Protective properties of detonation-deposited coatings from powders alloyed with aluminum and boron

Conclusions The corrosion resistance of detonation-deposited coatings from aluminum- and boron-containing PKh20N80 alloy, nickel, and stainless steel powders markedly surpasses that of constructional steel. The electrochemical properties of such detonation-deposited coatings are determined by their composition and thickness. The basis material is effectively protected against corrosion by 600-Mm-thick coatings. Under conditions of corrosive and mechanical wear detonation-deposited coatings from aluminum- and boron-containing 20% Cr-80% Ni alloy, nickel, and stainless steel powders operate satisfactorily under loads of not more than 5 MPa. The results of service tests have demonstrated the usefulness of detonation-deposited coatings from alloyed powders. Coating with powder of composition III was found to increase the useful life of certain parts of spraying equipment two to two and a half times.Translated from Poroshkovaya Metallurgiya, No. 8 (272), pp. 52–55, August, 1985.     

Durability of sheet molding compounds: Influence of hydrothermal aging on morphology and molecular mobility at microscopic scale

The physicochemical aging for parts of Sheet Molding Compound should be considered for their lifetime management and reusability. This material has a complex morphology and contains porosity due to the process and to shrinkage compensation. This SMC study has two complementary approaches. One describes the morphological consequences of water uptake, showing the decrease in the total amount and the fractal dimension of micro-voids by scanning electron microscopy and image processing. The other shows, by mechanical spectrometry, the effect of water on physical or chemical bonds. In both cases, the “low profile agent” in SMC plays an important role. The molecular mobility was taken as a sensor parameter for the structural changes at the molecular scale, highlighting and quantifying the first steps of the aging. The loss factor level increases, and the activation energies are modified, even for the first aging days. The analysis shows recovery for the material near the relaxation peak of the low profile agent, since the curve recovers its initial shape.     

Scandinavian Thins on Top of Cake: New and Improved Algorithms for Stacking and Packing

We show how to compute the smallest rectangle that can enclose any polygon, from a given set of polygons, in nearly linear time; we also present a PTAS for the problem, as well as a linear-time algorithm for the case when the polygons are rectangles themselves. We prove that finding a smallest convex polygon that encloses any of the given polygons is NP-hard, and give a PTAS for minimizing the perimeter of the convex enclosure. We also give efficient algorithms to find the smallest rectangle simultaneously enclosing a given pair of convex polygons.     

A method for determination of the coordinates of a low-altitude target

Operation of a monopulse meter of the objects?? angular coordinates under the multipath propagation conditions during tracking of the objects located at small elevation angles above the underlying surface, the so-called low-altitude targets (LATs), is analyzed. A method for measuring the LAT angular coordinates, which is based on separation of the aperture plane of the meter??s antenna system into four identical subapertures (partial channels of the meter) so that the phase centers of these subapertures are located pairwise symmetrically in the horizontal and vertical planes and are arranged into a rhombic structure, is proposed. Combinations of the output signals of these subapertures used for formation of the meter??s discriminator curves (DCs) are analyzed. Relationships that are used in construction of the operation algorithm of the beam handling system in tracking of a LAT and ensure independence of the DC shape on the characteristics of the underlying surface are derived. An algorithm for determination of the LAT coordinates is described and the results of simulation of the meter operation are presented.