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Determination of Electromagnetic Emitter Position from Passive Radar Bearings as Linear Least Squares Problem

100%
Kawalec A., Kojdecki M., Wajszczyk B.
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EN
Mathematical formulation of an inverse problem of radiolocation is discussed. Determination of electromagnetic emitter position from passive radar bearings is transformed into a linear least squares problem and equivalent system of normal equations. Eventually spatial localisation of emitter is reduced to solving system of linear algebraic equations with entries of coefficient matrix and free term depending on bearings in a nonlinear way. Regularisation algorithm is proposed.
2
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Crystalline Microstructure of Corundum Fillers Determined from Powder X-Ray Diffraction Patterns

76%
Kojdecki M., Bastida J., De la Torre F., Pardo P., Ibáńez R., Urquiola M.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
1000-1003
EN
X-ray-diffraction microstructural analysis was performed for corundum powders produced from Bayer aluminium hydroxides in different ways and for high purity corundum powders produced from other raw materials. Crystalline microstructure characterised by prevalent crystallite shape, volume-weighted crystallite size distribution and second-order crystalline lattice strain distribution was determined through modelling crystallite shapes as hexagonal prisms, with the resulting mean volume-weighted standardised crystallite size in the range 406-1941 Å, height-to-base-diagonal ratio in the range 0.68-0.94 and the mean-absolute second-order strain in the range 0.028-0.087%. Crystallite size distributions were found to be well approximated as bimodal logarithmic-normal ones and consequently four types of microstructure were recognized as depending on precursors and methods of production.
3
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Application of Modified Interference Wedge Method in Measurements of Indices of Refraction and Birefringence of Nematic Liquid Crystals

76%
Kowiorski K., Kędzierski J., Raszewski Z., Kojdecki M., Herman J., Miszczyk E., Piecek W.
Acta Physica Polonica A
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2013
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vol. 124
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issue 6
946-948
EN
Wedge cell filled with a homogeneously oriented nematic liquid crystal was exploited as an interference wedge to measuring indices of refraction. Interference fringes from the wedge were observed in polarised light in reflection or transmission mode of a polarisation microscope to determining ordinary and extraordinary indices of refraction or birefringence (i.e. anisotropy of both indices). The interference fringes close to wedge apex were uniform and could be well described in two-beam interference approximation. The refractive indices were computed with using simple formulae involving only distances between subsequent fringes in a cell filled with the liquid crystal and an empty reference cell. Several new highly-birefringent nematic mixtures produced in the Military University of Technology were investigated. The 6CHBT nematic was used as the reference material.
4
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X-ray Diffraction Microstructural Analysis of Swelling by Ethylene Glycol in Two Reference Clay Minerals

76%
García Tomás F., Kojdecki M., Pardo P., Ibańez R., Álvarez Larena A., Bastida J.
Acta Physica Polonica A
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2016
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vol. 130
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issue 4
876-879
EN
Kaolinite and montmorillonite are two clay minerals with different structures: dioctahedral 1:1 without layer charge and dioctahedral 2:1 with low layer charge. X-ray-diffraction microstructural analysis of two fractions of two reference clays (with kaolinite or montmorillonite) from the Clay Minerals Society Source Clay Repository were performed by the Voigt function method to provide microstructural data not available in the baseline studies of this Repository. A rough agreement was found between crystallite sizes determined from X-ray diffraction patterns and from images by field-emission scanning electron microscopy. In addition, the influence of swelling by ethylene-glycol on crystallite size was studied by the mentioned method. Two factors were found to affect the crystallite size variation in ethylene-glycol-treated clay minerals: (i) the increase of the unit cell in [001] direction due to the interlayer absorption of ethylene glycol molecules in the case of swelling minerals and (ii) the physisorption at the surfaces of the crystallites. Both effects operate in the case of montmorillonite, whereas just the latter one is expected in kaolinite.
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