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<p>  </p> <p><strong>Background: </strong></p> <p>Torsades de pointes (TdP) is a polymorphic ventricular tachycardia (VT) associated with heart rate-corrected QT interval (QTc) prolongation on the electrocardiogram (ECG). TdP can cause sudden cardiac arrest (SCA), a catastrophic outcome. The antiarrhythmic drugs dofetilide and sotalol can cause QTc prolongation and arrhythmias, as can more than 200 other medications available on global markets. Heart failure (HF) with reduced ejection fraction (HFrEF) is a risk factor for drug-induced TdP, and HFrEF heightens sensitivity to drug-induced QTc lengthening. However, ~55% of patients with HF have preserved, rather than reduced, ejection fraction. It remains unknown whether patients with HF with preserved ejection fraction (HFpEF) are at increased risk for drug-induced VT/SCA. Assessment of the risk of drug-induced VT/SCA in HFpEF patients is important, so that recommendations can be made regarding the safety of QTc-prolonging drugs and need for enhanced ECG monitoring in this population. </p> <p><strong>Objective:</strong></p> <p>In aim 1, we sought to determine the risk of VT and SCA associated with dofetilide and sotalol in patients with HFpEF. In aim 2, we were able to use QTc interval to determine the odds of dofetilide/sotalol-associated QT interval prolongation in patients with HFpEF. In Aim 3, we investigated the influence of HFpEF on VT and SCA associated with a broader group of drugs known to cause TdP (“known “TdP drugs”), as designated by the QT drugs list at www.crediblemeds.org. </p> <p><strong>Methods:</strong></p> <p>In aim 1, we used Medicare claims (2014-2016) and ICD-9/10 codes to identify patients taking the QT interval-prolonging drugs dofetilide or sotalol, which are used commonly in patients with HF and atrial fibrillation, as well as non-dofetilide or sotalol users among 3 groups: HFpEF, HFrEF, and no HF. Multinomial propensity score-matching was performed. Cochran–Mantel–Haenszel statistics and standardized differences were used to compare baseline characteristics. A generalized Cox proportional hazards model was used to estimate hazard ratios (HRs) and test the association of VT and SCA among dofetilide/sotalol users, HFpEF, HFrEF, and no HF.</p> <p>In Aim 2, the data source was electronic health records from the Indiana Network for Patient Care (February 2010 to May 2021). After removing patients with overlapping diagnoses of HFpEF and HFrEF, no diagnosis code, absence of QT interval records, and no validated record of using dofetilide or sotalol, we identified patients taking dofetilide or sotalol among three groups: HFrEF, HFpEF, and no HF. Cochran–Mantel–Haenszel statistics were used to compare baseline characteristics. QT interval prolongation was defined as heart rate-corrected QT (QTc) > 500 ms during dofetilide/sotalol therapy. Unadjusted odds ratios (OR) of QT interval prolongation were determined by univariate analysis, and adjusted ORs were determined by generalized estimating equations (GEE) with logit link to account for an individual cluster with different times of hospitalization and covariates.</p> <p>In aim 3, we used Medicare enrollment in fee-for-service medical and pharmacy benefits (2014 to 2016) and ICD-9/10 codes, we identified patients taking drugs known to cause torsades de pointes (TdP drugs; www.crediblemeds.org) and non-TdP drug users among three groups: HFrEF, HFpEF, and no HF. Multinomial propensity score-matching was performed to minimize baseline differences in covariates (patient demographics, comorbidities, health care utilization and drug history). Cochran–Mantel–Haenszel statistics and standardized differences were used to compare baseline characteristics. A generalized Cox proportional hazards model was used to estimate HRs and test the association of VT and SCA among TdP drug users with HFpEF, HFrEF, and no HF.</p> <p><strong>Results:</strong></p> <p>In Aim 1, VT and SCA occurred in 166 (10.68%) and 16 (1.03%), respectively, of 1,554 dofetilide/sotalol users with HFpEF, 543 (38.76%) and 40 (2.86%) of 1,401 dofetilide/sotalol users with HFrEF, and 245 (5.06%) and 13 (0.27%) of 4,839 dofetilide/sotalol users with no HF. The adjusted HR for VT in patients with HFrEF was 7.00 (95% CI 6.12-8.02) and in patients with HFpEF was 1.99 (1.71-2.32). The risk of VT associated with dofetilide/sotalol was increased across the overall study population (HR: 2.47 [1.89-3.23]). Use of dofetilide/sotalol increased the risk of VT in patients with HFrEF (HR: 1.53 [1.07-2.20]) and in those with HFpEF (HR: 2.34 [1.11-4.95]). However, while the overall risk of SCA was increased in patients with HFrEF (HR: 5.19 [4.10-6.57]) and HFpEF (HR: 2.53 [1.98-3.23]) compared to patients with no HF, dofetilide/sotalol use was not significantly associated with an increased risk of SCA.</p> <p>In Aim 2, QTc prolongation associated with dofetilide/sotalol occurred in 51.2% of patients with HFpEF, 70.1% of patients with HFrEF, and 29.4% of patients with no HF. After adjusting for age, sex, race, serum potassium and magnesium concentrations, kidney function, concomitant drug therapy, and comorbid conditions, the adjusted odds of having QTc interval larger than 500ms during the hospital stay were 5.23 [3.15-8.67] for HFrEF and 1.98 [1.17-3.33] for HFpEF with no HF as the reference group. </p> <p>In Aim 3, of 23,910 known TdP drug users with HFrEF, VT and SCA occurred in 4,263 (17.8%) and 493 (2.1%) patients, respectively. In comparison, among 31,359 known TdP drug users with HFpEF, VT and SCA occurred in 1,570 (5.0%) and 340 (1.1%) patients. VT and SCA occurred in 3,154 (0.8%) and 528 (0.1%) of 384,824 known TdP drug users without HF. The overall HR of both VT and SCA was increased in patients with HFrEF (HR: 7.18 [6.13-8.40])  and in those with HFpEF (HR: 2.09 [1.80-2.42]). The risk of VT associated with known TdP drugs was increased across the overall population (HR: 1.34 [1.20-1.51]). Use of known TdP drugs significantly increased the risk of VT and SCA in patients with HFrEF (HR: 1.34 [1.07-1.67]), but not in patients with HFpEF.</p> <p><strong>Conclusion:</strong></p> <p>HFpEF may exhibit an enhanced response to drug-associated VT, and is associated with a higher risk of drug-associated QTc interval prolongation. Further study is needed to identify methods to minimize this risk for patients with HFpEF requiring therapy with dofetilide, sotalol, or drugs known to cause TdP. </p>

I takt med att hållbar utveckling blir mer aktuellt och det ställs högre krav på produkter att eftersträva såväl FN:s klimatmål som målen för Grön teknik, arbetar företag aktivt för att effektivisera sina produkter. Effektiviteten för en roterande värmeväxlare innefattar främst den termiska verkningsgraden, vilket beror på hur mycket värme som återvinns från byggnadens utgående luft till den ingående. Studier påvisar att värmeöverföringen i rotorns folie från rotorns varma till kalla sida (longitudinell termisk konduktivitet) reducerar rotorns verkningsgrad. Denna studie undersöker hur slitsar i en rotors folie påverkar den longitudinella termiska konduktiviteten. Den metod som främst tillämpats är experiment som har utförts på en enskild plan folie och miniatyrrotorer. För respektive uppsättning jämförs en modell med och utan slitsar samt att resultatet ställs i korrelation med teori inom värmeledning. Ett förslag på applicering av slitsar i produktion presenteras och tillämpas för att skapaden prototyp som testas experimentellt. Slitsarnas konstellation bestäms dels utifrån appliceringsmetoden, men även handberäkningar och numeriska beräkningar genom finita elementmetoden. Flera experiment har genomförts där samtliga påvisar att slitsar i materialet medför en lägre termisk konduktivitet. Utifrån resultaten uppmättes en reducering av materialets termiska konduktivitet upp till 29,5 %. Vidare diskuteras osäkerheten med resultatet vilka bland annat innefattar värmeförluster, mätosäkerhet och den mänskliga faktorn. Slutligen presenteras utvecklingspotential med studien och förslag på framtida arbeten. Studien anses vara unik i sitt slag och därmed en grund för förhoppningsvis många intressanta framtida arbeten. / As sustainable development is getting more relevant and higher demands are placed on products to pursue the UN climate goals and the goals for Green Tech, companies areactively working to make their products more efficient. The efficiency of a heat wheelincludes mainly the thermal efficiency which depend on how much heat that is recycled from the extracted air to the supply air of a building. Studies show that heat whichtransfers through the material in the heat wheel from the hot side to the cold side (longitudinal thermal conductivity) reduces the efficiency. This study examines how the application of slits in the heat wheels material affect the longitudinal thermal conductivity. The main method used in this study are experiment which have been conducted both on a single piece of foil and on a heat wheel. For each set, a model with and without slits are compared whose results are placed in correlation with the theory of thermal conductivity. A suggestion of the slits application in the production are presented and used to make the prototype which are tested through experiment. The constellation of the slits aredetermined through the method of application, analytical calculations and numerical simulations by the finite element method. Several experiments have been conducted and all demonstrate that the application of slits in the material generate a lower thermal conductivity. Based on the results, a reduction of the materials thermal conductivity measured up to 29,5 %. Furthermore, the uncertainty of the results are discussed which includes, among other things, heat loss,measurement uncertainty and human error. Finally, development possibilities with the study will be presented with some suggestions for future work. The study is considered unique by its nature and therefore, hopefully a solid foundation for future studies.

Reduced-order models are frequently used in the simulation of complex flows to overcome the high computational cost of direct numerical simulations, especially for three-dimensional nonlinear problems. Proper orthogonal decomposition, as one of the most commonly used tools to generate reduced-order models, has been utilized in many engineering and scientific applications. Its original promise of computationally efficient, yet accurate approximation of coherent structures in high Reynolds number turbulent flows, however, still remains to be fulfilled. To balance the low computational cost required by reduced-order modeling and the complexity of the targeted flows, appropriate closure modeling strategies need to be employed. In this dissertation, we put forth two new closure models for the proper orthogonal decomposition reduced-order modeling of structurally dominated turbulent flows: the dynamic subgrid-scale model and the variational multiscale model. These models, which are considered state-of-the-art in large eddy simulation, are carefully derived and numerically investigated. Since modern closure models for turbulent flows generally have non-polynomial nonlinearities, their efficient numerical discretization within a proper orthogonal decomposition framework is challenging. This dissertation proposes a two-level method for an efficient and accurate numerical discretization of general nonlinear proper orthogonal decomposition closure models. This method computes the nonlinear terms of the reduced-order model on a coarse mesh. Compared with a brute force computational approach in which the nonlinear terms are evaluated on the fine mesh at each time step, the two-level method attains the same level of accuracy while dramatically reducing the computational cost. We numerically illustrate these improvements in the two-level method by using it in three settings: the one-dimensional Burgers equation with a small diffusion parameter, a two-dimensional flow past a cylinder at Reynolds number Re = 200, and a three-dimensional flow past a cylinder at Reynolds number Re = 1000. With the help of the two-level algorithm, the new nonlinear proper orthogonal decomposition closure models (i.e., the dynamic subgrid-scale model and the variational multiscale model), together with the mixing length and the Smagorinsky closure models, are tested in the numerical simulation of a three-dimensional turbulent flow past a cylinder at Re = 1000. Five criteria are used to judge the performance of the proper orthogonal decomposition reduced-order models: the kinetic energy spectrum, the mean velocity, the Reynolds stresses, the root mean square values of the velocity fluctuations, and the time evolution of the proper orthogonal decomposition basis coefficients. All the numerical results are benchmarked against a direct numerical simulation. Based on these numerical results, we conclude that the dynamic subgrid-scale and the variational multiscale models are the most accurate. We present a rigorous numerical analysis for the discretization of the new models. As a first step, we derive an error estimate for the time discretization of the Smagorinsky proper orthogonal decomposition reduced-order model for the Burgers equation with a small diffusion parameter. The theoretical analysis is numerically verified by two tests on problems displaying shock-like phenomena. We then present a thorough numerical analysis for the finite element discretization of the variational multiscale proper orthogonal decomposition reduced-order model for convection-dominated convection-diffusion-reaction equations. Numerical tests show the increased numerical accuracy over the standard reduced-order model and illustrate the theoretical convergence rates. We also discuss the use of the new reduced-order models in realistic applications such as airflow simulation in energy efficient building design and control problems as well as numerical simulation of large-scale ocean motions in climate modeling. Several research directions that we plan to pursue in the future are outlined. / Ph. D.

Ultrasound acoustic energy transfer (UAET) is an emerging contactless technology that offers the capability to safely and efficiently power sensors and devices while eliminating the need to replace batteries, which is of interest in many applications. It has been proposed to recharge and communicate with implanted medical devices, thereby eliminating the need for invasive and expensive surgery and also to charge sensors inside enclosed metal containers typically found in automobiles, nuclear power plants, space stations, and aircraft engines. In UAET, energy is transferred through the reception of acoustic waves by a piezoelectric receiver that converts the energy of acoustic waves to electrical voltage. It has been shown that UAET outperforms the conventional CET technologies that use electromagnetic waves to transfer energy, including inductive coupling and capacitative coupling. To date, the majority of research on UAET systems has been limited to modeling and proof-of-concept experiments, mostly in the linear regime, i.e., under small levels of acoustic pressure that result in small amplitude longitudinal vibrations and linearized piezoelectricity. Moreover, existing models are based on the "piston-like" deformation assumption of the transmitter and receiver, which is only accurate for thin disks and does not accurately account for radiation effects. The linear models neglect nonlinear effects associated with the nonlinear acoustic wave propagation as well as the receiver's electroelastic nonlinearities on the energy transfer characteristics, which become significant at high source strengths. In this dissertation, we present experimentally-validated analytical and numerical multiphysics modeling approaches aimed at filling a knowledge gap in terms of considering resonant acoustic-piezoelectric structure interactions and nonlinear effects associated with high excitation levels in UAET systems. In particular, we develop a reduced-order model that can accurately account for the radiation effects and validate it by performing experiments on four piezoelectric disks with different aspect ratios. Next, we study the role of individual sources of nonlinearity on the output power characteristics. First, we consider the effects of electroelastic nonlinearities. We show that these nonlinearities can shift the optimum load resistance when the acoustic medium is fluid. Next, we consider the nonlinear wave propagation and note that the shock formation is associated with the dissipation of energy, and as such, shock formation distance is an essential design parameter for high-intensity UAET systems. We then present an analytical approach capable of predicting the shock formation distance and validate it by comparing its prediction with finite element simulations and experimental results published in the literature. Finally, we experimentally investigate the effects of both the nonlinearity sources on the output power characteristics of the UAET system by considering a high intensity focused ultrasound source and a piezoelectric disk receiver. We determine that the system's efficiency decreases, and the maximum voltage output position drifts towards the source as the source strength is increased. / Doctor of Philosophy / Advancements in electronics that underpinned the development of low power sensors and devices have transformed many fields. For instance, it has led to the innovation of implanted medical devices (IMDs) such as pacemakers and neurostimulators that perform life-saving functions. They also find applications in condition monitoring and wireless sensing in nuclear power plants, space stations, automobiles and aircraft engines, where the sensors are enclosed within sealed metal containers, vacuum/pressure vessels or located in a position isolated from the operator by metal walls. In all these applications, it is desired to communicate with and recharge the sensors wirelessly. Such a mechanism can eliminate the need for invasive and expensive surgeries to replace batteries of IMDs and preserve the structural integrity of metal containers by eliminating the need for feed through wires. It has been shown that ultrasound acoustic energy transfer (UAET) outperforms conventional wireless power transfer techniques. However, existing models are based on several assumptions that limit their potential and do not account for effects that become dominant when a higher output power is desired. In this dissertation, we present experimentally validated numerical and theoretical investigations to fill those knowledge gaps. We also provide crucial design recommendations based on our findings for the efficient implementation of UAET technology.

In this dissertation, we consider two different strategies for improving the projection-based reduced order model (ROM) accuracy: (I) adding closure terms to the standard ROM; (II) using Lagrangian data to improve the ROM basis. Following strategy (I), we propose a new data-driven reduced order model (ROM) framework that centers around the hierarchical structure of the variational multiscale (VMS) methodology and utilizes data to increase the ROM accuracy at a modest computational cost. The VMS methodology is a natural fit for the hierarchical structure of the ROM basis: In the first step, we use the ROM projection to separate the scales into three categories: (i) resolved large scales, (ii) resolved small scales, and (iii) unresolved scales. In the second step, we explicitly identify the VMS-ROM closure terms, i.e., the terms representing the interactions among the three types of scales. In the third step, we use available data to model the VMS-ROM closure terms. Thus, instead of phenomenological models used in VMS for standard numerical discretizations (e.g., eddy viscosity models), we utilize available data to construct new structural VMS-ROM closure models. Specifically, we build ROM operators (vectors, matrices, and tensors) that are closest to the true ROM closure terms evaluated with the available data. We test the new data-driven VMS-ROM in the numerical simulation of four test cases: (i) the 1D Burgers equation with viscosity coefficient $nu = 10^{-3}$; (ii) a 2D flow past a circular cylinder at Reynolds numbers $Re=100$, $Re=500$, and $Re=1000$; (iii) the quasi-geostrophic equations at Reynolds number $Re=450$ and Rossby number $Ro=0.0036$; and (iv) a 2D flow over a backward facing step at Reynolds number $Re=1000$. The numerical results show that the data-driven VMS-ROM is significantly more accurate than standard ROMs. Furthermore, we propose a new hybrid ROM framework for the numerical simulation of fluid flows. This hybrid framework incorporates two closure modeling strategies: (i) A structural closure modeling component that involves the recently proposed data-driven variational multiscale ROM approach, and (ii) A functional closure modeling component that introduces an artificial viscosity term. We also utilize physical constraints for the structural ROM operators in order to add robustness to the hybrid ROM. We perform a numerical investigation of the hybrid ROM for the three-dimensional turbulent channel flow at a Reynolds number $Re = 13,750$. In addition, we focus on the mathematical foundations of ROM closures. First, we extend the verifiability concept from large eddy simulation to the ROM setting. Specifically, we call a ROM closure model verifiable if a small ROM closure model error (i.e., a small difference between the true ROM closure and the modeled ROM closure) implies a small ROM error. Second, we prove that a data-driven ROM closure (i.e., the data-driven variational multiscale ROM) is verifiable. For strategy (II), we propose new Lagrangian inner products that we use together with Eulerian and Lagrangian data to construct new Lagrangian ROMs. We show that the new Lagrangian ROMs are orders of magnitude more accurate than the standard Eulerian ROMs, i.e., ROMs that use standard Eulerian inner product and data to construct the ROM basis. Specifically, for the quasi-geostrophic equations, we show that the new Lagrangian ROMs are more accurate than the standard Eulerian ROMs in approximating not only Lagrangian fields (e.g., the finite time Lyapunov exponent (FTLE)), but also Eulerian fields (e.g., the streamfunction). We emphasize that the new Lagrangian ROMs do not employ any closure modeling to model the effect of discarded modes (which is standard procedure for low-dimensional ROMs of complex nonlinear systems). Thus, the dramatic increase in the new Lagrangian ROMs' accuracy is entirely due to the novel Lagrangian inner products used to build the Lagrangian ROM basis. / Doctor of Philosophy / Reduced order models (ROMs) are popular in physical and engineering applications: for example, ROMs are widely used in aircraft designing as it can greatly reduce computational cost for the aircraft's aeroelastic predictions while retaining good accuracy. However, for high Reynolds number turbulent flows, such as blood flows in arteries, oil transport in pipelines, and ocean currents, the standard ROMs may yield inaccurate results. In this dissertation, to improve ROM's accuracy for turbulent flows, we investigate three different types of ROMs. In this dissertation, both numerical and theoretical results show that the proposed new ROMs yield more accurate results than the standard ROM and thus can be more useful.

Introduktion: Låg energitillgänglighet (LEA) är ett förekommande problem hos elitsatsandeungdomar inom uthållighetsidrotter. Det är ett resultat av att individens energiintag är lägreän individens energiförbrukning. Följderna av LEA är bland annat nedsatt prestation, skador,hormonell påverkan och ökade risker för psykiska följdsjukdomar. Förebyggande insatseranses viktiga för att motverka LEA, och där tränare har en viktig roll i arbetet.Syftet: Studiens syfte är att undersöka vilka kunskaper tränare för ungdomar inomuthållighetsidrotter har om LEA och vilka kunskaper tränare har om konsekvenser relateradetill LEA. Metod: Enkätundersökning. Enkäten skickades ut till tränare inom elitsatsande verksamhetersom arbetar med ungdomar 15–24 år inom uthållighetsidrotter. 53 tränare inkluderades istudien. Analysmetoden som studien utgått ifrån är tematisk analys. Resultatet: Tränarna själva skattade sina kunskaper om LEA som goda eller mycket goda.92,5% av tränarna uppgav att de var medvetna om tecken på LEA och kunde redogöra förtecken som överensstämmer med litteratur. Tränarna kunde även ange negativa konsekvenserav LEA som rör idrottarens fysiologi, psykologi och prestation. 90,6% av tränarnarapporterade att de arbetar förebyggande för att motverka LEA. Tränarna angav flera olikaarbetsmetoder, vilket lyfts som positivt utifrån tidigare forskning. Konklusion: Studien visar att tränare känner till tecken i teorin men har svårt att omsätta deti praktiska arbetet. Tränarna uppgav en högre svarsfrekvens av fysiologiska konsekvenser pålång sikt och en lägre svarsfrekvens av vilka långvariga konsekvenser LEA har förprestationen. Inom det förebyggande arbetet bestod det mest frekventa arbetet av utbildning,samtal med aktiva och påminnelser om energibehov. Framtida forskning bör undersöka hurde aktiva upplever det förebyggande arbetet och undersöka skillnader i det förebyggandearbetet mellan idrotter där prevalensen av LEA är hög.

År 2022 stod järn- och stålindustrin för ca 12,5% av Sveriges totala CO2-utsläpp, där den främsta utsläppskällan är reduktion av järnmalm i masugn. En attraktiv väg för att minska utsläppen från masugnen är att ersätta denna med direktreduktion med vätgas för att producera järnsvamp, som sedan kan smältas i en ljusbågsugn. Denna teknik har potentialen att minska CO2-utsläppen med upp till 98% jämfört med masugnsprocessen. För att minska utsläppen ytterligare kan tekniker för CO2-avskiljning implementeras.  Syftet med detta arbete är att undersöka hur CO2-avskiljning kan implementeras i ett system som använder direktreduktion med vätgas, samt smältning av järnsvamp i ljusbågsugn. Målen med arbetet har varit att formulera ett processkoncept för detta system, för att sedan modellera denna process och utföra en tekno-ekonomisk analys. Arbetets frågeställningar har varit ifall det var mer fördelaktigt med hög eller låg CO2-halt i rökgaserna, ifall ett uppkolningssteg är mer fördelaktigt än uppkolning i ljusbågsugnen, samt ifall den avskilda koldioxiden bör lagras eller återanvändas i processen. En ytterligare frågeställning var även hur lönsamheten av CO2-avskiljning påverkas med avseende på kostnad för utsläppsrättigheter för CO2.  Systemets omfattning sträckte sig från direktreduktionsschaktet till uppvärmningsugnen innan valsning. De CO2-innehållande rökgaserna från de olika processtegen skickades in i en kalciumloopingenhet, som var den valda tekniken för CO2-avskiljning. Ett basfall utan CO2-avskiljning samt åtta scenarion med CO2-avskiljning ställdes upp baserat på frågeställningarna, där dessa sedan modellerades i Microsoft Excel. Resultaten från modellen utvärderades utifrån energirelaterade och ekonomiska prestandaindikatorer där alla scenarion jämfördes mot varandra, samt mot basfallet. Resultaten från arbetet visade att CO2-avskiljning med kalciumlooping kan minska CO2-utsläppen från detta system med 90-91%. Energianvändningen ökade för alla fall som använder CO2-avskiljning, där den lägsta ökningen jämfört med referensfallet var med 4% och den högsta med 40%. Alla scenarion medförde ökade kostnader för systemet jämfört med basfallet. Det scenario där endast koldioxidavskiljning adderades hade lägst kostnad av dessa fall. Detta scenario medförde en ökad produktionskostnad på 240 SEK/ton stål och det skulle krävas en kostnad för utsläppsrätter på 2200 SEK/ton CO2 för att investeringen ska uppnå en återbetalningstid på 25 år.  Utifrån analysen av arbetets olika scenarion, är det mest fördelaktigt att endast addera kalciumloopingtekniken på den befintliga processen. Att stänga ugnarna är fördelaktigt ur ett energiperspektiv, men blir kostsamt ekonomiskt. Därför kan detta vara ett bra alternativ om en ny anläggning ska byggas att då bygga ugnarna stängda. Ett separat uppkolningssteg kan vara ett alternativ för att uppkolning i ljusbågsugnen, men medför både ökad energianvändning samt ökade kostnader. Metanisering visade sig inte vara fördelaktigt utifrån ett ekonomiskt och energiperspektiv på grund av det stora elbehovet som detta medför, dock ger återanvändning av CO2 stora möjligheter till recirkulering av kol i processen vilket gör att upp till 92% av kolbehovet kan täckas av återanvänt kol. / In 2022, the iron and steel industry accounted for approximately 12.5% of Sweden's total CO2 emissions, with the primary source of emissions being the reduction of iron ore in a blast furnace. An attractive way to reduce emissions from the blast furnace is to replace it with direct reduction using hydrogen to produce direct reduced iron, which can then be melted in an electric arc furnace. This technology has the potential to reduce CO2 emissions by up to 98% compared to the blast furnace process. To further reduce emissions, carbon capture technologies can be implemented. The purpose of this work is to investigate how carbon capture can be implemented in a system that uses hydrogen direct reduction and melting of direct reduced iron in an electric arc furnace. The objectives of this work were to formulate a process concept for this system, then model this process and perform a techno-economic analysis. The research questions addressed whether it was more advantageous to have a high or low CO2 concentration in the flue gases, whether a separate carburizing step was more advantageous than carburizing the steel in the electric arc furnace, and whether the captured CO2 should be stored or reused in the process. An additional research question was how the profitability of carbon capture is affected by the cost of CO2 emission allowances. The scope of the system extended from the direct reduction shaft to the reheating furnace before rolling. The CO2 containing flue gases from the various process steps were fed into a calcium looping unit, which was the chosen technology for carbon capture. One base case without carbon capture and eight scenarios with carbon capture were set up based on the research questions, and these were then modeled in Microsoft Excel. The results from the model were evaluated based on energy-related and economic performance indicators, with all scenarios compared against each other and against the base case. The results of this work showed that carbon capture with calcium looping can reduce CO2 emissions from this system by 90-91%. Energy demand increased for all cases using carbon capture, with the lowest increase compared to the reference case being 4% and the highest 40%. All scenarios resulted in increased costs for the system compared to the base case. The scenario where only carbon capture was added had the lowest cost among these cases. This scenario resulted in an increased production cost of 240 SEK/ton of steel, and a CO2 emission allowance cost of 2200 SEK/ton CO2 would be required for the investment to achieve a payback time of 25 years. Based on the analysis of the various scenarios, it is most advantageous to only add the calcium looping technology to the existing process. Closing the furnaces is advantageous from an energy perspective but becomes costly economically. Therefore, this could be a good option if a new plant is to be built, as the furnaces could then be built closed. A separate carburizing step could be an alternative to carburizing in the electric arc furnace, but it entails both increased energy demand and higher costs. Methanation proved not to be advantageous from an economic and energy perspective due to the large electricity demand it entails, but the reuse of CO2 offers great possibilities for carbon recycling in the process, which means that up to 92% of the carbon demand can be covered by reused carbon.