介绍了一种用8位精简指令集计算机(Recluced Instraction Set Computer,RISC)结构单片机中将PWM波转换为模拟电压输出的D/A转换的实现方法。分析了脉宽调制(PWM)频率、占空比调节精度和积分器之间的关系。在此基础上设计出一种使用AVR...介绍了一种用8位精简指令集计算机(Recluced Instraction Set Computer,RISC)结构单片机中将PWM波转换为模拟电压输出的D/A转换的实现方法。分析了脉宽调制(PWM)频率、占空比调节精度和积分器之间的关系。在此基础上设计出一种使用AVR系列单片机MEGA16内部定时/计数器产生PWM信号,再利用通用电路把PWM信号转换成直流电压信号的硬件电路。其最大线性误差只有0.5%,且成本低廉。展开更多
Studies on the metamorphic and related magmatic rocks within the Jiangnan Orogen,southern China,are important to understand the formation and evolution of this Neoproterozoic orogen because they can provide evidence f...Studies on the metamorphic and related magmatic rocks within the Jiangnan Orogen,southern China,are important to understand the formation and evolution of this Neoproterozoic orogen because they can provide evidence for revealing the tectonic evolution of the South China Block.Following on from earlier attempts at stratigraphic correlation and creating a framework for the low-grade metamorphosed basement,new first-hand information on the composition and deformation of the East Jiangnan Orogen basement indicates that the sedimentary rocks in the north are composed of the sequential Shangxi Group(Gp)and the overlying Likou Gp,with a clear regional unconformity in between.The Likou Gp includes the Zhentou Formation(Fm.)and the Dengjia Fm.,with the previously named Puling Fm.only basalt interbeds within the Dengjia Fm.The Xucun granodiorite pluton of^830 Ma intrudes the Shangxi Gp,thereby resulting in a 100 mwide hornfels zone within the wall rocks,indicating that the formation of the group occurred earlier than that of the pluton.By contrast,the southern metamorphic rocks of the Xikou Gp and the overlying Jingtan Fm.are flaky,disordered,and strongly deformed.The Jingtan Fm.is roughly equivalent to the Heshangzhen Gp and includes the Zhoujiacun conglomerates in the lower part and a rhyolite in the upper part with interbedded basalt.This assessment of Neoproterozoic stratigraphic sequences and magmatic rocks in the east of the Jiangnan Orogen differs from and rectifies previous studies,emphasizing that explanation of analytical results,particularly geochronology,should be consistent with facts gathered in the field.展开更多
A numerical analysis was carried out to study the moving boundary problem in the physical process of pulsed Nd-YAG laser surface melting prior to vaporization.The enthalpy method was applied to solve this two-phase ax...A numerical analysis was carried out to study the moving boundary problem in the physical process of pulsed Nd-YAG laser surface melting prior to vaporization.The enthalpy method was applied to solve this two-phase axisymmetrical mehing problem.Computational results of tempera ture fields were obtained,which provide useful information to practical lair treatment processing. The validity of enthalpy method in solving such problems is presented.展开更多
文摘介绍了一种用8位精简指令集计算机(Recluced Instraction Set Computer,RISC)结构单片机中将PWM波转换为模拟电压输出的D/A转换的实现方法。分析了脉宽调制(PWM)频率、占空比调节精度和积分器之间的关系。在此基础上设计出一种使用AVR系列单片机MEGA16内部定时/计数器产生PWM信号,再利用通用电路把PWM信号转换成直流电压信号的硬件电路。其最大线性误差只有0.5%,且成本低廉。
基金financially supported by the National Nature Sciences Foundation of China(grant Nos 41430211,41872201)。
文摘Studies on the metamorphic and related magmatic rocks within the Jiangnan Orogen,southern China,are important to understand the formation and evolution of this Neoproterozoic orogen because they can provide evidence for revealing the tectonic evolution of the South China Block.Following on from earlier attempts at stratigraphic correlation and creating a framework for the low-grade metamorphosed basement,new first-hand information on the composition and deformation of the East Jiangnan Orogen basement indicates that the sedimentary rocks in the north are composed of the sequential Shangxi Group(Gp)and the overlying Likou Gp,with a clear regional unconformity in between.The Likou Gp includes the Zhentou Formation(Fm.)and the Dengjia Fm.,with the previously named Puling Fm.only basalt interbeds within the Dengjia Fm.The Xucun granodiorite pluton of^830 Ma intrudes the Shangxi Gp,thereby resulting in a 100 mwide hornfels zone within the wall rocks,indicating that the formation of the group occurred earlier than that of the pluton.By contrast,the southern metamorphic rocks of the Xikou Gp and the overlying Jingtan Fm.are flaky,disordered,and strongly deformed.The Jingtan Fm.is roughly equivalent to the Heshangzhen Gp and includes the Zhoujiacun conglomerates in the lower part and a rhyolite in the upper part with interbedded basalt.This assessment of Neoproterozoic stratigraphic sequences and magmatic rocks in the east of the Jiangnan Orogen differs from and rectifies previous studies,emphasizing that explanation of analytical results,particularly geochronology,should be consistent with facts gathered in the field.
基金the National Natural Science Foundation of China and the Chinese Academy of Sciences
文摘A numerical analysis was carried out to study the moving boundary problem in the physical process of pulsed Nd-YAG laser surface melting prior to vaporization.The enthalpy method was applied to solve this two-phase axisymmetrical mehing problem.Computational results of tempera ture fields were obtained,which provide useful information to practical lair treatment processing. The validity of enthalpy method in solving such problems is presented.
