Explore further © 2010 PhysOrg.com As the researchers explain, the key to improving an LED’s energy-conversion efficiency lies in extracting the light generated in the semiconductor with the highest efficiency possible. However, the strong internal reflection in the semiconductor makes efficient light extraction very difficult, since light tends to remain inside the semiconductor. Most techniques to improve the light extraction efficiency have high production costs, but finding a highly efficient, low-cost light extraction technique is essential for popularizing LED lighting.The AIST researchers, XueLun Wang and Mutsuo Ogura, were able to design a semiconductor to take advantage of the effects of evanescent waves for improving light extraction efficiency. As the scientists explain, evanescent waves are a special kind of light existing only near a reflection interface. When two evanescent waves meet, they are efficiently transformed into light. In their experiments, the researchers fabricated a GaAs/AlGaAs nanostructure with V-shaped grooves and even smaller ridges between the grooves. They then deposited a 150-nm-thick layer of SiO2 onto the nanostructure. This design enabled evanescent waves to form and couple at the semiconductor-SiO2 and SiO2-air interfaces on flat planes at the tops of the ridges, resulting in an increase of the amount of light that could be extracted.Photoluminescence studies revealed that the SiO2-coated semiconductor’s light-emitting layer at the ridges was enhanced by a factor of 1.7. According to a press release, the light-extraction efficiency builds upon and exceeds the 50% efficiency of a similar technique, although the exact efficiency of the current design is not mentioned. In contrast, uncoated light-emitting semiconductor materials deposited on flat substrates only enable a few percent of the light generated in the semiconductor to be extracted; for example, GaAs has only a 2% efficiency.One advantage of the new design is that it doesn’t require any significant changes to the conventional LED fabrication process, which should keep fabrication costs low. The method could also be used with other materials, such as indium tin oxide or zinc oxide as the coating, and AlGaInP-based and GaN-based semiconductor materials, which can be used to develop visible LEDs with ultra-high light extraction efficiency. Citation: New way to extract light from semiconductors could lead to ultra-high efficiency LEDs (2010, May 14) retrieved 18 August 2019 from https://phys.org/news/2010-05-semiconductors-ultra-high-efficiency.html The illustration in (a) shows evanescent waves coupling at two interfaces on the flat planes of a ridge. Figure (b) shows the simulated electromagnetic field intensity of the structure. Image credit: AIST. Advances in Solid-state Lighting Promise Higher Energy Efficiency and Greater Design Flexibility (PhysOrg.com) — By fabricating ridges coated with silicon dioxide (SiO2) on the surface of a semiconductor, scientists from the National Institute of Advanced Industrial Science and Technology (AIST) in Japan have shown how to extract light from a semiconductor with an extremely high efficiency. The new technique could lead to the development of low-cost, ultra-high efficiency LEDs for lighting and display applications. With the widespread use of LEDs, researchers estimate that global electricity consumption could be reduced by 10% or more, which could save about $120 billion over the next 20 years. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
Two different epitaxial graphene materials combined to a monolithic transistor. Image from Nature Communications 3, Article number: 957 doi:10.1038/ncomms1955 (Phys.org) — Researchers in Germany appear to have found a way to create a monolithic (integrated) graphene transistor, using a lithographic process applied to silicon carbide, a breakthrough that could lead to computers based on graphene chips, rather than those that use silicon. This is significant because researchers are beginning to see the light at the end of the tunnel regarding the degree to which silicon can be used to make smaller and smaller chips. Using graphene wouldn’t necessarily allow for smaller chips, but because it conducts electricity faster, it would allow for faster chips without having to downsize. The German researchers working with another group from Sweden, describe the new process in their paper published in the journal Nature Communications. Journal information: Nature Communications Citation: Researchers devise a way to a create graphene transistor (2012, July 18) retrieved 18 August 2019 from https://phys.org/news/2012-07-graphene-transistor.html Explore further IBM introduces new graphene transistor © 2012 Phys.org More information: Tailoring the graphene/silicon carbide interface for monolithic wafer-scale electronics, Nature Communications 3, Article number: 957 doi:10.1038/ncomms1955AbstractGraphene is an outstanding electronic material, predicted to have a role in post-silicon electronics. However, owing to the absence of an electronic bandgap, graphene switching devices with high on/off ratio are still lacking. Here in the search for a comprehensive concept for wafer-scale graphene electronics, we present a monolithic transistor that uses the entire material system epitaxial graphene on silicon carbide (0001). This system consists of the graphene layer with its vanishing energy gap, the underlying semiconductor and their common interface. The graphene/semiconductor interfaces are tailor-made for ohmic as well as for Schottky contacts side-by-side on the same chip. We demonstrate normally on and normally off operation of a single transistor with on/off ratios exceeding 104 and no damping at megahertz frequencies. In its simplest realization, the fabrication process requires only one lithography step to build transistors, diodes, resistors and eventually integrated circuits without the need of metallic interconnects. By now everyone has heard that graphene is expected to take the world by storm over the next few years as ways are found to make use of its amazing properties (it’s just one carbon atom thick and is the fastest conductor ever found). The problem of course is in trying to work with such a thin material; it’s hard to connect to other metals such as electrodes and breaks easily. Another problem is that it’s not a natural semiconductor, which is a material that is conductive in one state and to not conductive in another. Semiconductors are what allow computers to store “1s” and “0s”. Thus, to use graphene in a computer, a way needs to be found to allow it to behave as a semiconductor so that transistors can be fashioned. That way appears to have now been found.The new research is based on earlier research that found that if the crystal, silicon carbide is baked just right, the silicon atoms on its surface are pushed out of it leaving just a single layer of carbon, i.e. graphene. The result is a material that suggests a transistor is possible due to the graphene layer remaining affixed to more layers of silicon carbide (which is a semiconductor) below it. To make a transistor, the team used a high energy beam of charged atoms to etch channels into the material to create the parts needed for a transistor to run; namely, gates, drains and sources. They also found that using oxygen gas during the etching of the middle channel converted it from a contact into a gate. The end result is a fully functioning transistor.Because the researchers scaled up the transistor size to allow for easier research, it’s not yet known how much faster the new transistor actually is, or how fast those might be once they are scaled down. What is now known though, is that it can be done, and that is the breakthrough computer engineers have been waiting for. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
Explore further © 2017 Phys.org This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. More information: J0811+4730: the most metal-poor star-forming dwarf galaxy known, arXiv:1709.00202 [astro-ph.GA] arxiv.org/abs/1709.00202AbstractWe report the discovery of the most metal-poor dwarf star-forming galaxy (SFG) known to date, J0811+4730. This galaxy, at a redshift z=0.04444, with a SDSS g-band absolute magnitude M_g = -15.41 mag and a stellar mass M* = 10^6.24} – 10^6.29 Msun, was selected by inspecting the spectroscopic data base in the Data Release 13 (DR13) of the Sloan Digital Sky Survey (SDSS). LBT/MODS spectroscopic observations reveal its oxygen abundance to be 12 + log O/H = 6.98 +/- 0.02, the lowest ever observed for a SFG. J0811+4730 strongly deviates from the main-sequence defined by SFGs in the emission-line diagnostic diagrams and the metallicity – luminosity diagram. These differences are caused mainly by the extremely low oxygen abundance in J0811+4730, which is ~10 times lower than that in main-sequence SFGs with similar luminosities. By fitting the spectral energy distributions of the Sloan Digital Sky Survey (SDSS) and LBT spectra, we find that a considerable fraction of the galaxy stellar mass was formed during the most recent burst of star formation. Metal-poor star-forming galaxies are considered to be the best local analogs of dwarf galaxies at high redshifts that played an essential role in the reionization of the universe. Due to their proximity they offer an excellent opportunity for astronomers to conduct detailed observations and studies that are not possible when it comes to high-redshift galaxies.J0811+4730 was first identified in 2016 by the Sloan Digital Sky Survey (SDSS) as a compact dwarf SFG with a potential very low metallicity. At a redshift of about 0.04, this galaxy has a SDSS g-band absolute magnitude of -15.41 and a star formation rate of approximately 0.48 solar masses per year.Now, new spectroscopic observations conducted by a team of astronomers led by Yuri Izotov of the Main Astronomical Observatory in Kiev, Ukraine, reveal that this galaxy is extremely metal-deficient.For their studies, the researchers used LBT’s two spectrographs equipped with high-resolution CCDs. The observations, carried out in February 2017, allowed the team to obtain spectra of J0811+4730, crucial for measuring its element abundances, including its extremely low metallicity.”In this paper we present Large Binocular Telescope (LBT) spectrophotometric observations of the compact star-forming galaxy (SFG) J0811+4730 selected from the Data Release 13 (DR13) of the Sloan Digital Sky Survey (SDSS),” the astronomers wrote in the paper.The researchers were able to measure the oxygen content of J0811+4730 and compare it with models to estimate its metallicity. They found that the oxygen abundance of this star-forming galaxy is the lowest ever observed for an SFG. Such low oxygen abundance compared with models indicates that J0811+4730 is the most metal-poor dwarf SFG so far discovered.”J0811+4730 strongly deviates from the main sequence defined by SFGs in the emission-line diagnostic diagrams and the metallicity – luminosity diagram,” the paper reads.The scientists emphasized that J0811+4730 is strongly offset in oxygen abundance, which was also detected in other galaxies with very low metallicities. However, the cause of this offset is still debated.Some researchers attribute these deviations to the enhanced brightnesses of the galaxies undergoing active star formation. Others assume that these galaxies can also be chemically unevolved objects with a short star formation history, having metallicities too low for their high luminosities. Furthermore, one hypothesis suggests such offset may be caused by the infall of gas from galactic halos.”This offset can probably be explained by a combination of its chemically unevolved nature, an enhanced brightness of its star-forming regions, and gas infall resulting in the dilution of the more metal-rich gas in the inner region by the outer more metal-poor gas in the halo,” the authors of the paper concluded. Astronomers discover the most metal-poor galaxy in the local universe Citation: The most metal-poor dwarf star-forming galaxy found (2017, September 5) retrieved 18 August 2019 from https://phys.org/news/2017-09-metal-poor-dwarf-star-forming-galaxy.html (Phys.org)—Using the Large Binocular Telescope (LBT), a group of astronomers has found that the star-forming galaxy (SFG) J0811+4730 is the most metal-poor dwarf SFG known to date. The finding is detailed in a paper published online on Sept. 1 on the arXiv pre-print repository. The rest-frame LBT spectrum of J0811+4730 uncorrected for extinction. Credit: Izotov et al., 2017.
French Artist Thomas Henriot’s exhibition titled, Across the City brings together Thomas encapsulates his experience of numerous journeys in Morocco, Lebanon, Togo, China, Argentina, Oman, Mali, Mauritania, USA, Cuba, Brazil and particularly India. India marked an essential stage in his approach which places his paintings in the heart of a different culture, in a concentration close to meditation.His drawings are Ink on Japanese rice paper scrolls 45 centimetres wide and sometimes up to 25 metres long which he unwinds as the progression of the drawing goes along, composing in a near-spontaneous way. Also Read – ‘Playing Jojo was emotionally exhausting’The artist uses his art as a link and a language to create contact with unknown spectators who witness the elaboration of his works.He juxtaposes in figurative motif, landscapes, architectures, characters, the rubbing of real elements which are at his disposal around him. The liveliness, its continuity, the magnitude of the movement give an originality to all these travel documentaries, album of memories.The artist draws on the ground several works in a row without interruption, in public, and the presence of his body in working, leaves its mark forever in these rolls carried with him, light and nomadic paintings.The experience of his numerous journeys in India, and particularly to Banaras, marked an essential stage to his approach which places his paintings in the heart of a different culture, in a concentration close to the realm of meditation.When: Till 15 DecemberWhere: Gallery Romain Rolland, Alliance Francais
Managed by the band members themselves, the festival was conceived purely out of love and their passion for music. Possibly the only artist-driven festival, CLONEfest showcases some of the best talents from across the country. The 2013 CLONEfest was held in Delhi over 28 and 29 December with an impressive line-up that included Advaita, Sundog Project, The Limited Experience, Moonshine, Frame/Frame, Contraband and The Urban Earlyman.We caught up with Surojit Dev, Drummer for Them Clones for some candid Q and A – here are the excerpts… Also Read – ‘Playing Jojo was emotionally exhausting’Tell us about how you guys came together as a band.I don’t think this question is relevant anymore as none of the earlier members are there apart from me 🙂 And also the name… how did the name come to be?We always had parallel careers going from start. So, we thought whenever we would be on stage or even creating new music, it would be clones of ourselves.What inspires you guys to create music, who are your idols?Our clones who face the daily life. Also Read – Leslie doing new comedy special with NetflixTell us about your first break and how the journey has been since.Depends what do you mean by first break. Ours isn’t a rags to riches story. So! Some memorable moments for you guys?Any packed house with fans singing our tunes are memorable moments. Irrespective of bigger or smaller venues. What suggestions would you have for newbies who want to make it big?Keep at it. Everything else will follow. How has Delhi been for you guys? What do you guys have planned for this show?Its home. So it is always special. Hence, different renditions of CLONEfest only happens here and nowhere else. What next for you guys?More new tunes. Possibly an album. However, this is not an announcement.
For the first time ever, Delhi will witness Yakshagana performance, a theatre form that combines dance, music, dialogue, costume, makeup and stage techniques with a unique style and form, which is popular in coastal Karnataka. The night-long performance will be held on July 11 at Delhi Karnataka Sangha auditorium. The show is organised by Delhi-based South Kanara Club in association with some local organisations. Yakshagana has been traditionally performed from dusk to dawn, but recently, it was reduced to a
Kolkata: An FIR was lodged on Wednesday against unknown persons for the stampede at a railway overbridge in Howrah’s Santragachhi station that killed two people and injured a dozen, a Government Railway Police (GRP) official said. The tragedy happened around 6 p.m. on Tuesday at the busy railway junction station under the South Eastern Railway due to overcrowding on the overbridge as commuters hurriedly tried to reach their designated platforms after an announcement of two trains coming simultaneously on two adjacent tracks was made. Also Read – Rain batters Kolkata, cripples normal life “An FIR has been registered under various sections of the IPC for voluntarily causing grievous hurt and death by negligence against the unknown persons who might be responsible for the incident,” an officer from Santragachhi GRP told IANS. The railway authorities confirmed the death of two persons in a release and said it has ordered an enquiry into the matter. “Kala Kanti Singh, 32, of East Midnapore and Taser Sardar, 61, of Murshidabad were declared dead and 12 others sustained injuries due to overcrowding and heavy rush at the Santragachhi railway station on Tuesday. Also Read – Speeding Jaguar crashes into Mercedes car in Kolkata, 2 pedestrians killed “Railway authority has ordered an enquiry in connection with the unfortunate incident,” the release said. The department had also announced a compensation package of Rs 5 lakh each to the families of the deceased, Rs 1 lakh for the seriously injured and Rs 50,000 for those with minor injuries. Chief Minister Mamata Banerjee met the injured on Tuesday evening at the hospital. She also said that the railways “negligence and callousness” caused the tragedy as she ordered an administrative probe on behalf of the state government. “Security of people should not be compromised, and railway should take proper care of the people. Railway is the lifeline of the country, it should not be derailed,” she had said.
Delhi Tourism is back with the annual Teej Festival at Dilli Haat in Janakpuri that has a lot in store for the visitors. A festival of feasts and celebrations, Teej marks the welcome of the monsoon season during the month of ‘Shravan’ or ‘Saawan.’ The festival is primarily dedicated to Goddess Parvati and her union with Lord Shiva. Hence, it is also said to be an auspicious occasion for married women to be blessed with marital bliss. It is widely celebrated by women in North India especially in the state of Rajasthan. Also Read – American Crime Story 3 to chronicle Clinton’s impeachmentOne of the highlighting features of Teej is the coming together of women enjoying the Teej Jhula, a swing hung from trees in villages and towns. The celebrations are accompanied applying Mehendi and sharing festive delicacies.The festival will be celebrated with an array of events lined up to mark this uplifting occasion. The main attractions of the event will include Mehandikars, Churi and Rakhi Stalls, Languishing Arts, Handicraft and Handloom items, home décor, Rajasthani food and other delectables amidst Cultural Programme by Department of Tourism, Govternment of Rajasthan on August 5 and August 6. Sahitya Kala Parishad, GNCTD will be on August 7. The competitions that will be organised include, Rangoli Competition on August 5 , Bindi Competition on August 6 ,Mehandi Competition on August 7 starting 11AM onwards to 10 PM.
Getting inducted in the ‘Hall of Fame’ is considered as the ultimate accolade for PR professionals and Sudhir Sobti, Chief Manager (PR and Publicity), Delhi Tourism and Transportation Development Corporation (DTTDC), Govt of Delhi, in recognition to his exceptional services in the field of PR and Communication for over the last two decades has been conferred the prestigious ‘Hall of Fame’ award during the 11th Global Communication Conclave held in Bengaluru, Karnataka organised by the Public Relations Council of India (PRCI). Also Read – Add new books to your shelfSudhir Sobti has been a resolute and articulate PR and communications professional during his more than 20 years of service, . The PRCI is a national-level registered body of professionals in the field of Public Relations, Communications, Advertising and allied fields. It has a membership of over 2,000, and has over 26 Chapters across India plus one in Dubai as well. Plans are afoot to launch two new chapters overseas, one each in Sri Lanka and Melbourne.The PRCI organizes a global conference every year where eminent professionals from India and overseas are invited to talk and share their experiences. This year’s conference theme was “Disruption”. The organisation also recognises individuals and organisations for their efforts and contribution of Public Relation professionals in their respective fields.