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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Planned Investigations to Address Acute Central Nervous System Effects of Space Radiation Exposure with Human Performance Data

This work intends to generate evidence of acute, incremental human performance decrement similar to that due to space radiation andits impacts on the brain, to accompany ongoing human performance modeling work. The planned work will explore the boundaries of human behavioral and performance decrement after exposure to stress, which may be expected based in part on rodent responses found afterexposure to ionizing radiation. The collection of evidence via simulation studies can characterize real human errors toward determining what stress levels lead to significantly-low levels of performance (below permissible outcome limits) which would imperilmission accomplishment. If mission-relevant animal-study-linked tasks are used, human and animal performance levels may be aligned to enable quantitative assignment of permissible exposure limits based on animal exposure studies. Ultimately, a transfer function between the performances of exposed rodents and humans under stress can be developed using shared impairment mechanisms.

human performance↗
DOE OSTI2016

Quantum Mechanical Screening of Single-Atom Bimetallic Alloys for the Selective Reduction of CO 2 to C 1 Hydrocarbons

Electrocatalytic reduction of CO 2 to energy-rich hydrocarbons such as alkanes, alkenes, and alcohols is a very challenging task. So far, only copper has proven to be capable of such a conversion. Here, we report density functional theory (DFT) calculations combined with the Poisson-Boltzmann implicit solvation model to show that single-atom alloys (SAAs) are promising electrocatalysts for CO 2 reduction to C 1 hydrocarbons in aqueous solution. The majority component of the SAAs studied is either gold or silver, in combination with isolated single atoms, M (M = Cu, Ni, Pd, Pt, Co, Rh, and Ir), replacing surface atoms. We envision that the SAA behaves as a one-pot tandem catalyst: first gold (or silver) reduces CO 2 to CO, and the newly formed CO is then captured by M and is further reduced to C 1 hydrocarbons such as methane or methanol. We studied 28 SAAs, and found about half of them selectively favor the CO 2 reduction reaction over the competing hydrogen evolution reaction. Most of those promising SAAs contain M = Co, Rh, or Ir. The reaction mechanism of two SAAs, Rh@Au(100) and Rh@Ag(100), is explored in detail. Both of them reduce CO 2 to methane but via different pathways. For Rh@Au(100), reduction occurs through the pathway *CO → *CHO → *CHOH → *CH + H 2 O (l) → *CH 2 + H 2 O (l) → *CH 3 + H 2 O (l) → * + H 2 O (l) + CH 4(g) ; whereas, for Rh@Ag(100), the pathway is *CO → *CHO → *CH 2 O→ *OCH 3 → *O + CH 4(g) → *OH + CH 4(g) →* + H 2 O (l) + CH 4(g) . The minimum applied voltages to drive the two electrocatalytic systems are -1.01 and -1.12 V RHE for Rh@Au(100) and Rh@Ag(100), respectively, at which the Faradaic efficiencies for CO 2 reduction to CO are 60% for gold and 90% for silver. This suggests that SAA can efficiently reduce CO 2 to methane with as small as 40% loss to the hydrogen evolution reaction for Rh@Au(100) and as small as 10% for Rh@Ag(100). Lastly, we hope these computational results can stimulate experimental efforts to explore the use of SAA to catalyze CO 2 electrochemical reduction to hydrocarbons.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Performance of Julia for High Energy Physics Analyses

We argue that the Julia programming language is a compelling alternative to currently more common implementations in Python and C++ for common data analysis workflows in high energy physics. We compare the speed of implementations of different workflows in Julia with those in Python and C++. Furthermore, our studies show that the Julia implementations are competitive for tasks that are dominated by computational load rather than data access. For work that is dominated by data access, we demonstrate an application with concurrent file reading and parallel data processing.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2023

Code modernization strategies for short-range non-bonded molecular dynamics simulations

Modern HPC systems are increasingly relying on greater core counts and wider vector registers. Thus, applications need to be adapted to fully utilize these hardware capabilities. One class of applications that can benefit from this increase in parallelism are molecular dynamics simulations. In this paper, we describe our efforts at modernizing the ESPResSo++ simulation package for molecular dynamics by restructuring its particle data layout for efficient memory accesses and applying vectorization techniques to benefit the calculation of short-range non-bonded forces, which results in an overall three times speedup and serves as a baseline for further optimizations. We also implement fine-grained parallelism for multi-core CPUs through HPX, a C++ runtime system which uses lightweight threads and an asynchronous many-task approach to maximize concurrency. Our goal is to evaluate the performance of an HPX-based approach compared to the bulk-synchronous MPI-based implementation. This requires the introduction of an additional layer to the domain decomposition scheme that defines the task granularity. On spatially inhomogeneous systems, which impose a corresponding load-imbalance in traditional MPI-based approaches, we demonstrate that by choosing an optimal task size, the efficient work-stealing mechanisms of HPX can overcome the overhead of communication resulting in an overall 1.4 times speedup compared to the baseline MPI version.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2014

Reproducibility of quantitative measures of binding potential in rat striatum: A test re-test study using DTBZ dynamic PET studies

There is great interest in the study of dopamine (DA) pathways due to the increasing number of patients with illnesses related to the dopaminergic system and molecular imaging based in Positron Emission Tomography (PET) has been proven helpful for this task. Among the different radiopharmaceuticals available to study DA interaction, [{sup 11}C]Dihydrotetrabenazine (DTBZ) has a high affinity for the vesicular monoamine transporter type 2 (VMAT2) and its binding potential (BP) is a marker of DA terminal integrity. This paper reports on the intersubject reproducibility of BP measurements in rat striatum with [11C]DTBZ using the Logańs method.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2017

Kokkos' Task DAG Capabilities.

This report documents the ASC/ATDM Kokkos deliverable "Production Portable Dy- namic Task DAG Capability." This capability enables applications to create and execute a dynamic task DAG ; a collection of heterogeneous computational tasks with a directed acyclic graph (DAG) of "execute after" dependencies where tasks and their dependencies are dynamically created and destroyed as tasks execute. The Kokkos task scheduler executes the dynamic task DAG on the target execution resource; e.g. a multicore CPU, a manycore CPU such as Intel's Knights Landing (KNL), or an NVIDIA GPU. Several major technical challenges had to be addressed during development of Kokkos' Task DAG capability: (1) portability to a GPU with it's simplified hardware and micro- runtime, (2) thread-scalable memory allocation and deallocation from a bounded pool of memory, (3) thread-scalable scheduler for dynamic task DAG, (4) usability by applications.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2018

Production of High Performance Lubricants from Cellulosic Sugar

Certain classes of fatty acids are valuable raw materials that can used to produce bio-based lubricants; however, their broader use has been limited by the high cost and limited availability. The project described in this report was focused on producing a fatty acid methyl ester (FAME) of a specific chain length from cellulosic sugars. Development of a biological pathway and engineered organisms for production of low-cost FAME from cellulosic sugar is a novel and potentially disruptive technology that is supportive of BETO’s mission to displace all fractions of a barrel of crude oil. The project was organized around four tasks that focus on A) production pathway engineering, B) host strain engineering, C) assembly of production pathway in host strain, and D) fermentation process development. Pathway engineering focused on discovery and improvement of two key pathway enzymes, namely 3-keto acetyl CoA synthase (KAS) and wax ester synthase (WES). Both enzymes were improved using a variety of enzyme engineering and mutagenesis approaches, and assembled into a host strain with relevant additional pathway genes and genome modifications. Assembled strains were evaluated in 2-L benchtop fermenters using a commercially produced cellulosic hydrolysate to supply carbon source for FAME production. These evaluations demonstrated that performance targets and final milestones were met or exceeded for sugar uptake rate, product titer, product specificity, and production rate.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Initial Site-Specific De-Inventory Report for Big Rock Point

This report has been developed to satisfy solicitation number 6400013399 under subcontract number 4000138474 issued by UT-Battelle, LLC, managing contractor of Oak Ridge National Laboratory to AREVA Federal Services (AFS). The purpose of this report is to assist the United States (U.S.) Department of Energy (DOE) in laying the groundwork for implementing an integrated waste management system. This includes preparing for future large-scale transport of Spent Nuclear Fuel (SNF), High-Level Radioactive Waste (HLW) and Greater Than Class C (GTCC) Low-Level Radioactive Waste (LLW). This report addresses the tasks, equipment, and interfaces necessary for the complete de-inventory of the Big Rock Point (BRP) site on the eastern shore of Lake Michigan about 4 miles north of Charlevoix and approximately 11 miles west of Petoskey, MI. As such, this report is intended to provide information useful for planning options within the integrated waste management system.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2026

Phenomena Identification and Ranking Tables (PIRT) analysis of wind turbine blade leading edge erosion

Leading edge erosion (LEE) of wind turbine blades has been identified as a major factor in decreased wind turbine blade lifetimes and energy output over time. Accordingly, the International Energy Agency Wind Technology Collaboration Programme (IEA Wind TCP) has created the Task 46 Phase 2 to undertake cooperative research in the key topic of blade erosion. The purpose of Task 46 Erosion Phase 2 is to further improve understanding of erosion driving factors, develop datasets and model tools to enhance prediction of leading-edge erosion likelihood, identify damage at the earliest possible stage and advance potential solutions. The scope of work covers several technical areas, reflecting the multidisciplinary nature of the challenge. Participants in the task are given in Table 1.

17 WIND ENERGY↗
NASA NTRS1972

Effects of n-dominance and group composition on task efficiency in laboratory triads.

Task-oriented triads were formed into various homogeneous and heterogeneous combinations according to their scores on the n-dominance personality trait of the Edwards Personal Preference Schedule. Five group categories were used. The group task required a consensus decision on each trial. High cooperation and interdependence were reinforced by partially restricting the communication network. Results showed heterogeneous groups significantly better at organizing their group communication processes. They consequently performed the task more efficiently than homogeneous triads.

Lampkin, E. C.↗
NASA NTRS1975

Results of an investigation elevon hinge moments and dual panel elevon effectiveness using an .0405-scale model (16-0) of the configuration 140C space shuttle orbiter in the Rockwell International NAAL low speed wind tunnel (OA119B)

Experimental aerodynamic investigations were conducted on a sting mounted .0405-scale representation of the 140C outer mold line space shuttle orbiter in a 7.75 x 11.00 foot low speed wind tunnel during the time period from August 22, 1974 to September 6, 1974. The primary test objectives were to define dual panel elevon/aileron effectiveness and to investigate elevon hinge-moments for the 140C orbiter configuration with wing/elevon upper hingeline sealing flapper doors. The elevon parametric variations, consisting of the basic elevons with 6 inch gaps and flapper doors, elevons with no flapper doors and completely open upper hingeline gap, and an entirely sealed solid elevon, were tested with elevon deflections from +20 to -35 deg at various aileron deflections. Aerodynamic force and moment data were measured in the body axis system by a 2.5 inch task type internal strain gage balance.

Mennell, R. C.↗
NASA NTRS1977

Improvement of the mechanical and thermal properties of the metallized polycarbonate capacitor

Changes were studied which enable polycarbonate metallized film capacitors to withstand 500 thermal shock cycles while maintaining electrical characteristic integrity without becoming intermittent, and without losing hermeticity. The task was for metallized polycarbonate film capacitors designed to meet MIL-C-39022/9 and MIL-C-83421/1. The capacitor design improvements implemented were the insertion of a rubber washer between spray cap and end seal and the utilization of a flexible lead assembly. One hundred fifty capacitors incorporating the design improvements were manufactured and subsequently underwent 500 thermal shock cycles. One hundred forty nine capacitors survived the test. Failure analysis revealed that the lone failure was due to a poor solder joint, initially detected in pre-screening tests as having poor dissipation factor and equivalent series resistance measurement readings.

Kellerman, H. J.↗
NASA NTRS1985

An investigation of the 'von Restorff' phenomenon in post-test workload ratings

The von Restorff effect in post-task ratings of task difficulty is examined. Nine subjects performed a hovercraft simulation task which combined elements of skill-based tracking and rule- and knowledge-based process control for five days of one hour sessions. The effects of isolated increases in workload on rating of task performance, and on the number of command errors and river band hits are analyzed. It is observed that the position of the workload increase affects the number of bank hits and command errors. The data reveal that factors not directly related to the task performance influence subjective rating, and post-task ratings of workload are biased.

Thornton, D. C.↗
NASA NTRS1991

Refinement of ground reference data with segmented image data

One of the ways to determine ground reference data (GRD) for satellite remote sensing data is to photo-interpret low altitude aerial photographs and then digitize the cover types on a digitized tablet and register them to 7.5 minute U.S.G.S. maps (that were themselves digitized). The resulting GRD can be registered to the satellite image or, vice versa. Unfortunately, there are many opportunities for error when using digitizing tablet and the resolution of the edges for the GRD depends on the spacing of the points selected on the digitizing tablet. One of the consequences of this is that when overlaid on the image, errors and missed detail in the GRD become evident. An approach is discussed for correcting these errors and adding detail to the GRD through the use of a highly interactive, visually oriented process. This process involves the use of overlaid visual displays of the satellite image data, the GRD, and a segmentation of the satellite image data. Several prototype programs were implemented which provide means of taking a segmented image and using the edges from the reference data to mask out these segment edges that are beyond a certain distance from the reference data edges. Then using the reference data edges as a guide, those segment edges that remain and that are judged not to be image versions of the reference edges are manually marked and removed. The prototype programs that were developed and the algorithmic refinements that facilitate execution of this task are described.

Robinson, Jon W.↗