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Alexander Eychmüller - One of the best experts on this subject based on the ideXlab platform.
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Implementation of High-Quality Warm-White Light-Emitting Diodes by a Model-Experimental Feedback Approach Using Quantum Dot–Salt Mixed Crystals
2015Co-Authors: Marcus Adam, Talha Erdem, Gordon M. Stachowski, Zeliha Soran-erdem, Josephine F. L. Lox, Christoph Bauer, Jan Poppe, Hilmi Volkan Demir, Nikolai Gaponik, Alexander EychmüllerAbstract:In this work, a model-experimental feedback approach is developed and applied to fabricate high-quality, warm-white light-emitting diodes based on quantum dots (QDs) as color-conversion materials. Owing to their unique chemical and physical properties, QDs offer huge potential for lighting applications. Nevertheless, both emission stability and processability of the QDs are limited upon usage from solution. Incorporating them into a solid ionic matrix overcomes both of these drawbacks, while preserving the initial optical properties. Here borax (Na2B4O7·10H2O) is used as a host matrix because of its lower solubility and thereby reduced ionic strength in water in comparison with NaCl. This guarantees the stability of high-quality CdSe/ZnS QDs in the aqueous phase during crystallization and results in a 3.4 times higher loading amount of QDs within the borax crystals compared to NaCl. All steps from the synthesis via mixed crystal preparation to the warm-white LED preparation are verified by applying the model-experimental feedback, in which experimental data and numerical results provide feedback to each other recursively. These measures are taken to ensure a high luminous efficacy of optical radiation (LER) and a high color rendering index (CRI) of the final device as well as a correlated color temperature (CCT) comparable to an Incandescent Bulb. By doing so, a warm-white LED with a LER of 341 lm/Wopt, a CCT of 2720 K and a CRI of 91.1 is produced. Finally, we show that the emission stability of the QDs within the borax crystals on LEDs driven at high currents is significantly improved. These findings indicate that the proposed warm-white light-emitting diodes based on QDs-in-borax hold great promise for quality lighting
Eychmüller A. - One of the best experts on this subject based on the ideXlab platform.
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Implementation of High-Quality Warm-White Light-Emitting Diodes by a Model-Experimental Feedback Approach Using Quantum Dot-Salt Mixed Crystals
'American Chemical Society (ACS)', 2015Co-Authors: Adam M., Erdem T., Stachowski G.m., Soran-erdem Z., Lox J.f.l., Bauer C., Poppe J., Demir H., Gaponik N., Eychmüller A.Abstract:In this work, a model-experimental feedback approach is developed and applied to fabricate high-quality, warm-white light-emitting diodes based on quantum dots (QDs) as color-conversion materials. Owing to their unique chemical and physical properties, QDs offer huge potential for lighting applications. Nevertheless, both emission stability and processability of the QDs are limited upon usage from solution. Incorporating them into a solid ionic matrix overcomes both of these drawbacks, while preserving the initial optical properties. Here borax (Na2B4O7·10H2O) is used as a host matrix because of its lower solubility and thereby reduced ionic strength in water in comparison with NaCl. This guarantees the stability of high-quality CdSe/ZnS QDs in the aqueous phase during crystallization and results in a 3.4 times higher loading amount of QDs within the borax crystals compared to NaCl. All steps from the synthesis via mixed crystal preparation to the warm-white LED preparation are verified by applying the model-experimental feedback, in which experimental data and numerical results provide feedback to each other recursively. These measures are taken to ensure a high luminous efficacy of optical radiation (LER) and a high color rendering index (CRI) of the final device as well as a correlated color temperature (CCT) comparable to an Incandescent Bulb. By doing so, a warm-white LED with a LER of 341 lm/Wopt, a CCT of 2720 K and a CRI of 91.1 is produced. Finally, we show that the emission stability of the QDs within the borax crystals on LEDs driven at high currents is significantly improved. These findings indicate that the proposed warm-white light-emitting diodes based on QDs-in-borax hold great promise for quality lighting. © 2015 American Chemical Society
Mcloughlin Ian - One of the best experts on this subject based on the ideXlab platform.
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Investigating the Cognitive Response of Brake Lights in Initiating Braking Action Using EEG
'Institute of Electrical and Electronics Engineers (IEEE)', 2021Co-Authors: Palaniappan Ramaswamy, Mouli Surej, Bowman Howard, Mcloughlin IanAbstract:Half of all road accidents result from either lack of driver attention or from maintaining insufficient separation between vehicles. Collision from the rear, in particular, has been identified as the most common class of accident in the UK, and its influencing factors have been widely studied for many years. Rear-mounted stop lamps, illuminated when braking, are the primary mechanism to alert following drivers to the need to reduce speed or brake. This paper develops a novel brain response approach to measuring subject reaction to different brake light designs. A variety of off-the-shelf brake light assemblies are tested in a physical simulated driving environment to assess the cognitive reaction times of 22 subjects. Eight pairs of LED-based and two pairs of Incandescent Bulb-based brake light assemblies are used and electroencephalogram (EEG) data recorded. Channel Pz is utilised to extract the P3 component evoked during the decision making process that occurs in the brain when a participant decides to lift their foot from the accelerator and depress the brake. EEG analysis shows that both Incandescent Bulb-based lights are statistically slower to evoke cognitive responses than all tested LED-based lights. Between the LED designs, differences are evident, but not statistically significant, attributed to the significant amount of movement artifact in the EEG signal
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Incandescent Bulb and LED Brake Lights:Novel Analysis of Reaction Times
'Institute of Electrical and Electronics Engineers (IEEE)', 2021Co-Authors: Palaniappan Ramaswamy, Mouli Surej, Bowman Howard, Fringi Evangelia, Mcloughlin IanAbstract:Rear-end collision accounts for around 8% of all vehicle crashes in the UK, with the failure to notice or react to a brake light signal being a major contributory cause. Meanwhile traditional Incandescent brake light Bulbs on vehicles are increasingly being replaced by a profusion of designs featuring LEDs. In this paper, we investigate the efficacy of brake light design using a novel approach to recording subject reaction times in a simulation setting using physical brake light assemblies. The reaction times of 22 subjects were measured for ten pairs of LED and Incandescent Bulb brake lights. Three events were investigated for each subject, namely the latency of brake light activation to accelerator release (BrakeAcc), the latency of accelerator release to brake pedal depression (AccPdl), and the cumulative time from light activation to brake pedal depression (BrakePdl). To our knowledge, this is the first study in which reaction times have been split into BrakeAcc and AccPdl. Results indicate that the two brake lights containing Incandescent Bulbs led to significantly slower reaction times compared to eight tested LED lights. BrakeAcc results also show that experienced subjects were quicker to respond to the activation of brake lights by releasing the accelerator pedal. Interestingly, analysis also revealed that the type of brake light influenced the AccPdl time, although experienced subjects did not always act quicker than inexperienced subjects. Overall, the study found that different designs of brake light can significantly influence driver response times
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Incandescent Bulb and LED Brake Lights:Novel Analysis of Reaction Times
'Institute of Electrical and Electronics Engineers (IEEE)', 2020Co-Authors: Palaniappan Ramaswamy, Mouli Surej, Bowman Howard, Fringi Evangelina, Mcloughlin IanAbstract:Rear-end collision accounts for around 8% of all vehicle crashes in the UK, with the failure to notice or react to a brake light signal being a major contributory cause. Meanwhile traditional Incandescent brake light Bulbs on vehicles are increasingly being replaced by a profusion of designs featuring LEDs. In this paper, we investigate the efficacy of brake light design using a novel approach to recording subject reaction times in a simulation setting using physical brake light assemblies. The reaction times of 22 subjects were measured for ten pairs of LED and Incandescent Bulb brake lights. Three events were investigated for each subject, namely the latency of brake light activation to accelerator release (BrakeAcc), the latency of accelerator release to brake pedal depression (AccPdl), and the cumulative time from light activation to brake pedal depression (BrakePdl). To our knowledge, this is the first study in which reaction times have been split into BrakeAcc and AccPdl. Results indicate that the two brake lights containing Incandescent Bulbs led to significantly slower reaction times compared to the tested eight LED lights. BrakeAcc results also show that experienced subjects were quicker to respond to the activation of brake lights by releasing the accelerator pedal. Interestingly, the analysis also revealed that the type of brake light influenced the AccPdl time, although experienced subjects did not always act quicker than inexperienced subjects. Overall, the study found that different designs of brake light can significantly influence driver response times.Comment: 10 pages, 18 figure
Monsoriu Serra, Juan Antonio - One of the best experts on this subject based on the ideXlab platform.
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Determining the efficiency of optical sources using the smartphone's ambient light sensor
'IOP Publishing', 2017Co-Authors: Sans, Jose Angel, Gea-pinal J., Giménez M.h., Esteve Martínez, Anna Raquel, Solbes Matarredona Jordi, Monsoriu Serra, Juan AntonioAbstract:This work reports the use of a smartphone's ambient light sensor as a valuable tool to study and characterize the efficiency of an optical source. Here, we have measured both luminous efficacy and efficiency of several optical sources (Incandescent Bulb and halogen lamp) as a function of the electric power consumed and the distance to the optical detector. The illuminance of LEDs as a function of the distance to the optical detector is characterized for different wavelength emissions. Analysis of the results confirms an inverse-square law of the illuminance with the detector-source distance and shows good agreement with values obtained by classical experiments. This experience will trigger awareness in students in terms of sustainability, light propagation and efficiency of different optical sources
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Determining the efficiency of optical sources using a smartphone's ambient light sensor
'IOP Publishing', 2017Co-Authors: Sans-tresserras, Juan Ángel, Gea Pinal Juan, Giménez Valentín, Marcos Herminio, Esteve A. R., Solbes J., Monsoriu Serra, Juan AntonioAbstract:This work reports the use of a smartphone’s ambient light sensor as a valuable tool to study and characterize the efficiency of an optical source. Here, we have measured both luminous efficacy and efficiency of several optical sources (Incandescent Bulb and halogen lamp) as a function of the electric power consumed and the distance to the optical detector. The illuminance of LEDs as a function of the distance to the optical detector is characterized for different wavelength emissions. Analysis of the results confirms an inverse-square law of the illuminance with the detector–source distance and shows good agreement with values obtained by classical experiments. This experience will trigger awareness in students in terms of sustainability, light propagation and efficiency of different optical sources.The authors would like to thank the Institute of Education Sciences, Universitat Politecnica de Valencia (Spain), for the support of the teaching innovation groups MOMA and e-MACAFI, and the financial support of Project PIME-2015-B18. The authors also acknowledge the financial support of project EDU2015-69701-P by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund. J A Sans acknowledges Ramon y Cajal fellowship program for financial support.Sans-Tresserras, JÁ.; Gea Pinal, J.; Gimenez Valentin, MH.; Esteve, AR.; Solbes, J.; Monsoriu Serra, JA. (2017). Determining the efficiency of optical sources using a smartphone's ambient light sensor. European Journal of Physics. 38(2):1-9. doi:10.1088/1361-6404/aa51a9S1938
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Determining the efficiency of optical sources using a smartphone's ambient light sensor
'IOP Publishing', 2017Co-Authors: Sans-tresserras, Juan Ángel, Gea Pinal Juan, Giménez Valentín, Marcos Herminio, Esteve A. R., Solbes J., Monsoriu Serra, Juan AntonioAbstract:This work reports the use of a smartphone’s ambient light sensor as a valuable tool to study and characterize the efficiency of an optical source. Here, we have measured both luminous efficacy and efficiency of several optical sources (Incandescent Bulb and halogen lamp) as a function of the electric power consumed and the distance to the optical detector. The illuminance of LEDs as a function of the distance to the optical detector is characterized for different wavelength emissions. Analysis of the results confirms an inverse-square law of the illuminance with the detector–source distance and shows good agreement with values obtained by classical experiments. This experience will trigger awareness in students in terms of sustainability, light propagation and efficiency of different optical sources.The authors would like to thank the Institute of Education Sciences, Universitat Politecnica de Valencia (Spain), for the support of the teaching innovation groups MOMA and e-MACAFI, and the financial support of Project PIME-2015-B18. The authors also acknowledge the financial support of project EDU2015-69701-P by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund. J A Sans acknowledges Ramon y Cajal fellowship program for financial support.Sans-Tresserras, JÁ.; Gea Pinal, J.; Giménez Valentín, MH.; Esteve, AR.; Solbes, J.; Monsoriu Serra, JA. (2017). Determining the efficiency of optical sources using a smartphone's ambient light sensor. European Journal of Physics. 38(2):1-9. https://doi.org/10.1088/1361-6404/aa51a9S1938
Marcus Adam - One of the best experts on this subject based on the ideXlab platform.
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Implementation of High-Quality Warm-White Light-Emitting Diodes by a Model-Experimental Feedback Approach Using Quantum Dot–Salt Mixed Crystals
2015Co-Authors: Marcus Adam, Talha Erdem, Gordon M. Stachowski, Zeliha Soran-erdem, Josephine F. L. Lox, Christoph Bauer, Jan Poppe, Hilmi Volkan Demir, Nikolai Gaponik, Alexander EychmüllerAbstract:In this work, a model-experimental feedback approach is developed and applied to fabricate high-quality, warm-white light-emitting diodes based on quantum dots (QDs) as color-conversion materials. Owing to their unique chemical and physical properties, QDs offer huge potential for lighting applications. Nevertheless, both emission stability and processability of the QDs are limited upon usage from solution. Incorporating them into a solid ionic matrix overcomes both of these drawbacks, while preserving the initial optical properties. Here borax (Na2B4O7·10H2O) is used as a host matrix because of its lower solubility and thereby reduced ionic strength in water in comparison with NaCl. This guarantees the stability of high-quality CdSe/ZnS QDs in the aqueous phase during crystallization and results in a 3.4 times higher loading amount of QDs within the borax crystals compared to NaCl. All steps from the synthesis via mixed crystal preparation to the warm-white LED preparation are verified by applying the model-experimental feedback, in which experimental data and numerical results provide feedback to each other recursively. These measures are taken to ensure a high luminous efficacy of optical radiation (LER) and a high color rendering index (CRI) of the final device as well as a correlated color temperature (CCT) comparable to an Incandescent Bulb. By doing so, a warm-white LED with a LER of 341 lm/Wopt, a CCT of 2720 K and a CRI of 91.1 is produced. Finally, we show that the emission stability of the QDs within the borax crystals on LEDs driven at high currents is significantly improved. These findings indicate that the proposed warm-white light-emitting diodes based on QDs-in-borax hold great promise for quality lighting
