The remarkable mechanical performance of biological materials is based on intricate structure-function relationships. Nanoindentation has become the primary tool for characterising biological materials, as it allows to relate structural changes to variations in mechanical properties on small scales. However, the respective theoretical background and associated interpretation of the parameters m...

Nanoindentation tests using the Berkovich indenter tip were performed on 50 and 200 nm thick polycrystalline gold films deposited on hard substrates. Gold film hardness increased with the indentation depth due to the influence of the substrate. A procedure based on the Joslin-Oliver method was introduced to correct for the substrate effect. The method utilizes the fact that the measured elastic...

Different hardness measures as Vickers, Brinell and Meyer hardness are discussed with respect to their physical interpretation. Meyer hardness is found to be best suited as a measure of plastic properties. The outline of a depth sensing nanoindentation experiment is described, and particular emphasis is given to the correct deduction of the contact area from indenter penetration data. Experimen...

This study evaluated the Knoop hardness of Enforce resin cement activated by the either chemical/physical or physical mode, and light cured directly and through ceramic (HeraCeram) or composite resin (Artglass). Light curing were performed with either conventional halogen light (QTH; XL2500) for 40 s or xenon plasma arc (PAC; Apollo 95E) for 3 s. Bovine incisors had their buccal surfaces flatte...

As one-more problems are widely used in both proving and analyzing the security of various cryptographic schemes, it is of fundamental importance to investigate the hardness of the one-more problems themselves. Bresson et al. (CT-RSA ’08) first showed that it is difficult to rely the hardness of some onemore problems on the hardness of their “regular” ones. Pass (STOC ’11) then gave a stronger ...

Nuclear stiffness, expressed as a hardness derivative, appears to be a good measure of the slope of global hardness. The authors analyze molecular states for which hardness has a maximum value. Maximum hardness principle (MHP) has been discussed. At the ground state hardness function does not obtain a maximum value versus spatial coordinates within a constant number of electrons (N), but is so ...

Algorithmic research strives to develop fast algorithms for fundamental problems. Despite its many successes, however, many problems still do not have very efficient algorithms. For years researchers have explained the hardness for key problems by proving NP-hardness, utilizing polynomial time reductions to base the hardness of key problems on the famous conjecture P 6= NP. For problems that al...

Method In order to identify the changes in the body the experiment was conducted by maintaining the standing posture for two hours by using three sorts of shoes state and four sorts of mats as an object of 9 test subjects. The Mat used in the experiment was designed on the basis of Elasticity 15% and 35%, Hardness 25Hs and 45Hs. As to the state of shoes, the experiment was progressed by dividin...

Hrušková M., Švec I. (2009): Wheat hardness in relation to other quality factors. Czech J. Food Sci., 27: 240–248. The analysis of the wheat hardness relation to other quality features was done with a set of 281 variety and commercial wheat samples, planted during the years of 2003–2006 in Central Bohemia and south Moravia areas. Technological quality was evaluated for grain, milling process, a...

The aim of this study was to evaluate the effect of the increase of energy density on Knoop hardness of Z250 and Esthet-X composite resins. Cylindrical cavities (3 mm in diameter X 3 mm in depth) were prepared on the buccal surface of 144 bovine incisors. The composite resins were bulk-inserted and polymerized using different light-curing units and times: conventional QTH (quartz-tungsten-halog...