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Search Results: 1 - 10 of 1490 matches for " Micha? Dyrda "
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Developments of a new mirror technology for the Cherenkov Telescope Array
Jerzy Micha?owski,Michal Dyrda,Jacek Niemiec,Maciej Sowiński,Marek Stodulski
Physics , 2015,
Abstract: The Cherenkov Telescope Array (CTA) observatory for very high-energy gamma rays will consist of about a hundred of imaging atmospheric Cherenkov telescopes (IACTs) of different size with a total reflective area of about 10,000 m$^2$. Here we present a novel technology for the production of IACT mirrors that has been developed in the Institute of Nuclear Physics PAS in Krakow, Poland. The mirrors are made by cold-slumping of the front reflecting aluminium-coated panel and the rear panel interspaced with aluminium spacers. Each panel is built of two glass panels laminated with a layer of a fibreglass tissue in between for reinforcement of the structure against mechanical damage. The mirror structure is open and does not require a perfect sealing needed in closed-type designs. It prohibits water to be trapped inside and enables a proper ventilation of the mirror. Full-size hexagonal prototype mirrors produced for the medium-sized CTA telescopes will be presented together with the results of recent comprehensive optical and durability tests. Their design will be compared to the earlier technology developed at INP PAS that used a rigid flat open support structure with a reflective layer made by cold-slumping of the coated glass panel to the cast-in-mould spherical epoxy resin layer.
Discovery of VHE gamma-rays from the radio galaxy PKS 0625-354 with H.E.S.S
Michal Dyrda,Alicja Wierzcholska,Olivier Hervet,Rafal Moderski,Mateusz Janiak,Micha? Ostrowski,?ukasz Stawarz,for the H. E. S. S. Collaboration
Physics , 2015,
Abstract: Most of the extragalactic objects detected so far in the very high energy (VHE) regime are blazars, but the discovered nearby radio galaxies: M87, Cen A and NGC 1275 of type FRI seem to constitute a new class of VHE emitters. The radio galaxy PKS 0625-354 was observed and detected ($\sim$6$\sigma$) with the H.E.S.S. phase I telescopes in 2012, above an energy threshold of 250 GeV. The time-averaged VHE energy spectrum is well characterized by a power law model. The broad-band light curve, including the available multiwavelength data, as well as the VHE data gathered with H.E.S.S. will be presented.
Single-Mirror Small-Size Telescope structure for the Cherenkov Telescope Array
Jacek Niemiec,Jerzy Micha?owski,MichaDyrda,Wojciech Kochański,Jaromir Ludwin,Marek Stodulski,Pawe? Zió?kowski,Pawe? ?ychowski for the CTA Consortium
Physics , 2013,
Abstract: A single-mirror small-size (1M-SST) Davies-Cotton telescope has been proposed for the southern observatory of the Cherenkov Telescope Array (CTA) by a consortium of scientific institutions from Poland, Switzerland, and Germany. The telescope has a 4 m diameter reflector and will be equipped with a fully digital camera based on Geiger avalanche photodiodes (APDs). Such a design is particularly interesting for CTA because it represents a very simple, reliable, and cheap solution for a SST. Here we present the design and the characteristics of the mechanical structure of the 1M-SST telescope and its drive system. We also discuss the results of a finite element method analysis in order to demonstrate the conformance of the design with the CTA specifications and scientific objectives. In addition, we report on the current status of the construction of a prototype telescope structure at the Institute of Nuclear Physics PAS in Krakow.
Spin Hall effect in AA-stacked bilayer graphene
A. Dyrda,J. Barna?
Physics , 2013, DOI: 10.1016/j.ssc.2014.02.023
Abstract: Intrinsic spin Hall effect in the AA-stacked bilayer graphene is studied theoretically. The low-energy electronic spectrum for states in the vicinity of the Dirac points is obtained from the corresponding $\mathbf{k}\cdot\mathbf{p}$ Hamiltonian. The spin Hall conductivity in the linear response regime is determined within the Green function formalism. Conditions for the existence of spin Hall insulator phase are also analyzed, and it is shown that the spin Hall insulator phase can exist for a sufficiently large spin-orbit coupling, which opens a gap in the spectrum. The electric field perpendicular to the graphene plane leads then to reduction of the gap width and suppression of the spin Hall insulator phase. The low temperature spin Nernst effect is also calculated from the zero temperature spin Hall conductivity.
Assessment of the Erosive Wear Kinetics of Epoxy Coatings Modified with Nanofillers  [PDF]
Danuta Kotnarowska, Micha? Przerwa
Journal of Surface Engineered Materials and Advanced Technology (JSEMAT) , 2013, DOI: 10.4236/jsemat.2013.31A013
Abstract:

The paper presents results of investigation on the erosive wear kinetics of epoxy coatings modified with alumina or silica nanoparticles. Natural weathering caused a decrease of their erosive wear resistance. After a 3-year natural weathering, highest erosive wear resistance showed the epoxy coating modified with alumina nanoparticles.

Dust production 680-850 million years after the Big Bang
Micha? J. Micha?owski
Physics , 2015, DOI: 10.1051/0004-6361/201525644
Abstract: Dust plays an important role in our understanding of the Universe, but it is not obvious yet how the dust in the distant universe was formed. I derived the dust yields per asymptotic giant branch (AGB) star and per supernova (SN) required to explain dust masses of galaxies at z=6.3-7.5 (680-850 million years after the Big Bang) for which dust emission has been detected (HFLS3 at z=6.34, ULAS J1120+0641 at z=7.085, and A1689-zD1 at z=7.5), or unsuccessfully searched for. I found very high required yields, implying that AGB stars could not contribute substantially to dust production at these redshifts, and that SNe could explain these dust masses, but only if they do not destroy most of the dust they form (which is unlikely given the upper limits on the SN dust yields derived for galaxies where dust is not detected). This suggests that the grain growth in the interstellar medium is likely required at these early epochs.
Dust production 0.7-1.5 billion years after the Big Bang
Micha? J. Micha?owski
Physics , 2015,
Abstract: Cosmic dust is an important component of the Universe, and its origin, especially at high redshifts, is still unknown. I present a simple but powerful method of assessing whether dust observed in a given galaxy could in principle have been formed by asymptotic giant branch (AGB) stars or supernovae (SNe). Using this method I show that for most of the galaxies with detected dust emission between z=4 and z=7.5 (1.5-0.7 billion years after the Big Bang) AGB stars are not numerous and efficient enough to be responsible for the measured dust masses. Supernovae could account for most of the dust, but only if all of them had efficiencies close to the maximal theoretically allowed value. This suggests that a different mechanism is responsible for dust production at high redshifts, and the most likely possibility is the grain growth in the interstellar medium.
Comparative Balancing of Non-Redox and Redox Electrolytic Systems and Its Consequences  [PDF]
Anna Maria Micha?owska-Kaczmarczyk, Tadeusz Micha?owski
American Journal of Analytical Chemistry (AJAC) , 2013, DOI: 10.4236/ajac.2013.410A1006
Abstract: In this paper, it is proved that linear combination 2·f(O) - f(H) of elemental balances: f(O) for O and f(H) for H is linearly independent on charge and elemental/core balances for all redox systems of any degree of complexity; it is the primary form of the Generalized Electron Balance (GEB), , considered as the Approach II to GEB. The Approach II is equivalent to the Approach I based on the principle of common pool of electrons. Both Approaches are illustrated on an example of titration of acidified (H2SO4) solution of H2C2O4 with KMnO4. It is also stated, on an example of titration of the same solution with NaOH, that 2·f(O) - f(H) is a linear combination of charge and elemental/core balances, i.e. it is not an independent balance when related to the non-redox system. These properties of 2·f(O) - f(H) can be extended on redox and non-redox systems, of any degree of complexity,
Calculation of Solubility of Oxyquinolinates  [PDF]
Anna M. Micha?owska-Kaczmarczyk, Tadeusz Micha?owski
Journal of Analytical Sciences, Methods and Instrumentation (JASMI) , 2014, DOI: 10.4236/jasmi.2014.43010
Abstract:

The solubilities (s, mol/L) of different oxyquinolinates (oxinates, MeL2) are calculated using the formulae obtained according to elementary algebra, with the use of Excel spreadsheets. The calculations are involved with solution of algebraic equation of the third degree, obtained on the basis of concentration balances. The root of this equation, , is then inserted into the charge balance, and resolved according to zeroing procedure. In principle, the calculations are related to aqueous media. Nonetheless, the extension on liquid-liquid extraction systems is also proposed.

Simplex Optimization and Its Applicability for Solving Analytical Problems  [PDF]
Anna Maria Micha?owska-Kaczmarczyk, Tadeusz Micha?owski
Journal of Applied Mathematics and Physics (JAMP) , 2014, DOI: 10.4236/jamp.2014.27080
Abstract:

Formulation of the simplex matrix referred to n-D space, is presented in terms of the scalar product of vectors, known from elementary algebra. The principles of a simplex optimization procedure are presented on a simple example, with use of a target function taken as a criterion of optimization, where accuracy and precision are treated equally in searching optimal conditions of a gravimetric analysis. 

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