Analysis of Influence on the Grid of Input Part of Special Power Source 113 kW / 1 kA DC

This paper compares some variants of power circuit configurations for a special power DC source 110 V / 1 kA. The requirement for the source was to ensure minimum ripple of the output current and reduced EMC-disturbance generated from this DC-source to the supply network and to other surrounding equipments

An Investigation of the Erosion Wear of Pitched Blade Impellers in a Solid-Liquid Suspension

This paper reports on a study of the erosion wear mechanism of the blades of pitched blade impellers in a solid-liquid suspension in order to determine the effect of the impeller speed n as well as the concentration and size of the solid particles on its wear rate. A four-blade pitched blade impeller (pitch angle α = 30°), pumping downwards, was investigated in a pilot plant fully baffled agitated vessel with a water suspension of corundum. The results of  experiments show that the erosion wear rate of the impeller blades is proportional to n2.7 and that the rate exhibits a monotonous dependence (increase) with increasing size of the particles. However, the erosion rate of the pitched blade impellerreaches a maximum at a certain concentration, and above this value it decreases as the proportion of solid particles increases. All results of the investigation are valid under a turbulent flow regime of the agitated batch

Study of the Discharge Stream from a Standard Rushton turbine impeller

The discharge stream from a standard Rushton turbine impeller exhibits special flow properties different from the characteristics of the velocity field in other parts of the volume of an agitated liquid in a cylindrical baffled vessel, e.g. two prevailing components of the mean velocity (radial and tangential), high rate of turbulent energy dissipation and anisotropy of turbulence in this region. At the same time, the discharge stream plays an important role in mixing operations, above all in liquid-liquid and gas-liquid systems.This paper deals with theoretical and experimental studies of the velocity field and flow of angular momentum in a discharge stream from a standard Rushton turbine impeller in a cylindrical baffled flat bottomed vessel under turbulent regime of flow of an agitated liquid with emphasis on describing the ensemble averaged values over the whole interval of the tangential coordinate around the vessel perimeter

The Tangential Force Affecting the Radial Baffles in a Stirred Vessel: Analysis of the Macro-instability Related Component

Experimental data obtained by measuring the tangential component of the force affecting radial baffles in a flat-bottomed cylindrical mixing vessel stirred with a Rushton turbine impeller is analysed. Spectral analysis of the experimental data demonstrated the presence of its macro-instability (MI) related low-frequency component embedded in the total force. Two distinct dimensionless frequencies (both directly proportional to the impeller speed of rotation N) of the occurence of the MI component were detected: a lower frequency of approximately 0.025N and a higher frequency of about 0.085N. The relative magnitude QMI of the MI-related component of the total tangential force was evaluated by a combination of proper orthogonal decomposition (POD) and spectral analysis. The values of magnitude QMI varied in the interval [rom approximately 0.05 to 0.30. The magnitude QMI takes maximum values at low Reynolds number values (in laminar and transitional regions). In the turbulent region (ReM >20000) the QMI value is low and practically constant. The dependence oj the QMI values on vertical position in the vessel is only marginal. The results suggest that the magnitude of the MI component of the force is significantly influenced by the liquid viscosity and density

STIRRED FLUIDIZED-BED DRYER OF REGENERATED ION EXCHANGER PARTICLES

This article describes intensification of the fluidized-bed drying process for regenerated spherical-shape ion exchanger particles in the batch mode, achieved by a mechanical stirrer in the fluidized bed layer of the dried particles. The effect of the mechanical stirring system on the drying process was examined. Calculations as well as results of comparison measurements provide evidence of a favourable effect of stirring on the total drying time as compared to the initial unstirred system. The regenerated ion exchanger particles pass to the fluid state in a shorter time and the ultimate total drying time is thus more than 60% shorter

Study of Wear of Pitched Blade Impellers in a Solid-Liquid Suspension

A study was made of the erosion wear of the blades of pitched blade impellers in a suspension of silicious sand (CV= 5 %, d=0.325 mm, degree of hardness "7.5") in water under a turbulent flow regime of agitated charge when complete homogeneity of the suspension was achieved. Two aims of the study were defined: the dependence of the rate of the erosion process of the impeller blades on impeller frequency of revolution and on the size of the mixing equipment. Experiments were carried out on pilot plant mixing equipment of two sizes (geometrically similar) made of stainless steel (diameters of cylindrical vessels T1 = 200 mm and T2 = 300 mm, diameters of impellers D1 = 100 mm and D2= 66. 7 mm, impeller off bottom clearances h1 = 100 mm and h2= 66. 7 mm, respectively) equipped with four radial baffles (width b1 = 30 mm, b2 =20 mm, respectively) and an impeller with four inclined plane blades (pitch angle α =30°, 45°, relative blade with W/D = 0.2) made of rolled brass (Brinnel hardness 40-50 BM) always pumping the liquid downwards towards the float vessel bottom. The wear of the impeller was described by an analytical approximation in exponential form with two parameters (the wear rate constant k and the geometrical parameters of the worn blade C) calculated by the least squares method from the experimentally found profile of the worn leading edge of the impeller blades. While the wear rate constant exhibits a monotonous dependence on the pitch angle only, the geometric parameter is dependent both on the pitch angle and in linear form on the impeller tip speed. Thus in the procedure for scaling up the rate of erosion wear of the pitched blade impellers in a suspension of higher solid particle hardness, the decision process parameters are the impeller blade pitch angle and the impeller tip speed

Frequency and Magnitude Analysis of the Macro-instability Related Component of the Tangential Force Affecting Radial Baffles in a Stirred Vessel

Experimental data obtained by measuring the tangential component of force affecting radial baffles in a flat-bottomed cylindrical mixing vessel stirred with pitched blade impellers is analysed. The maximum mean tangential force is detected at the vessel bottom. The mean force value increases somewhat with decreasing impeller off-bottom clearance and is noticeably affected by the number of impeller blades. Spectral analysis of the experimental data clearly demonstrated the presence of its macro-instability (MI) related low-frequency component embedded in the total force at all values of impeller Reynolds number. The dimensionless frequency of the occurrence of the MI force component is independent of stirring speed, position along the baffle, number of impeller blades and liquid viscosity. Its mean value is about 0.074. The relative magnitude (QMI) of the MI-related component of the total force is evaluated by a combination of proper orthogonal decomposition (POD) and spectral analysis. Relative magnitude QMI was analysed in dependence on the frequency of the impeller revolution, the axial position of the measuring point in the vessel, the number of impeller blades, the impeller off-bottom clearance, and liquid viscosity. Higher values of QMI are observed at higher impeller off-bottom clearance height and (generally) QMI decreases slightly with increasing impeller speed. The QMI value decreases in the direction from vessel bottom to liquid level. No evident difference was observed between 4 blade and 6 blade impellers. Liquid viscosity has only a marginal impact on the QMI value

Erosion Wear of Axial Flow Impellersin a Solid-liquid Suspension

A study was made of the erosion wear of the blades of pitched blade impellers in a suspension of waste gypsum from a thermal power station (vol. concentration CV=18.3 %, particle mean diameter d=0.1 mm, degree of hardness “2.5”) and silicious sand (CV=10 %, d=0.4 mm, degree of hardness “7.5”) in water under a turbulent flow regime of agitated charge when complete homogeneity of the suspension was achieved. Experiments were carried out on pilot plant mixing equipment made of stainless steel (diameter of cylindrical vessel T=390 mm, diameter of impeller D=100 mm, impeller off-bottom clearance h=100 mm) equipped with four wall radial baffles (width b=39 mm) and an impeller with four inclined plane blades (pitch angle α =20°, 30°, 45°, relative blade width W/D=0.2) made either of rolled brass (Brinell hardness 40–50 BH) or of structural steel (Brinell hardness 100–120 BH) always pumping the liquid downwards towards the flat vessel bottom. Two erosion process mechanisms appear, depending on the hardness of the solid particles in the suspension: while the particles of gypsum (lower hardness) generate a uniform sheet erosion over the whole surface of the impeller blade, the particles of silicious sand (higher hardness) generate wear of the leading edge of the impeller blades, together with a reduction of the surface of the worn blade. The hardness of the impeller blade also affects the rate of the erosion process: the higher the hardness of the impeller blade, the lower the wear rate of the blade. This study consists of a description of the kinetics of the erosion process of both mechanisms in dependence on the pitch angle of the tested impellers. While the wear of the leading edge of the blade exhibits a monotonous dependence on the pitch angle, the sheet erosion exhibits the maximum rate within the interval of the pitch angles tested α ϵ <20°; 45°>.However, generally the pitch angle α =45° seems to be the most convenient angle of blade inclination when both investigated mechanisms of the blade erosion process are considered at their minimum rate

Evolutionary theories of homosexuality

Tato práce se zabývá mužskou homosexualitou z evolučního hlediska. V první části poskytuje přehled poznatků o genetickém a imunologickém původu homosexuality u muže, které následně slouží jako teoretický základ pro hlavní část práce. Vzhledem k tomu, že homosexuálové zanechávají méně potomstva než heterosexuálové, je na místě si položit otázku, jakými mechanismy je mužská homosexualita v populaci udržována a jaký by případně mohl být její evoluční význam. Práce shrnuje pět nejvlivnějších teorií, které byly zkonstruovány za účelem zodpovězení této otázky. Práce rovněž uvádí a kriticky hodnotí výsledky empirických výzkumů, které podporují jednotlivé teorie, či svědčí proti nim.This thesis deals with male homosexuality from an evolutionary viewpoint. In the first part, it provides a review of knowledge about the genetic and immunological origin of male homosexuality, this consequently serves as a theoretical base for the main part of the thesis. Regarding the fact that homosexuals leave less offspring than heterosexuals do, it is appropriate to raise a question by which mechanism is male homosexuality maintained in population and what could eventually be its evolutionary role. The thesis summarizes five most influential theories which were constructed in a purpose to answer this question. The thesis also posits and critically evaluates results of empirical research that support particular theories or give evidence against them.Katedra filosofie a dějin přírodních vědDepartment of Philosophy and History of SciencePřírodovědecká fakultaFaculty of Scienc

Documentary Film from the Copyright Point of View

Hlavním cílem této diplomové práce s názvem Dokumentární film z hlediska autorského práva je prozkoumat a zhodnotit autorskoprávní specifika dokumentárních filmů. Nejprve je popsán dokumentární film jakožto kulturní fenomén se zvláštním vztahem k realitě - jsou uvedeny jeho možné definice, třídění a nastíněny etické otázky, které nabízí. Poté následuje krátký exkurz do dějin ochrany audiovizuálních děl (jak na území ČR, tak v mezinárodním kontextu), přičemž detailněji jsou rozvedeny části týkající se přímo dokumentárního filmu. V další části se práce věnuje pojmu audiovizuální dílo a autorství audiovizuálního díla podle účinného českého autorského zákona č. 121/2000 Sb. a snaží se vymezit hranice tohoto pojmu a jeho možné výklady zejména ve vztahu k dokumentárním a dalším non- fikčním filmům. Poté následuje kapitola zabývající se právní povahou protagonistů dokumentárního filmu neboli sociálních herců, která se liší od herců v hraném filmu, neboť sociální herci nepředvádějí umělecké výkony ve smyslu autorského zákona. Na tuto kapitolu navazuje část týkající se ochrany osobnosti sociálních herců v dokumentárních filmech, která se řídí obecnou úpravou ochrany osobnosti v zákoně č. 89/2012 Sb. občanském zákoníku, což může při tvorbě dokumentárních filmů vyvolávat značné problémy. Další kapitola se pak...The aim of this thesis Documentary Film from the Copyright Point of View is to explore and evaluate copyright specifics of documentary cinema. Chapter One describes documentary film as a culture phenomenon with peculiar relationship to reality. It shows possible definitions and classifications and outlines some of the ethical questions connected with the documentary cinema. Then follows a brief excursion into the history of copyright protection of audiovisual works (both in the Czech Republic and in the international context), with emphasis on speciality of documentary films protection. Chapter Three examines terms audiovisual work and authorship of an audiovisual work as defined in effective Czech Act No. 121/2000 Coll. on Copyright and Rights Related to Copyright and tries to mark boundaries of these terms and its possible interpretation especially in relation to the documentary and other non-fiction films. Next chapter deals with the legal nature of protagonists of documentary or social actors which differs from legal nature of the actors in fiction films, because social actors does not perform artistic performances as defined in Czech Copyright Act. Subsequent Chapter Five analyzes protection of personal rights of social actors in documentary films which is governed by general protection of...Institute of Copyright, Industrial Property and Competition LawÚstav práva autorského, práv průmyslových a práva soutěžníhoPrávnická fakultaFaculty of La