- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Spectra (UV-Visible, IR transmission) of Sc3+, Fe3+ and Cu2+ tri-doped LiNbO <sub/>3</sub> crystals with various [Li]/[Nb] ratios
摘要： The Sc:Fe:Cu:LiNbO3 crystals were grown with Fe3+(0.3 wt.%), Cu2+(0.1 wt.%) and Sc3+(1 mol.%) by the Czochralski method with various [Li]/[Nb] ratios (0.946, 1.05, 1.20 and 1.38). The influence of the [Li]/[Nb] ratios on the defect structure of Sc:Fe:Cu:LiNbO3 crystals was analyzed by the UV-Visible spectra and IR transmission spectra. The spectra show that the absorption edge shift to the red with [Li]/[Nb] ratios enhancing. The Sc:Fe:Cu:LiNbO3 crystals with [Li]/[Nb] ratio of 1.05 is nearly stoichiometric. A new narrow OH- associated vibrational peak at 3505 cm-1 was revealed in Sc:Fe:Cu:LiNbO3 crystals with the ratio of [Li]/[Nb] = 1.38. It is attributed to the (Sc2-Nb)-(OH)-. The results show that the defect structure changes with the [Li]/[Nb] ratios variation.
关键词： IR transmission spectrum,Sc:Fe:Cu:LiNbO3 crystal,UV-Visible spectrum
更新于2025-09-23 15:22:29
-
[IEEE 2018 International Conference of the Biometrics Special Interest Group (BIOSIG) - Darmstadt (2018.9.26-2018.9.28)] 2018 International Conference of the Biometrics Special Interest Group (BIOSIG) - A benchmark database of visible and thermal paired face images across multiple variations
摘要： Although visible face recognition systems have grown as a major area of research, they are still facing serious challenges when operating in uncontrolled environments. In attempt to overcome these limitations, thermal imagery has been investigated as a promising direction to extend face recognition technology. However, the reduced number of databases acquired in thermal spectrum limits its exploration. In this paper, we introduce a database of face images acquired simultaneously in visible and thermal spectra under various variations: illumination, expression, pose and occlusion. Then, we present a comparative study of face recognition performances on both modalities against each variation and the impact of bimodal fusion. We prove that thermal spectrum rivals with the visible spectrum not only in the presence of illumination changes, but also in case of expression and poses changes.
关键词： visible spectrum,thermal spectrum,pose,score-level fusion,sensor-level fusion,occlusion,expression,illumination,face database
更新于2025-09-23 15:22:29
-
[IEEE 2018 International Conference and Exposition on Electrical And Power Engineering (EPE) - Iasi, Romania (2018.10.18-2018.10.19)] 2018 International Conference and Exposition on Electrical And Power Engineering (EPE) - Analysis of Light Design in the Lighting Laboratory of the Riga Technical University
摘要： Given the fact that it is required to increase the efficiency of energy consumption in the premises, it is necessary to develop an effective lighting design that can be used both in old buildings and in new projects. To achieve a lower overall energy consumption by a building without sacrificing the quality of lighting, effective lighting modeling is needed, which allows to obtain reliable results for models as close as possible to real life, taking into account energy-saving lighting devices, integration of daylight in order to reduce energy consumption and maintenance costs, etc. The research evaluates possibility to measure luminance of light sources and detect sources of glare, using ordinary digital single-lens reflex camera (DSLR) and image editing software. Methodology and workflow is presented. The results then are discussed and ways to improve the accuracy of the measurements are highlighted.
关键词： visible spectrum,light measurements,digital camera,fluctuations,Dialux,glare
更新于2025-09-23 15:22:29
-
Validation of spectrophotometric determination of chlorogenic acid in fermentation broth and fruits
摘要： A fast and accurate ultraviolet-visible (UV-vis) spectrophotometric method was established to determine the presence of chlorogenic acid (CGA) according to potassium ferricyanide-Fe (III) detection system. The reaction temperature and pH level greatly influenced the CGA absorption spectrum. Maximum UV-vis absorption wavelength occurred at 790 nm under the optimum conditions (at 25 ℃ and pH 7.0). The results of UV-vis were further assessed by comparing the results with those of high-performance liquid chromatography (HPLC). The proposed method showed a wide linear sensing range of 10.0-800.0 μg mL-1 (R2 = 0.9996) and a high degree of precision (%R.S.D. < 1.50) and recovery (%R.S.D. > 3.39). Results of CGA and HPLC methods correlated well with each other. The proposed accurate, rapid, sensitive, low-cost, and high-throughput method was successfully used to quantify CGA in fermentation broth and fruits (Mango). Therefore, it may be applied for measuring CGA in biological samples.
关键词： Ultraviolet-visible spectrum,Chlorogenic acid,biological samples,high-throughput,HPLC
更新于2025-09-23 15:21:21
-
Full-visible-spectrum lighting enabled by an excellent cyan-emitting garnet phosphor
摘要： The development of phosphor materials with outstanding photoluminescence properties is critical for next-generation high-quality solid-state white lighting. As there is a blue-green cavity existed in the emission spectra of the traditional phosphor-converted white-light-emitting diodes (w-LEDs), cyan-emitting phosphor serves an important function in compensating the spectral gap to realize the “full-visible-spectrum lighting”. Herein, we reported the discovery of an efficient cyan-emitting Ce3+-doped Ca2YHf2Al3O12 (CYHAO) garnet phosphor with good thermal stability. The as-prepared CYHAO:Ce3+ phosphor exhibited a broad excitation band in the range of 360 to 460 nm with a maximum at 408 nm, making this phosphor compatible with an efficient 400 nm NUV-emitting LED chip. Under the 408 nm excitation, the optimal sample of CYHAO:0.03Ce3+ exhibited bright broadband cyan emission (λem = 493 nm; bandwidth = 100 nm) together with extra-high internal quantum efficiency (IQE) of 89.5% and external quantum efficiency (EQE) of 69.1%. Notably, the as-prepared CYHAO:0.03Ce3+ phosphor showed good thermal stability (64.2% of emission intensity retained at 423K) and excellent color stability when working in the temperature range of 303-463 K. Importantly, the constructed w-LED device exhibited bright well-distributed warm white light with high color rendering index (CRI; Ra = 93.5 and R12 = 90.4) and low correlated color temperature (3700 K) under 60 mA driven current, indicating that the title cyan phosphor can be utilized as the compensation of the blue-green cavity to apply in full-visible-spectrum lighting. Furthermore, these findings provide new insights into exploring high-performance cyan phosphors for NUV-pumped high-CRI warm w-LEDs.
关键词： White LEDs,Color rendering index,Cyan emissions,Phosphors,Full-visible-spectrum lighting
更新于2025-09-23 15:21:01
-
Cyan phosphors for full-visible-spectrum lighting: shining new light on high-CRI white pc-LEDs
摘要： Nowadays, solid-state lighting sources based on white light-emitting diodes (LEDs) are extensively replacing the traditional illumination devices (incandescent and fluorescent lamps) due to their unique and appealing properties, such as high efficiency, high brightness, long working lifetime, small size, fast response time and eco-friendliness. Because of this, white LEDs have permeated deeply into many important sectors, including indoor and outdoor lightings, signals, displays and therapeutic applications. In order to make sure that white LEDs can provide artificial lighting source with good color quality and high vision performance, there are several important figures of merit that are used to characterize white LEDs: color rendering index (CRI), correlated color temperature, luminous efficacy of radiation and luminous efficacy.
关键词： full-visible-spectrum lighting,Cyan phosphors,high-CRI white pc-LEDs
更新于2025-09-19 17:13:59
-
European Microscopy Congress 2016: Proceedings || Improving 3d correlation in integrated correlated light and electron microscopy using confocal laser scanning microscopy
摘要： Integrated optoelectronics for fast and efficient light detection and imaging in the infrared and visible spectrum.
关键词： optoelectronics,visible spectrum,light detection,infrared,imaging
更新于2025-09-16 10:30:52
-
Carbon Dots exhibiting Concentration-Dependent Full-Visible-Spectrum Emission for Light-Emitting Diode Applications
摘要： Carbon dots (CDs) that exhibit emission over the whole visible spectrum are desired for using in light-emitting diodes. Here, CDs displaying tunable fluorescence over the whole visible region are synthesized. Different concentrations of CDs are uniformly dispersed in epoxy resin and coated on 405-nm LED chips to obtain monochrome blue, cyan, green, yellow, red, and deep red LEDs that yield a color gamut covering 99.4% of the National Television Standards Committee (NTSC) standard. These monochrome LEDs display similar stability decay curves. Furthermore, warm and neutral white LEDs are produced by coating cyan- and red-emitting CD layers on 405-nm LED chips, achieving color rendering indexes (CRI) of 96.4 and 96.6, respectively. Two fluorescent conversion layers derived from one material at different concentrations simplifies the preparation of high-CRI white LEDs. The uniform weak changes of the cyan and red PL peaks during operation ensures the high stability of these CD-based white LEDs. This research provides a new avenue to develop low-cost, easy-to-prepare CDs with tunable emission colors as alternative phosphors for LED-based high-performance displays and lighting.
关键词： full-visible-spectrum emission,monochrome light-emitting diodes,concentration-dependent spectrum-tunable carbon dots,high color rendering index,white-light-emitting diodes
更新于2025-09-12 10:27:22
-
Strong bulk photovoltaic effect in chiral crystals in the visible spectrum
摘要： Structurally chiral materials hosting multifold fermions with large topological number have attracted considerable attention because of their naturally long surface Fermi arcs and bulk quantized circular photogalvanic effect (CPGE). Multifold fermions only appear in metallic states, and therefore most studies so far have only focused on the semimetals in compounds with chiral crystal structures. In this work, we show that the structurally chiral topological trivial insulators are also exotic states, which is interesting from the application point of view, owing to their natural advantage to host a large bulk photovoltaic effect in the visible wavelength region. In recent decades, the shift current in the visible wavelength region was limited to be 10 μA/V2 in all the experimentally measured reports. By scanning the insulators with chiral structure, we found a class of compounds with photoconductivity ranging from ～20 to ～80 μA/V2, which is comparable to the largest reported shift current. This work illustrates that the compounds with chiral structure can host both quantum CPGE and a strong shift current in the second-order optical response. Moreover, this work offers a good platform for the study of the shift current and its future application by putting the focus on insulators with chiral lattices, so far overlooked in photovoltaic technologies.
关键词： photoconductivity,chiral crystals,shift current,bulk photovoltaic effect,visible spectrum
更新于2025-09-12 10:27:22
-
Impact of Overlapping Fe/TiO <sub/>2</sub> Prepared by Sol-Gel and Dip-Coating Process on CO <sub/>2</sub> Reduction
摘要： Fe-doped TiO2 (Fe/TiO2) film photocatalyst was prepared by sol-gel and dip-coating process to extend its photoresponsivity to the visible spectrum. To promote the CO2 reduction performance with the photocatalyst, some types of base materials used for coating Fe/TiO2, which were netlike glass fiber and Cu disc, were investigated. The characterization of prepared Fe/TiO2 film coated on netlike glass fiber and Cu disc was analyzed by SEM and EPMA. In addition, the CO2 reduction performance of Fe/TiO2 film coated on netlike glass disc, Cu disc, and their overlap was tested under a Xe lamp with or without ultraviolet (UV) light, respectively. The results show that the concentration of produced CO increases by Fe doping irrespective of base material used under the illumination condition with UV light as well as that without UV light. Since the electron transfer between two overlapped photocatalysts is promoted, the peak concentration of CO for the Fe/TiO2 double overlapping is approximately 1.5 times as large as the Fe/TiO2 single overlapping under the illumination condition with UV light, while the promotion ratio is approximately 1.1 times under that without UV light.
关键词： UV light,Fe-doped TiO2,visible spectrum,photocatalyst,dip-coating,sol-gel,CO2 reduction
更新于2025-09-09 09:28:46