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Shaoan Zhang,Yuanxing Li,Wenfeng Li,Zhenzhang Li,Minfan Qiu,Zhongfei Mu,Yang Li,Yihua Hu 한국물리학회 2019 Current Applied Physics Vol.19 No.9
High brightness and precise adjustment of luminescence colour of phosphors are two main targets in the research of phosphor-converted white LEDs. However, few feasible strategy can be employed to achieve the multicolortunable luminescence under the premise of maintaining high quantum efficiency. Here, we demonstrate a highefficiency energy-transfer process from Tb3+ to Eu3+ ions with a higher luminescent quantum efficiency (64.5% and 53.4%, respectively), and green-red multicolor emission in Lu2GeO5 host via varying the doping content of Tb3+ and Eu3+ ions. Besides, Lu2GeO5:Tb3+, Lu2GeO5: Eu3+ and Lu2GeO5: Tb3+, Eu3+ all exhibit weak thermal quenching which ensures the stable use of white LED device in the high temperature environment. This paper provides a novel multicolor-tunable phosphor with high brightness, efficient energy transfer and weak thermal quenching, which presents a potential application for UV-converted white LEDs.
An Distributed Method for Calculating Entropy of Large-scale Sequential Data
Zhen Zhang,Hongqiang Li,Rize Jin 한국정보통신학회 2021 2016 INTERNATIONAL CONFERENCE Vol.12 No.1
Various IoT devices constantly generate data in terms of time, which may form a large-scale of sequential data. Entropy calculation of a big data input will lead to unacceptable time, even not able to obtain the output. In this paper, we propose a distributed method for accelerating the entropy calculation process. Utilize a high performance host sever to deploy a distributed computing platform by server virtualization technique. Run independent R environment for the entropy calculation in multiple computing nodes and adopt Java multi-thread technique in one control node. From the experiment results and the analysis, we can conclude that the proposed distributed scheme is efficient and feasible for dealing with large-scale sequential data.
Zhen Zhang,Hui Hua Huang,Xiang Ma,Guanghui Li,Yong Wang,Guo Sun,Yinglai Teng,Rian Yan,Ning Zhang,AiJun Li 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.53 No.-
A new and efficient technique is described for the production of diacylglycerols (DAGs) by the esterification of oleic acid with glycerol catalyzed by diatomite-loaded SO4 2/TiO2. DAGs show some potential health benefits compared to triacylglycerols, and also can be used to produce the novel industrial plasticizer epoxy fatty acid methyl ester in material science. Diatomite-loaded SO4 2/TiO2 catalyst was prepared and characterized, and the selected conditions for the synthesis of DAGs were determined to be: reaction time = 6.0 h, temperature = 210 C, catalyst loading = 0.1% of the oleic acid weight, and mass ratio of oleic acid to glycerol = 2:1. Under these conditions, DAGs yield reached 59.6% with a purity of 69.6% after a one-stage molecular distillation. Diatomite-loaded SO4 2/TiO2 as a solid catalyst could be recycled and reused with high catalytic efficiency. Under the same conditions, diatomite-loaded SO4 2/TiO2 showed a better catalytic performance than the commercial solid acid SO4 2/ZrO2-Al2O3. Based on this, a two-step reaction method for the production of DAGs was performed and provided a yield similar to the one-step method (58.3% vs. 59.6%), but with a shorter reaction time (4 h vs. 6 h). It is concluded that a two-step reaction method could be a better alternative to the one-step production of DAGs in the presence of diatomite-loaded SO4 2/TiO2.