用红外光谱研究具有互穿网络结构的pH/温度双重敏感性微凝胶的相转变行为

采用傅立叶变换红外光谱仪测试了由聚(N-异丙基丙烯酰胺)(PNIPA)和聚丙烯酸(PAA)两种聚合物网络形成的具有互穿聚合物网络结构(IPN)的pH/温度双重敏感性微凝胶D2O分散液,通过差谱技术对不同pH值和温度条件下的红外吸收光谱进行处理,研究微凝胶相转变过程中分子链微环境的变化.结果表明,随着D2O介质的pH值增...     

Comparison of the formation process and properties of epitaxial graphenes on Si- and C-face 6Hben SiC substrates

In this paper, the epitaxial graphene layers grown on Si- and C-face 6H-SiC substrates are investigated under a low pressure of 400 Pa at 1600 ℃. By using atomic force microscopy and Raman spectroscopy, we find that there are distinct differences in the formation and the properties between the epitaxial graphene layers grown on the Si-face and the C-face substrates, including the hydrogen etching process, the stacking type, and the number of layers. Hopefully, our results will be useful for improving the quality of the epitaxial graphene on SiC substrate.     

Fabrications and characterizations of high performance 1.2 kV,3.3 kV,and 5.0 kV class 4H–SiC power SBDs

In this paper, 1.2 kV, 3.3 kV, and 5.0 kV class 4H–SiC power Schottky barrier diodes(SBDs)are fabricated with three N-type drift layer thickness values of 10 μm, 30 μm, and 50 μm, respectively. The avalanche breakdown capabilities,static and transient characteristics of the fabricated devices are measured in detail and compared with the theoretical predictions. It is found that the experimental results match well with the theoretical calculation results and are very close to the 4H–SiC theoretical limit line. The best achieved breakdown voltages(BVs) of the diodes on the 10 μm, 30 μm, and 50 μm epilayers are 1400 V, 3320 V, and 5200 V, respectively. Differential specific-on resistances(R_(on-sp)) are 2.1 m?·cm~2,7.34m?·cm~2, and 30.3 m?·cm~2, respectively.     

Compressed ghost edge imaging

In this Letter, we propose an advanced framework of ghost edge imaging, named compressed ghost edge imaging(CGEI). In the scheme, a set of structured speckle patterns with pixel shifting illuminate on an unknown object.The output is collected by a bucket detector without any spatial resolution. By using a compressed sensing algorithm, we obtain horizontal and vertical edge information of the unknown object with the bucket detector detection results and the known structured speckle patterns. The edge is finally constructed via twodimensional edge information. The experimental and numerical simulations results show that the proposed scheme has a higher quality and reduces the number of measurements, in comparison with the existing edge detection schemes based on ghost imaging.     

Influence of geometrical parameters on the behaviour of SiC merged PiN Schottky rectifiers with junction termination extension

This paper investigates the behaviours of 4H--SiC merged PiN Schottky (MPS) rectifiers with junction termination extension (JTE) by extensive numerical simulations. The simulated results show that the present model matches the experimental data very well. The influences of the JTE design parameters such as the doping concentration and length of the JTE on the breakdown characteristics are discussed in detail. Then the temperature sensitivity of the forward behaviour is studied in terms of the different designs of 4H--SiC MPS with JTE, which provides a particularly useful guideline for the optimal design of MPS rectifiers with JTE.     

Relationship of annealing time and intrinsic defects of unintentionally doped 4H-SiC

With annealing temperature kept at 1573 K, the effects of annealing time on stability of the intrinsic defects in epitaxial unintentionally doped 4H-SiC prepared by low pressure chemical vapour deposition have been studied by electron spin resonance (ESR) and low temperature photoluminescence. This paper reports the results shown that annealing time has an important effect on the intrinsic defects in unintentionally doped 4H-SiC when annealing temperature kept at 1573 K. When the annealing time is less than 30 min, the intensity of ESR and photoluminescence is increasing with annealing time prolonged, and reaches the maximum when annealing time is 30 min. Then the intensity of ESR and photoluminescence is rapidly decreased with the longer annealing time, and much less than that of as-grown 4H-SiC when annealing time is 60 min, which should be related with the interaction among the intrinsic defects during the annealing process.     

增韧改性高温耐烧蚀硼酚醛树脂的红外光谱研究

硼酚醛树脂是一种耐热性极佳的聚合物,但其存在脆性大、易断裂的缺陷。通过引入端羧基丁腈橡胶对硼酚醛树脂进行增韧改性,显著改善了硼酚醛树脂的力学性能。通过傅里叶变换红外光谱对端羧基丁腈橡胶与硼酚醛树脂的反应原理进行了分析,明确了羧基丁腈橡胶与硼酚醛树脂的主要反应过程,为后续的相关研究提供了一定的理论基础。     

A Novel Tunable Dual-frequency Laser with Large Frequency Difference

1　ＩｎｔｒｏｄｕｃｔｉｏｎＢｉｒｅｆｒｉｎｇｅｎｔｄｕａｌ ｆｒｅｑｕｅｎｃｙｌａｓｅｒ[1] ｉｓｂａｓｅｄｏｎｍｏｄｅ ｓｐｌｉｔｔｉｎｇｔｅｃｈｎｏｌｏｇｙ[2 ] ａｎｄａｂｉｒｅｆｒｉｎｇｅｎｔｅｌｅｍｅｎｔｉｓｉｎｓｅｒｔｅｄｉｎｔｈｅｒｅｓｏｎａｎｔｃａｖｉｔｙｏｆｔｈｅｌａｓｅｒｔｏ ｐｒｏｄｕｃｅｄｉｆｆｅｒｅｎｔｆｒｅｑｕｅｎｃｉｅｓ.Ｔｈｅｆｒｅｑｕｅｎｃｙｄｉｆｆｅｒｅｎｃｅｃａｎｂｅｔｕｎｅｄｂｙｃｈａｎｇｉｎｇｔｈｅｏｐｔｉｃａｌｃｈａｒａｃｔｅｒｉｓｔｉｃｓｏｆｔｈｅｉｎｔｒａ…     

方形晶格夹层板减振性能仿真与优化

采用显式有限元方法,以传输损耗系数(TLC)为评价指标,研究了以钢为边界、铜和硅橡胶交替填充的方形晶格夹层板的减振性能,分析了方形填充尺寸对结构减振性能的影响。首先建立方形晶格夹层板的有限元仿真模型,其次引入传输损耗系数作为目标函数,运用遗传算法对方形晶格夹层板的减振性能进行优化,针对不同应用场景,得到的优化结果表明方形晶格夹层板具有不同减振范围的可调谐性。最后分析优化后的拓扑结构在不同频率下的位移场,可以看出其仍是在局部共振机理作用下,表现出对低频弹性波的强衰减,为拓宽夹层板的低频减振性能与可制造性提供了新的设计思路。     

科学素质教育课程“现代科学技术概论”的建设研究与思考——一个科学与人文教育交叉、融合的好载体

紧扣时代脉搏的科学素质教育课程“现代科学技术概论”深受学生欢迎,丰富的专题式知识内容体系吸引了公众的目光;优质资源的精心打造使课程建设颇具特色;教学方法与教学模式的创新别致新颖……透过现代科技知识展现的科学故事及人文历史背景,领略素质教育、感悟科学思想、培育精神品格,提升校园文化.