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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.
21

Aplikace degree-day modelu akumulace a tání sněhu v povodí Ptačího potoka / Application of degree-day accumulation and snowmelt model in the Ptačí Brook basin

Beitlerová, Hana January 2012 (has links)
Snow accumulation and snowmelt research is one of the most important hydrological issues in mountain areas World-wide. Spring snowmelt, usually in the combination with intensive rainfall or high air temperature, is one of the most common causes of flooding in the Czech Republic. Mathematical modeling of hydrological processes belongs to effective instruments of flood protection and finds its use in a variety of areas. For example, water management, hydrological forecasts for agriculture, information for dam regulation or for recreational areas and water sports are all affected. This thesis focuses on snow accumulation and snowmelt modeling with use of the empirical Degree-day method. This method is based on the relationship between snowmelt rate and air temperature. The American HAC-HMS programme is used for the simulation of hydrological processes. The main goal of this thesis is to calibrate the model and to simulate snow accumulation, snowmelt and run-off from the watershed. The experimental basin 'Ptačí potok' is situated in the central part of the Šumava Mountains, in altitude of about 1,200 m. Two winter seasons, 2011 and 2012, were simulated. Simulations showed high reliability and correct calibration of the Temperature index snowmelt model. Simulations of the snow water equivalent evolution...
22

Investigations of Reaction Cross Sections for Protons and <sup>3</sup>He / Undersökningar av reaktionstvärsnitt för protoner och <sup>3</sup>He

Lantz, Mattias January 2005 (has links)
<p>The reaction cross section gives the probability that a particle will undergo a nonelastic process when passing through a nuclear medium. Therefore reaction cross section data are of importance both for theoretical studies and for applications in such diverse fields as medicine, biology, astrophysics and accelerator-driven transmutation of nuclear waste.</p><p>There exist many data sets with angular distributions of elastic scattering, but very few measurements of the complementary reaction cross section have been performed. The measurement is in principle simple but has in practice proved to be very difficult to perform, and the relatively limited amount of experimental data displays some serious inconsistencies.</p><p>Results from measurements of reaction cross sections are presented for:</p><p>• <sup>3</sup>He on <sup>9</sup>Be, <sup>12</sup>C, <sup>16</sup>O, <sup>28</sup>Si, <sup>40</sup>Ca, <sup>58,60</sup>Ni, <sup>112,116,118,120,124</sup>Sn and <sup>208</sup>Pb at 96, 138 and 167 MeV</p><p>• protons on <sup>12</sup>C, <sup>40</sup>Ca, <sup>90</sup>Zr and <sup>208</sup>Pb at six energies in the energy range 80-180 MeV, and on </p><p><sup>58</sup>Ni at 81 MeV. </p><p>Experimental uncertainties were 3-9% for <sup>3</sup>He and 1.5-8% for protons.</p><p>The apparatus and the experimental method used for the measurements of reaction cross sections, using a modified attenuation technique, is described. The detection method enables simultaneous measurements of reaction cross sections for five different sizes of the solid angles in steps from 99.0 to 99.8% of the total solid angle. The final results are obtained by extrapolation to the full solid angle.</p><p>Experimental results are compared with predictions from optical model calculations using phenomenological global optical potentials.</p><p>Phenomenological parametrizations of reaction cross sections for scattering of projectiles on targets are presented. The parametrizations show that reaction cross sections are very sensitive to matter distributions at very large radii of both the projectile and the target. For protons the derived relations makes it possible to predict the reaction cross sections on targets for which no experimental data exist.</p>
23

Investigations of Reaction Cross Sections for Protons and 3He / Undersökningar av reaktionstvärsnitt för protoner och 3He

Lantz, Mattias January 2005 (has links)
The reaction cross section gives the probability that a particle will undergo a nonelastic process when passing through a nuclear medium. Therefore reaction cross section data are of importance both for theoretical studies and for applications in such diverse fields as medicine, biology, astrophysics and accelerator-driven transmutation of nuclear waste. There exist many data sets with angular distributions of elastic scattering, but very few measurements of the complementary reaction cross section have been performed. The measurement is in principle simple but has in practice proved to be very difficult to perform, and the relatively limited amount of experimental data displays some serious inconsistencies. Results from measurements of reaction cross sections are presented for: • 3He on 9Be, 12C, 16O, 28Si, 40Ca, 58,60Ni, 112,116,118,120,124Sn and 208Pb at 96, 138 and 167 MeV • protons on 12C, 40Ca, 90Zr and 208Pb at six energies in the energy range 80-180 MeV, and on 58Ni at 81 MeV. Experimental uncertainties were 3-9% for 3He and 1.5-8% for protons. The apparatus and the experimental method used for the measurements of reaction cross sections, using a modified attenuation technique, is described. The detection method enables simultaneous measurements of reaction cross sections for five different sizes of the solid angles in steps from 99.0 to 99.8% of the total solid angle. The final results are obtained by extrapolation to the full solid angle. Experimental results are compared with predictions from optical model calculations using phenomenological global optical potentials. Phenomenological parametrizations of reaction cross sections for scattering of projectiles on targets are presented. The parametrizations show that reaction cross sections are very sensitive to matter distributions at very large radii of both the projectile and the target. For protons the derived relations makes it possible to predict the reaction cross sections on targets for which no experimental data exist.
24

Towards RANS Parameterization of Vertical Mixing by Langmuir Turbulence in Shallow Coastal Shelves

Sinha, Nityanand 01 January 2013 (has links)
Langmuir turbulence in the upper ocean is generated by the interaction between the wind-driven shear current and the Stokes drift velocity induced by surface gravity waves. In homogenous (neutrally stratified) shallow water, the largest scales of Langmuir turbulence are characterized by full-depth Langmuir circulation (LC). LC consists of parallel counter-rotating vortices aligned roughly in the direction of the wind. In shallow coastal shelves, LC has been observed engulfing the entire water column, interacting with the boundary layer and serving as an important mechanism for sediment re-suspension. In this research, large-eddy simulations (LES) of Langmuir turbulence with full-depth LC in a wind-driven shear current have revealed deviations from classical log-layer dynamics in the surface and bottom of the water column. For example, mixing due to full-depth LC induces a large wake region eroding the classical bottom (bed) log-law velocity profile. Meanwhile, near the surface, Stokes drift shear serves to intensify small scale eddies leading to enhanced mixing and disruption of the surface velocity log-law. The modified surface and bottom log-layer dynamics induced by Langmuir turbulence and full-depth LC have important implications on Reynolds-averaged Navier-Stokes simulations (RANSS) of the general coastal ocean circulation. Turbulence models in RANSS are typically calibrated under the assumption of log-layer dynamics, which could potentially be invalid during occurrence of Langmuir turbulence and associated full-depth LC. A K-Profile Parameterization (KPP) of the Reynolds shear stress in RANSS is introduced capturing the basic mechanisms by which shallow water Langmuir turbulence and full-depth LC impact the mean flow. Single water column RANS simulations with the new parameterization are presented showing good agreement with LES
25

Βελτιστοποίηση σχεδιαστικών παραμέτρων τριφασικής ασύγχρονης μηχανής με τη μέθοδο των πεπερασμένων στοιχείων

Δούβαλη, Αγγελική 15 February 2011 (has links)
Η παρούσα διπλωματική εργασία εκπονήθηκε στο τμήμα Ηλεκτρολόγων Μηχανικών και Τεχνολογίας Υπολογιστών του Πανεπιστημίου Πατρών. Πραγματεύεται τη βελτιστοποίηση των σχεδιαστικών παραμέτρων της τριφασικής ασύγχρονης μηχανής με στόχο την επίτευξη μεγιστοποίησης της ροπής εκκίνησης και ελαχιστοποίησης του ρεύματος εκκίνησης. Μελετήθηκε η σχέση που υπάρχει ανάμεσα στα γεωμετρικά χαρακτηριστικά (διαστάσεις) και στις επιδόσεις και τη γενικότερη λειτουργία της μηχανής. Η σχεδίαση και η παραμετροποίηση του τριφασικού επαγωγικού κινητήρα βραχυκυκλωμένου κλωβού που μελετήθηκε, έγινε μέσω του προγράμματος «Opera» της Vector Fields, το οποίο χρησιμοποιεί τη μέθοδο των πεπερασμένων στοιχείων. Όσον αφορά τη διαδικασία της εύρεσης του βέλτιστου μοντέλου, αυτή πραγματοποιήθηκε με τη βοήθεια του εργαλείου Optimizer που παρέχεται από το πρόγραμμα «Opera». Στη συνέχεια μελετήθηκε και αξιολογήθηκε το αρχικό και το βέλτιστο μοντέλο ώστε να αποκτηθεί σαφής εικόνα για τη λειτουργία τους καθώς επίσης και για τις διαφορές που παρουσιάζουν. Στο πρώτο κεφάλαιο παρουσιάζεται η βελτιστοποίηση σαν έννοια αρχικά και στη συνέχεια περιγράφονται τα βήματα που ακολουθούνται για το σωστό ορισμό ενός προβλήματος βελτιστοποίησης. Γίνεται μια ταξινόμηση των προβλημάτων σύμφωνα με την πολυπλοκότητα, το μέγεθος και την ταχύτητα εύρεσης της λύσης. Επιπλέον, αναφέρονται και αναλύονται οι κυριότερες μέθοδοι βελτιστοποίησης και όσες χρησιμοποιούνται περισσότερο με βάση τη βιβλιογραφία. Στο δεύτερο κεφάλαιο παρουσιάζονται οι βασικές αρχές κατασκευής και λειτουργίας της τριφασικής ασύγχρονης μηχανής. Μέσα από αυτή την ανάλυση προκύπτουν συμπεράσματα για τα πιθανά πεδία λειτουργίας της Α.Μ. στα οποία μπορεί να υπεισέλεθει ζήτημα βελτιστοποίησης. Αναφέρονται και σχολιάζονται για κάθε πεδίο τα μεγέθη και τα φυσικά φαινόμενα που συμμετέχουν. Επίσης, μελετώνται οι σχεδιαστικές παράμετροι του στάτη και του δρομέα που καθορίζουν τη χαρακτηριστική ροπής-στροφών και την απόδοση της μηχανής και οι οποίες στη συνέχεια θα χρησιμοποιηθούν στο δικό μας πρόβλημα. Το τρίτο καφάλαιο, περιγράφει τη διαδικασία παραμετροποίησης του μοντέλου του προς μελέτη τριφασικού ασύγχρονου κινητήρα βραχυκυκλωμένου κλωβού στο πρόγραμμα Opera. Εξηγείται η πορεία σχεδίασης για κάθε «κομμάτι» της μηχανής ξεχωριστά ξεκινώντας από το στάτη, συνεχίζοντας με το δρομέα και τέλος με την εισαγωγή του διακένου. Υπάρχουν επίσης αναφορές σχετικές με την ανάλυση και μετ-επεξεργασία του μοντέλου. Ακόμη, δίνεται ένα τμήμα του αρχείου στο οποίο υπάρχει το παραμετροποιημένο μοντέλο σαν μια πρώτη εικόνα για το πώς αυτό δημιουργήθηκε. Η παραμετροποίηση έγινε κατά το μεγαλύτερο μέρος της στο περιβάλλον εργασίας του Pre and Post Processor του Opera-2D και κατά ένα μικρότερο μέρος γράφτηκε κώδικας. Στο τέταρτο κεφάλαιο καθορίζεται και διατυπώνεται πλέον το πρόβλημα που θα μας απασχολήσει στην παρούσα εργασία. Το κεφάλαιο αυτό αποτελεί έναν πλήρη «οδηγό χρήσης» του εργαλείου Optimizer που χρησιμοποιήθηκε για την εύρεση του βέλτιστου μοντέλου στην περίπτωση που αυτό είναι σχεδιασμένο στις δύο διαστάσεις με τη βοήθεια του προγράμματος Opera-2D. Αναφέρονται με κάθε λεπτομέρεια τα βήματα που ακολουθούνται ώστε να μπορέσει ένα οποιοδήποτε μοντέλο να δοθεί για βελτιστοποίηση στο συγκεκριμένο πρόγραμμα όπως επίσης και τα βήματα για τον ορισμό των αντικειμενικών συναρτήσεων, των σχεδιαστικών παραμέτρων και των περιορισμών στον Optimizer. Υπάρχουν επισημάνσεις και παρατηρήσεις στα σημεία που αντιμετωπίστηκαν οι περισσότερες δυσκολίες και καθυστερήσεις κατά τη διάρκεια εκπόνησης της εργασίας. Τέλος, στο πέμπτο κεφάλαιο παρουσιάζονται τα αποτελέσμα της βελτιστοποίησης, αναλύεται το αρχικό και το βέλτιστο μοντέλο, γίνεται αντιπαραβολή των αποτελεσμάτων, πραγματοποιείται σύγκριση των δύο μοντέλων και τελικά διατυπώνονται τα συμπεράσματα που προκύπτουν. / -
26

Modelagem paramétrica de pórticos rolantes: estabilidade estrutural e otimização. / Gantry cranes parametric modeling: structural stability and optimization.

Gustavo Sobue 29 July 2005 (has links)
O objetivo deste trabalho é desenvolver uma ferramenta de automatização de cálculo para projeto estrutural de pórticos rolantes. Com o apoio da geração automática de um modelo de elementos finitos e um memorial de cálculo, o projeto estrutural desses equipamentos pode ser rapidamente verificado quanto ao limite de escoamento do material e resistência à flambagem. Optou-se pela utilização do método dos elementos finitos para o cálculo estrutural, pois se trata de uma ferramenta de cálculo moderna, que permite avaliar soluções para as quais não há ferramentas analíticas disponíveis. Porém, o tempo para geração de modelos de cálculo pode ser longo em relação ao cronograma do projeto, principalmente se houver a necessidade de se alterar a geometria inicial ou se existirem várias condições de carregamento a serem analisadas. A utilização de um pré-processador permite que várias alternativas sejam analisadas para escolha da que melhor atenda aos requisitos de projeto e de custo. Assim como ocorre com outras estruturas de engenharia, não existe uma equação de dimensionamento, mas sim de verificação; as estruturas ótimas são procuradas por tentativa e erro com base na experiência do projetista. Para facilitar a busca de uma estrutura ótima, implementou-se também uma rotina para otimizar as estruturas metálicas do pórtico. Adotou-se como função objetivo nesta implementação a minimização da massa, o que no caso dos pórticos implica em redução da área da seção transversal das vigas. Como restrições a esta redução adotaram-se o limite de escoamento do material e limite de estabilidade da estrutura (flambagem). Foram utilizados os aplicativos Excel (Microsoft), Ansys (Ansys Inc.) e Mathcad (Mathsoft) de maneira integrada a fim de se obter uma interface amigável, uma análise estrutural confiável e a elaboração automática de um memorial de cálculo. / The objective of this work is to develop a tool to generate an automatic structural design of gantry cranes. With an automatic generation of finite element models and also a design report, this routine allows a fast verification against yield of material and structural instability. The use of the finite element method was chosen for the structural design because it is a modern analysis tool that permits the evaluation of geometric configurations for which there are no analytical formulations available. However, the time necessary to build these models may be high, especially if there are changes in the initial geometry and many load cases. The use of a pre-processor allows the evaluation of a series of geometric alternatives, within which would be chosen the one with the lowest cost that attends the client’s specifications. Like many other engineering problems, there are no direct equations to find an adequate structure; there are only verification procedures available; the optimum structures are searched by trial and error, based on the designers’ experience. To accelerate this search process, an optimization routine was developed. Mass reduction was adopted as the objective function, which leads to reduction of the cross section area of the beams. Yield strength and buckling were adopted as restrictions to this optimization. Excel (Microsoft), Ansys (Ansys Inc) and Mathcad (Mathsoft) software were integrated to provide an user-friendly interface, reliable structural analysis and an automatic report generation.
27

UKF-SLAM Implementation for the Optical Navigation System of a Lunar Lander

Garcia, Laura January 2017 (has links)
No description available.
28

Estimativa das funções de recuperação de reservas minerais usando copulas / Estimation of recovers function of mineral reserves using copulas

Carmo, Frederico Augusto Rosa do 24 August 2006 (has links)
Orientador: Armando Zaupa Remacre / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Geociencias / Made available in DSpace on 2018-08-07T09:52:07Z (GMT). No. of bitstreams: 1 Carmo_FredericoAugustoRosado_D.pdf: 2790866 bytes, checksum: 70c1d59f281ee0f7a09af528c73582a9 (MD5) Previous issue date: 2006 / Resumo: O objetivo principal desta tese foi desenvolver a metodologia de cópulas aplicada ao problema de estimativas de reservas condicionadas, corrigindo erros de tonelagem e quantidade de minério de um projeto, via uma abordagem diferente da simulação estocástica condicional. É apresentado um resumo teórico que fundamenta o estudo de cópulas. Inicia-se com a apresentação de definições e conceitos importantes da estatística e da probabilidade. Após uma discussão sobre medidas de correlação, é introduzido o conceito de cópulas, desde sua definição e propriedades básicas até o estudo de alguns tipos de cópulas essenciais para a aplicação nesta tese. É discutida toda a fundamentação teórica desenvolvida para o cálculo de recursos recuperáveis. Os conceitos de curvas de tonelagem e teores são introduzidos, pois são a base da parametrização de reservas minerais. É mostrado como a cópula pode ser utilizada num dos pontos principais da geoestatística mineira, principalmente no que diz respeito ao erro das estimativas. Discorre-se primeiramente sobre o conceito de validação cruzada, apresentando a definição de reserva ilusória, ótima e ideal. É definida a reserva ideal utilizando o conceito de cópulas, onde a krigagem, a simulação seqüencial gaussiana e a cópula são comparadas, mostrando as conseqüências da sobreestimativa e da subestimativa em projetos de cava e seqüenciamento na mineração / Abstract: The aim of this thesis was to develop the applied methodology of copulas in the problem of conditional reserves estimation. The copulas have a different approach from sequential gaussian simulation and in this thesis was used to correct the tonnage and ore quantity of a mining project. It is presented a theoretical summary that is the bases to the study of copulas. It is also' presented a set of definitions and important concepts of the statistics and the probability. After a discussion about correlation measures, is introducing the concept of copulas, begining with the definition and basic properties until the study of some types of essential copulas that was applied in this thesis. Whole the theoretical fundamentation is discussed to developed the calculation of recoverable resources. The concepts of tonnage and grades curves are introduced, therefore they are the base of the parametrization of mineral reserves. It is shown how the copulas can be used in the main points of the mining geostatistics, mainly in what concerns the estimation errors. Firstly the cross validation concept is presented and the illusory, best and ideal reserves are defined. The ideal reserves is defined using the concept of copulas, and the results are compared with the kriging and sequential gaussian simulation. With this comparisons is possible shown the consequences of the upper-estimation and under estimation in an open pit projects and sequential mining layout / Doutorado / Administração e Politica de Recursos Minerais / Doutor em Ciências
29

Rozpoznávání hudebních nástrojů ze zvukových nahrávek za pomoci technik Music Information Retrieval / Musical instruments recognition from audio records using Music information retrieval techniques

Kárník, Radoslav January 2019 (has links)
This paper discusses design and implementation of classifying system for recognition of musical instruments from audio records with use of Musical Information Retrieval techniques. In the first part, paper describes parameters used for instrument classification, calculation of said parameters from records and reduction of feature vector. Next part is devoted to tuning and implementation of various classifiers with focus on neural networks. These classifiers ar further tested on records from IRMAS dataset wchich contain 11 musical instruments playing solo or with other instruments. Results of classifiers tested on different parameters and different numbers of instruments are discussed in the last part.
30

Comparing trigonometric interpolation against the Barycentric form of Lagrange interpolation : A battle of accuracy, stability and cost

Söderqvist, Beatrice January 2022 (has links)
This report analyzes and compares Barycentric Lagrange interpolation to Cardinal Trigonometric interpolation, with regards to computational cost and accuracy. It also covers some edge case scenarios which may interfere with the accuracy and stability. Later on, these two interpolation methods are applied on parameterized curves and surfaces, to compare and contrast differences with the standard one dimensional scenarios. The report also contains analysis of and comparison with regular Lagrange interpolation. The report concludes that Barycentric Lagrange interpolation is generally speaking more computationally efficient, and that the inherent need for periodicity makes Cardinal Trigonometric interpolation less reliable in comparison. On the other hand, Barycentric Lagrange interpolation is difficult to implement for higher dimensional problems, and also relies heavily on Chebyshev spaced nodes, something which can cause issues in a practical application of interpolation. Given ideal scenarios, Cardinal Trigonometric interpolation is more accurate, and for periodic functions generally speaking better than Barycentric Lagrange interpolation. Regular Lagrange interpolation is found to be unviable due to the comparatively big computational cost.

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