1,720,976 research outputs found
Accurate sensitivity in optically preamplified direct-detection
No full textWe present a novel model for calculating the bit error rate in optical communication systems in the case of on–off keying intensity modulation and optically preamplified direct detection. The model accounts for the intersymbol interference and is based on the Laguerre photon-count probability distribution predicted by photodetection theory. For a non-return-to-zero modulation format an accurate value of the sensitivity for a quantum-limited receiver of 33.9 photons/bit is obtained
Rf-sputtering growth of stoichiometric amorphous TeO2 thin films
No full textAmorphous stoichiometric thin films of TeO2 have been successfully grown by reactive rf-sputtering deposition. The proper choice of deposition parameters such as the rf power, the Ar/O2 composition and pressure of the sputtering gas, the substrate temperature, enabled us to obtain TeOx films of different thickness (up to 2.4 μm) with constant and reproducible optical and structural characteristics. The x value was calculated from RBS measurements to be equal to 2.04 ± 0.08 and all films showed good optical transparency in the visible and near infrared range. The structure of the films was studied by XRD, TEM and SAD, and it was found to be amorphous with the presence of rare and small Te crystallites
New design for trackless LCPV Modules with low-aspect ratio for compatibility with standard panels
No full textWe introduce and experimentally demonstrate a novel design for trackless LCPV modules with low-aspect ratio for compatibility with standard PV panels. This solution, named Gondola, enables a reduction of the silicon usage by up to a factor three, while keeping an aspect ratio of less than 0.3. The wide angular acceptance of the concentrator is compatible with both seasonal and daily angular sunlight excursions, removes the need for any tracking systems, and achieve more than 80% yearly-averaged optical collection efficiency with respect to standard panels. The design can be also tuned to address different orientation in the installation, without impairing the optical performance of the concentrato
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Trackless LCPV modules: a competitive solution?
No full textThe economical sustainability and competitiveness
of trackless stationary low concentration photovoltaic
(LCPV) modules employing Silicon cells is discussed, as
proceeding from detailed expressions for the Levelized Cost
of Electricity (LCoE). The model here introduced accounts
for the performance of concentrating optics in terms of a
newly defined yearly averaged effective optical performance
ratio, Pro,eff. By comparing the LCoEs of standard and
LCPV modules, threshold conditions for Pro,eff and for the
cost of concentrating optics can be mapped, in dependence
on the geometrical concentration, on the cell efficiency and
on other sensitive design parameters. In view of
competitiveness on the energy market, elevated Pro,eff has
more economical relevance than either high geometrical
gain or reduced cost of the optics. Results highlight that
stationary LCPV is a viable approach to leverage the
exploitation of high-efficiency Si cells on the PV market. We
consider this to be a promising evolution strategy for
Silicon-based PV modules
Gold Electroless Deposition by Water-Based and Alcoholic Solutions
No full textDeposition of contacts is a major issue for the preparation of CdZnTe-based detectors. In particular, due to CdZnTe thermal instability above
150 degree Celsius, thermal annealing of contacts after deposition is not possible. Also for this reason, mechanical stability of contacts is
usually poor. In this frame, we have studied mechanical and electrical properties of gold electroless deposited contacts prepared from waterbased
and alcoholic solutions. While electrical I-V characteristics are similar in the two cases, showing the typical ???S??? behavior of two
diodes in ???back to back??? configuration, contacts prepared from alcoholic solutions show a much better mechanical stability and can
overcome a typical adhesive tape test. The contact structure obtained by water-based and alcoholic solutions has been studied by different
techniques, such as Scanning Electron Microscopy, Auger spectroscopy, and Transmission Electron Microscopy. The results of the
characterization are discussed in order to explain the different mechanical behavior of the contacts prepared according to the two preparation
procedures
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
- …
