Hexagonal boron nitride (h-BN) was added into polymer blends of methyl-vinyl-silicone rubber (MVQ) and ethylene-vinyl-acetate copolymer (EVA) to prepare thermally conductive and electrically insulating composites by m...Hexagonal boron nitride (h-BN) was added into polymer blends of methyl-vinyl-silicone rubber (MVQ) and ethylene-vinyl-acetate copolymer (EVA) to prepare thermally conductive and electrically insulating composites by melt processing method. According to Young’s equation, the wettability coefficient points out that the dispersion of h-BN in EVA is thermodynamically more favorable than in MVQ. The result of SEM showed that h-BN was selectively located in EVA. There existed double percolation effect in h-BN/MVQ/EVA ternary composites, which resulted in promoting for both mechanical properties and thermal conductivity. The thermal conductivity of h-BN/MVQ/EVA composites were related with h-BN content and EVA/MVQ ratio. When EVA content was 30 wt% in the matrix blend, the relatively increased rate of thermal conductivity of h-BN/MVQ/EVA composites was the highest. The tensile strength and the elongation at break were mainly related with the EVA content in polymer matrix. The increasing amount of EVA and h-BN in the composites resulted in a decrease in dielectric constant.展开更多
用51%的Percoll分离液和DEAE-纤维素层析柱,从自然感染的黄鳝(Monopterus albusZuiew)中分离鳝锥虫(Trypanosoma monopteriChen et Hsieh,1964)。对含虫血液样品分别以2.1×103r/min、2.5×103r/min、2.9×103r/min、3.3...用51%的Percoll分离液和DEAE-纤维素层析柱,从自然感染的黄鳝(Monopterus albusZuiew)中分离鳝锥虫(Trypanosoma monopteriChen et Hsieh,1964)。对含虫血液样品分别以2.1×103r/min、2.5×103r/min、2.9×103r/min、3.3×103r/min、3.6×103r/min离心5、10、15、20min,观察红细胞的去除和鳝锥虫存留百分数,结果表明:2.9×103r/min离心15min分离效果最佳。离心分离的混悬液含有锥虫、白细胞、血栓细胞和极少的红细胞,悬混液再经DEAE-纤维素过柱,得到纯净的鳝锥虫。过柱后光学显微镜观察,锥虫形态正常,运动活泼,无血细胞。本方法具有耗时短、回收率高的特点,是把梯度分离和离子交换结合在一起的一种快速有效方法,为鳝锥虫的进一步研究奠定了基础。另外,此方法还可以作为快速、准确检测自然状态下黄鳝是否感染锥虫的手段,为鳝锥虫的流行病学研究提供可靠的数据。展开更多
Taking low permeability cores of Daqing oilfield for example,the flow characteristics at low velocity were studied with the self-designed micro-flux measuring instrument.Considering the throat distribution and capilla...Taking low permeability cores of Daqing oilfield for example,the flow characteristics at low velocity were studied with the self-designed micro-flux measuring instrument.Considering the throat distribution and capillary model,the thickness of fluid boundary layer under different pressure gradients was calculated,and the mechanism and influencing factors of nonlinear percolation were discussed.The results show that the percolation curve of ultra-low rocks is nonlinear,and apparent permeability is not a constant which increases with pressure gradient.The absorption boundary layer decreases with the increase of pressure gradient,and changes significantly especially in low pressure gradient,which is the essence of nonlinear percolation.The absorption boundary layer is also found to be impacted by the surface property of rocks.展开更多
文摘Hexagonal boron nitride (h-BN) was added into polymer blends of methyl-vinyl-silicone rubber (MVQ) and ethylene-vinyl-acetate copolymer (EVA) to prepare thermally conductive and electrically insulating composites by melt processing method. According to Young’s equation, the wettability coefficient points out that the dispersion of h-BN in EVA is thermodynamically more favorable than in MVQ. The result of SEM showed that h-BN was selectively located in EVA. There existed double percolation effect in h-BN/MVQ/EVA ternary composites, which resulted in promoting for both mechanical properties and thermal conductivity. The thermal conductivity of h-BN/MVQ/EVA composites were related with h-BN content and EVA/MVQ ratio. When EVA content was 30 wt% in the matrix blend, the relatively increased rate of thermal conductivity of h-BN/MVQ/EVA composites was the highest. The tensile strength and the elongation at break were mainly related with the EVA content in polymer matrix. The increasing amount of EVA and h-BN in the composites resulted in a decrease in dielectric constant.
文摘用51%的Percoll分离液和DEAE-纤维素层析柱,从自然感染的黄鳝(Monopterus albusZuiew)中分离鳝锥虫(Trypanosoma monopteriChen et Hsieh,1964)。对含虫血液样品分别以2.1×103r/min、2.5×103r/min、2.9×103r/min、3.3×103r/min、3.6×103r/min离心5、10、15、20min,观察红细胞的去除和鳝锥虫存留百分数,结果表明:2.9×103r/min离心15min分离效果最佳。离心分离的混悬液含有锥虫、白细胞、血栓细胞和极少的红细胞,悬混液再经DEAE-纤维素过柱,得到纯净的鳝锥虫。过柱后光学显微镜观察,锥虫形态正常,运动活泼,无血细胞。本方法具有耗时短、回收率高的特点,是把梯度分离和离子交换结合在一起的一种快速有效方法,为鳝锥虫的进一步研究奠定了基础。另外,此方法还可以作为快速、准确检测自然状态下黄鳝是否感染锥虫的手段,为鳝锥虫的流行病学研究提供可靠的数据。
基金Project(2008ZX05013) supported by the National Science and Technology Project of ChinaProject(10672187) supported by the National Natural Science Foundation of China
文摘Taking low permeability cores of Daqing oilfield for example,the flow characteristics at low velocity were studied with the self-designed micro-flux measuring instrument.Considering the throat distribution and capillary model,the thickness of fluid boundary layer under different pressure gradients was calculated,and the mechanism and influencing factors of nonlinear percolation were discussed.The results show that the percolation curve of ultra-low rocks is nonlinear,and apparent permeability is not a constant which increases with pressure gradient.The absorption boundary layer decreases with the increase of pressure gradient,and changes significantly especially in low pressure gradient,which is the essence of nonlinear percolation.The absorption boundary layer is also found to be impacted by the surface property of rocks.
