Encontrado(s) 2241593 resultado(s)
Encontrada(s) 224160 página(s)
Encontrada(s) 224160 página(s)
- Noguer Figueras, Albert
Actualmente, debido a la contaminación generada por los motores diesel están surgiendo nuevas restricciones medioambientales en el sector naval. El uso del gasoil está disminuyendo a causa de las emisiones tóxicas que genera su combustión. Por lo tanto, es conveniente investigar sobre nuevos sistemas de propulsión menos contaminantes. Recientemente, la principal apuesta de los buques mercantes para lograr estos requisitos medioambientales es el uso del GNL como combustible. Por esta razón, la demanda de barcos que incorporan motores de gas está aumentando muy rápidamente. Aunque en ocasiones, las navieras deciden modificar ciertas partes del motor de diesel y otros sistemas del barco para que pase a consumir gas natural. El proyecto se estructura en 6 capítulos que tienen como objetivo mostrar una posible solución a este problema que tiene el sector naval. En primer lugar, se ha realizado una introducción sobre el GNL como combustible utilizado en los buques mercantes. El segundo capítulo introduce las diferentes tipologías de remolcadores que encontramos según la ubicación del propulsor y tipo de hélice. Al mismo tiempo, dependiendo de las operaciones y funciones encontramos también distintos tipos de buques. En el tercer capítulo se describe el remolcador escogido y las funciones que realiza. Además, incluye las características de los dos motores principales fabricados por Rolls-Royce y sus respectivas especificaciones del sistema de propulsión Aquamaster. En cuarto lugar, encontramos las características del motor de gas. También se incluye una comparativa entre el motor de gas y el de diesel. Para diseñar la nueva sala de máquinas esta comparativa será necesaria para saber qué elementos modificar. En el siguiente capítulo, se especifica los elementos y sistemas que deberán ser modificados con la finalidad de que el remolcador pase a consumir gas natural. Finalmente, en el último apartado se resume el proyecto presentando y las conclusiones obtenidas teniendo en cuenta el contenido del cuerpo del trabajo.
- Gómez Val, Ricardo
- Ramírez-Casas, J.
- Navarro Ezquerra, Antonia
In Catalonia during 19th century there was a process of industrialization following the Llobregat river. One of the traditional materials used historically in building had been lime mortar. Natural cement began to be used from the middle of the 19th century in order to improve quality and characteristics of mortar elements. Barcelona experimented a huge urban expansion during the second half of 19th century. In order to do new buildings it was necessary to develop new techniques and materials. Antoni Gaudi finished his studies in 1876 and he began working in Barcelona since then. He had learned from traditional materials and techniques at his father workshop in his hometown. He also learned from new technologies at School of Architecture in Barcelona. Güell family were a wealthy family who owned different industries around Catalonia, following Llobregat river. They were the founders of a Portland factory in Spain, at Castellar de N’Hug in 1904. Before that date some Portland cement shipments had arrived and had been used in Barcelona’s buildings imported from France. They asked to a young architect, Antoni Gaudi to build their family house in the centre of Barcelona, near the harbour. Palau Güell built from 1886 to 1890 was the first important project done by Antoni Gaudi. In this building, Gaudi was able of studying and experimenting different technologies and materials that he would later use in other buildings as Mila’s House or Sagrada Familia. Palau Güell is built during a period of confluence between traditional and industrial techniques. There are some traditional techniques as paintings or plaster coatings with other more industrialised as the use of pavements and finishing which they answer to a will of seriation and standardizing. There is a neat debate between technique and art and the relationship between production and design. Gaudi was focused in order to introduce new technologies to buildings and to enhance traditional ones. In Palau Güell different mortars are used as binder materials and as fastening material for façades and pavements. This different way of using mortars lead us to do research in some areas of Palau Güell obtaining interesting results in the use of natural cements. This lab research has allowed us to understand the development of mortars by Antoni Gaudi. This research proves how Gaudi was an architect related to traditional techniques but looking to its development through research and experimentation., Peer Reviewed
- Ribas Vila, Immaculada
- Companys Pascual, Ramón
- Tort-Martorell Llabrés, Xavier
This paper proposes an Iterated Local Search (ILS) procedure and an Iterated Greedy (IG) algorithm, which are both combined with a variable neighbourhood search (VNS), for dealing with the flow shop problem with blocking, in order to minimize the total tardiness of jobs. The structure of both algorithms is very similar, but they differ in the way that the search is diversified in the space of solutions. In the ILS algorithm, the diversification is performed by a perturbation mechanism that takes into account some characteristics of the problem; whereas the perturbation in the IG is performed through a deconstruction and construction phase proposed in the literature that has been proven to be very effective in dealing also with the makespan criterion. Moreover, the algorithms have been tested with three initial solution procedures. The computation of these algorithms when evaluated against an algorithm from the literature has shown their good performance.
Ver en: http://hdl.handle.net/2117/17098
5 mitos sobre el hábitat popular en tela de juicio: un estudio sobre barrios populares en Argentina, 5 myths on social habitat in question: a study on informal neighbourhoods in Argentina
- Lescano, Patricia
- Piasek, Gonzalo
- Gandino, Rafaela
La presente ponencia discute algunas cuestiones vinculadas al mejoramiento de vivienda y hábitat en barrios populares, en el marco del proceso de reurbanización que está enfrentando la Argentina. La misma se pregunta si ciertas creencias comunes en torno a la vivienda popular y los barrios populares - como ser la densidad, la cantidad de hogares, el material constructivo, la posibilidad de acceso a crédito, la inversión en mejoramiento - se dan de la forma que creemos “en el sentido común”, a partir del análisis de una encuesta realizada en 8 barrios con miras a problematizar algunas de estas cuestiones. En una palabra se trata de un intento por abrir el debate en torno de la reurbanización de barrios populares en Argentina y la región., This paper discusses some new ideas related to habitat and housing improvement in low-income neighborhoods, within the framework of the re-urbanization process that Argentina is currently facing. It questions whether certain common sense beliefs in regards to low-income housing and neighborhoods - such as density, quantity of homes, construction materials, credit access, possibility to invest in housing improvement - take the actual form that these common beliefs entail, by analyzing the results of a survey held in eight (8) neighborhoods in cities of different provinces in Argentina. This work is, in a few words, an attempt to not close but open the debate on re-urbanization of low-income neighborhoods in Argentina and the region for further discussion., Peer Reviewed
- Reddi, D.
- Keralavarma, S. M.
In this paper, an isotropic porous metal plasticity model accounting for both void growth by diﬀuse plastic deformation and void ‘coalescence’ by localization of plastic ﬂow in the inter-void ligaments is presented. Predictions for the eﬀective stress-strain response, evolution of damage and the strains to failure are obtained by integrating the model numerically under triaxial proportional loading conditions. The model predictions are compared with results from micromechanical ﬁnite element simulations of the average response of voided unit cells under similar loading conditions. It is shown that the model predictions for the failure strains as a function of the loading path are in good qualitative agreement with the results of the cell model simulations.
- Aguilar Plazaola, José Agustín
- Husar, Attila Peter
Proton Exchange Membrane Fuel Cells (PEMFC) are a promising technology for substitution of hydrocarbon powerdrives and battery based electrical supply systems. However, below-required durability is still an important factor that hinders its widespread use, thus, novel operating approaches are required to surpass this shortcoming. The present abstract presents a line of research directed towards the of analysis and definition of load profile characteristics in order to design controllers and operation strategies that optimize cell efficiency and durability. Degradation of the catalyst layer, commonly composed of platinum supported on carbon (Pt/C), mainly due to platinum loss by oxidation/dissolution and the resulting reduction of Electrochemical Active Surface Area (ECSA), is the main issue reducing the durability of PEMFC., Peer Reviewed
- Bayat, Fardin
- Moslemi, Hamid
The objective of adaptive techniques is to obtain a mesh which is optimal in the sense that the computational costs involved are minimal under the constraint that the error in the finite element solution is acceptable within a certain limit. But adaptive FEM procedure imposes extra computational cost to the solution. If we repeat the adaptive process without any limit, it will reduce efficiency of remeshing procedure. Sometimes it is better to take an initial very fine mesh instead of multilevel mesh refinement. So it is needed to estimate the computational cost of adaptive finite element technique and compare it with the FEM computational cost. The remeshing procedure can be optimized by balancing these computational costs.
- Than, V.-D.
- Roux, J-N.
- Tang, A.-M.
- Pereira, J.-M.
We use Discrete Element Method (DEM) simulations in three dimensions (3D) to study the quasistatic response of very loose assemblies of frictional spherical grains to an isotropic compression in the presence of a small amount of an interstitial liquid, which gives rise to capillary menisci and attractive forces. Previous results obtained in 2D  are generalized to systems that may be observed in the laboratory. We study the influence of the initial assembling process and of various micromechanical parameters on the plastic compression curves, from very loose states assembled at low P∗ to maximally compressed ones in which capillary cohesion is negligible at large P∗. We also show how the plastic response along those compression curves is influenced by rolling resistance in contacts.
- Díaz Cort, Josep
- Cucker Farkas, J.F.
This survey presents some of the recent developments in the field of structural complexity. The survey does not intend to give an exhaustive look in each one of the areas of structural complexity which have been developed recently, but just the ones the authors believe have had a greater impact on the field.
- Mellado González, Juan Pedro
- Sarkar, Sutanu
- Zhou, Ye
Turbulence developed from Rayleigh-Taylor instability between two compressible miscible fluids in an unbounded domain is addressed in this paper. It is demonstrated that the turbulent Mach number in the turbulent core has an upper bound, independent of the density ratio under a broad range of initial mean configurations. The initial thermodynamic state of the system determines the amount of potential energy per unit mass involved in the turbulent mixing stage, and thus the characteristic level of turbulent fluctuations that is achievable is linked to the characteristic speed of sound such that the turbulent Mach number is limited. For the particular case of an ideal gas, this bound on the turbulent Mach number is found to be between 0.25 and 0.6, depending on the particular initial thermodynamic state. Hence, intrinsic compressibility effects those owing to large Mach number are likely to be limited in the turbulent stage of a pure Rayleigh-Taylor problem. This result is confirmed by large-eddy simulations LES of systems with density jumps at the interface of 3: 1, a density ratio for which there is extensive data available in the literature. The LES predictions of the mixing depth growth and overall mixing agree with results previously obtained in incompressible configurations with a negligibly small Mach number, and the data fully describing the Reynolds stresses and the budget of the resolved turbulent kinetic energy equation are provided., Peer Reviewed