US: people are ice-skating at the beach and walking on the ocean
hya hya.net 2018-01-12 18:57:10
US: people are ice-skating at the
beach and walking on the ocean
It's so cold in the United States people are ice-skating at the beach and walking on the ocean.While the cold snap blanketing the United States and Canada has ravaged some parts, it has given some people the opportunity to ice-skate and walk on water.
The weather is so cold that you need some advice about keep warm. Let's see some scientific knowledge to learn how to keep warm.
The body is a thermostat, and itself is a source of heat, which produces heat continuously. These calories need to be released. If the heat is released less or slower, the body will feel hot, such as summer. If the heat is released more or faster, the body will feel cold, such as winter. When the body feels cold, it will consciously add clothes. It's not a human instinct to add clothes, but a life experience. Why do you keep warm when you add clothes? The so-called warmth, in fact, is to prevent the loss of heat.
There are mainly three forms of heat loss: heat conduction, thermal convection and thermal radiation. Heat radiation means that every heating body will radiate electromagnetic waves to the surrounding area. The form of heat propagation is mainly reflected in the microscopic field. In the 80s of *20 century, the new material of space cotton developed for astronauts by the US was to add aluminum foil to the fibers, which led to the radiation of the human body radiated back to the body by the aluminum foil, while accelerating the movement of the human cells and completing the insulation effect. If you wear a piece of iron made of clothes, it will feel cold, because the iron is a good heat conduction body, the heat conductivity is very high. The thermal conductivity of commonly used clothing materials is relatively low, of which the lowest thermal conductivity of down is (5.930), and the thermal conductivity of wool is about 15% higher than that of down. (6.986), and the thermal conductivity of cotton is about 39% higher than that of down. (9.717). In addition, there is an indicator that can measure the heat conduction effect of the fiber, which is the heat preservation rate. The higher the value, the better the heat preservation effect. The heat preservation rate of eiderdown is the highest (81.3%) in common fibers, and the insulation rate of wool is about 6.5% lower than that of down products (74.81%), and the insulation rate of cotton is about 18% lower than that of down ones (63%).
The combination of heat conductivity and heat preservation rate two can draw the conclusion that the warmth retention effect of the feather is best under the same thickness. However, although the numerical value is superior, but if the thickness of wool or cotton and other materials is increased, the heating effect can exceed the feather. This is in line with the experience of human life: the thicker the clothing is, the warmer it is. Human beings have another experience of life: the thicker the clothes become, the more clumsy. Besides, the fiber with good heating effect is still unable to achieve 0 thermal conductivity and 100% heat preservation rate. Can do so "absolutely warm" material, only air. For example, the "double glazing" often installed on the windows of the home, with a layer of air between the two layers of glass. In a room with double glass, it usually feels warmer.
It's a good thing to sleep on a soft warm mattress when you feel cold.
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