Category Archive: Research Highlights

Mar 12

3D Visualization of Textures in Metals and Alloys

In a separate article, we described how one can use the neo-Eulerian orientation representations to create new 3D visualizations of the Rodrigues Fundamental Zones in homochoric, cubochoric, 3D stereographic, Euler and Rodrigues-Frank orientation representations. In the present article, we use these visualization modes to illustrate how one can represent Orientation Distribution Functions as 3D objects. …

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Feb 10

Electron Channeling Pattern Dictionary Indexing Manuscript

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One of our recent papers on dictionary indexing of electron channeling patterns (ECPs) was just accepted for publication in Microscopy & Microanalysis.  The original final submitted manuscript can be found HERE. The figure below represents one of the simulated ECPs from Fig. 5 of the manuscript; it is a false color version and will be …

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Oct 20

3D Visualization of neo-Eulerian and other rotation representations

3D visualization of rotations and crystallographic fundamental zones [This page provides Supplementary Material for the following paper: (DOI:10.1107/S1600576717001157) P. G. Callahan, M. Echlin, T. M. Pollock, S. Singh and M. De Graef, "Three-dimensional texture visualization approaches: theoretical analysis and examples", J. Appl. Cryst. (2017) 50.] 3D rotations are typically represented in terms of 3x3 rotation …

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Nov 12

New Release of EMsoft Package

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EMSoft 3.1 Release It is our pleasure to announce the release of the EMsoft 3.1 software package for the dynamical simulation of electron back-scattered diffraction patterns (EBSD), electron channeling patterns (ECP), and electron Kossel patterns (EKP), Dictionary Indexing for EBSD and ECP, along with a series of smaller support programs. This release once again focuses …

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Jul 01

Software for Time Interlaced Model Based Iterative Reconstruction (TIMBIR)

Summary The time-interlaced model-based iterative reconstruction (TIMBIR) [1,2] is a method for 4D time-space reconstruction of data acquired using synchrotron X-ray computed tomography. TIMBIR is a synergistic combination of two innovations. The first innovation, interlaced view sampling, is a novel method of data acquisition which distributes the view angles more evenly in time. The second …

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Sep 15

3D Model-Based Iterative Reconstruction for Synchrotron Tomography

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Introduction and Theory Synchrotron based X-ray tomography is widely used for three dimensional imaging of material samples. Typically, reconstructions are done using analytical reconstruction techniques such as filtered back projection (FBP) or Fourier reconstruction methods like gridrec. However, direct reconstruction of synchrotron data typically result in strong ring and streak artifacts in the reconstruction. The …

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Sep 08

A predictive data mining approach for microstructure optimization

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We ask and seek answers for these questions: can we identify the microstructure that is theoretically predicted to yield a desired property demanded by a selected application? What if what's demanded is a combination of multiple properties? What if there're more than one microstructure that yield the same property? Can we identify the complete space (or as much of it …

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Aug 26

A unified markov random field/marked point process image model and its application to computational materials

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Both Markov Random Field (MRF) and Marked Point Process (MPP) models have their limitations in image analysis. While MRF is a pixel-based representation, it is useful for imposing local constraints, but global constraints are not easily modeled. On the contrary, it is convenient to model global constraints, such as geometric shape and object interactions, within the MPP  framework. However, …

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Aug 26

Modeling dynamical scattering using Bethe potentials

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Our research focuses on determing the optimal criterion for using the so-called Bethe potentials to reduce the matrix size in electron dynamical scattering calculations and thus the computational time. Electron micrographs display a rich variety of contrast features such as thickness change, bending and defects in the materials. It is important to understand these features …

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Aug 25

Analysis and representation of microstructure data

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Recent improvements in experimental and computational techniques in material characterization have led to a vast amount of data on the microstructure and deformation of heterogeneous media. This information is traditionally arrayed in pixels, on grids. The massive extent of data in this form renders identifying key features difficult, and the cost of digital storage expensive. Our following research highlights introduce ways of efficient representation, construction, and analysis.

Aug 22

A new fortran-90 library for 3D rotation conversions

This page describes a fortran-90 module, rotations3D.f90, that provides functions, both in single and double precision, to convert between seven different rotation parameterizations. Fortran-90 source code implementing the 3D rotation conversion functions is available for download (zip file containing the 3Drotations module, along with an example program and associated input file).  3D rotations are frequently needed in a …

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Aug 18

Cubochoric coordinates: a new parameterization of 3D rotations

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The contents of this page were extracted from a manuscript in press in Modeling and Simulations in Materials Science and Engineering (MSMSE).  Contact M. De Graef for additional information.Fortran-90 source code that implements this rotation parameterization is available for download (zip file containing so3-sampler.f90; compiles with gfortran).  This program asks the user for a sampling rate and …

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Aug 18

Unusual microstructure of Zn_{45}Au_{30}Cu_{25} with satisfaction of the cofactor conditions

The cofactor conditions, as the conditions of compatibility between phases consist of two main subconditions: (CC1) , which means the middle principle stretch of the transformation is unity, (CC2) (a.v2)(n.v2)=0 where the vector n is the normal of twinning plane, the vector a corresponds to the twinning shear and the vector v2 is the undistorted …

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Aug 18

High Temporal Resolution CT Reconstruction Using Interlaced View Sampling

The state of the art in computed tomography in material science applications uses Filtered Back Projection (FBP) as the reconstruction algorithm and acquires views progressively from 0 to 180 degrees in fixed angular steps. In medical applications, by using Model Based Iterative Reconstructions (MBIR) instead of FBP, significant gains in reconstruction quality has been achieved. However, high temporal resolution …

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