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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 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Factors Affecting the Battery Performance of Anthraquinone-based Organic Cathode Materials

Two organic cathode materials based on poly(anthraquinonyl sulfide) structure with different substitution positions were synthesized and their electrochemical behavior and battery performances were investigated. The substitution positions on the anthraquinone structure, binders for electrode preparation and electrolyte formulations have been found to have significant effects on the battery performances of such organic cathode materials. The substitution position with less steric stress has higher capacity, longer cycle life and better high-rate capability. Polyvinylidene fluoride binder and ether-based electrolytes are favorable for the high capacity and long cycle life of the quinonyl organic cathodes.

36 MATERIALS SCIENCE↗
NASA NTRS2005

Mapping From an Instrumented Glove to a Robot Hand

An algorithm has been developed to solve the problem of mapping from (1) a glove instrumented with joint-angle sensors to (2) an anthropomorphic robot hand. Such a mapping is needed to generate control signals to make the robot hand mimic the configuration of the hand of a human attempting to control the robot. The mapping problem is complicated by uncertainties in sensor locations caused by variations in sizes and shapes of hands and variations in the fit of the glove. The present mapping algorithm is robust in the face of these uncertainties, largely because it includes a calibration sub-algorithm that inherently adapts the mapping to the specific hand and glove, without need for measuring the hand and without regard for goodness of fit. The algorithm utilizes a forward-kinematics model of the glove derived from documentation provided by the manufacturer of the glove. In this case, forward-kinematics model signifies a mathematical model of the glove fingertip positions as functions of the sensor readings. More specifically, given the sensor readings, the forward-kinematics model calculates the glove fingertip positions in a Cartesian reference frame nominally attached to the palm. The algorithm also utilizes an inverse-kinematics model of the robot hand. In this case, inverse-kinematics model signifies a mathematical model of the robot finger-joint angles as functions of the robot fingertip positions. Again, more specifically, the inverse-kinematics model calculates the finger-joint commands needed to place the fingertips at specified positions in a Cartesian reference frame that is attached to the palm of the robot hand and that nominally corresponds to the Cartesian reference frame attached to the palm of the glove. Initially, because of the aforementioned uncertainties, the glove fingertip positions calculated by the forwardkinematics model in the glove Cartesian reference frame cannot be expected to match the robot fingertip positions in the robot-hand Cartesian reference frame. A calibration must be performed to make the glove and robot-hand fingertip positions correspond more precisely. The calibration procedure involves a few simple hand poses designed to provide well-defined fingertip positions. One of the poses is a fist. In each of the other poses, a finger touches the thumb. The calibration subalgorithm uses the sensor readings from these poses to modify the kinematical models to make the two sets of fingertip positions agree more closely.

Goza, Michael↗
DOE OSTI2020

Beam test performance of prototype silicon detectors for the Outer Tracker for the Phase-2 Upgrade of CMS

A new CMS tracker detector will be installed for operation at the High Luminosity LHC (HL-LHC). This detector comprises modules with two closely spaced parallel sensor plates and front-end ASICs capable of transmitting tracking information to the CMS Level-1 (L1) trigger at the 40 MHz beam crossing rate. The inclusion of tracking information in the L1 trigger decision will be essential for selecting events of interest efficiently at the HL-LHC. The CMS Binary Chip (CBC)has been designed to read out and correlate hits from pairs of tracker sensors, forming so called track stubs. For the first time, a prototype irradiated module and a full-sized module, both equipped with the version 2 of the CBC, have been operated in test beam facilities. The efficiency of the stub finding logic of the modules for various angles of incidence has been studied. The ability of the modules to reject tracks with transverse momentum less than 2 GeV has been demonstrated. For modules built with irradiated sensors, no significant drop in the stub finding performance has been observed. Results from the beam tests are described in this paper.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Extreme Scale De Novo Metagenome Assembly

Metagenome assembly is the process of transforming a set of short, overlapping, and potentially erroneous DNA segments from environmental samples into the accurate representation of the underlying microbiomes's genomes. State-of-the-art tools require big shared memory machines and cannot handle contemporary metagenome datasets that exceed Terabytes in size. In this paper, we introduce the MetaHipMer pipeline, a high-quality and high-performance metagenome assembler that employs an iterative de Bruijn graph approach. MetaHipMer leverages a specialized scaffolding algorithm that produces long scaffolds and accommodates the idiosyncrasies of metagenomes. MetaHipMer is end-to-end parallelized using the Unified Parallel C language and therefore can run seamlessly on shared and distributed-memory systems. Experimental results show that MetaHipMer matches or outperforms the state-of-the-art tools in terms of accuracy. Ultimately, MetaHipMer scales efficiently to large concurrencies and is able to assemble previously intractable grand challenge metagenomes. We demonstrate the unprecedented capability of MetaHipMer by computing the first full assembly of the Twitchell Wetlands dataset, consisting of 7.5 billion reads - size 2.6 TBytes.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

Introduction to an MCGIDI Mini-App and Performance Comparisons with XSBench

In high-performance Monte Carlo (MC) radiation transport codes, cross section lookups often account for the majority of computational expens. In response to this observation, a number of nuclear data mini-apps have been developed to profile and optimize the lookup process. A review of these mini-apps can be found in Ref. In contrast to a fully fledged MC code, nuclear data mini-apps do not feature particle tracking; instead, the cross section lookup process is considered in isolation, a simplification that allows for easier implementation and evaluation of various lookup schemes and techniques. GIDI+, as described on its public repository1, is ...a collection of C++ libraries for accessing evaluated and processed nuclear data stored in the Generalized Nuclear Database Structure (GNDS). In addition to reading GNDS files, GIDI+ has functions to sum and collapse multi-group data as needed by deterministic transport codes, and to sample GNDS data as needed by Monte Carlo transport codes. Certain modes of Mercury, a LLNL-developed MC radiation transport code, utilize GIDI+ for cross section lookups. Specifically, Mercury uses the MCGIDI library contained within GIDI+ to perform lookups on GPUs. A mini-app exercising MCGIDI’s cross section lookup capabilities would prove useful for optimization, which in turn could improve the performance of client codes such as Mercury. Such a mini-app could also be used to assess the performance of MCGIDI compared to other nuclear data mini-apps. In this document, we introduce a nuclear data mini-app built with the MCGIDI library. The MCGIDI mini-app (MCGIDI-MA) was developed to closely resemble the methodology present in XSBench, a nuclear data mini-app developed at Argonne National Laboratory. The remainder of this section provides an overview on XSBench. Section 2 describes MCGIDI-MA and its usage. Section 3 contains performance results of MCGIDI-MA on LLNL’s Lassen and Quartz compute platforms, as well as comparisons to XSBench performance where appropriate. In Section 4, we present a summary of our findings.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Sequential slip transfer of mixed-character dislocations across Σ3 coherent twin boundary in FCC metals: a concurrent atomistic-continuum study

Sequential slip transfer across grain boundaries (GB) has an important role in size-dependent propagation of plastic deformation in polycrystalline metals. For example, the Hall–Petch effect, which states that a smaller average grain size results in a higher yield stress, can be rationalised in terms of dislocation pile-ups against GBs. In spite of extensive studies in modelling individual phases and grains using atomistic simulations, well-accepted criteria of slip transfer across GBs are still lacking, as well as models of predicting irreversible GB structure evolution. Slip transfer is inherently multiscale since both the atomic structure of the boundary and the long-range fields of the dislocation pile-up come into play. In this work, concurrent atomistic-continuum simulations are performed to study sequential slip transfer of a series of curved dislocations from a given pile-up on Σ3 coherent twin boundary (CTB) in Cu and Al, with dominant leading screw character at the site of interaction. A Frank-Read source is employed to nucleate dislocations continuously. It is found that subject to a shear stress of 1.2 GPa, screw dislocations transfer into the twinned grain in Cu, but glide on the twin boundary plane in Al. Moreover, four dislocation/CTB interaction modes are identified in Al, which are affected by (1) applied shear stress, (2) dislocation line length, and (3) dislocation line curvature. Our results elucidate the discrepancies between atomistic simulations and experimental observations of dislocation-GB reactions and highlight the importance of directly modeling sequential dislocation slip transfer reactions using fully 3D models.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Online Junction Temperature Monitoring Using Intelligent Gate Drive for SiC Power Devices

Junction temperature is a prime design/operation parameter, as well as, a main indicator of device's health condition for power electronics converters. Compared to its silicon (Si) counterparts, it is more critical for silicon carbide (SiC) devices due to the reliability concern determined by the immaturity of new material and packaging. This paper presents a practical implementation using an intelligent gate drive for online junction temperature monitoring of SiC devices based on turn-off delay time as the thermo-sensitive electrical parameter. First, the sensitivity of turn-off delay time on the junction temperature for fast switching SiC devices is analyzed. A gate impedance regulation assist circuit is proposed to enhance the sensitivity by a factor of 60 and approach 736 ps/°C tested in the case study with little penalty on the power conversion performance. Next, an online monitoring unit based on gate assist circuits is developed to monitor the turn-off delay time in real time with the resolution less than 104 ps. As a result, the micro-controller is capable of “reading” junction temperature during the converter operation. Finally, a SiC-based half-bridge inverter is constructed with an intelligent gate drive consisting of the gate impedance regulation circuit and online turn-off delay time monitoring unit. Experimental results demonstrate the feasibility and accuracy of the proposed approach.

42 ENGINEERING↗
DOE OSTI2014

The simulation of 3D mass models in 2D digital mammography and breast tomosynthesis

Purpose: This work proposes a new method of building 3D breast mass models with different morphological shapes and describes the validation of the realism of their appearance after simulation into 2D digital mammograms and breast tomosynthesis images. Methods: Twenty-five contrast enhanced MRI breast lesions were collected and each mass was manually segmented in the three orthogonal views: sagittal, coronal, and transversal. The segmented models were combined, resampled to have isotropic voxel sizes, triangularly meshed, and scaled to different sizes. These masses were referred to as nonspiculated masses and were then used as nuclei onto which spicules were grown with an iterative branching algorithm forming a total of 30 spiculated masses. These 55 mass models were projected into 2D projection images to obtain mammograms after image processing and into tomographic sequences of projection images, which were then reconstructed to form 3D tomosynthesis datasets. The realism of the appearance of these mass models was assessed by five radiologists via receiver operating characteristic (ROC) analysis when compared to 54 real masses. All lesions were also given a breast imaging reporting and data system (BIRADS) score. The data sets of 2D mammography and tomosynthesis were read separately. The Kendall's coefficient of concordance was used for the interrater observer agreement assessment for the BIRADS scores per modality. Further paired analysis, using the Wilcoxon signed rank test, of the BIRADS assessment between 2D and tomosynthesis was separately performed for the real masses and for the simulated masses. Results: The area under the ROC curves, averaged over all observers, was 0.54 (95% confidence interval [0.50, 0.66]) for the 2D study, and 0.67 (95% confidence interval [0.55, 0.79]) for the tomosynthesis study. According to the BIRADS scores, the nonspiculated and the spiculated masses varied in their degrees of malignancy from normal (BIRADS 1) to highly suggestive for malignancy (BIRADS 5) indicating the required variety of shapes and margins of these models. The assessment of the BIRADS scores for all observers indicated good agreement based on Kendall's coefficient for both the 2D and the tomosynthesis evaluations. The paired analysis of the BIRADS scores between 2D and tomosynthesis for each observer revealed consistent behavior for the real and simulated masses. Conclusions: A database of 3D mass models, with variety of shapes and margins, was validated for the realism of their appearance for 2D digital mammography and for breast tomosynthesis. This database is suitable for use in future observer performance studies whether in virtual clinical trials or in patient images with simulated lesions.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Vertically Aligned Carbon Nanofiber based Biosensor Platform for Glucose Sensor

Vertically aligned carbon nanofibers (VACNFs) have recently become an important tool for biosensor design. Carbon nanofibers (CNF) have excellent conductive and structural properties with many irregularities and defect sites in addition to exposed carboxyl groups throughout their surfaces. These properties allow a better immobilization matrix compared to carbon nanotubes and offer better resolution when compared with the FET-based biosensors. VACNFs can be deterministically grown on silicon substrates allowing optimization of the structures for various biosensor applications. Two VACNF electrode architectures have been employed in this study and a comparison of their performances has been made in terms of sensitivity, sensing limitations, dynamic range, and response time. The usage of VACNF platform as a glucose sensor has been verified in this study by selecting an optimum architecture based on the VACNF forest density. Read More: http://www.worldscientific.com/doi/abs/10.1142/S0129156414500062

Al Mamun, Khandaker A.↗
DOE OSTI2019

Adiak

Adiak is a computer science data management interface tool for collecting metadata about an application's runs and disseminating it to tools that subscribe to this data. Examples of this metadata could be what user is running an application, what systems it runs on, or application provided name/value pairs. Adiak's capabilities include automated reading of system-level metadata, and a generic type system for applications to register their own name/value metadata. Adiak is currently designed to provide a standard interface that can be integrated with MPI-based applications that run on high performance computing systems. Example tools that use Adiak metadata include performance analysis tools and workflow tools. By allowing the application to specify metadata to Adiak, which then disseminates it to tools, application developers do not have to write to tool-specific interfaces.

LeGendre, MatthewP↗
DOE OSTI2015

Metagenomic analysis of planktonic microbial consortia from a non-tidal urban-impacted segment of James River

Knowledge of the diversity and ecological function of the microbial consortia of James River in Virginia, USA, is essential to developing a more complete understanding of the ecology of this model river system. Metagenomic analysis of James River's planktonic microbial community was performed for the first time using an unamplified genomic library and a 16S rDNA amplicon library prepared and sequenced by Ion PGM and MiSeq, respectively. From the 0.46-Gb WGS library (GenBank:SRR1146621; MG-RAST:4532156.3), 4 x 10 6 reads revealed >3 x 10 6 genes, 240 families of prokaryotes, and 155 families of eukaryotes. From the 0.68-Gb 16S library (GenBank:SRR2124995; MG-RAST:4631271.3; EMB:2184), 4 x 10 6 reads revealed 259 families of eubacteria. Results of the WGS and 16S analyses were highly consistent and indicated that more than half of the bacterial sequences were Proteobacteria , predominantly Comamonadaceae . The most numerous genera in this group were Acidovorax (including iron oxidizers, nitrotolulene degraders, and plant pathogens), which accounted for 10 % of assigned bacterial reads. Polaromonas were another 6 % of all bacterial reads, with many assignments to groups capable of degrading polycyclic aromatic hydrocarbons. Albidiferax (iron reducers) and Variovorax (biodegraders of a variety of natural biogenic compounds as well as anthropogenic contaminants such as polycyclic aromatic hydrocarbons and endocrine disruptors) each accounted for an additional 3% of bacterial reads. Comparison of these data to other publically-available aquatic metagenomes revealed that this stretch of James River is highly similar to the upper Mississippi River, and that these river systems are more similar to aquaculture and sludge ecosystems than they are to lakes or to a pristine section of the upper Amazon River. Altogether, these analyses exposed previously unknown aspects of microbial biodiversity, documented the ecological responses of microbes to urban effects, and revealed the noteworthy presence of 22 human-pathogenic bacterial genera (e.g., Enterobacteriaceae , pathogenic Pseudomonadaceae , and ‘Vibrionales' ) and 6 pathogenic eukaryotic genera (e.g., Trypanosomatidae and Vahlkampfiidae). This information about pathogen diversity may be used to promote human epidemiological studies, enhance existing water quality monitoring efforts, and increase awareness of the possible health risks associated with recreational use of James River.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Magnetic Microcalorimeter (MMC) Gamma Detectors with Ultra-High Energy Resolution

The goal of this LCP is to develop ultra-high resolution gamma-ray detectors based on magnetic microcalorimeters (MMCs) for accurate measurements of nuclear decay data and NDA of nuclear materials. For highest energy resolution, we are introducing erbium-doped silver (Ag:Er) as a novel sensor material and implement several geometry and design changes to improve the signal-to-noise ratio. The detector sensitivity will be increased by developing arrays of 32 Ag:Er pixels read out by 16 SQUID preamplifiers, and by developing a cryogenic Compton veto to reduce the spectral background. For highest energy resolution we will operate the MMC detector arrays in a dilution refrigerator with a base temperature <10 mK. The detector performance and utility will be demonstrated with radioactive sources of interest to the safeguards community. In FY16 and FY17, we had purchased a liquid-cryogen-free dilution refrigerator and installed 16 SQUID preamplifiers and writing for MMC detector operation at ~10 mK. We have also developed the process to fabricate the first Ag:Er-based MMCs, built prototype detector arrays and tested them with different radioactive sources. We have also shown that our MMC detectors can achieve the LCP goal of an energy resolution below 50 eV as needed to resolve most closelyspaced lines of interest for NDA. The goals for FY18 were then 1) to optimize the MMC design based on the measured detector characteristics and to increase the array size to 32-pixels for increased sensitivity, and 2) to demonstrate the utility of MMC gamma-ray detectors in applications relevant in nuclear safeguards.

42 ENGINEERING↗
NASA NTRS1983

An iterative approach to region growing using associative memories

Region growing, often given as a classical example of the recursive control structures used in image processing which are often awkward to implement in hardware where the intent is the segmentation of an image at raster scan rates, is addressed in light of the postulate that any computation which can be performed recursively can be performed easily and efficiently by iteration coupled with association. Attention is given to an algorithm and hardware structure able to perform region labeling iteratively at scan rates. Every pixel is individually labeled with an identifier which signifies the region to which it belongs. Difficulties otherwise requiring recursion are handled by maintaining an equivalence table in hardware transparent to the computer, which reads the labeled pixels. A simulation of the associative memory has demonstrated its effectiveness.

Snyder, W. E.↗
NASA NTRS1983

Operation of integrating indium antimonide linear arrays at 65 K and below

The combination of a FET switch non-CCD readout architecture with high-quality mesa-photovoltaic indium-antimonide detector material has led to high-performance integrating linear imagers in the 1- to 5-micron region. These devices operate in the temperature regime below 100 K and provide very good dark current and responsivity uniformity (+ or - 2 percent). Test data will show performance at 65 K for a 512-element array and 46 K for a 128-element array. Useful integration times of 3600 seconds at 46 K and greater than 12 seconds at 65 K have been achieved. For both devices, kTC read noise levels of less than 1200 electrons have been measured.

Bailey, G. C.↗
NASA NTRS1988

Sports Training

Practitioners of martial arts have long seen a need for a precise method of measuring the power of a karate kick or a boxer's punch in training and competition. Impax sensor is a piezoelectric film less than one thousandth of an inch thick, yet extremely durable. They give out a voltage impulse when struck, the greater the force of impact, the higher the voltage. The impulse is transmitted to a compact electronics package where voltage is translated into a force-pounds reading shown on a digital display. Impax, manufactured by Impulse Technology, Inc. is used by martial arts instructors, practitioners, U.S. Olympic Committee Training Center, football blocking sleds, and boxers as well as police defensive tactics, providing a means of evaluating the performance of recruits.

Source record↗
NASA NTRS2009

Improved Signal Chains for Readout of CMOS Imagers

An improved generic design has been devised for implementing signal chains involved in readout from complementary metal oxide/semiconductor (CMOS) image sensors and for other readout integrated circuits (ICs) that perform equivalent functions. The design applies to any such IC in which output signal charges from the pixels in a given row are transferred simultaneously into sampling capacitors at the bottoms of the columns, then voltages representing individual pixel charges are read out in sequence by sequentially turning on column-selecting field-effect transistors (FETs) in synchronism with source-follower- or operational-amplifier-based amplifier circuits. The improved design affords the best features of prior source-follower-and operational- amplifier-based designs while overcoming the major limitations of those designs. The limitations can be summarized as follows: a) For a source-follower-based signal chain, the ohmic voltage drop associated with DC bias current flowing through the column-selection FET causes unacceptable voltage offset, nonlinearity, and reduced small-signal gain. b) For an operational-amplifier-based signal chain, the required bias current and the output noise increase superlinearly with size of the pixel array because of a corresponding increase in the effective capacitance of the row bus used to couple the sampled column charges to the operational amplifier. The effect of the bus capacitance is to simultaneously slow down the readout circuit and increase noise through the Miller effect.

Pain, Bedabrata↗
NASA NTRS2011

Astronaut Demographic Database: Everything You Want to Know About Astronauts and More

A wealth of information regarding the astronaut population is available that could be especially useful to researchers. However, until now, it has been difficult to obtain that information in a systematic way. Therefore, this "astronaut database" began as a way for researchers within the Behavioral Health and Performance Group to keep track of the ever growing astronaut corps population. Before our effort, compilation of such data could be found, but not in a way that was easily acquired or accessible. One would have to use internet search engines, read through lengthy and potentially inaccurate informational sites, or read through astronaut biographies compiled by NASA. Astronauts are a unique class of individuals and, by examining such information, which we dubbed "Demographics," we hoped to find some commonalities that may be useful for other research areas and future research topics. By organizing the information pertaining to astronauts1 in a formal, unified catalog, we believe we have made the information more easily accessible, readily useable, and user friendly. Our end goal is to provide this database to others as a highly functional resource within the research community. Perhaps the database can eventually be an official, published document for researchers to gain full access.

Keeton, Kathryn↗