1,720,999 research outputs found
BEXUS 23 OSCAR: Solar Cell I-V Monitoring System for Space Environments
No full textNovel thin film solar cells exhibit unprecedented specific power, which is a key figure of merit for space applications. To get a first indication of their possible degradation in space environments, the OSCAR (‘Optical Sensors based on CARbon materials’) team has built a solar cell performance monitoring system and deployed it on the BEXUS 23 flight. This paper reports the design, testing and performance of said system. Our system
performed impeccably over its 4h mission course, maintaining communication and reliably reporting solar cell I-V curves. It forms a guideline for anyone who needs to measure millivolts and microamperes in similar conditions, monitor solar cells on remote locations or wants to follow up on degradation of thin film solar cells in space
ESA–BEXUS project: OSCAR - Zonne-Energie Voor De Planeet Aarde En Verder
No full textZonne–energie is ontegensprekelijk één van de belangrijkste en duurzaamste oplossingen voor de globale energie– en klimaatuitdagingen waar onze planeet voor staat. Nieuwe generatie printbare, plooibare en ultra–dunnen zonnecellen kunnen bovendien leiden tot tal van nieuwe toepassingen, gaande van energie–bevoorrading voor draag bare elektronica (smartphones, tablets, …) tot grensverleggende toepassingen voor toekomstige ruimtereizen. Printbare organische en perovskiet–zonnecellen zijn namelijk de wereldkampioenen qua verhouding energie–opbrengst versus gewicht. Voor toekomstige ruimtevaartmissies hebben deze zonnecellen dus de bijzondere voordelen dat ze een ultra–licht gewicht hebben, plooibaar en uitvouwbaar zijn en bovendien ter plaatse (in ruimteschepen of in ruimtestations op bijvoorbeeld de Maan of op Mars) kunnen geprint worden.
Door deelname aan het BEXUS–programma (Balloon Experiments for University Students) van de Europese ruimtevaartorganisatie ESA, hebben een team van negen UHasselt–doctoraatstudenten en studenten Fysica (Miguel–Angel Beynaerts, Ilaria Cardinaletti, Rob Cornelissen, Jaroslav Hruby, Steven Nagels, Dieter Schreurs, Jelle Vodnik, Tim Vangerven & Koen Wouters) een wereldrecord gebroken qua gebruik van printbare zonnecellen op grote hoogte. Met het OSCAR–project (Optical Sensors based on CARbon Materials) hebben ze voor het eerste de prestaties van printbare zonnecellen en van een nieuwe magnetische–veldsensor bestudeerd in echte ruimtevaartcondities. Vanuit het lanceerstation Kiruna in Zweden werd een onderzoeksballon in de stratosfeer gebracht — op 32 kilometer hoogte (3x hoogte van vliegtuigtrajecten) — waarbij extreme condities heersen zoals lage luchtdruk, lage temperaturen (tot wel –60 graden Celsius) en een pak meer straling van de zon
BEXUS 23 OSCAR: Solar Cell I-V Monitoring System for Space Environments
No full textNovel thin film solar cells exhibit unprecedented specific power, which is a key figure of merit for space applications. To get a first indication of their possible degradation in space environments, the OSCAR (‘Optical Sensors based on CARbon materials’) team has built a solar cell performance monitoring system and deployed it on the BEXUS 23 flight. This paper reports the design, testing and performance of said system. Our system
performed impeccably over its 4h mission course, maintaining communication and reliably reporting solar cell I-V curves. It forms a guideline for anyone who needs to measure millivolts and microamperes in similar conditions, monitor solar cells on remote locations or wants to follow up on degradation of thin film solar cells in space
ESA–BEXUS project: OSCAR - Zonne-Energie Voor De Planeet Aarde En Verder
No full textZonne–energie is ontegensprekelijk één van de belangrijkste en duurzaamste oplossingen voor de globale energie– en klimaatuitdagingen waar onze planeet voor staat. Nieuwe generatie printbare, plooibare en ultra–dunnen zonnecellen kunnen bovendien leiden tot tal van nieuwe toepassingen, gaande van energie–bevoorrading voor draag bare elektronica (smartphones, tablets, …) tot grensverleggende toepassingen voor toekomstige ruimtereizen. Printbare organische en perovskiet–zonnecellen zijn namelijk de wereldkampioenen qua verhouding energie–opbrengst versus gewicht. Voor toekomstige ruimtevaartmissies hebben deze zonnecellen dus de bijzondere voordelen dat ze een ultra–licht gewicht hebben, plooibaar en uitvouwbaar zijn en bovendien ter plaatse (in ruimteschepen of in ruimtestations op bijvoorbeeld de Maan of op Mars) kunnen geprint worden.
Door deelname aan het BEXUS–programma (Balloon Experiments for University Students) van de Europese ruimtevaartorganisatie ESA, hebben een team van negen UHasselt–doctoraatstudenten en studenten Fysica (Miguel–Angel Beynaerts, Ilaria Cardinaletti, Rob Cornelissen, Jaroslav Hruby, Steven Nagels, Dieter Schreurs, Jelle Vodnik, Tim Vangerven & Koen Wouters) een wereldrecord gebroken qua gebruik van printbare zonnecellen op grote hoogte. Met het OSCAR–project (Optical Sensors based on CARbon Materials) hebben ze voor het eerste de prestaties van printbare zonnecellen en van een nieuwe magnetische–veldsensor bestudeerd in echte ruimtevaartcondities. Vanuit het lanceerstation Kiruna in Zweden werd een onderzoeksballon in de stratosfeer gebracht — op 32 kilometer hoogte (3x hoogte van vliegtuigtrajecten) — waarbij extreme condities heersen zoals lage luchtdruk, lage temperaturen (tot wel –60 graden Celsius) en een pak meer straling van de zon
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
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Systematic study on the lifetime of inverted polymer : fullerene solar cells
No full textLAUREA MAGISTRALENelle ultime decadi, uno dei problemi su cui si è concentrata la ricerca scienti
ca è quello della produzione energetica. ciò ha reso lo sfruttamento di
fonti rinnovabili un punto di grande interesse socio-economico.
Lo sviluppo di tecnologie per convertire l'energia solare in elettricità si è
evoluto negli ultimi anni, passando da una prima generazione di pannelli
fotovoltaici in Silicio cristallino, a una seconda, in cui si utilizzano Silicio
amorfo e varie leghe, con cui si possono fabbricare pannelli sottili. In questi
anni è stata introdotta una terza generazione di celle solari, tra cui quelle
organiche.
Questi dispositivi sono chiamati Organic PhotoVoltaics (OPV) e sfruttano
materiali organici per la generazione di corrente. Si tratta di una tecnologia
sviluppata circa 30 anni fa, che sta raggiungendo e cienze via via più elevate
e promette costi di realizzazione molto ridotti.
Un problema legato all'utilizzo di questi materiali organici risiede nella loro
stabilità. Questi composti tendono infatti a essere sensibili alla radiazione
solare, in particolare nella regione degli Ultra Violetti (UV), alle alte temperature,
e all'ossigeno e l'umidità presenti nell'atmosfera.
Seppure la penetrazione di agenti dall'atmosfera e di raggi UV può essere
ridotta tramite l'utilizzo di apposite barriere, queste risultano tanto più costose
quanto più devono schermare.
È dunque evidente che bisogna comprendere quali sono i meccanismi che
comportano la perdita delle funzionalità dei dispositivi, in modo da poter
prendere azioni mirate per prolungarne la durabilità e raggiungere tempi di
vita dei moduli che ne permettano la commercializzazione.
A tal proposito, sempre più gruppi si sono interessati allo studio della stabilit
à degli OPV, per caratterizzare la degradazione manifestata e individuarne
le cause.
Questo elaborato presenta un'indagine sistematica sulla stabilità di celle solari
organiche con materiale attivo costituito dalla miscela di un polimero
con un derivato del fullerene. Numerosi campioni sono stati preparati e invecchiati
in diverse condizioni, per poter analizzare gli e etti provenienti
dai singoli fattori di stress. In particolare, si sono studiati i danni causati
dall'aria, dall'alta temperatura, e dalla luce.The constant search for e cient sustainable energy sources also triggered the
development of new photovoltaic technologies. Solar cells employing organic
semiconductors have been demonstrated roughly 30 years ago and since then
their power conversion e ciency has signi cantly increased.
Although the performances of Organic PhotoVoltaics (OPVs) approach the
required 10% for their market introduction, their limited stability represents
one of the challenges of this new technology.
Commercial applications require device lifetimes of several years, which were
only demonstrated on few laboratory devices.
During operation, modules are exposed to long hours of solar illumination,
from Ultra Violet radiation to Infra Reds, the latter inducing a raise in temperature
that can potentially harm the devices. Meanwhile, the solar cells
need to be protected from oxidizing agents that can penetrate from the atmosphere.
This requires the use of packaging that can constitute a large part
of the nal cost of the module.
All these factors acting on the operating devices contribute to degradation.
It is important to understand the nature of the degradation mechanisms taking
place, in order to act against it, and prolong device lifetimes.
We propose a systematic study on the stability of organic solar cells with
an inverted architecture. This architecture employs the transparent electrode
as electron extracting contact. This architecture proved to be highly
stable in air, thus it represents an interesting approach for further lifetime
testing.
We prepared a large amount of samples employing a polymer:fullerene blend
as active layer, and we aged them in di erent environments to observe their
failure mechanisms.
Since ambient atmosphere, temperature and light are the main stress factors
for our devices, we investigated their independent e ect on a variety of
cells employing di erent photo-active blends and top contact materials. This
comparison allows us to investigate the origin of the degradation as well as
to propose improvements towards better device stability
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