The Physics of Human Thermography
James Stewart Campbell, M. Nathaniel Mead in Human Medical Thermography, 2023
The term “emissivity” in thermal imaging refers to the ability of a surface to emit or absorb radiation within 9–10-μm infrared range. The range of emissivity runs from 1.0 (the ideal emitter/absorber) to 0.0 (the ideal reflector). In physics, a blackbody is an object that has an emissivity of 1.0. None of the incident radiation is reflected from or passes through a perfect blackbody. Thus, a blackbody completely absorbs all radiant energy reaching it, and simultaneously emits radiant energy. If not otherwise heated or cooled, it eventually attains a temperature equal to its environment and then maintains that energy balance.
Protocol for Standardized Data Collection in Humans
U. Snekhalatha, K. Palani Thanaraj, Kurt Ammer in Artificial Intelligence-Based Infrared Thermal Image Processing and Its Applications, 2023
Thermal images obtained under uncontrolled conditions cannot be analyzed in a scientific way, since they have anecdotical value at best. A major source of uncertainty in both the image content and thermometry results is the location where thermal images are recorded. Thus, infrared thermal images used in medicine must be recorded under controlled conditions in a specially designed examination space. The room should have a minimum size of 2 × 3 m, but larger rooms are preferable. The budget for estimating the least distance in one direction includes the following:30 cm distance from the wall to the subject to be imaged plus30 cm distance between the wall and camera operator plus1 m distance behind the camera to operate the camera and its controlling computer plusThe distance between the camera and an individual to take an image of the upper or lower part of the human body or an object of 1.2 m height. For total body thermograms, the distance must be calculated for an object of 2.2 m height. This distance portion is determined by the optical features of the lens such as the field of view.Other important structural features of the examination room are:Blacked out or obscured windows with double glazing.Fluorescent not tungsten or halogen lighting.Non-reflective surfaces where possible. Since emissivity and reflectivity are surface properties, surface roughness is of higher importance than surface color. A shiny, and smooth, black-colored surface reflects more incident radiation than a mat, slightly rough surface in white color.Water supply and a wash basin are helpful when cold water provocation should be conducted.Temperature control of the examination room is a prime requirement. The air conditioning equipment should be located so that direct draughts are not directed at the subject being imaged, and that overall air speed is kept as low as possible (less than 0.3 m/s). Air flow directed to the hoofs of a horse at speeds ranging from 0.5 to 1 m/s over 1.3–2 to 3–4 m/s affected the temperature reading from thermograms recorded in this condition (Westermann et al., 2013). A suspended perforated ceiling with ducts diffusing the air distribution evenly over the room at air-flow speeds between 0.1 and 0.13 m/s is ideal. Calculation of heat load per room/person was proposed (Love, 1985). The air conditioning system should stabilize room temperature for 1 hour within ± 0.5°C.
Modeling and investigating the effect of parasol installation on solar radiant temperature reduction using COMSOL Multiphysics
Published in International Journal of Occupational Safety and Ergonomics, 2023
Farideh Golbabaei, Esmaeil Karami, Majid Shahi, Zahra Safari, Kaykāvus Azrah
The total diffuse outgoing radiative flux at any point is called radiosity (J). This radiosity is the sum of diffusively reflected and emitted radiation: ϵ = surface emissivity (unit: 1), a dimensionless number in the range 0 ≤ ϵ ≤ 1 (the diffuse-gray surface hypothesis corresponds to surfaces where ϵ is independent of the radiation wavelength); eb(T) = blackbody hemispherical total emissive power (W/m2), which according to the Stefan–Boltzmann law is the power radiated across all wavelengths and depends on the fourth power of the temperature; T = surface temperature (K); ρd =reflectivity fractions of body; G = incoming radiative heat flux, or irradiation (W/m2).
Hygro-thermo-mechanical performance of wheelchair cushion technologies in the prevention of pressure ulcers and moisture-associated skin damages
Published in Assistive Technology, 2023
Fabien Bogard, Guillaume Polidori, Sébastien Murer, Chadi Maalouf, Yannick Blancheteau, Hervé Quinart, Fabien Beaumont
In order to determine the role played by each type of cushion in heat evacuation, an experimental methodology has been developed. Regarding the acquisition of thermal mappings, emissivity variations were avoided and constant environmental reflection was ensured by capturing all infrared images perpendicularly to the seat. The “thermally thin” properties of the wheelchair seat material were initially assessed. This hypothesis consists in assuming that the thickness of the fabric is small enough to consider that the thermal field is identical on both faces of the seat. Once verified, all further infrared thermography images, whether with or without cushions, were captured on the top surface of the seat material after the participant had seated for 45 minutes. The cushion was then quickly removed, ensuring immediate image acquisition. This procedure is mandatory, due to the “thermally thin” characteristics of the seat material: the thermal field may evolve within seconds once the heat source (i.e., human body) is removed. Two states were therefore defined. The first state, called reference state, consists in positioning the subject directly on the seat fabric and calculating the heat flux
Infrared thermography as control of handheld IPL device for home-use
Published in Journal of Cosmetic and Laser Therapy, 2018
Hrvoje Glavaš, Marko Vukobratović, Tomislav Keser
Specific measurement spot where the skin temperature is close to the body core temperature is in the corner of the eyes where the lacrimal or tear duct comes to the surface (23). Infrared thermal camera does not measure temperature, in fact, it just records thermal radiation from surface. Software embedded in camera presents apparent temperature according to the input parameters and most important parameter in that process is emissivity. FLIR emissivity tables recommend value of 0.98 for skin. The emissivity of human skin, according to data from 1973, is constant value of 0.98 for very dark skin and 0.97 for light skin between wavelengths of 2 and 14 µm. For forehead skin emissivity of 0.98 should be used according to (24).
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- Reflectance
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