Deploying SiC BJTs in an 800-V switched-mode power supply for hybrid & electric vehicles

An SMPS for hybrid electric vehicle and electric vehicle applications is presented. The use of SiC BJTs in the primary-side switching circuitry is investigated. Practical deployment aspects are addressed. Particular attention is given to the design of the BJT base driver stage and a bespoke turn-on switching-aid circuit. Mathematical design calculations are not presented, but the proposed circuitry is demonstrated in a 1-kW isolated-output DC-DC converter operating from 800 V and supplying 48 V at a switching frequency of 60 kHz. Full-load efficiency was evaluated at 93.3% using a calorimeter

The unusual Kuiper belt object 2003 SQ317

We report photometric observations of Kuiper belt object 2013 SQ317 obtained between 2011 August 21 and 2011 November 1 at the 3.58 m New Technology Telescope, La Silla. We obtained a rotational lightcurve for 2013 SQ317 with a large peak-to-peak photometric range 0.85+/-0.05 mag, and a periodicity, P=7.210+/-0.001 hr. We also measure a nearly neutral broadband colour B-R=1.05+/-0.18 mag and a phase function with slope beta=0.95+/-0.41 mag/deg. The large lightcurve range implies an extremely elongated shape for 2013 SQ317, possibly as a single elongated object but most simply explained as a compact binary. If modelled as a compact binary near hydrostatic equilibrium, the bulk density of 2013 SQ317 is near 2670 kg m^(-3). If 2003 SQ317 is instead a single, elongated object, then its equilibrium density is about 860 kg m^(-3). These density estimates become uncertain at the 30% level if we relax the hydrostatic assumption and account for solid, "rubble pile"-type configurations. 2013 SQ317 has been associated with the Haumea family based on its orbital parameters and near-infrared colour; we discuss our findings in this context. If confirmed as a close binary, 2013 SQ317 will be the second object of its kind identified in the Kuiper belt.Comment: 8 pages, 10 figures, 4 tables. Submitted to MNRA

Extreme asteroids in the Pan-STARRS 1 Survey

Using the first 18 months of the Pan-STARRS 1 survey we have identified 33 candidate high-amplitude objects for follow-up observations and carried out observations of 22 asteroids. 4 of the observed objects were found to have observed amplitude $A_{obs}\geq 1.0$ mag. We find that these high amplitude objects are most simply explained by single rubble pile objects with some density-dependent internal strength, allowing them to resist mass shedding even at their highly elongated shapes. 3 further objects although below the cut-off for 'high-amplitude' had a combination of elongation and rotation period which also may require internal cohesive strength, depending on the density of the body. We find that none of the 'high-amplitude asteroids' identified here require any unusual cohesive strengths to resist rotational fission. 3 asteroids were sufficiently observed to allow for shape and spin pole models to be determined through light curve inversion. 45864 was determined to have retrograde rotation with spin pole axes $\lambda=218\pm 10^{\circ}, \beta=-82\pm 5^{\circ}$ and asteroid 206167 was found to have best fit spin pole axes $\lambda= 57 \pm 5^{\circ}$, $\beta=-67 \pm 5^{\circ}$. An additional object not initially measured with $A_{obs}>1.0$ mag, 49257, was determined to have a shape model which does suggest a high-amplitude object. Its spin pole axes were best fit for values $\lambda=112\pm 6^{\circ}, \beta=6\pm 5^{\circ}$. In the course of this project to date no large super-fast rotators ($P_{rot} < 2.2$ h) have been identified.Comment: 31 pages; accepted by A

Security information sharing via Twitter: 'Heartbleed' as a case study

The current paper outlines an exploratory case study in which we examined the extent to which specific communities of Twitter users engaged with the debate about the security threat known as ‘Heartbleed’ in the first few days after this threat was exposed. The case study explored which professional groups appeared to lead the debate about Heartbleed, the nature of the communication (tweets and retweets), and evidence about behaviour change. Using keywords from the Twitter user profiles, six occupational groups were identified, each of which were likely to have a direct interest in learning about Heartbleed (including legal, financial, entrepreneurial, press, and IT professionals). The groups participated to different degrees in the debate about Heartbleed. This exploratory case study provides an insight into information sharing, potential communities of influence, and points for future research in the absence of a voice of authority in the field of cybersecurity

Functional privacy concerns of older adults about pervasive health-monitoring systems

Technologies designed to support ageing can be deemed to be ageist in that they often exhibit a benevolent paternalism that tries to ‘protect’ older people. Often this involves gathering extensive data to monitor physical and cognitive decline at the expense of an individual’s privacy, with an underlying, often implicit, assumption that older adults no longer need much privacy. We consider such issues in the context of a project which seeks to promote the well-being of older adults. We conducted interviews with 20 older adults (10 males, 10 females, mean age=73) to ask, under what health and wellbeing circumstances would they wish to protect their privacy? Using thematic analysis, we uncovered six distinct reasons why older adults want to maintain privacy: protection from harm, autonomy, to present a positive social identity, to break free from social norms, to protect others, and to protect their own self-concept. We conclude that privacy is a highly valued resource for older adults and one that enables them to live fulfilling lives. We consider the design implications of our findings, noting that designers should aim to protect privacy from the outset, rather than viewing privacy as a ‘bolt-on’ that would inhibit data collection under specific circumstances. These concerns speak to the ‘paternalism’ agenda, in that older adults should be considered as active agents in the management of their own data disclosures