741 research outputs found
Luminescence dating of ditch fills from the Headland Archaeology Ltd. excavation of Newry Ring Fort, Northern Ireland
This study supports a new investigation into the construction, occupation and utilisation history of a Mediaeval ring fort near Newry, southwest Northern Ireland
(section 2). Optically stimulated luminescence (OSL) profiling and age determinations have been made for two sequences of sediments accumulated in the ring ditch surrounding the fort, and potential has been assessed for TL dating of a Souterrain-Ware sherd from a pit feature within the site complex (section 3). The archaeological significance of the age determinations has been reviewed in the light of the luminescence results and the samplesâ depositional contexts, to constrain the deposition/formation dates of the sampled sediments (section 6).<p></p>
A total of 31 profiling (sections 5.1, 5.2) and 12 age (section 5.5) determinations were made. Profiling measurements were made using simplified equivalent dose
determination procedures on polymineral coarse and hydrofluoric etched sand-sized mineral grains (sections 4.2.2). Dose rate determinations were made using thick
source beta counting, high-resolution gamma spectrometry, field gamma spectrometry, measured water contents and calculated cosmic dose rates (sections 4.2.1 and 5.3). Equivalent dose determinations were made (sections 4.2.2, 5.4) using the OSL signals from sand sized grains of quartz separated from each sample.<p></p>
The luminescence behaviour of the Newry Ringfort samples was generally very good. Profiling indicated variable levels of residual luminescence signal through the
sections (sections 5.1, 5.2), but OSL on the etched fraction was found to be least affected, and measurements on fully prepared quartz for dating appeared even less so
(sections 6.1, 6.2). Dose rates ranged from 2.6 to 3.9 mGy/a, De values from the dating samples ranged from 0.7 to 5.0 Gy. Estimates of sediment accumulation date ranged from 410AD to 1750AD (section 5.5). Uncertainties on the age estimates were commonly around 3%, but young samples with scattered equivalent dose distributions had estimated age uncertainties of up to 11%.<p></p>
The external dose rate to the sherd was estimated to be 1.33 mGy/a ± 0.12 (sections 6.3, 7). Precision was limited by uncertainties in average water content during burial
rather than heterogeneity in the gamma radiation field: providing the range of sediment radioactivity at a site can be assessed, and the average burial water contents
of sherds excavated from it can be well constrained, then it is likely that sherds from around a site could be dated with sufficient precision to establish a broad chronology
for Souterrain-Ware.<p></p>
The earliest sediments in the ditch of the ringfort indicated that its construction predates the end of the 6th Century AD (sections 6.4, 7). These and other OSL age
estimates indicated continued occupation until the mid 11th Century, or phases of occupation in the 7th, 9th and 11th Centuries. Results from the base of a colluvial soil
sealing these layers indicate that the site was set to cultivation at or around the time of the Norman invasion of Ireland (1169AD), rather than in the post Mediaeval period.
Abandonment of the ringfort must have occurred at the time of the invasion or in the century before it. Samples from throughout the colluvial soil also indicated that it
continued to accumulate until at least the 18th Century, and probably into the 20th Century
KADoNiS-: The astrophysical -process database
The KADoNiS- project is an online database for cross sections relevant to
the -process. All existing experimental data was collected and reviewed.
With this contribution a user-friendly database using the KADoNiS (Karlsruhe
Astrophysical Database of Nucleosynthesis in Stars) framework is launched,
including all available experimental data from (p,), (p,n),
(p,), (,), (,n) and (,p) reactions in
or close to the respective Gamow window with cut-off date of August 2012
(www.kadonis.org/pprocess).Comment: Proceedings Nuclear Data Conference 2013, published in Nuclear Data
Sheets 120 (2014) 19
Chaotic behavior of the lattice Yang-Mills on CUDA
The Yang-Mills fields plays important role in the strong interaction, which describes the quark gluon plasma. The non-Abelian gauge theory provides the theoretical background understanding of this topic. The real time evolution of the classical fields is derived by the Hamiltonian for SU(2) gauge field tensor. The microcanonical equations of motion is solved on 3 dimensional lattice and chaotic dynamics was searched by the monodromy matrix. The entropy-energy relation was presented by Kolmogorov-Sinai entropy. We used block Hessenberg reduction to compute the eigenvalues of the current matrix. While the purely CPU based algorithm can handle effectively only a small amount of values, the GPUs provide enough performance to give more computing power to solve the problem
Interpretation of runaway electron synchrotron and bremsstrahlung images
The crescent spot shape observed in DIII-D runaway electron synchrotron
radiation images is shown to result from the high degree of anisotropy in the
emitted radiation, the finite spectral range of the camera and the distribution
of runaways. The finite spectral camera range is found to be particularly
important, as the radiation from the high-field side can be stronger by a
factor than the radiation from the low-field side in DIII-D. By
combining a kinetic model of the runaway dynamics with a synthetic synchrotron
diagnostic we see that physical processes not described by the kinetic model
(such as radial transport) are likely to be limiting the energy of the
runaways. We show that a population of runaways with lower dominant energies
and larger pitch-angles than those predicted by the kinetic model provide a
better match to the synchrotron measurements. Using a new synthetic
bremsstrahlung diagnostic we also simulate the view of the Gamma Ray Imager
(GRI) diagnostic used at DIII-D to resolve the spatial distribution of
runaway-generated bremsstrahlung.Comment: 21 pages, 11 figure
SOFT: A synthetic synchrotron diagnostic for runaway electrons
Improved understanding of the dynamics of runaway electrons can be obtained
by measurement and interpretation of their synchrotron radiation emission.
Models for synchrotron radiation emitted by relativistic electrons are well
established, but the question of how various geometric effects -- such as
magnetic field inhomogeneity and camera placement -- influence the synchrotron
measurements and their interpretation remains open. In this paper we address
this issue by simulating synchrotron images and spectra using the new synthetic
synchrotron diagnostic tool SOFT (Synchrotron-detecting Orbit Following
Toolkit). We identify the key parameters influencing the synchrotron radiation
spot and present scans in those parameters. Using a runaway electron
distribution function obtained by Fokker-Planck simulations for parameters from
an Alcator C-Mod discharge, we demonstrate that the corresponding synchrotron
image is well-reproduced by SOFT simulations, and we explain how it can be
understood in terms of the parameter scans. Geometric effects are shown to
significantly influence the synchrotron spectrum, and we show that inherent
inconsistencies in a simple emission model (i.e. not modeling detection) can
lead to incorrect interpretation of the images.Comment: 24 pages, 12 figure
Thermodynamic hierarchies of evolution equations
Non-equilibrium thermodynamics with internal variables introduces a natural
hierarchical arrangement of evolution equations. Three examples are shown: a
hierarchy of linear constitutive equations in thermodynamic rhelogy with a
single internal variable, a hierarchy of wave equations in the theory of
generalized continua with dual internal variables and a hierarchical
arrangement of the Fourier equation in the theory of heat conduction with
current multipliers.Comment: 7 pages, 1 figur
Deviation from the Fourier law in room-temperature heat pulse experiments
We report heat pulse experiments at room temperature that cannot be described
by Fourier's law. The experimental data is modelled properly by the
Guyer--Krumhansl equation, in its over-diffusion regime. The phenomenon is due
to conduction channels with differing conductivities, and parallel to the
direction of the heat flux.Comment: 9 pages, 4 figure
Second order equation of motion for electromagnetic radiation back-reaction
We take the viewpoint that the physically acceptable solutions of the
Lorentz--Dirac equation for radiation back-reaction are actually determined by
a second order equation of motion, the self-force being given as a function of
spacetime location and velocity. We propose three different methods to obtain
this self-force function. For two example systems, we determine the second
order equation of motion exactly in the nonrelativistic regime via each of
these three methods, the three methods leading to the same result. We reveal
that, for both systems considered, back-reaction induces a damping proportional
to velocity and, in addition, it decreases the effect of the external force.Comment: 13 page
- âŠ