scholarly journals Passive detection of gamma ray shadows from small-scale soil surface anomalies

2009 ◽  
Vol 114 (B8) ◽  
Author(s):  
John Furey ◽  
Cliff Morgan ◽  
Morris Fields
Keyword(s):  
Gamma Ray ◽  
Soil Surface ◽  
Small Scale ◽  
Passive Detection ◽  
Small Scale Soil

scholarly journals Rare earth oxide tracking coupled with 3D soil surface modelling: an opportunity to study small-scale soil redistribution

2020 ◽  
Vol 20 (5) ◽  
pp. 2405-2417 ◽  
Author(s):  
Judit Alexandra Szabó ◽  
Csilla Király ◽  
Máté Karlik ◽  
Adrienn Tóth ◽  
Zoltán Szalai ◽  
...  
Keyword(s):  
Rare Earth ◽  
Soil Surface ◽  
Rare Earth Oxide ◽  
Small Scale ◽  
Surface Modelling ◽  
Soil Redistribution ◽  
Small Scale Soil

scholarly journals GAMMA RAYS FROM SMALL SCALE STRUCTURES ON LONG COSMIC STRINGS

1993 ◽  
Vol 02 (02) ◽  
pp. 183-195 ◽  
Author(s):  
M. MOHAZZAB ◽  
R. BRANDENBERGER
Keyword(s):  
Gamma Rays ◽  
Gamma Ray ◽  
Cosmic Strings ◽  
Unit Length ◽  
Formation Rate ◽  
Long Strings ◽  
Small Scale ◽  
Scale Structures ◽  
Cusp Formation ◽  
Small Scale Structures

The formation of cusps on long cosmic strings is discussed and the probability of cusp formation is estimated. The energy distribution of the gamma-ray background due to cusp annihilation on long strings is calculated and compared to observations. Under optimistic assumptions about the cusp formation rate, we find that strings with a mass per unit length μ less than Gμ=10−14 will have an observable effect. However, it is shown that the gamma-ray bursters cannot be attributed to long ordinary strings (or loops).

Mapping detailed soil property using small scale soil type maps and sparse typical samples

2013 ◽  
Vol 23 (6) ◽  
pp. 680-691 ◽  
Author(s):  
Shujie Zhang ◽  
Axing Zhu ◽  
Wenliang Liu ◽  
Jing Liu ◽  
Lin Yang
Keyword(s):  
Soil Type ◽  
Soil Property ◽  
Small Scale ◽  
Small Scale Soil

From a Large to a Small Scale Soil Map: Top-Down Against Bottom-Up Approaches

2008 ◽  
pp. 203-212
Author(s):  
F. Carré ◽  
H.I. Reuter ◽  
J. Daroussin ◽  
O. Scheurer
Keyword(s):  
Small Scale ◽  
Top Down ◽  
Bottom Up ◽  
Soil Map ◽  
Small Scale Soil

scholarly journals Laboratory development of a vertically oriented penetrometer for shallow seabed characterization

2016 ◽  
Vol 53 (1) ◽  
pp. 93-102 ◽  
Author(s):  
Fauzan Sahdi ◽  
David J. White ◽  
Christophe Gaudin ◽  
Mark F. Randolph ◽  
Noel Boylan
Keyword(s):  
Soil Surface ◽  
Site Investigation ◽  
Soil Strength ◽  
Small Scale ◽  
Soil Parameters ◽  
Embedment Depth ◽  
Fine Grained ◽  
Centrifuge Models ◽  
Measured Resistance ◽  
And Performance

Current site investigation practice for offshore pipeline design relies on soil parameters gathered from boreholes or in situ test soundings to depths of 1–2 m below the mudline. At these depths, the fine-grained seabed is very soft and possesses low undrained strength, which can be difficult to measure. This paper describes a centrifuge test programme undertaken to evaluate the feasibility and performance of a novel penetrometer designed to assess the shallow strength of soft seabed over continuous horizontal profiles. This device is termed the vertically oriented penetrometer (VOP). Tests were performed on a normally consolidated kaolin sample, with the VOP translated horizontally at velocities ranging from 1 to 30 mm/s, after embedding the VOP at 30 and 45 mm depths. All tests involved many cycles of VOP forward and backward movement to assess its potential to derive the ratio of intact to fully remoulded strength. Strength determination is achieved by dragging the VOP at a specified embedment depth along the soil surface, and deriving the soil strength from the measured resistance as if the VOP were a laterally loaded pile. The VOP is shown to yield comparable strength measurements to that of a T-bar penetrometer. The VOP is a potentially valuable addition to the range of tools used to characterize soil strength, both in small-scale centrifuge models and, following practical development, potentially also in the field.

scholarly journals The effects of cosmic rays on the formation of Milky Way-mass galaxies in a cosmological context

2020 ◽  
Vol 497 (2) ◽  
pp. 1712-1737 ◽  
Author(s):  
Tobias Buck ◽  
Christoph Pfrommer ◽  
Rüdiger Pakmor ◽  
Robert J J Grand ◽  
Volker Springel
Keyword(s):  
Cosmic Rays ◽  
Milky Way ◽  
Gamma Ray ◽  
Transport Model ◽  
Formation Rate ◽  
Wave Model ◽  
Alfven Wave ◽  
Small Scale ◽  
Density Peaks ◽  
The Impact

ABSTRACT We investigate the impact of cosmic rays (CRs) and different modes of CR transport on the properties of Milky Way-mass galaxies in cosmological magnetohydrodynamical simulations in the context of the AURIGA project. We systematically study how advection, anisotropic diffusion, and additional Alfvén-wave cooling affect the galactic disc and the circumgalactic medium (CGM). Global properties such as stellar mass and star formation rate vary little between simulations with and without various CR transport physics, whereas structural properties such as disc sizes, CGM densities, or temperatures can be strongly affected. In our simulations, CRs affect the accretion of gas on to galaxies by modifying the CGM flow structure. This alters the angular momentum distribution that manifests itself as a difference in stellar and gaseous disc size. The strength of this effect depends on the CR transport model: CR advection results in the most compact discs while the Alfvén-wave model resembles more the AURIGA model. The advection and diffusion models exhibit large (r ∼ 50 kpc) CR pressure-dominated gas haloes causing a smoother and partly cooler CGM. The additional CR pressure smoothes small-scale density peaks and compensates for the missing thermal pressure support at lower CGM temperatures. In contrast, the Alfvén-wave model is only CR pressure dominated at the disc–halo interface and only in this model the gamma-ray emission from hadronic interactions agrees with observations. In contrast to previous findings, we conclude that details of CR transport are critical for accurately predicting the impact of CR feedback on galaxy formation.

scholarly journals PARTICLE ACCELERATION, MAGNETIC FIELD GENERATION, AND ASSOCIATED EMISSION IN COLLISIONLESS RELATIVISTIC JETS

2008 ◽  
Vol 17 (10) ◽  
pp. 1761-1767 ◽  
Author(s):  
K.-I. NISHIKAWA ◽  
Y. MIZUNO ◽  
G. J. FISHMAN ◽  
P. HARDEE
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Small Scale ◽  
Spectral Structure ◽  
Relativistic Jets ◽  
Weibel Instability ◽  
Electron Positron ◽  
Jitter Radiation

Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma-ray bursts (GRBs), and galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations using injected relativistic electron-ion (electron-positron) jets show that acceleration occurs within the downstream jet. Shock acceleration is an ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electrons' transverse deflection behind the jet head. The "jitter" radiation from deflected electrons has different properties to synchrotron radiation which assumes a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.

scholarly journals GRB spectral parameter modeling

2010 ◽  
Vol 6 (S274) ◽  
pp. 243-245
Author(s):  
Gregory D. Fleishman ◽  
Fedor A. Urtiev
Keyword(s):  
Synchrotron Radiation ◽  
Electric Fields ◽  
Large Scale ◽  
Gamma Ray ◽  
Small Scale ◽  
Random Waves ◽  
Spectral Parameters ◽  
Random Magnetic Field ◽  
Cross Correlations ◽  
Accelerated Particles

AbstractFireball model of the gamma-ray bursts (GRBs) predicts generation of numerous internal shocks, which efficiently accelerate charged particles and generate relatively small-scale stochastic magnetic and electric fields. The accelerated particles diffuse in space due to interaction with the random waves and so emit so called Diffusive Synchrotron Radiation (DSR) in contrast to standard synchrotron radiation they would produce in a large-scale regular magnetic fields. In this contribution we present key results of detailed modeling of the GRB spectral parameters, which demonstrate that the non-perturbative DSR emission mechanism in a strong random magnetic field is consistent with observed distributions of the Band parameters and also with cross-correlations between them.

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