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In this work, a physics-of-failure (PoF) reliability prediction methodology is combined with statistical models to consider the interaction between the lumen depreciation and catastrophic failures of LEDs. The current in each LED may redistribute when the catastrophic failure occurs in one of LEDs in an array, thus affecting the operation conditions of the entire LED array. A physics-of-failure based...
Diverse solar irradiance spectra can be observed under different conditions of time, date, location, weather, etc. Since the solar irradiance spectrum is required by certain scientific and engineering applications, obtaining accurate spectral data is essential. Measurements by spectrophotometers are able to achieve accurate real-time data with high resolution, but at high expense. While in some engineering...
In this paper, the optical degradation mechanisms of mid-power white-light LEDs, were studied by using high temperature operation life tests, according to the IES standard LM-80-08. As a consequence, it is found that, (1) the degradation mechanisms are different for LED packages aged at different case temperatures; (2) the optical degradation is a result of combination of chip-related degradation...
In this paper, the thermal stability and the colour shifting of remote phosphor plates, made from Bisphenol-A polycarbonate (BPA-PC), are studied. In this study, the remote-phosphor and lens of BPA-PC samples of 3 mm thickness were thermally aged at temperature range 100 to 140 ºC. Results show that thermal ageing leads to a significant decrease in the luminous flux and chromatic properties of plates...
Light emitting diode (LED) as the new light source has the advantages of power saving, environment-friendly, long lifetime and no pollution compared with fluorescent and incandescent lights. But the disadvantage of LED is low light lumen that only 10%~20% input power transform into the light, and 80%~90% into the heat. The junction temperature of LED is so high as to induce the lifetime declining...
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