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Microcontroller Hardware
Published in Syed R. Rizvi, Microcontroller Programming, 2016
The earliest discovery leading to the development of the liquid-crystal display (LCD) technology, the discovery of liquid crystals, dates from 1888. An LCD is a thin, flat electronic visual display that uses the light-modulating properties of liquid crystals (LCs). Figure 3.10 shows a low-cost LCD that can display 2 lines by 16 characters for a hobby project. An LCD controls the reflection of available light, whereas an LED display generates or emits light energy as current is passed through the individual segments. The available light may simply be ambient light such as sunlight or normal room lighting; reflective LCDs use ambient light. Alternatively, the available light might be provided by a small light source that is part of the display unit; backlit LCDs use this method. LCDs are used in a wide range of applications including computer monitors, televisions, instrument panels, aircraft cockpit displays, etc. They are common in battery-operated consumer devices such as video players, gaming devices, clocks, digital watches, calculators, and telephones due to very low power consumption compared to LEDs. On the other hand, LEDs have the advantage of a much brighter display, which, unlike reflective LCDs, is easily visible in dark or poorly lit areas.
Stand-Alone Photovoltaic Systems
Published in Roger Messenger, Homayoon “Amir” Abtahi, Photovoltaic Systems Engineering, 2017
Roger Messenger, Homayoon “Amir” Abtahi
In any case, once a light source and a suitable fixture for the source are chosen, for an outdoor lighting system, the available light from the fixture, expressed in lumens, can be obtained from the formula Lumens=(FC×area)/(CU)/MF/RCR), where FC is the desired illumination level in foot-candles, area is the area to be illuminated, measured in ft2, CU is the coefficient of utilization of the fixture, MF is the maintenance factor of the fixture, and RCR is the room cavity ratio. The coefficient of utilization of a fixture is a measure of the fraction of light available from the lamp that is directed to the surface to be illuminated. The maintenance factor of the fixture provides a means of estimating the amount of light from a fixture that can be lost as the fixture and lamp get dirty and the room cavity ratio is a measure of the amount of light from the fixture that will be absorbed by the room and its contents. A good fixture will have a CU of 0.8 or more and a MF of 0.9 or more. Of course, the MF is dependent upon the environment in which the fixture operates and the maintenance interval for the fixture. The RCR depends upon room size, wall color, floor color, and room contents. A room full of dark colors will appear darker because it is darker. Outdoors, the RCR is generally assumed to be 1.0. Indoors, the RCR is generally <1.
Light & Color
Published in Samuel Mills, Fundamentals of ARCHITECTURAL LIGHTING, 2018
The chart gives approximate correlated color temperatures for some more available light sources along with the comparative values associated with natural sunlight and skylight. Blue and white LED sources have a color temperature, others do not, and colors may be specified in a wavelength in nanometers (nm), at peak output. LED sources are not perfectly monochromatic, but have wavelengths over a small region of the spectrum. Some have a cool temperature at full output and a warmer color when dimmed.
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 the measured variation in the radiation intensity, an effort is made to evaluate the effect of the variation of light source strength on the temperature distribution in the human tissue. A commercially available light source of power rating 400 W is considered. The source from which the light intensity is emitted, is aligned at a height from the tissue in such a way that the centres of both the surfaces are inline. From the isolux diagram (Figure 2), it can be noted that the intensity on the considered domain varies such that it is highest at the centre. Figure 10(a) shows the comparison of both the constant and variable light source models. In this study, the domain size is fixed as 0.05 × 0.05 m. It can be noted that both the models yield similar temperature field at the centre. However, in the case of the variable light source model, a temperature drop of about 0.05 °C is observed due to higher intensity variation near the boundaries. Further, the comparative study of the temperature field after the cooling stage is made. Figure 10(b) shows the temperature along the horizontal symmetric line of the considered domain. It can be observed that the variation in temperature is not significant and varies in the range of 0.005 °C. Both the temperature profiles almost overlap with each other. Therefore, using the variable source model, it can be concluded that no such significant variation in the temperature field is noticed after the cooling stage. As a result, the same size and the location of tumour have been depicted by both the models.
Evaluating the feasibility of a personal particle exposure monitor in outdoor and indoor microenvironments in Shanghai, China
Published in International Journal of Environmental Health Research, 2019
Kan Wang, Fei-er Chen, William Au, Zhuohui Zhao, Zhao-lin Xia
The Plantower PMS 7003 is a low-cost (¥100), commercially available light-scattering particle monitor. Air is drawn through the sensing chamber by means of a convection current from a built-in fan. The precise working volume of the sensing chamber is 0.1 l. The air inside it will be exposed to a laser-induced light, and scattered light with specific angle is detected by a photo-diode detector. The laser wavelength was not available from the manufacturer, but the working laser wavelength of PMS 1003 was estimated at 650 ± 10nm with a Lambda 35 spectrophotometer (Kelly et al. 2017). There is a light-trap contained at the back of the chamber to prevent spurious scattering of laser light. While passing through the chamber, particles scatter light and the intensity of the light received by the phototransistor is directly correlated with the concentration of particles. The light scattering of particles falls into different regimes, and the Mie theory is applied to convert the light scattering into PM1, PM2.5 and PM10 concentrations.
Comparing Measures of Average Color Fidelity
Published in LEUKOS, 2018
To get a more complete picture of the differences between CIE Ra and IES Rf, a large set of 4945 SPDs with varied gamut shape was compiled. It includes the following: 211 Commercially available light sources from the TM-30-15 Calculator Tool Library, including: