SEARCH · Engineering Papers
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.
The Xyce™ Parallel Electronic Simulator has been written to support the simulation needs of Sandia National Laboratories’ electrical designers. Xyce™ is a SPICE-compatible simulator with the ability to solve extremely large circuit problems on large-scale parallel computing platforms, but also includes support for most popular parallel and serial computers.
The Xyce™ Parallel Electronic Simulator has been written to support the simulation needs of Sandia National Laboratories’ electrical designers. Xyce™ is a SPICE-compatible simulator with the ability to solve extremely large circuit problems on large-scale parallel computing platforms, but also includes support for most popular parallel and serial computers. For up-to-date information not available at the time these notes were produced, please visit the Xyce™ web page at http://xyce.sandia.gov.
The Xyce™ Parallel Electronic Simulator has been written to support the simulation needs of Sandia National Laboratories’ electrical designers. Xyce™ is a SPICE-compatible simulator with the ability to solve extremely large circuit problems on large-scale parallel computing platforms, but also includes support for most popular parallel and serial computers.
Complete air-collector system to meet needs of single-family dwelling is designed to operate in any region of United States except extreme north and south. Design can be scaled up or down to accomodate wide range of heating and hot-water requirements for single-family, multi-family, or commercial buildings without significantly changing design concept.
The co-ordinated LANDSAT-aircraft mission flown on 16 July to the west of San Nicolas Island shows a number of interesting features. There is considerable structure in the Band 4 (0.76 to 0.90 microns) reflectance on km to 10 km scales in otherwise complete cloud cover. In extremely light winds, the C130 performed a series of runs throughout the boundary layer and above for a period of approximately 90 mins on either side of the LANDSAT overpass time. Because of the light winds, the same features can be recognized on the various aircraft penetrations and composited. Furthermore, the accurate renavigation of the aircraft positions enables these to be unambiguously related to the features seen on the LANDSAT image. Early indications suggest that the reflectance features are related to local thickenings on the cloud layer, associated with slightly deeper convection rising into the overlying stratiform deck. If this is true, then LANDSAT images could possibly be used to remotely infer aspects of the convective regime within the boundary layer. In addition, the LANDSAT images also display a quasi-linear feature extending for some 50 km, although only a km or so wide. This feature was, in fact, photographed from the C130 flying just above cloud top and termed a 'cloud-cliff'. It is clearly a rapid and sizeable local change in cloud top height and is therefore presumably a propagating feature. An explanation is still outstanding, but it appears to resemble an undular bore. Further descriptions of this unexpected feature, and its possible origin will be discussed.
Tropical deforestation generally leads to large losses of carbon and nitrogen. The Premontane Wet Forest Life Zone is subject to the highest rate of deforestation in Central America, and carbon and nutrient losses in from these fertile soils is very rapid and extreme. Losses of 2000 to 3000 kgN/ha have been reported. Losses of this magnitude could be extremely significant on a regional or global scale if even a small proportion of this nitrogen is lost as nitrous oxide to the atmosphere or through leaching of nitrate to rivers. This study seeks to measure the rates and regulation of nitrogen transformations, and the pathways of nitrogen losses following land clearing and burning at a site in the Premontane Wet Forest Life Zone near Turrialba, Costa Rica.
Despite excellent progress in recent years in understanding coronal heating, there remain many crucial questions that are still unanswered. Limitations in the observations are one important reason. Both theoretical and observational considerations point to the importance of small spatial scales, impulsive energy release, strong dynamics, and extreme plasma nonuniformity. As a consequence, high spatial resolution, broad temperature coverage, high temperature fidelity, and sensitivity to velocities and densities are all critical observational parameters. Current instruments lack one or more of these properties, and this has led to considerable ambiguity and confusion. In this talk, I will discuss recent ideas about coronal heating and emphasize that high spatial resolution observations, especially spectroscopic observations, are needed to make major progress on this important problem.
Conference Poster-Introduction Extreme ultraviolet (EUV) waves are large-scale propagating disturbances observed in the solar corona, frequently associated with coronal mass ejections and flares (Thompson et al., 1999, Thompson & Myers 2009). They appear as faint, extended structures propagating from a source region across the structured solar corona, making them difficult to isolate and measure. To further the understanding of EUV waves, we have constructed the Automated Wave Analysis and REduction (AWARE) algorithm for the measurement of EUV waves (Ireland et al, submitted). AWARE is implemented using the persistence transform, simple image processing operations and the RANSAC algorithm.
Extreme ultraviolet (EUV) waves are large-scale propagating disturbances observed in the solar corona, frequently associated with coronal mass ejections and flares. They appear as faint, extended structures propagating from a source region across the structured solar corona. To measure these waves, we have constructed the Automated Wave Analysis and REduction (AWARE) algorithm. AWARE is implemented in two stages. In the first stage, we use simple image processing techniques to isolate the propagating, brightening wave fronts as they move across the corona. In the second stage, AWARE measures the distance, velocity and acceleration of that wave front across the Sun. We explore the use of the Huygens principle, dynamic time warping and a simple parametric representation of the wave front as potential methods for detecting and tracking non-radial EUV wave propagation.
New images of young stars are revolutionizing our understanding of planet formation. ALMA detects large grains in planet‐forming disks with few AU scale resolution and scattered light imaging with extreme adaptive optics systems reveal small grains suspended on the disks’ flared surfaces. Tantalizing evidence for young exoplanets is emerging from line observations of CO and H‐alpha. In this white paper, we explore how even higher angular resolution can extend our understanding of the key stages of planet formation, to resolve accreting circumplanetary disks themselves, and to watch planets forming in situ for the nearest star‐forming regions. We focus on infrared observations which are sensitive to thermal emission in the terrestrial planet formation zone and allow access to molecular tracers in warm ro‐vibrational states. Successful planet formation theories will not only be able to explain the diverse features seen in disks, but will also be consistent with the rich exoplanet demographics from RV and transit surveys. While we are far from exhausting ground‐based techniques, the ultimate combination of high angular resolution and high infrared sensitivity can only be achieved through mid‐infrared space interferometry.
APD undertakes space missions to explore the nature of the universe at its largest scales, its earliest moments, and its most extreme conditions; missions that study how galaxies and stars formed and evolved to shape the universe we see today; and missions that seek out and characterize planets and planetary systems orbiting other stars. Since such ambitious missions require technologies that exceed today's state of the art, APD established the SAT program to mature key technologies that enable these future missions, from demonstrated feasibility (i.e., Technology Readiness Level, or TRL, of 3), to the point where they can be incorporated into NASA flight missions (i.e., TRL 6). APD set up three science-themed Programs, COR, ExEP, and PCOS, to address three fundamental questions: “How did we get here?” (COR), “Are we alone?” (ExEP), and “How does the universe work?” (PCOS). The COR, ExEP, and PCOS Program Offices support their respective Programs, including managing SAT and other midTRL-directed projects.
Wind loading and the fluctuating pressure loads it creates on PV panel surfaces are associated with multiple degradation mechanisms and failures. Modest wind speeds create reversing loads that can initiate cell cracks and weather cracked cells. Stronger wind speeds and extreme weather events can lead to larger scale forces and the aerodynamic instability known as torsional galloping. All these effects are dependent on the complex coupling between wind speed, panel orientation, and a myriad of other hardware and site-specific factors. In this work, we present the latest developments from our work to build an open-source, high-performance computing (HPC) fluid dynamics solver to predict and mitigate these effects. This simulation package allows users to easily specify different array layouts, solar-tracking angles, panel geometries, and weather conditions before automatically generating a refined computational mesh and solving for the unsteady loading on each panel surface. Small domains (e.g., a single panel row in isolation) can be solved on a modern laptop, while larger domains or very high-fidelity studies can be solved on distributed or HPC resources with minimal modifications to the underlying problem specification. We present preliminary case studies obtained using this simulation package and highlight how increased wind speeds combined with sub-optimal tracking angles can exacerbate degradation drivers.
Ionosphere-magnetosphere coupling phenomena are extremely complex and diverse, involving a whole series of processes operating over a wide range of spatial and temporal scales. One of the fundamental aspects of understanding this coupling is the polar wind, which is a dominant mechanism of mass transport from the ionospheric source region to the magnetosphere and strongly influences the plasma parameters above the F2 density peak. The combined effects of photoelectrons, and the ponderomotive force will be presented based on our polar wind model. The presence of photoelectrons and low frequency oscillations (that create the ponderomotive force) increase ion outflows. It is also demonstrated that large-amplitude low-frequency waves (LFW) may generate lower hybrid waves (LHW) in the auroral zone. The excitation of LHW by a LF wave may lead to the appearance of an additional channel of energy transfer from, for example, Alfven or fast magnetosonic waves, to particles. This process then influences the formation of the plasma distribution function at the expense of acceleration in the tail of the distribution during the collapse of the LHW. The ion energization due to the LHW can be comparable with that produced by the ponderomotive force of the LFW.
Direct Numerical Simulations of realistic combustion devices are extremely challenging due to the wide separation of scales in the simulation, for example an internal combustion (IC) engine chamber, and the flame thickness of a high-pressure flame. The PeleLMeX solver uses adaptive mesh refinement (AMR) to evolve multi-species reacting flows in the low Mach number limit at the Exascale and relies on an embedded boundary (EB) approach to represent complex geometries. In that framework, the EB geometries often give rise to very small cut-cells along the boundary, which translate into extreme ill-conditioning of the pressure-projection, with eigenvalues that span 15-16 orders of magnitude. In this talk, we focus on the case of a typical IC piston bowl geometry for which we present on a novel approach towards solving these nearly singular linear systems with ILU-based, C-AMG smoothers on massively parallel architectures. In particular, we use scaling and equilibration algorithms to handle the non-normality of the upper triangular factors. This enables us to approximate the highly sequential triangular solve algorithm, embedded in the AMG smoothing-solve phase, with Jacobi iterations. This approximation can be written as a convergent Neumann series whose terms are composed of highly parallel sparse matrix vector multiplications. The result is an algorithm that substantially decreases setup and solve time, compared to state-of-the-art, for these challenging linear systems.
Focal Area(s): We will use unsupervised machine learning methods to identify and quantify the influence of large scale natural modes of climate variability to gain insight into the observed and simulated seasonal average and extreme precipitation changes. Science Challenge: A recent paper, led by co-PI Mark Risser, finds that although much of the variability in seasonal average and extreme precipitation over CONUS is unforced, the effect of large-scale modes of circulation variability (such as ENSO, AMO, PNA, etc.) can be detected and attributed. However, it is unclear whether or not unsupervised learning methods can (a) replicate this finding or (b) yield insight into possible nonlinear behavior that was not captured in the initial statistical analysis. Further work would entail extending this framework to other global land areas.
As the Space Community endeavors to reach new heights of exploration, materials for extreme environment are on the forefront of research. One such material would include polymer aerogels; lightweight solids with nano-scale pore size, high internal surface area, low thermal conductivity, and extremely high porosities. Due to these interesting properties, aerogels are ideal as thermal insulators but are by no means limited to this application. The high porosity and surface area also make aerogels an ideal host system for particle incorporation for applications such as catalyst supports, sensor platforms, and vibro-acoustic mitigating materials. Polymer aerogels also have the potential to combat issues found in extraterrestrial environments such as dust and radiation mitigation. Herein, current research will be discussed as it pertains to Space exploration.
Reviewing recent literature, we report that changes in extreme heat event characteristics such as magnitude, frequency, and duration are highly sensitive to changes in mean global-scale warming. Numerous studies have detected significant changes in the observed occurrence of extreme heat events, irrespective of how such events are defined. Further, a number of these studies have attributed present-day changes in the risk of individual heat events and the documented global-scale increase in such events to anthropogenic-driven warming. Advances in process-based studies of heat events have focused on the proximate land-atmosphere interactions through soil moisture anomalies, and changes in occurrence of the underlying atmospheric circulation associated with heat events in the mid-latitudes. While evidence for a number of hypotheses remains limited, climate change nevertheless points to tail risks of possible changes in heat extremes that could exceed estimates generated from model outputs of mean temperature. We also explore risks associated with compound extreme events and nonlinear impacts associated with extreme heat.
An electric power grid is one of the complex infrastructures, and because of its complex nature, there is simply no way that outages can be completely avoided. Thus, a modern society that depends on reliable electric supply requires a resilient electric system that can recover from disruptions while integrating emerging smart grid technologies. Here, this article presents a novel approach for service restoration in a modern power distribution system with controllable switches and distributed generation (DG) resources for any kind of outage. The proposed framework supports both the traditional service restoration using feeder reconfiguration and the grid-forming DG-assisted intentional islands that are dynamically sized using algorithms based on the fault scenario, available resources, and priority of loads. The problem is formulated as a mixed-integer linear program that incorporates critical system connectivity and operating constraints. Simulations are performed to demonstrate the effectiveness of the proposed approach using a large-scale four-feeder 1069-bus three-phase unbalanced distribution test system. It is demonstrated that the framework is effective in utilizing all available resources in quickly restoring the power supply to improve resiliency during extreme events and is scalable for a large-scale unbalanced power distribution system.