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Sunglasses allow better vision in bright daylight, and may protect one's eyes against damage from high levels of ultraviolet light. Typical sunglasses are darkened for protection against bright light or glare; some specialized glasses are clear in dark or indoor conditions, but turn into sunglasses when in bright light. Most sunglasses do not have corrective power in the lenses; however, special prescription sunglasses can be ordered. Specialized glasses may be used for viewing specific visual information (such as stereoscopy) or 3D glasses for viewing three-dimensional movies. Sometimes glasses with no corrective power in the lenses are worn simply for aesthetic or fashion purposes. Even with glasses used for vision correction, a wide range of designs are available for fashion purposes, using plastic, wire, and other materials.
Reverse flushing can be done automatically: the backwash is done by hydraulic valve opening and hydraulic cylinder pistons, which are controlled by the backwash controller. The anti-flushing controller can accurately control the hydraulic valve and hydraulic cylinder according to the differential pressure value from the filter inlet and outlet, and the power of the controller comes from the pressure of the line itself.
Is a new type of ballastless track, with reinforced concrete slabs, and under the big board with emulsified asphalt cement mortar as the first adjustment layers (or overlay on a cushion of high molecular elastic material layer) consisting of orbit. This kind of track is suitable for stone roadbed or non - ballasted deck. The asphalt concrete bearing layer shall be installed on the soil foundation. This kind of track integrity is good, the line is stable, the maintenance workload is small, but the cost is high, the construction period is long. Japanese railways have been used in the Shinkansen
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