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Recently, customers are demanding for hot rolled strip products to have tight oxide scales on the surfaces. Therefore, high finishing rolling temperature, low coiling temperature and fast finishing rolling speed have to be used to obtain tight oxide scale, which is different from conventional controlled rolling. In order to ensure the mechanical properties at the same time, a framework consisting of the Bayesian neural network and multi-objective particle swarm optimization has been established to determine the optimal hot strip rolling parameters. Due to excellent generalization ability, the Bayesian neural network was employed to develop the model for the prediction of mechanical properties of hot rolled automotive beam steels. The accuracy between the measured and predicted values was within ±30 MPa and ±4% for strength and elongation, respectively, providing a reliable model for the optimal process design. By applying multi-objective particle swarm optimization, the optimized hot rolling process was obtained for the production of hot rolled automotive beam steel with "Tight Oxide Scale". Industrial trials have been carried out, which showed good agreement with the optimized hot strip rolling processes. It has been theoretically and practically proven that the optimal process design framework can effectively locate the optimal processing window for hot strip rolling.

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Wheat grain yield mainly comes from the accumulation and redistribution of the material after anthesis, the objectives of this study were to assess the contribution of pre-and post-anthesis dry matter, fertilizer nitrogen (N) and soil native N assimilation to grain yield of winter wheat (Triticum aestivum L.). [Method] Field experiments were conducted to investigate the effects of seeding rates (150, 225 and 300 seeds m −2) at three N rates (0, 150, 225 kg N ha −1) on accumulation and remobilization of dry matter and N from different sources, and grain yield from 2008 to 2010. The experiment sites were located in the Middle and Lower Yangtze River Basin in China. A 15 N micro-plot experiment was designed with the three seeding rates at rate of 150 and 225 kg N ha −1. [Results] The grain yield increased at higher N rate (225 kg N ha −1) and the optimum seeding rate (225 seeds m −2), and yield differences mainly depended on the number of spikes per unit area and were positively correlated with leaf area index. The higher N rate and seeding rate increased post-anthesis remobilisation amount of organic matter from leaves and stems and accumulation amount in grain that helped improve grain yield, but decreased remobilization efficiency and the contribution of remobilized dry matter to grain yield. Both post-anthesis N accumulation and remobilization of N from the different sources increased with increasing N rate and seeding rate. For fertilizer N, remobilization efficiency and the contribution of remobilized N to grain increased with increasing N rate and seeding rate, whereas for soil N, remobilization efficiency and contribution of N remobilization to grain N (CNRG) decreased. Fertilizer N remobilized to grain more easily than soil N, and top-dressed N remobilized to grain more easily than basal N. The correlation showed increasing remobilization of fertilizer N and post-anthesis accumulation of soil N were beneficial to improving grain yield. [Conclusion] In conclusion, for higher grain yield and nitrogen recovery, combining N fertilization at 225 kg N ha −1 with seeding rate at 225 seeds m −2 was recommended to wheat management in the Middle and Lower Yangtze River Basin.