Numerical Simulation of Temperature Field Optimization to Enhance Nitrogen Transfer in GaN Crystal Growth by the Na-Flux Method.

Improved nitrogen transport is crucial for enhancing the growth rate of GaN crystals using the Na-flux method. This study investigates the nitrogen transport mechanism during the growth of GaN crystals by the Na-flux method using a combination of numerical simulations and experiments. The results indicate that the temperature field affects the effect of nitrogen transfer, and we propose a novel bottom ring heating approach to optimize the temperature field and enhance nitrogen transfer during the growth of GaN crystals.

Monitoring European data with prospective space-time scan statistics: predicting and evaluating emerging clusters of COVID-19 in European countries.

Background: Coronavirus disease 2019 (COVID-19) has become a pandemic infectious disease and become a serious public health crisis. As the COVID-19 pandemic continues to spread, it is of vital importance to detect COVID-19 clusters to better distribute resources and optimizing measures. This study helps the surveillance of the COVID-19 pandemic and discovers major space-time clusters of reported cases in European countries.