The problem of magnetic control for three-axis stability of a spacecraft is examined. Two controllers, a proportional-derivative controller and a constant coefficient linear quadratic regulator, are applied to the system of equations describing the motion of the spacecraft. The stability of each is checked for different spacecraft configurations through simulations, and the results for gravity-gradient stable and non gravity-gradient stable spacecraft are compared. An optimization technique is implemented in an attempt to obtain the best performance from the controller. For every spacecraft configuration, a set of gains can be chosen for implementation in the controller that stabilizes the linear and nonlinear equations of motion for the spacecraft. / Master of Science

No / The finite element simulation of a selection of two- and three-dimensional flow problems is presented, based upon the use of four different constitutive models for polymer melts (Oldroyd-B, Rolie-Poly, Pom-Pom and XPP). The mathematical and computational models are first introduced, before their application to a range of visco-elastic flows is described. Results demonstrate that the finite element models used here are able to re-produce predictions made by other published numerical simulations and, significantly, by carefully conducted physical experiments using a commercial-grade polystyrene melt in a three-dimensional contraction geometry. The paper also presents a systematic comparison and evaluation of the differences between two- and three-dimensional simulations of two different flow regimes: flow of an Oldroyd-B fluid around a cylinder and flow of a Rolie-Poly fluid into the contraction geometry. This comparison allows new observations to be made concerning the relatively poor quality of two-dimensional simulations for flows in even quite deep channels.

A two-dimensional structural analysis design approach has been the universally accepted method for a small structural engineering design firm. The tools to perform the analysis have been paper and pencil, calculators and more recently personal computers with two-dimensional software. With the introduction of three-dimensional software, a major shift is occurring on how small structural engineering firms approach analysis and design. This thesis research reviews the analysis of an existing building utilizing the standard two-dimensional approach, including horizontal diaphragm-action within wood floors. This study also reviews the research performed on horizontal diaphragms and investigates the use of three-dimensional, finite element modeling (RISA-3D) for the analysis of horizontal diaphragms. It is shown that the three-dimensional model can provide results similar to the two-dimensional hand calculations. However, the thickness of the diaphragm elements has to be significantly modified for flexible diaphragm action. The experience described herein is useful for structural engineer interfacing within three-dimensional CAD systems. The thesis concludes with a discussion on the challenges facing small structural engineering firms, including computer based technologies, engineering expertise to develop contract documents and review shop drawings, and outsourcing of design services.

Thesis (M.S. in Computer Science)--Naval Postgraduate School, September 2003. / Thesis advisor(s): Don Brutzman, Curtis Blais. Includes bibliographical references (p. 103-104). Also available online.

According to the statistics about civil transportation aircraft Environmental Control system (ECS), the three-wheel high pressure water separation system (HPWS) and low pressure water separation system (LPWS) are the most common choices for the 150-seat airliners. Although the former has become the mainstream configuration for air conditioning pack, the latter is still used on Boeing 737-600/700. In order to compare the two configurations and choose the better one for a specific aircraft, simulation and analysis are done. The cabin heat load is calculated at first in order to calculate required engine bleed air mass flow. Then a specific aircraft is defined so that required structural dimensions and cabin comfort indexes can be obtained based on Airbus 320. Thirdly, the component models are built by Matlab/Simulink according to the fundamental knowledge of heat transfer and aerodynamics, the working principles and mechanical dimensions of the components, the ambient environmental parameters and some data from Airbus 320. Consequently, the complete system model can be assembled. After confirming the validity of the model by checking the required ram air mass flow and temperature deviation of the state points referred to Airbus 320, the simulation model is used to do analyze the specific aircraft. Finally, through comparing the different values of ram air mass flow and turbine expansion ratio, as well as the system mass, economic cost and reliability, the better configuration is selected. It can be summarized that the three-wheel LPWS requires less ram air mass flow (0.012kg/s) and a little lower expansion ratio (0.02) than the HPWS, and it also has lower weight (63% of HPWS), lower (83% of HPWS) cost and higher reliability (140% of HPWS), thus it is the suitable configuration for the specific aircraft.

Thesis (PHD)--University of Montana, 2009. / Contents viewed on April 30, 2010. Title from author supplied metadata. Includes bibliographical references.

Η παρούσα διπλωματική εργασία πραγματεύεται τη μελέτη και κατασκευή ενός τριφασικού αντιστροφέα και το συγχρονισμό-σύνδεση αυτού με το τριφασικό δίκτυο. Η εργασία εκπονήθηκε στο Εργαστήριο Ηλεκτρομηχανικής Μετατροπής Ενέργειας του Τμήματος Ηλεκτρολόγων Μηχανικών και Τεχνολογίας Υπολογιστών της Πολυτεχνικής Σχολής του Πανεπιστημίου Πατρών. Σκοπός της εργασίας αυτής είναι η μελέτη και η κατασκευή ενός τριφασικού αντιστροφέα, ο οποίος θα συνδεθεί με το τριφασικό δίκτυο και θα αποτελέσει μέρος ενός συστήματος με πηγή ενέργειας μία συστοιχία κυψελών καυσίμου (fuel cells) και ενός μετατροπέα ανύψωσης συνεχούς τάσης σε συνεχή, με διαδοχική αγωγή δύο παράλληλων κλάδων (interleaved boost converter). Η είσοδος του τριφασικού αντιστροφέα συνδέεται στην έξοδο του μετατροπέα ανύψωσης συνεχούς τάσης σε συνεχή, με διαδοχική αγωγή δύο παράλληλων κλάδων, ο οποίος τροφοδοτεί τον αντιστροφέα με σταθερή τάση 80 V. Στην έξοδο του αντιστροφέα πρόκειται να συνδεθεί ένα φίλτρο LC για την αποκοπή των υψίσυχνων σημάτων της τάσης και στη συνέχεια ένας τριφασικός μετασχηματιστής, ο οποίος προσφέρει γαλβανική απομόνωση και ανυψώνει την τάση στην επιθυμητή τιμή, που είναι και η τιμή της τάσης του δικτύου. Καταρχάς έγινε θεωρητική μελέτη των ανανεώσιμων πηγών ενέργειας, του τριφασικού αντιστροφέα, του φίλτρου LC, του τριφασικού μετασχηματιστή, καθώς και μεθόδων συγχρονισμού με το δίκτυο. Επίσης έγινε μελέτη με το πρόγραμμα εξομοίωσης MATLAB/Simulink της διασύνδεσης του αντιστροφέα με το δίκτυο. Τέλος ακολούθησε η κατασκευή της διάταξης και η διεξαγωγή πλήθους πειραματικών δοκιμών. / The present diploma thesis deals with the design and manufacture of a three-phase inverter to synchronize and connect to the three-phase grid. This work was developed in the Laboratory of Electromechanical Energy Conversion at the Department of Electrical Engineering and Computer Technology of the School of Engineering in the University of Patras, Greece. The purpose of this thesis is the design and manufacture of a three-phase inverter, which will be connected to the three-phase grid and will be part of a system with source of energy a fuel cell stack and an interleaved boost converter, with two parallel branches. The input of the three-phase inverter is connected to the output of the interleaved boost converter with two parallel branches, which feeds the inverter with a dc voltage of 80 V. The output of the inverter is connected to an LC filter, in order to cut off the high frequency voltage signals and subsequently a three-phase transformer, which provides galvanic isolation and lifts the voltage to the appropriate value, which is the voltage value of the grid. At first a theoretical study of the renewable sources of energy, the three-phase inverter, the LC filter, the three-phase transformer, as well as the methods of synchronization with the grid was made. Study was also made with the simulation program MATLAB/Simulink at the interface of the inverter to the grid. Finally the construction of the device followed and numerous experimental trials were conducted.

abstract: Microfluidics is the study of fluid flow at very small scales (micro -- one millionth of a meter) and is prevalent in many areas of science and engineering. Typical applications include lab-on-a-chip devices, microfluidic fuel cells, and DNA separation technologies. Many of these microfluidic devices rely on micron-resolution velocimetry measurements to improve microchannel design and characterize existing devices. Methods such as micro particle imaging velocimetry (microPIV) and micro particle tracking velocimetry (microPTV) are mature and established methods for characterization of steady 2D flow fields. Increasingly complex microdevices require techniques that measure unsteady and/or three dimensional velocity fields. This dissertation presents a method for three-dimensional velocimetry of unsteady microflows based on spinning disk confocal microscopy and depth scanning of a microvolume. High-speed 2D unsteady velocity fields are resolved by acquiring images of particle motion using a high-speed CMOS camera and confocal microscope. The confocal microscope spatially filters out of focus light using a rotating disk of pinholes placed in the imaging path, improving the ability of the system to resolve unsteady microPIV measurements by improving the image and correlation signal to noise ratio. For 3D3C measurements, a piezo-actuated objective positioner quickly scans the depth of the microvolume and collects 2D image slices, which are stacked into 3D images. Super resolution microPIV interrogates these 3D images using microPIV as a predictor field for tracking individual particles with microPTV. The 3D3C diagnostic is demonstrated by measuring a pressure driven flow in a three-dimensional expanding microchannel. The experimental velocimetry data acquired at 30 Hz with instantaneous spatial resolution of 4.5 by 4.5 by 4.5 microns agrees well with a computational model of the flow field. The technique allows for isosurface visualization of time resolved 3D3C particle motion and high spatial resolution velocity measurements without requiring a calibration step or reconstruction algorithms. Several applications are investigated, including 3D quantitative fluorescence imaging of isotachophoresis plugs advecting through a microchannel and the dynamics of reaction induced colloidal crystal deposition. / Dissertation/Thesis / Ph.D. Mechanical Engineering 2011

Orientadores: Inacio Maria Dal Fabbro, Adilson Machado Enes / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola / Made available in DSpace on 2018-08-24T11:36:45Z (GMT). No. of bitstreams: 1 Fracarolli_JulianaAparecida_D.pdf: 5319280 bytes, checksum: 4488936faca98d4c091c7703b2fd0ca0 (MD5) Previous issue date: 2014 / Resumo: Técnicas ópticas vêm sendo utilizadas para diversas finalidades técnicas e científicas. Algumas técnicas ópticas se caracterizam como métodos robustos, de baixo custo, não invasivos e não destrutivos para avaliação de materiais diversos, como produtos agrícolas, havendo aplicações desde a engenharia até a área da saúde humana e animal. Neste trabalho propõem-se a avaliação de frutos através da combinação de duas técnicas ópticas cujos estudos vêm comprovando suas aplicabilidades como métodos alternativos e inovadores, os quais empregam equipamentos de baixo custo na aquisição dos dados, permitindo automação de processos de seleção e classificação de produtos. Uma dessas técnicas é conhecida como Biospeckle, a qual fornece informações referentes à qualidade do material biológico em nível de estruturas celulares e a outra é o escaneamento com linha laser, que permite a obtenção de geometria do objeto nos eixos Xi (i = 1,2,3). O objetivo é proceder a um levantamento topográfico digital de materiais biológicos combinando o posicionamento geométrico dos pontos da imagem com informações referentes à atividade biológica. Foi realizada ainda a diferenciação entre frutos de formato variado, a classificação de frutos por formato, classe, coloração e defeitos por meio de processamento de imagens. Dessa forma é possível observar frutos com irregularidades superficiais, maturidade, danos mecânicos e latentes, entre outros. Esta pode se tornar a base para a seleção automática de produtos agrícolas. Foram utilizados um emissor de linha laser de diodo com 632 nm de comprimento de onda, luz branca difusa, câmera CCD, computador, mesa óptica, mamões, peras, tomates e esferas de isopor, bem como softwares ImageJ, Octave, Matlab. Foram desenvolvidos cinco programas computacionais para processamento das imagens. Foram realizados cinco experimentos, a saber: (1) Avaliação da Maturidade de Frutos; (2) Reconstrução Tridimensional e Mapeamento da Bioatividade; (3) Detecção de Formato Variado; (4) Mapeamento por Formato, Classe e Coloração; (5) Detecção de Defeitos. Na Avaliação da Maturidade foram correlacionados índices de maturidade tradicionais (parâmetros de Hunter L a b, pH, Sólidos Solúveis Totais (SST), a relação Sólidos Solúveis Totais e Acidez Total Titulável (SST/ATT), Módulo de Elasticidade, massa e diâmetro) e a técnica óptica Biospeckle, pelo cálculo do Momento de Inércia (MI). Para a Reconstrução Tridimensional os frutos foram rotacionados através de um motor de passo. A cada passo do motor, o fruto foi iluminado pela linha laser projetada e fotografado para obtenção dos dados de geometria e Biospeckle pelo método LASCA (Laser Speckle Contrast Analysis). Foi analisada a correlação entre os índices de maturidade tradicionais e os valores de MI na avaliação da maturidade. Esta tese mostra que é possível avaliar a maturidade dos frutos através do Biospeckle. Obteve-se um mapa tridimensional que integra as informações de topografia e bioatividade do fruto. Obteve-se, ainda, a detecção de formato variado, a classificação de frutos por mapeamento por formato, classe e coloração e detecção de defeitos através de software / Abstract: Optical techniques have been used for both technical and scientific purposes. Optical techniques are usually characterized as being robust, inexpensive, non-invasive and non-destructive methods in to evaluate a diversity of materials which include agricultural derived products. It also shows applications ranging from engineering to human and animal health. In this doctoral dissertation, a new technique to evaluate some fruit properties is proposed. It combines two optical techniques (i.e. Biospeckle and Scan-line laser) whose applicability has been demonstrated as being alternative and innovative. The new proposed technique allows low-cost data acquisition, automation of the entire process, and a proper selection and classification method of vegetable bodies (e.g. fruits). Biospeckle allows obtaining information regarding the quality level of biological material into cellular structures. Scan-line laser enables the attainment of the object geometry on the axes Xi (i=1,2,3). The main purpose of this doctoral dissertation is to obtain a digital survey of biological materials (i.e. papaya, pear and tomato) integrating both geometric positioning and information concerning to its biological activity. The differentiation between different fruit shapes, fruit sorting by size, class, color and defects through image processing was also carried out. Thus it was also possible to observe fruits with surface irregularities, maturity, and mechanical damage, among others. This is the basis proposed for the automatic selection of agricultural products. The following materials were employed in the tests: a line-emitting diode laser with a wavelength of 632 nm, diffuse white light, CCD camera, computer, optical table, papaya, pear and tomato fruits and polystyrene spheres. The softwares utilized were: ImageJ, Octave, Matlab. A total of five computer programs were developed for the image processing procedures. Five experiments were performed: (1) Maturity Assessment of Fruits; (2) Three Dimensional Reconstruction and Mapping of Bioactivity; (3) Miscellaneous Format Detection; (4) Mapping Format, Class and Coloration; (5) Defect Detection. In Maturity Assessment there were correlated traditional methods to verify the maturity (the Hunter parameters L a b, pH, Total Soluble Solids (TSS), the relationship between Total Soluble Solids and Titratable Acidity (TSS/TA), Modulus of Elasticity, weight and diameter) and the optical technique Biospeckle by calculating the Moment of Inertia (MI). For the Three Dimensional Reconstruction the fruits were rotated by a stepper motor. At every step of the motor, the fruit was illuminated by the projected laser line and photographed in order to obtain both geometric and biospeckle data by the LASCA (Laser Speckle Contrast Analysis) method. The correlation between traditional methods for the maturity assessment and values of MI was analyzed. This doctoral dissertation shows that it is possible to evaluate the maturity of fruits through Biospeckle. A three-dimensional map that includes topographical information and bioactivity of the fruit was generated. Also a software can now detect variations in size, classify fruit shapes, color and class as well as defect detection efficiently. / Doutorado / Maquinas Agricolas / Doutora em Engenharia Agrícola

This thesis covers improvements on the upperbounds for ropelength of a specific class of algebraic knots.