How effective is albedo modification (solar radiation management geoengineering) in preventing sea-level rise from the Greenland Ice Sheet?
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54 ENVIRONMENTAL SCIENCES↗
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Results for “MODIFICATIONS”
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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Plastic scintillators modifications for a selective radiation detection
Recent developments of plastic scintillators are reviewed, from January 2000 to June 2015. All examples are distributed into the main application, i.e. how the plastic scintillator was modified to enhance the detection towards a given radiation particle. The main characteristics of these newly created scintillators and their detection properties are given. (authors)
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Effect of water vapor on plasma processing at atmospheric pressure: polymer etching and surface modification by an Ar/H 2 O plasma jet
In this study, we evaluate the effect of water vapor on the plasma processing of materials using a model system consisting of a well-characterized radio-frequency (RF) plasma jet, controlled gaseous environment, and polystyrene (PS) as target material. We find that the effluent of Ar/H 2 O plasma jet is capable of (1) etching polymers with relatively high etch rate and (2) weakly oxidizing the etched polymer surface by forming O containing moieties. When increasing the treatment distance between the polymer and the Ar/H 2 O plasma, we find that the polymer etch rate drops exponentially whereas the O elemental composition of the etched surface shows a maximum at intermediate treatment distance. The OH density in the Ar/H 2 O jet was measured near the substrate surface by laser induced fluorescence (LIF), and the density change of the OH radicals with treatment distance is found to be consistent with the exponential decrease of polymer etch rate, which indicates that OH may play a dominant role in the polymer etching process. A control experiment of Ar/H 2 plasma shows that the observed fast polymer etching by Ar/H 2 O plasma cannot be attributed to H atoms. By correlating the OH flux with the polymer etch rate, we estimated the etching reaction coefficient (number of C atoms removed per OH radical from the gas phase) of OH radicals as ~10 -2 . The polymer etch rate of Ar/H 2 O plasma is enhanced as the substrate temperature is lowered, which can be explained by the enhanced surface adsorption of gas phase species. For the same molecular admixture concentration and plasma power, we find that Ar/H 2 O/O 2 plasma has much reduced etching efficiency compared to either Ar/H 2 O or Ar/O 2 plasma.
36 MATERIALS SCIENCE↗
Synthesis, Crystal Structure, and Topology–Symmetry Analysis of a New Modification of NaIn[IO{sub 3}]{sub 4}
Crystals of new iodate NaIn[IO{sub 3}]{sub 4} were prepared by the hydrothermal synthesis. The unit cell parameters are a = 7.2672(2) Å, b = 15.2572(6) Å, c = 15.0208(6) Å, β = 101.517(3)°, sp. gr. P2{sub 1}/c. The formula was determined during the structure determination and refinement of a twinned crystal based on a set of reflections from the atomic planes of the major individual. The refinement with anisotropic displacement parameters was performed for both twin components to the final R factor of 0.050. The In and Na atoms are in octahedral coordination formed by oxygen atoms. The oxygen octahedra are arranged into columns by sharing edges, and the columns are connected by isolated umbrella-like [IO{sub 3}]{sup –} groups to form layers. The new structure is most similar to the isoformular iodate NaIn[IO{sub 3}]{sub 4}, which crystallizes in the same sp. gr. P2{sub 1}/c and is structurally similar, but has a twice smaller unit cell and is characterized by another direction of the monoclinic axis. The structural similarity and difference between the two phases were studied by topologysymmetry analysis. The formation of these phases is related to different combinations of identical one-dimensional infinite chains of octahedra.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Modification of the Monte Carlo method for calculation of the influence of unknown placement of solid radioactive waste on the uncertainty of dose fields at different overall container dimensions
An approach to estimating the uncertainty of initial data in calculations by the Monte Carlo method is considered. The relative geometrical position of parts of the analyzed system is assumed to be unknown. The influence of different approximations in the description of the geometrical shape of system objects is studied. The effect of unknown location and approximate shape description of solid radioactive waste in the container on the magnitude of dose fields is considered for photon transport problems.
61 RADIATION PROTECTION AND DOSIMETRY↗
Application of diffuse discharges of atmospheric pressure formed by runaway electrons for modification of copper and stainless steel surface
The results of studies devoted to the influence of a runaway electron pre-ionized diffuse discharge (REP DD) formed in air and nitrogen at atmospheric pressure on the surface of copper and stainless steel are presented. Nanosecond high-voltage pulses were used to obtain REP DD in different gases at high pressures in a chamber with a flat anode and a cathode possessing a small radius of curvature. This mode of discharge was implemented owing to the generation of runaway electrons and X-rays. The conditions under which the surface of copper and stainless steel was cleaned from carbon and oxidized are described.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Modification of the properties of ferromagnetic layers based on A{sup 3}B{sup 5} compounds by pulsed laser annealing
Laser annealing experiments were performed in order to increase the concentration of electrically active manganese in the layers of A{sup 3}B{sup 5}: Mn semiconductors. An LPX-200 KrF excimer laser with a wavelength of 248 nm and a pulse duration of ~30 ns was used. It is shown experimentally that at a pulse energy of an excimer laser of >230 mJ/cm{sup 2}, the hole concentration in GaAs: Mn layers increases to 3 × 10{sup 20} cm{sup –3}. The negative magnetoresistance and the anomalous Hall effect with a hysteresis loop for annealed GaAs: Mn samples remain the same up to 80–100 K. Similar changes are observed for InAs: Mn layers as a result of laser annealing.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Analysis of Thermal Physical Processes and Peculiarities of Modification of a Steel Surface by Pulsed Plasma Flows
The temperature gradient and melting depth of the surface of iron-based alloys under the action of high-temperature pulsed plasma beams have been estimated and compared with the experimental data. It has been shown that the steel surface melts under the action of a pulsed plasma flow at an energy density of 15–20 J/cm{sup 2}; the heat front propagates to a depth of up to 20 μm, the thickness of the molten layer being less than 10 μm. The characteristic size of the microstructure formed as a result of thermal perturbation is estimated at 17 nm. The formation of new phases with crystallite sizes that vary in the range of 16–270 nm is demonstrated experimentally. It has been shown that the formation of nanosize crystalline structure and modified near-surface region are the main factors responsible for strengthening steels.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Modification of Optical Characteristics of a Polymer Composite Material under Irradiation
Polymer composites based on polystyrene and modified SiO{sub 2} are synthesized. Effect of the SiO{sub 2} concentration on the surface (thermostatic) properties of the composites is analyzed. Surfaces of composites with different SiO{sub 2} concentrations are microscopically studied. Minor amounts of spherical agglomerates are obtained at relatively high SiO{sub 2} concentrations, and the size of the agglomerates may amount to 80 μm at a SiO{sub 2} concentration of 30 wt %. Variations in the integral absorbance of solar radiation are studied for the polymer composites irradiated with vacuum-UV radiation at a temperature of 125°C.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Surface Modification of Silver Iodide Films by Electron Irradiation
It has been found experimentally that electron irradiation of polycrystalline AgI films leads to the formation of a nanocrystalline silver particle monolayer. With an increase in the irradiation time, the nanoparticle size grows but the concentration of the particles first increases and then drops. Formation mechanisms of the nanoparticles and the dynamics of their growth have been considered. Ostwald’s ripening, fieldinduced migration, and nanoparticle charge variation during irradiation by low-energy electrons have been shown to be the main processes responsible for the above effects.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Study of Interfacial Interactions Using Thing Film Surface Modification: Radiation and Oxidation Effects in Materials
Interfaces play a key role in dictating the long-term stability of materials under the influence of radiation and high temperatures. For example, grain boundaries affect corrosion by way of providing kinetically favorable paths for elemental diffusion, but they can also act as sinks for defects and helium generated during irradiation. Likewise, the retention of high-temperature strength in nanostructured, oxide-dispersion strengthened steels depends strongly on the stoichiometric and physical stability of the (Y, Ti)-oxide particles/matrix interface under radiation and high temperatures. An understanding of these interfacial effects at a fundamental level is important for the development of materials for extreme environments of nuclear reactors. The goal of this project is to develop an understanding stability of interfaces by depositing thin films of materials on substrates followed by ion irradiation of the film-substrate system at elevated temperatures followed by post-irradiation oxidation treatments. Specifically, the research will be performed by depositing thin films of yttrium and titanium (~500 nm) on Fe-12%Cr binary alloy substrate. Y and Ti have been selected as thin-film materials because they form highly stable protective oxides layers. The Fe-12%Cr binary alloy has been selected because it is representative of ferritic steels that are widely used in nuclear systems. The absence of other alloying elements in this binary alloy would allow for a clearer examination of structures and compositions that evolve during high-temperature irradiations and oxidation treatments. The research is divided into four specific tasks: (1) sputter deposition of 500 nm thick films of Y and Ti on Fe-12%Cr alloy substrates, (2) ion irradiation of the film-substrate system with 2MeV protons to a dose of 2 dpa at temperatures of 300°C, 500°C, and 700°C, (3) oxidation of as-deposited and ion-irradiated samples in a controlled oxygen environment at 500°C and 700°C, (4) multi-scale computational modeling involving first- principle molecular dynamics (FPMD) and coarse-grained dissipative particle dynamics (DPD) approaches to develop theories underlying the evolution and stability of structures and phases. Samples from Tasks 1 to 3 (above) will be rigorously characterized and analyzed using scanning electron microscopy, Auger electron microscopy, x-ray diffraction, Rutherford back scatter spectroscopy, and transmission electron microscopy. Expected outcomes of the experimental work include a quantitative understanding film-substrate interface mixing, evolution of defects and other phases at the interface, interaction of interfaces with defects, and the ability of the Y and Ti films to mitigate irradiation-assisted oxidation.The aforementioned experimental work will be closely coupled with multi-scale molecular dynamics (MD) modeling to understand the reactions at the surface, the transport of oxidant through the thin film, and the stabilities of the deposited thin films under radiation and oxidation. Simulations of materials property changes under conditions of radiation and oxidation require multiple size domains and a different simulation scheme for each of these domains. This will be achieved by coupling the FPMD and coarse-grained kinetic Monte Carlo (KMC). This will enable the comparison of the results of each simulation approach with the experimental results.
36 MATERIALS SCIENCE↗
Bio-Amphiphilic Surface Modification of Cellulosic Nanomaterials (Final Report)
There is, and always has been, a drive to push for advancing materials to higher performing properties. A common method to achieve such results with materials is incorporating reinforcing filler materials. However, regarding microstructural reinforcing with materials science’s highest performing fillers, carbon nanotubes and cellulose nanofibers, there are obstacles to overcome with difficult mixing into polymer composites. Cellulose nanofibers, however, have the desirable potential to be a market viable reinforcing filler as a renewable and sustainable resource, but it is necessary to overcome its inherent compounding difficulties. Powdermet under a US Department of Energy SBIR Grant DE-SC0017679 has demonstrated the ability for a natural bio-amphiphilic surface modifier that has improved the compatibilization of cellulose nanofibers into polyethylene composites. Powdermet’s natural bio-amphiphilic platelet surfactant improved cellulose in polyethylene composite mechanical properties. Impact strength increased by 20% for the demonstrations in this program.
36 MATERIALS SCIENCE↗
Improving the Manufacture of High-Precision Machines by Assembly Modifications
It is possible to improve the quality of high-precision manufacturing products by adopting an individualized approach to the assembly process and testing possible component configurations in computer simulations.
42 ENGINEERING↗
The Mars Pathfinder Propulsion Line Thermal Design: Testing, Analysis and Pre-Launch Modifications
The Mars Pathfinder (MPF) spacecraft (S/C), launched in December 1996, is the second mission in NASA's Discovery Program. The MPF mission is primarily an engineering demonstration of key technologies and concepts for eventual use in future missions to Mars.
Mars Pathfinder Pre-Launch Modification↗
Operational modification of the Mars Exploration Rovers flight software
The Mars Exploration Rovers (MER)Flight Software (FSW) was designed from the outset to be modified during operations. This paper discusses the content of the uplink products that are sent to the Rover, the planning of the Patch and Load activities, the testing of the products and prcedures, and the actual operations themselves.
patch↗
Surface Modification of Ti-6Al-4V for Dust Adhesion Mitigation in Lunar Exploration
Explore the source record for details and available documents.
Lunar dust, Harsh environment, Adhesion mitigation↗
Medium Modification of Jet Fragmentation in Au+Au Collisions at root SNN=200 and #8201; and #8201;GeV Measured in Direct Photon-Hadron Correlations
N/A
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Compressed Natural Gas Vehicle Maintenance Facility Modification Handbook
To ensure the safety of personnel and facilities, vehicle maintenance facilities are required by law and by guidelines of the National Fire Protection Association (NFPA) and the International Fire Code (IFC) to exhibit certain design features. They are also required to be fitted with certain fire protection equipment and devices because of the potential for fire or explosion in the event of fuel leakage or spills. All fuels have an explosion or fire potential if specific conditions are present. This handbook covers the primary elements that must be considered when developing a CNG vehicle maintenance facility design that will protect against the ignition of natural gas releases. It also discusses specific protocols and training needed to ensure safety.
cng, maintenance facility, compressed natural gas,↗