Mr. Yutao Zhou Profile

Yutao Zhou

at Rensselaer Polytechnic Institute

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Author

Publications (4)

SPIE Journal Paper | 1 November 2005

Photovoltaic-powered light-emitting diode lighting systems

Yutao Zhou, Nadarajah Narendran

OE, Vol. 44, Issue 11, 111311, (November 2005) https://doi.org/10.1117/12.10.1117/1.2130109

KEYWORDS: Light sources and illumination, Light emitting diodes, LED lighting, Light sources, Solar cells, Lamps, Photovoltaics, Solar energy, Buildings, General lighting

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Proceedings Article | 8 September 2005 Paper

The challenges of optically designing roadway lighting

John Van Derlofske, Michele McColgan, Yutao Zhou, Jie Chen

Proceedings Volume 5942, 59420A (2005) https://doi.org/10.1117/12.619969

KEYWORDS: Light sources and illumination, Optical design, Roads, Pollution, Nonimaging optics, Lamps, Prototyping, Fourier transforms, Reflectors, Computer aided design

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Proceedings Article | 20 October 2004 Paper

Performance of PV-powered LED lighting systems for buildings

Yutao Zhou, Nadarajah Narendran

Proceedings Volume 5530, (2004) https://doi.org/10.1117/12.561350

KEYWORDS: Light sources and illumination, LED lighting, Light emitting diodes, Light sources, Lamps, Solar cells, Photovoltaics, Buildings, General lighting, Solar energy

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Proceedings Article | 26 January 2004 Paper

Evaluation of light-emitting diodes for signage applications

Jean Paul Freyssinier, Yutao Zhou, Vasudha Ramamurthy, Andrew Bierman, John Bullough, Nadarajah Narendran

Proceedings Volume 5187, (2004) https://doi.org/10.1117/12.507875

KEYWORDS: Light emitting diodes, Neon, Modulation, Manufacturing, Diffusers, Light sources and illumination, Spatial frequencies, Temperature metrology, Lamps, Transmittance

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This paper outlines two parts of a study designed to evaluate the use of light-emitting diodes (LEDs) in channel-letter signs. The first part of the study evaluated the system performance of red LED signs and white LED signs against reference neon and cold-cathode signs. The results show a large difference between the actual performance and potential savings from red and white LEDs. Depending on the configuration, a red LED sign could use 20% to 60% less power than a neon sign at the same light output. The light output of the brightest white LED sign tested was 15% lower than the cold-cathode reference, but its power was 53% higher. It appears from this study that the most efficient white LED system is still 40% less efficient than the cold-cathode system tested. One area that offers a great potential for further energy savings is the acrylic diffuser of the signs. The acrylic diffusers measured absorb between 60% and 66% of the light output produced by the sign. Qualitative factors are also known to play an important role in signage systems. One of the largest issues with any new lighting technology is its acceptance by the end user. Consistency of light output and color among LEDs, even from the same manufacturing batch, and over time, are two of the major issues that also could affect the advantages of LEDs for signage applications. To evaluate different signage products and to identify the suitability of LEDs for this application, it is important to establish a criterion for brightness uniformity. Building upon this information, the second part of the study used human factors evaluations to determine a brightness-uniformity criterion for channel-letter signs. The results show that the contrast modulation between bright and dark areas within a sign seems to elicit the strongest effect on how people perceive uniformity. A strong monotonic relationship between modulation and acceptability was found in this evaluation. The effect of contrast seems to be stronger than that of spatial frequency or background luminance, particularly for contrast modulation values of less than 0.20 or greater than 0.60. A sign with luminance variations of less than 20% would be accepted by at least 80% of the population in any given context.

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