Rcaction mechanism between Mg(NH₂)₂ and LiH are investigated with a B3LYP method of density functional theory. Geometries and harmonic vibration frequencies of reactants,intermediates,transition states and products are calculated at B3LYP/6-311G(d,P) level.Vibration analysis and intrinsic reaction coordinates(IRC) calculation at the same level are applied to validate connection of stationarv points. It indicates that the reaction has three stages.They are the first step of hydrogen substitution,the second step of hydrogen substitution and isomerization after removal of hydrogen.There are two pathways, in which a channel of the second step of alignment hydrogen suhstitution reaction is the main channel.The two hydrogen atoms in H₂ released are from Mg(NH₂)₂ and Lilt.

A transfer matrix method is discussed,and precision of the method is controlled.It is shown that the transfer matrix method and the intergral iterative method show same results for a general confocal resonator.Convergence problem of the intergral iterative method can be solved and laser resonators can be analyzed by the transfer matrix mothod with reasonable control of calculation precision.

A sound isolator with axisymmetric periodic groove structures is given for eliminating drill collar wave.Sound isolation effect with different groove's depth (H),length,number,section shape and thickness of the drill collar is studied.With rectangle section shape,decreasing thickness of the drill collar and increasing H,isolation effect of the acoustic isolator can be increased.It can get a maximum of 36 dB sound attenuation which meets requirement of the sound isolator in LWD.

In a fluid model of DBD(dielectric barrier discharge) with atmospheric pressure, a finite difference algorithm with fixed grids is adopted to solve two-dimensional fluid continuous equations by using four-order and six-order phase error FCT(flux-corrected transport) methods, respectively. With uniform initial conditions, spatial evolution of the electron density during avalanche propagation is studied. Two FCT algorithms are compared in detail. The simulation agrees with theoretical and experimental results. It demonstrates high accuracy and precision of the FCT method.

Gauss-Newton optimization technique is a method with less computation time and rapid convergence speed, but it requires better initial conditions. It is a tickler to lose its role or to bring about local-extreme-value problems. Under the circumstances, an improved damping form of Gauss-Newton optimization technique is presented to avoid these problems. By using the diagonal damping matrix, the damping role will be changed according to the relative modified amounts of the inversion parameters. The good effect is obtained when this approach is used in the inversion problem of the high frequency electromagnetic wave logging.