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At least 1,171 records · Page 65

Summary Report of the Reactive CO 2 Capture: Process Integration for the New Carbon Economy Workshop

Decarbonization of our global economy is required to limit planetary warming to +1.5⁰C above pre-industrial levels, an ambitious goal set into motion by the Paris agreement. Given the scale and urgency, the solution demands international, cross-sector advancements spanning policy, social responsibility, and technology, with emphasis on step changes over incremental changes. To that end, technological revolutions that disrupt the status quo need to be envisioned and enacted. One potential technological revolution is the production of fuels, chemicals, and materials from carbon dioxide (CO 2 ) as the starting feedstock, leveraging renewable energy as the driving force. Over the past decades, significant research, development, and deployment has occurred on technologies for capturing CO 2 from point sources or the air and utilizing this CO 2 as a working fluid or as a chemical reactant; however, most of this work has been siloed in these two categories. Recently, an emerging field has started to explore the direct integration of CO 2 capture and conversion technologies as a means to reduce overall energy demand (i.e., avoid energy penalty of CO 2 desorption/regeneration of capture media) and capital expense through process intensification. This strategy represents an opportunity to leapfrog forward this technological revolution. However, the field is in its infancy and the technologies are at an early stage of development, thus it is critically important to define and assess the value proposition of this strategy relative to alternatives (e.g., separated capture and conversion technologies, fuels and chemicals derived from renewable feedstocks like biomass, and industrial electrification) to chart a path forward. To identify next steps, we organized a workshop titled “Reactive CO 2 Capture: Process Integration for the New Carbon Economy” which was held in Golden, Colorado, February 18–19, 2020. The focus of this workshop was to discuss approaches for merging CO 2 capture and CO 2 conversion/utilization systems into what we denoted as an integrated "reactive capture" strategy. By our definition, reactive capture of CO 2 is the coupled process of capturing CO 2 from a mixed gas stream and converting it into a valuable product without going through a purified CO 2 intermediate (see full definition in the Introduction section). This report seeks to summarize feedback from the approximately 125 participants and subject matter experts in attendance from academia, industry, U.S. Department of Energy (DOE), and DOE national laboratories. The workshop agenda is included in Appendix A and the full list of attendees can be found in Appendix B. To elucidate a path forward, we first asked the attendees to define what success would look like for reactive capture in the short term (0–5 years), midterm (5–10 years), and long term (10+ years) and then asked them to answer four questions related to how we could achieve that success: (1) What are the key barriers and challenges to success? (2) What are needed activities to overcome barriers and challenges? (3) What opportunities will arise from these activities? (4) What is a target outcome and what metrics need to be met?

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

Smooth Pursuit of Flicker-Defined Motion

We examined the pursuit response to stimuli defined by space-variant flicker of a dense random dot carrier pattern. On each frame, every element of the pattern could change polarity, with a probability given by a two-dimensional Gaussian distribution. A normal distribution produces a circular region of twinkle, while inverting the distribution results in a spot of static texture in a twinkling surround. In this latter case, the carrier texture could be stationary, or could move with the twinkle modulator,thereby producing first-order motion in the region of the spot. While the twinkle-defined spot produces a strong sensation of motion, the complementary stimulus defined by the absence of twinkle does not;when viewed peripherally, it appears to move in steps even when the generating distribution moves smoothly. We examined pursuit responses to these stimuli using two techniques: 1) the eye movement correlogram, obtained by cross-correlating eye velocity with the velocity of a randomly-moving stimulus; and 2) delayed visual feedback, where transient stabilization of a target can produce spontaneous oscillations of the eye, with a period empirically observed to vary linearly with the applied delay. Both techniques provide an estimate of the internal processing time, which can be as short as100 milliseconds for a first-order target. Assessed by the correlogram method, the response to flicker defined motion is delayed by more than 100 milliseconds, and significantly weaker (especially in the vertical dimension). When initially presented in the delayed feedback condition, purely saccadic oscillation is observed. One subject eventually developed smooth oscillations (albeit with significant saccadic intrusions), showing a period-versus-delay slope similar to that observed for first-order targets. This result is somewhat surprising, given that we interpret the slope of the period-versus-delayfunction as reflecting the balance between position- and velocity-sensitive inputs to pursuit.

smooth pursuit↗

Solving modal equations of motion with initial conditions using MSC/NASTRAN DMAP. Part 1: Implementing exact mode superposition

Within the MSC/NASTRAN DMAP (Direct Matrix Abstraction Program) module TRD1, solving physical (coupled) or modal (uncoupled) transient equations of motion is performed using the Newmark-Beta or mode superposition algorithms, respectively. For equations of motion with initial conditions, only the Newmark-Beta integration routine has been available in MSC/NASTRAN solution sequences for solving physical systems and in custom DMAP sequences or alters for solving modal systems. In some cases, one difficulty with using the Newmark-Beta method is that the process of selecting suitable integration time steps for obtaining acceptable results is lengthy. In addition, when very small step sizes are required, a large amount of time can be spent integrating the equations of motion. For certain aerospace applications, a significant time savings can be realized when the equations of motion are solved using an exact integration routine instead of the Newmark-Beta numerical algorithm. In order to solve modal equations of motion with initial conditions and take advantage of efficiencies gained when using uncoupled solution algorithms (like that within TRD1), an exact mode superposition method using MSC/NASTRAN DMAP has been developed and successfully implemented as an enhancement to an existing coupled loads methodology at the NASA Lewis Research Center.

Abdallah, Ayman A.↗

Investigation of crew performance in a multi-vehicle supervisory control task

Crew information processing and decision making in a supervisory control task which is loosely based on the mission of future generation helicopters is measured and represented. Subjects control the motion and activities of their own vehicle and direct the activities of four additional craft. The task involves searching an uncertain environment for cargo and enemies, returning cargo to home base and destroying enemies while attempting to avoid destruction of the scout and the supervised vehicles. A series of experiments with two-person crews and one-person crews were performed. Resulting crew performance was modeled with the objective of describing and understanding the information processing strategies utilized. Of particular interest are problem simplification strategies under time stress and high work load, simplification and compensation in the one-person cases, crew coordination in the two-person cases, and the relationship between strategy and errors in all cases. The results should provide some insight into the effective use of aids, particularly aids based on artificial intelligence, for similar tasks. The simulation is described which is used for the study and some preliminary results from the first two-person crew study are discussed.

Miller, R. A.↗

Vacuum Plasma Spray Forming of Tungsten Lorentz Force Accelerator Components

The Vacuum Plasma Spray (VPS) Laboratory at NASA's Marshall Space Flight Center has developed and demonstrated a fabrication technique using the VPS process to form anode sections for a Lorentz force accelerator from tungsten. Lorentz force accelerators are an attractive form of electric propulsion that provides continuous, high-efficiency propulsion at useful power levels for such applications as orbit transfers or deep space missions. The VPS process is used to deposit refractory metals such as tungsten onto a graphite mandrel of the desired shape. Because tungsten is reactive at high temperatures, it is thermally sprayed in an inert environment where the plasma gun melts and accelerates the metal powder onto the mandrel. A three-axis robot inside the chamber controls the motion of the plasma spray torch. A graphite mandrel acts as a male mold, forming the required contour and dimensions of the inside surface of the anode. This paper describes the processing techniques, design considerations, and process development associated with the VPS forming of the Lorentz force accelerator.

Zimmerman, Frank R.↗

Real-space inversion and super-resolution of ultrafast scattering

Ultrafast scattering using x-rays or electrons is an emerging method to obtain structure dynamics at the atomic lengthscales and timescales. However, directly resolving in real-space atomic motions is inherently limited by the finite detector range and the probe energy. So, as a result, the time-resolved signal interpretation is mostly done in reciprocal space and relies on modeling and simulations of specific structures and processes. Here, we introduce a model-free approach to directly resolve scattering signals in real space, surpassing the diffraction limit, using scattering kernels and signal priors that naturally arise from the measurement constraints. We demonstrate the approach on simulated and experimental data, recover multiple atomic motions at sub-angstrom resolutions, and discuss the recovery accuracy and resolution limits versus signal fidelity. The approach offers a robust path to obtain high-resolution real-space information of atomic-scale structure dynamics using current time-resolved x-ray or electron scattering sources.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

All-Atom Biomolecular Simulation in the Exascale Era

Exascale supercomputers have opened the door to dynamic simulations, facilitated by AI/ML techniques, that model biomolecular motions over unprecedented length and time scales. This new capability holds the potential to revolutionize our understanding of fundamental biological processes. Herein we report on some of the major advances that were discussed at a recent CECAM workshop in Pisa, Italy, on the topic with a primary focus on atomic-level simulations. First, we highlight examples of current large-scale biomolecular simulations and the future possibilities enabled by crossing the exascale threshold. Next, we discuss challenges to be overcome in optimizing the usage of these powerful resources. Finally, we close by listing several grand challenge problems that could be investigated with this new computer architecture.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

The integrated miniaturized electrostatic analyzer: A space plasma environment sensor

The integrated Miniaturized Electrostatic Analyzer (iMESA) was a satellite-based ionospheric sensor that operated on NASA’s Space Test Program Satellite (STPSat-3) from December 2013 to July 2019. The instrument’s scientific objective was to (1) measure the plasma density in low Earth orbit, (2) measure the plasma temperature in low Earth orbit, and (3) quantify the spacecraft potential with respect to the ambient plasma potential in the ionosphere. iMESA sampled the ionosphere every 10 s by measuring the ion current density through the ESA as a result of the motion of the spacecraft through the plasma. Current density spectra were transmitted to the ground where they were post-processed into ion density spectra and then analyzed numerically to determine the ion density, ion temperature, and spacecraft potential. This article discusses the instrument design and simulation, the determination of a geometric factor, and data processing procedures and evaluates the final data product with regard to the mission success criteria. Here, the ion density and ion temperature captured by the iMESA instrument are on the same order and range as the values predicted in the literature. The spacecraft potential was also quantified. The conclusion after the evaluation of the instrument’s data product is that the scientific mission is successful on all three points.

47 OTHER INSTRUMENTATION↗

Site Density Functional Theory and Structural Bioinformatics Analysis of the SARS-CoV Spike Protein and hACE2 Complex

The entry of the SARS-CoV-2, a causative agent of COVID-19, into human host cells is mediated by the SARS-CoV-2 spike (S) glycoprotein, which critically depends on the formation of complexes involving the spike protein receptor-binding domain (RBD) and the human cellular membrane receptor angiotensin-converting enzyme 2 (hACE2). Using classical site density functional theory (SDFT) and structural bioinformatics methods, we investigate binding and conformational properties of these complexes and study the overlooked role of water-mediated interactions. Analysis of the three-dimensional reference interaction site model (3DRISM) of SDFT indicates that water mediated interactions in the form of additional water bridges strongly increases the binding between SARS-CoV-2 spike protein and hACE2 compared to SARS-CoV-1-hACE2 complex. By analyzing structures of SARS-CoV-2 and SARS-CoV-1, we find that the homotrimer SARS-CoV-2 S receptor-binding domain (RBD) has expanded in size, indicating large conformational change relative to SARS-CoV-1 S protein. Protomer with the up-conformational form of RBD, which binds with hACE2, exhibits stronger intermolecular interactions at the RBD-ACE2 interface, with differential distributions and the inclusion of specific H-bonds in the CoV-2 complex. Further interface analysis has shown that interfacial water promotes and stabilizes the formation of CoV-2/hACE2 complex. This interaction causes a significant structural rigidification of the spike protein, favoring proteolytic processing of the S protein for the fusion of the viral and cellular membrane. Moreover, conformational dynamics simulations of RBD motions in SARS-CoV-2 and SARS-CoV-1 point to the role in modification of the RBD dynamics and their impact on infectivity.

3DRISM↗

Fluorescent photography of spray droplets using a laser light source

Monochromatic laser emission transformed by a fluorescent process into droplet emission over a wavelength band provides high light intensities for obtaining adequate time resolution to stop droplet motion in photographic spray studies. Experiments showed that the Q-switched laser-optical harmonic generator combination produced sharp, well-exposed droplet images.

Groeneweg, J.↗

The geology of the moon.

With traditional astronomical methods in the background, geological exploration of the Moon has developed rapidly, but logically, since the dawn of the space age. As a result of these tremendous strides forward, we have been forced to revise our views of a cold, rigid moon built predominantly from stony meteorites. The interior of the moon is hot; the distant past has seen not only major impacts but also extensive volcanism altering the lunar surface, and major motions within the moon. Even today, weak moonquakes remain to remind us of the past upheavals that accompanied the geological processes now being unraveled through detailed studies of the lunar rocks.

Fielder, G.↗

Drogue parachute deployment dynamics of the space shuttle solid rocket booster

Theoretical analysis and experimental investigations are presented for two deployment concepts of the drogue parachute deployment for the space shuttle solid rocket booster. The analysis represents the motion of three coupled rigid bodies, with one of the bodies having variable mass and moment of inertia. The unfurling process of the parachute from the bag is idealized as the flow of a continuum out of a control surface. The pilot parachute or tethered nose cap is modeled as a flexible pendulum with a nonlinear spring and a moving support. Measured wind tunnel test data compare reasonably well with the theory.

Banerjee, A. K.↗

Vestibular influences on other sensory and motor processes

Vestibular effects on perceptual and motor processes are widespread. It is shown that gyrovisual modulation may take three forms: (1) gyrovisual inhibition (monitoring tasks and spurious motion); (2) gyrovisual facilitation (tracking); and (3) gyrovisual conflict (motion sickness and disorientation in flight).

Clark, B.↗

Analytical study of the time dependent spacecraft-plasma interaction

A study of the time dependent interaction of an initially uniform equilibrium plasma with a plane conducting surface was made in order to achieve a more complete understanding of the dynamics of the charging process and of the approach to the floating potential on the surface. Numerical solutions of the cold ion equations of motion in conjunction with equilibrium electrons and Poisson's equation show the formation of an ion-rich sheath near the surface and the coupling of the non-neutral region to the undisturbed plasma through a quasineutral rarefaction. Analytical treatment of the quasineutral region showed excellent agreement (within 1 percent) with the numerical results.

Cipolla, J. W., Jr.↗

Direct integration of transient rotor dynamics

An implicit method was developed for integrating the equations of motion for a lumped mass model of a rotor dynamics system. As an aside, a closed form solution to the short bearing theory was also developed for a damper with arbitrary motion. The major conclusions are that the method is numerically stable and that the computation time is proportional to the number of elements in the rotor dynamics model rather than to the cube of the number. This computer code allowed the simulation of a complex rotor bearing system experiencing nonlinear transient motion and displayed the vast amount of results in an easily understood motion picture format - a 10 minute, 16 millimeter, color, sound motion picture supplement. An example problem with 19 mass elements in the rotor dynamics model took 0.7 second of central processing unit time per time step on an IBM 360-67 computer in a time sharing mode.

Kascak, A. F.↗

Vestibulo-spinal reflex mechanisms

The specific objectives of experiments designed to investigate postural reflex behavior during sustained weightlessness are discussed. The first is to investigate, during prolonged weightlessness with Hoffmann response (H-reflex) measurement procedures, vestibulo-spinal reflexes associated with vestibular (otolith) responses evoked during an applied linear acceleration. This objective includes not only an evaluation of otolith-induced changes in a major postural muscle but also an investigation with this technique of the adaptive process of the vestibular system and spinal reflex mechanisms to this unique environment. The second objective is to relate space motion sickness to the results of this investigation. Finally, a return to the vestibulo-spinal and postural reflexes to normal values following the flight will be examined. The flight experiment involves activation of nerve tissue (tibial N) with electrical shock and the recording of resulting muscle activity (soleus) with surface electrodes. Soleus/spinal H-reflex testing procedures will be used in conjuction with linear acceleration through the subject's X-axis.

Reschke, M. F.↗

Thermocapillary flows and their stability: Effects of surface layers and contamination

The fluid mechanics and heat transfer of motions driven by surface tension gradients (Marangoni convection) were analyzed theoretically to obtain an understanding of the convection accompanying the process of growing high quality single crystals from the melt in a mu-g environment. The geometries considered include two dimensional liquid filled slots and axisymmetric float zone configurations.

Davis, S. H.↗

A full field, 3-D velocimeter for microgravity crystallization experiments

The programming and algorithms needed for implementing a full-field, 3-D velocimeter for laminar flow systems and the appropriate hardware to fully implement this ultimate system are discussed. It appears that imaging using a synched pair of video cameras and digitizer boards with synched rails for camera motion will provide a viable solution to the laminar tracking problem. The algorithms given here are simple, which should speed processing. On a heavily loaded VAXstation 3100 the particle identification can take 15 to 30 seconds, with the tracking taking less than one second. It seeems reasonable to assume that four image pairs can thus be acquired and analyzed in under one minute.

Brodkey, Robert S.↗