11,465 research outputs found
The effect of school quality on educational attainment and wages
The paper examines the effects of school pupil-teacher ratios and type of school on educational attainment and wages using the British National Child Development survey (NCDS). The NCDS is a panel survey which has followed a cohort of individuals born in March 1958, and has a rich set of background variables recorded throughout the individual's life. The results suggest that, once we control for ability and family background, the pupil-teacher ratio has no impact on educational qualifications or on male wages. It has an impact on women’s wages at the age of 33, particularly those of low ability. We also find evidence that those who attend selective schools have better educational outcomes and, in the case of men, higher wages at the age of 33. The impact is higher for the type of individuals who are less likely not to attend selective schools, but for whom a comparison group does exist among those attending
A first order Tsallis theory
We investigate first-order approximations to both i) Tsallis' entropy
and ii) the -MaxEnt solution (called q-exponential functions ). It is
shown that the functions arising from the procedure ii) are the MaxEnt
solutions to the entropy emerging from i). The present treatment is free of the
poles that, for classic quadratic Hamiltonians, appear in Tsallis' approach, as
demonstrated in [Europhysics Letters {\bf 104}, (2013), 60003]. Additionally,
we show that our treatment is compatible with extant date on the ozone layer.Comment: 4 figures adde
Normalized ghost imaging
We present an experimental comparison between different iterative ghost imaging algorithms. Our experimental setup utilizes a spatial light modulator for generating known random light fields to illuminate a partially-transmissive object. We adapt the weighting factor used in the traditional ghost imaging algorithm to account for changes in the efficiency of the generated light field. We show that our normalized weighting algorithm can match the performance of differential ghost imaging
Electronic Properties of Molecules and Surfaces with a Self\uad-Consistent Interatomic van der Waals Density Functional.
How strong is the effect of van der Waals (vdW) interactions on the electronic properties of molecules
and extended systems? To answer this question, we derived a fully self-consistent implementation of the
density-dependent interatomic vdW functional of Tkatchenko and Scheffler [Phys. Rev. Lett. 102, 073005
(2009)]. Not surprisingly, vdW self-consistency leads to tiny modifications of the structure, stability, and
electronic properties of molecular dimers and crystals. However, unexpectedly large effects were found in
the binding energies, distances, and electrostatic moments of highly polarizable alkali-metal dimers. Most
importantly, vdW interactions induced complex and sizable electronic charge redistribution in the vicinity
of metallic surfaces and at organic-metal interfaces. As a result, a substantial influence on the computed
work functions was found, revealing a nontrivial connection between electrostatics and long-range electron
correlation effects
Efficient estimation of AUC in a sliding window
In many applications, monitoring area under the ROC curve (AUC) in a sliding
window over a data stream is a natural way of detecting changes in the system.
The drawback is that computing AUC in a sliding window is expensive, especially
if the window size is large and the data flow is significant.
In this paper we propose a scheme for maintaining an approximate AUC in a
sliding window of length . More specifically, we propose an algorithm that,
given , estimates AUC within , and can maintain this
estimate in time, per update, as the window slides.
This provides a speed-up over the exact computation of AUC, which requires
time, per update. The speed-up becomes more significant as the size of
the window increases. Our estimate is based on grouping the data points
together, and using these groups to calculate AUC. The grouping is designed
carefully such that () the groups are small enough, so that the error stays
small, () the number of groups is small, so that enumerating them is not
expensive, and () the definition is flexible enough so that we can
maintain the groups efficiently.
Our experimental evaluation demonstrates that the average approximation error
in practice is much smaller than the approximation guarantee ,
and that we can achieve significant speed-ups with only a modest sacrifice in
accuracy
Tuning the atomic and domain structure of epitaxial films of multiferroic BiFeO3
Recent works have shown that the domain walls of room-temperature
multiferroic BiFeO3 (BFO) thin films can display distinct and promising
functionalities. It is thus important to understand the mechanisms underlying
domain formation in these films. High-resolution x-ray diffraction and
piezo-force microscopy, combined with first-principles simulations, have
allowed us to characterize both the atomic and domain structure of BFO films
grown under compressive strain on (001)-SrTiO3, as a function of thickness. We
derive a twining model that describes the experimental observations and
explains why the 71o domain walls are the ones commonly observed in these
films. This understanding provides us with a new degree of freedom to control
the structure and, thus, the properties of BiFeO3 thin films.Comment: RevTeX; 4 two-column pages; 4 color figures. Figure 2b does not seem
to display well. A proper version can be found in the source fil
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