蜂窝缺陷的红外无损检测及有限元模拟

蜂窝结构在使用过程中,常见的缺陷有脱粘和积水。红外无损检测技术通过对试件主动加热,利用热像仪采集试件表面的红外辐射变化,从而检测出物体的缺陷信息。实验结果表明,蜂窝积水位置的温度要低于参考区域的温度。基于这一现象,利用Ansys有限元软件模拟了蜂窝结构的脉冲红外热成像检测过程,并与实际脉冲红外热成像用于表面下识别检测实验结果进行对比,验证了模拟结果的正确性。对蜂窝结构的积水、脱粘和积油缺陷模拟并进行对比识别,为实际实验提供理论基础。     

Experimental Investigation on Terahertz Spectra of Amphetamine Type Stimulants

The spectral absorption features of three amphetamine-type stimulants （ATS） belonging to illicit drugs have been studied with terahertz （THz） time-domain spectroscopy （THz-TDS） and the characteristic absorption spectra （fingerprint spectra） are obtained in the range from 0.2 to 2.5 THz. Fingerprint spectra of illicit drugs in terahertz band are bases to detect and to inspect nondestructively illicit drugs with terahertz technique. With fingerprint spectra of illicit drugs and strong penetrability for cloths, paper bags and leathered or plastic luggage terahertz technique would be better than other techniques in illicit drugs detection and inspection. Thus, this work would contribute to the building of corresponding fingerprint spectra database of illicit drugs and provide experimental bases for using of terahertz detection apparatus in drugs nondestructive detection and inspection in the future.     

Fabrication of YBCO／YSZ and YBCO／MgO thick films using electrophoretic deposition with top-seeded melt growth process

Superconducting thick films were grown on single crystals MgO and YSZ by electrophoretic deposition with Y_2BaCuO_5(Y211) addition. YBCO thick films were then accomplished by sintering the precursor films above the peritectic temperature. Single crystals of MgO (3×3×0.5 mm^3) were used as top-seed to control crystal structure of the thick films. As shown by scanning electron microscopy, the morphologies of YBCO/YSZ and YBCO/MgO thick films are spherulitic texture and platelet type. The critical temperature is ～89 K for the YBCO/YSZ thick film; the onset transition temperature is 86.4 K and the transition width is ～3 K for YBCO/MgO thick film. The critical current densities (as determined by Bean model) are, in A/cm^2, 3870 (77 K) for YBCO/YSZ thick films and 2399 (77 K) for YBCO/MgO thick films, which are comparable to the best J_c reported of the thick films prepared by the same method.     

被动式太赫兹图像目标检测研究

研究提出一种被动式太赫兹扫描成像的目标检测方法。用0.22 THz被动式扫描成像系统采集原始图像,在滤波去噪后用针孔像分析法获得太赫兹扫描成像系统的点扩展函数,进而用Lucy-Richardson算法重构图像,通过灰度变换和边缘检测增强图像对比度和目标分辨力。实验结果表明,算法能有效改善被动式太赫兹图像质量,提高成像系统探测隐藏可疑物的能力。     

高速扫描太赫兹系统在珐琅上的应用

珐琅在宫廷艺术品中享有重要地位，其制作工艺复杂，为了更好地分析珐琅的制作工艺，各种无损的科技手段都被用于珐琅的研究。太赫兹作为最后一个未被完全开发的波段，近年来被广泛应用于无损检测领域，例如通信、安检和航天等。将太赫兹技术应用于珐琅的保护和修复具有重要意义。本文搭建了基于异步光学采样（ASOPS）的高速扫描太赫兹系统，将此系统用于珐琅的反射成像研究。实验结果表明，胎体和掐丝结构的反射率较高，但边缘图案的反射率没有中间金属反射率高。掐丝结构的金属丝较细，太赫兹图像仍可以清晰地显示出它的形态，但并没有观察到不同珐琅釉料颜色的差别。珐琅片的内部至少有两层结构，分别为胎体层和掐丝釉料层。掐丝珐琅釉料层的表面并不平整而是呈现包络状，可能是在制作珐琅的最后一步磨光的过程中磨得不完全，底层的胎体平整而规则。