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An effort is underway at Sandia National Laboratories to develop a library of algorithms to search for potential interactions between surfaces represented by analytic and discretized topological entities. This effort is also developing algorithms to determine forces due to these interactions for transient dynamics applications. This document describes the Application Programming Interface (API) for the ACME (Algorithms for Contact in a Multiphysics Environment) library.

An analytical method employing digital image processing and a stereo logical model is developed and applied to macropore structure characterization. Digital images of porous particle cross-sections are collected and analyzed on an image processor to identify the two-dimensional pore profiles and to obtain the distribution for the equivalent radii of pore sections. A stereologieal model with improved numerical integration, approximation and data smoothing features is developed to unfold the size distribution of the three-dimensional pores from the two-dimensional data. The method is used to characterize the macropore structure of coal-derived chars. Presented results establish that the developed technique can quantify features of the macropore structure of chars that cannot be identified by indirect analytical methods.

of the external surfaces of bodies within the domain in an attempt to efficiently distribute computational work. This decomposition may or may not be the same as the volume decomposition associated with the host physics. The parallel contact global search phase is then employed to find and distribute surface entities (nodes and faces) that are needed to compute contact constraints between entities owned by different MPI ranks without further inter-rank communication. Key steps of the contact global search include computing bounding boxes, building surface entity (node and face) search trees and finding and distributing entities required to complete on-rank (local) spatial searches. To enable source-code portability and performance across a variety of different computer architectures, we implemented the algorithm using the Kokkos hardware abstraction library. While we targeted development towards machines with a GPU accelerator per MPI rank, we also report performance results for OpenMP with a conventional multi-core compute node per rank. Results here demonstrate a 47 % decrease in the time spent within the global search algorithm, comparing the reference ACME algorithm with the GPU implementation, on an 18M face problem using four MPI ranks. While further work remains to maximize performance on the GPU, this result illustrates the potential of the proposed implementation.Abstract This paper describes an approach that seeks to parallelize the spatial search associated with computational contact mechanics. In contact mechanics, the purpose of the spatial search is to find "nearest neighbors," which is the prelude to an imprinting search that resolves the interactions between the external surfaces of contacting bodies. In particular, we are interested in the contact global search portion of the spatial search associated with this operation on domain-decomposition-based meshes. Specifically, we describe an implementation that combines standard domain-decomposition-based MPI-parallel spatial search with thread-level parallelism (MPI-X) available on advanced computer architectures (those with GPU coprocessors). Our goal is to demonstrate the efficacy of the MPI-X paradigm in the overall contact search. Standard MPI-parallel implementations typically use a domain decomposition

The development of a captive sample microreactor, its integration into a video microscopy system, and its use for studies on coal pyrolysis are presented. The reactor can operate as a high-temperature microscope hot stage allowing for direct viewing of the pyrolysis process under an optical microscope equipped with a video camera. By using a microcomputer and specialized video equipment, process information such as elapsed time and reactor temperature are superimposed in alphanumeric form on the video signal. Complete histories of fast experiments can thus be stored on videotape for postprocessing and analysis of transient phenomena. The reactor is controlled via a microcomputer with custom-built analog interfaces. A digital algorithm combining internal model control and feedback control is implemented for accurate programming of the reactor temperature. Heating rates as high as 1000 °C/s can be achieved with good reproducibility. Some experimental results are presented to outline the capabilities of the apparatus and to suggest other potential applications.