High-purity silica samples were implanted at room temperature with 2-MeV Si ions or sequentially with 2-MeV Si and 10-MeV Au ions. Three photoluminescence bands associated with the presence of defects are identified in the as-implanted samples. After a heat treatment at 1100 °C, a line appears at 750 nm in Si-implanted samples. This line is attributed to the emission from localized states in Si nanocrystals. At this temperature, the defects are only partially annealed. In the case of the samples implanted sequentially with Si and Au ions, the Si nanocrystal emission band appears, even without heat treatment
A high accurately theoretical analysis for high uniformity illumination distribution on the ceiling of indoor lighting LED system based on the super-positions is proposed and performed. Starting from the non-uniform illumination distribution of two LED sources, the dependences of the uniformity ratio on the height of the LED source and the length of the ceiling are investigated. The low intensity in the region near the side-wall can be avoided by rotating the LED source with a small angle, but the low uniformity illumination distribution at the center of the ceiling still exists. The aim of this work proposes the alternative design and approach for several configurations and demonstrates that can be obtained high uniform illumination distribution. The redistributed factor of the illumination through the lens is also considered and calculated. The investigation of this work will be a general guideline for designing the high uniform LED indoor lighting systems as well as being valuable materials for the LED lighting manufacturing industry.
Light is generally important for human beings. Visible light supports vision and can modify circadian rhythm, and together with invisible light at longer or shorter wavelength can also make either a direct or indirect impact on human biological and mental health. For medical applications, several studies have shown success in using light to fasten the skin regeneration in burns and to cure diseases such as newborn jaundice. In daily life, an appropriate amount and time exposure to certain types of light can result in rising of alertness and mood improvement, which leads to noticeable growth in one’s productivity. Therefore, human centric lighting can modify lighting factors to make the best of the natural characteristics of light. The seek an ideal indoor lighting system is widely carried out not only by scientists but also by architects. A qualified luminaire is considered by many factors, including luminous productivity, visual comfort and expenses; meanwhile, the idealization of illuminance is also constructed in many ways, such as widening the lamp’s surface area, changing of luminaire’s positions and applying different methods to illuminate a surface. Approaching these problems, our idea is to study the uplighting method and freeform optics using low-cost acrylic lenses. By changing lens shape and optimizing the factors which affect the illuminance such as the irradiation angle and the distance between the luminaire and the reflection surfaces, we find the most effective lens and its peaks due to each factors using the ray-tracing simulation to obtain results concerning high uniformity of illumination.
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