2,630 research outputs found
Beneficiation of concentrated ultrafine suspensions with a Falcon UF concentrator
No full textFalcon concentrators are enhanced gravity separators designed for concentrating fine particles. The Falcon UF model is unique in that it is dedicated to beneficiation of ultrafines, one key feature being that it does not make use of any fluidization water. We investigated the physics of particle transport inside Falcon concentrators, and concluded that separation efficiency is governed by differential settling velocity. We derived and published a predictive model of the partition function under dilute conditions. We intend to extend the initial model to concentrated ultrafine suspensions for application to industrial scenarios by adding hindered settling to account for solid concentration effects
Fluid dynamics based modelling of the Falcon concentrator for ultrafine particle beneficiation
No full textEnhanced gravity separators are widely used in minerals beneficiation, as their superior gravity field enables them to separate particles within narrow classes of density and size. This study aims to shed light on the Falcon concentrator’s ability to separate particles within size and density ranges lower than usual, say 5 to 60 μm and 1.2 to 3.0 s.g. respectively. As differential particle settling is expected to be the prevailing separation mechanism under such conditions, this study presents the workings of a predictive Falcon separation model that embeds phenomenological fluid and particle flow simulation inside the Falcon’s flowing film. Adding to the novelty of modelling the Falcon concentrator
using a fluid mechanics approach, one point of practical significance within this work is the derivation of the Falcon’s partition function from fluid flow simulation results
Physical analysis and modeling of the Falcon concentrator for beneficiation of ultrafine particles
No full textA predictive model of the Falcon enhanced gravity separator has been derived from a physical analysis of its separation principle, and validated against experimental data. After summarizing the previous works that led to this model and the hypotheses on which they rely, the model is extended to cover a wide range of operating conditions and particle properties. The most significant development presented here is the extension of the analytical law to concentrated suspensions, which makes it applicable to actual plant operating conditions. Two examples of industrial use cases are described and studied by interrogation of the model: dredged sediment waste reduction and coal recovery from fine tailings. Comparisons with empirical studies available in the literature show a good agreement between model predictions and industrial data. The model is then used to identify separation efficiency limitations as well as possible solutions to overcome them. These two examples serve to show how this predictive model can be used to obtain valuable information to improve physical separation processes using a Falcon concentrator, or to evaluate Falcon separator’s abilities for new applications
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A Gravitational Redshift Determination Of The Mean Mass Of DBA White Dwarfs
No full textWe measure apparent velocities (v(app)) of the H alpha and H beta Balmer line cores for 16 helium-dominated white dwarfs (WDs) using optical spectra taken for the European Southern Observatory SN Ia progenitor survey (SPY). Following the gravitational redshift method employed by Falcon et al. [1], we find a mean apparent velocity of (v(app)) = 39.58 +/- 4.41 km s(-1) and use it to derive a mean mass of < M > = 0.701(-0.046)(+0.042) M(circle dot). Though the sample is small, the mean mass appears to be larger than the mean mass of DAs derived using the same method [0.647(-0.014)(+0.013) M(circle dot), 1]Astronom
2010 population status of the Peregrine Falcon in the Yukon Territory
No full textThis survey is the Yukon section of the Canada-wide periodic monitoring of the status of the Peregrine Falcon, a requirement of the Canadian Recovery Plan for the species. Historically, this effort began in the 1960’s when a population of the interior race of peregrine falcon (Falco peregrinus anatum) was first described breeding on the riparian cliffs of the rivers draining the central Yukon (Cade and Fyfe 1970). The birds’ numbers subsequently crashed and more recently have been recovering
A Gravitational Redshift Determination Of The Mean Mass Of White Dwarfs: DBA And DB Stars
No full textWe measure apparent velocities (nu(app)) of absorption lines for 36 white dwarfs (WDs) with helium-dominated atmospheres-16 dbAs and 20 dbs-using optical spectra taken for the European Southern Observatory SN Ia progenitor survey. We find a difference of 6.9 +/- 6.9 kms(-1) in the average apparent velocity of the H alpha lines versus that of the He I 5876 angstrom lines for our dbAs. This is a measure of the blueshift of this He line due to pressure effects. By using this as a correction, we extend the gravitational redshift method employed by Falcon et al. to use the apparent velocity of the He I 5876 angstrom line and conduct the first gravitational redshift investigation of a group of WDs without visible hydrogen lines. We use biweight estimators to find an average apparent velocity, <nu(app)>(BI), (and hence average gravitational redshift, <nu(g)>(BI)) for our WDs; from that we derive an average mass, < M >(BI). For the dbAs, we find <nu(app)>(BI) = 40.8 +/- 4.7 kms(-1) and derive < M >(BI) = 0.71(-0.05)(+0.04) M-circle dot. Though different from <nu(app)> of DAs (32.57 km s(-1)) at the 91% confidence level and suggestive of a larger dbA mean mass than that for normal DAs derived using the same method (0.647(-0.014)(+0.013) M-circle dot; Falcon et al.), we do not claim this as a stringent detection. Rather, we emphasize that the difference between <nu(app)>(BI) of the dbAs and <nu(app)> of normal DAs is no larger than 9.2 kms(-1), at the 95% confidence level; this corresponds to roughly 0.10 M-circle dot. For the dbs, we find <nu(He)(app)>(BI) = 42.9 +/- 8.49 km s(-1) after applying the blueshift correction and determine < M >(BI) = 0.74(-0.09)(+0.08) M-circle dot. The difference between <nu(He)(app)>(BI) of the dbs and <nu(app)> of DAs is <= 11.5 kms(-1) (similar to 0.12 M-circle dot), at the 95% confidence level. The gravitational redshift method indicates much larger mean masses than the spectroscopic determinations of the same sample by Voss et al. Given the small sample sizes, it is possible that systematic uncertainties are skewing our results due to the potential of kinematic substructures that may not average out. We estimate this to be unlikely, but a larger sample size is necessary to rule out these systematics.National Science Foundation AST-0909107, AST-0602288Norman Hackerman Advanced Research Program 003658-255-2007, 003658-0252-2009Institute for High Energy Density ScienceUniversity of Texas SystemSandia National LaboratoriesNational Physical Science ConsortiumDelaware Asteroseismic Research CenterNASA NNX11AG82G, HST-GO-11141McDonald Observator
2005 population status of the Peregrine Falcon in the Yukon Territory
No full textThis survey was the Yukon section of the Canada-wide periodic monitoring of the status of the Peregrine Falcon, a requirement of the Canadian Recovery Plan for the species. The Yukon, through the Northern Research Institute at Yukon College maintains a database spanning three decades tracking the fortunes of Yukon’s peregrines. Historically, this effort began in the 1960’s when a population of the interior race of peregrine falcon (Falco peregrinus anatum) was first described breeding on the riparian cliffs of the rivers draining the central Yukon (Cade and Fyfe 1970). The birds’ numbers subsequently crashed and more recently have been recovering. The Yukon Government has funded this effort in large part over the years; most recently as part of a biodiversity assessment partnership with Yukon College.Peer reviewe
Falcon 120687
No full textThe "Falcon" was the steam yacht of the Falconwood Company. She was built by George H. Notter in Buffalo, New York in 1887. She was more than 90 feet in length. In 1940, she was rigged as a barge. And, in 1951, the "Falcon" was scrapped
Aristotle on Time and Change
No full textAristotle's discussion of time is part of his Physics, which was an important part of the philosophical curriculum of late antiquity. Aristotle says that it is because nature is a principle of change that people must establish what change is. This chapter focuses on his scientific treatment of time. Aristotle begins his discussion of time by engaging in the examination of a set of puzzles (aporiai). He clearly indicates that this examination is embedded in the two‐stage inquiry. Aristotle develops, within his positive account of time, the conceptual tools to deal with a puzzle. The chapter shows how the definition of change advanced in the third book of the Physics contributes to the discussion of time developed in the fourth book
2015 population status of the peregrine falcon in the Yukon Territory
No full textThe 2015 survey was an attempt to visit a representative sample from all sub-populations of peregrine falcon known in the territory. The peregrine in the Yukon is thought of as a classic ‘metapopulation’ (McCullough, 1996). The groups, in part based on geographic separation Figure 1), are mostly identified by demographic performance differences. (The subgroup nesting on the ‘North Slope’ is considered to be of the tundrius race.) Past findings have been detailed in a series of reports and published papers dating from the early 1970’s (Cade & Fyfe 1970, Hayes & Mossop 1982, Mossop & Baird, 1985, Mossop 1986, Mossop & Hayes 1980, Mossop & Mowat 1990, Mossop, 1995, 2000, 2005, 2014).Peer reviewe
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