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A 1951 USAF resolution test chart is a microscopic optical resolution test device originally defined by the U.S. Air Force MIL-STD-150A standard of 1951. The design provides numerous small target shapes exhibiting a stepped assortment of precise spatial frequency specimens.
The chart contains rows of the letter "E" in various kinds of rotation. The patient is asked to state (usually by pointing) where the limbs of the E are pointing, "up, down, left or right." Depending on how far the patient can "read", his or her visual acuity is quantified. It works on the same principle as Snellen's distant vision chart.
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AN sizes range from -2 (dash two) to -32 in irregular steps, with each step equating to the OD (outside diameter) of the tubing in 1 ⁄ 16-inch increments. Therefore, a -8 AN size would be equal to 1 ⁄ 2 -inch OD tube.
An Electronic Navigational Chart (ENC) is a digital representation of a real-world geographical area for the purpose of Marine navigation.Real-world objects and areas of navigational significance, or to a lesser degree - informational significance, are portrayed through Raster facsimiles of traditional paper charts; or more commonly through vector images, which are able to scale their relative ...
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The main function of an OWSJ is to provide direct support for roof or floor deck and to transfer the load imposed on the deck to the structural frame i.e. beam and column. In order to accurately design an OWSJ, engineers consider the joist span between bearing points, joist spacing, slope, live loads , dead loads , collateral loads, seismic ...
The closed square butt weld is a type of square-groove joint with no spacing in between the pieces. This joint type is common with gas and arc welding. For thicker joints, the edge of each member of the joint must be prepared to a particular geometry to provide accessibility for welding and to ensure the desired weld soundness and strength.