目的:设计一套基于Android平台的精神疲劳检测系统,实时检测、监测被测对象的精神疲劳状态。方法:遵循准确性、易用性、便携性原则,利用脑电信号多尺度熵结合长短期记忆(long-short term memory,LSTM)人工神经网络模型,通过MindWave系...目的:设计一套基于Android平台的精神疲劳检测系统,实时检测、监测被测对象的精神疲劳状态。方法:遵循准确性、易用性、便携性原则,利用脑电信号多尺度熵结合长短期记忆(long-short term memory,LSTM)人工神经网络模型,通过MindWave系列单通道脑电信号采集设备,设计并实现包括移动端和服务器端两大部分的精神疲劳检测系统。其中移动端采用Android Studio作为开发工具,通过Java编程语言进行设计;服务器端采用Eclipse作为开发工具,在Tomcat运行环境下进行设计。结果:该系统不仅可以显示脑电信号波形图,专注度、冥想度曲线图,以及从原始脑电信号数据提取出来的α波、β波和θ波波形图,对精神疲劳等级进行量化,还可以存储用户数据,不断完善LSTM人工神经网络模型,从而使量化结果越来越准确。结论:基于Android平台的精神疲劳检测系统小型、便捷,能够简便、快速、实时地对用户精神疲劳状态进行检测与监测,可防止疲劳作业引发的安全事故。展开更多
Metal-halide perovskites are novel optoelectronic materials that are considered good candidates for solar harvesting and light emitting applications. In this study, we develop a reproducible and low-cost approach for ...Metal-halide perovskites are novel optoelectronic materials that are considered good candidates for solar harvesting and light emitting applications. In this study, we develop a reproducible and low-cost approach for synthesizing high- quality cesium lead halide perovskite （CsPbX3, X = CI, Br, and I or C1/Br and I/Br） nanocrystals （NCs） by direct heating of precursors in octadecene in air. Experimental results show that the particle size and composition of as-prepared CsPbX3 nanocrystals can be successfully tuned by a simple variation of reaction temperature. The emission peak positions of the as-prepared nanocrystals can be conveniently tuned from the UV to the NIR （360-700 nm） region, and the quantum yield of the as-obtained samples （green and red emissions） can reach up to 87%. The structures and chemical compositions of the as-obtained NCs were characterized by transmission electron microscopy, X-ray diffraction, and elemental analysis. This proposed synthetic route can yield large amounts of high-quality NCs with a one-batch reaction, usually on the gram scale, and could pave the way for further applications of perovskite-based light-emitting and photovoltaic solar cells.展开更多
Dimethyl sulfide-mediated electrochemical synthetic strategy for esterification of amino acids has been reported.A series of amino acids could react smoothly with alcohols,affording the desired esterification products...Dimethyl sulfide-mediated electrochemical synthetic strategy for esterification of amino acids has been reported.A series of amino acids could react smoothly with alcohols,affording the desired esterification products with good efficiency.Importantly,the tolerance of peptides and gram-scale synthesis shed light on the utility of this protocol.Mechanistically,the dimethyl sulfide as a mediator plays an essential role in the transformation of amino acids.展开更多
文摘目的:设计一套基于Android平台的精神疲劳检测系统,实时检测、监测被测对象的精神疲劳状态。方法:遵循准确性、易用性、便携性原则,利用脑电信号多尺度熵结合长短期记忆(long-short term memory,LSTM)人工神经网络模型,通过MindWave系列单通道脑电信号采集设备,设计并实现包括移动端和服务器端两大部分的精神疲劳检测系统。其中移动端采用Android Studio作为开发工具,通过Java编程语言进行设计;服务器端采用Eclipse作为开发工具,在Tomcat运行环境下进行设计。结果:该系统不仅可以显示脑电信号波形图,专注度、冥想度曲线图,以及从原始脑电信号数据提取出来的α波、β波和θ波波形图,对精神疲劳等级进行量化,还可以存储用户数据,不断完善LSTM人工神经网络模型,从而使量化结果越来越准确。结论:基于Android平台的精神疲劳检测系统小型、便捷,能够简便、快速、实时地对用户精神疲劳状态进行检测与监测,可防止疲劳作业引发的安全事故。
基金This work was supported by the National Natural Science Foundation of China （Nos. 21373097 and 51072067）.
文摘Metal-halide perovskites are novel optoelectronic materials that are considered good candidates for solar harvesting and light emitting applications. In this study, we develop a reproducible and low-cost approach for synthesizing high- quality cesium lead halide perovskite （CsPbX3, X = CI, Br, and I or C1/Br and I/Br） nanocrystals （NCs） by direct heating of precursors in octadecene in air. Experimental results show that the particle size and composition of as-prepared CsPbX3 nanocrystals can be successfully tuned by a simple variation of reaction temperature. The emission peak positions of the as-prepared nanocrystals can be conveniently tuned from the UV to the NIR （360-700 nm） region, and the quantum yield of the as-obtained samples （green and red emissions） can reach up to 87%. The structures and chemical compositions of the as-obtained NCs were characterized by transmission electron microscopy, X-ray diffraction, and elemental analysis. This proposed synthetic route can yield large amounts of high-quality NCs with a one-batch reaction, usually on the gram scale, and could pave the way for further applications of perovskite-based light-emitting and photovoltaic solar cells.
基金This work was supported by the National Natural Science Foundation of China(No.22031008)and the Science Foundation of Wuhan(No.2020010601012192)The Program of Introducing Talents of Discipline to Universities of China(111 Program)is also appreciatedThis work was dedicated to Professor Christian Bru-neau for his outstanding contribution to catalysis.
文摘Dimethyl sulfide-mediated electrochemical synthetic strategy for esterification of amino acids has been reported.A series of amino acids could react smoothly with alcohols,affording the desired esterification products with good efficiency.Importantly,the tolerance of peptides and gram-scale synthesis shed light on the utility of this protocol.Mechanistically,the dimethyl sulfide as a mediator plays an essential role in the transformation of amino acids.
