1,625 research outputs found
Orbit determination and control for the European Student Moon Orbiter
No full textThis paper presents the preliminary navigation and orbit determination analyses for the European Student Moon Orbiter. The severe constraint on the total mission Delta nu and the all-day piggy-back launch requirement imposed by the limited available budget, led to the choice of using a low-energy transfer, more specifically a Weak Stability Boundary one, with a capture into an elliptic orbit around the Moon. A particular navigation strategy was devised to ensure capture and fulfil the requirement for the uncontrolled orbit stability at the Moon. This paper presents a simulation of the orbit determination process, based on an extended Kalman filter, and the navigation strategy applied to the baseline transfer of the 2011-2012 window. The navigation strategy optimally allocates multiple Trajectory Correction Manoeuvres to target a so-called capture corridor. The capture corridor is defined, at each point along the transfer, by back-propagating the set of perturbed states at the Moon that provides an acceptable lifetime of the lunar orbit. (C) 2012 Elsevier Ltd. All rights reserved
On the survivability and detectability of terrestrial meteorites on the moon
No full textMaterials blasted into space from the surface of early Earth may preserve a unique record of our planet's early surface environment. Armstrong et al. (2002) pointed out that such materials, in the form of terrestrial meteorites, may exist on the Moon and be of considerable astrobiological interest if biomarkers from early Earth are preserved within them. Here, we report results obtained via the AUTODYN hydrocode to calculate the peak pressures within terrestrial meteorites on the lunar surface to assess their likelihood of surviving the impact. Our results confirm the order-of-magnitude estimates of Armstrong et al. (2002) that substantial survivability is to be expected, especially in the case of relatively low velocity (ca. 2.5 km/s) or oblique (≤45°) impacts, or both. We outline possible mechanisms for locating such materials on the Moon and conclude that searching for them would be a scientifically valuable activity for future lunar exploration
Controlling the quantum effects and erbium-carrier interaction using Si/SiO2 superlattices
No full textEr3+ photoluminescence properties of erbium-doped Si/SiO2 superlattices with sub-nm thin Si layers
No full textPoe's biopics : representations of the author in D.W. Griffith's Edgar Allen Poe and James Mcteigue's The raven
No full textLiterary biopics often reinforce romantic images regarding the creative process, emphasizing biographic and author-centered approaches to literature previously denounced by Roland Barthes (1977). Curiously, one of the most famous critics of such romantic conceptions, Edgar Allan Poe, has himself been a victim of this very same treatment, his literary production being taken as part and result of his controversial biography in a number of works. This article analyzes two biographical films, or biopics, about the renowned poet, D.W. Griffith’s Edgar Allen Poe (sic) (1909) and James McTeigue’s The Raven (2012). The analysis of these works indicates that both reinforce the merge of the artist’s life and oeuvre, as well as the blurring of borders between fact and fiction, author and character, high and mass culture, thus contributing to the characterization of the biopic as a fitting example of historiographic metafiction. (Hutcheon, 1988).Cinebiografias literárias frequentemente reforçam visões românticas quanto ao fazer artístico, reiterando a visão biografista e a centralidade do autor há muito denunciadas por Roland Barthes (1977). Curiosamente, um dos mais célebres críticos de tais concepções românticas, Edgar Allan Poe, viu-se vítima desse mesmo tratamento ao ter sua produção literária apropriada como parte e reflexo de sua controversa biografia em diversas obras. O presente artigo debruça-se sobre dois filmes biográficos, ou biopics, acerca do célebre poeta, Edgar Allen Poe (sic), de D.W. Griffith (1909), e O Corvo, de James McTeigue (2012). A análise das obras aponta que ambas reiteram a fusão entre vida e obrado artista, bem como o apagamento das fronteiras entre fato histórico e ficção, entre autor e personagem, alta cultura e cultura de massa, contribuindo para a caracterização do gênero biopic como um dos mais bem-acabados exemplos de metaficção historiográfica (Hutcheon, 1988)
Riparian Conveyances on Delaware River in and near Trenton County of Mercer from records of the former Riparian Commission State of New Jersey
No full textMap covers area from Lalor Street to Bridge Street along the Delaware River including Moon Island.
Map shows the grants on the Delaware River such as the grants to the city of Trenton, D.W. Lenox, American Bridge Company, the United New Jersey R.R. and Canal Co., and others
Use of orbiting reflectors to decrease the technological challenges of surviving the lunar night
No full textIn this paper the feasibility of using lunar reflectors to decrease the technological challenges of surviving the lunar night is investigated. This is achieved by attempting to find orbits in the two-body problem where the argument of periapsis is constantly Sun-pointing to maximise the time spent by the reflectors over the night-side of the Moon. Using these orbits the ability of reflectors of varying sizes to provide sufficient illumination to a target point on the surface is determined for scenarios where a latitude band is constantly illuminated and a scenario where a specific point is tracked. The optimum masses required for these far-term scenarios are large. However, a nearer-term scenario using low altitude orbits suggest that the effective duration of the lunar night can be reduced by up to 50% using a set of 300 parabolic reflectors of 100m radius with a total system mass of 370 tonnes. A system is also demonstrated that will allow a partial illumination of the craters in the Moon’s polar region for a mass up to 700kg
Author Correction:A cattle graph genome incorporating global breed diversity
No full textThe original version of this Article omitted from the author list the 12th and 13th authors Dennis Muhanguzi and Wilson Amanyire, who are from the ‘School of Biosecurity, Biotechnology and Laboratory Sciences (SBLS), College of Veterinary Medicine, Animal Resources and Biosecurity, Makerere University, P.O Box 7062, Kampala, Uganda’. Consequently, the final sentence of the Author Contributions incorrectly read ‘D.W., P.T., E.A.J.C., C.E., E.T.O., E.R.A., A. Tijjani, K.M., A.F., B.R.F., A.Q., U.C. and P.W. provided samples and expertise for the studies’. This has been replaced with ‘D.W., P.T., W.A., D.M., E.A.J.C., C.E., E.T.O., E.R.A., A. Tijjani, K.M., A.F., B.R.F., A.Q., U.C. and P.W. provided samples and expertise for the studies’. This has been corrected in both the PDF and HTML versions of the Article
Author Co-Citation Analysis (ACA): a powerful tool for representing implicit knowledge of scholar knowledge workers
No full textIn the last decade, knowledge has emerged as one of the most important and valuable organizational assets. Gradually this importance caused to emergence of new discipline entitled ―knowledge management‖. However one of the major challenges of knowledge management is conversion implicit or tacit knowledge to explicit knowledge. Thus Making knowledge visible so that it can be better accessed, discussed, valued or generally managed is a long-standing objective in knowledge management. Accordingly in this paper author co- citation analysis (ACA) will be proposed as an efficient technique of knowledge visualization in academia (Scholar knowledge workers)
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