Effect of Contact Residual Stress Relaxation on Fracture Strength of Indented Soda-Lime Glass

The strength of Vickers-indented soda-lime glass measured in air at room temperature steadily increases with time after indentation, whereas optical retardation steadily decreases in the same interval. Annealing after indentation causes further strength increase and retardation decrease. The results are consistent with Marshall and Lawn's treatment of the slow crack growth of indentation flaws driven by the combined influence of residual contact stress and applied stress. Post-indentation strengthening of indentation flaws can be explained without recourse to flaw blunting.     

Cone ratio data envelopment analysis and multi-objective programming

A new ‘cone ratio’ data envelopment analysis (DEA) model that substantially generalizes the Charnes-Cooper-Rhodes (CCR) model and the Charnes-Cooper-Thrall approach characterizing its efficiency classes is developed and studied. It allows for infinitely many decision-making units (DM Us) and arbitrary closed convex cones for the virtual multipliers as well as the cone of positivily of the vectors involved. Generalizations of linear programming and polar cone equalizations arc the analytical vehicles employed.     

Translational aspects of the modern genetics in head and neck cancers

Oral Cancer (OC) is one of the most recurrent cancers in the head and neck squamous cancer (SCCHN) category. Recently, the genome-wide association studies (GWAS) have gained growing interest in the scientific community. GWAS have identified several pathways involved in the interactions among general risk factors and genomic variants affecting SCCHN. This systematic overview aims to critically evaluate the latest data reported within the scientific literature. The aim was to investigate the impact of genetic aspects on SCCHN onset and prognosis, involving other clinical and systemic co-factors. PubMed, Google Scholar, and Cancer Genetics Web databases have been systematically investigated for original articles published in the last two years, reporting studies on the main queries addressed in this work. This review also comparatively describes the impact of environmental and pathological co-factors in different types of cancers, clarifying and updating the role of genetic factors in SCCHN onset and development. The main outcomes reported may be helpful to drive clinicians towards their clinical evaluations for the most appropriate therapeutic approach in SCCHN.     

A goal-focusing approach to analysis of intergenerational transfers of income

In place of classical utility conceptions, policy discussions for intergenerational transfers of income involve the balancing of several desirable social goals: maintaining or improving the standard of living of (i) the working popuuion, (ii) the retired population, and (iii) maintaining a stable intergenerational transfer system. The new method of goal focusing achieves both the trade-off analyses of utility function methods at Pareto-efficient points and due accounting for the effects of multiple objectives. A goal-focusing approach is herein developed for the detailed quantitative analysis of intergenerational income transfers of a national social security system.     

Ion Exchange of Soda-Lime Glass with Univalent Cations

Fhdeld-assisted and ordinary diffusion ion exchange of K⁺, Rb⁺hd Cs⁺, and Ag⁺ from nitrate salts with Na⁺ in soda-lime glass tubes were investigated between 700 and 735 K by application of various currents between 0 and 20.0 mA. An analysis of the field-assisted process with both a forward and a reverse field allowed calculation of the conductivity of the exchanged layer from the change of potential difference with time. Good agreement with experiment was found in both directions but anomalously high conductivities were observed in the Rb and Cs layers. Photoelastic measurements on rings sliced from the ion-exchanged tubes were used to calculate the residual stress arising from the ion exchange with the different cations. These results showed that other factors in addition to the ion size influence the magnitude of residual stress after exchange. The voltage-current relation during field-assisted ion exchange, along with the Nernst-Einstein equation, permitted calculation of the self-discussion coefficient of the exchanged cation in the exchanged layer. The self-diffusion coefficient was also estimated by applying the Nernst-Planck equation to results from unassisted ion-exchange experiments.     

Stress Buildup and Relaxation During Ion Exchange Strengthening of Glass

A soda-lime-silica glass was subjected to an ordinary ion exchange treatment in molten potassium nitrate at temperatures near and substantially below the strain point of the glass. Stress profiles were measured as a function of exchange temperature and time. At all temperatures, the measurements showed rapid relaxation of the surface stress and the development of a pronounced compression maximum in a short period. A simple viscoelastic model with composition-independent parameters was used to analyze the stress profiles. Neither Maxwell's nor Michelson's relaxation expression could satisfy both characteristics of the residual stress development. Reasons for discrepancies are discussed.     

Analysis of Field-Assisted Binary Ion Exchange

A differential equation was derived for ionic migration in a system with two mobile ions. Stationary solutions were obtained for the case where the slower ion follows the faster, which reduce to those obtained when diffusion is ignored. When the faster ion is "behind" the slower no stationary solutions are possible, but the diffusion term is not important for this case and appropriate solutions are readily obtained. However, by taking account of diffusion at the boundaries, where it is important, infinite gradients are avoided and concentration equilibrium is permitted at the glass-salt interface. The concentration distributions predicted from this approach are compared with those measured on glass that has been ion exchanged with electric field assistance. Although the agreement is reasonable, there is some discrepancy, due in part to the assumption of concentration-independent species mobility.     

Dissolution in Ceramic Systems: III, Boundary Layer Concentration Gradients

By use of electron microbeam probe analysis on quenched samples, the concentration distribution of CaO, A1₂O₃, and SiO₂ was determined across the boundary layer between molten calcium aluminum silicates and dissolving or growing sapphire and fused silica. A definite shift in the concentration ratios of the solvent components was found near the interface. Analysis of diffusion flux equations for a ternary system successfully related the shift in concentration ratio to the intrinsic diffusion coefficient for each component. For alumina dissolution in a melt rich in CaO, evidence of incongruent dissolution was observed with the formation of new phases, CaO· 6Al₂O₃ and CaO· 2A1₂O₃.