During the pressing of powder mixtures to make cemented carbide tools, the degree to which the powder spreads to fill the die and to which it compacts is uncertain. This leads to inconsistent dimensions and densities in the finished product. This performance changes with the composition of the powder, including the amount of pressing agent in the mixture, the particle size distribution and particle shape. One way to quantify the degree to which powder will spread to fill the mold evenly is using the property called 'flowability'. There are several techniques by which flowability can be measured, and each technique does not always give results that are consistent with other techniques. It is, therefore, important to know what technique(s) predict(s) the final behavior of the powder in this application before it is used in quality assurance or to design a process. Additionally, powder size distribution and shape metrics are measured using dynamic image analysis to investigate if there is any relationship between key values of these properties and compaction behavior. In this study, static Angle of repose, Tap Density, Hall flow time and Powder rheometry were benchmarked against each other and against the dimensions of presses and liquid phase sintered tool inserts to understand which technique had the strongest dependence on the compactability, which was defined as the ratio of the tallest dimension in the insert to the smallest. After the study, the results showed that a more extensive particle size distribution improves the compaction properties and that the powders with a higher resistance to a rotating blade tend to have better compaction properties. On the other hand, a clear pattern for the results of all measurement methods and the correlation between the compaction behavior of the carbide tools could not be discerned. In conclusion, the study showed that it is possible to determine a relationship between the results of measurement methods and the compaction behavior of powders. By using simple tests to predict the compactability properties, both money and time can be saved on the research of new, improved powder. Furthermore, the implementation of this study can lead to even better pressing and compactibility properties in the future for cemented carbide tools. / Vid pressning av pulverblandningar för tillverkning av hårdmetallverktyg är det osäkert i vilken grad pulvret sprider sig för att fylla matrisen och i vilken grad det komprimeras. Detta leder till inkonsekventa dimensioner och densitet i den färdiga produkten. Denna prestanda förändras med pulvrets sammansättning, inklusive mängden bindemedel som finns i blandningen, partikelstorleksfördelningen och partikelformen. Ett sätt att kvantifiera i vilken grad pulvret sprids för att fylla formen jämnt är att använda den egenskap som kallas "flytbarhet". Det finns flera tekniker för att mäta flytbarhet, och varje teknik ger inte alltid resultat som överensstämmer med andra tekniker. Det är därför viktigt att veta vilken eller vilka tekniker som förutsäger pulvrets slutliga beteende i denna tillämpning innan den används i kvalitetssäkring eller för att utforma en process. Vidare mäts pulvrets partikelstorleksfördelning och form med dynamisk bildanalys för att undersöka om det finns något samband mellan nyckelvärden för dessa egenskaper och komprimeringsbeteendet. I den här studien jämfördes statisk rasvinkel, tappdensitet, hallflödestid och pulverreometri samt med dimensionerna på pressar och sintrade verktygsinsatser i vätskefas för att förstå vilken teknik som hade det starkaste beroendet på kompatibiliteten, vilket definieras som förhållandet mellan den högsta dimensionen i insatsen och den minsta. Efter studien visade resultaten att en mer omfattande partikelstorleksfördelning förbättrar komprimeringsegenskaperna och att pulver med högre motståndskraft mot ett roterande blad tenderar att ha bättre komprimeringsegenskaper. Vidare kunde inte ett tydligt mönster för resultaten för alla mätmetoder och sambandet på komprimeringbeteendet för hårmetallverktygen urskiljas. Sammanfattningsvis visade studien på att det går att använda sig av mätmetoder för att kunna urskilja ett samband mellan resultaten på mätmetoderna och pulvers kompaktibillitetsegenskaper. Genom att använda sig av enkla mätningar för att kunna förutsäga kompaktibilitetsegenskaper samt komprimeringsbeteende kan både pengar respektive tid sparas. Vidare kan genomförandet av denna studie i framtiden leda till ännu bättre pressnings- samt kompaktibilitetsegenskaper för hårdmetallverktyg.

<p>This dissertation consists of three major chapters. The first chapter is dedicated to testing a novel gravity model of international trade, while the last two chapters explore cross-country commitment and implementation behavior within the World Trade Organization’s Trade Facilitation Agreement. </p> <p><strong>Chapter 1:</strong> I test a novel theoretical gravity model of international trade on firm-level export data from Colombia in 2018. The model assumes a power law relationship between trade flows and distance, with the distance elasticity resulting from two dynamic processes: firm-export growth captured in a Pareto distribution; and the growth of the distance over which those exports are sold. Although the model has been shown to work well in French data, its usefulness for interpreting data from other countries remains unexplored. I find evidence that the model fails in Colombia because some large firms contradict its assumptions by exhibiting shorter export distances compared to smaller firms in the sample. I hypothesize that these large firms are branches of foreign multinational corporations (MNCs). MNCs’ headquarters constraint the export growth of its affiliates as well as the markets they reach. While I cannot prove firms’ MNC affiliation, I use export sophistication as an imperfect metric to reflect MNC presence. When MNC affiliates are excluded from the sample, firm export distance rises faster with firm size, leading to improved predictions of the distance elasticity of trade in Colombia by the model. These findings have implications not only for the tested model but also for other theories that explain gravity in international trade through firm-level behavior.</p> <p><strong>Chapter 2:</strong> We use a new database of commitments made during the process of ratifying the Trade Facilitation Agreement (TFA) to study variation in countries’ commitment behavior. The TFA is a novel World Trade Organization agreement because it allows developing countries to select commitments from a menu of best practices in trade facilitation, rather than to consent, or not, to a comprehensive package of negotiated commitments. The operation of this <em>à la carte</em> approach to concluding trade agreements is worthy of study in its own right, but the commitment data also offer a high-level description of progress in an international effort to improve border management procedures around the globe. Our study uses data on TFA commitments to describe progress across subcomponents of the agreement. A regression model shows that the number of Type A trade facilitation commitments that a country made in the TFA ratification process depends on its level of development, population size, ability to control corruption, and foreign aid received to support trade facilitation. We use multidimensional scaling techniques to study differences in the content of national commitment bundles. This approach demonstrates that variation in the content of countries’ commitments is closely tied to the number of commitments made.</p> <p><strong>Chapter 3:</strong> This chapter examines the implementation progress of the Trade Facilitation Agreement (TFA) from 2019 to 2023. The TFA, which is the latest World Trade Organization agreement, came into force in 2017. In its novelty, it allows developing countries to set their own implementation schedule and adjust it if needed. This flexibility aligns implementation requirements with the capabilities of signatory countries, but introduces uncertainties in achieving complete global implementation and fully realizing the potential benefits of the agreement. Using data on the notified implementation dates for each measure of the TFA, this study describes the progress made in implementing different subcomponents of the agreement over a period of five years. A regression analysis suggests that the annual rate of progress towards achieving full TFA implementation does not vary based on country characteristics such as GDP per capita, population size, or landlocked status. Assuming that the tendency at which countries implement measures remains unchanged, I project that 95% of developing countries will achieve 95% TFA implementation between the years 2036 and 2047.</p>

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This thesis focuses on the topic of PBF-LB applied to titanium alloys. Of allalloys, an α + β is chosen, named Ti-6Al-4V. The selection of this particular alloy is driven by its current widespread use in many industrial applications where high strength coupled with low density are both desirable properties. For the last 50 years, parts made with this alloy have been cast or forged and then machined to achieve the final geometry. There is now an opportunity totransform this process chain by additive manufacturing, hence reducing material waste and achieving near net shape from powder feedstock. The process is summarised as follows: a laser selectively melts areas on a build plate where powder is pre-placed. Then a successive powder layer is spread and the process is repeated until completion. Upon removal of the part from the build plate, loose powder in the chamber is collected and recycled whenever possible. The design freedom provided by powder bed fusion methods enables production of intricate geometries and added functionality, despite the need for post-build consolidation and/or microstructural adjustments. Today’s fine and narrow powder cuts (e.g., 15-50μm) are designed to be coupled with low layer thicknesses (i.e., 30μm) to achieve smooth surfaces and high resolutions of small features e.g., internal cooling channels. However, costs associated with production of fine and narrow powder cuts are substantial as refinement of batches requires multiple sieving steps. In addition, resulting building times are considerably long (i.e., days), therefore a beneficial alternative could be that of exploring higher layer thicknesses together with wider and coarser powder cuts. The main idea of this work is to investigate the effects of employing a powder with a wider size distribution 15-90μm. The aim is to reduce the sievingrequired and consequently decrease the costs of developing and building parts made by PBF-LB. An extensive microstructural investigation is conducted on single tracks and cubes built with 27 different process parameter combinations, which also attempts to establish correlations between characteristics of tracks and responses measured in cubes. As a second step, the amount of residual porosity of asbuilt cubes is chosen as the discriminant for further mechanical testing of sub and super-β transus high-pressure heat treated material. / Den här avhandlingen fokuserar på additiv tillverkning av titanlegeringar med laser pulverbädd metoden. Den legering som främst är i fokus är Ti-6Al-4Vsom är en α+β legering. Anledningen till valet av denna titanlegering är att det är den vanligast förekommande titanlegeringen och att den används i ett antal olika industriella tillämpningar där hög styrka i kombination med låg vikt är önskvärda egenskaper. Under de senaste 50 åren har komponenter utav denna legering tillverkats med gjutning eller smide, följt av bearbetning till slutlig geometri. Med hjälp av additiv tillverkning finns nu en möjlighet att förändra tillverkningskedjan i vilket minskat materialspill och en mer nära-slutgeometri kan erhållas direkt genom användning av metallpulver som utgångsmaterial. Processen kan summeras enligt följande: en laser smälter ett förbestämt område på en byggplatta som täckts mer pulver. Därefter adderas ytterligare ett lager med metallpulver ovanpå, på vilket samma process sker igen, och igen osv, tills hela detaljen är färdigtillverkad. När detaljen ska tas loss ifrån byggplattan samlas det kvarvarande icke-smälta pulvret upp och återanvänds i så stor utsträckning som möjligt. Frihetsgraderna vid design i processen möjliggör tillverkning av komplexa geometrier och adderade funktionaliteter, även fast efterbehandling och/eller justeringar av mikrostrukturen kan behövas. Dagens smala pulverstorleksfördelning (tex 15-50μm) är avsedd att ge tunna lagertjocklekar (tex 30μm) för att åstadkomma en fin yta och hög upplösning av små geometrier, såsom exempelvis interna kylkanaler. Men kostnaderna som det innebär att framställa och sortera ut fina och smala kornstorleksfördelningarär avsevärd eftersom det innebär flera steg med silning. Vidare leder de tunnalagertjocklekarna till långa byggtider (typiskt dagar). Ett alternativ, som därför vore fördelaktigt, är att undersöka möjligheten med att bygga tjockare lager med en bredare och större pulverstorleksfördelning. Huvudfokuset i detta arbete fokuserar på att undersöka effekterna av att använda en bredare pulverpartikelstorleksfördelning 15-90μm, med syfte at minska silningsbehovet och därmed reducera kostnaden för att utveckla och tillverka detaljer med laser pulverbädd additiv tillverkning. En omfattande mikrostrukturundersökning har gjorts på enkelsträngar och kuber byggda med 27 olika processparameter-kombinationer, vilket samtidigt försöker identifiera korrelationer mellan enkelsträngarnas karaktäristik med resultaten uppmätta hos kuberna. I ett nästa steg har material, som tillverkats med processparametrar som renderade i minst/mest porer hos kuberna, mekaniskt provats efter att det högtrycksvärmebehandlats över- respektive under β-transus. / <p>Paper A is not included due to the copyright.</p><p>Paper B and C are to be submitted.</p>

The emphasis of this study is focusing on three-dimensional (3D) investigations of the manganese sulfide (MnS) inclusions characteristics in steels by using electrolytic extraction (EE). Two steel grades, 42CrMo4 and 157C, heat treated (HT) at 900 oC were investigated. 42CrMo4 steel samples were heat treated for 5, 10, 15 and 30 minutes while 157C steel samples were heat treated for 5 minutes. Samples of 42CrMo4 were taken from middle zone of an as-cast steel bar while that for grade 157C were taken from 3 different zones (centre, middle and surface). Inclusions were collected on film filters and analyzed by SEM for classification and determination of their characteristics including the size, number density (Nv), morphology and composition. The aspect ratio (AR) as well as particle size distribution (PSD) were also compared for steel samples conducted at various HT times. The result showed that EE is a reliable method of investigation inclusion characteristics. The inclusions were classified into 3 types according to their morphology and composition. Type I was elongated rod-like MnS, type II was coarsened sheet-like MnS and type III was spherical MnS inclusions. In addition, HT significantly reduced the Nv and fairly reduced AR but no significant reduction in size observed. The peak of PSD decreased with an increased HT time. The change of Nv, length, AR and PSD could be altered because of uneven inclusion distribution in filter and different sampling positions.

Pine tree substrate (PTS) is a relatively new substrate for container crop production. There are no detailed studies that elucidate how storage time impacts PTS chemical, physical, and biological aspects. The objective of this research was to determine how PTS storage time influenced PTS chemical and physical properties, nitrification, and plant growth. Pine tree substrate was manufactured by hammer-milling chips of loblolly pine trees (Pinus taeda L.) through two screen sizes, 4.76 mm (PTS) and 15.9 mm amended with peat (PTSP). PTS and PTSP were amended with lime at five rates. A peat-perlite mix (PL) served as a control treatment. Prepared substrates were placed in storage bags and stored in an open shed in Blacksburg, Virginia. Subsamples were taken at 1, 42, 84, 168, 270, and 365 days. At each subsampling day, twelve 1-L containers were filled with each substrate. Six containers were left fallow and six were planted with marigold (Tagetes erecta L. "Inca Gold") seedlings. Substrate was also collected from select treatments for Most Probable Number assays to estimate density of nitrifying microorganisms, and for chemical and physical property analyses. Pour-through extracts were collected from fallow containers at 0, 2, and 4 weeks, and from marigold containers at harvest for determination of pH, electrical conductivity, ammonium-N and nitrate-N. At harvest, marigold height, width, and dry weight were measured. At least 1 kg·m-3 lime for PTS, and 2 to 4 kg·m-3 lime for PTSP were needed to maintain pH values ≥ 5.5 for 365 days. Bound acidity of unlimed PTS increased but cation exchange capacity for unlimed PTS and PTSP decreased over 365 days. Carbon to nitrogen ratio and bulk density values were unchanged over time in all treatments. There were minor changes in particle size distribution for limed PTS and unlimed and limed PTSP. Marigold growth in PTS and PTSP was ≥ PL in all limed treatments, except at day 1. Nitrite-oxidizing microorganisms were present and nitrification occurred in PTS and PTSP at all subsampling days. Pine tree substrate is relatively stable in storage, but pH decreases, and lime addition may be necessary to offset this decrease. / Ph. D.

No / Microcarrier cell culture systems provide an attractive alternative to the conventional monolayer cell culture for cell amplification, due to their high surface area-to-volume ratio. Unlike enzymatic methods for removing cells from microcarriers after cell culture, which can lead to irreversible damage of the cells, microcarriers which release cells by temperature adjustment have been developed. This was achieved by grafting a temperature-responsive polymer, poly(N-isopropylacrylamide) (PNIPAAm), on the microcarrier surface. This review comprehensively presents various methods to prepare such thermo-responsive microcarriers based on PNIPAAm. These methods include the grafting-to technique, grafting-from technique, grafting-through technique, along with methods leading to PNIPAAm hydrogel beads, seeded polymerization, and non-covalent adsorption. The methods for controlling PNIPAAm grafting density, molecular weight and molecular architecture are also outlined. Further, the efficiency of cell attachment, proliferation and thermally-induced detachment of such thermo-responsive microcarriers is introduced and compared. (C) 2015 Elsevier Ltd. All rights reserved.

Climate change affects lakes, seas and running water globally, but the long-term effects on aquatic ecosystems, including fish communities, are complex and difficult to predict. Previous research has shown that changes in temperature, for example, can lead to shifts in fish species distribution and reductions in body size within fish communities. This study aims to investigate the impact of temperature on size distribution of individuals in fish communities by examining variations in so-called size spectrum and mean body size in ten Swedish lakes over the period 1994-2023. Data were collected from Swedish monitoring programs and analyzed using linear mixed-effects models. The result indicates a significant negative effect of temperature on the size spectrum and mean body size, meaning the number of small individuals increases while the number of large ones decreases. The size spectrum also shows a declining trend over time in several of the lakes, highlighting a shift in the size distribution of fish. These findings support the use of the size spectrum as an indicator of the impacts of climate change on freshwater ecosystems. The results of this study found a clearer link between temperature changes and size distribution compared to biomass, which supports the usefulness of size distribution as an indicator. Understanding these relationships is crucial for informing management and conservation strategies aimed at preserving lake ecosystems and the functions and ecosystem services that fish provide, including food and recreational opportunities. The study further contributes to the existing evidence that climate change is reshaping fish communities and aquatic ecosystems, underscoring the need for adaptive management to mitigate these effects and ensure sustainability of fish stocks for future generations. / Klimatförändringarna påverkar sjöar, hav och rinnande vatten globalt, men långsiktiga effekter på akvatiska ekosystem, inklusive fisksamhällens, är komplexa och svåra att förutse. Tidigare studier har visat att förändringar i temperatur till exempel kan leda till skiften i fiskarters utbredning och minskningar i kroppsstorlek i fisksamhällen. Denna studie syftar till att undersöka temperaturens inverkan på storleksfördelningen av individer i fisksamhällen genom att undersöka variation i det så kallade storleksspektrumets lutning och medelstorlek i tio svenska sjöar under perioden 1994–2023. Data samlades in från svenska övervakningsprogram för sjöar och analyserades med hjälp av linjära mixade effektmodeller. Resultaten indikerar en signifikant negativ effekt av temperatur på storleksspektrumets lutning och medelkroppsstorlek, dvs. antalet små individer ökar relativt antalet stora. Storlekspektrumets lutning visar också en nedåtgående trend över tid i flera av sjöarna, vilket belyser att fiskarnas storleksfördelning har skiftat mot relativt fler små individer i vissa sjöar. Dessa fynd styrker användningen av storleksspektrum som en indikator på klimatförändringarnas effekter på sötvattensekosystem. Resultat från denna studie visar också en tydligare koppling av förändrad temperatur på storleksfördelning än biomassor av fisk och växtplankton, vilket styrker nyttan av storleksfördelning som indikator. Att förstå dessa samband är avgörande för att vägleda förvaltnings- och bevarande strategier som syftar till att bevara sjöekosystem, de funktioner samt ekosystemtjänster som fiskar tillhandahåller, såsom mat och rekreationsmöjligheter. Studien bidrar till redan existerande bevis på att klimatförändringarna omformar fisksamhällen och akvatiska ekosystem, vilket tydliggör behovet av adaptiv förvaltning för att mildra dessa effekter och säkerställa starka fiskbestånd för framtida generationer.

This research investigates the optimization of the filtration and washing process during the transfer of X-Alfa production from a plant equipped with a centrifuge to a new plant equipped with a Nutsche filter dryer. The aim of this study is to determine the optimal pressure level to ensure an efficient isolation process at an industrial scale for three different filtrations, to assess the effects of increased pressure levels on the particle size distribution (PSD) within the filter cake, and to establish the most effective washing method for thoroughly removing N-methyl-2-pyrrolidone (NMP) content from the Molecule-11 intermediate. To achieve these objectives, the three filtrations were examined at different pressure levels on a laboratory scale. The collected filtration data were then used to estimate scaled-up filtration times at different pressures, enabling the determination of optimal pressure levels for the three filtrations. After that, the PSD was analyzed using microscopy and laser diffraction to ascertain the effect of pressure on the filter cakes. Finally, the washing process was investigated by washing equal amounts of filtered filter cakes with different numbers of wash cycles and different wash portions. The residual NMP content in the filter cake was then measured using 1H-NMR, and the amount of product loss to the process liquids was quantified using HPLC to identify the optimal washing method. Results indicated that the optimal pressure for the first filtration is 0.2 bar with a filtration time of approximately 22 minutes, and for the third filtration, it is 0.1 bar with a filtration time of about 4 minutes. No optimal pressure could be determined for the second filtration due to the negative compressibility index value generated by the used evaluation model. This negative value could have arisen from inhomogeneous suspensions that affected the filtration rate and consequently resulted in low linearity of the time/volume versus volume plots. Therefore, the experiment needs to be repeated for this filtration. Furthermore, increasing pressure levels during filtration showed no significant impact on PSD within the filter cakes. Finally, washing the filtered filter cakes with two wash cycles using half of the total wash volume in each cycle proved to be the optimal washing method, enhancing NMP removal efficiency by 30% compared to a single wash cycle using the same total wash volume. / Denna studie undersöker optimeringen av filtrerings- och tvättprocessen vid flyttningen av X-Alfa-produktionen från en fabrik utrustad med centrifug till en ny fabrik utrustad med Nutsche-filtertork. Syftet är att identifiera den optimala trycknivån för att uppnå en effektiv isoleringsprocess i fabriksskala för tre olika filtreringar, att undersöka hur en ökad trycknivå påverkar partikelstorleksfördelningen (PSD) i filterkakan samt att fastställa den bästa tvättmetoden för att maximalt avlägsna N-metyl-2-pyrrolidon (NMP) från molekyl-11-intermediatet. För detta syfte studerades först de tre filtreringar vid olika trycknivåer i en laboratorieskala och filtreringsdata som samlades in användes för att estimera uppskalade filtreringstider vid olika trycknivåer för att kunna därefter bestämma optimala trycknivåer för de tre filtreringar. Därefter analyserades PSD med hjälp av mikroskopi och laserdiffraktion för att bestämma tryckets påverkan på filterkakorna. Slutligen undersöktes tvättprocessen genom att tvätta lika mängder av filtrerade filterkakor med varierande antal tvättcykler och olika tvättportioner och därefter bestämdes den kvarvarande NMP-halt i filterkakan med hjälp av 1H-NMR och mängden förlorad produkt till processvätskorna med hjälp av HPLC för att sedan fastställa det optimala tvättmetoden. Resultatet visade att det optimala trycket för den första filtreringen är 0,2 bar med en filtreringstid på cirka 22 minuter och för den tredje filtreringen är det 0,1 bar med en filtreringstid på cirka 4 minuter. Inget optimalt tryck kunde fastställas för den andra filtreringen på grund av att den använda utvärderingsmodellen genererade ett negativt kompressibilitetsindex, vilket möjligtvis härstammar från inhomogena suspensioner som påverkade filtreringshastigheten och därmed resulterade i en icke-fullständig linjäritet av tid/volym mot volym-diagrammen. Därför krävs det att experimentet upprepas för denna filtrering. Ökningen av trycknivån under filtreringen visade ingen signifikant inverkan på PSD i filterkakorna och tvättningen av filtrerade filterkakor med två tvättcykler, där hälften av den totala mängden tvättvätska används i varje cykel, bevisades vara den optimala tvättmetoden med ett förbättrad NMP-borttagningseffektivitet på 30 vikt-% i jämfört med en cykels tvättning med samma total mängd tvättvätska.