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Search Results: 1 - 10 of 297586 matches for " J. Jezierski "
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Asymptotic Conformal Yano--Killing Tensors for Schwarzschild Metric
J. Jezierski
Physics , 1994, DOI: 10.1088/0264-9381/14/7/008
Abstract: The asymptotic conformal Yano--Killing tensor proposed in J. Jezierski, On the relation between metric and spin-2 formulation of linearized Einstein theory [GRG, in print (1994)] is analyzed for Schwarzschild metric and tensor equations defining this object are given. The result shows that the Schwarzschild metric (and other metrics which are asymptotically ``Schwarzschildean'' up to O(1/r^2) at spatial infinity) is among the metrics fullfilling stronger asymptotic conditions and supertranslations ambiguities disappear. It is also clear from the result that 14 asymptotic gravitational charges are well defined on the ``Schwarzschildean'' background.
Relationship between stream forces and parameters of the powder injection into metal bath
J. Jezierski,J. Szajnar
Archives of Materials Science and Engineering , 2007,
Abstract: Purpose: The pneumatic method of introduction of various powders into ladle or metallurgical furnaces is use because of its many advantages. There are no problems with use of injection lances in electric arc furnaces but in inductive furnaces or ladles, especially big ones the problem of metal flowing out of it may appear. This is the reason why the authors have maiden some experiments which results are presented in the article.Design/methodology/approach: The new lance with a flange was invented and used in powdered material injections experiments. The experimental plan was prepared that contain the most important parameters of pneumatic process. A statistical analysis was made to connect the results of the injection process with its parameters.Findings: The main conclusion is the influence of carrier gas pressure, lance inside diameter and mass concentration of diphase stream on the obtained results. The next one is that changing of the lance geometry could effectively improve the technological parameters of the process and that the new design of the injection lance is prepared properly.Research limitations/implications: The limitations of the results is that the experiments were only the “cold model” ones, without presence of molten metal. The only liquid medium used was water for experiments with stream distance measurement. The nest experiments are planned with injection of powder into laboratory induction furnaces for checking the obtained results.Practical implications: According to the authors, the new lance can be used for introducing a small quantity of the powdered material like modifiers or something like that.Originality/value: The approach to the problem of diphase stream forces and distance of stream in liquid is according to authors’ knowledge a new one. The lance with flange proposed for those usage is not present in literature and is an originality too. The paper could be interesting for all interested in problems of melting processes improving.
Character of diphase stream force in powder injection technique
J. Jezierski,J. Szajnar
Journal of Achievements in Materials and Manufacturing Engineering , 2007,
Abstract: Purpose: The method of pneumatic injection of powdered reagents into liquid alloys in some moment ofmelting process is known since many years. Mostly it is carrying out with use of submerged lance but in somecases that technique is difficult or impossible at all to use. This is the reason for making investigations in thefield of powders injection with non-submerged lance.Design/methodology/approach: The main experimental method was measurement and recording of timechangingdiphase stream force value with use of dedicated laboratory stand. The recorded data made possible toshow character of force in form of graphs and calculation of stream parameters. The last step was formulatingof statistical equations joining all important parameters of the process.Findings: In the course of the work was found a diphase stream force character (especially interesting are startand end point of injection). The influence of main pneumatic parameters on the force value was analyzed too.Research limitations/implications: The future experiments will be conducted with use of Fluent 6.2 programfor checking the results in computer simulations. The limitation is number of values being analyzed inexperimental plan.Practical implications: The invented lance can be used for powders pneumatic injection but only for smallits quantities (e.g. microalloying) because non-immersed lance should be used with low stream concentration.The usage of that lance can decrease liquid alloy heat losses (not introducing carrier gas into liquid) and lanceconsumption (non-immersed in liquid bath).Originality/value: The problem of stream force in powder injection process is in Poland only analyzed byDepartment of Foundry and nobody (in author’s opinion) was analyzed it with connection in powder injection.Originality of the researches is a computer recording and analyzing of the diphase stream force. The resultsshould interest every who wants to learn more about pneumatic powder injection.
Method and new lance for powder injection into liquid alloys
J. Jezierski,J. Szajnar
Journal of Achievements in Materials and Manufacturing Engineering , 2006,
Abstract: Purpose: The pneumatic powder injection into liquid alloys is known since many years. It is use in many metallurgical processes (recarburization, alloy additions introduction, desulphurization etc.). The problem in some cases is to prevent the carrier gas introduction into liquid bath.Design/methodology/approach: The objectives were achieved by researches with laboratory injection stand. The main research method was measurement of stream parameters and computation of pneumatic injection indexes.Findings: The new injection lance was invented and analyzed and this is one of the main subjects of this paper. The lance has a construction, that makes possible even complete elimination of carrier gas introduction into liquid metal with proper particles stream range. The paper shows the results of the tests of lances with various geometrical parameters and model experiments with diphase stream force measurement.Research limitations/implications: The future research should be made with various type of powdered materials to find the question what are the limits of changing the most important parameters (grain size, stream concentration etc.). The limitation is number of values being analyzed (in powder injection processes there are many) in experimental plan.Practical implications: The lance can be used for powders pneumatic injection but only for small its quantities (e.g. microalloying) because non-immersed lance should be used with low stream concentration. The usage of that lance can decrease liquid alloy heat losses (not introducing carrier gas into liquid) and lance consumption (non-immersed in liquid bath).Originality/value: The original value of the paper is taking into account the parameter called by authors “diphase stream force” on liquid metal surface being “attacked” by particles (or carrier gas stream). Nobody (in author’s opinion) was analyzed that problem with connection in powder injection processes. The paper can be helpful for everybody who is studying pneumatic injection processes.
Powder pneumatic injection as a tool for wastes utilization
J. Jezierski,K. Janerka
Archives of Materials Science and Engineering , 2009,
Abstract: Purpose: Metallurgical process generates many solid, gaseous and liquid wastes. Nowadays when environmental protection is one of the most important problems and when pollution limits are very tight as well, problem of the metallurgical wastes is a strategic one.Design/methodology/approach: In present days the metallurgical and foundry plant have to utilize their own wastes, especially these which are the most dangerous and toxic or have to render harm of its and transfer to another industry branch for further utilization. Nowadays the issue of wastes management has the place both in industrial practice and scientific field too. The presented work is a result of such an approach, where a cooperation between scientific and industrial partners gives good economical and ecological results.Findings: One of the very efficient method of utilization of furnace dusts from any melting furnace or the finest fractions of charging materials is pneumatic powder injection directly into molten metal bath. The method is pretty easy and cost effective in various conditions and its flexibility allows to implement it in almost every foundry or metallurgical plant.Research limitations/implications: Further experiments should be carried out to solve some additional problems appearing during powder injection processes to make them more efficient in various technological conditions.Practical implications: Nowadays in Poland operate more than ten industrial stands for powdered carburizers injection, installation of furnace dust injection back to the melting furnace or pneumatic inoculation of alloys (mostly in cast iron foundries).Originality/value: The paper presents a few modern solutions for recycling and utilization of furnace dusts (in cupolas and EAF’s) and pneumatic carburization with use of powdered carburizers which are very often in form of grinded graphite electrodes wastes. All of the mentioned results and method had been developed in Department of Foundry and some of the designs had been previously patented.
Properties of cast iron modifying with use of new inoculants
J. Jezierski,D. Bartocha
Journal of Achievements in Materials and Manufacturing Engineering , 2007,
Abstract: Purpose: Modification of various alloys is a well known process for improvement its properties by changing of microstructure character. In foundry technology it is connected mostly to cast iron production where many inoculants is used for obtaining some results like grain refinement, graphite inclusions proper distribution etc. Those changes caused that produced alloy have a much better properties especially mechanical ones.Design/methodology/approach: In the paper were presented some results of the experiments made for checking quality of the two new on Polish foundry market complex inoculants. On of them is a “graphite” inoculant (about 50% C) and second is Ba-Ca combination based inoculant. The experiments contained metallographic and quantitative metallographic analysis and wedge test bars analysis.Findings: These experiments proved a good quality of inoculants in the field of microstructure improvement (graphite size reduction) and a hard spot defects liquidation.Research limitations/implications: The next experiments are planned for checking the mechanical properties of the produced alloys.Practical implications: The inoculants being analysed are used in several Polish foundries now because of author’s good results.Originality/value: There were the first experiments with these materials although the methods of investigations are not novel or original. The results have a very big importance not only from scientific but from practical point of view too.
Quality and properties of the cast iron produced on the steel scrap base
K. Janerka,J. Jezierski,J. Szajnar
Archives of Materials Science and Engineering , 2012,
Abstract: Purpose: The goal of the article is to show the issue of the cast iron melting on the steel scrap base only (with no pig iron in charge). The particular interest was focused on the charging material chemical composition influence on the particular elements content in produced cast iron and its quality, too.Design/methodology/approach: The grey cast iron melting on the steel scrap base and recarburizers (anthracite, natural and synthetic graphite, petroleum coke) was conducted to achieve the goals of the experiments. The chemical composition, mechanical properties and microstructure was tested for each melt. Melting was conducted in inductive furnace of 20kg capacity.Findings: The experiments drawn to the conclusions that cast iron melted on the steel scrap base contains less impurities (sulfur and phosphorus) than this melted on the pig iron base. During the results further analysis the relationship between carburizer grade and both mechanical properties and microstructure of the produced cast iron was proved (microstructure heredity).Research limitations/implications: To finally prove the hypothesis regarding the microstructure heredity given in the article, further researches should be carried out with the anthracite use as a carburizer.Practical implications: The results achieved suggest that when anthracite is used as a carburizer it is possible to increase mechanical properties with no necessity of changing other process parameters. Regarding the fact that the anthracite is relatively cheap carburizer it may cause in consequence less expensive production along with the cast iron quality parameters increase. Originality/value: The issue of the materials microstructure heredity is not widely described in the literature and the experiments results presented in the article allow to create the hypothesis that this phenomenon is present in the metal alloys.
Local approach to thermodynamics of black holes
E. Czuchry,J. Jezierski,J. Kijowski
Physics , 2004,
Abstract: Hamiltonian description of gravitational field contained in a spacetime region with boundary $S$ being a null-like hypersurface (a wave front) is discussed. Complete generating formula for the Hamiltonian dynamics (with no surface integrals neglected) is presented. A quasi-local proof of the 1-st law of black holes thermodynamics is obtained as a consequence, in case when $S$ is a non-expanding horizon. The 0-th law and Penrose inequalities are discussed from this point of view.
Dynamics of gravitational field within a wave front and thermodynamics of black holes
E. Czuchry,J. Jezierski,J. Kijowski
Physics , 2004, DOI: 10.1103/PhysRevD.70.124010
Abstract: Hamiltonian dynamics of gravitational field contained in a spacetime region with boundary $S$ being a null-like hypersurface (a wave front) is discussed. Complete Hamiltonian formula for the dynamics (with no surface integrals neglected) is derived. A quasi-local proof of the first law of black holes thermodynamics is obtained as a consequence, in case when $S$ is a non-expanding horizon. The zeroth law and Penrose inequalities are discussed from this point of view.
The properties and structure of the carburizers
K. Janerka,J. Jezierski,M. Pawlyta
Archives of Foundry Engineering , 2010,
Abstract: The results of examinations of the carburizers for foundry industry were presented in the article. The commonly used carburizers were selected for the experiments (anthracite, natural and synthetic graphite, petroleum coke of various grades), cupola coke and charcoal as well. The experiments consist of bulk and standard density, screen analysis (on the basis of it the equivalent diameter was calculated) and the microstructure of the carburizers measurements. The chemical composition and basic properties of carburizers were described too.
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