低共熔溶剂在有机合成和萃取分离中的应用进展

低共熔溶剂也称为低共熔混合物或者深共熔溶剂。作为一种新型离子液体类似物,低共熔溶剂具有独特的物理化学性质和成本低廉、制备过程简单、无毒、无蒸气压、易生物降解等诸多优点,并且可以通过调节组成成分的结构和比例,赋予其特定的功能性及可调变性,因此在很多领域有着越来越广泛的应用。本文介绍了低共熔溶剂的常见氢键供体和氢键受体组成单元与分类,概括了近年来对低共熔溶剂形成机理的探究现状,综述了其作为萃取剂和溶剂在分离和有机反应中的应用,以及作为催化剂在酯化、Fridel-Crafts、环化、缩合和多组分反应等有机反应中的应用研究进展,就低共熔溶剂在研究、应用中存在的问题进行了探讨并指出了解决方法。低共熔溶剂必将以其丰富的结构及功能可调变性,成为最有发展前景的新一代溶剂和催化剂。

基于热成像的动态多目标温度智能监测仪设计

为了满足小型室内场所人员体温自动监测的需求,设计一款低成本的动态多目标温度智能监测仪。采用高分辨率微型热成像模块Lepton 3.5获取热红外图像,在STM32H743上搭载TensorFlow Lite深度学习框架,监测热红外图像中的人体并标记其温度,重点基于“滑动窗口”技术设计新的人体识别算法,解决了由于MCU算力不足导致的视频卡顿问题。实验结果表明,目标识别的准确率高达99.7%,监测多个动态目标温度时视频流畅。该温度监测仪体积小,成本低,监测目标多,适用于家庭、办公室和实验室等场所。

Combine S-N curve and fracture mechanics for fatigue life analysis of welded structures

Based on the evolution of fatigue cracks in welded structures,the fatigue life of welded structures was defined as the sum of the crack initiation life Ni and the crack propagation life Np.Correspondingly,a fatigue-life analysis method combining S-N curves and fracture mechanics theory was proposed.The equivalent structural stress method and the lower 99%boundary of the master S-N curve were used to evaluate Ni,and cracks at the end of the initiation stage were considered as semi-elliptical surface cracks.Moreover,Paris equation and the stress intensity factor range of the cracks were used to evaluate Np.Furthermore,the fatigue test results obtained from the running girder of cranes were used as a reference for comparison and verification of the results.The results revealed that the equivalent structural stress is a good indicator for the crack initiation behavior of complex welded structures.In addition,the predicted fatigue life corresponded closely to the testing life.

Cu-P合金变质过共晶铝硅合金时熔体搅拌工艺对变质效果的影响

针对过共晶铝硅合金经过P变质后初生硅仍然粗人大的问题,采用Cu-9%P合金变质处理Al-15%Si、Al-18%Si、Al-20%Si合金,变质处理后对熔体进行搅拌,研究了搅拌工艺对变质处理效果的影响,分析了熔体搅拌提高变质效果机理。结果表明,Cu-P合金变质过共晶铝硅合金时,对熔体进行搅拌可显著提高变质效果,初生硅最高可细化85%;在最佳搅拌时间内,搅拌强度越大、硅含量越高,变质效果越好;搅拌熔体迫使富P区域内AIP停止生长,熔体流动速度越快,对富PP区域内AlP的冲刷越强烈,越容易得到细小的AlP;搅拌熔体能够增加组织中初生α相的数量,搅拌工艺合适时,典型的共晶组织基本消失,可获得连续的α基体上均匀分布细小初生硅的凝固组织。