• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 244
  • 24
  • 14
  • 3
  • 2
  • Tagged with
  • 286
  • 92
  • 86
  • 24
  • 23
  • 20
  • 19
  • 19
  • 18
  • 15
  • 15
  • 15
  • 14
  • 14
  • 13
  • 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.
181

Dynamický model harmonické převodovky / Dynamic Model of Harmonic Gearbox

Garami, Boris January 2016 (has links)
This thesis deals with the design of a dynamic model of a harmonic drive. It includes a theoretical study aimed at the analysis of the harmonic drive gearing principle and its nonlinear properties. The first part of the practical section deals with the analytical calculation of the nondeformed geometry of the Flexspline. Based on these results, several simulations in ANSYS are created to identify torsional characteristics of a harmonic drive. These simulation models are further enhanced by the analysis of clearance, backlash and inaccuracies and their impact on torsional properties. By using MATLAB /Simulink, several dynamic submodels are created representing the individual characteristics of nonlinearities in harmonic drives. Furthermore, a comprehensive dynamic model is created of the mechatronic system which is describing all nonlinearities and kinematic error of the transmission. The dynamic model is also experimentally verified based on its damping properties.
182

Čerpadlo s difuzorem s použitím stochastických lopatek (oběžné kolo i difuzor) / The Pump with a Diffuser with Stochastic Blades (Runner and Diffuser)

Dobšáková, Lenka January 2016 (has links)
This doctoral thesis studies the non-uniform blade cascade for centrifugal pumps. Influence of non-uniform blade cascade is investigated on the impeller and diffuser. A non-uniform blading impeller of pumps in this doctoral thesis was examined in terms of influence on efficiency characteristic. The idea of using non-uniform blading is to obtain a flat efficiency characteristic. Then the centrifugal pump could be used on larger scale of power with achieving a sufficiently high efficiency. The work is based on experimental measurements and numerical simulations of non-uniform hydraulic pump components. Non-uniform impeller and the diffuser were newly designed for this research. A new measuring track of small submersible pumps was needed to design and build for measurements. Different pump combinations with conventional hydraulics on one working point and hydraulics with non-uniform were measured. All measurements were evaluated and characteristics of efficiency, head and power were obtained for each measured combination. Some of pump combinations (which were measured in experiment) were numerically simulated by program Ansys Fluent. Data needed to evaluate the characteristic of efficiency and specific energy were collected from each numerical simulation. A theoretical consideration concerns the influence of non-uniform blade cascade applied on diffuser. The suggestion how to decrease hydraulic losses in canals was done. The theoretical consideration how to make a flat efficiency characteristic was made.
183

Simulace momentové charakteristiky asynchronního stroje / Modeling of torque-speed characteristics of induction motor

Michalík, Marek January 2017 (has links)
This master thesis deals in first part with basic theory of an induction motor and principle of function. It also includes theory about higher harmonics of magnetic field and how asynchronous and synchronous torques are created. Various ways how to decrease effect of these torques are suggested. These findings are later applied in practical analytical calculation in second part, in which all parameters of motor are calculated from given dimensions of motor from technical documentation. This is done for basic and higher harmonics. After that a model of this motor was created in RMxprt program, which also calculated all parameters of this motor and created torque characteristic. This motor was also modelled in ANSYS Maxwell 2D. Additional simulations for finding out influence of harmonics on torque characteristic were also done in this software. Torque characteristic of motor was also practically measured in laboratory. All results were compared and evaluated.
184

Křemíkové sluneční články: experimentální studium a modelování základních materiálových parametrů / Silicon solar cells: methods for experimental study and evaluation of material parameters in advanced structures

Holovský, Jakub January 2012 (has links)
This work concerns with today's challenges of photoelectrical characterization methods in the research and development of thin film silicon solar cells. Relevant results are obtained only when photocurrent spectroscopy and measurement of current-voltage characteristics, are applied on the real structures that can however be multi-layered, multi-junction devices with nanostructured interfaces. Analytical and numerical optical models comprising light scattering are used for analysis of light absorption and for evaluation of optical absorption coefficient of silicon layers in sub-gap region. The slope of absorption edge and residual absorption in mid-gap indicate material disorder and defect density. Based on the investigation of electrical interaction between sub-cells in the dual-junction solar cell we developed new methods of evaluation of photocurrent spectra and current-voltage characteristics individually for each sub-cell with no need to contact them directly. Usability of Fourier Transform Photocurrent Spectroscopy as a robust method for photocurrent spectroscopy of amorphous silicon is thoroughly analyzed here. The issues of frequency dependence are addressed in detail and comparison with photothermal deflection spectroscopy is made.
185

Profese učitele z pohledu žáků, rodičů a učitelů vybrané základní školy / Teacher professions from the point of view of pupils, parents and of teacher selected primary school

Melenová, Lada January 2020 (has links)
This diploma thesis brings information about the perception of the teaching profession by secondary school students, their parents, and teachers of a selected primary school. The aim of the work is to find out with the help of questionnaires, how pupils and their parents subjectively see and perceive teachers and how the teachers who teach pupils themselves see their profession as a teacher. In the theoretical part, I deal with the historical development of education and the teaching profession in our territory. I also deal with the characteristics of the teaching profession by clarifying the very concept, personality traits, and typology of the teacher's personality. This section also includes chapters on the competence of the teacher, his authority and motivation to choose the teaching profession. In the last part, I deal with the current form of the teaching profession in primary school, the requirements for the profession, and including selected problems of our education. In the practical part, I used a questionnaire survey to evaluate the data obtained by individual respondents among students, parents, and teachers and then I analyzed the data of individual groups of respondents and drew a conclusion. Keywords profession, teacher, elementary school, parents, education, teacher's personality,...
186

Ženské postavy ve vybraných prózách Josefa Škvoreckého / Women Characters in the Selected Stories of Josef Škvorecký

Zamora, Juan January 2019 (has links)
The most frequent - but not the only - way of telling Josef Škvorecký's prose is with the first grammatical person of the singular from the point of view of a male figure, for example that of one of Danny Smiřický. But female characters also play an important role in the story. The aim of this thesis is to study the way in which female figures are shaped in some Škvorecký's prose works. Therefore, we want to study the order in which we learn information about them, what passages are devoted to their characteristics or what other data in the text is associated with them. We rely on the literature on the theory of the character (e. g. Hausenblas and Macurová) and on literature about the author (e. g. Kosková, Trenský, Solecki). Key words: Josef Škvorecký, character, woman, narrator, description, dialogue, Emöke, The Miracle Game, The End of the Nylon Age
187

Hydraulický modelový výzkum měrných clon určených pro stanovení průtoku vody v kruhových profilech s volnou hladinou / The hydraulic modelling research of specific shutter intended for determination of water flow in circular profiles with free surface

Heřmanová, Lenka January 2012 (has links)
The main outcome of this Thesis is a set of Q / h characteristic that was obtained extensive hydraulic model research measuring plate designed for the determination of water flow in circular profiles. The final Q / h characteristic are functions of angle and vertical cut remoteness of the top slot from the bottom of the measurement aperture. Part of the output is an overview of the expected values of uncertainties of measurement in practical use in a specific aperture in sewers and evaluation of impacts involved in determining the overall uncertainty of the flow. The performed hydraulic modeling research is therefore possible to determine Q / h and characteristics for circular sections of larger diameter and to determine their uncertainties when using specific plate. For the design and shape measuring plate of the profile with larger average output is part of a supplement for quick design of specific screens.
188

Časově proměnná filtrace signálů EKG / Time Varying Filters for ECG Signals

Peterek, Jan January 2013 (has links)
The aim of this master’s thesis is to create a multiband stop derived from Lynn filters for suppressing mains hum and baseline variation (drift). The first part of the thesis is focused on brief theoretical introduction to the distortion types affecting ECG signal and twelve lead connection. The following practical part describes free realizations of ECG filter and ECG signal filtration. The filter has been tested both on distorted and on non-distorted signal. Finally filters’ error rate was computed from CSE database signals.
189

Návrh letadlové energetické jednotky / Design of aircraft power unit

Poledno, Martin January 2010 (has links)
This diploma thesis deals with basic design and calculation of an aircraft power unit (APU). For desired shaft power the thermal cycle is calculated. Basic dimensions of compressor, turbine and exhaust system are calculated as well as thermodynamic parameters of air and hot gases along the motor. Corresponding compressor map, turbine map and characteristics of the exhaust system are designed. Based on these characteristics, an effective shaft power is being calculated in various off-design conditions. Dependency of the shaft power vs. altitude is also presented. All the calculations are made in MATLAB. Finally, simplified motor cross-section is created.
190

Modelování a simulace projektů zlepšujících tepelně-technické vlastnosti budov / Modelling and Simulation of Projects Improving the Thermal Properties of Buildings

Výskala, Miloslav Unknown Date (has links)
This doctoral thesis deals with the modelling of projects improving the thermal technical characteristics of buildings. The solution of this problem seems to be finding at least one cost-effective option. The basic method of evaluation of cost-effectiveness is represented by the compilation of all corresponding cash flows and their rendering in time through discounting. The aim of the docáral thesis is the processing and modeling of individual investment options related with improve the thermal-technical properties of buildings and finding a cost-optimal variants, ideally. One of the expected outputs is to develop a comprehensive methodology (modeling and simulation task) useful for defining all potential investment projects improving variant thermal-technical properties of the object.

Page generated in 0.0655 seconds