Stable porphyrin-oxygenated carbon nanomaterial dispersions were prepared by blending porphyrin solutions with hydroxyl groups modified multi-walled carbon nanotubes (MWNTs-OH) and graphene oxide (GO) dispersions, respectively. Optical nonlinearity and optical limiting (OL) property of these blends are investigated in nanosecond regime. Results show that the OL performance of the blends can be tuned by changing the concentrations ratio of porphyrin and oxygenated carbon nanomaterials. The high concentration of oxygenated carbon nanomaterial leads to the poor OL performance. However, with the moderate concentration, the blends exhibit the low threshold value of OL and the enhanced OL performance at high fluence region. The superior OL performance can be attributed to complementary mechanisms and possible photoinduced electron or energy transfer between porphyrin moiety and oxygenated carbon nanomaterials.

Pump-probe differential reflection and transmission spectroscopy is a very effective tool to study the nonequili-brium carrier dynamics of graphene. The reported sign of differential reflection from graphene is not explicitly explained and not consistent. Here, we study the differential reflection and transmission signals of graphene on a dielectric substrate. The results reveal the sign of differential reflection changes with the incident direction of the probe beam with respect to the substrate. The obtained theory can be applied to predict the differential signals of other two-dimensional materials placed on various dielectric substrates.

为了实现对钢管管端内外径、不圆度的自动化非接触快速测量, 设计并实现了一种钢管管端内外径测量系统。该系统利用转台带动激光三角法位移传感器绕钢管中轴线转动的方法来测量管端截面整个圆周的外径和内径尺寸, 然后利用圆心拟合算法修正转台中轴线与钢管中轴线不重合带来的误差。通过平移台自动调整测量截面与管端的距离, 大型升降台调节管心对齐高度, 双臂平移台调节可测量管径范围, 自动实现对不同管径钢管的非接触测量。实验结果表明: 系统测量精度小于0.05 mm; 重复性限小于等于5 μm; 每个管端截面测量500个点时, 测量时间小于25 s。 设计的系统具有精度高、操作简便、测量速度快的优点, 满足无缝钢管生产在线检测的要求, 并已经在天津天管元通管材制品有限公司通过离线测试。