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[3] [4] The Mohs scale is based on relative scratch hardness of different materials; with talc assigned a value of 1 and diamond assigned a value of 10. [5] Mohs's scale had two limitations: it was not linear, and most modern abrasives fall between 9 and 10.; [6] [7] so, later scientists attempted to increase resolution at the harder end of the ...
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The Turner-Sclerometer test consists of measuring the amount of load required to make a scratch. [1] [2] In test a weighted diamond point is drawn, once forward and once backward, over the smooth surface of the material to be tested. The hardness number is the weight in grams required to produce a standard scratch.
If HV is first expressed in N/mm 2 (MPa), or otherwise by converting from kgf/mm 2, then the tensile strength (in MPa) of the material can be approximated as σ u ≈ HV/ c, where c is a constant determined by yield strength, Poisson's ratio, work-hardening exponent and geometrical factors – usually ranging between 2 and 4. [9]
The 400mm f / 4 DO IS II USM, which replaced an earlier version of the same lens in 2014, [3] is one of only two Canon lenses that make use of diffractive optics (the other is the EF 70–300mm f/4.5–5.6 DO IS USM). The use of diffractive optics allows the lens to be significantly lighter than it might otherwise be.
The EF 200–400 mm f / 4L was first announced to be in development in February 2011 and a prototype was showcased at the 2011 CP+ tradeshow. [1] In November 2011, Canon announced that availability of the lens would be postponed to an unspecified later date. [2] The lens was only released more than a year later in May 2013. [3]
The sequence of lens designations may differ in literature. See also full list of Nikon designations, Sigma designations, Tamron designations and Tokina designations.. Nikon AF-S/Sigma HSM/Tamron USD or PZD: The lens contains an integrated ultrasonic focus motor based on piezoelectricity, which enables quiet or low noise autofocus operation.
The seemingly "simple" elementary brain-teaser asks one student "Reasonableness: Marty ate 4/6 of his pizza and Luis ate 5/6 of his pizza. Marty ate more pizza than Luis.