Search results for " LED"
showing 10 items of 79 documents
Development of a module of stacks of air-breathing microbial fuel cells to light-up a strip of LEDs
2018
Abstract This work focuses on scaling-up of the microbial fuel cells technology according to the principle of miniaturization and multiplication. Seven stacks of 16 mini-MFCs (electrodic area of 0.866 cm2) were built up leading to a big module of 112 MFCs. The electrical connection among the MFCs in the stacks and among the stacks into the modules was optimized in order to implement this technology. Results show that 1 MFC generates 1.22 mW while the optimization of the electric connection in order to achieve the maximum power results in 6.62 mW compared to the theoretical 182 mW, indicating the existence of large energy losses in the system. However, to light a LED there is not a threshold…
Zvaigžņotā Debess: 2008, Pavasaris
2008
Latvijas Zinātņu akadēmija, Latvijas Universitāte
Ce:YAG nanoparticles embedded in a PMMA matrix: preparation and characterization
2010
A Ce:YAG-poly(methyl methacrylate) composite was prepared using in situ polymerization by embedding the Ce:YAG nanopowder in a blend of methyl methacrylate (MMA) and 2-methacrylic acid (MAA) monomers and activating the photopolymerization using a radical initiator. The obtained nanocomposite was yellow and transparent. Its characterization was performed using transmission electron microscopy, small angle X-ray scattering, (13)C cross-polarization magic-angle spinning nuclear magnetic resonance, and photoluminescence spectroscopy. Results showed that Ce:YAG nanoparticles are well dispersed in the polymeric matrix whose structure is organized in a lamellar shape. The luminescence properties o…
Astronomiskās un dabas parādības aizvēsturē Ziemeļeiropā: atspoguļojums vēstures avotos un arheoloģiskajā materiālā
2021
Cilvēka dzīve aizvēsturē bija ļoti cieši saista ar dabu. Līdz ar pāreju uz ražotājsaimniecību vēlā akmens laikmeta beigās, bet īpaši sākot ar bronzas laikmetu, izveidojās ideoloģija, kurā centrālo vietu ieņēma Saule un ar to saistīto gadskārtu cikli. Solārā un lunārā simbolika plaši pārstāvēta Ziemeļeiropas, arī Latvijas arheoloģiskajā materiālā. Dabas un astronomiskās parādības minētas arī pirmajos rakstītajos avotos, bet to sekas – īpaši dabas katastrofu sekas, fiksējamas arī arheoloģiskajā materiālā.
Zvaigžņotā Debess: 2016, Vasara (232)
2016
Contents: “ZVAIGŽŅOTĀ DEBESS” FORTY YEARS AGO: A.Balklavs. New Studies and Conclusions on Nucleus of the Galaxy (abridged) ; U.Dzērvītis. Discussion on Planetary System of Barnard’s Star Continues (abridged) ; M.Eliāss. Meeting of Solar Radio Radiation Section (abridged) ; DEVELOPMENTS in SCIENCE: O.Dumbrājs. Neutrino Oscillations: from the Outset to the Nobel Prize ; R.Misa. Conversation with Andris Ambainis on Quantum Computing Science ; DISCOVERIES: F.Gahbauer. First Direct Detection of Gravitational Waves ; I.Pundure. ATLASGAL Survey of Milky Way Completed ; SPACE RESEARCH and EXPLORATION: J.Jaunbergs. The Story of Pluto’s Satellites ; K.Schwartz. Conducting Ice and Magnetic Field of Ur…
A simple method for measuring OLEDs efficiency
2015
External quantum efficiency (EQE) of organic light emitting diodes (OLEDs) is among the most important parameters for devices assessment and for comparing OLEDs performance. The EQE is the ratio of the total number of photons emitted by the OLED in all directions to the number of electrons injected.
Generation of white LED light by frequency downconversion using a perylene-based dye
2012
A high efficiency white light emitting diode (LED) was fabricated by generation of frequency down-conversion from a GaN/InGaN blue LED. In place of conventional inorganic phosphors, a perylene-based dye was used for colour conversion. The resulting hybrid structure is analysed by focusing on the visual performance of the realised LEDs employing the most relevant photometric parameters of a light source. Preparation of the organic polymer is described as well. The thermal stability of the dye was investigated and a simple structure which avoids colour degradation is proposed.
Zvaigžņotā Debess: 2017, Rudens (237)
2017
Contents: “ZVAIGŽŅOTĀ DEBESS” FORTY YEARS AGO: U.Dzērvītis. Dispute on Hubble’s Constant Value (abridged) ; E.Mūkins. Ten «Venera»’s: Devices, Journeys and Results (abridged) ; DEVELOPMENTS in SCIENCE: K.Schwartz. New Discoveries in the Orion Molecular Cloud Complex ; SPACE RESEARCH and EXPLORATION: J.Jaunbergs. Salty Emanations of Enceladus ; R.Misa. Voyager: the Longest and Farthest ; OBSERVATORIES and INSTRUMENTS: J.Kuzmanis. Dragon Looks at the Sky ; K.Salmiņš. On ILRS Technical Workshop 2017 in Riga ; CONFERENCES and MEETINGS: M.Sudārs. Trends of Space Infrastructure Development in Europe ; M.Gills. Congress of European Planetary Science 2017 in Riga ; FLASHBACK: N.Cimahoviča. On Whirl…
Stability improvement of PMMA and Lumogen® coatings for hybrid white LEDs
2014
Hybrid white LEDs employing perylene-based dyes for the frequency down-conversion of blue light, generated by a standard inorganic source, suffer from colour rendering variations due to the degradation of the organic molecule under prolonged irradiation. To avoid such inconvenient, proper encapsulation of the dyes in resins or other polymer matrices can prevent their accelerated ageing; nevertheless, embedding polymers can also exhibit significant bleaching caused by chemico-physical agents. Among all, polymethyl methacrilate (PMMA) is one of the most used materials for the fabrication of hybrid LEDs' colour conversion coatings, therefore its stability needs to be investigated.
Zvaigžņotā Debess: 2006, Rudens
2006
Latvijas Zinātņu akadēmija, Latvijas Universitāte