Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “small sample size”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,567 records · Page 87
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Hypervelocity impact effects on solar cells

One of the space hazards of concern is the problem of natural matter and space debris impacting spacecraft. In addition to mechanical damage, impact velocities greater than 5 km/sec can produce shock induced ionization effects with resultant surface charging and complex chemical interactions. The upper limit of the velocity distribution for these particles is on the order of 70 km/sec. The second source of particulate matter is due to the presence of man and the machinery needed to place satellites in orbit. This 'man made' component of the space debris consists of waste, rocket exhaust, and debris caused by satellite break-up. Most of the particles are small. However as the size increases, debris purposefully thrown overboard such as garbage and human waste, combined with paint chips, plastic, wire fragments, bolts, etc., become formidable hazards which completely dominate the distribution function for some orbits. These larger fragments can produce penetration and spalling of the thick metallic structures associated with spacecraft. The particles most often encountered are aluminum oxide, associated with fuel residue, and paint chips. These debris types can have a wide range of particle sizes. It has been stated that the design of spacecraft will have to take the debris evolution into account and provide additional suitable armor for key components in the near future. The purpose of this work was to subject samples from solar power arrays, one of the key components of any spacecraft, to a debris flux typical of what might be found in space, and measure the degradation of the power panels after impact.

Rose, M. Frank↗
NASA NTRS1998

Correlated Petrologic and Geochemical Characteristics of CO3 Chondrites

Many properties of CO3 chondrites have been shown previously to have resulted from thermal metamorphism; petrologic subtypes 3.0-3.7 have been assigned to members of the group. Additional properties that correlate with the metamorphic sequence but seem to have resulted from hydrothermal alteration include the modal abundance of amoeboid olivine inclusions (AOI), chondrule size, the types of refractory inclusions and whole rock O isotopic composition. The percentage of rimmed AOI increases with petrologic subtype. The rims most likely formed during hydrothermal alteration. The previously reported correlation between AOI abundance and chondrite subtype is probably an artifact due to the difficulty in recognizing small unrimmed AOI in the least metamorphosed CO3 chondrites. Because large (>=200 micron size) porphyritic chondrules have nearly the same mean size in all CO3 chondrites, it seems likely that the correlation between chondrule size and subtype is due to alteration of the smallest chondrules to the point of unrecognizability as complete objects in the more metamorphosed CO3 chondrites. The previously reported decrease in the proportion of melilite-rich refractory inclusions with increasing petrologic subtype may have resulted from more extensive hydrothermal alteration in CO3 .4-3.7 chondrites that converted primary melilite into Ca-pyroxene, andradite and nepheline. Alteration probably caused the preferential occurrence of O-16-poor oxygen isotopes in the more metamorphosed whole rock samples.

Rubin, Alan E.↗
NASA NTRS2014

Behavior of Particle Depots in Molten Silicon During Float-Zone Growth in Strong Magnetic Fields

Solar cells made from directionally solidified silicon cover 57% of the photovoltaic industry's market [1]. One major issue during directional solidification of silicon is the precipitation of foreign phase particles. These particles, mainly SiC and Si3N4, are precipitated from the dissolved crucible coating, which is made of silicon nitride, and the dissolution of carbon monoxide from the furnace atmosphere. Due to their hardness and size of several hundred micrometers, those particles can lead to severe problems during the wire sawing process for wafering the ingots. Additionally, SiC particles can act as a shunt, short circuiting the solar cell. Even if the particles are too small to disturb the wafering process, they can lead to a grit structure of silicon micro grains and serve as sources for dislocations. All of this lowers the yield of solar cells and reduces the performance of cells and modules. We studied the behaviour of SiC particle depots during float-zone growth under an oxide skin, and strong static magnetic fields. For high field strengths of 3T and above and an oxide layer on the sample surface, convection is sufficiently suppressed to create a diffusive like regime, with strongly dampened convection [2, 3]. To investigate the difference between atomically rough phase boundaries and facetted growth, samples with [100] and [111] orientation were processed.

Jauss, T.↗
NASA NTRS2016

Sylph: Life Detection Probe for a Europa Plume

Jupiter’s Galilean satellite Europa likely contains a vast, global, subsurface salt-water ocean. A singular telescope observation in 2012 indicated possible plume activity, in some ways similar to the continuous plume activity seen at Enceladus. If a Europan plume does expel ocean water into space, its vapor, ice grains, and dust grains could be analyzed by a spacecraft equipped with high-resolution mass spectrometers. Such plume measurements would be sufficient to measure the contextual habitability profile of the ocean, and to detect multiple signatures of life, should it exist in the ocean. Instrumented with MASPEX (Mass Spectrometer for Planetary Exploration) and SUDA (Surface Dust Analyzer), NASA’s planned Europa Mission now in development could theoretically conduct this investigation. However, the mission’s closest flyby altitude would be 25 km; due to Europa’s large gravity, frozen ocean spray containing non-volatile molecular species critical to biosignature detection can be sampled only within 5 km of the surface. The Europa Mission would not fly this low. Sylph is a concept for a complementary, free-flyer smallsat probe, about the same size as an office water-cooler bottle, that could be deployed by the Europa Mission as it conducts a plume fly-through. Sylph would execute a single ~2 km altitude plume pass below the main spacecraft. With a mass of 40 kg and a 24-hr life, the probe would autonomously navigate its low-altitude pass, and carry a dualchannel Mini-SUDA impact ionization mass spectrometer that would measure the composition of large grains, complementing the main spacecraft’s measurements of small grains and gas. Sylph is a novel smallsat concept: purpose-built configuration optimized for both the harsh Jovian environment and for Europan planetary-protection requirements, and built with advanced manufacturing methods from both deep space and smallsat components. For $80M (~4% marginal cost), the Europa Mission could buy a Sylph “insurance policy,” hedging the possibility that it does discover ocean plumes upon arrival in 2028. At less than 85 kg for probe and accommodations, the mission could carry two or three of the probes.

Sherwood, Brent↗
DOE OSTI2024

Nanocompression of 20 nm Silver Nanoparticles: In situ Aberration‐Corrected TEM and Atomistic Simulations

Single‐crystalline nanoparticles play an increasingly important role in a wide variety of fields including pharmaceuticals, advanced materials, catalysts for fuel cells, energy materials, as well as environmental detection and monitoring. Yet, the deformation mechanisms of very small nanoparticles are still poorly understood, in particular the role played by single dislocations and their interaction with surfaces. Here, in this work, silver nanoparticles with particularly small dimensions (≈20 nanometers in diameter) are compressed in situ in an aberration‐corrected transmission electron microscopy (TEM) and molecular dynamics (MD) simulations. During compression, the emergence of both dislocations and nanotwins are observed. However, these defects prove to be unstable and disappear upon removal of the indenter. Atomistic simulations confirm the role played by image stresses associated with the nearby surfaces and the reduction in dislocation line length as it approaches the free surface, thereby supporting the experimental observations. These results provide justification for the frequent observation of the absence of dislocations in nanoparticles of a few nanometers in size during in situ experiments, even after significant deformation. This phenomenon contributes to the self‐healing of samples through dislocation ejection toward the surfaces.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

A diffusive information preservation method for small Knudsen number flows

The direct simulation Monte Carlo (DSMC) method is a powerful particle-based method for modeling gas flows. It works well for relatively large Knudsen (Kn) numbers, typically larger than 0.01, but quickly becomes computationally intensive as Kn decreases due to its time step and cell size limitations. An alternative approach was proposed to relax or remove these limitations, based on replacing pairwise collisions with a stochastic model corresponding to the Fokker–Planck equation [J. Comput. Phys., 229, 1077 (2010); J. Fluid Mech., 680, 574 (2011)]. Similar to the DSMC method, the downside of that approach suffers from computationally statistical noise. To solve the problem, a diffusion-based information preservation (D-IP) method has been developed. The main idea is to track the motion of a simulated molecule from the diffusive standpoint, and obtain the flow velocity and temperature through sampling and averaging the IP quantities. To validate the idea and the corresponding model, several benchmark problems with Kn ∼ 10{sup −3}–10{sup −4} have been investigated. It is shown that the IP calculations are not only accurate, but also efficient because they make possible using a time step and cell size over an order of magnitude larger than the mean collision time and mean free path, respectively.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Long-Range Lamellar Alignment in Diblock Bottlebrush Copolymers via Controlled Oscillatory Shear

A simple strategy is presented to achieve well-ordered nanostructures in microphase-separated diblock bottlebrush copolymers (dbBB) for potential opportunities in nanotechnology that require large grain sizes and directed orientation. The unique architecture and relaxation processes of dbBBs offer a pathway to enhanced dynamic ordering and reorientation over macroscopic scales. Here, controlled shear is used to align lamellar domains. The high molecular mobility of dbBBs in the melt state, as shown by linear and nonlinear viscoelastic characterization, supports this alignment process. When subjected to large-amplitude oscillatory shear at controlled frequency (ω), strain amplitude (γ), and temperature (T shear ), microphase-separated lamellae transition into highly aligned states as determined by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). High throughput synchrotron SAXS is used to rapidly characterize microphase separation and lamellar alignment across the entire bulk sample. Lamellae align parallel to shear planes with an orientation order parameter (S) approaching S = 0.8 over a large cubic volume (V ~ mm 3 ).

36 MATERIALS SCIENCE↗
DOE OSTI2016

INVISIBLE ACTIVE GALACTIC NUCLEI. II. RADIO MORPHOLOGIES AND FIVE NEW H i 21 cm ABSORPTION LINE DETECTORS

This is the second paper directed toward finding new highly redshifted atomic and molecular absorption lines at radio frequencies. To this end, we selected a sample of 80 candidates for obscured radio-loud active galactic nuclei (AGNs) and presented their basic optical/near-infrared (NIR) properties in Paper I. In this paper, we present both high-resolution radio continuum images for all of these sources and H i 21 cm absorption spectroscopy for a few selected sources in this sample. A-configuration 4.9 and 8.5 GHz Very Large Array continuum observations find that 52 sources are compact or have substantial compact components with size <0.″5 and flux densities >0.1 Jy at 4.9 GHz. The 36 most compact sources were then observed with the Very Long Baseline Array at 1.4 GHz. One definite and 10 candidate Compact Symmetric Objects (CSOs) are newly identified, which is a detection rate of CSOs ∼three times higher than the detection rate previously found in purely flux-limited samples. Based on possessing compact components with high flux densities, 60 of these sources are good candidates for absorption-line searches. Twenty-seven sources were observed for H i 21 cm absorption at their photometric or spectroscopic redshifts with only six detections (five definite and one tentative). However, five of these were from a small subset of six CSOs with pure galaxy optical/NIR spectra (i.e., any AGN emission is obscured) and for which accurate spectroscopic redshifts place the redshifted 21 cm line in a radio frequency intereference (RFI)-free spectral “window” (i.e., the percentage of H i 21 cm absorption-line detections could be as high as ∼90% in this sample). It is likely that the presence of ubiquitous RFI and the absence of accurate spectroscopic redshifts preclude H i detections in similar sources (only 1 detection out of the remaining 22 sources observed, 13 of which have only photometric redshifts); that is, H i absorption may well be present but is masked by the RFI. Future searches for highly redshifted H i and molecular absorption can easily find more distant CSOs among bright, “blank field” radio sources, but will be severely hampered by an inability to determine accurate spectroscopic redshifts due to their lack of rest-frame UV continuum.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1999

Microscopy of Analogs for Martian Dust and Soil

The upcoming Mars 2001 lander will carry an atomic force microscope (AFM) as part of the Mars Environmental Compatibility Assessment (MECA) payload. By operating in a tapping mode, the AFM is capable of sub-nanometer resolution in three dimensions and can distinguish between substances of different compositions by employing phase-contrast imaging. Phase imaging is an extension of tapping-mode AFM that provides nanometer-scale information about surface composition not revealed in the topography. Phase imaging maps the phase of the cantilever oscillation during the tapping mode scan, hence detecting variations in composition, adhesion, friction, and viscoelasticity. Because phase imaging highlights edges and is not affected by large-scale height differences, it provides for clearer observation of fine features, such as grain edges, which can be obscured by rough topography. To prepare for the Mars 01 mission, we are testing the AFM on a lunar soil and terrestrial basaltic glasses to determine the AFMOs ability to define particle shapes and sizes and grain-surface textures. The test materials include the Apollo 17 soil 79221, which is a mixture of agglutinates, impact and volcanic beads, and mare and highland rock and mineral fragments. The majority of the lunar soil particles are less than 100 microns in size, comparable to the sizes estimated for Martian dust. The terrestrial samples are millimeter size basaltic glasses collected on Black Pointe at Mono Lake, just north of the Long Valley caldera in California. The basaltic glass formed by a phreatomagmatic eruption 13,000 years ago beneath a glacier that covered the Mono Lake region. Because basaltic glass formed by reworking of pyroclastic deposits may represent a likely source for Martian dunes, these basaltic glass samples represent plausible analogs to the types of particles that may be studied in sand dunes by the 01 lander and rover. We have used the AFM to examine several different soil particles at various resolutions. The instrument has demonstrated the ability to identify parallel ridges characteristic of twinning on a 150-micron plagioclase feldspar particle. Extremely small (10-100 nanometer) adhering particles are visible on the surface of the feldspar grain, and appear elongate with smooth surfaces. Phase contrast imaging of the nanometer particles shows several compositions to be present. When the AFM was applied to a 100-micron glass spherule, it was possible to define an extremely smooth surface.E Also visible on the surface of the glass spherule were chains of 100-nanometer- and-smaller impact melt droplets. Additional information is contained in the original extended abstract.

Anderson, M. A.↗
NASA NTRS2008

Space Debris Symposium (A6.) Measurements and Space Surveillance (1.): Measurements of the Small Particle Debris Cloud from the 11 January, 2007 Chinese Anti-satellite Test

On January 11, 2007, the Chinese military conducted a test of an anti-satellite (ASAT) system, destroying their own Fengyun-1C spacecraft with an interceptor missile. The resulting hypervelocity collision created an unprecedented number of tracked debris - more than 2500 objects. These objects represent only those large enough for the US Space Surveillance Network (SSN) to track - typically objects larger than about 5-10 cm in diameter. There are expected to be even more debris objects at sizes too small to be seen and tracked by the SSN. Because of the altitude of the target satellite (865 x 845 km orbit), many of the debris are expected to have long orbital lifetimes and contribute to the orbital debris environment for decades to come. In the days and weeks following the ASAT test, NASA was able to use Lincoln Laboratory s Haystack radar on several occasions to observe portions of the ASAT debris cloud. Haystack has the capability of detecting objects down to less than one centimeter in diameter, and a large number of centimeter-sized particles corresponding to the ASAT cloud were clearly seen in the data. While Haystack cannot track these objects, the statistical sampling procedures NASA uses can give an accurate statistical picture of the characteristics of the debris from a breakup event. For years computer models based on data from ground hypervelocity collision tests (e.g., the SOCIT test) and orbital collision experiments (e.g., the P-78 and Delta-180 on-orbit collisions) have been used to predict the extent and characteristics of such hypervelocity collision debris clouds, but until now there have not been good ways to verify these models in the centimeter size regime. It is believed that unplanned collisions of objects in space similar to ASAT tests will drive the long-term future evolution of the debris environment in near-Earth space. Therefore, the Chinese ASAT test provides an excellent opportunity to test the models used to predict the future debris environment. For this study, Haystack detection events are compared to model predictions to test the model assumptions, including debris size distribution, velocity distribution, and assumptions about momentum transfer between the target and interceptor. In this paper we will present the results of these and other measurements on the size and extent of collisional breakup debris clouds.

Matney, Mark J.↗
DOE OSTI2024

Data-driven nonlocal model for fragmentation in the crushing of solids

A technique is proposed for reproducing particle size distributions in three-dimensional simulations of the crushing and comminution of solid materials. The method is designed to produce realistic distributions over a wide range of loading conditions, especially for small fragments. In contrast to most existing methods, the new model does not explicitly treat the small-scale process of fracture. Instead, it uses measured fragment distributions from laboratory tests as the basic material property that is incorporated into the algorithm, providing a data-driven approach. The algorithm is implemented within a nonlocal peridynamic solver, which simulates the underlying continuum mechanics and contact interactions between fragments after they are formed. Finally, the technique is illustrated in reproducing fragmentation data from drop weight testing on sandstone samples.

58 GEOSCIENCES↗
DOE OSTI2011

Metastasis Infiltration: An Investigation of the Postoperative Brain-Tumor Interface

Purpose: This study aims to evaluate brain infiltration of metastatic tumor cells past the main tumor resection margin to assess the biological basis for the use of stereotactic radiosurgery treatment of the tumor resection cavity and visualized resection edge or clinical target volume. Methods and Materials: Resection margin tissue was obtained after gross total resection of a small group of metastatic lesions from a variety of primary sources. The tissue at the border of the tumor and brain tissue was carefully oriented and processed to evaluate the presence of tumor cells within brain tissue and their distance from the resection margin. Results: Microscopic assessment of the radially oriented tissue samples showed no tumor cells infiltrating the surrounding brain tissue. Among the positive findings were reactive astrocytosis observed on the brain tissue immediately adjacent to the tumor resection bed margin. Conclusions: The lack of evidence of metastatic tumor cell infiltration into surrounding brain suggests the need to target only a narrow depth of the resection cavity margin to minimize normal tissue injury and prevent treatment size-dependent stereotactic radiosurgery complications.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2018

Impact of rare earth ion size on the phase evolution of MoO3-containing aluminoborosilicate glass-ceramics

Transition metal and rare earth cations are important fission products present in used nuclear fuel, which in high concentrations tend to precipitate crystalline phases in vitreous nuclear waste forms. Two phases of particular interest are powellite (CaMoO 4 ) and oxyapatite (Ca 2 RE 8 (SiO 4 ) 6 O 2 ). The glass compositional dependencies controlling crystallization of these phases on cooling from the melt are poorly understood. In the present study, the effect of rare earth identity and modifier cation field strength on powellite and apatite crystallization were studied in a model MoO3-containing alkali/alkaline-earth aluminoborosilicate glass with focus on (1) influence of rare earth cation size (for RE 3+ : Ce, La, Nd, Sm, Er, Yb) and (2) influence of non-framework cations (RE 3+ , Mo 6+ , Na + , Ca 2+ ). Quenched glasses and glass-ceramics (obtained by slow cooling) were characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray absorption (XAS), and electron probe microanalysis (EPMA). All samples were X-ray amorphous upon quenching, except the Ce-containing composition which crystallized ceria (CeO 2 ), and the sample devoid of any rare earth cations which crystallized powellite (CaMoO 4 ). On heat treatment, powellite and oxyapatite crystallized in the majority of the samples with the former crystallizing in the volume, while the latter on the surface. The EPMA results confirmed a small concentration of boron in the oxyapatite crystal structure. RE cations were incorporated in the glass, as well as in powellite, oxyapatite, and in the case of Yb 3+ , keiviite (Yb 2 Si 2 O 7 ). Raman spectroscopy showed that the primary vibration band for molybdate MoO 4 2- in the glasses was strongly affected by the ionic field strength of the modifying cations (alkali, alkaline earth, and RE), suggesting their proximity to the MoO 4 2- ions in the glass, though the MoO bond length and coordination according to XAS suggested little local change.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Optical design for the single crystal neutron diffractometer Pioneer

Pioneer is a single-crystal neutron diffractometer optimized for small-volume samples and weak signals at the Second Target Station at Oak Ridge National Laboratory. This paper presents the preliminary optical design progress, focusing on the rationale behind key design choices. It covers the T 0 and bandwidth disk choppers, guide and beam control system, incident-beam polarizer, scattering beam collimators, and additional strategies. The chopper locations are selected to maximize neutron transport while taking advantage of standardized shielding structures. To accommodate the maintenance shield, operational shutter, and polarizing V-cavity, the guide design includes significant gaps. When these optical components are moved out of the beam path, oversized collimators, rather than guides, will be translated in. Pioneer will utilize slit packages to control beam size and divergence and a translatable polarizing V-cavity. Absorbing panels are strategically placed near the end station to minimize background. An oscillating radial collimator, operating in a shift mode, will be used with the vertical cylindrical detector, while a fixed multi-cone collimator will be used with the bottom flat detector. In conclusion, these collimators will enable the detection of weak signals when complex sample environments are used.

47 OTHER INSTRUMENTATION↗
DOE OSTI2019

High Strength and Deformation Mechanisms of A l0.3 CoCrFeNi High-Entropy Alloy Thin Films Fabricated by Magnetron Sputtering

Recently, high-entropy alloy thin films (HEATFs) with nanocrystalline structures and high hardness were developed by magnetron sputtering technique and have exciting potential to make small structure devices and precision instruments with sizes ranging from nanometers to micrometers. However, the strength and deformation mechanisms are still unclear. In this work, nanocrystalline Al0.3CoCrFeNi HEATFs with a thickness of ~4 μm were prepared. The microstructures of the thin films were comprehensively characterized, and the mechanical properties were systematically studied. It was found that the thin film was smooth, with a roughness of less than 5 nm. The chemical composition of the high entropy alloy thin film was homogeneous with a main single face-centered cubic (FCC) structure. Furthermore, it was observed that the hardness and the yield strength of the high-entropy alloy thin film was about three times that of the bulk samples, and the plastic deformation was inhomogeneous. Our results could provide an in-depth understanding of the mechanics and deformation mechanism for future design of nanocrystalline HEATFs with desired properties.

36 MATERIALS SCIENCE↗
NASA NTRS1984

Workshop on Water on Mars

The opening session of the Workshop focused on one of the most debated areas of Mars volatiles research-the size of the planet's past and present bulk water content. Current estimates of the inventory of H2O on Mars range from an equivalent layer of liquid 10-1000 meters deep averaged over the planet's surface. The most recent of these estimates, presented at the Workshop, is based on the now popular belief that the SNC class of meteorites represent actual samples of the Martian crust. From a model of planetary accretion and degassing founded on this assumption, it was determined that the present inventory of H2O on Mars is equivalent to a global layer no more than 50 meters deep. During the discussion generated by this estimate, several investigators expressed reservations about an H2O inventory as small as a few tens of meters, for it appears to directly contradict the seemingly abundant morphologic evidence that Mars is (or has been) water rich. Others, however, argued that the interpretation of much of this morphologic evidence is at best equivocal and that the case for a wet Mars is far from established. Atmospheric water vapor measurements, compiled by Earth based telescopes and the Viking Orbiter Mars Atmospheric Water Detectors (MAWD), now span a period of over six Martian years. Analysis of this data suggests that the seasonal cycle is governed by both the sublimation and condensation of H2O at the poles and by its adsorption/desorption within the regolith. So far, efforts to simulate the seasonal vapor cycle have failed to reproduce the observed behavior.

Clifford, S.↗
NASA NTRS1985

Distribution and Properties of Large Symmetric Knobs on Mars

Knobby terrain on Mars exists in a variety of forms from small closely spaced hills to widely separated large massifs. Fractional areal distributions of knobby terrain range from over 49% of the sampled area in regions of chaotic terrain to less than 5% along the cratered highland boundary in Amenthes and Aeolis. All symmetric knobs with long dimensions greater than or equal to 10 km were identified, mapped, and classified by shape. The spatial and dimensional distributions and shape characteristics of these features are discussed. The most common shape is elliptical: 79% of the knobs fall into this category, 11% were circular or round, 6% were triangular or wedge-shaped and the remaining 4% other shapes. All types show a roughly similar trend of rapidly decreasing number with increasing size, such that overall less than 10% of the knobs are larger than 20 km in long dimension. Circular knobs show the steepest fall-off in numbers with increasing diameter. Triangular knobs have a broader maximum with more than 65% falling in the 10 to 14 km range.

Frey, H.↗