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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.
31

Resposta aeroelástica à rajada 1-cosseno usando aproximação aerodinâmica não estacionária /

Ribeiro, Frederico Albuquerque. January 2019 (has links)
Orientador: Douglas Domingues Bueno / Resumo: Os fenômenos associados aos sistemas aeroelásticos definem uma importante classe de problemas envolvida no projeto de aeronaves. Algumas análises podem ser realizadas utilizando a formulação no domínio da frequência, porém, para alguns problemas específicos a análise no domínio do tempo mostra-se mais conveniente, especialmente para projeto de controladores e inclusão de não linearidades. Em particular, forças aerodinâmicas não estacionárias são tipicamente obtidas no domínio da frequência reduzida. Tais formulações não permitem de maneira direta, através de uma transformada inversa, obter modelos matemáticos no domínio do tempo e, portanto, é necessário o uso de um método de aproximação, como o de Roger-Abel. No entanto, uso deste método de aproximação apresenta algumas lacunas com relação ao significado físico e escolha dos parâmetros de atraso. Desta forma, o presente texto explora a influência dos estados de atraso demonstrando que é responsável pela correção da fase entre o movimento e as forças aerodinâmicas resultantes e, também, propõe uma forma de avaliação da qualidade da aproximação obtida. A partir da aproximação das cargas aerodinâmicas se obtém o modelo matemático do sistema aeroelástico, e através de simulações numéricas computacionais, tem-se a resposta do sistema aeroelástico no domínio do tempo devido à cargas de rajada $1-cosseno$. A partir da análise da resposta à rajada é possível avaliar condições em que a rajada se apresenta de maneira mais crítica para... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The phenomena associated with the aeroelastic systems define an important class of problems involved in aircraft design. Some analyzes may be performed in the frequency domain, however, for some specific problems time domain analysis is more convenient, especially for controller design and the inclusion of nonlinearities. In particular, non-stationary aerodynamic forces are typically obtained in the reduced frequency domain. Such formulations do not allow, by means of an inverse transform, to obtain mathematical models in the time domain, and therefore it is necessary to use an approximation method, such as that of Roger-Abel. However, the use of this approximation method presents some gaps with respect to the physical meaning and choice of lag parameters. In this way, the present text explores the influence of the lag states demonstrating that it is responsible for the correction of the phase between the movement and the resulting aerodynamic forces and also proposes a method to evaluate the quality of the approximation achieved. From the approximation of the aerodynamic loads the mathematical model of the aeroelastic system is obtained, and through computational numerical simulations, has the response of the aeroelastic system in the time domain due to the 1-cosine gust load. From the analysis of the response to the gust, it is possible to evaluate conditions in which the gust is presented in a more critical way for the study system. / Mestre
32

三向資料的主成分分析 / 3-way data principal component analysis

趙湘琪, Chao, Hsiang Chi Unknown Date (has links)
傳統的主成分分析(principal component analysis)法,只能分析二式二向的資料(2-mode 2-way data),若是要處裡三向三式的資料(3-mode 3-way data)或是更多維的資料,則必須用其它的方法。例如將某一向資料取平均數,再做分析。此法雖然可行,但卻忽略三向資料間可能潛藏的相關性。且社會科學的研究日趨複雜,三向資料也就更常見到,而我們可能也對三向資料間彼此的關聯感到興趣。因此在1960、1970年代,學者開始研究將主成分分析的模型加以擴展成適合分析三向資料的模型。本文除了介紹三向資料主成分分析所使用的Tucker3模型及其參數估計法外,也以28家股票上市公司為實例,探討資本結構影響因素於五年間(1989~1993年)在不同公司群組間的變化情形。
33

以最小平方法處理有限離散型條件分配相容性問題 / Addressing the compatibility issues of finite discrete conditionals by the least squares approach

李宛靜, Lee, Wan Ching Unknown Date (has links)
給定兩個有限離散型條件分配,我們可以去探討有關相容性及唯一性的問題。Tian et al.(2009)提出一個統合的方法,將相容性的問題轉換成具限制條件的線性方程系統(以邊際機率為未知數),並藉由 l_2-距離測量解之誤差,進而求出最佳解來。他們也提出了電腦數值計算法在檢驗相容性及唯一性時的準則。 由於 Tian et al.(2009)的方法是把邊際機率和為 1 的條件放置在線性方程系統中,從理論的觀點來看,我們認為該條件在此種做法下未必會滿足。因此,本文中將邊際機率和為 1 的條件從線性方程系統中抽離出來,放入限制條件中,再對修正後的問題求最佳解。 我們提出了兩個解決問題的方法:(一) LRG 法;(二) 干擾參數法。LRG 法是先不管機率值在 0 與 1 之間的限制,在邊際機率和為 1 的條件下,利用 Lagrange 乘數法導出解的公式,之後再利用 Rao-Ghangurde 法進行修正,使解滿足機率值在 0 與 1 之間的要求。干擾參數法是在 Lagrange 乘數法公式解中有關廣義逆矩陣的計算部份引進了微量干擾值,使近似的逆矩陣及解可快速求得。理論證明,引進干擾參數所增加的誤差不超過所選定的干擾值,易言之,由干擾參數法所求出的解幾近最佳解。故干擾參數法在處理相容性問題上,是非常實用、有效的方法。從進一步分析Lagrange 乘數法公式解的過程中,我們也發現了檢驗條件分配"理論"相容的充分條件。 最後,為了驗證 LRG 法與干擾參數法的可行性,我們利用 MATLAB 設計了程式來處理求解過程中的運算,並以 Tian et al.(2009)文中四個可涵蓋各種情況的範例來解釋說明處理的流程,同時將所獲得的結果和 Tian et al. 的結果做比較。 / Given two finite discrete conditional distributions, we could study the compatibility and uniqueness issues. Tian et al.(2009) proposed a unified method by converting the compatibility problem into a system of linear equations with constraints, in which marginal probability values are assumed unknown. It locates the optimum solution by means of the error of l_2 - discrepancy. They also provided criteria for determining the compatibility and uniqueness. Because the condition of sum of the marginal probability values being equal to one is in Tian et al.s’linear system, it might not be fulfilled by the optimum solution. By separating this condition from the linear system and adding into constraints, we would look for the optimum solution after modification. We propose two new methods: (1) LRG method and (2) Perturbation method. LRG method ignores the requirement of the probability values being between zero and one initially, it then uses the Lagrange multipliers method to derive the solution for a quadratic optimization problem subject to the sum of the marginal probability values being equal to 1. Afterward we use the Rao-Ghangurde method to modify the computed value to meet the requirement. The perturbation method introduces tiny perturbation parameter in finding the generalized inverse for the optimum solution obtained by the Lagrange multipliers method. It can be shown that the increased error is less than the perturbation value introduced. Thus it is a practical and effective method in dealing with compatibility issues. We also find some sufficient conditions for checking the compatibility of conditional distributions from further analysis on the solution given by Lagrange multipliers method. To show the feasibilities of LRG method and Perturbation method, we use MATLAB to device a program to conduct them. Several numerical examples raised by Tian et al.(2009) in their article are applied to illustrate our methods. Some comparisons with their method are also presented.
34

Optimering av blåsmaskinstyrning på Bromma reningsverk / Optimization of blower control at Bromma wastewater treatment plant

Wikén, Moa January 2017 (has links)
The aeration step is the most energy consuming process in the wastewater treatment plant, i.e. making the energy usage in this step more efficient is of great concern both in Sweden and world wide. There are some examples of previous studies investigating ways to make the ae- ration control more efficient, though most of these have focused on for example ammonium feedback control rather than blower control which is the main focus of this study. Bromma wastewater treatment plant installed three new blowers in december 2016 functioning as suppliers of air to the aeration step in the bioreactor. Since there are still three old blowers operating at the WWTP, there is a need to control two different types of blowers efficiently. This is challenging since the two blower types have different capacities, efficiency and maxi- mum/minimum air flows and a control strategy that optimizes the operation of these two blower types combined needs to take this into account. Operational data for the blowers was used to generate a second grade polynome for each blower type which gives the efficiency as a function of produced air flow. These polynomes were further utilized to build a script in MATLAB that chooses the most efficient number of blowers operating and at what air flows for a certain total aeration need. The least square method was used to calibrate a model for calculating energy consumption for the simulated control strate- gy. Calculations for energy consumption from the current control strategy and another strategy proposed by the blower deliverer Sulzer were made in order to decide whether the optimized control strategy was an improvement or not. The simulation results and the calculations for energy consumption indicates that the current control strategy at Bromma WWTP is almost as effective as the optimized control strategy. Both strategies sets the new blowers at the first places in the queue. The optimized strategy appears to be more efficient for flows that requires both new and old blowers operating. From the calculations of energy consumption, it was shown that the control strategy from Sulzer de- mands an energy consumption on levels in between the one for the current control strategy and the optimized control strategy. / Luftningssteget är den mest energikrävande processen i ett avloppsreningsverk. Det finns därför incitament till att effektivisera energianvändningen då en minskad elförbrukning är positivt både ur ett ekonomiskt perspektiv och ur ett resursmässigt perspektiv. Energibesparingar från luftningssteget har undersökts tidigare genom att främst studera optimering av syreregleringen och luftregulatorn. Det här projektet syftar till att uppnå en minskad effektförbrukning på Bromma reningsverk genom att optimera blåsmaskinsregulatorn, ett mer outforskat forskningsfält.  På Bromma reningsverk installerades den 16 december 2016 tre nya blåsmaskiner som ska försörja luftningssteget i den biologiska reningen med luft. Det innebär att det finns två olika typer av blåsmaskiner som är i drift på Bromma: den gamla modellen (HST9000) och den nya modellen (HST40). Då dessa två olika typer av blåsmaskiner har olika kapacitet och verkningsgrad är det viktigt att blåsmaskinsregulatorn använder en styrstrategi som ställer dessa maskiner i kö på ett optimalt energieffektivt sätt. Det är även viktigt att i så stor utsträckning som möjligt låta maskinerna generera luftflöden nära sin högsta verkningsgrad.  Driftinformation för blåsmaskinerna användes för att med hjälp av beräkningar i MATLAB kunna välja ut det effektivaste antalet maskiner i drift, avgöra vilken typ av maskiner som ska användas samt vilket luftflöde respektive maskin ska generera vid ett specifikt luftflödesbehov. Målet var att hitta en optimal styrstrategi för Bromma reningsverk, samt att undersöka om det fanns möjligheter till energibesparingar jämfört med nuvarande implementerade styrstrategi. Effektförbrukningsberäkningar gjordes för både den simulerade optimerade styrstrategin och den nuvarande. Ytterligare en styrstrategi, föreslagen av blåsmaskinsleverantören Sulzer, undersöktes också ur ett energiförbrukningsperspektiv för jämförelse.  Resultatet av simuleringen och effektberäkningen indikerar att den nuvarande styrningen i princip är lika energieffektiv som den simulerade optimala styrningen. I båda fallen kopplas de nya maskinerna in i första hand. Dock visar resultatet på att den simulerade styrningen är effektivare vid flöden där det krävs att de gamla blåsmaskinerna sätts i drift. Sulzers föreslagna styrstrategi är mer energieffektiv än nuvarande styrning, men inte lika effektiv som den optimerade styrstrategin.
35

Algoritmy detekce radarových cílů / Detection Algorithms of Radar Targets

Štukovská, Petra January 2021 (has links)
This thesis focuses on detection algorithms of radar targets, namely on group of techniques for removing of disturbing reflections from static objects - clutter and for suppression of distortion products caused by the phase noise of the transmitter and receiver. Methods for distortion suppression in received signal are designed for implementation in the developed active multistatic radar, which operates in the code division multiplex of several transmitters on single frequency. The aim of the doctoral thesis is to design, implement in tool for technical computing MATLAB and analyze the effectiveness and computational complexity of these techniques on simulated and real data.
36

Identifikace 3D objektů pro robotické aplikace / Identification of 3D objects for Robotic Applications

Hujňák, Jaroslav January 2020 (has links)
This thesis focuses on robotic 3D vision for application in Bin Picking. The new method based on Conformal Geometric Algebra (CGA) is proposed and tested for identification of spheres in Pointclouds created with 3D scanner. The speed, precision and scalability of this method is compared to traditional descriptors based method. It is proved that CGA maintains the same precision as the traditional method in much shorter time. The CGA based approach seems promising for the use in the future of robotic 3D vision for identification and localization of spheres.
37

Detekce zubů na 3D počítačovém polygonálním modelu čelisti / Tooth Detection of jaw 3D Computer Polygonal Model

Kantor, Roman January 2012 (has links)
This document discusses a problem of tooth detection on jaw 3D polygonal model. It describes known methods that can be used to reach expected results, such as their advantages and disadvantages. Considering this, I choose one solution that is closely described with all theory needed for its implementation.
38

[en] LINEAR ELASTIC FRACTURE MECHANICS ANALYSIS OF FATIGUE CRACK GROWTH UNDER COMPLEX LOADING USING THE DIGITAL IMAGE CORRELATION TECHNIQUE / [pt] ANÁLISE DO CRESCIMENTO DE TRINCAS DE FADIGA PELA MECÂNICA DE FRATURA ELASTICA LINEAR SOB CARGA COMPLEXA UTILIZANDO A TÉCNICA DE CORRELAÇÃO DE IMAGENS DIGITAIS

JORGE GUILLERMO DIAZ RODRIGUEZ 25 January 2019 (has links)
[pt] A avaliação da propagação de trincas de fadiga inclui a identificação da direção da trinca, o conhecimento do Fator de Intensidade de Tensões (SIF) equivalente, a determinação de uma taxa de crescimento de comprimento de trinca por número de ciclos da/dN e o estabelecimento de uma regra de propagação de trinca conectando SIF e da/dN, como uma regra de tipo Paris. Quando ocorrem cargas mistas e não proporcionais, esses parâmetros ainda não são totalmente compreendidos. Esta tese trata de algumas das variáveis que influenciam a propagação de trincas sob carregamento no modo misto não proporcional. A técnica de Correlação de Imagens Digitais (DIC) foi utilizada para a aquisição de imagens de corpos de prova submetidos a carregamento proporcional e não proporcional cíclico. Dois tipos de corpos de prova foram utilizados. Primeiramente, dois corpos de prova planos foram testados; um disk compact tension (DCT, em inglês) e um compact tension modificado (C (T) em inglês). Eles foram submetidos a carregamento cíclico induzindo o modo I de abertura de trinca ou modos I e II de abertura de trinca proporcionais. Em segundo lugar, os dados DIC adquiridos anteriormente, e em outro lugar, para cinco tubos finos sujeitos a carregamento cíclico foram analisados. Os tubos finos tiveram entalhes usinados a partir dos quais as trincas por fadiga iniciaram e se propagaram. Esses cinco tubos finos foram submetidos a diferentes casos de carga proporcional e não proporcional. Um corpo de prova tipo tubo fino foi exposto a carga axial e apresentou modo de abertura de trinca tipo I. Os outros quatro foram submetidos a carregamento de torção ou carga axial-torcional mista e exibiram todos os três modos de abertura de trinca I, II e III. Os campos de deslocamento adquiridos experimentalmente com a técnica DIC foram processados para calcular independentemente o SIF para cada modo de abertura existente usando formulações de mecânica de fratura elástica linear (MFLE). Uma formulação delas utilizou dados de deslocamento de campo completos adquiridos em pequenas áreas que circundavam a ponta da trinca. Outra formulação usou dados adquiridos de um par de pontos localizados ao longo dos flancos opostos das faces da trinca. Os SIFs determinados foram usados para encontrar os SIFs equivalentes e faixas de SIF equivalentes usando o critério da tensão máxima de tração (para ambas as versões 2D e 3D de combinações dos modos I-II e modos I-II-III respectivamente) que implicitamente incluíram o ângulo de propagação de trinca. Verificou-se que a inclusão do SIF no modo III experimentalmente determinado efetivamente faz diferença nas faixas do SIF e dos SIF equivalentes estimados. A curva da/dN versus faixa do SIF equivalente foi elaborado com as taxas de crescimento de trinca medidas experimentalmente e as faixas de SIF que foram encontradas usando a suposição amplamente aceita de que as trincas cresceram na direção que maximiza a tensão de tração. Para isso, extensões do modelo de Schollmann et. al. e bem como o modelo de Erdogan-Sih, que são geralmente aplicados ao carregamento proporcional, foram usados para determinar os SIFs equivalentes e faixas de SIF equivalentes para os casos de carregamento proporcional e não proporcional. Finalmente, a segunda zona da regra de Paris (da/dN versus faixa do SIF equivalente) foi plotada para os cinco casos de carregamento nos tubos finos mostrando que eles caíram dentro de uma faixa razoavelmente fina e dispersa. / [en] Fatigue crack propagation assessment includes identifying the crack direction, knowing the equivalent Stress Intensity Factor (SIF) range, determining a crack length growth rate per number of cycles (da/dN), and establishing a crack propagation rule connecting the equivalent SIF and da/dN rate, such as a Paris type of rule. When mixed and non-proportional loading occur, those parameters are not fully understood yet. This thesis deals with some of the variables that influence crack propagation under non-proportional mixed mode loading. The Digital Image Correlation (DIC) technique was used to acquire images of test specimens subjected to cyclic proportional and non-proportional loading. Two types of specimen samples were used. Firstly, two different plate test specimens were tested; a disk compact tension (DCT), and a modified compact tension, C(T). They were subjected cyclic loading inducing crack opening mode I or proportional crack opening modes I and II. Secondly, the previously and elsewhere acquired DIC data for five thin tubes subject to cyclic loading were analyzed. The thin tubes had pre-fabricated slit-notches from which fatigue cracks initiated and propagated. Those five thin tubes were subjected to different cases of proportional and non- proportional loading. One tube specimen was exposed to axial loading and presented mode I crack opening. The other four were subjected to torsion loading or mixed axial-torsional loading and exhibited all three I, II and III crack-opening modes. The experimentally acquired DIC displacement fields were processed to independently calculate SIF for each existing opening mode using linear elastic fracture mechanics (LEFM) formulations. One formulation used full field displacement data acquired in small areas that surrounded the crack tip. Another formulation used data acquired from a pair of points located along the opposite crack flanks. The determined SIFs were used to find equivalent SIFs and equivalent SIF ranges using the maximum tensile stress criterion (for both 2D and 3D versions of combinations of modes I-II and modes I-II-III respectively) which implicitly included the crack propagation angle. It was found that the inclusion of the experimentally determined mode III SIF indeed makes a difference in the determined equivalent SIF and equivalent SIF ranges. A da/dN versus equivalent SIF ranges plot was drafted with the experimentally measured crack growth rates and the SIF ranges that were found by using the widely accepted assumption that the cracks grew in the direction that maximizes the tensile stress. For this, extensions of the Schollmann et. al. model as well as of the Erdogan-Sih model, which are generally applied to proportional loading, were used to determine equivalent SIFs and equivalent SIF ranges for the cases of proportional and non-proportional loading. Finally, the second stage of the Paris rule (da/dN versus SIF range) was plotted for the five thin tubes loading cases showing that they fell inside a reasonably thin scattered band.
39

基因晶片實驗其樣本數之研究 / Sample Size Determination in a Microarray Experiment

黃東溪, Huang, Dong-Si Unknown Date (has links)
微陣列晶片是發展及應用較為成熟的生物晶片技術。由於微陣列實驗程序複雜,故資料常包含多種不同來源的實驗誤差,為了適當的區分實驗中來自處理、晶片及基因的效應,我們提出混合效應變異數分析模型來調整系統誤差。針對各基因在不同實驗環境的差異性假設檢定問題,利用最小平方法推導出點估計以及對應的檢定統計量。本研究介紹多重檢定問題中的族型一誤差,並證明在此模型下,Sidak調整法為適當的多重檢定方法。在給定族型一誤差率的顯著水準,利用檢定力的公式,運算出在預設檢定力的最低水準下所需最小樣本(晶片)數。最後我們透過電腦模擬,以蒙地卡羅法來估計檢定力與族型一誤差率,由模擬結果發現,採用此最小樣本數結果,其檢定力可達到預期的水準以上,並且其族型一誤差率皆適當地控制在顯著水準以內。
40

回転軸系の時間領域実験的同定法の開発とその応用に関する研究

安田, 仁彦, 叶, 建瑞, 神谷, 恵輔 03 1900 (has links)
科学研究費補助金 研究種目:基盤研究(C) 課題番号:10650238 研究代表者:安田 仁彦 研究期間:1998-1999年度

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