Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “route selection”

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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Catalytic Dehydrogenation of Alkanes by PCP–Pincer Iridium Complexes Using Proton and Electron Acceptors

Dehydrogenation to give olefins offers the most broadly applicable route to the chemical transformation of alkanes. Furthermore, transition-metal-based catalysts can selectively dehydrogenate alkanes using either olefinic sacrificial acceptors or a purge mechanism to remove H 2 ; both of these approaches have significant practical limitations. Here, we report the use of pincer-ligated iridium complexes to achieve alkane dehydrogenation by proton-coupled electron transfer, using pairs of oxidants and bases as proton and electron acceptors. Up to 97% yield was achieved with respect to oxidant and base, and up to 15 catalytic turnovers with respect to iridium, using t-butoxide as base coupled with various oxidants, including oxidants with very low reduction potentials. Mechanistic studies indicate that (pincer)IrH 2 complexes react with oxidants and base to give the corresponding cationic (pincer)IrH + complex, which is subsequently deprotonated by a second equivalent of base; this affords (pincer)Ir which is known to dehydrogenate alkanes and thereby regenerates (pincer)IrH 2 .

02 PETROLEUM↗
DOE OSTI2020

Octopus, a computational framework for exploring light-driven phenomena and quantum dynamics in extended and finite systems

Over the last few years, extraordinary advances in experimental and theoretical tools have allowed us to monitor and control matter at short time and atomic scales with a high degree of precision. An appealing and challenging route toward engineering materials with tailored properties is to find ways to design or selectively manipulate materials, especially at the quantum level. To this end, having a state-of-the-art ab initio computer simulation tool that enables a reliable and accurate simulation of light-induced changes in the physical and chemical properties of complex systems is of utmost importance. The first principles real-space-based Octopus project was born with that idea in mind, i.e., to provide a unique framework that allows us to describe non-equilibrium phenomena in molecular complexes, low dimensional materials, and extended systems by accounting for electronic, ionic, and photon quantum mechanical effects within a generalized time-dependent density functional theory. This article aims to present the new features that have been implemented over the last few years, including technical developments related to performance and massive parallelism. We also describe the major theoretical developments to address ultrafast light-driven processes, such as the new theoretical framework of quantum electrodynamics density-functional formalism for the description of novel light–matter hybrid states. Those advances, and others being released soon as part of the Octopus package, will allow the scientific community to simulate and characterize spatial and time-resolved spectroscopies, ultrafast phenomena in molecules and materials, and new emergent states of matter (quantum electrodynamical-materials).

74 ATOMIC AND MOLECULAR PHYSICS↗
NASA NTRSDate not supplied

A Predictive GNSS Performance Monitor for Autonomous Air Vehicles in Urban Environments

The emergence and development of advanced technologies and vehicle types has created a growing demand for the introduction of new forms of flight operations. These new and increasingly complex operational paradigms such as Advanced and Urban Air Mobility (AAM/UAM) present regulatory authorities and the aviation community with several design and implementation challenges – particularly for highly autonomous vehicles. An overarching and daunting task is finding methods to integrate these emerging operations without compromising safety or disrupting traditional airspace operations. A shift toward a more predictive risk mitigation capability becomes critical to meet this challenge. This paper focus on the development and testing of a prognostic service aimed at estimating the quality of Global Navigation Satellite System (GNSS) performance for an autonomous aircraft in complex environments. The intent of this function is to proactively reduce a flight operations risk of exposure to states that may induce poor or unacceptable navigation system performance by factoring in estimates of GNSS quality into pre-flight and/or in-flight route planning. Methodologies for producing quality estimates are specified and results are provided for selected simulation and flight test cases.

GNSS↗
DOE OSTI2024

Sustainable aviation fuels from biomass and biowaste via bio- and chemo-catalytic conversion: Catalysis, process challenges, and opportunities

Sustainable aviation fuel (SAF) production from biomass and biowaste streams is an attractive option for decarbonizing the aviation sector, one of the most-difficult-to-electrify transportation sectors. Despite ongoing commercialization efforts using ASTM-certified pathways (e.g., lipid conversion, Fischer-Tropsch synthesis), production capacities are still inadequate due to limited feedstock supply and high production costs. New conversion technologies that utilize lignocellulosic feedstocks are needed to meet these challenges and satisfy the rapidly growing market. Combining bio- and chemo-catalytic approaches can leverage advantages from both methods, i.e., high product selectivity via biological conversion, and the capability to build C-C chains more efficiently via chemical catalysis. Herein, conversion routes, catalysis, and processes for such pathways are discussed, while key challenges and meaningful R&D opportunities are identified to guide future research activities in the space. Bio and chemo-catalytic conversion primarily utilize the carbohydrate fraction of lignocellulose, leaving lignin as a waste product. This makes lignin conversion to SAF critical in order to utilize whole biomass, thereby lowering overall production costs while maximizing carbon efficiencies. Thus, lignin valorization strategies are also reviewed herein with vital research areas identified, such as facile lignin depolymerization approaches, highly integrated conversion systems, novel process configurations, and catalysts for the selective cleavage of aryl C–O bonds. The potential efficiency improvements available via integrated conversion steps, such as combined biological and chemo-catalytic routes, along with the use of different parallel pathways, are identified as key to producing all components of a cost-effective, 100% SAF.

09 BIOMASS FUELS↗
DOE OSTI2022

Highly selective and productive reduction of carbon dioxide to multicarbon products via in situ CO management using segmented tandem electrodes

Electrochemical CO 2 reduction provides a promising route to the sustainable generation of valuable chemicals and fuels. Tandem catalysts enable sequential CO 2 -to-CO and CO-to-multicarbon (C 2+ ) product conversions on complementary active sites, to produce high C 2+ Faradaic efficiency (FE). Unfortunately, previous tandem catalysts exhibit poor management of CO intermediates, which diminishes C 2+ FE. Here, we design segmented gas-diffusion electrodes (s-GDEs) in which a CO-selective catalyst layer (CL) segment at the inlet prolongs CO residence time in the subsequent C 2+ -selective segment, enhancing conversion. This phenomenon enables increases in both the CO utilization and C 2+ current density for a Cu/Ag s-GDE compared to pure Cu, by increasing the *CO coverage within the Cu CL. Lastly, we develop a Cu/Fe-N-C s-GDE with 90% C 2+ FE at C 2+ partial current density (j C2+ ) exceeding 1 A cm -2 . These results prove the importance of transport and establish design principles to improve C 2+ FE and j C2+ in tandem CO 2 reduction.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2017

Mechanistic Insights Evaluating Ag, Pb, and Ni as Electrocatalysts for Furfural Reduction from First-Principles Methods

Electrochemical reduction of furfural (ECRFF) emerges as an efficient and sustainable means to obtain high-value chemicals and biofuels with the activity and product selectivity being sensitive to cathode materials. In this work, elementary steps describing furfuryl alcohol (FA) and 2-methylfuran (MF) production routes in ECRFF are studied by using periodic density functional theory on Ag, Pb, and Ni, as alternative cathode materials. The established Brønsted–Evans–Polanyi (BEP) relationship has been proven to be reliable to estimate energy barriers of C–O bond cleavage. The intrinsic characters of Ag, Pb, and Ni are then summarized in free energy diagrams to reflect the FA and MF production trends as future guidelines to evaluate ECRFF activity and selectivity on these metals. On all metal surfaces, at both terrace and stepped sites, the first C–H or O–H hydrogenation step, producing respective mh6 or mh7 intermediates, influences overall FA production. On Ag and Pb, pathways involving the mh6 intermediate are thermodynamically and kinetically favored, whereas on Ni, both mh6 and mh7 routes are competitive due to strong interactions between the furan ring and the substrate. In addition, these partially hydrogenated intermediates can also undergo C–O bond cleavage with reduced energy barriers (compared to direct C–O bond cleavage in furfural), which opens potential paths for parallel MF production. Conversion of FA into MF catalyzed by these metallic cathodes was considered as well, although the high C–O bond cleavage energy barrier is likely to hinder this process.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Cyclic (Alkyl)(amino)carbene Ligands Enable Cu‐Catalyzed Markovnikov Protoboration and Protosilylation of Terminal Alkynes: A Versatile Portal to Functionalized Alkenes**

Abstract Regioselective hydrofunctionalization of alkynes represents a straightforward route to access alkenyl boronate and silane building blocks. In previously reported catalytic systems, high selectivity is achieved with a limited scope of substrates and/or reagents, with general solutions lacking. Herein, we describe a selective copper‐catalyzed Markovnikov hydrofunctionalization of terminal alkynes that is facilitated by strongly donating cyclic (alkyl)(amino)carbene (CAAC) ligands. Using this method, both alkyl‐ and aryl‐substituted alkynes are coupled with a variety of boryl and silyl reagents with high α‐selectivity. The reaction is scalable, and the products are versatile intermediates that can participate in various downstream transformations. Preliminary mechanistic experiments shed light on the role of CAAC ligands in this process.

Gao, Yang↗
DOE OSTI2016

Synthesis of α-MoC 1- x Nanoparticles with a Surface-Modified SBA-15 Hard Template: Determination of Structure-Function Relationships in Acetic Acid Deoxygenation

Surface modification of mesoporous SBA-15 silica generated a hydrophobic environment for a molybdenum diamine (Mo-diamine) precursor solution, enabling direct growth of isolated 1.9 ± 0.4 nm α-MoC 1-x nanoparticles (NPs) inside the pores of the support. The resulting NP catalysts are bifunctional, and compared to bulk α-MoC 1-x and β-Mo 2 C, the NPs exhibit a greater acid-site:H-site ratio and a fraction of stronger acid sites. The greater acid-site:H-site ratio results in higher decarbonylation (DCO) selectivity during acetic acid hydrodeoxygenation (HDO) reactions, and the stronger acid sites lead to higher activity and ketonization (KET) selectivity at high temperatures. Lastly, the hard-templating synthetic method could be a versatile route toward carbide NPs of varying size, composition, and phase, on a range of mesoporous oxide supports.

09 BIOMASS FUELS↗
DOE OSTI2019

Synthesis of Biomass-Derived Ethers for Use as Fuels and Lubricants

Ethers synthesized from biomass-derived compounds have exceptional properties as fuels, lubricants, and specialty chemicals and can serve as replacements for petroleum-derived products. Recent efforts have identified heterogeneous catalysts for the selective synthesis of ethers from alcohols, aldehydes, ketones, furans, esters, olefins, carboxylic acids, and other molecules derived from biomass. This Review highlights the scope of etherification reactions and provides insights into the choice of catalysts and reaction conditions best suited for producing targeted ethers from the available starting materials. First, the properties of ethers for specific applications and the methods by which synthons for ether synthesis can be obtained from biomass are discussed. Then the progress that has been made on the synthesis of ethers via the following methods is summarized: direct etherification of alcohols; reductive etherification of alcohols with aldehydes or ketones; etherification of furanic compounds, esters, and carboxylic acids; and the addition of alcohols to olefins. Next, the mechanisms of these reactions and catalyst properties required to promote them are discussed, with the goal of understanding how reaction conditions can be tuned to optimize catalyst activity and selectivity towards desired ethers. Finally, the Review closes by examining the tradeoffs between catalyst selectivity, activity, stability, and reaction conditions required to achieve the most economically and environmentally favorable routes to biomass-derived ethers.

09 BIOMASS FUELS↗
DOE OSTI2023

Towards improved conversion of wet waste to jet fuel with atomic layer deposition-coated hydrodeoxygenation catalysts

The conversion of wet waste-derived volatile fatty acids into jet fuel-range hydrocarbons is a promising route for increasing the production of sustainable aviation fuel; however, the cost and moderate alkane selectivity of Pt-based hydrodeoxygenation catalysts present challenges for commercialization. Here, to address this, we used atomic layer deposition to apply TiO 2 overcoats to Pt/Al 2 O 3 catalysts and create new interface sites that exhibited 8 times higher site time yield of the desirable n-alkane product than uncoated catalyst. Through TPR/TPD, XPS, CO DRIFTS, and DFT calculations, we found that the increased selectivity of the ALD-coated catalyst was due to the creation of O vacancies at the Pt-TiO 2 interface under reducing conditions, resulting in new Ti 3+ acid sites near the active metal. Maximum conversion and alkane selectivity during HDO was achieved with an ALD-coated 0.5% wt Pt catalyst, indicating that TiO 2 ALD can be used to maximize the utility of precious-metal catalysts.

09 BIOMASS FUELS↗
DOE OSTI2024

Layered Sn-Au Thin Films for Increased Electrochemical ATR-SEIRAS Enhancement

Operando electrochemical attenuated total reflection surface-enhanced infrared absorption spectroscopy (EC ATR-SEIRAS) is a valuable method for a fundamental understanding of electrochemical interfaces under real operating conditions. The applicability of this method depends on the ability to tune the optical and catalytic properties of an electrode film, and it thus requires unique optimization for any given material. Motivated by the growing interest in Sn-based electrocatalysts for selective reduction of CO2 to formate species, we investigate several Sn thin-film synthesis routes for the resulting SEIRA signal response. We compare the SEIRA performance of thermally evaporated metallic Sn to a series of Sn-based films on top of a SEIRA-active Au substrate (metallic Sn, oxide-derived metallic Sn, and metal oxide SnOx). Using alkanethiol self-assembled monolayers as a probe, we find that electrodepositing metallic catalyst films on top of SEIRA-active Au substrates yield higher signal relative to thermal evaporation as well as higher signal than the independent SEIRA-active Au underlayer. These observations come despite the fact that thermally evaporated Sn has a significantly higher surface roughness (and thus higher adsorbate population), suggesting specific SEIRA-magnifying effects for the stacked films. Finally, we applied these films to observe the electrochemical conversion of CO2. Differences are observed in spectral features based on the composition of the electrode being either metallic or oxide-derived metallic Sn, implying differences in their respective reaction pathways.

CO2 reduction↗
DOE OSTI2012

Structure and dynamics of the M3 muscarinic acetylcholine receptor

Acetylcholine, the first neurotransmitter to be identified, exerts many of its physiological actions via activation of a family of G-protein-coupled receptors (GPCRs) known as muscarinic acetylcholine receptors (mAChRs). Although the five mAChR subtypes (M1-M5) share a high degree of sequence homology, they show pronounced differences in G-protein coupling preference and the physiological responses they mediate. Unfortunately, despite decades of effort, no therapeutic agents endowed with clear mAChR subtype selectivity have been developed to exploit these differences. We describe here the structure of the G{sub q/11}-coupled M3 mAChR ('M3 receptor', from rat) bound to the bronchodilator drug tiotropium and identify the binding mode for this clinically important drug. This structure, together with that of the G{sub i/o}-coupled M2 receptor, offers possibilities for the design of mAChR subtype-selective ligands. Importantly, the M3 receptor structure allows a structural comparison between two members of a mammalian GPCR subfamily displaying different G-protein coupling selectivities. Furthermore, molecular dynamics simulations suggest that tiotropium binds transiently to an allosteric site en route to the binding pocket of both receptors. These simulations offer a structural view of an allosteric binding mode for an orthosteric GPCR ligand and provide additional opportunities for the design of ligands with different affinities or binding kinetics for different mAChR subtypes. Our findings not only offer insights into the structure and function of one of the most important GPCR families, but may also facilitate the design of improved therapeutics targeting these critical receptors.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1981

Practical aspects of instrumentation system installation, volume 13

A review of factors influencing installation of aircraft flight test instrumentation is presented. Requirements, including such factors as environment, reliability, maintainability, and system safety are discussed. The assessment of the mission profile is followed by an overview of electrical and mechanical installation factors with emphasis on shock/vibration isolation systems and standardization of the electric wiring installation, two factors often overlooked by instrumentation engineers. A discussion of installation hardware reviews the performance capabilities of wiring, connectors, fuses and circuit breakers, and a guide to proper selections is provided. The discussion of the installation is primarily concerned with the electrical wire routing, shield terminations and grounding. Also inclued are some examples of installation mistakes that could affect system accuracy. System verification procedures and special considerations such as sneak circuits, pyrotechnics, aircraft antenna patterns, and lightning strikes are discussed.

Borek, R. W.↗
NASA NTRS2012

An Information NEXUS: The NASA Global Hawk Link Module

The Link Module described in this paper was first developed for the NASA Global Hawk Pacific Mission (GloPAC), four flights of 30 hour duration, supporting the Aura Validation Experiment (AVE). Its second use was during the Genesis and Rapid Intensification Processes (GRIP) experiment, a NASA Earth Science field experiment to better understand how tropical storms form and develop into major hurricanes. In these missions, the Link module negotiated all communication over the high bandwidth Ku satellite link, archived al the science data from onboard experiments in a spatially enable database, routed command and control of the instruments from the Global Hawk Operations Center, and retransmitted select data sets directly to experimenters control and analysis systems. The availability of aggregated information from collections of sensors, and remote control capabilities, in real-time, is revolutionizing the way Airborne Science is being conducted. Also described is the next generation Link Module now being designed and tested to support the NASA Earth Venture missions, the Hurricane and Severe Storm Sentinel (HS3) mission, and Airborne Tropical Tropopause Experiment (ATTREX) mission. Advanced data fusion technologies being developed will further advance the Scientific productivity, flexibility and robustness of these systems. Historically, the Link module evolved from the instrument and communication interface controller used by NASA's Pathfinder and Pathfinder plus solar powered UAS's in the late 1990's. It later was expanded for use in the AIRDAS four channel scanner flown on the NASA Altus UAS, and then again to a module in the AMS twelve channel multispectral scanner flying on the NASA (Predator-b) Ikhana UAS. The current system is the next step in the evolution, a multi board system packaged in a Curtiss Wright MIL-spec, flight qualified enclosure.

Remote Sensing↗
NASA NTRS2017

Predicted Weather Display and Decision Support Interface for Flight Deck

A system and method for providing visual depictions of a predictive weather forecast for in-route vehicle trajectory planning. The method includes displaying weather information on a graphical display, displaying vehicle position information on the graphical display, selecting a predictive interval, displaying predictive weather information for the predictive interval on the graphical display, and displaying predictive vehicle position information for the predictive interval on the graphical display, such that the predictive vehicle position information is displayed relative to the predictive weather information, for in-route trajectory planning.

Johnson, Walter W.↗