1,852 research outputs found
Projected Impacts of U.S. Immigration on Per Capita Greenhouse Gas Emissions, 2050 and 2100
Immigration affects long-run projections of U.S. CO2 emissions, via the impacts on population scale, population aging, and labor supply. This article estimates the labor supply effects, complementing an earlier paper in which the authors have modeled the effects of scale and aging. Labor supply effects on future CO2 emissions are approximated based on recent survey data on earnings differences between immigrant and native-born households and on existing demographic projections. Gaps in average earnings are found to be substantial only for Hispanic immigrants, between 25 and 47 percent below native-born peers, depending on the age group and measure used. Impacts are estimated using a range of population projections and assumptions about future convergence, or assimilation, of the earnings of immigrants and their descendents to those of the descendents of the native-born population. If per capita earnings differences remain near current levels, the aggregate effects on per capita earnings and consumption are found to be affected more by the rate at which the immigrant population's earnings converge to native-born levels than by projected differences in future immigration. If assimilation is rapid, the impacts of immigration are proportional to the size of the first generation and negligible, regardless of the level of immigration. If future assimilation is impeded, the marginal impacts will be more substantial and vary with the level of immigration but still well below 10% in 2100 when calculated using the preferred measure of earning differences and only exceed 10% when the impacts are calculated using the alternate per capita earnings differences
Detecting Beyond-Einstein Polarizations of Continuous Gravitational Waves
The direct detection of gravitational waves with the next generation
detectors, like Advanced LIGO, provides the opportunity to measure deviations
from the predictions of General Relativity. One such departure would be the
existence of alternative polarizations. To measure these, we study a single
detector measurement of a continuous gravitational wave from a triaxial pulsar
source. We develop methods to detect signals of any polarization content and
distinguish between them in a model independent way. We present LIGO S5
sensitivity estimates for 115 pulsars.Comment: submitted to PR
A new code for parameter estimation in searches for gravitational waves from known pulsars
We describe the consistency testing of a new code for gravitational wave
signal parameter estimation in known pulsar searches. The code uses an
implementation of nested sampling to explore the likelihood volume. Using fake
signals and simulated noise we compare this to a previous code that calculated
the signal parameter posterior distributions on both a grid and using a crude
Markov chain Monte Carlo (MCMC) method. We define a new parameterisation of two
orientation angles of neutron stars used in the signal model (the initial phase
and polarisation angle), which breaks a degeneracy between them and allows more
efficient exploration of those parameters. Finally, we briefly describe
potential areas for further study and the uses of this code in the future.Comment: Accepted for proceedings of Amaldi 9 meetin
An Evidence Based Time-Frequency Search Method for Gravitational Waves from Pulsar Glitches
We review and expand on a Bayesian model selection technique for the
detection of gravitational waves from neutron star ring-downs associated with
pulsar glitches. The algorithm works with power spectral densities constructed
from overlapping time segments of gravitational wave data. Consequently, the
original approach was at risk of falsely identifying multiple signals where
only one signal was present in the data. We introduce an extension to the
algorithm which uses posterior information on the frequency content of detected
signals to cluster events together. The requirement that we have just one
detection per signal is now met with the additional bonus that the belief in
the presence of a signal is boosted by incorporating information from adjacent
time segments.Comment: 6 pages, 4 figures, submitted to AMALDI 7 proceeding
Advanced technologies for future ground-based, laser-interferometric gravitational wave detectors
We present a review of modern optical techniques being used and developed for the field of gravitational wave detection. We describe the current state-of-the-art of gravitational waves detector technologies with regard to optical layouts, suspensions and test masses. We discuss the dominant sources and noise in each of these subsystems and the developments that will help mitigate them for future generations of detectors. We very briefly summarise some of the novel astrophysics that will be possible with these upgraded detectors
An Evidence Based Search Method For Gravitational Waves From Neutron Star Ring-downs
The excitation of quadrupolar quasi-normal modes in a neutron star leads to
the emission of a short, distinctive, burst of gravitational radiation in the
form of a decaying sinusoid or `ring-down'. We present a Bayesian analysis
method which incorporates relevant prior information about the source and known
instrumental artifacts to conduct a robust search for the gravitational wave
emission associated with pulsar glitches and soft -ray repeater flares.
Instrumental transients are modelled as sine-Gaussian and their evidence, or
marginal likelihood, is compared with that of Gaussian white noise and
ring-downs via the `odds-ratio'. Tests using simulated data with a noise
spectral density similar to the LIGO interferometer around 1 kHz yield 50%
detection efficiency and 1% false alarm probability for ring-down signals with
signal-to-noise ratio . For a source at 15 kpc this requires an
energy of 1.3\times 10^{-5}M_{\astrosun}c^2 to be emitted as gravitational
waves.Comment: 14 pages, 12 figure
Population Aging and Future Carbon Emissions in the United States
Changes in the age composition of U.S. households over the next several decades could affect energy use and carbon dioxide emissions. this article incorporates population age structure into and energy-economic growth model with multiple dynasties of heterogenous households. The model is used to estimate and compare effects of population aging and technical change on baseline paths of U.S. energy use and emissions. Results show that population aging reduces long-term carbon dioxide emissions, by almost 40% in low population scenario, and effects of aging on emissions can be as large, or larger than effects of technical change in some cases
A more representative chamber: representation and the House of Lords
Since 1997 there has been substantive reform of the House of Lords in an effort to make the chamber ‘more democratic and more representative’. Whilst the Labour government failed to press ahead with any of the proposed plans for further reform following the removal of the bulk of the hereditary peers in 1999, it remained committed to the notion that such reform must make the second chamber ‘more representative’. The coalition government's programme advocates a long-term aspiration for a House wholly or mainly elected on the basis of proportional representation, and a short-term approach based on additional appointments to ensure a balance of the parties. What is clear in all of these proposals for reform is a desire for the House of Lords to become more representative than it is at present. However, what is less clear is what is meant by ‘representative’ – who the House of Lords is supposed to represent, and what form representation will take. Moreover, in proposing to make the chamber more representative, either through appointment or election, little attention has been paid to how the current House of Lords provides representation. This article examines these questions in the context of Pitkin's classic conceptions of representation and peers' attitudes towards their own representative rol
Observations on an Aileron-Flutter Instability Encountered on a 45 Degree Swept-Back Wing in Transonic and Supersonic Flight
In the course of a flight test of a supersonic research pilotless aircraft (the NACA RM-1), large-amplitude aileron oscillations, probably aileron compressibility flutter, were encountered in the transonic and supersonic speed ranges. The wing was oscillating at the same frequency as the aileron. The aircraft was equipped with 45 degree swept-back wings of symmetrical NASA 65-010 airfoil section. Completely mass-balanced ailerons with 20 degree beveled trailing edges were installed on the wings. The ailerons were free floating with no mechanical restraining force other than the friction of the aileron hinges and servomechanism bearings throughout the high-speed interval of flight
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