针对多向应变测量问题，采用凸台和圆环状基片结构设计了一种三向光纤布拉格光栅（FBG）应变传感器，实现了对结构三个方向应变的同步测量。通过振动试验台和不锈钢板进行了同电阻应变片的静态对比实验和振动监测实验。结果表明，FBG应变传感器和应变片在三个方向的静态应变曲线基本一致，相关系数分别为0.98、0.98和0.99。振动功率谱分析结果表明，FBG应变传感器和应变片均观察到了一次谐波和二次谐波，频率误差分别为2.77%和0.97%，且应变片还监测到了高次谐波信号。该传感器具有结构简单、尺寸小、测量精度高、定位准确等优点，在多向应变监测领域具有良好的应用前景。

针对光纤光栅应变计无法同时准确测量结构表面多个方向应变的问题, 该文设计了一种基于光纤布喇格光栅(FBG)的三向应变计。三向应变计采用圆环状基底结构, 并在基底上封装了3根互成角度的FBG, 适用于结构表面3个方向应变的同步测量。对封装后的应变计进行性能测试, 并进行了同电阻应变片的对比实验。结果表明, 应变计具有良好的线性, 最大迟滞误差为6.1%, 应变灵敏度在0°和90°方向分别提高约2.3倍和1.4倍。随着载荷的增加, 应变计的测量误差逐渐减小, 载荷大于1.5 kg后测量误差控制在±5%。

Because the brain edema has a crucial impact on morbidity and mortality, it is important to develop a noninvasive method to monitor the process of the brain edema effectively. When the brain edema occurs, the optical properties of the brain will change. The goal of this study is to access the feasibility and reliability of using noninvasive near-infrared spectroscopy (NIRS) monitoring method to measure the brain edema. Specifically, three models, including the water content changes in the cerebrospinal fluid (CSF), gray matter and white matter, were explored. Moreover, these models were numerically simulated by the Monte Carlo studies. Then, the phantom experiments were performed to investigate the light intensity which was measured at different detecting radius on the tissue surface. The results indicated that the light intensity correlated well with the conditions of the brain edema and the detecting radius. Briefly, at the detecting radius of 3.0 cm and 4.0 cm, the light intensity has a high response to the change of tissue parameters and optical properties. Thus, it is possible to monitor the brain edema noninvasively by NIRS method and the light intensity is a reliable and simple parameter to assess the brain edema.