Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “ALT”

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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Enhanced optophysical properties of poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3] thiadiazol-4,8-diyl)] via addition of TiO{sub 2} nanoparticles

This work investigated the effect on 5 wt% addition of TiO{sub 2} nanoparticles (NPs) on the optical absorption characteristics of Poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3] thiadiazol-4,8-diyl)] (F8BT). Both materials were mixed using solution blending method and then spin coated onto ITO-coated glass substrate at 1000 rpm for 30s. The optical properties of the nanocomposite were determined using UV-Vis spectroscopy. Compares to pristine film, the absorption peak of the nanocomposite film improved and shifted to longer wavelength indicating reduction in the direct and indirect band gaps. Better optophysical properties of F8BT/TiO{sub 2} nanocomposites is believed due to compatible band structures and efficient charge trapping effect displayed by the NPs.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Three-body Faddeev equations in two-particle Alt-Grassberger-Sandhas form with Distorted-Wave-Born-approximation amplitudes as effective potentials

A(d, p)B reactions on heavier nuclei are peripheral at sub-Coulomb energies and can be peripheral even at energies above the Coulomb barrier due to the presence of the distorted waves in the initial and final channels. Usually, to analyze such reactions the distorted-wave-Born-approximation (DWBA) is used. The DWBA amplitude for peripheral reactions is parametrized in terms of the asymptotic normalization coefficient (ANC) of the bound state B = (n A). However, in the DWBA, the coupling of the different channels is not taken into account explicitly. The three-body Faddeev equations written as the two-particle Alt-Grassberger-Sandhas (AGS) equations are very suitable for the analysis of the A(d, p)B reactions because they take into account explicitly the coupling of the different channels. It is well known that the overall normalization of the DWBA amplitude or even of the more advanced continuum-discretized coupled channels (CDCC) amplitude for peripheral reactions (both sub-Coulomb and above the Coulomb barrier) is determined by the ANC. However, it is not apparent that it is the case for the AGS solution due to the coupling of the (d, p) channel to other channels. In this paper, it is proved that the sub-Coulomb A(d, p)B reaction amplitude, which is a solution of the two-body AGS equations, is peripheral and is parametrized in terms of the ANC of the bound state B = (nA) if the corresponding DWBA amplitude is peripheral. Both nonlocal separable and local nuclear interaction potentials between the constituent particles are considered. To prove the peripheral character of the AGS amplitude for the sub-Coulomb A(d, p)B reactions the effective potentials are expressed in terms of the corresponding sub-Coulomb DWBA amplitudes of the different channels. The analysis of the A(d, p)B reactions above the Coulomb barrier requires the inclusion of the optical potentials. Hence, to analyze such reactions, the AGS equations are generalized by including the optical nuclear potentials in the same manner as it is done in the DWBA. The obtained AGS equations contain the DWBA effective potentials with distorted waves generated by the sum of the nuclear optical and the channel Coulomb potentials. It is shown that if the DWBA amplitude is peripheral than it is also the case for the AGS amplitude, which is also parametrized in terms of the ANC of the bound state B = (nA). Furthermore, the inclusion of the coupling of the different channels in the AGS formalism allows one to improve the treatment of the peripheral sub-Coulomb and above the Coulomb (d, p) reactions compared to the DWBA and CDCC method.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1977

ECLSS consumables analysis: ALT captive/active 1 and captive/active 3

A consumables analysis of the environmental control and life support system (ECLSS) was performed for approach and landing test (ALT) captive/active missions 1 through 3 and is also applicable to missions 4 and 5. The ECLSS configuration analyzed and the guidelines and assumptions used in performing the analysis are presented. A projection of ammonia temperatures and pressures during the captive/active 1 mission is also included. The resulting consumables, budgets are presented in tabular and graphic form. Adequate margins were obtained for all systems.

Steines, G. J.↗
NASA NTRS2003

Synthesis and Luminescence of Yellow/Orange-Emitting Poly[tris(2,5-dihexyloxy-l,4-phenylenevinylene)-alt-(l,3-phenylenevinylene)]s

Soluble yellow/orange-emitting poly[tris(2,5-dihexyloxy-1,4-phenylenevinylene)-alt- (1,3-phenylenevinylene)] derivatives (6) have been synthesized and characterized. These polymers contain oligo(p-phenylene vinylene) chromophores of equal conjugation length, which are linked to a m-phenylene unit. Optical comparison between 6 and its model compound 8 at room and low temperature reveals the similarity in their absorption and fluorescence band structures. The vibronic band structure of 6 is assigned with the aid of the spectroscopic data for 8 at low temperature. Polymers 6 are electroluminescent with emission lambda (sub max), at approximately 565 nm. By using the device configuration of ITO/PEDOT/6/Ca, the polymer exhibits an external EL efficiency as high as 0.46%.

Liao, Liang↗
NASA NTRS2006

Free Enterprise: Contributions of the Approach and Landing Test (ALT) Program to the Development of the Space Shuttle Orbiter

The space shuttle orbiter was the first spacecraft designed with the aerodynamic characteristics and in-atmosphere handling qualities of a conventional airplane. In order to evaluate the orbiter's flight control systems and subsonic handling characteristics, a series of flight tests were undertaken at NASA Dryden Flight Research Center in 1977. A modified Boeing 747 Shuttle Carrier Aircraft carried the Enterprise, a prototype orbiter, during eight captive tests to determine how well the two vehicles flew together and to test some of the orbiter s systems. The free-flight phase of the ALT program allowed shuttle pilots to explore the orbiter's low-speed flight and landing characteristics. The Enterprise provided realistic, in-flight simulations of how subsequent space shuttles would be flown at the end of an orbital mission. The fifth free flight, with the Enterprise landing on a concrete runway for the first time, revealed a problem with the space shuttle flight control system that made it susceptible to pilot-induced oscillation, a potentially dangerous control problem. Further research using various aircraft, particularly NASA Dryden's F-8 Digital-Fly-By-Wire testbed, led to correction of the problem before the first Orbital Test Flight.

Merlin, Peter W.↗
NASA NTRS2014

Flexible Polyimide Aerogel Cross-linked by Poly(maleic Anhydride-alt-alkylene)

Aerogels are potential materials for aerospace applications due to their lower thermal conductivity, lighter weight, and low dielectric constant. However, silica aerogels are restricted due to their inherent fragility, hygroscopic nature, and poor mechanical properties, especially in extreme aerospace environments. In order to fit the needs of aerospace applications, developing new thermal insulation materials that are flexible, and moisture resistant is needed. To this end, we fabricated a series of polyimide aerogels crosslinked with different poly(maleic anhydride-alt-alkylene)s as seen in Scheme 1. The polyimide oligomers were made with 3,3,4,4-biphenyltetracarboxylic dianhydride (BPDA), and different diamines or diamine combinations. The resulting aerogels have low density (0.06 gcm3 to 0.16 gcm3) and high surface area (240-440 m2g). The effect of the different backbone structures on density, shrinkage, porosity, surface area, mechanical properties, moisture resistance and thermal properties will be discussed. These novel polyalkylene-imide aerogels may be potential candidates for applications such as space suit insulation for planetary surface missions, insulation for inflatable structures for habitats, inflatable aerodynamic decelerators for entry, descent and landing (EDL) operations, and cryotank insulation for advance space propulsion systems. Scheme 1. Network of polyimide aerogels crosslinked with deifferent poly(maleic anhydride).

cross-link↗
DOE OSTI2012

ALT-3 Target & CMU Version 4

The third Advance Liner Technology (ALT-3) experiment is the next in a long tradition of collaborations between LANL and RFNC/VNIIEF in high-explosive pulsed-power. Here a VNIIEF provided Disk Explosive Magnetic Generator (DEMG) will drive a LANL provided experimental load and diagnostic package. The objective of the experiment is to explore the use of a cylindrical liner-ontarget in tera-Pascal equation of state measurement. This presentation will discuss version 4 of the experimental target and central measuring unit (CMU) along with R & D already performed in fabrication of the target.

36 MATERIALS SCIENCE↗
DOE OSTI2011

ALT-3 target design and simulations

ALT-3 is an experiment being designed in collaboration between Russian VNIIEF scientists and LANL that aims to conduct high velocity material experiments to measure shock velocities and pressures near 1 TPa. The DEMG (Disck Explosive Magnetic Generator) is used to drive> 60MA currents to accelerate an aluminum liner to speeds in excess of 20 km/s. 1-D and 2-D simulations of the aluminum target are presented with information on the free surface velocity profile, the state of the target, and the shock velocity in the target. 2-D simulations are presented showing the different targets available as well as a scenario with a perturbed liner impacter.

42 ENGINEERING↗
DOE OSTI2019

Materials Data on AlTe(WO4)2 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗
DOE OSTI2016

Processing temperature control of a diketopyrrolopyrrole- alt -thieno[2,3- b ]thiophene polymer for high-mobility thin-film transistors and polymer solar cells with high open-circuit voltages

Here, we synthesized a planar pDPPTTi-OD polymer based on diketopyrrolopyrrole (DPP) and thieno [2,3- b ] thiophene (TTi) and investigated the electrical properties of the pDPPTTi-OD polymer. pDPPTTi-OD films displayed a low optical bandgap of 1.57 eV, and HOMO and LUMO levels of –5.40 and –3.74 eV, respectively. The 150°C-annealed pDPPTTi-OD films showed a high hole mobility of 0.16 cm 2 V –1 s –1 in organic thin-film transistor (OTFT) devices. The photovoltaic properties of polymer solar cells (PSCs) incorporating the pDPPTTi-OD were also measured. A pDPPTTi-OD:PC 71 BM blend film was spin-coated at 25, 70 and 90 °C. High-temperature processing significantly improved the power conversion efficiency of PSCs by effectively reducing the PC 71 BM domain sizes, which improved the miscibility between pDPPTTi-OD and PC 71 BM. Furthermore, this work demonstrated that the TTi moiety is a useful donor building block for high-performance D–A type polymers in OTFTs and PSCs, and that processing temperatures should be controlled to fully realize the materials' beneficial intrinsic properties.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Symmetry Breaking in Side Chains Leading to Mixed Orientations and Improved Charge Transport in Isoindigo- alt -Bithiophene Based Polymer Thin Films

The selection of side chains is important in design of conjugated polymers. It not only affects their intrinsic physical properties, but also has an impact on thin film morphologies. Recent reports suggested that a face-on/edge-on bimodal orientation observed in polymer thin films may be responsible for a three-dimensional (3D) charge transport and leads to dramatically improved mobility in donor–acceptor based conjugated polymers. To achieve a bimodal orientation in thin films has been seldom explored from the aspect of molecular design. In this work, we demonstrate a design strategy involving the use of asymmetric side chains that enables an isoindigo-based polymer to adopt a distinct bimodal orientation, confirmed by the grazing incidence X-ray diffraction. As a result, the polymer presents an average high mobility of 3.8 ± 0.7 cm 2 V –1 s –1 with a maximum value of 5.1 cm 2 V –1 s –1 , in comparison with 0.47 and 0.51 cm 2 V –1 s –1 obtained from the two reference polymers. This study exemplifies a new strategy to develop the next generation polymers through understanding the property-structure relationship.

three-dimensional charge transport↗