Wear and Friction Modeling on Lifeboat Launch Systems

The RNLI provides search and rescue cover along the UK and RoI coast using a variety of lifeboats and launch techniques. In locations where there is no natural harbour it is necessary to use a slipway to launch the lifeboat into the sea. Lifeboat slipway stations consist of an initial section where the boat is held on rollers followed by an inclined keelway lined with low friction composite materials, the lifeboat is released from the top of the slipway and proceeds under its own weight into the water. The lifeboat is later recovered using a winch line. It is common to manually apply grease to the composite slipway lining before each launch and recovery in order to ensure sufficiently low friction for successful operation. With the introduction of the Tamar class lifeboat it is necessary to upgrade existing boathouses and standardise slipway operational procedures to ensure consistent operation. The higher contact pressures associated with the new lifeboat have led to issues of high friction and wear on the composite slipway linings and the manual application of grease to reduce friction is to be restricted due to environmental impact and cost factors. This paper presents a multidisciplinary approach to modelling slipway panel wear and friction using tribometer testing in conjunction with finite element analysis and slipway condition surveys to incorporate common real-world effects such as panel misalignments. Finally, it is shown that a freshwater lubrication system is effective, reducing cost and environmental impacts while maintaining good friction and wear performance

Gender violence in schools: taking the ‘girls-as-victims’ discourse forward

This paper draws attention to the gendered nature of violence in schools. Recent recognition that schools can be violent places has tended to ignore the fact that many such acts originate in unequal and antagonistic gender relations, which are tolerated and ‘normalised’ by everyday school structures and processes. After examining some key concepts and definitions, we provide a brief overview of the scope and various manifestations of gender violence in schools, noting that most research to date has focused on girls as victims of gender violence within a heterosexual context and ignores other forms such as homophobic and girl violence. We then move on to look at a few interventions designed to address gender violence in schools in the developing world and end by highlighting the need for more research and improved understanding of the problem and how it can be addressed

Which way up? Recognition of homologous DNA segments in parallel and antiparallel alignment

Homologous gene shuffling between DNA promotes genetic diversity and is an important pathway for DNA repair. For this to occur, homologous genes need to find and recognize each other. However, despite its central role in homologous recombination, the mechanism of homology recognition is still an unsolved puzzle. While specific proteins are known to play a role at later stages of recombination, an initial coarse grained recognition step has been proposed. This relies on the sequence dependence of the DNA structural parameters, such as twist and rise, mediated by intermolecular interactions, in particular electrostatic ones. In this proposed mechanism, sequences having the same base pair text, or are homologous, have lower interaction energy than those sequences with uncorrelated base pair texts; the difference termed the recognition energy. Here, we probe how the recognition energy changes when one DNA fragment slides past another, and consider, for the first time, homologous sequences in antiparallel alignment. This dependence on sliding was termed the recognition well. We find that there is recognition well for anti-parallel, homologous DNA tracts, but only a very shallow one, so that their interaction will differ little from the interaction between two nonhomologous tracts. This fact may be utilized in single molecule experiments specially targeted to test the theory. As well as this, we test previous theoretical approximations in calculating the recognition well for parallel molecules against MC simulations, and consider more rigorously the optimization of the orientations of the fragments about their long axes. The more rigorous treatment affects the recognition energy a little, when the molecules are considered rigid. However when torsional flexibility of the DNA molecules is introduced, we find excellent agreement between analytical approximation and simulation.Comment: Paper with supplemental material attached. 41 pages in all, 4 figures in main text, 3 figures in supplmental. To be submitted to Journa

Lie symmetries for two-dimensional charged particle motion

We find the Lie point symmetries for non-relativistic two-dimensional charged particle motion. These symmetries comprise a quasi-invariance transformation, a time-dependent rotation, a time-dependent spatial translation and a dilation. The associated electromagnetic fields satisfy a system of first-order linear partial differential equations. This system is solved exactly, yielding four classes of electromagnetic fields compatible with Lie point symmetries

The effect of hydrogen etching on 6H-SiC studied by temperature-dependent current-voltage and atomic force microscopy

6H–SiC was etched with hydrogen at temperatures between 1000 and 1450°C. The etchedSi-terminated face for the 6H‐SiC wafer was investigated by atomic force microscopy and temperature-dependent current–voltage (I–V–T)measurements. Mechanical polishing damage was effectively removed by hydrogen etching at temperatures above 1250°C. Atomic force microscopy images revealed that very good surface morphology, atomic layer flatness, and large and large step width were achieved. Schottky diode characteristics were investigated in detail by current–voltage and temperature-dependent current–voltage measurements, and the results showed a transition from defect assisted tunneling to thermionic emission as the annealingtemperature was increased from 1250 to 1450°C

Effect of n+-GaN subcontact layer on 4H–SiC high-power photoconductive switch

High-power photoconductive semiconductor switching devices were fabricated on 4H–SiC. In order to prevent current crowding, reduce the contact resistance, and avoid contact degradation, a highly n-doped GaN subcontact layer was inserted between the contact metal and the high resistivity SiC bulk. This method led to a two orders of magnitude reduction in the on-state resistance and, similarly, the photocurrent efficiency was increased by two orders of magnitude with the GaN subcontact layer following the initial high current operation. Both dry etching and wet etching were used to remove the GaN subcontact layer in the channel area. Wet etching was found to be more suitable than dry etching

Quality of relationships as predictors of outcomes in people with dementia: a systematic review protocol

INTRODUCTION: Serious adverse outcomes for people with dementia include institutionalisation, hospitalisation, death, development of behavioural and psychiatric symptoms, and reduced quality of life. The quality of the relationship between the person with dementia and their informal/family carer is thought to affect the risk of these outcomes. However, little is known about which aspects of relationship quality are important, or how they affect outcomes for people with dementia. METHODS AND ANALYSIS: This will be a systematic review of the literature. Electronic databases MEDLINE, EMBASE, Web of Science, PsycInfo, the Cochrane Database, ALOIS and OpenGrey will be searched from inception. 2 independent reviewers will screen results for eligibility with standardised criteria. Data will be extracted for relevant studies, and information on the associations between relationship quality and dementia outcomes will be synthesised. Meta-analysis will be performed if possible to calculate pooled effect sizes. Narrative synthesis will be performed if study heterogeneity rules out meta-analysis. ETHICS AND DISSEMINATION: Ethical review is not necessary as this review summarises data from previous studies. Results will be disseminated via peer-reviewed publication. Results will also be disseminated to a patient and public involvement group and an expert panel for their views on the findings and implications for future work. TRIAL REGISTRATION NUMBER: CRD42015020518

Excitonic recombination dynamics in non-polar GaN/AlGaN quantum wells

The optical properties of GaN/Al0.15Ga0.85N multiple quantum wells are examined in 8 K–300 K temperature range. Both polarized CW and time resolved temperature-dependent photoluminescence experiment are performed so that we can deduce the relative contributions of the non-radiative and radiative recombination processes. From the calculation of the proportion of the excitonic population having wave vector in the light cone, we can deduce the variation of the radiative decay time with temperature. We find part of the excitonic population to be localized in concert with the report of Corfdir et al. (Jpn. J. Appl. Phys., Part 2 52, 08JC01 (2013)) in case of a-plane quantum wells