scholarly journals Carotenoid biosynthesis of pak choi (Brassica rapassp.chinensis) sprouts grown under different light-emitting diodes during the diurnal course

2018 ◽  
Vol 17 (10) ◽  
pp. 1289-1300 ◽  
Author(s):  
K. Frede ◽  
M. Schreiner ◽  
R. Zrenner ◽  
J. Graefe ◽  
S. Baldermann
Keyword(s):  
Light Emitting Diodes ◽  
Carotenoid Biosynthesis ◽  
Pak Choi ◽  
Light Emitting ◽  
Diurnal Course ◽  
The Impact

This study highlights the impact of LEDs on the carotenoid biosynthesis in pak choi throughout the day.

Assessing the impact of the transition to Light Emitting Diodes based solar lighting systems in India

2013 ◽  
Vol 17 (4) ◽  
pp. 363-370 ◽  
Author(s):  
Santosh M. Harish ◽  
Shuba V. Raghavan ◽  
Milind Kandlikar ◽  
Gireesh Shrimali
Keyword(s):  
Light Emitting Diodes ◽  
Light Emitting ◽  
Solar Lighting ◽  
Lighting Systems ◽  
The Impact

Studies of Degradation in Nichia AlGaN/InGaN/GaN Blue Light Emitting Diodes Under Close to Normal Operating Conditions

1996 ◽  
Vol 421 ◽  
Author(s):  
M. Osiński ◽  
D. L. Barton ◽  
C. J. Helms ◽  
P. Perlin ◽  
N. H. Berg ◽  
...  
Keyword(s):  
Blue Light ◽  
Light Emitting Diodes ◽  
Defect Density ◽  
Degradation Process ◽  
Operating Conditions ◽  
Similar Amount ◽  
Life Testing ◽  
Light Emitting ◽  
High Pulsed Current ◽  
The Impact

AbstractThe reliability of devices fabricated in GaN and related alloys, especially under high current densities as would be found in lasers, has yet to be fully characterized. Our previous work [1] investigated the degradation of GaN-based blue light emitting diodes (LEDs) under high pulsed current stress. This work indicated a possible correlation between the high crystal defect density and failures caused by metal migration along these defect tubes. To assess the impact of this data on devices under more normal conditions, several LEDs from both older and more recent production lots were placed in a controlled temperature and current environment for several thousand hours. The test started with a constant 20 mA current for the first 1000 hours and continued for another 1650 hours at various currents up to 70 mA, all at a temperature of 23 °C. During this test, one of the older generation LED's output degraded by more than 50%. Subsequent failure analysis showed that this was caused by a crack which isolated part of the active region from the p-contact. The remaining LEDs were returned to life testing where the temperature was subsequently increased by 5 °C after each 500 hours of testing. The output from one of the newer LEDs dreiven at 70 mA degraded to 55% of its original value after 3600 hours and a second newer LED degraded by a similar amount after 4400 hours. The first failure, LED #16, did not exhibit a significant change in its I-V characteristics indicating that a change in the package transparency was a likely cause for the observed degradation. The second failure, LED #17, did show a noticeable change in its I-V characteristics. This device was subsequently returned to life testing where the degradation process will be monitored for further changes.

scholarly journals Long-Term Comparison of Attraction of Flying Insects to Streetlights after the Transition from Traditional Light Sources to Light-Emitting Diodes in Urban and Peri-Urban Settings

2019 ◽  
Vol 11 (22) ◽  
pp. 6198 ◽  
Author(s):  
Roy H. A. van Grunsven ◽  
Julia Becker ◽  
Stephanie Peter ◽  
Stefan Heller ◽  
Franz Hölker
Keyword(s):  
Light Emitting Diodes ◽  
Spectral Composition ◽  
Mercury Vapor ◽  
World Market ◽  
Relative Difference ◽  
Urban Setting ◽  
Light Sources ◽  
Urban Settings ◽  
Light Emitting ◽  
The Impact

Among the different light sources used for street lighting, light-emitting diodes (LEDs) are likely to dominate the world market in the coming years. At the same time, the spectral composition of nocturnal illumination is changing. Europe and many other areas worldwide have implemented bans on energy-inefficient lamps, such as the still very common mercury vapor lamps. However, the impact of artificial light on insects is mostly tested with light-traps or flight-intercept traps that are used for short periods only. By comparing the numbers of insects attracted by street lamps before and after replacing mercury vapor light sources (MV) with light emitting diodes, we assessed the impact in more typical (urban and peri-urban) settings over several years. We found that LED attracted approximately half of the number of insects compared to MV lights. Furthermore, most insect groups are less drawn by LED than by MV, while Hymenoptera are less attracted by MV than by LED. Thus, the composition of the attracted communities differed between the light sources, which may impact ecosystem processes and functions. In green peri-urban settings more insects are attracted than in an urban setting, but the relative difference between the light sources is the same.

The impact of active layer design on quantum efficiency of InGaN light emitting diodes

2012 ◽  
Author(s):  
F. Zhang ◽  
X. Li ◽  
S. Okur ◽  
V. Avrutin ◽  
Ü. Özgür ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
Active Layer ◽  
Light Emitting Diodes ◽  
Light Emitting ◽  
The Impact

scholarly journals Effect of Inhomogeneous Broadening in Ultraviolet III-Nitride Light-Emitting Diodes

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7890
Author(s):  
Friedhard Römer ◽  
Martin Guttmann ◽  
Tim Wernicke ◽  
Michael Kneissl ◽  
Bernd Witzigmann
Keyword(s):  
Active Region ◽  
Quantum Wells ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Inhomogeneous Broadening ◽  
Aluminium Content ◽  
Hole Density ◽  
Free Hole ◽  
Light Emitting ◽  
The Impact

In the past years, light-emitting diodes (LED) made of GaN and its related ternary compounds with indium and aluminium have become an enabling technology in all areas of lighting. Visible LEDs have yet matured, but research on deep ultraviolet (UV) LEDs is still in progress. The polarisation in the anisotropic wurtzite lattice and the low free hole density in p-doped III-nitride compounds with high aluminium content make the design for high efficiency a critical step. The growth kinetics of the rather thin active quantum wells in III-nitride LEDs makes them prone to inhomogeneous broadening (IHB). Physical modelling of the active region of III-nitride LEDs supports the optimisation by revealing the opaque active region physics. In this work, we analyse the impact of the IHB on the luminescence and carrier transport III-nitride LEDs with multi-quantum well (MQW) active regions by numerical simulations comparing them to experimental results. The IHB is modelled with a statistical model that enables efficient and deterministic simulations. We analyse how the lumped electronic characteristics including the quantum efficiency and the diode ideality factor are related to the IHB and discuss how they can be used in the optimisation process.

scholarly journals Increases in Shoot Tissue Pigments, Glucosinolates, and Mineral Elements in Sprouting Broccoli after Exposure to Short-duration Blue Light from Light Emitting Diodes

2013 ◽  
Vol 138 (1) ◽  
pp. 31-37 ◽  
Author(s):  
Dean A. Kopsell ◽  
Carl E. Sams
Keyword(s):  
Blue Light ◽  
Short Duration ◽  
Light Emitting Diodes ◽  
Mineral Elements ◽  
Light Emitting ◽  
Blue Led ◽  
Led Light ◽  
Shoot Tissue ◽  
Phytochemical Compounds ◽  
The Impact

Microgreens are specialty leafy crops harvested just above the roots after the first true leaves have emerged and are consumed fresh. Broccoli (Brassica oleacea var. italica) microgreens can accumulate significant concentrations of cancer-fighting glucosinolates as well as being a rich source of other antioxidant phytochemicals. Light-emitting diodes (LEDs) now provide the ability to measure impacts of narrow-band wavelengths of light on seedling physiology. The carotenoid zeaxanthin has been hypothesized to be a blue light receptor in plant physiology. The objective of this study was to measure the impact of short-duration blue light on phytochemical compounds, which impart the nutritional quality of sprouting broccoli microgreens. Broccoli microgreens were grown in a controlled environment under LEDs using growing pads. Seeds were cultured on the pads submerged in deionized water and grown under a 24-hour photoperiod using red (627 nm)/blue (470 nm) LEDs (350 μmol·m−2·s−1) at an air temperature of 23 °C. On emergence of the first true leaf, a complete nutrient solution with 42 mg·L−1 of nitrogen (N) was used to submerge the growing pads. At 13 days after sowing, broccoli plantlets were grown under either: 1) red and blue LED light (350 μmol·m−2·s−1); or 2) blue LED light (41 μmol·m−2·s−1) treatments for 5 days before harvest. The experiment was repeated three times. Frozen shoot tissues were freeze-dried and measured for carotenoids, chlorophylls, glucosinolates, and mineral elements. Comparing the two LED light treatments revealed the short-duration blue LED treatment before harvest significantly increased shoot tissue β-carotene (P ≤ 0.05), violaxanthin (P ≤ 0.01), total xanthophyll cycle pigments (P ≤ 0.05), glucoraphanin (P ≤ 0.05), epiprogoitrin (P ≤ 0.05), aliphatic glucosinolates (P ≤ 0.05), essential micronutrients of copper (Cu) (P = 0.02), iron (Fe) (P ≤ 0.01), boron (B), manganese (Mn), molybdenum (Mo), sodium (Na), zinc (Zn) (P ≤ 0.001), and the essential macronutrients of calcium (Ca), phosphorus (P), potassium (K), magnesium (Mg), and sulfur (S) (P ≤ 0.001). Results demonstrate management of LED lighting technology through preharvest, short-duration blue light acted to increase important phytochemical compounds influencing the nutritional value of broccoli microgreens.

Characterize and Retard the Impact of the Bias‐Induced Mobile Ions in CH 3 NH 3 PbBr 3 Perovskite Light‐Emitting Diodes

2021 ◽  
pp. 2101439
Author(s):  
Teng Lam Shen ◽  
Aswaghosh Loganathan ◽  
Thi Hoai Do ◽  
Chang‐Min Wu ◽  
Yu‐Ting Chen ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Light Emitting ◽  
Mobile Ions ◽  
The Impact

scholarly journals Comparison of ultraviolet light emitting diodes with traditional UV for greywater disinfection

2014 ◽  
Vol 5 (1) ◽  
pp. 17-27 ◽  
Author(s):  
M. J. Crook ◽  
B. Jefferson ◽  
O. Autin ◽  
J. MacAdam ◽  
A. Nocker
Keyword(s):  
Particle Size ◽  
Ultraviolet Light ◽  
Water Reuse ◽  
Light Emitting Diodes ◽  
Microbial Inactivation ◽  
Small Scale ◽  
Light Emitting ◽  
Uv Leds ◽  
The Impact ◽  
Ultraviolet Light Emitting Diodes

The current technological status of ultraviolet light emitting diodes (UV-LEDs) has reached a point where small-scale ultraviolet (UV) water disinfection applications, that is, for greywater reuse appear increasingly promising. This study compares the germicidal and economical aspects of UV-LEDs with traditional UV. Pure cultures and environmental greywater samples were exposed to different radiation doses from both UV sources with the germicidal effect comparative at equivalent doses. The impact of particle size on disinfection efficiency was investigated in two greywater fractions of varying mean particle size. Disinfection efficiency was found to be dependent on particle size with larger particles reducing microbial inactivation for both UV sources. Post-UV blending to detach particle-associated coliforms resulted in higher bacterial counts for both UV sources although to a lesser extent for UV-LEDs suggesting that it might be less affected by the presence of particles than traditional UV sources, possibly due to the UV radiation being emitted by multiple diodes at different angles compared to the traditional UV collimated beam setup. Nevertheless, removal of particles prior to UV disinfection is necessary to meet strict water reuse standards. Although UV-LEDs are currently prohibitively expensive, improvements in performance indicators might make this technology economically competitive within the next few years.

Sign in / Sign up

Export Citation Format

Share Document