scholarly journals Self-consistent Ring Model in Protoplanetary Disks: Temperature Dips and Substructure Formation

2021 ◽  
Vol 923 (1) ◽  
pp. 70
Author(s):  
Shangjia Zhang ◽  
Xiao Hu ◽  
Zhaohuan Zhu ◽  
Jaehan Bae
Keyword(s):  
Aerodynamic Drag ◽  
Thermal Structure ◽  
Protoplanetary Disks ◽  
Dust Concentration ◽  
Ring Model ◽  
Self Consistent ◽  
Shadowing Effect ◽  
Set Up ◽  
Dust Distribution ◽  
Dust Evolution

Abstract Rings and gaps are ubiquitous in protoplanetary disks. Larger dust grains will concentrate in gaseous rings more compactly due to stronger aerodynamic drag. However, the effects of dust concentration on the ring’s thermal structure have not been explored. Using MCRT simulations, we self-consistently construct ring models by iterating the ring’s thermal structure, hydrostatic equilibrium, and dust concentration. We set up rings with two dust populations having different settling and radial concentration due to their different sizes. We find two mechanisms that can lead to temperature dips around the ring. When the disk is optically thick, the temperature drops outside the ring, which is the shadowing effect found in previous studies adopting a single-dust population in the disk. When the disk is optically thin, a second mechanism due to excess cooling of big grains is found. Big grains cool more efficiently, which leads to a moderate temperature dip within the ring where big dust resides. This dip is close to the center of the ring. Such a temperature dip within the ring can lead to particle pileup outside the ring and feedback to the dust distribution and thermal structure. We couple the MCRT calculations with a 1D dust evolution model and show that the ring evolves to a different shape and may even separate to several rings. Overall, dust concentration within rings has moderate effects on the disk’s thermal structure, and a self-consistent model is crucial not only for protoplanetary disk observations but also for planetesimal and planet formation studies.

scholarly journals Thermal evolution of protoplanetary disks: from β-cooling to decoupled gas and dust temperatures

2020 ◽  
Vol 638 ◽  
pp. A102 ◽  
Author(s):  
Eduard I. Vorobyov ◽  
Ryoki Matsukoba ◽  
Kazuyuki Omukai ◽  
Manuel Guedel
Keyword(s):  
Thermal Evolution ◽  
Thermal Structure ◽  
Protoplanetary Disks ◽  
Gas Temperature ◽  
Numerical Hydrodynamics ◽  
Variable Nature ◽  
Dynamical Time ◽  
Envelope Material ◽  
Disk Evolution ◽  
Dust Evolution

Aims. We explore the long-term evolution of young protoplanetary disks with different approaches to computing the thermal structure determined by various cooling and heating processes in the disk and its surroundings. Methods. Numerical hydrodynamics simulations in the thin-disk limit were complemented with three thermal evolution schemes: a simplified β-cooling approach with and without irradiation, where the rate of disk cooling is proportional to the local dynamical time; a fiducial model with equal dust and gas temperatures calculated taking viscous heating, irradiation, and radiative cooling into account; and a more sophisticated approach allowing decoupled dust and gas temperatures. Results. We found that the gas temperature may significantly exceed that of dust in the outer regions of young disks thanks to additional compressional heating caused by the infalling envelope material in the early stages of disk evolution and slow collisional exchange of energy between gas and dust in low-density disk regions. However, the outer envelope shows an inverse trend, with the gas temperatures dropping below that of dust. The global disk evolution is only weakly sensitive to temperature decoupling. Nevertheless, separate dust and gas temperatures may affect the chemical composition, dust evolution, and disk mass estimates. Constant-β models without stellar and background irradiation fail to reproduce the disk evolution with more sophisticated thermal schemes because of the intrinsically variable nature of the β-parameter. Constant-β models with irradiation more closely match the dynamical and thermal evolution, but the agreement is still incomplete. Conclusions. Models allowing separate dust and gas temperatures are needed when emphasis is placed on the chemical or dust evolution in protoplanetary disks, particularly in subsolar metallicity environments.

scholarly journals Entropic measure unveils country competitiveness and product specialization in the World trade web

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Gianluca Teza ◽  
Michele Caraglio ◽  
Attilio L. Stella
Keyword(s):  
Iterative Scheme ◽  
Entropy Function ◽  
Bipartite Networks ◽  
Complexity Measures ◽  
Wide Range ◽  
Self Consistent ◽  
Set Up ◽  
Technical Features ◽  
Country Competitiveness ◽  
Entropic Measure

AbstractWe show how the Shannon entropy function can be used as a basis to set up complexity measures weighting the economic efficiency of countries and the specialization of products beyond bare diversification. This entropy function guarantees the existence of a fixed point which is rapidly reached by an iterative scheme converging to our self-consistent measures. Our approach naturally allows to decompose into inter-sectorial and intra-sectorial contributions the country competitivity measure if products are partitioned into larger categories. Besides outlining the technical features and advantages of the method, we describe a wide range of results arising from the analysis of the obtained rankings and we benchmark these observations against those established with other economical parameters. These comparisons allow to partition countries and products into various main typologies, with well-revealed characterizing features. Our methods have wide applicability to general problems of ranking in bipartite networks.

scholarly journals Simulating Solar Global Magnetism in 3-D

2012 ◽  
Vol 10 (H16) ◽  
pp. 101-103
Author(s):  
A. S. Brun ◽  
A. Strugarek
Keyword(s):  
Magnetic Field ◽  
Recent Progress ◽  
Convection Zone ◽  
Thermal Structure ◽  
Solar Convection ◽  
Self Consistent ◽  
The Mean ◽  
The Magnetic Field

AbstractWe briefly present recent progress using the ASH code to model in 3-D the solar convection, dynamo and its coupling to the deep radiative interior. We show how the presence of a self-consistent tachocline influences greatly the organization of the magnetic field and modifies the thermal structure of the convection zone leading to realistic profiles of the mean flows as deduced by helioseismology.

scholarly journals Dust Concentration Changing Regularities and Dust Reduction Technology by Spray Negative Pressure in Fully Mechanized Mining Face

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Lirong Wu ◽  
Hongxuan Chen ◽  
Jiamin Li ◽  
Shican Fu ◽  
Yuyan Zhuang
Keyword(s):  
Negative Pressure ◽  
Flow Characteristics ◽  
Dust Concentration ◽  
Inlet Section ◽  
Coal Face ◽  
Dust Suppression ◽  
Mining Face ◽  
Dust Distribution ◽  
Dust Reduction ◽  
Ventilation Velocity

The dust concentration changing regularities are the basis to take dust depression measures, which is greatly influenced by the airflow. In the software of FLUENT, the value of ventilation velocity is set as a constant, which cannot express the real ventilation. According to the flow characteristics of the sublayer and data from Nicholas’ experiment, the ventilation velocity distribution formula of sublayer in the inlet section of fully mechanized caving coal face is deduced. The boundary condition of velocity is given by UDF. Taking the 3top1110 fully mechanized caving coal face as an example, the dust distribution in the process of coal mining and hydraulic support shifting was studied. According to the dust-spray coupling experiment, three types of nozzle are chosen based on the efficiency of dust suppression. Combining the dust migration rule and the characteristics of nozzles, the negative pressure-secondary dust suppression devices of spray were developed and applied. And the above measures have lowered the dust concentration effectively.

scholarly journals Including Dust Coagulation in Hydrodynamic Models of Protoplanetary Disks: Dust Evolution in the Vicinity of a Jupiter-mass Planet

2019 ◽  
Vol 885 (1) ◽  
pp. 91 ◽  
Author(s):  
Joanna Dra̧żkowska ◽  
Shengtai Li ◽  
Til Birnstiel ◽  
Sebastian M. Stammler ◽  
Hui Li
Keyword(s):  
Protoplanetary Disks ◽  
Hydrodynamic Models ◽  
Dust Evolution

Experimental and numerical analysis of the roller-bench endurance test on a motorscooter

2009 ◽  
Vol 223 (5) ◽  
pp. 639-650
Author(s):  
F Frendo ◽  
W Rosellini
Keyword(s):  
Structural Components ◽  
Endurance Test ◽  
Ring Model ◽  
Rigid Frame ◽  
Vertical Accelerations ◽  
Set Up ◽  
Displacement Transducers ◽  
Two Wheeler ◽  
Multi Body ◽  
Good Agreement

This paper describes an activity aimed at analysing the loads occurring on a two-wheeler during one of the most widespread tests among two-wheeler companies. In this test, the vehicle with additional ballasts, is positioned on two rollers, having synchronized rotational speed, and is subjected to loads coming from obstacles positioned on the rollers' surface. In order to achieve an in-depth understanding of the loads produced by the test, a vehicle was provided with displacement transducers, accelerometers, and strain gauges. At the same time, two multi-body models of the test were set up, in which the motorscooter had a rigid frame or a flexible frame respectively. The dynamics of the tyre was reproduced by the rigid ring model, where the tyre interacts with the wheel rim by means of linear and rotational springs and dampers. The loads from the obstacles are evaluated on the basis of a series of experimental curves (envelope properties of the tyre) directly obtained with the tyres and obstacle employed for the tests. The comparison between experimental and numerical results regarding suspension strokes, wheel vertical accelerations, and vertical and longitudinal loads showed fairly good agreement; it is also shown how the model having the rigid frame overestimates the peaks in the vertical load. The availability of an accurate model for this kind of test in the early phase of the development process of new vehicles, allows the design of structural components to be optimized.

scholarly journals Dust Evolution in Protoplanetary Disks

2018 ◽  
pp. 1-16
Author(s):  
Sean M. Andrews ◽  
Tilman Birnstiel
Keyword(s):  
Protoplanetary Disks ◽  
Dust Evolution

scholarly journals Dust Concentration and Emission in Protoplanetary Disks Vortices

2017 ◽  
Vol 850 (2) ◽  
pp. 115 ◽  
Author(s):  
Anibal Sierra ◽  
Susana Lizano ◽  
Pierre Barge
Keyword(s):  
Protoplanetary Disks ◽  
Dust Concentration

Modeling the Systematic Uncertainty of Photogrammetric Tracking of Human Motion

1997 ◽  
Vol 119 (2) ◽  
pp. 358-361 ◽  
Author(s):  
S. B. Bortolami ◽  
P. O. Riley ◽  
D. E. Krebs
Keyword(s):  
Uncertainty Modeling ◽  
Human Locomotion ◽  
Human Motion ◽  
Tracking Data ◽  
Total Uncertainty ◽  
Rotation Matrices ◽  
Self Consistent ◽  
Consistent Manner ◽  
Set Up ◽  
Derivatives Of

We address bias errors of photogrammetric tracking of four SELSPOT-II® cameras using active marker photogrammetry in a 2 m × 2 m × 2 m viewing volume for human locomotion measurements. We present uncertainty modeling regarding the first stage of equipment set up, which provides the camera frame to global frame rotation matrices and the distances among cameras. We also characterize the uncertainty due to the camera distortions of the bare system as compared to published performances achieved with a camera correction procedure. The particular approach is to qualify performances of photogrammetric tracking during routine operation and to identify the nature and magnitude of the uncertainty due to equipment set up and camera distortions as part of the total uncertainty in a self-consistent manner. We found that uncertainty of the camera frame to global frame rotation matrices produced rotation of the image and uncorrected camera hardware uncertainty produced dilatation or compression of the image twice the magnitude of that seen with camera correction. However, camera resolution remains as an equally important factor limiting the accuracy of photogrammetric tracking that can not be easily reduced numerically. In conclusion, the analysis elucidates how uncertainty propagates to numerical derivatives of the tracking data and prepares the groundwork for future development.

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