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Ali Ramazani's blog

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Molecular dynamics study of phonon transport in graphyne nanotubes

We determine the thermal conductivities of a, b, and g graphyne nanotubes (GNTs) as well as of carbon
nanotubes (CNTs) using molecular dynamics simulations and the Green-Kubo relationship over the
temperature range 50e400 K. We find that GNTs demonstrate considerably lower thermal conductivity
than CNTs with the same diameter and length. Among a (alpha), b (beta), and g (gama)-GNTs, g-GNT has the highest thermal
conductivity at all temperatures. By comparing the phonon transport properties of GNTs with CNTs, we

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A Hybrid Multi-Scale Model of Crystal Plasticity for Handling Stress Concentrations

Microstructural effects become important at regions of stress concentrators such as notches,
cracks and contact surfaces. A multiscale model is presented that efficiently captures microstructural
details at such critical regions. The approach is based on a multiresolution mesh that includes an
explicit microstructure representation at critical regions where stresses are localized. At regions farther
away from the stress concentration, a reduced order model that statistically captures the effect of the

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Modeling the Hydrophobicity of Nanoparticles and Their Interaction with Lipids and Proteins

We present a method of modeling nanoparticle (NP) hydrophobicity using coarse-grained molecular dynamics (CG MD) simulations, and apply this to the interaction of lipids with nanoparticles. To model at a coarse-grained level the wettability or hydrophobicity of a given material, we choose the MARTINI coarse-grained force field, and determine through simulation the contact angles of MARTINI water droplets residing on flat regular surfaces composed of various MARTINI bead types (C1, C2, etc.).

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Quantification of ferrite-martensite interface in dual phase steels: A first-principles study

The ferrite-martensite interfacial energy and equilibrium interfacial length as a function of martensite carbon content are assessed using first-principles atomistic simulations. The weight percent of carbon in the martensite phase was implicitly varied from 0.6 to 1.8 wt percent by modifying the lattice constant of body-centered tetragonal (BCT) martensite according to Kurdjumov and Kaminsky’s empirical expressions. With increasing carbon content, a decrease is found in both the interfacial energy and in the equilibrium distance between ferrite and martensite interfaces.

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Quantification of GNDs in DP steels (with three developed criteria)

The current work aims to predict the work-hardening behavior of dual-phase (DP) steel, focusing on the effect of transformation-induced geometrically necessary dislocations (GNDs). Equiaxed and banded microstructures were produced through suitable heat treatment cycles in a laboratory. Electron backscatter diffraction measurements were performed to characterize GNDs. The flow behavior was modeled within the micro-scale finite element method, considering the effect of the microstructures using the representative volume element (RVE) approach.

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Correlation between 2D and 3D flow curve modelling of DP steels using a microstructure-based RVE approach

Since real specimens deform three-dimensionally, 2D modeling approaches cannot predict the flow curve of the material precisely. The predicted flow curves obtained from 2D modeling can, however, be correlated to the 3D ones by introducing a correlation factor, We quantified by the stress ratio (σ3D/σ2D) based on the 2D and 3D RVE calculations for DP600 steels with various martensite phase fractions (Vm=0–50%) at different equivalent plastic strains varying from εpeq=0 to 0.1.

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Development and application of a microstructure-based approach to characterize and model failure initiation in DP steels using XFEM

We develop a microstructure-based model to characterize and model failure initiation in DP steels using an extended finite element method (XFEM) to simulate martensite cracking on the mesoscale combined with representative volume element (RVE) modeling. A mini tensile test with digital image correlation (DIC) analysis is linked to local SEM analysis to identify the local strain at which failure is initiated.

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Invitation to submit an abstract to ICME Mini-Symposium at MSE 2016, Germany

It would be my pleasure to invite you to submit your abstracts to the Mini-Symposium:

"Integrated Computational Materials Engineering (ICME) for Materials Design using Numerical Synchronized Approaches Linking Different Scale Algorithms"

which will be organized within the framework of the MSE 2016Conference in Darmstadt/Germany, Sep. 27th-29th.

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