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Results for “reasoning about programs”

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
DOE OSTI2013

Color Maintenance of LEDs in Laboratory and Field Applications

To date, consideration for parametric failure of LED products has largely been focused on lumen maintenance. However, color shift is a cause of early failure for some products, and is especially important to consider in certain applications, such as museum lighting, where visual appearance is critical. Field data collected by the U.S. Department of Energy's (DOE) GATEWAY program for LED lamps installed in museums shows that many have changed color beyond a reasonable tolerance well before their rated lifetimes have been reached. Laboratory data collected by DOE's CALiPER program between 2008 and 2010 reveals that many early LED products shifted beyond acceptable tolerances in as little as a few thousand hours. In contrast, data from the L Prize® program illustrates that commercially available LED products can have exemplary color stability that is unmatched by traditional light sources. In addition to presenting data from the aforementioned DOE programs, this report discusses the metrics used for communicating color shift, and provides guidance for end users on how to monitor chromaticity and what to look for in manufacturer warranties. Also covered are the physical changes that have been shown to lead to color shift in some types of LED packages. As with lamps and luminaires, the data presented for LED packages shows that a wide variety of products are available; in order for specifiers and consumers to make educated choices, more detailed and standardized information is necessary.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2015

Memory operation mechanism of fullerene-containing polymer memory

The memory operation mechanism in fullerene-containing nanocomposite gate insulators was investigated while varying the kind of fullerene in a polymer gate insulator. It was cleared what kind of traps and which positions in the nanocomposite the injected electrons or holes are stored in. The reason for the difference in the easiness of programming was clarified taking the role of the charging energy of an injected electron into account. The dependence of the carrier dynamics on the kind of fullerene molecule was investigated. A nonuniform distribution of injected carriers occurred after application of a large magnitude programming voltage due to the width distribution of the polystyrene barrier between adjacent fullerene molecules. Through the investigations, we demonstrated a nanocomposite gate with fullerene molecules having excellent retention characteristics and a programming capability. This will lead to the realization of practical organic memories with fullerene-containing polymer nanocomposites.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Topology optimization of 3D photonic crystals with complete bandgaps

The design of photonic crystals with complete bandgaps has recently received considerable research focus for numerous reasons. This work leverages well-known nonlinear programming techniques to alleviate the non-smoothness caused by degenerate eigenvalues such that topology optimization problems can be solved with the open-source IPOPT software. A fully-vectorial plane wave expansion technique is used with an iterative eigensolver to efficiently predict dispersion properties of candidate structures. Nonlinear programming is employed to solve the inverse problem of designing three-dimensional periodic structures that exhibit complete two-dimensional (2D) and three-dimensional (3D) photonic bandgaps. Mesh refinement is performed to alleviate the large computational burden of designing and analyzing photonic crystals, and a periodic density filter is implemented to impose a minimum feature size for manufacturability considerations.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2025

Connecting Minds: AI Use Cases to Bridge Power Systems and Large Language Models for Practical Applications

Recent advances in artificial intelligence (AI) and development of large language models (LLMs) present the opportunity to develop a new generation of power systems applications. In contrast with early power system AI applications based on structured numerical data, LLMs offer unique capabilities to perform logical reasoning using text documents, unstructured data, and application programming interface (API) calls to computational software. This paper seeks to bridge the knowledge gap between power systems engineers and LLM developers through a crosscutting explanation of use cases, characteristics, requirements, practical considerations from the perspectives of both LLM capabilities and industry needs. Specific focus is given to applications that can be realistically deployed by electric utilities. After introducing the architecture of LLMs and unique challenges of the power systems domain, this paper proposes twenty representative LLM applications grouped into categories of 1) power system operations, 2) asset management, 3) system planning and analytics, and 4) energy management and protection systems. Five use cases are presented within each category with descriptions of the motivation, objectives, approaches, example inputs / outputs, and benefits of each use case.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS1981

Experiment Requirements and Implementation Plan (ERIP) for semiconductor materials growth in low-G environment experiment no. MPS-77F087

Crystals of the intermetallic compound Pb1-xSnxTe will be grown in furnaces on the Space Shuttle. The reasons for conducting this growth in space, the program of investigation to develop the space experiment and the requirements that are placed on the Space Shuttle furnace are discussed. Also included are relevent thermophysical properties of Pb1-xSnxTe to the degree which they are known.

Crouch, R. K.↗
NASA NTRS1982

Space power subsystem automation technology

The technology issues involved in power subsystem automation and the reasonable objectives to be sought in such a program were discussed. The complexities, uncertainties, and alternatives of power subsystem automation, along with the advantages from both an economic and a technological perspective were considered. Whereas most spacecraft power subsystems now use certain automated functions, the idea of complete autonomy for long periods of time is almost inconceivable. Thus, it seems prudent that the technology program for power subsystem automation be based upon a growth scenario which should provide a structured framework of deliberate steps to enable the evolution of space power subsystems from the current practice of limited autonomy to a greater use of automation with each step being justified on a cost/benefit basis. Each accomplishment should move toward the objectives of decreased requirement for ground control, increased system reliability through onboard management, and ultimately lower energy cost through longer life systems that require fewer resources to operate and maintain. This approach seems well-suited to the evolution of more sophisticated algorithms and eventually perhaps even the use of some sort of artificial intelligence. Multi-hundred kilowatt systems of the future will probably require an advanced level of autonomy if they are to be affordable and manageable.

Graves, J. R.↗
NASA NTRS1981

Materials experiment carrier concepts definition study. Volume 1: Executive summary, part 2

The materials experiment carrier (MEC) is an optimized carrier for near term and advanced materials processing in space (MPS) research and commercial payloads. When coupled with the space platform (SP), the MEC can provide the extended duration, high power and low acceleration environment the MPS payload typically requires. The lowest cost, technically reasonable first step MEC that meets the MPS program missions objectives with minimum programmatic risks is defined. The effectiveness of the initial MEC/space platform idea for accommodating high priority, multidiscipline, R&D and commercial MPS payloads, and conducting MPS payload oprations at affordable funding and acceptable productivity levels is demonstrated.

Source record↗
NASA NTRS1984

Optimization in the systems engineering process

The objective is to look at optimization as it applies to the design process at a large aircraft company. The design process at Lockheed-Georgia is described. Some examples of the impact that optimization has had on that process are given, and then some areas that must be considered if optimization is to be successful and supportive in the total design process are indicated. Optimization must continue to be sold and this selling is best done by consistent good performance. For this good performance to occur, the future approaches must be clearly thought out so that the optimization methods solve the problems that actually occur during design. The visibility of the design process must be maintained as further developments are proposed. Careful attention must be given to the management of data in the optimization process, both for technical reasons and for administrative purposes. Finally, to satisfy program needs, provisions must be included to supply data to support program decisions, and to communicate with design processes outside of the optimization process. If designers fail to adequately consider all of these needs, the future acceptance of optimization will be impeded.

Lemmerman, L. A.↗
NASA NTRS1989

Expert systems applied to spacecraft fire safety

Expert systems are problem-solving programs that combine a knowledge base and a reasoning mechanism to simulate a human expert. The development of an expert system to manage fire safety in spacecraft, in particular the NASA Space Station Freedom, is difficult but clearly advantageous in the long-term. Some needs in low-gravity flammability characteristics, ventilating-flow effects, fire detection, fire extinguishment, and decision models, all necessary to establish the knowledge base for an expert system, are discussed.

Smith, Richard L.↗
NASA NTRS1999

A Framework for Dynamic Constraint Reasoning Using Procedural Constraints

Many complex real-world decision and control problems contain an underlying constraint reasoning problem. This is particularly evident in a recently developed approach to planning, where almost all planning decisions are represented by constrained variables. This translates a significant part of the planning problem into a constraint network whose consistency determines the validity of the plan candidate. Since higher-level choices about control actions can add or remove variables and constraints, the underlying constraint network is invariably highly dynamic. Arbitrary domain-dependent constraints may be added to the constraint network and the constraint reasoning mechanism must be able to handle such constraints effectively. Additionally, real problems often require handling constraints over continuous variables. These requirements present a number of significant challenges for a constraint reasoning mechanism. In this paper, we introduce a general framework for handling dynamic constraint networks with real-valued variables, by using procedures to represent and effectively reason about general constraints. The framework is based on a sound theoretical foundation, and can be proven to be sound and complete under well-defined conditions. Furthermore, the framework provides hybrid reasoning capabilities, as alternative solution methods like mathematical programming can be incorporated into the framework, in the form of procedures.

Jonsson, Ari K.↗
NASA NTRS2005

Operational Aspects of Space Radiation Analysis

Minimizing astronaut's short and long-term medical risks arising from exposure to ionizing radiation during space missions is a major concern for NASA's manned spaceflight program, particularly exploration missions. For ethical and legal reasons, NASA follows the "as low as reasonably achievable" (ALARA) principal in managing astronaut's radiation exposures. One implementation of ALARA is the response to space weather events. Of particular concern are energetic solar particle events, and in low Earth orbit (LEO), electron belt enhancements. To properly respond to these events, NASA's Space Radiation Analysis Group (SRAG), in partnership with the NOAA Space Environment Center (SEC), provides continuous flight support during U.S. manned missions. In this partnership, SEC compiles space weather data from numerous ground and space based assets and makes it available in near real-time to SRAG (along with alerts and forecasts), who in turn uses these data as input to models to calculate estimates of the resulting exposure to astronauts. These calculations and vehicle instrument data form the basis for real-time recommendations to flight management. It is also important to implement ALARA during the design phase. In order to appropriately weigh the risks associated with various shielding and vehicle configuration concepts, the expected environment must be adequately characterized for nominal and worst case scenarios for that portion of the solar cycle and point in space. Even with the best shielding concepts and materials in place (unlikely), there will be numerous occasions where the crew is at greater risk due to being in a lower shielded environment (short term transit or lower shielded vehicles, EVAs), so that accurate space weather forecasts and nowcasts, of particles at the relevant energies, will be crucial to protecting crew health and safety.

Weyland, M. D.↗
NASA NTRS2006

FuzzObserver

Fuzzy Feature Observation Planner for Small Body Proximity Observations (FuzzObserver) is a developmental computer program, to be used along with other software, for autonomous planning of maneuvers of a spacecraft near an asteroid, comet, or other small astronomical body. Selection of terrain features and estimation of the position of the spacecraft relative to these features is an essential part of such planning. FuzzObserver contributes to the selection and estimation by generating recommendations for spacecraft trajectory adjustments to maintain the spacecraft's ability to observe sufficient terrain features for estimating position. The input to FuzzObserver consists of data from terrain images, including sets of data on features acquired during descent toward, or traversal of, a body of interest. The name of this program reflects its use of fuzzy logic to reason about the terrain features represented by the data and extract corresponding trajectory-adjustment rules. Linguistic fuzzy sets and conditional statements enable fuzzy systems to make decisions based on heuristic rule-based knowledge derived by engineering experts. A major advantage of using fuzzy logic is that it involves simple arithmetic calculations that can be performed rapidly enough to be useful for planning within the short times typically available for spacecraft maneuvers.

Howard, Ayanna↗
NASA NTRS2018

A Markov Decision Process Framework for Optimal Airport Reconfiguration

The airport runway configuration is defined as a combination set of runways for arrivals and departures used at a point during operation of the airport. An optimal configuration of these runways depends on a number of factors, including traffic demand, wind magnitude and direction, other adverse weather conditions, and noise restrictions, among others. Based on the current state of these factors and predictions of traffic demand and weather conditions, runway configuration changes are made and coordinated between tower controller, other air traffic control facilities, pilots, and ground personnel. Reconfigurations can be quite disruptive to airport operations; minimizing their frequency and scheduling them well in advance is essential for mitigating some of the added workload for controllers and pilots. Unfortunately, deciding on an appropriate time to change is challenging for human decision makers. Not only do multiple factors need to be evaluated, but the uncertainty in their forecasts must also be considered. Previous optimization methods, such as mixed linear integer programming, have been proposed. Although these methods can reason over a large set of variables, they do not systematically handle the uncertainty associated with weather movement, traffic demands, and other variables. In this work, we introduce a Markov Decision Process (MDP)-based decision making framework which can reason effectively over the inherent uncertainties and make optimal decisions on if/when to change the airport configuration. In a prototype implementation, we present a single runway with three aircraft and utilize knowledge of the forecasted wind speed and direction to determine whether to keep or change the current runway configuration. Our aim through this work is to present a framework for airport reconfiguration which can be scalable to additional aircraft, multiple runways, and various input parameters. This technique will optimize the airport reconfiguration procedure by providing a proactive approach, optimizing not just at the next optimal opportunity for a reconfiguration based on varying atmospheric and traffic conditions in the terminal airspace, but also anticipating future necessary reconfigurations. This will eliminate the inefficiencies of frequent changes currently associated with runway reconfiguration procedures.

runway reconfiguration↗
NASA NTRSDate not supplied

Long-Term Corrosivity at NASA Kennedy Space Center as a Function of Distance and Time from the Atlantic Ocean

Long-term data to record both seasonal and notional bounding values for corrosivity at multiple sites at NASA Kennedy Space Center was needed to make better materials choices for NASA-based ground and spaceflight programs. The data was valuable for two key reasons, 1) to measure corrosion rate and chloride concentration as a function of time and distance from the Atlantic Ocean, and 2) compare the corrosivity at launchpad and site-specific areas to the more accelerated conditions at the KSC Beachside Atmospheric Corrosion Test Site for coating and materials performance prediction. Sites were chosen from 45 meter (150 feet) to 8 kilometers (5 miles) from the Atlantic Ocean and corrosion variables at each site were measured throughout each year from June 2017 to April 2023, except the Beachside site, which includes data from November 2010. The summary includes corrosivity data and coating performance comparisons at select sites, which will be used as the updated NASA corrosivity standard for corrosion control requirements.

NASA↗
DOE OSTI2017

The Difficulty of Defining the Terms Credible and Unlikely for Nuclear Criticality Safety Purposes

During the last revision of the ANSI/ANS-8.1-2014, extensive efforts were made by the working group (ANS-8.1) to ensure the statements in the standard clearly reflected their intent This effort involved the review of each requirement and recommendation in the standard. In some cases, definitions were added to the standard glossary to minimize ambiguity in the standard (e.g., “process conditions” or “parameter”). The working group also considered adding definitions for the words “credible” and “unlikely” because definitions had been provided to the nuclear criticality safety (NCS) community from the US Department of Energy that caused confusion at some sites. A Nuclear Regulatory Commission document intends for licensees to provide appropriate definitions for these words in their site license. The purpose of this paper is to discuss why the working group ultimately decided not to include definitions for credible and unlikely in the 2014 revision of ANS-8.1

96 KNOWLEDGE MANAGEMENT AND PRESERVATION↗
DOE OSTI2017

AGR Equipment and Materials Disposition

Fabrication of low-enriched experimental nuclear reactor fuel for the Advanced Gas Reactor (AGR) Fuel Development and Qualification program has concluded after several years of effort. Residual chemicals, uranium compounds, fuel intermediates and fuel compacts need to be dispositioned in an economically and environmentally sound manner that maximizes, within reason, the preservation and repurposing of valuable materials. Government Furnished Equipment (GFE), procured with AGR program funds, are also to be dispositioned as economically as reasonably possible while seeking to maintain the functionality of BWXT equipment and repurposing of stand-alone GFE. Any stand-alone equipment that cannot be repurposed will either be abandoned in place, with BWXT consent, or discarded to an appropriate waste repository.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

AGR Equipment and Materials Disposition

Fabrication of low-enriched experimental nuclear reactor fuel for the Advanced Gas Reactor (AGR) Fuel Development and Qualification program has concluded after several years of effort. Residual chemicals, uranium compounds, fuel intermediates and fuel compacts need to be dispositioned in an economically and environmentally sound manner that maximizes, within reason, the preservation and repurposing of valuable materials. Government Furnished Equipment (GFE), procured with AGR program funds, are also to be dispositioned as economically as reasonably possible while seeking to maintain the functionality of BWX Technologies, Inc. (BWXT) equipment and repurposing of stand-alone GFE. Any stand-alone equipment that cannot be repurposed will either be abandoned in place, with BWXT consent, or discarded to an appropriate waste repository. Representatives for the United States Department of Energy may intervene in intended disposition of specific equipment or materials. Revision 3 on document

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2019

AGR Equipment and Materials Disposition

Fabrication of low-enriched experimental nuclear reactor fuel for the Advanced Gas Reactor (AGR) Fuel Development and Qualification program has concluded after several years of effort. Residual chemicals, uranium compounds, fuel intermediates and fuel compacts need to be dispositioned in an economically and environmentally sound manner that maximizes, within reason, the preservation and repurposing of valuable materials. Government Furnished Equipment (GFE), procured with AGR program funds, are also to be dispositioned as economically as reasonably possible while seeking to maintain the functionality of BWX Technologies, Inc. (BWXT) equipment and repurposing of stand-alone GFE. Any stand-alone equipment that cannot be repurposed will either be abandoned in place, with BWXT consent, or discarded to an appropriate waste repository. Representatives for the United States Department of Energy may intervene in intended disposition of specific equipment or materials.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗