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World’s first discovery of a new indicator of human thermal status


Thermal comfort is judged based on two indicators: skin temperature and skin conductance. However, a model for determining human thermal comfort using two indicators is problematic in that it has a low coefficient of determination and low reliability of judgment. This created a need to discover a new indicator of human thermal comfort, capable to resolve the issue.

World’s first discovery of a human comfort indicator

People are becoming increasingly interested in health. The abundance of health-related information allows us to look after our physical health, but the importance of mental health is often unrecognized. Different people experience different emotions, and a person experiences different emotions depending on the time of day and situation. However, the focus is usually on analyzing air temperature, humidity, and other aspects of the surrounding environment without examining the signs of emotions apparent in people. Professor Young-Ho Cho and his research team are aware of the importance of mental health and have focused on the methods to measure mental health for a decade. In particular, they have concentrated their efforts on developing a simple and accurate method to identify human emotions such as comfort, impression, and stress. Later they became the first researchers in the world to discover new physiological skin signs, including skin elasticity and goose bumps, capable to identify and judge human emotions.

Value and effects of human thermal comfort measured through skin hardness

The thermal comfort experienced by humans can be determined based on variations in skin temperature and skin conductance. While previous methods examined only skin temperature and conductivity, Professor Cho and his research team observed skin elasticity based on the hardening of skin in colder temperatures and identified a new index that increases the accuracy and reliability of thermal comfort judgments. They attracted the attention of renowned overseas journals and media as they were the first in the world to consider the hardness of skin as an indicator of human thermal comfort.

First, the research team conducted a study on 30 participants to establish that skin hardness is independent of existing indicators. The results found that the variance inflation factor of skin hardness, skin temperature, and skin conductance was in the range of 1.68~2.04, which suggests that skin hardness is independent (variance inflation factor of 5 or less) of skin temperature and skin conductance. The coefficient of determination for skin hardness (0.6302) was similar to that for skin temperature (0.5414) and perspiration rate (0.6176), providing experimental evidence that skin hardness is an effective indicator for judging human thermal comfort. The present study added skin hardness to existing thermal comfort indicators (skin temperature, skin conductance), thereby increasing the coefficient of determination by 17.6% and reliability of judgment by 23.5% to produce a more reliable human thermal comfort model. The findings are expected to have a major impact on new industry/business creation as they can be applied to such devices as personalized smart air conditioners by learning individual models. Based on these research findings, Professor Cho is developing a technology to determine the prognosis or status of cancer by using physiological signs apparent on the surface of cancer cells. “A technology is important not in its own right, but according to the purpose it will be used for,” he emphasized, adding that he will strive to demonstrate the effectiveness of new artificial intelligence in biological or medical fields to evaluate the mental or physical status of humans using physiological signs as indicators.

Prof. Young-Ho Cho
2018 KI Annual Report


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