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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.
151

Znalec encyklopedie / Encyclopedia Expert

Krč, Martin January 2009 (has links)
This project focuses on a system that answers questions formulated in natural language. Firstly, the report discusses problems associated with question answering systems and some commonly employed approaches. Emphasis is laid on shallow methods, which do not require many linguistic resources. The second part describes our work on a system that answers factoid questions, utilizing Czech Wikipedia as a source of information. Answer extraction is partly based on specific features of Wikipedia and partly on pre-defined patterns. Results show that for answering simple questions, the system provides significant improvements in comparison with a standard search engine.
152

Elektromagnetická analýza a modelování asynchronního stroje s plným rotorem / Electromagnetic analysis and modeling of a solid rotor induction machine

Bílek, Vladimír January 2021 (has links)
Tato diplomová práce se zabývá elektromagnetickou analýzou a modelováním asynchronního stroje s plným rotorem. Tato práce tedy zahrnuje literární rešerši na téma vysokootáčkových elektrických strojů s porovnáním s klasickými elektrickými stroji s převodovkou a popisem jejich výhod či nevýhod, rozdělení vysokootáčkových elektrických strojů s plnými rotory a srovnání jejich výhod či nevýhod, kde se tato práce nejvíce soustřeďuje na vysokootáčkové asynchronní stroje s plnými rotory a jejich použití v průmyslu. Dále se tato práce zabývá metodami výpočtu elektrických asynchronních strojů s plnými rotory. Proto jsou zde uvedeny a popsány metody výpočtu stroje mezi které patří analytické metody i metoda konečných prvků. Vzhledem k povaze elektrických strojů s plnými rotory je hlavně kladen důraz v této práci na výpočet stroje pomocí metody konečných prvků ve 2D prostoru s využitím korekčních činitelů konců plných rotorů, které jsou zde velmi detailně popsány a rozděleny. Na základě dostupné literatury je vypočítaný elektrický stroj s plným rotorem pomocí MKP analýzy. Elektromagnetický výpočet stroje je automatizován pomocí skriptu vytvořeného v Pythonu. Dalším hlavním cílem této práce je popis tzv. náhradních modelů, uvedení jejich výhod či nevýhod, použití v jiných průmyslových odvětvích a hlavně použití náhradních modelů na elektrický stroj s plným rotorem. S využitím náhradních modelů je dále optimalizovaný vybraný asynchronní stroj s plným rotorem a to pomocí programů SymSpace a Optimizer. Pro samotnou optimalizaci byly uvažovány 3 návrhy stroje, které byly na závěr mezi sebou porovnány a to hlavně z hlediska jejich elektromagnetického výkonu.
153

Inovace systému chlazení točivých elektrických strojů s využitím CFD metod / Innovation of the Cooling System of Rotating Electrical Machines using CFD Methods

Sikora, Michal January 2011 (has links)
This thesis deal with design and implementation of innovative cooling method, intended primarily for medium-power synchronous generators. The main objective of this proposal is to remove the large heat exchanger connected to generator. This heat exchanger unduly increases the space requirements for the machine location. The proposed solution is to use a direct water-cooled stator. It is assumed that the rotor winding will be still cooled by air. Unlike current cooling system, the hot air from the rotor can be cooled in smaller cooler inside the generator. In this work are described methods which can be used for design of water cooling basic parameters, taking required temperatures into account. A small induction motor was selected for practical verification of the proposed cooling concept. This motor was modified into two variants - related to the old cooling of synchronous generators and related to the proposed solution. Both of these variants were measured and compared with each other. Subsequently, CFD models of these two variants were set up. Measured temperatures were used for debugging of models and identification of material properties of components of these machines. The final model of water-cooled variant also makes it possible to simulate the work of motor for higher performance and to determine the overload compared with the old cooling variant. Some knowledge and experience obtained from the small water-cooled induction machine were used in the design of water-cooling for large synchronous generator. In a similar way, CFD models of the old variant of cooling and proposed variant of water- cooling were created. Although these models were not verified by actual measurements on the generators, the results indicated that the application of water-cooling in this type of machine is appropriate and provides many benefits.
154

Komplexní analýza modálních vlastností elektrických strojů točivých / Complex analysis of modal properties of rotating electrical machines

Donát, Martin Unknown Date (has links)
This dissertation thesis deals with the computational modelling of the dynamic response of the rotating electrical machine structure on the application of the magnetic forces. Apart from the dynamic response of the ideal symmetrical machine, the influence of the air gap eccentricity on the dynamics response is studied in this work. A basic type of the air gap eccentricity, which is caused by eccentric mounting of the rotor pack on the shaft of the rotor, is considered. The calculations the dependence of the magnetic forces on the time and a misalignment of the rotor pack are performed as first. The computational model of the magnetic field of the rotating electrical machine, which is based on solution of the electromagnetic coupled field analysis by finite element method, is used for this purpose. An analysis of the influence of the unbalanced magnetic pull and the stiffness of some parts of the machine on the modal properties of the machine is performed in the second part of this thesis. A third part of this thesis is focused on the calculation of the dynamic response of the machine during the steady state operation of the machine and the influence of the rotor pack misalignment on the dynamic response is studied. The obtained results showed that the tangential components of the magnetic forces, which act on the stator pack, excite significant torsional vibration of the stator. Besides the vibration of the stator of the machine, the influence of the rotor pack misalignment on the sound power of the machine, vibration of the rotor, loads of rotor bearings and air gap eccentricity is studied in this thesis.
155

BSS model a kryptografie / The BSS model and cryptography

Hostáková, Kristina January 2016 (has links)
Real numbers are usually represented by various discrete objects such as floating points or partial decimal expansions. This is mainly because the clas- sical computability theory relates to computers which work with discrete data. Nevertheless, for theoretical purposes it is interesting to look at models of com- putation that deal with real numbers as with objects of unit size. A very natural such model was suggested by Blum, Shub and Smale in 1989. In 2012 Grigoriev and Nikolenko studied various cryptographic tasks involv- ing real numbers (for example, biometric authentication) and they considered the BSS machine model. In this work we focus on hard to invert functions in this model of computation. Our main theme is to analyse whether there are real functions of one variable that are easier to compute than to invert by a BSS machine. 1
156

Návrh optimálního složení mechanizačních prostředků pro pravidelný cyklus údržby staveb k vodohospodářským melioracím pozemků. / Proposal of optimum composition of the mechanization devices for the regular cycle maintenance of building for the wateragricultural meliorations of pieces of land

KRATOCHVÍLOVÁ, Miroslava January 2008 (has links)
In my diploma work I engage in the mechanization for the regular maintenance of building for the wateragricultural meliorations of piece of lands. The applicable mechanization: Dampr, Skrejpr, Dozer, graftmachine, bushescut{\dots}{\dots}{\dots}{\dots}{\dots} My proper work I engage on revitalization of pond names Hamerníků Doubí near by the village Lásenice. Out of the results of my proper work is evident, that the revitalization of ponds is very exacting and expensive work.
157

Metoda pro simulaci energetické náročnosti výrobních strojů v etapě vývoje / Method for Energy Efficience Simulation of Machine Tools in Design Stage

Tůma, Jiří Unknown Date (has links)
Ph.D. thesis is focused on the design of the method for simulation of energy demands of machine tool in operation at the stage of its development. Proposed method is developer on the basis of literature search in science and in industry. The method itself is composed of five related steps, that must be realised in the proper order in order to create a relevant energy profile of a machine tool. The output from the method are simulated data providing a course of comsumed energy and required power which are time dependent. Output data are obtained on the basis of the drive system simulation of machine tool through G-code, that is interpreted for simulation by the compiler into the matrix. It contains data necessary for controlling of machine tool, such as the required end points of the tool and required feed rates, to which is assigned a time value. G-code is partially time parametrized. It is then followed by full time parametrization through a of mathematical model of drive mechanisms and due the synergy of software for drive mechanisms control (Matlab Simulink) and software for physical simulation (MSC Adams) is processed into output data. As an input parameter figures also coefficient used as multiplier of the normal force of driving mechanisms, which is a function of feed rate. This loss function is obtained experimantally. In the context of Ph.D. thesis were conducted two experiments, used to verify the developed method. For each experiment is proceeded according to estabilished method and it is included a comparsion of simulation and measured data for various operating modes. The proposed method, described in the Ph.D. thesis, allows designers to summarize the energy demand of the proposed machine before its production. When correctly interpreted, the results of the method can serve as a basis for improving the energy profile and thereby increasing the energy efficiency of the machine tool.
158

Pasivní kompenzace teplotních deformací u obráběcího stroje / Passive compensation of a thermal deformation for a machine tool

Šabart, Adam January 2017 (has links)
This master thesis deals with passive compensation of a thermal deformation for a binder of portal machining center. The problem is solved by computational modeling with finite element method using ANSYS Workbench software. Afterwards mathematical optimization (also using ANSYS Workbench software) is used for finding binder parameters in order to reduce thermal deformation and its weight. The output is two new versions of binder which are compared to the original configuration.
159

Design průmyslového planetového mixéru / Design of Industrial Planetary Mixer

Škodová, Nina January 2017 (has links)
The diploma thesis is focused on the design of an industrial planetary mixer with a volume of 40 liters. The goal is to create a design that takes account of ergonomics and design and technology requirements.
160

Štípací stroj na dřevo / Wood-splitting machine

Důrek, Milan January 2017 (has links)
The master thesis done within the master study programme Transport vehicles and handing machinery presents a design of a wood splitting machine. The first part of the thesis is a literary review focused on current state in the field of wood splitting machines and on the overview of the most common wood species including their technical parameters. In the second part of the thesis, suitable machine components were chosen for the conceptual design of the wood splitter, taking into account predefined parameters. Then a machine frame was designed and its strength was verified by analytical and FEM method. Finally, drawing documentation for the machine, machine frame and splitting tool was created.

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