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Light Pollution and Prevention: An Introduction
Published in Tuan Anh Nguyen, Ram K. Gupta, Nanotechnology for Light Pollution Reduction, 2023
Abhinay Thakur, Richika Ganjoo, Ashish Kumar
Power consumption is increasing rapidly in today’s world due to urbanization in both established and emerging cities. Increased demand must be addressed, which may pose issues with existing systems and infrastructure. Furthermore, some negative effects of human activities inflict substantial harm to the environment (therefore energy resources), humans, and nature, as well as disrupting economic, societal, and environmental balances. For the environment, selecting the appropriate lighting product is critical. The most common reasons for streetlight lighting nowadays are investment rates and energy conservation. However, making the best decision is significantly more difficult. Though there’s an ongoing argument about the life term of LED tech and maintenance fees under various real-world settings, the technology’s energy effectiveness and the relatively minimal maintenance demands of long-lasting LED modules appear to substantiate the sustainability claim. However, LED devices are rapidly being offered and used for outdoor illumination as well as indoor lighting. Short-wavelength illuminants, such as metal halide or LEDs, can drastically enhance skyglow, inhibit melatonin, and interrupt sleep cycles. Furthermore, this blue-rich light causes glare, which reduces vision for the aged. To maximize the energy consumption of cold-white LEDs, filters that modify the spectral electric grid and produce warm-white light are required.
Fundamentals of Visible Light Communication
Published in Mohsen Kavehrad, Reza Aminikashani, Visible Light Communication Based Indoor Localization, 2019
Mohsen Kavehrad, Reza Aminikashani
As mentioned earlier, VLC systems mostly use semiconductor LEDs as transmitters due to their advantages and rapid developments in LED fabrication. Currently, lighting LEDs offer a transmission bandwidth range between 20 MHz to over 100 MHz, and as shown in Fig. 2.2, one LED bulb is composed of a number of LED chips. LED lighting offers many advantages over conventional lighting, such as low power consumption, low cost, high luminance efficiency, long lifetime, etc. For these reasons, LEDs have become strong in the lighting market compared to traditional lighting solutions [2]. Besides these advantages, the intensity of the light emitted by an LED light can be modulated rapidly as it is a semiconductor device. This way, the LED combines its function of lighting with that of a data communication transmission system. It should be noted that LEDs are an incoherent light source, that is, LED light is not monochromatic and LED generates light with a broad bandwidth.
Light Sources
Published in Toru Yoshizawa, Handbook of Optical Metrology, 2015
There are two basic types of LED emitting configurations: surface-emitting LEDs and edge-emitting LEDs. Schematic illustrations of both structures and the corresponding emission patterns are given in Figure 1.19. The light output of surface-emitting LEDs exits the device through a surface that is parallel to the plane of the active region, while an edge-emitting LED emits light from the edge of the active region. A quick comparison between both LED configurations shows that surface emitters have relatively simpler structure and are less expensive but have much larger emitting area (circular area with diameters of typically 20–50 μm). Therefore, the total LED optical output power is as high as or higher than the edge-emitting LEDs. However, the larger emitting area in addition to the Lambertian radiation emission pattern (light is emitted in all directions) and the low-to-moderate operating speeds impose limitations on the use of surface-emitting LEDs in fiber-optic communication systems, which require fast response time and high coupling efficiency to the optical fiber.
Sustainable partner selection and order allocation for strategic items: an integrated multi-stage decision-making model
Published in International Journal of Production Research, 2023
Chong Wu, Jing Gao, David Barnes
As one of the leading LED lamps manufacturers in China, Company Q designs, manufactures and sells high-end LED lamps and solar cells. Gallium arsenide substrate (GAS) is one of the key raw materials for LED lamps. The production of LED lamps is completely dependent on a sustainable supply of GAS, which has a very limited number of partners around China. At the same time, the LED lamp industry has significant potential environmental pollution problems due to the involvement of highly risky chemical materials (e.g. arsenide). Thus, how to achieve sustainable development is a prominent issue for the industry. Moreover, it is very difficult to check the quality of GAS raw material in the initial production phase of LED products manufacturing. The investigation of the quality of LED lamps, for instance for brightness and colour, can only be checked after the manufacturing process. If raw materials have a quality problem, this will result in a great loss of economic value, time, and reputation for Company Q. Therefore, it is vital to select the right partners and build a long-term partnership with excellent partners. With these goals in mind, Company Q requires an effective and efficient decision-making process and procurement solution.
Concurrent Solar-Illumination and Power Line Voice Communication for Indian Underground Coal Mines – An Experimental Study
Published in IETE Journal of Research, 2022
R. N. Raul, T. Maity, S. Palit
The conventional lamps may be replaced with modern LED lamps with suitable lumen capacities operating on LVDC (24 V DC) system powered by solar PV systems. LED lamps have some important advantages over the existing lighting systems such as energy efficiency, free from conversion losses, lower power consumption, less heat generation, greater life span, almost maintenance free, and being easily expandable [24]. Additionally, this LVDC system needs no shut down during disaster as its voltage is within the allowable intrinsically safe voltage level of 30 V [25]. Further, the use of such low voltage eliminates the statutory requirement of flame-proofing. In underground coal mines, the load due to lighting is 1–3% of the total load requirement [26]. As the lighting system in underground mines is in operation round the clock, the efficient use of low-powered LED lamps is bound to result in cost and energy savings at a considerable level.
Temporal Luminescence of Broadband Light-Emitting Diodes and Their Use for Generating Customizable White Light
Published in LEUKOS, 2020
Faiz Rahman, Anthony F. George
The second, related, topic that was studied in this work was the influence of the temporal luminescence behavior of LEDs on the synthesis of white light through color mixing. RGB LED color mixing is widely used for generating tunable wide spectrum white light (Muthu et al. 2002; Srividya et al. 2015). The light intensity of each LED is controlled by driving it with a pulse width modulated (PWM) waveform where the duty cycle determines the brightness of the LED (Lo et al. 2009; Okumura et al. 2018). In this case, LED luminescence buildup and decay times of several hundred microseconds to a few milliseconds are involved. Light fluxes from different LEDs then vary in time and PWM duty cycle can be used to control the chromaticity of white light generated through color mixing, as we show below.