Buoyancy effects on concurrent flame spread over thick PMMA.

The flammability of combustible materials in a spacecraft is important for fire safety applications because the conditions in spacecraft environments differ from those on earth. Experimental testing in space is difficult and expensive. However, reducing buoyancy by decreasing ambient pressure is a possible approach to simulate on-earth the burning behavior inside spacecraft environments. The objective of this work is to determine that possibility by studying the effect of pressure on concurrent flame spread, and by comparison with microgravity data, observe up to what point low-pressure can be used to replicate flame spread characteristics observed in microgravity. Specifically, this work studies the effect of pressure and microgravity on upward/concurrent flame spread over 10 mm thick polymethyl methacrylate (PMMA) slabs. Experiments in normal gravity were conducted over pressures ranging between 100 and 40 kPa and a forced flow velocity of 200 mm/s. Microgravity experiments were conducted during NASA's Spacecraft Fire Experiment (Saffire II), on board the Cygnus spacecraft at 100 kPa with an air flow velocity of 200 mm/s. Results show that reductions of pressure slow down the flame spread over the PMMA surface approaching that in microgravity. The data is correlated in terms of a non-dimensional mixed convection analysis that describes the convective heat transferred from the flame to the solid, and the primary mechanism controlling the spread of the flame. The extrapolation of the correlation to low pressures predicts well the flame spread rate obtained in microgravity in the Saffire II experiments. Similar results were obtained by the authors with similar experiments with a thin composite cotton/fiberglass fabric (published elsewhere). Both results suggest that reduced pressure can be used to approximately replicate flame behavior of untested gravity conditions for the burning of thick and thin solids. This work could provide guidance for potential ground-based testing for fire safety design in spacecraft and space habitats.

Evaluation of Spacecraft Smoke Detector Performance in the Low-Gravity Environment.

In the interest of fire prevention, most materials used in the interior construction of manned spacecraft are non-flammable, however, they do produce smoke when overheated. Spacecraft smoke detectors will ideally detect smoke generated by oxidative pyrolysis (such as smoldering) in order to allow the maximum time for the crew to respond before a larger flaming fire develops. An experiment on the International Space Station (ISS) characterized smoke from overheating common spacecraft materials. The following parameters were controlled: heating temperature, air flow past the samples and duration of aging. Two different spacecraft smoke detectors were included in the instrumentation and their performance with different smoke types has been evaluated. Additional equipment in the experiment included a thermal precipitator to sample particles for microscopic analysis upon return to Earth, and three commercial-off-the-shelf real-time instruments to measure particle mass and number concentration, and an ionization detector calibrated to estimate the first moment of the size distribution. Results from the ISS experiment show that smoke particles vary in morphology and average diameter, however, they are not significantly different from smoke particles generated in equivalent experiments performed in normal gravity. The two spacecraft smoke detectors did not successfully detect every type of smoke, which demonstrates that the next generation of spacecraft fire detectors must be improved and tested against smoke from relevant space materials.

The increasing use of cosmetic non-ionising radiation applications - types of procedures, potential risks to consumers and regulation in Australia.

In recent years, there has been a large increase in cosmetic applications using non-ionising radiation (NIR). These applications use various types of NIR such as lasers and ultrasound for numerous cosmetic outcomes such as epilation, skin rejuvenation and tattoo removal. Cosmetic NIR procedures are marketed as a low-cost and low-risk alternative to more invasive procedures. However, treatments with these devices always result in high NIR exposure to targeted tissue in order to ensure efficacy of treatment. Consequently, there is always a risk of adverse health effects from these procedures, which may be temporary or longer lasting. Research on the health risks of cosmetic NIR applications is lacking, particularly on the extent of poor treatment application or misuse. In Australia, except for the banning of solaria, there is no national regulation for the use of NIR devices for cosmetic purposes and only three states have established regulatory controls for certain optical cosmetic applications. To mitigate the impacts of this gap in oversight, the Australian Radiation Protection and Nuclear Safety Agency has published national advice for consumers and service providers that give information on cosmetic NIR treatments and the potential risks involved.

Polarization-driven reversible actuation in a photo-responsive polymer composite.

Light-responsive polymers and especially amorphous azopolymers with intrinsic anisotropic and polarization-dependent deformation photo-response hold great promises for remotely controlled, tunable devices. However, dynamic control requires reversibility characteristics far beyond what is currently obtainable via plastic deformation of such polymers. Here, we embed azopolymer microparticles in a rubbery elastic matrix at high density. In the resulting composite, cumulative deformations are replaced by reversible shape switching - with two reversible degrees of freedom defined uniquely by the writing beam polarization. We quantify the locally induced strains, including small creeping losses, directly by means of a deformation tracking algorithm acting on microscope images of planar substrates. Further, we introduce free-standing 3D actuators able to smoothly undergo multiple configurational changes, including twisting, roll-in, grabbing-like actuation, and even continuous, pivot-less shape rotation, all dictated by a single wavelength laser beam with controlled polarization.

Time- and Resource-Efficient Time-to-Collision Forecasting for Indoor Pedestrian Obstacles Avoidance.

As difficult vision-based tasks like object detection and monocular depth estimation are making their way in real-time applications and as more light weighted solutions for autonomous vehicles navigation systems are emerging, obstacle detection and collision prediction are two very challenging tasks for small embedded devices like drones. We propose a novel light weighted and time-efficient vision-based solution to predict Time-to-Collision from a monocular video camera embedded in a smartglasses device as a module of a navigation system for visually impaired pedestrians. It consists of two modules: a static data extractor made of a convolutional neural network to predict the obstacle position and distance and a dynamic data extractor that stacks the obstacle data from multiple frames and predicts the Time-to-Collision with a simple fully connected neural network. This paper focuses on the Time-to-Collision network's ability to adapt to new sceneries with different types of obstacles with supervised learning.

5G mobile networks and health-a state-of-the-science review of the research into low-level RF fields above 6 GHz.

The increased use of radiofrequency (RF) fields above 6 GHz, particularly for the 5 G mobile phone network, has given rise to public concern about any possible adverse effects to human health. Public exposure to RF fields from 5 G and other sources is below the human exposure limits specified by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). This state-of-the science review examined the research into the biological and health effects of RF fields above 6 GHz at exposure levels below the ICNIRP occupational limits. The review included 107 experimental studies that investigated various bioeffects including genotoxicity, cell proliferation, gene expression, cell signalling, membrane function and other effects. Reported bioeffects were generally not independently replicated and the majority of the studies employed low quality methods of exposure assessment and control. Effects due to heating from high RF energy deposition cannot be excluded from many of the results. The review also included 31 epidemiological studies that investigated exposure to radar, which uses RF fields above 6 GHz similar to 5 G. The epidemiological studies showed little evidence of health effects including cancer at different sites, effects on reproduction and other diseases. This review showed no confirmed evidence that low-level RF fields above 6 GHz such as those used by the 5 G network are hazardous to human health. Future experimental studies should improve the experimental design with particular attention to dosimetry and temperature control. Future epidemiological studies should continue to monitor long-term health effects in the population related to wireless telecommunications.

Mobile phone use and trends in the incidence of cancers of the parotid and other salivary glands.

BACKGROUND: There has been a significant increase in the use of mobile phones over the last three decades and a possible association with head cancers has been suggested, including cancers of the parotic and other salivary glands. We examined the incidence time trends of parotid and other salivary gland cancers in Australia to ascertain the influence of increased mobile phone use. METHODS: Analyses of incidence time trends were carried out using Poisson regression to estimate the annual percentage change (APC) in the incidence of salivary gland cancers of all available national registration data from 1982 to 2016, as well as specific time periods (1982-1993, 1994-2005, 2006-2016) representing changes in the prevalence of mobile phone use. RESULTS: The incidence of parotid gland cancer was stable for the periods 1982-1993 and 1994-2005. During 2006-2016 there was a large decrease in parotid gland cancer for males (APC: -3.71, 95 %CI: -6.66 to -0.67) and a large increase in females (4.80, 1.77-7.91) for adults aged 20-59 years. The incidence for other salivary gland cancers was stable during all the periods. CONCLUSIONS: The results do not indicate that mobile phone use increased the incidence of parotid or other salivary gland cancers. An increase in parotid gland cancer in females since 2006 may be attributed to other possible risk factors specific to this gender.

Whole organism concentration ratios in freshwater wildlife from an Australian tropical U mining environment and the derivation of a water radiological quality guideline value.

More than 10,000 whole organism concentration ratio (CRwo-water) values for freshwater wildlife were derived from radionuclide and stable element data representing an Australian tropical U mining environment. The CRwo-water values were summarised into five wildlife groups (bird, fish, mollusc, reptile and vascular plant). The summarised CRwo-water values represented 77 organism-element combinations. The CRwo-water values for U decay series elements were used in a tier 3 ERICA assessment. The assessment results were used to derive a water radiological quality guideline value (GV) for radiation protection of freshwater ecosystems in the context of the planned remediation of the Ranger U mine. The GV was an above-background water 226Ra activity concentration of 14 mBq L-1 (filtered fraction) or approximately 22 mBq L-1 (total fraction). The GV was based on the results of mollusc-bivalve as the limiting organism for the freshwater ecosystem.

Whole organism to tissue concentration ratios derived from an Australian tropical dataset.

Whole organism to tissue concentration ratios (CRwo-tissue) were derived for six wildlife groups (freshwater birds, freshwater bivalves, freshwater fishes, freshwater reptiles, freshwater vascular plants and terrestrial mammals). The wildlife groups and data represented species common to tropical northern Australia. Values of CRwo-tissue were derived for between 6 and 34 elements, depending upon wildlife group. The values were generally similar to international reference values. However, differences for some element-tissue combinations could affect radiation dose estimates for wildlife in certain environmental exposure situations, including uranium mining, where these data are intended to be applied.

On Simulating Concurrent Flame Spread in Reduced Gravity by Reducing Ambient Pressure.

The flammability of combustible materials in spacecraft environments is of importance for fire safety applications because the environmental conditions can greatly differ from those on earth, and a fire in a spacecraft could be catastrophic. Moreover, experimental testing in spacecraft environments can be difficult and expensive, so using ground-based tests to inform microgravity tests is vital. Reducing buoyancy effects by decreasing ambient pressure is a possible approach to simulate a spacecraft environment on earth. The objective of this work is to study the effect of pressure on material flammability, and by comparison with microgravity data, determine the extent to which reducing pressure can be used to simulate reduced gravity. Specifically, this work studies the effect of pressure and microgravity on upward/concurrent flame spread rates and flame appearance of a burning thin composite fabric made of 75% cotton and 25% fiberglass (Sibal). Experiments in normal gravity were conducted using pressures ranging between 100 and 30 kPa and a forced flow velocity of 20 cm/s. Microgravity experiments were conducted during NASA's Spacecraft Fire Experiment (Saffire), on board of the Orbital Corporation Cygnus spacecraft at 100 kPa and an air flow velocity of 20 cm/s. Results show that reductions of ambient pressure slow the flame spread over the fabric. As pressure is reduced, flame intensity is also reduced. Comparison with the concurrent flame spread rates in microgravity show that similar flame spread rates are obtained at around 30 kPa. The normal gravity and microgravity data is correlated in terms of a mixed convection non-dimensional parameter that describes the heat transferred from the flame to the solid surface. The correlation provides information about the similitudes of the flame spread process in variable pressure and reduced gravity environments, providing guidance for potential on-earth testing for fire safety design in spacecraft and space habitats.

Thin-filament pyrometry with a digital still camera.

A novel thin-filament pyrometer is presented. It involves a consumer-grade color digital still camera with 6 megapixels and 12 bits per color plane. SiC fibers were used and scanning-electron microscopy found them to be uniform with diameters of 13.9 micro m. Measurements were performed in a methane-air coflowing laminar jet diffusion flame with a luminosity length of 72 mm. Calibration of the pyrometer was accomplished with B-type thermocouples. The pyrometry measurements yielded gas temperatures in the range of 1400-2200 K with an estimated uncertainty of +/-60 K, a relative temperature resolution of +/-0.215 K, a spatial resolution of 42 mum, and a temporal resolution of 0.66 ms. Fiber aging for 10 min had no effect on the results. Soot deposition was less problematic for the pyrometer than for the thermocouple.

Theoretical study of the kinetics of the reactions Se + O2 --> Se + O and As + HCl --> AsCl + H.

Selenium and arsenic reactions believed to take place in the flue gases of coal combustion facilities were investigated. Prior theoretical work involving various As and Se species was completed using DFT and a broad range of ab initio methods. Building upon that work, the present study is a determination of the kinetic and thermodynamic parameters of the reactions, Se + O2 --> SeO + O and As + HCl --> AsCl + H at the CCSD/RCEP28VDZ and QCISD(T)/6-311++G(3df,3pd) levels of theory, respectively. Transition state theory was used in determining the kinetic rate constants along with collision theory as a means of comparison. The calculated K(eq) values are compared to experimental data, where available.

A theoretical study of properties and reactions involving arsenic and selenium compounds present in coal combustion flue gases.

Species of arsenic and selenium thought to be present in coal combustion flue gases were studied using density functional theory and a broad range of ab initio methods. At each level of theory, the calculated geometries and vibrational frequencies of each species as well as the reaction enthalpies of anticipated reactions were compared with experimental data where available. Comparisons between each calculation are given along with a discussion of the better performance of some theoretical calculations for a given species/reaction.