Results 1 - 10 of 52
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[en] As the development of extreme ultraviolet (EUV) lithography progresses, interest grows in the extension of traditional optical components to the EUV regime. The strong absorption of EUV by most materials and its extremely short wavelength, however, makes it very difficult to implement many components that are commonplace in the longer wavelength regimes. One such component is the diffractive optical element used, for example, in illumination systems to efficiently generate modified pupil fills. Here we demonstrate the fabrication and characterization of EUV binary phase-only computer-generated holograms allowing arbitrary far-field diffraction patterns to be generated
[en] Measurements of natural global and diffuse illuminance on four vertical surfaces exposed to north, east, south and west have been carried out at Arcavacata di Rende (Italy). In the work the mean hourly values of the global and diffuse luminous efficacy measured in the period of a year are presented. The hourly data have been compared with the predictions of many calculation models. The comparisons show that, for global efficacy, the differences among the various models are not significant, and the use of a model with a constant value of efficacy gives good predictions of global illuminance. For the prediction of diffuse illuminance the different models behave in a similar way if their coefficients are recalculated and, again, the use of a constant diffuse efficacy provides a good estimate of diffuse illuminance on vertical surfaces
[en] Daylighting is the efficient use of natural light in order to minimize the need for artificial light in buildings. A well thought out building designed with daylighting can have a number of significant benefits for building owners and occupants. Increasing levels of daylight within rooms can reduce electrical lighting loads by up to 70% in some cases. In this study, the daylighting system using mini dish and optical fiber was analyzed for application to the schoolroom by the simulation of ECOTECT and RADIANCE
[en] One demonstrated experimentally possibility of the controlled parametric transformation of femtosecond laser impulse frequency due to the parametric instability induced by phase cross modulation in the field of incidental pumping in quartz microstructured fiber. Amplitude and frequency shift of auxiliary components generated within the spectrum of a test field at the fibre output due to parametric four-wave interaction are controlled by variation of the pumping field intensity
[ru]Экспериментально продемонстрирована возможность эффективного управляемого параметрического преобразования частоты фемтосекундных лазерных импульсов за счет параметрической неустойчивости, индуцированной явлением фазовой кросс-модуляции в поле попутной накачки в кварцевом микроструктурированном волокне. Управление амплитудой и частотным сдвигом боковых компонент, генерируемых в спектре пробного поля на выходе волокна за счет параметрического четырехволнового взаимодействия, осуществляется путем изменения интенсивности поля накачки
[en] 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 oC. The control system is shown to have a robust property with respect to the plant uncertainty and the ambient temperature disturbance
[en] The 120-B-1 waste site, located in the 100-BC-1 Operable Unit of the Hanford Site, consisted of a concrete battery acid sump that was used from 1944 to 1969 to neutralize the spent sulfuric acid from lead cell batteries of emergency power packs and the emergency lighting system. The battery acid sump was associated with the 105-B Reactor Building and was located adjacent to the building's northwest corner. The results of verification sampling demonstrated that residual contaminant concentrations do not preclude any future uses and allow for unrestricted use of shallow zone soils. The results also showed that residual contaminant concentrations are protective of groundwater and the Columbia River
[en] Artificial light sources play an indispensable role in the daily life of any human being. This paper provides an overview of the present state of research in the science and technology of light sources. The paper includes a brief historical overview and a discussion of the properties that determine the performance of light sources. Existing technologies and future challenges for the lighting industry are presented in the domains of both electrical discharge lamps and solid-state light sources. Finally, the paper emphasizes the importance of taking a holistic view of the development of lighting systems in order to obtain high quality lighting that is needed for ensuring quality of life, health and security of end-users. (topical review)
[en] Lighting sources with a cold cathode are widely used in electronics. The lamps with a cold cathode are used primarily as sources of white light in optical scanners, digital indicators, display panels and signalling devices. In the paper the advantages of carbonaceous materials as emitters of cold electrons and the possibilities of using them to create a cathode in an electron lamp are discussed. (authors)
[en] Leds lighting is highly relevant for the horticultural industry. Compared to other light sources used for plant production, leds have several properties which are potentially useful in relation to horticulture. However, although LEDs technology has raised strong interest in research for extraterrestrial agriculture, current LEDs panel costs are still too high for commercial adoption in greenhouse sector, and their electrical efficacies do not compete with those of high-pressure sodium lamps, but several manufactures are working to address these issues. When LEDs become practical, their ability to based light sources specifically suitable for photosynthesis and other horticulturally relevant plant properties (i.e. low radiated heat; lighting from within the canopy) will render the narrow band spectrum of LEDs of particular interest for providing light to greenhouse horticulture. A general description of LEDs application and their technical characteristics is briefly reported.
[it]L'applicazione di LEDs (Light Emitting Diodes) come fonte di radiazione luminosa per l'orto-floro-vivaismo in serra si prospetta di notevole interesse economico oltre che colturale ed energetico. Lo sviluppo della nuova tecnologia di semiconduttori luminescenti come fonte di luce si presta particolarmente per l'accrescimento di piante in ambienti chiusi e controllati di dimensioni ridotte. I LEDS consentono una fonte di luce fredda che non interferisce con le esigenze di un microclima controllato nei confronti della temperatura dell'aria interna di un ambiente protetto. Attualmente i sistemi LEDs disponibili presentano un tempo di vita medio superiore a quello delle lampade utilizzate per fornire luce artificiale nelle serre e una efficienza non inferiore alle efficienze elettriche di conversione che si avvicinano alle fonti tradizionali piu usate, con una produzione spettrale ottimale vicino a quella della fotosintesi. Recentemente, i LEDs hanno assunto grande importanza per le ricerche mirate allo sviluppo di sistemi vegetali alimentari per lo Spazio, tuttavia il loro impiego come fonte di luce artificiale nelle serre presenta ancora un costo relativamente elevato. In ogni caso, il forte interesse manifestato da numerose imprese e produttori del comparto delle produzioni vegetali in serra lascia immaginare nel breve periodo una veloce riduzione dei costi. Si riportano in breve i dati e le applicazioni piu recenti dei LEDs nel comparto dei sistemi serra.
[en] This paper reports an experimental and simulation study on application of automated Venetian blind for daylighting in tropical climate. A horizontal blind system operating automatically under programmed control was constructed and integrated onto the glazed windows to form a window system with an automated blind in a room of a laboratory building. A dimming controller was also integrated to the lighting system of the room. Different operation schemes of the window system were devised and tested in the attempt to maximize energy savings while maintaining the quality of the visual environment in the room. Intensive measurement of illuminance of the interior space was undertaken during the experiments. A methodology for calculation of interior daylight illuminance and associated glare corresponding to the configurations of the experiments was adopted. The method was coded into a computer program. Results of calculation from the program agree well with those from experiments for all the schemes of operation conducted. The program was used to simulate the situation when each scheme of operation was implemented for a whole year. It was found that such window system with automated blind enabled energy savings of 80%, but a more sophisticated scheme also helped maintain the interior visual quality at high level.