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1
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Roughness Method to Estimate Fractal Dimension

100%
Błachowski A., Ruebenbauer K.
Acta Physica Polonica A
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2009
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vol. 115
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issue 3
636-640
EN
A method based on the pattern roughness was introduced for determination of the fractal dimension and tested for fractals like the Sierpiński carpet, the Sierpiński triangle, standard Cantor set, the Menger sponge and the Sierpiński tetrahedron. It was tested for non-fractal pattern like two- and four-dimensional gray scale random dust as well. It was found that for all these patterns the Hausdorff dimension is reproduced with relatively high accuracy. Roughness method is based on simple, fast and easy to implement algorithm applicable in any topological dimension. It is particularly suited for patterns being composed of the hierarchy of structures having the same topological dimension as the space embedding them. It is applicable to "fuzzy" patterns with overlapping structures, where other methods are useless. It is designed for pixelized structures, the latter structures resulting as typical experimental data sets.
2
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New Graphical Interface to the MOSGRAF Suite

100%
Duraj Ł., Ruebenbauer K.
Acta Physica Polonica A
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2011
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vol. 119
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issue 1
75-77
EN
A contribution is devoted to the recent development of the MOSGRAF suite used to process Mössbauer data and to generate reference functions for the modern spectrometers of the MsAa-x (x=1, 2, 3, 4) family. Newly developed interface is designed for the Microsoft Windows-XP® or higher system of this class. However one can use some older system of this class as well provided some plug-ins are installed additionally. The lowest useable system is Microsoft Windows-98® - 32-bit edition. The new version of the MOSGRAF suite is compatible with 32-bit and 64-bit systems. MOSGRAF is fully compatible with MsAa-x spectrometers, however a powerful tool to convert ASCII data files from other spectrometers is provided. Data processing programs are compiled by the high efficiency Fortran-90 Lahey-Fujitsu® compiler. One of the most important new features is the ability to process velocity calibration data obtained by the new method based on the measurement of the time lapse between fringes of the Michelson-Morley interferometer.
3
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Secondary Radiation Field Effects for the CEM Spectra

81%
Ruebenbauer K., Błachowski A., Żukrowski J.
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issue 6
953-961
EN
The secondary resonant radiation field and resonant absorption thickness effects on the Conversion Electron Mössbauer Spectroscopy spectra are analyzed for highly enriched resonant targets. It is shown that secondary field effect is important for the thick α-Fe foil enriched in the resonant isotope. Even for the polycrystalline sample traces of the coherent resonant field have been detected as the distortion of lines. Secondary field is discussed in detail. Suitable approximations to treat spectra originating from targets with significant resonant thickness developing secondary field composed of the incoherent and coherent parts are introduced. Finally, the formalism is applied to the high quality spectrum recorded for the enriched iron foil and correlation between contribution due to the secondary field and experimental line shape is investigated.
4
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Mössbauer spectroscopy of iron-based superconductors

81%
Błachowski A., Ruebenbauer K., Żukrowski J.
Annales Universitatis Mariae Curie-Skłodowska, sectio AAA – Physica
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2011
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vol. 66
125-141
EN
A brief review concerned with the application of the Mössbauer spectroscopy to the investigations of iron-based superconductors is given. An introduction is devoted to the description of the most important features of the Mössbauer spectroscopy followed by the discussion of the basic properties of iron-based superconductors. Our results obtained for FeSe, LiFeP and parent compounds of the ‘122’ family, i.e., for AFe2As2 (A=Ca, Ba, Eu) are discussed later on with particular attention paid to the spin density wave (SDW) magnetism exhibited by the parents of the ‘122’ family. It is found that incommensurate SDW contain many harmonics in these layered structures and evolve from almost separated magnetic sheets through quasi-triangular forms to almost rectangular shape with the lowered temperature.
5
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Early Design Stage of the MsAa-4 Mössbauer Spectrometer

81%
Błachowski A., Ruebenbauer K., Żukrowski J., Górnicki R.
Acta Physica Polonica A
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2008
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vol. 114
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issue 6
1707-1713
EN
Entirely new Mössbauer spectrometer MsAa-4 is currently under design and construction. New features as compared to the basic features of the previous generation MsAa-3 spectrometer could be summarized as follows. Completely digital processing of the γ-ray detector signal beyond the Gaussian shape filter/amplifier is to be implemented. The spectrometer is going to be able to accommodate external multiple detector heads. One could collect simultaneously up to 128 γ-ray spectra in 16384 channels of 32-bit each and up to 512 Mössbauer spectra in 4096 channels of 32-bit each provided the proper external multiple detector head is used. The count-rate per single detector is limited to about 10^5 counts per second total. Improved precision of the reference function from 12-bit to 16-bit is to be provided. The reference function is stored in 8192 channels per complete cycle. Addition of the random noise to the reference corner prism of the Michelson-Morley calibration inteferometer is to be introduced to avoid spurious fringes due to the phase lock-up. Integrated universal temperature controller being able to use variety of the temperature sensors is to be interconnected with the proper spectrometer. The spectrometer is now a stand-alone network device as it is equipped with the Ethernet connection to the outside world. Modular design and use of the strict standards allows easy reconfiguration for other applications than the Mössbauer spectroscopy.
6
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Interplay Between Spin Density Wave and Superconductivity in `122' Iron Pnictides: ^{57}Fe Mössbauer Study

61%
Błachowski A., Ruebenbauer K., Żukrowski J., Bukowski Z., Matusiak M., Karpinski J.
Acta Physica Polonica A
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2012
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vol. 121
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issue 4
726-729
EN
Iron-based superconductors Ba_{0.7}Rb_{0.3}Fe_{2}As_{2} and CaFe_{1.92}Co_{0.08}As_{2} of the `122' family have been investigated by means of the 14.41-keV Mössbauer transition in ^{57}Fe versus temperature ranging from the room temperature till 4.2 K. A comparison is made with the previously investigated parent compounds BaFe_{2}As_{2} and CaFe_{2}As_{2}. It has been found that Mössbauer spectra of these superconductors are composed of the magnetically split component due to development of spin density wave and non-magnetic component surviving even at lowest temperatures. The latter component is responsible for superconductivity. Hence, the superconductivity occurs in the part of the sample despite the sample is single phase. This phenomenon is caused by the slight variation of the dopant concentration across the sample (crystal).
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