Fonte de Iluminação LED – Avaliação dos Efeitos Fotobiológicos no Olho e Pele

Tendo por referência a diretiva 2006/95/CE, o trabalho desenvolvido no contexto da disciplina de Dissertação/Projeto/Estágio do Mestrado de Engenharia de Instrumentação e Metrologia, decorreu nas instalações do IEP (Instituto Electrotécnico Português) e teve como objetivo principal o desenvolvimento de um procedimento de avaliação dos efeitos fotobiológicos no olho e pele provocados por fontes de emissão contínua (LED), doravante designado método alternativo ao de referência. Os dois métodos, alternativo e de referência, utilizam respectivamente um foto-radiómetro multicanal e um espetro-radiómetro. O procedimento desenvolvido (método alternativo) de acordo com a norma EN/IEC62471) consiste na aquisição dos valores de irradiância com recurso a um foto-radiómetro e posterior determinação dos valores da radiância, com os quais se faz a avaliação dos efeitos fotobiológicos, para fontes de luz LED (Light Emitting Diode) ou GLS (General Lighting Service). A consulta detalhada da norma EN/IEC62471 e a pesquisa sobre os conceitos, definições, equipamentos e metodologias relacionadas com o tema em causa, constituiu o primeiro passo deste projecto. Com recurso aos dois equipamentos, uma fonte de luz LED (módulo de 12 lâmpadas LED) é avaliada em relação aos perigos (ou riscos) actínico UV e UV-A, ao perigo da luz azul e ainda o perigo térmico na retina e térmico na pele, permitindo fazer uma análise comparativa dos resultados. O método alternativo revelou-se bastante flexível e eficaz, proporcionando bons resultados em termos da irradiância e radiância dos referidos efeitos fotobiológicos. A comparação destes resultados com os valores limites de exposição mencionados na norma EN/IEC6247 permitiu afirmar que a fonte de luz LED avaliada não representa perigo fotobiológico para a saúde humana e classifica-se no grupo de risco “isento”. Uma vez cumpridos os objectivos, entendeu-se que seria uma mais-valia para o trabalho já realizado, estudar outro caso prático. Sendo assim, fez-se a avaliação da radiação de apenas um dos LED´s que constituíam a fonte usada nos ensaios anteriores, com o espetro-radiómetro (método de referência) e com uma distância de 200 mm entre a fonte e o medidor. Neste caso verificaram-se diferenças significativas nas quantidades obtidas quando comparadas com os valores normativos. Concluiu-se que o efeito fotobiológico da luz azul insere-se no grupo de “isento”, sem perigo para a saúde. Contudo, o efeito térmico da retina apresenta um aumento considerável da quantidade de radiância, embora dentro do grupo de risco “isento”. Esta classificação de grupos de risco. Face aos resultados obtidos, pode confirmar-se que as lâmpadas LED apresentam segurança fotobiológica, atendendo aos baixos valores de irradiância e radiância dos efeitos fotobiológicos estudados. Pode ainda afirmar-se que a utilização do foto-radiómetro em alternativa ao espetro-radiómetro se revela mais eficaz do ponto de vista de metodologia prática. Este trabalho demonstra a robustez desses dois equipamentos de avaliação dos efeitos fotobiológicos, e procura estabelecer uma linha de orientação para a prevenção dos efeitos adversos na pele e olhos de todos os seres humanos sujeitos à radiação ótica artificial. Quanto às incertezas de medições, em relação ao processo de medição com foto-radiómetro, a sua estimação não se realizou, devido a não rastreabilidade entre as medições indicadas pelo fabricante, no certificado de calibração e as medidas realizadas por outras entidades. Contudo, é propõe-se a sua realização em trabalhos futuros dentro desse âmbito. As incertezas dos resultados de medições com espetro-radiómetro foram parcialmente estimadas. Atendendo às potencialidades do sistema de medição, propõe-se como trabalho futuro, a aplicação da norma IEC62478, que faz parte da aplicação da norma EN/IEC62471 na avaliação do efeito da luz azul, com base na determinação da temperatura de cor correlacionada (CCT) de lâmpadas ou sistemas de lâmpadas incluindo luminárias. Os valores de irradiância e radiância adquiridos nos processos de avaliação, tanto com foto-radiómetro como espectro-radiómetro foram gravados em ficheiro Excel para um CD e anexados a este trabalho.

Temperature analysis during bonding of brackets using LED or halogen light base units

The purpose of our investigation is to compare the intrapulpal temperature changes following blue LED system and halogen lamp irradiation at the enamel surface of permanent teeth. The fixation of brackets using composite resin is more comfortable and faster when using a photo-curable composite. Several light sources can be used: halogens, arc plasma, lasers, and recently blue LED systems. An important aspect to be observed during such a procedures is the temperature change. In this study, we have used nine human extracted permanent teeth: three central incisors, three lateral incisors, and three canines. Teeth were exposed to two light sources: blue LED system (preliminary commercial model LEC 470-II) and halogen lamp (conventional photo-cure equipment). The surface of teeth was exposed for 20, 40, and 60 sec at the buccal and lingual enamel surface with an angle of 45 degrees. Temperature values measured by a thermistor placed at pulpar chamber were read in time intervals of 1 sec. We obtained plots showing the temperature evolution as a function of time for each experiment. There is a correlation between heating quantity and exposition time of light source: with increasing exposition time, heating increases into the pulpal chamber. The halogen lamp showed higher heating than the LED system, which showed a shorter time of cooling than halogen lamp. The blue LED system seems like the indicated light source for photo-cure of composite resin during the bonding of brackets. The fixation of brackets using composite resin is more comfortable and faster when using a photo-curable composite. Blue LED equipment did not heat during its use. This could permit a shorter clinical time of operation and better performance. © Mary Ann Liebert, Inc.

In vitro assessment of pulp chamber temperature of different teeth submitted to dental bleaching associated with LED/laser and halogen lamp appliances

This study sought to assess the pulp chamber temperature in different groups of human teeth that had been bleached using hydrogen peroxide gel activated with halogen lamps or hybrid LED/laser appliances. Four groups of ten teeth (maxillary central incisors, mandibular incisors, mandibular canines, and maxillary canines) were used. A digital thermometer with a K-type thermocouple was placed inside pulp chambers that had been filled with thermal paste. A 35% hydrogen peroxide-based red bleaching gel was applied to all teeth and photocured for a total of three minutes and 20 seconds (five activations of 40 seconds each), using light from an LED/laser device and a halogen lamp. The temperatures were gauged every 40 seconds and the data were analyzed by three-way ANOVA, followed by Tukey's test. Regardless of the light source, statistically significant differences were observed between the groups of teeth. The mean temperature values (±SD) were highest for maxillary central incisors and lowest for mandibular canines. The halogen lamp appliance produced more pulp chamber heating than the LED/laser appliance. The increase in irradiation time led to a significant increase in temperature.

Proposta de metodologia para criação e análise de cenários na continuidade do Programa Reluz, utilizando tecnologia LED em sistemas de iluminação pública

Pós-graduação em Engenharia Mecânica - FEG

Light emitting diode (LED) use in artificial lighting for broiler chicken production

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Iluminação de exteriores utilizando tecnologia LED: estudo de caso

This Graduate Work aims to exhibit the analyze of the applicability of LED technology in a real outdoor lighting situation, and this project’s illumination solution is compared with the initial proposal, the sodium vapor lamps. What is studied is an outdoor area, like the roads and parking lots of a plant. A light planning software is used for this comparison, and the results are displayed instantly, allowing rapid analysis of the project through a simulation. The medium illuminance is the same in both solutions for this case study and minimum rates set as standard were observed then the analysis are appropriate in this project. Various aspects are considered in order to obtain a comprehensive analysis of this project, such as economic, environmental and quality of lighting. LED technology in outdoor lighting is presented in its infancy, but promising. Solid state lamps show great advantages when compared with other technologies, such as discharge lamps, however there are some disadvantages tied to new products that are expected to be overcome with technological development and increased production

Merit function for the evaluation of color uniformity in the far field of LED spot lights

The scope of the present paper is the derivation of a merit function which predicts the visual perception of LED spot lights. The color uniformity level Usl is described by a linear regression function of the spatial color distribution in the far field. Hereby, the function is derived from four basic functions. They describe the color uniformity of spot lights through different features. The result is a reliable prediction for the perceived color uniformity in spot lights. A human factor experiment was performed to evaluate the visual preferences for colors and patterns. A perceived rank order was derived from the subjects’ answers and compared with the four basic functions. The correlation between the perceived rank order and the basic functions was calculated resulting in the definition of the merit function Usl. The application of this function is shown by a comparison of visual evaluations and measurements of LED retrofit spot lamps. The results enable a prediction of color uniformity levels of simulations and measurements concerning the visual perception. The function provides a possibility to evaluate the far field of spot lights without individual subjective judgment. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Validación de HP UV-LED para la detección en continuo de contaminantes en aguas continentales mediante fluorescencia

La preservación del medio ambiente, el avance en las técnicas para que el impacto de la actividad humana sobre la fauna y flora sea lo menor posible, hacen que se deban monitorizar los diversos indicadores de calidad. El presente estudio viene motivado debido a que actualmente existen sistemas de medida y control en continuo de la calidad de las aguas, al margen de los estudios de laboratorio por toma de muestras, a través de los cuales se obtienen indicadores de calidad. El desarrollo tecnológico en analizadores en continuo para la medida de fósforo, amonio, DBO y otros, hacen que cada vez se consiga un control más exhaustivo de la calidad en tiempo real. Sin embargo, la detección temprana de contaminantes que no deben encontrarse presentes en el agua, hacen que el desarrollo de sensores de detección de estos contaminantes sea de gran utilidad. A este respecto, las técnicas mediante fluorescencia presentan enormes ventajas, ya que no existe contacto directo con la muestra, reduciéndose el desgaste y alargando el tiempo entre mantenimientos, como se ha comprobado en numerosos desarrollos con tecnología láser. Para la producir fluorescencia, tradicionalmente se vienen utilizando en el laboratorio principalmente lámparas de gas y monocromadores. Los nuevos LED de alta potencia en el espectro ultravioleta son una alternativa muy interesante que además puede ser aplicada en los mencionados sistemas de medición en continuo. En este trabajo se realiza un estudio de viabilidad de estos dispositivos como fuentes de excitación para la producción de fluorescencia tomando como contaminantes los hidrocarburos. El funcionamiento en estaciones en continuo hace que se tenga que realizar además ensayos de vida acelerados, así como estudios de modos de trabajo. Al respecto de la fluorescencia producida, se estudia la influencia de factores que pueden afectar a las medidas, tales como la temperatura. El estudio del espectro y su análisis para la identificación del contaminante es otro de los puntos desarrollados en este trabajo. Por último, y dado que la monitorización se realiza en modo continuo, es necesario un sistema de comunicaciones compacto y fiable: en este apartado se analizan los metamateriales como solución tecnológica, ya que se adapta perfectamente a la filosofía de estas estaciones de medición. ABSTRACT Currently the monitoring of quality indicators is a need to preserve the environment and minimize the impact of human activity on the fauna and flora. Currently there are measuring systems and continuous monitoring of water quality, regardless of sampling laboratory studies, through which quality indicators are obtained. Technological development in continuous analyzers for the measurement of phosphorus, ammonia, BOD and others increasingly make a more comprehensive real-time quality control is achieved. However, early detection of contaminants that should not be present in the water, make the development of sensors for detecting these contaminants is very useful. In this regard, fluorescence techniques have huge advantages, since there is no direct contact with the sample, reducing wear and extending the time between maintenance, as has been demonstrated in numerous developments in laser technology. To produce fluoresce, traditionally are being used mainly gas lamps and monochromators at the laboratory. The new high-power LEDs in the ultraviolet spectrum are a very interesting alternative that can also be applied in the above continuous measurement systems. In this paper a viability study of these devices as excitation sources to produce fluorescence using hydrocarbon as contaminants is performed. The stations in continuous operation makes it necessary to also perform accelerated life tests and studies operating modes. In regard to the fluorescence produced, the influence of factors that may affect the measurements, such as temperature is studied. The study of the spectrum and analysis to identify the contaminant is another of the points developed in this work. Finally, since the monitoring is carried out in continuous mode, a compact and reliable communication is necessary: in this section metamaterials as a technological solution is analyzed since it fits perfectly with the philosophy of these measuring stations.

Depth of cure and surface microhardness of composite resin cured with blue LED curing lights

Objectives. This study examined the depth of cure and surface microhardness of Filtek Z250 composite resin (3M-Espe) (shades B1, A3, and C4) when cured with three commercially available tight emitting diode (LED) curing lights [E-light (GC), Elipar Freelight (3M-ESPE), 475H (RF Lab Systems)], compared with a high intensity quartz tungsten halogen (HQTH) light (Kerr Demetron Optilux 501) and a conventional quartz tungsten halogen (QTH) lamp (Sirona S1 dental unit). Methods. The effects of light source and resin shade were evaluated as independent variables. Depth of cure after 40 s of exposure was determined using the ISO 4049:2000 method, and Vickers hardness determined at 1.0 mm intervals. Results. HQTH and QTH lamps gave the greatest depth of cure. The three LED lights showed similar performances across all parameters, and each unit exceeded the ISO standard for depth of cure except GC ELight for shade B1. In terms of shade, LED lights gave greater curing depths with A3 shade, while QTH and HQTH tights gave greater curing depths with C4 shade. Hardness at the resin surface was not significantly different between LED and conventional curing lights, however, below the surface, hardness reduced more rapidly for the LED lights, especially at depths beyond 3 mm. Significance. Since the performance of the three LED lights meets the ISO standard for depth of cure, these systems appear suitable for routine clinical application for resin curing. (C) 2003 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

From Prosumer to Produser: Understanding User-Led Content Creation

Alvin Toffler’s image of the prosumer (1970, 1980, 1990) continues to influence in a significant way our understanding of the user-led, collaborative processes of content creation which are today labelled “social media” or “Web 2.0”. A closer look at Toffler’s own description of his prosumer model reveals, however, that it remains firmly grounded in the mass media age: the prosumer is clearly not the self-motivated creative originator and developer of new content which can today be observed in projects ranging from open source software through Wikipedia to Second Life, but simply a particularly well-informed, and therefore both particularly critical and particularly active, consumer. The highly specialised, high end consumers which exist in areas such as hi-fi or car culture are far more representative of the ideal prosumer than the participants in non-commercial (or as yet non-commercial) collaborative projects. And to expect Toffler’s 1970s model of the prosumer to describe these 21st-century phenomena was always an unrealistic expectation, of course. To describe the creative and collaborative participation which today characterises user-led projects such as Wikipedia, terms such as ‘production’ and ‘consumption’ are no longer particularly useful – even in laboured constructions such as ‘commons-based peer-production’ (Benkler 2006) or ‘p2p production’ (Bauwens 2005). In the user communities participating in such forms of content creation, roles as consumers and users have long begun to be inextricably interwoven with those as producer and creator: users are always already also able to be producers of the shared information collection, regardless of whether they are aware of that fact – they have taken on a new, hybrid role which may be best described as that of a produser (Bruns 2008). Projects which build on such produsage can be found in areas from open source software development through citizen journalism to Wikipedia, and beyond this also in multi-user online computer games, filesharing, and even in communities collaborating on the design of material goods. While addressing a range of different challenges, they nonetheless build on a small number of universal key principles. This paper documents these principles and indicates the possible implications of this transition from production and prosumption to produsage.

The user-led disruption : self-(re)broadcasting at Justin.tv and elsewhere

The rise of videosharing and self-(re)broadcasting Web services is posing new threats to a television industry already struggling with the impact of filesharing networks. This paper outlines these threats, focussing especially on the DIY re-broadcasting of live sports using Websites such as Justin.tv and a range of streaming media networks built on peer-to-peer filesharing technology.

Dancing the Thesis : Potentials and Pitfalls in Practice-led Research

Practice-led or multi modal theses (describing examinable outcomes of postgraduate study which comprise the practice of dancing/choreography with an accompanying exegesis) are an emerging strength of dance scholarship; a form of enquiry that has been gaining momentum for over a decade, particularly in Australia and the United Kingdom. It has been strongly argued that, in this form of research, legitimate claims to new knowledge are embodied predominantly within the practice itself (Pakes, 2003) and that these findings are emergent, contingent and often interstitial, contained within both the material form of the practice and in the symbolic languages surrounding the form. In a recent study on ‘dancing’ theses Phillips, Stock, Vincs (2009) found that there was general agreement from academics and artists that ‘there could be more flexibility in matching written language with conceptual thought expressed in practice’. The authors discuss how the seemingly intangible nature of danced / embodied research, reliant on what Melrose (2003) terms ‘performance mastery’ by the ‘expert practitioner’ (2006, Point 4) involving ‘expert’ intuition (2006, Point 5), might be accessed, articulated and validated in terms of alternative ways of knowing through exploring an ongoing dialogue in which the danced practice develops emergent theory. They also propose ways in which the danced thesis can be ‘converted’ into the required ‘durable’ artefact which the ephemerality of live performance denies, drawing on the work of Rye’s ‘multi-view’ digital record (2003) and Stapleton’s ‘multi-voiced audio visual document’(2006, 82). Building on a two-year research project (2007-2008) Dancing Between Diversity and Consistency: Refining Assessment in Postgraduate Degrees in Dance, which examined such issues in relation to assessment in an Australian context, the three researchers have further explored issues around interdisciplinarity, cultural differences and documentation through engaging with the following questions:  How do we represent research in which understandings, meanings and findings are situated within the body of the dancer/choreographer?  Do these need a form of ‘translating’ into textual form in order to be accessed as research?  What kind of language structures can be developed to effect this translation: metaphor, allusion, symbol?  How important is contextualising the creative practice?  How do we incorporate differing cultural inflections and practices into our reading and evaluation?  What kind of layered documentation can assist in producing a ‘durable’ research artefact from a non-reproduce-able live event?

The effective and the evocative : reflecting on practice-led research approaches in art and design

Early in the practice-led research debate, Steven Scrivener (2000, 2002) identified some general differences in the approach of artists and designers undertaking postgraduate research. His distinctions centered on the role of the artefact in problem-based research (associated with design) and creative-production research (associated with artistic practice). Nonetheless, in broader discussions on practice-led research, 'art and design' often continues to be conflated within a single term. In particular, marked differences between art and design methodologies, theoretical framing, research goals and research claims have been underestimated. This paper revisits Scrivener's work and establishes further distinctions between art and design research. It is informed by our own experiences of postgraduate supervision and research methods training, and an empirical study of over sixty postgraduate, practice-led projects completed at the Creative Industries Faculty of QUT between 2002 and 2008. Our reflections have led us to propose that artists and designers work with differing research goals (the evocative and the effective, respectively), which are played out in the questions asked, the creative process, the role of the artefact and the way new knowledge is evidenced. Of course, research projects will have their own idiosyncrasies but, we argue, marking out the poles at each end of the spectrum of art and design provides useful insights for postgraduate candidates, supervisors and methodologists alike.

Content, structure and orientations of the practice-led exegesis

The emergent field of practice-led research is a unique research paradigm that situates creative practice as both a driver and outcome of the research process. The exegesis that accompanies the creative practice in higher research degrees remains open to experimentation and discussion around what content should be included, how it should be structured, and its orientations. This paper contributes to this discussion by reporting on a content analysis of a large, local sample of exegeses. We have observed a broad pattern in contents and structure within this sample. Besides the introduction and conclusion, it has three main parts: situating concepts (conceptual definitions and theories), practical contexts (precedents in related practices), and new creations (the creative process, the artifacts produced and their value as research). This model appears to combine earlier approaches to the exegesis, which oscillated between academic objectivity in providing a context for the practice and personal reflection or commentary upon the creative practice. We argue that this hybrid or connective model assumes both orientations and so allows the researcher to effectively frame the practice as a research contribution to a wider field while doing justice to its invested poetics.