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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 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Probe compensation in cylindrical near-field scanning: A novel simulation methodology

Probe pattern compensation is essential in near-field scanning geometry, where there is a great need to accurately know far-field patterns at wide angular range. This paper focuses on a novel formulation and computer simulation to determine the precise need for and effect of probe compensation in cylindrical near-field scanning. The methodology is applied to a linear test array antenna and the NASA scatterometer radar antenna. The formulation is based on representing the probe by its equivalent tangential magnetic currents. The interaction between the probe equivalent aperture currents and the test antenna fields is obtained with the application of a reciprocity theorem. This allows us to obtain the probe vector output pickup integral which is proportional to the amplitude and phase of the electric field induced in the probe aperture with respect to its position to the test antenna. The integral is evaluated for each probe position on the required sampling point on a cylindrical near-field surface enclosing the antenna. The use of a hypothetical circular-aperture probe with a different radius permits us to derive closed-form expressions for its far-field radiation patterns. These results, together with the probe vector output pickup, allow us to perform computer simulated synthetic measurements. The far-field patterns of the test antenna are formulated based on cylindrical wave expansions of both the probe and test antenna fields. In the limit as the probe radius becomes very small, the probe vector output is the direct response of the near-field at a point, and no probe compensation is needed. Useful results are generated to compare the far-field pattern of the test antenna constructed from the knowledge of the simulated near-field with and without probe pattern compensation and the exact results. These results are important since they clearly illustrate the angular range over which probe compensation is needed. It has been found that a probe with an aperture radius of 0.25(lambda), 0.5(lambda), and 1(lambda) needs a little probe compensation, if any, near the test antenna main beam. In addition, a probe with low directivity may provide a better signal-to-noise ratio than a highly directive one. This is evident in test antenna patterns without probe compensation at wide angles.

Hussein, Ziad A.↗
NASA NTRS1994

Six degree of freedom fine motion positioning stage based on magnetic levitation

The design of a magnetically suspended six degree of freedom positioning system capable of nanometer positioning is presented. The sample holder is controlled in six degrees of freedom (DOF) over 300 micrometers of travel in the X, Y, and Z directions. A design and control summary and test results indicating stability and power dissipation are included in the paper. The system is vacuum compatible, uses commercially available materials, and requires minimal assembly and setup.

Arling, R. W.↗
NASA NTRS1994

Spectral analysis of ALH 84001, a meteorite from Mars

ALH 84001 has recently been reclassified as a meteorite from Mars (SNC) and contains more than 90% orthopyroxene with minor chromite and accessory phases of augite, maskelynite, and carbonate. This meteorite represents a new class of igneous material from Mars. We have measured reflectance spectra of ALH 84001 as a chip as a powder, dry sieved to less than 125 microns to compare with previous spectral analyses of SNCs and remote observations of Mars. Spectra of the chip and powder in the visible-to-near-infrared region are shown. These spectra are composites of data measured with the RELAB bidirectional spectrometer from 0.3 to 2.55 microns and a Nicolet FTIR for longer wavelengths. As expected, the spectra of the chip have negative slopes and are significantly darker than the spectrum of the particulate sample, which has a positive slope. The strong absorptions near 1 micron and 2 microns are characteristic of low-Ca pyroxene and have band rninima of 0.925 microns and 1.930 microns. The strong absorption near 3 microns is characteristic of water. There is a distinct flattening in the spectrum between 1.0 and 1.5 microns indicating the presence of an additional absorption. This is interpreted to be the result of Fe(2+) in the M1 site of low-Ca pyroxene. Mid-infrared spectra showing the Christiansen feature and the reststrahlen bands are shown for spectra of the powder and of three different locations on the chip. These spectra exhibit several features in this range, some of which are associated with a specific region on the chip. Each of the spectra includes a doublet reststrahlen peak near 1100/cm, and peaks near 880 and 500/cm, which are typical for low-Ca pyroxenes. Weaker features at 940-1000/cm, 600-750/cm, and 530-560/cm are present in spectra from some locations on the chip, but not others, implying compositional and textural variation.

Bishop, J.↗
NASA NTRS1994

Practical formulation of a positively conservative scheme

Approximate Riemann solvers have been highly successful for computing the Euler/Navier-Stokes equations, but linearized Riemann solvers are known to fail occasionally by predicting non-physical states with negative density or internal energy. Positively conservative schemes, in contrast, guarantee physical solutions from realistic input. The Harten-Lax-van Leer-Einfeldt (HLLE) scheme is a typical example of a positively conservative scheme. However, the HLLE scheme is highly dissipative at contact discontinuities and shear layers and thus it is not applicable to practicle simulations. An existing modification to the HLLE scheme, known as HLLEM, enhances the resolution to that of the Roe scheme. However, this modification violates the positivity of density and internal energy. Precise derivation of the modification yields a quatratic inequality and thus requires a case-by-case treatment. This Note describes a new, modified HLLE scheme that satisfies the positively conservative condition approximately. Sample computationa are included to demonstrate the resolution and the robustness of the scheme.

Obayashi, Shigeru↗
NASA NTRS2001

Development and Demonstration of a Self-Calibrating Pseudolite Array for Task Level Control of a Planetary Rover

Pseudolites can extend the availability of GPS-type positioning systems to a wide range of applications not possible with satellite-only GPS. One such application is Mars exploration, where the centimeter-level accuracy and high repeatability of CDGPS would make it attractive for rover positioning during autonomous exploration, sample collection, and habitat construction if it were available. Pseudolites distributed on the surface would allow multiple rovers and/or astronauts to share a common navigational reference. This would help enable cooperation for complicated science tasks, reducing the need for instructions from Earth and increasing the likelihood of mission success. Conventional GPS Pseudolite arrays require that the devices be pre-calibrated through a Survey of their locations, typically to sub-centimeter accuracy. This is a problematic task for robots on the surface of another planet. By using the GPS signals that the Pseudolites broadcast, however, it is possible to have the array self-survey its own relative locations, creating a SelfCalibrating Pseudolite Array (SCPA). This requires the use of GPS transceivers instead of standard pseudolites. Surveying can be done either at carrier- or code-phase levels. An overview of SCPA capabilities, system requirements, and self-calibration algorithms is presented in another work. The Aerospace Robotics Laboratory at Statif0id has developed a fully operational prototype SCPA. The array is able to determine the range between any two transceivers with either code- or carrier-phase accuracy, and uses this inter-transceiver ranging to determine the at-ray geometry. This paper presents results from field tests conducted at Stanford University demonstrating the accuracy of inter-transceiver ranging and its viability and utility for array localization, and shows how transceiver motion may be utilized to refine the array estimate by accurately determining carrier-phase integers and line biases. It also summarizes the overall system requirements and architecture, and describes the hardware and software used in the prototype system.

Rock, Stephen M.↗
NASA NTRS2004

Approaching Suspicious Substances Safely

A mineral identification tool that was developed for NASA's Mars Rover Technology Development program is now serving as a powerful tool for U.S. law enforcement agencies and military personnel to identify suspicious liquid and solid substances. The tool can measure unknown substances through glass and plastic packaging materials with the RamanProbe(TradeMark) focused fiber-optic probe. The probe length can be extended up to 200 meters to enable users to analyze potentially dangerous substances at a safe distance. In many cases, the spectrometer and personnel are kept in a safe zone while the probe is positioned next to the sample being analyzed. Being able to identify chemicals in remote locations also saves users time and labor, since otherwise the samples would need to be collected, transported, and prepared prior to measurement in the laboratory.

Source record↗
NASA NTRS2007

Association between Randall's Plaque and Calcifying Nanoparticles

Randall's plaques, first described by Alexander Randall in the 1930s, are small subepithelial calcifications in the renal papillae (RP) that also extend deeply into the renal medulla. Despite the strong correlation between the presence of these plaques and the formation of renal stones, the precise origin and pathogenesis of Randall s plaque formation remain elusive. The discovery of calcifying nanoparticles (CNP) and their detection in many calcifying processes of human tissues has raised hypotheses about their possible involvement in renal stone formation. We collected RP and blood samples from 17 human patients who had undergone laparoscopic nephrectomy due to neoplasia. Homogenized RP tissues and serum samples were cultured for CNP. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis were performed on fixed RP samples. Immunohistochemical staining (IHS) was applied on the tissue samples using CNP-specific monoclonal antibody (mAb). Randall s plaques were visible on gross inspection in 11 out of 17 collected samples. Cultures of all serum samples and 13 tissue homogenates had CNP growth within 4 weeks. SEM revealed spherical apatite formations in 14 samples, with calcium and phosphate peaks detected by EDS analysis. IHS was positive in 9 out of 17 samples. A strong link was found between the presence of Randall s plaques and the detection of CNP, also referred to as nanobacteria. These results suggest new insights into the etiology of Randall's plaque formation, and will help us understand the pathogenesis of stone formation. Further studies on this topic may lead us to new approaches on early diagnosis and novel medical therapies of kidney stone formation.

Ciftcioglu, Neva↗
NASA NTRS2011

Development of Sample Verification System for Sample Return Missions

This paper describes the development of a proof of-concept sample verification system (SVS) for in-situ mass measurement of planetary rock and soil sample in future robotic sample return missions. Our proof-of-concept SVS device contains a 10 cm diameter pressure sensitive elastic membrane placed at the bottom of a sample canister. The membrane deforms under the weight of accumulating planetary sample. The membrane is positioned in proximity to an opposing substrate with a narrow gap. The deformation of the membrane makes the gap to be narrower, resulting in increased capacitance between the two nearly parallel plates. Capacitance readout circuitry on a nearby printed circuit board (PCB) transmits data via a low-voltage differential signaling (LVDS) interface. The fabricated SVS proof-of-concept device has successfully demonstrated approximately 1pF/gram capacitance change

Electrodes↗
NASA NTRS2014

A Measurement of the Millimeter Emission and the Sunyaev-Zel'dovich Effect Associated with Low-Frequency Radio Sources

We present a statistical analysis of the millimeter-wavelength properties of 1.4 GHz-selected sources and a detection of the Sunyaev-Zel'dovich effect associated with the halos that host them. We stack data at 148, 218 and 277 GHz from the Atacama Cosmology Telescope at the positions of a large sample of radio AGN selected at 1.4 GHz. The thermal Sunyaev-Zel'dovich (SZ) effect associated with the halos that host the AGN is detected at the 5 sigma level through its spectral signature, representing a statistical detection of the SZ effect in some of the lowest mass halos (average M(sub 200) approximately equals 10(sup 13) solar mass h(sub 70)(exp −1) ) studied to date. The relation between the SZ effect and mass (based on weak lensing measurements of radio galaxies) is consistent with that measured by Planck for local bright galaxies. In the context of galaxy evolution models, this study confirms that galaxies with radio AGN also typically support hot gaseous halos. Adding Herschel observations allows us to show that the SZ signal is not significantly contaminated by dust emission. Finally, we analyze the contribution of radio sources to the angular power spectrum of the cosmic microwave background.

radio continuum↗
DOE OSTI2015

Methods and apparatuses for self-generating fault-tolerant keys in spread-spectrum systems

Self-generating fault-tolerant keys for use in spread-spectrum systems are disclosed. At a communication device, beacon signals are received from another communication device and impulse responses are determined from the beacon signals. The impulse responses are circularly shifted to place a largest sample at a predefined position. The impulse responses are converted to a set of frequency responses in a frequency domain. The frequency responses are shuffled with a predetermined shuffle scheme to develop a set of shuffled frequency responses. A set of phase differences is determined as a difference between an angle of the frequency response and an angle of the shuffled frequency response at each element of the corresponding sets. Each phase difference is quantized to develop a set of secret-key quantized phases and a set of spreading codes is developed wherein each spreading code includes a corresponding phase of the set of secret-key quantized phases.

42 ENGINEERING↗
DOE OSTI2019

Synchrophasor measurement method for power systems

A synchrophasor measurement method for a device configured to take synchronized measurements in a power system is provided. The synchrophasor measurement method includes receiving global positioning system (GPS)-synchronized samples of a signal sensed by the device from the power system; determining a level of distortion of the signal; selecting, based on the level of distortion, a computation method, the computation method being one of an improved zero-crossing (IZC) method and an enhanced phase-lock-loop (EPLL) method; performing the selected computation method to determine at least one parameter of the signal at a reporting frequency, which is at least twice a line frequency of the power system; and outputting, at the reporting frequency, the at least one parameter to an operator of the power system to allow the operator to perform at least one of a monitoring and a controlling of at least one element of the power system.

Yao, Wenxuan↗
DOE OSTI2019

Application of a Coincidence Ring Ratio Moderator Correction to the Assay of 235U Residues

Processing of irradiated UAl targets by NaOH dissolution for the extraction of 99Mo results in the creation of high-activity highly enriched uranium (HEU)–bearing residues that must be quantified. The HEU residues generated from this process are assayed using an Active Well Coincidence Counter (AWCC) that has been modified to accommodate >1 Sv/h gamma-ray exposure rates to provide a 235U mass value for each residues container. The HEU residues include a significant amount of residual moderator from the dissolution process. Fission product decay heat drives off much—but not all—of the hydrogen from the dissolution, leaving an unknown moderator content in the residues. The moderator content impacts the induced fission rate in the HEU, detection efficiency, and die-away time of the emitted neutrons and requires implementation of a moderator correction factor. Three moderator correction techniques have been implemented: an active coincidence ring ratio method, a conventional 252Cf Add-A-Source (AAS) measurement, and an AAS ring ratio measurement. The 252Cf AAS and the AAS ring ratio methods are potentially much faster, but they require additional sample handling and precise positioning of the residues container and the 252Cf source. This study was performed using a combination of Monte Carlo N-Particle (MCNP) [1] simulation and measurements. The impact of the moderator content on the AWCC measurement and the relative performance of the three moderator correction methods are presented.

Mcelroy Jr, Robert↗
DOE OSTI2023

Compressive creep flow determination in fluids

The present disclosure provides an apparatus and method of use thereof for compressive creep testing of materials in the presence of fluids. The apparatus includes a cantilever arm connected on a first end to a cantilever pivot and including a weight holder on a second end; a first platen connected to the cantilever arm via a swivel located between the first end and the second end; a reservoir; and a second platen disposed within the reservoir and positioned to secure a sample between the first platen and the second platen when a force is applied via the weight holder and the first platen to a sample. Electrical properties of the material can be monitored and measured during the compression creep testing.

King, Garnel↗
DOE OSTI2015

Identifying Important Ions and Positions in Mass Spectrometry Imaging Data Using CUR Matrix Decompositions

Mass spectrometry imaging enables label-free, high-resolution spatial mapping of the chemical composition of complex, biological samples. Typical experiments require selecting ions and/or positions from the images: ions for fragmentation studies to identify keystone compounds and positions for follow up validation measurements using microdissection or other orthogonal techniques. Unfortunately, with modern imaging machines, these must be selected from an overwhelming amount of raw data. Existing techniques to reduce the volume of data, the most popular of which are principle component analysis and non-negative matrix factorization, have the disadvantage that they return difficult-to-interpret linear combinations of actual data elements. In this work, we show that CX and CUR matrix decompositions can be used directly to address this selection need. CX and CUR matrix decompositions use empirical statistical leverage scores of the input data to provide provably good low-rank approximations of the measured data that are expressed in terms of actual ions and actual positions, as opposed to difficult-to-interpret eigenions and eigenpositions. We show that this leads to effective prioritization of information for both ions and positions. In particular, important ions can be found either by using the leverage scores as a ranking function and using a deterministic greedy selection algorithm or by using the leverage scores as an importance sampling distribution and using a random sampling algorithm; however, selection of important positions from the original matrix performed significantly better when they were chosen with the random sampling algorithm. Also, we show that 20 ions or 40 locations can be used to reconstruct the original matrix to a tolerance of 17% error for a widely studied image of brain lipids; and we provide a scalable implementation of this method that is applicable for analysis of the raw data where there are often more than a million rows and/or columns, which is larger than SVD-based low-rank approximation methods can handle. Lastly, these results introduce the concept of CX/CUR matrix factorizations to mass spectrometry imaging, describing their utility and illustrating principled algorithmic approaches to deal with the overwhelming amount of data generated by modern mass spectrometry imaging.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

High-speed measurement of rotational anisotropy nonlinear optical harmonic generation using position-sensitive detection

We present a method of performing high-speed rotational anisotropy nonlinear optical harmonic generation experiments at rotational frequencies of several hertz by projecting the harmonic light reflected at different angles from a sample onto a stationary position-sensitive detector. The high rotational speed of the technique, 10 3 to 10 4 times larger than existing methods, permits precise measurements of the crystallographic and electronic symmetries of samples by averaging over low frequency laser-power, beam-pointing, and pulse-width fluctuations. As a result, we demonstrate the sensitivity of our technique by resolving the bulk fourfold rotational symmetry of GaAs about its [001] axis using second-harmonic generation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

RICH (Robotic Interface Control & Handling) System for VULCAN

High flux neutron beam and high efficiency detectors warrant quick turn arounds of neutron diffraction measurements at the engineering materials diffractometer VULCAN. Efficient change and alignment of samples and automatic measurements at VULCAN are desired for better use of neutron beam time by users. In this work, we aim to develop a proof-of-concept Robotic Interactive Control & Handling System (RICH) for sample handling at VULCAN that could assist high throughput experiments and reduce the overhead time significantly. This was realized by a six-axis desktop robot with trained AI models. The trained AI models can recognize and locate samples in various types of positions in a live video stream. In addition, we developed smart algorithms which used our models on multiple cameras to recognize where samples are with respect to multiple point of views, and then using user-inputted parameters, align them to perform complex measurements.

42 ENGINEERING↗
DOE OSTI2017

Nanoconfinement platform for nanostructure quantification via grazing-transmission X-ray scattering

A nano-confinement platform that may allow improved quantification of the structural order of nanometer-scale systems. Sample-holder `chips` are designed for the GTSAXS experimental geometry. The platform involves fabricated nanostructured sample holders on and in one or more corners of a substrate support where the sample material of interest is positioned at the corner of the substrate support. In an embodiment, the substrate material making up the substrate support beneath the sample-holding area is removed. A scattering x-ray sample platform includes a substrate support arranged in a parallelepiped form, having a substantially flat base and a substantially flat top surface, the top surface being substantially parallel with the base, the parallelepiped having a plurality of corners. At least one corner of the substrate support has a sample holding area formed in the top surface of the substrate support and within a predetermined distance from the corner. The sample holding area includes a regular array of nano-wells formed in the top surface of the substrate support.

36 MATERIALS SCIENCE↗