1,223 research outputs found
Models of dust around Europa and Ganymede
We use numerical models, supported by our laboratory data, to predict the
dust densities of ejecta outflux at any altitude within the Hill spheres of
Europa and Ganymede. The ejecta are created by micrometeoroid bombardment and
five different dust populations are investigated as sources of dust around the
moons. The impacting dust flux (influx) causes the ejection of a certain amount
of surface material (outflux). The outflux populates the space around the
moons, where a part of the ejecta escapes and the rest falls back to the
surface. These models were validated against existing Galileo DDS (Dust
Detector System) data collected during Europa and Ganymede flybys.
Uncertainties of the input parameters and their effects on the model outcome
are also included. The results of this model are important for future missions
to Europa and Ganymede, such as JUICE (JUpiter ICy moon Explorer), recently
selected as ESA's next large space mission to be launched in 2022
Local molecular and global connectomic contributions to cross-disorder cortical abnormalities
Contains fulltext :
253170.pdf (Publisher’s version ) (Open Access
Assessing the Quality of Permanent Sample Plot Databases for Growth Modelling in Forest Plantations
Informed plantation management requires a good database, since the quality of information depends on the quality of data, growth models and other planning tools. There are several important questions concerning permanent plots: how many plots, where to put them, and how to manage them. Plot measurement procedures are also important. This paper illustrates graphical procedures to evaluate existing databases, to identify areas of weakness, and to plan remedial sampling. Two graphs, one of site index versus age, another with stocking versus tree size, may provide a good summary of the site and stand conditions represented in the database. However, it is important that these variables, especially site index, can be determined reliably. Where there is doubt about the efficacy of site index estimates, it is prudent to stratify the database according to geography, soil/geology or yield level (total basal area or volume production). Established permanent plot systems may sample a limited range of stand conditions, and clinal designs are an efficient way to supplement such data to provide a better basis for silvicultural inference. Procedures are illustrated with three data sets: teak plantations in Burma, Norway spruce in Denmark, and a clinal spacing experiment in India
Adaptive cluster expansion for the inverse Ising problem: convergence, algorithm and tests
We present a procedure to solve the inverse Ising problem, that is to find
the interactions between a set of binary variables from the measure of their
equilibrium correlations. The method consists in constructing and selecting
specific clusters of variables, based on their contributions to the
cross-entropy of the Ising model. Small contributions are discarded to avoid
overfitting and to make the computation tractable. The properties of the
cluster expansion and its performances on synthetic data are studied. To make
the implementation easier we give the pseudo-code of the algorithm.Comment: Paper submitted to Journal of Statistical Physic
Consistent Anisotropic Repulsions for Simple Molecules
We extract atom-atom potentials from the effective spherical potentials that
suc cessfully model Hugoniot experiments on molecular fluids, e.g., and
. In the case of the resulting potentials compare very well with the
atom-atom potentials used in studies of solid-state propertie s, while for
they are considerably softer at short distances. Ground state (T=0K) and
room temperatu re calculations performed with the new potential resolve
the previous discrepancy between experimental and theoretical results.Comment: RevTeX, 5 figure
A Dissipative-Particle-Dynamics Model for Simulating Dynamics of Charged Colloid
A mesoscopic colloid model is developed in which a spherical colloid is
represented by many interacting sites on its surface. The hydrodynamic
interactions with thermal fluctuations are taken accounts in full using
Dissipative Particle Dynamics, and the electrostatic interactions are simulated
using Particle-Particle-Particle Mesh method. This new model is applied to
investigate the electrophoretic mobility of a charged colloid under an external
electric field, and the influence of salt concentration and colloid charge are
systematically studied. The simulation results show good agreement with
predictions from the electrokinetic theory.Comment: 17 pages, 8 figures, submitted to the proceedings of High Performance
Computing in Science & Engineering '1
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