25,799 research outputs found
Analysis and test evaluation of the dynamic response and stability of three advanced turboprop models
Results of dynamic response and stability wind tunnel tests of three 62.2 cm (24.5 in) diameter models of the Prop-Fan, advanced turboprop, are presented. Measurements of dynamic response were made with the rotors mounted on an isolated nacelle, with varying tilt for nonuniform inflow. One model was also tested using a semi-span wing and fuselage configuration for response to realistic aircraft inflow. Stability tests were performed using tunnel turbulence or a nitrogen jet for excitation. Measurements are compared with predictions made using beam analysis methods for the model with straight blades, and finite element analysis methods for the models with swept blades. Correlations between measured and predicted rotating blade natural frequencies for all the models are very good. The IP dynamic response of the straight blade model is reasonably well predicted. The IP response of the swept blades is underpredicted and the wing induced response of the straight blade is overpredicted. Two models did not flutter, as predicted. One swept blade model encountered an instability at a higher RPM than predicted, showing predictions to be conservative
Exponential Distributions in a Mechanical Model for Earthquakes
We study statistical distributions in a mechanical model for an earthquake
fault introduced by Burridge and Knopoff [R. Burridge and L. Knopoff, {\sl
Bull. Seismol. Soc. Am.} {\bf 57}, 341 (1967)]. Our investigations on the size
(moment), time duration and number of blocks involved in an event show that
exponential distributions are found in a given range of the paramenter space.
This occurs when the two kinds of springs present in the model have the same,
or approximately the same, value for the elastic constants. Exponential
distributions have also been seen recently in an experimental system to model
earthquake-like dynamics [M. A. Rubio and J. Galeano, {\sl Phys. Rev. E} {\bf
50}, 1000 (1994)].Comment: 11 pages, uuencoded (submitted to Phys. Rev. E
Orbital moment of a single Co atom on a Pt(111) surface - a view from correlated band theory
The orbital magnetic moment of a Co adatom on a Pt(111) surface is calculated
in good agreement with experimental data making use of the LSDA+U method. It is
shown that both electron correlation induced orbital polarization and
structural relaxation play essential roles in orbital moment formation. The
microscopic origins of the orbital moment enhancement are discussed
An Exploratory Study of Forces and Frictions affecting Large-Scale Model-Driven Development
In this paper, we investigate model-driven engineering, reporting on an
exploratory case-study conducted at a large automotive company. The study
consisted of interviews with 20 engineers and managers working in different
roles. We found that, in the context of a large organization, contextual forces
dominate the cognitive issues of using model-driven technology. The four forces
we identified that are likely independent of the particular abstractions chosen
as the basis of software development are the need for diffing in software
product lines, the needs for problem-specific languages and types, the need for
live modeling in exploratory activities, and the need for point-to-point
traceability between artifacts. We also identified triggers of accidental
complexity, which we refer to as points of friction introduced by languages and
tools. Examples of the friction points identified are insufficient support for
model diffing, point-to-point traceability, and model changes at runtime.Comment: To appear in proceedings of MODELS 2012, LNCS Springe
Report of visiting committee : an evaluation of Itawamba Junior College and Agricultural High School, April 6-9, 1953
https://egrove.olemiss.edu/ms_school_surveys/1017/thumbnail.jp
Final state interactions and hadron quenching in cold nuclear matter
I examine the role of final state interactions in cold nuclear matter in
modifying hadron production on nuclear targets with leptonic or hadronic beams.
I demonstrate the extent to which available experimental data in
electron-nucleus collisions can give direct information on final state effects
in hadron-nucleus and nucleus-nucleus collisions. For hadron-nucleus
collisions, a theoretical estimate based on a parton energy loss model tested
in lepton-nucleus collisions shows a large effect on mid-rapidity hadrons at
fixed target experiments. At RHIC energy, the effect is large for negative
rapidity hadrons, but mild at midrapidity. This final state cold hadron
quenching needs to be taken into account in jet tomographic analysis of the
medium created in nucleus-nucleus collisions.Comment: 14 pages, 7 figure
The Australia Telescope campaign to study southern class I methanol masers
The Australia Telescope Compact Array (ATCA) and the Mopra facility have been
used to search for new southern class I methanol masers at 9.9, 25 (J=5) and
104 GHz, which are thought to trace more energetic conditions in the interface
regions of molecular outflows, than the widespread class I masers at 44 and 95
GHz. One source shows a clear outflow association.Comment: 2 pages, 1 figure (composed from 3 files), to appear in proceedings
of IAU Symposium 242 "Astrophysical masers and their environment" (eds. J.
Chapman and W. Baan
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