According to the US magazine "New Age of Science and Technology" reported on December 7, US military rations are usually freeze-dried viscous foods. They are rushing with such "unsubstantiated" food. The level of rations needs to be improved. . Recently, the United States military developed a world-class sandwich that is still fresh and edible after being placed for two years.
In general, the process of food spoilage is accompanied by a variety of chemical and biological reactions. Some reactions are caused by the food itself, and some are caused by external bacteria. However, these reactions require the participation of water and oxygen. Therefore, the U.S. military does not need to try to change the properties of ingredients to extend the shelf life of foods. They only need to find ways to keep the sandwiches away from water and oxygen.
In order to achieve these goals, food science experts begin by studying ingredients or ingredients such as sugar, salt, honey, etc., because they contain both water and moisture at the same time without leakage. A piece of fresh tomato on the sandwich will quickly soak the bread, but the jam or honey will not transmit water to the bread even if it is full of moisture. Using materials like the latter that can lock in moisture is the key to extend the shelf life of the food. Where
Isolating oxygen seems to be more difficult than isolating moisture. Scientists' practice is to pack the sandwich in a sealed bag and place a small package of oxygen in it. This small package is the size of a teabag and contains iron filings. Iron chips remove the oxygen inside the bag by rusting and further absorb the moisture that may be present in the air inside the bag.
Without water and oxygen, sandwiches can be kept in the bag for two years without rot. Surveys show that soldiers seem to like this kind of food.
1. Features of tape measure
Gift rulers are used for advertising and promotion. They are divided into Steel tape (steel tape) and leather tape (PVC plastic fiber tape). They are usually cute and compact. Tape measures are also called measuring tools. Eighty-five percent of the world's tape measures are exported from China.
2, the characteristics of the tape measure
(1) The tape measure is too deformed and will not fail
Why didn't it fail? The spring in the tape measure is very long, and its range from completely relaxed to fully tightened is very large. The entire stroke of the tape measure includes it, and there is a margin at both ends, so the tape measure will not fail.
(2) Pull one meter long and pull two meters long, there is no difference in tension
The spring of the tape measure is very thin, and the amount of deformation when it is tightened is also small, so the reaction force is very small, and the force change is not felt when the rule is pulled.
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