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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 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

3D printing of calcined clay-limestone-based cementitious materials

This paper aims to investigate the influences of high Portland cement substitutions (>60 wt%) by low-grade calcined clay (CC) and limestone (LF) on 3D concrete printability, stiffness evolution and early-age hydration. Results show that, with the same dosage of admixtures (superplasticizer and viscosity modifier), increasing LF and CC content reduced the slump, flowability and initial material flow rate, and significantly improved the buildability of fresh mixtures, which can be attributed to the reduced water film thickness (WFT). Furthermore, the stiffness evolution and SSA{sub total} development up to the first 3 h were accelerated by increasing CC content, which can also be linked to the change of WFT, and consumption of superplasticizer for the dispersion induced by hydration products. Additionally, the dilution effect on compressive strength and hydration caused by the high cement replacement was observed.

36 MATERIALS SCIENCE↗
DOE OSTI2013

BROAD N{sub 2}H{sup +} EMISSION TOWARD THE PROTOSTELLAR SHOCK L1157-B1

We present the first detection of N{sub 2}H{sup +} toward a low-mass protostellar outflow, namely, the L1157-B1 shock, at ∼0.1 pc from the protostellar cocoon. The detection was obtained with the IRAM 30 m antenna. We observed emission at 93 GHz due to the J = 1-0 hyperfine lines. Analysis of this emission coupled with HIFI CHESS multiline CO observations leads to the conclusion that the observed N{sub 2}H{sup +}(1-0) line originated from the dense (≥10{sup 5} cm{sup –3}) gas associated with the large (20''-25'') cavities opened by the protostellar wind. We find an N{sub 2}H{sup +} column density of a few 10{sup 12} cm{sup –2} corresponding to an abundance of (2-8) × 10{sup –9}. The N{sub 2}H{sup +} abundance can be matched by a model of quiescent gas evolved for more than 10{sup 4} yr, i.e., for more than the shock kinematical age (≅2000 yr). Modeling of C-shocks confirms that the abundance of N{sub 2}H{sup +} is not increased by the passage of the shock. In summary, N{sub 2}H{sup +} is a fossil record of the pre-shock gas, formed when the density of the gas was around 10{sup 4} cm{sup –3}, and then further compressed and accelerated by the shock.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1994

Chemical and Thermal Analysis

Thermal decomposition activation energies have been determined using two methods of Thermogravimetric Analysis (TGA), with good correlation being obtained between the two techniques. Initial heating curves indicated a two-component system for Coflon (i.e. polymer plus placticizer) but a single component system for Tefzel. Two widely differing activation energies were for Coflon supported this view, 15 kcl/mol being associated with plasticizer, and 40 kcal/mol with polymer degradation. With Tefzel, values were 40-45 kcal/mol, the former perhaps being associated with a low molecular weight fraction. Appropriate acceleration factors have been determined. Thermomechanical Analysis (TMA) has shown considerable dimensional change during temperature cycles. For unaged pipe sections heating to 100 C and then holding the temperature resulted in a stable thickness increase of 2%, whereas the Coflon thickness decreased continuously, reaching -4% in 2.7 weeks. Previously strained tensile bars of Tefzel expanded on cooling during TMA. SEM performed on H2S-aged Coflon samples showed significant changes in both physical and chemical nature. The first may have resulted from explosive decompression after part of the aging process. Chemically extensive dehydrofluorination was indicated, and sulfur was present as a result of the aging. These observations indicate that chemical attack of PVDF can occur in some circumstances.

Bulluck, J. W.↗
DOE OSTI2011

TESTING A PREDICTIVE THEORETICAL MODEL FOR THE MASS LOSS RATES OF COOL STARS

The basic mechanisms responsible for producing winds from cool, late-type stars are still largely unknown. We take inspiration from recent progress in understanding solar wind acceleration to develop a physically motivated model of the time-steady mass loss rates of cool main-sequence stars and evolved giants. This model follows the energy flux of magnetohydrodynamic turbulence from a subsurface convection zone to its eventual dissipation and escape through open magnetic flux tubes. We show how Alfven waves and turbulence can produce winds in either a hot corona or a cool extended chromosphere, and we specify the conditions that determine whether or not coronal heating occurs. These models do not utilize arbitrary normalization factors, but instead predict the mass loss rate directly from a star's fundamental properties. We take account of stellar magnetic activity by extending standard age-activity-rotation indicators to include the evolution of the filling factor of strong photospheric magnetic fields. We compared the predicted mass loss rates with observed values for 47 stars and found significantly better agreement than was obtained from the popular scaling laws of Reimers, Schroeder, and Cuntz. The algorithm used to compute cool-star mass loss rates is provided as a self-contained and efficient computer code. We anticipate that the results from this kind of model can be incorporated straightforwardly into stellar evolution calculations and population synthesis techniques.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Towards validation of combined-accelerated stress testing through failure analysis of polyamide-based photovoltaic backsheets

Abstract Novel methods for advancing reliability testing of photovoltaic (PV) modules and materials have recently been developed. Combined-accelerated stress testing (C-AST) is one such method which has demonstrated reliable reproduction of some field-failures which were not reproducible by standard certification tests. To increase confidence and assist in the development of C-AST, and other new testing protocols, it is important to validate that the failure modes observed and mechanisms induced are representative of those observed in the field, and not the product of unrealistic stress conditions. Here we outline a method using appropriate materials characterization and modelling to validate the failure mechanisms induced in C-AST such that we can increase confidence in the test protocol. The method is demonstrated by applying it to a known cracking failure of a specific polyamide (PA)-based backsheet material. We found that the failure of the PA-based backsheet was a result of a combination of stress factors. Photo-oxidation from ultra-violet (UV) radiation exposure caused a reduction in fracture toughness, which ultimately lead to the cracking failure. We show that the chemical and structural changes observed in the backsheet following C-AST aging were also observed in field-aged samples. These results increase confidence that the conditions applied in C-AST are representative of the field and demonstrates our approach to validating the failure mechanisms induced.

14 SOLAR ENERGY↗
DOE OSTI2012

Rate-based degradation modeling of lithium-ion cells

Accelerated degradation testing is commonly used as the basis to characterize battery cell performance over a range of stress conditions (e.g., temperatures). Performance is measured by some response that is assumed to be related to the state of health of the cell (e.g., discharge resistance). Often, the ultimate goal of such testing is to predict cell life at some reference stress condition, where cell life is defined to be the point in time where performance has degraded to some critical level. These predictions are based on a degradation model that expresses the expected performance level versus the time and conditions under which a cell has been aged. Usually, the degradation model relates the accumulated degradation to the time at a constant stress level. The purpose of this article is to present an alternative framework for constructing a degradation model that focuses on the degradation rate rather than the accumulated degradation. One benefit of this alternative approach is that prediction of cell life is greatly facilitated in situations where the temperature exposure is not isothermal. This alternative modeling framework is illustrated via a family of rate-based models and experimental data acquired during calendar-life testing of high-power lithium-ion cells.

25 ENERGY STORAGE↗
DOE OSTI2017

Statistical Analysis of Supernova Remnants in the Large Magellanic Cloud

We construct the most complete sample of supernova remnants (SNRs) in any galaxy—the Large Magellanic Cloud (LMC) SNR sample. We study their various properties such as spectral index (α), size, and surface brightness. We suggest an association between the spatial distribution and environment density of LMC SNRs, and their tendency to be located around supergiant shells. We find evidence that the 16 known type Ia LMC SNRs are expanding in a lower density environment compared to the Core-Collapse (CC) type. The mean diameter of our entire population (74) is 41 pc, which is comparable to nearby galaxies. We did not find any correlation between the type of SN explosion, ovality, or age. The N(<D) relationship with slope a = 0.96 implies that the randomized diameters are readily mimicking such an exponent. The rate of SNe occurring in the LMC is estimated to be ∼1 per 200 yr. The mean α of the entire LMC SNR population is −0.52, which is typical of most SNRs. However, our estimates show a clear flattening of the synchrotron α as the remnants age. As predicted, the CC SNRs in our sample are significantly brighter radio emitters than type Ia remnants. We also estimate the Σ--D relation for the LMC to have a slope ∼3.8, which is comparable with other nearby galaxies. We also find the residency time of electrons in the galaxy (4.0–14.3 Myr), implying that SNRs should be the dominant mechanism for the production and acceleration of CRs.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Recent seawater intrusion into deep aquifer determined by the radioactive noble-gas isotopes 81 Kr and 39 Ar

Radioactive noble-gas isotopes tracers 81 Kr and 39 Ar are used for the first time to measure the residence times of deep (~1000 m) saline coastal groundwater, and to determine its connection mode with the sea. The average rate of seawater intrusion into the deep aquifer in Israel, located near the Mediterranean Sea, is estimated. 81 Kr-ages of the saline water samples, found to be younger than 40 ka, contradict previously estimated ages of up to several million years based on hydrogeological considerations. The new results imply a stronger and more recent connection between the aquifer and the sea, and indicate that the intrusion occurred during the sea-level rise that began about 20 ka ago. These coastal aquifers need to be managed with caution because lowering of the adjacent fresh water level due to over pumping could accelerate seawater intrusion in a relatively short time. As a result, this study demonstrates the suitability of these two noble-gas tracers for the examination of hydrogeological systems in general and for the study of seawater intrusion in particular.

39Ar↗
DOE OSTI2018

Doing the impossible: Why neural networks can be trained at all

As deep neural networks grow in size, from thousands to millions to billions of weights, the performance of those networks becomes limited by our ability to accurately train them. A common naive question arises: if we have a system with billions of degrees of freedom, don't we also need billions of samples to train it? Of course, the success of deep learning indicates that reliable models can be learned with reasonable amounts of data. Similar questions arise in protein folding, spin glasses and biological neural networks. With effectively infinite potential folding/spin/wiring configurations, how does the system find the precise arrangement that leads to useful and robust results? Simple sampling of the possible configurations until an optimal one is reached is not a viable option even if one waited for the age of the universe. On the contrary, there appears to be a mechanism in the above phenomena that forces them to achieve configurations that live on a low-dimensional manifold, avoiding the curse of dimensionality. In the current work we use the concept of mutual information between successive layers of a deep neural network to elucidate this mechanism and suggest possible ways of exploiting it to accelerate training.

deep learning, training, curse of dimensionality, ↗
NASA NTRS2014

Assessing the Risk of Crew Injury Due to Dynamic Loads During Spaceflight

Spaceflight requires tremendous amounts of energy to achieve Earth orbit and to attain escape velocity for interplanetary missions. Although the majority of the energy is managed in such a way as to limit the accelerations on the crew, several mission phases may result in crew exposure to dynamic loads. In the automotive industry, risk of serious injury can be tolerated because the probability of a crash is remote each time a person enters a vehicle, resulting in a low total risk of injury. For spaceflight, the level of acceptable injury risk must be lower to achieve a low total risk of injury because the dynamic loads are expected on each flight. To mitigate the risk of injury due to dynamic loads, the NASA Human Research Program has developed a research plan to inform the knowledge gaps and develop relevant tools for assessing injury risk. The risk of injury due to dynamic loads can be further subdivided into extrinsic and intrinsic risk factors. Extrinsic risk factors include the vehicle dynamic profile, seat and restraint design, and spacesuit design. Human tolerance to loads varies considerably depending on the direction, amplitude, and rise-time of acceleration therefore the orientation of the body to the dynamic vector is critical to determining crew risk of injury. Although a particular vehicle dynamic profile may be safe for a particular design, the seat, restraint, and suit designs can affect the risk of injury due to localized effects. In addition, characteristics intrinsic to the crewmember may also contribute to the risk of injury, such as crewmember sex, age, anthropometry, and deconditioning due to spaceflight, and each astronaut may have a different risk profile because of these factors. The purpose of the research plan is to address any knowledge gaps in the risk factors to mitigate injury risk. Methods for assessing injury risk have been well documented in other analogous industries and include human volunteer testing, human exposure to dynamic environments, post-mortem human subject (PMHS) testing, animal testing, anthropomorphic test devices (ATD), dynamic models of the human, numerical models of ATDs, and numerical models of the human. Each has inherent strengths and limitations. For example, human volunteer testing is advantageous because a population can be selected that is similar to the astronaut corps; however, because of the inherent ethical limitations, only sub-injurious conditions can be tested. PMHSs can be tested in a variety of conditions including injurious levels, but the responses are not completely analogous to living human subjects. In addition, it is exceedingly difficult to select a PMHS population that is similar to the astronaut corps. ATDs are currently widely used in the automotive industry and military because they are highly repeatable and durable. Unfortunately, because they are mechanical models of the human body, the biofidelity of the responses are limited to dynamic conditions used to validate the ATD. Numerical models of the ATD, in addition to the strengths and limitations for ATDs, are easy to use for a variety of designs before a design is fabricated, but also have additional limitations for ATDs, are easy to use for a variety of designs before a design is fabricated, but also have additional uncertainty. Dynamic models are simple and easy to use, but do not account for localized effects of the seat and suit. Finally, numerical models of the human have the potential to have the most advantages; however, the current models are not validated for the conditions expected during spaceflight. To properly assess spaceflight conditions with numerical human models, human data would be needed to optimize the model responses for those conditions. Using the appropriate assessment method with the knowledge gained for each risk factor, an appropriate approach for mitigating the risk of injury due to dynamic loads can be developed ensuring crew safety in future NASA vehicles.

Somers, J. T.↗
DOE OSTI2022

Evaluating the Durability of Balance of Systems Components Using Combined-Accelerated Stress Testing

The degradation of photovoltaic (PV) balance of systems (BoS) components is not well-studied, but the consequences include offline modules, strings, and inverters; system shutdown; arc faults; and fires. A utility provider experienced a ~30% failure rate in their power transfer chain, originally attributed to branch connectors. Field-failed specimen assemblies were therefore examined, consisting of cable connector, branch connector, and discrete fuse components. Previous papers and presentations have focused on the development of the test method using a benchtop prototype. This presentation covers the early results of C-AST aging of static and dynamic specimens.

balance of systems↗
DOE OSTI2018

Concept of Operations: National Technology Test Bed Network for Water Resource Recovery

There is an urgency to advancing wastewater technologies due to aging water infrastructure and emerging regulations. A crosscutting working group proposes a conceptual design for a test bed network to understand and evaluate wastewater technologies to drive acceptance and deployment of new technologies to enhance performance. The working group includes contributors from the U.S. Department of Energy, the U.S. Environmental Protection Agency, the U.S. National Science Foundation, and the Water Research Foundation (formerly known as the Water Environment & Reuse Foundation). Upgrading today's aging wastewater treatment infrastructure to a new generation of water resource recovery facilities (WRRFs) requires the development and deployment of innovative technologies. The path to technology adoption depends on expensive, time consuming, and often repetitive cycles of testing and validation. Existing water resource recovery technology testing facilities (e.g., test beds) are underutilized and cannot, by themselves, broaden technology uptake. It has been proposed that technology adoption could be accelerated by a network linking these test facilities with innovators, manufacturers, utilities, regulators, policymakers, and educators. This document proposes a structure for a National Test bed Network (TBN) for water resource recovery. The concepts for its operation are explored herein. This document identifies drivers to launch a TBN and critical needs for successful implementation of the network. An important driver to technology implementation at WRRFs is the relationship between local utilities and state regulators. The TBN could provide access to validated performance data and facilitate deployment. To link the stakeholders and accelerate deployment, the TBN will require standards for methods, data quality, data management, and data security. These standards will enable validation of performance and will expand the “toolbox” that utilities and regulators could consider. Design, set up, and launch of this toolbox is beyond the scope of operations of utilities and regulators and will likely require external support to achieve full operation. Herein, a pathway is proposed to achieve this full operation. This document defines the function of a WRRF TBN. It also proposes a structure for the TBN to achieve its stated goals and mission. Finally, this document summarizes findings from several sources, including a series of workshops about the TBN concept, operators of test beds in ancillary industries, and discussions with regulators and permitting agencies. A description of this work was published in the peer-reviewed literature (Mihelcic 2017).

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2017

Environmental exposure to TiO 2 nanomaterials incorporated in building material

Nanomaterials are increasingly being used to improve the properties and functions of common building materials. A new type of self-cleaning cement incorporating TiO 2 nanomaterials (TiO 2 -NMs) with photocatalytic properties is now marketed. This promising cement might provide air pollution-reducing properties but its environmental impact must be validated. During cement use and aging, an altered surface layer is formed that exhibits increased porosity. The surface layer thickness alteration and porosity increase with the cement degradation rate. The hardened cement paste leaching behavior has been fully documented, but the fate of incorporated TiO 2 -NMs and their state during/after potential release is currently unknown. In this study, photocatalytic cement pastes with increasing initial porosity were leached at a lab-scale to produce a range of degradation rates concerning the altered layer porosity and thickness. No dissolved Ti was released during leaching, only particulate TiO 2 -NM release was detected. The extent of release from this batch test simulating accelerated worst-case scenario was limited and ranged from 18.7 ± 2.1 to 33.5 ± 5.1 mg of Ti/m 2 of cement after 168 h of leaching. TiO 2 -NMs released into neutral aquatic media (simulate pH of surface water) were not associated or coated by cement minerals. The TiO 2 -NM release mechanism is suspected to start from freeing of TiO 2 -NMs in the altered layer pore network due to partial cement paste dissolution followed by diffusion into the bulk pore solution to the surface. The extent of TiO 2 -NM release was not solely related to the cement degradation rate.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1986

Determination of cosmogenic Ca-41 in a meteorite with tandem accelerator mass spectrometry

The first use of tandem accelerator mass spectrometry (TAMS) to measure the content of Ca-41 in a natural sample, the iron Bogou meteorite, is reported. Ca in the samples was extracted by hydroxide precipitation and purified by means of a caution exchange resin (AG 50W-X8). After adding 4 percent ammonium oxide, the precipitate was ignited to CaO in a quartz vial at about 1100 C. The Ca-41/Ca ratios were determined following acceleration by alternate measurements of the Ca-40 beam current in an image Faraday cup. Ca-41 particles were also measured using a gas counter. The measured Ca-41/Ca ratio was 3.8 + or -0.6 x 10 to the 12th, which corresponds to a Ca-41 activity of 6.9 + or -1.1 d.p.m. per kg. Calculation of the half-life of Ca-41 in the Bogou meteorite yielded an age of 103,000 years.

Kubik, P. W.↗
NASA NTRS2011

Universal Heliophysical Processes

The physical processes in the heliospace are a direct consequence of the Sun s mass and electromagnetic emissions. There has been enormous progress in studying these processes since the dawn of the space age half a century ago. The heliospace serves as a great laboratory to study numerous physical processes, using the vast array of ground and spacebased measurements of various physical quantities. The observational capabilities collectively form the Great Observatory to make scientific investigations not envisioned by individual instrument teams. The International Heliophysical Year (IHY) program has been promoting scientific investigations on the universality of physical processes such as shocks, particle acceleration, dynamo, magnetic reconnection, magnetic flux ropes, plasma-neutral matter interactions, turbulence, and several other topics. This chapter highlights scientific deliberations on these and related topics that took place during the IAGA session on "Universal Heliophysical Processes" in Sopron, Hungary. The session featured several invited and contributed papers that focused on observations, theory and modeling of the universal heliophysical processes.

Gopalswamy, Natchimuthuk↗
DOE OSTI2022

Upgrade and Operation of the ATLAS Radiation Interlock System (ARIS)

ATLAS (the Argonne Tandem Linac Accelerator Sys-tem) is a superconducting heavy ion accelerator which can accelerate nearly all stable, and some unstable, iso-topes between hydrogen and uranium. Prompt radiation fields from gamma and or neutron are typically below 1 rem/hr at 30 cm, but are permitted up to 300 rem/hr at 30 cm. The original ATLAS Radiation Interlock System (ARIS), hereafter referred to as ARIS 1.0 was installed 30 years ago. While it has been a functional critical safe-ty system, its age has exposed the facility to high risk of temporary shutdown due to failure of obsolete compo-nents. Topics discussed will be architecture, hardware improvements, functional improvements, and operation permitting personnel access to areas with low levels of radiation.

Blomberg, B. R.↗
DOE OSTI2014

Development of an Accelerated Microbial Procedure (Final Report)

Cool-roof coating technologies make buildings more energy efficient, reducing energy consumption as well as air pollution in temperate and hot climates. The performance of a cool roof can diminish significantly when exposed to adverse environmental agents such as dust, soot, and pollens as well as microorganisms. There is currently no equivalent method to accelerate testing of cool roof erformance. We developed an experimental procedure to test cool roof samples using a defined mixture of both photoautotrophic and heterotrophic microorganisms that would produce an equivalent, faster test for biodeterioration. The mixture consists of 6 bacterial, 3 algal, and 4 fungal species suspended in rich media. Microbial biofilms developed rapidly on the coating surface. Any cool-roof technology could be tested using this microbial aging procedure. If the surface of a material is accessible to the microbial mixture, the growth of a microbial biofilm could reduce the solar reflectance to less than 50% of its initial value within 2 months. Thus, it completes the test cycle required by the ENERGY STAR ® program in only 2 months instead of 3 years by the biofilm alone.

14 SOLAR ENERGY↗
DOE OSTI2013

Large-Grain Superconducting Gun Cavity Testing Program Phase One Closing Report

This report details the experimental configuration and RF testing results for the first phase of a large-grained niobium electron gun cavity testing program being conducted in the Small Vertical Testing Facility in the Collider-Accelerator Department. This testing is meant to explore multi-pacting in the cavity and shed light on the behavior of a counterpart cavity of identical geometry installed in the Energy Recovery LINAC being constructed in the Collider-Accelerator Department at Brookhaven National Laboratory. This test found that the Q of the large-grained cavity at 4 K reached ~6.5 × 10 8 and at 2 K reached a value of ~6 × 10 9 . Both of these values are about a factor of 10 lower than would be expected for this type of cavity given the calculated surface resistance and the estimated geometry factor for this half-cell cavity. In addition, the cavity reached a peak voltage of 0.6 MV before there was sig-nificant decline in the Q value and a substantial increase in field emission. This relatively low volt-age, coupled with the low Q and considerable field emission suggest contamination of the cavity interior, possibly during experimental assembly. The results may also suggest that additional chemical etching of the interior surface of the cavity may be beneficial. Throughout the course of testing, various challenges arose including slow helium transfer to the cryostat and cable difficulties. These difficulties and others were eventually resolved, and the re-port discusses the operating experience of the experiment thus far and the plans for future work aimed at exploring the nature of multipacting with a copper cathode inserted into the cavity.

43 PARTICLE ACCELERATORS↗