scholarly journals Diffusion Models for Magnetic Ap Stars

1993 ◽  
Vol 138 ◽  
pp. 458-472
Author(s):  
J. Babel
Keyword(s):  
Mass Loss ◽  
Diffusion Theory ◽  
Transport Processes ◽  
Line Profiles ◽  
Loss Model ◽  
Spectrum Synthesis ◽  
On Line ◽  
Ap Stars ◽  
Diffusion Mass ◽  
Made In

AbstractProgress made in spectroscopy and in the diffusion theory permits now to make severe comparisons, based on line profiles, between theory and observation.We first review transport processes which are present in the atmospheric layers of Ap stars and discuss their relative importance. We then show that mass loss could play a key role for the creation of abundance maps. A mass loss model is proposed for 53 Cam and is compared, by spectrum synthesis, with visible and IUE high resolutions observations. The model accounts well for the line profiles of several elements with an exception for Ti. Furthermore, the abundance stratification predicted by this model gives close agreement with the large variation of the abundances of Cr and Fe found between the visible and UV domains. The diffusion-mass loss model finally permits to give a simple interpretation of the peculiar Ca II K lines observed in many Ap SrCrEu stars and in particular in 53 Cam, β CrB and HD 191742.

scholarly journals A Diffusion Mass-Loss Model for the Ap Star 53 Cam

1993 ◽  
Vol 137 ◽  
pp. 275-277
Author(s):  
J. Babel
Keyword(s):  
Mass Loss ◽  
Time Variation ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Spectral Features ◽  
Loss Model ◽  
A Value ◽  
Upper Limits ◽  
Ap Stars ◽  
Diffusion Mass

AbstractThe mechanism and properties of mass loss are poorly known for Ap stars. Present upper limits on the mass loss rate are of 10−10 M⊙yr−1, a value which does not permit any element separation. Abundance maps could be a very powerful tool to constrain the mass loss rate and the wind geometry of Ap stars, as surface abundances are sensitive to rates as small as 10−15 M⊙yr−1. We here propose a diffusion-mass loss model for 53 Cam and compute abundance distributions in the photosphere of 53 Cam. The mass loss geometry is determined from the Ca II K line profile and its time variation. We obtain that the diffusion-mass loss model explains many spectral features of 53 Cam, both in the UV and visible domains.

scholarly journals Chemical Separation vs Rotation in a and F-Stars

1993 ◽  
Vol 138 ◽  
pp. 474-489
Author(s):  
Paul Charbonneau
Keyword(s):  
Mass Loss ◽  
Convection Zone ◽  
Chemical Separation ◽  
Chemical Abundances ◽  
Loss Model ◽  
Peculiar Stars ◽  
Thermally Driven ◽  
Chemically Peculiar Stars ◽  
F Stars ◽  
Diffusion Mass

AbstractThe role played by rotationally-induced mixing in the diffusion-based models for non-magnetic chemically peculiar stars is investigated. This paper focuses on one specific rotationally controlled mixing mechanism, namely thermally-driven meridional circulation. Its effects on the time evolution of chemical abundances are illustrated by means of three specific examples. The first two concern the diffusion model for FmAm stars, where it is shown that while circulation has a determining influence on the settling of Helium, it has no significant effect on the diffusion of heavier metals once the He superficial convection zone has disappeared. The third example is concerned with the diffusion/mass loss model for λBootis stars. It is shown that the inclusion of circulation prevents the appearance of generalized underabundances at any epoch of the evolution, indicating that the diffusion/mass loss model for these objects must be abandoned.

Validation of On-line Respiration Meter and its Applications by Computer Simulation

1992 ◽  
Vol 26 (5-6) ◽  
pp. 1355-1363 ◽  
Author(s):  
C-W. Kim ◽  
H. Spanjers ◽  
A. Klapwijk
Keyword(s):  
Steady State ◽  
Activated Sludge ◽  
Respiration Rate ◽  
Oxygen Demand ◽  
Operating Conditions ◽  
Mass Balances ◽  
Short Term ◽  
Respiration Rates ◽  
On Line ◽  
Made In

An on-line respiration meter is presented to monitor three types of respiration rates of activated sludge and to calculate effluent and influent short term biochemical oxygen demand (BODst) in the continuous activated sludge process. This work is to verify if the calculated BODst is reliable and the assumptions made in the course of developing the proposed procedure were acceptable. A mathematical model and a dynamic simulation program are written for an activated sludge model plant along with the respiration meter based on mass balances of BODst and DO. The simulation results show that the three types of respiration rate reach steady state within 15 minutes under reasonable operating conditions. As long as the respiration rate reaches steady state the proposed procedure calculates the respiration rate that is equal to the simulated. Under constant and dynamic BODst loading, the proposed procedure is capable of calculating the effluent and influent BODst with reasonable accuracy.

Evolutionary Intelligent Data Warehousing Approach to Knowledge Discovery Systems: Dynamic Cubing

2019 ◽  
Vol 13 ◽  
Author(s):  
Harkiran Kaur ◽  
Kawaljeet Singh ◽  
Tejinder Kaur
Keyword(s):  
Knowledge Discovery ◽  
Data Warehouse ◽  
Business Intelligence ◽  
End Users ◽  
Processing Stage ◽  
Information Update ◽  
On Line ◽  
Analytical Processing ◽  
Warehouse Operations ◽  
Made In

Background: Numerous E – Migrants databases assist the migrants to locate their peers in various countries; hence contributing largely in communication of migrants, staying overseas. Presently, these traditional E – Migrants databases face the issues of non – scalability, difficult search mechanisms and burdensome information update routines. Furthermore, analysis of migrants’ profiles in these databases has remained unhandled till date and hence do not generate any knowledge. Objective: To design and develop an efficient and multidimensional knowledge discovery framework for E - Migrants databases. Method: In the proposed technique, results of complex calculations related to most probable On-Line Analytical Processing operations required by end users, are stored in the form of Decision Trees, at the pre- processing stage of data analysis. While browsing the Cube, these pre-computed results are called; thus offering Dynamic Cubing feature to end users at runtime. This data-tuning step reduces the query processing time and increases efficiency of required data warehouse operations. Results: Experiments conducted with Data Warehouse of around 1000 migrants’ profiles confirm the knowledge discovery power of this proposal. Using the proposed methodology, authors have designed a framework efficient enough to incorporate the amendments made in the E – Migrants Data Warehouse systems on regular intervals, which was totally missing in the traditional E – Migrants databases. Conclusion: The proposed methodology facilitate migrants to generate dynamic knowledge and visualize it in the form of dynamic cubes. Applying Business Intelligence mechanisms, blending it with tuned OLAP operations, the authors have managed to transform traditional datasets into intelligent migrants Data Warehouse.

scholarly journals Measuring mass-loss rates and constraining shock physics using X-ray line profiles of O stars from the Chandra archive

2014 ◽  
Vol 439 (1) ◽  
pp. 908-923 ◽  
Author(s):  
David H. Cohen ◽  
Emma E. Wollman ◽  
Maurice A. Leutenegger ◽  
Jon O. Sundqvist ◽  
Alex W. Fullerton ◽  
...  
Keyword(s):  
Mass Loss ◽  
Line Profiles ◽  
Shock Physics ◽  
X Ray ◽  
Loss Rates

scholarly journals Radiative-transfer modelling of funnel flows

2007 ◽  
Vol 3 (S243) ◽  
pp. 83-94
Author(s):  
Tim J. Harries
Keyword(s):  
Numerical Methods ◽  
Radiative Transfer ◽  
Emission Line ◽  
Main Sequence ◽  
Line Profiles ◽  
Stellar Radius ◽  
Transfer Modelling ◽  
Synthetic Line ◽  
Made In ◽  
Geometry And Kinematics

AbstractEmission line profiles from pre-main-sequence objects accreting via magnetically-controlled funnel flows encode information on the geometry and kinematics of the material on stellar radius scales. In order to extract this information it is necessary to perform radiative-transfer modelling of the gas to produce synthetic line profiles. In this review I discuss the physics that needs to be included in such models, and the numerical methods and assumptions that are used to render the problem tractable. I review the progress made in the field over the last decade, and summarize the main successes and failures of the modelling work.

Digital twins and modeling of the transporting-technological processes for on-line dispatch control in open pit mining

2020 ◽  
pp. 55-58
Author(s):  
I. O. Temkin ◽  
◽  
A. V. Myaskov ◽  
S. A. Deryabin ◽  
U. A. Rzazade ◽  
...  
Keyword(s):  
3D Models ◽  
Transport Processes ◽  
Open Pit Mine ◽  
Open Pit ◽  
Open Pit Mining ◽  
Russian Science ◽  
Digital Platform ◽  
Technological Processes ◽  
Digital Twins ◽  
On Line

This article discusses modern modeling technologies which open up new capabilities for creating a digital platform for open pit mining management. The specific details of the construction of an intelligent digital platform for the management of transport processes during mineral mining are discussed. A brief overview of the methods and tools for modeling technological processes in open pit mining is given. The stages to be overcome on the path of digital transformation of mines using dynamic 3D models are presented. It is proposed to use software environments of the gaming industry platforms and virtual reality systems as tools for the dynamic 3D modeling of objects. The classes of agents are introduced for the convenience of structuring the tasks to be solved. The basic functional and instrumental elements of the intelligent platform being developed at the present time are given, and also a simplified structure of the technological process control system in an open pit mine, including the prediction module, is presented. The principles of work are described, and the advantages of the specific tool for creating digital 3D models are also discussed. The results obtained in modeling a stage of a transport cycle in an open pit mine are reported. The research was supported by the Russian Science Foundation, Grant No. 19-17-00184.

Influence of Chemical Heterogeneities on Line Profiles

2014 ◽  
pp. 142-170
Keyword(s):  
Probability Distribution Function ◽  
Lattice Parameter ◽  
Line Profiles ◽  
Line Broadening ◽  
Diffraction Vector ◽  
Composition Fluctuation ◽  
Evaluation Procedures ◽  
Edgeworth Series ◽  
On Line ◽  
Diffraction Peaks

The chemical composition fluctuation in a material may cause line broadening due to the variation of the lattice parameter, which yields a distribution of the profile centers scattered from different volumes of the material. The nature of line broadening induced by chemical heterogeneities is similar to a microstrain-like broadening in the sense that the peak width increases with the magnitude of the diffraction vector. However, the dependence of compositional broadening on the orientation of diffraction vector (i.e. the anisotropic nature of this effect) differs very much from other types of strain broadening (e.g. from that caused by dislocations). The anisotropic line broadening caused by composition fluctuation is parameterized for different crystal systems and incorporated into the evaluation procedures of peak profiles. This chapter shows that the composition probability distribution function can be determined from the moments of the experimental line profiles using the Edgeworth series. The concentration fluctuations in decomposed solid solutions can also be determined from the intensity distribution in the splitted diffraction peaks.

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