4,608 research outputs found
Understanding panel conditioning: an examination of social desirability bias in self-reported height and weight in panel surveys using experimental data
Typically reliant on self-reports from panel data, a growing body of literature suggests that relative body weight can have negative effects on labour market outcomes. Given the interest in the effects of relative weight in the social sciences, this paper addresses the question of whether repeated interviewing affects the quality of these data. A theory that focuses on the sensitivity of the questions rather than the survey context is proposed. Examining experimental panel data from Understanding Society using quantile-regression, the findings for women are consistent with the argument that conditioning reduces social desirability effects. The ameliorative effects of panel conditioning on social desirability bias in self-reported height and bodyweight appear to strengthen the association between relative weight and employment for men, but not women, however
The Extent of Multi-particle Quantum Non-locality
It is well known that entangled quantum states can be nonlocal: the
correlations between local measurements carried out on these states cannot
always be reproduced by local hidden variable models. Svetlichny, followed by
others, showed that multipartite quantum states are even more nonlocal than
bipartite ones in the sense that nonlocal classical models with (super-luminal)
communication between some of the parties cannot reproduce the quantum
correlations. Here we study in detail the kinds of nonlocality present in
quantum states. More precisely we enquire what kinds of classical communication
patterns cannot reproduce quantum correlations. By studying the extremal points
of the space of all multiparty probability distributions, in which all parties
can make one of a pair of measurements each with two possible outcomes, we find
a necessary condition for classical nonlocal models to reproduce the statistics
of all quantum states. This condition extends and generalises work of
Svetlichny and others in which it was shown that a particular class of
classical nonlocal models, the ``separable'' models, cannot reproduce the
statistics of all multiparticle quantum states. Our condition shows that the
nonlocality present in some entangled multiparticle quantum states is much
stronger than previously thought. We also study the sufficiency of our
condition.Comment: 10 pages, 2 figures, journal versio
Airborne water vapor DIAL system and measurements of water and aerosol profiles
The Lidar Applications Group at NASA Langley Research Center has developed a differential absorption lidar (DIAL) system for the remote measurement of atmospheric water vapor (H2O) and aerosols from an aircraft. The airborne H2O DIAL system is designed for extended flights to perform mesoscale investigations of H2O and aerosol distributions. This DIAL system utilizes a Nd:YAG-laser-pumped dye laser as the off-line transmitter and a narrowband, tunable Alexandrite laser as the on-line transmitter. The dye laser has an oscillator/amplifier configuration which incorporates a grating and prism in the oscillator cavity to narrow the output linewidth to approximately 15 pm. This linewidth can be maintained over the wavelength range of 725 to 730 nm, and it is sufficiently narrow to satisfy the off-line spectral requirements. In the Alexandrite laser, three intracavity tuning elements combine to produce an output linewidth of 1.1 pm. These spectral devices include a five-plate birefringent tuner, a 1-mm thick solid etalon and a 1-cm air-spaced etalon. A wavelength stability of +/- 0.35 pm is achieved by active feedback control of the two Fabry-Perot etalons using a frequency stabilized He-Ne laser as a wavelength reference. The three tuning elements can be synchronously scanned over a 150 pm range with microprocessor-based scanning electronics. Other aspects of the DIAL system are discussed
Initial Developments Toward an Active Noise Control System for Small Unmanned Aerial Systems
Small unmanned aerial systems have the potential to expand commercial markets from package delivery to infrastructure inspection. Many missions, however, require the vehicles to operate in close proximity to people, where community noise concerns could ultimately limit vehicle acceptability. Therefore, noise control technologies may be needed to achieve an acceptable noise signature and enable widespread use of these vehicles. The purpose of this paper is to assess the feasibility of using loudspeakers attached to the vehicle to actively reduce noise. More specifically, this initial study explores the possibility of using a single loudspeaker to reduce the noise from an isolated rotor. Tests performed in an anechoic chamber with a 7.6 cm diameter speaker and 23.9 cm diameter rotor are used to demonstrate the potential benefits and limitations of the concept. Results confirm that active noise control can work in this application with measured tonal reductions of over 30 dB in specific directions. However, since the radiation characteristics of the speaker are different than the rotor, amplification is observed in other directions. This technology has the potential to create a cone of silence, which could be steered during flight operations to minimize the impact on noise sensitive areas
Generating entanglement with linear optics
Entanglement is the basic building block of linear optical quantum
computation, and as such understanding how to generate it in detail is of great
importance for optical architectures. We prove that Bell states cannot be
generated using only 3 photons in the dual-rail encoding, and give strong
numerical evidence for the optimality of the existing 4 photon schemes. In a
setup with a single photon in each input mode, we find a fundamental limit on
the possible entanglement between a single mode Alice and arbitrary Bob. We
investigate and compare other setups aimed at characterizing entanglement in
settings more general than dual-rail encoding. The results draw attention to
the trade-off between the entanglement a state has and the probability of
postselecting that state, which can give surprising constant bounds on
entanglement even with increasing numbers of photons.Comment: 13 pages, 10 figures, 1 table, comments welcom
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