Debrecen, Hungary
Debrecen, Hungary

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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.

Pei J.C.,Joint Institute for Heavy Ion Research | Pei J.C.,University of Tennessee at Knoxville | Pei J.C.,Oak Ridge National Laboratory | Kruppa A.T.,Joint Institute for Heavy Ion Research | And 5 more authors.
Physical Review C - Nuclear Physics | Year: 2011

The quasiparticle energy spectrum of the Hartree-Fock-Bogoliubov (HFB) equations contains discrete bound states, resonances, and nonresonant continuum states. We study the structure of the unbound quasiparticle spectrum of weakly bound nuclei within several methods that do not rely on imposing scattering or outgoing boundary conditions. Various approximations are examined to estimate resonance widths. It is shown that the stabilization method works well for all HFB resonances except for very narrow ones. The Thomas-Fermi approximation to the nonresonant continuum has been shown to be very effective, especially for coordinate-space HFB calculations in large boxes that involve huge amounts of discretized quasiparticle continuum states. © 2011 American Physical Society.

Salma I.,Eötvös Loránd University | Dosztaly K.,Eötvös Loránd University | Borsos T.,Eötvös Loránd University | Soveges B.,Eötvös Loránd University | And 4 more authors.
Atmospheric Environment | Year: 2013

PM10 mass, particle number (N) and CO2 concentrations, particle number size distributions and meteorological parameters were determined with high time resolution, and daily aerosol samples were collected in the PM10-2.0 and PM2.0 size fractions for chemical analysis in the middle of a university lecture hall for one week. Median concentrations for the PM10 mass and N of 15.3 μg m-3 and 3.7 × 103 cm-3, respectively were derived. The data are substantially smaller than the related outdoor levels or typical values for residences. There were considerable concentration differences for workdays, weekends and various lectures. Main sources of PM10 mass include the usage of chalk sticks for writing, wiping the blackboard, ordinary movements and actions of students and cleaning. High PM10 mass concentration levels up to 100 μg m-3 were realised for short time intervals after wiping the blackboard. The mass concentrations decreased rapidly after the emission source ceased to be active. Two classes of coarse particles were identified. General indoor dust particles exhibited a residence time of approximately 35 min, while the residence time for the chalk dust particles was approximately 20 min as lower estimates. Emission source rate for wiping the blackboard was estimated to be between 8 and 14 mg min-1. This represents a substantial emission rate but the source is active only up to 1 min. Suspension of the chalk (made mainly of gypsum) dust particles was confirmed by enrichment of Ca and S in the hall with respect to ambient urban aerosol. Contribution of ambient aerosol via the heating, ventilation and air conditioning (HVAC) facility was considerable for time intervals when the indoor sources of PM10 mass were not intensive. The HVAC facility introduces, however, the major amount of aerosol particles from the outdoors as far as their number concentration is regarded. Mean contribution of ultrafine particles to the total particle number was (69 ± 7)%, which is smaller than for the related outdoor urban environment. This can indicate aged ultrafine aerosol. The major amounts of CO2 arrive from the corridors through open doors by infiltration. Spatial distribution of the PM10 mass concentration within the hall was derived by CFD modelling, and spatial inhomogeneities were obtained. © 2012 Elsevier Ltd.

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.

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.

Nandori I.,Mta Of Particle Physics Research Group | Nandori I.,Institute of Nuclear Research | Racz J.,Institute of Nuclear Research
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2012

The deterministic Landau-Lifshitz-Gilbert equation has been used to investigate the nonlinear dynamics of magnetization and the specific power loss in magnetic nanoparticles with uniaxial anisotropy driven by a rotating magnetic field, generalizing the results obtained for the isotropic case found by P. F. de Châtel, I. Nándori, J. Hakl, S. Mészáros, and K. Vad. As opposed to many applications of magnetization reversal in single-domain ferromagnetic particles, where losses must be minimized, in this paper, we study the mechanisms of dissipation used in cancer therapy by hyperthermia, which requires the enhancement of energy losses. We show that for circularly polarized field, the energy loss per cycle is decreased by the anisotropy compared to the isotropic case when only dynamical effects are taken into account. Thus, in this case, in the low-frequency limit, a better heating efficiency can be achieved for isotropic nanoparticles. The possible role of thermal fluctuations is also discussed. Results obtained are compared to experimental data. © 2012 American Physical Society.

Nandori I.,Mta Of Particle Physics Research Group | Nandori I.,Institute of Nuclear Research
Journal of High Energy Physics | Year: 2013

The functional renormalization group equation with a compactly supported smooth (CSS) regulator function is considered. It is demonstrated that in an appropriate limit the CSS regulator recovers the optimized one and it has derivatives of all orders. The more generalized form of the CSS regulator is shown to reduce to all major type of regulator functions (exponential, power-law) in appropriate limits. The CSS regulator function is tested by studying the critical behavior of the bosonized two-dimensional quantum electrodynamics in the local potential approximation and the sine-Gordon scalar theory for d < 2 dimensions beyond the local potential approximation. It is shown that a similar smoothing problem in nuclear physics has already been solved by introducing the so called Salamon-Vertse potential which can be related to the CSS regulator. © 2013, SISSA.

Nandori I.,Institute of Nuclear Research
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

Known results on two-dimensional quantum electrodynamics (QED2) have been used to study the dependence of functional renormalization group equations on renormalization schemes and approximations applied for its bosonized version. It is demonstrated that the singularity of flow equations can be avoided in the optimized and power-law schemes for the bosonized model and the drawback of renormalization on bosonization is shown: it is indicated that renormalization of QED2 possibly requires interaction terms corresponding to higher frequency modes of its bosonized version. © 2011 American Physical Society.

News Article | November 11, 2016

On 5 October, Ukraine became an associate Member State of CERN, following official notification to CERN that Ukraine’s parliament has ratified an agreement signed with CERN in October 2013. “Our hard and consistent work over the past two decades has been crowned today by a remarkable event – granting Ukraine the status of CERN associate member,” says Yurii Klymenko, Ukraine’s ambassador to the United Nations in Geneva. “It is an extremely important step on the way of Ukraine’s European integration.” Ukraine has been a long-time contributor to the ALICE, CMS and LHCb experiments at the LHC and to R&D in accelerator technology. Ukraine also operates a Tier-2 computing centre in the Worldwide LHC Computing Grid. Ukraine and CERN first signed a co-operation agreement in 1993, followed by a joint declaration in 2011, but Ukraine’s relationship with CERN dates back much further through the Joint Institute of Nuclear Research (JINR) in Dubna, Russia, of which Ukraine is a member. CERN-JINR co-operation in the field of high-energy accelerators started in the early 1960s, and ever since, the two institutions have formed a bridge between East and West that has made important contributions to the development of global, peaceful scientific co-operation. Associate membership will open a new era of co-operation that will strengthen the long-term partnership between CERN and the Ukrainian scientific community. It will allow Ukraine to participate in the governance of CERN, in addition to allowing Ukrainian scientists to become CERN staff and to participate in CERN’s training and career-development programmes. Finally, it will allow Ukrainian industry to bid for CERN contracts, thus opening up opportunities for industrial collaboration in areas of advanced technology. “It is a great pleasure to warmly welcome Ukraine into the CERN family,” says CERN Director-General Fabiola Gianotti.

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