| 1. |
- Andersson, Viktor, 1983
(författare)
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Excess heat utilisation in oil refineries - CCS and algae-based biofuels
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main objective of this thesis is to investigate two different concepts for CO2 mitigation, from a system perspective, in relation to the oil refining industry: CO2 capture and storage; and algae-based biofuels. For all these processes, process integration with an oil refinery is assumed. The oil refinery sector is a major emitter of CO2 and is responsible for 9% of the industrial emissions of CO2 worldwide. Oil refineries have large amounts of unused excess heat, which can be used to satisfy the heat demands of a CO2 capture plant, a land-based algal cultivation facility, or an algae-based biofuel process. The use of this excess heat significantly reduces the cost for CO2 capture, while an economic evaluation for algae-based biofuels has not been made.Since the amount of heat available from the oil refinery´s processes increase with decreasing temperature in the stripper reboiler, it was investigated how much heat was available at different temperatures. It was also investigated how the decreased temperature would affect the heat demand of CO2 capture processes that use MEA or ammonia as the absorbent. The findings show that it is possible to capture more CO2 using excess heat when the temperature in the stripper reboiler is decreased. For the MEA process, the lower limit of the temperature interval investigated showed the maximum CO2 capture rate, while the ammonia process benefitted from a lower temperature than the standard temperature but showed maximal CO2 capture rate above the lower limit. These results are valid only when using excess heat to satisfy the entire heat demand. At the case study refinery, the available excess heat could satisfy between 28% and 50% of the heat demand of the MEA process when treating the flue gases from all chimneys, depending on the temperature in the stripper reboiler. This utilisation of excess heat represents a way to reduce significantly the costs for CCS in an oil refinery. Land-based cultivation of algae proved to be unsuitable for the utilisation of excess heat. Since the cultivation pond is exposed to wind, rain, and cold, the heat demand fluctuates strongly over the year, making the pond an unstable recipient of the excess heat.Three types of biofuel processes based on microalgae and macroalgae were investigated with respect to integration with the oil refinery. For the algae-based biofuel processes, heat integration and material integration combined to increase the efficiency of the system. When two different build margin technologies (with different CO2 emission factors) are employed for electricity production, macroalgae-based biofuel production appears to be the more robust process from the perspective of CO2 due to the lower electricity demands of the algal cultivation and harvesting phases.
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| 2. |
- López, Cristian Daniel, 1990
(författare)
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Wideband THz Mixers and Components for the Next Generation of Receivers for Radioastronomy
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In recent decades, there has been a growing interest in THz research, leading to substantial improvements in technology and the emergence of new applications. In particular, the ever-evolving field of radio astronomy instrumentation has been pushing the limits of millimeter and sub-millimeter technology boundaries, redefining the state-of-the-art for wideband low-noise receivers. The technological roadmaps for radio astronomy applications, such as “The ALMA 2030 Wideband Sensitivity Upgrade”, set the requirements for the next generation of heterodyne receivers. Among these requirements, it establishes the need for a wider IF bandwidth and the possibility of covering multiple existing RF bands with a single receiver, e.g., combining ALMA bands 6 (211–275 GHz) and 7 (275–373 GHz), i.e., a ~56% fractional bandwidth. To build receivers with such a large fractional bandwidth, each of their components must be able to cover the required bandwidth with minimal insertion loss, or equivalently, add the minimum noise to the system. In particular, it is essential to focus on the components that are critical for the performance of such receivers, such as front-end waveguide components and the mixer chip. This thesis addresses this need and focuses on the design, simulation, fabrication, and characterization of ultra-wideband THz devices for the next generation of radio astronomy receivers. The thesis starts by presenting the development of waveguide passive components key to future ultra-wideband receivers, such as waveguide twists and power dividers. Waveguide twists are essential interconnection parts in most polarization-sensitive THz receivers that make use of orthomode transducers. Since compactness and low insertion loss are critical requirements, step-twists have become a promising solution. This work introduces novel designs for step twists covering the frequency ranges of 120-220 GHz and 210-375 GHz, i.e., 44% and 56% fractional bandwidth with 20 dB return loss, respectively. In the first design, the experimental verification showed an insertion loss of 0.4 dB, while the second demonstrated an insertion loss as low as 0.3 dB. Additionally, the thesis investigates waveguide power dividers, a fundamental component in the development of 2SB receivers for LO injection. It presents a waveguide power divider that incorporates a substrate-based element into a waveguide structure to enhance the output port’s isolation and matching in the frequency range of 150-220 GHz, i.e. 38% fractional bandwidth. THz mixers are implemented with thin-film technology. As a consequence, the waveguide-to-substrate transitions have a fundamental role in the performance and bandwidth of such systems. In this work, a waveguide-to-slotline superconducting transition based on substrateless finlines is proposed. Moreover, for the majority of modern mixers with Superconductor Insulator Superconductor (SIS) technology, the microstrip line topology is the most suitable. Hence, this work presents the development of a broadband slotline to microstrip transition based on Marchand baluns. Both transitions were experimentally verified at cryogenic temperatures. Remarkably, each of these transitions achieved a fractional bandwidth of ~56%, while the substrateless finline transition demonstrated an insertion loss of 0.5 dB, the Marchand Balun showed an insertion loss as low as 0.3 dB. The integration of the substrateless finline and the Marchand balun transitions served as the first approach to a platform for the development of an ultra-wideband SIS mixer. This platform evolved into the SIS mixer design for 210-375 GHz introduced in this thesis. The mixer chip represents a significant shift from traditional design approaches since the dielectric substrate is removed and replaced with a micromachined metallic substrate which integrates a metallic finline. The micromachined substrate is employed as a technological platform for the Nb-Al/AlN-Nb SIS junctions, the RF matching circuitry, and the IF output filter. The mixer features a designed IF bandwidth of 4-16 GHz. Furthermore, this thesis demonstrates the feasibility of micromachined metallic substrates as a technological platform for SIS devices.
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| 3. |
- Acuña, José, 1982-
(författare)
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Distributed thermal response tests : New insights on U-pipe and Coaxial heat exchangers in groundwater-filled boreholes
- 2013
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Konstnärligt arbete (övrigt vetenskapligt/konstnärligt)abstract
- U-pipe Borehole Heat Exchangers (BHE) are widely used today in ground source heating and cooling systems in spite of their less than optimal performance. This thesis provides a better understanding on the function of U-pipe BHEs and Investigates alternative methods to reduce the temperature difference between the circulating fluid and the borehole wall, including one thermosyphon and three different types of coaxial BHEs.Field tests are performed using distributed temperature measurements along U-pipe and coaxial heat exchangers installed in groundwater filled boreholes. The measurements are carried out during heat injection thermal response tests and during short heat extraction periods using heat pumps. Temperatures are measured inside the secondary fluid path, in the groundwater, and at the borehole wall. These type of temperature measurements were until now missing.A new method for testing borehole heat exchangers, Distributed Thermal Response Test (DTRT), has been proposed and demonstrated in U-pipe, pipe-in-pipe, and multi-pipe BHE designs. The method allows the quantification of the BHE performance at a local level.The operation of a U-pipe thermosyphon BHE consisting of an insulated down-comer and a larger riser pipe using CO2 as a secondary fluid has been demonstrated in a groundwater filled borehole, 70 m deep. It was found that the CO2 may be sub-cooled at the bottom and that it flows upwards through the riser in liquid state until about 30 m depth, where it starts to evaporate.Various power levels and different volumetric flow rates have been imposed to the tested BHEs and used to calculate local ground thermal conductivities and thermal resistances. The local ground thermal conductivities, preferably evaluated at thermal recovery conditions during DTRTs, were found to vary with depth. Local and effective borehole thermal resistances in most heat exchangers have been calculated, and their differences have been discussed in an effort to suggest better methods for interpretation of data from field tests.Large thermal shunt flow between down- and up-going flow channels was identified in all heat exchanger types, particularly at low volumetric flow rates, except in a multi-pipe BHE having an insulated central pipe where the thermal contact between down- and up-coming fluid was almost eliminated.At relatively high volumetric flow rates, U-pipe BHEs show a nearly even distribution of the heat transfer between the ground and the secondary fluid along the depth. The same applies to all coaxial BHEs as long as the flow travels downwards through the central pipe. In the opposite flow direction, an uneven power distribution was measured in multi-chamber and multi-pipe BHEs.Pipe-in-pipe and multi-pipe coaxial heat exchangers show significantly lower local borehole resistances than U-pipes, ranging in average between 0.015 and 0.040 Km/W. These heat exchangers can significantly decrease the temperature difference between the secondary fluid and the ground and may allow the use of plain water as secondary fluid, an alternative to typical antifreeze aqueous solutions. The latter was demonstrated in a pipe-in-pipe BHE having an effective resistance of about 0.030 Km/W.Forced convection in the groundwater achieved by injecting nitrogen bubbles was found to reduce the local thermal resistance in U-pipe BHEs by about 30% during heat injection conditions. The temperatures inside the groundwater are homogenized while injecting the N2, and no radial temperature gradients are then identified. The fluid to groundwater thermal resistance during forced convection was measured to be 0.036 Km/W. This resistance varied between this value and 0.072 Km/W during natural convection conditions in the groundwater, being highest during heat pump operation at temperatures close to the water density maximum.
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| 4. |
- Ekholm, Jennifer, 1992
(författare)
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Application of aerobic granular sludge for municipal wastewater treatment - Process performance and microbial community dynamics under fluctuating conditions
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Pressures of growing cities, competition for use of urban areas and higher influent loads, are pushing for innovative technologies for wastewater treatment with low demands for land footprint and costs. Furthermore, wastewater treatment is needed to move towards a circular economy by harvest of valuable resources such as nutrients and energy. Aerobic granular sludge (AGS) is a biofilm process without a carrier material for wastewater treatment, exhibiting efficient treatment performance, excellent settleability, high biomass retention, tolerance to toxicity and high loads of organic matter. In this thesis, the first implementation of the AGS process in the Nordic countries was studied to assess the treatment performance, microbial community structure, energy usage, land footprint, and volume needs. The results in this project suggested that selective sludge withdrawal, retaining long solids retention time, sufficient substrate availability, and operational flexibility are important factors for granulation. Both the AGS and parallel conventional activated sludge (CAS) process achieved stable organic matter, nitrogen, and phosphorus removal with low average effluent concentrations. Seasonal variations and environmental factors were identified as important for microbial community succession. The granular biofilm demonstrated higher biomass concentration, diversity, and lower seasonal fluctuations in community composition than the flocculent sludge. A one-year energy comparison resulted in lower specific energy usages (kWh m-3 and kWh reduced P.E.-1) and land footprint for the AGS compared to the CAS process. However, a potential for decreased energy usage was recognised for both systems, leading to the conclusion that operational optimisation and process design might be as important as the type of technology. Additionally, the influence of decreasing temperature on AGS was studied in lab-scale reactors, revealing different responses of the functional groups in the microbial community, and even various response of ASVs at the genus level. In conclusion, the AGS technology for municipal wastewater treatment under fluctuating conditions achieved low average effluent concentrations, was more compact and energy efficient compared to the CAS.
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| 5. |
- Grolig, Jan Gustav, 1986
(författare)
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Coated Ferritic Stainless Steels as Interconnects in Solid Oxide Fuel Cells - Material Development and Electrical Properties
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Solid oxide fuel cells (SOFCs) are attracting increasing interest as devices with potentialuses in decentralized and clean electricity and heat production. Several challengeswith respect to materials have to be overcome to achieve efficiencies and life-spansthat are sufficient for long-term applications.An important element of an SOFC stack is the interconnect component, which connectstwo adjacent fuel cell elements. Interconnects, which are commonly composedof ferritic stainless steels, have to be corrosion-resistant, mechanically stable and costoptimized.This work aimed to investigate economic solutions for interconnect materials and tounderstand the underlying mechanisms of degradation and electrical conduction ofthese materials. Mainly two substrates, a commercially available steel (AISI 441) anda ferritic stainless steel that was optimized for an SOFC application (Sandvik SanergyHT) were combined with different barrier coatings and exposed to a cathode-sideatmosphere. A method was developed that allows for the electrical characterizationof promising material systems and model alloys, thereby facilitating a fundamentalunderstanding of the dominant electrical conduction processes linked to the oxidescales that grow on interconnects. The AISI 441 steel coated with reactive elementsand cobalt showed good corrosion and chromium evaporation profiles, while AISI 441coated with cerium and cobalt also had promising electrical properties. The SanergyHT steel was examined with coatings of copper and iron and copper and manganese,respectively. The corrosion and chromium evaporation profiles of Sanergy HT wereimproved by coating with copper and iron. The copper and iron-coated Sanergy HTshowed lower area specific resistance values than cobalt-coated Sanergy HT. Chromia,which is the main constituent of oxide scales, was synthesized using differentmethods. The electrical properties of chromia were found to be sensitive to not onlyimpurities, but also heat treatment. Finally the electrical properties of cobalt- andcobalt cerium-coated Sanergy HT steels were investigated. It was revealed that theaddition of cerium improved the conductivity of the interconnect by both slowingdown chromia growth and preventing the outward diffusion of iron into the spinel.
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| 6. |
- Han, Joonsoo, 1990
(författare)
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Fundamentals of NH3-SCR and SOx chemistry over copper zeolite for the control of NOx and greenhouse gas (N2O) emissions
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The release of N2O over Cu-zeolite was investigated due to the critical contribution it makes to the atmosphere as one of the greenhouse gases (GHGs). An exhaust after-treatment system (EATS) for heavy-duty vehicles that uses Cu/SSZ-13 as the selective catalyst reduction (SCR) catalyst experiences not only a variety of flow, temperature and chemical conditions but is also exposed to various resulting contaminants. Among these, sulfur has been the focus of studies due to its critical deactivation of DeNOx performance, even at low concentration levels. Adsorption/desorption of sulfur species over Cu/SSZ-13 is connected closely to the lifetime of the SCR catalyst. The task of unravelling the synergistic effect of sulfur has on the formation of N2O during the NH3-SCR of NOx, while also reflecting realistic application conditions, is challenging. The ambition here is to gain a comprehensive understanding of the formation of N2O in the presence of sulfur species during the NH3-SCR of NOx at low temperature for NOx emissions control. Model catalysts were prepared to investigate a variety of copper species and ammonium nitrate (AN) within the CHA cage. It was found that the CHA structure promotes surface nitrate species in NO2-rich conditions, and an environment with strong polarity within the CHA cage was proposed as a feasible reason for the largest formation of ammonium nitrate compared to the MFI and BEA structures with medium and large pore/cage sizes. In addition, zeolite acidity was more a viable reason as to why ammonium nitrate is thermally stable in Cu/CHA compared to Cu/MFI and Cu/BEA than the pore-confinement effect, which has been used to explain the thermal stability of AN over Cu/zeolites. The IR signature of the ammonium nitrate was also obtained; it is believed that ammonium nitrate exists mainly by interacting with copper ions to form copper-ammonium nitrate within the CHA cage. Copper species and the adsorption of sulfur oxides (SO2/SO3) were investigated and their synergistic effects on the formation of N2O assessed. The SO3-poisoning effect was highlighted which, from an experimental aspect, is very challenging. We found two different states of sulfur species. SO2 and SO3 interaction with copper-monomers (Z1CuOH and Z2Cu) and copper-dimer (Z2Cu2O2) are possible. Sulfated Cu-dimer is lower in energy compared to its copper-monomers counterparts. SO3 interacts with both Z1CuOH and Z2Cu but SO2 mainly interacts with Z1CuOH. SO3-poisoning only causes (bi)sulfate (Z1HSO4), whereas SO2-poisoning can cause both (bi)sulfite (Z1HSO3) and (bi)sulfate (Z1HSO4). Taken together, out results well demonstrates why the SO3 exposure results in more critical chemical poisoning (irreversible deactivation) compared to the SO2 exposure to Cu/CHA. Finally, synergistical effect of sulfur, copper, and Brønsted sites were found for N2O formation under NO2-rich condition. Consequently, we found that sulfur promotes N2O intermediate formation but increasing Brønsted site density increases N2 selectivity, thereby, reducing N2O formation from Cu/CHA.
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| 7. |
- Luo, Xin, 1983
(författare)
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Characterization of nano-scale materials for interconnect and thermal dissipation application in electronics packaging
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis focuses on studies of nano-scale materials in electronic packaging applications with respect to following aspects: surface analysis of nano-scale oxide of lead-free solder particles, and thermal performance and mechanical property studies of nano-scale fiber and metal composite-based thermal interface materials. The composition and thickness of the solder oxide have a direct impact on the quality of interconnects and the reliability of a packaged system. The characterization of the nano-scale oxide of lead-free solder particles is investigated by transmission electron microscopy and scanning transmission electron microscopy. The solder powders are exposed to air at 150 oC for 0, 120 and 240 h. The oxide thickness is 6 nm and 50 nm measured by STEM for 0 h and 120 h samples, respectively. The increase in oxide thickness of solder particles is proportional to the rooting of the oxidation time. The intersection analysis method for analyzing Auger electron spectroscopy depth profiles is also presented which could be expand to analyze oxide of other alloy, i.e. Cu, Ag or stainless steel.In the next part of this thesis, a new composite design consisting of electrospun polyimide fiber networks and infiltrated metal matrix is presented. Three composites are fabricated including polyimide fiber-InSnBi, polyimide fiber-indium and polyimide fiber-SnAgCu composites. The microstructure of the composite is investigated by scanning electron microscopy, energy dispersive X-ray detector and X-ray diffraction, showing a good bonding between the fibers and the metal matrix. These composites demonstrate high thermal conductivity, low thermal contact resistance and reliable thermomechanical performance during thermal cycling. The polyimide fiber-indium composites are sandwiched between chips and heat spreaders with different packaged sizes to detect the junction temperature and junction-to-case thermal resistance. The shear strength of the polyimide fiber-indium composite between Sn surfaces can reach 4 MPa which is larger than that with Au and Cu surfaces. Both composites present good reliability during the humidity-heat aging tests. The polyimide fiber-indium composite’s ultimate tensile strength at 20 °C is five times higher than that of the pure indium, and the tensile strength of the composite exceeds the summation of those from its individual components. With the increase in temperature, the ultimate tensile strength declines but still precedes pure indium and the elongation at fracture increases. Contrary to most metallic materials, the ultimate tensile strength of the composite is inversely proportional to the logarithmic strain rate in a certain range. Finally, a new strengthening mechanism is presented based on mutually reinforcing structures formed by the indium and surrounding fibers, underlining the effect of compressing at the fiber-indium interfaces by dislocation pileups and slip pinning. The creep threshold of the composite corresponds to the fracture strength of the polyimide fiber, and the step-like sudden increases of the composite’s creep strain are due to the breakage of fibers. The fiber-indium interfaces are also beneficial to the composite’s creep resistance. In the final part of the thesis, two novel thermal interface materials are developed and characterized including boron nitride fiber-indium composite and carbon fiber-SnAgCu composite. Thermally conductive boron nitride fiber or carbon fiber is prepared via electrospinning and heat treatment. Afterward, the boron nitride/carbon fibers are sputtered with Ti/Au coatings and infiltrated with metal matrix. Good in-plane and through-plane thermal conductivity of the thermally conductive fiber-metal matrix composite are obtained using a laser flash apparatus.
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| 8. |
- Shahroozi, Zahra, 1992-
(författare)
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Survivability control using data-driven approaches and reliability analysis for wave energy converters
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Wave energy, with five times the energy density of wind and ten times the power density of solar, offers a compelling carbon-free electricity solution. Despite its advantages, ongoing debates surround the reliability and economic feasibility of wave energy converters (WECs). To address these challenges, this doctoral thesis is divided into four integral parts, focusing on optimizing the prediction horizon for power maximization, analyzing extreme waves' impact on system dynamics, ensuring reliability, and enhancing survivability in WECs.Part I emphasizes the critical importance of the prediction horizon for maximal power absorption in wave energy conversion. Using generic body shapes and modes, it explores the effect of dissipative losses, noise, filtering, amplitude constraints, and real-world wave parameters on the prediction horizon. Findings suggest achieving optimal power output may be possible with a relatively short prediction horizon, challenging traditional assumptions.Part II shifts focus to WEC system dynamics, analyzing extreme load scenarios. Based on a 1:30 scaled wave tank experiment, it establishes a robust experimental foundation, extending into numerical assessment of the WEC. Results underscore the importance of damping to alleviate peak forces. Investigating various wave representations highlights conservative characteristics of irregular waves, crucial for WEC design in extreme sea conditions.Part III explores the computational intricacies of environmental design load cases and fatigue analyses for critical mechanical components of the WEC. The analysis is conducted for hourly sea state damage and equivalent two-million-cycle loads. Finally, a comparison of safety factors between the ultimate limit state and fatigue limit state unfolds, illustrating the predominant influence of the ultimate limit state on point-absorber WEC design.Part IV, centers on elevating survivability strategies for WECs in extreme wave conditions. Three distinct controller system approaches leverage neural networks to predict and minimize the line force. Distinct variations emerge in each approach, spanning from rapid detection of optimal damping to integrating advanced neural network architectures into the control system with feedback. The incorporation of a controller system, refined through experimental data, showcases decreases in the line force, providing a practical mechanism for real-time force alleviation.This thesis aims to contribute uniquely to the goal of advancing wave energy conversion technology through extensive exploration.
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| 9. |
- Dahlin, Andreas, 1980
(författare)
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Nanoplasmonic Biosensors compatible with Artificial Cell Membranes
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Within life science, there is currently an intense search for novel techniques that enable efficient and reliable analysis of biomolecular interactions. Such methods have future applications within medical diagnostics and drug development, as well as within proteomic research in general. Lately, several concepts have emerged that are based on monitoring molecular binding to surfaces via optical, mechanical or electrical signal transduction. In particular, the plasmons associated with metallic nanoparticles are of interest since they offer a convenient way to monitor biomolecular interactions, also in a miniaturized format, by optical spectroscopy.This thesis describes the development of a biosensor based on the optical properties of nanoscale apertures in continuous metal films. The fabrication and characterization of the nanostructure is described, as well as surface modification protocols based on thiol chemistry for material-specific functionalization. In addition, an experimental setup for spectroscopy is presented together with data analysis algorithms for minimizing noise.It is emphasized that, from an experimental sensing perspective, nanoholes and nanoparticles have essentially the same plasmonic properties. However, the nanoholes offer several advantages because of the fact that the structure is physically different. In particular, it is shown how various artificial cell membranes can be spontaneously formed inside nanoholes. This makes the sensor compatible with studies of processes related to biological membranes. In this context, membrane-bound proteins are of special interest since they constitute a third of our genome and represent the target of half of the most common medical drugs. Potential future applications of the artificial membranes on the plasmonic nanostructures are discussed, with focus on probing transport across the membrane.
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| 10. |
- Kersten, Anton, 1991
(författare)
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Modular Battery Systems for Electric Vehicles based on Multilevel Inverter Topologies - Opportunities and Challenges
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Modular battery systems based on multilevel inverter (MLI) topologies can possibly overcome some shortcomings of two-level inverters when used for vehicle propulsion. The results presented in this thesis aim to point out the advantages and disadvantages, as well as the technical challenges, of modular vehicle battery systems based on MLIs in comparison to a conventional, two-level IGBT inverter drivetrain. The considered key aspects for this comparative investigation are the drive cycle efficiency, the inverter cost, the fault tolerance capability of the drivetrain and the conducted electromagnetic emissions. Extensive experiments have been performed to support the results and conclusions. In this work, it is shown that the simulated drive cycle efficiency of different low-voltage-MOSFET-based, cascaded seven-level inverter types is improved in comparison to a similarly rated, two-level IGBT inverter drivetrain. For example, the simulated WLTP drive cycle efficiency of a cascaded double-H-bridge (CDHB) inverter drivetrain in comparison to a two-level IGBT inverter, when used in a small passenger car, is increased from 94.24% to 95.04%, considering the inverter and the ohmic battery losses. In contrast, the obtained efficiency of a similar rated seven-level cascaded H-bridge (CHB) drivetrain is almost equal to that of the two-level inverter drivetrain, but with the help of a hybrid modulation technique, utilizing fundamental selective harmonic elimination at lower speeds, it could be improved to 94.85%. In addition, the CDHB and CHB inverters’ cost, in comparison to the two-level inverter, is reduced from 342€ to 202€ and 121€, respectively. Furthermore, based on a simple three-level inverter with a dual battery pack, it is shown that MLIs inherently allow for a fault tolerant operation. It is explained how the drivetrain of a neutral point clamped (NPC) inverter can be operated under a fault condition, so that the vehicle can drive with a limited maximum power to the next service station, referred to as limp home mode. Especially, the detection and localization of open circuit faults has been investigated and verified through simulations and experiments. Moreover, it is explained how to measure the conducted emissions of an NPC inverter with a dual battery pack according to the governing standard, CISPR 25, because the additional neutral point connection forms a peculiar three-wire DC source. To separate the measured noise spectra into CM, line-DM and phase-DMquantities, two hardware separators based on HF transformers are developed and utilized. It is shown that the CM noise is dominant. Furthermore, the CM noise is reduced by 3dB to 6dB when operating the inverter with three-level instead of two-level modulation.
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