超声换能器检测方法的研究

超声检测技术广泛使用在无损检测领域中,而换能器是超声工程中极其重要的技术和分支领域。超声换能器是一种电声能量转换器件,是超声检测技术中的关键,直接影响无损检测结果的可靠性,本文阐述了超声换能器的原理和测量接触换能器的检测方法,分析了A型换能器脉冲回波灵敏度校准的不确定度。     

以实施机关为主体的行政许可标准化评价

本文在分析我国行政许可评价制度的基础上,从标准化角度分析了行政许可评价制度的问题,在此基础上提出以实施机关为主体的行政许可标准化评价.     

依法治检下提高计量技术档案管理科学化水平的思考

计量技术档案除了可以显示出技术机构运行的情况,方便工作人员及时发现并调整体系运行过程中存在的问题,使所有工作有序进行以外,还为日常检定工作的溯源和改进提供了主要凭证和强大动力。在计量事业发展的同时,档案管理也发扬着其日益重要的作用,怎样管理好计量技术档案是当前依法治检中不可或缺的一项重要工作,该篇文章将围绕计量技术单位该怎样安排有限的人力资源,做好各项档案管理工作,保证在常规工作有条不紊的进行的同时,能科学化妥善保管各种工作档案来谈谈自己的理解。     

Composite bending-dominated hollow nanolattices: A stiff,cyclable mechanical metamaterial

Manufacturing ultralight and mechanical reliable materials has been a long-time challenge. Ceramic-based mechanical metamaterials provide significant opportunities to reverse their brittle nature and unstable mechanical properties and have great potential as strong, ultralight, and ultrastiff materials. However, the failure of ceramics nanolattice and degradation of strength/modulus with decreasing density are caused by buckling of the struts and failure of the nodes within the nanolattices, especially during cyclic loading. Here, we explore a new class of 3D ceramic-based metamaterials with a high strength–density ratio, stiffness, recoverability, cyclability, and optimal scaling factor. Deformation mode of the fabricated nanolattices has been engineered through the unique material design and architecture tailoring. Bending-dominated hollow nanolattice (B-H-Lattice) structure is employed to take advantages of its flexibility, while a few nanometers of carbonized mussel-inspired bio-polymer (C-PDA) is coherently deposited on ceramics’ nanolayer to enable non-buckling struts and bendable nodes during deformation, resulting in reliable mechanical properties and outperforming the current bending-dominated lattices (B-Lattices) and carbon-based cellulose materials. Meanwhile, the structure has comparable stiffness to stretching-dominated lattices (S-Lattices) while with better cyclability and reliability. The B-H-Lattices exhibit high specific stiffness (>10⁶?Pa·kg^?1·m^?3), low-density (～30?kg/m³), buckling-free recovery at 55% strain, and stable cyclic loading behavior under up to 15% strain. As one of the B-Lattices, the modulus scaling factor reaches 1.27, which is lowest among current B-Lattices. This study suggests that non-buckling behavior and reliable nodes are the key factors that contribute to the outstanding mechanical performance of nanolattice materials. A new concept of engineering the internal deformation behavior of mechanical metamaterial is provided to optimize their mechanical properties in real service conditions.