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It is also known as welding long rail line, which is a kind of line that welded normal rails without rail seam. The welding rail is not less than 200 meters long, and the actual application is usually 800~1000 meters or more. The long track is laid in the specified temperature range and fixed on the pillow. The long rail ends with a rail joint, while the middle part cannot scale up and down with the temperature. Therefore, there will be a great temperature pressure in the middle of the rail during the summer, which will produce a great temperature tension in winter. The greatest pressure on the rail and tension according to the years of rail laying and the highest temperature and minimum temperature calculation, rail tracks the maximum pressure should not cause to drum up by maximum tension should not cause rail fracture
A tyre is a circular, circular elastic rubber product that is rolled on various vehicles or mechanically. Usually mounted on a metal rim, it can support the body, cushion the impact, realize the contact with the road and guarantee the driving performance of the vehicle. Tyres are often used under the condition of complex and demanding, it when driving under various deformation, load, force and the function of the high and low temperature, so you must have high load-bearing performance, traction performance and buffer performance. At the same time, it is required to have high abrasion resistance and flexural flexibility, as well as low rolling resistance and heat resistance. Half of the world's rubber is used for tyre production, and the tyre is shown to use rubber.
Prevent the baby from getting calcium, first of all to breastfeed. Feeding the mother needs 1,200 mg of calcium a day. In the summer, after the birth of the child, the outdoor activities can be started in January, each day for 1~2 times, gradually increasing from 10 minutes to 1 hour. Can properly right supplement the right amount of vitamin D, as the children gradually big, should pay attention to diet diversification, correct the bad habit of partial eclipse, eat more food containing calcium and vitamins, such as dried small shrimps, black fungus, ribs, milk, liver, etc. In addition, nowadays many parents blindly do trace element detection for their children, in fact, do not need to. Six months or more children, if physical growth are within the normal range, nutrition is normal, no frequent respiratory tract, intestinal infection, generally do not occur the lack of trace elements, not blindly to check.
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