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At ordinary times, eustachian tube by extrusion and surrounding tissue in the export of nose pharynx ministry in closed state, but when the baby swallowing, chewing, sneezing, or crying, in order to maintain the balance of inside and outside the middle ear pressure, open eustachian tube is a moment. Because the baby's ear has not yet developed, eustachian tube is relatively short, low and flat, and position if you cross holding the baby, let him lie on your back with milk, milk bottle mouth open too large, bottles, vertical too straight, etc., are likely to cause the baby choking milk, and make the milk along the eustachian tube into the middle ear, induce otitis media.
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Space probe according to the detection of object is divided into lunar probe, probe and interplanetary spacecraft, small body such as a space probe to leave the speed of the earth must be large enough to overcome or get rid of the earth's gravity, realize the deep space flight. The probe orbits the heliocentric elliptical orbit (double-cut orbit) that is tangent to the earth's orbit and the planet's orbit, and may meet the target planet; Increase speed to change the orbit, flew to target the planet can shorten the time in order to ensure the detector fly the double track to the planetary orbits and tangent with the target when the target planets also run to it, must be chosen in the earth and the target planet at a particular moment of relative position detector. Detector can fly around the star, the use of planetary gravitational fields accelerate continuous multiple planets orbit the significant characteristic of space probe is, flying in space for long time, the ground cannot real-time remote control, so must have the ability of autonomous navigation; To fly outside the solar system, away from the sun, solar arrays, and nuclear energy systems; It is necessary to adopt special protective structure to withstand very severe space environment. Landing or walking on the surface of the moon or planet requires some special form of structure
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