A novel method of experimental determination of grain stresses and critical resolved shear stresses for slip and twin systems in a magnesium alloy

A novel original method of determination of stresses and critical resolved shear stresses (CRSSs) using neutron diffraction was proposed. In this method, based on the crystallite group method, the lattice strains were measured in different directions and using different reflections hkl during uniaxial deformation of magnesium alloy AZ31. The advantage of this method is that the stresses for groups of grains having similar orientations can be determined directly from measurement without any models used for data interpretation. The obtained results are unambiguous and do not depend on the models assumptions as in previous works. Moreover, it was possible for the first time to determine the uncertainty of the measured CRSS values and local stresses at groups of grains. The used methodology allowed for the determination of stress partitioning between grains having different orientations and for an explanation of the anisotropic mechanical behaviour of the strongly textured alloy. Finally, the CRSS values allowed for the validation of the type of intergranular interaction assumed in the elastic–plastic self-consistent model and for a significant reduction of the number of unknown parameters when the model is adjusted to the experimental data

A novel method of experimental determination of grain stresses and critical resolved shear stresses for slip and twin systems in a magnesium alloy

A novel original method of determination of stresses and critical resolved shear stresses (CRSSs) using neutron diffraction was proposed. In this method, based on the crystallite group method, the lattice strains were measured in different directions and using different reflections hkl during uniaxial deformation of magnesium alloy AZ31. The advantage of this method is that the stresses for groups of grains having similar orientations can be determined directly from measurement without any models used for data interpretation. The obtained results are unambiguous and do not depend on the models assumptions as in previous works. Moreover, it was possible for the first time to determine the uncertainty of the measured CRSS values and local stresses at groups of grains. The used methodology allowed for the determination of stress partitioning between grains having different orientations and for an explanation of the anisotropic mechanical behaviour of the strongly textured alloy. Finally, the CRSS values allowed for the validation of the type of intergranular interaction assumed in the elastic-plastic self-consistent model and for a significant reduction of the number of unknown parameters when the model is adjusted to the experimental data.Comment: 61 pages, 31 figures, 6 pages in Appendix, Accepted in Measuremen

Singly generated quasivarieties and residuated structures

A quasivariety K of algebras has the joint embedding property (JEP) iff it is generated by a single algebra A. It is structurally complete iff the free countably generated algebra in K can serve as A. A consequence of this demand, called "passive structural completeness" (PSC), is that the nontrivial members of K all satisfy the same existential positive sentences. We prove that if K is PSC then it still has the JEP, and if it has the JEP and its nontrivial members lack trivial subalgebras, then its relatively simple members all belong to the universal class generated by one of them. Under these conditions, if K is relatively semisimple then it is generated by one K-simple algebra. It is a minimal quasivariety if, moreover, it is PSC but fails to unify some finite set of equations. We also prove that a quasivariety of finite type, with a finite nontrivial member, is PSC iff its nontrivial members have a common retract. The theory is then applied to the variety of De Morgan monoids, where we isolate the sub(quasi)varieties that are PSC and those that have the JEP, while throwing fresh light on those that are structurally complete. The results illuminate the extension lattices of intuitionistic and relevance logics

A micro-CT study of the sinus tympani variation in humans

The posterior part of the tympanic cavity comprises a depression called the sinus tympani (ST). The said structure is of outmost importance, e.g., in surgical procedures involving the middle ear, as a pathology (microbial biofilm or cholesteatoma) present in this difficult to access location might hinder its effective treatment. The aim of the study was to evaluate anatomical variants of the sinus tympani in human adult petrous bones. For this purpose, 3D models of the ST were recreated from micro-CT scans of 44 dry petrous bone samples (19 female, 25 male), applying 3D Slicer, Meshmixer and MeshLab softwares. Anatomical variants of the ST were classified in terms of both shape and surface configuration. The internal configuration of the ST was classified as heterogeneous - containing small bony trabeculae and crests up to 1.0 mm in size, contrasting to homogeneous ST that characterizes a relatively smooth interior, or mere presence of minor depressions and mild folds. Female STs were more bowl-shaped (57.9%) than saccular (42.1%), and had heterogeneous surface configuration (52.6%) compared to homogeneous (47.4%). On the contrary, male STs were more saccular (52.0%) rather than bowl-shaped (48.0%), and predominantly had a heterogeneous surface (84.0%) over homogeneous (16.0%). A complex combination of ST features comprised of a saccular shape and heterogeneous surface occurred in 52.0% of males and in 15.8% of females (a statistically significant difference; p = 0.0254, Fisher’s exact test) seems to be clinically important because of its potential negative implication on health outcomes after surgery in case of e.g., cholesteatoma, and it may also favor chronic pathological processes

Metal foams as novel catalyst support in environmental processes

Metal foams are considered as promising catalyst carriers due to their high porosity, large specific surface area, and satisfactory thermal and mechanical stability. The study presents heat transfer and pressure drop experiments performed for seven foams of different pore densities made from diverse metals. Mass transfer characteristics are derived using the Chilton–Colburn analogy. It was found that the foams display much more intense heat/mass transfer than a monolith, comparable to packed bed. Next, the foams’ efficiencies have been compared, using 1D reactor modeling, in catalytic reactions displaying either slower (selective catalytic reduction of NOx) or faster kinetics (catalytic methane combustion). For the slow kinetics, the influence of carrier specific surface area at which catalyst can be deposited (i.e., catalyst amount) was decisive to achieve high process conversion and short reactor. For this case, monolith appears as the best choice assuming it’s the lowest pressure drop. For the fast reaction, the mass transfer becomes the limiting parameter, thus solid foams are the best solution