An extension of the characteristic angle method to the easy-plane spin-32 ferromagnet
Abstract The characteristic angle (CA) method [J. Phys. A 27 (1994) 5599], developed previously for the easy-plane spin-1 magnetic systems, has been successfully extended to the spin - 3 2 case. A compact form of the CA spin - 3 2 operator transformation is given. Then the ground state energy, the magnon dispersion relation and the spontaneous magnetization are discussed for an easy-plane spin - 3 2 ferromagnet by using the CA method. A comparison with the old theoretical methods is made.
Induced magnetization of an easy-plane spin-one ferromagnet
Abstract The characteristic angle (CA) method, which was introduced in a previous work, is applied to calculate the induced magnetization of an easy-plane spin-one ferromagnet. The harmonic approximation which is often applied in a spin-Bose expansion is found to be invalid and may even lead to wrong physical results when calculating the induced magnetization of the easy-plane spin-one ferromagnet. Then the complete Bose transformation (CBT) is used to transform the spin operator into a Bose operator, so that high-order terms in the Bose expansion can betaken into account based on an independent Bose representation. Comparison of the result calculated by the CBT and by the harmonic approximation shows that high-order terms in the CBT are helpful in determining a reasonable ground state and getting accurate physical results. Diagrams of the induced magnetization versus the external magnetic field for a simple-cubic lattice are presented for small and large anisotropy, respectively.
Reduction of gas flow nonuniformity in gas turbine engines by means of gas-dynamic methods
Gas flow nonuniformity is one of the main sources of rotor blade vibrations in the gas turbine engines. Usually, the flow circumferential nonuniformity occurs near the annular frames, located in the flow channel of the engine. This leads to the increased dynamic stresses in blades and as a consequence to the blade damage. The goal of the research was to find an acceptable method of reducing the level of gas flow nonuniformity as the source of dynamic stresses in the rotor blades. Two different methods were investigated during this research. Thus, this study gives the ideas about methods of improving the flow structure in gas turbine engine. On the basis of existing conditions (under development or existing engine) it allows the selection of the most suitable method for reducing gas flow nonuniformity.