Estimation of microblock sizes in mosaic crystals according to fast electron radiation characteristics

The possibilities of a previously proposed technique for determining the characteristic sizes of microblocks in mosaic aα-class crystals have been analyzed. Determination is performed according to the ratio between the measured and calculated values for the diffraction suppression of the fixed-energy bremsstrahlung yield. The limits of applicability of the technique have been revealedyesBelgorod State Universit

Narrowband Biphoton Generation due to Long-Lived Coherent Population Oscillations

We study the generation of paired photons due to the effect of four-wave mixing in an ensemble of pumped two-level systems that decay via an intermediate metastable state. The slow population relaxation of the metastable state to the ground state is utilized to create long-lived coherent population oscillation, leading to narrowband nonlinear response of the medium. The biphotons have a narrow bandwidth, long coherence time and length, which can be controlled by the pump field. In addition, the biphotons are antibunched, with antibunching period determined by the dephasing time. During this period, damped oscillations of the biphoton wavefunction occurs if the pump detuning is non-zero.Comment: 7 pages, 2 figure

Estimation of Crystal Sample Structure by Means of Fast Electron Radiation

An analysis is made of the dependence of the characteristics of X-ray radiation arising during the passage of fast electrons through the crystal on the quality of the internal structure of the sampleyesBS

Towards the electron EDM search. Theoretical study of PbF

We report ab initio relativistic correlation calculations of potential curves and spectroscopic constants for four lowest-lying electronic states of the lead monofluoride. We also calculated parameters of the spin-rotational Hamiltonian for the ground and the first excited states including P,T-odd and P-odd terms. In particular, we have obtained hyperfine constants of the $^{207}$Pb nucleus. For the $^2\Pi_{1/2}$ state $A_\perp=-6859.6$ MHz, $A_\|=9726.9$ MHz and for the A$^2\Sigma^+_{1/2}$ $A_\perp=1720.8$ MHz, $A_\|=3073.3$ MHz. Our values of the ground state hyperfine constants are in good agreement with the previous theoretical studies. We discuss and explain seeming disagreement in the sign of the constant $A_\perp$ with the recent experimental data. The effective electric field on the electron $E_{eff}$, which is important for the planned experiment to search for the electric dipole moment of the electron, is found to be 3.3 * 10^{10} V/cm

Influence of crystal mosaicity on the X-radiation characteristics observed at a small angle to the particle velocity direction

The experimentally measured yields of X-rays generated by 500-MeV electrons in oriented tungsten single crystals are analyzedye

Improved Vote Aggregation Techniques for the Geo-Wiki Cropland Capture Crowdsourcing Game

Crowdsourcing is a new approach for solving data processing problems for which conventional methods appear to be inaccurate, expensive, or time-consuming. Nowadays, the development of new crowdsourcing techniques is mostly motivated by so called Big Data problems, including problems of assessment and clustering for large datasets obtained in aerospace imaging, remote sensing, and even in social network analysis. By involving volunteers from all over the world, the Geo-Wiki project tackles problems of environmental monitoring with applications to flood resilience, biomass data analysis and classification of land cover. For example, the Cropland Capture Game, which is a gamified version of Geo-Wiki, was developed to aid in the mapping of cultivated land, and was used to gather 4.5 million image classifications from the Earth’s surface. More recently, the Picture Pile game, which is a more generalized version of Cropland Capture, aims to identify tree loss over time from pairs of very high resolution satellite images. Despite recent progress in image analysis, the solution to these problems is hard to automate since human experts still outperform the majority of machine learning algorithms and artificial systems in this field on certain image recognition tasks. The replacement of rare and expensive experts by a team of distributed volunteers seems to be promising, but this approach leads to challenging questions such as: how can individual opinions be aggregated optimally, how can confidence bounds be obtained, and how can the unreliability of volunteers be dealt with? In this paper, on the basis of several known machine learning techniques, we propose a technical approach to improve the overall performance of the majority voting decision rule used in the Cropland Capture Game. The proposed approach increases the estimated consistency with expert opinion from 77% to 86%