The effect of high-intensity gamma radiation on PETG and ASA polymer-based fused deposition modelled 3D printed parts

There is growing interest in the application of 3D printing for demanding environments subject to gamma radiation in areas such as the nuclear industry and space exploration. In this work, the effect of gamma radiation on fused deposition modelled 3D printed parts composed of polyethylene terephthalate glycol (PETG) and acrylic styrene acrylonitrile (ASA) polymers was studied. Dose levels of up to 2.25 MGy were applied to the printed components, doses equivalent to over 1 year operating near spent nuclear fuel cells. Infrared spectroscopy showed the evidence of cross-linking by the formation of peaks corresponding to –OH and C–H bonds. Tensile and hardness testing was used to assess changes in mechanical properties and showed a reduction in ultimate tensile stress and maximum strain in parts made from both polymers, but with PETG retaining greater strength and ductility than ASA, especially at intermediate gamma exposure. Young’s modulus and hardness showed either modest increases or a fairly flat response with exposure. Mechanical properties were heavily dependent on the build structure, with horizontal build samples pulled parallel to the filament direction being several times stronger than vertical build samples pulled normal to the layers. Non-irradiated samples pulled parallel to the filament direction were indicative of ductile failure, with rough surfaces, distinct infill and wall regions and evidence of thinning occurring after fracture, but irradiated fracture surfaces were flatter, smoother and without local thinning, suggesting gamma radiation-induced embrittlement in the material. For samples pulled perpendicular to the filament direction, all fractures occurred between layers, creating flat fracture surfaces with no evidence of necking and indicative of brittle failure regardless of whether the samples were irradiated

NURBS-enhanced finite element method (NEFEM) on quadrilateral meshes

This paper formulates quadrilateral elements for the NURBS-enhanced finite element method (NEFEM). The objective is to extend the application of NEFEM to problems where the use of quadrilateral elements is preferred. By leveraging a mapping, between reference and physical spaces, that encapsulates the exact boundary representation of the domain, a tight integration with computer aided design (CAD) systems is achieved. The contribution of this work is an enhanced quadrilateral finite element that incorporates the exact CAD geometry purely from the boundary representation (B-rep) from CAD and without the need for a whole volume representation (V-rep) as a NURBS entity. Numerical examples involving heat transfer and linear elastic problems are used to numerically demonstrate the optimal convergence properties of the method under mesh refinement

An investigation of the linguistic and deceptive characteristics of online grooming types

A defining feature of online grooming (OG) behaviour is the development of a deceptive relationship to hide the intent of sexual abuse. The OG discourse model proposes deceptive trust is central to entrapment and is predominantly achieved through language, yet it is unclear whether the intent of intimacy or sex impacts the communicative and deceptive properties of the chats. Fifty-seven chatlogs categorised according to the European OG Typology were analysed to address this gap. The results showed that whilst intentions might be distinct, adults develop positive/authentic social bonds with victims, and engage in strategies to match with victims who fulfil their goal for intimacy or sex. The impact of this study on the theoretical understanding of OG informs an updated and empirical definition of OG: “OG is when cyber-technology is used to build an emotional connection with a person to exploit their vulnerabilities and gain their trust causing harm and/or distress”

Global correlation analysis of strongly nonlinear frequency responses using the arclength-based separation and the Correlation-Map

Global correlation analysis is an important technique to quantify both the shape and amplitude differences between two response vectors. In linear dynamic systems, differences between two Frequency Response Functions (FRFs) are quantified as scalar number curves of the Global Shape Criterion (GSC) and the Global Amplitude Criterion (GAC), to represent FRF similarities at different frequencies. From linear to nonlinear, responses are usually obtained at different frequencies to form the Frequency Response Curve (FRC), replacing the FRF for dynamic analysis. Extending the concept of global correlation analysis from linear FRFs to nonlinear FRCs could quantify shape and amplitude similarities between nonlinear models. However, global correlation analysis for multivalued FRCs with a strong nonlinearity is hard to conduct, as strongly nonlinear correlation functions have complex multivalued phenomena with real/fake characteristics. In this paper, the Global Shape Curve Criterion (GSCC) and Global Amplitude Curve Criterion (GACC) are proposed for the correlation analysis of strongly nonlinear FRCs, which can quantify the similarity between two FRCs with different and complex multivalued phenomena. Through the arclength-based separation, multivalued FRCs are separated to single-valued response branches, in order to compute single-valued correlation functions that form the multivalued correlation function. The computed correlations contain the GSCC and GACC, which separately represent shape and amplitude differences between two FRCs at each frequency. The multivalued correlation function is represented as a Correlation-Map (C-MAP) to extract real correlation characteristics, for accurate correlation analysis. The multivalued correlation analysis is first verified on a 3 DOF model with a strong nonlinearity. Differences between the reference and initial multivalued FRCs are successfully quantified as scalar curves and the GACC may be more sensitive than the GSCC on models with a local nonlinearity. Then, the proposed method is further validated on an experimental 3 DOF model. Very complex 15-valued correlation functions between FRCs with different multivalued phenomena are established. Even so, the real correlations are still successfully extracted by the C-MAP. These show the validity and superiority of the proposed method

Lung disease characterised via synchrotron radiation micro-CT and digital volume correlation (DVC)

The study of lung mechanics is important to futureproof resilience against potential novel threats to lung health. Medical imaging provides insight to lung function. High-resolution, high-speed synchrotron radiation micro-CT imaging at SPring-8 (Japan) and in situ mechanics were used to characterize healthy and diseased airways. Synchrotron radiation was important to maximize speed and spatial resolution to map the lung architecture clearly. Links between global lung mechanical measurements (pressure-volume) and regional tissue strains were made. Tissue strains were computed from a sequence of tomograms during a respiratory cycle, demonstrating clear differences for the surfactant-free lungs compared to the controls. Poorly ventilated areas were identified within three-dimensional strain maps computed via digital volume correlation. Occluded pathways at low pressures were seen to be opened at higher pressures, augmenting the deformation pathways. The results will aid correlations between microscale and macroscale measurements and the potential impact on patient management guidelines for mechanical ventilation

Caffeine ingestion compromises thermoregulation and does not improve cycling time to exhaustion in the heat amongst males

Purpose Caffeine is a commonly used ergogenic aid for endurance events; however, its efficacy and safety have been questioned in hot environmental conditions. The aim of this study was to investigate the effects of acute caffeine supplementation on cycling time to exhaustion and thermoregulation in the heat. MethodsIn a double-blind, randomised, cross-over trial, 12 healthy caffeine-habituated and unacclimatised males cycled to exhaustion in the heat (35 °C, 40% RH) at an intensity associated with the thermoneutral gas exchange threshold, on two separate occasions, 60 min after ingesting caffeine (5 mg/kg) or placebo (5 mg/kg). ResultsThere was no effect of caffeine supplementation on cycling time to exhaustion (caffeine; 28.5 ± 8.3 min vs. placebo; 29.9 ± 8.8 min, P = 0.251). Caffeine increased pulmonary oxygen uptake by 7.4% (P = 0.003), heat production by 7.9% (P = 0.004), whole-body sweat rate by 21% (P = 0.008), evaporative heat transfer by 16.5% (P = 0.006) and decreased estimated skin blood flow by 14.1% (P 0.05). ConclusionThe greater heat production and storage, as indicated by a sustained increase in core temperature, corroborate previous research showing a thermogenic effect of caffeine ingestion. When exercising at the pre-determined gas exchange threshold in the heat, 5 mg/kg of caffeine did not provide a performance benefit and increased the thermal strain of participants

Treatment of Emerging Contaminants in Wastewater by Advanced Oxidation Processes

This study evaluated the effectiveness of ozonation and activated carbon for the degradation and removal of three main emerging contaminants (ECs) in wastewater; fluoranthene (FLT), di (2- ethyl hexyl) phthalate (DEHP) and cypermethrin (CYM). The effects of key semi-batch ozonation parameters related to gas-liquid mass transfer and reaction kinetics were identified for all contaminants. The degradation rates were evaluated in solutions of DI water, using concentration change of ozone and EC versus time. With an ozone gas concentration of 20 g/m3 NTP, the change in concentration from an initial concentration of 0.05 mg/L over time was measured using HPLC. To decrease by 75 %, it took less than a minute for FLT, two minutes for DEHP and six minutes for CYM. The adsorption of the emerging contaminants with granulated activated carbon (GAC) were evaluated in solutions of DI water at an initial concentration of 1 mg/L. For the decrease in concentration of 60 %, the time for each contaminant varied. For FLT this was achieved in 5 minutes, DEHP was decreased within 20 minutes, and it took CYM 20 minutes to reach this decrease. The effects of ozonation and adsorption onto GAC were also investigated in samples of final wastewater effluent

Working hours and health – key research topics in the past and future

Objective This paper discusses the past and present highlights of working hours and health research and identifies key research needs for the future.Method We analyzed over 220 original articles and reviews on working hours and health in the Scandinavian Journal of Work, Environment & Health published during the last 50 years. Key publications from other journals were also included.Results The majority of identified articles focussed on the effects of shift and night work, with fewer studying long and reduced working hours and work time control. We observed a transition from small-scale experimental and intensive field studies to large-scale epidemiological studies utilizing precise exposure assessment, reflecting the recent emergence of register-based datasets and the development of analytic methods and alternative study designs for randomized controlled designs. The cumulative findings provide convincing evidence that shift work and long working hours, which are often associated with night work and insufficient recovery, increase the risk of poor sleep and fatigue, sickness absence, occupational injuries, and several chronic health conditions such as cardiovascular diseases and cancer. The observed risks are strongly modified by individual and work-related factors.Conclusions Although the observed health risks of shift work and long working hours are mostly low or moderate, the widespread prevalence of exposure and the hazardousness of the many associated potential outcomes makes such working time arrangements major occupational health risks. Further research is needed to identify exposure–response associations, especially in relation to the chronic health effects, and to elucidate underlying pathways and effective personalized intervention strategies

Stability Analysis for Nonlinear Neutral Stochastic Functional Differential Equations

IIn this paper, we provide some sufficient conditions for the existence and uniqueness, the stochastic stability for the global solution of nonlinear neutral stochastic functional differential equation. When the drift term and the diffusion term satisfy a locally Lipschitz condition, and the Lyapunov monotonicity condition has a sign-changed time-varying coefficient, the existence and uniqueness of the global solution for such equation will be studied by using the Lyapunov-Krasovskii function and the theory of stochastic analysis. The stability in $p$th($p\geq 2$)-moment, the asymptotical stability in $p$th($p\geq 2$)-moment, and the exponential stability in $p$th($p\geq 2$)-moment will be investigated. Three different characterizations for these three kinds of stochastic stability in moment will be established, which are presented in terms of integration conditions, respectively. These results have seldom been reported in the existing literature. In addition, the almost surely exponential stability for the global solution of such equation is also discussed. Some discussions and comparisons are provided. Two examples are given to illustrate the effectiveness of the theoretical results obtained