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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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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Sub-baud coding

In a spread-spectrum communication system, a data sequence of +1's and -1's is expanded into a sequence of +x's (bottom bar) and -x's (bottom bar) where x (bottom bar) is a length n sequence of +1's and -1's. A sub-baud code is the assignment of a different such baud sequence to each of M users with the objective of reducing interference between users. It is shown that this interference can be described in terms of the even and odd correlation functions between pairs of sequences. A technique for deriving sub-baud codes from cyclic error-correcting codes is given, and a theorem proved which bounds the quality of the resultant code. A specific such cyclic code construction procedure is given which, for any M, yields a sub-baud code for which the mutual interference can be made arbitrarily small by choosing n sufficiently large.

Massey, J. L.↗
NASA NTRS1981

Power spectra of multi-h phase codes

A procedure is presented for calculating the power spectrum of the class of digital continuous-phase signals known as multi-h phase codes. These signals have been shown to have attractive power advantages over other uncoded digital schemes such as QPSK, and represent a bandwidth-efficient alternative to other coding techniques. The method is general, handling M-ary signaling, various frequency pulse shapes, and arbitrary sets of modulation indices. Numerical results are shown for several specific codes. In addition, the issue of spectral lines is resolved, and simple spectral approximations are developed.

Wilson, S. G.↗
DOE OSTI2020

Paving the Way for Net Zero Energy Codes through Performance Based Approaches

The prescriptive path is the most widely used approach for commercial code compliance in the United States. However, to achieve near-term net zero energy performance that many stakeholders in the buildings industry desire, it is clear that energy codes will need to transition from prescriptive to performance-based approaches. However, that transition is not without potential pitfalls. Among the concerns expressed by stakeholders are added complexity and cost, lack of confidence in energy modeling results, gamesmanship on the part of applicants, lack or qualified reviewers, challenges in promoting de-carbonization, and the inequity of trading long lived envelope efficiency for short lived measures such as building controls. This paper will discuss multiple approaches being evaluated and implemented by Pacific Northwest National Laboratory to improve the usability of the performance-based approach for both code compliance and beyond code programs to meet aggressive energy savings targets. A 'system performance' approach provides a simpler approach compared to whole building performance, while keeping tradeoffs limited to specific building systems. A simplified whole-building performance-based approach for small commercial buildings can cost effectively achieve deeper savings for buildings that typically follow the prescriptive compliance approach. Improved reporting and verification processes applied to the traditional performance path can provide greater confidence in simulation results and facilitate adoption of performance-based approaches. Prescriptive packages provide prescriptive solutions while targeting specific performance thresholds. This paper discusses the progress being made with each of these approaches and provides examples of their implementation in energy codes and beyond code programs.

Performance Based Codes, Appendix G, PRM, TSPR, Sy↗
DOE OSTI2022

Dataset for 'Ombadi, M. & Varadharajan, C. (2022). Urbanization and aridity mediate distinct salinity response to floods in rivers and streams across the Contiguous United States, Water Research'

This package contains data sets and code used to obtain the results in Ombadi, M., & Varadharajan, C. (2022). Urbanization and aridity mediate distinct salinity response to floods in rivers and streams across the Contiguous United States. Water Research, 118664. The folder "data" contains 259 .csv files, each of which has daily time series of concurrent streamflow (Q) and specific conductance (SC) for each of the sites used in this study originally downloaded from the USGS National Water Information System (NWIS; USGS, 2016). The number of data points in each of the files is at least 3650 (i.e. 10 years of daily measurements). The folder "RF_single_data" contains 259 .csv files, each of which include data used to train and test the Random Forest models at individual sites for predicting SC during days of floods. The folder "RF_regional_data" contains 3 .csv files, each of which include scaled data compiled from all sites within each climate zone (arid, temperate and wet). "metadata.csv" contains the physical properties of the 259 catchments corresponding to the sites used in this study; this data was extracted from GAGES-II dataset (Falcone et al., 2010). "RF_implementation.ipynb" is a Jupyter notebook with the code needed to implement the analysis using Random Forest models either for individual sites or for the regional models (for each climate zone). The code utilizes the data in the two folders: "RF_single_data" and "RF_regional_data" and the metadata.csv file.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2019

Benefits and Challenges of Model-based Software Engineering: Lessons Learned based on Qualitative and Quantitative Findings

Even though Model-based Software Engineering (MBSwE) techniques and Autogenerated Code (AGC) have been increasingly used to produce complex software systems, there is only anecdotal knowledge about the state-of-thepractice. Furthermore, there is a lack of empirical studies that explore the potential quality improvements due to the use of these techniques. This paper presents in-depth qualitative findings about development and Software Assurance (SWA) practices and detailed quantitative analysis of software bug reports of a NASA mission that used MBSwE and AGC. The mission’s flight software is a combination of handwritten code and AGC developed by two different approaches: one based on state chart models (AGC-M) and another on specification dictionaries (AGC-D). The empirical analysis of fault proneness is based on 380 closed bug reports created by software developers. Our main findings include: (1) MBSwE and AGC provide some benefits, but also impose challenges. (2) SWA done only at a model level is not sufficient. AGC code should also be tested and the models and AGC should always be kept in-sync. AGC must not be changed manually. (3) Fixes made to address an individual bug report were spread both across multiple modules and across multiple files. On average, for each bug report 1.4 modules, that is, 3.4 files were fixed. (4) Most bug reports led to changes in more than one type of file. The majority of changes to auto-generated source code files were made in conjunction to changes in either file with state chart models or XML files derived from dictionaries. (5) For newly developed files, AGC-M and handwritten code were of similar quality, while AGC-D files were the least fault prone.

Goseva-Popstojanova, Katerina↗
NASA NTRS1979

Concurrent error detecting codes for arithmetic processors

A method of concurrent error detection for arithmetic processors is described. Low-cost residue codes with check-length l and checkbase m = 2 to the l power - 1 are described for checking arithmetic operations of addition, subtraction, multiplication, division complement, shift, and rotate. Of the three number representations, the signed-magnitude representation is preferred for residue checking. Two methods of residue generation are described: the standard method of using modulo m adders and the method of using a self-testing residue tree. A simple single-bit parity-check code is described for checking the logical operations of XOR, OR, and AND, and also the arithmetic operations of complement, shift, and rotate. For checking complement, shift, and rotate, the single-bit parity-check code is simpler to implement than the residue codes.

Lim, R. S.↗
DOE OSTI2022

Critical review and analysis of hydrogen safety data collection tools

The wider adoption of hydrogen in multiple sectors of the economy requires that safety and risk issues be rigorously investigated. Quantitative Risk Assessment (QRA) is an important tool for enabling safe deployment of hydrogen fueling stations and is increasingly embedded in the permitting process. QRA requires reliability data, and currently hydrogen QRA is limited by the lack of hydrogen specific reliability data, thereby hindering the development of necessary safety codes and standards [1]. Four tools have been identified that collect hydrogen system safety data: H2Tools Lessons Learned, Hydrogen Incidents and Accidents Database (HIAD), National Renewable Energy Lab's (NREL) Composite Data Products (CDPs), and the Center for Hydrogen Safety (CHS) Equipment and Component Failure Rate Data Submission Form. This work critically reviews and analyzes these tools for their quality and usability in QRA. It is determined that these tools lay a good foundation, however, the data collected by these tools needs improvement for use in QRA. Areas in which these tools can be improved are highlighted, and can be used to develop a path towards adequate reliability data collection for hydrogen systems.

08 HYDROGEN↗
DOE OSTI2021

Review of Codes and Standards for Energy Storage Systems

This article identifies several examples of industry efforts and successes in removing gaps in energy storage (ES) Codes & Standards (C&S) by updating or creating and publishing new standards. A particular challenge discussed in this article is that while modern battery technologies including lithium ion (Li-ion) increase technical and economic viability of grid energy storage, newer battery technologies also present new or unknown risks to managing the safety of energy storage systems (ESS). There has been progress in filling gaps in published ES C&S that recognize and address the expanding range of technologies and their unique characteristics. However, there remain significant need and opportunity for researchers to contribute to the underlying knowledge base that informs development of technical references and standards, and ultimately the application of published standards for the effective and safe design and use of modern ESS.

Energy Storage, Codes and Standards↗
NASA NTRS1993

Ultraviolet spectropolarimetry of the Be star PP Carinae with the Wisconsin Ultraviolet Photo-Polarimeter Experiment

We present the first ultraviolet spectropolarimetric observations of the Be star PP Car, obtained with the Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE) aboard the Astro 1 mission. Usable polarization data were obtained from 1400 to 2330 A, along with a good spectrum from 1400 to 3200 A. These data show a lower polarization shortward of the Balmer jump than had been predicted by standard models, and a broad UV polarization dip around 1900 A is seen. These results are in agreement with those found from the WUPPE observations of two other Be stars, Xi Tau and Pi Aqr, which were published earlier. All these observations are an important probe of the Be circumstellar envelopes and demonstrate the need for the inclusion of metal-line effects in circumstellar disk models of Be star UV polarization.

Bjorkman, K. S.↗
NASA NTRS2004

Studies of Planet Formation Using a Hybrid N-Body + Planetesimal Code

The goal of our proposal was to use a hybrid multi-annulus planetesimal/n-body code to examine the planetesimal theory, one of the two main theories of planet formation. We developed this code to follow the evolution of numerous 1 m to 1 km planetesimals as they collide, merge, and grow into full-fledged planets. Our goal was to apply the code to several well-posed, topical problems in planet formation and to derive observational consequences of the models. We planned to construct detailed models to address two fundamental issues: (1) icy planets: models for icy planet formation will demonstrate how the physical properties of debris disks - including the Kuiper Belt in our solar system - depend on initial conditions and input physics; and (2) terrestrial planets: calculations following the evolution of 1-10 km planetesimals into Earth-mass planets and rings of dust will provide a better understanding of how terrestrial planets form and interact with their environment.

Kenyon, Scott J.↗
NASA NTRS2005

Studies of Planet Formation using a Hybrid N-body + Planetesimal Code

The goal of our proposal was to use a hybrid multi-annulus planetesimal/n-body code to examine the planetesimal theory, one of the two main theories of planet formation. We developed this code to follow the evolution of numerous 1 m to 1 km planetesimals as they collide, merge, and grow into full-fledged planets. Our goal was to apply the code to several well-posed, topical problems in planet formation and to derive observational consequences of the models. We planned to construct detailed models to address two fundamental issues: 1) icy planets - models for icy planet formation will demonstrate how the physical properties of debris disks, including the Kuiper Belt in our solar system, depend on initial conditions and input physics; and 2) terrestrial planets - calculations following the evolution of 1-10 km planetesimals into Earth-mass planets and rings of dust will provide a better understanding of how terrestrial planets form and interact with their environment. During the past year, we made progress on each issue. Papers published in 2004 are summarized. Summaries of work to be completed during the first half of 2005 and work planned for the second half of 2005 are included.

Kenyon, Scott J.↗
DOE OSTI2025

Development of a true single line of sight 3D hot-spot imaging for the National Ignition Facility

High resolution 3D self-emission x-ray imaging during inertial confinement fusion capsule implosion enables the measurement of the shape of the hotspot. While current 3D imaging capabilities use multiple lines of sight to perform image reconstruction, it would be highly desirable to use only one line of sight, as this would significantly reduce the number of windows in the target hohlraum and decrease their impacts on implosion symmetry. Such a goal is achievable using the zone plate coded imaging technique developed by N. M. Ceglio [Proc. SPIE 0106, 55-62 (1977)]. It consists of fielding a visible light Fresnel zone plate on shot to record a shadowgraph. Here, the image can then be reconstructed either by printing the shadowgraph on a transparent film and shining a suitable wavelength light through it or by numerical reconstruction. A new approach using numerical reconstruction is presented, and it relaxes the constraint by an order of magnitude on the optic design, thus enabling an easier fabrication process, as it allows a scaling-up of the optic dimensions. The design, fabrication process, and testing with an x-ray source of a prototype is presented. The reconstruction of an ~14.5 × 17 μm 2 broadband x-ray source was successful and shows that the performances are in line with expectation with an at least 5 mm axial resolution.

47 OTHER INSTRUMENTATION↗
DOE OSTI2021

Quantal diffusion description of isotope production via the multinucleon transfer mechanism in 48 Ca+ 238 U collisions

As an extension of previous work, we calculate the production cross section of heavy neutron-rich isotopes by employing the quantal diffusion description to 48 Ca+ 238 U collisions. The quantal diffusion is deduced from stochastic mean-field approach, and transport properties are determined in terms of time-dependent single-particle wave functions of the time-dependent Hartree-Fock theory. As a result, the approach allows for prediction of production cross sections without any adjustable parameters. Furthermore, the secondary cross sections by particle emission are calculated with the help of the statistical gemini++ code.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

STDA05-51 milestone

In the case for each of the tasks, implementation started in a private topic branch. That branch was later submitted as a merge request where the code was run through regression tests across multiple test platforms. The merge requests were also subjected to human reviewers for approval. After necessary modifications were made, the code was merged to VTK-m's master branch. Subsequently, documentation was written for the VTK-m User's Guide.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

ASME Code Revisions to Incorporate 316H and Alloy 617 Viscoplastic Constitutive Models to Section III, Division 5 and Code Case N-898

This report provides a final status update on work to develop and implement two new constitutive models for 316H stainless steel and the Ni-based Alloy 617 in Nonmandatory Appendix Z to the Section III, Division 5, Subsection HB, Subpart B ASME Boiler & Pressure Vessel Code rules covering the design and construction of Class A high temperature nuclear reactor components. This report summarizes the objections of the overall project and provides the final versions of the constitutive models proposed for incorporation into the ASME Code. The report also provides an update on the balloting status at ASME of the two proposed constitutive models. As of the time of writing (July 2022) the models are on-track to be approved by ASME after the August 2022 Code Week. If so, this will mean the 316H model will be published in the 2023 edition of the Code and the A617 model available as part of a revised Code Case immediately

36 MATERIALS SCIENCE↗
DOE OSTI2022

Simulation of the RF system with reversed phasing

In this paper we report on the ELEGANT simulation for the Electron Storage Ring (ESR) RF system with reversed phasing using the lattice version of 5.3 at 5 GeV energy. The full beam dynamics results, including energy spread, bunch length and centroid offset as a function of bunch number in the train are presented. Some of the RF system related parameters, required as the input for particle tracking simulations, have been calculated analytically using the RF system related equations. The obtained results has been compared with the results simulated by Tianmu Xin, Michael Blaskiewicz and Gabriele Bassi using C++ and the SPACE codes.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Thermal Hydraulic Experimental Test Article - Fiscal Year 2022 Final Report

The Thermal Hydraulic Experimental Test Article (THETA) is a METL vessel experiment designed for testing and validating sodium fast reactor components and phenomena. THETA has been scaled using a non-dimensional Richardson number approach to represent temperature distributions during nominal and loss of flow conditions in a sodium fast reactor (SFR), this analysis was detailed in the THETA FY19 report. The facility is being constructed with versatility in mind, allowing for the installation of various immersion heaters, heat pipes, and heat exchangers without significant facility modification. THETA was designed in collaboration with systems code experts to inform the geometry and sensor placement to acquire the highest value code validation data.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗