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Aquesta tesi es centra en la preparació de noves membranes polimèriques per a fotosíntesi artificial. Hem preparat i caracteritzat dos materials diferents, basats en Poli(epicloridina-co-òxid d’etilé) (PECH-co-EO), modificada amb metil 3,4,5-tris[4-(n-dodecan-1-iloxi)benziloxi]benzoat, al 20% (CP20) o 40% (CP40), respectivament. Per assolir propietats de transport eficients, es prepararen membranes orientades homeotròpicament mitjançant un tractament tèrmic. Seguidament, es van analitzar mitjançant anàlisi tèrmic dinàmo-mecànic (DMTA) i dièlectric (DETA). DETA i DMTA van confirmar que la presència del dendró dificulta el moviment dels copolímers; tanmateix, les membranes orientades i no orientades no mostraren una gran diferència, independentment de la quantitat del dendró. A més, vam estudiar les propietats de transport mitjançant proves de permeabilitat de protó i methanol i de voltametria d’escombrat lineal (LSV). Els resultats demostraren que tant en CP20 com en CP40, el transport de cations depèn de la presència de canals de transport definits, no afectats per la presència d’aigua; els experiments LSV realitzats amb diferents cations van demostrar que CP40 posseeix canals amb diàmetres més grans, i que les seves estructures internes són millor definides. D'altra banda, vam intentar millorar el rendiment en absorció de CO2 mitjançant l'ús de membranes de polisulfona amb dos additius diferents en contactors de membrana gas-líquid. Aquests additius estan basats en una polietilenimina comercial hiperramificada (LupasolG20), parcialment modificada amb clorur de benzoil (mG20) o fenilisocianat (UG20). Es prepararen membranes amb diferents quantitats d'additius per precipitació per inversió de fase i es caracteritzaren mitjançant diverses tècniques. Vam trobar que la presència de l'additiu millora molt les característiques de les membranes quant a captura de CO2, especialment la solubilitat, hidrofobicitat i resistència química a la solució aquosa alcalina absorbent, donant els millors resultats per al 5% d'additiu. La permeabilitat i absorció de CO2 van millorar amb tots dos additius, mostrant UG20 un millor rendiment. Esta tesis se centra en la preparación de nuevas membranas poliméricas para dispositivos de fotosíntesis artificial. Preparamos y caracterizamos dos materiales diferentes,basados en Poli(epiclorhidrina-co-óxido de etileno) injertados con 3,4,5-tris[4-(n-dodecan-1-iloxi)benciloxi] benzoato, en un 20% (CP20) o 40%(CP40), respectivamente.Para alcanzar unas propiedades de transporte eficientes, se prepararon membranas orientadas homeotrópicamente mediante un tratamiento térmico controlado y posteriormente se investigaron mediante análisis térmico dinamo-mecánico (DMTA) y análisis térmico dieléctrico (DETA).DMTA y DETA confirmaron que la injerción del dendrón dificulta seriamente los movimientos del copolímero, pero no mostraron grandes diferencias entre las membranas orientadas y las no orientadas, independientemente de la cantidad de dendrones. Además, las propiedades de transporte se estudiaron mediante experimentos de permeabilidad de protones y metanol y mediante voltamperometría de barrido lineal (LSV). Los resultados demostraron que en CP20 y CP40, el transporte de cationes dependía de la presencia de canales catiónicos definidos, no afectados por la presencia de agua;la comparación entre experimentos LSV realizados con diferentes cationes alcalinos sugiere que CP40 posee canales con diámetros más grandes y estructuras internas mejor definidas. Por otro lado, intentamos mejorar el rendimiento en absorción de CO2 mediante el uso de membranas de polisulfona con dos aditivos diferentes en contactores de membrana gas-líquido. Estos aditivos están basados en una polietilenimina commercial hiperramificada (LupasolG20) parcialmente modificada con cloruro de benzoílo (mG20) o fenilisocianato(UG20).Se prepararon membranas con diferentes cantidades de aditivos por precipitación por inversión de fase y se caracterizaron mediante varias técnicas.Se encontró que la presencia del aditivo mejoró mucho las características de las membranas en cuanto a captura de CO2, especialmente la solubilidad, hidrofobicidad y resistencia química a la solución acuosa alcalina absorbente, dando los mejores resultados para 5% de aditivo.El rendimiento de las membranas en términos de permeabilidad y absorción de CO2 mejoró con ambos aditivos, mostrando UG20 un mejor rendimiento. This doctoral thesis focuses on preparing novel polymeric membranes to be used in artificial photosynthesis devices. In particular, we are interested in membranes for both ion conductive and CO2 capture. We prepared and characterized two different materials, based on Poly(epichlorohydrin-co-ethylene oxide) (PECH-co-EO) grafted with potassium 3,4,5-tris[4-(n-dodecan-1-yloxy)benzyloxy] benzoate, containing 20% (CP20) or 40% (CP40) modified units, respectively. In order to reach efficient transport properties, homeotropically oriented membranes were prepared by a fine-tuned thermal annealing treatment and were subsequently investigated by dynamic mechanical thermal analysis (DMTA) and dielectric thermal analysis (DETA). DMTA and DETA confirmed that grafting with the dendron strongly hinders copolymer motions, but did not show great differences between unoriented and oriented membranes, regardless of the amount of dendrons. Moreover, transport properties were studied by methanol and proton conductivity experiment and by linear sweep voltammetry (LSV). Results demonstrated that in CP20 and CP40, cation transport depends on the presence of defined cationic channels, not affected by water presence; the comparison between LSV experiments performed with different alkaline cations suggests that CP40 possesses channels with larger diameters and better-defined inner structures. We focused on improving CO2 absorption performance by using two different additives in neat polysulfone as gas-liquid membrane contactors. These additives are amine additives based on hyperbranched Lupasol G20 partially grafted with benzoyl chloride (mG20) or phenyl isocyanate (UG20). Membranes with different amount of additives were prepared by phase inversion precipitation and characterized by several techniques. In general, it was found that the presence of the additive greatly improved the characteristics of the membranes as regards the CO2 capture, especially solubility, hydrophobicity and chemical resistance to the aqueous alkaline absorbent solution, giving the better results for 5% additive content. In summary, the performance of blend membranes in terms of CO2 permeability and absorption was improved by both additives, while UG20 demonstrates better performance compared to mG20.

The emergence of GaN devices have brought new challenges within power electronics especially consumer electronics since the voltage rating has not become as high as silicon carbide. This new emergence resulted in an increase in switching frequency capability of power electronics circuits and may be used to increase the efficiency of current topologies, decrease the profile, and cost of the total circuit. Since most important and expensive part of each SMPS is its inductor, the increase in switching frequency will result in a significant decrease in passive component size and potentially the total price of the circuit. Nowadays most people carry laptops, cellphones and in general a lot of handheld devices and all of them need charging. Previously, every single device has its own specific charger and as a result, you had to bring multiple cords and chargers to make sure you do not run out of battery. With the development of USB-C, the era of multiple chargers has ended. Instead, a single cable and a single high capacity charger or power bank is sufficient to carry through each day without running out of battery. This thesis will investigate a 60watt USB-C charger with power delivery to fast charge every USB-C compatible device. The objective is to modify an existing topology which has the least number of components and make it as efficient, small, and cost effective as possible.

In this paper, we present a novel approach for fine-tuning a decoder-side neural network in the context of image compression, such that the weight-updates are better compressible. At encoder side, we fine-tune a pre-trained artifact removal network on target data by using a compression objective applied on the weight-update. In particular, the compression objective encourages weight-updates which are sparse and closer to quantized values. This way, the final weight-update can be compressed more efficiently by pruning and quantization, and can be included into the encoded bitstream together with the image bitstream of a traditional codec. We show that this approach achieves reconstruction quality which is on-par or slightly superior to a traditional codec, at comparable bitrates. To our knowledge, this is the first attempt to combine image compression and neural network's weight update compression., Comment: Submission for CHALLENGE ON LEARNED IMAGE COMPRESSION (CLIC) 2019 (updated on 14 June 2019)

Light-field (LF) 3D displays are anticipated to be the next-generation 3D displays by providing smooth motion parallax, wide field of view (FOV), and higher depth range than the current autostereoscopic displays. The projection-based multi-view LF 3D displays bring the desired new functionalities through a set of projection engines creating light sources for the continuous light field to be created. Such displays require a high number of perspective views as an input to fully exploit the visualization capabilities and viewing angle provided by the LF technology. Delivering, processing and de/compressing this amount of views pose big technical challenges. However, when processing light fields in a distributed system, access patterns in ray space are quite regular, some processing nodes do not need all views, moreover the necessary views are used only partially. This trait could be exploited by partial decoding of pictures to help providing less complex and thus real-time operation. However, none of the recent video coding standards (e.g., Advanced Video Coding (AVC)/H.264 and High Efficiency Video Coding (HEVC)/H.265 standards) provides partial decoding of video pictures. Such feature can be achieved by partitioning video pictures into partitions that can be processed independently at the cost of lowering the compression efficiency. Examples of such partitioning features introduced by the modern video coding standards include slices and tiles, which enable random access into the video bitstreams with a specific granularity. In addition, some extra requirements have to be imposed on the standard partitioning tools in order to be applicable in the context of partial decoding. This leads to partitions called self-contained which refers to isolated or independently decodable regions in the video pictures. This work studies the problem of creating self-contained partitions in the conventional AVC/H.264 and HEVC/H.265 standards, and HEVC 3D extensions including multi-view (i.e., MV-HEVC) and 3D (i.e., 3D-HEVC) extensions using slices and tiles, respectively. The requirements that need to be fulfilled in order to build self-contained partitions are described, and an encoder-side solution is proposed. Further, the work examines how slicing/tiling can be used to facilitate random access into the video bitstreams, how the number of slices/tiles affects the compression ratio considering different prediction structures, and how much effect partial decoding has on decoding time. Overall, the experimental results indicate that the finer the partitioning is, the higher the compression loss occurs. The usage of self-contained partitions makes the decoding operation very efficient and less complex.

Light field 3D displays represent a major step forward in visual realism, providing glasses-free spatial vision of real or virtual scenes. Applications that capture and process live imagery have to process data captured by potentially tens to hundreds of cameras and control tens to hundreds of projection engines making up the human perceivable 3D light field using a distributed processing system. The associated massive data processing is difficult to scale beyond a specific number and resolution of images, limited by the capabilities of the individual computing nodes. The authors therefore analyze the bottlenecks and data flow of the light field conversion process and identify possibilities to introduce better scalability. Based on this analysis they propose two different architectures for distributed light field processing. To avoid using uncompressed video data all along the processing chain, the authors also analyze how the operation of the proposed architectures can be supported by existing image/video codecs. publishedVersion

Master's thesis in Petroleum engineering At the end of 20th century, the utilization of geothermal energy has increased by 150% forming a solid industry of relevant importance on global markets (Dickson & Fanelli, 2004). According to numerous analyses, this type of energy exploitation has a strong forecast of development in the future. High potential of progress is associated with complex studies to ensure the feasibility, safety and profitability of the investments. Numerical simulation of flows in geothermal exploitation is an essential tool to establish adequate results. The assessment of this process is a key factor for preparing schemes providing high overall efficiency (Vasini et al., 2017). Determining the most favorable parameters and approaches is the subject of plenty studies in the field of geothermal energy. This work analyzes the concept of geothermal energy and heat transfer in general, and in the wellbore. Furthermore, it investigates application of separate turbulence models on flow in concentric and eccentric annulus. Different assembly of pipes require adjusting diverse approaches to achieve finest results. When chosen models work for theoretical configurations, they do not automatically comply for the field cases. As for the eccentricity, the simulation shows valuable data of how the flow behaves in irregular, but very common position. Obtained results satisfy the benchmarks stated in the preceding researches. For instance, the thermal structures are more aroused near the outer wall of the assembly, than closer to the inner pipe. This outcome might be implemented in analyzing vortex generations in the annuli. Moreover, the study defines the dependence of heat transfer rate on the pipe materials. Conducted research might be used as an initial and easy to comprehend overview of the heat transfer phenomena in geothermal energy exploitation.

Master's thesis in Petroleum engineering The petroleum industry uses a variety of qualitative risk assessment methods for maintaining well integrity, such as well barrier schematics and barrier diagrams. Identifying barriers and using well barrier schematics are helpful tools in qualitative risk assessments. However, it is not yet clear if these methods can be applied for risk assessments in the geothermal industry. Geothermal wells often produce directly through the casing, instead of through production tubing, making it difficult to identify two independent barrier envelopes in accordance to NORSOK D-010. High temperatures and corrosion are the most common contributors to failure in geothermal wells. In this study, a hypothetical case of a downhole corrosion problem was assessed by means of conducting a qualitative risk analysis and identifying well barriers in a geothermal well. This study shows that qualitative risk assessment methods from the petroleum industry are applicable using minor adjustments to well barrier interpretation and barrier diagrams. Using NORSOK D-010 as a guideline, the study found that typical Icelandic high temperature geothermal wells may consist of a primary and a secondary barrier envelope with a common well barrier element at the wellhead. At shallow depths, the intermediate casing, often the anchor casing, acts as a secondary barrier against an aquifer. In addition, the study indicates that production of low enthalpy fluids and its financial impact might be the main concerns of downhole corrosion problems close to the production casing shoe. Findings in this study could form the foundation for raising the standard of risk assessment methods for high temperature geothermal wells, and the well barrier interpretations defined in this thesis may be suitable for a number of these types of wells.

Master's thesis in Petroleum engineering Injecting dissolved CO2 into deep saline aquifers is one of the more promising methods of alleviating greenhouse gas emissions. By simultaneously extracting the geothermally-heated brine in the aquifer, there is an opportunity to offset the energy consumption required by carbon capture and storage. This study uses a simulation tool to explore the effect of well placement on CO2-storing efficiency. Eight models with different well configurations were tried on a homogeneous aquifer. The study found that storing efficiency was heavily reliant on distance, especially vertical, between the wells and the vertical- to horizontal permeability ratio. For a given aquifer model, there exists a depth differential between wells that optimize injection- and production rates versus gas-breakthrough time.

Master's thesis in Petroleum engineering This research attempts to assess the effects of changing the injection times for CO2 solvent injection in the Solvent Assisted SAGD process and to study the phase behavior of Steam, Solvent and Oil. Simulations were conducted using the Computer Modeling Group simulation software STARS 2014. The research evaluates the effect of injection start time, solvent concentration and solvent selection on performance criteria such as Energy efficiency, Cumulative oil production, and Solvent recovered from the reservoir. The phase behavior over two individual horizontal study lines was investigated to try and explain the difference in solvent performance. The injection performance of the four different hydrocarbon solvents was compared to the Steam-only SAGD process. The effect of co-injecting CO2 with hydrocarbon solvents was compared to the same solvents without the non-condensable gas. Hexane was discovered to be the optimal solvent for energy efficiency and oil recovery at the cost of a suboptimal solvent recovery. The most optimal single-component concentration when considering the performance criteria lies in the range 20-30% by weight and an economic analysis would be needed to further narrow the range. The poor solvent recovery was remedied with Heptane which was shown to have an excellent solvent recovery and the two solvents were successfully co-injected. The proposed combination of solvents achieved better results than any single-component at the same concentration, which leads to the conclusion that there is a positive synergy between the two solvents. CO2 co-injection was tested with the previously investigated Hexane and Heptane solvents. It was found that there is a time period after starting hydrocarbon solvent injection where CO2 co-injection should not be initiated. There was however, a positive effect on the performance if the injection start time is delayed sufficiently. The most interesting conclusion drawn from the research was the positive synergy between solvents when looking at multiple performance criteria in unison and the reported time period after starting hydrocarbon solvent injection where CO2 injection should not be initiated.