Assumed-strain finite element technique for accurate modelling of plasticity problems

In this work a linear hexahedral element based on an assumed-strain finite element technique is presented for the solution of plasticity problems. The element stems from the NICE formulation and its extensions. Assumed gradient operators are derived via nodal integration from the kinematic-weighted residual; the degrees of freedom are only the displacements at the nodes. The adopted constitutive model is the classical associative von-Mises plasticity model with isotropic and kinematic hardening; in particular a double- step midpoint integration algorithm is adopted for the integration and solution of the relevant nonlinear evolution equations. Efficiency of the proposed method is assessed through simple benchmark problem and comparison with reference solutions

The qualitative method for a humanisation of research

Huge progress in scientific research, added to vast investments, have allowed to develop vaccines against the virus responsible for Sars-Cov-2 in times unimaginable, until recently (1). The use of these vaccines has documented their high efficacy and very low risk of adverse events. Undergoing vaccination campaigns around the world are changing the history of the COVID-19 pandemic. Never before has scientific research been a topic of widespread interest as in this period. [...]

Role of Polycarboxylate-ether superplasticizers on cement hydration kinetics and microstructural development

Polycarboxylate-ether (PCE) superplasticizers are a fundamental constituent of modern cementbased materials due to their impact on the rheology of the fresh mix and mechanical performance of the hardened material. The effect of PCEs on cement hydration kinetics has been known since their introduction in the early 1980s. However, detailed knowledge of the role played by PCE macromolecules on the basic mechanisms of cement hydration (dissolution, diffusion, precipitation) is still lacking. A better understanding of how such mechanisms are influenced by the addition of PCE is no doubt beneficial to the design of novel superplasticizing admixtures. Here, I report on some recent findings about the role of PCE superplasticizers on cement hydration kinetics and microstructural development. The interaction between PCE and C3S pastes was investigated by an ad-hoc kinetic model based on a combination of generalized forms of the Avrami and BNG (Boundary Nucleation and Growth) models. The model is used to fit the rate of C-S-H precipitation measured by in-situ X-ray powder diffraction combined with mass balance calculations. The results show that a switch from heterogeneous to homogeneous C-S-H nucleation occurs in the presence of PCEs and that the C-S-H growth rate decreases proportionally to the amount of PCE used. The predicted switch to homogeneous nucleation is in agreement with experimental results obtained by XRD-enhanced micro-tomography imaging, showing that, in the presence of PCE, C-S-H preferentially forms in the pore space rather than at the surface of clinker particles

Marble Architectural Elements and Liturgical Furniture of the Santa Giustina Basilica in Padova : New Archaeometric Data on the Importation of Proconnesian Marble in the Late Antique Adriatic

This paper examines eight marble samples from the architectural elements and liturgical furniture of the ecclesiastical complex of Santa Giustina in Padova (Italy), founded by the Rufus Venantius Opilio before AD 524. The provenance determination of the marbles was carried out by means of a multi-analytical approach combining mineralogical-petrographic investigations, performed by microscopic observations of thin sections, and the measurement of the ratios of stable carbon and oxygen isotopes. The results obtained were compared with up-to-date petrographic and isotopic databases (Antonelli and Lazzarini 2015), and they showed that the analyzed marbles come from the quarries of the island of Proconnesus in Asia Minor, modern Marmara Adasi (Turkey). Archaeometric evidence, together with the stylistic and functional analysis of the pieces, suggests the direct importation of a complete set of sculptures, shipped at different stages of workmanship from the workshops of Constantinople and expressly ordered by a single patron, who can be identified as Opilio, founder of the basilica of Santa Giustina and praetorian prefect at the court of King Theodoric

Fractional derivatives, memory kernels and solution of a free electron laser volterra type equation

The high gain free electron laser (FEL) equation is a Volterra type integro-differential equation amenable for analytical solutions in a limited number of cases. In this note, a novel technique, based on an expansion employing a family of two variable Hermite polynomials, is shown to provide straightforward analytical solutions for cases hardly solvable with conventional means. The possibility of extending the method by the use of expansion using different polynomials (two variable Legendre like) expansion is also discussed

lia of prehistoric metals in the central mediterranean area a review

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Low-Temperature Rapid Synthesis and Superconductivity of Fe-Based Oxypnictide Superconductors

we were able to develop a novel method to synthesize Fe-based oxypnictide superconductors. By using LnAs and FeO as the starting materials and a ball-milling process prior to solid-state sintering, Tc as high as 50.7 K was obtained with the sample of Sm 0.85Nd0.15FeAsO0.85F0.15 prepared by sintering at temperatures as low as 1173 K for times as short as 20 min.Comment: 2 pages,2 figures, 1 tabl

(In)Consistencies in responses to sodium bicarbonate supplementation: a randomised, repeated measures, counterbalanced and double-blind study

Objectives: Intervention studies do not account for high within-individual variation potentially compromising the magnitude of an effect. Repeat administration of a treatment allows quantification of individual responses and determination of the consistency of responses. We determined the consistency of metabolic and exercise responses following repeated administration of sodium bicarbonate (SB). Design and Methods: 15 physically active males (age 25 ± 4 y; body mass 76.0 ± 7.3 kg; height 1.77 ± 0.05 m) completed six cycling capacity tests at 110% of maximum power output (CCT 110% ) following ingestion of either 0.3 g.kg -1 BM of SB (4 trials) or placebo (PL, 2 trials). Blood pH, bicarbonate, base excess and lactate were determined at baseline, pre-exercise, post-exercise and 5-min post-exercise. Total work done (TWD) was recorded as the exercise outcome. Results: SB supplementation increased blood pH, bicarbonate and base excess prior to every trial (all p ≤0.001); absolute changes in pH, bicarbonate and base excess from baseline to pre-exercise were similar in all SB trials (all p > 0.05). Blood lactate was elevated following exercise in all trials (p ≤ 0.001), and was higher in some, but not all, SB trials compared to PL. TWD was not significantly improved with SB vs. PL in any trial (SB1: +3.6%; SB2 +0.3%; SB3: +2.1%; SB4: +6.7%; all p > 0.05), although magnitude-based inferences suggested a 93% likely improvement in SB4. Individual analysis showed ten participants improved in at least one SB trial above the normal variation of the test although five improved in none. Conclusions: The mechanism for improved exercise with SB was consistently in place prior to exercise, although this only resulted in a likely improvement in one trial. SB does not consistently improve high intensity cycling capacity, with results suggesting that caution should be taken when interpreting the results from single trials as to the efficacy of SB supplementation. Trial Registration: ClinicalTrials.gov NCT0247462

Fibre Reinforced Geopolymers as Inorganic Strengthening Composites for Masonry Structures

The study presents an assessment of externally bonded Fibre-Reinforced GeoPolymers (FRGPs) as strengthening material for masonry structures. Thanks to their tailored chemical and mechanical characteristics, geopolymer matrices can fulfil the restoration criteria for Built Heritage (BH) with the benefit of heat-resistant performances better than those of organic and inorganic matrices used in Externally Bonded Fibre Reinforced Polymers (EB-FRP) and Fabric-Reinforced Cementitious Matrix (FRCM) materials, respectively. This work is built on the outcomes of a previous investigation that proved the suitability of the developed geopolymer matrix for applications on clay bricks, revealing a good adhesion to masonry substrates and to embedded reinforcements. The behaviour of three FRGPs, including either a bi-directional basalt mesh, a bi-directional carbon mesh or a unidirectional Ultra High Strength Steel (UHSS) fabric, was explored by means of local tests on masonry sub-assemblages made of soft-mud clay bricks and hydraulic lime mortar. In overall, 9 single-lap shear tests on single bricks with a bonded length of 200 mm and 9 three-point bending tests on 2-brick slices, connected by a mortar joint and reinforced at the bottom face, were carried out. Lastly, the behaviour in alkaline environments of each reinforcement was investigated through tensile tests on coupons immersed for 28 days in alkaline solutions simulating the conditions of the geopolimeric matrices. Results confirmed the interesting potential of FRGPs for strengthening masonry elements, highlighting a good performance of steel and carbon reinforcements. On the other hand, precautions should be taken with basalt meshes that, as expected, were more sensitive to alkaline environment

A combined experimental and computational study of the pressure dependence of the vibrational spectrum of solid picene C_22H_14

We present high-quality optical data and density functional perturbation theory calculations for the vibrational spectrum of solid picene (C$_{22}$H$_{14}$) under pressure up to 8 GPa. First-principles calculations reproduce with a remarkable accuracy the pressure effects on both frequency and intensities of the phonon peaks experimentally observed . Through a detailed analysis of the phonon eigenvectors, We use the projection on molecular eigenmodes to unambiguously fit the experimental spectra, resolving complicated spectral structures, in a system with hundreds of phonon modes. With these projections, we can also quantify the loss of molecular character under pressure. Our results indicate that picene, despite a \sim 20 % compression of the unit cell, remains substantially a molecular solid up to 8 GPa, with phonon modes displaying a smooth and uniform hardening with pressure. The Grueneisen parameter of the 1380 cm^{-1} a_1 Raman peak ($\gamma_p=0.1$) is much lower than the effective value ($\gamma_d=0.8$) due to K doping. This is an indication that the phonon softening in K doped samples is mainly due to charge transfer and electron-phonon coupling.Comment: Replaced with final version (PRB