The German Ultrafine Aerosol Network (GUAN) has been continuously measuring the particle number size distribution (PNSD) and equivalent black carbon (eBC) mass concentration since 2009 at 17 atmospheric observatories in Germany, covering all environments from roadside to high-Alpine environments. GUAN provides us an opportunity to reduce the knowledge gaps about the spatio-temporal variation of sub-micrometer particles in different size ranges and eBC mass. These data are not only highly valuable for air pollution and health studies but also can help to reduce the uncertainties in the climate model predictions. With these long-term multi-site-category measurements, it was investigated for the first time how pollutant parameters interfere with spatial characteristics and site categories. Based on this first investigation, the long-term changes in size-resolved particle number concentrations (PNC) and eBC mass concentration were investigate to evaluate the effectiveness of the emission mitigation policies in Germany. The emission and pollutants near ground can be frequently transported to the free troposphere (FT) in the mountain areas. To identify if the decreased emissions at lower-altitudes have affected the aerosol loading in the aged, well-mixed FT air over Central Europe, the long-term trends in PNC and eBC mass concentration were analyzed for the FT and planetary boundary layer (PBL) conditions separately, at two high-Alpine observation sites. In summary, this dissertation aims to answer the following related scientific questions: Q1: How do the sub-micrometer PNSD, PNC, and eBC mass concentration interfere with spatial characteristics and site categories? (First publication) In the first publication (Sun et al., 2019), the spatio-temporal variability of aerosol parameters including PNSD, PNCs, and eBC mass concentration from the GUAN network were investigated for the period 2009−2014. Significant differences in the pollutant concentration were observed among various site categories. The six-year median value of sub-micrometer PNC (diameter range 20–800 nm) varies between 900 and 9000 cm−3, while median eBC mass concentration varies between 0.1 and 2.3 μg m-3 in 17 observation sites. PNCs in different size ranges were found in different spatial variabilities. A cross-correlation between PNSD and eBC mass concentration was analyzed to detect the influence of anthropogenic sources for different site categories. The size-dependent spatial variability analysis of PNCs extracted three size intervals: a higher spatial variability size range 10–30 nm, a transition size range 30–100 nm and a lower spatial variability size range 100–800 nm. Based on the evaluated spatial variability, the measured parameters at various sites were clustered by a hierarchical clustering approach, which revealed different spatial clusters for “source-driven” and “long-range transport” parameters. This result suggests that the traditional “site category” (i.e. urban, and regional background, etc.) concerning mainly the influence of local sources cannot always catch the variation of aerosol particle mass or number concentrations. The dominant factors for various parameter are different, leading to different variability and spatial distribution. The result of spatial clustering offers a sound scientific base to compare pollutant parameters measured in different locations and environments. By assessing the relationship between the measured parameters and geographical distance between different sites, the spatial variability of the aerosol parameters follows the “First Law of Geography” that everything is related to everything else, but near things are more related than distant things (Tobler, 1970). However, different parameters show different sensitivities on geographical distance. The analysis provides an important reference for setting up an observation network with a specific research purpose and is also useful for the regional scale dispersion models or land-use regression models. Q2: How do the sub-micrometer PNSD, PNC, and eBC mass concentration change at a decadal scale? Have the implementations of emission mitigation policies affected the observed decadal trend? (Second publication) In the second publication (Sun et al., 2020), long-term trends in atmospheric PNCs and eBC mass concentration for a 10 years period (2009–2018) were determined for 16 sites of the GUAN, ranging from roadside to high-Alpine. To ensure the data consistency for the trend detection, a thorough and detailed data quality check and data cleaning for the large GUAN dataset was performed. Statistically significant decreasing trends were found for 85% of the parameters and observation sites indicating an overall decreasing trend in sub-micrometer PNC (except N[10−30]) and eBC mass concentration all over Germany. Comparing the trends of measured parameters with the long-term change in total emission, we proofed that the observed trends of PNCs and eBC mass concentrations were mainly due to the emission reduction. The detailed diurnal and seasonal trends in eBC mass concentration and PNCs further confirmed that the observed decreasing trends were largely owing to the reduced emissions such as traffic emission, residential emission, and industry emission, etc. Moreover, the inter-annual changes of meteorological conditions and long-range transport pattern were found not to be the main reason for the decreases in pollutant parameters. This study suggests that a combination of emission mitigation policies can effectively improve the air quality over large spatial scales such as Germany. Given the relative novelty of the long-term measurements (PNSD, eBC mass concentration) in a network such as GUAN, the results proved to be quite robust and comprehensive. Q3: Have the decreased PNC and eBC mass concentration due to emission mitigation policies at the lower-altitudes affected the background air in lower FT over Central Europe? (Third publication) In the third publication (Sun et al., 2021), the long-term change of the eBC mass concentration and size-resolved PNCs were determined and analyzed at two high Alpine stations for the period 2009-2018: Schneefernerhaus at mountain Zugspitze in Germany (ZSF, 2671 m a.s.l.) and Jungfraujoch in Switzerland (JFJ, 3580 m a.s.l.). The trend analysis was performed for the FT and PBL-influenced conditions separately, aiming to assess whether the reduced emissions at lower-altitudes over Central Europe can affect the background air in the lower FT on a large spatial scale. The FT and PBL conditions at the two stations were segregated using the adaptive diurnal minimum variation selection (ADVS) method. The result showed that the FT condition in cold months is more prevalent than in warm months. Overall, the FT conditions frequency was ~25% and 6% in the cold and warm seasons at ZSF, respectively. At JFJ, the frequency of FT was ~45% and 10% in these two seasons, respectively. The PNC and eBC mass concentration showed a statistically significant decrease during PBL time. The observed decreasing trends in eBC mass concentration in the PBL-influenced condition are well consistent with the reported trends in total BC emission in Germany and Switzerland. For the FT conditions, decreases in PNC and eBC mass concentration over the years was detected at both sites, suggesting the background PNC and eBC mass in the lower FT over Central Europe has decreased as well. The implementation of emission mitigation policies is the most decisive factor but the weather pattern change over Central Europe also has contributed to the decreasing trends in FT condition.:List of Figures ……………………………………………………………………………………………..I List of Tables ..……………………………………………………………………………………………..I Abbreviations .……………………………………………………………………………………………II 1. Introduction …………………………………………………………………………………………….1 1.1 Role of atmospheric sub-micrometer aerosol particles…...………………………………………...1 1.2 Measurement of sub-micrometer particle number size distribution, particle number concentration, and eBC mass concentration…..……………………………………………….………………………….2 1.3 Previous long-term observations of PNSD, PNC, and eBC mass concentration…………………...4 1.4 Objectives...………………………………………………………………………………………….6 2. Data and Method…..……………………………………………………………………………………9 2.1 The German Ultrafine Aerosol Network (GUAN) …………………………………………………9 2.1.1 Measurement sites in GUAN…………………………………………………………………..10 2.1.2 Instrumental set-up.……….………………………………………………………….…………14 2.1.3 Quality assurance.………………………………………………………………………….……16 2.1.4 Data coverage…..………………………………………………………………………………..17 2.2. High-Alpine observatory Jungfraujoch (JFJ)……………………………………………………..18 2.2.1 Measurement site……….……………………………………………………………………….18 2.2.2 Instrumentation ..………………………………………………………………………………..19 2.3 Data analysis methods……………………………………………………………………………….19 2.3.1 Agglomerative hierarchical clustering….……………………………………………………...19 2.3.2 Customized Sen’s slope estimator…………………..…………………………………………...21 2.3.3 Generalized least-square regression and autoregressive bootstrap confidence intervals (GLS- ARB)…………………………………………………………………………………………………21 2.3.4 Seasonal Mann-Kendal test…..………………….………………………………………………22 2.3.5 Back-trajectory classification method….……………………………………………………...24 3. Results and Discussion…..………………………………………………………………………….27 3.1 First publication….…………………………………………………………………………………..27 3.1.1 Variability of black carbon mass concentrations, sub-micrometer particle number concentrations and size distributions: results of the German Ultrafine Aerosol Network ranging from city street to High Alpine locations……………………………………...………………………………………...27 3.1.2 Supporting information..……………………………………………………………………….41 3.2 Second publication…………………………………………………………………………………..45 3.2.1 Decreasing trends of particle number and black carbon mass concentrations at 16 observational sites in Germany from 2009 to 2018…..…………………………………………………………..45 3.2.2 Supporting information...……………………………………………………………………….66 3.3 Third publication……………………………...……………………………………………………..75 3.3.1 Long-term trends of black carbon and particle number concentration in the lower free troposphere in Central Europe…………………………………………………………………………75 3.3.2 Supporting information..…….……………………………………………………………….92 4. Summary and Conclusions..………………………………………………………………………… 95 5. Outlook….…………………………………………………………………………………………...99 Appendix A….………………………………………………………………………………………...100 Bibliography…………………………………………………………………………………………...101 Acknowledgements….…………………………………………………………………………………115

Tato práce se zaměřuje na oblast effervescentních sprejů a jejich aplikace na kapalné spalování s důrazem na průmyslové spalovací komory. Oba aspekty – modelování a experiment – jsou řešeny. Práce obsahuje obecný úvod, ve kterém jsou vysvětleny základní jevy rozpadu kapaliny a vířivého spalování a dále je představena effervescentní atomizace. Poté jsou popsány použité experimentální postupy jak pro měření spreje, tak pro měření tepelných toků do stěn při spalování. V následující kapitole jsou popsány numerické modely a jejich podstata je vysvětlena. Jsou zde uvedeny modely pro rozpad spreje, turbulenci a spalování použité během výzkumu. Vlastní výsledky práce jsou uvedeny formou samostatných článků (vydaných nebo přijatých) s dodatečnou částí věnovanou nepublikovaným relevantním výsledkům. Bylo zjištěno, že standardní modely sprejů jsou do jisté míry schopny popsat effervescentní spreje. Nicméně aby bylo možné predikovat plamen kapalného spreje, jsou zapotřebí detailnější modely sprejů, které dokáží přesně zachytit změnu průměrů kapek v radiálním a axiálním směru. Experimentální měření effervescentních sprejů bylo provedeno pomocí navrhnuté metodiky. Výsledky měření byly analyzovány s důrazem na radiální a axiální vývoj průměrů kapek a některé nové jevy byly popsány. Nepřímá úměrnost mezi gas-liquid-ratio a středním průměrem kapek byla potvrzena. Dále by popsán jev, kdy pro různé axiální vzdálenosti které dojde k úplnému převrácení závislosti středního průměru na axiální vzdálenosti. V závěru je uvedeno shrnutí, které rekapituluje hlavní výsledků a závěry. V závěrečných poznámkách je nastíněn možný budoucí postup. Experimentální data pro ověřování budoucích effervescentních modelů jsou poskytnuta.

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The durability of concrete is of major concern in all types of concrete structures where the combined effect of exposure conditions and the type and quality of the concrete material usually determines the rate of degradation. Furthermore, there are synergy effects between different deterioration mechanisms, which means that the combined rate of degradation is higher than the sum of the individual rates of each mechanism. Therefore, to accurately predict the residual service life of existing structures or when designing new structures, it is essential to consider all these aspects. This means that various chemical and physical processes, as well as how these interact, must be taken into account in models aiming to be used for service life predictions. This thesis presents the first part of a research project with the aim to investigate common deterioration mechanisms of concrete in hydraulic structures, and to improve the knowledge how these and other related phenomena can be described using mathematical models. The objective is also to study how different mechanisms interact and to find suitable approaches to account for these interactions in the models. To this end, a literature survey on commonly detected damage in hydraulic structures is presented. In addition, it also addresses in what types of and where in hydraulic structures the various damage types are usually observed. The mathematical models presented in this part of the project are focused on long-term water absorption in air-entrained concrete as well as on freezing of partially saturated air-entrained concrete. Both models are based on a multiphase description of concrete and poromechanics to describe the coupled hygro-thermo-mechanical behaviour. The thesis also presents some of the basic concepts of multiphase modelling of porous media, including discretization of the models using the finite element method (FEM). Furthermore, it covers the simplifications that are usually introduced in the general macroscopic balance equations for mass, energy and linear momentum when modelling cement-based materials. To verify the developed models and to show their capabilities, simulation results are compared with experimental data, in situ measurements and other simulations from the literature. The results indicate that both models perform well and can be used to predict long-term moisture conditions in hydraulic structures as well as freezing-induced strains in partially saturated air-entrained concrete, respectively. Even though no interactions with other deterioration mechanisms are included in the models, the development and use of these have given insights to which parameters that are important to consider in such extensions. Furthermore, based on the insights gained, the complexity of describing the full interactions between several mechanisms in mathematical models is also discussed. It is concluded that models aiming to be used for service life predictions of hydraulic structures in day-to-day engineering work need to be simplified. However, the type of advanced models presented in this thesis can serve as a basis to study which aspects and parameters that are essential to consider in simplified prediction models. / Beständigheten hos betong är av avgörande betydelse i alla typer av betongkonstruktioner där den kombinerade effekten av exponeringsförhållanden samt typ och kvalitet på betongmaterialet vanligtvis avgör nedbrytningshastigheten. Dessutom finns synergieffekter mellan olika nedbrytningsmekanismer som innebär att den kombinerade nedbrytningshastigheten är större än summan av de enskilda nedbrytningshastigheterna. För att noggrant kunna prediktera den återstående livislängden hos befintliga konstruktioner eller vid design av nya konstruktioner är det därför viktigt att ta hänsyn till samtliga av dessa aspekter. Detta innebär att olika kemiska och fysikaliska processer, samt hur dessa interagerar med varandra, måste tas i beaktande i modeller som avses användas för livslängdsbedömningar. Den här licentiatuppsatsen presenterar den första delen av ett forskningsprojekt där målet är att studera vanligt förekommande nedbrytningsmekanismer i vattenbyggnadskonstruktioner och att öka kunskapen om hur dessa och andra relaterade fenomen kan beskrivas med matematiska modeller. Målet är också att studera hur olika nedbrytningsmekanismer samverkar och att hitta lämpliga tillvägagångssätt att ta hänsyn till dessa interaktioner i modellerna. För detta ändamål presenteras en litteraturstudie avseende vanligt förekommande skador i vattenbyggnadskonstruktioner. Dessutom behandlar denna i vilka typer av vattenbyggnadskonstruktioner och var i dessa som de olika typerna av skador vanligtvis observeras. De matematiska modeller som presenteras i denna del av projektet är inriktade på långtidsabsorption av vatten i lufttillsatt betong samt på frysning i delvis vattenmättad lufttillsatt betong. Båda modellerna är baserade på en multifasbeskrivning av betong samt poromekanik för att beskriva det kopplade hydro-termo-mekaniska beteendet. Uppsatsen presenterar också några av de grundläggande koncepten gällande multifasmodellering av porösa material, inklusive diskretisering av modellerna genom användning av finita elementmetoden (FEM). Dessutom beskrivs de förenklingar som vanligtvis införs i de generella makroskopiska balansekvationerna för massa, energi och rörelsemängd då cementbaserade material modelleras. Simuleringsresultat från de utvecklade modellerna jämförs med försöksdata, fältmätningar samt andra simuleringsresultat från litteraturen för att verifiera modellerna samt visa hur de beter sig. Resultaten visar att båda modellerna ger tillfredställande resultat och kan användas för att uppskatta de långsiktiga fuktförhållandena i vattenbyggnadskonstruktioner samt frysinducerade töjningar i delvis vattenmättad lufttillsatt betong. Även om inga interaktioner mellan andra nedbrytningsmekanismer inkluderades i modellerna, så har utvecklingen samt användandet av dessa gett insikter gällande vilka parametrar som är viktiga att beakta i sådana vidareutvecklingar. Baserat på dessa insikter diskuteras också komplexiteten i att beskriva interaktionen mellan flertalet mekanismer i matematiska modeller. Det konstateras också att modeller som avses användas i dagligt ingenjörsarbete för livstidsbedömningar av vattenbyggnadskonstruktioner behöver förenklas. Däremot kan den typ av avancerade modeller som presenteras i denna uppsats användas som en grund för att studera vilka aspekter och parametrar som är viktiga att beakta i förenklade modeller. / <p>QC 20180403</p>

Title: Formation and transformation of atmospheric aerosol in boundary layer Author: Mgr. Adéla Holubová Šmejkalová Institute: Institute for Environmental Studies Supervisor: Ing. Vladimír Ždímal, Dr., Institute of Chemical Process Fundamen- tals of the CAS Training workplace: Institute of Chemical Process Fundamentals of the CAS Abstract: The experimental measurement of aerosol clusters from 1.17 nm in size was carried out from August 2016 till December 2018 at the National Atmospheric Observatory Košetice. Atmospheric conditions leading to aerosol clusters stabili- zation, fresh particles formation and particle growth were analyzed. Data of days with no new particle formation confrmed the connection between mixing layer height development and decrease of total aerosol number concentration together with lower gaseous pollutant concentrations. On the contrary, new particle for- mation process overcomes dilution of the atmosphere by increasing the number of freshly nucleated particles. Only decreasing gaseous pollutant concentrations were observed during these events. The atmospheric boundary layer was high du- ring new particle formation events that can mean enrichment of the atmosphere by other components transported by long-range transport or some transfer from the free troposphere. The measurement in...

In this study, the goal is to predict the microstructure evolution during and after the hot working of a martensitic stainless steel with 13% chromium using a physically-based model in the form of a MATLAB toolbox. This model is based on dislocation density theory and consists of coupled sets of evolution equations for dislocation, vacancies, recovery, recrystallization, and grain growth. The focus in this work is on the flow stress calculation and the effect of second phase particles on the strengthening mechanisms in the material at elevated temperatures. Recovery and recrystallization are also studied for this alloy during deformation and following stress relaxation. The experimental part of this work was performed with a Gleeble thermo-mechanical simulator over the temperature range of 850 to 1200°C. Samples were investigated later by a light optical microscope (LOM) and a scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscope (EDS). Hardness test and phase isolation were also performed on the samples and the results are compared with the modeling results. The model can satisfactorily predict the grain growth, recovery, recrystallization, and flow stress for this alloy. Further investigation on the second phase particles showed that the measured mean size of carbides has a good agreement with what is obtained from the model and the hardness values. On the other hand, the modeled volume fraction of the carbides followed a slightly different trend comparing to hardness values, and phase isolation results at temperatures higher than 1000°C. Additionally, the Ms temperature and fraction of the martensite phase are calculated for quenched samples where the results are following the measured hardness values. Finally, the Zener-Hollomon parameter (Z) and its relation to the flow stress and the activation energy for deformation are defined. The dynamic recrystallization (DRX) kinetic is modeled and the fraction DRX was calculated at various temperatures and strain rates for this alloy. / I denna studie är målet att förutsäga mikrostrukturutvecklingen under och efter varmbearbetning i ett martensitiskt rostfritt stål med 13 % krom med hjälp av en fysisk baserad modell i form av en MATLAB verktygslåda. Denna modell är baserad på en teori för dislokationstäthet och bestårav kopplade uppsättningar av evolutionsekvationer för dislokation, vakanser, återhämtning, rekristallisation och kornstillväxt. Fokus i detta arbete är beräkning av flytespänningen och effekten av sekundärfaspartiklar på härdningsmekanismerna i materialet vid höga temperaturer. Återhämtning och rekristallisation studeras också för denna legering under deformation och efter spänningsrelaxation. Den experimentella delen av detta arbete utfördes med en Gleeble termomekanisk simulator inom temperaturområdet 850 till 1200°C. Proverna undersöktes senare med ett ljust optiskt mikroskop (LOM) och svepelektronmikroskop(SEM) utrustad med energidispersiv spektroskopi (EDS). Hårdhetstest och fasisolering utfördes också på proverna och resultaten jämförs med modelleringsresultaten. Modellen på ett tillfredsställande sätt kan förutsäga korntillväxt, återhämtning, rekristallisation och flytspänningen för denna legering. Vidare undersökning av partiklarna i sekundärfasen visade att den uppmätta medelstorleken för karbider har bra överensstämmelse med vad som erhålls från modellen och hårdhetsvärdena. Den modellerade volymfraktionen av karbiderna följde en något annorlunda trend vid temperaturerna högre än 1000°C jämfört med hårdhetsvärden och fasisoleringsresultat. Dessutom beräknas Ms temperaturen och fraktionen av martensitfasen för släckta prover där resultaten följer de uppmätta hårdhetsvärdena. Slutligen definieras Zener-Hollomon-parametern (Z) och dess förhållande till flytspänningen och aktiveringsenergin för deformation. Den kinetiska dynamiska rekristallisation (DRX) modelleras och fraktionen DRX beräknades vidolika temperaturer och töjningshastigheter för denna legering.

[pt] Com as novas regulamentações ambientais proibindo o uso de fluidos de perfuração que apresentassem em sua composição elementos como óleo diesel, se fez necessário a busca por novos componentes que, além de serem eficazes em sua função, apresentassem característica de biodegradabilidade sendo, assim, menos danoso ao meio ambiente. A base do fluido de perfuração escolhida para se enquadrar as novas regras foi estudada neste trabalho com objetivo de avaliar a sua estabilidade e o seu comportamento reológico. O fluido trabalhado é uma emulsão inversa cuja fase contínua é a olefina e a fase dispersa, salmoura de NaCl, acrescido de um emulsificante primário, Cybermul, e um secundário, Cyberplus. Para retardar o processo de desestabilização, majoritariamente caracterizado pela sedimentação, em um segundo momento, foi adicionada a cal hidratada. Os testes realizados foram divididos em duas etapas: a primeira avaliando emulsões preparadas a 5000 rpm, 7500 rpm e 10000 rpm sem cal em sua composição e a segunda avaliando emulsões preparadas com a mesma velocidade de rotação, entretanto com cal hidratada. A principal variável adotada foi a velocidade de rotação com objetivo de ratificar o conhecimento de que quanto maior a velocidade de agitação durante a emulsificação, menores são as gotas geradas e, consequentemente, mais estável a emulsão. Os testes foram compostos por tensão interfacial, bottle test, distribuição do tamanho de gotas (microscopia e espalhamento dinâmico de luz) e testes de comportamento reológico, que incluem, tensão constante, curva de escoamento e varredura de tensão e tempo. Os resultados obtidos permitiram relacionar o tamanho das gotas geradas com a estabilidade da emulsão e com a sua viscosidade. / [en] Since new environmental regulations were established prohibiting the use of drilling fluids that had elements such as diesel in their composition, it was necessary to search for new components that, besides being effective in their function, had a biodegradability characteristic, thus being less harmful to the environment. The base of the drilling fluid chosen to fit the new rules was studied in this thesis in order to characterize its stability and rheological behavior. The fluid used is an inverse emulsion whose continuous phase is the olefin and the dispersed phase, brine, plus a primary emulsifier, Cybermul, and a secondary one, Cyberplus. To delay the destabilization process, mainly characterized by sedimentation, in a second moment, hydrated lime was added to the emulsion s composition. The tests performed were divided into two stages: the first, emulsions prepared at 5000 rpm, 7500 rpm and 10,000 rpm without lime in their composition were analyzed and the second, emulsions prepared at the same rotation velocities however with hydrated lime in their composition. The main variable adopted was the speed of rotation in order to confirm the knowledge that the higher is the speed of agitation during emulsification, the smaller are the drops generated and, consequently, the more stable is the emulsion. The tests consisted of interfacial tension, bottle test, droplet size distribution (microscopy and dynamic light scattering) and rheological behavior tests, which include, creep tests, flow curve and stress and time sweep tests. The results obtained allowed to relate the size of the drops with the emulsion s stability and with its viscosity.

The aim of this work was to systematically study how the microstructure evolution is affected by the carbon activity in WC-Ni cemented carbides. Seven WC-9.59at%Ni alloys with different carbon activity were sintered at 1500 °C. From investigating these alloys, the carbon window has been experimentally evaluated using light optical microscopy and compared to theoretical carbon window calculated using Thermo-Calc. The overall microstructure of cross sections and raw surfaces have been investigated using scanning electron microscopy. Finally, the WC grain size and distribution have been evaluated using electron backscatter diffraction. It was found that the experimental carbon window was slightly wider than the theoretical carbon window. The WC grain size increased and the grain size distribution got wider with increasing carbon activity. In addition, the largest WC grains showed the largest grain growth by increasing carbon activity. By comparing the present results of grain size and distribution of WC-Ni to previous results of WC-Co, it was found that the WC grain growth was more pronounced and more influenced by the carbon activity.

Return liquor from thermal hydrolysis process (THP) can significantly add to the nitrogen load of a wastewater treatment plant (WWTP) and introduce UV quenching substances to the wastewater stream when recycled. While there are mature technologies in place to handle the inorganic nitrogen produced due to the thermal pretreatment, organic nitrogen remains a parameter of concern for utilities employing THP pretreatment. The impact of operating conditions of the THP on dissolved organic nitrogen (DON) and UV absorbance in return liquor was investigated. Operating conditions studied were (1) operating temperature (2) solids retention time (SRT) in the anaerobic digester (3) THP flash pressure (4) the effect of co-digestion of sewage sludge with food waste and, (5) polymer conditioning. Operating temperature and polymer dose had the most significant impact on DON and UV quenching. It was found that an increase in operating temperature resulted in an increase in DON, which was primarily contributed by the hydrophilic fraction. An increase in temperature also resulted in increased UV254 absorbance. However, this trend was not linear and the increase was more pronounced when the temperature was increased from 150 C to 170 C. Increasing flash pressure from 25 psi to 45 psi did not have a significant impact on the return liquor. However, increasing the flash pressure to 75 psi increased the DON and UV254 absorbing compounds. Co-digesting the sludge with food waste resulted in a slight increase in DON and a decrease in dissolved organic carbon (DOC) and UV quenching compounds. Increasing the SRT from 10 days to 15 days resulted in a slight decrease in DON but did not have any impact on UV254 absorbance. Overall, it can be concluded that optimizing operating conditions of thermal hydrolysis process can result in decreased DON and UV quenching compounds in the recycle stream. / Master of Science

The performance of dental resin-based composites (RBCs) heavily depends on the characteristic properties of the individual filler fraction. As specific information regarding the properties of the filler fraction is often missing, the current study aims to characterize the filler fractions of several contemporary computer-aided design/computer-aided manufacturing (CAD/CAM) RBCs from a material science point of view. The filler fractions of seven commercially available CAD/CAM RBCs featuring different translucency variants were analysed using Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Spectroscopy (EDS), Micro-X-ray Computed Tomography (µXCT), Thermogravimetric Analysis (TG) and X-ray Diffractometry (XRD). All CAD/CAM RBCs investigated included midifill hybrid type filler fractions, and the size of the individual particles was clearly larger than the individual specifications of the manufacturer. The fillers in Shofu Block HC featured a sphericity of ≈0.8, while it was <0.7 in all other RBCs. All RBCs featured only X-ray amorphous phases. However, in Lava Ultimate, zircon crystals with low crystallinity were detected. In some CAD/CAM RBCs, inhomogeneities (X-ray opaque fillers or pores) with a size <80 µm were identified, but the effects were minor in relation to the total volume (<0.01 vol.%). The characteristic parameters of the filler fraction in RBCs are essential for the interpretation of the individual material’s mechanical and optical properties.