With multiple scattering theory of electrons we studied energy deposition of electrons within target and energy distribution on spot of X-ray production by Monte Carlo method as energetic electrons impinge into target vertically. It shows that spread of electrons within target is relevant to incident electron energy and target material. And 99% electron energy is deposited in a cylindrical zone. Energy deposition of electrons along incident direction increased with depth first, and then to a certain depth it decreased rapidly, which is in accordance with electron backscattering theory. These results illustrate that X-ray production zone is within a certain depth under target surface. In addition, simulation results of diamond indicate that diamond film is not recommended as an electron absorption grating, but as an excellent heat sink of target. It can be used as reference for design of microstructure X-ray tubes.

To explore motion characteristics of indoor respirable particles, Brownian force on particles is considered in motion probability model. Motion characteristics of 0.01 μm, 0.1 μm and 1 μm particles under conditions of up supply with up return and up supply with side return air forms were simulated with lattice Boltzmann method taking Re as 400, 1 000 and 2 000, respectively. It shows that range of particle spacial distribution increases with Re, and smaller particles affected more obvious by air turbulence and diffusion effect. Mean square displacement (MSD) of particles is inversely proportional to Re and diameter of particles. At same Re, MSD of particles is greater under up supply with side return air form, thus lower suspended particles and higher indoor air quality appears in up supply with side return air form.