67,058 research outputs found
Gender differences in paid and unpaid work: findings from a New Zealand birth cohort
This study uses data from a birth cohort of New Zealand-born 30-year-olds to examine gender differences in time use and satisfaction with time use.
The specific aims of the study are:
to examine gender difference in time spent in paid employment and unpaid work;
to examine the extent to which males and females are satisfied with their time use
Process for application of powder particles to filamentary materials
This invention is a process for the uniform application of polymer powder particles to a filamentary material in a continuous manner to form a uniform composite prepreg material. A tow of the filamentary material is fed under carefully controlled tension into a spreading unit, where it is spread pneumatically into an even band. The spread filamentary tow is then coated with polymer particles from a fluidized bed, after which the coated filamentary tow is fused before take-up on a package for subsequent utilization. This process produces a composite prepreg uniformly without imposing severe stress on the filamentary material, and without requiring long, high temperature residence times for the polymer
Neptune's Migration into a Stirred-Up Kuiper Belt: A Detailed Comparison of Simulations to Observations
Nbody simulations are used to examine the consequences of Neptune's outward
migration into the Kuiper Belt, with the simulated endstates being compared
rigorously and quantitatively to the observations. These simulations confirm
the findings of Chiang et al. (2003), who showed that Neptune's migration into
a previously stirred-up Kuiper Belt can account for the Kuiper Belt Objects
(KBOs) known to librate at Neptune's 5:2 resonance. We also find that capture
is possible at many other weak, high-order mean motion resonances, such as the
11:6, 13:7, 13:6, 9:4, 7:3, 12:5, 8:3, 3:1, 7:2, and the 4:1. The more distant
of these resonances, such as the 9:4, 7:3, 5:2, and the 3:1, can also capture
particles in stable, eccentric orbits beyond 50 AU, in the region of phase
space conventionally known as the Scattered Disk. Indeed, 90% of the simulated
particles that persist over the age of the Solar System in the so-called
Scattered Disk zone never had a close encounter with Neptune, but instead were
promoted into these eccentric orbits by Neptune's resonances during the
migration epoch. This indicates that the observed Scattered Disk might not be
so scattered. This model also produced only a handful of Centaurs, all of which
originated at Neptune's mean motion resonances in the Kuiper Belt. We also
report estimates of the abundances and masses of the Belt's various
subpopulations (e.g., the resonant KBOs, the Main Belt, and the so-called
Scattered Disk), and also provide upper limits on the abundance of Centaurs and
Neptune's Trojans, as well as upper limits on the sizes and abundances of
hypothetical KBOs that might inhabit the a>50 AU zone.Comment: 60 pages, 16 figures. Accepted for publication in the Astronomical
Journa
Robust randomized benchmarking of quantum processes
We describe a simple randomized benchmarking protocol for quantum information
processors and obtain a sequence of models for the observable fidelity decay as
a function of a perturbative expansion of the errors. We are able to prove that
the protocol provides an efficient and reliable estimate of an average
error-rate for a set operations (gates) under a general noise model that allows
for both time and gate-dependent errors. We determine the conditions under
which this estimate remains valid and illustrate the protocol through numerical
examples.Comment: 4+ pages, 1 figure, and 1 tabl
A Wide Field, Low Frequency Radio Survey of the Field of M31: I. Construction and Statistical Analysis of the Source Catalog
We present here the results of a 325 MHz radio survey of M31, conducted with
the A-configuration of the Very Large Array. The survey covered an area of 7.6
deg, and a total of 405 radio sources between \la6\arcsec and 170\arcsec
in extent were mapped with a resolution of 6\arcsec and a 1 sensitivity
of 0.6 \mjyb. For each source, its morphological class, major axis
, minor axis , position angle , peak flux ,
integrated flux density , spectral index and spectral curvature
parameter were calculated. A comparison of the flux and radial
distribution -- both in the plane of the sky and in the plane of M31 -- of
these sources with those of the XMM--LSS and WENSS radio surveys revealed that
a vast majority of sources detected are background radio galaxies. As a result
of this analysis, we expect that only a few sources are intrinsic to M31. These
sources are identified and discussed in an accompanying paper.Comment: 29 pages with 4 tables and 10 figures (JPEGs), accepted for
publication in ApJS. Full-resolution images available on reques
Hyperuniformity with no fine tuning in sheared sedimenting suspensions
Particle suspensions, present in many natural and industrial settings,
typically contain aggregates or other microstructures that can complicate
macroscopic flow behaviors and damage processing equipment. Recent work found
that applying uniform periodic shear near a critical transition can reduce
fluctuations in the particle concentration across all length scales, leading to
a hyperuniform state. However, this strategy for homogenization requires fine
tuning of the strain amplitude. Here we show that in a model of sedimenting
particles under periodic shear, there is a well-defined regime at low
sedimentation speed where hyperuniform scaling automatically occurs. Our
simulations and theoretical arguments show that the homogenization extends up
to a finite lengthscale that diverges as the sedimentation speed approaches
zero.Comment: 11 pages, 6 figure
Dynamical density functional theory analysis of the laning instability in sheared soft matter
Using dynamical density functional theory (DDFT) methods we investigate the
laning instability of a sheared colloidal suspension. The nonequilibrium
ordering at the laning transition is driven by non-affine particle motion
arising from interparticle interactions. Starting from a DDFT which
incorporates the non-affine motion, we perform a linear stability analysis that
enables identification of the regions of parameter space where lanes form. We
illustrate our general approach by applying it to a simple one-component fluid
of soft penetrable particles
Creating a community of learners among college faculty through the use of reflective practice
Effects of homeownership on children: the role of neighborhood characteristics and family income
This paper was presented at the conference "Policies to Promote Affordable Housing," cosponsored by the Federal Reserve Bank of New York and New York University's Furman Center for Real Estate and Urban Policy, February 7, 2002. It was part of Session 3: The Impact of Housing on People and Places.Housing ; Community development ; Demography ; Population ; Education
The Unequal Twins - Probability Distributions Aren't Everything
It is the common lore to assume that knowing the equation for the probability
distribution function (PDF) of a stochastic model as a function of time tells
the whole picture defining all other characteristics of the model. We show that
this is not the case by comparing two exactly solvable models of anomalous
diffusion due to geometric constraints: The comb model and the random walk on a
random walk (RWRW). We show that though the two models have exactly the same
PDFs, they differ in other respects, like their first passage time (FPT)
distributions, their autocorrelation functions and their aging properties
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