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Ballistic sunglasses or prescription eyeglasses must meet the same requirements. In brief, the U.S. military standard requires that ballistic eyewear must be able to withstand up to a 3.8 mm (.15 caliber) projectile at 195 m/s (640 ft/s)) for spectacles and 5.6 mm (.22 caliber) projectile at 168–171 m/s (550–560 ft/s) for goggles.
Measuring this zero penetration velocity (v 0) must take into account variability in armor performance and test variability. Ballistic testing has a number of sources of variability: the armor, test backing materials, bullet, casing, powder, primer and the gun barrel, to name a few. Variability reduces the predictive power of a determination of V0.
Cyanoacrylate adhesives may adhere to body parts, and injuries may occur when parts of the skin are torn off. [27] [28] Without force, however, the glue will spontaneously separate from the skin in time (up to four days). The glue can also cause chemical burns, and exposed skin should be washed with soap and warm water. [29]
A prescription of −1.00 +0.25 × 180 describes a lens that has a horizontal power of −1.00 D and a vertical power of −0.75 D. Only ophthalmologists write prescriptions in + cylinder. An optometrist would write a prescription in - (minus) cylinder. All spectacle and contact lenses would be made in minus cylinder.
The replacement for the S-SAPI in U.S. Army, the Enhanced Side Ballistic Inserts (ESBI, E-SBI), originally had only the 7 in × 8 in (180 mm × 200 mm) size, Small and medium were added later on. [14] The counterpart of the ESBI used by the U.S. Marines is called Enhanced Side Small Arms Protective Inserts (Enhanced S‐SAPI, Side ESAPI). [15]
GI glasses are eyeglasses issued by the American military to its service members. Dysphemisms for them include the most common " birth control glasses " ( BCGs ) and other variants. At one time, they were officially designated as regulation prescription glasses ( RPGs ).
If a sculpture is broken into several pieces, art conservators may reattach the pieces using an adhesive such as Paraloid B-72 or epoxy. If the sculpture is made of a transparent or semitransparent material (such as glass), the seam where the pieces are attached will usually be much less noticeable if the refractive index of the adhesive ...
The green strength of adhesives is the early development of bond strength of an adhesive. It indicated "that the adhesive bond is strong enough to be handled a short time after the adherents are mated but much before full cure is obtained." Usually, this strength is significantly lower than the final curing strength.