Abstracts of NASA-ASRDI publications relevant to aerospace safety research

Abstracts covering the following areas are presented: (1) oxygen technology; (2) fire safety; (3) accidents/incidents; (4) toxic spills; (5) aircraft safety; (6) structural failures; (7) nuclear systems; (8) fluid flow; and (9) zero gravity combustion

Directory of aerospace safety specialized information sources

Directory aids safety specialists in locating information sources and individual experts in engineering-related fields. Lists 170 organizations and approximately 300 individuals who can provide safety-related technical information in form of documentation, data, and consulting expertise. Information on hazard and failure cause identification, accident analysis, and materials characteristics are covered

What's better for our health? Conducting protective actions during a nuclear emergency or accepting a certain radiation dose?

The threat caused by ionising radiation has resulted in the establishment of strict radiation protection guidelines. This is especially true for severe nuclear power plant (NPP) accident scenarios, which may involve the release of significant amounts of ionising radiation. However, we believe that the fine balance between the benefit of a certain protective action (e.g. evacuation) and its risks is not always accounted for properly. Deaths and mental health problems have been associated with protective actions (e.g. evacuation) implemented in the response to the Fukushima Daiichi (NPP) accident in 2011. The protective actions were implemented consistent with international recommendations, to reduce radiation-induced health effects, even though the off-site effective doses were too low to indicate that there would be any discernible radiation-induced health effects. In this paper, we will provide a first step for the development of tools to evaluate the risk of protective actions versus the radiation-induced health risk. Over 50 papers were selected as useful from more than 600 reviewed papers to characterise the health impact of protective actions taken during different emergencies (including, technical and natural emergencies). An analysis was performed comparing the radiation-induced health effects averted by protective actions with the health effects associated with the protective actions. We concentrated our analysis on deaths and mental health problems associated with protective actions compared with the inferred radiation-induced deaths averted by the protective actions. Our analysis is stated in terms of absolute risk (cases per 1000) of health effects to allow for a direct comparison. It indicates that taking protective actions consistent with dose criteria typically used in many countries could result in more excess deaths than the inferred radiation-induced deaths prevented, as well as resulting in mental health problems. We identified that residents of facilities for long stays and the elderly are particularly vulnerable and a significant number of the deaths among the general public are associated with a lack of emergency preparedness provisions

Distributions of inherent structure energies during aging

We perform extensive simulations of a binary mixture Lennard-Jones system subjected to a temperature jump in order to study the time evolution of fluctuations during aging. Analyzing data from 1500 different aging realizations, we calculate distributions of inherent structure energies for different aging times and contrast them with equilibrium. We find that the distributions initially become narrower and then widen as the system equilibrates. For deep quenches, fluctuations in the glassy system differ significantly from those observed in equilibrium. Simulation results are partially captured by theoretical predictions only when the final temperature is higher than the mode coupling temperature.Comment: 5 pages, 4 figure

Dielectric study of the glass transition: correlation with calorimetric data

The glass transition in amorphous poly(ethylene terephthalate) is studied by thermally stimulated depolarization currents (TSDC) and differential scanning calorimetry (DSC). The ability of TSDC to decompose a distributed relaxation, as the glass transition, into its elementary components is demonstrated. Two polarization techniques, windows polarization (WP) and non-isothermal windows polarization (NIW), are employed to assess the influence of thermal history in the results. The Tool-Narayanaswami-Moynihan (TNM) model has been used to fit the TSDC spectra. The most important contributions to the relaxation comes from modes with non-linearity (x) around 0.7. Activation energies yield by this model are located around 1eV for polarization temperature (Tp) below 50C and they raise up to values higher than 8eV as Tp increases (up to 80C). There are few differences between results obtained with WP and NIW but, nonetheless, these are discussed. The obtained kinetic parameters are tested against DSC results in several conditions. Calculated DSC curves at several cooling and heating rates can reproduce qualitatively experimental DSC results. These results also demonstrate that modelization of the non-equilibrium kinetics involved in TSDC spectroscopy is a useful experimental tool for glass transition studies in polar polymers.Comment: 13 pages, 2 tables, 10 figures; minor change

Kovacs effects in an aging molecular liquid

We study by means of molecular dynamics simulations the aging behavior of a molecular model of ortho-terphenyl. We find evidence of a a non-monotonic evolution of the volume during an isothermal-isobaric equilibration process, a phenomenon known in polymeric systems as Kovacs effect. We characterize this phenomenology in terms of landscape properties, providing evidence that, far from equilibrium, the system explores region of the potential energy landscape distinct from the one explored in thermal equilibrium. We discuss the relevance of our findings for the present understanding of the thermodynamics of the glass state.Comment: RevTeX 4, 4 pages, 5 eps figure

Changing player behaviour in sport during the COVID-19 pandemic: Shake on it?

To prevent the spread of infection during matches and training activities is a major challenge facing all sports returning from the enforced COVID-19 shutdown. During training and matches, rugby league players make contact with others which can result in SARS-CoV-2 virus transmission. While these interactions characterise the appeal of the game, a number of them can be avoided, including shaking hands and conversing after the match. This paper presents a framework underpinned by behavioural science (capability, opportunity, motivation and behaviour model, COM-B) to support stakeholders in helping players adopt new social distance norms and behaviours. This framework helps to ensure the players have the capability, opportunity, and motivation to adopt new COVID-19 risk minimising behaviours, which they will need to commit to 100%

On the dependence of the avalanche angle on the granular layer thickness

A layer of sand of thickness h flows down a rough surface if the inclination is larger than some threshold value theta which decreases with h. A tentative microscopic model for the dependence of theta with h is proposed for rigid frictional grains, based on the following hypothesis: (i) a horizontal layer of sand has some coordination z larger than a critical value z_c where mechanical stability is lost (ii) as the tilt angle is increased, the configurations visited present a growing proportion $_s of sliding contacts. Instability with respect to flow occurs when z-z_s=z_c. This criterion leads to a prediction for theta(h) in good agreement with empirical observations.Comment: 6 pages, 2 figure