Search results for "photo"

Dynamical analysis of electron transport in RF cavities and photomultipliers tubes

2021

El objetivo de este trabajo es el estudio de la dinámica de haces y corrientes de electrones en cavidades aceleradoras de radiofrecuencia (RF) y en tubos fotomultiplicadores. Por una parte, los haces de electrones presentan una gran importancia histórica tanto en aplicaciones directas (televisiones, hornos de microondas, tratamiento del cáncer), como en la generación de radiación sincrotrón. La última generación de fuentes de rayos X muy brillantes se basa en los láseres de electrones libres (XFEL). No obstante, para producir los haces de electrones que emitirán dichos rayos X como radiación sincrotrón, se necesitan campos eléctricos de gran intensidad lo que produce que, debido a la emisió…

The Role of Excited Oxygen Molecules in the Formation of the Secondary Ozone Layer at 87 to 97 km

2018

The secondary ozone layer is located at elevations of 87 to 97 km in the upper mesosphere – lower thermosphere. It overlaps with the ionospheric D-layer. Daytime intensive UV radiation is dissociating O2 molecules to O atoms and photoexcitating O2 molecules up to 11.07eV level. Ozone photolysis between the wavelengths of 118.7–121.6 nm produces three oxygen atoms from one ozone molecule. Collision reactions of O2(B3 Σu —) and O2(X3 Σg —, υ≥26) with O2(X3 Σg —, υ=0) produce additional oxygen atoms. The number of oxygen atoms is maintained at such a high level that a small but significant ozone concentration survives. UV radiation weakens radically during the night. The number of O atoms show…

Mangiare, viaggiare, fotografare

2020

C’è un nesso, logico e narrativo al tempo stesso, che non si finirà mai di considerare fondamentale, nella nostra come in altre culture: è quello fra mangiare e viaggiare, gustare preziose ghiottonerie e incontrare in nuovi luoghi altre popolazioni. Certo, c’è la cucina di casa, le tradizioni gastronomiche locali, il chilometro zero. Ma sono per lo più invenzioni leggendarie, o quanto meno turistiche. E ci sono tante persone che per tutta la vita ingurgitano sempre la stessa cosa, di modo che la minima variazione di gusto le mette in crisi peggio che l’imbattersi in un idioma sconosciuto. Ma sono soggetti da guardare con allarmato sospetto, poiché sempre pronti a garantire la sedicente – e …

Provini. Sull'enunciazione fotografica

2020

Before the shutter release subtracts a certain fragment of existence from its continuous becoming, producing that "that-has-been" that Barthes recognized as the very essence of photographic art, the world is in front of the photographer with all its complexity: the infinite things that populate it, the infinite points of view from which it is possible to look at them, the infinite moments that mark their existence. In front of the man with the camera, an infinite number of photographs unfolds, many of which, unfortunately, completely incapable of provoking that jolt you get when an image is really good. How is it possible to describe and analyze photographic production? To think about it, t…

Politiche del reale. Sulla testimonianza fotografica

2021

Not only, as Barthes has shown, are photographs photographs are complex objects, endowed with a high degree of depth and of depth and considerable semantic possibilities but, as Floch has Floch argued, the testimonial one is only one effect of meaning among the many that they can produce. From this derives a twofold necessity. The first has to do with the caution that must characterize the approach to images. approach to images. A photograph is not a fact, it means it, and like every process of signification it presupposes a point of view a point of view, and therefore an ideology, which is revealed only when it becomes possible to only when it becomes possible to reconstruct what is missin…

Responsivity measurements of SiC photodiodes

2014

We investigated the technical features of three novel classes of 4H-SiC vertical Schottky UV photodiodes (henceforth, named SiC8, SiC10, SiC20) employing Ni2Si interdigitated strips whose pitch size is 8, 10 and 20 µm respectively [1] and based on the pinch-off surface effect.

The structural disorder of a silica network probed by site selective luminescence of the nonbridging oxygen hole centre

2011

We studied the inhomogeneous distribution of the luminescence band associated with the nonbridging oxygen hole centre in silica through site selective excitation/detection of the zero phonon line by a tunable laser source. Defects induced in the bulk of synthetic samples by γ and β exposure exhibit an increase of the inhomogeneous width from 0.071 to 0.086 eV on increasing the irradiation dose from 2 × 10(6) to 5 × 10(9) Gy. We also investigated two defect variants stabilized at the surface of the silica nanoparticles, (≡ Si-O)3 Si–O* and (≡ Si-O)2(H-O)Si-O*, whose inhomogeneous width was measured to be 0.042 eV and 0.060 eV, respectively. These results can be accounted for by the structura…

Radiation induced generation of Non-Bridging Oxygen Hole Center: intrinsic and extrinsic processes

2006

Stability of sol-gel silica glass for CPV and ultraviolet LED applications

2011

This paper concerns the characterization of silica glass obtained by a sol-gel technique as to its suitability in the terrestrial and space concentrated photovoltaic (CPV), and ultraviolet light emitting diode (UV LED) industrial sectors. The sol-gel material tested is produced by Evonik Industries and marketed under the brand name SAVOSIL™. The tests performed were aimed at determining the endurance of the material to radiation exposure and consist of exposure to gamma radiation and 355 nm UV laser light. In these tests the transmittance of the glass was measured before and after the exposure to the radiation to determine the effect of the radiation treatment. In the case of the test with …

Amorphous silicon nanotubes

2017

In the following, the attention will be focused on the silicon nanotube (SiNTs) that is a highly desired form of silicon for its fundamental role in the miniaturization trend of the electronic devices. After a description of the properties and applications of SiNTs and their fabrication methods, the attention will be focused on chemical vapour deposition (CVD) template synthesis that is the most usual synthetic method for this material. Then, galvanic template synthesis will be described as a general method for the fabrication of different metals and oxides nanostructures, therefore the use of this technique for synthesizing SiNTs will be detailed. Characterization methods will be also desc…