scholarly journals Time Variability of Accretion Flows: Effects of the Adiabatic Index and Gas Temperature

2008 ◽  
Vol 679 (1) ◽  
pp. 626-638 ◽  
Author(s):  
Monika Moscibrodzka ◽  
Daniel Proga
Keyword(s):  
Adiabatic Index ◽  
Time Variability ◽  
Gas Temperature ◽  
Accretion Flows

scholarly journals Decomposing the internal faraday rotation of black hole accretion flows

2020 ◽  
Vol 498 (4) ◽  
pp. 5468-5488
Author(s):  
Angelo Ricarte ◽  
Ben S Prather ◽  
George N Wong ◽  
Ramesh Narayan ◽  
Charles Gammie ◽  
...  
Keyword(s):  
Event Horizon ◽  
Faraday Rotation ◽  
Polarization Plane ◽  
Time Variability ◽  
Accretion Flows ◽  
Spatially Resolved ◽  
Rotation Measure ◽  
Linearly Polarized ◽  
General Relativistic ◽  
Sgr A

ABSTRACT Faraday rotation has been seen at millimeter wavelengths in several low-luminosity active galactic nuclei, including Event Horizon Telescope (EHT) targets M87* and Sgr A*. The observed rotation measure (RM) probes the density, magnetic field, and temperature of material integrated along the line of sight. To better understand how accretion disc conditions are reflected in the RM, we perform polarized radiative transfer calculations using a set of general relativistic magnetohydrodynamic (GRMHD) simulations appropriate for M87*. We find that in spatially resolved millimetre wavelength images on event horizon scales, the RM can vary by orders of magnitude and even flip sign. The observational consequences of this spatial structure include significant time-variability, sign-flips, and non-λ2 evolution of the polarization plane. For some models, we find that internal RM can cause significant bandwidth depolarization even across the relatively narrow fractional bandwidths observed by the EHT. We decompose the linearly polarized emission in these models based on their RM and find that emission in front of the mid-plane can exhibit orders of magnitude less Faraday rotation than emission originating from behind the mid-plane or within the photon ring. We confirm that the spatially unresolved (i.e. image integrated) RM is a poor predictor of the accretion rate, with substantial scatter stemming from time variability and inclination effects. Models can be constrained with repeated observations to characterize time variability and the degree of non-λ2 evolution of the polarization plane.

scholarly journals TIME EVOLUTION OF THE THREE-DIMENSIONAL ACCRETION FLOWS: EFFECTS OF THE ADIABATIC INDEX AND OUTER BOUNDARY CONDITION

2009 ◽  
Vol 705 (2) ◽  
pp. 1503-1521 ◽  
Author(s):  
Agnieszka Janiuk ◽  
Maciej Sznajder ◽  
Monika Mościbrodzka ◽  
Daniel Proga
Keyword(s):  
Boundary Condition ◽  
Time Evolution ◽  
Outer Boundary ◽  
Three Dimensional ◽  
Adiabatic Index ◽  
Accretion Flows

Neuroticism and Speed-Accuracy Tradeoff in Self-Paced Speeded Mental Addition and Comparison

2010 ◽  
Vol 31 (3) ◽  
pp. 130-137 ◽  
Author(s):  
Hagen C. Flehmig ◽  
Michael B. Steinborn ◽  
Karl Westhoff ◽  
Robert Langner
Keyword(s):  
Reaction Time ◽  
Response Speed ◽  
Time Variability ◽  
Reaction Time Variability ◽  
Comparison Task ◽  
Processing Efficiency ◽  
Mental Addition ◽  
Speed Accuracy ◽  
The Relationship ◽  
Accuracy Tradeoff

Previous research suggests a relationship between neuroticism (N) and the speed-accuracy tradeoff in speeded performance: High-N individuals were observed performing less efficiently than low-N individuals and compensatorily overemphasizing response speed at the expense of accuracy. This study examined N-related performance differences in the serial mental addition and comparison task (SMACT) in 99 individuals, comparing several performance measures (i.e., response speed, accuracy, and variability), retest reliability, and practice effects. N was negatively correlated with mean reaction time but positively correlated with error percentage, indicating that high-N individuals tended to be faster but less accurate in their performance than low-N individuals. The strengthening of the relationship after practice demonstrated the reliability of the findings. There was, however, no relationship between N and distractibility (assessed via measures of reaction time variability). Our main findings are in line with the processing efficiency theory, extending the relationship between N and working style to sustained self-paced speeded mental addition.

Recovering waste energy of the combined gas turbine system using paraffin melting

2020 ◽  
Vol 14 (4) ◽  
pp. 7481-7497
Author(s):  
Yousef Najjar ◽  
Abdelrahman Irbai
Keyword(s):  
Melting Process ◽  
Payback Period ◽  
Energy Utilization ◽  
Raw Material ◽  
Heat Transfer Fluid ◽  
Layered System ◽  
Exhaust Gas ◽  
Gas Temperature ◽  
Power Cycle ◽  
Waste Energy

This work covers waste energy utilization of the combined power cycle by using it in the candle raw material (paraffin) melting process and an economic study for this process. After a partial utilization of the burned fuel energy in a real bottoming steam power generation, the exhaust gas contains 0.033 of the initially burned energy. This tail energy with about 128 ºC is partly driven in the heat exchanger of the paraffin melting system. Ansys-Fluent Software was used to study the paraffin wax melting process by using a layered system that utilizes an increased interface area between the heat transfer fluid (HTF) and the phase change material (PCM) to improve the paraffin melting process. The results indicate that using 47.35 kg/s, which is 5% of the entire exhaust gas (881.33 kg/s) from the exit of the combined power cycle, would be enough for producing 1100 tons per month, which corresponds to the production quantity by real candle's factories. Also, 63% of the LPG cost will be saved, and the payback period of the melting system is 2.4 years. Moreover, as the exhaust gas temperature increases, the consumed power and the payback period will decrease.

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