Continuous monitoring of the health status of cement-based structures: electrical impedance measurements and remote monitoring solutions

<p class="Abstract">The continuous monitoring of cement-based structures and infrastructures is fundamental to optimize their service life and reduce maintenance costs. In the framework of the EnDurCrete project (GA no. 760639), a remote monitoring system based on electrical impedance measurements was developed. Electrical impedance is measured according to the Wenner’s method, using 4-electrode arrays embedded in concrete during casting, selecting alternating current as excitation, to avoid the polarization of both electrode/material interface and of material itself. With this measurement, it is possible to promptly identify events related to contaminants ingress or damages (e.g. cracks formation). Conductive additions are included in some elements to enhance signal-to-noise ratio, as well as the self-sensing properties of concrete. Specifically, a distributed sensor network was implemented<span style="text-decoration: line-through;">,</span> consisting of measurement nodes installed in the elements to be monitored, then connected to a central hub (RS-232 protocol). Nodes are realized with an embedded unit for electrical impedance measurements (EVAL-AD5940BIOZ board with AD5940 chip, by Analog Device) and a digital thermometer (DS18B20 by Maxim Integrated), enclosed in cabinets filled with an IP68 gel against moist-related problems. Data are available on a Cloud through Wi-Fi network or LTE modem, hence can be accessed remotely via a use-friendly multi-platform interface.</p>

A Framework of Runge–Kutta, Discontinuous Galerkin, Level Set and Direct Ghost Fluid Methods for the Multi-Dimensional Simulation of Underwater Explosions

This work describes the development of a hybrid framework of Runge–Kutta (RK), discontinuous Galerkin (DG), level set (LS) and direct ghost fluid (DGFM) methods for the simulation of near-field and early-time underwater explosions (UNDEX) in early-stage ship design. UNDEX problems provide a series of challenging issues to be solved. The multi-dimensional, multi-phase, compressible and inviscid fluid-governing equations must be solved numerically. The shock front in the solution field must be captured accurately while maintaining the total variation diminishing (TVD) properties. The interface between the explosive gas and water must be tracked without letting the numerical diffusion across the material interface lead to spurious pressure oscillations and thus the failure of the simulation. The non-reflecting boundary condition (NRBC) must effectively absorb the wave and prevent it from reflecting back into the fluid. Furthermore, the CFD solver must have the capability of dealing with fluid–structure interactions (FSI) where both the fluid and structural domains respond with significant deformation. These issues necessitate a hybrid model. In-house CFD solvers (UNDEXVT) are developed to test the applicability of this framework. In this development, code verification and validation are performed. Different methods of implementing non-reflecting boundary conditions (NRBCs) are compared. The simulation results of single and multi-dimensional cases that possess near-field and early-time UNDEX features—such as shock and rarefaction waves in the fluid, the explosion bubble, and the variation of its radius over time—are presented. Continuing research on two-way coupled FSI with large deformation is introduced, and together with a more complete description of the direct ghost fluid method (DGFM) in this framework will be described in subsequent papers.

Delirious New Zealand

<p>Delirious New Zealand proposes an alternative parliament, one that uses walls and boundaries to navigate authority and architecture. Walls are complex, they can range from a simple form of protection against elemental conditions, through to the reinforcement of borders between two countries with emphasis and polarising effect. Whilst variable, each instance is committed to division, and both are boundaries facilitated by architecture in the form of walls. Through design led research, three phases of investigation are developed across successive scales. Presented as 'Installing Boundaries', 'Housing Politics' and 'Political Infrastructure', each design outcome forms a larger body of work referred to as the design. Shape, Threshold, and Montage are the architectural principles that determine a given walls significance investigated at each scale. These three speculative propositions are not final outcomes for what an alternative parliament should be. Instead, Delirious New Zealand explores architectural boundaries as the material interface between those who govern and those governed. Koolhaas’s observations of the Berlin Wall – pre-demise – and his publication ‘Delirious New York’ highlight the significance of the authority of an architect, and habitational authority in the realisation and reality of architecture. The significance of a given boundary wall must then consider two things. One, the architectural elements that make up the wall itself. Two, the context within which a wall operates - be that social, political, economic etc. This thesis not only examines the design outcomes as being ‘about architecture’ in the form of the design, but also uses this as a platform to discuss ‘concepts of architecture’ more broadly. Accordingly, the concept of authority and architecture is discussed throughout the production and presentation of the three scales of investigation. A final critique in the form of a design discussion concludes this thesis, at which point the final act of installing boundaries is undertaken. ‘Delirious New Zealand’ considers parliament as a programmatic and contextual provocation for the design of architectural boundaries. In doing so, the segregated inhabitants are defined as the politicians and the people. Although political in programme, this thesis is not politically motivated nor intent on acting politically.</p>

Delirious New Zealand

<p>Delirious New Zealand proposes an alternative parliament, one that uses walls and boundaries to navigate authority and architecture. Walls are complex, they can range from a simple form of protection against elemental conditions, through to the reinforcement of borders between two countries with emphasis and polarising effect. Whilst variable, each instance is committed to division, and both are boundaries facilitated by architecture in the form of walls. Through design led research, three phases of investigation are developed across successive scales. Presented as 'Installing Boundaries', 'Housing Politics' and 'Political Infrastructure', each design outcome forms a larger body of work referred to as the design. Shape, Threshold, and Montage are the architectural principles that determine a given walls significance investigated at each scale. These three speculative propositions are not final outcomes for what an alternative parliament should be. Instead, Delirious New Zealand explores architectural boundaries as the material interface between those who govern and those governed. Koolhaas’s observations of the Berlin Wall – pre-demise – and his publication ‘Delirious New York’ highlight the significance of the authority of an architect, and habitational authority in the realisation and reality of architecture. The significance of a given boundary wall must then consider two things. One, the architectural elements that make up the wall itself. Two, the context within which a wall operates - be that social, political, economic etc. This thesis not only examines the design outcomes as being ‘about architecture’ in the form of the design, but also uses this as a platform to discuss ‘concepts of architecture’ more broadly. Accordingly, the concept of authority and architecture is discussed throughout the production and presentation of the three scales of investigation. A final critique in the form of a design discussion concludes this thesis, at which point the final act of installing boundaries is undertaken. ‘Delirious New Zealand’ considers parliament as a programmatic and contextual provocation for the design of architectural boundaries. In doing so, the segregated inhabitants are defined as the politicians and the people. Although political in programme, this thesis is not politically motivated nor intent on acting politically.</p>

Crack behaviour at the interface of a surface layer applied on a steel substrate by laser cladding

An influence of the bi-material interface between a steel substrate and a thin protective layer applied through laser cladding was investigated. A range of elastic properties and thicknesses of the layer were considered to cover the behaviour of a short crack in the selected materials such as bronze, nickel or cobalt alloys. The special case of the crack terminating directly at the interface was investigated, which is connected to the necessity of application of generalized approaches of linear elastic fracture mechanics. The results contribute to better understanding of fracture response of selected materials and to a more reliable decision on choosing a proper material of the protective layer.

A phase field crystal model for materials crystallization in the presence of of nanoscale pores

The present work focuses on the development of a relatively simple phase field crystal model for materials with nanoscale porous inclusions. We found that the pore's main effect is to act as a nucleation agent, promoting crystallization of material at the pore’s interface, followed by micro-structural evolution of the solid in the supercooled liquid. Details of the crystal around the pore are investigated in terms of the pore radius and density of material outside the pore. Moreover, details of the pore-material interface is investigated through the interfacial tension and pressure. Finally, the model is extended to investigate the effect of multiple pores on the kinetics of crystallization.

Three Dimensional Evaluation of Marginal Microleakage at the Adhesive Interface between Different Fissure Sealants and Enamel: Micro-CT Analysis

Summary Background/Aim: Sealing ability and adhesion to enamel of fissure sealants are quite critical in prevention of dental caries. The objective of the present study was to assess the marginal microleakage of different material-based pit and fissures with non-invasive and invasive techniques by using the Micro-CT method. Material and Methods: 30 extracted human permanent molars were randomly assigned to three sealant groups (n=10) as resin-based ClinPro, giomer-based BeautiSealant, and glass ionomer-based Fuji IX-GP. Half of each group was randomly divided into two parts as non-invasive and invasive techniques. The volumetric analysis of marginal microleakage between the enamel-material interface was performed by using Micro-CT. The results were analyzed with Student’s t, One-Way ANOVA, Tukey and Games-Howell tests. Statistical significance level was considered as 0.05. Results: In non-invasive technique, Fuji IX-GP showed statistically significantly lower marginal microleakage values than Clinpro (p=0.022). Other comparisons were not significant (p>0.05). However, in invasive technique, microleakage values both of Fuji IX-GP and BeautiSealant were significantly lower than Clinpro (p<0.001, p<0.001). Besides, regardless of the sealant material, the invasive technique showed significantly superior results than non-invasive technique regarding marginal microleakage. Conclusions: Considering the clinical conditions, it was concluded that glass ionomer-based Fuji IX-GP and giomer-based BeautiSealant could be used as alternative to resin based sealants. Additionally, invasive technique (fissure preparation) can be recommended to reduce marginal microleakage.

Performance evaluation of thermoelectric generators under cyclic heating

The effect of thermal cycling on thermoelectric generator (TEG) performance is investigated for six nominally identical samples subjected to the same heating cycle profile. All TEGs experienced performance degradation, with maximum power outputs between 28 % and 49 % of pre-cycling values and a post-cycling decrease in the dimensionless figure of merit ZT of 21 % to 49 %. Sudden significant power reductions and subsequent internal resistance increases were observed for all samples, indicative of internal damage to the structure of the TEGs arising from material interface separation and micro-crack formation.