Barcol hardness test the Barcol impressor was developed by Walter Colman as a hand-held, portable means of assessing the hardness of a material during World War II. The United States Army Air Corps required a hand-held method of checking the hardness of rivets due to concerns that aircraft could be sabotaged by replacing normal rivets with soft lead or wooden ones which would fail during flight. The impressor operates when the tip is pressed against the material in question. The hardness of the material determines how far the tip indents and this is transferred by a tension spring and lever to be read
Computational hardness assumption which is a computational hardness assumption about random instances of 3-SAT (sampled to maintain a specific ratio of clauses to variables). Average-case computational hardness assumptions are useful for proving average-case hardness in applications like statistics, where there is a natural distribution over inputs. Additionally, the planted clique hardness assumption has also been used to distinguish between polynomial and quasi-polynomial worst-case time complexity of other problems, similarly to the Exponential Time Hypothesis. The Unique Label Cover problem is a constraint satisfaction problem, where each constraint formula_60 involves two variables formula_77, and for each value of formula_26 there is a "unique" value