DSpace Collection:http://hdl.handle.net/11570/30572122020-06-03T22:59:04Z2020-06-03T22:59:04ZgLibrary: a Multimedia Contents Management System on the gridhttp://hdl.handle.net/11570/31295692018-10-01T17:29:39Z2006-01-01T00:00:00ZTitle: gLibrary: a Multimedia Contents Management System on the grid
Abstract: Nowadays huge amounts of information are searched and used by people from all over the world, but it is not always easy to find out what one is looking for. Search engines helps a lot, but they do not provide a standard and uniform way to make queries. The challenge of gLibrary is to design and develop a robust system to handle Multimedia Contents in a easy, fast and secure way exploiting the Grid.
Examples of Multimedia Contents are images, videos, music, all kind of electronic documents (PDF, Excel, PowerPoint, Word, HTML), E-Mails and so on. New types of content can be added easily into the system. Thanks to the fixed structure of the attributes per each content type, queries are easier to perform allowing the users to choose their search criteria among a predefined set of attributes.
The following are possible use examples:
- A user wants to look for all the comedies in which Jennifer Aniston performed together with Ben Stiller, produced in 2004 ; or find all the songs of Led Zeppelin
that last for more than 6 minutes;
- An user needs to find all the PowerPoint Presentation about Data Management System in 2005 run by Uncle Sam (fantasy name);
- A doctor wants to retrieve all the articles and presentations about lung cancer and download some lung X-ray images to be printed in his article for a scientific
magazine;
- (Google for storage) a job behaves as a “storage crawler”: it scans all the files stored in Storage Elements and publishes their related specific information into
gLibrary for later searches through their attributes.
Not all the users of the system have the same authority into the system. Three kind of users are enabled: gLibrary Generic Users, members of a Virtual Organization
recognized by the system, can browse the library and make queries. They can also retrieve the wanted files if the submitter user authorized them; gLibrary Submitter
Users can upload new entries attaching them the proper values for the defined attributes; finally gLibrary Administrator are allowed to define new content type
and elect Generic User granting them submission rights. A first level of security on single file is implemented: files uploaded to Storage Elements can be encrypted using a symmetric key. This will be placed in a special directory into the system and the submitter will define which users are the rights to read it.
All the application is built on top of the grid services offered by the EGEE middleware: actual data is stored in Storage Elements spread around the world, while the File Catalog keeps track of where they are located. A Metadata Catalog service is intensively used to contains the values of attributes and satisfy user’s queries. Finally, A Virtual Organization Membership Service comes in help to deal with authorization.2006-01-01T00:00:00ZCritical notes of Special Relativity: four-velocityhttp://hdl.handle.net/11570/30825092016-04-20T15:29:24Z2016-01-01T00:00:00ZTitle: Critical notes of Special Relativity: four-velocity
Abstract: In this paper, we shall consider - from a critical point of view - the definition of four-velocity. We consider a very precise definition of world line in space time. We emphasize that the space-time of Special Relativity must be considered as a pseudo-Riemaniann manifold, that is, a (topological) space endowed with a chart-atlas and a Riemann metric.
Nevertheless, we maintain the explanation at a very elementary level, by using essential basic knowledge coming from Mathematical Analysis.
Events and world-lines are elements or subsets of the space-time, therefore we cannot realize them as vectors, or subsets, of any vector space without the adoption of a reference frame. The importance of a reference frame is very well underlined and used explicitly. The definition of reference
frame is explicitly emphasized. Moreover, we identify reference frames, observers and charts of the assigned atlas. In other terms, from this point of view, Differential Geometry approach asserts that we cannot interpret or visualize or study the elements (or subsets) of the space-time without the intervention of some observer. As usual, the observers, i.e. reference frames, of our differentiable manifold are smoothly correlated. In some sense, space-time is unequivocally existing but not analyzable without the intervention of some observer. World-lines are defined as smooth curves
in space-time, such that, for any reference frame, they can be obtained as the graphics of convenient functions defined - by using the pre-chosen reference frame - on interval of the real line taking values on the Euclidean 3-space. We consider a very elementary example and show how to define world-lines of the space-time by using a reverse approach, starting from one fixed reference frame, hence going from the Minkovskian real (1,3)-space to the Minkovsky space time M4. Then, we explicitly define and consider the natural time parametrization of a world-line induced by a reference frame. So that we can define explicitly the natural time parameter of a particle with respect to a reference frame. Different versions of the same concept will be considered. Then, we consider the analytical definition of proper time of a moving point in the space time, starting from the natural parameter induced by a reference frame. In contrast with the usual exposition and explanation of proper time, we explicitly define the domain of the proper time and it's corresponding clear mathematical definition. We also consider the proper-time differential form, field of linear
forms attached with the natural parametrization of a world-line, explicitly noting the independence by reference frame of such differential form.
Finally, we define the four velocity of a particle in an unambiguous way and explicitly provide various expressions of it.2016-01-01T00:00:00ZForce fields and relativistic kinetic energyhttp://hdl.handle.net/11570/30753822016-03-04T12:43:09Z1989-01-01T00:00:00ZTitle: Force fields and relativistic kinetic energy
Abstract: In this paper, we define the positional fields of force associated with a relativistic material point and the kinetic energy of such a point. Then, we state and prove a theorem about the work of a positional field of force compatible with a relativistic particle. Finally, we propose new proofs of some classical results regarding these two concepts.1989-01-01T00:00:00ZAspetti medico-legali della Cartella Clinicahttp://hdl.handle.net/11570/30541792015-03-30T12:19:12Z2014-01-01T00:00:00ZTitle: Aspetti medico-legali della Cartella Clinica2014-01-01T00:00:00Z