With no explanation, label text_A→text_B with either "not_related" or "related".
text_A: Ryan Gosling was a star in a film directed by Derek Cianfrance.
text_B: The Lewis number -LRB- Le -RRB- is a dimensionless number defined as the ratio of thermal diffusivity to mass diffusivity .. dimensionless number. dimensionless number. thermal diffusivity. thermal diffusivity. mass diffusivity. mass diffusivity. It is used to characterize fluid flows where there is simultaneous heat and mass transfer .. fluid. fluid. It is defined as. where is the thermal diffusivity and is the mass diffusivity , is the thermal conductivity , the mixture-averaged diffusion coefficient , and the specific heat capacity at constant pressure .. thermal diffusivity. thermal diffusivity. mass diffusivity. mass diffusivity. The Lewis number can also be expressed in terms of the Prandtl number and the Schmidt number  :. Prandtl number. Prandtl number. Schmidt number. Schmidt number. It is named after Warren K. Lewis -LRB- 1882 -- 1975 -RRB- , who was the first head of the Chemical Engineering Department at MIT .. Warren K. Lewis. Warren K. Lewis. MIT. MIT. Some workers in the field of combustion assume -LRB- incorrectly -RRB- that the Lewis number was named for Bernard Lewis -LRB- 1899 -- 1993 -RRB- , who for many years was a major figure in the field of combustion research .
not_related.