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Glasses, also known as eyeglasses or spectacles, are devices consisting of glass or hard plastic lenses mounted in a frame that holds them in front of a person's eyes, typically using a bridge over the nose and arms which rest over the ears. Glasses are typically used for vision correction, such as with reading glasses and glasses used for nearsightedness. Safety glasses provide eye protection against flying debris for construction workers or lab technicians; these glasses may have protection for the sides of the eyes as well as in the lenses. Some types of safety glasses are used to protect against visible and near-visible light or radiation. Glasses are worn for eye protection in some sports, such as squash. Glasses wearers may use a strap to prevent the glasses from falling off during movement or sports. Wearers of glasses that are used only part of the time may have the glasses attached to a cord that goes around their neck, to prevent the loss of the glasses.
A substantial reduction in the seamless rail joint, reducing the impact of rail wheels through joint, which saves line maintenance costs, prolong the service life of rail, abate the locomotive vehicle noise, etc., therefore, developed rapidly. In the 1930s, German and American railroads began to carry out small test lines, and by 1981, the world had laid a seamless line of about 300,000 kilometers, of which China lay about 8,000 kilometers
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