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Addition of Ge to Cr-Ta-Si Laves phase-based alloys
No full textThe Cr-Cr2Ta system is of interest as a potential candidate for structural applications at temperatures that exceed those that can be tolerated by nickel-based superalloys. However, the oxidation resistance of alloys based on this system is currently insufficient. Previous work on the Cr-Cr3Si system suggests that Ge additions may also improve the oxidation resistance of alloys based on the Cr-Cr2Ta system. To ascertain whether such additions may be appropriate, the effect of Ge additions on the microstructure and mechanical properties of a Cr-10Ta-7Si alloy was investigated. The Laves phase in this system was unexpectedly found to decompose into a lamellar structure comprising a Cr solid solution and a cubic phase with an Fd-3m structure. The addition of Ge promotes this decomposition, as well as the formation of the A15 Cr3(Si,Ge) phase, at the expense of the Cr solid solution. The formation of the A15 phase increases the hardness of the alloy but has a detrimental effect on its ductility
Noise Source Analysis in Counter Rotating Open Rotors
No full textDue to their potential to reduce aircraft emissions, Counter Rotating Open Rotors (CROR) have seen a renewed interest in applications, from civil aviation to urban air mobility. However, there are concerns surrounding their acoustic emissions. In thework presented, we investigated the noise sources for a range of CROR configurations for a general aviation class aircraft. Numerical models are used to compute the aerodynamic and aeroacoustic performance of these configurations. Further dissection of the various CROR noise sources is then carried out in order to better understand their contribution to CROR noise, and to direct the design of future low-noise CROR. Noise reductions were observed when the rotor-rotor spacing was increased. Increased contraction of the wake requires the need for increased clipping to reduce the tip vortex interaction source. Noise reductions were also observed in the case of asynchronous rotational speeds. However, this was accompanied by a reduction in propulsive efficiency. Analysis of the CROR in non-axial flight demonstrated the need to evaluate noisereducing strategies at off-design conditions. Whilst the analysis proved the ability to reduce various CROR noise sources, it highlighted that trade-offs with aerodynamic performance is necessary
Hybrid Evolutionary-based Sparse Channel Estimation for IRS-assisted mmWave MIMO Systems
No full textThe intelligent reflecting surface (IRS)-assisted millimeter wave (mmWave) communication system has emerged as a promising technology for coverage extension and capacity enhancement. Prior works on IRS have mostly assumed perfect channel state information (CSI), which facilitates in deriving the upper-bound performance but is difficult to realize in practice due to passive elements of IRS without signal processing capabilities.In this paper, we propose a compressive channel estimation techniques for IRS-assisted mmWave multi-input and multioutput (MIMO) system. To reduce the training overhead, the inherent sparsity of mmWave channels is exploited. By utilizing the properties of Kronecker products, IRS-assisted mmWave channel is converted into a sparse signal recovery problem, which involves two competing cost function terms (measurement error and sparsity term). Existing sparse recovery algorithms solve the combined contradictory objectives function using a regularization parameter, which leads to a suboptimal solution. To address this concern, a hybrid multiobjective evolutionary paradigm is developed to solve the sparse recovery problem, which can overcome the difficulty in the choice of regularization parameter value. Simulation results show that under a wide range of simulation settings, the proposed method achieves competitive error performance compared to existing channel estimation methods
Telephone Interview for Cognitive Status (TICS) scores associate with cognitive impairment and Alzheimer’s disease pathology at death
No full textBackground: Early diagnosis of Alzheimer’s disease (AD) provides an opportunity for early intervention. Cognitive testing has proven to be a reliable way to identify individuals who may be at risk of AD. The Telephone Assessment for Cognitive Screening (TICS) is proficient in screening for cognitive impairment. However, its ability to identify those at risk of developing AD pathology is unknown. Objective: We aim to investigate associations between TICS scores, collected over a period of 13 years, and the cognitive status of participants at death. We also examine relationships between TICS scores and neuropathological indices of AD (CERAD score, Thal phase and Braak stage).Methods: Between 2004 and 2017, participants from The University of Manchester Longitudinal Study of Cognition in Normal Healthy Old Age underwent cognitive assessment using TICS. Scores from four time points were available for analysis. Cognitive impairment and AD pathology at death was evaluated in 101 participants.Results: TICS scores at time points 2, 3 and 4 were significantly lower in those cognitively impaired at death compared to those considered cognitively normal. There were significant negative correlations between TICS scores and CERAD score and Braak stage at time points 2 and 4. No correlations between Thal phase and TICS were found.Conclusion: Findings indicate that TICS could be used, not only to screen for cognitive impairment, but also to identify individuals at risk of developing AD pathology, many years before any overt symptoms occur. Once identified, ‘at risk’ individuals could be targeted for early interventions which could attenuate the progression of the disease
Local Oxidation of the Buried Epoxy-Amine / Iron Oxide Interphase
No full textEpoxy-amine resins continue to find widespread use as the binders of corrosion protective organic coatings. In service, exposure to the environment ultimately results in oxidative deterioration of epoxy coatings, limiting the performance lifetime. Whilst the mechanisms underpinning surface oxidation have been characterized, few studies have examined polymeric degradation in the polymer / metal interphase, the integrity of which is central to performance. This is in part due to the inaccessibility of the buried interphase, which lies beyond the resolution limits of most organic analysis techniques. In this study, two innovative approaches are used to examine early stages of oxidative degradation of the buried polymer/iron oxide interphase for diglycidyl ether of bisphenol-A (DGEBA) coatings cross-linked with an aliphatic amine hardener, triethylenetetraamine (TETA). First, high fractions of iron oxide interfaces are introduced into the resin systems using synthetic hematite, Fe2O3, magnetite, Fe3O4 and goethite, Fe(O)OH powders, and the oxidation process is monitored using conventional infrared spectroscopy. Next, the buried interphase of coatings applied to iron is examined directly using nanoscale cross-sectional infrared analysis (via the photothermal infrared, PTIR, atomic force microscopy technique, known as AFM-IR). Diffusion limited oxidation is shown to initiate at the buried polymer-metal interface and progress slowly into the polymer, in accordance with pre-established mechanisms, resulting in chemical gradients of <400 nm after 28 days exposure to mild thermal aging conditions (70 °C, 14% RH)
A 15.5 GHz detection of the galaxy cluster minihalo in RXJ1720.1+2638
No full textRXJ1720.1¸2638 is a cool-core, ‘relaxed-appearing’ cluster with a minihalo previously detected up to 8.4 GHz, confined by X-ray-detected cold fronts. We present observations of the minihalo at 13 – 18 GHz with the Arcminute Microkelvin Imager telescope, simultaneously modelling the Sunyaev–Zel’dovich signal of the cluster in conjunction with Planck and Chandra data in order to disentangle the non-thermal emission of the minihalo. We show that the previously-reported steepening of the minihalo emission at 8.4 GHz is not supported by the AMI data and that the spectrum is consistent with a single power-law up to 18 GHz. We also show the presence of a larger-scale component of the minihalo extending beyond the cold fronts. Both of these observations could be explained by the ‘hadronic’ or ‘secondary’ mechanism for the production of relativistic electrons, rather than the currently-favoured ‘re-acceleration’ mechanism and/or multiple episodes of jet activity from the active galactic nucleus in the brightest cluster galaxy
Practical applications of a social justice agenda in counselling and psychotherapy: The Relational Equality in Education Framework (REEF)
No full textRecently there has been an increasing focus on the social justice agenda in counselling and psychotherapy. In order to ensure that this does not merely function as rhetoric, therapists must consider how to translate their social justice values into action. This paper aims to extend current understandings of social justice by foregrounding an emphasis on relational equality and power. We consider the importance of educational settings as a site of social justice action for therapists and set out The Relational Equality in Education Framework as an illustration of ways in which therapists might work to enhance relational equality in education on micro, meso and macro levels. Such efforts would ensure the social justice work of therapists takes an important shift from rhetoric to action
Doped graphene/carbon black hybrid catalyst giving enhanced oxygen reduction reaction activity with high resistance to corrosion in proton exchange membrane fuel cells
No full textNitrogen doping of the carbon is an important method to improve the performance and durability of catalysts for proton exchange membrane fuel cells by platinum-nitrogen and carbon-nitrogen bonds. This study shows that p-phenyl groups and graphitic N acting bridges linking platinum and the graphene/carbon black (the ratio graphene/carbon black=2/3) hybrid support materials achieved the average size of platinum nanoparticles with (4.88 ± 1.79) nm. It improved the performance of the lower-temperature hydrogen fuel cell up to 0.934 W cm-2 at 0.60 V, which is 1.55 times greater than that of commercial Pt/C. Doping also enhanced the interaction between Pt and the support materials, and the resistance to corrosion, thus improving the durability of the low-temperature hydrogen fuel cell with a much lower decay of 10 mV at 0.80 A cm-2 after 30k cycles of an in-situ accelerated stress test of catalyst degradation than that of 92 mV in Pt/C, which achieves the target of Department of Energy (<30 mV). Meanwhile, Pt/NrEGO2-CB3 remains 78% of initial power density at 1.5 A cm-2 after 5k cycles of in-situ accelerated stress test of carbon corrosion, which is more stable than the power density of commercial Pt/C, keeping only 54% after accelerated stress test
Non-restrictive interventions to reduce self-harm amongst children in mental health inpatient settings: Systematic review and narrative synthesis
No full textRates of self-harm amongst children appear to be increasing. This presents challenges for practitioners responsible for maintaining the safety of children admitted to mental health inpatient settings. Policy guidelines recommend that practitioners should aim to avoid the use of restrictive practices for children. It is currently unclear, however, what evidence-based alternatives to restrictive practices are available. We aimed to identify what non-restrictive interventions have been proposed to reduce self-harm amongst children in mental health inpatient settings and to evaluate the evidence supporting their use in clinical practice. A systematic search of five databases (CINAHL, Embase, Ovid MEDLINE, APA Psycinfo, and Cochrane) was conducted to identify articles reporting on non-restrictive interventions aimed at reducing self-harm amongst children in mental health inpatient settings. Articles were quality assessed and relevant data were extracted and synthesised using narrative synthesis. Searches identified relatively few relevant articles (n=7) and these were generally of low methodological quality. The underlying theoretical assumptions and putative mechanisms of change for the interventions described were often unclear. Despite concerns about the rates of self-harm amongst children in mental health inpatient settings, there is a lack of high-quality research to inform clinical practice. There is an urgent need to develop effective and non-restrictive interventions aimed at reducing self-harm for children using inpatient mental health services. Intervention development should be theoretically informed and be conducted in collaboration with people who have lived experience of this issue
