252 research outputs found
Thermal noise and optomechanical features in the emission of a membrane-coupled compound cavity laser diode
We demonstrate the use of a compound optical cavity as linear displacement
detector, by measuring the thermal motion of a silicon nitride suspended
membrane acting as the external mirror of a near-infrared Littrow laser diode.
Fluctuations in the laser optical power induced by the membrane vibrations are
collected by a photodiode integrated within the laser, and then measured with a
spectrum analyzer. The dynamics of the membrane driven by a piezoelectric
actuator is investigated as a function of air pressure and actuator
displacement in a homodyne configuration. The high Q-factor ( at mbar) of the fundamental mechanical mode at kHz guarantees a detection sensitivity high enough for direct measurement
of thermal motion at room temperature ( pm RMS). The compound cavity
system here introduced can be employed as a table-top, cost-effective linear
displacement detector for cavity optomechanics. Furthermore, thanks to the
strong optical nonlinearities of the laser compound cavity, these systems open
new perspectives in the study of non-Markovian quantum properties at the
mesoscale
Atomic gallium laser spectroscopy with violet/blue diode lasers
We describe the operation of two GaN-based diode lasers for the laser
spectroscopy of gallium at 403 nm and 417 nm. Their use in an external cavity
configuration enabled the investigation of absorption spectroscopy in a gallium
hollow cathode. We have analyzed the Doppler broadened profiles accounting for
hyperfine and isotope structure and extracting both the temperature and
densities of the neutral atomic sample produced in the glow discharge. We have
also built a setup to produce a thermal atomic beam of gallium. Using the
GaN-based diode lasers we have studied the laser induced fluorescence and
hyperfine resolved spectra of gallium.Comment: 10 pages, 7 figure
Digital Preservation, Archival Science and Methodological Foundations for Digital Libraries
Digital libraries, whether commercial, public or personal, lie at the heart of the information society. Yet, research into their longâterm viability and the meaningful accessibility of their contents remains in its infancy. In general, as we have pointed out elsewhere, âafter more
than twenty years of research in digital curation and preservation the actual theories, methods and technologies that can either foster or ensure digital longevity remain
startlingly limited.â Research led by DigitalPreservationEurope (DPE) and the Digital
Preservation Cluster of DELOS has allowed us to refine the key research challenges â theoretical, methodological and technological â that need attention by researchers in digital libraries during the coming five to ten years, if we are to ensure that the materials held in our emerging digital libraries are to remain sustainable, authentic, accessible and understandable over time. Building on this work and taking the theoretical framework of archival science as bedrock, this paper investigates digital preservation and its foundational role if digital libraries are to have longâterm viability at the centre of the
global information society.
Indexing, browsing and searching of digital video
Video is a communications medium that normally brings together moving pictures with a synchronised audio track into a discrete piece or pieces of information. The size of a âpiece â of video can variously be referred to as a frame, a shot, a scene, a clip, a programme or an episode, and these are distinguished by their lengths and by their composition. We shall return to the definition of each of these in section 4 this chapter. In modern society, video is ver
Learning from Digital Library Evaluations
In this paper we analyse evaluation studies of the Europeana digital library from its launch in 2009 until today. Using Saracevicâs digital library evaluation framework, the studies are categorised by their constructs, contexts, criteria, and methodologies. Concentrating on studies that evaluate Europeana services or single components, we show gaps in the evaluation of certain Europeana aspects. Finally, we derive strategies for building an evaluation archive that serves as memory and supports comparisons.Im vorliegenden Artikel analysieren wir Evaluationsstudien der digitalen Bibliothek Europeana von 2009 bis heute. Unter BerĂŒcksichtigung von Saracevicâ Evaluationsframework fĂŒr digitale Bibliotheken werden die Studien nach ihren Konstrukten, Kontexten, Kriterien und Methodologien kategorisiert. Die Analyse konzentriert sich auf Studien, die Dienstleistungen oder einzelne Komponenten von Europeana evaluieren, und zeigt LĂŒcken in der Evaluation bestimmter Aspekte von Europeana auf. SchlieĂlich werden Strategien diskutiert, um ein Evaluationsarchiv zu entwickeln, welches sowohl der Langzeitarchivierung dient als auch Vergleiche von Evaluationsergebnissen unterstĂŒtzt.Peer Reviewe
Innovative learning models for prisoners
Prison education should be a top priority issue in most societies. Prison conditions must not infringe human rights and dignity and must offer meaningful treatment programmes in order to support inmates in their rehabilitation and reintegration in society. The use of ICTs within a penitentiary context plays a crucial role in that. The present Volume looks at the learning potential in prisons and reports on innovative (e-)learning pathways for basic skills education as designed and tested in Cyprus, Greece, Italy and Romania. Research investigated on what counts as âeducationalâ in such a complex context and how to combine relevant pieces in a âlearning mosaicâ (the broad range of any learning opportunity across it). This Volume argues that such an approach may be adopted in a wider European perspective within the frame of dynamic security
- âŠ