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Search Results: 1 - 10 of 297305 matches for " J. Ratajski "
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On transition functions and nonlinearity measures in gradient coatings
J. Ratajski,?. Szparaga
Journal of Achievements in Materials and Manufacturing Engineering , 2012,
Abstract: Purpose: In this paper the influence of the shape of transition functions between the single layers of multilayer coating on the final internal stresses states in the coating was investigated. Additionally the degree of nonlinearity and asymmetry of postulated gradient layers was calculated.Design/methodology/approach: Physical and mathematical models of the layers were created basing on classical theory of elasto-plastic materials. Computer model of the object (coating + substrate) describing internal strains and stresses states in layers, after deposition process, was created using FEM method.Findings: New concepts of nonlinearity and asymmetry measurability of transition function were introduced. Using predefined measures the dependence between internal stresses fields in postulated class of gradient layers and values of nonlinearity and asymmetry were obtained.Research limitations/implications: There are an infinite number of possible measures of heterogeneity and nonlinearity of the transition layers. Also there are infinitely many functions with the same measures of asymmetry and nonlinearity, but different mathematical forms, thus a functions of the same measures value form a kind of class of abstraction. So it is convenient to consider specific representatives of the given class and expand the obtained results to remaining representatives which is laborious and ambiguous task.Practical implications: Proposed measures of gradient layers will become a significant components of the PC software in future, which will upgrade the designing process of hard, wear resistant coatings architecture.Originality/value: A class of monotonic and asymmetric transition functions, describing continuous physicochemical material’s parameters changes in each layer of K-layered coating was created. Also a new measures of nonlinearity and asymmetry of transition function were introduced.
Formulas for Lagrangian and orthogonal degeneracy loci; the Q-polynomials approach
P. Pragacz,J. Ratajski
Mathematics , 1996,
Abstract: Let V be a vector bundle on a scheme X endowed with a nondegenerate symplectic or orthogonal form. Let G be a Grassmannian bundle parametrizing maximal isotropic subbundles of V. The main goal of the paper is to give formulas for the classes of the loci in G parametrizing those subbundles which intersect successive members of of a fixed flag of isotropic subbundles of V in dimensions greater than 1,2,3,... . The formulas which we give are quadratic expressions in Q-polynomials of the tautological bundle on G and flag S-polynomials of the members of the flag. These formulas globalize to Lagrangian and orthogonal degeneracy loci. They have especially nice form for the loci of points in X where two maximal isotropic subbundles intersect in dimension exceeding a given number. (A problem for finding formulas for these loci was posed by J. Harris several years ago.) In this case, our formulas are simple quadratic expressions of Q-polynomials applied to E and F. The work generalizes formulas given in [P.Pragacz, Algebro- geometric applications of Schur S- and Q-polynomials, SLN 1478 (1991), 130-191]. One of its applications is computation of the classes of Brill-Noether loci in Pryms in [De Concini, P. Pragacz, On the class of Brill-Noether loci for Prym varieties, Math. Ann. 302 (1995), 687-697].
Multi objective optimization of wear resistant TiAlN and TiN coatings deposite by PVD techniques
?. Szparaga,J. Ratajski,A. Zarychta
Archives of Materials Science and Engineering , 2011,
Abstract: Purpose: The goal of this paper is to determine, the optimal layer thickness of deposited coatings, in respect of thermal strain and stresses.Design/methodology/approach: For physical modelling purposes Cr, TiN and TiAlN layers were treated as a continuous medium, so the physical phenomena, occurring in the coating, are modelled based on a classical theory of stiffness. Computer model of the object (coating + substrate) describing strains and thermal stresses states in layers, after deposition process, was created using FEM method.Findings: The decisional objectives, based on various stresses fields in deposited coating, were defined. The set of optimal TiAlN and TiN layer thickness, in respect to created decision objectives was determined. Also method of optimal solutions set analysis, based on multidimensional, Euclidean metric was created.Research limitations/implications: There is a need to consider creation of a certain class of selection functions, as a standard, which will help to choose the optimal set of solutions - obtained in different multi objective optimization procedures. Of course, new and more detailed physical and mathematical models of the PVD processes are required.Practical implications: Proposed multi objective optimization procedure will become a component of the PC software in future, which will make design process of hard, wear resistant coatings architecture possible.Originality/value: Insertion of the base layer, below TiAlN and TiN tiers, was proposed, whose occurrence is reflected by the continuous change of the physical and chemical properties, across the coating thickness. Also method of optimal solutions set analysis, based on multidimensional, Euclidean metric was created.
Hard coatings for woodworking tools – a review
J. Ratajski,W. Gulbiński,J. Sta?kiewicz,J. Walkowicz
Journal of Achievements in Materials and Manufacturing Engineering , 2009,
Abstract: Purpose: The paper presents thorough analysis of the state-of the-art in the field of woodworking tools durability improvement. In comparison with the achievements of global leaders in the field, the technologies developed so far at the Institute of Mechatronics, Nanotechnology and Vacuum Technique, as well as the latest research works undertaken by the authors are presented.Design/methodology/approach: The specificity of machining conditions of wood and wood-derivative materials consists in simultaneous occurrence of very high working speed, extremely sharp cutting edges and high working temperature – on the one hand, and high anisotropy and low thermal conductivity of the machined material – on the other. The paper summarizes various ways, including selection of both tool materials and surface treatments, applied in order to increase the productivity of woodmachining.Findings: A systematic analysis has been made on the type of tool materials suitable for machining of different sorts of solid wood and wood-derivative materials. It was shown that all woodworking tool types, except for satellites, require development of dedicated surface engineering technologies improving significantly their durability. The main features of CVD and PVD surface treatment technologies were compared in relation to their application for woodmachining tools.Research limitations/implications: Based on the achievements to date IMN&VT undertook a project aimed at development of a new generation of surface treatment technologies for both cemented carbide and high speed steel tools. It is planned to develop three packages of PVD technologies for deposition of multilayer and duplex anti-wear coatings based on TiAlN, CrN and carbon.Originality/value: The paper constitutes concise but in-depth description of the contemporary trends in surface treatment of tools for woodmachining.
Precise formation the phase composition and the thickness of nitrided layers
J. Ratajski,R. Olik,T. Suszko,J. Dobrodziej
Journal of Achievements in Materials and Manufacturing Engineering , 2009,
Abstract: Purpose: The article presents the application of the duplex technology (nitriding plus PVD) to modification of the surface of pressure casting dies made of steel WCL (EN: X37CrMoV51). In this technology, there are clearly defined expectations regarding the properties of the surface layer of the dies obtained in the nitriding process. The main part of the article is presentation a complex system of designing, in-situ visualization and control of the gas nitriding process.Design/methodology/approach: In the conception of computer designing, analytical mathematical models and artificial intelligence methods were used.Findings: As a result, possibilities were obtained of the poly-optimization and poly-parametric simulations of the course of the process combined with a visualization of the value changes of the process parameters in the function of time, as well as possibilities to predict the properties of nitrided layers.Practical implications: Computer procedures make it possible to combine, in the duration of the process, the registered voltage and time runs with the models of the process.Originality/value: For in-situ visualization of the growth of the nitrided layer, computer procedures were developed which make use of the results of the correlations of direct and differential voltage and time runs of the process result sensor (magnetic sensor), with the proper layer growth stage.
Design, Control and in Situ Visualization of Gas Nitriding Processes
Jerzy Ratajski,Roman Olik,Tomasz Suszko,Jerzy Dobrodziej,Jerzy Michalski
Sensors , 2010, DOI: 10.3390/s100100218
Abstract: The article presents a complex system of design, in situ visualization and control of the commonly used surface treatment process: the gas nitriding process. In the computer design conception, analytical mathematical models and artificial intelligence methods were used. As a result, possibilities were obtained of the poly-optimization and poly-parametric simulations of the course of the process combined with a visualization of the value changes of the process parameters in the function of time, as well as possibilities to predict the properties of nitrided layers. For in situ visualization of the growth of the nitrided layer, computer procedures were developed which make use of the results of the correlations of direct and differential voltage and time runs of the process result sensor (magnetic sensor), with the proper layer growth stage. Computer procedures make it possible to combine, in the duration of the process, the registered voltage and time runs with the models of the process.
New components of the mercury’s perihelion precession  [PDF]
J. J. Smulsky
Natural Science (NS) , 2011, DOI: 10.4236/ns.2011.34034
Abstract: The velocity of perihelion rotation of Mercury's orbit relatively motionless space is computed. It is prove that it coincides with that calculated by the Newtonian interaction of the planets and of the compound model of the Sun’s rotation.
Simple General Purpose Ion Beam Deceleration System Using a Single Electrode Lens  [PDF]
J. Lopes, J. Rocha
World Journal of Engineering and Technology (WJET) , 2015, DOI: 10.4236/wjet.2015.33014
Abstract: Ion beam deceleration properties of a newly developed low-energy ion beam implantation system were studied. The objective of this system was to produce general purpose low-energy (5 to 15 keV) implantations with high current beam of hundreds of μA level, providing the most wide implantation area possible and allowing continuously magnetic scanning of the beam over the sample(s). This paper describes the developed system installed in the high-current ion implanter at the Laboratory of Accelerators and Radiation Technologies of the Nuclear and Technological Cam-pus, Sacavém, Portugal (CTN).
Constraints on velocity anisotropy of spherical systems with separable augmented densities
J. An
Physics , 2011, DOI: 10.1088/0004-637X/736/2/151
Abstract: If the augmented density of a spherical anisotropic system is assumed to be multiplicatively separable to functions of the potential and the radius, the radial function, which can be completely specified by the behavior of the anisotropy parameter alone, also fixes the anisotropic ratios of every higher-order velocity moment. It is inferred from this that the non-negativity of the distribution function necessarily limits the allowed behaviors of the radial function. This restriction is translated into the constraints on the behavior of the anisotropy parameter. We find that not all radial variations of the anisotropy parameter satisfy these constraints and thus that there exist anisotropy profiles that cannot be consistent with any separable augmented density.
On the augmented density of a spherical anisotropic dynamic system
J. An
Physics , 2010, DOI: 10.1111/j.1365-2966.2011.18324.x
Abstract: This paper presents a set of new conditions on the augmented density of a spherical anisotropic system that is necessary for the underlying two-integral phase-space distribution function to be non-negative. In particular, it is shown that the partial derivatives of the Abel transformations of the augmented density must be non-negative. Applied for the separable augmented densities, this recovers the result of van Hese et al. (2011).
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