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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.
421

Analýza vedlejších rozpočtových nákladů v závislosti na základních rozpočtových nákladech / Analysis accessory costs of budget in depending on the elementary costs of budget.

Studený, Marek January 2014 (has links)
The thesis deals with question of dependence accessory costs of budget on a elementary costs of budget. There is describe structure both kind of costs and then it is division to elementary parts. Next, there are identified their influencing factors. At the end of my thesis are costing real objects and is concluded there doesn´t exist a dependence between both costs.
422

Spolehlivost technických systémů / Reliability of Technical Systems

Ertl, Jakub January 2009 (has links)
The diploma project is focused on investigating the reliability of multi-state technical systems. A summary of the basic conception of renewal theory and stochastic processes is given in this paper. The possibility of solving multi-state systems reliability by using Markov models or simulation is shown. The software Reliab. S. M. S. O. 1.0 was created for solving non-homogeneous series, parallel, series-parallel and parallel-series systems. Outputs of this software are described in chapter 10. This work also contains $\beta$-factor method and theory of common-cause failures. The diploma project was supported by project from MSMT of the Czech Republic no. 1M06047 "Centre for Quality and Reliability of Production" and by grant from Grant Agency of the Czech Republic (Czech Science Foundation) reg. no. 103/08/1658 "Advanced optimum design of composed concrete structures".
423

Problém trhliny v blízkosti bimateriálové rozhraní / Problem of the crack terminating at the bimaterial interface

Svoboda, Miroslav January 2012 (has links)
The objective of this diploma thesis is the stress-strain analysis of the crack terminating at the orthotropic bi-material interface suggested as the plane problem of the linear fracture mechanics. The first part is engaged in basic relations of the linear fracture mechanics. The second part is focused on the singularity exponent evaluation for the crack impinging and generally inclined with respect to the bi-material interface. It follows the determination of the generalized stress intensity factors applying the analytical-numerical approach represented by the finite element analysis. The last part of this work is focused on the testing of algorithms applied to the specific crack and bi-material interface configurations. A conclusion discusses the influence of the bi-material mechanical properties and the angel of the crack inclination to the obtained numerical results.
424

Predikce creepového poškození polymerních trubek / Prediction of slow crack growth in polymer pressure pipes

Luky, Robin January 2012 (has links)
A new methodology of polymer pipe lifetime estimation taking into account residual stresses is described in this thesis. Engineering equations derived based on numerical simulations of a hydrostatic pressure test are proposed. Residual lifetime calculations were performed for different loading conditions using experimental data of a creep crack propagation in studied material and stress distribution in the pipe wall. The effects which significantly influence lifetime estimation were quantified with special focus on residual stresses.
425

Popis rozložení napětí v okolí bimateriálového vrubu pomocí zobecněného faktoru intenzity napětí / A study of the stress distribution around the bimaterial notch tip in the terms of the generalized stress intensity factor

Hrstka, Miroslav January 2012 (has links)
The presented diploma thesis deals with a problem of a generalized stress intensity factor determination and a consecutive study of stress distribution around the bimaterial notch tip, combining analytical and numerical methods. This task is possible to sectionalize into three parts. The first part is dedicated to the fundamentals of the linear fracture mechanics and the mechanics of composite materials. The second part deals with methods of anisotropic plane elasticity solution. Pursuant to the solution the computational models in the third part are created. The first model makes for determination of a singularity exponent eigenvalue by dint of Lekhnitskii-Eshelby-Stroh formalism. The second model makes for determination of the generalized stress intensity factor using psi-integral method, which is based on the Betti reciprocal theorem. All needed calculation are performed in the software ANSYS 12, Maple 12 and Silverforst FTN95. Results will be compared with the values obtained from a direct method of the generalised stress intensity factor determination.
426

Predikce tvaru čela šířící se únavové trhliny / Fatigue crack front shape estimation

Zouhar, Petr January 2016 (has links)
The presented master’s thesis deals with fatigue crack front shape estimation. The aim of this thesis is to create an iterative process leading to the real fatigue crack front shape. Thesis is solved using finite element method. The work is divided into two logical parts. The first part of the thesis describes the basic concepts of linear elastic fracture mechanic (LEFM), methods used for estimation of stress intensity factor and stress singularity exponent. The first part further describes some phenomenon’s accompanying the mechanism of fatigue crack growth as for example crack tip curving and crack closure. In the second part of the thesis there is studied an affect of the free surface on the fracture parameters, especially the affected distance from the free surface is determined. Based on the assumption of a constant stress intensity factor and stress singularity exponent along the crack front, an iterative process leading to fatigue crack front shape is presented. The accuracy of the result is discussed by comparing of obtained crack front shapes with experimental data at the end of the thesis.
427

Zvýšení bezpečnosti přistávacího manévru / Increasing landing maneuver safety

Zedníček, Václav January 2016 (has links)
Diploma thesis concerns methodology, safety and common pilot’s mistakes in phase of landing. It concludes statistics and landing accident reports of airplanes with maximum take-off weight of 5700 kg. It also concerns method of height estimating above ground. It describes usable systems for landing aid and suggests its own technical solutions for safety improvements based on poll.
428

Stavebně-fyzikální posouzení střešní konstrukce / Building physics assessment of the roof structure

Konopík, Petr January 2017 (has links)
This theses deals with a structural design comparison of heat insulations implementation in flat roofs in light of heat engineering. It also adverts to possible structural design in terms of heat insulations distribution in a flat roof. There are many materials options. I show the possibilities of material solution and also advantages and disadvantages of the single sealing materials at these layers. In the aplication part of this thesis I deal with possible concepts of insulation and solution for a specific roof of an older apartment house in Brno, where I conducted a constructive exploration. There was developed and evaluated a few options of solutions considering the heat insulator used. The following computational programs were used for the evaluations: TEPLO, AREA, CUBE 3D.
429

Das Konzept des effektiven Indenters für die Ermittlung des Elastizitätsmoduls und der Fließgrenze dünner Schichten

Herrmann, Matthias 27 May 2010 (has links)
Nanoindentations-Messungen haben in den letzten Jahrzehnten als Verfahren zur Ermittlung mechanischer Eigenschaften dünner Schichten stark an Bedeutung gewonnen. Für die Gewinnung eines tiefergreifenden Verständnisses des mechanischen Verhaltens dieser Schichten ist die Kenntnis des Elastizitätsmoduls und der Fließgrenze von essentieller Bedeutung – nicht zuletzt, da diese auch als Eingabeparameter für Simulationen des Materialverhaltens gefordert sind. Eine noch nicht im Detail verstandene Forschungsfrage bei der Kennwertermittlung ist die Berücksichtigung des Dünnschichtcharakters der Proben, deretwegen diese Untersuchungen im Wesentlichen immer noch einen Grundlagencharakter tragen und derzeit Gegenstand intensiver weltweiter Forschung sind. Auswege für eine solche Berücksichtigung existieren bisher nur für wenige Anwendungsfälle. Das Konzept des effektiven Indenters stellt eine Erweiterung der Auswerteansätze und damit neue Möglichkeit für die mechanische Charakterisierung der Dünnschichteigenschaften dar. In der vorliegenden Arbeit wird untersucht, inwieweit dieses Konzept zur Ermittlung des Elastizitätsmoduls dünner Schichten geeignet ist. Ebenso werden die Untersuchungen auf die Fließgrenze ausgeweitet. Beispielhaft kommen unterschiedliche Schichtmaterialien zum Einsatz, mit denen der Unterschied zwischen den Schicht-Substrat-Eigenschaften – Elastizitätsmodul und Fließgrenze – variiert werden kann. Durch Vergleich der für die BERKOVICH-Eindrücke erhaltenen Ergebnisse zu den mittels der Kugeleindrucksversuche bestimmten Werte – als etabliertes Messverfahren – wird festgestellt, dass o. g. Konzept prinzipiell für die oben angeführten Fragestellungen geeignet ist, insofern die erreichten Eindringtiefen im Vergleich zur Schichtdicke relativ gering sind. Physikalische Ursachen für dieses Verhalten werden vorgeschlagen und diskutiert. Ebenso wird eine spezielle Vorgehensweise des Konzepts des effektiven Indenters für die Charakterisierung von porösen sowie nichtporösen Low-k-Schichtmaterialien untersucht. Zusätzlich werden Finite-Elemente-Simulationen für grundlegende Betrachtungen zur Wirkungsweise des o. g. Konzepts anhand von massiven Proben herangezogen. / Considerable research effort has focused on measuring the mechanical properties of thin films via nanoindentation. To characterize the mechanical behavior of thin films, accurate determination of Young’s modulus and yield strength is required. For the purpose of modeling and dimensioning, these quantities serve as input parameters as well. An existing major challenge in the context of (nanoindentation) data analysis is the complete consideration of the layered structure of the specimen. In the literature, a few experimental and theoretical-based approaches have been developed to extract actual film properties. However, those approaches are only applicable under specific conditions and, hence, the problem is not satisfyingly solved to date. Therewith, investigations of accurately assessing mechanical properties of thin films, in general, or Young’s modulus and yield strength, in detail, are still part of ongoing research in the field of mechanical testing in materials research and development. The concept of the “effective indenter” is an extension of the current and established analysis of nanoindentation data and is a new possibility to determine mechanical properties of thin films. In this work, an investigation is given concerning the suitability of the model, in a specific approximation, for determining Young’s modulus of thin films. In a second step, the investigations are focused on the determination of yield strength. Film/substrate composites having a varying ratio of modulus and yield strength between film and substrate are chosen; BERKOVICH indentations are analyzed and spherical indentation experiments are used as second and independent technique. It is shown that the model is suitable to deliver Young’s modulus of thin films. However, a critical ratio of indentation depth to film thickness is identified; for ratios above this critical value, the model, in the present approximation, can no longer be used. Physical mechanisms that explain this finding are suggested and discussed. Moreover, the above-mentioned model is used to characterize the very specific class of materials of non-porous and porous low-k dielectric thin films in terms of yield strength and Young’s modulus. Finally, finite element modeling is used to study critical issues in applying the model of the “effective indenter” and its specific approximation used here for analysis of nanoindentation data for bulk materials.
430

Účinky L-serinu a vliv anestézie na regulaci krevního tlaku u normotenzních a hypertenzních potkanů / L-serine induced effects on blood pressure in normotensive and hypertensive rats: the influence of anesthesia

Bencze, Michal January 2012 (has links)
Anesthetics cause profound alterations in respiratory and cardiovascular systems. Our experiments demonstrated that different anesthetics caused different changes in blood pressure regulating components. The role of particular BP regulating systems was disclosed by their selective inhibition - sympathetic nervous system blocked by pentolinium (peripheral ganglionic blockade), renin-angiotensin system by captopril (angiotensin converting enzyme blocker) and nitric oxide production by L-NAME (nitric oxide synthase blocker). Components of blood pressure regulating mechanisms in conscious normotensive Wistar rats and spontaneously hypertensive rats were compared with four different groups of anesthetized rats by pentobarbital, ketamine-xylazine, chloralose-urethane and isoflurane. Each anesthesia caused different hemodynamic changes. If hemodynamic conditions should be similar to conscious rats, the most suitable anesthetic is pentobarbital. L-serine-induced effects represent endothelium-derived hyperpolarizing factor (EDHF)-mediated response, which is a type of endothelium-dependent regulation of vascular tone, independent of nitric oxide and prostacyclin production. Pronounced L-serine effects on blood pressure were shown in NO-deficient type of hypertension. Our study demonstrated its pronounced effects in...

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