Search NASA⌕ Search

SEARCH · Search NASA

Results for “IGS”

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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Complex expression patterns of lymphocyte-specific genes during the development of cartilaginous fish implicate unique lymphoid tissues in generating an immune repertoire

Cartilaginous fish express canonical B and T cell recognition genes, but their lymphoid organs and lymphocyte development have been poorly defined. Here, the expression of Ig, TCR, recombination-activating gene (Rag)-1 and terminal deoxynucleosidase (TdT) genes has been used to identify roles of various lymphoid tissues throughout development in the cartilaginous fish, Raja eglanteria (clearnose skate). In embryogenesis, Ig and TCR genes are sharply up-regulated at 8 weeks of development. At this stage TCR and TdT expression is limited to the thymus; later, TCR gene expression appears in peripheral sites in hatchlings and adults, suggesting that the thymus is a source of T cells as in mammals. B cell gene expression indicates more complex roles for the spleen and two special organs of cartilaginous fish-the Leydig and epigonal (gonad-associated) organs. In the adult, the Leydig organ is the site of the highest IgM and IgX expression. However, the spleen is the first site of IgM expression, while IgX is expressed first in gonad, liver, Leydig and even thymus. Distinctive spatiotemporal patterns of Ig light chain gene expression also are seen. A subset of Ig genes is pre-rearranged in the germline of the cartilaginous fish, making expression possible without rearrangement. To assess whether this allows differential developmental regulation, IgM and IgX heavy chain cDNA sequences from specific tissues and developmental stages have been compared with known germline-joined genomic sequences. Both non-productively rearranged genes and germline-joined genes are transcribed in the embryo and hatchling, but not in the adult.

Non-NASA Center↗
NASA NTRS1995

On the Feasibility of Satellite Altimeter Tomography

The time-varying field of sea surface height (SSH) reflects a large number of dynamical processes including a broad range of baroclinic waves. Inertia-gravity (IG) and Rossby waves (RW) are readily detected in power spectra F(k) of SSH spatial variations, as well as in wavenumber-frequency spectral, ,k), and autocorrelation functions W(). these statistical characteristics contain information on dynamical processes in the upper thermocline. We show that the well-known 3-segment shape of 1-d spectra (based on SSH variations along satellite tracks) is determined by the Internal Rossby radius of deformation and by the degree of nonlinearity of baroclinic IG waves. Analyzing altimeter-based spectra of SSH variations in the light of a recently proposed theory for IG wave turbulence, we demonstrate that baroclinic IG waves are typically highly nonlinear. For a number of mid- and high-latitude regions, the internal Rossby radius and the wave nonlinearity are estimated from T/P data and shown to agree with expected values. The degree of the wave nonlinearity is of great practical interest. In particular, it tells us about the intensity of internal wave breaking. Furthermore, estimating the velocity of baroclinic RW we derive additional information on the upper layer stratification. These experiments point to the feasibility of using observed SSH field statistics (such F(k) and W()) to monitor properties of and dynamical processes in the upper mixed layer of the ocean.

Satellite Altimeter↗
NASA NTRS2012

An Update on the CDDIS

The Crustal Dynamics Data Inforn1ation System (CoorS) supports data archiving and distribution activities for the space geodesy and geodynamics community. The main objectives of the system are to store space geodesy and geodynamics related data products in a central data bank, to maintain infom1ation about the archival of these data, and to disseminate these data and information in a timely mam1er to a global scientific research community. The archive consists of GNSS, laser ranging, VLBI, and OORIS data sets and products derived from these data. The coors is one of NASA's Earth Observing System Oata and Infom1ation System (EOSorS) distributed data centers; EOSOIS data centers serve a diverse user community and are tasked to provide facilities to search and access science data and products. The coors data system and its archive have become increasingly important to many national and international science communities, in pal1icular several of the operational services within the International Association of Geodesy (lAG) and its project the Global Geodetic Observing System (GGOS), including the International OORIS Service (IDS), the International GNSS Service (IGS), the International Laser Ranging Service (ILRS), the International VLBI Service for Geodesy and Astrometry (IVS), and the International Earth Rotation Service (IERS). The coors has recently expanded its archive to supp011 the IGS Multi-GNSS Experiment (MGEX). The archive now contains daily and hourly 3D-second and subhourly I-second data from an additional 35+ stations in RINEX V3 fOm1at. The coors will soon install an Ntrip broadcast relay to support the activities of the IGS Real-Time Pilot Project (RTPP) and the future Real-Time IGS Service. The coors has also developed a new web-based application to aid users in data discovery, both within the current community and beyond. To enable this data discovery application, the CDDIS is currently implementing modifications to the metadata extracted from incoming data and product files pushed to its archive. This poster will include background information about the system and its user communities, archive contents and updates, enhancements for data discovery, new system architecture, and future plans.

Noll, Carey↗
NASA NTRS2004

Real-time data flow and product generating for GNSS

The last IGS workshop with the theme 'Towards Real-Time' resulted in the design of a prototype for real-time data and sharing within the IGS. A prototype real-time network is being established that will serve as a test bed for real-time activities within the IGS. We review the developments of the prototype and discuss some of the existing methods and related products of real-time GNSS systems. Recommendations are made concerning real-time data distribution and product generation.

GPS↗
NASA NTRS2005

The New Tropospheric Product of the International GNSS Service

We compare this new approach for generating the IGS tropospheric products with the previous approach, which was based on explicit combination of total zenith delay contributions from the IGS ACs. The new approach enables the IGS to rapidly generate highly accurate and highly reliable total zenith delay time series for many hundreds of sites, thus increasing the utility of the products to weather modelers, climatologists, and GPS analysts. In this paper we describe this new method, and discuss issues of accuracy, quality control, utility of the new products and assess its benefits.

International GNSS Service (IGS)↗
DOE OSTI2020

Effect of Pressure and Thermal Cycling on Long-Term Oxidation in CO 2 and Supercritical CO 2

Concentrating solar power plant designers are interested in supercritical CO 2 (sCO 2 ) for the power block to achieve > 50% electrical efficiency at > 700 °C. The goal of this project was to develop a long-term (> 100 kh) lifetime model for sCO 2 compatibility using 10–15 kh laboratory exposures. Three Ni-based alloys (625, 282 and 740H) and an advanced austenitic stainless steel were evaluated here in long-term exposures at 700–800 °C using 500-h cycles in laboratory air, 0.1 MPa industrial grade (IG) CO 2 and 30 MPa supercritical IG CO 2 and using 10-h cycles in 0.1 MPa IG CO 2 and O 2 . Mass change data and quantification of the oxide scale thickness and depth of internal attack after 1000–10,000 h exposures at 750 °C indicate that these materials are compatible with the sCO 2 environments with modeling used to predict long-term behavior. Comparison of the 0.1 and 30 MPa 500-h cycle results did not show a significant effect of pressure on the reaction, and no significant internal carburization was observed under these conditions, even for the stainless steel, suggesting that chromia scales may be better C diffusion barriers than expected. For the Ni-based alloys, thermal cycling to simulate the solar duty cycle did not result in scale spallation after 15 kh in 10-h cycles or 4 kh in 1-h cycles at 750 °C. However, the stainless steel specimens formed an Fe-rich oxide after ~ 1500-h cumulative exposure time in both 1- and 10-h cycles.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Custom-form iron trifluoride Li-batteries using material extrusion and electrolyte exchanged ionogels

Custom-form factor batteries fabricated in non-conventional shapes can maximize the overall energy density of the systems they power, particularly when used in conjunction with energy dense materials (e.g., Li metal anodes and conversion cathodes). Additive manufacturing (AM), and specifically material extrusion (ME), have been shown as effective methods for producing custom-form cell components, particularly electrodes. However, the AM of several promising energy dense materials (conversion electrodes such as iron trifluoride) have yet to be demonstrated or optimized. Furthermore, the integration of multiple AM produced cell components, such as electrodes and separators, along with a custom package remains largely unexplored. In this work, iron trifluoride (FeF 3 ) and ionogel (IG) separators are conformally printed using ME onto non-planar surfaces to enable the fabrication of custom-form Li-FeF 3 batteries. Further, to demonstrate printing on non-planar surfaces, cathodes and separators were deposited onto cylindrical rods using a 5-axis ME printer. ME printed FeF 3 was shown to have performance commensurate with FeF 3 cast using conventional means, both in coin cell and cylindrical rod formats, with capacities exceeding 700 mAh/g on the first cycle and ranging between 600 and 400 mAh/g over the next 50 cycles. Additionally, a ME process for printing polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) based IGs directly onto FeF 3 is developed and enabled using an electrolyte exchange process. In coin cells, this process is shown to produce cells with similar capacity to cells built with Celgard separators out to 50 cycles, with the exception that cycling instabilities are observed during cycles 8–20. When using printed and exchanged IGs in a custom cylindrical cell package, 6 stable high-capacity cycles are achieved. Overall, this work demonstrates approaches for producing high-energy-density Li-FeF 3 cells in coin and cylindrical rod formats, which are translatable to customized, arbitrary geometries compatible with ME printing and electrolyte exchange.

25 ENERGY STORAGE↗
DOE OSTI2021

HVEM structures and mutants reveal distinct functions of binding to LIGHT and BTLA/CD160

HVEM is a TNF (tumor necrosis factor) receptor contributing to a broad range of immune functions involving diverse cell types. It interacts with a TNF ligand, LIGHT, and immunoglobulin (Ig) superfamily members BTLA and CD160. Assessing the functional impact of HVEM binding to specific ligands in different settings has been complicated by the multiple interactions of HVEM and HVEM binding partners. To dissect the molecular basis for multiple functions, we determined crystal structures that reveal the distinct HVEM surfaces that engage LIGHT or BTLA/CD160, including the human HVEM–LIGHT–CD160 ternary complex, with HVEM interacting simultaneously with both binding partners. Based on these structures, we generated mouse HVEM mutants that selectively recognized either the TNF or Ig ligands in vitro. Knockin mice expressing these muteins maintain expression of all the proteins in the HVEM network, yet they demonstrate selective functions for LIGHT in the clearance of bacteria in the intestine and for the Ig ligands in the amelioration of liver inflammation.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2022

MRI-Based Radiotherapy Planning to Reduce Rectal Dose in Excess of Tolerance

Background and Purpose. Chronic rectal toxicity significantly decreases the quality of life for men who receive radiotherapy for prostate cancer. The most significant predictor of rectal toxicity is rectal dose-volume exceeding tolerance. To minimize the volume of rectum in the high dose field, it is essential to accurately define the prostate-rectum interface. This can be challenging to do by computed tomography (CT) imaging alone. The current study was undertaken to formally demonstrate in a clinical trial setting that image-guided intensity-modulated radiation therapy (IG-IMRT) planning using magnetic resonance imaging (MRI) can reduce the volume of rectum exceeding 70 Gy, a validated metric that predicts the risk of late rectal toxicity. Materials and Methods. This prospective single-arm study enrolled 15 men treated with IG-IMRT for localized prostate cancer. All participants received a dedicated 3 Tesla MRI examination of the prostate in addition to a pelvic CT examination for treatment planning. Two volumetric modulated arc therapy (VMAT) plans with a prescription dose of 79.2 Gy were designed using identical constraints based on CT- and MRI-defined consensus volumes. The volume of rectum exposed to 70 Gy or more was compared using the Wilcoxon paired signed rank test. Results. For CT-based treatment plans, the median volume of rectum receiving 70 Gy or more was 9.3 cubic centimeters (cc) (IQR 7.0 to 10.2) compared with 4.9 cc (IQR 4.1 to 7.8) for MRI-based plans. This resulted in a median volume reduction of 2.1 cc (IQR 0.5 to 5.3, P < .001). Conclusions. Using MRI to plan prostate IG-IMRT to a dose of 79.2 Gy reduces the volume of rectum receiving radiation dose in excess of tolerance (70 Gy or more) and should be considered in men who are at high risk for late rectal toxicity and are not good candidates for other rectal sparing techniques such as hydrogel spacer. This trial is registered with NCT02470910.

Schmidt, Daniel R.↗
DOE OSTI2025

Mitigate Stress Corrosion Cracking (SCC) in High-strength Al Castings (CRADA 508)

Development of high strength, corrosion resistant, aluminum alloys is important to a number of industries, including automotive, aerospace, power, etc. Understanding how processing methods such as casting, chemistry, additives and recycle content affect an alloy’s microstructure and performance in real world environments is crucial to their implementation. One major concern is how the repeated exposure to saline solutions can be detrimental to the structural integrity of aluminum alloy components. This study was undertaken as a collaboration between Eck Industries and PNNL to investigate the stress corrosion cracking (SCC) and corrosion behavior of aluminum alloys. This work examines the SCC response of three different materials set. First is cast A206 Al alloy produced by three different casting techniques (i.e., permanent mold, and sand casting with and without chill) and with or without nano forming additives as potential grain refiners. The second materials set comprises Al alloy tubes extruded by PNNL’s ShAPE process and produced using raw material with three different ratios of twitch and pre-consumer Al 6061 scrap. Finally, the third materials set comprises two Al-Si-Mg-Fe alloys with controlled Si% and Fe% to mimic recycle grade Al alloys. The corrosion behavior of these materials was characterized using SCC testing and scanning electrochemical cell microscopy (SECCM) technique; mechanical behavior was characterized using tensile testing, and microstructure was characterized using optical and electron microscopy techniques. Of the A206 Al alloys, the samples with nano forming additives performed poorly compared to those without. The best SCC performance (i.e. least degradation in mechanical properties) was demonstrated by A206 alloy sand cast with chill while the permanent mold sample showed the worst SCC performance. The SECCM was performed on A206 alloy sand cast with chill to understand the effect of microstructure and determine the location-dependent corrosion properties on grain boundaries (GB) and inside grains (IG) on the sample. The corrosion potential and current measured on GB and IG at various points on the sample established that the GB locations are more cathodic and corrosive than the IG locations. Further work needs to be conducted to investigate the mechanisms behind the observed dependence of SCC on casting technique and nano forming additives. Among the ShAPE extruded tubes, SECCM data suggests the decreasing order of tendency to corrode as follows: 100% twitch > 75% twitch > 50% twitch. Finally, both variants of the Al-Si-Mg-Fe alloys showed a large volume fraction of Fe- and Si-containing intermetallics and additional work is needed to discern differences in their respective corrosion responses. In summary, correlating local electrochemical behavior (e.g. via SECCM) with micro/nanostructure, in conjunction with bulk mechanical behavior, can help identify the right fabrication method and alloy chemistry to minimize SCC issues in Al alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Cost Effective Electrochromic Glazing Repositioning For Insulating Glass & Secondary Windows

This project addressed both technical and economic objectives toward significantly increasing the availability of ElectroChromic (EC) dynamic architectural glass at reduced cost. In contrast to the prevailing industry location of the EC device layer on the exterior light of an Insulating Glass (IG) unit, Project Objectives assessed the feasibility of a) repositioning the device layer midway between two IG panes to configure triple glazing, and b) independently framed to enable positioning to the building interior independent of the original glass configured as a dynamic secondary window. Parallel research complementing both EC-IG and EC-WinSert configurations addressed integral Photo Voltaic, and ceiling mounted “broadcast” power to circumvent the significant onsite electrical con tracting normally associated with the installation of commercial EC glazing.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
NASA NTRS1982

Comparison of candidate IGRF models

Three candidate models for the International Geomagnetic Reference Field (IGRF) for the years 1965, 1970, 1975, and 1980 are evaluated using magnetic observatory and satellite data. The models were submitted by the USGS, the IGS, and NASA. Comparison based on annual means data shows the differences between models to be small, although the NASA model appears slightly more accurate in 1965 and 1975 and the IGS model in 1970. Evaluation with Magsat scalar and vector satellite data at 1980 shows the USGS and NASA models to be of comparable accuracy, while the IGS model displays larger residuals. The NASA model best represents the scalar POGO data at 1965 and 1970. Contoured differences between the models in components X, Y, Z, and F at the earth's surface at 1965, 1970, 1975 and 1980 are displayed and discussed.

Langel, R. A.↗
NASA NTRS1996

Spectra of Baroclinic Inertia-Gravity Wave Turbulence

Baroclinic inertia-gravity (IG) waves form a persistent background of thermocline depth and sea surface height oscillations. They also contribute to the kinetic energy of horizontal motions in the subsurface layer. Measured by the ratio of water particle velocity to wave phase speed, the wave nonlinearity may be rather high. Given a continuous supply of energy from external sources, nonlinear wave-wave interactions among IG waves would result in inertial cascades of energy, momentum, and wave action. Based on a recently developed theory of wave turbulence in scale-dependent systems, these cascades are investigated and IG wave spectra are derived for an arbitrary degree of wave nonlinearity. Comparisons with satellite-altimetry-based spectra of surface height variations and with energy spectra of horizontal velocity fluctuations show good agreement. The well-known spectral peak at the inertial frequency is thus explained as a result of the inverse cascade. Finally, we discuss a possibility of inferring the internal Rossby radius of deformation and other dynamical properties of the upper thermocline from the spectra of SSH (sea surface height) variations based on altimeter measurements.

Glazman, Roman E.↗
NASA NTRS2003

Integrated G and C Implementation within IDOS: A Simulink Based Reusable Launch Vehicle Simulation

The implementation of multiple Integrated Guidance and Control (IG&C) algorithms per flight phase within a vehicle simulation poses a daunting task to coordinate algorithm interactions with the other G&C components and with vehicle subsystems. Currently being developed by Universal Space Lines LLC (USL) under contract from NASA, the Integrated Development and Operations System (IDOS) contains a high fidelity Simulink vehicle simulation, which provides a means to test cutting edge G&C technologies. Combining the modularity of this vehicle simulation and Simulink s built-in primitive blocks provide a quick way to implement algorithms. To add discrete-event functionality to the unfinished IDOS simulation, Vehicle Event Manager (VEM) and Integrated Vehicle Health Monitoring (IVHM) subsystems were created to provide discrete-event and pseudo-health monitoring processing capabilities. Matlab's Stateflow is used to create the IVHM and Event Manager subsystems and to implement a supervisory logic controller referred to as the Auto-commander as part of the IG&C to coordinate the control system adaptation and reconfiguration and to select the control and guidance algorithms for a given flight phase. Manual creation of the Stateflow charts for all of these subsystems is a tedious and time-consuming process. The Stateflow Auto-builder was developed as a Matlab based software tool for the automatic generation of a Stateflow chart from information contained in a database. This paper describes the IG&C, VEM and IVHM implementations in IDOS. In addition, this paper describes the Stateflow Auto-builder.

Fisher, Joseph E.↗
NASA NTRS1999

Precise Clock Solutions Using Carrier Phase from GPS Receivers in the International GPS Service

As one of its activities as an Analysis Center in the International GPS Service (IGS), the Jet Propulsion Laboratory (JPL) uses data from a globally distributed network of geodetic-quality GPS receivers to estimate precise clock solutions, relative to a chosen reference, for both the GPS satellites and GPS receiver internal clocks, every day. The GPS constellation and ground network provide geometrical strength resulting in formal errors of about 100 p sec for these estimates. Some of the receivers in the global IGS network contain high quality frequency references, such as hydrogen masers. The clock solutions for such receivers are smooth at the 20-p sec level on time scales of a few minutes. There are occasional (daily to weekly) shifts at the microsec level, symptomatic of receiver resets, and 200-p sec-level discontinuities at midnight due to 1-day processing boundaries. Relative clock solutions among 22 IGS sites proposed as "fiducial" in the IGS/BIPM pilot project have been examined over a recent 4-week period. This allows a quantitative measure of receiver reset frequency as a function of site. For days and-sites without resets, the Allan deviation of the relative clock solutions is also computed for subdaily values of tau..

Zumberge, J. F.↗
NASA NTRS2004

International GPS Service 2001 - 2002 Technical Reports

Applications of the Global Positioning System (GPS) to Earth Science are numerous. The International GPS Service (IGS), a federation of government agencies and universities, plays an increasingly critical role in support of GPS-related research and engineering activities. Contributions from the IGS Governing Board and Central Bureau, analysis and data centers, station operators, and others constitute the 2001 / 2002 Technical Reports. Hard copies of each volume can be obtained by contacting the IGS Central Bureau at the Jet Propulsion Laboratory. This report is published in black and white. To view graphs or plots that use color to represent data trends or information, please refer to the online PDF version at http://igscb.jpl.nasa.gov/overview/pubs.html.

Gowey, Ken↗
NASA NTRS2004

CDDIS 2001 Global Data Center Report

The Crustal Dynamics Data Information System (CDDIS) has supported the International GPS Service (IGS) as a global data center since 1992. The CDDIS activities within the IGS during 2001 are summarized below; this report also includes any changes or enhancements made to the CDDIS during the past year. General CDDIS background and system information can be found in the CDDIS data center summary included in the IGS 1994 Annual Report (Noll, 1995) as well as the subsequent updates (Noll, 1996, Noll, 1997, Noll, 1998, Noll, 1999, and Noll, 2001).

Noll, Carey E.↗
NASA NTRS2004

CDDIS 2002 Global Data Center Report

The Crustal Dynamics Data Information System (CDDIS) has supported the International GPS Service (IGS) as a global data center since 1992. The CDDIS activities within the IGS during 2002 are summarized below; this report also includes any changes or enhancements made to the CDDIS during the past year. General CDDIS background and system information can be found in the CDDIS data center summary included in the IGS 1994 Annual Report (Noll, 1995) as well as the subsequent updates (Noll, 1996, Noll, 1997, Noll, 1998, Noll, 1999, and Noll, 2001).

Noll, Carey E.↗