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  • 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.
51

Odrůstání kultur a porostů založených prostokořenným a krytokořenným sadebním materiálem na území LS LČR Jablunkov

Baselides, Andrzej January 2018 (has links)
The aim of this diploma thesis is to evaluate the growth of cultures and stands estabilished using bare-rooted and ball-rooted planting stock on working-plan area, forest district Jablunkov. For this purpose a total of 23 stands were selected (evaluated) on 46 research plots on forest district Jablunkov. In addition, the two economically most important tree species were selected for research; Norway spruce (Picea abies L.Karst) and European beech (Fagus sylvatica L.). These areas were selected on the basis of geographic and typological differences of habitat. A minimum of 60 viable individuals from bare-rooted and ball-roted group were measured on each plot and also the root deformations of the selected tree species were measured. The following parameters were measured for each individual: the height of the above-ground parts, the last accretion, the thickness of the root collar, the number of branches, the length of the branches, the size of the assimilation apparatus. The following features have also been observed and evaluated: loss, vitality, damage, trunk shape, crown shape, and root system deformations. From the results it was found out that out of 23 stands, ball-rooted planting stock was evaluated as better in 16 cases, in 5 cases was better bare-rooted planting stock and in 2 cases no better variant was found. In assessing of the root system, it was found that up to 100 % of the root system deformation was found in both types of planting stock.
52

Vliv biotechniky sadby krytokořenného sadebního materiálu smrku ztepilého a buku lesního na odrůstání kultur a vývin jejich kořenového systému v 7. lesním vegetačním stupni

Koudelík, Lukáš January 2018 (has links)
The aim of the diploma thesis was to verify the influence of different seed plant biotechnics on the growth of cultures and development of the root system of the cryopreservation material of spruce and beech forest in the 7th forest vegetation stage. The monitoring was carried out at LS LČR Janovice on forest types 7P and 7K. As the main biotechnology for testing, the seedbed was planted, the seedbed was planted without and with overlay, the seedling was planted without overlapping and seeded with seedless forks without overlapping. The effect of the balloon overlay was also evaluated. To evaluate the influence of different plant biotechnology on the growth of the cultures and the development of the root system we mainly served the criteria of the height of the above-ground part, the thickness of the root neck, the size of the assimilation apparatus, the loss, the vitality, the development of the root system, etc. The best plant biotechnology was evaluated for the spruce spruce on the area 7P planting seedless pipe without overlap and on 7K area planted with seamless sowing. In the case of forest beech, 7P was evaluated as the best seedling without overlap and 7K seedbed without overlapping. The suitability of hole seedlings for both studied species and areas was confirmed. The effect of seedling on the deformation of the root system was confirmed.
53

Deformační analýza kmene při kácení

Veselý, Jiří January 2019 (has links)
This work deals with strain analysis of tree during felling. The main goal is to describe the origin of the deformation field. Another aim is to explain the effect of individual cuts on the size of deformation forces. Two relatively new methods in the field of wood are used to investigate the experimentally, namely digital image correlation (DIC) and finite element method. The work deals with methodical foundations for tree research during its felling. The DIC method measured seven trees in the forest when felling. Using the results obtained by this experiment, the numerical model was validated. This comparison suggested higher rigidity of the body using the finite element method compared to the actual tree, but the reaction was similar. With respect to the higher stiffness, the model was used to describe the deformation field inside the tree and to describe the effect of each cut on this field. The thesis also draws attention to the methodological errors that can occur during felling and which have been described in the experiment. Another output is an indication of the direction in which further measurements should be made and the errors that occurred during this measurement to avoid repetition.
54

Relaxace impaktních kráterů ve sluneční soustavě / Impact crater relaxation throughout the Solar System

Kihoulou, Martin January 2021 (has links)
Title: Impact crater relaxation throughout the Solar System Author: Martin Kihoulou Department: Department of Geophysics Supervisor: RNDr. Klára Kalousová, Ph.D., Department of Geophysics Abstract: In this thesis, we study the viscous relaxation of an impact-deformed icy shell of a dwarf planet Pluto. Motivation for this work is the position of Sputnik Planitia, a 1000 km wide, nitrogen-filled elliptic basin, which is located very close to Pluto-Charon tidal axis. Given this unlikely position on Pluto's sur- face, it was suggested that the basin was formed elsewhere and the whole body reoriented afterwards. For the reorientation to occur, the basin has to generate a positive gravity anomaly for which a combination of impact-related subsurface ocean uplift, ejecta blanket and accumulation of nitrogen ice was suggested. How- ever, to maintain the orientation towards the minimum principal axis of inertia until today, the ocean uplift must be present on timescales of billions of years, which may be achieved due to an insulating layer of high viscosity clathrates at the ice/ocean interface. We solve Pluto's ice shell evolution by the finite element method in 2D spherical axisymmetric geometry with an evolving free surface and assuming a viscous rheology. Our results show that the thermal effect of the im- pact...
55

Adaptive parameterization for Aerodynamic Shape Optimization in Aeronautical Applications / Adaptive parameterization for Aerodynamic Shape Optimization in Aeronautical Applications

Hradil, Jiří January 2015 (has links)
Cílem mé disertační práce je analyzovat a vyvinout parametrizační metodu pro 2D a 3D tvarové optimalizace v kontextu průmyslového aerodynamického návrhu letounu založeném na CFD simulacích. Aerodynamická tvarová optimalizace je efektivní nástroj, který si klade za cíl snížení nákladů na návrh letounů. Nástroj založený na automatickém hledání optimálního tvaru. Klíčovou částí úspěšného optimalizačního procesu je použití vhodné parametrizační metody, metody schopné garantovat možnost dosažení optimálního tvaru. Parametrizační metody obecně používané v oblasti aerodynamické tvarové optimalizace momentálně nejsou připravený na komplikované průmyslové aplikace vyskytující se u moderních dopravních letounů, které mají šípová zalomená křídla s winglety a motorovými gondolami, přechodové prvky spojující např. trup s křídlem atd.. Existuje tedy potřeba nalezení obecné parametrizační metody, která bude aplikovatelná na širokou škálu různých geometrických tvarů. Free-Form Deformation (FFD[1]) parametrizace může, vzhledem ke svým schopnostem při zacházení s geometrií, být odpovědí na tuto potřebu. Adaptivní parametrizace by se měla být schopna automaticky přizpůsobit danému tvaru tak, aby byly její kontrolní body vhodně rozmístěny. Což umožní dostatečnou kontrolu deformací objektu, která zaručí možnost vytvoření optimálního tvaru objektu a splnění geometrických omezení. Primární aplikací takové parametrizační metody je deformace tvaru objektu. Dalším navrhovaným cílem je modifikace FFD parametrizační metody pro současné deformace tvaru objektu a CFD výpočetní sítě, umožnující velké deformace objektu při zachování kvality výpočetní sítě.
56

Tahokov / Stretch metal

Dostál, Jan January 2018 (has links)
Controlled deformation. Under with conditions can the iron deformation process be affected? This work is focused on expanding steel profiles. Using various tests, I will confront the visual results with the technical possibilities of the material. Attempting to find a boundary that is still permissible in terms of maximum steel loading just before the material starts to fail. The resulting installation should show the enormous forces needed to distort the material, where the viewer will be directly confront with the process.
57

Dynamické změny v terénu / Dynamic Changes in the Terrain

Dvořák, Radim January 2007 (has links)
This thesis deals with design, implementation and analysis of the model for dynamic changes in the terrain. Present state of terrain deformation in OpenSceneGraph environment is described and available relevant software called TDS, which allows terrain adaptation to new inserted objects is presented. Special emphasis is placed on design of model for physically based terrain deformations that are caused by moving object or by bomb explosion. The results of simulation tests are presented and on the base of model analysis, the optimizations, which significantly improve final algorithm, are designed and realized.
58

Fyzikální vlastnosti jemnozrnných hořčíkových slitin připravených různými technologiemi / Physical properties of ultrafine-grained magnesium based alloys prepared by various severe plastic deformation techniques

Stráská, Jitka January 2014 (has links)
Title: Physical properties of ultrafine-grained magnesium based alloys prepared by various severe plastic deformation techniques Author: Jitka Stráská Department / Institute: Department of Physics of Materials Supervisor of the doctoral thesis: Doc. RNDr. Miloš Janeček, CSc. Abstract: The objective of the doctoral thesis is the complex investigation of ultrafine-grained magnesium alloy AZ31 prepared by two different severe plastic deformation techniques, in particular the hot extrusion followed by equal-channel angular pressing (EX-ECAP) and high pressure torsion (HPT). These severe plastic deformation methods, and as well as many others, are described in detail in the introductory theoretical section. Experimental results are summarized in the following experimental part of the thesis. Mechanical properties, lattice defect structure and especially microstructure were investigated using various experimental techniques. Thermal stability of ultrafine-grained microstructure of AZ31 after EX-ECAP was investigated and the activation energies for grain growth in different temperature ranges were calculated using kinetic equation for grain growth and Arrhenius equation. Results from the dislocation density measurements proved temperature ranges of the recovery and the following grain growth. Results from the...
59

Studium tvařitelnosti povlakovaných plechů s plazmo-chemickou předúpravou povrchu / Study of formability of coated sheets with plasma-chemical pretreatment of surface

Schwarzer, Emil Unknown Date (has links)
Theoretical part PhD thesis describes bending of sheets especially with a small bend radius and the distribution of deformation and describes the parameters of bent sheet. As the test sheets were treated by cataphoretic coating is this method described together with pretreatment of sheet. The practical part is focused on the principle multi-jet plasma system and treatment of the steel surface and examines the bent surfaces of the steel sheets with different variants of applying the coating. Selected samples are bent on the multifunction graduated bending jig and subjected to the Erichsen test and deduced results using plasma system and without the use of plasma system. In the experimental part were examined samples treated by multi-jet plasma system and subsequently bent on the multifunction graduated bending jig. Compares the results of individual experiments in system steel – base coat – plasma – topcoat. And also compares mutual combinations of various kinds of modifying the surfaces of steel samples with different coatings. Selected samples were tested for tensile test and the results were processed from this test. For selected samples was calculated hardening exponent. Another experiment consists in applying a circle at equal samples and subsequently the samples were bent under a defined radius and were determined tensile and compressive deformation. Samples of sheets were then embedded in the resin and then examined under a microscope, where they were divided into several categories and was determined optimal composition multi-jet plasma system for selected samples and the specific coatings on sheet plate with a maximum adhesion of the coating to the steel base. Selected measured values were subjected statistical control.
60

Nastavitelný rozchod kol zadní nápravy traktoru / Adjustable Track of Tractor Rear Axle

Šíbl, Michal January 2013 (has links)
This Master´s thesis deals with construction design adjustable track of tractor rear axle in a company Zetor Tractors a.s. At the very beginning there is an overview of different possibilities adjustable track from other world´s producers of tractors. Afterwards there is my constructional working from selection variant of suspension to final project. In this case the thesis contains required calculations of the whole device. Thesis also contains the stress and strain analysis of significant part of construction using a numerical approach of finite element method (FEM) and drawing documentation of the project constructed device.

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