Probability distributions of link durations with n disruptive channels: application to ground-space optical communications

We consider n independent disruptive channels with random availability periods and make use of channel diversity to maintain a link as often as possible. This situation arises when an optical link is to be maintained between a spacecraft and n ground stations affected by cloud coverage. Statistical independence between the stations and equal (un)availability duration distributions are assumed. Based on a given single-station (un)availability duration distribution, we derive analytically the network (un)availability duration distributions. Also derived is the distribution of the station operation duration within a network. Derived expressions allow evaluating the increase of the continuous operation duration of a station and the decrease of the network unavailability durations. © (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

mypoliticalspace – Making Politics Visible through Web 2.0

Web 2.0 is one of the later innovations in Internet-related developments. The term expresses less a new piece of technology but more new ways of using the Net; weblogs and social networks like myspace are among the most prominent examples of Web 2.0. Its catchphrase may be: you control your own data. Web 2.0 gimmicks bear new possibilities for young people, which are the heaviest users of the Internet, not only to get political information, but also to show and share their views and opinions. It also gives politicians a way of presenting themselves without any interference. In both ways it can contribute to a process of making politics visible. Besides assessing some data about political Internet usage the article tries to show some opportunities as well as problems related to making politics visible in Web 2.0

Politische Fernsehnachrichten im Vergleich: eine Inhaltsanalyse der Informationssendungen von ORF, ATVplus und ProSieben Austria

'Seit Anfang 2004 gibt es in Österreich neben der Zeit im Bild des ORF noch zwei weitere österreichische Fernseh-Nachrichtensendungen: ATVplus Aktuell und die ProSieben Austria Top News treten (werk-) täglich in Konkurrenz zur ZiB 1. Der Vergleich dieser drei voneinander unabhängigen TV-Nachrichten bietet sich auch unter dem Gesichtspunkt an, dass sich nun Sendungen einer öffentlich-rechtlichen Anstalt und von zwei privaten Anbietern gegenüberstehen. Der vorliegende Text fasst einige Ergebnisse einer Inhaltsanalyse der drei Sendungen zusammen, die von September bis Oktober 2004 und von Mai bis Juni 2005 durchgeführt wurde. Zentrale Fragestellung war, ob und wie sich Form und Inhalt der Nachrichten unterscheiden - besonders im Bereich der politischen Berichterstattung. Es zeigen sich insgesamt deutliche quantitative wie qualitative Unterschiede - einerseits im Hinblick auf Ausmaß und Inhalte der politischen Information, andererseits im Hinblick auf die Interpretation und Bewertung der Themen.' (Autorenreferat)'Since January 2004 there are three independent Austrian TV news broadcasts: Zeit im Bild, ATV-plus Aktuell and ProSieben Austria Top News. Taking advantage of this new situation the article summarizes the results of a content analysis of there three broadcasts, conducted from September until October 2004 and from May until June 2005. The core research question was to investigate into differences concerning the formal presentation and topics of the news, focusing on political issues. The fact that a public broadcast station (ORF, broadcasting Zeit im Bild) faces two private broadcast stations (ATVplus and ProSieben Austria) made such differences very likely, especially considering the quantitative dimensions of political information and the interpretation of political issues.' (author's abstract)

Zahlen in der politischen Kommunikation: methodische Anmerkungen zu einer Inhaltsanalyse von TV-Debatten anlässlich der Nationalratswahl 2006

'Im September 2006 trafen im Studio des ORF (Österreichischen Rundfunks) an zwölf Abenden die Spitzenpolitiker der bei der Nationalratswahl kandidierenden Parteien aufeinander. Die TV-Diskussionen fanden ein Millionenpublikum vor den Bildschirmen und eine ausführliche Begleitberichterstattung in anderen Massenmedien. Ein nicht unwesentlicher Bestandteil der Debatten war das Argumentieren mit Zahlen und Statistiken. Der vorliegende Beitrag fasst einige methodische Aspekte einer Untersuchung zusammen, die sich mit diesen Zahlen im Kontext politischer Kommunikation beschäftigt hat, und weist auf Probleme, offene Fragen und Anregungen für weitere vergleichbare Studien hin.' (Autorenreferat)'In September 2006, candidates of the Austrian political parties met on twelve evenings, broadcasted by public Austrian TV, to discuss their agenda for the upcoming federal election. These discussions attracted an audience of more than a million people and were covered extensively by other mass media. Arguments based on numbers and statistics played a major role in those debates. The article summarizes some methodical aspects of an analysis focusing on numbers in the context of political communication and, in addition, refers to problems, open questions and recommendations for related studies.' (author's abstract)

Des conditions de l'innovation dans la formation des étudiants-professeurs

En 2019, Bernard et Fluckiger titrent en introduction : « Innovation technologique, innovation pédagogique : une relation riche et contrastée ». Ils mettent en exergue les discours injonctifs des pouvoirs publics. Pourtant, selon Cros (1997), l’innovation est « le poumon de l’école ». Dans ce contexte contrasté, nous proposons une approche systémique. D’abord, nous quantifions trois communications institutionnelles, révélateurs des objectifs de l’exosystème. Dans cet environnement prescriptif pouvant conduire au rejet, nous présentons ensuite un microsystème de formation destiné à des sujets : des étudiants-professeurs. Nous évaluons alors les productions des étudiants-professeurs à l’aide de critères observant l’innovation technopédagogique. Enfin, nous tentons de déterminer des contraintes et des leviers en formation autorisant l’innovation technopédagogique

Optimization of bricks production by earth hypercompaction prior to firing

This paper presents an innovative method for the production of masonry bricks, which combines earth compaction and quick firing at low temperatures. Earth bricks were manufactured according to three different methods, i.e. extrusion, standard Proctor compaction and hypercompaction to 100 MPa. All bricks were fired inside an electrical furnace by rising the temperature at a quick rate of about 9 °C per minute to 280, 455, 640, 825 and 1000 °C, after which the furnace was turned off and left to cool to the atmosphere with the brick inside it. These firing temperatures and times are significantly lower than those employed for the manufacture of commercial bricks, which are typically exposed to a maximum of 1100 °C for at least 10 hours (Brick Industry Association, 2006). A testing campaign was performed to investigate the effect of quick firing on the porosity, strength, water durability and moisture buffering capacity of the different bricks. Quick firing of hypercompacted bricks at moderate temperatures, between 455 and 640 °C, is enough to attain very high levels of compressive strength, between 29 and 34 MPa, with a good to excellent moisture buffering capacity. These properties are better than those of commercially available bricks. The strength of hypercompacted bricks further increases to 53 MPa, a value similar to that of high-strength concrete, after quick firing at 825 °C. Earth densification prior to thermal treatment therefore improves material performance while enabling a significant reduction of firing temperatures and times compared to current bricks production methods

A microstructural insight into the hygro-mechanical behaviour of a stabilised hypercompacted earth

The use of raw earth as construction material can save embodied and operational energy because of low processing costs and passive regulation of indoor ambient conditions. Raw earth must however be mechanically and/or chemically stabilised to enhance stiffness, strength and water durability. In this work, stiffness and strength are enhanced by compacting raw earth to very high pressures up to 100 MPa while water durability is improved by using alkaline solutions and silicon based admixtures. The effect of these stabilisation methods on hygro-mechanical behaviour is explored and interpreted in terms of the microstructural features of the material. Stiffness and strength are defined at different humidity levels by unconfined compression tests while the moisture buffering capacity is measured by humidification/desiccation cycles as prescribed by the norm ISO 24353 (Hygrothermal performance of building materials and products determination of moisture adsorption/desorption properties in response to humidity variation. International Organization for Standardization, Geneva, 2008). As for the microstructural characterisation, different tests (i.e. X-ray diffractometry, Infrared Spectroscopy, Mercury Intrusion Porosimetry, Nitrogen Adsorption) are performed to analyse the effect of stabilisation on material fabric and mineralogy. Results indicate that the use of alkaline activators and silicon based admixtures significantly improves water durability while preserving good mechanical and moisture buffering properties. Similarly, the compaction to very high pressures results in high levels of stiffness and strength, which are comparable to those of standard masonry bricks. This macroscopic behaviour is then linked to the microscopic observations to clarify the mechanisms through which stabilisation affects the properties of raw earth at different scales

Experimental contribution to the study of the physic-mechanical behavior and durability of high-performance concretes based on ternary binder (cement, silica fume and granulated blast furnace slag)

Le béton à hautes performances (BHP) est un béton innovant largement utilisé dans la construction moderne. De nouvelles techniques de formulation et de conception du HPC ont permis d'obtenir des performances mécaniques et une durabilité remarquables par rapport au béton conventionnel. Les principaux avantages du HPC sont liés à sa faible porosité, sa très haute résistance mécanique et son excellente durabilité. La facilité d'application du HPC est obtenue par l'utilisation combinée de superplastifiant et d'ajout de minéraux, ce qui se traduit par une augmentation significative de la résistance à la compression tout en améliorant la maniabilité et la durabilité. L'utilisation d'un liant ternaire (ciment, fumée de silice et laitier granulé de haut fourneau broyé) dans la fabrication du HPC est une nouvelle avancée dans la construction durable qui offre des avantages économiques, techniques et écologiques. L'objectif de ce travail de recherche était d'améliorer les propriétés physico-mécaniques du HPC à base de liant ternaire en étudiant l'influence du remplacement du ciment par du laitier granulé et des fumées de silice. Les résultats des tests mécaniques montrent que les performances du HPC réalisé avec ces liants ternaires sont similaires au HPC témoin sans laitier granulé. Enfin, il est conclu que l'utilisation de tels liants est très bénéfique pour diminuer les problèmes environnementaux et améliorer la durabilité du HPC

A coherent optical link through the turbulent atmosphere

We describe the realization of a 5 km free space coherent optical link through the turbulent atmosphere between a telescope and a ground target. We present the phase noise of the link, limited mainly by atmospheric turbulence and mechanical vibrations of the telescope and the target. We discuss the implications of our results for applications, with particular emphasis on optical Doppler ranging to satellites and long distance frequency transfer.Comment: version 2, modified following comments from colleagues and reviewer