53,459 research outputs found
Implementation experiences of NASTRAN on CDC CYBER 74 SCOPE 3.4 operating system
The implementation of the NASTRAN system on the CDC CYBER 74 SCOPE 3.4 Operating System is described. The flexibility of the NASTRAN system made it possible to accomplish the change with no major problems. Various sizes of benchmark and test problems, ranging from two hours to less than one minute CP time were run on the CDC CYBER SCOPE 3.3, Univac EXEC-8, and CDC CYBER SCOPE 3.4. The NASTRAN installation deck is provided
Photovoltaic array: Power conditioner interface characteristics
The electrical output (power, current, and voltage) of flat plate solar arrays changes constantly, due primarily to changes in cell temperature and irradiance level. As a result, array loads such as dc-to-ac power conditioners must be capable of accommodating widely varying input levels while maintaining operation at or near the maximum power point of the array. The array operating characteristics and extreme output limits necessary for the systematic design of array load interfaces under a wide variety of climatic conditions are studied. A number of interface parameters are examined, including optimum operating voltage, voltage energy, maximum power and current limits, and maximum open circuit voltage. The effect of array degradation and I-V curve fill factor or the array power conditioner interface is also discussed. Results are presented as normalized ratios of power conditioner parameters to array parameters, making the results universally applicable to a wide variety of system sizes, sites, and operating modes
VTOL in ground effect flows for closely spaced jets
Results of a series of in ground effect twin jet tests are presented along with flow models for closely spaced jets to help predict pressure and upwash forces on simulated aircraft surfaces. The isolated twin jet tests revealed unstable fountains over a range of spacings and jet heights, regions of below ambient pressure on the ground, and negative pressure differential in the upwash flow field. A separate computer code was developed for vertically oriented, incompressible jets. This model more accurately reflects fountain behavior without fully formed wall jets, and adequately predicts ground isobars, upwash dynamic pressure decay, and fountain lift force variation with height above ground
Integrating remote sensing datasets into ecological modelling: a Bayesian approach
Process-based models have been used to simulate 3-dimensional complexities of
forest ecosystems and their temporal changes, but their extensive data
requirement and complex parameterisation have often limited their use for
practical management applications. Increasingly, information retrieved using
remote sensing techniques can help in model parameterisation and data
collection by providing spatially and temporally resolved forest information. In
this paper, we illustrate the potential of Bayesian calibration for integrating such
data sources to simulate forest production. As an example, we use the 3-PG
model combined with hyperspectral, LiDAR, SAR and field-based data to
simulate the growth of UK Corsican pine stands. Hyperspectral, LiDAR and
SAR data are used to estimate LAI dynamics, tree height and above ground
biomass, respectively, while the Bayesian calibration provides estimates of
uncertainties to model parameters and outputs. The Bayesian calibration
contrasts with goodness-of-fit approaches, which do not provide uncertainties
to parameters and model outputs. Parameters and the data used in the
calibration process are presented in the form of probability distributions,
reflecting our degree of certainty about them. After the calibration, the
distributions are updated. To approximate posterior distributions (of outputs
and parameters), a Markov Chain Monte Carlo sampling approach is used (25
000 steps). A sensitivity analysis is also conducted between parameters and
outputs. Overall, the results illustrate the potential of a Bayesian framework for
truly integrative work, both in the consideration of field-based and remotely
sensed datasets available and in estimating parameter and model output uncertainties
The Mass Function of Field Galaxies at 0.4 < z < 1.2 Derived From the MUNICS K-Selected Sample
We derive the number density evolution of massive field galaxies in the
redshift range 0.4 < z < 1.2 using the K-band selected field galaxy sample from
the Munich Near-IR Cluster Survey (MUNICS). We rely on spectroscopically
calibrated photometric redshifts to determine distances and absolute magnitudes
in the rest-frame K-band. To assign mass-to-light ratios, we use two different
approaches. First, we use an approach which maximizes the stellar mass for any
K-band luminosity at any redshift. We take the mass-to-light ratio of a Simple
Stellar Population (SSP) which is as old as the universe at the galaxy's
redshift as a likely upper limit. Second, we assign each galaxy a mass-to-light
ratio by fitting the galaxy's colours against a grid of composite stellar
population models and taking their M/L. We compute the number density of
galaxies more massive than 2 x 10^10 h^-2 Msun, 5 x 10^10 h^-2 Msun, and 1 x
10^11 h^-2 Msun, finding that the integrated stellar mass function is roughly
constant for the lowest mass limit and that it decreases with redshift by a
factor of ~ 3 and by a factor of ~ 6 for the two higher mass limits,
respectively. This finding is in qualitative agreement with models of
hierarchical galaxy formation, which predict that the number density of ~ M*
objects is fairly constant while it decreases faster for more massive systems
over the redshift range our data probe.Comment: 6 pages, 2 figures, to appear in the proceedings of the ESO/USM
Workshop "The Mass of Galaxies at Low and High Redshift", Venice (Italy),
October 24-26, 200
Limits on Non-Standard Top Quark Couplings from Electroweak Measurements
We calculate the typical size of loop corrections to electroweak observables
arising from non-standard and vertices. We use an
effective Lagrangian formalism based on the electroweak gauge group
. Limits on the non-standard model
top quark couplings from electroweak observables are presented and compared
with previously obtained limits.Comment: 9 pages, uses epsf.st
The Munich Near-Infrared Cluster Survey (MUNICS) - Number density evolution of massive field galaxies to z ~ 1.2 as derived from the K-band selected survey
We derive the number density evolution of massive field galaxies in the
redshift range 0.4 < z < 1.2 using the K-band selected field galaxy sample from
the Munich Near-IR Cluster Survey (MUNICS). We rely on spectroscopically
calibrated photometric redshifts to determine distances and absolute magnitudes
in the rest-frame K-band. To assign mass-to-light ratios, we use an approach
which maximizes the stellar mass for any K-band luminosity at any redshift. We
take the mass-to-light ratio, M/L_K, of a Simple Stellar Population (SSP) which
is as old as the universe at the galaxy's redshift as a likely upper limit.
This is the most extreme case of pure luminosity evolution and in a more
realistic model M/L_K will probably decrease faster with redshift due to
increased star formation. We compute the number density of galaxies more
massive than 2 10^10 h^-2 solar masses, 5 10^10 h^-2 solar masses, and 1 10^11
h^-2 solar masses, finding that the integrated stellar mass function is roughly
constant for the lowest mass limit and that it decreases with redshift by a
factor of roughly 3 and by a factor of roughly 6 for the two higher mass
limits, respectively. This finding is in qualitative agreement with models of
hierarchical galaxy formation, which predict that the number density of ~ M*
objects is fairly constant while it decreases faster for more massive systems
over the redshift range our data probe.Comment: 4 pages, 5 figures, accepted for publication in ApJ Letter
Large-Scale Structure in the NIR-Selected MUNICS Survey
The Munich Near-IR Cluster Survey (MUNICS) is a wide-area, medium-deep,
photometric survey selected in the K' band. The project's main scientific aims
are the identification of galaxy clusters up to redshifts of unity and the
selection of a large sample of field early-type galaxies up to z < 1.5 for
evolutionary studies. We created a Large Scale Structure catalog, using a new
structure finding technique specialized for photometric datasets, that we
developed on the basis of a friends-of-friends algorithm. We tested the
plausibility of the resulting galaxy group and cluster catalog with the help of
Color-Magnitude Diagrams (CMD), as well as a likelihood- and Voronoi-approach.Comment: 4 pages, to appear in "The Evolution of Galaxies III. From Simple
Approaches to Self-Consistent Models", proceedings of the 3rd EuroConference
on the evolution of galaxies, held in Kiel, Germany, July 16-20, 200
Atmospheric environment for space shuttle (STS-8) launch
Selected atmospheric conditions observed near Space Shuttle STS-8 launch time on August 30, 1983, at Kennedy Space Center, Florida are summarized. Values of ambient pressure, temperature, moisture, ground winds, visual observations (cloud), and winds aloft are included. The sequence of prelaunch Jimsphere measured vertical wind profiles is given. Also presented are wind and thermodynamic parameters representative of surface and aloft conditions in the SRB descent/impact ocean area. Final meteorological tapes, which consist of wind and thermodynamic parameters versus altitude, for STS-8 vehicle ascent and SRB descent/impact were constructed. The STS-8 ascent meteorological data tape was constructed
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