3,185 research outputs found
Attitude-referenced radiometer study. Part 2: Primary calibration system
A primary calibration system, PCS, for infrared radiometers has been developed, built, and tested. The system allows radiometers to be calibrated with less than 1 percent error for use in earth coverage horizon measurements, earth resources surveys, and synoptic meteorological measurement. The final design, fabrication and test of the PCS are reported. A detailed description of the PCS construction is presented, along with the results of a complete series of functional tests. Test to verify the source thermal characteristics, collimator reflectance, and output beam characteristics are described and their results presented
Searching for additional heating - [OII] emission in the diffuse ionized gas of NGC891, NGC4631 and NGC3079
We present spectroscopic data of ionized gas in the disk--halo regions of
three edge-on galaxies, NGC 891, NGC 4631 and NGC 3079, covering a wavelength
range from [\ion{O}{2}] 3727\AA to [\ion{S}{2}] 6716.4\AA.
The inclusion of the [\ion{O}{2}] emission provides new constraints on the
properties of the diffuse ionized gas (DIG), in particular, the origin of the
observed spatial variations in the line intensity ratios. We used three
different methods to derive electron temperatures, abundances and ionization
fractions along the slit. The increase in the [\ion{O}{2}]/H line ratio
towards the halo in all three galaxies requires an increase either in electron
temperature or in oxygen abundance. Keeping the oxygen abundance constant
yields the most reasonable results for temperature, abundances, and ionization
fractions. Since a constant oxygen abundance seems to require an increase in
temperature towards the halo, we conclude that gradients in the electron
temperature play a significant role in the observed variations in the optical
line ratios from extraplanar DIG in these three spiral galaxies.Comment: 43 pages, 29 figure
Computer Self-Efficacy, Digital Learners, and Completion Rates in the California Community College System
The importance of online learning in higher education has increased considerably over the last two decades. As a result, online learning has become an important area of research. The purpose of the study was to examine if higher levels of computer self-efficacy (CSE) contributed to online course completion among online California community college students. Guided by Bandura’s (1977) work on self-efficacy and the work of Compeau and Higgins (1995) and Howard (2014) on computer self-efficacy, this study revealed that there is no relationship between high levels of CSE and successful completion of the course. A judgement sample was used to select five online sections from a northern California community college in which 122 students participated. These students completed a Computer User Self-efficacy questionnaire which consisted of 12 questions on a six-point Likert scale as well as three questions regarding their perceived use of computers. Spearman’s Correlation Coefficient was conducted to see if a relationship existed between high levels of computer self-efficacy and course grades. The results showed that there was no statistically significant relationship between high levels of computer self-efficacy and course grades. The implication of this study suggests that computer self-efficacy may not be an important factor for today’s digital learner
Computer Self-Efficacy, Digital Learners, and Completion Rates in the California Community College System
The importance of online learning in higher education has increased considerably over the last two decades. As a result, online learning has become an important area of research. The purpose of the study was to examine if higher levels of computer self-efficacy (CSE) contributed to online course completion among online California community college students. Guided by Bandura’s (1977) work on self-efficacy and the work of Compeau and Higgins (1995) and Howard (2014) on computer self-efficacy, this study revealed that there is no relationship between high levels of CSE and successful completion of the course. A judgement sample was used to select five online sections from a northern California community college in which 122 students participated. These students completed a Computer User Self-efficacy questionnaire which consisted of 12 questions on a six-point Likert scale as well as three questions regarding their perceived use of computers. Spearman’s Correlation Coefficient was conducted to see if a relationship existed between high levels of computer self-efficacy and course grades. The results showed that there was no statistically significant relationship between high levels of computer self-efficacy and course grades. The implication of this study suggests that computer self-efficacy may not be an important factor for today’s digital learner
Catching GRBs with atmospheric Cherenkov telescopes
Fermi has shown GRBs to be a source of >10 GeV photons. We present an
estimate of the detection rate of GRBs with a next generation Cherenkov
telescope. Our predictions are based on the observed properties of GRBs
detected by Fermi, combined with the spectral properties and redshift
determinations for the bursts population by instruments operating at lower
energies. While detection of VHE emission from GRBs has eluded ground-based
instruments thus far, our results suggest that ground-based detection may be
within reach of the proposed Cherenkov Telescope Array (CTA), albeit with a low
rate, 0.25 - 0.5/yr. Such a detection would help constrain the emission
mechanism of gamma-ray emission from GRBs. Photons at these energies from
distant GRBs are affected by the UV-optical background light, and a
ground-based detection could also provide a valuable probe of the Extragalactic
Background Light (EBL) in place at high redshift.Comment: 4 pages, 3 figures, to appear in the Proceedings of "Gamma Ray Bursts
2010", held Nov. 1-4, 2010 in Annapolis, M
Word Adjacency Graph Modeling: Separating Signal From Noise in Big Data
There is a need to develop methods to analyze Big Data to inform patient-centered interventions for better health outcomes. The purpose of this study was to develop and test a method to explore Big Data to describe salient health concerns of people with epilepsy. Specifically, we used Word Adjacency Graph modeling to explore a data set containing 1.9 billion anonymous text queries submitted to the ChaCha question and answer service to (a) detect clusters of epilepsy-related topics, and (b) visualize the range of epilepsy-related topics and their mutual proximity to uncover the breadth and depth of particular topics and groups of users. Applied to a large, complex data set, this method successfully identified clusters of epilepsy-related topics while allowing for separation of potentially non-relevant topics. The method can be used to identify patient-driven research questions from large social media data sets and results can inform the development of patient-centered interventions
Exploring the phase diagram of the two-impurity Kondo problem
A system of two exchange-coupled Kondo impurities in a magnetic field gives
rise to a rich phase space hosting a multitude of correlated phenomena.
Magnetic atoms on surfaces probed through scanning tunnelling microscopy
provide an excellent platform to investigate coupled impurities, but typical
high Kondo temperatures prevent field-dependent studies from being performed,
rendering large parts of the phase space inaccessible. We present an integral
study of pairs of Co atoms on insulating Cu2N/Cu(100), which each have a Kondo
temperature of only 2.6 K. In order to cover the different regions of the phase
space, the pairs are designed to have interaction strengths similar to the
Kondo temperature. By applying a sufficiently strong magnetic field, we are
able to access a new phase in which the two coupled impurities are
simultaneously screened. Comparison of differential conductance spectra taken
on the atoms to simulated curves, calculated using a third order transport
model, allows us to independently determine the degree of Kondo screening in
each phase.Comment: paper: 14 pages, 4 figures; supplementary: 3 pages, 1 figure, 1 tabl
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