Influence of the notch-sharpening technique on styrene-acrylonitrile fracture behavior

The Centre Catala del Plastic and Universidad Rey Juan Carlos laboratories joined forces to investigate the effect of the notch-sharpening technique on the fracture parameters of styrene-acrylonitrile. Contact notch-sharpening techniques, such as razor tapping, razor sliding, and razor broaching, and a noncontact procedure, femtolaser, were analyzed. The fracture values of the samples with notches sharpened via contact techniques were divided into two groups: one with pop-in and the other with no pop-in in the load-displacement records; this resulted in the lowest and highest fracture toughnesses, respectively. The fracture parameters of the specimens with notches sharpened via a femtolaser were between those of the samples with notches sharpened via contact procedures in which pop-in occurred and those in which it did not. To explain these results, the crack front of the nontested specimens after sharpening was investigated in depth, we identified the type of damage and measured its size and the crack tip radii. The morphology of the crack front was related to the fractographic study.Postprint (author's final draft

Improving of the wear resistance of working parts agricultural machinery by the implementation of the effect of self-sharpening

The failure of the cutting elements of farm machinery is due to the blunting of cutting edges (increase of their radius) till the limit values. The most effective method for increasing the wear resistance of farm machinery is the realization of self-sharpening effect of the cutting elements. The testings took place in laboratory and field at the State Technical University of Kirovograd (Ukraine) in 2015. The technical equipment consists of the consolidated farmer plowshares by different methods as well as their samples, devicesfor measuring the wear resistance and thumbprint plowshares. It was determined the resistance to wear, the radius of curvature and the changing coefficient of the blades shape. The self-sharpening process was examined throughout the experiment.The results showed that the consolidated plowshares by the proposed technology (laser welding of the mixture (PS-14-60 + 6% В4С) compared to the traditional technology (volumetric heat treatment) have a blade radius 2.5 times lower, a wear 2.2 to 2.78 times lower and the self-sharpening process of the plowshares has been observed since the beginning of the wear until the time limit operation. The changing shape coefficient was respectively of 0.98 for the consolidated plowshares with alloy PS-14-60 + 6% B4C and 0.82 for those consolidated by volumetric heat treatment

Sharpening Sharpe Ratios

It is now well known that the Sharpe ratio and other related reward-to-risk measures may be manipulated with option-like strategies. In this paper we derive the general conditions for achieving the maximum expected Sharpe ratio. We derive static rules for achieving the maximum Sharpe ratio with two or more options, as well as a continuum of derivative contracts. The optimal strategy rules for increasing the Sharpe ratio. Our results have implications for performance measurement in any setting in which managers may use derivative contracts. In a performance measurement setting, we suggest that the distribution of high Sharpe ratio managers should be compared with that of the optimal Sharpe ratio strategy. This has particular application in the hedge fund industry where use of derivatives is unconstrained and manager compensation itself induces a non-linear payoff. The shape of the optimal Sharpe ratio leads to further conjectures. Expected returns being held constant, high Sharpe ratio strategies are, by definition, strategies that generate regular modest profits punctunated by occasional crashes. Our evidence suggests that the 'peso problem' may be ubiquitous in any investment management industry that rewards high Sharpe ratio managers.

On the Distribution of the Fourier Spectrum of Halfspaces

Bourgain showed that any noise stable Boolean function $f$ can be well-approximated by a junta. In this note we give an exponential sharpening of the parameters of Bourgain's result under the additional assumption that $f$ is a halfspace