Simulations of solar radiation have become increasingly common in recent years because of the rapid global development and deployment of solar energy technologies. The effect of air pollution on solar radiation is well known. However, few studies have attempting to evaluate the potential of the air pollution index in estimating solar radiation. In this study, meteorological data, solar radiation, and air pollution index data from three sites having different air pollution index conditions are used to develop random forest models. We propose different random forest models with and without considering air pollution index data, and then compare their respective performance with that of empirical methodologies. In addition, a variable importance approach based on random forest is applied in order to assess input variables. The results show that the performance of random forest models with air pollution index data is better than that of the empirical methodologies, generating 9.1-17.0% lower values of root-mean-square error in a fitted period and 2.0-17.4% lower values of root-mean-square error in a predicted period. Both the comparative results of different random forest models and variance importance indicate that applying air pollution index data is improves estimation of solar radiation. Also, although the air pollution index values varied largely from season to season, the random forest models appear more robust performances in different seasons than different models. The findings can act as a guide in selecting used variables to estimate daily solar radiation and improve the accuracy of solar radiation estimation.

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Structure and electronic properties of dysprosium-silicide nanowires on vicinal Si(001) Appl. Phys. Lett. 87, 083107 (2005); 10.1063/1.2032620Influence of strain, surface diffusion and Ostwald ripening on the evolution of nanostructures for erbium on Si (001) The growth behavior and morphology evolution of erbium silicide nanostructures are studied on the vicinal Si͑001͒ surface with a 4°miscut angle towards the ͓110͔ direction as the functions of annealing temperature, annealing time, and Er coverage. Three kinds of nanostructures can be observed on the surface: nanowires, rectangular nanoislands and square nanoislands. The experimental results reveal that nanowires in AlB 2 -type structure and the nanoislands in ThSi 2 -type structure can be formed at 600-650 and 700-750°C, respectively. At the final growth stage, the nanowires of erbium silicide undergo Ostwald ripening. At high coverage of two monolayers, many AlB 2 -type nanoislands will appear in a rectangular shape on the sample surface. According to the AlB 2 -type crystalline structure of ErSi 2 and the scanning tunneling microscopy results obtained on the flat and vicinal substrate surfaces, a model is suggested to describe the ErSi 2 /Si͑001͒ interfacial structure. This model explains the spatial orientation relationship between erbium silicide nanowire and Si dimer row, and is consistent with Er-induced ͑2 ϫ 3͒ reconstruction at the initial stage of Er growth on the Si͑001͒ surface.

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