240106 research outputs found
Sort by
Assessing the CFD applicability of chemical kinetic mechanisms for pure ammonia combustion
Full text linkAmmonia is a promising carbon-free fuel, but realising its potential for green energy requires combustion models that are both accurate and computationally efficient. While many reaction mechanisms have been proposed, few are designed with computational fluid dynamics (CFD) applications in mind. This study evaluates 11 mechanisms based on their predictions of laminar flame speed, peak flame temperature, NO emissions, computational cost, and minimum species timescales. One-dimensional flame simulations across equivalence ratios from 0.5 to 1.5 identified three different mechanisms as the most promising, though each showed trade-offs in computational cost, NO prediction, or laminar flame speed accuracy. Random forest regression showed that the minimum species time scale is a key factor for solution time, on par with the number of reactions. Mechanisms with OH* sub-mechanisms produced very short time scales, potentially limiting their CFD applicability. Overall, the results highlight the need to balance computational cost and accuracy in mechanism selection, and call for further development of reduced mechanisms that address CFD-relevant metrics, such as the minimum species time scale
A concept for high efficiency operation of a proton exchange membrane electrolyzer
No full textWe present fundamental calculations to identify operating conditions of a proton exchange membrane electrolyzer such that the product gases are exactly saturated with water vapor. The required stoichiometric flow ratios depend strongly on the electrolyzer temperature and reactant pressures, and they are below = 3 which necessitates a symmetric electrolyzer design and uniform water feeding. Preheating the incoming water leads to a voltage gain in the order of 50 mV, and it is shown, how the electrolyzer temperature can conceivably be controlled via the water flow rate. The analysis results in diagrams to determine suitable operating conditions for three different electrolyzer operation modes: standby operation to reduce the startup time, normal operation and high-power operation with efficiencies of 96%, 91%, and 86%, respectively. A comparison with literature data gives indications about the expected current densities at the respective voltages. Finally, it is suggested that electrolyzer operation where the anode side pressure is at a partial vacuum can facilitate the proposed operation mode as well as reduce the iridium loading
Outpatient versus inpatient surgery for ankle fractures:A randomized controlled non-inferiority trial
No full textBACKGROUND: Growing evidence supports a shift from inpatient to outpatient surgical treatment for ankle fractures. The primary aim of this study was to investigate the effect of inpatient versus outpatient surgery of ankle fractures on patient-reported outcome utilizing the Foot and Ankle Outcome Score (FAOS) at 12 weeks following surgery. Secondary aims were to report patients' satisfaction, adverse events, pain, physical function, and bone healing between inpatient and outpatient treatment.PATIENTS AND METHODS: The study design was a non-inferiority randomized controlled, non-blinded trial with a two-groups. Patients were randomized 1:1 to outpatient or inpatient surgical treatment. The primary outcome was the FAOS at 12 weeks. Secondary outcomes included patients' satisfaction, health-related quality of life, intensity of pain, bone union, and adverse events.RESULTS: A total of 44 patients were randomized to inpatient surgery and 42 patients to outpatient surgery. The final follow-up at 12 weeks following surgery was completed by 69 patients (80 %). The mean age of patients was 49.2 (SD 16.9), ranging from 18 to 80. Female sex represented 44 % of patients. The primary analysis revealed no statistically significant difference in FAOS subscale scores between inpatient and outpatient surgery at the 12-week follow-up Adjusted mean difference: Pain: -0.8 (95 % CI -10.7-9.0); Symptoms: 2.7 (95 % CI -6.9-12.5); ADL: -4.7 (95 % CI -13.6-4.3); Sport/Rec: 2.9 (95 % CI -15.2-9.3); and QOL: -0.7 (95 % CI -11.8-10.3). Comparable results were observed for secondary outcomes.CONCLUSION: This study showed no statistical nor clinically significant difference in FAOS subscale scores between inpatient and outpatient surgery for ankle fractures 12 weeks following surgery. Furthermore, patients' satisfaction and adverse events were comparable between inpatient and outpatient surgery 12 weeks following treatment. Results indicated that outpatient surgery for ankle fractures is highly feasible for selected patients and may be considered as routine for clinical practice.</p
“Jeg tror ikke, man kan blive arbejdsløs i Danmark, hvis man kan tysk”:Fremtidig brug af tysk blandt deltagere i kurser i Tysk som tillægskompetence
No full textFood Addiction Is Strongly Associated With Psychopathology and Reduced Psychological Well-Being Among Adults Irrespective of BMI
No full textBackground and Aims: Food addiction has been linked to psychopathology and reduced psychological well-being. Here, we investigated whether these associations are mainly driven by food addiction itself or mediated via an increase in BMI. Methods: Data stem from a nationwide survey from Denmark (n = 1474 participants). The survey questionnaire included the Yale Food Addiction Scale 2.0 (YFAS 2.0) measuring food addiction, questions on height and weight (to compute BMI), and a range of self-reported measures of psychopathology and psychological well-being. The association between food addiction and psychopathology/psychological well-being, stratified by weight category (normal weight (BMI 18.5-24.9), overweight (BMI 25–29.9) and obesity (BMI ≥ 30)), was assessed via multivariable regression analyses, adjusted for sex, age, socioeconomic status and BMI. Results: Across all BMI categories, having food addiction was strongly positively associated with psychopathology (depression, anxiety, and interpersonal sensitivity) and strongly negatively associated with psychological well-being (all p-values < 0.001), despite adjustment for BMI. These associations remained following exclusion of participants either having received a diagnosis of mental disorder or having redeemed a prescription for psychopharmacological treatment. Conclusion: The findings from this study are compatible with food addiction itself, and not increased BMI likely arising from it, being associated with psychopathology and reduced psychological well-being.</p
Gendered Labor Markets and Occupational Change in the Nordics
No full textRecent research on changes in the occupational structure in the Nordic region points in different directions. Some studies indicate upgrading of jobs with better quality, advanced skill requirements, and higher wages, while others show tendencies toward polarization in the skill distribution of jobs. The present article finds gendered patterns of upgrading or polarization in the occupational struc-ture in the Nordic countries in the years 2012–2019. The changes in the occupational structure have been more beneficial for women, who increasingly occupy higher-level positions. Especially, the public sector has served as a vehicle for high-level female positions. While previous research has stressed technological change, especially digitalization as the primary driver of change, this article argues that developments in the public sector also need to be considered to fully understand occupational change in the Nordic regio
Principles for Science Advise: A Comparative Framework of International Guidelines
No full textThe provision of sound scientific advice is a major resource for policy-making in contemporary societies. The key questions are how, where, when, and by whom science advice is organized and authorized. In order to provide a foundation for this, many institutions have launched a wide range of initiatives to establish principles for science advice. However, over the past two decades the volume of proposed principles has become overwhelming and perplexing. This problem of ‘principle proliferation’ poses a number of questions. Are the various sets of principles for science advice overlapping, leading to the emergence of global consensus, or, do they differ in significant ways? In order to answer these questions, this paper reports the results of a fine-grained analysis of several of the highest-profile sets of principles for science advice. We assess whether these principles are convergent, leading to agreed-upon principles, or divergent, leading to ambiguity over what constitutes sound scientific advice.The provision of sound scientific advice is a major resource for policy-making in contemporary societies. The key questions are how, where, when, and by whom science advice is organized and authorized. In order to provide a foundation for this, many institutions have launched a wide range of initiatives to establish principles for science advice. However, over the past two decades the volume of proposed principles has become overwhelming and perplexing. This problem of ‘principle proliferation’ poses a number of questions. Are the various sets of principles for science advice overlapping, leading to the emergence of global consensus, or, do they differ in significant ways? In order to answer these questions, this paper reports the results of a fine-grained analysis of several of the highest-profile sets of principles for science advice. We assess whether these principles are convergent, leading to agreed-upon principles, or divergent, leading to ambiguity over what constitutes sound scientific advice
