Division of images into areas of local extrema with a monotonic change in pixel brightness

In this paper, the problem of segmentation of halftone images is considered, in which areas of local maxima and minima (extrema) are distinguished with a monotonic change in the brightness of pixels from local extrema to the boundaries of areas. To solve this problem, a mathematical model is proposed and a segmentation algorithm is developed on the basis of counter-wave growing of local extremum regions. The developed algorithm differs from the known segmentation algorithms by using a set of brightness thresholds (by the number of regions), varying by one in each cycle, starting from the values of local extrema, taking into account the increase or decrease in brightness to select adjacent pixels that are attached to the regions formed from these local extrema. The algorithm provides a greater deviation of pixel brightness from the average value within the region compared to known segmentation algorithms. This does not allow evaluating its efficiency using known indicators based on the variance of the brightness within the region. In this regard, estimates of the monotonicity of changes in the brightness of regions are proposed based on a) the shortest distances from each pixel of the region to the corresponding local extremum along the routes determined by the maximum increase (for the region of the local maximum) or decrease (for the region of the local minimum) the brightness of pixels and b) taking into account the number pixels that break the monotony of the segment brightness change. Using these estimates, it is shown that the proposed algorithm provides segmentation of artificial and natural grayscale images with a monotonic change in the brightness of pixels in the areas of local extrema. These properties allow us to consider the developed algorithm as a basis for the selection of texels, spots, low-contrast objects in images.

The Influence of the Working Conditions of the Electrospark Granules Deposition on the Formation of Cracks in Ti-Al Intermetallic Coatings

Electrospark treatment of a titanium alloy Ti6Al4V in a mixture of granules allows the formation of intermetallic Ti-Al coatings. The coating structure is penetrated by a network of cracks with a thickness of 0.46 to 1.19 microns and a specific area of 1.5 to 3.4%. A change in the ratio of Ti to Al in the mixture of granules does not lead to a monotonic change in the thickness and number of cracks. A decrease in the pulse duration from 200 to 20 μs leads to a slight decrease in the thickness of cracks and significantly increases their total area from 2.1 to 3.4%. An increase in the discharge pulse repetition rate can significantly increase the thickness of cracks in Ti-Al electrospark coatings.

Individual variation in the development of the Western Vowel System of Utah

The BIT, BING, BET, BAT, BAN, BOOK, and BUT vowels of ten Utah English speakers (born 1883–1928) were analyzed over the course of several decades of their adult lives. Most speakers participated in the Western Vowel System by lowering BIT and BET, retracting BAT, and raising BAN, with some fronting BOOK and BUT. Speakers generally did not exhibit monotonic change across the years from expected positions for BET, BAT, and BAN, and for the most part for BOOK and BUT; however, most speakers showed change with regard to BIT, though speakers differed from each other on the direction of change. Even for those vowels with no consistent direction of intraindividual change, however, in many cases speakers were inconsistent in their production from year to year. Further, speakers’ envelopes of variation were different for various vowels, with the widest range of intraindividual variation in BET and BAT, less variation in BAN and BUT, and little in BIT and BOOK. It is suggested that the envelope of variation is at least as much as an important issue for studies of linguistic behavior across adulthood as any actual shift in linguistic behavior across real time.

Effect of Size Polydispersity on the Pitch of Nanorod Cholesterics

Many nanoparticle-based chiral liquid crystals are composed of polydisperse rod-shaped particles with considerable spread in size or shape, affecting the mesoscale chiral properties in, as yet, unknown ways. Using an algebraic interpretation of Onsager-Straley theory for twisted nematics, we investigate the role of length polydispersity on the pitch of nanorod-based cholesterics with a continuous length polydispersity, and find that polydispersity enhances the twist elastic modulus, K 2 , of the cholesteric material without affecting the effective helical amplitude, K t . In addition, for the infinitely large average aspect ratios considered here, the dependence of the pitch on the overall rod concentration is completely unaffected by polydispersity. For a given concentration, the increase in twist elastic modulus (and reduction of the helical twist) may be up to 50% for strong size polydispersity, irrespective of the shape of the unimodal length distribution. We also demonstrate that the twist reduction is reinforced in bimodal distributions, obtained by doping a polydisperse cholesteric with very long rods. Finally, we identify a subtle, non-monotonic change of the pitch across the isotropic-cholesteric biphasic region.