16,805 research outputs found
Collision Integrals for the Transport Properties of Dissociating Air at High Temperatures
Collision integrals for the transport properties of dissociating air at high temperature
Reply to [arXiv:1105.5147] "Are GRB 090423 and Similar Bursts due to Superconducting Cosmic Strings?"
The GRB outflow driven by superconducting cosmic strings is likely to be an
arc rather than a usually-considered spherical cap. In such a case, the
afterglows of the cosmic string GRBs could be basically consistent with the
observation of the high-redshift GRBs.Comment: 2 pages, 1 figure, to appear in Phys. Rev. Let
Discriminative Density-ratio Estimation
The covariate shift is a challenging problem in supervised learning that
results from the discrepancy between the training and test distributions. An
effective approach which recently drew a considerable attention in the research
community is to reweight the training samples to minimize that discrepancy. In
specific, many methods are based on developing Density-ratio (DR) estimation
techniques that apply to both regression and classification problems. Although
these methods work well for regression problems, their performance on
classification problems is not satisfactory. This is due to a key observation
that these methods focus on matching the sample marginal distributions without
paying attention to preserving the separation between classes in the reweighted
space. In this paper, we propose a novel method for Discriminative
Density-ratio (DDR) estimation that addresses the aforementioned problem and
aims at estimating the density-ratio of joint distributions in a class-wise
manner. The proposed algorithm is an iterative procedure that alternates
between estimating the class information for the test data and estimating new
density ratio for each class. To incorporate the estimated class information of
the test data, a soft matching technique is proposed. In addition, we employ an
effective criterion which adopts mutual information as an indicator to stop the
iterative procedure while resulting in a decision boundary that lies in a
sparse region. Experiments on synthetic and benchmark datasets demonstrate the
superiority of the proposed method in terms of both accuracy and robustness
What determines social service workers’ wages: A cross-country analysis using a Luxembourg Income Study
The study is aimed at exploring the influencing factor of wages among social service workers (SSWs) through a cross-country analysis. Using Luxembourg Income Study data, two aspects are emphasised: first, the trends and patterns of wage levels among SSWs. Second, the determining factors that influence their low wages at a cross-national level and how those factors are intersectionally intertwined to exacerbate the wage level. Three significant findings are confirmed: a universal gendered wage gap; a more significant wage gap for those on part-time and/or fractured contracts and employed in the private sector; and a substantial association between a higher education and higher wages. Two policy concerns are raised for discussion: first, tackling the gendered wage gap and ensuring more secure employment, and a guaranteed living wage for those employed in the private sector. Second, enhancing the professionalism for empowering their effective choices in the labour market is essential [148 words]
Solar modulation of cosmic ray intensity and solar flare events inferred from (14)C contents in dated tree rings
The delta 14C values in 42 rings of a white spruce grown in Mackenzie Delta was measured as a continuing effort of tracing the history of solar modulation of cosmic ray intensity. The delta 14C values in six rings were measured, in search of a 14C increase due to two large solar flares that occurred in 1942. The results are presented
Laboratory simulations of astrophysical jets and solar coronal loops: new results
An experimental program underway at Caltech has produced plasmas where the shape is neither fixed by the vacuum chamber nor fixed by an external coil set, but instead is determined by self-organization. The plasma dynamics is highly reproducible and so can be studied in considerable detail even though the morphology of the plasma is both complex and time-dependent. A surprising result has been the observation that self-collimating MHD-driven plasma jets are ubiquitous and play a fundamental role in the self-organization. The jets can be considered lab-scale simulations of astrophysical jets and in addition are intimately related to solar coronal loops. The jets are driven by the combination of the axial component of the J×B force and the axial pressure gradient resulting from the non-uniform pinch force associated with the flared axial current density. Behavior is consistent with a model showing that collimation results from axial non-uniformity of the jet velocity. In particular, flow stagnation in the jet frame compresses frozen-in azimuthal magnetic flux, squeezes together toroidal magnetic field lines, thereby amplifying the embedded toroidal magnetic field, enhancing the pinch force, and hence causing collimation of the jet
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