BN&Al2O3/环氧树脂复合材料粘接层对LED灯结温的影响

自制BN/EP(环氧树脂)复合材料和Al₂O₃/EP复合材料作为LED灯PCB板和散热铝块之间的粘接层材料,采用精密钻孔的方法用高精度测温仪测量LED灯正常工作时的温度分布,讨论粘接层对结温的影响,并与COMSOL Multiphysics软件模拟结果进行对比分析。实验测量LED结温与模拟结温变化趋势基本一致,结温会随着粘接层厚度的增加而上升、随着粘接层复合材料热导率的增加先快速降低而后趋于平缓。最终得到PCB板和散热铝块间最佳粘接层厚度和粘接层复合材料配比,当BN的质量分数为60%时,BN/EP复合材料粘接层的热导率最高,此时LED结温为75.2 ℃,比纯环氧树脂粘接层LED的结温降低了27.6 ℃。而Al₂O₃/EP复合材料粘接层LED的最低结温为78.2 ℃,此时Al₂O₃的质量分数为50%。     

胶束溶液中钙黄绿素-荧光桃红间荧光共振能量转移的研究及应用

研究了钙黄绿素-荧光桃红体系的荧光共振能量转移机理及其在蛋白质测定中的应用.实验表明:在聚乙烯醇存在下,于HAc-NaAc缓冲液(pH 5.30)中,钙黄绿素与荧光桃红之间能发生有效的能量转移.根据Frster理论,探讨了钙黄绿素与荧光桃红分子间能量转移机理.结果表明:蛋白质的加入使钙黄绿素-荧光桃红体系发生荧光猝灭...     

微波法合成1,ω-二(2,2-二氨基-1,3,4-噻二唑-5-)烷烃类化合物

以浓硫酸为催化剂,氨基硫脲(1)与二元羧酸(2a～2d)在微波辐射下经环合反应合成了四种新型的1,ω-二(2,2-二氨基-1,3,4-噻二唑-5-)烷烃类化合物,其结构经1H NMR和IR表征.最佳反应条件为:1 20mmol,n(1):n(2)=2.0:1.8,浓硫酸2.6 mL,中低火微波辐射6 min,产率77....     

基于开环振荡器阵列磁振荡效应的全光开关

We demonstrate an all-optical switching of the magnetic resonance properties associated with a metallic Split Ring Resonator（SRR） array. The periodically spaced elements are fabricated on a high-resistivity silicon wafer and probed by using conventional Terahertz （THz） time-domain spectroscopy. We use a continuous-wave laser diode to generate carriers in the gaps of the SRR elements. Using a sufficient power, this opti- cal excitation can create an effective short gap, which would switch the resonant properties of the metamaterial from that of an SRR array to that of a closed ring resonator array and leads to dramatic changes in the THz transmission. In the present experiment, the optically induced switching is associated with the magnetic reso- nance. However, with appropriate changes in the device structure, this approach can be extended to switch a medium with a negative real index of refraction to a medium with a positive real index of refraction. This opens the way to creat a broad new range of active devices.