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Lighting
Published in Stephen A. Roosa, Steve Doty, Wayne C. Turner, Energy Management Handbook, 2020
Eric A. Woodroof, Stan Walerczyk, Fred Hauber
Lumen: A unit of light flow, or luminous flux. The lumen rating of a lamp is a measure of the total light output of the lamp. One lumen is equal to the amount of light emitted per second in a unit solid angle of one steradian from a unit source of one candela.
Lighting
Published in Richard Vaillencourt, Simple Solutions to Energy Calculations, 2020
A lumen is equal to the luminous flux through a unitsolid angle (steradian) from a uniform point source of one candela, it is also equal to the flux striking a unit surface all points of which are at a unit distance from a uniform point source of one candela.
Glossary of Computer Vision Terms
Published in Edward R. Dougherty, Digital Image Processing Methods, 2020
Robert M. Haralick, Linda G. Shapiro
Luminous flux is radiant power evaluated according to its capacity to produce visual sensation. Luminous intensity in a given direction is measured in terms of luminous flux per steradian. The unit of luminous intensity is the candela. The luminance of a black body radiator at the temperature of solidification of platinum is 60 candelas per square centimeter. The unit of luminous flux is the lumen. The luminous flux emitted by a uniform point light source of luminous intensity of one candela in one steradian solid angle is one lumen.
Discomfort Glare from a Cyclic Source in Outdoor Lighting Conditions
Published in LEUKOS, 2022
Joffrey Girard, Céline Villa, Roland Brémond
In outdoor lighting, most models predict the mean level of discomfort from glare with respect to the background luminance (in or ) and to three factors characterizing the source (labeled here as “main factors”): its luminance (in or ), its solid angle (in steradian) and its eccentricity (in degree) in the observer’s field of view.2In most indoor lighting models, the Guth position index is preferred instead of . Most of these models have been established in static conditions, i.e. when the observer and the light sources are motionless and the sources’ main factors are constant over time. However, at night, road users see glaring lights (luminaires and/or headlamps) scrolling. Therefore, dynamic situations should also be considered, i.e. where the observer is in relative motion with respect to the light sources and the sources’ main factors are varying over time.
Effects of neighbourhood morphological characteristics on outdoor daylight and insights for sustainable urban design
Published in Journal of Asian Architecture and Building Engineering, 2022
Illuminance level (E) refers to the luminous flux per unit area of visible light (lumens, symbol: lm)4One lumen (1 lm) is defined as the luminous flux of light produced by a light source that emits one candela of luminous intensity over a solid angle of one steradian (1 cd). (Eq. 1), which represents the intensity of illumination on a given surface and is denoted by lux (symbol: lx). 1 lx is equal to 1 lumen per square meter (l lx = 1 lm/m2) (Fotios 2017). When a given surface is illuminated by multiple light sources simultaneously, the total illuminance of the surface means the sum of the illuminance generated by each light source. The horizontal illuminance level (HIL) of the site surface determines the adaptation of the eyes in the field of vision and serves as a visual background to highlight the target object. At present, HIL is a widely used lighting parameter in indoor and outdoor daylighting environment design (CIE 2000).
Study of hot stress dynamic IR thermography for detecting surface cancerous tissue
Published in Journal of Medical Engineering & Technology, 2020
Uddip Kashyap, Subhasish Sarkar, Sandip K. Saha
With an initial study of the model in a considered domain of area 0.05 × 0.05 m2, an effort is made to study the effect of the increased area by changing the solid angle value to 4 and 6 steradian, respectively. The limitation of consideration of solid angle comes at 6.28 when the exposure constitutes of a half-sphere. As the solid angle is varied to 4 steradians, the exposed tissue domain becomes a square of the length of 0.07 m. All other parameters are kept fixed from the previous consideration. As the total intensity from the source emitter remains constant, the overall strength is reduced due to the increase in domain size, as shown in Figure 11(a). It is observed that heating of the considered domain yields lower overall temperature of about 39.4 °C, as shown in Figure 11(b), in comparison with 41.6 °C for the domain size of 0.05 m. Further, the cooling of the considered domain is initiate for a period of 140 s. After cooling for 140 s, a temperature difference of approximately 0.6 °C is observed, which is due to the lower rate of heating of the considered domain size. This lower rate produces a lower temperature gradient between the healthy and malignant cells as the overall strength of the light source reduces.