21,540 research outputs found
Graph Dynamical Networks for Unsupervised Learning of Atomic Scale Dynamics in Materials
Understanding the dynamical processes that govern the performance of
functional materials is essential for the design of next generation materials
to tackle global energy and environmental challenges. Many of these processes
involve the dynamics of individual atoms or small molecules in condensed
phases, e.g. lithium ions in electrolytes, water molecules in membranes, molten
atoms at interfaces, etc., which are difficult to understand due to the
complexity of local environments. In this work, we develop graph dynamical
networks, an unsupervised learning approach for understanding atomic scale
dynamics in arbitrary phases and environments from molecular dynamics
simulations. We show that important dynamical information can be learned for
various multi-component amorphous material systems, which is difficult to
obtain otherwise. With the large amounts of molecular dynamics data generated
everyday in nearly every aspect of materials design, this approach provides a
broadly useful, automated tool to understand atomic scale dynamics in material
systems.Comment: 25 + 7 pages, 5 + 3 figure
The Parallel Complexity of Growth Models
This paper investigates the parallel complexity of several non-equilibrium
growth models. Invasion percolation, Eden growth, ballistic deposition and
solid-on-solid growth are all seemingly highly sequential processes that yield
self-similar or self-affine random clusters. Nonetheless, we present fast
parallel randomized algorithms for generating these clusters. The running times
of the algorithms scale as , where is the system size, and the
number of processors required scale as a polynomial in . The algorithms are
based on fast parallel procedures for finding minimum weight paths; they
illuminate the close connection between growth models and self-avoiding paths
in random environments. In addition to their potential practical value, our
algorithms serve to classify these growth models as less complex than other
growth models, such as diffusion-limited aggregation, for which fast parallel
algorithms probably do not exist.Comment: 20 pages, latex, submitted to J. Stat. Phys., UNH-TR94-0
Exploration of Reaction Pathways and Chemical Transformation Networks
For the investigation of chemical reaction networks, the identification of
all relevant intermediates and elementary reactions is mandatory. Many
algorithmic approaches exist that perform explorations efficiently and
automatedly. These approaches differ in their application range, the level of
completeness of the exploration, as well as the amount of heuristics and human
intervention required. Here, we describe and compare the different approaches
based on these criteria. Future directions leveraging the strengths of chemical
heuristics, human interaction, and physical rigor are discussed.Comment: 48 pages, 4 figure
Causes of breakage and disruption in a homogeniser
Many authors have written in the past regarding the exact causes of breakage and disruption in a high pressure homogeniser, but there has been little agreement. This paper investigates some of the most likely causes of the rupture of the walls of unicellular organisms and offers suggestions obtained from various papers and work carried out
Projection method for droplet dynamics on groove-textured surface with merging and splitting
The geometric motion of small droplets placed on an impermeable textured
substrate is mainly driven by the capillary effect, the competition among
surface tensions of three phases at the moving contact lines, and the
impermeable substrate obstacle. After introducing an infinite dimensional
manifold with an admissible tangent space on the boundary of the manifold, by
Onsager's principle for an obstacle problem, we derive the associated parabolic
variational inequalities. These variational inequalities can be used to
simulate the contact line dynamics with unavoidable merging and splitting of
droplets due to the impermeable obstacle. To efficiently solve the parabolic
variational inequality, we propose an unconditional stable explicit boundary
updating scheme coupled with a projection method. The explicit boundary
updating efficiently decouples the computation of the motion by mean curvature
of the capillary surface and the moving contact lines. Meanwhile, the
projection step efficiently splits the difficulties brought by the obstacle and
the motion by mean curvature of the capillary surface. Furthermore, we prove
the unconditional stability of the scheme and present an accuracy check. The
convergence of the proposed scheme is also proved using a nonlinear
Trotter-Kato's product formula under the pinning contact line assumption. After
incorporating the phase transition information at splitting points, several
challenging examples including splitting and merging of droplets are
demonstrated.Comment: 26 page
Sensitivity bond graphs
A sensitivity bond graph, of the same structure as the system bond graph, is shown to provide a simple and effective method of generating sensitivity functions of use in optimisation. The approach is illustrated in the context of partially known system parameter and state estimation
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