Nguyen Huu Khanh Nhan

Y2O3:Eu3+ phosphor: a novel solution for an increase in color rendering index of multi-chip white LED packages

Abstract In this study, a novel compound is synthesized by adding the red-emitting Y2O3:Eu3+ dopant to conformal phosphor package (CPP) or in-cup phosphor package (IPP), to be employed as a component in multi-chip white LEDs lamps (W-LEDs). It was found that this solution can enhance the color rendering index (CRI) of W-LEDs that have correlated color temperatures of 5600 K through 8500 K to more than 86. Besides, the impacts of the Y2O3:Eu3+ phosphor on the attenuation of light through the phosphor layers, CPP and IPP, are also demonstrated based on the Beer–Lambert law and Mie theory. These results provide important information for producing W-LEDs with higher CRI.

Red-emitting α-SrO·3B2O3:Sm2+ phosphor: an innovative application for increasing color quality and luminous flux of remote phosphor white LEDs

Abstract By adding red-emitting α-SrO·3B2O3:Sm2+ phosphor and SiO2 co-doping particles to yellow-emitting YAG:Ce phosphor compound, a novel method for improving lighting performance of white LEDs with remote phosphor structure, which have an average correlated color temperature (CCT) of 5600–8500 K, is proposed and demonstrated. By varying α-SrO·3B2O3:Sm2+ concentration from 2 to 30% and maintaining 5% SiO2, the obtained results indicated that color rendering index (CRI), color quality scale (CQS), and luminous flux can be increased significantly. Moreover, the Mie-scattering theory is employed to verify the scattering properties, which have an effect on the enhancement of color quality and luminous flux. The results prove a prospective practical solution for manufacturing remote phosphor white LED (RP-WLED) having higher color quality and luminous flux.

Design and kinetic energy of 3-DOF planar partly decoupled parallel manipulator

A new planar parallel manipulator is considered. The translational movements are decoupled from rotation. Kinetic energy of this mechanism is determined.

Improving Color Uniformity and Color Rending Index of Remote-Phosphor Packaging White Leds by Co-Doping Sio2 And Sr2si5n8:Eu2+ Particles

Abstract Based on some advantageous properties, such as fast response time, environment friendliness, small size, long lifetime, and high efficiency, white LEDs are increasingly used in common illumination applications. In this research, by co-doping of redemitting Sr2Si5N8:Eu2+ phosphor and adding SiO2 particles to yellow-emitting YAG:Ce phosphor compounds, a new approach for improving color uniformity and color rending index of remote-phosphor structure white LEDs is proposed and demonstrated. The obtained results clearly indicate that the color rendering index (CRI) and color uniformity (ΔCCT) significantly depend on Sr2Si5N8:Eu2+ concentration. The results provide a potential practical solution for manufacturing remote-phosphor white LEDs (RP-WLEDs) in the near future.

Novel lighting properties of white LEDs with two-layered remote phosphor package using red-emitting α-SrO·3B2O3:Sm2+ phosphor

Abstract This paper investigates a method for improving the lighting performance of white light-emitting diodes (WLEDs), packaged using two separating remote phosphor layers, yellow-emitting YAG:Ce phosphor layer and red-emitting α-SrO·3B2O3:Sm2+ phosphor layer. The thicknesses of these two layers are 800 μm and 200 μm, respectively. Both of them have been examined at average correlated color temperatures (CCT) of 7700 K and 8500 K. For this two-layer model, the concentration of red phosphor has been varied from 2 % to 30 % in the upper layer, while in the lower layer the yellow phosphor concentration was kept at 15 %. It was found interesting that the lighting properties, such as color rendering index (CRI) and luminous flux, are enhanced significantly, while the color uniformity is maintained at a level relatively close to the level in one-layer configuration (measured at the same correlated color temperature). Besides, the transmitted and reflected light of each phosphor layer have been revised by combining Kubelka-Munk and Mie-Lorenz theories. Through the analysis, it is demonstrated that the packaging configuration of two-layered remote phosphor that contains red-emitting α-SrO·3B2O3:Sm2+ phosphor particles provides a practical solution to general WLEDs lighting.

Increasing the color quality of the 7000K conformal packaging MCW-LEDs by varied red-emitting K2SiF6:Mn4+ conversion phosphor’s size

Abstract Phosphor-converted white light-emitting diodes (pc-WLEDs) are energy efficient and environmentally friendly light sources with a long lifetime, applicable in both display backlights and general lighting. In this research, we investigated the influence of the red-emitting K2SiF6:Mn4+ conversion phosphor on the color quality of the 7000K conformal packaging multi-chip white LEDs (MCW-LEDs). The effect of the red-emitting Ba2Si5N8Eu2+ convention phosphor is demonstrated based on Mie Theory by Mat Lab and Light Tools software. The research results indicated that the color quality of MCW-LEDs was crucially affected by the red-emitting K2SiF6:Mn4+ conversion phosphor’s size. This research demonstrated a significant recommendation for selecting and developing the phosphor materials for MCW-LEDs manufacturing.

Simulation Study of Void Aggregations in Amorphous ZnO

The simulations of microstructure have been done for amorphous zinc oxide by mean of molecular dynamic method. This work focused on two kinds of void aggregations: void clusters and void tubes. The results showed that many voids cluster nearby and created a lager cavity with volume seven times bigger than one of the oxygen atom. In addition, we found a void tube in low-density system, which consisted of 59 voids. Other local characteristics such as the pair radial distribution functions, bond-angle distributions, coordination number distributions, volume distribution of void cluster have also been calculated and presented here.

Improving the Angular Color Uniformity and the Lumen Output for White LED Lamps by Green Ce 0.67 Tb 0.33 MgAl 11 O 19 :Ce,Tb Phosphor

In this study, an innovative method for improving the lighting performance of multi-chip white LED lamps (MCW-LEDs) is proposed and demonstrated. By adding the green Ce0.67Tb0.33MgAl11O19: Ce,Tb (CeTb) phosphor to the phosphor layer of MCW-LEDs, the quality of emitting light can be enhanced and optimized. Furthermore, the influences of CeTb percentage concentration on the LEDs display are also investigated. The simulation results demonstrated that the lumen output and the angular color uniformity (ACU) of the conformal package MCW-LEDs having average CCTs of 7000 K and 8500 K can be enhanced significantly by green CeTb phosphor. Furthermore, by using Mie theory the simulation results could be proved and convinced thoroughly. This study shows that the green Ce0.67Tb0.33MgAl11O19: Ce,Tb (CeTb) phosphor is the prospective solution for improving optical quality of MCW-LEDs manufacturer.

Autocorrelation Properties of Walsh Function for Logic Synthesis FPGA

The objective of multi-level logic synthesis of FPGA is to find the “best” multi-level structure, where “best” in this case means an equivalent presentation that is optimal with respect to various parameters such as size, speed or power consumption. Four basic operations are used in order to reach this goal: decomposition, extraction, coverring and substitution. In this paper we propose a novel application of Walsh spectral transformation to the evaluation of Boolean function autocorrelation. The methods, operations in the transform domain has appeared to be more advantageous than traditional approaches, using operations in the Boolean domain, concerning both memory occupation and execution time on some classes of functions.

Logic synthesis FPGA — Covering problems with Walsh spectral representation

The objective of multi-level logic synthesis of FPGA is to find the “best” multi-level structure, where “best” in this case means an equivalent presentation that is optimal with respect to various parameters such as size, speed or power consumption… Five basic operations are used in order to reach this goal: decomposition, extraction, factoring, substitution and collapsing. In this paper we propose a novel application of Walsh spectral transformation to the evaluation of Boolean function autocorrelation. In particular, we present an algorithm with approach to solve the problems of covering based on the use of Walsh spectral presentation. The methods, operations in the transform domain has appeared to be more advantageous than traditional approaches, using operations in the Boolean domain, concerning both memory occupation and execution time on some classes of functions.