Timber is a building material that is becoming more common and of interest for use in high-rise buildings. One of the reasons is that timber requires less energy input for the manufacturing process of the material compared to non-wood based materials. When designing high- rise timber buildings it is of great significance to understand the dynamic behavior of the structure. One method to obtain the dynamic properties is to use Operational Modal Analysis, which is based on the structural response from operational use. Finite element (FE) analysis is a tool which can be used for dynamic analysis for large structures. In this study an Operation Modal Analysis (OMA) was conducted on a four-story timber building in Växjö. A finite element model was created of the same building using commercial FE packages. Based on the mode shapes and natural frequencies obtained from the OMA, the FE model was fine-tuned. The purpose of this thesis is to gain knowledge of which parameters that might have a significant role in finite element modelling for a structural dynamic analysis. The aim is to develop a finite element model that accurately simulates the dynamic behavior of the tested building. It was shown from the result that is possible with an enough detailed FE model to capture the dynamic behaviour of a structure. The parameters that had the largest effect on the result can be pointed to the mass and the stiffness of the structure. / Trä är ett byggnadsmaterial som börjar bli allt mer vanligt och är av intresse att använda som stommaterial för höga byggnader. En anledning till detta är att det krävs mindre energi i tillverkningsfasen för trä jämfört med stål och betong. Vid dimensionering av höga träbyggnader är det essentiellt att förstå byggnadens dynamiska egenskaper. För att ta fram en byggnads dynamiska egenskaper kan en metod som benämns Operational Modal Analysis (OMA) tillämpas vilken baseras på byggnadens rörelser vid daglig användning. Finita element (FE) metoden är ett verktyg som kan användas vid dynamisk analys för större byggnader. I detta arbete genomfördes en OMA för ett fyravåningshus med trästomme beläget i Växjö. Genom användning av kommersiella FE-mjukvaror togs en finita element modell av samma byggnad fram. Baserat på de egenfrekvenser och egenmoder erhållna från OMA, uppdaterades FE-modellen därefter. Syftet med detta arbete är att erhålla kunskap kring vilka parametrar som har betydelse vid FE-modellering med hänsyn till dynamisk analys. Syftet är även att validera den prototyp av datainsamlingsenhet som använts vid fältmätningen. Målet med arbetet är att ta fram en FE-modell som på ett korrekt sätt beskriver den testade byggnadens dynamiska beteende. Resultatet av arbetet påvisar att med en tillräckligt detaljerad FE-modell är det möjligt att erhålla en byggnads dynamiska egenskaper. De parametrar som har störst inverkan på resultatet är byggnadens styvhet och inkluderad massa.

<p>Predmet istraživanja prikazanih u okviru doktorske diseracije su samopobudne vibracije pri obradi glodanjem. Na osnovu detaljne analize zakonitosti nastanka samopobudnih vibracija uspostavljena je određena paralela između glodanja i mikrogkodanja, za slučajeve kada je dubina rezanja veća od radijusa rezne ivice alata. Za tako usvojene pretpostavke, razvijeni su modeli unapređene numeričke simulacije procesa glodanja i mikroglodanja. Razvijeni modeli su svestrano verifikovani, s jedne strane, u segmentima gde postoje podaci u literaturi; poređenjem sa rezultatima drugih autora, a sa druge strane poređenjem sa sopstvenim eksperimentalnim ispitivanjima. Za eksperimentalno definisanje granične dubine rezanja pri glodanju predložena je inovativna metoda tangenti, a pri mikroglodanju, imajući u vidu raspoloživu mernu opremu, metoda hrapavosti obrađene površine. Matematički modeli i eksperimentalne metode su verifikovani pri obradi tri karakteristične vrste materijala i na dva obradna sistema pri glodanju, odnosno jednom materijalu i jednom obradnom sistemu pri mikroglodanju. Rezultati istraživanja su prezentovani kroz dvanaest poglavlja čiji sadržaj se navodi u nastavku.</p><p>U prvom, uvodnom poglavlju, ukazano je na značaj istraživanja samopobudnih vibracija pri makro i mikroglodanju. Prikazana je i aktuelnost istraživanja analizom broja naučnih radova koji se bave problematikom samopobudnih vibracija u periodu od poslednjih dvadeset pet godina.<br />Kroz drugo poglavlje detaljno su prikazana dosadašnja istraživanja samopobudnih vibracija pri makroglodanju, dok su u trećem poglavlju prikazana istraživanja samopobudnih vibracija pri mikroglodanju. Izvršena je analiza uticajnih parametri na graničnu dubinu rezanja, koja predstavlja osnovni pokazatelj dinamičke stabilnosti kako makro, tako i mikroobradnih sistema.<br />Na osnovu saznanja prikazanih u okviru drugog i trećeg poglavlja u četvrtom poglavlju su definisani ciljevi i hipoteze istraživanja.<br />Matematičke metode za definisanje karte stabilnosti obradnog sistema, prikazane su u petom poglavlju. Prikazana su dva matematička modela za definisanje karte stabilnosti pri makroglodanju, model srednjeg ugla kontakta alata u zahvatu i model Furijeovih redova. Prezentovana je numerička simulacija procesa obrade glodanjem, namenjena prvenstveno za simulaciju sila rezanja. Polazeći od prethodno prikazane ideje u okviru ovog poglavlja je razvijena nova matematička metoda predikcije granične dubine rezanja - unapređena numerička simulacija procesa glodanja.<br />U okviru šestog poglavlja prikazane su eksperimentalne metode identifikacije vibracija mašina alatki, odnosno eksperimentalno određivanje modalnih parametara obradnih sistema kao i metode detekcije samopobudnih vibracija pri glodanju. U cilju definisanja granične dubine rezanja, prikazana je metoda frekventne analize vibracija pri glodanju, kao metoda koja se često koristi u savremenim eksperimentalnim istraživanjima. Međutim, i matematičke i eksperimentalne metode analize vibracija pri glodanju imaju određena ograničenja. Polazeći od prethodnog, razvijena je inovativna metoda tangenti, bazirana na ranije korišćenoj metodi u okviru Laboratorije za mašine alatke Instituta za proizvodno mašinstvo FTN u Novom Sadu, i primeni savremenih mernih sistema. Pored toga, u ovom poglavlju je eksperimentalno potvrđen uticaj samopobudnih vibracija na kvalitet obrađene površine i geometrijsku tačnost obratka.<br />Metodologija sprezanja matematički i eksperimentalno definisanih funkcija frekventnog odziva elemenata mašine alatke prikazana je u sedmom poglavlju. Prezentovane su jednačine sprezanja pomerajnih odziva matematmički definisanih funkcija frekventnog odziva alata i držača alata, bazirane na Ojlerovoj teoriji grede, sa eksperimentalno definisanom funkcijom frekventnog odziva sklopa glavnog vretena mašine alatke.<br />U okviru osmog poglavlja razvijen je matematički model sila rezanja pri mikroglodanju. Predloženi model sila rezanja, koji uzima u obzir silu trenja između leđne površine alata i obrađene površine, implementiran je u unapređenu numeričku simulaciju glodanja čime je omogućena njena primena za definisanje graničnih dubina rezanja pri mikroglodanju.</p><p>Verifikacija razvijenih numeričkih i eksperimentalnih metoda za ispitivanje vibracija pri makroglodanju je prikazana u devetom poglavlju. Sproveden je niz eksperimentalnih ispitivanja, pri kojima su određivane granične dubine glodanja pri obradi tri različita materijala obratka (Al7075, 42CrMo4 i Ti-6Al-4V) na dva obradna sistema. Na osnovu ovih ispitivanjima izvršena je verifikacija unapređene numeričke simulacije glodanja i inovativne metode tangenti.<br />U desetom poglavlju prikazana je verifikacija metoda analize samopobudnih vibracija pri mikroglodanju. Primenom metodologije sprezanja pomerajnih odziva, definisani su modalni parametri obradnog sistema za mikroobradu, potrebni za definisanje graničnih dubina rezanja, tj. karte stabilnosti, unapređenom numeričkom simulacijom mikroglodanja. Karta stabilnosti definisana razvijenom unapređenom numeričkom simulacijom, verifikovana je eksperimentalno i poređenjem sa literaturnim izvorima.<br />U jedanaestom poglavlju data su zaključna razmatranja, kritički osvrt na ostvarene rezultate, i pravci budućih istraživanja.<br />Dvanaesto poglavlje prikazuje pregled korišćene literature, koju čini 218 referenci većim delom citirane u samom radu, a u zasebnom poglavlju dati su prilozi.</p> / <p>The subject of research presented in the doctoral dissertation are self-excited vibrations in milling. Based on a detailed analysis of the self-excited vibrations occurrence, a certain parallel has been established between macro and micromilling, for cases when the depth of cut is greater than the cutting edge radius of the tool. For such adopted assumptions, models of advanced numerical simulation of macro and micromilling processes were developed. The developed models were comprehensively verified, on the one hand, by comparison with the results of other authors, and on the other hand by comparison with own experimental results. An innovative tangent method has been proposed for the experimental definition of the cutting depth limit in milling, and the method of machined surface roughness has been proposed for micromilling, having in mind the available measuring equipment. Mathematical models and experimental methods were verified by machining three characteristic types of materials on two machining systems in macromilling, and one material on one machining system in micromilling. The results of the research are presented through twelve chapters, the content of which is listed below.</p><p>In the first, introductory chapter, the importance of the research of self - excited vibrations in macro and micromilling is pointed out. The topicality of the research is also presented by analyzing the number of scientific papers dealing with the issue of self - excited vibrations in the period of the last twenty - five years.<br />The second chapter presents in detail the previous research on self-excited vibrations during macromilling, while the third chapter presents research on self-excited vibrations during micromilling. An analysis of the influential parameters on the cutting depth limit was performed, which is a basic indicator of the dynamic stability of both macro and micromachining systems.<br />Based on the findings presented in the second and third chapters, the fourth chapter defines the goals and hypotheses of the research.<br />Mathematical methods for defining the stability lobe diagram of the machining system are presented in the fifth chapter. Two mathematical models for defining the stability lobe diagram for macromachining are presented, the model of the tool&rsquo;s mean contact angle and the model of Fourier series. Numerical simulation of the milling process is presented, intended primarily for the simulation of cutting forces. Starting from the previously presented idea, a new mathematical method for predicting the cutting depth limit has been developed within this chapter - an improved numerical simulation of the milling process.<br />In the sixth chapter, experimental methods of machine tools vibration identification are presented, ie experimental determination of machining systems modal parameters as well as methods of self - excited vibrations detection during milling. In order to define the cutting depth limit, the method of vibrations frequency analysis during milling is presented, as a method that is often used in modern experimental research. However, both mathematical and experimental methods of milling vibration analysis have certain limitations. Starting from the previous one, an innovative tangent method was developed, based on the previously developed method, used within the Laboratory for Machine Tools, Institute of Production Engineering Facultz of Technical Sciences in Novi Sad, and the application of modern measuring systems. In addition, in this chapter, the influence of self - excited vibrations on the machined surface quality and the geometric accuracy of the workpiece is experimentally confirmed.<br />The methodology of machine tool elements mathematically and experimentally defined frequency response functions coupling is presented in the seventh chapter. The displacement responses coupling equations of mathematically defined tools and tool holders FRF&#39;s (based on Euler &#39;s beam theory) with the experimentally defined FRF of the machine tool main spindle assembly are presented.<br />Within the eighth chapter, a mathematical model of cutting forces in micromilling was developed. The proposed cutting forces model, which takes into account the friction force between the reliefe tool surface and the machined surface, is implemented in an advanced numerical micromilling simulation, which enables its application to define cutting depth limit in micromilling.</p><p>Verification of the developed numerical and experimental methods for vibrations analysis during macromachining is presented in the ninth chapter. A series of experimental tests were performed, during which the cutting depth limits were determined during the milling of three different workpiece materials (Al7075, 42CrMo4 and Ti-6Al-4V) on two machining systems.<br />In the tenth chapter, the verification of the methods of analysis of self-excited vibrations during micromilling is presented. Using the methodology of coupling displacement responses, the modal parameters of the machining system for micromachining are defined, needed to define the cutting depth limits, ie. stability lobe diagram, by advanced numerical micromilling simulation The stability lobe diagram, defined by the developed advanced numerical simulation, was verified experimentally and by comparison with literature sources.<br />The eleventh chapter provides concluding remarks, a critical review of the achieved results, and directions for future research.<br />The twelfth chapter presents an overview of the used literature, which consists of 218 references, mostly cited in the paper itself.</p>

Dans l’industrie manufacturière, la consommation d’énergie électrique est considérée comme l'un des problèmes majeurs qui est malheureusement liée systématiquement à l'émission de gaz contenant du dioxyde de carbone et amenant à l’effet de serre. Des études sur l’estimation de l’énergie électrique consommée par les machines outils sont développées par des chercheurs au cours des dernières décennie pour proposer des modèles d’estimation de cette énergie. Ces modèles sont soit empiriques soit théoriques et se limitent à tenir compte du comportement dynamique du système de coupe lors des opérations d’usinage. La contribution fondamentale de cette thèse de doctorat est la caractérisation du comportement non linéaire des efforts de coupe et du système de guidage lors de l’estimation de l’énergie consommée par une machine outil. La modélisation repose sur la détermination de l’effort de coupe et de l’effort des roulements qui sont variables en fonction du temps et qui sont déduites de l’écriture de l’équation de mouvement du système (broche ou machine-outil)discrétisé en éléments finis en utilisant la méthode de Newark couplée avec l’algorithme de Newton Raphson. Ces efforts de coupe et de roulements sont utilisés pour calculer la puissance puis l’énergie consommée par la table d’avance, la broche et par conséquent la machine outil. Afin de valider notre approche, la puissance et l’énergie obtenues à partir du modèle développé sont comparées avec la puissance et l’énergie obtenues avec un dispositif expérimental. Une étude paramétrique est réalisée pour mettre l’accent sur l’impact de la variation des paramètres de coupe sur la valeur de la puissance et de l’énergie consommées. On introduit par la suite des défauts d’usure et de montage au niveau des roulements et nous présentons leurs impacts sur le comportement énergétique de la machine. Une attention particulière a également été consacrée à développer un modèle d’optimisation des mouvement d’une machine outil globale minimisant à la fois l’énergie consommée, le temps de production, le coût et la rugosité de surface en respectant les consignes technologiques. / In manufacturing, the electrical energy consumption is considered as one of the major problems which are systematically related to the gas emission containing carbon dioxide and leading to the greenhouse effect. Studies based on the estimation of the machine tools energy consumption become the interest of researchers in recent decades.As a result, different models for energy estimating are developed in order to minimize the quantity of consumed energy. These models are either empirical or theoretical and are limited to taking into account the dynamic behavior of the cutting system during machining operations. The fundamental contribution of this doctoral thesis is the characterization of the nonlinear behavior of cutting and rolling forces during estimating the consumed energy by a machine tool. The developed approach is based on the determination of the variable cutting forces and bearings forces which are function of time. These forces are deduced by solving the equation of motion based on finite element method using Newark's method coupled with Newton Raphson's algorithm. These forces are used to calculate the power then the consumed energy by the axis feed, the spindle and therefore the machine tool. In order to validate our approach, the power and energy obtained from the model developed are compared with the power and energy obtained with an experimental device. A parametric study is carried out to focus on the impact of the variation of the cutting parameters on the value of the consumed power and energy. An interest is given for different types of defect (innerring spalling, outer ring spalling, eccentricity and unbalance) in order to study their impact on the spindle consumed power during approach and cutting phases under different rotating conditions. Particular attention has also been devoted to develop a global model for optimizing machine too lmovements that minimizes the consumed energy, the production time, the cost and the surface roughness with respect of the technological constraints.

This work discusses the dynamic predictions of compliant mechanisms using the Pseudo-Rigid-Body model (PRBM). In order to improve the number of mechanisms that can be modeled, this research develops and identifies several key concepts in the behavior of beam segments where both ends are fixed to a rigid body (fixed-fixed flexible segments). A model is presented, and several examples are discussed. The dynamic behavior of several compliant segments is predicted using the PRBM and the results are compared to finite element analysis and experimental results. Details are presented as to the transient behavior of a typical uniform rectangular cross section beam. The results of this study are extended and applied to compliant planar mechanisms. It is shown by comparison with finite element analysis and experimental results that the PRBM is a good model of the physical system's dynamic behavior. The method is also demonstrated for use with compliant microelectromechanical (MEMS) systems.

A key consideration in seismic design of buildings is to ensure that the lateral load resisting system has an appropriate combination of strength, stiffness and energy dissipation capacity. Hybrid coupled wall systems, in which steel beams are used to couple two or more reinforced concrete shear walls in series, can be designed to have these attributes and therefore have the potential to deliver good performance under severe seismic loading. This research presents an investigation of the seismic behavior of this type of structural system. System response of 12- and 18-story high prototypes is studied using transient finite element analyses that accounts for the most important aspects of material nonlinear behavior including concrete cracking, tension stiffening, and compressive behavior for both confined and unconfined concrete as well as steel yielding. The developed finite element models are calibrated using more detailed models developed in previous research and are validated through numerous comparisons with test results of reinforced concrete walls and wall-beam subassemblages. Suites of transient inelastic analyses are conducted to investigate pertinent parameters including hazard level, earthquake record scaling, dynamic base shear magnification, interstory drift, shear distortion, coupling beam plastic rotation, and wall rotation. Different performance measures are proposed to judge and compare the behavior of the various systems. The analyses show that, in general, hybrid coupled walls are particularly well suited for use in regions of high seismic risk. The results of the dynamic analyses are used to judge the validity of and to refine a previously proposed design method based on the capacity design concept and the assumption of behavior dominated by the first vibration mode. The adequacy of design based on the pushover analysis procedure as promoted in FEMA-356 (2000) is also investigated using the dynamic analysis results. Substantial discrepancies between both methods are observed, especially in the case of the 18-story system. A critical assessment of dynamic base shear magnification is also conducted, and a new method for estimating its effects is suggested. The method is based on a modal combination procedure that accounts for presence of a plastic hinge at the wall base. Finally, the validity of limitations in FEMA-368 (2000) on building height, particularly for hybrid coupled wall systems, is discussed.

No / A membrane-inspired evolutionary algorithm (MIEA) is a successful instance of a model linking membrane computing and evolutionary algorithms. This paper proposes the analysis of dynamic behaviors of MIEAs by introducing a set of population diversity and convergence measures. This is the first attempt to obtain additional insights into the search capabilities of MIEAs. The analysis is performed on the MIEA, QEPS (a quantum-inspired evolutionary algorithm based on membrane computing), and its counterpart algorithm, QIEA (a quantum-inspired evolutionary algorithm), using a comparative approach in an experimental context to better understand their characteristics and performances. Also the relationship between these measures and fitness is analyzed by presenting a tendency correlation coefficient to evaluate the importance of various population and convergence measures, which is beneficial to further improvements of MIEAs. Results show that QEPS can achieve better balance between convergence and diversity than QIEA, which indicates QEPS has a stronger capacity of balancing exploration and exploitation than QIEA in order to prevent premature convergence that might occur. Experiments utilizing knapsack problems support the above made statement.

本文模型來自於DeGroot (1974)的模型，以此模型為基礎延伸至兩產品之架構，並利用比較效果與網絡效果疲乏之間的交互作用，而得到了本文的定理2.。此定理2.可解釋許多市場上，廠商選擇其產品推出時間而影響其銷售量之變化。因此，本文對於兩廠商的競爭提出了一個新觀點：廠商因何時推出其產品，而能使得其產品成為主流。我們討論的不是價格或者品質的競爭，而在於產品相對推出的時間，因此，本文在定理2.得到了一個充分條件，這個條件讓廠商知道應何時推出其產品，而此產品可成為市場上之主流產品。

Les bioréacteurs de grandes dimensions, en raison de phénomènes de transfert limitant, sont le siège d’hétérogénéités se traduisant par des gradients locaux de concentration et température. Les microorganismes circulant au sein de ces bioréacteurs subissent donc des fluctuations environnementales qui peuvent affecter leur comportement aux niveaux métaboliques et/ou moléculaires. La réponse microbienne est fonction de la nature, de l’intensité, de la fréquence et de la durée de la perturbation. L’objectif de ce travail est l’étude quantitative de l’impact de l’intensité, la fréquence et l’amplitude d’un stress nutritionnel sur le comportement dynamique d’Escherichia coli, à savoir des ajouts pulsés de glucose lors de cultures continues en régime permanent. Un effort particulier est consacré au développement et à la validation des outils expérimentaux indispensables pour une caractérisation rigoureuse des dynamiques de réponses transitoires sur des échelles de temps allant de secondes à quelques minutes. Pour permettre le suivi in situ et en temps réel des changements métaboliques et moléculaires, une souche bioluminescente est mise en œuvre. Les réponses transitoires sont caractérisées par les vitesses spécifiques, les rendements, les profils d’induction transcriptionnelle, les temps caractéristiques. Selon les différents scenarii réalisés, l’ajustement du métabolisme face aux hétérogénéités de substrat est quantifié selon des échelles de temps aux niveaux macroscopiques et/ou moléculaires ; ces résultats originaux contribuent ainsi à l’implémentation des connaissances sur les interactions dynamiques entre les phénomènes biologiques et les phénomènes physiques ; l’enjeu réside à terme en l’amélioration des processus d’optimisation et d’extrapolation des bioprocédés par l’identification et la quantification des dynamiques des phénomènes limitants / Ineffective mixing entailing heterogeneity issues within industrial bioreactors have been reported to affect microbial metabolisms at cellular and/or molecular levels. Substrate gradients inside large-scale bioreactors are common environmental fluctuations that microorganisms would have to encouter along with the bioprocess. Depending on intensity, frequency and duration of those fluctuations, microorganisms may respond in a different manner. The objective of this work is to study the impact of intensity, frequency and amplitude of glucose perturbations on the dynamics of Escherichia coli responses. An E. coli bioluminescent strain is used for in situ and real-time monitoring of both metabolic and transcriptional changes. For this purpose, short-term glucose excess was simulated, using pulse-based experiments into glucose-limited chemostat cultures. In addition, an important effort is devoted to the development and validation of technical and mathematical tools in order to acquire quantitative and kinetic data on time scales from seconds to minutes. The transient responses are characterized, using specific rates, yields, transcriptional induction profiles and characteristic response times, and are compared in the different defined perturbation scenarios. The results reflected the fact that short-term heterogeneities of substrate affect both cell metabolism and regulation at macroscopic and/or molecular levels. Quantitative understandings of the dynamics during transient responses to environmental perturbations can thus shed light on the bioprocess optimization

Les spectres de bruit mesurés en cabine d’hélicoptère montrent que la boîte de transmission principale (BTP) est un des principaux contributeurs au bruit perçu par les usagers. Elle génère en effet plusieurs raies émergeant fortement du bruit large bande et dont les fréquences se situent dans la plage de sensibilité maximale de l’oreille humaine. Dans un contexte d’amélioration permanente du confort acoustique des usagers, un modèle numérique est développé pour prédire le comportement dynamique des BTP. Les équations du mouvement sont écrites sur la base de fonctions du temps représentatives des excitations générées par l’engrènement (raideur d’engrènement et erreurs de transmission). Plusieurs éléments de validation sont présentés pour confirmer la pertinence de la formulation proposée. Différents résultats numériques et expérimentaux de la littérature sont utilisés à des fins de comparaison, montrant que le modèle s’applique aux systèmes à simple étage de réduction, par engrenage cylindrique ou spiro-conique. La validation est ensuite étendue aux systèmes à deux étages de réduction et les résultats confirment que la formulation basée sur les erreurs de transmission permet de tenir compte des corrections de profil. Finalement, le modèle est utilisé pour diverses applications. Premièrement, l’influence des erreurs de pas sur le comportement dynamique de transmissions par engrenages est discutée, ainsi que l’influence combinée du niveau de chargement appliqué. Dans un second temps, la relation entre l’erreur de transmission dynamique et différents coefficients dynamiques est étudiée. Le contenu spectral de la réponse au niveau des roulements est ensuite analysé pour des systèmes à deux engrènements cylindriques et l’influence de différents paramètres est discutée. Enfin, une application est réalisée sur un système comprenant un engrenage cylindrique et un engrenage spiro-conique. Les phénomènes de couplage entre les étages successifs sont mis en évidence ainsi que la contribution des deux engrènements au contenu spectral de la réponse aux roulements. / Noise measurements have shown that helicopters main gearboxes highly contribute to the overall cabin noise. Gear mesh vibrations propagate through the shafts to the rolling element bearings and the casing which becomes a source of radiated noise. The latter is characterized by high-amplitude tones emerging from broadband noise whose frequencies lie in the range of maximum human ear sensitivity. In the context of continuous improvement in the acoustic comfort of helicopter passengers, it is therefore necessary to analyse and optimize gearbox vibrations in order to reduce casing noise radiations. The research work presented in this memoir is focused on the development of a numerical model dedicated to the prediction of gear system dynamic behaviour, comprising several gear stages and different types of gears. This model relies on classic beam and lumped parameter elements along with specific two-node gear elements for both cylindrical (spur, helical) and spiral-bevel gears. The equations of motion are developed based on time-varying functions representative of mesh excitations which comprise: (a) mesh stiffness functions, (b) quasi-static transmission error under load, and (c) kinematic (or no-load) transmission error. A number of comparisons with benchmark numerical and experimental results from the literature are presented which demonstrate that the proposed approach is sound as far as single-stage systems with spur, helical or spiral-bevel gears are considered. Validations are then extended to double-stage gears and, here again, it is confirmed that the proposed transmission error based formulation is accurate and can account for tooth shape modifications. In the second part of the memoir, several examples of application are presented and commented upon. First, the combined influence of tooth pitch errors and load on the dynamic behaviour of gear transmissions is tackled. An extended three-dimensional model and a reduced torsional version are then confronted in order to investigate the dependency between dynamic transmission errors and mesh force / root stress dynamic factors. Further investigations on bearing dynamic response in two-stage spur gear systems are conducted and the particular contributions of profile modifications are analysed. Finally, a system combining a cylindrical gear and a spiral-bevel gear is considered and particular attention is paid to the dynamic couplings between the various meshes and their influence on bearing dynamic responses.

This dissertation discusses the interaction between fuel cells and the DC-DC converter just connected across its terminals. For that, it presents a modified algorithm to represent the dynamic behavior of fuel cell stacks as much the current ripple effects from power converters on such cells. PEM type fuel cells (Proton Exchange Membrane) are studied to get a reasonable model of the electrochemical and electric characteristics of the involved phenomena in the generation of electric energy from fuel cells. A T filter is used as interface between the fuel cell and the DC-DC converter. This converter must prevent large current ripples going through the cell terminals as well as keeping constant the power flow between the FC and the link DC to prevent itself of possible current transient. To connect it to the grid it was used a three-phase DC-AC converter to inject or to absorb current from the grid at reduced ripple distortion and to stabilize the DC link voltage. DC current controllers were designed to curb the link DC and AC currents within reasonable limits. Validation of the model was carried out through computer simulation in order to have an evaluation of the control system behavior both for the stack and for the injection and/or absorption of energy. Also, theoretical results with practical data from a fuel stack were compared with respect to the load variation across its terminals. / Esta dissertação discute a interação entre as células de combustível e o conversor de potência conectado aos seus terminais. Para isto é apresentado um algoritmo modificado para a modelagem dinâmica de conversores chaveados tanto quanto um estudo sobre os efeitos das ondulações de corrente sobre as células. Células do tipo PEM (Proton Exchange Membrane) são estudadas, obtendo-se um modelo razoável para análise das características eletroquímicas e elétricas dos fenômenos envolvidos na geração de energia elétrica com células de combustível. Como interface utiliza-se um conversor CC-CC associado a um filtro do tipo T . Este conversor tem a função de evitar a grande ondulação de corrente absorvida pela célula bem como, manter constante o fluxo de potência entre a FC e o barramento CC evitando-se assim, possíveis transitórios nos terminais da célula. O projeto do conversor de potência prevê a conexão à rede da concessionária através de um conversor CC-CA trifásico para injetar ou absorver corrente da rede com reduzida distorção harmônica e estabilização da tensão do barramento CC. Foram projetados controladores para a corrente CC, a tensão CC e a corrente CA. Como formas de validação foram realizadas simulações para avaliar o comportamento dos sistemas de controle para a pilha e para a injeção e/ou absorção de energia. Também foram comparados os resultados teóricos com os dados práticos de uma pilha submetida à variação de carga em seus terminais.