大功率LED在线性及PWM调光下的电光转换效率及热分析

在相同输入电功率下,对大功率LED在线性及PWM两种调光模式下的光参数及电参数进行了测试。比较了LED在两种调光模式下的色温、光效及电光转换效率随输入功率的变化,得出在两种调光模式下,色温随平均输入电流的降低而降低,但线性调光模式下的色温漂移大于PWM调光模式下的色温漂移;光效及电光转换效率随平均输入电流的降低而升高,但在相同输入功率下,LED在PWM调光模式下的电光转换效率大于线性调光模式下的电光转换效率,且随平均输入电流的降低,线性调光模式下的电光转换效率的上升速度要快于PWM调光模式。利用T3STER热阻测试仪,建立LED的瞬态热阻抗模型。使用电子学热仿真分析方法对LED在两种调光模式下的电光转换效率随结温变化的规律进行了仿真分析。分析得出LED在PWM调光下的光电转换效率主要受结温温升的影响,而在线性调光下,电光转换效率除了受到结温温升的影响,还受到无效电流注入的影响。因此,LED在线性调光模式下电光转换效率的上升速度要快于PWM调光模式。     

影响频谱分析仪频率分辨率的因素

频率分辨率是频谱分析仪的一项重要技术指标,在介绍频谱分析仪原理的基础上,对频谱分析仪的分辨率带宽、频率选择性、本振残余调频和本振相位噪声参数进行了解析,从而使读者掌握各参数与频谱分析仪频率分辨率之间的关系,在选购频谱仪和实际测量时合理地考虑以上参数。     

在硅胶表面制备牛血红蛋白分子印迹聚合物

采用表面印迹法, 以乙烯基三甲氧基硅烷修饰的硅胶为载体, 丙烯酰胺为功能单体, N,N-亚甲基双丙烯酰胺为交联剂, 并将改性聚乙烯醇(PVA)作为辅助识别聚合物链(ARPCs)引入聚合体系中, 制备了牛血红蛋白分子印迹聚合物(MIP). 实验使用红外光谱分析了改性PVA的结构特征, 用扫描电镜(SEM)观察MIP的表面形貌, 考察了ARPCs的含量对MIP吸附性能的影响. 吸附动力学实验研究表明, 聚合体系中ARPCs的引入使MIP对模板牛血红蛋白(BHb)的吸附量明显提高|十二烷基磺酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)结果显示, MIP对BHb的特异性吸附能力明显提高.     

创新是QC小组持续发展的活力之源

本文通过介绍各种质量改进活动方式,提出:QC小组活动只有持续不断地创新,才能得以发展.     

TRANSFER MECHANISM OF QUININE DRUG ACROSS THE OIL/WATER (O/W) INTERFACE

The transfer phenomena of quinine drug at the aqueous 1,2- dichloroethane (DCE)interface have been studied by the current- scanning polarography. The relationships be-tween the wave height and pH of aqueous phase, concentration of quinine as well as therate of water drop are discussed. The effect of supporting electrolyte, buffer solution andthe nature of organic solvent on the polarographic wave is studied. The transfer char-acteristics of quinine in aqueous phase and in organic phase are compared, The mono- pro-tonated and diprotonated quinines can both transfer at the interface so as to produce twopolarographic waves. The transfer process of quinine at the interface is simultaneouslycontrolled by diffusion and reestablishment of the disturbed protonated equilibrium ofquinine. A further investigation is made by chronopotentiometry. On the basis of thetheoretical analysis, the formulae of the limiting current are derived and discussed. Thetheoretical results are in agreement with the experimental ones.     

Gamma induced changes in Makrofol/CdSe nanocomposite films

We applied an ex-situ casting procedure to prepare a nanocomposite (NCP) from Makrofol polycarbonate (PC) and CdSe nanoparticles. The CdSe nanoparticles were prepared by a thermolysis procedure in the presence of N₂ gas flow. Rietveld refinement of x-ray data illustrated that the CdSe adopts a cubic zinc blend structure of 6.057 Å lattice parameter and 2 nm typical grain size. Samples from the prepared NCP were exposed to γ dosages (20 kGy-250 kGy). The modifications induced in the NCP films owing to γ dosages have been studied. The γ irradiation (50 kGy-250 kGy) causes crosslinks that reduce the optical bandgap from 4.15 eV to 3.81 eV, associated with an increase in dielectric parameters and refractive index. This is attributed to an increase in the mass fraction of the disordered regions as specified by x-ray diffraction. The PC-CdSe NCP was found to have a reaction to color modification which makes it suitable for saleable reproduction on a printing press.