According to the perturbation theory, a distribution law of matrix element in secular equation is discovered in degenerate state and wave function property of the hydrogen atom.

A thermodynamic model of the gas_liquid_solid three phases equilibria is presented, combing an equation of state with a solution theory.

We have studied the feasibility of active vibration control of shuttle loom by using modern control theory and establishing the state-variable equation of the nexible beam and picking plate system.