Topology change from quantum instability of gauge theory on fuzzy CP

Many gauge theory models on fuzzy complex projective spaces will contain a strong instability in the quantum field theory leading to topology change. This can be thought of as due to the interaction between space–time via its noncommutativity and the fields (matrices) and it is related to the perturbative UV–IR mixing. We work out in detail the example of fuzzy CP²${\mathbf{CP}}^2$ and discuss at the level of the phase diagram the quantum transitions between the 3 spaces (space–times) CP²${\mathbf{CP}}^2$, S²${\mathbf{S}}^2$ and the 0-dimensional space consisting of a single point {0}$\{0\}$.     

Investigation of advanced strain-path dependent material models for sheet metal forming simulations

Sheet metal forming processes often involve complex loading sequences. To improve the prediction of some undesirable phenomena, such as springback, physical behavior models should be considered. This paper investigates springback behavior predicted by advanced elastoplastic hardening models which combine isotropic and kinematic hardening and take strain-path changes into account. A dislocation-based microstructural hardening model formulated from physical observations and the more classical cyclic model of Chaboche have been considered in this work. Numerical implementation was carried out in the ABAQUS software using a return mapping algorithm with a combined backward Euler and semi-analytical integration scheme of the constitutive equations. The capability of each model to reproduce transient hardening phenomena at abrupt strain-path changes has been shown via simulations of sequential rheological tests. A springback analysis of strip drawing tests was performed in order to emphasize the impact of several influential parameters, namely: process, numerical and behavior parameters. The effect of the two hardening models with respect to the process parameters has been specifically highlighted.     

Complexation of metal ions in Langmuir films formed with two amphiphilic dioxadithia crown ethers

The two new crown ethers presented in this study were synthesized in order to investigate two important features of ionophores, namely metal cation complexation and interfacial properties, and the way in which they interrelate. The two derivatives were conceived as analogs of membrane phospholipids with respect to their amphiphilicity and geometry. They contain a hydrophilic 1,1'-dioxo-3,3'-dithio-14-crown ether headgroup and bear two myristoyl or stearoyl lateral chains. The length of the myristoyl and stearoyl derivatives in an extended conformation is comparable with the thickness of the individual leaflets of cell membranes. The membrane-related and complexation properties of the two crown ether derivatives were studied in monomolecular films spread on pure water and on aqueous solutions of mono-, di-, and trivalent metal salts. The properties of the monolayers are described quantitatively using thermodynamic models. The compression isotherms of the monolayers formed on different subphases show a clear-cut differentiation of the monovalent and di- or trivalent cations with both ligands. This differentiation was interpreted in terms of conformational changes occurring in the crown ether derivatives upon complexation. Molecular modeling indicates that the mono- and divalent cations are coordinated differently by the ligands, yielding complexes with different conformations. The differences of the conformations of the mono- and di- or trivalent cation complexes may be important from the point of view of the interactions with lipid membranes and the biological activity of these potential ionophores.     

A new heat transfer analysis in machining based on two steps of 3D finite element modelling and experimental validation

Modelling machining operations allows estimating cutting parameters which are difficult to obtain experimentally and in particular, include quantities characterizing the tool-workpiece interface. Temperature is one of these quantities which has an impact on the tool wear, thus its estimation is important. This study deals with a new modelling strategy, based on two steps of calculation, for analysis of the heat transfer into the cutting tool. Unlike the classical methods, considering only the cutting tool with application of an approximate heat flux at the cutting face, estimated from experimental data (e.g. measured cutting force, cutting power), the proposed approach consists of two successive 3D Finite Element calculations and fully independent on the experimental measurements; only the definition of the behaviour of the tool-workpiece couple is necessary. The first one is a 3D thermomechanical modelling of the chip formation process, which allows estimating cutting forces, chip morphology and its flow direction. The second calculation is a 3D thermal modelling of the heat diffusion into the cutting tool, by using an adequate thermal loading (applied uniform or non-uniform heat flux). This loading is estimated using some quantities obtained from the first step calculation, such as contact pressure, sliding velocity distributions and contact area. Comparisons in one hand between experimental data and the first calculation and at the other hand between measured temperatures with embedded thermocouples and the second calculation show a good agreement in terms of cutting forces, chip morphology and cutting temperature.     

Strain localization analysis using a large deformation anisotropic elastic–plastic model coupled with damage

Sheet metal forming processes generally involve large deformations together with complex loading sequences. In order to improve numerical simulation predictions of sheet part forming, physically-based constitutive models are often required. The main objective of this paper is to analyze the strain localization phenomenon during the plastic deformation of sheet metals in the context of such advanced constitutive models. Most often, an accurate prediction of localization requires damage to be considered in the finite element simulation. For this purpose, an advanced, anisotropic elastic–plastic model, formulated within the large strain framework and taking strain-path changes into account, has been coupled with an isotropic damage model. This coupling is carried out within the framework of continuum damage mechanics. In order to detect the strain localization during sheet metal forming, Rice’s localization criterion has been considered, thus predicting the limit strains at the occurrence of shear bands as well as their orientation. The coupled elastic–plastic-damage model has been implemented in Abaqus/implicit. The application of the model to the prediction of Forming Limit Diagrams (FLDs) provided results that are consistent with the literature and emphasized the impact of the hardening model on the strain-path dependency of the FLD. The fully three-dimensional formulation adopted in the numerical development allowed for some new results – e.g. the out-of-plane orientation of the normal to the localization band, as well as more realistic values for its in-plane orientation.     

Organization of four thermotropic liquid crystals of different polarities on model liquid and solid surfaces

The thermodynamic and surface properties of four structurally related thermotropic liquid crystals (LC) were investigated to understand their organization at gas-liquid and gas-solid interfaces. In this study, LC with a benzoyloxy azobenzene mesogenic core substituted with heptyloxy and/or dioxyethylene ether groups were used. The propensity of the LC to form self-assembled multilayers was demonstrated in the films spread at the air/aqueous interface using the Langmuir technique and Brewster angle microscopy and on the solid surfaces of Chromosorb WHP and silica, using differential scanning calorimetry. On the basis of the results obtained, a molecular recognition mechanism underlying separation processes using LC as selectors in gas chromatography is proposed.     

Influence of Rare-Earth Substitution for Iron in FeCrMoCB Bulk Metallic Glasses

The effects of rare earth addition on the glass forming ability of Fe50-xCr15Mo14C15B6Mx （x =0, 2 and M=Y, Gd） bulks and ribbons are studied. The thermal and structural properties of the samples are measured by a combination of differential scanning calorimetry （DSC）, x-ray diffraction and scanning electron microscopy. Chemical compositions are checked by energy dispersive spectroscopy analysis. The copper mold casting technique leads to a fully amorphous structure up to 2mm only for compositions containing Y or Gd. In the case of ribbons, a fully amorphous phase is observed for all the compositions. The roles of Y and Gd are discussed on the basis of melting behavior analyzed by high-temperature DSC. Such elements act as oxygen scavengers, avoiding heterogeneous nucleation.     

Groups whose proper subgroups are Baer-by-Chernikov or Baer-by-(finite rank)

Our main result is that a locally graded group whose proper subgroups are Baer-by-Chernikov is itself Baer-by-Chernikov. We prove also that a locally (soluble-by-finite) group whose proper subgroups are Baer-by-(finite rank) is itself Baer-by-(finite rank) if either it is locally of finite rank but not locally finite or it has no infinite simple images.