4,149 research outputs found
Suggested hurricane operational scenario for GOES I-M
Improvements in tropical cyclone forecasts require optimum use of remote sensing capabilities, because conventional data sources cannot provide the necessary spatial and temporal data density over tropical and subtropical oceanic regions. In 1989, the first of a series of geostationary weather satellites, GOES 1-M, will be launched with the capability for simultaneous imaging and sounding. Careful scheduling of the GOES 1-M will enable measurements of both the wind and mass fields over the entire tropical cyclone activity area. The document briefly describes the GOES 1-M imager and sounder, surveys the data needs for hurricane forecasting, discusses how geostationary satellite observations help to meet them, and proposes a GOES 1-M schedule of observations and hurricane relevant derived products
An improved cell-volume analyzer
Design and operation of cell-volume analyzer friction, glaze ice, and studded tire effects on highway
Non-Equilibrium Dynamics and Superfluid Ring Excitations in Binary Bose-Einstein Condensates
We revisit a classic study [D. S. Hall {\it et al.}, Phys. Rev. Lett. {\bf
81}, 1539 (1998)] of interpenetrating Bose-Einstein condensates in the
hyperfine states and of Rb and observe striking new non-equilibrium
component separation dynamics in the form of oscillating ring-like structures.
The process of component separation is not significantly damped, a finding that
also contrasts sharply with earlier experimental work, allowing a clean first
look at a collective excitation of a binary superfluid. We further demonstrate
extraordinary quantitative agreement between theoretical and experimental
results using a multi-component mean-field model with key additional features:
the inclusion of atomic losses and the careful characterization of trap
potentials (at the level of a fraction of a percent).Comment: 4 pages, 3 figures (low res.), to appear in PR
Towards the architecture of an instructional multimedia database
The applicability of multimedia databases in education may be extended if they can serve multiple target groups, leading to affordable costs per unit for the user. In this contribution, an approach is described to build generic multimedia databases to serve that purpose. This approach is elaborated within the ODB Project ('Instructional Design of an Optical DataBase'); the term optical refers to the use of optical storage media to hold the audiovisual components. The project aims at developing a database in which a hypermedia encyclopedia is combined with instructional multimedia applications for different target groups at different educational levels. The architecture of the Optical Database will allow for switching between application types while working (for instance from tutorial instruction via the encyclopedia to a simulation and back). For instruction, the content of the database is thereby organized around so-called standard instruction routes: one route per target group. In the project, the teacher is regarded as the manager of instruction.\ud
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From that perspective, the database is primarily organized as a teaching facility. Central to the research is the condition that the architecture of the Optical Database has to enable teachers to select and tailor instruction routes to their needs in a way that is perceived as logical and easy to use
The First Detailed Abundances for M giants in Baade's Window from Infrared Spectroscopy
We report the first abundance analysis of 14 M giant stars in the Galactic
bulge, based on R=25,000 infrared spectroscopy (1.5-1.8um) using NIRSPEC at the
Keck II telescope. Because some of the bulge M giants reach high luminosities
and have very late spectral type, it has been suggested that they are the
progeny of only the most metal rich bulge stars, or possibly members of a
younger bulge population. We find the iron abundance and composition of the M
giants are similar to those of the K giants that have abundances determined
from optical high resolution spectroscopy: =-0.190 +/- 0.020 with a
1-sigma dispersion of 0.08 +/- 0.015. Comparing our bulge M giants to a control
sample of local disk M giants in the Solar vicinity, we find the bulge stars
are enhanced in alpha elements at the level of +0.3 dex relative to the Solar
composition stars, consistent with other studies of bulge globular clusters and
field stars. This small sample shows no dependence of spectral type on
metallicity, nor is there any indication that the M giants are the evolved
members of a subset of the bulge population endowed with special
characteristics such as relative youth or high metallicity. We also find low
12C/13C < 10, confirming the prsence of extra-mixing processes during the red
gaint phase of evolutionComment: 19 pages, 7 figures, accepted for publication in the Astrophysical
Journa
The chromosphere: gateway to the corona, or the purgatory of solar physics?
I argue that one should attempt to understand the solar chromosphere not only
for its own sake, but also if one is interested in the physics of: the corona;
astrophysical dynamos; space weather; partially ionized plasmas; heliospheric
UV radiation; the transition region. I outline curious observations which I
personally find puzzling and deserving of attention.Comment: To appear in the proceedings of the 25th NSO Workshop "Chromospheric
Structure and Dynamics. From Old Wisdom to New Insights", Memorie della
Societa' Astronomica Italiana, Eds. Tritschler et a
Residence Time Analysis of Rare-Gas Atoms Trapped At A Solid Surface
Recently a model based on an attractive square well and
impulsive repulsive potential between a gas and a solid
surface has been employed to estimate the fraction of
gas atoms trapped in the potential well at the solid
surface. A gas atom was considered trapped if it
transferred enough energy to the solid (as judged by the
thermal accommodation coefficient) to fall into the
potential well, i.e., to have negative total energy where
the zero of energy is assumed to be the infinitely separated
gas atom and solid with the gas atom at rest. The
criterion for gas trapping when considering experimental
scattering data has been the assumption that the trapped
gas is emitted from the surface with a random (cosine)
distribution. To assess the possibility that rare-gas
atoms may fall into the interatomic well with the metal
surface (i.e., be trapped according to the definition of
Ref. 1) and still be re-emitted from the surface in a
nonrandom distribution, some estimates of surface
residence times for the gas should be made. If such a
phenomenon as suggested above were to occur, then the
calculated trapping probability of the square well
model would be expected to be larger than those found
experimentally, as has been observed to be the case for
krypton and xenon interactions with a tungsten (110)
surface. The idea that a gas particle may execute
several vibrations at a surface and still not reach
thermodynamic equilibrium is not a new one. In this
paper the pertinent theory describing this effect is
presented, and empirical calculations estimating the
magnitude of the effect are presented
Structured evaluation of virtual environments for special-needs education
This paper describes the development of a structured approach to evaluate experiential and communication virtual learning environments (VLEs) designed specifically for use in the education of children with severe learning difficulties at the Shepherd special needs school in Nottingham, UK. Constructivist learning theory was used as a basis for the production of an evaluation framework, used to evaluate the design of three VLEs and how they were used by students with respect to this learning theory. From an observational field study of student-teacher pairs using the VLEs, 18 behaviour categories were identified as relevant to five of the seven constructivist principles defined by Jonassen (1994). Analysis of student-teacher behaviour was used to provide support for, or against, the constructivist principles. The results show that the three VLEs meet the constructivist principles in very different ways and recommendations for design modifications are put forward
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