18,914 research outputs found
Evaluation of a composite mobile holographic nondestructive test system
A simplified theoretical model for the interpretation of the double-exposure holographic interference fringe loci due to the general three-dimensional displacements was derived for the specific composite mobile holographic nondestructive test system. The model, representing a good approximation to a more tedious theoretical result, predicts that a combination of in-plane and out-of-plane displacements of the surface will produce concentric circular-shaped fringe patterns with locations of their center affected by the displacements. Appropriate experiments were designed and carried out for the test of the validity of the theory. These experiments include the taking of double-exposure holograms of in-plane translations and combined in-plane and out-of-plane translations. The simplified model agreed quite well with the experimental results. Experimentally observed effects due to the curvature of the test plate and the variations of the angles of incidence of the laser light suggest that in order for the simplified model to be able to predict the test results more accurately, incidence and reflection of the laser light should be chosen as nearly perpendicular to the surface of the tested object as possible
Intrastate Differences in Workers\u27 Compensation Costs: October 1986 Closed Case Study
It is the goal of this study to present an empirical description of the Michigan workers\u27 compensation system as of 1986 which will enable the comparison of the operation of the current system with the 1978 system in order to measure the impact of the policy changes implemented in the early 1980s
Final report : sixth (1962-63) Western Australian random sample laying test
FINAL REPORT SIXTH (1962-63) WESTERN AUSTRALIAN RANDOM SAMPLE LAYING TEST
Final Report to December, 1963, covering a period of 500 days (71 3/7 weeks), comprising a 150-day (21 3/7 week) rearing period and a 350-day (50-week) laying period
Shear Stress Measurements of Non-Spherical Particles in High Shear Rate Flows
The behavior of liquid-solid flows varies greatly depending on fluid viscosity; particle and liquid inertia; and collisions and near-collisions between particles. Shear stress measurements were made in a coaxial rheometer with a height to gap ratio (b/r0) of 11.7 and gap to outer radius ratio (h/b) of 0.166 that was specially designed to minimize the effects of secondary flows. Experiments were performed for a range of Reynolds numbers, solid fractions and ratio of particle to fluid densities. With neutrally buoyant particles, the dimensional shear stress exhibits a linear dependence on Reynolds number: the slope is monotonic but a non-linear function of the solid fraction. Though non-neutrally buoyant particles exhibit a similar linear dependence at higher Reynolds numbers, at lower values the shear stress exhibits a non-linear behavior in which the stress increases with decreasing Reynolds number due to particle settling
Explaining two circumnuclear star forming rings in NGC5248
The distribution of gas in the central kiloparsec of a galaxy has a
dynamically rapid evolution. Nonaxisymmetries in the gravitational potential of
the galactic disk, such as a large scale stellar bar or spiral, can lead to
significant radial motion of gaseous material from larger radii to the central
region. The large influx of gas and the subsequent star formation keep the
central region constantly changing. However, the ability of gas to reach the
nucleus proper to fuel an AGN phase is not guaranteed. Gas inflow can be halted
at a circumnuclear star forming ring several hundred parsec away. The nearby
galaxy NGC5248 is especially interesting in this sense since it is said to host
2 circumnuclear star forming rings at 100pc and 370pc from its quiescent
nucleus. Here we present new subarcsecond PdBI+30m CO(2-1) emission line
observations of the central region. For the first time the molecular gas
distribution at the smallest stellar ring is resolved into a gas ring,
consistent with the presence of a quiescent nucleus. However, the molecular gas
shows no ring structure at the larger ring. We combine analyses of the gaseous
and stellar content in the central kiloparsec of this galaxy to understand the
gas distribution and dynamics of this star forming central region. We discuss
the probability of two scenarios leading to the current observations, given our
full understanding of this system, and discuss whether there are really two
circumnuclear star forming rings in this galaxy.Comment: Accepted for publication in A&A, 14pages + long tabl
From gas to galaxies
The unsurpassed sensitivity and resolution of the Square Kilometer Array
(SKA) will make it possible for the first time to probe the continuum emission
of normal star forming galaxies out to the edges of the universe. This opens
the possibility for routinely using the radio continuum emission from galaxies
for cosmological research as it offers an independent probe of the evolution of
the star formation density in the universe. In addition it offers the
possibility to detect the first star forming objects and massive black holes.
In deep surveys SKA will be able to detect HI in emission out to redshifts of
and hence be able to trace the conversion of gas into stars
over an era where considerable evolution is taking place. Such surveys will be
able to uniquely determine the respective importance of merging and accreting
gas flows for galaxy formation over this redshift range (i.e. out to when the
universe was only one third its present age). It is obvious that only SKA will
able to see literally where and how gas is turned into stars.
These and other aspects of SKA imaging of galaxies will be discussed.Comment: To be published in New Astronomy Reviews, Elsevier, Amsterdam as part
of "Science with the Square Kilometre Array", eds. C. Carilli and S.
Rawlings. 18 pages + 13 figures; high resolution version and other chapters
of "Science with the Square Kilometre Array" available at
http://www.skatelescope.org/pages/science_gen.ht
- …