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Search Results: 1 - 10 of 200497 matches for " P. Warzecha "
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CFD modelling of non-metallic inclusions removal process in the T-type tundish
M. Warzecha,T. Merder,P. Warzecha
Journal of Achievements in Materials and Manufacturing Engineering , 2012,
Abstract: Purpose: The aim of performed research is to diagnose the possibilities of non-metallic inclusions removal from liquid steel flowing through the two-strand T-type tundish with its current configuration.Design/methodology/approach: Research were performed with numerical simulations. Initial conditions for inclusions distribution were obtained earlier with experimental measurements during industrial casting conditions.Findings: Numerical simulations let to investigate the flow field structure of liquid steel in the tundish and its impact on inclusions trajectories and separation from steel to the slag. Moreover it was found that standard boundary condition (trap) available in commercial code for disperse phase is not suitable to model complex physical phenomena occurring at the steel-slag interphase.Research limitations/implications: Commercial use of computational codes for the analysis of work and design of industrial facilities is a relatively inexpensive toolPractical implications: The research results presented in the paper can be used for steel production of high purity steels.Originality/value: Presented results may contribute to significant improvements in process efficiency of investigated tundish.
Flow modeling in a laboratory settling tank with optional counter-current or cross-current lamella
K. Ko?odziejczyk,M. Bana?,P. Warzecha
Journal of Achievements in Materials and Manufacturing Engineering , 2012,
Abstract: Purpose: Design of laboratory lamella settling tank used in the laboratory researches of sedimentation process, optionally in either cross-current or counter-current.Design/methodology/approach: This paper presents a selection of geometric parameters of the device made using numerical methods to analyze the flow in designed settling tank.Findings: As a result of analyses, of the final device design was developed that allows it to obtain the proper distribution of flow velocity. The simulations allowed the selection of the proper construction of the tank, in which the velocity distributions in successive channels are comparable to the fulfillment of lamella, which will allow it to charge uniform stream of liquid (suspension).Practical implications: The use of numerical methods of modeling the flow in the settling tank allowed to finetune the design of the device at the early stage, and in particular the parameters of the distribution of suspension.Originality/value: The settling tank allows sedimentation to take place in both configurations with the preservation of an identical sedimentation surface. This concept allows a comparison of processes in these systems at a given identical surface load.
Numerical and physical modelling of steel flow in a one-strand continuous casting tundish
M. Warzecha
Metalurgija , 2011,
Abstract: The article presents the results of numerical and water model studies of a steel flow in a one-strand continuous casting tundish. The flow field measurements are obtained at a 1:3 scale water model of the tundish with the Laser-Doppler Anemometry (LDA) method, during steady-state casting. The LDA-measurements are performed using the Reynolds-similarity criterion. Numerical simulations of the three-dimensional turbulent fluid flow in a tundish are carried out with the finite-volume commercial code FLUENT. Mathematical model, validated with experimental results, is used to simulate liquid steel flow through a 1:1 scale industrial facility – a 16 t tundish.
Depression and religiosity in older age
M Pokorski, A Warzecha
European Journal of Medical Research , 2011, DOI: 10.1186/2047-783x-16-9-401
Abstract: The prevalence of depression in old age is still a controversial issue and epidemiological studies estimate it, depending on the methodology and the population investigated, from about a dozen percentage points [1], through 40% [2], and to as much as about 70% [3] in persons over 65 years of age. There is, however, a consistent lay impression that, if depression already is present, advancingg old age may worsen its intensity. Depression is a multifactorial condition and encompasses such factors as the overall health status [4], the level of anxiety, or the ability to cope with stressful situations [5-7]. These factors assume distinct characteristics in old age as persons often demonstrate a greater sensitivity or dependence on the external influences. There is a high degree of overlap between these factors, symptoms, and concerns in depressive individuals; the details of which are not fully understood.A feature of older age often is increased religious activity consisting of one's internal subjective religious beliefs and their external expressions (individual and social behaviors, the practice of religious rites, etc.). A surge in religiosity in old age may be brought about by more mature understanding of the good in one's life or the inescapability of life twilight. The effect of religiosity on psychological health is, however, a contentious issue. Some authors report overall positive effects [8], others negate such an effect [9], while still others relate the effect to a specific disease, e.g., depression, and again the results are contradictory [10,11]. Contentiousness of the issue may likely stem from a variety of rather poorly comparable factors, related to age, health, and life conditions of subjects studied.The objectives of the present study were to investigate the relationships among depression, worry-anxiety, general health, and coping with stress and to assess the effect on them of religious activity in older age. Our working hypothesis was that religiou
Numerical analysis of the non-metallic inclusions distribution and separation in a two-strand tundish
M. Warzecha,T. Merder
Metalurgija , 2013,
Abstract: The tundish plays an important role in the challenging task of a “clean steel” production process. The flow of the liquid steel in tundish has a crucial influence on non-metallic inclusions distribution and separation. The article presents computational studies of non-metallic inclusions separation in a two-strand industrial tundish during steady-state casting. Tundish capacity is 7,5 t. First, flow structure in the tundish was investigated using water model of the industrial tundish in a 1:2 scale. The experimental results, regarding RTD characteristics were used to validate numerical model. With validated model, particle distribution and separation in the two-strand tundish were investigated numerically. For modelling the separation of particles at the fluid surface, a modified boundary condition has been implemented.
Relating Neuronal to Behavioral Performance: Variability of Optomotor Responses in the Blowfly
Ronny Rosner, Anne-Kathrin Warzecha
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0026886
Abstract: Behavioral responses of an animal vary even when they are elicited by the same stimulus. This variability is due to stochastic processes within the nervous system and to the changing internal states of the animal. To what extent does the variability of neuronal responses account for the overall variability at the behavioral level? To address this question we evaluate the neuronal variability at the output stage of the blowfly's (Calliphora vicina) visual system by recording from motion-sensitive interneurons mediating head optomotor responses. By means of a simple modelling approach representing the sensory-motor transformation, we predict head movements on the basis of the recorded responses of motion-sensitive neurons and compare the variability of the predicted head movements with that of the observed ones. Large gain changes of optomotor head movements have previously been shown to go along with changes in the animals' activity state. Our modelling approach substantiates that these gain changes are imposed downstream of the motion-sensitive neurons of the visual system. Moreover, since predicted head movements are clearly more reliable than those actually observed, we conclude that substantial variability is introduced downstream of the visual system.
Modelling of Flow Behaviour in a Six-Strand Continuous Casting Tundish
Merder, T.,Bogus?awski, A.,Warzecha, M.
Metalurgija , 2007,
Abstract: Mathematical modeling has been extensively used to study the fluid flow phenomena taking place in continuous casting tundish. The article presents an analysis of the hydrodynamic properties of a real industrial facility – a six-strand tundish of a capacity of 30 Mg liquid steel. As a result of numerical computations carried out, spatial distributions of the velocity vectors, fields of turbulence kinetic energy, temperature of steel flowing in the tundish and characteristics called RTD (Residence Time Distribution) were get. Calculations were carried out by commercial computer program FLUENT. The geometry and nodal point grid were generated in the GAMBIT program. Results of computer simulation were verificated on the industrial tundish.
Gas Mixing And Chemical Homogenization Of Steel In 100 T Ladle Furnace
Warzecha, M.,Jowsa, J.,Merder, T.
Metalurgija , 2007,
Abstract: The article presents numerical simulations of fluid flow and chemical homogenization of liquid steel in gas-stirred ladle with two asymmetric porous plugs. In this study mixing time is analyzed as a function of porous plug location. All calculations were carried out by commercial computer program Fluent using k-ε turbulence model. Results show the velocity vectors of liquid steel and tracer concentration field after alloy addition. Numerical calculations were used to get the mixing time of liquid steel as a function of gas flow rate and porous plugs location.
Numerical modeling of steel flow in the six-strand tundish with different flow control devices
Merder T.,Pieprzyca J.,Warzecha M.
Metalurgija , 2009,
Abstract: Numerical modelling have been extensively used to study the fluid flow phenomena taking place in continuous casting tundish. The paper presents the results of steel flow researches done on tundishs with a capacity of 22 Mg, with different flow control devices. The tundish is a “trough”-type designed for the continuous casting of slabs intended for small cross-section rolled products. In effect of mathematical calculations liquid steel velocity, turbulence intensity, turbulent kinetic energy and temperature distributions have been obtained. Calculations were passed by commercial computer program FLUENT.
Construction of Spectral Triples Starting from Fredholm Modules
E. Schrohe,M. Walze,J. -M. Warzecha
Physics , 1998,
Abstract: Let (A,H,F) be a p-summable Fredholm module where the algebra A= C \Gamma is generated by a discrete group of unitaries in L(H) which is of polynomial growth r. Then we construct a spectral triple (A,H,D) with F= sign D which is q-summable for each q > p+r+1. In case (A,H,F) is (p,\infty)-summable we obtain (q,\infty)-summability of (A,H,D) for each q > p+r+1.
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