Focusing high-energy x-rays by a PMMA compound x-ray lens on Beijing synchrotron radiation facility

The x-ray compound lens is a novel refractive x-ray optical device. This paper reports the authors' recent research on a polymethyl methacrylate (PMMA) compound x-ray lens. Firstly the designing and LIGA fabrication process for the PMMA compound x-ray lens are briefly described. Then, a method for theoretical analysis, as well as the experimental system for measurement is also introduced. Finally, the focusing spots for 8keV monochromatic x-rays by the PMMA compound x-ray lens are measured and analysed. According to the experimental results, it is concluded that the PMMA compound x-ray lens promises a good focusing performance under the high-energy x-rays.     

Φ125 mm光学级蓝宝石晶体生长

应用泡生法生长出φ125 mm×180 mm、质量为6 kg的蓝宝石晶体,晶体无色透明,绿光检测晶体内部无肉眼可见散射颗粒.晶体光学均匀性达到2.1×10~(-7),晶体沿a方向、c方向检测均无应力条纹.     

Optical properties of a three-dimensional chiral metamaterial

A three-dimensional chiral metamaterial with four-fold rotational symmetry is designed, and its optical properties are investigated by numerical simulations. The results show that this chiral metamaterial has the following features: high polarization conversion, perfect circular dichroism, and asymmetric transmission of circularly polarized light. A comparison of the results of chiral metamaterials without and with weak coupling between the constituent nanostructures enables us to confirm that the optical properties of our proposed nanostructure are closely related to the coupling between the single nanoparticles. This means that the coupling between nanoparticles can enhance the polarization conversion, circular dichroism, and asymmetric transmission. Due to the excellent optical properties, our metamaterial might have potential applications in the development of future multi-functional optical devices.     

DEIReconstructor:a software for diffraction enhanced imaging processing and tomography reconstruction

Diffraction enhanced imaging (DEI) has been widely applied in many fields, especially when imaging low-Z samples or when the difference in the attenuation coefficient between different regions in the sample is too small to be detected. Recent developments of this technique have presented a need for a new software package for data analysis. Here, the Diffraction Enhanced Image Reconstructor (DEIReconstructor), developed in Matlab, is presented. DEIReconstructor has a user-friendly graphical user interface and runs under any of the 32-bit or 64-bit Microsoft Windows operating systems including XP and Win7. Many of its features are integrated to support imaging preprocessing, extract absorption, refractive and scattering information of diffraction enhanced imaging and allow for parallel-beam tomography reconstruction for DEI-CT. Furthermore, many other useful functions are also implemented in order to simplify the data analysis and the presentation of results. The compiled software package is freely available.     

DEIReconstructor： a software for diffraction enhanced imaging processing and tomography reconstruction

Diffraction enhanced imaging （DEI） has been widely applied in many fields, especially when imaging low-Z samples or when the difference in the attenuation coefficient between different regions in the sample is too small to be detected. Recent developments of this technique have presented a need for a new software package for data analysis. Here, the Diffraction Enhanced Image Reconstructor （DEIReconstructor）, developed in Matlab, is presented. DEIReconstructor has a user-friendly graphical user interface and runs under any of the 32~bit or 64- bit Microsoft Windows operating systems including XP and WinT. Many of its features are integrated to support imaging preprocessing, extract absorption, refractive and scattering information of diffraction enhanced imaging and allow for parallel-beam tomography reconstruction for DEI-CT. Furthermore, many other useful functions are also implemented in order to simplify the data analysis and the presentation of results. The compiled software package is freely available.     

X射线衍射增强相衬成像的实验结果

报道了X射线衍射增强相衬成像的最新实验结果,简要论述了其原理,证明了衍射增强X射线相衬成像是一种高信噪比的成像方法,它比普通的X射线成像和层析(CT)具有高得多的分辨力,约为10μm,这在临床医学、材料科学及其它一些生物研究领域具有巨大的应用潜力。     

不稳定约束系统的多角度分析

不稳定约束相较于稳定约束增加了问题的复杂性,但不稳定约束问题蕴含了更多的处理手段.通过转换参考系,以及灵活选用适当形式的拉格朗日方程或能量积分,可实现多种途径求解.通过不同解法的对比,可验证教材中容易忽略的一些结论,如：理想约束不依赖于参考系的选择、理想约束力即使做实功也不影响保守系拉氏方程的适用等.通过对不稳定约束问题进行多角度分析,可以有效地提高学生对分析力学重要知识点的理解和运用能力.