On the Solar System-Debris Disk Connecction

OpenAIRE

Moro-Martin, Amaya

2007-01-01

This paper emphasizes the connection between solar and extra-solar debris disks: how models and observations of the Solar System are helping us understand the debris disk phenomenon, and vice versa, how debris disks are helping us place our Solar System into context.

RESOLVED MILLIMETER-WAVELENGTH OBSERVATIONS OF DEBRIS DISKS AROUND SOLAR-TYPE STARS

Energy Technology Data Exchange (ETDEWEB)

Steele, Amy; Hughes, A. Meredith [Department of Astronomy, Van Vleck Observatory, Wesleyan University, 96 Foss Hill Drive, Middletown, CT, 06459 (United States); Carpenter, John [Division of Physics, Mathematics, and Astronomy, MC249-17, California Institute of Technology, Pasadena, CA 91125 (United States); Ricarte, Angelo [J. W. Gibbs Laboratory, Department of Astronomy, Yale University, 260 Whitney Avenue, New Haven, CT 06511 (United States); Andrews, Sean M.; Wilner, David J. [Harvard-Smithsonian Center for Astrophysics, MS-42, 60 Garden Street, Cambridge, MA 02138 (United States); Chiang, Eugene, E-mail: asteele@wesleyan.edu [Department of Astronomy, 501 Campbell Hall, University of California, Berkeley, CA 94720-3411 (United States)

2016-01-01

The presence of debris disks around young main-sequence stars hints at the existence and structure of planetary systems. Millimeter-wavelength observations probe large grains that trace the location of planetesimal belts. The Formation and Evolution of Planetary Systems Spitzer Legacy survey of nearby young solar analogues yielded a sample of five debris disk-hosting stars with millimeter flux suitable for interferometric follow-up. We present observations with the Submillimeter Array (SMA) and the Combined Array for Research in Millimeter-wave Astronomy at ∼2″ resolution that spatially resolve the debris disks around these nearby (d ∼ 50 pc) stars. Two of the five disks (HD 377, HD 8907) are spatially resolved for the first time and one (HD 104860) is resolved at millimeter wavelengths for the first time. We combine our new observations with archival SMA and Atacama Large Millimeter/Submillimeter Array data to enable a uniform analysis of the full five-object sample. We simultaneously model the broadband photometric data and resolved millimeter visibilities to constrain the dust temperatures and disk morphologies, and perform a Markov Chain Monte Carlo analysis to fit for basic structural parameters. We find that the radii and widths of the cold outer belts exhibit properties consistent with scaled-up versions of the Solar System's Kuiper Belt. All the disks exhibit characteristic grain sizes comparable to the blowout size, and all the resolved observations of emission from large dust grains are consistent with an axisymmetric dust distribution to within the uncertainties. These results are consistent with comparable studies carried out at infrared wavelengths.

Computational investigation of hydrokinetic turbine arrays in an open channel using an actuator disk-LES model

Science.gov (United States)

Kang, Seokkoo; Yang, Xiaolei; Sotiropoulos, Fotis

2012-11-01

While a considerable amount of work has focused on studying the effects and performance of wind farms, very little is known about the performance of hydrokinetic turbine arrays in open channels. Unlike large wind farms, where the vertical fluxes of momentum and energy from the atmospheric boundary layer comprise the main transport mechanisms, the presence of free surface in hydrokinetic turbine arrays inhibits vertical transport. To explore this fundamental difference between wind and hydrokinetic turbine arrays, we carry out LES with the actuator disk model to systematically investigate various layouts of hydrokinetic turbine arrays mounted on the bed of a straight open channel with fully-developed turbulent flow fed at the channel inlet. Mean flow quantities and turbulence statistics within and downstream of the arrays will be analyzed and the effect of the turbine arrays as means for increasing the effective roughness of the channel bed will be extensively discussed. This work was supported by Initiative for Renewable Energy & the Environment (IREE) (Grant No. RO-0004-12), and computational resources were provided by Minnesota Supercomputing Institute.

A DWARF TRANSITIONAL PROTOPLANETARY DISK AROUND XZ TAU B

Energy Technology Data Exchange (ETDEWEB)

Osorio, Mayra; Macías, Enrique; Anglada, Guillem; Gómez, José F. [Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía s/n, E-18008 Granada (Spain); Carrasco-González, Carlos; Galván-Madrid, Roberto; Zapata, Luis; Rodríguez, Luis F. [Instituto de Radioastronomía y Astrofísica UNAM, Apartado Postal 3-72 (Xangari), 58089 Morelia, Michoacán (Mexico); Calvet, Nuria [Department of Astronomy, University of Michigan, 825 Dennison Building, 500 Church Street, Ann Arbor, MI 48109 (United States); Nagel, Erick [Departamento de Astronomía, Universidad de Guanajuato, Guanajuato, Gto 36240 (Mexico); Torrelles, José M. [Institut de Ciències de l’Espai (CSIC)-Institut de Ciències del Cosmos (UB)/IEEC, Martí i Franquès 1, E-08028 Barcelona (Spain); Zhu, Zhaohuan, E-mail: osorio@iaa.es [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

2016-07-01

We report the discovery of a dwarf protoplanetary disk around the star XZ Tau B that shows all the features of a classical transitional disk but on a much smaller scale. The disk has been imaged with the Atacama Large Millimeter/submillimeter Array (ALMA), revealing that its dust emission has a quite small radius of ∼3.4 au and presents a central cavity of ∼1.3 au in radius that we attribute to clearing by a compact system of orbiting (proto)planets. Given the very small radii involved, evolution is expected to be much faster in this disk (observable changes in a few months) than in classical disks (observable changes requiring decades) and easy to monitor with observations in the near future. From our modeling we estimate that the mass of the disk is large enough to form a compact planetary system.

A High-mass Protobinary System with Spatially Resolved Circumstellar Accretion Disks and Circumbinary Disk

Energy Technology Data Exchange (ETDEWEB)

Kraus, S.; Kluska, J.; Kreplin, A.; Bate, M.; Harries, T. J.; Hone, E.; Anugu, A. [School of Physics, Astrophysics Group, University of Exeter, Stocker Road, Exeter EX4 4QL (United Kingdom); Hofmann, K.-H.; Weigelt, G. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Monnier, J. D. [Department of Astronomy, University of Michigan, 311 West Hall, 1085 South University Avenue, Ann Arbor, MI 48109 (United States); De Wit, W. J. [ESO, Alonso de Cordova 3107, Vitacura, Santiago 19 (Chile); Wittkowski, M., E-mail: skraus@astro.ex.ac.uk [ESO, Karl-Schwarzschild-Str. 2, D-85748 Garching bei München (Germany)

2017-01-20

High-mass multiples might form via fragmentation of self-gravitational disks or alternative scenarios such as disk-assisted capture. However, only a few observational constraints exist on the architecture and disk structure of high-mass protobinaries and their accretion properties. Here, we report the discovery of a close (57.9 ± 0.2 mas = 170 au) high-mass protobinary, IRAS17216-3801, where our VLTI/GRAVITY+AMBER near-infrared interferometry allows us to image the circumstellar disks around the individual components with ∼3 mas resolution. We estimate the component masses to ∼20 and ∼18 M {sub ⊙} and find that the radial intensity profiles can be reproduced with an irradiated disk model, where the inner regions are excavated of dust, likely tracing the dust sublimation region in these disks. The circumstellar disks are strongly misaligned with respect to the binary separation vector, which indicates that the tidal forces did not have time to realign the disks, pointing toward a young dynamical age of the system. We constrain the distribution of the Br γ and CO-emitting gas using VLTI/GRAVITY spectro-interferometry and VLT/CRIRES spectro-astrometry and find that the secondary is accreting at a higher rate than the primary. VLT/NACO imaging shows L ′-band emission on (3–4)× larger scales than the binary separation, matching the expected dynamical truncation radius for the circumbinary disk. The IRAS17216-3801 system is ∼3× more massive and ∼5× more compact than other high-mass multiplies imaged at infrared wavelength and the first high-mass protobinary system where circumstellar and circumbinary dust disks could be spatially resolved. This opens exciting new opportunities for studying star–disk interactions and the role of multiplicity in high-mass star formation.

UNSTABLE PLANETARY SYSTEMS EMERGING OUT OF GAS DISKS

International Nuclear Information System (INIS)

Matsumura, Soko; Thommes, Edward W.; Chatterjee, Sourav; Rasio, Frederic A.

2010-01-01

The discovery of over 400 extrasolar planets allows us to statistically test our understanding of the formation and dynamics of planetary systems via numerical simulations. Traditional N-body simulations of multiple-planet systems without gas disks have successfully reproduced the eccentricity (e) distribution of the observed systems by assuming that the planetary systems are relatively closely packed when the gas disk dissipates, so that they become dynamically unstable within the stellar lifetime. However, such studies cannot explain the small semimajor axes a of extrasolar planetary systems, if planets are formed, as the standard planet formation theory suggests, beyond the ice line. In this paper, we numerically study the evolution of three-planet systems in dissipating gas disks, and constrain the initial conditions that reproduce the observed a and e distributions simultaneously. We adopt initial conditions that are motivated by the standard planet formation theory, and self-consistently simulate the disk evolution and planet migration, by using a hybrid N-body and one-dimensional gas disk code. We also take into account eccentricity damping, and investigate the effect of saturation of corotation resonances on the evolution of planetary systems. We find that the a distribution is largely determined in a gas disk, while the e distribution is determined after the disk dissipation. We also find that there may be an optimum disk mass which leads to the observed a-e distribution. Our simulations generate a larger fraction of planetary systems trapped in mean-motion resonances (MMRs) than the observations, indicating that the disk's perturbation to the planetary orbits may be important to explain the observed rate of MMRs. We also find a much lower occurrence of planets on retrograde orbits than the current observations of close-in planets suggest.

Redundant arrays of IDE drives

Energy Technology Data Exchange (ETDEWEB)

D.A. Sanders et al.

2002-01-02

The authors report tests of redundant arrays of IDE disk drives for use in offline high energy physics data analysis. Parts costs of total systems using commodity EIDE disks are now at the $4000 per Terabyte level. Disk storage prices have now decreased to the point where they equal the cost per Terabyte of Storage Technology tape silos. The disks, however, offer far better granularity; even small institutions can afford to deploy systems. The tests include reports on software RAID-5 systems running under Linux 2.4 using Promise Ultra 100{trademark} disk controllers. RAID-5 protects data in case of a single disk failure by providing parity bits. Tape backup is not required. Journaling file systems are used to allow rapid recovery from crashes. The data analysis strategy is to encapsulate data and CPU processing power. Analysis for a particular part of a data set takes place on the PC where the data resides. The network is only used to put results together. They explore three methods of moving data between sites; internet transfers, not pluggable IDE disks in FireWire cases, and DVD-R disks.

Redundant arrays of IDE drives

International Nuclear Information System (INIS)

Sanders, D.A.

2002-01-01

The authors report tests of redundant arrays of IDE disk drives for use in offline high energy physics data analysis. Parts costs of total systems using commodity EIDE disks are now at the $4000 per Terabyte level. Disk storage prices have now decreased to the point where they equal the cost per Terabyte of Storage Technology tape silos. The disks, however, offer far better granularity; even small institutions can afford to deploy systems. The tests include reports on software RAID-5 systems running under Linux 2.4 using Promise Ultra 100trademark disk controllers. RAID-5 protects data in case of a single disk failure by providing parity bits. Tape backup is not required. Journaling file systems are used to allow rapid recovery from crashes. The data analysis strategy is to encapsulate data and CPU processing power. Analysis for a particular part of a data set takes place on the PC where the data resides. The network is only used to put results together. They explore three methods of moving data between sites; internet transfers, not pluggable IDE disks in FireWire cases, and DVD-R disks

From circumstellar disks to planetary systems: observation and modeling of protoplanetary disks

OpenAIRE

Macías Quevedo, Enrique

2016-01-01

The existence of exoplanetary systems was first predicted after the discovery of accretion disks around young stars. Nowadays, with nearly 3500 exoplanets discovered, and almost 5000 more candidates identified by the Kepler space mission, planetary systems are now known to be ubiquitous around low-mass stars. The formation of these systems takes place during the stellar formation itself, from the dust and gas orbiting around the star in the protoplanetary disks. However, the process that lead...

AN EXPANDED VERY LARGE ARRAY AND CARMA STUDY OF DUSTY DISKS AND TORII WITH LARGE GRAINS IN DYING STARS

International Nuclear Information System (INIS)

Sahai, R.; Claussen, M. J.; Schnee, S.; Morris, M. R.; Sanchez Contreras, C.

2011-01-01

We report the results of a pilot multiwavelength survey in the radio continuum (X, Ka, and Q bands, i.e., from 3.6 cm to 7 mm) carried out with the Expanded Very Large Array (EVLA) in order to confirm the presence of very large dust grains in dusty disks and torii around the central stars in a small sample of post-asymptotic giant branch (pAGB) objects, as inferred from millimeter (mm) and submillimeter (submm) observations. Supporting mm-wave observations were also obtained with the Combined Array for Research in Millimeter-wave Astronomy toward three of our sources. Our EVLA survey has resulted in a robust detection of our most prominent submm emission source, the pre-planetary nebula (PPN) IRAS 22036+5306, in all three bands, and the disk-prominent pAGB object, RV Tau, in one band. The observed fluxes are consistent with optically thin free-free emission, and since they are insignificant compared to their submm/mm fluxes, we conclude that the latter must come from substantial masses of cool, large (mm-sized) grains. We find that the power-law emissivity in the cm-to-submm range for the large grains in IRAS22036 is ν β , with β = 1-1.3. Furthermore, the value of β in the 3-0.85 mm range for the three disk-prominent pAGB sources (β ≤ 0.4) is significantly lower than that of IRAS22036, suggesting that the grains in pAGB objects with circumbinary disks are likely larger than those in the dusty waists of pre-planetary nebulae.

Characterizing Protoplanetary Disks in a Young Binary in Orion

Science.gov (United States)

Powell, Jonas; Hughes, A. Meredith; Mann, Rita; Flaherty, Kevin; Di Francesco, James; Williams, Jonathan

2018-01-01

Planetary systems form in circumstellar disks of gas and dust surrounding young stars. One open question in the study of planet formation involves understanding how different environments affect the properties of the disks and planets they generate. Understanding the properties of disks in high-mass star forming regions (SFRs) is critical since most stars - probably including our Sun - form in those regions. By comparing the disks in high-mass SFRs to those in better-studied low-mass SFRs we can learn about the role environment plays in planet formation. Here we present 0.5" resolution observations of the young two-disk binary system V2434 Ori in the Orion Nebula from the Atacama Large Millimeter/submillimeter Array (ALMA) in molecular line tracers of CO(3-2), HCN(4-3), HCO+(4-3) and CS(7-6). We model each disk’s mass, radius, temperature structure, and molecular abundances, by creating synthetic images using an LTE ray-tracing code and comparing simulated observations with the ALMA data in the visibility domain. We then compare our results to a previous study of molecular line emission from a single Orion proplyd, modeled using similar methods, and to previously characterized disks in low-mass SFRs to investigate the role of environment in disk chemistry and planetary system formation.

Array-on-a-disk? How Blu-ray technology can be applied to molecular diagnostics.

Science.gov (United States)

Morais, Sergi; Tortajada-Genaro, Luis; Maquieira, Angel

2014-09-01

This editorial comments on the balance and perspectives of compact disk technology applied to molecular diagnostics. The development of sensitive, rapid and multiplex assays using Blu-ray technology for the determination of biomarkers, drug allergens, pathogens and detection of infections would have a direct impact on diagnostics. Effective tests for use in clinical, environmental and food applications require versatile and low-cost platforms as well as cost-effective detectors. Blu-ray technology accomplishes those requirements and advances on the concept of high density arrays for massive screening to achieve the demands of point of care or in situ analysis.

Angular momentum exchange by gravitational torques and infall in the circumbinary disk of the protostellar system L1551 NE

Energy Technology Data Exchange (ETDEWEB)

Takakuwa, Shigehisa; Ho, Paul T. P. [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China); Saito, Masao [Joint ALMA Observatory, Ave. Alonso de Cordova 3107, Vitacura, Santiago (Chile); Saigo, Kazuya [ALMA Project Office, National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588 (Japan); Matsumoto, Tomoaki [Faculty of Humanity and Environment, Hosei University, Chiyoda-ku, Tokyo 102-8160 (Japan); Lim, Jeremy [Department of Physics, University of Hong Kong, Pokfulam Road (Hong Kong); Hanawa, Tomoyuki, E-mail: takakuwa@asiaa.sinica.edu.tw [Center for Frontier Science, Chiba University, Inage-ku, Chiba 263-8522 (Japan)

2014-11-20

We report an ALMA observation of the Class I binary protostellar system L1551 NE in the 0.9 mm continuum, C{sup 18}O (3-2), and {sup 13}CO (3-2) lines at a ∼1.6 times higher resolution and a ∼6 times higher sensitivity than those of our previous SubMillimeter Array (SMA) observations, which revealed a r ∼ 300 AU scale circumbinary disk in Keplerian rotation. The 0.9 mm continuum shows two opposing U-shaped brightenings in the circumbinary disk and exhibits a depression between the circumbinary disk and the circumstellar disk of the primary protostar. The molecular lines trace non-axisymmetric deviations from Keplerian rotation in the circumbinary disk at higher velocities relative to the systemic velocity, where our previous SMA observations could not detect the lines. In addition, we detect inward motion along the minor axis of the circumbinary disk. To explain the newly observed features, we performed a numerical simulation of gas orbits in a Roche potential tailored to the inferred properties of L1551 NE. The observed U-shaped dust features coincide with locations where gravitational torques from the central binary system are predicted to impart angular momentum to the circumbinary disk, producing shocks and hence density enhancements seen as a pair of spiral arms. The observed inward gas motion coincides with locations where angular momentum is predicted to be lowered by the gravitational torques. The good agreement between our observation and model indicates that gravitational torques from the binary stars constitute the primary driver for exchanging angular momentum so as to permit infall through the circumbinary disk of L1551 NE.

Optimal Configurations of Wave Energy Converter Arrays with a Floating Body

Directory of Open Access Journals (Sweden)

Zhang Wanchao

2016-10-01

Full Text Available An array of floating point-absorbing wave energy converters (WECs is usually employed for extracting efficiently ocean wave energy. For deep water environment, it is more feasible and convenient to connect the absorbers array with a floating body, such as a semi-submersible bottom-moored disk, whose function is to act as the virtual seabed. In the present work, an array of identical floating symmetrically distributed cylinders in a coaxial moored disk as a wave energy device is proposed The power take-off (PTO system in the wave energy device is assumed to be composed of a linear/nonlinear damper activated by the buoys heaving motion. Hydrodynamic analysis of the examined floating system is implemented in frequency domain. Hydrodynamic interferences between the oscillating bodies are accounted for in the corresponding coupled equations. The array layouts under the constraint of the disk, incidence wave directions, separating distance between the absorbers and the PTO damping are considered to optimize this kind of WECs. Numerical results with regular waves are presented and discussed for the axisymmetric system utilizing heave mode with these interaction factors, in terms of a specific numbers of cylinders and expected power production.

MODELING DUST EMISSION OF HL TAU DISK BASED ON PLANET–DISK INTERACTIONS

International Nuclear Information System (INIS)

Jin, Sheng; Ji, Jianghui; Li, Shengtai; Li, Hui; Isella, Andrea

2016-01-01

We use extensive global two-dimensional hydrodynamic disk gas+dust simulations with embedded planets, coupled with three-dimensional radiative transfer calculations, to model the dust ring and gap structures in the HL Tau protoplanetary disk observed with the Atacama Large Millimeter/Submillimeter Array (ALMA). We include the self-gravity of disk gas and dust components and make reasonable choices of disk parameters, assuming an already settled dust distribution and no planet migration. We can obtain quite adequate fits to the observed dust emission using three planets with masses of 0.35, 0.17, and 0.26 M Jup at 13.1, 33.0, and 68.6 AU, respectively. Implications for the planet formation as well as the limitations of this scenario are discussed

Annular array technology for nondestructive turbine inspection. Final report

International Nuclear Information System (INIS)

Light, G.M.

1986-05-01

The Electric Power Research Institute (EPRI) funded Southwest Research Institute (SwRI) to fabricate and functionally test phased array transducers and an electronic control system with the intent of evaluating the phased array technology for use in the inspection of turbine disks. During this program a 13-element annular array and associated phased array electronics were fabricated and tested and the results of the tests compared to those predicted by theory. The prototype system performed well within the expected limits, and EPRI funded further work to fabricate and test a production unit. The production system consisted of a 25-element annular array and a 25-channel electronics system that had both pulser and receiver delay circuitry. In addition, during the program it was determined that miniaturized hybrid pulser/preamps would be needed to allow the phased array to work over distances exceeding 9.1 meters (30 feet) from the electronics. A circuit developed by SwRI was utilized and found to produce good pulsing capability that did not suffer from impedance mismatch. EPRI also funded (under a separate contract) the fabrication of a small scale static turbine test bed and a full scale dynamic test bed that contained full scale turbine geometries. These test beds were fabricated to enable the production phased array system to be evaluated on turbine disk surfaces. 26 figs

Properties of the disk system of globular clusters

International Nuclear Information System (INIS)

Armandroff, T.E.

1989-01-01

A large refined data sample is used to study the properties and origin of the disk system of globular clusters. A scale height for the disk cluster system of 800-1500 pc is found which is consistent with scale-height determinations for samples of field stars identified with the Galactic thick disk. A rotational velocity of 193 + or - 29 km/s and a line-of-sight velocity dispersion of 59 + or - 14 km/s have been found for the metal-rich clusters. 70 references

PLANETARY SYSTEM FORMATION IN THE PROTOPLANETARY DISK AROUND HL TAURI

Energy Technology Data Exchange (ETDEWEB)

Akiyama, Eiji; Hasegawa, Yasuhiro; Hayashi, Masahiko; Iguchi, Satoru, E-mail: eiji.akiyama@nao.ac.jp, E-mail: yasuhiro.hasegawa@nao.ac.jp [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

2016-02-20

We reprocess the Atacama Large Millimeter/Submillimeter Array (ALMA) long-baseline science verification data taken toward HL Tauri. Assuming the observed gaps are opened up by currently forming, unseen bodies, we estimate the mass of such hypothetical bodies based on the following two approaches: the Hill radius analysis and a more elaborate approach developed from the angular momentum transfer analysis in gas disks. For the former, the measured gap widths are used for estimating the mass of the bodies, while for the latter, the measured gap depths are utilized. We show that their masses are comparable to or less than the mass of Jovian planets. By evaluating Toomre’s gravitational instability (GI) condition and cooling effect, we find that the GI might be a mechanism to form the bodies in the outer region of the disk. As the disk might be gravitationally unstable only in the outer region of the disk, inward planetary migration would be needed to construct the current architecture of the observed disk. We estimate the gap-opening mass and show that type II migration might be able to play such a role. Combining GIs with inward migration, we conjecture that all of the observed gaps may be a consequence of bodies that might have originally formed at the outer part of the disk, and have subsequently migrated to the current locations. While ALMA’s unprecedented high spatial resolution observations can revolutionize our picture of planet formation, more dedicated observational and theoretical studies are needed to fully understand the HL Tauri images.

PLANETARY SYSTEM FORMATION IN THE PROTOPLANETARY DISK AROUND HL TAURI

International Nuclear Information System (INIS)

Akiyama, Eiji; Hasegawa, Yasuhiro; Hayashi, Masahiko; Iguchi, Satoru

2016-01-01

We reprocess the Atacama Large Millimeter/Submillimeter Array (ALMA) long-baseline science verification data taken toward HL Tauri. Assuming the observed gaps are opened up by currently forming, unseen bodies, we estimate the mass of such hypothetical bodies based on the following two approaches: the Hill radius analysis and a more elaborate approach developed from the angular momentum transfer analysis in gas disks. For the former, the measured gap widths are used for estimating the mass of the bodies, while for the latter, the measured gap depths are utilized. We show that their masses are comparable to or less than the mass of Jovian planets. By evaluating Toomre’s gravitational instability (GI) condition and cooling effect, we find that the GI might be a mechanism to form the bodies in the outer region of the disk. As the disk might be gravitationally unstable only in the outer region of the disk, inward planetary migration would be needed to construct the current architecture of the observed disk. We estimate the gap-opening mass and show that type II migration might be able to play such a role. Combining GIs with inward migration, we conjecture that all of the observed gaps may be a consequence of bodies that might have originally formed at the outer part of the disk, and have subsequently migrated to the current locations. While ALMA’s unprecedented high spatial resolution observations can revolutionize our picture of planet formation, more dedicated observational and theoretical studies are needed to fully understand the HL Tauri images

NEW DEBRIS DISKS IN NEARBY YOUNG MOVING GROUPS

Energy Technology Data Exchange (ETDEWEB)

Moór, A.; Kóspál, Á.; Ábrahám, P.; Kiss, Cs. [Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, P.O. Box 67, H-1525 Budapest (Hungary); Balog, Z.; Henning, Th. [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Csengeri, T. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Juhász, A., E-mail: moor@konkoly.hu [Institute of Astronomy, Madingley Road, Cambridge CB3, OHA (United Kingdom)

2016-08-01

A significant fraction of nearby young moving group members harbor circumstellar debris dust disks. Due to their proximity and youth, these disks are attractive targets for studying the early evolution of debris dust and planetesimal belts. Here we present 70 and 160 μ m observations of 31 systems in the β Pic moving group, and in the Tucana–Horologium, Columba, Carina, and Argus associations, using the Herschel Space Observatory . None of these stars were observed at far-infrared wavelengths before. Our Herschel measurements were complemented by photometry from the WISE satellite for the whole sample, and by submillimeter/millimeter continuum data for one source, HD 48370. We identified six stars with infrared excess, four of them are new discoveries. By combining our new findings with results from the literature, we examined the incidence and general characteristics of debris disks around Sun-like members of the selected groups. With their dust temperatures of <45 K the newly identified disks around HD 38397, HD 48370, HD 160305, and BD-20 951 represent the coldest population within this sample. For HD 38397 and HD 48370, the emission is resolved in the 70 μ m Photodetector Array Camera and Spectrograph images, the estimated radius of these disks is ∼90 au. Together with the well-known disk around HD 61005, these three systems represent the highest mass end of the known debris disk population around young G-type members of the selected groups. In terms of dust content, they resemble the hypothesized debris disk of the ancient solar system.

HNC IN PROTOPLANETARY DISKS

International Nuclear Information System (INIS)

Graninger, Dawn; Öberg, Karin I.; Qi, Chunhua; Kastner, Joel

2015-01-01

The distributions and abundances of small organics in protoplanetary disks are potentially powerful probes of disk physics and chemistry. HNC is a common probe of dense interstellar regions and the target of this study. We use the Submillimeter Array (SMA) to observe HNC 3–2 toward the protoplanetary disks around the T Tauri star TW Hya and the Herbig Ae star HD 163296. HNC is detected toward both disks, constituting the first spatially resolved observations of HNC in disks. We also present SMA observations of HCN 3–2 and IRAM 30 m observations of HCN and HNC 1–0 toward HD 163296. The disk-averaged HNC/HCN emission ratio is 0.1–0.2 toward both disks. Toward TW Hya, the HNC emission is confined to a ring. The varying HNC abundance in the TW Hya disk demonstrates that HNC chemistry is strongly linked to the disk physical structure. In particular, the inner rim of the HNC ring can be explained by efficient destruction of HNC at elevated temperatures, similar to what is observed in the ISM. However, to realize the full potential of HNC as a disk tracer requires a combination of high SNR spatially resolved observations of HNC and HCN and disk-specific HNC chemical modeling

HNC IN PROTOPLANETARY DISKS

Energy Technology Data Exchange (ETDEWEB)

Graninger, Dawn; Öberg, Karin I.; Qi, Chunhua [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Kastner, Joel, E-mail: dgraninger@cfa.harvard.edu [Center for Imaging Science, School of Physics and Astronomy, and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States)

2015-07-01

The distributions and abundances of small organics in protoplanetary disks are potentially powerful probes of disk physics and chemistry. HNC is a common probe of dense interstellar regions and the target of this study. We use the Submillimeter Array (SMA) to observe HNC 3–2 toward the protoplanetary disks around the T Tauri star TW Hya and the Herbig Ae star HD 163296. HNC is detected toward both disks, constituting the first spatially resolved observations of HNC in disks. We also present SMA observations of HCN 3–2 and IRAM 30 m observations of HCN and HNC 1–0 toward HD 163296. The disk-averaged HNC/HCN emission ratio is 0.1–0.2 toward both disks. Toward TW Hya, the HNC emission is confined to a ring. The varying HNC abundance in the TW Hya disk demonstrates that HNC chemistry is strongly linked to the disk physical structure. In particular, the inner rim of the HNC ring can be explained by efficient destruction of HNC at elevated temperatures, similar to what is observed in the ISM. However, to realize the full potential of HNC as a disk tracer requires a combination of high SNR spatially resolved observations of HNC and HCN and disk-specific HNC chemical modeling.

ALMA Survey of Lupus Protoplanetary Disks. II. Gas Disk Radii

Science.gov (United States)

Ansdell, M.; Williams, J. P.; Trapman, L.; van Terwisga, S. E.; Facchini, S.; Manara, C. F.; van der Marel, N.; Miotello, A.; Tazzari, M.; Hogerheijde, M.; Guidi, G.; Testi, L.; van Dishoeck, E. F.

2018-05-01

We present Atacama Large Millimeter/Sub-Millimeter Array (ALMA) Band 6 observations of a complete sample of protoplanetary disks in the young (∼1–3 Myr) Lupus star-forming region, covering the 1.33 mm continuum and the 12CO, 13CO, and C18O J = 2–1 lines. The spatial resolution is ∼0.″25 with a medium 3σ continuum sensitivity of 0.30 mJy, corresponding to M dust ∼ 0.2 M ⊕. We apply Keplerian masking to enhance the signal-to-noise ratios of our 12CO zero-moment maps, enabling measurements of gas disk radii for 22 Lupus disks; we find that gas disks are universally larger than millimeter dust disks by a factor of two on average, likely due to a combination of the optically thick gas emission and the growth and inward drift of the dust. Using the gas disk radii, we calculate the dimensionless viscosity parameter, α visc, finding a broad distribution and no correlations with other disk or stellar parameters, suggesting that viscous processes have not yet established quasi-steady states in Lupus disks. By combining our 1.33 mm continuum fluxes with our previous 890 μm continuum observations, we also calculate the millimeter spectral index, α mm, for 70 Lupus disks; we find an anticorrelation between α mm and millimeter flux for low-mass disks (M dust ≲ 5), followed by a flattening as disks approach α mm ≈ 2, which could indicate faster grain growth in higher-mass disks, but may also reflect their larger optically thick components. In sum, this work demonstrates the continuous stream of new insights into disk evolution and planet formation that can be gleaned from unbiased ALMA disk surveys.

Disk Operating System User's Guide

Science.gov (United States)

1972-05-01

This document serves the purpose of bringing together in one place most of the information a user needs to use the DDP-516 Disk Operating System, (DOS). DOS is a core resident, one user, console-oriented operating system which allows the user to cont...

Multimegawatt disk generator system for space applications

International Nuclear Information System (INIS)

Solbes, H.; Iwata, H.

1988-01-01

The conceptual design of a 100 megawatt - 500 seconds disk MHD generator system suitable as a burst power source for a space based neutral particle beam (NPB) is presented. The system features two disk generators operated in the magnetic field produced by a single circular superconducting magnet. Gelled reactants are used as the energy source. The oxidizer gel includes the alkali seed. The high heat flux areas of the power train are water cooled. Heat is rejected to a hydrogen stream which is also used for cooling of the exit section. The hydrogen is also used to mitigate the effects of the exhaust products of combustion on the platform. The two disk channels are operated in parallel. A dc to dc converter consolidates the channel's output into a single 100 kilovolt dc output. Critical development issues relevant to the development of such power systems are identified and discussed. A R and D plan aimed at establishing the technical feasibility of the proposed system is also presented

Solid-state disk amplifiers for fusion-laser systems

Energy Technology Data Exchange (ETDEWEB)

Martin, W.E.; Trenholme, J.B.; Linford, G.J.; Yarema, S.M.; Hurley, C.A.

1981-09-01

We review the design, performance, and operation of large-aperture (10 to 46 cm) solid-state disk amplifiers for use in laser systems. We present design data, prototype tests, simulations, and projections for conventional cylindrical pump-geometry amplifiers and rectangular pump-geometry disk amplifiers. The design of amplifiers for the Nova laser system is discussed.

Disk

NARCIS (Netherlands)

P.A. Boncz (Peter); L. Liu (Lei); M. Tamer Özsu

2008-01-01

htmlabstractIn disk storage, data is recorded on planar, round and rotating surfaces (disks, discs, or platters). A disk drive is a peripheral device of a computer system, connected by some communication medium to a disk controller. The disk controller is a chip, typically connected to the CPU of

Multimegawatt disk generator system for space applications

International Nuclear Information System (INIS)

Solbes, A.; Iwata, H.

1988-01-01

The conceptual design of a 100 megawatt - 500 seconds disk MHD generator system suitable as a burst power source for a space based neutral particle beam (NPB) is presented. The system features two disk generators operated in the magnetic field produced by a single circular superconducting magnet. Gelled reactants are used as the energy source. The oxidizer gel includes the alkali seed. The high heat flux areas of the power train are water cooled. Heat is rejected to a hydrogen stream which is also used for cooling of the exit section. The hydrogen is also used to mitigate the effects of the exhaust products of combustion on the platform. The two disk channels are operated in parallel. A dc to dc converter consolidates the channel's output into a single 100 kilovolt dc output

TRANSITIONAL DISKS AS SIGNPOSTS OF YOUNG, MULTIPLANET SYSTEMS

International Nuclear Information System (INIS)

Dodson-Robinson, Sarah E.; Salyk, Colette

2011-01-01

Although there has yet been no undisputed discovery of a still-forming planet embedded in a gaseous protoplanetary disk, the cleared inner holes of transitional disks may be signposts of young planets. Here, we show that the subset of accreting transitional disks with wide, optically thin inner holes of 15 AU or more can only be sculpted by multiple planets orbiting inside each hole. Multiplanet systems provide two key ingredients for explaining the origins of transitional disks. First, multiple planets can clear wide inner holes where single planets open only narrow gaps. Second, the confined, non-axisymmetric accretion flows produced by multiple planets provide a way for an arbitrary amount of mass transfer to occur through an apparently optically thin hole without overproducing infrared excess flux. Rather than assuming that the gas and dust in the hole are evenly and axisymmetrically distributed, one can construct an inner hole with apparently optically thin infrared fluxes by covering a macroscopic fraction of the hole's surface area with locally optically thick tidal tails. We also establish that other clearing mechanisms, such as photoevaporation, cannot explain our subset of accreting transitional disks with wide holes. Transitional disks are therefore high-value targets for observational searches for young planetary systems.

Deformation and Life Analysis of Composite Flywheel Disk and Multi-disk Systems

Science.gov (United States)

Arnold, S. M.; Saleeb, A. F.; AlZoubi, N. R.

2001-01-01

In this study an attempt is made to put into perspective the problem of a rotating disk, be it a single disk or a number of concentric disks forming a unit. An analytical model capable of performing an elastic stress analysis for single/multiple, annular/solid, anisotropic/isotropic disk systems, subjected to both pressure surface tractions, body forces (in the form of temperature-changes and rotation fields) and interfacial misfits is derived and discussed. Results of an extensive parametric study are presented to clearly define the key design variables and their associated influence. In general the important parameters were identified as misfit, mean radius, thickness, material property and/or load gradation, and speed; all of which must be simultaneously optimized to achieve the "best" and most reliable design. Also, the important issue of defining proper performance/merit indices (based on the specific stored energy), in the presence of multiaxiality and material anisotropy is addressed. These merit indices are then utilized to discuss the difference between flywheels made from PMC and TMC materials with either an annular or solid geometry. Finally two major aspects of failure analysis, that is the static and cyclic limit (burst) speeds are addressed. In the case of static limit loads, upper, lower, and out-of-plane bounds for disks with constant thickness are presented for both the case of internal pressure loading (as one would see in a hydroburst test) and pure rotation (as in the case of a free spinning disk). The results (interaction diagrams) are displayed graphically in designer friendly format. For the case of fatigue, a representative fatigue/life master curve is illustrated in which the normalized limit speed versus number of applied cycles is given for a cladded TMC disk application.

The properties of the disk system of globular clusters

Science.gov (United States)

Armandroff, Taft E.

1989-01-01

A large refined data sample is used to study the properties and origin of the disk system of globular clusters. A scale height for the disk cluster system of 800-1500 pc is found which is consistent with scale-height determinations for samples of field stars identified with the Galactic thick disk. A rotational velocity of 193 + or - 29 km/s and a line-of-sight velocity dispersion of 59 + or - 14 km/s have been found for the metal-rich clusters.

TRANSITION DISK CHEMISTRY AND FUTURE PROSPECTS WITH ALMA

International Nuclear Information System (INIS)

Cleeves, L. Ilsedore; Bergin, Edwin A.; Bethell, Thomas J.; Calvet, Nuria; Fogel, Jeffrey K. J.; Sauter, Jürgen; Wolf, Sebastian

2011-01-01

We explore the chemical structure of a disk that contains a large central gap of R ∼ 45 AU, as is commonly seen in transitional disk systems. In our chemical model of a disk with a cleared inner void, the midplane becomes revealed to the central star so that it is directly irradiated. The midplane material at the truncation radius is permissive to reprocessed optical heating radiation, but opaque to the photodissociating ultraviolet, creating an environment abundant in gas-phase molecules. Thus the disk midplane, which would otherwise for a full disk be dominated by near complete heavy element freeze-out, should become observable in molecular emission. If this prediction is correct this has exciting prospects for observations with the Atacama Large Millimeter/Submillimeter Array, as the inner transition region should thus be readily detected and resolved, especially using high-J rotational transitions excited in the high density midplane gas. Therefore, such observations will potentially provide us with a direct probe of the physics and chemistry at this actively evolving interface.

TRANSITION DISK CHEMISTRY AND FUTURE PROSPECTS WITH ALMA

Energy Technology Data Exchange (ETDEWEB)

Cleeves, L. Ilsedore; Bergin, Edwin A.; Bethell, Thomas J.; Calvet, Nuria; Fogel, Jeffrey K. J. [Department of Astronomy, University of Michigan, 825 Dennison Building, 500 Church St, Ann Arbor, MI 48109 (United States); Sauter, Juergen; Wolf, Sebastian [Christian-Albrechts-Universitaet zu Kiel, Institut fuer Theoretische Physik und Astrophysik, Leibnizstr. 15, 24098 Kiel (Germany)

2011-12-10

We explore the chemical structure of a disk that contains a large central gap of R {approx} 45 AU, as is commonly seen in transitional disk systems. In our chemical model of a disk with a cleared inner void, the midplane becomes revealed to the central star so that it is directly irradiated. The midplane material at the truncation radius is permissive to reprocessed optical heating radiation, but opaque to the photodissociating ultraviolet, creating an environment abundant in gas-phase molecules. Thus the disk midplane, which would otherwise for a full disk be dominated by near complete heavy element freeze-out, should become observable in molecular emission. If this prediction is correct this has exciting prospects for observations with the Atacama Large Millimeter/Submillimeter Array, as the inner transition region should thus be readily detected and resolved, especially using high-J rotational transitions excited in the high density midplane gas. Therefore, such observations will potentially provide us with a direct probe of the physics and chemistry at this actively evolving interface.

Percolation of binary disk systems: Modeling and theory

International Nuclear Information System (INIS)

Meeks, Kelsey; Pantoya, Michelle L.

2017-01-01

The dispersion and connectivity of particles with a high degree of polydispersity is relevant to problems involving composite material properties and reaction decomposition prediction and has been the subject of much study in the literature. This paper utilizes Monte Carlo models to predict percolation thresholds for a two-dimensional systems containing disks of two different radii. Monte Carlo simulations and spanning probability are used to extend prior models into regions of higher polydispersity than those previously considered. A correlation to predict the percolation threshold for binary disk systems is proposed based on the extended dataset presented in this work and compared to previously published correlations. Finally, a set of boundary conditions necessary for a good fit is presented, and a condition for maximizing percolation threshold for binary disk systems is suggested.

RESOLVED CO GAS INTERIOR TO THE DUST RINGS OF THE HD 141569 DISK

Energy Technology Data Exchange (ETDEWEB)

Flaherty, Kevin M.; Hughes, A. Meredith; Zachary, Julia [Van Vleck Observatory, Astronomy Department, Wesleyan University, 96 Foss Hill Drive, Middletown, CT 06459 (United States); Andrews, Sean M.; Qi, Chunhua; Wilner, David J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Boley, Aaron C.; White, Jacob A. [Department of Physics and Astronomy, University of British Columbia, Vancouver BC (Canada); Harney, Will [Department of Physics and Astronomy, Union College, Schenectady, NY (United States)

2016-02-10

The disk around HD 141569 is one of a handful of systems whose weak infrared emission is consistent with a debris disk, but still has a significant reservoir of gas. Here we report spatially resolved millimeter observations of the CO(3-2) and CO(1-0) emission as seen with the Submillimeter Array and CARMA. We find that the excitation temperature for CO is lower than expected from cospatial blackbody grains, similar to previous observations of analogous systems, and derive a gas mass that lies between that of gas-rich primordial disks and gas-poor debris disks. The data also indicate a large inner hole in the CO gas distribution and an outer radius that lies interior to the outer scattered light rings. This spatial distribution, with the dust rings just outside the gaseous disk, is consistent with the expected interactions between gas and dust in an optically thin disk. This indicates that gas can have a significant effect on the location of the dust within debris disks.

FORMATION OF MULTIPLE-SATELLITE SYSTEMS FROM LOW-MASS CIRCUMPLANETARY PARTICLE DISKS

International Nuclear Information System (INIS)

Hyodo, Ryuki; Ohtsuki, Keiji; Takeda, Takaaki

2015-01-01

Circumplanetary particle disks would be created in the late stage of planetary formation either by impacts of planetary bodies or disruption of satellites or passing bodies, and satellites can be formed by accretion of disk particles spreading across the Roche limit. Previous N-body simulation of lunar accretion focused on the formation of single-satellite systems from disks with large disk-to-planet mass ratios, while recent models of the formation of multiple-satellite systems from disks with smaller mass ratios do not take account of gravitational interaction between formed satellites. In the present work, we investigate satellite accretion from particle disks with various masses, using N-body simulation. In the case of accretion from somewhat less massive disks than the case of lunar accretion, formed satellites are not massive enough to clear out the disk, but can become massive enough to gravitationally shepherd the disk outer edge and start outward migration due to gravitational interaction with the disk. When the radial location of the 2:1 mean motion resonance of the satellite reaches outside the Roche limit, the second satellite can be formed near the disk outer edge, and then the two satellites continue outward migration while being locked in the resonance. Co-orbital satellites are found to be occasionally formed on the orbit of the first satellite. Our simulations also show that stochastic nature involved in gravitational interaction and collision between aggregates in the tidal environment can lead to diversity in the final mass and orbital architecture, which would be expected in satellite systems of exoplanets

Identifying Likely Disk-hosting M dwarfs with Disk Detective

Science.gov (United States)

Silverberg, Steven; Wisniewski, John; Kuchner, Marc J.; Disk Detective Collaboration

2018-01-01

M dwarfs are critical targets for exoplanet searches. Debris disks often provide key information as to the formation and evolution of planetary systems around higher-mass stars, alongside the planet themselves. However, less than 300 M dwarf debris disks are known, despite M dwarfs making up 70% of the local neighborhood. The Disk Detective citizen science project has identified over 6000 new potential disk host stars from the AllWISE catalog over the past three years. Here, we present preliminary results of our search for new disk-hosting M dwarfs in the survey. Based on near-infrared color cuts and fitting stellar models to photometry, we have identified over 500 potential new M dwarf disk hosts, nearly doubling the known number of such systems. In this talk, we present our methodology, and outline our ongoing work to confirm systems as M dwarf disks.

The Owens Valley Millimeter Array

International Nuclear Information System (INIS)

Padin, S.; Scott, S.L.; Woody, D.P.; Scoville, N.Z.; Seling, T.V.

1991-01-01

The telescopes and signal processing systems of the Owens Valley Millimeter Array are considered, and improvements in the sensitivity and stability of the instrument are characterized. The instrument can be applied to map sources in the 85 to 115 GHz and 218 to 265 GHz bands with a resolution of about 1 arcsec in the higher frequency band. The operation of the array is fully automated. The current scientific programs for the array encompass high-resolution imaging of protoplanetary/protostellar disk structures, observations of molecular cloud complexes associated with spiral structure in nearby galaxies, and observations of molecular structures in the nuclei of spiral and luminous IRAS galaxies. 9 refs

Implementing Journaling in a Linux Shared Disk File System

Science.gov (United States)

Preslan, Kenneth W.; Barry, Andrew; Brassow, Jonathan; Cattelan, Russell; Manthei, Adam; Nygaard, Erling; VanOort, Seth; Teigland, David; Tilstra, Mike; O'Keefe, Matthew;

The Circumstellar Disk and Asymmetric Outflow of the EX Lup Outburst System

Science.gov (United States)

Hales, A. S.; Pérez, S.; Saito, M.; Pinte, C.; Knee, L. B. G.; de Gregorio-Monsalvo, I.; Dent, B.; López, C.; Plunkett, A.; Cortés, P.; Corder, S.; Cieza, L.

2018-06-01

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations at 0.″3 resolution of EX Lup, the prototype of the EXor class of outbursting pre-main-sequence stars. The circumstellar disk of EX Lup is resolved for the first time in 1.3 mm continuum emission and in the J = 2–1 spectral line of three isotopologues of CO. At the spatial resolution and sensitivity achieved, the compact dust continuum disk shows no indications of clumps, fragments, or asymmetries above the 5σ level. Radiative transfer modeling constrains the characteristic radius of the dust disk to 23 au and the total dust mass to 1.0 × 10‑4 M ⊙ (33 M ⊕), similar to other EXor sources. The 13CO and C18O line emissions trace the disk rotation and are used to constrain the disk geometry, kinematics, and a total gas disk mass of 5.1 × 10‑4 M ⊙. The 12CO emission extends out to a radius of 200 au and is asymmetric, with one side deviating from Keplerian rotation. We detect blueshifted, 12CO arc-like emission located 0.″8 to the northwest and spatially disconnected from the disk emission. We interpret this extended structure as the brightened walls of a cavity excavated by an outflow, which are more commonly seen in FUor sources. Such outflows have also been seen in the borderline FU/EXor object V1647 Ori, but not toward EXor objects. Our detection provides evidence that the outflow phenomenon persists into the EXor phase, suggesting that FUor and EXor objects are a continuous population in which outflow activity declines with age, with transitional objects such as EX Lup and V1647 Ori.

Brown dwarf disks with ALMA

Energy Technology Data Exchange (ETDEWEB)

Ricci, L.; Isella, A. [Department of Astronomy, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States); Testi, L.; De Gregorio-Monsalvo, I. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany); Natta, A. [INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze (Italy); Scholz, A., E-mail: lricci@astro.caltech.edu [School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland)

2014-08-10

We present Atacama Large Millimeter/submillimeter Array continuum and spectral line data at 0.89 mm and 3.2 mm for three disks surrounding young brown dwarfs and very low mass stars in the Taurus star forming region. Dust thermal emission is detected and spatially resolved for all the three disks, while CO(J = 3-2) emission is seen in two disks. We analyze the continuum visibilities and constrain the disks' physical structure in dust. The results of our analysis show that the disks are relatively large; the smallest one has an outer radius of about 70 AU. The inferred disk radii, radial profiles of the dust surface density, and disk to central object mass ratios lie within the ranges found for disks around more massive young stars. We derive from our observations the wavelength dependence of the millimeter dust opacity. In all the three disks, data are consistent with the presence of grains with at least millimeter sizes, as also found for disks around young stars, and confirm that the early stages of the solid growth toward planetesimals occur also around very low-mass objects. We discuss the implications of our findings on models of solids evolution in protoplanetary disks, the main mechanisms proposed for the formation of brown dwarfs and very low-mass stars, as well as the potential of finding rocky and giant planets around very low-mass objects.

Replacing HDDs with Solid-State Flash Disks in PXIbus-Based Systems

International Nuclear Information System (INIS)

Zhao, Z W; Zeng, L

2006-01-01

New security features, constantly decreasing prices, solid-state Flash disks are becoming a popular alternative for replacing failure-prone mechanical Hard Disk Drives (HDDs) in PXIbus-based military systems. The key component in high-capacity solid-state Flash disks is NAND Flash, but with a specification that shows only 100,000-300,000 write/erase cycles, engineers may be concerned that the lifetime of Flash disks cannot meet their application requirements. With the right Flash management, Flash disks are able to provide the reliability and endurance that military applications need

DISK IMAGING SURVEY OF CHEMISTRY WITH SMA. II. SOUTHERN SKY PROTOPLANETARY DISK DATA AND FULL SAMPLE STATISTICS

International Nuclear Information System (INIS)

Oeberg, Karin I.; Qi Chunhua; Andrews, Sean M.; Espaillat, Catherine; Wilner, David J.; Fogel, Jeffrey K. J.; Bergin, Edwin A.; Pascucci, Ilaria; Kastner, Joel H.

2011-01-01

This is the second in a series of papers based on data from DISCS, a Submillimeter Array observing program aimed at spatially and spectrally resolving the chemical composition of 12 protoplanetary disks. We present data on six Southern sky sources-IM Lup, SAO 206462 (HD 135344b), HD 142527, AS 209, AS 205, and V4046 Sgr-which complement the six sources in the Taurus star-forming region reported previously. CO 2-1 and HCO + 3-2 emission are detected and resolved in all disks and show velocity patterns consistent with Keplerian rotation. Where detected, the emission from DCO + 3-2, N 2 H + 3-2, H 2 CO 3 03 - 2 02 and 4 14 - 3 13 , HCN 3-2, and CN 2 33/4/2 - 1 22/3/1 are also generally spatially resolved. The detection rates are highest toward the M and K stars, while the F star SAO 206462 has only weak CN and HCN emission, and H 2 CO alone is detected toward HD 142527. These findings together with the statistics from the previous Taurus disks support the hypothesis that high detection rates of many small molecules depend on the presence of a cold and protected disk midplane, which is less common around F and A stars compared to M and K stars. Disk-averaged variations in the proposed radiation tracer CN/HCN are found to be small, despite a two orders of magnitude range of spectral types and accretion rates. In contrast, the resolved images suggest that the CN/HCN emission ratio varies with disk radius in at least two of the systems. There are no clear observational differences in the disk chemistry between the classical/full T Tauri disks and transitional disks. Furthermore, the observed line emission does not depend on the measured accretion luminosities or the number of infrared lines detected, which suggests that the chemistry outside of 100 AU is not coupled to the physical processes that drive the chemistry in the innermost few AU.

Transport Coefficients for dense hard-disk systems

NARCIS (Netherlands)

Garcia-Rojo, R.; Luding, Stefan; Brey, J. Javier; Ooms, G.; Hoogendoorn, C.J.

2007-01-01

A study of the transport coefficients of a system of elastic hard disks, based on the use of Helfand-Einstein expressions is reported. The pressure, the viscosity, and the heat conductivity are examined for different density and system-size. While most transport coefficients agree with Enskog theory

A RING/DISK/OUTFLOW SYSTEM ASSOCIATED WITH W51 NORTH: A VERY MASSIVE STAR IN THE MAKING

International Nuclear Information System (INIS)

Zapata, Luis A.; Schilke, Peter; Menten, Karl; Ho, Paul T. P.; Rodriguez, Luis F.; Palau, Aina; Garrod, Robin T.

2009-01-01

Sensitive and high angular resolution (∼0.''4) SO 2 [22 2,20 → 22 1,21 ] and SiO[5 → 4] line and 1.3 and 7 mm continuum observations made with the Submillimeter Array (SMA) and the Very Large Array (VLA) toward the young massive cluster W51 IRS2 are presented. We report the presence of a large (of about 3000 AU) and massive (40 M sun ) dusty circumstellar disk and a hot gas molecular ring around a high-mass protostar or a compact small stellar system associated with W51 North. The simultaneous observations of the silicon monoxide molecule, an outflow gas tracer, further revealed a massive (200 M sun ) and collimated (∼14 0 ) outflow nearly perpendicular to the dusty and molecular structures suggesting thus the presence of a single very massive protostar with a bolometric luminosity on the order of 10 5 L sun . A molecular hybrid local thermodynamic equilibrium model of a Keplerian and infalling disk with an inner cavity and a central stellar mass of more than 60 M sun agrees well with the SO 2 [22 2,20 → 22 1,21 ] line observations. Finally, these results suggest that mechanisms, such as mergers of low- and intermediate-mass stars, might not be necessary for forming very massive stars.

THE NATURE OF TRANSITION CIRCUMSTELLAR DISKS. II. SOUTHERN MOLECULAR CLOUDS

Energy Technology Data Exchange (ETDEWEB)

Romero, Gisela A.; Schreiber, Matthias R.; Rebassa-Mansergas, Alberto [Departamento de Fisica y Astronomia, Universidad de Valparaiso, Valparaiso (Chile); Cieza, Lucas A. [Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); Merin, Bruno [Herschel Science Centre, ESAC (ESA), P.O. Box 78, 28691 Villanueva de la Canada, Madrid (Spain); Smith Castelli, Analia V. [Consejo Nacional de Investigaciones Cientificas y Tecnicas, Rivadavia 1917, C1033AAJ Buenos Aires (Argentina); Allen, Lori E. [Department of Astronomy, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065 (United States); Morrell, Nidia [Las Campanas Observatory, Carnegie Observatories, Casilla 601, La Serena (Chile)

2012-04-10

Transition disk objects are pre-main-sequence stars with little or no near-IR excess and significant far-IR excess, implying inner opacity holes in their disks. Here we present a multifrequency study of transition disk candidates located in Lupus I, III, IV, V, VI, Corona Australis, and Scorpius. Complementing the information provided by Spitzer with adaptive optics (AO) imaging (NaCo, VLT), submillimeter photometry (APEX), and echelle spectroscopy (Magellan, Du Pont Telescopes), we estimate the multiplicity, disk mass, and accretion rate for each object in our sample in order to identify the mechanism potentially responsible for its inner hole. We find that our transition disks show a rich diversity in their spectral energy distribution morphology, have disk masses ranging from {approx}<1 to 10 M{sub JUP}, and accretion rates ranging from {approx}<10{sup -11} to 10{sup -7.7} M{sub Sun} yr{sup -1}. Of the 17 bona fide transition disks in our sample, three, nine, three, and two objects are consistent with giant planet formation, grain growth, photoevaporation, and debris disks, respectively. Two disks could be circumbinary, which offers tidal truncation as an alternative origin of the inner hole. We find the same heterogeneity of the transition disk population in Lupus III, IV, and Corona Australis as in our previous analysis of transition disks in Ophiuchus while all transition disk candidates selected in Lupus V, VI turned out to be contaminating background asymptotic giant branch stars. All transition disks classified as photoevaporating disks have small disk masses, which indicates that photoevaporation must be less efficient than predicted by most recent models. The three systems that are excellent candidates for harboring giant planets potentially represent invaluable laboratories to study planet formation with the Atacama Large Millimeter/Submillimeter Array.

THE NATURE OF TRANSITION CIRCUMSTELLAR DISKS. II. SOUTHERN MOLECULAR CLOUDS

International Nuclear Information System (INIS)

Romero, Gisela A.; Schreiber, Matthias R.; Rebassa-Mansergas, Alberto; Cieza, Lucas A.; Merín, Bruno; Smith Castelli, Analía V.; Allen, Lori E.; Morrell, Nidia

2012-01-01

Transition disk objects are pre-main-sequence stars with little or no near-IR excess and significant far-IR excess, implying inner opacity holes in their disks. Here we present a multifrequency study of transition disk candidates located in Lupus I, III, IV, V, VI, Corona Australis, and Scorpius. Complementing the information provided by Spitzer with adaptive optics (AO) imaging (NaCo, VLT), submillimeter photometry (APEX), and echelle spectroscopy (Magellan, Du Pont Telescopes), we estimate the multiplicity, disk mass, and accretion rate for each object in our sample in order to identify the mechanism potentially responsible for its inner hole. We find that our transition disks show a rich diversity in their spectral energy distribution morphology, have disk masses ranging from ∼ JUP , and accretion rates ranging from ∼ –11 to 10 –7.7 M ☉ yr –1 . Of the 17 bona fide transition disks in our sample, three, nine, three, and two objects are consistent with giant planet formation, grain growth, photoevaporation, and debris disks, respectively. Two disks could be circumbinary, which offers tidal truncation as an alternative origin of the inner hole. We find the same heterogeneity of the transition disk population in Lupus III, IV, and Corona Australis as in our previous analysis of transition disks in Ophiuchus while all transition disk candidates selected in Lupus V, VI turned out to be contaminating background asymptotic giant branch stars. All transition disks classified as photoevaporating disks have small disk masses, which indicates that photoevaporation must be less efficient than predicted by most recent models. The three systems that are excellent candidates for harboring giant planets potentially represent invaluable laboratories to study planet formation with the Atacama Large Millimeter/Submillimeter Array.

The design of the high energy physics massive data migration system

International Nuclear Information System (INIS)

Shi Jingyan; Zang Dongsong; Cheng Yaodong

2010-01-01

High energy physics is the typical data massive computing application due to its huge experiment data. For example, the amount of BESⅢ experiment data reaches to 4PB. Hierarchical storage system is adapted for the application in which disk array and tape library are used. It is quite important to migrate massive data from disk array to tape library. The article introduces the design and realization for the high performance data migration system between disk array and tape library. Besides, the system provides web page as the friendly user interface. (authors)

Chunking of Large Multidimensional Arrays

Energy Technology Data Exchange (ETDEWEB)

Rotem, Doron; Otoo, Ekow J.; Seshadri, Sridhar

2007-02-28

Data intensive scientific computations as well on-lineanalytical processing applications as are done on very large datasetsthat are modeled as k-dimensional arrays. The storage organization ofsuch arrays on disks is done by partitioning the large global array intofixed size hyper-rectangular sub-arrays called chunks or tiles that formthe units of data transfer between disk and memory. Typical queriesinvolve the retrieval of sub-arrays in a manner that accesses all chunksthat overlap the query results. An important metric of the storageefficiency is the expected number of chunks retrieved over all suchqueries. The question that immediately arises is "what shapes of arraychunks give the minimum expected number of chunks over a query workload?"In this paper we develop two probabilistic mathematical models of theproblem and provide exact solutions using steepest descent and geometricprogramming methods. Experimental results, using synthetic workloads onreal life data sets, show that our chunking is much more efficient thanthe existing approximate solutions.

Water Masers and Accretion Disks in Galactic Nuclei

Science.gov (United States)

Greenhill, L. J.

2005-12-01

There are over 50 sources of H2O maser emission in type-2 active galactic nuclei, a large fraction discovered in the last two years. Interferometer maps of water masers are presently the only means by which structures ⪉ 1 pc from massive black holes can be mapped directly, which is particularly important for type-2 systems because edge-on orientation and obscuration complicate study by other means. Investigations of several sources have demonstrated convincingly that the maser emission traces warped accretion disks 0.1 to 1 pc from central engines of order 106-108 M⊙. The same may be true for almost half the known (but unmapped) sources, based on spectral characteristics consistent with emission from edge-on accretion disks. Mapping these sources is a high priority. Study of most recently discovered masers requires long baseline arrays that include 100-m class apertures and would benefit from aggregate bit rates on the order of 1 gigabit per second. The Square Kilometer Array should provide an order of magnitude boost in mapping sensitivity, but outrigger antennas will be needed to achieve necesssary angular resolutions, as may be space-borne antennas.

Finite Element Analysis of Flexural Vibrations in Hard Disk Drive Spindle Systems

Science.gov (United States)

LIM, SEUNGCHUL

2000-06-01

This paper is concerned with the flexural vibration analysis of the hard disk drive (HDD) spindle system by means of the finite element method. In contrast to previous research, every system component is here analytically modelled taking into account its structural flexibility and also the centrifugal effect particularly on the disk. To prove the effectiveness and accuracy of the formulated models, commercial HDD systems with two and three identical disks are selected as examples. Then their major natural modes are computed with only a small number of element meshes as the shaft rotational speed is varied, and subsequently compared with the existing numerical results obtained using other methods and newly acquired experimental ones. Based on such a series of studies, the proposed method can be concluded as a very promising tool for the design of HDDs and various other high-performance computer disk drives such as floppy disk drives, CD ROM drives, and their variations having spindle mechanisms similar to those of HDDs.

The Chemistry of Protostellar Jet-Disk Systems

Science.gov (United States)

Codella, Claudio

2017-11-01

The birth of a Sun-like star is a complex game played by several participants whose respective roles are not yet entirely clear. On the one hand, the star-to-be accretes matter from a collapsing envelope. The gravitational energy released in the process heats up the material surrounding the protostar, creating warm regions enriched by interstellar complex organic molecules (iCOMs, at least 6 atoms) called hot-corinos. On the other hand, the presence of angular momentum and magnetic fields leads to two consequences: (i) the formation of circumstellar disks; and (ii) substantial episodes of matter ejection, as e.g. collimated jets. Thanks to the combination of the high-sensitivities and high-angular resolu- tions provided by the advent of new telescopes such as ALMA and NOEMA, it is now possible to image in details the earliest stages of the Sun-like star formation, thus inspecting the inner ( effects connected with the accreting disk. In other words, it is time to study the protostellar jet-disk system as a whole. Several still unanswered questions can be addressed. What is the origin of the chemically enriched hot corinos: are they jet-driven shocked regions? What is the origin of the ejections: are they due to disk or stellar winds? Shocks are precious tool to attack these questions, given they enrich the gas phase with the species deposited onto the dust mantles and/or locked in the refractory dust cores. Basically, we have to deal with two kind of shocks: (i) high-velocity shocks produced by protostellar jets, and (ii) slow accretion shocks located close to the centrifugal barrier of the accretion disks. Both shocks are factories of iCOMs, which can be then efficiently used to follow both the kinematics and the chemistry of the inner protostellar systems. With this in mind, we will discuss recent results obtained in the framework of different observational campaigns at mm and sub-mm wavelengths.

Extraordinary light transmission through opaque thin metal film with subwavelength holes blocked by metal disks.

Science.gov (United States)

Li, Wen-Di; Hu, Jonathan; Chou, Stephen Y

2011-10-10

We observed that when subwavelength-sized holes in an optically opaque metal film are completely covered by opaque metal disks larger than the holes, the light transmission through the holes is not reduced, but rather enhanced. Particularly we report (i) the observation of light transmission through the holes blocked by the metal disks up to 70% larger than the unblocked holes; (ii) the observation of tuning the light transmission by varying the coupling strength between the blocking disks and the hole array, or by changing the size of the disks and holes; (iii) the observation and simulation that the metal disk blocker can improve light coupling from free space to a subwavelength hole; and (iv) the simulation that shows the light transmission through subwavelength holes can be enhanced, even though the gap between the disk and the metal film is partially connected with a metal. We believe these finding should have broad and significant impacts and applications to optical systems in many fields.

STEADY STATE DUST DISTRIBUTIONS IN DISK VORTICES: OBSERVATIONAL PREDICTIONS AND APPLICATIONS TO TRANSITIONAL DISKS

International Nuclear Information System (INIS)

Lyra, Wladimir; Lin, Min-Kai

2013-01-01

The Atacama Large Millimeter Array has returned images of transitional disks in which large asymmetries are seen in the distribution of millimeter sized dust in the outer disk. The explanation in vogue borrows from the vortex literature and suggests that these asymmetries are the result of dust trapping in giant vortices, excited via Rossby wave instabilities at planetary gap edges. Due to the drag force, dust trapped in vortices will accumulate in the center and diffusion is needed to maintain a steady state over the lifetime of the disk. While previous work derived semi-analytical models of the process, in this paper we provide analytical steady-steady solutions. Exact solutions exist for certain vortex models. The solution is determined by the vortex rotation profile, the gas scale height, the vortex aspect ratio, and the ratio of dust diffusion to gas-dust friction. In principle, all of these quantities can be derived from observations, which would validate the model and also provide constrains on the strength of the turbulence inside the vortex core. Based on our solution, we derive quantities such as the gas-dust contrast, the trapped dust mass, and the dust contrast at the same orbital location. We apply our model to the recently imaged Oph IRS 48 system, finding values within the range of the observational uncertainties

Near-Infrared Imaging Polarimetry of Inner Region of GG Tau A Disk

Science.gov (United States)

Yang, Yi; Hashimoto, Jun; Hayashi, Saeko S.; Tamura, Motohide; Mayama, Satoshi; Rafikov, Roman; Akiyama, Eiji; Carson, Joseph C.; Janson, Markus; Kwon, Jungmi;

NIRCam Coronagraphic Observations of Disks and Planetary Systems

Science.gov (United States)

Beichman, Charles A.; Ygouf, Marie; Gaspar, Andras; NIRCam Science Team

2017-06-01

The NIRCam coronagraph offers a dramatic increase in sensitivity at wavelengths of 3-5 um where young planets are brightest. While large ground-based telescopes with Extreme Adaptive Optics have an advantage in inner working angle, NIRCam's sensitivity will allow high precision photometry for known planets and searches for planets with masses below that of Saturn. For debris disk science NIRCam observations will address the scattering properties of dust, look for evidence of ices and tholins, and search for planets which affect the structure of the disk itself.The NIRCam team's GTO program includes medium-band filter observations of known young planets having 1-5 Jupiter masses. A collaborative program with the MIRI team will provide coronagraphic observations at longer wavelengths. The combined dataset will yield the exoplanet’s total luminosity and effective temperature, an estimate of the initial entropy of the newly-formed planet, and the retrieval of atmospheric properties.The program will also make deep searches for lower mass planets toward known planetary systems, nearby young M stars and debris disk systems. Achievable mass limits range from ~1 Jupiter mass beyond 20 AU for the brightest A stars to perhaps a Uranus mass within 10 AU for the closest M stars.We will discuss details of the coronagraphic program for both the exoplanet and debris disk cases with an emphasis on using APT to optimize the observations of target and reference stars.

System Identification of Mistuned Bladed Disks from Traveling Wave Response Measurements

Science.gov (United States)

Feiner, D. M.; Griffin, J. H.; Jones, K. W.; Kenyon, J. A.; Mehmed, O.; Kurkov, A. P.

2003-01-01

A new approach to modal analysis is presented. By applying this technique to bladed disk system identification methods, one can determine the mistuning in a rotor based on its response to a traveling wave excitation. This allows system identification to be performed under rotating conditions, and thus expands the applicability of existing mistuning identification techniques from integrally bladed rotors to conventional bladed disks.

DETECTION OF N{sub 2}D{sup +} IN A PROTOPLANETARY DISK

Energy Technology Data Exchange (ETDEWEB)

Huang, Jane; Öberg, Karin I. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2015-08-20

Observations of deuterium fractionation in the solar system, and in interstellar and circumstellar material, are commonly used to constrain the formation environment of volatiles. Toward protoplanetary disks, this approach has been limited by the small number of detected deuterated molecules, i.e., DCO{sup +} and DCN. Based on ALMA Cycle 2 observations toward the disk around the T Tauri star AS 209, we report the first detection of N{sub 2}D{sup +} (J = 3–2) in a protoplanetary disk. These data are used together with previous Submillimeter Array observations of N{sub 2}H{sup +} (J = 3–2) to estimate a disk-averaged D/H ratio of 0.3–0.5, an order of magnitude higher than disk-averaged ratios previously derived for DCN/HCN and DCO{sup +}/HCO{sup +} around other young stars. The high fractionation in N{sub 2}H{sup +} is consistent with model predictions. The presence of abundant N{sub 2}D{sup +} toward AS 209 also suggests that N{sub 2}D{sup +} and the N{sub 2}D{sup +}/N{sub 2}H{sup +} ratio can be developed into effective probes of deuterium chemistry, kinematics, and ionization processes outside the CO snow line of disks.

Development of nondestructive system for detecting the cracks in KTX brake disk using Rayleigh wave

International Nuclear Information System (INIS)

Kim, Min Soo; Lee, Ho Yong; Yeom, Yun Taek; Park, Jin Hyun; Song, Sung Jing; Kim, Hak Joon; Kwon, Sung Duck

2017-01-01

Recently, KTX (Korean Train Express) train stoppage accidents were mainly caused by malfunctioning equipment, aging and cracking of railway vehicles, crack breakages of brake disks, and breakages of brake disks. Breakage of brake disk can cause large-scale casualties such as high-speed collision and concern about derailment by hitting lower axle and wheel. Therefore, in this study, a brake disk with solid and ventilation type, which is the brake disk of a KTX train was modeled, and a dynamometer system was constructed to operate the disk. A Rayleigh wave was used to inspect the surface of the brake disk. An ultrasonic inspection module was developed for the brake disk by using a local immersion method due to the difficulty involved in ultrasonic inspection using an existing immersion method. In addition, the surface defects of the brake disk were evaluated using a dynamometer mock-up system and an ultrasonic inspection module of the brake disk

Development of nondestructive system for detecting the cracks in KTX brake disk using Rayleigh wave

Energy Technology Data Exchange (ETDEWEB)

Kim, Min Soo; Lee, Ho Yong [Korea Railroad Research Institute, Uiwang (Korea, Republic of); Yeom, Yun Taek; Park, Jin Hyun; Song, Sung Jing; Kim, Hak Joon [Dept. of Mechanical Engineering, Sungkyunkwan University, Suwon (Korea, Republic of); Kwon, Sung Duck [Dept. of Physics, Andong National University, Andong (Korea, Republic of)

2017-02-15

Recently, KTX (Korean Train Express) train stoppage accidents were mainly caused by malfunctioning equipment, aging and cracking of railway vehicles, crack breakages of brake disks, and breakages of brake disks. Breakage of brake disk can cause large-scale casualties such as high-speed collision and concern about derailment by hitting lower axle and wheel. Therefore, in this study, a brake disk with solid and ventilation type, which is the brake disk of a KTX train was modeled, and a dynamometer system was constructed to operate the disk. A Rayleigh wave was used to inspect the surface of the brake disk. An ultrasonic inspection module was developed for the brake disk by using a local immersion method due to the difficulty involved in ultrasonic inspection using an existing immersion method. In addition, the surface defects of the brake disk were evaluated using a dynamometer mock-up system and an ultrasonic inspection module of the brake disk.

Design and Optimization Method of a Two-Disk Rotor System

Science.gov (United States)

Huang, Jingjing; Zheng, Longxi; Mei, Qing

2016-04-01

An integrated analytical method based on multidisciplinary optimization software Isight and general finite element software ANSYS was proposed in this paper. Firstly, a two-disk rotor system was established and the mode, humorous response and transient response at acceleration condition were analyzed with ANSYS. The dynamic characteristics of the two-disk rotor system were achieved. On this basis, the two-disk rotor model was integrated to the multidisciplinary design optimization software Isight. According to the design of experiment (DOE) and the dynamic characteristics, the optimization variables, optimization objectives and constraints were confirmed. After that, the multi-objective design optimization of the transient process was carried out with three different global optimization algorithms including Evolutionary Optimization Algorithm, Multi-Island Genetic Algorithm and Pointer Automatic Optimizer. The optimum position of the two-disk rotor system was obtained at the specified constraints. Meanwhile, the accuracy and calculation numbers of different optimization algorithms were compared. The optimization results indicated that the rotor vibration reached the minimum value and the design efficiency and quality were improved by the multidisciplinary design optimization in the case of meeting the design requirements, which provided the reference to improve the design efficiency and reliability of the aero-engine rotor.

A deeply embedded young protoplanetary disk around L1489 IRS observed by the Submillimeter Array

DEFF Research Database (Denmark)

Brinch, C.; Crapsi, A.; Jørgensen, J. K.

2007-01-01

Context. Circumstellar disks are expected to form early in the process that leads to the formation of a young star, during the collapse of the dense molecular cloud core. Currently, it is not well understood at what stage of the collapse the disk is formed or how it subsequently evolves. Aims. We....... This misalignment of the angular momentum axes may be caused by a gradient within the angular momentum in the parental cloud, or if L1489 IRS is a binary system rather than just a single star. In the latter case, future observations looking for variability at sub-arcsecond scales may be able to constrain...

ALMA Dust Polarization Observations of Two Young Edge-on Protostellar Disks

Science.gov (United States)

Lee, Chin-Fei; Li, Zhi-Yun; Ching, Tao-Chung; Lai, Shih-Ping; Yang, Haifeng

2018-02-01

Polarized emission is detected in two young nearly edge-on protostellar disks in 343 GHz continuum at ∼50 au (∼0.″12) resolution with Atacama Large Millimeter/submillimeter Array. One disk is in HH 212 (Class 0) and the other in the HH 111 (early Class I) protostellar system. The polarization fraction is ∼1%. The disk in HH 212 has a radius of ∼60 au. The emission is mainly detected from the nearside of the disk. The polarization orientations are almost perpendicular to the disk major axis, consistent with either self-scattering or emission by grains aligned with a poloidal field around the outer edge of the disk because of the optical depth effect and temperature gradient; the presence of a poloidal field would facilitate the launching of a disk wind, for which there is already tentative evidence in the same source. The disk of HH 111 VLA 1 has a larger radius of ∼220 au and is thus more resolved. The polarization orientations are almost perpendicular to the disk major axis in the nearside, but more along the major axis in the farside, forming roughly half of an elliptical pattern there. It appears that toroidal and poloidal magnetic field may explain the polarization on the near and far sides of the disk, respectively. However, it is also possible that the polarization is due to self-scattering. In addition, alignment of dust grains by radiation flux may play a role in the farside. Our observations reveal a diversity of disk polarization patterns that should be taken into account in future modeling efforts.

Transport coefficients for dense hard-disk systems

NARCIS (Netherlands)

García-Rojo, R.; Luding, S.; Brey, J.J.

2006-01-01

A study of the transport coefficients of a system of elastic hard disks based on the use of Helfand-Einstein expressions is reported. The self-diffusion, the viscosity, and the heat conductivity are examined with averaging techniques especially appropriate for event-driven molecular dynamics

Resolved Dual-Frequency Observations of the Debris Disk Around AU Mic: Strengths of Bodies in the Collisional Cascade

Science.gov (United States)

Carter, Evan; Hughes, A. Meredith; Daley, Cail; Flaherty, Kevin; Pan, Margaret; Schlichting, Hilke; Chiang, Eugene; MacGregor, Meredith Ann; Wilner, David; Dent, Bill; Carpenter, John; Andrews, Sean; Moor, Attila; Kospal, Agnes

2018-01-01

Debris disks are hallmarks of mature planetary systems, with second-generation dust produced via collisions between pluto-like planetesimals. The vertical structure of a debris disk encodes unique information about the dynamical state of the system, particularly at millimeter wavelengths where gravitational effects dominate over the effects of stellar radiation. We present 450 μm Atacama Large Millimeter/sub-millimeter Array (ALMA) observations of the edge-on debris disk around AU Mic, a nearby (d = 9.91 ± 0.10 pc) M1-type star. The 0.3'' angular resolution of the data allows us to spatially resolve the scale height of the disk, complementing previous observations at a wavelength of 1.3 mm. By resolving the vertical structure of the disk at these two widely-separated frequencies, we are able to spatially resolve the spectral index and study variations in the grain size distribution as a function of disk radius. The comparison of scale heights for two different wavelengths and therefore particle sizes also constrains the velocity dispersion as a function of grain size, which allows us to probe the strengths of bodies in the collisional cascade for the first time outside the Solar System.

RESOLVED IMAGES OF LARGE CAVITIES IN PROTOPLANETARY TRANSITION DISKS

International Nuclear Information System (INIS)

Andrews, Sean M.; Wilner, David J.; Espaillat, Catherine; Qi Chunhua; Brown, J. M.; Hughes, A. M.; Dullemond, C. P.; McClure, M. K.

2011-01-01

Circumstellar disks are thought to experience a rapid 'transition' phase in their evolution that can have a considerable impact on the formation and early development of planetary systems. We present new and archival high angular resolution (0.''3 ∼ 40-75 AU) Submillimeter Array (SMA) observations of the 880 μm (340 GHz) dust continuum emission from 12 such transition disks in nearby star-forming regions. In each case, we directly resolve a dust-depleted disk cavity around the central star. Using two-dimensional Monte Carlo radiative transfer calculations, we interpret these dust disk structures in a homogeneous, parametric model framework by reproducing their SMA continuum visibilities and spectral energy distributions. The cavities in these disks are large (R cav = 15-73 AU) and substantially depleted of small (∼μm-sized) dust grains, although their mass contents are still uncertain. The structures of the remnant material at larger radii are comparable to normal disks. We demonstrate that these large cavities are relatively common among the millimeter-bright disk population, comprising at least 1 in 5 (20%) of the disks in the bright half (and ≥26% of the upper quartile) of the millimeter luminosity (disk mass) distribution. Utilizing these results, we assess some of the physical mechanisms proposed to account for transition disk structures. As has been shown before, photoevaporation models do not produce the large cavity sizes, accretion rates, and disk masses representative of this sample. A sufficient decrease of the dust optical depths in these cavities by particle growth would be difficult to achieve: substantial growth (to meter sizes or beyond) must occur in large (tens of AU) regions of low turbulence without also producing an abundance of small particles. Given those challenges, we suggest instead that the observations are most commensurate with dynamical clearing due to tidal interactions with low-mass companions-very young (∼1 Myr) brown

CYANIDE PHOTOCHEMISTRY AND NITROGEN FRACTIONATION IN THE MWC 480 DISK

Energy Technology Data Exchange (ETDEWEB)

Guzmán, V. V.; Öberg, K. I.; Loomis, R.; Qi, C., E-mail: vguzman@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2015-11-20

HCN is a commonly observed molecule in Solar System bodies and in interstellar environments. Its abundance with respect to CN is a proposed tracer of UV exposure. HCN is also frequently used to probe the thermal history of objects, by measuring its degree of nitrogen fractionation. To address the utility of HCN as a probe of disks, we present Atacama Large (sub-) Millimeter Array observations of CN, HCN, H{sup 13}CN, and HC{sup 15}N toward the protoplanetary disk around Herbig Ae star MWC 480, and of CN and HCN toward the disk around T Tauri star DM Tau. Emission from all molecules is clearly detected and spatially resolved, including the first detection of HC{sup 15}N in a disk. Toward MWC 480, CN emission extends radially more than 1″ exterior to the observed cut-off of HCN emission. Quantitative modeling further reveals very different radial abundance profiles for CN and HCN, with best-fit outer cut-off radii of >300 AU and 110 ± 10 AU, respectively. This result is in agreement with model predictions of efficient HCN photodissociation into CN in the outer-part of the disk where the vertical gas and dust column densities are low. No such difference in CN and HCN emission profiles are observed toward DM Tau, suggestive of different photochemical structures in Herbig Ae and T Tauri disks. We use the HCN isotopologue data toward the MWC 480 disk to provide the first measurement of the {sup 14}N/{sup 15}N ratio in a disk. We find a low disk averaged {sup 14}N/{sup 15}N ratio of 200 ± 100, comparable to what is observed in cloud cores and comets, demonstrating interstellar inheritance and/or efficient nitrogen fractionation in this disk.

THE VLA VIEW OF THE HL TAU DISK: DISK MASS, GRAIN EVOLUTION, AND EARLY PLANET FORMATION

Energy Technology Data Exchange (ETDEWEB)

Carrasco-González, Carlos; Rodríguez, Luis F.; Galván-Madrid, Roberto [Instituto de Radioastronomía y Astrofísica UNAM, Apartado Postal 3-72 (Xangari), 58089 Morelia, Michoacán, México (Mexico); Henning, Thomas; Linz, Hendrik; Birnstiel, Til; Boekel, Roy van; Klahr, Hubert [Max-Planck-Institut für Astronomie Heidelberg, Königstuhl 17, D-69117 Heidelberg (Germany); Chandler, Claire J.; Pérez, Laura [National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville Road, Socorro, NM 87801-0387 (United States); Anglada, Guillem; Macias, Enrique; Osorio, Mayra [Instituto de Astrofísica de Andalucía (CSIC), Apartado 3004, E-18080 Granada (Spain); Flock, Mario [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Menten, Karl [Jansky Fellow of the National Radio Astronomy Observatory (United States); Testi, Leonardo [European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching bei München (Germany); Torrelles, José M. [Institut de Ciències de l’Espai (CSIC-IEEC) and Institut de Ciències del Cosmos (UB-IEEC), Martí i Franquès 1, E-08028 Barcelona (Spain); Zhu, Zhaohuan, E-mail: c.carrasco@crya.unam.mx, E-mail: l.rodriguez@crya.unam.mx, E-mail: r.galvan@crya.unam.mx, E-mail: henning@mpia.de, E-mail: linz@mpia.de [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

2016-04-10

The first long-baseline ALMA campaign resolved the disk around the young star HL Tau into a number of axisymmetric bright and dark rings. Despite the very young age of HL Tau, these structures have been interpreted as signatures for the presence of (proto)planets. The ALMA images triggered numerous theoretical studies based on disk–planet interactions, magnetically driven disk structures, and grain evolution. Of special interest are the inner parts of disks, where terrestrial planets are expected to form. However, the emission from these regions in HL Tau turned out to be optically thick at all ALMA wavelengths, preventing the derivation of surface density profiles and grain-size distributions. Here, we present the most sensitive images of HL Tau obtained to date with the Karl G. Jansky Very Large Array at 7.0 mm wavelength with a spatial resolution comparable to the ALMA images. At this long wavelength, the dust emission from HL Tau is optically thin, allowing a comprehensive study of the inner disk. We obtain a total disk dust mass of (1–3) × 10{sup −3} M {sub ⊙}, depending on the assumed opacity and disk temperature. Our optically thin data also indicate fast grain growth, fragmentation, and formation of dense clumps in the inner densest parts of the disk. Our results suggest that the HL Tau disk may be actually in a very early stage of planetary formation, with planets not already formed in the gaps but in the process of future formation in the bright rings.

THE VLA VIEW OF THE HL TAU DISK: DISK MASS, GRAIN EVOLUTION, AND EARLY PLANET FORMATION

International Nuclear Information System (INIS)

Carrasco-González, Carlos; Rodríguez, Luis F.; Galván-Madrid, Roberto; Henning, Thomas; Linz, Hendrik; Birnstiel, Til; Boekel, Roy van; Klahr, Hubert; Chandler, Claire J.; Pérez, Laura; Anglada, Guillem; Macias, Enrique; Osorio, Mayra; Flock, Mario; Menten, Karl; Testi, Leonardo; Torrelles, José M.; Zhu, Zhaohuan

2016-01-01

The first long-baseline ALMA campaign resolved the disk around the young star HL Tau into a number of axisymmetric bright and dark rings. Despite the very young age of HL Tau, these structures have been interpreted as signatures for the presence of (proto)planets. The ALMA images triggered numerous theoretical studies based on disk–planet interactions, magnetically driven disk structures, and grain evolution. Of special interest are the inner parts of disks, where terrestrial planets are expected to form. However, the emission from these regions in HL Tau turned out to be optically thick at all ALMA wavelengths, preventing the derivation of surface density profiles and grain-size distributions. Here, we present the most sensitive images of HL Tau obtained to date with the Karl G. Jansky Very Large Array at 7.0 mm wavelength with a spatial resolution comparable to the ALMA images. At this long wavelength, the dust emission from HL Tau is optically thin, allowing a comprehensive study of the inner disk. We obtain a total disk dust mass of (1–3) × 10 −3 M ⊙ , depending on the assumed opacity and disk temperature. Our optically thin data also indicate fast grain growth, fragmentation, and formation of dense clumps in the inner densest parts of the disk. Our results suggest that the HL Tau disk may be actually in a very early stage of planetary formation, with planets not already formed in the gaps but in the process of future formation in the bright rings

Grand canonical simulations of hard-disk systems by simulated tempering

DEFF Research Database (Denmark)

Döge, G.; Mecke, K.; Møller, Jesper

2004-01-01

The melting transition of hard disks in two dimensions is still an unsolved problem and improved simulation algorithms may be helpful for its investigation. We suggest the application of simulating tempering for grand canonical hard-disk systems as an efficient alternative to the commonly......-used Monte Carlo algorithms for canonical systems. This approach allows the direct study of the packing fraction as a function of the chemical potential even in the vicinity of the melting transition. Furthermore, estimates of several spatial characteristics including pair correlation function are studied...

SOLAR SYSTEM ANALOGS AROUND IRAS-DISCOVERED DEBRIS DISKS

International Nuclear Information System (INIS)

Chen, Christine H.; Sheehan, Patrick; Watson, Dan M.; Manoj, P.; Najita, Joan R.

2009-01-01

We have rereduced Spitzer IRS spectra and reanalyzed the spectral energy distributions (SEDs) of three nearby debris disks: λ Boo, HD 139664, and HR 8799. We find that the thermal emission from these objects is well modeled using two single temperature black body components. For HR 8799 - with no silicate emission features despite a relatively hot inner dust component (T gr = 150 K) - we infer the presence of an asteroid belt interior to and a Kuiper Belt exterior to the recently discovered orbiting planets. For HD 139664, which has been imaged in scattered light, we infer the presence of strongly forward scattering grains, consistent with porous grains, if the cold, outer disk component generates both the observed scattered light and thermal emission. Finally, careful analysis of the λ Boo SED suggests that this system possesses a central clearing, indicating that selective accretion of solids onto the central star does not occur from a dusty disk.

Using Vertical Structure to Infer the Total Mass Hidden in a Debris Disk

Science.gov (United States)

Daley, Cail; Hughes, A. Meredith; Carter, Evan; Flaherty, Kevin; Stafford Lambros, Zachary; Pan, Margaret; Schlichting, Hilke; Chiang, Eugene; Wilner, David; Dent, Bill; Carpenter, John; Andrews, Sean; MacGregor, Meredith Ann; Moor, Attila; Kospal, Agnes

2018-01-01

Disks of optically thin debris dust surround ≥ 20% of main sequence stars and mark the final stage of planetary system evolution. The features of debris disks encode dynamical interactions between the dust and any unseen planets embedded in the disk. The vertical distribution of the dust is particularly sensitive to the total mass of planetesimal bodies in the disk, and is therefore well suited for constraining the prevalence of otherwise unobservable Uranus and Neptune analogs. Inferences of mass from debris disk vertical structure have previously been applied to infrared and optical observations of several systems, but the smaller particles traced by short-wavelength observations are ‘puffed up’ by radiation pressure, yielding only upper limits on the total embedded mass. The large grains that dominate the emission at millimeter wavelengths are essentially impervious to the effects of stellar radiation, and therefore trace the underlying mass distribution more directly. Here we present 1.3mm dust continuum observations of the debris disk around the nearby M star AU Mic with the Atacama Large Millimeter/submillimeter Array (ALMA). The 3 au spatial resolution of the observations, combined with the favorable edge-on geometry of the system, allows us to measure the vertical structure of a debris disk at millimeter wavelengths for the first time. We analyze the data using a ray-tracing code that translates a 2-D density and temperature structure into a model sky image of the disk. This model image is then compared directly to the interferometric data in the visibility domain, and the model parameters are explored using a Markov Chain Monte Carlo routine. We measure a scale height-to-radius ratio of 0.03, which we then compare to a theoretical model of steady-state, size-dependent velocity distributions in the collisional cascade to infer a total mass within the disk of ∼ 1.7 Earth masses. These measurements rule out the presence of a gas giant or Neptune

Interstellar Explorer Observations of the Solar System's Debris Disks

Science.gov (United States)

Lisse, C. M.; McNutt, R. L., Jr.; Brandt, P. C.

2017-12-01

Planetesimal belts and debris disks full of dust are known as the "signposts of planet formation" in exosystems. The overall brightness of a disk provides information on the amount of sourcing planetesimal material, while asymmetries in the shape of the disk can be used to search for perturbing planets. The solar system is known to house two such belts, the Asteroid belt and the Kuiper Belt; and at least one debris cloud, the Zodiacal Cloud, sourced by planetisimal collisions and Kuiper Belt comet evaporative sublimation. However these are poorly understood in toto because we live inside of them. E.g., while we know of the two planetesimal belt systems, it is not clear how much, if any, dust is produced from the Kuiper belt since the near-Sun comet contributions dominate near-Earth space. Understanding how much dust is produced in the Kuiper belt would give us a much better idea of the total number of bodies in the belt, especially the smallest ones, and their dynamical collisional state. Even for the close in Zodiacal cloud, questions remain concerning its overall shape and orientation with respect to the ecliptic and invariable planes of the solar system - they aren't explainable from the perturbations caused by the known planets alone. In this paper we explore the possibilities of using an Interstellar Explorer telescope placed at 200 AU from the sun to observe the brightness, shape, and extent of the solar system's debris disk(s). We should be able to measure the entire extent of the inner, near-earth zodiacal cloud; whether it connects smoothly into an outer cloud, or if there is a second outer cloud sourced by the Kuiper belt and isolated by the outer planets, as predicted by Stark & Kuchner (2009, 2010) and Poppe et al. (2012, 2016; Figure 1). VISNIR imagery will inform about the dust cloud's density, while MIR cameras will provide thermal imaging photometry related to the cloud's dust particle size and composition. Observing at high phase angle by looking

Formation and Atmosphere of Complex Organic Molecules of the HH 212 Protostellar Disk

Energy Technology Data Exchange (ETDEWEB)

Lee, Chin-Fei; Ho, Paul T. P.; Hirano, Naomi; Shang, Hsien [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 106, Taiwan (China); Li, Zhi-Yun [Astronomy Department, University of Virginia, Charlottesville, VA 22904 (United States); Zhang, Qizhou, E-mail: cflee@asiaa.sinica.edu.tw [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2017-07-01

HH 212 is a nearby (400 pc) Class 0 protostellar system recently found to host a “hamburger”-shaped dusty disk with a radius of ∼60 au, deeply embedded in an infalling-rotating flattened envelope. We have spatially resolved this envelope-disk system with the Atacama Large Millimeter/submillimeter Array at up to ∼16 au (0.″04) resolution. The envelope is detected in HCO{sup +} J = 4–3 down to the dusty disk. Complex organic molecules (COMs) and doubly deuterated formaldehyde (D{sub 2}CO) are detected above and below the dusty disk within ∼40 au of the central protostar. The COMs are methanol (CH{sub 3}OH), deuterated methanol (CH{sub 2}DOH), methyl mercaptan (CH{sub 3}SH), and formamide (NH{sub 2}CHO, a prebiotic precursor). We have modeled the gas kinematics in HCO{sup +} and COMs and found a centrifugal barrier (CB) at a radius of ∼44 au, within which a Keplerian rotating disk is formed. This indicates that HCO{sup +} traces the infalling-rotating envelope down to the CB and COMs trace the atmosphere of a Keplerian rotating disk within the CB. The COMs are spatially resolved for the first time, both radially and vertically, in the atmosphere of a disk in the earliest, Class 0 phase of star formation. Our spatially resolved observations of COMs favor their formation in the disk rather than a rapidly infalling (warm) inner envelope. The abundances and spatial distributions of the COMs provide strong constraints on models of their formation and transport in low-mass star formation.

Test of the periodic-orbit approximation in n-disk systems

International Nuclear Information System (INIS)

Wirzba, A.

1993-01-01

The scattering of a point particle in two dimensions from two (or three) equally-sized (and spaced) circular hard disks is one of the simplest classically hyperbolic scattering problems. Because of this simplicity such systems are well suited for the study of the semiclassical periodic-orbit approximation in the cycle expansion of the dynamical zeta function applied to a quantum-mechanical scattering problem. Especially the predictions of the semiclassical cycle expansion for the quantum-mechanical resonances can be tested in these n-disk systems. Whereas for high wave numbers the cycle expansion gives quite accurate results, there are systematic deviations for low wave numbers from the exact quantum-mechanical values. The low-lying quantum-mechanical resonance poles of the 2- and 3-disk problem are constructed and compared to the cycle-expansion results. The characteristic determinant of the scattering matrix is expanded in terms of simple traces which in turn are related to the classical periodic orbits and possible creeping contributions. It will be shown that for large separations of the disks the correct resonance-pole positions can be extracted just from the knowledge of the lowest traces whose semiclassical limit are the fundamental periodic orbits. Creeping-orbit corrections are shown to be small. (orig.)

Ultrasonic inspection method and system for detection of steeple cracking in turbine disk rims

International Nuclear Information System (INIS)

Birring, A.S.; Lamping, G.A.; Van der Veer, W.R.; Hanley, J.J.

1990-01-01

Steam turbine disks which operate under high cyclic stress in a moist environment can develop cracks in the disk-rim steeples. Detection of these cracks using nondestructive testing methods is necessary to assure safe operation and avoid unnecessary disk replacement. Both magnetic particle (MT) and ultrasonic testing (UT) can be used to inspect the steeples; however, UT can be used without removing the blades. A system for inspecting bladed steeples has been developed that can be applied on a range of disks including those in Westinghouse, General Electric, and Allis Chalmers turbines. The system performs an inspection as the turbine is rotated at slow speeds over turning rolls. This procedure greatly reduces inspection time because the inspection can be done without deblading the disk or resetting the inspection equipment for different rim segments

Fiscal 2000 achievement report on the research and development of nanometer controlled optical disk system; 2000 nendo nanometer seigyo hikari disk system no kenkyu kaihatsu seika hokokusho

Energy Technology Data Exchange (ETDEWEB)

NONE

2001-03-01

Development proceeded of nanometer controlled optical memory technologies as part of systematic research and development aiming at the reinforcement of industrial technology power in the field of data recording. Activities were conducted in the four fields of (1) high density signal processing technology, (2) high performance disk materials technology, (3) disk substrate fabrication technology, and (4) signal detection technology. Discussed in field (1) were multivalue ROM (read only memory) disk signal regeneration, SIL-LBR (solid immersion lens-laser beam recorder), dry etching process using RIE (reactive ion etching), SHG (second harmonic generation) blue laser, and a multivalue ROM disk evaluation system. Studied in field (2) were the evaluation of ROM disk performance dependent on recording materials, development of high density recording materials, and the evaluation of crystallization induction time using a static tester. Studied in the development of high density recording materials was the formation of microscopic recording marks in a phase shift/surface recording type disk comprising a 4-element (Ag-In-Sb-Te) recording layer and an Ag reflection layer. In fiscal 2000, an attempt was made at the 0.07 {mu}m level. (NEDO)

VISUALISASI DAN NAVIGASI MEDIA PENYIMPANAN DISK DENGAN MENGGUNAKAN METODE SPLIT SCREEN SYSTEM

Directory of Open Access Journals (Sweden)

Yulia yulia

2002-01-01

Full Text Available Disk is a very useful device to a computer to save data file. For that, is much needed to have a program that has a capability to represent, navigate, and operate that files. There are many computer programs that used to present, navigate, and operate disk files in text form with a lot of facilities, but only a few programs that can represent files in a graphic form and have special feature, like capability to find the biggest files that use disk space. This capability is very useful in disk file management. This software use split screen system method and tree map algorithm. Split screen system is used to navigate, where the monitor screen divided into two parts to visualize files in a disk, the small part (map navigator visualize the whole content of a drive or directory and the big part visualize the detail of a part according to focus box in the map navigator. A mouse can move focus box in the map navigator and the box size is the comparison between map navigator sizes with map view size. Tree map algorithm is used to calculate the size of box picture of the represented file. This algorithm needs a complete tree structure from a drive or directory that will be painted. The software to make this windows based program is Borland Delphi 5.0. Abstract in Bahasa Indonesia : Disk merupakan alat yang sangat bermanfaat bagi sebuah sistem komputer untuk menyimpan data berupa file. Untuk itu sangat dibutuhkan program yang dapat merepresentasikan, menavigasi dan mengoperasikan file-file tersebut. Banyak program komputer yang digunakan untuk merepresentasikan, menavigasi dan mengoperasikan file-file pada media penyimpanan disk dalam bentuk teks dengan berbagai macam fasilitas, tetapi sangat sedikit program yang merepresentasikan file-file dalam bentuk grafik atau secara visual serta mampu memberikan kelebihan-kelebihan tersendiri, seperti kemampuan untuk merepresentasikan file-file yang paling banyak menggunakan ruang media penyimpanan disk. Kemampuan

THE DISK IMAGING SURVEY OF CHEMISTRY WITH SMA. I. TAURUS PROTOPLANETARY DISK DATA

International Nuclear Information System (INIS)

Oeberg, Karin I.; Qi Chunhua; Andrews, Sean M.; Espaillat, Catherine; Van Kempen, Tim A.; Wilner, David J.; Fogel, Jeffrey K. J.; Bergin, Edwin A.; Pascucci, Ilaria

2010-01-01

Chemistry plays an important role in the structure and evolution of protoplanetary disks, with implications for the composition of comets and planets. This is the first of a series of papers based on data from DISCS, a Submillimeter Array survey of the chemical composition of protoplanetary disks. The six Taurus sources in the program (DM Tau, AA Tau, LkCa 15, GM Aur, CQ Tau, and MWC 480) range in stellar spectral type from M1 to A4 and offer an opportunity to test the effects of stellar luminosity on the disk chemistry. The disks were observed in 10 different lines at ∼3'' resolution and an rms of ∼100 mJy beam -1 at ∼0.5 km s -1 . The four brightest lines are CO 2-1, HCO + 3-2, CN 2 33/4/2 - 1 22/3/1 , and HCN 3-2, and these are detected toward all sources (except for HCN toward CQ Tau). The weaker lines of CN 2 22 -1 11 , DCO + 3-2, N 2 H + 3-2, H 2 CO 3 03 -2 02 , and 4 14 -3 13 are detected toward two to three disks each, and DCN 3-2 only toward LkCa 15. CH 3 OH 4 21 -3 1 2 and c-C 3 H 2 are not detected. There is no obvious difference between the T Tauri and Herbig Ae sources with regard to CN and HCN intensities. In contrast, DCO + , DCN, N 2 H + , and H 2 CO are detected only toward the T Tauri stars, suggesting that the disks around Herbig Ae stars lack cold regions for long enough timescales to allow for efficient deuterium chemistry, CO freeze-out, and grain chemistry.

AN IONIZED OUTFLOW FROM AB AUR, A HERBIG AE STAR WITH A TRANSITIONAL DISK

Energy Technology Data Exchange (ETDEWEB)

Rodríguez, Luis F.; Zapata, Luis A.; Ortiz-León, Gisela N.; Loinard, Laurent [Centro de Radioastronomía y Astrofísica, UNAM, Apdo. Postal 3-72 (Xangari), 58089 Morelia, Michoacán (Mexico); Dzib, Sergio A. [Max Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Macías, Enrique; Anglada, Guillem, E-mail: l.rodriguez@crya.unam.mx [Instituto de Astrofísica de Andalucía (CSIC), Apartado 3004, E-18080 Granada (Spain)

2014-09-20

AB Aur is a Herbig Ae star with a transitional disk. Transitional disks present substantial dust clearing in their inner regions, most probably because of the formation of one or more planets, although other explanations are still viable. In transitional objects, accretion is found to be about an order of magnitude smaller than in classical full disks. Since accretion is believed to be correlated with outflow activity, centimeter free-free jets are expected to be present in association with these systems, at weaker levels than in classical protoplanetary (full) systems. We present new observations of the centimeter radio emission associated with the inner regions of AB Aur and conclude that the morphology, orientation, spectral index, and lack of temporal variability of the centimeter source imply the presence of a collimated, ionized outflow. The radio luminosity of this radio jet is, however, about 20 times smaller than that expected for a classical system of similar bolometric luminosity. We conclude that centimeter continuum emission is present in association with stars with transitional disks, but at levels than are becoming detectable only with the upgraded radio arrays. On the other hand, assuming that the jet velocity is 300 km s{sup –1}, we find that the ratio of mass loss rate to accretion rate in AB Aur is ∼0.1, similar to that found for less evolved systems.

A radiographic image archive system on digital optical disks

International Nuclear Information System (INIS)

Mankovich, N.J.; Taira, R.K.; Cho, P.S.; Wong, W.K.; Stewart, B.K.; Huang, H.K.

1986-01-01

The recent introduction of projection computed radiography (CR) systems allows radiology departments to consider digital operation in over 90% of performed procedures. Ideally, current patient procedures from CT, CT, and MR along with laser-digitized historical films should be centrally stored at their full digital resolution. Magnetic disks, because of their limited storage capacity and expense, can only retain these data on a limited basis. The author devised an optical disk archive system which automatically stores images directly onto 2.6-gigabyte optical cartridges without recourse to film. This system is in full clinical operation in the UCLA Pediatric Radiology Section of the authors' department. From this experience they present (a) an analysis of the digital archiving requirements of the Pediatric Radiology Section based on CR, CT, MR, and laser digitized films; (b) the archive and retrieval methods along with performance statistics; and (c) the procedure for assuring digital image integrity

Comparison of central axis and jet ring coolant supply for turbine disk cooling on a SSME-HPOTP model

Science.gov (United States)

Kim, Y. W.; Metzger, D. E.

1992-01-01

The test facility, test methods and results are presented for an experimental study modeling the cooling of turbine disks in the blade attachment regions with multiple impinging jets, in a configuration simulating the disk cooling method employed on the Space Shuttle Main Engine oxygen turbopump. The study's objective was to provide a comparison of detailed local convection heat transfer rates obtained for a single center-supply of disk coolant with those obtained with the present flight configuration where disk coolant is supplied through an array of 19 jets located near the disk outer radius. Specially constructed disk models were used in a program designed to evaluate possible benefits and identify any possible detrimental effects involved in employing an alternate disk cooling scheme. The study involved the design, construction and testing of two full scale rotating model disks, one plane and smooth for baseline testing and the second contoured to the present flight configuration, together with the corresponding plane and contoured stator disks. Local heat transfer rates are determined from the color display of encapsulated liquid crystals coated on the disk in conjunction with use of a computer vision system. The test program was composed of a wide variety of disk speeds, flowrates, and geometrical configurations, including testing for the effects of disk boltheads and gas ingestion from the gas path region radially outboard of the disk-cavity.

ON THE COMMONALITY OF 10–30 AU SIZED AXISYMMETRIC DUST STRUCTURES IN PROTOPLANETARY DISKS

International Nuclear Information System (INIS)

Zhang, Ke; Bergin, Edwin A.; Schwarz, Kamber R.; Blake, Geoffrey A.; Cleeves, L. Ilsedore; Hogerheijde, Michiel; Salinas, Vachail

2016-01-01

An unsolved problem in step-wise core-accretion planet formation is that rapid radial drift in gas-rich protoplanetary disks should drive millimeter-/meter-sized particles inward to the central star before large bodies can form. One promising solution is to confine solids within small-scale structures. Here, we investigate dust structures in the (sub)millimeter continuum emission of four disks (TW Hya, HL Tau, HD 163296, and DM Tau), a sample of disks with the highest spatial resolution Atacama Large Millimeter/submillimeter Array observations to date. We retrieve the surface brightness distributions using synthesized images and fitting visibilities with analytical functions. We find that the continuum emission of the four disks is ∼axisymmetric but rich in 10–30 AU-sized radial structures, possibly due to physical gaps, surface density enhancements, or localized dust opacity variations within the disks. These results suggest that small-scale axisymmetric dust structures are likely to be common, as a result of ubiquitous processes in disk evolution and planet formation. Compared with recent spatially resolved observations of CO snow lines in these same disks, all four systems show enhanced continuum emission from regions just beyond the CO condensation fronts, potentially suggesting a causal relationship between dust growth/trapping and snow lines

ON THE COMMONALITY OF 10–30 AU SIZED AXISYMMETRIC DUST STRUCTURES IN PROTOPLANETARY DISKS

Energy Technology Data Exchange (ETDEWEB)

Zhang, Ke; Bergin, Edwin A.; Schwarz, Kamber R. [Department of Astronomy, University of Michigan, 1085 S. University Avenue, Ann Arbor, MI 48109 (United States); Blake, Geoffrey A. [Division of Geological and Planetary Sciences, California Institute of Technology, MC 150-21, Pasadena, CA 91125 (United States); Cleeves, L. Ilsedore [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Hogerheijde, Michiel; Salinas, Vachail, E-mail: kezhang@umich.edu [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands)

2016-02-10

An unsolved problem in step-wise core-accretion planet formation is that rapid radial drift in gas-rich protoplanetary disks should drive millimeter-/meter-sized particles inward to the central star before large bodies can form. One promising solution is to confine solids within small-scale structures. Here, we investigate dust structures in the (sub)millimeter continuum emission of four disks (TW Hya, HL Tau, HD 163296, and DM Tau), a sample of disks with the highest spatial resolution Atacama Large Millimeter/submillimeter Array observations to date. We retrieve the surface brightness distributions using synthesized images and fitting visibilities with analytical functions. We find that the continuum emission of the four disks is ∼axisymmetric but rich in 10–30 AU-sized radial structures, possibly due to physical gaps, surface density enhancements, or localized dust opacity variations within the disks. These results suggest that small-scale axisymmetric dust structures are likely to be common, as a result of ubiquitous processes in disk evolution and planet formation. Compared with recent spatially resolved observations of CO snow lines in these same disks, all four systems show enhanced continuum emission from regions just beyond the CO condensation fronts, potentially suggesting a causal relationship between dust growth/trapping and snow lines.

CONFIRMING THE PRIMARILY SMOOTH STRUCTURE OF THE VEGA DEBRIS DISK AT MILLIMETER WAVELENGTHS

Energy Technology Data Exchange (ETDEWEB)

Hughes, A. Meredith; Plambeck, Richard; Chiang, Eugene [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Wilner, David J.; Andrews, Sean M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Mason, Brian [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475 (United States); Carpenter, John M. [California Institute of Technology, Department of Astronomy, MC 105-24, Pasadena, CA 91125 (United States); Chiang, Hsin-Fang [Institute for Astronomy, University of Hawaii, 640 North Aohoku Place, Hilo, HI 96720 (United States); Williams, Jonathan P. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Hales, Antonio [Joint ALMA Observatory, Av. El Golf 40, Piso 18, Santiago (Chile); Su, Kate [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Dicker, Simon; Korngut, Phil; Devlin, Mark, E-mail: mhughes@astro.berkeley.edu [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States)

2012-05-01

Clumpy structure in the debris disk around Vega has been previously reported at millimeter wavelengths and attributed to concentrations of dust grains trapped in resonances with an unseen planet. However, recent imaging at similar wavelengths with higher sensitivity has disputed the observed structure. We present three new millimeter-wavelength observations that help to resolve the puzzling and contradictory observations. We have observed the Vega system with the Submillimeter Array (SMA) at a wavelength of 880 {mu}m and an angular resolution of 5''; with the Combined Array for Research in Millimeter-wave Astronomy (CARMA) at a wavelength of 1.3 mm and an angular resolution of 5''; and with the Green Bank Telescope (GBT) at a wavelength of 3.3 mm and angular resolution of 10''. Despite high sensitivity and short baselines, we do not detect the Vega debris disk in either of the interferometric data sets (SMA and CARMA), which should be sensitive at high significance to clumpy structure based on previously reported observations. We obtain a marginal (3{sigma}) detection of disk emission in the GBT data; the spatial distribution of the emission is not well constrained. We analyze the observations in the context of several different models, demonstrating that the observations are consistent with a smooth, broad, axisymmetric disk with inner radius 20-100 AU and width {approx}> 50 AU. The interferometric data require that at least half of the 860 {mu}m emission detected by previous single-dish observations with the James Clerk Maxwell Telescope be distributed axisymmetrically, ruling out strong contributions from flux concentrations on spatial scales of {approx}<100 AU. These observations support recent results from the Plateau de Bure Interferometer indicating that previous detections of clumpy structure in the Vega debris disk were spurious.

CONFIRMING THE PRIMARILY SMOOTH STRUCTURE OF THE VEGA DEBRIS DISK AT MILLIMETER WAVELENGTHS

International Nuclear Information System (INIS)

Hughes, A. Meredith; Plambeck, Richard; Chiang, Eugene; Wilner, David J.; Andrews, Sean M.; Mason, Brian; Carpenter, John M.; Chiang, Hsin-Fang; Williams, Jonathan P.; Hales, Antonio; Su, Kate; Dicker, Simon; Korngut, Phil; Devlin, Mark

2012-01-01

Clumpy structure in the debris disk around Vega has been previously reported at millimeter wavelengths and attributed to concentrations of dust grains trapped in resonances with an unseen planet. However, recent imaging at similar wavelengths with higher sensitivity has disputed the observed structure. We present three new millimeter-wavelength observations that help to resolve the puzzling and contradictory observations. We have observed the Vega system with the Submillimeter Array (SMA) at a wavelength of 880 μm and an angular resolution of 5''; with the Combined Array for Research in Millimeter-wave Astronomy (CARMA) at a wavelength of 1.3 mm and an angular resolution of 5''; and with the Green Bank Telescope (GBT) at a wavelength of 3.3 mm and angular resolution of 10''. Despite high sensitivity and short baselines, we do not detect the Vega debris disk in either of the interferometric data sets (SMA and CARMA), which should be sensitive at high significance to clumpy structure based on previously reported observations. We obtain a marginal (3σ) detection of disk emission in the GBT data; the spatial distribution of the emission is not well constrained. We analyze the observations in the context of several different models, demonstrating that the observations are consistent with a smooth, broad, axisymmetric disk with inner radius 20-100 AU and width ∼> 50 AU. The interferometric data require that at least half of the 860 μm emission detected by previous single-dish observations with the James Clerk Maxwell Telescope be distributed axisymmetrically, ruling out strong contributions from flux concentrations on spatial scales of ∼<100 AU. These observations support recent results from the Plateau de Bure Interferometer indicating that previous detections of clumpy structure in the Vega debris disk were spurious.

A mysterious dust clump in a disk around an evolved binary star system.

Science.gov (United States)

Jura, M; Turner, J

1998-09-10

The discovery of planets in orbit around the pulsar PSR1257+12 shows that planets may form around post-main-sequence stars. Other evolved stars, such as HD44179 (an evolved star which is part of the binary system that has expelled the gas and dust that make the Red Rectangle nebula), possess gravitationally bound orbiting dust disks. It is possible that planets might form from gravitational collapse in such disks. Here we report high-angular-resolution observations at millimetre and submillimetre wavelengths of the dusk disk associated with the Red Rectangle. We find a dust clump with an estimated mass near that of Jupiter in the outer region of the disk. The clump is larger than our Solar System, and far beyond where planet formation would normally be expected, so its nature is at present unclear.

Exploring Disks Around Planets

Science.gov (United States)

Kohler, Susanna

2017-07-01

Giant planets are thought to form in circumstellar disks surrounding young stars, but material may also accrete into a smaller disk around the planet. Weve never detected one of these circumplanetary disks before but thanks to new simulations, we now have a better idea of what to look for.Image from previous work simulating a Jupiter-mass planet forming inside a circumstellar disk. The planet has its own circumplanetary disk of accreted material. [Frdric Masset]Elusive DisksIn the formation of giant planets, we think the final phase consists of accretion onto the planet from a disk that surrounds it. This circumplanetary disk is important to understand, since it both regulates the late gas accretion and forms the birthplace of future satellites of the planet.Weve yet to detect a circumplanetary disk thus far, because the resolution needed to spot one has been out of reach. Now, however, were entering an era where the disk and its kinematics may be observable with high-powered telescopes (like the Atacama Large Millimeter Array).To prepare for such observations, we need models that predict the basic characteristics of these disks like the mass, temperature, and kinematic properties. Now a researcher at the ETH Zrich Institute for Astronomy in Switzerland, Judit Szulgyi, has worked toward this goal.Simulating CoolingSzulgyi performs a series of 3D global radiative hydrodynamic simulations of 1, 3, 5, and 10 Jupiter-mass (MJ) giant planets and their surrounding circumplanetary disks, embedded within the larger circumstellar disk around the central star.Density (left column), temperature (center), and normalized angular momentum (right) for a 1 MJ planet over temperatures cooling from 10,000 K (top) to 1,000 K (bottom). At high temperatures, a spherical circumplanetary envelope surrounds the planet, but as the planet cools, the envelope transitions around 64,000 K to a flattened disk. [Szulgyi 2017]This work explores the effects of different planet temperatures and

Convective heat and mass transfer in rotating disk systems

CERN Document Server

Shevchuk, Igor V

2009-01-01

The book describes results of investigations of a series of convective heat and mass transfer problems in rotating-disk systems. Methodology used included integral methods, self-similar and approximate analytical solutions, as well as CFD.

OT1_ipascucc_1: Understanding the Origin of Transition Disks via Disk Mass Measurements

Science.gov (United States)

Pascucci, I.

2010-07-01

Transition disks are a distinguished group of few Myr-old systems caught in the phase of dispersing their inner dust disk. Three different processes have been proposed to explain this inside-out clearing: grain growth, photoevaporation driven by the central star, and dynamical clearing by a forming giant planet. Which of these processes lead to a transition disk? Distinguishing between them requires the combined knowledge of stellar accretion rates and disk masses. We propose here to use 43.8 hours of PACS spectroscopy to detect the [OI] 63 micron emission line from a sample of 21 well-known transition disks with measured mass accretion rates. We will use this line, in combination with ancillary CO millimeter lines, to measure their gas disk mass. Because gas dominates the mass of protoplanetary disks our approach and choice of lines will enable us to trace the bulk of the disk mass that resides beyond tens of AU from young stars. Our program will quadruple the number of transition disks currently observed with Herschel in this setting and for which disk masses can be measured. We will then place the transition and the ~100 classical/non-transition disks of similar age (from the Herschel KP "Gas in Protoplanetary Systems") in the mass accretion rate-disk mass diagram with two main goals: 1) reveal which gaps have been created by grain growth, photoevaporation, or giant planet formation and 2) from the statistics, determine the main disk dispersal mechanism leading to a transition disk.

Collisional dynamics of perturbed particle disks in the solar system

Science.gov (United States)

Roberts, W. W.; Stewart, G. R.

1987-01-01

Investigations of the collisional evolution of particulate disks subject to the gravitational perturbation of a more massive particle orbiting within the disk are underway. Both numerical N-body simulations using a novel collision algorithm and analytical kinetic theory are being employed to extend our understanding of perturbed disks in planetary rings and during the formation of the solar system. Particular problems proposed for investigation are: (1) The development and testing of general criteria for a small moonlet to clear a gap and produce observable morphological features in planetary rings; (2) The development of detailed models of collisional damping of the wavy edges observed on the Encke division of Saturn's A ring; and (3) The determination of the extent of runaway growth of the few largest planetesimals during the early stages of planetary accretion.

1998 Annual Study Report. Standardization for securing interoperability between optical disk systems; 1998 nendo seika hokokusho. Hikari disk system no sogo un'yosei kakuho no tame no hyojunka

Energy Technology Data Exchange (ETDEWEB)

NONE

1999-03-01

This R and D program is aimed at securing interoperability between optical disk systems, based on the logical formats, to propose the draft international standards. For the volume/file structures proposed by ISO/IEC 13346, the universal disk format (UDF) proposed by the Optical Storage Technology Association (OSTA) is taken as the target file system, to improve the conformance test environments and develop the standards for advanced interoperability. The 1998 R and D themes include development of the UDF conformance testing tools for avoiding the interoperability-related problems involved in the UDF, which are actually observed, and investigations on the UAF specifications and preparation of the UAF-related standard evaluation systems for preparation of the draft standards for the Universal Accessible Filesystem (UAF), planned to be conducted in and after the next fiscal year, which allows, e.g., network seamless application of a variety of the future optical disks. (NEDO)

Radial Surface Density Profiles of Gas and Dust in the Debris Disk around 49 Ceti

Energy Technology Data Exchange (ETDEWEB)

Hughes, A. Meredith; Lieman-Sifry, Jesse; Flaherty, Kevin M.; Daley, Cail M. [Department of Astronomy, Van Vleck Observatory, Wesleyan University, 96 Foss Hill Drive, Middletown, CT 06459 (United States); Roberge, Aki [Exoplanets and Stellar Astrophysics Laboratory, NASA Goddard Space Flight Center, Code 667, Greenbelt, MD 20771 (United States); Kóspál, Ágnes; Moór, Attila; Ábrahám, Peter [Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, P.O. Box 67, 1525 Budapest (Hungary); Kamp, Inga [Kapteyn Astronomical Institute, University of Groningen, Postbus 800, 9700 AV Groningen (Netherlands); Wilner, David J.; Andrews, Sean M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-51, Cambridge, MA 02138 (United States); Kastner, Joel H., E-mail: amhughes@astro.wesleyan.edu [Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States)

2017-04-20

We present ∼0.″4 resolution images of CO(3–2) and associated continuum emission from the gas-bearing debris disk around the nearby A star 49 Ceti, observed with the Atacama Large Millimeter/Submillimeter Array (ALMA). We analyze the ALMA visibilities in tandem with the broadband spectral energy distribution to measure the radial surface density profiles of dust and gas emission from the system. The dust surface density decreases with radius between ∼100 and 310 au, with a marginally significant enhancement of surface density at a radius of ∼110 au. The SED requires an inner disk of small grains in addition to the outer disk of larger grains resolved by ALMA. The gas disk exhibits a surface density profile that increases with radius, contrary to most previous spatially resolved observations of circumstellar gas disks. While ∼80% of the CO flux is well described by an axisymmetric power-law disk in Keplerian rotation about the central star, residuals at ∼20% of the peak flux exhibit a departure from axisymmetry suggestive of spiral arms or a warp in the gas disk. The radial extent of the gas disk (∼220 au) is smaller than that of the dust disk (∼300 au), consistent with recent observations of other gas-bearing debris disks. While there are so far only three broad debris disks with well characterized radial dust profiles at millimeter wavelengths, 49 Ceti’s disk shows a markedly different structure from two radially resolved gas-poor debris disks, implying that the physical processes generating and sculpting the gas and dust are fundamentally different.

Modeling Protoplanetary Disks

Science.gov (United States)

Holman, Megan; Tubbs, Drake; Keller, L. D.

2018-01-01

Using spectra models with known parameters and comparing them to spectra gathered from real systems is often the only ways to find out what is going on in those real systems. This project uses the modeling programs of RADMC-3D to generate model spectra for systems containing protoplanetary disks. The parameters can be changed to simulate protoplanetary disks in different stages of planet formation, with different sized gaps in different areas of the disks, as well as protoplanetary disks that contain different types of dust. We are working on producing a grid of models that all have different variations in the parameters in order to generate a miniature database to use for comparisons to gathered spectra. The spectra produced from these simulations will be compared to spectra that have been gathered from systems in the Small Magellanic cloud in order to find out the contents and stage of development of that system. This allows us to see if and how planets are forming in the Small Magellanic cloud, a region which has much less metallicity than our own galaxy. The data we gather from comparisons between the model spectra and the spectra of systems in the Small Magellanic Cloud can then be applied to how planets may have formed in the early universe.

Submillimeter Array (SMA) Newsletter August 2011

OpenAIRE

Blundell, Raymond

2011-01-01

Submillimeter Array (SMA) Newsletter August 2011 Blundell, Raymond Submillimeter Array Newsletter | Number 12 | August 2011 CONTENTS 1 From the Director SCIENCE HIGHLIGHTS: 2 Faint Submillimeter Sources behind Massive Lensing Clusters 5 Millimeter Imaging of the β Pictoris Debris Disk: Evidence for a Planetesimal Belt 7 Physical Properties of the Circumnuclear Starburst Ring in the Barred Galaxy NGC1097 TECHNICAL HIGHLIGHTS: 9 ...

GIANT PLANET MIGRATION, DISK EVOLUTION, AND THE ORIGIN OF TRANSITIONAL DISKS

International Nuclear Information System (INIS)

Alexander, Richard D.; Armitage, Philip J.

2009-01-01

We present models of giant planet migration in evolving protoplanetary disks. Our disks evolve subject to viscous transport of angular momentum and photoevaporation, while planets undergo Type II migration. We use a Monte Carlo approach, running large numbers of models with a range in initial conditions. We find that relatively simple models can reproduce both the observed radial distribution of extrasolar giant planets, and the lifetimes and accretion histories of protoplanetary disks. The use of state-of-the-art photoevaporation models results in a degree of coupling between planet formation and disk clearing, which has not been found previously. Some accretion across planetary orbits is necessary if planets are to survive at radii ∼<1.5 AU, and if planets of Jupiter mass or greater are to survive in our models they must be able to form at late times, when the disk surface density in the formation region is low. Our model forms two different types of 'transitional' disks, embedded planets and clearing disks, which show markedly different properties. We find that the observable properties of these systems are broadly consistent with current observations, and highlight useful observational diagnostics. We predict that young transition disks are more likely to contain embedded giant planets, while older transition disks are more likely to be undergoing disk clearing.

Head-Disk Interface Technology: Challenges and Approaches

Science.gov (United States)

Liu, Bo

Magnetic hard disk drive (HDD) technology is believed to be one of the most successful examples of modern mechatronics systems. The mechanical beauty of magnetic HDD includes simple but super high accuracy positioning head, positioning technology, high speed and stability spindle motor technology, and head-disk interface technology which keeps the millimeter sized slider flying over a disk surface at nanometer level slider-disk spacing. This paper addresses the challenges and possible approaches on how to further reduce the slider disk spacing whilst retaining the stability and robustness level of head-disk systems for future advanced magnetic disk drives.

Debris Disks: Probing Planet Formation

OpenAIRE

Wyatt, Mark C.

2018-01-01

Debris disks are the dust disks found around ~20% of nearby main sequence stars in far-IR surveys. They can be considered as descendants of protoplanetary disks or components of planetary systems, providing valuable information on circumstellar disk evolution and the outcome of planet formation. The debris disk population can be explained by the steady collisional erosion of planetesimal belts; population models constrain where (10-100au) and in what quantity (>1Mearth) planetesimals (>10km i...

HYDROCARBON EMISSION RINGS IN PROTOPLANETARY DISKS INDUCED BY DUST EVOLUTION

Energy Technology Data Exchange (ETDEWEB)

Bergin, Edwin A.; Du, Fujun; Schwarz, K.; Zhang, K. [Department of Astronomy, University of Michigan, 311 West Hall, 1085 S. University Ave, Ann Arbor, MI 48109 (United States); Cleeves, L. Ilsedore [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Blake, G. A. [Division of Geological and Planetary Sciences, MC 150-21, California Institute of Technology, 1200 E California Blvd, Pasadena, CA 91125 (United States); Visser, R. [European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748, Garching (Germany)

2016-11-01

We report observations of resolved C{sub 2}H emission rings within the gas-rich protoplanetary disks of TW Hya and DM Tau using the Atacama Large Millimeter Array. In each case the emission ring is found to arise at the edge of the observable disk of millimeter-sized grains (pebbles) traced by submillimeter-wave continuum emission. In addition, we detect a C{sub 3}H{sub 2} emission ring with an identical spatial distribution to C{sub 2}H in the TW Hya disk. This suggests that these are hydrocarbon rings (i.e., not limited to C{sub 2}H). Using a detailed thermo-chemical model we show that reproducing the emission from C{sub 2}H requires a strong UV field and C/O > 1 in the upper disk atmosphere and outer disk, beyond the edge of the pebble disk. This naturally arises in a disk where the ice-coated dust mass is spatially stratified due to the combined effects of coagulation, gravitational settling and drift. This stratification causes the disk surface and outer disk to have a greater permeability to UV photons. Furthermore the concentration of ices that transport key volatile carriers of oxygen and carbon in the midplane, along with photochemical erosion of CO, leads to an elemental C/O ratio that exceeds unity in the UV-dominated disk. Thus the motions of the grains, and not the gas, lead to a rich hydrocarbon chemistry in disk surface layers and in the outer disk midplane.

Source to Accretion Disk Tilt

OpenAIRE

Montgomery, M. M.; Martin, E. L.

2010-01-01

Many different system types retrogradely precess, and retrograde precession could be from a tidal torque by the secondary on a misaligned accretion disk. However, a source to cause and maintain disk tilt is unknown. In this work, we show that accretion disks can tilt due to a force called lift. Lift results from differing gas stream supersonic speeds over and under an accretion disk. Because lift acts at the disk's center of pressure, a torque is applied around a rotation axis passing through...

Revealing the structure and dust content of debris disks on solar systems scales with GPI

Science.gov (United States)

Duchene, Gaspard; Fitzgerald, Michael P.; Kalas, Paul; Graham, James R.; Arriaga, Pauline; Bruzzone, Sebastian; Chen, Christine; Dawson, Rebekah Ilene; Dong, Ruobing; Draper, Zachary; Esposito, Thomas; Follette, Katherine; Hung, Li-Wei; Lawler, Samantha; Metchev, Stanimir; Millar-Blanchaer, Max; Murray-Clay, Ruth; Perrin, Marshall D.; Rameau, Julien; Wang, Jason; Wolff, Schuyler; Macintosh, Bruce; GPIES Team

2016-01-01

High contrast scattered light images offer the best prospect to assess the detailed geometry and structure of dusty debris disks. In turn, such images can yield profound insight on the architecture of the underlying planetary system as dust grains respond to the gravitational pull of planetary bodies. A new generation of extreme adaptive optics systems now enables an unprecedented exploration of circumstellar disks on solar system scales. Here we review the new science derived from over a dozen debris disks imaged with the Gemini Planet Imager (GPI) as part of the GPI Exoplanet Survey (GPIES). In addition to its exquisite imaging capability, GPI's polarimetric mode provides invaluable insight on the dust content of each disk, in most cases for the very first time. These early results typically reveal narrow belts of material with evacuated regions roughly 50-100 AU in radius, subtle asymmetries in structure and high degree of linear polarization. We will provide an overview of the disk observations made during the GPIES campaign to date and will discuss in more detail some of the most remarkable systems.This work is supported by grants NSF AST-0909188, -1411868, -1413718; NASA NNX-15AD95G, -14AJ80G, -11AD21G; and the NExSS research network.

Multi-level, automatic file management system using magnetic disk, mass storage system and magnetic tape

International Nuclear Information System (INIS)

Fujii, Minoru; Asai, Kiyoshi

1979-12-01

A simple, effective file management system using magnetic disk, mass storage system (MSS) and magnetic tape is described. Following are the concepts and techniques introduced in this file management system. (1) File distribution and continuity character of file references are closely approximated by memory retention function. A density function using the memory retention function is thus defined. (2) A method of computing the cost/benefit lines for magnetic disk, MSS and magnetic tape is presented. (3) A decision process of an optimal organization of file facilities incorporating file demands distribution to respective file devices, is presented. (4) A method of simple, practical, effective, automatic file management, incorporating multi-level file management, space management and file migration control, is proposed. (author)

PLANET-PLANET SCATTERING IN PLANETESIMAL DISKS. II. PREDICTIONS FOR OUTER EXTRASOLAR PLANETARY SYSTEMS

International Nuclear Information System (INIS)

Raymond, Sean N.; Armitage, Philip J.; Gorelick, Noel

2010-01-01

We develop an idealized dynamical model to predict the typical properties of outer extrasolar planetary systems, at radii comparable to the Jupiter-to-Neptune region of the solar system. The model is based upon the hypothesis that dynamical evolution in outer planetary systems is controlled by a combination of planet-planet scattering and planetary interactions with an exterior disk of small bodies ('planetesimals'). Our results are based on 5000 long duration N-body simulations that follow the evolution of three planets from a few to 10 AU, together with a planetesimal disk containing 50 M + from 10 to 20 AU. For large planet masses (M ∼> M Sat ), the model recovers the observed eccentricity distribution of extrasolar planets. For lower-mass planets, the range of outcomes in models with disks is far greater than that which is seen in isolated planet-planet scattering. Common outcomes include strong scattering among massive planets, sudden jumps in eccentricity due to resonance crossings driven by divergent migration, and re-circularization of scattered low-mass planets in the outer disk. We present the distributions of the eccentricity and inclination that result, and discuss how they vary with planet mass and initial system architecture. In agreement with other studies, we find that the currently observed eccentricity distribution (derived primarily from planets at a ∼ -1 and periods in excess of 10 years will provide constraints on this regime. Finally, we present an analysis of the predicted separation of planets in two-planet systems, and of the population of planets in mean-motion resonances (MMRs). We show that, if there are systems with ∼ Jupiter-mass planets that avoid close encounters, the planetesimal disk acts as a damping mechanism and populates MMRs at a very high rate (50%-80%). In many cases, resonant chains (in particular the 4:2:1 Laplace resonance) are set up among all three planets. We expect such resonant chains to be common among massive

New Constraints on Turbulence and Embedded Planet Mass in the HD 163296 Disk from Planet–Disk Hydrodynamic Simulations

Science.gov (United States)

Liu, Shang-Fei; Jin, Sheng; Li, Shengtai; Isella, Andrea; Li, Hui

2018-04-01

Recent Atacama Large Millimeter and Submillimeter Array (ALMA) observations of the protoplanetary disk around the Herbig Ae star HD 163296 revealed three depleted dust gaps at 60, 100, and 160 au in the 1.3 mm continuum as well as CO depletion in the middle and outer dust gaps. However, no CO depletion was found in the inner dust gap. To examine the planet–disk interaction model, we present results of 2D two fluid (gas + dust) hydrodynamic simulations coupled with 3D radiative transfer simulations. To fit the high gas-to-dust ratio of the first gap, we find that the Shakura–Sunyaev viscosity parameter α must be very small (≲ {10}-4) in the inner disk. On the other hand, a relatively large α (∼ 7.5× {10}-3) is required to reproduce the dust surface density in the outer disk. We interpret the variation of α as an indicator of the transition from an inner dead zone to the outer magnetorotational instability (MRI) active zone. Within ∼100 au, the HD 163296 disk’s ionization level is low, and non-ideal magnetohydrodynamic effects could suppress the MRI, so the disk can be largely laminar. The disk’s ionization level gradually increases toward larger radii, and the outermost disk (r> 300 au) becomes turbulent due to MRI. Under this condition, we find that the observed dust continuum and CO gas line emissions can be reasonably fit by three half-Jovian-mass planets (0.46, 0.46, and 0.58 {M}{{J}}) at 59, 105, and 160 au, respectively.

Spacecraft Multiple Array Communication System Performance Analysis

Science.gov (United States)

Hwu, Shian U.; Desilva, Kanishka; Sham, Catherine C.

2010-01-01

The Communication Systems Simulation Laboratory (CSSL) at the NASA Johnson Space Center is tasked to perform spacecraft and ground network communication system simulations, design validation, and performance verification. The CSSL has developed simulation tools that model spacecraft communication systems and the space and ground environment in which the tools operate. In this paper, a spacecraft communication system with multiple arrays is simulated. Multiple array combined technique is used to increase the radio frequency coverage and data rate performance. The technique is to achieve phase coherence among the phased arrays to combine the signals at the targeting receiver constructively. There are many technical challenges in spacecraft integration with a high transmit power communication system. The array combining technique can improve the communication system data rate and coverage performances without increasing the system transmit power requirements. Example simulation results indicate significant performance improvement can be achieved with phase coherence implementation.

MOLECULAR GAS IN YOUNG DEBRIS DISKS

International Nuclear Information System (INIS)

Moor, A.; Abraham, P.; Kiss, Cs.; Juhasz, A.; Kospal, A.; Pascucci, I.; Apai, D.; Henning, Th.; Csengeri, T.; Grady, C.

2011-01-01

Gas-rich primordial disks and tenuous gas-poor debris disks are usually considered as two distinct evolutionary phases of the circumstellar matter. Interestingly, the debris disk around the young main-sequence star 49 Ceti possesses a substantial amount of molecular gas and possibly represents the missing link between the two phases. Motivated to understand the evolution of the gas component in circumstellar disks via finding more 49 Ceti-like systems, we carried out a CO J = 3-2 survey with the Atacama Pathfinder EXperiment, targeting 20 infrared-luminous debris disks. These systems fill the gap between primordial and old tenuous debris disks in terms of fractional luminosity. Here we report on the discovery of a second 49 Ceti-like disk around the 30 Myr old A3-type star HD21997, a member of the Columba Association. This system was also detected in the CO(2-1) transition, and the reliable age determination makes it an even clearer example of an old gas-bearing disk than 49 Ceti. While the fractional luminosities of HD21997 and 49 Ceti are not particularly high, these objects seem to harbor the most extended disks within our sample. The double-peaked profiles of HD21997 were reproduced by a Keplerian disk model combined with the LIME radiative transfer code. Based on their similarities, 49 Ceti and HD21997 may be the first representatives of a so far undefined new class of relatively old (∼>8 Myr), gaseous dust disks. From our results, neither primordial origin nor steady secondary production from icy planetesimals can unequivocally explain the presence of CO gas in the disk of HD21997.

New ALMA Images of the HD 32297 and HD 61005 Debris Disks

Science.gov (United States)

MacGregor, Meredith Ann; Weinberger, Alycia; Wilner, David; Hughes, A. Meredith; debes, John Henry; Redfield, Seth; Donaldson, Jessica; Nesvold, Erika; Schneider, Glenn; Currie, Thayne; Roberge, Aki; Rodriguez, David

2018-01-01

HD 61005 (G-type star, “The Moth") and HD 32297 (A-type star) host two of the most iconic debris disks. Scattered light images show that both disks are nearly edge-on with dramatic swept-back wings of dust. Previous studies have proposed a range of mechanisms to explain this distinctive morphology including interactions with the interstellar medium, secular perturbations of grains by low-density, neutral interstellar gas, and gravitational interactions with an inclined, eccentric companion. We present new observations from the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.3 mm that provide the highest resolution images at millimeter wavelengths to date of both systems. Observations at millimeter wavelengths are especially critical to our understanding of the physical mechanisms shaping the structure of these disks, since the large grains that dominate emission at these wavelengths are less affected by stellar radiation and winds and more reliably trace the underlying planetesimal distribution. We fit models directly to the observed visibilities within a Markov Chain Monte Carlo (MCMC) framework to characterize the continuum emission and place constraints on the structure of these unique debris disks. Our new ALMA images reveal that despite differences in spectral type, both systems are best described by a two-component structure with (1) a parent body belt, and (2) an outer halo aligned with the scattered light disk. Such halos have typically been assumed to be composed of small grains visible in scattered light, so these images are some of the first observational evidence that larger grains may also populate extended halos. In addition, we detect significant 12CO gas emission from HD 32297, and determine a robust upper limit for HD 61005.

Resolution doubling in fluorescence microscopy with confocal spinning-disk image scanning microscopy.

Science.gov (United States)

Schulz, Olaf; Pieper, Christoph; Clever, Michaela; Pfaff, Janine; Ruhlandt, Aike; Kehlenbach, Ralph H; Wouters, Fred S; Großhans, Jörg; Bunt, Gertrude; Enderlein, Jörg

2013-12-24

We demonstrate how a conventional confocal spinning-disk (CSD) microscope can be converted into a doubly resolving image scanning microscopy (ISM) system without changing any part of its optical or mechanical elements. Making use of the intrinsic properties of a CSD microscope, we illuminate stroboscopically, generating an array of excitation foci that are moved across the sample by varying the phase between stroboscopic excitation and rotation of the spinning disk. ISM then generates an image with nearly doubled resolution. Using conventional fluorophores, we have imaged single nuclear pore complexes in the nuclear membrane and aggregates of GFP-conjugated Tau protein in three dimensions. Multicolor ISM was shown on cytoskeletal-associated structural proteins and on 3D four-color images including MitoTracker and Hoechst staining. The simple adaptation of conventional CSD equipment allows superresolution investigations of a broad variety of cell biological questions.

Circumstellar Gas in Young Planetary Debris Disks

Science.gov (United States)

Roberge, A.

Circumstellar (CS) disks orbiting young stars fall into two categories: primordial disks, composed of unprocessed interstellar dust and gas, and debris disks, produced by the destruction of solid planetary bodies. In the first class, the most abundant gas is H_2; in the second, it appears that the H_2 gas has disappeared, possibly through incorporation into gas giant planets. The lifetime of H_2 gas in a CS disk is therefore of great importance, as it dictates the timescale for the formation of giant planets. FUSE observations of H_2 in CS disk systems have shown that FUV absorption spectroscopy may sensitively probe for small amounts of gas along the line of sight to the star. Most importantly, the FUSE non-detection of H_2 gas in the Beta Pictoris disk suggests that the primordial gas lifetime is less than about 12 Myr, and that gas giant planets must form very quickly. However, this suggestion is based on one system, and needs to be tested in additional systems with a range of ages, especially since there are indications that age is not the only factor in the evolution of a CS disk. We propose for FUSE observations of 3 additional debris disk systems, Fomalhaut, HD3003, and HD2884. Fomalhaut is an intermediate age debris disk, one of the Fabulous Four CS disks first discovered in 1984. The other two disks are younger, with ages similar to that of Beta Pic. All three stars are brighter in the FUV than Beta Pic, permitting us to sensitively probe for traces of H_2 gas. We will also measure the amount of secondary atomic gas produced from planetary bodies in these disks, in an effort to understand the entire evolution of CS gas in young planetary systems.

Real-time disk scheduling in a mixed-media file system

NARCIS (Netherlands)

Bosch, H.G.P.; Mullender, Sape J.

2000-01-01

This paper presents our real-time disk scheduler called the Delta L scheduler, which optimizes unscheduled best-effort disk requests by giving priority to best-effort disk requests while meeting real-time request deadlines. Our scheduler tries to execute real-time disk requests as much as possible

Real-Time Disk Scheduling in a Mixed-Media File System

NARCIS (Netherlands)

Bosch, H.G.P.; Mullender, Sape J.

2000-01-01

This paper presents our real-time disk scheduler called the L scheduler, which optimizes unscheduled best-effort disk requests by giving priority to best-effort disk requests while meeting real-time request deadlines. Our scheduler tries to execute real-time disk requests as much as possible in the

YottaYotta announces new world record set for TCP disk-to-disk bulk transfer

CERN Document Server

2002-01-01

The Yottabyte NetStorage(TM) Company, today announced a new world record for TCP disk-to-disk data transfer using the company's NetStorager(R) System. The record-breaking demonstration transferred 5 terabytes of data between Chicago, Il. to Vancouver, BC and Ottawa, ON, at a sustained average throughput of 11.1 gigabits per second. Peak throughput exceeded 11.6 gigabits per second, more than 15-times faster than previous records for TCP transfer from disk-to-disk (1 page).

A COMMON SOURCE OF ACCRETION DISK TILT

International Nuclear Information System (INIS)

Montgomery, M. M.; Martin, E. L.

2010-01-01

Many different system types retrogradely precess, and retrograde precession could be from a tidal torque by the secondary on a misaligned accretion disk. However, a source that causes and maintains disk tilt is unknown. In this work, we show that accretion disks can tilt due to a force called lift. Lift results from differing gas stream supersonic speeds over and under an accretion disk. Because lift acts at the disk's center of pressure, a torque is applied around a rotation axis passing through the disk's center of mass. The disk responds to lift by pitching around the disk's line of nodes. If the gas stream flow ebbs, then lift also ebbs and the disk attempts to return to its original orientation. To first approximation, lift does not depend on magnetic fields or radiation sources but does depend on the mass and the surface area of the disk. Also, for disk tilt to be initiated, a minimum mass transfer rate must be exceeded. For example, a 10 -11 M sun disk around a 0.8 M sun compact central object requires a mass transfer rate greater than ∼ 8 x 10 -11 M sun yr -1 , a value well below the known mass transfer rates in cataclysmic variable dwarf novae systems that retrogradely precess and exhibit negative superhumps in their light curves and a value well below mass transfer rates in protostellar-forming systems.

DEBRIS DISKS IN THE SCORPIUS–CENTAURUS OB ASSOCIATION RESOLVED BY ALMA

Energy Technology Data Exchange (ETDEWEB)

Lieman-Sifry, Jesse; Hughes, A. Meredith; Flaherty, Kevin M. [Department of Astronomy, Van Vleck Observatory, Wesleyan University, 96 Foss Hill Drive, Middletown, CT 06459 (United States); Carpenter, John M. [Department of Astronomy, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States); Gorti, Uma [SETI Institute, Mountain View, CA (United States); Hales, Antonio [Atacama Large Millimeter/Submillimeter Array, Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura 763-0355, Santiago (Chile)

2016-09-01

We present a CO(2-1) and 1240 μ m continuum survey of 23 debris disks with spectral types B9-G1, observed at an angular resolution of 0.″5–1″ with the Atacama Large Millimeter/Submillimeter Array (ALMA). The sample was selected for large infrared excess and age ∼10 Myr, to characterize the prevalence of molecular gas emission in young debris disks. We identify three CO-rich debris disks, plus two additional tentative (3 σ) CO detections. Twenty disks were detected in the continuum at the >3 σ level. For the 12 disks in the sample that are spatially resolved by our observations, we perform an independent analysis of the interferometric continuum visibilities to constrain the basic dust disk geometry, as well as a simultaneous analysis of the visibilities and broadband spectral energy distribution to constrain the characteristic grain size and disk mass. The gas-rich debris disks exhibit preferentially larger outer radii in their dust disks, and a higher prevalence of characteristic grain sizes smaller than the blowout size. The gas-rich disks do not exhibit preferentially larger dust masses, contrary to expectations for a scenario in which a higher cometary destruction rate would be expected to result in a larger mass of both CO and dust. The three debris disks in our sample with strong CO detections are all around A stars: the conditions in disks around intermediate-mass stars appear to be the most conducive to the survival or formation of CO.

CAT - A Disk Cataloging System for the CP/M Operating System.

Science.gov (United States)

1980-08-04

MAC KM80 C02 sCQcwr *MAC MACROSO XC02 SCIN *MAC MACROSO XC02 SCIO, MAC M9CRO80 *C02 scLOIJT .*? AC M9LCRO80 XC02 44 CAT Interrupted 44 Chipter 5 -Page 6...7 A A088 167 ARMY SATELLITE COMMUNICATIONS AGENCY FORT MONMOUTH N.J F/S 9/2 CAT - A DISK CATALOGING SYSTEM FOR THE CP/ OPERATING SYSTEM.(U) UG 80...RECIPIENT’S CATALOG NUMBER 4. TITLE (and Subtitle) 5. TYPE OF REPORT & PERIOD COVERED S atsk Cat oging System for theP/M Final ..a.St. 6. PERFORMING ORG

Searching for Faint Traces of CO(2-1) and HCN(4-3) Gas In Debris Disks

Science.gov (United States)

Stafford Lambros, Zachary; Hughes, A. Meredith

2018-01-01

The surprising presence of molecular gas in the debris disks around main sequence stars provides an opportunity to study the dissipation of primordial gas and, potentially, the composition of gas in other solar systems. Molecular gas is not expected to survive beyond the pre-main sequence phase, and it is not yet clear whether the gas is a remnant of the primordial protoplanetary material or whether the gas, like the dust, is second-generation material produced by collisional or photodesorption from planetesimals, exocomets, or the icy mantles of dust grains. Here we present two related efforts to characterize the prevalence and properties of gas in debris disks. First, we place the lowest limits to date on the CO emission from an M star debris disk, using 0.3" resolution observations of CO(2-1) emission from the AU Mic system with the Atacama Large Millimeter/submillimeter Array (ALMA). We place a 3-sigma upper limit on the integrated flux of 0.39 Jy km/s, corresponding to a maximum CO mass of 5e10-6 (Earth Masses) if the gas is in LTE. We also present the results of an ALMA search for HCN(4-3) emission from the prototypical gas-rich debris disk around 49 Ceti at a spatial resolution of 0.3". Despite hosting one of the brightest CO-rich debris disks yet discovered, our observations of 49 Ceti also yield a low upper limit of 0.057 Jy km/s in the HCN line, leaving CO as the only molecule clearly detected in emission from a debris disk. We employ several methods of detecting faint line emission from debris disks, including a model based on Keplerian kinematics as well as a spectral shifting method previously used to detect faint CO emission from the Fomalhaut debris disk, and compare our results.

EVIDENCE FOR INFALLING GAS OF LOW ANGULAR MOMENTUM TOWARD THE L1551 NE KEPLERIAN CIRCUMBINARY DISK

Energy Technology Data Exchange (ETDEWEB)

Takakuwa, Shigehisa [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China); Saito, Masao [Joint ALMA Observatory, Ave. Alonso de Cordova 3107, Vitacura, Santiago (Chile); Lim, Jeremy [Department of Physics, University of Hong Kong, Pokfulam Road (Hong Kong); Saigo, Kazuya, E-mail: takakuwa@asiaa.sinica.edu.tw [ALMA Project Office, National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588 (Japan)

2013-10-10

We report follow-up C{sup 18}O(3-2) line observations of the Class I binary protostellar system L1551 NE with the Submillimeter Array in its compact and subcompact configurations. Our previous observations at a higher angular resolution in the extended configuration revealed a circumbinary disk exhibiting Keplerian motion. The combined data, with more extensive spatial coverage (∼140-2000 AU), verify the presence of a Keplerian circumbinary disk and reveal for the first time a distinct low-velocity (∼< ± 0.5 km s{sup –1} from the systemic velocity) component that displays a velocity gradient along the minor axis of the circumbinary disk. Our simple model that reproduces the main features seen in the position-velocity diagrams comprises a circumbinary disk exhibiting Keplerian motion out to a radius of ∼300 AU, beyond which the gas exhibits pure infall at a constant velocity of ∼0.6 km s{sup –1}. This velocity is significantly smaller than the expected free-fall velocity of ∼2.2 km s{sup –1} onto the L1551 NE protostellar mass of ∼0.8 M{sub ☉} at ∼300 AU, suggesting that the infalling gas is decelerated as it moves into regions of high gas pressure in the circumbinary disk. The discontinuity in angular momenta between the outer infalling gas and the inner Keplerian circumbinary disk implies an abrupt transition in the effectiveness at which magnetic braking is able to transfer angular momentum outward, a result perhaps of the different plasma β values and the ionization fractions between the outer and inner regions of the circumbinary disk.

Open and Closed Loop Parametric System Identification in Compact Disk Players

DEFF Research Database (Denmark)

Vidal, Enrique Sanchez; Stoustrup, Jakob; Andersen, Palle

2001-01-01

By measuring the current through the coil of the actuators in the optical pick-up in a compact disk player, open loop parametric system identification can be performed. The parameters are identified by minimizing the least-squares loss function of the ARX model. The only parameter which cannot be...... be identified in open loop is the optical gain. This is therefore estimated in closed loop. Practical results are analyzed and show very accurate estimates of the real parameters.......By measuring the current through the coil of the actuators in the optical pick-up in a compact disk player, open loop parametric system identification can be performed. The parameters are identified by minimizing the least-squares loss function of the ARX model. The only parameter which cannot...

Text experiments of disk chopper with supermirror converging system

International Nuclear Information System (INIS)

Aizawa, K.; Soyama, K.; Matsubayashi, M.; Suzuki, J.; Watanabe, N.

2001-01-01

We measured transportation property of neutron pulsed by disk chopper with three kinds of setting of supermirror guide at JRR-3M, JAERI. We confirmed a gain of supermirror converging system to narrow straight supermirror system. The gain is approximately same as the ratio of entrance width of converging guide to width of narrow straight guide. On the other hand, we did not get a gain of supermirror converging system to wide straight supermirror system which has a same width to entrance width of converging guide and we will plan more precisely experiment. (author)

SUBARU IMAGING OF ASYMMETRIC FEATURES IN A TRANSITIONAL DISK IN UPPER SCORPIUS

Energy Technology Data Exchange (ETDEWEB)

Mayama, S. [Center for the Promotion of Integrated Sciences, The Graduate University for Advanced Studies (SOKENDAI), Shonan International Village, Hayama-cho, Miura-gun, Kanagawa 240-0193 (Japan); Hashimoto, J.; Kusakabe, N.; Kuzuhara, M.; Takahashi, Y.; Akiyama, E. [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Muto, T. [Division of Liberal Arts, Kogakuin University, 1-24-2, Nishi-Shinjuku, Shinjuku-ku, Tokyo 163-8677 (Japan); Tsukagoshi, T.; Momose, M. [College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512 (Japan); Kudo, T.; Egner, S. [Subaru Telescope, 650 North A' ohoku Place, Hilo, HI 96720 (United States); Dong, R.; Brandt, T. [Department of Astrophysical Sciences, Princeton University, NJ 08544 (United States); Fukagawa, M. [Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan); Takami, M. [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 106, Taiwan (China); Wisniewski, J. P. [H L Dodge Department of Physics and Astronomy, University of Oklahoma, 440 West Brooks St. Norman, OK 73019 (United States); Follette, K. [Department of Astronomy and Steward Observatory, The University of Arizona, 933 North Cherry Avenue, Rm. N204, Tucson, AZ 85721-0065 (United States); Abe, L. [Laboratoire Hippolyte Fizeau, UMR6525, Universite de Nice Sophia-Antipolis, 28, avenue Valrose, F-06108 Nice Cedex 02 (France); Brandner, W. [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany); Carson, J., E-mail: mayama_satoshi@soken.ac.jp [Department of Physics and Astronomy, College of Charleston, 58 Coming Street, Charleston, SC 29424 (United States); and others

2012-12-01

We report high-resolution (0.07 arcsec) near-infrared polarized intensity images of the circumstellar disk around the star 2MASS J16042165-2130284 obtained with HiCIAO mounted on the Subaru 8.2 m telescope. We present our H-band data, which clearly exhibit a resolved, face-on disk with a large inner hole for the first time at infrared wavelengths. We detect the centrosymmetric polarization pattern in the circumstellar material as has been observed in other disks. Elliptical fitting gives the semimajor axis, semiminor axis, and position angle (P.A.) of the disk as 63 AU, 62 AU, and -14 Degree-Sign , respectively. The disk is asymmetric, with one dip located at P.A.s of {approx}85 Degree-Sign . Our observed disk size agrees well with a previous study of dust and CO emission at submillimeter wavelength with Submillimeter Array. Hence, the near-infrared light is interpreted as scattered light reflected from the inner edge of the disk. Our observations also detect an elongated arc (50 AU) extending over the disk inner hole. It emanates at the inner edge of the western side of the disk, extending inward first, then curving to the northeast. We discuss the possibility that the inner hole, the dip, and the arc that we have observed may be related to the existence of unseen bodies within the disk.

DISK DETECTIVE: DISCOVERY OF NEW CIRCUMSTELLAR DISK CANDIDATES THROUGH CITIZEN SCIENCE

Energy Technology Data Exchange (ETDEWEB)

Kuchner, Marc J.; McElwain, Michael; Padgett, Deborah L. [NASA Goddard Space Flight Center Exoplanets and Stellar Astrophysics Laboratory, Code 667 Greenbelt, MD 21230 (United States); Silverberg, Steven M.; Wisniewski, John P. [Homer L. Dodge Department of Physics and Astronomy The University of Oklahoma 440 W. Brooks St. Norman, OK 73019 (United States); Bans, Alissa S. [Valparaiso University, Department of Physics and Astronomy, Neils Science Center, 1610 Campus Drive East, Valparaiso, IN 46383 (United States); Bhattacharjee, Shambo [International Space University 1 Rue Jean-Dominique Cassini F-67400 Illkirch-Graffenstaden (France); Kenyon, Scott J. [Smithsonian Astrophysical Observatory 60 Garden Street Cambridge, MA 02138 (United States); Debes, John H. [Space Telescope Science Institute 3700 San Martin Dr. Baltimore, MD 21218 (United States); Currie, Thayne [National Astronomical Observatory of Japan 650 N A’ohokhu Place Hilo, HI 96720 (United States); García, Luciano [Observatorio Astronómico de Córdoba Universidad Nacional de Córdoba Laprida 854, X5000BGR, Córdoba (Argentina); Jung, Dawoon [Korea Aerospace Research Institute Lunar Exploration Program Office 169-84 Gwahak-ro, Yuseong-gu, Daejeon 34133 (Korea, Republic of); Lintott, Chris [Denys Wilkinson Building Keble Road Oxford, OX1 3RH (United Kingdom); Rebull, Luisa M. [Infrared Processing and Analaysis Center Caltech M/S 314-6 1200 E. California Blvd. Pasadena, CA 91125 (United States); Nesvold, Erika, E-mail: Marc.Kuchner@nasa.gov, E-mail: michael.w.mcelwain@nasa.gov, E-mail: deborah.l.padgett@nasa.gov, E-mail: carol.a.grady@nasa.gov, E-mail: silverberg@ou.edu, E-mail: wisniewski@ou.edu [Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road, NW, Washington, DC 20015-1305 (United States); Collaboration: Disk Detective Collaboration; and others

2016-10-20

The Disk Detective citizen science project aims to find new stars with 22 μ m excess emission from circumstellar dust using data from NASA’s Wide-field Infrared Survey Explorer ( WISE ) mission. Initial cuts on the AllWISE catalog provide an input catalog of 277,686 sources. Volunteers then view images of each source online in 10 different bands to identify false positives (galaxies, interstellar matter, image artifacts, etc.). Sources that survive this online vetting are followed up with spectroscopy on the FLWO Tillinghast telescope. This approach should allow us to unleash the full potential of WISE for finding new debris disks and protoplanetary disks. We announce a first list of 37 new disk candidates discovered by the project, and we describe our vetting and follow-up process. One of these systems appears to contain the first debris disk discovered around a star with a white dwarf companion: HD 74389. We also report four newly discovered classical Be stars (HD 6612, HD 7406, HD 164137, and HD 218546) and a new detection of 22 μ m excess around the previously known debris disk host star HD 22128.

DISK DETECTIVE: DISCOVERY OF NEW CIRCUMSTELLAR DISK CANDIDATES THROUGH CITIZEN SCIENCE

International Nuclear Information System (INIS)

Kuchner, Marc J.; McElwain, Michael; Padgett, Deborah L.; Silverberg, Steven M.; Wisniewski, John P.; Bans, Alissa S.; Bhattacharjee, Shambo; Kenyon, Scott J.; Debes, John H.; Currie, Thayne; García, Luciano; Jung, Dawoon; Lintott, Chris; Rebull, Luisa M.; Nesvold, Erika

2016-01-01

The Disk Detective citizen science project aims to find new stars with 22 μ m excess emission from circumstellar dust using data from NASA’s Wide-field Infrared Survey Explorer ( WISE ) mission. Initial cuts on the AllWISE catalog provide an input catalog of 277,686 sources. Volunteers then view images of each source online in 10 different bands to identify false positives (galaxies, interstellar matter, image artifacts, etc.). Sources that survive this online vetting are followed up with spectroscopy on the FLWO Tillinghast telescope. This approach should allow us to unleash the full potential of WISE for finding new debris disks and protoplanetary disks. We announce a first list of 37 new disk candidates discovered by the project, and we describe our vetting and follow-up process. One of these systems appears to contain the first debris disk discovered around a star with a white dwarf companion: HD 74389. We also report four newly discovered classical Be stars (HD 6612, HD 7406, HD 164137, and HD 218546) and a new detection of 22 μ m excess around the previously known debris disk host star HD 22128.

Disk Detective: Discovery of New Circumstellar Disk Candidates Through Citizen Science

Science.gov (United States)

Kuchner, Marc J.; Silverberg, Steven M.; Bans, Alissa S.; Bhattacharjee, Shambo; Kenyon, Scott J.; Debes, John H.; Currie, Thayne; Garcia, Luciano; Jung, Dawoon; Lintott, Chris;

Acoustic array systems theory, implementation, and application

CERN Document Server

Bai, Mingsian R; Benesty, Jacob

2013-01-01

Presents a unified framework of far-field and near-field array techniques for noise source identification and sound field visualization, from theory to application. Acoustic Array Systems: Theory, Implementation, and Application provides an overview of microphone array technology with applications in noise source identification and sound field visualization. In the comprehensive treatment of microphone arrays, the topics covered include an introduction to the theory, far-field and near-field array signal processing algorithms, practical implementations, and common applic

The Architecture of the GW Ori Young Triple-star System and Its Disk: Dynamical Masses, Mutual Inclinations, and Recurrent Eclipses

Science.gov (United States)

Czekala, Ian; Andrews, Sean M.; Torres, Guillermo; Rodriguez, Joseph E.; Jensen, Eric L. N.; Stassun, Keivan G.; Latham, David W.; Wilner, David J.; Gully-Santiago, Michael A.; Grankin, Konstantin N.; Lund, Michael B.; Kuhn, Rudolf B.; Stevens, Daniel J.; Siverd, Robert J.; James, David; Gaudi, B. Scott; Shappee, Benjamin J.; Holoien, Thomas W.-S.

2017-12-01

We present spatially and spectrally resolved Atacama Large Millimeter/submillimeter Array (ALMA) observations of gas and dust orbiting the pre-main-sequence hierarchical triple-star system GW Ori. A forward modeling of the 13CO and C18O J = 2–1 transitions permits a measurement of the total stellar mass in this system, 5.29+/- 0.09 {M}ȯ , and the circumtriple disk inclination, 137\\buildrel{\\circ}\\over{.} 6+/- 2\\buildrel{\\circ}\\over{.} 0. Optical spectra spanning a 35 yr period were used to derive new radial velocities and, coupled with a spectroscopic disentangling technique, revealed that the A and B components of GW Ori form a double-lined spectroscopic binary with a period of 241.50 ± 0.05 days; a tertiary companion orbits that inner pair with a period of 4218 ± 50 days. Combining the results from the ALMA data and the optical spectra with three epochs of astrometry in the literature, we constrain the individual stellar masses in the system ({M}{{A}}≈ 2.7 {M}ȯ , {M}{{B}}≈ 1.7 {M}ȯ , {M}{{C}}≈ 0.9 {M}ȯ ) and find strong evidence that at least one of the stellar orbital planes (and likely both) is misaligned with the disk plane by as much as 45°. A V-band light curve spanning 30 yr reveals several new ∼30-day eclipse events 0.1–0.7 mag in depth and a 0.2 mag sinusoidal oscillation that is clearly phased with the AB–C orbital period. Taken together, these features suggest that the A–B pair may be partially obscured by material in the inner disk as the pair approaches apoastron in the hierarchical orbit. Lastly, we conclude that stellar evolutionary models are consistent with our measurements of the masses and basic photospheric properties if the GW Ori system is ∼1 Myr old.

Disk Operating System--DOS. Teacher Packet. Learning Activity Packets.

Science.gov (United States)

Oklahoma State Dept. of Vocational and Technical Education, Stillwater. Curriculum and Instructional Materials Center.

The Learning Activity Packets (LAPs) contained in this manual are designed to assist the beginning user in understanding DOS (Disk Operating System). LAPs will not work with any version below DOS Version 3.0 and do not address the enhanced features of versions 4.0 or higher. These elementary activities cover only the DOS commands necessary to…

Optimization of disk generator performance for base-load power plant systems applications

International Nuclear Information System (INIS)

Teare, J.D.; Loubsky, W.J.; Lytle, J.K.; Louis, J.F.

1980-01-01

Disk generators for use in base-load MHD power plants are examined for both open-cycle and closed-cycle operating modes. The OCD cases are compared with PSPEC results for a linear channel; enthalpy extractions up to 23% with 71% isentropic efficiency are achievable with generator inlet conditions similar to those used in PSPEC, thus confirming that the disk configuration is a viable alternative for base-load power generation. The evaluation of closed-cycle disks includes use of a simplified cycle model. High system efficiencies over a wide range of power levels are obtained for effective Hall coefficients in the range 2.3 to 4.9. Cases with higher turbulence (implying β/sub eff/ less than or equal to 2.4) yield high system efficiencies at power levels of 100 to 500 MW/sub e/. All these CCD cases compare favorably with linear channels reported in the GE ECAS study, yielding higher isentropic efficiences for a given enthalpy extraction. Power densities in the range 70 to 170 MW/m 3 appear feasible, leading to very compact generator configurations

Modeling and analysis of the disk MHD generator component of a gas core reactor/MHD Rankine cycle space power system

International Nuclear Information System (INIS)

Welch, G.E.; Dugan, E.T.; Lear, W.E. Jr.; Appelbaum, J.G.

1990-01-01

A gas core nuclear reactor (GCR)/disk magnetohydrodynamic (MHD) generator direct closed Rankine space power system concept is described. The GCR/disk MHD generator marriage facilitates efficient high electric power density system performance at relatively high operating temperatures. The system concept promises high specific power levels, on the order of 1 kW e /kg. An overview of the disk MHD generator component magnetofluiddynamic and plasma physics theoretical modeling is provided. Results from a parametric design analysis of the disk MHD generator are presented and discussed

The SEEDS Direct Imaging Survey for Planets and Scattered Dust Emission in Debris Disk Systems

NARCIS (Netherlands)

Janson, M.; et al., [Unknown; Thalmann, C.

2013-01-01

Debris disks around young main-sequence stars often have gaps and cavities which for a long time have been interpreted as possibly being caused by planets. In recent years, several giant planet discoveries have been made in systems hosting disks of precisely this nature, further implying that

Audit: Automated Disk Investigation Toolkit

Directory of Open Access Journals (Sweden)

Umit Karabiyik

2014-09-01

Full Text Available Software tools designed for disk analysis play a critical role today in forensics investigations. However, these digital forensics tools are often difficult to use, usually task specific, and generally require professionally trained users with IT backgrounds. The relevant tools are also often open source requiring additional technical knowledge and proper configuration. This makes it difficult for investigators without some computer science background to easily conduct the needed disk analysis. In this paper, we present AUDIT, a novel automated disk investigation toolkit that supports investigations conducted by non-expert (in IT and disk technology and expert investigators. Our proof of concept design and implementation of AUDIT intelligently integrates open source tools and guides non-IT professionals while requiring minimal technical knowledge about the disk structures and file systems of the target disk image.

EARTH, MOON, SUN, AND CV ACCRETION DISKS

International Nuclear Information System (INIS)

Montgomery, M. M.

2009-01-01

Net tidal torque by the secondary on a misaligned accretion disk, like the net tidal torque by the Moon and the Sun on the equatorial bulge of the spinning and tilted Earth, is suggested by others to be a source to retrograde precession in non-magnetic, accreting cataclysmic variable (CV) dwarf novae (DN) systems that show negative superhumps in their light curves. We investigate this idea in this work. We generate a generic theoretical expression for retrograde precession in spinning disks that are misaligned with the orbital plane. Our generic theoretical expression matches that which describes the retrograde precession of Earths' equinoxes. By making appropriate assumptions, we reduce our generic theoretical expression to those generated by others, or to those used by others, to describe retrograde precession in protostellar, protoplanetary, X-ray binary, non-magnetic CV DN, quasar, and black hole systems. We find that spinning, tilted CV DN systems cannot be described by a precessing ring or by a precessing rigid disk. We find that differential rotation and effects on the disk by the accretion stream must be addressed. Our analysis indicates that the best description of a retrogradely precessing spinning, tilted, CV DN accretion disk is a differentially rotating, tilted disk with an attached rotating, tilted ring located near the innermost disk annuli. In agreement with the observations and numerical simulations by others, we find that our numerically simulated CV DN accretion disks retrogradely precess as a unit. Our final, reduced expression for retrograde precession agrees well with our numerical simulation results and with selective observational systems that seem to have main-sequence secondaries. Our results suggest that a major source to retrograde precession is tidal torques like that by the Moon and the Sun on the Earth. In addition, these tidal torques should be common to a variety of systems where one member is spinning and tilted, regardless if

Debris disks as signposts of terrestrial planet formation. II. Dependence of exoplanet architectures on giant planet and disk properties

Science.gov (United States)

Raymond, S. N.; Armitage, P. J.; Moro-Martín, A.; Booth, M.; Wyatt, M. C.; Armstrong, J. C.; Mandell, A. M.; Selsis, F.; West, A. A.

2012-05-01

We present models for the formation of terrestrial planets, and the collisional evolution of debris disks, in planetary systems that contain multiple marginally unstable gas giants. We previously showed that in such systems, the dynamics of the giant planets introduces a correlation between the presence of terrestrial planets and cold dust, i.e., debris disks, which is particularly pronounced at λ ~ 70 μm. Here we present new simulations that show that this connection is qualitatively robust to a range of parameters: the mass distribution of the giant planets, the width and mass distribution of the outer planetesimal disk, and the presence of gas in the disk when the giant planets become unstable. We discuss how variations in these parameters affect the evolution. We find that systems with equal-mass giant planets undergo the most violent instabilities, and that these destroy both terrestrial planets and the outer planetesimal disks that produce debris disks. In contrast, systems with low-mass giant planets efficiently produce both terrestrial planets and debris disks. A large fraction of systems with low-mass (M ≲ 30 M⊕) outermost giant planets have final planetary separations that, scaled to the planets' masses, are as large or larger than the Saturn-Uranus and Uranus-Neptune separations in the solar system. We find that the gaps between these planets are not only dynamically stable to test particles, but are frequently populated by planetesimals. The possibility of planetesimal belts between outer giant planets should be taken into account when interpreting debris disk SEDs. In addition, the presence of ~ Earth-mass "seeds" in outer planetesimal disks causes the disks to radially spread to colder temperatures, and leads to a slow depletion of the outer planetesimal disk from the inside out. We argue that this may explain the very low frequency of >1 Gyr-old solar-type stars with observed 24 μm excesses. Our simulations do not sample the full range of

An assumed mode method and finite element method investigation of the coupled vibration in a flexible-disk rotor system with lacing wires

Energy Technology Data Exchange (ETDEWEB)

Zhou, Shui-Ting; Huang, Hong-Wu [Hunan University, Changsha (China); Chiu, Yi-Jui; Yu, Guo-Fei [Xiamen University of Technology, Xiamen (China); Yang, Chia-Hao [Taipei Chengshih University of Science and Technology, Taipei (China); Jian, Sheng-Rui [I-Shou University, Kaohsiung (China)

2017-02-15

The Assumed mode method (AMM) and Finite element method (FEM) were used. Their results were compared to investigate the coupled shaft-torsion, disk-transverse, and blade-bending vibrations in a flexible-disk rotor system. The blades were grouped with a spring. The flexible-disk rotor system was divided into three modes of coupled vibrations: Shaft-disk-blade, disk-blade, and blade-blade. Two new modes of coupled vibrations were introduced, namely, lacing wires-blade and lacing wires-disk-blade. The patterns of change of the natural frequencies and mode shapes of the system were discussed. The results showed the following: first, mode shapes and natural frequencies varied, and the results of the AMM and FEM differed; second, numerical calculation results showed three influencing factors on natural frequencies, namely, the lacing wire constant, the lacing wire location, and the flexible disk; lastly, the flexible disk could affect the stability of the system as reflected in the effect of the rotational speed.

Superresolution upgrade for confocal spinning disk systems using image scanning microscopy (Conference Presentation)

Science.gov (United States)

Isbaner, Sebastian; Hähnel, Dirk; Gregor, Ingo; Enderlein, Jörg

2017-02-01

Confocal Spinning Disk Systems are widely used for 3D cell imaging because they offer the advantage of optical sectioning at high framerates and are easy to use. However, as in confocal microscopy, the imaging resolution is diffraction limited, which can be theoretically improved by a factor of 2 using the principle of Image Scanning Microscopy (ISM) [1]. ISM with a Confocal Spinning Disk setup (CSDISM) has been shown to improve contrast as well as lateral resolution (FWHM) from 201 +/- 20 nm to 130 +/- 10 nm at 488 nm excitation. A minimum total acquisition time of one second per ISM image makes this method highly suitable for 3D live cell imaging [2]. Here, we present a multicolor implementation of CSDISM for the popular Micro-Manager Open Source Microscopy platform. Since changes in the optical path are not necessary, this will allow any researcher to easily upgrade their standard Confocal Spinning Disk system at remarkable low cost ( 5000 USD) with an ISM superresolution option. [1]. Müller, C.B. and Enderlein, J. Image Scanning Microscopy. Physical Review Letters 104, (2010). [2]. Schulz, O. et al. Resolution doubling in fluorescence microscopy with confocal spinning-disk image scanning microscopy. Proceedings of the National Academy of Sciences of the United States of America 110, 21000-5 (2013).

Disk-to-Disk network transfers at 100 Gb/s

Science.gov (United States)

Barczyk, Artur; Gable, Ian; Hay, Marilyn; Leavett-Brown, Colin; Legrand, Iosif; Lewall, Kim; McKee, Shawn; McWilliam, Donald; Mughal, Azher; Newman, Harvey; Rozsa, Sandor; Savard, Yvan; Sobie, Randall J.; Tam, Thomas; Voicu, Ramiro

2012-12-01

A 100 Gbps network was established between the California Institute of Technology conference booth at the Super Computing 2011 conference in Seattle, Washington and the computing center at the University of Victoria in Canada. A circuit was established over the BCNET, CANARIE and Super Computing (SCInet) networks using dedicated equipment. The small set of servers at the endpoints used a combination of 10GE and 40GE technologies, and SSD drives for data storage. The configuration of the network and the server configuration are discussed. We will show that the system was able to achieve disk-to-disk transfer rates of 60 Gbps and memory-to-memory rates in excess of 180 Gbps across the WAN. We will discuss the transfer tools, disk configurations, and monitoring tools used in the demonstration.

Disk-to-Disk network transfers at 100 Gb/s

International Nuclear Information System (INIS)

Barczyk, Artur; Legrand, Iosif; Mughal, Azher; Newman, Harvey; Rozsa, Sandor; Voicu, Ramiro; Gable, Ian; Leavett-Brown, Colin; Lewall, Kim; Savard, Yvan; Sobie, Randall J; Hay, Marilyn; McWilliam, Donald; McKee, Shawn; Tam, Thomas

2012-01-01

A 100 Gbps network was established between the California Institute of Technology conference booth at the Super Computing 2011 conference in Seattle, Washington and the computing center at the University of Victoria in Canada. A circuit was established over the BCNET, CANARIE and Super Computing (SCInet) networks using dedicated equipment. The small set of servers at the endpoints used a combination of 10GE and 40GE technologies, and SSD drives for data storage. The configuration of the network and the server configuration are discussed. We will show that the system was able to achieve disk-to-disk transfer rates of 60 Gbps and memory-to-memory rates in excess of 180 Gbps across the WAN. We will discuss the transfer tools, disk configurations, and monitoring tools used in the demonstration.

EzArray: A web-based highly automated Affymetrix expression array data management and analysis system

Directory of Open Access Journals (Sweden)

Zhu Yuelin

2008-01-01

Full Text Available Abstract Background Though microarray experiments are very popular in life science research, managing and analyzing microarray data are still challenging tasks for many biologists. Most microarray programs require users to have sophisticated knowledge of mathematics, statistics and computer skills for usage. With accumulating microarray data deposited in public databases, easy-to-use programs to re-analyze previously published microarray data are in high demand. Results EzArray is a web-based Affymetrix expression array data management and analysis system for researchers who need to organize microarray data efficiently and get data analyzed instantly. EzArray organizes microarray data into projects that can be analyzed online with predefined or custom procedures. EzArray performs data preprocessing and detection of differentially expressed genes with statistical methods. All analysis procedures are optimized and highly automated so that even novice users with limited pre-knowledge of microarray data analysis can complete initial analysis quickly. Since all input files, analysis parameters, and executed scripts can be downloaded, EzArray provides maximum reproducibility for each analysis. In addition, EzArray integrates with Gene Expression Omnibus (GEO and allows instantaneous re-analysis of published array data. Conclusion EzArray is a novel Affymetrix expression array data analysis and sharing system. EzArray provides easy-to-use tools for re-analyzing published microarray data and will help both novice and experienced users perform initial analysis of their microarray data from the location of data storage. We believe EzArray will be a useful system for facilities with microarray services and laboratories with multiple members involved in microarray data analysis. EzArray is freely available from http://www.ezarray.com/.

Time Variability of the Dust Sublimation Zones in Pre-Main Sequence Disk Systems

Science.gov (United States)

Sitko, Michael L.; Carpenter, W. J.; Grady, C. A.; Russel, R. W.; Lynch, D. K.; Rudy, R. J.; Mazuk, S. M.; Venturini, C. C.; Kimes, R. L.; Beerman, L. C.;

THE KOZAI-LIDOV MECHANISM IN HYDRODYNAMICAL DISKS

International Nuclear Information System (INIS)

Martin, Rebecca G.; Nixon, Chris; Armitage, Philip J.; Lubow, Stephen H.; Price, Daniel J.; Doğan, Suzan; King, Andrew

2014-01-01

We use three-dimensional hydrodynamical simulations to show that a highly misaligned accretion disk around one component of a binary system can exhibit global Kozai-Lidov cycles, where the inclination and eccentricity of the disk are interchanged periodically. This has important implications for accreting systems on all scales, for example, the formation of planets and satellites in circumstellar and circumplanetary disks, outbursts in X-ray binary systems, and accretion onto supermassive black holes

THE COUPLED PHYSICAL STRUCTURE OF GAS AND DUST IN THE IM Lup PROTOPLANETARY DISK

Energy Technology Data Exchange (ETDEWEB)

Cleeves, L. Ilsedore; Öberg, Karin I.; Wilner, David J.; Huang, Jane; Loomis, Ryan A.; Andrews, Sean M.; Czekala, Ian, E-mail: ilse.cleeves@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2016-12-01

The spatial distribution of gas and solids in protoplanetary disks determines the composition and formation efficiency of planetary systems. A number of disks show starkly different distributions for the gas and small grains compared to millimeter–centimeter-sized dust. We present new Atacama Large Millimeter/Submillimeter Array observations of the dust continuum, CO, {sup 13}CO, and C{sup 18}O in the IM Lup protoplanetary disk, one of the first systems where this dust–gas dichotomy was clearly seen. The {sup 12}CO is detected out to a radius of 970 au, while the millimeter continuum emission is truncated at just 313 au. Based upon these data, we have built a comprehensive physical and chemical model for the disk structure, which takes into account the complex, coupled nature of the gas and dust and the interplay between the local and external environment. We constrain the distributions of gas and dust, the gas temperatures, the CO abundances, the CO optical depths, and the incident external radiation field. We find that the reduction/removal of dust from the outer disk exposes this region to higher stellar and external radiation and decreases the rate of freeze-out, allowing CO to remain in the gas out to large radial distances. We estimate a gas-phase CO abundance of 5% of the interstellar medium value and a low external radiation field ( G {sub 0} ≲ 4). The latter is consistent with that expected from the local stellar population. We additionally find tentative evidence for ring-like continuum substructure, suggestions of isotope-selective photodissociation, and a diffuse gas halo.

Gaps, Rings, and Non-Axisymmetric Structures in Protoplanetary Disks - From Simulations to ALMA Observations

OpenAIRE

Flock, M.; Ruge, J. P.; Dzyurkevich, N.; Henning, Th.; Klahr, H.; Wolf, S.

2014-01-01

International audience; Aims. Recent observations by the Atacama Large Millimeter/submillimeter Array (ALMA) of disks around young stars revealed distinct asymmetries in the dust continuum emission. In this work we wish to study axisymmetric and non-axisymmetric structures that are generated by the magneto-rotational instability in the outer regions of protoplanetary disks. We combine the results of state-of-the-art numerical simulations with post-processing radiative transfer (RT) to generat...

Verbatim Floppy Disk

CERN Multimedia

1976-01-01

Introduced under the name "Verbatim", Latin for "literally", these disks that sized more than 5¼ inches have become almost universal on dedicated word processing systems and personal computers. This format was replaced more slowly by the 3½-inch format, introduced for the first time in 1982. Compared to today, these large format disks stored very little data. In reality, they could only contain a few pages of text.

Capillarity-based preparation system for optical colorimetric sensor arrays.

Science.gov (United States)

Luo, Xiao-Gang; Yi, Xin; Bu, Xiang-Nan; Hou, Chang-Jun; Huo, Dan-Qun; Yang, Mei; Fa, Huan-Bao; Lei, Jin-Can

2017-03-01

In recent years, optical colorimetric sensor arrays have demonstrated beneficial features, including rapid response, high selectivity, and high specificity; as a result, it has been extensively applied in food inspection and chemical studies, among other fields. There are instruments in the current market available for the preparation of an optical colorimetric sensor array, but it lacks the corresponding research of the preparation mechanism. Therefore, in connection with the main features of this kind of sensor array such as consistency, based on the preparation method of contact spotting, combined with a capillary fluid model, Washburn equation, Laplace equation, etc., this paper develops a diffusion model of an optical colorimetric sensor array during its preparation and sets up an optical colorimetric sensor array preparation system based on this diffusion model. Finally, this paper compares and evaluates the sensor arrays prepared by the system and prepared manually in three aspects such as the quality of array point, response of array, and response result, and the results show that the performance index of the sensor array prepared by a system under this diffusion model is better than that of the sensor array of manual spotting, which meets the needs of the experiment.

THE INNER DISK STRUCTURE, DISK-PLANET INTERACTIONS, AND TEMPORAL EVOLUTION IN THE β PICTORIS SYSTEM: A TWO-EPOCH HST/STIS CORONAGRAPHIC STUDY

Energy Technology Data Exchange (ETDEWEB)

Apai, Dániel; Schneider, Glenn [Department of Astronomy and Steward Observatory, The University of Arizona, Tucson, AZ 85721 (United States); Grady, Carol A. [Eureka Scientific, 2452 Delmer, Suite 100, Oakland CA 96002 (United States); Wyatt, Mark C. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Lagrange, Anne-Marie [Université Grenoble Alpes, IPAG, F-38000, Grenoble (France); Kuchner, Marc J.; Stark, Christopher J. [NASA Goddard Space Flight Center, Exoplanets and Stellar Astrophysics Laboratory, Code 667, Greenbelt, MD 20771 (United States); Lubow, Stephen H., E-mail: apai@arizona.edu [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

2015-02-20

We present deep Hubble Space Telescope/Space Telescope Imaging Spectrograph coronagraphic images of the β Pic debris disk obtained at two epochs separated by 15 yr. The new images and the re-reduction of the 1997 data provide the most sensitive and detailed views of the disk at optical wavelengths as well as the yet smallest inner working angle optical coronagraphic image of the disk. Our observations characterize the large-scale and inner-disk asymmetries and we identify multiple breaks in the disk radial surface brightness profile. We study in detail the radial and vertical disk structure and show that the disk is warped. We explore the disk at the location of the β Pic b super-Jupiter and find that the disk surface brightness slope is continuous between 0.''5 and 2.''0, arguing for no change at the separations where β Pic b orbits. The two epoch images constrain the disk's surface brightness evolution on orbital and radiation pressure blow-out timescales. We place an upper limit of 3% on the disk surface brightness change between 3'' and 5'', including the locations of the disk warp, and the CO and dust clumps. We discuss the new observations in the context of high-resolution multi-wavelength images and divide the disk asymmetries in two groups: axisymmetric and non-axisymmetric. The axisymmetric structures (warp, large-scale butterfly, etc.) are consistent with disk structure models that include interactions of a planetesimal belt and a non-coplanar giant planet. The non-axisymmetric features, however, require a different explanation.

Optimal Chunking of Large Multidimensional Arrays for Data Warehousing

Energy Technology Data Exchange (ETDEWEB)

Otoo, Ekow J; Otoo, Ekow J.; Rotem, Doron; Seshadri, Sridhar

2008-02-15

Very large multidimensional arrays are commonly used in data intensive scientific computations as well as on-line analytical processingapplications referred to as MOLAP. The storage organization of such arrays on disks is done by partitioning the large global array into fixed size sub-arrays called chunks or tiles that form the units of data transfer between disk and memory. Typical queries involve the retrieval of sub-arrays in a manner that access all chunks that overlap the query results. An important metric of the storage efficiency is the expected number of chunks retrieved over all such queries. The question that immediately arises is"what shapes of array chunks give the minimum expected number of chunks over a query workload?" The problem of optimal chunking was first introduced by Sarawagi and Stonebraker who gave an approximate solution. In this paper we develop exact mathematical models of the problem and provide exact solutions using steepest descent and geometric programming methods. Experimental results, using synthetic and real life workloads, show that our solutions are consistently within than 2.0percent of the true number of chunks retrieved for any number of dimensions. In contrast, the approximate solution of Sarawagi and Stonebraker can deviate considerably from the true result with increasing number of dimensions and also may lead to suboptimal chunk shapes.

On the Dynamics of Rocking Motion of the Hard-Disk Drive Spindle Motor System

Science.gov (United States)

Wang, Joseph

Excessive rocking motion of the spindle motor system can cause track misregistration resulting in poor throughput or even drive failure. The chance of excessive disk stack rocking increases as a result of decreasing torsional stiffness of spindle motor bearing system due to the market demand for low profile hard drives. As the track density increases and the vibration specification becomes increasingly stringent, rocking motion of a spindle motor system deserves even more attention and has become a primary challenge for a spindle motor system designer. Lack of understanding of the rocking phenomenon combined with misleading paradox has presented a great difficulty in the effort of avoiding the rocking motion in the hard-disk drive industry. This paper aims to provide fundamental understanding of the rocking phenomenon of a rotating spindle motor system, to clarify the paradox in disk-drive industry and to provide a design guide to an optimized spindle system. This paper, theoretically and experimentally, covers a few important areas of industrial interest including the prediction of rocking natural frequencies and mode shape of a rotating spindle, free vibration, and frequency response under common forcing functions such as rotating and fixed-plane forcing functions. The theory presented here meets with agreeable experimental observation.

Degree-of-Freedom Strengthened Cascade Array for DOD-DOA Estimation in MIMO Array Systems.

Science.gov (United States)

Yao, Bobin; Dong, Zhi; Zhang, Weile; Wang, Wei; Wu, Qisheng

2018-05-14

In spatial spectrum estimation, difference co-array can provide extra degrees-of-freedom (DOFs) for promoting parameter identifiability and parameter estimation accuracy. For the sake of acquiring as more DOFs as possible with a given number of physical sensors, we herein design a novel sensor array geometry named cascade array. This structure is generated by systematically connecting a uniform linear array (ULA) and a non-uniform linear array, and can provide more DOFs than some exist array structures but less than the upper-bound indicated by minimum redundant array (MRA). We further apply this cascade array into multiple input multiple output (MIMO) array systems, and propose a novel joint direction of departure (DOD) and direction of arrival (DOA) estimation algorithm, which is based on a reduced-dimensional weighted subspace fitting technique. The algorithm is angle auto-paired and computationally efficient. Theoretical analysis and numerical simulations prove the advantages and effectiveness of the proposed array structure and the related algorithm.

WIND-ACCRETION DISKS IN WIDE BINARIES, SECOND-GENERATION PROTOPLANETARY DISKS, AND ACCRETION ONTO WHITE DWARFS

International Nuclear Information System (INIS)

Perets, Hagai B.; Kenyon, Scott J.

2013-01-01

Mass transfer from an evolved donor star to its binary companion is a standard feature of stellar evolution in binaries. In wide binaries, the companion star captures some of the mass ejected in a wind by the primary star. The captured material forms an accretion disk. Here, we study the evolution of wind-accretion disks, using a numerical approach which allows us to follow the long-term evolution. For a broad range of initial conditions, we derive the radial density and temperature profiles of the disk. In most cases, wind accretion leads to long-lived stable disks over the lifetime of the asymptotic giant branch donor star. The disks have masses of a few times 10 –5 -10 –3 M ☉ , with surface density and temperature profiles that follow broken power laws. The total mass in the disk scales approximately linearly with the viscosity parameter used. Roughly, 50%-80% of the mass falling into the disk accretes onto the central star; the rest flows out through the outer edge of the disk into the stellar wind of the primary. For systems with large accretion rates, the secondary accretes as much as 0.1 M ☉ . When the secondary is a white dwarf, accretion naturally leads to nova and supernova eruptions. For all types of secondary star, the surface density and temperature profiles of massive disks resemble structures observed in protoplanetary disks, suggesting that coordinated observational programs might improve our understanding of uncertain disk physics.

A Differential Polarized Light Interferometric System For Measuring Flatness Of Magnetic Disks

Science.gov (United States)

Jia, Wang; Da-Cheng, Li; Ye, Chen; Ling, Du; Mang, Cao

1987-01-01

A kind of differential polarizdd laser interferometric system for non-contact and dynamic measurement of the flatness characteristic of magnetic disks without the effect of the axial vibration is described in this papper.

Theory of Disk Accretion onto Magnetic Stars

Directory of Open Access Journals (Sweden)

Lai Dong

2014-01-01

Full Text Available Disk accretion onto magnetic stars occurs in a variety of systems, including accreting neutron stars (with both high and low magnetic fields, white dwarfs, and protostars. We review some of the key physical processes in magnetosphere-disk interaction, highlighting the theoretical uncertainties. We also discuss some applications to the observations of accreting neutron star and protostellar systems, as well as possible connections to protoplanetary disks and exoplanets.

Relativistic, accreting disks

International Nuclear Information System (INIS)

Abramowicz, M.A; Jaroszynski, M.; Sikora, M.

1978-01-01

An analytic theory of the hydrodynamical structure of accreting disks (without self-gravitation but with pressure) orbiting around and axially symmetric, stationary, compact body (e.g. black hole) is presented. The inner edge of the marginally stable accreting disk (i.e. disk with constant angular momentum density) has a sharp cusp located on the equatorial plane between rsub(ms) and rsub(mb). The existence of the cusp is also typical for any angular momentum distribution. The physical importance of the cusp follows from the close analogy with the case of a close binary system (L 1 Lagrange point on the Roche lobe). The existence of the cusp is thus a crucial phenomenon in such problems as boundary condition for the viscous stresses, accretion rate etc. (orig.) [de

Occultations from an Active Accretion Disk in a 72-day Detached Post-Algol System Detected by K2

DEFF Research Database (Denmark)

Zhou, G.; Rappaport, S.; Nelson, L.

2018-01-01

Disks in binary systems can cause exotic eclipsing events. MWC 882 (BD –22 4376, EPIC 225300403) is such a disk-eclipsing system identified from observations during Campaign 11 of the K2 mission. We propose that MWC 882 is a post-Algol system with a B7 donor star of mass in a 72-day orbit around...... an A0 accreting star of mass . The disk around the accreting star occults the donor star once every orbit, inducing 19-day long, 7% deep eclipses identified by K2 and subsequently found in pre-discovery All-Sky Automated Survey and All Sky Automated Survey for Supernovae observations. We coordinated...

THE SEEDS DIRECT IMAGING SURVEY FOR PLANETS AND SCATTERED DUST EMISSION IN DEBRIS DISK SYSTEMS

Energy Technology Data Exchange (ETDEWEB)

Janson, Markus; Brandt, Timothy D. [Department of Astrophysical Sciences, Princeton University, NJ 08544 (United States); Moro-Martin, Amaya [Department of Astrophysics, CAB (INTA-CSIC), Instituto Nacional de Tecnica Aerospacial, Torrejonde Ardoz, E-28850 Madrid (Spain); Usuda, Tomonori; Kudo, Tomoyuki; Egner, Sebastian [Subaru Telescope, 650 North Aohoku Place, Hilo, HI 96720 (United States); Thalmann, Christian [Astronomical Institute ' ' Anton Pannekoek' ' , University of Amsterdam, Science Park 904, 1098-XH Amsterdam (Netherlands); Carson, Joseph C. [Department of Physics and Astronomy, College of Charleston, 58 Coming Street, Charleston, SC 29424 (United States); Goto, Miwa [Universitaets-Sternwarte Muenchen, Ludwig-Maximilians-Universitaet, Scheinerstr. 1, D-81679 Munich (Germany); Currie, Thayne [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, M5S 3H4 Toronto, ON (Canada); McElwain, M. W. [Exoplanets and Stellar Astrophysics Laboratory, Code 667, Goddard Space Flight Center, Greenbelt, MD 2071 (United States); Itoh, Yoichi [Nishi-Harima Astronomical Observatory, Center for Astronomy, University of Hyogo, 407-2 Nishigaichi, Sayo, Hyogo 679-5313 (Japan); Fukagawa, Misato [Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043 (Japan); Crepp, Justin [Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States); Kuzuhara, Masayuki; Hashimoto, Jun; Kusakabe, Nobuhiko [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Abe, Lyu [Laboratoire Lagrange, UMR7239, University of Nice-Sophia Antipolis, CNRS, Observatoire de la Cote d' Azur, F-06300 Nice (France); Brandner, Wolfgang; Feldt, Markus, E-mail: janson@astro.princeton.edu [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany); and others

2013-08-10

Debris disks around young main-sequence stars often have gaps and cavities which for a long time have been interpreted as possibly being caused by planets. In recent years, several giant planet discoveries have been made in systems hosting disks of precisely this nature, further implying that interactions with planets could be a common cause of such disk structures. As part of the SEEDS high-contrast imaging survey, we are surveying a population of debris-disk-hosting stars with gaps and cavities implied by their spectral energy distributions, in order to attempt to spatially resolve the disk as well as to detect any planets that may be responsible for the disk structure. Here, we report on intermediate results from this survey. Five debris disks have been spatially resolved, and a number of faint point sources have been discovered, most of which have been tested for common proper motion, which in each case has excluded physical companionship with the target stars. From the detection limits of the 50 targets that have been observed, we find that {beta} Pic b-like planets ({approx}10 M{sub jup} planets around G-A-type stars) near the gap edges are less frequent than 15%-30%, implying that if giant planets are the dominant cause of these wide (27 AU on average) gaps, they are generally less massive than {beta} Pic b.

WIND-ACCRETION DISKS IN WIDE BINARIES, SECOND-GENERATION PROTOPLANETARY DISKS, AND ACCRETION ONTO WHITE DWARFS

Energy Technology Data Exchange (ETDEWEB)

Perets, Hagai B. [Technion-Israel Institute of Technology, Haifa (Israel); Kenyon, Scott J., E-mail: hperets@physics.technion.ac.il [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2013-02-20

Mass transfer from an evolved donor star to its binary companion is a standard feature of stellar evolution in binaries. In wide binaries, the companion star captures some of the mass ejected in a wind by the primary star. The captured material forms an accretion disk. Here, we study the evolution of wind-accretion disks, using a numerical approach which allows us to follow the long-term evolution. For a broad range of initial conditions, we derive the radial density and temperature profiles of the disk. In most cases, wind accretion leads to long-lived stable disks over the lifetime of the asymptotic giant branch donor star. The disks have masses of a few times 10{sup -5}-10{sup -3} M {sub Sun }, with surface density and temperature profiles that follow broken power laws. The total mass in the disk scales approximately linearly with the viscosity parameter used. Roughly, 50%-80% of the mass falling into the disk accretes onto the central star; the rest flows out through the outer edge of the disk into the stellar wind of the primary. For systems with large accretion rates, the secondary accretes as much as 0.1 M {sub Sun }. When the secondary is a white dwarf, accretion naturally leads to nova and supernova eruptions. For all types of secondary star, the surface density and temperature profiles of massive disks resemble structures observed in protoplanetary disks, suggesting that coordinated observational programs might improve our understanding of uncertain disk physics.

Melting of polydisperse hard disks

NARCIS (Netherlands)

Pronk, S.; Frenkel, D.

2004-01-01

The melting of a polydisperse hard-disk system is investigated by Monte Carlo simulations in the semigrand canonical ensemble. This is done in the context of possible continuous melting by a dislocation-unbinding mechanism, as an extension of the two-dimensional hard-disk melting problem. We find

Selections from 2016: Gaps in HL Tau's Protoplanetary Disk

Science.gov (United States)

Kohler, Susanna

2016-12-01

Editors note:In these last two weeks of 2016, well be looking at a few selections that we havent yet discussed on AAS Nova from among the most-downloaded paperspublished in AAS journals this year. The usual posting schedule will resume after the AAS winter meeting.Gas Gaps in the Protoplanetary Disk Around the Young Protostar HL TauPublished March 2016The dust (left) and gas (right) emission from HL Tau show that the gaps in its disk match up. [Yen et al. 2016]Main takeaway:At the end of last year, the Atacama Large Millimeter/Submillimeter Array released some of its first data including a spectacular observation of a dusty protoplanetary disk around the young star HL Tau. In this follow-up study, a team led by Hsi-Wei Yen (Academia Sinica Institute of Astronomy and Astrophysics, Taiwan) analyzed the ALMA data and confirmed the presence of two gaps in the gas of HL Taus disk, at radii of 28 and 69 AU.Why its interesting:The original ALMA image of HL Taus disk suggests the presence of gaps in disk, but scientists werent sure if they were caused by effects like gravitational instabilities or dust clumping, or if the gaps were created by the presence of young planets. Yen and collaborators showed that gaps in the disks gas line up with gaps in its dust, supporting the model in which these gaps have been carved out by newly formed planets.Added intrigue:The evidence for planets in this disk came as a bit of a surprise, since it was originally believed that it takes tens of millions of years to form planets from the dust of protoplanetary disks but HL Tau is only a million years old. These observations therefore suggest that planets start to form much earlier than we thought.CitationHsi-Wei Yen et al 2016 ApJL 820 L25. doi:10.3847/2041-8205/820/2/L25

A New M Dwarf Debris Disk Candidate in a Young Moving Group Discovered with Disk Detective

Science.gov (United States)

Silverberg, Steven M.; Kuchner, Marc J.; Wisniewski, John P.; Gagne, Jonathan; Bans, Alissa S.; Bhattacharjee, Shambo; Currie, Thayne R.; Debes, John R.; Biggs, Joseph R; Bosch, Milton

2016-01-01

We used the Disk Detective citizen science project and the BANYAN II Bayesian analysis tool to identify a new candidate member of a nearby young association with infrared excess. WISE J080822.18-644357.3, an M5.5-type debris disk system with significant excess at both 12 and 22 microns, is a likely member (approx.90% BANYAN II probability) of the approx.45 Myr old Carina association. Since this would be the oldest M dwarf debris disk detected in a moving group, this discovery could be an important constraint on our understanding of M dwarf debris disk evolution.

The role of records management professionals in optical disk-based document imaging systems in the petroleum industry

International Nuclear Information System (INIS)

Cisco, S.L.

1992-01-01

Analyses of the data indicated that nearly one third of the 83 companies in this study had implemented one or more document imaging systems. Companies with imaging systems mostly were large (more than 1,001 employees), and mostly were international in scope. Although records management professionals traditionally were delegated responsibility for acquiring, designing, implementing, and maintaining paper-based information systems and the records therein, when records were converted to optical disks, responsibility for acquiring, designing, implementing, and maintaining optical disk-based information systems and the records therein, was delegated more frequently to end user departments and IS/MIS/DP professionals than to records professionals. Records management professionals assert that the need of an organization for a comprehensive records management program is not served best when individuals who are not professional records managers are responsible for the records stored in optical disk-based information systems

Relativistic, accreting disks

Energy Technology Data Exchange (ETDEWEB)

Abramowicz, M A; Jaroszynski, M; Sikora, M [Polska Akademia Nauk, Warsaw

1978-02-01

An analytic theory of the hydrodynamical structure of accreting disks (without self-gravitation but with pressure) orbiting around an axially symmetric, stationary, compact body (e.g. black hole) is presented. The inner edge of the marginally stable accreting disk (i.e. disk with constant angular momentum density) has a sharp cusp located on the equatorial plane between r/sub ms/ and r/sub mb/. The existence of the cusp is also typical for any angular momentum distribution. The physical importance of the cusp follows from the close analogy with the case of a close binary system (L/sub 1/ Lagrange point on the Roche lobe). The existence of the cusp is thus a crucial phenomenon in such problems as boundary condition for the viscous stresses, accretion rate, etc.

HERSCHEL OBSERVATIONS OF THE T CHA TRANSITION DISK: CONSTRAINING THE OUTER DISK PROPERTIES

International Nuclear Information System (INIS)

Cieza, Lucas A.; Olofsson, Johan; Henning, Thomas; Harvey, Paul M.; Evans II, Neal J.; Pinte, Christophe; Augereau, Jean-Charles; Ménard, Francois; Merín, Bruno; Najita, Joan

2011-01-01

T Cha is a nearby (d ∼ 100 pc) transition disk known to have an optically thin gap separating optically thick inner and outer disk components. Huélamo et al. recently reported the presence of a low-mass object candidate within the gap of the T Cha disk, giving credence to the suspected planetary origin of this gap. Here we present the Herschel photometry (70, 160, 250, 350, and 500 μm) of T Cha from the 'Dust, Ice, and Gas in Time' Key Program, which bridges the wavelength range between existing Spitzer and millimeter data and provide important constraints on the outer disk properties of this extraordinary system. We model the entire optical to millimeter wavelength spectral energy distribution (SED) of T Cha (19 data points between 0.36 and 3300 μm without any major gaps in wavelength coverage). T Cha shows a steep spectral slope in the far-IR, which we find clearly favors models with outer disks containing little or no dust beyond ∼40 AU. The full SED can be modeled equally well with either an outer disk that is very compact (only a few AU wide) or a much larger one that has a very steep surface density profile. That is, T Cha's outer disk seems to be either very small or very tenuous. Both scenarios suggest a highly unusual outer disk and have important but different implications for the nature of T Cha. Spatially resolved images are needed to distinguish between the two scenarios.

HERSCHEL OBSERVATIONS OF THE T CHA TRANSITION DISK: CONSTRAINING THE OUTER DISK PROPERTIES

Energy Technology Data Exchange (ETDEWEB)

Cieza, Lucas A. [Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); Olofsson, Johan; Henning, Thomas [Max Planck Institut fuer Astronomie, Koenigstuhl 17, 69117 Heidelberg (Germany); Harvey, Paul M.; Evans II, Neal J. [Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States); Pinte, Christophe; Augereau, Jean-Charles; Menard, Francois [UJF-Grenoble 1/CNRS-INSU, Institut de Planetologie et d' Astrophysique de Grenoble (IPAG) UMR 5274, Grenoble, F-38041 (France); Merin, Bruno [Herschel Science Centre, European Space Agency (ESAC), P.O. Box 78, 28691 Villanueva de la Canada, Madrid (Spain); Najita, Joan, E-mail: lcieza@ifa.hawaii.edu [National Optical Astronomy Observatory, 950 N. Cherry Avenue, Tucson, AZ 86719 (United States)

2011-11-10

T Cha is a nearby (d {approx} 100 pc) transition disk known to have an optically thin gap separating optically thick inner and outer disk components. Huelamo et al. recently reported the presence of a low-mass object candidate within the gap of the T Cha disk, giving credence to the suspected planetary origin of this gap. Here we present the Herschel photometry (70, 160, 250, 350, and 500 {mu}m) of T Cha from the 'Dust, Ice, and Gas in Time' Key Program, which bridges the wavelength range between existing Spitzer and millimeter data and provide important constraints on the outer disk properties of this extraordinary system. We model the entire optical to millimeter wavelength spectral energy distribution (SED) of T Cha (19 data points between 0.36 and 3300 {mu}m without any major gaps in wavelength coverage). T Cha shows a steep spectral slope in the far-IR, which we find clearly favors models with outer disks containing little or no dust beyond {approx}40 AU. The full SED can be modeled equally well with either an outer disk that is very compact (only a few AU wide) or a much larger one that has a very steep surface density profile. That is, T Cha's outer disk seems to be either very small or very tenuous. Both scenarios suggest a highly unusual outer disk and have important but different implications for the nature of T Cha. Spatially resolved images are needed to distinguish between the two scenarios.

Megachannel γ--γ coincidence system using a PDP-8/E computer and moving-head disks

International Nuclear Information System (INIS)

Ruhter, W.D.; Camp, D.C.; Mann, L.G.; Niday, J.B.; Siemens, P.D.

1976-01-01

A megachannel pulse-height analysis system using a PDP-8/E computer and two moving-head disk memories has been developed. The system has a storage capacity of 220 memory locations, is capable of processing 1100 events/s, and provides on-line sorting and disk storage. An X- or Y-pulse-height spectrum in coincidence with one or several arbitrary pulse-height windows can be assembled in core for scope display and spectral analysis within 2 to 20 seconds. Reconstruction of a complete X- or Y-pulse-height spectrum requires about 3 minutes

Radiotherapy supporting system based on the image database using IS&C magneto-optical disk

Science.gov (United States)

Ando, Yutaka; Tsukamoto, Nobuhiro; Kunieda, Etsuo; Kubo, Atsushi

1994-05-01

Since radiation oncologists make the treatment plan by prior experience, information about previous cases is helpful in planning the radiation treatment. We have developed an supporting system for the radiation therapy. The case-based reasoning method was implemented in order to search old treatments and images of past cases. This system evaluates similarities between the current case and all stored cases (case base). The portal images of the similar cases can be retrieved for reference images, as well as treatment records which show examples of the radiation treatment. By this system radiotherapists can easily make suitable plans of the radiation therapy. This system is useful to prevent inaccurate plannings due to preconceptions and/or lack of knowledge. Images were stored into magneto-optical disks and the demographic data is recorded to the hard disk which is equipped in the personal computer. Images can be displayed quickly on the radiotherapist's demands. The radiation oncologist can refer past cases which are recorded in the case base and decide the radiation treatment of the current case. The file and data format of magneto-optical disk is the IS&C format. This format provides the interchangeability and reproducibility of the medical information which includes images and other demographic data.

Linear-array systems for aerospace NDE

International Nuclear Information System (INIS)

Smith, Robert A.; Willsher, Stephen J.; Bending, Jamie M.

1999-01-01

Rapid large-area inspection of composite structures for impact damage and multi-layered aluminum skins for corrosion has been a recognized priority for several years in both military and civil aerospace applications. Approaches to this requirement have followed two clearly different routes: the development of novel large-area inspection systems, and the enhancement of current ultrasonic or eddy-current methods to reduce inspection times. Ultrasonic inspection is possible with standard flaw detection equipment but the addition of a linear ultrasonic array could reduce inspection times considerably. In order to investigate their potential, 9-element and 17-element linear ultrasonic arrays for composites, and 64-element arrays for aluminum skins, have been developed to DERA specifications for use with the ANDSCAN area scanning system. A 5 m 2 composite wing surface has been scanned with a scan resolution of approximately 3 mm in 6 hours. With subsequent software and hardware improvements all four composite wing surfaces (top/bottom, left/right) of a military fighter aircraft can potentially be inspected in less than a day. Array technology has been very widely used in the medical ultrasound field although rarely above 10 MHz, whereas lap-joint inspection requires a pulse center-frequency of 12 to 20 MHz in order to resolve the separate interfaces in the lap joint. A 128 mm-long multi-element array of 5 mmx2 mm ultrasonic elements for use with the ANDSCAN scanning software was produced to a DERA specification by an NDT manufacturer with experience in the medical imaging field. This paper analyses the performance of the transducers that have been produced and evaluates their use in scanning systems of different configurations

Membangun Sistem Linux Mandrake Minimal Menggunakan Inisial Disk Ram

OpenAIRE

Wagito, Wagito

2006-01-01

Minimal Linux system is commonly used for special systems like router, gateway, Linux installer and diskless Linux system. Minimal Linux system is a Linux system that use a few facilities of all Linux capabilities. Mandrake Linux, as one of Linux distribution is able to perform minimal Linux system. RAM is a computer resource that especially used as main memory. A part of RAM's function can be changed into disk called RAM disk. This RAM disk can be used to run the Linux system. This ...

Digitized molecular diagnostics: reading disk-based bioassays with standard computer drives.

Science.gov (United States)

Li, Yunchao; Ou, Lily M L; Yu, Hua-Zhong

2008-11-01

We report herein a digital signal readout protocol for screening disk-based bioassays with standard optical drives of ordinary desktop/notebook computers. Three different types of biochemical recognition reactions (biotin-streptavidin binding, DNA hybridization, and protein-protein interaction) were performed directly on a compact disk in a line array format with the help of microfluidic channel plates. Being well-correlated with the optical darkness of the binding sites (after signal enhancement by gold nanoparticle-promoted autometallography), the reading error levels of prerecorded audio files can serve as a quantitative measure of biochemical interaction. This novel readout protocol is about 1 order of magnitude more sensitive than fluorescence labeling/scanning and has the capability of examining multiplex microassays on the same disk. Because no modification to either hardware or software is needed, it promises a platform technology for rapid, low-cost, and high-throughput point-of-care biomedical diagnostics.

Constraints on observing brightness asymmetries in protoplanetary disks at solar system scale

Science.gov (United States)

Brunngräber, Robert; Wolf, Sebastian

2018-04-01

We have quantified the potential capabilities of detecting local brightness asymmetries in circumstellar disks with the Very Large Telescope Interferometer (VLTI) in the mid-infrared wavelength range. The study is motivated by the need to evaluate theoretical models of planet formation by direct observations of protoplanets at early evolutionary stages, when they are still embedded in their host disk. Up to now, only a few embedded candidate protoplanets have been detected with semi-major axes of 20-50 au. Due to the small angular separation from their central star, only long-baseline interferometry provides the angular resolving power to detect disk asymmetries associated to protoplanets at solar system scales in nearby star-forming regions. In particular, infrared observations are crucial to observe scattered stellar radiation and thermal re-emission in the vicinity of embedded companions directly. For this purpose we performed radiative transfer simulations to calculate the thermal re-emission and scattered stellar flux from a protoplanetary disk hosting an embedded companion. Based on that, visibilities and closure phases are calculated to simulate observations with the future beam combiner MATISSE, operating at the L, M and N bands at the VLTI. We find that the flux ratio of the embedded source to the central star can be as low as 0.5 to 0.6% for a detection at a feasible significance level due to the heated dust in the vicinity of the embedded source. Furthermore, we find that the likelihood for detection is highest for sources at intermediate distances r ≈ 2-5 au and disk masses not higher than ≈10-4 M⊙.

Theoretical investigation of generator-collector microwell arrays for improving electroanalytical selectivity: application to selective dopamine detection in the presence of ascorbic acid.

Science.gov (United States)

Oleinick, Alexander; Zhu, Feng; Yan, Jiawei; Mao, Bingwei; Svir, Irina; Amatore, Christian

2013-06-24

Recessed generator-collector assemblies consisting of an array of recessed disks (generator electrodes) with a gold layer (collector electrode) deposited over the top-plane insulator reportedly allow increased selectivity and sensitivity during electrochemical detection of dopamine (DA) in the presence of ascorbic acid (AA), a situation which is frequently encountered. In sensor design, the potential of the disk electrodes is set to the wave plateau of DA, whereas the plane electrode is biased at the irreversible wave plateau of AA before the onset of the DA oxidation wave. Thus, AA is scavenged but DA is allowed to enter the nanocavities to be oxidized at the disk electrodes, and its signal is further amplified by redox cycling between disk and plane electrodes. Several different theoretical approaches are elaborated herein to analyze the behavior of the system, and their conclusions are successfully tested by experiments. This reveals the crucial role of the plane-electrode area which screens access to the recessed disks (i.e. acts as a diffusional Faraday cage) and simultaneously contributes to amplification of the analyte signal through positive feedback, as occurs in interdigitated arrays and scanning electrochemical microscopy. Simulations also allow for the evaluation of the benefits of different geometries inspired by the above design and different operating modes for increasing the sensor performance. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A PRIMER ON UNIFYING DEBRIS DISK MORPHOLOGIES

International Nuclear Information System (INIS)

Lee, Eve J.; Chiang, Eugene

2016-01-01

A “minimum model” for debris disks consists of a narrow ring of parent bodies, secularly forced by a single planet on a possibly eccentric orbit, colliding to produce dust grains that are perturbed by stellar radiation pressure. We demonstrate how this minimum model can reproduce a wide variety of disk morphologies imaged in scattered starlight. Five broad categories of disk shape can be captured: “rings,” “needles,” “ships-and-wakes,” “bars,” and “moths (a.k.a. fans),” depending on the viewing geometry. Moths can also sport “double wings.” We explain the origin of morphological features from first principles, exploring the dependence on planet eccentricity, disk inclination dispersion, and the parent body orbital phases at which dust grains are born. A key determinant in disk appearance is the degree to which dust grain orbits are apsidally aligned. Our study of a simple steady-state (secularly relaxed) disk should serve as a reference for more detailed models tailored to individual systems. We use the intuition gained from our guidebook of disk morphologies to interpret, informally, the images of a number of real-world debris disks. These interpretations suggest that the farthest reaches of planetary systems are perturbed by eccentric planets, possibly just a few Earth masses each.

A Primer on Unifying Debris Disk Morphologies

Science.gov (United States)

Lee, Eve J.; Chiang, Eugene

2016-08-01

A “minimum model” for debris disks consists of a narrow ring of parent bodies, secularly forced by a single planet on a possibly eccentric orbit, colliding to produce dust grains that are perturbed by stellar radiation pressure. We demonstrate how this minimum model can reproduce a wide variety of disk morphologies imaged in scattered starlight. Five broad categories of disk shape can be captured: “rings,” “needles,” “ships-and-wakes,” “bars,” and “moths (a.k.a. fans),” depending on the viewing geometry. Moths can also sport “double wings.” We explain the origin of morphological features from first principles, exploring the dependence on planet eccentricity, disk inclination dispersion, and the parent body orbital phases at which dust grains are born. A key determinant in disk appearance is the degree to which dust grain orbits are apsidally aligned. Our study of a simple steady-state (secularly relaxed) disk should serve as a reference for more detailed models tailored to individual systems. We use the intuition gained from our guidebook of disk morphologies to interpret, informally, the images of a number of real-world debris disks. These interpretations suggest that the farthest reaches of planetary systems are perturbed by eccentric planets, possibly just a few Earth masses each.

A PRIMER ON UNIFYING DEBRIS DISK MORPHOLOGIES

Energy Technology Data Exchange (ETDEWEB)

Lee, Eve J.; Chiang, Eugene, E-mail: evelee@berkeley.edu, E-mail: echiang@astro.berkeley.edu [Department of Astronomy, University of California Berkeley, Berkeley, CA 94720-3411 (United States)

2016-08-20

A “minimum model” for debris disks consists of a narrow ring of parent bodies, secularly forced by a single planet on a possibly eccentric orbit, colliding to produce dust grains that are perturbed by stellar radiation pressure. We demonstrate how this minimum model can reproduce a wide variety of disk morphologies imaged in scattered starlight. Five broad categories of disk shape can be captured: “rings,” “needles,” “ships-and-wakes,” “bars,” and “moths (a.k.a. fans),” depending on the viewing geometry. Moths can also sport “double wings.” We explain the origin of morphological features from first principles, exploring the dependence on planet eccentricity, disk inclination dispersion, and the parent body orbital phases at which dust grains are born. A key determinant in disk appearance is the degree to which dust grain orbits are apsidally aligned. Our study of a simple steady-state (secularly relaxed) disk should serve as a reference for more detailed models tailored to individual systems. We use the intuition gained from our guidebook of disk morphologies to interpret, informally, the images of a number of real-world debris disks. These interpretations suggest that the farthest reaches of planetary systems are perturbed by eccentric planets, possibly just a few Earth masses each.

Astrophysical disks Collective and Stochastic Phenomena

CERN Document Server

Fridman, Alexei M; Kovalenko, Ilya G

2006-01-01

The book deals with collective and stochastic processes in astrophysical discs involving theory, observations, and the results of modelling. Among others, it examines the spiral-vortex structure in galactic and accretion disks , stochastic and ordered structures in the developed turbulence. It also describes sources of turbulence in the accretion disks, internal structure of disk in the vicinity of a black hole, numerical modelling of Be envelopes in binaries, gaseous disks in spiral galaxies with shock waves formation, observation of accretion disks in a binary system and mass distribution of luminous matter in disk galaxies. The editors adaptly brought together collective and stochastic phenomena in the modern field of astrophysical discs, their formation, structure, and evolution involving the methodology to deal with, the results of observation and modelling, thereby advancing the study in this important branch of astrophysics and benefiting Professional Researchers, Lecturers, and Graduate Students.

Collisional dynamics of perturbed particle disks in the solar system. Annual technical progress report

International Nuclear Information System (INIS)

Roberts, W.W.; Stewart, G.R.

1987-03-01

Investigations of the collisional evolution of particulate disks subject to the gravitational perturbation of a more massive particle orbiting within the disk are underway. Both numerical N-body simulations using a novel collision algorithm and analytical kinetic theory are being employed to extend our understanding of perturbed disks in planetary rings and during the formation of the solar system. Particular problems proposed for investigation are: (1) The development and testing of general criteria for a small moonlet to clear a gap and produce observable morphological features in planetary rings; (2) The development of detailed models of collisional damping of the wavy edges observed on the Encke division of Saturn's A ring; and (3) The determination of the extent of runaway growth of the few largest planetesimals during the early stages of planetary accretion

GEMINI PLANET IMAGER OBSERVATIONS OF THE AU MICROSCOPII DEBRIS DISK: ASYMMETRIES WITHIN ONE ARCSECOND

International Nuclear Information System (INIS)

Wang, Jason J.; Graham, James R.; De Rosa, Robert J.; Kalas, Paul; Chiang, Eugene; Duchêne, Gaspard; Pueyo, Laurent; Chen, Christine; Greenbaum, Alexandra Z.; Nielsen, Eric L.; Millar-Blanchaer, Max; Ammons, S. Mark; Bulger, Joanna; Cardwell, Andrew; Goodsell, Stephen J.; Chilcote, Jeffrey K.; Doyon, René; Draper, Zachary H.; Esposito, Thomas M.; Fitzgerald, Michael P.

2015-01-01

We present Gemini Planet Imager (GPI) observations of AU Microscopii, a young M dwarf with an edge-on, dusty debris disk. Integral field spectroscopy and broadband imaging polarimetry were obtained during the commissioning of GPI. In our broadband imaging polarimetry observations, we detect the disk only in total intensity and find asymmetries in the morphology of the disk between the southeast (SE) and northwest (NW) sides. The SE side of the disk exhibits a bump at 1″ (10 AU projected separation) that is three times more vertically extended and three times fainter in peak surface brightness than the NW side at similar separations. This part of the disk is also vertically offset by 69 ± 30 mas to the northeast at 1″ when compared to the established disk midplane and is consistent with prior Atacama Large Millimeter/submillimeter Array and Hubble Space Telescope/Space Telescope Imaging Spectrograph observations. We see hints that the SE bump might be a result of detecting a horizontal sliver feature above the main disk that could be the disk backside. Alternatively, when including the morphology of the NW side, where the disk midplane is offset in the opposite direction ∼50 mas between 0.″4 and 1.″2, the asymmetries suggest a warp-like feature. Using our integral field spectroscopy data to search for planets, we are 50% complete for ∼4 M Jup planets at 4 AU. We detect a source, resolved only along the disk plane, that could either be a candidate planetary mass companion or a compact clump in the disk

Site-specific Pt deposition and etching on electrically and thermally isolated SiO2 micro-disk surfaces

International Nuclear Information System (INIS)

Saraf, Laxmikant V

2010-01-01

Electrically and thermally isolated surfaces are crucial for improving the detection sensitivity of microelectronic sensors. The site-specific in situ growth of Pt nano-rods on thermally and electrically isolated SiO 2 micro-disks using wet chemical etching and a focused ion/electron dual beam (FIB-SEM) is demonstrated. Fabrication of an array of micro-cavities on top of a micro-disk is also demonstrated. The FIB source is utilized to fabricate through-holes in the micro-disks. Due to the amorphous nature of SiO 2 micro-disks, the Ga implantation possibly modifies through-hole sidewall surface chemistry rather than affecting its transport properties. Some sensor design concepts based on micro-fabrication of SiO 2 micro-disks utilizing thermally and electrically isolated surfaces are discussed from the viewpoint of applications in photonics and bio-sensing.

THE LONG-TERM DYNAMICAL EVOLUTION OF DISK-FRAGMENTED MULTIPLE SYSTEMS IN THE SOLAR NEIGHBORHOOD

Energy Technology Data Exchange (ETDEWEB)

Li, Yun [Department of Astronomy, School of Physics, Peking University, Yiheyuan Lu 5, Haidian Qu, Beijing 100871 (China); Kouwenhoven, M. B. N. [Department of Mathematical Sciences, Xi’an Jiaotong-Liverpool University, 111 Ren’ai Road, Suzhou Dushu Lake Science and Education Innovation District, Suzhou Industrial Park, Suzhou 215123 (China); Stamatellos, D. [Jeremiah Horrocks Institute for Mathematics, Physics and Astronomy, University of Central Lancashire, Preston PR1 2HE (United Kingdom); Goodwin, Simon P., E-mail: t.kouwenhoven@xjtlu.edu.cn [Department of Physics and Astronomy, The University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom)

2016-11-10

The origin of very low-mass hydrogen-burning stars, brown dwarfs (BDs), and planetary-mass objects (PMOs) at the low-mass end of the initial mass function is not yet fully understood. Gravitational fragmentation of circumstellar disks provides a possible mechanism for the formation of such low-mass objects. The kinematic and binary properties of very low-mass objects formed through disk fragmentation at early times (<10 Myr) were discussed in our previous paper. In this paper we extend the analysis by following the long-term evolution of disk-fragmented systems up to an age of 10 Gyr, covering the ages of the stellar and substellar populations in the Galactic field. We find that the systems continue to decay, although the rates at which companions escape or collide with each other are substantially lower than during the first 10 Myr, and that dynamical evolution is limited beyond 1 Gyr. By t = 10 Gyr, about one third of the host stars are single, and more than half have only one companion left. Most of the other systems have two companions left that orbit their host star in widely separated orbits. A small fraction of companions have formed binaries that orbit the host star in a hierarchical triple configuration. The majority of such double-companion systems have internal orbits that are retrograde with respect to their orbits around their host stars. Our simulations allow a comparison between the predicted outcomes of disk fragmentation with the observed low-mass hydrogen-burning stars, BDs, and PMOs in the solar neighborhood. Imaging and radial velocity surveys for faint binary companions among nearby stars are necessary for verification or rejection of the formation mechanism proposed in this paper.

Equilibrium figures for beta Lyrae type disks

International Nuclear Information System (INIS)

Wilson, R.E.

1981-01-01

Accumulated evidence for a geometrically and optically thick disk in the β Lyrae system has now established the disk's basic external configuration. Since the disk has been constant in its main properties over the historical interval of β Lyrae observations and also seems to have a basically well-defined photosphere, it is now time to being consideration of its sturcture. Here, we compute equilibrium figures for self-gravitating disks around stars in binary systems as a start toward eventual computation of complete disk models. A key role is played by centrifugally limited rotation of the central star, which would naturally arise late in the rapid phase of mass transfer. Beta Lyrae is thus postulated to be a double-contact binary, which makes possible nonarbitrary separation of star and disk into separate structures. The computed equilibrium figures are three-dimensional, as the gravitation of the second star is included. Under the approximation that the gravitational potential of the disk is that of a thin wire and that the local disk angular velocity is proportional to u/sup n/ (u = distance from rotation axis), we comptue the total potential and locate equipotential surfaces. The centrifugal potential is written in a particularly convenient form which permits one to change the rotation law discontinuously (for example, at the star-disk coupling point) while ensuring that centrifugal potential and centrifigual force are continuous functions of position. With such a one-parameter rotation law, one can find equilibrium disk figures with dimensions very similar to those found in β Lyrae, but considerations of internal consistency demand at least a two-parameter law

The effect of transverse crack upon parametric instability of a rotor-bearing system with an asymmetric disk

Science.gov (United States)

Han, Qinkai; Chu, Fulei

2012-12-01

It is well known that either the asymmetric disk or transverse crack brings parametric inertia (or stiffness) excitation to the rotor-bearing system. When both of them appear in a rotor system, the parametric instability behaviors have not gained sufficient attentions. Thus, the effect of transverse crack upon parametric instability of a rotor-bearing system with an asymmetric disk is studied. First, the finite element equations of motion are established for the asymmetric rotor system. Both the open and breathing transverse cracks are taken into account in the model. Then, the discrete state transition matrix (DSTM) method is introduced for numerically acquiring the instability regions. Based upon these, some computations for a practical asymmetric rotor system with open or breathing transverse crack are conducted, respectively. Variations of the primary and combination instability regions induced by the asymmetric disk with the crack depth are observed, and the effect of the orientation angle between the crack and asymmetric disk on various instability regions are discussed in detail. It is shown that for the asymmetric angle around 0, the existence of transverse (either open or breathing) crack has attenuation effect upon the instability regions. Under certain crack depth, the instability regions could be vanished by the transverse crack. When the asymmetric angle is around π/2, increasing the crack depth would enhance the instability regions.

Design of UAVs-Based 3D Antenna Arrays for a Maximum Performance in Terms of Directivity and SLL

Directory of Open Access Journals (Sweden)

Jesus Garza

2016-01-01

Full Text Available This paper presents a design of UAVs-based 3D antenna arrays for a maximum performance in terms of directivity and side lobe level (SLL. This paper illustrates how to model the UAVs formation flight using 3D nonuniform antenna arrays. This design of 3D antenna arrays considers the optimization of the positions of the antenna elements to model the UAVs formation flight. In this case, a disk patch antenna is chosen to be used as element in each UAV. The disk patch antenna is formulated by the well-known cavity model. The synthesis process is carried out by the method of Differential Evolution for Multiobjective Optimization (DEMO. Furthermore, a comparison of the performance of 3D nonuniform antenna arrays is provided with respect to the most conventional arrays (circular, planar, linear, and the cubic for UAVs formation flight.

System level traffic shaping in disk servers with heterogeneous protocols

International Nuclear Information System (INIS)

Cano, Eric; Kruse, Daniele Francesco

2014-01-01

Disk access and tape migrations compete for network bandwidth in CASTORs disk servers, over various protocols: RFIO, Xroot, root and GridFTP. As there are a limited number of tape drives, it is important to keep them busy all the time, at their nominal speed. With potentially 100s of user read streams per server, the bandwidth for the tape migrations has to be guaranteed to a controlled level, and not the fair share the system gives by default. Xroot provides a prioritization mechanism, but using it implies moving exclusively to the Xroot protocol, which is not possible in short to mid-term time frame, as users are equally using all protocols. The greatest commonality of all those protocols is not more than the usage of TCP/IP. We investigated the Linux kernel traffic shaper to control TCP/ IP bandwidth. The performance and limitations of the traffic shaper have been understood in test environment, and satisfactory working point has been found for production. Notably, TCP offload engines' negative impact on traffic shaping, and the limitations of the length of the traffic shaping rules were discovered and measured. A suitable working point has been found and the traffic shaping is now successfully deployed in the CASTOR production systems at CERN. This system level approach could be transposed easily to other environments.

WEAK TURBULENCE IN THE HD 163296 PROTOPLANETARY DISK REVEALED BY ALMA CO OBSERVATIONS

Energy Technology Data Exchange (ETDEWEB)

Flaherty, Kevin M.; Hughes, A. Meredith [Van Vleck Observatory, Astronomy Department, Wesleyan University, 96 Foss Hill Drive, Middletown, CT 06459 (United States); Rosenfeld, Katherine A.; Andrews, Sean M.; Wilner, David J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Chiang, Eugene; Kerzner, Skylar [Department of Earth and Planetary Science, 307 McCone Hall, University of California, Berkeley, CA 94720 (United States); Simon, Jacob B. [Department of Space Studies, Southwest Research Institute, Boulder, CO 80302 (United States)

2015-11-10

Turbulence can transport angular momentum in protoplanetary disks and influence the growth and evolution of planets. With spatially and spectrally resolved molecular emission line measurements provided by (sub)millimeter interferometric observations, it is possible to directly measure non-thermal motions in the disk gas that can be attributed to this turbulence. We report a new constraint on the turbulence in the disk around HD 163296, a nearby young A star, determined from Atacama Large Millimeter/submillimeter Array Science Verification observations of four CO emission lines (the CO(3-2), CO(2-1), {sup 13}CO(2-1), and C{sup 18}O(2-1) transitions). The different optical depths for these lines permit probes of non-thermal line-widths at a range of physical conditions (temperature and density) and depths into the disk interior. We derive stringent limits on the non-thermal motions in the upper layers of the outer disk such that any contribution to the line-widths from turbulence is <3% of the local sound speed. These limits are approximately an order of magnitude lower than theoretical predictions for full-blown magnetohydrodynamic turbulence driven by the magnetorotational instability, potentially suggesting that this mechanism is less efficient in the outer (R ≳ 30 AU) disk than has been previously considered.

THICK-DISK EVOLUTION INDUCED BY THE GROWTH OF AN EMBEDDED THIN DISK

International Nuclear Information System (INIS)

Villalobos, Alvaro; Helmi, Amina; Kazantzidis, Stelios

2010-01-01

We perform collisionless N-body simulations to investigate the evolution of the structural and kinematical properties of simulated thick disks induced by the growth of an embedded thin disk. The thick disks used in the present study originate from cosmologically common 5:1 encounters between initially thin primary disk galaxies and infalling satellites. The growing thin disks are modeled as static gravitational potentials and we explore a variety of growing-disk parameters that are likely to influence the response of thick disks. We find that the final thick-disk properties depend strongly on the total mass and radial scale length of the growing thin disk, and much less sensitively on its growth timescale and vertical scale height as well as the initial sense of thick-disk rotation. Overall, the growth of an embedded thin disk can cause a substantial contraction in both the radial and vertical direction, resulting in a significant decrease in the scale lengths and scale heights of thick disks. Kinematically, a growing thin disk can induce a notable increase in the mean rotation and velocity dispersions of thick-disk stars. We conclude that the reformation of a thin disk via gas accretion may play a significant role in setting the structure and kinematics of thick disks, and thus it is an important ingredient in models of thick-disk formation.

8-inch IBM floppy disk

CERN Multimedia

1971-01-01

The 8-inch floppy disk was a magnetic storage disk for the data introduced commercially by IBM in 1971. It was designed by an IBM team as an inexpensive way to load data into the IBM System / 370. Plus it was a read-only bare disk containing 80 KB of data. The first read-write version was introduced in 1972 by Memorex and could contain 175 KB on 50 tracks (with 8 sectors per track). Other improvements have led to various coatings and increased capacities. Finally, it was surpassed by the mini diskette of 5.25 inches introduced in 1976.

Stratified Simulations of Collisionless Accretion Disks

Energy Technology Data Exchange (ETDEWEB)

Hirabayashi, Kota; Hoshino, Masahiro, E-mail: hirabayashi-k@eps.s.u-tokyo.ac.jp [Department of Earth and Planetary Science, The University of Tokyo, Tokyo, 113-0033 (Japan)

2017-06-10

This paper presents a series of stratified-shearing-box simulations of collisionless accretion disks in the recently developed framework of kinetic magnetohydrodynamics (MHD), which can handle finite non-gyrotropy of a pressure tensor. Although a fully kinetic simulation predicted a more efficient angular-momentum transport in collisionless disks than in the standard MHD regime, the enhanced transport has not been observed in past kinetic-MHD approaches to gyrotropic pressure anisotropy. For the purpose of investigating this missing link between the fully kinetic and MHD treatments, this paper explores the role of non-gyrotropic pressure and makes the first attempt to incorporate certain collisionless effects into disk-scale, stratified disk simulations. When the timescale of gyrotropization was longer than, or comparable to, the disk-rotation frequency of the orbit, we found that the finite non-gyrotropy selectively remaining in the vicinity of current sheets contributes to suppressing magnetic reconnection in the shearing-box system. This leads to increases both in the saturated amplitude of the MHD turbulence driven by magnetorotational instabilities and in the resultant efficiency of angular-momentum transport. Our results seem to favor the fast advection of magnetic fields toward the rotation axis of a central object, which is required to launch an ultra-relativistic jet from a black hole accretion system in, for example, a magnetically arrested disk state.

Practical and Secure Recovery of Disk Encryption Key Using Smart Cards

Science.gov (United States)

Omote, Kazumasa; Kato, Kazuhiko

In key-recovery methods using smart cards, a user can recover the disk encryption key in cooperation with the system administrator, even if the user has lost the smart card including the disk encryption key. However, the disk encryption key is known to the system administrator in advance in most key-recovery methods. Hence user's disk data may be read by the system administrator. Furthermore, if the disk encryption key is not known to the system administrator in advance, it is difficult to achieve a key authentication. In this paper, we propose a scheme which enables to recover the disk encryption key when the user's smart card is lost. In our scheme, the disk encryption key is not preserved anywhere and then the system administrator cannot know the key before key-recovery phase. Only someone who has a user's smart card and knows the user's password can decrypt that user's disk data. Furthermore, we measured the processing time required for user authentication in an experimental environment using a virtual machine monitor. As a result, we found that this processing time is short enough to be practical.

The multiple disk chopper neutron time-of-flight spectrometer at NIST

International Nuclear Information System (INIS)

Altorfer, F.B.; Cook, J.C.; Copley, J.R.D.

1995-01-01

A highly versatile multiple disk chopper neutron time-of-flight spectrometer is being installed at the Cold Neutron Research Facility of the National institute of Standards and Technology. This new instrument will fill an important gap in the portfolio of neutron inelastic scattering spectrometers in North America. It will be used for a wide variety of experiments such as studies of magnetic and vibrational excitations, tunneling spectroscopy, and quasielastic neutron scattering investigations of local and translational diffusion. The instrument uses disk choppers to monochromate and pulse the incident beam, and the energy changes of scattered neutrons are determined from their times-of-flight to a large array of detectors. The disks and the guide have been designed to make the instrument readily adaptable to the specific performance requirements of experimenters. The authors present important aspects of the design, as well as estimated values of the flux at the sample and the energy resolution for elastic scattering. The instrument should be operational in 1996

Oscillations of disks

CERN Document Server

Kato, Shoji

2016-01-01

This book presents the current state of research on disk oscillation theory, focusing on relativistic disks and tidally deformed disks. Since the launch of the Rossi X-ray Timing Explorer (RXTE) in 1996, many high-frequency quasiperiodic oscillations (HFQPOs) have been observed in X-ray binaries. Subsequently, similar quasi-periodic oscillations have been found in such relativistic objects as microquasars, ultra-luminous X-ray sources, and galactic nuclei. One of the most promising explanations of their origin is based on oscillations in relativistic disks, and a new field called discoseismology is currently developing. After reviewing observational aspects, the book presents the basic characteristics of disk oscillations, especially focusing on those in relativistic disks. Relativistic disks are essentially different from Newtonian disks in terms of several basic characteristics of their disk oscillations, including the radial distributions of epicyclic frequencies. In order to understand the basic processes...

Optimality based repetitive controller design for track-following servo system of optical disk drives.

Science.gov (United States)

Chen, Wentao; Zhang, Weidong

2009-10-01

In an optical disk drive servo system, to attenuate the external periodic disturbances induced by inevitable disk eccentricity, repetitive control has been used successfully. The performance of a repetitive controller greatly depends on the bandwidth of the low-pass filter included in the repetitive controller. However, owing to the plant uncertainty and system stability, it is difficult to maximize the bandwidth of the low-pass filter. In this paper, we propose an optimality based repetitive controller design method for the track-following servo system with norm-bounded uncertainties. By embedding a lead compensator in the repetitive controller, both the system gain at periodic signal's harmonics and the bandwidth of the low-pass filter are greatly increased. The optimal values of the repetitive controller's parameters are obtained by solving two optimization problems. Simulation and experimental results are provided to illustrate the effectiveness of the proposed method.

Studies of Young, Star-forming Circumstellar Disks

Science.gov (United States)

Bae, Jaehan

2017-08-01

Disks of gas and dust around forming stars - circumstellar disks - last only a few million years. This is a very small fraction of the entire lifetime of Sun-like stars, several billion years. Nevertheless, by the time circumstellar disks dissipate stars complete building up their masses, giant planets finish accreting gas, and terrestrial bodies are nearly fully grown and ready for their final assembly to become planets. Understanding the evolution of circumstellar disks are thus crucial in many contexts. Using numerical simulations as the primary tool, my thesis has focused on the studies of various physical processes that can occur throughout the lifetime of circumstellar disks, from their formation to dispersal. Chapters 2, 3, and 4 emphasize the importance of early evolution, during which time a forming star-disk system obtains mass from its natal cloud: the infall phase. In Chapter 2 and 3, I have modeled episodic outbursts of accretion in protostellar systems resulting from disk instabilities - gravitational instability and magnetorotational instability. I showed that outbursts occur preferentially during the infall phase, because the mass addition provides more favorable conditions for gravitational instability to initiate the outburst cycle, and that forming stars build up a significant fraction of their masses through repeated short-lived, episodic outbursts. The infall phase can also be important for the formation of planets. Recent ALMA observations revealed sets of bright and dark rings in circumstellar disks of young, forming stars, potentially indicating early formation of planets. In Chapter 4, I showed that infall streams can create radial pressure bumps near the outer edge of the mass landing on the disk, from which vortices can form, collecting solid particles very efficiently to make initial seeds of planets. The next three chapters highlight the role of planets in setting the observational appearance and the evolution of circumstellar disks

MEMBANGUN SISTEM LINUX MANDRAKE MINIMAL MENGGUNAKAN INISIAL DISK RAM

OpenAIRE

Wagito, Wagito

2009-01-01

        Minimal Linux system is commonly used for special systems like router, gateway, Linux installer and diskless Linux system. Minimal Linux system is a Linux system that use a few facilities of all Linux capabilities. Mandrake Linux, as one of Linux distribution is able to perform minimal Linux system.         RAM is a computer resource that especially used as main memory. A  part of RAM’s function can be changed into disk called RAM disk. This RAM disk can be used to run the Linux syste...

Stagger angle dependence of inertial and elastic coupling in bladed disks

Science.gov (United States)

Crawley, E. F.; Mokadam, D. R.

1984-01-01

Conditions which necessitate the inclusion of disk and shaft flexibility in the analysis of blade response in rotating blade-disk-shaft systems are derived in terms of nondimensional parameters. A simple semianalytical Rayleigh-Ritz model is derived in which the disk possesses all six rigid body degrees of freedom, which are elastically constrained by the shaft. Inertial coupling by the rigid body motion of the disk on a flexible shaft and out-of-plane elastic coupling due to disk flexure are included. Frequency ratios and mass ratios, which depend on the stagger angle, are determined for three typical rotors: a first stage high-pressure core compressor, a high bypass ratio fan, and an advanced turboprop. The stagger angle controls the degree of coupling in the blade-disk system. In the blade-disk-shaft system, the stagger angle determines whether blade-disk motion couples principally to the out-of-plane or in-plane motion of the disk on the shaft. The Ritz analysis shows excellent agreement with experimental results.

A SPATIALLY RESOLVED INNER HOLE IN THE DISK AROUND GM AURIGAE

International Nuclear Information System (INIS)

Hughes, A. Meredith; Andrews, Sean M.; Wilner, David J.; Qi Chunhua; Espaillat, Catherine; Calvet, Nuria; D'Alessio, Paola; Williams, Jonathan P.; Hogerheijde, Michiel R.

2009-01-01

We present 0.''3 resolution observations of the disk around GM Aurigae with the Submillimeter Array (SMA) at a wavelength of 860 μm and with the Plateau de Bure Interferometer at a wavelength of 1.3 mm. These observations probe the distribution of disk material on spatial scales commensurate with the size of the inner hole predicted by models of the spectral energy distribution (SED). The data clearly indicate a sharp decrease in millimeter optical depth at the disk center, consistent with a deficit of material at distances less than ∼20 AU from the star. We refine the accretion disk model of Calvet et al. based on the unresolved SED and demonstrate that it reproduces well the spatially resolved millimeter continuum data at both available wavelengths. We also present complementary SMA observations of CO J = 3-2 and J = 2-1 emission from the disk at 2'' resolution. The observed CO morphology is consistent with the continuum model prediction, with two significant deviations: (1) the emission displays a larger CO J = 3-2/J = 2-1 line ratio than predicted, which may indicate additional heating of gas in the upper disk layers; and (2) the position angle of the kinematic rotation pattern differs by 11 deg. ± 2 deg. from that measured at smaller scales from the dust continuum, which may indicate the presence of a warp. We note that photoevaporation, grain growth, and binarity are unlikely mechanisms for inducing the observed sharp decrease in opacity or surface density at the disk center. The inner hole plausibly results from the dynamical influence of a planet on the disk material. Warping induced by a planet could also potentially explain the difference in position angle between the continuum and CO data sets.

GEMINI PLANET IMAGER OBSERVATIONS OF THE AU MICROSCOPII DEBRIS DISK: ASYMMETRIES WITHIN ONE ARCSECOND

Energy Technology Data Exchange (ETDEWEB)

Wang, Jason J.; Graham, James R.; De Rosa, Robert J.; Kalas, Paul; Chiang, Eugene; Duchêne, Gaspard [Astronomy Department, University of California, Berkeley, Berkeley, CA 94720 (United States); Pueyo, Laurent; Chen, Christine; Greenbaum, Alexandra Z. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Nielsen, Eric L. [SETI Institute, Carl Sagan Center, 189 Bernardo Avenue, Mountain View, CA 94043 (United States); Millar-Blanchaer, Max [Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada); Ammons, S. Mark [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94040 (United States); Bulger, Joanna [School of Earth and Space Exploration, Arizona State University, P.O. Box 871404, Tempe, AZ 85287 (United States); Cardwell, Andrew; Goodsell, Stephen J. [Gemini Observatory, Casilla 603, La Serena (Chile); Chilcote, Jeffrey K. [Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada); Doyon, René [Institut de Recherche sur les Exoplanètes, Départment de Physique, Université de Montréal, Montréal, QC H3C 3J7 (Canada); Draper, Zachary H. [University of Victoria, 3800 Finnerty Road, Victoria, BC V8P 5C2 (Canada); Esposito, Thomas M.; Fitzgerald, Michael P. [Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, CA 90095 (United States); and others

2015-10-01

We present Gemini Planet Imager (GPI) observations of AU Microscopii, a young M dwarf with an edge-on, dusty debris disk. Integral field spectroscopy and broadband imaging polarimetry were obtained during the commissioning of GPI. In our broadband imaging polarimetry observations, we detect the disk only in total intensity and find asymmetries in the morphology of the disk between the southeast (SE) and northwest (NW) sides. The SE side of the disk exhibits a bump at 1″ (10 AU projected separation) that is three times more vertically extended and three times fainter in peak surface brightness than the NW side at similar separations. This part of the disk is also vertically offset by 69 ± 30 mas to the northeast at 1″ when compared to the established disk midplane and is consistent with prior Atacama Large Millimeter/submillimeter Array and Hubble Space Telescope/Space Telescope Imaging Spectrograph observations. We see hints that the SE bump might be a result of detecting a horizontal sliver feature above the main disk that could be the disk backside. Alternatively, when including the morphology of the NW side, where the disk midplane is offset in the opposite direction ∼50 mas between 0.″4 and 1.″2, the asymmetries suggest a warp-like feature. Using our integral field spectroscopy data to search for planets, we are 50% complete for ∼4 M{sub Jup} planets at 4 AU. We detect a source, resolved only along the disk plane, that could either be a candidate planetary mass companion or a compact clump in the disk.

Using Deduplicating Storage for Efficient Disk Image Deployment

Directory of Open Access Journals (Sweden)

Xing Lin

2015-08-01

Full Text Available Many clouds and network testbeds use disk images to initialize local storage on their compute devices. Large facilities must manage thousands or more images, requiring significant amounts of storage. At the same time, to provide a good user experience, they must be able to deploy those images quickly. Driven by our experience in operating the Emulab site at the University of Utah---a long-lived and heavily-used testbed---we have created a new service for efficiently storing and deploying disk images. This service exploits the redundant data found in similar images, using deduplication to greatly reduce the amount of physical storage required. In addition to space savings, our system is also designed for highly efficient image deployment---it integrates with an existing highly-optimized disk image deployment system, Frisbee, without significantly increasing the time required to distribute and install images. In this paper, we explain the design of our system and discuss the trade-offs we made to strike a balance between efficient storage and fast disk image deployment. We also propose a new chunking algorithm, called AFC, which enables fixed-size chunking for deduplicating allocated disk sectors. Experimental results show that our system reduces storage requirements by up to 3x while imposing only a negligible runtime overhead on the end-to-end disk-deployment process.

On the Dynamical Structure of the Jet System in the Disk with the Keplerian Rotation

Directory of Open Access Journals (Sweden)

Kyung-Sook Jeong

1989-06-01

Full Text Available The classical sloar wind theory proposed by Parker(1963 explains well the dynamics of the wind pheonomena such as stellar wind accretion disk. While the stellar wind system like the solar wind has the spherically symmetric wind structure, there are various jet phenomena which collimate the system into the narrow space. We can find these dynamical structures in SS433, in the optical jet of M87, and around the active galactic nulei. We present the dynamical structure of the jet system in disks, which conserves the angular momentum, with the Keplerian rotation and the strong relation between the geometrical cross section and the physical change of the jet stream on the basis of the hydrodynamic equations.

Zodiac II: Debris Disk Science from a Balloon

Science.gov (United States)

Bryden, Geoffrey; Traub, Wesley; Roberts, Lewis C., Jr.; Bruno, Robin; Unwin, Stephen; Backovsky, Stan; Brugarolas, Paul; Chakrabarti, Supriya; Chen, Pin; Hillenbrand, Lynne;

Gas Velocities Reveal Newly Born Planets in a Disk

Science.gov (United States)

Kohler, Susanna

2018-06-01

Occasionally, science comes together beautifully for a discovery and sometimes this happens for more than one team at once! Today we explore how two independent collaborations of scientists simultaneously found the very first kinematic evidence for young planets forming in a protoplanetary disk. Though they explored the same disk, the two teams in fact discovered different planets.Evidence for PlanetsALMAs view of the dust in the protoplanetary disk surrounding the young star HD 163296. Todays studies explore not the dust, but the gas of this disk. [ALMA (ESO/NAOJ/NRAO); A. Isella; B. Saxton (NRAO/AUI/NSF)]Over the past three decades, weve detected around 4,000 fully formed exoplanets. Much more elusive, however, are the young planets still in the early stages of formation; only a handful of these have been discovered. More observations of early-stage exoplanets are needed in order to understand how these worlds are born in dusty protoplanetary-disk environments, how they grow their atmospheres, and how they evolve.Recent observations by the Atacama Large Millimeter/submillimeter Array (ALMA) have produced stunning images of protoplanetary disks. The unprecedented resolution of these images reveals substructure in the form of gaps and rings, hinting at the presence of planets that orbit within the disk and clear out their paths as they move. But there are also non-planet mechanisms that could produce such substructure, like grain growth around ice lines, or hydrodynamic instabilities in the disk.How can we definitively determine whether there are nascent planets embedded in these disks? Direct direction of a point source in a dust gap would be a strong confirmation, but now we have the next best thing: kinematic evidence for planets, from the motion of a disks gas.Observations of carbon monoxide line emission at +1km/s from the systemic velocity (left) vs. the outcome of a computer simulation (right) in the Pinte et al. study. A visible kink occurs in the flow

A CLOSER LOOK AT THE LkCa 15 PROTOPLANETARY DISK

International Nuclear Information System (INIS)

Andrews, Sean M.; Rosenfeld, Katherine A.; Wilner, David J.; Bremer, Michael

2011-01-01

We present 870 μm observations of dust continuum emission from the LkCa 15 protoplanetary disk at high angular resolution (with a characteristic scale of 0.''25 = 35 AU), obtained with the IRAM Plateau de Bure interferometer and supplemented by slightly lower resolution observations from the Submillimeter Array. We fit these data with simple morphological models to characterize the spectacular ring-like emission structure of this disk. Our analysis indicates that a small amount of 870 μm dust emission (∼5 mJy) originates inside a large (40-50 AU radius) low optical depth cavity. This result can be interpreted either in the context of an abrupt decrease by a factor of ∼5 in the radial distribution of millimeter-sized dust grains or as indirect evidence for a gap in the disk, in agreement with previous inferences from the unresolved infrared spectrum and scattered light images. A preliminary model focused on the latter possibility suggests the presence of a low-mass (planetary) companion, having properties commensurate with those inferred from the recent discovery of LkCa 15b.

Magnetically Induced Disk Winds and Transport in the HL Tau Disk

International Nuclear Information System (INIS)

Hasegawa, Yasuhiro; Flock, Mario; Turner, Neal J.; Okuzumi, Satoshi

2017-01-01

The mechanism of angular momentum transport in protoplanetary disks is fundamental to understanding the distributions of gas and dust in the disks. The unprecedented ALMA observations taken toward HL Tau at high spatial resolution and subsequent radiative transfer modeling reveal that a high degree of dust settling is currently achieved in the outer part of the HL Tau disk. Previous observations, however, suggest a high disk accretion rate onto the central star. This configuration is not necessarily intuitive in the framework of the conventional viscous disk model, since efficient accretion generally requires a high level of turbulence, which can suppress dust settling considerably. We develop a simplified, semi-analytical disk model to examine under what condition these two properties can be realized in a single model. Recent, non-ideal MHD simulations are utilized to realistically model the angular momentum transport both radially via MHD turbulence and vertically via magnetically induced disk winds. We find that the HL Tau disk configuration can be reproduced well when disk winds are properly taken into account. While the resulting disk properties are likely consistent with other observational results, such an ideal situation can be established only if the plasma β at the disk midplane is β 0 ≃ 2 × 10 4 under the assumption of steady accretion. Equivalently, the vertical magnetic flux at 100 au is about 0.2 mG. More detailed modeling is needed to fully identify the origin of the disk accretion and quantitatively examine plausible mechanisms behind the observed gap structures in the HL Tau disk.

Magnetically Induced Disk Winds and Transport in the HL Tau Disk

Energy Technology Data Exchange (ETDEWEB)

Hasegawa, Yasuhiro; Flock, Mario; Turner, Neal J. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Okuzumi, Satoshi, E-mail: yasuhiro@caltech.edu [Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551 (Japan)

2017-08-10

The mechanism of angular momentum transport in protoplanetary disks is fundamental to understanding the distributions of gas and dust in the disks. The unprecedented ALMA observations taken toward HL Tau at high spatial resolution and subsequent radiative transfer modeling reveal that a high degree of dust settling is currently achieved in the outer part of the HL Tau disk. Previous observations, however, suggest a high disk accretion rate onto the central star. This configuration is not necessarily intuitive in the framework of the conventional viscous disk model, since efficient accretion generally requires a high level of turbulence, which can suppress dust settling considerably. We develop a simplified, semi-analytical disk model to examine under what condition these two properties can be realized in a single model. Recent, non-ideal MHD simulations are utilized to realistically model the angular momentum transport both radially via MHD turbulence and vertically via magnetically induced disk winds. We find that the HL Tau disk configuration can be reproduced well when disk winds are properly taken into account. While the resulting disk properties are likely consistent with other observational results, such an ideal situation can be established only if the plasma β at the disk midplane is β {sub 0} ≃ 2 × 10{sup 4} under the assumption of steady accretion. Equivalently, the vertical magnetic flux at 100 au is about 0.2 mG. More detailed modeling is needed to fully identify the origin of the disk accretion and quantitatively examine plausible mechanisms behind the observed gap structures in the HL Tau disk.

The Fabulous Four Debris Disks

Science.gov (United States)

Werner, Michael; Stapelfeldt, Karl

2004-09-01

This program is a comprehensive study of the four bright debris disks that were spatially resolved by IRAS: Beta Pictoris, Epsilon Eridani, Fomalhaut, and Vega. All SIRTF instruments and observing modes will be used. The program has three major objectives: (1) Study of the disk spatial structure from MIPS and IRAC imaging; (2) Study of the dust grain composition using the IRS and MIPS SED mode; and (3) companion searches using IRAC. The data from this program should lead to a detailed understanding of these four systems, and will provide a foundation for understanding all of the debris disks to be studied with SIRTF. Images and spectra will be compared with models for disk structure and dust properties. Dynamical features indicative of substellar companions' effects on the disks will be searched for. This program will require supporting observations of PSF stars, some of which have been included explicitly. In the majority of cases, the spectral observations require a preferred orientation to align the slits along the disk position angles. Detector saturation issues are still being worked for this program, and will lead to AOR modifications in subsequent submissions. The results from this program will be analyzed collaboratively by the IRAC, IRS, and MIPS teams and by general GTOs Jura and Werner.

Fuzzy pool balance: An algorithm to achieve a two dimensional balance in distribute storage systems

International Nuclear Information System (INIS)

Wu, Wenjing; Chen, Gang

2014-01-01

The limitation of scheduling modules and the gradual addition of disk pools in distributed storage systems often result in imbalances among their disk pools in terms of both disk usage and file count. This can cause various problems to the storage system such as single point of failure, low system throughput and imbalanced resource utilization and system loads. An algorithm named Fuzzy Pool Balance (FPB) is proposed here to solve this problem. The input of FPB is the current file distribution among disk pools and the output is a file migration plan indicating what files are to be migrated to which pools. FPB uses an array to classify the files by their sizes. The file classification array is dynamically calculated with a defined threshold named T max that defines the allowed pool disk usage deviations. File classification is the basis of file migration. FPB also defines the Immigration Pool (IP) and Emigration Pool (EP) according to the pool disk usage and File Quantity Ratio (FQR) that indicates the percentage of each category of files in each disk pool, so files with higher FQR in an EP will be migrated to IP(s) with a lower FQR of this file category. To verify this algorithm, we implemented FPB on an ATLAS Tier2 dCache production system. The results show that FPB can achieve a very good balance in both free space and file counts, and adjusting the threshold value T max and the correction factor to the average FQR can achieve a tradeoff between free space and file count.

Digital image processing software system using an array processor

International Nuclear Information System (INIS)

Sherwood, R.J.; Portnoff, M.R.; Journeay, C.H.; Twogood, R.E.

1981-01-01

A versatile array processor-based system for general-purpose image processing was developed. At the heart of this system is an extensive, flexible software package that incorporates the array processor for effective interactive image processing. The software system is described in detail, and its application to a diverse set of applications at LLNL is briefly discussed. 4 figures, 1 table

Chemistry in protoplanetary disks

Science.gov (United States)

Semenov, D. A.

2012-01-01

In this lecture I discuss recent progress in the understanding of the chemical evolution of protoplanetary disks that resemble our Solar system during the first ten million years. At the verge of planet formation, strong variations of temperature, density, and radiation intensities in these disks lead to a layered chemical structure. In hot, dilute and heavily irradiated atmosphere only simple radicals, atoms, and atomic ions can survive, formed and destroyed by gas-phase processes. Beneath the atmosphere a partly UV-shielded, warm molecular layer is located, where high-energy radiation drives rich chemistry, both in the gas phase and on dust surfaces. In a cold, dense, dark disk midplane many molecules are frozen out, forming thick icy mantles where surface chemistry is active and where complex (organic) species are synthesized.

A Pulsar and a Disk

Science.gov (United States)

Kohler, Susanna

2016-07-01

Recent, unusual X-ray observations from our galactic neighbor, the Small Magellanic Cloud, have led to an interesting model for SXP 214, a pulsar in a binary star system.Artists illustration of the magnetic field lines of a pulsar, a highly magnetized, rotating neutron star. [NASA]An Intriguing BinaryAn X-ray pulsar is a magnetized, rotating neutron star in a binary system with a stellar companion. Material is fed from the companion onto the neutron star, channeled by the objects magnetic fields onto a hotspot thats millions of degrees. This hotspot rotating past our line of sight is what produces the pulsations that we observe from X-ray pulsars.Located in the Small Magellanic Cloud, SXP 214 is a transient X-ray pulsar in a binary with a Be-type star. This star is spinning so quickly that material is thrown off of it to form a circumstellar disk.Recently, a team of authors led by JaeSub Hong (Harvard-Smithsonian Center for Astrophysics) have presented new Chandra X-ray observations of SXP 214, tracking it for 50 ks (~14 hours) in January 2013. These observations reveal some very unexpected behavior for this pulsar.X-ray PuzzleThe energy distribution of the X-ray emission from SXP 214 over time. Dark shades or blue colors indicate high counts, and light shades or yellow colors indicate low counts. Lower-energy X-ray emission appeared only later, after about 20 ks. [Hong et al. 2016]Three interesting pieces of information came from the Chandra observations:SXP 214s rotation period was measured to be 211.5 s an increase in the spin rate since the discovery measurement of a 214-second period. Pulsars usually spin down as they lose angular momentum over time so what caused this one to spin up?Its overall X-ray luminosity steadily increased over the 50 ks of observations.Its spectrum became gradually softer (lower energy) over time; in the first 20 ks, the spectrum only consisted of hard X-ray photons above 3 keV, but after 20 ks, softer X-ray photons below 2 ke

RAID Disk Arrays for High Bandwidth Applications

Science.gov (United States)

Moren, Bill

1996-01-01

High bandwidth applications require large amounts of data transferred to/from storage devices at extremely high data rates. Further, these applications often are 'real time' in which access to the storage device must take place on the schedule of the data source, not the storage. A good example is a satellite downlink - the volume of data is quite large and the data rates quite high (dozens of MB/sec). Further, a telemetry downlink must take place while the satellite is overhead. A storage technology which is ideally suited to these types of applications is redundant arrays of independent discs (RAID). Raid storage technology, while offering differing methodologies for a variety of applications, supports the performance and redundancy required in real-time applications. Of the various RAID levels, RAID-3 is the only one which provides high data transfer rates under all operating conditions, including after a drive failure.

Probing Disk Stratification by Combining X-ray and Disk Inclination Data for Taurus-Auriga

Science.gov (United States)

Arraki, Kenza S.; Daly, B.; Harding, M.; McCleary, J.; Cox, A. W.; Grady, C. A.; Woodgate, B. E.; Hamaguchi, K.; Wisniewski, J. P.; Brakken-Thal, S.; Hilton, G.; Bonfield, D.; Williger, G. M.

2010-01-01

Photoelectric neutral Hydrogen absorption, N(H), is a probe of the gas and dust column towards the star. Kastner et al. (2005) found a correlation between N(H) and proplyd aspect ratio in the Orion nebula cluster. We extend this study to Taurus-Auriga by combining publicly available N(H) data from the XMM-Newton Extended Survey of the Taurus molecular cloud (XEST), with published disk inclination data obtained from HST coronagraphic imagery and mm interferometry. Additional inclinations were derived from jet proper motion and radial velocity data obtained from archival HST imagery and the Apache Point Observatory 3.5m telescope's Goddard Fabry-Perot and DIS long-slit spectrograph. Both N(H) and extinction have linear relations with system inclination, where the extinction has a smaller slope than the N(H) trend. Correlations with system inclination demonstrate that the bulk of both N(H) and extinction arise in the disk rather than in remnant envelopes, nearby molecular cloud material, or foreground material. The deficit in extinction compared with predictions for ISM-like gas to dust ratios is consistent with grain growth and settling toward the disk midplane and stratification in disks occurring by 2 Myr. However, the disks remain gas-rich, indicating that giant planet formation is still feasible. We gratefully acknowledge the support of the NASA Motivating Undergraduates in Science and Technology (MUST) Project and of NASA's APRA program under WBS#399131.02.06.02.32. A grant of Director's Discretionary Time funded observing time at the Apache Point Observatory.

MULTIPLICITY, DISKS, AND JETS IN THE NGC 2071 STAR-FORMING REGION

Energy Technology Data Exchange (ETDEWEB)

Carrasco-Gonzalez, Carlos [Max-Planck-Institut fuer Radioastronomie (MPIfR), Auf dem Huegel 69, 53121 Bonn (Germany); Osorio, Mayra; Anglada, Guillem; Gomez, Jose F. [Instituto de Astrofisica de Andalucia, CSIC, Camino Bajo de Huetor 50, E-18008 Granada (Spain); D' Alessio, Paola; Rodriguez, Luis F. [Centro de Radioastronomia y Astrofisica UNAM, Apartado Postal 3-72 (Xangari), 58089 Morelia, Michoacan (Mexico); Torrelles, Jose M., E-mail: carrasco@mpifr-bonn.mpg.de [Instituto de Ciencias del Espacio (CSIC)-UB/IEEC, Universitat de Barcelona, Marti i Franques 1, E-08028 Barcelona (Spain)

2012-02-10

We present centimeter (cm) and millimeter (mm) observations of the NGC 2071 star-forming region performed with the Very Large Array (VLA) and Combined Array for Research in Millimeter-wave Astronomy (CARMA). We detected counterparts at 3.6 cm and 3 mm for the previously known sources IRS 1, IRS 2, IRS 3, and VLA 1. All these sources show spectral energy distributions (SEDs) dominated by free-free thermal emission at cm wavelengths and thermal dust emission at mm wavelengths, suggesting that all of them are associated with young stellar objects (YSOs). IRS 1 shows a complex morphology at 3.6 cm, with changes in the direction of its elongation. We discuss two possible explanations to this morphology: the result of changes in the direction of a jet due to interactions with a dense ambient medium, or that we are actually observing the superposition of two jets arising from two components of a binary system. Higher angular resolution observations at 1.3 cm support the second possibility, since a double source is inferred at this wavelength. IRS 3 shows a clear jet-like morphology at 3.6 cm. Over a timespan of four years, we observed changes in the morphology of this source that we interpret as due to ejection of ionized material in a jet. The emission at 3 mm of IRS 3 is angularly resolved, with a deconvolved size (FWHM) of {approx}120 AU, and seems to be tracing a dusty circumstellar disk perpendicular to the radio jet. An irradiated accretion disk model around an intermediate-mass YSO can account for the observed SED and spatial intensity profile at 3 mm, supporting this interpretation.

MULTIPLICITY, DISKS, AND JETS IN THE NGC 2071 STAR-FORMING REGION

International Nuclear Information System (INIS)

Carrasco-González, Carlos; Osorio, Mayra; Anglada, Guillem; Gómez, José F.; D'Alessio, Paola; Rodríguez, Luis F.; Torrelles, José M.

2012-01-01

We present centimeter (cm) and millimeter (mm) observations of the NGC 2071 star-forming region performed with the Very Large Array (VLA) and Combined Array for Research in Millimeter-wave Astronomy (CARMA). We detected counterparts at 3.6 cm and 3 mm for the previously known sources IRS 1, IRS 2, IRS 3, and VLA 1. All these sources show spectral energy distributions (SEDs) dominated by free-free thermal emission at cm wavelengths and thermal dust emission at mm wavelengths, suggesting that all of them are associated with young stellar objects (YSOs). IRS 1 shows a complex morphology at 3.6 cm, with changes in the direction of its elongation. We discuss two possible explanations to this morphology: the result of changes in the direction of a jet due to interactions with a dense ambient medium, or that we are actually observing the superposition of two jets arising from two components of a binary system. Higher angular resolution observations at 1.3 cm support the second possibility, since a double source is inferred at this wavelength. IRS 3 shows a clear jet-like morphology at 3.6 cm. Over a timespan of four years, we observed changes in the morphology of this source that we interpret as due to ejection of ionized material in a jet. The emission at 3 mm of IRS 3 is angularly resolved, with a deconvolved size (FWHM) of ∼120 AU, and seems to be tracing a dusty circumstellar disk perpendicular to the radio jet. An irradiated accretion disk model around an intermediate-mass YSO can account for the observed SED and spatial intensity profile at 3 mm, supporting this interpretation.

Two-dimensional Fast ESPRIT Algorithm for Linear Array SAR Imaging

Directory of Open Access Journals (Sweden)

Zhao Yi-chao

2015-10-01

Full Text Available The linear array Synthetic Aperture Radar (SAR system is a popular research tool, because it can realize three-dimensional imaging. However, owning to limitations of the aircraft platform and actual conditions, resolution improvement is difficult in cross-track and along-track directions. In this study, a twodimensional fast Estimation of Signal Parameters by Rotational Invariance Technique (ESPRIT algorithm for linear array SAR imaging is proposed to overcome these limitations. This approach combines the Gerschgorin disks method and the ESPRIT algorithm to estimate the positions of scatterers in cross and along-rack directions. Moreover, the reflectivity of scatterers is obtained by a modified pairing method based on “region growing”, replacing the least-squares method. The simulation results demonstrate the applicability of the algorithm with high resolution, quick calculation, and good real-time response.

Cluster Computing For Real Time Seismic Array Analysis.

Science.gov (United States)

Martini, M.; Giudicepietro, F.

A seismic array is an instrument composed by a dense distribution of seismic sen- sors that allow to measure the directional properties of the wavefield (slowness or wavenumber vector) radiated by a seismic source. Over the last years arrays have been widely used in different fields of seismological researches. In particular they are applied in the investigation of seismic sources on volcanoes where they can be suc- cessfully used for studying the volcanic microtremor and long period events which are critical for getting information on the volcanic systems evolution. For this reason arrays could be usefully employed for the volcanoes monitoring, however the huge amount of data produced by this type of instruments and the processing techniques which are quite time consuming limited their potentiality for this application. In order to favor a direct application of arrays techniques to continuous volcano monitoring we designed and built a small PC cluster able to near real time computing the kinematics properties of the wavefield (slowness or wavenumber vector) produced by local seis- mic source. The cluster is composed of 8 Intel Pentium-III bi-processors PC working at 550 MHz, and has 4 Gigabytes of RAM memory. It runs under Linux operating system. The developed analysis software package is based on the Multiple SIgnal Classification (MUSIC) algorithm and is written in Fortran. The message-passing part is based upon the LAM programming environment package, an open-source imple- mentation of the Message Passing Interface (MPI). The developed software system includes modules devote to receiving date by internet and graphical applications for the continuous displaying of the processing results. The system has been tested with a data set collected during a seismic experiment conducted on Etna in 1999 when two dense seismic arrays have been deployed on the northeast and the southeast flanks of this volcano. A real time continuous acquisition system has been simulated by

Secure Automated Microgrid Energy System

Science.gov (United States)

2016-12-01

O&M Operations and Maintenance PSO Power System Optimization PV Photovoltaic RAID Redundant Array of Independent Disks RBAC Role...elements of the initial study and operational power system model (feeder size , protective devices, generation sources, controllable loads, transformers...EW-201340) Secure Automated Microgrid Energy System December 2016 This document has been cleared for public release; Distribution Statement A

Radiative Transfer Modeling in Proto-planetary Disks

Science.gov (United States)

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.

SHADOWS CAST BY A WARP IN THE HD 142527 PROTOPLANETARY DISK

Energy Technology Data Exchange (ETDEWEB)

Marino, S.; Perez, S.; Casassus, S., E-mail: smarino@das.uchile.cl [Departamento de Astronomía, Universidad de Chile, Casilla 36-D Santiago (Chile)

2015-01-10

Detailed observations of gaps in protoplanetary disks have revealed structures that drive current research on circumstellar disks. One such feature is the two intensity nulls seen along the outer disk of the HD 142527 system, which are particularly well traced in polarized differential imaging. Here we propose that these are shadows cast by the inner disk. The inner and outer disk are thick, in terms of the unit-opacity surface in the H band, so that the shape and orientation of the shadows inform on the three-dimensional structure of the system. Radiative transfer predictions on a parametric disk model allow us to conclude that the relative inclination between the inner and outer disks is 70° ± 5°. This finding taps the potential of high-contrast imaging of circumstellar disks, and bears consequences on the gas dynamics of gapped disks, as well as on the physical conditions in the shadowed regions.

Occultations from an Active Accretion Disk in a 72-day Detached Post-Algol System Detected by K2

Science.gov (United States)

Zhou, G.; Rappaport, S.; Nelson, L.; Huang, C. X.; Senhadji, A.; Rodriguez, J. E.; Vanderburg, A.; Quinn, S.; Johnson, C. I.; Latham, D. W.; Torres, G.; Gary, B. L.; Tan, T. G.; Johnson, M. C.; Burt, J.; Kristiansen, M. H.; Jacobs, T. L.; LaCourse, D.; Schwengeler, H. M.; Terentev, I.; Bieryla, A.; Esquerdo, G. A.; Berlind, P.; Calkins, M. L.; Bento, J.; Cochran, W. D.; Karjalainen, M.; Hatzes, A. P.; Karjalainen, R.; Holden, B.; Butler, R. P.

2018-02-01

Disks in binary systems can cause exotic eclipsing events. MWC 882 (BD –22 4376, EPIC 225300403) is such a disk-eclipsing system identified from observations during Campaign 11 of the K2 mission. We propose that MWC 882 is a post-Algol system with a B7 donor star of mass 0.542+/- 0.053 {M}ȯ in a 72-day orbit around an A0 accreting star of mass 3.24+/- 0.29 {M}ȯ . The 59.9+/- 6.2 {R}ȯ disk around the accreting star occults the donor star once every orbit, inducing 19-day long, 7% deep eclipses identified by K2 and subsequently found in pre-discovery All-Sky Automated Survey and All Sky Automated Survey for Supernovae observations. We coordinated a campaign of photometric and spectroscopic observations for MWC 882 to measure the dynamical masses of the components and to monitor the system during eclipse. We found the photometric eclipse to be gray to ≈1%. We found that the primary star exhibits spectroscopic signatures of active accretion, and we observed gas absorption features from the disk during eclipse. We suggest that MWC 882 initially consisted of a ≈3.6 M ⊙ donor star transferring mass via Roche lobe overflow to a ≈2.1 M ⊙ accretor in a ≈7-day initial orbit. Through angular momentum conservation, the donor star is pushed outward during mass transfer to its current orbit of 72 days. The observed state of the system corresponds with the donor star having left the red giant branch ∼0.3 Myr ago, terminating active mass transfer. The present disk is expected to be short-lived (102 yr) without an active feeding mechanism, presenting a challenge to this model.

Disk Evolution and the Fate of Water

Science.gov (United States)

Hartmann, Lee; Ciesla, Fred; Gressel, Oliver; Alexander, Richard

2017-10-01

We review the general theoretical concepts and observational constraints on the distribution and evolution of water vapor and ice in protoplanetary disks, with a focus on the Solar System. Water is expected to freeze out at distances greater than 1-3 AU from solar-type central stars; more precise estimates are difficult to obtain due to uncertainties in the complex processes involved in disk evolution, including dust growth, settling, and radial drift, and the level of turbulence and viscous dissipation within disks. Interferometric observations are now providing constraints on the positions of CO snow lines, but extrapolation to the unresolved regions where water ice sublimates will require much better theoretical understanding of mass and angular momentum transport in disks as well as more refined comparison of observations with sophisticated disk models.

Contact statuses between functionally graded brake disk and pure pad disk

International Nuclear Information System (INIS)

Shahzamanian, M.M.; Sahari, B.B.; Bayat, M.; Mustapha, F.; Ismarrubie, Z.N.; Shahrjerdi, A.

2009-01-01

Full text: The contact statuses between functionally graded (FG) brake disks and pure pad disk are investigated by using finite element method (FEM). Two types of variation is considered for FG brake disk, the variation of materials are considered change in radial and thickness direction of disk. The material properties of these two types of FG brake disks are assumed to be represented by power-law distributions in the radius and thickness direction. The results are obtained and then compared. For the radial FG brake disk, the inner and outer surfaces are considered metal and ceramic respectively, and friction coefficient between metal surface and ceramic surface of FG brake dick with pad are considered 1.4 and 0.75 respectively. For the thickness FG brake disk the contact surface with pure pad brake disk is ceramic and the free surface is metal and friction coefficient between ceramic (contact) surface and pure pad brake disk is considered 0.75. In both types of FG brake disks the Coulomb contact friction is applied. Mechanical response of FG brake disks are compared and verified with the known results in the literatures. Three types of contact statuses are introduced as Sticking, Contact and Near Contact. The contact status between pad and disk for different values for pad thickness, grading index,n , and percentage of friction coefficient (λ) is shown. It can be seen that for all values of percentage of friction coefficient,λ , and grading indices, n, by increasing the thickness of pad cause the contact status changes from sticking to contact and then to near contact. (author)

CSI 2264: Probing the inner disks of AA Tauri-like systems in NGC 2264

Science.gov (United States)

McGinnis, P. T.; Alencar, S. H. P.; Guimarães, M. M.; Sousa, A. P.; Stauffer, J.; Bouvier, J.; Rebull, L.; Fonseca, N. N. J.; Venuti, L.; Hillenbrand, L.; Cody, A. M.; Teixeira, P. S.; Aigrain, S.; Favata, F.; Fűrész, G.; Vrba, F. J.; Flaccomio, E.; Turner, N. J.; Gameiro, J. F.; Dougados, C.; Herbst, W.; Morales-Calderón, M.; Micela, G.

2015-05-01

Context. The classical T Tauri star (CTTS) AA Tau has presented photometric variability that was attributed to an inner disk warp, caused by the interaction between the inner disk and an inclined magnetosphere. Previous studies of the young cluster NGC 2264 have shown that similar photometric behavior is common among CTTS. Aims: The goal of this work is to investigate the main causes of the observed photometric variability of CTTS in NGC 2264 that present AA Tau-like light curves, and verify if an inner disk warp could be responsible for their observed variability. Methods: In order to understand the mechanism causing these stars' photometric behavior, we investigate veiling variability in their spectra and u - r color variations and estimate parameters of the inner disk warp using an occultation model proposed for AA Tau. We also compare infrared Spitzer IRAC and optical CoRoT light curves to analyze the dust responsible for the occultations. Results: AA Tau-like variability proved to be transient on a timescale of a few years. We ascribe this variability to stable accretion regimes and aperiodic variability to unstable accretion regimes and show that a transition, and even coexistence, between the two is common. We find evidence of hot spots associated with occultations, indicating that the occulting structures could be located at the base of accretion columns. We find average values of warp maximum height of 0.23 times its radial location, consistent with AA Tau, with variations of on average 11% between rotation cycles. We also show that extinction laws in the inner disk indicate the presence of grains larger than interstellar grains. Conclusions: The inner disk warp scenario is consistent with observations for all but one star with AA Tau-like variability in our sample. AA Tau-like systems are fairly common, comprising 14% of CTTS observed in NGC 2264, though this number increases to 35% among systems of mass 0.7 M⊙ ≲ M ≲ 2.0 M⊙. Assuming random

A deep Spitzer survey of circumstellar disks in the young double cluster, h and χ Persei

Energy Technology Data Exchange (ETDEWEB)

Cloutier, Ryan; Currie, Thayne; Jayawardhana, Ray [University of Toronto, 50 St. George Street, Toronto, ON, M5S 2J7 (Canada); Rieke, George H. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065 (United States); Kenyon, Scott J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02140 (United States); Balog, Zoltan, E-mail: cloutier@cita.utoronto.ca, E-mail: currie@astro.utoronto.ca, E-mail: grieke@as.arizona.edu, E-mail: skenyon@cfa.harvard.edu [Max Planck Institute for Astrophysics, Königstuhl 17, D-69117 Heidelberg (Germany)

2014-12-01

We analyze very deep Infrared Array Camera and Multiband Imaging Photometer for Spitzer (MIPS) photometry of ∼12, 500 members of the 14 Myr old Double Cluster, h and χ Persei, building upon our earlier, shallower Spitzer Cycle 1 studies. Numerous likely members show infrared (IR) excesses at 8 μm and 24 μm, indicative of circumstellar dust. The frequency of stars with 8 μm excess is at least 2% for our entire sample, slightly lower (higher) for B/A stars (later type, lower mass stars). Optical spectroscopy also identifies gas in about 2% of systems, but with no clear trend between the presence of dust and gas. Spectral energy distribution modeling of 18 sources with detections at optical wavelengths through MIPS 24 μm reveals a diverse set of disk evolutionary states, including a high fraction of transitional disks, though similar data for all disk-bearing members would provide constraints. Using Monte Carlo simulations, we combine our results with those for other young clusters to study the global evolution of dust/gas disks. For nominal cluster ages, the e-folding times (τ{sub 0}) for the frequency of warm dust and gas are 2.75 Myr and 1.75 Myr, respectively. Assuming a revised set of ages for some clusters, these timescales increase to 5.75 and 3.75 Myr, respectively, implying a significantly longer typical protoplanetary disk lifetime than previously thought. In both cases, the transitional disk duration, averaged over multiple evolutionary pathways, is ≈1 Myr. Finally, 24 μm excess frequencies for 4-6 M {sub ☉} stars appear lower than for 1-2.5 M {sub ☉} stars in other 10-30 Myr old clusters.

Hydrodynamic simulations of accretion disks in cataclysmic variables

International Nuclear Information System (INIS)

Hirose, Masahito; Osaki, Yoji

1990-01-01

The tidal effects of secondary stars on accretion disks in cataclysmic variables are studied by two-dimensional hydrodynamical simulations. The time evolution of an accretion disk under a constant mass supply rate from the secondary is followed until it reaches a quasi-steady state. We have examined various cases of different mass ratios of binary systems. It is found that the accretion disk settles into a steady state of an elongated disk fixed in the rotating frame of the binary in a binary system with comparable masses of component stars. On the other hand, in the case of a low-mass secondary, the accretion disk develops a non-axisymmetric (eccentric) structure and finally settles into a periodically oscillating state in which a non-axisymmetric eccentric disk rotates in the opposite direction to the orbital motion of the binary in the rotating frame of the binary. The period of oscillation is a few percent longer than the orbital period of the binary, and it offers a natural explanation for the ''superhump'' periodicity of SU UMa stars. Our results thus confirm basically those of Whitehurst (1988, AAA 45.064.032) who discovered the tidal instability of an accretion disk in the case of a low-mass secondary. We then discuss the cause of the tidal instability. It is shown that the tidal instability of accretion disks is caused by a parametric resonance between particle orbits and an orbiting secondary star with a 1:3 period ratio. (author)

CONSTRAINTS ON COMPTON-THICK WINDS FROM BLACK HOLE ACCRETION DISKS: CAN WE SEE THE INNER DISK?

International Nuclear Information System (INIS)

Reynolds, Christopher S.

2012-01-01

Strong evidence is emerging that winds can be driven from the central regions of accretion disks in both active galactic nuclei and Galactic black hole binaries. Direct evidence for highly ionized, Compton-thin inner-disk winds comes from observations of blueshifted (v ∼ 0.05-0.1c) iron-K X-ray absorption lines. However, it has been suggested that the inner regions of black hole accretion disks can also drive Compton-thick winds—such winds would enshroud the inner disk, preventing us from seeing direct signatures of the accretion disk (i.e., the photospheric thermal emission, or the Doppler/gravitationally broadened iron Kα line). Here, we show that, provided the source is sub-Eddington, the well-established wind-driving mechanisms fail to launch a Compton-thick wind from the inner disk. For the accelerated region of the wind to be Compton-thick, the momentum carried in the wind must exceed the available photon momentum by a factor of at least 2/λ, where λ is the Eddington ratio of the source, ruling out radiative acceleration unless the source is very close to the Eddington limit. Compton-thick winds also carry large mass fluxes, and a consideration of the connections between the wind and the disk shows this to be incompatible with magneto-centrifugal driving. Finally, thermal driving of the wind is ruled out on the basis of the large Compton radii that typify black hole systems. In the absence of some new acceleration mechanisms, we conclude that the inner regions of sub-Eddington accretion disks around black holes are indeed naked.

FOMALHAUT'S DEBRIS DISK AND PLANET: CONSTRAINING THE MASS OF FOMALHAUT B FROM DISK MORPHOLOGY

International Nuclear Information System (INIS)

Chiang, E.; Kalas, P.; Graham, J. R.; Kite, E.; Clampin, M.

2009-01-01

Following the optical imaging of exoplanet candidate Fomalhaut b (Fom b), we present a numerical model of how Fomalhaut's debris disk is gravitationally shaped by a single interior planet. The model is simple, adaptable to other debris disks, and can be extended to accommodate multiple planets. If Fom b is the dominant perturber of the belt, then to produce the observed disk morphology it must have a mass M pl J , an orbital semimajor axis a pl > 101.5 AU, and an orbital eccentricity e pl = 0.11-0.13. These conclusions are independent of Fom b's photometry. To not disrupt the disk, a greater mass for Fom b demands a smaller orbit farther removed from the disk; thus, future astrometric measurement of Fom b's orbit, combined with our model of planet-disk interaction, can be used to determine the mass more precisely. The inner edge of the debris disk at a ∼ 133 AU lies at the periphery of Fom b's chaotic zone, and the mean disk eccentricity of e ∼ 0.11 is secularly forced by the planet, supporting predictions made prior to the discovery of Fom b. However, previous mass constraints based on disk morphology rely on several oversimplifications. We explain why our constraint is more reliable. It is based on a global model of the disk that is not restricted to the planet's chaotic zone boundary. Moreover, we screen disk parent bodies for dynamical stability over the system age of ∼ 100 Myr, and model them separately from their dust grain progeny; the latter's orbits are strongly affected by radiation pressure and their lifetimes are limited to ∼ 0.1 Myr by destructive grain-grain collisions. The single planet model predicts that planet and disk orbits be apsidally aligned. Fomalhaut b's nominal space velocity does not bear this out, but the astrometric uncertainties may be large. If the apsidal misalignment proves real, our calculated upper mass limit of 3M J still holds. If the orbits are aligned, our model predicts M pl = 0.5M J , a pl = 115 AU, and e pl = 0

Predesign of an experimental (5 to 10 MWt) disk MHD facility and prospects of commercial (1,000 MWt) MHD/steam systems

Energy Technology Data Exchange (ETDEWEB)

NONE

1990-07-01

Experimental disk MHD facilities are predesigned, and commercial-scale (1,000 MWt) MHD/steam systems are investigated. The predesigns of the disk MHD facilities indicate that enthalpy extraction is 8.7% for a 10 MWt open cycle MHD generator, and increases to 37% for a 5 MWt closed cycle MHD generator. Commercial (1,000 MWt) MHD/steam systems are studied for 4 types. Of these types, the open cycle disk MHD generator shows the lowest efficiency of 42.8%, while the closed cycle disk MHD generator the highest efficiency of 50.0%. The open cycle linear generator, although showing an efficiency of 49.4%, may be the lowest-cost type, when the necessary heat source, heat exchangers and the like are taken into consideration. For the design of superconducting magnet, it is necessary to further investigate whether the one for the test facility is applicable to the commercial systems. (NEDO)

NUMERICAL SIMULATIONS OF NATURALLY TILTED, RETROGRADELY PRECESSING, NODAL SUPERHUMPING ACCRETION DISKS

International Nuclear Information System (INIS)

Montgomery, M. M.

2012-01-01

Accretion disks around black hole, neutron star, and white dwarf systems are thought to sometimes tilt, retrogradely precess, and produce hump-shaped modulations in light curves that have a period shorter than the orbital period. Although artificially rotating numerically simulated accretion disks out of the orbital plane and around the line of nodes generate these short-period superhumps and retrograde precession of the disk, no numerical code to date has been shown to produce a disk tilt naturally. In this work, we report the first naturally tilted disk in non-magnetic cataclysmic variables using three-dimensional smoothed particle hydrodynamics. Our simulations show that after many hundreds of orbital periods, the disk has tilted on its own and this disk tilt is without the aid of radiation sources or magnetic fields. As the system orbits, the accretion stream strikes the bright spot (which is on the rim of the tilted disk) and flows over and under the disk on different flow paths. These different flow paths suggest the lift force as a source to disk tilt. Our results confirm the disk shape, disk structure, and negative superhump period and support the source to disk tilt, source to retrograde precession, and location associated with X-ray and He II emission from the disk as suggested in previous works. Our results identify the fundamental negative superhump frequency as the indicator of disk tilt around the line of nodes.

Study of data I/O performance on distributed disk system in mask data preparation

Science.gov (United States)

Ohara, Shuichiro; Odaira, Hiroyuki; Chikanaga, Tomoyuki; Hamaji, Masakazu; Yoshioka, Yasuharu

2010-09-01

Data volume is getting larger every day in Mask Data Preparation (MDP). In the meantime, faster data handling is always required. MDP flow typically introduces Distributed Processing (DP) system to realize the demand because using hundreds of CPU is a reasonable solution. However, even if the number of CPU were increased, the throughput might be saturated because hard disk I/O and network speeds could be bottlenecks. So, MDP needs to invest a lot of money to not only hundreds of CPU but also storage and a network device which make the throughput faster. NCS would like to introduce new distributed processing system which is called "NDE". NDE could be a distributed disk system which makes the throughput faster without investing a lot of money because it is designed to use multiple conventional hard drives appropriately over network. NCS studies I/O performance with OASIS® data format on NDE which contributes to realize the high throughput in this paper.

Spiral Arms, Infall, and Misalignment of the Circumbinary Disk from the Circumstellar Disks in the Protostellar Binary System L1551 NE

Energy Technology Data Exchange (ETDEWEB)

Takakuwa, Shigehisa [Department of Physics and Astronomy, Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima, Kagoshima 890-0065 (Japan); Saigo, Kazuya [ALMA Project Office, National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588 (Japan); Matsumoto, Tomoaki [Faculty of Humanity and Environment, Hosei University, Chiyoda-ku, Tokyo 102-8160 (Japan); Saito, Masao [Nobeyama Radio Observatory, National Astronomical Observatory of Japan, Minamimaki, Minamisaku, Nagano 384-1805 (Japan); Lim, Jeremy [Department of Physics, University of Hong Kong, Pokfulam Road (Hong Kong); Hanawa, Tomoyuki [Center for Frontier Science, Chiba University, Inage-ku, Chiba 263-8522 (Japan); Yen, Hsi-Wei; Ho, Paul T. P., E-mail: takakuwa@sci.kagoshima-u.ac.jp [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China)

2017-03-01

We report the ALMA Cycle 2 observations of the Class I binary protostellar system L1551 NE in the 0.9 mm continuum, C{sup 18}O (3–2), {sup 13}CO (3–2), SO (7{sub 8}–6{sub 7}), and CS (7–6) emission. At 0.″18 (=25 au) resolution, ∼4 times higher than that of our Cycle 0 observations, the circumbinary disk (CBD) as seen in the 0.9 mm emission is shown to be composed of a northern and a southern spiral arm, with the southern arm connecting to the circumstellar disk (CSD) around Source B. The western parts of the spiral arms are brighter than the eastern parts, suggesting the presence of an m = 1 spiral mode. In the C{sup 18}O emission, the infall gas motions in the interarm regions and the outward gas motions in the arms are identified. These observed features are well reproduced with our numerical simulations, where gravitational torques from the binary system impart angular momenta to the spiral-arm regions and extract angular momenta from the interarm regions. Chemical differentiation of the CBD is seen in the four molecular species. Our Cycle 2 observations have also resolved the CSDs around the individual protostars, and the beam-deconvolved sizes are 0.″29 × 0.″19 (=40 × 26 au) (P.A. = 144°) and 0.″26 × 0.″20 (=36 × 27 au) (P.A. = 147°) for Sources A and B, respectively. The position and inclination angles of these CSDs are misaligned with those of the CBD. The C{sup 18}O emission traces the Keplerian rotation of the misaligned disk around Source A.

ALMA OBSERVATIONS OF THE DEBRIS DISK AROUND THE YOUNG SOLAR ANALOG HD 107146

Energy Technology Data Exchange (ETDEWEB)

Ricci, L.; Carpenter, J. M.; Fu, B. [Department of Astronomy, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States); Hughes, A. M. [Department of Astronomy, Wesleyan University, Van Vleck Observatory, 96 Foss Hill Drive, Midletown, CT 06457 (United States); Corder, S. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Isella, A., E-mail: lricci@astro.caltech.edu [Department of Physics and Astronomy, Rice University, 6100 South Main, Houston, TX 77521-1892 (United States)

2015-01-10

We present the Atacama Large Millimeter/submillimeter Array (ALMA) continuum observations at a wavelength of 1.25 mm of the debris disk surrounding the ∼100 Myr old solar analog HD 107146. The continuum emission extends from about 30 to 150 AU from the central star with a decrease in the surface brightness at intermediate radii. We analyze the ALMA interferometric visibilities using debris disk models with radial profiles for the dust surface density parameterized as (1) a single power law, (2) a single power law with a gap, and (3) a double power law. We find that models with a gap of radial width ∼8 AU at a distance of ∼80 AU from the central star, as well as double power-law models with a dip in the dust surface density at ∼70 AU provide significantly better fits to the ALMA data than single power-law models. We discuss possible scenarios for the origin of the HD 107146 debris disk using models of planetesimal belts in which the formation of Pluto-sized objects trigger disruptive collisions of large bodies, as well as models that consider the interaction of a planetary system with a planetesimal belt and spatial variation of the dust opacity across the disk. If future observations with higher angular resolution and sensitivity confirm the fully depleted gap structure discussed here, a planet with a mass of approximately a few Earth masses in a nearly circular orbit at ∼80 AU from the central star would be a possible explanation for the presence of the gap.

ALMA OBSERVATIONS OF THE DEBRIS DISK AROUND THE YOUNG SOLAR ANALOG HD 107146

International Nuclear Information System (INIS)

Ricci, L.; Carpenter, J. M.; Fu, B.; Hughes, A. M.; Corder, S.; Isella, A.

2015-01-01

We present the Atacama Large Millimeter/submillimeter Array (ALMA) continuum observations at a wavelength of 1.25 mm of the debris disk surrounding the ∼100 Myr old solar analog HD 107146. The continuum emission extends from about 30 to 150 AU from the central star with a decrease in the surface brightness at intermediate radii. We analyze the ALMA interferometric visibilities using debris disk models with radial profiles for the dust surface density parameterized as (1) a single power law, (2) a single power law with a gap, and (3) a double power law. We find that models with a gap of radial width ∼8 AU at a distance of ∼80 AU from the central star, as well as double power-law models with a dip in the dust surface density at ∼70 AU provide significantly better fits to the ALMA data than single power-law models. We discuss possible scenarios for the origin of the HD 107146 debris disk using models of planetesimal belts in which the formation of Pluto-sized objects trigger disruptive collisions of large bodies, as well as models that consider the interaction of a planetary system with a planetesimal belt and spatial variation of the dust opacity across the disk. If future observations with higher angular resolution and sensitivity confirm the fully depleted gap structure discussed here, a planet with a mass of approximately a few Earth masses in a nearly circular orbit at ∼80 AU from the central star would be a possible explanation for the presence of the gap

KINEMATICS OF THE CO GAS IN THE INNER REGIONS OF THE TW Hya DISK

Energy Technology Data Exchange (ETDEWEB)

Rosenfeld, Katherine A.; Qi Chunhua; Andrews, Sean M.; Wilner, David J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Corder, Stuartt A. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Dullemond, C. P. [Institut fuer Theoretische Astrophysik, Universitaet Heidelberg, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Lin Shinyi [Department of Physics, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093 (United States); Hughes, A. M. [Department of Astronomy, University of California at Berkeley, 601 Campbell Hall, Berkeley, CA 94720 (United States); D' Alessio, Paola [Centro de Radioastronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, Apartado Postal 72-3 (Xangari), 58089 Morelia, Michoacan (Mexico); Ho, P. T. P. [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 106, Taiwan (China)

2012-10-01

We present a detailed analysis of the spatially and spectrally resolved {sup 12}CO J = 2-1 and J = 3-2 emission lines from the TW Hya circumstellar disk, based on science verification data from the Atacama Large Millimeter/submillimeter Array (ALMA). These lines exhibit substantial emission in their high-velocity wings (with projected velocities out to 2.1 km s{sup -1}, corresponding to intrinsic orbital velocities >20 km s{sup -1}) that trace molecular gas as close as 2 AU from the central star. However, we are not able to reproduce the intensity of these wings and the general spatio-kinematic pattern of the lines with simple models for the disk structure and kinematics. Using three-dimensional non-local thermodynamic equilibrium molecular excitation and radiative transfer calculations, we construct some alternative models that successfully account for these features by modifying either (1) the temperature structure of the inner disk (inside the dust-depleted disk cavity; r < 4 AU), (2) the intrinsic (Keplerian) disk velocity field, or (3) the distribution of disk inclination angles (a warp). The latter approach is particularly compelling because a representative warped disk model qualitatively reproduces the observed azimuthal modulation of optical light scattered off the disk surface. In any model scenario, the ALMA data clearly require a substantial molecular gas reservoir located inside the region where dust optical depths are known to be substantially diminished in the TW Hya disk, in agreement with previous studies based on infrared spectroscopy. The results from these updated model prescriptions are discussed in terms of their potential physical origins, which might include dynamical perturbations from a low-mass companion with an orbital separation of a few AU.

High-resolution observations of IRAS 08544-4431. Detection of a disk orbiting a post-AGB star and of a slow disk wind

Science.gov (United States)

Bujarrabal, V.; Castro-Carrizo, A.; Winckel, H. Van; Alcolea, J.; Contreras, C. Sánchez; Santander-García, M.; Hillen, M.

2018-06-01

Context. Aims: In order to study the effects of rotating disks in the post-asymptotic giant branch (post-AGB) evolution, we observe a class of binary post-AGB stars that seem to be systematically surrounded by equatorial disks and slow outflows. Although the rotating dynamics had only been well identified in three cases, the study of such structures is thought to be fundamental to the understanding of the formation of disks in various phases of the late evolution of binary stars and the ejection of planetary nebulae from evolved stars. Methods: We present ALMA maps of 12CO and 13CO J = 3-2 lines in the source IRAS 08544-4431, which belongs to the above mentioned class of objects. We analyzed the data by means of nebula models, which account for the expectedly composite source and can reproduce the data. From our modeling, we estimated the main nebula parameters, including the structure and dynamics and the density and temperature distributions. We discuss the uncertainties of the derived values and, in particular, their dependence on the distance. Results: Our observations reveal the presence of an equatorial disk in rotation; a low-velocity outflow is also found, probably formed of gas expelled from the disk. The main characteristics of our observations and modeling of IRAS 08544-4431 are similar to those of better studied objects, confirming our interpretation. The disk rotation indicates a total central mass of about 1.8 M⊙, for a distance of 1100 pc. The disk is found to be relatively extended and has a typical diameter of 4 × 1016 cm. The total nebular mass is 2 × 10-2 M⊙, of which 90% corresponds to the disk. Assuming that the outflow is due to mass loss from the disk, we derive a disk lifetime of 10 000 yr. The disk angular momentum is found to be comparable to that of the binary system at present. Assuming that the disk angular momentum was transferred from the binary system, as expected, the high values of the disk angular momentum in this and other

Free Vibration Analysis of a Spinning Flexible DISK-SPINDLE System Supported by Ball Bearing and Flexible Shaft Using the Finite Element Method and Substructure Synthesis

Science.gov (United States)

JANG, G. H.; LEE, S. H.; JUNG, M. S.

2002-03-01

Free vibration of a spinning flexible disk-spindle system supported by ball bearing and flexible shaft is analyzed by using Hamilton's principle, FEM and substructure synthesis. The spinning disk is described by using the Kirchhoff plate theory and von Karman non-linear strain. The rotating spindle and stationary shaft are modelled by Rayleigh beam and Euler beam respectively. Using Hamilton's principle and including the rigid body translation and tilting motion, partial differential equations of motion of the spinning flexible disk and spindle are derived consistently to satisfy the geometric compatibility in the internal boundary between substructures. FEM is used to discretize the derived governing equations, and substructure synthesis is introduced to assemble each component of the disk-spindle-bearing-shaft system. The developed method is applied to the spindle system of a computer hard disk drive with three disks, and modal testing is performed to verify the simulation results. The simulation result agrees very well with the experimental one. This research investigates critical design parameters in an HDD spindle system, i.e., the non-linearity of a spinning disk and the flexibility and boundary condition of a stationary shaft, to predict the free vibration characteristics accurately. The proposed method may be effectively applied to predict the vibration characteristics of a spinning flexible disk-spindle system supported by ball bearing and flexible shaft in the various forms of computer storage device, i.e., FDD, CD, HDD and DVD.

High-resolution submillimeter and near-infrared studies of the transition disk around Sz 91

Energy Technology Data Exchange (ETDEWEB)

Tsukagoshi, Takashi; Momose, Munetake [College of Science, Ibaraki University, Bunkyo 2-1-1, Mito 310-8512 (Japan); Hashimoto, Jun [Department of Physics and Astronomy, The University of Oklahoma, 440 West Brooks Street, Norman, OK 73019 (United States); Kudo, Tomoyuki; Saito, Masao; Ohashi, Nagayoshi; Kawabe, Ryohei; Akiyama, Eiji [National Astronomical Observatory Japan (NAOJ), Osawa 2-21-1, Mitaka, Tokyo 181-8588 (Japan); Andrews, Sean; Wilner, David [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Kitamura, Yoshimi [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Yoshinodai 3-1-1, Sagamihara, Kanagawa 229-8510 (Japan); Abe, Lyu [Lboratoire Lagrange (UMR 7293), Université de Nice-Sophia Antipolis, CNRS, Observatoire de la Côte d' Azur, 28 avenue Valrose, F-06108 Nice Cedex 2 (France); Brandner, Wolfgang [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Brandt, Timothy D. [Department of Astrophysical Sciences, Princeton University, Peyton Hall, Ivy Lane, Princeton, NJ 08544 (United States); Carson, Joseph [Department of Physics and Astronomy, College of Charleston, 58 Coming Street, Charleston, SC 29424 (United States); Currie, Thayne [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street M5S 3H4, Toronto, Ontario (Canada); Egner, Sebastian E.; Guyon, Olivier [Subaru Telescope, 650 North A' ohoku Place, Hilo, HI 96720 (United States); Goto, Miwa [Universitäts-Sternwarte München, Ludwig-Maximilians-Universität, Scheinerstr. 1, D-81679 München (Germany); Grady, Carol, E-mail: ttsuka@mx.ibaraki.ac.jp [Exoplanets and Stellar Astrophysics Laboratory, Code 667, Goddard Space Flight Center, Greenbelt, MD 20771 (United States); and others

2014-03-10

To reveal the structures of a transition disk around a young stellar object in Lupus, Sz 91 , we have performed aperture synthesis 345 GHz continuum and CO(3-2) observations with the Submillimeter Array (∼1''-3'' resolution) and high-resolution imaging of polarized intensity at the K{sub s} -band using the HiCIAO instrument on the Subaru Telescope (0.''25 resolution). Our observations successfully resolved the inner and outer radii of the dust disk to be 65 and 170 AU, respectively, which indicates that Sz 91 is a transition disk source with one of the largest known inner holes. The model fitting analysis of the spectral energy distribution reveals an H{sub 2} mass of 2.4 × 10{sup –3} M {sub ☉} in the cold (T < 30 K) outer part at 65 AU 3 × 10{sup –9} M {sub ☉}) of hot (T ∼ 180 K) dust possibly remains inside the inner hole of the disk. The structure of the hot component could be interpreted as either an unresolved self-luminous companion body (not directly detected in our observations) or a narrow ring inside the inner hole. Significant CO(3-2) emission with a velocity gradient along the major axis of the dust disk is concentrated on the Sz 91 position, suggesting a rotating gas disk with a radius of 420 AU. The Sz 91 disk is possibly a rare disk in an evolutionary stage immediately after the formation of protoplanets because of the large inner hole and the lower disk mass than other transition disks studied thus far.

Transport coefficients for dense hard-disk systems.

Science.gov (United States)

García-Rojo, Ramón; Luding, Stefan; Brey, J Javier

2006-12-01

A study of the transport coefficients of a system of elastic hard disks based on the use of Helfand-Einstein expressions is reported. The self-diffusion, the viscosity, and the heat conductivity are examined with averaging techniques especially appropriate for event-driven molecular dynamics algorithms with periodic boundary conditions. The density and size dependence of the results are analyzed, and comparison with the predictions from Enskog's theory is carried out. In particular, the behavior of the transport coefficients in the vicinity of the fluid-solid transition is investigated and a striking power law divergence of the viscosity with density is obtained in this region, while all other examined transport coefficients show a drop in that density range in relation to the Enskog's prediction. Finally, the deviations are related to shear band instabilities and the concept of dilatancy.

THE ROLE OF MULTIPLICITY IN DISK EVOLUTION AND PLANET FORMATION

Energy Technology Data Exchange (ETDEWEB)

Kraus, Adam L. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Dr., Honolulu, HI 96822 (United States); Ireland, Michael J. [Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, NSW 2006 (Australia); Hillenbrand, Lynne A. [California Institute of Technology, Department of Astrophysics, MC 249-17, Pasadena, CA 91125 (United States); Martinache, Frantz [National Astronomical Observatory of Japan, Subaru Telescope, Hilo, HI 96720 (United States)

2012-01-20

The past decade has seen a revolution in our understanding of protoplanetary disk evolution and planet formation in single-star systems. However, the majority of solar-type stars form in binary systems, so the impact of binary companions on protoplanetary disks is an important element in our understanding of planet formation. We have compiled a combined multiplicity/disk census of Taurus-Auriga, plus a restricted sample of close binaries in other regions, in order to explore the role of multiplicity in disk evolution. Our results imply that the tidal influence of a close ({approx}<40 AU) binary companion significantly hastens the process of protoplanetary disk dispersal, as {approx}2/3 of all close binaries promptly disperse their disks within {approx}<1 Myr after formation. However, prompt disk dispersal only occurs for a small fraction of wide binaries and single stars, with {approx}80%-90% retaining their disks for at least {approx}2-3 Myr (but rarely for more than {approx}5 Myr). Our new constraints on the disk clearing timescale have significant implications for giant planet formation; most single stars have 3-5 Myr within which to form giant planets, whereas most close binary systems would have to form giant planets within {approx}<1 Myr. If core accretion is the primary mode for giant planet formation, then gas giants in close binaries should be rare. Conversely, since almost all single stars have a similar period of time within which to form gas giants, their relative rarity in radial velocity (RV) surveys indicates either that the giant planet formation timescale is very well matched to the disk dispersal timescale or that features beyond the disk lifetime set the likelihood of giant planet formation.

CARBON ISOTOPE FRACTIONATION IN PROTOPLANETARY DISKS

International Nuclear Information System (INIS)

Woods, Paul M.; Willacy, Karen

2009-01-01

We investigate the gas-phase and grain-surface chemistry in the inner 30 AU of a typical protoplanetary disk (PPD) using a new model which calculates the gas temperature by solving the gas heating and cooling balance and which has an improved treatment of the UV radiation field. We discuss inner-disk chemistry in general, obtaining excellent agreement with recent observations which have probed the material in the inner regions of PPDs. We also apply our model to study the isotopic fractionation of carbon. Results show that the fractionation ratio, 12 C/ 13 C, of the system varies with radius and height in the disk. Different behavior is seen in the fractionation of different species. We compare our results with 12 C/ 13 C ratios in the solar system comets, and find a stark contrast, indicative of reprocessing.

A 100 au Wide Bipolar Rotating Shell Emanating from the HH 212 Protostellar Disk: A Disk Wind?

Science.gov (United States)

Lee, Chin-Fei; Li, Zhi-Yun; Codella, Claudio; Ho, Paul T. P.; Podio, Linda; Hirano, Naomi; Shang, Hsien; Turner, Neal J.; Zhang, Qizhou

2018-03-01

HH 212 is a Class 0 protostellar system found to host a “hamburger”-shaped dusty disk with a rotating disk atmosphere and a collimated SiO jet at a distance of ∼400 pc. Recently, a compact rotating outflow has been detected in SO and SO2 toward the center along the jet axis at ∼52 au (0.″13) resolution. Here we resolve the compact outflow into a small-scale wide-opening rotating outflow shell and a collimated jet, with the observations in the same S-bearing molecules at ∼16 au (0.″04) resolution. The collimated jet is aligned with the SiO jet, tracing the shock interactions in the jet. The wide-opening outflow shell is seen extending out from the inner disk around the SiO jet and has a width of ∼100 au. It is not only expanding away from the center, but also rotating around the jet axis. The specific angular momentum of the outflow shell is ∼40 au km s‑1. Simple modeling of the observed kinematics suggests that the rotating outflow shell can trace either a disk wind or disk material pushed away by an unseen wind from the inner disk or protostar. We also resolve the disk atmosphere in the same S-bearing molecules, confirming the Keplerian rotation there.

Scalability of RAID Systems

OpenAIRE

Li, Yan

2010-01-01

RAID systems (Redundant Arrays of Inexpensive Disks) have dominated backend storage systems for more than two decades and have grown continuously in size and complexity. Currently they face unprecedented challenges from data intensive applications such as image processing, transaction processing and data warehousing. As the size of RAID systems increases, designers are faced with both performance and reliability challenges. These challenges include limited back-end network band...

Modeling collisions in circumstellar debris disks

Science.gov (United States)

Nesvold, Erika

2015-10-01

Observations of resolved debris disks show a spectacular variety of features and asymmetries, including inner cavities and gaps, inclined secondary disks or warps, and eccentric, sharp-edged rings. Embedded exoplanets could create many of these features via gravitational perturbations, which sculpt the disk directly and by generating planetesimal collisions. In this thesis, I present the Superparticle Model/Algorithm for Collisions in Kuiper belts and debris disks (SMACK), a new method for simultaneously modeling, in 3-D, the collisional and dynamical evolution of planetesimals in a debris disk with planets. SMACK can simulate azimuthal asymmetries and how these asymmetries evolve over time. I show that SMACK is stable to numerical viscosity and numerical heating over 107 yr, and that it can reproduce analytic models of disk evolution. As an example of the algorithm's capabilities, I use SMACK to model the evolution of a debris ring containing a planet on an eccentric orbit and demonstrate that differential precession creates a spiral structure as the ring evolves, but collisions subsequently break up the spiral, leaving a narrower eccentric ring. To demonstrate SMACK's utility in studying debris disk physics, I apply SMACK to simulate a planet on a circular orbit near a ring of planetesimals that are experiencing destructive collisions. Previous simulations of a planet opening a gap in a collisionless debris disk have found that the width of the gap scales as the planet mass to the 2/7th power (alpha = 2/7). I find that gap sizes in a collisional disk still obey a power law scaling with planet mass, but that the index alpha of the power law depends on the age of the system t relative to the collisional timescale t coll of the disk by alpha = 0.32(t/ tcoll)-0.04, with inferred planet masses up to five times smaller than those predicted by the classical gap law. The increased gap sizes likely stem from the interaction between collisions and the mean motion

Renormalization group study of the melting of a two-dimensional system of collapsing hard disks

Science.gov (United States)

Ryzhov, V. N.; Tareyeva, E. E.; Fomin, Yu. D.; Tsiok, E. N.; Chumakov, E. S.

2017-06-01

We consider the melting of a two-dimensional system of collapsing hard disks (a system with a hard-disk potential to which a repulsive step is added) for different values of the repulsive-step width. We calculate the system phase diagram by the method of the density functional in crystallization theory using equations of the Berezinskii-Kosterlitz-Thouless-Halperin-Nelson-Young theory to determine the lines of stability with respect to the dissociation of dislocation pairs, which corresponds to the continuous transition from the solid to the hexatic phase. We show that the crystal phase can melt via a continuous transition at low densities (the transition to the hexatic phase) with a subsequent transition from the hexatic phase to the isotropic liquid and via a first-order transition. Using the solution of renormalization group equations with the presence of singular defects (dislocations) in the system taken into account, we consider the influence of the renormalization of the elastic moduli on the form of the phase diagram.

Accretion disks in active galactic nuclei

International Nuclear Information System (INIS)

Shields, G.A.

1989-01-01

Active galactic nuclei (AGN) have taunted astrophysicists for a quarter century. How do these objects produce huge luminosities---in some cases, far outshining our galaxy---from a region perhaps no larger than the solar system? Accretion onto supermassive black holes has been widely considered the best buy in theories of AGN. Much work has gone into accretion disk theory, searches for black holes in galactic nuclei, and observational tests. These efforts have not proved the disk model, but there is progress. Evidence for black holes in the nuclei of nearby galaxies is provided by observations of stellar velocities, and radiation from the disk's hot surface may be observed in the ultraviolet (UV) and neighboring spectral bands. In the review, the author describe some of the recent work on accretion disks in AGN, with an emphasis on points of contact between theory and observation

CT-guided percutaneous laser disk decompression for cervical and lumbar disk hernia

International Nuclear Information System (INIS)

Shimizu, Kanichiro; Koyama, Tutomu; Harada, Junta; Abe, Toshiaki

2008-01-01

Percutaneous laser disk decompression under X-ray fluoroscopy was first reported in 1987 for minimally invasive therapy of lumbar disk hernia. In patients with disk hernia, laser vaporizes a small portion of the intervertebral disk thereby reducing the volume and pressure of the affected disk. We present the efficacy and safety of this procedure, and analysis of fair or poor response cases. In our study, 226 cases of lumbar disk hernia and 7 cases of cervical disk hernia were treated under CT guided PLDD. Japan Orthopedic Association (JOA) score and Mac-Nab criteria were investigated to evaluate the response to treatment. Improvement ratio based on the JOA score was calculated as follows. Overall success rate was 91.6% in cases lumber disk hernia, and 100% in cases of cervical disk hernia. We experienced two cases with two cases with postoperative complication. Both cases were treated conservatively. The majority of acute cases and post operative cases were reported to be 'good' on Mac-Nab criteria. Cases of fair or poor response on Mac-Nab criteria were lateral type, foraminal stenosis or large disk hernia. CT-guided PLDD is a safe and accurate procedure. The overall success rate can be increased by carefully selecting patients. (author)

Disk Storage Server

CERN Multimedia

This model was a disk storage server used in the Data Centre up until 2012. Each tray contains a hard disk drive (see the 5TB hard disk drive on the main disk display section - this actually fits into one of the trays). There are 16 trays in all per server. There are hundreds of these servers mounted on racks in the Data Centre, as can be seen.

Development of portable phased array UT system for real-time flaw imaging

International Nuclear Information System (INIS)

Goto, M.

1995-01-01

Many functions and features of phased array UT technology must be useful for NDE in the industrial field. Some phased array UT systems have been developed for the inspection of nuclear pressure vessel and turbine components. However, phased array UT is still a special NDE technique and it has not been used widely in the past. The reasons of that are system size, cost, operator performance, equipment design and others. TOSHIBA has newly developed PC controlled portable phased array system to solve those problems. The portable phased array UT system is very compact and light but it is able to drive up to 32-channel linear array probe, to display real-time linear/sector B-scan, to display accumulated B-scan with an encoder and to display profile overlaid B-scan. The first applications were turbine component inspections for precise flaw investigation and flaw image data recording

Chemical Evolution of a Protoplanetary Disk

Science.gov (United States)

Semenov, Dmitry A.

2011-12-01

In this paper we review recent progress in our understanding of the chemical evolution of protoplanetary disks. Current observational constraints and theoretical modeling on the chemical composition of gas and dust in these systems are presented. Strong variations of temperature, density, high-energy radiation intensities in these disks, both radially and vertically, result in a peculiar disk chemical structure, where a variety of processes are active. In hot, dilute and heavily irradiated atmosphere only the most photostable simple radicals and atoms and atomic ions exist, formed by gas-phase processes. Beneath the atmosphere a partly UV-shielded, warm molecular layer is located, where high-energy radiation drives rich ion-molecule and radical-radical chemistry, both in the gas phase and on dust surfaces. In a cold, dense, dark disk midplane many molecules are frozen out, forming thick icy mantles where surface chemistry is active and where complex polyatomic (organic) species are synthesized. Dynamical processes affect disk chemical composition by enriching it in abundances of complex species produced via slow surface processes, which will become detectable with ALMA.

UNUSUALLY LUMINOUS GIANT MOLECULAR CLOUDS IN THE OUTER DISK OF M33

International Nuclear Information System (INIS)

Bigiel, F.; Blitz, L.; Plambeck, R. L.; Bolatto, A. D.; Leroy, A. K.; Walter, F.; Rosolowsky, E. W.; Lopez, L. A.

2010-01-01

We use high spatial resolution (∼7 pc) observations from the Combined Array for Research in Millimeter Wave Astronomy (CARMA) to derive detailed properties for eight giant molecular clouds (GMCs) at a galactocentric radius corresponding to approximately two CO scale lengths, or ∼0.5 optical radii (r 25 ), in the Local Group spiral galaxy M33. At this radius, molecular gas fraction, dust-to-gas ratio, and metallicity are much lower than in the inner part of M33 or in a typical spiral galaxy. This allows us to probe the impact of environment on GMC properties by comparing our measurements to previous data from the inner disk of M33, the Milky Way, and other nearby galaxies. The outer disk clouds roughly fall on the size-linewidth relation defined by extragalactic GMCs, but are slightly displaced from the luminosity-virial mass relation in the sense of having high CO luminosity compared to the inferred virial mass. This implies a different CO-to-H 2 conversion factor, which is on average a factor of 2 lower than the inner disk and the extragalactic average. We attribute this to significantly higher measured brightness temperatures of the outer disk clouds compared to the ancillary sample of GMCs, which is likely an effect of enhanced radiation levels due to massive star formation in the vicinity of our target field. Apart from brightness temperature, the properties we determine for the outer disk GMCs in M33 do not differ significantly from those of our comparison sample. In particular, the combined sample of inner and outer disk M33 clouds covers roughly the same range in size, line width, virial mass, and CO luminosity than the sample of Milky Way GMCs. When compared to the inner disk clouds in M33, however, we find even the brightest outer disk clouds to be smaller than most of their inner disk counterparts. This may be due to incomplete sampling or a potentially steeper cloud mass function at larger radii.

GMR biosensor arrays: a system perspective.

Science.gov (United States)

Hall, D A; Gaster, R S; Lin, T; Osterfeld, S J; Han, S; Murmann, B; Wang, S X

2010-05-15

Giant magnetoresistive biosensors are becoming more prevalent for sensitive, quantifiable biomolecular detection. However, in order for magnetic biosensing to become competitive with current optical protein microarray technology, there is a need to increase the number of sensors while maintaining the high sensitivity and fast readout time characteristic of smaller arrays (1-8 sensors). In this paper, we present a circuit architecture scalable for larger sensor arrays (64 individually addressable sensors) while maintaining a high readout rate (scanning the entire array in less than 4s). The system utilizes both time domain multiplexing and frequency domain multiplexing in order to achieve this scan rate. For the implementation, we propose a new circuit architecture that does not use a classical Wheatstone bridge to measure the small change in resistance of the sensor. Instead, an architecture designed around a transimpedance amplifier is employed. A detailed analysis of this architecture including the noise, distortion, and potential sources of errors is presented, followed by a global optimization strategy for the entire system comprising the magnetic tags, sensors, and interface electronics. To demonstrate the sensitivity, quantifiable detection of two blindly spiked samples of unknown concentrations has been performed at concentrations below the limit of detection for the enzyme-linked immunosorbent assay. Lastly, the multiplexing capability and reproducibility of the system was demonstrated by simultaneously monitoring sensors functionalized with three unique proteins at different concentrations in real-time. 2010 Elsevier B.V. All rights reserved.

A LARGE, MASSIVE, ROTATING DISK AROUND AN ISOLATED YOUNG STELLAR OBJECT

International Nuclear Information System (INIS)

Quanz, Sascha P.; Beuther, Henrik; Steinacker, Juergen; Linz, Hendrik; Krause, Oliver; Henning, Thomas; Birkmann, Stephan M.; Zhang Qizhou

2010-01-01

We present multi-wavelength observations and a radiative transfer model of a newly discovered massive circumstellar disk of gas and dust which is one of the largest disks known today. Seen almost edge-on, the disk is resolved in high-resolution near-infrared (NIR) images and appears as a dark lane of high opacity intersecting a bipolar reflection nebula. Based on molecular line observations, we estimate the distance to the object to be 3.5 kpc. This leads to a size for the dark lane of ∼10,500 AU but due to shadowing effects the true disk size could be smaller. In Spitzer/IRAC 3.6 μm images, the elongated shape of the bipolar reflection nebula is still preserved and the bulk of the flux seems to come from disk regions that can be detected due to the slight inclination of the disk. At longer IRAC wavelengths, the flux is mainly coming from the central regions penetrating directly through the dust lane. Interferometric observations of the dust continuum emission at millimeter wavelengths with the Submillimeter Array confirm this finding as the peak of the unresolved millimeter-emission coincides perfectly with the peak of the Spitzer/IRAC 5.8 μm flux and the center of the dark lane seen in the NIR images. Simultaneously acquired CO data reveal a molecular outflow along the northern part of the reflection nebula which seems to be the outflow cavity. An elongated gaseous disk component is also detected and shows signs of rotation. The emission is perpendicular to the molecular outflow and thus parallel to but even more extended than the dark lane in the NIR images. Based on the dust continuum and the CO observations, we estimate a disk mass of up to a few solar masses depending on the underlying assumptions. Whether the disk-like structure is an actual accretion disk or rather a larger-scale flattened envelope or pseudodisk is difficult to discriminate with the current data set. The existence of HCO + /H 13 CO + emission proves the presence of dense gas in the disk

Predictions for shepherding planets in scattered light images of debris disks

International Nuclear Information System (INIS)

Rodigas, Timothy J.; Hinz, Philip M.; Malhotra, Renu

2014-01-01

Planets can affect debris disk structure by creating gaps, sharp edges, warps, and other potentially observable signatures. However, there is currently no simple way for observers to deduce a disk-shepherding planet's properties from the observed features of the disk. Here we present a single equation that relates a shepherding planet's maximum mass to the debris ring's observed width in scattered light, along with a procedure to estimate the planet's eccentricity and minimum semimajor axis. We accomplish this by performing dynamical N-body simulations of model systems containing a star, a single planet, and an exterior disk of parent bodies and dust grains to determine the resulting debris disk properties over a wide range of input parameters. We find that the relationship between planet mass and debris disk width is linear, with increasing planet mass producing broader debris rings. We apply our methods to five imaged debris rings to constrain the putative planet masses and orbits in each system. Observers can use our empirically derived equation as a guide for future direct imaging searches for planets in debris disk systems. In the fortuitous case of an imaged planet orbiting interior to an imaged disk, the planet's maximum mass can be estimated independent of atmospheric models.

HOT HIGH-MASS ACCRETION DISK CANDIDATES

International Nuclear Information System (INIS)

Beuther, H.; Walsh, A. J.; Longmore, S. N.

2009-01-01

To better understand the physical properties of accretion disks in high-mass star formation, we present a study of a dozen high-mass accretion disk candidates observed at high spatial resolution with the Australia Telescope Compact Array (ATCA) in the high-excitation (4,4) and (5,5) lines of NH 3 . All of our originally selected sources were detected in both NH 3 transitions, directly associated with CH 3 OH Class II maser emission and implying that high-excitation NH 3 lines are good tracers of the dense gas components in hot-core-type targets. Only the one source that did not satisfy the initial selection criteria remained undetected. From the 11 mapped sources, six show clear signatures of rotation and/or infall motions. These signatures vary from velocity gradients perpendicular to the outflows, to infall signatures in absorption against ultracompact H II regions, to more spherical infall signatures in emission. Although our spatial resolution is ∼1000 AU, we do not find clear Keplerian signatures in any of the sources. Furthermore, we also do not find flattened structures. In contrast to this, in several of the sources with rotational signatures, the spatial structure is approximately spherical with sizes exceeding 10 4 AU, showing considerable clumpy sub-structure at even smaller scales. This implies that on average typical Keplerian accretion disks-if they exist as expected-should be confined to regions usually smaller than 1000 AU. It is likely that these disks are fed by the larger-scale rotating envelope structure we observe here. Furthermore, we do detect 1.25 cm continuum emission in most fields of view. While in some cases weak cm continuum emission is associated with our targets, more typically larger-scale H II regions are seen offset more than 10'' from our sources. While these H II regions are unlikely to be directly related to the target regions, this spatial association nevertheless additionally stresses that high-mass star formation rarely

Theory of Disk-to-Vesicle Transformation

Science.gov (United States)

Li, Jianfeng; Shi, An-Chang

2009-03-01

Self-assembled membranes from amphiphilic molecules, such as lipids and block copolymers, can assume a variety of morphologies dictated by energy minimization of system. The membrane energy is characterized by a bending modulus (κ), a Gaussian modulus (κG), and the line tension (γ) of the edge. Two basic morphologies of membranes are flat disks that minimize the bending energy at the cost of the edge energy, and enclosed vesicles that minimize the edge energy at the cost of bending energy. In our work, the transition from disk to vesicle is studied theoretically using the string method, which is designed to find the minimum energy path (MEP) or the most probable transition path between two local minima of an energy landscape. Previous studies of disk-to-vesicle transition usually approximate the transitional states by a series of spherical cups, and found that the spherical cups do not correspond to stable or meta-stable states of the system. Our calculation demonstrates that the intermediate shapes along the MEP are very different from spherical cups. Furthermore, some of these transitional states can be meta-stable. The disk-to-vesicle transition pathways are governed by two scaled parameters, κG/κ and γR0/4κ, where R0 is the radius of the disk. In particular, a meta-stable intermediate state is predicted, which may correspond to the open morphologies observed in experiments and simulations.

Development of Disk Rover, wall-climbing robot using permanent magnet disk

International Nuclear Information System (INIS)

Hirose, Shigeo; Tsutsumitake; Hiroshi; Toyama, Ryousei; Kobayashi, Kengo.

1992-01-01

A new type of wall climbing robot, named Disk Rover, using permanent magnet disks are developed. The newly introduced permanent magnet disk is to rotate the magnet disk on the surface of wall with partly contacted posture. It allows to produce high magnetic attraction force compared with conventional permanent wheel which utilizes only a small portion of the magnet installed around the wheel. The optimum design of the magnetic wheel is done by using finit element method and it is shown that the magnetic attraction force vs. weight ratio can be designed about three times higher than conventional type magnet wheel. The developed Disk Rover is 25 kg in weight including controller and battery, about 685 mm in diameter, 239 mm in height and has a pair of permanent magnet disks. It is demonstrated by the experiments that the Disk Rover can move around on the surface of the wall quite smoothly by radio control and has payload of about its own weight. Several considerations are also done in order to surmount bead weld. (author)

A DISTINCTIVE DISK-JET COUPLING IN THE SEYFERT-1 ACTIVE GALACTIC NUCLEUS NGC 4051

International Nuclear Information System (INIS)

King, A. L.; Miller, J. M.; Gueltekin, K.; Reynolds, M. T.; Cackett, E. M.; Fabian, A. C.; Markoff, S.; Nowak, M. A.; Rupen, M.

2011-01-01

We report on the results of a simultaneous monitoring campaign employing eight Chandra X-ray (0.5-10 keV) and six Very Large Array/Extended Very Large Array (8.4 GHz) radio observations of NGC 4051 over seven months. Evidence for compact jets is observed in the 8.4 GHz radio band; this builds on mounting evidence that jet production may be prevalent even in radio-quiet Seyferts. Assuming comparatively negligible local diffuse emission in the nucleus, the results also demonstrate an inverse correlation of L radio ∝ L -0.72±0.04 X-ray . If the A configuration is excluded in the case where diffuse emission plays a significant role, the relation is still L radio ∝ L X-ray -0.12±0.05 . Current research linking the mass of supermassive black holes and stellar-mass black holes in the 'low/hard' state to X-ray luminosities and radio luminosities suggests a 'fundamental plane of accretion onto black holes' that has a positive correlation of L radio ∝ L 0.67±0.12 X-ray . Our simultaneous results differ from this relation by more than 11σ (6σ excluding the A configuration), indicating that a separate mode of accretion and ejection may operate in this system. A review of the literature shows that the inverse correlation seen in NGC 4051 is seen in three other black hole systems, all of which accrete at near 10% of their Eddington luminosity, perhaps suggesting a distinct mode of disk-jet coupling at high Eddington fractions. We discuss our results in the context of disks and jets in black holes and accretion across the black hole mass scale.

THE VLA NASCENT DISK AND MULTIPLICITY SURVEY: FIRST LOOK AT RESOLVED CANDIDATE DISKS AROUND CLASS 0 AND I PROTOSTARS IN THE PERSEUS MOLECULAR CLOUD

Energy Technology Data Exchange (ETDEWEB)

Segura-Cox, Dominique M.; Harris, Robert J.; Looney, Leslie W. [Department of Astronomy, University of Illinois, Urbana, IL 61801 (United States); Tobin, John J. [Leiden Observatory, Leiden University, P.O. Box 9513, 2000-RA Leiden (Netherlands); Li, Zhi-Yun [Department of Astronomy, University of Virginia, Charlottesville, VA 22903 (United States); Chandler, Claire; Perez, Laura [National Radio Astronomy Observatory, Socorro, NM 87801 (United States); Kratter, Kaitlin [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Dunham, Michael M. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Sadavoy, Sarah [Max-Planck-Institut für Astronomie, D-69117 Heidelberg (Germany); Melis, Carl, E-mail: segurac2@illinois.edu [Center for Astrophysics and Space Sciences, University of California, San Diego, CA 92093 (United States)

2016-02-01

We present the first dust emission results toward a sample of seven protostellar disk candidates around Class 0 and I sources in the Perseus molecular cloud from the VLA Nascent Disk and Multiplicity (VANDAM) survey with ∼0.″05 or 12 AU resolution. To examine the surface brightness profiles of these sources, we fit the Ka-band 8 mm dust-continuum data in the u, v-plane to a simple, parametrized model based on the Shakura–Sunyaev disk model. The candidate disks are well-fit by a model with a disk-shaped profile and have masses consistent with known Class 0 and I disks. The inner-disk surface densities of the VANDAM candidate disks have shallower density profiles compared to disks around more evolved Class II systems. The best-fit model radii of the seven early-result candidate disks are R{sub c} > 10 AU; at 8 mm, the radii reflect lower limits on the disk size since dust continuum emission is tied to grain size and large grains radially drift inwards. These relatively large disks, if confirmed kinematically, are inconsistent with theoretical models where the disk size is limited by strong magnetic braking to <10 AU at early times.

Code-modulated interferometric imaging system using phased arrays

Science.gov (United States)

Chauhan, Vikas; Greene, Kevin; Floyd, Brian

2016-05-01

Millimeter-wave (mm-wave) imaging provides compelling capabilities for security screening, navigation, and bio- medical applications. Traditional scanned or focal-plane mm-wave imagers are bulky and costly. In contrast, phased-array hardware developed for mass-market wireless communications and automotive radar promise to be extremely low cost. In this work, we present techniques which can allow low-cost phased-array receivers to be reconfigured or re-purposed as interferometric imagers, removing the need for custom hardware and thereby reducing cost. Since traditional phased arrays power combine incoming signals prior to digitization, orthogonal code-modulation is applied to each incoming signal using phase shifters within each front-end and two-bit codes. These code-modulated signals can then be combined and processed coherently through a shared hardware path. Once digitized, visibility functions can be recovered through squaring and code-demultiplexing operations. Pro- vided that codes are selected such that the product of two orthogonal codes is a third unique and orthogonal code, it is possible to demultiplex complex visibility functions directly. As such, the proposed system modulates incoming signals but demodulates desired correlations. In this work, we present the operation of the system, a validation of its operation using behavioral models of a traditional phased array, and a benchmarking of the code-modulated interferometer against traditional interferometer and focal-plane arrays.

Variable H13CO+ Emission in the IM Lup Disk: X-Ray Driven Time-dependent Chemistry?

Science.gov (United States)

Cleeves, L. Ilsedore; Bergin, Edwin A.; Öberg, Karin I.; Andrews, Sean; Wilner, David; Loomis, Ryan

2017-07-01

We report the first detection of a substantial brightening event in an isotopologue of a key molecular ion, HCO+, within a protoplanetary disk of a T Tauri star. The H13CO+ J=3-2 rotational transition was observed three times toward IM Lup between 2014 July and 2015 May with the Atacama Large Millimeter/submillimeter Array. The first two observations show similar spectrally integrated line and continuum fluxes, while the third observation shows a doubling in the disk-integrated J=3-2 line flux compared to the continuum, which does not change between the three epochs. We explore models of an X-ray active star irradiating the disk via stellar flares, and find that the optically thin H13CO+ emission variation can potentially be explained via X-ray-driven chemistry temporarily enhancing the HCO+ abundance in the upper layers of the disk atmosphere during large or prolonged flaring events. If the HCO+ enhancement is indeed caused by an X-ray flare, future observations should be able to spatially resolve these events and potentially enable us to watch the chemical aftermath of the high-energy stellar radiation propagating across the face of protoplanetary disks, providing a new pathway to explore ionization physics and chemistry, including electron density, in disks.

The Advanced Gamma-ray Imaging System (AGIS): Topological Array Trigger

Science.gov (United States)

Smith, Andrew W.

2010-03-01

AGIS is a concept for the next-generation ground-based gamma-ray observatory. It will be an array of 36 imaging atmospheric Cherenkov telescopes (IACTs) sensitive in the energy range from 50 GeV to 200 TeV. The required improvements in sensitivity, angular resolution, and reliability of operation relative to the present generation instruments imposes demanding technological and cost requirements on the design of the telescopes and on the triggering and readout systems for AGIS. To maximize the capabilities of large arrays of IACTs with a low energy threshold, a wide field of view and a low background rate, a sophisticated array trigger is required. We outline the status of the development of a stereoscopic array trigger that calculates image parameters and correlates them across a subset of telescopes. Field Programmable Gate Arrays (FPGAs) implement the real-time pattern recognition to suppress cosmic rays and night-sky background events. A proof of principle system is being developed to run at camera trigger rates up to 10MHz and array-level rates up to 10kHz.

Identifying gaps in flaring Herbig Ae/Be disks using spatially resolved mid-infrared imaging. Are all group I disks transitional?

NARCIS (Netherlands)

Maaskant, K.M.; Honda, M.; Waters, L.; Tielens, A.G.G.M.; Dominik, C.; Min, M.; Verhoeff, A.; Meeus, G.; Ancker, van den M.

2013-01-01

Context. The evolution of young massive protoplanetary disks toward planetary systems is expected to correspond to structural changes in observational appearance, which includes the formation of gaps and the depletion of dust and gas. Aims: A special group of disks around Herbig Ae/Be stars do not

Identifying gaps in flaring Herbig Ae/Be disks using spatially resolved mid-infrared imaging. Are all group I disks transitional?

NARCIS (Netherlands)

Maaskant, K.M.; Honda, M.; Waters, L.B.F.M.; Tielens, A.G.G.M.; Dominik, C.; Min, M.; Verhoeff, A.; Meeus, G.; van den Ancker, M.

2013-01-01

Context. The evolution of young massive protoplanetary disks toward planetary systems is expected to correspond to structural changes in observational appearance, which includes the formation of gaps and the depletion of dust and gas. Aims. A special group of disks around Herbig Ae/Be stars do not

The CDF Run II disk inventory manager

International Nuclear Information System (INIS)

Hubbard, Paul; Lammel, Stephan

2001-01-01

The Collider Detector at Fermilab (CDF) experiment records and analyses proton-antiproton interactions at a center-of-mass energy of 2 TeV. Run II of the Fermilab Tevatron started in April of this year. The duration of the run is expected to be over two years. One of the main data handling strategies of CDF for Run II is to hide all tape access from the user and to facilitate sharing of data and thus disk space. A disk inventory manager was designed and developed over the past years to keep track of the data on disk, to coordinate user access to the data, and to stage data back from tape to disk as needed. The CDF Run II disk inventory manager consists of a server process, a user and administrator command line interfaces, and a library with the routines of the client API. Data are managed in filesets which are groups of one or more files. The system keeps track of user access to the filesets and attempts to keep frequently accessed data on disk. Data that are not on disk are automatically staged back from tape as needed. For CDF the main staging method is based on the mt-tools package as tapes are written according to the ANSI standard

Smearing of mass accretion rate variation by viscous processes in accretion disks in compact binary systems

Science.gov (United States)

Ghosh, A.; Chakrabarti, Sandip K.

2016-09-01

Variation of mass supply rate from the companion can be smeared out by viscous processes inside an accretion disk. Hence, by the time the flow reaches the inner edge, the variation in X-rays need not reflect the true variation of the mass supply rate at the outer edge. However, if the viscosity fluctuates around a mean value, one would expect the viscous time scale t_{{visc}} also to spread around a mean value. In high mass X-ray binaries, which are thought to be primarily wind-fed, the size of the viscous Keplerian disk is smaller and thus such a spread could be lower as compared to the low mass X-ray binaries which are primarily fed by Roche lobe overflow. If there is an increasing or decreasing trend in viscosity, the interval between enhanced emission would be modified systematically. In the absence of a detailed knowledge about the variation of mass supply rates at the outer edge, we study ideal circumstances where modulation must take place exactly in orbital time scales, such as when there is an ellipticity in the orbit. We study a few compact binaries using long term All Sky monitor (ASM) data (1.5-12 keV) of Rossi X-ray Timing Explorer (RXTE) and all sky survey data (15-50 keV) of Swift satellites by different methods to look for such smearing effects and to infer what these results can tell us about the viscous processes inside the respective disks. We employ three different methods to seek imprints of periodicity on the X-ray variation and found that in all the cases, the location of the peak in the power density spectra is consistent with the orbital frequencies. Interestingly, in high mass X-ray binaries the peaks are sharp with high rms values, consistent with a small Keplerian disk in a wind fed system. However, in low mass X-ray binaries with larger Keplerian disk component, the peaks are spreaded out with much lower rms values. X-ray reflections, or superhump phenomena which may also cause such X-ray modulations would not be affected by the size of

Further comments on the geometrical efficiency of a parallel-disk source and detector system

International Nuclear Information System (INIS)

Ruby, L.

1994-01-01

A derivation is presented for a previously published formula, which determines the geometrical efficiency of a parallel-disk source and detector system. The formula involves an integral over a product of two Bessel functions. An algebraic approximation to the integral is also discussed. (orig.)

How do giant planetary cores shape the dust disk? HL Tau system

OpenAIRE

Picogna, Giovanni; Kley, Wilhelm

2015-01-01

We are observing, thanks to ALMA, the dust distribution in the region of active planet formation around young stars. This is a powerful tool to connect observations with theoretical models and improve our understandings of the processes at play. We want to test how a multi-planetary system shapes its birth disk and study the influence of the planetary masses and particle sizes on the final dust distribution. Moreover, we apply our model to the HL Tau system in order to obtain some insights on...

Childhood to adolescence: dust and gas clearing in protoplanetary disks

Science.gov (United States)

Brown, Joanna Margaret

Disks are ubiquitous around young stars. Over time, disks dissipate, revealing planets that formed hidden by their natal dust. Since direct detection of young planets at small orbital radii is currently impossible, other tracers of planet formation must be found. One sign of disk evolution, potentially linked to planet formation, is the opening of a gap or inner hole in the disk. In this thesis, I have identified and characterized several cold disks with large inner gaps but retaining massive primordial outer disks. While cold disks are not common, with ~5% of disks showing signs of inner gaps, they provide proof that at least some disks evolve from the inside-out. These large gaps are equivalent to dust clearing from inside the Earth's orbit to Neptune's orbit or even the inner Kuiper belt. Unlike more evolved systems like our own, the central star is often still accreting and a large outer disk remains. I identified four cold disks in Spitzer 5-40 μm spectra and modeled these disks using a 2-D radiative transfer code to determine the gap properties. Outer gap radii of 20-45 AU were derived. However, spectrophotometric identification is indirect and model-dependent. To validate this interpretation, I observed three disks with a submillimeter interferometer and obtained the first direct images of the central holes. The images agree well with the gap sizes derived from the spectrophotometry. One system, LkH&alpha 330, has a very steep outer gap edge which seems more consistent with gravitational perturbation rather than gradual processes, such as grain growth and settling. Roughly 70% of cold disks show CO v=1&rarr 0 gas emission from the inner 1 AU and therefore are unlikely to have evolved due to photoevaporation. The derived rotation temperatures are significantly lower for the cold disks than disks without gaps. Unresolved (sub)millimeter photometry shows that cold disks have steeper colors, indicating that they are optically thin at these wavelengths, unlike

Disk cloning program 'Dolly+' for system management of PC Linux cluster

International Nuclear Information System (INIS)

Atsushi Manabe

2001-01-01

The Dolly+ is a Linux application program to clone files and disk partition image from a PC to many others. By using several techniques such as logical ring connection, multi threading and pipelining, it could achieve high performance and scalability. For example, in typical condition, installations to a hundred PCs takes almost equivalent time for two PCs. Together with the Intel PXE and the RedHat kickstart, automatic and very fast system installation and upgrading could be performed

RESONANCE TRAPPING IN PROTOPLANETARY DISKS. I. COPLANAR SYSTEMS

International Nuclear Information System (INIS)

Lee, Aaron T.; Thommes, Edward W.; Rasio, Frederic A.

2009-01-01

Mean-motion resonances (MMRs) are likely to play an important role both during and after the lifetime of a protostellar gas disk. We study the dynamical evolution and stability of planetary systems containing two giant planets on circular orbits near a 2:1 resonance and closer. We find that by having the outer planet migrate inward, the two planets can capture into either the 2:1, 5:3, or 3:2 MMR. We use direct numerical integrations of ∼1000 systems in which the planets are initially locked into one of these resonances and allowed to evolve for up to ∼10 7 yr. We find that the final eccentricity distribution in systems which ultimately become unstable gives a good fit to observed exoplanets. Next, we integrate ∼500 two-planet systems in which the outer planet is driven to continuously migrate inward, resonantly capturing the inner planet; the systems are evolved until either instability sets in or the planets reach the star. We find that although the 5:3 resonance rapidly becomes unstable under migration, the 2:1 and 3:2 are very stable. Thus the lack of observed exoplanets in resonances closer than 2:1, if it continues to hold up, may be a primordial signature of the planet formation process.

What Sets the Radial Locations of Warm Debris Disks?

Energy Technology Data Exchange (ETDEWEB)

Ballering, Nicholas P.; Rieke, George H.; Su, Kate Y. L.; Gáspár, András, E-mail: ballerin@email.arizona.edu [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)

2017-08-20

The architectures of debris disks encode the history of planet formation in these systems. Studies of debris disks via their spectral energy distributions (SEDs) have found infrared excesses arising from cold dust, warm dust, or a combination of the two. The cold outer belts of many systems have been imaged, facilitating their study in great detail. Far less is known about the warm components, including the origin of the dust. The regularity of the disk temperatures indicates an underlying structure that may be linked to the water snow line. If the dust is generated from collisions in an exo-asteroid belt, the dust will likely trace the location of the water snow line in the primordial protoplanetary disk where planetesimal growth was enhanced. If instead the warm dust arises from the inward transport from a reservoir of icy material farther out in the system, the dust location is expected to be set by the current snow line. We analyze the SEDs of a large sample of debris disks with warm components. We find that warm components in single-component systems (those without detectable cold components) follow the primordial snow line rather than the current snow line, so they likely arise from exo-asteroid belts. While the locations of many warm components in two-component systems are also consistent with the primordial snow line, there is more diversity among these systems, suggesting additional effects play a role.

A SIGNIFICANTLY LOW CO ABUNDANCE TOWARD THE TW Hya PROTOPLANETARY DISK: A PATH TO ACTIVE CARBON CHEMISTRY?

International Nuclear Information System (INIS)

Favre, Cécile; Cleeves, L. Ilsedore; Bergin, Edwin A.; Qi, Chunhua; Blake, Geoffrey A.

2013-01-01

In this Letter we report the CO abundance relative to H 2 derived toward the circumstellar disk of the T-Tauri star TW Hya from the HD (1 – 0) and C 18 O (2 – 1) emission lines. The HD (1 – 0) line was observed by the Herschel Space Observatory Photodetector Array Camera and Spectrometer whereas C 18 O (2 – 1) observations were carried out with the Submillimeter Array at a spatial resolution of 2.''8 × 1.''9 (corresponding to ∼151 × 103 AU). In the disk's warm molecular layer (T > 20 K) we measure a disk-averaged gas-phase CO abundance relative to H 2 of χ(CO) = (0.1-3) × 10 –5 , substantially lower than the canonical value of χ(CO) = 10 –4 . We infer that the best explanation of this low χ(CO) is the chemical destruction of CO followed by rapid formation of carbon chains, or perhaps CO 2 , that can subsequently freeze-out, resulting in the bulk mass of carbon locked up in ice grain mantles and oxygen in water. As a consequence of this likely time-dependent carbon sink mechanism, CO may be an unreliable tracer of H 2 gas mass

Environmental photobioreactor array (EPBRA) systems and apparatus related thereto

Science.gov (United States)

Kramer, David; Zegarac, Robert; Lucker, Ben F.; Hall, Christopher; Abernathy, Casey; Carpenter, Joel; Cruz, Jeffrey

2017-11-14

A system is described herein that comprises one or more modular environmental photobioreactor arrays, each array containing two or more photobioreactors, wherein the system is adapted to monitor each of the photobioreactors and/or modulate the conditions with each of the photobioreactors. The photobioreactors are also adapted for measurement of multiple physiological parameters of a biomass contained therein. Various methods for selecting and characterizing biomass are also provided. In one embodiment, the biomass is algae.

DUST DISTRIBUTION IN THE β PICTORIS CIRCUMSTELLAR DISKS

International Nuclear Information System (INIS)

Ahmic, Mirza; Croll, Bryce; Artymowicz, Pawel

2009-01-01

We present three-dimensional models of dust distribution around β Pictoris that produce the best fits to the Hubble Space Telescope/Advanced Camera for Surveys' images obtained by Golimowski and coworkers. We allow for the presence of either one or two separate axisymmetric dust disks. The density models are analytical, radial two power laws joined smoothly at a crossover radius with density exponentially decreasing away from the midplane of the disks. Two-disk models match the data best, yielding a reduced χ 2 of ∼1.2. Our two-disk model reproduces many of the asymmetries reported in the literature and suggests that it is the secondary (tilted) disk which is largely responsible for them. Our model suggests that the secondary disk is not constrained to the inner regions of the system (extending out to at least 250 AU) and that it has a slightly larger total area of dust than the primary, as a result of slower falloff of density with radius and height. This surprising result raises many questions about the origin and dynamics of such a pair of disks. The disks overlap, but can coexist owing to their low optical depths and therefore long mean collision times. We find that the two disks have dust replenishment times on the order of 10 4 yr at ∼100 AU, hinting at the presence of planetesimals that are responsible for the production of second generation dust. A plausible conjecture, which needs to be confirmed by physical modeling of the collisional dynamics of bodies in the disks, is that the two observed disks are derived from underlying planetesimal disks; such disks would be anchored by the gravitational influence of planets located at less than 70 AU from β Pic that are themselves in slightly inclined orbits.

Transitional Disks Associated with Intermediate-Mass Stars: Results of the SEEDS YSO Survey

Science.gov (United States)

Grady, C.; Fukagawa, M.; Maruta, Y.; Ohta, Y.; Wisniewski, J.; Hashimoto, J.; Okamoto, Y.; Momose, M.; Currie, T.; McElwain, M.;

Seeded inert gas driven disk generator

International Nuclear Information System (INIS)

Joshi, N.K.; Venkatramani, N.; Rohatgi, V.K.

1987-01-01

This report outlines the present status of work being carried out in closed cycle MHD and disk generators. It gives the basic principles and discusses a proposal for setting up an experimental facility to study nonequilibrium plasmas using an inert gas driven disk generator. Disk geometry is a near ideal geometry for plasma studies since it has single or few pair electrodes combined with near perfect insulating walls. The proposed outlay of facility with components and subsystem is given. The facility may also be used to study the concept of fully ionized seed and to develop advanced diagnostic techniques. The absic equation describing the working parameters of such a system is also given in the Appendix. (author). 57 refs

Understanding Floppy Disks.

Science.gov (United States)

Valentine, Pamela

1980-01-01

The author describes the floppy disk with an analogy to the phonograph record, and discusses the advantages, disadvantages, and capabilities of hard-sectored and soft-sectored floppy disks. She concludes that, at present, the floppy disk will continue to be the primary choice of personal computer manufacturers and their customers. (KC)

Disk laser: a new generation of industrial lasers

Science.gov (United States)

Brockmann, Rüdiger; Havrilla, David

2009-02-01

The disk laser concept aggregates high efficiency, excellent beam quality, high average and peak power with moderate cost and high reliability. Therefore it became one major technology in industrial laser material processing. In several large scale installations in the automotive industry, high power cw- systems make already use of the high brightness and high efficiency of disk lasers, e.g. in remote welding [1,2]. Other applications including cutting, drilling, deep welding and hybrid welding are arising. This report highlights the latest results in cw disk laser development. A 1.5 kW source with a beam parameter product (BPP) of 2 mm mrad is described as well as the demonstration of a 14 kW system out of three disks with a BPP of 8 mm mrad. The future prospects regarding increased power and even further improved productivity and economics are presented. A new industrial disk laser series with output powers up to 16 kW and a beam parameter product of 8 mm*mrad will enable both, new applications in the thick sheet area and very cost efficient high productive applications like welding and cutting of thin sheets.

IR thermocycler for centrifugal microfluidic platform with direct on-disk wireless temperature measurement system

Science.gov (United States)

Burger, J.; Gross, A.; Mark, D.; Roth, G.; von Stetten, F.; Zengerle, R.

2011-06-01

The direct on-disk wireless temperature measurement system [1,2] presented at μTAS 2010 was further improved in its robustness. We apply it to an IR thermocycler as part of a centrifugal microfluidic analyzer for polymerase chain reactions (PCR). This IR thermocycler allows the very efficient direct heating of aqueous liquids in microfluidic cavities by an IR radiation source. The efficiency factor of this IR heating system depends on several parameters. First there is the efficiency of the IR radiator considering the transformation of electrical energy into radiation energy. This radiation energy needs to be focused by a reflector to the center of the cavity. Both, the reflectors shape and the quality of the reflecting layer affect the efficiency. On the way to the center of the cavity the radiation energy will be diminished by absorption in the surrounding air/humidity and especially in the cavity lid of the microfluidic disk. The transmission spectrum of the lid material and its thickness is of significant impact. We chose a COC polymer film with a thickness of 150 μm. At a peak frequency of the IR radiator of ~2 μm approximately 85 % of the incoming radiation energy passes the lid and is absorbed within the first 1.5 mm depth of liquid in the cavity. As we perform the thermocycling for a PCR, after heating to the denaturation temperature of ~ 92 °C we need to cool down rapidly to the primer annealing temperature of ~ 55 °C. Cooling is realized by 3 ventilators venting air of room temperature into the disk chamber. Due to the air flow itself and an additional rotation of the centrifugal microfluidic disk the PCR reagents in the cavities are cooled by forced air convection. Simulation studies based upon analogous electrical models enable to optimize the disk geometry and the optical path. Both the IR heater and the ventilators are controlled by the digital PID controller HAPRO 0135 [3]. The sampling frequency is set to 2 Hz. It could be further increased up

A Two-Pass Exact Algorithm for Selection on Parallel Disk Systems.

Science.gov (United States)

Mi, Tian; Rajasekaran, Sanguthevar

2013-07-01

Numerous OLAP queries process selection operations of "top N", median, "top 5%", in data warehousing applications. Selection is a well-studied problem that has numerous applications in the management of data and databases since, typically, any complex data query can be reduced to a series of basic operations such as sorting and selection. The parallel selection has also become an important fundamental operation, especially after parallel databases were introduced. In this paper, we present a deterministic algorithm Recursive Sampling Selection (RSS) to solve the exact out-of-core selection problem, which we show needs no more than (2 + ε ) passes ( ε being a very small fraction). We have compared our RSS algorithm with two other algorithms in the literature, namely, the Deterministic Sampling Selection and QuickSelect on the Parallel Disks Systems. Our analysis shows that DSS is a (2 + ε )-pass algorithm when the total number of input elements N is a polynomial in the memory size M (i.e., N = M c for some constant c ). While, our proposed algorithm RSS runs in (2 + ε ) passes without any assumptions. Experimental results indicate that both RSS and DSS outperform QuickSelect on the Parallel Disks Systems. Especially, the proposed algorithm RSS is more scalable and robust to handle big data when the input size is far greater than the core memory size, including the case of N ≫ M c .

Shifting of the resonance location for planets embedded in circumstellar disks

Science.gov (United States)

Marzari, F.

2018-03-01

Context. In the early evolution of a planetary system, a pair of planets may be captured in a mean motion resonance while still embedded in their nesting circumstellar disk. Aims: The goal is to estimate the direction and amount of shift in the semimajor axis of the resonance location due to the disk gravity as a function of the gas density and mass of the planets. The stability of the resonance lock when the disk dissipates is also tested. Methods: The orbital evolution of a large number of systems is numerically integrated within a three-body problem in which the disk potential is computed as a series of expansion. This is a good approximation, at least over a limited amount of time. Results: Two different resonances are studied: the 2:1 and the 3:2. In both cases the shift is inwards, even if by a different amount, when the planets are massive and carve a gap in the disk. For super-Earths, the shift is instead outwards. Different disk densities, Σ, are considered and the resonance shift depends almost linearly on Σ. The gas dissipation leads to destabilization of a significant number of resonant systems, in particular if it is fast. Conclusions: The presence of a massive circumstellar disk may significantly affect the resonant behavior of a pair of planets by shifting the resonant location and by decreasing the size of the stability region. The disk dissipation may explain some systems found close to a resonance but not locked in it.

The Dynamics of Truncated Black Hole Accretion Disks. I. Viscous Hydrodynamic Case

Energy Technology Data Exchange (ETDEWEB)

Hogg, J. Drew; Reynolds, Christopher S. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)

2017-07-10

Truncated accretion disks are commonly invoked to explain the spectro-temporal variability in accreting black holes in both small systems, i.e., state transitions in galactic black hole binaries (GBHBs), and large systems, i.e., low-luminosity active galactic nuclei (LLAGNs). In the canonical truncated disk model of moderately low accretion rate systems, gas in the inner region of the accretion disk occupies a hot, radiatively inefficient phase, which leads to a geometrically thick disk, while the gas in the outer region occupies a cooler, radiatively efficient phase that resides in the standard geometrically thin disk. Observationally, there is strong empirical evidence to support this phenomenological model, but a detailed understanding of the dynamics of truncated disks is lacking. We present a well-resolved viscous, hydrodynamic simulation that uses an ad hoc cooling prescription to drive a thermal instability and, hence, produce the first sustained truncated accretion disk. With this simulation, we perform a study of the dynamics, angular momentum transport, and energetics of a truncated disk. We find that the time variability introduced by the quasi-periodic transition of gas from efficient cooling to inefficient cooling impacts the evolution of the simulated disk. A consequence of the thermal instability is that an outflow is launched from the hot/cold gas interface, which drives large, sub-Keplerian convective cells into the disk atmosphere. The convective cells introduce a viscous θ − ϕ stress that is less than the generic r − ϕ viscous stress component, but greatly influences the evolution of the disk. In the truncated disk, we find that the bulk of the accreted gas is in the hot phase.

Orbital Evolution of Moons in Weakly Accreting Circumplanetary Disks

Energy Technology Data Exchange (ETDEWEB)

Fujii, Yuri I.; Gressel, Oliver [Niels Bohr International Academy, The Niels Bohr Institute, Blegdamsvej 17, DK-2100, Copenhagen Ø (Denmark); Kobayashi, Hiroshi [Department of Physics, Nagoya University, Furo-cho, Showa-ku, Nagoya, Aichi, 464-8602 (Japan); Takahashi, Sanemichi Z., E-mail: yuri.fujii@nbi.ku.dk [Astronomical Institute, Tohoku University, 6-3 Aramaki, Aoba-ku, Sendai, 980-8578 (Japan)

2017-04-01

We investigate the formation of hot and massive circumplanetary disks (CPDs) and the orbital evolution of satellites formed in these disks. Because of the comparatively small size-scale of the sub-disk, quick magnetic diffusion prevents the magnetorotational instability (MRI) from being well developed at ionization levels that would allow MRI in the parent protoplanetary disk. In the absence of significant angular momentum transport, continuous mass supply from the parental protoplanetary disk leads to the formation of a massive CPD. We have developed an evolutionary model for this scenario and have estimated the orbital evolution of satellites within the disk. We find, in a certain temperature range, that inward migration of a satellite can be stopped by a change in the structure due to the opacity transitions. Moreover, by capturing second and third migrating satellites in mean motion resonances, a compact system in Laplace resonance can be formed in our disk models.

HERSCHEL's ''COLD DEBRIS DISKS'': BACKGROUND GALAXIES OR QUIESCENT RIMS OF PLANETARY SYSTEMS?

Energy Technology Data Exchange (ETDEWEB)

Krivov, A. V.; Loehne, T.; Mutschke, H.; Neuhaeuser, R. [Astrophysikalisches Institut und Universitaetssternwarte, Friedrich-Schiller-Universitaet Jena, Schillergaesschen 2-3, D-07745 Jena (Germany); Eiroa, C.; Marshall, J. P.; Mustill, A. J. [Departamento de Fisica Teorica, Facultad de Ciencias, Universidad Autonoma de Madrid, Cantoblanco, E-28049 Madrid (Spain); Montesinos, B. [Departamento de Astrofisica, Centro de Astrobiologia (CAB, CSIC-INTA), ESAC Campus, P.O. Box 78, E-28691 Villanueva de la Canada, Madrid (Spain); Del Burgo, C. [Instituto Nacional de Astrofisica, Optica y Electronica (INAOE), Apartado Postal 51 y 216, 72000 Puebla, Pue. (Mexico); Absil, O. [Institut d' Astrophysique et de Geophysique, Universite de Liege, Allee du 6 Aout 17, B-4000 Liege (Belgium); Ardila, D. [NASA Herschel Science Center, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Augereau, J.-C.; Ertel, S.; Lebreton, J. [UJF-Grenoble 1/CNRS-INSU, Institut de Planetologie et d' Astrophysique de Grenoble (IPAG), UMR 5274, F-38041 Grenoble (France); Bayo, A. [European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago (Chile); Bryden, G. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Danchi, W. [NASA Goddard Space Flight Center, Exoplanets and Stellar Astrophysics, Code 667, Greenbelt, MD 20771 (United States); Liseau, R. [Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, SE-43992, Onsala (Sweden); Mora, A. [ESA-ESAC Gaia SOC, P.O. Box 78, E-28691 Villanueva de la Canada, Madrid (Spain); Pilbratt, G. L., E-mail: krivov@astro.uni-jena.de [ESA Astrophysics and Fundamental Physics Missions Division, ESTEC/SRE-SA, Keplerlaan 1, 2201 AZ Noordwijk (Netherlands); and others

2013-07-20

than a few kilometers in size. If larger planetesimals were present, then they would stir the disk, triggering a collisional cascade and thus causing production of small debris, which is not seen. Thus, planetesimal formation, at least in the outer regions of the systems, has stopped before 'cometary' or 'asteroidal' sizes were reached.

Radial Transport and Meridional Circulation in Accretion Disks

Energy Technology Data Exchange (ETDEWEB)

Philippov, Alexander A. [Department of Astrophysical Sciences, Princeton University, Ivy Lane, Princeton, NJ 08540 (United States); Rafikov, Roman R., E-mail: sashaph@princeton.edu [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States)

2017-03-10

Radial transport of particles, elements and fluid driven by internal stresses in three-dimensional (3D) astrophysical accretion disks is an important phenomenon, potentially relevant for the outward dust transport in protoplanetary disks, origin of the refractory particles in comets, isotopic equilibration in the Earth–Moon system, etc. To gain better insight into these processes, we explore the dependence of meridional circulation in 3D disks with shear viscosity on their thermal stratification, and demonstrate a strong effect of the latter on the radial flow. Previous locally isothermal studies have normally found a pattern of the radial outflow near the midplane, switching to inflow higher up. Here we show, both analytically and numerically, that a flow that is inward at all altitudes is possible in disks with entropy and temperature steeply increasing with height. Such thermodynamic conditions may be typical in the optically thin, viscously heated accretion disks. Disks in which these conditions do not hold should feature radial outflow near the midplane, as long as their internal stress is provided by the shear viscosity. Our results can also be used for designing hydrodynamical disk simulations with a prescribed pattern of the meridional circulation.

Sensor Arrays and Electronic Tongue Systems

Directory of Open Access Journals (Sweden)

Manel del Valle

2012-01-01

Full Text Available This paper describes recent work performed with electronic tongue systems utilizing electrochemical sensors. The electronic tongues concept is a new trend in sensors that uses arrays of sensors together with chemometric tools to unravel the complex information generated. Initial contributions and also the most used variant employ conventional ion selective electrodes, in which it is named potentiometric electronic tongue. The second important variant is the one that employs voltammetry for its operation. As chemometric processing tool, the use of artificial neural networks as the preferred data processing variant will be described. The use of the sensor arrays inserted in flow injection or sequential injection systems will exemplify attempts made to automate the operation of electronic tongues. Significant use of biosensors, mainly enzyme-based, to form what is already named bioelectronic tongue will be also presented. Application examples will be illustrated with selected study cases from the Sensors and Biosensors Group at the Autonomous University of Barcelona.

MIGRATION OF EXTRASOLAR PLANETS: EFFECTS FROM X-WIND ACCRETION DISKS

International Nuclear Information System (INIS)

Adams, Fred C.; Cai, Mike J.; Lizano, Susana

2009-01-01

Magnetic fields are dragged in from the interstellar medium during the gravitational collapse that forms star/disk systems. Consideration of mean field magnetohydrodynamics in these disks shows that magnetic effects produce sub-Keplerian rotation curves and truncate the inner disk. This Letter explores the ramifications of these predicted disk properties for the migration of extrasolar planets. Sub-Keplerian flow in gaseous disks drives a new migration mechanism for embedded planets and modifies the gap-opening processes for larger planets. This sub-Keplerian migration mechanism dominates over Type I migration for sufficiently small planets (m P ∼ + ) and/or close orbits (r ∼< 1 AU). Although the inclusion of sub-Keplerian torques shortens the total migration time by only a moderate amount, the mass accreted by migrating planetary cores is significantly reduced. Truncation of the inner disk edge (for typical system parameters) naturally explains final planetary orbits with periods P ∼ 4 days. Planets with shorter periods, P ∼ 2 days, can be explained by migration during FU-Orionis outbursts, when the mass accretion rate is high and the disk edge moves inward. Finally, the midplane density is greatly increased at the inner truncation point of the disk (the X-point); this enhancement, in conjunction with continuing flow of gas and solids through the region, supports the in situ formation of giant planets.

Modeling of a diode-pumped thin-disk cesium vapor laser

Science.gov (United States)

An, Guofei; Cai, He; Liu, Xiaoxu; Han, Juhong; Zhang, Wei; Wang, Hongyuan; Wang, You

2018-03-01

A diode pumped alkali laser (DPAL) provides a significant potential for construction of high-powered lasers. Until now, a series of models have been established to analyze the kinetic process and most of them are based on the end-pumped alkali laser system in which the vapor cell are usually cylindrical and cuboid. In this paper, a mathematic model is constructed to investigate the kinetic processes of a diode pumped thin-disk cesium vapor laser, in which the cesium vapor and the buffer gases are beforehand filled in a sealed glass cell with a thin-disk structure. We systemically study the influences of the cell temperature and cell thickness on the output features of a thin-disk DPAL. Further, we study the thin-disk DPAL with the W-shaped resonator and multiple-disk configuration. To the best of our knowledge, there have not been any similar reports so far.

Equilibrium configuration of a stratus floating above accretion disks: Full-disk calculation

Science.gov (United States)

Itanishi, Yusuke; Fukue, Jun

2017-06-01

We examine floating strati above a luminous accretion disk, supported by the radiative force from the entire disk, and calculate the equilibrium locus, which depends on the disk luminosity and the optical depth of the stratus. Due to the radiative transfer effect (albedo effect), the floating height of the stratus with a finite optical depth generally becomes high, compared with the particle case. In contrast to the case of the near-disk approximation, moreover, the floating height becomes yet higher in the present full-disk calculation, since the intense radiation from the inner disk is taken into account. As a result, when the disk luminosity normalized by the Eddington luminosity is ˜0.3 and the stratus optical depth is around unity, the stable configuration disappears at around r ˜ 50 rg, rg being the Schwarzschild radius, and the stratus would be blown off as a cloudy wind consisting of many strati with appropriate conditions. This luminosity is sufficiently smaller than the Eddington one, and the present results suggest that the radiation-driven cloudy wind can be easily blown off from the sub-Eddington disk, and this can explain various outflows observed in ultra-fast outflow objects as well as in broad-absorption-line quasars.

Noise characteristics of barium ferrite particulate rigid disks

Science.gov (United States)

Kodama, Naoki; Inoue, Hitoshi; Spratt, Geoffrey; Uesaka, Yasutaro; Katsumoto, Masayuki

1991-04-01

This paper discusses the relationship between the noise characteristics and magnetic properties of longitudinal barium ferrite (Ba-F) rigid disks with different switching field distributions (SFD). The magnetomotive force dependencies of reverse dc-erase (RDC) noise are measured and compared with SFD values. Coated disks with acicular magnetic particles have dips and thin-film disks peaks in the RDC. In Ba-F disks, both cases are observed depending on the SFD values, though the depths or heights of the RDC noise are much smaller than those of coated disks with acicular particles or thin-film disks. Disks with small SFD values have peaks, and disks with large SFD values have dips. In order to find the relationship between noise properties and magnetic properties, interparticle interactions in Ba-F disks are investigated. Reverse dc remanence Id(H) and ac-demagnetized isothermal remanence Ir(H) are measured. Both are normalized by the saturation remanence. The deviation from the noninteracting system, ΔM = Id(H) - [1ΔM=Id(H)-[1- 2Ir(H)] and an interaction field factor (IFF) given by (H'r - Hr)/Hc, are derived from these remanent properties. Here, H'r is the field corresponding to 50% of the remanent magnetization, Hr is remanence coercivity. In Ba-F disks, ΔM shows positive interactions, and the peak heights of ΔM increase and IFF decrease with decreasing SFD values. Positive interactions between Ba-F particles seem to be caused by particle stacking. Therefore, particle stacking results in small SFD values and peak-type RDC noise.

THE LONG-TERM EVOLUTION OF PHOTOEVAPORATING PROTOPLANETARY DISKS

Energy Technology Data Exchange (ETDEWEB)

Bae, Jaehan; Hartmann, Lee [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48105 (United States); Zhu Zhaohuan [Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Peyton Hall, Princeton, NJ 08544 (United States); Gammie, Charles, E-mail: jaehbae@umich.edu, E-mail: lhartm@umich.edu, E-mail: zhuzh@astro.princeton.edu, E-mail: gammie@illinois.edu [Department of Astronomy, University of Illinois Urbana-Champaign, 1002 W. Green Street, Urbana, IL 61801 (United States)

2013-09-01

We perform calculations of our one-dimensional, two-zone disk model to study the long-term evolution of the circumstellar disk. In particular, we adopt published photoevaporation prescriptions and examine whether the photoevaporative loss alone, coupled with a range of initial angular momenta of the protostellar cloud, can explain the observed decline of the frequency of optically thick dusty disks with increasing age. In the parameter space we explore, disks have accreting and/or non-accreting transitional phases lasting for {approx}< 20% of their lifetime, which is in reasonable agreement with observed statistics. Assuming that photoevaporation controls disk clearing, we find that the initial angular momentum distribution of clouds needs to be weighted in favor of slowly rotating protostellar cloud cores. Again, assuming inner disk dispersal by photoevaporation, we conjecture that this skewed angular momentum distribution is a result of fragmentation into binary or multiple stellar systems in rapidly rotating cores. Accreting and non-accreting transitional disks show different evolutionary paths on the M-dot-R{sub wall} plane, which possibly explains the different observed properties between the two populations. However, we further find that scaling the photoevaporation rates downward by a factor of 10 makes it difficult to clear the disks on the observed timescales, showing that the precise value of the photoevaporative loss is crucial to setting the clearing times. While our results apply only to pure photoevaporative loss (plus disk accretion), there may be implications for models in which planets clear disks preferentially at radii of the order of 10 AU.

Fiscal 2000 project for development of international standards for supporting novel industries. Standardization for enhanced interoperability between optical disk systems; 2000 nendo shinki sangyo shiengata kokusai hyojun kaihatsu jigyo seika hokokusho. Hikari disk system no sogo un'yosei kakuho no tame no hyojunka

Energy Technology Data Exchange (ETDEWEB)

NONE

2001-03-01

Research and development was carried out for the enhancement of logical format-based interoperability between optical disk systems for the purpose of presenting propositions for international standards. That is, UDF (universal disk format) defined by OSTA (Optical Storage Technology Association) was taken up against the volume/file structure defined by ISO/IEC13346, and efforts were exerted to substantiate environments for its compatibility test and to develop specifications to achieve such enhanced interoperability. In this fiscal year, specifications were drafted for application program interfaces for the UDF-based file system and UDF security augmentation. These would be presented to IEC (International Electrotechnical Commission) and OSTA, respectively. Their Japanese versions were submitted to the Ministry of Economy, Trade and Industry of Japan, for publication as standard-related information. Maintenance of UAF (universal accessible file) system-compliance test tools were accomplished in response to user requirements and to the updating of UDF-compliance test disk specification. (NEDO)

RINGED SUBSTRUCTURE AND A GAP AT 1 au IN THE NEAREST PROTOPLANETARY DISK

Energy Technology Data Exchange (ETDEWEB)

Andrews, Sean M.; Wilner, David J.; Bai, Xue-Ning; Öberg, Karin I.; Ricci, Luca [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Zhu, Zhaohuan [Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Peyton Hall, Princeton, NJ 08544 (United States); Birnstiel, Tilman [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Carpenter, John M. [Joint ALMA Observatory (JAO), Alonso de Cordova 3107, Vitacura-Santiago de Chile (Chile); Pérez, Laura M. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Hughes, A. Meredith [Department of Astronomy, Wesleyan University, Van Vleck Observatory, 96 Foss Hill Drive, Middletown, CT 06457 (United States); Isella, Andrea, E-mail: sandrews@cfa.harvard.edu [Department of Physics and Astronomy, Rice University, 6100 Main Street, Houston, TX 77005 (United States)

2016-04-01

We present long baseline Atacama Large Millimeter/submillimeter Array (ALMA) observations of the 870 μm continuum emission from the nearest gas-rich protoplanetary disk, around TW Hya, that trace millimeter-sized particles down to spatial scales as small as 1 au (20 mas). These data reveal a series of concentric ring-shaped substructures in the form of bright zones and narrow dark annuli (1–6 au) with modest contrasts (5%–30%). We associate these features with concentrations of solids that have had their inward radial drift slowed or stopped, presumably at local gas pressure maxima. No significant non-axisymmetric structures are detected. Some of the observed features occur near temperatures that may be associated with the condensation fronts of major volatile species, but the relatively small brightness contrasts may also be a consequence of magnetized disk evolution (the so-called zonal flows). Other features, particularly a narrow dark annulus located only 1 au from the star, could indicate interactions between the disk and young planets. These data signal that ordered substructures on ∼au scales can be common, fundamental factors in disk evolution and that high-resolution microwave imaging can help characterize them during the epoch of planet formation.

Online performance evaluation of RAID 5 using CPU utilization

Science.gov (United States)

Jin, Hai; Yang, Hua; Zhang, Jiangling

1998-09-01

Redundant arrays of independent disks (RAID) technology is the efficient way to solve the bottleneck problem between CPU processing ability and I/O subsystem. For the system point of view, the most important metric of on line performance is the utilization of CPU. This paper first employs the way to calculate the CPU utilization of system connected with RAID level 5 using statistic average method. From the simulation results of CPU utilization of system connected with RAID level 5 subsystem can we see that using multiple disks as an array to access data in parallel is the efficient way to enhance the on-line performance of disk storage system. USing high-end disk drivers to compose the disk array is the key to enhance the on-line performance of system.

submitter Simulation-Based Performance Analysis of the ALICE Mass Storage System

CERN Document Server

Vickovic, L; Celar, S

2016-01-01

CERN – the European Organization for Nuclear Research today, in the era of big data, is one of the biggest data generators in the world. Especially interesting is transient data storage system in the ALICE experiment. With the goal to optimize its performance this paper discusses a dynamic, discrete event simulation model of disk based Storage Area Network (SAN) and its usage for the performance analyses. Storage system model is based on modular, bottom up approach and the differences between measured and simulated values vary between 1.5 % and 4 % depending on the simulated component. Once finished, simulation model was used for detailed performance analyses. Among other findings it showed that system performances can be seriously affected if the array stripe size is larger than the size of cache on individual disks in the array, which so far has been completely ignored in the literature.

Vibration and flutter of mistuned bladed-disk assemblies

Science.gov (United States)

Kaza, K. R. V.; Kielb, R. E.

1984-01-01

An analytical model for investigating vibration and flutter of mistuned bladed disk assemblies is presented. This model accounts for elastic, inertial and aerodynamic coupling between bending and torsional motions of each individual blade, elastic and inertial couplings between the blades and the disk, and aerodynamic coupling among the blades. The disk was modeled as a circular plate with constant thickness and each blade was represented by a twisted, slender, straight, nonuniform, elastic beam with a symmetric cross section. The elastic axis, inertia axis, and the tension axis were taken to be noncoincident and the structural warping of the section was explicitly considered. The blade aerodynamic loading in the subsonic and supersonic flow regimes was obtained from two-dimensional unsteady, cascade theories. All the possible standing wave modes of the disk and traveling wave modes of the blades were included. The equations of motion were derived by using the energy method in conjunction with the assumed mode shapes for the disk and the blades. Continuities of displacement and slope at the blade-disk junction were maintained. The equations were solved to investigate the effects of blade-disk coupling and blade frequency mistuning on vibration and flutter. Results showed that the flexibility of practical disks such as those used for current generation turbofans did not have a significant influence on either the tuned or mistuned flutter characteristics. However, the disk flexibility may have a strong influence on some of the system frequencies and on forced response.

ALIGNMENT OF PROTOSTARS AND CIRCUMSTELLAR DISKS DURING THE EMBEDDED PHASE

International Nuclear Information System (INIS)

Spalding, Christopher; Batygin, Konstantin; Adams, Fred C.

2014-01-01

Star formation proceeds via the collapse of a molecular cloud core over multiple dynamical timescales. Turbulence within cores results in a spatially non-uniform angular momentum of the cloud, causing a stochastic variation in the orientation of the disk forming from the collapsing material. In the absence of star-disk angular momentum coupling, such disk-tilting would provide a natural mechanism for the production of primordial spin-orbit misalignments in the resulting planetary systems. However, owing to high accretion rates in the embedded phase of star formation, the inner edge of the circumstellar disk extends down to the stellar surface, resulting in efficient gravitational and accretional angular momentum transfer between the star and the disk. Here, we demonstrate that the resulting gravitational coupling is sufficient to suppress any significant star-disk misalignment, with accretion playing a secondary role. The joint tilting of the star-disk system leads to a stochastic wandering of star-aligned bipolar outflows. Such wandering widens the effective opening angle of stellar outflows, allowing for more efficient clearing of the remainder of the protostar's gaseous envelope. Accordingly, the processes described in this work provide an additional mechanism responsible for sculpting the stellar initial mass function

ALMA Shows that Gas Reservoirs of Star-forming Disks over the Past 3 Billion Years Are Not Predominantly Molecular

Energy Technology Data Exchange (ETDEWEB)

Cortese, Luca; Catinella, Barbara; Janowiecki, Steven, E-mail: luca.cortese@uwa.edu.au [International Centre for Radio Astronomy Research, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009 (Australia)

2017-10-10

Cold hydrogen gas is the raw fuel for star formation in galaxies, and its partition into atomic and molecular phases is a key quantity for galaxy evolution. In this Letter, we combine Atacama Large Millimeter/submillimeter Array and Arecibo single-dish observations to estimate the molecular-to-atomic hydrogen mass ratio for massive star-forming galaxies at z ∼ 0.2 extracted from the HIGHz survey, i.e., some of the most massive gas-rich systems currently known. We show that the balance between atomic and molecular hydrogen in these galaxies is similar to that of local main-sequence disks, implying that atomic hydrogen has been dominating the cold gas mass budget of star-forming galaxies for at least the past three billion years. In addition, despite harboring gas reservoirs that are more typical of objects at the cosmic noon, HIGHz galaxies host regular rotating disks with low gas velocity dispersions suggesting that high total gas fractions do not necessarily drive high turbulence in the interstellar medium.

STRUCTURE AND EVOLUTION OF CIRCUMBINARY DISKS AROUND SUPERMASSIVE BLACK HOLE BINARIES

International Nuclear Information System (INIS)

Rafikov, Roman R.

2013-01-01

We explore properties of circumbinary disks around supermassive black hole (SMBH) binaries in centers of galaxies by reformulating standard viscous disk evolution in terms of the viscous angular momentum flux F J . If the binary stops gas inflow and opens a cavity in the disk, then the inner disk evolves toward a constant-F J (rather than a constant M-dot ) state. We compute disk properties in different physical regimes relevant for SMBH binaries, focusing on the gas-assisted evolution of systems starting at separations 10 –4 – 10 –2 pc, and find the following. (1) Mass pileup at the inner disk edge caused by the tidal barrier accelerates binary inspiral. (2) Binaries can be forced to merge even by a disk with a mass below that of the secondary. (3) Torque on the binary is set non-locally, at radii far larger than the binary semi-major axis; its magnitude does not reflect disk properties in the vicinity of the binary. (4) Binary inspiral exhibits hysteresis—it depends on the past evolution of the disk. (5) The Eddington limit can be important for circumbinary disks even if they accrete at sub-Eddington rates, but only at late stages of the inspiral. (6) Gas overflow across the orbit of the secondary can be important for low secondary mass, high- M-dot systems, but mainly during the inspiral phase dominated by the gravitational wave emission. (7) Circumbinary disks emit more power and have harder spectra than constant M-dot disks; their spectra are very sensitive to the amount of overflow across the secondary orbit

The protoplanetary system HD 100546 in Hα polarized light from SPHERE/ZIMPOL. A bar-like structure across the disk gap?

Science.gov (United States)

Mendigutía, I.; Oudmaijer, R. D.; Garufi, A.; Lumsden, S. L.; Huélamo, N.; Cheetham, A.; de Wit, W. J.; Norris, B.; Olguin, F. A.; Tuthill, P.

2017-12-01

Context. HD 100546 is one of the few known pre-main-sequence stars that may host a planetary system in its disk. Aims: This work aims to contribute to our understanding of HD 100546 by analyzing new polarimetric images with high spatial resolution. Methods: Using VLT/SPHERE/ZIMPOL with two filters in Hα and the adjacent continuum, we have probed the disk gap and the surface layers of the outer disk, covering a region disk are more polarized than the SW and NE regions. This asymmetry can be explained from a preferential scattering angle close to 90° and is consistent with previous polarization images. The outer disk in our observations extends from 13 ± 2 to 45 ± 9 au, with a position angle and inclination of 137 ± 5° and 44 ± 8°, respectively. The comparison with previous estimates suggests that the disk inclination could increase with the stellocentric distance, although the different measurements are still consistent within the error bars. In addition, no direct signature of the innermost candidate companion is detected from the polarimetric data, confirming recent results that were based on intensity imagery. We set an upper limit to its mass accretion rate 3σ) of a 20 au bar-like structure that crosses the gap through the central region of HD 100546. Conclusions: In the absence of additional data, it is tentatively suggested that the bar could be dust dragged by infalling gas that radially flows from the outer disk to the inner region. This could represent an exceptional case in which a small-scale radial inflow is observed in a single system. If this scenario is confirmed, it could explain the presence of atomic gas in the inner disk that would otherwise accrete on to the central star on a timescale of a few months/years, as previously indicated from spectro-interferometric data, and could be related with additional (undetected) planets.

Titius-Bode laws in the solar system. 2: Build your own law from disk models

Science.gov (United States)

Dubrulle, B.; Graner, F.

1994-02-01

Simply respecting both scale and rotational invariance, it is easy to construct an endless collection of theoretical models predicting a Titius-Bode law, irrespective to their physical content. Due to the numerous ways to get the law and its intrinsic arbitrariness, it is not a useful constraint on theories of solar system formation. To illustrate the simple elegance of scale-invariant methods, we explicitly cook up one of the simplest examples, an infinitely thin cold gaseous disk rotating around a central object. In that academic case, the Titius-Bode law holds during the linear stage of the gravitational instability. The time scale of the instability is of the order of a self-gravitating time scale, (G rhod)-1/2, where rhod is the disk density. This model links the separation between different density maxima with the ratio MD/MC of the masses of the disk and the central object; for instance, MD/MC of the order of 0.18 roughly leads to the observed separation between the planets. We discuss the boundary conditions and the limit of the Wentzel-Kramer-Brillouin (WKB) approximation.

MIPS Observations of the Fabulous Four Debris Disks

Science.gov (United States)

Su, K. Y. L.; Stansberry, J. A.; Rieke, G. H.; Trilling, D. E.; Stapelfeldt, K. R.; Werner, M. W.; Beichman, C.; Chen, C.; Marengo, M.; Megeath, T.; Backman, D.; van Cleve, J.

2004-12-01

The Multiband Imaging Photometer for Spitzer (MIPS) provides long-wavelength capability with imaging bands at 24, 70, and 160 um. We will present the MIPS images of the Fabulous Four Debris Disks: Beta Pictoris (A5 V), Epsilon Eridani (K2 V), Fomalhaut (A3 V) and Vega (A0 V). These systems discovered by IRAS possess large far-infrared excess emission above photosphere, indicating the existence of a circumstellar dusty disk. Given the main-sequence ages of these stars ( ˜12 Myr for Beta Pictoris, ˜730 Myr for Epsilon Eridani, ˜200 Myr for Fomalhaut, and ˜350 Myr for Vega), the dust in the systems could not be primordial as it would have been removed by radiation pressure and Poynting-Robertson drag on relatively short time scales ( ˜1E4 yr). The second-generation dust in such debris disks is thought to arise primarily from collisions between planetesimals (asteroids) and from cometary activity; however, details about the debris formation and evolution are not well understood. With the sensitivity and angular resolution of the Spitizer Space Telescope, the structures of these nearby debris disks were mapped in great detail to study the disks' spatial structures at mid- to far-infrared wavelengths. These high spatial resolution images provide unprecedented new constraints on the the dust properties in the systems and limits on the origin of dusty debris. Support for this work was provided by NASA through Contract Number 960785 issued by JPL/Caltech.

THE EVOLUTION OF PROTOPLANETARY DISKS IN THE ARCHES CLUSTER

International Nuclear Information System (INIS)

Olczak, C.; Kaczmarek, T.; Pfalzner, S.; Harfst, S.; Portegies Zwart, S.

2012-01-01

Most stars form in a cluster environment. These stars are initially surrounded by disks from which potentially planetary systems form. Of all cluster environments, starburst clusters are probably the most hostile for planetary systems in our Galaxy. The intense stellar radiation and extreme density favor rapid destruction of circumstellar disks via photoevaporation and stellar encounters. Evolving a virialized model of the Arches cluster in the Galactic tidal field, we investigate the effect of stellar encounters on circumstellar disks in a prototypical starburst cluster. Despite its proximity to the deep gravitational potential of the Galactic center, only a moderate fraction of members escapes to form an extended pair of tidal tails. Our simulations show that encounters destroy one-third of the circumstellar disks in the cluster core within the first 2.5 Myr of evolution, preferentially affecting the least and most massive stars. A small fraction of these events causes rapid ejection and the formation of a weaker second pair of tidal tails that is overpopulated by disk-poor stars. Two predictions arise from our study. (1) If not destroyed by photoevaporation protoplanetary disks of massive late B- and early O-type stars represent the most likely hosts of planet formation in starburst clusters. (2) Multi-epoch K- and L-band photometry of the Arches cluster would provide the kinematically selected membership sample required to detect the additional pair of disk-poor tidal tails.

VLA and CARMA observations of protostars in the Cepheus clouds: Sub-arcsecond proto-binaries formed via disk fragmentation

Energy Technology Data Exchange (ETDEWEB)

Tobin, John J.; Looney, Leslie W. [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States); Chandler, Claire J. [National Radio Astronomy Observatory, Socorro, NM (United States); Wilner, David J.; Bourke, Tyler L. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Loinard, Laurent; D' Alessio, Paola [Centro de Radioastronomía y Astrofísica, UNAM, Apartado Postal 3-72 (Xangari), 58089 Morelia, Michoacán (Mexico); Chiang, Hsin-Fang [Institute for Astronomy and NASA Astrobiology Institute, University of Hawaii at Manoa, Hilo, HI 96720 (United States); Hartmann, Lee; Calvet, Nuria [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Kwon, Woojin, E-mail: jtobin@nrao.edu [SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD Groningen (Netherlands)

2013-12-20

We present observations of three Class 0/I protostars (L1157-mm, CB230 IRS1, and L1165-SMM1) using the Karl G. Jansky Very Large Array (VLA) and observations of two (L1165-SMM1 and CB230 IRS1) with the Combined Array for Research in Millimeter-wave Astronomy (CARMA). The VLA observations were taken at wavelengths of λ = 7.3 mm, 1.4 cm, 3.3 cm, 4.0 cm, and 6.5 cm with a best resolution of ∼0.''06 (18 AU) at 7.3 mm. The L1165-SMM1 CARMA observations were taken at λ = 1.3 mm with a best resolution of ∼0.''3 (100 AU) and the CB230 IRS1 observations were taken at λ = 3.4 mm with a best resolution of ∼3'' (900 AU). We find that L1165-SMM1 and CB230 IRS1 have probable binary companions at separations of ∼0.''3 (100 AU) from detections of secondary peaks at multiple wavelengths. The position angles of these companions are nearly orthogonal to the direction of the observed bipolar outflows, consistent with the expected protostellar disk orientations. We suggest that these companions may have formed from disk fragmentation; turbulent fragmentation would not preferentially arrange the binary companions to be orthogonal to the outflow direction. For L1165-SMM1, both the 7.3 mm and 1.3 mm emission show evidence of a large (R > 100 AU) disk. For the L1165-SMM1 primary protostar and the CB230 IRS1 secondary protostar, the 7.3 mm emission is resolved into structures consistent with ∼20 AU radius disks. For the other protostars, including L1157-mm, the emission is unresolved, suggesting disks with radii <20 AU.

RESOLVING THE CIRCUMSTELLAR DISK AROUND THE MASSIVE PROTOSTAR DRIVING THE HH 80-81 JET

Energy Technology Data Exchange (ETDEWEB)

Carrasco-Gonzalez, Carlos [Max-Planck-Institut fuer Radioastronomie (MPIfR), Auf dem Huegel 69, 53121 Bonn (Germany); Galvan-Madrid, Roberto [European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching (Germany); Anglada, Guillem; Osorio, Mayra [Instituto de Astrofisica de Andalucia, CSIC, Camino Bajo de Huetor 50, E-18008 Granada (Spain); D' Alessio, Paola; Rodriguez, Luis F. [Centro de Radioastronomia y Astrofisica UNAM, Apartado Postal 3-72 (Xangari), 58089 Morelia, Michoacan (Mexico); Hofner, Peter [Physics Department, New Mexico Tech, 801 Leroy Pl., Socorro, NM 87801 (United States); Linz, Hendrik [Max-Planck-Institut fuer Astronomie (MPIA), Koenigstuhl 17, 69117 Heidelberg (Germany); Araya, Esteban D., E-mail: carrasco@mpifr-bonn.mpg.de [Physics Department, Western Illinois University, 1 University Circle, Macomb, IL 61455 (United States)

2012-06-20

We present new high angular resolution observations toward the driving source of the HH 80-81 jet (IRAS 18162-2048). Continuum emission was observed with the Very Large Array at 7 mm and 1.3 cm, and with the Submillimeter Array at 860 {mu}m, with angular resolutions of {approx}0.''1 and {approx}0.''8, respectively. Submillimeter observations of the sulfur oxide (SO) molecule are reported as well. At 1.3 cm the emission traces the well-known radio jet, while at 7 mm the continuum morphology is quadrupolar and seems to be produced by a combination of free-free and dust emission. An elongated structure perpendicular to the jet remains in the 7 mm image after subtraction of the free-free contribution. This structure is interpreted as a compact accretion disk of {approx}200 AU radius. Our interpretation is favored by the presence of rotation in our SO observations observed at larger scales. The observations presented here add to the small list of cases where the hundred-AU scale emission from a circumstellar disk around a massive protostar has been resolved.

Frequency multiplexed superconducting quantum interference device readout of large bolometer arrays for cosmic microwave background measurements.

Science.gov (United States)

Dobbs, M A; Lueker, M; Aird, K A; Bender, A N; Benson, B A; Bleem, L E; Carlstrom, J E; Chang, C L; Cho, H-M; Clarke, J; Crawford, T M; Crites, A T; Flanigan, D I; de Haan, T; George, E M; Halverson, N W; Holzapfel, W L; Hrubes, J D; Johnson, B R; Joseph, J; Keisler, R; Kennedy, J; Kermish, Z; Lanting, T M; Lee, A T; Leitch, E M; Luong-Van, D; McMahon, J J; Mehl, J; Meyer, S S; Montroy, T E; Padin, S; Plagge, T; Pryke, C; Richards, P L; Ruhl, J E; Schaffer, K K; Schwan, D; Shirokoff, E; Spieler, H G; Staniszewski, Z; Stark, A A; Vanderlinde, K; Vieira, J D; Vu, C; Westbrook, B; Williamson, R

2012-07-01

A technological milestone for experiments employing transition edge sensor bolometers operating at sub-Kelvin temperature is the deployment of detector arrays with 100s-1000s of bolometers. One key technology for such arrays is readout multiplexing: the ability to read out many sensors simultaneously on the same set of wires. This paper describes a frequency-domain multiplexed readout system which has been developed for and deployed on the APEX-SZ and South Pole Telescope millimeter wavelength receivers. In this system, the detector array is divided into modules of seven detectors, and each bolometer within the module is biased with a unique ∼MHz sinusoidal carrier such that the individual bolometer signals are well separated in frequency space. The currents from all bolometers in a module are summed together and pre-amplified with superconducting quantum interference devices operating at 4 K. Room temperature electronics demodulate the carriers to recover the bolometer signals, which are digitized separately and stored to disk. This readout system contributes little noise relative to the detectors themselves, is remarkably insensitive to unwanted microphonic excitations, and provides a technology pathway to multiplexing larger numbers of sensors.

Antenna array geometry optimization for a passive coherent localisation system

Science.gov (United States)

Knott, Peter; Kuschel, Heiner; O'Hagan, Daniel

2012-11-01

Passive Coherent Localisation (PCL), also known as Passive Radar, making use of RF sources of opportunity such as Radio or TV Broadcasting Stations, Cellular Phone Network Base Stations, etc. is an advancing technology for covert operation because no active radar transmitter is required. It is also an attractive addition to existing active radar stations because it has the potential to discover low-flying and low-observable targets. The CORA (Covert Radar) experimental passive radar system currently developed at Fraunhofer-FHR features a multi-channel digital radar receiver and a circular antenna array with separate elements for the VHF- and the UHF-range and is used to exploit alternatively Digital Audio (DAB) or Video Broadcasting (DVB-T) signals. For an extension of the system, a wideband antenna array is being designed for which a new discone antenna element has been developed covering the full DVB-T frequency range. The present paper describes the outline of the system and the numerical modelling and optimisation methods applied to solve the complex task of antenna array design: Electromagnetic full wave analysis is required for the parametric design of the antenna elements while combinatorial optimization methods are applied to find the best array positions and excitation coefficients for a regular omni-directional antenna performance. The different steps are combined in an iterative loop until the optimum array layout is found. Simulation and experimental results for the current system will be shown.

Accretion Disks around Young Stars: An Observational Perspective

Science.gov (United States)

Ménard, F.; Bertout, C.

Accretion disks are pivotal elements in the formation and early evolution of solar-like stars. On top of supplying the raw material, their internal conditions also regulate the formation of planets. Their study therefore holds the key to solve this long standing mystery: how did our Solar System form? This chapter focuses on observational studies of the circumstellar environment, and in particular of circumstellar disks, associated with pre-main sequence solar-like stars. The direct measurement of disk parameters poses an obvious challenge: at the distance of the typical star forming regions ( e.g. 140 pc for Taurus), a planetary system like ours (with diameter simeq50 AU out to Pluto, but excluding the Kuiper belt which could extend much farther out) subtends only 0.35''. Yet its surface brightness is low in comparison to the bright central star and high angular and high contrast imaging techniques are required if one hopes to resolve and measure these protoplanetary disks. Fortunately, capable instruments providing 0.1'' resolution or better and high contrast have been available for just about 10 years now. They are covering a large part of the electromagnetic spectrum, from the UV/Optical with HST and the near-infrared from ground-based adaptive optics systems, to the millimetric range with long-baseline radio interferometers. It is therefore not surprising that our knowledge of the structure of the disks surrounding low-mass stars has made a gigantic leap forward in the last decade. In the following pages we will attempt to describe, in a historical perpective, the road that led to the idea that most solar-like stars are surrounded by an accretion disk at one point in their early life and how, nowadays, their structural and physical parameters can be estimated from direct observations. We will follow by a short discussion of a few of the constraints available regarding the evolution and dissipation of these disks. This last topic is particularly relevant today

INNER EDGES OF COMPACT DEBRIS DISKS AROUND METAL-RICH WHITE DWARFS

Energy Technology Data Exchange (ETDEWEB)

Rafikov, Roman R.; Garmilla, Jose A., E-mail: rrr@astro.princeton.edu, E-mail: garmilla@astro.princeton.edu [Department of Astrophysical Sciences, Princeton University, Ivy Lane, Princeton, NJ 08540 (United States)

2012-12-01

A number of metal-rich white dwarfs (WDs) are known to host compact, dense particle disks, which are thought to be responsible for metal pollution of these stars. In many such systems, the inner radii of disks inferred from their spectra are so close to the WD that particles directly exposed to starlight must be heated above 1500 K and are expected to be unstable against sublimation. To reconcile this expectation with observations, we explore particle sublimation in H-poor debris disks around WDs. We show that because of the high metal vapor pressure the characteristic sublimation temperature in these disks is 300-400 K higher than in their protoplanetary analogs, allowing particles to survive at higher temperatures. We then look at the structure of the inner edges of debris disks and show that they should generically feature superheated inner rims directly exposed to starlight with temperatures reaching 2500-3500 K. Particles migrating through the rim toward the WD (and rapidly sublimating) shield the disk behind them from strong stellar heating, making the survival of solids possible close to the WD. Our model agrees well with observations of WD+disk systems provided that disk particles are composed of Si-rich material such as olivine, and have sizes in the range {approx}0.03-30 cm.

INNER EDGES OF COMPACT DEBRIS DISKS AROUND METAL-RICH WHITE DWARFS

International Nuclear Information System (INIS)

Rafikov, Roman R.; Garmilla, José A.

2012-01-01

A number of metal-rich white dwarfs (WDs) are known to host compact, dense particle disks, which are thought to be responsible for metal pollution of these stars. In many such systems, the inner radii of disks inferred from their spectra are so close to the WD that particles directly exposed to starlight must be heated above 1500 K and are expected to be unstable against sublimation. To reconcile this expectation with observations, we explore particle sublimation in H-poor debris disks around WDs. We show that because of the high metal vapor pressure the characteristic sublimation temperature in these disks is 300-400 K higher than in their protoplanetary analogs, allowing particles to survive at higher temperatures. We then look at the structure of the inner edges of debris disks and show that they should generically feature superheated inner rims directly exposed to starlight with temperatures reaching 2500-3500 K. Particles migrating through the rim toward the WD (and rapidly sublimating) shield the disk behind them from strong stellar heating, making the survival of solids possible close to the WD. Our model agrees well with observations of WD+disk systems provided that disk particles are composed of Si-rich material such as olivine, and have sizes in the range ∼0.03-30 cm.

Inner Edges of Compact Debris Disks around Metal-rich White Dwarfs

Science.gov (United States)

Rafikov, Roman R.; Garmilla, José A.

2012-12-01

A number of metal-rich white dwarfs (WDs) are known to host compact, dense particle disks, which are thought to be responsible for metal pollution of these stars. In many such systems, the inner radii of disks inferred from their spectra are so close to the WD that particles directly exposed to starlight must be heated above 1500 K and are expected to be unstable against sublimation. To reconcile this expectation with observations, we explore particle sublimation in H-poor debris disks around WDs. We show that because of the high metal vapor pressure the characteristic sublimation temperature in these disks is 300-400 K higher than in their protoplanetary analogs, allowing particles to survive at higher temperatures. We then look at the structure of the inner edges of debris disks and show that they should generically feature superheated inner rims directly exposed to starlight with temperatures reaching 2500-3500 K. Particles migrating through the rim toward the WD (and rapidly sublimating) shield the disk behind them from strong stellar heating, making the survival of solids possible close to the WD. Our model agrees well with observations of WD+disk systems provided that disk particles are composed of Si-rich material such as olivine, and have sizes in the range ~0.03-30 cm.

Utilization of antenna arrays in HF systems

Directory of Open Access Journals (Sweden)

Louis Bertel

2009-06-01

Full Text Available

Different applications of radio systems are based on the implementation of antenna arrays. Classically, radio direction

finding operates with a multi channel receiving system connected to an array of receiving antennas. More

recently, MIMO architectures have been proposed to increase the capacity of radio links by the use of antenna

arrays at both the transmitter and receiver.

The first part of this paper describes some novel experimental work carried out to examine the feasibility of applying

MIMO techniques for communications within the HF radio band. A detailed correlation analysis of a variety

of different antenna array configurations is presented. The second section of the paper also deals with HF

MIMO communications, focusing on the problem from a modelling point of view. The third part presents a sensitivity

analysis of different antenna array structures for HF direction finding applications. The results demonstrate

that when modelling errors, heterogeneous antenna arrays are more robust in comparison to homogeneous structures

2TB hard disk drive

CERN Multimedia

This particular object was used up until 2012 in the Data Centre. It slots into one of the Disk Server trays. Hard disks were invented in the 1950s. They started as large disks up to 20 inches in diameter holding just a few megabytes (link is external). They were originally called "fixed disks" or "Winchesters" (a code name used for a popular IBM product). They later became known as "hard disks" to distinguish them from "floppy disks (link is external)." Hard disks have a hard platter that holds the magnetic medium, as opposed to the flexible plastic film found in tapes and floppies.

Disk storage at CERN

CERN Document Server

Mascetti, L; Chan, B; Espinal, X; Fiorot, A; Labrador, H Gonz; Iven, J; Lamanna, M; Presti, G Lo; Mościcki, JT; Peters, AJ; Ponce, S; Rousseau, H; van der Ster, D

2015-01-01

CERN IT DSS operates the main storage resources for data taking and physics analysis mainly via three system: AFS, CASTOR and EOS. The total usable space available on disk for users is about 100 PB (with relative ratios 1:20:120). EOS actively uses the two CERN Tier0 centres (Meyrin and Wigner) with 50:50 ratio. IT DSS also provide sizeable on-demand resources for IT services most notably OpenStack and NFS-based clients: this is provided by a Ceph infrastructure (3 PB) and few proprietary servers (NetApp). We will describe our operational experience and recent changes to these systems with special emphasis to the present usages for LHC data taking, the convergence to commodity hardware (nodes with 200-TB each with optional SSD) shared across all services. We also describe our experience in coupling commodity and home-grown solution (e.g. CERNBox integration in EOS, Ceph disk pools for AFS, CASTOR and NFS) and finally the future evolution of these systems for WLCG and beyond.

Disk storage at CERN

Science.gov (United States)

Mascetti, L.; Cano, E.; Chan, B.; Espinal, X.; Fiorot, A.; González Labrador, H.; Iven, J.; Lamanna, M.; Lo Presti, G.; Mościcki, JT; Peters, AJ; Ponce, S.; Rousseau, H.; van der Ster, D.

2015-12-01

CERN IT DSS operates the main storage resources for data taking and physics analysis mainly via three system: AFS, CASTOR and EOS. The total usable space available on disk for users is about 100 PB (with relative ratios 1:20:120). EOS actively uses the two CERN Tier0 centres (Meyrin and Wigner) with 50:50 ratio. IT DSS also provide sizeable on-demand resources for IT services most notably OpenStack and NFS-based clients: this is provided by a Ceph infrastructure (3 PB) and few proprietary servers (NetApp). We will describe our operational experience and recent changes to these systems with special emphasis to the present usages for LHC data taking, the convergence to commodity hardware (nodes with 200-TB each with optional SSD) shared across all services. We also describe our experience in coupling commodity and home-grown solution (e.g. CERNBox integration in EOS, Ceph disk pools for AFS, CASTOR and NFS) and finally the future evolution of these systems for WLCG and beyond.

Gas in the Terrestrial Planet Region of Disks: CO Fundamental Emission from T Tauri Stars

Science.gov (United States)

2003-06-01

planetary systems: protoplanetary disks — stars: variables: other 1. INTRODUCTION As the likely birthplaces of planets, the inner regions of young...both low column density regions, such as disk gaps , and temperature inversion regions in disk atmospheres can produce significant emission. The esti...which planetary systems form. The moti- vation to study inner disks is all the more intense today given the discovery of planets outside the solar system

Hole-y Debris Disks, Batman! Where are the planets?

Science.gov (United States)

Bailey, V.; Meshkat, T.; Hinz, P.; Kenworthy, M.; Su, K. Y. L.

2014-03-01

Giant planets at wide separations are rare and direct imaging surveys are resource-intensive, so a cheaper marker for the presence of giant planets is desirable. One intriguing possibility is to use the effect of planets on their host stars' debris disks. Theoretical studies indicate giant planets can gravitationally carve sharp boundaries and gaps in their disks; this has been seen for HR 8799, β Pic, and tentatively for HD 95086 (Su et al. 2009, Lagrange et al. 2010, Moor et al. 2013). If more broadly demonstrated, this link could help guide target selection for next generation direct imaging surveys. Using Spitzer MIPS/IRS spectral energy distributions (SEDs), we identify several dozen systems with two-component and/or large inner cavity disks (aka Hole-y Debris Disks). With LBT/LBTI, VLT/NaCo, GeminiS/NICI, MMT/Clio and Magellan/Clio, we survey a subset these SEDselected targets (~20). In contrast to previous disk-selected planet surveys (e.g.: Janson et al. 2013, Wahhaj et al. 2013) we image primarily in the thermal IR (L'-band), where planet-to-star contrast is more favorable and background contaminants less numerous. Thus far, two of our survey targets host planet-mass companions, both of which were discovered in L'-band after they were unrecognized or undetectable in H-band. For each system in our sample set, we will investigate whether the known companions and/or companions below our detection threshold could be responsible for the disk architecture. Ultimately, we will increase our effective sample size by incorporating detection limits from surveys that have independently targeted some of our systems of interest. In this way we will refine the conditions under which disk SED-based target selection is likely to be useful and valid.

DIRECT DETECTION OF PRECURSORS OF GAS GIANTS FORMED BY GRAVITATIONAL INSTABILITY WITH THE ATACAMA LARGE MILLIMETER/SUBMILLIMETER ARRAY

Energy Technology Data Exchange (ETDEWEB)

Mayer, Lucio [Center for Theoretical Astrophysics and Cosmology, Institute for Computational Science, University of Zurich, Winterthurerstrasse 190, CH-8057 Zürich (Switzerland); Peters, Thomas [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching (Germany); Pineda, Jaime E. [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching (Germany); Wadsley James; Rogers, Patrick, E-mail: p.rogers@marianopolis.edu [Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1 (Canada)

2016-06-01

Phases of gravitational instability are expected in the early phases of disk evolution, when the disk mass is still a substantial fraction of the mass of the star. Disk fragmentation into sub-stellar objects could occur in the cold exterior part of the disk. Direct detection of massive gaseous clumps on their way to collapse into gas giant planets would offer an unprecedented test of the disk instability model. Here we use state-of-the-art 3D radiation-hydro simulations of disks undergoing fragmentation into massive gas giants, post-processed with RADMC-3D to produce dust continuum emission maps. These are then fed into the Common Astronomy Software Applications (CASA) ALMA simulator. The synthetic maps show that both overdense spiral arms and actual clumps at different stages of collapse can be detected with the Atacama Large Millimeter/submillimeter Array (ALMA) in the full configuration at the distance of the Ophiuchus star forming region (125 pc). The detection of clumps is particularly effective at shorter wavelengths (690 GHz) combining two resolutions with multi-scale clean. Furthermore, we show that a flux-based estimate of the mass of a protoplanetary clump can be comparable to a factor of three higher than the gravitationally bound clump mass. The estimated mass depends on the assumed opacity, and on the gas temperature, which should be set using the input of radiation-hydro simulations. We conclude that ALMA has the capability to detect “smoking gun” systems that are a signpost of the disk instability model for gas giant planet formation.

Distributed data acquisition system for Pachmarhi array of Cverenkov telescopes

Science.gov (United States)

Upadhya, S. S.; Acharya, B. S.; Bhat, P. N.; Chitnis, V. R.; D'Souza, A. I.; Francis, P. J.; Gothe, K. S.; Joshi, S. R.; Majumdar, P.; Manogaran, M.; Nagesh, B. K.; Pose, M. S.; Purohit, P. N.; Rahman, M. A.; Rao, K. K.; Rao, S. K.; Sharma, S. K.; Singh, B. B.; Stanislaus, A. J.; Sudersanan, P. V.; Venkatesh Murthy, B. L.; Vishwanath, P. R.

2002-03-01

Pachmarhi Array of Cverenkov Telescopes consists of 25 Telescopes distributed within an area of 8000m2. The array was designed to detect and process faint Cverenkov light flashes that lasts for a few nanoseconds, produced in the atmosphere by celestial VHE ?-rays or cosmic rays. In this experiment, the arrival time and amplitude of fast tiny pulses have to be measured and recorded from each of 175 photo-tubes in a shortest possible time. In view of the complexity of the system, the entire array is divided into 4 sectors. A Distributed Data Acquisition System developed for the purpose consists of independent Sector Data Acquisition Systems and a Master Data Acquisition System. The distributed data acquisition and monitoring system are built using PC's which are networked through LAN. The entire software for DDAS was developed in-house in C language under LINUX environment. Also, most of the hardware barring a few fast digitization modules were designed and fabricated in-house. The design features, implementation strategy as well as the performance of the whole system are discussed.

Magnetohydrodynamics of accretion disks

International Nuclear Information System (INIS)

Torkelsson, U.

1994-04-01

The thesis consists of an introduction and summary, and five research papers. The introduction and summary provides the background in accretion disk physics and magnetohydrodynamics. The research papers describe numerical studies of magnetohydrodynamical processes in accretion disks. Paper 1 is a one-dimensional study of the effect of magnetic buoyancy on a flux tube in an accretion disk. The stabilizing influence of an accretion disk corona on the flux tube is demonstrated. Paper 2-4 present numerical simulations of mean-field dynamos in accretion disks. Paper 11 verifies the correctness of the numerical code by comparing linear models to previous work by other groups. The results are also extended to somewhat modified disk models. A transition from an oscillatory mode of negative parity for thick disks to a steady mode of even parity for thin disks is found. Preliminary results for nonlinear dynamos at very high dynamo numbers are also presented. Paper 3 describes the bifurcation behaviour of the nonlinear dynamos. For positive dynamo numbers it is found that the initial steady solution is replaced by an oscillatory solution of odd parity. For negative dynamo numbers the solution becomes chaotic at sufficiently high dynamo numbers. Paper 4 continues the studies of nonlinear dynamos, and it is demonstrated that a chaotic solution appears even for positive dynamo numbers, but that it returns to a steady solution of mixed parity at very high dynamo numbers. Paper 5 describes a first attempt at simulating the small-scale turbulence of an accretion disk in three dimensions. There is only find cases of decaying turbulence, but this is rather due to limitations of the simulations than that turbulence is really absent in accretion disks

Preparation of thin actinide metal disks using a multiple disk casting technique

International Nuclear Information System (INIS)

Conner, W.V.

1975-01-01

A casting technique has been developed for preparing multiple actinide metal disks which have a minimum thickness of 0.006 inch. This technique was based on an injection casting procedure which utilizes the weight of a tantalum metal rod to force the molten metal into the mold cavity. Using the proper mold design and casting parameters, it has been possible to prepare ten 1/2 inch diameter neptunium or plutonium metal disks in a single casting, This casting technique is capable of producing disks which are very uniform. The average thickness of the disks from a typical casting will vary no more than 0.001 inch and the variation in the thickness of the individual disks will range from 0.0001 to 0.0005 inch. (Auth.)

Preparation of thin actinide metal disks using a multiple disk casting technique

International Nuclear Information System (INIS)

Conner, W.V.

1976-01-01

A casting technique has been developed for preparing multiple actinide metal disks which have a minimum thickness of 0.006 inch. This technique was based on an injection casting procedure which utilizes the weight of a tantalum metal rod to force the molten metal into the mold cavity. Using the proper mold design and casting parameters, it has been possible to prepare ten 1/2 inch diameter neptunium or plutonium metal disks in a single casting. This casting technique is capable of producing disks which are very uniform. The average thickness of the disks from a typical casting will vary no more than 0.001 inch and the variation in the thickness of the individual disks will range from 0.0001 to 0.0005 inch. (author)

The detection and study of pre-planetary disks

Science.gov (United States)

Sargent, A. I.; Beckwith, S. V. W.

1994-01-01

A variety of evidence suggests that at least 50% of low-mass stars are surrounded by disks of the gas and dust similar to the nebula that surrounded the Sun before the formation of the planets. The properties of these disks may bear strongly on the way in which planetary systems form and evolve. As a result of major instrumental developments over the last decade, it is now possible to detect and study the circumstellar environments of the very young, solar-type stars in some detail, and to compare the results with theoretical models of the early solar system. For example, millimeter-wave aperture synthesis imaging provides a direct means of studying in detail the morphology, temperature and density distributions, velocity field and chemical constituents in the outer disks, while high resolution, near infrared spectroscopy probes the inner, warmer parts; the emergence of gaps in the disks, possibly reflecting the formation of planets, may be reflected in the variation of their dust continuum emission with wavelength. We review progress to date and discuss likely directions for future research.

A production throughput forecasting system in an automated hard disk drive test operation using GRNN

Energy Technology Data Exchange (ETDEWEB)

Samattapapong, N.; Afzulpurkar, N.

2016-07-01

The goal of this paper is to develop a pragmatic system of a production throughput forecasting system for an automated test operation in a hard drive manufacturing plant. The accurate forecasting result is necessary for the management team to response to any changes in the production processes and the resources allocations. In this study, we design a production throughput forecasting system in an automated test operation in hard drive manufacturing plant. In the proposed system, consists of three main stages. In the first stage, a mutual information method was adopted for selecting the relevant inputs into the forecasting model. In the second stage, a generalized regression neural network (GRNN) was implemented in the forecasting model development phase. Finally, forecasting accuracy was improved by searching the optimal smoothing parameter which selected from comparisons result among three optimization algorithms: particle swarm optimization (PSO), unrestricted search optimization (USO) and interval halving optimization (IHO). The experimental result shows that (1) the developed production throughput forecasting system using GRNN is able to provide forecasted results close to actual values, and to projected the future trends of production throughput in an automated hard disk drive test operation; (2) An IHO algorithm performed as superiority appropriate optimization method than the other two algorithms. (3) Compared with current forecasting system in manufacturing, the results show that the proposed system’s performance is superior to the current system in prediction accuracy and suitable for real-world application. The production throughput volume is a key performance index of hard disk drive manufacturing systems that need to be forecast. Because of the production throughput forecasting result is useful information for management team to respond to any changing in production processes and resources allocation. However, a practically forecasting system for

A reduced, yet functional, nectary disk integrates a complex system of floral nectar secretion in the genus Zeyheria (Bignoniaceae

Directory of Open Access Journals (Sweden)

Silvia Rodrigues Machado

Full Text Available ABSTRACT The genus Zeyheria (Bignoniaceae comprises only two species, both of which have been described as possessing a reduced and non-functional nectary disk. Despite the importance of this evolutionary change in the floral nectary, these functional assumptions have been based on disk size and on the distribution, abundance and histochemistry of corolla-borne trichomes. By combining methods on light and electron microscopy, here we investigated the functionality of the reduced nectary disk and describe all of the tissues and structures of the nectar chamber in order to determine the sites of floral nectar secretion in both Zeyheria species. . Our data find the floral nectary traits of both species to be very similar, although differing in their cellular contents. Subcellular evidence in both species indicated that disk, stipe and petal axils were, predominantly, involved in hydrophilic secretion, while capitate glandular trichomes produced lipophilic secretion and papillae produced mixed secretion. Our study shows that in spite of its reduced size, the reduced disk functions in nectar secretion in both species of Zeyheria. This kind of nectary system is a novelty for Bignoniaceae, since it comprises several tissues and structures functioning in an integrated fashion.

Disk storage management for LHCb based on Data Popularity estimator

Science.gov (United States)

Hushchyn, Mikhail; Charpentier, Philippe; Ustyuzhanin, Andrey

2015-12-01

This paper presents an algorithm providing recommendations for optimizing the LHCb data storage. The LHCb data storage system is a hybrid system. All datasets are kept as archives on magnetic tapes. The most popular datasets are kept on disks. The algorithm takes the dataset usage history and metadata (size, type, configuration etc.) to generate a recommendation report. This article presents how we use machine learning algorithms to predict future data popularity. Using these predictions it is possible to estimate which datasets should be removed from disk. We use regression algorithms and time series analysis to find the optimal number of replicas for datasets that are kept on disk. Based on the data popularity and the number of replicas optimization, the algorithm minimizes a loss function to find the optimal data distribution. The loss function represents all requirements for data distribution in the data storage system. We demonstrate how our algorithm helps to save disk space and to reduce waiting times for jobs using this data.

Disk storage management for LHCb based on Data Popularity estimator

CERN Document Server

INSPIRE-00545541; Charpentier, Philippe; Ustyuzhanin, Andrey

2015-12-23

This paper presents an algorithm providing recommendations for optimizing the LHCb data storage. The LHCb data storage system is a hybrid system. All datasets are kept as archives on magnetic tapes. The most popular datasets are kept on disks. The algorithm takes the dataset usage history and metadata (size, type, configuration etc.) to generate a recommendation report. This article presents how we use machine learning algorithms to predict future data popularity. Using these predictions it is possible to estimate which datasets should be removed from disk. We use regression algorithms and time series analysis to find the optimal number of replicas for datasets that are kept on disk. Based on the data popularity and the number of replicas optimization, the algorithm minimizes a loss function to find the optimal data distribution. The loss function represents all requirements for data distribution in the data storage system. We demonstrate how our algorithm helps to save disk space and to reduce waiting times ...

Disk storage management for LHCb based on Data Popularity estimator

International Nuclear Information System (INIS)

Hushchyn, Mikhail; Charpentier, Philippe; Ustyuzhanin, Andrey

2015-01-01

This paper presents an algorithm providing recommendations for optimizing the LHCb data storage. The LHCb data storage system is a hybrid system. All datasets are kept as archives on magnetic tapes. The most popular datasets are kept on disks. The algorithm takes the dataset usage history and metadata (size, type, configuration etc.) to generate a recommendation report. This article presents how we use machine learning algorithms to predict future data popularity. Using these predictions it is possible to estimate which datasets should be removed from disk. We use regression algorithms and time series analysis to find the optimal number of replicas for datasets that are kept on disk. Based on the data popularity and the number of replicas optimization, the algorithm minimizes a loss function to find the optimal data distribution. The loss function represents all requirements for data distribution in the data storage system. We demonstrate how our algorithm helps to save disk space and to reduce waiting times for jobs using this data. (paper)

The HIP 79977 debris disk in polarized light

Science.gov (United States)

Engler, N.; Schmid, H. M.; Thalmann, Ch.; Boccaletti, A.; Bazzon, A.; Baruffolo, A.; Beuzit, J. L.; Claudi, R.; Costille, A.; Desidera, S.; Dohlen, K.; Dominik, C.; Feldt, M.; Fusco, T.; Ginski, C.; Gisler, D.; Girard, J. H.; Gratton, R.; Henning, T.; Hubin, N.; Janson, M.; Kasper, M.; Kral, Q.; Langlois, M.; Lagadec, E.; Ménard, F.; Meyer, M. R.; Milli, J.; Mouillet, D.; Olofsson, J.; Pavlov, A.; Pragt, J.; Puget, P.; Quanz, S. P.; Roelfsema, R.; Salasnich, B.; Siebenmorgen, R.; Sissa, E.; Suarez, M.; Szulagyi, J.; Turatto, M.; Udry, S.; Wildi, F.

2017-11-01

Context. Debris disks are observed around 10 to 20% of FGK main-sequence stars as infrared excess emission. They are important signposts for the presence of colliding planetesimals and therefore provide important information about the evolution of planetary systems. Direct imaging of such disks reveals their geometric structure and constrains their dust-particle properties. Aims: We present observations of the known edge-on debris disk around HIP 79977 (HD 146897) taken with the ZIMPOL differential polarimeter of the SPHERE instrument. We measure the observed polarization signal and investigate the diagnostic potential of such data with model simulations. Methods: SPHERE-ZIMPOL polarimetric data of the 15 Myr-old F star HIP 79977 (Upper Sco, 123 pc) were taken in the Very Broad Band (VBB) filter (λc = 735 nm, Δλ = 290 nm) with a spatial resolution of about 25 mas. Imaging polarimetry efficiently suppresses the residual speckle noise from the AO system and provides a differential signal with relatively small systematic measuring uncertainties. We measure the polarization flux along and perpendicular to the disk spine of the highly inclined disk for projected separations between 0.2'' (25 AU) and 1.6'' (200 AU). We perform model calculations for the polarized flux of an optically thin debris disk which are used to determine or constrain the disk parameters of HIP 79977. Results: We measure a polarized flux contrast ratio for the disk of (Fpol)disk/F∗ = (5.5 ± 0.9) × 10-4 in the VBB filter. The surface brightness of the polarized flux reaches a maximum of SBmax = 16.2 mag arcsec-2 at a separation of 0.2''-0.5'' along the disk spine with a maximum surface brightness contrast of 7.64 mag arcsec-2. The polarized flux has a minimum near the star 1''. This can be explained by a radial blow-out of small grains. The data are modelled as a circular dust belt with a well defined disk inclination I = 85( ± 1.5)° and a radius between r0 = 60 and 90 AU. The radial

Optical demodulation system for digitally encoded suspension array in fluoroimmunoassay

Science.gov (United States)

He, Qinghua; Li, Dongmei; He, Yonghong; Guan, Tian; Zhang, Yilong; Shen, Zhiyuan; Chen, Xuejing; Liu, Siyu; Lu, Bangrong; Ji, Yanhong

2017-09-01

A laser-induced breakdown spectroscopy and fluorescence spectroscopy-coupled optical system is reported to demodulate digitally encoded suspension array in fluoroimmunoassay. It takes advantage of the plasma emissions of assembled elemental materials to digitally decode the suspension array, providing a more stable and accurate recognition to target biomolecules. By separating the decoding procedure of suspension array and adsorption quantity calculation of biomolecules into two independent channels, the cross talk between decoding and label signals in traditional methods had been successfully avoided, which promoted the accuracy of both processes and realized more sensitive quantitative detection of target biomolecules. We carried a multiplexed detection of several types of anti-IgG to verify the quantitative analysis performance of the system. A limit of detection of 1.48×10-10 M was achieved, demonstrating the detection sensitivity of the optical demodulation system.

New generation of compact high power disk lasers

Science.gov (United States)

Feuchtenbeiner, Stefanie; Zaske, Sebastian; Schad, Sven-Silvius; Gottwald, Tina; Kuhn, Vincent; Kumkar, Sören; Metzger, Bernd; Killi, Alexander; Haug, Patrick; Speker, Nicolai

2018-02-01

New technological developments in high power disk lasers emitting at 1030 nm are presented. These include the latest generation of TRUMPF's TruDisk product line offering high power disk lasers with up to 6 kW output power and beam qualities of up to 4 mm*mrad. With these compact devices a footprint reduction of 50% compared to the previous model could be achieved while at the same time improving robustness and increasing system efficiency. In the context of Industry 4.0, the new generation of TruDisk lasers features a synchronized data recording of all sensors, offering high-quality data for virtual analyses. The lasers therefore provide optimal hardware requirements for services like Condition Monitoring and Predictive Maintenance. We will also discuss its innovative and space-saving cooling architecture. It allows operation of the laser under very critical ambient conditions. Furthermore, an outlook on extending the new disk laser platform to higher power levels will be given. We will present a disk laser with 8 kW laser power out of a single disk with a beam quality of 5 mm*mrad using a 125 μm fiber, which makes it ideally suited for cutting and welding applications. The flexibility of the disk laser platform also enables the realization of a wide variety of beam guiding setups. As an example a new scheme called BrightLine Weld will be discussed. This technology allows for an almost spatter free laser welding process, even at high feed rates.

ON THE TRANSITIONAL DISK CLASS: LINKING OBSERVATIONS OF T TAURI STARS AND PHYSICAL DISK MODELS

International Nuclear Information System (INIS)

Espaillat, C.; Andrews, S.; Qi, C.; Wilner, D.; Ingleby, L.; Calvet, N.; Hernández, J.; Furlan, E.; D'Alessio, P.; Muzerolle, J.

2012-01-01

Two decades ago 'transitional disks' (TDs) described spectral energy distributions (SEDs) of T Tauri stars with small near-IR excesses, but significant mid- and far-IR excesses. Many inferred this indicated dust-free holes in disks possibly cleared by planets. Recently, this term has been applied disparately to objects whose Spitzer SEDs diverge from the expectations for a typical full disk (FD). Here, we use irradiated accretion disk models to fit the SEDs of 15 such disks in NGC 2068 and IC 348. One group has a 'dip' in infrared emission while the others' continuum emission decreases steadily at all wavelengths. We find that the former have an inner disk hole or gap at intermediate radii in the disk and we call these objects 'transitional disks' and 'pre-transitional disks' (PTDs), respectively. For the latter group, we can fit these SEDs with FD models and find that millimeter data are necessary to break the degeneracy between dust settling and disk mass. We suggest that the term 'transitional' only be applied to objects that display evidence for a radical change in the disk's radial structure. Using this definition, we find that TDs and PTDs tend to have lower mass accretion rates than FDs and that TDs have lower accretion rates than PTDs. These reduced accretion rates onto the star could be linked to forming planets. Future observations of TDs and PTDs will allow us to better quantify the signatures of planet formation in young disks.

Optic disk findings in hypervitaminosis A.

Science.gov (United States)

Marcus, D F; Turgeon, P; Aaberg, T M; Wiznia, R A; Wetzig, P C; Bovino, J A

1985-07-01

Three cases of papilledema secondary to chronic excessive vitamin A intake are presented, and the optic disk changes are documented with intravenous fluorescein angiography. Two of the three patients reported in this study were symptomatic with blurred vision and systemic complaints. The symptoms of blurred vision and systemic complaints disappeared within one week, and papilledema resolved over several months after discontinuance of vitamin A. The fluorescein angiographic changes observed in the optic disk of patients with hypervitaminosis A are similar to those associated with other known causes of papilledema. Since vitamin A is a nonprescription drug, and its indiscriminate use is potentially great, any history of vitamin ingestion should be elicited during the evaluation of papilledema.

On-line monitoring system of PV array based on internet of things technology

Science.gov (United States)

Li, Y. F.; Lin, P. J.; Zhou, H. F.; Chen, Z. C.; Wu, L. J.; Cheng, S. Y.; Su, F. P.

2017-11-01

The Internet of Things (IoT) Technology is used to inspect photovoltaic (PV) array which can greatly improve the monitoring, performance and maintenance of the PV array. In order to efficiently realize the remote monitoring of PV operating environment, an on-line monitoring system of PV array based on IoT is designed in this paper. The system includes data acquisition, data gateway and PV monitoring centre (PVMC) website. Firstly, the DSP-TMS320F28335 is applied to collect indicators of PV array using sensors, then the data are transmitted to data gateway through ZigBee network. Secondly, the data gateway receives the data from data acquisition part, obtains geographic information via GPS module, and captures the scenes around PV array via USB camera, then uploads them to PVMC website. Finally, the PVMC website based on Laravel framework receives all data from data gateway and displays them with abundant charts. Moreover, a fault diagnosis approach for PV array based on Extreme Learning Machine (ELM) is applied in PVMC. Once fault occurs, a user alert can be sent via E-mail. The designed system enables users to browse the operating conditions of PV array on PVMC website, including electrical, environmental parameters and video. Experimental results show that the presented monitoring system can efficiently real-time monitor the PV array, and the fault diagnosis approach reaches a high accuracy of 97.5%.

Development of a set of equations for incorporating disk flexibility effects in rotordynamical analyses

Science.gov (United States)

Flowers, George T.; Ryan, Stephen G.

1991-01-01

Rotordynamical equations that account for disk flexibility are developed. These equations employ free-free rotor modes to model the rotor system. Only transverse vibrations of the disks are considered, with the shaft/disk system considered to be torsionally rigid. Second order elastic foreshortening effects that couple with the rotor speed to produce first order terms in the equations of motion are included. The approach developed in this study is readily adaptable for usage in many of the codes that are current used in rotordynamical simulations. The equations are similar to those used in standard rigid disk analyses but with additional terms that include the effects of disk flexibility. An example case is presented to demonstrate the use of the equations and to show the influence of disk flexibility on the rotordynamical behavior of a sample system.

Method and system for homogenizing diode laser pump arrays

Science.gov (United States)

Bayramian, Andy J

2013-10-01

An optical amplifier system includes a diode pump array including a plurality of semiconductor diode laser bars disposed in an array configuration and characterized by a periodic distance between adjacent semiconductor diode laser bars. The periodic distance is measured in a first direction perpendicular to each of the plurality of semiconductor diode laser bars. The diode pump array provides a pump output propagating along an optical path and characterized by a first intensity profile measured as a function of the first direction and having a variation greater than 10%. The optical amplifier system also includes a diffractive optic disposed along the optical path. The diffractive optic includes a photo-thermo-refractive glass member. The optical amplifier system further includes an amplifier slab having an input face and position along the optical path and separated from the diffractive optic by a predetermined distance. A second intensity profile measured at the input face of the amplifier slab as a function of the first direction has a variation less than 10%.

Evaluation of an Automated System for Reading and Interpreting Disk Diffusion Antimicrobial Susceptibility Testing of Fastidious Bacteria.

Science.gov (United States)

Idelevich, Evgeny A; Becker, Karsten; Schmitz, Janne; Knaack, Dennis; Peters, Georg; Köck, Robin

2016-01-01

Results of disk diffusion antimicrobial susceptibility testing depend on individual visual reading of inhibition zone diameters. Therefore, automated reading using camera systems might represent a useful tool for standardization. In this study, the ADAGIO automated system (Bio-Rad) was evaluated for reading disk diffusion tests of fastidious bacteria. 144 clinical isolates (68 β-haemolytic streptococci, 28 Streptococcus pneumoniae, 18 viridans group streptococci, 13 Haemophilus influenzae, 7 Moraxella catarrhalis, and 10 Campylobacter jejuni) were tested on Mueller-Hinton agar supplemented with 5% defibrinated horse blood and 20 mg/L β-NAD (MH-F, Oxoid) according to EUCAST. Plates were read manually with a ruler and automatically using the ADAGIO system. Inhibition zone diameters, indicated by the automated system, were visually controlled and adjusted, if necessary. Among 1548 isolate-antibiotic combinations, comparison of automated vs. manual reading yielded categorical agreement (CA) without visual adjustment of the automatically determined zone diameters in 81.4%. In 20% (309 of 1548) of tests it was deemed necessary to adjust the automatically determined zone diameter after visual control. After adjustment, CA was 94.8%; very major errors (false susceptible interpretation), major errors (false resistant interpretation) and minor errors (false categorization involving intermediate result), calculated according to the ISO 20776-2 guideline, accounted to 13.7% (13 of 95 resistant results), 3.3% (47 of 1424 susceptible results) and 1.4% (21 of 1548 total results), respectively, compared to manual reading. The ADAGIO system allowed for automated reading of disk diffusion testing in fastidious bacteria and, after visual validation of the automated results, yielded good categorical agreement with manual reading.

Thin disk models of Anomalous X-ray Pulsars

Energy Technology Data Exchange (ETDEWEB)

Yavuz Eksi, K.; Ali Alpar, M

2004-06-01

We discuss the options of the fall-back disk model of Anomalous X-Ray Pulsars (AXPs). We argue that the power-law index of the mass inflow rate during the propeller stage can be lower than those employed in earlier models. We take into account the effect of the super-critical mass inflow at the earliest stages on the inner radius of the disk and argue that the system starts as a propeller. Our results show that, assuming a fraction of the mass inflow is accreted onto the neutron star, the fall-back disk scenario can produce AXPs for acceptable parameters.

Beam-Forming Concentrating Solar Thermal Array Power Systems

Science.gov (United States)

Cwik, Thomas A. (Inventor); Dimotakis, Paul E. (Inventor); Hoppe, Daniel J. (Inventor)

2016-01-01

The present invention relates to concentrating solar-power systems and, more particularly, beam-forming concentrating solar thermal array power systems. A solar thermal array power system is provided, including a plurality of solar concentrators arranged in pods. Each solar concentrator includes a solar collector, one or more beam-forming elements, and one or more beam-steering elements. The solar collector is dimensioned to collect and divert incoming rays of sunlight. The beam-forming elements intercept the diverted rays of sunlight, and are shaped to concentrate the rays of sunlight into a beam. The steering elements are shaped, dimensioned, positioned, and/or oriented to deflect the beam toward a beam output path. The beams from the concentrators are converted to heat at a receiver, and the heat may be temporarily stored or directly used to generate electricity.

THE SPITZER INFRARED SPECTROGRAPH SURVEY OF PROTOPLANETARY DISKS IN ORION A. I. DISK PROPERTIES

Energy Technology Data Exchange (ETDEWEB)

Kim, K. H. [Korea Astronomy and Space Science Institute (KASI), 776, Daedeokdae-ro, Yuseong-gu, Daejeon 305-348 (Korea, Republic of); Watson, Dan M.; Manoj, P.; Forrest, W. J. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States); Furlan, Elise [Infrared Processing and Analysis Center, Caltech, 770 S. Wilson Avenue, Pasadena, CA 91125 (United States); Najita, Joan [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Sargent, Benjamin [Center for Imaging Science and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Dr., Rochester, NY 14623 (United States); Hernández, Jesús [Centro de Investigaciones de Astronomía, Apdo. Postal 264, Mérida 5101-A (Venezuela, Bolivarian Republic of); Calvet, Nuria [Department of Astronomy, University of Michigan, 830 Dennison Building, 500 Church Street, Ann Arbor, MI 48109 (United States); Adame, Lucía [Facultad de Ciencias Físico-Matemáticas, Universidad Autónoma de Nuevo León, Av. Universidad S/N, San Nicolás de los Garza, Nuevo León, C.P. 66451, México (Mexico); Espaillat, Catherine [Department of Astronomy, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States); Megeath, S. T. [Ritter Astrophysical Research Center, Department of Physics and Astronomy, University of Toledo, 2801 W. Bancroft St., Toledo, OH 43606 (United States); Muzerolle, James, E-mail: quarkosmos@kasi.re.kr [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); and others

2016-09-01

We present our investigation of 319 Class II objects in Orion A observed by Spitzer /IRS. We also present the follow-up observations of 120 of these Class II objects in Orion A from the Infrared Telescope Facility/SpeX. We measure continuum spectral indices, equivalent widths, and integrated fluxes that pertain to disk structure and dust composition from IRS spectra of Class II objects in Orion A. We estimate mass accretion rates using hydrogen recombination lines in the SpeX spectra of our targets. Utilizing these properties, we compare the distributions of the disk and dust properties of Orion A disks with those of Taurus disks with respect to position within Orion A (Orion Nebular Cluster [ONC] and L1641) and with the subgroups by the inferred radial structures, such as transitional disks (TDs) versus radially continuous full disks (FDs). Our main findings are as follows. (1) Inner disks evolve faster than the outer disks. (2) The mass accretion rates of TDs and those of radially continuous FDs are statistically significantly displaced from each other. The median mass accretion rate of radially continuous disks in the ONC and L1641 is not very different from that in Taurus. (3) Less grain processing has occurred in the disks in the ONC compared to those in Taurus, based on analysis of the shape index of the 10 μ m silicate feature ( F {sub 11.3}/ F {sub 9.8}). (4) The 20–31 μ m continuum spectral index tracks the projected distance from the most luminous Trapezium star, θ {sup 1} Ori C. A possible explanation is UV ablation of the outer parts of disks.

PLANETESIMAL DISK MICROLENSING

International Nuclear Information System (INIS)

Heng, Kevin; Keeton, Charles R.

2009-01-01

Motivated by debris disk studies, we investigate the gravitational microlensing of background starlight by a planetesimal disk around a foreground star. We use dynamical survival models to construct a plausible example of a planetesimal disk and study its microlensing properties using established ideas of microlensing by small bodies. When a solar-type source star passes behind a planetesimal disk, the microlensing light curve may exhibit short-term, low-amplitude residuals caused by planetesimals several orders of magnitude below Earth mass. The minimum planetesimal mass probed depends on the photometric sensitivity and the size of the source star, and is lower when the planetesimal lens is located closer to us. Planetesimal lenses may be found more nearby than stellar lenses because the steepness of the planetesimal mass distribution changes how the microlensing signal depends on the lens/source distance ratio. Microlensing searches for planetesimals require essentially continuous monitoring programs that are already feasible and can potentially set constraints on models of debris disks, the progeny of the supposed extrasolar analogues of Kuiper Belts.

A CHEMICAL VIEW OF PROTOSTELLAR-DISK FORMATION IN L1527

International Nuclear Information System (INIS)

Sakai, Nami; Oya, Yoko; Watanabe, Yoshimasa; Yamamoto, Satoshi; Sakai, Takeshi; Hirota, Tomoya; Ceccarelli, Cecilia; Kahane, Claudine; Lopez-Sepulcre, Ana; Lefloch, Bertrand; Vastel, Charlotte; Bottinelli, Sandrine; Caux, Emmanuel; Coutens, Audrey; Aikawa, Yuri; Takakuwa, Shigehisa; Yen, Hsi-Wei; Ohashi, Nagayoshi

2014-01-01

Subarcsecond images of the rotational line emissions of CCH, CS, H 2 CO, and CH 3 OH have been obtained toward the low-mass protostar IRAS 04368+2557 in L1527 as one of the early science projects of the Atacama Large Millimeter/submillimeter Array. The intensity distributions of CCH and CS show a double-peaked structure along the edge-on envelope with a dip toward the protostar position, whereas those of H 2 CO and CH 3 OH are centrally peaked. By analyzing the position-velocity diagrams along the envelope, CCH and CS are found to reside mainly in the envelope, where the gas is infalling with conservation of its angular momentum. They are almost absent inward of the centrifugal barrier (a half of the centrifugal radius). Although H 2 CO exists in the infalling rotating envelope, it also resides in the disk component inside the centrifugal barrier to some extent. On the other hand, CH 3 OH seems to exist around the centrifugal barrier and in the disk component. Hence, the drastic chemical change occurs at the centrifugal barrier. A discontinuous infalling motion as well as the gas-grain interaction would be responsible for the chemical change. This result will put an important constraint on initial chemical compositions for chemical evolution of protostellar disks

Dusty disks around young stars

NARCIS (Netherlands)

Verhoeff, A.

2009-01-01

Stars are formed through the collapse of giant molecular clouds. During this contraction the matter spins up and naturally forms a circumstellar disk. Once accretion comes to a halt, these disks are relatively stable. Some disks are known to last up to 10 Myrs. Most disks however, dissipate on

[Total cervical disk replacement--implant-specific approaches: keel implant (Prodisc-C intervertebral disk prosthesis)].

Science.gov (United States)

Korge, Andreas; Siepe, Christoph J; Heider, Franziska; Mayer, H Michael

2010-11-01

Dynamic intervertebral support of the cervical spine via an anterolateral approach using a modular artificial disk prosthesis with end-plate fixation by central keel fixation. Cervical median or mediolateral disk herniations, symptomatic cervical disk disease (SCDD) with anterior osseous, ligamentous and/or discogenic narrowing of the spinal canal. Cervical fractures, tumors, osteoporosis, arthrogenic neck pain, severe facet degeneration, increased segmental instability, ossification of posterior longitudinal ligament (OPLL), severe osteopenia, acute and chronic systemic, spinal or local infections, systemic and metabolic diseases, known implant allergy, pregnancy, severe adiposity (body mass index > 36 kg/m2), reduced patient compliance, alcohol abuse, drug abuse and dependency. Exposure of the anterior cervical spine using the minimally invasive anterolateral approach. Intervertebral fixation of retainer screws. Intervertebral diskectomy. Segmental distraction with vertebral body retainer and vertebral distractor. Removal of end-plate cartilage. Microscopically assisted decompression of spinal canal. Insertion of trial implant to determine appropriate implant size, height and position. After biplanar image intensifier control, drilling for keel preparation using drill guide and drill bit, keel-cut cleaner to remove bone material from the keel cut, radiologic control of depth of the keel cut using the corresponding position gauge. Implantation of original implant under lateral image intensifier control. Removal of implant inserter. Functional postoperative care and mobilization without external support, brace not used routinely, soft brace possible for 14 days due to postoperative pain syndromes. Implantation of 100 cervical Prodisc-C disk prostheses in 78 patients (average age 48 years) at a single center. Clinical and radiologic follow-up 24 months postoperatively. Significant improvement based on visual analog scale and Neck Disability Index. Radiologic

Dual-Alloy Disks are Formed by Powder Metallurgy

Science.gov (United States)

Harf, F. H.; Miner, R. V.; Kortovich, C. S.; Marder, J. M.

1982-01-01

High-performance disks have widely varying properties from hub to rim. Dual property disk is fabricated using two nickel-base alloys, AF-115 for rim and Rene 95 for hub. Dual-alloy fabrication may find applications in automobiles, earth-moving equipment, and energy conversion systems as well as aircraft powerplants. There is potential for such applications as shafts, gears, and blades.

Fast, Capacious Disk Memory Device

Science.gov (United States)

Muller, Ronald M.

1990-01-01

Device for recording digital data on, and playing back data from, memory disks has high recording or playback rate and utilizes available recording area more fully. Two disks, each with own reading/writing head, used to record data at same time. Head on disk A operates on one of tracks numbered from outside in; head on disk B operates on track of same number in sequence from inside out. Underlying concept of device applicable to magnetic or optical disks.

Mass distributions in disk galaxies

NARCIS (Netherlands)

Martinsson, Thomas; Verheijen, Marc; Bershady, Matthew; Westfall, Kyle; Andersen, David; Swaters, Rob

We present results on luminous and dark matter mass distributions in disk galaxies from the DiskMass Survey. As expected for normal disk galaxies, stars dominate the baryonic mass budget in the inner region of the disk; however, at about four optical scale lengths (hR ) the atomic gas starts to

Optical Tip Clearance Measurements as a Tool for Rotating Disk Characterization

Directory of Open Access Journals (Sweden)

Iker García

2017-01-01

Full Text Available An experimental investigation on the vibrational behavior of a rotating disk by means of three optical fiber sensors is presented. The disk, which is a scale model of the real disk of an aircraft engine, was assembled in a wind tunnel in order to simulate real operation conditions. The pressure difference between the upstream and downstream sides of the disk causes an airflow that might force the disk to vibrate. To characterize this vibration, a set of parameters was determined by measuring the tip clearance of the disk: the amplitude, the frequency and the number of nodal diameters in the disk. All this information allowed the design of an upgraded prototype of the disk, whose performance was also characterized by the same method. An optical system was employed for the measurements, in combination with a strain gauge mounted on the disk surface, which served to confirm the results obtained. The data of the strain gauge coincided closely with those provided by the optical fiber sensors, thus demonstrating the suitability of this innovative technique to evaluate the vibrational behavior of rotating disks.

PROTOPLANETARY DISK MASSES IN IC348: A RAPID DECLINE IN THE POPULATION OF SMALL DUST GRAINS AFTER 1 Myr

International Nuclear Information System (INIS)

Lee, Nicholas; Williams, Jonathan P.; Cieza, Lucas A.

2011-01-01

We present a 1.3 mm continuum survey of protoplanetary disks in the 2-3 Myr old cluster, IC348, with the Submillimeter Array. We observed 85 young stellar objects and detected 10 with 1.3 mm fluxes greater than 2 mJy. The brightest source is a young embedded protostar driving a molecular outflow. The other nine detections are dusty disks around optically visible stars. Our millimeter flux measurements translate into total disk masses ranging from 2 to 6 Jupiter masses. Each detected disk has strong mid-infrared emission in excess of the stellar photosphere and has Hα equivalent widths larger than the average in the cluster and indicative of ongoing gas accretion. The disk mass distribution, however, is shifted by about a factor of 20 to lower masses, compared to that in the ∼1 Myr old Taurus and Ophiuchus regions. These observations reveal the rapid decline in the number of small dust grains in disks with time and probably their concomitant growth beyond millimeter sizes. Moreover, if IC348 is to form planets in the same proportion as detected in the field, these faint millimeter detections may represent the best candidates in the cluster to study the progression from planetesimals to planets.

Moving mode shape function approach for spinning disk and asymmetric disc brake squeal

Science.gov (United States)

Kang, Jaeyoung

2018-06-01

The solution approach of an asymmetric spinning disk under stationary friction loads requires the mode shape function fixed in the disk in the assumed mode method when the equations of motion is described in the space-fixed frame. This model description will be termed the 'moving mode shape function approach' and it allows us to formulate the stationary contact load problem in both the axisymmetric and asymmetric disk cases. Numerical results show that the eigenvalues of the time-periodic axisymmetric disk system are time-invariant. When the axisymmetry of the disk is broken, the positive real parts of the eigenvalues highly vary with the rotation of the disk in the slow speeds in such application as disc brake squeal. By using the Floquet stability analysis, it is also shown that breaking the axisymmetry of the disc alters the stability boundaries of the system.

Angular Momentum in Disk Wind Revealed in the Young Star MWC 349A

Energy Technology Data Exchange (ETDEWEB)

Zhang, Qizhou; Claus, Brian; Watson, Linda; Moran, James, E-mail: qzhang@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge MA 02138 (United States)

2017-03-01

Disk winds are thought to play a critical role in star birth. As winds extract excess angular momentum from accretion disks, matter in the disk can be transported inward to the star to fuel mass growth. However, observational evidence of wind carrying angular momentum has been very limited. We present Submillimeter Array (SMA) observations of the young star MWC 349A in the H26 α and H30 α recombination lines. The high signal-to-noise ratios made possible by the maser emission process allow us to constrain the relative astrometry of the maser spots to milli-arcsecond precision. Previous observations of the H30 α line with the SMA and the Plateau de Bure interferometer (PdBI) showed that masers are distributed in the disk and wind. Our new high-resolution observations of the H26 α line reveal differences in spatial distribution from that of the H30 α line. H26 α line masers in the disk are excited in a thin annulus with a radius of about 25 au, while the H30 α line masers are formed in a slightly larger annulus with a radius of 30 au. This is consistent with expectations for maser excitation in the presence of an electron density variation of approximately R {sup −4}. In addition, the H30 α and H26 α line masers arise from different parts in the wind. This difference is also expected from maser theory. The wind component of both masers exhibits line-of-sight velocities that closely follow a Keplerian law. This result provides strong evidence that the disk wind extracts significant angular momentum, thereby facilitating mass accretion in the young star.

High-resolution imaging using a wideband MIMO radar system with two distributed arrays.

Science.gov (United States)

Wang, Dang-wei; Ma, Xiao-yan; Chen, A-Lei; Su, Yi

2010-05-01

Imaging a fast maneuvering target has been an active research area in past decades. Usually, an array antenna with multiple elements is implemented to avoid the motion compensations involved in the inverse synthetic aperture radar (ISAR) imaging. Nevertheless, there is a price dilemma due to the high level of hardware complexity compared to complex algorithm implemented in the ISAR imaging system with only one antenna. In this paper, a wideband multiple-input multiple-output (MIMO) radar system with two distributed arrays is proposed to reduce the hardware complexity of the system. Furthermore, the system model, the equivalent array production method and the imaging procedure are presented. As compared with the classical real aperture radar (RAR) imaging system, there is a very important contribution in our method that the lower hardware complexity can be involved in the imaging system since many additive virtual array elements can be obtained. Numerical simulations are provided for testing our system and imaging method.

Evolution of magnetic disk subsystems

Science.gov (United States)

Kaneko, Satoru

1994-06-01

The higher recording density of magnetic disk realized today has brought larger storage capacity per unit and smaller form factors. If the required access performance per MB is constant, the performance of large subsystems has to be several times better. This article describes mainly the technology for improving the performance of the magnetic disk subsystems and the prospects of their future evolution. Also considered are 'crosscall pathing' which makes the data transfer channel more effective, 'disk cache' which improves performance coupling with solid state memory technology, and 'RAID' which improves the availability and integrity of disk subsystems by organizing multiple disk drives in a subsystem. As a result, it is concluded that since the performance of the subsystem is dominated by that of the disk cache, maximation of the performance of the disk cache subsystems is very important.

Use of ultrasonic array method for positioning multiple partial discharge sources in transformer oil.

Science.gov (United States)

Xie, Qing; Tao, Junhan; Wang, Yongqiang; Geng, Jianghai; Cheng, Shuyi; Lü, Fangcheng

2014-08-01

Fast and accurate positioning of partial discharge (PD) sources in transformer oil is very important for the safe, stable operation of power systems because it allows timely elimination of insulation faults. There is usually more than one PD source once an insulation fault occurs in the transformer oil. This study, which has both theoretical and practical significance, proposes a method of identifying multiple PD sources in the transformer oil. The method combines the two-sided correlation transformation algorithm in the broadband signal focusing and the modified Gerschgorin disk estimator. The method of classification of multiple signals is used to determine the directions of arrival of signals from multiple PD sources. The ultrasonic array positioning method is based on the multi-platform direction finding and the global optimization searching. Both the 4 × 4 square planar ultrasonic sensor array and the ultrasonic array detection platform are built to test the method of identifying and positioning multiple PD sources. The obtained results verify the validity and the engineering practicability of this method.

SPICES: Spectro-Polarimetric Imaging and Characterization of Exoplanetary Systems - From Planetary Disks To Nearby Super Earths

Science.gov (United States)

Boccaletti, Anthony; Schneider, Jean; Traub, Wes; Lagage, Pierre-Olivier; Stam, Daphne; Gratton, Raffaele; Trauger, John; Cahoy, Kerri; Snik, Frans; Baudoz, Pierre;

Analyzing data distribution on disk pools for dCache

Energy Technology Data Exchange (ETDEWEB)

Halstenberg, S; Jung, C; Ressmann, D [Forschungszentrum Karlsruhe, Steinbuch Centre for Computing, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)

2010-04-01

Most Tier-1 centers of LHC Computing Grid are using dCache as their storage system. dCache uses a cost model incorporating CPU and space costs for the distribution of data on its disk pools. Storage resources at Tier-1 centers are usually upgraded once or twice a year according to given milestones. One of the effects of this procedure is the accumulation of heterogeneous hardware resources. For a dCache system, a heterogeneous set of disk pools complicates the process of weighting CPU and space costs for an efficient distribution of data. In order to evaluate the data distribution on the disk pools, the distribution is simulated in Java. The results are discussed and suggestions for improving the weight scheme are given.

STELLAR MASS DEPENDENT DISK DISPERSAL

International Nuclear Information System (INIS)

Kennedy, Grant M.; Kenyon, Scott J.

2009-01-01

We use published optical spectral and infrared (IR) excess data from nine young clusters and associations to study the stellar mass dependent dispersal of circumstellar disks. All clusters older than ∼3 Myr show a decrease in disk fraction with increasing stellar mass for solar to higher mass stars. This result is significant at about the 1σ level in each cluster. For the complete set of clusters we reject the null hypothesis-that solar and intermediate-mass stars lose their disks at the same rate-with 95%-99.9% confidence. To interpret this behavior, we investigate the impact of grain growth, binary companions, and photoevaporation on the evolution of disk signatures. Changes in grain growth timescales at fixed disk temperature may explain why early-type stars with IR excesses appear to evolve faster than their later-type counterparts. Little evidence that binary companions affect disk evolution suggests that photoevaporation is the more likely mechanism for disk dispersal. A simple photoevaporation model provides a good fit to the observed disk fractions for solar and intermediate-mass stars. Although the current mass-dependent disk dispersal signal is not strong, larger and more complete samples of clusters with ages of 3-5 Myr can improve the significance and provide better tests of theoretical models. In addition, the orbits of extra-solar planets can constrain models of disk dispersal and migration. We suggest that the signature of stellar mass dependent disk dispersal due to photoevaporation may be present in the orbits of observed extra-solar planets. Planets orbiting hosts more massive than ∼1.6 M sun may have larger orbits because the disks in which they formed were dispersed before they could migrate.

THE MASS DEPENDENCE BETWEEN PROTOPLANETARY DISKS AND THEIR STELLAR HOSTS

International Nuclear Information System (INIS)

Andrews, Sean M.; Rosenfeld, Katherine A.; Kraus, Adam L.; Wilner, David J.

2013-01-01

We present a substantial extension of the millimeter (mm) wave continuum photometry catalog for circumstellar dust disks in the Taurus star-forming region, based on a new ''snapshot'' λ = 1.3 mm survey with the Submillimeter Array. Combining these new data with measurements in the literature, we construct a mm-wave luminosity distribution, f(L mm ), for Class II disks that is statistically complete for stellar hosts with spectral types earlier than M8.5 and has a 3σ depth of roughly 3 mJy. The resulting census eliminates a longstanding selection bias against disks with late-type hosts, and thereby demonstrates that there is a strong correlation between L mm and the host spectral type. By translating the locations of individual stars in the Hertzsprung-Russell diagram into masses and ages, and adopting a simple conversion between L mm and the disk mass, M d , we confirm that this correlation corresponds to a statistically robust relationship between the masses of dust disks and the stars that host them. A Bayesian regression technique is used to characterize these relationships in the presence of measurement errors, data censoring, and significant intrinsic scatter: the best-fit results indicate a typical 1.3 mm flux density of ∼25 mJy for 1 M ☉ hosts and a power-law scaling L mm ∝M * 1.5-2.0 . We suggest that a reasonable treatment of dust temperature in the conversion from L mm to M d favors an inherently linear M d ∝M * scaling, with a typical disk-to-star mass ratio of ∼0.2%-0.6%. The measured rms dispersion around this regression curve is ±0.7 dex, suggesting that the combined effects of diverse evolutionary states, dust opacities, and temperatures in these disks imprint a full width at half-maximum range of a factor of ∼40 on the inferred M d (or L mm ) at any given host mass. We argue that this relationship between M d and M * likely represents the origin of the inferred correlation between giant planet frequency and host star mass in the

The Mass Dependence between Protoplanetary Disks and their Stellar Hosts

Science.gov (United States)

Andrews, Sean M.; Rosenfeld, Katherine A.; Kraus, Adam L.; Wilner, David J.

2013-07-01

We present a substantial extension of the millimeter (mm) wave continuum photometry catalog for circumstellar dust disks in the Taurus star-forming region, based on a new "snapshot" λ = 1.3 mm survey with the Submillimeter Array. Combining these new data with measurements in the literature, we construct a mm-wave luminosity distribution, f(L mm), for Class II disks that is statistically complete for stellar hosts with spectral types earlier than M8.5 and has a 3σ depth of roughly 3 mJy. The resulting census eliminates a longstanding selection bias against disks with late-type hosts, and thereby demonstrates that there is a strong correlation between L mm and the host spectral type. By translating the locations of individual stars in the Hertzsprung-Russell diagram into masses and ages, and adopting a simple conversion between L mm and the disk mass, Md , we confirm that this correlation corresponds to a statistically robust relationship between the masses of dust disks and the stars that host them. A Bayesian regression technique is used to characterize these relationships in the presence of measurement errors, data censoring, and significant intrinsic scatter: the best-fit results indicate a typical 1.3 mm flux density of ~25 mJy for 1 M ⊙ hosts and a power-law scaling L_mm ∝ M_{\\ast}^{1.5-2.0}. We suggest that a reasonable treatment of dust temperature in the conversion from L mm to Md favors an inherently linear Md vpropM * scaling, with a typical disk-to-star mass ratio of ~0.2%-0.6%. The measured rms dispersion around this regression curve is ±0.7 dex, suggesting that the combined effects of diverse evolutionary states, dust opacities, and temperatures in these disks imprint a full width at half-maximum range of a factor of ~40 on the inferred Md (or L mm) at any given host mass. We argue that this relationship between Md and M * likely represents the origin of the inferred correlation between giant planet frequency and host star mass in the exoplanet

Manipulation of magnetic vortex parameters in disk-on-disk nanostructures with various geometry

Directory of Open Access Journals (Sweden)

Maxim E. Stebliy

2015-03-01

Full Text Available Magnetic nanostructures in the form of a sandwich consisting of two permalloy (Py disks with diameters of 600 and 200 nm separated by a nonmagnetic interlayer are studied. Magnetization reversal of the disk-on-disk nanostructures depends on the distance between centers of the small and big disks and on orientation of an external magnetic field applied during measurements. It is found that manipulation of the magnetic vortex chirality and the trajectory of the vortex core in the big disk is only possible in asymmetric nanostructures. Experimentally studied peculiarities of a motion path of the vortex core and vortex parameters by the magneto-optical Kerr effect (MOKE magnetometer are supported by the magnetic force microscopy imaging and micromagnetic simulations.

Global Simulations of the Inner Regions of Protoplanetary Disks with Comprehensive Disk Microphysics

Energy Technology Data Exchange (ETDEWEB)

Bai, Xue-Ning, E-mail: xbai@cfa.harvard.edu [Institute for Theory and Computation, Harvard-Smithsonian Center for Astrophysics, 60 Garden St., MS-51, Cambridge, MA 02138 (United States)

2017-08-10

The gas dynamics of weakly ionized protoplanetary disks (PPDs) are largely governed by the coupling between gas and magnetic fields, described by three non-ideal magnetohydrodynamical (MHD) effects (Ohmic, Hall, ambipolar). Previous local simulations incorporating these processes have revealed that the inner regions of PPDs are largely laminar and accompanied by wind-driven accretion. We conduct 2D axisymmetric, fully global MHD simulations of these regions (∼1–20 au), taking into account all non-ideal MHD effects, with tabulated diffusion coefficients and approximate treatment of external ionization and heating. With the net vertical field aligned with disk rotation, the Hall-shear instability strongly amplifies horizontal magnetic field, making the overall dynamics dependent on initial field configuration. Following disk formation, the disk likely relaxes into an inner zone characterized by asymmetric field configuration across the midplane, which smoothly transitions to a more symmetric outer zone. Angular momentum transport is driven by both MHD winds and laminar Maxwell stress, with both accretion and decretion flows present at different heights, and modestly asymmetric winds from the two disk sides. With anti-aligned field polarity, weakly magnetized disks settle into an asymmetric field configuration with supersonic accretion flow concentrated at one side of the disk surface, and highly asymmetric winds between the two disk sides. In all cases, the wind is magneto-thermal in nature, characterized by a mass loss rate exceeding the accretion rate. More strongly magnetized disks give more symmetric field configuration and flow structures. Deeper far-UV penetration leads to stronger and less stable outflows. Implications for observations and planet formation are also discussed.

Global Simulations of the Inner Regions of Protoplanetary Disks with Comprehensive Disk Microphysics

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Bai, Xue-Ning

2017-08-01

The gas dynamics of weakly ionized protoplanetary disks (PPDs) are largely governed by the coupling between gas and magnetic fields, described by three non-ideal magnetohydrodynamical (MHD) effects (Ohmic, Hall, ambipolar). Previous local simulations incorporating these processes have revealed that the inner regions of PPDs are largely laminar and accompanied by wind-driven accretion. We conduct 2D axisymmetric, fully global MHD simulations of these regions (˜1-20 au), taking into account all non-ideal MHD effects, with tabulated diffusion coefficients and approximate treatment of external ionization and heating. With the net vertical field aligned with disk rotation, the Hall-shear instability strongly amplifies horizontal magnetic field, making the overall dynamics dependent on initial field configuration. Following disk formation, the disk likely relaxes into an inner zone characterized by asymmetric field configuration across the midplane, which smoothly transitions to a more symmetric outer zone. Angular momentum transport is driven by both MHD winds and laminar Maxwell stress, with both accretion and decretion flows present at different heights, and modestly asymmetric winds from the two disk sides. With anti-aligned field polarity, weakly magnetized disks settle into an asymmetric field configuration with supersonic accretion flow concentrated at one side of the disk surface, and highly asymmetric winds between the two disk sides. In all cases, the wind is magneto-thermal in nature, characterized by a mass loss rate exceeding the accretion rate. More strongly magnetized disks give more symmetric field configuration and flow structures. Deeper far-UV penetration leads to stronger and less stable outflows. Implications for observations and planet formation are also discussed.

Two-Dimensional DOA Estimation Using Arbitrary Arrays for Massive MIMO Systems

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Alban Doumtsop Lonkeng

2017-01-01

Full Text Available With the quick advancement of wireless communication networks, the need for massive multiple-input-multiple-output (MIMO to offer adequate network capacity has turned out to be apparent. As a portion of array signal processing, direction-of-arrival (DOA estimation is of indispensable significance to acquire directional data of sources and to empower the 3D beamforming. In this paper, the performance of DOA estimation for massive MIMO systems is analyzed and compared using a low-complexity algorithm. To be exact, the 2D Fourier domain line search (FDLS MUSIC algorithm is studied to mutually estimate elevation and azimuth angle, and arbitrary array geometry is utilized to represent massive MIMO systems. To avoid the computational burden in estimating the data covariance matrix and its eigenvalue decomposition (EVD due to the large-scale sensors involved in massive MIMO systems, the reduced-dimension data matrix is applied on the signals received by the array. The performance is examined and contrasted with the 2D MUSIC algorithm for different types of antenna configuration. Finally, the array resolution is selected to investigate the performance of elevation and azimuth estimation. The effectiveness and advantage of the proposed technique have been proven by detailed simulations for different types of MIMO array configuration.

Ultraino: An Open Phased-Array System for Narrowband Airborne Ultrasound Transmission.

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Marzo, Asier; Corkett, Tom; Drinkwater, Bruce W

2018-01-01

Modern ultrasonic phased-array controllers are electronic systems capable of delaying the transmitted or received signals of multiple transducers. Configurable transmit-receive array systems, capable of electronic steering and shaping of the beam in near real-time, are available commercially, for example, for medical imaging. However, emerging applications, such as ultrasonic haptics, parametric audio, or ultrasonic levitation, require only a small subset of the capabilities provided by the existing controllers. To meet this need, we present Ultraino, a modular, inexpensive, and open platform that provides hardware, software, and example applications specifically aimed at controlling the transmission of narrowband airborne ultrasound. Our system is composed of software, driver boards, and arrays that enable users to quickly and efficiently perform research in various emerging applications. The software can be used to define array geometries, simulate the acoustic field in real time, and control the connected driver boards. The driver board design is based on an Arduino Mega and can control 64 channels with a square wave of up to 17 Vpp and /5 phase resolution. Multiple boards can be chained together to increase the number of channels. The 40-kHz arrays with flat and spherical geometries are demonstrated for parametric audio generation, acoustic levitation, and haptic feedback.

Gait Dynamics Sensing Using IMU Sensor Array System

Directory of Open Access Journals (Sweden)

Slavomir Kardos

2017-01-01

Full Text Available The article deals with a progressive approach in gait sensing. It is incorporated by IMU (Inertia Measurement Unit complex sensors whose field of acting is mainly the motion sensing in medicine, automotive and other industry, self-balancing systems, etc. They allow acquiring the position and orientation of an object in 3D space. Using several IMU units the sensing array for gait dynamics was made. Based on human gait analysis the 7-sensor array was designed to build a gait motion dynamics sensing system with the possibility of graphical interpretation of data from the sensing modules in real-time graphical application interface under the LabVIEW platform. The results of analyses can serve as the information for medical diagnostic purposes. The main control part of the system is microcontroller, whose function is to control the data collection and flow, provide the communication and power management.

Burst Testing and Analysis of Superalloy Disks With a Dual Grain Microstructure

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Gayda, John; Kantzos, Pete

2006-01-01

Elastic-plastic finite element analyses of room temperature burst tests on four superalloy disks were conducted and reported in this paper. Two alloys, Rene 104 (General Electric Aircraft Engines) and Alloy 10 (Honeywell Engines & Systems), were studied. For both alloys an advanced dual microstructure disk, fine grain bore and coarse grain rim, were analyzed and compared with conventional disks with uniform microstructures, coarse grain for Rene 104 and fine grain for Alloy 10. The analysis and experimental data were in good agreement up to burst. At burst, the analysis underestimated the speed and growth of the Rene 104 disks, but overestimated the speed and growth of the Alloy 10 disks. Fractography revealed that the Alloy 10 disks displayed significant surface microcracking and coalescence in comparison to Rene 104 disks. This phenomenon may help explain the differences between the Alloy 10 disks and the Rene 104 disks, as well as the observed deviations between analytical and experimental data at burst.

RGD-modified lipid disks as drug carriers for tumor targeted drug delivery

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Gao, Jie; Xie, Cao; Zhang, Mingfei; Wei, Xiaoli; Yan, Zhiqiang; Ren, Yachao; Ying, Man; Lu, Weiyue

2016-03-01

Melittin, the major component of the European bee venom, is a potential anticancer candidate due to its lytic properties. However, in vivo applications of melittin are limited due to its main side effect, hemolysis, especially when applied through intravenous administration. The polyethylene glycol-stabilized lipid disk is a novel type of nanocarrier, and the rim of lipid disks has a high affinity to amphiphilic peptides. In our study, a c(RGDyK) modified lipid disk was developed as a tumor targeted drug delivery system for melittin. Cryo-TEM was used to confirm the shape and size of lipid disks with or without c(RGDyK) modification. In vitro and in vivo hemolysis analyses revealed that the hemolysis effect significantly decreased after melittin associated with lipid disks. Importantly, the results of our in vivo biodistribution and tumor growth inhibitory experiments showed that c(RGDyK) modification increased the distribution of lipid disks in the tumor and the anticancer efficacy of melittin loaded lipid disks. Thus, we successfully achieved a targeted drug delivery system for melittin and other amphiphilic peptides with a good therapeutic effect and low side effects.

DETECTIONS OF TRANS-NEPTUNIAN ICE IN PROTOPLANETARY DISKS

Energy Technology Data Exchange (ETDEWEB)

McClure, M. K.; Calvet, N.; Bergin, E.; Cleeves, L. I. [Department of Astronomy, The University of Michigan, 500 Church Street, 830 Dennison Bldg., Ann Arbor, MI 48109 (United States); Espaillat, C. [Department of Astronomy, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States); D' Alessio, P. [Centro de Radioastronomía y Astrofísica, Universidad NacionalAUtónoma de México, 58089 Morelia, Michoacán (Mexico); Watson, D. M. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States); Manoj, P. [Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005 (India); Sargent, B., E-mail: melisma@umich.edu, E-mail: ncalvet@umich.edu, E-mail: ebergin@umich.edu, E-mail: cleeves@umich.edu, E-mail: cce@bu.edu, E-mail: p.dalessio@crya.unam.mx, E-mail: dmw@pas.rochester.edu, E-mail: manoj.puravankara@tifr.res.in, E-mail: baspci@rit.edu [Center for Imaging Science and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States)

2015-02-01

We present Herschel Space Observatory PACS spectra of T Tauri stars, in which we detect amorphous and crystalline water ice features. Using irradiated accretion disk models, we determine the disk structure and ice abundance in each of the systems. Combining a model-independent comparison of the ice feature strength and disk size with a detailed analysis of the model ice location, we estimate that the ice emitting region is at disk radii >30 AU, consistent with a proto-Kuiper belt. Vertically, the ice emits most below the photodesorption zone, consistent with Herschel observations of cold water vapor. The presence of crystallized water ice at a disk location (1) colder than its crystallization temperature and (2) where it should have been re-amorphized in ∼1 Myr suggests that localized generation is occurring; the most likely cause appears to be micrometeorite impact or planetesimal collisions. Based on simple tests with UV models and different ice distributions, we suggest that the SED shape from 20 to 50 μm may probe the location of the water ice snowline in the disk upper layers. This project represents one of the first extra-solar probes of the spatial structure of the cometary ice reservoir thought to deliver water to terrestrial planets.

Reduced-Rank Array Modes of the California Current Observing System

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Moore, Andrew M.; Arango, Hernan G.; Edwards, Christopher A.

2018-01-01

The information content of the ocean observing array spanning the U.S. west coast is explored using the reduced-rank array modes (RAMs) derived from a four-dimensional variational (4D-Var) data assimilation system covering a period of three decades. RAMs are an extension of the original formulation of array modes introduced by Bennett (1985) but in the reduced model state-space explored by the 4D-Var system, and reveal the extent to which this space is activated by the observations. The projection of the RAMs onto the empirical orthogonal functions (EOFs) of the 4D-Var background error correlation matrix provides a quantitative measure of the effectiveness of the measurements in observing the circulation. It is found that much of the space spanned by the background error covariance is unconstrained by the present ocean observing system. The RAM spectrum is also used to introduce a new criterion to prevent 4D-Var from overfitting the model to the observations.

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

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