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Remote Sensing Technique
Published in Ajai, Rimjhim Bhatnagar, Desertification and Land Degradation, 2022
The effect of absorption is to restrict the regions of the electromagnetic spectrum available for remote sensing. Therefore, the electromagnetic radiation that passes through the atmosphere without much attenuation, called atmospheric windows, is used for earth observation. The atmospheric window region covers 0.4–1.3, 1.5–1.8, 2.2–2.6, 3.0–3.6, 4.2–5.0, 7.0–15.0 μm and 1–30 cm. While designing/defining imaging sensors for the remote sensing satellites, those regions of the EM spectrum should be avoided which are heavily afflicted by the scattering and absorption by atmospheric molecules. Even within the atmospheric window, there are absorption bands due to molecules which should be avoided while choosing the spectral region for observation.
Passive and Free Cooling of Buildings
Published in Atul Sharma, Amritanshu Shukla, Renu Singh, Low Carbon Energy Supply Technologies and Systems, 2020
Sašo Medved, Suzana Domjan, Ciril Arkar
The common feature of both techniques of natural cooling is that they exploit the natural processes of cold generation, such as radiative or evaporative cooling and environment cold. The cold of the environment is a phenomenon that results from the transfer of heat from the surface of the earth through an “atmospheric window” to the space, whose temperature is near to the absolute zero (0 K). This process occurs throughout the day but is more noticeable at night, since the surfaces then do not receive solar irradiation. The “atmospheric window” is radiative property of Earth’s atmosphere that transmits almost all irradiation with wavelengths between 8 and 12 μm, which are exactly the wavelengths at which the environment surface areas and buildings envelope structures emit the largest heat flux. In nature, the effect of environment radiate cooling can be noticed in the cold stored in ambient air as well as in the shallow layer of the soil. Another natural phenomenon that can be utilized by passive as well as by free cooling is the evaporation of water droplets into the outdoor or indoor air. To evaporate, energy needed is transferred from the surrounding air. This has happened on the leaves of greenery and trees and on water surfaces. As a result, air is moisturized but cooled as well.
Air pollution and climate change
Published in Abhishek Tiwary, Ian Williams, Air Pollution, 2018
Note that the wavelength scale of the solar radiation spectrum has been expanded relative to that for terrestrial radiation. High absorption can have no influence if there is no radiation there to absorb, and although GHGs are effective absorbers in the 1–5 μm region, there is little longwave energy there due to the separation of the black-body distributions. Between 5 and 20 μm all the GHGs have important absorption bands, and above 20 μm the atmosphere is opaque due to absorption by water vapour. The region between 8 and 13 μm (the narrow spike centred on 10 μm in Figure 11.8) is known as the atmospheric window because its relative transparency allows the passage of radiation to the ground from space and vice versa. Water vapour absorption is confined to bands – for example, the high absorption between 5 and 8 μm is due to one such band. Water is not active in the window between 8 and 13 μm, although there is a narrow absorption band at 9.7 μm due to ozone. Beyond 14 μm, transmission is suppressed again by both water vapour and carbon dioxide.
The formation and properties of glasses based on Ga2S3-Bi2S3 system
Published in Journal of Asian Ceramic Societies, 2020
Kohei Kadono, Mikiya Furukawa, Shigeru Yamamoto, Takashi Wakasugi, Arifumi Okada
With increased attention on security and safety in society, the demand for infrared surveillance systems is growing rapidly. These infrared systems generally use infrared radiations in wavelengths ranging from 3 to 5 μm and 8 to 13 μm; these wavelength ranges are known as atmospheric windows [1–4]. The radiation from a black body at approximately 310 K, the human body temperature, has a spectrum with a peak at 9.4 μm expanding a tail to the long-wavelength side. Thus, it is very important to build up infrared systems composed of optics, utilizing materials that are transparent in the infrared region covering the latter range of the atmospheric windows. To data, crystal materials, i.e. germanium and zinc selenide, have been conventionally utilized to fabricate these optics. However, the lower formability of the crystals causes the poor cost performance of these materials.
Research on heat reflective coating technology of asphalt pavement
Published in International Journal of Pavement Engineering, 2022
Yuanzhao Chen, Zhenxia Li, Siqing Ding, Xiaolan Yang, Tengteng Guo
Functional fillers refer to the materials that are involved in cooling function in the coating, and play a decisive role in the heat reflection performance of the coating. As the main functional filler, Titanium dioxide has the characteristics of high refractive index, strong light scattering ability, high UV shielding, strong stability and oxidation resistance, high reflectance ratio to near-infrared radiation and significant shielding of solar thermal radiation. However, in view of the high cost of titanium dioxide, diatomite and hollow glass beads, which also have a cooling function, were used to replace some titanium dioxide in the coating to reduce costs. Due to the weak absorption ability of the atmosphere in the wavelength range of 8 ∼ 13.5 μm, and the infrared radiation intensity in the atmosphere is mainly derived from the radiation of water vapour, CO2, O3 and suspended particles in the atmosphere by studying the relationship between the infrared radiation intensity and the wavelength and direction, in which the absorption ability of CO2 and water vapour in the wavelength range of 8 ∼ 13.5 μm is weak, so the external radiation in this range has a strong penetrating power on the atmosphere, which can send energy directly to the outer space; this wavelength range is called ‘infrared window’ or ‘atmospheric window’ in related fields (Li 2016). According to Kirchhoff’s law, a good absorber must also be a good emitter. The absorption peak of silica at 1100 cm−1 (wavelength about 9 μm) is strong and wide so that it can absorb the solar radiation in the wavelength range of 8 ∼ 13.5 μm, and then emit it to the external space through the atmospheric window, to reduce the temperature of asphalt pavement and alleviate the heat island effect in cities. Thus, silica was also added as the functional filler. Additives