Search results for " objects"
showing 10 items of 186 documents
Semidirect products of internal groupoids
2010
We give a characterization of those finitely complete categories with initial object and pushouts of split monomorphisms that admit categorical semidirect products. As an application we examine the case of groupoids with fixed set of objects. Further, we extend this to the internal case. (C) 2010 Elsevier B.V. All rights reserved.
X-ray emission mechanisms in protostellar jets
2005
Prompted by the recent detection of X-ray emission from Herbig-Haro objects, we studied the interaction between a supersonic jet originating from a young stellar object and the ambient medium; our aim is to investigate the mechanisms causing the X-ray emission. Our model takes into account the radiative losses from optically in plasmas and Spitzer's thermal conduction including saturation effects. We explored the parameter space defined by the density contrast between the ambient medium and the jet and by the Mach number, to infer the configurations which can give rise to X-ray emission. From the models, we derived the X-ray emission as it would be observed with Chandra/ACIS-I and XMM-Newto…
Slow/Fast. Piccoli oggetti al di là dell'interno
2020
Contemporary behavioural scenarios change quickly, linked to habits aimed at continuous displacements, with variable panoramas and places of reference. Human activities, traditionally related with the domestic interior, are located outside. New paces and frenetic ways of life reduce to a minimum the time dedicated to primary needs, primarily the need for eating. Lunch breaks are quick and optimised, the rituals of "eating together around the table" have changed profoundly, often relegated to a few small occasions. The result is an essential relapse into the world of objects, ready to condense the ritual of solitary consumption of the meal, in a simple and immediate, rapid gesture. At the sa…
Una casa senza pareti. Visioni dal mondo del design del XXI secolo
2020
The domestic environment, as a space in continuous evolution, is called today to respond to some socio-cultural transformations, largely due to pressing technological innovations, which have profoundly changed the relationships between people and between them and the space of the house. These transformations redesign private spaces with a massive encroachment of the public sphere into the private one and vice versa, creating large areas of permeability in the confines of the house. The article analyzes some aspects of this phenomenon, intersecting the disciplinary contribution of design with the architectural and interior design, through some contemporary case studies.
Searching the internet for learning materials through didactic indicators
2007
Internet offers a huge amount of didactic materials that can be used in creating new online courses. However, those materials need a deep analysis to understand their context and contents before their potential use. As a consequence, the search of didactic material in internet is often quite tedious and time consuming so the searcher usually limits his/her analysis to the first found web pages . To help users in finding efficiently and timely the most appropriate online materials, we have developed a system, called SAXEF (System for Automatic eXtraction of lEearning object Features), that is capable to automatically extract the didactic indicators (a sort of DNA) of any web page (or group o…
(recensione) Jessica Moss, Aristotle on the Apparent Good
2012
Collisionless shock heating of heavy ions in SN 1987A
2019
Astrophysical shocks at all scales, from those in the heliosphere up to the cosmological shock waves, are typically "collisionless", because the thickness of their jump region is much shorter than the collisional mean free path. Across these jumps, electrons, protons, and ions are expected to be heated at different temperatures. Supernova remnants (SNRs) are ideal targets to study collisionless processes because of their bright post-shock emission and fast shocks. Although optical observations of Balmer-dominated shocks in young SNRs showed that the post-shock proton temperature is higher than the electron temperature, the actual dependence of the post-shock temperature on the particle mass…
Indications of a Si-rich bilateral jet of ejecta in the Vela SNR observed with XMM-Newton
2017
Context. The Vela supernova remnant displays several ejecta, which are fragment-like features protruding beyond the front of its primary blast shock wave. They appear to be "shrapnel", bowshock-shaped relics of the supernova explosion. One of these pieces of shrapnel (A), located in the northeastern edge of the remnant, is peculiar because its X-ray spectrum exhibits a high Si abundance, in contrast to the other observed ejecta fragments, which show enhanced O, Ne, and Mg abundances. Aims. In this Letter we present the analysis of another ejecta fragment located opposite to shrapnel A with respect to the center of the shell, in the southwestern boundary of the remnant, named shrapnel G. We …
The nearest X-ray emitting protostellar jet (HH 154) observed with Hubble
2008
Context. The jet coming from the YSO binary L1551 IRS5 is the closest astrophysical jet known. It is therefore a unique laboratory for studies of outflow mechanisms and of the shocks occurring when expanding material hits the ambient medium as well as of how the related processes influence the star- (and planet-) forming process. Aims. The optical data are related to other data covering the spectrum from the optical band to X-rays with goal of understanding the energetics of low-mass star jets, in general, and of this jet in particular. We study the time evolution of the jet, by measuring the proper motions of knots as they progress outwards from the originating source. Methods. The nebulos…
3D objects descriptors methods: Overview and trends
2017
International audience; Object recognition or object's category recognition under varying conditions is one of the most astonishing capabilities of human visual system. The scientists in computer vision have been trying for decades to reproduce this ability by implementing algorithms and providing computers with appropriate tools. Hence, several intelligent systems have been proposed. To act in this field, numerous approaches have been proposed. In this paper we present an overview of the current trend in 3D objects recognition and describe some representative state of the art methods, highlighting their limits and complexity.