Laterally deformable nanomechanical zeroth-order gratings: anomalous diffraction studied by rigorous coupled-wave analysis

We describe a novel optomechanical device that produces strong reflectance and polarization modulation of incident light. The structure is based on a suspended nanomechanical grating with lateral deformability, and rigorous coupled-wave analysis has been used to fully model the optical properties of the device. The grating consists of two interdigitated gratings that may be moved with respect to each other with an applied force. The structures proposed here are designed to be readily manufacturable with device processing developed for surface-micromachined microelectromechanical systems and with known microelectromechanical systems materials, such as silicon, silicon nitride, and amorphous diamond. As the spacing of the grating is changed, an anomalous diffraction effect is observed, a Wood's type anomaly in which there exists a resonance in propagating leaky modes within the grating, resulting in a dramatic change in the reflectance characteristics for slight changes in the grating. One of the unique features of this structure is that a reflected optical signal can be used to detect subangstrom in-plane motion of structures greater than 10 nm.     

Aufnahme von Spurenmengen Antimon (Radioantimon) durch Metalloxidhydrat-Niederschläge, 2. Mitt.: Oxidhydrate von Yttrium,Lanthan und Ytterbium

Uptake of carrier-free radioantimony (¹²⁵Sb) by the hydrated oxides of Y, La and Yb is influenced strongly by the aging of the precipitates: Coprecipitated radioantimony is released from the precipitates as aging proceeds, uptake is reduced strongly if preformed precipitates are aged. Such influence of aging of these hydrated oxides is not found for the uptake of all trace elements. Uptake of radioantimony due to coprecipitation exceeds sorption on preformed precipitates by about one order of magnitude. Thus, coprecipitated radioantimony is predominantly incorporated into the precipitate particles. Only a small fraction is adsorbed on the surface. The dependance of the uptake on pH and addition of NaCl was determined.     

超声溶栓

超声溶栓长期为人们所重点研究。本文对超声溶栓技术进行了综述，着重介绍和分析了其发展历史、溶栓机理、技术特点和研究现状，最后对以后的研究工作提出了一些看法。     

多通道超声兰姆波检测板状结构中的裂纹

超声兰姆(Lamb)波在结构缺陷检测方面愈来愈受到重视,但目前Lamb波的应用局限于单信号源激励,单通道接收的方法,容易受到噪声干扰,其后续的信号分析处理也比较复杂。本文旨在采用多通道Lamb波对板状结构中的裂纹进行定量分析与诊断。在铝板的表面凿刻出不同深度的凹槽作为裂纹,通过线阵换能器采集在一定传播距离内的多通道Lamb波信号,并采用二维傅里叶变换分析在不同深度的裂纹下,Lamb波模式能量的变化规律。结果表明,相对于完好铝板中的Lamb波信号,裂纹的存在会使Lamb波发生模式转换现象,并且转换模式能量百分比随裂纹深度的增加而线性增加。其结果为Lamb波评价板状结构中的裂纹状况提供了一种可能的方法。     

超声表观积分背散射系数评价新生儿骨状况的可行性研究

新生儿骨发育状况的超声评价有重要意义。本文研究用超声背散射信号来评价新生儿骨发育状况的可行性。提出将超声表观积分背散射系数(AIB)用于评价新生儿松质骨状况,研究了不同超声频率下AIB与婴儿体重、出生天数之间的关系。研究结果表明,足月儿的AIB明显大于早产儿的AIB;足月儿的体重和AIB相关性较弱;早产儿的AIB参数和出生天数具有较高的正相关性(R=0.633)。说明超声背散射信号及其参数AIB可用于评价新生儿松质骨发育状况。     

有监督学习的超声背散射方法在骨质评价中的应用

在超声背散射方法评价骨质的实际应用中,如何更为准确地判断测量对象是否为骨质疏松是一个重要问题。提出一种有监督学习的超声背散射评价方法,根据超声背散射离体实验的信号处理结果,对松质骨样本使用支撑向量机和自适应增强的有监督学习算法进行预测和分类。研究结果表明,有监督学习的超声背散射评价方法分类的准确率为80.00%~82.86%,并且对骨质疏松的样本具有较高的特异性(特异度>92.3%)。因此有监督学习的超声背散射评价方法具有有效性,评价效果优于现有的其它定量超声方法,对超声背散射方法的在体应用有一定帮助。