333 research outputs found
Numerical solution of the eXtended Pom-Pom model for viscoelastic free surface flows
In this paper we present a finite difference method for solving two-dimensional viscoelastic unsteady free surface flows governed by the single equation version of the eXtended Pom-Pom (XPP) model. The momentum equations are solved by a projection method which uncouples the velocity and pressure fields. We are interested in low Reynolds number flows and, to enhance the stability of the numerical method, an implicit technique for computing the pressure condition on the free surface is employed. This strategy is invoked to solve the governing equations within a Marker-and-Cell type approach while simultaneously calculating the correct normal stress condition on the free surface. The numerical code is validated by performing mesh refinement on a two-dimensional channel flow. Numerical results include an investigation of the influence of the parameters of the XPP equation on the extrudate swelling ratio and the simulation of the Barus effect for XPP fluids
Complementarity of information sent via different bases
We discuss quantitatively the complementarity of information transmitted by a
quantum system prepared in a basis state in one out of several different
mutually unbiased bases (MUBs). We obtain upper bounds on the information
available to a receiver who has no knowledge of which MUB was chosen by the
sender. These upper bounds imply a complementarity of information encoded via
different MUBs and ultimately ensure the security in quantum key distribution
protocols.Comment: 9 pages, references adde
The WHAM Northern Sky Survey and the Nature of the Warm Ionized Medium in the Galaxy
The Wisconsin H-Alpha Mapper (WHAM) has completed a velocity-resolved map of
diffuse H-alpha emission of the entire northern sky, providing the first
comprehensive picture of both the distribution and kinematics of diffuse
ionized gas in the Galaxy. WHAM continues to advance our understanding of the
physical conditions of the warm ionized medium through observations of other
optical emission lines throughout the Galactic disk and halo. We discuss some
highlights from the survey, including an optical window into the inner Galaxy
and the relationship between HI and HII in the diffuse ISM.Comment: 9 pages, 3 figures. To be published in "How does the Galaxy work?",
eds. E.J. Alfaro, E. Perez & J. Franco, Kluwer, held 23-27 June 2003 in
Granada, Spain. Higher resolution version available at
http://www.astro.wisc.edu/~madsen/prof/pubs.htm
Interstellar MHD Turbulence and Star Formation
This chapter reviews the nature of turbulence in the Galactic interstellar
medium (ISM) and its connections to the star formation (SF) process. The ISM is
turbulent, magnetized, self-gravitating, and is subject to heating and cooling
processes that control its thermodynamic behavior. The turbulence in the warm
and hot ionized components of the ISM appears to be trans- or subsonic, and
thus to behave nearly incompressibly. However, the neutral warm and cold
components are highly compressible, as a consequence of both thermal
instability in the atomic gas and of moderately-to-strongly supersonic motions
in the roughly isothermal cold atomic and molecular components. Within this
context, we discuss: i) the production and statistical distribution of
turbulent density fluctuations in both isothermal and polytropic media; ii) the
nature of the clumps produced by thermal instability, noting that, contrary to
classical ideas, they in general accrete mass from their environment; iii) the
density-magnetic field correlation (or lack thereof) in turbulent density
fluctuations, as a consequence of the superposition of the different wave modes
in the turbulent flow; iv) the evolution of the mass-to-magnetic flux ratio
(MFR) in density fluctuations as they are built up by dynamic compressions; v)
the formation of cold, dense clouds aided by thermal instability; vi) the
expectation that star-forming molecular clouds are likely to be undergoing
global gravitational contraction, rather than being near equilibrium, and vii)
the regulation of the star formation rate (SFR) in such gravitationally
contracting clouds by stellar feedback which, rather than keeping the clouds
from collapsing, evaporates and diperses them while they collapse.Comment: 43 pages. Invited chapter for the book "Magnetic Fields in Diffuse
Media", edited by Elisabete de Gouveia dal Pino and Alex Lazarian. Revised as
per referee's recommendation
Avaliação e adaptação do Índice de Severidade de Seca de Palmer (PDSI) e do Índice Padronizado de Precipitação (SPI) às condições climáticas do Estado de São Paulo
Effect of niobium on corrosion resistance to sulfuric acid of 430 ferritic stainless steel
Grain Destruction in Interstellar Shocks
Interstellar shock waves can erode and destroy grains present in the shocked
gas, primarily as the result of sputtering and grain-grain collisions.
Uncertainties in current estimates of sputtering yields are reviewed. Results
are presented for the simple case of sputtering of fast grains being stopped in
cold gas. An upper limit is derived for sputtering of refractory grains in
C-type MHD shocks: shock speeds v_s \gtrsim 50 \kms are required for return
of more than 30\% of the silicate to the gas phase. Sputtering can also be
important for removing molecular ice mantles from grains in two-fluid MHD shock
waves in molecular gas. Recent estimates of refractory grain lifetimes against
destruction in shock waves are summarized, and the implications of these short
lifetimes are discussed.Comment: To appear in Shocks in Astrophysics, ed. T.J. Millar. Talk given at
conference Shocks in Astrophysics, Manchester, Jan. 1995. 13 pages with 6
figures: uuencoded compressed postscript. Also available as POPe-633 on
http://astro.princeton.edu/~library/prep.htm
Use of a type IIB external skeletal fixator in experimental tarsocrural arthrodesis in dogs
The Pharmacogenetics Research Network: From SNP Discovery to Clinical Drug Response
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109975/1/cpt6100087.pd
- …