The power reflected in a SAW RAC

Considerations relating to the design of surface-acoustic-wave (SAW) reflective array pulse compressors (RACS), including the effect of array width on power reflected, the transmitted beam profile and the effect of randomized arrays, are discussed. Only a first-order analysis is used. Potential misunderstandings of these issues that could arise from the existing literature are clarified.     

AN EXPERIMENTAL-NUMERICAL METHOD FOR MEASURING CRACK PROPAGATING VELOCITIES UNDER STRESS WAVE LOADING

An experimental-numerical method for measuring dynamic crack propagating velocities under stress wave loading is established in this paper. The experiments of the three-point bend specimen are done on the improved Hopkinson bar. Deflection of loading point, dynamic load and instantaneous crack length are measured, then crack propagating velocities are calculated. Experiments on 40Cr steel show that the results given by this method have a good agreement with that obtained by the resistance fracture gage method. Therefore this method is feasible for measuring crack propagating velocities under high loading rate and will have wide application.     

测量技术在欧洲的发展

目前,对于棒材和坯料尺寸还没有普遍实行测定。但在不久将来,随着生产的提高,快速轧机的建立,以及轧制工艺自动化的实现,测定它们的尺寸,对于达到理想的轧机性能,将必不可少。为此,采用自动仪表进行测定,非常必要。本文对这些测定方法及仪表进行了综合性的概要说明。在谈到接触式或非接触式测定方法时,重点放在非接触式方法上,因为后者特别适合于上述特殊场合。现在各种物理测量原理,如X和γ射线的吸收、影象技术、微波、涡流、以及光学方法(从影象强度比较到各种扫描系统),都成功地得到了应用。本文还讨论了各种几何图形的     

低能耗合成氨生产的联合能量回收系统

采用氨生产能量回收系统的现有装置,可以使每吨氨的能耗从8.4×10~6千卡降为7.0×10~6千卡。