11,581 research outputs found
Operational applications of NOAA-VHRR imagery in Alaska
Near-real time operational applications of NOAA satellite enhanced thermal infrared imagery to snow monitoring for river flood forecasts, and a photographic overlay technique of imagery to enhance snowcover are presented. Ground truth comparisons show a thermal accuracy of approximately + or - 1 C for detection of surface radiative temperatures. The application of NOAA imagery to flood mapping is also presented
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
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
A study of the break-up characteristics of Chena River Basin using ERTS imagery
The author has identified the following significant results. The Chena River Basin was selected because of the availability of ground truth data for comparison. Very good agreement for snow distribution and rates of ablation was found between the ERTS-1 imagery, the snowmelt model, and field measurements. Monitoring snowmelt rates for relatively small basins appears to be practical. The main limitation of the ERTS-1 imagery is the interval of coverage. More frequent overflights providing coverage are needed for the study of transient hydrologic events. ERTS-1 data is most useful when used in conjunction with snowmelt prediction models and existing snow course data. These results should prove very useful in preliminary assessment of hydrologic conditions in ungaged watersheds and will provide a tool for month-to-month volume forecasting
Break-up characteristics of the Chena River watershed, central Alaska
The author has identified the following significant results. The snow melt for a small watershed (5130 sq km) in Central Alaska was successfully monitored with ERTS-1 imagery. Aerial photography was used as supporting data for periods without satellite coverage. Comparison both with actual measurements and with a computer model showed good agreement
On the Frequency of Potential Venus Analogs from Kepler Data
The field of exoplanetary science has seen a dramatic improvement in
sensitivity to terrestrial planets over recent years. Such discoveries have
been a key feature of results from the {\it Kepler} mission which utilizes the
transit method to determine the size of the planet. These discoveries have
resulted in a corresponding interest in the topic of the Habitable Zone (HZ)
and the search for potential Earth analogs. Within the Solar System, there is a
clear dichotomy between Venus and Earth in terms of atmospheric evolution,
likely the result of the large difference ( factor of two) in incident
flux from the Sun. Since Venus is 95\% of the Earth's radius in size, it is
impossible to distinguish between these two planets based only on size. In this
paper we discuss planetary insolation in the context of atmospheric erosion and
runaway greenhouse limits for planets similar to Venus. We define a ``Venus
Zone'' (VZ) in which the planet is more likely to be a Venus analog rather than
an Earth analog. We identify 43 potential Venus analogs with an occurrence rate
(\eta_{\venus}) of and for M
dwarfs and GK dwarfs respectively.Comment: 6 pages, 3 figures, 2 tables. Accepted for publication in the
Astrophysical Journal Letters. More information and graphics can be found at
the Habitable Zone Gallery (http://hzgallery.org
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