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Influence of Plastic Deformation on the Residual Stress Distribution and Fatigue Behaviour of High Strength Steels Welds
Mráz, Ľ. ; Karlsson, L. ; Hamak, I. ; Mikula, Pavol ; Vrána, Miroslav
The effects of plastic deformation and cyclic loading on residual stress distribution have been studied at welds in high strength 800 MPa steel. Effects of residual stress levels on fatigue life are also presented. Tensile loading was used to induce precisely controlled plastic deformation at weld toes. Residual stress distributions were measured by neutron diffraction. The influence of fatigue loading on the residual stress level was much smaller than that of plastic deformation. A large drop of residual stresses in the vicinity of the welds was recognised after local straining at the level of 2%. Stresses decreased with up to 550 MPa in the region around the weld toe. The effect of local plastic deformation on fatigue properties was also found to be significant. Fatigue strength more than doubled compared to the non-strained as-welded condition.
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Neutron diffraction analysis of residual strain/stress distribution in the vicinity of high strength welds
Mráz, Ľ. ; Karlsson, L. ; Hamak, I. ; Vrána, Miroslav ; Mikula, Pavol
Residual stresses resulting from non homogeneous heat distribution during welding process belong to most significant factor influencing behavior of welded structures. These stresses are responsible for defect occurrence during welding and they are also responsible for crack initiation and propagation at the either static or dynamic load. The significant effect of weld metal chemical composition as well as the effect of fatigue load and local plastic deformation on residual stress distribution and fatigue life have been recognized for high strength steels welds. The changes in residual stress distribution have then positive effect on cold cracking behavior and also on fatigue properties of the welds [1-3]. Several experimental methods, both destructive and non-destructive, such as hole drilling method, X-ray diffraction, neutron diffraction and others, have been used to examine residual stress distribution in all three significant orientations in the vicinity of the welds. The present contribution summarizes the results of neutron diffraction measurements of residual stress distribution in the vicinity of single-pass high-strength-steel welds having different chemical composition as well as the influence of fatigue load and local plastic deformation. It has been observed that the chemical composition of the weld metal has a significant influence on the stress distribution around the weld. Similarly, by aplying both cyclic load or pre-stress load on the specimens, stress relaxation was observed even in the region of approximately 40 mm far from the weld toe.
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Current possibilities of breeding and production of whitefish in the Czech Republic
MRÁZ, Luděk
The main goals of this thesis are description of a quite complicated peled breeding topic in the Czech Republic, evaluation of inconsistent taxonomical data, biology and ecology of the Coregonus maraena and Coregonus peled. The approach to peled breeding is in detail evaluated recently as well as in the past. Methods of breeding, fishing out, fish tank breeding and fish transfer are addressed. The questionary survey among peled producers was used for critical evaluation of their experience. The factors that discourage producers from peled breeding (eutrophication, predation by cormorants or otter as well as technological difficulties) were stated. Due to these factors the peled production is limited despite the stabile market demand. The case study of peled production was realized. In the condition of huge fish stock (carp and grass carp) the main negative impacts were confirmed.
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Censorship in today's internet media
Mráz, Lukáš ; Lábová, Alena (referee) ; Šmíd, Milan (advisor)
Bachelor thesis "Censorship in today's internet media" deals with various forms of censorship of internet media nationwide and worldwide. It is analyzing the mechanisms in non-democratic countries which restrict freedom of expression and reception of information communication and even what purport is filtered in countries which respect human rights. This thesis summarizes the options which may defend internet censorship and analyzes the current situation of spreading illegal software and multimedia. It seeks the existing trends in the area of internet communication with notions such as anonymity and free discussion. And therefore it contemplates the relations between censorship, human rights and political situation in the world.
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New technologies and film music at the turn of the 21st century
Mráz, Lukáš ; Klimeš, Ivan (referee) ; Kopecký, Pavel (advisor)
This work deals with the relationship between modern sound technologies and the aesthetics of modern film music. The research era has been from early 90's to the present. The main goal of this work is to define the aesthetic quality that huge developments in the field of tone generators helped to bring into the area of film music, and describe in detail the major features of this type of sound technology. The phenomena which relates chosen sound, musical software and hardware are analyzed as well as the role of video-games and technological innovations, which had a big influence on creating the aesthetics of modern film music. The method of this work is analyzing the depending technological components of tone generators, the inside structure and the entire developing and social context and effects, which have for aesthetics of the film music. Next this work is also trying to answer the question why are some of the aspects of technology preferred more than the others. It watches the influence of commerce and the shape of the social nets, where the authors and users of the sample technologies meet.
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Breeding burbot (Lota lota L.)in the Czech Republic
MRÁZ, Luděk
Zabývám se chovem mníka jednovousého různými metodami chovu a to od váčkového plůdku až po ročka (jednoletou rybu) s možným výhledem do budoucna jako s tržní rybou. Také srovnávám poloumělý a umělý způsob výtěru. Krátce se zmiňuji i o chovu v zahraničí především Polsko a Německo. Navrhuji opatření na zvýšení produkce a uplatnění mníka na našem trhu jako konzumní ryby.
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Napoleon´s theorem
MRÁZ, Luděk
The target of the this diploma thesis called ''The Napoleon's theorem'' is a detailed concentration on this theorem, where the process of so called ''regularization'' is described. Under the investigation of the Napoleon's theorem this diploma thesis is concerned with a lot of proofs, properties and then their generalization in a plane and in space. Pictures, which can help the reader to understand this problem are supplemented in this diploma thesis.
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Use of paper folding techniques in teaching mathematics
MRÁZ, Luděk
The target of the Bachelor's thesis "Use of paper folding techniques in teaching mathematics" is to highlight the importance of origami in mathematics and its subsequent use as a suitable tool in lessons of mathematics in primary or in secondary schools. Most of the work is devoted to practical problems. It means constructions of planar and spatial figures and solving interesting or problematic tasks which are accompanied by graphics solutions and proofs.
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