548 research outputs found
Supersonic dusty-gas flows with Knudsen effect in interphase momentum exchange
No full textOn the basis of the two-continuum model of dilute gas-solid suspensions, the dynamic behavior of inertial particles in supersonic dusty-gas flows past a blunt body is studied for moderate Reynolds numbers, when the Knudsen effect in the interphase momentum exchange is significant. The limits of the inertial particle deposition regime in the space of governing parameters are found numerically under the assumption of the slip and free-molecule flow regimes around particles. As a model problem, the flow structure is obtained for a supersonic dusty-gas point-source flow colliding with a hypersonic flow of pure gas. The calculations performed using the full Lagrangian approach for the near-symmetry-axis region and the free-molecular flow regime around the particles reveal a multi-layer structure of the dispersed-phase density with a sharp accumulation of the particles in some thin regions between the bow and termination shock waves
Twitter Application Development For Dummies
No full textGet the guide to planning, developing and monetizing apps for Twitter!. Twitter is the one of the hottest trends in social networking. With several million users, Twitter's popularity is growing everyday. Twitter will continue to increase user base while third-party companies keep popping up all over to make money building Twitter apps for phones, advertising tools, analytics/management tools and more. Some of the most popular Twitter apps include TwitPic, Twhirl, TweetDeck, and FriendorFollow. With this book, author Dusty Reagan uses one of his unpublished Twitter app ideas and takes you thr
Flow properties of a dusty-gas point source in a supersonic free stream
No full textBy using Lagrangian method, the flow properties of a dusty-gas point source in a supersonic free stream were studied and the particle parameters in the near-symmetry-axis region were obtained. It is demonstrated that fairly inertial particles travel along oscillating and intersecting trajectories between the bow and termination shock waves. In this region,formation of "multi-layer structure" in particle distribution with alternating low- and highdensity layers is revealed. Moreover, sharp accumulation of particles occurs near the envelopes of particle trajectories
Non-stationary effects in hypersonic nonuniform dusty-gas flow past a blunt body
No full textIn the framework of the two-fluid model, a hypersonic flow of a nonuniform dusty gas with low inertial (non-depositing) particles around a blunt body is considered. The particle mass concentration is assumed to be small, so that the effect of particles on the carrier phase is significant only inside the boundary layer where the particles accumulate. Stepshaped and harmonic nonuniformities of the particle concentration ahead of the bow shock wave are considered and the corresponding nonstationary distributions of the particle concentration in the shock layer are studied. On the basis of numerical study gf nonstationary two-phase boundary layer equations derived by the matched asymptotic expansion method, the effects of free-stream particle concentration nonuniformities on the thermal flux and the friction coefficient in the neighborhood of stagnation point are investigated, in particular, the most "dangerous" nonuniformity periods are found
DESHIMA 2.0: Rapid redshift surveys and multi-line spectroscopy of dusty galaxies
No full textWe present a feasibility study for the high-redshift galaxy part of the
Science Verification Campaign with the 220-440 GHz DESHIMA 2.0 integrated
superconducting spectrometer on the ASTE telescope. The first version of the
DESHIMA 2.0 chip has been recently manufactured and tested in the lab. Based on
these realistic performance measurements, we evaluate potential target samples
and prospects for detecting the [CII] and CO emission lines. The planned
observations comprise two distinct, but complementary objectives: (1) acquiring
spectroscopic redshifts for dusty galaxies selected in far-infrared/mm-wave
continuum surveys; (2) multi-line observations to infer physical conditions in
dusty galaxies.Comment: Expanded version of the article for the conference proceedings for
the 9th International Workshop on Low Temperature Detectors (submitted to
JLTP, 1st November 2021). Added minor corrections and an extra panel for Fig.
2 (2021/11/2). Updated Figure 3 (2022/1/13
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A Baroclinic Model of turbulent dusty flows
No full textThe problem considered here is the numerical simulation of the turbulent dusty flow induced by explosions over soil surfaces. Some of the unresolved issues are: (1) how much dust is scoured from such surfaces; (2) where does the dust go in the boundary layer; (3) what is the dusty boundary layer height versus time; (4) what are the dusty boundary layer profiles; (5) how much of the dust mass becomes entrained into the dust stem; and (6) where does the dust go in the buoyant cloud? The author proposes a Baroclinic Model for flows with large density variations that actually calculates the turbulent mixing and transport of dust on an adaptive grid. The model is based on the following idealizations: (1) a loose dust bed; (2) an instantaneous shock fluidization of the dust layer; (3) the dust and air are in local equilibrium (so air viscosity enforces the no-slip condition); (4) the dust-air mixture is treated as a continuum dense fluid with zero viscosity; and (5) the turbulent mixing is dominated by baroclinically-generated vorticity. These assumptions lead to an inviscid set of conservation laws for the mixture, which are solved by means of a high-order Godunov algorithm for gasdynamics. Adaptive Mesh Refinement (AMR) is used to capture the turbulent mixing processes on the grid. One of the unique characteristics of these flows is that mixing occurs because vorticity is produced by an inviscid, baroclinic mechanism. A number of examples are presented to illustrate these baroclinic effects including shock interactions with dense-gas layers and dust beds, and dusty wall jets of airblast precursors. The conclusion of these studies is that dusty boundary layers grow because of mass entrainment from the fluidized bed (and not because of viscous wall drag) as proven by the Mass Integral Equation
The dusty torus in the Circinus galaxy: a dense disk and the torus funnel
No full textContext. With infrared interferometry it is possible to resolve the nuclear dust distributions that are commonly associated with the dusty torus in active galactic nuclei (AGN). The Circinus galaxy hosts the closest Seyfert 2 nucleus and previous interferometric observations have shown that its nuclear dust emission is particularly well resolved.Aims. The aim of the present interferometric investigation is to better constrain the dust morphology in this active nucleus.Methods. To this end, extensive new observations were carried out with the MID-infrared Interferometric instrument (MIDI) at the Very Large Telescope Interferometer, leading to a total of 152 correlated flux spectra and differential phases between 8 and 13 μm. To interpret this data, we used a model consisting of black-body emitters with a Gaussian brightness distribution and with dust extinction.Results. The direct analysis of the data and the modelling confirm that the emission is distributed in two distinct components: a disk-like emission component with a size (FWHM) of ~0.2 × 1.1 pc and an extended component with a size of ~0.8 × 1.9 pc. The disk-like component is elongated along PA ~ 46° and oriented perpendicular to the ionisation cone and outflow. The extended component is responsible for 80% of the mid-infrared emission. It is elongated along PA ~ 107°, which is roughly perpendicular to the disk component and thus in polar direction. It is interpreted as emission from the inner funnel of an extended dust distribution and shows a strong increase in the extinction towards the south-east. We find both emission components to be consistent with dust at T ~ 300 K, that is we find no evidence of an increase in the temperature of the dust towards the centre. From this we infer that most of the near-infrared emission probably comes from parsec scales as well. We further argue that the disk component alone is not sufficient to provide the necessary obscuration and collimation of the ionising radiation and outflow. The material responsible for this must instead be located on scales of ~1 pc, surrounding the disk. We associate this material with the dusty torus.Conclusions. The clear separation of the dust emission into a disk-like emitter and a polar elongated source will require an adaptation of our current understanding of the dust emission in AGN. The lack of any evidence of an increase in the dust temperature towards the centre poses a challenge for the picture of a centrally heated dust distribution
Jersey Youth Justice Review 2018
No full textThe Jersey Youth Justice Review was commissioned by the States of Jersey Government. Three main points of reference guided the drafting of the terms of reference: the Independent Jersey Care Inquiry (2017), which recommended Jersey move towards a welfare-based model of youth justice; the effective ratification of the United Nations Convention on the Rights of the Child (1989); and the Report commissioned by the States of Jersey, 'Youth Justice: Options for Change' (Evans et al). The Lead author of the Report is Jonathan Evans with contributions from Dusty Kennedy (Assistant Police and Crime Commissioner in South Wales) and Brian Heath (Chief Probation Officer for Jersey Probation and After-Care Service). Assistance was also provided by the Jersey Youth Justice Review Steering Group
ALMA and Herschel observations of the prototype dusty and polluted white dwarf G29-38
No full textJF gratefully acknowledges the support of the STFC via an Ernest Rutherford Fellowship. AB acknowledges the support of the ANR-2010 BLAN-0505-01 (EXOZODI). MCW and OP are grateful for the support of the European Union through ERC grant number 279973.ALMA Cycle 0 and Herschel PACS observations are reported for the prototype, nearest, and brightest example of a dusty and polluted white dwarf, G29-38. These long-wavelength programmes attempted to detect an outlying, parent population of bodies at 1–100 au, from which originates the disrupted planetesimal debris that is observed within 0.01 au and which exhibits LIR/L* = 0.039. No associated emission sources were detected in any of the data down to LIR/L* ∼ 10−4, generally ruling out cold dust masses greater than 1024–1025 g for reasonable grain sizes and properties in orbital regions corresponding to evolved versions of both asteroid and Kuiper belt analogues. Overall, these null detections are consistent with models of long-term collisional evolution in planetesimal discs, and the source regions for the disrupted parent bodies at stars like G29-38 may only be salient in exceptional circumstances, such as a recent instability. A larger sample of polluted white dwarfs, targeted with the full ALMA array, has the potential to unambiguously identify the parent source(s) of their planetary debris.Peer reviewe
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