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With the growing interconnection among distant power grids, low‐frequency oscillation problem across wide area arises in some modern power systems. This oscillation problem is commonly regarded as lack of damping in inter‐area oscillation modes in the sense of small signal stability. Solutions to this problem need to be implemented in the power systems. On the other hand, wind power especially largescale wind farms are increasingly integrated into modern power systems and bring new challenges to power system operation and control. The influence of wind power integration on system oscillation performance needs to be investigated. And according to some grid code requirements, power system oscillation damping improvement supplied by wind farms might become necessary. Under this circumstance, the present dissertation aims at studying oscillation damping control strategies using different components in the power system; investigating the possible influence of large‐scale wind power integration on system oscillation performance; developing oscillation mitigation strategies for wind farms; and coordinating various damping controllers in the power system. For the power system operation aspect, an optimal power flow (OPF) strategy is introduced, with system oscillation damping considered in the constraints of the optimization process. The method is validated by simulations in two test systems. For the power system control aspect, an optimal PMU placement method is used so as to provide full topological observability of the target power system and to provide wide‐area signals for damping controllers while minimizing the total PMU installation cost. Power system stabilizer (PSS) designs with both local input signal and wide‐area input signal are studied and compared. The PSS design is based on residue method and a residue identification technique is used. Furthermore, a particle swarm optimization (PSO) based coordinating strategy to select the locations, input signals and parameters of multiple PSSs is proposed. Simulation results show that this method is able to find a group of PSSs to improve the target mode damping to a certain level, while keeping the total magnitude of the PSSs low (so that the outputs from the PSSs could be kept low).A supplementary damping controller is integrated in the control system of a static synchronous series compensator (SSSC). The design is also based on residue method and residue identification. Simulation results show the effectiveness of this damping controller under different operating conditions of the SSSC. Influence of a direct‐drive‐full‐convertor based wind farm ancillary frequency control and voltage control on power system oscillation performance is investigated by observing the oscillation damping change in relation with the change of the ancillary controller parameters. Furthermore, the forced oscillation in the power system activated by the wind power oscillation due to wind shear and tower shadow effects is analyzed. The forced oscillation amplitude is found to be dependent on the location of the wind farm, the amplitude and frequency of the wind power oscillation and the damping ratio of the system oscillation modes. To mitigate the forced oscillation, two types of controllers are designed to reduce the wind power oscillation amplitude and to increase system oscillation mode damping ratio, respectively. The former controller is implemented in individual wind turbines; the latter controller is implemented in the wind farm level as a supplementary damping controller.Finally, the coordinating selection and parameter design strategy for PSS is extended for all types of damping controllers (including PSS in synchronous generator, SSSC damping controller and wind farm damping controller). Simulation results show the effectiveness of this strategy for coordinating various damping controllers.

Interaktionen mellem af vandbølger og en cirkulær konstruktion, det såkaldte "wave run-up" fænomen er undersøgt. Dette run-up fænomen er blevet simuleret ved brug af CFD modeller.Den numeriske model (NS3) anvendt i dette studie er blevet verificeret på flere måder. Regelmæssige og såkaldte "monsterbølger" (freak- eller rogue waves) er blevet genereret i en numerisk bølgetank med en let hældning for at undersøge "wave run-up" på en cirkulær cylinder. Fra et beregningsmæssigt synspunkt er denne form for undersøgelse "billig". I øvrigt er den numeriske model præsenteret i denne afhandling sammenlignet med de målte resultater fra forsøget og en god sammenhæng er observeret.Udover denne numeriske undersøgelse, er et omfattende skalaforsøg udført. I forsøget er "wave run-up" på en tynd cirkulær cylinder i en uregelmæssig søtilstand blevet målt med bølgemålere placeret tæt på cylinderen. Baseret på passende analysemetoder er de indsamlede data blevet analyseret med strømfunktionsteorien for at opnå de relevante parametre til brug i den af den forudsagte "wave run-up" formel. En analytisk tilgang er blevet fulgt og løst for individuelle bølger. Maksimal "run-up" og 2% "run-up" er blev undersøgt for at opnå en bedre forståelse af fænomenet. Ifølge resultaterne fra denne analyse er det blevet fastslået, at "run-up" højder i høj grad er påvirket af bølgestejlheden på dybt vand. Samlet set er resultatet af dette studie, at den forenklede model af "wave run-up" på en slank cirkulær cylinder præsenteret i denne afhandling er det mest nyttigt redskab til platformsdesignere. This study has investigated the interaction of water waves with a circular structure known as wave run-up phenomenon. This run-up phenomenon has been simulated by the use of computational fluid dynamic models.The numerical model (NS3) used in this study has been verified rigorously against a number of cases. Regular and freak waves have been generated in a numerical wave tank with a gentle slope in order to address the study of the wave run-up on a circular cylinder. From the computational side it can be said that it is inexpensive. Furthermore, the comparison of the current numerical model presented in this thesis with the measured results from the experiments has shown a good agreement.Besides this numerical study, model scale experiments have been conducted where the wave run-up on a slender circular cylinder in irregular sea state was measured with surface gauges located close to the cylinder. Based on appropriate analysis the collected data has been analysed with the stream function theory to obtain the relevant parameters for the use of the predicted wave run-up formula. An analytical approach has been pursued and solved for individual waves. Maximum run-up and 2% run-up were studied to get a better understanding of the phenomenon. According to the results from this analysis it has been established that the run-up heights are largely influenced by the deep water wave steepness. Overall, the outcome of this research is that the simplified model presented in this thesis of the wave run-up on a slender circular cylinder is the most useful tool for platform designers.

Letvægtsbyggeri i træ vinder i øjeblikket indpas på grund af lave produktionsomkostninger og et miljøvenligt omdømme. Moderne produktionsteknikker muliggør præfabrikation af væg- og gulvelementer og sågar hele rum-elementer kan præfabrikeres. Anvendelsen af præfabrikation medvirker til at sikre en høj produktionskvalitet samt til at minimere både produktionsomkostningerne og risikoen for uforudsete hændelser og dyre forsinkelser af byggeriet.Den europæiske beregningsstandard EN 12354, der er baseret på en simplificeret statistisk energyanalyse (SEA) af delsystemer, er et værdifuldt værktøj tilberegning af flanketransmission af både luft- og strukturbåren lyd. Desværre opfylder lette bygningskonstruktioner typisk ikke forudsætningerne for ideelle delsystemer i SEA, hvorfor anvendelsen af EN 12354 kan resultere i upræcise resultater for letvægtskonstruktioner. Letvægtsbyggeri har ofte problemer med transmission af lavfrekvent lyd, da den lavere vægt af konstruktionerne påvirker lydisolationen negativt, særligt i det lavfrekvente område. Desuden ses det ofte, at lydisolationen varierer markant mellem tilsyneladende ens konstruktioner i lette boliger. Bedre beregningsmetoder er nødvendige for udviklingen af bedre konstruktioner, og dermed også for den fremtidige udbredelse af letvægtsbyggeri. For at kunne forbedre såvel beregningsmetoderne som selve konstruktionerne er det nødvendigt at kende kilderne til—samt størrelsen af—den observerede variation mellem tilsyneladende ens konstruktioner. For at kunne opnå en forståelse af årsagerne til disse variationer er det nødvendigt at undersøge delkonstruktioner og samlinger, eftersom kompleksiteten af hele bygninger nemt kan føre til at forkerte konklusioner drages, da letvægtsbygninger typisk ikke opfører sig som deterministiske systemer.Denne Ph.D.-afhandling omhandler forskellige emner relateret til de ovenstående problemstillinger. Først præsenteres en artikel der beskæftiger sig med modaltætheden i periodisk afstivede plader i det mellem- og højfrekvente område. Modaltætheden i sådanne plader er ikke uniformt fordelt, men i stedet har den en fluktuerende tæthed med tilhørende udbredelsesbånd og stopbånd. I artiklen vises det hvordan de strukturelle egensvingninger kan inddeles i to grupper således at den ene gruppe har stopbånd og udbredelsesbånd, men den anden gruppe har en næsten uniform modaltæthed. Den foreslåede tilgang til SEA for periodiske strukturer er da at betragte en periodisk afstivet plade som to SEA delsystemer: Ét delsystem indeholdende egensvingninger relateret til bølgeudbredelse parallelt med afstivningerne og et andet delsystem indeholdende egensvingninger relateret til bølgeudbredelse vinkelret på afstivningen. I artiklen benyttes Monte Carlosimuleringer til at undersøge modaltætheden for nominelt ens, periodisk afstivede plader.Efterfølgende præsenteres to artikler, hvori Finite-Element modeller udnyttes til parametriske undersøgelser af koblingsfænomener i letvægts-vægpaneler i det lavfrekvente område. Den ene artikel undersøger effekten af at inkludere luften inden i de enkelte celler i en pladebeklædt træskeletvæg, mens den anden artikel betragter en lignende vægkonstruktion, men fokuserer på forskellige strategier for modeleringen af koblingen mellem pladerne og træskelettet. Når FE modeller baseres på plade- og bjælketeori, kan koblingen mellem en plade og en bjælke modeleres enten som en linjekobling eller som diskrete punktkoblinger. Benyttes der derimod tredimensionelle kontinuumelementer i modellen, er situationen mere kompliceret. Undersøgelserne i de to artikler er foretaget som parametriske studier af FE modeller i den kommercielle softwarepakke ABAQUS.Slutteligt præsenteres en eksperimentel del af afhandlingen, hvori der fokuseres på usikkerheder og variation i træsamlinger. Ti ens plade/bjælke T-samlinger undersøges med eksperimentel modalanalyse og resultaterne diskuteres. Yderligere gennemføres en numerisk undersøgelse af robustheden af to højere-ordens metoder til bestemmelse af modalparametre og anvendeligheden for træsamlinger diskuteres. Resultaterne viser at der er signifikant forskel på de estimerede dæmpningsværdier for egensvingninger med stærk kobling mellem de strukturelle delelementer. Lightweight wood frame buildings are becoming popular due to low production price and a reputation of being friendly to the environment. Modern production techniques allow for factory assembly of panel modules—like walls and floors—or even complete rooms preassembled as volume elements. The high degree of off-site assembly allows for a high quality production and helps minimize both production costs and the risk of unforeseen events that could otherwise lead to costly delays.The standard EN 12354, describing a simplified statistical energy analysis (SEA) subsystem approach, provides a valuable tool to predict the flanking transmission of air-borne and structure borne sound already at the design stage. However, lightweight building structures typically do not meet the requirements for ideal SEA subsystems and, therefore, applying the EN 12354 standard to lightweight building structures may result in imprecise predictions. Furthermore, lightweight buildings have low-frequency problems due to the low mass of the structure and often unpredictability (variation) between the building acoustic performance of supposedly identical dwellings can be observed. Therefore, better prediction methods are essential to the development of better designs and thus to the future of lightweight buildings. In order to improve both structures and prediction models, the sources—and magnitude—of variation must be determined. In the pursuit of understanding of the nature of this variation, simplified structures and junctions need to be considered, as the complexity of complete buildings can lead to conclusions which are possibly not true for similar buildings due to the non-deterministic nature of lightweight buildings.The present doctoral thesis covers various topics related to the issues mentioned above. First, a paper about the modal density of ribbed plates at mid/high frequencies is presented. The modal density in such plates is not a uniform distribution, but instead it undergoes an undulating behavior with corresponding pass bands and stop bands. It is demonstrated, how the modes can be divided in two groups, where one group shows pass band/stop band behavior, while the other has a nearly uniform distribution of modes. The suggested approach for SEA adaptation is to consider a ribbed plate as two SEA subsystems: One that contains modes related to waves traveling in the direction orthogonal to the ribs, while the other subsystem contains modes related to waves traveling parallel to the rib stiffeners. The investigations utilize Monte Carlo simulations to examine the behavior of nominally identical plates.Next, two papers that utilize the Finite-Element Method, focusing on aspects of modeling ribbed wall panels in the low-frequency range, are discussed. One paper investigates the effect of including an acoustic medium (air) inside the bays of a single-stud double-plate wall panel, while the other paper considers different approaches for modeling plate/frame couplings in FE models, which utilize full three-dimensional, solid continuum finite-elements. When using structural elements such as beams and shells, couplings may be modeled as either line or point coupling. However, when utilizing full three-dimensional, solid finite-elements, the scenario is not that simple. The investigations of both papers are carried out as parametric studies in the commercial FE package ABAQUS.Finally, an experimental part, that focuses on the uncertainty and variation in wooden junctions, is included. Ten nominally identical plate/beam T-junctions are tested using experimental modal analysis, and the results are discussed. Furthermore, a numerical study of the robustness of two higher-order modal parameter estimation methods is conducted in order to assess the applicability of modal analysis on such junctions. The results demonstrate significant variation in the estimated modal damping at modes with strong coupling between different parts of the structure.

Bladet beskriver fugtpåvirkninger, -mekanismer og materialer samt forskellige metoders anvendelse i bygninger med kældervægge udført af beton, letklinkerbeton og fundamentsblokke

A numerical model simulating the sediment transport due to plunging breaking waves has been developed. The model is two-dimensional, assuming conditions in the long-shore direction invariable. A plunging breaker is simulated by superimposing a non-breaking wave with a jet.Based on the description of the sediment transport rates, a simple model describing the morphological changes has been applied to simulate the evolution of a plunge point generated vorticity included, the bottom topography from the experiments by Dette & Uliczka was not in equilibrium according to the model.

Glasfacader er et stadigt mere dominerende valg af facadeløsning til kontorbyggeri. Glas har altid været attraktivt og spændende og har været et symbol på magt, penge og prestige. Facaden er et kommunikationsmiddel, et billede af prestige of magt. Glasfacaden lider dog voldsomt når energiforbruget af bygninger analyseres. Glasfacaden bidrager til højere energibehov til opvarmning, køling, osv. Glasfacaden har derfor behov for at overvinde væsentlige udfordringer for at forblive en attraktiv facade løsning i fremtidens nul energi byggeri.Ved brug af energiberegningsprogrammer og termisk simulerings værktøjer foretages den indledende analyse i denne afhandling af glasfacadens potentiale for en typisk kontorbygning i Danmark med glasfacade der opfylder energikravene fra 2008, for at mindske energibehovet til bygningsdrift som følge heraf. Denne simple analyse definerer de nøgleteknologier, der efterfølgende fokuseres på. Fokuseringen på hver enkelt teknologi udføres ved brugen af fuldskala forsøg af hver enkelt teknologi under varierende randbetingelser.Resultaterne fra demonstrationsforsøgene bliver efterfulgt af en udvikling af numeriske modeller tilknyttet de enkelte teknologier til brug i termiske simuleringsprogrammer samt til implementering i produktudvikling. Resultaterne fra den indledende analyse viser potentialet af en dynamisk facade, som muliggør variation af varmetabet, solenergitransmittansen, dagslys transmittans, masse transport og termisk energilagring. Potentialet fra denne analyse viser at for en typisk kontorbygning med den dynamiske glasfacade i sammenligning med den statiske glasfacade kan reducere bygningers energibehov til bygningsdrift med ca. 75 %. Fokusset flyttes derfor til de anvendte teknologier, der vedrører dynamisk U-værdi, dynamisk g-værdi, termisk energilagring og styringsstrategier for de anvendte facade teknologier. Fuldskala forsøgene anvendes til demonstration af de enkelte teknologiers ydeevne samt til validering af de udviklede numeriske modeller. De udviklede modeller viser en god beskrivelse af de anvendte teknologiers funktion og karakteristika både i termiske simuleringsprogrammer såvel som i koblingen mellem styring i termiske simuleringsprogrammer og fuldskala bygnings styringssystemer. Potentialet af facadens styringsstrategi vist numerisk, viser energibesparelsespotentialer for køling, opvarmning og belysning på mellem 50 % og 88 % som følge af facadens design og brug.De opnåede resultater fra den indledende analyse efterfulgt af udviklingen af de numeriske modeller af de anvendte facade teknologier, viser at der er væsentlige energibesparelser at hente i udformningen af den dynamiske facade. Energibesparelserne skal dog undersøges nærmere under mere kontrollerede laboratorieforhold for at kunne danne mere præcise data og numeriske modeller af de anvendte teknologier. Den videre udvikling af dynamiske facadeteknologier, som er i stand til at kontrollere energibalancen over facaden i samspil med brugere for at kunne udnytte og forstår det fulde potentiale af adaptive glasfacader. Glazed facades are becoming an increasingly dominant choice of facades for office buildings. Glass has always been attractive and intriguing and has been a symbol of power, money and prestige. The façade is a means of communicating an image of prestige and power. However the glazed suffers tremendously when analyzing the energy usage of a building. Glazed façade contribute to higher energy demand for heating. cooling, etc. The glazed façade therefore has significant challenges to overcome in order to remain as an attractive envelope solution in future zero-energy-building concepts.Through the use of energy calculation software and thermal building simulation software the initial analysis in this thesis strives towards defining the potential of controlling the energy transport across the façade. The simple analysis defines the key technologies to focus on as a result. The focus on each technology is to perform full-scale experiments on each technology showing the performance of the technology under varying boundary conditions. The results from the demonstration are then followed by a numerical model development of the technologies applied for use in thermal building simulation software as well as in practical façade control systemsThe results from the initial analysis show the performance of a dynamic façade which enables the variation of the heat transfer, transmitted irradiance, transmitted natural light, mass transport and thermal energy storage. The potential from this analysis show that the dynamic façade opposed to the static façade can decrease energy demand for building services by approximately 75 %. The focus is therefore on analyzing the used technologies which concern dynamic U-value, dynamic g-value, thermal energy storage and control strategies for dynamic facades. The full-scale experiments are used as demonstration and for validation of the performance of the developed numerical models. The developed numerical models show a good description of the applied technologies and show that the variation of the technologies function and characteristics can both be done through use of thermal building simulation software as well as full-scale experiments. The façade control system, which uses the results from the developed numerical models of the dynamic façade technologies, can lower the energy demand for heating, cooling and lighting as a results of the heat transfer across the façade by between 50 % and 88 %.The obtained results from the initial analysis through the developed numerical models to the final analysis show that there are significant energy savings in the design of the dynamic façade. The energy savings need to be further investigated under laboratory conditions generating more precise data and description of the used technologies. The further development of dynamic façade technologies which are able to control the energy balance across the façade is also necessary to analyze the behavior in practice and to gain knowledge of the human interaction with the adaptive glazed façade.

Nyt studie har vist, at den genetiske risikovurdering af type 2-diabetes kan forbedres betydeligt ved at inkludere genomisk information fra syv andre korrelerede egenskaber.

The present thesis deals with the transport phenomena of estuarine cohesive sediment from a laboratory and a numerical point of view. The cohesive sediment used throughout the whole process was natural mud from the Danish part of the Wadden sea, Ho Bay. In the laboratory, the work was concentrated on studies of the settling velocity of particles under conditions with various salinities and suspended sediment concentrations, erosion of deposited material and compression and consolidation of deposited material due to self-weight.As part the project, equipments for settling, consolidation and erosion experiments were developed. The settling and consolidation experiments were carried out in a transparent cylinder with a diameter of 190 mm and variable height. The erosion experiments were carried out in a circular flume with a mea diameter of 1700 mm, a width of 200 mm and a depth of 260 mm.A one dimensional numerical model was developed describing the material distribution in suspension and within the bed and the transfer processes, namely, erosion and deposition. The model was calibrated using the laboratory experiments.

Gennem de sidste årtier har begrebet arbejdsmiljø konstant været i fokus. Det hænger både sammen med en stigende miljøbevidsthed og voksende krav til livskvaliteter. Arbejdsmiljøet omfatter en lang række områder som f.eks. fysisk- og psykisk arbejdsmiljø, sikker hed, akustik, støj, termisk miljø, luftkvalitet etc. Alle sammen områder der har stor betydning for det almene velbefindende såvel på arbejdet som i fritiden.