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A three-dimensional mathematical model is developed based on the Navier-Stokes momentum equation and the low Reynolds number turbulence k-ε equation. This model comprehensively considers energy conservation,molten steel solidification and the influence of the mushy zone on the flow process. Heat flux obtained through an inverse heat transfer model combined with measured temperature is set as the boundary condition to the coupling model,to investigate fluid flow,heat transfer and solidification in the continuous casting mold. It is found that liquid steel flow has important influence on the distributions of temperature and heat flux,and the solidification process is governed by a synthetic action of fluid flow and heat flux. The proposed model and the non-uniform characteristic of solidification can provide reference for further investigation on longitudinal cracks and other surface defects during continuous casting.

There are sufficient illumination resources and strong solar radiation in Shiyang River Basin. It is of great significance to estimate the total solar radiation accurately for agricultural production in Shiyang River Basin. In order to evaluate the simulation accuracy of common total solar radiation models in the Shiyang River Basin and determine the model suitable for the estimation of total solar radiation in the Shiyang River Basin, this paper selects 5 types of total solar radiation models based on the meteorological data of Shiyang River Experimental Station of China Agricultural University from 2014 to 2018. Five indexes, namely determination coefficient R2, mean absolute error MAE, root mean square error RMSE, consistency index d and overall evaluation index GPI are used to evaluate the suitability of the solar total radiation model based on different weather types. The results show that the comprehensive model based on percentage of sunshine, average daily temperature and relative humidity has the best simulation effect. In sunny weather, the cubic function A-P model has the best simulation effect. In cloudy weather, the comprehensive model has the best simulation effect, and the estimation model of total solar radiation in Shiyang River Basin based on weather combination is proposed, which provides a further model support for the estimation of total solar radiation in Shiyang River Basin. [ABSTRACT FROM AUTHOR]

Seasonal variation of heavy metal contents in leaves and their relationships with soil heavy metal pollution levels were studied through measuring and analyzing the leaves of the common tree species in Beijing and soil heavy metal contents, to detect heavy metal accumulation ability of plant leaves. The results showed that: (1) the contents of Cu, Pb, Zn in plant leaves first decreased and then increased, again declined with changing the seasons (from spring to winter). Cr concentration showed the trend of first increase and then decrease from spring to winter, and the highest in the autumn; the accumulation capacities of Cu for Babylonica and Japonica were higher in the spring, summer and autumn, while Tabuliformis was in winter; the higher accumulation capacities for Cr, Pb were Japonica and Platycladus, and in winter were Platycladus and Bungeana; the higher accumulation capacities for Zn were Babylonica and Bungeana, while Platycladus in winter; (2) the pollution degree of four kinds of heavy metals (Cu, Cr, Pb, Zn) from downtown to suburbs showed that: Jingshan (C =2.48, C is contamination factor) > Olympic (C = 1.27) > Songshan (C = 1.20) > Shuiguan (C = 1. 18); (3) the heavy metals concentration of same plant leaves in the water of the Great Wall changed larger, but those in the other three areas showed that: Jingshan > Olympic > Songshan; the ability of same species leaf to absorb different sorts of heavy metals showed that: Zn >Cu >Pb >Cr; the difference between Zn content and Cr content was significant (P <0.01); (4) the relationship between heavy metal content in plant leaves and soil heavy metal pollution levels presented a quadratic polynomial relation; the significant correlation was found between other three heavy metal contents of plant samples and soil samples, but they were not the case for the Cu, and the correlation coefficients were above 0. 9.

Organic light-emitting devices (OLEDs) with emission peak at 520 nm were designed. The electroluminescence (EL) spectra including the integrated intensity, the peak width at half height, and the intensity and the position of the peak of the EL spectra of the OLEDs and microcavity OLEDs (MOLEDs), the total thickness of organic layers which is changeable, were calculated and theoretically analyzed with the thickness of the layer of NPB and light-emitting layer of Alq3 ranging from 10 to 100 nm, respectively. According to these studies, it was found that the optimized OLEDs should be constructed with 70 nm NPB and 62 nm Alq3, and this structure should be more suitable to configurate the MOLEDs. These results suggest that the suitable structure of OLEDs/MOLEDs could be designed with help of theoretical calculation, which is also helpful to the light-emitting properties of OLEDs and MOLEDs.

Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), UV-Vis spectra, laser nano size detector (LNSD) and scanning electron microscope (SEM) were employed to analyze the characters and structure of enzyme and octenyl succinic anhydride modified starch. The results indicated that the enzymatic starch reacted with octenyl succinic anhydride, bringing only octenyl succinic anhydride groups but not any other groups. The esterification of enzymatic starch only took place in amorphous region, but had no effect on the crystal form of starch granule. The clarity of EOSS increased with the increase in substitution degree. The particle size of oil emulsion made by EOSS was fine and well-distributed, meaning that the emulsion has excellent emulsibility and emulsifying stability. The embedding of oil encapsulated with EOSS is fine. It can be concluded that the properties of EOSS is excellent, and can be used as emulsifier and wall material of microcapsule.