声学所提出薄板裂纹成像的新方法

<正>随着薄板工件的广泛应用,薄板裂纹的检测问题变得尤其重要。超声lamb波具有传播距离远、衰减小等特点,已经广泛应用于薄板结构的无损检测。但lamb波具有频散特性,不能用在某些传统超声成像方法中。逆时偏移方法借鉴于地球物理学,目前已应用于超声检测各个领域。前人采用可消除频散影响的导波法对薄板裂纹成像进行了数值模拟,但效果较差,且实验与模拟结果不一致。     

MEMS压电水听器和矢量水听器研究进展*

基于微电子机械系统制造技术的MEMS压电水听器和矢量水听器具有小型化、低功耗、低成本、易成阵、无源、噪音低等优点。对基于ZnO薄膜的MEMS水听器和矢量水听器进行了研究,测试结果表明,硅微压电水听器的灵敏度为-192 d B(ref.1 V/μPa),基本达到实用化的要求。MEMS压电矢量水听器等效声压灵敏度为-229.5 d B(ref.1 V/μPa),比同类型压阻式MEMS矢量水听器的灵敏度高17 d B,但还未达到实用化要求。为了进一步提高MEMS矢量水听器的灵敏度,设计了具有U形槽的压电复合悬臂梁结构和电极串联结构,采用具有更高压电系数的掺钒ZnO薄膜作为压电层,并对MEMS制备工艺进行了改进,有望显著提高MEMS矢量水听器的灵敏度。     

Bending Analysis of Functionally Graded One-Dimensional Hexagonal Piezoelectric Quasicrystal Multilayered Simply Supported Nanoplates Based on Nonlocal Strain Gradient Theory

In this study,the nonlocal strain gradient theory is adopted to investigate the static bending deformation of a functionally graded (FG) multilayered nanoplate ...     

光学薄膜损伤表面三维微观形貌的仿真与重构

通过对激光作用薄膜元件后的损伤过程和图像损伤特征进行分析与研究,借助光学薄膜损伤表面三维微观形貌的重构,揭示薄膜元件损伤机理.基于白光干涉显微原理,采集薄膜损伤表面的干涉显微三维云数据,运用Delaunay三角剖分法构建损伤表面的三角网格模型,通过可视化仿真,实现了损伤表面三维微观形貌的再现.结果表明:实验测试的Hf0...     

Isolation,Purification, and Anti-Aging Activity of Melanin from Lachnum singerianum

Intracellular melanin from Lachnum singerianum YM296 (LIM) was obtained by the method of microwave-assisted extraction. On the basis of single factor experiment, the optimum microwave-assisted extraction conditions of LIM using Box–Behnken design were as follows: NaOH concentration, 1.05 mol/L; ratio of raw material to liquid ratio, 1:14.72 (g/mL); microwave time, 118.70 s; and microwave power, 320 W. Under these conditions, the extraction yield of LIM was 11.08 %, and 40.43 % higher than that of extraction by alkali extraction and acid precipitation. The results showed that microwave-assisted extraction could increase the extraction yield of LIM. Three homogeneous components were fractionated from LIM by Sephadex G-15 column. LIM-a was the main homogeneous component, accounting for 75.7 % of the total content of the homogeneous components. Aged mice model were induced by injecting d-galactose, and the aged mice were given LIM-a of different dosages, respectively. The results showed that LIM-a can significantly increase body weight, thymus indexes, and spleen indexes of the aged mice; effectively elevate the levels of SOD, GSH-PX, and CAT; and decrease the level of MDA in mice liver homogenate, brain homogenate, and serum, indicating that LIM-a had significant anti-aging activity.     

Fréchet differentiability of solution mappings for semilinear second order evolution equations

In this paper we establish the strong Fréchet differentiability of maps from the set of initial values and forcing terms into the set of solutions for semilinear second order evolution equations. Also, under the weaker conditions of nonlinear terms we establish the strong Gâteaux differentiability of the solution maps. An application of results to semilinear strongly damped wave equations is given.     

Regarch模型的几何遍历性及伴随几何遍历性

本文引入随机环境干扰,将非线性时间序列GARCH模型推广为REGARCH模型,并讨论REGARCH模型的几何遍历性及伴随几何遍历性。     

离子色谱法同时测定植物生长调节剂中氯化胆碱、甲哌鎓及N-甲基哌啶

建立了一种离子色谱-抑制电导同时测定植物生长调节剂中主要活性成分氯化胆碱、甲哌鎓以及杂质N-甲基哌啶的快速检测方法。 样品经稀释过膜后直接进样分析, 采用阳离子交换色谱柱thermo scientific ionpac CG17 （50 mm×4 mm） + CS17 （250 mm×4 mm）,以10 mmol·L^-1甲烷磺酸溶液等度淋洗,可在10 min内完成以上目标分析物的检测,且常规阳离子（Li⁺、 Na⁺、 NH₄⁺、 K⁺、 Mg²⁺和Ca²⁺）不会干扰对3种化合物的测定。 在优化后的最佳色谱条件下,氯化胆碱的线性范围为0.1~500 mg·L^-1,甲哌鎓的线性范围为0.5~500 mg·L^-1,N-甲基哌啶的线性范围为0.4~200 mg·L^-1,3种化合物线性相关系数（r）均大于0.999 4,线性关系良好。 3种目标分析物的检出限（信噪比S/N = 3）为28.0~112.5 μg·L^-1,定量限（信噪比S/N = 10）为93.5~375.0 μg·L^-1,峰面积的相对标准偏差（RSD, n = 6）均小于0.47%,表明方法具有较好的重现性。 该检测方法简单方便,已成功应用于商品化植物生长调节剂中3种成分质量浓度的测定,实际样品加标回收率为96.0%~103.6%。 可应用于相关植物生长调节剂原料及成品的质量控制。     

复合材料层合板的可靠性和优化问题的研究进展

纤维增强复合材料是由高强度、低密度的纤维材料与基体组成, 具有很多其它材料所不具有的特性, 其应用范围越来越大. 复合材料的机械性能与加工制造等过程密切相关, 其材料性能的离散度较大, 因此考虑不确定性因素的结构可靠性分析非常必要. 可设计性是复合材料的另一个特点, 因此复合材料结构的优化设计也是研究的热点之一. 本文讨论了复合材料层合板结构的可靠性分析方法, 优化设计, 可靠性优化设计以及鲁棒优化等, 并对其发展趋势作出展望.