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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Heavy Ion Irradiation Fluence Dependence for Single-Event Upsets in a NAND Flash Memory

We investigated the single-event effect (SEE) susceptibility of the Micron 16 nm NAND flash, and found that the single-event upset (SEU) cross section varied inversely with cumulative fluence. We attribute the effect to the variable upset sensitivities of the memory cells. Furthermore, the effect impacts only single cell upsets in general. The rate of multiple-bit upsets remained relatively constant with fluence. The current test standards and procedures assume that SEU follow a Poisson process and do not take into account the variability in the error rate with fluence. Therefore, traditional SEE testing techniques may underestimate the on-orbit event rate for a device with variable upset sensitivity.

NAND flash memory↗
DOE OSTI2020

Effect of directed aging on nonlinear elasticity and memory formation in a material

Disordered solids often change their elastic response as they slowly age. Using experiments and simulations, we study how aging disordered planar networks under an applied stress affects their nonlinear elastic response. We are able to modify dramatically the elastic properties of our systems in the nonlinear regime. Using simulations, we study two models for the microscopic evolution of properties of such a material; the first considers changes in the material strength, while the second considers distortions in the microscopic geometry. Both models capture different aspects of the experiments including the encoding of memories of the aging history of the system and the dramatic effects on the material’s nonlinear elastic properties. Our results demonstrate how aging can be used to create complex elastic behavior in the nonlinear regime.

36 MATERIALS SCIENCE↗
NASA NTRS1991

Memory implications of the spin-value effect in soft multilayers

New multilayer permalloy materials with thin separation layers that have significantly increased M-R coefficients at room temperature have the potential for substantially increasing both the speed and density of M-R memories. An analysis in the following discussion shows that the bit density at a given performance level is related to the product of M-R response and sheet resistivity when operating at the current-density limit. With a doubling of both sheet resistivity and M-R response over existing materials, the bit area can be reduced by about a factor of 4. Alternatively, if the bit area is kept the same, signal output is increased by a factor of 4 and circuit time constants can be reduced by a factor of 16.

Pohm, A. V.↗
DOE OSTI2014

Total ionizing dose effect of γ-ray radiation on the switching characteristics and filament stability of HfOx resistive random access memory

The total ionizing dose (TID) effect of gamma-ray (γ-ray) irradiation on HfOx based resistive random access memory was investigated by electrical and material characterizations. The memory states can sustain TID level ∼5.2 Mrad (HfO{sub 2}) without significant change in the functionality or the switching characteristics under pulse cycling. However, the stability of the filament is weakened after irradiation as memory states are more vulnerable to flipping under the electrical stress. X-ray photoelectron spectroscopy was performed to ascertain the physical mechanism of the stability degradation, which is attributed to the Hf-O bond breaking by the high-energy γ-ray exposure.

36 MATERIALS SCIENCE↗
NASA NTRS2003

Mitigating Upsets in SRAM-Based FPGAs from the Xilinx Virtex 2 Family

Static random access memory (SRAM) upset rates in field programmable gate arrays (FPGAs) from the Xilinx Virtex 2 family have been tested for radiation effects on configuration memory, block RAM and the power-on-reset (POR) and SelectMAP single event functional interrupts (SEFIs). Dynamic testing has shown the effectiveness and value of Triple Module Redundancy (TMR) and partial reconfiguration when used in conjunction. Continuing dynamic testing for more complex designs and other Virtex 2 capabilities (i.e., I/O standards, digital clock managers (DCM), etc.) is scheduled.

SEE testing↗
DOE OSTI2018

An Empirical Roofline Methodology for Quantitatively Assessing Performance Portability

System and node architectures continue to diversify to better balance on-node computation, memory capacity, memory bandwidth, interconnect bandwidth, power, and cost for specific computational workloads. For many application developers, achieving performance portability (effectively exploiting the capabilities of multiple architectures) is a desired goal. Unfortunately, dramatically different per-node performance coupled with differences in machine balance can lead to developers being unable to determine whether they have attained performance portability or simply written portable code. The Roofline model provides a means of quantitatively assessing how well a given application makes use of a target platform’s computational capabilities. In this paper, we extend the Roofline model so that it 1) empirically captures a more realistic set of performance bounds for CPUs and GPUs, 2) factors in the true cost of different floating-point instructions when counting FLOPs, 3) incorporates the effects of different memory access patterns, and 4) with appropriate pairing of code performance and Roofline ceiling, facilitates the performance portability analysis.

Computer Science↗
DOE OSTI2016

Thermodynamics of multicaloric effects in multiferroic materials: application to metamagnetic shape-memory alloys and ferrotoroidics

In this paper, we develop a general thermodynamic framework to investigate multicaloric effects in multiferroic materials. This is applied to the study of both magnetostructural and magnetoelectric multiferroics. Landau models with appropriate interplay between the corresponding ferroic properties (order parameters) are proposed for metamagnetic shape-memory and ferrotoroidic materials, which, respectively, belong to the two classes of multiferroics. For each ferroic property, caloric effects are quantified by the isothermal entropy change induced by the application of the corresponding thermodynamically conjugated field. The multicaloric effect is obtained as a function of the two relevant applied fields in each class of multiferroics. It is further shown that multicaloric effects comprise the corresponding contributions from caloric effects associated with each ferroic property and the cross-contribution arising from the interplay between these ferroic properties. Finally, this article is part of the themed issue ‘Taking the temperature of phase transitions in cool materials’.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1988

Shape memory alloys: New materials for future engineering

Shape memory is a new material property. An alloy which experiences relative severe plastic deformation resumes its original shape again after heating by 10 to 100 C. Besides simple shape memory, in similar alloys there is the second effect where the change in shape is caused exclusively by little temperature change. In pseudo-elasticity, the alloy exhibits a rubber-like behavior, i.e., large, reversible deformation at little change in tension. Beta Cu and beta NiTi alloys have been used in practice. The probability is that soon alloys based on Fe will become available. Recently increasing applications for this alloy were found in various areas of technology, even medical technology. A review with 24 references is given, including properties, production, applications and fundamental principles of the shape memory effect.

Hornbogen, E.↗
DOE OSTI2019

The Influence of High-Energy Krypton Ion Implantation Temperature on Structure and Properties of Ni–Ti Alloy

The influence of the temperature of implantation of Ni–Ti shape memory alloy with {sub 84}Kr{sup 15+}ions at the energy E = 147 MeV on its structural-phase state is investigated. At the implantation temperatures 250 and 300°С, within the projective range Rp and out-range area the following processes and phenomena are observed: new formation of the martensitic В19'-phase, formation of nano-sized particles of the R-phase, increase in resistivity due to the formation of radiation-defect structures, strengthening of the alloy in the austenitic structural-phase state, and longer phase-transition temperature intervals.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

APOE effect on Alzheimer's disease biomarkers in older adults with significant memory concern

This study assessed apolipoprotein E (APOE) ε4 carrier status effects on Alzheimer's disease imaging and cerebrospinal fluid (CSF) biomarkers in cognitively normal older adults with significant memory concerns (SMC). Cognitively normal, SMC, and early mild cognitive impairment participants from Alzheimer's Disease Neuroimaging Initiative were divided by APOE ε4 carrier status. Diagnostic and APOE effects were evaluated with emphasis on SMC. Additional analyses in SMC evaluated the effect of the interaction between APOE and [ 18 F]Florbetapir amyloid positivity on CSF biomarkers. SMC ε4+ showed greater amyloid deposition than SMC ε4-, but no hypometabolism or medial temporal lobe (MTL) atrophy. SMC ε4+ showed lower amyloid beta 1-42 and higher tau/p-tau than ε4-, which was most abnormal in APOE ε4+ and cerebral amyloid positive SMC. Lastly, SMC APOE ε4+ show abnormal changes in amyloid and tau biomarkers, but no hypometabolism or MTL neurodegeneration, reflecting the at-risk nature of the SMC group and the importance of APOE in mediating this risk.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Modeling the Coupled Chemo-Thermo-Mechanical Behavior of Amorphous Polymer Networks.

Amorphous polymers exhibit a rich landscape of time-dependent behavior including viscoelasticity, structural relaxation, and viscoplasticity. These time-dependent mechanisms can be exploited to achieve shape-memory behavior, which allows the material to store a programmed deformed shape indefinitely and to recover entirely the undeformed shape in response to specific environmental stimulus. The shape-memory performance of amorphous polymers depends on the coordination of multiple physical mechanisms, and considerable opportunities exist to tailor the polymer structure and shape-memory programming procedure to achieve the desired performance. The goal of this project was to use a combination of theoretical, numerical and experimental methods to investigate the effect of shape memory programming, thermo-mechanical properties, and physical and environmental aging on the shape memory performance. Physical and environmental aging occurs during storage and through exposure to solvents, such as water, and can significantly alter the viscoelastic behavior and shape memory behavior of amorphous polymers. This project – executed primarily by Professor Thao Nguyen and Graduate Student Rui Xiao at Johns Hopkins University in support of a DOE/NNSA Presidential Early Career Award in Science and Engineering (PECASE) – developed a theoretical framework for chemothermo- mechanical behavior of amorphous polymers to model the effects of physical aging and solvent-induced environmental factors on their thermoviscoelastic behavior.

36 MATERIALS SCIENCE↗
NASA NTRS2016

Heavy Ion Irradiation Fluence Dependence for Single-Event Upsets of NAND Flash Memory

We investigated the single-event effect (SEE) susceptibility of the Micron 16 nm NAND flash, and found the single-event upset (SEU) cross section varied inversely with fluence. The SEU cross section decreased with increasing fluence. We attribute the effect to the variable upset sensitivities of the memory cells. The current test standards and procedures assume that SEU follow a Poisson process and do not take into account the variability in the error rate with fluence. Therefore, heavy ion irradiation of devices with variable upset sensitivity distribution using typical fluence levels may underestimate the cross section and on-orbit event rate.

Single Event Effects (SEE)↗
NASA NTRS1979

Cosmic ray-induced soft errors in static MOS memory cells

Previous analytical models were extended to predict cosmic ray-induced soft error rates in static MOS memory devices. The effect is due to ionization and can be introduced by high energy, heavy ion components of the galactic environment. The results indicate that the sensitivity of memory cells is directly related to the density of the particular MOS technology which determines the node capacitance values. Hence, CMOS is less sensitive than e.g., PMOS. In addition, static MOS memory cells are less sensitive than dynamic ones due to differences in the mechanisms of storing bits. The flip-flop of a static cell is inherently stable against cosmic ray-induced bit flips. Predicted error rates on a CMOS RAM and a PMOS shift register are in general agreement with previous spacecraft flight data.

Sivo, L. L.↗
DOE OSTI2014

Effects of Transcranial Direct Current Stimulation (tDCS) on Human Memory.

Training a person in a new knowledge base or skill set is extremely time consuming and costly, particularly in highly specialized domains such as the military and the intelligence community. Recent research in cognitive neuroscience has suggested that a technique called transcranial direct current stimulation (tDCS) has the potential to revolutionize training by enabling learners to acquire new skills faster, more efficiently, and more robustly (Bullard et al., 2011). In this project, we tested the effects of tDCS on two types of memory performance that are critical for learning new skills: associative memory and working memory. Associative memory is memory for the relationship between two items or events. It forms the foundation of all episodic memories, so enhancing associative memory could provide substantial benefits to the speed and robustness of learning new information. We tested the effects of tDCS on associative memory, using a real-world associative memory task: remembering the links between faces and names. Working memory refers to the amount of information that can be held in mind and processed at one time, and it forms the basis for all higher-level cognitive processing. We investigated the degree of transfer between various working memory tasks (the N-back task as a measure of verbal working memory, the rotation-span task as a measure of visuospatial working memory, and Raven's progressive matrices as a measure of fluid intelligence) in order to determine if tDCS-induced facilitation of performance is task-specific or general.

Matzen, Laura E.↗
DOE OSTI2014

Mind racing: The influence of exercise on long-term memory consolidation

Over time, regular exercise can lower the risk for age-related decline in cognition. However, the immediate effects of exercise on memory consolidation in younger adults have not been fully investigated. As such, in two experiments, the effects of exercise were assessed on three different memory tasks. These included paired-associate learning, procedural learning and text memory. Results indicate that performance on procedural learning and situation model memory was increased with exercise, regardless of if participants exercised before or after encoding. No benefit of exercise was found for paired-associate learning. These findings suggest that intense exercise may benefit certain types of memory consolidation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Multi-Level Memory Algorithmics for Large, Sparse Problems

In this report, we abstract eleven papers published during the project and describe preliminary unpublished results that warrant follow-up work. The topic is multi-level memory algorithmics, or how to effectively use multiple layers of main memory. Modern compute nodes all have this feature in some form.

97 MATHEMATICS AND COMPUTING↗