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"Jones, Jim"
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Coupling of turbulent and non-turbulent flow regimes within pyroclastic density currents
The internal dynamics of pyroclastic density currents are not easily observed. Experiments reveal how the underflow and turbulent ash-cloud regimes within pyroclastic flows are dynamically coupled through a zone of intermediate turbulence.
Volcanic eruptions are at their most deadly when pyroclastic density currents sweep across landscapes to devastate everything in their path
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,
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. The internal dynamics underpinning these hazards cannot be directly observed
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. Here we present a quantitative view inside pyroclastic density currents by synthesizing their natural flow behaviour in large-scale experiments. The experiments trace flow dynamics from initiation to deposition, and can explain the sequence and evolution of real-world deposits. We show that, inside pyroclastic density currents, the long-hypothesized non-turbulent underflow and fully turbulent ash-cloud regions
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,
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are linked through a hitherto unrecognized middle zone of intermediate turbulence and concentration. Bounded by abrupt jumps in turbulence, the middle zone couples underflow and ash-cloud regions kinematically. Inside this zone, strong feedback between gas and particle phases leads to the formation of mesoscale turbulence clusters. These extremely fast-settling dendritic structures dictate the internal stratification and evolution of pyroclastic density currents and allow the underflows to grow significantly during runout. Our experiments reveal how the underflow and ash-cloud regions are dynamically related—insights that are relevant to the forecasting of pyroclastic density current behaviour in volcanic hazard models.
Journal Article
The Big Empty
\"Synopsis: 1886. Tommy Stallings, deputy sheriff of Colfax County, is tracking a bad man. Jake Flynt robs banks. He hates sodbusters and has a nasty habit of taking his bullwhip to them, after which he burns them for fun. The man is a psychopathic monster and the gang he has assembled is a \"who's who\" of bad hombrâes in the Territory. . . horse thieves, murderers, and bank robbers. Stallings must track them down on the rolling plains of northern New Mexico known as the Big Empty. The land goes on forever, the wind blows like a banshee, and you never know who waits over the next rise. Tough duty for a young man who a few years earlier was a drifting cowboy trailing steers up to Colorado. His job is complicated by the fact that a young Irishman, Garrett O'Donnell, was witnessed participating in a bank robbery in Cimarrâon. Although O'Donnell has a controversial and mysterious past, Tommy knows he's no outlaw. Why on earth would a dirt-poor rancher with a wife and two young children throw in with these desperadoes? The young deputy is concerned with justice. If he has to bend the law here and there, he doesn't mind. The plot twists and turns through a backdrop of romance, political intrigue, friendships, and family relationships. Bodies pile up at an alarming rate as Jake Flynt goes on a murderous rampage. It all comes to a head in a showdown on top of Black Mesa out in the Big Empty\"-- Provided by publisher.
Book
Generation of air lubrication within pyroclastic density currents
Pyroclastic density currents are highly dangerous ground-hugging currents from volcanoes that cause >50% of volcanic fatalities globally. These hot mixtures of volcanic particles and gas exhibit remarkable fluidity, which allows them to transport thousands to millions of tonnes of volcanic material across the Earth’s surface over tens to hundreds of kilometres, bypassing tortuous flow paths and ignoring rough substrates and flat and upsloping terrain. Their fluidity is attributed to an internal process that counters granular friction. However, it is difficult to measure inside pyroclastic density currents to quantify such a friction-defying mechanism. Here we show, through large-scale experiments and numerical multiphase modelling, that pyroclastic density currents generate their own air lubrication. This forms a near-frictionless basal region. Air lubrication develops under high basal shear when air is locally forced downwards by reversed pressure gradients and displaces particles upward. We show that air lubrication is enhanced through a positive feedback mechanism, explaining how pyroclastic density currents are able to propagate over slopes much shallower than the angle of repose of any natural granular material. This discovery necessitates a re-evaluation of hazard models that aim to predict the velocity, runout and spreading of pyroclastic density currents.Pyroclastic density currents are able to travel large distances because they generate their own air lubrication, according to large-scale laboratory experiments.
Journal Article
The snow lion
Caro is too shy to make friends in her new neighborhood until she meets a mysterious Snow Lion, who plays with her and encourages her to meet other children.
Book
Food smoke generation by frictional heating
Smoke can be generated by frictional heating where a plank of wood is pressed against a spinning wheel. Here, a plank of kānuka (12 × 12 × 150 mm), a common New Zealand food smoking wood, is pressed against a wheel (diameter 123 mm) with a knurled surface (asperities, 200 μm). Wheel speed (2500–3500 rpm), pressing force (9.8–68.7 N) and chamber temperature (ambient − 200 °C) were varied. Measurements were performed of the plank wear rate, power draw and, in the ambient trials, the frictional interface temperature. Three distinctive wear behaviours appear: no smouldering with no wear, steady smouldering at an intermediate rate (
ca
. 0.1 mm/s), and steady smouldering at a high rate (
ca
. 0.4 mm/s). The transition between these two steady wear behaviours occurs sooner when pressing force and chamber temperature are increased and are characterized by marked reductions in the coefficient of friction, from
ca
. 0.6–0.9 to < 0.1. The transition is also associated with an order of magnitude change from
ca
. 1 to 10 mm of wear per kilojoule of expended frictional energy. While the precise frictional interface temperature and the heat sinks are difficult to quantify, the transition between these steady wear behaviours signals an exothermic shift in the heat of reaction, indicating the increased contribution of secondary reactions to the overall energetics. These results underlie the difficulty in achieving steady and consistent smoke production in frictional food smoke generators.
Journal Article
Marvel Knights Fantastic Four : the complete collection. Vol. 1
The far-out Fantastic Four join the hard-hitting Marvel Knights imprint! The FF must regroup to overcome the one threat their incredible powers cannot defeat - bankruptcy! And when Reed, Sue and Ben take Franklin on a camping trip to the Pine Barrens, what they find is a strange creature that may well be the Jersey Devil! While New York freezes in the icy grip of winter, an old foe resurfaces with a grudge: Namor! But soon the team's deepest fears and doubts are spreading from their dreams to the waking world. Their old villain Psycho-Man may hold the key, but he's ... dying?! And blind sculptress Alicia Masters has her sight restored -but at what cost? Plus, witness the ultimate Thing/Hulk battle -it's a knock-down, drag-out slobber knocker that will rattle your molars!
Book
Turbulent particle-gas feedback exacerbates the hazard impacts of pyroclastic density currents
Causing one-third of all volcanic fatalities, pyroclastic density currents create destruction far beyond our current scientific explanation. Opportunities to interrogate the mechanisms behind this hazard have long been desired, but pyroclastic density currents persistently defy internal observation. Here we show, through direct measurements of destruction-causing dynamic pressure in large-scale experiments, that pressure maxima exceed theoretical values used in hazard assessments by more than one order of magnitude. These distinct pressure excursions occur through the clustering of high-momentum particles at the peripheries of coherent turbulence structures. Particle loading modifies these eddies and generates repeated high-pressure loading impacts at the frequency of the turbulence structures. Collisions of particle clusters against stationary objects generate even higher dynamic pressures that account for up to 75% of the local flow energy. To prevent severe underestimation of damage intensities, these multiphase feedback processes must be considered in hazard models that aim to mitigate volcanic risk globally.
Journal Article
Batman : Knightfall
Volume 1: \"The inmates of Gotham City's Arkham Asylum are loose, and Batman is in hot pursuit of The Joker, the Riddler, Poison Ivy, Killer Croc, Scarecrow and more. Pushed to the limit, the Dark Knight comes face to face with Bane, a hyper-pumped-up monstrosity, who delivers a crippling blow that changes Batman's destiny forever. Batman: Knightfall Vol. 1 presents the epic battle between Batman and one of his greatest foes of all time, Bane.\"-- Provided by publisher.
Book
AMGE Based on Element Agglomeration
This paper contains the main ideas for an AMGe (algebraic multigrid for finite elements) method based on element agglomeration. In the method, coarse grid elements are formed by agglomerating fine grid elements. Compatible interpolation operators are constructed which yield coarse grid basis functions with a minimal energy property. Heuristics based on interpolation quality measures are used to guide the agglomeration procedure. The performance of the resulting method is demonstrated in two-level numerical experiments.
Journal Article