299,228 research outputs found
The uncertainties associated with sediment fingerprinting suspended and recently deposited fluvial sediment in the Nene river basin
The use of tracers within a sediment fingerprinting framework has become a commonly used technique for investigating the sources of fine sediment. However, uncertainties associated with tracer behaviour have been cited as major potential limitations to sediment fingerprinting methodologies. This paper aims to determine the differences between fingerprinting results derived using different groups of tracer properties and to determine the role of organic matter content, particle size, and within-source variability in tracer concentrations on the observed differences. A mean difference of 24.1% between the predicted contributions of sediment originating from channel banks was found when using different tracer groups. Mean differences between tracer group predictions were lower, at between 8% and 11%, when fingerprinting contributions from urban street dusts. Organic matter content and / or particle size showed little indication that they caused differences between tracer group predictions. The within-source variability in tracer concentrations and small contrasts between the tracer concentrations of different source groups were identified as probable causes of inherent uncertainty in the fingerprinting predictions. We determined that the ratio of the percentage difference between median tracer concentrations in the source groups and the average within-source tracer concentration coefficient of variation could indicate the likely uncertainty in model predictions prior to tracer use
Global Tracer Facility Longitudinal Global Tracer Survey 2021 (Year 6) - Survey Instrument
This survey instrument for the Year 6 Global Tracer Facility (GTF) Global Tracer Survey 2021 outlines the survey sections, area of focus, type of question and response options. The research report based on findings collected using this instrument will be published in June 2022
Global Tracer Facility Longitudinal Global Tracer Survey 2023 (Year 8) - Survey Instrument
This survey instrument for the Year 8 Global Tracer Facility (GTF) Global Tracer Survey 2023 outlines the survey sections, area of focus, type of question and response options
GTF Global Tracer Survey 2022 (Year 7) - Survey Instrument Items
This survey instrument for the Year 7 Global Tracer Facility (GTF) Global Tracer Survey 2022 outlines the survey sections, area of focus, type of question and response options. The questions in the survey relate to the Australian development scholarship/fellowship which participants have previously completed
Nucleosynthesis in thermonuclear supernovae with tracers: convergence and variable mass particles
Nucleosynthetic yield predictions for multi-dimensional simulations of
thermonuclear supernovae generally rely on the tracer particle method to obtain
isotopic information of the ejected material for a given supernova simulation.
We investigate how many tracer particles are required to determine converged
integrated total nucleosynthetic yields. For this purpose, we conduct a
resolution study in the number of tracer particles for different hydrodynamical
explosion models at fixed spatial resolution. We perform hydrodynamic
simulations on a co-expanding Eulerian grid in two dimensions assuming
rotational symmetry for both pure deflagration and delayed detonation Type Ia
supernova explosions. Within a given explosion model, we vary the number of
tracer particles to determine the minimum needed for the method to give a
robust prediction of the integrated yields of the most abundant nuclides. For
the first time, we relax the usual assumption of constant tracer particle mass
and introduce a radially vary- ing distribution of tracer particle masses. We
find that the nucleosynthetic yields of the most abundant species (mass
fraction > 10E-5) are reasonably well predicted for a tracer number as small as
32 per axis and direction - more or less independent of the explosion model. We
conclude that the number of tracer particles that were used in extant published
works appear to have been sufficient as far as integrated yields are concerned
for the most copiously produced nuclides. Additionally we find that a suitably
chosen tracer mass distribution can improve convergence for nuclei produced in
the outer layer of the supernova where the constant tracer mass prescription
suffers from poor spatial resolution.Comment: 9 pages, 5 figures, accepted for publication in MNRA
The effect of forcing on the spatial structure and spectra of chaotically advected passive scalars
The stationary distribution of passive tracers chaotically advected by a
two-dimensional large-scale flow is investigated. The tracer field is force by
resetting the value of the tracer in certain localised regions. This problem is
mathematically equivalent to advection in open flows and results in a fractal
tracer structure. The spectral exponent of the tracer field is different from
that for a passive tracer with the usual additive forcing (the so called
Batchelor spectrum) and is related to the fractal dimension of the set of
points that have never visited the forcing regions. We illustrate this
behaviour by considering a time-periodic flow whose effect is equivalent to a
simple two-dimensional area-preserving map. We also show that similar structure
in the tracer field is found when the flow is aperiodic in time.Comment: 7 pages, 9 figure
SIMULATION STUDY ON WATERFLOOD FRONT: BLOCK HADE OF TARIM OILFIELD IN NORTHWEST CHINA
Block Hade consist of a deep thin sandstone reservoir of two sub-layer reservoirs. The thickness is
about 1.5 m for each layer. The two-layer “staircase” horizontal well is used for recovery. In order
to determine water displacement front and edge water movement, tracer test is conducted in the
reservoir. But the cycle of field tracer monitoring is about 150-360 days. This prevented the efficient
monitoring of waterflood swept area and waterflood advance direction and velocity, after the cycle
of tracer monitoring. Conservation of mass with respect to tracer flow and history performance
matching of tracer enabled the study of water-flood front and edge-water advance. The simulation result
is basically consistent with the monitored field tracer results. Therefore, numerical model can be used to
conduct a longer monitoring period. It can make up for the disadvantage of the complexity of the
tracer monitoring setup, its implementation, and time-consuming monitoring cycle. The water-flood
front, water-flood swept area, advancing velocity and the predominant water injection direction can be
obtained. Furthermore, it is possible to evaluate and predict the injection-production well interaction and
can also provide a reliable basis to deploy reasonable flood patterns to enhance oil recovery
Global-mean Vertical Tracer Mixing in Planetary Atmospheres II: Tidally Locked Planets
In Zhang Showman (2018, hereafter Paper I), we developed an analytical
theory of 1D eddy diffusivity for global-mean vertical tracer
transport in a 3D atmosphere. We also presented 2D numerical simulations on
fast-rotating planets to validate our theory. On a slowly rotating planet such
as Venus or a tidally locked planet (not necessarily a slow-rotator) such as a
hot Jupiter, the tracer distribution could exhibit significant longitudinal
inhomogeneity and tracer transport is intrinsically 3D. Here we study the
global-mean vertical tracer transport on tidally locked planets using 3D
tracer-transport simulations. We find that our analytical theory in
Paper I is validated on tidally locked planets over a wide parameter space.
strongly depends on the large-scale circulation strength, horizontal
mixing due to eddies and waves and local tracer sources and sinks due to
chemistry and microphysics. As our analytical theory predicted, on
tidally locked planets also exhibit three regimes In Regime I where the
chemical and microphysical processes are uniformly distributed across the
globe, different chemical species should be transported via different eddy
diffusivity. In Regime II where the chemical and microphysical processes are
non-uniform---for example, photochemistry or cloud formation that exhibits
strong day-night contrast---the global-mean vertical tracer mixing does not
always behave diffusively. In the third regime where the tracer is long-lived,
non-diffusive effects are significant. Using species-dependent eddy
diffusivity, we provide a new analytical theory of the dynamical quench points
for disequilibrium tracers on tidally locked planets from first principles.Comment: Accepted at ApJ, 16 pages, 12 figures. This is the part II. Part I is
"Global-mean Vertical Tracer Mixing in Planetary Atmospheres I: Theory and
Fast-rotating Planets
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