3D Experimental investigation of the hygro-mechanical behaviour of wood at cellular and sub-cellular scale: detection of local deformations

The swelling/shrinkage of spruce wood samples (Picea Abies) is documented with high resolution XRay Tomography and advanced image analysis tools. We report the reversible moisture-induced global and local deformations at the cellular and sub-cellular scales. In particular, we present sophisticated methods for detecting local deformations in the cell wall. Insight is given on the hygromechanical behaviour of wood cell material and on the role of ultra-cellular components in wood, such as bordered pits and rays

Crystallization of hydrated and anhydrous salts in porous limestone resolved by synchrotron X-ray microtomography

ACLInternational audienceThe crystallization processes of two anhydrous salts (NaCl and Na 2SO4) and one hydrated (sodium sulfate) salt in the pore space of a natural building stone, Savonnières limestone, are studied. We imaged the salt solution distribution before and after crystallization and the solid crystal distribution in between repeated crystallization cycles using synchrotron X-ray microtomography. This technique proves to be very useful to study salt crystallization processes at the pore scale. The use of simultaneous phase-and-amplitude retrieval during X-ray tomographic reconstruction allows a clear segmentation of sodium sulfate solution and hydrated sodium sulfate crystals without the need for a dopant. Salt crystals can precipitate under unconfined as well as confined conditions in the multiple pore systems of Savonnières limestone, depending on their interconnection. Salt solution and salt crystals are located in mechanically weak zones of the limestone, which can be linked to damage patterns observed in this stone after repeated salt weathering cycles. The distribution and the process of pore filling by salt crystals that are revealed here advance the understanding of salt damage in porous media and may open ways to perform remediation. © 2014 Elsevier B.V. All rights reserved

Segmentation of salt solution and hydrated salt crystals in porous limestone

This paper presents how simultaneous phase-and-amplitude retrieval during X-ray tomographic reconstruction allows a clear segmentation of sodium sulfate solution and hydrated sodium sulfate crystals in Savonnières limestone without the need for a dopant. This technique could be very useful to study salt crystallization processes at the pore scale, in order to improve the understanding and remediation of salt damage in porous media

Investigating ePortfolios from Teacher Training to the Workplace

This study investigates the transfer of ePortfolio practice from teacher training to the workplace, drawing on three case studies of secondary school teachers from different disciplines (IT, science, maths and foreign languages) who built their ePortfolios during pre-service training. It examines why teachers continue or cease ePortfolio practice, their trainers’ and supervisors’ perceptions of ePortfolio transfer, and the perceived usefulness of continuing ePortfolio practice at work. It also explores the hypothesis that ePortfolio practices, as a process, may be more subject to transfer than ePortfolios themselves, and compares results to other interviews with in-service teachers made during the preparation of this study and to the latest research on ePortfolio practice in teacher training. The study adopts a practical method of enquiry, based on artefacts produced by teachers. The theoretical framework is based on Cultural-Historical Activity Theory (CHAT) and Technology Acceptance Model (TAM) to analyse external and internal causes that may impact on transfer of ePortfolio practice. The main research method was face to face and computer mediated semi-structured interviews, together with post-interview questionnaires and analysis of teachers’ ePortfolio artefacts. The findings reveal that teachers’ ePortfolio practice rapidly fades after they begin work, or in many cases is never transferred. Analysis shows that the main reason for this is the lack of perceived usefulness of the ePortfolio at the workplace, together with the absence of communities of practice within schools where participants were working: social or geographical variables such as provenance, sex or age do not appear to play a role. The conclusion suggests separating the teaching of the use of ePortfolio management systems from the teaching of ePortfolio practices and offers a model for studying the latter which pays particular attention to the impact of the tensions between different elements which CHAT identifies

Enterprise Experience into the Integration of Human-Centered Design and Kanban

he integration of Human-Centered Design (HCD) and Agile Software Development (ASD) promises the development of competitive products comprising a good User Experience (UX). This study has investigated the integration of HCD and Kanban with the aim to gain industrial experiences in a real world context. A case study showed that requirements flow into the development process in a structured manner by adding a design board. To this end, the transparency concerning recurring requirements increased. We contribute to the body of knowledge of software development by providing practical insights into Human-Centered Agile Development (HCAD). On one hand, it is shown that the integration of HCD and Kanban leads to a product with a good UX and makes the development process more human-centered. On the other hand, we conclude that a cross-functional collaboration speeds up product development.Ministerio de Economía y Competitividad TIN2013-46928-C3-3-RMinisterio de Economía y Competitividad TIN2015-71938-RED

Dedicated TEM study from the core structure of adiabatic shear bands in dynamical deformed Ti6Al4V

Metals and alloys deformed at high strain rates, which are occurring during impact or metal forming situations can suffer from premature failure due to the introduction of so called adiabatic shear bands (ASB). Very high strains occur in these narrow bands of localized deformation. In case of Ti6Al4V these bands are a known mechanism of failure [1,2], Although the main mechanism for adiabatic shearing is the competition between strain hardening and thermal softening, a detailed model of their structure and its role in the formation mechanism is not yet known. In this work a dedicated TEM study of the core structure in these adiabatic shear bands is presented