2,694 research outputs found
Combining phase field crystal methods with a Cahn-Hilliard model for binary alloys
During phase transitions certain properties of a material change, such as
composition field and lattice-symmetry distortions. These changes are typically
coupled, and affect the microstructures that form in materials. Here, we
propose a 2D theoretical framework that couples a Cahn-Hilliard (CH) model
describing the composition field of a material system, with a phase field
crystal (PFC) model describing its underlying microscopic configurations. We
couple the two continuum models via coordinate transformation coefficients. We
introduce the transformation coefficients in the PFC method, to describe affine
lattice deformations. These transformation coefficients are modeled as
functions of the composition field. Using this coupled approach, we explore the
effects of coarse-grained lattice symmetry and distortions on a phase
transition process. In this paper, we demonstrate the working of the CH-PFC
model through three representative examples: First, we describe base cases with
hexagonal and square lattice symmetries for two composition fields. Next, we
illustrate how the CH-PFC method interpolates lattice symmetry across a diffuse
composition phase boundary. Finally, we compute a Cahn-Hilliard type of
diffusion and model the accompanying changes to lattice symmetry during a phase
transition process.Comment: 9 pages, 5 figure
Religious Roots for the Puritan Morality Laws During the Interregnum
During the decade of the 1650s, England had no King or Queen. Instead, an increasingly monarchical parliamentary system of government reigned. This government was controlled by Puritans, a hardline sect of Protestant Christianity. Although they were a religious minority and their laws relating to morality were unpopular, the Puritans pursued this policies with religious zeal linking seemingly innocuous activities, such as cock-fighting or a may-pole celebration with the supposed evils of Catholicism. Legal documents such as “March 1654: An Ordinance for prohibiting Cock-matches” and..
Modeling Grain Boundaries using a Phase Field Technique
We propose a two dimensional frame-invariant phase field model of grain
impingement and coarsening. One dimensional analytical solutions for a stable
grain boundary in a bicrystal are obtained, and equilibrium energies are
computed. We are able to calculate the rotation rate for a free grain between
two grains of fixed orientation. For a particular choice of functional
dependencies in the model the grain boundary energy takes the same analytic
form as the microscopic (dislocation) model of Read and Shockley.Comment: 4 pages, 2 figure
Li-diffusion accelerates grain growth in intercalation electrodes: a phase-field study
Grain boundary migration is driven by the boundary's curvature and external
loads such as temperature and stress. In intercalation electrodes an additional
driving force results from Li-diffusion. That is, Li-intercalation induces
volume expansion of the host-electrode, which is stored as elastic energy in
the system. This stored energy is hypothesized as an additional driving force
for grain boundaries and edge dislocations. Here, we apply the 2D
Cahn-Hilliardphase-field-crystal (CH-PFC) model to investigate the coupled
interactions between highly mobile Li-ions and host-electrode lattice
structure, during an electrochemical cycle. We use a polycrystalline
FePO/ LiFePO electrode particle as a model system. We compute grain
growth in the FePO electrode in two parallel studies: In the first study,
we electrochemically cycle the electrode and calculate Li-diffusion assisted
grain growth. In the second study, we do not cycle the electrode and calculate
the curvature-driven grain growth. External loads, such as temperature and
stress, did not differ across studies. We find the mean grain-size increases by
in the electrochemically cycled electrode particle. By contrast, in
the absence of electrochemical cycling, we find the mean grain-size increases
by in the electrode particle. These CH-PFC computations suggest that
Li-intercalation accelerates grain-boundary migration in the host-electrode
particle. The CH-PFC simulations provide atomistic insights on
diffusion-induced grain-boundary migration, edge dislocation movement and
triple-junction drag-effect in the host-electrode microstructure.Comment: 11 pages, 9 figure
Red Bean Monday
The process of filmmaking starts with an idea and is brought forth to reality through a collaborative effort.
This paper will include the process of producing a film through each step from the conception to completion of my thesis film “Red Bean Monday.”
I will thoroughly discuss the writing, producing, cinematography, directing, editing, sound, technology, and workflow. I will also discuss things I have learned as a filmmaker through the successes and failures that I determined based on surveys from audience participation
Red Bean Monday
The process of filmmaking starts with an idea and is brought forth to reality through a collaborative effort.
This paper will include the process of producing a film through each step from the conception to completion of my thesis film “Red Bean Monday.”
I will thoroughly discuss the writing, producing, cinematography, directing, editing, sound, technology, and workflow. I will also discuss things I have learned as a filmmaker through the successes and failures that I determined based on surveys from audience participation
\u27To The Dishonor of God\u27: Religious Roots for Puritan Morality Laws During the Interregnum
During the decade of the 1650s, England had no King or Queen. Instead, an increasingly monarchical parliamentary system of government reigned. This government was controlled by Puritans, a hardline sect of Protestant Christianity. Although they were a religious minority and their laws relating to morality were unpopular, the Puritans pursued these policies with religious zeal linking seemingly innocuous activities, such as cock-fighting or a may-pole celebration with the supposed evils of Catholicism. Legal documents such as “March 1654: An Ordinance for prohibiting Cock-matches” and “June 1657: An Act for the better observation of the Lord’s Day” ban activities based on associations with drinking and gambling, and then in a speech by Oliver Cromwell (1564), those activities are linked with Catholicism. This demonstrates the integral role religious thought played in Puritan laws. This project is the study of how one group with a radical vision of society used language to link domestic and foreign policy to Godliness and sin, despite a lack of popular support or resulting political gain
Economic and Environmental Impacts of Adoption of Genetically Modified Rice in California
Crop Production/Industries, Research and Development/Tech Change/Emerging Technologies,
Thermodynamic phase-field model for microstructure with multiple components and phases: the possibility of metastable phases
A diffuse-interface model for microstructure with an arbitrary number of
components and phases was developed from basic thermodynamic and kinetic
principles and formalized within a variational framework. The model includes a
composition gradient energy to capture solute trapping, and is therefore suited
for studying phenomena where the width of the interface plays an important
role. Derivation of the inhomogeneous free energy functional from a Taylor
expansion of homogeneous free energy reveals how the interfacial properties of
each component and phase may be specified under a mass constraint. A diffusion
potential for components was defined away from the dilute solution limit, and a
multi-obstacle barrier function was used to constrain phase fractions. The
model was used to simulate solidification via nucleation, premelting at phase
boundaries and triple junctions, the intrinsic instability of small particles,
and solutal melting resulting from differing diffusivities in solid and liquid.
The shape of metastable free energy surfaces is found to play an important role
in microstructure evolution and may explain why some systems premelt at phase
boundaries and phase triple junctions while others do not.Comment: 14 pages, 8 figure
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