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Debrecen, Hungary

Kovacs J.,Debrecen University | Nagy S.,Debrecen University | Nandori I.,Institute of Nuclear Research | Sailer K.,Debrecen University
Journal of High Energy Physics | Year: 2011

The low energy infrared scaling of the multi-color 2-dimensional quantum chromodynamics is determined in the framework of its bosonized model by using the functional renormalization group method in the local potential approximation. The model exhibits a single phase with a superuniversal effective potential. © SISSA 2011.

Shu G.W.,Chung Yuan Christian University | Lin J.Y.,National Chiao Tung University | Jian H.T.,Chung Yuan Christian University | Shen J.L.,Chung Yuan Christian University | And 6 more authors.
Optics Express | Year: 2013

Spatially-resolved electroluminescence (EL) images in the triple-junction InGaP/InGaAs/Ge solar cell have been investigated to demonstrate the subcell coupling effect. Upon irradiating the infrared light with an energy below bandgap of the active layer in the top subcell, but above that in the middle subcell, the EL of the top subcell quenches. By analysis of EL intensity as a function of irradiation level, it is found that the coupled p-n junction structure and the photovoltaic effect are responsible for the observed EL quenching. With optical coupling and photoswitching effects in the multi-junction diode, a concept of infrared image sensors is proposed. © 2012 Optical Society of America.

Kavasi N.,University of Pannonia | Kovacs T.,University of Pannonia | Nemeth C.,University of Pannonia | Szabo T.,Hospital of Tapolca | And 4 more authors.
Radiation Measurements | Year: 2015

Different legislation systems can be found in the world concerning radon levels at workplaces. Following the European Union suggestion, a reference level for radon concentration in the air at workplaces was established in several European countries. In Hungary, the relevant legislation has come into effect on 1 January 2003. The determination of average radon concentration might present a problem, especially in places where the monthly average concentrations vary to a great extent. For example, the monthly averages measured in a hospital cave used for treating respiratory diseases showed a 24-fold difference depending on the chosen month. In such cases, attention should be paid when choosing the months and using the results of measurements for dose assessment. Another uncertainty emerges when estimating the annual dose, based on the data coming from long-term measurements, usually using integrated methods such as track detectors. There is a considerable difference between the averages measured during the working hours and over the total time (including nights and weekends), mostly in the cases of rooms with frequent air change like schools, kindergartens and ventilated workplaces. This can lead to a significant overestimation in dose calculation. Special attention needs to be paid to workplaces such as mines, tunnels and open air uranium tailings sites. This paper discusses the possible inaccuracies caused by the improper selection of time periods and methods in the measurements of the average radon concentration at workplaces. © 2005 Elsevier Ltd. All rights reserved.

Hornyak I.,Debrecen University | Kruppa A.T.,Institute of Nuclear Research
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012

The two-body Coulomb scattering problem is solved using the standard complex-scaling method. The explicit enforcement of the scattering boundary condition is avoided. Splitting of the scattering wave function based on the Coulomb modified plane wave is considered. This decomposition leads to a three-dimensional Schrödinger equation with a source term. Partial-wave expansion is carried out and the asymptotic form of the solution is determined. This splitting does not lead to simplification of the scattering boundary condition if complex scaling is invoked. An alternative splitting carried out only on the partial-wave level is introduced and this method is proven to be very useful. The scattered part of the wave function tends to zero at large interparticle distances. This property permits easy numerical solution: the scattered part of the wave function can be expanded on a bound-state-type basis. The method can be applied not only for a pure Coulomb potential but also in the presence of a short-range interaction. © 2012 American Physical Society.

Kazama M.,Chiba University | Shinotsuka H.,Chiba University | Ohori Y.,Chiba University | Niki K.,Chiba University | And 2 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

We study the angular and energy dependence of surface and bulk plasmon losses accompanying deep core excitations in simple metals. Here full multiple scatterings of photoelectrons are taken into account before and after the plasmon losses within the quantum Landau formula, which can describe overall features of the photoemission bands. For example, multiple plasmon loss features can be calculated by use of the formula. Two simple metals, Al and Na, are studied here. The depth profiles of the plasmon losses are strongly influenced by the elastic scatterings. The model assuming single elastic scatterings overestimates the losses from deep emitters due to the forward focusing effects, whereas the model accounting for full multiple scatterings gives a much rapidly decaying function of the depth due to the defocusing effects and rich structures due to the photoelectron diffraction. The single elastic scattering approximation gives a poor result both for the depth profiles and for the loss spectra. The present multiple scattering calculations successfully explain the azimuthal dependence of the loss spectra, which reflect the local geometry around the emitters. © 2014 American Physical Society.

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