Feasibility and reliability analysis of LCC DC grids and LCC/VSC hybrid DC grids

Power system interconnections using high-voltage direct-current (HVDC) technologies between different areas can be an effective solution to enhance system efficiency and reliability. Particularly, the multi-terminal DC grids, that could balance and ensure resource adequacy, increase asset utilization and reduce costs. In this paper, the technical feasibility of building DC grids using the line commutated converter based (LCC) and voltage source converter based (VSC) HVDC technologies are discussed. Apart from presenting the technical challenges of building LCC DC grids and LCC/VSC hybrid DC grids, the reliability modeling and analysis of these DC grids are also presented. First, the detailed reliability model of the modular multi-level converters (MMCs) with series connected high-voltage and low-voltage bridges are developed. The active mode redundancy design is considered for the reliability model. To this end, a comprehensive whole system reliability model of the studied systems is developed. The reliability model of each subsystem is modeled in detail. Various reliability indices are calculated using this whole system reliability model. The impacts of the redundancy design of the MMCs on these indices are presented. The studies of this paper provide useful guidance for DC grid design and reliability analysis

At blive på sporet: Nye perspektiver og bæredygtige løsninger på uddannelsesfrafald for unge voksne

Denne rapport er udgivet af Aarhus Universitet, Danmarks institut for Pædagogik og Uddannelse, som afslutning på forskningsprojektet At blive på sporet. Nye perspektiver og bæredygtige løsninger på uddannelsesfrafald for unge voksne i 2017-2019. Forskningsprojektet har haft fokus på de beslutningsprocesser, der fører til frafald blandt unge voksne, samt implementering og forankring af bæredygtige strategier og metoder til fastholdelse. Rapporten beskriver forskningsprojektets teoretiske udgangspunkt, metode og resultater. Vi ønsker med projektets resultater at give inspiration til uddannelsesinstitutioner, der udbyder uddannelse til unge voksne. Samtidig vil vi pege på forskningscirkler som et rum for kompetenceudvikling af lærere/vejledere, der arbejder med ny praksis til nedbringelse af frafald. Forskningsprojektet er støttet af Velux Fonden med midler fra fondens HUMpraxis-program, som fokuserer på at fremme et ligeværdigt samarbejde og vidensudveksling mellem forskere og praksisaktører inden for social-, aldrings- eller miljøområdet. Bevillingen har muliggjort etablering af et treårigt samarbejde mellem forskerteamet og i alt 14 skoler, seks erhvervsskoler og otte voksenuddannelsescentre (VUC). Projektteamet retter stor tak til de skoler, som har deltaget og engageret sig i udforskning af de beslutningsprocesser, der leder til frafald

At blive på sporet: Nye perspektiver og bæredygtige løsninger på uddannelsesfrafald for unge voksne

Denne rapport er udgivet af Aarhus Universitet, Danmarks institut for Pædagogik og Uddannelse, som afslutning på forskningsprojektet At blive på sporet. Nye perspektiver og bæredygtige løsninger på uddannelsesfrafald for unge voksne i 2017-2019. Forskningsprojektet har haft fokus på de beslutningsprocesser, der fører til frafald blandt unge voksne, samt implementering og forankring af bæredygtige strategier og metoder til fastholdelse. Rapporten beskriver forskningsprojektets teoretiske udgangspunkt, metode og resultater. Vi ønsker med projektets resultater at give inspiration til uddannelsesinstitutioner, der udbyder uddannelse til unge voksne. Samtidig vil vi pege på forskningscirkler som et rum for kompetenceudvikling af lærere/vejledere, der arbejder med ny praksis til nedbringelse af frafald. Forskningsprojektet er støttet af Velux Fonden med midler fra fondens HUMpraxis-program, som fokuserer på at fremme et ligeværdigt samarbejde og vidensudveksling mellem forskere og praksisaktører inden for social-, aldrings- eller miljøområdet. Bevillingen har muliggjort etablering af et treårigt samarbejde mellem forskerteamet og i alt 14 skoler, seks erhvervsskoler og otte voksenuddannelsescentre (VUC). Projektteamet retter stor tak til de skoler, som har deltaget og engageret sig i udforskning af de beslutningsprocesser, der leder til frafald

Decision-Making Processes Among Potential Dropouts in Vocational Education and Training and Adult Learning

Context: Aiming at gaining knowledge about students' thoughts and actions in deciding to stay in or drop out of an educational programme, an empirical study was conducted on dropout among 18-24-year-old students in VET and basic general adult learning. Approach: In order to pursue this aim, the study combined two sets of data: weekly student surveys and interviews with these same students. While the surveys provide a weekly snapshot of the students' thoughts regarding the probability of them continuing in the programme, their satisfaction with the educational programme as a whole, the specific lessons they attend, and the atmosphere at the school, the interviews contribute with detailed descriptions of the students' thoughts on the same matters. Findings: Based on the students' answers over an eight-week period, it was possible to trace a graph illustrating changes in the students' attitudes. These graphs can be placed within four categories of development: the stable, the positive, the unstable, and the negative. The latter can furthermore be differentiated as reflecting a stable decline, a fluctuating decline, or a sudden decline. In the interviews, the aim was to elicit the individual students' thoughts and actions at the points when their graphs took a turn. Conclusions: The findings show that the students' thoughts and actions concern matters both inside and outside the school. Furthermore, seemingly trivial matters in the students' lives are shown to have a potentially decisive influence on the students' thoughts about staying in or dropping out of a programme. These findings confirm the importance of focusing on students' decision-making processes in research on dropout. However, further research is needed to increase understanding of processes leading to decisions to drop out of education, including the qualification of methods to capture these processes

Cardiovascular disease, chronic kidney disease, and diabetes mortality burden of cardiometabolic risk factors from 1980 to 2010: A comparative risk assessment

Background: High blood pressure, blood glucose, serum cholesterol, and BMI are risk factors for cardiovascular diseases and some of these factors also increase the risk of chronic kidney disease and diabetes. We estimated mortality from cardiovascular diseases, chronic kidney disease, and diabetes that was attributable to these four cardiometabolic risk factors for all countries and regions from 1980 to 2010. Methods: We used data for exposure to risk factors by country, age group, and sex from pooled analyses of population-based health surveys. We obtained relative risks for the effects of risk factors on cause-specific mortality from meta-analyses of large prospective studies. We calculated the population attributable fractions for each risk factor alone, and for the combination of all risk factors, accounting for multicausality and for mediation of the effects of BMI by the other three risks. We calculated attributable deaths by multiplying the cause-specific population attributable fractions by the number of disease-specific deaths. We obtained cause-specific mortality from the Global Burden of Diseases, Injuries, and Risk Factors 2010 Study. We propagated the uncertainties of all the inputs to the final estimates. Findings: In 2010, high blood pressure was the leading risk factor for deaths due to cardiovascular diseases, chronic kidney disease, and diabetes in every region, causing more than 40% of worldwide deaths from these diseases; high BMI and glucose were each responsible for about 15% of deaths, and high cholesterol for more than 10%. After accounting for multicausality, 63% (10·8 million deaths, 95% CI 10·1-11·5) of deaths from these diseases in 2010 were attributable to the combined effect of these four metabolic risk factors, compared with 67% (7·1 million deaths, 6·6-7·6) in 1980. The mortality burden of high BMI and glucose nearly doubled from 1980 to 2010. At the country level, age-standardised death rates from these diseases attributable to the combined effects of these four risk factors surpassed 925 deaths per 100 000 for men in Belarus, Kazakhstan, and Mongolia, but were less than 130 deaths per 100 000 for women and less than 200 for men in some high-income countries including Australia, Canada, France, Japan, the Netherlands, Singapore, South Korea, and Spain. Interpretation: The salient features of the cardiometabolic disease and risk factor epidemic at the beginning of the 21st century are high blood pressure and an increasing effect of obesity and diabetes. The mortality burden of cardiometabolic risk factors has shifted from high-income to low-income and middle-income countries. Lowering cardiometabolic risks through dietary, behavioural, and pharmacological interventions should be a part of the global response to non-communicable diseases. Funding: UK Medical Research Council, US National Institutes of Health. © 2014 Elsevier Ltd

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements