An External Circular Crack in an Infinite Solid Under Axisymmetric Heat Flux Loading in the Framework of Fractional Thermoelasticity

In a real solid there are different types of defects. During sudden cooling, near cracks, there can appear high thermal stresses. In this paper, the time-fractional heat conduction equation is studied in an infinite space with an external circular crack with the interior radius R in the case of axial symmetry. The surfaces of a crack are exposed to the constant heat flux loading in a circular ring R<r<ρ. The stress intensity factor is calculated as a function of the order of time-derivative, time, and the size of a circular ring and is presented graphically.

Fecal Microbiota Transplantation: What’s New?

The gut microbiota is composed of trillions of different microorganisms: bacteria, archaea, phages and protozoa, which represent a real solid organ, with an approximate weight of 2 kg [...]

Design of a prototype bioresorbable tibial implant in a sheep model

The purpose of this study was the design of a prototype calcium polyphosphate tibial implant for implantation into a sheep. In the design, several design parameters were considered: CPP implant structural strength, the maximum allowed micromotion of the structure at the interface with bone and the possibility of the surgeon implementing the necessary geometric changes on the bone elements during implant surgical insertion. A fininte element analysis facilitated the design and allowed for the effects of the various geometric parameters investigated. This analysis was based on a real solid model of the sheep tibial bone based on the CT scans of a five year old sheep, and several were the geometeric parameters investigated. The approach of the finite element analysis was very conservative, in the meaning that the load applied was purposely increased in order to account for any possibly unknown factors that may exist and not implemented in the analysis.

Design of a prototype bioresorbable tibial implant in a sheep model

The purpose of this study was the design of a prototype calcium polyphosphate tibial implant for implantation into a sheep. In the design, several design parameters were considered: CPP implant structural strength, the maximum allowed micromotion of the structure at the interface with bone and the possibility of the surgeon implementing the necessary geometric changes on the bone elements during implant surgical insertion. A fininte element analysis facilitated the design and allowed for the effects of the various geometric parameters investigated. This analysis was based on a real solid model of the sheep tibial bone based on the CT scans of a five year old sheep, and several were the geometeric parameters investigated. The approach of the finite element analysis was very conservative, in the meaning that the load applied was purposely increased in order to account for any possibly unknown factors that may exist and not implemented in the analysis.

Pt(II) Derivatives with Rollover-Coordinated 6-substituted 2,2′-bipyridines: Ligands with Multiple Personalities

We report here the synthesis, characterization and behavior of a series of Pt(II) cyclometalated rollover complexes with two substituted bipyridines, 6-ethyl-2,2′-bipyridine (bpy6Et) and 6-methoxy-2,2′-bipyridine (bpy6OMe), in comparison with previously studied 2,2′-bipyridine complexes. The two ligands have similar steric hindrance but different electronic properties. As a result, the reactivity of the two series of complexes follows very different routes. In particular, the new complexes behave differently towards protonation reactions, differences given by substituents and ancillary ligands, added to the presence of several nucleophilic centers. Reaction of complex [Pt(bpy6OMe-H)(PPh3)Me)] with [H3O⋅18-crown-6][BF4] results in a retro-rollover reaction whose final product is the cationic adduct [Pt(bpy6OMe)(PPh3)Me)]+. Surprisingly, only the isomer with the cis-PPh3-OMe geometry is formed; in spite of an expected instability due to steric hindrance, Density-Functional theory (DFT) calculations showed that this isomer is the most stable. This result shows that the cone angle is far from being a real “solid cone” and should lead to a different interpretation of well-known concepts concerning steric bulk of ligands, such as cone angle. Proton affinity values of ligands, neutral complexes and their protonated counterparts were analyzed by means of DFT calculations, allowing a comparison of their properties.

METHOD OF THE RESEARCH OF OXIDIZABLE METAL HEATING BY SOFTWARE SUITES OF ENGINEERING ANALYSIS

The article is devoted to the development of a method for modeling the heating of oxidized metal billets, in which the dimensions and thickness of the scale layer vary with time. The approach used in this development facilitates the appliance of modern software packages for the analysis of objects with varying geometry; and due to this the complexity of developing mathematical models of several metallurgical processes can be dramatically reduced. To simulate the process of metal oxidation, the method of equivalent thermal conductivity was used. The experimental verification of the method is performed and the possibility of its use for improving the methods of controlling the processes of industrial heating is shown. This method was worked out during experiments on the furnace №3 with walking beam of the mill 150 at Nizhne-Serginsk Hardware and Metallurgical Plant. Calculations were made to determine the thickness of the scale layer, which varies with time; the corresponding dependencies were constructed. The problem was solved by ANSYS Multiphysics software package as a problem of non-stationary heat conduction with boundary conditions of the first kind. During modeling, a finite-element grid was constructed, sufficiently detailed to obtain reliable results and, at the same time, allowing to solve the problem on low-power computers. In the course of solution, a number of simplifications were applied, in particular, simplification of the computational algorithm, in which the thickness of the scale layer is uniquely determined by surface temperature of the billet. Temperature distribution along the billet’s thickness was determined. Graphs and isotherms were constructed to compare values of the temperatures in metal and in scale layer. Also, a comparison of the temperature differences in the scale layer determined by the calculation method was made for the furnace and experimental conditions. In this study, the problem is considered as nonstationary, with varying boundaries. The research object is preparation of the metal (real solid) with scale layer, increasing with time. When solving a problem, this real solid was replaced by a conditional one with constant averaged dimensions. According to the equality of thermophysical processes, properties of the conditional solid were determined, whose change is equivalent to the dimensions of the real solid.

New quantum simulations with ultracold Ytterbium gases

In recent years, the unprecedented experimental control of the laws of quantum mechanics has led to the so-called quantum technology revolution, a terminology adopted to refer to the applications in which quantum properties play a prominent role. Also the fundamental physics has benefited from these advancements with the development of quantum simulators, controlled quantum platforms engineered in such a way to emulate the physics of complex systems difficult to investigate with classical approaches. The present work deals with the simulation of some fundamental properties of quantum-Hall systems by means of degenerate fermionic Ytterbium atoms confined in artificial periodic potentials. Extreme regimes, inaccessible to real solid-state system, have been explored, paving the way to the observation of exotic phases of matter.