LANZHOU, July 24 (Xinhua) -- Due to the COVID-19 pandemic, 57-year-old Long Ruijun, a professor at Lanzhou University in northwest China's Gansu Province, turned to online lectures to help old friends in Pakistan fight energy and food shortages. Long used to routinely visit the country from 2016 to 2019 to share agricultural techniques and skills with experts and farmers there. "The landscape and climate in Gansu are similar to that in Pakistan, especially in the northern region," he said. "So t...