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At least 1,171 records · Page 65
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Progress Report on Alloy 617 Notched Specimen Testing

Creep behavior of Alloy 617 has been extensively characterized to support the development of a draft Code Case to qualify Alloy 617 in Section III division 5 of the ASME Boiler and Pressure Vessel Code. This will allow use of Alloy 617 in construction of nuclear reactor components at elevated temperatures and longer periods of time (up to 950°C and 100,000 hours). Prior to actual use, additional concerns not considered in the ASME code need to be addressed. Code Cases are based largely on uniaxial testing of smooth gage specimens. In service conditions, components will generally be under multi axial loading. There is also the concern of the behavior at discontinuities, such as threaded components. To address the concerns of multi axial creep behavior and at geometric discontinuities, notched specimens have been designed to create conditions representative of the states that service components experience. Two general notch geometries have been used for these series of tests: U notch and V notch specimens. The notches produce a tri axial stress state, though not uniform across the specimen. Characterization of the creep behavior of the U notch specimens and the creep rupture behavior of the V notch specimens provides a good approximation of the behavior expected of actual components. Preliminary testing and analysis have been completed and are reported in this document. This includes results from V notch specimens tested at 900°C and 800°C. Failure occurred in the smooth gage section of the specimen rather than at the root of the notch, though some damage was present at the root of the notch, where initial stress was highest. This indicates notch strengthening behavior in this material at these temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Spider silk MASP1 and MASP2 proteins as carbon fiber precursors

The objective of this project is to develop an unconventional non-petroleum based carbon fiber precursor which has the potential to be produced in high yield and quantities. Methods will be developed to produce pilot-scale quantities of fibers from spider silk proteins with mechanical properties at least 75% that of the natural dragline silk fibers in tensile strength and elongations of less than 5%. The precursor fibers will be converted to carbon fibers, with a goal of >250Ksi strength and 1-2% elongation. Cost analysis will be performed and the process optimized. Task 1: Subtask 1. Protein production: We exceeded the go/ no go milestone of 1.0g/L of one of the spider silk protein (MSp2) purified last FY and have now increased from 5L to 500L fermentations. We have made a series of changes to the purification protocol from the initial report last FY. These led to a reduction in the time needed for the purification and reduced the purification costs by nearly 90%. Subtask 2. Fiber spinning: The major focus has been to produce more material to send 24 fiber thread to ONRL. We are still developing the methodology to successfully spin 24 fiber yarns. This involves both the spinning dope solutions as well as the methods to keep the fibers from fusing during the post spin stretch. The second area of focus has been to standardize the spin dopes for making the fibers. We now know that the conductivity (indicative of salt remaining with the protein after purification) is an important factor in successful spinning as is the pH. We now know that we need to be below 600 uS conductivity and that the most effective pH is protein dependent. Subtask 3. Silkworm silk: We have found the transgenic silkworms made using gene replacement at the fibroin light chain instead of heavy chain as we did previously have a higher tensile strength. See figures below showing the curve for the top end of the cocoon fibers. This tensile strength is the same as the average for spider dragline silk. Task 2. Carbonization: The major accomplishment in the latter part of the work is that the ONRL group has successfully heated the spider silk protein fibers all the way up to 1700°C and produced a very competitive carbon fiber based on mechanical properties. Several important factors were discovered during these initial trials: 1) the ramp speed for increasing the temperature is critical; 2) maintaining tension on the fiber during the heating process because as it is heated it tends to expand; and 3) narrow temperature window in which stretching the fiber during heating leads to much better final materials. Task 3. Techno-Economic Methods: The techno-economic analysis was expanded to determine the relative cost of production with the bacterial production system compared to the transgenic alfalfa and goat production systems. The comparisons show two important things. For all systems the key factor in the final price is the amount of spider silk protein produced for whatever measure of volume or weight is used. Second alfalfa can be the cheapest but is subject to the possible regulatory control unless the US develops a more comprehensive approach to GMOs. The silkworm analysis was not completed due to a variety of confounding factors. The primary one was that if the production were shifted overseas then the cost would likely be nearly equivalent to current silk prices of $5-15/kg. However if concerns about the location of production is important then it would need to be done in the US and initial costs would be much higher but if the later scenario is utilized then the cost would be lowered but it was not possible to calculate exact costs.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Magnesium Diboride thin Films, multilayers, and coatings for SRF cavities

Superconducting radio frequency (SRF) cavities currently use low-temperature superconductor niobium, and the Nb SRF cavities have approached the performance levels predicted theoretically. Compared to Nb, MgB 2 becomes superconducting at a much higher temperature and promises a better RF performance in terms of higher quality factor Q and higher acceleration capability. An MgB 2 SRF technology can significantly reduce the operating costs of particle accelerators when these potentials are realized. This project aimed to advance the development of an MgB 2 SRF technology. It had two main objectives: (1) materials issues of MgB 2 thin films and multilayers related to their applications in SRF cavities; and (2) coating single-cell cavities for testing at RF frequencies. The key technical thrust of the project is the deposition of high quality clean MgB 2 films and coatings by the hybrid physical-chemical vapor deposition (HPCVD) technique, which was developed in my group. We have achieved technical progress in each of the two areas. For the first objective, we have confirmed that MgB 2 thin film coatings can be used to effectively enhance the vortex penetration field of an SRF cavity. A vortex is a normal region in the shape of spaghetti that threads through a superconductor. Its existence is due to an applied magnetic field that is greater than a so-called lower critical field, H c1 . Once a vortex enters the superconductor, its movement leads to loss. This has been shown to be the reason for an SRF cavity to break down. Thus, enhancing the magnetic field for a vortex to enter the superconductor that forms the SRF cavity has be a goal of intense research. To this end, Gurevich proposed that a coating of thin superconductor layer can impede the vortex entrance. In this project, we have done two important experiment to test this concept. One, we showed that the enhancement of H c1 can be achieved by using in both epitaxial and polycrystalline MgB 2 films. Although H c1 is low for bulk MgB 2 samples, about 600 Oe at 5 K, it increases with decreasing film thickness, reaching 1880 Oe when the film thickness is 100 nm. Two, we coated Nb ellipsoids with MgB 2 films to achieve an “inverse cavity” configuration, mimicking the coating of an actual RF cavity. Our results demonstrate that it is indeed possible to increase the vortex penetration field of a cavity by a substantial amount (~600 Oe) by coating it with a thin MgB 2 film. For the second objective, we modified the existing HPCVD system to be able to coat a 3.9 GHz SRF cavity, and using a stainless steel mock cavity showed that a uniform film with good superconducting property can be grown across the cavity interior. Further, we successfully deposited MgB 2 on Cu disc. The two results combined demonstrate that it is possible to coat Cu cavities with high quality MgB 2 films using HPCVD. MgB 2 coated Cu could open up a possibility of using SRF cavities at 20–25 K with cryocoolers.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Effects of Laser Etching on the Corrosion Susceptibility of SAVY 4000 and Hagan Containers

Since the late 1990’s, the Hagan container was used as the primary container for packaging of plutonium-bearing materials. The Hagan design consisted of a threaded closure, a Viton® ORing, a carbon-carbon filter, and a 304L stainless steel (SS) body. Over the years, Hagans have shown vulnerability in their design [1]. In 2008, The Department of Energy (DOE) issued DOE M 441.1-1, Nuclear Material Packaging Manual, which detailed an approach to obtain highconfidence in containers by including specific design requirements, material contents and an approach to determine life span from said contents, and surveillance techniques [2]. In response to both the vulnerability issues with the Hagan and DOE M 441.1-1, the SAVY 4000 container with its twist style closure, Viton® O-Ring, Fiberfrax-Gortex filter, and annealed 316L SS body, was designed as the replacement for Hagan containers, but only for a short term lifespan of 5 years [1]. However, both the Hagan and SAVY 4000 are being pushed to maintain a lifespan of 40 years. Therefore, proper confidence must be placed on each component of each container to last a minimum of 40 years. So far, the biggest concern found during surveillance of these containers is corrosion and the potential for failure by corrosion. One concern is that the containers fail due to stress corrosion cracking (SCC), especially around the weld between the collar and the body as welds leave residual stresses. One advantage the SAVY 4000 has is that the body is annealed, but its weld is still susceptible as it was welded after annealing [3, 4]. Moreover, 316L SS is known to have a higher pitting resistance (pits are a precursor to SCC and can also lead to extensive failure of the material), than 304L SS [4]. During recent surveillance activities, two SAVY 4000’s containing Solution Assay Instrument (SAI) solutions were opened. The SAI SAVY 4000’s contained plutonium (Pu) in 3M HCl solution in plastic volumetric flasks placed inside of polyethylene bags. Historically, a SAVY 4000 containing an SAI solution is packaged for 3 weeks, however, these particular containers were not reopened until 14 months later. When opened, brown-red corrosion product was found all over the inside of the container as shown in Figure 1.

36 MATERIALS SCIENCE↗
DOE OSTI2017

UPC++ Programmer’s Guide (v1.0 2017.9)

UPC++ is a C++11 library that provides Asynchronous Partitioned Global Address Space (APGAS) programming. It is designed for writing parallel programs that run efficiently and scale well on distributed-memory parallel computers. The APGAS model is single program, multiple-data (SPMD), with each separate thread of execution (referred to as a rank, a term borrowed from MPI) having access to local memory as it would in C++. However, APGAS also provides access to a global address space, which is allocated in shared segments that are distributed over the ranks. UPC++ provides numerous methods for accessing and using global memory. In UPC++, all operations that access remote memory are explicit, which encourages programmers to be aware of the cost of communication and data movement. Moreover, all remote-memory access operations are by default asynchronous, to enable programmers to write code that scales well even on hundreds of thousands of cores.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

UPC++ Programmer’s Guide, v1.0-2018.3.0

UPC++ is a C++11 library that provides Partitioned Global Address Space (PGAS) programming. It is designed for writing parallel programs that run efficiently and scale well on distributed-memory parallel computers. The PGAS model is single program, multiple-data (SPMD), with each separate thread of execution (referred to as a rank, a term borrowed from MPI) having access to local memory as it would in C++. However, PGAS also provides access to a global address space, which is allocated in shared segments that are distributed over the ranks. UPC++ provides numerous methods for accessing and using global memory. In UPC++, all operations that access remote memory are explicit, which encourages programmers to be aware of the cost of communication and data movement. Moreover, all remote-memory access operations are by default asynchronous, to enable programmers to write code that scales well even on hundreds of thousands of cores.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2017

XPRESS: eXascale PRogramming Environment and System Software, Final Report

The University of Oregon (UO) was a partner in the XPRESS project together with Sandia National Laboratories (SNL), Indiana University (IU), Lawrence Berkeley National Laboratory (LBL), Louisiana State University (LSU), Oak Ridge National Laboratory (ORNL), University of Houston (UH), and University of North Carolina (RENCI). UO's objective in the project was to develop "APEX (Asynchronous Performance Environment for eXascale)": performance measurement, analysis, feedback and control infrastructure to asynchronous tasking runtimes, specifically HPX (LSU) and HPX-5 (IU). During the project period, our efforts focused on the need to measure complex tasking models where the traditional instrumentation methods would not work due to an absent/meaningless call-path context and runtime control of task pre-emption and resumption, usually on a different operating system thread. In addition to the challenges of performance measurement, we developed a framework to provide information from all levels of the stack (hardware, operating system, runtime, application) to a feedback & control mechanism for controlling concurrency, task granularity, networking parameters, and other aspects of execution in order to improve execution performance, throughput and/or efficiency. UO demonstrated these developments on leading edge HPC machines at large scale, including a 2017 Gordon Bell submission in which APEX was used to optimize key bottlenecks in an astrophysics application. The following final report summarizes our accomplishments during the XPRESS project.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2018

Targeting Maturation and Quality Control of Photosynthetic Membrane Proteins

Plsp1 is a type I signal peptidase that is responsible for removing the targeting signal peptide from passenger proteins upon their delivery to the thylakoid lumen. Plsp1 is itself a resident of the thylakoid membrane, with a single membrane anchor and the catalytic domain facing the lumen. Work to uncover the targeting mechanism for this protein has been underway in the Inoue lab from the previous DOE funding period has established that Plsp1 is targeted at the thylakoid by the Sec1 translocase, and that it passes through a high molecular weight intermediate in the stroma en route to the thylakoid membrane. During this funding period we have demonstrated by MS/MS of immunoprecipitated samples that the high molecular weight complex containing Plsp1 in the stroma contains primarily the α1 and β1 forms of Cpn60 in approximately equal amounts. Mixing experiments with overexpressed purified proteins have reproduced the Cpn60/Plsp1 complex. Surprisingly, the co-chaperonins Cpn10 and Cpn20 were not detected in the immunoprecipitated sample, even though they are able to bind to the Cpn60/Plsp1 complex formed in mixing experiments. We have further confirmed that the addition of purified stromal cpSecA1 results in a decrease in the amount of Plsp1 successfully incorporated into the thylakoid membrane. We are currently working on experiments to describe the conditions for the handoff between Cpn60 and cpSec1 in the stroma prior to membrane targeting. The structure of Plsp1 can be inferred by threading its sequence onto the structure of its E. coli homologue LepB to contain a single membrane anchor followed by a soluble structure consisting of ten β strands. In the last DOE funding period it was determined that the transmembrane domain not only acts as the membrane anchor, but probably mediates the interaction with cpSecA1. We have now determined that the binding to Cpn60 is likely mediated by β strands 1 and 2. What is the mechanism and significance of oxidative folding of Plsp1? It was found during the last DOE funding period that Plsp1 purified after overexpression in E. coli loses its peptidase activity upon reduction of its conserved cysteines. We have now determined that Plsp1 undergoes a measurable conformational change upon reduction, both by monitoring susceptibility to protease and by native tryptophan fluorescence. We have also shown that Plsp1 is at least partly, and likely completely, oxidized in the thylakoid lumen. While these results were not unexpected, experiments on Plsp1 in vivo were completely surprising. We have known for years (from work conducted with prior DOE funding) that a Plsp1 knockout is embryo lethal. Accordingly, given that reduction of the isolated protein inactivates it, we expected that plants in which one or both of the cysteine pair were mutated would also lead to a severe mutant phenotype. This was not observed, and in fact, these mutants complemented fully the plsp1 plants. This lead to the hypothesis that either association with an interacting protein or with the membrane preserves Plsp1structure even when the disulfides are reduced. Work performed in the last DOE funding cycle revealed that Pgrl1, a protein reportedly involved in cyclic electron flow, interacts stably with Plsp1. However, the Plsp1 cysteine-less mutants are still able to compliment the plsp1 mutant even in the pgrl1 knockout mutant background. We have also found that in vitro activity of Plsl1 is not abolished by reduction in thylakoids that have been permeabilized by low concentrations of detergent, whereas the activity of fully extracted protein is. This points to membrane association as the condition important to activity, and by extension, structure preservation. We are presently working to isolate Plsp1 in a lipid nanodisk to test this hypothesis.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

DARMA-Kokkos Data and Execution Interoperability WBS 2.3.1.04 Milestone 16 (ECP Milestone Report)

DARMA (Distributed Asynchronous Resilient Models for Applications) is a runtime library supporting the Sandia ATDM (Advanced Technology Development and Mitigation) program. The main application drivers fall within the ECP milestone 2.2.5.03 ADNN03-ASC ATDM SNL Application, which includes applications that require load balancing and asynchronous communication for high performance. The DARMA runtime infrastructure has been modified to be compatible with Kokkos/OpenMP parallelization within tasks, which is a critical requirement for high performance for the Sandia ATDM apps. DARMA development has occurred in parallel with a verification milestone for ATDM in FY18. For FY19, DARMA should impact ATDM by enabling dynamic load balancing and communication through only incremental changes to the existing verified MPI codes. DARMA can now support the intra-kernel thread parallelization in the parent MPI apps, allowing DARMA to be easily added without rewriting individual math kernels. The results presented here demonstrate the DARMA results for an MPI mini-app.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

Program Fuzzing on High Performance Computing Resources

American Fuzzy Lop (AFL) is an evolutionary fuzzer that is strategically implemented as a tool for discovering bugs in software during vulnerability research. This work seeks to understand how to best implement AFL on the High-Performance Computing resources available on the unclassified network at Sandia National Laboratories. We investigate various methods of executing AFL, requesting varying numbers of tasks on single compute nodes with 36 physical cores and 72 total threads. A Python script called Blue Claw is presented as an automated testbed generator tool to assist in the tedious process of creating and executing experiments of any scale and duration.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

Design, Synthesis and Characterization of Triptycene-Containing Macromolecules with Hierarchically Controlled Architectures as Functional Membrane Materials for Energy Applications

This DOE CAREER award supported the Guo research group at the University of Notre Dame in its efforts to develop hierarchically functional polymer membrane materials based on iptycene unit to enable energy-efficient molecular separations and fast ion transport in polymeric membranes. To do this, the Guo group engaged in three major research objectives, each exploiting a unique molecular motif offered by iptycene units: (1) developing glassy microporous polymers with exquisitely tailored free volume microporosity for ultra-fast and selective gas transport; (2) developing robust PEO-rich multicomponent polymers via supramolecular reinforcement for CO 2 -selective membranes; and (3) developing ion-containing, nanophase separated multiblock copolymers with suppressed water swelling and fast proton transport for hydrogen fuel cells. Through the research in this project, the iptycene strategy has established a new paradigm of macromolecular design for harnessing free volume microporosity and specific structure motifs to facilitate fast and selective molecular and ion transport in polymers. The results from this project not only provide new fundamental knowledge to the membrane community and broader materials community, but also bridge the technical gaps via providing robust high performance polymer materials for a wide range of applications that impact energy and environmental sustainability. This technical report summarizes the major accomplishments of the study of these innovative polymer membrane materials in this project. For example, introducing triptycene unit into polybenzoxazole structures led to superior size sieving properties, which, along with their ultrahigh gas permeability, placed these polymers among the best gas separation membranes ever reported; the study of PEO-based model network structures demonstrated for the first time that crosslink inhomogeneity (i.e., uneven distribution of crosslink sites)–an previously unexplored structure parameter, plays a significant role in regulating gas transport, ushering in a completely new dimension in the design of crosslinked polymers with broad applicability; exploiting the unique supramolecular interlocking and chain threading interactions and the internal free volume offered by iptycene units addressed the grand challenge of excessive water swelling encountered by conventional ion-containing polymers while allowing nanophase separated membrane morphologies enabling fast ion transport. The new polymer membrane materials and the new macromolecular design strategies developed from this project hold great potential for a much wider applicability beyond gas separations and polyelectrolyte membranes.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Conceptual Design for Replaceable Paddle for the Saltstone Production Facility (SPF) Mixer

The primary objective of this task was to provide a recommendation for a replaceable paddle that could be incorporated into the Saltstone Production Facility (SPF) process. The replaceable paddle concept was proposed given the time it took to replace the existing paddle designs was approximately a week of downtime. Two different types of replaceable paddles were considered, a split paddle and a replaceable tip paddle. The split paddle design was developed; however, a review of the drawings by maintenance personnel determined that changeout of the new design would take about the same time/effort as replacing the existing paddles. Five different replaceable tip designs were considered: side attachment, V neck, straight notch, angled notch, and dovetail. The recommended replaceable tip design was the angled notch, which includes a central hub with two angled notches, where the replaceable tips are secured to the hub using two ½” – 13 Unified National Coarse Threads (UNC) socket head cap screws (SHCS). Design drawing for both the flat and helical paddle blades are complete and are included in Appendix A. A structural calculation (M-CLC-Z-00137) was performed on this design which determined the design is structurally adequate for normal or extreme loads that would be encountered in the SPF READCOTM mixer. This calculation is included in Appendix C. Based on the calculation, mechanical failure will not limit the life of the tip or tip attachment. The quantity of erosion will be the primary driver dictating tip replacement schedules.

42 ENGINEERING↗
DOE OSTI2019

Next-Generation Analysis and Visualization Platform for Manufacturing and Engineering Workflows (Final Report)

Advanced manufacturing and engineering are fundamental to the economic strength and national security of the United States. With the introduction of advanced modeling and simulation practices in manufacturing and engineering over the last several decades, we are producing better products, more quickly, and at decreased cost. Through the adoption of high-performance computing (HPC) enabled workflows, in small- to medium-sized manufacturers and engineering firms, which employ fewer than 500 people, is renewing United States manufacturing and engineering. Despite successes, there are significant barriers to widespread adoption of these tools. Our Phase I SBIR project, Next-Generation Analysis and Visualization Platform for Manufacturing and Engineering Workflows, aims to address several of these barriers. Our project helped us evaluate the feasibility and benefits and mitigate risks of asynchronous processing for analysis and visualization workflows. We evaluated the impact of asynchronous, non-blocking communication can have on the user experience in a complex visualization application. Besides the impact on users, we wanted to understand the impacts on developers (development application programming interfaces (APIs))and generated applications (robustness and stability). Any asynchronous platform implementation is bound to rely on multiple threads which can make the programming model extraordinarily complex and prone to bugs. If not managed carefully, the complexity and resulting instability would be an unacceptable evolution for widely used production tools like ParaView and putting the success of the Phase II project at risk.

42 ENGINEERING↗
DOE OSTI2018

Advanced Data Structures for Improved Cyber Resilience and Awareness in Untrusted Environments: LDRD Report

This report summarizes the work performed under the project "Advanced Data Structures for Improved Cyber Resilience and Awareness in Untrusted Environments." The goal of the project was to design, analyze, and test new data structures for cybersecurity applications. We had two major thrusts: 1) using new/improved write-optimized data structures and/or algorithms to better man- age and analyze high-speed massive-volume cyberstreams, and 2) adding security features to data structures at minimum cost. Write optimization allows data structures to better use secondary memory to store and search a larger amount of useful information. Secondary memory is large compared to main memory, but data movement to and from secondary memory must be carefully managed to run quickly enough to keep up with fast streams. The first thrust included managing cyberstreams in parallel, both multi-threaded and distributed, and improving the benchmarking infrastructure for testing new streaming data structures. We considered both (near) real-time discovery of particular patterns, and improved logging for improved forensics. We considered two kinds of security-feature problem. The first was high-performance history- independent external-memory data structures. These provide certain protections to data if a disk is stolen. We also prove some trade-offs between speed and security in this setting. The second data-security problem is more secure data look-up in secret-shared data bases. This report summarizes the project's major accomplishments, with the background to under- stand these accomplishments. It gathers the abstracts and references for the six refereed publications that have appeared as part of this work. We summarize several accomplishments that will be submitted for publication. We then archive one piece of partial work that is not likely to be published in the near future: validation of history-independent data structure implementations.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

A Need for Better Management of Heterogenous HPC Resources

Achieving computational rates beyond the petascale requires an increasing amount of heterogeneity in our highperformance computing (HPC) hardware. This heterogeneity, in turn, means that a node of an HPC system can no longer be considered a monolithic resource. Rather, a node has many individual components such as processors, cores, SMT threads, accelerators, and tierd memories that must be further allocated and managed by... something. Currently, that something is an ad-hoc mix of arguments and environments when launching jobs. We follow the same process used on prior HPC systems with nodes of uniform components; unfortunately, the shims introduced to provide the additional specification of node-level components are inconsistent and unwieldy. As we shall see, even at our current moderate level of heterogeneity our effective utilization of HPC software is hampered by poor resource management. Future systems will continue to grow in heterogeneity both in number and type of resources. Our current approach to resource management cannot scale. We need a more cohesive approach to managing heterogeneous resources in HPC systems.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

Simulations of Neutron Time-of-Flight Method by Inelastic Scattering Carbon-12 using MCNP6 and Geant4

A neutron spectroscopy technique using neutron time-of-flight (TOF) with gamma tagging from inelastic scattering on carbon-12 was examined using MCNP6 and Geant4. Experimental data for the 12 C(n,n'$γ$) reaction from D. Spaargaren and C.C. Jonken was used to supplement the simulations due to their limitations with modeling correlated particles on an event-by-event basis. The MCNP and Geant4 models relied on different methods to determine the efficiencies and were compared against each other for validation of the results. The total efficiency of coincident detection as determined by MCNP is around 6.32E-11. That is, around 6 events will be detected per 100 billion source neutrons. It was found that the amount of neutrons which lose energy to elastic scattering is not negligible, and efforts to reconstruct the beam energy from the detected neutrons must take this into account. Running on 40 computer cores in multi-threading mode, the Geant4 model could simulate about half a billion source neutrons per hour. In the absence of biasing methods, Geant4 can not simulate the efficiency in any reasonable amount of time given current computing power. Further efforts will be made to introduce biasing to the simulation to verify the MCNP results.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Software Requirements for ATDM On-Node Resource Management

This report outlines the software requirements for on-node resource management in the Advanced Simulation and Computing (ASC) Advanced Technology Development and Mitigation (ATDM) project at Sandia National Laboratories (SNL). The need for on-node resource management has arisen from the componentization of the software stack. Componentization aids in managing complexity and making software more composable and reusable. However, components must compete for limited on-node resources for execution (e.g., cores and hardware threads) and memory. The requirements documented in this report support an effort to manage this contention, avoiding oversubscription of resources and enabling their efficient deployment for application execution.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2016

Hierarchical Task-Data Parallelism using Kokkos and Qthreads

This report describes a new capability for hierarchical task-data parallelism using Sandia's Kokkos and Qthreads, and evaluation of this capability with sparse matrix Cholesky factorization and social network triangle enumeration mini-applications. Hierarchical task-data parallelism consists of a collection of tasks with executes-after dependences where each task contains data parallel operations performed on a team of hardware threads. The collection of tasks and dependences form a directed acyclic graph of tasks - a task DAG. Major challenges of this research and development effort include: portability and performance across multicore CPU; manycore Intel Xeon Phi, and NVIDIA GPU architectures; scalability with respect to hardware concurrency and size of the task DAG; and usability of the application programmer interface (API).

97 MATHEMATICS AND COMPUTING↗