För att generera ett ljusfält krävs en fokalstack. Fokal stacken kommer att skapas med programvaran Blender. En fokalstack kan ses som mappen som innehåller alla bilderna med olika fokus från en scen. Fokalstack kommer att i denna studie innehålla bilder från samma scen men med olika fokallängeder vilket kommer att göra så att bilderna har olika delar av scenen i fokus. I Blender tillägget ska användaren kunna bestämma hur många bilder som ska skapas och hur fokusdistansen ska skilja sig mellan bilderna. Efter att fokal stacken har skapats kommer den att användas i ljusfältgenereringsalgoritmer för att utvärdera resultatet. Utvärderingen kommer att baseras på tiden det tar att generera ljusfältet och medelvärdet av PSNR. Algoritmerna kommer först att utvärderas individuellt med 35, 41, 50, 60 och 70 fokal stack-bilder. Därefter kommer algoritmerna att jämföras med varandra. Målet med arbetet är att skapa ett Blender-tillägg som möjliggör skapandet av en fokal stack med önskade parametrar, såsom antalet bilder och fokusdistansvariation. Studien har visat att skapandet av ljusfält var effektivare med SART-algoritmerna jämfört med algoritmer som krävde träningsmodelle / A light field requires a focal stack for its generation, and in this study, the focal stack will be created using the software Blender. A focal stack is what the folder containing the different images is called. This study will have the focal stack containing images from a stationary camera with different focal length. Focal length is the parameter deciding what regions is in focus of the scene. An addon will be developed to enable users to create a focal stack from a scene in Blender, allowing them to specify the desired focal length and the number of images. Once the focal stack is generated, it will be utilized in light field generating algorithms to evaluate the time taken to create the light field and the average PSNR value compared to the focal stack. The algorithms will first be evaluated independently with focal stack sizes of 35, 41, 50, 60, and 70 images. Following this, the algorithms will be compared to each other. The study's objective was to create a Blender addon and use the generated focal stacks to assess the performance of light field generation methods. The study demonstrated that light field creation was more effective using the SART algorithms compared to the algorithm requiring model training beforehand.

The primary objective of ventilation in a building is to ensure that the Indoor Air Quality (IAQ), together with the heating system, keep the thermal climate at an acceptable level. Meaning the deployment of ventilation air at the appropriate temperature rate supplied to meet the thermal climate into the parts of the building where residents reside. In Sweden, the two most commonly used ventilation strategies are stack ventilation and forced extract ventilation. Both methods utilize exhaust openings in kitchens and sanitary areas, while fresh air is drawn from either permeable external walls or through inlets located near windows and as distant as possible from the exhaust openings (Manz & Huber, 2000). Stack-effect ventilation, also known as buoyancy ventilation, utilizes convective forces. Thus, vertical interior openings such as stairways or atriums play an essential role in the distribution of air and its suitability. Utilizing additional building elements such as a chimney enhances the stack-effect ventilation by elevating the height of the “vertical core” of warm air within the structure. The disparity in density (the difference in temperature between hot and cold) increases as a result of the amplification of pressure disparities (Liu et al., 2010). Hence, larger differences in pressure between the inside and outside will result in an increased driving force for the stack effect by enhancing the convective currents. The principle operates by drawing cooler air from the exterior,generally from the bottom or sides of the building, into the building. The air is then gradually heated and ascends through the vertical core due to convective forces, before being ultimately discharged through the chimney (Savin & Jardinier, 2009). The architectural proposal seeks to adhere to sustainable building development by employing deliberate steps that incorporate a combination of principles and strategies based on the theory of convection. In order to acquire knowledge and validation, an extensive investigation of case studies was carried out, with the works of Philippe Rahm serving as the fundamental basis for further development. Furthermore, a laboratory environment was established to conduct physical tests as well as virtual simulations (CFD) in order to gain deeper understanding and accuracy regarding the relationship between convective forces and geometry. The thesis set out to place a bet based on the notion of consciousness, in terms of implementation of chosen principles, using materials with low embodied carbon, and employing a strategic geometric relationship. This approach enabled the design of an architectural proposal that is both responsive and educative, while also addressing the existing knowledge gap between different professions.

Abstract There are many reasons for sharing a photo of a printout. The intention might be to copy the image for personal use or experience an interesting ad with friends. With watermarking, the images can also carry side information and with specialized watermarking methods the information can be read with a mobile device camera. In digital image watermarking, information is hidden on an image in such a way that a computer can read the hidden information but a human cannot discern it. The aim of this thesis is to research the process in which the watermarked image is printed and then read with a digital camera or a camera phone from the printed image. In order to survive the process, the watermark must survive multiple attacks. Some of the attacks occur during printing as the image is halftoned, others when the image is recaptured with a camera, in which case the camera might be rotated around multiple axis. These attacks may cause a loss of synchronization of the watermark and make the extraction impossible. The main objective of the thesis is thus to develop methods that are robust to the printing and capturing process, especially for the situations when the capturing angle is large. This problem contains the circumstances in which the synchronization is lost and the camera lens is not focused properly. In this work, research on digital image watermarking, computational photography and mobile phones are combined. The contributions of this thesis lie in two main parts: First, two print-cam robust methods are proposed, one based on a frame and the other on autocorrelation for synchronization. These two are then used as a basis for an algorithm that recovers the watermark even after camera rotation and image blurring caused by the narrow depth of focus of the lens. The algorithm is later refined and implemented for a mobile phone. The results show that the method is highly robust to capturing the watermark without errors in angles up to 60° with processing times acceptable for real-life applications. / Tiivistelmä On olemassa useita syitä tulosteesta otetun valokuvan jakamiseen. Aikomuksena voi olla kopioida kuva omaan käyttöön tai jakaa mielenkiintoinen ilmoitus ystävien kanssa. Vesileimauksessa kuvaan voidaan sijoittaa lisätietoa ja erityisillä menetelmillä tieto voidaan myöhemmin lukea mobiililaitteen kameralla. Digitaalisten kuvien vesileimauksen tavoite on piilottaa tietoa kuvaan siten, että tietokone pystyy lukemaan piilotetun informaation, siinä missä ihminen ei pysty sitä havaitsemaan. Tämän väitöskirjan tavoitteena on tutkia prosessia, missä vesileimattu kuva tulostetaan ja vesileima luetaan digitaalisella kameralla tai kamerapuhelimella tulosteesta. Selviytyäkseen tästä prosessista, vesileiman on kestettävä useita hyökkäyksiä. Osa hyökkäyksistä esiintyy tulostuksen aikana, kun kuva rasteroidaan, ja osa valokuvatessa, jolloin kamera voi olla kiertynyt. Näiden hyökkäysten seurauksena vesileiman synkronointi voi kadota, jolloin vesileiman lukeminen ei enää onnistu. Väitöskirjan päätavoitteena on siis kehittää tulostuksen ja valokuvauksen kestäviä vesileimausmenetelmiä erityisesti niitä tilanteita varten, jolloin kuvauskulma on suuri. Tämä ongelma sisältää olosuhteet, joissa synkronointi menetetään, ja kun kameran linssi ei ole kohdistunut oikein. Työssä yhdistetään digitaalinen kuvien vesileimaus, laskennallinen valokuvaus ja matkapuhelimet. Tutkimus voidaan jakaa kahteen osa-alueeseen: Ensimmäisessä kehitetään kaksi tulostuksen ja valokuvauksen kestävää menetelmää, joista toinen perustuu kehykseen ja toinen autokorrelaatioon synkronoinnin säilyttämiseksi. Toisessa osassa näitä menetelmiä hyödynnetään algoritmissa, joka kykenee vesileiman lukemiseen myös silloin kun kameran kiertyminen on voimakasta ja objektiivin kapea tarkennussyvyys aiheuttaa sumeita alueita kuvassa. Tutkimustyön lopussa tätä algoritmia viedään eteenpäin ja testataan matkapuhelinalustalla. Tulokset osoittavat menetelmän kestävän kameran kiertymistä 60°:seen saakka suoritusajoilla, jotka ovat hyväksyttäviä sovelluskäyttöön.

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The rapid pace of digitalization has resulted in increased management of software development, and today a majority of startups are reliant on software. How to manage software development projects is a well-researched area and agile methods are widely adopted by companies in all industries and sizes. However, prior to working with agile methods or any other software development methodology, the founders and management of a startup have to make several technical decisions that could potentially affect the whole software development process and the company's success. Furthermore, studies show that only three programming languages are known by more than 50% of developers, suggesting that the potential effects of technical decisions stretch outside the software development process.  By performing a multiple-case study on startups with a mixed-methodology approach, the researcher has analyzed the literature, interviewed several founders and Chief Technology Officers, and quantitatively analyzed hundreds of thousand lines of code, to find how to organize to make better technical decisions in order to enhance growth and generate less technical debt. The results show that the effects of technical decisions stretch outside the software development process, having an apparent effect on a startup's ability to attract and retain talent. Furthermore, the results show that access to talent is an important but not deciding factor in technical decision-making. Additionally, it is found that in the initial stage of a startup, ease of development and speed are important factors in technical decisions as the main objective is to find product-market fit. When product-market fit has been found and the startup matures, the focus shifts and quality and durability are becoming prominent factors. It is found that scooping features only to implement the absolute core functionality is an effective approach to develop quickly and generate less technical debt while maintaining customer satisfaction. Lastly, it is found that programming language affects the number of issues generated per line of code and the time spent on building features. However, as found in the literature, there is no evidence of this being related to the type of programming language.  The findings have both practical and academic implications. In academics, this thesis lays the foundation for further studies and provides new insights into the field of startups in general, and technical decision-making in particular. For practitioners, this thesis provides a basis for discussion and execution of technical decisions in the early stages of a startup. / Den snabba digitaliseringen har resulterat i en ökad ledning av mjukvaruutveckling och idag är majoriteten av startups beroende av någon form av mjukvara. Hur man leder mjukvaruutvecklingsprojekt är ett välutforskat område och agila metoder är välanvända i företag i alla industrier och storlekar. Innan man arbetar med agila metoder eller någon annan mjukvarutvecklingsmetod så måste grundarna och ledningen ta flera tekniska beslut som potentiellt kan påverka hela mjukvaruutvecklingsprocessen och företagets framgång. Samtidigt finns det studier som visar att endast tre programmeringsspråk hanteras av mer än 50% av utvecklarna, vilket indikerar att de potentiella effekterna av tekniska beslut sträcker sig långt utanför mjukvaruutvecklingsprocessen.  Genom att utföra en flerfallsstudie på startups med både kvalitativa och kvantitativa moment, har forskaren analyserat literaturen, intervjuat flertalet grundare och tekniska chefer, och kvantitativt analyserat hundratusentals rader kod, för att undersöka hur startups kan organisera sig för att ta bättre tekniska beslut som förbättrar tillväxten samt genererar mindre teknisk skuld. Resultaten visar att effekten av tekniska beslut sträcker sig långt utanför mjukvaruutvecklingsprocessen genom att ha en direkt påverkan på startups möjlighet att attrahera och behålla talang. Tillgången till talang visar sig även vara en viktig faktor i teknisk beslutsfattande, däremot är den inte en avgörande faktor. Dessutom visar resultaten att i det initiala stadiet av en startup så är enkelhet och hastighet viktiga faktorer i tekniskt beslutsfattande eftersom fokus ligger på att hitta produkt-marknads-anpassning. När produkt-marknads-anpassning är funnen och startupen mognar, så skiftar dessa faktorerna över till kvalité och hållbarhet. Resultaten visar även att en effektiv metod för att utveckla snabbt och skapa mindre teknisk skuld är att skala ner förfrågningar till dess absolut grundfunktionalitet, samtidigt visade det sig att kundnöjdheten inte minskade. Slutligen visar resultaten att val av programmeringsspråk har en effekt på antalet issues genererade per rad kod och även tiden spenderad för att bygga features. Däremot, precis som i tidigare forskning, finns det inga bevis på att det är relaterat till typen av programmeringsspråk.  Resultaten har både praktiska och akademiska implikationer. I den akademiska världen så lägger detta arbetet en grund för framtida forskning och ger nya insikter i startupfältet generellt, och tekniskt beslutsfattande i startups i synnerhet. För utövare, lägger detta arbetet en bra bas för diskussion och verkställande av tekniska beslut i startups.

An alternative indirect integration regime of porous low-k materials was investigated. Based on a single Damascene structure the intra level dielectric SiO2 or damaged ULK was removed by using HF:H2O solutions to create free standing metal lines. The free spaces between the metal lines were refilled with a spin-on process of a low-k material. The persistence of barrier materials and copper against HF solutions, the gap fill behavior of the used spin on glass on different structure sizes and the main challenges which have to solve in the future are shown in this study.

Energy markets feature a wide range of unusual price behaviour along with a complicated dependence structure between electricity, natural gas, coal and carbon, as well as other variables. We approach this broad modelling challenge by firstly developing a structural framework to modelling spot electricity prices, through an analysis of the underlying supply and demand factors which drive power prices, and the relationship between them. We propose a stochastic model for fuel prices, power demand and generation capacity availability, as well as a parametric form for the bid stack function which maps these price drivers to the spot electricity price. Based on the intuition of cost-related bids from generators, the model describes mathematically how different fuel prices drive different portions of the bid stack (i.e., the merit order) and hence influence power prices at varying levels of demand. Using actual bid data, we find high correlations between the movements of bids and the corresponding fuel prices (coal and gas). We fit the model to the PJM and New England markets in the US, and assess the performance of the model, in terms of capturing key properties of simulated price trajectories, as well as comparing the model’s forward prices with observed data. We then discuss various mathematical techniques (explicit solutions, approximations, simulations and other numerical techniques) for calibrating to observed fuel and electricity forward curves, as well as for pricing of various single and multi-commodity options. The model reveals that natural gas prices are historically the primary driver of power prices over long horizons in both markets, with shorter term dynamics driven also by fluctuations in demand and reserve margin. However, the framework developed in this thesis is very flexible and able to adapt to different markets or changing conditions, as well as capturing automatically the possibility of changes in the merit order of fuels. In particular, it allows us to begin to understand price movements in the recently-formed carbon emissions markets, which add a new level of complexity to energy price modelling. Thus, the bid stack model can be viewed as more than just an original and elegant new approach to spot electricity prices, but also a convenient and intuitive tool for understanding risks and pricing contracts in the global energy markets, an important, rapidly-growing and fascinating area of research.

Amplitude-versus-offset, AVO, approximations allow the estimation of various properties from pre-stack seismic gathers. Recently it has been suggested that fluid mobility is a controlling factor in pore pressure equalisation and can result in anomalous velocity dispersion in the seismic bandwidth. However, current approximations all assume an elastic subsurface and are unable to account for velocity dispersion. I have applied existing methodologies to a real dataset to qualitatively detect and interpret spectral amplitude anomalies. Three areas had AVO and spectral signature consistent with frequency-dependent AVO theory. The results suggest that it is feasible to measure such effects on real data in the presence of random noise. It would imply that the relaxation parameter, tau, is larger in the field than has been measured in water-saturated real and synthetic sandstones in the laboratory. I extended a two-term AVO approximation by accounting for velocity dispersion and showed how the resultant reflection coefficient becomes frequency-dependent. I then used this to measure P- and S-wave reflectivity dispersion using spectrally-balanced amplitudes. The inversion was able to quantify the affect of the P-wave velocity dispersion as an instantaneous effect on the reflection. NMO stretch was an issue at the far offsets and I limited myself to the near offsets and effectively measured only the P-wave reflectivity dispersion. I showed how the P-wave reflectivity dispersion signs depend on the AVO classification of the reflection whilst the magnitude depends on the crack density of my model. I showed how the effect of noise and thin-bed tuning can enter uncertainties into the interpretation of spectral anomalies. Whilst it is possible to detect frequency-dependent AVO signatures on pre-stack gathers, the interpretation remains non-unique. I have quantitatively measured a new physical property, reflectivity dispersion, from pre-stack seismic data. I have presented a method of detecting and measuring velocity dispersion in pre-stack gathers but there remain ambiguities in the interpretation of such results. The approach incorporates spectrally decomposed data in an extended AVO inversion scheme. Future work should investigate the application of the methodology to a real seismic dataset.

M. Tech. (Engineering Department Applied Electronics and Electronic Communication, Faculty of Engineering) Vaal University of Technology / This study presents the design of a proton exchange membrane fuel cell stack that can be used to replace conventional sources of electrical energy in an uninterruptible power supply system, specifically for use in the telecommunications industry. One of the major concerns regarding the widespread commercialization of fuel cells is the high cost associated with fuel cell components and their manufacturing. A fuel cell design is presented in which existing, low-cost, technologies are used in the manufacture of cell components. For example, printed circuit boards are used in the manufacturing of bipolar flow plates to significantly reduce the cost of fuel cells. The first objective was to design, construct and test a single fuel cell and small fuel cell stack in order to evaluate the use of printed circuit boards in bipolar plate manufacturing. Since the use of copper in a fuel cell environment was found to reduce the lifetime of the cells, the bipolar plates were coated with a protective layer of nickel and chrome. These coatings proved to increase the lifetime of the cells significantly. Power outputs of more than 4 W per cell were achieved. The second objective was to analyze a small fuel cell stack in order to obtain a model for predicting the performance of larger stacks. A mathematical model was developed which was then used to design an electronic circuit equivalent of a fuel cell stack. Both models were adapted to predict the performance of a fuel cell stack containing any number of cells. The models were proven to be able to accurately predict the performance of a fuel cell stack by comparing simulated results with practical performance data. Finally, the circuit equivalent of a fuel cell stack was used to evaluate the capability of a switch mode boost converter to maintain a constant voltage when driven by a fuel cell stack, even under varying load conditions. Simulation results showed the ability of the boost converter to maintain a constant output voltage. The use of supercapacitors as a replacement for batteries as a secondary energy source was also evaluated.

Com o recente desenvolvimento de tecnologias de redes de altas taxas de transmissão, tais como Asynchronous Transfer Mode (ATM), o problema da carência por largura de banda foi solucionado. A questão atual é a implementação de sistemas que suportem os protocolos ATM de forma nativa e integral. Atualmente tem-se utilizado aplicativos tradicionais baseados nos protocolos TCP(UDP)/IP no topo da pilha de protocolos ATM. Tal modelo traz redundâncias que implicam diretamente em aumento de overhead na comunicação. Muitos modelos têm sido desenvolvidos para levar de forma direta a aplicação os serviços ATM. O propósito deste trabalho foi comparar o desempenho de transmissões de dados utilizando os protocolos TCP(UDP)/IP sobre ATM com transmissões de dados no modo ATM nativo. Para tal, utilizamos a plataforma de pesquisa HARP do sistema operacional FreeBSD. Tal plataforma implementa o modelo Classical IP sobre ATM utilizando os serviços AAL5 e ainda fornece uma API para sockets ATM permitindo que uma aplicação tenha acesso direto a camada AALS. Testes de taxa de transmissão, perda de células, e atraso na rede, foram realizados com base na modificação de parâmetros relacionados à aplicação e sistema operacional, tais como tamanho da mensagem sendo transmitida e tamanho dos buffers de socket. / The solution for the lack of bandwidth was solved by the recent development of high speed networks technologies, such as Asynchronous Transfer Mode - ATM. The question now is the implementation of systems, which provide support for ATM protocols in an integral way. Nowadays, legacy network applications, based in TCP/IP protocols have been used on top of ATM protocol stack. Such approach generates redundances that have as consequence an increase in the communication overhead. Many models have been developed to provide ATM services directly to applications. The goal of this study was to evaluate the performance of data transfers comparing the TCP/IP protocols over ATM with the performance of data transfers in native ATM mode. The Host ATM Research Plataform (HARP) was utilized on the FreeBSD operating system. This plataform implements Classical IP over ATM, utilizing AAL5 services. Furthermore, it provides an API for ATM sockets, allowing that an application directly access the AAL5 services. Measurements of throughput and investigations about cell loss and delay were carried out altering parameters related to the application and operating system. The parameters adopted were message size and socket buffer sizes.