Researchers conducted experiments on coal to study the pore structure and found that medium-high rank coal has pores ranging from 0.8 nm to 1.5 nm with varying surface curvature. They used a mathematical function to describe the pore size variation and derived an equation for liquid-solid adsorption. By analyzing data from coal mines, they found that their equation was more effective than the traditional Langmuir equation in guiding coalbed methane production.