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Search Results: 1 - 10 of 324893 matches for " S. Kotowski "
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Modelling and simulation of plasma spraying process with a use of Jets&Poudres program
S. Kotowski,J. Sieniawski,M. Góral
Journal of Achievements in Materials and Manufacturing Engineering , 2012,
Abstract: Purpose: Plasma spraying is one of the basic methods of coating deposition used in many branches of industry, especially in aviation and power industry. The process is applied in the aircraft engineering for obtaining the sealing coats, anti-abrasive coatings and, above all, metallic layers, ceramic layers as well as thermal barrier coatings. The comprehensive characterisation of the plasma spraying process requires taking into consideration 50-60 parameters, which confirms its complexity. The purpose of this article is to describe the functioning of the program, presentation of its simulation capabilities, including the parameters of the plasma spraying process, which can be controlled in the program.Design/methodology/approach: The authors present in the article the model of plasma spraying process and describe the simulation of the process with a use of Jets&Poudres software. It is based on the GENMIX code (GENral MIXing) developed by B. Spalding and S. Patankar for analysis of the two-dimensional, parabolic flows characterized by large values of Reynolds and Péclet number.Findings: Jets&Poudres enables tracking the current position, velocity and the fusion process of powder particles as well as conducting the basic analysis of obtained coating formed during the plasma spraying process.Practical implications: Jets&Poudres enables determination of parameters of plasma spraying process in order to obtain better coating thickness distribution and improve the coating efficiency - ratio between the weight of the spray pattern deposited on a big flat plate and the weight of powder injected.Originality/value: Jets&Poudres is one of few available tools based on comprehensive model of plasma spraying under atmospheric pressure which makes possible to perform simulation of the whole process.
Random groups and Property (T): ?uk's theorem revisited
Marcin Kotowski,Michal Kotowski
Mathematics , 2011, DOI: 10.1112/jlms/jdt024
Abstract: We provide a full and rigorous proof of a theorem attributed to \.Zuk, stating that random groups in the Gromov density model for d > 1/3 have property (T) with high probability. The original paper had numerous gaps, in particular, crucial steps involving passing between different models of random groups were not described. We fix the gaps using combinatorial arguments and a recent result concerning perfect matchings in random hypergraphs. We also provide an alternative proof, avoiding combinatorial difficulties and relying solely on spectral properties of random graphs in G(n, p) model.
Influence of turbine blade geometry on thickness of TBCs deposited by VPA and PS-PVD methods
M. Góral,J. Sieniawski,S. Kotowski,M. Pytel
Archives of Materials Science and Engineering , 2012,
Abstract: Purpose: The authors presented in the article the influence of the jet engine turbine blade profile on the thickness and microstructure of thermal barrier coatings.Design/methodology/approach: The assessment of model blade made of ZS6K alloy used in the first stage of the turbine engine was performed. The diffusion aluminide coating as well as the thermal barrier coating were deposited on the blade surface with a use of the out of pack method. The zirconia stabilized by yttrium oxide coating was deposited by PS-PVD method The research was performed with a use of light- and scanning microscopy.Findings: It has been proven, that the thickest coating was found on the leading edge and trailing edge of the blade. In those places the coating thickness was approx. 20-30% larger than in the other areas on turbine blade.Research limitations/implications: The research was performed with a use of light- and scanning microscopy.Practical implications: The obtained results indicate that it is possible to create the thermal barrier coating by PS-PVD process on the first stage turbine blades of the aircraft engine. It indicates the possibility of application of this process in the industrial practice.Originality/value: The new method for TBC coating production were used.
The PS-PVD method - formation of columnar TBCs on CMSX-4 superalloy
M. Góral,S. Kotowski,M. Drajewicz,J. Sieniawski
Journal of Achievements in Materials and Manufacturing Engineering , 2012,
Abstract: Purpose: The new plasma spraying method.Design/methodology/approach: The single crystal CMSX-4 nickel alloy was used as base material. The diffusion aluminide layer was deposited during the CVD process and was used as bond-coat. The zirconium oxide stabilized by yttrium oxide was utilized as the deposition material.Findings: It was proved, that there is a possibility of obtaining the ceramic layer using the PS-PVD process.Research limitations/implications: The thickness analysis and the chemical composition analysis by light and scanning electron microscopy were performed.Practical implications: This process can be used in aerospace industry to form oxidation resistant coatings.Originality/value: In article Plasma Spraying Physical Vapour Deposition Process was described.
Universal nonlinear entanglement witnesses
Marcin Kotowski,Michal Kotowski,Marek Kus
Physics , 2010, DOI: 10.1103/PhysRevA.81.062318
Abstract: We give a universal recipe for constructing nonlinear entanglement witnesses able to detect non-classical correlations in arbitrary systems of distinguishable and/or identical particles for an arbitrary number of constituents. The constructed witnesses are expressed in terms of expectation values of observables. As such they are, at least in principle, measurable in experiments
Two Antigenically Indistinguishable Viruses in a Population
Radoslaw Nielek,Aleksander Wawer,Romuald Kotowski
Lecture Notes in Engineering and Computer Science , 2008,
Zapobieganie i leczenie powik ań ze strony przewodu pokarmowego wywo anych niesteroidowymi lekami przeciwzapalnymi
Jaros?aw Regu?a,Bronis?aw Kotowski
Polish Gastroenterology , 2004,
Abstract: Stale rosn ce spo ycie niesteroidowych leków przeciwzaplanych (NLPZ) oraz ryzyko gro nych powik ań ze strony przewodu pokarmowego zwi zane z ich spo ywaniem powoduj , e niezwykle istotne s skuteczne sposoby zapobiegania im i leczenia. W profilaktyce stosuje si inhibitory pompy protonowej (IPP), je li pacjent przyjmuje klasyczny NLPZ lub rezygnuje si z tej grupy leków na rzecz selektywnych inhibitorów COX-2. W leczeniu powik ań wiod c rol odgrywaj IPP. Dodatkowo u pacjentów z infekcj Helicobacter pylori stwierdzan przed wprowadzeniem leczenia NLPZ, istotne w zapobieganiu powik aniom jest leczenie eradykacyjne a u osób z infekcj , przyjmuj cych kardioprotekcyjne dawki ASA poza eradykacj , w grupach ryzyka, stosuje si równie IPP.
Space-Charge-Limited Current Fluctuations in Organic Semiconductors
A. Carbone,B. K. Kotowska,D. Kotowski
Physics , 2005, DOI: 10.1103/PhysRevLett.95.236601
Abstract: Low-frequency current fluctuations are investigated over a bias range covering {\em ohmic}, {\em trap-filling} and {\em space-charge-limited current} regimes in polycrystalline polyacenes. The relative current noise power spectral density ${\cal S}(f)$ is constant in the {\em ohmic} region, steeply increases at the {\em trap-filling transition} region and decreases in the {\em space-charge-limited-current} region. The {\em noise peak} at the {\em trap-filling transition} is accounted for within a {\em continuum percolation model}. As the quasi-Fermi level crosses the trap level, intricate insulating paths nucleate within the ohmic matrix, determining the onset of non-equilibrium conditions at the interface between the insulating and conducting phase. The {\em noise peak} is written in terms of the free and trapped charge carrier densities.
$f^{-γ}$ Current Fluctuations in Organic Semiconductors: Evidence for Percolation
A. Carbone,B. K. Kotowska,D. Kotowski
Physics , 2006, DOI: 10.1140/epjb/e2006-00146-5
Abstract: The $f^{-\gamma}$ sloped current noise power spectra, observed in organic semiconductors, have been interpreted within a {\em variable range hopping} mechanism of the fluctuations. The relative current noise power spectral density ${\cal S}(f)=S_I(f)/I^2$ exhibits a maximum at the {\em trap-filling transition} between the {\em ohmic} and the {\em space-charge-limited-current} regime [Phys. Rev. Lett., {\bf 95}, 236601, 2005]. Here, we discuss the electronic conditions determining the crossover from ohmic to space-charge-limited transport. These arguments shed further light on the need to adopt a {\em percolative} fluctuation picture to account for the competition between insulating and conductive phases coexisting at the {\em transition}, where small changes in the external bias lead to dramatic effects in the fluctuations.
Non-Liouville groups with return probability exponent at most 1/2
Micha? Kotowski,Bálint Virág
Mathematics , 2014, DOI: 10.1214/ECP.v20-3774
Abstract: We construct a finitely generated group $G$ without the Liouville property such that the return probability of a random walk satisfies $p_{2n}(e,e) \gtrsim e^{-n^{1/2 + o(1)}}$. Recent results suggest that $1/2$ is indeed the smallest possible return probability exponent for non-Liouville groups. Our construction is based on permutational wreath products over tree-like Schreier graphs and the analysis of large deviations of inverted orbits on such graphs.
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