24,018 research outputs found
DSIF station schedules
System manages Deep Space Instrumentation Facilities /DSIF/ equipment construction and modification planning. Versatile program applies to such tasks as employee time and task schedules, pay schedules, operations schedules, and plant and equipment procurement, construction, modification or service
Gravity from the extension of spatial diffeomorphisms
The possibility of the extension of spatial diffeomorphisms to a larger
family of symmetries in a class of classical field theories is studied. The
generator of the additional local symmetry contains a quadratic kinetic term
and a potential term which can be a general (not necessarily local) functional
of the metric. From the perspective of the foundation of Einstein's gravity our
results are positive: The extended constraint algebra is either that of
Einstein's gravity, or ultralocal gravity. If our goal is a simple modification
of Einstein's gravity that for example makes it perturbatively renormalizable,
as has recently been suggested, then our results show that there is no such
theory within this class.Comment: 34 page
The relationships between high latitude convection reversals and the energetic particle morphology observed by the Atmosphere Explorer
Simultaneous measurements of the auroral zone particle precipitation and the ion convection velocity by Atmosphere Explorer show a consistent difference between the location of the poleward boundary of the auroral particle precipitation and the ion convection reversal. The difference of about 1.5 degrees of invariant latitude is such that some part of the antisunward convection lies wholly within the auroral particle precipitation region. The nature of the convection reversals within the precipitation region suggests that in this region the convection electric field is generated on closed field lines that connect in the magnetosphere to the low latitude boundary layer
Inferring the three-dimensional distribution of dust in the Galaxy with a non-parametric method: Preparing for Gaia
We present a non-parametric model for inferring the three-dimensional (3D)
distribution of dust density in the Milky Way. Our approach uses the extinction
measured towards stars at different locations in the Galaxy at approximately
known distances. Each extinction measurement is proportional to the integrated
dust density along its line-of-sight. Making simple assumptions about the
spatial correlation of the dust density, we can infer the most probable 3D
distribution of dust across the entire observed region, including along sight
lines which were not observed. This is possible because our model employs a
Gaussian Process to connect all lines-of-sight. We demonstrate the capability
of our model to capture detailed dust density variations using mock data as
well as simulated data from the Gaia Universe Model Snapshot. We then apply our
method to a sample of giant stars observed by APOGEE and Kepler to construct a
3D dust map over a small region of the Galaxy. Due to our smoothness constraint
and its isotropy, we provide one of the first maps which does not show the
"fingers of god" effect.Comment: Minor changes applied. Final version accepted for publication in A&A.
15 pages, 17 figure
Persistent Homology in Sparse Regression and its Application to Brain Morphometry
Sparse systems are usually parameterized by a tuning parameter that
determines the sparsity of the system. How to choose the right tuning parameter
is a fundamental and difficult problem in learning the sparse system. In this
paper, by treating the the tuning parameter as an additional dimension,
persistent homological structures over the parameter space is introduced and
explored. The structures are then further exploited in speeding up the
computation using the proposed soft-thresholding technique. The topological
structures are further used as multivariate features in the tensor-based
morphometry (TBM) in characterizing white matter alterations in children who
have experienced severe early life stress and maltreatment. These analyses
reveal that stress-exposed children exhibit more diffuse anatomical
organization across the whole white matter region.Comment: submitted to IEEE Transactions on Medical Imagin
Decomposition of NO studied by infrared emission and CO laser absorption
A diagnostic technique for monitoring the concentration of NO using absorption of CO laser radiation was developed and applied in a study of the decomposition kinetics of NO. Simultaneous measurements of infrared emission by NO at 5.3 microns were also made to validate the laser absorption technique. The data were obtained behind incident shocks in NO-N2O-Ar (or Kr) mixtures, with temperatures in the range 2400-4100 K. Rate constants for dominant reactions were inferred from comparisons with computer simulations of the reactive flow
Basic linear algebra subprograms for FORTRAN usage
A package of 38 low level subprograms for many of the basic operations of numerical linear algebra is presented. The package is intended to be used with FORTRAN. The operations in the package are dot products, elementary vector operations, Givens transformations, vector copy and swap, vector norms, vector scaling, and the indices of components of largest magnitude. The subprograms and a test driver are available in portable FORTRAN. Versions of the subprograms are also provided in assembly language for the IBM 360/67, the CDC 6600 and CDC 7600, and the Univac 1108
Buildings and users with visual impairment::uncovering factors for accessibility using BIT-Kit
In this paper, we report on the experiences of visually impaired users in navigating buildings. We focus on an investigation of the way-finding experiences by 10 participants with varying levels of visual ability, as they undertook a way-finding task in an unfamiliar public building. Through applying the BIT-Kit framework in this preliminary user study, we were able to uncover 54 enabling and disabling interactions within the case study building. While this building adhered to building legislation, our findings identified a number of accessibility problems including, issues associated with using doors, hazards caused by building finishes, and difficulty in knowing what to do in the case of an emergency evacuation. This user study has demonstrated a disparity between design guidance and the accessibility needs of building users. It has uncovered evidence to enable architects to begin to design for the real needs of users who have a range of visual impairment. Furthermore, it has instigated discussion of how BIT-Kit's evidence could be incorporated into digital modelling tools currently used in architectural practice
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