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Warm white emission of LaSr_(2)F_(7):Dy^(3+)/Eu^(3+)NPs with excellent thermal stability for indoor illumination

Journal of Materials Science & Technology 2020年第19期54卷 230-239页

作者： Yongbin Hua Jae Su Yu Department of Electronic Engineering Institute for Wearable Convergence ElectronicsKyung Hee UniversityYongin-siGyeonggi-do 17104Republic of Korea

The novel single Dy^(3+)-activated and Dy^(3+)/Eu^(3+)co-activated LaSr_(2)F_(7) NPs-based phosphors were successfully synthesized via a simple precipitation reaction method at room *** phase formations and cell parameters of single Dy^(3+)-activated and Dy^(3+)/Eu^(3+)co-activated LaSr_(2)F_(7) NPs were verified in detail by the Rietveld refinement technique based on the recorded X-ray diffraction *** doping concentration of single Dy^(3+)-activated LaSr_(2)F_(7) NPs was optimized to be 0.1 mol with the concentration quenching dominated by the electric dipole-dipole ***,a variety of Eu^(3+)-activated La_(0.9)Sr_(2)F_(7):0.1Dy^(3+)NPs exhibited tunable luminescent properties and emitted warm white light in close to standard warm white light under 363 nm *** valid energy transfer(ET)efficiency from Dy^(3+) to Eu^(3+) ions was estimated to be about 86.02%based on the emission intensity while the electric dipole-quadrupole interaction dominated the concentration quenching mechanism in ET ***,the thermal quenching of the obtained samples was studied,showing the excellent thermal *** the results manifest that Eu^(3+)-activated LaSr_(2)F_(7):Dy^(3+)NPs could emit warm white light with excellent thermal stability for indoor illumination.

关键词： Warm white light Energy transfer Thermal stability chromaticity coordinates

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Establishment of a metric to characterize retroreflector properties using a consumer-grade colour camera

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Transportation Safety and Environment 2023年第1期5卷 31-40页

作者： Huayang He Wenying Su Qiutong Cheng National Center of Metrization for Equipments of Roads and Bridges Research Institute of Highway Ministry of TransportBeijing 100088China Division of Optical Metrology National Institute of MetrologyBeijing 100029China

The coefficients of retroreflection and chromaticity coordinates are critical metrics for determining the quality of a ***,conventional retroreflection measurement techniques rely heavily on the night-time colour,size and characteristics of thesample being *** complicates the measurement process and leads to deviations in the test *** addition,chromaticitycannot be determined using this ***,it is necessary to improve the measurement accuracy,simplify themeasurement process and achieve themeasurement of the traffic sign RA and chromaticity coordinates *** this study,an improved method for retroreflector characterization using imaging was *** allowed for the measurement of the coefficientsof retroreflection and the chromaticity coordinates simultaneously,and only a white standard sample was required for *** primary components of the proposed system included a lighting projector,a receiver,two motorized rotational stages,a retroreflective sample holder and customized software that using scaling factors to convert a digital signal into sample retroreflectioncoefficients and retroreflective chromaticity *** experimental results indicated that the raw data output from thecamera exhibited a positive correlation relationship with the luminous flux from the surface of the *** maximummeasurementerrors for the retroreflection and chromaticity were−12.2 cd/(lx·m2)and−2.09%,*** was inexpensiveand convenient,used a commercially available digital camera,could help to identify defects in retroreflection and chromaticity forretroreflective sheeting and led to increased accessibility for the quality control of retroreflective sheeting.

关键词： camera chromaticity coordinates coefficient of retroreflection retroreflective sheeting retroreflector

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APPLICATION OF BP NEURAL NETWORK IN COLOR TEMPERATURE CALCULATION

APPLICATION OF BP NEURAL NETWORK IN COLOR TEMPERATURE CALCUL...

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2009中国宁波国际计算机科学与技术学术大会

作者： Guanyun Xiao Hongxia Zhao Zhiyang Luo Mechanical Engineering Department Jinggangshan University

One of the important indexes of light source is its color rendering property,which is directly interfered the objects’ colors reflected to our *** object with good color rendering property is less of color distortion,so we need to test the parameters of light *** popular method for getting the relative color temperature has three steps,which is to firstly obtain color tri-stimulus values X,Y and Z from PR-655 spectraScan colorimeter,and then to calculate chromaticity coordinates of light source separately,at last to solve the relative color temperature with *** method is very complicated for the calculation,therefore,we try to set up the conversion relation between color temperature of light source and chromaticity coordinates（u,v） with neural network.

关键词： Color Temperature Neural Network chromaticity coordinates

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