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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.

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All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

First-Order System Least Squares for Velocity-Vorticity-Pressure Form of the Stokes Equations, with Application to Linear Elasticity

In this paper, we study the least-squares method for the generalized Stokes equations (including linear elasticity) based on the velocity-vorticity-pressure formulation in d = 2 or 3 dimensions. The least squares functional is defined in terms of the sum of the L(exp 2)- and H(exp -1)-norms of the residual equations, which is weighted appropriately by by the Reynolds number. Our approach for establishing ellipticity of the functional does not use ADN theory, but is founded more on basic principles. We also analyze the case where the H(exp -1)-norm in the functional is replaced by a discrete functional to make the computation feasible. We show that the resulting algebraic equations can be uniformly preconditioned by well-known techniques.

Cai, Zhiqiang↗
NASA NTRS2002

A Localized Tau Method PDE Solver

In this paper we present a new form of the collocation method that allows one to find very accurate solutions to time marching problems without the unwelcome appearance of Gibb's phenomenon oscillations. The basic method is applicable to any partial differential equation whose solution is a continuous, albeit possibly rapidly varying function. Discontinuous functions are dealt with by replacing the function in a small neighborhood of the discontinuity with a spline that smoothly connects the function segments on either side of the discontinuity. This will be demonstrated when the solution to the inviscid Burgers equation is discussed.

Cottam, Russell↗
NASA NTRS2018

Modified Geometric Truncation of the Scattering Phase Function

Phase function of light scattering on large atmospheric particles has very strong peak in forward direction constituting a challenge for accurate numerical calculations of radiance required in remote sensing problems. Scaling transformation replaces original phase function with a sum of the delta function and a new regular smooth phase function. Geometric truncation is one of the ways to construct such a smooth function. The replacement phase function coincides with the original one outside the forward cone and preserves the asymmetry parameter. It has discontinuity at the cone. Another simple functional form of the replacement phase function within the cone is suggested. It enables continuity and allows for a number of modifications. Three of them are considered in this study: preserving asymmetry parameter, providing continuity of the 1st derivative of the phase function, and preserving mean scattering angle. Yet another problem addressed in this study is objective selection of the width of the forward cone. That angle affects truncation fraction and values of the phase function within the cone. A heuristic approach providing unambiguous criterion of selection of the truncation angle is proposed. The approach has easy numerical implementation. Suggested modifications were tested on cloud phase function using discrete ordinates and Monte Carlo methods. It was shown that the modifications provide better accuracy of the radiance computation compare to the original geometric truncation with discrete ordinates while continuous derivative approach provides significant gain in computer time with Monte Carlo simulations.

Alexander Radkevich↗
DOE OSTI2021

Comparative Virulence and Genomic Analysis of Streptococcus suis Isolates

Streptococcus suis is a zoonotic bacterial swine pathogen causing substantial economic and health burdens to the pork industry. Mechanisms used by S. suis to colonize and cause disease remain unknown and vaccines and/or intervention strategies currently do not exist. Studies addressing virulence mechanisms used by S. suis have been complicated because different isolates can cause a spectrum of disease outcomes ranging from lethal systemic disease to asymptomatic carriage. The objectives of this study were to evaluate the virulence capacity of nine United States S. suis isolates following intranasal challenge in swine and then perform comparative genomic analyses to identify genomic attributes associated with swine-virulent phenotypes. No correlation was found between the capacity to cause disease in swine and the functional characteristics of genome size, serotype, sequence type (ST), or in vitro virulence-associated phenotypes. A search for orthologs found in highly virulent isolates and not found in non-virulent isolates revealed numerous predicted protein coding sequences specific to each category. While none of these predicted protein coding sequences have been previously characterized as potential virulence factors, this analysis does provide a reliable one-to-one assignment of specific genes of interest that could prove useful in future allelic replacement and/or functional genomic studies. Collectively, this report provides a framework for future allelic replacement and/or functional genomic studies investigating genetic characteristics underlying the spectrum of disease outcomes caused by S. suis isolates.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1988

A study of the use of linear programming techniques to improve the performance in design optimization problems

This project has two objectives. The first is to determine whether linear programming techniques can improve performance when handling design optimization problems with a large number of design variables and constraints relative to the feasible directions algorithm. The second purpose is to determine whether using the Kreisselmeier-Steinhauser (KS) function to replace the constraints with one constraint will reduce the cost of total optimization. Comparisons are made using solutions obtained with linear and non-linear methods. The results indicate that there is no cost saving using the linear method or in using the KS function to replace constraints.

Young, Katherine C.↗
DOE OSTI2025

SineKAN: Kolmogorov-Arnold Networks using sinusoidal activation functions

Recent work has established an alternative to traditional multi-layer perceptron neural networks in the form of Kolmogorov-Arnold Networks (KAN). The general KAN framework uses learnable activation functions on the edges of the computational graph followed by summation on nodes. The learnable edge activation functions in the original implementation are basis spline functions (B-Spline). Here, we present a model in which learnable grids of B-Spline activation functions are replaced by grids of re-weighted sine functions (SineKAN). We evaluate numerical performance of our model on a benchmark vision task. We show that our model can perform better than or comparable to B-Spline KAN models and an alternative KAN implementation based on periodic cosine and sine functions representing a Fourier Series. Further, we show that SineKAN has numerical accuracy that could scale comparably to dense neural networks (DNNs). Compared to the two baseline KAN models, SineKAN achieves a substantial speed increase at all hidden layer sizes, batch sizes, and depths. Current advantage of DNNs due to hardware and software optimizations are discussed along with theoretical scaling. Additionally, properties of SineKAN compared to other KAN implementations and current limitations are also discussed.

Reinhardt, Eric↗
DOE OSTI2023

Asymmetric Electrode Work Function Customization via Top Electrode Replacement in Ferroelectric and Field–Induced Ferroelectric Hafnium Zirconium Oxide Thin Films

Non-volatile memory device structures such as ferroelectric random-access memory and ferroelectric tunnel junctions employ switchable spontaneous polarization to hold binary states. These devices can potentially benefit from the imposition of spontaneous internal biases and their resulting effect on the polarization properties of the ferroelectric (or field-induced ferroelectric/ antiferroelectric) layer. While HfO 2 -based thin films are ideal candidates for implementation into these devices due to their scalability and silicon compatibility, the phase purity of these oxides is sensitive to the selection of electrode material, preventing incorporation of asymmetric electrode layers into such structures. Within this work, electrode replacement following post-metallization anneal processing is introduced as a route to achieve ferroelectric and field-induced ferroelectric Hf x Zr 1–x O 2 (HZO) thin films with electrode-independent phase constitutions. The effects of this process and the corresponding internal biases imposed across the HZO layers due to asymmetric work functions are investigated. It is shown that internal biases vary in magnitude in accordance with prediction based on the work functions of the replaced electrode layers and affect remanent polarization magnitudes. Accordingly, electrode replacement presents a processing route that can readily produce HZO films with spontaneous internal biases and electrode- independent phase constitutions, facilitating implementation of these ferroelectrics into the next generation device structures.

36 MATERIALS SCIENCE↗
NASA NTRS2011

A Model of Reduced Kinetics for Alkane Oxidation Using Constituents and Species for N-Heptane

The reduction of elementary or skeletal oxidation kinetics to a subgroup of tractable reactions for inclusion in turbulent combustion codes has been the subject of numerous studies. The skeletal mechanism is obtained from the elementary mechanism by removing from it reactions that are considered negligible for the intent of the specific study considered. As of now, there are many chemical reduction methodologies. A methodology for deriving a reduced kinetic mechanism for alkane oxidation is described and applied to n-heptane. The model is based on partitioning the species of the skeletal kinetic mechanism into lights, defined as those having a carbon number smaller than 3, and heavies, which are the complement of the species ensemble. For modeling purposes, the heavy species are mathematically decomposed into constituents, which are similar but not identical to groups in the group additivity theory. From analysis of the LLNL (Lawrence Livermore National Laboratory) skeletal mechanism in conjunction with CHEMKIN II, it is shown that a similarity variable can be formed such that the appropriately non-dimensionalized global constituent molar density exhibits a self-similar behavior over a very wide range of equivalence ratios, initial pressures and initial temperatures that is of interest for predicting n-heptane oxidation. Furthermore, the oxygen and water molar densities are shown to display a quasi-linear behavior with respect to the similarity variable. The light species ensemble is partitioned into quasi-steady and unsteady species. The reduced model is based on concepts consistent with those of Large Eddy Simulation (LES) in which functional forms are used to replace the small scales eliminated through filtering of the governing equations; in LES, these small scales are unimportant as far as the overwhelming part of dynamic energy is concerned. Here, the scales thought unimportant for recovering the thermodynamic energy are removed. The concept is tested by using tabular information from the LLNL skeletal mechanism in conjunction with CHEMKIN II utilized as surrogate ideal functions replacing the necessary functional forms. The test reveals that the similarity concept is indeed justified and that the combustion temperature is well predicted, but that the ignition time is over-predicted, a fact traced to neglecting a detailed description of the processes leading to the heavies chemical decomposition. To palliate this deficiency, functional modeling is incorporated into this conceptual reduction in addition to the modeling the evolution of the global constituent molar density, the enthalpy evolution of the heavies, the contribution to the reaction rate of the unsteady lights from other light species and from the heavies, the molar density evolution of oxygen and water, and the mole fractions of the quasisteady light species. The model is compact in that there are only nine species-related progress variables. Results are presented showing the performance of the model for predicting the temperature and species evolution. The model reproduces the ignition time over a wide range of equivalence ratios, initial pressure, and initial temperature.

Harstad, Kenneth G.↗
DOE OSTI2026

OptiMX

OptiMX is a GUI-oriented program with principal aim to be an easy to use, yet comprehensive, interactive accelerator optics design and analysis tool. It was originally developed starting in the 1990s as an MS Windows centric application using the commercial Borland OWL framework. In the spring of 2014, a decision was made to port OptiM to Qt, a modern, portable and open framework. As much as possible, the original interface was preserved.While a significant amount of refactoring was required, the underlying physics has been for the most, left unchanged. The custom plots of the original application have been replaced with functional equivalents based on a stable and well-established library (qwt). With very few minor exceptions the new refactored OptiMX should be a drop-in replacement for the original OWL version.

Lebedev, ValeriA. [Joint Inst. for Nuclear Researc↗
NASA NTRS2000

Generalized Wall Function for Complex Turbulent Flows

A generalized wall function was proposed by Shih et al., (1999). It accounts the effect of pressure gradients on the flow near the wall. Theory shows that the effect of pressure gradients on the flow in the inertial sublayer is very significant and the standard wall function should be replaced by a generalized wall function. Since the theory is also valid for boundary layer flows toward separation, the generalized wall function may be applied to complex turbulent flows with acceleration, deceleration, separation and recirculation. This paper is to verify the generalized wall function with numerical simulations for boundary layer flows with various adverse and favorable pressure gradients, including flows about to separate. Furthermore, a general procedure of implementation of the generalized wall function for National Combustion Code (NCC) is described, it can be applied to both structured and unstructured CFD codes.

Shih, Tsan-Hsing↗
NASA NTRS1998

A Fresh Look at Coupled-Oscillator Spatial Power Combining

Quasi-optical oscillators were proposed a little more than ten years ago as a means of developing the power levels needed for applications at millimeter frequencies using large numbers of individual semiconductor devices each of which produces only a modest amount of power [J.W. Mink, IEEE Trans. MTT., vol. 34, p. 273, 19861. An operating system was demonstrated soon after [Z.B. Popovic et. al, Int. J. Infrared and Millimeter Waves, v. 9, p. 647, 1988] in the form of a so-called grid oscillator. This device constituted a rectangular array of oscillating devices that are mutually coupled so that they oscillator coherently. The interconnecting lines in one direction serve as radiators so that the oscillators radiate directly, and the radiated fields add. Subsequently, coupled oscillators using resonant transmission line lengths was demonstrated by Mortazawi and Itoh [IEEE Trans. MTT., vol. 38, p. 86,1990). In recent work, coupled-oscillator power combiners have received less attention, with amplifier/combiners receiving more attention. Specific weaknesses of spatial-combining oscillators have motivated this transition. Namely, the oscillators employ low-Q resonators (resulting in low signal quality) and no clear means of modulation has been identified until recently. In this presentation, we review coupled-oscillator combiners in broad terms, indicating the features that make particular systems viable. We indicate how these features can be reconciled to functional requirements for system applications. Comparisons are drawn between two approaches to obtain mutual coupling: One employs low-Q oscillator circuits at each site, with concomitantly high propensity for the oscillators to couple. The other approach employs moderate-Q oscillators at each site with the concomitant requirement to tune the oscillators so that they share a range of frequencies over which they can couple and lock. In either case, precise frequency control and modulation can be achieved through locking to an external frequency source that ensures high quality signals. A recent development in coupled-oscillator arrays provides a means for beam-steering the radiation field of coupled oscillators through de-tuning of the edge elements in the array. This detuning introduces a progressive phase shift across the oscillator array. This 0 suggests architectures that can replace the functionality of a phased array without the cost 0 incurred by phase shifters. A comprehensive theory of the phase interactions among devices in such arrays is under development [e.g., Pogorzelski, York, and Maccarini, 1998 AP-S International Symposium, Atlanta, GA. June, 19981.

Pearson, L.W.↗
DOE OSTI2023

SmallTAL: Real-Time Egocentric Online Temporal Action Localization for the Data-Impoverished

Abstract We propose a real-time, online temporal action localization system that requires a small amount of annotated data. The main challenges we address are high intra-class variability and a large and diverse background class. We address these using a flexible frame descriptor, dynamic time warping, and a novel approach to database construction. Our solution receives egocentric RGB-D streams as input and makes predictions at regular temporal intervals. We validate our approach by localizing actions in a digital twin of an electrical substation, in which certain objects have been replaced by functional virtual replicas.

Computer Science↗
DOE OSTI2023

Tools for Assessing Performance: FY23-Q1 Report [Slides]

LANL was tasked with working with NREL to implement QUIC within the TAP API by the end of Q1, FY2023. If QUICURB cannot be implemented in a way that it can be run outside of the QUIC platform, there will be no further R&D funding for QUIC development. QUIC includes a graphical user interface that imports and preprocesses the various input data streams (3D building databases, ambient wind, vegetation, etc.) and writes them in a format that the QUICURB Fortran executable requires. In order to interface with the TAP API, a Python script was developed that would replace the functionality previously only available within QUICGUI. LANL worked with NREL to test the Python script to ensure that it was operation and fulfilled the requirements.

58 GEOSCIENCES↗
NASA NTRS1966

Orbital tube flare for tubing connectors

Marshall engineering personnel have developed and are now refining a new and unique method of mechanically flaring tubing. The system eliminates the use of the conventional split backing die which is used with most tube-flaring equipment. The Marshall-developed tool is adapted for use on standard Leonard 3-CP-HD flaring machines. The stationary split backing die is replaced in function with a die ring, whose i.d.-surface rolls or orbits around the o.d. of the tube flare zone. An i.d.-flaring cone moves axially and forces the metal against the rolling die to form the flare. Major advantages of this system are the elimination of flash, or split die marks, on the back angle of the flare, and improved flare-surface finishes, permitting more uniform sealing characteristics and improvements of the total geometric configuration of the flare as required by the MSFC specification MC-146. The Orbital Adapter system of tooling is currently being used to manufacture flared tube hardware for the Saturn V S-IO space launch vehicle at MSFC, for the Agena space launch vehicle (used for the Gemini project) at Lockheed, Sunnyvale, for LEM checkout equipment for Grumman, and for the Saturn S-IV-B space launch vehicle by Douglas Aircraft Company. Several other aerospace firms are evaluating the system for possible incorporation on their tube flaring requirements. Marshall engineers are now concentrating their efforts on refining and reducing the total cost of the overall system.

Tubing↗
NASA NTRS1978

Delta launch Canadian communications satellite Telesat-D (Anik-B)

Telesat-D (Anik-B) is the first of a series of three (Telesat-D, -E, -F) second generation satellites developed for Telesat/Canada. These second generation satellites will replace three first generation HS-333 satellites (Telesat-A, -B, -C) developed for Telesat/CNADA AND LAUNCHED BY Delta 2914 vehicles in 1972, 1973, and 1975 and successfully placed in orbit as Anik-A1, -A2, -A3. The Telesat-D(Anik-B) satellite will be place in sync-transfer orbit by a Delta 3914 launch vehicle, currently scheduled for launch on December 15, 1978. The Telesat-E and -F(Anik-C1 and -C2) missions are scheduled for launch on the Space Shuttle in 1981 to replace the function of the Anik-A2 and -A3 (Telesat-B, and -C) satellites. The Anik-B will provide point-to-point voice, TV, and data communications traffic to Canada's ten provinces.

Source record↗
NASA NTRS1979

Computer-automated opponent for manned air-to-air combat simulations

Two versions of a real-time digital-computer program that operates a fighter airplane interactively against a human pilot in simulated air combat were evaluated. They function by replacing one of two pilots in the Langley differential maneuvering simulator. Both versions make maneuvering decisions from identical information and logic; they differ essentially in the aerodynamic models that they control. One is very complete, but the other is much simpler, primarily characterizing the airplane's performance (lift, drag, and thrust). Both models competed extremely well against highly trained U.S. fighter pilots.

Hankins, W. W., III↗
NASA NTRS1982

Analytic optical potentials for nucleon-nucleus nucleus-nucleus collisions involving light and medium nuclei

Utilizing an optical model potential approximation to the exact nucleus-nucleus multiple-scattering series, optical potentials for nucleon-nucleus and nucleus-nucleus collisions are analytically derived. These expressions are applicable to light and medium cosmic ray nuclei as their single-particle density distributions are analytically determined, without approximation, from their actual harmonic well charge density distributions. Pauli correlation effects are included through the use of a simple Gaussian function to replace the usual expression obtained in the infinite nuclear matter approximation.

Bidasaria, H. B.↗
NASA NTRS1992

Programmability in AIPS++

AIPS++ is an Astronomical Information Processing System being designed and implemented by an international consortium of NRAO and six other radio astronomy institutions in Australia, India, the Netherlands, the United Kingdom, Canada, and the USA. AIPS++ is intended to replace the functionality of AIPS, to be more easily programmable, and will be implemented in C++ using object-oriented techniques. Programmability in AIPS++ is planned at three levels. The first level will be that of a command-line interpreter with characteristics similar to IDL and PV-Wave, but with an intensive set of operations appropriate to telescope data handling, image formation, and image processing. The third level will be in C++ with extensive use of class libraries for both basic operations and advanced applications. The third level will allow input and output of data between external FORTRAN programs and AIPS++ telescope and image databases. In addition to summarizing the above programmability characteristics, this talk will given an overview of the classes currently being designed for telescope data calibration and editing, image formation, and the 'toolkit' of mathematical 'objects' that will perform most of the processing in AIPS++.

Hjellming, R. M.↗