DSpace Collection:

A complete analysis of axial piston pump leakage and output flow ripples

Mon, 18 Mar 2013 16:32:36 GMT

Title: A complete analysis of axial piston pump leakage and output flow ripples Authors: Bergadà Granyó, Josep Maria; Kumar, Sushil; Davies, Dyfyr Ll.; Watton, John

The effect of oil pressure and temperature on barrel film thickness and barrel dynamics of an axial piston pump

Mon, 18 Mar 2013 16:28:19 GMT

Title: The effect of oil pressure and temperature on barrel film thickness and barrel dynamics of an axial piston pump Authors: Bergadà Granyó, Josep Maria; Davies, Dyfyr Ll.; Kumar, Sushil; Watton, John

The effect of piston grooves performance in an axial piston pumps via CFD analysis

Mon, 18 Mar 2013 14:29:00 GMT

Title: The effect of piston grooves performance in an axial piston pumps via CFD analysis Authors: Kumar, Sushil; Bergadà Granyó, Josep Maria

Principios para el análisis de la evacuación de edificios mediante redes dinámicas de flujo

Thu, 11 Oct 2012 13:15:32 GMT

Title: Principios para el análisis de la evacuación de edificios mediante redes dinámicas de flujo Authors: Casadesús Pursals, Salvador; Garriga Garzón, Federico Abstract: Para el estudio del problema de la evacuación de edificios se ha recurrido a diferentes disciplinas y a diferentes tipos de modelos. Asimismo, entre los modelos matemáticos utilizados existen numerosas posibilidades. En este trabajo se estudia la evacuación de edificios mediante redes dinámicas de flujo, que corresponden a una solución determinista en un entorno discreto. Con este modelo se dispone de la evolución de las magnitudes que caracterizan el problema en intervalos regulares de tiempo, obteniendo un conocimiento preciso y fiable del desarrollo de la evacuación, y siendo posible, además, la obtención de soluciones óptimas, las propuestas que són capaces de determinar las condiciones que minimizan tiempos de evacuación y maximizan flujos de salida.

Optimal low-thrust transfers between libration point orbits

Mon, 09 Jul 2012 10:55:30 GMT

Title: Optimal low-thrust transfers between libration point orbits Authors: Ren, Yuan; Pergola, Pierpaolo; Fantino, Elena; Thiere, B. Abstract: Over the past three decades, ballistic and impulsive trajectories between libration point orbits (LPOs) in the Sun–Earth–Moon system have been investigated to a large extent. It is known that coupling invariant manifolds of LPOs of two different circular restricted three-body problems (i.e., the Sun–Earth and the Earth–Moon systems) can lead to significant mass savings in specific transfers, such as from a low Earth orbit to the Moon’s vicinity. Previous investigations on this issuemainly considered the use of impulsive maneuvers along the trajectory. Here we investigate the dynamical effects of replacing impulsive V’s with low-thrust trajectory arcs to connect LPOs using invariant manifold dynamics. Our investigation shows that the use of low-thrust propulsion in a particular phase of the transfer and the adoption of a more realistic Sun–Earth–Moon four-body model can provide better and more propellant-efficient solution. For this purpose, methods have been developed to compute the invariant tori and their manifolds in this dynamical model

A numerical investigation of wind tunnel model deformations caused by the twin-sting support system

Mon, 07 Nov 2011 19:18:12 GMT

Title: A numerical investigation of wind tunnel model deformations caused by the twin-sting support system Authors: Flores Le Roux, Roberto Maurice; Ortega, Enrique; Oñate Ibáñez de Navarra, Eugenio

Star visibility and tracking from the Space Station

Fri, 07 Oct 2011 18:50:45 GMT

Title: Star visibility and tracking from the Space Station Authors: Bernacca, Pier Luigi; Facchinetti, Claudia; Fantino, Elena Abstract: Purpose of the present study is to provide algorithms for and examples of how to simulate star visibility and tracking by a Telescope attached to the main truss of the International Space Station (ISS). The sky visibility of a Telescope is limited by accommodation constraints on the truss, by obstructions caused by Station’s structural elements along with other payloads, by Sun and Moon’s light and by ram atomic Oxygen. It is also limited by Station’s orbit and attitude. The above limiting agents have been modeled vis-a-vis NASA nominal specifications and knowledge of the ambient environment. These models have been used to write algorithms and to produce examples of visibility and tracking at single star level. The above analysis has been used to describe in detail how to simulate star visibility and tracking of an observing program all over the sky by a plausible wide field Telescope operated only during successive 80 days coast periods in the declination’s range −71° to 71°. Simulation is mandatory in advance of real observations. The analysis rests on the feasibility study, funded by the Italian Space Agency (ASI), of a Telescope designed for accommodation on ISS. The present visibility and tracking study enables observations planning and it is introductory to any engineering algorithm devoted to mechanically drive pointing and tracking of celestial targets from the Space Station. Since question might arise whether ISS-based Astronomy is nowadays scientifically worthwhile, a brief summary of the science rationale in Ultraviolet, useful to Astrophysics and Cosmology, is offered to the curious Astrophysicist who can decide on his own. From an operational point of view it is concluded that an observing programme can be carried out provided photon re-centering techniques are applied to the raw data, in order to free them from the effects of ISS vibrations.

Two mechanisms of natural transport in the Solar System

Mon, 25 Jul 2011 07:57:26 GMT

Title: Two mechanisms of natural transport in the Solar System Authors: Ren, Yuan; Gomez Muntaner, Gerard; Masdemont Soler, Josep; Fantino, Elena Abstract: In this paper, two natural transport mechanisms in Solar System are considered. The first is a short-time transport, and is based on the existence of ‘‘pseudo-heteroclinic’’ connections between libration point orbits of pairs of Sun–planet planar circular restricted three-body problems (PCR3BP). The stable and unstable manifolds associated with the libration point orbits of different Sun–planet PCR3BP systems are computed. Then the intersections between the inner and the outer manifolds of all the consecutive planets in the Solar System are explored. The second mechanism, which is common and qualitatively well understood in two-degrees of freedom Hamiltonian systems, corresponds to a long-time transport, and is the result of the strongly chaotic motion of the minor body in the PCR3BP. In this contribution, we present an analysis of the natural transport in the Solar System based on these two mechanisms. In particular, we discuss the key properties of the natural transport, such as the possibility of transfering between two specified celestial bodies, the type of transport and the time of flight. The final objective is to provide a deeper dynamical insight into the exchange mechanisms of natural material in the Solar System.

‘Low-cost educational videos’ for engineering students: a new concept based on video streaming and YouTube channels

Wed, 25 May 2011 16:32:15 GMT

Title: ‘Low-cost educational videos’ for engineering students: a new concept based on video streaming and YouTube channels Authors: Garriga Garzón, Federico; Rajadell Carreras, Manuel; García-Almiñana, Daniel; Suñé Torrents, Albert; Fernández Alarcón, Vicenç; Simó Guzmán, Pep; Algaba Joaquín, Inés María; Albareda Sambola, Maria; Salán Ballesteros, Maria Núria; Amante García, Beatriz; Enache, Cristina Mihaela; Bravo Ibarra, Edna Rocío Abstract: There are many papers that present the problems of educational videos: need of a high number of resources to create them, excess of information in the majority of videos, gaps of information between videos and the rest of materials of the courses, etc. This paper introduces the concept ‘low-cost educational video’, which attempts to solve to a large extent the problems that have been identified in the educational videos. To this end, an empirical research is conducted with 487 students and various lecturers and professors in three undergraduate degrees: Mechanical Engineering, Industrial Engineering and Management (in face-to-face as well as semi-distance modalities), and Aeronautical Engineering at the Universitat Politècnica de Catalunya (Spain). In order to achieve this goal, we introduce the process and the required resources for the creation and the diffusion of these low-cost educational videos. The results are analysed taking a literature-based questionnaire as a starting point and within the principles of good practice in higher education framework. The main research findings revealed an improved student motivation and an increase of the perceived efficiency in the learning and teaching processes, without substantially raising costs.

Intangible liabilities: beyond models of intellectual assets

Thu, 24 Feb 2011 15:03:06 GMT

Title: Intangible liabilities: beyond models of intellectual assets Authors: García Parra, Mercedes; Simó Guzmán, Pep; Sallán Leyes, José María; Mundet Hiern, Joan Abstract: Purpose – Most models of intellectual capital measurment equal intellectual capital with intellectual assets. Nevertheless, companies sometimes must incur liabilities to make intellectual assets truly actionable. This fact suggests the existence of intangible liabilities. The aim of this paper is to refine the methods of assessment of intellectual capital by refining and extending the concept of intangible liabilities. Design/methodology/approach – The paper consists of a literature review of prior conceptualisations of intangible liabilities, and an empirical exploration of the employer-employee relationships that can originate intangible liabilities. Findings – The results of the empirical research show that a non-fulfilment of perceived obligations by the company might cause organisational members to refrain from deploying their organisational knowledge in organisational processes. Thus, these obligations can be conceptualised as intangible liabilities. Research limitations/implications – The research has only explored intangible liabilities related to organisational members. Future research should explore the intangible liabilities that an organisation can incur with other constituencies, e.g. suppliers and clients. Practical implications – Managers can improve their models of intellectual capital measurement taking into account not only the intangible assets, but also the intangible liabilities. Taking into account intangible liabilities should bring awareness of the conditions that might hinder the deployment of organisational knowledge. Originality/value – The study brings a more refined, theoretically- and empirically-based conceptualisation of intangible liabilities than those provided so far, aiding to develop a more robust theory of intellectual capital measurement.

Objetive Measure of Woven Fabrics Cover Factor by Image Processing

Mon, 04 Oct 2010 11:18:20 GMT

Title: Objetive Measure of Woven Fabrics Cover Factor by Image Processing Authors: Tapias Anton, Montserrat; Rallo Capdevila, Miguel; Escofet Soteras, Jaume; Algaba Joaquín, Inés María; Riva Juan, Ascensión

The hydrostatic/hydrodynamic behaviour of an axial piston pump slipper with multiple lands

Wed, 01 Sep 2010 08:15:43 GMT

Title: The hydrostatic/hydrodynamic behaviour of an axial piston pump slipper with multiple lands Authors: Bergadà Granyó, Josep Maria; Watton, John; Haynes, Jonathan M; Davies, Dyfyr Ll. Abstract: This study considers an analytical approach towards the understanding of the hydrostatic leakage and lift characteristic of a flat slipper of the type used for piston/slipper units within an axial piston pump or motor. In particular it considers a slipper design incorporating a groove on the slipper face and also includes the effect of motion around its associated swash plate. A new set of equations are developed and in generic form for a slipper with any number of grooves. Experimental comparisons are then undertaken and extended to include the effect of relative motion around the swash plate and slipper tilt. A CFD study of the slipper is also presented. Comparisons between analytical, experimental and CFD results show a very good agreement, validating the equations presented and extending the conclusions when tilt and tangential speed are considered.

Heating of saturated porous media in practice: several causes of local thermal non-equilibrium

Fri, 04 Jun 2010 15:48:09 GMT

Title: Heating of saturated porous media in practice: several causes of local thermal non-equilibrium Authors: Virto Albert, Luis; Carbonell Ventura, Montserrat; Castilla López, Roberto; Gámez Montero, Pedro Javier Abstract: In recent years the industrial applications of porous materials has shown a growing relevance. Most of the technological thermal processes in porous media involve time-dependent thermal conditions. Therefore, the temperature at each point of the material also changes in time. In order to correctly carry out the technological process, it becomes necessary to know the temperature distribution inside the material. This is a problem of heat conduction in a fluid saturated porous media subject to a lack of local thermal equilibrium (LTNE). The purpose of this paper is to elucidate the several causes of LTNE, even in steady or quasi steady heat transfer processes in saturated porous media, and to evaluate the influence of structural characteristic of porous media and the presence of surfactant in the saturating liquid phase.

Video stream and teaching channels: quantitative analysis of the use of low-cost educational videos on the web

Wed, 02 Jun 2010 09:29:34 GMT

Title: Video stream and teaching channels: quantitative analysis of the use of low-cost educational videos on the web Authors: Rajadell Carreras, Manuel; Amante García, Beatriz; García-Almiñana, Daniel; Simó Guzmán, Pep; Fernández Alarcón, Vicenç; Algaba Joaquín, Inés María; Salán Ballesteros, Maria Núria; Enache, Cristina Mihaela; Albareda Sambola, Maria; Bravo Ibarra, Edna Rocío; Suñé Torrents, Albert

Basic principle for the solution of the building evacuation problem

Wed, 03 Mar 2010 14:12:38 GMT

Title: Basic principle for the solution of the building evacuation problem Authors: Casadesús Pursals, Salvador; Garriga Garzón, Federico Abstract: Nowadays, there exist different offers to find the solution of the building evacuation problem. As we analyze in the state of the art, this problem can be studied from different perspectives and even as a problem of optimization considering different objectives. We can wonder on which is the most suitable formulation and the response can be as confusing as saying that it depends on our aims. The more important things to study the ideal building evacuation, understood as the distribution of the occupants towards the exits that achieves the minimal evacuation time, are the valid principles for any formulation of the problem. One of them appears in the present work. To expose the principle, we use graphical procedures that are applied to the optimization of the enclosure evacuation. In the exposed procedure, speeds and constant flows of traffic are considered to model the movement of the persons. Ways and possible delays in the beginning of the bulging evacuation are studied. Description: Article publicat originalment a: "Journal of industrial engineering and management", vol. 2, núm. 3, p. 499-516. DOI No 10.3926/jiem.2009.v2n3.p499-516.