scholarly journals Testing the auto-abrasion hypothesis for dust production using diatomite dune sediments from the Bodélé Depression in Chad

Sedimentology ◽  
2017 ◽  
Vol 65 (4) ◽  
pp. 1322-1330 ◽  
Author(s):  
Charlie S. Bristow ◽  
Torsten H. Moller
Keyword(s):  
Dust Production ◽  
Bodele Depression

scholarly journals Carbon star wind models at solar and sub-solar metallicities: a comparative study

2019 ◽  
Vol 623 ◽  
pp. A119 ◽  
Author(s):  
S. Bladh ◽  
K. Eriksson ◽  
P. Marigo ◽  
S. Liljegren ◽  
B. Aringer
Keyword(s):  
Mass Loss ◽  
Agb Stars ◽  
Carbon Stars ◽  
Dust Production ◽  
Grain Sizes ◽  
Solar Metallicity ◽  
Effective Temperatures ◽  
Carbon Excess ◽  
Thermal Pulses ◽  
Loss Rates

Context. The heavy mass loss observed in evolved stars on the asymptotic giant branch (AGB) is usually attributed to dust-driven winds, but it is still an open question how much AGB stars contribute to the dust production in the interstellar medium, especially at lower metallicities. In the case of C-type AGB stars, where the wind is thought to be driven by radiation pressure on amorphous carbon grains, there should be significant dust production even in metal-poor environments. Carbon stars can manufacture the building blocks needed to form the wind-driving dust species themselves, irrespective of the chemical composition they have, by dredging up carbon from the stellar interior during thermal pulses. Aims. We investigate how the mass loss in carbon stars is affected by a low-metallicity environment, similar to the Large and Small Magellanic Clouds (LMC and SMC). Methods. The atmospheres and winds of C-type AGB stars are modeled with the 1D spherically symmetric radiation-hydrodynamical code Dynamic Atmosphere and Radiation-driven Wind models based on Implicit Numerics (DARWIN). The models include a time-dependent description for nucleation, growth, and evaporation of amorphous carbon grains directly out of the gas phase. To explore the metallicity-dependence of mass loss we calculate model grids at three different chemical abundances (solar, LMC, and SMC). Since carbon may be dredged up during the thermal pulses as AGB stars evolve, we keep the carbon abundance as a free parameter. The models in these three different grids all have a current mass of one solar mass; effective temperatures of 2600, 2800, 3000, or 3200 K; and stellar luminosities equal to logL*∕L⊙ = 3.70, 3.85, or 4.00. Results. The DARWIN models show that mass loss in carbon stars is facilitated by high luminosities, low effective temperatures, and a high carbon excess (C–O) at both solar and subsolar metallicities. Similar combinations of effective temperature, luminosity, and carbon excess produce outflows at both solar and subsolar metallicities. There are no large systematic differences in the mass-loss rates and wind velocities produced by these wind models with respect to metallicity, nor any systematic difference concerning the distribution of grain sizes or how much carbon is condensed into dust. DARWIN models at subsolar metallicity have approximately 15% lower mass-loss rates compared to DARWIN models at solar metallicity with the same stellar parameters and carbon excess. For both solar and subsolar environments typical grain sizes range between 0.1 and 0.5 μm, the degree of condensed carbon varies between 5 and 40%, and the gas-to-dust ratios between 500 and 10 000. Conclusions. C-type AGB stars can contribute to the dust production at subsolar metallicities (down to at least [Fe∕H] = −1) as long as they dredge up sufficient amounts of carbon from the stellar interior. Furthermore, stellar evolution models can use the mass-loss rates calculated from DARWIN models at solar metallicity when modeling the AGB phase at subsolar metallicities if carbon excess is used as the critical abundance parameter instead of the C/O ratio.

Methods to measure Dust Production and Deposition Rates in Buildings

1999 ◽  
Vol 72 (4) ◽  
pp. 329-340 ◽  
Author(s):  
Yong Cheng Chen ◽  
E.M. Barber ◽  
Yunahui Zhang ◽  
R.W. Besant ◽  
S. Sokhansanj
Keyword(s):  
Dust Production ◽  
Deposition Rates

Estimation of Graphite Dust Production in a Pebble-Bed Type Nuclear Reflector

2014 ◽  
Author(s):  
Ji-Ho Kang ◽  
Eung Seon Kim ◽  
Seungyon Cho
Keyword(s):  
Adhesive Wear ◽  
Cell Model ◽  
Estimation Method ◽  
Unit Cell ◽  
Contact Forces ◽  
Dust Explosion ◽  
Dust Production ◽  
Pebble Bed ◽  
Normal Contact ◽  
Contact Points

In this study, an estimation method of graphite dust production in the pebble-bed type reflector region of Korean HCSB (Helium-Cooled Solid Breeder) TBM (Test Blanket Module) in the ITER (International Thermonuclear Experimental Reactor) project using FEM (Finite Element Method) was proposed and the amount of dust production was calculated. A unit-cell model of uniformly arranged pebbles was defined with appropriate thermal and mechanical loadings. A commercial FEM program, Abaqus V6.10 was used to model and solve the stress field under multiple contact constraints between pebbles in the unit-cell. Resulting normal contact forces and slip distances on contact points were applied into the Archard adhesive wear equation to calculate the amount of graphite dust. The friction effect on contact points was investigated. The calculation result showed that the amount of graphite dust production was estimated to 2.22∼3.67e−4 g/m3 which was almost linearly proportional to the friction coefficient. The analysis results will be used as the basis data for the consecutive study of dust explosion.

Dust production in supernovae

2004 ◽  
Vol 48 (7-8) ◽  
pp. 611-614 ◽  
Author(s):  
L. Dunne ◽  
H. Morgan ◽  
S. Eales ◽  
R. Ivison ◽  
M. Edmunds
Keyword(s):  
Dust Production

Microwave-assisted extraction of wild apple fruit dust-production of polyphenol-rich extracts from filter tea factory by-products

2016 ◽  
Vol 40 (4) ◽  
pp. e12508 ◽  
Author(s):  
Branimir Pavlić ◽  
Abdulhakim Naffati ◽  
Tijana Hojan ◽  
Jelena Vladić ◽  
Zoran Zeković ◽  
...  
Keyword(s):  
Apple Fruit ◽  
Microwave Assisted Extraction ◽  
Dust Production ◽  
Microwave Assisted ◽  
Assisted Extraction ◽  
By Products

scholarly journals 523676 (2013 UL10): the first active red centaur

2018 ◽  
Vol 620 ◽  
pp. A93 ◽  
Author(s):  
E. Mazzotta Epifani ◽  
E. Dotto ◽  
S. Ieva ◽  
D. Perna ◽  
P. Palumbo ◽  
...  
Keyword(s):  
Production Rate ◽  
Canary Islands ◽  
Colour Index ◽  
Nucleus Size ◽  
Dust Production ◽  
La Palma ◽  
Upper Limit ◽  
Nucleus Surface ◽  
Perihelion Passage

Aims. We present observations of 523676 (2013 UL10), a centaur orbiting between Jupiter and Uranus that is dynamically similar to the few tens of active centaurs that are currently known. Methods. We analysed visible BVR images of the centaur obtained at the Telescopio Nazionale Galileo (La Palma, Canary Islands, Spain) to investigate the weak comet-like activity and to derive information on the nucleus surface colours and size. Results. Centaur 523676 (2013 UL10) is the only centaur known so far that has both comet-like activity and red surface colours: its nucleus has a colour index [B – R] = 1.88 ± 0.11. The nucleus R magnitude (R = 20.93 ± 0.09) allowed us to derive an upper limit for its nucleus size of D ≤ 10 km. We estimated its dust production rate to be Qd ~ 10 kg s−1 at 6.2 au (just after its perihelion passage), resulting in a timescale for the surface blanketing process τB of approximately tens of years, which is very short with respect to typical dynamical lifetime inside the group. Future monitoring of 523676 (2013 UL10) is needed to further constrain the blanketing model for active centaurs and its timescale.

scholarly journals Modelling of dust generation, transport and remobilization in full-metal fusion reactors

2022 ◽  
Author(s):  
Svetlana Ratynskaia ◽  
Ladislas Vignitchouk ◽  
Panagiotis Tolias
Keyword(s):  
Initial Conditions ◽  
External Input ◽  
Dust Particles ◽  
Fusion Reactors ◽  
Dust Production ◽  
Dust Transport ◽  
Dust Generation ◽  
Wall Interaction ◽  
And Migration ◽  
Generation Mechanisms

Abstract The design, licensing and operation of magnetic confinement fusion reactors impose various limitations on the amount of metallic dust particles residing inside the plasma chamber. In this context, predictive studies of dust production and migration constitute one of the main sources of relevant data. These are mainly conducted using dust transport codes, which rely on coupled dust-plasma and dust-wall interaction models, and require external input on the dust and droplet initial conditions. Some particularities of dust modelling in reactor-relevant conditions are analyzed with an emphasis on dust generation mechanisms relevant for disruption scenarios and on dust remobilization mechanisms relevant for ramp-up scenarios. Emerging topics such as dust production by runaway electron impact and pre-plasma remobilization of magnetic dust are also discussed.

scholarly journals Homogeneized modeling of mineral dust emissions over Europe and Africa using the CHIMERE model

2014 ◽  
Vol 7 (3) ◽  
pp. 3441-3480 ◽  
Author(s):  
R. Briant ◽  
L. Menut ◽  
G. Siour ◽  
C. Prigent
Keyword(s):  
Air Quality ◽  
Main Part ◽  
Roughness Length ◽  
Mineral Dust ◽  
Satellite Observations ◽  
Production Model ◽  
Dust Production ◽  
Dust Emissions ◽  
Sahel Region ◽  
Agricultural Areas

Abstract. In the region including Africa and Europe, the main part of mineral dust emissions is observed in Africa. The particles are thus transported towards Europe and constitute a non-negligible part of the surface aerosols measured and controlled in the framework of the European air quality legislation. The modelling of these African dust emissions fluxes and transport is widely studied and complex parameterizations are already used in regional to global model for this Sahara-Sahel region. In a lesser extent, mineral dust emissions occur locally in Europe, mainly over agricultural areas. Their modelling is generally poorly done or just ignored. But in some cases, this contribution may be important and may impact the European air quality budget. In this study, we propose an homogeneized calculations of mineral dust fluxes for Europe and Africa. For that, we extended the CHIMERE dust production model (DPM) by using new soil and surface datasets, and the global aeolian roughness length dataset provided by GARLAP from microwave and visible satellite observations. This DPM is detailed along with academic tests case results and simulation on a real case results.

scholarly journals Narrow-band photometry of Long Period Comets with TRAPPIST telescopes in 2019-2020

2020 ◽  
Author(s):  
Youssef Moulane ◽  
Emmanuel Jehin ◽  
Francisco José Pozuelos ◽  
Jean Manfroid ◽  
Zouhair Benkhaldoun ◽  
...  
Keyword(s):  
Solar System ◽  
Production Rate ◽  
Heliocentric Distance ◽  
Narrow Band ◽  
Maximum Activity ◽  
The Sun ◽  
Water Production ◽  
Dust Production ◽  
Long Period ◽  
Water Production Rate

<p>Long Period Comets (LPCs) have orbital periods longer than 200 years, perturbed from their resting place in the Oort cloud. Such gravitational influences may send these icy bodies on a path towards the center of the Solar system in highly elliptical orbits. In this work, we present the activity and composition evolution of several LPCs observed with both TRAPPIST telescopes (TS and TN) during the period of 2019-2020. These comets include: C/2017 T2 (PANSTARRS), C/2018 Y1 (Iwamoto), C/2018 W2 (Africano), and disintegrated comet C/2019 Y4 (ATLAS). We monitored the OH, NH, CN, C<sub>2</sub> and C<sub>3</sub> production rates evolution and their chemical mixing ratios with respect to their distances to the Sun as well as the dust production rate proxy (A(0)fp) during the journey of these comets into the inner Solar system.</p> <p><strong>C/2017 T2 (PANSTARRS)</strong> is a very bright comet which was discovered on October 2, 2017 when it was 9.20 au from the Sun. We started observing this comet with TS at the beginning of August 2019 when it was at 3.70 au. The comet made the closest approach to the Earth on December 28, 2019 at a distance of 1.52 au and it passed the perihelion on May 4, 2020 at 1.61 au. The water production rate of the comet reached a maximum of (4,27±0,12)10<sup>28 </sup>molecules/s and its dust production rate (A(0)fp(RC)) also reached the peak of 5110±25 cm on January 26, 2020, when the comet was at 2.08 au from the Sun (-100 days pre-perihelion). At the time of writing, we still monitoring the activity of the comet with TN at heliocentric distance of 1.70 au. Our observations show that C/2017 T2 is a normal LPC.</p> <p><strong>C/2018 Y1 (Iwamoto)</strong> is a nearly parabolic comet with a retrograde orbit discovered on December 18, 2018 by Japanese amateur astronomer Masayuki Iwamoto. We monitored the activity and composition of Iwamoto with both TN and TS telescopes from January to March 2019. The comet reached its maximum activity on January 29, 2019 when it was at 1.29 au from the Sun (-8 days pre-perihelion) with Q(H<sub>2</sub>O)=(1,68±0,05)10<sup>28 </sup>molecules/s and A(0)fp(RC)= 92±5 cm. These measurements show that it was a dust-poor comet compared to the typical LPCs.</p> <p><strong>C/2018 W2 (Africano) </strong>was discovered on November 27, 2018 at Mount Lemmon Survey with a visual magnitude of 20. The comet reached its perihelion on September 6, 2019 when it was at 1.45 au from the Sun. We monitored the comet from July 2019 (r<sub>h</sub>=1.71 au) to January 2020 (r<sub>h</sub>=2.18 au) with both TN and TS telescopes. The comet reached its maximum activity on September 21, 15 days post-perihelion (r<sub>h</sub>=1.47 au) with Q(H<sub>2</sub>O)=(0,40±0,03)10<sup>28 </sup>molecules/s.</p> <p><strong>C/2019 Y4 (ATLAS)</strong> is a comet with a nearly parabolic orbit discovered on December 18, 2019 by the ATLAS survey. We started to follow its activity and composition with broad- and narrow-band filters with the TN telescope on February 22, 2019 when it was at 1.32 au from the Sun until May 3, 2020 when the comet was at a heliocentric distance of 0.90 au inbound. The comet activity reached a maximum on March 22 (r<sub>h</sub>=1.65 au) 70 days before perihelion. At that time, the water-production rate reached (1,53±0,04)10<sup>28 </sup>molecules/s and the A(0)fp reached (1096±14) cm in the red filter. After that, the comet began to fade and disintegrated into several fragments.</p>

scholarly journals Constraining planetesimal stirring: how sharp are debris disc edges?

2021 ◽  
Vol 503 (4) ◽  
pp. 5100-5114
Author(s):  
Sebastian Marino
Keyword(s):  
Surface Density ◽  
Semimajor Axis ◽  
Rayleigh Distribution ◽  
Outer Edge ◽  
The Other ◽  
Dust Production ◽  
Array Data ◽  
Disc Surface ◽  
Sharp Edges ◽  
Good Agreement

ABSTRACT The dust production in debris discs by grinding collisions of planetesimals requires their orbits to be stirred. However, stirring levels remain largely unconstrained, and consequently the stirring mechanisms as well. This work shows how the sharpness of the outer edge of discs can be used to constrain the stirring levels. Namely, the sharper the edge the lower the eccentricity dispersion must be. For a Rayleigh distribution of eccentricities (e), I find that the disc surface density near the outer edge can be parametrized as tanh [(rmax  − r)/lout], where rmax  approximates the maximum semimajor axis and lout defines the edge smoothness. If the semimajor axis distribution has sharp edges erms is roughly 1.2lout/rmax  or erms = 0.77lout/rmax  if semimajor axes have diffused due to self-stirring. This model is fitted to Atacama Large Millimeter/submillimeter Array data of five wide discs: HD 107146, HD 92945, HD 206893, AU Mic, and HR 8799. The results show that HD 107146, HD 92945, and AU Mic have the sharpest outer edges, corresponding to erms values of 0.121 ± 0.05, $0.15^{+0.07}_{-0.05}$, and 0.10 ± 0.02 if their discs are self-stirred, suggesting the presence of Pluto-sized objects embedded in the disc. Although these stirring values are larger than typically assumed, the radial stirring of HD 92945 is in good agreement with its vertical stirring constrained by the disc height. HD 206893 and HR 8799, on the other hand, have smooth outer edges that are indicative of scattered discs since both systems have massive inner companions.

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