6,420 research outputs found
Feasibility study of an optical radiometer for determining the composition of the Mars atmosphere from shock layer radiation during entry, volume II Final report
Optical radiometer feasibility study for determining composition of Mars atmosphere from shock layer radiation during entry - instrumentatio
Sea ice-atmosphere interaction: Application of multispectral satellite data in polar surface energy flux estimates
The application of multi-spectral satellite data to estimate polar surface energy fluxes is addressed. To what accuracy and over which geographic areas large scale energy budgets can be estimated are investigated based upon a combination of available remote sensing and climatological data sets. The general approach was to: (1) formulate parameterization schemes for the appropriate sea ice energy budget terms based upon the remotely sensed and/or in-situ data sets; (2) conduct sensitivity analyses using as input both natural variability (observed data in regional case studies) and theoretical variability based upon energy flux model concepts; (3) assess the applicability of these parameterization schemes to both regional and basin wide energy balance estimates using remote sensing data sets; and (4) assemble multi-spectral, multi-sensor data sets for at least two regions of the Arctic Basin and possibly one region of the Antarctic. The type of data needed for a basin-wide assessment is described and the temporal coverage of these data sets are determined by data availability and need as defined by parameterization scheme. The titles of the subjects are as follows: (1) Heat flux calculations from SSM/I and LANDSAT data in the Bering Sea; (2) Energy flux estimation using passive microwave data; (3) Fetch and stability sensitivity estimates of turbulent heat flux; and (4) Surface temperature algorithm
Electroweak form factors of heavy-light mesons -- a relativistic point-form approach
We present a general relativistic framework for the calculation of the
electroweak structure of heavy-light mesons within constituent-quark models. To
this aim the physical processes in which the structure is measured, i.e.
electron-meson scattering and semileptonic weak decays, are treated in a
Poincar\'e invariant way by making use of the point-form of relativistic
quantum mechanics. The electromagnetic and weak meson currents are extracted
from the 1- and 1--exchange amplitudes that result from a
Bakamjian-Thomas type mass operator for the respective systems. The covariant
decomposition of these currents provides the electromagnetic and weak
(transition) form factors. Problems with cluster separability, which are
inherent in the Bakamjian-Thomas construction, are discussed and it is shown
how to keep them under control. It is proved that the heavy-quark limit of the
electroweak form factors leads to one universal function, the Isgur-Wise
function, confirming that the requirements of heavy-quark symmetry are
satisfied. A simple analytical expression is given for the Isgur-Wise function
and its agreement with a corresponding front-form calculation is verified
numerically. Electromagnetic form factors for and and weak
-decay form factors are calculated with a simple
harmonic-oscilllator wave function and heavy-quark symmetry breaking due to
finite masses of the heavy quarks is discussed.Comment: 20 pages, 14 figure
Switched Control of Electron Nuclear Spin Systems
In this article, we study control of electron-nuclear spin dynamics at
magnetic field strengths where the Larmor frequency of the nucleus is
comparable to the hyperfine coupling strength. The quantization axis for the
nuclear spin differs from the static B_0 field direction and depends on the
state of the electron spin. The quantization axis can be switched by flipping
the state of electron spin, allowing for universal control on nuclear spin
states. We show that by performing a sequence of flips (each followed by a
suitable delay), we can perform any desired rotation on the nuclear spins,
which can also be conditioned on the state of the electron spin. These
operations, combined with electron spin rotations can be used to synthesize any
unitary transformation on the coupled electron-nuclear spin system. We discuss
how these methods can be used for design of experiments for transfer of
polarization from the electron to the nuclear spins
Elucidating the Species Limits and Range Boundaries of the African Yellow House Bats, Genus \u3cem\u3eScotophilus\u3c/em\u3e
Many of Kenya’s vesper bat species (Vespertilionidae) are weakly distinguished from one another, resulting in uncertainty with field and museum identification. These complexities set up Scotophilus as a case study for practical application of the Biological, Morphological, and Phylogenetic Species Concepts. Clear understanding of geographic variation is needed to apply currently available species names and, where needed, to propose new names. I analyzed variation in cranial morphology using geometric morphometric analysis and quantified pelage color variation in the African Yellow house bat genus Scotophilus to examine species limits and morphological overlap among populations. These analyses identify diagnostic characters and range boundaries for these species and clarify the application of existing names to Kenyan bats. The geometric morphometric and pelage analyses conducted here are a first step in untangling Scotophilus taxonomy, although more studies are needed to classify taxa sufficiently and accurately
Sea ice - atmosphere interaction: Application of multispectral satellite data in polar surface energy flux estimates
In the past six months, work has continued on energy flux sensitivity studies, ice surface temperature retrievals, corrections to Advanced Very High Resolution Radiometer (AVHRR) thermal infrared data, modelling of cloud fraction retrievals, and radiation climatologies. We tentatively conclude that the SSM/I may not provide accurate enough estimates of ice concentration and type to improve our shorter term energy flux estimates. SSM/I derived parameters may still be applicable in longer term climatological flux characterizations. We hold promise for a system coupling observation to a ice deformation model. Such a model may provide information on ice distribution which can be used in energy flux calculations. Considerable variation was found in modelled energy flux estimates when bulk transfer coefficients are modulated by lead fetch. It is still unclear what the optimum formulation is and this will be the subject of further work. Data sets for ice surface temperature retrievals were assembled and preliminary data analysis was started. Finally, construction of a conceptual framework for further modelling of the Arctic radiation flux climatology was started
Effect of a rotating propeller on the separation angle of attack and distortion in ducted propeller inlets
The present study represents an extension of an earlier wind tunnel experiment performed with the P&W 17-in. Advanced Ducted Propeller (ADP) Simulator operating at Mach 0.2. In order to study the effects of a rotating propeller on the inlet flow, data were obtained in the UTRC 10- by 15-Foot Large Subsonic Wind Tunnel with the same hardware and instrumentation, but with the propeller removed. These new tests were performed over a range of flow rates which duplicated flow rates in the powered simulator program. The flow through the inlet was provided by a remotely located vacuum source. A comparison of the results of this flow-through study with the previous data from the powered simulator indicated that in the conventional inlet the propeller produced an increase in the separation angle of attack between 4.0 deg at a specific flow of 22.4 lb/sec-sq ft to 2.7 deg at a higher specific flow of 33.8 lb/sec-sq ft. A similar effect on separation angle of attack was obtained by using stationary blockage rather than a propeller
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