A LED spectrometer has been constructed for qualitative spectrometry using certain wavelenghts. The LEDs and the photodiode are being controlled with a microcontroller that is connected to a computer to power the components and save data. The spectroanalysis made with the LED spectrometer were significantly different to a standard spectrometer, concluding that more analysis should be made until a final product is ready. Some areas of improvements are suggested.

Les systèmes d'éclairage artificiels sont couramment utilisés pour la croissance des plantes en serre ou environnement contrôlé (culture hydroponique, hors sol, etc...). Leur principale fonction est d'améliorer la qualité et la quantité de la production agricole indépendamment des saisons et de l'ensoleillement. L'utilisation d'une source de rayonnement artificielle pour plantes (PARS pour "Plant Artificial Radiation Sources") signifie que la lumière du soleil n'a pas été l'unique source de lumière pour la production agricole, mais qu'elle a été remplacé ou complété par une source artificielle (PARS). Les serres ou les complexes de culture hydroponique avec éclairage artificiel (Plant Factory with Artificial Lighting, "PFAL"), notamment à LED, sont une technologie innovante pour l'agriculture moderne susceptible de changer fondamentalement certains concepts. Cependant, certaines difficultés persistent avec ces nouvelles techniques. Tout d'abord, par manque de formation ou d'information, certaines personnes ne comprennent pas les caractéristiques techniques des sources de lumière artificielle moderne. Deuxièmement, les mécanismes de photobiologie sous différents spectres sont encore mal définis en fonction des espèces de plantes. Troisièmement, le secteur agricole est une grande entité qui présente également une grande complexité de part la variabilité des cultures. En conséquence, les "PARS" ont généralement une faible efficacité et présentent une consommation énergétique élevée, ce qui devient le principal obstacle pour leur application. Les PARS et leurs systèmes sont la technique de base pour développer l'horticulture contrôlée, en particulier dans la culture hydroponique qui n'utilisent que les sources d'éclairage artificielle. Toutefois, la consommation d'énergie et les défauts de conception deviennent des difficultés rédhibitoires à leur mise en oeuvre. Par conséquent, la sélection d'une source de lumière efficace et l'optimisation des systèmes d'éclairage sont d'une grande importance. Connaître le type de spectre optimal pour une variété de plante ou d'algue nécessite donc des études plus approfondies. Les diodes électroluminescentes (LED) pour l'éclairage constituent une source de lumière de dernière génération compatible avec les puissances lumineuses nécessaires à la croissance de plantes. Par rapport aux sources traditionnelles, elles présentent des avantages incomparables tels qu'un rendement élevé, une longue durée de vie, un rayonnement relativement simple à contrôler par rapport aux sources de lumières classiques, une lumière dite "froide" (pas d'émission infra-rouge), de petite taille, robuste, etc. En outre, les systèmes d'éclairage à LED ("LED Lighting Systems", LLS) utilisent une alimentation en courant continu, ce qui est plus fiable et plus facile à contrôler. Par conséquent, les "LLS" deviennent de plus en plus populaire pour les chercheurs, ingénieurs, fabricants, biologistes et industriels du secteur agronomique. En particulier, les applications des LEDs pour la production agricole suscitent une vive attention dans le monde ces dernières années. Les sources de lumière à LED sont connues comme étant le choix idéal en horticulture sous conditions contrôlées (notamment vis-à-vis de leur faible consommation énergétique). / Artificial lighting systems can be used for plant growth in protected horticulture. Their main function is to improve the quality and quantity of agricultural products. Plant factory and greenhouse with supplemental lighting are the concrete manifestation of protected horticulture. The applications of Plant Artificial Radiation Sources (PARS) mean that the sunlight has not been the unique light source for agricultural production but can be replaced by PARS. Especially, Plant Factory with Artificial Lighting (PFAL) is an innovative technology for modern agriculture that fundamentally change the concept of farming. However, there are some problems for this new technique. First, some people do not understand well the characteristics of artificial light source. Second, photobiology mechanism under different spectra is not clear enough for all the species. Third, agricultural field is a large system of great complexity. As a result, the PARS usually have low efficiency and high energy consumption, which become the main obstacles for plant applications. PARS and their systems are the core technique to develop protected horticulture, especially for plant factory that can only use PARS for photosynthesis and agricultural production. However, the high energy consumption and design flaws become the bottleneck problems. Therefore, how to select the light sources and optimize the lighting systems are of great importance. Which kind of spectrum is optimal for plants or algae needs further study. Light emitting diode (LED) is the fourth (the latest) generation light source. Compared with traditional light sources, it has unparalleled advantages such as high efficiency, long lifetime, flexible spectrum, cool light, small size, robust, etc. Besides, LED lighting systems (LLS) use DC power supply, which is more reliable and easier to control. Therefore, LLS become more and more popular to the researchers, engineers, manufacturers and biologists. Particularly, LED applications for agricultural production also attract broad attention in the world in recent years. LED is known as the ideal choice to spread in the protected horticulture.

Resumo: O objetivo deste estudo in vitro foi comparar os efeitos da fotoativação pelos sistemas luz halógena e LED na adesão de braquetes ortodônticos em diferentes tempos pós-colagem (imediato, 24h e 7d). Braquetes com adesivo pré-aplicado (Gemini series; APC adhesive precoated brackets; 3M Unitek, USA) foram colados na superfície vestibular de dentes bovinos. O esmalte dos dentes foi condicionado utilizando-se o primer auto-condicionante (Transbond SEP, 3M Unitek, USA) em todos os espécimes, conforme recomendações do fabricante. Setenta e dois dentes foram divididos em 2 grupos (n=36), conforme o sistema de fotoativação (luz halógena ou LED) e sub-divididos (n=12) de acordo com o tempo pós-colagem. Para os grupos luz halógena, o tempo de fotoativação foi de 20s e para os grupos LED foi de 10s. O teste de resistência ao cisalhamento foi realizado com auxílio de uma máquina de ensaios universal nos diferentes tempos pós-colagem: imediato, 24h e 7d. O valor médio de adesão para os grupos luz halógena foi de 20,01±5,24MPa e, para os grupos fotoativados pelo sistema LED 17,35±5,07MPa, sendo estes resultados estatisticamente diferentes. Quando comparado o efeito do tempo pós-colagem, os resultados revelaram que os valores de adesão foram significantemente maiores para o tempo de 7d. O resultado do teste ANOVA 2 - fatores revelou não existir diferença estatística entre a interação sistema de fotoativação e tempos pós-colagem. O teste de Tukey mostrou que para as 4 condições experimentais nos tempos imediato e 24h, os resultados não diferiram estatisticamente, independentemente do sistema de fotoativação. Somente com relação ao grupo luz halógena-7d, os resultados mostraram diferenças estatisticamente significantes. O grupo LED-7d desempenhou comportamento intermediário entre os grupos. O índice de adesivo remanescente não revelou diferenças... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The objective of this in vitro study was to compare the effects of polymerization using halogen and LED system on shear bond strengths (SBS) at different debond times of immediately, 24 hours and 7 days after bonding. Pre-coated brackets (Gemini series; 3M Unitek, USA) were bonded to bovine incisors in all specimens. Teeth were conditioned with a self-etching primer (Transbond SEP, 3M Unitek, USA) as recommended by the manufacturer for all groups. Seventy two bovine teeth were divided in 2 groups (n=36) according to the polymerization system (halogen or LED) and subdivided (n=12) according to the debond time. For the halogen groups light-cure time was 20 seconds and for the LED groups light-cure time was 10 seconds. The shear bond test was performed with a universal testing machine at the different times of immediately, 24 hours and 7 days after bonding. Mean values of SBS for the halogen groups was (20,01±5,24 MPa) and (17,35±5,07MPa) for the LED groups with statistical difference between the groups. When comparing the different debond times, results revealed that SBS were significantly greater for the 7 days period. Two-way ANOVA test showed no statistical difference between the co-relation of light source and debond times. Results of Tukey test revealed that the four experimental conditions established for the immediately and 24 hours times did not differ statistically, but differed for the seven day period with the halogen system. The LED seven day condition performed as an intermediately result. The Adhesive Remanescent Index revealed no significative differences among all groups. As a conclusion it is reliable that although halogen groups differed from LED groups, the SBS mean values are greater than those clinically accepted.

No description available.

This thesis deals with the design of LED matrix array contains 150 LEDs. In the first part, the thesis identifies source of light like OLED and LED and provide an overview of their lifetime, reliability and basic principle of design systems with LEDs. The thesis then describe design of LED matrix array, deals with power supply of this LED array and with cooling of LED. Finally the thesis describes a software for contol of LED matrix array.

This thesis deals with controlling a color graphic LED display using an FPGA. The first half of the theoretical part of this paper describes the properties of the used FPGA, the data source and a principle of controlling an RGB LED display. The second half describes an implementation of pulse width modulation and binary code modulation which enables the control of brightness of the display and of color depth of every sub-pixel. The practical part on the other hand describes the designing and the implementation of this module in the VHDL language. Then it explains the transfer of image data from Blackfin processor to the memory via PPI interface, the subsequent process of reading data from the memory, conversion of the data to a serial format and finally it describes the process of sending the data to the LED controller. The module was realized on the Digilent Atlys development board equipped with the Spartan-6 FPGA and was tested on a 32x20 light panel for the firm Ing. Ivo Herman, CSc.

Dans ce manuscrit, je présente mon travail dédié à la réalisation et à la caractérisation des émetteurs et détecteurs de lumière à base de nanofils de nitrures. Je détaille la fabrication des dispositifs utilisant des outils de nanofabrication à l’état de l’art, ainsi que l'étude de leurs propriétés électriques et optiques.Le premier chapitre résume brièvement les propriétés de base des semi-conducteurs nitrures et décrit les méthodes d’élaboration des nanofils. Dans le deuxième chapitre, je présente mon travail sur la fabrication et la caractérisation de LED à nanofil unique InGaN/GaN ayant un contact transparent en graphène pour l’injection des trous. L'électroluminescence des LEDs à nanofils uniques montre l'impact de la forme du contact sur les propriétés d'émission. En particulier, la position du contact détermine l'évolution spectrale avec le courant d'injection. À savoir, pour un contact étendu et un contact localisé sur le plan m, l’émission passe du vert au bleu en fonction du courant d’injection alors que pour un contact localisé sur la jonction entre le plan m et le plan semipolaire l'émission reste verte.Dans le troisième chapitre, je décris la fabrication et la caractérisation des LEDs à nanofils uniques fabriqués à partir d'une matrice de nanofils verticaux avec une morphologie des contacts identique à celle mise en œuvre pour les LEDs à base d’ensemble de nanofils. L'émission montre une évolution similaire à celle observée pour les LEDs à nanofils uniques avec un contact latéral. L’influence de la morphologie des contacts sur l'électroluminescence ouvre la possibilité de contrôler la couleur d'émission de la LED à l'étape de la fabrication. J'ai utilisé un traitement par plasma de fluor afin de réduire la conductivité de la coquille GaN dopé p et d’inhiber l'injection électrique dans la région riche en In du puits quantique. En outre, j'ai analysé l'effet de l’inhomogénéité d'injection. Afin d'améliorer l’homogénéité, j'ai développé un système de contact par le haut permettant d’injecter les électrons directement dans la sous-couche n-GaN. Les LEDs fabriquées selon cette procédure montrent un rendement amélioré avec 65% de nanofils actifs contre 19% pour une procédure standard.Le dernier chapitre est consacré à l'étude des photodétecteurs à nanofils de nitrure. Je décris d'abord la fabrication et la caractérisation d'un photodétecteur de rayonnement ultraviolet basé sur un ensemble de nanofils de GaN avec un contact transparent en graphène. Ensuite, des détecteurs à nanofils uniques InGaN / GaN ont été fabriqués fonctionnant dans la gamme spectrale du visible à ultraviolet. L'influence de la morphologie de contact est également étudiée en comparant deux types de contacts, à savoir un contact métallique localisé et un contact étendu en oxyde d'indium-étain (ITO). Dans la dernière partie, je présente une technique pour la fabrication de photodétecteurs flexibles basée sur des ensembles de nanofils verticaux et je discute leurs performances. / In this manuscript, I present my work dedicated to the realization and characterization of nitride nanowire light emitters and detectors. I detail the device fabrication using state-of-the-art nanofabrication tools as well as the investigation of their electrical and optical properties.First chapter briefly summarizes the nitride semiconductor basic properties and discusses the present status of nanowire elaboration. In the second chapter, I present my work on the fabrication and in-depth characterization of single nanowire InGaN/GaN LEDs with a transparent graphene contact for hole injection. Reference single wire LEDs with metal contacts are also investigated for comparison. The electroluminescence of single nanowire LEDs evidences the impact of the contact layout on the emission properties. In particular, the position of the contact determines the spectral evolution with injection current. Namely, for an extended contact and a contact localized on the m-plane, a transition from the green to blue emission is observed whereas for a localized contact on the m-plane/semipolar plane junction the emission remains green.In the third chapter, I describe the fabrication and characterize single wire LEDs made out of a vertical NW array with the contacting scheme identical to array LEDs. The emission shows a similar evolution as the lateral-contacted single nanowire LEDs. The dependence of the electroluminescence on the contact morphology opens the way to control the LED emission color at the device processing stage. I used fluorine plasma treatment to reduce the conductivity of the p-doped GaN shell for inhibiting the electrical injection in the In-rich region of the quantum well. Furthermore, I analyze the injection inhomogeneity effect. In order to avoid this effect, I developed a top down contacting scheme with electrons injected directly into n-GaN underlayer, which is called “front contacting” process. The “front contacting” LEDs show an enhanced yield of active nanowires from 19% to 65%.The last chapter is dedicated to the study of nitride nanowire photodetectors. I first describe the fabrication and characterization of a GaN ultraviolet (UV) photodetector based on a NW array with a transparent graphene contact. Moreover, single NW InGaN/GaN detectors were fabricated operating in the visible to ultraviolet spectral range. The influence of the contact morphology is also investigated by comparing two types of contacts, namely a partial metal contact and an indium tin oxide (ITO) conformal contact, respectively. In the last part, I present an up-to-date technique for fabricating flexible photodetectors based on vertical NW arrays and I discuss their performances.

Energieffektiviserande åtgärder har stor betydelse för den totala effekten på vårt klimat. Lägre energiåtgång leder till reducerade koldioxidutsläpp och att naturens resurser inte belastas lika hårt. En av de mest kostnadseffektiva åtgärderna för att minska byggnaders miljöpåverkan har visats vara att investera i den energieffektiva belysningsteknik LED, och i kombination med dagsljus- och närvarostyrning finns en stor potential att spara energi.Syftet med detta examensarbete är att studera hur bland annat elförbrukningen, värme- och kylbehovet, ljusmiljön och driftkostnaderna för en belysningsanläggning påverkas av att byta ut traditionell belysning mot LED i befintliga kontorslokaler, samt implementering av dagsljus- och närvarostyrning. Detta har gjorts genom bland annat el- och ljusmätningar, flertalet datorsimuleringar, enkätundersökningar och intervjuer som en del i ett befintligt projekt med ÅF Lighting, som gick ut på att två olika LED-lösningar installerades på två kontorsplan på ÅF:s huvudkontor i Solna. Med hjälp av datorsimuleringar har undersökningar gjorts av bland annat kontorens tillgång till dagsljus i DIVA-for-Rhino, kontorens ljusnivåer i diaLUX, hur kyl - och värmebehovet påverkas i IDA ICE 4.7, ekonomiska besparingar i ecoCALC samt belysningens elförbrukning i Mitec Monitor.Elmätningar under en månad av de nya belysningsanläggningarna på plan 5 och plan 10 visade på en reducering av belysningens elförbrukning på 71,6 % respektive 68,1 % under denna period.Energisimuleringar över ett år i IDA ICE visade att den totala energianvändningen för båda kontorslandskapen reducerades med cirka 12-14 % efter bytet till LED-belysningen och implementeringen av dagsljus- och närvarostyrning. Största faktorn till denna besparing är att kylbehovet för plan 5 och plan 10 kunde reduceras med 19 % respektive 17 %, eftersom den mer energieffektiva belysningen och styrningen av denna genererar mindre värme än den befintliga belysningen. Simuleringarna visade även att belysningens totala årliga elförbrukning reducerades med 70 % på plan 5 och 63 % på plan 10.En grundlig LCC för de nya belysningslösningarna på plan 5 och plan 10 visade att investeringskostnaderna för de nya LED-lösningarna är högre än den totala driftkostnaden över livscykeln för den befintliga belysningen. Dock är driftkostnaderna för de nya lösningarna mindre än en tredjedel av kostnaderna att driva den befintliga belysningen, och de totala koldioxidutsläppen kan reduceras med närmare 70 % i och med utbytet.Denna fallstudie har visat att det finns enorm potential att spara energi och minska driftkostnaderna genom att investera i energieffektiv LED-belysning i kombination av dagsljus-och närvarostyrning, samtidigt som det kan ha positiv inverkan på ljusmiljön. Dock är investeringskostnaderna av de nya LED-lösningarna för stora för att installation av just dessa lösningar ska vara ekonomiskt försvarbart idag. / An important measure to reduce buildings’ environmental impact is to make the artificial lighting more effective, which is the biggest electricity consumer of Swedish office buildings and accounts for more than 30 % of the total electricity consumption.A case study has been carried out in this master thesis as a part in an existing project with ÅF Lighting, where new strategic avenues has been explored in which to combine day- and electrical light in office landscapes in a smarter, more energy-efficient manner and at the same time improve the lighting environment.Two office spaces at the own head office of ÅF in Solna, Stockholm has been used in the case study, where two different LED lighting solutions got installed. One with pendant luminaries, desk lamps and downlights, and one with only recessed luminaires.Through several computer simulations, electricity and light measurements, questionnaires, interviews etc., it has been investigated how the heat and cooling load, electricity consumption, lighting quality and operating costs has been affected of the change of the lighting system. The lighting environment, daylight conditions, heat and cooling load, economical savings and electricity consumption for the two offices has been investigated in diaLUX, DIVA-for-Rhino, IDA ICE 4.7, ecoCALC and Mitec Monitor, respectively. The electricity measurements showed that the lighting solutions’ electricity consumption got reduced with 71,6 % on floor 5 and 68,1 % on floor 10 with the new LED lighting solutions and control systems during the investigated month.Through the IDA ICE energy simulations over a year it was shown that the total yearly cooling load to floor 5 and floor 10 got reduced with 19 % and 17 %, which can be explained by the lesser heat gain from the more energy efficient lighting and the controlling of this. Though a small increase in heating load, the total energy consumption got reduced with around 12-14 % on both floors. The simulations also showed that the total electricity consumption of the lighting got reduced with 70 % for floor 5 and 63 % for floor 10 after the change to the new LED lighting solutions and implementation of control systems.The LCC for the new lighting solutions showed that these have a higher investment cost than the total operation cost for the existing solution over the life cycle. However, the costs to run the LED solutions are less than a third of the operation costs for the existing solution, and after the exchange the carbon dioxide emissions can be reduced with close to 70 %.Through this case study it has been shown that the energy consumption from lighting can be highly reduced with the installation of energy efficient lighting in combination with smart control systems, and it can also have a positive effect on the lighting environment. However, the high investment costs of the LED solutions lead to the conclusion that installation of these solutions today is not economically justifiable.

No description available.

Master of Arts - Arts / Local Economic Development is a viable mechanism for economic growth for South Africa. National Government has thus has set in place a number of policies and pieces of legislation that encourage local government to participate in LED strategies. Integrated Development Plans are the most comprehensive of the legislation and force local government to engage with LED policy. The new legislation, has led to a fundamental shift in development strategy for South Africa. In Mpumalanga in particular, the development strategy has shifted from regional development to local development. This strategy has been prompted by the IDP policy yet many municipalities do not have the capacity to effectively draw up an IDP. Municipalities often simply use IDPs as wish lists of what they would like to achieve but can not within their current budgets. The National Government strategy of IDPs is forcing policy on local government that is not necessarily needed but could simply be a strategy to have more control over local government. This study explores the shift in government development policy and the capacity of local government to fulfill its new role. The Mpumalanga experience of IDPs and LED forms the focus of this empirical study.