles sobre la problemática, análisis sobre los programas actualmente en uso y propuestas de mejora sobre el cálculo de los precios de los troqueles para fabricación de piezas metálicas serán estudiadas en este trabajo.
Categories: Novetats

Using static connections to improve elastic optical networks performance

dj., 02/01/2018 - 14:08
Using static connections to improve elastic optical networks performance Comellas Colomé, Jaume; Vicario, L.; Junyent Giralt, Gabriel Network resources are poorly used in Elastic Optical Networks under dynamic traffic conditions. A hybrid scheme where some resources are statically allocated and the remaining ones are devoted to dynamic traffic, is proposed and evaluated.
Categories: Novetats

Estalvi de recursos en el cultiu de blat de moro mitjançant l'ús d'imatges obtingudes amb UAV

dj., 02/01/2018 - 14:06
Estalvi de recursos en el cultiu de blat de moro mitjançant l'ús d'imatges obtingudes amb UAV Prieto Márquez, Kelly El present treball té com a objectiu estudiar la problemàtica del l’ús excessiu dels recursos en l’activitat agrícola. Basant-se principalment en el recurs hídric i l’adob nitrogenat. D’altra banda, s’avalua la viabilitat de l’ús de tècniques innovadores per a la solució d’aquesta problemàtica. Es pretén mostrar la utilitat d’imatges multiespectrals obtingudes amb UAS / RPAS, (Sistemes aeris no pilotats/ sistemes aeris pilotats remotament) per al control d’un cultiu extensiu, posant en pràctica l’anomenada agricultura de precisió. Per a aquesta avaluació s’escull un cultiu de blat de moro. En aquest projecte s’estudiarà la viabilitat d’utilitzar la tecnologia innovadora esmentada per a millorar l’eficiència del cultiu, garantint el correcte ús i l’òptima conservació del recurs hídric i de l’adob nitrogenat. D’altra banda, s’estudiarà la relació entre ambdós recursos. A partir de les imatges obtingudes a partir d’una càmera multiespectral instal·lada al drone (UAS / RPAS), es pretén calcular els índexs de vegetació (NDVI, GNDVI, NDRE, SAVI), per tal d’analitzar la variabilitat de la collita experimental. A més, s’estudiarà la sensibilitat d’aquests índexs per tal d’avaluar l’addició de diferents quantitats d’adob nitrogenat al cultiu.
Categories: Novetats

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