Comparison between corrosion behaviour of implant alloys Ti6Al7Nb and Ti6Al4Zr in artificial saliva

The present paper investigates two different titanium alloys: Ti6Al7Nb – a well‐established implant biomaterial and Ti6Al4Zr – a relatively new titanium alloy. Roughness is evaluated with atomic force microscopy (AFM) and the hydrophilic/hydrophobic balance by contact angle measurements. Furthermore, an extensive characterization was done in order to evaluate and compare the electrochemical behaviour for both titanium alloys in artificial Fusayama and Afnor saliva, at different immersion times, and consisted of Tafel plots, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Also, metals ions release was measured using inductively coupled plasma mass spectrometry (ICP‐MS). In both studied artificial saliva, Ti6Al4Zr alloy presents a better electrochemical behaviour according to corrosion rates from both electrochemical techniques and ICP‐MS.     

The conditioning of comfort

This commentary considers how the insights from the Building Research & Information 2008 special issue on ‘Comfort in a Lower Carbon Society’ impact upon our understanding of the nature of comfort demand; their importance and relevance to the theory and policies of building comfort; and the commentary draws upon changing comfort practices in other parts of the world. One of the most important contributions of the collection is to situate comfort historically and technically, but also to give attention to the social consequences of air-conditioning. Air-conditioning has brought with it an encapsulation of home within house and has led to significant changes in the social geography of home and neighbourhood. The social, material and discursive facets of air-conditioning are globalizing at a rapid pace, fostered by the spread of inappropriate building practices, faith in modern scientific solutions to achieving comfort, and new ideas about the human body. Local knowledge about climate and comfort is waning in many parts of the world, and cooling comfort increasingly relegated to technical experts. This collection makes an important contribution to understanding how air-conditioning has become pervasive and suggests new lines of thinking in the crucial effort to move towards a less carbon-intensive comfort regime.

Ce commentaire explique comment les informations contenues dans le récent numéro spécial de Building Research & Information consacré au confort dans une société sobre en carbone ont une influence sur la nature de la demande de confort, sur son importance et sur sa pertinence par rapport à la théorie et aux politiques de confort; il s'appuie également sur des pratiques de confort qui évoluent dans d'autres parties du monde. L'une des contributions les plus importantes de cette collection est de resituer le confort sur le plan historique et technique mais aussi de prêter attention aux conséquences sociales de la climatisation. Avec la climatisation, le foyer se trouve encapsulé dans la maison, ce qui a conduit à des changements significatifs de la géographie sociale du foyer et du voisinage. Les aspects sociaux, matériels et discursifs de la climatisation se mondialisent à un rythme rapide, favorisés par des pratiques de construction inappropriées qui se répandent, par la foi dans des solutions scientifiques modernes pour obtenir le confort et de nouvelles idées sur le corps humain. Les connaissances locales sur le climat et le confort s'estompent dans de nombreuses parties du monde et le confort par le refroidissement est de plus en plus remis dans les mains d'experts techniques. Cette collection est une contribution importante qui explique comment la climatisation est envahissante et suggère de nouveaux axes de réflexion concernant l'effort à faire pour évoluer vers un état de confort exigeant moins de carbone.

Mots clés: comportement adaptatif, agence, climatisation, confort, consumérisme, demande d'énergie, satisfaction des occupants, géographie sociale, consommation durable     

Enabling and measuring innovation in the construction industry

Innovation is vital to successful, long-term company performance in the construction industry. Understanding the innovation process, how innovation can be enhanced and how it can be measured are key steps to managing and enhancing innovation. The factors that affect innovation on a project were identified, as well as how these factors can be used to measure the level of innovation on a project, and the practices and processes that encourage and facilitate innovative changes. Case studies of construction projects in the United States revealed three necessary components of innovation: idea generation, opportunity and diffusion. A variety of practices are used to optimize each component including support and commitment from the owner/client and firm upper management, workforce and project team integration and diversity. Applying the practices identified in the research leads to enhanced innovation through better communication among project team members, integration of the design and construction disciplines, more efficient designs, development of unique ways of completing work and sharing of the lessons learned. The end result of innovation will be projects that successfully meet and exceed cost, quality, schedule and safety goals.     

Accelerated material data generation for viscoplastic material models based on complex LCF and incremental creep tests

Viscoplastic material models are quite important for realistic characterization of deformation behaviour of high-temperature components. However, their material parameter adjustment is expensive and usually requires extensive material testing. The high-temperature deformation behaviour of cast iron GJS X SiMo 4.1 was determined by accelerated complex material testing methods in order to establish a cost-effective identification of viscoplastic material model parameters. Incremental creep tests with mixed-load and temperature steps, together with relaxation and stepped-tensile tests, were carried out in order to determine the stress-dependent creep strain rate at characteristic temperatures and stresses. The cyclic plastic deformation behaviour was studied with complex low-cycle fatigue (C-LCF) evaluations at varying strain rates, amplitudes and temperatures. Thereafter, the results were employed to identify material model parameters of a Chaboche-type viscoplastic material model, which was applied to represent the cyclic deformation and creep behaviour with a correct representation of strain-rate effects at low strain rates.     

Analysis of compaction and life‐time prediction of porous polymer membranes: influence of morphology,diffusion and creep behaviour

In membrane applications, large values of permeability and selectivity are generally desired during the whole period of application. The permeability of porous polymer membranes often is reduced by the effect of compaction. Compaction of polymer membranes is a time‐dependent process which is strongly determined by the viscoelastic properties of the polymer and its plasticisation caused by the feed medium (e.g. a liquid medium or a process gas in the case of porous support structures). In this study, the time‐dependent compaction of porous polymer membranes under pressure is modelled. The influence of viscoelastic and diffusion properties of the polymer material on the permeability of the membrane is analysed for different types of membrane morphologies. The life‐time of a porous polymer membrane is associated with the time at which the glass transition is achieved in a creep experiment. Equations are derived in order to estimate the maximum life‐time of polymer membranes based on compaction. The analysis reveals that the diffusion coefficient, the average retardation time in creep, the magnitude of creep compliance and the time–temperature–pressure shift factor strongly influence compaction of microporous membranes. Generally, a larger tortuosity at constant porosity yields a lower life‐time of the membrane. Buckling of cell struts is the dominant failure mechanism in porous membranes with a very high porosity and allows an estimation of life‐time. © 2016 Society of Chemical Industry     

Exploration of domestic water demand attitudes using qualitative and quantitative social research methods

The sustainable evolution of the urban water system requires the recognition of uncertainty embedded in both climate and human behaviour. A challenge that water managers and policy makers need to tackle, is to understand the way the society’s water demand behaviour is affected. The inaccuracy between attitudes and behaviours and the cognitive association of water use to living standards, hinders the projection of society’s response to management’s measures. Thus, it is necessary to identify leverage points, where water demand management policies should aim their efforts. This work presents two parts of a social research held in Athens: quantitative questionnaire gathering information regarding the domestic water demand attitudes and behaviours; and a series of qualitative interviews aimed at exploring in-depth, the domestic water use attitudes, and behaviours. This work presents the design and results of both methods and the combination of the quantitative results with insights from the qualitative work.     

In-situ tensile tests under SEM and X-ray computed micro-tomography aimed at studying a self-healing matrix composite submitted to different thermomechanical cycles

Ceramic matrix composite (CMC) based on SiC fibres and matrix is gradually introduced in aeronautical application, mostly in hottest parts of engines. Three dimensional (3D) structured materials are good candidates for complex parts such as turbine blades. Material is submitted to mechanical stresses at high temperatures in oxidizing and corrosive environments for long durations. During thermomechanical cycles, damage, oxidation and healing-phenomenon occur and develop in the material. X-ray computed micro-tomography (μCT) and tensile test under scanning electron microscopy (SEM) are experimental means to study these phenomenons. These techniques are implemented for the understanding of the behaviour of the oxide (solid or liquid) in the crack of the material. The influence of the oxide in the crack was analyzed during tensile test under SEM or μCT. The observation allows to determine the influence of the oxide on the reclosure of the crack during the unloading.     

Fiber size effects on mechanical behaviours of SiC fibres-reinforced Ti3AlC2 matrix composites

In this study, different diameters SiC fibres-reinforced Ti₃AlC₂ matrix composites were fabricated via hot-pressing. The mechanical behaviours of the obtained composites were evaluated at room temperature by using 4-point bending testing. The results show that the flexural strength and damage tolerance are significantly higher for smaller diameter fibres-containing composites than for large diameter fibres-containing ones. In addition, the mechanical properties of the composites were improved when smaller diameter fibres partially replaced large diameter fibres and the improvement increased with increase of the amount of smaller diameter fibre. Furthermore, the fracture fashion of the composites depended on fibre diameters used.     

An integrated approach for tactical monitoring and data-driven spread forecasting of wildfires

In recent times there have been increasing efforts to integrate technology into wildfire management, especially in the fields of tactical monitoring and simulation. On the one hand, thermal infrared imaging (TIR) systems have been installed aboard surveillance aircraft including unmanned systems (UAS). On the other, there exists a variety of models and simulators able to forecast the fire spread. However, both fields currently present significant limitations. While relevant information is still extracted manually from aerial thermal imagery and is most times merely qualitative, simulators’ accuracy on fire spread prediction has proved insufficient. To solve these issues, this article presents a twofold methodology to couple meaningful automated wildfire monitoring with accurate fire spread forecasting. The main goals are to, firstly, automatically process aerial TIR imagery so that valuable information can be produced in real time during the event and, secondly, use this information to adjust a Rothermel-based simulator in order to improve its accuracy on-line. The fire perimeter location is tracked automatically through an unsupervised edge detector. Afterwards, an assimilation module uses the remotely sensed data to optimise the simulator's fuel and wind parameters, which are assumed to remain constant for a certain period of time. Subsequently, the optimum parameters’ values are used to issue a fire evolution forecast. All outputs are projected onto the corresponding Digital Terrain Model (DTM) and integrated into a Geographic Information System (GIS) for visualization. The global system was validated using two large-scale experiments. If these algorithms can be applied to a sufficiently rich and varied set of experimental data and further developed to cope with more complex scenarios, they could eventually be incorporated into a fire management decision support system.     

Design and fabrication of electro‐conductive polymer nanocomposites with mechanical and thermal resistance

The commencement of the industrial revolution paved the way for the fabrication of flexible polymers with high‐strength metalloceramics as novel materials of all kinds. Fabricating metal–ceramic/polymer conductive composites is one such dimension followed for the present research work making use of the properties of the three components. Electroless deposition, for permanent metallic coating, was performed to coat Al₂O₃ with metallic Cu followed by the inclusion of the Cu–Al₂O₃ filler into a poly(vinyl chloride) (PVC) matrix. X‐ray diffraction and energy‐dispersive X‐ray studies predicted a prominent growth of metallic Cu crystallites onto Al₂O₃ with an increased average size and variation in elemental composition, respectively, when compared to pristine Al₂O₃. Morphological behaviour via scanning electron microscopy also envisioned uniform Cu coating onto Al₂O₃ and a homogeneous dispersion throughout the polymer matrix. When incorporated into PVC, electrical conductivity analysis highlighted a distinct variation in composite phases from insulating (7.14 × 10^?16 S cm^?1) to semiconducting behaviour (8.33 × 10^?5 S cm^?1) as a function of Cu–Al₂O₃ filler. Mechanical behaviour (tensile strength, Young's modulus and elongation at break) and thermal properties of the prepared composites also indicated a substantial improvement in material strength with Cu–Al₂O₃ incorporation. The enhanced electrical conductivity along with improved thermomechanical status with significant filler–matrix interaction permits the potential usage of such novel composites in a range of state‐of‐the‐art semiconducting electronic devices. © 2018 Society of Chemical Industry