T-folds as Poisson-Lie plurals

In previous papers we have presented many purely bosonic solutions of Generalized Supergravity Equations obtained by Poisson-Lie T-duality and plurality of flat and Bianchi cosmologies. In this paper we focus on their compactifications and identify solutions that can be interpreted as T-folds. To recognize T-folds we adopt the language of Double Field Theory and discuss how Poisson-Lie T-duality/plurality fits into this framework. As a special case we confirm that all non-Abelian T-duals can be compactified as T-folds.Comment: v3 - published versio

Implementation of Overlay on High-Carbon Steel

Import 23/07/2015Diplomová práce se zabývá navařováním vysokouhlíkové oceli UIC 900 A. Tato ocel se využívá pro výrobu kolejnic. Teoretická část práce se zabývá základními technologiemi využívanými pro navařování kolejnic, rozdělením základních materiálů používaných pro výrobu kolejnic a k ním využívaných přídavných materiálů pro navařování. Dále výpočtem vneseného tepla a uhlíkového ekvivalentu. V experimentální části práce, byly určeny základní a přídavné materiály. Na vzorcích byly provedeny metalografické analýzy. Dále na vzorcích proběhlo měření tvrdosti HV 10 a ve vybraných oblastech měření mikrotvrdostí HV 0,1. Cílem diplomové práce je posouzení vhodnosti druhu přídavných materiálů, množství vneseného tepla do návaru s ohledem na vznik nežádoucích struktur a vad vyskytujících se v návaru.The thesis deals with high carbon steel welding UIC 900 A. This steel is used for the production of rails. The theoretical part deals with the basic technology used for welding rails dividing the basic materials used for the production of rails and it used filler materials for welding. Furthermore, the calculation of heat input and the carbon equivalent. In the experimental part of the work, they were designed base and filler metals. The samples were carried out metallurgical analysis. Further samples was measuring the hardness of HV 10 and in selected areas of microhardness HV 0.1. The thesis aims to assess the suitability of the type of auxiliary materials, the amount of heat input to the weld with respect to the formation of undesirable structures and defects occurring in the weld.345 - Katedra mechanické technologievýborn

Poisson-Lie transformations and Generalized Supergravity Equations

In this paper we investigate Poisson-Lie transformation of dilaton and vector field J appearing in Generalized Supergravity Equations. While the formulas appearing in literature work well for isometric sigma models, we present examples for which Generalized Supergravity Equations are not preserved. Therefore, we suggest modification of these formulas.Comment: published versio

Zavarljivost čelika s visokim udjelom mangana

Nowadays one of the most important parts, which are used in railway industry, are crossings, and principally the dynamic component of the operation exposures. A Mangalloy, also called as manganese steel or Hadfield steel, is a steel with alloys containing an average 13 % of manganese and is unique for the reason that it combines high toughness and ductility with great work-hardening capacity. The wear resistance before the contact wear depends on the level of the surface hardening intensity, and the hardening process during operation consequently [1, 2, 3]. As abrasion resistance is proper to increase the carbon level above 1,4 % and moreover, it could cause a problem in obtaining a homogenous austenitic structure which would be sufficiently free of carbide bordered grains [4].Jedan od najvažnijih dijelova koji se danas koriste na željeznici su dijelovi na cestovnim prijelazima preko pruge i uglavnom dinamička komponenta izložena djelovanju. Mangalloy, također poznat kao čelik s manganom ili Hadfield čelik, je čelik s legurama koje u prosjeku sadrže 13 % mangana i jedinstven je po tome što povezuje visoku žilavost i duktilnost s velikom sposobnošću radnog otvrdnjivanja. Otpornost na trošenje prije kontaktnog trošenja ovisi o intenzitetu otvrdnjavanja površine i postupku otvrdnjavanja tijekom rada [1, 2, 3,]. Budući da se zbog otpornosti abraziji povećava postotak ugljika iznad 1,4 % i više, može se pojaviti problem postizanja homogene austenitne strukture koja bi bila bez zrnaca karbida [4].Web of Science23375274

Investigation of Heat Affected Zone of Steel P92 Using the Thermal Cycle Simulator

This work is focused on mechanical properties and microstructure of heat affected zone (HAZ) of steel P92. The thermal cycle simulator was used for modeling a fine grained zone of HAZ. Hardness and impact toughness were measured on simulated samples. Microstructural analysis using optical microscopy was performed on selected samples. Achieved results were compared with the values of a real welded joint. The thermal cycle simulator allows transferring the properties of very small HAZ to the sufficiently large sample where the tests of the mechanical properties can be performed. A satisfactory accordance was found when comparing the microstructure and mechanical properties of real welds and simulated samples

Abrasive waterjet (AWJ) titanium tangential turning evaluation

The paper deals with abrasive waterjet titanium tangential turning. Titanium grade 3 with a diameter of 55 mm was used as an experimental material. Technological conditions of turning tests were the same by gradually changing value of traverse speed (vf = 1,5; 3; 4,5; 6; 7,5 mm·min-1). Experiment tests were performed by using continuous abrasive waterjet of pressure p = 400MPa, by rotation n = 60 rpm of workpiece. The abrasive particles (Barton Garnet) were fed to the waterjet in the amount of 0,4 kg·min-1. It was determined that acceleration of traverse speed did not increase the surface profile parameters.Web of Science53454053

Study of the properties of solders reinforced with tungsten carbides

HLAVATÝ Petr. Studium vlastností pájek s vloženými karbidy wolframu, Vysoká škola báňská - Technická univerzita Ostrava. Katedra mechanické technologie, Fakulta strojní. Školitel: prof. Ing. Petr Mohyla, Ph.D. Současným trendem ve strojírenství a stavebnictví je prodlužování životnosti součástí pomocí nových materiálů a technologií. Při provozu zařízení dochází k opotřebení dílů v extrémně namáhaných místech, kdy je nutné celou součást vyměnit nebo renovovat opotřebenou část. Materiály těchto strojních součástí podléhají řadě druhů opotřebení například abraze, adheze, eroze, apod. Renovační procesy mají za cíl prodloužit životnost zařízení. Disertační práce se zabývá studiem vlastností nánosových vrstev vytvořených pájením za použití kyslíkoacetylenového plamene, metodou pájení 912 s ukotvenými částicemi karbidu wolframu. V práci byly použity tři typy pájek WSC 553, Z-Terradur a Durit CS, nanášené na základní materiál S235JR. K hlavním cílům práce patří analýzy strukturních přeměn a metalurgických dějů u tří typů nánosových vrstev s rozdílnou velikostí částic karbidu wolframu. Jednotlivé typy vrstev byly podrobeny abrazivnímu testu RWAT (Rubber Wheel Abrasion Test), dále bylo provedeno hodnocení mikrotvrdosti vybraných míst, metalografické posouzení a chemický rozbor vrstev pomocí elektronové mikroskopie a porovnání množství a velikosti částic karbidu wolframu na finální životnost povrchu. Výsledkem disertační práce je posouzení vlastností rozdílných nánosových vrstev s vloženými zrny karbidu wolframu s cílem prodloužení životnosti součástí používaných v praxi při zachování bezpečnosti provozu.HLAVATÝ Petr. Study of the properties of solders reinforced with tungsten carbides, Ostrava, 2022. Dissertation Thesis. VSB - Technical University of Ostrava Department of Mechanical Technology, Faculty of Mechanical Engineering. Supervisor: prof. Ing. Petr Mohyla, Ph.D. The current trend in the engineering and construction industry is to extend the life of components using new materials and technologies. During the operation of the equipment, wear of parts occurs in extremely stressed components, when it is necessary to replace the entire part or renovate the worn part. The materials of these machine parts are subject to many types of wear, such as abrasion, adhesion, erosion, etc. Renovation processes aim to extend the life of the equipment. The dissertation thesis deals with the study of the properties of deposition layers created by soldering using an oxyacetylene flame, brazing method 912 with anchored tungsten carbide particles. Three types of solder WSC 553, Z-Terradur and Durit CS were used in the work, applied on base material S235JR. The main objectives of the thesis include the analysis of structural transformations and metallurgical processes in three types of deposit layers with different sizes of tungsten carbide particles. Individual types of layers were subjected to the RWAT (Rubber Wheel Abrasion Test) test, the analysis of microhardness of selected areas were also assessed, metallographic assessment and chemical analysis of the layers using electron microscopy and comparison of the amount and sizes of tungsten carbide particles on the final life of the surface. The result of the dissertation thesis is an assessment of the properties of different solders with embedded tungsten carbides layers grains with the aim of extending the service life of the components used in practice while maintaining operational safety.345 - Katedra mechanické technologievyhově

Effect of fatty acids on lipid metabolism and weight reduction

Fat tissue plays a main role in the development of the metabolic syndrome. Many components of the metabolic syndrome may be improved by dietary arrangements, including an increased intake of n-3 PUFA. In addition to the positive effect of n-3 PUFA, a possible effect of a higher calcium intake on influencing weight loss and energy metabolism has also been discussed for a long time. In addition to nutritional factors, genetic factors significantly contribute to influencing weight and lipid and glucose metabolism. In study A, 40 obese women were observed during three weeks of weight reduction management. Women were randomly divided into two groups. The first group received yogurt enriched with n-3 PUFA, and the second group consumed yoghurt without the supplementation. The results show that low-dose supplementation with n-3 PUFA in yogurt in combination with a reduced energy intake increases n-3 PUFA content in serum lipids and prevents adverse changes in the composition of FA in serum after a short-term low-calorie diet. In study B, we monitored the influence of n-3 PUFA supplementation on short-term weight management with VLCD in 20 women with severe obesity, who were randomly divided into two groups. The first group received VLCD enriched with n-3 PUFA, the second group VLCD with a placebo. The addition of..