Inherent work suit buoyancy distribution:effects on lifejacket self-righting performance

Introduction: Accidental immersion in cold water is an occupational risk. Work suits and life jackets (LJ) should work effectively in combination to keep the airway clear of the water (freeboard) and enable self-righting. We hypothesized that inherent buoyancy, in the suit or LJ, would be beneficial for enabling freeboard, but its distribution may influence LJ self-righting. Methods: Six participants consented to complete nine immersions. Suits and LJ tested were: flotation suit (FLOAT; 85 N inherent buoyancy); oilskins 1 (OS-1) and 2 (OS-2), both with no inherent buoyancy; LJs (inherent buoyancy/buoyancy after inflation/total buoyancy), LJ-1 50/150/200 N, LJ-2 0/290/290 N, LJ-3 80/190/270 N. Once dressed, the subject entered an immersion pool where uninflated freeboard, self-righting performance, and inflated freeboard were measured. Data were compared using Friedman’s test to the 0.05 alpha level. Results: All suits and LJs enabled uninflated and inflated freeboard, but differences were seen between the suits and LJs. Self-righting was achieved on 43 of 54 occasions, irrespective of suit or LJ. On all occasions that self-righting was not achieved, this occurred in an LJ that included inherent buoyancy (11/54 occasions). Of these 11 failures, 8 occurred (73% of occasions) when the FLOAT suit was being worn. Discussion: LJs that included inherent buoyancy, that are certified as effective on their own, worked less effectively from the perspective of self-righting in combination with a work suit that also included inherent buoyancy. Equipment that is approved for use in the workplace should be tested in combination to ensure adequate performance in an emergency scenario

Response maxima in time-modulated turbulence: Direct Numerical Simulations

The response of turbulent flow to time-modulated forcing is studied by direct numerical simulations of the Navier-Stokes equations. The large-scale forcing is modulated via periodic energy input variations at frequency $\omega$. The response is maximal for frequencies in the range of the inverse of the large eddy turnover time, confirming the mean-field predictions of von der Heydt, Grossmann and Lohse (Phys. Rev. E 67, 046308 (2003)). In accordance with the theory the response maximum shows only a small dependence on the Reynolds number and is also quite insensitive to the particular flow-quantity that is monitored, e.g., kinetic energy, dissipation-rate, or Taylor-Reynolds number. At sufficiently high frequencies the amplitude of the kinetic energy response decreases as $1/\omega$. For frequencies beyond the range of maximal response, a significant change in phase-shift relative to the time-modulated forcing is observed.Comment: submitted to Europhysics Letters (EPL), 8 pages, 8 Postscript figures, uses epl.cl

Towards Baselines for Shoulder Surfing on Mobile Authentication

Given the nature of mobile devices and unlock procedures, unlock authentication is a prime target for credential leaking via shoulder surfing, a form of an observation attack. While the research community has investigated solutions to minimize or prevent the threat of shoulder surfing, our understanding of how the attack performs on current systems is less well studied. In this paper, we describe a large online experiment (n=1173) that works towards establishing a baseline of shoulder surfing vulnerability for current unlock authentication systems. Using controlled video recordings of a victim entering in a set of 4- and 6-length PINs and Android unlock patterns on different phones from different angles, we asked participants to act as attackers, trying to determine the authentication input based on the observation. We find that 6-digit PINs are the most elusive attacking surface where a single observation leads to just 10.8% successful attacks, improving to 26.5\% with multiple observations. As a comparison, 6-length Android patterns, with one observation, suffered 64.2% attack rate and 79.9% with multiple observations. Removing feedback lines for patterns improves security from 35.3\% and 52.1\% for single and multiple observations, respectively. This evidence, as well as other results related to hand position, phone size, and observation angle, suggests the best and worst case scenarios related to shoulder surfing vulnerability which can both help inform users to improve their security choices, as well as establish baselines for researchers.Comment: Will appear in Annual Computer Security Applications Conference (ACSAC

VARIATIONS IN SALINITY STRUCTURE IN SASKATCHEWAN’S DEVONIAN CARBONATES

Industry provided and public domain geochemical and isotopic data from 1950 to present day were collected for the purpose of this research. The intent of this study is to better understand the groundwater flow patterns and hydrochemistry in Devonian carbonates within the Saskatchewan and Williston basins. The Birdbear, Duperow, Souris River, and Dawson Bay formations are of interest owing to their proximity to the mining units of the Prairie Evaporite Formation. Due to the undesirable outcomes of groundwater interacting with the soluble minerals of the mining unit, the understanding of the nature of the water contained in the overlying units is of great importance. The creation of a comprehensive database has allowed for graphical as well as spatial analysis of water chemistry data within the basin. In addition, it is now possible to assess for patterns of variation and to attempt to track chemical evolution at a regional scale through the manipulation of this data. By combining data on water chemistry, interpreting the salinity characteristics and expressing the results in a spatial context, information on mineral precipitation, dissolution, and fluid migration were obtained. Patterns found were then utilized to assess regional scale hydrogeology, recharge and discharge. Through a graphical and regional assessment of the stratigraphic hydrochemistry it has been shown that the four units differ. The Birdbear, Duperow, Souris River, and Dawson Bay formations were shown to comprise of an end member type system ranging from meteoric water dominated to original syndepositional evaporated sea water dominated chemistries. Ratios of Na to Cl and Br to Cl, TDS concentrations, as well as δD and δ18O isotope values of water samples have demonstrated Birdbear and Duperow formations have seen the greatest influence from meteoric water input and halite dissolution while the Dawson Bay Formation shows a signature indicative of syndepositional evaporated sea water. The Souris River Formation consists of a mixture of these two end-member hydrochemistries. At a regional scale, the four formations follow known trends in hydrogeology, with recharge indicated in in the south and south west sides of the basins, and discharge in the north and north east along the Manitoba escarpment. Concentrations of TDS also support the location of previously mapped large-scale evaporite dissolution features. It has been shown using TDS, Na/Cl, and δH2/δO18 that the signature of a water sample from a stratigraphic unit in the center of the basin can look identical to that of the signature of a different stratigraphy at the basin edge. Resultant variation in salinities, indicating the different sources of ground water as well as the evolution through various degrees of water rock interaction, has raised questions on the validity of attempting to use chemistry to stratigraphically fingerprint water samples. It has been shown groundwater salinity characteristics have a great degree of variability depending on the location in the basin. Therefore when attempting to use chemistry to determine which stratigraphic horizon a water sample comes from it is essential that both a thorough regional and local scale hydrochemical analysis are done

Component-specific modeling

Accomplishments are described for a 3 year program to develop methodology for component-specific modeling of aircraft hot section components (turbine blades, turbine vanes, and burner liners). These accomplishments include: (1) engine thermodynamic and mission models, (2) geometry model generators, (3) remeshing, (4) specialty three-dimensional inelastic structural analysis, (5) computationally efficient solvers, (6) adaptive solution strategies, (7) engine performance parameters/component response variables decomposition and synthesis, (8) integrated software architecture and development, and (9) validation cases for software developed