Dendrite growth direction measurements : understanding the solute advancement in continuous casting of steel

Maintaining competitiveness in steel manufacturing requires improving process efficiency and production volume whilst enhancing product quality and performance. This is particularly challenging for producing value-added advanced steel grades such as advanced high strength steels and electrical steels. These grades due to higher weight percentage of alloying elements cause difficulties in various stages of upstream and downstream processing, and this includes continuous casting, wherein high solute levels are critical towards macro-segregation. Interface growth direction in systems with more than one component is dictated by the solute profile ahead of the moving solidification front. Understanding the profile of growth direction with casting process parameters during the progress of casting will provide an important perspective towards reducing the macro-segregation in the cast product. In the present study, two steel slab samples from conventional slab caster under the influence of electromagnetic brake (EMBR) at Tata Steel in IJmuiden (The Netherlands) have been investigated for dendrite deflection measurements. The samples showed a transition zone where a change in the deflection behavior occurs. Also, the magnitude of the deflection angle decreases away from the slab surface. Correlating these experimental data with modeled fluid flow profile will help in improving the understanding of the dynamic nature of the solute advancement so that the casting parameters can be optimized to improve product quality

Sugar-Sweetened Beverage Intake Trends in US Adolescents and Their Association with Insulin Resistance-Related Parameters

The purpose of this study was to evaluate current sugar-sweetened beverage (SSB) consumption trends and their association with insulin resistance-related metabolic parameters and anthropometric measurements by performing a cross-sectional analysis of the NHANES data during the years 1988–1994 and 1999–2004. Main outcome measures included SSB consumption trends, a homeostasis model assessment of insulin resistance, blood pressure, waist circumference, body mass index, and fasting concentrations of total cholesterol, HDL-cholesterol, LDL-cholesterol, and triglycerides. Although overall SSB consumption has increased, our data suggest that this increase was primarily due to an increase in the amount of SSBs consumed by males in the high-SSB intake group alone. Multivariate linear regression analyses also showed that increased SSB consumption was independently associated with many adverse health parameters. Factors other than SSB consumption must therefore be contributing to the increasing prevalence of obesity and metabolic syndrome in the majority of US children

Effect of surface roughness on optical heating of metals

Heating by absorption of light is a commonly used technique to ensure a fast temperature increase of metallic samples. The rate of heating when using optical heating depends critically on the absorption of light by a sample. Here, the reflection and scattering of light from UV to IR by surfaces with different roughness of iron-based alloy samples (Fe, 1 wt-% Cr) is investigated. A combination of ellipsometric and optical scattering measurements is used to derive a simplified parametrisation which can be used to obtain the absorption of light from random rough metal surfaces, as prepared through conventional grinding and polishing techniques. By modelling the ellipsometric data of the flattest sample, the pseudodielectric function of the base material is derived. Describing an increased roughness by a Maxwell-Garnett model does not yield a reflectivity which follows the experimentally observed sum of scattered and reflected intensities. Therefore, a simple approach is introduced, based on multiple reflections, where the number of reflections depends on the surface roughness. This approach describes the data well, and is subsequently used to estimate the fraction of absorbed energy. Using numerical modelling, the effect on the heating rate is investigated. A numerical example is analysed, which shows that slight changes in roughness may result in big differences of the energy input into a metallic sample, with consequences on the achieved temperatures. Though the model oversimplifies reality, it provides a physically intuitive approach to estimate trends

Cross-connection structure of locally inverse semigroups

Locally inverse semigroups are regular semigroups whose idempotents form pseudo-semilattices. We characterize the categories that correspond to locally inverse semigroups in the realm of Nambooripad's cross-connection theory. Further, we specialize our cross-connection description of locally inverse semigroups to inverse semigroups and completely 0-simple semigroups, obtaining structure theorems for these classes. In particular, we show that the structure theorem for inverse semigroups can be obtained using only one category, quite analogous to the Ehresmann-Schein-Nambooripad Theorem; for completely 0-simple semigroups, we show that cross-connections coincide with structure matrices, thus recovering the Rees Theorem by categorical tools. © 2023 World Scientific Publishing Company

Group extensions and graphs

NOTICE: this is the author’s version of a work that was accepted for publication in Expositiones Mathematicae. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Expositiones Mathematicae, [Volume 34, Issue 3, 2016, Pages 327-334] DOI#10.1016/j.exmath.2015.07.005¨A classical result of Gaschütz affirms that given a finite A-generated group G and a prime p, there exists a group G# and an epimorphism phi: G# ---> G whose kernel is an elementary abelian p-group which is universal among all groups satisfying this property. This Gaschütz universal extension has also been described in the mathematical literature with the help of the Cayley graph. We give an elementary and self-contained proof of the fact that this description corresponds to the Gaschütz universal extension. Our proof depends on another elementary proof of the Nielsen-Schreier theorem, which states that a subgroup of a free group is free.This work has been supported by the grant MTM-2014-54707-C3-1-P of the Ministerio de Economia y Competitividad (Spain). The first author is also supported by Project No. 11271085 from the National Natural Science Foundation of China. The second author is supported by the predoctoral grant AP2010-2764 (Programa FPU, Ministerio de Educacion, Spain).Ballester Bolinches, A.; Cosme-Llópez, E.; Esteban Romero, R. (2016). Group extensions and graphs. Expositiones Mathematicae. 34(3):327-334. https://doi.org/10.1016/j.exmath.2015.07.005S32733434

Closures of regular languages for profinite topologies

The Pin-Reutenauer algorithm gives a method, that can be viewed as a descriptive procedure, to compute the closure in the free group of a regular language with respect to the Hall topology. A similar descriptive procedure is shown to hold for the pseudovariety A of aperiodic semigroups, where the closure is taken in the free aperiodic omega-semigroup. It is inherited by a subpseudovariety of a given pseudovariety if both of them enjoy the property of being full. The pseudovariety A, as well as some of its subpseudovarieties are shown to be full. The interest in such descriptions stems from the fact that, for each of the main pseudovarieties V in our examples, the closures of two regular languages are disjoint if and only if the languages can be separated by a language whose syntactic semigroup lies in V. In the cases of A and of the pseudovariety DA of semigroups in which all regular elements are idempotents, this is a new result.PESSOA French-Portuguese project Egide-Grices 11113YM, "Automata, profinite semigroups and symbolic dynamics".FCT -- Fundação para a Ciência e a Tecnologia, respectively under the projects PEst-C/MAT/UI0144/2011 and PEst-C/MAT/UI0013/2011.ANR 2010 BLAN 0202 01 FREC.AutoMathA programme of the European Science Foundation.FCT and the project PTDC/MAT/65481/2006 which was partly funded by the European Community Fund FEDER

Describing semigroups with defining relations of the form xy=yz xy and yx=zy and connections with knot theory

We introduce a knot semigroup as a cancellative semigroup whose defining relations are produced from crossings on a knot diagram in a way similar to the Wirtinger presentation of the knot group; to be more precise, a knot semigroup as we define it is closely related to such tools of knot theory as the twofold branched cyclic cover space of a knot and the involutory quandle of a knot. We describe knot semigroups of several standard classes of knot diagrams, including torus knots and torus links T(2, n) and twist knots. The description includes a solution of the word problem. To produce this description, we introduce alternating sum semigroups as certain naturally defined factor semigroups of free semigroups over cyclic groups. We formulate several conjectures for future research