1,720,965 research outputs found
Measurement of 5-eV atomic oxygen using carbon-based films: preliminary results
Full text linkCarbon-based sensors have been developed to measure the atmospheric neutral atomic oxygen (AO) flux experienced by spacecraft in low Earth orbit. Thin- and thick-film carbon sensor elements were deposited onto an alumina substrate between thick-film gold tracks and silver palladium solder pads. AO flux is deduced by measuring resistance changes as the carbon film erodes and applying a simple theory. A wide range of responses were observed that are dependent on the deposition process and post deposition annealing. The deposition methods used were dc magnetron sputtering, e-beam evaporation, and screen-printing. The sensors tested compare favorably with similar silver-based sensors that have been flown previously on small satellite missions with significant mass/power constraints
Screen printed carbon sensors for atomic oxygen measurement
No full textCarbon-based atomic oxygen actinometers sensors were produced by screen-printing high and low carbon inks onto an alumina substrate between thick film gold tracks and palladium contacts. The performance of the sensors was evaluated by exposure to atomic oxygen in a plasma asher and a pulsed laser facility (ATOX) and compared with that of evaporated and sputtered thin film carbon sensors. All three types of sensor exhibited linear resistance increase with fluence and demonstrated sensitivity to flux change. The lower erosion yield and greater thickness makes the screen-printed sensors more suitable for high fluence/long duration missions
Carbon-based atomic oxygen sensors
No full textCarbon-based sensors have been developed to measure the atmospheric neutral atomic oxygen (AO) flux experienced by spacecraft in low Earth orbit (LEO). Thick- and thin film carbon sensor elements were deposited on an alumina substrate between thick film gold tracks and silver palladium solder pads. AO flux is deduced by measuring resistance changes as the carbon film erodes, and applying a simple theory. Measured resistance increases during exposure in a ground-based AO facility compare favourably with theoretical predictions. These sensors appear to offer a number of advantages compared with similar silver-based sensors that have been flown previously, particularly for small satellite missions with significant mass/power constraints
LEO atomic oxygen measurements: experiment design and preliminary results
No full textRecently two University of Southampton flight experiments intended to measure the LEO atomic oxygen (AO) flux or fluence have been launched. The first forms part of the Southampton Transient Oxygen and Radiation Monitor (STORM) instrument package that is included as part of the European Materials Exposure and Degradation Experiment on EuTEF (MEDET) module now residing on the external pay load facility of the Columbus laboratory on the International Space Station (ISS). The atomic oxygen detectors on STORM comprise screen-printed thick films of a carbon-polymer resistive ink and also thin sputtered films of zinc oxide. The second is a relatively simple experiment package comprising thick-film carbon-polymer sensors similar to those on STORM; this experiment is currently being flown on the Canadian CanX-2 nano-satellite mission. The design and mode of operation of both types of AO sensor will be described and the current status of both of these experiments will be reviewed
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
Development of small reliable atomic oxygen sensors of polymeric filled carbon resistor compositions
No full textThe development of carbon-based sensors for the measurement of atomic oxygen
No full textThis paper describes preliminary results of atomic oxygen (AO) exposures on a variety of carbon-based films and assesses their suitability for sensing atomic oxygen in low Earth orbit (LEO), by means of actinometry (measurement of film electrical resistance). Atomic oxygen exposures were carried out using the ESA-ESTEC ATOX pulsed atomic oxygen facility to energies of 5ev (~8km/s) with fluences of up to 7.9 x10^19 atoms/cm2. The carbon types exposed were electron beam (e-beam) vacuum evaporated and d.c magnetron sputtered carbon. Raman and X-ray photoelectron spectroscopy techniques have so far been used to characterise the carbon
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
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