This diploma thesis deals with the determination of lifetime and computational modeling of stress strain states arising in the body of the steam turbine valve. Due to the high temperature of the inlet steam, the creep of the material which fundamentally affects its final lifetime is also considered in the calculation. The lifetime is evaluated by four different procedures using the finite element method via the ANSYS software. The results are compared at the end of this work. One of the chapters is focused on solving the problem of the creep in the ANSYS software environment.

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This diploma thesis deals with the influence of range of reconstruction on the price of building construction. Effect of the extent of reconstruction consists in comparing of the total costs of the bridge during reconstruction of the top of the bridge leaving the main structure and during the reconstruction realized with the exchange of the main supporting structure. The total costs incurred are expected for 60 years.

Den Fokus dieser Arbeit bildet die Untersuchung und die konzeptionelle Verbesserung der wichtigsten Eigenschaften organischer Leuchtdioden (OLED) – die Lebensdauer und die Quantenausbeute, welche sich durch die interne und externe Quanteneffizienz kategorisieren lässt. Es werden monochrome pin- Strukturen betrachtet, welche die Basis für Displays und weiße Multifarben- OLEDs darstellen. Die Auswirkung der Ladungsbalance auf die interne Quanteneffizienz wird untersucht. Dabei finden Triplettemitter Verwendung, da diese aus spinstatistischen Gründen viermal effizienter als fluoreszente Substanzen sind. Für hohe Effizienzen ist die ambipolare Ladungs- und Exzitonenverteilung in der Emissionsschicht mit breiter und zentraler Rekombinationszone anzustreben. Dies wird durch einen energetisch barrierefreien Schichtaufbau über die Auswahl der Matrix-, Blocker- und Transportmaterialien bezüglich geeigneter Transportniveaus und Ladungsträgerbeweglichkeiten erreicht. Bei roten OLEDs wird durch den Austausch des Lochblockers mit geeignetem LUMO die Elektroneninjektion in die löcherleitende Emissionsschicht erhöht und dadurch die Ladungsbalance maximiert. Damit werden externe Quanteneffizienzen von 20% erzielt, was dem Maximum der internen Quanteneffizienz von 100% entspricht. Des Weiteren werden neue Konzepte zur höheren Lichtauskopplung entwickelt. Aufgrund interner Totalreflexionen bleiben 80% der Photonen in Organikund Substratmoden gefangen was die externe Quanteneffizienz begrenzt. Eine deutliche Reduzierung dieser Moden wird bei OLEDs mit stärkeren Mikrokavitäten durch ITO/Silber-Anoden festgestellt. Die energetische und räumliche Umverteilung der Photonen verringert Totalreflexionen womit die Auskopplung bzw. die externe Quanteneffizienz um den Faktor 1,5 erhöht wird. Für rote OLEDs werden dadurch Rekordwerte von 26% externer Quanteneffizienz und einer Leistungseffizienz von 81 lm/W erzielt. Die auftretende winkelabhängige Farbverschiebung kann durch streuende Mikrolinsenfolien reduziert werden. Für verbesserte Auskopplung ohne Farbverschiebung werden Streukonzepte mit rauen Schichten getestet. Kristalline Schichten innerhalb der Organik beeinflussen allerdings den elektrischen Teil der OLED. Dies wird durch extrinsische Verlagerung der Streuschicht ausgeschlossen. Weiterhin wird die intrinsische Degradation von OLEDs mit phosphoreszenten Iridium-Emittern untersucht. Als Hauptursache werden strominduzierte chemische Reaktionen zwischen Emittermolekülen und anderen umgebenden Substanzen identifiziert. Die Akkumulation von Ladungsträgern und Exzitonen fördert diese Reaktionen. Als Zerstörungsmechanismus wird die Dissoziation der Iridium-Emitter mit folgender irreversibler Komplexbildung der Fragmente mit Umgebungsmaterialien wie dem Lochblocker festgestellt. Die OLED-Lebensdauer korreliert dabei doppelt- logarithmisch mit der Anzahl der Komplexe. Die chemische Reaktivität der Umgebungsmaterialien bestimmt die Stärke der Komplexbildung. Mit inerten Substanzen konnte bei roten OLEDs mit 10 Millionen Stunden bei Display-Helligkeit ein Weltrekord erzielt werden. Die geringe Degradation erfordert Extrapolationsmethoden. Es wird ein gestreckt exponentielles Verhalten der Helligkeitsabnahme beobachtet. Eine neue Fehleranalyse der Extrapolation ermöglicht die Angabe von Lebensdauer-Infima bei sehr stabilen OLEDs.

Organic solar cells promise electricity generation at very low cost, and higher installation flexibility as compared to inorganic solar cells. The lower cost is achieved by cheaper semiconductors and easier manufacturing processes. The flexibility is naturally given by these ultra-thin, amorphous layers. Also the power conversion efficiency can be high enough for many applications. The organic molecules have to withstand the constant excitation by photons, transport of energy in form of excitons and charge. A small but significant amount of these photons has energy over the absorption gap, the excess of energy must be released without breaking the molecular bonds. In consequence, the solar cells can also heat up to temperatures at above 80°C. The objective of this work is to answer the question if the small molecules organic solar cells can be stable enough to operate under a very long time. The stability of organic doped layers in an organic solar cell is also addressed. This work starts with a general introduction followed by the description of the experimental procedures. The aging experiments of the solar cell were done with a self developed equipment. The fabrication of this equipment (a set of measurement boxes) was necessary to maintain the conditions, under which a solar cell can be aged, as constant as possible. The measurement boxes were used to control the electrical load of the cell, its temperature, the illumination intensity, and its electric connection to the IxV measurement equipment. A software package was also developed to control the equipment and to facilitate the work and visualization of the high volume of collected data. The model solar cells chosen for the aging experiments were donor-acceptor heterojunctions devices formed with the well-known materials C60 and ZnPc. Two basic different structures were analyzed, because they offered reasonable performance and potentially long lifetime: the flat heterojunction (FHJ) and the mixed heterojunction in a Metal-Insulator-p-Semiconductor (m-i-p) configuration. Variations of the FHJ and of the m-i-p structures are also used to verify the limits of the stability of electrically p- and n- doped organic semiconducting layers. The least stable solar cells are the FHJ devices. These devices show a fast initial decrease of all their characteristic conversion parameters but the Voc. After a few hundred hours, the saturation current (current under a reverse bias of 1 V) was almost stable. The saturation current is related to the number of absorbing centers, the decrease indicates that the degradation of the absorbing centers has stopped. With wavelength resolved external quantum efficiency measurements and chemical analysis, it was found that the degradation is related to the oxidation of C60. It was also shown that the use of organic dopants do not significantly affect the lifetime. The results show that the m-i-p solar cells are more stable than the FHJ devices. They are also stable under high temperatures up to 105°C. Outdoor testing also showed that the solar cells remained chemically, electrically and mechanically stable during a 900 h test.

Die bei Textilbetonbauteilen üblicherweise zum Einsatz kommenden Bewehrungen können sowohl aus Carbon oder AR-Glas bestehen. Aufgrund des Preises und der Verfügbarkeit hat AR-Glas gegenüber Carbon allerdings eine deutlich größere Verbreitung am Markt. Trotz der chemischen Modifikation zur Verbesserung der Alkalibeständigkeit von AR-Gläsern gegenüber E-Glas, kann bei AR-Gläsern ein nennenswerter Festigkeitsverlust infolge der Alkalität des Betons innerhalb der Lebensdauer eines Bauwerks festgestellt werden. Eine Möglichkeit den langfristigen Festigkeitsverlust zu reduzieren, ist der Aufbau einer Diffusionsbarriere um die einzelnen Rovings durch eine polymere Tränkung. Im Rahmen der vorliegenden Veröffentlichung werden mögliche Tränkungsmaterialien sowie die Auswirkungen dieser auf die Dauerhaftigkeit der textilen Bewehrungen anhand von Versuchen bewertet und ein Modell zur Prognose des langfristigen Festigkeitsverlustes polymermodifizierter Bewehrungen vorgestellt. / The reinforcement in TRC (Textile Reinforced Concrete) is usually made of alkali-resistant glass rovings due to their low price and availability on the market, but even the glass composition is changed compares to E-glass to increase its alkali resistance the durability in concrete is known to be unsatisfactory. One possibility to increase the durability is the application of a diffusion barrier around the reinforcement. The diffusion barrier can be made out of reactive polymeric coatings. Within the paper the results regarding the durability of AR-glass reinforcement achieved with a variety of reactive materials, mainly epoxy resins, will be presented as well as discussed. In addition to the results achieved in the laboratory, a model which allows long term predictions of the durability of polymer impregnated AR-glass reinforcements will be presented.

More and more pressure is exerted on railway infrastructure due to an increasing transportation demand and population density. Instead of expanding the net, a possible solution could lie in the enlargement of the capacity by operating longer trains rather than more short ones. However, close attention has to be paid to the behaviour and the lifetime of the infrastructure under these changed loads. In special bridges are delicate aspects in this matter. In the current thesis the simply supported Banafjäl bridge located on the Bothnia Line in the North of Sweden is studied more in detail with regards to this aspect. It is a high-speed composite railway bridge with a span of 42 m. A detailed 3D finite element (FE) model is made available. However in order to make reliable predictions about the behaviour under increasing train length loads, it had to be further improved. Different methods of calibrating measured response data to an existing FE model, finite element model updating (FEMU), are available and a detailed overview is given at the beginning of this thesis. Next a sensitivity analysis was performed to select the material parameters which are most influential for the result and will be updated. In the following, FEMU is carried out by means of two iterative updating methods, genetic and gradient-based optimization, after which also a combination of these two is implemented. Two objective functions are chosen and it is shown that all methods converge to a global optimal solution. After adjusting the initial model with the updated parameter values, a fatigue analysis on this updated model is carried out for high-speed trains of multiple lengthsby means of the Palmgren-Miner rule. The fatigue is found to increase with increasing train length and in particular when the speed approaches resonance speed. By extension an operating chart is created to indicate the maximum amount of train passages per day in function of speed and train length for a type 4 fatigue train. Furthermore, damping has been shown to have a positive effect on the fatigue, the larger this effect for shorter trains. The static behaviour has been proven not to be a problem and so will solely the weight of trains induce little to no fatigue problems in this particular bridge.

The electric grid is important in modern society, so the outages should be few. The transmission grid should have a real high availability, since it transports electrical energy across the country. Then, it is difficult to plan outages for maintenance and installation. This thesis lists twenty surveys about failures of circuit breakers and disconnectors, with data about the cause and the lifetime. It also contains a survey of about forty condition-measuring methods for circuit breakers and disconnectors, mostly applicable to the electric contacts and the mechanical parts. As there is no published method to monitor the electric contacts at voltages around 400 kV, a system with IR sensors has been installed at the nine contacts of six disconnectors. The purpose is to avoid outages for maintenance by estimating the condition of the contacts while the disconnectors are still connected to high voltage. The measured temperatures are collected by radio and regressed against the square of the current, since the best exponent for the current was found to be 2.0. The coefficient of determination $R^2$ is high, greater than 0.9. This gives for each contact a regression coefficient, which can serve as an estimate of the condition of the contact. The higher the coefficient is, the more heat is produced at the contact, which can damage the material. This enables a ranking of the different contacts and shows which the worst ones are. This coefficient can also give a dynamic rating of the disconnector. / Elnätet är viktigt i det moderna samhället, så antalet avbrott bör vara lågt. Särskilt stamnätet bör ha en särskilt hög tillgänglighet, då det transporterar elektrisk energi tvärsöver landet. Då blir det svårt att planera avbrott för underhåll och utbyggnad. Denna avhandling tar upp tjugo studier av fel i brytare och frånskiljare med data om felorsak och livslängd. Den har också en översikt av ett fyrtiotal olika metoder för tillståndsmätningar för brytare och frånskiljare, som huvudsakligen rör de elektriska kontakterna och de mekaniska delarna. Eftersom det inte finns någon beskriven metod för att övervaka elektriska kontakter för spänningar på runt 400 kV, har ett system med IR sensorer installerats på de nio kontakterna på sex frånskiljare. Målet är att minska antalet avbrott för underhåll genom att skatta skicket hos kontakterna, när frånskiljarna fortfarande är kopplade till högspänning. De uppmätta temperaturerna tas emot genom radio och behandlas genom regression mot kvadraten av strömmen, då den bästa exponenten för strömmen visade sig vara 2,0. Förklaringsfaktorn $R^2$ är hög, över 0,9. För varje kontakt ger det en regressionskoefficient, som blir en skattning av kontaktens skick. Ju högre koefficienten är, desto mer värme utvecklas det i kontakten, vilket kan leda till skador på materialet. Kontakternas olika koefficienter ger en rankordning dem och därmed en möjlighet att prioritera vilken frånskiljare som ska underhållas först. Systemet kan också användas för att minska eller öka den tillåtna strömmen baserat på skicket. / <p>QC 20150522</p>

Wireless sensor networks (WSNs) groups specialized transducers that provide sensing services to Internet of Things (IoT) devices with limited energy and storage resources. Since replacement or recharging of batteries in sensor nodes is almost impossible, power consumption becomes one of the crucial design issues in WSN. Clustering algorithm plays an important role in power conservation for the energy constrained network. Choosing a cluster head (CH) can appropriately balance the load in the network thereby reducing energy consumption and enhancing lifetime. This paper focuses on an efficient CH election scheme that rotates the CH position among the nodes with higher energy level as compared to other. The algorithm considers initial energy, residual energy, and an optimum value of CHs to elect the next group of CHs for the network that suits for IoT applications, such as environmental monitoring, smart cities, and systems. Simulation analysis shows the modified version performs better than the low energy adaptive clustering hierarchy protocol by enhancing the throughput by 60%, lifetime by 66%, and residual energy by 64%.

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