The radio jet in 3C120 at very long baseline interferometry and Very Large Array scales

1986 ◽  
Vol 64 (4) ◽  
pp. 452-455 ◽  
Author(s):  
R. C. Walker
Keyword(s):  
Power Law ◽  
Unit Length ◽  
Minimum Energy ◽  
Physical Parameters ◽  
Very Large Array ◽  
The Core ◽  
Long Baseline ◽  
Wide Range ◽  
Order Of Magnitude ◽  
Power Law Function

The radio jet and lobes of 3C 120 have been mapped on scales from 1 pc to over 400 kpc. The observations show that the jet is continuous from the parsec scales, where superluminal motions are seen, to over 100 kpc. The wide range of scales observed allows an underlying power-law function of central-jet brightness vs. distance from the core to be distinguished from order-of-magnitude local-brightness fluctuations. The power law has an index of about −2.2 (preliminary result). Following the usual minimum-energy assumptions, we find this index gives an energy per unit length of the jet that is nearly constant and a magnetic field that scales with the inverse of the core distance. It appears that the basic physical parameters of the jet are established on subparsec scales, where there are relativistic motions, and evolve in a simple manner for over five orders of magnitude in distance from the core.

Effect of Melting on Mixed Convection Heat and Mass Transfer in a Non-Newtonian Fluid Saturated Non-Darcy Porous Medium

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
R. R. Kairi ◽  
P. V. S. N. Murthy
Keyword(s):  
Mass Transfer ◽  
Porous Medium ◽  
Mixed Convection ◽  
Heat And Mass Transfer ◽  
Newtonian Fluid ◽  
Power Law ◽  
Soret Effect ◽  
Physical Parameters ◽  
Convection Heat ◽  
Wide Range

In this paper, we investigate the influence of melting on mixed convection heat and mass transfer from vertical flat plate in a non-Newtonian fluid-saturated non-Darcy porous medium including the prominent Soret effect. The wall and the ambient medium are maintained at constant but different levels of temperature and concentration such that the heat and mass transfer occurs from the wall to the medium. The Ostwald–de Waele power law model is used to characterize the non-Newtonian fluid behavior. A similarity solution for the transformed governing equations is obtained. The numerical computation is carried out for various values of the nondimensional physical parameters. The variation of temperature, concentration, and heat and mass transfer coefficients with the power law index, mixed convection parameter, inertia parameter, melting parameter, Soret number, buoyancy ratio, and Lewis number is discussed for a wide range of values of these parameters.

scholarly journals Coalescence of Molecular Filaments

2020 ◽  
Author(s):  
Nanda Kumar ◽  
Doris Arzoumanian ◽  
Alexander Men'shchikov ◽  
Pedro Palmeirim ◽  
Shu-Ichiro Inutsuka
Keyword(s):  
Surface Density ◽  
Unit Length ◽  
Radial Profile ◽  
Equal Mass ◽  
Star Forming ◽  
Filament System ◽  
Density Maps ◽  
Wide Range ◽  
Diffuse Cloud ◽  
Order Of Magnitude

Abstract Star-forming molecular filaments are found to display a spectrum of line-masses (mass per unit length)1. This spectrum is thought to influence key observational parameters of star formation2 including the core and stellar initial mass function1. The exact mechanism producing the wide-range of line-masses is unknown, even though, higher surface densities are often observed at the intersection of filaments in hub-filament systems3. Here we show that cascades of lower density filaments coalescing to form higher density filaments and eventually hubs. By performing a multi-scale decomposition of surface density maps of the MonR2 star-forming region, which displays a spiral-shaped hub-filament system4, the coalescence effect is detected in two consecutive cascading steps (the surface density jumps by an order of magnitude at each step) before merging at the central hub which is found to be a dense network of short high-density filaments (as opposed to its view as a massive clump). The radial density structure of the dense-gas component of the hub-filament system shows a power-law dependence of NH2 ∝ r−2 over the scale of ∼5 pc, a feature previously found only at scales of 0.1 pc in star-forming cores5. It appears that the hub-filament system is mimicking the radial profile of an isothermal sphere, at parsec scales, a feature not known until now. This behavior is not seen for the diffuse cloud (NH2 ∝ r−0.5) which holds nearly equal mass. The filamentary nature of the hub implies that only some (embedded in the filaments), and not all, stellar seeds within the hub can become massive stars.

Computational Modeling of Enhanced Laminar Flow Heat Transfer in Viscoplastic Fluids in Corrugated-Plate Channels

2002 ◽  
Author(s):  
Hossam M. Metwally ◽  
Raj M. Manglik
Keyword(s):  
Heat Transfer ◽  
Yield Stress ◽  
Power Law ◽  
Flow Behavior ◽  
Shear Thinning ◽  
Bingham Plastic ◽  
Wide Range ◽  
Order Of Magnitude ◽  
Colburn Factor ◽  
Power Law Index

The enhanced heat transfer in laminar viscoplastic, shear thinning, Herschel-Bulkley fluid flows in sinusoidal corrugated-plate channels is investigated. With uniform-temperature plate walls, periodically developed flows are considered for a wide range of flow rates (10 ≤ Reg ≤ 700) and pseudoplastic flow behavior indices (n = 0.54, 0.8, and 1.0; the latter representing a Bingham plastic). The effects of fluid yield stress are simulated for the case where τy = 1.59 N/m2, representing a 0.5% xantham gum aqueous solution. Typical velocity and temperature distributions, along with extended results for isothermal friction factor ƒ and Colburn factor j are presented. The effect of the yield stress is found to be most dominant at low Reg regardless of the power law index n, and the recirculation or swirl in the wall trough regions is weaker than in the cases of Newtonian and power-law liquids. At higher Reg, the performance of the Herschel-Bulkley fluid asymptotically approaches that of the non-yield-stress power-law fluid. At low Reg, the yield stress increases ƒ by an order of magnitude and j is enhanced because of the higher wall gradients imposed by the plug-like flow field. The relative heat transfer enhancement, represented by the ratio (j/ƒ), and the role of the fluid yield stress and shear-thinning (or pseudoplastic) behaviors are also discussed.

scholarly journals Why Do Precipitation Intensities Tend to Follow Gamma Distributions?

2019 ◽  
Vol 76 (11) ◽  
pp. 3611-3631 ◽  
Author(s):  
Cristian Martinez-Villalobos ◽  
J. David Neelin
Keyword(s):  
Power Law ◽  
Daily Precipitation ◽  
Present Theory ◽  
Physical Parameters ◽  
Precipitation Distribution ◽  
Climate Conditions ◽  
Gamma Distributions ◽  
Wide Range ◽  
Distribution Shifts ◽  
Averaging Time

Abstract The probability distribution of daily precipitation intensities, especially the probability of extremes, impacts a wide range of applications. In most regions this distribution decays slowly with size at first, approximately as a power law with an exponent between 0 and −1, and then more sharply, for values larger than a characteristic cutoff scale. This cutoff is important because it limits the probability of extreme daily precipitation occurrences in current climate. There is a long history of representing daily precipitation using a gamma distribution—here we present theory for how daily precipitation distributions get their shape. Processes shaping daily precipitation distributions can be separated into nonprecipitating and precipitating regime effects, the former partially controlling how many times in a day it rains, and the latter set by single-storm accumulations. Using previously developed theory for precipitation accumulation distributions—which follow a sharper power-law range (exponent < −1) with a physically derived cutoff for large sizes—analytical expressions for daily precipitation distribution power-law exponent and cutoff are calculated as a function of key physical parameters. Precipitating and nonprecipitating regime processes both contribute to reducing the power-law range exponent for the daily precipitation distribution relative to the fundamental exponent set by accumulations. The daily precipitation distribution cutoff is set by the precipitating regime and scales with moisture availability, with important consequences for future distribution shifts under global warming. Similar results extend to different averaging periods, providing insight into how the precipitation intensity distribution evolves as a function of both underlying physical climate conditions and averaging time.

Magnetic Fields in the Relativistic Jets of Active Galactic Nuclei

2018 ◽  
Vol 14 (S342) ◽  
pp. 189-196
Author(s):  
Denise C. Gabuzda
Keyword(s):  
Active Galactic Nuclei ◽  
Very Long Baseline Interferometry ◽  
Galactic Nuclei ◽  
Outward Current ◽  
Relativistic Jets ◽  
Local Effects ◽  
Very Large Array ◽  
Long Baseline ◽  
Wide Range ◽  
Jet Axis

AbstractAn abundance of information about the magnetic (B) fields of relativistic AGN jets has been obtained through radio polarization observations made on a wide range of scales, from the parsec scales probed by Very Long Baseline Interferometry to the kiloparsec scales probed by instruments such as the the Jansky Very Large Array and e-MERLIN. The observed radio emission is synchrotron radiation, for which the linear polarization angles in optically thin regions is orthogonal to the local synchrotron B fields. The characteristic B field structures observed for these jets on parsec scales are described. A key question is whether B field structures observed in particular AGN jets come about primarily due to “global” effects such as the intrinsic B field of the jet itself, which is expected to be helical, or local phenomena such as shocks, shear and bending of the jets. Observational criteria that can be used to try to distinguish between various possible origins for observed B field structures are described. There is now considerable evidence that the relativistic jets of AGNs do indeed carry helical B fields, with the observed polarization also sometimes appreciably influenced by local effects. Patterns seen in the helical B field components, indicated for example by Faraday rotation observations, provide unique information about the processes involved in the generation of these helical B fields. The collected observations on parsec and kiloparsec scales provide weighty evidence that an important role is played by the action of a cosmic “battery” that acts to generate an inward current along the jet axis and an outward current in a more extended region surrounding the jet.

RANGE-ENERGY RELATIONS FOR LIGHT NUCLEI IN AIR AND NUCLEAR EMULSION

1956 ◽  
Vol 34 (2) ◽  
pp. 203-215 ◽  
Author(s):  
D. L. Livesey
Keyword(s):  
Experimental Data ◽  
Power Law ◽  
Experimental Error ◽  
Nuclear Emulsion ◽  
Empirical Method ◽  
Light Nuclei ◽  
Stopping Power ◽  
Wide Range ◽  
Power Law Function ◽  
Energy Relations

An empirical method has been developed for estimating the effective charge of ions between Z = 3 and Z = 10 over a wide range of velocities in air and nuclear emulsion. The results are used in conjunction with a power-law function for the variation of stopping-power with velocity to derive range–energy relations for these ions. The curves are compared with all available experimental data, and agreement within the limits of experimental error is obtained in all cases except those of fluorine and neon ions in air.

scholarly journals Determination of physical parameters of particle-accelerating colliding-wind binaries based on generalized partition considerations

2018 ◽  
Vol 620 ◽  
pp. A144 ◽  
Author(s):  
M. De Becker
Keyword(s):  
Minimum Energy ◽  
High Energy ◽  
Critical Discussion ◽  
Local Magnetic Field ◽  
Physical Parameters ◽  
Relativistic Electrons ◽  
Thermal Physics ◽  
Long Period ◽  
Wide Range

The sub-set of massive binaries known to accelerate particles, the so-called category of particle-accelerating colliding-wind binaries (PACWBs), constitutes a valuable laboratory for investigating the non-thermal physics in stellar environments. In particular, their synchrotron emitter status allows us to derive some basic properties of their population of relativistic electrons. In this paper, considerations about energy partitions (not restricted to equipartition or minimum energy) are developed to derive relevant physical parameters of PACWBs in an appropriate assumption context. This approach was applied to three PACWBs with known stellar wind and orbital parameters, along with rather well-known radio properties. For long-period systems, a local magnetic field of the order of 0.1–10 mG was determined for a wide range of assumptions on partition parameters, while values of a few G are obtained for the shorter period system we investigated. Normalization parameters of the relativistic electron populations were also determined. Synchrotron self-absorption appears to be an unlikely turn-over process for long-period systems, while it may compete with free-free absorption for a shorter period object. Our results are discussed in the context of the energy budget of non-thermal processes in PACWBs, and prospects for high energy emission are also addressed. The sensitivity of this approach, applied for the first time to PACWBs, was also investigated through a critical discussion of the dependence of determined physical quantities on adopted and assumed parameters. Even though this method is certainly not adequate to reproduce the physics of PACWBs in detail, it offers the advantage of allowing for the determination of valuable average quantities provided a few fundamental parameters and measurements are known, without the need of any detailed hydrodynamic and radiative modelling. In the absence of any relevant measurement of non-thermal radiation in the high-energy domain, the method presented here constitutes the most straightforward and accessible approach to date to discuss physical parameters that are relevant for the non-thermal physics of PACWBs.

scholarly journals Parsec-scale properties of the radio brightest jetted AGN at z > 6

2020 ◽  
Vol 643 ◽  
pp. L12
Author(s):  
C. Spingola ◽  
D. Dallacasa ◽  
S. Belladitta ◽  
A. Caccianiga ◽  
M. Giroletti ◽  
...  
Keyword(s):  
Lorentz Factor ◽  
Physical Parameters ◽  
Viewing Angle ◽  
Microwave Background ◽  
Very Large Array ◽  
X Ray ◽  
Inverse Compton Scattering ◽  
Long Baseline ◽  
Scale Properties ◽  
Very Long Baseline Array

We present Director’s Discretionary Time multi-frequency observations obtained with the Jansky Very Large Array and the Very Long Baseline Array (VLBA) of the blazar PSO J030947.49+271757.31 (hereafter PSO J0309+27) at z = 6.10 ± 0.03. The milliarcsecond angular resolution of our VLBA observations at 1.5, 5, and 8.4 GHz unveils a bright one-sided jet extended for ∼500 parsecs in projection. This high-z radio-loud active galactic nucleus is resolved into multiple compact sub-components that are embedded in a more diffuse and faint radio emission that enshrouds them in a continuous jet structure. We directly derive limits on some physical parameters from observable quantities such as viewing angle and Lorentz and Doppler factors. If PSO J0309+27 is a genuine blazar, as suggested by its X-ray properties, then we find that its bulk Lorentz factor must be relatively low (lower than 5). This value would be in favour of a scenario currently proposed to reconcile the paucity of high-z blazars with current predictions. Nevertheless, we cannot exclude that PSO J0309+27 is seen under a larger viewing angle, which would imply that the X-ray emission must be enhanced, for example, by inverse Compton scattering with the cosmic microwave background. More stringent constraints on the bulk Lorentz factor in PSO J0309+27 and on these factors in the other high-z blazars are necessary to test whether their properties are intrinsically different from those of the low-z blazar population.

Duoethnography: A Polytheoretical Approach to (Re)Storing, (Re)Storying the Meanings That One Gives

2020 ◽  
pp. 396-423
Author(s):  
John Joseph Norris ◽  
Richard D. Sawyer
Keyword(s):  
Social Justice ◽  
Critical Theory ◽  
Third Space ◽  
The Third ◽  
The Core ◽  
Wide Range ◽  
Core Elements ◽  
Feminist Inquiry

This chapter summarizes the advancement of duoethnography throughout its fifteen-year history, employing examples from a variety of topics in education and social justice to provide a wide range of approaches that one may take when conducting a duoethnography. A checklist articulates what its cofounders consider the core elements of duoethnographies, additional features that may or may not be employed and how some studies purporting to be duoethnographies may not be so. The chapter indicates connections between duoethnography and a number of methodological concepts including the third space, the problematics of representation, feminist inquiry, and critical theory using published examples by several duoethnographers.

Static and dynamic response of sandwich beams with lattice and pantographic cores

2021 ◽  
pp. 109963622110338
Author(s):  
Yury Solyaev ◽  
Arseniy Babaytsev ◽  
Anastasia Ustenko ◽  
Andrey Ripetskiy ◽  
Alexander Volkov
Keyword(s):  
Mechanical Performance ◽  
Lattice Structure ◽  
Unit Length ◽  
Experimental Tests ◽  
Plane Geometry ◽  
Sandwich Beams ◽  
Static Tests ◽  
Three Point Bending ◽  
The Core ◽  
The Impact

Mechanical performance of 3d-printed polyamide sandwich beams with different type of the lattice cores is investigated. Four variants of the beams are considered, which differ in the type of connections between the elements in the lattice structure of the core. We consider the pantographic-type lattices formed by the two families of inclined beams placed with small offset and connected by stiff joints (variant 1), by hinges (variant 2) and made without joints (variant 3). The fourth type of the core has the standard plane geometry formed by the intersected beams lying in the same plane (variant 4). Experimental tests were performed for the localized indentation loading according to the three-point bending scheme with small span-to-thickness ratio. From the experiments we found that the plane geometry of variant 4 has the highest rigidity and the highest load bearing capacity in the static tests. However, other three variants of the pantographic-type cores (1–3) demonstrate the better performance under the impact loading. The impact strength of such structures are in 3.5–5 times higher than those one of variant 4 with almost the same mass per unit length. This result is validated by using numerical simulations and explained by the decrease of the stress concentration and the stress state triaxiality and also by the delocalization effects that arise in the pantographic-type cores.

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