Accés i Recuperació de Continguts en Líni@ (ARC@) : la gestió dels materials docents a la UOC

Arc@ té per objectiu millorar el procés d'aprenentatge de l'estudiant i facilitar l'eficiència en els processos de gestió docent i de continguts. Amb independència de la ubicació del material docent, s'han establert mecanismes en XML que permeten importar/exportar la informació des dels diferents aplicatius existents, indexar i organitzar aquesta informació per a la seva transformació i tractament posterior.

Estimation of zero-sequence impedance of undergrounds cables for single-phase fault location in distribution systems with electric arc

This paper focus on the problem of locating single-phase faults in mixed distribution electric systems, with overhead lines and underground cables, using voltage and current measurements at the sending-end and sequence model of the network. Since calculating series impedance for underground cables is not as simple as in the case of overhead lines, the paper proposes a methodology to obtain an estimation of zero-sequence impedance of underground cables starting from previous single-faults occurred in the system, in which an electric arc occurred at the fault location. For this reason, the signal is previously pretreated to eliminate its peaks voltage and the analysis can be done working with a signal as close as a sinus wave as possible

Faint arc-minute extended radio emission around Cygnus X-3

Aims.We revisit the vicinity of the microquasar Cygnus X-3 at radio wavelengths. We aim to improve our previous search for possible associated extended radio features/hot spots in the position angle of the Cygnus X-3 relativistic jets focusing on shorter angular scales than previously explored. Methods.Our work is mostly based on analyzing modern survey and archive radio data, mainly including observations carried out with the Very Large Array and the Ryle Telescopes. We also used deep near-infrared images that we obtained in 2005. Results.We present new radio maps of the Cygnus X-3 field computed after combining multi-configuration Very Large Array archive data at 6 cm and different observing runs at 2 cm with the Ryle Telescope. These are probably among the deepest radio images of Cygnus X-3 reported to date at cm wavelengths. Both interferometers reveal an extended radio feature within a few arc-minutes of the microquasar position, thus making our detection more credible. Moreover, this extended emission is possibly non-thermal, although this point still needs confirmation. Its physical connection with the microquasar is tentatively considered under different physical scenarios. We also report on the serendipitous discovery of a likely Fanaroff-Riley type II radio galaxy only away from Cygnus X-3.

Late Neogene lacustrine record and paleogeography in the Quillagua-Llamara basin, Central Andean fore-arc (Northern Chile)

The Cenozoic QuillaguaLlamara basin (northern Chile, Central Andes) is an asymmetrical, intramassif fore-arc basin with a relatively wide northern sector separated from a narrower southward extension by a basement threshold. The north- ern sector was characterised by a noticeable Oligocene?late Neogene alluvial-fan and lacustrine dominated deposition which resulted in sequences up to 900 m thick, whereas the southern sector was often a bypass zone with thinner fluvial and lacustrine sediment accumulation.

Cela Espín, X. i Revilla Calvo, V., Annexos de Jaume Buxeda i Garrigós i Miquel Ângel Cau Ontiveros; Mariana Pérez-Sala i Rodés; Eva Orri Terrado i Alicia Estrada Martín.: La transició del municipium d'Iluro a Alarona (Mataró). Cultura material i transformacions d"un espai urbà entre els segles V i VII dC. Laietania, 15, 2004

Aquest llibre reuneix un estudi arqueològic extraordinàriament acurat referit a tot un seguit d'actuacions detectades a partir del registre arqueològic, que caracteritzen l'espai urbà de l'antiga Iluro durant el període de l'Antiguitat tardana. S'hi estudia amb molt deteniment cadascuna de les accions detectades -així com tot el mobiliari ceràmic relacionat- amb la finalitat de situar-les correctament en el temps, però també per entendre, a través de la cultura material, la dinàmica que pren la ciutat a les darreries de l'Antiguitat; per a poder intuir, més que saber, quina societat es desenvolupa darrere d¿aquests contenidors plens de productes alimentaris arribats d¿un ultramar llunyà i alhora molt proper; una societat capaç de respondre a l¿estímul exterior amb una producció pròpia que competirà o substituirà una gran part de la que ve de fora.

Morphological and Magnetic Properties of Superparamagnetic Carbon-Coated Fe Nanoparticles Produced by Arc Discharge.

Spherical carbon coated iron particles of nanometric diameter in the 510 nm range have been produced by arc discharge at near-atmospheric pressure conditions (using 58·10 4 Pa of He). The particles exhibit a crystalline dense iron core with an average diameter 7.4 ± 2.0 nm surrounded by a sealed carbon shell, shown by transmission electron microscopy (TEM), selected-area diffrac- tion (SAED), energy-dispersive X-ray analysis (STEM-EDX) and electron energy loss spectroscopy (EELS). The SAED, EDX and EELS results indicate a lack of traces of core oxidized phases showing an efficient protection role of the carbon shell. The magnetic properties of the nanoparticles have been investigated in the 5300 K temperature range using a superconducting quantum interference device (SQUID). The results reveal a superparamagnetic behaviour with an average monodomain diameter of 7.6 nm of the nanoparticles. The zero field cooled and field cooled (ZFC-FC)magnetization curves show a blocking temperature (TB)at room temperature very suitable for biomedical applications (drug delivery, magnetic resonance imaging MRI, hyperthermia).

Morphological and Magnetic Properties of Superparamagnetic Carbon-Coated Fe Nanoparticles Produced by Arc Discharge.

Spherical carbon coated iron particles of nanometric diameter in the 5-10 nm range have been produced by arc discharge at near-atmospheric pressure conditions (using 5-8·10 4 Pa of He). The particles exhibit a crystalline dense iron core with an average diameter 7.4 ± 2.0 nm surrounded by a sealed carbon shell, shown by transmission electron microscopy (TEM), selected-area diffrac- tion (SAED), energy-dispersive X-ray analysis (STEM-EDX) and electron energy loss spectroscopy (EELS). The SAED, EDX and EELS results indicate a lack of traces of core oxidized phases showing an efficient protection role of the carbon shell. The magnetic properties of the nanoparticles have been investigated in the 5-300 K temperature range using a superconducting quantum interference device (SQUID). The results reveal a superparamagnetic behaviour with an average monodomain diameter of 7.6 nm of the nanoparticles. The zero field cooled and field cooled (ZFC-FC)magnetization curves show a blocking temperature (TB)at room temperature very suitable for biomedical applications (drug delivery, magnetic resonance imaging-MRI-, hyperthermia).