scholarly journals Effect of thermal flux inhibition on the coupling of core with hot corona in a laser irradiated plasma pellet

1989 ◽  
Vol 7 (1) ◽  
pp. 111-117 ◽  
Author(s):  
D. P. Singh ◽  
J. J. E. Herrera ◽  
M. Vaselli
Keyword(s):  
Thermal Flux ◽  
Laser Wavelength ◽  
Hot Electron ◽  
Flux Transport ◽  
The Core ◽  
Flux Limit ◽  
Plasma Ablation ◽  
Analytic Expressions ◽  
Order Of Magnitude ◽  
Hot Corona

The effect of thermal flux transport inhibition on the coupling of the spherical dense pellet core with the hot electron halo produced at the plasma resonance layer has been investigated. The analytic expressions for the core-corona coupling and the optimum temperature of the overlapping region (at which this coupling is maximum) have been derived as a function of ‘flux limit’ parameter and the laser wavelength. Relevant calculations indicate that the core-corona coupling is sensitive to the mean electron temperature and the scaling of its maximum value with the laser wavelength remains absolutely unaffected by plasma ablation. The subsequent results on laser wavelength scaling are compared and contrasted with the predictions of other investigations. The heat transfer from the hot electron cloud to the dense core can be increased by an order of magnitude in case of the uninhibited flux.

scholarly journals Thermal effects of hot electron halo in a laser-imploded Z-layered plasma pellet

1990 ◽  
Vol 8 (3) ◽  
pp. 421-426
Author(s):  
V. Palleschi ◽  
D. P. Singh ◽  
M. A. Harith ◽  
M. Vaselli
Keyword(s):  
Electron Temperature ◽  
Coupling Efficiency ◽  
Mean Free Path ◽  
Positive Influence ◽  
Laser Wavelength ◽  
Critical Surface ◽  
Hot Electron ◽  
The Core ◽  
Electron Mean Free Path ◽  
Hot Corona

Coupling of the core with the surrounding corona of hot electrons produced around the plasma critical surface in a spherically symmetric laser-imploded Z-layered plasma target has been analyzed. Considering that the energy equipartition exists between the cold electrons of the core and the hot coronal electrons in the core–corona overlapping region, the analytic expression for core–corona coupling has been derived. The efficiency of heat transfer from the hot corona to the cold core depends on the laser wavelength, mean electron temperature in the ablation region, and the width of the Z-layer in the plasma pellet. Numerical results indicate that short wavelength lasers are favorable for efficient heating of the core by the surrounding hot corona. The core-corona coupling increases primarily with the mean electron temperature up to a certain extent and beyond that further laser flux transfer to the hot corona results in decoupling of the core from the corona. The presence of Z-layer is likely to reduce the electron mean free path in the ablation region and affects the laser wavelength scaling of the core-corona coupling. It is also found to have positive influence on the maximum coupling efficiency of the core with the hot corona.

scholarly journals Hydrodynamics of supercritical region in laser ablated plasmas

1989 ◽  
Vol 7 (3) ◽  
pp. 589-595
Author(s):  
M. Vaselli ◽  
V. Palleschi ◽  
D. P. Singh
Keyword(s):  
Numerical Range ◽  
Thermal Flux ◽  
Plasma Temperature ◽  
Emission Spectra ◽  
Spherical Geometry ◽  
X Rays ◽  
Flux Limit ◽  
Plasma Density Profile ◽  
Plasma Ablation ◽  
Order Of Magnitude

The laser ablated plasma flow and subsequent plasma density profile in steep plasma temperature gradient in spherical geometry are studied. Using local flux-limited model of heat flow the effect of flux-inhibition on the hydrodynamics of plasma ablation zone is investigated. The radial variation of thermal flux through local flux-limited model with recently accepted numerical range of flux-limit ≈ 10% of the free streaming is in close agreement with Spitzer's classical thermal conduction reduced by about an order of magnitude which may be attributed to the presence of megagauss level self-generated magnetic fields as predicted earlier to interpret experimental observations on X-rays emission spectra.

Influence of Hot Electron Scattering and Electron–Phonon Interactions on Thermal Boundary Conductance at Metal/Nonmetal Interfaces

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
Ashutosh Giri ◽  
Brian M. Foley ◽  
Patrick E. Hopkins
Keyword(s):  
Phonon Scattering ◽  
Energy Levels ◽  
Golden Rule ◽  
Energy Coupling ◽  
Hot Electron ◽  
Nonequilibrium Electron ◽  
Simplified Approach ◽  
Thermal Boundary Conductance ◽  
Order Of Magnitude ◽  
Unique Mechanism

It has recently been demonstrated that under certain conditions of electron nonequilibrium, electron to substrate energy coupling could represent a unique mechanism to enhance heat flow across interfaces. In this work, we present a coupled thermodynamic and quantum mechanical derivation of electron–phonon scattering at free electron metal/nonmetal substrate interfaces. A simplified approach to the Fermi's Golden Rule with electron energy transitions between only three energy levels is adopted to derive an electron–phonon diffuse mismatch model, that account for the electron–phonon thermal boundary conductance at metal/insulator interfaces increases with electron temperature. Our approach demonstrates that the metal-electron/nonmetal phonon conductance at interfaces can be an order of magnitude larger than purely phonon driven processes when the electrons are driven out of equilibrium with the phonons, consistent with recent experimental observations.

scholarly journals Megaparsec-scale structure around the protocluster core SPT2349–56 at z = 4.3

2020 ◽  
Vol 495 (3) ◽  
pp. 3124-3159 ◽  
Author(s):  
Ryley Hill ◽  
Scott Chapman ◽  
Douglas Scott ◽  
Yordanka Apostolovski ◽  
Manuel Aravena ◽  
...  
Keyword(s):  
Luminosity Function ◽  
Far Infrared ◽  
Main Structure ◽  
Star Forming ◽  
Galaxy Groups ◽  
The Core ◽  
Order Of Magnitude ◽  
Number Counts ◽  
Limited Coverage

ABSTRACT We present an extensive ALMA spectroscopic follow-up programme of the $z\, {=}\, 4.3$ structure SPT2349–56, one of the most actively star-forming protocluster cores known, to identify additional members using their [C ii] 158 μm and CO(4–3) lines. In addition to robustly detecting the 14 previously published galaxies in this structure, we identify a further 15 associated galaxies at $z\, {=}\, 4.3$, resolving 55$\, {\pm }\,$5 per cent of the 870 μm flux density at 0.5 arcsec resolution compared to 21 arcsec single-dish data. These galaxies are distributed into a central core containing 23 galaxies extending out to 300 kpc in diameter, and a northern extension, offset from the core by 400 kpc, containing three galaxies. We discovered three additional galaxies in a red Herschel-SPIRE source 1.5 Mpc from the main structure, suggesting the existence of many other sources at the same redshift as SPT2349–56 that are not yet detected in the limited coverage of our data. An analysis of the velocity distribution of the central galaxies indicates that this region may be virialized with a mass of (9$\pm 5)\, {\times }\, 10^{12}$  M⊙, while the two offset galaxy groups are about 30 and 60 per cent less massive and show significant velocity offsets from the central group. We calculate the [C ii] and far-infrared number counts, and find evidence for a break in the [C ii] luminosity function. We estimate the average SFR density within the region of SPT2349–56 containing single-dish emission (a proper diameter of 720 kpc), assuming spherical symmetry, to be roughly 4$\, {\times }\, 10^4$ M⊙ yr−1 Mpc−3; this may be an order of magnitude greater than the most extreme examples seen in simulations.

scholarly journals GRID-SITES: Gridded Solar Iterative Temperature Emission Solver for Fast DEM Inversion

Solar Physics ◽  
2019 ◽  
Vol 294 (10) ◽  
Author(s):  
James Pickering ◽  
Huw Morgan
Keyword(s):  
Emission Measure ◽  
Inversion Method ◽  
Multiple Channels ◽  
Differential Emission Measure ◽  
The Core ◽  
Data Inversion ◽  
Core Method ◽  
Input Dataset ◽  
Order Of Magnitude ◽  
General Measurement

Abstract The increasing size of solar datasets demands highly efficient and robust analysis methods. This paper presents an approach that can increase the computational efficiency of differential emission measure (DEM) inversions by an order of magnitude or higher, with the efficiency factor increasing with the size of the input dataset. The method, named the Gridded Solar Iterative Temperature Emission Solver (Grid-SITES) is based on grouping pixels according to the similarity of their intensities in multiple channels, and solving for one DEM per group. This is shown to be a valid approach, given a sufficiently high number of grid bins for each channel. The increase in uncertainty arising from the quantisation of the input data is small compared to the general measurement and calibration uncertainties. In this paper, we use the Solar Iterative Temperature Emission Solver (SITES) as the core method for the DEM inversion, although Grid-SITES provides a general framework which may be used with any DEM inversion method, or indeed any large multi-dimensional data inversion problem. The method is particularly efficient for processing larger images, offering a factor of 30 increase in speed for a 10 megapixel image. For a time series of observations, the gridded results can be passed sequentially to each new image, with new populated bins added as required. This process leads to increasing efficiency with each new image, with potential for a ${\approx\,}100$≈100 increase in efficiency dependent on the size of the images.

High Rayleigh number thermal convection in a shallow laterally heated cavity

1993 ◽  
Vol 440 (1909) ◽  
pp. 273-289 ◽  
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Rayleigh Number ◽  
Hadley Circulation ◽  
Large Contribution ◽  
The Core ◽  
Vertical Boundary ◽  
Order Of Magnitude ◽  
End Wall ◽  
Lateral Heat

The flow near the end of a shallow laterally heated cavity enters a nonlinear convective régime when the Rayleigh number R , based on cavity height, is of the same order of magnitude as the aspect ratio L (length/height). In the present work the asymptotic structure of the flow that develops in the limit as is R/L →∞ considered for the case where the horizontal surfaces of the cavity are thermally insulated. A model is discussed in which the formation of a vertical boundary layer on the end wall involves an unexpectedly large contribution to the local ambient temperature field. Expulsion of fluid from the base of the layer, and its subsequent return to the core through a horizontal boundary layer, maintains the necessary lateral heat transfer in the cavity. Implications of the model for the flow throughout the cavity are also discussed. The evolution of the end-zones leads to a change in the amplitude of the main Hadley circulation when R = O ( L 12/7 ). Various properties of the solution for this new régime are determined, including the Nusselt number for the lateral heat transfer, which is found to be proportional to L 3/7 . A comparison is made with both numerical and experimental results.

Identification of preferential flow effects on hydraulic conductivity measurements using a fluorescent tracer

2000 ◽  
Vol 37 (2) ◽  
pp. 479-484
Author(s):  
Tom A Al ◽  
David W Blowes
Keyword(s):  
Hydraulic Conductivity ◽  
Measurement Errors ◽  
Preferential Flow ◽  
Conductivity Measurements ◽  
Fine Grained ◽  
The Core ◽  
Core Samples ◽  
Dye Tracer ◽  
Order Of Magnitude ◽  
Constant Head

Core samples were collected from fractured and unfractured zones within fine-grained, unconsolidated mine tailings. The hydraulic conductivity of the core samples was measured in a constant-head permeameter. A fluorescent dye tracer was added to the constant-head reservoir in the permeameter. The tests were run for approximately 48 h, then the cores were sectioned to observe the distribution of dye. Flow through the fractures results in hydraulic conductivity measurements up to one order of magnitude greater than that of unfractured tailings. Observations of the dye distribution in samples following permeameter measurements are used to identify cases where preferential flow in fractures has influenced the hydraulic conductivity measurements. The dye tracer distribution also indicates where measurement errors may be suspected due to flow leakage around the core sample.Key words: tracers, hydraulic conductivity, fractures, tailings.

scholarly journals Differential and enhanced response to climate forcing in diarrheal disease due to rotavirus across a megacity of the developing world

2016 ◽  
Vol 113 (15) ◽  
pp. 4092-4097 ◽  
Author(s):  
Pamela P. Martinez ◽  
Aaron A. King ◽  
Mohammad Yunus ◽  
A. S. G. Faruque ◽  
Mercedes Pascual
Keyword(s):  
Rural Areas ◽  
Disease Surveillance ◽  
Developing World ◽  
Diarrheal Disease ◽  
Monsoon Season ◽  
Climate Forcing ◽  
Force Of Infection ◽  
The Core ◽  
Order Of Magnitude ◽  
Endemic Transmission

The role of climate forcing in the population dynamics of infectious diseases has typically been revealed via retrospective analyses of incidence records aggregated across space and, in particular, over whole cities. Here, we focus on the transmission dynamics of rotavirus, the main diarrheal disease in infants and young children, within the megacity of Dhaka, Bangladesh. We identify two zones, the densely urbanized core and the more rural periphery, that respond differentially to flooding. Moreover, disease seasonality differs substantially between these regions, spanning variation comparable to the variation from tropical to temperate regions. By combining process-based models with an extensive disease surveillance record, we show that the response to climate forcing is mainly seasonal in the core, where a more endemic transmission resulting from an asymptomatic reservoir facilitates the response to the monsoons. The force of infection in this monsoon peak can be an order of magnitude larger than the force of infection in the more epidemic periphery, which exhibits little or no postmonsoon outbreak in a pattern typical of nearby rural areas. A typically smaller peak during the monsoon season nevertheless shows sensitivity to interannual variability in flooding. High human density in the core is one explanation for enhanced transmission during troughs and an associated seasonal monsoon response in this diarrheal disease, which unlike cholera, has not been widely viewed as climate-sensitive. Spatial demographic, socioeconomic, and environmental heterogeneity can create reservoirs of infection and enhance the sensitivity of disease systems to climate forcing, especially in the populated cities of the developing world.

Motivating Game-Based Learning Efforts in Higher Education

2015 ◽  
Vol 13 (2) ◽  
pp. 54-72 ◽  
Author(s):  
Gina Moylan ◽  
Ann W. Burgess ◽  
Charles Figley ◽  
Michael Bernstein
Keyword(s):  
Higher Education ◽  
Serious Games ◽  
Core Curriculum ◽  
Game Based Learning ◽  
The Core ◽  
Current State ◽  
Considerable Research ◽  
Order Of Magnitude ◽  
K 12 ◽  
Academic Content

Though there is considerable research to support using Game-Based Learning (GBL) in higher education, its implementation is lagging behind K-12 education by an order of magnitude. By considering the current state of GBL from leadership, primary consumer, academic and technical perspectives, the authors frame the main issues involved with successfully implementing these efforts. These issues involve obtaining the resources required to make mature serious games that are similar in presentation, functionality and effectiveness to the commercial-based products so widely used today, while ensuring that they are imbued with academic content worthy of college curricula. After motivating a compelling case for GBL, despite a number of constraints and difficulties, the authors present two higher education efforts that are designed to augment the core curriculum for undergraduate and graduate level courses associated with the field of Trauma—a field enhanced by virtual efforts due to its challenging subject matter.

scholarly journals A centrally concentrated sub-solar-mass starless core in the Taurus L1495 filamentary complex

2019 ◽  
Vol 71 (4) ◽  
Author(s):  
Kazuki Tokuda ◽  
Kengo Tachihara ◽  
Kazuya Saigo ◽  
Phillipe André ◽  
Yosuke Miyamoto ◽  
...  
Keyword(s):  
Star Formation ◽  
Initial Conditions ◽  
Volume Density ◽  
Mass Star ◽  
Brown Dwarf ◽  
Solar Mass ◽  
Star Forming ◽  
The Core ◽  
Order Of Magnitude ◽  
Low Mass

Abstract The formation scenario of brown dwarfs is still unclear because observational studies to investigate its initial condition are quite limited. Our systematic survey of nearby low-mass star-forming regions using the Atacama Compact Array (aka the Morita array) and the IRAM 30-m telescope in 1.2 mm continuum has identified a centrally concentrated starless condensation with a central H2 volume density of ∼106 cm−3, MC5-N, connected to a narrow (width ∼0.03 pc) filamentary cloud in the Taurus L1495 region. The mass of the core is $\sim {0.2\!-\!0.4}\, M_{\odot }$, which is an order of magnitude smaller than typical low-mass pre-stellar cores. Taking into account a typical core to star formation efficiency for pre-stellar cores (∼20%–40%) in nearby molecular clouds, brown dwarf(s) or very low-mass star(s) may be going to be formed in this core. We have found possible substructures at the high-density portion of the core, although much higher angular resolution observation is needed to clearly confirm them. The subsequent N2H+ and N2D+ observations using the Nobeyama 45-m telescope have confirmed the high-deuterium fractionation (∼30%). These dynamically and chemically evolved features indicate that this core is on the verge of proto-brown dwarf or very low-mass star formation and is an ideal source to investigate the initial conditions of such low-mass objects via gravitational collapse and/or fragmentation of the filamentary cloud complex.

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