3. Skin thermal behavior

The human body emits electromagnetic radiation, like all bodies [22]. Since its temperature is close to that of the environment (~300C), the entire spectrum of this radiation lies in the area of thermal infrared. At the same time, our body absorbs thermal radiation from the environment. The skin emits as nearly perfect black body (emissivity = 0.98) and based on the Wien's law, the wavelength for the maximum of its emission is at 9.5 μm. Therefore, thermal imaging devices such as thermal infrared cameras designed for human body inspection operate in the range of 7–14 μm.

• 0.2–0.3 mg/mL: The person has a slight euphoria and shyness, a laxity, a loss of coordina-

• 0.4–0.6 mg/mL: The person can have a sense of well-being, relaxation, reduction of inhibitions, warmth, and euphoria. It may also present some minor thought and memory dysfunction, attention deficit reduction. Finally, feelings may be more intense and behavior

• 0.7–0.9 mg/mL: The person thinks he can work better than he actually does (overestimating his potential). There will be little decrease in balance, speech, vision, hearing, and reaction time. He is euphoric. His judgment and self-control are diminishing.

Driving with a blood alcohol concentration of 0.8–2.9 mg/mL is a criminal offense and if the person is legally drunk. Also, if the alcohol concentration in the blood is above 3.0 mg/mL,

The relationship between alcohol concentration in the blood and alcohol in the exhaled air should be highlighted. The amount of alcohol contained in 1 mL of blood is the same as the amount of alcohol contained in 2100 mL alveolar air. This corresponds to 0.24 mg/L of alveolar air. According to the above, for an average adult weighing 300–400 mL of pure alcohol, death

Alcohol contained in a drink is almost absorbed by the gastric tube. The absorption rate of

• The fullness or emptiness of the stomach. Full feed slows absorption while full absorption

• The type of food in the stomach: fatty foods cause a greater deceleration in albumin

• The type of drink: beverages with CO2 (carbonate) are absorbed faster because carbonate

• The alcohol content of the beverage: beverages with 10–20% alcohol are absorbed faster. • Individual factors: alcohol dependence (chronic drinkers), mood, particularity of gastric

Alcohol is distributed more rapidly to the tissues that have the greatest perfusion, but over time, it is redistributed everywhere. The greater the amount of water contained in a tissue, the more it is influenced by alcohol, for example, blood and nervous tissue. Conversely, it occurs in

The human body emits electromagnetic radiation, like all bodies [22]. Since its temperature is close to that of the environment (~300C), the entire spectrum of this radiation lies in the area

is between 2 and 3 hours instead of 45–90 minutes (most people after 1 hour).

tion and perhaps a little dizziness.

148 Human-Robot Interaction - Theory and Application

death occurs from alcohol poisoning.

alcohol depends mainly on:

absorption while less starch.

and intestinal mucosa.

3. Skin thermal behavior

fat and bone tissues.

ions accelerate stomach emptying.

Finally, attention, logic and memory are diminishing.

more intense.

occurs.

The use of infrared radiation has become popular as infrared thermography [22] in medicine, since the 1960s to record the temperature of human skin. Infrared thermography is the technique that measures the heat (infrared radiation) emitted by the body and displays the temperature distribution on the surface of the body. Measurements are made with special cameras that detect infrared without coming into contact with the body. The intensity of the thermal radiation is transformed into an electrical signal and this in a color thermogram, in which the hottest spots are presented in stronger colors. An infrared image is an optical map of surface skin temperature that can provide accurate temperature measurement but cannot quantify blood flow on the skin. In order to explain the thermographic images, it is necessary to have a good understanding of the physiological mechanism of blood flow on the skin and the factors that affect the heat transfer to it. From our understanding regarding blood flow on the skin, heat transfer between tissues and skin temperature has changed rapidly over the past 40 years, allowing us to better represent and understand thermal measurements. At the same time, the improvement in camera sensitivity coupled with improved CCD technology and the development of computational imaging systems have improved the noninvasive thermography method.

Modern technology provides accurate temperature measurement with accuracy better than 0.05C without getting in or touching the skin. These systems produce high-resolution images at high speed and the measurements are quantitative. When measuring the temperature of the skin under the influence of a cold environment, its temperature distribution is heterogeneous. On the contrary, the temperature distribution of the skin is more homogeneous in warm conditions. During exposure to heat or intensive exercise, the blood flow in the skin may be increased in order to increase the consumption potential. When the human being is exposed to a cold environment, the surface of the skin restricts the flow of blood and thus becomes a perfect insulator. In these hypothermic conditions, our skin works to maintain the core body temperature.

Another procedure for controlling blood flow to the skin is dynamic thermography which includes local cooling or heating of the skin [23]. The ability of blood to transfer heat between the various levels of tissues to the skin can be predicted by models. These models are based not only on conductivity, tissue density, specific heat, and temperature of the tissues, but also their metabolic needs as well as the speed flow of the blood. A disadvantage of infrared thermography is that it cannot directly demonstrate that the increase in temperature is due to the increase in blood flow. One way to prove this is to combine infrared thermography with other direct blood flow control techniques such as Laser Doppler.
