采用直流热阴极PCVD(Plasma chemical vapor deposition)法间歇生长模式制备金刚石膜,通过加入周期性的刻蚀阶段清除金刚石膜在一定生长期中形成的石墨和非晶碳等杂质,实现了金刚石膜生长的质量调控。间歇式生长过程分为沉积阶段和刻蚀...采用直流热阴极PCVD(Plasma chemical vapor deposition)法间歇生长模式制备金刚石膜,通过加入周期性的刻蚀阶段清除金刚石膜在一定生长期中形成的石墨和非晶碳等杂质,实现了金刚石膜生长的质量调控。间歇式生长过程分为沉积阶段和刻蚀阶段,两个阶段交替进行。采用Raman光谱、SEM和XRD对所制金刚石膜的品质进行了表征,并与同样生长条件下连续生长模式制备的金刚石膜样品进行了比较。结果表明,当单个生长周期为30 min(沉积时间为20 min、刻蚀时间为10 min)时,直流热阴极PCVD法间歇生长模式制备的金刚石膜中的非金刚石相杂质含量低于连续间歇生长模式制备的金刚石膜。展开更多
在详细分析MOSFET输出电容对CLLLC谐振变换器运行原理和工作特性影响的基础上,针对MOSFET输出电容在续流阶段会产生振荡的问题,提出一种优化的参数设计方法,可在保持自然软开关特性的同时减轻振荡;针对由输出电容引起的变换器轻空载工...在详细分析MOSFET输出电容对CLLLC谐振变换器运行原理和工作特性影响的基础上,针对MOSFET输出电容在续流阶段会产生振荡的问题,提出一种优化的参数设计方法,可在保持自然软开关特性的同时减轻振荡;针对由输出电容引起的变换器轻空载工作时输出电压漂高的问题,采取电压滞环间歇模式控制,可有效将输出电压调节至额定值,同时降低变换器轻空载工作时的损耗;最后,搭建了一台1 k W、400 V/48 V的实验样机,实验结果证明了所提优化设计和控制策略的正确性和可行性。展开更多
A numerical study was conducted to seek an optimized dimension of jet chamber in the pulsating impinging flow.The flow and heat transfer effect of the pulsation flow through a jet chamber was investigated.The numerica...A numerical study was conducted to seek an optimized dimension of jet chamber in the pulsating impinging flow.The flow and heat transfer effect of the pulsation flow through a jet chamber was investigated.The numerical results indicate that heat transfer effective enhances near the stagnation region for the intermittent pulsed flow with jet chamber compared to that without jet chamber.Simulations of the flow through a jet chamber show that the heat transfer rate on the impingement surface is highly dependent on the velocity at the position which is really close to target surface.Examination of the velocity field suggests that the velocity exists a maximum value as the axis distance increases.In addition,the velocity at the jet hole is enlarged by the jet chamber due to the entrainment effect,and the velocity is amplified even greater as the size of the jet chamber becomes bigger.Nevertheless,the velocity declines quickly while the flow axis distance is more than a certain range,leading to poor heat transfer.Thus,intermittent pulsed flow with jet chamber is suggested as a method of improving heat transfer by employing larger dimensions of jet chamber for appropriate jet-to-surface spacing.展开更多
文摘探讨4种不同运动时间和间歇模式的大强度间歇运动(HIIT)诱发愉悦情绪和享受感的效果差异。方法:将75名大学生随机分配至运动30 s间歇30 s组、运动1 min间歇1 min组、运动30 s间歇1min组和运动1 min间歇2 min组,分别于运动前、运动后即刻和20 min测量其享受感,并对运动中的疲劳感、愉悦情绪和享受感进行测试。结果:1)运动30 s间歇1 min HIIT相比运动1 min间歇2 min,运动30 s间歇30 s HIIT相比运动1 min间歇1 min HIIT均可诱发更积极的愉悦情绪。运动30 s间歇1 min HIIT诱发的愉悦情绪最高,运动1 min间歇1 min HIIT诱发的愉悦情绪最低。2)1:1间歇模式HIIT诱发的享受感水平低于1:2间歇模式,并且与运动30 s间歇30 s、运动1 min间歇1 min HIIT相比,运动1min间歇2 min HIIT诱发的享受感水平更高。3)运动30 s间歇1 min HIIT诱发的享受感水平显著高于运动1 min间歇1 min,相同间歇模式HIIT诱发的享受感水平没有显著差异。结论:1)运动时间和间歇时间等量时,运动时间越长,愉悦情绪越低,运动时间小于间歇时间的HIIT诱发的愉悦情绪更高。2)间歇期长的HIIT诱发的享受感水平更高,相同间歇模式的运动时间长短不影响运动后产生的享受感。3)短时间多组数HIIT是诱发愉悦情绪的最佳方案,长时间的间歇期HIIT是诱发享受感的最佳方案。
文摘在详细分析MOSFET输出电容对CLLLC谐振变换器运行原理和工作特性影响的基础上,针对MOSFET输出电容在续流阶段会产生振荡的问题,提出一种优化的参数设计方法,可在保持自然软开关特性的同时减轻振荡;针对由输出电容引起的变换器轻空载工作时输出电压漂高的问题,采取电压滞环间歇模式控制,可有效将输出电压调节至额定值,同时降低变换器轻空载工作时的损耗;最后,搭建了一台1 k W、400 V/48 V的实验样机,实验结果证明了所提优化设计和控制策略的正确性和可行性。
基金Project(51306088)supported by the National Natural Science Foundation of ChinaProject(NJ20160039)supported by the Fundamental Research Funds for the Central Universities,China
文摘A numerical study was conducted to seek an optimized dimension of jet chamber in the pulsating impinging flow.The flow and heat transfer effect of the pulsation flow through a jet chamber was investigated.The numerical results indicate that heat transfer effective enhances near the stagnation region for the intermittent pulsed flow with jet chamber compared to that without jet chamber.Simulations of the flow through a jet chamber show that the heat transfer rate on the impingement surface is highly dependent on the velocity at the position which is really close to target surface.Examination of the velocity field suggests that the velocity exists a maximum value as the axis distance increases.In addition,the velocity at the jet hole is enlarged by the jet chamber due to the entrainment effect,and the velocity is amplified even greater as the size of the jet chamber becomes bigger.Nevertheless,the velocity declines quickly while the flow axis distance is more than a certain range,leading to poor heat transfer.Thus,intermittent pulsed flow with jet chamber is suggested as a method of improving heat transfer by employing larger dimensions of jet chamber for appropriate jet-to-surface spacing.
