Some Results of the Educational Experiment APIS (Cervantes Mission on Board ISS)

Some results of the analysis of the pictures taken along the performance of the Análisis de Propiedades Inerciales de Sólidos, Analysis of the Inertia Properties of Solid Bodies (APIS) experiment carried out in the Cervantes mission on board ISS, are presented. APIS was an educational experiment devoted to take advantage of the unique conditions of absence of relative gravity forces of a space platform such as ISS, to show some of the characteristics of the free rotational motion of a solid body, which are impossible to carry out on earth. This field of experimental research has application to aerospace engineering science (e.g. attitude control of spacecrafts), to astrophysical sciences (e.g. state of rotation and tumbling motions of asteroids) and to engineering education. To avoid the effect of the ambient atmosphere loads on the motion, the test body is placed inside a sphere, which reduces the effect of the aerodynamic forces to just friction. The drastic reduction of the effect of the surrounding air during the short duration of the experimental sequences allows us to compare the actual motion with the known solutions for the solid body rotation in vacuum. In this paper, some selected, relevant sequences of the sphere enclosing a body with a nominal cylindrical inertia tensor, put into rotation by the astronaut, are shown; the main problems to extract the information concerning the characteristic parameters of the motion are outlined, and some of the results obtained concerning the motion of the test probe are included, which show what seems to be a curious and unexpected solution of the Euler equations for the solid body rotation in vacuum, without energy dissipation, when the angular momentum is almost perpendicular to the axisymmetry axis

Creep curve measurement to support wear and adhesion modelling, using a continuously variable creep twin disc machine

Predictive modelling of wear and adhesion at rolling-sliding contacts such as a railway rail and wheel depends on understanding the relationship between slip and shear force at the contact surface, i.e. the creep verses force curve. This paper describes a new approach to creep curve measurement using a twin disc machine running with a continuous programmed variation of creep, enabling an entire creep curve to be defined in a single experiment. The work focuses on very low levels of creep, ranging from zero to 1%, and shows clear correlation between the creep curve gradient and the full slip friction coefficient for dry and lubricated contacts. Comparison of data generated using the new approach with that generated using multiple tests each at a single creep level shows good agreement. Comparison is also made between the twin disc data and results for full size three dimensional rail-wheel contacts to examine how two and three dimensional contact adhesion data are related. The data generated has application in wear and rolling contact fatigue modelling, but the original motivation for the research was generation of creep curves to support prediction of low adhesion conditions at the rail-wheel interface based upon monitored running conditions prior to brake application. The range of contact conditions investigated includes those experienced in service and during driver training, with the correlation found between creep curve gradient (measurable prior to braking) and full slip friction coefficient (not measurable until brakes are applied) representing a key finding

Aplicação de silício, em hidroponia, na conservação pós-colheita de alface americana 'Lucy Brown' minimamente processada

Este trabalho teve por objetivo verificar o efeito da aplicação de silício em hidroponia na conservação pós-colheita de alface americana 'Lucy Brown' minimamente processada. As alfaces foram cultivadas hidroponicamente e a fonte de silício utilizada foi o silicato de potássio nas concentrações de 0; 28; 56; e 84mg L-1. Após a colheita, as folhas selecionadas foram lavadas em água corrente, semiprocessadas mediante o corte de 20mm de largura e sanitizadas por imersão em Sumaveg(r). Estas foram centrifugadas manualmente e acondicionadas em sacos de polipropileno, que, posteriormente, foram selados e armazenados a 3ºC e 85±3% de umidade relativa (UR). Durante 16 dias de armazenamento, foram avaliadas a cada quatro dias e em triplicata, a composição gasosa, a firmeza, o teor de clorofila e de acidez titulável, as atividades das enzimas polifenoloxidase e peroxidase e as análises microbiológicas. Até o 4odia de armazenamento, observaram-se reduções nos níveis de O2para todos os tratamentos, no entanto, para os níveis de CO2, houve aumentos percentuais de 5% no tratamento com 28mg L-1de silício. As maiores concentrações de silício mantiveram maior firmeza das folhas. Os teores de clorofila total se mantiveram estáveis durante o período de armazenamento. A atividade da enzima polifenoloxidase reduziu até o 8° dia. A atividade da peroxidase apresentou aumento durante o período avaliado, na concentração de 84mg L-1de silício. A contagem microbiana de coliformes termotolerantes e totais manteve-se baixa durante o armazenamento. A concentração de 84mg L-1de silício propiciou maior firmeza das folhas das alfaces minimamente processadas, deixando-as mais túrgidas e conservando sua vida útil por 16 dia

Meteoroid Orbits Available from the IAU Meteor Data Center

Since it was founded early in the 1980′s, the IAU Meteor Data Center (IAU MDC) has accumulated a large number of the meteoroid orbits measured worldwide so as to make these freely available to all interested researchers. The total number of orbits available is about 68,000, of which about 6,000 were determined using optical techniques (photographic or TV), the bulk having been detected using decameter radars. The observation sites range from various locations in the U.S.A., Canada, Australia, and in the former Soviet Union and Czechoslovakia; radar orbits from the Soviet Equatorial Expedition to Somalia are also archived. About 39,000 of the 62,000 radar orbits are derived from the Harvard Radar Meteor Project. Most of these programs were carried out during the 1960's and 1970′s, but still represent our best knowledge of the orbital distribution of interplanetary particles in the size range from 100 μm to 1 meter. A new survey currently in progress in New Zealand has so far rendered over 350,000 orbits, and it is anticipated that these will soon become available through the IAU MDC. Presently the 68,000 orbits archived in the IAU MDC are only available on magnetic recording media, but it is planned that they will shortly be made accessible via anonymous ftp.</jats:p

No Meteor Storms Expected from P/Machholz 2

AbstractP/1994 P1 Machholz 2 is the first Earth-crossing shortperiod comet to have been observed to have split since 3D/Biela about 150 years ago, and that fragmentation resulted in the Andromedid meteor storms of 1872 and 1885. Thus a pertinent question is whether meteor storms might result from P/Machholz 2 in the foreseeable future. Here we integrate its orbit to ascertain when the node might next occur near a heliocentric distance of 1 AU, and find that this is not anticipated far over 1000yr, although some meteor activity in ∽300yr is possible. On such time-scales the recently-released debris will have dispersed, so that meteor storms are not expected from this comet. </jats:p

When Might 2P/Encke Have Produced Meteor Storms?

Abstract2P/Encke is the only Earth-crossing short-period comet to have a meteoroid/dust trail identified in the data collected by IRAS Such trails have been suggested by Kresák to be the cause of meteor storms, these occurring when the comet/trail node is near 1 AU and the Earth happens to pass through the trail. Here we present the results of integrations of variational orbits of 2P/Encke (the differences in the assumed initial semi-major axes representing the order of changes that could occur due to non-gravitational effects) from which we derive indications of when this comet may have produced meteor storms in the past. Pairs of sets of storms are expected about 300 yr apart, but the effects of chaotic dynamical evolution (and our ignorance of 2P/Encke's non-gravitational forces for any but the last two centuries) mean that we cannot define the epochs in which these may have occurred to better than 200 BC to AD 500 for the last pair, and 3600 to 1800 BC for the previous pair. Looking forwards in time, no meteor storm due to 2P/Encke will occur for at least 600 yr.</jats:p

Meteoroid Orbits Determined by Southern Hemisphere Radar

AbstractA radar meteor orbit facility of novel design has been developed at the University of Canterbury. Synchronous digital noise averaging,impulse suppression and meteor echo recognition using a microprocessor system, along with high gain antennas, allow a limiting radar magnitude of about +13 to be achieved, making this the most sensitive meteor orbit radar to’ date. An exhaustive survey of faint sporadic meteors will be carried out, along with an investigation of the little-known Southern showers. Since the observatory is ideally located with respect to the Eta Aquarid radiant, a programme of observations during the Comet Halley perihelion epoch is planned.</jats:p