• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 144
  • 12
  • Tagged with
  • 156
  • 87
  • 79
  • 72
  • 67
  • 65
  • 48
  • 36
  • 31
  • 28
  • 27
  • 26
  • 25
  • 24
  • 22
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Zkoumání vybraných vlastností neupraveného a tepelně upraveného smrkového a modřínového dřeva z pohledu vhodnosti na výrobu šindele

Hlobil, Vladimír January 2015 (has links)
The aim of this thesis is the analysis and comparison of selected material properties of spruce, larch, heat-treated spruce and larch in terms of suitability for the production of wood roof shingles. Monitoring and comparing characteristics are durability of the wood material against the brown rot fungus, compressive strength across the fiber, bending strength and modulus of elasticity. Tested material and its selected properties are compared as for use in the manufacture and installation of wooden shingles.
32

Vliv rychlosti mobilních energetických prostředků na hladinu akustického tlaku / Effect of speed mobile power resources on the sound level

SKALIČKA, Jiří January 2015 (has links)
The thesis is focused on evaluating of noise pollution environment of mobile energy devices of various classes with respect to the speed of mobile the energy resource. The first part oft eoretical research focuses on the physical properties of noise and effect on people. The second part describes the reasons for noise, its intensity at the mobile energy resources with its average values. In the practical part are performed measurement of noise emissions with the surrounding environment. There is suggested measures to reduce the noise level, ventually there is recommended optimal operating speed movement of vehicles.
33

Hodnocení kvality provedení ručně stříkaného betonu / Evaluating the quality of implementation of the hand shotcrete

Kopecký, Lukáš Unknown Date (has links)
Currently, the high speed and low price are required for construction works in the modern architecture. Therefore, it is necessary to deal with verifying the quality of the constructions. Dissertation thesis is focused on evaluating the quality of the execution of sprayed concrete without accelerating additives applied by spraying by a dry way manually-sprayed. The quality of shotcrete was judged on the basis of standardized both non-destructive and destructive methods using sprayed samples. The quality of shotcrete was assessed in terms of strength of sprayed concrete in pressure, density and homogeneity judged on the basis of the velocity of sound samples. The destructive method was carried out on the core samples which were pressured on the hydraulic press, as the non-destructive method was used ultrasonic passageway method based on the propagation velocity of the ultrasonic pulse. On the basis of our results and their mutual correlations, it has been proposed the modifications of the general equal used for predicting the strength of the sprayed concrete tested by our strength class, which leads to a potential reduction in the number of cores on the real structure, and therefore reduce the price of implementation of qualitative tests and increase effectiveness of carrying out tests on the construction place.
34

Fyzikální jevy při dopravě vzduchu / Physical phenomena in air transport

Bělehrádek, Lukáš January 2018 (has links)
The aim of this thesis is to design an air conditioning system of a flat unit in two variants of piping. The piping system of the first floor is installed into the floor in one variant, in the other it is in the ceiling. Data received from measurements within the experiment have been used for the design. The result of the measurement are minor loss coefficient implemented for bending pipes and pressure losses caused by rubbing. These values are used for dimensioning piping variants. Both types of piping are described in the theoretical part and the method of how the experiment had been processed.
35

Podélné indexové struktury v optických vláknech / Longitudinal index structures in optical fibers

Polreich, Štěpán January 2018 (has links)
This thesis describes basic concepts, principles and properties of optical fibers. Considerable part is devoted to fiber gratings that are created by a change in the refractive index in the optical fiber core. In this work is described description, principle, method od production and distribution of gratings on Bragg gratings, gratings with long period and chirped gratings. In this thesis are also presented different types of lasers and their advantages over other lasers. A large part deals with the description of the femtosecond laser, with which the structures will be later made into the material. In addition, the laser modes are differentiated, this is a mode of micro-machining and modification or a change in refractive index of the material. The last part deals with change the refractive index in planar technology, the creation of a groove for fastening the fiber and attempts to write the gratings into the optical fiber. Created fiber sensor are tested for temperature and tensile changes. Finally, the practical use of sensors made by femtosecond laser and the advantages over UV laser and phase mask techniques are presented.
36

Využití 3D tisku v TZB / Using 3D printing in HVAC

Malovaný, Ondřej January 2019 (has links)
In the experimental part of this thesis there is an assessment of pressure bearing capacity of cylindrical nozzles printed using a 3D printer. In the theoretical part of this diploma thesis there are outlined the types of additive technologies focusing on the development of FDM printers, open designs and RepRap project. Descripti-on of the production process of 3D printing and application of additive technolo-gies in the field of HVAC. In the project part, the design of the forced ventilation of the Sports Hall is solved. The object is assessed in terms of heat losses and profits for priority rooms of functional units. Heat load coverage is carried out by air-conditioning equipment. In addition, a project is drawn up which contains all the text and drawings, including technical specifications and regulatory schemes.
37

Experimentální ověření vlivu typu vláken na chování vláknobetonů / Experimental Investigation of the Influence of the Type of Fibres on the Behaviour of Fibre Concrete

Hanuš, Petr January 2019 (has links)
This diploma thesis deals with the comparison of different properties of fibre-reinforced concrete according to the type of fibres. The main monitored property is flexural strength, tested on prisms with a cross section of 150x150 mm and a length of 600 mm. Four concretes of natural aggregate and four concrete of lightweight aggregate were prepared for the experiment. There were 2 reference concrete and 6 fibre-reinforced concrete. Three types of fibres were used: steel, polypropylene and glass. More than 2500 kg of concrete was produced. The aim of the thesis is to assess the influence of fibres on the flexural strength and other characteristics of fibre-reinforced concrete.
38

Diagnostika mostu poškozeného požárem / Diagnosis of the fire damaged bridge

Olejková, Sabina January 2019 (has links)
This thesis is about assessment of a bridge construction influenced by fire accident. The bridge is situated at the highway D46 beyond the town Držovice. Within this construction research, there will be mentioned diagnostic methods – A non- destructive method (Ultrasonic pulse method and hardness tests) and destructive methods (borehole and tear off tests). For find out in which way was the concrete of the bridge damaged and hurt while facing a high temperature of fire, there were taken samples, which were analyzed by physical and chemical test. We can analyze composition and microstructure of the concrete. The result of this tests will be evaluated, and the actions of a remediation will be suggested.
39

Struktura a mechanické vlastnosti materiálů na bázi hořčíku zpracovaných metodou HPT / Structure and mechanical properties of magnesium materials processed by HPT

Poloprudský, Jakub January 2019 (has links)
This thesis is focused on processing of pure magnesium by high pressure torsion method (HPT). This process belongs to the group of intensive plastic deformation methods (SPD). SPD methods are in the centre of scientific interest for several decades. Theoretical part of this thesis puts an effort to summarize basic knowledge and principles of SPD methods with extra focus on method HPT. As theoretical part continues magnesium as technical material is presented. Influence of SPD on use and properties of pure magnesium is then presented. This trend is further developed in effort to describe the effect of individual HPT process variables on the properties of pure magnesium and its alloys. Focus of practical part of this thesis is in influence of number of revolutions. Samples were processed at 1/8, 1/4, 1/2, 1, 4 and 8 turns at room temperature. Speed of process was 1rpm and applied pressure was 6 GPa. The structure of commercially pure magnesium prepared by casting and moulding were observed with focus on differences caused by input material. The structure was observed by both light microscopy and back scattered electron diffraction (EBSD), focusing on structure development, grain size and grain orientation. Compared to other works on similar topic, the emphasis here is on observing the microhardness on the vertical edge of the sample. The hardness shows a steep increase right after 1/8 of a turn. With increasing number of turns gradual homogenization of microhardness is presented accompanied by slight decrease in microhardness. No trend in microhardness relative to the distance from anvil has occurred. Structure observed with EBSD shows a bimodal character with larger grains oriented in the same direction. The three-point bending test didn’t end up as expected, and the approach to evaluation of magnesium-based HPT needs to be re-evaluated for future work. A three-point bending test was designed for the initial assessment of the basic mechanical properties of the material.
40

Porovnání hlučnosti stranových vyústek odlišných konstrukcí / Comparison of noise generated by differently constructed vents

Bernard, Jan January 2019 (has links)
This diploma thesis deals with comparing noise levels of three side vents of different constructions, which are used for distribution and directing of ventilation air in a cabin of an automobile. The fundamental knowledge of the physical and physiological acoustics is described in the introduction part of this study. Following the introduction part there is a brief explanation of the car air conditioning system (HVAC system) as well as are explained the acoustic properties of specific elements of this system. The study also deals with dividing ventilation vents and describes the vast traceable types of automobile vents. Prior to the description of the experiment, which was conducted as a part of this study, the procedures and results of the measurements carried out in other theses are explained. Measurement of noise levels of the compared vents was carried out in a semi-anechoic chamber under the ČSN ISO 3475 standardization. To clarify increase of noise generated by the vent in an interior of an automobile, additional measurement of noise was carried out in a cabin of Porsche Cayenne 2018. From the gathered results we can conclude that under the constant flow, (of 60 square meters per hour) louder vents are those with higher pressure loss. This pressure loss is dependant primarily on the speed of the flow in the vent, as well as on the number and the adjustment of the deflectors. In a cabin of an automobile, the noise produced by the vent is negligible in comparison with total noise in an interior of a car. However, in the area surrounding the air flowing out from the vent, (approximately 0,7 meters from it) the level of acoustic pressure increases significantly.

Page generated in 0.0771 seconds