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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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Spatial distribution of aerosols burden and evaluation of changes in aerosol optical depth using multi-approach observations in tropical region
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Coupled thermal-hydrological-mechanical behavior of rock mass surrounding a high-temperature thermal energy storage cavern at shallow depth
The present study is aimed at numerically examining the thermal-hydrological-mechanical (THM) processes within the rock mass surrounding a cavern used for thermal energy storage (TES). We considered a cylindrical rock cavern with a height of 50 m and a radius of 10 m storing thermal energy of 350ºC as a conceptual TES model and simulated its operation for 30 years using THM coupled numerical modeling. At first, the insulator performance was not considered for the purpose of investigating the possible coupled THM behavior of the surrounding rock mass; then, the effects of an insulator were examined for different insulator thicknesses. The key concerns were focused on the hydro-thermal multiphase flow and heat transport in the rock mass around the thermal storage cavern, the effect of evaporation of rock mass, thermal impact on near the ground surface and the mechanical behavior of the surrounding rock mass. It is shown that the rock temperature around the cavern rapidly increased in the early stage and, consequently, evaporation of groundwater occurred, raising the fluid pressure. However, evaporation and multiphase flow did not have a significant effect on the heat transfer and mechanical behavior in spite of the high-temperature (350ºC) heat source. The simulations showed that large-scale heat flow around a cavern was expected to be conductiondominated for a reasonable value of rock mass permeability. Thermal expansion as a result of the heating of the rock mass from the storage cavern led to a ground surface uplift on the order of a few centimeters and to the development of tensile stress above the storage cavern, increasing the potentials for shear and tensile failures after a few years of the operation. Finally, the analysis showed that high tangential stress in proximity of the storage cavern can some shear failure and local damage, although large rock wall failure could likely be controlled with appropriate insulators and reinforcement.
[{sup 18}F]fluoromisonidazole and a New PET System With Semiconductor Detectors and a Depth of Interaction System for Intensity Modulated Radiation Therapy for Nasopharyngeal Cancer
Purpose: The impact of a new type of positron emission tomography (New PET) with semiconductor detectors using {sup 18}F-labeled fluoromisonidazole (FMISO)-guided intensity modulated radiation therapy (IMRT) was compared with a state-of-the-art PET/computed tomography (PET/CT) system in nasopharyngeal cancer (NPC) patients. Methods and Materials: Twenty-four patients with non-NPC malignant tumors (control group) and 16 patients with NPC were subjected to FMISO-PET. The threshold of the tumor-to-muscle (T/M) ratio in each PET scan was calculated. The hypoxic volume within the gross tumor volume (GTVh) was determined using each PET ({sub NewPET}GTVh and {sub PET/CT}GTVh, respectively). Dose escalation IMRT plans prescribing 84 Gy to each GTVh were carried out. Results: The threshold of the T/M ratio was 1.35 for New PET and 1.23 for PET/CT. The mean volume of {sub NewPET}GTVh was significantly smaller than that of {sub PET/CT}GTVh (1.5 {+-} 1.6 cc vs 4.7 {+-} 4.6 cc, respectively; P=.0020). The dose escalation IMRT plans using New PET were superior in dose distribution to those using PET/CT. Dose escalation was possible in all 10 New PET-guided plans but not in 1 PET/CT-guided plan, because the threshold dose to the brainstem was exceeded. Conclusions: New PET was found to be useful for accurate dose escalation in FMISO-guided IMRT for patients with NPC.
Effect of thickness of planar nozzles on erosion depth of levee soils subjected to plunging water
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GD-OES study of the influence of second phase particles on the deuterium depth distribution in dispersion-strengthened tungsten
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High energy X-ray characterization of the microstructure of PuGa alloy samples at macroscopic depths and non-ambient conditions
High energy (95 keV) X-rays were utilized to characterize the microstructure of eight PuGa alloy samples at room temperature and during cooling to ∼10 K. The samples had different Ga content (nominally 0-3.4 at.%), age, and history. A ninth sample, similarly characterized with neutron diffraction, was included to extend the Ga range to 7 at.%. The samples span the range from single phase α (monoclinic) to δ (face-centered cubic) PuGa, as well as a two-phase α′/δ sample. The crystallographic textures, phase fractions, lattice parameters and dislocation densities of each sample were evaluated through distinct analysis techniques. The textures of the samples were modest. In each case, the dislocation densities were relatively high, comparable to cold worked metals and metals exposed to similar radiation dose. At room temperature, the lattice parameters determined in the predominantly single-phase samples were larger than expected based on the nominal Ga concentration. The observed lattice thermal expansions of the single-phase δ samples to 10 K are self-consistent across the samples and consistent with previous measurements reported in the literature. Significantly larger thermal lattice strain is observed in the δ phase of the two-phase material due to mechanical constraint from the α′ phase, which has a three times larger thermal expansion and is much harder than the δ phase. In conclusion, the results demonstrate the unique value of high-energy X-rays for relatively routine microstructural characterization of Pu alloy samples.
Critical velocity of a uniformly moving load on a beam supported by a finite depth foundation
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Depth-sensing indentation of nanomaterials and nanostructures
Due to its capacity for applying ultralow loads and detecting nanometer-scale deflections, nanoindentation has been used to investigate the mechanical behavior of various material configurations at the micro- and nano-scales. The emphasis of the article is on the nanoscale deformation of nanoparticles, micro/nanopillars, microbeams, micro/nanofibers, nanocomposites, membranes and monolayer films, which are all ubiquitous structures in nanotechnology. The small volumes of these structures have led to the elucidation of material deformation mechanisms that are not the same as their bulk counterparts. Advances in instrumentation have enabled nanoindentation experiments to be conducted in situ in conjunction with scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), electrical contact resistance (ECR) measurements, atomic force microscopy (AFM), among others, and examples of these studies will be discussed.
In-depth quantitative analysis of the microstructures produced by Surface Mechanical Attrition Treatment (SMAT)
Electron BackScattered Diffraction (EBSD) maps are used to characterize quantitatively the graded microstructure formed by Surface Mechanical Attrition Treatment (SMAT) and applied here to the 316L stainless steel. In particular, the analysis of GNDs – coupled with relevant and reliable criteria – was used to depict the thickness of each zone identified in the SMAT-affected layers: (i) the “ultrafine grain” (UFG) zone present at the extreme top surface, (ii), the “transition zone” where grains were fragmented under the heavy plastic deformation and, finally, (iii) the “deformed zone” where initial grains are simply deformed. The interest of this procedure is illustrated through the comparative analysis of the effect of some SMAT processing parameters (amplitude of vibration and treatment duration). The UFG and transition zones are more significantly modified than the overall affected thickness under our tested conditions. - Highlights: • EBSD maps are used to characterize quantitatively the microstructure of SMAT treated samples. • Calculation of the GND density to quantify strain gradients • A new method to depict the different zone thicknesses in the SMAT affected layer • Effects of SMAT processing parameters on the surface microstructure evolution.
Tip radius variation with elastic indentation depth
The reduced elastic modulus of a material is measured with a nanoindenter probe that is operated in the tapping mode. The resonant frequency of a freely oscillating cantilever is reduced when contact is made between the indenter tip and surface under investigation. It’s shown using elasticity theory that the elastic deformation is a function of the indenter tip radius. A deeper penetration within the elastic range can change the tip radius, and introduce an error of 10% in calculating the reduced elastic modulus.
Real time depth-of-interaction correction for coded-aperture, gamma-ray images
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Initial results of tests of depth markers as a surface diagnostic for fusion devices
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Improved tritium retention modeling with reaction-diffusion code TMAP and bulk depth profiling capability
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