排序方式: 共有63条查询结果,搜索用时 93 毫秒
61.
62.
介绍实际工作中开展轨距尺检定装置的量值比对情况,包括比对的实施方案、比对方法、比对过程、使用测长机测量轨距尺传递标准的测量方法和轨距尺检定装置量值比对测量结果的不确定度评定等方面.分析参比实验室和主导实验室试验数据,得到对比结果,针对发现的问题提出改进建议. 相似文献
63.
[Objectives]This study seeks to expand the bandgap frequency band, reduce the bandgap starting frequency and analyze and optimize the bandgap parameters of acoustic metamaterials. [Methods]The influence of geometrical and material parameters on the bandgap properties of acoustic metamaterials is analyzed, and a method for maximizing the bandgap width is proposed. The multi-objective optimization problem is converted into a single objective optimization problem by normalizing the bandgap frequency coefficients. Structural material conversion is achieved via the material selection optimization method, and the optimization equations of bandgap parameters are established on the basis of weight-lightening. For chiral acoustic metamaterials, the material properties (density and wave velocity) and geometric parameters (scatterer diameter, ligament thickness and coating thickness) are defined as design variables, and the comprehensive optimization of structural parameters and material selection of acoustic metamaterials based on weight-lightening are implemented. [Results]The optimization results show that the bandgap width increases by 27.7% and the lower bound frequency decreases by 1048 Hz, thereby achieving the goal of expanding the bandgap width based on lightweight acoustic metamaterials. The acoustic transmission analysis of the finite chiral acoustic metamaterial structure is then carried out to verify the effectiveness of the proposed method. [Conclusions]The results show that the goal of lightweight acoustic metamaterials can be effectively achieved by integrating the comprehensive optimization of structural parameters and materials. As such, this study provides references for the design of new-type acoustic metamaterials. © 2023 Authors. All rights reserved. 相似文献