A METHOD FOR COUPLING DYNAMICAL AND COLLISIONAL EVOLUTION OF DUST IN CIRCUMSTELLAR DISKS: THE EFFECT OF A DEAD ZONE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Charnoz, Sebastien; Taillifet, Esther, E-mail: charnoz@cea.fr

Dust is a major component of protoplanetary and debris disks as it is the main observable signature of planetary formation. However, since dust dynamics are size-dependent (because of gas drag or radiation pressure) any attempt to understand the full dynamical evolution of circumstellar dusty disks that neglect the coupling of collisional evolution with dynamical evolution is thwarted because of the feedback between these two processes. Here, a new hybrid Lagrangian/Eulerian code is presented that overcomes some of these difficulties. The particles representing 'dust clouds' are tracked individually in a Lagrangian way. This system is then mapped on an Eulerian spatialmore » grid, inside the cells of which the local collisional evolutions are computed. Finally, the system is remapped back in a collection of discrete Lagrangian particles, keeping their number constant. An application example of dust growth in a turbulent protoplanetary disk at 1 AU is presented. First, the growth of dust is considered in the absence of a dead zone and the vertical distribution of dust is self-consistently computed. It is found that the mass is rapidly dominated by particles about a fraction of a millimeter in size. Then the same case with an embedded dead zone is investigated and it is found that coagulation is much more efficient and produces, in a short timescale, 1-10 cm dust pebbles that dominate the mass. These pebbles may then be accumulated into embryo-sized objects inside large-scale turbulent structures as shown recently.« less

Automatically generated code for relativistic inhomogeneous cosmologies

NASA Astrophysics Data System (ADS)

Bentivegna, Eloisa

2017-02-01

The applications of numerical relativity to cosmology are on the rise, contributing insight into such cosmological problems as structure formation, primordial phase transitions, gravitational-wave generation, and inflation. In this paper, I present the infrastructure for the computation of inhomogeneous dust cosmologies which was used recently to measure the effect of nonlinear inhomogeneity on the cosmic expansion rate. I illustrate the code's architecture, provide evidence for its correctness in a number of familiar cosmological settings, and evaluate its parallel performance for grids of up to several billion points. The code, which is available as free software, is based on the Einstein Toolkit infrastructure, and in particular leverages the automated code generation capabilities provided by its component Kranc.

Photoionization modeling of the LWS fine-structure lines in IR bright galaxies

NASA Technical Reports Server (NTRS)

Satyapal, S.; Luhman, M. L.; Fischer, J.; Greenhouse, M. A.; Wolfire, M. G.

1997-01-01

The long wavelength spectrometer (LWS) fine structure line spectra from infrared luminous galaxies were modeled using stellar evolutionary synthesis models combined with photoionization and photodissociation region models. The calculations were carried out by using the computational code CLOUDY. Starburst and active galactic nuclei models are presented. The effects of dust in the ionized region are examined.

Two-fluid dusty shocks: simple benchmarking problems and applications to protoplanetary discs

NASA Astrophysics Data System (ADS)

Lehmann, Andrew; Wardle, Mark

2018-05-01

The key role that dust plays in the interstellar medium has motivated the development of numerical codes designed to study the coupled evolution of dust and gas in systems such as turbulent molecular clouds and protoplanetary discs. Drift between dust and gas has proven to be important as well as numerically challenging. We provide simple benchmarking problems for dusty gas codes by numerically solving the two-fluid dust-gas equations for steady, plane-parallel shock waves. The two distinct shock solutions to these equations allow a numerical code to test different forms of drag between the two fluids, the strength of that drag and the dust to gas ratio. We also provide an astrophysical application of J-type dust-gas shocks to studying the structure of accretion shocks on to protoplanetary discs. We find that two-fluid effects are most important for grains larger than 1 μm, and that the peak dust temperature within an accretion shock provides a signature of the dust-to-gas ratio of the infalling material.

Migration of tungsten dust in tokamaks: role of dust-wall collisions

NASA Astrophysics Data System (ADS)

Ratynskaia, S.; Vignitchouk, L.; Tolias, P.; Bykov, I.; Bergsåker, H.; Litnovsky, A.; den Harder, N.; Lazzaro, E.

2013-12-01

The modelling of a controlled tungsten dust injection experiment in TEXTOR by the dust dynamics code MIGRAINe is reported. The code, in addition to the standard dust-plasma interaction processes, also encompasses major mechanical aspects of dust-surface collisions. The use of analytical expressions for the restitution coefficients as functions of the dust radius and impact velocity allows us to account for the sticking and rebound phenomena that define which parts of the dust size distribution can migrate efficiently. The experiment provided unambiguous evidence of long-distance dust migration; artificially introduced tungsten dust particles were collected 120° toroidally away from the injection point, but also a selectivity in the permissible size of transported grains was observed. The main experimental results are reproduced by modelling.

Dusty Donuts: Modeling the Reverberation Response of the Circumnuclear Dusty Torus Emission in AGN

NASA Astrophysics Data System (ADS)

Almeyda, Triana R.

The obscuring circumnuclear torus of dusty molecular gas is one of the major components of AGN (active galactic nuclei), yet its size, composition, and structure are not well understood. These properties can be studied by analyzing the temporal variations of the infrared (IR) dust emission from the torus in response to variations in the AGN continuum luminosity; a technique known as reverberation mapping. In a recent international campaign 12 AGN were monitored using the Spitzer Space Telescope and several ground-based telescopes, providing a unique set of well-sampled mid-IR and optical light curves which are required in order to determine the approximate sizes of the tori in these AGN. To help extract structural information contained in the data a computer model, TORMAC, has been developed that simulates the reverberation response of the clumpy torus emission. Given an input optical light curve, the code computes the emission of a 3D ensemble of dust clouds as a function of time at selected IR wavelengths, taking into account light travel delays. A large library of torus reverberation response simulations has been constructed, to investigate the effects of various geometrical and structural properties such as inclination, cloud distribution, disk half-opening angle, and radial depth. The effects of dust cloud orientation, cloud optical depth, anisotropy of the illuminating AGN radiation field, dust cloud shadowing, and cloud occultation are also explored in detail. TORMAC was also used to generate synthetic IR light curves for the Seyfert 1 galaxy, NGC 6418, using the observed optical light curve as the input, to investigate how the torus and dust cloud properties incorporated in the code affect the results obtained from reverberation mapping. This dissertation presents the most comprehensive investigation to date showing that radiative transfer effects within the torus and anisotropic illumination of the torus can strongly influence the torus IR response at different wavelengths, and should be accounted for when interpreting reverberation mapping data. TORMAC provides a powerful modeling tool that can generate simulated IR light curves for direct comparison to observations. As many types of astronomical sources are both variable and embedded in, or surrounded, by dust, TORMAC also has applications for dust reverberation studies well beyond the AGN observed in the Spitzer monitoring campaign.

PAHFIT: Properties of PAH Emission

NASA Astrophysics Data System (ADS)

Smith, J. D.; Draine, Bruce

2012-10-01

PAHFIT is an IDL tool for decomposing Spitzer IRS spectra of PAH emission sources, with a special emphasis on the careful recovery of ambiguous silicate absorption, and weak, blended dust emission features. PAHFIT is primarily designed for use with full 5-35 micron Spitzer low-resolution IRS spectra. PAHFIT is a flexible tool for fitting spectra, and you can add or disable features, compute combined flux bands, change fitting limits, etc., without changing the code. PAHFIT uses a simple, physically-motivated model, consisting of starlight, thermal dust continuum in a small number of fixed temperature bins, resolved dust features and feature blends, prominent emission lines (which themselves can be blended with dust features), as well as simple fully-mixed or screen dust extinction, dominated by the silicate absorption bands at 9.7 and 18 microns. Most model components are held fixed or are tightly constrained. PAHFIT uses Drude profiles to recover the full strength of dust emission features and blends, including the significant power in the wings of the broad emission profiles. This means the resulting feature strengths are larger (by factors of 2-4) than are recovered by methods which estimate the underlying continuum using line segments or spline curves fit through fiducial wavelength anchors.

Complete Decoding and Reporting of Aviation Routine Weather Reports (METARs)

NASA Technical Reports Server (NTRS)

Lui, Man-Cheung Max

2014-01-01

Aviation Routine Weather Report (METAR) provides surface weather information at and around observation stations, including airport terminals. These weather observations are used by pilots for flight planning and by air traffic service providers for managing departure and arrival flights. The METARs are also an important source of weather data for Air Traffic Management (ATM) analysts and researchers at NASA and elsewhere. These researchers use METAR to correlate severe weather events with local or national air traffic actions that restrict air traffic, as one example. A METAR is made up of multiple groups of coded text, each with a specific standard coding format. These groups of coded text are located in two sections of a report: Body and Remarks. The coded text groups in a U.S. METAR are intended to follow the coding standards set by National Oceanic and Atmospheric Administration (NOAA). However, manual data entry and edits made by a human report observer may result in coded text elements that do not follow the standards, especially in the Remarks section. And contrary to the standards, some significant weather observations are noted only in the Remarks section and not in the Body section of the reports. While human readers can infer the intended meaning of non-standard coding of weather conditions, doing so with a computer program is far more challenging. However such programmatic pre-processing is necessary to enable efficient and faster database query when researchers need to perform any significant historical weather analysis. Therefore, to support such analysis, a computer algorithm was developed to identify groups of coded text anywhere in a report and to perform subsequent decoding in software. The algorithm considers common deviations from the standards and data entry mistakes made by observers. The implemented software code was tested to decode 12 million reports and the decoding process was able to completely interpret 99.93 of the reports. This document presents the deviations from the standards and the decoding algorithm. Storing all decoded data in a database allows users to quickly query a large amount of data and to perform data mining on the data. Users can specify complex query criteria not only on date or airport but also on weather condition. This document also describes the design of a database schema for storing the decoded data, and a Data Warehouse web application that allows users to perform reporting and analysis on the decoded data. Finally, this document presents a case study correlating dust storms reported in METARs from the Phoenix International airport with Ground Stops issued by Air Route Traffic Control Centers (ATCSCC). Blowing widespread dust is one of the weather conditions when dust storm occurs. By querying the database, 294 METARs were found to report blowing widespread dust at the Phoenix airport and 41 of them reported such condition only in the Remarks section of the reports. When METAR is a data source for an ATM research, it is important to include weather conditions not only from the Body section but also from the Remarks section of METARs.

Time-dependent modeling of dust injection in semi-detached ITER divertor plasma

NASA Astrophysics Data System (ADS)

Smirnov, Roman; Krasheninnikov, Sergei

2017-10-01

At present, it is generally understood that dust related issues will play important role in operation of the next step fusion devices, i.e. ITER, and in the development of future fusion reactors. Recent progress in research on dust in magnetic fusion devises has outlined several topics of particular concern: a) degradation of fusion plasma performance; b) impairment of in-vessel diagnostic instruments; and c) safety issues related to dust reactivity and tritium retention. In addition, observed dust events in fusion edge plasmas are highly irregular and require consideration of temporal evolution of both the dust and the fusion plasma. In order to address the dust-related fusion performance issues, we have coupled the dust transport code DUSTT and the edge plasma transport code UEDGE in time-dependent manner, allowing modeling of transient dust-induced phenomena in fusion edge plasmas. Using the coupled codes we simulate burst-like injection of tungsten dust into ITER divertor plasma in semi-detached regime, which is considered as preferable ITER divertor operational mode based on the plasma and heat load control restrictions. Analysis of transport of the dust and the dust-produced impurities, and of dynamics of the ITER divertor and edge plasma in response to the dust injection will be presented. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences, under Award Number DE-FG02-06ER54852.

Dust-wall and dust-plasma interaction in the MIGRAINe code

NASA Astrophysics Data System (ADS)

Vignitchouk, L.; Tolias, P.; Ratynskaia, S.

2014-09-01

The physical models implemented in the recently developed dust dynamics code MIGRAINe are described. A major update of the treatment of secondary electron emission, stemming from models adapted to typical scrape-off layer temperatures, is reported. Sputtering and plasma species backscattering are introduced from fits of available experimental data and their relative importance to dust charging and heating is assessed in fusion-relevant scenarios. Moreover, the description of collisions between dust particles and plasma-facing components, based on the approximation of elastic-perfectly plastic adhesive spheres, has been upgraded to take into account the effects of particle size and temperature.

SPAMCART: a code for smoothed particle Monte Carlo radiative transfer

NASA Astrophysics Data System (ADS)

Lomax, O.; Whitworth, A. P.

2016-10-01

We present a code for generating synthetic spectral energy distributions and intensity maps from smoothed particle hydrodynamics simulation snapshots. The code is based on the Lucy Monte Carlo radiative transfer method, I.e. it follows discrete luminosity packets as they propagate through a density field, and then uses their trajectories to compute the radiative equilibrium temperature of the ambient dust. The sources can be extended and/or embedded, and discrete and/or diffuse. The density is not mapped on to a grid, and therefore the calculation is performed at exactly the same resolution as the hydrodynamics. We present two example calculations using this method. First, we demonstrate that the code strictly adheres to Kirchhoff's law of radiation. Secondly, we present synthetic intensity maps and spectra of an embedded protostellar multiple system. The algorithm uses data structures that are already constructed for other purposes in modern particle codes. It is therefore relatively simple to implement.

An L-stable method for solving stiff hydrodynamics

NASA Astrophysics Data System (ADS)

Li, Shengtai

2017-07-01

We develop a new method for simulating the coupled dynamics of gas and multi-species dust grains. The dust grains are treated as pressure-less fluids and their coupling with gas is through stiff drag terms. If an explicit method is used, the numerical time step is subject to the stopping time of the dust particles, which can become extremely small for small grains. The previous semi-implicit method [1] uses second-order trapezoidal rule (TR) on the stiff drag terms and it works only for moderately small size of the dust particles. This is because TR method is only A-stable not L-stable. In this work, we use TR-BDF2 method [2] for the stiff terms in the coupled hydrodynamic equations. The L-stability of TR-BDF2 proves essential in treating a number of dust species. The combination of TR-BDF2 method with the explicit discretization of other hydro terms can solve a wide variety of stiff hydrodynamics equations accurately and efficiently. We have implemented our method in our LA-COMPASS (Los Alamos Computational Astrophysics Suite) package. We have applied the code to simulate some dusty proto-planetary disks and obtained very good match with astronomical observations.

Ray-tracing 3D dust radiative transfer with DART-Ray: code upgrade and public release

NASA Astrophysics Data System (ADS)

Natale, Giovanni; Popescu, Cristina C.; Tuffs, Richard J.; Clarke, Adam J.; Debattista, Victor P.; Fischera, Jörg; Pasetto, Stefano; Rushton, Mark; Thirlwall, Jordan J.

2017-11-01

We present an extensively updated version of the purely ray-tracing 3D dust radiation transfer code DART-Ray. The new version includes five major upgrades: 1) a series of optimizations for the ray-angular density and the scattered radiation source function; 2) the implementation of several data and task parallelizations using hybrid MPI+OpenMP schemes; 3) the inclusion of dust self-heating; 4) the ability to produce surface brightness maps for observers within the models in HEALPix format; 5) the possibility to set the expected numerical accuracy already at the start of the calculation. We tested the updated code with benchmark models where the dust self-heating is not negligible. Furthermore, we performed a study of the extent of the source influence volumes, using galaxy models, which are critical in determining the efficiency of the DART-Ray algorithm. The new code is publicly available, documented for both users and developers, and accompanied by several programmes to create input grids for different model geometries and to import the results of N-body and SPH simulations. These programmes can be easily adapted to different input geometries, and for different dust models or stellar emission libraries.

TRUST. I. A 3D externally illuminated slab benchmark for dust radiative transfer

NASA Astrophysics Data System (ADS)

Gordon, K. D.; Baes, M.; Bianchi, S.; Camps, P.; Juvela, M.; Kuiper, R.; Lunttila, T.; Misselt, K. A.; Natale, G.; Robitaille, T.; Steinacker, J.

2017-07-01

Context. The radiative transport of photons through arbitrary three-dimensional (3D) structures of dust is a challenging problem due to the anisotropic scattering of dust grains and strong coupling between different spatial regions. The radiative transfer problem in 3D is solved using Monte Carlo or Ray Tracing techniques as no full analytic solution exists for the true 3D structures. Aims: We provide the first 3D dust radiative transfer benchmark composed of a slab of dust with uniform density externally illuminated by a star. This simple 3D benchmark is explicitly formulated to provide tests of the different components of the radiative transfer problem including dust absorption, scattering, and emission. Methods: The details of the external star, the slab itself, and the dust properties are provided. This benchmark includes models with a range of dust optical depths fully probing cases that are optically thin at all wavelengths to optically thick at most wavelengths. The dust properties adopted are characteristic of the diffuse Milky Way interstellar medium. This benchmark includes solutions for the full dust emission including single photon (stochastic) heating as well as two simplifying approximations: One where all grains are considered in equilibrium with the radiation field and one where the emission is from a single effective grain with size-distribution-averaged properties. A total of six Monte Carlo codes and one Ray Tracing code provide solutions to this benchmark. Results: The solution to this benchmark is given as global spectral energy distributions (SEDs) and images at select diagnostic wavelengths from the ultraviolet through the infrared. Comparison of the results revealed that the global SEDs are consistent on average to a few percent for all but the scattered stellar flux at very high optical depths. The image results are consistent within 10%, again except for the stellar scattered flux at very high optical depths. The lack of agreement between different codes of the scattered flux at high optical depths is quantified for the first time. Convergence tests using one of the Monte Carlo codes illustrate the sensitivity of the solutions to various model parameters. Conclusions: We provide the first 3D dust radiative transfer benchmark and validate the accuracy of this benchmark through comparisons between multiple independent codes and detailed convergence tests.

An Icy Kuiper-Belt Around the Young Solar-Type Star HD 181327

NASA Technical Reports Server (NTRS)

Lebreton, J.; Augereau, J.-C.; Thi, W.-F.; Roberge, A.; Donaldson, J.; Schneider, G.; Maddison, S. T.; Menard, F.; Riviere-Marichalar, P.; Mathews, G. S.;

Project summaries

NASA Technical Reports Server (NTRS)

1990-01-01

Lunar base projects, including a reconfigurable lunar cargo launcher, a thermal and micrometeorite protection system, a versatile lifting machine with robotic capabilities, a cargo transport system, the design of a road construction system for a lunar base, and the design of a device for removing lunar dust from material surfaces, are discussed. The emphasis on the Gulf of Mexico project was on the development of a computer simulation model for predicting vessel station keeping requirements. An existing code, used in predicting station keeping requirements for oil drilling platforms operating in North Shore (Alaska) waters was used as a basis for the computer simulation. Modifications were made to the existing code. The input into the model consists of satellite altimeter readings and water velocity readings from buoys stationed in the Gulf of Mexico. The satellite data consists of altimeter readings (wave height) taken during the spring of 1989. The simulation model predicts water velocity and direction, and wind velocity.

Modeling the Anomalous Microwave Emission with Spinning Nanoparticles: No PAHs Required

NASA Astrophysics Data System (ADS)

Hensley, Brandon S.; Draine, B. T.

2017-02-01

In light of recent observational results indicating an apparent lack of correlation between the anomalous microwave emission (AME) and mid-infrared emission from polycyclic aromatic hydrocarbons, we assess whether rotational emission from spinning silicate and/or iron nanoparticles could account for the observed AME without violating observational constraints on interstellar abundances, ultraviolet extinction, and infrared emission. By modifying the SpDust code to compute the rotational emission from these grains, we find that nanosilicate grains could account for the entirety of the observed AME, whereas iron grains could be responsible for only a fraction, even for extreme assumptions on the amount of interstellar iron concentrated in ultrasmall iron nanoparticles. Given the added complexity of contributions from multiple grain populations to the total spinning dust emission, as well as existing uncertainties due to the poorly constrained grain size, charge, and dipole moment distributions, we discuss generic, carrier-independent predictions of spinning dust theory and observational tests that could help identify the AME carrier(s).

Long-term variability of dust events in Iceland (1949-2011)

NASA Astrophysics Data System (ADS)

Dagsson-Waldhauserova, P.; Arnalds, O.; Olafsson, H.

2014-06-01

Long-term frequency of atmospheric dust observations was investigated for the southern part of Iceland and merged with results obtained from the Northeast Iceland (Dagsson-Waldhauserova et al., 2013). In total, over 34 dust days per year on average occurred in Iceland based on conventionally used synoptic codes for dust. Including codes 04-06 into the criteria for dust observations, the frequency was 135 dust days annually. The Sea Level Pressure (SLP) oscillation controlled whether dust events occurred in NE (16.4 dust days annually) or in southern part of Iceland (about 18 dust days annually). The most dust-frequent decade in S Iceland was the 1960s while the most frequent decade in NE Iceland was the 2000s. A total of 32 severe dust storms (visibility < 500 m) was observed in Iceland with the highest frequency during the 2000s in S Iceland. The Arctic dust events (NE Iceland) were typically warm and during summer/autumn (May-September) while the Sub-Arctic dust events (S Iceland) were mainly cold and during winter/spring (March-May). About half of dust events in S Iceland occurred in winter or at sub-zero temperatures. A good correlation was found between PM10 concentrations and visibility during dust observations at the stations Vik and Storhofdi. This study shows that Iceland is among the dustiest areas of the world and dust is emitted the year-round.

Circumstellar dust in symbiotic novae

NASA Astrophysics Data System (ADS)

Jurkic, Tomislav; Kotnik-Karuza, Dubravka

2015-08-01

Physical properties of the circumstellar dust and associated physical mechanisms play an important role in understanding evolution of symbiotic binaries. We present a model of inner dust regions around the cool Mira component of the two symbiotic novae, RR Tel and HM Sge, based on the long-term near-IR photometry, infrared ISO spectra and mid-IR interferometry. Pulsation properties and long-term variabilities were found from the near-IR light curves. The dust properties were determined using the DUSTY code which solves the radiative transfer. No changes in pulsational parameters were found, but a long-term variations with periods of 20-25 years have been detected which cannot be attributed to orbital motion.Circumstellar silicate dust shell with inner dust shell temperatures between 900 K and 1300 K and of moderate optical depth can explain all the observations. RR Tel showed the presence of an optically thin CS dust envelope and an optically thick dust region outside the line of sight, which was further supported by the detailed modelling using the 2D LELUYA code. Obscuration events in RR Tel were explained by an increase in optical depth caused by the newly condensed dust leading to the formation of a compact dust shell. HM Sge showed permanent obscuration and a presence of a compact dust shell with a variable optical depth. Scattering of the near-IR colours can be understood by a change in sublimation temperature caused by the Mira variability. Presence of large dust grains (up to 4 µm) suggests an increased grain growth in conditions of increased mass loss. The mass loss rates of up to 17·10-6 MSun/yr were significantly higher than in intermediate-period single Miras and in agreement with longer-period O-rich AGB stars.Despite the nova outburst, HM Sge remained enshrouded in dust with no significant dust destruction. The existence of unperturbed dust shell suggests a small influence of the hot component and strong dust shielding from the UV flux. By the use of the CLOUDY code, we have showed that a high-density gas region can effectively stop most of the UV flux from the white dwarf and provide the observed dust shielding.

Scattering and Absorption Properties of Polydisperse Wavelength-sized Particles Covered with Much Smaller Grains

NASA Technical Reports Server (NTRS)

Dlugach, Jana M.; Mishchenko, Michael I.; Mackowski, Daniel W.

2012-01-01

Using the results of direct, numerically exact computer solutions of the Maxwell equations, we analyze scattering and absorption characteristics of polydisperse compound particles in the form of wavelength-sized spheres covered with a large number of much smaller spherical grains.The results pertain to the complex refractive indices1.55 + i0.0003,1.55 + i0.3, and 3 + i0.1. We show that the optical effects of dusting wavelength-sized hosts by microscopic grains can vary depending on the number and size of the grains as well as on the complex refractive index. Our computations also demonstrate the high efficiency of the new superposition T-matrix code developed for use on distributed memory computer clusters.

Dust grains from the heart of supernovae

NASA Astrophysics Data System (ADS)

Bocchio, M.; Marassi, S.; Schneider, R.; Bianchi, S.; Limongi, M.; Chieffi, A.

2016-03-01

Dust grains are classically thought to form in the winds of asymptotic giant branch (AGB) stars. However, there is increasing evidence today for dust formation in supernovae (SNe). To establish the relative importance of these two classes of stellar sources of dust, it is important to know the fraction of freshly formed dust in SN ejecta that is able to survive the passage of the reverse shock and be injected in the interstellar medium. With this aim, we have developed a new code, GRASH_Rev, that allows following the dynamics of dust grains in the shocked SN ejecta and computing the time evolution of the mass, composition, and size distribution of the grains. We considered four well-studied SNe in the Milky Way and Large Magellanic Cloud: SN 1987A, CasA, the Crab nebula, and N49. These sources have been observed with both Spitzer and Herschel, and the multiwavelength data allow a better assessment the mass of warm and cold dust associated with the ejecta. For each SN, we first identified the best explosion model, using the mass and metallicity of the progenitor star, the mass of 56Ni, the explosion energy, and the circumstellar medium density inferred from the data. We then ran a recently developed dust formation model to compute the properties of freshly formed dust. Starting from these input models, GRASH_Rev self-consistently follows the dynamics of the grains, considering the effects of the forward and reverse shock, and allows predicting the time evolution of the dust mass, composition, and size distribution in the shocked and unshocked regions of the ejecta. All the simulated models aagree well with observations. Our study suggests that SN 1987A is too young for the reverse shock to have affected the dust mass. Hence the observed dust mass of 0.7-0.9 M⊙ in this source can be safely considered as indicative of the mass of freshly formed dust in SN ejecta. Conversely, in the other three SNe, the reverse shock has already destroyed between 10-40% of the initial dust mass. However, the largest dust mass destruction is predicted to occur between 103 and 105 yr after the explosions. Since the oldest SN in the sample has an estimated age of 4800 yr, current observations can only provide an upper limit to the mass of SN dust that will enrich the interstellar medium, the so-called effective dust yields. We find that only between 1-8% of the currently observed mass will survive, resulting in an average SN effective dust yield of (1.55 ± 1.48) × 10-2M⊙. This agrees well with the values adopted in chemical evolution models that consider the effect of the SN reverse shock. We discuss the astrophysical implications of our results for dust enrichment in local galaxies and at high redshift.

Development of an occupational airborne chemical exposure matrix

PubMed Central

Kurmi, O. P.; Chambers, H.; Lam, K. B. H.; Fishwick, D.

2016-01-01

Background Population-based studies of the occupational contribution to chronic obstructive pulmonary disease generally rely on self-reported exposures to vapours, gases, dusts and fumes (VGDF), which are susceptible to misclassification. Aims To develop an airborne chemical job exposure matrix (ACE JEM) for use with the UK Standard Occupational Classification (SOC 2000) system. Methods We developed the ACE JEM in stages: (i) agreement of definitions, (ii) a binary assignation of exposed/not exposed to VGDF, fibres or mists (VGDFFiM), for each of the individual 353 SOC codes and (iii) assignation of levels of exposure (L; low, medium and high) and (iv) the proportion of workers (P) likely to be exposed in each code. We then expanded the estimated exposures to include biological dusts, mineral dusts, metals, diesel fumes and asthmagens. Results We assigned 186 (53%) of all SOC codes as exposed to at least one category of VGDFFiM, with 23% assigned as having medium or high exposure. We assigned over 68% of all codes as not being exposed to fibres, gases or mists. The most common exposure was to dusts (22% of codes with >50% exposed); 12% of codes were assigned exposure to fibres. We assigned higher percentages of the codes as exposed to diesel fumes (14%) compared with metals (8%). Conclusions We developed an expert-derived JEM, using a strict set of a priori defined rules. The ACE JEM could also be applied to studies to assess risks of diseases where the main route of occupational exposure is via inhalation. PMID:27067914

Development of an occupational airborne chemical exposure matrix.

PubMed

Sadhra, S S; Kurmi, O P; Chambers, H; Lam, K B H; Fishwick, D

2016-07-01

Population-based studies of the occupational contribution to chronic obstructive pulmonary disease generally rely on self-reported exposures to vapours, gases, dusts and fumes (VGDF), which are susceptible to misclassification. To develop an airborne chemical job exposure matrix (ACE JEM) for use with the UK Standard Occupational Classification (SOC 2000) system. We developed the ACE JEM in stages: (i) agreement of definitions, (ii) a binary assignation of exposed/not exposed to VGDF, fibres or mists (VGDFFiM), for each of the individual 353 SOC codes and (iii) assignation of levels of exposure (L; low, medium and high) and (iv) the proportion of workers (P) likely to be exposed in each code. We then expanded the estimated exposures to include biological dusts, mineral dusts, metals, diesel fumes and asthmagens. We assigned 186 (53%) of all SOC codes as exposed to at least one category of VGDFFiM, with 23% assigned as having medium or high exposure. We assigned over 68% of all codes as not being exposed to fibres, gases or mists. The most common exposure was to dusts (22% of codes with >50% exposed); 12% of codes were assigned exposure to fibres. We assigned higher percentages of the codes as exposed to diesel fumes (14%) compared with metals (8%). We developed an expert-derived JEM, using a strict set of a priori defined rules. The ACE JEM could also be applied to studies to assess risks of diseases where the main route of occupational exposure is via inhalation. © Crown copyright 2016.

Measurement of circumsolar ratio in high dust loading regions using a photographic method

NASA Astrophysics Data System (ADS)

Al-Ansary, Hany; Shafiq, Talha; Rizvi, Arslan; El-Leathy, Abdelrahman

2017-06-01

Performance of concentrating solar power (CSP) plants is highly affected by direct normal irradiance (DNI). However, it is also important to consider circumsolar radiation in any simulation of a CSP plant, especially in desert regions where dust loading in the atmosphere is expected. There are a number of methods to measure circumsolar radiation. However, most of them require expensive instrumentation. This work introduces a simple method to estimate circumsolar radiation. It involves taking high-resolution photographs of the sun and processing them using a computer code that identifies the sun's disk. The code then uses pixel intensities to obtain the solar intensity distribution across the sun's disk and in the aureole region. The solar intensity distribution is then used to obtain the circumsolar ratio (CSR) which represents the shape of the sun. To test this method, numerous photos of the sun were taken during the month of April and September 2016 at King Saud University in Riyadh, Saudi Arabia. Riyadh is a region that is well known for high dust-loading, especially during the summer. Two days of different atmospheric conditions were selected in September for comparative analysis. Results show that this method produces repeatable results, and that the CSR can increase significantly due to high dust loading and passing clouds. The CSR is found to be a strong function of DNI, ranging from about 4.5% at DNI values above 800 W/m2 and increasing to as much as 8.5% when DNI drops to about 400 W/m2, due to passing clouds. Furthermore, the results show that circumsolar ratio tends to be high in the early morning and late afternoon due to the high air mass, while its values tend to be lowest around solar noon when the air mass is lowest.

3D Radiative Transfer Code for Polarized Scattered Light with Aligned Grains

NASA Astrophysics Data System (ADS)

Pelkonen, V. M.; Penttilä, A.; Juvela, M.; Muinonen, K.

2017-12-01

Polarized scattered light has been observed in cometary comae and in circumstellar disks. It carries information about the grains from which the light scattered. However, modelling polarized scattered light is a complicated problem. We are working on a 3D Monte Carlo radiative transfer code which incorporates hierarchical grid structure (octree) and the full Stokes vector for both the incoming radiation and the radiation scattered by dust grains. In octree grid format an upper level cell can be divided into 8 subcells by halving the cell in each of the three axis. Levels of further refinement of the grid may be added, until the desired resolution is reached. The radiation field is calculated with Monte Carlo methods. The path of the model ray is traced in the cloud: absorbed intensity is counted in each cell, and from time to time, the model ray is scattered towards a new direction as determined by the dust model. Due to the non-spherical grains and the polarization, the scattering problem will be the main issue for the code and most time consuming. The scattering parameters will be taken from the models for individual grains. We can introduce populations of different grain shapes into the dust model, and randomly select, based on their amounts, from which shape the model ray scatters. Similarly, we can include aligned and non-aligned subpopulations of these grains, based on the grain alignment calculations, to see which grains should be oriented with the magnetic field, or, in the absence of a magnetic field close to the comet nucleus, with another axis of alignment (e.g., the radiation direction). The 3D nature of the grid allows us to assign these values, as well as density, for each computational cell, to model phenomena like e.g., cometary jets. The code will record polarized scattered light towards one or more observer directions within a single simulation run. These results can then be compared with the observations of comets at different phase angles, or, in the case of other star systems, of circumstellar disks, to help us study these objects. We will present tests of the code in development with simple models.

Rationale for classification of combustible gases, vapors and dusts with reference to the National Electrical Code

NASA Astrophysics Data System (ADS)

1982-07-01

Serious reservations about the entire classification procedure of chemical compounds present in electrical equipment environments and the precepts on which it is based are discussed. Although some tests were conducted on selected key compounds, the committee primarily considered the chemical similarity of compounds and other known flammability properties and relied heavily on the experience and intuition of its members. The committee also recommended that the NEC grouping of dusts be changed in some ways and has reclassified dusts according to the modified version of the code.

Analysis of Physical Properties of Dust Suspended in the Mars Atmosphere

NASA Technical Reports Server (NTRS)

Snook, Kelly; McKay, Chris; Cantwell, Brian

1998-01-01

Methods for iteratively determining the infrared optical constants for dust suspended in the Mars atmosphere are described. High quality spectra for wavenumbers from 200 to 2000 1/cm were obtained over a wide range of view angles by the Mariner 9 spacecraft, when it observed a global Martian dust storm in 1971-2. In this research, theoretical spectra of the emergent intensity from Martian dust clouds are generated using a 2-stream source-function radiative transfer code. The code computes the radiation field in a plane-parallel, vertically homogeneous, multiply scattering atmosphere. Calculated intensity spectra are compared with the actual spacecraft data to iteratively retrieve the optical properties and opacity of the dust, as well as the surface temperature of Mars at the time and location of each measurement. Many different particle size distributions a-re investigated to determine the best fit to the data. The particles are assumed spherical and the temperature profile was obtained from the CO2 band shape. Given a reasonable initial guess for the indices of refraction, the searches converge in a well-behaved fashion, producing a fit with error of less than 1.2 K (rms) to the observed brightness spectra. The particle size distribution corresponding to the best fit was a lognormal distribution with a mean particle radius, r(sub m) 0.66 pm, and variance, omega(sup 2) = 0.412 (r(sub eff) = 1.85 microns, v(sub eff) =.51), in close agreement with the size distribution found to be the best fit in the visible wavelengths in recent studies. The optical properties and the associated single scattering properties are shown to be a significant improvement over those used in existing models by demonstrating the effects of the new properties both on heating rates of the Mars atmosphere and in example spectral retrieval of surface characteristics from emission spectra.

Constraining dust properties in circumstellar envelopes of C-stars in the Small Magellanic Cloud: optical constants and grain size of carbon dust

NASA Astrophysics Data System (ADS)

Nanni, Ambra; Marigo, Paola; Groenewegen, Martin A. T.; Aringer, Bernhard; Girardi, Léo; Pastorelli, Giada; Bressan, Alessandro; Bladh, Sara

2016-10-01

We present a new approach aimed at constraining the typical size and optical properties of carbon dust grains in circumstellar envelopes (CSEs) of carbon-rich stars (C-stars) in the Small Magellanic Cloud (SMC). To achieve this goal, we apply our recent dust growth description, coupled with a radiative transfer code to the CSEs of C-stars evolving along the thermally pulsing asymptotic giant branch, for which we compute spectra and colours. Then, we compare our modelled colours in the near- and mid-infrared (NIR and MIR) bands with the observed ones, testing different assumptions in our dust scheme and employing several data sets of optical constants for carbon dust available in the literature. Different assumptions adopted in our dust scheme change the typical size of the carbon grains produced. We constrain carbon dust properties by selecting the combination of grain size and optical constants which best reproduce several colours in the NIR and MIR at the same time. The different choices of optical properties and grain size lead to differences in the NIR and MIR colours greater than 2 mag in some cases. We conclude that the complete set of observed NIR and MIR colours are best reproduced by small grains, with sizes between ˜0.035 and ˜0.12 μm, rather than by large grains between ˜0.2 and 0.7 μm. The inability of large grains to reproduce NIR and MIR colours seems independent of the adopted optical data set. We also find a possible trend of the grain size with mass-loss and/or carbon excess in the CSEs of these stars.

Progress of IRSN R&D on ITER Safety Assessment

NASA Astrophysics Data System (ADS)

Van Dorsselaere, J. P.; Perrault, D.; Barrachin, M.; Bentaib, A.; Gensdarmes, F.; Haeck, W.; Pouvreau, S.; Salat, E.; Seropian, C.; Vendel, J.

2012-08-01

The French "Institut de Radioprotection et de Sûreté Nucléaire" (IRSN), in support to the French "Autorité de Sûreté Nucléaire", is analysing the safety of ITER fusion installation on the basis of the ITER operator's safety file. IRSN set up a multi-year R&D program in 2007 to support this safety assessment process. Priority has been given to four technical issues and the main outcomes of the work done in 2010 and 2011 are summarized in this paper: for simulation of accident scenarios in the vacuum vessel, adaptation of the ASTEC system code; for risk of explosion of gas-dust mixtures in the vacuum vessel, adaptation of the TONUS-CFD code for gas distribution, development of DUST code for dust transport, and preparation of IRSN experiments on gas inerting, dust mobilization, and hydrogen-dust mixtures explosion; for evaluation of the efficiency of the detritiation systems, thermo-chemical calculations of tritium speciation during transport in the gas phase and preparation of future experiments to evaluate the most influent factors on detritiation; for material neutron activation, adaptation of the VESTA Monte Carlo depletion code. The first results of these tasks have been used in 2011 for the analysis of the ITER safety file. In the near future, this R&D global programme may be reoriented to account for the feedback of the latter analysis or for new knowledge.

Validation and Verification of LADEE Models and Software

NASA Technical Reports Server (NTRS)

Gundy-Burlet, Karen

2013-01-01

The Lunar Atmosphere Dust Environment Explorer (LADEE) mission will orbit the moon in order to measure the density, composition and time variability of the lunar dust environment. The ground-side and onboard flight software for the mission is being developed using a Model-Based Software methodology. In this technique, models of the spacecraft and flight software are developed in a graphical dynamics modeling package. Flight Software requirements are prototyped and refined using the simulated models. After the model is shown to work as desired in this simulation framework, C-code software is automatically generated from the models. The generated software is then tested in real time Processor-in-the-Loop and Hardware-in-the-Loop test beds. Travelling Road Show test beds were used for early integration tests with payloads and other subsystems. Traditional techniques for verifying computational sciences models are used to characterize the spacecraft simulation. A lightweight set of formal methods analysis, static analysis, formal inspection and code coverage analyses are utilized to further reduce defects in the onboard flight software artifacts. These techniques are applied early and often in the development process, iteratively increasing the capabilities of the software and the fidelity of the vehicle models and test beds.

STARDUST-U experiments on fluid-dynamic conditions affecting dust mobilization during LOVAs

NASA Astrophysics Data System (ADS)

Poggi, L. A.; Malizia, A.; Ciparisse, J. F.; Tieri, F.; Gelfusa, M.; Murari, A.; Del Papa, C.; Giovannangeli, I.; Gaudio, P.

2016-07-01

Since 2006 the Quantum Electronics and Plasma Physics (QEP) Research Group together with ENEA FusTech of Frascati have been working on dust re-suspension inside tokamaks and its potential capability to jeopardize the integrity of future fusion nuclear plants (i.e. ITER or DEMO) and to be a risk for the health of the operators. Actually, this team is working with the improved version of the "STARDUST" facility, i.e. "STARDUST-Upgrade". STARDUST-U facility has four new air inlet ports that allow the experimental replication of Loss of Vacuum Accidents (LOVAs). The experimental campaign to detect the different pressurization rates, local air velocity, temperature, have been carried out from all the ports in different accident conditions and the principal results will be analyzed and compared with the numerical simulations obtained through a CFD (Computational Fluid Dynamic) code. This preliminary thermo fluid-dynamic analysis of the accident is crucial for numerical model development and validation, and for the incoming experimental campaign of dust resuspension inside STARDUST-U due to well-defined accidents presented in this paper.

Accelerating Dust Storm Simulation by Balancing Task Allocation in Parallel Computing Environment

NASA Astrophysics Data System (ADS)

Gui, Z.; Yang, C.; XIA, J.; Huang, Q.; YU, M.

2013-12-01

Dust storm has serious negative impacts on environment, human health, and assets. The continuing global climate change has increased the frequency and intensity of dust storm in the past decades. To better understand and predict the distribution, intensity and structure of dust storm, a series of dust storm models have been developed, such as Dust Regional Atmospheric Model (DREAM), the NMM meteorological module (NMM-dust) and Chinese Unified Atmospheric Chemistry Environment for Dust (CUACE/Dust). The developments and applications of these models have contributed significantly to both scientific research and our daily life. However, dust storm simulation is a data and computing intensive process. Normally, a simulation for a single dust storm event may take several days or hours to run. It seriously impacts the timeliness of prediction and potential applications. To speed up the process, high performance computing is widely adopted. By partitioning a large study area into small subdomains according to their geographic location and executing them on different computing nodes in a parallel fashion, the computing performance can be significantly improved. Since spatiotemporal correlations exist in the geophysical process of dust storm simulation, each subdomain allocated to a node need to communicate with other geographically adjacent subdomains to exchange data. Inappropriate allocations may introduce imbalance task loads and unnecessary communications among computing nodes. Therefore, task allocation method is the key factor, which may impact the feasibility of the paralleling. The allocation algorithm needs to carefully leverage the computing cost and communication cost for each computing node to minimize total execution time and reduce overall communication cost for the entire system. This presentation introduces two algorithms for such allocation and compares them with evenly distributed allocation method. Specifically, 1) In order to get optimized solutions, a quadratic programming based modeling method is proposed. This algorithm performs well with small amount of computing tasks. However, its efficiency decreases significantly as the subdomain number and computing node number increase. 2) To compensate performance decreasing for large scale tasks, a K-Means clustering based algorithm is introduced. Instead of dedicating to get optimized solutions, this method can get relatively good feasible solutions within acceptable time. However, it may introduce imbalance communication for nodes or node-isolated subdomains. This research shows both two algorithms have their own strength and weakness for task allocation. A combination of the two algorithms is under study to obtain a better performance. Keywords: Scheduling; Parallel Computing; Load Balance; Optimization; Cost Model

Radiative transfer and radiative driving of outflows in active galactic nuclei and starbursts

NASA Astrophysics Data System (ADS)

Novak, G. S.; Ostriker, J. P.; Ciotti, L.

2012-12-01

To facilitate the study of black hole fuelling, star formation and feedback in galaxies, we outline a method for treating the radial forces on interstellar gas due to absorption of photons by dust grains. The method gives the correct behaviour in all of the relevant limits [dominated by the central point source; dominated by the distributed isotropic source; optically thin; optically thick to ultraviolet (UV)/optical; optically thick to infrared (IR)] and reasonably interpolates between the limits when necessary. The method is explicitly energy conserving so that UV/optical photons that are absorbed are not lost, but are rather redistributed to the IR where they may scatter out of the galaxy. We implement the radiative transfer algorithm in a two-dimensional hydrodynamical code designed to study feedback processes in the context of early-type galaxies. We find that the dynamics and final state of simulations are measurably but only moderately affected by radiative forces on dust, even when assumptions about the dust-to-gas ratio are varied from zero to a value appropriate for the Milky Way. In simulations with high gas densities designed to mimic ultraluminous IR galaxies with a star formation rate of several hundred solar masses per year, dust makes a more substantial contribution to the dynamics and outcome of the simulation. We find that, despite the large opacity of dust to UV radiation, the momentum input to the flow from radiation very rarely exceeds L/c due to two factors: the low opacity of dust to the re-radiated IR and the tendency for dust to be destroyed by sputtering in hot gas environments. We also develop a simplification of our radiative transfer algorithm that respects the essential physics but is much easier to implement and requires a fraction of the computational cost.

Constraining Dust Properties in Circumstellar Envelopes of C-Stars in the Small Magellanic Cloud: Optical Constants And Grain Size Of Carbon Dust

NASA Astrophysics Data System (ADS)

Nanni, Ambra; Marigo, Paola; Groenewegen, Martin A. T.; Aringer, Berhard; Girardi, Léo; Pastorelli, Giada; Bressan, Alessandro; Bladh, Sara

2016-07-01

We present our recent investigation aimed at constraining the typical size and optical properties of carbon dust grains in Circumstellar envelopes (CSEs) of carbon-rich stars (C-stars) in the Small Magellanic Cloud (SMC).We applied our recent dust growth model, coupled with a radiative transfer code, to the dusty CSEs of C-stars along the TP-AGB phase, for which we computed spectra and colors. We then compared our modeled colors in the Near and Mid Infrared (NIR and MIR) bands with the observed ones, testing different assumptions in our dust scheme and employing different optical constants data sets for carbon dust. We constrained the optical properties of carbon dust by identifying the combinations of typical grain size and optical constants data set which simultaneously reproduce several colors in the NIR and MIR wavelengths. In particular, the different choices of optical properties and grain size lead to differences in the NIR and MIR colors greater than two magnitudes in some cases. We concluded that the complete set of selected NIR and MIR colors are best reproduced by small grains, with sizes between 0.06 and 0.1 mum, rather than by large grains of 0.2-0.4 mum. The inability of large grains to reproduce NIR and MIR colors is found to be independent of the adopted optical data set and the deviations between models and observations tend to increase for increasing grain sizes. We also find a possible trend of the typical grain size with mss-loss and/or carbon-excess in the CSEs of these stars.The work presented is preparatory to future studies aimed at calibrating the TP-AGB phase through resolved stellar populations in the framework of the STARKEY project.

Elastic-plastic adhesive impacts of tungsten dust with metal surfaces in plasma environments

NASA Astrophysics Data System (ADS)

Ratynskaia, S.; Tolias, P.; Shalpegin, A.; Vignitchouk, L.; De Angeli, M.; Bykov, I.; Bystrov, K.; Bardin, S.; Brochard, F.; Ripamonti, D.; den Harder, N.; De Temmerman, G.

2015-08-01

Dust-surface collisions impose size selectivity on the ability of dust grains to migrate in scrape-off layer and divertor plasmas and to adhere to plasma-facing components. Here, we report first experimental evidence of dust impact phenomena in plasma environments concerning low-speed collisions of tungsten dust with tungsten surfaces: re-bouncing, adhesion, sliding and rolling. The results comply with the predictions of the model of elastic-perfectly plastic adhesive spheres employed in the dust dynamics code MIGRAINe for sub- to several meters per second impacts of micrometer-range metal dust.

Dust composition and mass-loss return from the luminous blue variable R71 in the LMC

NASA Astrophysics Data System (ADS)

Guha Niyogi, S.; Min, M.; Meixner, M.; Waters, L. B. F. M.; Seale, J.; Tielens, A. G. G. M.

2014-09-01

Context. We present an analysis of mid- and far-infrared (IR) spectrum and spectral energy distribution (SED) of the luminous blue variable (LBV) R71 in the Large Magellanic Cloud (LMC). Aims: This work aims to understand the overall contribution of high-mass LBVs to the total dust-mass budget of the interstellar medium (ISM) of the LMC and compare this with the contribution from low-mass asymptotic giant branch (AGB) stars. As a case study, we analyze the SED of R71. Methods: We compiled all the available photometric and spectroscopic observational fluxes from various telescopes for a wide wavelength range (0.36-250 μm). We determined the dust composition from the spectroscopic data, and derived the ejected dust mass, dust mass-loss rate, and other dust shell properties by modeling the SED of R71. We noted nine spectral features in the dust shell of R71 by analyzing Spitzer Space Telescope spectroscopic data. Among these, we identified three new crystalline silicate features. We computed our model spectrum by using 3D radiative transfer code MCMax. Results: Our model calculation shows that dust is dominated by amorphous silicates, with some crystalline silicates, metallic iron, and a very tiny amount of polycyclic aromatic hydrocarbon (PAH) molecules. The presence of both silicates and PAHs indicates that the dust has a mixed chemistry. We derived a dust mass of 0.01 M⊙, from which we arrive at a total ejected mass of ≈5 M⊙. This implies a time-averaged dust mass-loss rate of 2.5 × 10-6 M⊙ yr-1 with an explosion about 4000 years ago. We assume that the other five confirmed dusty LBVs in the LMC loose mass at a similar rate, and estimate the total contribution to the mass budget of the LMC to be ≈10-5 M⊙ yr-1, which is comparable to the contribution by all the AGB stars in the LMC. Conclusions: Based on our analysis on R71, we speculate that LBVs as a class may be an important dust source in the ISM of the LMC.

Grid of Supergiant B[e] Models from HDUST Radiative Transfer

NASA Astrophysics Data System (ADS)

Domiciano de Souza, A.; Carciofi, A. C.

2012-12-01

By using the Monte Carlo radiative transfer code HDUST (developed by A. C. Carciofi and J..E. Bjorkman) we have built a grid of models for stars presenting the B[e] phenomenon and a bimodal outflowing envelope. The models are particularly adapted to the study of B[e] supergiants and FS CMa type stars. The adopted physical parameters of the calculated models make the grid well adapted to interpret high angular and high spectral observations, in particular spectro-interferometric data from ESO-VLTI instruments AMBER (near-IR at low and medium spectral resolution) and MIDI (mid-IR at low spectral resolution). The grid models include, for example, a central B star with different effective temperatures, a gas (hydrogen) and silicate dust circumstellar envelope with a bimodal mass loss presenting dust in the denser equatorial regions. The HDUST grid models were pre-calculated using the high performance parallel computing facility Mésocentre SIGAMM, located at OCA, France.

An Icy Kuiper Belt Around the Young Solar-type Star HD 181327

NASA Technical Reports Server (NTRS)

Lebreton, J.; Augereau, J.-C.; Thi, W.-F.; Roberge, A.; Donaldson, J; Schneider, G.; Maddison, S. T.; Menard, F.; Riviere-Marichalar, P.; Matthews, G. S.;

THE OBSCURED FRACTION OF ACTIVE GALACTIC NUCLEI IN THE XMM-COSMOS SURVEY: A SPECTRAL ENERGY DISTRIBUTION PERSPECTIVE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lusso, E.; Hennawi, J. F.; Richards, G. T.

2013-11-10

The fraction of active galactic nucleus (AGN) luminosity obscured by dust and re-emitted in the mid-IR is critical for understanding AGN evolution, unification, and parsec-scale AGN physics. For unobscured (Type 1) AGNs, where we have a direct view of the accretion disk, the dust covering factor can be measured by computing the ratio of re-processed mid-IR emission to intrinsic nuclear bolometric luminosity. We use this technique to estimate the obscured AGN fraction as a function of luminosity and redshift for 513 Type 1 AGNs from the XMM-COSMOS survey. The re-processed and intrinsic luminosities are computed by fitting the 18 bandmore » COSMOS photometry with a custom spectral energy distribution fitting code, which jointly models emission from hot dust in the AGN torus, from the accretion disk, and from the host galaxy. We find a relatively shallow decrease of the luminosity ratio as a function of L{sub bol}, which we interpret as a corresponding decrease in the obscured fraction. In the context of the receding torus model, where dust sublimation reduces the covering factor of more luminous AGNs, our measurements require a torus height that increases with luminosity as h ∝ L{sub bol}{sup 0.3-0.4}. Our obscured-fraction-luminosity relation agrees with determinations from Sloan Digital Sky Survey censuses of Type 1 and Type 2 quasars and favors a torus optically thin to mid-IR radiation. We find a much weaker dependence of the obscured fraction on 2-10 keV luminosity than previous determinations from X-ray surveys and argue that X-ray surveys miss a significant population of highly obscured Compton-thick AGNs. Our analysis shows no clear evidence for evolution of the obscured fraction with redshift.« less

Mars Atmospheric Temperature and Dust Storm Tracking

NASA Image and Video Library

2016-06-09

This graphic overlays Martian atmospheric temperature data as curtains over an image of Mars taken during a regional dust storm. The temperature profiles extend from the surface to about 50 miles (80 kilometers) up. Temperatures are color coded, ranging from minus 243 degrees Fahrenheit (minus 153 degrees Celsius) where coded purple to minus 9 F (minus 23 C) where coded red. The temperature data and global image were both recorded on Oct. 18, 2014, by instruments on NASA's Mars Reconnaissance Orbiter: Mars Climate Sounder and Mars Color Imager. On that day a regional dust storm was active in the Acidalia Planitia region of northern Mars, at the upper center of this image. A storm from this area in typically travels south and grows into a large regional storm in the southern hemisphere during southern spring. That type of southern-spring storm and two other large regional dust storms repeat as a three-storm series most Martian years. The pattern has been identified from their effects on atmospheric temperature in a layer about 16 miles (25 kilometers) above the surface. http://photojournal.jpl.nasa.gov/catalog/PIA20747

Planet formation: is it good or bad to have a stellar companion?

NASA Astrophysics Data System (ADS)

Marzari, F.; Thebault, P.; Scholl, H.

2010-04-01

Planet formation in binary star systems is a complex issue due to the gravitational perturbations of the companion star. One of the crucial steps of the core-accretion model is planetesimal accretion into large protoplanets which finally coalesce into planets. In a planetesimal swarm surrounding the primary star, the average mutual impact velocity determines if larger bodies form or if the population is grinded down to dust, halting the planet formation process. This velocity is strongly influenced by the companion gravitational pull and by gas drag. The combined effect of these two forces may act in favour of or against planet formation, setting a lower or equal probability of the existence of extrasolar planets around single or binary stars. Planetesimal accretion in binaries has been studied so far with two different approaches. N-body codes based on the assumption that the disk is axisymmetric are very cost-effective since they allow the study of the mutual relative velocity with limited CPU usage. A large amount of planetesimal trajectories can be computed making it possible to outline the regions around the star where planet formation is possible. The main limitation of the N-body codes is the axisymmetric assumption. The companion perturbations affect not only the planetesimal orbits, but also the gaseous disk, by forcing spiral density waves. In addition, the overall shape of the disk changes from circular to elliptic. Hybrid codes have been recently developed which solve the equations for the disk with a hydrodynamical grid code and use the computed gas density and velocity vector to calculate an accurate value of the gas drag force on the planetesimals. These codes are more complex and may compute the trajectories of only a limited number of planetesimals.

The Electric Environment of Martian Dust Devils

NASA Astrophysics Data System (ADS)

Barth, E. L.; Farrell, W. M.; Rafkin, S. C.

2017-12-01

While Martian dust devils have been monitored through decades of observations, we have yet to study their possible electrical effects from in situ instrumentation. However, evidence for the existence of active electrodynamic processes on Mars is provided by laboratory studies of analog material and field campaigns of dust devils on Earth. We have enabled our Mars regional scale atmospheric model (MRAMS) to estimate an upper limit on electric fields generated through dust devil circulations by including charged particles as defined from the Macroscopic Triboelectric Simulation (MTS) code. MRAMS is used to investigate the complex physics of regional, mesoscale, and microscale atmospheric phenomena on Mars; it is a 3-D, nonhydrostatic model, which permits the simulation of atmospheric flows with large vertical accelerations, such as dust devils. MTS is a 3-D particle code which quantifies charging associated with swirling, mixing dust grains; grains of pre-defined sizes and compositions are placed in a simulation box and allowed to move under the influence of winds and gravity. Our MRAMS grid cell size makes our results most applicable to dust devils of a few hundred meters in diameter. We have run a number of simulations to understand the sensitivity of the electric field strength to the particle size and abundance and the amount of charge on each dust grain. We find that Efields can indeed develop in Martian dust convective features via dust grain filtration effects. The overall value of these E-fields is strongly dependent upon dust grain size, dust load, and lifting efficiency, and field strengths can range from 100s of mV/m to 10s of kV/m.

Assessment of aerosol's mass concentrations from measured linear particle depolarization ratio (vertically resolved) and simulations

NASA Astrophysics Data System (ADS)

Nemuc, A.; Vasilescu, J.; Talianu, C.; Belegante, L.; Nicolae, D.

2013-11-01

Multi-wavelength depolarization Raman lidar measurements from Magurele, Romania are used in this study along with simulated mass-extinction efficiencies to calculate the mass concentration profiles of different atmospheric components, due to their different depolarization contribution to the 532 nm backscatter coefficient. Linear particle depolarization ratio (δpart) was computed using the relative amplification factor and the system-dependent molecular depolarization. The low depolarizing component was considered as urban/smoke, with a mean δpart of 3%, while for the high depolarizing component (mineral dust) a mean δpart of 35% was assumed. For this study 11 months of lidar measurements were analysed. Two study cases are presented in details: one for a typical Saharan dust aerosol intrusion, 10 June 2012 and one for 12 July 2012 when a lofted layer consisting of biomass burning smoke extended from 3 to 4.5 km height. Optical Properties of Aerosols and Clouds software package (OPAC) classification and conversion factors were used to calculate mass concentrations. We found that calibrated depolarization measurements are critical in distinguishing between smoke-reach aerosol during the winter and dust-reach aerosol during the summer, as well as between elevated aerosol layers having different origins. Good agreement was found between lidar retrievals and DREAM- Dust REgional Atmospheric Model forecasts in cases of Saharan dust. Our method was also compared against LIRIC (The Lidar/Radiometer Inversion Code) and very small differences were observed.

Assessment of aerosol's mass concentrations from measured linear particle depolarization ratio (vertically resolved) and simulations

NASA Astrophysics Data System (ADS)

Nemuc, A.; Vasilescu, J.; Talianu, C.; Belegante, L.; Nicolae, D.

2013-06-01

Multiwavelength depolarization Raman lidar measurements from Magurele, Romania are used in this study along with simulated mass-extinction efficiencies to calculate the mass concentrations profiles of different atmospheric components, due to their different depolarization contribution to the 532 nm backscatter coefficient. Linear particle depolarization ratio (δpart) was computed using the relative amplification factor and the system-dependent molecular depolarization. The low depolarizing component was considered as urban/smoke, with a mean δpart of 3%, while for the high depolarizing component (mineral dust) a mean δpart of 35% was assumed. For this study 11 months of lidar measurements were analyzed. Two study cases are presented in details: one for a typical Saharan dust aerosol intrusion, 10 June 2012 and one for 12 July 2012 when a lofted layer consisting of biomass burning smoke extended from 3 to 4.5 km height. Optical Properties of Aerosols and Clouds software package (OPAC) classification and conversion factors were used to calculate mass concentrations. We found that calibrated depolarization measurements are critical to distinguish between smoke-reach aerosol during the winter and dust-reach aerosol during the summer, as well as between elevated aerosol layers having different origins. Good agreement was found between lidar retrievals and DREAM- Dust REgional Atmospheric Model forecasts in cases of Saharan dust. Our method was also compared against LIRIC (The Lidar/Radiometer Inversion Code) and very small differences were observed.

The effect of dust charge variation, due to ion flow and electron depletion, on dust levitation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Land, Victor; Douglass, Angela; Qiao Ke

2011-11-29

Using a fluid model, the plasma densities, electron temperature and ion Mach number in front of a powered electrode in different plasma discharges is computed. The dust charge is computed using OML theory for Maxwellian electrons and ions distributed according to a shifted-Maxwellian. By assuming force balance between gravity and the electrostatic force, the dust levitation height is obtained. The importance of the dust charge variation is investigated.

Computer Model Predicts the Movement of Dust

NASA Technical Reports Server (NTRS)

2002-01-01

A new computer model of the atmosphere can now actually pinpoint where global dust events come from, and can project where they're going. The model may help scientists better evaluate the impact of dust on human health, climate, ocean carbon cycles, ecosystems, and atmospheric chemistry. Also, by seeing where dust originates and where it blows people with respiratory problems can get advanced warning of approaching dust clouds. 'The model is physically more realistic than previous ones,' said Mian Chin, a co-author of the study and an Earth and atmospheric scientist at Georgia Tech and the Goddard Space Flight Center (GSFC) in Greenbelt, Md. 'It is able to reproduce the short term day-to-day variations and long term inter-annual variations of dust concentrations and distributions that are measured from field experiments and observed from satellites.' The above images show both aerosols measured from space (left) and the movement of aerosols predicted by computer model for the same date (right). For more information, read New Computer Model Tracks and Predicts Paths Of Earth's Dust Images courtesy Paul Giroux, Georgia Tech/NASA Goddard Space Flight Center

Dusty Plasmas in Planetary Magnetospheres Award

NASA Technical Reports Server (NTRS)

Horanyi, Mihaly

2005-01-01

This is my final report for the grant Dusty Plasmas in Planetary Magnetospheres. The funding from this grant supported our research on dusty plasmas to study: a) dust plasma interactions in general plasma environments, and b) dusty plasma processes in planetary magnetospheres (Earth, Jupiter and Saturn). We have developed a general purpose transport code in order to follow the spatial and temporal evolution of dust density distributions in magnetized plasma environments. The code allows the central body to be represented by a multipole expansion of its gravitational and magnetic fields. The density and the temperature of the possibly many-component plasma environment can be pre-defined as a function of coordinates and, if necessary, the time as well. The code simultaneously integrates the equations of motion with the equations describing the charging processes. The charging currents are dependent not only on the instantaneous plasma parameters but on the velocity, as well as on the previous charging history of the dust grains.

A fast code for channel limb radiances with gas absorption and scattering in a spherical atmosphere

NASA Astrophysics Data System (ADS)

Eluszkiewicz, Janusz; Uymin, Gennady; Flittner, David; Cady-Pereira, Karen; Mlawer, Eli; Henderson, John; Moncet, Jean-Luc; Nehrkorn, Thomas; Wolff, Michael

2017-05-01

We present a radiative transfer code capable of accurately and rapidly computing channel limb radiances in the presence of gaseous absorption and scattering in a spherical atmosphere. The code has been prototyped for the Mars Climate Sounder measuring limb radiances in the thermal part of the spectrum (200-900 cm-1) where absorption by carbon dioxide and water vapor and absorption and scattering by dust and water ice particles are important. The code relies on three main components: 1) The Gauss Seidel Spherical Radiative Transfer Model (GSSRTM) for scattering, 2) The Planetary Line-By-Line Radiative Transfer Model (P-LBLRTM) for gas opacity, and 3) The Optimal Spectral Sampling (OSS) for selecting a limited number of spectral points to simulate channel radiances and thus achieving a substantial increase in speed. The accuracy of the code has been evaluated against brute-force line-by-line calculations performed on the NASA Pleiades supercomputer, with satisfactory results. Additional improvements in both accuracy and speed are attainable through incremental changes to the basic approach presented in this paper, which would further support the use of this code for real-time retrievals and data assimilation. Both newly developed codes, GSSRTM/OSS for MCS and P-LBLRTM, are available for additional testing and user feedback.

Are neighborhood-level characteristics associated with indoor allergens in the household?

PubMed

Rosenfeld, Lindsay; Rudd, Rima; Chew, Ginger L; Emmons, Karen; Acevedo-García, Dolores

2010-02-01

Individual home characteristics have been associated with indoor allergen exposure; however, the influence of neighborhood-level characteristics has not been well studied. We defined neighborhoods as community districts determined by the New York City Department of City Planning. We examined the relationship between neighborhood-level characteristics and the presence of dust mite (Der f 1), cat (Fel d 1), cockroach (Bla g 2), and mouse (MUP) allergens in the household. Using data from the Puerto Rican Asthma Project, a birth cohort of Puerto Rican children at risk of allergic sensitization (n = 261), we examined associations between neighborhood characteristics (percent tree canopy, asthma hospitalizations per 1,000 children, roadway length within 100 meters of buildings, serious housing code violations per 1000 rental units, poverty rates, and felony crime rates), and the presence of indoor allergens. Allergen cutpoints were used for categorical analyses and defined as follows: dust mite: >0.25 microg/g; cat: >1 microg/g; cockroach: >1 U/g; mouse: >1.6 microg/g. Serious housing code violations were statistically significantly positively associated with dust mite, cat, and mouse allergens (continuous variables), adjusting for mother's income and education, and all neighborhood-level characteristics. In multivariable logistic regression analyses, medium levels of housing code violations were associated with higher dust mite and cat allergens (1.81, 95%CI: 1.08, 3.03 and 3.10, 95%CI: 1.22, 7.92, respectively). A high level of serious housing code violations was associated with higher mouse allergen (2.04, 95%CI: 1.15, 3.62). A medium level of housing code violations was associated with higher cockroach allergen (3.30, 95%CI: 1.11, 9.78). Neighborhood-level characteristics, specifically housing code violations, appear to be related to indoor allergens, which may have implications for future research explorations and policy decisions.

Data Release of UV to Submillimeter Broadband Fluxes for Simulated Galaxies from the EAGLE Project

NASA Astrophysics Data System (ADS)

Camps, Peter; Trčka, Ana; Trayford, James; Baes, Maarten; Theuns, Tom; Crain, Robert A.; McAlpine, Stuart; Schaller, Matthieu; Schaye, Joop

2018-02-01

We present dust-attenuated and dust emission fluxes for sufficiently resolved galaxies in the EAGLE suite of cosmological hydrodynamical simulations, calculated with the SKIRT radiative transfer code. The post-processing procedure includes specific components for star formation regions, stellar sources, and diffuse dust and takes into account stochastic heating of dust grains to obtain realistic broadband fluxes in the wavelength range from ultraviolet to submillimeter. The mock survey includes nearly half a million simulated galaxies with stellar masses above {10}8.5 {M}ȯ across six EAGLE models. About two-thirds of these galaxies, residing in 23 redshift bins up to z = 6, have a sufficiently resolved metallic gas distribution to derive meaningful dust attenuation and emission, with the important caveat that the same dust properties were used at all redshifts. These newly released data complement the already publicly available information about the EAGLE galaxies, which includes intrinsic properties derived by aggregating the properties of the smoothed particles representing matter in the simulation. We further provide an open-source framework of Python procedures for post-processing simulated galaxies with the radiative transfer code SKIRT. The framework allows any third party to calculate synthetic images, spectral energy distributions, and broadband fluxes for EAGLE galaxies, taking into account the effects of dust attenuation and emission.

Aspherical dust dynamics code for GIADA experiment in the coma of 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Ivanovski, Stavro; Zakharov, Vladimir; Della Corte, Vincenzo; Lucarelli, Francesca; Crifo, Jean-Francois; Rotundi, Alessandra; Fulle, Marco

2014-05-01

In 2014, the ESA ROSETTA probe is on its way to face its main scientific objectives by encountering and landing on comet 67P/Churyumov- Gerasimenko. One of the in-situ instrument on board ROSETTA is GIADA (Grain Impact Analyzer and Dust Accumulator)[1], which will measure individual dust grain mass, number density and velocity in the immediate vicinity of the cometary nucleus. Based on the state-of-the-art 3D+t dust coma model [3,4] we developed a 3D+t aspherical dust dynamical code Giaspheria (GIADA aspherical dust analyzer) which treats aspherical dust motion to support the scientific objectives of GIADA. We report the latest improvements in Giaspheria[5,6,7] and the distinctions in the dust dynamics of spherical and aspherical grains using gas solutions for a spherical nucleus not yet data-calibrated. We consider motion of homogeneous, isothermal polygonal convex bodies (close to ellipsoid of revolution with different aspect ratios of axes), moving under influence of three forces: aerodynamic , gravitational and torque. We use the gas distribution (density, velocity, temperature) for a spherical nucleus discussed in [4,8]. We estimate the aerodynamic force from expressions for free molecular interactions and postulate the distribution function of ejection velocity and the distribution function of initial orientation on the surface of the nucleus. We show the dust distribution of aspherical grains at three different heliocentric distances (3AU, 2AU and 1.3 AU) by means of GIPSI simulated GIADA measurements during these stages of the mission. As an input for GIPSI simulations we use the dust and velocity distributions prevised by Giaspheria computations. Acknowledgements: This research has been supported by the Italian Space Agency (ASI) (Ref: n. I/032/05/0) [1] Della Corte V. et al, (2014), Journal of Astronomical Instrumentation (in press). [2] Colangeli, L., et al., Space Science Reviews, Volume 128, Numbers 1-4, 803-821, 2007 [3] Zakharov, V.V., Rodionov A.V., Crifo J.-F., Fulle M., EPSC-DPS , p. 126, 2011 [4] Crifo, J.-F., Loukianov, G.A., Rodionov, A. V., and Zakharov, V. V., Icarus 176, pp. 192-219, 2005 [5] Ivanovski, S. L., Zakharov, V.V., Crifo J.-F., Della Corte V., Rotundi A., EPSC-DPS, p.1371, 2011 [6] Ivanovski, S. L., Zakharov, V.V., Crifo J.-F., Della Corte V., Rotundi A., Vol 7, EPSC2012-592, 2012 [7] Ivanovski, S. L., Zakharov, V.V., Crifo J.-F., Della Corte V., Rotundi A., Vol. 15, EGU2013-11417, 2013 [8] Crifo, J-F., Lukianov,G.A., Rodionov,A.V., Khanlarov,G.O. ,Zakharov,V.V. Icarus Vol.156, 249-268, 2002 [9] Zakharov,V.V., Rodionov, A. V., Lukianov,G.A., Crifo, J-F.,Icarus Vol. 201, I1, p.358-380, 2009

Fast camera observations of injected and intrinsic dust in TEXTOR

NASA Astrophysics Data System (ADS)

Shalpegin, A.; Vignitchouk, L.; Erofeev, I.; Brochard, F.; Litnovsky, A.; Bozhenkov, S.; Bykov, I.; den Harder, N.; Sergienko, G.

2015-12-01

Stereoscopic fast camera observations of pre-characterized carbon and tungsten dust injection in TEXTOR are reported, along with the modelling of tungsten particle trajectories with MIGRAINe. Particle tracking analysis of the video data showed significant differences in dust dynamics: while carbon flakes were prone to agglomeration and explosive destruction, spherical tungsten particles followed quasi-inertial trajectories. Although this inertial nature prevented any validation of the force models used in MIGRAINe, comparisons between the experimental and simulated lifetimes provide a direct evidence of dust temperature overestimation in dust dynamics codes. Furthermore, wide-view observations of the TEXTOR interior revealed the main production mechanism of intrinsic carbon dust, as well as the location of probable dust remobilization sites.

Numerical Prediction of Dust. Chapter 10

NASA Technical Reports Server (NTRS)

Benedetti, Angela; Baldasano, J. M.; Basart, S.; Benincasa, F.; Boucher, O.; Brooks, M.; Chen, J. P.; Colarco, P. R.; Gong, S.; Huneeus, N.;

Developing Subdomain Allocation Algorithms Based on Spatial and Communicational Constraints to Accelerate Dust Storm Simulation

PubMed Central

Gui, Zhipeng; Yu, Manzhu; Yang, Chaowei; Jiang, Yunfeng; Chen, Songqing; Xia, Jizhe; Huang, Qunying; Liu, Kai; Li, Zhenlong; Hassan, Mohammed Anowarul; Jin, Baoxuan

2016-01-01

Dust storm has serious disastrous impacts on environment, human health, and assets. The developments and applications of dust storm models have contributed significantly to better understand and predict the distribution, intensity and structure of dust storms. However, dust storm simulation is a data and computing intensive process. To improve the computing performance, high performance computing has been widely adopted by dividing the entire study area into multiple subdomains and allocating each subdomain on different computing nodes in a parallel fashion. Inappropriate allocation may introduce imbalanced task loads and unnecessary communications among computing nodes. Therefore, allocation is a key factor that may impact the efficiency of parallel process. An allocation algorithm is expected to consider the computing cost and communication cost for each computing node to minimize total execution time and reduce overall communication cost for the entire simulation. This research introduces three algorithms to optimize the allocation by considering the spatial and communicational constraints: 1) an Integer Linear Programming (ILP) based algorithm from combinational optimization perspective; 2) a K-Means and Kernighan-Lin combined heuristic algorithm (K&K) integrating geometric and coordinate-free methods by merging local and global partitioning; 3) an automatic seeded region growing based geometric and local partitioning algorithm (ASRG). The performance and effectiveness of the three algorithms are compared based on different factors. Further, we adopt the K&K algorithm as the demonstrated algorithm for the experiment of dust model simulation with the non-hydrostatic mesoscale model (NMM-dust) and compared the performance with the MPI default sequential allocation. The results demonstrate that K&K method significantly improves the simulation performance with better subdomain allocation. This method can also be adopted for other relevant atmospheric and numerical modeling. PMID:27044039

Circumstellar Dust in Symbiotic Novae

NASA Astrophysics Data System (ADS)

Jurkic, T.; Kotnik-Karuza, D.

2015-12-01

We present a model of inner dust regions around the cool Mira component of the two symbiotic novae, RR Tel and HM Sge, based on the near-IR photometry, ISO spectra and mid-IR interferometry. The dust properties were determined using the DUSTY code. A compact circumstellar silicate dust shell with inner dust shell temperatures between 900 K and 1300 K and of moderate optical depth can explain all the observations. RR Tel shows the presence of an equatorially enhanced dust density during minimum obscuration. Obscuration events are explained by an increase in optical depth caused by the newly condensed dust. The mass loss rates are significantly higher than in intermediate-period single Miras but in agreement with longer-period O-rich AGB stars.

Dust settling in magnetorotationally driven turbulent discs - I. Numerical methods and evidence for a vigorous streaming instability

NASA Astrophysics Data System (ADS)

Balsara, Dinshaw S.; Tilley, David A.; Rettig, Terrence; Brittain, Sean D.

2009-07-01

In this paper, we have used the RIEMANN code for computational astrophysics to study the interaction of a realistic distribution of dust grains with gas at specific radial locations in a vertically stratified protostellar accretion disc. The disc was modelled to have the density and temperature of a minimum mass solar nebula, and shearing box simulations at radii of 0.3 and 10 au are reported here. The disc was driven to a fully developed turbulence via the magnetorotational instability (MRI). The simulations span three gas scaleheights about the disc's midplane. We find that the inclusion of standard dust-to-gas ratios does not have any significant effect on the MRI even when the dust sediments to the midplane of the accretion disc. The density distribution of the dust of all sizes reached a Gaussian profile within two scaleheights of the disc's midplane. The vertical scaleheights of these Gaussian profiles are shown to be proportional to the reciprocal of the square root of the dust radius when large spherical dust grains are considered. This result is consistent with theoretical expectation. The largest two families of dust in one of our simulations show a strong tendency to settle to the midplane of the accretion disc. The large dust tends to organize itself into elongated clumps of high density. The dynamics of these clumps is shown to be consistent with a streaming instability. The streaming instability is seen to be very vigorous and persistent once it forms. Each stream of high-density dust displays a reduced rms velocity dispersion. The velocity directions within the streams are also aligned relative to the mean shear, providing further evidence that we are witnessing a streaming instability. The densest clumpings of large dust are shown to form where the streams intersect. We have also shown that the mean free path and collision time for dust that participates in the streaming instability are reduced by almost two orders of magnitude relative to the average mean free paths and collision times. The rms velocities between the grains also need to fall below a minimum threshold in order for the grains to stick and we show that a small amount of the large dust in our 10 au simulation should have a propensity for grain coalescence. The results of our simulations are likely to be useful for those who model spectral energy distributions of protostellar discs and also for those who model dust coagulation and growth.

Inferring giant planets from ALMA millimeter continuum and line observations in (transition) disks

NASA Astrophysics Data System (ADS)

Facchini, S.; Pinilla, P.; van Dishoeck, E. F.; de Juan Ovelar, M.

2018-05-01

Context. Radial gaps or cavities in the continuum emission in the IR-mm wavelength range are potential signatures of protoplanets embedded in their natal protoplanetary disk are. Hitherto, models have relied on the combination of mm continuum observations and near-infrared scattered light images to put constraints on the properties of embedded planets. Atacama Large Millimeter/submillimeter Array (ALMA) observations are now probing spatially resolved rotational line emission of CO and other chemical species. These observations can provide complementary information on the mechanism carving the gaps in dust and additional constraints on the purported planet mass. Aims: We investigate whether the combination of ALMA continuum and CO line observations can constrain the presence and mass of planets embedded in protoplanetary disks. Methods: We post-processed azimuthally averaged 2D hydrodynamical simulations of planet-disk models, in which the dust densities and grain size distributions are computed with a dust evolution code that considers radial drift, fragmentation, and growth. The simulations explored various planet masses (1 MJ ≤ Mp ≤ 15 MJ) and turbulent parameters (10-4 ≤ α ≤ 10-3). The outputs were then post-processed with the thermochemical code DALI, accounting for the radially and vertically varying dust properties. We obtained the gas and dust temperature structures, chemical abundances, and synthetic emission maps of both thermal continuum and CO rotational lines. This is the first study combining hydrodynamical simulations, dust evolution, full radiative transfer, and chemistry to predict gas emission of disks hosting massive planets. Results: All radial intensity profiles of 12CO, 13CO, and C18O show a gap at the planet location. The ratio between the location of the gap as seen in CO and the peak in the mm continuum at the pressure maximum outside the orbit of the planet shows a clear dependence on planet mass and is independent of disk viscosity for the parameters explored in this paper. Because of the low dust density in the gaps, the dust and gas components can become thermally decoupled and the gas becomes colder than the dust. The gaps seen in CO are due to a combination of gas temperature dropping at the location of the planet and of the underlying surface density profile. Both effects need to be taken into account and disentangled when inferring gas surface densities from observed CO intensity profiles; otherwise, the gas surface density drop at the planet location can easily be overestimated. CO line ratios across the gap are able to quantify the gas temperature drop in the gaps in observed systems. Finally, a CO cavity not observed in any of the models, only CO gaps, indicating that one single massive planet is not able to explain the CO cavities observed in transition disks, at least without additional physical or chemical mechanisms.

Eulerian-Lagrangian CFD modelling of pesticide dust emissions from maize planters

NASA Astrophysics Data System (ADS)

Devarrewaere, Wouter; Foqué, Dieter; Nicolai, Bart; Nuyttens, David; Verboven, Pieter

2018-07-01

An Eulerian-Lagrangian 3D computational fluid dynamics (CFD) model of pesticide dust drift from precision vacuum planters in field conditions was developed. Tractor and planter models were positioned in an atmospheric computational domain, representing the field and its edges. Physicochemical properties of dust abraded from maize seeds (particle size, shape, porosity, density, a.i. content), dust emission rates and exhaust air velocity values at the planter fan outlets were measured experimentally and implemented in the model. The wind profile, the airflow pattern around the machines and the dust dispersion were computed. Various maize sowing scenarios with different wind conditions, dust properties, planter designs and vacuum pressures were simulated. Dust particle trajectories were calculated by means of Lagrangian particle tracking, considering nonspherical particle drag, gravity and turbulent dispersion. The dust dispersion model was previously validated with wind tunnel data. In this study, simulated pesticide concentrations in the air and on the soil in the different sowing scenarios were compared and discussed. The model predictions were similar to experimental literature data in terms of concentrations and drift distance. Pesticide exposure levels to bees during flight and foraging were estimated from the simulated concentrations. The proposed CFD model can be used in risk assessment studies and in the evaluation of dust drift mitigation measures.

29 CFR Appendix A to Subpart S of... - References for Further Information

Code of Federal Regulations, 2014 CFR

2014-07-01

... Safety, Health, and Environmental Training. ANSI/IEEE C2-2002 National Electrical Safety Code. ANSI K61.1.... NFPA 59-2004 Utility LP-Gas Plant Code. NFPA 70-2002 National Electrical Code. (See also NFPA 70-2005.... NMAB 353-3-1980 Classification of Combustible Dust in Accordance with the National Electrical Code. [72...

29 CFR Appendix A to Subpart S of... - References for Further Information

Code of Federal Regulations, 2011 CFR

2011-07-01

... Safety, Health, and Environmental Training. ANSI/IEEE C2-2002 National Electrical Safety Code. ANSI K61.1.... NFPA 59-2004 Utility LP-Gas Plant Code. NFPA 70-2002 National Electrical Code. (See also NFPA 70-2005.... NMAB 353-3-1980 Classification of Combustible Dust in Accordance with the National Electrical Code. [72...

29 CFR Appendix A to Subpart S of... - References for Further Information

Code of Federal Regulations, 2012 CFR

2012-07-01

... Safety, Health, and Environmental Training. ANSI/IEEE C2-2002 National Electrical Safety Code. ANSI K61.1.... NFPA 59-2004 Utility LP-Gas Plant Code. NFPA 70-2002 National Electrical Code. (See also NFPA 70-2005.... NMAB 353-3-1980 Classification of Combustible Dust in Accordance with the National Electrical Code. [72...

29 CFR Appendix A to Subpart S of... - References for Further Information

Code of Federal Regulations, 2013 CFR

2013-07-01

... Safety, Health, and Environmental Training. ANSI/IEEE C2-2002 National Electrical Safety Code. ANSI K61.1.... NFPA 59-2004 Utility LP-Gas Plant Code. NFPA 70-2002 National Electrical Code. (See also NFPA 70-2005.... NMAB 353-3-1980 Classification of Combustible Dust in Accordance with the National Electrical Code. [72...

Estimating the dust production rate of carbon stars in the Small Magellanic Cloud

NASA Astrophysics Data System (ADS)

Nanni, Ambra; Marigo, Paola; Girardi, Léo; Rubele, Stefano; Bressan, Alessandro; Groenewegen, Martin A. T.; Pastorelli, Giada; Aringer, Bernhard

2018-02-01

We employ newly computed grids of spectra reprocessed by dust for estimating the total dust production rate (DPR) of carbon stars in the Small Magellanic Cloud (SMC). For the first time, the grids of spectra are computed as a function of the main stellar parameters, i.e. mass-loss rate, luminosity, effective temperature, current stellar mass and element abundances at the photosphere, following a consistent, physically grounded scheme of dust growth coupled with stationary wind outflow. The model accounts for the dust growth of various dust species formed in the circumstellar envelopes of carbon stars, such as carbon dust, silicon carbide and metallic iron. In particular, we employ some selected combinations of optical constants and grain sizes for carbon dust that have been shown to reproduce simultaneously the most relevant colour-colour diagrams in the SMC. By employing our grids of models, we fit the spectral energy distributions of ≈3100 carbon stars in the SMC, consistently deriving some important dust and stellar properties, i.e. luminosities, mass-loss rates, gas-to-dust ratios, expansion velocities and dust chemistry. We discuss these properties and we compare some of them with observations in the Galaxy and Large Magellanic Cloud. We compute the DPR of carbon stars in the SMC, finding that the estimates provided by our method can be significantly different, between a factor of ≈2-5, than the ones available in the literature. Our grids of models, including the spectra and other relevant dust and stellar quantities, are publicly available at http://starkey.astro.unipd.it/web/guest/dustymodels.

Are Neighborhood-Level Characteristics Associated with Indoor Allergens in the Household?

PubMed Central

Rosenfeld, Lindsay; Rudd, Rima; Chew, Ginger L.; Emmons, Karen; Acevedo-García, Dolores

2010-01-01

Background Individual home characteristics have been associated with indoor allergen exposure; however, the influence of neighborhood-level characteristics has not been well-studied. We defined neighborhoods as community districts determined by the New York Department of City Planning. Objective We examined the relationship between neighborhood-level characteristics and the presence of dust mite (Der f 1), cat (Fel d 1), cockroach (Bla g 2), and mouse (MUP) allergens in the household. Methods Using data from the Puerto Rican Asthma Project, a birth cohort of Puerto Rican children at risk of allergic sensitization (n=261) we examined associations between neighborhood characteristics (percent tree canopy, asthma hospitalizations per 1000 children, roadway length within 100 meters of buildings, serious housing code violations per 1000 rental units, poverty rates, and felony crime rates) and the presence of indoor allergens. Allergen cutpoints were used for categorical analyses and defined as follows: dust mite: >0.25 μg/g; cat: >1 μg/g; cockroach: >1 U/g; mouse: >1.6 μg/g. Results Serious housing code violations were statistically significantly positively associated with dust mite, cat and mouse allergens (continuous variables), adjusting for mother's income and education, and all neighborhood-level characteristics. In multivariable logistic regression analyses, medium levels of housing code violations were associated with higher dust mite and cat allergens (1.81, 95%CI: 1.08, 3.03 and 3.10, 95%CI: 1.22, 7.92, respectively). A high level of serious housing code violations was associated with higher mouse allergen (2.04, 95%CI: 1.15, 3.62). A medium level of housing code violations was associated with higher cockroach allergen (3.30, 95%CI: 1.11, 9.78). Conclusions Neighborhood-level characteristics, specifically housing code violations, appear to be related to indoor allergens, which may have implications for future research explorations and policy decisions. PMID:20100024

Extensive computation of albedo contrast between martian dust devil tracks and their neighboring regions

NASA Astrophysics Data System (ADS)

Statella, Thiago; Pina, Pedro; da Silva, Erivaldo Antônio

2015-04-01

We have developed a method to compute the albedo contrast between dust devil tracks and their surrounding regions on Mars. It is mainly based on Mathematical Morphology operators and uses all the points of the edges of the tracks to compute the values of the albedo contrast. It permits the extraction of more accurate and complete information, when compared to traditional point sampling, not only providing better statistics but also permitting the analysis of local variations along the entirety of the tracks. This measure of contrast, based on relative quantities, is much more adequate to establish comparisons at regional scales and in multi-temporal basis using imagery acquired in rather different environmental and operational conditions. Also, the substantial increase in the details extracted may permit quantifying differential depositions of dust by computing local temporal fading of the tracks with consequences on a better estimation of the thickness of the top most layer of dust and the minimum value needed to create dust devils tracks. The developed tool is tested on 110 HiRISE images depicting regions in the Aeolis, Argyre, Eridania, Noachis and Hellas quadrangles. As a complementary evaluation, we also performed a temporal analysis of the albedo in a region of Russell crater, where high seasonal dust devil activity was already observed before, comprising the years 2007-2012. The mean albedo of the Russell crater is in this case indicative of dust devil tracks presence and, therefore, can be used to quantify dust devil activity.

Characterizing the UV-to-NIR shape of the dust attenuation curve of IR luminous galaxies up to z ˜ 2

NASA Astrophysics Data System (ADS)

Lo Faro, B.; Buat, V.; Roehlly, Y.; Alvarez-Marquez, J.; Burgarella, D.; Silva, L.; Efstathiou, A.

2017-12-01

In this work, we investigate the far-ultraviolet (UV) to near-infrared (NIR) shape of the dust attenuation curve of a sample of IR-selected dust obscured (ultra)luminous IR galaxies at z ∼ 2. The spectral energy distributions (SEDs) are fitted with Code Investigating GALaxy Emission, a physically motivated spectral-synthesis model based on energy balance. Its flexibility allows us to test a wide range of different analytical prescriptions for the dust attenuation curve, including the well-known Calzetti and Charlot & Fall curves, and modified versions of them. The attenuation curves computed under the assumption of our reference double power-law model are in very good agreement with those derived, in previous works, with radiative transfer (RT) SED fitting. We investigate the position of our galaxies in the IRX-β diagram and find this to be consistent with greyer slopes, on average, in the UV. We also find evidence for a flattening of the attenuation curve in the NIR with respect to more classical Calzetti-like recipes. This larger NIR attenuation yields larger derived stellar masses from SED fitting, by a median factor of ∼1.4 and up to a factor ∼10 for the most extreme cases. The star formation rate appears instead to be more dependent on the total amount of attenuation in the galaxy. Our analysis highlights the need for a flexible attenuation curve when reproducing the physical properties of a large variety of objects.

Estimating dust production rate of carbon-rich stars in the Small Magellanic Cloud

NASA Astrophysics Data System (ADS)

Nanni, A.; Marigo, P.; Groenewegen, M. A. T.; Aringer, B.; Pastorelli, G.; Rubele, S.; Girardi, L.; Bressan, A.; Bladh, S.

We compute a grid of spectra describing dusty Circumstellar Envelopes of Thermally Pulsing Asymptotic Giant Branch carbon-rich stars by employing a physically grounded description for dust growth. The optical constants for carbon dust have been selected in order to reproduce simultaneously the most important color-color diagrams in the Near and Mid Infrared bands. We fit the Spectral Energy Distribution of ≈2000 carbon-rich in the Small Magellanic Cloud and we compute their total dust production rate. We compare our results with the ones in the literature. Different choices of the dust-to-gas ratio and outflow expansion velocity adopted in different works, yield, in some cases, a total dust budget about three times lower than the one derived from our scheme, with the same optical data set for carbon dust.

Large and small-scale structures and the dust energy balance problem in spiral galaxies

NASA Astrophysics Data System (ADS)

Saftly, W.; Baes, M.; De Geyter, G.; Camps, P.; Renaud, F.; Guedes, J.; De Looze, I.

2015-04-01

The interstellar dust content in galaxies can be traced in extinction at optical wavelengths, or in emission in the far-infrared. Several studies have found that radiative transfer models that successfully explain the optical extinction in edge-on spiral galaxies generally underestimate the observed FIR/submm fluxes by a factor of about three. In order to investigate this so-called dust energy balance problem, we use two Milky Way-like galaxies produced by high-resolution hydrodynamical simulations. We create mock optical edge-on views of these simulated galaxies (using the radiative transfer code SKIRT), and we then fit the parameters of a basic spiral galaxy model to these images (using the fitting code FitSKIRT). The basic model includes smooth axisymmetric distributions along a Sérsic bulge and exponential disc for the stars, and a second exponential disc for the dust. We find that the dust mass recovered by the fitted models is about three times smaller than the known dust mass of the hydrodynamical input models. This factor is in agreement with previous energy balance studies of real edge-on spiral galaxies. On the other hand, fitting the same basic model to less complex input models (e.g. a smooth exponential disc with a spiral perturbation or with random clumps), does recover the dust mass of the input model almost perfectly. Thus it seems that the complex asymmetries and the inhomogeneous structure of real and hydrodynamically simulated galaxies are a lot more efficient at hiding dust than the rather contrived geometries in typical quasi-analytical models. This effect may help explain the discrepancy between the dust emission predicted by radiative transfer models and the observed emission in energy balance studies for edge-on spiral galaxies.

Java application for the superposition T-matrix code to study the optical properties of cosmic dust aggregates

NASA Astrophysics Data System (ADS)

Halder, P.; Chakraborty, A.; Deb Roy, P.; Das, H. S.

2014-09-01

In this paper, we report the development of a java application for the Superposition T-matrix code, JaSTA (Java Superposition T-matrix App), to study the light scattering properties of aggregate structures. It has been developed using Netbeans 7.1.2, which is a java integrated development environment (IDE). The JaSTA uses double precession superposition codes for multi-sphere clusters in random orientation developed by Mackowski and Mischenko (1996). It consists of a graphical user interface (GUI) in the front hand and a database of related data in the back hand. Both the interactive GUI and database package directly enable a user to model by self-monitoring respective input parameters (namely, wavelength, complex refractive indices, grain size, etc.) to study the related optical properties of cosmic dust (namely, extinction, polarization, etc.) instantly, i.e., with zero computational time. This increases the efficiency of the user. The database of JaSTA is now created for a few sets of input parameters with a plan to create a large database in future. This application also has an option where users can compile and run the scattering code directly for aggregates in GUI environment. The JaSTA aims to provide convenient and quicker data analysis of the optical properties which can be used in different fields like planetary science, atmospheric science, nano science, etc. The current version of this software is developed for the Linux and Windows platform to study the light scattering properties of small aggregates which will be extended for larger aggregates using parallel codes in future. Catalogue identifier: AETB_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AETB_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 571570 No. of bytes in distributed program, including test data, etc.: 120226886 Distribution format: tar.gz Programming language: Java, Fortran95. Computer: Any Windows or Linux systems capable of hosting a java runtime environment, java3D and fortran95 compiler; Developed on 2.40 GHz Intel Core i3. Operating system: Any Windows or Linux systems capable of hosting a java runtime environment, java3D and fortran95 compiler. RAM: Ranging from a few Mbytes to several Gbytes, depending on the input parameters. Classification: 1.3. External routines: jfreechart-1.0.14 [1] (free plotting library for java), j3d-jre-1.5.2 [2] (3D visualization). Nature of problem: Optical properties of cosmic dust aggregates. Solution method: Java application based on Mackowski and Mischenko's Superposition T-Matrix code. Restrictions: The program is designed for single processor systems. Additional comments: The distribution file for this program is over 120 Mbytes and therefore is not delivered directly when Download or Email is requested. Instead a html file giving details of how the program can be obtained is sent. Running time: Ranging from few minutes to several hours, depending on the input parameters. References: [1] http://www.jfree.org/index.html [2] https://java3d.java.net/

Simulating Coupling Complexity in Space Plasmas: First Results from a new code

NASA Astrophysics Data System (ADS)

Kryukov, I.; Zank, G. P.; Pogorelov, N. V.; Raeder, J.; Ciardo, G.; Florinski, V. A.; Heerikhuisen, J.; Li, G.; Petrini, F.; Shematovich, V. I.; Winske, D.; Shaikh, D.; Webb, G. M.; Yee, H. M.

2005-12-01

The development of codes that embrace 'coupling complexity' via the self-consistent incorporation of multiple physical scales and multiple physical processes in models has been identified by the NRC Decadal Survey in Solar and Space Physics as a crucial necessary development in simulation/modeling technology for the coming decade. The National Science Foundation, through its Information Technology Research (ITR) Program, is supporting our efforts to develop a new class of computational code for plasmas and neutral gases that integrates multiple scales and multiple physical processes and descriptions. We are developing a highly modular, parallelized, scalable code that incorporates multiple scales by synthesizing 3 simulation technologies: 1) Computational fluid dynamics (hydrodynamics or magneto-hydrodynamics-MHD) for the large-scale plasma; 2) direct Monte Carlo simulation of atoms/neutral gas, and 3) transport code solvers to model highly energetic particle distributions. We are constructing the code so that a fourth simulation technology, hybrid simulations for microscale structures and particle distributions, can be incorporated in future work, but for the present, this aspect will be addressed at a test-particle level. This synthesis we will provide a computational tool that will advance our understanding of the physics of neutral and charged gases enormously. Besides making major advances in basic plasma physics and neutral gas problems, this project will address 3 Grand Challenge space physics problems that reflect our research interests: 1) To develop a temporal global heliospheric model which includes the interaction of solar and interstellar plasma with neutral populations (hydrogen, helium, etc., and dust), test-particle kinetic pickup ion acceleration at the termination shock, anomalous cosmic ray production, interaction with galactic cosmic rays, while incorporating the time variability of the solar wind and the solar cycle. 2) To develop a coronal mass ejection and interplanetary shock propagation model for the inner and outer heliosphere, including, at a test-particle level, wave-particle interactions and particle acceleration at traveling shock waves and compression regions. 3) To develop an advanced Geospace General Circulation Model (GGCM) capable of realistically modeling space weather events, in particular the interaction with CMEs and geomagnetic storms. Furthermore, by implementing scalable run-time supports and sophisticated off- and on-line prediction algorithms, we anticipate important advances in the development of automatic and intelligent system software to optimize a wide variety of 'embedded' computations on parallel computers. Finally, public domain MHD and hydrodynamic codes had a transforming effect on space and astrophysics. We expect that our new generation, open source, public domain multi-scale code will have a similar transformational effect in a variety of disciplines, opening up new classes of problems to physicists and engineers alike.

Science & Technology Review September 2005

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aufderheide III, M B

2005-07-19

This month's issue has the following articles: (1) The Pursuit of Fusion Energy--Commentary by William H. Goldstein; (2) A Dynamo of a Plasma--The self-organizing magnetized plasmas in a Livermore fusion energy experiment are akin to solar flares and galactic jets; (3) How One Equation Changed the World--A three-page paper by Albert Einstein revolutionized physics by linking mass and energy; (4) Recycled Equations Help Verify Livermore Codes--New analytic solutions for imploding spherical shells give scientists additional tools for verifying codes; and (5) Dust That.s Worth Keeping--Scientists have solved the mystery of an astronomical spectral feature in interplanetary dust particles.

Non-conservative evolution in Algols: where is the matter?

NASA Astrophysics Data System (ADS)

Deschamps, R.; Braun, K.; Jorissen, A.; Siess, L.; Baes, M.; Camps, P.

2015-05-01

Context. There is indirect evidence of non-conservative evolutions in Algols. However, the systemic mass-loss rate is poorly constrained by observations and generally set as a free parameter in binary-star evolution simulations. Moreover, systemic mass loss may lead to observational signatures that still need to be found. Aims: Within the "hotspot" ejection mechanism, some of the material that is initially transferred from the companion star via an accretion stream is expelled from the system due to the radiative energy released on the gainer's surface by the impacting material. The objective of this paper is to retrieve observable quantities from this process and to compare them with observations. Methods: We investigate the impact of the outflowing gas and the possible presence of dust grains on the spectral energy distribution (SED). We used the 1D plasma code Cloudy and compared the results with the 3D Monte-Carlo radiative transfer code Skirt for dusty simulations. The circumbinary mass-distribution and binary parameters were computed with state-of-the-art binary calculations done with the Binstar evolution code. Results: The outflowing material reduces the continuum flux level of the stellar SED in the optical and UV. Because of the time-dependence of this effect, it may help to distinguish between different ejection mechanisms. If present, dust leads to observable infrared excesses, even with low dust-to-gas ratios, and traces the cold material at large distances from the star. By searching for this dust emission in the WISE catalogue, we found a small number of Algols showing infrared excesses, among which the two rather surprising objects SX Aur and CZ Vel. We find that some binary B[e] stars show the same strong Balmer continuum as we predict with our models. However, direct evidence of systemic mass loss is probably not observable in genuine Algols, since these systems no longer eject mass through the hotspot mechanism. Furthermore, owing to its high velocity, the outflowing material dissipates in a few hundred years. If hot enough, the hotspot may produce highly ionised species, such as Si iv, and observable characteristics that are typical of W Ser systems. Conclusions: If present, systemic mass loss leads to clear observational imprints. These signatures are not to be found in genuine Algols but in the closely related β Lyraes, W Serpentis stars, double periodic variables, symbiotic Algols, and binary B[e] stars. We emphasise the need for further observations of such objects where systemic mass loss is most likely to occur. Appendices are available in electronic form at http://www.aanda.org

Measurement of net electric charge and dipole moment of dust aggregates in a complex plasma.

PubMed

Yousefi, Razieh; Davis, Allen B; Carmona-Reyes, Jorge; Matthews, Lorin S; Hyde, Truell W

2014-09-01

Understanding the agglomeration of dust particles in complex plasmas requires knowledge of basic properties such as the net electrostatic charge and dipole moment of the dust. In this study, dust aggregates are formed from gold-coated mono-disperse spherical melamine-formaldehyde monomers in a radiofrequency (rf) argon discharge plasma. The behavior of observed dust aggregates is analyzed both by studying the particle trajectories and by employing computer models examining three-dimensional structures of aggregates and their interactions and rotations as induced by torques arising from their dipole moments. These allow the basic characteristics of the dust aggregates, such as the electrostatic charge and dipole moment, as well as the external electric field, to be determined. It is shown that the experimental results support the predicted values from computer models for aggregates in these environments.

DirtyGrid I: 3D Dust Radiative Transfer Modeling of Spectral Energy Distributions of Dusty Stellar Populations

NASA Astrophysics Data System (ADS)

Law, Ka-Hei; Gordon, Karl D.; Misselt, Karl A.

2018-06-01

Understanding the properties of stellar populations and interstellar dust has important implications for galaxy evolution. In normal star-forming galaxies, stars and the interstellar medium dominate the radiation from ultraviolet (UV) to infrared (IR). In particular, interstellar dust absorbs and scatters UV and optical light, re-emitting the absorbed energy in the IR. This is a strongly nonlinear process that makes independent studies of the UV-optical and IR susceptible to large uncertainties and degeneracies. Over the years, UV to IR spectral energy distribution (SED) fitting utilizing varying approximations has revealed important results on the stellar and dust properties of galaxies. Yet the approximations limit the fidelity of the derived properties. There is sufficient computer power now available that it is now possible to remove these approximations and map out of landscape of galaxy SEDs using full dust radiative transfer. This improves upon previous work by directly connecting the UV, optical, and IR through dust grain physics. We present the DIRTYGrid, a grid of radiative transfer models of SEDs of dusty stellar populations in galactic environments designed to span the full range of physical parameters of galaxies. Using the stellar and gas radiation input from the stellar population synthesis model PEGASE, our radiative transfer model DIRTY self-consistently computes the UV to far-IR/sub-mm SEDs for each set of parameters in our grid. DIRTY computes the dust absorption, scattering, and emission from the local radiation field and a dust grain model, thereby physically connecting the UV-optical to the IR. We describe the computational method and explain the choices of parameters in DIRTYGrid. The computation took millions of CPU hours on supercomputers, and the SEDs produced are an invaluable tool for fitting multi-wavelength data sets. We provide the complete set of SEDs in an online table.

Star and Planet Formation through Cosmic Time

NASA Astrophysics Data System (ADS)

Lee, Aaron Thomas

The computational advances of the past several decades have allowed theoretical astrophysics to proceed at a dramatic pace. Numerical simulations can now simulate the formation of individual molecules all the way up to the evolution of the entire universe. Observational astrophysics is producing data at a prodigious rate, and sophisticated analysis techniques of large data sets continue to be developed. It is now possible for terabytes of data to be effectively turned into stunning astrophysical results. This is especially true for the field of star and planet formation. Theorists are now simulating the formation of individual planets and stars, and observing facilities are finally capturing snapshots of these processes within the Milky Way galaxy and other galaxies. While a coherent theory remains incomplete, great strides have been made toward this goal. This dissertation discusses several projects that develop models of star and planet forma- tion. This work spans large spatial and temporal scales: from the AU-scale of protoplanetary disks all the way up to the parsec-scale of star-forming clouds, and taking place in both contemporary environments like the Milky Way galaxy and primordial environments at redshifts of z 20. Particularly, I show that planet formation need not proceed in incremental stages, where planets grow from millimeter-sized dust grains all the way up to planets, but instead can proceed directly from small dust grains to large kilometer-sized boulders. The requirements for this model to operate effectively are supported by observations. Additionally, I draw suspicion toward one model for how you form high mass stars (stars with masses exceeding 8 Msun), which postulates that high-mass stars are built up from the gradual accretion of mass from the cloud onto low-mass stars. I show that magnetic fields in star forming clouds thwart this transfer of mass, and instead it is likely that high mass stars are created from the gravitational collapse of large clouds. This work also provides a sub-grid model for computational codes that employ sink particles accreting from magnetized gas. Finally, I analyze the role that radiation plays in determining the final masses of the first stars to ever form in the universe. These stars formed in starkly different environments than stars form in today, and the role of the direct radiation from these stars turns out to be a crucial component of primordial star formation theory. These projects use a variety of computational tools, including the use of spectral hydrodynamics codes, magneto-hydrodynamics grid codes that employ adaptive mesh refinement techniques, and long characteristic ray tracing methods. I develop and describe a long characteristic ray tracing method for modeling hydrogen-ionizing radiation from stars. Additionally, I have developed Monte Carlo routines that convert hydrodynamic data used in smoothed particle hydrodynamics codes for use in grid-based codes. Both of these advances will find use beyond simulations of star and planet formation and benefit the astronomical community at large.

Inference of dust opacities for the 1977 Martian great dust storms from Viking Lander 1 pressure data

NASA Technical Reports Server (NTRS)

Zurek, R. W.

1981-01-01

The tidal heating components for the dusty Martian atmosphere are computed based on dust optical parameters estimated from Viking Lander imaging data, and used to compute the variation of the tidal surface pressure components at the Viking Lander sites as a function of season and the total vertical extinction optical depth of the atmosphere. An atmospheric tidal model is used which is based on the inviscid, hydrostatic primitive equations linearized about a motionless basic state the temperature of which varies only with height, and the profiles of the tidal forcing components are computed using a delta-Eddington approximation to the radiative transfer equations. Comparison of the model results with the observed variations of surface pressure and overhead dust opacity at the Viking Lander 1 site reveal that the dust opacities and optical parameters derived from imaging data are roughly representative of the global dust haze necessary to reproduce the observed surface pressure amplitudes, with the exception of the model-inferred asymmetry parameter, which is smaller during the onset of a great storm. The observed preferential enhancement of the semidiurnal tide with respect to the diurnal tide during dust storm onset is shown to be due primarily to the elevation of the tidal heating source in a very dusty atmosphere.

Influence of emissivity on behavior of metallic dust particles in plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tanaka, Y.; Smirnov, R. D.; Pigarov, A. Yu.

Influence of thermal radiation emissivity on the lifetime of a dust particle in plasmas is investigated for different fusion relevant metals (Li, Be, Mo, and W). The thermal radiation is one of main cooling mechanisms of the dust in plasmas especially for dust with evaporation temperature higher than 2500 K. In this paper, the temperature- and radius-dependent emissivity of dust particles is calculated using Mie theory and temperature-dependent optical constants for the above metallic materials. The lifetime of a dust particle in uniform plasmas is estimated with the calculated emissivity using the dust transport code DUSTT[A. Pigarov et al., Physicsmore » of Plasmas 12, 122508 (2005)], considering other dust cooling and destruction processes such as physical and chemical sputtering, melting and evaporation, electron emission etc. The use of temperature-dependent emissivity calculated with Mie theory provides a longer lifetime of the refractory metal dust particle compared with that obtained using conventional emissivity constants in the literature. The dynamics of heavy metal dust particles are also presented using the calculated emissivity in a tokamak plasma.« less

Light scattering by planetary-regolith analog samples: computational results

NASA Astrophysics Data System (ADS)

Väisänen, Timo; Markkanen, Johannes; Hadamcik, Edith; Levasseur-Regourd, Anny-Chantal; Lasue, Jeremie; Blum, Jürgen; Penttilä, Antti; Muinonen, Karri

2017-04-01

We compute light scattering by a planetary-regolith analog surface. The corresponding experimental work is from Hadamcik et al. [1] with the PROGRA2-surf [2] device measuring the polarization of dust particles. The analog samples are low density (volume fraction 0.15 ± 0.03) agglomerates produced by random ballistic deposition of almost equisized silica spheres (refractive index n=1.5 and diameter 1.45 ± 0.06 µm). Computations are carried out with the recently developed codes entitled Radiative Transfer with Reciprocal Transactions (R2T2) and Radiative Transfer Coherent Backscattering with incoherent interactions (RT-CB-ic). Both codes incorporate the so-called incoherent treatment which enhances the applicability of the radiative transfer as shown by Muinonen et al. [3]. As a preliminary result, we have computed scattering from a large spherical medium with the RT-CB-ic using equal-sized particles with diameters of 1.45 microns. The preliminary results have shown that the qualitative characteristics are similar for the computed and measured intensity and polarization curves but that there are still deviations between the characteristics. We plan to remove the deviations by incorporating a size distribution of particles (1.45 ± 0.02 microns) and detailed information about the volume density profile within the analog surface. Acknowledgments: We acknowledge the ERC Advanced Grant no. 320773 entitled Scattering and Absorption of Electromagnetic Waves in Particulate Media (SAEMPL). Computational resources were provided by CSC - IT Centre for Science Ltd, Finland. References: [1] Hadamcik E. et al. (2007), JQSRT, 106, 74-89 [2] Levasseur-Regourd A.C. et al. (2015), Polarimetry of stars and planetary systems, CUP, 61-80 [3] Muinonen K. et al. (2016), extended abstract for EMTS.

Simulation of windblown dust transport from a mine tailings impoundment using a computational fluid dynamics model

NASA Astrophysics Data System (ADS)

Stovern, Michael; Felix, Omar; Csavina, Janae; Rine, Kyle P.; Russell, MacKenzie R.; Jones, Robert M.; King, Matt; Betterton, Eric A.; Sáez, A. Eduardo

2014-09-01

Mining operations are potential sources of airborne particulate metal and metalloid contaminants through both direct smelter emissions and wind erosion of mine tailings. The warmer, drier conditions predicted for the Southwestern US by climate models may make contaminated atmospheric dust and aerosols increasingly important, due to potential deleterious effects on human health and ecology. Dust emissions and dispersion of dust and aerosol from the Iron King Mine tailings in Dewey-Humboldt, Arizona, a Superfund site, are currently being investigated through in situ field measurements and computational fluid dynamics modeling. These tailings are heavily contaminated with lead and arsenic. Using a computational fluid dynamics model, we model dust transport from the mine tailings to the surrounding region. The model includes gaseous plume dispersion to simulate the transport of the fine aerosols, while individual particle transport is used to track the trajectories of larger particles and to monitor their deposition locations. In order to improve the accuracy of the dust transport simulations, both regional topographical features and local weather patterns have been incorporated into the model simulations. Results show that local topography and wind velocity profiles are the major factors that control deposition.

Simulation of windblown dust transport from a mine tailings impoundment using a computational fluid dynamics model.

PubMed

Stovern, Michael; Felix, Omar; Csavina, Janae; Rine, Kyle P; Russell, MacKenzie R; Jones, Robert M; King, Matt; Betterton, Eric A; Sáez, A Eduardo

2014-09-01

Mining operations are potential sources of airborne particulate metal and metalloid contaminants through both direct smelter emissions and wind erosion of mine tailings. The warmer, drier conditions predicted for the Southwestern US by climate models may make contaminated atmospheric dust and aerosols increasingly important, due to potential deleterious effects on human health and ecology. Dust emissions and dispersion of dust and aerosol from the Iron King Mine tailings in Dewey-Humboldt, Arizona, a Superfund site, are currently being investigated through in situ field measurements and computational fluid dynamics modeling. These tailings are heavily contaminated with lead and arsenic. Using a computational fluid dynamics model, we model dust transport from the mine tailings to the surrounding region. The model includes gaseous plume dispersion to simulate the transport of the fine aerosols, while individual particle transport is used to track the trajectories of larger particles and to monitor their deposition locations. In order to improve the accuracy of the dust transport simulations, both regional topographical features and local weather patterns have been incorporated into the model simulations. Results show that local topography and wind velocity profiles are the major factors that control deposition.

Simulation of windblown dust transport from a mine tailings impoundment using a computational fluid dynamics model

PubMed Central

Stovern, Michael; Felix, Omar; Csavina, Janae; Rine, Kyle P.; Russell, MacKenzie R.; Jones, Robert M.; King, Matt; Betterton, Eric A.; Sáez, A. Eduardo

2014-01-01

Mining operations are potential sources of airborne particulate metal and metalloid contaminants through both direct smelter emissions and wind erosion of mine tailings. The warmer, drier conditions predicted for the Southwestern US by climate models may make contaminated atmospheric dust and aerosols increasingly important, due to potential deleterious effects on human health and ecology. Dust emissions and dispersion of dust and aerosol from the Iron King Mine tailings in Dewey-Humboldt, Arizona, a Superfund site, are currently being investigated through in situ field measurements and computational fluid dynamics modeling. These tailings are heavily contaminated with lead and arsenic. Using a computational fluid dynamics model, we model dust transport from the mine tailings to the surrounding region. The model includes gaseous plume dispersion to simulate the transport of the fine aerosols, while individual particle transport is used to track the trajectories of larger particles and to monitor their deposition locations. In order to improve the accuracy of the dust transport simulations, both regional topographical features and local weather patterns have been incorporated into the model simulations. Results show that local topography and wind velocity profiles are the major factors that control deposition. PMID:25621085

Probing the pre-PN Mass Loss Histories in the PPN Dust Shells

NASA Astrophysics Data System (ADS)

Ueta, T.

2001-12-01

Proto-planetary nebulae (PPNs) are immediate progenitors of planetary nebulae (PNs) rapidly evolving over a relatively short time scale. Unlike the full-fledged PNs, the circumstellar dust shells of PPNs have neither been photo-ionized nor been swept up by fast winds. Since the PPN shells retain pristine fossil records of mass loss histories of these stars during the pre-PN phases, these dust shells provide ideal astronomical laboratories in which to investigate the origin of complex PN structures that we observe. We have conducted imaging surveys of the PPN shells in mid-infrared and optical wavelengths, probing the dust distribution directly via mid-infrared thermal dust emission arising from the shells and indirectly via dust-scattered stellar optical emission passing through the shells. From these surveys, we have found that (1) the PPN shells are intrinsically axisymmetric due to equatorially-enhanced superwind mass loss that occurred immediately before the beginning of the PPN phase, and (2) the variable degree of equatorial enhancement in the shells, which is probably related to the progenitor mass, has resulted in different optical depths and morphologies. To characterize the PPN shell geometries, we have developed and employed a 2.5 dimensional radiative transfer code that treats dust absorption, reemission, and an/isotropic scattering in any axisymmetric system illuminated by a central energy source. In the code, the dust optical properties are derived from the laboratory-measured refractive index using Mie theory allowing a distribution of sizes for each species in each composition layer in the shell. Our numerical analysis would be able to de-project and recover 3-D geometrical quantities, such as the pole-to-equator density ratio, from the observational data. These model calculations would provide constraining parameters for hydrodynamical models intended to generate equatorial enhancements during dust mass loss as well as initial parameters for magneto-hydrodynamical models aimed to reproduce highly complex PN morphologies.

Investigation of dust formations in the atmosphere on the basis of satellite observations

NASA Astrophysics Data System (ADS)

Ivanchik, M. V.; Kliushnikov, S. I.; Krovotyntsev, V. A.; Serebrennikov, A. N.

1984-06-01

A method for the computer processing of space photographs is described which makes it possible to determine dust formations in the atmosphere. Dust formations are identified according to the character of contrast-density distribution. Processed images are compared with actinometric data collected in a dust storm area (Conakry, Guinea, May 1983).

Computer Simulation of the Hydrodynamic Processes of Cyclone Dust Collectors

NASA Astrophysics Data System (ADS)

Plashikhin, S. V.

2016-09-01

In the present paper, the gas-dynamic flow structures in dust collectors with an internal louvered element and an external dust hopper and the traditional design of the NIIOGAZ type have been considered. The character of motion of particles of various median diameters in a cyclone dust collector has also been investigated. A survey has been made of the literature of foreign and home authors dealing with questions of filtration of solid particles in the gas flow in apparatuses of the centrifugal type [1, 2]. The arrangement and principle of operation of the cyclone dust collector is presented. The computational modeling of the flow was carried out by solving Reynolds-averaged Navier-Stokes (RANS) equations by the CFD method with the use of a k-ɛ turbulence model for four modes of operation of the apparatus.

Dust Around Herbig Ae Stars: Additional Constraints from their Photometric and Polarimetric Variability

NASA Technical Reports Server (NTRS)

Krivova, N. A.; Ilin, V. B.; Fischer, O.

1996-01-01

For the Herbig Ae stars with Algol-like minima (UX Ori, WW Vul, etc), the effects of circumstellar dust include: excess infrared emission, anomalous ultraviolet extinction, the 'blueing' of the stars in minima accompanying by an increase of intrinsic polarization. Using a Monte-Carlo code for polarized radiation transfer we have simulated these effects and compared the results obtained for different models with the observational data available. We found that the photometric and polarimetric behavior of the stars provided essential additional constraints on the circumstellar dust models. The models with spheroidal shell geometry and compact (non-fluffy) dust grains do not appear to be able to explain all the data.

Dust environment and dynamical history of a sample of short-period comets

NASA Astrophysics Data System (ADS)

Pozuelos, F. J.; Moreno, F.; Aceituno, F.; Casanova, V.; Sota, A.; López-Moreno, J. J.; Castellano, J.; Reina, E.; Diepvens, A.; Betoret, A.; Häusler, B.; Gonález, C.; Rodríguez, D.; Bryssinck, E.; Cortés, E.; García, F.; García, F.; Limón, F.; Grau, F.; Fratev, F.; Baldrís, F.; Rodriguez, F. A.; Montalbán, F.; Soldán, F.; Muler, G.; Almendros, I.; Temprano, J.; Bel, J.; Sánchez, J.; Lopesino, J.; Báez, J.; Hernández, J. F.; Martín, J. L.; Ruiz, J. M.; Vidal, J. R.; Gaitán, J.; Salto, J. L.; Aymamí, J. M.; Bosch, J. M.; Henríquez, J. A.; Martín, J. J.; Lacruz, J.; Tremosa, L.; Lahuerta, L.; Reszelsky, M.; Rodríguez, M.; Camarasa, M.; Campas, M.; Canales, O.; Dekelver, P. J.; Moreno, Q.; Benavides, R.; Naves, R.; Dymoc, R.; García, R.; Lahuerta, S.; Climent, T.

2014-08-01

Aims: In this work, we present an extended study of the dust environment of a sample of short-period comets and their dynamical history. With this aim, we characterize the dust tails when the comets are active, and we make a statistical study to determine their dynamical evolution. The targets selected were 22P/Kopff, 30P/Reinmuth 1, 78P/Gehrels 2, 115P/Maury, 118P/Shoemaker-Levy 4, 123P/West-Hartley, 157P/Tritton, 185/Petriew, and P/2011 W2 (Rinner). Methods: We use two different observational data sets: a set of images taken at the Observatorio de Sierra Nevada and, the Afρ curves provided by the amateur astronomical association Cometas-Obs. To model these observations, we use our Monte Carlo dust tail code. From this analysis, we derive the dust parameters, which best describe the dust environment: dust loss rates, ejection velocities, and size distribution of particles. On the other hand, we use a numerical integrator to study the dynamical history of the comets, which allows us to determine with a 90% confidence level the time spent by these objects in the region of Jupiter family comets. Results: From the Monte Carlo dust tail code, we derived three categories according to the amount of dust emitted: weakly active (115P, 157P, and Rinner), moderately active (30P, 123P, and 185P), and highly active (22P, 78P, and 118P). The dynamical studies showed that the comets of this sample are young in the Jupiter family region, where the youngest ones are 22P (~100 yr), 78P (~500 yr), and 118P (~600 yr). The study points to a certain correlation between comet activity and time spent in the Jupiter family region, although this trend is not always fulfilled. The largest particle sizes are not tightly constrained, so that the total dust mass derived should be regarded as a lower limit. Appendices are available in electronic form at http://www.aanda.org

Surface wind accuracy for modeling mineral dust emissions: Comparing two regional models in a Bodélé case study

NASA Astrophysics Data System (ADS)

Laurent, B.; Heinold, B.; Tegen, I.; Bouet, C.; Cautenet, G.

2008-05-01

After a decade of research on improving the description of surface and soil features in desert regions to accurately model mineral dust emissions, we now emphasize the need for deeper evaluating the accuracy of modeled 10-m surface wind speeds U 10 . Two mesoscale models, the Lokal-Modell (LM) and the Regional Atmospheric Modeling System (RAMS), coupled with an explicit dust emission model have previously been used to simulate mineral dust events in the Bodélé region. We compare LM and RAMS U 10 , together with measurements at the Chicha site (BoDEx campaign) and Faya-Largeau meteorological station. Surface features and soil schemes are investigated to correctly simulate U 10 intensity and diurnal variability. The uncertainties in dust emissions computed with LM and RAMS U 10 and different soil databases are estimated. This sensitivity study shows the importance of accurate computation of surface winds to improve the quantification of regional dust emissions from the Bodélé

Dusty disc-planet interaction with dust-free simulations

NASA Astrophysics Data System (ADS)

Chen, Jhih-Wei; Lin, Min-Kai

2018-05-01

Protoplanets may be born into dust-rich environments if planetesimals formed through streaming or gravitational instabilities, or if the protoplanetary disc is undergoing mass loss due to disc winds or photoevaporation. Motivated by this possibility, we explore the interaction between low mass planets and dusty protoplanetary discs with focus on disc-planet torques. We implement Lin & Youdin's newly developed, purely hydrodynamic model of dusty gas into the PLUTO code to simulate dusty protoplanetary discs with an embedded planet. We find that for imperfectly coupled dust and high metallicity, e.g. Stokes number 10-3 and dust-to-gas ratio Σd/Σg = 0.5, a `bubble' develops inside the planet's co-orbital region, which introduces unsteadiness in the flow. The resulting disc-planet torques sustain large amplitude oscillations that persists well beyond that in simulations with perfectly coupled dust or low dust-loading, where co-rotation torques are always damped. We show that the desaturation of the co-rotation torques by finite-sized particles is related to potential vorticity generation from the misalignment of dust and gas densities. We briefly discuss possible implications for the orbital evolution of protoplanets in dust-rich discs. We also demonstrate Lin & Youdin's dust-free framework reproduces previous results pertaining to dusty protoplanetary discs, including dust-trapping by pressure bumps, dust settling, and the streaming instability.

Investigating the size, shape and surface roughness dependence of polarization lidars with light-scattering computations on real mineral dust particles: Application to dust particles' external mixtures and dust mass concentration retrievals

NASA Astrophysics Data System (ADS)

Mehri, Tahar; Kemppinen, Osku; David, Grégory; Lindqvist, Hannakaisa; Tyynelä, Jani; Nousiainen, Timo; Rairoux, Patrick; Miffre, Alain

2018-05-01

Our understanding of the contribution of mineral dust to the Earth's radiative budget is limited by the complexity of these particles, which present a wide range of sizes, are highly-irregularly shaped, and are present in the atmosphere in the form of particle mixtures. To address the spatial distribution of mineral dust and atmospheric dust mass concentrations, polarization lidars are nowadays frequently used, with partitioning algorithms allowing to discern the contribution of mineral dust in two or three-component particle external mixtures. In this paper, we investigate the dependence of the retrieved dust backscattering (βd) vertical profiles with the dust particle size and shape. For that, new light-scattering numerical simulations are performed on real atmospheric mineral dust particles, having determined mineralogy (CAL, DOL, AGG, SIL), derived from stereogrammetry (stereo-particles), with potential surface roughness, which are compared to the widely-used spheroidal mathematical shape model. For each dust shape model (smooth stereo-particles, rough stereo-particles, spheroids), the dust depolarization, backscattering Ångström exponent, lidar ratio are computed for two size distributions representative of mineral dust after long-range transport. As an output, two Saharan dust outbreaks involving mineral dust in two, then three-component particle mixtures are studied with Lyon (France) UV-VIS polarization lidar. If the dust size matters most, under certain circumstances, βd can vary by approximately 67% when real dust stereo-particles are used instead of spheroids, corresponding to variations in the dust backscattering coefficient as large as 2 Mm- 1·sr- 1. Moreover, the influence of surface roughness in polarization lidar retrievals is for the first time discussed. Finally, dust mass-extinction conversion factors (ηd) are evaluated for each assigned shape model and dust mass concentrations are retrieved from polarization lidar measurements. From spheroids to stereo-particles, ηd increases by about 30%. We believe these results may be useful for our understanding of the spatial distribution of mineral dust contained in an aerosol external mixture and to better quantify dust mass concentrations from polarization lidar experiments.

Charging and shielding of a non-spherical dust grain in a plasma

NASA Astrophysics Data System (ADS)

Zhao, L.; Delzanno, G.

2013-12-01

The interaction of objects with a plasma is a classic problem of plasma physics. Originally, it was investigated in the framework of probe theory but more recently its interest has grown in connection with space and complex or dusty plasmas. It is customary to assume that the dust grains are spherical, and theories such as the Orbital Motion Limited (OML) theory are usually applied to calculate the dust charge. However, in nature dust grains have a variety of sizes and shapes. It is therefore natural to ask about the influence of the dust shape on the charging and shielding process. In order to answer this question, we study the charging and shielding of a non-spherical dust grain immersed in a Maxwellian plasma at rest. We consider prolate ellipsoids, varying parametrically the aspect ratio while keeping the surface area constant. The study is conducted with CPIC [1], a newly developed Particle-In-Cell code in curvilinear geometry that conforms to objects of arbitrary shape. For a plasma with temperature ratio equal to unity and for a dust grain with characteristic size of the order of the Debye length, it is shown that the floating potential has a very weak dependence on the geometry, while the charge on the grain increases by a factor of three when the aspect ratio changes from one (a sphere) to hundred (a needle-like ellipsoid). These results are consistent with the higher capacitance of ellipsoidal dust grains, but also indicate that the screening length depends on the geometry. Scaling studies of the dependence of the charging time and screening length on the aspect ratio and plasma conditions are presented, including theoretical considerations to support the numerical results. [1] G.L. Delzanno, et al, ';CPIC: a curvilinear Particle-In-Cell code for plasma-material interaction studies', under review.

The circumbinary dusty disk of upsilon Sgr revealed by mid-IR interferometric observations with the VLTI/MIDI

NASA Astrophysics Data System (ADS)

Bonneau, D.; Netolický, M.; Chesneau, O.; Harmanec, P.; Koubský, P.; Mourard, D.; Stee, P.

2008-11-01

The first mid-IR interferometric observations of a hydrogen-deficient binary star, υ Sgr, were carried out using the MIDI/VLTI instrument between April 2007 and May 2008. The dusty circumbinary envelope is resolved in the N band (8-13.5 μ m), and has a typical size of 20 x 14 mas. The calibrated fringe visibilities, the mid-IR spectrum and the SED were fitted using models computed with the radiative transfer code MC3D using several mixtures of carbon and silicate dust, in order to determine the geometry and chemical composition of the envelope. The best model we obtain is a geometrically thin and dense disk with an inner radius of R_{in} ≃ 6.0AU and a scale height h_{100} ≃ 3.5 AU. The inclination of the disk is i ≃ 50° and its position angle is PA ≃ 80°. The chemical composition of the dust is approximatelya ratio of 60% of carbon dust and 40% of silicate dust. We constrained for the first time the geometry and the chemistry of the circumbinary dusty envelope of υ Sgr. It is now clear that the components of υ Sgr are massive stars (> 10 M_⊙) and the results are compatible with evolutionary scenario proposed by Delgado & Thomas (1981) of a binary with massive components experiencing several phases of important mass transfer leading to the hydrogen-deficient primary star. However, complementary spectro-interferometric observations in the near infrared and the visible are mandatory to investigate the complex structure of the inner circumstellar environment and directly resolve the stellar components of the υ Sgr system.

Hierarchical Models for Type Ia Supernova Light Curves in the Optical and Near Infrared

NASA Astrophysics Data System (ADS)

Mandel, Kaisey; Narayan, G.; Kirshner, R. P.

2011-01-01

I have constructed a comprehensive statistical model for Type Ia supernova optical and near infrared light curves. Since the near infrared light curves are excellent standard candles and are less sensitive to dust extinction and reddening, the combination of near infrared and optical data better constrains the host galaxy extinction and improves the precision of distance predictions to SN Ia. A hierarchical probabilistic model coherently accounts for multiple random and uncertain effects, including photometric error, intrinsic supernova light curve variations and correlations across phase and wavelength, dust extinction and reddening, peculiar velocity dispersion and distances. An improved BayeSN MCMC code is implemented for computing probabilistic inferences for individual supernovae and the SN Ia and host galaxy dust populations. I use this hierarchical model to analyze nearby Type Ia supernovae with optical and near infared data from the PAIRITEL, CfA3, and CSP samples and the literature. Using cross-validation to test the robustness of the model predictions, I find that the rms Hubble diagram scatter of predicted distance moduli is 0.11 mag for SN with optical and near infrared data versus 0.15 mag for SN with only optical data. Accounting for the dispersion expected from random peculiar velocities, the rms intrinsic prediction error is 0.08-0.10 mag for SN with both optical and near infrared light curves. I discuss results for the inferred intrinsic correlation structures of the optical-NIR SN Ia light curves and the host galaxy dust distribution captured by the hierarchical model. The continued observation and analysis of Type Ia SN in the optical and near infrared is important for improving their utility as precise and accurate cosmological distance indicators.

An automated and integrated framework for dust storm detection based on ogc web processing services

NASA Astrophysics Data System (ADS)

Xiao, F.; Shea, G. Y. K.; Wong, M. S.; Campbell, J.

2014-11-01

Dust storms are known to have adverse effects on public health. Atmospheric dust loading is also one of the major uncertainties in global climatic modelling as it is known to have a significant impact on the radiation budget and atmospheric stability. The complexity of building scientific dust storm models is coupled with the scientific computation advancement, ongoing computing platform development, and the development of heterogeneous Earth Observation (EO) networks. It is a challenging task to develop an integrated and automated scheme for dust storm detection that combines Geo-Processing frameworks, scientific models and EO data together to enable the dust storm detection and tracking processes in a dynamic and timely manner. This study develops an automated and integrated framework for dust storm detection and tracking based on the Web Processing Services (WPS) initiated by Open Geospatial Consortium (OGC). The presented WPS framework consists of EO data retrieval components, dust storm detecting and tracking component, and service chain orchestration engine. The EO data processing component is implemented based on OPeNDAP standard. The dust storm detecting and tracking component combines three earth scientific models, which are SBDART model (for computing aerosol optical depth (AOT) of dust particles), WRF model (for simulating meteorological parameters) and HYSPLIT model (for simulating the dust storm transport processes). The service chain orchestration engine is implemented based on Business Process Execution Language for Web Service (BPEL4WS) using open-source software. The output results, including horizontal and vertical AOT distribution of dust particles as well as their transport paths, were represented using KML/XML and displayed in Google Earth. A serious dust storm, which occurred over East Asia from 26 to 28 Apr 2012, is used to test the applicability of the proposed WPS framework. Our aim here is to solve a specific instance of a complex EO data and scientific model integration problem by using a framework and scientific workflow approach together. The experimental result shows that this newly automated and integrated framework can be used to give advance near real-time warning of dust storms, for both environmental authorities and public. The methods presented in this paper might be also generalized to other types of Earth system models, leading to improved ease of use and flexibility.

Long-term variability of dust events in Iceland (1949-2011)

NASA Astrophysics Data System (ADS)

Dagsson-Waldhauserova, P.; Arnalds, O.; Olafsson, H.

2014-12-01

The long-term frequency of atmospheric dust observations was investigated for the southern part of Iceland and interpreted together with earlier results obtained from northeastern (NE) Iceland (Dagsson-Waldhauserova et al., 2013). In total, over 34 dust days per year on average occurred in Iceland based on conventionally used synoptic codes for dust observations. However, frequent volcanic eruptions, with the re-suspension of volcanic materials and dust haze, increased the number of dust events fourfold (135 dust days annually). The position of the Icelandic Low determined whether dust events occurred in the NE (16.4 dust days annually) or in the southern (S) part of Iceland (about 18 dust days annually). The decade with the most frequent dust days in S Iceland was the 1960s, but the 2000s in NE Iceland. A total of 32 severe dust storms (visibility < 500 m) were observed in Iceland with the highest frequency of events during the 2000s in S Iceland. The Arctic dust events (NE Iceland) were typically warm, occurring during summer/autumn (May-September) and during mild southwesterly winds, while the subarctic dust events (S Iceland) were mainly cold, occurring during winter/spring (March-May) and during strong northeasterly winds. About half of the dust events in S Iceland occurred in winter or at sub-zero temperatures. A good correlation was found between particulate matter (PM10) concentrations and visibility during dust observations at the stations Vík and Stórhöfði. This study shows that Iceland is among the dustiest areas of the world and that dust is emitted year-round.

Simulating galactic dust grain evolution on a moving mesh

NASA Astrophysics Data System (ADS)

McKinnon, Ryan; Vogelsberger, Mark; Torrey, Paul; Marinacci, Federico; Kannan, Rahul

2018-05-01

Interstellar dust is an important component of the galactic ecosystem, playing a key role in multiple galaxy formation processes. We present a novel numerical framework for the dynamics and size evolution of dust grains implemented in the moving-mesh hydrodynamics code AREPO suited for cosmological galaxy formation simulations. We employ a particle-based method for dust subject to dynamical forces including drag and gravity. The drag force is implemented using a second-order semi-implicit integrator and validated using several dust-hydrodynamical test problems. Each dust particle has a grain size distribution, describing the local abundance of grains of different sizes. The grain size distribution is discretised with a second-order piecewise linear method and evolves in time according to various dust physical processes, including accretion, sputtering, shattering, and coagulation. We present a novel scheme for stochastically forming dust during stellar evolution and new methods for sub-cycling of dust physics time-steps. Using this model, we simulate an isolated disc galaxy to study the impact of dust physical processes that shape the interstellar grain size distribution. We demonstrate, for example, how dust shattering shifts the grain size distribution to smaller sizes resulting in a significant rise of radiation extinction from optical to near-ultraviolet wavelengths. Our framework for simulating dust and gas mixtures can readily be extended to account for other dynamical processes relevant in galaxy formation, like magnetohydrodynamics, radiation pressure, and thermo-chemical processes.

Dust around the Cool Component of D-Type Symbiotic Binaries

NASA Astrophysics Data System (ADS)

Jurkic, Tomislav; Kotnik-Karuza, Dubravka

2018-04-01

D type symbiotic binaries are an excellent astrophysical laboratory for investigation of the dust properties and dust formation under the influence of theMira stellar wind and nova activity and of the mass loss and mass transfer between components in such a widely separated system. We present a study of the properties of circumstellar dust in symbiotic Miras by use of long-term near-IR photometry and colour indices. The published JHKL magnitudes of o Ceti, RX Pup, KM Vel, V366 Car, V835 Cen, RR Tel, HM Sge and R Aqr have been collected, analyzed and corrected for short-term variations caused by Mira pulsations. Assuming spherical temperature distribution of the dust in the close neighbourhood of the Mira, the DUSTY code was used to solve the radiative transfer in order to determine the dust temperature and its properties in each particular case. Common dust properties of the symbiotic Miras have been found, suggesting similar conditions in the condensation region of the studied symbiotic Miras. Silicate dust with the inner dust shell radius determined by the dust condensation and with the dust temperature of 900-1200 K can fully explain the observed colour indices. R Aqr is an exception and showed lower dust temperature of 650 K. Obscuration events visible in light curves can be explained by variable dust optical depth with minimal variations of other dust properties. More active symbioticMiras that underwent recent nova outbursts showed higher dust optical depths and larger maximum grain sizes of the order of μm, which means that the post-nova activity could stimulate the dust formation and the grain growth. Optically thicker dust shells and higher dust condensation temperatures have been found in symbiotic Miras compared to their single counterparts, suggesting different conditions for dust production.

Simulating the dust content of galaxies: successes and failures

NASA Astrophysics Data System (ADS)

McKinnon, Ryan; Torrey, Paul; Vogelsberger, Mark; Hayward, Christopher C.; Marinacci, Federico

2017-06-01

We present full-volume cosmological simulations, using the moving-mesh code arepo to study the coevolution of dust and galaxies. We extend the dust model in arepo to include thermal sputtering of grains and investigate the evolution of the dust mass function, the cosmic distribution of dust beyond the interstellar medium and the dependence of dust-to-stellar mass ratio on galactic properties. The simulated dust mass function is well described by a Schechter fit and lies closest to observations at z = 0. The radial scaling of projected dust surface density out to distances of 10 Mpc around galaxies with magnitudes 17 < I < 21 is similar to that seen in Sloan Digital Sky Survey data, albeit with a lower normalization. At z = 0, the predicted dust density of Ωdust ≈ 1.3 × 10-6 lies in the range of Ωdust values seen in low-redshift observations. We find that the dust-to-stellar mass ratio anticorrelates with stellar mass for galaxies living along the star formation main sequence. Moreover, we estimate the 850 μm number density functions for simulated galaxies and analyse the relation between dust-to-stellar flux and mass ratios at z = 0. At high redshift, our model fails to produce enough dust-rich galaxies, and this tension is not alleviated by adopting a top-heavy initial mass function. We do not capture a decline in Ωdust from z = 2 to 0, which suggests that dust production mechanisms more strongly dependent on star formation may help to produce the observed number of dusty galaxies near the peak of cosmic star formation.

Dust grains from the heart of supernovae

NASA Astrophysics Data System (ADS)

Bocchio, Marco; Marassi, Stefania; Schneider, Raffaella; Bianchi, Simone; Limongi, Marco; Chieffi, A.

2016-06-01

Dust grains are classically thought to form in the winds of asymptotic giant branch (AGB) stars. However, there is increasing evidence today for dust formation in supernovae (SNe). To establish the relative importance of these two classes of stellar sources of dust, it is important to know the fraction of freshly formed dust in SN ejecta that is able to survive the passage of the reverse shock and be injected in the interstellar medium. We have developed a new code (GRASH_Rev) which follows the newly-formed dust evolution throughout the supernova explosion until the merging of the forward shock with the circumstellar ISM. We have considered four well studied SNe in the Milky Way and Large Magellanic Cloud: SN1987A, CasA, the Crab Nebula, and N49. For all the simulated models, we find good agreement with observations and estimate that between 1 and 8% of the observed mass will survive, leading to a SN dust production rate of (3.9± 3.7)×10^(-4) MM_{⊙})/yr in the Milky Way. This value is one order of magnitude larger than the dust production rate by AGB stars but insufficient to counterbalance the dust destruction by SNe, therefore requiring dust accretion in the gas phase.

The effects of electrostatic charging on the dust distribution at Halley's Comet

NASA Technical Reports Server (NTRS)

Horanyi, M.; Mendis, D. A.

1986-01-01

The distribution of fine dust near Comet Halley at its 1910 and 1986 apparitions is investigated by means of computer simulations, taking the effects of EM forces due to the dust electrostatic charge into account. It is found that the nucleus spin period and orbital obliquity estimated by Sekanina and Larson (1984) from the 1910 observations are unaffected by these EM forces because the 1910 dust morphology involved mainly large grains. For 1986, the orientation of the smaller dust is shown to depend on the interplanetary magnetic field, with implications for the dust distribution encountered by the Halley probes.

A Climatology of Dust-Emission Events over North Africa Based on 27 Years of Surface Observations

NASA Astrophysics Data System (ADS)

Cowie, S.; Knippertz, P.; Schepanski, K.

2012-04-01

The huge quantity of mineral dust emitted annually from North Africa makes this area crucial to the global dust cycle. Once in the atmosphere, dust aerosols have a significant impact on the global radiation budget, clouds, the carbon cycle and can even act as a fertilizer to rain forests in South America. Current model estimates of dust production from North Africa are uncertain. At the heart of this problem is insufficient understanding of key dust emitting processes such as haboobs (cold pools generated through evaporation of convective precipitation), low-level jets (LLJs), and dry convection (dust devils and dust plumes). Scarce observations in this region, in particular in the Sahara, make model evaluation difficult. This work uses long-term surface observations from the MIDAS data set (~120 stations in the arid part of North Africa) to explore the diurnal, seasonal, decadal and geographical variations in dust emission events and their associated wind thresholds. The threshold values are determined from probability density functions of observed 10-minute anemomenter wind speeds. Emission events are defined using the present weather codes (WW) of SYNOP reports. These codes represent events of smaller intensity such as "Dust or sand raised by wind" to severe dust storms. During the 27-year study period (1984-2011) stations are required to have a minimum of 1000 dust observations to be included in the analysis. Dust emission frequency (DEF) is calculated for different time intervals (e.g. monthly, 3-hourly) taking into account the different number of measurements available at each station. North of 25°N a maximum during March-May is evident and relatively consistent over the whole North African region. Wind-speed thresholds for dust emission north of 25°N are higher than south of 25°N in the Sahel, where station-to-station variability is larger, and enhanced DEF activity during February-March is observed. The variability in this region is closely linked to the advance and retreat of the summer monsoon. The diurnal cycle in DEF shows reflections of the individual emission mechanisms. At night, winds are usually light and dust emission is low. Many stations show a sharp increase in wind speed and DEF between 06 and 09 UTC, a probable result of the downward mixing of momentum from nocturnal LLJs. Peaks at both midday and 15 UTC are common in the diurnal cycles of both winds and DEF. Midday peaks are likely due to small scale dry convection, while the afternoon peaks may contain signals from both dry convection and gusty winds associated with haboob outflows. Into the evening and overnight the DEF signal gets smaller and is often caused by long-lived haboobs.

The Python Sky Model: software for simulating the Galactic microwave sky

NASA Astrophysics Data System (ADS)

Thorne, B.; Dunkley, J.; Alonso, D.; Næss, S.

2017-08-01

We present a numerical code to simulate maps of Galactic emission in intensity and polarization at microwave frequencies, aiding in the design of cosmic microwave background experiments. This python code builds on existing efforts to simulate the sky by providing an easy-to-use interface and is based on publicly available data from the WMAP (Wilkinson Microwave Anisotropy Probe) and Planck satellite missions. We simulate synchrotron, thermal dust, free-free and anomalous microwave emission over the whole sky, in addition to the cosmic microwave background, and include a set of alternative prescriptions for the frequency dependence of each component, for example, polarized dust with multiple temperatures and a decorrelation of the signals with frequency, which introduce complexity that is consistent with current data. We also present a new prescription for adding small-scale realizations of these components at resolutions greater than current all-sky measurements. The usefulness of the code is demonstrated by forecasting the impact of varying foreground complexity on the recovered tensor-to-scalar ratio for the LiteBIRD satellite. The code is available at: https://github.com/bthorne93/PySM_public.

Dust emission modelling around a stockpile by using computational fluid dynamics and discrete element method

NASA Astrophysics Data System (ADS)

Derakhshani, S. M.; Schott, D. L.; Lodewijks, G.

2013-06-01

Dust emissions can have significant effects on the human health, environment and industry equipment. Understanding the dust generation process helps to select a suitable dust preventing approach and also is useful to evaluate the environmental impact of dust emission. To describe these processes, numerical methods such as Computational Fluid Dynamics (CFD) are widely used, however nowadays particle based methods like Discrete Element Method (DEM) allow researchers to model interaction between particles and fluid flow. In this study, air flow over a stockpile, dust emission, erosion and surface deformation of granular material in the form of stockpile are studied by using DEM and CFD as a coupled method. Two and three dimensional simulations are respectively developed for CFD and DEM methods to minimize CPU time. The standard κ-ɛ turbulence model is used in a fully developed turbulent flow. The continuous gas phase and the discrete particle phase link to each other through gas-particle void fractions and momentum transfer. In addition to stockpile deformation, dust dispersion is studied and finally the accuracy of stockpile deformation results obtained by CFD-DEM modelling will be validated by the agreement with the existing experimental data.

Efficient radiative transfer methods for continuum and line transfer in large three-dimensional models

NASA Astrophysics Data System (ADS)

Juvela, Mika J.

The relationship between physical conditions of an interstellar cloud and the observed radiation is defined by the radiative transfer problem. Radiative transfer calculations are needed if, e.g., one wants to disentangle abundance variations from excitation effects or wants to model variations of dust properties inside an interstellar cloud. New observational facilities (e.g., ALMA and Herschel) will bring improved accuracy both in terms of intensity and spatial resolution. This will enable detailed studies of the densest sub-structures of interstellar clouds and star forming regions. Such observations must be interpreted with accurate radiative transfer methods and realistic source models. In many cases this will mean modelling in three dimensions. High optical depths and observed wide range of linear scales are, however, challenging for radiative transfer modelling. A large range of linear scales can be accessed only with hierarchical models. Figure 1 shows an example of the use of a hierarchical grid for radiative transfer calculations when the original model cloud (L=10 pc, =500 cm-3) was based a MHD simulation carried out on a regular grid (Juvela & Padoan, 2005). For computed line intensities an accuracy of 10% was still reached when the number of individual cells (and the run time) was reduced by a factor of ten. This illustrates how, as long as cloud is not extremely optically thick, most of the emission comes from a small sub-volume. It is also worth noting that while errors are ~10% for any given point they are much smaller when compared with intensity variations. In particular, calculations on hierarchical grid recovered the spatial power spectrum of line emission with very good accuracy. Monte Carlo codes are used widely in both continuum and line transfer calculations. Like any lambda iteration schemes these suffer from slow convergence when models are optically thick. In line transfer Accelerated Monte Carlo methods (AMC) present a partial solution to this problem (Juvela & Padoan, 2000; Hogerheijde & van der Tak, 2000). AMC methods can be used similarly in continuum calculations to speed up the computation of dust temperatures (Juvela, 2005). The sampling problems associated with high optical depths can be solved with weighted sampling and the handling of models with τV ~ 1000 is perfectly feasible. Transiently heated small dust grains pose another problem because the calculation of their temperature distribution is very time consuming. However, a 3D model will contain thousands of cells at very similar conditions. If dust temperature distributions are calculated only once for such a set an approximate solution can be found in a much shorter time time. (Juvela & Padoan, 2003; see Figure 2a). MHD simulations with Automatic Mesh Refinement (AMR) techniques present an exciting development for the modelling of interstellar clouds. Cloud models consist of a hierarchy of grids with different grid steps and the ratio between the cloud size and the smallest resolution elements can be 106 or even larger. We are currently working on radiative transfer codes (line and continuum) that could be used efficiently on such grids (see Figure 2b). The radiative transfer problem can be solved relatively independently on each of the sub-grids. This means that the use of convergence acceleration methods can be limited to those sub-grids where they are needed and, on the other hand, parallelization of the code is straightforward.

Polarization and studies of evolved star mass loss

NASA Astrophysics Data System (ADS)

Sargent, Benjamin; Srinivasan, Sundar; Riebel, David; Meixner, Margaret

2012-05-01

Polarization studies of astronomical dust have proven very useful in constraining its properties. Such studies are used to constrain the spatial arrangement, shape, composition, and optical properties of astronomical dust grains. Here we explore possible connections between astronomical polarization observations to our studies of mass loss from evolved stars. We are studying evolved star mass loss in the Large Magellanic Cloud (LMC) by using photometry from the Surveying the Agents of a Galaxy's Evolution (SAGE; PI: M. Meixner) Spitzer Space Telescope Legacy program. We use the radiative transfer program 2Dust to create our Grid of Red supergiant and Asymptotic giant branch ModelS (GRAMS), in order to model this mass loss. To model emission of polarized light from evolved stars, however, we appeal to other radiative transfer codes. We probe how polarization observations might be used to constrain the dust shell and dust grain properties of the samples of evolved stars we are studying.

Amorphous carbon in the disk around the post-AGB binary HR 4049. Discerning dust species with featureless opacity curves

NASA Astrophysics Data System (ADS)

Acke, B.; Degroote, P.; Lombaert, R.; de Vries, B. L.; Smolders, K.; Verhoelst, T.; Lagadec, E.; Gielen, C.; Van Winckel, H.; Waelkens, C.

2013-03-01

Context. Infrared spectroscopy has been extensively used to determine the mineralogy of circumstellar dust. The identification of dust species with featureless opacities, however, is still ambiguous. Here we present a method to lift the degeneracy using the combination of infrared spectroscopy and interferometry. Aims: The binary post-AGB star HR 4049 is surrounded by a circumbinary disk viewed at a high inclination angle. Apart from gaseous emission lines and molecular emission bands of polycyclic aromatic hydrocarbons (PAH), diamonds, and fullerenes, the 2-25 μm infrared spectrum is featureless. The goal of the paper is to identify the dust species responsible for the smooth spectrum. Methods: We gathered high-angular-resolution measurements in the near- and mid-infrared with the VLTI interferometric instruments AMBER and MIDI. The data set is expanded with archival Geneva optical photometry, ISO-SWS and Spitzer-IRS infrared spectroscopy, and VISIR N-band images and spectroscopy. We computed a grid of radiative-transfer models of the circumbinary disk of HR 4049 using the radiative-transfer code MCMax. We searched for models that provide good fits simultaneously to all available observations. Results: We find that the variable optical extinction towards the primary star is consistent with the presence of very small (0.01 μm) iron-bearing dust grains or amorphous carbon grains. The combination of the interferometric constraint on the disk extent and the shape of the infrared spectrum points to amorphous carbon as the dominant source of opacity in the circumbinary disk of HR 4049. The disk is optically thick to the stellar radiation in the radial direction. At infrared wavelengths it is optically thin. The PAH emission is spatially resolved in the VISIR data and emanates from a region with an extent of several hundreds of AU, with a projected photocenter displacement of several tens of AU from the disk center. The PAHs most likely reside in a bipolar outflow. Conclusions: Dust species with featureless opacity curves, such as metallic iron and amorphous carbon, can be identified by combining infrared spectroscopy and high-angular-resolution measurements. In essence, this is because the temperatures of the dust species are notably different at the same physical distance to the star. Appendices A and B are available in electronic form at http://www.aanda.org

Gas Cavities inside Dust Cavities in Disks Inferred from ALMA Observations

NASA Astrophysics Data System (ADS)

van der Marel, Nienke; van Dishoeck, Ewine F.; Bruderer, Simon; Pinilla, Paola; van Kempen, Tim; Perez, Laura; Isella, Andrea

2016-01-01

Protoplanetary disks with cavities in their dust distribution, also named transitional disks, are expected to be in the middle of active evolution and possibly planet formation. In recent years, millimeter-dust rings observed by ALMA have been suggested to have their origin in dust traps, caused by pressure bumps. One of the ways to generate these is by the presence of planets, which lower the gas density along their orbit and create pressure bumps at the edge. We present spatially resolved ALMA Cycle 0 and Cycle 1 observations of CO and CO isotopologues of several famous transitional disks. Gas is found to be present inside the dust cavities, but at a reduced level compared with the gas surface density profile of the outer disk. The dust and gas emission are quantified using the physical-chemical modeling code DALI. In the majority of these disks we find clear evidence for a drop in gas density of at least a factor of 10 inside the cavity, whereas the dust density drops by at least a factor 1000. The CO isotopologue observations reveal that the gas cavities are significantly smaller than the dust cavities. These gas structures suggest clearing by one or more planetary-mass companions.

Multi-decadal and seasonal variability of dust observations in West Greenland.

NASA Astrophysics Data System (ADS)

Bullard, Joanna E.; Mockford, Tom

2017-04-01

Since the early 1900s expedition records from west Greenland have reported local dust storms. The Kangerlussuaq region, near the inland ice, is dry (mean annual precipitation <160 mm) with, on average, 150 snow-free days per year. The main local dust sources are active, proglacial outwash plains although reworking of loess deposits may also be important. This paper presents an analysis of 70-years of dust storm observations (1945-2015) based on WMO weather codes 6 (dust haze), 7 (raised dust or sand) and 9 (distant or past dust storm) and associated wind data. The 70-year average number of dust observations days is 5 per year but variable ranging from 0 observations to 23 observations in 1985. Over the past 7 decades the number of dust days has increased from <30 in 1945-54 to >75 in 1995-2004 and 2005-2015. The seasonality of dust observations has remained consistent throughout most of the period. Dust days occur all year round but are most frequent in May-June and September-October and are associated with minimum snow cover and glacial meltwater-driven sediment supply to the outwash plains during spring and fall flood events. Wind regime is bimodal dominated by katabatic winds from the northeast, which are strongest and most frequent during winter months (Nov-Jan), with less frequent, southwesterly winds generated by Atlantic storms mostly confined to spring (May, June). The southwesterly winds are those most likely to transport dust onto the Greenland ice sheet.

VizieR Online Data Catalog: Dust properties of major-merger galaxy pairs (Domingue+, 2016)

NASA Astrophysics Data System (ADS)

Domingue, D. L.; Cao, C.; Xu, C. K.; Jarrett, T. H.; Ronca, J.; Hill, E.; Jacques, A.

2018-04-01

We present an analysis of dust properties of a sample of close major-merger galaxy pairs selected by Ks magnitude and redshift. The pairs represent the two populations of spiral-spiral (S+S) and mixed morphology spiral-elliptical (S+E). The Code Investigating GALaxy Emission (CIGALE) software is used to fit dust models to the Two Micron All Sky Survey, Wide-Field Infrared Survey Explorer, and Herschel flux density measurements, and to derive the parameters describing the polycyclic aromatic hydrocarbons contribution, interstellar radiation field, and photodissociation regions. Model fits verify our previous Spitzer Space Telescope analysis that S+S and S+E pairs do not have the same level of enhancement of star formation and differ in dust composition. (1 data file).

Motion of dust particles in nonuniform magnetic field and applicability of smoothed particle hydrodynamics simulation

NASA Astrophysics Data System (ADS)

Saitou, Y.

2018-01-01

An SPH (Smoothed Particle Hydrodynamics) simulation code is developed to reproduce our findings on behavior of dust particles, which were obtained in our previous experiments (Phys. Plasmas, 23, 013709 (2016) and Abst. 18th Intern. Cong. Plasma Phys. (Kaohsiung, 2016)). Usually, in an SPH simulation, a smoothed particle is interpreted as a discretized fluid element. Here we regard the particles as dust particles because it is known that behavior of dust particles in complex plasmas can be described using fluid dynamics equations in many cases. Various rotation velocities that are difficult to achieve in the experiment are given to particles at boundaries in the newly developed simulation and motion of particles is investigated. Preliminary results obtained by the simulation are shown.

Optical image of a cometary nucleus: 1980 flyby of Comet Encke

NASA Technical Reports Server (NTRS)

Wells, W. C.; Benson, R. S.; Anderson, A. D.; Gal, G.

1974-01-01

The feasibility was investigated of obtaining optical images of a cometary nucleus via a flyby of Comet Encke. A physical model of the dust cloud surrounding the nucleus was developed by using available physical data and theoretical knowledge of cometary physics. Using this model and a Mie scattering code, calculations were made of the absolute surface brightness of the dust in the line of sight of the on-board camera and the relative surface brightness of the dust compared to the nucleus. The brightness was calculated as a function of heliocentric distance and for different phase angles (sun-comet-spacecraft angle).

DUST CAPTURE AND LONG-LIVED DENSITY ENHANCEMENTS TRIGGERED BY VORTICES IN 2D PROTOPLANETARY DISKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Surville, Clément; Mayer, Lucio; Lin, Douglas N. C., E-mail: clement.surville@physik.uzh.ch

We study dust capture by vortices and its long-term consequences in global two-fluid inviscid disk simulations using a new polar grid code RoSSBi. We perform the longest integrations so far, several hundred disk orbits, at the highest resolution attainable in global disk simulations with dust, namely, 2048 × 4096 grid points. We vary a wide range of dust parameters, most notably the initial dust-to-gas ratio ϵ varies in the range of 10{sup −4}–10{sup −2}. Irrespective of the value of ϵ , we find rapid concentration of the dust inside vortices, reaching dust-to-gas ratios of the order of unity inside themore » vortex. We present an analytical model that describes this dust capture process very well, finding consistent results for all dust parameters. A vortex streaming instability develops, which invariably causes vortex destruction. After vortex dissipation large-scale dust rings encompassing a disk annulus form in most cases, which sustain very high dust concentration, approaching ratios of the order of unity; they persist as long as the duration of the simulations. They are sustained by a streaming instability, which manifests itself in high-density dust clumps at various scales. When vortices are particularly long-lived, rings do not form but dust clumps inside vortices can survive a long time and would likely undergo collapse by gravitational instability. Rings encompass almost an Earth mass of solid material, while even larger masses of dust do accumulate inside vortices in the earlier stage. We argue that rapid planetesimal formation would occur in the dust clumps inside the vortices as well as in the post-vortex rings.« less

Dust Capture and Long-lived Density Enhancements Triggered by Vortices in 2D Protoplanetary Disks

NASA Astrophysics Data System (ADS)

Surville, Clément; Mayer, Lucio; Lin, Douglas N. C.

2016-11-01

We study dust capture by vortices and its long-term consequences in global two-fluid inviscid disk simulations using a new polar grid code RoSSBi. We perform the longest integrations so far, several hundred disk orbits, at the highest resolution attainable in global disk simulations with dust, namely, 2048 × 4096 grid points. We vary a wide range of dust parameters, most notably the initial dust-to-gas ratio ɛ varies in the range of 10-4-10-2. Irrespective of the value of ɛ, we find rapid concentration of the dust inside vortices, reaching dust-to-gas ratios of the order of unity inside the vortex. We present an analytical model that describes this dust capture process very well, finding consistent results for all dust parameters. A vortex streaming instability develops, which invariably causes vortex destruction. After vortex dissipation large-scale dust rings encompassing a disk annulus form in most cases, which sustain very high dust concentration, approaching ratios of the order of unity they persist as long as the duration of the simulations. They are sustained by a streaming instability, which manifests itself in high-density dust clumps at various scales. When vortices are particularly long-lived, rings do not form but dust clumps inside vortices can survive a long time and would likely undergo collapse by gravitational instability. Rings encompass almost an Earth mass of solid material, while even larger masses of dust do accumulate inside vortices in the earlier stage. We argue that rapid planetesimal formation would occur in the dust clumps inside the vortices as well as in the post-vortex rings.

CSM interaction and dust formation in SN 2010jl .

NASA Astrophysics Data System (ADS)

Krafton, K.; Clayton, G. C.

The origin of dust in galaxies >1 Gyr old has remained an unsolved mystery for over a decade. One proposed solution is dust produced by core collapse supernovae (CCSNe). Theorists have shown that 0.1-1 M⊙ of dust must be produced per supernova for this to work as an explanation for the dust in young galaxies. SN 1987A has produced ˜1 M⊙ of dust since its detonation. However, most supernovae have been found to only produce 10-4 - 10-2 M⊙ of dust. The energetic type IIn SN 2010jl is located in UGC 5189, in a dense shell of CSM. As dust condenses in the SN ejecta, we see, (1) a sudden decrease in continuum brightness in the visible due to increased dust extinction, (2) the development of an infrared excess in the SN light curve arising from dust grains absorbing high-energy photons and re-emitting them in the infrared, and (3) the development of asymmetric, blue-shifted emission-line profiles, caused by dust forming in the ejecta, and preferentially extinguishing redshifted emission. A dense circumstellar material (CSM) may increase the dust production by supernovae. We observe signs of strong interaction between the SN ejecta and a dense CSM in SN 2010jl. SN 2010jl has been a source of much debate in the CCSN community, particularly over when and how much dust it formed. The light curve shows strong signs of dust formation after 260 days. Arguments over these subjects have been based on the evolution of the light curve and spectra. We present new optical and IR photometry, as well as optical spectroscopy, of SN 2010jl over 2000 days. We estimate dust masses using the DAMOCLES and MOCASSIN radiative transfer codes.

Characterization and Modeling of Dust Emissions from an Instrumented Mine Tailings Site

NASA Astrophysics Data System (ADS)

Betterton, E. A.; Stovern, M.; Saez, A.; Csavina, J. L.; Felix Villar, O. I.; Field, J. P.; Rine, K. P.; Russell, M. R.; Saliba, P.

2012-12-01

Mining operations are potential sources of airborne particulate metal and metalloid contaminants through both direct smelter emissions and wind erosion of mine tailings. The warmer, drier conditions predicted for the Southwestern US by climate models may make contaminated atmospheric dust and aerosols increasingly important, due to potential deleterious effects on human health and ecology. Dust emissions and dispersion of contaminants from the Iron King Mine tailings in Dewey-Humboldt, Arizona, a Superfund site, are currently being investigated through in situ field measurements and computational fluid dynamics modeling. These tailings are heavily contaminated with lead and arsenic. We report on the chemical characterization of atmospheric dust and aerosol sampled near the mine tailings. Instrumented eddy flux towers were also setup on the mine tailings to give both spatial and temporal dust observations. The eddy flux towers have multiple DUSTTRAK monitors as well as weather stations. These in situ observations allow us to assess spatial distribution of suspended particulate. Using the DUSTTRAK flux tower observations at 10-second resolution in conjunction with a computational fluid dynamics model, we have been able to model dust transport from the mine tailings to downwind areas. In order to improve the accuracy of the dust transport simulations both regional topographical features and local weather patterns have been incorporated into the model simulations.

Constraining the Structure of the Transition Disk HD 135344B (SAO 206462) by Simultaneous Modeling of Multiwavelength Gas and Dust Observations

NASA Technical Reports Server (NTRS)

Carmona, A.; Pinte, C.; Thi, W. F.; Benisty, M.; Menard, F.; Grady, C.; Kamp, I.; Woitke, P.; Olofsson, J.; Roberge, A.;

Khuzestan dust phenomenon: a content analysis of most widely circulated newspapers.

PubMed

Mojadam, Mehdi; Matlabi, Mohammad; Haji, Alireza; Cheraghi, Maria; Bitaraf, Saeid; Khafaie, Morteza Abdullatif

2018-06-01

Dust is an atmospheric phenomenon that causes adverse environmental effects. It is deemed to have harmful effects on health, economics, and climate. This study aimed to analyze the content published on the phenomenon of dust in the widely circulated newspapers in Iran. We investigated the content of all national and provincial newspapers that were published between July and August 2014. Data on the materials related to the dust phenomenon in the newspapers were categorized and coded. From a total of 510 newspaper issues, 143 articles were devoted to the dust phenomenon which 74.1% of them were published in provincial newspapers. Among the national newspapers, Hamshahri newspaper with 16 headlines and from the provincial newspapers; Karoon with 23 headlines published the highest number of articles on dust phenomenon. 45.5% of content on dust were printed on the first page of the newspapers. The most common approach to the type of content published in these newspapers was an interview. Moreover, we noticed that 28.7% of the content published in the newspapers was related to the health issue. The media plays an important role in the transmission of health information. Weaknesses in addressing the causes of dust occurrence and also in providing solutions for the dust control and prevention were noticeable in the content published in the newspaper. It seems necessary to take practical measures to disseminate relevant information to dust and also address the needs of the target audience community influenced by the dust phenomenon properly.

Large-Eddy Simulations of Dust Devils and Convective Vortices

NASA Astrophysics Data System (ADS)

Spiga, Aymeric; Barth, Erika; Gu, Zhaolin; Hoffmann, Fabian; Ito, Junshi; Jemmett-Smith, Bradley; Klose, Martina; Nishizawa, Seiya; Raasch, Siegfried; Rafkin, Scot; Takemi, Tetsuya; Tyler, Daniel; Wei, Wei

2016-11-01

In this review, we address the use of numerical computations called Large-Eddy Simulations (LES) to study dust devils, and the more general class of atmospheric phenomena they belong to (convective vortices). We describe the main elements of the LES methodology. We review the properties, statistics, and variability of dust devils and convective vortices resolved by LES in both terrestrial and Martian environments. The current challenges faced by modelers using LES for dust devils are also discussed in detail.

Quantifying The Effect Of Scattering Upon The Retrieved Dust Opacity In The Martian Atmosphere, As Deduced From Mro/mcs Measurements

NASA Astrophysics Data System (ADS)

Howett, Carly; Irwin, P. G.; Teanby, N.; Calcutt, S. B.; Lolachi, R.; Bowles, N.; Schofield, J. T.; McCleese, D. J.

2007-10-01

Mars Climate Sounder data from September to November 2006 is analysed to determine the effect of scattering upon the retrieved dust opacity in the atmosphere of Mars. The inclusion of scattering in dust retrievals makes them significantly more computationally expensive. Thus, understanding the regimes in which scattering plays a less significant role could considerably decrease the computational time of analysing the extensive MCS dataset. Temperature profiles were initially retrieved using Nemesis, Oxford University's multivariate retrieval algorithm, at each location using MCS' A1, A2 and A3 channels (595 to 665 cm-1 ).Using these temperature profiles, and by assuming the characteristics of the dust particles to be comparable to those of Wolff and Clancy (2003), the dust opacity was retrieved using the B1 channel of MCS (290 to 340 cm-1 ) with and without scattering. The effect of scattering on the fit to the MCS data and on the derived vertical dust profile at various locations across the planet are presented. Particular emphasis is placed upon understanding the spatial and temporal variations of atmospheric regimes in which scattering plays a significant role.

Evolution of thermally pulsing asymptotic giant branch stars - II. Dust production at varying metallicity

NASA Astrophysics Data System (ADS)

Nanni, Ambra; Bressan, Alessandro; Marigo, Paola; Girardi, Léo

2013-09-01

We present the dust ejecta of the new stellar models for the thermally pulsing asymptotic giant branch (TP-AGB) phase computed with the COLIBRI code. We use a formalism of dust growth coupled with a stationary wind for both M- and C-stars. In the original version of this formalism, the most efficient destruction process of silicate dust in M-giants is chemisputtering by H2 molecules. For these stars, we find that dust grains can only form at relatively large radial distances (r ˜ 5R*), where they cannot be efficiently accelerated, in agreement with other investigations. In the light of recent laboratory results, we also consider the alternative case that the condensation temperature of silicates is determined only by the competition between growth and free evaporation processes (i.e. no chemisputtering). With this latter approach we obtain dust condensation temperatures that are significantly higher (up to Tcond ˜ 1400 K) than those found when chemisputtering is included (Tcond ˜ 900 K), and in better agreement with condensation experiments. As a consequence, silicate grains can remain stable in inner regions of the circumstellar envelopes (r ˜ 2 R*), where they can rapidly grow and can be efficiently accelerated. With this modification, our models nicely reproduce the observed trend between terminal velocities and mass-loss rates of Galactic M-giants. For C-stars the formalism is based on the homogeneous growth scheme where the key role is played by the carbon over oxygen excess. The models reproduce fairly well the terminal velocities of Galactic stars and there is no need to invoke changes in the standard assumptions. At decreasing metallicity the carbon excess becomes more pronounced and the efficiency of dust formation increases. This trend could be in tension with recent observational evidence in favour of a decreasing efficiency, at decreasing metallicity. If confirmed by more observational data, it would indicate that either the amount of the carbon excess, determined by the complex interplay between mass-loss, third dredge-up and hot-bottom burning, or the homogeneous growth scheme should be revised. Finally, we analyse the differences in the total dust production of M-stars that arise from the use of the two approaches (i.e. with or without chemisputtering). We find that, in spite of the differences in the expected dust stratification, for a given set of TP-AGB models, the ejecta are only weakly sensitive to the specific assumption. This work also shows that the properties of TP-AGB circumstellar envelopes are important diagnostic tools that may be profitably added to the traditional calibrators for setting further constraints on this complex phase of stellar evolution.

Propierties of dust in circumstellar gas around Wolf-Rayet stars

NASA Astrophysics Data System (ADS)

Jiménez-Hernández, P.; Arthur, S. J.; Toalá, J. A.

2017-11-01

Using archive photometric observations from Herschel (70μm, 100μm, 160μm and 250μm), Spitzer (24μm) and WISE (22μm and 12μm) we obtained infrared SED's of nebulae around the Wolf-Rayet stars WR 124, WR 16 and WR 7. We used the photoionization code Cloudy to construct models of the nebulae, taking into account the spectrum of the central star and varying the density and distance of the photoionized shell as well as the size distribution and chemical composition of the dust grains mixed with the gas, and we compared the resulting SEDs with the observations in order to study the properties of the dust in these objects. We discuss whether the dust properties depend on the spectral type of the central star and the age of the nebulae.

Gas and dust from solar metallicity AGB stars

NASA Astrophysics Data System (ADS)

Ventura, P.; Karakas, A.; Dell'Agli, F.; García-Hernández, D. A.; Guzman-Ramirez, L.

2018-04-01

We study the asymptotic giant branch (AGB) evolution of stars with masses between 1 M⊙and8.5 M⊙. We focus on stars with a solar chemical composition, which allows us to interpret evolved stars in the Galaxy. We present a detailed comparison with models of the same chemistry, calculated with a different evolution code and based on a different set of physical assumptions. We find that stars of mass ≥3.5 M⊙ experience hot bottom burning at the base of the envelope. They have AGB lifetimes shorter than ˜3 × 105 yr and eject into their surroundings gas contaminated by proton-capture nucleosynthesis, at an extent sensitive to the treatment of convection. Low-mass stars with 1.5 M⊙ ≤ M ≤ 3 M⊙ become carbon stars. During the final phases, the C/O ratio grows to ˜3. We find a remarkable agreement between the two codes for the low-mass models and conclude that predictions for the physical and chemical properties of these stars, and the AGB lifetime, are not that sensitive to the modelling of the AGB phase. The dust produced is also dependent on the mass: low-mass stars produce mainly solid carbon and silicon carbide dust, whereas higher mass stars produce silicates and alumina dust. Possible future observations potentially able to add more robustness to the present results are also discussed.

Modelling dust rings in early-type galaxies through a sequence of radiative transfer simulations and 2D image fitting

NASA Astrophysics Data System (ADS)

Bonfini, P.; González-Martín, O.; Fritz, J.; Bitsakis, T.; Bruzual, G.; Cervantes Sodi, B.

2018-07-01

A large fraction of early-type galaxies (ETGs) hosts prominent dust features, and central dust rings are arguably the most interesting among them. We present here `Lord of the Rings', a new methodology which allows to integrate the extinction by dust rings in a 2D-fittingmodelling of the surface brightness distribution. Our pipeline acts in two steps, first using the surface-fitting software GALFIT to determine the unabsorbed stellar emission, and then adopting the radiative transfer code SKIRT to apply dust extinction. We apply our technique to NGC 4552 and NGC 4494, two nearby ETGs. We show that the extinction by a dust ring can mimic, in a surface brightness profile, a central point source (e.g. an unresolved nuclear stellar cluster or an active galactic nucleus; AGN) superimposed to a `core' (i.e. a central flattening of the stellar light commonly observed in massive ETGs). We discuss how properly accounting for dust features is of paramount importance to derive correct fluxes, especially for low-luminosity AGNs (LLAGNs). We suggest that the geometries of dust features are strictly connected with how relaxed is the gravitational potential, i.e. with the evolutionary stage of the host galaxy. Additionally, we find hints that the dust mass contained in the ring relates to the AGN activity.

Modelling dust rings in early-type galaxies through a sequence of radiative transfer simulations and 2D image fitting

NASA Astrophysics Data System (ADS)

Bonfini, P.; González-Martín, O.; Fritz, J.; Bitsakis, T.; Bruzual, G.; Sodi, B. Cervantes

2018-05-01

A large fraction of early-type galaxies (ETGs) host prominent dust features, and central dust rings are arguably the most interesting among them. We present here `Lord Of The Rings' (LOTR), a new methodology which allows to integrate the extinction by dust rings in a 2D fitting modelling of the surface brightness distribution. Our pipeline acts in two steps, first using the surface fitting software GALFIT to determine the unabsorbed stellar emission, and then adopting the radiative transfer code SKIRT to apply dust extinction. We apply our technique to NGC 4552 and NGC 4494, two nearby ETGs. We show that the extinction by a dust ring can mimic, in a surface brightness profile, a central point source (e.g. an unresolved nuclear stellar cluster or an active galactic nucleus; AGN) superimposed to a `core' (i.e. a central flattening of the stellar light commonly observed in massive ETGs). We discuss how properly accounting for dust features is of paramount importance to derive correct fluxes especially for low luminosity AGNs (LLAGNs). We suggest that the geometries of dust features are strictly connected with how relaxed is the gravitational potential, i.e. with the evolutionary stage of the host galaxy. Additionally, we find hints that the dust mass contained in the ring relates to the AGN activity.

Two Key Parameters Controlling Particle Clumping Caused by Streaming Instability in the Dead-zone Dust Layer of a Protoplanetary Disk

NASA Astrophysics Data System (ADS)

Sekiya, Minoru; Onishi, Isamu K.

2018-06-01

The streaming instability and Kelvin–Helmholtz instability are considered the two major sources causing clumping of dust particles and turbulence in the dust layer of a protoplanetary disk as long as we consider the dead zone where the magnetorotational instability does not grow. Extensive numerical simulations have been carried out in order to elucidate the condition for the development of particle clumping caused by the streaming instability. In this paper, a set of two parameters suitable for classifying the numerical results is proposed. One is the Stokes number that has been employed in previous works and the other is the dust particle column density that is nondimensionalized using the gas density in the midplane, Keplerian angular velocity, and difference between the Keplerian and gaseous orbital velocities. The magnitude of dust clumping is a measure of the behavior of the dust layer. Using three-dimensional numerical simulations of dust particles and gas based on Athena code v. 4.2, it is confirmed that the magnitude of dust clumping for two disk models are similar if the corresponding sets of values of the two parameters are identical to each other, even if the values of the metallicity (i.e., the ratio of the columns density of the dust particles to that of the gas) are different.

Dust in the Primary Classroom.

ERIC Educational Resources Information Center

Pritchard, Alan

1990-01-01

Described is the use of a commercial computer software package, "Dust," to enhance mathematical learning in the classroom. Samples of mathematics problems presented in this game which is a simulation of an adventure in outer space are presented. (CW)

Computation of scattering matrix elements of large and complex shaped absorbing particles with multilevel fast multipole algorithm

NASA Astrophysics Data System (ADS)

Wu, Yueqian; Yang, Minglin; Sheng, Xinqing; Ren, Kuan Fang

2015-05-01

Light scattering properties of absorbing particles, such as the mineral dusts, attract a wide attention due to its importance in geophysical and environment researches. Due to the absorbing effect, light scattering properties of particles with absorption differ from those without absorption. Simple shaped absorbing particles such as spheres and spheroids have been well studied with different methods but little work on large complex shaped particles has been reported. In this paper, the surface Integral Equation (SIE) with Multilevel Fast Multipole Algorithm (MLFMA) is applied to study scattering properties of large non-spherical absorbing particles. SIEs are carefully discretized with piecewise linear basis functions on triangle patches to model whole surface of the particle, hence computation resource needs increase much more slowly with the particle size parameter than the volume discretized methods. To improve further its capability, MLFMA is well parallelized with Message Passing Interface (MPI) on distributed memory computer platform. Without loss of generality, we choose the computation of scattering matrix elements of absorbing dust particles as an example. The comparison of the scattering matrix elements computed by our method and the discrete dipole approximation method (DDA) for an ellipsoid dust particle shows that the precision of our method is very good. The scattering matrix elements of large ellipsoid dusts with different aspect ratios and size parameters are computed. To show the capability of the presented algorithm for complex shaped particles, scattering by asymmetry Chebyshev particle with size parameter larger than 600 of complex refractive index m = 1.555 + 0.004 i and different orientations are studied.

Type Ia Supernova Light Curve Inference: Hierarchical Models for Nearby SN Ia in the Optical and Near Infrared

NASA Astrophysics Data System (ADS)

Mandel, Kaisey; Kirshner, R. P.; Narayan, G.; Wood-Vasey, W. M.; Friedman, A. S.; Hicken, M.

2010-01-01

I have constructed a comprehensive statistical model for Type Ia supernova light curves spanning optical through near infrared data simultaneously. The near infrared light curves are found to be excellent standard candles (sigma(MH) = 0.11 +/- 0.03 mag) that are less vulnerable to systematic error from dust extinction, a major confounding factor for cosmological studies. A hierarchical statistical framework incorporates coherently multiple sources of randomness and uncertainty, including photometric error, intrinsic supernova light curve variations and correlations, dust extinction and reddening, peculiar velocity dispersion and distances, for probabilistic inference with Type Ia SN light curves. Inferences are drawn from the full probability density over individual supernovae and the SN Ia and dust populations, conditioned on a dataset of SN Ia light curves and redshifts. To compute probabilistic inferences with hierarchical models, I have developed BayeSN, a Markov Chain Monte Carlo algorithm based on Gibbs sampling. This code explores and samples the global probability density of parameters describing individual supernovae and the population. I have applied this hierarchical model to optical and near infrared data of over 100 nearby Type Ia SN from PAIRITEL, the CfA3 sample, and the literature. Using this statistical model, I find that SN with optical and NIR data have a smaller residual scatter in the Hubble diagram than SN with only optical data. The continued study of Type Ia SN in the near infrared will be important for improving their utility as precise and accurate cosmological distance indicators.

The EDIT-COMGEOM Code

DTIC Science & Technology

1975-09-01

This report assumes a familiarity with the GIFT and MAGIC computer codes. The EDIT-COMGEOM code is a FORTRAN computer code. The EDIT-COMGEOM code...converts the target description data which was used in the MAGIC computer code to the target description data which can be used in the GIFT computer code

Simulations of dusty plasmas using a special-purpose computer system designed for gravitational N-body problems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yamamoto, K.; Mizuno, Y.; Hibino, S.

2006-01-15

Simulations of dusty plasmas were performed using GRAPE-6, a special-purpose computer designed for gravitational N-body problems. The collective behavior of dust particles, which are injected into the plasma, was studied by means of three-dimensional computer simulations. As an example of a dusty plasma simulation, experiments on Coulomb crystals in plasmas are simulated. Formation of a quasi-two-dimensional Coulomb crystal has been observed under typical laboratory conditions. Another example was to simulate movement of dust particles in plasmas under microgravity conditions. Fully three-dimensional spherical structures of dust clouds have been observed. For the simulation of a dusty plasma in microgravity with 3x10{supmore » 4} particles, GRAPE-6 can perform the whole operation 1000 times faster than by using a Pentium 4 1.6 GHz processor.« less

Occurrence of polybrominated diphenyl ethers in indoor air and dust in Hangzhou, China: Level, role of electric appliances, and human exposure.

PubMed

Sun, Jianqiang; Wang, Qianwen; Zhuang, Shulin; Zhang, Anping

2016-11-01

This study investigated the occurrence of 8 polybrominated diphenyl ether (PBDE) congeners from homes (n = 20), offices (n = 20), air conditioners (n = 6), and computers (n = 6). High detection frequencies for most of the congeners were observed, indicating continued widespread use of Penta-, Octa- and Deca-BDE mixtures. The median concentrations of ∑PBDEs were 119 and 194 pg m -3 for home air and office air, respectively. Regarding dust, the median concentrations of ∑PBDEs were 239 and 437 ng g -1 for home and office dust, respectively. The ratios of the median concentrations of BDE-209 to ∑PBDEs were approximately 0.95 and 0.87 for home dust and office dust, respectively. The median concentrations of ∑PBDEs were 359 ng g -1 and 350 ng g -1 for dust on air conditioner filters and the back cabinet of the computer, respectively. The ratios of the median concentrations of BDE-209 to ∑PBDEs were approximately 0.58 and 0.46 for air conditioner and computer samples. Running air conditioners contributed to ΣPBDEs in office air through direct and indirect pathways. The daily intake of PBDEs was estimated to be 2630 pg (kg bw) -1 day -1 for toddlers in homes and 319 pg (kg bw) -1 day -1 for adults in homes and offices. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ultraviolet Radiative Transfer Modeling of Nearby Galaxies with Extraplanar Dusts

NASA Astrophysics Data System (ADS)

Shinn, Jong-Ho; Seon, Kwang-Il

2015-12-01

In order to examine their relation to the host galaxy, the extraplanar dusts of six nearby galaxies are modeled, employing a three-dimensional Monte Carlo radiative transfer code. The targets are from the highly inclined galaxies that show dust-scattered ultraviolet halos, and the archival Galaxy Evolution Explorer FUV band images were fitted with the model. The observed images are generally well-reproduced by two dust layers and one light source layer, whose vertical and radial distributions have exponential profiles. We obtained several important physical parameters, such as star formation rate (SFRUV), face-on optical depth, and scale-heights. Three galaxies (NGC 891, NGC 3628, and UGC 11794) show clear evidence for the existence of an extraplanar dust layer. However, it is found that the remaining three targets (IC 5249, NGC 24, and NGC 4173) do not necessarily need a thick dust disk to model the ultraviolet (UV) halo, because its contribution is too small and the UV halo may be caused by the wing part of the GALEX point spread function. This indicates that the galaxy samples reported to have UV halos may be contaminated by galaxies with negligible extraplanar (halo) dust. The galaxies showing evidence of an extraplanar dust layer fall within a narrow range on the scatter plots between physical parameters such as SFRUV and extraplanar dust mass. Several mechanisms that could possibly produce the extraplanar dust are discussed. We also found a hint that the extraplanar dust scale-height might not be much different from the polycyclic aromatic hydrocarbon emission characteristic height.

Short-Time Mass Variation in Natural Atmospheric Dust.

DTIC Science & Technology

1979-11-01

many years. When the Krakatoa volcano in the South Pacific erupted in 1883, ejecting tons of dust into the high atmosphere, people from many parts of the...Flight Center, AL 35812 Commander Naval Ocean Systems Center (Code 4473) Commander ATTN: Technical Library US Army Missile R&D Command San Diego, CA...PO Box 67 ATTN: DRDMI-TBD APO San Francisco, CA 96555 US Army Missile R&D Command Redstone Arsenal, AL 35809 Director NOAA/ERL/APCL R31 Commander RB3

Electrical characteristics of simulated tornadoes

NASA Astrophysics Data System (ADS)

Zimmerman, M. I.; Farrell, W. M.; Barth, E. L.; Lewellen, D. C.; Lewellen, W. S.; Perlongo, N. J.; Jackson, T.

2012-12-01

It is well known that tornadoes and dust devils have the ability to accumulate significant, visible clouds of debris. Collisions between sand-like debris species produce different electric charges on different types of grains, which convect along different trajectories around the vortex. Thus, significant charge separations and electric currents are possible, which as the vortex fluctuates over time are thought to produce ULF radiation signatures that have been measured in the field. These electric and magnetic fields may contain valuable information about tornado structure and genesis, and may be critical in driving electrochemical processes within dust devils on Mars. In the present work, existing large eddy simulations of debris-laden tornadoes performed at West Virginia University are coupled with a new debris-charging and advection code developed at Goddard Space Flight Center to investigate the detailed (meter-resolution) fluid-dynamic origins of electromagnetic fields within terrestrial vortices. First results are presented, including simulations of the electric and magnetic fields that would be observed by a near-surface, instrument-laden probe during a direct encounter with a tornado. This research was supported by an appointment to the NASA Postdoctoral Program at the Goddard Space Flight Center, administered by Oak Ridge Associated Universities through a contract with NASA. The generous allocation of computing resources by Dr. Timothy J. Stubbs is gratefully acknowledged.

Physical and dynamical properties of the anomalous comet 249P/LINEAR

NASA Astrophysics Data System (ADS)

Fernández, Julio A.; Licandro, Javier; Moreno, Fernando; Sosa, Andrea; Cabrera-Lavers, Antonio; de León, Julia; Birtwhistle, Peter

2017-10-01

Images and low-resolution spectra of the near-Earth Jupiter family comet (JFC) 249P/LINEAR in the visible range obtained with the instrument OSIRIS in the 10.4 m Gran Telescopio Canarias (GTC) (La Palma, Spain) on January 3, 4, 6 and February 6, 2016 are presented, together with a series of images obtained with the 0.4m telescope of the Great Shefford Observatory obtained on Oct. 22 and 27, and Nov. 1 and 24, 2006. The reflectance spectrum of 249P is similar to that of a B-type asteroid. The comet has an absolute (visual) nuclear magnitude HV = 17.0 ± 0.4 , which corresponds to a radius of about 1-1.3 km for a geometric albedo ∼ 0.04 - 0.07 . From the analysis of GTC images using a Monte Carlo dust tail code we find that the time of maximum dust ejection rate was around 1.6 days before perihelion. The analysis of the dust tails during the 2006 and 2016 perihelion approaches reveals that, during both epochs, the comet repeated the same dust ejection pattern, with a similar short-lived activity period of about 20 days (FWHM) around perihelion and a dust loss rate peaking at 145 ± 50 kg/s. The total dust mass ejected during its last perihelion passage was (2.5 ± 0.9) × 108 kg, almost all this mass being emitted before the first observation of January 3, 2016. The activity onset, duration, and total ejected mass were very similar during the 2006 perihelion passage. This amount of dust mass is very low as compared with that from other active JFCs. The past orbital evolution of 249P and 100 clones were also followed over a time scale of ∼ 5 × 104 yr. The object and more than 60% of the clones remained bound to the near-Earth region for the whole computed period, keeping its perihelion distance within the range q ≃ 0.4 - 1.1 au. The combination of photometric and spectroscopic observations and dynamical studies show that the near-Earth comet 249P/LINEAR has several peculiar features that clearly differentiate it from typical JFCs. We may be in front of a new class of near-Earth JFC whose source region is not the distant trans-neptunian population, but much closer in the asteroid belt. Therefore, 249P/LINEAR may be a near-Earth counterpart of the so-called main-belt comets or active asteroids.

The circumbinary dusty disk around the hydrogen-deficient binary star υ Sagittarii

NASA Astrophysics Data System (ADS)

Netolický, M.; Bonneau, D.; Chesneau, O.; Harmanec, P.; Koubský, P.; Mourard, D.; Stee, P.

2009-06-01

Aims: The aim of this paper is to determine the properties of the dusty environment of the hydrogen-deficient binary system υ Sgr, whose binary properties and other characteristics are poorly known. Methods: We obtained the first mid-IR interferometric observations of υ Sgr using the instrument MIDI of the VLTI used with different pairs of 1.8 m and 8 m telescopes. The calibrated visibilities, the N band spectrum, and the SED were compared with disk models computed with the MC3D code to determine the geometry and chemical composition of the envelope. Results: υ Sgr is unresolved with an 8 m telescope at 8.7 μm. We propose a disk model that agrees with the measured visibilities and the SED, consisting of a geometrically thin disk with an inner radius R_in = 6.0+0.5-1.5 AU and a scale height h100 = 3.5+2.0-1.5 AU. The chemical composition of the dust is approximately 60% of carbon dust and 40% of silicate dust, as a consequence of several episodes of mass transfers, whose chemistry was imprinted in the dust composition. We also constrain the inclination of the disk i = 50°+10°-20° and its orientation position angle PA = 80°+10°-5°. Conclusions: The mid-infrared interferometric observations of the binary star υ Sgr allowed us to constrain the geometry of the circumbinary dusty envelope. By defining the inclination and PA of the system with better accuracy than before, these observations restrict the parameter space for the orbital parameters and thus the nature of the stars orbiting in this system. Based on observations made with the Very Large Telescope Interferometer at Paranal Observatory under program 079.D-0115. Visibility data are only available in electronic form at the CDS website.

Dust cyclone research in the 21st century

USDA-ARS?s Scientific Manuscript database

Research to meet the demand for ever more efficient dust cyclones continues after some eighty years. Recent trends emphasize design optimization through computational fluid dynamics (CFD) and testing design subtleties not modeled by semi-empirical equations. Improvements to current best available ...

Gravitational Instability of Small Particles in Stratified Dusty Disks

NASA Astrophysics Data System (ADS)

Shi, J.; Chiang, E.

2012-12-01

Self-gravity is an attractive means of forming the building blocks of planets, a.k.a. the first-generation planetesimals. For ensembles of dust particles to aggregate into self-gravitating, bound structures, they must first collect into regions of extraordinarily high density in circumstellar gas disks. We have modified the ATHENA code to simulate dusty, compressible, self-gravitating flows in a 3D shearing box configuration, working in the limit that dust particles are small enough to be perfectly entrained in gas. We have used our code to determine the critical density thresholds required for disk gas to undergo gravitational collapse. In the strict limit that the stopping times of particles in gas are infinitesimally small, our numerical simulations and analytic calculations reveal that the critical density threshold for gravitational collapse is orders of magnitude above what has been commonly assumed. We discuss how finite but still short stopping times under realistic conditions can lower the threshold to a level that may be attainable. Nonlinear development of gravitational instability in a stratified dusty disk. Shown are volume renderings of dust density for the bottom half of a disk at t=0, 6, 8, and 9 Omega^{-1}. The initial disk first develops shearing density waves. These waves then steep and form long extending filament along the azimuth. These filaments eventually break and form very dense dust clumps. The time evolution of the maximum dust density within the simulation box. Run std32 stands for a standard run which has averaged Toomre's Q=0.5. Qgtrsim 1.0 for the rest runs in the plot (Z1 has twice metallicity than the standard; Q1 has twice Q_g, the Toomre's Q for the gas disk alone; M1 has twice the dust-to-gas ratio than the standard at the midplane; R1 is constructed so that the midplane density exceeds the Roche criterion however the Toomre's Q is above unity.)

Mars atmospheric dust properties: A synthesis of Mariner 9, Viking, and Phobos observations

NASA Technical Reports Server (NTRS)

Clancy, R. T.; Lee, S. W.; Gladstone, G. R.

1993-01-01

We have modified a doubling-and-adding code to reanalyze the Mariner 9 IRIS spectra of Mars atmospheric dust as well as Viking IRTM EPF sequences in the 7, 9, and 20 micron channels. The code is capable of accurate emission/ absorption/scattering radiative transfer calculations over the 5-30 micron wavelength region for variable dust composition and particle size inputs, and incorporates both the Viking IRTM channel weightings and the Mariner 9 IRIS wavelength resolution for direct comparisons to these datasets. We adopt atmospheric temperature profiles according to the algorithm of Martin (1986) in the case of the Viking IRTM comparisons, and obtained Mariner 9 IRIS temperature retrievals from the 15 micron CO2 band for the case of the IRIS comparisons. We consider palagonite as the primary alternative to the montmorillonite composition of Mars atmospheric dust, based on several considerations. Palagonite absorbs in the ultraviolet and visible wavelength region due to its Fe content. Palagonite is also, in principal, consistent with the observed lack of clays on the Mars surface. Furthermore, palagonite does not display strong, structured absorption near 20 microns as does montmorillonite (in conflict with the IRIS observations). We propose that a palagonite composition with particle sizes roughly one-half that of the Toon et al. (1977) determination provide a much improved model to Mars atmospheric dust. Since palagonite is a common weathering product of terrrestrial basalts, it would not be unreasonable for palagonite to be a major surface component for Mars. The lack of even a minor component of Al-rich clays on the surface of Mars could be consistent with a palagonite composition for Mars dust if the conditions for basalt weathering on Mars were sufficiently anhydrous. Variations in palagonite composition could also lead to the inability of the modeled palagonite to fit the details of the 9 micron absorbtion indicated by the IRIS observations.

Distribution and fate of polybrominated diphenyl ethers in indoor environments of elementary schools.

PubMed

Wu, Q; Baek, S-Y; Fang, M; Chang, Y-S

2010-06-01

Polybrominated diphenyl ethers (PBDEs) are considered harmful to human health because of their toxicities and persistence in environments. In the current study, the distribution and fate of PBDEs in classrooms and computer rooms in 17 elementary schools in South Korea have been described. Eight congeners (brominated diphenyl ether-28, -47, -99, -100, -153, -154, -183, and -209) in air, floor dust, and product surface dust were measured. While Sigma(8)PBDEs in the air in classrooms showed considerable variations (0.659-1600 pg/m(3), arithmetic mean +/- s.d.: 377 +/- 441 pg/m(3)), those in computer rooms were somewhat similar (134-220 pg/m(3), arithmetic mean +/- s.d.: 169 +/- 40 pg/m(3)). Sigma(8)PBDEs in floor dust varied over a wide range, from 453 to 45,700 ng/g, for all rooms. Based on congener patterns, two groups were created--CL-1 that is dominated by high-brominated congeners and CL-2 primarily comprising low-brominated congeners--for both air and floor dust of classrooms. Surface dust had low concentrations, ranged from ND to 181, from ND to 128, and from ND to 256 pg/cm(2) for desk/chair sets, lockers, and playing tools, respectively. Pearson correlation coefficients were calculated individually for air, floor dust, and surface dust. The results indicate that both surface dust and floor dust may act as a secondary source of PBDEs in indoor environments after emission from facilities. Children have been estimated to have a higher potential exposure to PBDEs than adults. Since children spend most of their day time at school, PBDE distributions in school environments should be a matter of great concern.

Model of Image Artifacts from Dust Particles

NASA Technical Reports Server (NTRS)

Willson, Reg

2008-01-01

A mathematical model of image artifacts produced by dust particles on lenses has been derived. Machine-vision systems often have to work with camera lenses that become dusty during use. Dust particles on the front surface of a lens produce image artifacts that can potentially affect the performance of a machine-vision algorithm. The present model satisfies a need for a means of synthesizing dust image artifacts for testing machine-vision algorithms for robustness (or the lack thereof) in the presence of dust on lenses. A dust particle can absorb light or scatter light out of some pixels, thereby giving rise to a dark dust artifact. It can also scatter light into other pixels, thereby giving rise to a bright dust artifact. For the sake of simplicity, this model deals only with dark dust artifacts. The model effectively represents dark dust artifacts as an attenuation image consisting of an array of diffuse darkened spots centered at image locations corresponding to the locations of dust particles. The dust artifacts are computationally incorporated into a given test image by simply multiplying the brightness value of each pixel by a transmission factor that incorporates the factor of attenuation, by dust particles, of the light incident on that pixel. With respect to computation of the attenuation and transmission factors, the model is based on a first-order geometric (ray)-optics treatment of the shadows cast by dust particles on the image detector. In this model, the light collected by a pixel is deemed to be confined to a pair of cones defined by the location of the pixel s image in object space, the entrance pupil of the lens, and the location of the pixel in the image plane (see Figure 1). For simplicity, it is assumed that the size of a dust particle is somewhat less than the diameter, at the front surface of the lens, of any collection cone containing all or part of that dust particle. Under this assumption, the shape of any individual dust particle artifact is the shape (typically, circular) of the aperture, and the contribution of the particle to the attenuation factor for a given pixel is the fraction of the cross-sectional area of the collection cone occupied by the particle. Assuming that dust particles do not overlap, the net transmission factor for a given pixel is calculated as one minus the sum of attenuation factors contributed by all dust particles affecting that pixel. In a test, the model was used to synthesize attenuation images for random distributions of dust particles on the front surface of a lens at various relative aperture (F-number) settings. As shown in Figure 2, the attenuation images resembled dust artifacts in real test images recorded while the lens was aimed at a white target.

Size and density sorting of dust grains in SPH simulations of protoplanetary discs

NASA Astrophysics Data System (ADS)

Pignatale, F. C.; Gonzalez, J.-F.; Cuello, Nicolas; Bourdon, Bernard; Fitoussi, Caroline

2017-07-01

The size and density of dust grains determine their response to gas drag in protoplanetary discs. Aerodynamical (size × density) sorting is one of the proposed mechanisms to explain the grain properties and chemical fractionation of chondrites. However, the efficiency of aerodynamical sorting and the location in the disc in which it could occur are still unknown. Although the effects of grain sizes and growth in discs have been widely studied, a simultaneous analysis including dust composition is missing. In this work, we present the dynamical evolution and growth of multicomponent dust in a protoplanetary disc using a 3D, two-fluid (gas+dust) smoothed particle hydrodynamics code. We find that the dust vertical settling is characterized by two phases: a density-driven phase that leads to a vertical chemical sorting of dust and a size-driven phase that enhances the amount of lighter material in the mid-plane. We also see an efficient radial chemical sorting of the dust at large scales. We find that dust particles are aerodynamically sorted in the inner disc. The disc becomes sub-solar in its Fe/Si ratio on the surface since the early stage of evolution but sub-solar Fe/Si can be also found in the outer disc-mid-plane at late stages. Aggregates in the disc mimic the physical and chemical properties of chondrites, suggesting that aerodynamical sorting played an important role in determining their final structure.

Development of a high resolution interstellar dust engineering model - overview of the project

NASA Astrophysics Data System (ADS)

Sterken, V. J.; Strub, P.; Soja, R. H.; Srama, R.; Krüger, H.; Grün, E.

2013-09-01

Beyond 3 AU heliocentric distance, the flow of interstellar dust through the solar system is a dominant component of the total dust population. The modulation of this flux with the solar cycle and the position in the solar system has been predicted by theoretical studies since the seventies. The modulation was proven to exist by matching dust trajectory simulations with real spacecraft data from Ulysses in 1998. The modulations were further analyzed and studies in detail in 2012. The current ESA interplanetary meteoroid model IMEM includes an interstellar dust component, but this component was modelled only with straight line trajectories through the solar system. For the new ESA IMEX model, a high-resolution interstellar dust component is implemented separately from a dust streams module. The dust streams module focuses on dust in streams that was released from comets (cf. Abstract R. Soja). Parallel processing techniques are used to improve computation time (cf. Abstract P. Strub). The goal is to make predictions for the interstellar dust flux as close to the Sun as 1 AU or closer, for future space mission design.

Water Around a Carbon Star

NASA Image and Video Library

2010-09-01

This ESA Herschel image shows IRC+10216, also known as CW Leonis, a star rich in carbon where astronomers were surprised to find water. This color-coded image shows the star, surrounded by a clumpy envelope of dust.

MAJOR-MERGER GALAXY PAIRS AT Z = 0: DUST PROPERTIES AND COMPANION MORPHOLOGY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Domingue, Donovan L.; Ronca, Joseph; Hill, Emily

We present an analysis of dust properties of a sample of close major-merger galaxy pairs selected by K {sub s} magnitude and redshift. The pairs represent the two populations of spiral–spiral (S+S) and mixed morphology spiral–elliptical (S+E). The Code Investigating GALaxy Emission software is used to fit dust models to the Two Micron All Sky Survey, Wide-Field Infrared Survey Explorer , and Herschel flux density measurements, and to derive the parameters describing the polycyclic aromatic hydrocarbons contribution, interstellar radiation field, and photodissociation regions. Model fits verify our previous Spitzer Space Telescope analysis that S+S and S+E pairs do not havemore » the same level of enhancement of star formation and differ in dust composition. The spirals of mixed-morphology galaxy pairs do not exhibit the enhancements in interstellar radiation field and therefore dust temperature for spirals in S+S pairs in contrast to what would be expected according to standard models of gas redistribution due to encounter torques. This suggests the importance of the companion environment/morphology in determining the dust properties of a spiral galaxy in a close major-merger pair.« less

Effects of photophoresis on the dust distribution in a 3D protoplanetary disc

NASA Astrophysics Data System (ADS)

Cuello, N.; Gonzalez, J.-F.; Pignatale, F. C.

2016-05-01

Photophoresis is a physical process based on momentum exchange between an illuminated dust particle and its gaseous environment. Its net effect in protoplanetary discs (PPD) is the outward transport of solid bodies from hot to cold regions. This process naturally leads to the formation of ring-shaped features where dust piles up. In this work, we study the dynamical effects of photophoresis in PPD by including the photophoretic force in the two-fluid (gas+dust) smoothed particle hydrodynamics (SPH) code developed by Barrière-Fouchet et al. (2005). We find that the conditions of pressure and temperature encountered in the inner regions of PPD result in important photophoretic forces, which dramatically affect the radial motion of solid bodies. Moreover, dust particles have different equilibrium locations in the disc depending on their size and their intrinsic density. The radial transport towards the outer parts of the disc is more efficient for silicates than for iron particles, which has important implications for meteoritic composition. Our results indicate that photophoresis must be taken into account in the inner regions of PPD to fully understand the dynamics and the evolution of the dust composition.

The Interplay between Radiation Pressure and the Photoelectric Instability in Optically Thin Disks of Gas and Dust

NASA Astrophysics Data System (ADS)

Richert, Alexander J. W.; Lyra, Wladimir; Kuchner, Marc J.

2018-03-01

In optically thin disks, dust grains are photoelectrically stripped of electrons by starlight, heating nearby gas and possibly creating a dust clumping instability—the photoelectric instability (PeI)—that significantly alters global disk structure. In the current work, we use the Pencil Code to perform the first numerical models of the PeI that include stellar radiation pressure on dust grains in order to explore the parameter regime in which the instability operates. In some models with low gas and dust surface densities, we see a variety of dust structures, including sharp concentric rings. In the most gas- and dust-rich models, nonaxisymmetric clumps, arcs, and spiral arms emerge that represent dust surface density enhancements of factors of ∼5–20. In one high gas surface density model, we include a large, low-order gas viscosity and find that it observably smooths the structures that form in the gas and dust, suggesting that resolved images of a given disk may be useful for deriving constraints on the effective viscosity of its gas. Our models show that radiation pressure does not preclude the formation of complex structure from the PeI, but the qualitative manifestation of the PeI depends strongly on the parameters of the system. The PeI may provide an explanation for unusual disk morphologies, such as the moving blobs of the AU Mic disk, the asymmetric dust distribution of the 49 Ceti disk, and the rings and arcs found in the HD 141569A disk.

Dust in circumstellar disks

NASA Astrophysics Data System (ADS)

Rodmann, Jens

2006-02-01

This thesis presents observational and theoretical studies of the size and spatial distribution of dust particles in circumstellar disks. Using millimetre interferometric observations of optically thick disks around T Tauri stars, I provide conclusive evidence for the presence of millimetre- to centimetre-sized dust aggregates. These findings demonstrate that dust grain growth to pebble-sized dust particles is completed within less than 1 Myr in the outer disks around low-mass pre-main-sequence stars. The modelling of the infrared spectral energy distributions of several solar-type main-sequence stars and their associated circumstellar debris disks reveals the ubiquity of inner gaps devoid of substantial amounts of dust among Vega-type infrared excess sources. It is argued that the absence of circumstellar material in the inner disks is most likely the result of the gravitational influence of a large planet and/or a lack of dust-producing minor bodies in the dust-free region. Finally, I describe a numerical model to simulate the dynamical evolution of dust particles in debris disks, taking into account the gravitational perturbations by planets, photon radiation pressure, and dissipative drag forces due to the Poynting-Robertson effect and stellar wind. The validity of the code it established by several tests and comparison to semi-analytic approximations. The debris disk model is applied to simulate the main structural features of a ring of circumstellar material around the main-sequence star HD 181327. The best agreement between model and observation is achieved for dust grains a few tens of microns in size locked in the 1:1 resonance with a Jupiter-mass planet (or above) on a circular orbit.

Far-infrared and dust properties of present-day galaxies in the EAGLE simulations

NASA Astrophysics Data System (ADS)

Camps, Peter; Trayford, James W.; Baes, Maarten; Theuns, Tom; Schaller, Matthieu; Schaye, Joop

2016-10-01

The Evolution and Assembly of GaLaxies and their Environments (EAGLE) cosmological simulations reproduce the observed galaxy stellar mass function and many galaxy properties. In this work, we study the dust-related properties of present-day EAGLE galaxies through mock observations in the far-infrared and submm wavelength ranges obtained with the 3D dust radiative transfer code SKIRT. To prepare an EAGLE galaxy for radiative transfer processing, we derive a diffuse dust distribution from the gas particles and we re-sample the star-forming gas particles and the youngest star particles into star-forming regions that are assigned dedicated emission templates. We select a set of redshift-zero EAGLE galaxies that matches the K-band luminosity distribution of the galaxies in the Herschel Reference Survey (HRS), a volume-limited sample of about 300 normal galaxies in the Local Universe. We find overall agreement of the EAGLE dust scaling relations with those observed in the HRS, such as the dust-to-stellar mass ratio versus stellar mass and versus NUV-r colour relations. A discrepancy in the f250/f350 versus f350/f500 submm colour-colour relation implies that part of the simulated dust is insufficiently heated, likely because of limitations in our sub-grid model for star-forming regions. We also investigate the effect of adjusting the metal-to-dust ratio and the covering factor of the photodissociation regions surrounding the star-forming cores. We are able to constrain the important dust-related parameters in our method, informing the calculation of dust attenuation for EAGLE galaxies in the UV and optical domain.

Probing Cosmic Infrared Sources: A Computer Modeling Approach

DTIC Science & Technology

1992-06-01

developed to study various physical phenomena involving dust grains, e.g., molecule formation on grains, grain formation in expanding circumstellar...EVALUATION OF METHODS OF ANALYSIS IN INFRARED ASTR9?NOMY 16 4.0 THEORETICAL STUDIES INVOLVING DUST GRAINS., 16 4.1 Theory of Molecule Formation on Dust Grains...17 4.2 Modeling Grain Formation in Stellar Outflows 7 18 4.3 Infrared Emission from Fractal Grains * 19 4.4 Photochemistry in Circumstellar Envelopes

Performance estimation of a Venturi scrubber using a computational model for capturing dust particles with liquid spray.

PubMed

Pak, S I; Chang, K S

2006-12-01

A Venturi scrubber has dispersed three-phase flow of gas, dust, and liquid. Atomization of a liquid jet and interaction between the phases has a large effect on the performance of Venturi scrubbers. In this study, a computational model for the interactive three-phase flow in a Venturi scrubber has been developed to estimate pressure drop and collection efficiency. The Eulerian-Lagrangian method is used to solve the model numerically. Gas flow is solved using the Eulerian approach by using the Navier-Stokes equations, and the motion of dust and liquid droplets, described by the Basset-Boussinesq-Oseen (B-B-O) equation, is solved using the Lagrangian approach. This model includes interaction between gas and droplets, atomization of a liquid jet, droplet deformation, breakup and collision of droplets, and capture of dust by droplets. A circular Pease-Anthony Venturi scrubber was simulated numerically with this new model. The numerical results were compared with earlier experimental data for pressure drop and collection efficiency, and gave good agreements.

Statistical simulations of the dust foreground to cosmic microwave background polarization

NASA Astrophysics Data System (ADS)

Vansyngel, F.; Boulanger, F.; Ghosh, T.; Wandelt, B.; Aumont, J.; Bracco, A.; Levrier, F.; Martin, P. G.; Montier, L.

2017-07-01

The characterization of the dust polarization foreground to the cosmic microwave background (CMB) is a necessary step toward the detection of the B-mode signal associated with primordial gravitational waves. We present a method to simulate maps of polarized dust emission on the sphere that is similar to the approach used for CMB anisotropies. This method builds on the understanding of Galactic polarization stemming from the analysis of Planck data. It relates the dust polarization sky to the structure of the Galactic magnetic field and its coupling with interstellar matter and turbulence. The Galactic magnetic field is modeled as a superposition of a mean uniform field and a Gaussian random (turbulent) component with a power-law power spectrum of exponent αM. The integration along the line of sight carried out to compute Stokes maps is approximated by a sum over a small number of emitting layers with different realizations of the random component of the magnetic field. The model parameters are constrained to fit the power spectra of dust polarization EE, BB, and TE measured using Planck data. We find that the slopes of the E and B power spectra of dust polarization are matched for αM = -2.5, an exponent close to that measured for total dust intensity but larger than the Kolmogorov exponent - 11/3. The model allows us to compute multiple realizations of the Stokes Q and U maps for different realizations of the random component of the magnetic field, and to quantify the variance of dust polarization spectra for any given sky area outside of the Galactic plane. The simulations reproduce the scaling relation between the dust polarization power and the mean total dust intensity including the observed dispersion around the mean relation. We also propose a method to carry out multifrequency simulations, including the decorrelation measured recently by Planck, using a given covariance matrix of the polarization maps. These simulations are well suited to optimize component separation methods and to quantify the confidence with which the dust and CMB B-modes can be separated in present and future experiments. We also provide an astrophysical perspective on our phenomenological modeling of the dust polarization spectra.

Equilibrium chemistry down to 100 K. Impact of silicates and phyllosilicates on the carbon to oxygen ratio

NASA Astrophysics Data System (ADS)

Woitke, P.; Helling, Ch.; Hunter, G. H.; Millard, J. D.; Turner, G. E.; Worters, M.; Blecic, J.; Stock, J. W.

2018-06-01

We have introduced a fast and versatile computer code, GGCHEM, to determine the chemical composition of gases in thermo-chemical equilibrium down to 100 K, with or without equilibrium condensation. We have reviewed the data for molecular equilibrium constants, kp(T), from several sources and discussed which functional fits are most suitable for low temperatures. We benchmarked our results against another chemical equilibrium code. We collected Gibbs free energies, ΔGf⊖, for about 200 solid and liquid species from the NIST-JANAF database and the geophysical database SUPCRTBL. We discussed the condensation sequence of the elements with solar abundances in phase equilibrium down to 100 K. Once the major magnesium silicates Mg2SiO4[s] and MgSiO3[s] have formed, the dust to gas mass ratio jumps to a value of about 0.0045 which is significantly lower than the often assumed value of 0.01. Silicate condensation is found to increase the carbon to oxygen ratio (C/O) in the gas from its solar value of 0.55 up to 0.71, and, by the additional intake of water and hydroxyl into the solid matrix, the formation of phyllosilicates at temperatures below 400 K increases the gaseous C/O further to about 0.83. Metallic tungsten (W) is the first condensate found to become thermodynamically stable around 1600-2200 K (depending on pressure), several hundreds of Kelvin before subsequent materials such as zirconium dioxide (ZrO2) or corundum (Al2O3) can condense. We briefly discuss whether tungsten, despite its low abundance of 2 × 10-7 times the silicon abundance, could provide the first seed particles for astrophysical dust formation. GGCHEM code is publicly available at http://https://github.com/pw31/GGchemTable D.1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/614/A1

ALMA unveils rings and gaps in the protoplanetary system HD 169142: signatures of two giant protoplanets

NASA Astrophysics Data System (ADS)

Fedele, D.; Carney, M.; Hogerheijde, M. R.; Walsh, C.; Miotello, A.; Klaassen, P.; Bruderer, S.; Henning, Th.; van Dishoeck, E. F.

2017-04-01

The protoplanetary system HD 169142 is one of the few cases where a potential candidate protoplanet has recently been detected by direct imaging in the near-infrared. To study the interaction between the protoplanet and the disk itself, observations of the gas and dust surface density structure are needed. This paper reports new ALMA observations of the dust continuum at 1.3 mm, 12CO, 13CO, and C18O J = 2-1 emission from the system HD 169142 (which is observed almost face-on) at an angular resolution of 0.3 arcsec × 0.2 arcsec ( 35 × 20 au). The dust continuum emission reveals a double-ring structure with an inner ring between 0.17 arcsec{-0.28 arcsec} ( 20-35 au) and an outer ring between 0.48 arcsec{-0.64 arcsec} ( 56-83 au). The size and position of the inner ring is in good agreement with previous polarimetric observations in the near-infrared and is consistent with dust trapping by a massive planet. No dust emission is detected inside the inner dust cavity (R ≲ 20 au) or within the dust gap ( 35-56 au) down to the noise level. In contrast, the channel maps of the J = 2-1 line of the three CO isotopologs reveal gas inside the dust cavity and dust gap. The gaseous disk is also much larger than the compact dust emission; it extends to 1.5 arcsec ( 180 au) in radius. This difference and the sharp drop of the continuum emission at large radii point to radial drift of large dust grains (>μm size). Using the thermo-chemical disk code dali, we modeled the continuum and the CO isotopolog emission to quantitatively measure the gas and dust surface densities. The resulting gas surface density is reduced by a factor of 30-40 inward of the dust gap. The gas and dust distribution indicate that two giant planets shape the disk structure through dynamical clearing (dust cavity and gap) and dust trapping (double-ring dust distribution).

Modeling the emission, transport and deposition of contaminated dust from a mine tailing site.

PubMed

Stovern, Michael; Betterton, Eric A; Sáez, A Eduardo; Villar, Omar Ignacio Felix; Rine, Kyle P; Russell, Mackenzie R; King, Matt

2014-01-01

Mining operations are potential sources of airborne particulate metal and metalloid contaminants through both direct smelter emissions and wind erosion of mine tailings. The warmer, drier conditions predicted for the Southwestern US by climate models may make contaminated atmospheric dust and aerosols increasingly important, due to potential deleterious effects on human health and ecology. Dust emissions and dispersion of contaminants from the Iron King Mine tailings in Dewey-Humboldt, Arizona, a Superfund site, are currently being investigated through in situ field measurements and computational fluid dynamics modeling. These tailings are significantly contaminated with lead and arsenic with an average soil concentration of 1616 and 1420 ppm, respectively. Similar levels of these contaminants have also been measured in soil samples taken from the area surrounding the mine tailings. Using a computational fluid dynamics model, we have been able to model dust transport from the mine tailings to the surrounding region. The model includes a distributed Eulerian model to simulate fine aerosol transport and a Lagrangian approach to model fate and transport of larger particles. In order to improve the accuracy of the dust transport simulations both regional topographical features and local weather patterns have been incorporated into the model simulations.

Experimental Study and Computational Simulations of Key Pebble Bed Thermo-mechanics Issues for Design and Safety

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tokuhiro, Akira; Potirniche, Gabriel; Cogliati, Joshua

2014-07-08

An experimental and computational study, consisting of modeling and simulation (M&S), of key thermal-mechanical issues affecting the design and safety of pebble-bed (PB) reactors was conducted. The objective was to broaden understanding and experimentally validate thermal-mechanic phenomena of nuclear grade graphite, specifically, spheres in frictional contact as anticipated in the bed under reactor relevant pressures and temperatures. The contact generates graphite dust particulates that can subsequently be transported into the flowing gaseous coolent. Under postulated depressurization transients and with the potential for leaked fission products to be adsorbed onto graphite 'dust', there is the potential for fission products to escapemore » from the primary volume. This is a design safety concern. Furthermore, earlier safety assessment identified the distinct possibility for the dispersed dust to combust in contact with air if sufficient conditions are met. Both of these phenomena were noted as important to design review and containing uncertainty to warrant study. The team designed and conducted two separate effects tests to study and benchmark the potential dust-generation rate, as well as study the conditions under which a dust explosion may occure in a standardized, instrumented explosion chamber.« less

Cohesion, granular solids, granular liquids, and their connection to small near-Earth objects

NASA Astrophysics Data System (ADS)

Sánchez, P.; Scheeres, D.

2014-07-01

During the last 15 years or so, the Planetary Sciences community has been using Discrete Element Method (DEM) simulation codes to study small near-Earth objects (NEOs). In general, these codes treat gravitational aggregates as conglomerates of spherical particles; a good approximation given that many asteroids are self-gravitating granular media. Unfortunately, the degree of sophistication of these codes, and our own understanding, has not been high enough as to appropriately represent realistic physical properties of granular matter. In particular, angles of friction (θ) and cohesive strength (σ_c) of the aggregates were rarely taken in consideration and this could have led to unrealistic dynamics, and therefore, unrealistic conclusions about the dynamical evolution of small NEOs. In our research, we explore the failure mechanics of spherical (r=71 m) and ellipsoidal (r_1=92 m) self-gravitating aggregates with different angles of friction and values for their cohesive strength, in order to better understand the geophysics of rubble-pile asteroids. In particular we focused on the deformation and different disruption modes provoked by an always increasing angular velocity (spin rate). Scaling arguments allow us to regard simulations with the same aggregate size and different σ_c as equivalent to simulations of aggregates of different size and the same σ_c. We use a computational code that implements a Soft-Sphere DEM. The aggregates are composed by 3,000 spherical solid spheres (7--10 m) with 6 degrees of freedom. The code calculates normal, as well as, frictional (tangential) contact forces by means of soft potentials and the aggregate as a whole mimics the effect of non- spherical particles through the implementation of rolling friction. Cohesive forces, and a cohesive stress, are calculated as the net effect of the sum of the van der Waals forces between the smaller regolith, sand and dust (powder) that are present in real asteroids [1]. These finer materials form a matrix of sorts that holds the bigger boulders together. The aggregates were slowly spun up to disruption controlling for angle of friction, cohesion and global shape. Systems with no frictional forces had θ≈ 12° and are in effect granular liquids in the best case scenario. Systems with only surface-surface friction had θ≈ 25°, which is typical in laboratory experiments with spherical glass beads. Systems that also implemented rolling friction had θ≈ 35°, which is typical of non-cohesive granular media on the Earth. How much each aggregate deformed before disruption was directly related to the angle of friction. The greater θ allowed for much less deformation before disruption. Cohesive forces on the other hand controlled the mode of disruption and maximum spin rate and showed that the change from shedding to fission is continuous and therefore, they should not be seen as different disruption processes. The figure shows the deformation and disruption of three initially spherical aggregates (left) and three initially ellipsoidal aggregates (right) with increasing cohesive strength from left to right (θ≈ 35°). Through scaling arguments we could also see these aggregates as having the exact same σ_c=25 Pa but different sizes. If we do that, the aggregates measure about 1.6 km, 5 km, and 22 km, and the particles, or groups of particles being detached now have similar sizes. This has now become a problem of resolution, i.e., the number and size of particles used in a simulation. These results start to raise fundamental questions regarding the difference between shedding and fission. Is it shedding when it is dust grain by dust grain ejection from the main body or when it is in groups of 10, 100, or 100,000 dust particles? Is it fission when a 1-m piece of the asteroid detaches or when it splits in the middle? Which values of θ and σ_c are realistic? These and other questions will be explored.

Introducing GAMER: A fast and accurate method for ray-tracing galaxies using procedural noise

DOE Office of Scientific and Technical Information (OSTI.GOV)

Groeneboom, N. E.; Dahle, H., E-mail: nicolaag@astro.uio.no

2014-03-10

We developed a novel approach for fast and accurate ray-tracing of galaxies using procedural noise fields. Our method allows for efficient and realistic rendering of synthetic galaxy morphologies, where individual components such as the bulge, disk, stars, and dust can be synthesized in different wavelengths. These components follow empirically motivated overall intensity profiles but contain an additional procedural noise component that gives rise to complex natural patterns that mimic interstellar dust and star-forming regions. These patterns produce more realistic-looking galaxy images than using analytical expressions alone. The method is fully parallelized and creates accurate high- and low- resolution images thatmore » can be used, for example, in codes simulating strong and weak gravitational lensing. In addition to having a user-friendly graphical user interface, the C++ software package GAMER is easy to implement into an existing code.« less

Introducing GAMER: A Fast and Accurate Method for Ray-tracing Galaxies Using Procedural Noise

NASA Astrophysics Data System (ADS)

Groeneboom, N. E.; Dahle, H.

2014-03-01

We developed a novel approach for fast and accurate ray-tracing of galaxies using procedural noise fields. Our method allows for efficient and realistic rendering of synthetic galaxy morphologies, where individual components such as the bulge, disk, stars, and dust can be synthesized in different wavelengths. These components follow empirically motivated overall intensity profiles but contain an additional procedural noise component that gives rise to complex natural patterns that mimic interstellar dust and star-forming regions. These patterns produce more realistic-looking galaxy images than using analytical expressions alone. The method is fully parallelized and creates accurate high- and low- resolution images that can be used, for example, in codes simulating strong and weak gravitational lensing. In addition to having a user-friendly graphical user interface, the C++ software package GAMER is easy to implement into an existing code.

A treecode to simulate dust-plasma interactions

NASA Astrophysics Data System (ADS)

Thomas, D. M.; Holgate, J. T.

2017-02-01

The interaction of a small object with surrounding plasma is an area of plasma-physics research with a multitude of applications. This paper introduces the plasma octree code pot, a microscopic simulator of a spheroidal dust grain in a plasma. pot uses the Barnes-Hut treecode algorithm to perform N-body simulations of electrons and ions in the vicinity of a chargeable spheroid, employing also the Boris particle-motion integrator and Hutchinson’s reinjection algorithm from SCEPTIC; a description of the implementation of all three algorithms is provided. We present results from pot simulations of the charging of spheres in magnetised plasmas, and of spheroids in unmagnetized plasmas. The results call into question the validity of using the Boltzmann relation in hybrid PIC codes. Substantial portions of this paper are adapted from chapters 4 and 5 of the first author’s recent PhD dissertation.

Thermodynamics and Charging of Interstellar Iron Nanoparticles

NASA Astrophysics Data System (ADS)

Hensley, Brandon S.; Draine, B. T.

2017-01-01

Interstellar iron in the form of metallic iron nanoparticles may constitute a component of the interstellar dust. We compute the stability of iron nanoparticles to sublimation in the interstellar radiation field, finding that iron clusters can persist down to a radius of ≃4.5 Å, and perhaps smaller. We employ laboratory data on small iron clusters to compute the photoelectric yields as a function of grain size and the resulting grain charge distribution in various interstellar environments, finding that iron nanoparticles can acquire negative charges, particularly in regions with high gas temperatures and ionization fractions. If ≳10% of the interstellar iron is in the form of ultrasmall iron clusters, the photoelectric heating rate from dust may be increased by up to tens of percent relative to dust models with only carbonaceous and silicate grains.

Brominated and organophosphate flame retardants in indoor dust of Jeddah, Kingdom of Saudi Arabia: Implications for human exposure.

PubMed

Ali, Nadeem; Eqani, Syed Ali Musstjab Akber Shah; Ismail, Iqbal Mohammad Ibrahim; Malarvannan, Govindan; Kadi, Mohammad W; Albar, Hussain Mohammed Salem; Rehan, Mohammad; Covaci, Adrian

2016-11-01

Different flame retardants (FRs) namely polybrominated diphenyl ethers (PBDEs), emerging brominated/chlorinated flame retardants (Br/Cl FRs), and organophosphate FRs (OPFRs) were analyzed in cars, air conditioner (AC) filters and floor dust of different households from Jeddah, Kingdom of Saudi Arabia (KSA). To the best of our knowledge, this is first study in literature reporting emerging Br/Cl FRs and OPFRs in AC filter dust and also first to report on their occurrence in dust from KSA. Chlorinated alkyl phosphate, penta-BDEs, BDE-209, and decabromodiphenylethane (DBDPE) were the major chemicals in dust samples from all microenvironments. ΣOPFRs occurred at median concentrations (ng/g dust) of 15,400, 10,500, and 3750 in AC filter, car and house floor dust, respectively. For all analyzed chemicals, relatively lower levels were observed in floor dust than car and AC filter dust. The profiles of FRs in car dust were different from AC filter and floor dust, which reflected their wider application as FR and plasticizer in variety of household and commercial products. For toddlers, assuming high dust intake and 95th percentile concentrations, the computed exposure estimation for BDE-99 was higher than RfD values. Copyright © 2016 Elsevier B.V. All rights reserved.

Differential Ablation of Cosmic Dust and Implications for the Relative Abundances of Atmospheric Metals

NASA Astrophysics Data System (ADS)

McNeil, W. J.

1997-09-01

Metals in the Earth's atmosphere are of interest and importance for several reasons. Emission lines from the sodium layer are used for wave front corrections in imaging space objects. The ionospheric metals present background contamination for remote sensing and tracking of space- born objects. Ionization during meteor showers may also interfere with communications. Although it is generally accepted that extraterrestrial material is the source of metals in the atmospheric, the relative abundances of mesospheric metals and ions present us with a conundrum. Lidar observations have consistently shown that the abundances of neutral metals in the atmospheric and the abundances of these metals in the meteoric material that falls to earth are significantly disproportionate. For example, the column density of neutral sodium is perhaps two orders of magnitude larger than that of calcium, while the abundances in meteorites are approximately equal. To complicate matters further, ion mass spectroscopy has shown that the abundances of the meteoric ions match reasonably well those in the meteorites. We present here a model that attempts to address these discrepancies. At the heart of the model is the concept of differential ablation, which suggests that more volatile metals sublimate earlier in the descent of a cosmic dust particle than do the less volatile components. The modeling is carried out comprehensively, beginning with the heating and vaporization of the dust particles. The vaporization rate is computed as a function of altitude from an ensemble of particles to give a deposition function which is then injected into a fully time-dependent kinetic code which allows for vertical diffusion and includes diurnal dependence through both the models of the major atmospheric components and through transport of the ions due to electric fields.

Using RADMC-3D to model the radiative transfer of spectral lines in protoplanetary disks and envelopes

NASA Astrophysics Data System (ADS)

DeVries, John; Terebey, Susan

2018-06-01

Protoplanetary disks are the birthplaces of planets in our universe. Observations of these disks with radio telescopes like the Atacama Large Millimeter Array (ALMA) offer great insight into the star and planet formation process. Comparing theories of formation with observations requires tracing the energy transfer via electromagnetic radiation, known as radiative transfer. To determine the temperature distribution of circumstellar material, a Monte Carlo code (Whitney et al. [1]) was used to to perform the radiative transfer through dust. The goal of this research is to utilize RADMC-3D [2] to handle the spectral line radiative transfer computations. An existing model of a rotating ring was expanded to include emission from the C18O isotopologue of carbon monoxide using data from the Leiden Atomic and Molecular Database (LAMDA). This feature of our model compliments ALMA's ability to measure C18O line emission, a proxy for disk rotation. In addition to modeling gas in the protoplanetary disk, dust also plays an important role. The generic description of absorption and scattering for dust provided by RADMC-3D was changed in favor of a more physically-realistic description with OH5 grains. This description is more appropriate in high-density regions of the envelope around a protostar. Further improvements, such as consideration for the finite resolution of observations, have been implemented. The task at present is to compare our model with observations of protoplanetary systems like L1527. Some results of these comparisons will be presented.[1] Whitney et al. 2013, ApJS, 207:30[2] RADMC-3D: http://www.ita.uni-heidelberg.de/~dullemond/software/radmc-3d/

The Properties and Fate of the Galactic Center G2 Cloud

NASA Astrophysics Data System (ADS)

Shcherbakov, Roman V.

2014-03-01

The object G2 was recently discovered descending into the gravitational potential of the supermassive black hole (BH) Sgr A*. We test the photoionized cloud scenario, determine the cloud properties, and estimate the emission during the pericenter passage. The incident radiation is computed starting from the individual stars at the locations of G2. The radiative transfer calculations are conducted with CLOUDY code and 2011 broadband and line luminosities are fitted. The spherically symmetric, tidally distorted, and magnetically arrested cloud shapes are tested with both the interstellar medium dust and 10 nm graphite dust. The best-fitting magnetically arrested model has the initial density n init = 1.8 × 105 cm-3, initial radius R init = 2.2 × 1015 cm = 17 mas, mass m cloud = 4 M Earth, and dust relative abundance A = 0.072. It provides a good fit to 2011 data, is consistent with the luminosities in 2004 and 2008, and reaches an agreement with the observed size. We revise down the predicted radio and X-ray bow shock luminosities to be below the quiescent level of Sgr A*, which readily leads to non-detection in agreement to observations. The magnetic energy dissipation in the cloud at the pericenter coupled with more powerful irradiation may lead to an infrared source with an apparent magnitude m_{L^{\\prime }}\\approx 13.0. No shock into the cloud and no X-rays are expected from cloud squeezing by the ambient gas pressure. Larger than previously estimated cloud mass m cloud = (4-20) M Earth may produce a higher accretion rate and a brighter state of Sgr A* as the debris descend onto the BH.

3D dust clouds (Yukawa Balls) in strongly coupled dusty plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Melzer, A.; Passvogel, M.; Miksch, T.

2010-06-16

Three-dimensional finite systems of charged dust particles confined to concentric spherical shells in a dusty plasma, so-called 'Yukawa balls', have been studied with respect to their static and dynamic properties. Here, we review the charging of particles in a dusty plasma discharge by computer simulations and the respective particle arrangements. The normal mode spectrum of Yukawa balls is measured from the 3D thermal Brownian motion of the dust particles around their equilibrium positions.

Airborne Sunphotometer, Airborne in-situ, Space-borne, and Ground-Based Measurements of Troposoheric Aerosol in Ace-2

NASA Technical Reports Server (NTRS)

Schmid, Beat; Collins, D.; Gasso, S.; Ostrom, E.; Powell, D.; Welton, E.; Durkee, P.; Livingstron, J.; Russell, P.; Flagan, R.;

Dust Cloud Modeling and Propagation Effects for Radar and Communications Codes

DTIC Science & Technology

1978-11-01

particles can be described by a power law probabi 1it Y d i st r i ut i on with a power exponent of 4. Four is a typical value for dust particlIs from...loose unconsolidated soils such as desert alluviun, blust ,eera ted from a nuclear cratering explosion in rock and cohes ive soil s haN pO,,e r exponent ...da p = power law exponent amin = minimum particle diameter in the distribution (cm) a = maximum particle diameter in the distribution (cm).max The log

Protoplanetary Disks and Planet Formation a Computational Perspective

NASA Astrophysics Data System (ADS)

Backus, Isaac

In this thesis I present my research on the early stages of planet formation. Using advanced computational modeling techniques, I study global gas and gravitational dynamics in proto- planetary disks (PPDs) on length scales from the radius of Jupiter to the size of the solar system. In that environment, I investigate the formation of gas giants and the migration, enhancement, and distribution of small solids--the precursors to planetesimals and gas giant cores. I examine numerical techniques used in planet formation and PPD modeling, especially methods for generating initial conditions (ICs) in these unstable, chaotic systems. Disk simulation outcomes may depend strongly on ICs, which may explain results in the literature. I present the largest suite of high resolution PPD simulations to-date and argue that direct fragmentations of PPDs around M-Dwarfs is a plausible path to rapidly forming gas giants. I implement dust physics to track the migration of centimeter and smaller dust grains in very high resolution PPD simulations. While current dust methods are slow, with strict resolution and/or time-stepping requirements, and have some serious numerical issues, we can still demonstrate that dust does not concentrate at the pressure maxima of spiral arms, an indication that spiral features observed in the dust component are at least as well resolved in the gas. Additionally, coherent spiral arms do not limit dust settling. We suggest a novel mechanism for disk fragmentation at large radii driven by dust accretion from the surrounding nebula. We also investigate self induced dust traps, a mechanism which may help explain the growth of solids beyond meter sizes. We argue that current apparent demonstrations of this mechanism may be due to numerical artifacts and require further investigation.

Remote sensing of dust in the Solar system and beyond using wavelength dependence of polarization

NASA Astrophysics Data System (ADS)

Kolokolova, L.

2011-12-01

For a long time, the main polarimetric tool to study dust in the Solar system has been the dependence of polarization on phase (scattering) angle. Surprisingly, a variety of cosmic dusts (interplanetary and cometary dust, dust on the surfaces of asteroids and in debris disks) possesses a very similar phase dependence of polarization with a negative bowl-shaped part at small phase angles and a positive bell-shaped region with maximum polarization around 95-105 deg. Numerous laboratory and theoretical simulations showed that a polarimetric phase curve of this shape is typical for fluffy materials, e.g., porous, aggregated particles. By contrast, the wavelength dependence of polarization is different for different types of dust. In the visual, polarization decreases with wavelength (negative gradient) for asteroids and interplanetary dust, but usually increases with wavelength (positive gradient) for cometary dust. In debris disks both signs of the spectral gradient of polarization have been found. Moreover, it was found that a cometary positive spectral gradient can change to a negative one as observations move to longer (near-infrared) wavelengths (Kelley et al. AJ, 127, 2398, 2004) and some comets(Kiselev et al. JQSRT, 109, 1384, 2008) have negative gradient even in the visible. The diversity of the spectral dependence of polarization therefore gives us hope that it can be used for characterization of the aggregates that represent different types of cosmic dust. To accomplish this, the physics behind the spectral dependence of polarization need to be revealed. Our recent study shows that the spectral dependence of polarization depends on the strength of electromagnetic interaction between the monomers in aggregates. The strength of the interaction mainly depends on how many monomers the electromagnetic wave covers on the light path equal to one wavelength. Since the electromagnetic interaction depolarizes the light, the more particles a single wavelength covers the smaller is the polarization of the scattered light. Thus, at a given monomer size the polarization decreases as wavelength increases resulting in the negative spectral gradient of polarization. However, this tendency occurs only for rather compact aggregates. For porous particles, an increase of wavelength may not increase the number of the covered monomers. In this case, polarization increases with wavelength as a result of decreasing monomer's size parameter. We performed computer modeling of light scattering by aggregates of different porosity using MSTM (multisphere T-matrix) code by D. Mackowski (see http://eng.auburn.edu/users/dmckwski/scatcodes/). The results show that for each porosity a critical wavelength exists at which the spectral gradient of polarization changes from positive to negative. The electromagnetic interaction is also stronger for more transparent materials which in turn affects the value of the critical wavelength. Thus, measurements of polarization over a broad range of wavelength can be a powerful tool to study the porosity and composition of dust in a variety of cosmic environments, especially when detailed phase dependence of polarization cannot be established (e.g. for TNO and other distant objects).

Remote sensing of mineral dust aerosol using AERI during the UAE2: A modeling and sensitivity study

NASA Astrophysics Data System (ADS)

Hansell, R. A.; Liou, K. N.; Ou, S. C.; Tsay, S. C.; Ji, Q.; Reid, J. S.

2008-09-01

Numerical simulations and sensitivity studies have been performed to assess the potential for using brightness temperature spectra from a ground-based Atmospheric Emitted Radiance Interferometer (AERI) during the United Arab Emirates Unified Aerosol Experiment (UAE2) for detecting/retrieving mineral dust aerosol. A methodology for separating dust from clouds and retrieving the dust IR optical depths was developed by exploiting differences between their spectral absorptive powers in prescribed thermal IR window subbands. Dust microphysical models were constructed using in situ data from the UAE2 and prior field studies while composition was modeled using refractive index data sets for minerals commonly observed around the UAE region including quartz, kaolinite, and calcium carbonate. The T-matrix, finite difference time domain (FDTD), and Lorenz-Mie light scattering programs were employed to calculate the single scattering properties for three dust shapes: oblate spheroids, hexagonal plates, and spheres. We used the Code for High-resolution Accelerated Radiative Transfer with Scattering (CHARTS) radiative transfer program to investigate sensitivity of the modeled AERI spectra to key dust and atmospheric parameters. Sensitivity studies show that characterization of the thermodynamic boundary layer is crucial for accurate AERI dust detection/retrieval. Furthermore, AERI sensitivity to dust optical depth is manifested in the strong subband slope dependence of the window region. Two daytime UAE2 cases were examined to demonstrate the present detection/retrieval technique, and we show that the results compare reasonably well to collocated AERONET Sun photometer/MPLNET micropulse lidar measurements. Finally, sensitivity of the developed methodology to the AERI's estimated MgCdTe detector nonlinearity was evaluated.

Dust-concentration measurement based on Mie scattering of a laser beam

PubMed Central

Yu, Xiaoyu; Shi, Yunbo; Wang, Tian; Sun, Xu

2017-01-01

To realize automatic measurement of the concentration of dust particles in the air, a theory for dust concentration measurement was developed, and a system was designed to implement the dust concentration measurement method based on laser scattering. In the study, the principle of dust concentration detection using laser scattering is studied, and the detection basis of Mie scattering theory is determined. Through simulation, the influence of the incident laser wavelength, dust particle diameter, and refractive index of dust particles on the scattered light intensity distribution are obtained for determining the scattered light intensity curves of single suspended dust particles under different characteristic parameters. A genetic algorithm was used to study the inverse particle size distribution, and the reliability of the measurement system design is proven theoretically. The dust concentration detection system, which includes a laser system, computer circuitry, air flow system, and control system, was then implemented according to the parameters obtained from the theoretical analysis. The performance of the designed system was evaluated. Experimental results show that the system performance was stable and reliable, resulting in high-precision automatic dust concentration measurement with strong anti-interference ability. PMID:28767662

Results of comparative RBMK neutron computation using VNIIEF codes (cell computation, 3D statics, 3D kinetics). Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grebennikov, A.N.; Zhitnik, A.K.; Zvenigorodskaya, O.A.

1995-12-31

In conformity with the protocol of the Workshop under Contract {open_quotes}Assessment of RBMK reactor safety using modern Western Codes{close_quotes} VNIIEF performed a neutronics computation series to compare western and VNIIEF codes and assess whether VNIIEF codes are suitable for RBMK type reactor safety assessment computation. The work was carried out in close collaboration with M.I. Rozhdestvensky and L.M. Podlazov, NIKIET employees. The effort involved: (1) cell computations with the WIMS, EKRAN codes (improved modification of the LOMA code) and the S-90 code (VNIIEF Monte Carlo). Cell, polycell, burnup computation; (2) 3D computation of static states with the KORAT-3D and NEUmore » codes and comparison with results of computation with the NESTLE code (USA). The computations were performed in the geometry and using the neutron constants presented by the American party; (3) 3D computation of neutron kinetics with the KORAT-3D and NEU codes. These computations were performed in two formulations, both being developed in collaboration with NIKIET. Formulation of the first problem maximally possibly agrees with one of NESTLE problems and imitates gas bubble travel through a core. The second problem is a model of the RBMK as a whole with imitation of control and protection system controls (CPS) movement in a core.« less

A New 3D Multi-fluid Dust Model: A Study of the Effects of Activity and Nucleus Rotation on Dust Grain Behavior at Comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Shou, Y.; Combi, M.; Toth, G.; Tenishev, V.; Fougere, N.; Jia, X.; Rubin, M.; Huang, Z.; Hansen, K.; Gombosi, T.

2017-11-01

Improving our capability to interpret observations of cometary dust is necessary to deepen our understanding of the role of dust in the formation of comets and in altering the cometary environments. Models including dust grains are in demand to interpret observations and test hypotheses. Several existing models have taken into account the gas-dust interaction, varying sizes of dust grains and the cometary gravitational force. In this work, we develop a multi-fluid dust model based on the BATS-R-US code. This model not only incorporates key features of previous dust models, but also has the capability of simulating time-dependent phenomena. Since the model is run in the rotating comet reference frame, the centrifugal and Coriolis forces are included. The boundary conditions on the nucleus surface can be set according to the distribution of activity and the solar illumination. The Sun revolves around the comet in this frame. A newly developed numerical mesh is also used to resolve the real-shaped nucleus in the center and to facilitate prescription of the outer boundary conditions that accommodate the rotating frame. The inner part of the mesh is a box composed of Cartesian cells and the outer surface is a smooth sphere, with stretched cells filled in between the box and the sphere. Our model achieved comparable results to the Direct Simulation Monte Carlo method and the Rosetta/OSIRIS observations. It is also applied to study the effects of the rotating nucleus and the cometary activity and offers interpretations of some dust observations of comet 67P/Churyumov-Gerasimenko.

Modelling supernova line profile asymmetries to determine ejecta dust masses: SN 1987A from days 714 to 3604

NASA Astrophysics Data System (ADS)

Bevan, Antonia; Barlow, M. J.

2016-02-01

The late-time optical and near-IR line profiles of many core-collapse supernovae exhibit a red-blue asymmetry as a result of greater extinction by internal dust of radiation emitted from the receding parts of the supernova ejecta. We present here a new code, DAMOCLES, that models the effects of dust on the line profiles of core-collapse supernovae in order to determine newly formed dust masses. We find that late-time dust-affected line profiles may exhibit an extended red scattering wing (as noted by Lucy et al. 1989) and that they need not be flux-biased towards the blue, although the profile peak will always be blueshifted. We have collated optical spectra of SN 1987A from a variety of archival sources and have modelled the Hα line from days 714 to 3604 and the [O I] 6300,6363 Å doublet between days 714 and 1478. Our line profile fits rule out day 714 dust masses >3 × 10-3 M⊙ for all grain types apart from pure magnesium silicates, for which no more than 0.07 M⊙ can be accommodated. Large grain radii ( ≥ 0.6 μm) are generally required to fit the line profiles even at the earlier epochs. We find that a large dust mass (≥0.1 M⊙) had formed by day 3604 and infer that the majority of the present dust mass must have formed after this epoch. Our findings agree with recent estimates from spectral energy distribution fits for the dust mass evolution of SN 1987A and support the inference that the majority of SN 1987A's dust formed many years after the initial explosion.

GAMA/G10-COSMOS/3D-HST: the 0 < z < 5 cosmic star formation history, stellar-mass, and dust-mass densities

NASA Astrophysics Data System (ADS)

Driver, Simon P.; Andrews, Stephen K.; da Cunha, Elisabete; Davies, Luke J.; Lagos, Claudia; Robotham, Aaron S. G.; Vinsen, Kevin; Wright, Angus H.; Alpaslan, Mehmet; Bland-Hawthorn, Joss; Bourne, Nathan; Brough, Sarah; Bremer, Malcolm N.; Cluver, Michelle; Colless, Matthew; Conselice, Christopher J.; Dunne, Loretta; Eales, Steve A.; Gomez, Haley; Holwerda, Benne; Hopkins, Andrew M.; Kafle, Prajwal R.; Kelvin, Lee S.; Loveday, Jon; Liske, Jochen; Maddox, Steve J.; Phillipps, Steven; Pimbblet, Kevin; Rowlands, Kate; Sansom, Anne E.; Taylor, Edward; Wang, Lingyu; Wilkins, Stephen M.

2018-04-01

We use the energy-balance code MAGPHYS to determine stellar and dust masses, and dust corrected star formation rates for over 200 000 GAMA galaxies, 170 000 G10-COSMOS galaxies, and 200 000 3D-HST galaxies. Our values agree well with previously reported measurements and constitute a representative and homogeneous data set spanning a broad range in stellar-mass (108-1012 M⊙), dust-mass (106-109 M⊙), and star formation rates (0.01-100 M⊙yr-1), and over a broad redshift range (0.0 < z < 5.0). We combine these data to measure the cosmic star formation history (CSFH), the stellar-mass density (SMD), and the dust-mass density (DMD) over a 12 Gyr timeline. The data mostly agree with previous estimates, where they exist, and provide a quasi-homogeneous data set using consistent mass and star formation estimators with consistent underlying assumptions over the full time range. As a consequence our formal errors are significantly reduced when compared to the historic literature. Integrating our CSFH we precisely reproduce the SMD with an interstellar medium replenishment factor of 0.50 ± 0.07, consistent with our choice of Chabrier initial mass function plus some modest amount of stripped stellar mass. Exploring the cosmic dust density evolution, we find a gradual increase in dust density with lookback time. We build a simple phenomenological model from the CSFH to account for the dust-mass evolution, and infer two key conclusions: (1) For every unit of stellar mass which is formed 0.0065-0.004 units of dust mass is also formed. (2) Over the history of the Universe approximately 90-95 per cent of all dust formed has been destroyed and/or ejected.

Scattering Properties of Large Irregular Cosmic Dust Particles at Visible Wavelengths

DOE Office of Scientific and Technical Information (OSTI.GOV)

Escobar-Cerezo, J.; Palmer, C.; Muñoz, O.

The effect of internal inhomogeneities and surface roughness on the scattering behavior of large cosmic dust particles is studied by comparing model simulations with laboratory measurements. The present work shows the results of an attempt to model a dust sample measured in the laboratory with simulations performed by a ray-optics model code. We consider this dust sample as a good analogue for interplanetary and interstellar dust as it shares its refractive index with known materials in these media. Several sensitivity tests have been performed for both structural cases (internal inclusions and surface roughness). Three different samples have been selected tomore » mimic inclusion/coating inhomogeneities: two measured scattering matrices of hematite and white clay, and a simulated matrix for water ice. These three matrices are selected to cover a wide range of imaginary refractive indices. The selection of these materials also seeks to study astrophysical environments of interest such as Mars, where hematite and clays have been detected, and comets. Based on the results of the sensitivity tests shown in this work, we perform calculations for a size distribution of a silicate-type host particle model with inclusions and surface roughness to reproduce the experimental measurements of a dust sample. The model fits the measurements quite well, proving that surface roughness and internal structure play a role in the scattering pattern of irregular cosmic dust particles.« less

Very Large Telescope Interferometer observations of the dust geometry around R Coronae Borealis stars

NASA Astrophysics Data System (ADS)

Bright, S. N.; Chesneau, O.; Clayton, G. C.; De Marco, O.; Leão, I. C.; Nordhaus, J.; Gallagher, J. S.

2011-06-01

We are investigating the formation and evolution of dust around the hydrogen-deficient supergiants known as R Coronae Borealis (RCB) stars. We aim to determine the connection between the probable merger past of these stars and their current dust-production activities. We carried out high angular resolution interferometric observations of three RCB stars, namely RY Sgr, V CrA and V854 Cen, with the mid-infrared interferometer (MIDI) on the Very Large Telescope Interferometer (VLTI), using two telescope pairs. The baselines ranged from 30 to 60 m, allowing us to probe the dusty environment at very small spatial scales (˜50 mas or 400R★). The observations of the RCB star dust environments were interpreted using both geometrical models and one-dimensional radiative transfer codes. From our analysis, we find that asymmetric circumstellar material is apparent in RY Sgr, may also exist in V CrA and is possible for V854 Cen. Overall, we find that our observations are consistent with dust forming in clumps ejected randomly around the RCB star so that over time they create a spherically symmetric distribution of dust. However, we conclude that the determination of whether there is a preferred plane of dust ejection must wait until a time series of observations are obtained. Based on observations made with the Very Large Telescope Interferometer at Paranal Observatory under programme 079.D-0415.

Determining the forsterite abundance of the dust around asymptotic giant branch stars

NASA Astrophysics Data System (ADS)

de Vries, B. L.; Min, M.; Waters, L. B. F. M.; Blommaert, J. A. D. L.; Kemper, F.

2010-06-01

Aims: We present a diagnostic tool to determine the abundance of the crystalline silicate forsterite in AGB stars surrounded by a thick shell of silicate dust. Using six infrared spectra of high mass-loss oxygen rich AGB stars we obtain the forsterite abundance of their dust shells. Methods: We use a monte carlo radiative transfer code to calculate infrared spectra of dust enshrouded AGB stars. We vary the dust composition, mass-loss rate and outer radius. We focus on the strength of the 11.3 and the 33.6 μm forsterite bands, that probe the most recent (11.3 μm) and older (33.6 μm) mass-loss history of the star. Simple diagnostic diagrams are derived, allowing direct comparison to observed band strengths. Results: Our analysis shows that the 11.3 μm forsterite band is a robust indicator for the forsterite abundance of the current mass-loss period for AGB stars with an optically thick dust shell. The 33.6 μm band of forsterite is sensitive to changes in the density and the geometry of the emitting dust shell, and so a less robust indicator. Applying our method to six high mass-loss rate AGB stars shows that AGB stars can have forsterite abundances of 12% by mass and higher, which is more than the previously found maximum abundance of 5%.

Weapon Physicist Declassifies Rescued Nuclear Test Films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spriggs, Greg; Moye, Jim

2017-03-15

The U.S. conducted 210 atmospheric nuclear tests between 1945 and 1962, with multiple cameras capturing each event at around 2,400 frames per second. But in the decades since, around 10,000 of these films sat idle, scattered across the country in high-security vaults. Not only were they gathering dust, the film material itself was slowly decomposing, bringing the data they contained to the brink of being lost forever. For the past five years, Lawrence Livermore National Laboratory (LLNL) weapon physicist Greg Spriggs and a crack team of film experts, archivists and software developers have been on a mission to hunt down,more » scan, reanalyze and declassify these decomposing films. The goals are to preserve the films’ content before it’s lost forever, and provide better data to the post-testing-era scientists who use computer codes to help certify that the aging U.S. nuclear deterrent remains safe, secure and effective.« less

Spherically symmetric cosmological spacetimes with dust and radiation — numerical implementation

NASA Astrophysics Data System (ADS)

Lim, Woei Chet; Regis, Marco; Clarkson, Chris

2013-10-01

We present new numerical cosmological solutions of the Einstein Field Equations. The spacetime is spherically symmetric with a source of dust and radiation approximated as a perfect fluid. The dust and radiation are necessarily non-comoving due to the inhomogeneity of the spacetime. Such a model can be used to investigate non-linear general relativistic effects present during decoupling or big-bang nucleosynthesis, as well as for investigating void models of dark energy with isocurvature degrees of freedom. We describe the full evolution of the spacetime as well as the redshift and luminosity distance for a central observer. After demonstrating accuracy of the code, we consider a few example models, and demonstrate the sensitivity of the late time model to the degree of inhomogeneity of the initial radiation contrast.

Helmet-Cam: tool for assessing miners’ respirable dust exposure

PubMed Central

Cecala, A.B.; Reed, W.R.; Joy, G.J.; Westmoreland, S.C.; O’Brien, A.D.

2015-01-01

Video technology coupled with datalogging exposure monitors have been used to evaluate worker exposure to different types of contaminants. However, previous application of this technology used a stationary video camera to record the worker’s activity while the worker wore some type of contaminant monitor. These techniques are not applicable to mobile workers in the mining industry because of their need to move around the operation while performing their duties. The Helmet-Cam is a recently developed exposure assessment tool that integrates a person-wearable video recorder with a datalogging dust monitor. These are worn by the miner in a backpack, safety belt or safety vest to identify areas or job tasks of elevated exposure. After a miner performs his or her job while wearing the unit, the video and dust exposure data files are downloaded to a computer and then merged together through a NIOSH-developed computer software program called Enhanced Video Analysis of Dust Exposure (EVADE). By providing synchronized playback of the merged video footage and dust exposure data, the EVADE software allows for the assessment and identification of key work areas and processes, as well as work tasks that significantly impact a worker’s personal respirable dust exposure. The Helmet-Cam technology has been tested at a number of metal/nonmetal mining operations and has proven to be a valuable assessment tool. Mining companies wishing to use this technique can purchase a commercially available video camera and an instantaneous dust monitor to obtain the necessary data, and the NIOSH-developed EVADE software will be available for download at no cost on the NIOSH website. PMID:26380529

Dust to planetesimals - Settling and coagulation in the solar nebula

NASA Technical Reports Server (NTRS)

Weidenschilling, S. J.

1980-01-01

The behavior of solid particles in a low-mass solar nebula during settling to the central plane and the formation of planetesimals is discussed. The gravitational instability in a dust layer and collisional accretion are examined as possible mechanisms of planetesimal formation. The shear between the gas and a dust layer is considered along with the differences in the planetesimal formation mechanisms between the inner and outer nebula. A numerical model for computing simultaneous coagulation and settling is described.

Adhesive Contact Sweeper

NASA Technical Reports Server (NTRS)

Patterson, Jonathan D.

1993-01-01

Adhesive contact sweeper removes hair and particles vacuum cleaner leaves behind, without stirring up dust. Also cleans loose rugs. Sweeper holds commercially available spools of inverted adhesive tape. Suitable for use in environments in which air kept free of dust; optics laboratories, computer rooms, and areas inhabited by people allergic to dust. For carpets, best used in tandem with vacuum cleaner; first pass with vacuum cleaner removes coarse particles, and second pass with sweeper extracts fine particles. This practice extends useful life of adhesive spools.

The Far-Infrared Spectrum of ARP 220

DTIC Science & Technology

2004-05-27

parameters that have been allowed to vary in our models of the ER are the dust temperature Td , the diameter d (within the range 500–800 pc), and the...the silicate absorption observed in S99. The nuclei account for the required flux at 24.5 and 1300 m with Td 106 K, significantly warmer than the...dust opacity; is again fixed to 2, and the dust temperature Td (shown in the insert panel of Fig. 5b) has been computed from the requirement that the

Cosmic dust-ion-acoustic waves, spherical modified Kadomtsev-Petviashvili model, and symbolic computation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao Yitian; Tian Bo; State Key Laboratory of Software Development Environment, Beijing University of Aeronautics and Astronautics, Beijing 100083

2006-11-15

The spherical modified Kadomtsev-Petviashvili (smKP) model is hereby derived with symbolic computation for the dust-ion-acoustic waves with zenith-angle perturbation in a cosmic dusty plasma. Formation and properties of both dark and bright smKP nebulons are obtained and discussed. The relevance of those smKP nebulons to the supernova shells and Saturn's F-ring is pointed out, and possibly observable nebulonic effects for the future cosmic plasma experiments are proposed. The difference of the smKP nebulons from other types of nebulons is also analyzed.

Development and application of the GIM code for the Cyber 203 computer

NASA Technical Reports Server (NTRS)

Stainaker, J. F.; Robinson, M. A.; Rawlinson, E. G.; Anderson, P. G.; Mayne, A. W.; Spradley, L. W.

1982-01-01

The GIM computer code for fluid dynamics research was developed. Enhancement of the computer code, implicit algorithm development, turbulence model implementation, chemistry model development, interactive input module coding and wing/body flowfield computation are described. The GIM quasi-parabolic code development was completed, and the code used to compute a number of example cases. Turbulence models, algebraic and differential equations, were added to the basic viscous code. An equilibrium reacting chemistry model and implicit finite difference scheme were also added. Development was completed on the interactive module for generating the input data for GIM. Solutions for inviscid hypersonic flow over a wing/body configuration are also presented.

Dynamical Modeling of Comet Dust: The STARDUST and ROSETTA Mission Targets

NASA Astrophysics Data System (ADS)

Kelley, M. S.; Reach, W. T.

2003-12-01

Comets 81P/Wild 2 and 67P/Churyumov-Gerasimenko are the respective targets for the NASA STARDUST and ESA ROSETTA missions. As such, the dust environment of each comet is of particular importance, simultaneously being a key to mission success (e.g. dust collection) and a possible spacecraft hazard (impacts with large particles). We present dynamical modeling of the comae and dust trails of comets 81P/Wild 2 and 67P/Churyumov-Gerasimenko and compare these models to ground-based observations. At the heart of our code is the 15th order integrator described by Everhart (1985, IAU Colloq. 83, 185-202). We integrate the radiation and gravitational forces acting on a dust particle due to the Sun and planets to determine a released particle's position relative to the parent comet at the time of an observation (either by telescope or spacecraft). Comparing zero ejection velocity syndyne curves to observations we obtain a first order estimate of the dust trail particle sizes, which typically range near the millimeter sizes or larger. If we input best guesses for ejection velocities, sizes, and emission histories into a Monte-Carlo integration we can simulate a coma and provide a particle size distribution estimate for various spacecraft impact parameters on large scales.

Differences in the Gas and Dust Distribution in the Transitional Disk of a Sun-like Young Star, PDS 70

NASA Astrophysics Data System (ADS)

Long, Zachary C.; Akiyama, Eiji; Sitko, Michael; Fernandes, Rachel B.; Assani, Korash; Grady, Carol A.; Cure, Michel; Danchi, William C.; Dong, Ruobing; Fukagawa, Misato; Hasegawa, Yasuhiro; Hashimoto, Jun; Henning, Thomas; Inutsuka, Shu-Ichiro; Kraus, Stefan; Kwon, Jungmi; Lisse, Carey M.; Baobabu Liu, Hauyu; Mayama, Satoshi; Muto, Takayuki; Nakagawa, Takao; Takami, Michihiro; Tamura, Motohide; Currie, Thayne; Wisniewski, John P.; Yang, Yi

2018-05-01

We present ALMA 0.87 mm continuum, HCO+ J = 4–3 emission line, and CO J = 3–2 emission line data of the disk of material around the young, Sun-like star PDS 70. These data reveal the existence of a possible two-component transitional disk system with a radial dust gap of 0.″42 ± 0.″05, an azimuthal gap in the HCO+ J = 4–3 moment zero map, as well as two bridge-like features in the gas data. Interestingly these features in the gas disk have no analog in the dust disk making them of particular interest. We modeled the dust disk using the Monte Carlo radiative transfer code HOCHUNK3D using a two-disk component. We find that there is a radial gap that extends from 15 to 60 au in all grain sizes, which differs from previous work.

Local geological dust in the area of Rome (Italy): linking mineral composition, size distribution and optical properties to radiative transfer modelling

NASA Astrophysics Data System (ADS)

Pietrodangelo, Adriana; Salzano, Roberto; Bassani, Cristiana; Pareti, Salvatore; Perrino, Cinzia

2015-04-01

Airborne mineral dust plays a key role in the energy balance of the Earth - atmosphere coupled system. The microphysical and optical properties of dust drive the direct radiative effects and are in turn influenced by the dust mineralogical composition. The latter varies largely, depending on the geology of the source region. Knowledge gaps still exist about relationships between the scattering and absorption of solar and terrestrial radiation by mineral dust and its mineralogical, size distribution and particle morphology features; this also affects the reliability of radiative transfer (RT) modelling estimates (Hansell et al., 2011). In this study, these relationships were investigated focusing on the crustal suspended PM10 dust, sourced from outcropping rocks of the local geological domains around Rome (Latium, Italy). The mineral composition variability of the Latium rocks ranges from the silicate-dominated (volcanics domain) to the calcite-dominated (travertine), through lithological materials composed in different proportions by silicates, silica and calcite, mainly (limestone series, siliciclastic series) (Cosentino et al., 2009). This peculiarity of the Latium region was thus exploited to investigate the behavior of the size distribution, optical properties and radiative transfer at BOA (Bottom Of Atmosphere) of the suspended dust PM10 fraction with the variability of mineral composition. Elemental source profiles of the same dust samples were previously determined (Pietrodangelo et al., 2013). A multi-faceted analysis was performed, and outcomes from the following approaches were merged: individual-particle scanning electron microscopy combined with X-ray energy-dispersive microanalysis (SEM XEDS), bulk mineralogical analysis by X-ray diffraction (XRD), size distribution fit of the individual-particle data set and modelling of the dust optical and radiative properties. To this aim, the 6SV atmospheric radiative transfer code (Kotchenova et al., 2008; Vermote et al., 1997) was employed, which computes aerosol optical properties (single-scattering albedo, asymmetry parameter, extinction coefficient, scattering coefficient, phase function) by the Mie Theory, and simulates the downward flux at BOA (FdBOA) by solving the radiative transfer equation. Conditions of dryness and of spherical particle shape were applied to all parts of this work. The size distribution fitting to the log-normal function appears unimodal, both for the volcanics and travertine domains, the first showing coarser mode than the latter. Volume distributions of quartz, feldspar, kaolinite and calcite fall in the coarse fraction, showing maximum around 5µm (aerodynamic diameter); differences in the curve height suggest particle density variety among mineral species. The single-scattering albedo highlights the weak absorption of travertine, with respect to volcanics, along the visible and Near-InfraRed (NIR) spectral domain. The asymmetry parameter indicates that the volcanics dust appears composed by particles with highly forward scattering, mainly in the Near-InfraRed (NIR) spectral domain, while the travertine shows more isotropic particles. Finally, both volcanics and travertine dusts leave the direct component of FdBOA unchanged, while the diffuse component depends strongly on the mineral composition. Hansell, R.A., et al. (2011), Atmos. Chem. Phys. Cosentino, D., et al. (2009), Quaternary Research Pietrodangelo, A., et al. (2013), Atmos. Env. Kotchenova, S.Y., et al. (2008), Appl. Optics Vermote, E.F., et al. (1997), IEEE Trans. Geosci. Remote Sens.

Retrieving cloud, dust and ozone abundances in the Martian atmosphere using SPICAM/UV nadir spectra

NASA Astrophysics Data System (ADS)

Willame, Y.; Vandaele, A. C.; Depiesse, C.; Lefèvre, F.; Letocart, V.; Gillotay, D.; Montmessin, F.

2017-08-01

We present the retrieval algorithm developed to analyse nadir spectra from SPICAM/UV aboard Mars-Express. The purpose is to retrieve simultaneously several parameters of the Martian atmosphere and surface: the dust optical depth, the ozone total column, the cloud opacity and the surface albedo. The retrieval code couples the use of an existing complete radiative transfer code, an inversion method and a cloud detection algorithm. We describe the working principle of our algorithm and the parametrisation used to model the required absorption, scattering and reflection processes of the solar UV radiation that occur in the Martian atmosphere and at its surface. The retrieval method has been applied on 4 Martian years of SPICAM/UV data to obtain climatologies of the different quantities under investigation. An overview of the climatology is given for each species showing their seasonal and spatial distributions. The results show a good qualitative agreement with previous observations. Quantitative comparisons of the retrieved dust optical depths indicate generally larger values than previous studies. Possible shortcomings in the dust modelling (altitude profile) have been identified and may be part of the reason for this difference. The ozone results are found to be influenced by the presence of clouds. Preliminary quantitative comparisons show that our retrieved ozone columns are consistent with other results when no ice clouds are present, and are larger for the cases with clouds at high latitude. Sensitivity tests have also been performed showing that the use of other a priori assumptions such as the altitude distribution or some scattering properties can have an important impact on the retrieval.

Modelling soil dust aerosol in the Bodélé depression during the BoDEx campaign

NASA Astrophysics Data System (ADS)

Tegen, I.; Heinold, B.; Todd, M.; Helmert, J.; Washington, R.; Dubovik, O.

2006-05-01

We present regional model simulations of the dust emission events during the Bodélé Dust Experiment (BoDEx) that was carried out in February and March 2005 in Chad. A box model version of the dust emission model is used to test different input parameters for the emission model, and to compare the dust emissions computed with observed wind speeds to those calculated with wind speeds from the regional model simulation. While field observations indicate that dust production occurs via self-abrasion of saltating diatomite flakes in the Bodélé, the emission model based on the assumption of dust production by saltation and using observed surface wind speeds as input parameters reproduces observed dust optical thicknesses well. Although the peak wind speeds in the regional model underestimate the highest wind speeds occurring on 10-12 March 2005, the spatio-temporal evolution of the dust cloud can be reasonably well reproduced by this model. Dust aerosol interacts with solar and thermal radiation in the regional model; it is responsible for a decrease in maximum daytime temperatures by about 5 K at the beginning the dust storm on 10 March 2005. This direct radiative effect of dust aerosol accounts for about half of the measured temperature decrease compared to conditions on 8 March. Results from a global dust model suggest that the dust from the Bodélé is an important contributor to dust crossing the African Savannah region towards the Gulf of Guinea and the equatorial Atlantic, where it can contribute up to 40% to the dust optical thickness.

Modelling soil dust aerosol in the Bodélé depression during the BoDEx campaign

NASA Astrophysics Data System (ADS)

Tegen, I.; Heinold, B.; Todd, M.; Helmert, J.; Washington, R.; Dubovik, O.

2006-09-01

We present regional model simulations of the dust emission events during the Bodélé Dust Experiment (BoDEx) that was carried out in February and March 2005 in Chad. A box model version of the dust emission model is used to test different input parameters for the emission model, and to compare the dust emissions computed with observed wind speeds to those calculated with wind speeds from the regional model simulation. While field observations indicate that dust production occurs via self-abrasion of saltating diatomite flakes in the Bodélé, the emission model based on the assumption of dust production by saltation and using observed surface wind speeds as input parameters reproduces observed dust optical thicknesses well. Although the peak wind speeds in the regional model underestimate the highest wind speeds occurring on 10-12 March 2005, the spatio-temporal evolution of the dust cloud can be reasonably well reproduced by this model. Dust aerosol interacts with solar and thermal radiation in the regional model; it is responsible for a decrease in maximum daytime temperatures by about 5 K at the beginning the dust storm on 10 March 2005. This direct radiative effect of dust aerosol accounts for about half of the measured temperature decrease compared to conditions on 8 March. Results from a global dust model suggest that the dust from the Bodélé is an important contributor to dust crossing the African Savannah region towards the Gulf of Guinea and the equatorial Atlantic, where it can contribute up to 40% to the dust optical thickness.

Parameterizing the interstellar dust temperature

NASA Astrophysics Data System (ADS)

Hocuk, S.; Szűcs, L.; Caselli, P.; Cazaux, S.; Spaans, M.; Esplugues, G. B.

2017-08-01

The temperature of interstellar dust particles is of great importance to astronomers. It plays a crucial role in the thermodynamics of interstellar clouds, because of the gas-dust collisional coupling. It is also a key parameter in astrochemical studies that governs the rate at which molecules form on dust. In 3D (magneto)hydrodynamic simulations often a simple expression for the dust temperature is adopted, because of computational constraints, while astrochemical modelers tend to keep the dust temperature constant over a large range of parameter space. Our aim is to provide an easy-to-use parametric expression for the dust temperature as a function of visual extinction (AV) and to shed light on the critical dependencies of the dust temperature on the grain composition. We obtain an expression for the dust temperature by semi-analytically solving the dust thermal balance for different types of grains and compare to a collection of recent observational measurements. We also explore the effect of ices on the dust temperature. Our results show that a mixed carbonaceous-silicate type dust with a high carbon volume fraction matches the observations best. We find that ice formation allows the dust to be warmer by up to 15% at high optical depths (AV> 20 mag) in the interstellar medium. Our parametric expression for the dust temperature is presented as Td = [ 11 + 5.7 × tanh(0.61 - log 10(AV) ]χuv1/5.9, where χuv is in units of the Draine (1978, ApJS, 36, 595) UV field.

THERMODYNAMICS AND CHARGING OF INTERSTELLAR IRON NANOPARTICLES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hensley, Brandon S.; Draine, B. T., E-mail: brandon.s.hensley@jpl.nasa.gov

Interstellar iron in the form of metallic iron nanoparticles may constitute a component of the interstellar dust. We compute the stability of iron nanoparticles to sublimation in the interstellar radiation field, finding that iron clusters can persist down to a radius of ≃4.5 Å, and perhaps smaller. We employ laboratory data on small iron clusters to compute the photoelectric yields as a function of grain size and the resulting grain charge distribution in various interstellar environments, finding that iron nanoparticles can acquire negative charges, particularly in regions with high gas temperatures and ionization fractions. If ≳10% of the interstellar ironmore » is in the form of ultrasmall iron clusters, the photoelectric heating rate from dust may be increased by up to tens of percent relative to dust models with only carbonaceous and silicate grains.« less

Catastrophic Disruption of Comet ISON

NASA Technical Reports Server (NTRS)

Keane, Jacqueline V.; Milam, Stefanie N.; Coulson, Iain M.; Kleyna, Jan T.; Sekanina, Zdenek; Kracht, Rainer; Riesen, Timm-Emmanuel; Meech, Karen J.; Charnley, Steven B.

2016-01-01

We report submillimeter 450 and 850 microns dust continuum observations for comet C/2012 S1 (ISON) obtained at heliocentric distances 0.31-0.08 au prior to perihelion on 2013 November 28 (rh?=?0.0125 au). These observations reveal a rapidly varying dust environment in which the dust emission was initially point-like. As ISON approached perihelion, the continuum emission became an elongated dust column spread out over as much as 60? (greater than 10(exp 5) km in the anti-solar direction. Deconvolution of the November 28.04 850 microns image reveals numerous distinct clumps consistent with the catastrophic disruption of comet ISON, producing approximately 5.2?×?10(exp 10) kg of submillimeter-sized dust. Orbital computations suggest that the SCUBA-2 emission peak coincides with the comet's residual nucleus.

Contamination Analysis Tools

NASA Technical Reports Server (NTRS)

Brieda, Lubos

2015-01-01

This talk presents 3 different tools developed recently for contamination analysis:HTML QCM analyzer: runs in a web browser, and allows for data analysis of QCM log filesJava RGA extractor: can load in multiple SRS.ana files and extract pressure vs. time dataC++ Contamination Simulation code: 3D particle tracing code for modeling transport of dust particulates and molecules. Uses residence time to determine if molecules stick. Particulates can be sampled from IEST-STD-1246 and be accelerated by aerodynamic forces.

Dust Emission Modeling Incorporating Land Cover Parameterizations in the Chihuahuan Desert and Dissemination of Data Suites

NASA Astrophysics Data System (ADS)

Olgin, J. G.; Pennington, D. D.; Webb, N.

2017-12-01

A variety of models have been developed to better understand dust emissions - from initial erosive event to entrainment to transport through the atmosphere. Many of these models have been used to analyze dust emissions by representing atmospheric and surface variables, such as wind and soil moisture respectively, in a numerical model to determine the resulting dust emissions. Pertinent to modeling these variables, there are three important factors influencing emissions: 1) Friction velocity threshold based on wind interactions with dust, 2) horizontal flux (saltation) of dust and 3) vertical dust flux. While all of the existing models incorporate these processes, additional improvements are needed to yield results reflective of recorded data of dust events. Our investigation focuses on explicitly identifying specific land cover (LC) elements unique to the Chihuahan desert that contribute to aerodynamic roughness length (Zo); a main component to dust emission and key to provide results more representative of known dust events in semi-arid regions. These elements will be formulated into computer model inputs by conducting analysis (e.g. geostatistics) on field and satellite data to ascertain core LC characteristics responsible for affecting wind velocities (e.g. wind shadowing effects), which are conducive to dust emissions. This inputs will be used in a modified program using the Weather and Research Forecast model (WRF) to replicate previously recorded dust events. Results from this study will be presented here.

FIREFLY (Fitting IteRativEly For Likelihood analYsis): a full spectral fitting code

NASA Astrophysics Data System (ADS)

Wilkinson, David M.; Maraston, Claudia; Goddard, Daniel; Thomas, Daniel; Parikh, Taniya

2017-12-01

We present a new spectral fitting code, FIREFLY, for deriving the stellar population properties of stellar systems. FIREFLY is a chi-squared minimization fitting code that fits combinations of single-burst stellar population models to spectroscopic data, following an iterative best-fitting process controlled by the Bayesian information criterion. No priors are applied, rather all solutions within a statistical cut are retained with their weight. Moreover, no additive or multiplicative polynomials are employed to adjust the spectral shape. This fitting freedom is envisaged in order to map out the effect of intrinsic spectral energy distribution degeneracies, such as age, metallicity, dust reddening on galaxy properties, and to quantify the effect of varying input model components on such properties. Dust attenuation is included using a new procedure, which was tested on Integral Field Spectroscopic data in a previous paper. The fitting method is extensively tested with a comprehensive suite of mock galaxies, real galaxies from the Sloan Digital Sky Survey and Milky Way globular clusters. We also assess the robustness of the derived properties as a function of signal-to-noise ratio (S/N) and adopted wavelength range. We show that FIREFLY is able to recover age, metallicity, stellar mass, and even the star formation history remarkably well down to an S/N ∼ 5, for moderately dusty systems. Code and results are publicly available.1

Cratering Studies in Thin Plastic Films

NASA Astrophysics Data System (ADS)

Shu, A. J.; Bugiel, S.; Gruen, E.; Horanyi, M.; Munsat, T. L.; Srama, R.

2014-12-01

Thin plastic films, such as Polyvinylidene Fluoride (PVDF), have been used as protective coatings or dust detectors on a number of missions including the Dust Counter and Mass Analyzer (DUCMA) instrument on Vega 1 and 2, the High Rate Detector (HRD) on the Cassini Mission, and the Student Dust Counter (SDC) on New Horizons. These types of detectors can be used on the lunar surface or in lunar orbit to detect dust grain size distributions and velocities. Due to their low power requirements and light weight, large surface area detectors can be built for observing low dust fluxes. The SDC dust detector is made up of a permanently polarized layer of PVDF coated on both sides with a thin layer (≈ 1000 Å) of aluminum nickel. The operation principle is that a micrometeorite impact removes a portion of the metal surface layer exposing the permanently polarized PVDF underneath. This causes a local potential near the crater changing the surface charge of the metal layer. The dimensions and shape of the crater determine the strength of the potential and thus the signal generated by the PVDF. The theoretical basis for signal interpretation uses a crater diameter scaling law which was not intended for use with PVDF. In this work, a crater size scaling law has been experimentally determined, and further simulation work is being done to enhance our understanding of the mechanisms of crater formation. LS-Dyna, a smoothed particle hydrodynamics (SPH) code from the Livermore Software Technology Corp. was chosen to simulate micrometeorite impacts. It is capable of incorporating key physics phenomena, including fracture, heat transfer, melting, etc. Furthermore, unlike Eulerian methods, SPH is gridless allowing large deformities without the inclusion of unphysical erosion algorithms. Material properties are accounted for using the Grüneisen Equation of State. The results of the SPH model can then be fed into electrostatic relaxation models to enhance the fidelity of interpretation of charge signals from a PVDF detector. An electrostatic relaxation code was also used to determine the theoretical charge produced by the PVDF detector given a crater of specific depth and diameter. Experimental results and preliminary simulation results and conclusions will be presented.

Smart Dust--Friend or Foe?

ERIC Educational Resources Information Center

Roman, Harry T.

2012-01-01

Nanotechnology is now making it possible to create radically new tiny machines and sensors on par with the size of dust motes. This technology is rapidly progressing and will make profound impacts on the nation's global competitiveness. It promises to be a most pervasive technological advance, comparable to what computers did for an individual's…

TORUS: Radiation transport and hydrodynamics code

NASA Astrophysics Data System (ADS)

Harries, Tim

2014-04-01

TORUS is a flexible radiation transfer and radiation-hydrodynamics code. The code has a basic infrastructure that includes the AMR mesh scheme that is used by several physics modules including atomic line transfer in a moving medium, molecular line transfer, photoionization, radiation hydrodynamics and radiative equilibrium. TORUS is useful for a variety of problems, including magnetospheric accretion onto T Tauri stars, spiral nebulae around Wolf-Rayet stars, discs around Herbig AeBe stars, structured winds of O supergiants and Raman-scattered line formation in symbiotic binaries, and dust emission and molecular line formation in star forming clusters. The code is written in Fortran 2003 and is compiled using a standard Gnu makefile. The code is parallelized using both MPI and OMP, and can use these parallel sections either separately or in a hybrid mode.

Closure on the single scattering albedo in the WRF-Chem framework using data from the MILAGRO campaign

NASA Astrophysics Data System (ADS)

Barnard, J. C.; Fast, J. D.; Paredes-Miranda, G.; Arnott, W. P.

2009-02-01

Data from the MILAGRO field campaign, which took place in the Mexico City Metropolitan Area (MCMA) during March 2006, is used to perform a closure experiment between aerosol chemical properties and aerosol optical properties. Measured aerosol chemical properties, obtained from the MILAGRO T1 site, are fed to two different "chemical to optical properties" modules. One module uses a sectional approach and is identical to that used in the WRF-Chem model, while the other is based on a modal approach. This modal code is employed as an independent check on the WRF-Chem module. Both modules compute aerosol optical properties and, in particular, the single-scattering albedo, ϖ0, as a function of time. The single-scattering albedos are compared to independent measurements obtained from a photoacoustic spectrometer (PAS). Because chemical measurements of the aerosol coarse mode were not available, and the inlet of the PAS could not ingest aerosols larger than about 2 to 3 μm, we focus here on the fine-mode ϖ0. At 870 nm, the wavelength of the PAS measurements, the agreement between the computed (modal and WRF-Chem) and observed fine-mode ϖ0, averaged over the course of the campaign, is reasonably good. The observed ϖ0 value is 0.77, while for both modules, the calculated value was 0.75 resulting in a difference of 0.02 between observations and both computational approaches. This difference is less than the uncertainty of the observed ϖ0 values (6%, or 0.05), and therefore "closure" is achieved, at least for mean values. After adjusting some properties of black carbon absorption and mass concentration within plausible uncertainty limits, the two modules simulate well the diurnal variation of ϖ0, and the absorption coefficient, Babs, but are less successful in calculating the variation of the scattering coefficient, Bscat. This difficulty is probably caused by the presence of larger particles during the day when windblown dust is ubiquitous; this dust likely increases the proportion of large particles introduced into the PAS. The dust also contributes to a very large aerosol mass loading in the coarse mode, and neglect of the coarse mode may cause significant errors, estimated to be as large as 0.07, in the calculation and measurement of ambient ϖ0. Finally, the observed ϖ0 is compared to the ϖ0 computed by the full WRF-Chem model, which includes prognostic aerosol chemistry. Unlike the results discussed above, a comparison between observed and simulated ϖ0 values reveals major differences. This large discrepancy is probably due, in part, to poor characterization of emissions near the T1 site, particularly black carbon emissions.

Seasonal Temperature Pattern Indicating Martian Dust Storms

NASA Image and Video Library

2016-06-09

This graphic shows Martian atmospheric temperature data related to seasonal patterns in occurrence of large regional dust storms. The data shown here were collected by the Mars Climate Sounder instrument on NASA's Mars Reconnaissance Orbiter over the course of one-half of a Martian year, during 2012 and 2013. The color coding indicates daytime temperatures of a layer of the atmosphere centered about 16 miles (25 kilometers) above ground level, corresponding to the color-key bar at the bottom of the graphic. Three regional dust storms indicated by increased temperatures are labeled A, B and C. A similar sequence of three large regional dust storms has been seen in atmosphere-temperature data from five other Martian years. The vertical axis is latitude on Mars, from the north pole at the top to south pole at the bottom. Each graphed data point is an average for all Martian longitudes around the planet. The horizontal axis is the time of year, spanning from the beginning of Mars' southern-hemisphere spring (on the left) to the end of southern-hemisphere summer. This is the half of the year when large Martian dust storms are most active. http://photojournal.jpl.nasa.gov/catalog/PIA20746

Constraining the Post-Thermal Pulse Mass-Loss History of R Scl with SOFIA/FORCAST

NASA Astrophysics Data System (ADS)

Hankins, Matthew; Herter, Terry; maercker, matthias; Lau, Ryan M.; Sloan, Greg

2018-06-01

R Sculptoris (R Scl) is a nearby (~370 pc) carbon star with a massive circumstellar shell (Mshell∼7×10‑3 M⊙) which is thought to have been produced by a thermal pulse event ∼2200 years ago. We observed R Scl with the Faint Object InfraRed CAMera for the SOFIA Telescope (FORCAST) at 19.7, 25.2, 31.5, 34.8, and 37.1 μm to study its circumstellar dust emission. Maps of the infrared emission were used to examine the morphology and temperature structure of the spatially extended dust emission. We used the radiative transfer code DUSTY to fit the radial density profile of the circumstellar material, and find that a geometrically thin dust shell cannot reproduce the observed emission. Instead, a second dust component is needed to model the emission. This component, which lies interior to the dust shell, traces the post-thermal pulse mass loss of R Scl and is indicative of a slow decline in the star’s mass loss over thousands of years. This result is at odds with 'classical' thermal pulse models but is consistent with earlier observations of molecular gas in R Scl’s circumstellar environment.

Dust Radiative Transfer Modeling of the Infrared Ring around the Magnetar SGR 1900+14

DOE Office of Scientific and Technical Information (OSTI.GOV)

Natale, G.; Rea, N.; Torres, D. F.

2017-03-01

A peculiar infrared ring-like structure was discovered by Spitzer around the strongly magnetized neutron star SGR 1900+14. This infrared (IR) structure was suggested to be due to a dust-free cavity, produced by the Soft Gamma-ray Repeaters (SGRs) Giant Flare occurring in 1998, and kept illuminated by surrounding stars. Using a 3D dust radiative transfer code, we aimed to reproduce the emission morphology and the integrated emission flux of this structure assuming different spatial distributions and densities for the dust, and different positions for the illuminating stars. We found that a dust-free ellipsoidal cavity can reproduce the shape, flux, and spectrummore » of the ring-like IR emission, provided that the illuminating stars are inside the cavity and that the interstellar medium has high gas density ( n {sub H} ∼ 1000 cm{sup −3}). We further constrain the emitting region to have a sharp inner boundary and to be significantly extended in the radial direction, possibly even just a cavity in a smooth molecular cloud. We discuss possible scenarios for the formation of the dustless cavity and the particular geometry that allows it to be IR-bright.« less

Using Nadir and Directional Emissivity as a Probe of Particle Microphysical Properties

NASA Astrophysics Data System (ADS)

Pitman, Karly M.; Wolff, Michael J.; Bandfield, Joshua L.; Clayton, Geoffrey C.

Real surfaces are not expected to be diffuse emitters, thus observed emissivity values of surface dust deposits are a function of viewing geometry. Attempts to model infrared emission spectral profiles of surface dust deposits at nadir have not yet matured to match the sophistication of astrophysical dust radiative transfer codes. In the absence of strong thermal gradients, directional emissivity may be obtained theoretically via a combination of reciprocity and Kirchhoff's Law. Owing to a lack of laboratory data on directional emissivity for comparison, theorists have not explored the potential utility of directional emissivity as a direct probe of surface dust microphysical properties. Motivated by future analyses of MGS/TES emission phase function (EPF) sequences and the upcoming Mars Exploration Rover mini-TES dataset, we explore the effects of dust particle size and composition on observed radiances at nadir and off-nadir geometries in the TES spectral regime using a combination of multiple scattering radiative transfer and Mie scattering algorithms. Comparisons of these simulated spectra to laboratory spectra of standard mineral assemblages will also be made. This work is supported through NASA grant NAGS-9820 (MJW) and LSU Board of Regents (KMP).

Planetesimal formation by sweep-up coagulation

NASA Astrophysics Data System (ADS)

Windmark, Fredrik; Birnstiel, Til; Ormel, Chris W.; Dullemond, Cornelis P.

2013-07-01

The formation of planetesimals is often accredited to collisional sticking of dust grains in the protoplanetary disk. The exact process is however unknown, as collisions between larger aggregates tend to lead to fragmentation or bouncing rather than sticking. These growth barriers tend to halt the dust growth already at millimeters or centimeters in size, which is far below the kilometer-sizes that are needed for gravity to aid in the accretion. To study how far dust coagulation can proceed, we have developed a new collision model based on the latest laboratory experiments, and have used it together with a dust-size evolution code capable of resolving all grain interactions in the protoplanetary disk. We find that for the general dust population, bouncing and fragmenting collisions prevent the growth above millimeter-sizes. However, a small number of lucky particles can grow larger than the rest by only interacting at low, sticky velocities. As they grow, they become increasingly resilient to fragmentation caused by the small grains. In this way, two populations are formed: One which remains small due to the collisional barriers, and one that continues to grow by sweeping up the smaller grains around them.

Wood-related occupations, wood dust exposure, and sinonasal cancer.

PubMed

Hayes, R B; Gerin, M; Raatgever, J W; de Bruyn, A

1986-10-01

A case-control study was conducted to examine the relations between type of woodworking and the extent of wood dust exposure to the risks for specific histologic types of sinonasal cancer. In cooperation with the major treatment centers in the Netherlands, 116 male patients newly diagnosed between 1978 and 1981 with primary malignancies of epithelial origin of this site were identified for study. Living controls were selected from the municipal registries, and deceased controls were selected from the national death registry. Interviews were completed for 91 (78%) cases and 195 (75%) controls. Job histories were coded by industry and occupation. An index of exposure was developed to classify the extent of occupational exposure to wood dust. When necessary, adjustment was made for age and usual cigarette use. The risk for nasal adenocarcinoma was elevated by industry for the wood and paper industry (odds ratio (OR) = 11.9) and by occupation for those employed in furniture and cabinet making (OR = 139.8), in factory joinery and carpentry work (OR = 16.3), and in association with high-level wood dust exposure (OR = 26.3). Other types of nasal cancer were not found to be associated with wood-related industries or occupations. A moderate excess in risk for squamous cell cancer (OR = 2.5) was associated with low-level wood dust exposure; however, no dose-response relation was evident. The association between wood dust and adenocarcinoma was strongest for those employed in wood dust-related occupations between 1930 and 1941. The risk of adenocarcinoma did not appear to decrease for at least 15 years after termination of exposure to wood dust. No cases of nasal adenocarcinoma were observed in men whose first exposure to wood dust occurred after 1941.

The dust masses in the remnants of Cas A, SN1993J and SN 1980K

NASA Astrophysics Data System (ADS)

Barlow, Mike; Bevan, Antonia

2016-06-01

Using a recently developed 3D Monte Carlo dust line-scattering and absorption code, Bevan & Barlow (2016, MNRAS) have modeled the red-blue line asymmetries in the late-time Hα and [O i] spectra of SN 1987A caued by the preferential absorption by internal dust particles of redshifted photons from the far side of the ejecta. They found dust masses that grew from ≤ 10-3 M⊙ on day 714 to ≥ 0.10 M⊙ by day 3604, a trend that agrees with the day 615 - 9200 SED modeling results of Wesson et al. (2015) for SN 1987A, for which Herschel and ALMA observations indicate a dust mass of ˜0.7 M⊙ by day 9200. Similar red-blue emission line asymmetries are often observed in the late-time optical spectra of other supernova ejecta and remnants. With the aim of increasing the number of SNR dust mass determinations, we have modeled the red-blue emission line asymmetries in the late-time optical spectra of SN 1993J and SN 1980K published by Milisavljevic & Fesen (2013), as well as modeling similar red-blue line asymmetries seen in the integrated optical spectrum of Cas A published by Milisavljevic et al. (2013). Depending on grain composition, clumped dust masses of 0.1-0.4 M⊙ are required to provide fits to the Year-31 Hα and [O i] line profiles of SN 1980K, while fits to the Year-16 [O ii] and [O iii] line profiles of SN 1993J require up to 0.18 M⊙ of clumped ejecta dust. For Cas A, the fits to its [O i], [O ii] and [O iii] integrated line profiles require about 1 M⊙ of internal dust to be present.

THE FORMATION OF THE PRIMITIVE STAR SDSS J102915+172927: EFFECT OF THE DUST MASS AND THE GRAIN-SIZE DISTRIBUTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bovino, S.; Banerjee, R.; Grassi, T.

Understanding the formation of the extremely metal-poor star SDSS J102915+172927 is of fundamental importance to improve our knowledge on the transition between the first and second generation of stars in the universe. In this paper, we perform three-dimensional cosmological hydrodynamical simulations of dust-enriched halos during the early stages of the collapse process including a detailed treatment of the dust physics. We employ the astrochemistry package krome coupled with the hydrodynamical code enzo assuming grain-size distributions produced by the explosion of core-collapse supernovae (SNe) of 20 and 35 M {sub ⊙} primordial stars, which are suitable to reproduce the chemical patternmore » of the SDSS J102915+172927 star. We find that the dust mass yield produced from Population III SNe explosions is the most important factor that drives the thermal evolution and the dynamical properties of the halos. Hence, for the specific distributions relevant in this context, the composition, the dust optical properties, and the size range have only minor effects on the results due to similar cooling functions. We also show that the critical dust mass to enable fragmentation provided by semi-analytical models should be revised, as we obtain values one order of magnitude larger. This determines the transition from disk fragmentation to a more filamentary fragmentation mode, and suggests that likely more than one single SN event or efficient dust growth should be invoked to get such high dust content.« less

Non-smoking Chronic Obstructive Pulmonary Disease Attributed to Occupational Exposure to Silica Dust.

PubMed

Tsuchiya, Kazuo; Toyoshima, Mikio; Kamiya, Yosuke; Nakamura, Yutaro; Baba, Satoshi; Suda, Takafumi

2017-01-01

An 85-year-old, never-smoking man presented with exertional dyspnea. He had been exposed to silica dust in the work place. Chest computed tomography revealed bronchial wall thickening without emphysema. A pulmonary function test showed airflow obstruction without impaired gas transfer. Airway hyperresponsiveness and reversibility were not evident. A transbronchial lung biopsy showed findings suggestive of mineral dust exposure, such as fibrosis and slight pigmentation of bronchioles. He was diagnosed with non-smoking chronic obstructive pulmonary disease (COPD) due to occupational exposure to silica dust. His symptoms were improved using an inhaled long-acting bronchodilator. The clinical characteristics of non-smoking COPD are discussed in this report.

Model of Dust Thermal Emission of Comet 67p-Churyumov-Gerasimenko for the Rosetta-MIRO Instrument

NASA Technical Reports Server (NTRS)

Gicquel, Adeline; Bockelee-Morvan, Dominique; Leyrat, Cedric; Zakharov, Vladimir; Crovisier, Jacques; Biver, Nicolas; Gulkis, Samuel

2013-01-01

The ESA's Rosetta spacecraft will arrive at comet 67P/Churyumov-Gerasimenko in 2014. The study of gas and dust emission is primary objective of several instruments on the Rosetta spacecraft, including the Microwave Instrument for the Rosetta Orbiter (MIRO). We developed a model of dust thermal emission to estimate the detectability of dust in the vicinity of the nucleus with MIRO. Our model computes the power received by the MIRO antenna in limb viewing as a function of the geometry of the observations and the physical properties of the grains. We show that detection in the millimeter and submillimeter channels can be achieved near perihelion.

Implementation of a 3D mixing layer code on parallel computers

NASA Technical Reports Server (NTRS)

Roe, K.; Thakur, R.; Dang, T.; Bogucz, E.

1995-01-01

This paper summarizes our progress and experience in the development of a Computational-Fluid-Dynamics code on parallel computers to simulate three-dimensional spatially-developing mixing layers. In this initial study, the three-dimensional time-dependent Euler equations are solved using a finite-volume explicit time-marching algorithm. The code was first programmed in Fortran 77 for sequential computers. The code was then converted for use on parallel computers using the conventional message-passing technique, while we have not been able to compile the code with the present version of HPF compilers.

Modelling of the sublimation of icy grains in the coma of comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Gicquel, A.; Vincent, J.-B.; Shi, X.; Sierks, H.; Rose, M.; Güttler, C.; Tubiana, C.

2015-10-01

The ESA (European Space Agency) Rosetta spacecraft was launched on 2 March 2004, to reach comet 67P/Churyumov-Gerasimenko in August 2014. Since March 2014, images of the nucleus and the coma (gas and dust) of the comet have been acquired by the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) camera system [1] using both, the wide angle camera (WAC) and the narrow angle camera (NAC). The orbiter will be maintained in the vicinity of the comet until perihelion (Rh=1.3 AU) or even until Rh=1.8 AU post-perihelion (December 2015). Nineteen months of uninterrupted, close-up observations of the gas and dust coma will be obtained and will help to characterize the evolution of comet gas and dust activity during its approach to the Sun. Indeed, for the first time, we will follow the development of a comet's coma from a close distance. Also the study of the dust-gas interaction in the coma will highlight the sublimation of icy grains. Even if the sublimation of icy grains is known, it is not yet integrated in a complete dust-gas model. We are using the Direct Simulation Monte Carlo (DSMC) method to study the gas flow close to the nucleus. The code called PI-DSMC (www.pidsmc. com) can simulate millions of molecules for multiple species.When the gas flow is simulated, we inject the dust particle with a zero velocity and we take into account the 3 forces acting on the grains in a cometary environment (drag force, gravity and radiative pressure). We used the DLL (Dynamic Link Library) model to integrate the sublimation of icy grains in the gas flowand allow studying the effect of the additional gas on the dust particle trajectories. For a quantitative analysis of the sublimation of icy, outflowing grains we will consider an ensemble of grains of various radii with different compositions [2] The evolution of the grains, once they are ejected into the coma, depends on their initial size, their composition and the heliocentric distance (because the temperature of the grain is higher close to the Sun). The grain temperatures will be derived by assuming equilibrium between the energy absorbed from the Sun, the energy re-radiated in the infrared, and the cooling by sublimation. We will use Mie theory [3, 4] to compute the scattering properties of an assumed grain (grain size, shape and composition, including mineralogy and porosity). We follow the evolution of grains until the icy layer sublimates completely. Once ejected in the gas flow, the generated molecules have no preferred direction. First results highlighted that the sublimation has a significant influence on the dust trajectories and generates a gas cloud that moves with the velocity of the icy grains. Our model can produce artificial images for a wide range of parameters, including outgassing rate, surface temperature, dust properties and sublimation of icy grains. The results of this model will be compared to the images obtained with OSIRIS camera and to the published data from other instruments.

Boundary Layer Regimes Conducive to Formation of Dust Devils on Mars

NASA Astrophysics Data System (ADS)

Williams, B.; Nair, U. S.

2014-12-01

Dust devils on Mars contribute to maintenance of background atmospheric aerosol loading and thus dust radiative forcing, which is an important modulator of Martian climate. Dust devils also cause surface erosion and change in surface albedo which impacts radiative energy budget. Thus there is a need for parameterizing dust devil impacts in Martian climate models. In this context it is important to understand environmental conditions that are favorable for formation of dust devils on Mars and associated implications for diurnal, seasonal, and geographical variation of dust devil occurrence. On earth, prior studies show that thresholds of ratio of convective and friction scale velocities may be used to identify boundary layer regimes that are conducive to formation of dust devils. On earth, a w*/u* ratio in excess of 5 is found to be conducive for formation of dust devils. In this study, meteorological observations collected during the Viking Lander mission are used to constrain Martian boundary layer model simulations, which is then used to estimate w*/u* ratio. The w*/u* ratio is computed for several case days during which dust devil occurrence was detected. A majority of dust devils occurred in convective boundary layer regimes characterized by w*/u* ratios exceeding 10. The above described analysis is being extended to other mars mission landing sites and results from the extended analysis will also be presented.

On the interpretation of the optical spectra of L-type dwarfs

NASA Astrophysics Data System (ADS)

Pavlenko, Ya.; Zapatero Osorio, M. R.; Rebolo, R.

2000-03-01

We present synthetic optical spectra in the red and far-red (640-930 nm) of a sample of field L dwarfs suitably selected to cover this new spectral class, and the brown dwarf GL 229B. We have used the recent ``dusty'' atmospheres by Tsuji (\\cite{tsuji00}) and by Allard (\\cite{allard99}), and a synthesis code (Pavlenko et al. \\cite{pav95}) working under LTE conditions which considers the chemical equilibrium of more than 100 molecular species and the detailed opacities for the most relevant bands. Our computations show that the alkali elements Li, Na, K, Rb, and Cs govern the optical spectra of the objects in our sample, with Na and K contributing significantly to block the optical emergent radiation. Molecular absorption bands of oxides (TiO and VO) and hydrides (CrH, FeH and CaH) also dominate at these wavelengths in the early L-types showing a strength that progressively decreases for later types. We find that the densities of these molecules in the atmospheres of our objects are considerably smaller by larger factors than those predicted by chemical equilibrium considerations. This is consistent with Ti and V atoms being depleted into grains of dust. In order to reproduce the overall shape of the optical spectra of our observations an additional opacity is required to be implemented in the computations. We have modelled it with a simple law of the form adeg \\ (nu / nu deg)N, with N = 4, and found that this provides a sufficiently good fit to the data. This additional opacity could be due to molecular/dust absorption or to dust scattering. We remark that the equivalent widths and intensities of the alkali lines are highly affected by this opacity. In particular, the lithium resonance line at 670.8 nm, which is widely used as a substellarity discriminator, is more affected by the additional opacity than by the natural depletion of neutral lithium atoms into molecular species. Our theoretical spectra displays a rather strong resonance feature even at very cool effective temperatures ( ~ 1000 K); depending on the effective temperature and on the amount of dust in the atmospheres of very cool dwarfs, it might be possible to achieve the detection of lithium even at temperatures this cool. Changes in the physical conditions governing dust formation in L-type objects will cause variability of the alkali lines, particularly of the shorter wavelength lines. Based on observations made with the William Herschel Telescope (WHT) operated on the island of La Palma by the Isaac Newton Group at the Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias; and on observations obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. This observatory was made possible by the generous financial support of the W.M. Keck Foundation.

Improvement in Clouds and the Earth's Radiant Energy System/Surface and Atmosphere Radiation Budget Dust Aerosol Properties, Effects on Surface Validation of Clouds and Radiative Swath

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rutan, D.; Rose, F.; Charlock, T.P.

2005-03-18

Within the Clouds and the Earth's Radiant Energy System (CERES) science team (Wielicki et al. 1996), the Surface and Atmospheric Radiation Budget (SARB) group is tasked with calculating vertical profiles of heating rates, globally, and continuously, beneath CERES footprint observations of Top of Atmosphere (TOA) fluxes. This is accomplished using a fast radiative transfer code originally developed by Qiang Fu and Kuo-Nan Liou (Fu and Liou 1993) and subsequently highly modified by the SARB team. Details on the code and its inputs can be found in Kato et al. (2005) and Rose and Charlock (2002). Among the many required inputsmore » is characterization of the vertical column profile of aerosols beneath each footprint. To do this SARB combines aerosol optical depth information from the moderate-resolution imaging spectroradiometer (MODIS) instrument along with aerosol constituents specified by the Model for Atmosphere and Chemical Transport (MATCH) of Collins et al. (2001), and aerosol properties (e.g. single scatter albedo and asymmetry parameter) from Tegen and Lacis (1996) and OPAC (Hess et al. 1998). The publicly available files that include these flux profiles, called the Clouds and Radiative Swath (CRS) data product, available from the Langley Atmospheric Sciences Data Center (http://eosweb.larc.nasa.gov/). As various versions of the code are completed, publishable results are named ''Editions.'' After CRS Edition 2A was finalized it was found that dust aerosols were too absorptive. Dust aerosols have subsequently been modified using a new set of properties developed by Andy Lacis and results have been released in CRS Edition 2B. This paper discusses the effects of changing desert dust aerosol properties, which can be significant for the radiation budget in mid ocean, a few thousand kilometers from the source regions. Resulting changes are validated via comparison of surface observed fluxes from the Saudi Solar Village surface site (Myers et al. 1999), and the E13 site at the Atmospheric Radiation Measurement (ARM), Southern Great Plains (SGP) central facility.« less

CATASTROPHIC DISRUPTION OF COMET ISON

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keane, Jacqueline V.; Kleyna, Jan T.; Riesen, Timm-Emmanuel

2016-11-10

We report submillimeter 450 and 850 μ m dust continuum observations for comet C/2012 S1 (ISON) obtained at heliocentric distances 0.31–0.08 au prior to perihelion on 2013 November 28 ( r {sub h} = 0.0125 au). These observations reveal a rapidly varying dust environment in which the dust emission was initially point-like. As ISON approached perihelion, the continuum emission became an elongated dust column spread out over as much as 60″ (>10{sup 5} km) in the anti-solar direction. Deconvolution of the November 28.04 850 μ m image reveals numerous distinct clumps consistent with the catastrophic disruption of comet ISON, producingmore » ∼5.2 × 10{sup 10} kg of submillimeter-sized dust. Orbital computations suggest that the SCUBA-2 emission peak coincides with the comet's residual nucleus.« less

Lidar Ice nuclei estimates and how they relate with airborne in-situ measurements

NASA Astrophysics Data System (ADS)

Marinou, Eleni; Amiridis, Vassilis; Ansmann, Albert; Nenes, Athanasios; Balis, Dimitris; Schrod, Jann; Binietoglou, Ioannis; Solomos, Stavros; Mamali, Dimitra; Engelmann, Ronny; Baars, Holger; Kottas, Michael; Tsekeri, Alexandra; Proestakis, Emmanouil; Kokkalis, Panagiotis; Goloub, Philippe; Cvetkovic, Bojan; Nichovic, Slobodan; Mamouri, Rodanthi; Pikridas, Michael; Stavroulas, Iasonas; Keleshis, Christos; Sciare, Jean

2018-04-01

By means of available ice nucleating particle (INP) parameterization schemes we compute profiles of dust INP number concentration utilizing Polly-XT and CALIPSO lidar observations during the INUIT-BACCHUS-ACTRIS 2016 campaign. The polarization-lidar photometer networking (POLIPHON) method is used to separate dust and non-dust aerosol backscatter, extinction, mass concentration, particle number concentration (for particles with radius > 250 nm) and surface area concentration. The INP final products are compared with aerosol samples collected from unmanned aircraft systems (UAS) and analyzed using the ice nucleus counter FRIDGE.

Physical-mathematical model of condensation process of the sub-micron dust capture in sprayer scrubber

NASA Astrophysics Data System (ADS)

Shilyaev, M. I.; Khromova, E. M.; Grigoriev, A. V.; Tumashova, A. V.

2011-09-01

A physical-mathematical model of the heat and mass exchange process and condensation capture of sub-micron dust particles on the droplets of dispersed liquid in a sprayer scrubber is proposed and analysed. A satisfactory agreement of computed results and experimental data on soot capturing from the cracking gases is obtained.

40 CFR 194.23 - Models and computer codes.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 26 2013-07-01 2013-07-01 false Models and computer codes. 194.23... General Requirements § 194.23 Models and computer codes. (a) Any compliance application shall include: (1... obtain stable solutions; (iv) Computer models accurately implement the numerical models; i.e., computer...

40 CFR 194.23 - Models and computer codes.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 26 2012-07-01 2011-07-01 true Models and computer codes. 194.23... General Requirements § 194.23 Models and computer codes. (a) Any compliance application shall include: (1... obtain stable solutions; (iv) Computer models accurately implement the numerical models; i.e., computer...

40 CFR 194.23 - Models and computer codes.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 25 2014-07-01 2014-07-01 false Models and computer codes. 194.23... General Requirements § 194.23 Models and computer codes. (a) Any compliance application shall include: (1... obtain stable solutions; (iv) Computer models accurately implement the numerical models; i.e., computer...

40 CFR 194.23 - Models and computer codes.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Models and computer codes. 194.23... General Requirements § 194.23 Models and computer codes. (a) Any compliance application shall include: (1... obtain stable solutions; (iv) Computer models accurately implement the numerical models; i.e., computer...

40 CFR 194.23 - Models and computer codes.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 25 2011-07-01 2011-07-01 false Models and computer codes. 194.23... General Requirements § 194.23 Models and computer codes. (a) Any compliance application shall include: (1... obtain stable solutions; (iv) Computer models accurately implement the numerical models; i.e., computer...

An efficient and accurate technique to compute the absorption, emission, and transmission of radiation by the Martian atmosphere

NASA Technical Reports Server (NTRS)

Lindner, Bernhard Lee; Ackerman, Thomas P.; Pollack, James B.

1990-01-01

CO2 comprises 95 pct. of the composition of the Martian atmosphere. However, the Martian atmosphere also has a high aerosol content. Dust particles vary from less than 0.2 to greater than 3.0. CO2 is an active absorber and emitter in near IR and IR wavelengths; the near IR absorption bands of CO2 provide significant heating of the atmosphere, and the 15 micron band provides rapid cooling. Including both CO2 and aerosol radiative transfer simultaneously in a model is difficult. Aerosol radiative transfer requires a multiple scattering code, while CO2 radiative transfer must deal with complex wavelength structure. As an alternative to the pure atmosphere treatment in most models which causes inaccuracies, a treatment was developed called the exponential sum or k distribution approximation. The chief advantage of the exponential sum approach is that the integration over k space of f(k) can be computed more quickly than the integration of k sub upsilon over frequency. The exponential sum approach is superior to the photon path distribution and emissivity techniques for dusty conditions. This study was the first application of the exponential sum approach to Martian conditions.

Analyze and predict VLTI observations: the Role of 2D/3D dust continuum radiative transfer codes

NASA Astrophysics Data System (ADS)

Pascucci, I.; Henning, Th; Steinacker, J.; Wolf, S.

2003-10-01

Radiative Transfer (RT) codes with image capability are a fundamental tool for preparing interferometric observations and for interpreting visibility data. In view of the upcoming VLTI facilities, we present the first comparison of images/visibilities coming from two 3D codes that use completely different techniques to solve the problem of self-consistent continuum RT. In addition, we focus on the astrophysical case of a disk distorted by tidal interaction with by-passing stars or internal planets and investigate for which parameters the distortion can be best detected in the mid-infrared using the mid-infrared interferometric device MIDI.

2D/3D Dust Continuum Radiative Transfer Codes to Analyze and Predict VLTI Observations

NASA Astrophysics Data System (ADS)

Pascucci, I.; Henning, Th.; Steinacker, J.; Wolf, S.

Radiative Transfer (RT) codes with image capability are a fundamental tool for preparing interferometric observations and for interpreting visibility data. In view of the upcoming VLTI facilities, we present the first comparison of images/visibilities coming from two 3D codes that use completely different techniques to solve the problem of self-consistent continuum RT. In addition, we focus on the astrophysical case of a disk distorted by tidal interaction with by-passing stars or internal planets and investigate for which parameters the distortion can be best detected in the mid-infrared using the mid-infrared interferometric device MIDI.

Dust radiative effect over Europe, Mediterranean, Sahara and Middle East from a radiative transfer model using BSC-DREAM8b aerosol optical data

NASA Astrophysics Data System (ADS)

Papadimas, Christos; Gkikas, Antonis; Hatzianastassiou, Nikos; Matsoukas, Christos; Kazadzis, Stelios; Basart, Sara; Baldasano, Jose; Vardavas, Ilias

2013-04-01

The arid regions of Saharan desert and Middle East are the world's major dust sources. However, dust particles from these areas are transported to nearby regions, through favourable synoptic conditions, even reaching remote locations in Europe or in the Arctic. This transport is very important in numerous aspects. One of its most important effects is on the radiation budget, and more specifically on solar radiation, through the aerosol direct radiative effect (DRE). Previous studies have shown that this effect is great under dust load conditions. Therefore, it is very important to simulate dust transport processes and associated radiative effects. The simulation of dust production, transport and removal is done by numerical models, which however have their own limitations as to the consideration of physical and dynamical processes as well as their initial conditions. On the other hand, the computation of dust DRE is ideally done with radiative transfer models (RTMs), which however imply uncertainties associated with the input aerosol optical properties. The most important aerosol optical properties used in RTMs and climate models are aerosol optical depth (AOD), single scattering albedo (SSA) and asymmetry parameter (AP). The main target of the present study is to reduce the uncertainties of dust DRE by using a detailed spectral RTM and an acknowledged regional and meso-scale model describing the distribution of dust. The combined use of these tools is applied to the region covering the deserts of Sahara, Arabian Peninsula and Middle East, and the neighbouring Mediterranean basin and European continent (extending from 15°N to 60°N and from 21°W to 54°E). The computations are performed on a monthly mean basis, refer to the 11-year period 2000-2010, and quantify the effects of dust on the reflected solar radiation at the top of atmosphere (DRETOA), on the absorbed solar radiation within the atmosphere (DREatmab), and on the downwelling and absorbed solar radiation at the surface (DREsurf and DREsurfnet, respectively). The RTM takes into account all physical parameters of the Earth-Atmosphere system that interact with solar radiation, namely ozone, carbon dioxide, methane, water vapour, clouds (low, middle, high), aerosol and atmospheric molecules (Rayleigh scattering) as well as surface reflection. Emphasis is given to aerosol optical properties (AOD, SSA and AP) which are all obtained from the dust regional BSC-DREAM8b model. Detailed analysis is undertaken of the modelled aerosol properties, and the spatial and temporal (seasonal and year by year) variation of these properties and of the model DREs are thoroughly investigated. In addition, the computed DREs are inter-compared with corresponding ones obtained with the same RTM using aerosol data from satellites (e.g. MODIS) or other datasets (e.g. Global Aerosol DataSet, GADS and Hamburg Aerosol Climatology, HAC).

Reverberation Mapping the Dusty Torus in Active Galactic Nuclei: the Influence of Torus Geometry and Structure on the Measured Reverberation Radius

NASA Astrophysics Data System (ADS)

Almeyda, Triana

2018-01-01

The obscuring circumnuclear dusty torus is a cornerstone of AGN unification, yet its shape, composition, and structure have not been well constrained. Infrared (IR) interferometry can partially resolve the dust structures in nearby AGN. However, the size and structure of the torus can also be investigated at all redshifts by reverberation mapping, that is, analyzing the temporal variability of the torus dust emission in response to changes in the AGN luminosity. In simple models, the lag between the AGN optical continuum variations and the torus IR response is directly related to the effective size of the emitting region. However, the IR response is sensitive to many poorly constrained variables including the geometry and illumination of the torus, which complicates the interpretation of measured reverberation lags. I will present results from the first comprehensive analysis of the multi-wavelength IR torus response, showing how various structural and geometrical torus parameters influence the measured lag. A library of torus response functions has been computed using a new code, TORMAC, which simulates the temporal response of the IR emission of a 3D ensemble of dust clouds given an input optical light curve. TORMAC accounts for anisotropic emission from the dust clouds, inter-cloud and AGN-cloud shadowing, and anisotropic illumination of the torus by the AGN continuum source. We can use the model grid to quantify the relationship between the lag and the effective size of the torus for various torus parameters at any selected wavelength. Although the shapes of the response functions vary widely over our grid parameter range, the reverberation lag provides an estimate of the effective torus radius that is always within a factor of 2.5. TORMAC can also be used to model observed IR light curves; we present preliminary simulations for the “changing-look” Seyfert galaxy, NGC 6418, which exhibited large IR variability during a recent Spitzer monitoring campaign. This work will aid in the interpretation of reverberation mapping measurements, especially for the new VEILS wide field near-IR extragalactic time domain survey, whose aim is to use AGN IR reverberation mapping lags as cosmological standard candles.

Towards universal hybrid star formation rate estimators

NASA Astrophysics Data System (ADS)

Boquien, M.; Kennicutt, R.; Calzetti, D.; Dale, D.; Galametz, M.; Sauvage, M.; Croxall, K.; Draine, B.; Kirkpatrick, A.; Kumari, N.; Hunt, L.; De Looze, I.; Pellegrini, E.; Relaño, M.; Smith, J.-D.; Tabatabaei, F.

2016-06-01

Context. To compute the star formation rate (SFR) of galaxies from the rest-frame ultraviolet (UV), it is essential to take the obscuration by dust into account. To do so, one of the most popular methods consists in combining the UV with the emission from the dust itself in the infrared (IR). Yet, different studies have derived different estimators, showing that no such hybrid estimator is truly universal. Aims: In this paper we aim at understanding and quantifying what physical processes fundamentally drive the variations between different hybrid estimators. In so doing, we aim at deriving new universal UV+IR hybrid estimators to correct the UV for dust attenuation at local and global scales, taking the intrinsic physical properties of galaxies into account. Methods: We use the CIGALE code to model the spatially resolved far-UV to far-IR spectral energy distributions of eight nearby star-forming galaxies drawn from the KINGFISH sample. This allows us to determine their local physical properties, and in particular their UV attenuation, average SFR, average specific SFR (sSFR), and their stellar mass. We then examine how hybrid estimators depend on said properties. Results: We find that hybrid UV+IR estimators strongly depend on the stellar mass surface density (in particular at 70 μm and 100 μm) and on the sSFR (in particular at 24 μm and the total infrared). Consequently, the IR scaling coefficients for UV obscuration can vary by almost an order of magnitude: from 1.55 to 13.45 at 24 μm for instance. This result contrasts with other groups who found relatively constant coefficients with small deviations. We exploit these variations to construct a new class of adaptative hybrid estimators based on observed UV to near-IR colours and near-IR luminosity densities per unit area. We find that they can reliably be extended to entire galaxies. Conclusions: The new estimators provide better estimates of attenuation-corrected UV emission than classical hybrid estimators published in the literature. Taking naturally variable impact of dust heated by old stellar populations into account, they constitute an important step towards universal estimators.

Remote sensing of mesospheric dust layers using active modulation of PMWE by high-power radio-waves

NASA Astrophysics Data System (ADS)

Cohen, M.; Zhang, X.; Cohen, M.; Mahmoudian, A.; Scales, W.; Kosch, M. J.; M Farahani, M.; Mohebalhojeh, A.

2016-12-01

So-called polar mesospheric winter echoes (PMWE) are radar echoes observed during winter at altitudes around 50-80 km and are much weaker than their PMSE (Polar Mesospheric Summer Echoes) counterpart. Unlike PMSE, PMWE are less studied and understood. Breaking of gravity waves and the associated turbulence are proposed as the major source for PMWE echoes. The action of neutral turbulence alone does not appear to give a good explanation for PMWE. PMWE is also attributed to Bragg scatter from electron irregularities which result from charging of free electrons onto sub-visible particles. The temporal behavior of PMWE response to HF pump heating can be employed to diagnose the charged dust layer. Specifically, the rise and fall time of radar echo strength as well as relaxation and recovery time after heater turn-on and off are distinct parameters that are a function of radar frequency. This work presents the first study of the modulation of PMWE by artificial radiowave heating using computational modeling and experimental observation in different radar frequency bands. Variation of dust plasma parameters associated with PMWE such as dust radius, dust density, recombination rate, electron- and dust-neutral collision frequencies, photo-detachment current and electron temperature enhancement ratio are included. Computational results derived from different sets of parameters are considered and compared with recent observations at EISCAT using 224 MHz and 56 MHz radars. The agreement between the model results and the observations show the high potential of remote sensing of dust and plasma parameters associated with PMWE. Measurement of Te/Ti using ISR and simultaneous observations in two frequency bands may lead to a more accurate estimation of dust density and radius. The enhancement of backscattered signal in the HF band during PMWE heating is predicted for the first time. The required background dust-plasma parameters as well as heater power (Te/Ti) for the observation of turn-on overshoot are investigated. It has been shown that the similarity of the temporal evolution of radar echoes in HF band and average charge on the dust particles can be used to study the fundamental physics associated with the dust charging in the PMWE source region. The possibilities of perusing PMWE heating experiments at HAARP will be discussed.

Potential transport pathways of dust emanating from the playa of Ebinur Lake, Xinjiang, in arid northwest China

NASA Astrophysics Data System (ADS)

Ge, Yongxiao; Abuduwaili, Jilili; Ma, Long; Wu, Na; Liu, Dongwei

2016-09-01

In this paper, the HYSPLIT model, driven with reanalysis meteorological data from 1978 to 2013, was used to understand the potential transport characteristics of dust and salt dust emanating from the playa of Ebinur Lake in arid northwest China. Daily air parcel trajectories were computed forward for 8 days from an origin centered over Ebinur Lake at 100 m above ground level. Air parcel trajectory density plots were mapped for seven levels: 0-100 m agl., 100-500 m agl., 500-1000 m agl., 1000-1500 m agl., 1500-2000 m agl., 2000-3000 m agl., and 3000-5000 m agl. These show that potential dust transport pathways have clear seasonal differentiation. The potential transport distance of dust and salt dust is greatest in spring and summer. In autumn and winter, the potential transport of the high-density air trajectory is below 1000 m traveling a shorter distance. Potential dust transport pathways showed notifying directivity in different seasons and heights. Southeast in spring and summer, and north to northeast in autumn and winter are the two main potential transport channels of dust and salt dust. Accordingly, dust and salt dust from the playa of Ebinur Lake may influence the atmospheric processes and biogeochemical cycles of a vast region. The main area of influence of dust and salt dust is close to the source area, and will significantly accelerate the melting of snow and ice in the Tianshan Mountains. This highlights the urgent need to combine remote sensing, isotope and other methods to further research the transport characteristics of dust and salt dust from the playa of the Ebinur Lake.

Dust temperature distributions in star-forming condensations

NASA Technical Reports Server (NTRS)

Xie, Taoling; Goldsmith, Paul F.; Snell, Ronald L.; Zhou, Weimin

1993-01-01

The FIR spectra of the central IR condensations in the dense cores of molecular clouds AFGL 2591. B335, L1551, Mon R2, and Sgr B2 are reanalyzed here in terms of the distribution of dust mass as a function of temperature. FIR spectra of these objects can be characterized reasonably well by a given functional form. The general shapes of the dust temperature distributions of these objects are similar and closely resemble the theoretical computations of de Muizon and Rouan (1985) for a sample of 'hot centered' clouds with active star formation. Specifically, the model yields a 'cutoff' temperature below which essentially no dust is needed to interpret the dust emission spectra, and most of the dust mass is distributed in a broad temperature range of a few tens of degrees above the cutoff temperature. Mass, luminosity, average temperature, and column density are obtained, and it is found that the physical quantities differ considerably from source to source in a meaningful way.

Multiyear Simulations of the Martian Water Cycle with the Ames General Circulation Model

NASA Technical Reports Server (NTRS)

Haberle, R. M.; Schaeffer, J. R.; Nelli, S. M.; Murphy, J. R.

2003-01-01

Mars atmosphere is carbon dioxide dominated with non-negligible amounts of water vapor and suspended dust particles. The atmospheric dust plays an important role in the heating and cooling of the planet through absorption and emission of radiation. Small dust particles can potentially be carried to great altitudes and affect the temperatures there. Water vapor condensing onto the dust grains can affect the radiative properties of both, as well as their vertical extent. The condensation of water onto a dust grain will change the grain s fall speed and diminish the possibility of dust obtaining high altitudes. In this capacity, water becomes a controlling agent with regard to the vertical distribution of dust. Similarly, the atmosphere s water vapor holding capacity is affected by the amount of dust in the atmosphere. Dust is an excellent green house catalyst; it raises the temperature of the atmosphere, and thus, its water vapor holding capacity. There is, therefore, a potentially significant interplay between the Martian dust and water cycles. Previous research done using global, 3-D computer modeling to better understand the Martian atmosphere treat the dust and the water cycles as two separate and independent processes. The existing Ames numerical model will be employed to simulate the relationship between the Martian dust and water cycles by actually coupling the two cycles. Water will condense onto the dust, allowing the particle's radiative characteristics, fall speeds, and as a result, their vertical distribution to change. Data obtained from the Viking, Mars Pathfinder, and especially the Mars Global Surveyor missions will be used to determine the accuracy of the model results.

Computer Description of Black Hawk Helicopter

DTIC Science & Technology

1979-06-01

Model Combinatorial Geometry Models Black Hawk Helicopter Helicopter GIFT Computer Code Geometric Description of Targets 20. ABSTRACT...description was made using the technique of combinatorial geometry (COM-GEOM) and will be used as input to the GIFT computer code which generates Tliic...rnHp The data used bv the COVART comtmter code was eenerated bv the Geometric Information for Targets ( GIFT )Z computer code. This report documents

Computational fluid dynamic modeling of a medium-sized surface mine blasthole drill shroud

PubMed Central

Zheng, Y.; Reed, W.R.; Zhou, L.; Rider, J.P.

2016-01-01

The Pittsburgh Mining Research Division of the U.S. National Institute for Occupational Safety and Health (NIOSH) recently developed a series of models using computational fluid dynamics (CFD) to study airflows and respirable dust distribution associated with a medium-sized surface blasthole drill shroud with a dry dust collector system. Previously run experiments conducted in NIOSH’s full-scale drill shroud laboratory were used to validate the models. The setup values in the CFD models were calculated from experimental data obtained from the drill shroud laboratory and measurements of test material particle size. Subsequent simulation results were compared with the experimental data for several test scenarios, including 0.14 m3/s (300 cfm) and 0.24 m3/s (500 cfm) bailing airflow with 2:1, 3:1 and 4:1 dust collector-to-bailing airflow ratios. For the 2:1 and 3:1 ratios, the calculated dust concentrations from the CFD models were within the 95 percent confidence intervals of the experimental data. This paper describes the methodology used to develop the CFD models, to calculate the model input and to validate the models based on the experimental data. Problem regions were identified and revealed by the study. The simulation results could be used for future development of dust control methods for a surface mine blasthole drill shroud. PMID:27932851

DESPOTIC - a new software library to Derive the Energetics and SPectra of Optically Thick Interstellar Clouds

NASA Astrophysics Data System (ADS)

Krumholz, Mark R.

2014-01-01

I describe DESPOTIC, a code to Derive the Energetics and SPectra of Optically Thick Interstellar Clouds. DESPOTIC represents such clouds using a one-zone model, and can calculate line luminosities, line cooling rates, and in restricted cases line profiles using an escape probability formalism. It also includes approximate treatments of the dominant heating, cooling and chemical processes for the cold interstellar medium, including cosmic ray and X-ray heating, grain photoelectric heating, heating of the dust by infrared and ultraviolet radiation, thermal cooling of the dust, collisional energy exchange between dust and gas, and a simple network for carbon chemistry. Based on these heating, cooling and chemical rates, DESPOTIC can calculate clouds' equilibrium gas and dust temperatures, equilibrium carbon chemical state and time-dependent thermal and chemical evolution. The software is intended to allow rapid and interactive calculation of clouds' characteristic temperatures, identification of their dominant heating and cooling mechanisms and prediction of their observable spectra across a wide range of interstellar environments. DESPOTIC is implemented as a PYTHON package, and is released under the GNU General Public License.

User manual for semi-circular compact range reflector code: Version 2

NASA Technical Reports Server (NTRS)

Gupta, Inder J.; Burnside, Walter D.

1987-01-01

A computer code has been developed at the Ohio State University ElectroScience Laboratory to analyze a semi-circular paraboloidal reflector with or without a rolled edge at the top and a skirt at the bottom. The code can be used to compute the total near field of the reflector or its individual components at a given distance from the center of the paraboloid. The code computes the fields along a radial, horizontal, vertical or axial cut at that distance. Thus, it is very effective in computing the size of the sweet spot for a semi-circular compact range reflector. This report describes the operation of the code. Various input and output statements are explained. Some results obtained using the computer code are presented to illustrate the code's capability as well as being samples of input/output sets.

Gaps and rings carved by vortices in protoplanetary dust

NASA Astrophysics Data System (ADS)

Barge, Pierre; Ricci, Luca; Carilli, Christopher Luke; Previn-Ratnasingam, Rathish

2017-09-01

Context. Large-scale vortices in protoplanetary disks are thought to form and survive for long periods of time. Hence, they can significantly change the global disk evolution and particularly the distribution of the solid particles embedded in the gas, possibly explaining asymmetries and dust concentrations recently observed at submillimeter and millimeter wavelengths. Aims: We investigate the spatial distribution of dust grains using a simple model of protoplanetary disk hosted by a giant gaseous vortex. We explore the dependence of the results on grain size and deduce possible consequences and predictions for observations of the dust thermal emission at submillimeter and millimeter wavelengths. Methods: Global 2D simulations with a bi-fluid code are used to follow the evolution of a single population of solid particles aerodynamically coupled to the gas. Possible observational signatures of the dust thermal emission are obtained using simulators of ALMA and Nest Generation Very Large Array (ngVLA) observations. Results: We find that a giant vortex not only captures dust grains with Stokes number St< 1 but can also affect the distribution of larger grains (with St 1) carving a gap associated with a ring composed of incompletely trapped particles. The results are presented for different particle sizes and associated with their possible signatures in disk observations. Conclusions: Gap clearing in the dust spatial distribution could be due to the interaction with a giant gaseous vortex and their associated spiral waves without the gravitational assistance of a planet. Hence, strong dust concentrations at short sub-mm wavelengths associated with a gap and an irregular ring at longer mm and cm wavelengths could indicate the presence of an unseen gaseous vortex.

Surface chemistry in photodissociation regions

NASA Astrophysics Data System (ADS)

Esplugues, G. B.; Cazaux, S.; Meijerink, R.; Spaans, M.; Caselli, P.

2016-06-01

Context. The presence of dust can strongly affect the chemical composition of the interstellar medium. We model the chemistry in photodissociation regions (PDRs) using both gas-phase and dust-phase chemical reactions. Aims: Our aim is to determine the chemical compositions of the interstellar medium (gas/dust/ice) in regions with distinct (molecular) gas densities that are exposed to radiation fields with different intensities. Methods: We have significantly improved the Meijerink PDR code by including 3050 new gas-phase chemical reactions and also by implementing surface chemistry. In particular, we have included 117 chemical reactions occurring on grain surfaces covering different processes, such as adsorption, thermal desorption, chemical desorption, two-body reactions, photo processes, and cosmic-ray processes on dust grains. Results: We obtain abundances for different gas and solid species as a function of visual extinction, depending on the density and radiation field. We also analyse the rates of the formation of CO2 and H2O ices in different environments. In addition, we study how chemistry is affected by the presence/absence of ice mantles (bare dust or icy dust) and the impact of considering different desorption probabilities. Conclusions: The type of substrate (bare dust or icy dust) and the probability of desorption can significantly alter the chemistry occurring on grain surfaces, leading to differences of several orders of magnitude in the abundances of gas-phase species, such as CO, H2CO, and CH3OH. The type of substrate, together with the density and intensity of the radiation field, also determine the threshold extinction to form ices of CO2 and H2O. We also conclude that H2CO and CH3OH are mainly released into the gas phase of low, far-ultraviolet illuminated PDRs through chemical desorption upon two-body surface reactions, rather than through photodesorption.

ENVIRONMENTAL CFD SIMULATION AND VISUALIZATION: EXAMPLES IN SUPPORT OF THE RECONSTRUCTION OF THE SMOKE/DUST PLUME FROM THE WORLD TRADE CENTER SITE FOLLOWING THE EVENTS OF SEPTEMBER 11, 2001

EPA Science Inventory

The Poster will present the process of Computational Fluid Dynamics (CFD) simulations through examples supporting the reconstruction of the smoke/dust plumes following the collapse of the WTC towers on September 11, 2001.

Understanding the pathway of toxic air polluta...

Optical Extinction Measurements of Dust Density in the GMRO Regolith Test Bin

NASA Technical Reports Server (NTRS)

Lane, J.; Mantovani, J.; Mueller, R.; Nugent, M.; Nick, A.; Schuler, J.; Townsend, I.

2016-01-01

A regolith simulant test bin was constructed and completed in the Granular Mechanics and Regolith Operations (GMRO) Lab in 2013. This Planetary Regolith Test Bed (PRTB) is a 64 sq m x 1 m deep test bin, is housed in a climate-controlled facility, and contains 120 MT of lunar-regolith simulant, called Black Point-1 or BP-1, from Black Point, AZ. One of the current uses of the test bin is to study the effects of difficult lighting and dust conditions on Telerobotic Perception Systems to better assess and refine regolith operations for asteroid, Mars and polar lunar missions. Low illumination and low angle of incidence lighting pose significant problems to computer vision and human perception. Levitated dust on Asteroids interferes with imaging and degrades depth perception. Dust Storms on Mars pose a significant problem. Due to these factors, the likely performance of telerobotics is poorly understood for future missions. Current space telerobotic systems are only operated in bright lighting and dust-free conditions. This technology development testing will identify: (1) the impact of degraded lighting and environmental dust on computer vision and operator perception, (2) potential methods and procedures for mitigating these impacts, (3) requirements for telerobotic perception systems for asteroid capture, Mars dust storms and lunar regolith ISRU missions. In order to solve some of the Telerobotic Perception system problems, a plume erosion sensor (PES) was developed in the Lunar Regolith Simulant Bin (LRSB), containing 2 MT of JSC-1a lunar simulant. PES is simply a laser and digital camera with a white target. Two modes of operation have been investigated: (1) single laser spot - the brightness of the spot is dependent on the optical extinction due to dust and is thus an indirect measure of particle number density, and (2) side-scatter - the camera images the laser from the side, showing beam entrance into the dust cloud and the boundary between dust and void. Both methods must assume a mean particle size in order to extract a number density. The optical extinction measurement yields the product of the 2nd moment of the particle size distribution and the extinction efficiency Qe. For particle sizes in the range of interest (greater than 1 micrometer), Qe approximately equal to 2. Scaling up of the PES single laser and camera system is underway in the PRTB, where an array of lasers penetrate a con-trolled dust cloud, illuminating multiple targets. Using high speed HD GoPro video cameras, the evolution of the dust cloud and particle size density can be studied in detail.

Hanford meteorological station computer codes: Volume 9, The quality assurance computer codes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burk, K.W.; Andrews, G.L.

1989-02-01

The Hanford Meteorological Station (HMS) was established in 1944 on the Hanford Site to collect and archive meteorological data and provide weather forecasts and related services for Hanford Site approximately 1/2 mile east of the 200 West Area and is operated by PNL for the US Department of Energy. Meteorological data are collected from various sensors and equipment located on and off the Hanford Site. These data are stored in data bases on the Digital Equipment Corporation (DEC) VAX 11/750 at the HMS (hereafter referred to as the HMS computer). Files from those data bases are routinely transferred to themore » Emergency Management System (EMS) computer at the Unified Dose Assessment Center (UDAC). To ensure the quality and integrity of the HMS data, a set of Quality Assurance (QA) computer codes has been written. The codes will be routinely used by the HMS system manager or the data base custodian. The QA codes provide detailed output files that will be used in correcting erroneous data. The following sections in this volume describe the implementation and operation of QA computer codes. The appendices contain detailed descriptions, flow charts, and source code listings of each computer code. 2 refs.« less

Nep-Akari Evolution with Redshift of Dust Attenuation in 8 ㎛ Selected Galaxies

NASA Astrophysics Data System (ADS)

Buat, V.; Oi, N.; Burgarella, D.; Malek, K.; Matsuhara, H.; Murata, K.; Serjeant, S.; Takeuchi, T. T.; Malkan, M.; Pearson, C.; Wada, T.

2017-03-01

We built a 8um selected sample of galaxies in the NEP-AKARI field by defining 4 redshift bins with the four AKARI bands at 11, 15, 18 and 24 microns (0.15

A dust spectral energy distribution model with hierarchical Bayesian inference - I. Formalism and benchmarking

NASA Astrophysics Data System (ADS)

Galliano, Frédéric

2018-05-01

This article presents a new dust spectral energy distribution (SED) model, named HerBIE, aimed at eliminating the noise-induced correlations and large scatter obtained when performing least-squares fits. The originality of this code is to apply the hierarchical Bayesian approach to full dust models, including realistic optical properties, stochastic heating, and the mixing of physical conditions in the observed regions. We test the performances of our model by applying it to synthetic observations. We explore the impact on the recovered parameters of several effects: signal-to-noise ratio, SED shape, sample size, the presence of intrinsic correlations, the wavelength coverage, and the use of different SED model components. We show that this method is very efficient: the recovered parameters are consistently distributed around their true values. We do not find any clear bias, even for the most degenerate parameters, or with extreme signal-to-noise ratios.

User's manual for semi-circular compact range reflector code

NASA Technical Reports Server (NTRS)

Gupta, Inder J.; Burnside, Walter D.

1986-01-01

A computer code was developed to analyze a semi-circular paraboloidal reflector antenna with a rolled edge at the top and a skirt at the bottom. The code can be used to compute the total near field of the antenna or its individual components at a given distance from the center of the paraboloid. Thus, it is very effective in computing the size of the sweet spot for RCS or antenna measurement. The operation of the code is described. Various input and output statements are explained. Some results obtained using the computer code are presented to illustrate the code's capability as well as being samples of input/output sets.

Highly fault-tolerant parallel computation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spielman, D.A.

We re-introduce the coded model of fault-tolerant computation in which the input and output of a computational device are treated as words in an error-correcting code. A computational device correctly computes a function in the coded model if its input and output, once decoded, are a valid input and output of the function. In the coded model, it is reasonable to hope to simulate all computational devices by devices whose size is greater by a constant factor but which are exponentially reliable even if each of their components can fail with some constant probability. We consider fine-grained parallel computations inmore » which each processor has a constant probability of producing the wrong output at each time step. We show that any parallel computation that runs for time t on w processors can be performed reliably on a faulty machine in the coded model using w log{sup O(l)} w processors and time t log{sup O(l)} w. The failure probability of the computation will be at most t {center_dot} exp(-w{sup 1/4}). The codes used to communicate with our fault-tolerant machines are generalized Reed-Solomon codes and can thus be encoded and decoded in O(n log{sup O(1)} n) sequential time and are independent of the machine they are used to communicate with. We also show how coded computation can be used to self-correct many linear functions in parallel with arbitrarily small overhead.« less

An emulator for minimizing computer resources for finite element analysis

NASA Technical Reports Server (NTRS)

Melosh, R.; Utku, S.; Islam, M.; Salama, M.

1984-01-01

A computer code, SCOPE, has been developed for predicting the computer resources required for a given analysis code, computer hardware, and structural problem. The cost of running the code is a small fraction (about 3 percent) of the cost of performing the actual analysis. However, its accuracy in predicting the CPU and I/O resources depends intrinsically on the accuracy of calibration data that must be developed once for the computer hardware and the finite element analysis code of interest. Testing of the SCOPE code on the AMDAHL 470 V/8 computer and the ELAS finite element analysis program indicated small I/O errors (3.2 percent), larger CPU errors (17.8 percent), and negligible total errors (1.5 percent).

A generalized one-dimensional computer code for turbomachinery cooling passage flow calculations

NASA Technical Reports Server (NTRS)

Kumar, Ganesh N.; Roelke, Richard J.; Meitner, Peter L.

1989-01-01

A generalized one-dimensional computer code for analyzing the flow and heat transfer in the turbomachinery cooling passages was developed. This code is capable of handling rotating cooling passages with turbulators, 180 degree turns, pin fins, finned passages, by-pass flows, tip cap impingement flows, and flow branching. The code is an extension of a one-dimensional code developed by P. Meitner. In the subject code, correlations for both heat transfer coefficient and pressure loss computations were developed to model each of the above mentioned type of coolant passages. The code has the capability of independently computing the friction factor and heat transfer coefficient on each side of a rectangular passage. Either the mass flow at the inlet to the channel or the exit plane pressure can be specified. For a specified inlet total temperature, inlet total pressure, and exit static pressure, the code computers the flow rates through the main branch and the subbranches, flow through tip cap for impingement cooling, in addition to computing the coolant pressure, temperature, and heat transfer coefficient distribution in each coolant flow branch. Predictions from the subject code for both nonrotating and rotating passages agree well with experimental data. The code was used to analyze the cooling passage of a research cooled radial rotor.

Modeling and simulation of dust behaviors behind a moving vehicle

NASA Astrophysics Data System (ADS)

Wang, Jingfang

Simulation of physically realistic complex dust behaviors is a difficult and attractive problem in computer graphics. A fast, interactive and visually convincing model of dust behaviors behind moving vehicles is very useful in computer simulation, training, education, art, advertising, and entertainment. In my dissertation, an experimental interactive system has been implemented for the simulation of dust behaviors behind moving vehicles. The system includes physically-based models, particle systems, rendering engines and graphical user interface (GUI). I have employed several vehicle models including tanks, cars, and jeeps to test and simulate in different scenarios and conditions. Calm weather, winding condition, vehicle turning left or right, and vehicle simulation controlled by users from the GUI are all included. I have also tested the factors which play against the physical behaviors and graphics appearances of the dust particles through GUI or off-line scripts. The simulations are done on a Silicon Graphics Octane station. The animation of dust behaviors is achieved by physically-based modeling and simulation. The flow around a moving vehicle is modeled using computational fluid dynamics (CFD) techniques. I implement a primitive variable and pressure-correction approach to solve the three dimensional incompressible Navier Stokes equations in a volume covering the moving vehicle. An alternating- direction implicit (ADI) method is used for the solution of the momentum equations, with a successive-over- relaxation (SOR) method for the solution of the Poisson pressure equation. Boundary conditions are defined and simplified according to their dynamic properties. The dust particle dynamics is modeled using particle systems, statistics, and procedure modeling techniques. Graphics and real-time simulation techniques, such as dynamics synchronization, motion blur, blending, and clipping have been employed in the rendering to achieve realistic appearing dust behaviors. In addition, I introduce a temporal smoothing technique to eliminate the jagged effect caused by large simulation time. Several algorithms are used to speed up the simulation. For example, pre-calculated tables and display lists are created to replace some of the most commonly used functions, scripts and processes. The performance study shows that both time and space costs of the algorithms are linear in the number of particles in the system. On a Silicon Graphics Octane, three vehicles with 20,000 particles run at 6-8 frames per second on average. This speed does not include the extra calculations of convergence of the numerical integration for fluid dynamics which usually takes about 4-5 minutes to achieve steady state.

29 CFR 1926.407 - Hazardous (classified) locations.

Code of Federal Regulations, 2012 CFR

2012-07-01

... Electrical Code, lists or defines hazardous gases, vapors, and dusts by “Groups” characterized by their... the class, group, and operating temperature or temperature range, based on operation in a 40-degree C... be marked to indicate the group. (C) Fixed general-purpose equipment in Class I locations, other than...

29 CFR 1926.407 - Hazardous (classified) locations.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Electrical Code, lists or defines hazardous gases, vapors, and dusts by “Groups” characterized by their... the class, group, and operating temperature or temperature range, based on operation in a 40-degree C... be marked to indicate the group. (C) Fixed general-purpose equipment in Class I locations, other than...

Preliminary result of the analysis of T Sagittarrii data and modeling

NASA Astrophysics Data System (ADS)

Menut, Jean-Luc; Chesneau, Olivier; Lopez, Bruno; Berruyer, Nicole; Graser, Uwe; Niccolini, Gilles; Dutrey, Anne; Perrin, Guy S.

2004-10-01

This document shows the first results of the study of the environment of the S star T Sagittarii. Observational constraints are obtained through 10 μm long baseline interferometry with MIDI at the VLTI. Models of the dust envelope are simulated with a monte-carlo radiative transfer code.

Sarcoid-resembling granulomatous lung disease secondary to occupational magnetite iron dust exposure.

PubMed

Xiao, Lewis; Kookana, Anil; McClure, Robert; Heraganahally, Subash

2018-08-01

Non-caseating granulomatous pulmonary conditions resembling sarcoidosis secondary to industrial/occupation exposure to magnetite iron ore dusts have been rarely documented in the literature. This is a case report of a 58-year-old blast crew member involved in iron ore/magnetite mining who presented with a 12-month history of chronic dry cough. High-resolution computed tomography revealed bilateral interstitial opacities. Lung biopsy demonstrated sarcoid-like granulomatous inflammation. Oral corticosteroid treatment improved the cough. Radiological features did not resolve despite treatment and yet remained stable following no subsequent exposure to iron mining dust.

Dust grain characterization — Direct measurement of light scattering

NASA Astrophysics Data System (ADS)

BartoÅ, P.; Pavlů, J.

2018-01-01

Dust grains play a key role in dusty plasma since they interact with the plasma we can use them to study plasma itself. The grains are illuminated by visible light (e.g., a laser sheet) and the situation is captured with camera. Despite of simplicity, light scattering on similar-to-wavelength sized grains is complex phenomenon. Interaction of the electromagnetic wave with material has to be computed with respect to Maxwell equations — analytic solution is nowadays available only for several selected shapes like sphere, coated sphere, or infinite cylinder. Moreover, material constants needed for computations are usually unknown. For computation result verification and material constant determination, we designed and developed a device directly measur­ing light scattering profiles. Single dust grains are trapped in the ultrasonic field (so called "acoustic levitation") and illuminated by the laser beam. Scattered light is then measured by a photodiode mounted on rotating platform. Synchronous detection is employed for a noise reduction. This setup brings several benefits against conventional methods: (1) it works in the free air, (2) the measured grain is captured for a long time, and (3) the grain could be of arbitrary shape.

Efficient Proximity Computation Techniques Using ZIP Code Data for Smart Cities †

PubMed Central

Murdani, Muhammad Harist; Hong, Bonghee

2018-01-01

In this paper, we are interested in computing ZIP code proximity from two perspectives, proximity between two ZIP codes (Ad-Hoc) and neighborhood proximity (Top-K). Such a computation can be used for ZIP code-based target marketing as one of the smart city applications. A naïve approach to this computation is the usage of the distance between ZIP codes. We redefine a distance metric combining the centroid distance with the intersecting road network between ZIP codes by using a weighted sum method. Furthermore, we prove that the results of our combined approach conform to the characteristics of distance measurement. We have proposed a general and heuristic approach for computing Ad-Hoc proximity, while for computing Top-K proximity, we have proposed a general approach only. Our experimental results indicate that our approaches are verifiable and effective in reducing the execution time and search space. PMID:29587366

Efficient Proximity Computation Techniques Using ZIP Code Data for Smart Cities †.

PubMed

Murdani, Muhammad Harist; Kwon, Joonho; Choi, Yoon-Ho; Hong, Bonghee

2018-03-24

In this paper, we are interested in computing ZIP code proximity from two perspectives, proximity between two ZIP codes ( Ad-Hoc ) and neighborhood proximity ( Top-K ). Such a computation can be used for ZIP code-based target marketing as one of the smart city applications. A naïve approach to this computation is the usage of the distance between ZIP codes. We redefine a distance metric combining the centroid distance with the intersecting road network between ZIP codes by using a weighted sum method. Furthermore, we prove that the results of our combined approach conform to the characteristics of distance measurement. We have proposed a general and heuristic approach for computing Ad-Hoc proximity, while for computing Top-K proximity, we have proposed a general approach only. Our experimental results indicate that our approaches are verifiable and effective in reducing the execution time and search space.

Cloudy - simulating the non-equilibrium microphysics of gas and dust, and its observed spectrum

NASA Astrophysics Data System (ADS)

Ferland, Gary J.

2014-01-01

Cloudy is an open-source plasma/spectral simulation code, last described in the open-access journal Revista Mexicana (Ferland et al. 2013, 2013RMxAA..49..137F). The project goal is a complete simulation of the microphysics of gas and dust over the full range of density, temperature, and ionization that we encounter in astrophysics, together with a prediction of the observed spectrum. Cloudy is one of the more widely used theory codes in astrophysics with roughly 200 papers citing its documentation each year. It is developed by graduate students, postdocs, and an international network of collaborators. Cloudy is freely available on the web at trac.nublado.org, the user community can post questions on http://groups.yahoo.com/neo/groups/cloudy_simulations/info, and summer schools are organized to learn more about Cloudy and its use (http://cloud9.pa.uky.edu gary/cloudy/CloudySummerSchool/). The code’s widespread use is possible because of extensive automatic testing. It is exercised over its full range of applicability whenever the source is changed. Changes in predicted quantities are automatically detected along with any newly introduced problems. The code is designed to be autonomous and self-aware. It generates a report at the end of a calculation that summarizes any problems encountered along with suggestions of potentially incorrect boundary conditions. This self-monitoring is a core feature since the code is now often used to generate large MPI grids of simulations, making it impossible for a user to verify each calculation by hand. I will describe some challenges in developing a large physics code, with its many interconnected physical processes, many at the frontier of research in atomic or molecular physics, all in an open environment.

Volume accumulator design analysis computer codes

NASA Technical Reports Server (NTRS)

Whitaker, W. D.; Shimazaki, T. T.

1973-01-01

The computer codes, VANEP and VANES, were written and used to aid in the design and performance calculation of the volume accumulator units (VAU) for the 5-kwe reactor thermoelectric system. VANEP computes the VAU design which meets the primary coolant loop VAU volume and pressure performance requirements. VANES computes the performance of the VAU design, determined from the VANEP code, at the conditions of the secondary coolant loop. The codes can also compute the performance characteristics of the VAU's under conditions of possible modes of failure which still permit continued system operation.

"Hour of Code": Can It Change Students' Attitudes toward Programming?

ERIC Educational Resources Information Center

Du, Jie; Wimmer, Hayden; Rada, Roy

2016-01-01

The Hour of Code is a one-hour introduction to computer science organized by Code.org, a non-profit dedicated to expanding participation in computer science. This study investigated the impact of the Hour of Code on students' attitudes towards computer programming and their knowledge of programming. A sample of undergraduate students from two…

Talking about Code: Integrating Pedagogical Code Reviews into Early Computing Courses

ERIC Educational Resources Information Center

Hundhausen, Christopher D.; Agrawal, Anukrati; Agarwal, Pawan

2013-01-01

Given the increasing importance of soft skills in the computing profession, there is good reason to provide students withmore opportunities to learn and practice those skills in undergraduate computing courses. Toward that end, we have developed an active learning approach for computing education called the "Pedagogical Code Review"…

Particle sizes and composition of Mars atmospheric dust based upon Viking and Mariner 9 observations

NASA Technical Reports Server (NTRS)

Clancy, R. T.; Lee, S. W.; Gladstone, G. R.

1993-01-01

Mars atmospheric dust can play an important role in the thermal structure of the Mars atmosphere during periods of high dust loading. However, the radiative properties of Mars atmospheric dust remain uncertain due to uncertain definitions of the dust composition and size distribution. The analysis by Toon et al., of Mariner 9 IRIS spectra during the 1971-1972 global dust storm indicated a reasonable match between the modeled 9-micron absorption of montmorillinite and the observed 9-micron absorption. Toon et al. also determined that an effective (cross-section weighted) mean radius of 2.5 microns (R(sub mode) = 0.4 microns) provided a consistent fit of montmorillinite to the IRIS dust spectra at 9 microns. Pollack et al. analyzed Viking lander observations of atmospheric extinction and scattering at visible-near IR wavelengths (0.5-1.0 microns), and obtained consistency with the Toon et al. dust size distribution when the effects of nonspherical particle shapes were included. An additional, minor (1 percent) component of visible-ultraviolet absorbing material was required to model the derived visible (0.86) and ultraviolet (0.4-0.6) single-scattering albedos of the dust, since montmorillinite does not absorb sufficiently in this wavelength region. A combined analysis of the Viking IRTM and Mariner 9 observations was conducted to reassess the model of Mars atmospheric ultraviolet-to-infrared measurements of dust absorption and scattering. The optical constants for palagonite are incorporated in a doubling-adding radiative transfer model of the Mars atmosphere to simulate Mariner 9 IRIS spectra as well as the Viking IRTM IR band observations. Visible and ultraviolet single-scattering albedos based on the Hansen and Travis Mie scattering code were also derived. A tentative conclusion is that smaller dust particles (R(sub mode) = 0.15 microns, cross-section weighted mean R = 1.2 microns) composed of palagonite provide a much improved fit to the Mariner 9 IRIS spectra; agreement with the observed ratio of visible-to-infrared extinction opacities; and ultraviolet and visible single-scattering albedos comparable to their observed values.

Evaluation of the Community Multiscale Air Quality (CMAQ) ...

EPA Pesticide Factsheets

The Community Multiscale Air Quality (CMAQ) model is a state-of-the-science air quality model that simulates the emission, transport and fate of numerous air pollutants, including ozone and particulate matter. The Computational Exposure Division (CED) of the U.S. Environmental Protection Agency develops the CMAQ model and periodically releases new versions of the model that include bug fixes and various other improvements to the modeling system. In the fall of 2016, CMAQ version 5.1.1 will be released. This new version of CMAQ will contain important bug fixes to several issues that were identified in CMAQv5.1 (the current public release version of the CMAQ model), and additionally include updates to other portions of the code. Some specific model updates include a new implementation of the wind-blown dust calculation in CMAQv5.1.1 which fixes several bugs that were identified in the current implementation of wind-blown dust in CMAQv5.1. Several other major updates to the model include an update to the calculation of aerosols; implementation of full halogen chemistry (CMAQv5.1 contains a partial implementation of halogen chemistry), which is particularly important for hemispheric applications of the CMAQ model, as halogen chemistry is need to accurately simulation the destruction of ozone over the ocean; and the new carbon bond 6 (CB6) chemical mechanism. Several annual, and numerous episodic, CMAQv5.1.1 simulations will be performed to assess the impact of these

Guidelines for developing vectorizable computer programs

NASA Technical Reports Server (NTRS)

Miner, E. W.

1982-01-01

Some fundamental principles for developing computer programs which are compatible with array-oriented computers are presented. The emphasis is on basic techniques for structuring computer codes which are applicable in FORTRAN and do not require a special programming language or exact a significant penalty on a scalar computer. Researchers who are using numerical techniques to solve problems in engineering can apply these basic principles and thus develop transportable computer programs (in FORTRAN) which contain much vectorizable code. The vector architecture of the ASC is discussed so that the requirements of array processing can be better appreciated. The "vectorization" of a finite-difference viscous shock-layer code is used as an example to illustrate the benefits and some of the difficulties involved. Increases in computing speed with vectorization are illustrated with results from the viscous shock-layer code and from a finite-element shock tube code. The applicability of these principles was substantiated through running programs on other computers with array-associated computing characteristics, such as the Hewlett-Packard (H-P) 1000-F.

Computer Security for the Computer Systems Manager.

DTIC Science & Technology

1982-12-01

power sources essential to system availabilit y. Environsental degradation can cause system collapse or simply make the arer uncomforable work in...attack (civil disobedience, military as- sault, arson, locting, sabotage, vanlilism) * fire • smoke, dust, and dirt intrusion * bursting water pipes

The Helicopter Antenna Radiation Prediction Code (HARP)

NASA Technical Reports Server (NTRS)

Klevenow, F. T.; Lynch, B. G.; Newman, E. H.; Rojas, R. G.; Scheick, J. T.; Shamansky, H. T.; Sze, K. Y.

1990-01-01

The first nine months effort in the development of a user oriented computer code, referred to as the HARP code, for analyzing the radiation from helicopter antennas is described. The HARP code uses modern computer graphics to aid in the description and display of the helicopter geometry. At low frequencies the helicopter is modeled by polygonal plates, and the method of moments is used to compute the desired patterns. At high frequencies the helicopter is modeled by a composite ellipsoid and flat plates, and computations are made using the geometrical theory of diffraction. The HARP code will provide a user friendly interface, employing modern computer graphics, to aid the user to describe the helicopter geometry, select the method of computation, construct the desired high or low frequency model, and display the results.

Longwave radiative effects of Saharan dust during the ICE-D campaign

NASA Astrophysics Data System (ADS)

Brooke, Jennifer; Havemann, Stephan; Ryder, Claire; O'Sullivan, Debbie

2017-04-01

The Havemann-Taylor Fast Radiative Transfer Code (HT-FRTC) is a fast radiative transfer model based on Principal Components. Scattering has been incorporated into HT-FRTC which allows simulations of aerosol as well as clear-sky atmospheres. This work evaluates the scattering scheme in HT-FRTC and investigates dust-affected brightness temperatures using in-situ observations from Ice in Clouds Experiment - Dust (ICE-D) campaign. The ICE-D campaign occurred during August 2015 and was based from Cape Verde. The ICE-D campaign is a multidisciplinary project which achieved measurements of in-situ mineral dust properties of the dust advected from the Sahara, and on the aerosol-cloud interactions using the FAAM BAe-146 research aircraft. ICE-D encountered a range of low (0.3), intermediate (0.8) and high (1.3) aerosol optical depths, AODs, and therefore provides a range of atmospheric dust loadings in the assessment of dust scattering in HT-FRTC. Spectral radiances in the thermal infrared window region (800 - 1200 cm-1) are sensitive to the presence of mineral dust; mineral dust acts to reduce the upwelling infrared radiation caused by the absorption and re-emission of radiation by the dust layer. ARIES (Airborne Research Interferometer Evaluation System) is a nadir-facing interferometer, measuring infrared radiances between 550 and 3000 cm-1. The ARIES spectral radiances are converted to brightness temperatures by inversion of the Planck function. The mineral dust size distribution is important for radiative transfer applications as it provides a measure of aerosol scattering. The longwave spectral mineral dust optical properties including the mass extinction coefficients, single scattering albedos and the asymmetry parameter have been derived from the mean ICE-D size distribution. HT-FRTC scattering simulations are initialised with vertical mass fractions which can be derived from extinction profiles from the lidar along with the specific extinction coefficient, kext (m2/g) at 355 nm. In general the comparison between the lidar retrieval of aerosol extinction coefficients and in-situ measurements show a good agreement. The root mean square of the brightness temperature residuals in the window region for observations (ARIES) minus model simulations for i) clear-sky, ii) HT-FRTC 'line-by-line' scattering and, iii) HT-FRTC fast scattering are calculated. For the ICE-D case studies mineral dust impacts on the brightness temperature of the background on the order of 1 - 1.5 K.

Enhanced fault-tolerant quantum computing in d-level systems.

PubMed

Campbell, Earl T

2014-12-05

Error-correcting codes protect quantum information and form the basis of fault-tolerant quantum computing. Leading proposals for fault-tolerant quantum computation require codes with an exceedingly rare property, a transversal non-Clifford gate. Codes with the desired property are presented for d-level qudit systems with prime d. The codes use n=d-1 qudits and can detect up to ∼d/3 errors. We quantify the performance of these codes for one approach to quantum computation known as magic-state distillation. Unlike prior work, we find performance is always enhanced by increasing d.

Convergence acceleration of the Proteus computer code with multigrid methods

NASA Technical Reports Server (NTRS)

Demuren, A. O.; Ibraheem, S. O.

1992-01-01

Presented here is the first part of a study to implement convergence acceleration techniques based on the multigrid concept in the Proteus computer code. A review is given of previous studies on the implementation of multigrid methods in computer codes for compressible flow analysis. Also presented is a detailed stability analysis of upwind and central-difference based numerical schemes for solving the Euler and Navier-Stokes equations. Results are given of a convergence study of the Proteus code on computational grids of different sizes. The results presented here form the foundation for the implementation of multigrid methods in the Proteus code.

Implementation of radiation shielding calculation methods. Volume 1: Synopsis of methods and summary of results

NASA Technical Reports Server (NTRS)

Capo, M. A.; Disney, R. K.

1971-01-01

The work performed in the following areas is summarized: (1) Analysis of Realistic nuclear-propelled vehicle was analyzed using the Marshall Space Flight Center computer code package. This code package includes one and two dimensional discrete ordinate transport, point kernel, and single scatter techniques, as well as cross section preparation and data processing codes, (2) Techniques were developed to improve the automated data transfer in the coupled computation method of the computer code package and improve the utilization of this code package on the Univac-1108 computer system. (3) The MSFC master data libraries were updated.

Nonuniform code concatenation for universal fault-tolerant quantum computing

NASA Astrophysics Data System (ADS)

Nikahd, Eesa; Sedighi, Mehdi; Saheb Zamani, Morteza

2017-09-01

Using transversal gates is a straightforward and efficient technique for fault-tolerant quantum computing. Since transversal gates alone cannot be computationally universal, they must be combined with other approaches such as magic state distillation, code switching, or code concatenation to achieve universality. In this paper we propose an alternative approach for universal fault-tolerant quantum computing, mainly based on the code concatenation approach proposed in [T. Jochym-O'Connor and R. Laflamme, Phys. Rev. Lett. 112, 010505 (2014), 10.1103/PhysRevLett.112.010505], but in a nonuniform fashion. The proposed approach is described based on nonuniform concatenation of the 7-qubit Steane code with the 15-qubit Reed-Muller code, as well as the 5-qubit code with the 15-qubit Reed-Muller code, which lead to two 49-qubit and 47-qubit codes, respectively. These codes can correct any arbitrary single physical error with the ability to perform a universal set of fault-tolerant gates, without using magic state distillation.

Characterizing the Variable Dust Permeability of Planet-induced Gaps

NASA Astrophysics Data System (ADS)

Weber, Philipp; Benítez-Llambay, Pablo; Gressel, Oliver; Krapp, Leonardo; Pessah, Martin E.

2018-02-01

Aerodynamic theory predicts that dust grains in protoplanetary disks will drift radially inward on comparatively short timescales. In this context, it has long been known that the presence of a gap opened by a planet can significantly alter the dust dynamics. In this paper, we carry out a systematic study employing long-term numerical simulations aimed at characterizing the critical particle size for retention outside a gap as a function of particle size, as well as various key parameters defining the protoplanetary disk model. To this end, we perform multifluid hydrodynamical simulations in two dimensions, including different dust species, which we treat as pressureless fluids. We initialize the dust outside of the planet’s orbit and study under which conditions dust grains are able to cross the gap carved by the planet. In agreement with previous work, we find that the permeability of the gap depends both on dust dynamical properties and the gas disk structure: while small dust follows the viscously accreting gas through the gap, dust grains approaching a critical size are progressively filtered out. Moreover, we introduce and compute a depletion factor that enables us to quantify the way in which higher viscosity, smaller planet mass, or a more massive disk can shift this critical size to larger values. Our results indicate that gap-opening planets may act to deplete the inner reaches of protoplanetary disks of large dust grains—potentially limiting the accretion of solids onto forming terrestrial planets.

Mixing weight determination for retrieving optical properties of polluted dust with MODIS and AERONET data

NASA Astrophysics Data System (ADS)

Chang, Kuo-En; Hsiao, Ta-Chih; Hsu, N. Christina; Lin, Neng-Huei; Wang, Sheng-Hsiang; Liu, Gin-Rong; Liu, Chian-Yi; Lin, Tang-Huang

2016-08-01

In this study, an approach in determining effective mixing weight of soot aggregates from dust-soot aerosols is proposed to improve the accuracy of retrieving properties of polluted dusts by means of satellite remote sensing. Based on a pre-computed database containing several variables (such as wavelength, refractive index, soot mixing weight, surface reflectivity, observation geometries and aerosol optical depth (AOD)), the fan-shaped look-up tables can be drawn out accordingly for determining the mixing weights, AOD and single scattering albedo (SSA) of polluted dusts simultaneously with auxiliary regional dust properties and surface reflectivity. To validate the performance of the approach in this study, 6 cases study of polluted dusts (dust-soot aerosols) in Lower Egypt and Israel were examined with the ground-based measurements through AErosol RObotic NETwork (AERONET). The results show that the mean absolute differences could be reduced from 32.95% to 6.56% in AOD and from 2.67% to 0.83% in SSA retrievals for MODIS aerosol products when referenced to AERONET measurements, demonstrating the soundness of the proposed approach under different levels of dust loading, mixing weight and surface reflectivity. Furthermore, the developed algorithm is capable of providing the spatial distribution of the mixing weights and removing the requirement to assume that the dust plume properties are uniform. The case study further shows the spatially variant dust-soot mixing weight would improve the retrieval accuracy in AODmixture and SSAmixture about 10.0% and 1.4% respectively.

Experimental Phase Functions of Millimeter-sized Cosmic Dust Grains

NASA Astrophysics Data System (ADS)

Muñoz, O.; Moreno, F.; Vargas-Martín, F.; Guirado, D.; Escobar-Cerezo, J.; Min, M.; Hovenier, J. W.

2017-09-01

We present the experimental phase functions of three types of millimeter-sized dust grains consisting of enstatite, quartz, and volcanic material from Mount Etna, respectively. The three grains present similar sizes but different absorbing properties. The measurements are performed at 527 nm covering the scattering angle range from 3° to 170°. The measured phase functions show two well-defined regions: (I) soft forward peaks and (II) a continuous increase with the scattering angle at side- and back-scattering regions. This behavior at side- and back-scattering regions is in agreement with the observed phase functions of the Fomalhaut and HR 4796A dust rings. Further computations and measurements (including polarization) for millimeter-sized grains are needed to draw some conclusions about the fluffy or compact structure of the dust grains.

Star and Dust Formation Activities in AzTEC-3, a Starburst Galaxy at z = 5.3

NASA Astrophysics Data System (ADS)

Dwek, Eli; Staguhn, Johannes G.; Arendt, Richard G.; Capak, Peter L.; Kovacs, Attila; Benford, Dominic J.; Fixsen, Dale; Karim, Alexander; Leclercq, Samuel; Maher, Stephen F.; Moseley, Samuel H.; Schinnerer, Eva; Sharp, Elmer H.

2011-09-01

Analyses of high-redshift ultraluminous infrared (IR) galaxies traditionally use the observed optical to submillimeter spectral energy distribution (SED) and estimates of the dynamical mass as observational constraints to derive the star formation rate (SFR), the stellar mass, and age of these objects. An important observational constraint neglected in the analysis is the mass of dust giving rise to the IR emission. In this paper we add this constraint to the analysis of AzTEC-3. Adopting an upper limit to the mass of stars and a bolometric luminosity for this object, we construct different stellar and chemical evolutionary scenarios, constrained to produce the inferred dust mass and observed luminosity before the associated stellar mass exceeds the observational limit. We use the PÉGASE population synthesis code and a chemical evolution model to follow the evolution of the galaxy's SED and its stellar and dust masses as a function of galactic age for seven different stellar initial mass functions (IMFs). We find that the model with a Top Heavy IMF provided the most plausible scenario consistent with the observational constraints. In this scenario the dust formed over a period of ~200 Myr, with an SFR of ~500 M sun yr-1. These values for the age and SFR in AzTEC-3 are significantly higher and lower, respectively, from those derived without the dust mass constraint. However, this scenario is not unique, and others cannot be completely ruled out because of the prevailing uncertainties in the age of the galaxy, its bolometric luminosity, and its stellar and dust masses. A robust result of our models is that all scenarios require most of the radiating dust mass to have been accreted in molecular clouds. Our new procedure highlights the importance of a multiwavelength approach, and of the use of dust evolution models in constraining the age and the star formation activity and history in galaxies.

STAR AND DUST FORMATION ACTIVITIES IN AzTEC-3, A STARBURST GALAXY AT z = 5.3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dwek, Eli; Staguhn, Johannes G.; Arendt, Richard G.

2011-09-01

Analyses of high-redshift ultraluminous infrared (IR) galaxies traditionally use the observed optical to submillimeter spectral energy distribution (SED) and estimates of the dynamical mass as observational constraints to derive the star formation rate (SFR), the stellar mass, and age of these objects. An important observational constraint neglected in the analysis is the mass of dust giving rise to the IR emission. In this paper we add this constraint to the analysis of AzTEC-3. Adopting an upper limit to the mass of stars and a bolometric luminosity for this object, we construct different stellar and chemical evolutionary scenarios, constrained to producemore » the inferred dust mass and observed luminosity before the associated stellar mass exceeds the observational limit. We use the PEGASE population synthesis code and a chemical evolution model to follow the evolution of the galaxy's SED and its stellar and dust masses as a function of galactic age for seven different stellar initial mass functions (IMFs). We find that the model with a Top Heavy IMF provided the most plausible scenario consistent with the observational constraints. In this scenario the dust formed over a period of {approx}200 Myr, with an SFR of {approx}500 M{sub sun} yr{sup -1}. These values for the age and SFR in AzTEC-3 are significantly higher and lower, respectively, from those derived without the dust mass constraint. However, this scenario is not unique, and others cannot be completely ruled out because of the prevailing uncertainties in the age of the galaxy, its bolometric luminosity, and its stellar and dust masses. A robust result of our models is that all scenarios require most of the radiating dust mass to have been accreted in molecular clouds. Our new procedure highlights the importance of a multiwavelength approach, and of the use of dust evolution models in constraining the age and the star formation activity and history in galaxies.« less

Why Is Improvement of Earth System Models so Elusive? Challenges and Strategies from Dust Aerosol Modeling

NASA Technical Reports Server (NTRS)

Miller, Ronald L.; Garcia-Pando, Carlos Perez; Perlwitz, Jan; Ginoux, Paul

2015-01-01

Past decades have seen an accelerating increase in computing efficiency, while climate models are representing a rapidly widening set of physical processes. Yet simulations of some fundamental aspects of climate like precipitation or aerosol forcing remain highly uncertain and resistant to progress. Dust aerosol modeling of soil particles lofted by wind erosion has seen a similar conflict between increasing model sophistication and remaining uncertainty. Dust aerosols perturb the energy and water cycles by scattering radiation and acting as ice nuclei, while mediating atmospheric chemistry and marine photosynthesis (and thus the carbon cycle). These effects take place across scales from the dimensions of an ice crystal to the planetary-scale circulation that disperses dust far downwind of its parent soil. Representing this range leads to several modeling challenges. Should we limit complexity in our model, which consumes computer resources and inhibits interpretation? How do we decide if a process involving dust is worthy of inclusion within our model? Can we identify a minimal representation of a complex process that is efficient yet retains the physics relevant to climate? Answering these questions about the appropriate degree of representation is guided by model evaluation, which presents several more challenges. How do we proceed if the available observations do not directly constrain our process of interest? (This could result from competing processes that influence the observed variable and obscure the signature of our process of interest.) Examples will be presented from dust modeling, with lessons that might be more broadly applicable. The end result will either be clinical depression or there assuring promise of continued gainful employment as the community confronts these challenges.

Green's function methods in heavy ion shielding

NASA Technical Reports Server (NTRS)

Wilson, John W.; Costen, Robert C.; Shinn, Judy L.; Badavi, Francis F.

1993-01-01

An analytic solution to the heavy ion transport in terms of Green's function is used to generate a highly efficient computer code for space applications. The efficiency of the computer code is accomplished by a nonperturbative technique extending Green's function over the solution domain. The computer code can also be applied to accelerator boundary conditions to allow code validation in laboratory experiments.

Distribution of Dust from Kuiper Belt Objects

NASA Technical Reports Server (NTRS)

Gorkavyi, Nick N.; Ozernoy, Leonid; Taidakova, Tanya; Mather, John C.; Fisher, Richard (Technical Monitor)

2000-01-01

Using an efficient computational approach, we have reconstructed the structure of the dust cloud in the Solar system between 0.5 and 100 AU produced by the Kuiper belt objects. Our simulations offer a 3-D physical model of the 'kuiperoidal' dust cloud based on the distribution of 280 dust particle trajectories produced by 100 known Kuiper belt objects; the resulting 3-D grid consists of 1.9 x 10' cells containing 1.2 x 10" particle positions. The following processes that influence the dust particle dynamics are taken into account: 1) gravitational scattering on the eight planets (neglecting Pluto); 2) planetary resonances; 3) radiation pressure; and 4) the Poynting-Robertson (P-R) and solar wind drags. We find the dust distribution highly non-uniform: there is a minimum in the kuiperoidal dust between Mars and Jupiter, after which both the column and number densities of kuiperoidal dust sharply increase with heliocentric distance between 5 and 10 AU, and then form a plateau between 10 and 50 AU. Between 25 and 45 AU, there is an appreciable concentration of kuiperoidal dust in the form of a broad belt of mostly resonant particles associated with Neptune. In fact, each giant planet possesses its own circumsolar dust belt consisting of both resonant and gravitationally scattered particles. As with the cometary belts simulated in our related papers, we reveal a rich and sophisticated resonant structure of the dust belts containing families of resonant peaks and gaps. An important result is that both the column and number dust density are more or less flat between 10 and 50 AU, which might explain the surprising data obtained by Pioneers 10 & 11 and Voyager that the dust number density remains approximately distance-independent in this region. The simulated kuiperoidal dust, in addition to asteroidal and cometary dust, might represent a third possible source of the zodiacal light in the Solar system.

VLTI monitoring of the dust formation event of the Nova V1280 Scorpii

NASA Astrophysics Data System (ADS)

Chesneau, O.; Banerjee, D. P. K.; Millour, F.; Nardetto, N.; Sacuto, S.; Spang, A.; Wittkowski, M.; Ashok, N. M.; Das, R. K.; Hummel, C.; Kraus, S.; Lagadec, E.; Morel, S.; Petr-Gotzens, M.; Rantakyro, F.; Schöller, M.

2008-08-01

Context: We present the first high spatial-resolution monitoring of the dust-forming nova V1280 Sco, performed with the Very Large Telescope Interferometer (VLTI). Aims: These observations promise to improve the distance determination of such events and constrain the mechanisms leading to very efficient dust formation under the harsh physical conditions encountered in novae ejecta. Methods: Spectra and visibilities were regularly acquired between the onset of dust formation, 23 days after discovery (or 11 days after maximum), and day 145, using the beam-combiner instruments AMBER (near-IR) and MIDI (mid-IR). These interferometric observations were complemented by near-infrared data from the 1.2 m Mt. Abu Infrared Observatory, India. The observations are initially interpreted in terms of simple uniform models; however more complex models, probably involving a second shell, are required to explain data acquired following t=110 d after outburst. This behavior is in accordance with the light curve of V1280 Sco, which exhibits a secondary peak at about t=106 d, followed by a new, steep decline, suggesting a new dust-forming event. Spherical dust shell models generated with the DUSTY code are used to investigate the parameters of the main dust shell. Results: Using uniform disk models, these observations allow us to determine an apparent linear expansion rate for the dust shell of 0.35 ± 0.03 mas day-1 and the approximate ejection time of the matter in which dust formed of t_ejec = 10.5 ± 7 d, i.e. close to the maximum brightness. This information, combined with the expansion velocity of 500 ± 100 km s-1, implies a distance estimate of 1.6 ± 0.4 kpc. The sparse uv coverage does not enable deviations from spherical symmetry to be clearly discerned. The dust envelope parameters were determined. The dust mass generated was typically 2-8 × 10-9 M_⊙ day-1, with a probable peak in production at about 20 days after the detection of dust and another peak shortly after t=110 d, when the amount of dust in the shell was estimated as 2.2 × 10-7 M_⊙. Considering that the dust-forming event lasted at least 200-250 d, the mass of the ejected material is likely to have exceeded 10-4 M_⊙. The conditions for the formation of multiple shells of dust are also discussed. Based on observations made with the Very Large Telescope Interferometer at Paranal Observatory under programs 278.D-5053, 279.D-5014 and 079.D-0415.

Analytical modeling of operating characteristics of premixing-prevaporizing fuel-air mixing passages. Volume 2: User's manual

NASA Technical Reports Server (NTRS)

Anderson, O. L.; Chiappetta, L. M.; Edwards, D. E.; Mcvey, J. B.

1982-01-01

A user's manual describing the operation of three computer codes (ADD code, PTRAK code, and VAPDIF code) is presented. The general features of the computer codes, the input/output formats, run streams, and sample input cases are described.

Interrelating meteorite and asteroid spectra at UV-Vis-NIR wavelengths using novel multiple-scattering methods

NASA Astrophysics Data System (ADS)

Martikainen, Julia; Penttilä, Antti; Gritsevich, Maria; Muinonen, Karri

2017-10-01

Asteroids have remained mostly the same for the past 4.5 billion years, and provide us information on the origin, evolution and current state of the Solar System. Asteroids and meteorites can be linked by matching their respective reflectance spectra. This is difficult, because spectral features depend strongly on the surface properties, and meteorite surfaces are free of regolith dust present in asteroids. Furthermore, asteroid surfaces experience space weathering which affects their spectral features.We present a novel simulation framework for assessing the spectral properties of meteorites and asteroids and matching their reflectance spectra. The simulations are carried out by utilizing a light-scattering code that takes inhomogeneous waves into account and simulates light scattering by Gaussian-random-sphere particles large compared to the wavelength of the incident light. The code uses incoherent input and computes phase matrices by utilizing incoherent scattering matrices. Reflectance spectra are modeled by combining olivine, pyroxene, and iron, the most common materials that dominate the spectral features of asteroids and meteorites. Space weathering is taken into account by adding nanoiron into the modeled asteroid spectrum. The complex refractive indices needed for the simulations are obtained from existing databases, or derived using an optimization that utilizes our ray-optics code and the measured spectrum of the material.We demonstrate our approach by applying it to the reflectance spectrum of (4) Vesta and the reflectance spectrum of the Johnstown meteorite measured with the University of Helsinki integrating-sphere UV-Vis-NIR spectrometer.Acknowledgments. The research is funded by the ERC Advanced Grant No. 320773 (SAEMPL).

Dust control by air-blocking shelves and dust collector-to-bailing airflow ratios for a surface mine drill shroud

PubMed Central

Zheng, Y.; Reed, W.R.; Potts, J.D.; Li, M.; Rider, J.P.

2018-01-01

The National Institute for Occupational Safety and Health (NIOSH) recently developed a series of validated models utilizing computational fluid dynamics (CFD) to study the effects of air-blocking shelves on airflows and respirable dust distribution associated with medium-sized surface blasthole drill shrouds as part of a dry dust collector system. Using validated CFD models, three different air-blocking shelves were included in the present study: a 15.2-cm (6-in.)-wide shelf; a 7.6-cm (3-in.)-wide shelf; and a 7.6-cm (3-in.)-wide shelf at four different shelf heights. In addition, the dust-collector-to-bailing airflow ratios of 1.75:1, 1.5:1, 1.25:1 and 1:1 were evaluated for the 15.2-cm (6-in.)-wide air-blocking shelf. This paper describes the methodology used to develop the CFD models. The effects of air-blocking shelves and dust collector-to-bailing airflow ratios were identified by the study, and problem regions were revealed under certain conditions.

Instrument study of the Lunar Dust eXplorer (LDX) for a lunar lander mission

NASA Astrophysics Data System (ADS)

Li, Yanwei; Srama, Ralf; Henkel, Hartmut; Sternovsky, Zoltan; Kempf, Sascha; Wu, Yiyong; Grün, Eberhard

2014-11-01

One of the highest-priority issues for a future human or robotic lunar exploration is the lunar dust. This problem should be studied in depth in order to develop an environment model for a future lunar exploration. A future ESA lunar lander mission requires the measurement of dust transport phenomena above the lunar surface. Here, we describe an instrument design concept to measure slow and fast moving charged lunar dust which is based on the principle of charge induction. LDX has a low mass and measures the speed and trajectory of individual dust particles with sizes below one micrometer. Furthermore, LDX has an impact ionization target to monitor the interplanetary dust background. The sensor consists of three planes of segmented grid electrodes and each electrode is connected to an individual charge sensitive amplifier. Numerical signals were computed using the Coulomb software package. The LDX sensitive area is approximately 400 cm2. Our simulations reveal trajectory uncertainties of better than 2° with an absolute position accuracy of better than 2 mm.

Shock tubes and waves; Proceedings of the Sixteenth International Symposium, Rheinisch-Westfaelische Technische Hochschule, Aachen, Federal Republic of Germany, July 26-31, 1987

NASA Astrophysics Data System (ADS)

Groenig, Hans

Topics discussed in this volume include shock wave structure, propagation, and interaction; shocks in condensed matter, dusty gases, and multiphase media; chemical processes and related combustion and detonation phenomena; shock wave reflection, diffraction, and focusing; computational fluid dynamic code development and shock wave application; blast and detonation waves; advanced shock tube technology and measuring technique; and shock wave applications. Papers are presented on dust explosions, the dynamics of shock waves in certain dense gases, studies of condensation kinetics behind incident shock waves, the autoignition mechanism of n-butane behind a reflected shock wave, and a numerical simulation of the focusing process of reflected shock waves. Attention is also given to the equilibrium shock tube flow of real gases, blast waves generated by planar detonations, modern diagnostic methods for high-speed flows, and interaction between induced waves and electric discharge in a very high repetition rate excimer laser.

Asynchronously Coupled Models of Ice Loss from Airless Planetary Bodies

NASA Astrophysics Data System (ADS)

Schorghofer, N.

2016-12-01

Ice is found near the surface of dwarf planet Ceres, in some main belt asteroids, and perhaps in NEOs that will be explored or even mined in future. The simple but important question of how fast ice is lost from airless bodies can present computational challenges. The thermal cycle on the surface repeats on much shorter time-scales than ice retreats; one process acts on the time-scale of hours, the other over billions of years. This multi-scale situation is addressed with asynchronous coupling, where models with different time steps are woven together. The sharp contrast at the retreating ice table is dealt with with explicit interface tracking. For Ceres, which is covered with a thermally insulating dust mantle, desiccation rates are orders of magnitude slower than had been calculated with simpler models. More model challenges remain: The role of impact devolatization and the time-scale for complete desiccation of an asteroid. I will also share my experience with code distribution using GitHub and Zenodo.

A multi-approach feature extractions for iris recognition

NASA Astrophysics Data System (ADS)

Sanpachai, H.; Settapong, M.

2014-04-01

Biometrics is a promising technique that is used to identify individual traits and characteristics. Iris recognition is one of the most reliable biometric methods. As iris texture and color is fully developed within a year of birth, it remains unchanged throughout a person's life. Contrary to fingerprint, which can be altered due to several aspects including accidental damage, dry or oily skin and dust. Although iris recognition has been studied for more than a decade, there are limited commercial products available due to its arduous requirement such as camera resolution, hardware size, expensive equipment and computational complexity. However, at the present time, technology has overcome these obstacles. Iris recognition can be done through several sequential steps which include pre-processing, features extractions, post-processing, and matching stage. In this paper, we adopted the directional high-low pass filter for feature extraction. A box-counting fractal dimension and Iris code have been proposed as feature representations. Our approach has been tested on CASIA Iris Image database and the results are considered successful.

Automated apparatus and method of generating native code for a stitching machine

NASA Technical Reports Server (NTRS)

Miller, Jeffrey L. (Inventor)

2000-01-01

A computer system automatically generates CNC code for a stitching machine. The computer determines the locations of a present stitching point and a next stitching point. If a constraint is not found between the present stitching point and the next stitching point, the computer generates code for making a stitch at the next stitching point. If a constraint is found, the computer generates code for changing a condition (e.g., direction) of the stitching machine's stitching head.

Modeling cometary photopolarimetric characteristics with Sh-matrix method

NASA Astrophysics Data System (ADS)

Kolokolova, L.; Petrov, D.

2017-12-01

Cometary dust is dominated by particles of complex shape and structure, which are often considered as fractal aggregates. Rigorous modeling of light scattering by such particles, even using parallelized codes and NASA supercomputer resources, is very computer time and memory consuming. We are presenting a new approach to modeling cometary dust that is based on the Sh-matrix technique (e.g., Petrov et al., JQSRT, 112, 2012). This method is based on the T-matrix technique (e.g., Mishchenko et al., JQSRT, 55, 1996) and was developed after it had been found that the shape-dependent factors could be separated from the size- and refractive-index-dependent factors and presented as a shape matrix, or Sh-matrix. Size and refractive index dependences are incorporated through analytical operations on the Sh-matrix to produce the elements of T-matrix. Sh-matrix method keeps all advantages of the T-matrix method, including analytical averaging over particle orientation. Moreover, the surface integrals describing the Sh-matrix elements themselves can be solvable analytically for particles of any shape. This makes Sh-matrix approach an effective technique to simulate light scattering by particles of complex shape and surface structure. In this paper, we present cometary dust as an ensemble of Gaussian random particles. The shape of these particles is described by a log-normal distribution of their radius length and direction (Muinonen, EMP, 72, 1996). Changing one of the parameters of this distribution, the correlation angle, from 0 to 90 deg., we can model a variety of particles from spheres to particles of a random complex shape. We survey the angular and spectral dependencies of intensity and polarization resulted from light scattering by such particles, studying how they depend on the particle shape, size, and composition (including porous particles to simulate aggregates) to find the best fit to the cometary observations.

Fast ray-tracing algorithm for circumstellar structures (FRACS). II. Disc parameters of the B[e] supergiant CPD-57°,2874 from VLTI/MIDI data

NASA Astrophysics Data System (ADS)

Domiciano de Souza, A.; Bendjoya, P.; Niccolini, G.; Chesneau, O.; Borges Fernandes, M.; Carciofi, A. C.; Spang, A.; Stee, P.; Driebe, T.

2011-01-01

Context. B[e] supergiants are luminous, massive post-main sequence stars exhibiting non-spherical winds, forbidden lines, and hot dust in a disc-like structure. The physical properties of their rich and complex circumstellar environment (CSE) are not well understood, partly because these CSE cannot be easily resolved at the large distances found for B[e] supergiants (typically ⪆1 kpc). Aims: From mid-IR spectro-interferometric observations obtained with VLTI/MIDI we seek to resolve and study the CSE of the Galactic B[e] supergiant CPD-57° 2874. Methods: For a physical interpretation of the observables (visibilities and spectrum) we use our ray-tracing radiative transfer code (FRACS), which is optimised for thermal spectro-interferometric observations. Results: Thanks to the short computing time required by FRACS (<10 s per monochromatic model), best-fit parameters and uncertainties for several physical quantities of CPD-57° 2874 were obtained, such as inner dust radius, relative flux contribution of the central source and of the dusty CSE, dust temperature profile, and disc inclination. Conclusions: The analysis of VLTI/MIDI data with FRACS allowed one of the first direct determinations of physical parameters of the dusty CSE of a B[e] supergiant based on interferometric data and using a full model-fitting approach. In a larger context, the study of B[e] supergiants is important for a deeper understanding of the complex structure and evolution of hot, massive stars. Based on VLTI/MIDI observations collected at the European Southern Observatory (ESO), Paranal, Chile under ESO Programmes 074.D-0101 and 078.D-0213. Also based on observations at the ESO 2.2-m telescope, La Silla, Chile, under agreement with the Observatório Nacional-MCT (Brazil).Figure 5 is only available in electronic form at http://www.aanda.org

Computer codes developed and under development at Lewis

NASA Technical Reports Server (NTRS)

Chamis, Christos C.

1992-01-01

The objective of this summary is to provide a brief description of: (1) codes developed or under development at LeRC; and (2) the development status of IPACS with some typical early results. The computer codes that have been developed and/or are under development at LeRC are listed in the accompanying charts. This list includes: (1) the code acronym; (2) select physics descriptors; (3) current enhancements; and (4) present (9/91) code status with respect to its availability and documentation. The computer codes list is grouped by related functions such as: (1) composite mechanics; (2) composite structures; (3) integrated and 3-D analysis; (4) structural tailoring; and (5) probabilistic structural analysis. These codes provide a broad computational simulation infrastructure (technology base-readiness) for assessing the structural integrity/durability/reliability of propulsion systems. These codes serve two other very important functions: they provide an effective means of technology transfer; and they constitute a depository of corporate memory.

Estimation of micrometeorites and satellite dust flux surrounding Mars in the light of MAVEN results

NASA Astrophysics Data System (ADS)

Pabari, J. P.; Bhalodi, P. J.

2017-05-01

Recently, MAVEN observed dust around Mars from ∼150 km to ∼1000 km and it is a puzzling question to the space scientists about the presence of dust at orbital altitudes and about its source. A continuous supply of dust from various sources could cause existence of dust around Mars and it is expected that the dust could mainly be from either the interplanetary source or the Phobos/Deimos. We have studied incident projectiles or micrometeorites at Mars using the existing model, in this article. Comparison of results with the MAVEN results gives a new value of the population index S, which is reported here. The index S has been referred in a power law model used to describe the number of impacting particles on Mars. In addition, the secondary ejecta from natural satellites of Mars can cause a dust ring or torus around Mars and remain present for its lifetime. The dust particles whose paths are altered by the solar wind over its lifetime, could present a second plausible source of dust around Mars. We have investigated escaping particles from natural satellites of Mars and compared with the interplanetary dust flux estimation. It has been found that flux rate at Mars is dominated (∼2 orders of magnitude higher) by interplanetary particles in comparison with the satellite originated dust. It is inferred that the dust at high altitudes of Mars could be interplanetary in nature and our expectation is in agreement with the MAVEN observation. As a corollary, the mass loss from Martian natural satellites is computed based on the surface erosion by incident projectiles.

Reactivity effects in VVER-1000 of the third unit of the kalinin nuclear power plant at physical start-up. Computations in ShIPR intellectual code system with library of two-group cross sections generated by UNK code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zizin, M. N.; Zimin, V. G.; Zizina, S. N., E-mail: zizin@adis.vver.kiae.ru

2010-12-15

The ShIPR intellectual code system for mathematical simulation of nuclear reactors includes a set of computing modules implementing the preparation of macro cross sections on the basis of the two-group library of neutron-physics cross sections obtained for the SKETCH-N nodal code. This library is created by using the UNK code for 3D diffusion computation of first VVER-1000 fuel loadings. Computation of neutron fields in the ShIPR system is performed using the DP3 code in the two-group diffusion approximation in 3D triangular geometry. The efficiency of all groups of control rods for the first fuel loading of the third unit ofmore » the Kalinin Nuclear Power Plant is computed. The temperature, barometric, and density effects of reactivity as well as the reactivity coefficient due to the concentration of boric acid in the reactor were computed additionally. Results of computations are compared with the experiment.« less

Reactivity effects in VVER-1000 of the third unit of the kalinin nuclear power plant at physical start-up. Computations in ShIPR intellectual code system with library of two-group cross sections generated by UNK code

NASA Astrophysics Data System (ADS)

Zizin, M. N.; Zimin, V. G.; Zizina, S. N.; Kryakvin, L. V.; Pitilimov, V. A.; Tereshonok, V. A.

2010-12-01

The ShIPR intellectual code system for mathematical simulation of nuclear reactors includes a set of computing modules implementing the preparation of macro cross sections on the basis of the two-group library of neutron-physics cross sections obtained for the SKETCH-N nodal code. This library is created by using the UNK code for 3D diffusion computation of first VVER-1000 fuel loadings. Computation of neutron fields in the ShIPR system is performed using the DP3 code in the two-group diffusion approximation in 3D triangular geometry. The efficiency of all groups of control rods for the first fuel loading of the third unit of the Kalinin Nuclear Power Plant is computed. The temperature, barometric, and density effects of reactivity as well as the reactivity coefficient due to the concentration of boric acid in the reactor were computed additionally. Results of computations are compared with the experiment.

Users manual and modeling improvements for axial turbine design and performance computer code TD2-2

NASA Technical Reports Server (NTRS)

Glassman, Arthur J.

1992-01-01

Computer code TD2 computes design point velocity diagrams and performance for multistage, multishaft, cooled or uncooled, axial flow turbines. This streamline analysis code was recently modified to upgrade modeling related to turbine cooling and to the internal loss correlation. These modifications are presented in this report along with descriptions of the code's expanded input and output. This report serves as the users manual for the upgraded code, which is named TD2-2.

An Object-Oriented Approach to Writing Computational Electromagnetics Codes

NASA Technical Reports Server (NTRS)

Zimmerman, Martin; Mallasch, Paul G.

1996-01-01

Presently, most computer software development in the Computational Electromagnetics (CEM) community employs the structured programming paradigm, particularly using the Fortran language. Other segments of the software community began switching to an Object-Oriented Programming (OOP) paradigm in recent years to help ease design and development of highly complex codes. This paper examines design of a time-domain numerical analysis CEM code using the OOP paradigm, comparing OOP code and structured programming code in terms of software maintenance, portability, flexibility, and speed.

Turbulent AGN tori .

NASA Astrophysics Data System (ADS)

Schartmann, M.; Meisenheimer, K.; Klahr, H.; Camenzind, M.; Wolf, S.; Henning, Th.

Recently, the MID-infrared Interferometric instrument (MIDI) at the VLTI has shown that dust tori in the two nearby Seyfert galaxies NGC 1068 and the Circinus galaxy are geometrically thick and can be well described by a thin, warm central disk, surrounded by a colder and fluffy torus component. By carrying out hydrodynamical simulations with the help of the TRAMP code \\citep{schartmann_Klahr_99}, we follow the evolution of a young nuclear star cluster in terms of discrete mass-loss and energy injection from stellar processes. This naturally leads to a filamentary large scale torus component, where cold gas is able to flow radially inwards. The filaments open out into a dense and very turbulent disk structure. In a post-processing step, we calculate observable quantities like spectral energy distributions or images with the help of the 3D radiative transfer code MC3D \\citep{schartmann_Wolf_03}. Good agreement is found in comparisons with data due to the existence of almost dust-free lines of sight through the large scale component and the large column densities caused by the dense disk.

Evaluation of applicability of high-resolution multiangle imaging photo-polarimetric observations for aerosol atmospheric correction

NASA Astrophysics Data System (ADS)

Kalashnikova, Olga; Garay, Michael; Xu, Feng; Diner, David; Seidel, Felix

2016-07-01

Multiangle spectro-polarimetric measurements have been advocated as an additional tool for better understanding and quantifying the aerosol properties needed for atmospheric correction for ocean color retrievals. The central concern of this work is the assessment of the effects of absorbing aerosol properties on remote sensing reflectance measurement uncertainty caused by neglecting UV-enhanced absorption of carbonaceous particles and by not accounting for dust nonsphericity. In addition, we evaluate the polarimetric sensitivity of absorbing aerosol properties in light of measurement uncertainties achievable for the next generation of multi-angle polarimetric imaging instruments, and demonstrate advantages and disadvantages of wavelength selection in the UV/VNIR range. In this work a vector Markov Chain radiative transfer code including bio-optical models was used to quantitatively evaluate in water leaving radiances between atmospheres containing realistic UV-enhanced and non-spherical aerosols and the SEADAS carbonaceous and dust-like aerosol models. The phase matrices for the spherical smoke particles were calculated using a standard Mie code, while those for non-spherical dust particles were calculated using the numerical approach developed for modeling dust for the AERONET network of ground-based sunphotometers. As a next step, we have developed a retrieval code that employs a coupled Markov Chain (MC) and adding/doubling radiative transfer method for joint retrieval of aerosol properties and water leaving radiance from Airborne Multiangle SpectroPolarimetric Imager-1 (AirMSPI-1) polarimetric observations. The AirMSPI-1 instrument has been flying aboard the NASA ER-2 high altitude aircraft since October 2010. AirMSPI typically acquires observations of a target area at 9 view angles between ±67° at 10 m resolution. AirMSPI spectral channels are centered at 355, 380, 445, 470, 555, 660, and 865 nm, with 470, 660, and 865 reporting linear polarization. We tested prototype retrievals by comparing the retrieved aerosol concentration, size distribution, water-leaving radiance, and chlorophyll concentrations from Airborne Multiangle SpectroPolarimetric Imager-1 (AirMSPI-1) observations to values reported by the USC SeaPRISM AERONET-OC site off the coast of California. The retrieval was then applied to a variety of costal regions in California to evaluate variability in the water-leaving radiance under different atmospheric conditions. We will present results, and will discuss algorithm sensitivity and potential applications for future space-borne coastal monitoring.

Analysis of Dust Devils on Mars using CFD

NASA Astrophysics Data System (ADS)

Lange, C. F.; Chen, K.; Davis, J. A.; Gheynani, B. T.

2009-05-01

Recent Mars missions have reported evidence of the existence of dust devils. A detailed study of vortex dynamics will provide a better understanding of this swirling flow of the Martian atmosphere. Further, it is believed that there is a relationship between dust devils and water transport. Recently, the Phoenix Mars mission, designed to investigate ice water and natural events on Mars, has successfully finished. The Phoenix Surface Stereo Imager (SSI) camera captured images of the passage of dust devils over or close to the lander. Additionally, dustless devils, which have similar vortex characteristics but insufficient strength to raise dust from the surface, have been detected in the lander's pressure measurements. It was found that dust devils occur mainly in the early afternoon. Because of this, numerical models of a vortex generator are used to study the physics of this complex swirling flow and the effect of dust devils on the transport of water vapour from the regolith. Characteristic parameters such as core radius and swirl ratio are being explored for scaling factors. Scaling factors will be studied and tested, comparing the small and large scales of numerically generated vortices and laboratory generated vortices. Small scale of numerical models of atmospheric vortices are studied using a commercial software package, ANSYS/CFX11.0 with finite volume method (FVM). Large eddy simulations (LES) of planetary boundary layers are based on NCAR LES code to simulate convective vertical vortices that naturally form in quiescent convective boundary layers (CBL) over homogeneous flat surfaces. This will help to find the approximate location and physical characteristics of the vortices on the surface. The numerical models of atmospheric vortices and the experimental vortex generator validations will help to define the water vapour cycle on Mars.

Dust environment and dynamical history of a sample of short-period comets . II. 81P/Wild 2 and 103P/Hartley 2

NASA Astrophysics Data System (ADS)

Pozuelos, F. J.; Moreno, F.; Aceituno, F.; Casanova, V.; Sota, A.; López-Moreno, J. J.; Castellano, J.; Reina, E.; Climent, A.; Fernández, A.; San Segundo, A.; Häusler, B.; González, C.; Rodriguez, D.; Bryssinck, E.; Cortés, E.; Rodriguez, F. A.; Baldris, F.; García, F.; Gómez, F.; Limón, F.; Tifner, F.; Muler, G.; Almendros, I.; de los Reyes, J. A.; Henríquez, J. A.; Moreno, J. A.; Báez, J.; Bel, J.; Camarasa, J.; Curto, J.; Hernández, J. F.; González, J. J.; Martín, J. J.; Salto, J. L.; Lopesino, J.; Bosch, J. M.; Ruiz, J. M.; Vidal, J. R.; Ruiz, J.; Sánchez, J.; Temprano, J.; Aymamí, J. M.; Lahuerta, L.; Montoro, L.; Campas, M.; García, M. A.; Canales, O.; Benavides, R.; Dymock, R.; García, R.; Ligustri, R.; Naves, R.; Lahuerta, S.; Pastor, S.

2014-11-01

Aims: This paper is a continuation of the first paper in this series, where we presented an extended study of the dust environment of a sample of short-period comets and their dynamical history. On this occasion, we focus on comets 81P/Wild 2 and 103P/Hartley 2, which are of special interest as targets of the spacecraft missions Stardust and EPOXI. Methods: As in the previous study, we used two sets of observational data: a set of images, acquired at Sierra Nevada and Lulin observatories, and the Afρ data as a function of the heliocentric distance provided by the amateur astronomical association Cometas-Obs. The dust environment of comets (dust loss rate, ejection velocities, and size distribution of the particles) was derived from our Monte Carlo dust tail code. To determine their dynamical history we used the numerical integrator Mercury 6.2 to ascertain the time spent by these objects in the Jupiter family Comet region. Results: From the dust analysis, we conclude that both 81P/Wild 2 and 103P/Hartley 2 are dusty comets, with an annual dust production rate of 2.8 × 109 kg yr-1 and (0.4-1.5) × 109 kg yr-1, respectively. From the dynamical analysis, we determined their time spent in the Jupiter family Comet region as ~40 yr in the case of 81P/Wild 2 and ~1000 yr for comet 103P/Hartley 2. These results imply that 81P/Wild 2 is the youngest and the most active comet of the eleven short-period comets studied so far, which tends to favor the correlation between the time spent in JFCs region and the comet activity previously discussed.

Computer Description of the Field Artillery Ammunition Supply Vehicle

DTIC Science & Technology

1983-04-01

Combinatorial Geometry (COM-GEOM) GIFT Computer Code Computer Target Description 2& AfTNACT (Cmne M feerve shb N ,neemssalyan ify by block number) A...input to the GIFT computer code to generate target vulnerability data. F.a- 4 ono OF I NOV 5S OLETE UNCLASSIFIED SECUOITY CLASSIFICATION OF THIS PAGE...Combinatorial Geometry (COM-GEOM) desrription. The "Geometric Information for Tarqets" ( GIFT ) computer code accepts the CO!-GEOM description and

Brominated and phosphate flame retardants (FRs) in indoor dust from different microenvironments: Implications for human exposure via dust ingestion and dermal contact.

PubMed

Zheng, Xiaobo; Qiao, Lin; Covaci, Adrian; Sun, Runxia; Guo, Huiying; Zheng, Jing; Luo, Xiaojun; Xie, Qilai; Mai, Bixian

2017-10-01

Indoor dust has been widely used to monitor flame retardants (FRs) in indoor environment, but most studies only focused on floor dust. In the present study, FRs were examined in indoor dust from different locations. Dust from air conditioner (AC) filters, beddings, floor, and windows in bedrooms, and dust from AC filters, printer table surface, computer table surface, floor, and windows in offices were collected, respectively. Polybrominated diphenyl ether congener 209 (BDE 209) and decabromodiphenyl ethane (DBDPE) were the most abundant brominated flame retardants (BFRs), and tris(chloroisopropyl) phosphate (TCIPP), tris(1,3-dichloroisopropyl) phosphate (TDCIPP), and triphenyl phosphate (TPHP) were the most abundant phosphate flame retardants (PFRs). In bedrooms, the AC filter dust had the highest median levels of BDE 209 (536 ng/g) and DBDPE (2720 ng/g), while bed dust had the highest median levels of ΣPFRs (2750 ng/g) among dust samples. In offices, printer table dust had higher median levels of BDE 209 (1330 ng/g), DBDPE (8470 ng/g), and ΣPFRs (11,000 ng/g) than those in other dust samples. The high dust ingestion values of BDE 209, DBDPE, and individual PFR were 0.28, 1.20, and <0.01-0.32 ng/kg bw/day and 7.37, 31.2, and <0.01-4.54 ng/kg bw/day for BDE 209, DBDPE, and individual PFR for adults and toddlers, respectively. The high dermal exposure values of individual PFR during sleeping were <0.01-0.23 and <0.01-0.36 ng/kg bw/day for adults and toddlers, respectively. More human exposure pathways other than dust ingestion should be considered, such as the dermal contact with beddings and furniture. Copyright © 2017 Elsevier Ltd. All rights reserved.

48 CFR 252.227-7013 - Rights in technical data-Noncommercial items.

Code of Federal Regulations, 2011 CFR

2011-10-01

... causing a computer to perform a specific operation or series of operations. (3) Computer software means computer programs, source code, source code listings, object code listings, design details, algorithms... or will be developed exclusively with Government funds; (ii) Studies, analyses, test data, or similar...

48 CFR 252.227-7013 - Rights in technical data-Noncommercial items.

Code of Federal Regulations, 2012 CFR

2012-10-01

... causing a computer to perform a specific operation or series of operations. (3) Computer software means computer programs, source code, source code listings, object code listings, design details, algorithms... or will be developed exclusively with Government funds; (ii) Studies, analyses, test data, or similar...

48 CFR 252.227-7013 - Rights in technical data-Noncommercial items.

Code of Federal Regulations, 2014 CFR

2014-10-01

... causing a computer to perform a specific operation or series of operations. (3) Computer software means computer programs, source code, source code listings, object code listings, design details, algorithms... or will be developed exclusively with Government funds; (ii) Studies, analyses, test data, or similar...

48 CFR 252.227-7013 - Rights in technical data-Noncommercial items.

Code of Federal Regulations, 2010 CFR

2010-10-01

... causing a computer to perform a specific operation or series of operations. (3) Computer software means computer programs, source code, source code listings, object code listings, design details, algorithms... developed exclusively with Government funds; (ii) Studies, analyses, test data, or similar data produced for...

Antenna pattern study, task 2

NASA Technical Reports Server (NTRS)

Harper, Warren

1989-01-01

Two electromagnetic scattering codes, NEC-BSC and ESP3, were delivered and installed on a NASA VAX computer for use by Marshall Space Flight Center antenna design personnel. The existing codes and certain supplementary software were updated, the codes installed on a computer that will be delivered to the customer, to provide capability for graphic display of the data to be computed by the use of the codes and to assist the customer in the solution of specific problems that demonstrate the use of the codes. With the exception of one code revision, all of these tasks were performed.

Diagnostics and characterization of nanodust and nanodusty plasmas★

NASA Astrophysics Data System (ADS)

Greiner, Franko; Melzer, Andrè; Tadsen, Benjamin; Groth, Sebastian; Killer, Carsten; Kirchschlager, Florian; Wieben, Frank; Pilch, Iris; Krüger, Harald; Block, Dietmar; Piel, Alexander; Wolf, Sebastian

2018-05-01

Plasmas growing or containing nanometric dust particles are widely used and proposed in plasma technological applications for production of nano-crystals and surface deposition. Here, we give a compact review of in situ methods for the diagnostics of nanodust and nanodusty plasmas, which have been developed in the framework of the SFB-TR24 to fully characterize these systems. The methods include kinetic Mie ellipsometry, angular-resolved Mie scattering, and 2D imaging Mie ellipsometry to get information about particle growth processes, particle sizes and particle size distributions. There, also the role of multiple scattering events is analyzed using radiative transfer simulations. Computed tomography and Abel inversion techniques to get the 3D dust density profiles of the particle cloud will be presented. Diagnostics of the dust dynamics yields fundamental dust and plasma properties like particle charges and electron and ion densities. Since nanodusty plasmas usually form dense dust clouds electron depletion (Havnes effect) is found to be significant.

Effective mie-scattering and CO2 absorption in the dust-laden Martian atmosphere and its impact on radiative-convective temperature changes in the lower scale heights

NASA Technical Reports Server (NTRS)

Pallmann, A. J.

1976-01-01

A time dependent computer model of radiative-convective-conductive heat transfer in the Martian ground-atmosphere system was refined by incorporating an intermediate line strength CO2 band absorption which together with the strong-and weak-line approximation closely simulated the radiative transmission through a vertically inhomogeneous stratification. About 33,000 CO2 lines were processed to cover the spectral range of solar and planetary radiation. Absorption by silicate dust particulates, was taken into consideration to study its impact on the ground-atmosphere temperature field as a function of time. This model was subsequently attuned to IRIS, IR-radiometric and S-band occultation data. Satisfactory simulations of the measured IRIS spectra were accomplished for the dust-free condition. In the case of variable dust loads, the simulations were sufficiently fair so that some inferences into the effect of dust on temperature were justified.

TIME VARIATION OF AV AND RV FOR TYPE Ia SUPERNOVAE BEHIND INTERSTELLAR DUST

NASA Astrophysics Data System (ADS)

Huang, Xiaosheng; Biederman, M.; Herger, B.; Aldering, G. S.

2014-01-01

TIME VARIATION OF AV AND RV FOR TYPE Ia SUPERNOVAE BEHIND NON-UNIFORM INTERSTELLAR DUST ABSTRACT We investigate the time variation of the visual extinction, AV, and the total-to-selective extinction ratio, RV, resulting from interstellar dust in front of an expanding photospheric disk of a type Ia supernova (SN Ia). We simulate interstellar dust clouds according to a power law power spectrum and produce extinction maps that either follow a pseudo-Gaussian distribution or a lognormal distribution. The RV maps are produced through a correlation between AV and RV. With maps of AV and RV generated in each case (pseudo-Gaussian and lognormal), we then compute the effective AV and RV for a SN as its photospheric disk expands behind the dust screen. We find for a small percentage of SNe the AV and RV values can vary by a large factor from day to day in the first 40 days after explosion.

Mid-Infrared Long-Baseline Interferometry of the Symbiotic Mira Star RX Pup with the VLTI/MIDI Instrument

NASA Astrophysics Data System (ADS)

Driebe, T.; Hofmann, K.-H.; Ohnaka, K.; Schertl, D.; Weigelt, G.; Wittkowski, M.

We present mid-infrared long-baseline interferometric observations of the symbiotic Mira star RX Pup obtained with the VLTI/MIDI instrument in prism mode within the framework of the Science Demonstration Time (SDT) program in Feb. 2004. Four visibility measurements have been carried out using the unit telescopes UT2 and UT3, with projected baseline lengths ranging from 34.7 to 46.5 m.As we show by means of radiative transfer modelin with the code DUSTY [3], the wavelength dependence of the visibility and the N-band spectrum measured with MIDI can be interpreted as thesignature of a circumstellar dust shell which is dominated by silicate dust.

Simulations of dust in interacting galaxies

NASA Astrophysics Data System (ADS)

Jonsson, Patrik

This dissertation studies the effects of dust in N-body simulations of interacting galaxies. A new Monte-Carlo radiative-transfer code, Sunrise , is used in conjunction with hydrodynamic simulations. Results from radiative- transfer calculations in over 20 SPH simulations of disk-galaxy major mergers (Cox, 2004) are presented. Dust has a profound effect on the appearance of these simulations. At peak luminosities, 90% of the bolometric luminosity is absorbed by dust. The dust obscuration increases with luminosity in such a way that the brightness at UV/ visual wavelengths remains roughly constant. A general relationship between the fraction of energy absorbed and the ratio of bolometric luminosity to baryonic mass is found to hold in galaxies with metallicities >0.7 [Special characters omitted.] over a factor of 50 in mass. The accuracy to which the simulations describe observed starburst galaxies is evaluated by comparing them to observations by Meurer et al. (1999) and Heckman et al. (1998). The simulations are found to follow a relation similar to the IRX-b relation found by Meurer et al. (1999) when similar luminosity objects are considered. The highest-luminosity simulated galaxies depart from this relation and occupy the region where local LIRGs/ULIRGs are found. Comparing to the Heckman et al. (1998) sample, the simulations are found to obey the same relations between UV luminosity, UV color, IR luminosity, absolute blue magnitude and metallicity as the observations. This agreement is contingent on the presence of a realistic mass-metallicity relation, and Milky-Way-like dust. SMC-like dust results in far too red a UV continuum slope. On the whole, the agreement between the simulated and observed galaxies is impressive considering that the simulations have not been fit to agree with the observations, and we conclude that the simulations provide a realistic replication of the real universe. The simulations are used to study the performance of star-formation indicators in the presence of dust. The far-infrared luminosity is found to be reliable. In contrast, the Ha and far-ultraviolet luminosities suffer severely from dust attenuation, and dust corrections can only partially remedy the situation.

Dust-trapping Rossby vortices in protoplanetary disks

NASA Astrophysics Data System (ADS)

Meheut, H.; Meliani, Z.; Varniere, P.; Benz, W.

2012-09-01

Context. One of the most challenging steps in planet formation theory is the one leading to the formation of planetesimals of kilometre size. A promising scenario involves the existence of vortices able to concentrate a large amount of dust and grains in their centres. Up to now this scenario has mostly been studied in 2D razor thin disks. A 3D study including, simultaneously, the formation and resulting dust concentration of the vortices with vertical settling, is still missing. Aims: The Rossby wave instability self-consistently forms 3D vortices, which have the unique quality of presenting a large-scale vertical velocity in their centre. Here we aim to study how this newly discovered effect can alter the dynamic evolution of the dust. Methods: We performed global 3D simulations of the RWI in a radially and vertically stratified disk using the code MPI-AMRVAC. After the growth phase of the instability, the gas and solid phases are modelled by a bi-fluid approach, where the dust is considered as a fluid without pressure. Both the drag force of the gas on the dust and the back reaction of the dust on the gas are included. Multiple grain sizes from 1 mm to 5 cm are used with a constant density distribution. Results: We obtain in a short timescale a high concentration of the largest grains in the vortices. Indeed, in 3 rotations the dust-to-gas density ratio grows from 10-2 to unity leading to a concentration of mass up to that of Mars in one vortex. The presence of the radial drift is also at the origin of a dust pile-up at the radius of the vortices. Lastly, the vertical velocity of the gas in the vortex causes the sedimentation process to be reversed, the mm size dust is lifted and higher concentrations are obtained in the upper layer than in the midplane. Conclusions: The Rossby wave instability is a promising mechanism for planetesimal formation, and the results presented here can be of particular interest in the context of future observations of protoplanetary disks.

Recent Upgrades to the NASA Ames Mars General Circulation Model: Applications to Mars' Water Cycle

NASA Astrophysics Data System (ADS)

Hollingsworth, Jeffery L.; Kahre, M. A.; Haberle, R. M.; Montmessin, F.; Wilson, R. J.; Schaeffer, J.

2008-09-01

We report on recent improvements to the NASA Ames Mars general circulation model (GCM), a robust 3D climate-modeling tool that is state-of-the-art in terms of its physics parameterizations and subgrid-scale processes, and which can be applied to investigate physical and dynamical processes of the present (and past) Mars climate system. The most recent version (gcm2.1, v.24) of the Ames Mars GCM utilizes a more generalized radiation code (based on a two-stream approximation with correlated k's); an updated transport scheme (van Leer formulation); a cloud microphysics scheme that assumes a log-normal particle size distribution whose first two moments are treated as atmospheric tracers, and which includes the nucleation, growth and sedimentation of ice crystals. Atmospheric aerosols (e.g., dust and water-ice) can either be radiatively active or inactive. We apply this version of the Ames GCM to investigate key aspects of the present water cycle on Mars. Atmospheric dust is partially interactive in our simulations; namely, the radiation code "sees" a prescribed distribution that follows the MGS thermal emission spectrometer (TES) year-one measurements with a self-consistent vertical depth scale that varies with season. The cloud microphysics code interacts with a transported dust tracer column whose surface source is adjusted to maintain the TES distribution. The model is run from an initially dry state with a better representation of the north residual cap (NRC) which accounts for both surface-ice and bare-soil components. A seasonally repeatable water cycle is obtained within five Mars years. Our sub-grid scale representation of the NRC provides for a more realistic flux of moisture to the atmosphere and a much drier water cycle consistent with recent spacecraft observations (e.g., Mars Express PFS, corrected MGS/TES) compared to models that assume a spatially uniform and homogeneous north residual polar cap.

The circumstellar environment of the B[e] star GG Car: an interferometric modeling

NASA Astrophysics Data System (ADS)

Domiciano de Souza, A.; Borges Fernandes, M.; Carciofi, A. C.; Chesneau, O.

2015-01-01

The research of stars with the B[e] phenomenon is still in its infancy, with several unanswered questions. Physically realistic models that treat the formation and evolution of their complex circumstellar environments are rare. The code HDUST (developed by A. C. Carciofi and J. Bjorkman) is one of the few existing codes that provides a self-consistent treatment of the radiative transfer in a gaseous and dusty circumstellar environment seen around B[e] supergiant stars. In this work we used the HDUST code to study the circumstellar medium of the binary system GG Car, where the primary component is probably an evolved B[e] supergiant. This system also presents a disk (probably circumbinary), which is responsible for the molecular and dusty signatures seen in GG Car spectra. We obtained VLTI/MIDI data on GG~Car at eight baselines, which allowed to spatially resolve the gaseous and dusty circumstellar environment. From the interferometric visibilities and SED modeling with HDUST, we confirm the presence of a compact ring, where the hot dust lies. We also show that large grains can reproduce the lack of structure in the SED and visibilities across the silicate band. We conclude the dust condensation site is much closer to the star than previously thought. This result provides stringent constraints on future theories of grain formation and growth around hot stars.

Experimental Phase Functions of Millimeter-sized Cosmic Dust Grains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muñoz, O.; Moreno, F.; Guirado, D.

We present the experimental phase functions of three types of millimeter-sized dust grains consisting of enstatite, quartz, and volcanic material from Mount Etna, respectively. The three grains present similar sizes but different absorbing properties. The measurements are performed at 527 nm covering the scattering angle range from 3° to 170°. The measured phase functions show two well-defined regions: (i) soft forward peaks and (ii) a continuous increase with the scattering angle at side- and back-scattering regions. This behavior at side- and back-scattering regions is in agreement with the observed phase functions of the Fomalhaut and HR 4796A dust rings. Furthermore » computations and measurements (including polarization) for millimeter-sized grains are needed to draw some conclusions about the fluffy or compact structure of the dust grains.« less

Martian atmospheric radiation budget

NASA Technical Reports Server (NTRS)

Lindner, Bernhard Lee

1994-01-01

A computer model is used to study the radiative transfer of the martian winter-polar atmosphere. Solar heating at winter-polar latitudes is provided predominately by dust. For normal, low-dust conditions, CO2 provides almost as much heating as dust. Most heating by CO2 in the winter polar atmosphere is provided by the 2.7 micron band between 10 km and 30 km altitude, and by the 2.0 micron band below 10 km. The weak 1.3 micron band provides some significant heating near the surface. The minor CO2 bands at 1.4, 1.6, 4.8 and 5.2 micron are all optically thin, and produce negligible heating. O3 provides less than 10 percent of the total heating. Atmospheric cooling is predominantly thermal emission by dust, although CO2 15 micron band emission is important above 20 km altitude.

48 CFR 252.227-7013 - Rights in technical data-Noncommercial items.

Code of Federal Regulations, 2013 CFR

2013-10-01

... causing a computer to perform a specific operation or series of operations. (3) Computer software means computer programs, source code, source code listings, object code listings, design details, algorithms... funds; (ii) Studies, analyses, test data, or similar data produced for this contract, when the study...

COMPUTING THE DUST DISTRIBUTION IN THE BOW SHOCK OF A FAST-MOVING, EVOLVED STAR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Marle, A. J.; Meliani, Z.; Keppens, R.

2011-06-20

We study the hydrodynamical behavior occurring in the turbulent interaction zone of a fast-moving red supergiant star, where the circumstellar and interstellar material collide. In this wind-interstellar-medium collision, the familiar bow shock, contact discontinuity, and wind termination shock morphology form, with localized instability development. Our model includes a detailed treatment of dust grains in the stellar wind and takes into account the drag forces between dust and gas. The dust is treated as pressureless gas components binned per grain size, for which we use 10 representative grain size bins. Our simulations allow us to deduce how dust grains of varyingmore » sizes become distributed throughout the circumstellar medium. We show that smaller dust grains (radius <0.045 {mu}m) tend to be strongly bound to the gas and therefore follow the gas density distribution closely, with intricate fine structure due to essentially hydrodynamical instabilities at the wind-related contact discontinuity. Larger grains which are more resistant to drag forces are shown to have their own unique dust distribution, with progressive deviations from the gas morphology. Specifically, small dust grains stay entirely within the zone bound by shocked wind material. The large grains are capable of leaving the shocked wind layer and can penetrate into the shocked or even unshocked interstellar medium. Depending on how the number of dust grains varies with grain size, this should leave a clear imprint in infrared observations of bow shocks of red supergiants and other evolved stars.« less

Parallel Computation of the Jacobian Matrix for Nonlinear Equation Solvers Using MATLAB

NASA Technical Reports Server (NTRS)

Rose, Geoffrey K.; Nguyen, Duc T.; Newman, Brett A.

2017-01-01

Demonstrating speedup for parallel code on a multicore shared memory PC can be challenging in MATLAB due to underlying parallel operations that are often opaque to the user. This can limit potential for improvement of serial code even for the so-called embarrassingly parallel applications. One such application is the computation of the Jacobian matrix inherent to most nonlinear equation solvers. Computation of this matrix represents the primary bottleneck in nonlinear solver speed such that commercial finite element (FE) and multi-body-dynamic (MBD) codes attempt to minimize computations. A timing study using MATLAB's Parallel Computing Toolbox was performed for numerical computation of the Jacobian. Several approaches for implementing parallel code were investigated while only the single program multiple data (spmd) method using composite objects provided positive results. Parallel code speedup is demonstrated but the goal of linear speedup through the addition of processors was not achieved due to PC architecture.

Dust aerosol properties and radiative forcing observed in spring during 2001-2014 over urban Beijing, China.

PubMed

Yu, Xingna; Lü, Rui; Kumar, K Raghavendra; Ma, Jia; Zhang, Qiuju; Jiang, Yilun; Kang, Na; Yang, Suying; Wang, Jing; Li, Mei

2016-08-01

The ground-based characteristics (optical and radiative properties) of dust aerosols measured during the springtime between 2001 and 2014 were investigated over urban Beijing, China. The seasonal averaged aerosol optical depth (AOD) during spring of 2001-2014 was about 0.78 at 440 nm. During dust days, higher AOD occurred associated with lower Ångström exponent (AE). The mean AE440-870 in the springtime was about 1.0, indicating dominance of fine particles over the region. The back-trajectory analysis revealed that the dust was transported from the deserts of Inner Mongolia and Mongolia arid regions to Beijing. The aerosol volume size distribution showed a bimodal distribution pattern, with its highest peak observed in coarse mode for all episodes (especially for dust days with increased volume concentration). The single scattering albedo (SSA) increased with wavelength on dust days, indicating the presence of more scattering particles. Furthermore, the complex parts (real and imaginary) of refractive index showed distinct characteristics with lower imaginary values (also scattering) on dust days. The shortwave (SW; 0.2-4.0 μm) and longwave (LW; 4-100 μm) aerosol radiative forcing (ARF) values were computed from the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model both at the top of atmosphere (TOA) and the bottom of atmosphere (BOA) during dust and non-dust (dust free) days, and the corresponding heating rates and forcing efficiencies were also estimated. The SW (LW) ARF, therefore, produced significant cooling (warming) effects at both the TOA and the BOA over Beijing.

User Instructions for the Systems Assessment Capability, Rev. 1, Computer Codes Volume 3: Utility Codes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eslinger, Paul W.; Aaberg, Rosanne L.; Lopresti, Charles A.

2004-09-14

This document contains detailed user instructions for a suite of utility codes developed for Rev. 1 of the Systems Assessment Capability. The suite of computer codes for Rev. 1 of Systems Assessment Capability performs many functions.

Microbes and Microstructure: Dust's Role in the Snowpack Evolution

NASA Astrophysics Data System (ADS)

Lieblappen, R.; Courville, Z.; Fegyveresi, J. M.; Barbato, R.; Thurston, A.

2017-12-01

Dust is a primary vehicle for transporting microbial communities to polar and alpine snowpacks both through wind distribution (dry deposition) and snowfall events (wet deposition). The resulting microbial community diversity in the snowpack may then resemble the source material properties rather than its new habitat. Dust also has a strong influence on the microstructural properties of snow, resulting in changes to radiative and mechanical properties. As local reductions in snowpack albedo lead to enhanced melting and a heterogeneous snow surface, the microbial communities are also impacted. Here we study the impact of the changing microstructure in the snowpack, its influence on microbial function, and the fate of dust particles within the snow matrix. We seek to quantify the changes in respiration and water availability with the onset of melt. Polar samples were collected from the McMurdo Ice Shelf, Antarctica in February, 2017, while alpine samples were collected from Silverton, CO from October to May, 2017 as part of the Colorado Dust on Snow (CDOS) network. At each site, coincident meteorological data provides temperature, wind, and radiative measurements. Samples were collected immediately following dust deposition events and after subsequent snowpack evolution. We used x-ray micro-computed tomography to quantify the microstructural evolution of the snow, while also imaging the microstructural distribution of the dust within the snow. The dust was then collected and analyzed for chemical and microbial activity.

Effect of Thin Cirrus Clouds on Dust Optical Depth Retrievals From MODIS Observations

NASA Technical Reports Server (NTRS)

Feng, Qian; Hsu, N. Christina; Yang, Ping; Tsay, Si-Chee

2011-01-01

The effect of thin cirrus clouds in retrieving the dust optical depth from MODIS observations is investigated by using a simplified aerosol retrieval algorithm based on the principles of the Deep Blue aerosol property retrieval method. Specifically, the errors of the retrieved dust optical depth due to thin cirrus contamination are quantified through the comparison of two retrievals by assuming dust-only atmospheres and the counterparts with overlapping mineral dust and thin cirrus clouds. To account for the effect of the polarization state of radiation field on radiance simulation, a vector radiative transfer model is used to generate the lookup tables. In the forward radiative transfer simulations involved in generating the lookup tables, the Rayleigh scattering by atmospheric gaseous molecules and the reflection of the surface assumed to be Lambertian are fully taken into account. Additionally, the spheroid model is utilized to account for the nonsphericity of dust particles In computing their optical properties. For simplicity, the single-scattering albedo, scattering phase matrix, and optical depth are specified a priori for thin cirrus clouds assumed to consist of droxtal ice crystals. The present results indicate that the errors in the retrieved dust optical depths due to the contamination of thin cirrus clouds depend on the scattering angle, underlying surface reflectance, and dust optical depth. Under heavy dusty conditions, the absolute errors are comparable to the predescribed optical depths of thin cirrus clouds.

Levels and profiles of organochlorines and flame retardants in car and house dust from Kuwait and Pakistan: implication for human exposure via dust ingestion.

PubMed

Ali, Nadeem; Ali, Lulwa; Mehdi, Toufeer; Dirtu, Alin C; Al-Shammari, Fatema; Neels, Hugo; Covaci, Adrian

2013-05-01

There are only few studies documenting indoor pollution in the Middle East and the Indian subcontinent. In present study, we have evaluated the occurrence of various organochlorines (OCs) and flame retardants (FRs) in dust from cars and houses of Pakistan and Kuwait. Polybrominated diphenyl ethers (PBDEs), novel brominated flame retardants (NBFRs), organophosphate FRs (PFRs), polychlorinated biphenyls (PCBs), and organochlorine pesticides (OCPs) were investigated in indoor dust from urban houses (N=15 per country) and cars (N=15 per country). PFRs were the major analytes in all four microenvironments, followed by PBDEs>NBFRs>OCPs>PCBs. For all classes of analytes, relatively lower levels were observed in car and house dust from Pakistan than Kuwait. Levels of ∑PBDEs, ∑NBFRs and ∑PFRs were higher in car dust, while ∑OCPs and ∑PCBs were higher in house dust from both countries. ∑PFRs occurred at average concentrations of 16,900, 87,900, 475, and 2500ng/g in Kuwaiti house and car, and Pakistani house and car dust, respectively. For both countries, the profiles of analytes in car dust were different from those in the house dust. Different exposure scenarios using 5th percentile, median, mean, and 95th percentile levels were estimated for adult, taxi drivers and toddlers. For Kuwaiti toddlers, assuming high dust intake and mean and 95th percentile concentrations, the values computed for ∑OCPs (1500ng/kg bw/day) were higher than RfD values, while for ∑PCBs (14.5ng/kg bw/day) it was only two-fold lower than the corresponding RfDs. Copyright © 2013 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu Zhaohuan; Dong Ruobing; Nelson, Richard P.

By carrying out two-dimensional two-fluid global simulations, we have studied the response of dust to gap formation by a single planet in the gaseous component of a protoplanetary disk-the so-called dust filtration mechanism. We have found that a gap opened by a giant planet at 20 AU in an {alpha} = 0.01, M-dot =10{sup -8} M{sub Sun} yr{sup -1} disk can effectively stop dust particles larger than 0.1 mm drifting inward, leaving a submillimeter (submm) dust cavity/hole. However, smaller particles are difficult to filter by a gap induced by a several M{sub J} planet due to (1) dust diffusion andmore » (2) a high gas accretion velocity at the gap edge. Based on these simulations, an analytic model is derived to understand what size particles can be filtered by the planet-induced gap edge. We show that a dimensionless parameter T{sub s} /{alpha}, which is the ratio between the dimensionless dust stopping time and the disk viscosity parameter, is important for the dust filtration process. Finally, with our updated understanding of dust filtration, we have computed Monte Carlo radiative transfer models with variable dust size distributions to generate the spectral energy distributions of disks with gaps. By comparing with transitional disk observations (e.g., GM Aur), we have found that dust filtration alone has difficulties depleting small particles sufficiently to explain the near-IR deficit of moderate M-dot transitional disks, except under some extreme circumstances. The scenario of gap opening by multiple planets studied previously suffers the same difficulty. One possible solution is to invoke both dust filtration and dust growth in the inner disk. In this scenario, a planet-induced gap filters large dust particles in the disk, and the remaining small dust particles passing to the inner disk can grow efficiently without replenishment from fragmentation of large grains. Predictions for ALMA have also been made based on all these scenarios. We conclude that dust filtration with planet(s) in the disk is a promising mechanism to explain submm observations of transitional disks but it may need to be combined with other processes (e.g., dust growth) to explain the near-IR deficit of some systems.« less

Development of a model and computer code to describe solar grade silicon production processes

NASA Technical Reports Server (NTRS)

Gould, R. K.; Srivastava, R.

1979-01-01

Two computer codes were developed for describing flow reactors in which high purity, solar grade silicon is produced via reduction of gaseous silicon halides. The first is the CHEMPART code, an axisymmetric, marching code which treats two phase flows with models describing detailed gas-phase chemical kinetics, particle formation, and particle growth. It can be used to described flow reactors in which reactants, mix, react, and form a particulate phase. Detailed radial gas-phase composition, temperature, velocity, and particle size distribution profiles are computed. Also, deposition of heat, momentum, and mass (either particulate or vapor) on reactor walls is described. The second code is a modified version of the GENMIX boundary layer code which is used to compute rates of heat, momentum, and mass transfer to the reactor walls. This code lacks the detailed chemical kinetics and particle handling features of the CHEMPART code but has the virtue of running much more rapidly than CHEMPART, while treating the phenomena occurring in the boundary layer in more detail.

ELECTRIC CHARGING OF DUST AGGREGATES AND ITS EFFECT ON DUST COAGULATION IN PROTOPLANETARY DISKS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okuzumi, Satoshi

2009-06-20

Mutual sticking of dust aggregates is the first step toward planetesimal formation in protoplanetary disks. In spite that the electric charging of dust particles is well recognized in some contexts, it has been largely ignored in the current modeling of dust coagulation. In this study, we present a general analysis of the dust charge state in protoplanetary disks, and then demonstrate how the electric charging could dramatically change the currently accepted scenario of dust coagulation. First, we describe a new semianalytical method to calculate the dust charge state and gas ionization state self-consistently. This method is far more efficient thanmore » previous numerical methods, and provides a general and clear description of the charge state of a gas-dust mixture. Second, we apply this analysis to compute the collisional cross section of growing aggregates taking their charging into account. As an illustrative example, we focus on early evolutionary stages where the dust has been thought to grow into fractal (D {approx} 2) aggregates with a quasi-monodisperse (i.e., narrow) size distribution. We find that, for a wide range of model parameters, the fractal growth is strongly inhibited by the electric repulsion between colliding aggregates and eventually 'freezes out' on its way to the subsequent growth stage involving collisional compression. Strong disk turbulence would help the aggregates to overcome this growth barrier, but then it would cause catastrophic collisional fragmentation in later growth stages. These facts suggest that the combination of electric repulsion and collisional fragmentation would impose a serious limitation on dust growth in protoplanetary disks. We propose a possible scenario of dust evolution after the freezeout. Finally, we point out that the fractal growth of dust aggregates tends to maintain a low ionization degree and, as a result, a large magnetorotationally stable region in the disk.« less

Sensitivity of spectral climate signals to the emissions of atmospheric dust

NASA Astrophysics Data System (ADS)

Xu, X.; Wang, J.; Wang, Y.; Henze, D. K.; Zhang, L.

2015-12-01

Mineral dust particles profoundly influence the Earth climate due to their varied affects on the radiation and cloud physics. The knowledge of dust emissions from daily to seasonal scales is thus important for interpreting the past and predicting the future climate changes. Satellite measured radiances in the shortwave and thermal infrared are sensitive to the amount and properties of mineral dust present in the atmosphere. Therefore, the climate (i.e., monthly averages) of these reflectance spectra could contain valuable information on the change of dust emissions. In this work, we investigate the feasibility of using the climate of spectral radiances for recovering dust emissions. An observation simulation system (OSS) that incorporates the Unified Linearized Vector Radiative Transfer Model (UNL-VRTM) with forward and adjoint global chemistry transport models (GEOS-Chem and FIM-Chem) has been applied to generate synthetic hyperspectral climate data in the shortwave and thermal infrared (TIR) for summer 2008. Along with the calculation of radiances at the top of the atmosphere (TOA), the OSS also computes their Jacobians of these synthetic data to dust optical depth, plume height, and effective radius, as well as the adjoint gradients of spectral radiances to dust emissions. We found that the brightness temperature (BT) in the TIR spectra at TOA is sensitive to both of the dust plume height and particle size. For the same relative changes of these parameters, BT shows largest change with respect to particle size at the wavenumber of 890-1200 cm-1. This demonstrates the potential for retrieving three-dimensional dust information along with the particle size from hyperspectral TIR measurements. We also assess the information content of monthly versus instantaneous radiances for constraining dust emissionsthe from the calculated adjoint gradients. Our analysis may guide new applications of long-term spectral radiance measurements (such as those from GOME, AIRS, IASI, and CrIS instruments) to constrain dust sources, and thus reduce uncertainty in our broader understanding of the impacts of mineral dust on climate.

Implementation of Parallel Computing Technology to Vortex Flow

NASA Technical Reports Server (NTRS)

Dacles-Mariani, Jennifer

1999-01-01

Mainframe supercomputers such as the Cray C90 was invaluable in obtaining large scale computations using several millions of grid points to resolve salient features of a tip vortex flow over a lifting wing. However, real flight configurations require tracking not only of the flow over several lifting wings but its growth and decay in the near- and intermediate- wake regions, not to mention the interaction of these vortices with each other. Resolving and tracking the evolution and interaction of these vortices shed from complex bodies is computationally intensive. Parallel computing technology is an attractive option in solving these flows. In planetary science vortical flows are also important in studying how planets and protoplanets form when cosmic dust and gases become gravitationally unstable and eventually form planets or protoplanets. The current paradigm for the formation of planetary systems maintains that the planets accreted from the nebula of gas and dust left over from the formation of the Sun. Traditional theory also indicate that such a preplanetary nebula took the form of flattened disk. The coagulation of dust led to the settling of aggregates toward the midplane of the disk, where they grew further into asteroid-like planetesimals. Some of the issues still remaining in this process are the onset of gravitational instability, the role of turbulence in the damping of particles and radial effects. In this study the focus will be with the role of turbulence and the radial effects.

Comparison of two computer codes for crack growth analysis: NASCRAC Versus NASA/FLAGRO

NASA Technical Reports Server (NTRS)

Stallworth, R.; Meyers, C. A.; Stinson, H. C.

1989-01-01

Results are presented from the comparison study of two computer codes for crack growth analysis - NASCRAC and NASA/FLAGRO. The two computer codes gave compatible conservative results when the part through crack analysis solutions were analyzed versus experimental test data. Results showed good correlation between the codes for the through crack at a lug solution. For the through crack at a lug solution, NASA/FLAGRO gave the most conservative results.

Computational Predictions of the Performance Wright 'Bent End' Propellers

NASA Technical Reports Server (NTRS)

Wang, Xiang-Yu; Ash, Robert L.; Bobbitt, Percy J.; Prior, Edwin (Technical Monitor)

2002-01-01

Computational analysis of two 1911 Wright brothers 'Bent End' wooden propeller reproductions have been performed and compared with experimental test results from the Langley Full Scale Wind Tunnel. The purpose of the analysis was to check the consistency of the experimental results and to validate the reliability of the tests. This report is one part of the project on the propeller performance research of the Wright 'Bent End' propellers, intend to document the Wright brothers' pioneering propeller design contributions. Two computer codes were used in the computational predictions. The FLO-MG Navier-Stokes code is a CFD (Computational Fluid Dynamics) code based on the Navier-Stokes Equations. It is mainly used to compute the lift coefficient and the drag coefficient at specified angles of attack at different radii. Those calculated data are the intermediate results of the computation and a part of the necessary input for the Propeller Design Analysis Code (based on Adkins and Libeck method), which is a propeller design code used to compute the propeller thrust coefficient, the propeller power coefficient and the propeller propulsive efficiency.

The NGST and the Zodiacal Light in the Solar System

NASA Technical Reports Server (NTRS)

Gorkavyi, Nick; Ozernoy, Leonid; Mather, John; Taidakova, Tanya

1999-01-01

We develop a physical model of the zodiacal cloud incorporating the real dust sources of asteroidal, cometary, and kuiperoidal origin. Using the inferred distribution of the zodiacal dust, we compute its thermal emission and scattering at several wavelengths (1.25, 5, and 20 micron) as a function of NGST location assumed to be at 1 AU or 3 AU. Areas on the sky with a minimum of zodiacal light are determined.

Light Scattering by Wavelength-Sized Particles "Dusted" with Subwavelength-Sized Grains

NASA Technical Reports Server (NTRS)

Mishchenko, Michael I.; Dlugach, Janna M.; Mackowski, Daniel W.

2011-01-01

The numerically exact superposition T-matrix method is used to compute the scattering cross sections and the Stokes scattering matrix for polydisperse spherical particles covered with a large number of much smaller grains. We show that the optical effect of the presence of microscopic dust on the surfaces of wavelength-sized, weakly absorbing particles is much less significant than that of a major overall asphericity of the particle shape.

Detecting stellar-wind bubbles through infrared arcs in H II regions

NASA Astrophysics Data System (ADS)

Mackey, Jonathan; Haworth, Thomas J.; Gvaramadze, Vasilii V.; Mohamed, Shazrene; Langer, Norbert; Harries, Tim J.

2016-02-01

Mid-infrared arcs of dust emission are often seen near ionizing stars within H II regions. A possible explanations for these arcs is that they could show the outer edges of asymmetric stellar wind bubbles. We use two-dimensional, radiation-hydrodynamics simulations of wind bubbles within H II regions around individual stars to predict the infrared emission properties of the dust within the H II region. We assume that dust and gas are dynamically well-coupled and that dust properties (composition, size distribution) are the same in the H II region as outside it, and that the wind bubble contains no dust. We post-process the simulations to make synthetic intensity maps at infrared wavebands using the torus code. We find that the outer edge of a wind bubble emits brightly at 24 μm through starlight absorbed by dust grains and re-radiated thermally in the infrared. This produces a bright arc of emission for slowly moving stars that have asymmetric wind bubbles, even for cases where there is no bow shock or any corresponding feature in tracers of gas emission. The 24 μm intensity decreases exponentially from the arc with increasing distance from the star because the dust temperature decreases with distance. The size distribution and composition of the dust grains has quantitative but not qualitative effects on our results. Despite the simplifications of our model, we find good qualitative agreement with observations of the H II region RCW 120, and can provide physical explanations for any quantitative differences. Our model produces an infrared arc with the same shape and size as the arc around CD -38°11636 in RCW 120, and with comparable brightness. This suggests that infrared arcs around O stars in H II regions may be revealing the extent of stellar wind bubbles, although we have not excluded other explanations.

Dust Processing in Supernova Remnants: Spitzer MIPS SED and IRS Observations

NASA Technical Reports Server (NTRS)

Hewitt, John W.; Petre, Robert; Katsuda Satoru; Andersen, M.; Rho, J.; Reach, W. T.; Bernard, J. P.

2011-01-01

We present Spitzer MIPS SED and IRS observations of 14 Galactic Supernova Remnants previously identified in the GLIMPSE survey. We find evidence for SNR/molecular cloud interaction through detection of [OI] emission, ionic lines, and emission from molecular hydrogen. Through black-body fitting of the MIPS SEDs we find the large grains to be warm, 29-66 K. The dust emission is modeled using the DUSTEM code and a three component dust model composed of populations of big grains, very small grains, and polycyclic aromatic hydrocarbons. We find the dust to be moderately heated, typically by 30-100 times the interstellar radiation field. The source of the radiation is likely hydrogen recombination, where the excitation of hydrogen occurred in the shock front. The ratio of very small grains to big grains is found for most of the molecular interacting SNRs to be higher than that found in the plane of the Milky Way, typically by a factor of 2--3. We suggest that dust shattering is responsible for the relative over-abundance of small grains, in agreement with prediction from dust destruction models. However, two of the SNRs are best fit with a very low abundance of carbon grains to silicate grains and with a very high radiation field. A likely reason for the low abundance of small carbon grains is sputtering. We find evidence for silicate emission at 20 $\\mu$m in their SEDs, indicating that they are young SNRs based on the strong radiation field necessary to reproduce the observed SEDs.

A two-dimensional particle-in-cell model of a dusty plasma

NASA Technical Reports Server (NTRS)

Young, B.; Cravens, T. E.; Armstrong, T. P.; Friauf, R. J.

1994-01-01

Dusty plasmas are present in comets, in the ring systems of the outer planets, and in the interstellar medium. A two-dimensional particle-in-cell (PIC) model of a dusty plasma is presented in this paper. The PIC code is best suited for modeling the plasma-dust interaction for large grains, with diameters of the order of a centimeter. We have modeled the charging process for an individual dust grain and the associated potential pattern in the surrounding plasma. We have also considered the case of a large number of grains in a plasma, with intergrain separations of the order of the Debye length, and have shown that the plasma becomes depleted and the charge on a dust grain is reduced, as other workers in this field have predicted (cf. C. K. Goertz, 1989). We examine the electron and ion distribution functions in the vicinity of a charged grain and demonstrate that the ions near a grain have clearly been accelerated by the electrostatic potential.

Proceduracy: Computer Code Writing in the Continuum of Literacy

ERIC Educational Resources Information Center

Vee, Annette

2010-01-01

This dissertation looks at computer programming through the lens of literacy studies, building from the concept of code as a written text with expressive and rhetorical power. I focus on the intersecting technological and social factors of computer code writing as a literacy--a practice I call "proceduracy". Like literacy, proceduracy is a human…

Computer Code Aids Design Of Wings

NASA Technical Reports Server (NTRS)

Carlson, Harry W.; Darden, Christine M.

1993-01-01

AERO2S computer code developed to aid design engineers in selection and evaluation of aerodynamically efficient wing/canard and wing/horizontal-tail configurations that includes simple hinged-flap systems. Code rapidly estimates longitudinal aerodynamic characteristics of conceptual airplane lifting-surface arrangements. Developed in FORTRAN V on CDC 6000 computer system, and ported to MS-DOS environment.

Cloud Computing for Complex Performance Codes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Appel, Gordon John; Hadgu, Teklu; Klein, Brandon Thorin

This report describes the use of cloud computing services for running complex public domain performance assessment problems. The work consisted of two phases: Phase 1 was to demonstrate complex codes, on several differently configured servers, could run and compute trivial small scale problems in a commercial cloud infrastructure. Phase 2 focused on proving non-trivial large scale problems could be computed in the commercial cloud environment. The cloud computing effort was successfully applied using codes of interest to the geohydrology and nuclear waste disposal modeling community.

APC: A New Code for Atmospheric Polarization Computations

NASA Technical Reports Server (NTRS)

Korkin, Sergey V.; Lyapustin, Alexei I.; Rozanov, Vladimir V.

2014-01-01

A new polarized radiative transfer code Atmospheric Polarization Computations (APC) is described. The code is based on separation of the diffuse light field into anisotropic and smooth (regular) parts. The anisotropic part is computed analytically. The smooth regular part is computed numerically using the discrete ordinates method. Vertical stratification of the atmosphere, common types of bidirectional surface reflection and scattering by spherical particles or spheroids are included. A particular consideration is given to computation of the bidirectional polarization distribution function (BPDF) of the waved ocean surface.

Exploring the inner parsecs of active galactic nuclei using near-infrared high resolution polarimetric simulations with MontAGN

NASA Astrophysics Data System (ADS)

Grosset, L.; Rouan, D.; Gratadour, D.; Pelat, D.; Orkisz, J.; Marin, F.; Goosmann, R.

2018-04-01

Aims: In this paper we aim to constrain the properties of dust structures in the central first parsecs of active galactic nuclei (AGN). Our goal is to study the required optical depth and composition of different dusty and ionised structures. Methods: We developed a radiative transfer code called Monte Carlo for Active Galactic Nuclei (MontAGN), which is optimised for polarimetric observations in the infrared. With both this code and STOKES, designed to be relevant from the hard X-ray band to near-infrared wavelengths, we investigate the polarisation emerging from a characteristic model of the AGN environment. For this purpose, we compare predictions of our models with previous infrared observations of NGC 1068, and try to reproduce several key polarisation patterns revealed by polarisation mapping. Results: We constrain the required dust structures and their densities. More precisely, we find that the electron density inside the ionisation cone is about 2.0 × 109 m-3. With structures constituted of spherical grains of constant density, we also highlight that the torus should be thicker than 20 in term of K-band optical depth to block direct light from the centre. It should also have a stratification in density: a less dense outer rim with an optical depth at 2.2 μm typically between 0.8 and 4 for observing the double scattering effect previously proposed. Conclusions: We bring constraints on the dust structures in the inner parsecs of an AGN model supposed to describe NGC 1068. When compared to observations, this leads to an optical depth of at least 20 in the Ks band for the torus of NGC 1068, corresponding to τV ≈ 170, which is within the range of current estimation based on observations. In the future, we will improve our study by including non-uniform dust structures and aligned elongated grains to constrain other possible interpretations of the observations.

Characterizing the Evolution of Circumstellar Systems with the Hubble Space Telescope and the Gemini Planet Imager

NASA Astrophysics Data System (ADS)

Wolff, Schuyler; Schuyler G. Wolff

2018-01-01

The study of circumstellar disks at a variety of evolutionary stages is essential to understand the physical processes leading to planet formation. The recent development of high contrast instruments designed to directly image the structures surrounding nearby stars, such as the Gemini Planet Imager (GPI) and coronagraphic data from the Hubble Space Telescope (HST) have made detailed studies of circumstellar systems possible. In my thesis work I detail the observation and characterization of three systems. GPI polarization data for the transition disk, PDS 66 shows a double ring and gap structure with a temporally variable azimuthal asymmetry. This evolved morphology could indicate shadowing from some feature in the innermost regions of the disk, a gap-clearing planet, or a localized change in the dust properties of the disk. Millimeter continuum data of the DH Tau system places limits on the dust mass that is contributing to the strong accretion signature on the wide-separation planetary mass companion, DH Tau b. The lower than expected dust mass constrains the possible formation mechanism, with core accretion followed by dynamical scattering being the most likely. Finally, I present HST scattered light observations of the flared, edge-on protoplanetary disk ESO H$\\alpha$ 569. I combine these data with a spectral energy distribution to model the key structural parameters such as the geometry (disk outer radius, vertical scale height, radial flaring profile), total mass, and dust grain properties in the disk using the radiative transfer code MCFOST. In order to conduct this work, I developed a new tool set to optimize the fitting of disk parameters using the MCMC code \\texttt{emcee} to efficiently explore the high dimensional parameter space. This approach allows us to self-consistently and simultaneously fit a wide variety of observables in order to place constraints on the physical properties of a given disk, while also rigorously assessing the uncertainties in those derived properties.

Gas in the protoplanetary disc of HD 169142: Herschel's view

NASA Astrophysics Data System (ADS)

Meeus, G.; Pinte, C.; Woitke, P.; Montesinos, B.; Mendigutía, I.; Riviere-Marichalar, P.; Eiroa, C.; Mathews, G. S.; Vandenbussche, B.; Howard, C. D.; Roberge, A.; Sandell, G.; Duchêne, G.; Ménard, F.; Grady, C. A.; Dent, W. R. F.; Kamp, I.; Augereau, J. C.; Thi, W. F.; Tilling, I.; Alacid, J. M.; Andrews, S.; Ardila, D. R.; Aresu, G.; Barrado, D.; Brittain, S.; Ciardi, D. R.; Danchi, W.; Fedele, D.; de Gregorio-Monsalvo, I.; Heras, A.; Huelamo, N.; Krivov, A.; Lebreton, J.; Liseau, R.; Martin-Zaidi, C.; Mora, A.; Morales-Calderon, M.; Nomura, H.; Pantin, E.; Pascucci, I.; Phillips, N.; Podio, L.; Poelman, D. R.; Ramsay, S.; Riaz, B.; Rice, K.; Solano, E.; Walker, H.; White, G. J.; Williams, J. P.; Wright, G.

2010-07-01

In an effort to simultaneously study the gas and dust components of the disc surrounding the young Herbig Ae star HD 169142, we present far-IR observations obtained with the PACS instrument onboard the Herschel Space Observatory. This work is part of the open time key program GASPS, which is aimed at studying the evolution of protoplanetary discs. To constrain the gas properties in the outer disc, we observed the star at several key gas-lines, including [OI] 63.2 and 145.5 μm, [CII] 157.7 μm, CO 72.8 and 90.2 μm, and o-H2O 78.7 and 179.5 μm. We only detect the [OI] 63.2 μm line in our spectra, and derive upper limits for the other lines. We complement our data set with PACS photometry and 12/13CO data obtained with the Submillimeter Array. Furthermore, we derive accurate stellar parameters from optical spectra and UV to mm photometry. We model the dust continuum with the 3D radiative transfer code MCFOST and use this model as an input to analyse the gas lines with the thermo-chemical code ProDiMo. Our dataset is consistent with a simple model in which the gas and dust are well-mixed in a disc with a continuous structure between 20 and 200 AU, but this is not a unique solution. Our modelling effort allows us to constrain the gas-to-dust mass ratio as well as the relative abundance of the PAHs in the disc by simultaneously fitting the lines of several species that originate in different regions. Our results are inconsistent with a gas-poor disc with a large UV excess; a gas mass of 5.0 ± 2.0 × 10-3 M⊙ is still present in this disc, in agreement with earlier CO observations. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Herschel-PACS observation of the 10 Myr old T Tauri disk TW Hya. Constraining the disk gas mass

NASA Astrophysics Data System (ADS)

Thi, W.-F.; Mathews, G.; Ménard, F.; Woitke, P.; Meeus, G.; Riviere-Marichalar, P.; Pinte, C.; Howard, C. D.; Roberge, A.; Sandell, G.; Pascucci, I.; Riaz, B.; Grady, C. A.; Dent, W. R. F.; Kamp, I.; Duchêne, G.; Augereau, J.-C.; Pantin, E.; Vandenbussche, B.; Tilling, I.; Williams, J. P.; Eiroa, C.; Barrado, D.; Alacid, J. M.; Andrews, S.; Ardila, D. R.; Aresu, G.; Brittain, S.; Ciardi, D. R.; Danchi, W.; Fedele, D.; de Gregorio-Monsalvo, I.; Heras, A.; Huelamo, N.; Krivov, A.; Lebreton, J.; Liseau, R.; Martin-Zaidi, C.; Mendigutía, I.; Montesinos, B.; Mora, A.; Morales-Calderon, M.; Nomura, H.; Phillips, N.; Podio, L.; Poelman, D. R.; Ramsay, S.; Rice, K.; Solano, E.; Walker, H.; White, G. J.; Wright, G.

2010-07-01

Planets are formed in disks around young stars. With an age of ~10 Myr, TW Hya is one of the nearest T Tauri stars that is still surrounded by a relatively massive disk. In addition a large number of molecules has been found in the TW Hya disk, making TW Hya the perfect test case in a large survey of disks with Herschel-PACS to directly study their gaseous component. We aim to constrain the gas and dust mass of the circumstellar disk around TW Hya. We observed the fine-structure lines of [O i] and [C ii] as part of the open-time large program GASPS. We complement this with continuum data and ground-based 12 CO 3-2 and 13CO 3-2 observations. We simultaneously model the continuum and the line fluxes with the 3D Monte-Carlo code MCFOST and the thermo-chemical code ProDiMo to derive the gas and dust masses. We detect the [O i] line at 63 μm. The other lines that were observed, [O i] at 145 μm and [C ii] at 157 μm, are not detected. No extended emission has been found. Preliminary modeling of the photometric and line data assuming [ 12CO] /[ 13CO] = 69 suggests a dust mass for grains with radius <1 mm of ~1.9 × 10-4 M⊙ (total solid mass of 3 × 10-3 M⊙) and a gas mass of (0.5-5) × 10-3 M⊙. The gas-to-dust mass may be lower than the standard interstellar value of 100. Herschel is an ESA space observatory with science instruments provided by Principal Investigator consortia. It is open for proposals for observing time from the worldwide astronomical community.Appendix is only available in electronic form at http://www.aanda.org

A Climatology of dust emission in northern Africa using surface observations from 1984-2012

NASA Astrophysics Data System (ADS)

Cowie, Sophie; Knippertz, Peter; Marsham, John

2014-05-01

The huge quantity of mineral dust emitted annually from northern Africa makes this area crucial to the global dust cycle. Once in the atmosphere, dust aerosols have a significant impact on the global radiation budget, clouds, the carbon cycle and can even act as a fertilizer to rain forests in South America. Current model estimates of dust production from northern Africa are uncertain. At the heart of this problem is insufficient understanding of key dust emitting processes such as haboobs (cold pools generated through evaporation of convective precipitation), low-level jets (LLJs) and dry convection (dust devils and dust plumes). Scarce observations in this region, in particular in the Sahara, make model evaluation difficult. This work uses long-term surface observations from 70 stations situated in the Sahara and Sahel to explore the diurnal, seasonal and geographical variations in dust emission events and thresholds. Quality flags are applied to each station to indicate a day-time bias or gaps in the time period 1984-2012. The frequency of dust emission (FDE) is calculated using the present weather codes (WW) of SYNOP reports, where WW = 07,08,09,30-35 and 98. Thresholds are investigated by estimating the wind speeds for which there is a 25%, 50% and 75% probability of dust emission. The 50% threshold is used to calculate strong wind frequency (SWF) and the diagnostic parameter dust uplift potential (DUP); a thresholded cubic function of wind-speed which quantifies the dust generating power of winds. Stations are grouped into 6 areas (North Algeria, Central Sahara, Egypt, West Sahel, Central Sahel and Sudan) for more in-depth analysis of these parameters. Spatially, thresholds are highest in northern Algeria and lowest in the Sahel around the latitude band 16N-21N. Annual mean FDE is anti-correlated with the threshold, showing the importance of spatial variations in thresholds for mean dust emission. The annual cycles of FDE and SWF for the 6 grouped areas are highly correlated (0.95 to 0.99). These correlations are barely reduced when annual-mean thresholds are used, showing that seasonal variations in thresholds are not the main control on the seasonal variations in FDE. Relationships between annual cycles in FDE and DUP are more complex than between FDE and SWF, reflecting the seasonal variations in the types and intensities of dust events. FDE is highest in spring north of 23N. South of this, where stations are directly influenced by the summer monsoon, the annual cycle in FDE is much more variable. Half of the total DUP occurs at wind-speeds greater than ~ 28 ms-1, which highlights the importance of rare high-energy wind events. The likely meteorological mechanisms generating these patterns are discussed.

Hypercube matrix computation task

NASA Technical Reports Server (NTRS)

Calalo, Ruel H.; Imbriale, William A.; Jacobi, Nathan; Liewer, Paulett C.; Lockhart, Thomas G.; Lyzenga, Gregory A.; Lyons, James R.; Manshadi, Farzin; Patterson, Jean E.

1988-01-01

A major objective of the Hypercube Matrix Computation effort at the Jet Propulsion Laboratory (JPL) is to investigate the applicability of a parallel computing architecture to the solution of large-scale electromagnetic scattering problems. Three scattering analysis codes are being implemented and assessed on a JPL/California Institute of Technology (Caltech) Mark 3 Hypercube. The codes, which utilize different underlying algorithms, give a means of evaluating the general applicability of this parallel architecture. The three analysis codes being implemented are a frequency domain method of moments code, a time domain finite difference code, and a frequency domain finite elements code. These analysis capabilities are being integrated into an electromagnetics interactive analysis workstation which can serve as a design tool for the construction of antennas and other radiating or scattering structures. The first two years of work on the Hypercube Matrix Computation effort is summarized. It includes both new developments and results as well as work previously reported in the Hypercube Matrix Computation Task: Final Report for 1986 to 1987 (JPL Publication 87-18).

Calculation of Water Drop Trajectories to and About Arbitrary Three-Dimensional Bodies in Potential Airflow

NASA Technical Reports Server (NTRS)

Norment, H. G.

1980-01-01

Calculations can be performed for any atmospheric conditions and for all water drop sizes, from the smallest cloud droplet to large raindrops. Any subsonic, external, non-lifting flow can be accommodated; flow into, but not through, inlets also can be simulated. Experimental water drop drag relations are used in the water drop equations of motion and effects of gravity settling are included. Seven codes are described: (1) a code used to debug and plot body surface description data; (2) a code that processes the body surface data to yield the potential flow field; (3) a code that computes flow velocities at arrays of points in space; (4) a code that computes water drop trajectories from an array of points in space; (5) a code that computes water drop trajectories and fluxes to arbitrary target points; (6) a code that computes water drop trajectories tangent to the body; and (7) a code that produces stereo pair plots which include both the body and trajectories. Code descriptions include operating instructions, card inputs and printouts for example problems, and listing of the FORTRAN codes. Accuracy of the calculations is discussed, and trajectory calculation results are compared with prior calculations and with experimental data.

Utilizing GPUs to Accelerate Turbomachinery CFD Codes

NASA Technical Reports Server (NTRS)

MacCalla, Weylin; Kulkarni, Sameer

2016-01-01

GPU computing has established itself as a way to accelerate parallel codes in the high performance computing world. This work focuses on speeding up APNASA, a legacy CFD code used at NASA Glenn Research Center, while also drawing conclusions about the nature of GPU computing and the requirements to make GPGPU worthwhile on legacy codes. Rewriting and restructuring of the source code was avoided to limit the introduction of new bugs. The code was profiled and investigated for parallelization potential, then OpenACC directives were used to indicate parallel parts of the code. The use of OpenACC directives was not able to reduce the runtime of APNASA on either the NVIDIA Tesla discrete graphics card, or the AMD accelerated processing unit. Additionally, it was found that in order to justify the use of GPGPU, the amount of parallel work being done within a kernel would have to greatly exceed the work being done by any one portion of the APNASA code. It was determined that in order for an application like APNASA to be accelerated on the GPU, it should not be modular in nature, and the parallel portions of the code must contain a large portion of the code's computation time.

PASCO: Structural panel analysis and sizing code: Users manual - Revised

NASA Technical Reports Server (NTRS)

Anderson, M. S.; Stroud, W. J.; Durling, B. J.; Hennessy, K. W.

1981-01-01

A computer code denoted PASCO is described for analyzing and sizing uniaxially stiffened composite panels. Buckling and vibration analyses are carried out with a linked plate analysis computer code denoted VIPASA, which is included in PASCO. Sizing is based on nonlinear mathematical programming techniques and employs a computer code denoted CONMIN, also included in PASCO. Design requirements considered are initial buckling, material strength, stiffness and vibration frequency. A user's manual for PASCO is presented.

Computation of Reacting Flows in Combustion Processes

NASA Technical Reports Server (NTRS)

Keith, Theo G., Jr.; Chen, Kuo-Huey

1997-01-01

The main objective of this research was to develop an efficient three-dimensional computer code for chemically reacting flows. The main computer code developed is ALLSPD-3D. The ALLSPD-3D computer program is developed for the calculation of three-dimensional, chemically reacting flows with sprays. The ALL-SPD code employs a coupled, strongly implicit solution procedure for turbulent spray combustion flows. A stochastic droplet model and an efficient method for treatment of the spray source terms in the gas-phase equations are used to calculate the evaporating liquid sprays. The chemistry treatment in the code is general enough that an arbitrary number of reaction and species can be defined by the users. Also, it is written in generalized curvilinear coordinates with both multi-block and flexible internal blockage capabilities to handle complex geometries. In addition, for general industrial combustion applications, the code provides both dilution and transpiration cooling capabilities. The ALLSPD algorithm, which employs the preconditioning and eigenvalue rescaling techniques, is capable of providing efficient solution for flows with a wide range of Mach numbers. Although written for three-dimensional flows in general, the code can be used for two-dimensional and axisymmetric flow computations as well. The code is written in such a way that it can be run in various computer platforms (supercomputers, workstations and parallel processors) and the GUI (Graphical User Interface) should provide a user-friendly tool in setting up and running the code.

NASA Rotor 37 CFD Code Validation: Glenn-HT Code

NASA Technical Reports Server (NTRS)

Ameri, Ali A.

2010-01-01

In order to advance the goals of NASA aeronautics programs, it is necessary to continuously evaluate and improve the computational tools used for research and design at NASA. One such code is the Glenn-HT code which is used at NASA Glenn Research Center (GRC) for turbomachinery computations. Although the code has been thoroughly validated for turbine heat transfer computations, it has not been utilized for compressors. In this work, Glenn-HT was used to compute the flow in a transonic compressor and comparisons were made to experimental data. The results presented here are in good agreement with this data. Most of the measures of performance are well within the measurement uncertainties and the exit profiles of interest agree with the experimental measurements.

Final report for the Tera Computer TTI CRADA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davidson, G.S.; Pavlakos, C.; Silva, C.

1997-01-01

Tera Computer and Sandia National Laboratories have completed a CRADA, which examined the Tera Multi-Threaded Architecture (MTA) for use with large codes of importance to industry and DOE. The MTA is an innovative architecture that uses parallelism to mask latency between memories and processors. The physical implementation is a parallel computer with high cross-section bandwidth and GaAs processors designed by Tera, which support many small computation threads and fast, lightweight context switches between them. When any thread blocks while waiting for memory accesses to complete, another thread immediately begins execution so that high CPU utilization is maintained. The Tera MTAmore » parallel computer has a single, global address space, which is appealing when porting existing applications to a parallel computer. This ease of porting is further enabled by compiler technology that helps break computations into parallel threads. DOE and Sandia National Laboratories were interested in working with Tera to further develop this computing concept. While Tera Computer would continue the hardware development and compiler research, Sandia National Laboratories would work with Tera to ensure that their compilers worked well with important Sandia codes, most particularly CTH, a shock physics code used for weapon safety computations. In addition to that important code, Sandia National Laboratories would complete research on a robotic path planning code, SANDROS, which is important in manufacturing applications, and would evaluate the MTA performance on this code. Finally, Sandia would work directly with Tera to develop 3D visualization codes, which would be appropriate for use with the MTA. Each of these tasks has been completed to the extent possible, given that Tera has just completed the MTA hardware. All of the CRADA work had to be done on simulators.« less

Operations analysis (study 2.1). Program listing for the LOVES computer code

NASA Technical Reports Server (NTRS)

Wray, S. T., Jr.

1974-01-01

A listing of the LOVES computer program is presented. The program is coded partially in SIMSCRIPT and FORTRAN. This version of LOVES is compatible with both the CDC 7600 and the UNIVAC 1108 computers. The code has been compiled, loaded, and executed successfully on the EXEC 8 system for the UNIVAC 1108.

Analysis of the Length of Braille Texts in English Braille American Edition, the Nemeth Code, and Computer Braille Code versus the Unified English Braille Code

ERIC Educational Resources Information Center

Knowlton, Marie; Wetzel, Robin

2006-01-01

This study compared the length of text in English Braille American Edition, the Nemeth code, and the computer braille code with the Unified English Braille Code (UEBC)--also known as Unified English Braille (UEB). The findings indicate that differences in the length of text are dependent on the type of material that is transcribed and the grade…

A MATLAB based 3D modeling and inversion code for MT data

NASA Astrophysics Data System (ADS)

Singh, Arun; Dehiya, Rahul; Gupta, Pravin K.; Israil, M.

2017-07-01

The development of a MATLAB based computer code, AP3DMT, for modeling and inversion of 3D Magnetotelluric (MT) data is presented. The code comprises two independent components: grid generator code and modeling/inversion code. The grid generator code performs model discretization and acts as an interface by generating various I/O files. The inversion code performs core computations in modular form - forward modeling, data functionals, sensitivity computations and regularization. These modules can be readily extended to other similar inverse problems like Controlled-Source EM (CSEM). The modular structure of the code provides a framework useful for implementation of new applications and inversion algorithms. The use of MATLAB and its libraries makes it more compact and user friendly. The code has been validated on several published models. To demonstrate its versatility and capabilities the results of inversion for two complex models are presented.

Microparticle Separation by Cyclonic Separation

NASA Astrophysics Data System (ADS)

Karback, Keegan; Leith, Alexander

2017-11-01

The ability to separate particles based on their size has wide ranging applications from the industrial to the medical. Currently, cyclonic separators are primarily used in agriculture and manufacturing to syphon out contaminates or products from an air supply. This has led us to believe that cyclonic separation has more applications than the agricultural and industrial. Using the OpenFoam computational package, we were able to determine the flow parameters of a vortex in a cyclonic separator in order to segregate dust particles to a cutoff size of tens of nanometers. To test the model, we constructed an experiment to separate a test dust of various sized particles. We filled a chamber with Arizona test dust and utilized an acoustic suspension technique to segregate particles finer than a coarse cutoff size and introduce them into the cyclonic separation apparatus where they were further separated via a vortex following our computational model. The size of the particles separated from this experiment will be used to further refine our model. Metropolitan State University of Denver, Colorado University of Denver, Dr. Randall Tagg, Dr. Richard Krantz.

Simulation of Dust Radiative Impact on the Red Sea Using Coupled Regional Ocean/Atmosphere Modeling System

NASA Astrophysics Data System (ADS)

Stenchikov, G. L.; Osipov, S.

2016-12-01

This study focuses on the Middle East regional climate response to the dust aerosol radiative forcing. MODIS and SEVIRI satellite observations show extremely high (exceeding 1) dust optical depths over the southern Red Sea during the summer season. The significant north-to-south gradient of the dust optical depth over the Red Sea persists throughout the entire year. The radiative forcing of dust at the sea surface exceeds 120 Wm-2. The effect of this forcing to the Red Sea thermal regime and circulations is not well quantified yet. Therefore here we employ the Regional Ocean Modeling system (ROMS) fully coupled with the Weather Research and Forecasting (WRF) model to study the impact of dust on the Red Sea. The WRF was modified to interactively account for the radiative effect of dust. Daily spectral optical properties of dust are computed using Mie, T-matrix and geometric optics approaches, and are based on the SEVIRI climatological optical depth. The WRF model parent and nested domains are configured over the Middle East and North Africa (MENA) region and over the Red Sea with 30 and 10 km resolution, respectively. The ROMS model over the Red Sea has 2 km grid spacing. The simulations show that, in the equilibrium response, dust causes 0.5-0.7K cooling of the Red Sea surface waters, and weakens the overturning circulation in the Red Sea. The salinity distribution, fresh water and heat budgets are significantly perturbed. This indicates that dust plays an important role in formation of the Red Sea energy balance and circulation regimes, and has to be thoroughly accounted for in the future modeling studies.

Applications of automatic differentiation in computational fluid dynamics

NASA Technical Reports Server (NTRS)

Green, Lawrence L.; Carle, A.; Bischof, C.; Haigler, Kara J.; Newman, Perry A.

1994-01-01

Automatic differentiation (AD) is a powerful computational method that provides for computing exact sensitivity derivatives (SD) from existing computer programs for multidisciplinary design optimization (MDO) or in sensitivity analysis. A pre-compiler AD tool for FORTRAN programs called ADIFOR has been developed. The ADIFOR tool has been easily and quickly applied by NASA Langley researchers to assess the feasibility and computational impact of AD in MDO with several different FORTRAN programs. These include a state-of-the-art three dimensional multigrid Navier-Stokes flow solver for wings or aircraft configurations in transonic turbulent flow. With ADIFOR the user specifies sets of independent and dependent variables with an existing computer code. ADIFOR then traces the dependency path throughout the code, applies the chain rule to formulate derivative expressions, and generates new code to compute the required SD matrix. The resulting codes have been verified to compute exact non-geometric and geometric SD for a variety of cases. in less time than is required to compute the SD matrix using centered divided differences.

Fundamentals, current state of the development of, and prospects for further improvement of the new-generation thermal-hydraulic computational HYDRA-IBRAE/LM code for simulation of fast reactor systems

NASA Astrophysics Data System (ADS)

Alipchenkov, V. M.; Anfimov, A. M.; Afremov, D. A.; Gorbunov, V. S.; Zeigarnik, Yu. A.; Kudryavtsev, A. V.; Osipov, S. L.; Mosunova, N. A.; Strizhov, V. F.; Usov, E. V.

2016-02-01

The conceptual fundamentals of the development of the new-generation system thermal-hydraulic computational HYDRA-IBRAE/LM code are presented. The code is intended to simulate the thermalhydraulic processes that take place in the loops and the heat-exchange equipment of liquid-metal cooled fast reactor systems under normal operation and anticipated operational occurrences and during accidents. The paper provides a brief overview of Russian and foreign system thermal-hydraulic codes for modeling liquid-metal coolants and gives grounds for the necessity of development of a new-generation HYDRA-IBRAE/LM code. Considering the specific engineering features of the nuclear power plants (NPPs) equipped with the BN-1200 and the BREST-OD-300 reactors, the processes and the phenomena are singled out that require a detailed analysis and development of the models to be correctly described by the system thermal-hydraulic code in question. Information on the functionality of the computational code is provided, viz., the thermalhydraulic two-phase model, the properties of the sodium and the lead coolants, the closing equations for simulation of the heat-mass exchange processes, the models to describe the processes that take place during the steam-generator tube rupture, etc. The article gives a brief overview of the usability of the computational code, including a description of the support documentation and the supply package, as well as possibilities of taking advantages of the modern computer technologies, such as parallel computations. The paper shows the current state of verification and validation of the computational code; it also presents information on the principles of constructing of and populating the verification matrices for the BREST-OD-300 and the BN-1200 reactor systems. The prospects are outlined for further development of the HYDRA-IBRAE/LM code, introduction of new models into it, and enhancement of its usability. It is shown that the program of development and practical application of the code will allow carrying out in the nearest future the computations to analyze the safety of potential NPP projects at a qualitatively higher level.

Performance assessment of KORAT-3D on the ANL IBM-SP computer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alexeyev, A.V.; Zvenigorodskaya, O.A.; Shagaliev, R.M.

1999-09-01

The TENAR code is currently being developed at the Russian Federal Nuclear Center (VNIIEF) as a coupled dynamics code for the simulation of transients in VVER and RBMK systems and other nuclear systems. The neutronic module in this code system is KORAT-3D. This module is also one of the most computationally intensive components of the code system. A parallel version of KORAT-3D has been implemented to achieve the goal of obtaining transient solutions in reasonable computational time, particularly for RBMK calculations that involve the application of >100,000 nodes. An evaluation of the KORAT-3D code performance was recently undertaken on themore » Argonne National Laboratory (ANL) IBM ScalablePower (SP) parallel computer located in the Mathematics and Computer Science Division of ANL. At the time of the study, the ANL IBM-SP computer had 80 processors. This study was conducted under the auspices of a technical staff exchange program sponsored by the International Nuclear Safety Center (INSC).« less

The Interplanetary Meteoroid Environment for eXploration

NASA Astrophysics Data System (ADS)

Soja, R.; Sommer, M.; Srama, R.; Strub, P.; Grün, E.; Rodmann, J.; Vaubaillon, J.; Hornig, A.; Bausch, L.

2014-07-01

The Interplanetary Meteoroid Environment for eXploration (IMEX) project, funded by the European Space Agency (ESA), aims to characterize dust trails and streams produced by comets in the inner solar system. The goal is to predict meteor showers at any position or time in the solar system, such as at specific spacecraft or planets. This model will allow for the assessment of the dust impact hazard to spacecraft, which is important because hypervelocity impacts of micrometeoroids can damage or destroy spacecraft or their subsystems through physical damage or electromagnetic effects. Such considerations are particularly important in the context of human exploration of the solar system. Additionally, such a model will allow for scientific study of specific trails and their connections to observed dust phenomena, such as cometary trails and new meteor showers at Earth. We have recently expanded the model to include explicit integrations of large numbers of particles from each comet, utilizing the Constellation platform to perform the calculations. This is a distributed computing system, where currently 10,000 users are donating their idle computing time at home and thus generating a virtual supercomputer of 40,000 host PCs connected via the Internet (aerospaceresearch.net). This form of citizen science provides the required computing performance for simulating millions of particles ejected by each of the ˜400 comets, while developing the relationship between scientists and the general public. The result will be a unique set of saved orbital information for a large number of cometary streams, allowing efficient computation of their locations at any point in space and time. Here we will present the results from several test streams and discuss the progress towards obtaining the full set of integrated particles for each of the selected ˜400 short-period comets. individual Constellation users for their computing time.

Image computing techniques to extrapolate data for dust tracking in case of an experimental accident simulation in a nuclear fusion plant.

PubMed

Camplani, M; Malizia, A; Gelfusa, M; Barbato, F; Antonelli, L; Poggi, L A; Ciparisse, J F; Salgado, L; Richetta, M; Gaudio, P

2016-01-01

In this paper, a preliminary shadowgraph-based analysis of dust particles re-suspension due to loss of vacuum accident (LOVA) in ITER-like nuclear fusion reactors has been presented. Dust particles are produced through different mechanisms in nuclear fusion devices, one of the main issues is that dust particles are capable of being re-suspended in case of events such as LOVA. Shadowgraph is based on an expanded collimated beam of light emitted by a laser or a lamp that emits light transversely compared to the flow field direction. In the STARDUST facility, the dust moves in the flow, and it causes variations of refractive index that can be detected by using a CCD camera. The STARDUST fast camera setup allows to detect and to track dust particles moving in the vessel and then to obtain information about the velocity field of dust mobilized. In particular, the acquired images are processed such that per each frame the moving dust particles are detected by applying a background subtraction technique based on the mixture of Gaussian algorithm. The obtained foreground masks are eventually filtered with morphological operations. Finally, a multi-object tracking algorithm is used to track the detected particles along the experiment. For each particle, a Kalman filter-based tracker is applied; the particles dynamic is described by taking into account position, velocity, and acceleration as state variable. The results demonstrate that it is possible to obtain dust particles' velocity field during LOVA by automatically processing the data obtained with the shadowgraph approach.

Image computing techniques to extrapolate data for dust tracking in case of an experimental accident simulation in a nuclear fusion plant

NASA Astrophysics Data System (ADS)

Camplani, M.; Malizia, A.; Gelfusa, M.; Barbato, F.; Antonelli, L.; Poggi, L. A.; Ciparisse, J. F.; Salgado, L.; Richetta, M.; Gaudio, P.

2016-01-01

In this paper, a preliminary shadowgraph-based analysis of dust particles re-suspension due to loss of vacuum accident (LOVA) in ITER-like nuclear fusion reactors has been presented. Dust particles are produced through different mechanisms in nuclear fusion devices, one of the main issues is that dust particles are capable of being re-suspended in case of events such as LOVA. Shadowgraph is based on an expanded collimated beam of light emitted by a laser or a lamp that emits light transversely compared to the flow field direction. In the STARDUST facility, the dust moves in the flow, and it causes variations of refractive index that can be detected by using a CCD camera. The STARDUST fast camera setup allows to detect and to track dust particles moving in the vessel and then to obtain information about the velocity field of dust mobilized. In particular, the acquired images are processed such that per each frame the moving dust particles are detected by applying a background subtraction technique based on the mixture of Gaussian algorithm. The obtained foreground masks are eventually filtered with morphological operations. Finally, a multi-object tracking algorithm is used to track the detected particles along the experiment. For each particle, a Kalman filter-based tracker is applied; the particles dynamic is described by taking into account position, velocity, and acceleration as state variable. The results demonstrate that it is possible to obtain dust particles' velocity field during LOVA by automatically processing the data obtained with the shadowgraph approach.

Numerical simulation of "An American Haboob"

NASA Astrophysics Data System (ADS)

Vukovic, A.; Vujadinovic, M.; Pejanovic, G.; Andric, J.; Kumjian, M. R.; Djurdjevic, V.; Dacic, M.; Prasad, A. K.; El-Askary, H. M.; Paris, B. C.; Petkovic, S.; Nickovic, S.; Sprigg, W. A.

2013-10-01

A dust storm of fearful proportions hit Phoenix in the early evening hours of 5 July 2011. This storm, an American haboob, was predicted hours in advance because numerical, land-atmosphere modeling, computing power and remote sensing of dust events have improved greatly over the past decade. High resolution numerical models are required for accurate simulation of the small-scales of the haboob process, with high velocity surface winds produced by strong convection and severe downbursts. Dust productive areas in this region consist mainly of agricultural fields, with soil surfaces disturbed by plowing and tracks of land in the high Sonoran desert laid barren by ongoing draught. Model simulation of the 5 July 2011 dust storm uses the coupled atmospheric-dust model NMME-DREAM with 3.5 km horizontal resolution. A mask of the potentially dust productive regions is obtained from the land cover and the Normalized Difference Vegetation Index (NDVI) data from the Moderate Resolution Imaging Spectroradiometer (MODIS). Model results are compared with radar and other satellite-based images and surface meteorological and PM10 observations. The atmospheric model successfully hindcasted the position of the front in space and time, with about 1 h late arrival in Phoenix. The dust model predicted the rapid uptake of dust and high values of dust concentration in the ensuing storm. South of Phoenix, over the closest source regions (~ 25 km), the model PM10 surface dust concentration reached ~ 2500 μg m-3, but underestimated the values measured by the PM10stations within the city. Model results are also validated by the MODIS aerosol optical depth (AOD), employing deep blue (DB) algorithms for aerosol loadings. Model validation included Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), equipped with the lidar instrument, to disclose the vertical structure of dust aerosols as well as aerosol subtypes. Promising results encourage further research and application of high-resolution modeling and satellite-based remote sensing to warn of approaching severe dust events and reduce risks for safety and health.

Profugus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Evans, Thomas; Hamilton, Steven; Slattery, Stuart

Profugus is an open-source mini-application (mini-app) for radiation transport and reactor applications. It contains the fundamental computational kernels used in the Exnihilo code suite from Oak Ridge National Laboratory. However, Exnihilo is production code with a substantial user base. Furthermore, Exnihilo is export controlled. This makes collaboration with computer scientists and computer engineers difficult. Profugus is designed to bridge that gap. By encapsulating the core numerical algorithms in an abbreviated code base that is open-source, computer scientists can analyze the algorithms and easily make code-architectural changes to test performance without compromising the production code values of Exnihilo. Profugus is notmore » meant to be production software with respect to problem analysis. The computational kernels in Profugus are designed to analyze performance, not correctness. Nonetheless, users of Profugus can setup and run problems with enough real-world features to be useful as proof-of-concept for actual production work.« less

Self-Consistent Simulation of the Brownian Stage of Dust Growth

NASA Technical Reports Server (NTRS)

Kempf, S.; Pfalzner, S.; Henning, Th.

1996-01-01

It is a widely accepted view that in proto-planetary accretion disks the collision and following sticking of dust particles embedded in the gas eventually leads to the formation of planetesimals (coagulation). For the smallest dust grains, Brownian motion is assumed to be the dominant source of their relative velocities leading to collisions between these dust grains. As the dust grains grow they eventually couple to the turbulent motion of the gas which then drives the coagulation much more efficiently. Many numerical coagulation simulations have been carried out to calculate the fractal dimension of the aggregates, which determines the duration of the ineffective Brownian stage of growth. Predominantly on-lattice and off-lattice methods were used. However, both methods require simplification of the astrophysical conditions. The aggregates found by those methods had a fractal dimension of approximately 2 which is equivalent to a constant, mass-independent friction time. If this value were valid for the conditions in an accretion disk, this would mean that the coagulation process would finally 'freeze out' and the growth of a planetesimal would be impossible within the lifetime of an accretion disk. In order to investigate whether this fractal dimension is model independent, we simulate self-consistently the Brownian stage of the coagulation by an N-particle code. This method has the advantage that no further assumptions about homogeneity of the dust have to be made. In our model, the dust grains are considered as aggregates built up of spheres. The equation of motion of the dust grains is based on the probability density for the diffusive transport within the gas atmosphere. Because of the very low number density of the dust grains, only 2-body-collisions have to be considered. As the Brownian stage of growth is very inefficient, the system is to be simulated over long periods of time. In order to find close particle pairs of the system which are most likely to undergo a collision, we use a particle-in-cell (PIC) method for the early stages of the simulation where the system is still very homogeneous and a tree method later when the particles are more clustered.

A Computational Investigation of Various Water-Induced Explosion Mitigation Mechanisms

DTIC Science & Technology

2007-01-01

Guidelines for Evaluating the Characteristics of Vapor Cloud Explosions, Flash Fires, and BLEVEs , Center for Chemical Process Safety, AIChE, New York, NY...1994. [6]. Liebman and J. K. Richmond, Suppression of Coal Dust Explosions by Passive Water Barriers in a single Entry Mine , U.S. Bureau of Mines ...R.I. 8294, 1974. [7]. Liebman, J. Corry and J. K. Richmond, Water Barriers for Suppressing Coal Dust Explosions, U.S. Bureau of Mines R.I. 8170

Fast H.264/AVC FRExt intra coding using belief propagation.

PubMed

Milani, Simone

2011-01-01

In the H.264/AVC FRExt coder, the coding performance of Intra coding significantly overcomes the previous still image coding standards, like JPEG2000, thanks to a massive use of spatial prediction. Unfortunately, the adoption of an extensive set of predictors induces a significant increase of the computational complexity required by the rate-distortion optimization routine. The paper presents a complexity reduction strategy that aims at reducing the computational load of the Intra coding with a small loss in the compression performance. The proposed algorithm relies on selecting a reduced set of prediction modes according to their probabilities, which are estimated adopting a belief-propagation procedure. Experimental results show that the proposed method permits saving up to 60 % of the coding time required by an exhaustive rate-distortion optimization method with a negligible loss in performance. Moreover, it permits an accurate control of the computational complexity unlike other methods where the computational complexity depends upon the coded sequence.

2,445 Hours of Code: What I Learned from Facilitating Hour of Code Events in High School Libraries

ERIC Educational Resources Information Center

Colby, Jennifer

2015-01-01

This article describes a school librarian's experience with initiating an Hour of Code event for her school's student body. Hadi Partovi of Code.org conceived the Hour of Code "to get ten million students to try one hour of computer science" (Partovi, 2013a), which is implemented during Computer Science Education Week with a goal of…

Corneal permeability for cement dust: prognosis for occupational safety

NASA Astrophysics Data System (ADS)

Kalmykov, R. V.; Popova, D. V.; Kamenskikh, T. G.; Genina, E. A.; Tuchin, V. V.; Bashkatov, A. N.

2018-02-01

The high dust content in air of a working zone causes prevalence of pathologies of the anterior segment of the eye of workers of cement production. Therefore, studying of features of cement dust impact on structure of a cornea and development of ways of eye protection from this influence is relevant. In this work experimental studies were carried out with twenty eyes of ten rabbits. OCTtomography was used to monitor the light attenuation coefficient of the cornea in vitro during the permeability of cement dust and/or keratoprotector (Systein Ultra). The permeability coefficients of the cornea for water, cement dust and keratoprotector were measured. A computer model allowing one to analyze the diffusion of these substances in the eye cornea was developed. It was shown that 1) the cement dust falling on the eye cornea caused pronounced dehydration of the tissue (thickness decreasing) and led to the increase of the attenuation coefficient, which could affect the deterioration of the eyesight of workers in the conditions of cement production; 2) the application of the keratoprotector to the eye cornea when exposed by cement dust, slowed significantly the dehydration process and did not cause the increase of the attenuation coefficient that characterized the stabilization of visual functions. At this, the keratoprotector itself did not cause dehydration and led to the decrease of the attenuation coefficient, which could allow it to be used for a long time in the order to protect the organ of vision from the negative effects of cement dust.

Numerical algorithm comparison for the accurate and efficient computation of high-incidence vortical flow

NASA Technical Reports Server (NTRS)

Chaderjian, Neal M.

1991-01-01

Computations from two Navier-Stokes codes, NSS and F3D, are presented for a tangent-ogive-cylinder body at high angle of attack. Features of this steady flow include a pair of primary vortices on the leeward side of the body as well as secondary vortices. The topological and physical plausibility of this vortical structure is discussed. The accuracy of these codes are assessed by comparison of the numerical solutions with experimental data. The effects of turbulence model, numerical dissipation, and grid refinement are presented. The overall efficiency of these codes are also assessed by examining their convergence rates, computational time per time step, and maximum allowable time step for time-accurate computations. Overall, the numerical results from both codes compared equally well with experimental data, however, the NSS code was found to be significantly more efficient than the F3D code.

User's Manual for FEMOM3DR. Version 1.0

NASA Technical Reports Server (NTRS)

Reddy, C. J.

1998-01-01

FEMoM3DR is a computer code written in FORTRAN 77 to compute radiation characteristics of antennas on 3D body using combined Finite Element Method (FEM)/Method of Moments (MoM) technique. The code is written to handle different feeding structures like coaxial line, rectangular waveguide, and circular waveguide. This code uses the tetrahedral elements, with vector edge basis functions for FEM and triangular elements with roof-top basis functions for MoM. By virtue of FEM, this code can handle any arbitrary shaped three dimensional bodies with inhomogeneous lossy materials; and due to MoM the computational domain can be terminated in any arbitrary shape. The User's Manual is written to make the user acquainted with the operation of the code. The user is assumed to be familiar with the FORTRAN 77 language and the operating environment of the computers on which the code is intended to run.

Selection of a computer code for Hanford low-level waste engineered-system performance assessment

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGrail, B.P.; Mahoney, L.A.

Planned performance assessments for the proposed disposal of low-level waste (LLW) glass produced from remediation of wastes stored in underground tanks at Hanford, Washington will require calculations of radionuclide release rates from the subsurface disposal facility. These calculations will be done with the aid of computer codes. Currently available computer codes were ranked in terms of the feature sets implemented in the code that match a set of physical, chemical, numerical, and functional capabilities needed to assess release rates from the engineered system. The needed capabilities were identified from an analysis of the important physical and chemical process expected tomore » affect LLW glass corrosion and the mobility of radionuclides. The highest ranked computer code was found to be the ARES-CT code developed at PNL for the US Department of Energy for evaluation of and land disposal sites.« less

User's manual for a material transport code on the Octopus Computer Network

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naymik, T.G.; Mendez, G.D.

1978-09-15

A code to simulate material transport through porous media was developed at Oak Ridge National Laboratory. This code has been modified and adapted for use at Lawrence Livermore Laboratory. This manual, in conjunction with report ORNL-4928, explains the input, output, and execution of the code on the Octopus Computer Network.

Performance analysis of three dimensional integral equation computations on a massively parallel computer. M.S. Thesis

NASA Technical Reports Server (NTRS)

Logan, Terry G.

1994-01-01

The purpose of this study is to investigate the performance of the integral equation computations using numerical source field-panel method in a massively parallel processing (MPP) environment. A comparative study of computational performance of the MPP CM-5 computer and conventional Cray-YMP supercomputer for a three-dimensional flow problem is made. A serial FORTRAN code is converted into a parallel CM-FORTRAN code. Some performance results are obtained on CM-5 with 32, 62, 128 nodes along with those on Cray-YMP with a single processor. The comparison of the performance indicates that the parallel CM-FORTRAN code near or out-performs the equivalent serial FORTRAN code for some cases.

Computer Description of the M561 Utility Truck

DTIC Science & Technology

1984-10-01

GIFT Computer Code Sustainabi1ity Predictions for Army Spare Components Requirements for Combat (SPARC) 20. ABSTRACT (Caotfmia «a NWM eitim ft...used as input to the GIFT computer code to generate target vulnerability data. DO FORM V JAM 73 1473 EDITION OF I NOV 65 IS OBSOLETE Unclass i f ied...anaLyiis requires input from the Geometric Information for Targets ( GIFT ) ’ computer code. This report documents the combina- torial geometry (Com-Geom

TEMPEST: A three-dimensional time-dependent computer program for hydrothermal analysis: Volume 2, Assessment and verification results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eyler, L L; Trent, D S; Budden, M J

During the course of the TEMPEST computer code development a concurrent effort was conducted to assess the code's performance and the validity of computed results. The results of this work are presented in this document. The principal objective of this effort was to assure the code's computational correctness for a wide range of hydrothermal phenomena typical of fast breeder reactor application. 47 refs., 94 figs., 6 tabs.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amblard, A.; Riguccini, L.; Temi, P.

We compute the properties of a sample of 221 local, early-type galaxies with a spectral energy distribution (SED) modeling software, CIGALEMC. Concentrating on the star-forming (SF) activity and dust contents, we derive parameters such as the specific star formation rate (sSFR), the dust luminosity, dust mass, and temperature. In our sample, 52% is composed of elliptical (E) galaxies and 48% of lenticular (S0) galaxies. We find a larger proportion of S0 galaxies among galaxies with a large sSFR and large specific dust emission. The stronger activity of S0 galaxies is confirmed by larger dust masses. We investigate the relative proportionmore » of active galactic nuclei (AGNs) and SF galaxies in our sample using spectroscopic Sloan Digital Sky Survey data and near-infrared selection techniques, and find a larger proportion of AGN-dominated galaxies in the S0 sample than the E one. This could corroborate a scenario where blue galaxies evolve into red ellipticals by passing through an S0 AGN active period while quenching its star formation. Finally, we find a good agreement comparing our estimates with color indicators.« less

Light Scattering by Lunar Exospheric Dust: What could be Learned from LRO LAMP and LADEE UVS?

NASA Astrophysics Data System (ADS)

Glenar, D. A.; Stubbs, T. J.; Richard, D. T.; Stern, S. A.; Retherford, K. D.; Gladstone, R.; Feldman, P. D.; Colaprete, A.; Delory, G. T.

2011-12-01

Two complementary spectrometers, namely the Lunar Reconnaissance Orbiter, Lyman Alpha Mapping Project (LAMP) and the planned Lunar Atmosphere and Dust Environment Explorer (LADEE) Ultraviolet Explorer (UVS) will carry out sensitive searches for high altitude exospheric dust, via detection of scattered sunlight. The combined spectral coverage of these instruments extends from far-UV to near-IR wavelengths. Over this wavelength range, grain size parameter (X=2πr/λ, with r the grain radius and λ the wavelength) changes dramatically, which makes broad wavelength coverage a good diagnostic of grain size. Utilizing different pointing geometries, both LAMP and UVS are able to observe dust over a range of scattering angles, as well as measure the dust vertical profile via limb measurements at multiple tangent heights. We summarize several categories of information that can be inferred from the data sets, using broadband simulations of horizon glow as observed at the limb. Grain scattering properties used in these simulations were computed for multiple grain shapes using Discrete-Dipole theory. Some cautionary remarks are included regarding the use of Mie theory to interpret scattering measurements.

The influence of commenting validity, placement, and style on perceptions of computer code trustworthiness: A heuristic-systematic processing approach.

PubMed

Alarcon, Gene M; Gamble, Rose F; Ryan, Tyler J; Walter, Charles; Jessup, Sarah A; Wood, David W; Capiola, August

2018-07-01

Computer programs are a ubiquitous part of modern society, yet little is known about the psychological processes that underlie reviewing code. We applied the heuristic-systematic model (HSM) to investigate the influence of computer code comments on perceptions of code trustworthiness. The study explored the influence of validity, placement, and style of comments in code on trustworthiness perceptions and time spent on code. Results indicated valid comments led to higher trust assessments and more time spent on the code. Properly placed comments led to lower trust assessments and had a marginal effect on time spent on code; however, the effect was no longer significant after controlling for effects of the source code. Low style comments led to marginally higher trustworthiness assessments, but high style comments led to longer time spent on the code. Several interactions were also found. Our findings suggest the relationship between code comments and perceptions of code trustworthiness is not as straightforward as previously thought. Additionally, the current paper extends the HSM to the programming literature. Copyright © 2018 Elsevier Ltd. All rights reserved.

Adiabatic topological quantum computing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cesare, Chris; Landahl, Andrew J.; Bacon, Dave

Topological quantum computing promises error-resistant quantum computation without active error correction. However, there is a worry that during the process of executing quantum gates by braiding anyons around each other, extra anyonic excitations will be created that will disorder the encoded quantum information. Here, we explore this question in detail by studying adiabatic code deformations on Hamiltonians based on topological codes, notably Kitaev’s surface codes and the more recently discovered color codes. We develop protocols that enable universal quantum computing by adiabatic evolution in a way that keeps the energy gap of the system constant with respect to the computationmore » size and introduces only simple local Hamiltonian interactions. This allows one to perform holonomic quantum computing with these topological quantum computing systems. The tools we develop allow one to go beyond numerical simulations and understand these processes analytically.« less

Adiabatic topological quantum computing

DOE PAGES

Cesare, Chris; Landahl, Andrew J.; Bacon, Dave; ...

2015-07-31

Topological quantum computing promises error-resistant quantum computation without active error correction. However, there is a worry that during the process of executing quantum gates by braiding anyons around each other, extra anyonic excitations will be created that will disorder the encoded quantum information. Here, we explore this question in detail by studying adiabatic code deformations on Hamiltonians based on topological codes, notably Kitaev’s surface codes and the more recently discovered color codes. We develop protocols that enable universal quantum computing by adiabatic evolution in a way that keeps the energy gap of the system constant with respect to the computationmore » size and introduces only simple local Hamiltonian interactions. This allows one to perform holonomic quantum computing with these topological quantum computing systems. The tools we develop allow one to go beyond numerical simulations and understand these processes analytically.« less

Modeling photopolarimetric characteristics of comet dust as a polydisperse mixture of polyshaped rough spheroids

NASA Astrophysics Data System (ADS)

Kolokolova, L.; Das, H.; Dubovik, O.; Lapyonok, T.

2013-12-01

It is widely recognized now that the main component of comet dust is aggregated particles that consist of submicron grains. It is also well known that cometary dust obey a rather wide size distribution with abundant particles whose size reaches dozens of microns. However, numerous attempts of computer simulation of light scattering by comet dust using aggregated particles have not succeeded to consider particles larger than a couple of microns due to limitations in the memory and speed of available computers. Attempts to substitute aggregates by polydisperse solid particles (spheres, spheroids, cylinders) could not consistently reproduce observed angular and spectral characteristics of comet brightness and polarization even in such a general case as polyshaped (i.e. containing particles of a variety of aspect ratios) mixture of spheroids (Kolokolova et al., In: Photopolarimetry in Remote Sensing, Kluwer Acad. Publ., 431, 2004). In this study we are checking how well cometary dust can be modeled using modeling tools for rough spheroids. With this purpose we use the software package described in Dubovik et al. (J. Geophys. Res., 111, D11208, doi:10.1029/2005JD006619d, 2006) that allows for a substantial reduction of computer time in calculating scattering properties of spheroid mixtures by means of using pre-calculated kernels - quadrature coefficients employed in the numerical integration of spheroid optical properties over size and shape. The kernels were pre-calculated for spheroids of 25 axis ratios, ranging from 0.3 to 3, and 42 size bins within the size parameter range 0.01 - 625. This software package has been recently expanded with the possibility of simulating not only smooth but also rough spheroids that is used in present study. We consider refractive indexes of the materials typical for comet dust: silicate, carbon, organics, and their mixtures. We also consider porous particles accounting on voids in the spheroids through effective medium approach. The roughness of the spheroids is considered as a normal distribution of particle surface slopes and can be of different degree depending on the standard deviation of the distribution, σ, where σ=0 corresponds to smooth surface and σ=0.5 describes severely rough surface (see Young et al., J. Atm. Sci., 70, 330, 2012). We perform computations for two wavelengths, typical for blue (447nm) and red (640nm) cometary continuum filters. We compare phase angle dependence of polarization and brightness and their spectral change obtained with the rough-spheroid model with those observed for comets (e.g. Kolokolova et al., In: Comets 2, Arizona Press, 577, 2004) to see how well rough spheroids can reproduce cometary low albedo, red color, red polarimetric color, negative polarization at small phase angles and polarization maximum at medium phase angles.

Fast Computation of the Two-Point Correlation Function in the Age of Big Data

NASA Astrophysics Data System (ADS)

Pellegrino, Andrew; Timlin, John

2018-01-01

We present a new code which quickly computes the two-point correlation function for large sets of astronomical data. This code combines the ease of use of Python with the speed of parallel shared libraries written in C. We include the capability to compute the auto- and cross-correlation statistics, and allow the user to calculate the three-dimensional and angular correlation functions. Additionally, the code automatically divides the user-provided sky masks into contiguous subsamples of similar size, using the HEALPix pixelization scheme, for the purpose of resampling. Errors are computed using jackknife and bootstrap resampling in a way that adds negligible extra runtime, even with many subsamples. We demonstrate comparable speed with other clustering codes, and code accuracy compared to known and analytic results.

A new physically-based windblown dust emission ...

EPA Pesticide Factsheets

Dust has significant impacts on weather and climate, air quality and visibility, and human health; therefore, it is important to include a windblown dust emission module in atmospheric and air quality models. In this presentation, we summarize our efforts in development of a physics-based windblown dust emission scheme and its implementation in the CMAQ modeling system. The new model incorporates the effect of the surface wind speed, soil texture, soil moisture, and surface roughness in a physically sound manner. Specifically, a newly developed dynamic relation for the surface roughness length in this model is believed to adequately represent the physics of the surface processes involved in the dust generation. Furthermore, careful attention is paid in integrating the new windblown dust module within the CMAQ to ensure that the required input parameters are correctly configured. The new model is evaluated for the case studies including the continental United States and the Northern hemisphere, and is shown to be able to capture the occurrence of the dust outbreak and the level of the soil concentration. We discuss the uncertainties and limitations of the model and briefly describe our path forward for further improvements. The National Exposure Research Laboratory (NERL) Computational Exposure Division (CED) develops and evaluates data, decision-support tools, and models to be applied to media-specific or receptor-specific problem areas. CED uses modeling-based

Survival and in-vessel redistribution of beryllium droplets after ITER disruptions

NASA Astrophysics Data System (ADS)

Vignitchouk, L.; Ratynskaia, S.; Tolias, P.; Pitts, R. A.; De Temmerman, G.; Lehnen, M.; Kiramov, D.

2018-07-01

The motion and temperature evolution of beryllium droplets produced by first wall surface melting after ITER major disruptions and vertical displacement events mitigated during the current quench are simulated by the MIGRAINe dust dynamics code. These simulations employ an updated physical model which addresses droplet-plasma interaction in ITER-relevant regimes characterized by magnetized electron collection and thin-sheath ion collection, as well as electron emission processes induced by electron and high-Z ion impacts. The disruption scenarios have been implemented from DINA simulations of the time-evolving plasma parameters, while the droplet injection points are set to the first-wall locations expected to receive the highest thermal quench heat flux according to field line tracing studies. The droplet size, speed and ejection angle are varied within the range of currently available experimental and theoretical constraints, and the final quantities of interest are obtained by weighting single-trajectory output with different size and speed distributions. Detailed estimates of droplet solidification into dust grains and their subsequent deposition in the vessel are obtained. For representative distributions of the droplet injection parameters, the results indicate that at most a few percents of the beryllium mass initially injected is converted into solid dust, while the remaining mass either vaporizes or forms liquid splashes on the wall. Simulated in-vessel spatial distributions are also provided for the surviving dust, with the aim of providing guidance for planned dust diagnostic, retrieval and clean-up systems on ITER.

Design of convolutional tornado code

NASA Astrophysics Data System (ADS)

Zhou, Hui; Yang, Yao; Gao, Hongmin; Tan, Lu

2017-09-01

As a linear block code, the traditional tornado (tTN) code is inefficient in burst-erasure environment and its multi-level structure may lead to high encoding/decoding complexity. This paper presents a convolutional tornado (cTN) code which is able to improve the burst-erasure protection capability by applying the convolution property to the tTN code, and reduce computational complexity by abrogating the multi-level structure. The simulation results show that cTN code can provide a better packet loss protection performance with lower computation complexity than tTN code.

Cosmic Genes in the Cretaceous-Tertiary transition

NASA Astrophysics Data System (ADS)

Wallis, M. K.

2003-07-01

It is proposed that genes coding for Aib-polypeptides arose early on in the K/T transition, presumed from the Earth's accretion of interplanetary (comet) dust. Aib-fungi flourished because of the evolutionary advantage of novel antibiotics. The stress on Cretaceous biology led directly and indirectly to mass species extinctions, including many dinosaur species, in the epoch preceding the Chicxulub impact.

Ground Vehicle CFD at TARDEC

DTIC Science & Technology

2012-05-21

Cooling Sytem: StarCCM+ Blast / Crew Safety: LS- Dyna Fatigue & FEA: Abaqus / NCode Each code run with ~40-80 CPUs on TARDEC HPC Models...suppression, blast solid modeling have particular scaling problems because of the use of Lagrangian particles Example: Dust modeling for engine...for technology demonstrator vehicles UNCLASSIFIED 9 Example CFD Interest Areas • Underbody mine blast • HVAC design / interior cooling

Where on Mars Does Carbon Dioxide Frost Form Often?

NASA Image and Video Library

2016-07-08

This map shows the frequency of carbon dioxide frost's presence at sunrise on Mars, as a percentage of days year-round. Carbon dioxide ice more often covers the ground at night in some mid-latitude regions than in polar regions, where it is generally absent for much of summer and fall. Color coding is based on data from the Mars Climate Sounder instrument on NASA's Mars Reconnaissance Orbiter. A color-key bar below the map shows how colors correspond to frequencies. Yellow indicates high frequencies, identifying areas where carbon dioxide ice is present on the ground at night during most of the year. Blue identifies areas where it is rarely present; red is intermediate. Areas without color coding are regions where carbon dioxide frost is not detected at any time of year. The areas with highest frequency of overnight carbon dioxide frost correspond to regions with surfaces of loose dust, which do not retain heat well, compared to rockier areas. Those areas also have some of the highest mid-afternoon temperatures on the planet. The dust surface heats up and cools off rapidly. http://photojournal.jpl.nasa.gov/catalog/PIA20758

Modeling Well Sampled Composite Spectral Energy Distributions of Distant Galaxies via an MCMC-driven Inference Framework

NASA Astrophysics Data System (ADS)

Pasha, Imad; Kriek, Mariska; Johnson, Benjamin; Conroy, Charlie

2018-01-01

Using a novel, MCMC-driven inference framework, we have modeled the stellar and dust emission of 32 composite spectral energy distributions (SEDs), which span from the near-ultraviolet (NUV) to far infrared (FIR). The composite SEDs were originally constructed in a previous work from the photometric catalogs of the NEWFIRM Medium-Band Survey, in which SEDs of individual galaxies at 0.5 < z < 2.0 were iteratively matched and sorted into types based on their rest-frame UV-to-NIR photometry. In a subsequent work, MIPS 24 μm was added for each SED type, and in this work, PACS 100 μm, PACS160 μm, SPIRE 25 μm, and SPIRE 350 μm photometry have been added to extend the range of the composite SEDs into the FIR. We fit the composite SEDs with the Prospector code, which utilizes an MCMC sampling to explore the parameter space for models created by the Flexible Stellar Population Synthesis (FSPS) code, in order to investigate how specific star formation rate (sSFR), dust temperature, and other galaxy properties vary with SED type.This work is also being used to better constrain the SPS models within FSPS.

Three-dimensional turbopump flowfield analysis

NASA Technical Reports Server (NTRS)

Sharma, O. P.; Belford, K. A.; Ni, R. H.

1992-01-01

A program was conducted to develop a flow prediction method applicable to rocket turbopumps. The complex nature of a flowfield in turbopumps is described and examples of flowfields are discussed to illustrate that physics based models and analytical calculation procedures based on computational fluid dynamics (CFD) are needed to develop reliable design procedures for turbopumps. A CFD code developed at NASA ARC was used as the base code. The turbulence model and boundary conditions in the base code were modified, respectively, to: (1) compute transitional flows and account for extra rates of strain, e.g., rotation; and (2) compute surface heat transfer coefficients and allow computation through multistage turbomachines. Benchmark quality data from two and three-dimensional cascades were used to verify the code. The predictive capabilities of the present CFD code were demonstrated by computing the flow through a radial impeller and a multistage axial flow turbine. Results of the program indicate that the present code operated in a two-dimensional mode is a cost effective alternative to full three-dimensional calculations, and that it permits realistic predictions of unsteady loadings and losses for multistage machines.

High altitude chemically reacting gas particle mixtures. Volume 3: Computer code user's and applications manual. [rocket nozzle and orbital plume flow fields

NASA Technical Reports Server (NTRS)

Smith, S. D.

1984-01-01

A users manual for the RAMP2 computer code is provided. The RAMP2 code can be used to model the dominant phenomena which affect the prediction of liquid and solid rocket nozzle and orbital plume flow fields. The general structure and operation of RAMP2 are discussed. A user input/output guide for the modified TRAN72 computer code and the RAMP2F code is given. The application and use of the BLIMPJ module are considered. Sample problems involving the space shuttle main engine and motor are included.

Development of numerical methods for overset grids with applications for the integrated Space Shuttle vehicle

NASA Technical Reports Server (NTRS)

Chan, William M.

1995-01-01

Algorithms and computer code developments were performed for the overset grid approach to solving computational fluid dynamics problems. The techniques developed are applicable to compressible Navier-Stokes flow for any general complex configurations. The computer codes developed were tested on different complex configurations with the Space Shuttle launch vehicle configuration as the primary test bed. General, efficient and user-friendly codes were produced for grid generation, flow solution and force and moment computation.

Research in Computational Aeroscience Applications Implemented on Advanced Parallel Computing Systems

NASA Technical Reports Server (NTRS)

Wigton, Larry

1996-01-01

Improving the numerical linear algebra routines for use in new Navier-Stokes codes, specifically Tim Barth's unstructured grid code, with spin-offs to TRANAIR is reported. A fast distance calculation routine for Navier-Stokes codes using the new one-equation turbulence models is written. The primary focus of this work was devoted to improving matrix-iterative methods. New algorithms have been developed which activate the full potential of classical Cray-class computers as well as distributed-memory parallel computers.

ISSYS: An integrated synergistic Synthesis System

NASA Technical Reports Server (NTRS)

Dovi, A. R.

1980-01-01

Integrated Synergistic Synthesis System (ISSYS), an integrated system of computer codes in which the sequence of program execution and data flow is controlled by the user, is discussed. The commands available to exert such control, the ISSYS major function and rules, and the computer codes currently available in the system are described. Computational sequences frequently used in the aircraft structural analysis and synthesis are defined. External computer codes utilized by the ISSYS system are documented. A bibliography on the programs is included.

An Infrared Study of the Circumstellar Material Associated with the Carbon Star R Sculptoris

NASA Astrophysics Data System (ADS)

Hankins, M. J.; Herter, T. L.; Maercker, M.; Lau, R. M.; Sloan, G. C.

2018-01-01

The asymptotic giant branch (AGB) star R Sculptoris (R Scl) is one of the most extensively studied stars on the AGB. R Scl is a carbon star with a massive circumstellar shell (M shell ∼ 7.3 × 10‑3 M ⊙) that is thought to have been produced during a thermal pulse event ∼2200 years ago. To study the thermal dust emission associated with its circumstellar material, observations were taken with the Faint Object InfraRed CAMera for the SOFIA Telescope (FORCAST) at 19.7, 25.2, 31.5, 34.8, and 37.1 μm. Maps of the infrared emission at these wavelengths were used to study the morphology and temperature structure of the spatially extended dust emission. Using the radiative-transfer code DUSTY, and fitting the spatial profile of the emission, we find that a geometrically thin dust shell cannot reproduce the observed spatially resolved emission. Instead, a second dust component in addition to the shell is needed to reproduce the observed emission. This component, which lies interior to the dust shell, traces the circumstellar envelope of R Scl. It is best fit by a density profile with n ∝ r α , where α ={0.75}-0.25+0.45 and a dust mass of {M}d={9.0}-4.1+2.3× {10}-6 {M}ȯ . The strong departure from an r ‑2 law indicates that the mass-loss rate of R Scl has not been constant. This result is consistent with a slow decline in the post-pulse mass loss that has been inferred from observations of the molecular gas.

User's manual for a two-dimensional, ground-water flow code on the Octopus computer network

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naymik, T.G.

1978-08-30

A ground-water hydrology computer code, programmed by R.L. Taylor (in Proc. American Society of Civil Engineers, Journal of Hydraulics Division, 93(HY2), pp. 25-33 (1967)), has been adapted to the Octopus computer system at Lawrence Livermore Laboratory. Using an example problem, this manual details the input, output, and execution options of the code.

Interactive Synthesis of Code Level Security Rules

DTIC Science & Technology

2017-04-01

Interactive Synthesis of Code-Level Security Rules A Thesis Presented by Leo St. Amour to The Department of Computer Science in partial fulfillment...of the requirements for the degree of Master of Science in Computer Science Northeastern University Boston, Massachusetts April 2017 DISTRIBUTION...Abstract of the Thesis Interactive Synthesis of Code-Level Security Rules by Leo St. Amour Master of Science in Computer Science Northeastern University

The adaption and use of research codes for performance assessment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liebetrau, A.M.

1987-05-01

Models of real-world phenomena are developed for many reasons. The models are usually, if not always, implemented in the form of a computer code. The characteristics of a code are determined largely by its intended use. Realizations or implementations of detailed mathematical models of complex physical and/or chemical processes are often referred to as research or scientific (RS) codes. Research codes typically require large amounts of computing time. One example of an RS code is a finite-element code for solving complex systems of differential equations that describe mass transfer through some geologic medium. Considerable computing time is required because computationsmore » are done at many points in time and/or space. Codes used to evaluate the overall performance of real-world physical systems are called performance assessment (PA) codes. Performance assessment codes are used to conduct simulated experiments involving systems that cannot be directly observed. Thus, PA codes usually involve repeated simulations of system performance in situations that preclude the use of conventional experimental and statistical methods. 3 figs.« less

Topological color codes on Union Jack lattices: a stable implementation of the whole Clifford group

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katzgraber, Helmut G.; Theoretische Physik, ETH Zurich, CH-8093 Zurich; Bombin, H.

We study the error threshold of topological color codes on Union Jack lattices that allow for the full implementation of the whole Clifford group of quantum gates. After mapping the error-correction process onto a statistical mechanical random three-body Ising model on a Union Jack lattice, we compute its phase diagram in the temperature-disorder plane using Monte Carlo simulations. Surprisingly, topological color codes on Union Jack lattices have a similar error stability to color codes on triangular lattices, as well as to the Kitaev toric code. The enhanced computational capabilities of the topological color codes on Union Jack lattices with respectmore » to triangular lattices and the toric code combined with the inherent robustness of this implementation show good prospects for future stable quantum computer implementations.« less

The field experiments and model of the natural dust deposition effects on photovoltaic module efficiency.

PubMed

Jaszczur, Marek; Teneta, Janusz; Styszko, Katarzyna; Hassan, Qusay; Burzyńska, Paulina; Marcinek, Ewelina; Łopian, Natalia

2018-04-20

The maximisation of the efficiency of the photovoltaic system is crucial in order to increase the competitiveness of this technology. Unfortunately, several environmental factors in addition to many alterable and unalterable factors can significantly influence the performance of the PV system. Some of the environmental factors that depend on the site have to do with dust, soiling and pollutants. In this study conducted in the city centre of Kraków, Poland, characterised by high pollution and low wind speed, the focus is on the evaluation of the degradation of efficiency of polycrystalline photovoltaic modules due to natural dust deposition. The experimental results that were obtained demonstrated that deposited dust-related efficiency loss gradually increased with the mass and that it follows the exponential. The maximum dust deposition density observed for rainless exposure periods of 1 week exceeds 300 mg/m 2 and the results in efficiency loss were about 2.1%. It was observed that efficiency loss is not only mass-dependent but that it also depends on the dust properties. The small positive effect of the tiny dust layer which slightly increases in surface roughness on the module performance was also observed. The results that were obtained enable the development of a reliable model for the degradation of the efficiency of the PV module caused by dust deposition. The novelty consists in the model, which is easy to apply and which is dependent on the dust mass, for low and moderate naturally deposited dust concentration (up to 1 and 5 g/m 2 and representative for many geographical regions) and which is applicable to the majority of cases met in an urban and non-urban polluted area can be used to evaluate the dust deposition-related derating factor (efficiency loss), which is very much sought after by the system designers, and tools used for computer modelling and system malfunction detection.

Infrared observations of the dust coma

NASA Technical Reports Server (NTRS)

Campins, Humberto C.; Tokunaga, Alan T.

1988-01-01

The main infrared observational results were briefly reviewed at the start of this session. The new results are summarized. All of these results have yet to be synthesized into a self-consistent picture of the dust grain composition, dust production history, outburst mechanisms, and composition of the nucleus. The workshop discussion was helpful in pointing out problems faced by theorists, such as data quality, the lack of the proper theory for computing the scattering and emission of irregular particles, and in some cases the lack of optical constants of realistic materials. It is expected that the gross spectral and dynamical properties of Halley's Comet can be understood in time, even if the details of the observations and the theoretical calculations continue to vex us in the future.

Accurate Modeling of Ionospheric Electromagnetic Fields Generated by a Low-Altitude VLF Transmitter

DTIC Science & Technology

2007-08-31

latitude) for 3 different grid spacings. 14 8. Low-altitude fields produced by a 10-kHz source computed using the FD and TD codes. The agreement is...excellent, validating the new FD code. 16 9. High-altitude fields produced by a 10-kHz source computed using the FD and TD codes. The agreement is...again excellent. 17 10. Low-altitude fields produced by a 20-k.Hz source computed using the FD and TD codes. 17 11. High-altitude fields produced

Multidisciplinary High-Fidelity Analysis and Optimization of Aerospace Vehicles. Part 1; Formulation

NASA Technical Reports Server (NTRS)

Walsh, J. L.; Townsend, J. C.; Salas, A. O.; Samareh, J. A.; Mukhopadhyay, V.; Barthelemy, J.-F.

2000-01-01

An objective of the High Performance Computing and Communication Program at the NASA Langley Research Center is to demonstrate multidisciplinary shape and sizing optimization of a complete aerospace vehicle configuration by using high-fidelity, finite element structural analysis and computational fluid dynamics aerodynamic analysis in a distributed, heterogeneous computing environment that includes high performance parallel computing. A software system has been designed and implemented to integrate a set of existing discipline analysis codes, some of them computationally intensive, into a distributed computational environment for the design of a highspeed civil transport configuration. The paper describes the engineering aspects of formulating the optimization by integrating these analysis codes and associated interface codes into the system. The discipline codes are integrated by using the Java programming language and a Common Object Request Broker Architecture (CORBA) compliant software product. A companion paper presents currently available results.

Analysis of airborne antenna systems using geometrical theory of diffraction and moment method computer codes

NASA Technical Reports Server (NTRS)

Hartenstein, Richard G., Jr.

1985-01-01

Computer codes have been developed to analyze antennas on aircraft and in the presence of scatterers. The purpose of this study is to use these codes to develop accurate computer models of various aircraft and antenna systems. The antenna systems analyzed are a P-3B L-Band antenna, an A-7E UHF relay pod antenna, and traffic advisory antenna system installed on a Bell Long Ranger helicopter. Computer results are compared to measured ones with good agreement. These codes can be used in the design stage of an antenna system to determine the optimum antenna location and save valuable time and costly flight hours.

THC-MP: High performance numerical simulation of reactive transport and multiphase flow in porous media

NASA Astrophysics Data System (ADS)

Wei, Xiaohui; Li, Weishan; Tian, Hailong; Li, Hongliang; Xu, Haixiao; Xu, Tianfu

2015-07-01

The numerical simulation of multiphase flow and reactive transport in the porous media on complex subsurface problem is a computationally intensive application. To meet the increasingly computational requirements, this paper presents a parallel computing method and architecture. Derived from TOUGHREACT that is a well-established code for simulating subsurface multi-phase flow and reactive transport problems, we developed a high performance computing THC-MP based on massive parallel computer, which extends greatly on the computational capability for the original code. The domain decomposition method was applied to the coupled numerical computing procedure in the THC-MP. We designed the distributed data structure, implemented the data initialization and exchange between the computing nodes and the core solving module using the hybrid parallel iterative and direct solver. Numerical accuracy of the THC-MP was verified through a CO2 injection-induced reactive transport problem by comparing the results obtained from the parallel computing and sequential computing (original code). Execution efficiency and code scalability were examined through field scale carbon sequestration applications on the multicore cluster. The results demonstrate successfully the enhanced performance using the THC-MP on parallel computing facilities.

Parameterization of dust emissions in the global atmospheric chemistry-climate model EMAC: impact of nudging and soil properties

NASA Astrophysics Data System (ADS)

Astitha, M.; Lelieveld, J.; Abdel Kader, M.; Pozzer, A.; de Meij, A.

2012-11-01

Airborne desert dust influences radiative transfer, atmospheric chemistry and dynamics, as well as nutrient transport and deposition. It directly and indirectly affects climate on regional and global scales. Two versions of a parameterization scheme to compute desert dust emissions are incorporated into the atmospheric chemistry general circulation model EMAC (ECHAM5/MESSy2.41 Atmospheric Chemistry). One uses a globally uniform soil particle size distribution, whereas the other explicitly accounts for different soil textures worldwide. We have tested these two versions and investigated the sensitivity to input parameters, using remote sensing data from the Aerosol Robotic Network (AERONET) and dust concentrations and deposition measurements from the AeroCom dust benchmark database (and others). The two versions are shown to produce similar atmospheric dust loads in the N-African region, while they deviate in the Asian, Middle Eastern and S-American regions. The dust outflow from Africa over the Atlantic Ocean is accurately simulated by both schemes, in magnitude, location and seasonality. Approximately 70% of the modelled annual deposition data and 70-75% of the modelled monthly aerosol optical depth (AOD) in the Atlantic Ocean stations lay in the range 0.5 to 2 times the observations for all simulations. The two versions have similar performance, even though the total annual source differs by ~50%, which underscores the importance of transport and deposition processes (being the same for both versions). Even though the explicit soil particle size distribution is considered more realistic, the simpler scheme appears to perform better in several locations. This paper discusses the differences between the two versions of the dust emission scheme, focusing on their limitations and strengths in describing the global dust cycle and suggests possible future improvements.

Injection of mineral dust into the free troposphere during fire events observed with polarization lidar at Limassol, Cyprus

NASA Astrophysics Data System (ADS)

Nisantzi, A.; Mamouri, R. E.; Ansmann, A.; Hadjimitsis, D.

2014-06-01

Four-year observations (2010-2014) with EARLINET polarization lidar and AERONET sun/sky photometer at Limassol (34.7° N, 33° E), Cyprus, were used to study the soil dust content in lofted fire smoke plumes advected from Turkey. This first systematic attempt to characterize less than 3 days old smoke plumes in terms of particle depolarization contributes to the more general effort to properly describe the life cycle of free-tropospheric smoke-dust mixtures from the emission event to phases of long-range transport (>4 days after emission). We found significant differences in the particle depolarization ratio (PDR) with values from 9-18% in lofted aerosol layers when Turkish fires contributed to the aerosol burden and of 3-13% when Turkish fires were absent. High Ångström exponents of 1.4-2.2 during all these events with lofted smoke layers, occuring between 1 and 3 km height, suggest the absence of a pronounced particle coarse mode. When plotted vs. the travel time (spatial distance between Limassol and last fire area), PDR decreased strongly from initial values around 16-18% (one day travel) to 4-8% after 4 days of travel caused by deposition processes. This behavior was found to be in close agreement with the literature. Computation of particle extinction coefficient and mass concentrations, separately for fine-mode dust, coarse-mode dust, and non-dust aerosol components show extinction-related dust fractions of the order of 10% (for PDR = 4%, travel times >4 days) and 50% (PDR = 15%, one day travel time) and mass-related dust fractions of 25% (PDR = 4%) to 80% (PDR = 15%). Biomass burning should be considered as another source of free tropospheric soil dust.

A new 3D multi-fluid dust model: a study of the effects of activity and nucleus rotation on the dust grains' behavior in the cometary environment

NASA Astrophysics Data System (ADS)

Shou, Y.; Combi, M. R.; Toth, G.; Fougere, N.; Tenishev, V.; Huang, Z.; Jia, X.; Hansen, K. C.; Gombosi, T. I.; Bieler, A. M.; Rubin, M.

2016-12-01

Cometary dust observations may deepen our understanding of the role of dust in the formation of comets and in altering the cometary environment. Models including dust grains are in demand to interpret observations and test hypotheses. Several existing models have taken into account the gas-dust interaction, varying sizes of dust grains and the cometary gravitational force. In this work, we develop a multi-fluid dust model based on BATS-R-US in the University of Michigan's Space Weather Modeling Framework (SWMF). This model not only incorporates key features of previous dust models, but also has the capability of simulating time-dependent phenomena. Since the model is running in the rotating comet reference frame with a real shaped nucleus in the computational domain, the fictitious centrifugal and Coriolis forces are included. The boundary condition on the nucleus surface can be set according to the distribution of activity and the solar illumination. The Sun, which drives sublimation and the radiation pressure force, revolves around the comet in this frame. A newly developed numerical mesh is also used to resolve the real shaped nucleus in the center and to facilitate prescription of the outer boundary conditions that accommodate the rotating frame. The inner part of the grid is a box composed of Cartesian cells and the outer surface is a smooth sphere, with stretched cells filled in between the box and the sphere. The effects of the rotating nucleus and the activity region on the surface are discussed and preliminary results are presented. This work has been partially supported by grant NNX14AG84G from the NASA Planetary Atmospheres Program, and US Rosetta contracts JPL #1266313, JPL #1266314 and JPL #1286489.

DustPedia: A Definitive Study of Cosmic Dust in the Local Universe

NASA Astrophysics Data System (ADS)

Davies, J. I.; Baes, M.; Bianchi, S.; Jones, A.; Madden, S.; Xilouris, M.; Bocchio, M.; Casasola, V.; Cassara, L.; Clark, C.; De Looze, I.; Evans, R.; Fritz, J.; Galametz, M.; Galliano, F.; Lianou, S.; Mosenkov, A. V.; Smith, M.; Verstocken, S.; Viaene, S.; Vika, M.; Wagle, G.; Ysard, N.

2017-04-01

The European Space Agency has invested heavily in two cornerstones missions: Herschel and Planck. The legacy data from these missions provides an unprecedented opportunity to study cosmic dust in galaxies so that we can, for example, answer fundamental questions about the origin of the chemical elements, physical processes in the interstellar medium (ISM), its effect on stellar radiation, its relation to star formation and how this relates to the cosmic far-infrared background. In this paper we describe the DustPedia project, which enables us to develop tools and computer models that will help us relate observed cosmic dust emission to its physical properties (chemical composition, size distribution, and temperature), its origins (evolved stars, supernovae, and growth in the ISM), and the processes that destroy it (high-energy collisions and shock heated gas). To carry out this research, we combine the Herschel/Planck data with that from other sources of data, and provide observations at numerous wavelengths (≤slant 41) across the spectral energy distribution, thus creating the DustPedia database. To maximize our spatial resolution and sensitivity to cosmic dust, we limit our analysis to 4231 local galaxies (v< 3000 km s-1) selected via their near-infrared luminosity (stellar mass). To help us interpret this data, we developed a new physical model for dust (THEMIS), a new Bayesian method of fitting and interpreting spectral energy distributions (HerBIE) and a state-of-the-art Monte Carlo photon-tracing radiative transfer model (SKIRT). In this, the first of the DustPedia papers, we describe the project objectives, data sets used, and provide an insight into the new scientific methods we plan to implement.

A mini outburst from the nightside of comet 67P/Churyumov-Gerasimenko observed by the OSIRIS camera on Rosetta

NASA Astrophysics Data System (ADS)

Knollenberg, J.; Lin, Z. Y.; Hviid, S. F.; Oklay, N.; Vincent, J.-B.; Bodewits, D.; Mottola, S.; Pajola, M.; Sierks, H.; Barbieri, C.; Lamy, P.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J. L.; Bertini, I.; Cremonese, G.; Davidsson, B.; Da Deppo, V.; Debei, S.; De Cecco, M.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Ip, W.-H.; Jorda, L.; Keller, H. U.; Kührt, E.; Kramm, J. R.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez Moreno, J. J.; Marzari, F.; Naletto, G.; Thomas, N.; Güttler, C.; Preusker, F.; Scholten, F.; Tubiana, C.

2016-12-01

Context. On 12 March 2015 the OSIRIS WAC camera onboard the ESA Rosetta spacecraft orbiting comet 67P/Churyumov-Gerasimenko observed a small outburst originating from the Imhotep region at the foot of the big lobe of the comet. These measurements are unique since it was the first time that the initial phase of a transient outburst event could be directly observed. Aims: We investigate the evolution of the dust jet in order to derive clues about the outburst source mechanism and the ejected dust particles, in particular the dust mass, dust-to-gas ratio and the particle size distribution. Methods: Analysis of the images and of the observation geometry using comet shape models in combination with gasdynamic modeling of the transient dust jet were the main tools used in this study. Synthetic images were computed for comparison with the observations. Results: Analysis of the geometry revealed that the source region was not illuminated until 1.5 h after the event implying true nightside activity was observed. The outburst lasted for less than one hour and the average dust production rate during the initial four minutes was of the order of 1 kg/s. During this time the outburst dust production rate was approximately constant, no sign for an initial explosion could be detected. For dust grains between 0.01-1 mm a power law size distribution characterized by an index of about 2.6 provides the best fit to the observed radiance profiles. The dust-to-gas ratio of the outburst jet is in the range 0.6-1.8.

Code of Ethical Conduct for Computer-Using Educators: An ICCE Policy Statement.

ERIC Educational Resources Information Center

Computing Teacher, 1987

1987-01-01

Prepared by the International Council for Computers in Education's Ethics and Equity Committee, this code of ethics for educators using computers covers nine main areas: curriculum issues, issues relating to computer access, privacy/confidentiality issues, teacher-related issues, student issues, the community, school organizational issues,…

Vertical Distribution of Aerosols and Water Vapor Using CRISM Limb Observations

NASA Astrophysics Data System (ADS)

Smith, M. D.; Wolff, M. J.; Clancy, R. T.; CRISM Science; Operations Teams

2011-12-01

Near-infrared spectra taken in a limb-viewing geometry by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on-board the Mars Reconnaissance Orbiter (MRO) provide a useful tool for probing atmospheric structure. Specifically, the observed radiance as a function of wavelength and height above the limb allows the vertical distribution of both dust and ice aerosols to be retrieved. These data serve as an important supplement to the aerosol profiling provided by the MRO/MCS instrument allowing independent validation and giving additional information on particle physical and scattering properties through multi-wavelength studies. A total of at least ten CRISM limb observations have been taken so far covering a full Martian year. Each set of limb observations nominally contains about four dozen scans across the limb giving pole-to-pole coverage for two orbits at roughly 100 and 290 W longitude over the Tharsis and Syrtis/Hellas regions, respectively. At each longitude, limb scans are spaced roughly 10 degrees apart in latitude, with a vertical spatial resolution on the limb of roughly 800 m. Radiative transfer modeling is used to model the observations. We compute synthetic CRISM limb spectra using a discrete-ordinates radiative transfer code that accounts for multiple scattering from aerosols and accounts for spherical geometry of the limb observations by integrating the source functions along curved paths in that coordinate system. Retrieved are 14-point vertical profiles for dust and water ice aerosols with resolution of 0.4 scale heights between one and six scale heights above the surface. After the aerosol retrieval is completed, the abundances of CO2 (or surface pressure) and H2O gas are retrieved by matching the depth of absorption bands at 2000 nm for carbon dioxide and at 2600 nm for water vapor. In addition to the column abundance of water vapor, limited information on its vertical structure can also be retrieved depending on the signal available from aerosol scattering. Significant differences are seen in the retrieved vertical profiles of dust and water ice as a function of season. Dust typically extends to higher altitudes during the perihelion season. Ice aerosols are often observed to cap the dust layer during all seasons. Water vapor is observed to be deeply mixed in the perihelion season and confined near the surface in the aphelion season. The CRISM limb-geometry observations support the quantitative retrieval of aerosol and gas vertical profiles. These quantities cannot be retrieved using nadir observations, and they enable the study of important new science questions. The CRISM limbs also serve as a valuable supplement to the MRO/MCS limb profiles, enabling validation and multi-wavelength comparisons. Additional CRISM limb-geometry sets will continue to be taken approximately every two months (~30 degrees of Ls) as operations allow.

Properties of a local dust storm on Mars' Atlantis Chaos by means of radiative transfer modeling.

NASA Astrophysics Data System (ADS)

Oliva, Fabrizio; Altieri, Francesca; Geminale, Anna; Bellucci, Giancarlo; D'Aversa, Emiliano; Carrozzo, Giacomo; Sindoni, Giuseppe; Grassi, Davide

2017-04-01

In this study we present the analysis of the dust properties in a local storm imaged in the Atlantis Chaos region on Mars by the OMEGA spectrometer (Bibring et al., 2004) on March 2nd 2005 (ORB1441_5). By means of an inverse radiative transfer code we study the dust properties across the region and try to infer the connection be-tween the local storm dynamics and the orography. OMEGA is a visible and near-IR mapping spectrometer, operating in the spectral range 0.38-5.1 μm with three separate channels with different spectral resolution. The instrument's IFOV is 1.2 mrad. To analyze the storm properties we have used the inverse radiative transfer model MITRA (Oliva et al., 2016; Sindoni et al., 2013) to retrieve the effective radius reff, the optical depth at 880 nm τ880 and the top pressure tp of the dust layer. We used the Mars Climate Database (MCD, Forget et al., 1999) to obtain the atmospheric properties of the studied region to be used as input in our model. Moreover we used the optical constants from Wolff et al. (2009) to describe the dust composition. The properties from the surface have been obtained by ap-plying the SAS method (Geminale et al., 2015) to observations of the same region relatively clear from dust. All retrievals have been performed in the spectral range 500 ÷ 2500 nm. Here we describe the result from our analysis carried out on selected regions of the storm and characterized by a different optical depth of the dust. Aknowledgements: This study has been performed within the UPWARDS project and funded in the context of the European Union's Horizon 2020 Programme (H2020-Compet-08-2014), grant agreement UPWARDS-633127. References: Bibring, J-P. et al., 2004. OMEGA: Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité. Mars Express: the scientific payload, Ed. by Andrew Wilson, scientific coordination: Agustin Chicarro. ESA SP-1240, Noordwijk, Netherlands: ESA Publications Division, ISBN 92-9092-556-6, 2004, p. 37 - 49. Forget, F. et al., 1999. Improved general circulation models of the Martian atmosphere from the surface to above 80 km. Journal of Geophysical Research, Volume 104, Issue E10, 24155-24176. Geminale, A. et al., 2015. Removal of atmospheric features in near infrared spectra by means of principal components analysis and target transformation on Mars: I. Method. Icarus 253, 51-65. Oliva, F. et al., 2016. Clouds and hazes vertical structure of a Saturn's giant vortex from Cassini/VIMS-V data analysis. Icarus 278, 215-237. Sindoni, G. et al., 2013. Development of a Monte-Carlo Radiative Transfer Code for the Juno/JIRAM Limb Measurements. European Planetary Science Congress 2013, 8-13 September, London, UK. Wolff, M.J. et al., 2009. Wavelength dependence of dust aerosol single scattering albedo as observed by the Compact Reconnaissance Imaging Spectrometer. Journal of Geophysical Research, Vol. 114, E00D04.

Dust modeling of the combined ALMA and SPHERE datasets of HD 163296. Is HD 163296 really a Meeus group II disk?

NASA Astrophysics Data System (ADS)

Muro-Arena, G. A.; Dominik, C.; Waters, L. B. F. M.; Min, M.; Klarmann, L.; Ginski, C.; Isella, A.; Benisty, M.; Pohl, A.; Garufi, A.; Hagelberg, J.; Langlois, M.; Menard, F.; Pinte, C.; Sezestre, E.; van der Plas, G.; Villenave, M.; Delboulbé, A.; Magnard, Y.; Möller-Nilsson, O.; Pragt, J.; Rabou, P.; Roelfsema, R.

2018-06-01

Context. Multiwavelength observations are indispensable in studying disk geometry and dust evolution processes in protoplanetary disks. Aims: We aim to construct a three-dimensional model of HD 163296 that is capable of reproducing simultaneously new observations of the disk surface in scattered light with the SPHERE instrument and thermal emission continuum observations of the disk midplane with ALMA. We want to determine why the spectral energy distribution of HD 163296 is intermediary between the otherwise well-separated group I and group II Herbig stars. Methods: The disk was modeled using the Monte Carlo radiative transfer code MCMax3D. The radial dust surface density profile was modeled after the ALMA observations, while the polarized scattered light observations were used to constrain the inclination of the inner disk component and turbulence and grain growth in the outer disk. Results: While three rings are observed in the disk midplane in millimeter thermal emission at 80, 124, and 200 AU, only the innermost of these is observed in polarized scattered light, indicating a lack of small dust grains on the surface of the outer disk. We provide two models that are capable of explaining this difference. The first model uses increased settling in the outer disk as a mechanism to bring the small dust grains on the surface of the disk closer to the midplane and into the shadow cast by the first ring. The second model uses depletion of the smallest dust grains in the outer disk as a mechanism for decreasing the optical depth at optical and near-infrared wavelengths. In the region outside the fragmentation-dominated regime, such depletion is expected from state-of-the-art dust evolution models. We studied the effect of creating an artificial inner cavity in our models, and conclude that HD 163296 might be a precursor to typical group I sources.

A Sensitivity Study on the Effects of Particle Chemistry, Asphericity and Size on the Mass Extinction Efficiency of Mineral Dust in the Earth's Atmosphere: From the Near to Thermal IR

NASA Technical Reports Server (NTRS)

Hansell, R. A., Jr.; Reid, J. S.; Tsay, S. C.; Roush, T. L.; Kalashnikova, O. V.

2011-01-01

To determine a plausible range of mass extinction efficiencies (MEE) of terrestrial atmospheric dust from the near to thermal IR, sensitivity analyses are performed over an extended range of dust microphysical and chemistry perturbations. The IR values are subsequently compared to those in the near-IR, to evaluate spectral relationships in their optical properties. Synthesized size distributions consistent with measurements, model particle size, while composition is defined by the refractive indices of minerals routinely observed in dust, including the widely used OPAC/Hess parameterization. Single-scattering properties of representative dust particle shapes are calculated using the T-matrix, Discrete Dipole Approximation and Lorenz-Mie light-scattering codes. For the parameterizations examined, MEE ranges from nearly zero to 1.2 square meters per gram, with the higher values associated with non-spheres composed of quartz and gypsum. At near-IR wavelengths, MEE for non-spheres generally exceeds those for spheres, while in the thermal IR, shape-induced changes in MEE strongly depend on volume median diameter (VMD) and wavelength, particularly for MEE evaluated at the mineral resonant frequencies. MEE spectral distributions appear to follow particle geometry and are evidence for shape dependency in the optical properties. It is also shown that non-spheres best reproduce the positions of prominent absorption peaks found in silicates. Generally, angular particles exhibit wider and more symmetric MEE spectral distribution patterns from 8-10 micrometers than those with smooth surfaces, likely due to their edge-effects. Lastly, MEE ratios allow for inferring dust optical properties across the visible-IR spectrum. We conclude the MEE of dust aerosol are significant for the parameter space investigated, and are a key component for remote sensing applications and the study of direct aerosol radiative effects.

Embedding Secure Coding Instruction into the IDE: Complementing Early and Intermediate CS Courses with ESIDE

ERIC Educational Resources Information Center

Whitney, Michael; Lipford, Heather Richter; Chu, Bill; Thomas, Tyler

2018-01-01

Many of the software security vulnerabilities that people face today can be remediated through secure coding practices. A critical step toward the practice of secure coding is ensuring that our computing students are educated on these practices. We argue that secure coding education needs to be included across a computing curriculum. We are…

Calculation of water drop trajectories to and about arbitrary three-dimensional lifting and nonlifting bodies in potential airflow

NASA Technical Reports Server (NTRS)

Norment, H. G.

1985-01-01

Subsonic, external flow about nonlifting bodies, lifting bodies or combinations of lifting and nonlifting bodies is calculated by a modified version of the Hess lifting code. Trajectory calculations can be performed for any atmospheric conditions and for all water drop sizes, from the smallest cloud droplet to large raindrops. Experimental water drop drag relations are used in the water drop equations of motion and effects of gravity settling are included. Inlet flow can be accommodated, and high Mach number compressibility effects are corrected for approximately. Seven codes are described: (1) a code used to debug and plot body surface description data; (2) a code that processes the body surface data to yield the potential flow field; (3) a code that computes flow velocities at arrays of points in space; (4) a code that computes water drop trajectories from an array of points in space; (5) a code that computes water drop trajectories and fluxes to arbitrary target points; (6) a code that computes water drop trajectories tangent to the body; and (7) a code that produces stereo pair plots which include both the body and trajectories. Accuracy of the calculations is discussed, and trajectory calculation results are compared with prior calculations and with experimental data.

Debugging Techniques Used by Experienced Programmers to Debug Their Own Code.

DTIC Science & Technology

1990-09-01

IS. NUMBER OF PAGES code debugging 62 computer programmers 16. PRICE CODE debug programming 17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 119...Davis, and Schultz (1987) also compared experts and novices, but focused on the way a computer program is represented cognitively and how that...of theories in the emerging computer programming domain (Fisher, 1987). In protocol analysis, subjects are asked to talk/think aloud as they solve

A COTS-Based Replacement Strategy for Aging Avionics Computers

DTIC Science & Technology

2001-12-01

Communication Control Unit. A COTS-Based Replacement Strategy for Aging Avionics Computers COTS Microprocessor Real Time Operating System New Native Code...Native Code Objec ts Native Code Thread Real - Time Operating System Legacy Function x Virtual Component Environment Context Switch Thunk Add-in Replace

Interpreting the evolution of galaxy colours from z = 8 to 5

NASA Astrophysics Data System (ADS)

Mancini, Mattia; Schneider, Raffaella; Graziani, Luca; Valiante, Rosa; Dayal, Pratika; Maio, Umberto; Ciardi, Benedetta

2016-11-01

We attempt to interpret existing data on the evolution of the UV luminosity function and UV colours, β, of galaxies at 5 ≤ z ≤ 8, to improve our understanding of their dust content and interstellar medium properties. To this aim, we post-process the results of a cosmological hydrodynamical simulation with a chemical evolution model, which includes dust formation by supernovae and intermediate-mass stars, dust destruction in supernova shocks, and grain growth by accretion of gas-phase elements in dense gas. We find that observations require a steep, Small Magellanic Cloud-like extinction curve and a clumpy dust distribution, where stellar populations younger than 15 Myr are still embedded in their dusty natal clouds. Investigating the scatter in the colour distribution and stellar mass, we find that the observed trends can be explained by the presence of two populations: younger, less massive galaxies where dust enrichment is mainly due to stellar sources, and massive, more chemically evolved ones, where efficient grain growth provides the dominant contribution to the total dust mass. Computing the IR-excess-UV colour relation, we find that all but the dustiest model galaxies follow a relation shallower than the Meurer et al. one, usually adopted to correct the observed UV luminosities of high-z galaxies for the effects of dust extinction. As a result, their total star formation rates might have been overestimated. Our study illustrates the importance to incorporate a proper treatment of dust in simulations of high-z galaxies, and that massive, dusty, UV-faint galaxies might have already appeared at z ≲ 7.

PARAVT: Parallel Voronoi tessellation code

NASA Astrophysics Data System (ADS)

González, R. E.

2016-10-01

In this study, we present a new open source code for massive parallel computation of Voronoi tessellations (VT hereafter) in large data sets. The code is focused for astrophysical purposes where VT densities and neighbors are widely used. There are several serial Voronoi tessellation codes, however no open source and parallel implementations are available to handle the large number of particles/galaxies in current N-body simulations and sky surveys. Parallelization is implemented under MPI and VT using Qhull library. Domain decomposition takes into account consistent boundary computation between tasks, and includes periodic conditions. In addition, the code computes neighbors list, Voronoi density, Voronoi cell volume, density gradient for each particle, and densities on a regular grid. Code implementation and user guide are publicly available at https://github.com/regonzar/paravt.

The STAGS computer code

NASA Technical Reports Server (NTRS)

Almroth, B. O.; Brogan, F. A.

1978-01-01

Basic information about the computer code STAGS (Structural Analysis of General Shells) is presented to describe to potential users the scope of the code and the solution procedures that are incorporated. Primarily, STAGS is intended for analysis of shell structures, although it has been extended to more complex shell configurations through the inclusion of springs and beam elements. The formulation is based on a variational approach in combination with local two dimensional power series representations of the displacement components. The computer code includes options for analysis of linear or nonlinear static stress, stability, vibrations, and transient response. Material as well as geometric nonlinearities are included. A few examples of applications of the code are presented for further illustration of its scope.

Holonomic surface codes for fault-tolerant quantum computation

NASA Astrophysics Data System (ADS)

Zhang, Jiang; Devitt, Simon J.; You, J. Q.; Nori, Franco

2018-02-01

Surface codes can protect quantum information stored in qubits from local errors as long as the per-operation error rate is below a certain threshold. Here we propose holonomic surface codes by harnessing the quantum holonomy of the system. In our scheme, the holonomic gates are built via auxiliary qubits rather than the auxiliary levels in multilevel systems used in conventional holonomic quantum computation. The key advantage of our approach is that the auxiliary qubits are in their ground state before and after each gate operation, so they are not involved in the operation cycles of surface codes. This provides an advantageous way to implement surface codes for fault-tolerant quantum computation.

Comparison of two- and three-dimensional flow computations with laser anemometer measurements in a transonic compressor rotor

NASA Technical Reports Server (NTRS)

Chima, R. V.; Strazisar, A. J.

1982-01-01

Two and three dimensional inviscid solutions for the flow in a transonic axial compressor rotor at design speed are compared with probe and laser anemometers measurements at near-stall and maximum-flow operating points. Experimental details of the laser anemometer system and computational details of the two dimensional axisymmetric code and three dimensional Euler code are described. Comparisons are made between relative Mach number and flow angle contours, shock location, and shock strength. A procedure for using an efficient axisymmetric code to generate downstream pressure input for computationally expensive Euler codes is discussed. A film supplement shows the calculations of the two operating points with the time-marching Euler code.

Development of MCNPX-ESUT computer code for simulation of neutron/gamma pulse height distribution

NASA Astrophysics Data System (ADS)

Abolfazl Hosseini, Seyed; Vosoughi, Naser; Zangian, Mehdi

2015-05-01

In this paper, the development of the MCNPX-ESUT (MCNPX-Energy Engineering of Sharif University of Technology) computer code for simulation of neutron/gamma pulse height distribution is reported. Since liquid organic scintillators like NE-213 are well suited and routinely used for spectrometry in mixed neutron/gamma fields, this type of detectors is selected for simulation in the present study. The proposed algorithm for simulation includes four main steps. The first step is the modeling of the neutron/gamma particle transport and their interactions with the materials in the environment and detector volume. In the second step, the number of scintillation photons due to charged particles such as electrons, alphas, protons and carbon nuclei in the scintillator material is calculated. In the third step, the transport of scintillation photons in the scintillator and lightguide is simulated. Finally, the resolution corresponding to the experiment is considered in the last step of the simulation. Unlike the similar computer codes like SCINFUL, NRESP7 and PHRESP, the developed computer code is applicable to both neutron and gamma sources. Hence, the discrimination of neutron and gamma in the mixed fields may be performed using the MCNPX-ESUT computer code. The main feature of MCNPX-ESUT computer code is that the neutron/gamma pulse height simulation may be performed without needing any sort of post processing. In the present study, the pulse height distributions due to a monoenergetic neutron/gamma source in NE-213 detector using MCNPX-ESUT computer code is simulated. The simulated neutron pulse height distributions are validated through comparing with experimental data (Gohil et al. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 664 (2012) 304-309.) and the results obtained from similar computer codes like SCINFUL, NRESP7 and Geant4. The simulated gamma pulse height distribution for a 137Cs source is also compared with the experimental data.

EAC: A program for the error analysis of STAGS results for plates

NASA Technical Reports Server (NTRS)

Sistla, Rajaram; Thurston, Gaylen A.; Bains, Nancy Jane C.

1989-01-01

A computer code is now available for estimating the error in results from the STAGS finite element code for a shell unit consisting of a rectangular orthotropic plate. This memorandum contains basic information about the computer code EAC (Error Analysis and Correction) and describes the connection between the input data for the STAGS shell units and the input data necessary to run the error analysis code. The STAGS code returns a set of nodal displacements and a discrete set of stress resultants; the EAC code returns a continuous solution for displacements and stress resultants. The continuous solution is defined by a set of generalized coordinates computed in EAC. The theory and the assumptions that determine the continuous solution are also outlined in this memorandum. An example of application of the code is presented and instructions on its usage on the Cyber and the VAX machines have been provided.

CFD Modeling of Free-Piston Stirling Engines

NASA Technical Reports Server (NTRS)

Ibrahim, Mounir B.; Zhang, Zhi-Guo; Tew, Roy C., Jr.; Gedeon, David; Simon, Terrence W.

2001-01-01

NASA Glenn Research Center (GRC) is funding Cleveland State University (CSU) to develop a reliable Computational Fluid Dynamics (CFD) code that can predict engine performance with the goal of significant improvements in accuracy when compared to one-dimensional (1-D) design code predictions. The funding also includes conducting code validation experiments at both the University of Minnesota (UMN) and CSU. In this paper a brief description of the work-in-progress is provided in the two areas (CFD and Experiments). Also, previous test results are compared with computational data obtained using (1) a 2-D CFD code obtained from Dr. Georg Scheuerer and further developed at CSU and (2) a multidimensional commercial code CFD-ACE+. The test data and computational results are for (1) a gas spring and (2) a single piston/cylinder with attached annular heat exchanger. The comparisons among the codes are discussed. The paper also discusses plans for conducting code validation experiments at CSU and UMN.

On the error statistics of Viterbi decoding and the performance of concatenated codes

NASA Technical Reports Server (NTRS)

Miller, R. L.; Deutsch, L. J.; Butman, S. A.

1981-01-01

Computer simulation results are presented on the performance of convolutional codes of constraint lengths 7 and 10 concatenated with the (255, 223) Reed-Solomon code (a proposed NASA standard). These results indicate that as much as 0.8 dB can be gained by concatenating this Reed-Solomon code with a (10, 1/3) convolutional code, instead of the (7, 1/2) code currently used by the DSN. A mathematical model of Viterbi decoder burst-error statistics is developed and is validated through additional computer simulations.

New double-byte error-correcting codes for memory systems

NASA Technical Reports Server (NTRS)

Feng, Gui-Liang; Wu, Xinen; Rao, T. R. N.

1996-01-01

Error-correcting or error-detecting codes have been used in the computer industry to increase reliability, reduce service costs, and maintain data integrity. The single-byte error-correcting and double-byte error-detecting (SbEC-DbED) codes have been successfully used in computer memory subsystems. There are many methods to construct double-byte error-correcting (DBEC) codes. In the present paper we construct a class of double-byte error-correcting codes, which are more efficient than those known to be optimum, and a decoding procedure for our codes is also considered.

Electrical Characteristics of Simulated Tornadoes and Dust Devils

NASA Technical Reports Server (NTRS)

Zimmerman, Michael I.; Farrell, William M.; Barth, E. L.; Lewellen, W. S.; Perlongo, N. J.; Jackson, T. L.

2012-01-01

It is well known that tornadoes and dust devils have the ability to accumulate significant, visible clouds of debris. Collisions between sand-like debris species produce different electric charges on different types of grains, which convect along different trajectories around the vortex. Thus, significant charge separations and electric currents are possible, which as the vortex fluctuates over time are thought to produce ULF radiation signatures that have been measured in the field. These electric and magnetic fields may contain valuable information about tornado structure and genesis, and may be critical in driving electrochemical processes within dust devils on Mars. In the present work, existing large eddy simulations of debris-laden tornadoes performed at West Virginia University are coupled with a new debris-charging and advection code developed at Goddard Space Flight Center to investigate the detailed (meter-resolution) fluid-dynamic origins of electromagnetic fields within terrestrial vortices. First results are presented, including simulations of the electric and magnetic fields that would be observed by a near-surface, instrument-laden probe during a direct encounter with a tornado.

Multiwavelength studies of the gas and dust disc of IRAS 04158+2805

NASA Astrophysics Data System (ADS)

Glauser, A. M.; Ménard, F.; Pinte, C.; Duchêne, G.; Güdel, M.; Monin, J.-L.; Padgett, D. L.

2008-07-01

We present a study of the circumstellar environment of IRAS 04158+2805 based on multi-wavelength observations and models. Images in the optical and near-infrared, a polarisation map in the optical, and mid-infrared spectra were obtained with VLT-FORS1, CFHT-IR, and Spitzer-IRS. Additionally we used an X-ray spectrum observed with Chandra. We interpret the observations in terms of a central star surrounded by an axisymmetric circumstellar disc, but without an envelope, to test the validity of this simple geometry. We estimate the structural properties of the disc and its gas and dust content. We modelled the dust disc with a 3D continuum radiative transfer code, MCFOST, based on a Monte-Carlo method that provides synthetic scattered light images and polarisation maps, as well as spectral energy distributions. We find that the disc images and spectral energy distribution narrowly constrain many of the disc model parameters, such as a total dust mass of 1.0-1.75×10-4 M_⊙ and an inclination of 62°-63°. The maximum grain size required to fit all available data is of the order of 1.6-2.8 μm although the upper end of this range is loosely constrained. The observed optical polarisation map is reproduced well by the same disc model, suggesting that the geometry we find is adequate and the optical properties are representative of the visible dust content. We compare the inferred dust column density to the gas column density derived from the X-ray spectrum and find a gas-to-dust ratio along the line of sight that is consistent with the ISM value. To our knowledge, this measurement is the first to directly compare dust and gas column densities in a protoplanetary disc. Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii. Based also on data collected at ESO/VLT during observation program 68-C.0171.

ALMA continuum observations of the protoplanetary disk AS 209. Evidence of multiple gaps opened by a single planet

NASA Astrophysics Data System (ADS)

Fedele, D.; Tazzari, M.; Booth, R.; Testi, L.; Clarke, C. J.; Pascucci, I.; Kospal, A.; Semenov, D.; Bruderer, S.; Henning, Th.; Teague, R.

2018-02-01

This paper presents new high angular resolution ALMA 1.3 mm dust continuum observations of the protoplanetary system AS 209 in the Ophiuchus star forming region. The dust continuum emission is characterized by a main central core and two prominent rings at r = 75 au and r = 130 au intervaled by two gaps at r = 62 au and r = 103 au. The two gaps have different widths and depths, with the inner one being narrower and shallower. We determined the surface density of the millimeter dust grains using the 3D radiative transfer disk code DALI. According to our fiducial model the inner gap is partially filled with millimeter grains while the outer gap is largely devoid of dust. The inferred surface density is compared to 3D hydrodynamical simulations (FARGO-3D) of planet-disk interaction. The outer dust gap is consistent with the presence of a giant planet (Mplanet 0.7 MSaturn); the planet is responsible for the gap opening and for the pile-up of dust at the outer edge of the planet orbit. The simulations also show that the same planet could be the origin of the inner gap at r = 62 au. The relative position of the two dust gaps is close to the 2:1 resonance and we have investigated the possibility of a second planet inside the inner gap. The resulting surface density (including location, width and depth of the two dust gaps) are in agreement with the observations. The properties of the inner gap pose a strong constraint to the mass of the inner planet (Mplanet < 0.1 MJ). In both scenarios (single or pair of planets), the hydrodynamical simulations suggest a very low disk viscosity (α < 10‑4). Given the young age of the system (0.5-1 Myr), this result implies that the formation of giant planets occurs on a timescale of ≲1 Myr. The reduced image (FITS file) is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/610/A24

SOURCELESS STARTUP. A MACHINE CODE FOR COMPUTING LOW-SOURCE REACTOR STARTUPS

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacMillan, D.B.

1960-06-01

>A revision to the sourceless start-up code is presented. The code solves a system of differential equations encountered in computing the probability distribution of activity at an observed power level during reactor start-up from a very low source level. (J.R.D.)

Computer-assisted coding and clinical documentation: first things first.

PubMed

Tully, Melinda; Carmichael, Angela

2012-10-01

Computer-assisted coding tools have the potential to drive improvements in seven areas: Transparency of coding. Productivity (generally by 20 to 25 percent for inpatient claims). Accuracy (by improving specificity of documentation). Cost containment (by reducing overtime expenses, audit fees, and denials). Compliance. Efficiency. Consistency.

A Mid-Infrared Study of the Circumstellar Dust Composition and Phase Behavior of Oxygen-rich Mira Variables

NASA Astrophysics Data System (ADS)

Guth, Tina

2017-08-01

The elements essential as building blocks of life, such as carbon and oxygen, have long been considered to come from exploding stars, known as supernovae. However, in the last several years, observations obtained with improved telescopes and instruments have shown that these heavier elements, i.e. elements beyond helium, are readily found in mass-loss products of stars called Asymptotic Giant Branch (AGB) stars. The sub-category of AGB stars that have regular pulsation periods of 200 - 500 days, called Mira variables, are of particular interest. These regular pulsators are quite bright in both the optical and infrared wavelengths, and exhibit large changes in magnitude that are easily observable. Studying their circumstellar dust environment allows astronomers to determine the presence of compounds, such as silicates and oxides, which are indicative of common elements found on Earth - oxygen, carbon, and silicon. Mira variables are dynamic stars, which implies that the circumstellar dust composition should change as the star goes through its pulsation cycle. In order to study the dust behavior with pulsational phase, repeated infrared observations were obtained with the Spitzer Space Telescope. This infrared, space-based telescope was launched in 2003 and carries the Infrared Spectrograph (IRS) instrument, which produces brightness versus wavelength, i.e. a spectrum (Houck et al., 2004). Due to the pulsation period of these stars, they were observed approximately monthly during the campaign run in 2008-9. This work focuses on the high-resolution data over a wavelength range of 9.8 - 40 microns because it provides a high signal-to-noise ratio and examines the part of the spectrum where dust features are most apparent. The full dataset obtained with Spitzer consists of 25 stars and covers nearly 100 spectra spanning all three chemical subclasses, however the focus of this dissertation is on investigating the dusty environment of oxygen-rich Mira variables. First, an identical data reduction process was applied to the dataset. To determine the dust composition in the circumstellar environment, the publically available 1-D radiative transfer modeling code, DUSTY (Ivezic et al., 1999), was implemented with key physical parameters, such as stellar temperature, inner dust boundary temperature, and optical depth, kept the same for all stars to help elucidate changes with phase. Because a simple blackbody fit does not adequately characterize the dust composition in the circumstellar environment, the 1-D hydrostatic, spherical local thermodynamic equilibrium (LTE) model grid code called MARCS was used (Gustafsson et al., 2008), which includes the molecular and atomic opacities that are characteristic of AGB spectra. MARCS only extends to a wavelength range of 20 micron, hence a power-law function is combined with the spectral energy distribution (SED) from MARCS to provide a reasonable source function for input in DUSTY. For the oxygen-rich Miras investigated, there are clear indications that the dust composition changes with phase over fairly short time scales, and that there are trends in the required dust species that correlate with the SE (silicate emission) classification (Sloan and Price, 1998) of the star. Iron oxide (FeO) is present in the dust composition of all stars, while aluminum oxide (Al2O3) shifts from being porous to compact for SE1-3 to SE7-8, respectively. The dust species pyroxene is only present in SE7-8 classes to account for a broad emission feature centered at 18 micron. The "13 micron feature", which is a well-known yet unidentified feature in the astronomical community is only present in SE1-4 classes, while completely absent in the other SE classes. In this work, the focus was not on identifying the 13 micron feature, though several constituents can be ruled out. Other dust constituents, such as water ice and sulfides, were considered but the shapes of their opacity curves do not fit with the observed features in the spectra. This study has shown several interesting and potentially unique results, such as changes in the dust continuum with phase over short timescales (i.e. roughly 30 days), the presence of iron oxide in all SE classes, and the appearance of a broad emission feature ranging from 19.5 micron to 25 micron in certain SE classes. Obtaining more phase sampling would help in cementing some of these results, while comparison to the other chemical subclasses in the study can provide insight in potential correlations between the subclasses. More detailed investigation into some of the "unique" features, such as the "13 micron feature", is presently limited due to availability of optical constant tables for other dust species.

Hypercube matrix computation task

NASA Technical Reports Server (NTRS)

Calalo, R.; Imbriale, W.; Liewer, P.; Lyons, J.; Manshadi, F.; Patterson, J.

1987-01-01

The Hypercube Matrix Computation (Year 1986-1987) task investigated the applicability of a parallel computing architecture to the solution of large scale electromagnetic scattering problems. Two existing electromagnetic scattering codes were selected for conversion to the Mark III Hypercube concurrent computing environment. They were selected so that the underlying numerical algorithms utilized would be different thereby providing a more thorough evaluation of the appropriateness of the parallel environment for these types of problems. The first code was a frequency domain method of moments solution, NEC-2, developed at Lawrence Livermore National Laboratory. The second code was a time domain finite difference solution of Maxwell's equations to solve for the scattered fields. Once the codes were implemented on the hypercube and verified to obtain correct solutions by comparing the results with those from sequential runs, several measures were used to evaluate the performance of the two codes. First, a comparison was provided of the problem size possible on the hypercube with 128 megabytes of memory for a 32-node configuration with that available in a typical sequential user environment of 4 to 8 megabytes. Then, the performance of the codes was anlyzed for the computational speedup attained by the parallel architecture.

Bistatic radar cross section of a perfectly conducting rhombus-shaped flat plate

NASA Astrophysics Data System (ADS)

Fenn, Alan J.

1990-05-01

The bistatic radar cross section of a perfectly conducting flat plate that has a rhombus shape (equilateral parallelogram) is investigated. The Ohio State University electromagnetic surface patch code (ESP version 4) is used to compute the theoretical bistatic radar cross section of a 35- x 27-in rhombus plate at 1.3 GHz over the bistatic angles 15 deg to 142 deg. The ESP-4 computer code is a method of moments FORTRAN-77 program which can analyze general configurations of plates and wires. This code has been installed and modified at Lincoln Laboratory on a SUN 3 computer network. Details of the code modifications are described. Comparisons of the method of moments simulations and measurements of the rhombus plate are made. It is shown that the ESP-4 computer code provides a high degree of accuracy in the calculation of copolarized and cross-polarized bistatic radar cross section patterns.

ASR4: A computer code for fitting and processing 4-gage anelastic strain recovery data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warpinski, N.R.

A computer code for analyzing four-gage Anelastic Strain Recovery (ASR) data has been modified for use on a personal computer. This code fits the viscoelastic model of Warpinski and Teufel to measured ASR data, calculates the stress orientation directly, and computes stress magnitudes if sufficient input data are available. The code also calculates the stress orientation using strain-rosette equations, and its calculates stress magnitudes using Blanton's approach, assuming sufficient input data are available. The program is written in FORTRAN, compiled with Ryan-McFarland Version 2.4. Graphics use PLOT88 software by Plotworks, Inc., but the graphics software must be obtained by themore » user because of licensing restrictions. A version without graphics can also be run. This code is available through the National Energy Software Center (NESC), operated by Argonne National Laboratory. 5 refs., 3 figs.« less

Navier-Stokes Simulation of Homogeneous Turbulence on the CYBER 205

NASA Technical Reports Server (NTRS)

Wu, C. T.; Ferziger, J. H.; Chapman, D. R.; Rogallo, R. S.

1984-01-01

A computer code which solves the Navier-Stokes equations for three dimensional, time-dependent, homogenous turbulence has been written for the CYBER 205. The code has options for both 64-bit and 32-bit arithmetic. With 32-bit computation, mesh sizes up to 64 (3) are contained within core of a 2 million 64-bit word memory. Computer speed timing runs were made for various vector lengths up to 6144. With this code, speeds a little over 100 Mflops have been achieved on a 2-pipe CYBER 205. Several problems encountered in the coding are discussed.

Acute eosinophilic pneumonia in a New York City firefighter exposed to World Trade Center dust.

PubMed

Rom, William N; Weiden, Michael; Garcia, Roberto; Yie, Ting An; Vathesatogkit, Pratan; Tse, Doris B; McGuinness, Georgeann; Roggli, Victor; Prezant, David

2002-09-15

We report a sentinel case of acute eosinophilic pneumonia in a firefighter exposed to high concentrations of World Trade Center dust during the rescue effort from September 11 to 24. The firefighter presented with a Pa(O2) of 53 mm Hg and responded to oxygen and corticosteroids. Computed tomography scan showed patchy ground glass density, thickened bronchial walls, and bilateral pleural effusions. Bronchoalveolar lavage recovered 70% eosinophils, with only 1% eosinophils in peripheral blood. Eosinophils were not degranulated and increased levels of interleukin-5 were measured in bronchoalveolar lavage and serum. Mineralogic analysis counted 305 commercial asbestos fibers/10(6) macrophages including those with high aspect ratios, and significant quantities of fly ash and degraded fibrous glass. Acute eosinophilic pneumonia is a rare consequence of acute high dust exposure. World Trade Center dust consists of large particle-size silicates, but fly ash and asbestos fibers may be found in bronchoalveolar lavage cells.

NASA Tech Briefs, March 2009

NASA Technical Reports Server (NTRS)

2009-01-01

Topics covered include: Improved Instrument for Detecting Water and Ice in Soil; Real-Time Detection of Dust Devils from Pressure Readings; Determining Surface Roughness in Urban Areas Using Lidar Data; DSN Data Visualization Suite; Hamming and Accumulator Codes Concatenated with MPSK or QAM; Wide-Angle-Scanning Reflectarray Antennas Actuated by MEMS; Biasable Subharmonic Membrane Mixer for 520 to 600 GHz; Hardware Implementation of Serially Concatenated PPM Decoder; Symbolic Processing Combined with Model-Based Reasoning; Presentation Extensions of the SOAP; Spreadsheets for Analyzing and Optimizing Space Missions; Processing Ocean Images to Detect Large Drift Nets; Alternative Packaging for Back-Illuminated Imagers; Diamond Machining of an Off-Axis Biconic Aspherical Mirror; Laser Ablation Increases PEM/Catalyst Interfacial Area; Damage Detection and Self-Repair in Inflatable/Deployable Structures; Polyimide/Glass Composite High-Temperature Insulation; Nanocomposite Strain Gauges Having Small TCRs; Quick-Connect Windowed Non-Stick Penetrator Tips for Rapid Sampling; Modeling Unsteady Cavitation and Dynamic Loads in Turbopumps; Continuous-Flow System Produces Medical-Grade Water; Discrimination of Spore-Forming Bacilli Using spoIVA; nBn Infrared Detector Containing Graded Absorption Layer; Atomic References for Measuring Small Accelerations; Ultra-Broad-Band Optical Parametric Amplifier or Oscillator; Particle-Image Velocimeter Having Large Depth of Field; Enhancing SERS by Means of Supramolecular Charge Transfer; Improving 3D Wavelet-Based Compression of Hyperspectral Images; Improved Signal Chains for Readout of CMOS Imagers; SOI CMOS Imager with Suppression of Cross-Talk; Error-Rate Bounds for Coded PPM on a Poisson Channel; Biomorphic Multi-Agent Architecture for Persistent Computing; and Using Covariance Analysis to Assess Pointing Performance.

Simulation of Aerosols and Chemistry with a Unified Global Model

NASA Technical Reports Server (NTRS)

Chin, Mian

2004-01-01

This project is to continue the development of the global simulation capabilities of tropospheric and stratospheric chemistry and aerosols in a unified global model. This is a part of our overall investigation of aerosol-chemistry-climate interaction. In the past year, we have enabled the tropospheric chemistry simulations based on the GEOS-CHEM model, and added stratospheric chemical reactions into the GEOS-CHEM such that a globally unified troposphere-stratosphere chemistry and transport can be simulated consistently without any simplifications. The tropospheric chemical mechanism in the GEOS-CHEM includes 80 species and 150 reactions. 24 tracers are transported, including O3, NOx, total nitrogen (NOy), H2O2, CO, and several types of hydrocarbon. The chemical solver used in the GEOS-CHEM model is a highly accurate sparse-matrix vectorized Gear solver (SMVGEAR). The stratospheric chemical mechanism includes an additional approximately 100 reactions and photolysis processes. Because of the large number of total chemical reactions and photolysis processes and very different photochemical regimes involved in the unified simulation, the model demands significant computer resources that are currently not practical. Therefore, several improvements will be taken, such as massive parallelization, code optimization, or selecting a faster solver. We have also continued aerosol simulation (including sulfate, dust, black carbon, organic carbon, and sea-salt) in the global model to cover most of year 2002. These results have been made available to many groups worldwide and accessible from the website http://code916.gsfc.nasa.gov/People/Chin/aot.html.

The investigation of tethered satellite system dynamics

NASA Technical Reports Server (NTRS)

Lorenzini, E.

1985-01-01

The tether control law to retrieve the satellite was modified in order to have a smooth retrieval trajectory of the satellite that minimizes the thruster activation. The satellite thrusters were added to the rotational dynamics computer code and a preliminary control logic was implemented to simulate them during the retrieval maneuver. The high resolution computer code for modelling the three dimensional dynamics of untensioned tether, SLACK3, was made fully operative and a set of computer simulations of possible tether breakages was run. The distribution of the electric field around an electrodynamic tether in vacuo severed at some length from the shuttle was computed with a three dimensional electrodynamic computer code.

Experimental and computational surface and flow-field results for an all-body hypersonic aircraft

NASA Technical Reports Server (NTRS)

Lockman, William K.; Lawrence, Scott L.; Cleary, Joseph W.

1990-01-01

The objective of the present investigation is to establish a benchmark experimental data base for a generic hypersonic vehicle shape for validation and/or calibration of advanced computational fluid dynamics computer codes. This paper includes results from the comprehensive test program conducted in the NASA/Ames 3.5-foot Hypersonic Wind Tunnel for a generic all-body hypersonic aircraft model. Experimental and computational results on flow visualization, surface pressures, surface convective heat transfer, and pitot-pressure flow-field surveys are presented. Comparisons of the experimental results with computational results from an upwind parabolized Navier-Stokes code developed at Ames demonstrate the capabilities of this code.

Emission from small dust particles in diffuse and molecular cloud medium

NASA Technical Reports Server (NTRS)

Bernard, J. P.; Desert, X.

1990-01-01

Infrared Astronomy Satellite (IRAS) observations of the whole galaxy has shown that long wavelength emission (100 and 60 micron bands) can be explained by thermal emission from big grains (approx 0.1 micron) radiating at their equilibrium temperature when heated by the InterStellar Radiation Field (ISRF). This conclusion has been confirmed by continuum sub-millimeter observations of the galactic plane made by the EMILIE experiment at 870 microns (Pajot et al. 1986). Nevertheless, shorter wavelength observations like 12 and 25 micron IRAS bands, show an emission from the galactic plane in excess with the long wavelength measurements which can only be explained by a much hotter particles population. Because dust at equilibrium cannot easily reach high temperatures required to explain this excess, this component is thought to be composed of very small dust grains or big molecules encompassing thermal fluctuations. Researchers present here a numerical model that computes emission, from Near Infrared Radiation (NIR) to Sub-mm wavelengths, from a non-homogeneous spherical cloud heated by the ISRF. This model fully takes into account the heating of dust by multi-photon processes and back-heating of dust in the Visual/Infrared Radiation (VIS-IR) so that it is likely to describe correctly emission from molecular clouds up to large A sub v and emission from dust experiencing temperature fluctuations. The dust is a three component mixture of polycyclic aromatic hydrocarbons, very small grains, and classical big grains with independent size distributions (cut-off and power law index) and abundances.

Computer search for binary cyclic UEP codes of odd length up to 65

NASA Technical Reports Server (NTRS)

Lin, Mao-Chao; Lin, Chi-Chang; Lin, Shu

1990-01-01

Using an exhaustive computation, the unequal error protection capabilities of all binary cyclic codes of odd length up to 65 that have minimum distances at least 3 are found. For those codes that can only have upper bounds on their unequal error protection capabilities computed, an analytic method developed by Dynkin and Togonidze (1976) is used to show that the upper bounds meet the exact unequal error protection capabilities.

A Combinatorial Geometry Computer Description of the MEP-021A Generator Set

DTIC Science & Technology

1979-02-01

Generator Computer Description Gasoline Generator GIFT MEP-021A 20. ABSTRACT fCbntteu* an rararaa eta* ft namamwaay anal Identify by block number) This... GIFT code is also stored on magnetic tape for future vulnerability analysis. 00,] 󈧚*7,1473 EDITION OF • NOV 65 IS OBSOLETE UNCLASSIFIED SECURITY...the Geometric Information for Targets ( GIFT ) computer code. The GIFT code traces shotlines through a COM-GEOM description from any specified attack

Optimizing a liquid propellant rocket engine with an automated combustor design code (AUTOCOM)

NASA Technical Reports Server (NTRS)

Hague, D. S.; Reichel, R. H.; Jones, R. T.; Glatt, C. R.

1972-01-01

A procedure for automatically designing a liquid propellant rocket engine combustion chamber in an optimal fashion is outlined. The procedure is contained in a digital computer code, AUTOCOM. The code is applied to an existing engine, and design modifications are generated which provide a substantial potential payload improvement over the existing design. Computer time requirements for this payload improvement were small, approximately four minutes in the CDC 6600 computer.

Unaligned instruction relocation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bertolli, Carlo; O'Brien, John K.; Sallenave, Olivier H.

In one embodiment, a computer-implemented method includes receiving source code to be compiled into an executable file for an unaligned instruction set architecture (ISA). Aligned assembled code is generated, by a computer processor. The aligned assembled code complies with an aligned ISA and includes aligned processor code for a processor and aligned accelerator code for an accelerator. A first linking pass is performed on the aligned assembled code, including relocating a first relocation target in the aligned accelerator code that refers to a first object outside the aligned accelerator code. Unaligned assembled code is generated in accordance with the unalignedmore » ISA and includes unaligned accelerator code for the accelerator and unaligned processor code for the processor. A second linking pass is performed on the unaligned assembled code, including relocating a second relocation target outside the unaligned accelerator code that refers to an object in the unaligned accelerator code.« less

Unaligned instruction relocation

DOEpatents

Bertolli, Carlo; O'Brien, John K.; Sallenave, Olivier H.; Sura, Zehra N.

2018-01-23

In one embodiment, a computer-implemented method includes receiving source code to be compiled into an executable file for an unaligned instruction set architecture (ISA). Aligned assembled code is generated, by a computer processor. The aligned assembled code complies with an aligned ISA and includes aligned processor code for a processor and aligned accelerator code for an accelerator. A first linking pass is performed on the aligned assembled code, including relocating a first relocation target in the aligned accelerator code that refers to a first object outside the aligned accelerator code. Unaligned assembled code is generated in accordance with the unaligned ISA and includes unaligned accelerator code for the accelerator and unaligned processor code for the processor. A second linking pass is performed on the unaligned assembled code, including relocating a second relocation target outside the unaligned accelerator code that refers to an object in the unaligned accelerator code.

Computer algorithm for coding gain

NASA Technical Reports Server (NTRS)

Dodd, E. E.

1974-01-01

Development of a computer algorithm for coding gain for use in an automated communications link design system. Using an empirical formula which defines coding gain as used in space communications engineering, an algorithm is constructed on the basis of available performance data for nonsystematic convolutional encoding with soft-decision (eight-level) Viterbi decoding.

A new zenith-looking narrow-band radiometer-based system (ZEN) for dust aerosol optical depth monitoring

NASA Astrophysics Data System (ADS)

Almansa, A. Fernando; Cuevas, Emilio; Torres, Benjamín; Barreto, África; García, Rosa D.; Cachorro, Victoria E.; de Frutos, Ángel M.; López, César; Ramos, Ramón

2017-02-01

A new zenith-looking narrow-band radiometer based system (ZEN), conceived for dust aerosol optical depth (AOD) monitoring, is presented in this paper. The ZEN system comprises a new radiometer (ZEN-R41) and a methodology for AOD retrieval (ZEN-LUT). ZEN-R41 has been designed to be stand alone and without moving parts, making it a low-cost and robust instrument with low maintenance, appropriate for deployment in remote and unpopulated desert areas. The ZEN-LUT method is based on the comparison of the measured zenith sky radiance (ZSR) with a look-up table (LUT) of computed ZSRs. The LUT is generated with the LibRadtran radiative transfer code. The sensitivity study proved that the ZEN-LUT method is appropriate for inferring AOD from ZSR measurements with an AOD standard uncertainty up to 0.06 for AOD500 nm ˜ 0.5 and up to 0.15 for AOD500 nm ˜ 1.0, considering instrumental errors of 5 %. The validation of the ZEN-LUT technique was performed using data from AErosol RObotic NETwork (AERONET) Cimel Electronique 318 photometers (CE318). A comparison between AOD obtained by applying the ZEN-LUT method on ZSRs (inferred from CE318 diffuse-sky measurements) and AOD provided by AERONET (derived from CE318 direct-sun measurements) was carried out at three sites characterized by a regular presence of desert mineral dust aerosols: Izaña and Santa Cruz in the Canary Islands and Tamanrasset in Algeria. The results show a coefficient of determination (R2) ranging from 0.99 to 0.97, and root mean square errors (RMSE) ranging from 0.010 at Izaña to 0.032 at Tamanrasset. The comparison of ZSR values from ZEN-R41 and the CE318 showed absolute relative mean bias (RMB) < 10 %. ZEN-R41 AOD values inferred from ZEN-LUT methodology were compared with AOD provided by AERONET, showing a fairly good agreement in all wavelengths, with mean absolute AOD differences < 0.030 and R2 higher than 0.97.

Improving Estimated Optical Constants With MSTM and DDSCAT Modeling

NASA Astrophysics Data System (ADS)

Pitman, K. M.; Wolff, M. J.

2015-12-01

We present numerical experiments to determine quantitatively the effects of mineral particle clustering on Mars spacecraft spectral signatures and to improve upon the values of refractive indices (optical constants n, k) derived from Mars dust laboratory analog spectra such as those from RELAB and MRO CRISM libraries. Whereas spectral properties for Mars analog minerals and actual Mars soil are dominated by aggregates of particles smaller than the size of martian atmospheric dust, the analytic radiative transfer (RT) solutions used to interpret planetary surfaces assume that individual, well-separated particles dominate the spectral signature. Both in RT models and in the refractive index derivation methods that include analytic RT approximations, spheres are also over-used to represent nonspherical particles. Part of the motivation is that the integrated effect over randomly oriented particles on quantities such as single scattering albedo and phase function are relatively less than for single particles. However, we have seen in previous numerical experiments that when varying the shape and size of individual grains within a cluster, the phase function changes in both magnitude and slope, thus the "relatively less" effect is more significant than one might think. Here we examine the wavelength dependence of the forward scattering parameter with multisphere T-matrix (MSTM) and discrete dipole approximation (DDSCAT) codes that compute light scattering by layers of particles on planetary surfaces to see how albedo is affected and integrate our model results into refractive index calculations to remove uncertainties in approximations and parameters that can lower the accuracy of optical constants. By correcting the single scattering albedo and phase function terms in the refractive index determinations, our data will help to improve the understanding of Mars in identifying, mapping the distributions, and quantifying abundances for these minerals and will address long-standing questions on fundamental physics in the martian surface (e.g., what is the fundamental scattering unit for closely packed dust or regolith grains?). This work was supported by NASA's Mars Fundamental Research Program and performed with the Pleiades cluster courtesy of NASA's Advanced Supercomputing Division.

Solar Array Panels With Dust-Removal Capability

NASA Technical Reports Server (NTRS)

Dawson, Stephen; Mardesich, Nick; Spence, Brian; White, Steve

2004-01-01

It has been proposed to incorporate piezoelectric vibrational actuators into the structural supports of solar photovoltaic panels, for the purpose of occasionally inducing vibrations in the panels in order to loosen accumulated dust. Provided that the panels were tilted, the loosened dust would slide off under its own weight. Originally aimed at preventing obscuration of photovoltaic cells by dust accumulating in the Martian environment, the proposal may also offer an option for the design of solar photovoltaic panels for unattended operation at remote locations on Earth. The figure depicts a typical lightweight solar photovoltaic panel comprising a backside grid of structural spars that support a thin face sheet that, in turn, supports an array of photovoltaic cells on the front side. The backside structure includes node points where several spars intersect. According to the proposal, piezoelectric buzzers would be attached to the node points. The process of designing the panel would be an iterative one that would include computational simulation of the vibrations by use of finite- element analysis to guide the selection of the vibrational frequency of the actuators and the cross sections of the spars to maximize the agitation of dust.

Features of tropospheric and stratospheric dust.

PubMed

Elterman, L; Wexler, R; Chang, D T

1969-05-01

A series of 119 profiles obtained over New Mexico comprise aerosol attenuation coefficients vs altitude to about 35 km. These profiles show the existence of several features. A surface convective dust layer extending up to about 5 km is seasonally dependent. Also, a turbidity maximum exists below the tropopause. The altitude of an aerosol maximum in the lower stratosphere is located just below that of the minimum temperature. The colder the minimum temperature, the greater is the aerosol content of the layer. This relationship suggests that the 20-km dust layer is due to convection in tropical air and advection to higher latitudes. Computed averages of optical thickness show that abatement of stratospheric dust from the Mt. Agung eruption became evident in April 1964. Results based on seventy-nine profiles characterizing volcanic dust abatement indicate that above 26 km, the aerosol scale height averages 3.75 km. Extrapolating with this scale height, tabulations are developed for uv, visible, and ir attenuation to 50 km. Optical mixing ratios are used to examine the aerosol concentrations at various altitudes, including a layer at 26 km having an optical thickness 10(-3) for 0.55-micro wavelength.

H2O grain size and the amount of dust in Mars' residual north polar cap

NASA Technical Reports Server (NTRS)

Kieffer, Hugh H.

1990-01-01

In Mars' north polar cap, the probable composition of material residual from the annual condensation cycle is a mixture of fine dust and H2O grains of comparable size and abundance. However, metamorphism of such material will gradually lower its albedo by increasing the size of the H2O grains only. If the cap is undergoing net annual sublimation (as inferred from water vapor observations), late summer observations should be of old ice with H2O grain sizes of 100 microns or more. Ice of this granularity containing 30 percent fine dust has a reflectivity similar to that of dust alone; the observed albedo and computed ice grain size imply dust concentrations of 1 part per 1000 or less. The brightness of the icy areas conflicts with what would be expected for a residual cap deposited by an annual cycle similar to that observed by Viking and aged for thousands of years. The residual cap surface cannot be 'old dirty' ice. It could be old, coarse, and clean; or it could be young, fine, and dirty. This brings into question both the source of the late summer water vapor and the formation rate of laminated terrain.

Simulation of the Processes of Formation of a Dust Cloud in a Vacuum and in the Absence of Gravitation

NASA Astrophysics Data System (ADS)

Avdeev, A. V.; Boreisho, A. S.; Ivakin, S. V.; Moiseev, A. A.; Savin, A. V.; Sokolov, E. I.; Smirnov, P. G.

2018-01-01

This article is devoted to the simulation of the processes of formation of dust clouds in the absence of gravitation, which is necessary for understanding the processes proceeding in dust clusters in outer space, upper planetary atmosphere, and on the surface of space objects, as well as for evaluating the possibilities of creating disperse structures with given properties. The chief aim of the simulation is to determine the general laws of the dynamics of the dust cloud at the initial stage of its formation. With the use of the original approach based on the particle-in-cell method that permits investigating the mechanics of large ensembles of particles on contemporary computational platforms, we consider the mechanics of a dusty medium in the process of its excitation in a closed container due to the vibration of the walls, and then in the process of particle scattering when the container opens in outer space. The main formation mechanisms of a dust formation have been elucidated, and the possibilities of mathematical simulation for predicting spatial and time characteristics of disperse structures have been shown.

H2O grain size and the amount of dust in Mars' residual North polar cap

USGS Publications Warehouse

Kieffer, H.H.

1990-01-01

In Mars' north polar cap the probable composition of material residual from the annual condensation cycle is a mixture of fine dust and H2O grains of comparable size and abundance. However, metamorphism of such material will gradually lower its albedo by increasing the size of the H2O grains only. If the cap is undergoing net annual sublimation (as inferred from water vapor observations), late summer observations should be of old ice with H2O grain sizes of 100 ??m or more. Ice of this granularity containing 30% fine dust has a reflectivity similar to that of dust alone; the observed albedo and computed ice grain size imply dust concentrations of 1 part per 1000 or less. The brightness of the icy areas conflicts with what would be expected for a residual cap deposited by an annual cycle similar to that observed by Viking and aged for thousands of years. The residual cap surface cannot be "old dirty' ice. It could be old, coarse, and clean; or it could be young, fine, and dirty. This brings into question both the source of the late summer water vapor and the formation rate of laminated terrain. -Author

Radiative Transfer Modeling in Proto-planetary Disks

NASA Astrophysics Data System (ADS)

Kasper, David; Jang-Condell, Hannah; Kloster, Dylan

2016-01-01

Young Stellar Objects (YSOs) are rich astronomical research environments. Planets form in circumstellar disks of gas and dust around YSOs. With ever increasing capabilities of the observational instruments designed to look at these proto-planetary disks, most notably GPI, SPHERE, and ALMA, more accurate interfaces must be made to connect modeling of the disks with observation. PaRTY (Parallel Radiative Transfer in YSOs) is a code developed previously to model the observable density and temperature structure of such a disk by self-consistently calculating the structure of the disk based on radiative transfer physics. We present upgrades we are implementing to the PaRTY code to improve its accuracy and flexibility. These upgrades include: creating a two-sided disk model, implementing a spherical coordinate system, and implementing wavelength-dependent opacities. These upgrades will address problems in the PaRTY code of infinite optical thickness, calculation under/over-resolution, and wavelength-independent photon penetration depths, respectively. The upgraded code will be used to better model disk perturbations resulting from planet formation.

Studies of Planet Formation Using a Hybrid N-Body + Planetesimal Code

NASA Technical Reports Server (NTRS)

Kenyon, Scott J.

2004-01-01

The goal of our proposal was to use a hybrid multi-annulus planetesimal/n-body code to examine the planetesimal theory, one of the two main theories of planet formation. We developed this code to follow the evolution of numerous 1 m to 1 km planetesimals as they collide, merge, and grow into full-fledged planets. Our goal was to apply the code to several well-posed, topical problems in planet formation and to derive observational consequences of the models. We planned to construct detailed models to address two fundamental issues: (1) icy planets: models for icy planet formation will demonstrate how the physical properties of debris disks - including the Kuiper Belt in our solar system - depend on initial conditions and input physics; and (2) terrestrial planets: calculations following the evolution of 1-10 km planetesimals into Earth-mass planets and rings of dust will provide a better understanding of how terrestrial planets form and interact with their environment.

Inner disk clearing around the Herbig Ae star HD 139614: Evidence for a planet-induced gap?

NASA Astrophysics Data System (ADS)

Matter, A.; Labadie, L.; Augereau, J. C.; Kluska, J.; Crida, A.; Carmona, A.; Gonzalez, J. F.; Thi, W. F.; Le Bouquin, J.-B.; Olofsson, J.; Lopez, B.

2016-02-01

Spatially resolving the inner dust cavity (or gap) of the so-called (pre-)transitional disks is a key to understanding the connection between the processes of planetary formation and disk dispersal. The disk around the Herbig star HD 139614 is of particular interest since it presents a pretransitional nature with an au-sized gap structure that is spatially resolved by mid-infrared interferometry in the dust distribution. With the aid of new near-infrared interferometric observations, we aim to characterize the 0.1-10 au region of the HD 139614 disk further and then identify viable mechanisms for the inner disk clearing. We report the first multiwavelength modeling of the interferometric data acquired on HD 139614 with the VLTI instruments PIONIER, AMBER, and MIDI, complemented by Herschel/PACS photometric measurements. We first performed a geometrical modeling of the new near-infrared interferometric data, followed by radiative transfer modeling of the complete dataset using the code RADMC3D. We confirm the presence of a gap structure in the warm μm-sized dust distribution, extending from about 2.5 au to 6 au, and constrained the properties of the inner dust component: e.g., a radially increasing dust surface density profile, and a depletion in dust of ~103 relative to the outer disk. Since self-shadowing and photoevaporation appears unlikely to be responsible for the au-sized gap of HD 139614, we thus tested if dynamical clearing could be a viable mechanism using hydrodynamical simulations to predict the structure of the gaseous disk. Indeed, a narrow au-sized gap is consistent with the expected effect of the interaction between a single giant planet and the disk. Assuming that small dust grains are well coupled to the gas, we found that an approximately 3 Mjup planet located at ~4.5 au from the star could, in less than 1 Myr, reproduce most of the aspects of the dust surface density profile, while no significant depletion (in gas) occurred in the inner disk, in contrast to the dust. However, this "dust-depleted" inner disk could be explained by the expected dust filtration by the gap and the efficient dust growth/fragmentation occurring in the inner disk regions. Our results support the hypothesis of a giant planet opening a gap and shaping the inner region of the HD 139614 disk. This makes HD 139614 an exciting candidate specifically for witnessing planet-disk interaction. Based on observations collected at the European Southern Observatory, Chile (ESO IDs : 385.C-0886, 087.C-0811, 089.C-0456, and 190.C-0963).

GOODS-Herschel: dust attenuation properties of UV selected high redshift galaxies

NASA Astrophysics Data System (ADS)

Buat, V.; Noll, S.; Burgarella, D.; Giovannoli, E.; Charmandaris, V.; Pannella, M.; Hwang, H. S.; Elbaz, D.; Dickinson, M.; Magdis, G.; Reddy, N.; Murphy, E. J.

2012-09-01

Context. Dust attenuation in galaxies is poorly known, especially at high redshift. And yet the amount of dust attenuation is a key parameter to deduce accurate star formation rates from ultraviolet (UV) rest-frame measurements. The wavelength dependence of the dust attenuation is also of fundamental importance to interpret the observed spectral energy distributions (SEDs) and to derive photometric redshifts or physical properties of galaxies. Aims: We want to study dust attenuation at UV wavelengths at high redshift, where the UV is redshifted to the observed visible light wavelength range. In particular, we search for a UV bump and related implications for dust attenuation determinations. Methods: We use photometric data in the Chandra Deep Field South (CDFS), obtained in intermediate and broad band filters by the MUSYC project, to sample the UV rest-frame of 751 galaxies with 0.95 < z < 2.2. When available, infrared (IR) Herschel/PACS data from the GOODS-Herschel project, coupled with Spitzer/MIPS measurements, are used to estimate the dust emission and to constrain dust attenuation. The SED of each source is fit using the CIGALE code. The amount of dust attenuation and the characteristics of the dust attenuation curve are obtained as outputs of the SED fitting process, together with other physical parameters linked to the star formation history. Results: The global amount of dust attenuation at UV wavelengths is found to increase with stellar mass and to decrease as UV luminosity increases. A UV bump at 2175 Å is securely detected in 20% of the galaxies, and the mean amplitude of the bump for the sample is similar to that observed in the extinction curve of the LMC supershell region. This amplitude is found to be lower in galaxies with very high specific star formation rates, and 90% of the galaxies exhibiting a secure bump are at z < 1.5. The attenuation curve is confirmed to be steeper than that of local starburst galaxies for 20% of the galaxies. The large dispersion found for these two parameters describing the attenuation law is likely to reflect a wide diversity of attenuation laws among galaxies. The relations between dust attenuation, IR-to-UV flux ratio, and the slope of the UV continuum are derived for the mean attenuation curve found for our sample. Deviations from the average trends are found to correlate with the age of the young stellar population and the shape of the attenuation curve. Table of multi-colour photometry for the 751 galaxies is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/545/A141

Counter tube window and X-ray fluorescence analyzer study

NASA Technical Reports Server (NTRS)

Hertel, R.; Holm, M.

1973-01-01

A study was performed to determine the best design tube window and X-ray fluorescence analyzer for quantitative analysis of Venusian dust and condensates. The principal objective of the project was to develop the best counter tube window geometry for the sensing element of the instrument. This included formulation of a mathematical model of the window and optimization of its parameters. The proposed detector and instrument has several important features. The instrument will perform a near real-time analysis of dust in the Venusian atmosphere, and is capable of measuring dust layers less than 1 micron thick. In addition, wide dynamic measurement range will be provided to compensate for extreme variations in count rates. An integral pulse-height analyzer and memory accumulate data and read out spectra for detail computer analysis on the ground.

New Insights into the Nature of Transition Disks from a Complete Disk Survey of the Lupus Star-forming Region

NASA Astrophysics Data System (ADS)

van der Marel, Nienke; Williams, Jonathan P.; Ansdell, M.; Manara, Carlo F.; Miotello, Anna; Tazzari, Marco; Testi, Leonardo; Hogerheijde, Michiel; Bruderer, Simon; van Terwisga, Sierk E.; van Dishoeck, Ewine F.

2018-02-01

Transition disks with large dust cavities around young stars are promising targets for studying planet formation. Previous studies have revealed the presence of gas cavities inside the dust cavities, hinting at recently formed, giant planets. However, many of these studies are biased toward the brightest disks in the nearby star-forming regions, and it is not possible to derive reliable statistics that can be compared with exoplanet populations. We present the analysis of 11 transition disks with large cavities (≥20 au radius) from a complete disk survey of the Lupus star-forming region, using ALMA Band 7 observations at 0.″3 (22–30 au radius) resolution of the 345 GHz continuum, 13CO and C18O 3–2 observations, and the spectral energy distribution of each source. Gas and dust surface density profiles are derived using the physical–chemical modeling code DALI. This is the first study of transition disks of large cavities within a complete disk survey within a star-forming region. The dust cavity sizes range from 20 to 90 au radius, and in three cases, a gas cavity is resolved as well. The deep drops in gas density and large dust cavity sizes are consistent with clearing by giant planets. The fraction of transition disks with large cavities in Lupus is ≳ 11 % , which is inconsistent with exoplanet population studies of giant planets at wide orbits. Furthermore, we present a hypothesis of an evolutionary path for large massive disks evolving into transition disks with large cavities.

On the Use of Statistics in Design and the Implications for Deterministic Computer Experiments

NASA Technical Reports Server (NTRS)

Simpson, Timothy W.; Peplinski, Jesse; Koch, Patrick N.; Allen, Janet K.

1997-01-01

Perhaps the most prevalent use of statistics in engineering design is through Taguchi's parameter and robust design -- using orthogonal arrays to compute signal-to-noise ratios in a process of design improvement. In our view, however, there is an equally exciting use of statistics in design that could become just as prevalent: it is the concept of metamodeling whereby statistical models are built to approximate detailed computer analysis codes. Although computers continue to get faster, analysis codes always seem to keep pace so that their computational time remains non-trivial. Through metamodeling, approximations of these codes are built that are orders of magnitude cheaper to run. These metamodels can then be linked to optimization routines for fast analysis, or they can serve as a bridge for integrating analysis codes across different domains. In this paper we first review metamodeling techniques that encompass design of experiments, response surface methodology, Taguchi methods, neural networks, inductive learning, and kriging. We discuss their existing applications in engineering design and then address the dangers of applying traditional statistical techniques to approximate deterministic computer analysis codes. We conclude with recommendations for the appropriate use of metamodeling techniques in given situations and how common pitfalls can be avoided.

Revealing the Structure of a Pre-Transitional Disk: The Case of the Herbig F Star SAO 206462 (HD 135344B)

NASA Astrophysics Data System (ADS)

Grady, C. A.; Schneider, G.; Sitko, M. L.; Williger, G. M.; Hamaguchi, K.; Brittain, S. D.; Ablordeppey, K.; Apai, D.; Beerman, L.; Carpenter, W. J.; Collins, K. A.; Fukagawa, M.; Hammel, H. B.; Henning, Th.; Hines, D.; Kimes, R.; Lynch, D. K.; Ménard, F.; Pearson, R.; Russell, R. W.; Silverstone, M.; Smith, P. S.; Troutman, M.; Wilner, D.; Woodgate, B.; Clampin, M.

2009-07-01

SAO 206462 (HD 135344B) has previously been identified as a Herbig F star with a circumstellar disk with a dip in its infrared excess near 10 μm. In combination with a low accretion rate estimated from Br γ, it may represent a gapped, but otherwise primordial or "pre-transitional" disk. We test this hypothesis with Hubble Space Telescope coronagraphic imagery, FUV spectroscopy and imagery and archival X-ray data, and spectral energy distribution (SED) modeling constrained by the observed system inclination, disk outer radius, and outer disk radial surface brightness (SB) profile using the Whitney Monte Carlo Radiative Transfer Code. The essentially face-on (i lsim 20°) disk is detected in scattered light from 0farcs4 to 1farcs15 (56-160 AU), with a steep (r -9.6) radial SB profile from 0farcs6 to 0farcs93. Fitting the SB data requires a concave upward or anti-flared outer disk, indicating substantial dust grain growth and settling by 8 ± 4 Myr. The warm dust component is significantly variable in near to mid-IR excess and in temperature. At its warmest, it appears confined to a narrow belt from 0.08 to 0.2 AU. The steep SED for this dust component is consistent with grains with a<= 2.5 μm. For cosmic carbon to silicate dust composition, conspicuous 10 μm silicate emission would be expected and is not observed. This may indicate an elevated carbon to silicate ratio for the warm dust, which is not required to fit the outer disk. At its coolest, the warm dust can be fit with a disk from 0.14 to 0.31 AU, but with a higher inclination than either the outer disk or the gaseous disk, providing confirmation of the high inclination inferred from mid-IR interferometry. In tandem, the compositional and inclination difference between the warm dust and the outer dust disk suggests that the warm dust may be of second-generation origin, rather than a remnant of a primordial disk component. With its near face-on inclination, SAO 206462's disk is a prime location for planet searches. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

Design and optimization of a portable LQCD Monte Carlo code using OpenACC

NASA Astrophysics Data System (ADS)

Bonati, Claudio; Coscetti, Simone; D'Elia, Massimo; Mesiti, Michele; Negro, Francesco; Calore, Enrico; Schifano, Sebastiano Fabio; Silvi, Giorgio; Tripiccione, Raffaele

The present panorama of HPC architectures is extremely heterogeneous, ranging from traditional multi-core CPU processors, supporting a wide class of applications but delivering moderate computing performance, to many-core Graphics Processor Units (GPUs), exploiting aggressive data-parallelism and delivering higher performances for streaming computing applications. In this scenario, code portability (and performance portability) become necessary for easy maintainability of applications; this is very relevant in scientific computing where code changes are very frequent, making it tedious and prone to error to keep different code versions aligned. In this work, we present the design and optimization of a state-of-the-art production-level LQCD Monte Carlo application, using the directive-based OpenACC programming model. OpenACC abstracts parallel programming to a descriptive level, relieving programmers from specifying how codes should be mapped onto the target architecture. We describe the implementation of a code fully written in OpenAcc, and show that we are able to target several different architectures, including state-of-the-art traditional CPUs and GPUs, with the same code. We also measure performance, evaluating the computing efficiency of our OpenACC code on several architectures, comparing with GPU-specific implementations and showing that a good level of performance-portability can be reached.

Development of a thermal and structural analysis procedure for cooled radial turbines

NASA Technical Reports Server (NTRS)

Kumar, Ganesh N.; Deanna, Russell G.

1988-01-01

A procedure for computing the rotor temperature and stress distributions in a cooled radial turbine is considered. Existing codes for modeling the external mainstream flow and the internal cooling flow are used to compute boundary conditions for the heat transfer and stress analyses. An inviscid, quasi three-dimensional code computes the external free stream velocity. The external velocity is then used in a boundary layer analysis to compute the external heat transfer coefficients. Coolant temperatures are computed by a viscous one-dimensional internal flow code for the momentum and energy equation. These boundary conditions are input to a three-dimensional heat conduction code for calculation of rotor temperatures. The rotor stress distribution may be determined for the given thermal, pressure and centrifugal loading. The procedure is applied to a cooled radial turbine which will be tested at the NASA Lewis Research Center. Representative results from this case are included.

COMPUTATION OF GLOBAL PHOTOCHEMISTRY WITH SMVGEAR II (R823186)

EPA Science Inventory

A computer model was developed to simulate global gas-phase photochemistry. The model solves chemical equations with SMVGEAR II, a sparse-matrix, vectorized Gear-type code. To obtain SMVGEAR II, the original SMVGEAR code was modified to allow computation of different sets of chem...

Computational strategies for three-dimensional flow simulations on distributed computer systems. Ph.D. Thesis Semiannual Status Report, 15 Aug. 1993 - 15 Feb. 1994

NASA Technical Reports Server (NTRS)

Weed, Richard Allen; Sankar, L. N.

1994-01-01

An increasing amount of research activity in computational fluid dynamics has been devoted to the development of efficient algorithms for parallel computing systems. The increasing performance to price ratio of engineering workstations has led to research to development procedures for implementing a parallel computing system composed of distributed workstations. This thesis proposal outlines an ongoing research program to develop efficient strategies for performing three-dimensional flow analysis on distributed computing systems. The PVM parallel programming interface was used to modify an existing three-dimensional flow solver, the TEAM code developed by Lockheed for the Air Force, to function as a parallel flow solver on clusters of workstations. Steady flow solutions were generated for three different wing and body geometries to validate the code and evaluate code performance. The proposed research will extend the parallel code development to determine the most efficient strategies for unsteady flow simulations.

Computerized systems analysis and optimization of aircraft engine performance, weight, and life cycle costs

NASA Technical Reports Server (NTRS)

Fishbach, L. H.

1979-01-01

The computational techniques utilized to determine the optimum propulsion systems for future aircraft applications and to identify system tradeoffs and technology requirements are described. The characteristics and use of the following computer codes are discussed: (1) NNEP - a very general cycle analysis code that can assemble an arbitrary matrix fans, turbines, ducts, shafts, etc., into a complete gas turbine engine and compute on- and off-design thermodynamic performance; (2) WATE - a preliminary design procedure for calculating engine weight using the component characteristics determined by NNEP; (3) POD DRG - a table look-up program to calculate wave and friction drag of nacelles; (4) LIFCYC - a computer code developed to calculate life cycle costs of engines based on the output from WATE; and (5) INSTAL - a computer code developed to calculate installation effects, inlet performance and inlet weight. Examples are given to illustrate how these computer techniques can be applied to analyze and optimize propulsion system fuel consumption, weight, and cost for representative types of aircraft and missions.

A Combinatorial Geometry Computer Description of the M9 ACE (Armored Combat Earthmover) Vehicle

DTIC Science & Technology

1984-12-01

program requires as input the M9 target descriptions as processed by the Geometric Information for Targets ( GIFT ) ’ computer code. The first step is...model of the target. This COM-GEOM target description is used as input to the Geometric Information For Targets ( GIFT ) computer code. Among other...things, the GIFT code traces shotlines through a COM-GEOM description from any specified aspect, listing pertinent information about each component hit

Clear-Sky Closure Studies of Tropospheric Aerosol and Water Vapor During ACE-2 Using Airborne Sunphotometer, Airborne In-Situ, Space-Borne, and Ground-Based Measurements

NASA Technical Reports Server (NTRS)

Schmid, Beat; Collins, Donald R.; Gasso, Santiago; Oestroem, Elisabeth; Powell, Donna M.; Welton, Ellsworth J.; Durkee, Philip A.; Livingston, John M.; Russell, Philip B.; Flagan, Richard C.;

Cliffs versus plains: Can ROSINA/COPS and OSIRIS data of comet 67P/Churyumov-Gerasimenko in autumn 2014 constrain inhomogeneous outgassing?

NASA Astrophysics Data System (ADS)

Marschall, R.; Mottola, S.; Su, C. C.; Liao, Y.; Rubin, M.; Wu, J. S.; Thomas, N.; Altwegg, K.; Sierks, H.; Ip, W.-H.; Keller, H. U.; Knollenberg, J.; Kührt, E.; Lai, I. L.; Skorov, Y.; Jorda, L.; Preusker, F.; Scholten, F.; Vincent, J.-B.; Osiris Team; Rosina Team

2017-09-01

Context. This paper describes the modelling of gas and dust data acquired in the period August to October 2014 from the European Space Agency's Rosetta spacecraft when it was in close proximity to the nucleus of comet 67P/Churyumov-Gerasimenko. Aims: With our 3D gas and dust comae models this work attempts to test the hypothesis that cliff activity on comet 67P/Churyumov-Gerasimenko can solely account for the local gas density data observed by the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) and the dust brightnesses seen by the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) in the considered time span. Methods: The model uses a previously developed shape model of the nucleus. From this, the water sublimation rates and gas temperatures at the surface are computed. The gas expansion is modelled with a 3D Direct Simulation Monte Carlo algorithm. A dust drag algorithm is then used to compute dust volume number densities in the coma, which are then converted to brightnesses using Mie theory and a line-of-sight integration. Furthermore we have studied the impact of topographic re-radiation on the models. Results: We show that gas activity from only cliff areas produces a fit to the ROSINA/COPS data that is as statistically good as a purely insolation-driven model. In contrast, pure cliff activity does not reproduce the dust brightness observed by OSIRIS and can thus be ruled out. On the other hand, gas activity from the Hapi region in addition to cliff activity produces a statistically better fit to the ROSINA/COPS data than purely insolation-driven outgassing and also fits the OSIRIS observations rather well. We found that topographic re-radiation does not contribute significantly to the sublimation behaviour of H2O but plays an important role in how the gas flux interacts with the irregular shape of the nucleus. Conclusions: We demonstrate that fits to the observations are non-unique. We can conclude however that gas and dust activity from cliffs and the Hapi region are consistent with the ROSINA/COPS and OSIRIS data sets for the considered time span and are thus a plausible solution. Models with activity from low gravitational slopes alone provide a statistically inferior solution.

Characterizing the Properties of a Woven SiC/SiC Composite Using W-CEMCAN Computer Code

NASA Technical Reports Server (NTRS)

Murthy, Pappu L. N.; Mital, Subodh K.; DiCarlo, James A.

1999-01-01

A micromechanics based computer code to predict the thermal and mechanical properties of woven ceramic matrix composites (CMC) is developed. This computer code, W-CEMCAN (Woven CEramic Matrix Composites ANalyzer), predicts the properties of two-dimensional woven CMC at any temperature and takes into account various constituent geometries and volume fractions. This computer code is used to predict the thermal and mechanical properties of an advanced CMC composed of 0/90 five-harness (5 HS) Sylramic fiber which had been chemically vapor infiltrated (CVI) with boron nitride (BN) and SiC interphase coatings and melt-infiltrated (MI) with SiC. The predictions, based on the bulk constituent properties from the literature, are compared with measured experimental data. Based on the comparison. improved or calibrated properties for the constituent materials are then developed for use by material developers/designers. The computer code is then used to predict the properties of a composite with the same constituents but with different fiber volume fractions. The predictions are compared with measured data and a good agreement is achieved.

Robust digital image inpainting algorithm in the wireless environment

NASA Astrophysics Data System (ADS)

Karapetyan, G.; Sarukhanyan, H. G.; Agaian, S. S.

2014-05-01

Image or video inpainting is the process/art of retrieving missing portions of an image without introducing undesirable artifacts that are undetectable by an ordinary observer. An image/video can be damaged due to a variety of factors, such as deterioration due to scratches, laser dazzling effects, wear and tear, dust spots, loss of data when transmitted through a channel, etc. Applications of inpainting include image restoration (removing laser dazzling effects, dust spots, date, text, time, etc.), image synthesis (texture synthesis), completing panoramas, image coding, wireless transmission (recovery of the missing blocks), digital culture protection, image de-noising, fingerprint recognition, and film special effects and production. Most inpainting methods can be classified in two key groups: global and local methods. Global methods are used for generating large image regions from samples while local methods are used for filling in small image gaps. Each method has its own advantages and limitations. For example, the global inpainting methods perform well on textured image retrieval, whereas the classical local methods perform poorly. In addition, some of the techniques are computationally intensive; exceeding the capabilities of most currently used mobile devices. In general, the inpainting algorithms are not suitable for the wireless environment. This paper presents a new and efficient scheme that combines the advantages of both local and global methods into a single algorithm. Particularly, it introduces a blind inpainting model to solve the above problems by adaptively selecting support area for the inpainting scheme. The proposed method is applied to various challenging image restoration tasks, including recovering old photos, recovering missing data on real and synthetic images, and recovering the specular reflections in endoscopic images. A number of computer simulations demonstrate the effectiveness of our scheme and also illustrate the main properties and implementation steps of the presented algorithm. Furthermore, the simulation results show that the presented method is among the state-of-the-art and compares favorably against many available methods in the wireless environment. Robustness in the wireless environment with respect to the shape of the manually selected "marked" region is also illustrated. Currently, we are working on the expansion of this work to video and 3-D data.