LEUKOS
The Journal of the Illuminating Engineering Society of North America Volume 3 Number 3 January 2007
Editorial
Articles
MELVIN W. FIRST, KEVIN F. BANAHAN, AND THOMAS S. DUMYAHN
Seven years of experience operating upper-room ultraviolet irradiation systems (UVGI) in 14 homeless shelters in six cities has taught the Tuberculosis Ultraviolet Shelter Study (TUSS) many valuable lessons about maintaining uninterrupted UV services and acceptable intervals between UV lamp changes and cleaning activities. One year (9,000 hours) of continuous illumination resulted in a reduction in UVC output of the two types of low pressure mercury lamps by 17% for the quartz, instant start tubular lamp and 25% for the preheat compact lamps. The reduction over time was due to metal accumulations on the inside of the glass plus increasing opaqueness due to UV irradiation. Cleaning frequency was found to be highly site-specific. Lamp failure was infrequent and within the manufacturers’ stated life period.
QIFEI TU AND LI ZHOU
With the fast development of LED technologies, LEDs are potential light sources for automotive headlamps. This paper discussed the color differences of traffic signs under LEDs in comparison with the halogen lamp, and the importance of the detail spectral power distribution to the color rendering performance of the light source.
OWEN HOWLETT, LISA HESCHONG, AND JON MCHUGH
Metrics of the quantity and quality of daylight are essential for assessing whether buildings provide good or even adequate daylighting for the purposes of human health and wellbeing, visual comfort, and energy saving. At present there are only a few metrics of daylight that are used by designers and researchers. Most of these are very simple, they are based on illuminance and they do not have a proven record in research or usage. Luminance maps offer a richer source of data, and the potential to create new types of metric that will more accurately quantify the quantity and quality of daylight. Recent advantages in camera technology make luminance quick and convenient to measure and to record, opening the way to the development of new luminance-based metrics. This report investigates several potential luminance-based daylight metrics, using real data from surveyed spaces. The metrics are assessed for their stability over time, their ease, accuracy and repeatability of measurement, and their variation between spaces. Several luminance metrics are proposed as being suitable for further investigation and field trials, and eventual incorporation into design guidance.
STEFFEN FRANKE, HEINZ SCHOEPP, OLIVER LANGENSCHEIDT, RALF METHLING, HELMUT HESS, AND HARTMUT SCHNEIDENBACH
High-intensity discharge lamps (HID lamps) cover a wide range of applications. However, HID lamps contain mercury. For lower environmental pollution mercury-free HID lamps are under investigation. This article reports experimental results substituting mercury by noble gases. Lamps with neon, argon, and xenon are compared with a mercury containing pendant. In contrast to one-component plasmas containing only one of the elements Hg, Ne, Ar or Xe, multicomponent plasmas containing additionally TlI and TmI3 show a completely different behavior of their electrical and photometric properties, which are discussed.
FARHANG AFSHAR
Exciting acoustic resonances (ARs) in High Intensity Discharge (HID) lamps is an important cause of instabilities of the lamp discharge. When conditions for generating ARs are satisfied, the discharge instability occurs only after a time interval (onset time of the AR excitation). Measuring of the onset time for the occurrence of instabilities after satisfying conditions for the excitation of ARs helps in better understanding of this phenomenon. This paper addresses a measuring method for determining this time constant for different AR frequencies. For instance, in this work, an onset time for AR driven instabilities for an OSRAM HCI-T 70W WDL lamp is determined which is below 1 ms. Some other properties of the time response of the lamp discharge to adding or removing of a power ripple, such as its deflection time and its offset time is investigated.
