7,196 research outputs found
ASTROP2 users manual: A program for aeroelastic stability analysis of propfans
A user's manual is presented for the aeroelastic stability and response of propulsion systems computer program called ASTROP2. The ASTROP2 code preforms aeroelastic stability analysis of rotating propfan blades. This analysis uses a two-dimensional, unsteady cascade aerodynamics model and a three-dimensional, normal-mode structural model. Analytical stability results from this code are compared with published experimental results of a rotating composite advanced turboprop model and of nonrotating metallic wing model
Stellar Mixing and the Primordial Lithium Abundance
We compare the properties of recent samples of the lithium abundances in halo
stars to one another and to the predictions of theoretical models including
rotational mixing, and we examine the data for trends with metal abundance. We
find from a KS test that in the absence of any correction for chemical
evolution, the Ryan, Norris, & Beers (1999} sample is fully consistent with
mild rotational mixing induced depletion and, therefore, with an initial
lithium abundance higher than the observed value. Tests for outliers depend
sensitively on the threshold for defining their presence, but we find a
1045% probability that the RNB sample is drawn from the rotationally mixed
models with a 0.2 dex median depletion (with lower probabilities corresponding
to higher depletion factors). When chemical evolution trends (Li/H versus Fe/H)
are treated in the linear plane we find that the dispersion in the RNB sample
is not explained by chemical evolution; the inferred bounds on lithium
depletion from rotational mixing are similar to those derived from models
without chemical evolution. We find that differences in the equivalent width
measurements are primarily responsible for different observational conclusions
concerning the lithium dispersion in halo stars. The standard Big Bang
Nucleosynthesis predicted lithium abundance which corresponds to the deuterium
abundance inferred from observations of high-redshift, low-metallicity QSO
absorbers requires halo star lithium depletion in an amount consistent with
that from our models of rotational mixing, but inconsistent with no depletion.Comment: 39 pages, 9 figures; submitted Ap
Analytical flutter investigation of a composite propfan model
A theoretical model and an associated computer program for predicting subsonic bending-torsion flutter in propfans are presented. The model is based on two-dimensional unsteady cascade strip theory and three-dimensional steady and unsteady lifting surface aerodynamic theory in conjunction with a finite element structural model for the blade. The analytical results compare well with published experimental data. Additional parametric studies are also presented illustrating the effects on flutter speed of steady aeroelastic deformations, blade setting angle, rotational speed, number of blades, structural damping, and number of modes
General bounds on the Wilson-Dirac operator
Lower bounds on the magnitude of the spectrum of the Hermitian Wilson-Dirac
operator H(m) have previously been derived for 0<m<2 when the lattice gauge
field satisfies a certain smoothness condition. In this paper lower bounds are
derived for 2p-2<m<2p for general p=1,2,...,d where d is the spacetime
dimension. The bounds can alternatively be viewed as localisation bounds on the
real spectrum of the usual Wilson-Dirac operator. They are needed for the
rigorous evaluation of the classical continuum limit of the axial anomaly and
index of the overlap Dirac operator at general values of m, and provide
information on the topological phase structure of overlap fermions. They are
also useful for understanding the instanton size-dependence of the real
spectrum of the Wilson-Dirac operator in an instanton background.Comment: 26 pages, 2 figures. v3: Completely rewritten with new material and
new title; to appear in Phys.Rev.
Image Exploitation-A Forefront Area for UAV Application
Image exploitation, an innovative image utilisation program uses high revisit multisensor, multiresolution imagery from unmanned air vehicle or other reconnaissance platform for intelligent information gathering. This paper describes the imagc exploitation system developed at the Aeronautical Dcvclopment Establishment, Bangalore, for the remotely piloted vehicle (RPV) Nishonr and highlights two major areas (i) In-flight imagc exploitation, and (ii) post-flight imagc cxploitatlon. In-flight imagc study includes real-timeenhancement of images frames during RPV flight. target acquisition. calculation of geo-location of targets, distance and area computation, and image-to-map correspondence. Post-flight image exploitation study includes image restoration, classtfication of terrain, 3-D depth computation using stereo vision and shape from shading techniques. The paper shows results obtained in each of these areas from actual flight trials
On the continuum limit of fermionic topological charge in lattice gauge theory
It is proved that the fermionic topological charge of SU(N) lattice gauge
fields on the 4-torus, given in terms of a spectral flow of the Hermitian
Wilson--Dirac operator, or equivalently, as the index of the Overlap Dirac
operator, reduces to the continuum topological charge in the classical
continuum limit when the parameter is in the physical region .Comment: latex, 18 pages. v2: Several comments added. To appear in J.Math.Phy
Conjunctive Water Use Planning with Water Quality Constraints in Tooele Valley, Utah
The need for more efficient water management is gaining recognition due to the increased cost of water supply, the growth in the demand for water, and greater environmental and social impacts of water programs. Conjunctive use of surfact and groundwater resources provides opportunities for increasing net benefits to the water users. Past conjunctive use studies, however, have usually not included water quality constraints. In Tooele valley, Utah, spatial variation of groundwater qualtity (total dissolved solids) is significant. The areas of good (400-500 mg/1), fair (500-1,000 mg/1), and poor (1,000-3,000 mg/1) quality groundwaters were identified in an earlier study by the USGS. The water quality dimension was incorporated into the conjunctive use planning to account for crop yield changes due to changes in salinity levels in irrigation water. The possibilities for increasing total net benefits by blending surface and groundwater of different qualities were examined by developing a linear programming optimization model. The optimization model provides for mixing the different qualities of water available for the cops to maximize benefits. It applies linear programming to the Tooele Valley water supply system and optimizes over three locations, four coprs, and five qualities of water of differing costs. The groundwater withdrawals at the locations dictated by the optimization model were input to the Tooele Valley groundwater simulation model developed by USGS to study the effects on the valley\u27s principal artesian aquifer. Economic analyses of the probable scenarios of future agricultural development in Tooele Valley did not suggest that extensive increases in groundwater with drawals will occur. Economic infeasibility of major increases in groundwater extraction is a limiting factor for agricultural development in most parts of the valley. Groundwater mining therefore does not seem like a major future problem. The areas where new wells can be drilled without interference causing technological diseconomies are indicated. Profitable application of blending technology to irrigated agriculture in Tooele Valley is not possible without making a drastic shift to some higher valued crop such as fruit trees. All surface water sources should be fully utilized before developing additional and expensive groundwater. Even though an additional 20,000 to 25,000 ac-ft of groundwater can be extracted without mining, there would be a high risk of destroying natural phreatophyte habitats and degradation of water quality in at least some parts of the artesian aquifer
Development of a task-level robot programming and simulation system
An ongoing project in developing a Task-Level Robot Programming and Simulation System (TARPS) is discussed. The objective of this approach is to design a generic TARPS that can be used in a variety of applications. Many robotic applications require off-line programming, and a TARPS is very useful in such applications. Task level programming is object centered in that the user specifies tasks to be performed instead of robot paths. Graphics simulation provides greater flexibility and also avoids costly machine setup and possible damage. A TARPS has three major modules: world model, task planner and task simulator. The system architecture, design issues and some preliminary results are given
Scaling and Eigenmode Tests of the Improved Fat Clover Action
We test a recently proposed improved lattice-fermion action, the fat link
clover action, examining indicators of pathological small-quark-mass lattice
artifacts ("exceptional configurations") on quenched lattices of spacing 0.12
fm and studying scaling properties of the light hadron spectrum for lattice
spacing a=0.09 and 0.16 fm. We show that the action apparently has fewer
problems with pathological lattice artifacts than the conventional
nonperturbatively improved clover action and its spectrum scales just as well.Comment: 15 pp RevTeX, 5 Postscript figures, submitted to Phys. Rev.
Rearranged section order and added an analysis of fluctuations of the pion
correlato
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