Swift UVOT Grism Observations of Nearby Type Ia Supernovae - I. Observations and Data Reduction

Ultraviolet (UV) observations of Type Ia supernovae (SNe Ia) are useful tools for understanding progenitor systems and explosion physics. In particular, UV spectra of SNe Ia, which probe the outermost layers, are strongly affected by the progenitor metallicity. In this work, we present 120 Neil Gehrels Swift Observatory UV spectra of 39 nearby SNe Ia. This sample is the largest UV (lambda < 2900 A) spectroscopic sample of SNe Ia to date, doubling the number of UV spectra and tripling the number of SNe with UV spectra. The sample spans nearly the full range of SN Ia light-curve shapes (delta m(B) ~ 0.6-1.8 mag). The fast turnaround of Swift allows us to obtain UV spectra at very early times, with 13 out of 39 SNe having their first spectra observed >~ 1 week before peak brightness and the earliest epoch being 16.5 days before peak brightness. The slitless design of the Swift UV grism complicates the data reduction, which requires separating SN light from underlying host-galaxy light and occasional overlapping stellar light. We present a new data-reduction procedure to mitigate these issues, producing spectra that are significantly improved over those of standard methods. For a subset of the spectra we have nearly simultaneous Hubble Space Telescope UV spectra; the Swift spectra are consistent with these comparison data.Comment: Accepted for publication in MNRA

Increasing safe design practice within the engineering curriculum

CONTEXT The Australian Work Health and Safety Strategy 2012-2022 contains two national Action Areas of direct relevance to Engineering Educators: Healthy and safe by design and Health and safety capabilities. The need for designs to be safe, and for student engineers to develop competencies in this area, is not new. However, poor design of machinery plant and powered tools continues to kill and injure Australian workers. Safe Work Australia (2014) reports that between 2006 and 2011, 63 workrelated deaths were determined to be caused by the unsafe design of machinery plant and power tools, or design-related factors contributed to the fatality. A further 125 fatalities were considered as possibly design-related. It is sad fact that many of these deaths were preventable with existing design solutions. Good design can eliminate (or minimise the impact of) the major physical, biomechanical and psychosocial hazards associated with work. From an engineering education perspective it is necessary to increase awareness amongst educators and students of these processes such that consideration of safe design is inherent to the engineering design process and not simply an added regulatory requirement. PURPOSE Safe design is not a separate activity or series of activities, but is integral to the engineering process regardless of sector or discipline. This paper reviews the role of engineering educators in understanding, promoting and embedding safe design principles within the engineering curricula. APPROACH The paper explores how safe design has been incorporated into engineering education since the early 1990s, and assesses the effectiveness of available resources and teaching practice. Changes to the legislative environment throughout this time are also described, to provide context and articulate implications for engineering educators. RESULTS The importance of safe design is recognised and resources do exist to support engineering educators to embed safe design principles within curriculum. The paper provides a series of recommendations to mainstream the available resources, highlights characteristics of effective practice and identifies areas for further professional development of engineering educators who are not familiar with safe design principles. CONCLUSIONS In order to develop graduates who are safe design practitioners, the model of engineering design introduced within the engineering curriculum must demonstrate that safe design is an inherent user requirement for all projects. This requires engineering educators to be familiar with human centred engineering design and how this impacts traditional technical design outcomes.Bernadette Foley, Prue Howard, Yvonne Toft and Mike Hur

Experiences of Support Following Autism Diagnosis in Adulthood

This study aimed to explore experiences of support after adulthood autism diagnosis. In this mixed-methods survey study of 137 adults, we found that most common formal supports received were counselling and mental health. Common unmet support needs were sensory sensitivities and accessing other services. Cost, lack of information, and fear of not being taken seriously were common barriers. Informal support was mainly helpful for self-understanding and emotions toward diagnosis. Qualitative findings included difficulties accessing formal support, need for practical quality-of-life supports and support from autistic peers and online communities. Based on these findings, future development of supportive interventions should address unmet needs, improve access, and explore the integration of autistic peer support and online support into formal services

A binary symmetric based hybrid meta-heuristic method for solving mixed integer unit commitment problem integrating with significant plug-in electric vehicles

Conventional unit commitment is a mixed integer optimization problem and has long been a key issue for power system operators. The complexity of this problem has increased in recent years given the emergence of new participants such as large penetration of plug-in electric vehicles. In this paper, a new model is established for simultaneously considering the day-ahead hourly based power system scheduling and a significant number of plug-in electric vehicles charging and discharging behaviours. For solving the problem, a novel hybrid mixed coding meta-heuristic algorithm is proposed, where V-shape symmetric transfer functions based binary particle swarm optimization are employed. The impact of transfer functions utilised in binary optimization on solving unit commitment and plug-in electric vehicle integration are investigated in a 10 unit power system with 50,000 plug-in electric vehicles. In addition, two unidirectional modes including grid to vehicle and vehicle to grid, as well as a bi-directional mode combining plug-in electric vehicle charging and discharging are comparatively examined. The numerical results show that the novel symmetric transfer function based optimization algorithm demonstrates competitive performance in reducing the fossil fuel cost and increasing the scheduling flexibility of plug-in electric vehicles in three intelligent scheduling modes

The Core of the Participatory Budgeting Problem

In participatory budgeting, communities collectively decide on the allocation of public tax dollars for local public projects. In this work, we consider the question of fairly aggregating the preferences of community members to determine an allocation of funds to projects. This problem is different from standard fair resource allocation because of public goods: The allocated goods benefit all users simultaneously. Fairness is crucial in participatory decision making, since generating equitable outcomes is an important goal of these processes. We argue that the classic game theoretic notion of core captures fairness in the setting. To compute the core, we first develop a novel characterization of a public goods market equilibrium called the Lindahl equilibrium, which is always a core solution. We then provide the first (to our knowledge) polynomial time algorithm for computing such an equilibrium for a broad set of utility functions; our algorithm also generalizes (in a non-trivial way) the well-known concept of proportional fairness. We use our theoretical insights to perform experiments on real participatory budgeting voting data. We empirically show that the core can be efficiently computed for utility functions that naturally model our practical setting, and examine the relation of the core with the familiar welfare objective. Finally, we address concerns of incentives and mechanism design by developing a randomized approximately dominant-strategy truthful mechanism building on the exponential mechanism from differential privacy

Experimental Investigation of a Broadband High-Temperature Superconducting Terahertz Mixer Operating at Temperatures Between 40 and 77 K

© 2017, Springer Science+Business Media, LLC. This paper presents a systematic investigation of a broadband thin-film antenna-coupled high-temperature superconducting (HTS) terahertz (THz) harmonic mixer at relatively high operating temperature from 40 to 77 K. The mixer device chip was fabricated using the CSIRO established step-edge YBa2Cu3O7-x (YBCO) Josephson junction technology, packaged in a well-designed module and cooled in a temperature adjustable cryocooler. Detailed experimental characterizations were carried out for the broadband HTS mixer at both the 200 and 600 GHz bands in harmonic mixing mode. The DC current-voltage characteristics (IVCs), bias current condition, local oscillator (LO) power requirement, frequency response, as well as conversion efficiency under different bath temperatures were thoroughly investigated for demonstrating the frequency down-conversion performance

Swift UVOT grism observations of nearby Type Ia supernovae – II. Probing the progenitor metallicity of SNe Ia with ultraviolet spectra

Ultraviolet (UV) observations of Type Ia supernovae (SNe Ia) are crucial for constraining the properties of their progenitor systems. Theoretical studies predicted that the UV spectra, which probe the outermost layers of an SN, should be sensitive to the metal content of the progenitor. Using the largest SN Ia UV (λ < 2900 Å) spectroscopic sample obtained from Neil Gehrels Swift Observatory, we investigate the dependence of UV spectra on metallicity. For the first time, our results reveal a correlation (∼2σ) between SN Ia UV flux and hostgalaxy metallicities, with SNe in more metal-rich galaxies (which are likely to have higher progenitor metallicities) having lower UV flux level. We find that this metallicity effect is only significant at short wavelengths (λ 2700 Å), which agrees well with the theoretical predictions. We produce UV spectral templates for SNe Ia at peak brightness. With our sample, we could disentangle the effect of light-curve shape and metallicity on the UV spectra. We also examine the correlation between the UV spectra and SN luminosities as parametrized by Hubble residuals. However, we do not see a significant trend with Hubble residuals. This is probably due to the large uncertainties in SN distances, as the majority of our sample members are extremely nearby (redshift z 0.01). Future work with SNe discovered in the Hubble flow will be necessary to constrain a potential metallicity bias on SN Ia cosmology