White LEDs with superhigh luminous efficacy could satisfy all general lighting needs

first_img(PhysOrg.com) — Researchers from the Nichia Corporation in Tokushima, Japan, have set an ambitious goal: to develop a white LED that can replace every interior and exterior light bulb currently used in homes and offices. The properties of their latest white LED – a luminous flux of 1913 lumens and a luminous efficacy of 135 lumens per watt at 1 amp – enable it to emit more light than a typical 20-watt fluorescent bulb, as well as more light for a given amount of power. With these improvements, the researchers say that the new LED can replace traditional fluorescent bulbs for all general lighting applications, and also be used for automobile headlights and LCD backlighting. Design improvements All three white LEDs are based on a blue LED die, which is coated with a yellow phosphor to achieve a wider emission spectrum. When blue emission from the LED die mixes with the yellow fluorescence from the phosphor, the device produces white light. Since the red part of the emitted spectrum was initially low, the researchers also added some red phosphor to enhance the red emission and create a more balanced spectra. Overall, the researchers noted that the color reproduction in this design is the highest of all white light sources.To optimize the luminous efficacy, the researchers focused on a key problem of LEDs: the electrodes tend to absorb some of the light that could otherwise exit the device and increase its luminosity. To reduce absorption at the electrode, the researchers used an indium-tin oxide contact as one of the electrodes, and also used a patterned sapphire substrate to scatter the light so that it could more efficiently exit the device. The researchers also optimized the device to reduce the operating voltage from 3.08 to 2.80 V.With these design improvements and the resulting enhancements in luminous efficacy, the new white LEDs provide further evidence that solid-state lighting can meet a wide variety of our future lighting requirements. Narukawa said that, although these LEDs are expensive compared to commercialized LEDs, he predicts that the price will come down in the future. He also plans to further enhance the luminous efficacy of the white LEDs for general lighting applications. Copyright 2010 PhysOrg.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com. The cross-sectional structure of (a) a conventional LED and (b) a new high efficacy LED with the patterned sapphire substrate and ITO contact as p-type electrode, which reduce the optical absorption and improve the extraction efficiency. Credit: Yuko Narukawa, et al. The Nichia researchers, Yukio Narukawa, et al., have published the results in a recent study in the Journal of Physics D: Applied Physics. The team fabricated three types of high-luminous efficacy white LEDs, each of which utilized a variety of improvements in device structure to improve their luminosity, or brightness, and reduce their operating voltage.The researchers focused on two measurement criteria. One was luminous flux (measured in lumens), which measures the light’s luminosity as perceived by the human eye, whose sensitivity varies for different wavelengths. The second criteria was luminous efficacy (measured in lumens per watt), which measures the amount of luminous flux achieved with a given amount of power. By the numbersBriefly looking at the history of a few different types of light sources helps provide some context for the LED’s recent rapid progress. The incandescent bulb, which was developed in 1879, had an initial luminous efficacy of 1.5 lm/W, which improved to 16 lm/W over the next 130 years. Fluorescent bulbs, first developed in 1938, achieved a luminosity increase of 50 to 100 lm/W over the next 60 years. The progress of white LEDs is much more pronounced: since their commercialization in 1996, white LEDs’ luminous efficacy has increased from 5 lm/W to today’s commercial white LED of 150 lm/W, the highest luminous efficacy of all white light sources. The theoretical limit for white LEDs is about 260-300 lm/W.Now, the Nichia researchers have taken the white LED’s luminous efficacy a step further, achieving values as high as 265 lm/W at 5 mA of current, or 249 lm/W at 20 mA, values that nearly reach the theoretical limit. However, the downside of this specific design is that the luminous flux is quite low, about 14.4 lm. By modifying the design, the researchers demonstrated two other white LEDs: one with values of 203 lm and 183 lm/W at 350 mA, and one (as mentioned above) with values of 1913 lm and 135 lm/W at 1 A. This last white LED was fabricated by connecting four high-power blue LED dies in series. More information: Yukio Narukawa, et al. “White light emitting diodes with super-high luminous efficacy.” J. Phys. D: Appl. Phys. 43 (2010) 354002 (6pp). DOI:10.1088/0022-3727/43/35/354002• PhysOrg.com iPhone / iPad Apps• PhysOrg.com Audio Podcasts / iTunes• PhysOrg.com Android apps (new version available)• Join PhysOrg.com on Facebook!• Follow PhysOrg.com on Twitter!center_img Explore further Citation: White LEDs with super-high luminous efficacy could satisfy all general lighting needs (2010, August 31) retrieved 18 August 2019 from https://phys.org/news/2010-08-white-super-high-luminous-efficacy.html The history of luminous efficacy in different types of lighting shows the rapid improvements in white LEDs. The years in which the white light sources were developed are also shown. Credit: Yukio Narukawa, et al. Universal Display First to Achieve 30 Lumens Per Watt White OLED 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.last_img read more

Blue light allows for making carbonnitrogen bonds without energetically unfavorable reactions

center_img More information: Andrew J. Musacchio et al. Catalytic intermolecular hydroaminations of unactivated olefins with secondary alkyl amines, Science (2017). DOI: 10.1126/science.aal3010AbstractThe intermolecular hydroamination of unactivated alkenes with simple dialkyl amines remains an unsolved problem in organic synthesis. We report a catalytic protocol for efficient additions of cyclic and acyclic secondary alkyl amines to a wide range of alkyl olefins with complete anti-Markovnikov regioselectivity. In this process, carbon-nitrogen bond formation proceeds through a key aminium radical cation intermediate that is generated via electron transfer between an excited-state iridium photocatalyst and an amine substrate. These reactions are redox-neutral and completely atom-economical, exhibit broad functional group tolerance, and occur readily at room temperature under visible light irradiation. Certain tertiary amine products generated through this method are formally endergonic relative to their constituent olefin and amine starting materials and thus are not accessible via direct coupling with conventional ground-state catalysts. © 2017 Phys.org Citation: Blue light allows for making carbon-nitrogen bonds without ‘energetically unfavorable’ reactions (2017, February 17) retrieved 18 August 2019 from https://phys.org/news/2017-02-blue-carbon-nitrogen-bonds-energetically-unfavorable.html Proposed catalytic cycle for hydroamination. Credit: (c) Science (2017). DOI: 10.1126/science.aal3010last_img read more

New outbursts detected in a peculiar active dwarf nova MN Draconis

first_img Astronomers detect flickering from the star EF Aquilae More information: MN Draconis – peculiar, active dwarf nova in the period gap, arXiv:1703.06742 [astro-ph.SR] arxiv.org/abs/1703.06742AbstractContext: We present results of an extensive world-wide observing campaign of MN Draconis. Aims: MN Draconis is a poorly known active dwarf nova in the period gap and is one of the only two known cases of period gap SU UMa objects showing the negative superhumps. Photometric behaviour of MN Draconis poses a challenge for existing models of the superhump and superoutburst mechanisms. Therefore, thorough investigation of peculiar systems, such as MN Draconis, is crucial for our understanding of evolution of the close binary stars. Methods: To measure fundamental parameters of the system, we collected photometric data in October 2009, June-September 2013 and June-December 2015. Analysis of the light curves, O−C diagrams and power spectra was carried out. Results: During our three observational seasons we detected four superoutburts and several normal outbursts. Based on the two consecutive superoutbursts detected in 2015, the supercycle length was derived P_sc = 74 +/- 0.5 days and it has been increasing with a rate of P_dot = 3.3 x 10^(-3) during last twelve years. Based on the positive and negative superhumps we calculated the period excess epsilon = 5.6% +/- 0.1%, the period deficit epsilon_ = 2.5% +/- 0.6%, and in result, the orbital period P_orb = 0.0994(1) days (143.126 +/- 0.144 min). We updated the basic light curve parameters of MN Draconis. Conclusions: MN Draconis is the first discovered SU UMa system in the period gap with increasing supercycle length. (Phys.org)—A team of astronomers led by Karolina Bąkowska of the Nicolaus Copernicus Astronomical Center in Warsaw, Poland, has discovered several new outbursts in a peculiar, active dwarf nova known as MN Draconis. The results of new observations, which could provide better understanding of dwarf novae in general, were published Mar. 20 in a paper on arXiv.org. Explore further Citation: New outbursts detected in a peculiar, active dwarf nova MN Draconis (2017, March 28) retrieved 18 August 2019 from https://phys.org/news/2017-03-outbursts-peculiar-dwarf-nova-mn.html MN Draconis (MN Dra for short) is an active SU Ursae Majoris-type (SU UMa-type) dwarf nova (DN). It is a poorly known active DN in the period gap and currently one of the only two known cases of period gap SU UMa objects showcasing quasi-periodic oscillations called superhumps.Superhumps are observed in light curves of SU UMa systems during superoutbursts. Most common are positive superhumps – oscillations with periods a few percent longer than their orbital periods. However, MN Draconis exhibits negative superhumps, which means that the oscillations have periods that are slightly shorter than orbital periods.SU UMa-type stars like MN Draconis are characterized by short orbital periods (shorter than 2.5 hours) and by the occurrence of superoutbursts, which are less frequent but one magnitude brighter than normal outbursts. Outbursts in MN Draconis were first spotted in 2002-2003. These observations derived the supercycle period (timespan between two successive superoutbursts) of MN Draconis to be about 60 days—one of the shortest among the values known in SU UMa stars. Now, Bąkowska and her colleagues present the results of an extensive world-wide observational campaign, which provided new essential information about this peculiar dwarf nova.The new observations were carried out in 2009, 2013 and 2015. The astronomers used several ground-based observatories, including the Skinakas Observatory in Greece, the Poznan Astronomical Observatory, the Warsaw University Observatory (both located in Poland), the Borowiec Station in Italy, the Antelope Hills Observatory and the MDM Observatory (both in the U.S.). The observations allowed the team to measure fundamental parameters of the system by collecting photometric data and analysing the light curves, O − C diagrams as well as power spectra.The scientists detected four superoutbursts and several normal outbursts. They also managed to characterize the occurrence of superhumps in superoutbursts, in outbursts, and in quiescence, along with their rates of change. Moreover, the researchers refined the supercycle length and possible changes in the superoutburst occurrence rate.”Based on the two consecutive superoutbursts detected in 2015, the supercycle length was derived Psc = 74 ± 0.5 days and it has been increasing with a rate of P = 3.3 × 10−3 during last 12 years,” the paper reads.The authors noted that MN Draconis is the first discovered SU UMa system in the period gap with increasing supercycle length. It means that the occurrence of superoutbursts in this object has been constantly decreasing in recent decades. Such increased supercycle length could be crucial for our understanding of the future evolution of dwarf novae.”MN Dra is another example of an active DN located in the period gap. It is worth noting that this star is not only a challenge for existing models of the superhump and superoutburst mechanisms, but also it presents other intriguing behaviours, in particular the increasing supercycle length,” the researchers concluded. © 2017 Phys.org The light curve of MN Dra during superoutbursts folded with Psc = 74 days. Black circles correspond to the June – July 2015 superoutburst and grey circles represent the September 2015 superoutburst. Credit: Bąkowska et al., 2017. 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.last_img read more

SSYs for unorganised sector workers see major boost

first_imgKolkata: In a significant improvement in the social security schemes for the workers in unorganised sectors, the Bengal government has completed the digitalisation of data of more than 55 lakh beneficiaries in the state so far.The state Labour department, the implementing authority of the Samajik Suraksha Yojana (SSY), has set a target to include 1.2 crore beneficiaries within the schemes, aiming to provide income security and various social benefits to the people engaged in unorganised sectors. Also Read – Heavy rain hits traffic, flightsSSY schemes were introduced by the state government in 2017, following the initiative of Chief Minister Mamata Banerjee, who laid an emphasis on the improvement of socio-economic conditions of the people working in various unorganised sectors. Prodded by the Chief Minister, the state Labour department chalked out an elaborate plan for a comprehensive coverage of social benefits.The various schemes that are falling under the SSY are State Assisted Scheme of Provident Fund for Unorganised Workers (SASPFUW), West Bengal Unorganised Sector Workers Health Security Scheme (WBUSWHSS), Social Security Scheme for Construction Workers (BOCWA), West Bengal Transport Workers Social Security Scheme (WBTWSSS) and West Bengal Bidi Workers’ Welfare Scheme (WBBWWS). To provide uniform benefits to each and every unorganised worker, the common benefits of all these schemes were integrated and converged into a single and more comprehensive scheme for the benefits of the beneficiaries, many of whom are illiterate. Also Read – Speeding Jaguar crashes into Merc, 2 B’deshi bystanders killedAs per the latest available report, digitalisation work has been done for 55,39,368 beneficiaries in the state so far. According to sources in the Labour department, many more beneficiaries have already been brought under the SSY schemes, the data of whom are yet to be uploaded in the system. The department has a target of bringing 1.2 crore people under this scheme and upload their data in the online system, so that every individual in the state can avail the benefits of the social schemes of the state government. The state government had also received an award in the national arena for the conceptualisation and effective implementation of the schemes, a senior official of the department said. SSY is one of the best labour welfare schemes that have brought about a change in the lives of people across the state. The digitalisation of data has helped the department to maintain a centralised information system, where all the information related to any individual is available at the click of a mouse.This will bring more transparency in the system and maintain the records of beneficiaries. The online maintenance of data will also help the department to check multiple entries. For example, earlier there was a possibility that an individual could apply for some benefits from two districts simultaneously. But the digitalisation of data is helping the department check such incidents.Unorganised workers are getting financial assistance of Rs 20,000 per annum for any ailment and the amount extends up to Rs 60,000 per annum in case of hospitalisation. They are also entitled to get provident fund after the age of 60.The state government also extends financial assistance to the beneficiaries, so that their children can pursue higher studies. Workers in hazardous jobs also get benefits under the scheme. Construction workers are entitled to get additional benefits like invalid pension and family pension. Transport workers are also entitled to get additional medical benefits and family pension.last_img read more

CBI questions Mathew Samuel again

first_imgKolkata: The Central Bureau of Investigation (CBI) questioned the former CEO of Narada News Mathew Samuel once again on Friday, sources said. Samuel went to the office of CBI in Kolkata in connection with the Narada sting operation case. Sources said that the CBI officers have questioned Mathew in connection with the original video footages of the sting operation. It has been learnt that the investigating officers have not got a satisfactory answer in this connection.Sources said that the matter related to the Muchipara case in which a former Central minister from Bihar had received a call demanding extortion money of Rs 5 crore and was threatened with some video footages. Storage devices containing video footages were recovered from a hotel room at Muchipara.last_img read more

Centre to pay jute mills only after full payment to farmers labourers

first_imgKolkata: In a stride to ensure that jute farmers and labourers get their desired benefits, the Centre will make it mandatory for the mill owners to make their payments in its entirety before getting the entire payment of the government orders.The decision of the Centre comes in the wake of a section of farmers and labourers complaining of not getting the benefits that they deserve. “The jute industry used to get payments against the order regularly. Why are the farmers and labourers complaining about it? Now, we are making it mandatory, that if you do not pay the farmers or labourers or any way abdicate the responsibility, we will not give you the order,” Union Textile minister Smriti Irani said during an interactive session organised by the Indian Chamber of Commerce. Also Read – Rain batters Kolkata, cripples normal lifeThe jute industry, according to the minister has a ready order worth Rs 5,000-5,500 crore every year (in terms of sacking). “We give such huge orders so that the jute industry stays alive. The sum is given to the jute industry in terms of order so that the farmers and labourers can get the benefits out of it,” she maintained. Irani urged the industry to go for innovation and come forward in taking new initiatives and said the Centre has been focusing on how to transform small size firms into mid-size entities. Elaborating on innovation, she touched upon technical textiles that are finding its application in automobiles, interior decoration, healthcare, industrial safety among others. Also Read – Speeding Jaguar crashes into Mercedes car in Kolkata, 2 pedestrians killedIrani said the industry should work closely with the government so that the policies framed by the latter may be implemented effectively. Later, addressing the Annual General Meeting at the Merchants’ Chamber of Commerce, she said the government has increased the import duty on some textile products to protect domestic manufacturing. “India looks at the trade war between China and the US as an opportunity and not as a challenge. India would be benefited from the trade war not only through policy intervention but also through industry practices,” she added.last_img read more

Ensure a summer full of sparkle with right jewellery

first_imgIts that time of year when everyone is busy making travel plans with friends and family. Deciding on what to pack for your vacation is never easy and it often requires more thought than the destination itself To ensure you have a stress-free vacation, Experts list some must have travel looks. Gemstones: Summer is for bright and colourful outfits. Incorporating the colour trend in your jewellery is a great way to keep you vibrant and energized. Pieces with amethyst, which is also the Pantone color of the year, beautifully coloured tourmalines and other gemstones, are a must to carry on your travels. Also Read – Add new books to your shelfVersatile pieces: Even though we suggest you travel only with the essential pieces and stay light, keeping versatile jewellery that can be paired with both formal and casual outfits is extremely helpful. Detachable earrings, stackable rings and layered necklaces are a must have in your travel case. Rose gold: Rose Gold is a universally flattering metal that usually looks great with any colour or clothing. It looks amazing when paired with soft pastels and neutral colour themes while keeping you right on trend! Also Read – Over 2 hours screen time daily will make your kids impulsiveKeep it quirky: For those of you who like to stay quirky in style, animal renditions of jewellery are unique and are an extremely cool accessory for vacations. This trend is especially seen in pendants, studs and rings and is go to jewellery for all destination types. Lightweight: The most important rule when you are travelling is to keep your baggage as light as possible. This goes for your jewellery as well. Dainty, light pieces in pendants, earrings, rings and bracelets, that are easy to carry and store. Preferably a selection of those that can be paired with more than one look are the most apt. Plan according to your destination: Your choice of jewellery should be synonymous to your travel destination. For a beach holiday we suggest you team your classic black or a bright shade swimsuit or shorts and tee with minimalist pendants or layered neck chains. Layered necklaces are a big trend for the summer and will add just the right amount of bling to your casual outfit.Minimalistic pieces: Minimalist pendants and earrings are vacation essentials. Incorporating geometry through neckpieces and studs, that are easy to carry and minimalistic in look ensures convenience and style.last_img read more

CCIC promotes Indian craft

first_imgIn an endeavour to promote Indian handicrafts and the spirit of craftsmanship, Central Cottage Industries Corporation (CCIC) has organised an exhibition cum sale titled ‘Sculpted Renditions’ – of an exquisite collection of sculptures and artefacts in its showroom at Janpath, New Delhi.The exhibition will be open to view from 10 am till 7 pm every day until September 16.One can browse through some of the finest masterpieces of traditional Indian dexterity. The exhibition showcases a vast collection of statuettes, figurines, and replicas of our ancient mythological deities with intricate works in stones, bronze, and wood craft. A Special display of ‘Lord Ganesha’ has also been put on the occasion of Ganesh Chaturthi. Also Read – Add new books to your shelfThe ongoing exhibition is an initiative by CCIC in order to promote Indian crafts, encourage the craftspersons and to present their creations with a view to increase the awareness about handmade sculptures and artefacts to a wider audience.Central Cottage Industries Corporation of India Ltd. (CCIC), a public sector undertaking under the Ministry of Textiles is engaged in the promotion and retail marketing of best of authentic Indian Handloom and Handicraft products through its showrooms in New Delhi, Mumbai, Bengaluru, Chennai, Kolkata Hyderabad, Patna, and Varanasi.CCIC sources its merchandise directly from, weavers, master weavers, craftsperson, Shilpgurus, National Awardees, and Clusters. CCIC is dedicated to the development of Indian crafts and craft person, providing a unique platform for showcasing their art.last_img read more