Continuous light-emitting Diode (LED) lighting for improving food quality

OpenAIRE

Lu, C; Bian, Z

2016-01-01

Lighting-emitting diodes (LEDs) have shown great potential for plant growth and development, with higher luminous efficiency and positive impact compared with other artificial lighting. The combined effects of red/blue or/and green, and white LED light on plant growth and physiology, including chlorophyll fluorescence, nitrate content and phytochemical concentration before harvest, were investigated. The results showed that continuous light (CL)\\ud exposure at pre-harvest can effectively redu...

Final report LED solutions for public lighting; Eindrapportage LED oplossingen voor openbare verlichting

Energy Technology Data Exchange (ETDEWEB)

NONE

2010-04-15

This report examines if and how LED can be used for public lighting on a large scale. Pilot projects in 29 municipalities were assessed to test the usefulness of LED lighting. This final report provides answers to the questions that relate to the feasibility of the deployment of LED in public lighting and provides some practical pointers. [Dutch] Er is onderzocht of, en zo ja op welke wijze, LED grootschalig toegepast kan worden in de openbare verlichting (OVL). In 29 gemeenten in Nederland zijn proefprojecten geevalueerd om LED verlichting te toetsen op bruikbaarheid. Deze eindrapportage geeft antwoord op vragen die betrekking hebben op de haalbaarheid van de toepassing van LED binnen de OVL en geeft wat praktische aandachtspunten.

High Output LED-Based Profile Lighting Fixture

DEFF Research Database (Denmark)

Török, Lajos; Beczkowski, Szymon; Munk-Nielsen, Stig

2011-01-01

Recent developments in power light emitting diode (LED) industry have made LEDs suitable for being efficiently used in high intensity lighting fixtures instead of the commonly used high intensity discharge (HID) lamps. A high output LEDbased profile-light fixture is presented in this paper...

[LED lights in dermatology].

Science.gov (United States)

Noé, C; Pelletier-Aouizerate, M; Cartier, H

2017-04-01

The use in dermatology of light-emitting diodes (LEDs) continues to be surrounded by controversy. This is due mainly to poor knowledge of the physicochemical phases of a wide range of devices that are difficult to compare to one another, and also to divergences between irrefutable published evidence either at the level of in vitro studies or at the cellular level, and discordant clinical results in a variety of different indications: rejuvenation, acne, wound healing, leg ulcers, and cutaneous inflammatory or autoimmune processes. Therapeutic LEDs can emit wavelengths ranging from the ultraviolet, through visible light, to the near infrared (247-1300 nm), but only certain bands have so far demonstrated any real value. We feel certain that if this article remains factual, then readers will have a different, or at least more nuanced, opinion concerning the use of such LED devices in dermatology. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

Plant growth regulation by the light of LEDs; LED ko wo tsukatta shokubutsu saibai gijutsu

Energy Technology Data Exchange (ETDEWEB)

Watanabe, H. [Mitsubishi Chemical Co., Tokyo (Japan). Yokohama Research Center

1996-03-01

Light Emitting Diode (LED) has not only an excellent display function for the luminescent device but also a superior feature without other lamps as light source for plant growth. It was National Aeronautics and Space Administration (NASA) to find out such merit for this light source for plant growth and try at first to use for plant growth at the space. They began to examine the LED application to the light source for the plant growth at the space since a stage at high cost of the LED, to develop some researches centered at cultivation of lettuce, wheat, and others. Finding out future possibility of cost-down of the LEDs on the cost/performance and large merits of the LEDs for control of the plant growth and plant physiology, authors have conducted some cultivation experiments of the plants using the LEDs for light source some years ago. In this papers, characterizations, actual possibility, and future developments of the LEDs for the light sources of the plant growth, are introduced. 5 refs., 4 figs.

New Framework of Sustainable Indicators for Outdoor LED (Light Emitting Diodes Lighting and SSL (Solid State Lighting

Directory of Open Access Journals (Sweden)

Annika K. Jägerbrand

2015-01-01

Full Text Available Light emitting diodes (LEDs and SSL (solid state lighting are relatively new light sources, but are already widely applied for outdoor lighting. Despite this, there is little available information allowing planners and designers to evaluate and weigh different sustainability aspects of LED/SSL lighting when making decisions. Based on a literature review, this paper proposes a framework of sustainability indicators and/or measures that can be used for a general evaluation or to highlight certain objectives or aspects of special interest when choosing LED/SSL lighting. LED/SSL lighting is reviewed from a conventional sustainable development perspective, i.e., covering the three dimensions, including ecological, economic and social sustainability. The new framework of sustainable indicators allow prioritization when choosing LED/SSL products and can thereby help ensure that short-term decisions on LED/SSL lighting systems are in line with long-term sustainability goals established in society. The new framework can also be a beneficial tool for planners, decision-makers, developers and lighting designers, or for consumers wishing to use LED/SSL lighting in a sustainable manner. Moreover, since some aspects of LED/SSL lighting have not yet been thoroughly studied or developed, some possible future indicators are suggested.

LED lighting increases the ecological impact of light pollution irrespective of color temperature.

Science.gov (United States)

Pawson, S M; Bader, M K-F

Recognition of the extent and magnitude of night-time light pollution impacts on natural ecosystems is increasing, with pervasive effects observed in both nocturnal and diurnal species. Municipal and industrial lighting is on the cusp of a step change where energy-efficient lighting technology is driving a shift from “yellow” high-pressure sodium vapor lamps (HPS) to new “white” light-emitting diodes (LEDs). We hypothesized that white LEDs would be more attractive and thus have greater ecological impacts than HPS due to the peak UV-green-blue visual sensitivity of nocturnal invertebrates. Our results support this hypothesis; on average LED light traps captured 48% more insects than were captured with light traps fitted with HPS lamps, and this effect was dependent on air temperature (significant light × air temperature interaction). We found no evidence that manipulating the color temperature of white LEDs would minimize the ecological impacts of the adoption of white LED lights. As such, large-scale adoption of energy-efficient white LED lighting for municipal and industrial use may exacerbate ecological impacts and potentially amplify phytosanitary pest infestations. Our findings highlight the urgent need for collaborative research between ecologists and electrical engineers to ensure that future developments in LED technology minimize their potential ecological effects.

Agnosia for accents in primary progressive aphasia☆

Science.gov (United States)

Fletcher, Phillip D.; Downey, Laura E.; Agustus, Jennifer L.; Hailstone, Julia C.; Tyndall, Marina H.; Cifelli, Alberto; Schott, Jonathan M.; Warrington, Elizabeth K.; Warren, Jason D.

2013-01-01

As an example of complex auditory signal processing, the analysis of accented speech is potentially vulnerable in the progressive aphasias. However, the brain basis of accent processing and the effects of neurodegenerative disease on this processing are not well understood. Here we undertook a detailed neuropsychological study of a patient, AA with progressive nonfluent aphasia, in whom agnosia for accents was a prominent clinical feature. We designed a battery to assess AA's ability to process accents in relation to other complex auditory signals. AA's performance was compared with a cohort of 12 healthy age and gender matched control participants and with a second patient, PA, who had semantic dementia with phonagnosia and prosopagnosia but no reported difficulties with accent processing. Relative to healthy controls, the patients showed distinct profiles of accent agnosia. AA showed markedly impaired ability to distinguish change in an individual's accent despite being able to discriminate phonemes and voices (apperceptive accent agnosia); and in addition, a severe deficit of accent identification. In contrast, PA was able to perceive changes in accents, phonemes and voices normally, but showed a relatively mild deficit of accent identification (associative accent agnosia). Both patients showed deficits of voice and environmental sound identification, however PA showed an additional deficit of face identification whereas AA was able to identify (though not name) faces normally. These profiles suggest that AA has conjoint (or interacting) deficits involving both apperceptive and semantic processing of accents, while PA has a primary semantic (associative) deficit affecting accents along with other kinds of auditory objects and extending beyond the auditory modality. Brain MRI revealed left peri-Sylvian atrophy in case AA and relatively focal asymmetric (predominantly right sided) temporal lobe atrophy in case PA. These cases provide further evidence for the

Agnosia for accents in primary progressive aphasia.

Science.gov (United States)

Fletcher, Phillip D; Downey, Laura E; Agustus, Jennifer L; Hailstone, Julia C; Tyndall, Marina H; Cifelli, Alberto; Schott, Jonathan M; Warrington, Elizabeth K; Warren, Jason D

2013-08-01

As an example of complex auditory signal processing, the analysis of accented speech is potentially vulnerable in the progressive aphasias. However, the brain basis of accent processing and the effects of neurodegenerative disease on this processing are not well understood. Here we undertook a detailed neuropsychological study of a patient, AA with progressive nonfluent aphasia, in whom agnosia for accents was a prominent clinical feature. We designed a battery to assess AA's ability to process accents in relation to other complex auditory signals. AA's performance was compared with a cohort of 12 healthy age and gender matched control participants and with a second patient, PA, who had semantic dementia with phonagnosia and prosopagnosia but no reported difficulties with accent processing. Relative to healthy controls, the patients showed distinct profiles of accent agnosia. AA showed markedly impaired ability to distinguish change in an individual's accent despite being able to discriminate phonemes and voices (apperceptive accent agnosia); and in addition, a severe deficit of accent identification. In contrast, PA was able to perceive changes in accents, phonemes and voices normally, but showed a relatively mild deficit of accent identification (associative accent agnosia). Both patients showed deficits of voice and environmental sound identification, however PA showed an additional deficit of face identification whereas AA was able to identify (though not name) faces normally. These profiles suggest that AA has conjoint (or interacting) deficits involving both apperceptive and semantic processing of accents, while PA has a primary semantic (associative) deficit affecting accents along with other kinds of auditory objects and extending beyond the auditory modality. Brain MRI revealed left peri-Sylvian atrophy in case AA and relatively focal asymmetric (predominantly right sided) temporal lobe atrophy in case PA. These cases provide further evidence for the

Sequenced subjective accents for brain-computer interfaces

Science.gov (United States)

Vlek, R. J.; Schaefer, R. S.; Gielen, C. C. A. M.; Farquhar, J. D. R.; Desain, P.

2011-06-01

Subjective accenting is a cognitive process in which identical auditory pulses at an isochronous rate turn into the percept of an accenting pattern. This process can be voluntarily controlled, making it a candidate for communication from human user to machine in a brain-computer interface (BCI) system. In this study we investigated whether subjective accenting is a feasible paradigm for BCI and how its time-structured nature can be exploited for optimal decoding from non-invasive EEG data. Ten subjects perceived and imagined different metric patterns (two-, three- and four-beat) superimposed on a steady metronome. With an offline classification paradigm, we classified imagined accented from non-accented beats on a single trial (0.5 s) level with an average accuracy of 60.4% over all subjects. We show that decoding of imagined accents is also possible with a classifier trained on perception data. Cyclic patterns of accents and non-accents were successfully decoded with a sequence classification algorithm. Classification performances were compared by means of bit rate. Performance in the best scenario translates into an average bit rate of 4.4 bits min-1 over subjects, which makes subjective accenting a promising paradigm for an online auditory BCI.

Unidirectional visible light communication and illumination with LEDs

NARCIS (Netherlands)

Li, S.; Pandharipande, A.; Willems, F.M.J.

2016-01-01

Visible light communication (VLC) with light emitting diodes (LEDs) has attracted interest for interactive and networked lighting control, and consumer infotainment applications. In this paper, we propose an LED system for jointly achieving unidirectional VLC while providing flicker-free

Development of high-performance solar LED lighting system

KAUST Repository

Huang, B.J.; Wu, M.S.; Hsu, P.C.; Chen, J.W.; Chen, K.Y.

2010-01-01

The present study developed a high-performance charge/discharge controller for stand-alone solar LED lighting system by incorporating an nMPPO system design, a PWM battery charge control, and a PWM battery discharge control to directly drive the LED. The MPPT controller can then be removed from the stand-alone solar system and the charged capacity of the battery increases 9.7%. For LED driven by PWM current directly from battery, a reliability test for the light decay of LED lamps was performed continuously for 13,200 h. It has shown that the light decay of PWM-driven LED is the same as that of constant-current driven LED. The switching energy loss of the MOSFET in the PWM battery discharge control is less than 1%. Three solar-powered LED lighting systems (18 W, 100 W and 150 W LED) were designed and built. The long-term outdoor field test results have shown that the system performance is satisfactory with the control system developed in the present study. The loss of load probability for the 18 W solar LED system is 14.1% in winter and zero in summer. For the 100 W solar LED system, the loss of load probability is 3.6% in spring. © 2009 Elsevier Ltd. All rights reserved.

Development of high-performance solar LED lighting system

International Nuclear Information System (INIS)

Huang, B.J.; Wu, M.S.; Hsu, P.C.; Chen, J.W.; Chen, K.Y.

2010-01-01

The present study developed a high-performance charge/discharge controller for stand-alone solar LED lighting system by incorporating an nMPPO system design, a PWM battery charge control, and a PWM battery discharge control to directly drive the LED. The MPPT controller can then be removed from the stand-alone solar system and the charged capacity of the battery increases 9.7%. For LED driven by PWM current directly from battery, a reliability test for the light decay of LED lamps was performed continuously for 13,200 h. It has shown that the light decay of PWM-driven LED is the same as that of constant-current driven LED. The switching energy loss of the MOSFET in the PWM battery discharge control is less than 1%. Three solar-powered LED lighting systems (18 W, 100 W and 150 W LED) were designed and built. The long-term outdoor field test results have shown that the system performance is satisfactory with the control system developed in the present study. The loss of load probability for the 18 W solar LED system is 14.1% in winter and zero in summer. For the 100 W solar LED system, the loss of load probability is 3.6% in spring.

Development of high-performance solar LED lighting system

KAUST Repository

Huang, B.J.

2010-08-01

The present study developed a high-performance charge/discharge controller for stand-alone solar LED lighting system by incorporating an nMPPO system design, a PWM battery charge control, and a PWM battery discharge control to directly drive the LED. The MPPT controller can then be removed from the stand-alone solar system and the charged capacity of the battery increases 9.7%. For LED driven by PWM current directly from battery, a reliability test for the light decay of LED lamps was performed continuously for 13,200 h. It has shown that the light decay of PWM-driven LED is the same as that of constant-current driven LED. The switching energy loss of the MOSFET in the PWM battery discharge control is less than 1%. Three solar-powered LED lighting systems (18 W, 100 W and 150 W LED) were designed and built. The long-term outdoor field test results have shown that the system performance is satisfactory with the control system developed in the present study. The loss of load probability for the 18 W solar LED system is 14.1% in winter and zero in summer. For the 100 W solar LED system, the loss of load probability is 3.6% in spring. © 2009 Elsevier Ltd. All rights reserved.

Accent Identification by Adults with Aphasia

Science.gov (United States)

Newton, Caroline; Burns, Rebecca; Bruce, Carolyn

2013-01-01

The UK is a diverse society where individuals regularly interact with speakers with different accents. Whilst there is a growing body of research on the impact of speaker accent on comprehension in people with aphasia, there is none which explores their ability to identify accents. This study investigated the ability of this group to identify the…

Integration of organic LEDs with inorganic LEDs for a hybrid lighting system

Science.gov (United States)

Kong, H. J.; Park, J. W.; Kim, Y. M.

2013-01-01

We demonstrate that a surface-emitting hybrid light source can be realized by a combination of organic and inorganic light-emitting devices (LEDs). To this end, a blue inorganic LED bar is deployed at one side of a transparent light guide plate (LGP), and a yellow organic LED (OLED) is in contact with the rear surface of the LGP. In such a configuration, it is found that the overall luminance is almost equivalent to the sum of the luminances measured from each light source, and the overall luminance uniformity is determined mainly by the luminance uniformity of the OLED panel at high luminances. We have achieved a white color showing the Commission Internationale d'Eclairage (CIE) chromaticity coordinates of (x = 0.34, y = 0.33), the power efficiency of 9.3 lm/W, the luminance uniformity of 63% at the luminance of 3100 cd m-2, the color rendering index as high as 89.3, and the correlated color temperature finely tunable within the range between 3000 and 8000 K. Such a system facilitates color tuning by adjusting their luminous intensities and hence the implementation of the emotional lighting system.

Integration of organic LEDs with inorganic LEDs for a hybrid lighting system

International Nuclear Information System (INIS)

Kong, H J; Kim, Y M; Park, J W

2013-01-01

We demonstrate that a surface-emitting hybrid light source can be realized by a combination of organic and inorganic light-emitting devices (LEDs). To this end, a blue inorganic LED bar is deployed at one side of a transparent light guide plate (LGP), and a yellow organic LED (OLED) is in contact with the rear surface of the LGP. In such a configuration, it is found that the overall luminance is almost equivalent to the sum of the luminances measured from each light source, and the overall luminance uniformity is determined mainly by the luminance uniformity of the OLED panel at high luminances. We have achieved a white color showing the Commission Internationale d'Eclairage (CIE) chromaticity coordinates of (x = 0.34, y = 0.33), the power efficiency of 9.3 lm/W, the luminance uniformity of 63% at the luminance of 3100 cd m –2 , the color rendering index as high as 89.3, and the correlated color temperature finely tunable within the range between 3000 and 8000 K. Such a system facilitates color tuning by adjusting their luminous intensities and hence the implementation of the emotional lighting system. (paper)

Two-way visible light communication and illumination with LEDs

NARCIS (Netherlands)

Li, S.; Pandharipande, A.; Willems, F.M.J.

2017-01-01

Visible light communications (VLC) with light-emitting diodes (LEDs) has attracted applications, such as data communications, lighting control, and light interaction. In this paper, we propose a system by which two LED devices are used for two-way VLC while also providing illumination. We consider

FOREIGN ACCENT PERCEPTION IN PROFESSIONAL DISCOURSE

Directory of Open Access Journals (Sweden)

Tyurina, S.Yu.

2017-09-01

Full Text Available This paper examines the attitude to the accent in professional discourse. The paper focuses on linguistic approach to accent, thus, the communicative effect of accent in professional discourse is evaluated. Discourse is considered as one of the key concepts of contemporary thinking. The key goal is to study how native speaking and non-native speaking people evaluate the accents in professional sphere. The study is considered to have important implications due to academic and professional mobility. Both quantitative and qualitative methods to collect and analyze data were used. The results of the research may be interesting for phoneticians and ESP teachers.

Signal processing for LED lighting systems : illumination rendering and sensing

NARCIS (Netherlands)

Yang, H.

2010-01-01

Solid state lighting, employing high brightness light emitting diodes (LEDs), is becoming increasingly widely used. The advantages of LEDs include high radiative efficiency, long lifetime, limited heat generation and superior tolerance to humidity. Another important advantage of LED lighting systems

Accent Imitation Positively Affects Language Attitudes

Directory of Open Access Journals (Sweden)

Patti eAdank

2013-05-01

Full Text Available People in conversation tend to accommodate the way they speak. It has been assumed that this tendency to imitate each other’s speech patterns serves to increase liking between partners in a conversation. Previous experiments examined the effect of perceived social attractiveness on the tendency to imitate someone else’s speech and found that vocal imitation increased when perceived attractiveness was higher. The present experiment extends this research by examining the inverse relationship and examines how overt vocal imitation affects attitudes. Participants listened to sentences spoken by two speakers of a regional accent (Glaswegian of English. They vocally repeated (speaking in their own accent without imitating the sentences spoken by a Glaswegian speaker, and subsequently imitated sentences spoken by a second Glaswegian speaker (order counterbalanced across participants. After each repeating or imitation session, participants completed a questionnaire probing the speakers’ perceived power, competence, and social attractiveness. Imitating had a positive effect on the perceived social attractiveness of the speaker compared to repeating. These results are interpreted in light of Communication Accommodation Theory.

Accent imitation positively affects language attitudes.

Science.gov (United States)

Adank, Patti; Stewart, Andrew J; Connell, Louise; Wood, Jeffrey

2013-01-01

People in conversation tend to accommodate the way they speak. It has been assumed that this tendency to imitate each other's speech patterns serves to increase liking between partners in a conversation. Previous experiments examined the effect of perceived social attractiveness on the tendency to imitate someone else's speech and found that vocal imitation increased when perceived attractiveness was higher. The present experiment extends this research by examining the inverse relationship and examines how overt vocal imitation affects attitudes. Participants listened to sentences spoken by two speakers of a regional accent (Glaswegian) of English. They vocally repeated (speaking in their own accent without imitating) the sentences spoken by a Glaswegian speaker, and subsequently imitated sentences spoken by a second Glaswegian speaker (order counterbalanced across participants). After each repeating or imitation session, participants completed a questionnaire probing the speakers' perceived power, competence, and social attractiveness. Imitating had a positive effect on the perceived social attractiveness of the speaker compared to repeating. These results are interpreted in light of Communication Accommodation Theory.

On-off switching patterns for smart LED lighting

NARCIS (Netherlands)

Linnartz, J.P.M.G.; Schenk, T.C.W.; Feri, L.; Yang, Hongming; Tjalkens, T.J.; Willems, F.M.J.

2009-01-01

This paper formulates a new communication problem for smart LED lighting sys tems designed for light effect control. It introduces the key requirements imposed on the design of the LED driving sequences, which include multiple access, arbi trary duty cycle and no disturbance caused on the normal

Processing changes when listening to foreign-accented speech

Directory of Open Access Journals (Sweden)

Carlos eRomero-Rivas

2015-03-01

Full Text Available This study investigates the mechanisms responsible for fast changes in processing foreign-accented speech. Event Related brain Potentials (ERPs were obtained while native speakers of Spanish listened to native and foreign-accented speakers of Spanish. We observed a less positive P200 component for foreign-accented speech relative to native speech comprehension. This suggests that the extraction of spectral information and other important acoustic features was hampered during foreign-accented speech comprehension. However, the amplitude of the N400 component for foreign-accented speech comprehension decreased across the experiment, suggesting the use of a higher level, lexical mechanism. Furthermore, during native speech comprehension, semantic violations in the critical words elicited an N400 effect followed by a late positivity. During foreign-accented speech comprehension, semantic violations only elicited an N400 effect. Overall, our results suggest that, despite a lack of improvement in phonetic discrimination, native listeners experience changes at lexical-semantic levels of processing after brief exposure to foreign-accented speech. Moreover, these results suggest that lexical access, semantic integration and linguistic re-analysis processes are permeable to external factors, such as the accent of the speaker.

LED-based high-speed visible light communications

Science.gov (United States)

Chi, Nan; Shi, Meng; Zhao, Yiheng; Wang, Fumin; Shi, Jianyang; Zhou, Yingjun; Lu, Xingyu; Qiao, Liang

2018-01-01

We are seeing a growing use of light emitting diodes (LEDs) in a range of applications including lighting, TV and backlight board screen, display etc. In comparison with the traditional incandescent and fluorescent light bulbs, LEDs offer long life-space, much higher energy efficiency, high performance cost ratio and above all very fast switching capability. LED based Visible Light Communications (VLC) is an emerging field of optical communications that focuses on the part of the electromagnetic spectrum that humans can see. Depending on the transmission distance, we can divide the whole optical network into two categories, long haul and short haul. Visible light communication can be a promising candidate for short haul applications. In this paper, we outline the configuration of VLC, its unique benefits, and describe the state of the art research contributions consisting of advanced modulation formats including adaptive bit loading OFDM, carrierless amplitude and phase (CAP), pulse amplitude modulation (PAM) and single carrier Nyquist, linear equalization and nonlinear distortion mitigation based on machine learning, quasi-balanced coding and phase-shifted Manchester coding. These enabling technologies can support VLC up to 10Gb/s class free space transmission.

Evaluation of OLED and edge-lit LED lighting panels

Science.gov (United States)

Mou, Xi; Narendran, Nadarajah; Zhu, Yiting; Freyssinier, Jean Paul

2016-09-01

Solid-state lighting (SSL) offers a new technology platform for lighting designers and end-users to illuminate spaces with low energy demand. Two types of SSL sources include organic light-emitting diodes (OLEDs) and light-emitting diodes (LEDs). OLED is an area light source, and its primary competing technology is the edge-lit LED panel. Generally, both of these technologies are considered similar in shape and appearance, but there is little understanding of how people perceive discomfort glare from large area light sources. The objective of this study was to evaluate discomfort glare for the two lighting technologies under similar operating conditions by gathering observers' reactions. The human factors study results showed no statistically significant difference in human response to discomfort glare between OLED and edge-lit LED panels when the two light sources produced the same lighting stimulus. This means both technologies appeared equally glary beyond a certain luminance.

Japanese Attitudes toward English Accents.

Science.gov (United States)

Chiba, Reiko; And Others

1995-01-01

Examined the attitudes of 169 Japanese university students toward varieties of spoken English. Results found that the students with more instrumental motivation were more positive toward nonnative English accents than those with less instrumental motivation, and that the students' familiarity with accents had an influence on their acceptance of…

Solution of multi-element LED light sources development automation problem

Science.gov (United States)

Chertov, Aleksandr N.; Gorbunova, Elena V.; Korotaev, Valery V.; Peretyagin, Vladimir S.

2014-09-01

The intensive development of LED technologies resulted in the creation of multicomponent light sources in the form of controlled illumination devices based on usage of mentioned LED technologies. These light sources are used in different areas of production (for example, in the food industry for sorting products or in the textile industry for quality control, etc.). The use of LED lighting products in the devices used in specialized lighting, became possible due to wide range of colors of light, LED structures (which determines the direction of radiation, the spatial distribution and intensity of the radiation, electrical, heat, power and other characteristics), and of course, the possibility of obtaining any shade in a wide dynamic range of brightness values. LED-based lighting devices are notable for the diversity of parameters and characteristics, such as color radiation, location and number of emitters, etc. Although LED technologies have several advantages, however, they require more attention if you need to ensure a certain character of illumination distribution and/or distribution of the color picture at a predetermined distance (for example, at flat surface, work zone, area of analysis or observation). This paper presents software designed for the development of the multicomponent LED light sources. The possibility of obtaining the desired color and energy distribution at the zone of analysis by specifying the spatial parameters of the created multicomponent light source and using of real power, spectral and color parameters and characteristics of the LEDs is shown as well.

CMOS-compatible plenoptic detector for LED lighting applications.

Science.gov (United States)

Neumann, Alexander; Ghasemi, Javad; Nezhadbadeh, Shima; Nie, Xiangyu; Zarkesh-Ha, Payman; Brueck, S R J

2015-09-07

LED lighting systems with large color gamuts, with multiple LEDs spanning the visible spectrum, offer the potential of increased lighting efficiency, improved human health and productivity, and visible light communications addressing the explosive growth in wireless communications. The control of this "smart lighting system" requires a silicon-integrated-circuit-compatible, visible, plenoptic (angle and wavelength) detector. A detector element, based on an offset-grating-coupled dielectric waveguide structure and a silicon photodetector, is demonstrated with an angular resolution of less than 1° and a wavelength resolution of less than 5 nm.

"Light-box" accelerated growth of poinsettias: LED-only illumination

Science.gov (United States)

Weerasuriya, Charitha; Detez, Stewart; Hock Ng, Soon; Hughes, Andrew; Callaway, Michael; Harrison, Iain; Katkus, Tomas; Juodkazis, Saulius

2018-01-01

For the current commercialized agricultural industry which requires a reduced product lead time to customer and supply all year round, an artificial light emitting diodes (LEDs)-based illumination has high potential due to high efficiency of electrical-to-light conversion. The main advantage of the deployed Red Green Blue Amber LED lighting system is colour mixing capability, which means ability to generate all the colours in the spectrum by using three or four primary colours LEDs. The accelerated plant growth was carried out in a "light-box" which was made to generate an artificial day/night cycle by moving the colour mixing ratio along the colour temperature curve of the chromaticity diagram. The control group of plants form the same initial batch was grown on the same shelf in a greenhouse at the same conditions with addition of artificial illumination by incandescent lamps for few hours. Costs and efficiency projections of LED lamps for horticultural applications is discussed together with required capital investment. The total cost of the "light-box" including LED lamps and electronics was 850 AUD.

A Neural Marker for Social Bias Toward In-group Accents.

Science.gov (United States)

Bestelmeyer, Patricia E G; Belin, Pascal; Ladd, D Robert

2015-10-01

Accents provide information about the speaker's geographical, socio-economic, and ethnic background. Research in applied psychology and sociolinguistics suggests that we generally prefer our own accent to other varieties of our native language and attribute more positive traits to it. Despite the widespread influence of accents on social interactions, educational and work settings the neural underpinnings of this social bias toward our own accent and, what may drive this bias, are unexplored. We measured brain activity while participants from two different geographical backgrounds listened passively to 3 English accent types embedded in an adaptation design. Cerebral activity in several regions, including bilateral amygdalae, revealed a significant interaction between the participants' own accent and the accent they listened to: while repetition of own accents elicited an enhanced neural response, repetition of the other group's accent resulted in reduced responses classically associated with adaptation. Our findings suggest that increased social relevance of, or greater emotional sensitivity to in-group accents, may underlie the own-accent bias. Our results provide a neural marker for the bias associated with accents, and show, for the first time, that the neural response to speech is partly shaped by the geographical background of the listener. © The Author 2014. Published by Oxford University Press.

Accent detection and social cognition: evidence of protracted learning.

Science.gov (United States)

Creel, Sarah C

2018-03-01

How and when do children become aware that speakers have different accents? While adults readily make a variety of subtle social inferences based on speakers' accents, findings from children are more mixed: while one line of research suggests that even infants may be acutely sensitive to accent unfamiliarity, other studies suggest that 5-year-olds have difficulty identifying accents as different from their own. In an attempt to resolve this paradox, the current study assesses American children's sensitivity to American vs. Dutch accents in two situations. First, in an eye-tracked sentence processing paradigm where children have previously shown sensitivity to a salient social distinction (gender) from voice cues, 3-5-year-old children showed no sensitivity to accent differences. Second, in a social decision-making task where accent sensitivity has been found in 5-year-olds, an age gradient appeared, suggesting that familiar accent preferences emerge slowly between 3 and 7 years. Counter to claims that accent is an early, salient signal of social group, results are more consistent with a protracted learning hypothesis that children need extended exposure to native-language sound patterns in order to detect that an accent deviates from their own. A video abstract of this article can be viewed at: https://www.youtube.com/watch?v=BQAgy3IFYXA. © 2017 John Wiley & Sons Ltd.

The use of light-emitting diodes (LED in commercial layer production

Directory of Open Access Journals (Sweden)

R Borille

2013-06-01

Full Text Available Artificial lighting is one of the most powerful management tools available to commercial layer producers. Artificial light allows anticipating or delaying the beginning of lay, improving egg production, and optimizing feed efficiency. This study aimed at comparing the performance of commercial layers submitted to lighting using different LED colors or conventional incandescent lamps. The study was carried out in a layer house divided in isolated environments in order to prevent any influenced from the neighboring treatments. In total, 360 Isa Brown layers, with an initial age of 56 weeks, were used. The following light sources were used: blue LED, yellow LED, green LED, red LED, white LED, and 40W incandescent light. Birds in all treatment were submitted to a 17-h continuous lighting program, and were fed a corn and soybean meal-based diet. A completely randomized experimental design with subplots was applied, with 24 treatments (six light sources and four periods of three replicates. Egg production (% was significantly different (p0.05 by light source. It was concluded that the replacement of incandescent light bulbs by white and red LEDs does not cause any negative effect on the egg production of commercial layers.

Goniometric characterization of LED based greenhouse lighting

DEFF Research Database (Denmark)

Thorseth, Anders; Lindén, Johannes; Corell, Dennis Dan

2015-01-01

This paper describes a demonstration of goniospectroradiometry for characterizations of new light emitting diode (LED) based luminaries for enhanced photosynthesis in greenhouses. It highlights the differences between measurement of the traditional high pressure sodium (HPS) luminaries and the LED...

Linguistic Processing of Accented Speech Across the Lifespan

Directory of Open Access Journals (Sweden)

Alejandrina eCristia

2012-11-01

Full Text Available In most of the world, people have regular exposure to multiple accents. Therefore, learning to quickly process accented speech is a prerequisite to successful communication. In this paper, we examine work on the perception of accented speech across the lifespan, from early infancy to late adulthood. Unfamiliar accents initially impair linguistic processing by infants, children, younger adults, and older adults, but listeners of all ages come to adapt to accented speech. Emergent research also goes beyond these perceptual abilities, by assessing links with production and the relative contributions of linguistic knowledge and general cognitive skills. We conclude by underlining points of convergence across ages, and the gaps left to face in future work.

LED Context Lighting System in Residential Areas

Directory of Open Access Journals (Sweden)

Sook-Youn Kwon

2014-01-01

Full Text Available As issues of environment and energy draw keen interest around the globe due to such problems as global warming and the energy crisis, LED with high optical efficiency is brought to the fore as the next generation lighting. In addition, as the national income level gets higher and life expectancy is extended, interest in the enhancement of life quality is increasing. Accordingly, the trend of lightings is changing from mere adjustment of light intensity to system lighting in order to enhance the quality of one’s life as well as reduce energy consumption. Thus, this study aims to design LED context lighting system that automatically recognizes the location and acts of a user in residential areas and creates an appropriate lighting environment. The proposed system designed in this study includes three types of processing: first, the creation of a lighting environment index suitable for the user’s surroundings and lighting control scenarios and second, it measures and analyzes the optical characteristics that change depending on the dimming control of lighting and applies them to the index. Lastly, it adopts PIR, piezoelectric, and power sensor to grasp the location and acts of the user and create a lighting environment suitable for the current context.

Fuselage mounted anti-collision lights utilizing high power LEDs

Science.gov (United States)

Lundberg, John; Machi, Nicolo; Mangum, Scott; Singer, Jeffrey

2005-09-01

As LEDs continue to improve in efficacy and total light output, they are increasingly finding their way in to new applications in the aviation industry as well as adjacent markets. One function that is particularly challenging and may reap substantial benefits from this new technology is the fuselage mounted anti-collision light. Anti-collision lights provide conspicuity for the aircraft by periodically emitting bright flashes of light. The color, light distribution and intensity levels for these lights are all closely regulated through Federal Aviation Regulation (FAR) documents. These lighting requirements, along with thermal, environmental and aerodynamic requirements, drive the overall design. In this paper, we will discuss the existing technologies used in anti-collision lights and the advantages and challenges associated with an LED solution. Particular attention will be given to the optical, thermal, electrical and aerodynamic aspects associated with an LED approach. A specific case study will be presented along with some of the challenges that have arisen during the design process. These challenges include the addition of an integrated covert anti-collision lighting.

Application of high-brightness LEDs in aircraft position lights

Science.gov (United States)

Machi, Nicolo; Mangum, Scott; Singer, Jeffrey M.

2004-10-01

Solid state lighting devices have made their way into a number of niche markets and continue to make inroads into other markets as their price / performance ratios improve. One of these markets is aviation lighting. Although this paper will focus on the use of LEDs for aircraft position lights, much of the discussion is applicable to other installations on the interior and exterior of the aircraft. The color, light distribution and intensity levels for a position light are all closely regulated through Code of Federal Regulation (CFR; formerly Federal Aviation Regulation (FAR)) documents. These lighting requirements, along with harsh thermal and environmental requirements, drive the design. In this paper, we will look at these requirements and discuss what is required in order to use LEDs for this type of application. We will explore the optical, thermal and electrical issues associated with the use of LEDs for position lights and examine the specific case study of the Astreon forward position lights. Finally, we will discuss some of the challenges that we see with solid state lighting in current and future aircraft applications.

Effect of light dispersion of LED curing lights on resin composite polymerization.

Science.gov (United States)

Vandewalle, Kraig S; Roberts, Howard W; Andrus, Jeffrey L; Dunn, William J

2005-01-01

This study evaluated the effect of light dispersion of halogen and LED curing lights on resin composite polymerization. One halogen (Optilux 501, SDS/Kerr, Orange, CA, USA) and five light-emitting diode (LED) curing lights (SmartLite iQ, Dentsply Caulk, Milford, DE, USA; LEDemetron 1, SDS/Kerr; FLASHlite 1001, Discus Dental, Culver City, CA, USA; UltraLume LED 5, Ultradent Products, South Jordan, UT, USA; Allegro, Den-Mat, Santa Maria, CA, USA) were used in this study. Specimens (8 mm diameter by 2 mm thick) were made in polytetrafluoroethylene molds using hybrid (Z100, 3M ESPE, St. Paul, MN, USA) and microfill (A110, 3M ESPE) composite resins. The top surface was polymerized for 5 seconds with the curing light guide tip positioned at a distance of 1 and 5 mm. Degree of conversion (DC) of the composite specimens was analyzed on the bottom surface using micro-Fourier Transform Infrared (FTIR) spectroscopy (Perkin-Elmer FTIR Spectrometer, Wellesley, PA, USA) 10 minutes after light activation. DC at the bottom of the 2 mm specimen was expressed as a percentage of the mean maximum DC. Five specimens were created per curing light and composite type (n=5). Percent mean DC ratios and SDs were calculated for each light under each testing condition. Data were analyzed by analysis of variance (ANOVA)/Tukey's test (alpha = .05). A beam analyzer (LBA-700, Spiricon, Logan, UT, USA) was used to record the emitted light from the curing lights at 0 and 5 mm distances (n=5). A Top Hat factor was used to compare the quality of the emitted beam profile (LBA/PC, Spiricon). The divergence angle from vertical was also determined in the x- and y-axes (LBA/PC). Mean values and SDs were calculated for each light under each testing condition (0 and 5 mm, x- and y-axes) and analyzed by a two-way ANOVA/Tukey's test (alpha = .05). For DC ratios, significant differences were found based on curing light and curing distance (p < .05). At 1 mm, Optilux 501 and FLASHlite 1001 produced significantly

Materials and Designs for High-Efficacy LED Light Engines

Energy Technology Data Exchange (ETDEWEB)

Ibbetson, James [Cree, Inc., Durham, NC (United States); Gresback, Ryan [Cree, Inc., Durham, NC (United States)

2017-09-28

Cree, Inc. conducted a narrow-band downconverter (NBD) materials development and implementation program which will lead to warm-white LED light engines with enhanced efficacy via improved spectral efficiency with respect to the human eye response. New red (600-630nm) NBD materials could result in as much as a 20% improvement in warm-white efficacy at high color quality relative to conventional phosphor-based light sources. Key program innovations included: high quantum yield; narrow peak width; minimized component-level losses due to “cross-talk” and light scattering among red and yellow-green downconverters; and improved reliability to reach parity with conventional phosphors. NBD-enabled downconversion efficiency gains relative to conventional phosphors yielded an end-of-project LED light engine efficacy of >160 lm/W at room temperature and 35 A/cm2, with a correlated color temperature (CCT) of ~3500K and >90 CRI (Color Rending Index). NBD-LED light engines exhibited equivalent luminous flux and color point maintenance at >1,000 hrs. of highly accelerated reliability testing as conventional phosphor LEDs. A demonstration luminaire utilizing an NBD-based LED light engine had a steady-state system efficacy of >150 lm/W at ~3500K and >90 CRI, which exceeded the 2014 DOE R&D Plan luminaire milestone for FY17 of >150 lm/W at just 80 CRI.

Warm white LEDs lighting over Ra=95 and its applications

Science.gov (United States)

Kobashi, Katsuya; Taguchi, Tsunemasa

2007-02-01

We have for the first time developed warm white LEDs lighting using a combination of near ultraviolet LED and three-band (red, green and blue) white phosphors. This LED has the average color-rendering index Ra=96. Moreover, special color-rendering index R9 (red) and R15 (face color of Japanese) are estimated to be 95 and 97, respectively. We will describe the results of evaluation on the medical lighting applications such as operation, treatment and endoscope experiments, application to the LED fashions and application to the Japanese antique art (ink painting) lighting.

The Development of LED-Based Dental Light Using a Multiplanar Reflector Design

Directory of Open Access Journals (Sweden)

Chi-Chang Hsieh

2014-01-01

Full Text Available A multiplanar reflector was designed to enhance the application efficiency of light-emitting diode (LED light sources that can be employed as LED-based dental lights. This study used a high-power LED developed by Nichia, that is, a single LED capable of providing a total luminous flux of 120 lm, as the primarily light source to design and develop an LED-based dental light. This LED complies with the international standards and regulations stipulated in ISO 9680:2007. The light spots produced by the prototype were rectangular, with a length of 200 mm and a width of 100 mm. These light spots achieved maximum illumination of 12,000 lux. The use of LEDs can reduce energy consumption from 50 W to 3 W, providing an energy saving of more than 90%.

LED Lighting in a Performing Arts Building

Energy Technology Data Exchange (ETDEWEB)

Miller, N. J.; Kaye, S. M. [Univ. of Florida, Gainesville, FL (United States); Coleman, P. M. [Univ. of Florida, Gainesville, FL (United States); Wilkerson, A. M.; Perrin, T. E.; Sullivan, G. P. [Efficiency Solutions, Inc., Richland, WA (United States)

2014-07-31

At the University of Florida in Gainesville, the DOE Solid-State Lighting GATEWAY program evaluated LED architectural and theatrical lighting in four academic/performance-related spaces within the Nadine McGuire Theatre + Dance Pavilion. Due to a wise choice of products and luminaire light distributions, the change brought significant quality improvements including improved controllability and color.

Current-voltage model of LED light sources

DEFF Research Database (Denmark)

Beczkowski, Szymon; Munk-Nielsen, Stig

2012-01-01

Amplitude modulation is rarely used for dimming light-emitting diodes in polychromatic luminaires due to big color shifts caused by varying magnitude of LED driving current and nonlinear relationship between intensity of a diode and driving current. Current-voltage empirical model of light...

[Study on the safety of blue light leak of LED].

Science.gov (United States)

Shen, Chong-Yu; Xu, Zheng; Zhao, Su-Ling; Huang, Qing-Yu

2014-02-01

In this paper, the blue light properties of LED illumination devices have been investigated. Against the status quo of China's LED lighting, we measured the spectrum component of LED lamps and analyzed the photobiological safety under the current domestic and international standards GB/T 20145-2006/CIE S009/E: 2002 and IEC62471: 2006 standards as well as CTL-0744_2009-laser resolution, which provides the reference to the manufacture of LED lighting lamps as well as related safety standards and laws. If the radiance intensity of blue light in LED is lower than 100 W x m(-2) x Sr(-1), there is no harm to human eyes. LEDs will not cause harm to human eyes under normal use, but we should pay attention to the protection of special populations (children), and make sure that they avoid looking at a light source for a long time. The research has found that the blue-rich lamps can affect the human rule of work and rest, and therefore, the LED lamps with color temperature below 4 000 K and color rendering index of 80 are suitable for indoor use. At the same time, the lamps with different parameters should be selected according to the different distances.

Stolephorus sp Behavior in Different LED (Light Emitting Diode) Color and Light Intensities

Science.gov (United States)

Fitri Aristi, D. P.; Ramadanita, I. A.; Hapsari, T. D.; Susanto, A.

2018-02-01

This research aims to observe anchovy (Stolephorus sp) behavior under different LED light intensities that affect eye physiology (cell cone structure). The materials used were Stolephorus sp taken from the waters off Jepara and 13 and 10 watt light emitting diode (LED). The research method was an experiment conducted from March through August 2015 in the waters off Jepara. Data analysis of visual histology and fish respond was carried out at the fishing gear material laboratory, anatomy and cultivate. Cone cell structure (mosaic cone) of Stolephorus sp forms a connected regular square pattern with every single cone surrounded by four double cones, which indicate that anchovies are sensitive to light. The 13 watt LED (628 lux) has faster response than the 10 watt LED (531 lux) as it has wider and higher emitting intensity, which also attracts fish to gather quicker.

Efficient conceptual design for LED-based pixel light vehicle headlamps

Science.gov (United States)

Held, Marcel Philipp; Lachmayer, Roland

2017-12-01

High-resolution vehicle headlamps represent a future-oriented technology that can be used to increase traffic safety and driving comfort. As a further development to the current Matrix Beam headlamps, LED-based pixel light systems enable ideal lighting functions (e.g. projection of navigation information onto the road) to be activated in any given driving scenario. Moreover, compared to other light-modulating elements such as DMDs and LCDs, instantaneous LED on-off toggling provides a decisive advantage in efficiency. To generate highly individualized light distributions for automotive applications, a number of approaches using an LED array may be pursued. One approach is to vary the LED density in the array so as to output the desired light distribution. Another notable approach makes use of an equidistant arrangement of the individual LEDs together with distortion optics to formulate the desired light distribution. The optical system adjusts the light distribution in a manner that improves resolution and increases luminous intensity of the desired area. An efficient setup for pixel generation calls for one lens per LED. Taking into consideration the limited space requirements of the system, this implies that the luminous flux, efficiency and resolution image parameters are primarily controlled by the lens dimensions. In this paper a concept for an equidistant LED array arrangement utilizing distortion optics is presented. The paper is divided into two parts. The first part discusses the influence of lens geometry on the system efficiency whereas the second part investigates the correlation between resolution and luminous flux based on the lens dimensions.

Light emitting diodes (LED): applications in forest and native plant nurseries

Science.gov (United States)

Thomas D. Landis; Jeremiah R. Pinto; R. Kasten Dumroese

2013-01-01

It was quotes like this that made us want to learn more about light emitting diodes (LED). Other than knowing that LEDs were the latest innovation in artificial lighting, we knew that we had a lot to learn. So we started by reviewing some of the basics. The following review is a brief synopsis of how light affects plants and some discussion about LED lighting. If you...

Visual color matching system based on RGB LED light source

Science.gov (United States)

Sun, Lei; Huang, Qingmei; Feng, Chen; Li, Wei; Wang, Chaofeng

2018-01-01

In order to study the property and performance of LED as RGB primary color light sources on color mixture in visual psychophysical experiments, and to find out the difference between LED light source and traditional light source, a visual color matching experiment system based on LED light sources as RGB primary colors has been built. By simulating traditional experiment of metameric color matching in CIE 1931 RGB color system, it can be used for visual color matching experiments to obtain a set of the spectral tristimulus values which we often call color-matching functions (CMFs). This system consists of three parts: a monochromatic light part using blazed grating, a light mixing part where the summation of 3 LED illuminations are to be visually matched with a monochromatic illumination, and a visual observation part. The three narrow band LEDs used have dominant wavelengths of 640 nm (red), 522 nm (green) and 458 nm (blue) respectively and their intensities can be controlled independently. After the calibration of wavelength and luminance of LED sources with a spectrophotometer, a series of visual color matching experiments have been carried out by 5 observers. The results are compared with those from CIE 1931 RGB color system, and have been used to compute an average locus for the spectral colors in the color triangle, with white at the center. It has been shown that the use of LED is feasible and has the advantages of easy control, good stability and low cost.

Photobiocatalytic alcohol oxidation using LED light sources

NARCIS (Netherlands)

Rauch, M.C.R.; Schmidt, S.; Arends, I.W.C.E.; oppelt, K.; Kara, S; Hollmann, F.

2016-01-01

The photocatalytic oxidation of NADH using a flavin photocatalyst and a simple blue LED light source is reported. This in situ NAD+ regeneration system can be used to promote biocatalytic, enantioselective oxidation reactions. Compared to the traditional use of white light bulbs this method enables

Future Solid State Lighting using LEDs and Diode Lasers

DEFF Research Database (Denmark)

Petersen, Paul Michael

2014-01-01

applications. Within the coming years, it is expected that the efficiency of blue laser diodes will approach the efficiency of infrared diode lasers. This will enable high efficiency white light generation with very high lumen per watt values. SSL today is mainly based on phosphor converted blue light emitting......Lighting accounts for 20% of all electrical energy usage. Household lighting and commercial lighting such as public and street lighting are responsible for significant greenhouse gas emissions. Therefore, currently many research initiatives focus on the development of new light sources which shows...... significant savings. Solid state lighting (SSL) based on LEDs is today the most efficient light source for generation of high quality white light. Diode lasers, however, have the potential of being more efficient than LEDs for the generation of white light. A major advantage using diode lasers for solid state...

A new LED light source for display cases

DEFF Research Database (Denmark)

Dam-Hansen, Carsten; Petersen, Paul Michael

Abstract: We report a new LED light source suitable for illumination of gold objects. It has a variable correlated color temperature from 2760 K to 2200 K with a high color rendering index up to 97.......Abstract: We report a new LED light source suitable for illumination of gold objects. It has a variable correlated color temperature from 2760 K to 2200 K with a high color rendering index up to 97....

High-Voltage LED Light Engine with Integrated Driver

Energy Technology Data Exchange (ETDEWEB)

Soer, Wouter [Lumileds LLC, San Jose, CA (United States)

2016-02-29

LED luminaires have seen dramatic changes in cost breakdown over the past few years. The LED component cost, which until recently was the dominant portion of luminaire cost, has fallen to a level of the same order as the other luminaire components, such as the driver, housing, optics etc. With the current state of the technology, further luminaire performance improvement and cost reduction is realized most effectively by optimization of the whole system, rather than a single component. This project focuses on improving the integration between LEDs and drivers. Lumileds has developed a light engine platform based on low-cost high-power LEDs and driver topologies optimized for integration with these LEDs on a single substrate. The integration of driver and LEDs enables an estimated luminaire cost reduction of about 25% for targeted applications, mostly due to significant reductions in driver and housing cost. The high-power LEDs are based on Lumileds’ patterned sapphire substrate flip-chip (PSS-FC) technology, affording reduced die fabrication and packaging cost compared to existing technology. Two general versions of PSS-FC die were developed in order to create the desired voltage and flux increments for driver integration: (i) small single-junction die (0.5 mm²), optimal for distributed lighting applications, and (ii) larger multi-junction die (2 mm² and 4 mm²) for high-power directional applications. Two driver topologies were developed: a tapped linear driver topology and a single-stage switch-mode topology, taking advantage of the flexible voltage configurations of the new PSS-FC die and the simplification opportunities enabled by integration of LEDs and driver on the same board. A prototype light engine was developed for an outdoor “core module” application based on the multi-junction PSS-FC die and the single-stage switch-mode driver. The light engine meets the project efficacy target of 128 lm/W at a luminous flux

LED Street Lighting Solutions: Flagstaff, Arizona as a Case Study

Science.gov (United States)

Hall, Jeffrey C.

2018-01-01

Dark-sky protection in Flagstaff, Arizona extends back to 1958, with the first ordinance in the City banning advertising floodlights. The current ordinance, adopted in 1989, is comprehensive and has played a critical role in maintaining the quality of the night sky for astronomy, tourism, public enjoyment, and other purposes. Flagstaff, like many communities around the world, is now working on a transition from legacy bulb-based technology to LED for its outdoor lighting. The City, Lowell Observatory, the U. S. Naval Observatory, and the Flagstaff Dark Skies Coalition have been working intensively for two years to identify an LED-based street lighting solution that will preserve the City's dark skies while meeting municipal needs. We will soon be installing test fixtures for an innovative solution incorporating narrow-band amber LED and modest amounts of low-CCT white LED. In this talk, I will review the types of LEDs available for outdoor lighting and discuss the plans for Flagstaff's street lighting in the LED era, which we hope will be a model for communities worldwide.

Integrated Automotive High-Power LED-Lighting Systems in 3D-MID Technology

NARCIS (Netherlands)

Thomas, W.

2014-01-01

The growing energy consumption of lighting as well as rising luminous efficacies and -fluxes of high-power Light Emitting Diodes (LEDs) have contributed to the widespread use of LEDs in modern lighting systems. One of the most prominent users of the LED-technology is automotive (exterior) lighting.

White light-emitting diodes (LEDs) using (oxy)nitride phosphors

International Nuclear Information System (INIS)

Xie, R-J; Hirosaki, N; Sakuma, K; Kimura, N

2008-01-01

(Oxy)nitride phosphors have attracted great attention recently because they are promising luminescent materials for phosphor-converted white light-emitting diodes (LEDs). This paper reports the luminescent properties of (oxy)nitride phosphors in the system of M-Si-Al-O-N (M = Li, Ca or Sr), and optical properties of white LEDs using a GaN-based blue LED and (oxy)nitride phosphors. The phosphors show high conversion efficiency of blue light, suitable emission colours and small thermal quenching. The bichromatic white LEDs exhibit high luminous efficacy (∼55 lm W -1 ) and the multi-phosphor converted white LEDs show high colour rendering index (Ra 82-95). The results indicate that (oxy)nitride phosphors demonstrate their superior suitability to use as down-conversion luminescent materials in white LEDs

Accents in the workplace: their effects during a job interview.

Science.gov (United States)

Deprez-Sims, Anne-Sophie; Morris, Scott B

2010-12-01

As the workplace becomes increasingly global, organizations are more likely to employ persons from other countries whose accents clearly identify them as different from the local workforce. Understanding the impact of accents in the workplace is important because accents can be salient in the same way as ethnicity, age, gender, and skin color and may be a source of employment discrimination. The present study looked at the influence of accents on the evaluation of job applicants during an interview for a human resource manager position. Participants from the US were asked to evaluate an applicant with one of three accents (Midwestern US, French, Colombian) by listening to an audiofile. The results showed that the applicant with the Midwestern US accent was evaluated more positively than the applicant with the French accent; however, the applicant with the Colombian accent did not receive an evaluation that differed significantly from those given to the applicants with either the French or the Midwestern US accent. Analyses of process variables indicated that the bias against the French-accented applicant was mediated by perceived lower similarity. These results are consistent with the similarity-attraction hypothesis, which states that demographic variables will impact judgments to the extent to which they make the decision-maker view the applicant as similar or dissimilar. The ability of accent to trigger bias highlights the importance of considering the full array of characteristics that can lead to discrimination in employment settings. Research on employment discrimination has traditionally focused on visual cues such as gender and ethnicity, but in an interview situation, the way the applicant speaks is also important.

Improving “color rendering” of LED lighting for the growth of lettuce

Science.gov (United States)

Han, Tao; Vaganov, Vitaliy; Cao, Shixiu; Li, Qiang; Ling, Lili; Cheng, Xiaoyao; Peng, Lingling; Zhang, Congzhi; Yakovlev, Alexey N.; Zhong, Yang; Tu, Mingjing

2017-04-01

Light plays a vital role on the growth and development of plant. On the base of white light with high color rendering to the benefit of human survival and life, we proposed to improve “color rendering” of LED lighting for accelerating the growth of lettuce. Seven spectral LED lights were adopted to irradiate the lettuces under 150 μmol·m-2·s-1 for a 16 hd-1 photoperiod. The leaf area and number profiles, plant biomass, and photosynthetic rate under the as-prepared LED light treatments were investigated. We let the absorption spectrum of fresh leaf be the emission spectrum of ideal light and then evaluate the “color rendering” of as-prepared LED lights by the Pearson product-moment correlation coefficient and CIE chromaticity coordinates. Under the irradiation of red-yellow-blue light with high correlation coefficient of 0.587, the dry weights and leaf growth rate are 2-3 times as high as the sharp red-blue light. The optimized LED light for lettuce growth can be presumed to be limited to the angle (about 75°) between the vectors passed through the ideal light in the CIE chromaticity coordinates. These findings open up a new idea to assess and find the optimized LED light for plant growth.

Setup of a LED light-pulser system for the OLYMPUS experiment; Aufbau eines LED-Lichtpulsersystems fuer das OLYMPUS-Experiment

Energy Technology Data Exchange (ETDEWEB)

Rehman, Waqaas

2011-12-15

The aim of this thesis consists in the construction and test of an external light-calibration system based on light-emitting diodes (LED) for the application at the symmetric Moller/Bhabha (SYMB) luminosity monitor. In chapter 2 the theoretical foundations of the OLYMPUS experiment, especially of the SYMB luminosity monitor are explained. Thereafter in chapter 3 the details of the setup of the OLYMPUS experiment and the fundamental properties of the SYMB detectors are discussed. In chapter 4 the whole concept of the LED light-pulser system is treated. In chapter 5 then test measurements with the ready LED light-pulser system are described. Thereby the light source shall be optimized in the shape that thereafter light pulses with short signal width are producable. Also different measurements for the unique characterization of the systems are performed. In chapter 6 light-intensity measurements during the operation of the LED light-pulser system are described.

Anti-glare LED lamps with adjustable illumination light field.

Science.gov (United States)

Chen, Yung-Sheng; Lin, Chung-Yi; Yeh, Chun-Ming; Kuo, Chie-Tong; Hsu, Chih-Wei; Wang, Hsiang-Chen

2014-03-10

We introduce a type of LED light-gauge steel frame lamp with an adjustable illumination light field that does not require a diffusion plate. Base on the Monte Carlo ray tracing method, this lamp has a good glare rating (GR) of 17.5 at 3050 lm. Compared with the traditional LED light-gauge steel frame lamp (without diffusion plate), the new type has low GR. The adjustability of the illumination light field could improve the zebra effect caused by the inadequate illumination light field of the lamp. Meanwhile, we adopt the retinal image analysis to discuss the influence of GR on vision. High GR could reflect stray light on the retinal image, which will reduce vision clarity and hasten the feeling of eye fatigue.

Progress in extremely high brightness LED-based light sources

Science.gov (United States)

Hoelen, Christoph; Antonis, Piet; de Boer, Dick; Koole, Rolf; Kadijk, Simon; Li, Yun; Vanbroekhoven, Vincent; Van De Voorde, Patrick

2017-09-01

Although the maximum brightness of LEDs has been increasing continuously during the past decade, their luminance is still far from what is required for multiple applications that still rely on the high brightness of discharge lamps. In particular for high brightness applications with limited étendue, e.g. front projection, only very modest luminance values in the beam can be achieved with LEDs compared to systems based on discharge lamps or lasers. With dedicated architectures, phosphor-converted green LEDs for projection may achieve luminance values up to 200-300 Mnit. In this paper we report on the progress made in the development of light engines based on an elongated luminescent concentrator pumped by blue LEDs. This concept has recently been introduced to the market as ColorSpark High Lumen Density LED technology. These sources outperform the maximum brightness of LEDs by multiple factors. In LED front projection, green LEDs are the main limiting factor. With our green modules, we now have achieved peak luminance values of 2 Gnit, enabling LED-based projection systems with over 4000 ANSI lm. Extension of this concept to yellow and red light sources is presented. The light source efficiency has been increased considerably, reaching 45-60 lm/W for green under practical application conditions. The module architecture, beam shaping, and performance characteristics are reviewed, as well as system aspects. The performance increase, spectral range extensions, beam-shaping flexibility, and cost reductions realized with the new module architecture enable a breakthrough in LED-based projection systems and in a wide variety of other high brightness applications.

Design for The Indoor Visible Light Communication Application System Based on LED Visible Light

Directory of Open Access Journals (Sweden)

Lian Wenyu

2017-01-01

Full Text Available This paper designs an indoor visible light communication application system based on LED. The system can modulate the original signal one or more times, move to a specific frequency band, transmit on the power line, in the LED terminal use this module to decode, restore the Ethernet signals. This design is applicable to the simplicity of the LED visible light communication applications, which provide the premise and guarantee for the construction of smart home network.

Malaysian University Students’ Attitudes towards Six Varieties of Accented Speech in English

Directory of Open Access Journals (Sweden)

Zainab Thamer Ahmed

2014-10-01

Full Text Available Previous language attitude studies indicated that in many countries all over the world, English language learners perceived native accents either American or British, more positively than the non-native accents such as the Japanese, Korean, and Austrian accents. However, in Malaysia it is still unclear which accent Malaysian learners of English tend to perceive more positively (Pillai 2009. The verbal-guise technique and accent recognition item were adopted as indirect and direct instruments in gathering data to obtain data to clarify the inquiry. The sample includes 120 Malaysian university students and they were immersed in several speech accent situations to elicit feedback on their perceptions. Essentially two research questions are addressed: 1 What are Malaysian university students’ attitudes toward native and non-native English accents? 2 How familiar are students with accents?  The results indicated that the students had a bias towards in-group accent, meaning that they evaluated non-native lecturers’ accents more positively. These results supported the ‘social identity theory’ consistent with many previous language attitude studies of this nature. The Malaysian students were seen to be able to distinguish between native and non-native accents although there was much confusion between British and American accents.

The influence of talker and foreign-accent variability on spoken word identification.

Science.gov (United States)

Bent, Tessa; Holt, Rachael Frush

2013-03-01

In spoken word identification and memory tasks, stimulus variability from numerous sources impairs performance. In the current study, the influence of foreign-accent variability on spoken word identification was evaluated in two experiments. Experiment 1 used a between-subjects design to test word identification in noise in single-talker and two multiple-talker conditions: multiple talkers with the same accent and multiple talkers with different accents. Identification performance was highest in the single-talker condition, but there was no difference between the single-accent and multiple-accent conditions. Experiment 2 further explored word recognition for multiple talkers in single-accent versus multiple-accent conditions using a mixed design. A detriment to word recognition was observed in the multiple-accent condition compared to the single-accent condition, but the effect differed across the language backgrounds tested. These results demonstrate that the processing of foreign-accent variation may influence word recognition in ways similar to other sources of variability (e.g., speaking rate or style) in that the inclusion of multiple foreign accents can result in a small but significant performance decrement beyond the multiple-talker effect.

Effect of Led Lighting Colors for Laying Japanese Quails

Directory of Open Access Journals (Sweden)

KC Nunes

Full Text Available ABSTRACT Time of exposure and light intensity rearing house may affect the performance and egg quality of laying quails. This research aimed at evaluating the live performance, egg quality, biometry of the reproductive system, and the gastrointestinal tract of Japanese quails (Coturnix coturnix japonica exposed to artificial light-emitting diodes (LED of different colors in comparison with fluorescent lamps. A total of 240 Japanese quails were distributed in completely randomized experimental design with four treatments (fluorescent lamp, and green, red, or blue LED lamps with six replicates of 10 birds each. Average egg weight and eggshell thickness were different (p0.05. The oviduct of 64-d-old hens exposed to green LED lighting was shorter (p<0.05 than those exposed to the fluorescent lamp. Red LED can be used to replace the fluorescent lamps, as they promote the same live performance, egg quality, and morphological development of the reproductive tract of laying Japanese quails.

Control and Driving Methods for LED Based Intelligent Light Sources

OpenAIRE

Beczkowski, Szymon

2012-01-01

High power light-emitting diodes allow the creation of luminaires capable of generating saturated colour light at very high efficacies. Contrary to traditional light sources like incandescent and high-intensity discharge lamps, where colour is generated using filters, LEDs use additive light mixing, where the intensity of each primary colour diode has to be adjusted to the needed intensity to generate specified colour. The function of LED driver is to supply the diode with power needed to ach...

Effect of LED lighting on the cooling and heating loads in office buildings

International Nuclear Information System (INIS)

Ahn, Byung-Lip; Jang, Cheol-Yong; Leigh, Seung-Bok; Yoo, Seunghwan; Jeong, Hakgeun

2014-01-01

Highlights: • Application of heat control strategy reduces total energy consumption of LED lighting. • Convective heat from LED lighting should be emitted outdoors during cooling period. • Seasonal optimization of convective heat lowers total energy consumption. - Abstract: LED lighting has the potential to provide energy savings, and in many countries, there are policies to encourage its use owing to its higher efficiency and longer life in comparison to other lighting fixtures. However, since 75–85% of the light electric power in LED lights is still generated as heat, the sole use of LED lighting in a building could have a negative effect on the cooling load. In this paper, we study the heating properties of LED lighting and establish a management strategy to exploit these properties to reduce the energy used for heating and cooling of buildings. Using a simulation program, the energy consumption of the Green Building in Daejeon, Korea, and the virtual building provided by the U.S. Department of Energy (DOE) was computed according for different light fixtures. A control strategy is more applicable to LED lighting than to general fluorescent lighting, especially for the cooling of a building, because the use of a return-air duct and the heat sinks on the LED fixtures allow the heat to be better directed. Deployment of LED lights in combination with such a control strategy can help to increase the energy efficiency of a building

Demonstration Assessment of Light-Emitting Diode (LED) Parking Lot Lighting in Leavenworth, KS

Energy Technology Data Exchange (ETDEWEB)

Myer, Michael; Kinzey, Bruce R.; Curry, Ku' uipo

2011-05-06

This report describes the process and results of a demonstration of solid-state lighting (SSL) technology in a commercial parking lot lighting application, under the U.S. Department of Energy (DOE) Solid-State Lighting Technology GATEWAY Demonstration Program. The parking lot is for customers and employees of a Walmart Supercenter in Leavenworth, Kansas and this installation represents the first use of the LED Parking Lot Performance Specification developed by the DOE’s Commercial Building Energy Alliance. The application is a parking lot covering more than a half million square feet, lighted primarily by light-emitting diodes (LEDs). Metal halide wall packs were installed along the building facade. This site is new construction, so the installed baseline(s) were hypothetical designs. It was acknowledged early on that deviating from Walmart’s typical design would reduce the illuminance on the site. Walmart primarily uses 1000W pulse-start metal halide (PMH) lamps. In order to provide a comparison between both typical design and a design using conventional luminaires providing a lower illuminance, a 400W PMH design was also considered. As mentioned already, the illuminance would be reduced by shifting from the PMH system to the LED system. The Illuminating Engineering Society of North America (IES) provides recommended minimum illuminance values for parking lots. All designs exceeded the recommended illuminance values in IES RP-20, some by a wider margin than others. Energy savings from installing the LED system compared to the different PMH systems varied. Compared to the 1000W PMH system, the LED system would save 63 percent of the energy. However, this corresponds to a 68 percent reduction in illuminance as well. In comparison to the 400W PMH system, the LED system would save 44 percent of the energy and provide similar minimum illuminance values at the time of relamping. The LED system cost more than either of the PMH systems when comparing initial costs

Effect of LED light on seeds of Capsicum annuum L. var. serrano

Directory of Open Access Journals (Sweden)

Alejandra María Moreno-Jiménez

2017-11-01

Full Text Available Serrano pepper (Capsicum annuum L. is a crop of economic, nutritional and medicinal importance; so it is necessary to increase its production and improve its characteristics. The objective of this research was to evaluate the stimulatory effect of light emitting diodes (LEDs on serrano pepper seedlings. Germination percentage, stem length, leaf width, leaf length, number of leaves, total chlorophyll content and carotenoid content were analyzed. The seeds were exposed to white, blue and red LED light, using fluorescent light as a control and a photoperiod of 11/13 hours. Once germinated, the seedlings continued with exposure to light for 30 days. After the laboratory conditions, the seedlings were transferred to a greenhouse for 60 days. The results show that there were no significant differences between LED light treatments on seed germination. The variables stem length, leaf width and leaf length, were favored with red light. Blue and red LEDs highlighted by increasing the number of leaves. Seedlings treated with blue light showed the highest content of photosynthetic pigments (chlorophyll= 0.84 mg g-1, carotenoid= 0.12 mg g-1. In conclusion, the red LED light is effective for the growth of serrano pepper seedlings, while the production of photosynthetic pigments was favored by blue LED light.   Keywords: peppers, light-emitting diodes, germination, growth, photosynthetic pigments

Interior LED Lighting Technology. Navy Energy Technology Validation (Techval) Program

Science.gov (United States)

2015-09-01

usually on most of the time. • Consider replacing existing CFL, high-intensity discharge (HID), or halogen lamp light fixtures/ lamps with LED fixtures... lamps . What is the Technology? An LED is a semiconductor-diode that emits light when power is applied. A driver is used, much as a ballast, to...available in integrated luminaires that can be used to replace existing luminaires. LEDs are also available as direct replacement lamps for many

LED; Zum Thema LED

Energy Technology Data Exchange (ETDEWEB)

NONE

2010-07-01

This collection of articles on the subject of light emitting diodes (LED) provides technical information on LED technology, examines latest developments and provides examples of LED use in practice. An 'ABC' of LED technology is presented and fifteen common LED mistakes are noted. The chances and risks of LED use are discussed as is the retrofitting of lighting installations with LEDs. The use of LEDs in street lighting is examined. The journal also includes interviews with architects and a lighting designer. Practical examples of the use of LEDs include the refurbished parliamentary library in Berne, their use in the bird sanctuary headquarters in Sempach, Switzerland, as well as LED use in sales outlets. Also, the use of LED lighting in a spa gazebo in Lucerne is examined.

Focus, accent, and argument structure: effects on language comprehension.

Science.gov (United States)

Birch, S; Clifton, C

1995-01-01

Four experiments investigated the effect of syntactic argument structure on the evaluation and comprehension of utterances with different patterns of pitch accents. Linguistic analyses of the relation between focus and prosody note that it is possible for certain accented constituents within a broadly focused phrase to project focus to the entire phrase. We manipulated focus requirements and accent in recorded question-answer pairs and asked listeners to make linguistic judgments of prosodic appropriateness (Experiments 1 and 3) or to make judgments based on meaningful comprehension (Experiments 2 and 4). Naive judgments of prosodic appropriateness were generally consistent with the linguistic analyses, showing preferences for utterances in which contextually new noun phrases received accent and old noun phrases did not, but suggested that an accented new argument NP was not fully effective in projecting broad focus to the entire VP. However, the comprehension experiments did demonstrate that comprehension of a sentence with broad VP focus was as efficient when only a lexical argument NP received accent as when both NP and verb received accent. Such focus projection did not occur when the argument NP was an "independent quantifier" such as nobody or everything. The results extend existing demonstrations that the ease of understanding spoken discourse depends on appropriate intonational marking of focus to cases where certain structurally-defined words can project focus-marking to an entire phrase.

EVALUATION OF ADOPTION OF LED LIGHTING TECHNOLOGY IN MALAYSIA

OpenAIRE

Khorasanizadeh, Hasti

2017-01-01

Electrical energy consumption in Malaysia is rapidly increasing with illumination being the second largest contributor to this increment. Light Emitting Diode (LED) could be a viable option to reduce the illumination based energy consumption. LEDs are energy efficient and easier to recycle compared to traditional lighting sources such as incandescent and fluorescent lamps. They also have longer life time and lower failure rate. In this thesis, the feasibility of replacing...

Universal fixture design for body mounted LED lights

Science.gov (United States)

Hajra, Debdyut

2017-09-01

Today LED headlamps, armbands and ankle-bands, shoe-lights etc. have become very popular. These find extensive use in search and rescue operations, mining, carving, etc. and are also used by individuals during hiking, trekking, running, etc. during dark hours. They serve two main purposes: they provide sufficient illumination in low light conditions and they are used to indicate the presence of a person after dark. These have the same basic requirements. They must produce sufficient light, have high durability, long battery life, must be light weight and energy efficient. This paper discusses possibilities of designing a universal LED fixture can be designed so that it meets the respective needs of everyone irrespective of their background and industry. It discusses the materials to be used for its different body parts, innovative clip design for attachment with support structures like head and armbands, helmets, shoes, etc.

Reliable LED Lighting Technologies: Key Factors and Procurement Guidance

Energy Technology Data Exchange (ETDEWEB)

Davis, Lynn; Arquit Niederberger, Anne

2015-10-08

Abstract— Lighting systems have the ability to transform the economic and educational infrastructure of disadvantaged communities, and eradicating “light poverty” has become one of the primary goals of the International Year of Light 2015. Solid-state lighting (SSL) technology, based on light-emitting diode (LED) light sources, has emerged as the next generation of lighting technology, with a current global market penetration of roughly 5%. This paper will report on recent research on understanding SSL lighting system reliability (failure modes, environmental stressors, electrical power quality); discuss the implications of SSL technology reliability for providing lighting services; and suggest practical approaches to ensure SSL reliability to benefit humanity. Among the key findings from this work is that LED sources can be extremely reliable, withstanding a broad range of environmental stresses without failure. Nonetheless, SSL lighting systems can have a negative impact on electrical power reliability, as well as on the affordability of lighting services, without attention to the quality of the accompanying power infrastructure. It is therefore critical to ensure that the performance of the power supply electronics used in lighting systems is matched to the quality of the power source, when evaluating energy efficient lighting choices.

A high-performance stand-alone solar PV power system for LED lighting

KAUST Repository

Huang, B. J.

2010-06-01

The present study developed a high-performance solar PV power technology for the LED lighting of a solar home system. The nMPPO (near-Maximum-Power- Point- Operation) design is employed in system design to eliminate MPPT. A feedback control system using pulse width modulation (PWM) technique was developed for battery charging control which can increase the charging capacity by 78%. For high-efficiency lighting, the LED is directly driven by battery using a PWM discharge control to eliminate a DC/DC converter. Two solar-powered LED lighting systems (50W and 100W LED) were built. The long-term outdoor tests have shown that the loss of load probability for full-night lighting requirement is zero for 50W LED and 3.6% for 100W LED. © 2010 IEEE.

VLC-based indoor location awareness using LED light and image sensors

Science.gov (United States)

Lee, Seok-Ju; Yoo, Jong-Ho; Jung, Sung-Yoon

2012-11-01

Recently, indoor LED lighting can be considered for constructing green infra with energy saving and additionally providing LED-IT convergence services such as visible light communication (VLC) based location awareness and navigation services. For example, in case of large complex shopping mall, location awareness to navigate the destination is very important issue. However, the conventional navigation using GPS is not working indoors. Alternative location service based on WLAN has a problem that the position accuracy is low. For example, it is difficult to estimate the height exactly. If the position error of the height is greater than the height between floors, it may cause big problem. Therefore, conventional navigation is inappropriate for indoor navigation. Alternative possible solution for indoor navigation is VLC based location awareness scheme. Because indoor LED infra will be definitely equipped for providing lighting functionality, indoor LED lighting has a possibility to provide relatively high accuracy of position estimation combined with VLC technology. In this paper, we provide a new VLC based positioning system using visible LED lights and image sensors. Our system uses location of image sensor lens and location of reception plane. By using more than two image sensor, we can determine transmitter position less than 1m position error. Through simulation, we verify the validity of the proposed VLC based new positioning system using visible LED light and image sensors.

LEDs light up the world

Energy Technology Data Exchange (ETDEWEB)

Mather, N.

2004-06-30

A lighting system using light-emitting diodes, and privately financed by a Canadian engineering professor at the University of Calgary, has been set up in a village in Nepal in 2000. Since then, through the efforts of the 'Light Up The World' Foundation, established by Dr. Irvine-Halliday, projects have lit up thousands of homes in the Philippines, India, Afghanistan, the Galapagos Islands, Mexico, Sri Lanka, and Angola. Although the goal of the project is primarily to provide lighting for reading and writing for school-children, the project has been the source of many other advantages; creation of enterprise, increased employment, enhanced income, gender equality, and improvements in health and safety among them. Since LED lamps in most cases replace kerosene lamps, the system also has significant environmental benefits. The system as originally envisioned creates electricity by pedal-powered generator, or by solar panels connected to a battery, depending on what is available at each home. Each home is connected to the power supply and supplied with low-energy diode lamps. The lights are extremely efficient and many homes can be equipped with them using less energy than it takes to power a single 100-watt light bulb. 5 photos.

Development of Key Technologies for White Lighting Based on Light-Emitting Diodes (LEDs)

Energy Technology Data Exchange (ETDEWEB)

Werner Goetz; Bill Imler; James Kim; Junko Kobayashi; Andrew Kim; Mike Krames; Rick Mann; Gerd Mueller-Mach; Anneli Munkholm; Jonathan Wierer

2004-03-31

This program was organized to focus on materials development issues critical to the acceleration of solid-state lighting, and was split into three major thrust areas: (1) study of dislocation density reduction for GaN grown on sapphire using 'cantilever epitaxy', and the impact of dislocation density on the performance of state-of-the-art high-power LEDs; (2) the evaluation of in situ techniques for monitoring gas phase chemistry and the properties of GaN-based layers during metal-organic vapor phase epitaxy (MOCVD), and (3) feasibility for using semiconductor nanoparticles ('quantum dots') for the down-conversion of blue or ultraviolet light to generate white light. The program included a partnership between Lumileds Lighting (epitaxy and device fabrication for high power LEDs) and Sandia National Laboratories (cantilever epitaxy, gas phase chemistry, and quantum dot synthesis). Key findings included: (1) cantilever epitaxy can provide dislocation density reduction comparable to that of more complicated approaches, but all in one epitaxial growth step; however, further improvements are required to realize significant gains in LED performance at high drive currents, (2) in situ tools can provide detailed knowledge about gas phase chemistry, and can be used to monitor and control epitaxial layer composition and temperature to provide improved yields (e.g., a fivefold increase in color targeting is demonstrated for 540nm LEDs), and (3) quantum efficiency for quantum dots is improved and maintained up to 70% in epoxy thin films, but further work is necessary to increase densification (absorption) and robustness before practical application to LEDs.

MudGet: Reproduction of the desired lighting environment using a smart-LED

Directory of Open Access Journals (Sweden)

Yong Hwi Kim

2017-07-01

Full Text Available With the emergence of smart LEDs, lighting based interior design is becoming popular. However, most of the smart LED-based lighting systems rely on expert-human intervention to create a desired atmosphere. For convenience, commercial lighting systems offer a number of options but their usability is fairly restricted. Therefore, an intuitive interface is required for novice users to generate the desired lighting environment. In this paper, we have developed a software, named MudGet, which automatically extracts the light mood from a digital image and controls the LED lamps to reproduce a desired lighting effect according to the extracted light mood. In our method, the light mood is regarded as a set of the representative colors of the digital image. The representative colors are extracted by utilizing K-means clustering algorithm. The dimming parameters are set for which each of the LED lamps create the lighting environment with the mood extracted by the software. To evaluate the feasibility of mood reproduction qualitatively, the degree of similarity between the light mood in the digital image and the reproduced result using LEDs is evaluated by a user study under a miniaturized experimental set. We observe that users can easily produce a desired atmosphere through the proposed MudGet software.

Conduction-driven cooling of LED-based automotive LED lighting systems for abating local hot spots

Science.gov (United States)

Saati, Ferina; Arik, Mehmet

2018-02-01

Light-emitting diode (LED)-based automotive lighting systems pose unique challenges, such as dual-side packaging (front side for LEDs and back side for driver electronics circuit), size, harsh ambient, and cooling. Packaging for automotive lighting applications combining the advanced printed circuit board (PCB) technology with a multifunctional LED-based board is investigated with a focus on the effect of thermal conduction-based cooling for hot spot abatement. A baseline study with a flame retardant 4 technology, commonly known as FR4 PCB, is first compared with a metal-core PCB technology, both experimentally and computationally. The double-sided advanced PCB that houses both electronics and LEDs is then investigated computationally and experimentally compared with the baseline FR4 PCB. Computational models are first developed with a commercial computational fluid dynamics software and are followed by an advanced PCB technology based on embedded heat pipes, which is computationally and experimentally studied. Then, attention is turned to studying different heat pipe orientations and heat pipe placements on the board. Results show that conventional FR4-based light engines experience local hot spots (ΔT>50°C) while advanced PCB technology based on heat pipes and thermal spreaders eliminates these local hot spots (ΔT<10°C), leading to a higher lumen extraction with improved reliability. Finally, possible design options are presented with embedded heat pipe structures that further improve the PCB performance.

White LEDs and modules in chip-on-board technology for general lighting

Science.gov (United States)

Hartmann, Paul; Wenzl, Franz P.; Sommer, Christian; Pachler, Peter; Hoschopf, Hans; Schweighart, Marko; Hartmann, Martin; Kuna, Ladislav; Jakopic, Georg; Leising, Guenther; Tasch, Stefan

2006-08-01

At present, light-emitting diode (LED) modules in various shapes are developed and designed for the general lighting, advertisement, emergency lighting, design and architectural markets. To compete with and to surpass the performance of traditional lighting systems, enhancement of Lumen output and the white light quality as well as the thermal management and the luminary integration are key factors for success. Regarding these issues, white LEDs based on the chip-on-board (COB) technology show pronounced advantages. State-of-the-art LEDs exploiting this technology are now ready to enter the general lighting segments. We introduce and discuss the specific properties of the Tridonic COB technology dedicated for general lighting. This technology, in combination with a comprehensive set of tools to improve and to enhance the Lumen output and the white light quality, including optical simulation, is the scaffolding for the application of white LEDs in emerging areas, for which an outlook will be given.

Occupancy-based illumination control of LED lighting systems

NARCIS (Netherlands)

Caicedo Fernandez, D.R.; Pandharipande, A.; Leus, G.

2011-01-01

Light emitting diode (LED)-based systems are considered to be the future of lighting. We consider the problem of energy-efficient illumination control of such systems. Energy-efficient system design is based on two aspects: localised information on occupancy and optimisation of dimming levels of the

Innovations in LED lighting for reduced-ESM crop production in space

Science.gov (United States)

Massa, Gioia; Mitchell, Cary; Bourget, C. Michael; Morrow, Robert

In controlled-environment crop production such as will be practiced at the lunar outpost and Mars base, the single most energy-demanding aspect is electric lighting for plant growth, including energy costs for energizing lamps as well as for removing excess heat. For a variety of reasons, sunlight may not be a viable option as the main source of crop lighting off-Earth and traditional electric lamps for crop lighting have numerous drawbacks for use in a space environment. A collaborative research venture between the Advanced Life Support Crops Group at Purdue University and the Orbital Technologies Corporation (ORBITEC) has led to the development of efficient, reconfigurable LED lighting technologies for crop growth in an ALSS. The light sources use printed-circuit red and blue LEDs, which are individually tunable for a range of photosynthetic photon fluxes and photomorphogenic plant responses. Initial lighting arrays have LEDs that can be energized from the bottom upward when deployed in a vertical, intracanopy configuration, allowing the illumination to be tailored for stand height throughout the cropping cycle. Preliminary testing with the planophile crop cowpea (Vigna unguiculata L. Walp, breeding line IT87D-941-1), resulted in optimizing internal reflectance of growth compartments by lining walls, floor, and a movable ceiling with white Poly film, as well as by determining optimal planting density and plant positioning. Additionally, these light strips, called "lightsicles", can be configured into an overhead plane of light engines. When intracanopy and overhead-LED-lit cowpea crop production was compared, cowpea plants grown with intracanopy lighting had much greater understory leaf retention and produced more dry biomass per kilowatt-hour of lighting energy than did overhead-lit plants. The efficiency of light capture is reduced in overhead-lit scenarios due to mutual shading of lower leaves by upper leaves in closed canopies leading to premature abscission

Newly patented process enables low-cost solution for increasing white light spectrum of LEDs

Science.gov (United States)

Spanard, Jan-Marie

2017-10-01

A newly patented process for completing the spectral light array emitted by LED bulbs provides a low-cost method for producing better human centered lighting (HCL). This process uses non-luminescent colorant filters, filling out the jagged LED spectral emission into a full, white light array. While LED bulbs have the distinct economic advantages of using less energy, producing less heat and lasting years longer than traditional incandescent bulbs, the persistent metameric failure of LED bulbs has resulted in slower, and sometimes reluctant, adoption of LED lighting by the residential, retail and architectural markets. Adding missing wavelengths to LED generated bulbs via colorant filters increases the aesthetic appeal of the light by decreasing current levels of metameric failure, reducing the `flatness', `harshness', and `dullness' of LED generated light reported by consumers. LED phosphor-converted light can be successfully tuned to "whiter" white light with selective color filtering using permanent, durable transparent pigments. These transparent pigments are selectively applied in combination with existing manufacturing technologies and utilized as a final color-tuning step in bulb design. The quantity of emitted light chosen for color filtering can be adjusted from 1% to 100% of emitted light, creating a custom balance of light quantity with light quality. This invention recognizes that "better light" is frequently chosen over "more light" in the consumer marketplace.

A comparative study of fluorescent and LED lighting in industrial facilities

Science.gov (United States)

Perdahci PhD, C.; Akin BSc, H. C.; Cekic Msc, O.

2018-05-01

Industrial facilities have always been in search for reducing outgoings and minimizing energy consumption. Rapid developments in lighting technology require more energy efficient solutions not only for industries but also for many sectors and for households. Addition of solid-state technology has brought LED lamps into play and with LED lamp usage, efficacy level has reached its current values. Lighting systems which uses fluorescent and LED lamps have become the prior choice for many industrial facilities. This paper presents a comparative study about fluorescent and LED based indoor lighting systems for a warehouse building in an industrial facility in terms of lighting distribution values, colour rendering, power consumption, energy efficiency and visual comfort. Both scenarios have been modelled and simulated by using Relux and photometric data for the luminaires have been gathered by conducting tests and measurements in an accredited laboratory.

Malaysian University Students' Attitudes towards Six Varieties of Accented Speech in English

Science.gov (United States)

Ahmed, Zainab Thamer; Abdullah, Ain Nadzimah; Heng, Chan Swee

2014-01-01

Previous language attitude studies indicated that in many countries all over the world, English language learners perceived native accents, either American or British, more positively than the non-native accents such as the Japanese, Korean, and Austrian accents. However, in Malaysia it is still unclear which accent Malaysian learners of English…

Perception of Foreign Accent Syndrome Speech and Its Relation to Segmental Characteristics

Science.gov (United States)

Dankovicova, Jana; Hunt, Claire

2011-01-01

Foreign accent syndrome (FAS) is an acquired neurogenic disorder characterized by altered speech that sounds foreign-accented. This study presents a British subject perceived to speak with an Italian (or Greek) accent after a brainstem (pontine) stroke. Native English listeners rated the strength of foreign accent and impairment they perceived in…

Intelligent control of dynamic LED lighting; Intelligent styring af dynamisk LED belysning. Slutrapport

Energy Technology Data Exchange (ETDEWEB)

Thorseth, A.; Corell, D.; Hansen, Soeren S.; Dam-Hansen, C.; Petersen, Paul Michael

2013-01-15

The project has resulted in a prototype of a new intelligent lighting control system. The control system enables the end user to control his or her own local lighting environment (lighting zone) according to individual preferences and needs. The report provides a description of how the developed intelligent lighting system is composed and functions. The system is designed as a work lamp that enables dynamic change of the light color scheme according to a number of light control algorithms. It is specifically designed in relation to user tests of the intelligent lighting system, which is carried out in the final part of the project. An intelligent and advanced control of LED lighting was developed, which enables optimization of the user's light conditions in a given situation. Based on a number of known parameters, the system can control lighting so that at any time optimal light conditions are created, using a minimum of electric power. (LN)

Two French-Speaking Cases of Foreign Accent Syndrome: An Acoustic-Phonetic Analysis

Science.gov (United States)

Roy, Johanna-Pascale; Macoir, Joel; Martel-Sauvageau, Vincent; Boudreault, Carol-Ann

2012-01-01

Foreign accent syndrome (FAS) is an acquired neurologic disorder in which an individual suddenly and unintentionally speaks with an accent which is perceived as being different from his/her usual accent. This study presents an acoustic-phonetic description of two Quebec French-speaking cases. The first speaker presents a perceived accent shift to…

Effect of LED light quality on in vitro shoot proliferation and growth of ...

African Journals Online (AJOL)

As an alternative to conventional lighting systems, light emitting diode (LED) has been ... The objective of this study was to determine the effects of different LED light quality on ... Key words: Light quality, micropropagation, orchid, chlorophyll.

Visible light communication based vehicle positioning using LED street light and rolling shutter CMOS sensors

Science.gov (United States)

Do, Trong Hop; Yoo, Myungsik

2018-01-01

This paper proposes a vehicle positioning system using LED street lights and two rolling shutter CMOS sensor cameras. In this system, identification codes for the LED street lights are transmitted to camera-equipped vehicles through a visible light communication (VLC) channel. Given that the camera parameters are known, the positions of the vehicles are determined based on the geometric relationship between the coordinates of the LEDs in the images and their real world coordinates, which are obtained through the LED identification codes. The main contributions of the paper are twofold. First, the collinear arrangement of the LED street lights makes traditional camera-based positioning algorithms fail to determine the position of the vehicles. In this paper, an algorithm is proposed to fuse data received from the two cameras attached to the vehicles in order to solve the collinearity problem of the LEDs. Second, the rolling shutter mechanism of the CMOS sensors combined with the movement of the vehicles creates image artifacts that may severely degrade the positioning accuracy. This paper also proposes a method to compensate for the rolling shutter artifact, and a high positioning accuracy can be achieved even when the vehicle is moving at high speeds. The performance of the proposed positioning system corresponding to different system parameters is examined by conducting Matlab simulations. Small-scale experiments are also conducted to study the performance of the proposed algorithm in real applications.

Danish-accented Chinese

DEFF Research Database (Denmark)

Wang, Lei; Sloos, Marjoleine 莱娜; Zhang, Chun

In search for a linguistic basis for the education of Chinese as a foreign language CFL in Denmark, we set up a new line of investigation into CFL. This research focuses on the phonetics and phonology of Mandarin Chinese as compared to Danish. Considering the sound systems of both languages, we......-ba /pha pa/ ta-da /tha ta/ ka-ga / kha-ka/ For L2 acquisition it is held that same and new phonemes are (relatively) easy acquired, whereas similar but not identical sounds are difficult to learn. New sounds are initially mapped onto the L1 phoneme inventory (Kuhl 1991). For Danish, this would predict...... instruction, which pitch contours do the Danish learners of Chinese use on neutral tones and to what extent does their production match that of native speakers? Future research may include Norwegian and Swedish-accented Chinese and a comparison between the different Germanic accents of CFL. Reference Kuhl, P...

Hybrid sunlight/LED illumination and renewable solar energy saving concepts for indoor lighting.

Science.gov (United States)

Tsuei, Chih-Hsuan; Sun, Wen-Shing; Kuo, Chien-Cheng

2010-11-08

A hybrid method for using sunlight and light-emitting diode (LED) illumination powered by renewable solar energy for indoor lighting is simulated and presented in this study. We can illuminate an indoor space and collect the solar energy using an optical switching system. When the system is turned off, the full spectrum of the sunlight is concentrated by a concentrator, to be absorbed by solar photovoltaic devices that provide the electricity to power the LEDs. When the system is turned on, the sunlight collected by the concentrator is split into visible and non-visible rays by a beam splitter. The visible rays pass through the light guide into a light box where it is mixed with LED light to ultimately provide uniform illumination by a diffuser. The non-visible rays are absorbed by the solar photovoltaic devices to provide electrical power for the LEDs. Simulation results show that the efficiency of the hybrid sunlight/LED illumination with the renewable solar energy saving design is better than that of LED and traditional lighting systems.

Adapting to foreign-accented speech: The role of delay in testing

NARCIS (Netherlands)

Witteman, M.J.; Bardhan, N.P.; Weber, A.C.; McQueen, J.M.

2011-01-01

Understanding speech usually seems easy, but it can become noticeably harder when the speaker has a foreign accent. This is because foreign accents add considerable variation to speech. Research on foreign-accented speech shows that participants are able to adapt quickly to this type of variation.

Light out-coupling from LEDs by means of metal nanoparticles; Lichtauskopplung aus LEDs mittels Metallnanoteilchen

Energy Technology Data Exchange (ETDEWEB)

Goehler, Tino

2010-12-17

The external quantum efficiency of light-emitting diodes (LEDs) based on Al- GaAs/InGaAlP is limited by total internal reflection because of the high refractive index (typically between 3 and 4) of the semiconductor. Metal nanoparticles (MNP) deposited on the surface of the LED can be used as dipole scatterers in order to enhance the emission of the LED. In this thesis, first, single gold nanoparticles of various sizes deposited on such an LED were investigated. A clear enhancement is detected as long as the dipole plasmon resonance of the particle is at a shorter wavelength than the LED emission. If the plasmon resonance coincides with the LED emission or is at a larger wavelength, the enhancement turns into suppression. Numerical simulations indicate that this latter effect is mainly caused by the particle quadrupole resonance producing extra absorption. Arrays of MNPs can be produced by a special mask technique called ''Fischer pattern nanolithography'' and manipulated in shape and size by additional steps. Originally, the MNPs produced by this technique are triangular in shape and turn out to suppress the LED emission. After transformation of the particles to spheres, a clear enhancement was detected. Light that would otherwise remain trapped inside the substrate is coupled out by resonant plasmonic scattering. Investigations on analogous structures on a transparent high-index material (GaP) indicate a stronger coupling between the particles than expected on the basis of literature data. (orig.)

Direct battery-driven solar LED lighting using constant-power control

KAUST Repository

Huang, Bin-Juine

2012-11-01

A direct battery-driven LED lighting technique using constant-power control is proposed in the present study. A system dynamics model of LED luminaire was derived and used in the design of the feedback constant-power control system. The test result has shown that the power of 18. W and 100. W LED luminaires can be controlled accurately with error at 2-5%. A solar LED street lighting system using constant-power and dimming control was designed and built for field test in a remote area. The long-term performance was satisfactory and no any failure since the installation. Since no high-power capacitor is used in the present constant-power control circuit, a longer lifetime is expected. © 2012 Elsevier Ltd.

What makes a rhythm complex? The influence of musical training and accent type on beat perception.

Science.gov (United States)

Bouwer, Fleur L; Burgoyne, J Ashley; Odijk, Daan; Honing, Henkjan; Grahn, Jessica A

2018-01-01

Perception of a regular beat in music is inferred from different types of accents. For example, increases in loudness cause intensity accents, and the grouping of time intervals in a rhythm creates temporal accents. Accents are expected to occur on the beat: when accents are "missing" on the beat, the beat is more difficult to find. However, it is unclear whether accents occurring off the beat alter beat perception similarly to missing accents on the beat. Moreover, no one has examined whether intensity accents influence beat perception more or less strongly than temporal accents, nor how musical expertise affects sensitivity to each type of accent. In two experiments, we obtained ratings of difficulty in finding the beat in rhythms with either temporal or intensity accents, and which varied in the number of accents on the beat as well as the number of accents off the beat. In both experiments, the occurrence of accents on the beat facilitated beat detection more in musical experts than in musical novices. In addition, the number of accents on the beat affected beat finding more in rhythms with temporal accents than in rhythms with intensity accents. The effect of accents off the beat was much weaker than the effect of accents on the beat and appeared to depend on musical expertise, as well as on the number of accents on the beat: when many accents on the beat are missing, beat perception is quite difficult, and adding accents off the beat may not reduce beat perception further. Overall, the different types of accents were processed qualitatively differently, depending on musical expertise. Therefore, these findings indicate the importance of designing ecologically valid stimuli when testing beat perception in musical novices, who may need different types of accent information than musical experts to be able to find a beat. Furthermore, our findings stress the importance of carefully designing rhythms for social and clinical applications of beat perception, as not

Design and radiation tests on a LED based emergency evacuation directional lighting

CERN Document Server

Trikoupis, Nikolaos

2017-01-01

A LED (Light Emitting Diode) based directional lighting system has been designed to indicate the best evacuation direction for applications like the Large Hadron Collider (LHC) tunnel. The design includes constraints for redundancy required by safety systems and for components selection by radiation effects. Most of the literature for radiation effects on LEDs concern digital communications systems, although some recent reports do exist for visible spectrum power LEDs and the reduction in light output versus dose is coherent with the results presented in this paper. Prototype lighting units were irradiated in CERN’s CHARM facility up to a Total Integrated Dose (TID) of 870 Gy and no failures were observed. This paper describes the basic design, presents field tests and the effects of radiation on the LEDs luminance.

Life-Cycle Assessment of Energy and Environmental Impacts of LED Lighting Products, Part 3: LED Environmental Testing

Energy Technology Data Exchange (ETDEWEB)

Tuenge, Jason R.; Hollomon, Brad; Dillon, Heather E.; Snowden-Swan, Lesley J.

2013-03-01

This report covers the third part of a larger U.S. Department of Energy (DOE) project to assess the life-cycle environmental and resource impacts in the manufacturing, transport, use, and disposal of light-emitting diode (LED) lighting products in relation to incumbent lighting technologies. All three reports are available on the DOE website (www.ssl.energy.gov/tech_reports.html). • Part 1: Review of the Life-Cycle Energy Consumption of Incandescent, Compact Fluorescent and LED Lamps; • Part 2: LED Manufacturing and Performance; • Part 3: LED Environmental Testing. Parts 1 and 2 were published in February and June 2012, respectively. The Part 1 report included a summary of the life-cycle assessment (LCA) process and methodology, provided a literature review of more than 25 existing LCA studies of various lamp types, and performed a meta-analysis comparing LED lamps with incandescent and compact fluorescent lamps (CFLs). Drawing from the Part 1 findings, Part 2 performed a more detailed assessment of the LED manufacturing process and used these findings to provide a comparative LCA taking into consideration a wider range of environmental impacts. Both reports concluded that the life-cycle environmental impact of a given lamp is dominated by the energy used during lamp operation—the upstream generation of electricity drives the total environmental footprint of the product. However, a more detailed understanding of end-of-life disposal considerations for LED products has become increasingly important as their installation base has grown. The Part 3 study (reported herein) was undertaken to augment the LCA findings with chemical analysis of a variety of LED, CFL, and incandescent lamps using standard testing procedures. A total of 22 samples, representing 11 different models, were tested to determine whether any of 17 elements were present at levels exceeding California or Federal regulatory thresholds for hazardous waste. Key findings include: • The selected

Health risks occurring when color is percepted under led lighting

Directory of Open Access Journals (Sweden)

V.A. Kaptsov

2017-06-01

Full Text Available The article deals with problems of color perception under LED lighting. We revealed that inadequate perception of a signal color by a driver led to greater risks of transport accidents. We reviewed both Jung-Helmholtz three-color hypothesis and a modern one based on fiber-optical approach to functioning of "Mueller cells and cones" system. We made an attempt to explain a number of effects related to visibility curves and time delays when defining color of light signals. Our research on assessing influence exerted by LED lighting on functional state and working capacity of railway workers during which we applied occupational selection techniques revealed negative changes. We proved there was a decrease in functional resistance to color sense between red and green signals as well as longer response time for complicated sight-motor reaction and significant decrease in readiness to emergency actions (resistance to monotony in examined individuals. The article also contains data on time peculiarities which are characteristic for defining signals color in relation to red signal (650 nm. We showed that when red color LEDs with wave length much shorter than 650 nm were used in signaling devices it caused risks of inadequate color detection, longer reaction to inhibiting signals, and greater possibility of transport accidents and negative events in everyday life. These peculiarities should be taken into account when designing traffic lights and other signaling devices which provide transport safety. We also proved that signaling traffic lights for transport systems should be designed allowing for physiology of color perception by a human visual analyzer; application of LEDs with wave length shorter than 650 nm should be absolutely excluded

Savings in Cooling Energy with a Thermal Management System for LED Lighting in Office Buildings

Directory of Open Access Journals (Sweden)

Byung-Lip Ahn

2015-06-01

Full Text Available Light-emitting diode (LED lighting should be considered for lighting efficiency enhancement, however, waste heat from light-emitting diode (LED lighting increases the internal cooling load during the summer season. In order to solve this problem we propose a thermal management system for light-emitting diode (LED lighting with a heat exchanger module integrated with the building’s heating, ventilation, and air conditioning (HVAC system to move the lighting’s waste heat outdoors. An experiment was carried out to investigate the thermal effects in a test chamber and the heat exchange rate between the heat sink and the duct air. The heat generated by the light-emitting diode (LED lighting was calculated as 78.1% of light-emitting diode (LED input power and the heat exchange rate of the lighting heat exchange module was estimated to be between 86.5% and 98.1% according to the light-emitting diode (LED input power and the flow rate of air passing the heat sink. As a result, the average light-emitting diode (LED lighting heat contribution rate for internal heat gain was determined as 0.05; this value was used to calculate the heating and cooling energy demand of the office building through an energy simulation program. In the simulation results, the cooling energy demand was reduced by 19.2% compared with the case of conventionally installed light-emitting diode (LED lighting.

Fundamentals of solid-state lighting LEDs, OLEDs, and their applications in illumination and displays

CERN Document Server

Khanna, Vinod Kumar

2014-01-01

History and Basics of LightingChronological History of LightingLearning Objectives How Early Man Looked at the ""Sun"" The Need for Artificial Light Sources First Steps in the Evolution of Artificial Lighting The First Solid-State Lighting Device The First Practical Electrical Lighting Device The Incandescent Filament Lamp Mercury and Sodium Vapor Lamps The Fluorescent Lamp The Compact Fluorescent Lamp Revolution in the World of Lighting: Advent of Light-Emitting Diodes Birth of the First LED and the Initial Stages of LED Development The Father of the LED: Holonyak Jr. The Post-1962 Developmen

LED Light to improve Strawberry Flavour, Quality and Production

NARCIS (Netherlands)

Hanenberg, M.A.A.; Janse, J.; Verkerke, W.

2016-01-01

A current demonstration in the greenhouses of Wageningen UR in Bleiswijk (the Netherlands) shows positive results of LED light on the quality and production of strawberries (Fragaria x ananassa). In this demonstration two strawberry cultivars, Elsanta and Sonata, are exposed to three different light

Uniformity of LED light illumination in application to direct imaging lithography

Science.gov (United States)

Huang, Ting-Ming; Chang, Shenq-Tsong; Tsay, Ho-Lin; Hsu, Ming-Ying; Chen, Fong-Zhi

2016-09-01

Direct imaging has widely applied in lithography for a long time because of its simplicity and easy-maintenance. Although this method has limitation of lithography resolution, it is still adopted in industries. Uniformity of UV irradiance for a designed area is an important requirement. While mercury lamps were used as the light source in the early stage, LEDs have drawn a lot of attention for consideration from several aspects. Although LED has better and better performance, arrays of LEDs are required to obtain desired irradiance because of limitation of brightness for a single LED. Several effects are considered that affect the uniformity of UV irradiance such as alignment of optics, temperature of each LED, performance of each LED due to production uniformity, and pointing of LED module. Effects of these factors are considered to study the uniformity of LED Light Illumination. Numerical analysis is performed by assuming a serious of control factors to have a better understanding of each factor.

Imaging camera system of OYGBR-phosphor-based white LED lighting

Science.gov (United States)

Kobashi, Katsuya; Taguchi, Tsunemasa

2005-03-01

The near-ultraviolet (nUV) white LED approach is analogous to three-color fluorescent lamp technology, which is based on the conversion of nUV radiation to visible light via the photoluminescence process in phosphor materials. The nUV light is not included in the white light generation from nUV-based white LED devices. This technology can thus provide a higher quality of white light than the blue and YAG method. A typical device demonstrates white luminescence with Tc=3,700 K, Ra > 93, K > 40 lm/W and chromaticity (x, y) = (0.39, 0.39), respectively. The orange, yellow, green and blue OYGB) or orange, yellow, red, green and blue (OYRGB) device shows a luminescence spectrum broader than of an RGB white LED and a better color rendering index. Such superior luminous characteristics could be useful for the application of several kinds of endoscope. We have shown the excellent pictures of digestive organs in a stomach of a dog due to the strong green component and high Ra.

Design of High Efficiency Illumination for LED Lighting

Directory of Open Access Journals (Sweden)

Yong-Nong Chang

2013-01-01

Full Text Available A high efficiency illumination for LED street lighting is proposed. For energy saving, this paper uses Class-E resonant inverter as main electric circuit to improve efficiency. In addition, single dimming control has the best efficiency, simplest control scheme and lowest circuit cost among other types of dimming techniques. Multiple serial-connected transformers used to drive the LED strings as they can provide galvanic isolation and have the advantage of good current distribution against device difference. Finally, a prototype circuit for driving 112 W LEDs in total was built and tested to verify the theoretical analysis.

Smart street lighting : The advantages of LED street lighting and a smart control system in Uppsala municipality

OpenAIRE

Sjöberg, Inga; Gidén Hember, Amanda; Wallerström, Carolina

2017-01-01

The purpose of this bachelor thesis is to examine how LED street lights and a smart street light control system can reduce the energy consumption, costs and in extension the CO2 equivalents in a geographically delimited area. In 2015 the municipality of Sala installed LED armatures connected to a smart control system in the whole municipality. The smart control system enables for instance adjustment of the light intensity at specific times during the day and a supervision of the street light ...

Bilingual and Monolingual Children Prefer Native-Accented Speakers

Directory of Open Access Journals (Sweden)

Andre L. eSouza

2013-12-01

Full Text Available Adults and young children prefer to affiliate with some individuals rather than others. Studies have shown that monolingual children show in-group biases for individuals who speak their native language without a foreign accent (Kinzler, Dupoux, & Spelke, 2007. Some studies have suggested that bilingual children are less influenced than monolinguals by language variety when attributing personality traits to different speakers (Anisfeld & Lambert, 1964, which could indicate that bilinguals have fewer in-group biases and perhaps greater social flexibility. However, no previous studies have compared monolingual and bilingual children’s reactions to speakers with unfamiliar foreign accents. In the present study, we investigated the social preferences of 5-year-old English and French monolinguals and English-French bilinguals. Contrary to our predictions, both monolingual and bilingual preschoolers preferred to be friends with native-accented speakers over speakers who spoke their dominant language with an unfamiliar foreign accent. This result suggests that both monolingual and bilingual children have strong preferences for in-group members who use a familiar language variety, and that bilingualism does not lead to generalized social flexibility.

Bilingual and monolingual children prefer native-accented speakers.

Science.gov (United States)

Souza, André L; Byers-Heinlein, Krista; Poulin-Dubois, Diane

2013-01-01

Adults and young children prefer to affiliate with some individuals rather than others. Studies have shown that monolingual children show in-group biases for individuals who speak their native language without a foreign accent (Kinzler et al., 2007). Some studies have suggested that bilingual children are less influenced than monolinguals by language variety when attributing personality traits to different speakers (Anisfeld and Lambert, 1964), which could indicate that bilinguals have fewer in-group biases and perhaps greater social flexibility. However, no previous studies have compared monolingual and bilingual children's reactions to speakers with unfamiliar foreign accents. In the present study, we investigated the social preferences of 5-year-old English and French monolinguals and English-French bilinguals. Contrary to our predictions, both monolingual and bilingual preschoolers preferred to be friends with native-accented speakers over speakers who spoke their dominant language with an unfamiliar foreign accent. This result suggests that both monolingual and bilingual children have strong preferences for in-group members who use a familiar language variety, and that bilingualism does not lead to generalized social flexibility.

The Use of Light-Emitting Diodes (LEDs) as Green and Red/Far-Red Light Sources in Plant Physiology.

Science.gov (United States)

Jackson, David L.; And Others

1985-01-01

The use of green, red, and far-red light-emitting diodes (LEDs) as light sources for plant physiological studies is outlined and evaluated. Indicates that LED lamps have the advantage over conventional light sources in that they are lightweight, low-cost, portable, easily constructed, and do not require color filters. (Author/DH)

Demonstration of LED Retrofit Lamps at the Jordan Schnitzer Museum of Art

Energy Technology Data Exchange (ETDEWEB)

Miller, Naomi J.

2011-09-01

The Jordan Schnitzer Museum of Art in Eugene, Oregon, houses a remarkable permanent collection of Asian art and antiquities, modern art, and sculpture, and also hosts traveling exhibitions. In the winter and spring of 2011, a series of digital photographs by artist Chris Jordan, titled "Running the Numbers," was exhibited in the Coeta and Donald Barker Special Exhibitions Gallery. These works graphically illustrate waste (energy, money, health, consumer objects, etc.) in contemporary culture. The Bonneville Power Administration and the Eugene Water and Electricity Board provided a set of Cree 12W light-emitting diode (LED) PAR38 replacement lamps (Cree LRP38) for the museum to test for accent lighting in lieu of their standard Sylvania 90W PAR38 130V Narrow Flood lamps (which draw 78.9W at 120V). At the same time, the museum tested LED replacement lamps from three other manufacturers, and chose the Cree lamp as the most versatile and most appropriate color product for this exhibit. The lamps were installed for the opening of the show in January 2011. This report describes the process for the demonstration, the energy and economic results, and results of a survey of the museum staff and gallery visitors on four similar clusters of art lighted separately by four PAR38 lamps.

Design of High Efficiency Illumination for LED Lighting

OpenAIRE

Chang, Yong-Nong; Cheng, Hung-Liang; Kuo, Chih-Ming

2013-01-01

A high efficiency illumination for LED street lighting is proposed. For energy saving, this paper uses Class-E resonant inverter as main electric circuit to improve efficiency. In addition, single dimming control has the best efficiency, simplest control scheme and lowest circuit cost among other types of dimming techniques. Multiple serial-connected transformers used to drive the LED strings as they can provide galvanic isolation and have the advantage of good current distribution against de...

Large area flexible lighting foils using distributed bare LED dies on polyester substrates

NARCIS (Netherlands)

Ende, D.A. van den; Kusters, R.H.L.; Cauwe, M.; Waal, A. van der; Brand, J. van den

2013-01-01

Integration of LEDs on flexible foil substrates is of interest for flexible lighting applications and for backlights for flexible displays. Such a large area lighting device can be made by integrating a matrix of closely spaced LEDs on a flexible foil substrate. Preferably, these LEDs are integrated

Demonstration Assessment of Light-Emitting Diode (LED) Post-Top Lighting at Central Park in New York City

Energy Technology Data Exchange (ETDEWEB)

Myer, Michael; Goettel, Russell T.; Kinzey, Bruce R.

2012-09-30

A review of five post-top light-emitting diode (LED) pedestrian luminaires installed in New York City's Central Park for possible replacement to the existing metal halide post-top luminaire. This report reviews the energy savings potential and lighting delivered by the LED post-top luminaires.

A summary of LED lighting impacts on health

Directory of Open Access Journals (Sweden)

Cosmin Ticleanu

2017-06-01

Full Text Available Lighting can affect the health of people in buildings. This goes beyond the safety aspects of providing enough illumination to see by; lighting affects mood and human circadian rhythms, while poor lighting can cause glare, headaches, eyestrain, aches and pains associated with poor body posture or, in extreme cases, skin conditions and various types of sight loss. These aspects ought to be considered by designers and building owners and occupiers in order to improve the lit environment and use adequate lighting and lighting controls that meet the recommendations of codes and standards. Various types of lighting can have different impacts depending on their spectral, optical and electrical characteristics. This paper discusses potential impacts of LED lighting on human health, and is based on a recent BRE review of research investigating the most typical effects of lighting on human health.

Automatically identifying characteristic features of non-native English accents

NARCIS (Netherlands)

Bloem, Jelke; Wieling, Martijn; Nerbonne, John; Côté, Marie-Hélène; Knooihuizen, Remco; Nerbonne, John

2016-01-01

In this work, we demonstrate the application of statistical measures from dialectometry to the study of accented English speech. This new methodology enables a more quantitative approach to the study of accents. Studies on spoken dialect data have shown that a combination of representativeness (the

Comparative Phenotypical and Molecular Analyses of Arabidopsis Grown under Fluorescent and LED Light

Directory of Open Access Journals (Sweden)

Franka Seiler

2017-06-01

Full Text Available Comparative analyses of phenotypic and molecular traits of Arabidopsis thaliana grown under standardised conditions is still a challenge using climatic devices supplied with common light sources. These are in most cases fluorescent lights, which have several disadvantages such as heat production at higher light intensities, an invariable spectral output, and relatively rapid “ageing”. This results in non-desired variations of growth conditions and lowers the comparability of data acquired over extended time periods. In this study, we investigated the growth behaviour of Arabidopsis Col0 under different light conditions, applying fluorescent compared to LED lamps, and we conducted physiological as well as gene expression analyses. By changing the spectral composition and/or light intensity of LEDs we can clearly influence the growth behaviour of Arabidopsis and thereby study phenotypic attributes under very specific light conditions that are stable and reproducible, which is not necessarily given for fluorescent lamps. By using LED lights, we can also roughly mimic the sun light emission spectrum, enabling us to study plant growth in a more natural-like light set-up. We observed distinct growth behaviour under the different light regimes which was reflected by physiological properties of the plants. In conclusion, LEDs provide variable emission spectra for studying plant growth under defined, stable light conditions.

Direct battery-driven solar LED lighting using constant-power control

KAUST Repository

Huang, Bin-Juine; Chen, Chun-Wei; Hsu, Po-Chien; Tseng, Wei-Min; Wu, Min-Sheng

2012-01-01

A direct battery-driven LED lighting technique using constant-power control is proposed in the present study. A system dynamics model of LED luminaire was derived and used in the design of the feedback constant-power control system. The test result

Demonstration Assessment of Light-Emitting Diode (LED) Roadway Lighting, I-35W Bridge, Minneapolis, Minnesota, Phase I Report

Energy Technology Data Exchange (ETDEWEB)

Kinzey, B. R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Myer, M. A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2009-08-01

On the I-35W Bridge in Minneapolis, Minnesota, the GATEWAY program conducted a two-phase demonstration of LED roadway lighting on the main span, which is one of the country's oldest continuously operated exterior LED lighting installations. The Phase I report provides an overview of initial project results including lighting performance, economic performance, and potential energy savings.

Illuminating the Pecking Order in Off-Grid Lighting: A Demonstration of LED Lighting for Saving Energy in the Poultry Sector

Energy Technology Data Exchange (ETDEWEB)

Tracy, Jennifer; Mills, Evan

2010-11-06

The Lumina Project and Lighting Africa conducted a full-scale field test involving a switch from kerosene to solar-LED lighting for commercial broiler chicken production at an off-grid farm in Kenya. The test achieved lower operating costs, produced substantially more light, improved the working environment, and had no adverse effect on yields. A strategy using conventional solar-fluorescent lighting also achieved comparable yields, but entailed a six-fold higher capital cost and significantly higher recurring battery replacement costs. Thanks to higher energy and optical efficiencies, the LED system provided approximately twice the illumination to the chicken-production area and yet drew less than half the power.At the study farm, 3000 chickens were grown in each of three identical houses under kerosene, fluorescent, and LED lighting configurations. Under baseline conditions, a yearly expenditure of 1,200 USD is required to illuminate the three houses with kerosene. The LED system eliminates this fuel use and expense with a corresponding simple payback time of 1.5 years, while the solar-fluorescent system has a payback time of 9.3 years. The corresponding reduction in fuel expenditure in both cases represents a 15percent increase in after-tax net income (revenues minus expenses) across the entire business operation. The differential cost-effectiveness between the LED and fluorescent systems would be substantially greater if the fluorescent system were upsized to provide the same light as the LED system. Providing light with the fluorescent or LED systems is also far more economical than connecting to the grid in this case. The estimated grid-connection cost at this facility is 1.7 million Kenya Schillings (approximately 21,250 USD), which is nearly six-times the cost of the fluorescent system and 35-times the cost of the LED system.The LED system also confers various non-energy benefits. The relative uniformity of LED lighting, compared to the fluorescent or

Psychogenic Foreign Accent Syndrome: a new case

Directory of Open Access Journals (Sweden)

Stefanie eKeulen

2016-04-01

Full Text Available This paper presents the case of a 33-year-old, right-handed, French-speaking Belgian lady who was involved in a car accident as a pedestrian. Six months after the incident she developed a German/Flemish-like accent. The patient’s medical history, the onset of the FAS and the possible psychological causes of the accent change are analyzed. Relevant neuropsychological, neurolinguistic and psychodiagnostic test results are presented and discussed. The psychodiagnostic interview and testing will receive special attention, because these have been underreported in previous FAS case reports. Furthermore, an accent rating experiment was carried out in order to assess the foreign quality of the patient’s speech. Pre- and post-morbid spontaneous speech samples were analyzed phonetically to identify the pronunciation characteristics associated with this type of FAS. Several findings were considered essential in the diagnosis of psychogenic FAS: the psychological assessments as well as the clinical interview confirmed the presence of psychological problems, while neurological damage was excluded by means of repeated neuroimaging and neurological examinations. The type and nature of the speech symptoms and the accent fluctuations associated with the patient's psychological state cannot be explained by a neurological disorder. Moreover, the indifference of the patient towards her condition may also suggest a psychogenic etiology, as the opposite is usually observed in neurogenic FAS patients.

Communications and sensing of illumination contributins in a power LED lighting system

NARCIS (Netherlands)

Linnartz, J.P.M.G.; Feri, L.; Yang, Hongming; Colak, S.B.; Schenk, T.C.W.

2008-01-01

In recent years, LED technology emerged as a prime candidate for the future illumination light source, due to high energy efficiency and long life time. In addition, LEDs offer a superior flexibility in terms of colors and shapes, which leads to a potentially infinite variety of available light

Efficient and versatile light. LEDs save energy and open up manifold possibilities of design; Effizientes und vielseitiges Licht. LEDs sparen Energie und eroeffnen zahlreiche Designmoeglichkeiten

Energy Technology Data Exchange (ETDEWEB)

Fiebig, Michael [OSRAM Opto Semicondutors GmbH, Muenchen (Germany). Bereich Marketing und Business Development

2010-07-01

Light bulbs leave the European market step by step. These conventional light sources are too inefficient in the private and conventional sector. There are a lot of alternatives to light bulbs. But no technology will be able to save as much energy as light emitting diodes (LED) in the future. Today, these LEDs meet us in most different applications. Continuously new areas of application are opened up in order to reduce the power requirement clearly for the production of artificial light. Apart from energy conservation diodes also enable untold possibilities. In the future, light can be still more flexibly used owing to LED. LEDs are ideal light sources for planners and designers.

Double-Grating Displacement Structure for Improving the Light Extraction Efficiency of LEDs

Directory of Open Access Journals (Sweden)

Zhibin Wang

2012-01-01

Full Text Available To improve the light extraction efficiency of light-emitting diodes (LEDs, grating patterns were etched on GaN and silver film surfaces. The grating-patterned surface etching enabled the establishment of an LED model with a double-grating displacement structure that is based on the surface plasmon resonance principle. A numerical simulation was conducted using the finite difference time domain method. The influence of different grating periods for GaN surface and silver film thickness on light extraction efficiency was analyzed. The light extraction efficiency of LEDs was highest when the grating period satisfied grating coupling conditions. The wavelength of the highest value was also close to the light wavelength of the medium. The plasmon resonance frequencies on both sides of the silver film were affected by silver film thickness. With increasing film thickness, plasmon resonance frequency tended toward the same value and light extraction efficiency reached its maximum. When the grating period for the GaN surface was 365 nm and the silver film thickness was 390 nm, light extraction efficiency reached a maximum of 55%.

Pitch structure, but not selective attention, affects accent weightings in metrical grouping.

Science.gov (United States)

Prince, Jon B

2014-10-01

Among other cues, pitch and temporal accents contribute to grouping in musical sequences. However, exactly how they combine remains unclear, possibly because of the role of structural organization. In 3 experiments, participants rated the perceived metrical grouping of sequences that either adhered to the rules of tonal Western musical pitch structure (musical key) or did not (atonal). The tonal status of sequences did not provide any grouping cues and was irrelevant to the task. Experiment 1 established equally strong levels of pitch leap accents and duration accents in baseline conditions, which were then recombined in subsequent experiments. Neither accent type was stronger or weaker for tonal and atonal contexts. In Experiment 2, pitch leap accents dominated over duration accents, but the extent of this advantage was greater when sequences were tonal. Experiment 3 ruled out an attentional origin of this effect by replicating this finding while explicitly manipulating attention to pitch or duration accents between participant groups. Overall, the presence of tonal pitch structure made the dimension of pitch more salient at the expense of time. These findings support a dimensional salience framework in which the presence of organizational structure prioritizes the processing of the more structured dimension regardless of task relevance, independent from psychophysical difficulty, and impervious to attentional allocation.

In the Right Place at the Right Time: Asian English Accents in a Listening Test for Healthcare Professions

Science.gov (United States)

Suebsook, Khwanchanok; Adunyarittigun, Dumrong

2016-01-01

The rise of medical tourism and the increasing number of international patients from Asian countries have led Thai healthcare professionals to serve a lot of Asian patients and to encounter a complexity of language use in their workplace. There is a necessity for these professionals to strive for an understanding of Asian accents spoken by the…

Wireless high-speed data transmission with phosphorescent white-light LEDs

NARCIS (Netherlands)

Grubor, J.; Lee, S.C.J.; Langer, K-D.; Koonen, A.M.J.; Walewski, J.

2007-01-01

Wireless transmission exceeding 100 Mbit/s is demonstrated using a phosphorescent white-light LED in a lighting-like scenario. The data rate was achieved by detecting the blue part of the optical spectrum and applying discrete multi-tone modulation.

Effects of age and hearing loss on recognition of unaccented and accented multisyllabic words

Science.gov (United States)

Gordon-Salant, Sandra; Yeni-Komshian, Grace H.; Fitzgibbons, Peter J.; Cohen, Julie I.

2015-01-01

The effects of age and hearing loss on recognition of unaccented and accented words of varying syllable length were investigated. It was hypothesized that with increments in length of syllables, there would be atypical alterations in syllable stress in accented compared to native English, and that these altered stress patterns would be sensitive to auditory temporal processing deficits with aging. Sets of one-, two-, three-, and four-syllable words with the same initial syllable were recorded by one native English and two Spanish-accented talkers. Lists of these words were presented in isolation and in sentence contexts to younger and older normal-hearing listeners and to older hearing-impaired listeners. Hearing loss effects were apparent for unaccented and accented monosyllabic words, whereas age effects were observed for recognition of accented multisyllabic words, consistent with the notion that altered syllable stress patterns with accent are sensitive for revealing effects of age. Older listeners also exhibited lower recognition scores for moderately accented words in sentence contexts than in isolation, suggesting that the added demands on working memory for words in sentence contexts impact recognition of accented speech. The general pattern of results suggests that hearing loss, age, and cognitive factors limit the ability to recognize Spanish-accented speech. PMID:25698021

Life-Cycle Assessment of Energy and Environmental Impacts of LED Lighting Products Part 2: LED Manufacturing and Performance

Energy Technology Data Exchange (ETDEWEB)

Scholand, Michael; Dillon, Heather E.

2012-05-01

Part 2 of the project (this report) uses the conclusions from Part 1 as a point of departure to focus on two objectives: producing a more detailed and conservative assessment of the manufacturing process and providing a comparative LCA with other lighting products based on the improved manufacturing analysis and taking into consideration a wider range of environmental impacts. In this study, we first analyzed the manufacturing process for a white-light LED (based on a sapphire-substrate, blue-light, gallium-nitride LED pumping a yellow phosphor), to understand the impacts of the manufacturing process. We then conducted a comparative LCA, looking at the impacts associated with the Philips Master LEDbulb and comparing those to a CFL and an incandescent lamp. The comparison took into account the Philips Master LEDbulb as it is now in 2012 and then projected forward what it might be in 2017, accounting for some of the anticipated improvements in LED manufacturing, performance and driver electronics.

What makes a rhythm complex? The influence of musical training and accent type on beat perception

NARCIS (Netherlands)

Bouwer, F.L.; Burgoyne, J.A.; Odijk, D.; Honing, H.; Grahn, J.A.

2018-01-01

Perception of a regular beat in music is inferred from different types of accents. For example, increases in loudness cause intensity accents, and the grouping of time intervals in a rhythm creates temporal accents. Accents are expected to occur on the beat: when accents are “missing” on the beat,

DC Grids for Smart LED-Based Lighting: The EDISON Solution

Directory of Open Access Journals (Sweden)

Steffen Thielemans

2017-09-01

Full Text Available This paper highlights the benefits and possible drawbacks of a DC-based lighting infrastructure for powering Light Emitting Diode (LED-lamps. It also evaluates the efforts needed for integrating the so called smart lighting and other sensor/actuator based control systems, and compares existing and emerging solutions. It reviews and discusses published work in this field with special focus on the intelligent DC-based infrastructure named EDISON that is primarily dedicated to lighting, but is applicable to building automation in general. The EDISON “PowerLAN” consists of a DC-based infrastructure that offers telecommunication abilities and can be applied to lighting retrofitting scenarios for buildings. Its infrastructure allows simple and efficient powering of DC-oriented devices like LED lamps, sensors and microcontrollers, while offering a wired communication channel. This paper motivates the design choices for organizing DC lighting grids and their associated communication possibilities. It also shows how the EDISON based smart lighting solution is evolving today to include new communication technologies and to further integrate other parts of building management solutions through the OneM2M (Machine to Machine service bus.

Simulation of multicomponent light source for optical-electronic system of color analysis objects

Science.gov (United States)

Peretiagin, Vladimir S.; Alekhin, Artem A.; Korotaev, Valery V.

2016-04-01

Development of lighting technology has led to possibility of using LEDs in the specialized devices for outdoor, industrial (decorative and accent) and domestic lighting. In addition, LEDs and devices based on them are widely used for solving particular problems. For example, the LED devices are widely used for lighting of vegetables and fruit (for their sorting or growing), textile products (for the control of its quality), minerals (for their sorting), etc. Causes of active introduction LED technology in different systems, including optical-electronic devices and systems, are a large choice of emission color and LED structure, that defines the spatial, power, thermal and other parameters. Furthermore, multi-element and color devices of lighting with adjustable illumination properties can be designed and implemented by using LEDs. However, devices based on LEDs require more attention if you want to provide a certain nature of the energy or color distribution at all the work area (area of analysis or observation) or surface of the object. This paper is proposed a method of theoretical modeling of the lighting devices. The authors present the models of RGB multicomponent light source applied to optical-electronic system for the color analysis of mineral objects. The possibility of formation the uniform and homogeneous on energy and color illumination of the work area for this system is presented. Also authors showed how parameters and characteristics of optical radiation receiver (by optical-electronic system) affect on the energy, spatial, spectral and colorimetric properties of a multicomponent light source.

Investigation of structure in the modular light pipe component for LED automotive lamp

Science.gov (United States)

Chen, Hsi-Chao; Zhou, Yang; Huang, Chien-Sheng; Jhong, Wan-Ling; Cheng, Bo-Wei; Jhang, Jhe-Ming

2014-09-01

Light-Emitting Diodes (LEDs) have the advantages of small length, long lifetime, fast response time (μs), low voltage, good mechanical properties and environmental protection. Furthermore, LEDs could replace the halogen lamps to avoid the mercury pollution and economize the use of energy. Therefore, the LEDs could instead of the traditional lamp in the future and became an important light source. The proposal of this study was to investigate the effects of the structure and length of the reflector component for a LED automotive lamp. The novel LED automotive lamp was assembled by several different modularization columnar. The optimized design of the different structure and the length to the reflector was simulated by software TracePro. The design result must met the vehicle regulation of United Nations Economic Commission for Europe (UNECE) such as ECE-R19 etc. The structure of the light pipe could be designed by two steps structure. Then constitute the proper structure and choose different power LED to meet the luminous intensity of the vehicle regulation. The simulation result shows the proper structure and length has the best total luminous flux and a high luminous efficiency for the system. Also, the stray light could meet the vehicle regulation of ECE R19. Finally, the experimental result of the selected structure and length of the light pipe could match the simulation result above 80%.

A white–cyan-red LED system for low correlated colour temperature lighting

DEFF Research Database (Denmark)

Chakrabarti, Maumita; Thorseth, Anders; Corell, Dennis Dan

2015-01-01

A white LED complemented by cyan and red LEDs is a good candidate for achieving high colour rendering at low correlated colour temperatures. This is usually very difficult with commercially available white LEDs. In addition, the system is able to replace incandescent lighting in many applications...... to 2400 K. Within this range the white light is characterized by a high general colour rendering index (Ra>90), special colour rendering indices for saturated red objects (R9>85), and low chromaticity distance (Duv) from the Planckian locus (Duv

Light extraction from GaN-based LED structures on silicon-on-insulator substrates

Energy Technology Data Exchange (ETDEWEB)

Tripathy, S.; Teo, S.L.; Lin, V.K.X.; Chen, M.F. [Institute of Materials Research and Engineering, A*STAR (Agency for Science, Technology, and Research), 117602 (Singapore); Dadgar, A.; Krost, A. [Institut fuer Exerimentelle Physik, Otto-von Guericke Universitaet Magdeburg, Universitaetsplatz 1, 39016 Magdeburg (Germany); AZZURRO Semiconductors AG, Universitaetsplatz 1, 39016 Magdeburg (Germany); Christen, J. [Institut fuer Exerimentelle Physik, Otto-von Guericke Universitaet Magdeburg, Universitaetsplatz 1, 39016 Magdeburg (Germany)

2010-01-15

Nano-patterning of GaN-based devices is a promising technology in the development of high output power devices. Recent researches have been focused on the realization of two-dimensional (2D) photonic crystal (PhC) structure to improve light extraction efficiency and to control the direction of emission. In this study, we have demonstrated improved light extraction from green light emitting diode (LED) structures on thin silicon-on-insulator (SOI) substrates using surface nanopatterning. Scanning electron microscopy (SEM) is used to probe the size, shape, and etch depth of nano-patterns on the LED surfaces. Different types of nanopatterns were created by e-beam lithography and inductively coupled plasma etching. The LED structures after post processing are studied by photoluminescence (PL) measurements. The GaN nanophotonic structures formed by ICP etching led to more than five-fold increase in the intensity of the green emission. The improved light extraction is due to the combination of SOI substrate reflectivity and photonic structures on top GaN LED surfaces. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

LED and Halogen Light Transmission through a CAD/CAM Lithium Disilicate Glass-Ceramic.

Science.gov (United States)

Pereira, Carolina Nemesio de Barros; De Magalhães, Cláudia Silami; Daleprane, Bruno; Peixoto, Rogéli Tibúrcio Ribeiro da Cunha; Ferreira, Raquel da Conceição; Cury, Luiz Alberto; Moreira, Allyson Nogueira

2015-01-01

The effect of thickness, shade and translucency of CAD/CAM lithium disilicate glass-ceramic on light transmission of light-emitting diode (LED) and quartz-tungsten-halogen units (QTH) were evaluated. Ceramic IPS e.max CAD shades A1, A2, A3, A3.5, high (HT) and low (LT) translucency were cut (1, 2, 3, 4 and 5 mm). Light sources emission spectra were determined. Light intensity incident and transmitted through each ceramic sample was measured to determine light transmission percentage (TP). Statistical analysis used a linear regression model. There was significant interaction between light source and ceramic translucency (p=0.008) and strong negative correlation (R=-0.845, pceramic thickness and TP. Increasing one unit in thickness led to 3.17 reduction in TP. There was no significant difference in TP (p=0.124) between shades A1 (ß1=0) and A2 (ß1=-0.45) but significant reduction occurred for A3 (ß1=-0.83) and A3.5 (ß1=-2.18). The interaction QTH/HT provided higher TP (ß1=0) than LED/HT (ß1=-2.92), QTH/LT (ß1=-3.75) and LED/LT (ß1=-5.58). Light transmission was more effective using halogen source and high-translucency ceramics, decreased as the ceramic thickness increased and was higher for the lighter shades, A1 and A2. From the regression model (R2=0.85), an equation was obtained to estimate TP value using each variable ß1 found. A maximum TP of 25% for QTH and 20% for LED was found, suggesting that ceramic light attenuation could compromise light cured and dual cure resin cements polymerization.

Bivariate constant stress degradation model: LED lighting system reliability estimation with two-stage modelling

NARCIS (Netherlands)

Sari, J.K.; Newby, M.J.; Brombacher, A.C.; Tang, L.C.

2009-01-01

Light-emitting diode (LED) lamp has received great attention as a potential replacement for the more commercially available lighting technology, such as incandescence and fluorescence lamps. LED which is the main component of LED lamp has a very long lifetime. This means that no or very few failures

LED lighting for greenhouses. Final report; LED belysning til vaeksthuse. Slutrapport

Energy Technology Data Exchange (ETDEWEB)

OEstergaard, J.E. (Syddansk Univ. (SDU). Erhvervsinnovation og Teknologi, Odense (Denmark))

2011-01-15

The project had 3 main objectives: 1) To develop a prototype of a LED-based luminaire that can replace the existing glasshouse horticultural lighting. The project have developed a working prototype and experimentally replaced the traditional HPS luminaires in a controlled growing area. The project succeeded in producing plants of comparable quality. However, the project shows that the prototype can be improved by: x) being further integrated into the existing horticultural production technology (eg climate computers and purchase of electricity) x) adapting configuration of luminaires specifically to each plant variety x) adapting different cooling technologies to match specific customer needs x) In some cases being combined with heat input to optimize the overall economy. 2) To achieve an effective electricity savings of 50-80% - equivalent to a value of approx. DKK 5 million for a medium sized nursery. The verified electricity savings was 40%. In test setups and in well defined and controllable production areas the prototypes achieved electricity savings of > 50%. It is expected that a new generation of LEDs (Q3 2010) will allow for greater power savings. 3) To continue prototype development and initiate commercialization of the project through the company Fionia Lighting A/S. The shareholders of the company have allocated capital to the company to allow us to address the main challenges in commercializing the technology. It is expected that the company will enter a strategic alliance with a major industrial player in the beginning of 2011. (Author)

Color design model of high color rendering index white-light LED module.

Science.gov (United States)

Ying, Shang-Ping; Fu, Han-Kuei; Hsieh, Hsin-Hsin; Hsieh, Kun-Yang

2017-05-10

The traditional white-light light-emitting diode (LED) is packaged with a single chip and a single phosphor but has a poor color rendering index (CRI). The next-generation package comprises two chips and a single phosphor, has a high CRI, and retains high luminous efficacy. This study employs two chips and two phosphors to improve the diode's color tunability with various proportions of two phosphors and various densities of phosphor in the silicone used. A color design model is established for color fine-tuning of the white-light LED module. The maximum difference between the measured and color-design-model simulated CIE 1931 color coordinates is approximately 0.0063 around a correlated color temperature (CCT) of 2500 K. This study provides a rapid method to obtain the color fine-tuning of a white-light LED module with a high CRI and luminous efficacy.

Secrecy Dimming Capacity in Multi-LED PAM-Based Visible Light Communications

Directory of Open Access Journals (Sweden)

Byung Wook Kim

2017-01-01

Full Text Available Recently, mobile cloud computing (MCC has gained a lot of interest for researchers building the next-generation mobile applications. Because unauthorized access may cause serious problems, security and privacy with MCC have become significant issues. This paper addresses the secrecy dimming capacity of secure transmission in MCC over visible light communication (VLC channels. By obtaining the entropy-maximizing symbol probability of multiple light emitting diode- (LED- based pulse amplitude modulation (PAM, mathematical analysis of the secrecy dimming capacity of VLC was derived. Simulation results show that the secure transmission ability of multi-LED-based VLC is determined according to the number of activated LEDs and target dimming level. This can be a guideline for practical VLC-based mobile network designers intending to secure wireless transmission and to decide on the number of activated LEDs at target dimming level to operate.

Development of Efficient UV-LED Phosphor Coatings for Energy Saving Solid State Lighting

International Nuclear Information System (INIS)

Uwe Happek

2006-01-01

The University of Georgia, in collaboration with GE Global Research, has investigated the relevant quenching mechanism of phosphor coatings used in white light devices based on UV LEDs. The final goal of the project was the design and fabrication of a high-efficacy white light UV-LED device through improved geometry and optimized phosphor coatings. At the end of the research period, which was extended to seamlessly carry over the research to a follow-up program, we have demonstrated a two-fold improvement in the conversion efficiency of a white light LED device, where the increase efficacy is due to both improved phosphor quantum efficiency and lamp geometry. Working prototypes have been displayed at DOE sponsored meetings and during the final presentation at the DOE Headquarters in Washington, DC. During the first phase of the project, a fundamental understanding of quenching processes in UV-LEDs was obtained, and the relationships that describe the performance of the phosphor as a function of photon flux, temperature, and phosphor composition were established. In the second phase of the project, these findings were then implemented to design the improved UV-LED lamp. In addition, our research provides a road map for the design of efficient white light LEDs, which will be an important asset during a follow-up project led by GE

Illumination sensing in LED lighting systems based on frequency-division multiplexing

NARCIS (Netherlands)

Yang, Hongming; Bergmans, J.W.M.; Schenk, T.C.W.

2009-01-01

Recently, light emitting diode (LED) based illumination systems have attracted considerable research interest. Such systems normally consist of a large number of LEDs. In order to facilitate the control of such high-complexity system, a novel signal processing application, namely illumination

Demonstration Assessment of Light-Emitting Diode (LED) Roadway Lighting at the I-35W Bridge, Minneapolis, MN

Energy Technology Data Exchange (ETDEWEB)

Kinzey, Bruce R.; Myer, Michael

2009-08-31

This report describes the process and results of a demonstration of solid-state lighting (SSL) technology conducted in 2009 at the recently reconstructed I-35W bridge in Minneapolis, MN. The project was supported under the U.S. Department of Energy (DOE) Solid-State Lighting GATEWAY Technology Demonstration Program. Other participants in the demonstration project included the Minnesota Department of Transportation (Mn/DOT), Federal Highways Administration (FHWA), and BetaLED™ (a division of Ruud Lighting). Pacific Northwest National Laboratory (PNNL) conducted the measurements and analysis of the results. DOE has implemented a three-year evaluation of the LED luminaires in this installation in order to develop new longitudinal field data on LED performance in a challenging, real-world environment. This document provides information through the initial phase of the I-35W bridge project, up to and including the opening of the bridge to the public and the initial feedback received on the LED lighting installation from bridge users. Initial findings of the evaluation are favorable, with minimum energy savings level of 13% for the LED installation relative to the simulated base case using 250W high-pressure sodium (HPS) fixtures. The LEDs had an average illuminance level of 0.91 foot candles compared to 1.29 fc for the HPS lamps. The LED luminaires cost $38,000 more than HPS lamps, yielding a lengthy payback period, however the bridge contractor had offered to include the LED luminaires as part of the construction package at no additional cost. One potentially significant benefit of the LEDs in this installation is avoiding rolling lane closures on the heavily-traveled interstate bridge for the purpose of relamping the HPS fixtures. Rolling lane closures involve multiple crew members and various maintenance and safety vehicles, diversion of traffic, as well as related administrative tasks (e.g., approvals, scheduling, etc.). Mn/DOT records show an average cost of

Automaticity and stability of adaptation to a foreign-accented speaker

NARCIS (Netherlands)

Witteman, M.J.; Bardhan, N.P.; Weber, A.C.; McQueen, J.M.

2015-01-01

In three cross-modal priming experiments we asked whether adaptation to a foreign-accented speaker is automatic, and whether adaptation can be seen after a long delay between initial exposure and test. Dutch listeners were exposed to a Hebrew-accented Dutch speaker with two types of Dutch words:

A Short Note on Accent-Bias, Social Identity and Ethnocentrism

Science.gov (United States)

Chakraborty, Rahul

2017-01-01

This paper discusses the interrelations among accent-based biases, social identity and ethnocentrism. Construction of social identity creates a set of ethnocentric values within a person, which indirectly or directly plays a pivotal role in generating accent related biases. Starting with Tajfel's (1959) social identity theory and then the…

Bridging “green gap” of LEDs: Giant light output enhancement and directional control of LEDs via embedded nano-void photonic crystals

KAUST Repository

Tsai, Yu-Lin

2015-11-23

Green LEDs do not show the same level of performance as their blue and red cousins, greatly hindering the solid-state lighting development, which is so-called “green gap”. In this work, nano-void photonic crystals (NVPCs) were fabricated to embed within the GaN/InGaN green LEDs by using epitaxial lateral overgrowth (ELO) and nano-sphere lithography techniques. The NVPCs act as an efficient scattering back-reflector to outcouple the guided and downward photons, which not only boosting light extraction efficiency of LEDs with an enhancement of 78% but also collimating the view angle of LEDs from 131.5゜to 114.0゜. This could be because the highly scattering nature of NVPCs which reduce the interference giving rise to Fabry-Perot resonance. Moreover, due to the threading dislocation suppression and strain relief by the NVPCs, the internal quantum efficiency was increased by 25% and droop behavior was reduced from 37.4% to 25.9%. The enhancement of light output power can be achieved as high as 151% at a driving current of 350 mA. Giant light output enhancement and directional control via NVPCs points the way towards a promising avenue of solid-state lighting.

Bridging “green gap” of LEDs: Giant light output enhancement and directional control of LEDs via embedded nano-void photonic crystals

KAUST Repository

Tsai, Yu-Lin; Liu, Che-Yu; Krishnan, Chirenjeevi; Lin, Da-Wei; Chu, You-Chen; Chen, Tzu-Pei; Shen, Tien-Lin; Kao, Tsung-Sheng; Charlton, Martin; Yu, Peichen; Lin, Chien-Chung; Kuo, Hao-Chung; He, Jr-Hau

2015-01-01

Green LEDs do not show the same level of performance as their blue and red cousins, greatly hindering the solid-state lighting development, which is so-called “green gap”. In this work, nano-void photonic crystals (NVPCs) were fabricated to embed within the GaN/InGaN green LEDs by using epitaxial lateral overgrowth (ELO) and nano-sphere lithography techniques. The NVPCs act as an efficient scattering back-reflector to outcouple the guided and downward photons, which not only boosting light extraction efficiency of LEDs with an enhancement of 78% but also collimating the view angle of LEDs from 131.5゜to 114.0゜. This could be because the highly scattering nature of NVPCs which reduce the interference giving rise to Fabry-Perot resonance. Moreover, due to the threading dislocation suppression and strain relief by the NVPCs, the internal quantum efficiency was increased by 25% and droop behavior was reduced from 37.4% to 25.9%. The enhancement of light output power can be achieved as high as 151% at a driving current of 350 mA. Giant light output enhancement and directional control via NVPCs points the way towards a promising avenue of solid-state lighting.

The cinema LED lighting system design based on SCM

Science.gov (United States)

En, De; Wang, Xiaobin

2010-11-01

A LED lighting system in the modern theater and the corresponding control program is introduced. Studies show that moderate and mutative brightness in the space would attract audiences' attention on the screen easily. SCM controls LED dynamically by outputting PWM pulse in different duty cycle. That cinema dome lights' intensity can vary with the plot changed, make people get a better view of experience. This article expounds the architecture of hardware system in the schedule and the control flow of the host of the solution. Besides, it introduces the design of software as well. At last, the system which is proved energy-saving, reliable, good visual effect and having using value by means of producing a small-scale model, which reproduce the whole system and achieves the desired result.

Measurements of UGR of LED light by a DSLR colorimeter

Science.gov (United States)

Hsu, Shau-Wei; Chen, Cheng-Hsien; Jiaan, Yuh-Der

2012-10-01

We have developed an image-based measurement method on UGR (unified glare rating) of interior lighting environment. A calibrated DSLR (digital single-lens reflex camera) with an ultra wide-angle lens was used to measure the luminance distribution, by which the corresponding parameters can be automatically calculated. A LED lighting was placed in a room and measured at various positions and directions to study the properties of UGR. The testing results are fitted with visual experiences and UGR principles. To further examine the results, a spectroradiometer and an illuminance meter were respectively used to measure the luminance and illuminance at the same position and orientation of the DSLR. The calculation of UGR by this image-based method may solve the problem of non-uniform luminance-distribution of LED lighting, and was studied on segmentation of the luminance graph for the calculations.

Does seeing an Asian face make speech sound more accented?

Science.gov (United States)

Zheng, Yi; Samuel, Arthur G

2017-08-01

Prior studies have reported that seeing an Asian face makes American English sound more accented. The current study investigates whether this effect is perceptual, or if it instead occurs at a later decision stage. We first replicated the finding that showing static Asian and Caucasian faces can shift people's reports about the accentedness of speech accompanying the pictures. When we changed the static pictures to dubbed videos, reducing the demand characteristics, the shift in reported accentedness largely disappeared. By including unambiguous items along with the original ambiguous items, we introduced a contrast bias and actually reversed the shift, with the Asian-face videos yielding lower judgments of accentedness than the Caucasian-face videos. By changing to a mixed rather than blocked design, so that the ethnicity of the videos varied from trial to trial, we eliminated the difference in accentedness rating. Finally, we tested participants' perception of accented speech using the selective adaptation paradigm. After establishing that an auditory-only accented adaptor shifted the perception of how accented test words are, we found that no such adaptation effect occurred when the adapting sounds relied on visual information (Asian vs. Caucasian videos) to influence the accentedness of an ambiguous auditory adaptor. Collectively, the results demonstrate that visual information can affect the interpretation, but not the perception, of accented speech.

Assessing the use of Low Voltage UV-light Emitting Miniature LEDs for Marine Biofouling Control

Science.gov (United States)

2016-07-01

of that required to drive traditional UV mercury lamps . Secondly, given their small size and relatively low cost, UV LEDs provide ease of maintenance...UNCLASSIFIED UNCLASSIFIED Assessing the use of Low Voltage UV -light Emitting Miniature LEDs for Marine Biofouling Control Richard...settling organisms. The introduction of miniature UV light emitting diodes ( LEDs ) as a light source enables them to be embedded into thin, flexible

LED surgical lighting system with multiple free-form surfaces for highly sterile operating theater application.

Science.gov (United States)

Liu, Peng; Zhang, Yaqin; Zheng, Zhenrong; Li, Haifeng; Liu, Xu

2014-06-01

Although the ventilation system is widely employed in the operating theater, a strictly sterile surgical environment still cannot be ensured because of laminar disturbance, which is mainly caused by the surgical lighting system. Abandoning traditional products, we propose an LED surgical lighting system, which can alleviate the laminar disturbance and provide an appropriate lighting condition for surgery. It contains a certain amount of LED lens units, which are embedded in the ceiling and arranged around the air supply smallpox. The LED lens unit integrated with an LED light source and a free-form lens is required to produce a uniform circular illumination with a large tolerance to the change of lighting distance. To achieve such a dedicated lens, two free-form refractive surfaces, which are converted into two ordinary differential equations by the design method presented in this paper, are used to deflect the rays. The results show that the LED surgical lighting system can provide an excellent illumination environment for surgery, and, apparently, the laminar disturbance also can be relieved.

Monochromic radiation through light-emitting diode (LED positively augments in vitro shoot regeneration in Orchid (Dendrobium sonia

Directory of Open Access Journals (Sweden)

Vandita Billore

2017-07-01

Full Text Available Monochromatic lights emitted by light-emitting diodes (LEDs have generated great interest for efficient and controlled growth in vitro, especially of plants which are endangered or require specific intensity and wavelength of light. In the present study, we have evaluated the effect of monochromatic LEDs on in vitro morphogenesis: growth, proliferation of shoot cultures, and rooting of Dendrobium sonia. Different light sources viz. white LEDs (W, blue LEDs (B, yellow LEDs (Y and red LEDs (R were tested under photoperiod of 16 h of exposure and 8 h of dark. The frequency of morphogenesis depended on the wavelength of the applied monochromatic light. Higher wavelength monochromatic light (yellow light was observed to induce higher shoot proliferation (98%, early PLB (protocorm-like bodies formation, differentiation into green buds and shoot initiation as compared to red, blue and white light treatments. Yellow light also yielded higher number of shoots per explants (29 shoots/explant than red, blue and white light treatments. The results suggest that the monochromatic light sources stimulate morphogenic effects on in vitro culture of Dendrobium sonia, and that yellow light treatment can be used to enhance the efficiency of micropropagation.

Response of Eustoma Leaf Phenotype and Photosynthetic Performance to LED Light Quality

Directory of Open Access Journals (Sweden)

Md Zohurul Kadir Roni

2017-10-01

Full Text Available In a controlled environment, light from light-emitting diodes (LEDs has been associated with affecting the leaf characteristics of Eustoma. LEDs help plant growth and development, yet little is known about photosynthetic performance and related anatomical features in the early growth stage of Eustoma leaves. In this study, we examined the effects of blue (B, red (R, and white (W LEDs on the photosynthetic performance of Eustoma leaves, as well as leaf morphology and anatomy including epidermal layer thickness, palisade cells, and stomatal characteristics. Leaves grown under B LEDs were thicker and had a higher chlorophyll content than those grown under the R and W LEDs. Leaves under B LEDs had greater net photosynthetic rates (A, stomatal conductance (gs, and transpiration rates (E, especially at a higher photon flux density (PPFD, that resulted in a decrease in the intercellular CO2 concentration (Ci, than leaves under the W and R LEDs. B LEDs resulted in greater abaxial epidermal layer thickness and palisade cell length and width than the R and W LED treatments. The palisade cells also developed a more cylindrical shape in response to the B LEDs. B LED leaves also showed greater guard cell length, breadth, and area, and stomatal density, than W or R LEDs, which may contribute to increased A, gs and E at higher PPFDs.

Assessment of filament led bulbs with respect to temporal light artefacts

DEFF Research Database (Denmark)

Lindén, Johannes; Thorseth, Anders; Corell, Dennis Dan

2017-01-01

Temporal light artefacts, abbreviated TLAs (including flicker, stroboscopic effect and phantom arrays), i.e. undesired time modulation in luminance from a light source, has shown to be a threat to wider SSL adoption especially related to dimming functions and low-quality LED products. This is due...... to the effects that both noticeable and unperceivable TLAs have on human perception and wellbeing. In the present work a number of filament LED bulbs, currently available on the market, are assessed primarily with respect to TLAs, but also with respect to photometric, colorimetric and efficiency properties...

Demonstration Assessment of Light-Emitting Diode (LED) Roadway Lighting on Lija Loop in Portland, OR

International Nuclear Information System (INIS)

Kinzey, Bruce R.; Myer, Michael

2009-01-01

This report describes the process and results of a demonstration of solid-state lighting (SSL) technology in a residential street lighting application, under the U.S. Department of Energy GATEWAY Solid-State Lighting Technology Demonstration Program. In this project, eight 100W (nominal) high-pressure sodium cobra head fixtures were replaced with a like number of LED street light luminaires manufactured by Leotek, Inc. The Leotek product achieved an estimated payback in the Lija Loop installation of about 20 years for replacement scenarios and a much shorter 7.6 years for new installations. Much of the associated energy savings (55%) supporting these payback periods, however, were achieved by reducing average horizontal photopic illuminance a similar amount (53%). Examined from a different perspective, the measured performance suggests that the Leotek product is at approximate parity with the HPS cobra head in terms of average delivered photopic illumination for a given power consumption. HPS comprises the second most efficacious street lighting technology available, exceeded only by low pressure sodium (LPS). LPS technology is not considered suitable for most street lighting applications due to its monochromatic spectral output and poor color rendering ability; therefore, this LED product is performing at an efficiency level comparable to its primary competition in this application.

Novel Coatings for Enhancement of Light-Emitting Diodes (LEDs)

Science.gov (United States)

2006-10-28

quantum efficiency of LEDs. SAIC’s strength is this area is a proprietary nonimaging optics code. In consultation with Lumileds, SAIC developed designs for...five different optical ele- ments that collect and project light from a LED. The simulations showed that the designs achieve a significant improvement... optical microscope at 100x power the coating is not visible. Fire sample 6DecO4P1 in tube furnace As a first test, sample 6Dec04P1 was progressively

A Multi-Perspective Investigation of Attitudes towards English Accents in Hong Kong: Implications for Pronunciation Teaching

Science.gov (United States)

Chan, Jim Y. H.

2016-01-01

The study reported in this article examined Hong Kong students' attitudes towards English accents from three interrelated perspectives: (1) their awareness of accents, (2) their perception of accents in relation to the dimensions of status and solidarity, and (3) their choice of accents in various local language-using contexts. By means of the…

The nanorod approach: GaN NanoLEDs for solid state lighting

Energy Technology Data Exchange (ETDEWEB)

Waag, Andreas; Wang, Xue; Fuendling, Soenke; Ledig, Johannes; Erenburg, Milena; Neumann, Richard; Al Suleiman, Mohamed; Merzsch, Stephan; Wei, Jiandong; Li, Shunfeng; Wehmann, Hergo H. [Institut fuer Halbleitertechnik, TU Braunschweig, Hans-Sommer-Strasse 66, 38106 Braunschweig (Germany); Bergbauer, Werner; Strassburg, Martin [OSRAM Opto Semiconductors GmbH, Leibnizstr. 4, 93055 Regensburg (Germany); Trampert, Achim; Jahn, Uwe; Riechert, Henning [Paul-Drude-Institut fuer Festkoerperelektronik, Hausvogteiplatz 5-7, 10117 Berlin (Germany)

2011-07-15

Vertically aligned GaN nanorods have recently obtained substantial interest as a new approach to solid state lighting. In comparison to conventional planar LEDs, 3D NanoLEDs are expected to offer substantial advantageous: very low defect density, quasi free-standing, no strain due to mismatch of thermal expansion coefficients, no substrate bending even when grown on large area silicon. Core-shell strategies are another very interesting aspect. The active LED surface per wafer could be increased by more than one order of magnitude. However, most of these advantages have not yet been proven in real devices, which would include a quantitative comparison of light emission. Related to the 3D character, there are also technological risks. In the following we will discuss the main developments which have paved the way up to this point, including a detailed discussion of possible benefits and risks connected with the NanoLED approach (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Light outputs of LED with various refractive indices and geometrical structures of encapsulants

Energy Technology Data Exchange (ETDEWEB)

Kim, Kyung-Tae [Chosun University, Gwangju (Korea, Republic of); Jo, Kyoung-Woo; Hwang, Jung-Ha; Kwon, Ho-Ki [LG Innotek Co., Ltd., Seoul (Korea, Republic of); Park, Si-Hyun [Yeungnam University, Gyeongsan (Korea, Republic of)

2010-12-15

In this paper we present the results of experiments and simulations for the light output power from LEDs for various refractive indices and the geometrical structures of the LED encapsulants. InGaN-based LED chips were fabricated and were bonded in Ag reflector cups within polyphthalamide (PPA) chip carriers; then, encapsulants with various refractive indices and the geometrical structures were fabricated onto them by using a dispensing method. The light output power with the encapsulant was shown to increase with the refractive index of the encapsulant materials in the case of a spherical encapsulant while it decreased in the case of a flat geometry encapsulant. We performed ray tracing simulations for the LED light output and confirmed that the simulation results were consistent with our experimentally measured results. In addition, the light output with the encapsulant rapidly increased with the sidewall angle of the chip carrier in the case of the flat encapsulant while it was not affected by the sidewall angle, remaining constant, in the case of the spherical geometry.

Light outputs of LED with various refractive indices and geometrical structures of encapsulants

International Nuclear Information System (INIS)

Kim, Kyung-Tae; Jo, Kyoung-Woo; Hwang, Jung-Ha; Kwon, Ho-Ki; Park, Si-Hyun

2010-01-01

In this paper we present the results of experiments and simulations for the light output power from LEDs for various refractive indices and the geometrical structures of the LED encapsulants. InGaN-based LED chips were fabricated and were bonded in Ag reflector cups within polyphthalamide (PPA) chip carriers; then, encapsulants with various refractive indices and the geometrical structures were fabricated onto them by using a dispensing method. The light output power with the encapsulant was shown to increase with the refractive index of the encapsulant materials in the case of a spherical encapsulant while it decreased in the case of a flat geometry encapsulant. We performed ray tracing simulations for the LED light output and confirmed that the simulation results were consistent with our experimentally measured results. In addition, the light output with the encapsulant rapidly increased with the sidewall angle of the chip carrier in the case of the flat encapsulant while it was not affected by the sidewall angle, remaining constant, in the case of the spherical geometry.

Spatial layout optimization design of multi-type LEDs lighting source based on photoelectrothermal coupling theory

Science.gov (United States)

Xue, Lingyun; Li, Guang; Chen, Qingguang; Rao, Huanle; Xu, Ping

2018-03-01

Multiple LED-based spectral synthesis technology has been widely used in the fields of solar simulator, color mixing, and artificial lighting of plant factory and so on. Generally, amounts of LEDs are spatially arranged with compact layout to obtain the high power density output. Mutual thermal spreading among LEDs will produce the coupled thermal effect which will additionally increase the junction temperature of LED. Affected by the Photoelectric thermal coupling effect of LED, the spectrum of LED will shift and luminous efficiency will decrease. Correspondingly, the spectral synthesis result will mismatch. Therefore, thermal management of LED spatial layout plays an important role for multi-LEDs light source system. In the paper, the thermal dissipation network topology model considering the mutual thermal spreading effect among the LEDs is proposed for multi-LEDs system with various types of power. The junction temperature increment cased by the thermal coupling has the great relation with the spatial arrangement. To minimize the thermal coupling effect, an optimized method of LED spatial layout for the specific light source structure is presented and analyzed. The results showed that layout of LED with high-power are arranged in the corner and low-power in the center. Finally, according to this method, it is convenient to determine the spatial layout of LEDs in a system having any kind of light source structure, and has the advantages of being universally applicable to facilitate adjustment.

The Design and Comparison of Central and Distributed Light Sensored Smart LED Lighting Systems

Directory of Open Access Journals (Sweden)

Mehmet Ali Özçelik

2018-01-01

Full Text Available There is a lack of published peer-reviewed research comparing the efficiencies of distributed versus central sensor-controlled LED lighting systems. This research proposes improving the smart illumination of a room with external fenestration using central and distributed light sensors. The optical and electrical measurements of the daylight have been made in the case where the light was not distributed evenly and not sufficient. Test results show that the proposed distributed light sensor illumination system has increased the efficiency by 28% when compared to the proposed central system. It has also been shown that the two tested systems are more cost-effective than common smart illumination systems.

A Simple, Small-Scale Lego Colorimeter with a Light-Emitting Diode (LED) Used as Detector

Science.gov (United States)

Asheim, Jonas; Kvittingen, Eivind V.; Kvittingen, Lise; Verley, Richard

2014-01-01

This article describes how to construct a simple, inexpensive, and robust colorimeter from a few Lego bricks, in which one light-emitting diode (LED) is used as a light source and a second LED as a light detector. The colorimeter is suited to various grades and curricula.

Technical Feasibility Assessment of LED Roadway Lighting on the Golden Gate Bridge

Energy Technology Data Exchange (ETDEWEB)

Tuenge, Jason R.

2012-09-01

Subsequent to preliminary investigations by the Golden Gate Bridge Highway & Transportation District (GGB), in coordination with Pacific Gas & Electric (PG&E), the GATEWAY Demonstration program was asked to evaluate the technical feasibility of replacing existing roadway lighting on the bridge with products utilizing LED technology. GGB and PG&E also indicated interest in induction (i.e., electrodeless fluorescent) technology, since both light source types feature rated lifetimes significantly exceeding those of the existing high-pressure sodium (HPS) and low-pressure sodium (LPS) products. The goal of the study was to identify any solutions which would reduce energy use and maintenance without compromising the quantity or quality of existing illumination. Products used for roadway lighting on the historic bridge must be installed within the existing amber-lensed shoebox-style luminaire housings. It was determined that induction technology does not appear to represent a viable alternative for the roadway luminaires in this application; any energy savings would be attributable to a reduction in light levels. Although no suitable LED retrofit kits were identified for installation within existing luminaire housings, several complete LED luminaires were found to offer energy savings of 6-18%, suggesting custom LED retrofit kits could be developed to match or exceed the performance of the existing shoeboxes. Luminaires utilizing ceramic metal halide (CMH) were also evaluated, and some were found to offer 28% energy savings, but these products might actually increase maintenance due to the shorter rated lamp life. Plasma technology was evaluated, as well, but no suitable products were identified. Analysis provided in this report was completed in May 2012. Although LED technologies are expected to become increasingly viable over time, and product mock-ups may reveal near-term solutions, some options not currently considered by GGB may ultimately merit evaluation. For

Accent modulates access to word meaning: Evidence for a speaker-model account of spoken word recognition.

Science.gov (United States)

Cai, Zhenguang G; Gilbert, Rebecca A; Davis, Matthew H; Gaskell, M Gareth; Farrar, Lauren; Adler, Sarah; Rodd, Jennifer M

2017-11-01

Speech carries accent information relevant to determining the speaker's linguistic and social background. A series of web-based experiments demonstrate that accent cues can modulate access to word meaning. In Experiments 1-3, British participants were more likely to retrieve the American dominant meaning (e.g., hat meaning of "bonnet") in a word association task if they heard the words in an American than a British accent. In addition, results from a speeded semantic decision task (Experiment 4) and sentence comprehension task (Experiment 5) confirm that accent modulates on-line meaning retrieval such that comprehension of ambiguous words is easier when the relevant word meaning is dominant in the speaker's dialect. Critically, neutral-accent speech items, created by morphing British- and American-accented recordings, were interpreted in a similar way to accented words when embedded in a context of accented words (Experiment 2). This finding indicates that listeners do not use accent to guide meaning retrieval on a word-by-word basis; instead they use accent information to determine the dialectic identity of a speaker and then use their experience of that dialect to guide meaning access for all words spoken by that person. These results motivate a speaker-model account of spoken word recognition in which comprehenders determine key characteristics of their interlocutor and use this knowledge to guide word meaning access. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

The neural processing of foreign-accented speech and its relationship to listener bias

Directory of Open Access Journals (Sweden)

Han-Gyol eYi

2014-10-01

Full Text Available Foreign-accented speech often presents a challenging listening condition. In addition to deviations from the target speech norms related to the inexperience of the nonnative speaker, listener characteristics may play a role in determining intelligibility levels. We have previously shown that an implicit visual bias for associating East Asian faces and foreignness predicts the listeners’ perceptual ability to process Korean-accented English audiovisual speech (Yi et al., 2013. Here, we examine the neural mechanism underlying the influence of listener bias to foreign faces on speech perception. In a functional magnetic resonance imaging (fMRI study, native English speakers listened to native- and Korean-accented English sentences, with or without faces. The participants’ Asian-foreign association was measured using an implicit association test (IAT, conducted outside the scanner. We found that foreign-accented speech evoked greater activity in the bilateral primary auditory cortices and the inferior frontal gyri, potentially reflecting greater computational demand. Higher IAT scores, indicating greater bias, were associated with increased BOLD response to foreign-accented speech with faces in the primary auditory cortex, the early node for spectrotemporal analysis. We conclude the following: (1 foreign-accented speech perception places greater demand on the neural systems underlying speech perception; (2 face of the talker can exaggerate the perceived foreignness of foreign-accented speech; (3 implicit Asian-foreign association is associated with decreased neural efficiency in early spectrotemporal processing.

Monolithically Integrated Light Feedback Control Circuit for Blue/UV LED Smart Package

NARCIS (Netherlands)

Koladouz Esfahani, Z.; Tohidian, M.; van Zeijl, H.W.; Kolahdouz, Mohammadreza; Zhang, G.Q.

2017-01-01

Given the performance decay of high-power light-emitting diode (LED) chips over time and package condition changes, having a reliable output light for sensitive applications is a point of concern. In this study, a light feedback control circuit, including blue-selective photodiodes, for

Study and Implementation of White Power-LED Based Indoor Lighting Application for the Healthcare Sector

Science.gov (United States)

Chakraborty, A.; Ganguly, R.

With the current technological growth in the field of device fabrication, white power-LED's are available for solid state lighting applications. This is a paradigm shift from electrical lighting to electronic lighting. The implemented systems are showing some promise by saving a considerable amount of energy as well as providing a good and acceptable illumination level. However, the `useful life' of such devices is an important parameter. If the proper device is not chosen, the desired reliability and performance will not be obtained. In the present work, different parameters associated with reliability of such LED's are studied. Four different varieties of LED's are put to test the `useful life' as per IESNA LM 79 standard. From the results obtained, the proper LED is chosen for further application. Subsequently, lighting design is done for a hospital waiting room (indoor application) with 24 × 7 lighting requirements for replacement of existing CFLs there. The calculations show that although the initial cost is higher for LED based lighting, yet the savings on energy and replacement of the lamp results in a payback time of less than a year.

LEDWIRE: A Versatile Networking Platform for Smart LED Lighting Applications Using LIN-Bus and WSNs

Directory of Open Access Journals (Sweden)

Dimitrios D. Piromalis

2016-05-01

Full Text Available In this paper, the architecture of a versatile networking and control platform for Light-Emitting Diode (LED lighting applications is presented, based on embedded wireless and wired networking technologies. All the possible power and control signals distribution topologies of the lighting fixtures are examined with particular focus on dynamic lighting applications with design metrics as the cost, the required wiring installation expenses and maintenance complexity. The proposed platform is optimized for applications where the grouping of LED-based lighting fictures clusters is essential, as well as their synchronization. With such an approach, the distributed control and synchronization of LED lighting fixtures' clusters is performed through a versatile network that uses the single wire Local Interconnect Network (LIN bus. The proposed networking platform is presented in terms of its physical layer architecture, its data protocol configuration, and its functionality for smart control. As a proof of concept, the design of a LED lighting fixture together with a LIN-to-IEEE802.15.4/ZigBee data gateway is presented.

[Hygienic aspects of the use of LED light sources for general illumination in schools].

Science.gov (United States)

Kuchma, V R; Sukhareva, L M; Teksheva, L M; Stepanova, M I; Sazaniuk, Z I

2013-01-01

For the time present becoming more common semiconductor sources of artificial lighting has become a more and more frequent practice. With the aim to study the impact of LEDs on the health of schoolchildren studies in experimental conditions (specially equipped classrooms) were performed. The comparative analysis of the state of vision, mental health and emotional state of pupils in primary, middle and high schools under fluorescent and LED lighting, meeting to the regulatory requirements, has revealed that the physiological cost of schooling in the use of LED units in classrooms is lower than in a traditional, fluorescent lighting.

Processing and Comprehension of Accented Speech by Monolingual and Bilingual Children

Science.gov (United States)

McDonald, Margarethe; Gross, Megan; Buac, Milijana; Batko, Michelle; Kaushanskaya, Margarita

2018-01-01

This study tested the effect of Spanish-accented speech on sentence comprehension in children with different degrees of Spanish experience. The hypothesis was that earlier acquisition of Spanish would be associated with enhanced comprehension of Spanish-accented speech. Three groups of 5-6-year-old children were tested: monolingual…

Audiovisual cues benefit recognition of accented speech in noise but not perceptual adaptation.

Science.gov (United States)

Banks, Briony; Gowen, Emma; Munro, Kevin J; Adank, Patti

2015-01-01

Perceptual adaptation allows humans to recognize different varieties of accented speech. We investigated whether perceptual adaptation to accented speech is facilitated if listeners can see a speaker's facial and mouth movements. In Study 1, participants listened to sentences in a novel accent and underwent a period of training with audiovisual or audio-only speech cues, presented in quiet or in background noise. A control group also underwent training with visual-only (speech-reading) cues. We observed no significant difference in perceptual adaptation between any of the groups. To address a number of remaining questions, we carried out a second study using a different accent, speaker and experimental design, in which participants listened to sentences in a non-native (Japanese) accent with audiovisual or audio-only cues, without separate training. Participants' eye gaze was recorded to verify that they looked at the speaker's face during audiovisual trials. Recognition accuracy was significantly better for audiovisual than for audio-only stimuli; however, no statistical difference in perceptual adaptation was observed between the two modalities. Furthermore, Bayesian analysis suggested that the data supported the null hypothesis. Our results suggest that although the availability of visual speech cues may be immediately beneficial for recognition of unfamiliar accented speech in noise, it does not improve perceptual adaptation.

High power light emitting diode (LED) arrays versus halogen light polymerization of oral biomaterials: Barcol hardness, compressive strength and radiometric properties.

Science.gov (United States)

Mills, Robin W; Uhl, Alexander; Blackwell, Gordon B; Jandt, Klaus D

2002-07-01

The clinical performance of light polymerized dental composites is greatly influenced by the quality of the light curing unit (LCU) used. Commonly used halogen LCUs have some specific drawbacks such as decreasing light output with time. This may result in a low degree of monomer conversion of the composites with negative clinical implications. Previous studies have shown that blue light emitting diode (LED) LCUs have the potential to polymerize dental composites without having the drawbacks of halogen LCUs. Since these studies were carried out LED technology has advanced significantly and commercial LED LCUs are now becoming available. This study investigates the Barcol hardness as a function of depth, and the compressive strength of dental composites that had been polymerized for 40 or 20s with two high power LED LCU prototypes, a commercial LED LCU, and a commercial halogen LCU. In addition the radiometric properties of the LCUs were characterized. The two high power prototype LED LCUs and the halogen LCU showed a satisfactory and similar hardness-depth performance whereas the hardness of the materials polymerized with the commercial LED LCU rapidly decreased with sample depth and reduced polymerization time (20 s). There were statistically significant differences in the overall compressive strengths of composites polymerized with different LCUs at the 95% significance level (p = 0.0016) with the two high power LED LCU prototypes and the halogen LCU forming a statistically homogenous group. In conclusion, LED LCU polymerization technology can reach the performance level of halogen LCUs. One of the first commercial LED LCUs however lacked the power reserves of the high power LED LCU prototypes.

Thermal, optical, and electrical engineering of an innovative tunable white LED light engine

Science.gov (United States)

Trivellin, Nicola; Meneghini, Matteo; Ferretti, Marco; Barbisan, Diego; Dal Lago, Matteo; Meneghesso, Gaudenzio; Zanoni, Enrico

2014-02-01

Color temperature, intensity and blue spectrum of the light affects the ganglion receptors in human brain stimulating the human nervous system. With this work we review different methods for obtaining tunable light emission spectra and propose an innovative white LED lighting system. By an in depth study of the thermal, electrical and optical characteristics of GaN and GaP based compound semiconductors for optoelectronics a specific tunable spectra has been designed. The proposed tunable white LED system is able to achieve high CRI (above 95) in a large CCT range (3000 - 5000K).

Study of LED layout in indoor visible light communication and performance analysis

Science.gov (United States)

Wang, Jiaan; Che, Ying; Wang, Xinlan; Guo, Linyang; Li, Jing

2017-10-01

Light emitting diodes(LED) could provide both illumination and data communication in indoor visible light communication(VLC) that owns the modulation bandwith from several from several MHz to seneral hundreds of MHz. The layout of LED plays an important role in maintaining a steady optical power distribution over the receiving plane. The existing rectangular LED layout does not provide a full coverage on the receiving plane leaving receiving optical power outage area, which in turn affects the best performance of the VLC system. This paper design a circular layout scheme of LED in 5mX5mX3m room based on the criterion of the illumination minimum mean square deviation. The influence of the distribution of the intensity of illumination with the radius of 1m and 1.5m,for including the wall reflection and not including the wall reflection, and make a comparison with rectangular LED layout of illumination distribution, when the number of LEDs with rectangular layout as same as circular layout. Including the number of LEDs are 4 and 16.For a specific simulation parameters as following:height of receiving plane is 0.85m,a single LEDs is composed of 60X60 LED chips, the parameters of a single chip is that transmitting power is 20mW,center luminous intensity is 0.73cd.semiangle at half power is 70deg.The parameters of concentrator is that photodiode area is 1cm2,photodiode responsivity is 0.4,field of view at the receiver is 85deg.Other parameters are that reflective index of concentrator is 1.5,reflectivity of wall is 0.8.Circular layout and rectangular layout are analyzed through simulation of the received optical power distribution, signal noise ratio distribution in non line of sight(including the wall reflection) and line of sight(not including the wall reflection),when the number of the LED is different. It is clear from the results that the received optical power distribution of non line of sight is better than line of sight, when the number of the LED are same, but

Solid State pH Sensor Based on Light Emitting Diodes (LED) As Detector Platform

Science.gov (United States)

Lau, King Tong; Shepherd, R.; Diamond, Danny; Diamond, Dermot

2006-01-01

A low-power, high sensitivity, very low-cost light emitting diode (LED)-based device developed for low-cost sensor networks was modified with bromocresol green membrane to work as a solid-state pH sensor. In this approach, a reverse-biased LED functioning as a photodiode is coupled with a second LED configured in conventional emission mode. A simple timer circuit measures how long (in microsecond) it takes for the photocurrent generated on the detector LED to discharge its capacitance from logic 1 (+5 V) to logic 0 (+1.7 V). The entire instrument provides an inherently digital output of light intensity measurements for a few cents. A light dependent resistor (LDR) modified with similar sensor membrane was also used as a comparison method. Both the LED sensor and the LDR sensor responded to various pH buffer solutions in a similar way to obtain sigmoidal curves expected of the dye. The pKa value obtained for the sensors was found to agree with the literature value.

Effect of LED-LCU light irradiance distribution on mechanical properties of resin based materials

International Nuclear Information System (INIS)

Magalhães Filho, T.R.; Weig, K.M.; Costa, M.F.; Werneck, M.M.; Barthem, R.B.; Costa Neto, C.A.

2016-01-01

The objective of this study is to analyze the light power distribution along the tip end of the light guide of three LED-LCUs (Light Curing Units) and to evaluate its effect on the mechanical properties of a polymer based dental composite. Firstly, the light power distribution over the whole area of LED-LCU light guide surface was analyzed by three methods: visual projection observation, spectral measurement and optical spectral analysis (OSA). The light power distribution and the total irradiance were different for the three LEDs used, but the wavelength was within the camphorquinone absorption spectrum. The use of a blank sheet was quite on hand to make a qualitative analysis of a beam, and it is costless. Secondly, specimens of a hybrid composite with approximately 8 mm diameter and 2 mm thickness were produced and polymerized by 20 s exposition time to each LED-LCU. Thirdly, the elastic modulus (E) and hardness (HV) were measured throughout the irradiated area by instrumented micro-indentation test (IIT), allowing to correlate localized power and mechanical properties. Both E and HV showed to be very sensitive to local power and wavelength dependent, but they followed the beam power profile. It was also shown that the mechanical properties could be directly correlated to the curing process. Very steep differences in mechanical properties over very short distances may impair the material performance, since residual stresses can easily be built over it. - Highlights: • A resin based composite (RBC) was polymerized by three different Light Emitting Diodes. • Each LED had its beam profile visually, wavelength and power analyzed. • The effective polymerization power (EPP) varied from 28% to 52% of the total beam power. • Wavelength seems to be as relevant as power in the light curing process. • Mechanical properties depend on the simultaneous effect of wavelength and power.

Effect of LED-LCU light irradiance distribution on mechanical properties of resin based materials

Energy Technology Data Exchange (ETDEWEB)

Magalhães Filho, T.R.; Weig, K.M. [Faculdade de Odontologia, Universidade Federal Fluminense, Rua São Paulo 28, CEP 24020-150 Niterói (Brazil); Engenharia Metalúrgica e de Materiais (COPPE), Universidade Federal do Rio de Janeiro, CP 68505, CEP: 21941-972 Rio de Janeiro (Brazil); Costa, M.F. [Engenharia Metalúrgica e de Materiais (COPPE), Universidade Federal do Rio de Janeiro, CP 68505, CEP: 21941-972 Rio de Janeiro (Brazil); Werneck, M.M. [Engenharia Elétrica (COPPE), Universidade Federal do Rio de Janeiro, CP 68504, CEP: 21941-972 Rio de Janeiro (Brazil); Barthem, R.B. [Instituto de Física, Universidade Federal do Rio de Janeiro, CP 68528, CEP: 21941-972 Rio de Janeiro (Brazil); Costa Neto, C.A., E-mail: celio@metalmat.ufrj.br [Engenharia Metalúrgica e de Materiais (COPPE), Universidade Federal do Rio de Janeiro, CP 68505, CEP: 21941-972 Rio de Janeiro (Brazil)

2016-06-01

The objective of this study is to analyze the light power distribution along the tip end of the light guide of three LED-LCUs (Light Curing Units) and to evaluate its effect on the mechanical properties of a polymer based dental composite. Firstly, the light power distribution over the whole area of LED-LCU light guide surface was analyzed by three methods: visual projection observation, spectral measurement and optical spectral analysis (OSA). The light power distribution and the total irradiance were different for the three LEDs used, but the wavelength was within the camphorquinone absorption spectrum. The use of a blank sheet was quite on hand to make a qualitative analysis of a beam, and it is costless. Secondly, specimens of a hybrid composite with approximately 8 mm diameter and 2 mm thickness were produced and polymerized by 20 s exposition time to each LED-LCU. Thirdly, the elastic modulus (E) and hardness (HV) were measured throughout the irradiated area by instrumented micro-indentation test (IIT), allowing to correlate localized power and mechanical properties. Both E and HV showed to be very sensitive to local power and wavelength dependent, but they followed the beam power profile. It was also shown that the mechanical properties could be directly correlated to the curing process. Very steep differences in mechanical properties over very short distances may impair the material performance, since residual stresses can easily be built over it. - Highlights: • A resin based composite (RBC) was polymerized by three different Light Emitting Diodes. • Each LED had its beam profile visually, wavelength and power analyzed. • The effective polymerization power (EPP) varied from 28% to 52% of the total beam power. • Wavelength seems to be as relevant as power in the light curing process. • Mechanical properties depend on the simultaneous effect of wavelength and power.

The study of LED light source illumination conditions for ideal algae cultivation

Science.gov (United States)

Tsai, Chun-Chin; Huang, Chien-Fu; Chen, Cin-Fu; Yue, Cheng-Feng

2017-02-01

Utilizing LED light source modules with 3 different RGB colors, the illumination effect of different wavelengths had been investigated on the growth curve of the same kind of micro algae. It was found that the best micro algae culturing status came out with long wavelength light such as red light (650 670 nm). Based on the same condition for a period of 3 weeks , the grown micro algae population density ratio represented by Optical Density (O.D.) ratio is 1?0.4?0.7 corresponding to growth with Red, Green, Blue light sources, respectively. Mixing 3 types and 2 types of LEDs with different parameters, the grown micro algae population densities were compared in terms of O.D. Interestingly enough, different light sources resulted in significant discoloration on micro algae growth, appearing yellow, brown, green, etc. Our experiments results showed such discoloration effect is reversible. Based on the same lighting condition, micro algae growth can be also affected by incubator size, nutrition supply, and temperature variation. In recent years, micro algae related technologies have been international wise a hot topic of energy and environmental protection for research and development institutes, and big energy companies among those developed countries. There will be an economically prosperous future. From this study of LED lighting to ideal algae cultivation, it was found that such built system would be capable of optimizing artificial cultivation system, leading to economic benefits for its continuous development. Since global warming causing weather change, accompanying with reducing energy sources and agriculture growth shortage are all threatening human being survival.

Garden's lighting by led-luminaries supplied by photovoltaic

International Nuclear Information System (INIS)

Vasilev, H.; Angelov, A.; Ganchev, G.

2006-01-01

The implementation of the project by investment entirely of Denima 2001 Ltd. for garden illumination of the part of the public garden 'Studentski' is consider. The illumination installation is implemented by PV batteries and by luminaries made up by fluorescent laps and LED. The goals of this pilot project are to make a comparative analyses and observation for the operation of the light system for future development

Bonding bare die LEDs on PET foils for lighting applications: Thermal design modeling and bonding experiments

NARCIS (Netherlands)

Ende, D.A. van den; Kusters, R.H.L.; Cauwe, M.; Waal, A. van der; Brand, J. van den

2012-01-01

Integration of LEDs on flexible foil substrates is of interest for flexible lighting applications and flexible photonic devices. A matrix of LEDs on a foil combined with a diffuser can be a potential alternative for flexible OLED lighting devices. Preferably, these LEDs are integrated in an

Design and fabrication of adjustable red-green-blue LED light arrays for plant research

Directory of Open Access Journals (Sweden)

Kenitz J Dustin

2005-08-01

Full Text Available Abstract Background Although specific light attributes, such as color and fluence rate, influence plant growth and development, researchers generally cannot control the fine spectral conditions of artificial plant-growth environments. Plant growth chambers are typically outfitted with fluorescent and/or incandescent fixtures that provide a general spectrum that is accommodating to the human eye and not necessarily supportive to plant development. Many studies over the last several decades, primarily in Arabidopsis thaliana, have clearly shown that variation in light quantity, quality and photoperiod can be manipulated to affect growth and control developmental transitions. Light emitting diodes (LEDs has been used for decades to test plant responses to narrow-bandwidth light. LEDs are particularly well suited for plant growth chambers, as they have an extraordinary life (about 100,000 hours, require little maintenance, and use negligible energy. These factors render LED-based light strategies particularly appropriate for space-biology as well as terrestrial applications. However, there is a need for a versatile and inexpensive LED array platform where individual wavebands can be specifically tuned to produce a series of light combinations consisting of various quantities and qualities of individual wavelengths. Two plans are presented in this report. Results In this technical report we describe the practical construction of tunable red-green-blue LED arrays to support research in plant growth and development. Two light fixture designs and corresponding circuitry are presented. The first is well suited for a laboratory environment for use in a finite area with small plants, such as Arabidopsis. The second is expandable and appropriate for growth chambers. The application of these arrays to early plant developmental studies has been validated with assays of hypocotyl growth inhibition/promotion and phototropic curvature in Arabidopsis seedlings

Computer numerical control (CNC) lithography: light-motion synchronized UV-LED lithography for 3D microfabrication

International Nuclear Information System (INIS)

Kim, Jungkwun; Allen, Mark G; Yoon, Yong-Kyu

2016-01-01

This paper presents a computer-numerical-controlled ultraviolet light-emitting diode (CNC UV-LED) lithography scheme for three-dimensional (3D) microfabrication. The CNC lithography scheme utilizes sequential multi-angled UV light exposures along with a synchronized switchable UV light source to create arbitrary 3D light traces, which are transferred into the photosensitive resist. The system comprises a switchable, movable UV-LED array as a light source, a motorized tilt-rotational sample holder, and a computer-control unit. System operation is such that the tilt-rotational sample holder moves in a pre-programmed routine, and the UV-LED is illuminated only at desired positions of the sample holder during the desired time period, enabling the formation of complex 3D microstructures. This facilitates easy fabrication of complex 3D structures, which otherwise would have required multiple manual exposure steps as in the previous multidirectional 3D UV lithography approach. Since it is batch processed, processing time is far less than that of the 3D printing approach at the expense of some reduction in the degree of achievable 3D structure complexity. In order to produce uniform light intensity from the arrayed LED light source, the UV-LED array stage has been kept rotating during exposure. UV-LED 3D fabrication capability was demonstrated through a plurality of complex structures such as V-shaped micropillars, micropanels, a micro-‘hi’ structure, a micro-‘cat’s claw,’ a micro-‘horn,’ a micro-‘calla lily,’ a micro-‘cowboy’s hat,’ and a micro-‘table napkin’ array. (paper)

Study of LED modulation effect on the photometric quantities and beam homogeneity of automotive lighting

Science.gov (United States)

Koudelka, Petr; Hanulak, Patrik; Jaros, Jakub; Papes, Martin; Latal, Jan; Siska, Petr; Vasinek, Vladimir

2015-07-01

This paper discusses the implementation of a light emitting diode based visible light communication system for optical vehicle-to-vehicle (V2V) communications in road safety applications. The widespread use of LEDs as light sources has reached into automotive fields. For example, LEDs are used for taillights, daytime running lights, brake lights, headlights, and traffic signals. Future in the optical vehicle-to-vehicle (V2V) communications will be based on an optical wireless communication technology that using LED transmitter and a camera receiver (OCI; optical communication image sensor). Utilization of optical V2V communication systems in automotive industry naturally brings a lot of problems. Among them belongs necessity of circuit implementation into the current concepts of electronic LED lights control that allows LED modulation. These circuits are quite complicated especially in case of luxury cars. Other problem is correct design of modulation circuits so that final vehicle lightning using optical vehicle-to-vehicle (V2V) communication meets standard requirements on Photometric Quantities and Beam Homogeneity. Authors of this article performed research on optical vehicle-to-vehicle (V2V) communication possibilities of headlight (Jaguar) and taillight (Skoda) in terms of modulation circuits (M-PSK, M-QAM) implementation into the lamp concepts and final fulfilment of mandatory standards on Photometric Quantities and Beam Homogeneity.

A new method to manipulate broiler chicken growth and metabolism: Response to mixed LED light system

Science.gov (United States)

Yang, Yefeng; Yu, Yonghua; Pan, Jinming; Ying, Yibin; Zhou, Hong

2016-05-01

Present study introduced a new method to manipulate broiler chicken growth and metabolism by mixing the growth-advantage LED. We found that the green/blue LED mixed light system (G-B and G × B) have the similar stimulatory effect on chick body weight with single green light and single blue light (G and B), compared with normal artificial light (P = 0.028). Moreover, the percentage of carcass was significantly greater in the mixed light (G × B) when compared with the single light (P = 0.003). Synchronized with body weight, the mixed light (G-B and G × B) had a significant improved influence on the feed conversion of birds compared with normal light (P = 0.002). A significant improvement in feed conversion were found in mixed light (G × B) compared with single LED light (P = 0.037). G group resulted in a greater high-density lipoprotein cholesterol level than B group (P = 0.002), whereas B group resulted in a greater low-density lipoprotein cholesterol level than G group (P = 0.017). The mixed light significantly increased the birds’ glucose level in comparison with the single light (P = 0.003). This study might establish an effective strategy for maximizing growth of chickens by mixed LED technology.

A design of LED adaptive dimming lighting system based on incremental PID controller

Science.gov (United States)

He, Xiangyan; Xiao, Zexin; He, Shaojia

2010-11-01

As a new generation energy-saving lighting source, LED is applied widely in various technology and industry fields. The requirement of its adaptive lighting technology is more and more rigorous, especially in the automatic on-line detecting system. In this paper, a closed loop feedback LED adaptive dimming lighting system based on incremental PID controller is designed, which consists of MEGA16 chip as a Micro-controller Unit (MCU), the ambient light sensor BH1750 chip with Inter-Integrated Circuit (I2C), and constant-current driving circuit. A given value of light intensity required for the on-line detecting environment need to be saved to the register of MCU. The optical intensity, detected by BH1750 chip in real time, is converted to digital signal by AD converter of the BH1750 chip, and then transmitted to MEGA16 chip through I2C serial bus. Since the variation law of light intensity in the on-line detecting environment is usually not easy to be established, incremental Proportional-Integral-Differential (PID) algorithm is applied in this system. Control variable obtained by the incremental PID determines duty cycle of Pulse-Width Modulation (PWM). Consequently, LED's forward current is adjusted by PWM, and the luminous intensity of the detection environment is stabilized by self-adaptation. The coefficients of incremental PID are obtained respectively after experiments. Compared with the traditional LED dimming system, it has advantages of anti-interference, simple construction, fast response, and high stability by the use of incremental PID algorithm and BH1750 chip with I2C serial bus. Therefore, it is suitable for the adaptive on-line detecting applications.

The health risks associated with energy efficient fluorescent, LEDs, and artificial lighting

Science.gov (United States)

Panahi, Allen

2014-09-01

With the phasing out of incandescent lamps in many countries, the introduction of new LED based light sources and luminaries sometimes raise the question of whether the spectral characteristics of the LED and other energy savings Fluorescent lights including the popular CFLs are suitable to replace the traditional incandescent lamps. These concerns are sometimes raised particularly for radiation emissions in the UV and Blue parts of the spectrum. This paper aims to address such concerns for the common `white light' sources typically used in household and other general lighting used in the work place. Recent studies have shown that women working the night shift have an increased probability of developing breast cancer. We like to report on the findings of many studies done by medical professionals, in particular the recent announcement of AMA in the US and many studies conducted in the UK, as well as the European community to increase public awareness on the long term health risks of the optical and opto-biological effects on the human health caused by artificial lighting.

An Investigation of LED Street Lighting's Impact on Sky Glow

Energy Technology Data Exchange (ETDEWEB)

Kinzey, Bruce R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Perrin, Tess E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Miller, Naomi J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Kocifaj, Miroslav [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Aube, Martin [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lamphar, Hector A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2017-04-25

A significant amount of public attention has recently focused on perceived impacts of converting street lighting from incumbent lamp-based products to LED technology. Much of this attention pertains to the higher content of short wavelength light (commonly referred to as "blue light") of LEDs and its attendant influences on sky glow (a brightening of the night sky that can interfere with astronomical observation and may be associated with a host of other issues). The complexity of this topic leads to common misunderstandings and misperceptions among the public, and for this reason the U.S. Department of Energy Solid-State Lighting Program embarked on a study of sky glow using a well-established astronomical model to investigate some of the primary factors influencing sky glow. This report details the results of the investigation and attempts to present those results in terms accessible to the general lighting community. The report also strives to put the results into a larger context, and help educate interested readers on various topics relevant to the issues being discussed.

Improvement of illumination uniformity for LED flat panel light by using micro-secondary lens array.

Science.gov (United States)

Lee, Hsiao-Wen; Lin, Bor-Shyh

2012-11-05

LED flat panel light is an innovative lighting product in recent years. However, current flat panel light products still contain some drawbacks, such as narrow lighting areas and hot spots. In this study, a micro-secondary lens array technique was proposed and applied for the design of the light guide surface to improve the illumination uniformity. By using the micro-secondary lens array, the candela distribution of the LED flat panel light can be adjusted to similar to batwing distribution to improve the illumination uniformity. The experimental results show that the enhancement of the floor illumination uniformity is about 61%, and that of the wall illumination uniformity is about 20.5%.

A color management system for multi-colored LED lighting

DEFF Research Database (Denmark)

Chakrabarti, Maumita; Thorseth, Anders; Jepsen, Jørgen

2015-01-01

A new color control system is described and implemented for a five–color LED light engine, covering a wide white gamut. The system combines a new way of using pre-calibrated look-up tables and a rule-based optimization of chromaticity distance from the Planckian locus with a calibrated color sensor....... The color sensor monitors the chromaticity of the mixed light providing the correction factor for the current driver by using the generated look-up table. The long term stability and accuracy of the system will be experimentally investigated with target tolerance within a circle radius 0.0011 in the uniform...

Fluorescence image excited by a scanning UV-LED light

Science.gov (United States)

Tsai, Hsin-Yi; Chen, Yi-Ju; Huang, Kuo-Cheng

2013-03-01

An optical scanning system using UV-LED light to induced fluorescence technology can enhance a fluorescence image significantly in a short period. It has several advantages such as lower power consumption, no scattering effect in skins, and multilayer images can be obtained to analyze skin disease. From the experiment results, the light intensity increases with increase spot size and decrease scanning speed, but the image resolution is oppositely. Moreover, the system could be widely used in clinical diagnosis and photodynamic therapy for skin disease because even the irradiated time of fluorescence substance is short but it will provide accurately positioning of fluorescence object.

Enhanced light extraction from GaN-based LEDs with a bottom-up assembled photonic crystal

International Nuclear Information System (INIS)

Gong Haibo; Hao Xiaopeng; Wu Yongzhong; Cao Bingqiang; Xia Wei; Xu Xiangang

2011-01-01

Highlights: → Polystyrene (PS) microspheres were employed as a template. → A noninvasive photonic crystal was fabricated on the surface of GaN-based LED. → Periodic arrangement of bowl-like holes served as a photonic crystal with gradually changed fill factors. → The electroluminescence intensity of LED with a photonic crystal was significantly enhanced. - Abstract: Photonic crystal (PhC) structure is an efficient tool for light extraction from light-emitting diodes (LEDs). The fabrication of a large area PhC structure on the light output surface of LEDs often involves sophisticated equipments such as nanoimprint lithography machine. In this study a monolayer of polystyrene (PS) microspheres was employed as a template to fabricate a noninvasive photonic crystal of indium tin oxide (ITO) on the surface of GaN-based LED. PS spheres can help to form periodic arrangement of bowl-like holes, a photonic crystal with gradually changed fill factors. Importantly, the electroluminescence intensity of LED with a photonic crystal was significantly enhanced by 1.5 times compared to that of the conventional one under various forward injection currents.

Enhanced light extraction from GaN-based LEDs with a bottom-up assembled photonic crystal

Energy Technology Data Exchange (ETDEWEB)

Gong Haibo [State Key Lab of Crystal Materials, Shandong University, Jinan, 250100 (China); School of Materials Science and Engineering, University of Jinan, Jinan, 250022 (China); Hao Xiaopeng, E-mail: xphao@sdu.edu.cn [State Key Lab of Crystal Materials, Shandong University, Jinan, 250100 (China); Wu Yongzhong [State Key Lab of Crystal Materials, Shandong University, Jinan, 250100 (China); Cao Bingqiang [School of Materials Science and Engineering, University of Jinan, Jinan, 250022 (China); Xia Wei [Shandong Huaguang Optoelectronics Company, Ltd., Jinan, 250101 (China); Xu Xiangang [State Key Lab of Crystal Materials, Shandong University, Jinan, 250100 (China); Shandong Huaguang Optoelectronics Company, Ltd., Jinan, 250101 (China)

2011-08-15

Highlights: > Polystyrene (PS) microspheres were employed as a template. > A noninvasive photonic crystal was fabricated on the surface of GaN-based LED. > Periodic arrangement of bowl-like holes served as a photonic crystal with gradually changed fill factors. > The electroluminescence intensity of LED with a photonic crystal was significantly enhanced. - Abstract: Photonic crystal (PhC) structure is an efficient tool for light extraction from light-emitting diodes (LEDs). The fabrication of a large area PhC structure on the light output surface of LEDs often involves sophisticated equipments such as nanoimprint lithography machine. In this study a monolayer of polystyrene (PS) microspheres was employed as a template to fabricate a noninvasive photonic crystal of indium tin oxide (ITO) on the surface of GaN-based LED. PS spheres can help to form periodic arrangement of bowl-like holes, a photonic crystal with gradually changed fill factors. Importantly, the electroluminescence intensity of LED with a photonic crystal was significantly enhanced by 1.5 times compared to that of the conventional one under various forward injection currents.

High-power LED light sources for optical measurement systems operated in continuous and overdriven pulsed modes

Science.gov (United States)

Stasicki, Bolesław; Schröder, Andreas; Boden, Fritz; Ludwikowski, Krzysztof

2017-06-01

The rapid progress of light emitting diode (LED) technology has recently resulted in the availability of high power devices with unprecedented light emission intensities comparable to those of visible laser light sources. On this basis two versatile devices have been developed, constructed and tested. The first one is a high-power, single-LED illuminator equipped with exchangeable projection lenses providing a homogenous light spot of defined diameter. The second device is a multi-LED illuminator array consisting of a number of high-power LEDs, each integrated with a separate collimating lens. These devices can emit R, G, CG, B, UV or white light and can be operated in pulsed or continuous wave (CW) mode. Using an external trigger signal they can be easily synchronized with cameras or other devices. The mode of operation and all parameters can be controlled by software. Various experiments have shown that these devices have become a versatile and competitive alternative to laser and xenon lamp based light sources. The principle, design, achieved performances and application examples are given in this paper.

The role of training structure in perceptual learning of accented speech.

Science.gov (United States)

Tzeng, Christina Y; Alexander, Jessica E D; Sidaras, Sabrina K; Nygaard, Lynne C

2016-11-01

Foreign-accented speech contains multiple sources of variation that listeners learn to accommodate. Extending previous findings showing that exposure to high-variation training facilitates perceptual learning of accented speech, the current study examines to what extent the structure of training materials affects learning. During training, native adult speakers of American English transcribed sentences spoken in English by native Spanish-speaking adults. In Experiment 1, training stimuli were blocked by speaker, sentence, or randomized with respect to speaker and sentence (Variable training). At test, listeners transcribed novel English sentences produced by unfamiliar Spanish-accented speakers. Listeners' transcription accuracy was highest in the Variable condition, suggesting that varying both speaker identity and sentence across training trials enabled listeners to generalize their learning to novel speakers and linguistic content. Experiment 2 assessed the extent to which ordering of training tokens by a single factor, speaker intelligibility, would facilitate speaker-independent accent learning, finding that listeners' test performance did not reliably differ from that in the no-training control condition. Overall, these results suggest that the structure of training exposure, specifically trial-to-trial variation on both speaker's voice and linguistic content, facilitates learning of the systematic properties of accented speech. The current findings suggest a crucial role of training structure in optimizing perceptual learning. Beyond characterizing the types of variation listeners encode in their representations of spoken utterances, theories of spoken language processing should incorporate the role of training structure in learning lawful variation in speech. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Knoop hardness of ten resin composites irradiated with high-power LED and quartz-tungsten-halogen lights.

Science.gov (United States)

Price, Richard B T; Felix, Corey A; Andreou, Pantelis

2005-05-01

This study compared a high-power light-emitting-diode (LED) curing light (FreeLight 2, 3M ESPE) with a quartz-tungsten-halogen (QTH) light (TriLight, 3M ESPE) to determine which was the better at photo-polymerising 10 resin composites. Class I preparations were prepared 4-mm deep into human teeth and filled with 10 different composites. The composites were irradiated for 50% or 100% of their recommended times using the LED light, and for 100% of their recommended times with the QTH light on either the high or medium power setting. Fifteen minutes later, the Knoop hardness of the composites was measured to a depth of 3.5 mm from the surface. When irradiated by the LED light for their recommended curing times, the Knoop hardness of all 10 composites stayed above 80% of the maximum hardness of the composite to a depth of at least 1.5 mm; three composites maintained a Knoop hardness that was more than 80% of their maximum hardness to a depth of 3.5 mm. Repeated measurements analysis of variance indicated that all the two-way and three-way interactions between the curing light, depth, and composite were significant (p hardness values. The LED light, used for the composite manufacturer's recommended time, was ranked the best at curing the composites to a depth of 3mm (p power setting.

Combined daylight and intelligent LED lighting - getting the daylight into the buildings; Kombineret dagslys og intelligent LED belysning - fae dagslys ind i bygningerne. Slutrapport

Energy Technology Data Exchange (ETDEWEB)

Dam-Hansen, C.; Corell, D.D.; Thorseth, A.; Behrensdorff Poulsen, P. [Technical Univ. of Denmark, DTU Fotonik, DTU Risoe Campus, Roskilde (Denmark); Markvart, J.; Iversen, A.; Logadottir, A. [Aalborg Univ., Statens Byggeforskningsinstitut (SBi), Koebenhavn (Denmark)

2013-03-15

The main result of the project is the construction of the new intelligent and dynamic LED lighting system for demonstration and research purposes, and a number of extensive user testing is completed. The LED lighting system is a total system for office lighting with ceiling fixtures and desk lamps, which has made it possible to create a general and workplace lighting in two offices each with two work places. The system is installed in a day light laboratory for such two office spaces. All lamps can be controlled via a developed computer interface, and the desk lamps are further manually controllable by a user via two buttons for color temperature and brightness, respectively. The new intelligent and dynamic lighting system is based on color mixing LED technology and makes it possible to control the color composition, color coordinates and thus the color temperature of the light. Control-wise, the system is pre-programmed to produce white light with a correlated color temperature from 2700 K to 7000 K. The color composition is optimized from the desire for a very good color given at a general CRI value of 92-97 over the area. The system can be dimmed 20-100 %, with no significant change in the light's color properties. A mini-spectrometer is calibrated and built-in in the system and provides the current estimate of daylight brightness and color temperature through measurement of daylight color scheme in the visible range. The system uses daylight properties to control the light from the LED lighting system. The results of user tests show, that the developed possibility to automatically control of light in the office depending on the daylight color temperature is considered to be equally preferred and results in equally satisfied users as a traditional lighting system with even lighting in the room. On the other hand, user results showed that there were both energy savings and more satisfied users to be gained by providing users the opportunity to self-adjust either

Testing a high-power LED based light source for hyperspectral imaging microscopy

Science.gov (United States)

Klomkaew, Phiwat; Mayes, Sam A.; Rich, Thomas C.; Leavesley, Silas J.

2017-02-01

Our lab has worked to develop high-speed hyperspectral imaging systems that scan the fluorescence excitation spectrum for biomedical imaging applications. Hyperspectral imaging can be used in remote sensing, medical imaging, reaction analysis, and other applications. Here, we describe the development of a hyperspectral imaging system that comprised an inverted Nikon Eclipse microscope, sCMOS camera, and a custom light source that utilized a series of high-power LEDs. LED selection was performed to achieve wavelengths of 350-590 nm. To reduce scattering, LEDs with low viewing angles were selected. LEDs were surface-mount soldered and powered by an RCD. We utilized 3D printed mounting brackets to assemble all circuit components. Spectraradiometric calibration was performed using a spectrometer (QE65000, Ocean Optics) and integrating sphere (FOIS-1, Ocean Optics). Optical output and LED driving current were measured over a range of illumination intensities. A normalization algorithm was used to calibrate and optimize the intensity of the light source. The highest illumination power was at 375 nm (3300 mW/cm2), while the lowest illumination power was at 515, 525, and 590 nm (5200 mW/cm2). Comparing the intensities supplied by each LED to the intensities measured at the microscope stage, we found there was a great loss in power output. Future work will focus on using two of the same LEDs to double the power and finding more LED and/or laser diodes and chips around the range. This custom hyperspectral imaging system could be used for the detection of cancer and the identification of biomolecules.

Speaker and Accent Variation Are Handled Differently: Evidence in Native and Non-Native Listeners

Science.gov (United States)

Kriengwatana, Buddhamas; Terry, Josephine; Chládková, Kateřina; Escudero, Paola

2016-01-01

Listeners are able to cope with between-speaker variability in speech that stems from anatomical sources (i.e. individual and sex differences in vocal tract size) and sociolinguistic sources (i.e. accents). We hypothesized that listeners adapt to these two types of variation differently because prior work indicates that adapting to speaker/sex variability may occur pre-lexically while adapting to accent variability may require learning from attention to explicit cues (i.e. feedback). In Experiment 1, we tested our hypothesis by training native Dutch listeners and Australian-English (AusE) listeners without any experience with Dutch or Flemish to discriminate between the Dutch vowels /I/ and /ε/ from a single speaker. We then tested their ability to classify /I/ and /ε/ vowels of a novel Dutch speaker (i.e. speaker or sex change only), or vowels of a novel Flemish speaker (i.e. speaker or sex change plus accent change). We found that both Dutch and AusE listeners could successfully categorize vowels if the change involved a speaker/sex change, but not if the change involved an accent change. When AusE listeners were given feedback on their categorization responses to the novel speaker in Experiment 2, they were able to successfully categorize vowels involving an accent change. These results suggest that adapting to accents may be a two-step process, whereby the first step involves adapting to speaker differences at a pre-lexical level, and the second step involves adapting to accent differences at a contextual level, where listeners have access to word meaning or are given feedback that allows them to appropriately adjust their perceptual category boundaries. PMID:27309889

Raman study of the effect of LED light on grafted bone defects

Science.gov (United States)

Soares, Luiz G. G. P.; Aciole, Jouber M. S.; Aciole, Gilbeth T. S.; Barbosa, Artur F. S.; Silveira-Júnior, Landulfo; Pinheiro, Antônio L. B.

2013-03-01

Benefits of the isolated or combined use light and biomaterials on bone healing have been suggested. Our group has used several models to assess the effects of laser on bone. A Raman spectral analysis on surgical bone defects grafted or not with Hydroxyapatite (HA), treated or not with LED was carried out. 40 rats were divided into 4 groups. On Group I the defect was filled with the clot. On Group II, the defect was filled with the HA. On groups III the defect was filled with Clot and further irradiated with LED and on group IV the defects was filled with the HA and further irradiated with LED. LED (λ850 +/- 10nm, 150mW, A= 0.5cm2, 68s, 20 J/cm2 per session, 140 J/cm2 per treatment) was applied at 48 h intervals during 15 days. Specimens were taken after 15 and 30 days after surgery and kept on liquid nitrogen, and underwent Raman analysis. For this, the peak of hydroxyapatite (~960 cm-1) was used as marker of bone mineralization. Significant difference was observed at both times (p<0.05). When the biomaterial was used higher peaks were observed. Association with LED further improved the intensity. Conclusion: It is concluded that LED light improved the effect of the HA.

Slim planar apparatus for converting LED light into collimated polarized light uniformly emitted from its top surface.

Science.gov (United States)

Teng, Tun-Chien; Tseng, Li-Wei

2014-10-20

This study proposes a slim planar apparatus for converting nonpolarized light from a light-emitting diode (LED) into an ultra-collimated linearly polarized beam uniformly emitted from its top surface. The apparatus was designed based on a folded-bilayer configuration comprising a light-mixing collimation element, polarization conversion element, and polarization-preserving light guide plate (PPLGP) with an overall thickness of 5 mm. Moreover, the apparatus can be extended transversally by connecting multiple light-mixing collimation elements and polarization conversion elements in a side-by-side configuration to share a considerably wider PPLGP, so the apparatus can have theoretically unlimited width. The simulation results indicate that the proposed apparatus is feasible for the maximal backlight modules in 39-inch liquid crystal panels. In the case of an apparatus with a 480 × 80 mm emission area and two 8-lumen LED light sources, the average head-on polarized luminance and spatial uniformity over the emission area was 5000 nit and 83%, respectively; the vertical and transverse angular distributions of the emitting light were only 5° and 10°, respectively. Moreover, the average degree of polarization and energy efficiency of the apparatus were 82% and 72%, respectively. As compared with the high-performance ultra-collimated nonpolarized backlight module proposed in our prior work, not only did the apparatus exhibit outstanding optical performance, but also the highly polarized light emissions actually increased the energy efficiency by 100%.

Rectangular illumination using a secondary optics with cylindrical lens for LED street light.

Science.gov (United States)

Chen, Hsi-Chao; Lin, Jun-Yu; Chiu, Hsuan-Yi

2013-02-11

The illumination pattern of an LED street light is required to have a rectangular distribution at a divergence-angle ratio of 7:3 for economical illumination. Hence, research supplying a secondary optics with two cylindrical lenses was different from free-form curvature for rectangular illumination. The analytical solution for curvatures with different ratio rectangles solved this detail by light tracing and boundary conditions. Similarities between the experiments and the simulation for a single LED and a 9-LED module were analyzed by Normalized Cross Correlation (NCC), and the error rate was studied by the Root Mean Square (RMS). The tolerance of position must be kept under ± 0.2 mm in the x, y and z directions to ensure that the relative illumination is over 99%.

Yuma Border Patrol Lighting Retrofit: Final LED System Performance Assessment of Trial and Full Installation

Energy Technology Data Exchange (ETDEWEB)

Andrea Wilkerson, Gregory P Sullivan, Robert G Davis, Sarah Safranek

2018-04-30

Along the Yuma Sector Border Patrol Area in Yuma, Arizona, the GATEWAY program conducted a trial evaluation in which the incumbent quartz metal halide area lighting was replaced with LED at three pole locations, and illuminance measurements were recorded initially and at 2500 hours, 5000 hours, 7000, and 11,000 hours of operation. Additionally, four second-generation LED luminaires installed as part of the full installation were evaluated initially and again after 4,000 hours of operation. While the initial energy, lighting quality, and maintenance benefits relative to the incumbent high-pressure sodium system were very satisfactory, the study raises important questions regarding the long-term performance of LED lighting systems in high-temperature environments.

LED lighting and the Next Generation of Greenhouse for Tomatoes. Proof of Principle; LED belichting en Het Nieuwe Telen bij tomaat. Proof of Principle

Energy Technology Data Exchange (ETDEWEB)

Dueck, T.; Janse, J.; Eveleens, B. [Wageningen UR Glastuinbouw, Wageningen (Netherlands); Nieboer, S.; Valstar, W.; Grootscholten, M. [GreenQ Improvement Centre, Bleiswijk (Netherlands)

2012-08-15

In this Proof of Principle project a tomato crop was grown under artificial lighting with the aim of 30% energy saving at the same level of production. Tomatoes (cultivar Komeett) were illuminated with 110 {mu}mol m{sup -2} s{sup -1} HPS (High Pressure Sodium) above the crop and 85 {mu}mol m{sup -2} s{sup -1} LED interlighting. The LEDs hung in 2 rows, approximately 40 cm above the lower leaves and the second strand at 40 or 70 cm above that. There were two types of LEDs used: production LEDs (light efficiency 1.6 {mu}mol m{sup -2} s{sup -1}, 87% red/13% blue) and inter-lighting LEDs (light efficiency 1.9 {mu}mol m{sup -2} s{sup -1}, 95% red/5% blue), with the same light intensity. At the start, the crop was given as much light as it could handle, and because the crop developed so well, the stem density was increased relatively early. This resulted in high fruit load, while insufficient light was available to compensate for the low levels of sunlight in the winter. In the 192 cm row spacing system the plants were too close to each other. Additional problems occurred with trace elements, lesser bumble bee activity, and a moist greenhouse climate which weakened the crop in the winter. Thus Botrytis occurred on the leaves and stems. The crop struggled with its recovery until early spring with more sunlight. Compared to a reference crop with 79 kg m{sup -2} tomatoes, 75 kg m{sup -2} were produced under-production LEDs, and 80 kg m{sup -2} under the interlighting LEDs, mainly because latter LEDs were used longer during the summer. 30% of the energy for dehumidification and heat energy, and 27% of the electricity was saved, relative to the reference crop. Thus it appears possible to save 30% energy with a near identical production [Dutch] In dit Proof of Principle project is een belichte tomatenteelt geteeld met als doel 30% energiebesparing bij een gelijke productie. Tomaten van het ras Komeett werden belicht met 110 {mu}mol m{sup -2} s{sup -1} SON-T belichting boven

GATEWAY Demonstrations: Philadelphia International Airport Apron Lighting: LED System Performance in a Trial Installation

Energy Technology Data Exchange (ETDEWEB)

Davis, Robert G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wilkerson, Andrea M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2015-10-30

This report documents a trial installation of LED apron lighting that replaced the existing high-pressure sodium luminaires at Philadelphia International Airport. Such high-mast applications remain challenging for LED technology, and the lessons learned from this project may help facility managers and LED product manufacturers better meet those challenges.

Perceptual accent rating and attribution in psychogenic FAS: some further evidence challenging Whitaker’s operational definition.

Directory of Open Access Journals (Sweden)

Stefanie eKeulen

2016-03-01

Full Text Available A 40-year-old, non-aphasic, right-handed, and polyglot (L1: French, L2: Dutch, L3: English woman with a 12 year history of addiction to opiates and psychoactive substances, and clear psychiatric problems, presented with a foreign accent of sudden onset in L1. Speech evolved towards a mostly fluent output, despite a stutter-like behavior and a marked grammatical output disorder. The psychogenic etiology of the accent foreignness was construed based upon the patient’s complex medical history, and psychodiagnostic, neuropsychological, and neurolinguistic assessments. The presence of a foreign accent was affirmed by a perceptual accent rating and attribution experiment. It is argued that this patient provides additional evidence demonstrating the outdatedness of Whitaker’s (1982 definition of Foreign Accent Syndrome, as only one of the four operational criteria was unequivocally applicable to our patient: her accent foreignness was not only recognized by her relatives and the medical staff, but also by a group of native French-speaking laymen. However, our patient defied the three remaining criteria, as central nervous system damage could not conclusively be demonstrated, psychodiagnostic assessment raised the hypothesis of a conversion disorder, and the patient was a polyglot whose newly gained accent was associated with a range of foreign languages, which exceeded the ones she spoke.

Time Effectiveness of Ultraviolet C Light (UVC Emitted by Light Emitting Diodes (LEDs in Reducing Stethoscope Contamination

Directory of Open Access Journals (Sweden)

Gabriele Messina

2016-09-01

Full Text Available Today it is well demonstrated that stethoscopes can be as contaminated as hands, which are a recognized source of Health-Care Associated Infections (HCAIs. Ultraviolet C (UVC light has proven disinfection capacity and the innovative UVC technology of Light Emitting Diode (LED shows several potential benefits. To verify whether the use of UVC LEDs is effective and reliable in stethoscope membrane disinfection after prolonged use, a pre-post intervention study was conducted. A total of 1668 five-minute cycles were performed on two UVC LEDs to simulate their use; thereafter, their disinfection capacity was tested on stethoscope membranes used on a previously auscultated volunteer. Then, a further 1249 cycles were run and finally the LEDs were tested to assess performance in reducing experimental contamination by Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli on the stethoscope membrane. Baseline volunteer contamination identified 104 Colony Forming Units (CFUs while treated Petri dishes had 12 and 15 CFUs (p < 0.001. Statistically significant differences (p < 0.001 were also found relating to the reduction of specific bacteria: in particular, after treatment no CFU were observed for S. aureus and E. coli. UVC LEDs demonstrated the capacity to maintain high levels of disinfection after more than 240 h of use and they were effective against common microorganisms that are causative agents of HCAIs.

Time Effectiveness of Ultraviolet C Light (UVC) Emitted by Light Emitting Diodes (LEDs) in Reducing Stethoscope Contamination.

Science.gov (United States)

Messina, Gabriele; Fattorini, Mattia; Nante, Nicola; Rosadini, Daniele; Serafini, Andrea; Tani, Marco; Cevenini, Gabriele

2016-09-23

Today it is well demonstrated that stethoscopes can be as contaminated as hands, which are a recognized source of Health-Care Associated Infections (HCAIs). Ultraviolet C (UVC) light has proven disinfection capacity and the innovative UVC technology of Light Emitting Diode (LED) shows several potential benefits. To verify whether the use of UVC LEDs is effective and reliable in stethoscope membrane disinfection after prolonged use, a pre-post intervention study was conducted. A total of 1668 five-minute cycles were performed on two UVC LEDs to simulate their use; thereafter, their disinfection capacity was tested on stethoscope membranes used on a previously auscultated volunteer. Then, a further 1249 cycles were run and finally the LEDs were tested to assess performance in reducing experimental contamination by Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli on the stethoscope membrane. Baseline volunteer contamination identified 104 Colony Forming Units (CFUs) while treated Petri dishes had 12 and 15 CFUs (p < 0.001). Statistically significant differences (p < 0.001) were also found relating to the reduction of specific bacteria: in particular, after treatment no CFU were observed for S. aureus and E. coli. UVC LEDs demonstrated the capacity to maintain high levels of disinfection after more than 240 h of use and they were effective against common microorganisms that are causative agents of HCAIs.

Stakeholder Values and Perspectives when Implementing Led Lights on Navy Ships

Science.gov (United States)

2014-06-01

Human Factors in Lighting Freymiller, 2009, from Boyce, 2003) LEDs have no known cause of headaches due to flicker and the electronic magnetic...reoccurrence of dimming and flickering can reoccur. There should be further research conducted on how a headache affects the loss of productivity on...Walls, P. M. (2011, Dec). Eye disease resulting from increased use of fluorescent lighting as a climate change mitigation strategy. Retrieved from

Effects of LED or laser phototherapy on bone defects grafted with MTA and irradiated with laser or LED light: a comparative Raman spectroscopic study

Science.gov (United States)

Pinheiro, Antonio L. B.; Soares, Luiz G. P.; Barbosa, Artur Felipe S.; Silveira, Landulfo, Jr.

2012-03-01

We studied peaks of calcium hydroxyapatite - CHA on defects grafted with MTA, treated or not with Light Emitting Diode - LED or IR Laser. 54 rats were divided in 6 groups each subdivided into 3 subgroups (15,21,30d). LED (λ850 +/- 10nm) or IR Laser (λ850 nm) was applied over (LED) or in 4 points around the defect at 48 h intervals for 15 days. Raman readings were taken at the surface of the defect. The smaller overall intensity of the peak was found in Group MTA + Laser (1510.2 +/- 274.1) and the highest on Group LED (2322 +/- 715). There were no statistically significant differences between non-irradiated subjects on regards the CHA peaks. On the other hand, there were statistically significant differences between the Group Clot and LED, Clot and Laser, and Clot and MTA + Laser (p =0.01, p = 0.02, p = 0.003). There were no significant differences between Group MTA and MTA + LED (p=0.2) but significant differences were seen between Groups MTA and MTA + Laser (p=0.01). Significant differences were also observed between Groups LED and Laser (p <0.001) and between Groups MTA + LED and MTA + Laser (p=0.009). MTA, due to its characteristics, seemed to be directly affected by the light. However, the use of either phototherapy positively affected bone healing similarly as observed on different studies using other biomaterials. The overall analysis of our results indicated that the use of either light source resulted in a better, more advanced, and of quality bone repair.

Lighting and social practices - what role does lighting play for low energy house (LEH) households and LED frontrunners?

DEFF Research Database (Denmark)

Jensen, Charlotte Louise

As lighting in Danish households consume approximately 1.3 TWh every year, reducing electricity consumption from lighting is important. Studies have shown that a mere substitution of inefficient lighting technologies towards more efficient ones may not be possible, as many social and cultural...... dimensions influence how people use and relate to lighting. Assessing how very distinctive contexts of households (that diverge from an exemplary kind of household), such as low energy houses and LED frontrunner households, use and understand lighting, may give some insight into what may trigger or hamper...

LED Lighting – Modification of Growth, Metabolism, Yield and Flour Composition in Wheat by Spectral Quality and Intensity

Directory of Open Access Journals (Sweden)

István Monostori

2018-05-01

Full Text Available The use of light-emitting diode (LED technology for plant cultivation under controlled environmental conditions can result in significant reductions in energy consumption. However, there is still a lack of detailed information on the lighting conditions required for optimal growth of different plant species and the effects of light intensity and spectral composition on plant metabolism and nutritional quality. In the present study, wheat plants were grown under six regimens designed to compare the effects of LED and conventional fluorescent lights on growth and development, leaf photosynthesis, thiol and amino acid metabolism as well as grain yield and flour quality of wheat. Benefits of LED light sources over fluorescent lighting were manifested in both yield and quality of wheat. Elevated light intensities made possible with LEDs increased photosynthetic activity, the number of tillers, biomass and yield. At lower light intensities, blue, green and far-red light operated antagonistically during the stem elongation period. High photosynthetic activity was achieved when at least 50% of red light was applied during cultivation. A high proportion of blue light prolonged the juvenile phase, while the shortest flowering time was achieved when the blue to red ratio was around one. Blue and far-red light affected the glutathione- and proline-dependent redox environment in leaves. LEDs, especially in Blue, Pink and Red Low Light (RedLL regimens improved flour quality by modifying starch and protein content, dough strength and extensibility as demonstrated by the ratios of high to low molecular weight glutenins, ratios of glutenins to gliadins and gluten spread values. These results clearly show that LEDs are efficient for experimental wheat cultivation, and make it possible to optimize the growth conditions and to manipulate metabolism, yield and quality through modification of light quality and quantity.

Interaction of LED light with coinitiator-containing composite resins: effect of dual peaks.

Science.gov (United States)

Sim, Jae-Seong; Seol, Hyo-Joung; Park, Jeong-Kil; Garcia-Godoy, Franklin; Kim, Hyung-Il; Kwon, Yong Hoon

2012-10-01

Recently the colour stability of composite resins has been an issue due to the emphasis on the aesthetics of restored teeth. The purpose of the present study was to investigate how dual-peak LED units affect the polymerization of coinitiator-containing composite resins. Five composite resins [coinitiator-containing: Aelite LS Posterior (AL), Tetric EvoCeram (TE), and Vit-l-escence (VI); only CQ-containing: Grandio (GD) and Filtek Z350 (Z3)] were light cured using four different light-curing units (LCUs). Among them, Bluephase G2 (BP) and G-light (GL) were dual-peak LED LCUs. Microhardness, polymerization shrinkage, flexural, and compressive properties were measured. BP and GL had no consistent effect on the microhardness of AL, TE, and VI on the top and bottom surfaces of resin specimens. Among the specimens, AL and VI showed the least (9.86-10.41 μm) and greatest (17.58-19.21 μm) polymerization shrinkage, respectively. However, the effect of BP and GL on the shrinkage of specimens was not consistent. Among the specimens, GD showed the greatest flexural properties [strength (FS) and modulus (FM)] and TE showed the lowest flexural and compressive properties [strength (CS) and modulus (CM)]. In same resin product, maximum FS and CS differences due to the different LCUs were 10.3-21.0% and 3.6-9.2%, respectively. Furthermore, the influences of BP and GL on FS and CS were not consistent. The tested dual-peak LED LCUs had no consistent synergic effect on the polymerization of coinitiator-containing composite resins as compared with QTH and single-peak LED LCUs. The dual-peak LED LCUs achieve a similar degree of polymerization in coinitiator-composite resins as QTH and single-peak LED LCUs did. Choice of LCU does not appear to be a determinant of the light curing of coinitiator-composite resins. Copyright © 2012 Elsevier Ltd. All rights reserved.

Development and future of ultraviolet light-emitting diodes: UV-LED will replace the UV lamp

Science.gov (United States)

Muramoto, Yoshihiko; Kimura, Masahiro; Nouda, Suguru

2014-06-01

Ultraviolet light-emitting diodes (UV-LEDs) have started replacing UV lamps. The power per LED of high-power LED products has reached 12 W (14 A), which is 100 times the values observed ten years ago. In addition, the cost of these high-power LEDs has been decreasing. In this study, we attempt to understand the technologies and potential of UV-LEDs.

Application of 265-nm UVC LED Lighting to Sterilization of Typical Gram Negative and Positive Bacteria

Science.gov (United States)

Lee, Yong Wook; Yoon, Hyung Do; Park, Jae-Hyoun; Ryu, Uh-Chan

2018-05-01

UV LED lightings have been displacing conventional UV lamps due to their high efficiency, long lifetime, etc. A sterilizing lighting was prepared by assembling a UV LED module composed of 265-nm UVC LEDs and a silica lens array with a driver module comprised of a driver IC controlling pulse width modulation and constant current. The silica lens array was designed and fabricated to focus UV beam and simultaneously to give a uniform light distribution over specimens. Then pasteurizing effect of the lighting was analyzed for four kinds of bacteria and one yeast which are dangerous to people with low immunity. Sterilizing tests on these germs were carried out at the both exposure distances of 10 and 100 mm for various exposure durations up to 600 s.

The invisible minority: revisiting the debate on foreign-accented speakers and upward mobility in the workplace.

Science.gov (United States)

Akomolafe, Soji

2013-01-01

Of some of the major types of discrimination, the one that gets the least attention is national origin discrimination and in particular, accent discrimination, especially when it comes to upward mobility in the workplace. Yet, unlike other forms of discrimination, accent discrimination is rarely a subject of any robust public debate. This paper is a modest attempt to help establish a framework for understanding the relative neglect to which the discourse on accent discrimination has been subjected vis-a-vis the overall national debate on diversity. Hopefully, in the process, it will stimulate a more robust conversation on the plight of foreign-accented speakers.

From One to Multiple Accents on a Test of L2 Listening Comprehension

Science.gov (United States)

Ockey, Gary J.; French, Robert

2016-01-01

Concerns about the need for assessing multidialectal listening skills for global contexts are becoming increasingly prevalent. However, the inclusion of multiple accents on listening assessments may threaten test fairness because it is not practical to include every accent that may be encountered in the language use domain on these tests. Given…

Perception of contrastive bi-syllabic lexical stress in unaccented and accented words by younger and older listeners

Science.gov (United States)

Gordon-Salant, Sandra; Yeni-Komshian, Grace H.; Pickett, Erin J.; Fitzgibbons, Peter J.

2016-01-01

This study examined the ability of older and younger listeners to perceive contrastive syllable stress in unaccented and Spanish-accented cognate bi-syllabic English words. Younger listeners with normal hearing, older listeners with normal hearing, and older listeners with hearing impairment judged recordings of words that contrasted in stress that conveyed a noun or verb form (e.g., CONduct/conDUCT), using two paradigms differing in the amount of semantic support. The stimuli were spoken by four speakers: one native English speaker and three Spanish-accented speakers (one moderately and two mildly accented). The results indicate that all listeners showed the lowest accuracy scores in responding to the most heavily accented speaker and the highest accuracy in judging the productions of the native English speaker. The two older groups showed lower accuracy in judging contrastive lexical stress than the younger group, especially for verbs produced by the most accented speaker. This general pattern of performance was observed in the two experimental paradigms, although performance was generally lower in the paradigm without semantic support. The findings suggest that age-related difficulty in adjusting to deviations in contrastive bi-syllabic lexical stress produced with a Spanish accent may be an important factor limiting perception of accented English by older people. PMID:27036250

Analysis of Shade Matching in Natural Dentitions Using Intraoral Digital Spectrophotometer in LED and Filtered LED Light Sources.

Science.gov (United States)

Chitrarsu, Vijai Krishnan; Chidambaranathan, Ahila Singaravel; Balasubramaniam, Muthukumar

2017-10-31

To evaluate the shade matching capabilities in natural dentitions using Vita Toothguide 3D-Master and an intraoral digital spectrophotometer (Vita Easyshade Advance 4.0) in various light sources. Participants between 20 and 40 years old with natural, unrestored right maxillary central incisors, no history of bleaching, orthodontic treatment, or malocclusion and no rotations were included. According to their shades, subjects were randomly selected and grouped into A1, A2, and A3. A total of 100 participants (50 male and 50 female) in each group were chosen for this study. Shade selection was made between 10 am and 2 pm for all light sources. The same examiner selected the shade of natural teeth with Vita Toothguide 3D-Master under natural light within 2 minutes. Once the Vita Toothguide 3D-Masterwas matched with the maxillary right central incisor, the L*, a*, and b* values, chroma, and hue were recorded with Vita Easyshade Advance 4.0 by placing it on the shade tab under the same light source. The values were statistically analyzed using one-way ANOVA and Tukey's HSD post hoc test with SPSS v22.0 software. The mean ∆E* ab values for shades A1, A2, and A3 for groups 1, 2, and 3 were statistically significantly different from each other (p spectrophotometer showed statistically significant differences in shade matching compared to Vita Toothguide 3D-Master. Incandescent light showed more accurate shade matching than the filtered LED, LED, and daylight. © 2017 by the American College of Prosthodontists.

Smart LED allocation scheme for efficient multiuser visible light communication networks.

Science.gov (United States)

Sewaiwar, Atul; Tiwari, Samrat Vikramaditya; Chung, Yeon Ho

2015-05-18

In a multiuser bidirectional visible light communication (VLC), a large number of LEDs or an LED array needs to be allocated in an efficient manner to ensure sustainable data rate and link quality. Moreover, in order to support an increasing or decreasing number of users in the network, the LED allocation is required to be performed dynamically. In this paper, a novel smart LED allocation scheme for efficient multiuser VLC networks is presented. The proposed scheme allocates RGB LEDs to multiple users in a dynamic and efficient fashion, while satisfying illumination requirements in an indoor environment. The smart LED array comprised of RGB LEDs is divided into sectors according to the location of the users. The allocated sectors then provide optical power concentration toward the users for efficient and reliable data transmission. An algorithm for the dynamic allocation of the LEDs is also presented. To verify its effective resource allocation feature of the proposed scheme, simulations were performed. It is found that the proposed smart LED allocation scheme provides the effect of optical beamforming toward individual users, thereby increasing the collective power concentration of the optical signals on the desirable users and resulting in significantly increased data rate, while ensuring sufficient illumination in a multiuser VLC environment.

Application of Photocatalysts and LED Light Sources in Drinking Water Treatment

Directory of Open Access Journals (Sweden)

Gopal Achari

2013-09-01

Full Text Available This study investigates a cross-section of TiO2 compositions for which existing evidence suggests the prospect of improved performance compared to standard Degussa P25. In the context of a program aimed toward a 365 nm LED based photo-reactor, the question is whether a distinctly superior photocatalyst composition for drinking water treatment is now available that would shape design choices. An answer was sought by synthesizing several photocatalysts with reported high reactivity in some context in the literature, and by performing photocatalysts reactivity tests using common pollutants of water system including Natural Organic Matter (NOM and Emerging Contaminants (ECs from the pesticide and pharmaceutical classes. 365 nm Light Emitting Diodes (LEDs were used as the irradiation source. Since LEDs are now available in the UV, we did not examine the TiO2 modifications that bring band gap excitation into the region beyond 400 nm. The results suggest that the choice of the photocatalyst should be best made to fit the reactor design and photocatalyst mounting constraints such as mass transport, reactive surface, and light field. No photocatalyst composition overall, superior for all classes emerged.

Development and future of ultraviolet light-emitting diodes: UV-LED will replace the UV lamp

International Nuclear Information System (INIS)

Muramoto, Yoshihiko; Kimura, Masahiro; Nouda, Suguru

2014-01-01

Ultraviolet light-emitting diodes (UV-LEDs) have started replacing UV lamps. The power per LED of high-power LED products has reached 12 W (14 A), which is 100 times the values observed ten years ago. In addition, the cost of these high-power LEDs has been decreasing. In this study, we attempt to understand the technologies and potential of UV-LEDs. (invited article)

SILAR-Based Application of Various Nanopillars on GaN-Based LED to Enhance Light-Extraction Efficiency

Directory of Open Access Journals (Sweden)

S. C. Shei

2013-01-01

Full Text Available We reported the various nanopillars on GaN-based LED to enhance light-extraction efficiency prepared by successive ionic layer adsorption and reaction method (SILAR. Indium tin oxide (ITO with thickness of 1 μm as transparent contact layer was grown to improve the electrical characteristics of the LEDs, including series resistance and operating voltage. SILAR-deposition ZnO nanoparticles on SiO2 were used as etching nanomasks. Multiple nanopillars were simultaneously formed on overall surfaces of ITO p- and n-GaN by ICP etching. The proposed GaN-based LEDs with nanopillars increase light output power by 7%–20.3% (at 20 mA over that of regular GaN-based LEDs. The difference in light output power can be attributed to differences in materials and shapes of nanopillars, resulting in a reduction in Fresnel reflection by the roughened surface of GaN-based LEDs.

Demonstration Assessment of Light-Emitting Diode (LED) Parking Lot Lighting at T.J.Maxx in Manchester, NH Phase I

Energy Technology Data Exchange (ETDEWEB)

Myer, Michael; Goettel, Russell T.

2010-06-29

A report describing the process and results of replacing existing parking lot lighting, looking at a LED option with occupancy sensors, and conventional alternates. Criteria include payback, light levels, occupant satisfaction. This report is Phase I of II. Phase I deals with initial installation.

Demonstration of 575-Mb/s downlink and 225-Mb/s uplink bi-directional SCM-WDM visible light communication using RGB LED and phosphor-based LED.

Science.gov (United States)

Wang, Yuanquan; Wang, Yiguang; Chi, Nan; Yu, Jianjun; Shang, Huiliang

2013-01-14

We propose and experimentally demonstrate a novel full-duplex bi-directional subcarrier multiplexing (SCM)-wavelength division multiplexing (WDM) visible light communication (VLC) system based on commercially available red-green-blue (RGB) light emitting diode (LED) and phosphor-based LED (P-LED) with 575-Mb/s downstream and 225-Mb/s upstream transmission, employing various modulation orders of quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM). For the downlink, red and green colors/wavelengths are assigned to carry useful information, while blue chip is just kept lighting to maintain the white color illumination, and for the uplink, the low-cost P-LED is implemented. In this demonstration, pre-equalization and post-equalization are also adopted to compensate the severe frequency response of LEDs. Using this scheme, 4-user downlink and 1-user uplink transmission can be achieved. Furthermore, it can support more users by adjusting the bandwidth of each sub-channel. Bit error rates (BERs) of all links are below pre-forward-error-correction (pre-FEC) threshold of 3.8x 10(-3) after 66-cm free-space delivery. The results show that this scheme has great potential in the practical VLC system.

Output blue light evaluation for phosphor based smart white LED wafer level packages.

Science.gov (United States)

Kolahdouz, Zahra; Rostamian, Ali; Kolahdouz, Mohammadreza; Ma, Teng; van Zeijl, Henk; Zhang, Kouchi

2016-02-22

This study presents a blue light detector for evaluating the output light of phosphor based white LED package. It is composed of a silicon stripe-shaped photodiode designed and implemented in a 2 μm BiCMOS process which can be used for wafer level integration of different passive and active devices all in just 5 lithography steps. The final device shows a high selectivity to blue light. The maximum responsivity at 480 nm is matched with the target blue LED illumination. The designed structure have better responsivity compared to simple photodiode structure due to reducing the effect of dead layer formation close to the surface because of implantation. It has also a two-fold increase in the responsivity and quantum efficiency compared to previously similar published sensors.

Effect of Accent and Dialect on Employability

Science.gov (United States)

Carlson, Holly K.; McHenry, Monica A.

2006-01-01

This study was designed to determine how ethnicity, the amount of perceived accent or dialect, and comprehensibility affect a speaker's employability. Sixty human resource specialists judged 3 female potential applicants. The applicants represented speakers of Spanish-influenced English, Asian-influenced English, and African American Vernacular…

Comparative Evaluation of Shear Bond Strength and Debonding Characteristics using Conventional Halogen Light Curing Unit and LED Light Curing Unit: An in vitro Study

Directory of Open Access Journals (Sweden)

Amit Bhardwaj

2013-01-01

Conclusion: The result of this study showed promise for the orthodontic application of LED as light curing units and 20 seconds of exposure time is adequate for both LED and Halogen light, since increasing the curing time to 40 seconds showed no significant difference.

Color Degradation of Textiles with Natural Dyes and of Blue Scale Standards Exposed to White LED Lamps:Evaluation of White LED Lamps for Effectiveness as Museum Lighting

Science.gov (United States)

Ishii, Mie; Moriyama, Takayoshi; Toda, Masahiro; Kohmoto, Kohtaro; Saito, Masako

White light-emitting diodes (LED) are well suited for museum lighting because they emit neither UV nor IR radiation, which damage artifacts. The color degradation of natural dyes and blue scale standards (JIS L 0841) by white LED lamps are examined, and the performance of white LED lamps for museum lighting is evaluated. Blue scale standard grades 1-6 and silk fabrics dyed with 22 types of natural dyes classified as mid to highly responsive in a CIE technical report (CIE157:2004) were exposed to five types of white LED lamps using different luminescence methods and color temperatures. Color changes were measured at each 15000 lx·hr (500 lx at fabric surface × 300 hr) interval ten times. The accumulated exposure totaled 150000 lx·hr. The data on conventional white LED lamps and previously reported white fluorescent (W) and museum fluorescent (NU) lamps was evaluated. All the white LED lamps showed lower fading rates compared with a W lamp on a blue scale grade 1. The fading rate of natural dyes in total was the same between an NU lamp (3000 K) and a white LED lamp (2869 K). However, yellow natural dyes showed higher fading rates with the white LED lamp. This tendency is due to the high power characteristic of the LED lamp around 400-500 nm, which possibly contributes to the photo-fading action on the dyes. The most faded yellow dyes were Ukon (Curcuma longa L.) and Kihada (Phellodendron amurense Rupr.), and these are frequently used in historic artifacts such as kimono, wood-block prints, and scrolls. From a conservation point of view, we need to continue research on white LED lamps for use in museum lighting.

The way you say it, the way I feel it: emotional word processing in accented speech

Science.gov (United States)

Hatzidaki, Anna; Baus, Cristina; Costa, Albert

2015-01-01

The present study examined whether processing words with affective connotations in a listener's native language may be modulated by accented speech. To address this question, we used the Event Related Potential (ERP) technique and recorded the cerebral activity of Spanish native listeners, who performed a semantic categorization task, while listening to positive, negative and neutral words produced in standard Spanish or in four foreign accents. The behavioral results yielded longer latencies for emotional than for neutral words in both native and foreign-accented speech, with no difference between positive and negative words. The electrophysiological results replicated previous findings from the emotional language literature, with the amplitude of the Late Positive Complex (LPC), associated with emotional language processing, being larger (more positive) for emotional than for neutral words at posterior scalp sites. Interestingly, foreign-accented speech was found to interfere with the processing of positive valence and go along with a negativity bias, possibly suggesting heightened attention to negative words. The manipulation employed in the present study provides an interesting perspective on the effects of accented speech on processing affective-laden information. It shows that higher order semantic processes that involve emotion-related aspects are sensitive to a speaker's accent. PMID:25870577

Optimization of colour quality of LED lighting with reference to memory colours

OpenAIRE

Smet, Kevin; Ryckaert, Wouter; Pointer, Michael R.; Deconinck, Geert; Hanselaer, Peter

2012-01-01

Simulated and real tri- and tetrachromatic light-emitting-diode (LED) clusters were optimized for luminous efficacy of radiation (LER) and the memory colour quality metric developed by the authors. The simulated clusters showed no significant differences in achievable colour quality and LER between the different cluster types investigated. The real clusters (composed of commercially available LEDs) showed substantial differences in achievable colour quality and LER between the different clus...

Examination of the LED Source in Traffic Lights and the Effect of Airborne Dirt on its Performance

Directory of Open Access Journals (Sweden)

Amela Softić

2017-05-01

Full Text Available The performed evaluation consisted of two phases: measurement of the illumination levels of (new LED system and carrying out the public opinion poll on the subjective visual performance of LED in traffic lights. The results of the measured levels of illumination show that deposition of dirt considerably affects its values. The survey results confirm an overall positive impression on LED performances in traffic lights.

Phosphors for near UV-Emitting LED's for Efficacious Generation of White Light

Energy Technology Data Exchange (ETDEWEB)

McKittrick, Joanna [Univ. of California, San Diego, CA (United States)

2013-09-30

1) We studied phosphors for near-UV (nUV) LED application as an alternative to blue LEDs currently being used in SSL systems. We have shown that nUV light sources could be very efficient at high current and will have significantly less binning at both the chip and phosphor levels. We identified phosphor blends that could yield 4100K lamps with a CRI of approximately 80 and LPWnUV,opt equal to 179 for the best performing phosphor blend. Considering the fact that the lamps were not optimized for light coupling, the results are quite impressive. The main bottleneck is an optimum blue phosphor with a peak near 440 nm with a full width half maximum of about 25 nm and a quantum efficiency of >95%. Unfortunately, that may be a very difficult task when we want to excite a phosphor at ~400 nm with a very small margin for Stokes shift. Another way is to have all the phosphors in the blend having the excitation peak at 400 nm or slightly shorter wavelength. This could lead to a white light source with no body color and optimum efficacy due to no self-absorption effects by phosphors in the blend. This is even harder than finding an ideal blue phosphor, but not necessarily impossible. 2) With the phosphor blends identified, light sources using nUV LEDs at high current could be designed with comparable efficacy to those using blue LEDs. It will allow us to design light sources with multiple wattages using the same chips and phosphor blends simply by varying the input current. In the case of blue LEDs, this is not currently possible because varying the current will lower the efficacy at high current and alter the color point. With improvement of phosphor blends, control over CRI could improve. Less binning at the chip level and also at the phosphor blend level could reduce the cost of SSL light sources. 3) This study provided a deeper understanding of phosphor characteristics needed for LEDs in general and nUV LEDs in particular. Two students received Ph.D. degrees and three

Design of an Oximeter Based on LED-LED Configuration and FPGA Technology

OpenAIRE

Stojanovic, Radovan; Karadaglic, Dejan

2013-01-01

A fully digital photoplethysmographic (PPG) sensor and actuator has been developed. The sensing circuit uses one Light Emitting Diode (LED) for emitting light into human tissue and one LED for detecting the reflectance light from human tissue. A Field Programmable Gate Array (FPGA) is used to control the LEDs and determine the PPG and Blood Oxygen Saturation (SpO2). The configurations with two LEDs and four LEDs are developed for measuring PPG signal and Blood Oxygen Saturation (SpO2). N-LEDs...

Solid State pH Sensor Based on Light Emitting Diodes (LED) As Detector Platform

OpenAIRE

Lau, King Tong; Shepherd, R.; Diamond, Danny; Diamond, Dermot

2006-01-01

A low-power, high sensitivity, very low-cost light emitting diode (LED)-based device developed for low-cost sensor networks was modified with bromocresol green membrane to work as a solid-state pH sensor. In this approach, a reverse-biased LED functioning as a photodiode is coupled with a second LED configured in conventional emission mode. A simple timer circuit measures how long (in microsecond) it takes for the photocurrent generated on the detector LED to discharge its capacitance from lo...

Red light emitting solid state hybrid quantum dot-near-UV GaN LED devices

International Nuclear Information System (INIS)

Song, Hongjoo; Lee, Seonghoon

2007-01-01

We produced core-shell (CdSe)ZnSe quantum dots by direct colloidal chemical synthesis and the surface-passivation method-an overcoating of the core CdSe with a larger-bandgap material ZnSe. The (CdSe)ZnSe quantum dots(QDs) play the role of a colour conversion centre. We call these quantum dots nanophosphors. We fabricated red light emitting hybrid devices of (CdSe)ZnSe QDs and a near-UV GaN LED by combining red light emitting (CdSe)ZnSe quantum dots (as a colour conversion centre) with a near-UV(NUV) GaN LED chip (as an excitation source). A few good red phosphors have been known for UV excitation wavelengths, and red phosphors for UV excitation have been sought for a long time. Here we tested the possibility of using (CdSe)ZnSe QDs as red nanophosphors for UV excitation. The fabricated red light emitting hybrid device of (CdSe)ZnSe and a NUV GaN LED chip showed a good luminance. We demonstrated that the (CdSe)ZnSe quantum dots were promising red nanophosphors for NUV excitation and that a red LED made of QDs and a NUV excitation source was a highly efficient hybrid device

Off-grid energy services for the poor: Introducing LED lighting in the Millennium Villages Project in Malawi

International Nuclear Information System (INIS)

Adkins, Edwin; Eapen, Sandy; Kaluwile, Flora; Nair, Gautam; Modi, Vijay

2010-01-01

Lanterns that use light-emitting diodes (LEDs) powered by batteries, which are in turn charged by grid electricity or small solar panels, have emerged as a cost-competitive alternative to kerosene and other fuel-based lighting technologies, offering brighter light for longer duration at equal or lower cost over time. This paper presents lessons learned from the introduction of solar LED lanterns in rural Malawi. We discuss a market-based program using new and existing local commercial structures such as vendors and cooperatives to sell lanterns to village households without subsidy. The paper addresses issues of enterprise development, community interactions, and survey data on lighting use and expenditure patterns before and after LED lantern introduction. Households that purchased a lantern reported high levels of satisfaction with the LED lanterns as well as savings in annual kerosene expenditure comparable to the price of the lantern. These households also reported monthly incomes comparable to the price of the LED lanterns whereas non-adopters surveyed reported monthly incomes about half this level, suggesting a need for financing options to maximize adoption among poorer populations in rural areas. These results suggest that similar market based models of LED lighting technology dissemination have the potential to be replicated and scaled up in other off-grid regions in developing countries. However, viability of local cooperatives and supply chains for lantern products over the medium-to-long term remain to be assessed.

Solid State pH Sensor Based on Light Emitting Diodes (LED As Detector Platform

Directory of Open Access Journals (Sweden)

Dermot Diamond

2006-08-01

Full Text Available A low-power, high sensitivity, very low-cost light emitting diode (LED-baseddevice developed for low-cost sensor networks was modified with bromocresol greenmembrane to work as a solid-state pH sensor. In this approach, a reverse-biased LEDfunctioning as a photodiode is coupled with a second LED configured in conventionalemission mode. A simple timer circuit measures how long (in microsecond it takes for thephotocurrent generated on the detector LED to discharge its capacitance from logic 1 ( 5 Vto logic 0 ( 1.7 V. The entire instrument provides an inherently digital output of lightintensity measurements for a few cents. A light dependent resistor (LDR modified withsimilar sensor membrane was also used as a comparison method. Both the LED sensor andthe LDR sensor responded to various pH buffer solutions in a similar way to obtainsigmoidal curves expected of the dye. The pKa value obtained for the sensors was found toagree with the literature value.

Is a {mu}mol a {mu}mol? Growth and development of chrysanthemum cultivated under SON-T lighting and under LED-lighting; Is a {mu}mol a {mu}mol? Groei en ontwikkeling van chrysant geteeld onder SON-T belichting en onder LED verlichting

Energy Technology Data Exchange (ETDEWEB)

Meinen, E.; Marcelis, L.F.M.; Steenhuizen, J.W.; Dueck, T.A.

2009-12-15

Description of an experiment that was conducted, comparing LED lamps and SON-T (high pressure sodium) lamps. In climate rooms with LED (96% red sodium lamps) or SON-T lamps (without daylight), chrysanthemums were cultivated at two light intensities. Although the air temperature was the same in both treatments, the leaf temperature was clearly higher in the case of SON-T as a result of heat radiation. In the case of LED a more round leaves were observed. Plants cultivated under SON-T light developed closed crops much quicker and required a shorter reaction time (10 to 14 days at high and low light intensity). Yet, the harvest weight of the branches was the same. The net leaf photosynthesis was lower in chrysanthemums cultivated under LED lighting compared to plants cultivated under SON-T lighting. This is probably due to long-term cultivation under a spectrum of almost exclusively red light. The differences between SON-T and LED with regard to light color and heat radiation have significant consequences for growth and development. [Dutch] Een experiment is uitgevoerd om LED lampen en SON-T (hogedruk natriumlampen) lampen te vergelijken. In klimaatkamers met LED (96% rood en 4% blauw) of SON-T lampen (zonder daglichttoetreding) werden chrysanten geteeld bij 2 lichtintensiteiten. Hoewel de luchttemperatuur identiek was bij beide behandelingen was de bladtemperatuur duidelijk hoger bij SON-T als gevolg van warmtestraling. Onder LED belichting werd meer 'bol blad' waargenomen. Planten geteeld onder SON-T belichting ontwikkelden sneller een gesloten gewas en hadden een kortere reactietijd (10 tot 14 dagen bij hoge en lage lichtintensiteit). Maar het oogstgewicht van de takken was gelijk. De netto actuele bladfotosynthese was lager bij chrysanten geteeld onder LED belichting vergeleken met planten geteeld onder SON-T belichting. Dit is waarschijnlijk toe te schrijven aan langdurige teelt onder een spectrum met vrijwel alleen rood licht. De verschillen tussen SON

Hybrid GaN LED with capillary-bonded II–VI MQW color-converting membrane for visible light communications

International Nuclear Information System (INIS)

Santos, Joao M M; Jones, Brynmor E; Schlosser, Peter J; Herrnsdorf, Johannes; Guilhabert, Benoit; McKendry, Jonathan J D; Hastie, Jennifer E; Laurand, Nicolas; Dawson, Martin D; Watson, Scott; Kelly, Anthony E; De Jesus, Joel; Garcia, Thor A; Tamargo, Maria C

2015-01-01

The rapid emergence of gallium-nitride (GaN) light-emitting diodes (LEDs) for solid-state lighting has created a timely opportunity for optical communications using visible light. One important challenge to address this opportunity is to extend the wavelength coverage of GaN LEDs without compromising their modulation properties. Here, a hybrid source for emission at 540 nm consisting of a 450 nm GaN micro-sized LED (micro-LED) with a micron-thick ZnCdSe/ZnCdMgSe multi-quantum-well color-converting membrane is reported. The membrane is liquid-capillary-bonded directly onto the sapphire window of the micro-LED for full hybridization. At an injection current of 100 mA, the color-converted power was found to be 37 μW. At this same current, the −3 dB optical modulation bandwidth of the bare GaN and hybrid micro-LEDs were 79 and 51 MHz, respectively. The intrinsic bandwidth of the color-converting membrane was found to be power-density independent over the range of the micro-LED operation at 145 MHz, which corresponds to a mean carrier lifetime of 1.9 ns. (paper)

Quality attributes of LED lighting. Current state-of-the-art , advantages, problem areas and potential for development - Final report; Qualitaetsmerkmale der LED-Beleuchtung. Aktueller Stand der Technik, Vorteile, Problempunkte und Entwicklungspotential - Schlussbericht

Energy Technology Data Exchange (ETDEWEB)

Gasser, S.

2009-09-15

The present report describes the state-of-the-art of LED technology for room lighting in June 2009, based on internet research, expert interviews as well as a workshop with experts. Of the 20 attributes determined, three key quality characteristics crucial for the breakthrough of LED technology were identified: (i) Energy efficiency: with values of 50 - 70 lumen/watt when in usage, current LED lamps on the market are comparable to energy saving lamps. Experts expect the luminous efficiency to double within the next five years. Declaration is often poor: instead of efficiency in real-life usage many producers declare unrealistic lab measurement results; sometimes even fantasy values are declared. (ii) Light quality: Today's good LEDs reach colour rendering attributes which are comparable to those of halogen lamps and usually better than the CFL's (colour rendering index 80 to 90, with a continuous light spectrum). (iii) Lamp life: A lamp life of up to 50,000 hours can only be reached if the heat dissipation is secured and if the Control gears quality keeps up with the LED's life time. According to the experts, many of today's LED products on the market don't meet these two requirements. Strong uncertainty is caused by inconsistent declaration and partly missing standardisation. With the ANSI standard, the US is ahead of Europe in this matter. Today LED lighting is attractive and economic where its unique advantages can be applied: directional light, very long life-span, no heat in the luminous flux, UV-free light, colour modulation, dimming with little losses. Interesting applications today include: (i) Professional field: operating time > 3,000 hours per year, e.g. shop illumination or downlights in a hall (hotel, administration, etc.). Further spotlights in museums, working place table light fixtures, hybrid solutions (e.g. indirect fluorescent lamp, direct LED). (ii) Domestic field: working place and reading lamps (low luminance, no heat

Self-reported Impacts of LED Lighting Technology Compared to Fuel-based Lighting on Night Market Business Prosperity in Kenya

Energy Technology Data Exchange (ETDEWEB)

Johnstone, Peter; Jacobson, Arne; Mills, Evan; Mumbi, Maina

2009-02-11

The notion of"productive use" is often invoked in discussions about whether new technologies improve productivity or otherwise enhance commerce in developing-country contexts. It an elusive concept,especially when quantitative measures are sought. Improved and more energy efficient illumination systems for off-gridapplication--the focus of the Lumina Project--provide a case in which a significant productivity benefit can be imagined, given the importance of light to the successful performance of many tasks, and the very low quality of baseline illumination provided by flame-based source. This Research Note summarizes self-reported quantitative and qualitative impacts of switching to LED lighting technology on the prosperity of night-market business owners and operators. The information was gathered in the context of our 2008 market testing field work in Kenya?s Rift Valley Province, which was performed in the towns of Maai Mahiu and Karagita by Arne Jacobson, Kristen Radecsky, Peter Johnstone, Maina Mumbi, and others. Maai Mahiu is a crossroads town; provision of services to travelers and freight carriers is a primary income source for the residents. In contrast, the primary income for Karagita's residents is from work in the large, factory style flower farms on the eastern shores of Lake Naivasha that specialize in producing cut flowers for export to the European market. According to residents, both towns had populations of 6,000 to 8,000 people in June 2008. We focused on quantifying the economics of fuel-based and LED lighting technology in the context of business use by night market vendors and shop keepers. Our research activities with the business owners and operators included baseline measurement of their fuel-based lighting use, an initial survey, offering for sale data logger equipped rechargeable LED lamps, monitoring the adoption of the LED lamps, and a follow-up survey.

Ultrabroad linewidth orange-emitting nanowires LED for high CRI laser-based white lighting and gigahertz communications

KAUST Repository

Janjua, Bilal

2016-08-10

Group-III-nitride laser diode (LD)-based solid-state lighting device has been demonstrated to be droop-free compared to light-emitting diodes (LEDs), and highly energy-efficient compared to that of the traditional incandescent and fluorescent white light systems. The YAG:Ce3+ phosphor used in LD-based solid-state lighting, however, is associated with rapid degradation issue. An alternate phosphor/LD architecture, which is capable of sustaining high temperature, high power density, while still intensity- and bandwidth-tunable for high color-quality remained unexplored. In this paper, we present for the first time, the proof-of-concept of the generation of high-quality white light using an InGaN-based orange nanowires (NWs) LED grown on silicon, in conjunction with a blue LD, and in place of the compound-phosphor. By changing the relative intensities of the ultrabroad linewidth orange and narrow-linewidth blue components, our LED/LD device architecture achieved correlated color temperature (CCT) ranging from 3000 K to above 6000K with color rendering index (CRI) values reaching 83.1, a value unsurpassed by the YAG-phosphor/blue-LD counterpart. The white-light wireless communications was implemented using the blue LD through on-off keying (OOK) modulation to obtain a data rate of 1.06 Gbps. We therefore achieved the best of both worlds when orange-emitting NWs LED are utilized as “active-phosphor”, while blue LD is used for both color mixing and optical wireless communications.

Report on the investigational study on the technical trend of temperature control materials for high efficiency LED lighting use; Kokoritsu LED shomeiyo no ondo seigyo zairyo no gijutsu doko ni kansuru chosa kenkyu hokokusho

Energy Technology Data Exchange (ETDEWEB)

NONE

2001-03-01

For the purpose of the innovative conservation of lighting use energy, a project is being promoted with the aim of developing light emitted diode (LED) and commercializing lighting use light source substituting for fluorescent light. In this study, the following were conducted: literature survey on Peltier materials as temperature control materials for high efficiency LED lighting and the making of them as elements, extraction of technical subjects in the commercialization of LED cooling use Peltier element materials, market surveys/analyses were made of the fields of application including the LED cooling use field. As a result, for the commercialization of temperature control use Peltier elements of lighting use LED, the desirable performance index is 5x10{sup -5}/K or more. Bi{sub 2}Te{sub 3} elements which are now commercially available as Peltier elements are not good in performance and have the toxicity problem. As a candidate of temperature control use materials of lighting use LED, Mg{sub 2} (Sn, Si) or clathrate system are regarded, but the point, etc. were pointed out that it is necessary to improve thermoelectric characteristics. (NEDO)

Multispectral digital lensless holographic microscopy: from femtosecond laser to white light LED

International Nuclear Information System (INIS)

Garcia-Sucerquia, J

2015-01-01

The use of femtosecond laser radiation and super bright white LED in digital lensless holographic microscopy is presented. For the ultrafast laser radiation two different configurations of operation of the microscope are presented and the dissimilar performance of each one analyzed. The microscope operating with a super bright white light LED in combination with optical filters shows very competitive performance as it is compared with more expensive optical sources. The broadband emission of both radiation sources allows the multispectral imaging of biological samples to obtain spectral responses and/or full color images of the microscopic specimens; sections of the head of a Drosophila melanogaster fly are imaged in this contribution. The simple, solid, compact, lightweight, and reliable architecture of digital lensless holographic microscopy operating with broadband light sources to image biological specimens exhibiting micrometer-sized details is evaluated in the present contribution. (paper)

Tapering-induced enhancement of light extraction efficiency of nanowire deep ultraviolet LED by theoretical simulations

KAUST Repository

Lin, Ronghui

2018-04-21

A nanowire (NW) structure provides an alternative scheme for deep ultraviolet light emitting diodes (DUV-LEDs) that promises high material quality and better light extraction efficiency (LEE). In this report, we investigate the influence of the tapering angle of closely packed AlGaN NWs, which is found to exist naturally in molecular beam epitaxy (MBE) grown NW structures, on the LEE of NW DUV-LEDs. It is observed that, by having a small tapering angle, the vertical extraction is greatly enhanced for both transverse magnetic (TM) and transverse electric (TE) polarizations. Most notably, the vertical extraction of TM emission increased from 4.8% to 24.3%, which makes the LEE reasonably large to achieve high-performance DUV-LEDs. This is because the breaking of symmetry in the vertical direction changes the propagation of the light significantly to allow more coupling into radiation modes. Finally, we introduce errors to the NW positions to show the advantages of the tapered NW structures can be projected to random closely packed NW arrays. The results obtained in this paper can provide guidelines for designing efficient NW DUV-LEDs.

Tapering-induced enhancement of light extraction efficiency of nanowire deep ultraviolet LED by theoretical simulations

KAUST Repository

Lin, Ronghui; Galan, Sergio Valdes; Sun, Haiding; Hu, Yangrui; Alias, Mohd Sharizal; Janjua, Bilal; Ng, Tien Khee; Ooi, Boon S.; Li, Xiaohang

2018-01-01

A nanowire (NW) structure provides an alternative scheme for deep ultraviolet light emitting diodes (DUV-LEDs) that promises high material quality and better light extraction efficiency (LEE). In this report, we investigate the influence of the tapering angle of closely packed AlGaN NWs, which is found to exist naturally in molecular beam epitaxy (MBE) grown NW structures, on the LEE of NW DUV-LEDs. It is observed that, by having a small tapering angle, the vertical extraction is greatly enhanced for both transverse magnetic (TM) and transverse electric (TE) polarizations. Most notably, the vertical extraction of TM emission increased from 4.8% to 24.3%, which makes the LEE reasonably large to achieve high-performance DUV-LEDs. This is because the breaking of symmetry in the vertical direction changes the propagation of the light significantly to allow more coupling into radiation modes. Finally, we introduce errors to the NW positions to show the advantages of the tapered NW structures can be projected to random closely packed NW arrays. The results obtained in this paper can provide guidelines for designing efficient NW DUV-LEDs.

Shhh… I Need Quiet! Children's Understanding of American, British, and Japanese-accented English Speakers.

Science.gov (United States)

Bent, Tessa; Holt, Rachael Frush

2018-02-01

Children's ability to understand speakers with a wide range of dialects and accents is essential for efficient language development and communication in a global society. Here, the impact of regional dialect and foreign-accent variability on children's speech understanding was evaluated in both quiet and noisy conditions. Five- to seven-year-old children ( n = 90) and adults ( n = 96) repeated sentences produced by three speakers with different accents-American English, British English, and Japanese-accented English-in quiet or noisy conditions. Adults had no difficulty understanding any speaker in quiet conditions. Their performance declined for the nonnative speaker with a moderate amount of noise; their performance only substantially declined for the British English speaker (i.e., below 93% correct) when their understanding of the American English speaker was also impeded. In contrast, although children showed accurate word recognition for the American and British English speakers in quiet conditions, they had difficulty understanding the nonnative speaker even under ideal listening conditions. With a moderate amount of noise, their perception of British English speech declined substantially and their ability to understand the nonnative speaker was particularly poor. These results suggest that although school-aged children can understand unfamiliar native dialects under ideal listening conditions, their ability to recognize words in these dialects may be highly susceptible to the influence of environmental degradation. Fully adult-like word identification for speakers with unfamiliar accents and dialects may exhibit a protracted developmental trajectory.

Tuning the light in senior care: Evaluating a trial LED lighting system at the ACC Care Center in Sacramento, CA

Energy Technology Data Exchange (ETDEWEB)

Davis, Robert G.; Wilkerson, Andrea M.; Samla, Connie; Bisbee, Dave

2016-08-31

This report summarizes the results from a trial installation of light-emitting diode (LED) lighting systems in several spaces within the ACC Care Center in Sacramento, CA. The Sacramento Municipal Utility District (SMUD) coordinated the project and invited the U.S. Department of Energy (DOE) to document the performance of the LED lighting systems as part of a GATEWAY evaluation. DOE tasked the Pacific Northwest National Laboratory (PNNL) to conduct the investigation. SMUD and ACC staff coordinated and completed the design and installation of the LED systems, while PNNL and SMUD staff evaluated the photometric performance of the systems. ACC staff also track behavioral and health measures of the residents; some of those results are reported here, although PNNL staff were not directly involved in collecting or interpreting those data. The trial installation took place in a double resident room and a single resident room, and the corridor that connects those (and other) rooms to the central nurse station. Other spaces in the trial included the nurse station, a common room called the family room located near the nurse station, and the ACC administrator’s private office.

A high-performance stand-alone solar PV power system for LED lighting

KAUST Repository

Huang, B. J.; Hsu, P. C.; Wu, M. S.; Chen, K.Y.

2010-01-01

The present study developed a high-performance solar PV power technology for the LED lighting of a solar home system. The nMPPO (near-Maximum-Power- Point- Operation) design is employed in system design to eliminate MPPT. A feedback control system

The sunstone – an intelligent platform for pv led lighting in the urban environment

DEFF Research Database (Denmark)

Poulsen, Peter Behrensdorff; Dam-Hansen, Carsten; Harboe, Rene Kirstein

and maintenance. Such markets are interesting for solar energy powered LED applications since the additional price due to the PV and LEDs are hugely offset by the savings of avoiding digging up and repaving the road when laying a cable to the grid and avoid the investment and man-power cost of replacing light...

The effect of perceived regional accents on individual economic behavior: a lab experiment on linguistic performance, cognitive ratings and economic decisions.

Directory of Open Access Journals (Sweden)

Stephan Heblich

Full Text Available Does it matter if you speak with a regional accent? Speaking immediately reveals something of one's own social and cultural identity, be it consciously or unconsciously. Perceiving accents involves not only reconstructing such imprints but also augmenting them with particular attitudes and stereotypes. Even though we know much about attitudes and stereotypes that are transmitted by, e.g. skin color, names or physical attractiveness, we do not yet have satisfactory answers how accent perception affects human behavior. How do people act in economically relevant contexts when they are confronted with regional accents? This paper reports a laboratory experiment where we address this question. Participants in our experiment conduct cognitive tests where they can choose to either cooperate or compete with a randomly matched male opponent identified only via his rendering of a standardized text in either a regional accent or standard accent. We find a strong connection between the linguistic performance and the cognitive rating of the opponent. When matched with an opponent who speaks the accent of the participant's home region--the in-group opponent--, individuals tend to cooperate significantly more often. By contrast, they are more likely to compete when matched with an accent speaker from outside their home region, the out-group opponent. Our findings demonstrate, firstly, that the perception of an out-group accent leads not only to social discrimination but also influences economic decisions. Secondly, they suggest that this economic behavior is not necessarily attributable to the perception of a regional accent per se, but rather to the social rating of linguistic distance and the in-group/out-group perception it evokes.

Study of system dynamics model and control of a high-power LED lighting luminaire

International Nuclear Information System (INIS)

Huang, B.-J.; Hsu, P.-C.; Wu, M.-S.; Tang, C.-W.

2007-01-01

The purpose of the present study is to design a current control system which is robust to the system dynamics uncertainty and the disturbance of ambient temperature to assure a stable optical output property of LED. The system dynamics model of the LED lighting system was first derived. A 96 W high-power LED luminaire was designed and built in the present study. The linearly perturbed system dynamics model for the LED luminaire is derived experimentally. The dynamics model of LED lighting system is of a multiple-input-multiple-output (MIMO) system with two inputs (applied voltage and ambient temperature) and two outputs (forward current and heat conducting body temperature). A step response test method was employed to the 96 W LED luminaire to identify the system dynamics model. It is found that the current model is just a constant gain (resistance) and the disturbance model is of first order, both changing with operating conditions (voltage and ambient temperature). A feedback control system using PI algorithm was designed using the results of the system dynamics model. The control system was implemented on a PIC microprocessor. Experimental results show that the control system can stably and accurately control the LED current to a constant value at the variation of ambient temperature up to 40 o C. The control system is shown to have a robust property with respect to the plant uncertainty and the ambient temperature disturbance

The importance of a near-native accent. : Do the Dutch speak English or Double Dutch?

NARCIS (Netherlands)

drs. Frans Hermans

2014-01-01

The importance of a near-native accent. This talk will discuss whether or not it is important for EFL-teachers to try and achieve a near-native generally accepted accent for their students. The focus will be on the credibility of non-native speakers of English while speaking English in a

Design of an Oximeter Based on LED-LED Configuration and FPGA Technology

Directory of Open Access Journals (Sweden)

Radovan Stojanovic

2013-01-01

Full Text Available A fully digital photoplethysmographic (PPG sensor and actuator has been developed. The sensing circuit uses one Light Emitting Diode (LED for emitting light into human tissue and one LED for detecting the reflectance light from human tissue. A Field Programmable Gate Array (FPGA is used to control the LEDs and determine the PPG and Blood Oxygen Saturation (SpO2. The configurations with two LEDs and four LEDs are developed for measuring PPG signal and Blood Oxygen Saturation (SpO2. N-LEDs configuration is proposed for multichannel SpO2 measurements. The approach resulted in better spectral sensitivity, increased and adjustable resolution, reduced noise, small size, low cost and low power consumption.

Design of an oximeter based on LED-LED configuration and FPGA technology.

Science.gov (United States)

Stojanovic, Radovan; Karadaglic, Dejan

2013-01-04

A fully digital photoplethysmographic (PPG) sensor and actuator has been developed. The sensing circuit uses one Light Emitting Diode (LED) for emitting light into human tissue and one LED for detecting the reflectance light from human tissue. A Field Programmable Gate Array (FPGA) is used to control the LEDs and determine the PPG and Blood Oxygen Saturation (S(p)O(2)). The configurations with two LEDs and four LEDs are developed for measuring PPG signal and Blood Oxygen Saturation (S(p)O(2)). N-LEDs configuration is proposed for multichannel S(p)O(2) measurements. The approach resulted in better spectral sensitivity, increased and adjustable resolution, reduced noise, small size, low cost and low power consumption.

Development of Advanced Manufacturing Methods for Warm White LEDs for General Lighting

Energy Technology Data Exchange (ETDEWEB)

Deshpande, Anirudha; Kolodin, Boris; Jacob, Cherian; Chowdhury, Ashfaqul; Kuenzler, Glenn; Sater, Karen; Aesram, Danny; Glaettli, Steven; Gallagher, Brian; Langer, Paul; Setlur, Anant; Beers, Bill

2012-03-31

GE Lighting Solutions will develop precise and efficient manufacturing techniques for the “remote phosphor” platform of warm-white LED products. In volume, this will be demonstrated to drive significant materials, labor and capital productivity to achieve a maximum possible 53% reduction in overall cost. In addition, the typical total color variation for these white LEDs in production will be well within the ANSI bins and as low as a 4-step MacAdam ellipse centered on the black body curve. Achievement of both of these objectives will be demonstrated while meeting a performance target of > 75 lm/W for a warm-white LED and a reliability target of <30% lumen drop / <2-step MacAdam ellipse shift, estimated over 50,000 hrs.

Acquisition of stress and pitch accent in English-Spanish bilingual children

Science.gov (United States)

Kim, Sahyang; Andruski, Jean; Nathan, Geoffrey S.; Casielles, Eugenia; Work, Richard

2005-09-01

Although understanding of prosodic development is considered crucial for understanding of language acquisition in general, few studies have focused on how children develop native-like prosody in their speech production. This study will examine the acquisition of lexical stress and postlexical pitch accent in two English-Spanish bilingual children. Prosodic characteristics of English and Spanish are different in terms of frequent stress patterns (trochaic versus penultimate), phonetic realization of stress (reduced unstressed vowel versus full unstressed vowel), and frequent pitch accent types (H* versus L*+H), among others. Thus, English-Spanish bilingual children's prosodic development may provide evidence of their awareness of language differences relatively early during language development, and illustrate the influence of markedness or input frequency in prosodic acquisition. For this study, recordings from the children's one-word stage are used. Durations of stressed and unstressed syllables and F0 peak alignment are measured, and pitch accent types in different accentual positions (nuclear versus prenuclear) are transcribed using American English ToBI and Spanish ToBI. Prosodic development is compared across ages within each language and across languages at each age. Furthermore, the bilingual children's productions are compared with monolingual English and Spanish parents' productions.

GATEWAY Demonstrations: Tuning the Light in Senior Care: Evaluating a Trial LED Lighting System at the ACC Care Center in Sacramento, CA

Energy Technology Data Exchange (ETDEWEB)

Davis, Robert G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Wilkerson, Andrea M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Samla, Connie [Sacramento Municipal Utility District, Sacramento, CA (United States); Bisbee, Dave [Sacramento Municipal Utility District, Sacramento, CA (United States)

2016-08-31

The GATEWAY program documented the performance of tunable-white LED lighting systems installed in several spaces within the ACC Care Center, a senior-care facility in Sacramento, CA. The project results included energy savings and improved lighting quality, as well as other possible health-related benefits that may have been attributable, at least in part, to the lighting changes.

LED arrays as cost effective and efficient light sources for widefield microscopy.

Directory of Open Access Journals (Sweden)

Dinu F Albeanu

Full Text Available New developments in fluorophores as well as in detection methods have fueled the rapid growth of optical imaging in the life sciences. Commercial widefield microscopes generally use arc lamps, excitation/emission filters and shutters for fluorescence imaging. These components can be expensive, difficult to maintain and preclude stable illumination. Here, we describe methods to construct inexpensive and easy-to-use light sources for optical microscopy using light-emitting diodes (LEDs. We also provide examples of its applicability to biological fluorescence imaging.

Efficient light extraction from GaN LEDs using gold-coated ZnO nanoparticles

KAUST Repository

Alhadidi, A.

2015-11-01

We experimentally demonstrate the effect of depositing gold-coated ZnO nanoparticles on the surface of GaN multi-quantum well LED structures. We show that this method can significantly increase the amount of extracted light.

User evaluation of eight led light sources with different special colour rendering indices R9

DEFF Research Database (Denmark)

Markvart, Jakob; Iversen, Anne; Logadottir, Asta

2013-01-01

In this study we evaluated the influence of the special colour rendering index R9 on subjective red colour perception and Caucasian skin appearance among untrained test subjects. The light sources tested are commercially available LED based light sources with similar correlated colour temperature...

P1-16: The Effect of Visual Stimuli of LED Lighting by Color Temperature and Illuminance Control on Attention and Meditation Level of Mind

Directory of Open Access Journals (Sweden)

Chan-Su Lee

2012-10-01

Full Text Available Recently LED (Lighting Emitting Diode lighting sources are applied not only for displays like LED BLU (back light unit TV but also for general lighting like LED lamps for home and office. The color temperature, or chromaticity, and brightness of LED lighting can be easily controlled. Preferred combinations between illuminance and color temperature of lighting depend on daily living activities (Oi et al., 2007 Symposium on Design of Artificial Environments 214–215. Changes in intensity can be more easily detected than color changes (Almeida et al., 2009 Perception 38 1109–1117. We investigated whether the illumination stimuli of LED lighting can enhance attention and relaxation level by controlling color temperature and illuminance according to activities. EEG signals are used to estimate attention and relaxation levels of human subjects under different lighting conditions. Nine participants with normal eye sight and color vision participated in the experiments with four different activities under different illumination conditions. LED lighting with color temperature 3600 K in 240 lux is used for relaxation activities, and LED lighting with 6600 K in 794 lux is used for the task which requires attention. These lighting conditions are compared with conventional lighting condition with 4600 K in 530 lux. Preliminary experiment results show that low color temperature with low illumination intensity of LED lighting enhances relaxation level and high color temperature with high illuminance improves attention level compared with conventional lighting environment without illuminance and color temperature changes.

GATEWAY Demonstrations: Tuning Hospital Lighting: Evaluating Tunable LED Lighting at the Swedish Hospital Behavioral Health Unit in Seattle

Energy Technology Data Exchange (ETDEWEB)

Wilkerson, Andrea [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Davis, Robert G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Clark, Edward [ZGF Architects LLP, Seattle, WA (United States)

2017-08-23

The GATEWAY program evaluated a tunable LED lighting system installed in the new Swedish Medical Behavioral Health Unit in Seattle that incorporates color-tunable luminaires in common areas, and uses advanced controls for dimming and color tuning, with the goal of providing a better environment for staff and patients. The report reviews the design of the tunable lighting system, summarizes two sets of measurements, and discusses the circadian, energy, and commissioning implications as well as lessons learned from the project.

The influence of LED lighting on task accuracy: time of day, gender and myopia effects

Science.gov (United States)

Rao, Feng; Chan, A. H. S.; Zhu, Xi-Fang

2017-07-01

In this research, task errors were obtained during performance of a marker location task in which the markers were shown on a computer screen under nine LED lighting conditions; three illuminances (100, 300 and 500 lx) and three color temperatures (3000, 4500 and 6500 K). A total of 47 students participated voluntarily in these tasks. The results showed that task errors in the morning were small and nearly constant across the nine lighting conditions. However in the afternoon, the task errors were significantly larger and varied across lighting conditions. The largest errors for the afternoon session occurred when the color temperature was 4500 K and illuminance 500 lx. There were significant differences between task errors in the morning and afternoon sessions. No significant difference between females and males was found. Task errors for high myopia students were significantly larger than for the low myopia students under the same lighting conditions. In summary, the influence of LED lighting on task accuracy during office hours was not gender dependent, but was time of day and myopia dependent.

Green LED as an Effective Light Source for Curing Acrylate-Based Dental Resins in Combination with Irgacure 784

Directory of Open Access Journals (Sweden)

Katalin Bukovinszky

2018-01-01

Full Text Available Low intensity green light emitting diodes (LED were shown to be an effective light source to induce the photopolymerization of an acrylate-based photocurable dental restorative resin mixture of bisphenol A glycerolate dimethacrylate (BisGMA, triethylene glycol dimethacrylate (TEGDMA, and diurethane dimethacrylate (UDMA, in combination with fluorinated diaryl titanocene (Irgacure 784. Dental matrices were prepared by the LED light source at different intensities. The mechanical properties, such as Vickers microhardness, compressive strength, diametric tensile strength, flexural strength, and E-modulus of the created samples, were investigated. The kinetics of the photopolymerization was followed by Raman spectroscopy and conversion values were determined. It was found that, despite its narrow-emission range centered at a wavelength of 531 nm, the green LED light source is suitable for the preparation of dental matrices with good mechanical properties and high conversion values.

Luminescence and the light emitting diode the basics and technology of leds and the luminescence properties of the materials

CERN Document Server

Williams, E W; Pamplin, BR

2013-01-01

Luminescence and the Light Emitting Diode: The Basics and Technology of LEDS and the Luminescence Properties of the Materials focuses on the basic physics and technology of light emitting diodes (LEDS) and pn junction lasers as well as their luminescence properties. Optical processes in semiconductors and the useful devices which can be made are discussed. Comprised of 10 chapters, this book begins with an introduction to the crystal structure and growth, as well as the optical and electrical properties of LED materials. The detailed fabrication of the LED is then considered, along with the lu

Technology Analysis of Global Smart Light Emitting Diode (LED Development Using Patent Data

Directory of Open Access Journals (Sweden)

Sangsung Park

2017-08-01

Full Text Available Technological developments related to smart light emitting diode (LED systems have progressed rapidly in recent years. In this paper, patent documents related to smart LED technology are collected and analyzed to understand the technology development of smart LED systems. Most previous studies of the technology were dependent on the knowledge and experience of domain experts, using techniques such as Delphi surveys or technology road-mapping. These approaches may be subjective and lack robustness, because the results can vary according to the selected expert groups. We therefore propose a new technology analysis methodology based on statistical modeling to obtain objective and relatively stable results. The proposed method consists of visualization based on Bayesian networks and a linear count model to analyze patent documents related to smart LED technology. Combining these results, a global hierarchical technology structure is created that can enhance the sustainability in smart LED system technology. In order to show how this methodology could be applied to real-world problems, we carry out a case study on the technology analysis of smart LED systems.

An Advantage for Age? Self-Concept and Self-Regulation as Teachable Foundations in Second Language Accent

Science.gov (United States)

Moyer, Alene

2018-01-01

Age of onset has long been assumed to predict outcomes in second/foreign language accent. Yet beyond early childhood, acquiring a new accent has much to do with social-affective factors such as learner identity and motivation, as well as cognitive factors such as learning strategies (Pfenninger, 2017). Newer perspectives acknowledge this…

The Posterior Fossa and Foreign Accent Syndrome : Report of Two New Cases and Review of the Literature

NARCIS (Netherlands)

Keulen, Stefanie; Mariën, Peter; van Dun, Kim; Bastiaanse, Roelien; Manto, Mario; Verhoeven, Jo

Foreign accent syndrome is a rare motor speech disorder that causes patients to speak their language with a non-native accent. In the neurogenic condition, the disorder develops after lesions in the language dominant hemisphere, often affecting Broca's area, the insula, the supplementary motor area

A controlled trial of the Litebook light-emitting diode (LED light therapy device for treatment of Seasonal Affective Disorder (SAD

Directory of Open Access Journals (Sweden)

Telner John

2007-08-01

Full Text Available Abstract Background Recent research has emphasized that the human circadian rhythm system is differentially sensitive to short wavelength light. Light treatment devices using efficient light-emitting diodes (LEDs whose output is relatively concentrated in short wavelengths may enable a more convenient effective therapy for Seasonal Affective Disorder (SAD. Methods The efficacy of a LED light therapy device in the treatment of SAD was tested in a randomized, double-blind, placebo-controlled, multi-center trial. Participants aged 18 to 65 with SAD (DSM-IV major depression with seasonal pattern were seen at Baseline and Randomization visits separated by 1 week, and after 1, 2, 3 and 4 weeks of treatment. Hamilton Depression Rating Scale scores (SIGH-SAD were obtained at each visit. Participants with SIGH-SAD of 20 or greater at Baseline and Randomization visits were randomized to active or control treatment: exposure to the Litebook LED treatment device (The Litebook Company Ltd., Alberta, Canada which delivers 1,350 lux white light (with spectral emission peaks at 464 nm and 564 nm at a distance of 20 inches or to an inactivated negative ion generator at a distance of 20 inches, for 30 minutes a day upon awakening and prior to 8 A.M. Results Of the 26 participants randomized, 23 completed the trial. Mean group SIGH-SAD scores did not differ significantly at randomization. At trial end, the proportions of participants in remission (SIGH-SAD less than 9 were significantly greater (Fisher's exact test, and SIGH-SAD scores, as percent individual score at randomization, were significantly lower (t-test, with active treatment than with control, both in an intent-to-treat analysis and an observed cases analysis. A longitudinal repeated measures ANOVA analysis of SIGH-SAD scores also indicated a significant interaction of time and treatment, showing superiority of the Litebook over the placebo condition. Conclusion The results of this pilot study support

Pointed and plateau-shaped pitch accents in North Frisian

DEFF Research Database (Denmark)

Niebuhr, Oliver; Hoekstra, Jarich

2015-01-01

for language documentation and conservation purposes. We selected a small part of this corpus – interviews of 10 elderly speakers – and conducted multiparametric F0 and duration measurements, focusing on nuclear rising-falling pitch accent patterns. We found strong evidence for a phonological pitch...

Patterns of Light Chasing the Spectrum from Aristotle to LEDs

CERN Document Server

Beeson, Steven

2008-01-01

Light is all around us – even when we do not see it. Our eyes do not detect the higher energy and shorter-than-visible-wavelength ultraviolet radiation, yet we know it is there from the sunburn we receive in Arizona. We know that window glass can block ultraviolet rays so we do not get a burn while driving with the windows rolled up. Our eyes do not detect the low-energy, long-wavelength infrared (IR) radiation but we know it exists from discussions of war applications and televised images of guided weapons targets. We also know about radio waves from the little boxes that talk to us and x-rays from the dentist's office. Patterns of Light, Chasing the Spectrum from Aristotle to LEDs, written by Steve Beeson and Jim Mayer starts with the visible – the straight path of light. It continues with chapters detailing reflection (mirrors, storefront windows) and refraction (eyeglasses, binoculars). Color is then introduced with the query "Why is the sky blue?" After answering that and other similar questions ("Wh...

Being the corresponding accents of red in one interior and one exterior as

OpenAIRE

Sandeva, Vaska; Despot, Katerina; Namicev, Petar; Ignatov, Aleksandar

2013-01-01

What is the emphasis in the interior and what is exterior accent? Thair next goal is to attract attention and to clarify the answer to his location i.e. to highlight the special effect of the composition, which we have set. The color is the emphasis that has been selected for analysis. From the color palette, accent color is red, a primary color and while contrast to green or color that represented 60% of the exterior and is dominant. Ability of the human eye to focus and take depending on th...

Effects of melatonin injection or green-wavelength LED light on the antioxidant system in goldfish (Carassius auratus) during thermal stress.

Science.gov (United States)

Jung, Seo Jin; Choi, Young Jae; Kim, Na Na; Choi, Ji Yong; Kim, Bong-Seok; Choi, Cheol Young

2016-05-01

We tested the mitigating effects of melatonin injections or irradiation from green-wavelength light-emitting diodes (LEDs) on goldfish (Carassius auratus) exposed to thermal stress (high water temperature, 30 °C). The effects of the two treatments were assessed by measuring the expression and activity levels of the antioxidant enzymes, superoxide dismutase and catalase, plasma hydrogen peroxide, lipid hydroperoxide, and lysozyme. In addition, a comet assay was conducted to confirm that high water temperature damaged nuclear DNA. The expression and activity of the antioxidant enzymes, plasma hydrogen peroxide, and lipid hydroperoxide were significantly higher after exposure to high temperature and were significantly lower in fish that received melatonin or LED light than in those that received no mitigating treatment. Plasma lysozyme was significantly lower after exposure to high temperature and was significantly higher after exposure to melatonin or LED light. The comet assay revealed that thermal stress caused a great deal of damage to nuclear DNA; however, treatment with melatonin or green-wavelength LED light prevented a significant portion of this damage from occurring. These results indicate that, although high temperatures induce oxidative stress and reduce immune system strength in goldfish, both melatonin and green-wavelength LED light inhibit oxidative stress and boost the immune system. LED treatment increased the antioxidant and immune system activity more significantly than did melatonin treatment. Copyright © 2016 Elsevier Ltd. All rights reserved.

Foreign accent, cognitive load and intelligibility of EMI lectures

DEFF Research Database (Denmark)

Jensen, Christian; Thøgersen, Jacob

2017-01-01

This study investigated the effect of foreign accent on the understanding of spoken texts in two different contexts: (1) when listeners extract surface level meaning of simple utterances, labelled “intelligibility in simple tasks” (IS) below, and (2) when they answer content questions to a complex...

Smart lighting using LED luminaries

NARCIS (Netherlands)

Bhardwaj, S.; Ozcelebi, T.; Lukkien, J.J.

2010-01-01

The target of a smart lighting system is to control light sources in an environment (e.g. home, office) adaptively according to user contexts and preferences. Literature work in this area focuses on traditional light sources such as incandescent and fluorescent lights, whereas this paper takes a

Efficient Personalized Mispronunciation Detection of Taiwanese-Accented English Speech Based on Unsupervised Model Adaptation and Dynamic Sentence Selection

Science.gov (United States)

Wu, Chung-Hsien; Su, Hung-Yu; Liu, Chao-Hong

2013-01-01

This study presents an efficient approach to personalized mispronunciation detection of Taiwanese-accented English. The main goal of this study was to detect frequently occurring mispronunciation patterns of Taiwanese-accented English instead of scoring English pronunciations directly. The proposed approach quickly identifies personalized…

ACCENT-BIAFLUX workshop 2005, trace gas and aerosol flux measurement and techniques. Abstract book

Energy Technology Data Exchange (ETDEWEB)

Werner, A.; Soerensen, L.L. (eds.)

2005-04-01

The woorkshop trace gas and aerosol flux measurement techniques in the second meeting within the Biosphere Atmosphere Exchange of Pollutions (BIAFLUX) group in the EU-network project Atmospheric Composition Change (ACCENT). The goal of the workshop is to obtain an overview of techniques for measurements of gas and aerosol fluxes and to gather the knowledge of uncertainties in flux measurements and calculations. The workshop is funded by ACCENT. The abstract book presents abstracts of 21 oral presentations and 26 poster presentations. (LN)

A hypothesis on improving foreign accents by optimizing variability in vocal learning brain circuits

OpenAIRE

Simmonds, Anna J.

2015-01-01

Rapid vocal motor learning is observed when acquiring a language in early childhood, or learning to speak another language later in life. Accurate pronunciation is one of the hardest things for late learners to master and they are almost always left with a non-native accent. Here, I propose a novel hypothesis that this accent could be improved by optimizing variability in vocal learning brain circuits during learning. Much of the neurobiology of human vocal motor learning has been inferred fr...

Yuma Border Patrol Area Lighting Retrofit LED System Performance in a Trial Installation – Two Years Later

Energy Technology Data Exchange (ETDEWEB)

Wilkerson, Andrea M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Sullivan, Gregory P. [Efficiency Solutions, Inc, Richland, WA (United States); Davis, Robert G. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2016-05-21

Documentation of the Yuma Sector Border Patrol Area lighting LED trial demonstration continues to provide a better understanding of LED technology performance in a high ambient temperature and high solar radiation environment. Measured data at the project site showed illuminances changing more rapidly than anticipated. As previously predicted, the causes for these observed changes are mostly if not completely explained by dirt accumulation. The laboratory measurements showed not only the effect of dirt on lumen output, but also on the distribution of light exiting the luminaire.

Disparity in Cutaneous Pigmentary Response to LED vs Halogen Incandescent Visible Light: Results from a Single Center, Investigational Clinical Trial Determining a Minimal Pigmentary Visible Light Dose.

Science.gov (United States)

Soleymani, Teo; Cohen, David E; Folan, Lorcan M; Okereke, Uchenna R; Elbuluk, Nada; Soter, Nicholas A

2017-11-01

Background: While most of the attention regarding skin pigmentation has focused on the effects of ultraviolet radiation, the cutaneous effects of visible light (400 to 700nm) are rarely reported. The purpose of this study was to investigate the cutaneous pigmentary response to pure visible light irradiation, examine the difference in response to different sources of visible light irradiation, and determine a minimal pigmentary dose of visible light irradiation in melanocompetent subjects with Fitzpatrick skin type III - VI. The study was designed as a single arm, non-blinded, split-side dual intervention study in which subjects underwent visible light irradiation using LED and halogen incandescent light sources delivered at a fluence of 0.14 Watts/cm2 with incremental dose progression from 20 J/cm2 to 320 J/cm2. Pigmentation was assessed by clinical examination, cross-polarized digital photography, and analytic colorimetry. Immediate, dose-responsive pigment darkening was seen with LED light exposure in 80% of subjects, beginning at 60 Joules. No pigmentary changes were seen with halogen incandescent light exposure at any dose in any subject. This study is the first to report a distinct difference in cutaneous pigmentary response to different sources of visible light, and the first to demonstrate cutaneous pigment darkening from visible LED light exposure. Our findings raise the concern that our increasing daily artificial light surroundings may have clandestine effects on skin biology. J Drugs Dermatol. 2017;16(11):1105-1110..

Improvement in light-output efficiency of near-ultraviolet InGaN-GaN LEDs fabricated on stripe patterned sapphire substrates

International Nuclear Information System (INIS)

Lee, Y.J.; Hsu, T.C.; Kuo, H.C.; Wang, S.C.; Yang, Y.L.; Yen, S.N.; Chu, Y.T.; Shen, Y.J.; Hsieh, M.H.; Jou, M.J.; Lee, B.J.

2005-01-01

InGaN/GaN multi-quantum wells near ultraviolet light-emitting diodes (LEDs) were fabricated on a patterned sapphire substrate (PSS) with parallel stripe along the sapphire direction by using low-pressure metal-organic chemical vapor deposition (MOCVD). The forward- and reverse-bias electrical characteristics of the stripe PSS LEDs are, respectively, similar and better than those of conventional LEDs on sapphire substrate. The output power of the epoxy package of stripe PSS LED was 20% higher than that of the conventional LEDs. The enhancement of output power is due not only to the reduction of dislocation density but also to the release of the guided light in LEDs by the geometric shape of the stripe PSS, according to the ray-tracing analysis

Color homogeneity in LED spotlights

NARCIS (Netherlands)

Prins, C.R.

2013-01-01

Color variation in the light output of white LEDs is a common problem in LED lighting. We aim to design LED spotlights with a uniform color output while keeping the cost of the system low and the energy efficiency high. Therefore we design a special optic to eliminate the color variation of the LED.

Best practices : bus signage for persons with visual impairments : light-emitting diode (LED) signs

Science.gov (United States)

2004-01-01

This best-practices report provides key information regarding the use of Light-Emitting Diode (LED) sign technologies to present destination and route information on transit vehicles. It will assist managers and engineers in the acquisition and use o...

Investigation on bandgap, diffraction, interference, and refraction effects of photonic crystal structure in GaN/InGaN LEDs for light extraction.

Science.gov (United States)

Patra, Saroj Kanta; Adhikari, Sonachand; Pal, Suchandan

2014-06-20

In this paper, we have made a clear differentiation among bandgap, diffraction, interference, and refraction effects in photonic crystal structures (PhCs). For observing bandgap, diffraction, and refraction effects, PhCs are considered on the top p-GaN surface of light emitting diodes (LEDs), whereas for interference effect, hole type PhCs are considered to be embedded within n-GaN layer of LED. From analysis, it is observed that at a particular lattice periodicity, for which bandgap lies within the wavelength of interest shows a significant light extraction due to inhibition of guided mode. Beyond a certain periodicity, diffraction effect starts dominating and light extraction improves further. The interference effect is observed in embedded photonic crystal LEDs, where depth of etching supports constructive interference of outward light waves. We have also shed light on refraction effects exhibited by the PhCs and whether negative refraction properties of PhCs may be useful in case of LED light extraction.

Assessing the Performance of LED-Based Flashlights Available in the Kenyan Off-Grid Lighting Market

Energy Technology Data Exchange (ETDEWEB)

Tracy, Jennifer; Jacobson, Arne; Mills, Evan

2010-03-02

Low cost rechargeable flashlights that use LED technology are increasingly available in African markets. While LED technology holds promise to provide affordable, high quality lighting services, the widespread dissemination of low quality products may make it difficult to realize this potential. This study includes performance results for three brands of commonly available LED flashlights that were purchased in Kenya in 2009. The performance of the flashlights was evaluated by testing five units for each of the three brands. The tests included measurements of battery capacity, time required to charge the battery, maximum illuminance at one meter, operation time and lux-hours from a fully charged battery, light distribution, and color rendering. All flashlights tested performed well below the manufacturers? rated specifications; the measured battery capacity was 30-50percent lower than the rated capacity and the time required to fully charge the battery was 6-25percent greater than the rated time requirement. Our analysis further shows that within each brand there is considerable variability in each performance indicator. The five samples within a single brand varied from each other by as much as 22percent for battery capacity measurements, 3.6percent for the number of hours required for a full charge, 23percent for maximum initial lux, 38percent for run time, 11percent for light distribution and by as much as 200percent for color rendering. Results obtained are useful for creating a framework for quality assurance of off-grid LED products and will be valuable for informing consumers, distributors and product manufacturers about product performance.

Relationship between the change of ethological status and concentration of certain cytokines in blood in experimental desynchronosis under led lighting.

Science.gov (United States)

Osikov, M V; Ogneva, O I

2016-01-01

Changing the natural rhythm of day and night leads to the development of DS, disruption of coordinated muscular activity, adequate behavioral activity, a decrease of attention in the performance of night work by experts in various fields. Changes ethological status may potentiate or weaken the changes in the indices of immune status, contribute to the formation of allostatic load at desynchronosis. To investigate the relationship between changes ethological status and concentration of certain cytokines in peripheral blood in experimental desynchronosis under LED lighting. The study was performed on 158 adult guinea pigs, which were randomly assigned into 2 groups: 1 group- animals in the conditions of standard fixed (12 h light / 12 h dark) LED lighting (SFSDO); 2 group- animals with jet lag in terms of LED lighting (DESSDO). Light desynchronosis created by keeping animals at clock coverage for 30 days. Behavioral activity was studied in the test «open field» cognitive function was assessed using aqueous «labyrinth» Morris. By ELISA was determined on the apparatus in the peripheral blood concentration of interleukin - 4 (IL-4), interferon-gamma (IFN-g), melatonin, cortisol via specific for guinea pig test systems. It was found that in animals of DS in terms of LED lighting in the dynamics of 10-30 days of observation show signs of anxiety, depression orienting-exploratory behavior, reduce the long-term memory and learning ability, spatial orientation disorders. It found that when a jet lag LED lighting conditions for 10 days, 20 days and 30 days in peripheral blood melatonin concentration decreases, the concentration of cortisol rises. In peripheral blood decreased IL-4 concentrations of 20 and 30 days, reducing the concentration of IFN-g at 30 days. Based on the results of correlation analysis, ethological change status and progress of cognitive function with a decrease in the blood concentration of IL-4 and IFN-g, the concentration of melatonin increase

Investing in Their Future: Portland’s Purchase and Conversion of an LED Street Lighting System

Energy Technology Data Exchange (ETDEWEB)

Kinzey, B. R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Rosinbum, T. [Portland Bureau of Transportation, Portland, OR (United States)

2015-08-28

During the ongoing process of converting its streetlights from high-pressure sodium to LED, the city of Portland, Oregon, purchased a large portion of its street lighting system and encountered a range of issues among the stakeholders. This report identifies some of the challenges involved and discusses how they were addressed, in order to help inform and facilitate future lighting transitions elsewhere.

USER EVALUATION OF EIGHT LED LIGHT SOURCES WITH DIFFERENTSPECIAL COLOUR RENDERING INDICES R9

DEFF Research Database (Denmark)

Markvart, Jakob; Iversen, Anne; Logadóttir, Ásta

2013-01-01

In this study we evaluated the influence of the special colour rendering index R9 on subjective red colour perception and Caucasian skin appearance among untrained test subjects. The light sources tested are commercially available LED based light sources with similar correlated colour temperature...... and general colour rendering index, but with varying R9. It was found that the test subjects in general are more positive towards light sources with higher R9. The shift from a majority of negative responses to a majority of positive responses is found to occur at R9 values of ~20....

Beyond conventional c-plane GaN-based light emitting diodes: A systematic exploration of LEDs on semi-polar orientations

Science.gov (United States)

Monavarian, Morteza

Despite enormous efforts and investments, the efficiency of InGaN-based green and yellow-green light emitters remains relatively low, and that limits progress in developing full color display, laser diodes, and bright light sources for general lighting. The low efficiency of light emitting devices in the green-to-yellow spectral range, also known as the "Green Gap", is considered a global concern in the LED industry. The polar c-plane orientation of GaN, which is the mainstay in the LED industry, suffers from polarization-induced separation of electrons and hole wavefunctions (also known as the "quantum confined Stark effect") and low indium incorporation efficiency that are the two main factors that contribute to the Green Gap phenomenon. One possible approach that holds promise for a new generation of green and yellow light emitting devices with higher efficiency is the deployment of nonpolar and semi-polar crystallographic orientations of GaN to eliminate or mitigate polarization fields. In theory, the use of other GaN planes for light emitters could also enhance the efficiency of indium incorporation compared to c-plane. In this thesis, I present a systematic exploration of the suitable GaN orientation for future lighting technologies. First, in order to lay the groundwork for further studies, it is important to discuss the analysis of processes limiting LED efficiency and some novel designs of active regions to overcome these limitations. Afterwards, the choice of nonpolar orientations as an alternative is discussed. For nonpolar orientation, the (1100)-oriented (mo-plane) structures on patterned Si (112) and freestanding m-GaN are studied. The semi-polar orientations having substantially reduced polarization field are found to be more promising for light-emitting diodes (LEDs) owing to high indium incorporation efficiency predicted by theoretical studies. Thus, the semi-polar orientations are given close attention as alternatives for future LED technology

Large-signal modulation characteristics of a GaN-based micro-LED for Gbps visible-light communication

Science.gov (United States)

Tian, Pengfei; Wu, Zhengyuan; Liu, Xiaoyan; Fang, Zhilai; Zhang, Shuailong; Zhou, Xiaolin; Liu, Kefu; Liu, Ming-Gang; Chen, Shu-Jhih; Lee, Chia-Yu; Cong, Chunxiao; Hu, Laigui; Qiu, Zhi-Jun; Zheng, Lirong; Liu, Ran

2018-04-01

The large-signal modulation characteristics of a GaN-based micro-LED have been studied for Gbps visible-light communication. With an increasing signal modulation depth the modulation bandwidth decreases, which matches up with the increase in the sum of the signal rise time and fall time. By simulating the band diagram and the carrier recombination rate of the micro-LED under large-signal modulation, carrier recombination and the carrier sweep-out effect are analyzed and found to be the dominant mechanisms behind the variation of modulation bandwidth. These results give further insight into improving the modulation bandwidth for high-speed visible-light communication.

Energy-Saving Automation and LED Lighting Systems in Industry, Transport, Building and Municipal Sector

Directory of Open Access Journals (Sweden)

V.P. Klimenko

2013-09-01

Full Text Available Protocol of diverse technological data unification providing the ability to scale with a minimal increase in auxiliary information volume that allows its usage, ranging from the simplest microcontrollers to integration of automation equipment in global systems was designed for industrial automation systems. Basic technical solutions implemented in development of LED lighting systems of salon subway cars, including a schematic diagram of the lamp, the main technical characteristics of the lamp power supply, the peculiarities of developed design of LED modules are described.

Can You Understand Me? Speaking Robots and Accented Speech

Science.gov (United States)

Moussalli, Souheila; Cardoso, Walcir

2017-01-01

The results of our previous research on the pedagogical use of Speaking Robots (SRs) revealed positive effects on motivating students to practice their oral skills in a stress-free environment. However, our findings indicated that the SR was sometimes unable to understand students' foreign accented speech. In this paper, we report the results of a…

Color homogeneity in LED spotlights

NARCIS (Netherlands)

Prins, C.R.; Tukker, T.W.; IJzerman, W.L.; Thije Boonkkamp, ten J.H.M.

2014-01-01

LED is a rising technology in the field of lighting. Halogen spotlights are nowadays replaced by LED spotlights because of their energy efficiency and long lifetime. However, color variation in the light output is a common problem. Poorly designed LED spotlights tend to have yellowish or bluish

Very High Frequency Resonant DC/DC Converters for LED Lighting

DEFF Research Database (Denmark)

Madsen, Mickey Pierre; Knott, Arnold; Andersen, Michael A. E.

2013-01-01

This paper presents a very high frequency DC/DC converter for LED lighting. Several resonant topologies are compared and their usability discussed. At the end the resonant SEPIC converter is chosen based on the achievable power density and total bill of material. Simulations of a 51 MHz converter...... with 40 V input and 15 V output are made. The simulation shows possibility of achieving efficiency up to 87 % even with a HEXFET Power MOSFET. Three prototypes of the simulated converter are implemented showing good correlation with simulations. The prototypes have efficiencies up to 84 % and power...

Effect of buck driver ripple on BER performance in visible light communication using LED

NARCIS (Netherlands)

Deng, X.; Linnartz, J.P.M.G.; Arulandu, K.; Zhou, G.; Wu, Y.

2015-01-01

This paper analyses the communication performance for visible light communication (VLC) with Manchester encoded amplitude modulation. In particular, it considers the ripple generated by the LED driver as an important noise contribution for VLC. The ripple depends on the oscillation frequency of the

Implantable wireless powered light emitting diode (LED) for near-infrared photoimmunotherapy: device development and experimental assessment in vitro and in vivo.

Science.gov (United States)

Nakajima, Kohei; Kimura, Toshihiro; Takakura, Hideo; Yoshikawa, Yasuo; Kameda, Atsushi; Shindo, Takayuki; Sato, Kazuhide; Kobayashi, Hisataka; Ogawa, Mikako

2018-04-13

The aim of this study was to develop and assess a novel implantable, wireless-powered, light-emitting diode (LED) for near-infrared photoimmunotherapy (NIR-PIT). NIR-PIT is a recently developed cancer therapy that uses NIR light and antibody-photosensitizer conjugates and is able to induce cancer-specific cell death. Due to limited light penetration depth it is currently unable to treat tumors in deep tissues. Use of implanted LED might potentially overcome this limitation. The wireless LED system was able to emit NIR light up to a distance of 20 cm from the transmitter coil by using low magnetic fields as compliant with limits for use in humans. Results indicated that the LED system was able to kill tumor cells in vitro and to suppress tumor growth in implanted tumor-bearing mice. Results indicated that the proposed implantable wireless LED system was able to suppress tumor growth in vivo . These results are encouraging as wireless LED systems such as the one here developed might be a possible solution to treat tumors in deep regions in humans. Further research in this area would be important. An implantable LED system was developed. It consisted of a LED capsule including two LED sources and a receiver coil coupled with an external coil and power source. Wireless power transmission was guaranteed by using electromagnetic induction. The system was tested in vitro by using EGFR-expressing cells and HER2-expressing cells. The system was also tested in vivo in tumor-bearing mice.

DESIGNING CLIENT OF ANDROID-BASED LED INTELLIGENT LIGHTING SYSTEM AND ITS IMPLEMENTATION%基于 Android 的 LED 智能照明系统客户端的设计与实现

Institute of Scientific and Technical Information of China (English)

胡艳蕊; 宋开新; 秦会斌; 张明准

2016-01-01

To get rid of the way of controlling home lighting with traditional mechanical switches and to make full use of the advantages of smart phones and other mobile equipment resources,we proposed the Android-based LED intelligent lighting systems,and designed and developed the Android-based client of LED intelligent lighting system.We used WiFi to control home lighting equipment,it can not only control the on and off,timing,dimming and colouring of individual light and lights group,but can also select and edit different lighting effects in scene patterns according to the needs of different environments,as well as can dynamically add new lights through code scanning. Moreover,in intelligent light control module we called the China Weather Network API interface and the phone built-in light sensor to automatically control the colour and brightness of the light,the function advertising has also been added to the client.We tested the client system and the lighting module in a wireless network environment,the feasibility and practicality of the LED intelligent lighting system client has been proven.%为了摆脱用传统机械式开关控制家居照明的方式，充分利用智能手机等移动设备资源，提出基于 Android 的 LED 智能照明系统，设计开发基于 Android 的 LED 智能照明系统客户端。利用 WiFi 控制家居照明设备，不仅可以控制单个灯和各组灯的开关、定时、调光和调色，而且可以根据对不同环境的需求在情景模式中选择和编辑不同的灯光效果，还可以通过扫码动态添加新灯等。并且在智能光控模块中调用了中国天气网 API 接口和手机自带的光线传感器来自动调节灯光的颜色和亮度，该客户端还增加了广告功能。把该客户端系统和灯具模块放在无线网络环境中进行测试，验证了该 LED 智能照明系统客户端的可行性和实用性。

Fabrication of moth-eye structure on p-GaN layer of GaN-based LEDs for improvement of light extraction

International Nuclear Information System (INIS)

Hong, Eun-Ju; Byeon, Kyeong-Jae; Park, Hyoungwon; Hwang, Jaeyeon; Lee, Heon; Choi, Kyungwoo; Jung, Gun Young

2009-01-01

Moth-eye structures were produced on a p-GaN top cladding layer by UV imprint and inductively coupled plasma (ICP) etch processes in order to improve the light extraction efficiency of GaN-based green light-emitting diodes (LEDs). The height and shape of moth-eye structures were adjusted by controlling the thickness of Cr mask layer and ICP etching time. The transmittance of LED device stacks with moth-eye structure was increased up to 1.5-2.5 times, compared to identical LED sample without moth-eye structure and the intensity of photoluminescence from the InGaN multi-quantum well layer of LED sample with moth-eye structure was 5-7 times higher than that of the LED sample without the moth-eye structure.

The Accent-protocol: a framework for benchmarking and model evaluation

NARCIS (Netherlands)

Builtjes, P.J.H.; Grewe, V.; Moussiopoulos, N.; Borrego, C.; Isaksen, I.S.A.; Volz-Thomas, A.

2011-01-01

We summarise results from a workshop on “Model Benchmarking and Quality Assurance” of the EU-Network of Excellence ACCENT, including results from other activities (e.g. COST Action 732) and publications. A formalised evaluation protocol is presented, i.e. a generic formalism describing the procedure

Generation of solar spectrum by using LEDs

Science.gov (United States)

Lu, Pengzhi; Yang, Hua; Pei, Yanrong; Li, Jing; Xue, Bin; Wang, Junxi; Li, Jinmin

2016-09-01

Light emitting diode (LED) has been recognized as an applicable light source for indoor and outdoor lighting, city beautifying, landscape facilities, and municipal engineering etc. Conventional LED has superior characteristics such as long life time, low power consumption, high contrast, and wide viewing angle. Recently, LED with high color-rendering index and special spectral characteristics has received more and more attention. This paper is intended to report a solar spectrum simulated by multichip LED light source. The typical solar spectrum of 5500k released by CIE was simulated as a reference. Four types of LEDs with different spectral power distributions would be used in the LED light source, which included a 430nm LED, a 480nm LED, a 500nm LED and a white LED. In order to obtain better simulation results, the white LED was achieved by a 450nm LED chip with the mixture of phosphor. The phosphor combination was prepared by mixing green phosphor, yellow phosphor and red phosphor in a certain proportion. The multichip LED light source could provide a high fidelity spectral match with the typical solar spectrum of 5500k by adjusting injection current to each device. The luminous flux, CIE chromaticity coordinate x, y, CCT, and Ra were 104.7 lm, 0.3337, 0.3681, 5460K, and 88.6, respectively. Because of high color-rendering index and highly match to the solar spectrum, the multichip LED light source is a competitive candidate for applications where special spectral is required, such as colorimetric measurements, visual inspection, gemstone identification and agriculture.

Indian accent text-to-speech system for web browsing

Indian Academy of Sciences (India)

This paper describes a 'web reader' which 'reads out' the textual contents of a selected web page in Hindi or in English with Indian accent. The content of the page is downloaded and parsed into suitable textual form. It is then passed on to an indigenously developed text-to-speech system for Hindi/Indian English, ...

Research on the Effect of Electrical Signals on Growth of Sansevieria under Light-Emitting Diode (LED Lighting Environment.

Directory of Open Access Journals (Sweden)

Liguo Tian

Full Text Available The plant electrical signal has some features, e.g. weak, low-frequency and time-varying. To detect changes in plant electrical signals, LED light source was used to create a controllable light environment in this study. The electrical signal data were collected from Sansevieria leaves under the different illumination conditions, and the data was analyzed in time domain, frequency domain and time-frequency domain, respectively. These analyses are helpful to explore the relationship between changes in the light environment and electrical signals in Sansevieria leaves. The changes in the plant electrical signal reflected the changes in the intensity of photosynthesis. In this study, we proposed a new method to express plant photosynthetic intensity as a function of the electrical signal. That is, the plant electrical signal can be used to describe the state of plant growth.

Research on the Effect of Electrical Signals on Growth of Sansevieria under Light-Emitting Diode (LED) Lighting Environment

Science.gov (United States)

Tian, Liguo; Meng, Qinghao; Wang, Liping; Dong, Jianghui; Wu, Hai

2015-01-01

The plant electrical signal has some features, e.g. weak, low-frequency and time-varying. To detect changes in plant electrical signals, LED light source was used to create a controllable light environment in this study. The electrical signal data were collected from Sansevieria leaves under the different illumination conditions, and the data was analyzed in time domain, frequency domain and time–frequency domain, respectively. These analyses are helpful to explore the relationship between changes in the light environment and electrical signals in Sansevieria leaves. The changes in the plant electrical signal reflected the changes in the intensity of photosynthesis. In this study, we proposed a new method to express plant photosynthetic intensity as a function of the electrical signal. That is, the plant electrical signal can be used to describe the state of plant growth. PMID:26121469

GATEWAY Report Brief: Evaluating Tunable LED Lighting in the Swedish Medical Behavioral Health Unit

Energy Technology Data Exchange (ETDEWEB)

None, None

2017-08-23

Summary of a GATEWAY report evaluation of a tunable LED lighting system installed in the new Swedish Medical Behavioral Health Unit in Seattle that incorporates color-tunable luminaires in common areas, and uses advanced controls for dimming and color tuning, with the goal of providing a better environment for staff and patients. The report reviews the design of the tunable lighting system, summarizes two sets of measurements, and discusses the circadian, energy, and commissioning implications as well as lessons learned from the project.

Effects of melatonin and green-wavelength LED light on the physiological stress and immunity of goldfish, Carassius auratus, exposed to high water temperature.

Science.gov (United States)

Jung, Seo Jin; Kim, Na Na; Choi, Young Jae; Choi, Ji Yong; Choi, Young-Ung; Heo, Youn Seong; Choi, Cheol Young

2016-10-01

This study investigated the effects of increasing water temperature (22-30 °C) on the physiological stress response and immunity of goldfish, Carassius auratus, and the ability of green light-emitting diode (LED) irradiation or melatonin injections to mitigate this temperature-induced stress. To evaluate the effects of either green-wavelength LED light or melatonin on stress in goldfish, we measured plasma triiodothyronine (T3), thyroxine (T4), and thyroid hormone receptor (TR) mRNA expression; plasma cortisol and glucose; and immunoglobulin M (IgM) and lysozyme mRNA expression. The thyroid hormone activities, TR mRNA expression, and plasma cortisol and glucose were higher in goldfish exposed to high-temperature water, but were lower after exposure to melatonin or green-wavelength LED light. Lysozyme mRNA expression and plasma IgM activity and protein expression were lower after exposure to high water temperatures and higher after melatonin or green-wavelength LED light treatments. Therefore, high water temperature induced stress and decreased immunity; however, green-wavelength LED light and melatonin treatments mitigated the effects of stress and enhanced immunity. The benefits of melatonin decreased with time, whereas those of green-wavelength LED treatment did not.

Catalyst-free activation of peroxides under visible LED light irradiation through photoexcitation pathway

Energy Technology Data Exchange (ETDEWEB)

Gao, Yaowen [Department of Environmental Engineering, Wuhan University, Wuhan, 430079 (China); Shenzhen Research Institute of Wuhan University, Shenzhen, 518057 (China); Li, Yixi; Yao, Linyu; Li, Simiao; Liu, Jin [Department of Environmental Engineering, Wuhan University, Wuhan, 430079 (China); Zhang, Hui, E-mail: eeng@whu.edu.cn [Department of Environmental Engineering, Wuhan University, Wuhan, 430079 (China); Shenzhen Research Institute of Wuhan University, Shenzhen, 518057 (China)

2017-05-05

Highlights: • Persulfate could decolorize Rhodamine B (RhB) directly via non-radical reactions. • LED lamps emitting white light were utilized as the visible light source. • Dyes could activate peroxides through photoexcitation pathway. • Decolorization of dyes and production of radicals were achieved simultaneously. • The catalyst-free peroxide/dye/Vis process was effective in a broad pH range. - Abstract: Catalysts are known to activate peroxides to generate active radicals (i.e., hydroxyl radical (·OH) and sulfate radical (SO{sub 4}·{sup −})) under certain conditions, but the activation of peroxides in the absence of catalysts under visible light irradiation has been rarely reported. This work demonstrates a catalyst-free activation of peroxides for the generation of ·OH and/or SO{sub 4}·{sup −} through photoexcited electron transfer from organic dyes to peroxides under visible LED light irradiation, where Rhodamine B (RhB) and Eosin Y (EY) were selected as model dyes. The formation of ·OH and/or SO{sub 4}·{sup −} in the reactions and the electron transfer from the excited dyes to peroxides were validated via electron paramagnetic resonance (EPR), photoluminescence (PL) spectra and cyclic voltammetry (CV). The performance of the peroxide/dye/Vis process was demonstrated to be altered depending on the target substrate. Meanwhile, the peroxide/dye/Vis process was effective for simultaneous decolorization of dyes and production of active radicals under neutral even or basic conditions. The findings of this study clarified a novel photoexcitation pathway for catalyst-free activation of peroxides under visible light irradiation, which could avoid the secondary metal ion (dissolved or leached) pollution from the metal-based catalysts and expand the application range of the peroxide-based catalytic process.

White LED with High Package Extraction Efficiency

International Nuclear Information System (INIS)

Yi Zheng; Stough, Matthew

2008-01-01

The goal of this project is to develop a high efficiency phosphor converting (white) Light Emitting Diode (pcLED) 1-Watt package through an increase in package extraction efficiency. A transparent/translucent monolithic phosphor is proposed to replace the powdered phosphor to reduce the scattering caused by phosphor particles. Additionally, a multi-layer thin film selectively reflecting filter is proposed between blue LED die and phosphor layer to recover inward yellow emission. At the end of the project we expect to recycle approximately 50% of the unrecovered backward light in current package construction, and develop a pcLED device with 80 lm/W e using our technology improvements and commercially available chip/package source. The success of the project will benefit luminous efficacy of white LEDs by increasing package extraction efficiency. In most phosphor-converting white LEDs, the white color is obtained by combining a blue LED die (or chip) with a powdered phosphor layer. The phosphor partially absorbs the blue light from the LED die and converts it into a broad green-yellow emission. The mixture of the transmitted blue light and green-yellow light emerging gives white light. There are two major drawbacks for current pcLEDs in terms of package extraction efficiency. The first is light scattering caused by phosphor particles. When the blue photons from the chip strike the phosphor particles, some blue light will be scattered by phosphor particles. Converted yellow emission photons are also scattered. A portion of scattered light is in the backward direction toward the die. The amount of this backward light varies and depends in part on the particle size of phosphors. The other drawback is that yellow emission from phosphor powders is isotropic. Although some backward light can be recovered by the reflector in current LED packages, there is still a portion of backward light that will be absorbed inside the package and further converted to heat. Heat generated

Spectral design flexibility of LED brings better life

Science.gov (United States)

Ou, Haiyan; Corell, Dennis; Ou, Yiyu; Poulsen, Peter B.; Dam-Hansen, Carsten; Petersen, Paul-Michael

2012-03-01

Light-emitting diodes (LEDs) are penetrating into the huge market of general lighting because they are energy saving and environmentally friendly. The big advantage of LED light sources, compared to traditional incandescent lamps and fluorescent light tubes, is the flexible spectral design to make white light using different color mixing schemes. The spectral design flexibility of white LED light sources will promote them for novel applications to improve the life quality of human beings. As an initial exploration to make use of the spectral design flexibility, we present an example: 'no blue' white LED light source for sufferers of disease Porphyria. An LED light source prototype, made of high brightness commercial LEDs applying an optical filter, was tested by a patient suffering from Porphyria. Preliminary results have shown that the sufferer could withstand the light source for much longer time than the standard light source. At last future perspectives on spectral design flexibility of LED light sources improving human being's life will be discussed, with focus on the light and health. The good health is ensured by the spectrum optimized so that vital hormones (melatonin and serotonin) are produced during times when they support human daily rhythm.

Evaluation of Uniformity and Glare Improvement with Low Energy Efficiency Losses in Street Lighting LED Luminaires Using Laser-Sintered Polyamide-Based Diffuse Covers

Directory of Open Access Journals (Sweden)

Alfonso Gago-Calderón

2018-04-01

Full Text Available Energy saving in street lighting is garnering more interest and has become a priority in municipal management. Therefore, LED luminaires are gradually becoming prevalent in our cities. Beyond their energy/economic saving potential, quality in public lighting installations concerns aspects such as uniformity and glare which must be maintained if not improved in any installation renewal project using this technology. The high light intensity generated in a discrete point in LED packages and its directional nature result in significant deficiencies in these last two parameters. To soften these effects, translucent covers are being used as one of the most common solutions with the drawback of significant light intensity losses. The objective of this paper is to evaluate the behavior of LED luminaire’s polyamide-based optical covers manufactured with a laser-sintered process. These are designed to improve glare and uniformity output, to minimize light output reductions, and to be industrially manufactured with no increment of cost for their lighting equipment compared to conventional transparent polycarbonate solutions. A laboratory and field lighting test study has been applied to different covers with the same LED lamp and luminaire to compare the performance of three different solutions built with different polymeric materials and with different light transmission surface textures. The photometric results have been observed and discussed to demonstrate the ability to significantly improve the lighting performance of LED luminaires—illuminance and uniformity levels and discomfort and disability glare indexes— using an improved optic cover.

White LEDs as broad spectrum light sources for spectrophotometry: demonstration in the visible spectrum range in a diode-array spectrophotometric detector.

Science.gov (United States)

Piasecki, Tomasz; Breadmore, Michael C; Macka, Mirek

2010-11-01

Although traditional lamps, such as deuterium lamps, are suitable for bench-top instrumentation, their compatibility with the requirements of modern miniaturized instrumentation is limited. This study investigates the option of utilizing solid-state light source technology, namely white LEDs, as a broad band spectrum source for spectrophotometry. Several white light LEDs of both RGB and white phosphorus have been characterized in terms of their emission spectra and energy output and a white phosphorus Luxeon LED was then chosen for demonstration as a light source for visible-spectrum spectrophotometry conducted in CE. The Luxeon LED was fixed onto the base of a dismounted deuterium (D(2) ) lamp so that the light-emitting spot was geometrically positioned exactly where the light-emitting spot of the original D(2) lamp is placed. In this manner, the detector of a commercial CE instrument equipped with a DAD was not modified in any way. As the detector hardware and electronics remained the same, the change of the deuterium lamp for the Luxeon white LED allowed a direct comparison of their performances. Several anionic dyes as model analytes with absorption maxima between 450 and 600 nm were separated by CE in an electrolyte of 0.01 mol/L sodium tetraborate. The absorbance baseline noise as the key parameter was 5 × lower for the white LED lamp, showing clearly superior performance to the deuterium lamp in the available, i.e. visible part of the spectrum. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Accent, Identity, and a Fear of Loss? ESL Students' Perspectives

Science.gov (United States)

McCrocklin, Shannon; Link, Stephanie

2016-01-01

Because many theorists propose a connection between accent and identity, some theorists have justifiably been concerned about the ethical ramifications of L2 pronunciation teaching. However, English-as-a-second-language (ESL) students often state a desire to sound like native speakers. With little research into ESL students' perceptions of links…

Active tracking system for visible light communication using a GaN-based micro-LED and NRZ-OOK.

Science.gov (United States)

Lu, Zhijian; Tian, Pengfei; Chen, Hong; Baranowski, Izak; Fu, Houqiang; Huang, Xuanqi; Montes, Jossue; Fan, Youyou; Wang, Hongyi; Liu, Xiaoyan; Liu, Ran; Zhao, Yuji

2017-07-24

Visible light communication (VLC) holds the promise of a high-speed wireless network for indoor applications and competes with 5G radio frequency (RF) system. Although the breakthrough of gallium nitride (GaN) based micro-light-emitting-diodes (micro-LEDs) increases the -3dB modulation bandwidth exceptionally from tens of MHz to hundreds of MHz, the light collected onto a fast photo receiver drops dramatically, which determines the signal to noise ratio (SNR) of VLC. To fully implement the practical high data-rate VLC link enabled by a GaN-based micro-LED, it requires focusing optics and a tracking system. In this paper, we demonstrate an active on-chip tracking system for VLC using a GaN-based micro-LED and none-return-to-zero on-off keying (NRZ-OOK). Using this novel technique, the field of view (FOV) was enlarged to 120° and data rates up to 600 Mbps at a bit error rate (BER) of 2.1×10 -4 were achieved without manual focusing. This paper demonstrates the establishment of a VLC physical link that shows enhanced communication quality by orders of magnitude, making it optimized for practical communication applications.

LED Virtual Simulation based on Web3D

OpenAIRE

Lilan Liu; Liu Han; Zhiqi Lin; Manping Li; Tao Yu

2014-01-01

Regarding to the high price and low market popularity of current LED indoor lighting products, a LED indoor lighting platform is proposed based on Web3D technology. The internet virtual reality technology is integrated and applied into the LED collaborative e-commerce website with Virtools. According to the characteristics of the LED indoor lighting products, this paper introduced the method to build encapsulated model and three characteristics of LED lighting: geometrical, optical and behavi...

Light-controlled microwave whispering-gallery-mode quasi-optical resonators at 50W LED array illumination

Directory of Open Access Journals (Sweden)

V. B. Yurchenko

2015-08-01

Full Text Available We present experimental observations of light-controlled resonance effects in microwave whispering-gallery-mode quasi-optical dielectric-semiconductor disk resonators in the frequency band of 5 GHz to 20 GHz arising due to illumination from a light emitting diode (LED of 50W power range. We obtain huge enhancement of photo-sensitivity (growing with the resonator Q-factor that makes light-microwave interaction observable with an ordinary light (no laser at conventional brightness (like an office lighting in quasi-optical microwave structures at rather long (centimeter-scale wavelength. We also demonstrate non-conventional photo-response of Fano resonances when the light suppresses one group of resonances and enhances another group. The effects could be used for the optical control and quasi-optical switching of microwave propagation through either one or another frequency channel.

Optimized lighting method of applying shaped-function signal for increasing the dynamic range of LED-multispectral imaging system

Science.gov (United States)

Yang, Xue; Hu, Yajia; Li, Gang; Lin, Ling

2018-02-01

This paper proposes an optimized lighting method of applying a shaped-function signal for increasing the dynamic range of light emitting diode (LED)-multispectral imaging system. The optimized lighting method is based on the linear response zone of the analog-to-digital conversion (ADC) and the spectral response of the camera. The auxiliary light at a higher sensitivity-camera area is introduced to increase the A/D quantization levels that are within the linear response zone of ADC and improve the signal-to-noise ratio. The active light is modulated by the shaped-function signal to improve the gray-scale resolution of the image. And the auxiliary light is modulated by the constant intensity signal, which is easy to acquire the images under the active light irradiation. The least square method is employed to precisely extract the desired images. One wavelength in multispectral imaging based on LED illumination was taken as an example. It has been proven by experiments that the gray-scale resolution and the accuracy of information of the images acquired by the proposed method were both significantly improved. The optimum method opens up avenues for the hyperspectral imaging of biological tissue.

Protocol for Determining Ultraviolet Light Emitting Diode (UV-LED) Fluence for Microbial Inactivation Studies.

Science.gov (United States)

Kheyrandish, Ataollah; Mohseni, Madjid; Taghipour, Fariborz

2018-06-15

Determining fluence is essential to derive the inactivation kinetics of microorganisms and to design ultraviolet (UV) reactors for water disinfection. UV light emitting diodes (UV-LEDs) are emerging UV sources with various advantages compared to conventional UV lamps. Unlike conventional mercury lamps, no standard method is available to determine the average fluence of the UV-LEDs, and conventional methods used to determine the fluence for UV mercury lamps are not applicable to UV-LEDs due to the relatively low power output, polychromatic wavelength, and specific radiation profile of UV-LEDs. In this study, a method was developed to determine the average fluence inside a water suspension in a UV-LED experimental setup. In this method, the average fluence was estimated by measuring the irradiance at a few points for a collimated and uniform radiation on a Petri dish surface. New correction parameters were defined and proposed, and several of the existing parameters for determining the fluence of the UV mercury lamp apparatus were revised to measure and quantify the collimation and uniformity of the radiation. To study the effect of polychromatic output and radiation profile of the UV-LEDs, two UV-LEDs with peak wavelengths of 262 and 275 nm and different radiation profiles were selected as the representatives of typical UV-LEDs applied to microbial inactivation. The proper setup configuration for microorganism inactivation studies was also determined based on the defined correction factors.

Effects of regiolects on the perception of developmental foreign accent syndrome

NARCIS (Netherlands)

Tops, Wim; Neimeijer, Silke; Mariën, Peter

Foreign accent syndrome (FAS) is a relatively rare speech motor disorder in which the pro- nunciation of an affected speaker is perceived as distinctly foreign by listeners of the same language community. Because of various close semiological resemblances with apraxia of speech, FAS has been

High-aggregate-capacity visible light communication links using stacked multimode polymer waveguides and micro-pixelated LED arrays

Science.gov (United States)

Bamiedakis, N.; McKendry, J. J. D.; Xie, E.; Gu, E.; Dawson, M. D.; Penty, R. V.; White, I. H.

2018-02-01

In recent years, light emitting diodes (LEDs) have gained renewed interest for use in visible light communication links (VLC) owing to their potential use as both high-quality power-efficient illumination sources as well as low-cost optical transmitters in free-space and guided-wave links. Applications that can benefit from their use include optical wireless systems (LiFi and Internet of Things), in-home and automotive networks, optical USBs and short-reach low-cost optical interconnects. However, VLC links suffer from the limited LED bandwidth (typically 100 MHz). As a result, a combination of novel LED devices, advanced modulation formats and multiplexing methods are employed to overcome this limitation and achieve high-speed (>1 Gb/s) data transmission over such links. In this work, we present recent advances in the formation of high-aggregate-capacity low cost guided wave VLC links using stacked polymer multimode waveguides and matching micro-pixelated LED (μLED) arrays. μLEDs have been shown to exhibit larger bandwidths (>200 MHz) than conventional broad-area LEDs and can be formed in large array configurations, while multimode polymer waveguides enable the formation of low-cost optical links onto standard PCBs. Here, three- and four-layered stacks of multimode waveguides, as well as matching GaN μLED arrays, are fabricated in order to generate high-density yet low-cost optical interconnects. Different waveguide topologies are implemented and are investigated in terms of loss and crosstalk performance. The initial results presented herein demonstrate good intrinsic crosstalk performance and indicate the potential to achieve >= 0.5 Tb/s/mm2 aggregate interconnection capacity using this low-cost technology.

LEDs light spectrum effect on the success of fragmentation and growth of the leather coral Sarcophyton spp.

Directory of Open Access Journals (Sweden)

João Chambel

2014-06-01

Full Text Available The increasing demand for soft corals is reflected on the high attention of the scientific community during the last decades, with several studies focus on production techniques and optimization of coral husbandry (Schlacher et al., 2007;Sella and Benayahu, 2010. However, coral culture success is influenced by the interaction of different factors, such as water movement, temperature, nutrients, heterotrophic feeding and light conditions (Rocha et al., 2013a. Light plays a key role in the growth, reproduction and physiology of scleractinian corals that host phototrophic symbionts and it has been found that the photoresponse of corals is species-specific. Several studies have already focused on the effects of irradiance on coral and its algal symbionts (Osinga et al., 2011. Although, only a few works have investigated the role of the spectral quality of light on coral photobiology, physiology and growth (Rocha et al., 2013b. In the present study, we hypothesize that light spectrum can influence the growth performance of scleractinian corals when exposed at identical intensities of photosynthetically active radiation (PAR. To test our hypothesis we evaluated the effect of contrasting light spectra with an identical PAR of 70 ± 10 μmol quantam−2.s−1emitted by T8 fluorescent lamps (used as a control treatment and three different colours of Light Emitting Diode (LED, white, blue and red. It was evaluated survival and growth rates of Sarcophyton spp., an important scleractinian coral in the marine aquarium trade and for the bioprospecting of marine natural compounds. Replicated coral fragments were obtained from two mother colonies and were exposed to the four types of light spectrum for a period of 30 days. At the end of the experiment period, the results showed 100% of survival in coral fragments, and specific growth rate (SGR of 0,055 ± 0,09 %/day in control group and 0,091 ± 0,019 %/day, 0,210 ± 0,031 %/day and 0,380 ± 0,245 %/day in

LED Lighting in a Performing Arts Building at the University of Florida

Energy Technology Data Exchange (ETDEWEB)

Miller, Naomi J.; Kaye, Stan; Coleman, Patricia; Wilkerson, Andrea M.; Perrin, Tess E.; Sullivan, Gregory P.

2014-07-01

The U.S. DOE GATEWAY Demonstration Program supports demonstrations of high-performance solid-state lighting (SSL) products in order to develop empirical data and experience with the in-the-field applications of this advanced lighting technology. This report describes the process and results of the 2013 - 2014 GATEWAY demonstration of SSL technology in the Nadine McGuire Theatre and Dance Pavilion at the University of Florida, Gainesville, FL. The LED solutions combined with dimming controls utilized in four interior spaces - the Acting Studio, Dance Studio, Scene Shop, and Dressing Room - received high marks from instructors, students/performers, and reduced energy use in all cases. The report discusses in depth and detail of each project area including specifications, energy savings, and user observations. The report concludes with lessons learned during the demonstration.

Thermal, spectral, and surface properties of LED light-polymerized bulk fill resin composites.

Science.gov (United States)

Pişkin, Mehmet Burçin; Atalı, Pınar Yılmaz; Figen, Aysel Kantürk

2015-02-01

The aim of this study was to evaluate the thermal, spectral, and surface properties of four different bulk fill materials – SureFil SDR (SDR, Dentsplay DETREY), QuixFil (QF, Dentsplay DETREY), X-tra base (XB, Voco) X-tra fil (XF, Voco) – polymerized by light-emitting diode (LED). Resin matrix, filler type, size and amount, and photoinitiator types influence the degree of conversion. LED-cured bulk fill composites achieved sufficient polymerization. Scanning electron microscope (SEM) analysis revealed different patterns of surface roughness, depending on the composite material. Bulk fill materials showed surface characteristics similar to those of nanohybrid composites. Based on the thermal analysis results, glass transition (T(g)) and initial degradation (T(i)) temperatures changed depending on the bulk fill resin composites.

“Gallia and Gaul, French and Welsh” (MWW, 3.1.89: Transposing Shakespeare’s ‘Favourite’ Foreign Accents into French

Directory of Open Access Journals (Sweden)

Lacroix Mylène

2017-12-01

Full Text Available The Merry Wives of Windsor has long been compared to a great babel of languages. The play contains a smattering of Spanish, Italian and Dutch and even a whole scene dedicated to the mistranslation of Latin. A large part of the play’s humour also heavily relies on the foreign accents of two characters: the French Doctor Caius and the Welsh parson Sir Hugh Evans. If Christopher Luscombe’s 2008/2010 production of The Merry Wives at Shakespeare’s Globe theatre in London bears testimony to the success of cross-language and accent-based comedy as a source of laughter on today’s English stage, it seems rather implausible, at first sight, that French translations, adaptations and stagings of these accents and linguistic idiosyncrasies should be greeted with the same degree of hilarity. Indeed, how should the Welsh and French accents, both representing real stumbling blocks for French-speaking translators of the play, be transposed into French? What translation strategies can the latter devise? And to what extent can some of those strategies be said to be politically correct? Focusing on Shakespeare’s ‘favorite’ (predominant accents and the significance and impact of such linguistic comedy, I shall examine the question of their problematic translation through the analysis and comparison of a number of translations and stagings of The Merry Wives of Windsor into French.

Accentedness and intelligibility of Mandarin-accented English for Chinese, Koreans and Americans

DEFF Research Database (Denmark)

Hardman, Jocelyn

2014-01-01

English is used as a lingua franca not only throughout Asia, but also in Inner Circle countries for academic purposes. Due to wide variation in L2 English speech, however, mutual intelligibility is an increasing concern. Since accentedness does not necessarily correlate with intelligibility...... and results have been mixed as to the benefit of interlanguage match, a study focused on the academic context investigated the extent to which Mandarin-accented English was intelligible to L1 Mandarin listeners, as compared to Koreans and Americans, and whether intelligibility varied by talker segmental...... revealed that listener L1 and word familiarity were significant predictors of intelligibility, but that talker segmental production accuracy was not. A clear benefit for interlanguage match was found for the Mandarin L1 listeners with Mandarin-accented English as compared to the Korean listeners, however...

Comparative Study of Lettuce and Radish Grown Under Red and Blue Light-Emitting Diodes (LEDs) and White Fluorescent Lamps

Science.gov (United States)

Mickens, Matthew A.

2012-01-01

Growing vegetable crops in space will be an essential part of sustaining astronauts during long-term missions. To drive photosynthesis, red and blue light-emitting diodes (LEDs) have attracted attention because of their efficiency, longevity, small size, and safety. In efforts to optimize crop production, there have also been recent interests in analyzing the subtle effects of green light on plant growth, and to determine if it serves as a source of growth enhancement or suppression. A comparative study was performed on two short cycle crops of lettuce (Outredgeous) and radish (Cherry Bomb) grown under two light treatments. The first treatment being red and blue LEDs, and the second treatment consisting of white fluorescent lamps which contain a portion of green light. In addition to comparing biomass production, physiological characterizations were conducted on how the light treatments influence morphology, water use, chlorophyll content, and the production of A TP within plant tissues.

The Effect of Vocal Training Methods on Improving Turkish Accent Defects

Science.gov (United States)

Aycan, Kivanc; Evren, Gul Fahriye

2016-01-01

Problem Statement: Despite analyses of how vocal training methods can correct or improve Turkish-language accent defects, for most voice educators, the most important methods continue to be breathe management control and correct vocalization exercises. We therefore sought to demonstrate the relationship of song lyrics to breathe control, accent…

Artificial LED lighting enhances growth characteristics and total phenolic content of Ocimum basilicum, but variably affects transplant success

NARCIS (Netherlands)

Bantis, Filippos; Ouzounis, Theoharis; Radoglou, Kalliopi

2016-01-01

The morphological and phytochemical characteristics of two Ocimum basilicum cultivars (Lettuce Leaf, and Red Rubin-mountain Athos hybrid) under artificial lighting were investigated. Four LED light treatments [AP673L (high red and high red:far-red), G2 (high red and low red:far-red), AP67

Trapping of Rift Valley Fever (RVF vectors using Light Emitting Diode (LED CDC traps in two arboviral disease hot spots in Kenya

Directory of Open Access Journals (Sweden)

Tchouassi David P

2012-05-01

Full Text Available Abstract Background Mosquitoes’ response to artificial lights including color has been exploited in trap designs for improved sampling of mosquito vectors. Earlier studies suggest that mosquitoes are attracted to specific wavelengths of light and thus the need to refine techniques to increase mosquito captures following the development of super-bright light-emitting diodes (LEDs which emit narrow wavelengths of light or very specific colors. Therefore, we investigated if LEDs can be effective substitutes for incandescent lamps used in CDC light traps for mosquito surveillance, and if so, determine the best color for attraction of important Rift Valley Fever (RFV vectors. Methods The efficiency of selected colored LED CDC light traps (red, green, blue, violet, combination of blue-green-red (BGR to sample RVF vectors was evaluated relative to incandescent light (as control in a CDC light trap in two RVF hotspots (Marigat and Ijara districts in Kenya. In field experiments, traps were baited with dry ice and captures evaluated for Aedes tricholabis, Ae. mcintoshi, Ae. ochraceus, Mansonia uniformis, Mn. africana and Culex pipiens, following Latin square design with days as replicates. Daily mosquito counts per treatment were analyzed using a generalized linear model with Negative Binomial error structure and log link using R. The incidence rate ratios (IRR that mosquito species chose other treatments instead of the control, were estimated. Results Seasonal preference of Ae.mcintoshi and Ae. ochraceus at Ijara was evident with a bias towards BGR and blue traps respectively in one trapping period but this pattern waned during another period at same site with significantly low numbers recorded in all colored traps except blue relative to the control. Overall results showed that higher captures of all species were recorded in control traps compared to the other LED traps (IRR  Conclusion Based on our trapping design and color, none of the LEDs

Progress in characterizing the multidimensional color quality properties of white LED light sources

Science.gov (United States)

Teunissen, Kees; Hoelen, Christoph

2016-03-01

With the introduction of solid state light sources, the variety in emission spectra is almost unlimited. However, the set of standardized parameters to characterize a white LED light source, such as correlated color temperature (CCT) and CIE general color rendering index (Ra), is known to be limited and insufficient for describing perceived differences between light sources. Several characterization methods have been proposed over the past decades, but their contribution to perceived color quality has not always been validated. To gain more insight in the relevant characteristics of the emission spectra for specific applications, we have conducted a perception experiment to rate the attractiveness of three sets of objects, including fresh food, packaging materials and skin tones. The objects were illuminated with seven different combinations of Red, Green, Blue, Amber and White LEDs, all with the same CCT and illumination level, but with differences in Ra and color saturation. The results show that, in general, object attractiveness does not correlate well with Ra, but shows a positive correlation with saturation increase for two out of three applications. There is no clear relation between saturation and skin tone attractiveness, partly due to differences in preference between males and females. A relative gamut area index (Ga) represents the average change in saturation and a complementary color vector graphic shows the direction and magnitude of chromatic differences for the eight CIE-1974 test-color samples. Together with the CIE general color rendering index (Ra) they provide useful information for designing and optimizing application specific emission spectra.

LED Lighting System Reliability Modeling and Inference via Random Effects Gamma Process and Copula Function

Directory of Open Access Journals (Sweden)

Huibing Hao

2015-01-01

Full Text Available Light emitting diode (LED lamp has attracted increasing interest in the field of lighting systems due to its low energy and long lifetime. For different functions (i.e., illumination and color, it may have two or more performance characteristics. When the multiple performance characteristics are dependent, it creates a challenging problem to accurately analyze the system reliability. In this paper, we assume that the system has two performance characteristics, and each performance characteristic is governed by a random effects Gamma process where the random effects can capture the unit to unit differences. The dependency of performance characteristics is described by a Frank copula function. Via the copula function, the reliability assessment model is proposed. Considering the model is so complicated and analytically intractable, the Markov chain Monte Carlo (MCMC method is used to estimate the unknown parameters. A numerical example about actual LED lamps data is given to demonstrate the usefulness and validity of the proposed model and method.

A Difference in Cutaneous Pigmentary Response to LED Versus Halogen Incandescent Visible Light: A Case Report from a Single Center, Investigational Clinical Trial Determining a Minimal Pigmentary Visible Light Dose.

Science.gov (United States)

Soleymani, Teo; Soter, Nicholas A; Folan, Lorcan M; Elbuluk, Nada; Okereke, Uchenna R; Cohen, David E

2017-04-01

BACKGROUND: While most of the attention regarding skin pigmentation has focused on the effects on ultraviolet radiation, the cutaneous effects of visible light (400 to 700nm) are rarely reported. In this report, we describe a case of painful erythema and induration that resulted from direct irradiation of UV-naïve skin with visible LED light in a patient with Fitzpatrick type II skin. METHODS AND RESULTS: A 24-year-old healthy woman with Fitzpatrick type II skin presented to our department to participate in a clinical study. As part of the study, the subject underwent visible light irradiation with an LED and halogen incandescent visible light source. After 5 minutes of exposure, the patient complained of appreciable pain at the LED exposed site. Evaluation demonstrated erythema and mild induration. There were no subjective or objective findings at the halogen incandescent irradiated site, which received equivalent fluence (0.55 Watts / cm2). The study was halted as the subject was unable to tolerate the full duration of visible light irradiation. CONCLUSION: This case illustrates the importance of recognizing the effects of visible light on skin. While the vast majority of investigational research has focused on ultraviolet light, the effects of visible light have been largely overlooked and must be taken into consideration, in all Fitzpatrick skin types. J Drugs Dermatol. 2017;16(4):388-392..

Monochromatic light-emitting diode (LED source in layers hens during the second production cycle

Directory of Open Access Journals (Sweden)

Rodrigo Borille

2015-09-01

Full Text Available ABSTRACTLight is an important environmental factor for birds, allowing not only their vision, but also influencing their physiological responses, such as behavioral and reproductive activity. The objective of this experiment was to evaluate the impact of different colors of monochromatic light (LED sources in laying hens production during the second laying cycle. The study was conducted in an experimental laying house during 70 days. A total of 300 laying hens Isa Brown® genetic strain, aged 95 weeks, in the second laying cycle were used in the study. The artificial light sources used were blue, yellow, green, red and white. The light regimen was continuous illumination of 17 h per day (12 h natural and 5 h artificial in a daily light regimen of 17L:5D (light: dark. The Latin Square design was adopted with five treatments (five colors divided into five periods, and five boxes, with six replicates of ten birds in each box. The production and egg quality were evaluated. The different colors of light source did not affect production parameters or egg quality (p > 0.05. The monochromatic light source may be considered as an alternative to artificial lighting in laying hens during the second production cycle.

The Use of Ultra-Violet (UV) Light Emitting Diodes (LEDS) in an Advanced Oxidation Process (AOP) with Brilliant Blue FCF as an Indicator

Science.gov (United States)

2015-03-26

LEDs have the potential to replace mercury lamps in many UV processes, as well as open the door to new applications of UV light based on their unique...al. 2007, Autin, Romelot, et al. 2013). UV LEDs in AOPs While most data on AOP experimentation are based on experiments that use mercury lamps ...metaldehyde in solution. Their experiments found that similar UV light exposure levels from UV LEDs and traditional mercury lamps produced similar

The possible ocular hazards of LED dental illumination applications.

Science.gov (United States)

Stamatacos, Catherine; Harrison, Janet L

2013-01-01

The use of high-intensity illumination via Light-Emitting Diode (LED) headlamps is gaining in popularity with dentists and student dentists. Practitioners are using LED headlamps together with magnifying loupes, overhead LED illumination and fiber-optic dental handpieces for long periods of time. Although most manufacturers of these LED illuminators advertise that their devices emit "white" light, these still consist of two spectral bands--the blue spectral band, with its peak at 445 nm, and the green with its peak at 555 nm. While manufacturers suggest that their devices emit "white" light, spectral components of LED lights from different companies are significantly different. Dental headlamp manufacturers strive to create a white LED, and they advertise that this type of light emitted from their product offers bright white-light illumination. However, the manufacturing of a white LED light is done through selection of a white LED-type based on the peak blue strength in combination with the green peak strength and thus creating a beam-forming optic, which determines the beam quality. Some LED illuminators have a strong blue-light component versus the green-light component. Blue-light is highly energized and is close in the color spectrum to ultraviolet-light. The hazards of retinal damage with the use of high-intensity blue-lights has been well-documented. There is limited research regarding the possible ocular hazards of usage of high-intensity illuminating LED devices. Furthermore, the authors have found little research, standards, or guidelines examining the possible safety issues regarding the unique dental practice setting consisting of the combined use of LED illumination systems. Another unexamined component is the effect of high-intensity light reflective glare and magnification back to the practitioner's eyes due to the use of water during dental procedures. Based on the result of Dr. Janet Harrison's observations of beginning dental students in a

Dim-light photoreceptor of chub mackerel Scomber japonicus and the photoresponse upon illumination with LEDs of different wavelengths.

Science.gov (United States)

Jang, Jun-Chul; Choi, Mi-Jin; Yang, Yong-Soo; Lee, Hyung-Been; Yu, Young-Moon; Kim, Jong-Myoung

2016-06-01

To study the absorption characteristics of rhodopsin, a dim-light photoreceptor, in chub mackerel (Scomber japonicus) and the relationship between light wavelengths on the photoresponse, the rod opsin gene was cloned into an expression vector, pMT4. Recombinant opsin was transiently expressed in COS-1 cells and reconstituted with 11-cis-retinal. Cells containing the regenerated rhodopsin were solubilized and subjected to UV/Vis spectroscopic analysis in the dark and upon illumination. Difference spectra from the lysates indicated an absorption maximum of mackerel rhodopsin around 500 nm. Four types of light-emitting diode (LED) modules with different wavelengths (red, peak 627 nm; cyan, 505 nm; blue, 442 nm; white, 447 + 560 nm) were constructed to examine their effects on the photoresponse in chub mackerel. Behavioral responses of the mackerels, including speed and frequencies acclimated in the dark and upon LED illumination, were analyzed using an underwater acoustic camera. Compared to an average speed of 22.25 ± 1.57 cm/s of mackerel movement in the dark, speed increased to 22.97 ± 0.29, 24.66 ± 1.06, 26.28 ± 2.28, and 25.19 ± 1.91 cm/s upon exposure to red, blue, cyan, and white LEDs, respectively. There were increases of 103.48 ± 1.58, 109.37 ± 5.29, 118.48 ± 10.82, and 109.43 ± 3.92 %, respectively, in the relative speed of the fishes upon illumination with red, blue, cyan, and white LEDs compared with that in the dark (set at 100 %). Similar rate of wavelength-dependent responses was observed in a frequency analysis. These results indicate that an LED emitting a peak wavelength close to an absorption maximum of rhodopsin is more effective at eliciting a response to light.

Non-imaging optics for LED-lighting

NARCIS (Netherlands)

Berg, van den J.B.; Castro, R.M.; Draisma, J.; Evers, J.H.M.; Hendriks, M.; Krehel, O.; Kryven, I.; Mora, K.; Szabó, B.T.; Zwiernik, P.W.; Boon, M.A.A.

2013-01-01

In this report, several methods are investigated to rapidly compute the light intensity function, either in the far field or on a finite-distance screen, of light emanating from a light fixture with a given shape. Different shapes are considered, namely polygonal and (piecewise) smooth. In the first

The Concept of Fashion Design on the Basis of Color Coordination Using White LED Lighting

Science.gov (United States)

Mizutani, Yumiko; Taguchi, Tsunemasa

This thesis focuses on the development of fashion design, especially a dress coordinated with White LED Lighting (=LED). As for the design concept a fusion of the advanced science and local culture was aimed for. For such a reason this development is a very experimental one. Here in particular I handled an Imperial Court dinner dress for the last Japanese First Lady, Mrs. Akie Abe who wore it at the Imperial Court dinner for the Indonesian First Couple held on November 2006 to. This dress made by Prof. T. Taguchi and I open up a new field in the dress design.

ZnO-nanorods: A possible white LED phosphor

Science.gov (United States)

Sarangi, Sachindra Nath; T., Arun; Ray, Dinseh K.; Sahoo, Pratap Kumar; Nozaki, Shinji; Sugiyama, Noriyuki; Uchida, Kazuo

2017-05-01

The white light-emitting diodes (LEDs) have drawn much attention to replace conventional lighting sources because of low energy consumption, high light efficiency and long lifetime. Although the most common approach to produce white light is to combine a blue LED chip and a yellow phosphor, such a white LED cannot be used for a general lighting application, which requires a broad luminescence spectrum in the visible wavelength range. We have successfully chemically synthesized the ZnO nanorods showing intense broad luminescence in the visible wavelength range and made a white LED using the ZnO nanorods as phosphor excited with a blue LED. Their lengths and diameters were 2 - 10 μm and 200 - 800 nm, respectively. The wurtzite structure was confirmed by the x-ray diffraction measurement. The PL spectrum obtained by exciting the ZnO nanorods with the He-Cd laser has two peaks, one associated with the near band-edge recombination and the other with recombination via defects. The peak intensity of the near band-edge luminescence at 388 nm is much weaker than that of the defect-related luminescence. The latter luminescence peak ranges from 450 to 850 nm and broad enough to be used as a phosphor for a white LED. A white LED has been fabricated using a blue LED with 450 nm emission and ZnO nanorod powders. The LED performances show a white light emission and the electroluminescence measurement shows a stiff increase in white light intensity with increasing blue LED current. The Commission International de1'Eclairage (CIE) chromaticity colour coordinates of 450 nm LED pumped white emission shows a coordinate of (0.31, 0.32) for white LED at 350 mA. These results indicate that ZnO nanorods provides an alternate and effective approach to achieve high-performance white LEDs and also other optoelectronic devices.

Color-filter-free spatial visible light communication using RGB-LED and mobile-phone camera.

Science.gov (United States)

Chen, Shih-Hao; Chow, Chi-Wai

2014-12-15

A novel color-filter-free visible-light communication (VLC) system using red-green-blue (RGB) light emitting diode (LED) and mobile-phone camera is proposed and demonstrated for the first time. A feature matching method, which is based on the scale-invariant feature transform (SIFT) algorithm for the received grayscale image is used instead of the chromatic information decoding method. The proposed method is simple and saves the computation complexity. The signal processing is based on the grayscale image computation; hence neither color-filter nor chromatic channel information is required. A proof-of-concept experiment is performed and high performance channel recognition is achieved.

Multi-band transmission color filters for multi-color white LEDs based visible light communication

Science.gov (United States)

Wang, Qixia; Zhu, Zhendong; Gu, Huarong; Chen, Mengzhu; Tan, Qiaofeng

2017-11-01

Light-emitting diodes (LEDs) based visible light communication (VLC) can provide license-free bands, high data rates, and high security levels, which is a promising technique that will be extensively applied in future. Multi-band transmission color filters with enough peak transmittance and suitable bandwidth play a pivotal role for boosting signal-noise-ratio in VLC systems. In this paper, multi-band transmission color filters with bandwidth of dozens nanometers are designed by a simple analytical method. Experiment results of one-dimensional (1D) and two-dimensional (2D) tri-band color filters demonstrate the effectiveness of the multi-band transmission color filters and the corresponding analytical method.

Design of a lighting system with high-power LEDs, large area electronics, and light management structure in the LUMENTILE European project

Science.gov (United States)

Carraro, L.; Simonetta, M.; Benetti, G.; Tramonte, A.; Capelli, G.; Benedetti, M.; Randone, E. M.; Ylisaukko-oja, A.; Keränen, K.; Facchinetti, T.; Giuliani, G.

2017-02-01

LUMENTILE (LUMinous ElectroNic TILE) is a project funded by the European Commission with the goal of developing a luminous tile with novel functionalities, capable of changing its color and interact with the user. Applications include interior/exterior tile for walls and floors covering, high-efficiency luminaries, and advertising under the form of giant video screens. High overall electrical efficiency of the tile is mandatory, as several millions of square meters are foreseen to be installed each year. Demand is for high uniformity of the illumination of the top tile surface, and for high optical extraction efficiency. These features are achieved by smart light management, using a new approach based on light guiding slab and spatially selective light extraction obtained using both diffusion and/or reflection from the top and bottom interfaces of the optical layer. Planar and edge configurations for the RGB LEDs are considered and compared. A square shape with side length from 20cm to 60cm is considered for the tiles. The electronic circuit layout must optimize the electrical efficiency, and be compatible with low-cost roll-to-roll production on flexible substrates. LED heat management is tackled by using dedicated solutions that allow operation in thermally harsh environment. An approach based on OLEDs has also been considered, still needing improvement on emitted power and ruggedness.

Potential environmental impacts of light-emitting diodes (LEDs): metallic resources, toxicity, and hazardous waste classification.

Science.gov (United States)

Lim, Seong-Rin; Kang, Daniel; Ogunseitan, Oladele A; Schoenung, Julie M

2011-01-01

Light-emitting diodes (LEDs) are advertised as environmentally friendly because they are energy efficient and mercury-free. This study aimed to determine if LEDs engender other forms of environmental and human health impacts, and to characterize variation across different LEDs based on color and intensity. The objectives are as follows: (i) to use standardized leachability tests to examine whether LEDs are to be categorized as hazardous waste under existing United States federal and California state regulations; and (ii) to use material life cycle impact and hazard assessment methods to evaluate resource depletion and toxicity potentials of LEDs based on their metallic constituents. According to federal standards, LEDs are not hazardous except for low-intensity red LEDs, which leached Pb at levels exceeding regulatory limits (186 mg/L; regulatory limit: 5). However, according to California regulations, excessive levels of copper (up to 3892 mg/kg; limit: 2500), Pb (up to 8103 mg/kg; limit: 1000), nickel (up to 4797 mg/kg; limit: 2000), or silver (up to 721 mg/kg; limit: 500) render all except low-intensity yellow LEDs hazardous. The environmental burden associated with resource depletion potentials derives primarily from gold and silver, whereas the burden from toxicity potentials is associated primarily with arsenic, copper, nickel, lead, iron, and silver. Establishing benchmark levels of these substances can help manufacturers implement design for environment through informed materials substitution, can motivate recyclers and waste management teams to recognize resource value and occupational hazards, and can inform policymakers who establish waste management policies for LEDs.

Evaluation of wear rate of dental composites polymerized by halogen or LED light curing units

Directory of Open Access Journals (Sweden)

Alaghehmand H.

2006-08-01

Full Text Available Background and Aim: Sufficient polymerization is a critical factor to obtain optimum physical properties and clinical efficacy of resin restorations. The aim of this study was to evaluate wear rates of composite resins polymerized by two different systems Light Emitting Diodes (LED to and Halogen lamps. Materials and Methods: In this laboratory study, 20 specimens of A3 Tetric Ceram composite were placed in brass molds of 2*10*10 mm dimensions and cured for 40 seconds with 1 mm distance from surface. 10 specimens were cured with LED and the other 10 were cured with Halogen unit. A device with the ability to apply force was developed in order to test the wear of composites. After storage in distilled water for 10 days, the specimens were placed in the wear testing machine. A chrome cobalt stylus with 1.12 mm diameter was applied against the specimens surfaces with a load of 2 kg. The weight of each samples before and after 5000, 10000, 20000, 40000, 80000 and 120000 cycles was measured using an electronic balance with precision of 10-4 grams. Data were analyzed using t test and paired t test. P0.05. Conclusion: Based on the results of this study, LED and halogen light curing units resulted in a similar wear rate in composite resin restorations.

Design Secondary Optical System Applied in White-LED General Illumination

International Nuclear Information System (INIS)

Chen Chen; Zhang Xianhui

2011-01-01

As a new generation of light source, LED has many advantages that other light sources do not have. However, due to the nonuniform lighting of LED, secondary LED optical system design is particularly important. Freeform surface tailoring method, an important method of lighting design, establishes a light intensity change model after smooth surface refraction (reflection) of the light and simplifies the solution process for more complex issues of solution using the free surface tailoring method. Based on this method, secondary LED optical system is designed, and the light intensity distribution is simulated after LED light passes through the secondary optical system. The results show that the method has not only simplified the calculation process of the free surface tailoring method, but also the designed LED secondary optical system has achieved the purpose of uniform lighting to a certain degree.

More than a boundary shift: Perceptual adaptation to foreign-accented speech reshapes the internal structure of phonetic categories.

Science.gov (United States)

Xie, Xin; Theodore, Rachel M; Myers, Emily B

2017-01-01

The literature on perceptual learning for speech shows that listeners use lexical information to disambiguate phonetically ambiguous speech sounds and that they maintain this new mapping for later recognition of ambiguous sounds for a given talker. Evidence for this kind of perceptual reorganization has focused on phonetic category boundary shifts. Here, we asked whether listeners adjust both category boundaries and internal category structure in rapid adaptation to foreign accents. We investigated the perceptual learning of Mandarin-accented productions of word-final voiced stops in English. After exposure to a Mandarin speaker's productions, native-English listeners' adaptation to the talker was tested in 3 ways: a cross-modal priming task to assess spoken word recognition (Experiment 1), a category identification task to assess shifts in the phonetic boundary (Experiment 2), and a goodness rating task to assess internal category structure (Experiment 3). Following exposure, both category boundary and internal category structure were adjusted; moreover, these prelexical changes facilitated subsequent word recognition. Together, the results demonstrate that listeners' sensitivity to acoustic-phonetic detail in the accented input promoted a dynamic, comprehensive reorganization of their perceptual response as a consequence of exposure to the accented input. We suggest that an examination of internal category structure is important for a complete account of the mechanisms of perceptual learning. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Design and Implementation of a Smart LED Lighting System Using a Self Adaptive Weighted Data Fusion Algorithm

Directory of Open Access Journals (Sweden)

Wen-Tsai Sung

2013-12-01

Full Text Available This work aims to develop a smart LED lighting system, which is remotely controlled by Android apps via handheld devices, e.g., smartphones, tablets, and so forth. The status of energy use is reflected by readings displayed on a handheld device, and it is treated as a criterion in the lighting mode design of a system. A multimeter, a wireless light dimmer, an IR learning remote module, etc. are connected to a server by means of RS 232/485 and a human computer interface on a touch screen. The wireless data communication is designed to operate in compliance with the ZigBee standard, and signal processing on sensed data is made through a self adaptive weighted data fusion algorithm. A low variation in data fusion together with a high stability is experimentally demonstrated in this work. The wireless light dimmer as well as the IR learning remote module can be instructed directly by command given on the human computer interface, and the reading on a multimeter can be displayed thereon via the server. This proposed smart LED lighting system can be remotely controlled and self learning mode can be enabled by a single handheld device via WiFi transmission. Hence, this proposal is validated as an approach to power monitoring for home appliances, and is demonstrated as a digital home network in consideration of energy efficiency.

Design and Implementation of a Smart LED Lighting System Using a Self Adaptive Weighted Data Fusion Algorithm

Science.gov (United States)

Sung, Wen-Tsai; Lin, Jia-Syun

2013-01-01

This work aims to develop a smart LED lighting system, which is remotely controlled by Android apps via handheld devices, e.g., smartphones, tablets, and so forth. The status of energy use is reflected by readings displayed on a handheld device, and it is treated as a criterion in the lighting mode design of a system. A multimeter, a wireless light dimmer, an IR learning remote module, etc. are connected to a server by means of RS 232/485 and a human computer interface on a touch screen. The wireless data communication is designed to operate in compliance with the ZigBee standard, and signal processing on sensed data is made through a self adaptive weighted data fusion algorithm. A low variation in data fusion together with a high stability is experimentally demonstrated in this work. The wireless light dimmer as well as the IR learning remote module can be instructed directly by command given on the human computer interface, and the reading on a multimeter can be displayed thereon via the server. This proposed smart LED lighting system can be remotely controlled and self learning mode can be enabled by a single handheld device via WiFi transmission. Hence, this proposal is validated as an approach to power monitoring for home appliances, and is demonstrated as a digital home network in consideration of energy efficiency.

Demonstration of a large-size horizontal light-field display based on the LED panel and the micro-pinhole unit array

Science.gov (United States)

Yang, Le; Sang, Xinzhu; Yu, Xunbo; Liu, Boyang; Liu, Li; Yang, Shenwu; Yan, Binbin; Du, Jingyan; Gao, Chao

2018-05-01

A 54-inch horizontal-parallax only light-field display based on the light-emitting diode (LED) panel and the micro-pinhole unit array (MPUA) is demonstrated. Normally, the perceived 3D effect of the three-dimensional (3D) display with smooth motion parallax and abundant light-field information can be enhanced with increasing the density of viewpoints. However, the density of viewpoints is inversely proportional to the spatial display resolution for the conventional integral imaging. Here, a special MPUA is designed and fabricated, and the displayed 3D scene constructed by the proposed horizontal light-field display is presented. Compared with the conventional integral imaging, both the density of horizontal viewpoints and the spatial display resolution are significantly improved. In the experiment, A 54-inch horizontal light-field display with 42.8° viewing angle based on the LED panel with the resolution of 1280 × 720 and the MPUA is realized, which can provide natural 3D visual effect to observers with high quality.

Ultrabroad linewidth orange-emitting nanowires LED for high CRI laser-based white lighting and gigahertz communications

KAUST Repository

Janjua, Bilal; Ng, Tien Khee; Zhao, Chao; Oubei, Hassan M.; Shen, Chao; Prabaswara, Aditya; Alias, Mohd Sharizal; Alhamoud, Abdullah Ali; Alatawi, Abdullah Awaad; Albadri, Abdulrahman M.; Alyamani, Ahmed Y.; El-Desouki, Munir M.; Ooi, Boon S.

2016-01-01

intensity- and bandwidth-tunable for high color-quality remained unexplored. In this paper, we present for the first time, the proof-of-concept of the generation of high-quality white light using an InGaN-based orange nanowires (NWs) LED grown on silicon

The role of planum temporale in processing accent variation in spoken language comprehension.

NARCIS (Netherlands)

Adank, P.M.; Noordzij, M.L.; Hagoort, P.

2012-01-01

A repetitionsuppression functional magnetic resonance imaging paradigm was used to explore the neuroanatomical substrates of processing two types of acoustic variationspeaker and accentduring spoken sentence comprehension. Recordings were made for two speakers and two accents: Standard Dutch and a

An engineering method to estimate the junction temperatures of light-emitting diodes in multiple LED application

International Nuclear Information System (INIS)

Fu, Xing; Hu, Run; Luo, Xiaobing

2014-01-01

Acquiring the junction temperature of light emitting diode (LED) is essential for performance evaluation. But it is hard to get in the multiple LED applications. In this paper, an engineering method is presented to estimate the junction temperatures of LEDs in multiple LED applications. This method is mainly based on an analytical model, and it can be easily applied with some simple measurements. Simulations and experiments were conducted to prove the feasibility of the method, and the deviations among the results obtained by the present method with those by simulation as well as experiments are less than 2% and 3%, respectively. In the final part of this study, the engineering method was used to analyze the thermal resistances of a street lamp. The material of lead frame was found to affect the system thermal resistance mostly, and the choice of solder material strongly depended on the material of the lead frame.

Bactericidal effect of blue LED light irradiated TiO2/Fe3O4 particles on fish pathogen in seawater

International Nuclear Information System (INIS)

Cheng, T.C.; Yao, K.S.; Yeh, N.; Chang, C.I.; Hsu, H.C.; Gonzalez, F.; Chang, C.Y.

2011-01-01

This study uses blue LED light (λ max = 475 nm) activated TiO 2 /Fe 3 O 4 particles to evaluate the particles' photocatalytic activity efficiency and bactericidal effects in seawater of variable salinities. Different TiO 2 to Fe 3 O 4 mole ratios have been synthesized using sol-gel method. The synthesized particles contain mainly anatase TiO 2 , Fe 3 O 4 and FeTiO 3 . The study has identified TiO 2 /Fe 3 O 4 's bactericidal effect to marine fish pathogen (Photobacterium damselae subsp. piscicida BCRC17065) in seawater. The SEM photo reveals the surface destruction in bacteria incubated with blue LED irradiated TiO 2 /Fe 3 O 4 . The result of this study indicates that 1) TiO 2 /Fe 3 O 4 acquires photocatalytic activities in both the freshwater and the seawater via blue LED irradiation, 2) higher photocatalytic activities appear in solutions of higher TiO 2 /Fe 3 O 4 mole ratio, and 3) photocatalytic activity decreases as salinity increases. These results suggest that the energy saving blue LED light is a feasible light source to activate TiO 2 /Fe 3 O 4 photocatalytic activities in both freshwater and seawater.

The role of planum temporale in processing accent variation in spoken language comprehension

NARCIS (Netherlands)

Adank, P.M.; Noordzij, M.L.; Hagoort, P.

2012-01-01

A repetition–suppression functional magnetic resonance imaging paradigm was used to explore the neuroanatomical substrates of processing two types of acoustic variation—speaker and accent—during spoken sentence comprehension. Recordings were made for two speakers and two accents: Standard Dutch and

Compressive strength measurements of hybrid dental composites treated with dry heat and light emitting diodes (LED post cure treatment

Directory of Open Access Journals (Sweden)

Jenny Krisnawaty

2014-11-01

Full Text Available Hybrid composites are mostly used on large cavities as restorative dental materials, whether it is used directly or indirectly. The mechanical properties of composite resin shall increase if it is treated with post cure treatment. The aim of this study is to evaluate compressive strength differences between dry heat and Light Emitting Diodes (LED treatment on the hybrid dental composite. A quasi-experimental was applied on this research with a total of 30 samples that were divided into two groups. Each sample was tested using LLOYD Universal Testing Machine with 1 mm/min speed to evaluate the compressive strength. The compressive strength results were marked when the sample was broken. The results of two groups were then analyzed using t-test statistical calculation. The results of this study show that post cure treatment on hybrid composite using LED light box (194.138 MPa was lower than dry heat treatment (227.339 MPa, which was also significantly different from statistical analysis. It can be concluded that compressive strength of LED light box was lower than dry heat post-cure treatment on the hybrid composite resin.

Spectral Design Flexibility of LED Brings Better life

DEFF Research Database (Denmark)

Ou, Haiyan; Corell, Dennis Dan; Ou, Yiyu

2012-01-01

Light-emitting diodes (LEDs) are penetrating into the huge market of general lighting because they are energy saving and environmentally friendly. The big advantage of LED light sources, compared to traditional incandescent lamps and fluorescent light tubes, is the flexible spectral design to make...

Modeling the effects of phosphor converted LED lighting to the night sky of the Haleakala Observatory, Hawaii

Science.gov (United States)

Aubé, M.; Simoneau, A.; Wainscoat, R.; Nelson, L.

2018-05-01

The goal of this study is to evaluate the current level of light pollution in the night sky at the Haleakala Observatory on the island of Maui in Hawaii. This is accomplished with a numerical model that was tested in the first International Dark Sky Reserve located in Mont-Mégantic National Park in Canada. The model uses ground data on the artificial light sources present in the region of study, geographical data, and remotely sensed data for: 1) the nightly upward radiance; 2) the terrain elevation; and, 3) the ground spectral reflectance of the region. The results of the model give a measure of the current state of the sky spectral radiance at the Haleakala Observatory. Then, using the current state as a reference point, multiple light conversion plans are elaborated and evaluated using the model. We can thus estimate the expected impact of each conversion plan on the night sky radiance spectrum. A complete conversion to white (LEDs) with (CCT) of 4000K and 3000K are contrasted with a conversion using (PC) amber (LEDs). We include recommendations concerning the street lamps to be used in sensitive areas like the cities of Kahului and Kihei and suggest best lighting practices related to the color of lamps used at night.

Activation of Wnt/β-catenin signaling is involved in hair growth-promoting effect of 655-nm red light and LED in in vitro culture model.

Science.gov (United States)

Han, Le; Liu, Ben; Chen, Xianyan; Chen, Haiyan; Deng, Wenjia; Yang, Changsheng; Ji, Bin; Wan, Miaojian

2018-04-01

Activation of the Wnt/β-catenin signaling pathway plays an important role in hair follicle morphogenesis and hair growth. Recently, low-level laser therapy (LLLT) was evaluated for stimulating hair growth in numerous clinical studies, in which 655-nm red light was found to be most effective and practical for stimulating hair growth. We evaluated whether 655-nm red light + light-emitting diode (LED) could promote human hair growth by activating Wnt/β-catenin signaling. An in vitro culture of human hair follicles (HFs) was irradiated with different intensities of 655-nm red light + LED, 21 h7 (an inhibitor of β-catenin), or both. Immunofluorescence staining was performed to assess the expression of β-catenin, GSK3β, p-GSK3β, and Lef1 in the Wnt/β-catenin signaling. The 655-nm red light + LED not only enhanced hair shaft elongation, but also reduced catagen transition in human hair follicle organ culture, with the greatest effectiveness observed at 5 min (0.839 J/cm 2 ). Additionally, 655-nm red light + LED enhanced the expression of β-catenin, p-GSK3β, and Lef1, signaling molecules of the Wnt/β-catenin pathway, in the hair matrix. Activation of Wnt/β-catenin signaling is involved in hair growth-promoting effect of 655-nm red light and LED in vitro and therefore may serve as an alternative therapeutic option for alopecia.

Optical characterization of ultrabright LEDs

International Nuclear Information System (INIS)

Benavides, Juan Manuel; Webb, Robert H.

2005-01-01

Ultrabright light emitting diodes (LEDs) are a new light source for visual psychophysics and microscopy. The new LEDs are intended primarily for room and exterior illumination, and the manufacturers' specifications are adequate for that. However, we use them as light sources in situations where a more complete characterization may be useful. For one set of LEDs we have measured the radiometric intensity and its distribution in space and wavelength, and we have tested for interactions of these variables and their dependence on driver configuration. We describe techniques for making these measurements and give a link to a simple calculator for converting among radiometric and photometric measures, as well as an evaluation of the safety considerations these very bright sources demand

An overview of LED applications for general illumination

Science.gov (United States)

Pelka, David G.; Patel, Kavita

2003-11-01

This paper begins by reviewing the current state of development of LEDs, their existing markets as well as their potential for energy conservation and their potential for gaining market share in the general illumination market. It discusses LED metrics such as chip size, lumens per watt, thermal resistance, and the recommended maximum current rating. The paper then goes on to consider the importance of non-imaging optics for both optically efficient and extremely compact LED lighting systems. Finally, microstructures useful for controlling the fields-of-view of LED lighting systems are considered and described in some detail. An extremely efficient and cost effective microstructure, called kinoform diffusers, is shown to have very unique properties that make this technology almost ideal for shaping the output beams of LED lighting systems. It concludes by illustrating some general illumination LED lighting systems

Effectiveness of composite resin polymerization using light-emitting diodes (LEDs or halogen-based light-curing units Efetividade de polimerização de uma resina composta fotopolimerizada por diodos emissores de luz (LEDs ou luz halógena