Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “GAMS”

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.

61 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

Jake Garn Mission Simulator and Training Facility, Building 5, Historical Documentation

In response to President George W. Bush's announcement in January 2004 that the Space Shuttle Program (SSP) would end in 2010, the National Aeronautics and Space Administration (NASA) completed a nation-wide historical survey and evaluation of NASA-owned facilities and properties (real property assets) at all its Centers and component facilities. The buildings and structures which supported the SSP were inventoried and assessed as per the criteria of eligibility for listing in the National Register of Historic Places (NRHP) in the context of this program. This study was performed in compliance with Section 110 of the National Historic Preservation Act (NHPA) of 1966 (Public Law 89-665), as amended; the National Environmental Policy Act (NEPA) of 1969 (Public Law 91-190); Executive Order (EO) 11593: Protection and Enhancement of the Cultural Environment; EO 13287, Preserve America, and other relevant legislation. As part of this nation-wide study, in September 2006, historical survey and evaluation of NASA-owned and managed facilities at was conducted by NASA's Lyndon B. Johnson Space Center (JSC) in Houston, Texas. The results of this study are presented in a report entitled, "Survey and Evaluation of NASA-owned Historic Facilities and Properties in the Context of the U.S. Space Shuttle Program, Lyndon B. Johnson Space Center, Houston, Texas," prepared in November 2007 by NASA JSC's contractor, Archaeological Consultants, Inc. As a result of this survey, the Jake Gam Mission Simulator and Training Facility (Building 5) was determined eligible for listing in the NRHP, with concurrence by the Texas State Historic Preservation Officer (SHPO). The survey concluded that Building 5 is eligible for the NRHP under Criteria A and C in the context of the U.S. Space Shuttle program (1969-2010). Because it has achieved significance within the past 50 years, Criteria Consideration G applies. At the time of this documentation, Building 5 was still used to support the SSP as an astronaut training facility. This documentation package precedes any undertaking as defined by Section 106 of the NHPA, as amended, and implemented in 36 CFR Part 800, as NASA JSC has decided to proactively pursue efforts to mitigate the potential adverse affects of any future modifications to the facility. It includes a historical summary of the Space Shuttle program; the history of JSC in relation to the SSP; a narrative of the history of Building 5 and how it supported the SSP; and a physical description of the structure. In addition, photographs documenting the construction and historical use of Building 5 in support of the SSP, as well as photographs of the facility documenting the existing conditions, special technological features, and engineering details, are included. A contact sheet printed on archival paper, and an electronic copy of the work product on CD, are also provided.

Slovinac, Trish↗
NASA NTRS2015

Compositional and Microstructural Evolution of Olivine During Pulsed Laser Irradiation: Insights Based on a FIB/Field-Emission TEM Study

Introduction: The use of pulsed laser irradiation to simulate the short duration, high-energy conditions characteristic of micrometeorite impacts is now an established approach in experimental space weathering studies. The laser generates both melt and vapor deposits that contain nanophase metallic Fe (npFe(sup 0)) grains with size distributions and optical properties similar to those in natural impact-generated melt and vapor deposits. There remains uncertainty, however, about how well lasers simulate the mechanical work and internal (thermal) energy partitioning that occurs in actual impacts. We are currently engaged in making a direct comparison between the products of laser irradiation and experimental/natural hypervelocity impacts. An initial step reported here is to use analytical TEM is to attain a better understanding of how the microstructure and composition of laser deposits evolve over multiple cycles of pulsed laser irradiation. Experimental Methods: We irradiated pressed-powder pellets of San Carlos olivine (Fo(sub 90)) with up to 99 rastered pulses of a GAM ArF excimer laser. The irradiated surface of the sample were characterized by SEM imaging and areas were selected for FIB cross sectioning for TEM study using an FEI Quanta dual-beam electron/focused ion beam instrument. FIB sections were characterized using a JEOL2500SE analytical field-emission scanning transmission electron microscope (FE-STEM) optimized for quantitative element mapping at less than 10 nm spatial resolutions. Results: In the SEM the 99 pulse pressed pellet sample shows a complex, inhomogeneous, distribution of laser-generated material, largely concentrated in narrow gaps and larger depressions between grains. Local concentrations of npFe0 spherules 0.1 to 1 micrometers in size are visible within these deposits in SEM back-scatter images. Fig. 1 shows bright-field STEM images of a FIB cross-section of a one of these deposits that continuously covers the top and sloping side of an olivine grain. The deposit has 3 microstructurally distinct sub-layers composed of silicate glass with varying modal fractions and size distributions of npFe( sup 0) spherules, along with nanocrystalline silicate material. A relatively thin (50-300 nm) topmost surface layer has a high-concentration of npFe0 spherules 5-20 nm in size. Element mapping shows the layer to be enriched in Fe by a factor of 2.5 relative to the olivine substrate, with Mg and Si depleted by 20% and 10% respectively. This is compositionally complementary to the underlying, middle layer of the deposit that is depleted in Fe, enriched in Mg and has a much lower npFe0 concentration. A third layer of nanocrystalline olivine occurs at the substrate interface. Discussion: The FE-STEM results suggest the topmost layer is a vapor deposit, underlain by a thicker microstructurally complex melt-generated layer. The compositional relations suggest the melt layer was partially vaporized, preferentially losing more volatile elements (e.g., Fe). The vaporized material re-condensed to form the thin, npFe(sup 0)-rich surface deposit during or immediately after the scan cycle. Nanocrystalline olivine that grew within the melt layer as it formed and cooled is similar in volume and microstructure to what we have observed in the impact melt lining of a micrometeorite impact crater in olivine. This suggest the time-temperature relations attained in the laser sample may not be too different from a micrometeorite impact. Our TEM observations, however, do not show evidence for the same level of mechanical dam-age (e.g., fracturing) seen around the natural micrometeorite crater.

Christoffersen, R.↗
DOE OSTI2022

Spatiotemporal Modeling of Real World Backsheets Field Survey Data: Hierarchical (Multilevel) Generalized Additive Models: Preprint

Assessing photovoltaic module backsheet durability is critical to increasing module lifetime. Lab based accelerating testing has recently failed to predict large scale failures of widely adopted polymeric materials. Field surveyed data is critical to assess the performance of component lifetime. Using a documented field survey protocol, 13 field surveys where conducted. Each measurement is encoded with it's spatial location in respect to the other modules. By combining field survey data on degradation predictors with real time satellite weather data, data-driven predictive models of backsheet degradation were trained. LOESS models were constructed to investigate the spatial dependence of measurements. It was found that micro-climatic effects like treelines, ground surface changes, and elevation changes effected the magnitude and variance of the measurements. A GAM model was created to predict the value of degradation based on measured predictors. The model includes variables on the climate of the system and the location of each measurement in the PV mounting structure. The model performed well with an adj:R2 of 0:95 for yellowness index prediction. The model was cross-validated using k-folds.

backsheet↗
DOE OSTI2022

Tuning the Mechanical and Electric Properties of Conjugated Polymer Semiconductors: Side–Chain Design Based on Asymmetric Benzodithiophene Building Blocks

Understanding molecular design rules for stretchable polymer semiconductors is important for enabling next generation stretchable electronic circuits. To simultaneously improve both electrical properties and mechanical stretchability, a design strategy is reported in introducing conjugated rigid fused-rings with bulky side groups in semiconducting polymers. In this work, the understanding of this design concept is improved by systematically investigating the effect of different types of bulky side groups asymmetrically substituted on conjugated polymer semiconductor backbones. Specifically, four types of side groups are investigated, including naphthalene (NaPh), biphenyl (PhPh), thienylphenyl (ThPh), and alkylphenyl (C4Ph), asymmetrically substituted on benzodithiophene units, namely asy-BDT. With the four types of side groups installed on BDT-containing conjugated polymers in an asymmetrical fashion, it is observed that they reduced the polymer chain aggregation and film crystallinity, hence improving the film stretchability. Furthermore, the fully conjugated polymer back-bone allows maintenance of good charge carrier mobilities. Specifically, polymer PDPP-C4Ph (with C4Ph side groups) shows the highest mobility in the fully stretchable transistor and maintained its mobility even after being subjected to hundreds of stretching-releasing cycles at 25% strain. Altogether, the results provide anunderstanding of the use of asymmetrically substituted fused-ring conjugated polymer structures to tune mechanical and charge transport properties.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Tuning the Mobility of Indacenodithiophene-Based Conjugated Polymers via Coplanar Backbone Engineering

Conjugated polymers based on indacenodithiophene-benzothiadiazole (IDT-BT) have attracted great interest due to their high charge carrier mobilities while being low crystallinity (i.e. near-amorphous.) They represent a promising design strategy to achieve both excellent stretchability and electrical performance. Here, we describe an approach on structural modifications of IDT-BT, namely by introducing non-covalent interactions and substituting building blocks to promote extended coplanar backbones. We systematically investigated the effects of structural modifications on backbone conformation, polymer aggregations, and charge carrier mobilities. Among the investigated polymers, the fluorinated derivative IDT-FBT demonstrated the highest charge carrier mobility of 5.19 cm 2 /Vs, along with low activation energy and Urbach energy indicating its low energy disorder level. The high mobility was attributed to the higher backbone planarity reinforced by S···F and H···F non-covalent interactions and improved interchain interactions through strong aggregation. In conclusion, our findings indicate that increasing backbone coplanarity may further improve mobility in low crystallinity conjugated polymers.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Hydride-Containing Eight-Electron Pt/Ag Superatoms: Structure, Bonding, and Multi-NMR Studies

Recent reports on hydride-doped noble metal nanoclusters strongly suggest that the encapsulated hydride is a part of the superatom core, but no accurate location of the hydride could be experimentally proved, so far. Here, we report herein a hydride-doped eight-electron platinum/silver alloy nanocluster in which the position of four-coordinated hydride was determined by neutron diffraction for the first time. X-ray structures of [PtHAg 19 (dtp/desp) 12 ] (dtp = S 2 P(O n Pr) 2 , 1; dsep = Se 2 P(O i Pr) 2 , 2) describe a central platinum hydride (PtH) unit encapsulated within a distorted Ag 12 icosahedron, the resulting (PtH)@Ag 12 core being stabilized by an outer sphere made up of 7 capping silver atoms and 12 dichalcogenolates. Solid-state structures of 1 and 2 differ somewhat in the spatial configuration of their outer spheres, resulting in overall different symmetries, C 1 and C 3 , respectively. Whereas the multi-NMR spectra of 2 in solution at 173 K reveal that the structure of C 3 symmetry is the predominant one, 1 H and 195 Pt NMR spectra of 1 at the same temperature disclose the presence of isomers of both C 1 and C 3 symmetry. DFT calculations found both isomers to be very close in energy, supporting the fact that they co-exist in solution. They also show that the [PtH@Ag 12 ] 5+ kernel can be viewed as a closed-shell superatomic core, the μ4-hydride electron contributing to its eight-electron count. On the other hand, the 1s(H) orbital contributes only moderately to the superatomic orbitals, being mainly involved in the building of a Pt–H bonding electron pair with the 5d z 2 (Pt) orbital.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2012

Hybrid Ground Station Technology for RF and Optical Communication Links

To support future enhancements of NASA's deep space and planetary communications and tracking services, the Jet Propulsion Laboratory is developing a hybrid ground station that will be capable of simultaneously supporting RF and optical communications. The main reason for adding optical links to the existing RF links is to significantly increase the capacity of deep space communications in support of future solar system exploration. It is envisioned that a mission employing an optical link will also use an RF link for telemetry and emergency purposes, hence the need for a hybrid ground station. A hybrid station may also reduce operations cost by requiring fewer staff than would be required to operate two stations. A number of approaches and techniques have been examined. The most promising ones have been prototyped for field examination and validation.

Radio frequency (RF) communications↗