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The main purpose of this work is to present the ESR spectra and calculate the spin Hamiltonian parameters of 14 N and 15 N impurities in natural diamond. The ESR spectra of diamond crystal were measured on ESR spectrometer operating at X-band microwave frequency. The results of ESR spectra show that the diamond has a P1 center. This center gives rise to three strong resonance absorption peaks at θ = 90°, φ = 0° due to hyperfine interaction between electron spin and nuclear spin of 14 N . The ESR spectra of 15 N impurity consist of two satellites at the same rotation angle (φ). The effects of isolated substitution nitrogen on carbon atom produced a symmetric distortion from Td to C3V symmetry. According to this symmetry, the resonance magnetic field positions of ESR spectra for the rotation angles of 0°, 90° and 180° are almost overlap. The g-factor values and spin Hamiltonian parameters of 14 N and 15 N are: g = 2.0019, A⊥ = 29.73, A‖ = 40.24 and g = 2.0019, A⊥ = −39.90, A‖ = −57.05, respectively.

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In the field of superconductivity the most interesting area is the studying of the mechanism of the high Tc superconductor (HTS). Understanding of this mechanism, we can raise the critical temperature (Tc). There are many proposals theoretical descriptions for HTS. We focus on the spin density wave (SDW) and charge density wave (CDW), the static wave of spin density and charge density arising from the nesting property of Fermi surface that were observed in the superconductor. The model Hamiltonian of superconductor having SDW and CDW coexistence was studied by Greens function method. The analytic expression of zero-temperature gap of superconductor with the coexistence of the SDW and CDW were derived. By varying the effective potential, the phase diagram of the SDW and CDW was constructed then the band structure and density of states (DOS) of coexistent phase were also studied.

Design for gravimeter capacitor, the first model contains dielectric constant κ in partially filled with material and the second contain dielectric constant κ 1 in space between the cylinder is half-filled by a semi-cylindrical. Thus, capacitance varies in accordance with the length of the device in the cylindrical conductor or when the length of the device in the cylindrical capacitor varies in accordance with at various test locations. It can easily be shown that a change in height of approximately 1 m results in a change in the gravitational acceleration of Δg =-0.0031 cm/s 2 whereas the value of the gravitational acceleration at Ramkhamhaeng university Bangkok, Thailand used as the reference point was equal to 978.310 cm/s 2 .