Normally buttress dams are made of concrete and feature a series braces called buttresses along the downstream side of the dam to prevent the natural flow of water. The Daniel-Johnson Dam in Quebec, Canada is a multiple arch buttress dam.
SHA-1 HMAC Generation. In cryptography, a keyed-hash message authentication code (HMAC) is a specific construction for calculating a message authentication code (MAC) involving a cryptographic hash function in combination with a secret cryptographic key.he following is a Python implementation of HMAC-MD5: Python includes an hmac module, so the function above can be replaced by a shorter version. The following is a PHP implementation of HMAC-SHA1: PHP includes an hmac function, so the example above can be replaced by a shorter version.
Shellac is a resin secreted by the female lac bug, on trees in the forests of India and Thailand. It is processed and sold as dry flakes (pictured at right) and dissolved in ethanol to make liquid shellac, which is used as a brush-on colorant, food glaze and wood finish.Shellac functions as a tough natural primer, sanding sealant, tannin-blocker, odour-blocker, stain, and high-gloss varnish.he thickness (concentration) of shellac is measured by the unit pound cut, referring to the amount (in pounds) of shellac flakes dissolved in a gallon of denatured alcohol. For example: a 1-lb. cut of shellac is the strength obtained by dissolving one pound of shellac flakes in a gallon of alcohol.