P-arch
Not a member yet
966 research outputs found
Sort by
The NURAXI web-based learning environment architecture
Get PDFThe fast evolution of today world impels corporations to provide their employees just-in-time training, adapted training and more generally continuous education. To be able to satisfy this demand, authors need means to specify once didactic material and then to reuse, select, adapt and distribute it to different users in different contexts.
Since September 1998, Mediatech is developing the NURAXI multimedia research platform aimed at the design, generation, deployment, management and use of intelligent distance learning environments. NURAXI interacts with the user on the basis of the competency assessment (initial, on-going progress and final), the individual learning style and collaborative learning. Our solution is departing from a document type based organization of courses and training material towards a functionality and competency based model. We consider models and structures for information, knowledge and competencies more appropriate to the new on-line delivery environment than the document-based old one (html-based or not). From a technological point of view, this was made possible by the recent arrival of XML technology, coupled with Java and Web application technology
A distance learning environment architecture
Get PDFThis paper presents the core architecture of NURAXI, a multimedia research platform aimed at the design, generation, deployment, management and use of intelligent distance learning environments. It describes the actors and services that are involved in the production and use of intelligent distance learning environments, the structures that are at the heart of the environment, and the processes that use these structures. The competence notion is the central component around which both author's and student's interactions gravitate. An author generates the training material on the basis of competencies to be acquired by a student, and the means to get them, i.e. the related activities and contents. A student accesses the pedagogical material by first selecting his/her learning objectives. The training path is made of dynamically created pedagogical activities. Examples of implemented activities are also shown in the paper. The platform presents a number of interesting features including re-usability of didactic components; adaptability of the training material to the student model; dynamic definition of the training path; modularity, and interoperability thanks to the adoption of standard and open solutions in terms of document structures, ontologies, design and implementation techniques. All these advantages derive from the integration of technologies such as the XML paradigm, Servlets, Software Agents, and Distributed Databases
Fluid-solid interaction modeling for sloshing flows in flexible tanks
Get PDFThe scope of the presentation is to review our ongoing research on the numerical modeling of sloshing in deformable tanks
Prototipo di bollettino mensile di bilancio idrologico in atmosfera nella regione mediterranea: simulazione numerica con un modello meteorologico nei due trimestri prototipali
Get PDFLa presente relazione riassume l'attività svolta nell'ambito della prima fase della convenzione CRS4-DSTNPC \prototipo del bollettino mensile di bilancio idrologico in atmosfera". In particolare è descritta l'analisi delle metodologie utilizzabili rispetto agli obbiettivi del progetto, i criteri addottati per la selezione dei due periodi prototipali e le integrazioni numeriche ottenute mediante il Modello di circolazione atmosferica ad Area Limitata (LAM) nei due periodi trimestrali scelti. Vengono discussi, inoltre, il bilancio idrologico atmosferico ottenuto utilizzando le analisi meteorologiche e le medie mensili di precipitazione sulla Sardegna relativamente al periodo dal 1986 al 1988 e presentata una descrizione del
codice LAM (BOLAM) utilizzato per eseguire i run previsti dalla convenzione
Gas premixed combustion at high turbulence. Turbulent flame closure combustion model
Get PDFThis paper is devoted to analyze the special class of turbulent premixed flames that we call intermediate steady propagation (ISP) flames. These flames are common to industrial premixed combustion chambers which operate at intensive turbulence when velocity
pulsations are significantly higher than the flamelet combustion velocity. They are characterized by a practically constant turbulent combustion velocity, controlled by turbulence, chemistry and molecular processes, and by an increasing flame width, controlled mainly by turbulent diffusion.
The main content of this work is a description of physical backgrounds and outcome of the original asymptotical (i.e., valid at high Re and Da numbers) premixed combustion model, that, from a methodological point of view, is close to Kolmogorov analysis of
developed turbulence at high Re numbers. Our analysis starts from the thickened and strongly wrinkled flamelets combustion mechanism. Quantitative results for this model are based on the Kolmogorov assumption of the equilibrium fine-scale turbulence and
on additional assumption of the universal small-scale structure of the wrinkled flamelet sheet. From this background it is possible to deduce formulas for the thickened flamelets parameters and the flamelet sheet area and hence the turbulent combustion velocity of
the premixed flame.
These formulas are used for the closure of the combustion equation written in terms of a progress variable leading to the so called turbulent flame closure (TFC) model for the numerical simulation of ISP flames. Consistent to the ISP flames, in this work the concept of countergradient transport phenomenon in premixed combustion is analyzed
ViVa: sistema acquisizione geometrie arteriose. Descrizione generale.
Get PDFLo scopo di questa attività era di produrre un modulo software in grado di estrarre una caratterizzazione geometrica dei vasi sanguigni a partire da dati volumetrici ottenuti da macchine di acquisizione di tipo clinico, ad esempio TAC a spirale
Modelling turbulent premixed combustion in the intermediate steady propagation regime
Get PDFNumerical simulation and comparison with standard experimental data of turbulent premixed combustion occurring at large Reynolds and moderately large Damkohler numbers (a situation which is typical in industrial burners) have been presented. The simulation has been performed in the framework of the Turbulent Flame-speed Closure (TFC) combustion model, developed in [1]-[4], which makes use of a theoretical expression for the turbulent combustion velocity for the closure of the progress variable transport equation. This model is based on the concept of Intermediate Steady Propagatioin (ISP) regime of combustion in real combustors, i.e. when the turbulent flame propagates with equilibrium turbulent flame
speed but has flame brush thickness growing according to the turbulent dispersion law.
These ISP flames precede usually analysed 1-D stationary flames and from the theoretical point of view they are in fact intermediate asymptotic of the combustion process between the period of formation of developed turbulent flames and 1-D stationary flames. Numerical results of turbulent premixed combustion in a two dimensional planar channel at parameters that correspond to real industrial combustors have been compared with corresponding standard experimental data on a high speed turbulent premixed flame [9]. Finally, it has been explained in the framework of the TFC combustion model that "countergradient diffusion", i.e. the necessity to use a negative effective diffusion coeficient to describe experimental heat and progress variable fluxes inside the flame, is an inherent feature of turbulent premixed flames and is connected with direct dependence of the second order velocity-scalars correlation on combustion. It has been shown that the existence of the countergradient diffusion phenomenon is not in contradiction with the actual increasing of the flame brush width
CAVALCADE: a system for collaborative prototyping
No full textThe proceedings have been published by the Town Council of Laval as a book of 200 pages. This publication has received a ISBN number (ISBN 2-9513952-0-5, June 1999)Prototype design and testing is an indispensable stage of any project development in many fields of activity, such as aeronautical, spatial, automotive industries or architecture. Scientists and engineers rely on prototyping for a visual confirmation and validation of both their ideas and concepts. Using computers for designing digital prototypes is not a new idea since CAD applications are nowadays widely used. In this paper we present how new advances in 3D interaction and real time visualisation research domains lead to the development of a collaborative and really interactive system for virtual prototyping. This work is supported by the European Community through the ESPRIT programme 4.161-17
Three-dimensional graphics
Get PDFThree-dimensional graphics is the area of computer graphics that deals with producing two-dimensional representations, or images, of three-dimensional synthetic scenes, as seen from a given viewing configuration. The level of sophistication of these images may vary from simple wire-frame representations, where objects are depicted as a set of segment lines, with no data on surfaces and volumes, to photorealistic rendering, where illumination effects are computed using the physical laws of light propagation. All the different approaches are based on the metaphor of a virtual camera positioned in 3D space and looking at the scene. Hence, independently from the rendering algorithm used, producing an image of the scene always requires the resolution of the following problems: 1. Modeling geometric relationships among scene objects, and in particular efficiently representing the situation in 3D space of objects and virtual cameras; 2. Culling and clipping, i.e. efficiently determining which objects are visible from the virtual camera; 3. Projecting visible objects on the film plane of the virtual camera in order to render them. This chapter provides an introduction to the field by presenting the standard approaches for solving the aforementioned problems.168-17
Numerical methodologies for the simulation of liquid metal flows
Get PDFThe fluid-dynamic modelling for the simulation of the Lead-Bismuth flow in the EADF was reviewed. The general form of the non-dimensional governing equation was derived, and the analysis of the orders of magnitude of the different terms in the case of a the liquid metal flows in the EADF was performed, through a flow-Mach number asymptotic analysis. It was found that the resulting form of the equations is the one commonly used in commercial CFD codes for the simulation of liquid flows, which can then be used for our applications.
The most common numerical methods for flow-Mach number applications were also presented.
These methods are general and can be applied to liquid metal flows without any modification.
The peculiarity of the numerical simulation of liquid metal flows lies in the modelling of the turbulent heat transfer, due to the flow Prandtl number of this type of fluids. This subject is discussed in [21]