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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 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Assimilation of Passive and Active Microwave Soil Moisture Retrievals

Root-zone soil moisture is an important control over the partition of land surface energy and moisture, and the assimilation of remotely sensed near-surface soil moisture has been shown to improve model profile soil moisture [1]. To date, efforts to assimilate remotely sensed near-surface soil moisture at large scales have focused on soil moisture derived from the passive microwave Advanced Microwave Scanning Radiometer (AMSR-E) and the active Advanced Scatterometer (ASCAT; together with its predecessor on the European Remote Sensing satellites (ERS. The assimilation of passive and active microwave soil moisture observations has not yet been directly compared, and so this study compares the impact of assimilating ASCAT and AMSR-E soil moisture data, both separately and together. Since the soil moisture retrieval skill from active and passive microwave data is thought to differ according to surface characteristics [2], the impact of each assimilation on the model soil moisture skill is assessed according to land cover type, by comparison to in situ soil moisture observations.

Draper, C. S.↗
NASA NTRS2017

Machine Learning Approaches to Increasing Value of Spaceflight Omics Databases

The number of spaceflight bioscience mission opportunities is too small to allow all relevant biological and environmental parameters to be experimentally identified. Simulated spaceflight experiments in ground-based facilities (GBFs), such as clinostats, are each suitable only for particular investigations -- a rotating-wall vessel may be 'simulated microgravity' for cell differentiation (hours), but not DNA repair (seconds) -- and introduce confounding stimuli, such as motor vibration and fluid shear effects. This uncertainty over which biological mechanisms respond to a given form of simulated space radiation or gravity, as well as its side effects, limits our ability to baseline spaceflight data and validate mission science. Machine learning techniques autonomously identify relevant and interdependent factors in a data set given the set of desired metrics to be evaluated: to automatically identify related studies, compare data from related studies, or determine linkages between types of data in the same study. System-of-systems (SoS) machine learning models have the ability to deal with both sparse and heterogeneous data, such as that provided by the small and diverse number of space biosciences flight missions; however, they require appropriate user-defined metrics for any given data set. Although machine learning in bioinformatics is rapidly expanding, the need to combine spaceflight/GBF mission parameters with omics data is unique. This work characterizes the basic requirements for implementing the SoS approach through the System Map (SM) technique, a composite of a dynamic Bayesian network and Gaussian mixture model, in real-world repositories such as the GeneLab Data System and Life Sciences Data Archive. The three primary steps are metadata management for experimental description using open-source ontologies, defining similarity and consistency metrics, and generating testing and validation data sets. Such approaches to spaceflight and GBF omics data may soon enable unique insight into which measured phenomena correlate to biological mechanisms that are truly affected by spaceflight conditions; which are most likely to be confounded by other variables; and which are insufficiently characterized, significantly increasing existing and future science return from ISS and spaceflight missions.

Gentry, Diana↗
NASA NTRS1986

Engine studies for future subsonic cruise missiles

A comparative study was conducted to investigate the performance and cost benefits of future engine concepts for subsonic strategic cruise missile propulsion. Technology advancements were projected for component efficiencies, materials and bearing lubrication. Engine configurations studied were an advanced simple cycle (conventional) turbofan and a recuperated turbofan. Results showed the two engines require virtually the same size missile to fly the designated mission. However, there was lower life cycle cost for the advanced simple cycle turbofan engine.

Pampreen, Ron↗
DOE OSTI2015

A comparative density functional study on electrical properties of layered penta-graphene

We present a comparative study of the influence of the number of layers, the biaxial strain in the range of −3% to 3%, and the stacking misalignments on the electronic properties of a new 2D carbon allotrope, penta-graphene (PG), based on hybrid-functional method within the density functional theory (DFT). In comparison with local exchange-correlation approximation in the DFT, the hybrid-functional provides an accurate description on the degree of p{sub z} orbitals localization and bandgap. Importantly, the predicted bandgap of few-layer PG has a weak layer dependence. The bandgap of monolayer PG is 3.27 eV, approximately equal to those of GaN and ZnO; and the bandgap of few-layer PG decreases slowly with the number of layers (N) and converge to 2.57 eV when N ≥ 4. Our calculations using HSE06 functional on few-layer PG reveal that bandgap engineering by stacking misalignment can further tune the bandgap down to 1.37 eV. Importantly, there is no direct-to-indirect bandgap transition in PG by varying strain, layer number, and stacking misalignment. Owing to its tunable, robustly direct, and wide bandgap characteristics, few-layer PG is promising for optoelectronic and photovoltaic applications.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1981

Advanced general aviation comparative engine/airframe integration study

The NASA Advanced Aviation Comparative Engine/Airframe Integration Study was initiated to help determine which of four promising concepts for new general aviation engines for the 1990's should be considered for further research funding. The engine concepts included rotary, diesel, spark ignition, and turboprop powerplants; a conventional state-of-the-art piston engine was used as a baseline for the comparison. Computer simulations of the performance of single and twin engine pressurized aircraft designs were used to determine how the various characteristics of each engine interacted in the design process. Comparisons were made of how each engine performed relative to the others when integrated into an airframe and required to fly a transportation mission.

Huggins, G. L.↗
DOE OSTI2019

Conservation and diversity in the secondary forward photodynamics of red/green cyanobacteriochromes

Cyanobacteriochromes (CBCRs) are photosensitive proteins that are distantly related to the phytochrome family of photoreceptors and, like phytochromes, exhibit photoactivity initiated by the excited-state photoisomerization of a covalently bound bilin chromophore. The canonical red/green photoswitching sub-family is the most studied class of CBCRs studied to date. Recently, a comparative study of the ultrafast (100 fs–10 ns) forward photodynamics of nine red/green photoswitching CBCR domains isolated from Nostoc punctiforme were reported (S. M. Gottlieb, P. W. Kim, C.-W. Chang, S. J. Hanke, R. J. Hayer, N. C. Rockwell, S. S. Martin, J. C. Lagarias and D. S. Larsen, Conservation and Diversity in the Primary Forward Photodynamics of Red/Green Cyanobacteriochromes, Biochemistry, 2015, 54, 1028–1042). We extend this study by characterizing the secondary (10 ns–1 ms) forward photodynamics of eight red/green photoswitching CBCRs from N. punctiforme with broadband time-resolved absorption spectroscopy. We demonstrate that the dynamics of these representative red/green CBCRs can be separated into two coexisting pathways involving a photoactive pathway that is successful in generating the terminal light-adapted 15E P g population and an unsuccessful pathway that stalls after generating a meta-stable Lumi-O f intermediate. The photoactive pathway evolves through a similar mechanism from excitation of the dark-adapted 15Z P r state to generate a far-red absorbing Lumi-R f and then via a succession of blue-shifting photointermediates to ultimately generate the 15E P g state. This suggests a steady deviation from planarity of the bilin chromophore during the dynamics. While, the general mechanism for this evolution is conserved among these CBCBs, the timescales of these dynamics deviate significantly. Only half of the characterized CBCRs exhibit the unproductive pathways due to photoexcitation of dark-adapted 15Z P o sub-population that upon photoexcitation generates a meta-stable Lumi-O f intermediate, which eventually decays back to the 15Z P o subpopulation. 15Z P o is ascribed the horizontal Asp657 configuration that disrupts H-bonding with the chromophore in the dark-adapted state; its presence can be identified via enhanced absorption of high-energy tail of the electronic absorption spectrum.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1979

Wave propagation in ducts using the finite element method

The paper outlines a comparative study designed to assess and compare the accuracy of the finite element method (FEM) for linear and quadratic elements as applied to problems in duct acoustics. The acoustic disturbances are assumed to be irrotational and isentropic so that the problem can be formulated in terms of the acoustic velocity potential. It is shown that for the case of plane wave propagation in a hard-walled annular cylinder, the accuracy of the FEM solution can be increased at higher frequencies by using quadratic triangular elements instead of linear triangular elements. Evidence is presented to enhance the confidence in applying the developed FEM by comparing results with those obtained by other independently developed numerical approaches such as an integral equation technique and a finite difference method.

Majjigi, R. K.↗
NASA NTRS1983

Scientific program in planetary atmospheric studies

The Voyager encounters with Jupiter led to two main areas of investigation: (1) the definition of the structure and composition of the upper atmosphere and the interaction of the magnetosphere and atmosphere, and (2) the study of the plasma torus using the EUV (Extreme Ultraviolet) data in conjunction with ground-based and in-situ measurements. In the course of these investigations, the atmosphere studies were extended to a comparative study with the bound atmospheres of Saturn and Titan; and the torus study expanded to include the extended atmospheres of Titan (the H torus) and the rings of Saturn.

Broadfoot, A. L.↗
NASA NTRS1993

Structural Efficiencies Of Fluted-Core Graphite/Epoxy Panels

Report discusses one concept providing alternative to some aluminum structural components of wings: fluted core panels made of graphite/epoxy material. Includes description of structural-efficiency study of fluted-core sandwich panels of two different configurations. Results of study compared with results of similar study of conventional aluminum panels and blade-stiffened graphite/epoxy panels.

Jegley, Dawn C.↗
NASA NTRS2016

Examining Metasomatism in Low fO2 Environments: Exploring Sulfidation Reactions in Various Planetary Bodies

Hydrothermal systems are common on Earth in a variety of tectonic environments and at different temperature and pressure conditions. These systems are commonly dominated by H2O, and they are responsible for element transport and the production of ore deposits. Unlike the Earth (fO2~FMQ), many other planetary bodies (e.g., Moon and asteroids) have fO2 environments that are more reduced (IW+/-2), and H2O is not the important solvent responsible for element transport. One example of a texture that could result from element transport and metasomatism, which appears to occur on numerous planetary bodies, is sulfide-silicate intergrowths. These subsolidus assemblages are interpreted to form as a result of sulfidation reactions from a S-rich fluid phase. The composition of fluids may vary within and among parent bodies and could be sourced from magmatic (e.g. Moon) or impact processes (e.g. HED meteorites and Moon). For example, it has been previously demonstrated on the Moon that the interaction of olivine with a hydrogen- and sulfur-bearing vapor phase altered primary mineral assemblages, producing sulfides (e.g. troilite) and orthopyroxene. Formation of these types of "sulfidation" assemblages can be illustrated with the following reaction: Fe2SiO4(ol) + 1/2 S(2 system) = FeS(troi)+ FeSiO3(opx) + 1/2 O2 system. The products of this reaction, as seen in lunar rocks, is a vermicular or "worm-like" texture of intergrown orthopyroxene and troilite. Regardless of the provenance of the S-bearing fluid, the minerals in these various planetary environments reacted in the same manner to produce orthopyroxene and troilite. Although similar textures have been identified in a variety of parent bodies, a comparative study on the compositions and the origins of these sulfide-silicate assemblages has yet to be undertaken. The intent of this study is to examine and compare sulfide-silicate intergrowths from various planetary bodies to explore their petrogenesis and examine the nature of low fO2 (IW+/-2) element migration and sulfidation reactions.

Srinivasan, P.↗
DOE OSTI2014

Comparative ion insertion study into a nanostructured vanadium oxide in aqueous salt solutions

We present a comparative study for the electrochemical insertion of different cations into a nanostructured vanadium oxide material. The oxide is hydrothemally synthesized and electrically characterized by variable temperature measurements. The electrochemical reactions are performed in aqueous chloride solutions of lithium, sodium, potassium, and ammonium, and the electrochemical behavior of various cycles are correlated with visual changes in the vanadium oxide nanosheets as observed by scanning electron microscopy. We note an increase in the specific charge per cycle in the cases of sodium and ammonium ions only, correlated with minimal physical changes to the nanosheets. The differing behavior of the various ions has implications for their use in electrical energy storage applications.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

In Patients with Localized and Resectable Gastric Cancer, What is the Optimal Extent of Lymph Node Dissection—D1 Versus D2 Versus D3?

Background: Despite advances in the treatment of patients with gastric cancer, the debate over the optimal extent of lymphadenectomy continues. Method: A review of the classification, rationale for, and boundaries of lymphadenectomy is presented. A review of the available literature comparing D1 versus D2 versus D3 lymphadenectomy was performed and included randomized controlled trials, and prospective and retrospective comparative and non-comparative studies. Results: Earlier studies demonstrated increased morbidity with D2 compared with D1 lymphadenectomy, with no significant survival benefit. More recent studies have demonstrated survival benefit of a pancreas and spleen-sparing D2 lymphadenectomy in patients with advanced, node-positive tumors. Para-aortic/D3 dissections contribute to increased morbidity, with no survival benefit. Conclusions: In patients with resectable gastric adenocarcinoma, a D2 lymph node dissection preserving the pancreas and spleen should be considered standard for optimal staging and treatment, provided it is performed by surgeons with sufficient expertise. Extended lymph node dissections beyond D2 should not be routinely performed as it has been shown to have increased morbidity, with no improvement in outcomes. While systemic chemotherapy should be considered standard in patients undergoing D2 lymphadenectomy, the role of adjuvant radiation continues to evolve.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
NASA NTRS1987

Comparing the effectiveness of software testing strategies

This study compares the results of code reading, functional testing, and structural testing in three aspects of software testing: fault detection effectiveness, fault detection cost, and classes of faults detected. Thirty two professional programmers and 42 advanced students applied the three techniques to four unit-sized programs in a fractional experimental design. The major results of this study are the following: (1) With the professional programmers, code reading detected more software faults and had a higher detection rate than did functional or structural testing, while functional testing detected more faults than did structural testing, but functional and structural testing were not different in fault detection rate. (2) In one advanced student subject group, code reading and functional testing were not different in faults found, but were superior to structural testing, while in the other advanced student subject group there was no difference among the techniques. (3) With the advanced student subjects, the three techniques were not different in fault deteciton rate. (4) Number of faults observed, fault detection rate, and total effort in detection depended on the type of software tested. (5) Code reading detected more interface faults than did the other methods. (6) Functional testing detected more control faults than did the other methods. (7) When asked to estimate the percentage of faults detected, code readers gave the most accurate estimates while functional testers gave the least accurate estimates. Appendix B includes the source code for the word.

Basili, Victor R.↗
DOE OSTI2013

A critical comparison of ten disposable cup LCAs

Disposable cups can be made from conventional petro-plastics, bioplastics, or paperboard (coated with petro-plastics or bioplastics). This study compared ten life cycle assessment (LCA) studies of disposable cups with the aim to evaluate the robustness of their results. The selected studies have only one impact category in common, namely climate change with global warming potential (GWP) as its category indicator. Quantitative GWP results of the studies were closer examined. GWPs within and across each study show none of the cup materials to be consistently better than the others. Comparison of the absolute GWPs (after correction for the cup volume) also shows no consistent better or worse cup material. An evaluation of the methodological choices and the data sets used in the studies revealed their influence on the GWP. The differences in GWP can be attributed to a multitude of factors, i.e., cup material and weight, production processes, waste processes, allocation options, and data used. These factors basically represent different types of uncertainty. Sensitivity and scenario analyses provided only the influence of one factor at once. A systematic and simultaneous use of sensitivity and scenario analyses could, in a next research, result in more robust outcomes. -- Highlights: • Conflicting results from life cycle assessment (LCA) on disposable cups • GWP results of LCAs did not point to a best or worst cup material. • Differences in GWP results are due to methodological choices and data sets used. • Standardized LCA: transparency of LCA studies, but still different in approaches.

54 ENVIRONMENTAL SCIENCES↗