Search NASA⌕ Search

SEARCH · Search NASA

Results for “SMI”

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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Convergence of the SMI and the diagonally loaded SMI algorithms with weak interference

Approximations for the power levels at the output of an adaptive array that uses the diagonally loaded sample-matrix inversion (SMI) algorithm are derived. Diagonal loading is a technique where the diagonal of the covariance matrix is augmented with a positive or negative constant prior to inversion. This paper examines how the signal-to-interference-plus-noise ratio (SINR) and signal-to-interference ratio (SIR) at the array output vary with the number of samples taken when the input signals are CW. It is shown that positive loading produces more rapid convergence with a reduction in output SIR. Negative loading provides an improved SIR level, but positive loading produces more rapid convergence. Negative loading provides an improved SIR level, but the output power levels are erratic and slow to converge. Simulation results which verify the theoretical procedure are given.

Ganz, Matthew W.↗
NASA NTRS1987

SMI adaptive antenna arrays for weak interfering signals

The performance of adaptive antenna arrays is studied when a sample matrix inversion (SMI) algorithm is used to control array weights. It is shown that conventional SMI adaptive antennas, like other adaptive antennas, are unable to suppress weak interfering signals (below thermal noise) encountered in broadcasting satellite communication systems. To overcome this problem, the SMI algorithm is modified. In the modified algorithm, the covariance matrix is modified such that the effect of thermal noise on the weights of the adaptive array is reduced. Thus, the weights are dictated by relatively weak coherent signals. It is shown that the modified algorithm provides the desired interference protection. The use of defocused feeds as auxiliary elements of an SMI adaptive array is also discussed.

Gupta, I. J.↗
NASA NTRS1989

An experimental SMI adaptive antenna array for weak interfering signals

A modified sample matrix inversion (SMI) algorithm designed to increase the suppression of weak interference is implemented on an existing experimental array system. The algorithm itself is fully described as are a number of issues concerning its implementation and evaluation, such as sample scaling, snapshot formation, weight normalization, power calculation, and system calibration. Several experiments show that the steady state performance (i.e., many snapshots are used to calculate the array weights) of the experimental system compares favorably with its theoretical performance. It is demonstrated that standard SMI does not yield adequate suppression of weak interference. Modified SMI is then used to experimentally increase this suppression by as much as 13dB.

Dilsavor, R. L.↗
NASA NTRS1991

An experimental SMI adaptive antenna array simulator for weak interfering signals

An experimental sample matrix inversion (SMI) adaptive antenna array for suppressing weak interfering signals is described. The experimental adaptive array uses a modified SMI algorithm to increase the interference suppression. In the modified SMI algorithm, the sample covariance matrix is redefined to reduce the effect of thermal noise on the weights of an adaptive array. This is accomplished by subtracting a fraction of the smallest eigenvalue of the original covariance matrix from its diagonal entries. The test results obtained using the experimental system are compared with theoretical results. The two show a good agreement.

Dilsavor, Ronald S.↗
NASA NTRS1986

SMI adaptive antenna arrays for weak interfering signals

The performance of adaptive antenna arrays in the presence of weak interfering signals (below thermal noise) is studied. It is shown that a conventional adaptive antenna array sample matrix inversion (SMI) algorithm is unable to suppress such interfering signals. To overcome this problem, the SMI algorithm is modified. In the modified algorithm, the covariance matrix is redefined such that the effect of thermal noise on the weights of adaptive arrays is reduced. Thus, the weights are dictated by relatively weak signals. It is shown that the modified algorithm provides the desired interference protection.

Gupta, Inder J.↗
NASA NTRS1989

Analysis of modified SMI method for adaptive array weight control

An adaptive array is applied to the problem of receiving a desired signal in the presence of weak interference signals which need to be suppressed. A modification, suggested by Gupta, of the sample matrix inversion (SMI) algorithm controls the array weights. In the modified SMI algorithm, interference suppression is increased by subtracting a fraction F of the noise power from the diagonal elements of the estimated covariance matrix. Given the true covariance matrix and the desired signal direction, the modified algorithm is shown to maximize a well-defined, intuitive output power ratio criterion. Expressions are derived for the expected value and variance of the array weights and output powers as a function of the fraction F and the number of snapshots used in the covariance matrix estimate. These expressions are compared with computer simulation and good agreement is found. A trade-off is found to exist between the desired level of interference suppression and the number of snapshots required in order to achieve that level with some certainty. The removal of noise eigenvectors from the covariance matrix inverse is also discussed with respect to this application. Finally, the type and severity of errors which occur in the covariance matrix estimate are characterized through simulation.

Dilsavor, R. L.↗
DOE OSTI2020

Materials Data on SmI by Materials Project

SmI is Tungsten Carbide structured and crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Sm is bonded in a 6-coordinate geometry to six equivalent I atoms. All Sm–I bond lengths are 3.25 Å. I is bonded in a 6-coordinate geometry to six equivalent Sm atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SmY(CoNi)2 by Materials Project

SmY(CoNi)2 is Hexagonal Laves-derived structured and crystallizes in the orthorhombic Imm2 space group. The structure is three-dimensional. Sm is bonded in a 12-coordinate geometry to four equivalent Y, six equivalent Co, and six equivalent Ni atoms. There are two shorter (3.13 Å) and two longer (3.14 Å) Sm–Y bond lengths. There are four shorter (3.00 Å) and two longer (3.02 Å) Sm–Co bond lengths. There are four shorter (2.96 Å) and two longer (3.05 Å) Sm–Ni bond lengths. Y is bonded in a 12-coordinate geometry to four equivalent Sm, six equivalent Co, and six equivalent Ni atoms. All Y–Co bond lengths are 3.01 Å. There are four shorter (2.96 Å) and two longer (3.06 Å) Y–Ni bond lengths. Co is bonded to three equivalent Sm, three equivalent Y, two equivalent Co, and four equivalent Ni atoms to form CoSm3Y3Co2Ni4 cuboctahedra that share corners with eight equivalent NiSm3Y3Co4Ni2 cuboctahedra, corners with ten equivalent CoSm3Y3Co2Ni4 cuboctahedra, edges with six equivalent CoSm3Y3Co2Ni4 cuboctahedra, faces with six equivalent CoSm3Y3Co2Ni4 cuboctahedra, and faces with twelve equivalent NiSm3Y3Co4Ni2 cuboctahedra. There are one shorter (2.51 Å) and one longer (2.52 Å) Co–Co bond lengths. All Co–Ni bond lengths are 2.57 Å. Ni is bonded to three equivalent Sm, three equivalent Y, four equivalent Co, and two equivalent Ni atoms to form NiSm3Y3Co4Ni2 cuboctahedra that share corners with eight equivalent CoSm3Y3Co2Ni4 cuboctahedra, corners with ten equivalent NiSm3Y3Co4Ni2 cuboctahedra, edges with six equivalent NiSm3Y3Co4Ni2 cuboctahedra, faces with six equivalent NiSm3Y3Co4Ni2 cuboctahedra, and faces with twelve equivalent CoSm3Y3Co2Ni4 cuboctahedra. There are one shorter (2.56 Å) and one longer (2.57 Å) Ni–Ni bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SmY(MnGe)4 by Materials Project

SmY(MnGe)4 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Sm is bonded in a 8-coordinate geometry to eight equivalent Ge atoms. All Sm–Ge bond lengths are 3.10 Å. Y is bonded in a 8-coordinate geometry to eight equivalent Ge atoms. All Y–Ge bond lengths are 3.09 Å. Mn is bonded to four Ge atoms to form a mixture of edge and corner-sharing MnGe4 tetrahedra. All Mn–Ge bond lengths are 2.43 Å. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to four equivalent Sm, four equivalent Mn, and one Ge atom. The Ge–Ge bond length is 2.65 Å. In the second Ge site, Ge is bonded in a 9-coordinate geometry to four equivalent Y, four equivalent Mn, and one Ge atom. The Ge–Ge bond length is 2.61 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on SmY(Co2Ni3)2 by Materials Project

SmY(Co2Ni3)2 crystallizes in the orthorhombic Pmmm space group. The structure is three-dimensional. Sm is bonded in a 6-coordinate geometry to six Co and twelve Ni atoms. All Sm–Co bond lengths are 2.83 Å. All Sm–Ni bond lengths are 3.16 Å. Y is bonded in a 6-coordinate geometry to six Co and twelve Ni atoms. All Y–Co bond lengths are 2.83 Å. There are eight shorter (3.15 Å) and four longer (3.16 Å) Y–Ni bond lengths. There are two inequivalent Co sites. In the first Co site, Co is bonded in a 12-coordinate geometry to one Sm, two equivalent Y, and six Ni atoms. There are two shorter (2.43 Å) and four longer (2.44 Å) Co–Ni bond lengths. In the second Co site, Co is bonded in a 12-coordinate geometry to two equivalent Sm, one Y, and six Ni atoms. All Co–Ni bond lengths are 2.44 Å. There are three inequivalent Ni sites. In the first Ni site, Ni is bonded to four equivalent Sm, four equivalent Co, and four equivalent Ni atoms to form NiSm4Co4Ni4 cuboctahedra that share corners with sixteen NiSm2Y2Co4Ni4 cuboctahedra, edges with ten NiSm2Y2Co4Ni4 cuboctahedra, and faces with ten NiSm4Co4Ni4 cuboctahedra. All Ni–Ni bond lengths are 2.45 Å. In the second Ni site, Ni is bonded to four equivalent Y, four equivalent Co, and four equivalent Ni atoms to form NiY4Co4Ni4 cuboctahedra that share corners with sixteen NiSm2Y2Co4Ni4 cuboctahedra, edges with ten NiSm2Y2Co4Ni4 cuboctahedra, and faces with ten NiY4Co4Ni4 cuboctahedra. All Ni–Ni bond lengths are 2.45 Å. In the third Ni site, Ni is bonded to two equivalent Sm, two equivalent Y, four Co, and four Ni atoms to form a mixture of face, edge, and corner-sharing NiSm2Y2Co4Ni4 cuboctahedra. There are one shorter (2.45 Å) and one longer (2.46 Å) Ni–Ni bond lengths.

36 MATERIALS SCIENCE↗
NASA NTRS1989

Analysis of Modified SMI Method for Adaptive Array Weight Control

An adaptive array is used to receive a desired signal in the presence of weak interference signals which need to be suppressed. A modified sample matrix inversion (SMI) algorithm controls the array weights. The modification leads to increased interference suppression by subtracting a fraction of the noise power from the diagonal elements of the covariance matrix. The modified algorithm maximizes an intuitive power ratio criterion. The expected values and variances of the array weights, output powers, and power ratios as functions of the fraction and the number of snapshots are found and compared to computer simulation and real experimental array performance. Reduced-rank covariance approximations and errors in the estimated covariance are also described.

Dilsavor, Ronald Louis↗
DOE OSTI2020

Prospective associations among relationship abuse, sexual harassment and bullying in a community sample of sexual minority and exclusively heterosexual youth

ABSTRACT Introduction Sexual minority youth (SMY) are at significantly greater risk for experiencing adolescent relationship abuse (ARA) than exclusively heterosexual youth, yet little is known about the factors that elevate their risks for such abuse. Peer victimization (i.e., bullying, sexual harassment) has been associated with ARA among heterosexual youth. SMY experience higher rates of peer victimization than heterosexual youth, suggesting that it may be a risk factor for ARA among these youth. Using longitudinal data from a community sample of adolescents recruited from the northeastern US, we examined whether sexual identity was associated prospectively with ARA, and whether that relationship would be indirect, and mediated via bullying and sexual harassment at a 12‐month follow‐up. We expected to find higher rates of peer victimization and ARA among SMY than heterosexual youth, and we expected that sexual harassment and bullying would predict subsequent relationship abuse. Methods Adolescents ( N = 800; 58% female; 81% European‐American; 19% SMY) between 13 and 15 years ( M = 14.45, SD = 0.85) completed a web survey at baseline, 6‐months and 12‐months. Results Consistent with prior studies, SMY reported higher rates of bullying, sexual harassment, and relationship abuse than heterosexual youth. SMY who reported sexual harassment at baseline were more likely to report relationship abuse over time. Contrary to our expectations, however, bully victimization did not predict subsequent relationship abuse. Conclusions Sexual harassment can be particularly harmful for SMY because it targets gender and sexual identity at a formative developmental period and puts youth at risk for relationship abuse.

Hequembourg, Amy L.↗
DOE OSTI2021

Combined Technologies for In Situ Remediation of Tc-99 and U in Subsurface Sediments

In this study, combinations of chemical remedies were tested in bench-scale batch experiments to evaluate a two-step reduction-sequestration approach to effectively stabilize high concentrations of inorganic contaminant mixtures. Bench tests simulated contaminant and geochemical conditions of a perched aquifer located within the Central Plateau at the Hanford Site, located in southeastern Washington State (USA). Pairwise combinations of a reductant [e.g., zero valent iron, sulfur modified iron (SMI), or calcium polysulfide] and a sequestering agent [e.g., calcite, apatite, or dilute alkaline solution (e.g., NaOH)] were evaluated for immobilization and stabilization of technetium (Tc) (50,000 pCi/L), uranium (U) (150 mg/L), and nitrate (NO 3 ) (200 mg/L) in high ionic strength groundwater. The results of these batch studies demonstrated that reduction by SMI and sequestration in apatite or calcite are the most effective combination for these contaminant mixtures and conditions. Aqueous concentrations of Tc and U decreased by 95.6% ± 2.5% and 101.1% ± 5.2%, respectively, with SMI-apatite and 98.3% ± 0.0% and 101.2% ± 5.2%, respectively, with SMI-calcite. Sequential extractions showed that sequestered contaminants had limited capacity for re-oxidation; in fact, less than 10% of immobilized Tc and U was recovered by selective extraction of mineral phases most susceptible to oxidation. In addition, X-ray absorption near edge structure analysis of the sediment samples treated with SMI-calcite showed the presence of only U(IV), while both U(IV) and U(VI) were present in the SMI apatite combination [ratio of 0.43 U(IV):0.59 U(VI)].This study describes preliminary results that a two-step approach for stabilizing contaminant mixtures of long-lived radionuclides can be effective at reducing contaminant fluxes to groundwater from vadose and perched water zones.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2021

A New Experimental Station for Liquid Interface X-Ray Scattering At NSLS-II Beamline 12-ID

Open Platform and Liquids Scattering (OPLS) is a new experimental station recently built and currently being commissioned at the Soft Matter Interfaces (SMI) beamline 12-ID at NSLS-II. The new instrument expands SMI’s beamline scientific capabilities via the addition of X-ray scattering techniques from liquid surfaces and interfaces. The design of this new instrument, located inside the 12-ID beamline shielding enclosure (hutch B), is based on a single Ge (111) crystal deflector, which bounces the incident x-ray beam downward towards a liquid sample which must be maintained in a horizontal orientation (gravity-driven consideration). The OPLS instrument has a variable deflector-to-sample distance ranging from 0.6 m to 1.5 m. X-ray detectors are mounted on a 2-theta scattering arm located downstream of the sample location. The 2-theta arm is designed to hold up to three X-ray detectors, with fixed 2-theta angular offsets, each dedicated to a different X-ray technique such as X-ray reflectivity, grazing-incidence X-ray scattering, and small- and wide-angle X-ray scattering. Currently, the OPLS experimental station intercepts the SMI beam that otherwise propagates to the experimental endstation located in hutch C and can be retracted to a ’parking’ position laterally out of this beam to allow installation of a removable beam pipe that is needed to support operations in hutch C. The design of OPLS is flexible enough to quickly adapt to a planned future configuration of the SMI beamline in which a OPLS is illuminated separately from the main SMI branch via a second, canted undulator source and a separate photon delivery system. In this future configuration, both branches will be able to operate independently and simultaneously.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Spectral Induced Polarization-Biogeochemical Relationships for Remediation Amendment Monitoring

Geophysical tools such as electrical resistivity (ER) can indirectly monitor subsurface changes in response to remedial injections. These methods exhibit relatively low spatial resolution compared to sediment core characterization but are advantageous due to the ability to collect measurements non-intrusively over time across large volumes of the subsurface. Moreover, along with confirmatory groundwater or core sampling, geophysical methods can be used during active biogeochemical remedies to monitor short-term contaminant transformations and mobility, as well as part of an overall strategy for long-term monitoring of subsurface contaminated sites. The use of alternating current spectral induced polarization (SIP) provides significantly more information than conventional geophysical methods like direct current ER. SIP allows for monitoring changes in both solution and surface conductivity by separation of real and imaginary conductivity, respectively, as well as surface capacitance. In principle, SIP can measure indicators of remedy progression such as precipitation reactions that sequester contaminants, potentially providing a better indication of amendment delivery and reactivity as compared to conventional ER methods. However, multiple processes and material properties have overlapping (interacting) electrical responses across a range of frequencies. Hence, the purpose of this scoping study was to evaluate if SIP can be used to monitor (a) amendment delivery and (b) precipitation and reactivity of amendments under consideration at Hanford. SIP measurements were collected in fully saturated columns packed with sand and Hanford formation sediments containing (a) amendments that were highly conductive with significant capacitance (zero valent iron – ZVI, sulfur modified iron – SMI) and (b) amendments that exhibited low electrical conductivity with a small capacitance (calcite, apatite, bismuth). The sand was a quartz material with homogenous particle size that exhibited a relatively low surface conductivity. It was used as a control for comparison with the sediments from the Hanford Site, which have a greater surface conductivity because of their complex mineralogy and heterogeneous particle size distribution and may have complex interactions with amendments. The amendment mass fraction was varied to represent the different stages and subsurface locations associated with the delivery of a remedy. The primary objective was to identify the solution and solid surface changes associated with the delivery amendments and their secondary reactions within the subsurface. The figure below summarizes results for the amendments tested through this project. The SIP phase shift or imaginary conductivity change for the high conductivity amendments was more than 10 times that of the low conductivity amendments, highlighting the relative ease of detection of ZVI and SMI independent of the background signal from sand or Hanford sediments. The ZVI phase shift and imaginary conductivity changes occur primarily at high frequency (> 100 Hz) whereas SMI changes were at low frequency (0.01 to 10 Hz). SIP signals of SMI also increased over time and the maximum shifted to lower frequencies. The low conductivity amendments (calcite, abiotic and biotic apatite, bismuth subnitrate) exhibited relatively small phase and imaginary conductivity changes when added to sediments. The changes were above minimum detection limits (0.5 mrad for phase shift, 0.03 µS/cm for imaginary conductivity) for the highest concentration except for the commercial bismuth material. The lowest amendment concentration that can be detected is likely sediment specific, as minerals in sediments (clays, magnetite, Fe-oxides) have some capacitance and, therefore, exhibit a variable phase shift.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Surface-Mediated Interconnections of Nanoparticles in Cellulosic Fibrous Materials toward 3D Sensors

Fibrous materials serve as an intriguing class of 3D materials to meet the growing demands for flexible, foldable, biocompatible, biodegradable, dis- posable, inexpensive, and wearable sensors and the rising desires for higher sensitivity, greater miniaturization, lower cost, and better wearability. The use of such materials for the creation of a fibrous sensor substrate that interfaces with a sensing film in 3D with the transducing electronics is however difficult by conventional photolithographic methods. Here, a highly effective pathway featuring surface-mediated interconnection (SMI) of metal nanoclusters (NCs) and nanoparticles (NPs) in fibrous materials at ambient conditions is demon- strated for fabricating fibrous sensor substrates or platforms. Bimodally distrib- uted gold–copper alloy NCs and NPs are used as a model system to demonstrate the semiconductive-to-metallic conductivity transition, quantized capacitive charging, and anisotropic conductivity characteristics. Upon coupling SMI of NCs/NPs as electrically conductive microelectrodes and surface-mediated assembly (SMA) of the NCs/NPs as chemically sensitive interfaces, the resulting fibrous chemiresistors function as sensitive and selective sensors for gaseous and vaporous analytes. Finally, this new SMI–SMA strategy has significant implications for manufacturing high-performance fibrous platforms to meet the growing demands of the advanced multifunctional sensors and biosensors.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Small Molecule Inhibitor-Modulated Al 2 O 3 Atomic Layer Deposition on Monolayer MoS 2 for Controlled Nucleation

The integration of ultrathin dielectrics on two-dimensional (2D) semiconductors is essential for advancing beyond-Si electronics. However, the intrinsic inertness of van der Waals 2D basal planes remains a primary bottleneck to achieving uniform dielectric nucleation and growth. Here, in this study, we introduce a small molecule inhibitor (SMI)-modulated thermal atomic layer deposition (ALD) strategy, exemplified by aluminum oxide (Al 2 O 3 ) ALD on monolayer molybdenum disulfide (1L MoS 2 ) with acetic acid (HAc) SMI. The ABC-type sequence comprises HAc inhibitor (A), trimethylaluminum (TMA) precursor (B), and deionized H 2 O coreactant (C). In situ quartz crystal microbalance (QCM) studies reveal robust HAc adsorption on Al 2 O 3 and suppression of subsequent oxide growth on HAc-passivated surfaces. When applied to 1L MoS 2 , this inhibitory pathway enables HAc to selectively passivate nascent Al 2 O 3 nuclei formed on the MoS 2 surface, limiting their three-dimensional (3D) island coarsening and redirecting precursor adsorption toward the uncovered basal plane. Consequently, nearly continuous ultrathin (∼1.5 nm) Al 2 O 3 films are achieved on 1L MoS 2 with markedly improved uniformity compared to standard Al 2 O 3 ALD using TMA and H 2 O, as validated by atomic force microscopy (AFM), cross-sectional scanning transmission electron microscopy (STEM), and energy-dispersive X-ray spectroscopy (EDS). Density functional theory (DFT) calculations further provide atomistic insight into HAc-modulated Al 2 O 3 nucleation, corroborating the energetic preference of HAc for Al 2 O 3 over MoS 2 and attenuated TMA adsorption on HAc-passivated surfaces. Spatially resolved Raman spectroscopy also confirms that the HAc-modulated process preserves the structural integrity of 1L MoS 2 , with only minimal strain and doping perturbations observed after dielectric deposition. This SMI-modulated approach offers a broadly applicable framework for controlling ALD nucleation across various inhibitors, ALD chemistries, and 2D materials, opening opportunities for reliable dielectric integration in next-generation nanoelectronics.

36 MATERIALS SCIENCE↗