Enhancing lighting performance of white LED lamps by green emitting Ce,Tb phosphor

With the development of high-efficiency and high-power Light-Emitting Diodes (LEDs), it has become possible to use LEDs in lighting and illumination. In last decades, developing a new method for improving lumen output and Angular Color Uniformity (ACU) is the main direction in LED technology. In this paper, an innovative approach for enhancing lighting performance (lumen output and angular color uniformity) of Multi-Chip White LED lamps (MCW-LEDs) was proposed and demonstrated by mixing the green Ce0.67Tb0.33MgAl11O19: Ce,Tb (CeTb) phosphor into their phosphor compounding. With varying CeTb concentration, ACU and lumen output with Conformal Phosphor Package (CPP) and In-cup Phosphor Package (IPP) are calculated, displayed and analyzed. The results show that the lumen output and the ACU of 7000 K and 8500 K MCW-LEDs increased remarkably in comparison with the older works. Using green CeTb is a prospective method for improving lighting performance of MCW-LEDs in future

Influence of scattering enhancement particles CaCO3, CaF2, SiO2 and TiO2 on color uniformity of white LEDs

In this paper, the influence of scattering enhancement particles CaCO3, CaF2, SiO2 and TiO2, adding to YAG:Ce phosphor compounding, on color uniformity of white LEDs (W-LEDs) was presented. Firstly, the physical model of multi-chip W-LEDs is simulated and demonstrated by using commercial LightTools 8.1.0 program. After that, the influence of scattering enhancement particles on color uniformity is calculated and analyzed. With using the Monte Carlo simulation and the Mie-scattering theory, the color uniformity improvement of an 8500~K W-LEDs is demonstrated convincingly. From the researched results, the best color uniformity can be accomplished with TiO2 articles. The results and discussions provided a practical approach for higher-quality manufacturing W-LEDs

Enhancement of color rendering index for white light LED lamps by red Y2O3:EU3+ phosphor

We present an application of the red Y2O3:Eu3+ dopant phosphor compound for reaching the color rendering index as high as 86. The Multi-Chip White LED lamps (MCW-LEDs) with high Correlated Color Temperatures (CCTs) including 7000 K and 8500 K are employed in this study. Besides, the impacts of the Y2O3:Eu3+ phosphor on the attenuation of light through phosphor layers of the various packages is also demonstrated based on the Beer-Lambert law. Simulation results provide important conclusion for selecting and developing the phosphor materials in MCW-LEDs manufacturing

The impact of petty corruption on firm innovation in Vietnam

Corruption has been found to have complex effects on firm innovation.Limited theoretical and empirical evidence to date has been rather inconclusive. This study employs econometric estimation techniques to analyze data from small and medium manufacturing enterprises in Vietnam to assess the impact of petty corruption on firm innovation. The empirical results tend to support the "greasing" impact of corruption on innovation. Specifically, informal payments by Vietnamese firms are shown to encourage overall innovation, product improvement, innovation and new innovation. In view of the commonplace business practice of paying small informal fees to speed up transactions in the inefficient public sector in Vietnam, this finding is not entirely unexpected, though troubling

Literature Review of Knowledge Sharing and Issues Raised for Vietnamese Universities

This study aims to review previous studies in the field of knowledge sharing. Data being used in this study was collected from researches related to the topic of knowledge sharing. We summarize literature on knowledge sharing in terms of (i) Necessity of knowledge sharing, (ii) Supporting from information and communication technology tools (ICT), (iii) Context of knowledge sharing, (iv) Participants knowledge sharing, (v) Receiver knowledge and (vi) advantages and disadvantages when participating in knowledge sharing. Some implications are recommended for Vietnamese universities to better support knowledge sharing activities in Vietnam and around the world. Keywords: Knowledge management, Knowledge sharing, Information technology, Management information system. DOI: 10.7176/JESD/10-18-17 Publication date:September 30th 201