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The microstructural evolution and oxidation behaviour of shot-peened S30432 stainless steel during exposure in steam environment in a real double reheat USC power plant has been investigated through microstructural characterisation using electron microscopes. The results indicated that shot-peening treatment introduced a thick deformation layer to the material, and this deformation layer consisted of an outer nanostructured layer and an inner layer with deformation bands. During thermal exposure, the nanostructured layer experienced extensive recrystallisation and coarsening, and numerous σ particles were found to precipitate in the deformation layer as well. Furthermore, a double layer structured oxide formed on the material, and the oxide layer grew slowly after exposure for 6219 h, which was related to the formation of a thin and dense SiO2 layer at the metal/oxide interface. The mechanism of the microstructural evolution and oxidation has been discussed. [ABSTRACT FROM AUTHOR]

A method is presented for optimal load dispatch in large-scale hydropower plants using a genetic algorithm integrated with simulated annealing. The genetic algorithm overcomes dependence on an initial value and provides parallel processing and fast convergence, whereas simulated annealing prevents prematurity and retrieving of the local instead of the global optimum. Thus, the integrated genetic-simulated annealing algorithm improves efficiency and robustness to obtain solutions close to the global optimum. We evaluated the proposed algorithm to determine the optimal load dispatch of 32 units of the Three Gorges Hydropower Plant in China. Test results show that the minimum water consumption obtained using the proposed algorithm is similar to the optimum obtained from a previously proposed "improved" genetic algorithm when the total load of the plant is relatively high. However, for reduced load, the proposed algorithm clearly outperforms the "improved" genetic algorithm. [ABSTRACT FROM AUTHOR]