基于突变理论设冷水泵转轴功能安全完整性评估

面向核电设备冷却水泵(简称核电设冷水泵)转轴的功能安全评估是减少核电设备安全问题的重要手段之一。针对核电设冷水泵转轴故障突变时功能安全评估问题,提出了一种基于突变理论的核电设冷水泵转轴功能安全完整性评估方法。首先,从核电设冷水泵转轴多传感器监测数据中提取故障特征,故障特征融合结果作为预测参数;其次,采用预测参数构建转轴性能衰退轨迹路径,基于蒙特卡罗方法计算转轴累积失效概率;最后,基于尖点突变理论计算转轴危险失效概率,并评估转轴功能安全完整性等级,并采用核电设冷水泵转轴状态监测数据进行了实验验证。结果表明,当核电设冷水泵转轴存在故障突变时,基于突变理论结合性能衰退状态监测的方法,可以提高核电设冷水泵转轴功能安全完整性评估结果的准确性。     

基于边缘像元投影的微小轴承亚像素边缘检测

对于微小轴承的内径测量,基于机器视觉的非接触测量技术具有广阔的应用前景。针对轴承的边缘像素点,投影将感光像元划分成感光值不同的两个部分,像素单元的最终灰度值为投影两侧局部灰度统计值的面积加权平均值,取该像素的矩形邻域,并对其邻域灰度值进行高斯加权处理,将边缘投影按泰勒公式展开为二次曲线得到高精度亚像素边缘。针对微小轴承进行实验,将本文算法与基于直线拟合的方法进行比较,每毫米包括约217.18个像素,检测的圆度提高0.04%以上,标准差减少不少于7.27%,因此可更准确获取微小轴承内径的亚像素边缘。     

压电微夹钳的位移自感知反馈复合控制*

采用自感知方法获取压电微夹钳钳指位移,构成自感知反馈复合控制系统。根据反映钳指位移、表面电荷、夹持力、驱动电压之间关系的压电悬臂梁Smits方程,提出了基于电流积分的钳指位移自感知方法;引入死区算子对传统PI模型进行改进,建立了压电微夹钳钳指位移的迟滞模型;以对偏差的抛物线积分、对输出的先行微分分别代替常规PID控制器中的积分项和微分项,设计出了压电微夹钳的改进PID反馈控制器;将前馈控制器与PID反馈控制器相结合,并采用自感知反馈方式,设计出了压电微夹钳的闭环控制系统。实验结果表明:在自感知反馈复合控制作用下,压电微夹钳对5μm阶跃参考位移的响应时间为0.24 s,若不考虑噪声影响,稳态误差几乎为零;在最大位移为14.7μm的变幅值三角波参考位移以及最大位移为14.1μm的任意波形参考位移作用下,压电微夹钳的自感知反馈复合控制亦可取得良好的控制效果,其稳态误差中线在-0.02~0.04μm之间变化。自感知反馈控制的实验结果与传感器反馈控制基本相同,从而表明压电微夹钳的自感知反馈控制是有效的。     

大口径长条形反射镜组件自重变形的仿真与试验

研究了空间光学遥感器的大口径长条形反射镜组件在自重载荷作用下的面形变化,实验验证和定量分析了Zernike多项式拟合法以及球面方程拟合法得到的仿真分析结果的精度。介绍了Zernike多项式拟合法以及球面方程拟合法的基本原理,分别用这两种算法对大口径长条形反射镜组件在自重载荷作用下的面形变化进行了仿真分析。根据误差合成原理,提出了依据翻转前后两个状态的面形检测结果计算镜面面形变化的方法;针对离轴反射镜在面形检测过程中存在离轴量与镜面像散互相补偿的现象,求解了离轴量变化量与镜面像散的关系。试验结果显示:Zernike多项式拟合法的计算精度为74.2%,而球面方程拟合法的计算精度为12.6%;对仿真分析结果的误差评价表明,采用有限元法得到的仿真分析结果的理论精度值为10%左右,与球面方程拟合方法的计算精度12.6%基本吻合。研究表明,由于Zernike多项式拟合法自身的局限性,不适合对长条形反射镜面形变化进行拟合,而球面方程拟合法的计算精度能够满足工程要求。     

Comparative Study of Ultrasonication-Induced and Naturally Self-Assembled Silk Fibroin-Wool Keratin Hydrogel Biomaterials

This study reports the formation of biocompatible hydrogels using protein polymers from natural silk cocoon fibroins and sheep wool keratins. Silk fibroin protein contains β-sheet secondary structures, allowing for the formation of physical cross-linkers in the hydrogels. Comparative studies were performed on two groups of samples. In the first group, ultrasonication was used to induce a quick gelation of a protein aqueous solution, enhancing the ability of Bombyx mori silk fibroin chains to quickly entrap the wool keratin protein molecules homogenously. In the second group, silk/keratin mixtures were left at room temperature for days, resulting in naturally-assembled gelled solutions. It was found that silk/wool blended solutions can form hydrogels at different mixing ratios, with perfectly interconnected gel structure when the wool content was less than 30 weight percent (wt %) for the first group (ultrasonication), and 10 wt % for the second group (natural gel). Differential scanning calorimetry (DSC) and temperature modulated DSC (TMDSC) were used to confirm that the fibroin/keratin hydrogel system was well-blended without phase separation. Fourier transform infrared spectroscopy (FTIR) was used to investigate the secondary structures of blended protein gels. It was found that intermolecular β-sheet contents significantly increase as the system contains more silk for both groups of samples, resulting in stable crystalline cross-linkers in the blended hydrogel structures. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to analyze the samples’ characteristic morphology on both micro- and nanoscales, which showed that ultrasonic waves can significantly enhance the cross-linker formation and avoid phase separation between silk and keratin molecules in the blended systems. With the ability to form cross-linkages non-chemically, these silk/wool hydrogels may be economically useful for various biomedical applications, thanks to the good biocompatibility of protein molecules and the various characteristics of hydrogel systems.     

Identification of Autophagy in the Pine Wood Nematode Bursaphelenchus xylophilus and the Molecular Characterization and Functional Analysis of Two Novel Autophagy-Related Genes,BxATG1 and BxATG8

The pine wood nematode, Bursaphelenchus xylophilus, causes huge economic losses in pine forests, has a complex life cycle, and shows the remarkable ability to survive under unfavorable and changing environmental conditions. This ability may be related to autophagy, which is still poorly understood in B. xylophilus and no autophagy-related genes have been previously characterized. In this study, transmission electron microscopy was used to confirm that autophagy exists in B. xylophilus. The full-length cDNAs of BxATG1 and BxATG8 were first cloned from B. xylophilus, and BxATG1 and BxATG8 were characterized using bioinformatics methods. The expression pattern of the autophagy marker BxATG8 was investigated using in situ hybridization (ISH). BxATG8 was expressed in esophageal gland and hypodermal seam cells. We tested the effects of RNA interference (RNAi) on BxATG1 and BxATG8. The results revealed that BxATG1 and BxATG8 were likely associated with propagation of nematodes on fungal mats. This study confirmed the molecular characterization and functions of BxATG1 and BxATG8 in B. xylophilus and provided fundamental information between autophagy and B. xylophilus.     

A new converter for improving efficiency of multi-actuators fluid power system

This paper is concerned with the application of energy efficient fluid power in mobile robots system and proposes a new fluid power converter system which is analogous to a boost converter in power electronics. The fluid power converter system is based on the principle of pulse-width modulation. The fluid power converter has an effect akin to an electrical switched inductance transformer, wherein the output pressure or flow rate can be stepped up or down. Using an inductive reactance device (an inertia mass-block), the output flow and pressure can be varied to meet the load by a means that does not rely on dissipation of power (the resistance control). The simulation model based on the mathematics models of the components is built to analyse the performance of the fluid power converter. It is clearly shown that the fluid power converter has higher energy efficiency than conventional resistance control manners.

     

热轧低密度钢Fe-1.80Mn-1.05Al-0.09C的高温热塑性

采用Gleeble 3500热模拟试验机对一种低合金系热轧低密度钢进行了高温(760～1200℃)热塑性研究,并结合光学显微镜、体视显微镜以及扫描电镜对拉断后的断口附近组织和断口形貌进行了表征。结果表明,随着拉伸温度升高,断口面积逐渐缩小,韧窝也逐渐变大变深,断面收缩率总体表现良好,均达到80%以上,表现出了良好的高温热塑性。但是试验钢在900～1000℃进行拉伸时,出现了多处颈缩现象,900～1000℃时存在理论塑性低谷区,应避免在900～1000℃进行铸坯矫直或轧制。     

压水堆燃料包壳锆合金中第二相腐蚀行为研究进展

锆合金是目前唯一大规模商用的压水堆燃料包壳材料,其耐水侧腐蚀性能是影响核反应堆安全性与经济性的重要因素。微量合金元素(Fe、Nb等)主要以第二相的形式弥散分布在锆合金基体中,但可对锆合金的腐蚀行为产生显著影响。本文比较了不同锆合金中第二相的差异,综述了锆合金中典型第二相的腐蚀行为及其影响因素。分别比较了二元及三元第二相中主要合金元素Fe和Nb的腐蚀过程,总结了不同水化学条件下第二相腐蚀产物的差异及其对锆合金基体腐蚀行为的影响,并指出当前针对第二相腐蚀行为研究中存在的不足。最后,对锆合金第二相腐蚀行为研究趋势进行了展望,先进微观表征手段可进一步完善含Fe、Nb元素第二相的腐蚀机理研究,将为提高我国新型锆合金包壳材料的耐腐蚀性能提供理论参考。