Molekylers inverkan på plasmans lösgörande i DIII-D med hjälp av UEDGE

Future fusion power plants will operate in detached divertor conditions to reduce the power loads to the divertor targets to acceptable levels. The onset of divertor detachment is experimentally observed at lower separatrix densities than predicted by simulations, which may potentially be explained by molecular effects. This thesis investigates the impact of including molecules on divertor detachment in DIII-D low-confinement mode plasmas using the edge fluid code UEDGE. Parameter scans in electron separatrix density are carried out for deuterium plasmas with intrinsic carbon impurities. Corresponding scans are carried out with diffusive fluid, deuterium molecules with varying, but spatially constant temperatures included in UEDGE. The model considers molecular dissociation, where the dissociation energy is extracted from the electron energy equation. The Franck-Condon energy is returned through the atom energy equation. The scans were evaluated in configurations with the ion ∇B drift in the direction of the lower divertor excluded and included. The simulations were compared to assess the effect of molecules and drifts on the separatrix density required for outer divertor detachment. Including molecules, but excluding cross-field drifts, resulted in a 25% reduction in separatrix density required for detachment onset. This is an effect of dissociative cooling of the electrons. Increasing the molecular temperature from 0.025 eV to 1 eV was found to shift the onset of plasma detachment to 9% higher separatrix densities. Increasing the molecular temperature increases the total power in the domain, which causes the increase in separatrix density required for detachment. Including drifts increased the separatrix density for detachment by 10%, for the no-molecule simulations. This effect is due to cross-field drifts causing divertor asymmetries toward the inner divertor leg. For the simulations including molecules and considering drifts, a stable, high-density, radiative region formed inside the core domain for for separatrix densities above 1.6×10^19 per cubic meter. No increase in separatrix density for divertor detachment was observed. The radiating region inside the core domain is due to drift-driven flows increasing the densities inside the core domain where the strongly radiating impurities become confined. The thesis shows that molecular effects have a pronounced role on divertor detachment in UEDGE. However, further investigations are required to assess the validity of the constants used in the UEDGE molecular model.Framtidens fusionskraftverk kommer verka under förhållanden då plasman är lösgjord från divertorn, och divertorns värmebelastning reducerats markant. Experimentellt observerade separatrix-densiteter för plasmans lösgörande är lägre än vad som förutses av fluid-simulationer, och kan delvis vara ett resultat av molekylära processer. Detta arbete utvärderar molekylers inverkan på plasmans lösgörande i svagt sammanhållna DIII-D plasman med hjälp av multifluidkoden UEDGE. Plasmans egenskaper undersöks som funktion av elektronernas separatrix-densitet för deuterium-plasman med kolorenheter. Simulationer utförs i UEDGE med diffunderande, fluida deuterium-molekyler med olika, i rymden konstanta, temperaturer exkluderade samt inkluderade. Den molekylära modellen i UEDGE beaktar dissociation av molekyler till två atomer, som minskar elektronfluidens energi med dissociationsenergin. Atomfluidens energi ökar med Franck-Condon energin i dissociationsprocessen. Simulationerna utförs med jonernas ∇B-strömningar i riktning mot den nedre divertorn exkluderade samt inkluderade. Simulationernas resultat jämförs och molekylernas samt strömningarnas effekt på plasmans lösgörande från den yttre divertorn utvärderas. Separatrix-densiteten för lösgörande minskar med 25% då molekyler inkluderas, för de strömningsfria simulationerna. Detta är ett resultat av elektronernas dissociativa energiförlust. Då molekylernas temperatur ökas från 0.025 eV till 1 eV ökar separatrix-densiteten för plasmans lösgörande med 9%. En ökning i molekylernas temperatur resulterar i en ökning av plasmans totala energi, som leder till högre separatrix-densiteter för plasmans lösgörande. Då strömningar beaktas ökar separatrix-densiteten för lösgörande med 10%, för simulationer exkluderande molekyler. Detta beror på en asymmetrisk förskjutning av plasmans densitet mot den inre divertorn orsakad av strömningarna. För simulationer som inkluderar molekyler och strömningar uppstår en stabil, starkt radiativ region med hög densitet i kärnan då separatrix-densiteten överskrider 1.6×10^19 per kubikmeter. Ingen förändring i separatrix-densiteten för plasmans lösgörande observeras. Den radiativa regionen är ett resultat av strömningar, som ökar densiteten i plasmans kärna var radiativa orenheter fängslas. Atbetets slutsats är att molekylära processer har en uppenbar inverkan på plasmans lösgörande i UEDGE. Dock bör vidare arbeten undersöka huruvida de konstanter som används i UEDGE är välgrundade

Learning from graphs with structural variation

We study the effect of structural variation in graph data on the predictive performance of graph kernels. To this end, we introduce a novel, noise-robust adaptation of the GraphHopper kernel and validate it on benchmark data, obtaining modestly improved predictive performance on a range of datasets. Next, we investigate the performance of the state-of-the-art Weisfeiler-Lehman graph kernel under increasing synthetic structural errors and find that the effect of introducing errors depends strongly on the dataset.Comment: Presented at the NIPS 2017 workshop "Learning on Distributions, Functions, Graphs and Groups

Education, earnings, and inequality in Brazil, 1982-98 - implications for education policy

The educational attainment of Brazil's labor force, has gradually increased over the past two decades. At the same time, the government has pursued a series of economic structural adjustment policies. The authors investigate how these simultaneous advances have altered the relationship between labor market earnings, and education. They find that the returns to education in the labor market, fundamentally changed between 1982, and 1998. While the returns to tertiary education increased sharply, the returns to primary education dropped by 26 percent, and those to lower secondary, by 35 percent. Moreover, the authors argue, the marginal reduction in wage inequality that occurred in this period was linked primarily to a reduction in the returns to schooling, and only secondarily, to a more equitable distribution of schooling. The findings suggest that the supply of highly skilled labor is inadequate to meet demand. That suggests a need for policy action aimed at increasing access to, and completion of tertiary education. Increasing the supply of highly skilled labor, would improve prospects for both economic growth, and reduce wage inequality.Public Health Promotion,Curriculum&Instruction,Decentralization,Teaching and Learning,Health Monitoring&Evaluation,Teaching and Learning,Curriculum&Instruction,Gender and Education,Health Monitoring&Evaluation,Girls Education

The negative side of cohomology for Calabi-Yau categories

We study integer-graded cohomology rings defined over Calabi-Yau categories. We show that the cohomology in negative degree is a trivial extension of the cohomology ring in non-negative degree, provided the latter admits a regular sequence of central elements of length two. In particular, the product of elements of negative degrees are zero. As corollaries we apply this to Tate-Hochschild cohomology rings of symmetric algebras, and to Tate cohomology rings over group algebras. We also prove similar results for Tate cohomology rings over commutative local Gorenstein rings.Comment: 14 page

”La vile multitude” – Marx og Pariserkommunen

'The VILE MULTITUDE' - MARX AND THE PARIS COMMUNEThe entire purpose of Marx’s work is to enable the working class to act as a revolutionary subject, i.e. as its own liberator, destined to overthrow capitalism. However, this paper demonstrates that this view, which has political validity, is supplemented by another more nuanced and more theoretically interesting understanding of revolutionary upheavals in Marx’s work. This more subtle approach is found particularly in his political analyses, and the paper specifically interprets his writings on the Paris Commune in this light. It is argued that in Marx’s analysis of the actual events, it is not the working classes of Paris that make the revolution. Rather, the revolution is triggered by a series of extraordinary circumstances, and by external agents. It produces an undecidedness, here referred to as a multitude, which is only après coup seized and defined by the working classes. Finally, the paper details how this reading has consequences for a Marxist understanding of politics in general and revolutionary upheavals in particular