National Repository of Grey Literature 313 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Loranthus europaeus Jacq. verzus druhy r. Quercus L. resp. Carpinus L. =: Loranthus europaeus Jacq. vs. Quercus L. resp. Carpinus L. genera. /
Kubíček, Jan
A better understanding of host – hemiparasite association can lead to deepening and improving strategies, which would result in a long-term sustainability of their mutual balance or prosperity of urban and forest vegetation growth. The aim of the thesis is to describe and explore periodicity and dynamics of hemiparasite (Loranthus europaeus Jacq.) on various host woody species (Quercus petraea (Matt) Liebl., Carpinus betulus L., Prunus spinosa L.), options of the host support and means of a careful removal of parasite. However, to determine the progress of the infestation in time was the primary aim of the thesis. The research has been carried out in Brno – Kohoutovice and National Park Podyjí. The emergence of both hemiparasite´s and host´s phenophases were mutually compared in the critical conditions. The variation of the growth modules of mistletoe was compared in relation to the host species. The growth and fruit yield of the host and hemiparasite were analysed after the application of fertilizer based on the variations of the mineral content of leaves and soil. Between the years 2011-2015, 1599 stems were monitored for the degree of infestation by mistletoe. The results indicate that the vitality of the hemiparasite depends on the type of host. Fertilizer application improved the growth of the host. Arboricide application on the leaves of the hemiparasite was proven to be efficient. The abundance of hemiparasite increases with the increasing diameter at breast height (DBH), time and mutual interaction. The amount of hemiparasite slightly increases with the lower DBH. However, with the increasing DBH the mentioned phenomenon decreases. The trees with high DBH even show the decrease in the mistletoe infestation in time. Nevertheless, the decrease was accompanied by negative effect – gradual reduction of the crown and loss of the host tree branches. Hemiparasite is able to eradicate the whole stand. Hence, the necessity of paying attention to this issue since the young age of the individual trees. It is necessary to protect trees against stress aspects which can accelerate the negative effect of hemiparasite on the host.
Inspection of welded joints of loading ramps
Ertl, Roman ; Mrňa, Libor (referee) ; Kubíček, Jaroslav (advisor)
This master's thesis is focused on problem of welding of loading ramps and inspection of their welded joints. The aim of this thesis is to inspect the welds of loading ramps with regarding to the appearance of defects. The literature review of the research issues of the MIG welding technology and welding of aluminium and its alloys is described in this thesis. There is also described destructive and non-destructive inspection of welds that can be applied to inspection of loading ramps. Theoretical description is followed by an experimental part of the thesis. Experimental part is focused on the three destructive tests (the tensile, the macroscopic and the hardness test) of samples of loading ramps, which are made of EN AW-6005A T6.
Thermal spray by electric arc
Eliáš, Vojtěch ; Sigmund, Marián (referee) ; Kubíček, Jaroslav (advisor)
This thesis deals with the issue of thermal spraying by means of an electric arc. First of all, a theoretical part is processed using a literary study dealing with corrosion and thermal spraying technology. The experimental part contains a description of the technological procedure and evaluation of four thermally sprayed samples. Zinacor 850, consisting of 85% zinc and 15% aluminum, was used as a coating. The evaluation involves measurements of thickness, adhesion and roughness as well as the macro-structural analysis of the coating. Two samples showed unusually low adhesion, and all samples also had a large fluctuation of the measured thicknesses. This was also confirmed by the macro-structural analysis, which showed that the sample with low adhesion also had high porosity. These defects may have multiple causes, but the recommendation for further practice is to reduce the spraying distance from the base material.
Renovation of casting molds by laser cladding technology
Cicha, Tereza ; Kubíček, Jaroslav (referee) ; Mrňa, Libor (advisor)
The diploma thesis deals with study of laser cladding technology and possibilities of its use in renovation of casting molds made of hot-work tool steel. The theoretical part describes methods of laser cladding, testing methods and characteristics of the base material and its heat treatment. In the experimental part the test clads, and the metallographic samples were made. The samples were evaluated in terms of macrostructure and microstructure, especially clad geometry, dilution, and defects like pores and cracks. Microhardness was also measured. In conclusion a technical and economic evaluation was performed.
Evaluation of quality welds on chains for harvester
Teuer, Tomáš ; Kubíček, Jaroslav (referee) ; Sigmund, Marián (advisor)
The diploma thesis examines the influence of setting welding parameters and welding process on the resulting structure and strength of the welded joint of harvester chains. The theoretical part discusses the problem of weldability of pine steels by using method “135” with the possibility of destructive or non-destructive testing of welded joints. In the practical part, this matter is examined on a specific weldment, the harvester chain. Cross member with a cube welded in two ways by method 135, followed by an assessment of the performance of welds. The results of the evaluation are written down in the manual.
Cryogenic cell for study of water ice in ESEM microscope
Krutil, Vojtěch ; Kubíček, Jaroslav (referee) ; Urban, Pavel (advisor)
The presented thesis focuses on designing a cryogenic cell for the study of water ice in an environmental scanning electron microscope (ESEM). This cell allows the study ice in the temperature range 80 K – 300 K in a nitrogen gas environment with a pressure of up to 400 Pa. The cell is cooled by a flow cooling system, where liquid or gaseous nitrogen is used as a refrigerant. The cell consists of a double-walled vessel with vacuum insulation, a flow-through heat exchanger, a sample well, and a cooled cell lid. The heat exchanger was designed to be able to dissipate the heat load at the level of 1 W. The exchanger is equipped with an electric resistance heater with an output of approximately 60 W, enabling heating of the sample at speeds of up to 100 K·min-1. The design also includes an LN2 gateway located on the door of the vacuum chamber of the microscope, to which the capillaries of the heat exchanger for the intake and outlet of refrigerant are connected. During the experimental verification of the cryogenic cell in the test vacuum chamber with a pressure of GN2 ~ 400 Pa, the limit temperature of 77.5 K on the sample well was reached.
Utilization of laser welding methods for fixation of electrotechnical sheet bundles
Adam, Tomáš ; Kubíček, Jaroslav (referee) ; Mrňa, Libor (advisor)
Thesis deals with individual technologies of packaging stator sheets and their use in practice. The greatest emphasis is placed on welding technologies, especially on the differences between the individual methods. The experimental part of the thesis is focused on finding suitable parameters for welding the stator package using a laser with a special wobling head. The samples were evaluated in terms of penetration depth, the number of defects, especially pores and grain coarsening.
Accelerate handling strength in 2K PUR adhesives
Slatinská, Jana ; Žák, Ladislav (referee) ; Kubíček, Jaroslav (advisor)
This paper is devoted to accelerating the time to obtain the handling strength of two-component polyurethane adhesive, which was newly purchased by the company Magna Exterios (Bohemia) and had to be tested. In order to speed up the analysis of the problem, methods of IR emitters and temperature chambers were selected to be compared with curing using only the ambient atmosphere. In the second part of this paper, the maximum strength of the bond which withstand the test without damage was measured. The results show that the method of accelerating curing process using an IR emitter is the fastest, but the economic side of things must be taken into account, because it is also the most expensive option of acceleration. The temperature chamber is almost twice as slower, but cheaper. At the end of the thesis, the economic efficiency of the new adhesive line solution is evaluated and how much money can be ideally saved.
Welding thin-walled pipes made of stainless steels
Naď, Tomáš ; Sigmund, Marián (referee) ; Kubíček, Jaroslav (advisor)
The bachelor's thesis deals with technology of welding of thin-walled stainless steel pipes and the analysis of weldability of stainless steels. The theoretical part provides a basic description of the material's weldability and the basic defects in welding, the characteristics of stainless steels, their division, marking, alloying and a general overview of their weldability. The experimental part describes selected welding technologies used for the production of thin-walled stainless steel pipes (LBW, PAW, HFIW). Finally, the technology used to weld the presented samples of thin-walled pipes is ascertained and the macrostructure of the weld are compared.
Welding the frame of the tandem bicycle
Rajm, Vojtěch ; Sigmund, Marián (referee) ; Kubíček, Jaroslav (advisor)
In the first part of thesis were compared frames of two different bicycles and according to this comparison was designed a geometry of tandem bicycle. In a next part were described the most common materials in cycling industry and theirs advantages and disadvantages. According to the comparison, the steel EN 25CrMo was considered as the most suitable material for its low prize and high strength. After that is described weldability of steels and types of cracks which are one of the most casual defects in welded materials. In another part of thesis are theoretically described kinds of suitable welding methods for bicycle frames. As the most suitable are methods in shielding gases MIG/MAG and TIG. As the best method was chose TIG welding. In a practical part of thesis are compared these methods experimentally. Tubes from selected material were welded by MAG and TIG. The TIG welding proved again as better because of deeper and tough welds.

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