The analysis of large-scale watershed processes and development of an efficient and integrated modelling platform is the focus of this research. The research focused on developing a series of modelling tools that can be used in the simulation of the overall response of a watershed based on a localized or distributed hydrologic event. This is achieved through the introduction of a hybrid modelling concept using a combination of empirically based lumped hydrologic processes and a physics-based distributed model representation. The watershed simulation model (GFLOOD) was developed to account for the complexity of the watershed including the variations in climate, soils, topography, and landuse conditions across the watershed. GFLOOD stands for Guelph Flood Forecasting Model, a river basin or watershed scale flow prediction model. Two major modelling components of the GFLOOD model are the time parameters (time of concentration (Tc) and recession constant (K)) and the channel routing component. Each of these modelling components is evaluated separately. The equations developed in this study for estimating the time parameters can be used as an initial estimate for Tc and K for ungauged basins, and through calibration and/or sensitivity analysis the values of Tc and K can be finalized. The Saint Venant equations for flood routing are solved by transforming the momentum equation into a partial differential equation which has six parameters related to cross-sectional area and discharge of the channel, left floodplain and right floodplain. The simplified dynamic model was further modified to account for transmission losses, evaporation losses and bank storage within the channel. The model was compared with the solutions of the general dynamic wave model, diffusion wave model and the more complex dynamic wave model. The comparison shows that there is good agreement between the results of the simplified dynamic model and the other models however, the simplified dynamic model is easier to formulate and compute than the other models. The complete GFLOOD model was applied to the Welland River Watershed within Southern Ontario. The model was evaluated for its ability to predict streamflow and water levels along the main branch of the Welland River.

The study is experimentally inclined, with a high target precision for performance measurement. A comprehensive programme of measurements was carried out in a two-storey building, having a massive structure and dating from 1970. Measurements were made continuously during the heating season from a total of about 70 points. Readings were taken every 30 seconds, and the mean values stored in a computer every 15 minutes. Analysis of the results have been concentrated on: * Thermal inertia, and particularly that of cooling mechanisms. * Time delays in heat flows through the building envelope in response to variations in ambient temperature. * The amount of solar input beneficially retained when operating with night setback and with normal operation. The results indicate that the building has both a long time constant, of about 200 h, and a short one, of about 1.5 h. The magnitude of the shorter time constant depends on the thermal capacity of the interior of the building (furniture, curtains etc.), and can be regarded as having some validity for other apartment building stock. Analyses of temperature gradients in the internal surfaces of the exterior walls indicate that the building's ventilation system, which was originally constructed as an exhaust air ventilation system, but with the inflow of fresh air blocked off, generates a dynamic insulation effect. Calculations indicate that this effect can provide a saving of 6 % of the total heating requirement, excluding that for domestic hot water. Investigation of the static heat requirement with and without night set-back indicate a considerable potential annual saving of heating energy, amounting to a maximum of 13 %, provided that the building is heated in accordance with a prescribed strategy. A 'comfort indoor temperature' has also been determined, being the temperature above which the occupants of the building consume excessive heating energy. Theoretical models have been derived to illustrate the short time constant and to analyse the dynamic insulation effect noted. / <p>Diss. Umeå : Umeå universitet, 1987</p> / digitalisering@umu

Η δυναμική ανάλυση των ηλεκτρικών μηχανών αποτελεί ένα πολύ σημαντικό πεδίο της μελέτης των ηλεκτρομηχανικών συστημάτων. Στην παρούσα διπλωματική θα ασχοληθούμε με τη δυναμική ανάλυση της σύγχρονης μηχανής που συναντάμε στην μετατροπή μεγάλης ποσότητας μηχανικής ενέργειας σε ηλεκτρική. Στόχος της παρούσας διπλωματικής είναι η μελέτη της συμπεριφοράς της σύγχρονης μηχανής σε περίπτωση μεταβατικών φαινόμενων, καθώς, επίσης, ο προσδιορισμός των μεγεθών, των παραμέτρων και των σταθερών χρόνου της μηχανής, που καθορίζουν τη συμπεριφορά της, στην περίπτωση τέτοιων φαινομένων. Οι χαρακτηριστικές παράμετροι των μεταβατικών και υπομεταβατικών αντιδράσεων και των σταθερών χρόνου της σύγχρονης μηχανής που επιχειρήθηκαν να προσδιοριστούν, χρησιμοποιούνται εδώ και 75 χρόνια, ώστε να δίνουν μια πρώτη προσέγγιση του μεγέθους των ρευμάτων βραχυκυκλώματος καθώς και το ρυθμό με τον οποίο αυτά μειώνονται. Επιπροσθέτως, η γνώση των μεγεθών αυτών δίνει τη δυνατότητα υπολογισμού των μηχανικών καταπονήσεων των τυλιγμάτων του στάτη που είναι αποτέλεσμα των υπερβολικών ρευμάτων που διαρρέουν τη μηχανή κατά τη διάρκεια ηλεκτρικών διαταραχών που υφίστανται οι ακροδέκτες της. / The dynamic analysis of electrical machines constitutes a very important field of the study of electromechanical systems. In the present project we will deal with the dynamic analysis of synchronous machine that we meet in the transformation of mechanical energy into electrical. The goal of present thesis is the study of the behavior of synchronous machine in case of transient phenomena and the determination of the parameters and time constants that determine its operation in such phenomena. The characteristic parameter of transient and subtransient reactances and time constants of synchronous machines that we tried to determine, have been used about 75 years, and for many purposes. Initially, such reactances and time constants were calculated to give both machine designers, and users, of synchronous machines a first-hand knowledge of-short-circuit current magnitudes and their rate of change. Such magnitudes are important in establishing switchgear fault rating. This knowledge also enables mechanical stresses to be calculated between armature winding resulting from excessive currents that occur during electrical disturbances at or near the synchronous machines terminals. In addition, protective schemes could be devised so that relays could be correctly calibrated to trip armature or field circuit breakers, and thus remove faulted machines from the power systems.

La problématique développée dans cette thèse est le diagnostic des piles à combustible (PAC) de type « Proton Exchange Membrane » (PEM). Nous avons choisi d’axer ces travaux sur différentes méthodes de diagnostic, séparées en deux grandes thématiques, relativement différentes et donc indépendantes, qui forment les deux parties de cette thèse. Dans la première partie, intitulée « Méthodes de diagnostic des fuites internes », nous nous focaliserons sur un type de dégradation des PAC, celle de la membrane, et de sa conséquence principale, l’augmentation des fuites internes. Après avoir fait l’inventaire des différentes techniques de diagnostic possibles, nous avons eu l’opportunité d’en tester certaines sur un stack (empilement de cellules élémentaires) dégradé dont nous disposions. La voltammétrie cyclique semble la plus intéressante en terme de précision. Cependant, pour le diagnostic complet d’un stack, le niveau de fuite de chaque cellule doit être évalué. Il apparaît que cette opération est extrêmement chronophage ; nous avons donc dû mettre au point des méthodes alternatives à celles rencontrées fréquemment dans la littérature. Nous avons d’une part appliqué la voltammétrie cyclique directement aux bornes du stack et parallèlement nous avons mis au point une technique nouvelle de diagnostic des fuites internes d’une PAC. Ces méthodes seront testées sur trois stacks comportant chacun un nombre différent de cellules. La deuxième partie de ce manuscrit est intitulée « Méthodes de diagnostic en gaz actifs ». Nous aborderons dans un premier temps une méthode bien connue, la Spectroscopie d’Impédance Electrochimique (SIE). L’utilisation de cette technique soulève deux problématiques : le choix d’un modèle approprié pour décrire des phénomènes physico-chimiques variés puis la difficulté de converger vers un jeu unique de paramètres une fois le modèle établi. Partant de ce constat, nous avons développé une technique originale d’exploitation des SIE, basée sur un modèle électrique sans a priori, dont la construction va se faire automatiquement étape par étape. Cet algorithme sera validé de manière théorique sur des simulations, puis nous confirmerons son potentiel sur des données expérimentales issues d’essais de vieillissement de monocellules. Parallèlement, nous avons développé une technique alternative à la spectroscopie d’impédance, basée sur l’exploitation d’échelons de courant. Cette méthode permet d’extraire un spectre de constantes de temps sans passer par de l’identification paramétrique. Après une première validation théorique grâce à des simulations, nous avons éprouvé cette technique avec d’une part les données de vieillissement mentionnées précédemment ainsi qu’avec des données issues d’un essai d’engorgement d’une monocellule. Nous confirmerons que cette technique est bien adaptée pour effectuer du diagnostic en cours de fonctionnement. / This thesis deals with Proton Exchange Membrane Fuel Cell (PEMFC) diagnosis. Several methods will be treated, that have been divided into two main issues. These issues are quite independent and constitute the two parts of the manuscript. The first part, entitled “internal leakage detection methods”, concerns a major fault in PEMFC: membrane permeation. The consequence is the increase of internal leakage, or crossover. First, several diagnosis techniques are listed, and some of them are tested on a faulty stack. Cyclic voltammetry seems to be a good choice, but needs a lot of time to be performed on a large scale stack. Indeed, to achieve a satisfying level of diagnosis, the crossover of every cell in the stack has to be evaluated. New diagnosis techniques are needed to shorten the test phase. Cyclic voltammetry is performed directly at the stack level, while concurrently a new method is investigated to measure all cell crossovers simultaneously. Validation is done by experiments on three different stacks with different numbers of cells. The second part is entitled “diagnosis methods with active gases”. In a first time the well-known Electrochemical Impedance Spectroscopy (EIS) technique has been used as a characterization tool. But two issues arise from the EIS use: the choice of an appropriate model that describes all the electrochemical phenomena and the difficulty to obtain a unique set of parameters after the fitting stage. To solve these issues, an algorithm has been developed. It is based on an electrical circuit model built automatically step by step, which does not require the knowledge of every phenomenon of the studied system. The algorithm is validated theoretically by numerical simulations and then by experimental data collected from ageing tests with single cells. Secondly, a method alternative to EIS has been investigated, based on the fuel cell voltage response to current steps. A time-constant spectrum can be extracted from this response without the need of parameter identification process. After a first validation thanks to numerical simulations, this algorithm has been tested with the ageing data previously mentioned and also with a flooding experiment performed on a single cell. The time-constant spectrum seems to be an appropriate tool for fuel cell online diagnosis.

L'intégration des sources d'énergies renouvelables sur le réseau électrique est complexe en raison de leur nature intermittente et décentralisée. Le micro-réseau est une approche prometteuse pour interconnecter des générateurs distribués (DGs) locaux, alimenter des charges locales et également échanger de l'énergie avec le réseau électrique de manière contrôlée. Ce mode de production/consommation locales permet d'éviter la transmission d'électricité sur de longues distances, et implique donc une plus grande efficacité. Ces travaux se concentrent sur l'analyse et le contrôle du micro-réseau continu afin que les DGs se répartissent l'alimentation des charges et qu'ils maintiennent également la tension du bus continu. À l'équilibre, les contraintesde la commande du statisme classique (droop control) pour un système comportant de multiples DGs sont analysés, et une méthode de compensation mixte est proposée pour améliorer simultanément le maintien en tension et le partage du courant de charge. En dynamique, le modèle global du système est construit en introduisant une inductance virtuelle dans le circuit équivalent du DG, puis plusieurs modèles d'ordre réduit sont examinés pour vérifier leur efficacité dans l'analyse de la stabilité du système. Un modèle multi-échelle d'ordre réduit (RMM) est proposé afin de conserver les contraintes temporelles ainsi que de réduire la complexité du système. Enfin, une méthode basée sur le contrôle de rejet de perturbation active (ADRC) est présentée afin de mettre en oeuvre le contrôle local de la tension des DG en prenant en compte l'échelle de temps. Cette méthode permet d'améliorer la dynamique du système de contrôle en ajustant la largeur de bande passante de la commande et de l'observateur. Les analyses et les méthodes de contrôle proposées sont vérifiées par des essais expérimentaux dans notre plateforme au laboratoire. / The direct integration of renewable energy resources to the utility grid is pretty tough due to their intermittent feature and dispersed nature. Microgrid is one promising approach to gather the local distributed generators (DGs), supply local loads as well as exchange power with the utility grid as a controllable unit. This local-generation-localconsumption mode is able to avoid the long distance power transmission, thus can benefit a higher efficiency. The control aim of DC microgrids is to make the multiple DGs share the load properly as well as maintain the DCbus voltage stable. In steady state, the constrains of the classic droop control in multiple DGs environment are analyzed, and a mixed compensation method using common current is proposed to improve the voltage and load sharing performance simultaneously. In dynamic state, the system comprehensive model is constructed by the introduction of virtual inductor in the equivalent circuit of the DG, then several reduced-order models are examined to check their effectiveness for the system stability analysis. A reduced-order multi-scale model (RMM) is proposedto keep major time scale information as well as reduce the system complexity. Finally, an active disturbance rejection control (ADRC) based control method is proposed to realize the time scale droop control. It can effectively adjust the dynamic of the local control by adjusting the bandwidth of the Linear Extend State Observer or/and the controller. The proposed analysis and control methods are verified by experimental tests in our laboratory platform.

Two separate problems are to be investigated in this thesis. The first problem is the propagation of waves through a short rod (or slug) of viscoelastic material. The second problem is the study of impact of a short viscoelastic rod (or slug) on a stationary semi-infinite viscoelastic. rod. The viscoelastic materials are modelled as standard linear solids which involve 3 material parameters and the motion is treated. as one-dimensional. For the first study, a viscoelastic slug is placed between two semi-infinite elastic rods and a wave initiated in the first rod is transmitted through the slug into the second rod. The objective is to relate the transmitted signal to the material parameters of the slug. We solve the governing system of partial differential equations using the Laplace transform and we examine the propagating velocity discontinuity using discontinuity analysis and the limit theorem of the Laplace transform. We then approximate the solution of the propagating disturbance using the regular perturbation method. We invert the Laplace transformed solution numerically to obtain the transmitted signal for several viscosity time constants and ratios of acoustic impedances. We compare the results obtained using the above techniques. In the second problem, we first model the impact and solve the governing system of partial differential equations in the Laplace transform domain. Then we examine the propagating stress and velocity discontinuities using discontinuity analysis. We approximate the solutions of the propagating stress and velocity using the regular and multiple scales perturbation methods. In this problem, we first consider the slug is elastic and the rod is viscoelastic. Secondly, we consider the slug is viscoelastic and the rod is elastic and thirdly, we consider both materials are viscoelastic. Numerically we invert the Laplace transformed solutions for the interface stress and interface velocity for several viscosity time constants and ratios of acoustic impedances to determine whether the slug and the rod part company or remain in contact. Then we compare the results obtained using the discontinuity analysis, regular and multiple scales perturbation methods.

No description available.

Dialogue Enhancement (DE) is a process used in audio delivery systems to improve the clarity, intelligibility, and overall quality of the spoken dialogue in audio content. It is primarily used when dialogue is masked by music, surrounding noise, or other audio sources. This thesis project involves experiments to find the optimal time and frequency resolution needed for a DE system. The time resolution focuses on experimenting with various attack/release times for a DE system. The frequency domain analysis investigates whether people prefer a noise spectrum-dependent gain over a conventional full-band gain. The research methodology comprises three main parts. The first part focuses on system setup and choosing content/vectors to be used for the experiments. Next, the experiments are designed for time and frequency resolution. An exponential smoothing model is used to amplify/attenuate the dialogue stream at various times of attack/release. For the frequency counterpart, a banded gain model is designed which uses banded noise levels as input. Subsequently, a modified subjective listening test is designed to evaluate the experiments designed. The responses recorded for various types of content-noise combinations from the listeners are recorded and analyzed. Finally, the main outcome of this research emphasizes the advantages of a DE system. Further, it paves the way for further exploration of DE models and rigorous testing schemes with expert listeners. / Dialogue Enhancement (DE) är en process som används i ljudleveranssystem för att förbättra tydligheten, förståeligheten och den övergripande kvaliteten på den talade dialogen i ljudinnehåll. Det används främst när dialog maskeras av musik, omgivande brus eller andra ljudkällor. Detta examensarbete omfattar experiment för att hitta den optimala tids- och frekvensupplösningen för ett DEsystem. Tidsupplösningsexperimenten fokuserar på olika attack- och releasetider för ett DE-system. Frekvensdomänanalysen undersöker om människor föredrar en brusspektrumberoende förstärkning framför en konventionell fullbandsförstärkning. Forskningsmetodiken består av tre huvuddelar. Den första delen fokuserar på systeminställning och val av innehåll/vektorer som ska användas för experimenten. Därefter designas tids- och frekvensupplösningsexperimenten. En exponentiell tidsenvelopp används för att förstärka/dämpa dialogen vid olika tider för attack/release. För frekvensdomänexperimenten används en bandad förstärkningsmodell som använder bandade brusnivåer som insignal. I den tredje delen utformas ett subjektivt lyssningstest för att utvärdera experimenten. Lyssnarnas svar för olika typer av innehåll-bruskombinationer registreras och analyseras. Det huvudsakliga resultatet av denna forskning betonar fördelarna med ett DEsystem. Vidare banar det väg för utforskning av fler DE-modeller och rigorösa testscheman med expertlyssnare.