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4H Silicon carbide (SiC) is widely recognized as one of the most advanced wide bandgap semiconductors used in the production of high-efficiency power electronic devices. Impurities play a crucial role in achieving the desired electrical properties in 4H-SiC, yet the understanding of impurities in this material remains limited. In this study, first-principles formation-energy calculations were employed to establish a comprehensive database of formation-energy diagrams for impurities in 4H-SiC. This database includes valuable information on site preference, lattice distortion, solubility, and charge transition levels (CTLs) of the impurities. The site preference for each impurity is closely related to factors such as the Fermi energy, chemical potential, and the impurity species itself. To assess the lattice distortion caused by each impurity, a comparison was made between the volume changes before and after doping. Moreover, the solubility of each impurity was determined using the detailed balance theory, thereby enabling a direct measure of the maximum impurity concentration achievable in the material. Based on the CTLs, the impurities in 4H-SiC were classified into four categories: n-type impurities, p-type impurities, amphoteric impurities, and non-electroactive impurities. This comprehensive property database for impurities in 4H-SiC provides valuable insights for tailoring the material properties through controlled doping, thereby ultimately leading to enhanced performance of power electronic devices. [ABSTRACT FROM AUTHOR]

Radiative divertor is an effective method for the divertor heat flux control, but excessive core impurity radiation can deteriorate the confinement in tokamaks. In recent EAST experiments, the compatibility of divertor detachment and impurity control with good core confinement (H98,y2 ∼1) has been achieved simultaneously by combining an upstream deuterium (D2) puff and divertor argon (Ar) seeding. Both experimental and SOLPS-ITER modeling reveal that additional D2 puff can further mitigate the target heat load and facilitate the detachment. The SOLPS-ITER results also show that the D2 puff makes a limited contribution to the Ar line radiation but a significant contribution to the neutral radiation in the SOL and divertor regions. The physical mechanism behind the effect of the D2 puff on the Ar retention is also revealed by the modeling. The increase in the Ar velocity is the major reason for the improved Ar retention in the partial detachment state. The increase in vAr is mainly caused by the strengthening of frictional drag of D+, which is because the additional D2 puff increases the pressure gradient force (FPG) and the electric field force (FE) on D+. Further analysis reveals that in the deep detachment state, some other negative effects play a dominant role in determining the Ar retention, such as the shift of the region of the Ar+ ionization source, the decrease in the strength of the Ar+ ionization source, and the net force on the Ar ions near the target. [ABSTRACT FROM AUTHOR]

Aerodynamic performance of wind turbine governs the overall energy efficiency, which has been an ever-lasting research focus in the field of wind power technology. Due to the coupling effect among the highly complex environmental and structural uncertainties, the practical aerodynamic performance may not be reliably predicted. To aggravate, this performance declines with time in service. It is of great significance to efficiently and reliably assess the impact of uncertain factors and reduce these influences on wind turbine aerodynamic performance. This paper establishes an uncertainty analysis and robustness optimization model of wind turbine aerodynamic performance considering wind speed and pitch angle error uncertainties. An approach combined the no-instrusive probabilistic collocation method is used, and the blade element momentum theory is applied to quantify influences of variable uncertainties on NREL 5 MW wind turbine aerodynamic performance. The optimization target is to reduce the sensitivity of wind turbine aerodynamic performance to uncertainties, as well as maintain capture power. The results show that the wind turbine aerodynamic and mechanical performance will be greatly affected with uncertain factors. By optimizing and adjusting wind turbine rotor speed and blade pitch angle, the wind turbine rotor power and thrust load variation can be reduced to 9.14% and 9.36%, respectively, which indeed reduces the uncertainty effects. [ABSTRACT FROM AUTHOR]