18 May 2020

PUBLICATION NOTICE: Phase-Field Simulations of Solidification in Support of Additive Manufacturing Processes

Abstract: For purposes relating to force protection through advancments in multiscale materials modeling, this report explores the use of the phase-field method for simulating microstructure solidification of metallic alloys. Specifically, its utility was examined with respect to a series of increasingly complex solidification problems, ranging from one dimensional, isothermal solidification of pure metals to two-dimensional, directional solidification of non-isothermal, binary alloys. Parametric studies involving variations in thermal gradient, pulling velocity, and anisotropy were also considered, and used to assess the conditions for which dendritic and/or columnar microstructures may be generated. In preparation, a systematic derivation of the relevant governing equations is provided along with the prescribed method of solution.

13 May 2020

PUBLICATION NOTICE: Assessment for Soil Reuse Standards at McMurdo Station

Abstract:  The soils at McMurdo Station in Antarctica contain hydrocarbons derived from accidental fuel spills and industrial development. The current practice for contaminated soils is to remove any material with concentrations greater than 100 mg/kg of total petroleum hydrocarbons (TPH) and to transport them to the United States for disposal. Any soils that contain concentrations of TPH less than 100 mg/kg can be reused on-site. While this is the current standard practice, there remains little evidence to verify that 100 mg/kg is an appropriate reuse standard. Moreover, the current practice is based on the guidelines for cleanup values in California (the port of entry where the soils are currently shipped for treatment and disposal), which has few environmental similarities with Antarctica. In the present study, we investigate current regulations for cleanup and soil reuse in U.S. states, Canadian territories, and other countries with cold climates. We also discuss case studies from Arctic and Antarctic regions where soil has been reused after treatment. Additionally, we present a site conceptual model for risk assessment based on known site information and recommend future focus areas for addressing hydrocarbon-contaminated soils at McMurdo Station.

13 May 2020

PUBLICATION NOTICE: Technical Feasibility of Creating a Beach Grain Size Database with Citizen Scientists

ABSTRACT:  The goal of this Coastal and Hydraulics Engineering Technical Note (CHETN) is to investigate the feasibility of collecting beach grain size information with images collected by citizen scientists to build a globally accessible database. Engaging citizen scientists in scientific information collection through crowdsourcing has become a more popular and cost-effective way to collect large amounts of data while increasing interest in the research through public engagement (Irwin 2018). Citizen scientists equipped with their personal smartphones allow for very large datasets to be collected that would otherwise be financially or logistically impossible. Additionally, it provides an opportunity to educate and engage the general public.

12 May 2020

PUBLICATION NOTICE: Seismic Testing of an Indigenous Material Troop Constructible Building

Abstract: An indigenous materials construction system was developed by a Small Business Innovative Research project – Small Business Innovative Research (SBIR) project Contract W9132T-15-C-0002. The results of that project included the construction of a full scale 16 foot by 32-foot troop constructible building that was tested on the Engineer Research and Development Center, Construction Engineering Research Laboratory (ERDC-CERL) shake table. This report documents the seismic testing of this building. The building consisted of prefabricated frames with interior and exterior wall panels and roof and ceiling panels. The building was tested with 30-second-long synthetic seismic motions, which began at low levels. The test amplitude was increased so that the final test conducted used motions based on a spectral acceleration tied to the highest seismic hazard in the United States. The base of the building was badly damaged in this final test, but it remained stable, demonstrating relatively good behavior. This report documents the measured response to these motions and the performance of the building.

12 May 2020

PUBLICATION NOTICE: Fenton’s Reagent Treatability Study for Hydrocarbon-Contaminated Soils, McMurdo Station, Antarctica

ABSTRACT:  Hydrocarbon-contaminated soil is distributed heterogeneously at McMurdo Station, Antarctica, which has served for over 60 years as the logistics hub for the U.S. Antarctic Program. Here we investigated the treatability of McMurdo Station’s contaminated soil with chemical oxidation. Our study collected five soil samples in 2018 and 2019, of which two contained high levels (>100 mg/kg) of total petroleum hydrocarbons (TPH) suitable for the treatability study. One soil (ITC) was characterized by 1250 mg/kg of predominantly midrange (n-C8 to n-C16) hydrocarbons, and the other (Soil Pile) was characterized by 3500 mg/kg of predominantly heavy molecular weight (>n-C21) hydrocarbons. We investigated the treatability of these soils with both Fenton’s Reagent (pH < 3 with Fe2+) and modified Fenton’s Reagent (chelated Fe2+), each with hydrogen peroxide concentrations of 3% and 10%. Soil slurries were placed on a shaker table at 100 rpm and 4°C for up to 21 days. TPH concentrations were reduced by approximately 50% for ITC; however, the oxidative treatments did not out-perform controls. All treatments and controls yielded no significant reduction in Soil Pile TPH. Poor performance by these chemical oxidation treatments indicates that remediation of hydrocarbons at these sites may require further soil processing in combination with chemical oxidation or alternative treatment technologies.

12 May 2020

PUBLICATION NOTICE: AIS Data Case Study: St. Louis Area Commercial Vessel Fleeting Activity and Potential River Training Structures

Abstract: The US Army Corps of Engineers (USACE), St. Louis District (MVS), needed to examine commercial river traffic patterns before designing new river training structures to reduce maintenance dredging costs in the St. Louis Harbor area of the Middle Mississippi River (MMR). The MMR is considered to be that portion of the Mississippi River from the confluence of the Missouri River down to the Ohio River, and the Upper Mississippi River (UMR) is everything north of the Missouri River. MVS analyzed historic Automatic Identification System (AIS) data, which provide georeferenced and timestamped position reports for commercial vessels, to reveal river use patterns. The Mississippi River within the MVS area of responsibility is heavily trafficked by the shipping industry and includes numerous loading facilities and fleeting areas that are outside of the main navigation channel. This work identified previously unknown fleeting areas in locations that were being considered for siting of river training structures. These areas were then removed from potential construction consideration, thus avoiding conflict with shipping industry river use.

7 May 2020

PUBLICATION NOTICE: Using Morton Codes to Partition Faceted Geometry: An Architecture for Terabyte-Scale Geometry Models

Abstract: The Virtual Environment for Sensor Performance Assessment (VESPA) project requires enormous, high-fidelity landscape models to generate synthetic sensor imagery with little to no artificial artifacts. These high-fidelity landscapes require a memory footprint substantially larger than a single High Performance Computer’s (HPC) compute node’s local memory. Processing geometries this size requires distributing the geometry over multiple compute nodes instead of including a full copy in each compute node, the common approach in parallel modeling applications. To process these geometric models in parallel memory on a high-performance computing system, the Geometry Engine component of the VESPA project includes an architecture for partitioning the geometry spatially using Morton codes and MPI (Message Passing Interface) collective communication routines. The methods used for this partitioning process will be addressed in this report. Incorporating this distributed architecture into the Geometry Engine provides the capability to distribute and perform parallel ray casting on landscape geometries over a Terabyte in size. Test case timings demonstrate scalable speedups as the number of processes are increased on an HPC machine.