Langevin refers to the work of French physicist Paul Langevin, who is known for his contributions to statistical mechanics and the theory of Brownian motion. He developed a mathematical framework to describe the random movement of particles suspended in a fluid, which helped to confirm the existence of atoms and molecules. In addition to his work on Brownian motion, Langevin also contributed to the field of ultrasonics and invented the Langevin transducer, a device that converts electrical energy into mechanical vibrations. His research has had a lasting impact on various scientific fields, including physics, engineering, and materials science.