14,094 research outputs found
Short period eclipsing binary candidates identified using SuperWASP
We present light curves and periods of 53 candidates for short period eclipsing binary stars identified by SuperWASP. These include 48 newly identified objects with periods <2 × 10^4 s (~0.23 d), as well as the shortest period binary known with main sequence components (GSC2314–0530 = 1SWASP J022050.85 + 332047.6) and four other previously known W UMa stars (although the previously reported periods for two of these four are shown to be incorrect). The period distribution of main sequence contact binaries shows a sharp cut-off at a lower limit of around 0.22 d, but until now, very few systems were known close to this limit. These new candidates will therefore be important for understanding the evolution of low mass stars and to allow investigation of the cause of the period cut-off
Modulation and heliocentric gradient of low energy cosmic rays near solar minimum, 1965
Modulation and heliocentric gradient of low energy cosmic rays near solar minimum, 196
A survey of the total radiation in space observed by the OGO satellites, 5 September 1964 - 27 May 1968
Graphical and tabular summaries of ionization rates in space recorded by OGO spacecraft ion chamber
Planar motion of a human being under the action of a body-fixed thrust
Weightless astronaut maneuvering device for directional and attitude control feasibility study using two body system equations of motio
Experimental investigation of planar motions of a human being under the action of a body- fixed thrust
Planar motion of human being subjected to action of body-fixed forc
Elevated temperature deformation of thoria dispersed nickel-chromium
The deformation behavior of thoria nickel-chromium (TD-NiCr) was examined over the temperature range 593 C (1100 F) to 1260 C (2300 F) in tension and compression and at 1093 C (2000 F) in creep. Major emphasis was placed on: (1) the effects of the material and test related variables (grain size, temperature, stress and strain rate) on the deformation process; and (2) the evaluation of single crystal TD-NiCr material produced by a directional recrystallization process. Elevated temperature yield strength levels and creep activation enthalpies were found to increase with increasing grain size reaching maximum values for the single crystal TD-NiCr. Stress exponent of the steady state creep rate was also significantly higher for the single crystal TD-NiCr as compared to that determined for the polycrystalline materials. The elevated temperature deformation of TD-NiCr was analyzed in terms of two concurrent, parallel processes: diffusion controlled grain boundary sliding, and dislocation motion
Influence of crystal structure on charge carrier effective masses in BiFeO
Ferroelectric-based photovoltaics have shown great promise as a source of
renewable energy, thanks to their in-built charge separation capability, yet
their efficiency is often limited by low charge carrier mobilities. In this
work, we compare the photovoltaic prospects of various phases of the
multiferroic material BiFeO by evaluating their charge carrier effective
masses using first-principles simulations. We identify a tetragonal phase with
the promising combination of a large spontaneous polarisation and relatively
light charge carriers. From a systematic study of the octahedral distortions
present in BiFeO, we explain the relationship between structure and
effective masses in terms of the changes to the orbital character and overlap
at the band edges that result from changes in the geometry. The findings in
this study provide some design principles to engineer desired effective masses
in BiFeO and similar materials through manipulation of their crystal
structures in experimentally accessible ways.Comment: 12 pages, 10 figure
Description of data plots from the University of Minnesota ion chamber and electron spectrometer on OGO-1 and OGO-3
Data plots obtained from ion chamber and electron spectrometer experiments aboard OGO A and OGO C satellite
Simulations for Multi-Object Spectrograph Planet Surveys
Radial velocity surveys for extra-solar planets generally require substantial
amounts of large telescope time in order to monitor a sufficient number of
stars. Two of the aspects which can limit such surveys are the single-object
capabilities of the spectrograph, and an inefficient observing strategy for a
given observing window. In addition, the detection rate of extra-solar planets
using the radial velocity method has thus far been relatively linear with time.
With the development of various multi-object Doppler survey instruments, there
is growing potential to dramatically increase the detection rate using the
Doppler method. Several of these instruments have already begun usage in large
scale surveys for extra-solar planets, such as FLAMES on the VLT and Keck ET on
the Sloan 2.5m wide-field telescope.
In order to plan an effective observing strategy for such a program, one must
examine the expected results based on a given observing window and target
selection. We present simulations of the expected results from a generic
multi-object survey based on calculated noise models and sensitivity for the
instrument and the known distribution of exoplanetary system parameters. We
have developed code for automatically sifting and fitting the planet candidates
produced by the survey to allow for fast follow-up observations to be
conducted. The techniques presented here may be applied to a wide range of
multi-object planet surveys.Comment: 15 pages, 10 figures, accepted for publication in MNRA
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