Studies upon the effect of abrasive grain size on technological quality during the AWJ cutting of S235JR steel

The influence of the abrasive grain size on the technological quality of the intersection of non-alloy structural steel S235JR, is presented. The experiment was carried out on a high-pressure water-jet APW 2010BB abrasive cutting machine using the abrasive garnet #80 and #120. Studies included the assessment of intersection surface macrostructure: slit width, shape defects and surface roughness. Experiment has confirmed that the size of abrasive grains significantly influences the macrostructure of the intersection surface. Smoother cuts can be made with finer grains, but finer abrasive particles have less kinetic energy, leading to reduction in the erosion capacity of the water-jet. The study was carried out at variable feedrate, therefore it was possible to determine the influence of the feedrate on the average square surface deviation. Increasing the feedrate resulted in a decrease in the entire width of the cut slit, which was especially noticeable in the lower cut zone of the workpiece.

Hyperbolicity related problems for complete intersection varieties

In this paper we examine different problems regarding complete intersection varieties of high multidegree in a smooth complex projective variety. First we prove an existence theorem for jet differential equations that generalizes a theorem of Diverio. Then we show how one can deduce hyperbolicity for generic complete intersections of high multidegree and high codimension from the known results on hypersurfaces. Finally, motivated by a conjecture of Debarre, we focus on the positivity of the cotangent bundle of complete intersections, and prove some results towards this conjecture; among other things, we prove that a generic complete intersection surface of high multidegree in a projective space of dimension at least four has an ample cotangent bundle.

NON-FACTORIAL NODAL COMPLETE INTERSECTION THREEFOLDS

We give a bound on the minimal number of singularities of a nodal projective complete intersection threefold which contains a smooth complete intersection surface that is not a Cartier divisor.