SEARCH · Engineering Papers

Results for “Strategy”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3

All sources NASA NTRS DOE OSTI

DOE OSTI2024

1. Physical Security Engineering by Design for Nuclear Facilities; 2. Nuclear Power Plant Site Security Management – A Security Strategy; 3. The UAE Women in Nuclear Energy Security

1. Security by design, or SeBD, is a comprehensive approach that integrates the physical protection system of a nuclear plant into every stage of its existence. This includes planning, designing, constructing, commissioning, and operating the facility, using a combination of analytical, physical, technological, and procedural measures. Essentially, SeBD involves intentionally applying and incorporating security into all aspects of design and operation throughout the entire lifecycle of a facility. By implementing this methodology throughout various phases such as program development, process implementation, staff training and procedures management in conjunction with plant equipment, facilities can be optimized to minimize security risks without compromising functional design requirements. This ultimately improves the overall security posture of the site and reduces the need for costly modifications or additional security resources post-design. 2. A site security strategy is a living document that is revised on a periodic or event-driven basis, ensuring that site security operations and corresponding procedures provide long-term, effective protection for the entire nuclear power plant (NPP) site. A site security strategy aims to mitigate threats across the entire NPP site via in-depth defense approaches and mutual support; therefore, if a layer is omitted or altered, then the effect across all layers must be re-evaluated. Therefore, the aim of the site security strategy is to provide an appropriate, scalable security regime that deters, denies, delays, and detects incidents and, equally importantly, reassures legitimate users and the regulator that due diligence and regulatory compliance have been achieved, ensuring that the site is safe and secure. Robust access control for vehicles and pedestrians is at the heart of the strategy. Vehicle and pedestrian searching and screening are seen as the strongest mitigation methods against vehicle- and pedestrian-borne attacks. The security strategy must also be supported through comprehensive staff training and the development of robust processes, procedures, and planning. If all these measures are to be effective, then training must be implemented during each phase of construction, partial operation/commissioning, and full operation. No single element of site security is completely isolated from the influence of other elements. Ideally, consideration of all key elements will result in a security strategy that is integrated and proportional to the threat and that does not over specify individual security solutions through the application of isolated measures but rather applies a holistic, all-encompassing approach. 3. When women enter the labor force, numerous positive outcomes emerge, including increased GDP, educational gains, and decreased maternal mortality. Despite these benefits, women's employment rates and equality vary significantly worldwide as does support for women in the workforce. This paper will explore the multifaceted benefits of women's employment, the factors influencing labor force participation rates, and the urgency to achieve gender equality as outlined in the 2015 United Nations Sustainable Development Goals (SDGs). It will then examine the emerging presence of women in the traditionally male-dominated nuclear field, specifically within the United Arab Emirates (UAE) as a testament to their resilience and determination to break social norms and advance gender equality.

Zineddin, Dr. Z.↗

DOE OSTI2024

An orbital strategy for regulating the Jahn–Teller effect

ABSTRACT The Jahn–Teller effect (JTE) arising from lattice–electron coupling is a fascinating phenomenon that profoundly affects important physical properties in a number of transition-metal compounds. Controlling JT distortions and their corresponding electronic structures is highly desirable to tailor the functionalities of materials. Here, we propose a local coordinate strategy to regulate the JTE through quantifying occupancy in the ${{d}_{{{z}^2}}}$ and ${{d}_{{{x}^2} - {{y}^2}}}$ orbitals of Mn and scrutinizing the symmetries of the ligand oxygen atoms in MnO6 octahedra in LiMn2O4 and Li0.5Mn2O4. The effectiveness of such a strategy has been demonstrated by constructing P2-type NaLixMn1–xO2 oxides with different Li/Mn ordering schemes. In addition, this strategy is also tenable for most 3d transition-metal compounds in spinel and perovskite frameworks, indicating the universality of local coordinate strategy and the tunability of the lattice–orbital coupling in transition-metal oxides. This work demonstrates a useful strategy to regulate JT distortion and provides useful guidelines for future design of functional materials with specific physical properties.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

NASA NTRS2024

Additional Aviation Sustainability Strategies

Emissions from the aviation sector are expected to grow significantly in the next few decades due to growing demand for aviation. The U.S. fleet size has increased significantly in the past 20 years, growing from 2,132 aircraft to 5,485 aircraft. Similarly from 1990 to 2019, aviation emissions more than doubled, growing faster than any other transportation mode. These emissions include carbon dioxide (CO2), as well as non-CO2 sources including nitrogen oxides (NOx), sulfur dioxide (SO2), water (H2O), and particulate matter (soot). However, this report focuses specifically on CO2 emissions because the impacts from CO2 are well-understood and long-lived. There are also many climate goals tied to CO2 emissions, including the US Aviation Climate Action Plan which is pushing for net-zero in 2050. CO2 is a greenhouse, or heat-trapping, gas that comes from the extraction and burning of fossil fuels, from wildfires, and natural processes like volcanoes. Greenhouse gases absorb heat radiating from the Earth’s surface and release it in all directions, including back toward Earth’s surface. By adding more CO2 to the atmosphere, humans amplify the natural greenhouse effect, causing global temperature to rise. Since the onset of industrial times in 1750, human activities have raised atmospheric CO2 by 50%. Considering this challenge, the United States has set a climate goal to achieve net-zero CO2 emissions in the U.S. aviation sector by 2050 to reduce the environmental impact of aviation. Net-zero emissions refers to the amount of greenhouse gases (GHGs), such as CO2, methane or SO2, that are removed from the atmosphere being equal to those emitted by human activity. This contrasts with carbon-neutrality, which refers to no net release of carbon dioxide to the atmosphere, especially through offsetting emissions, that could be accomplished through a series of actions. As of 2022, the goal of net-zero has been adopted by much of the aviation industry including multiple airlines and countries. To reach net-zero by 2050, sustainable aviation fuels (SAFs) are identified as the technology that could provide the greatest impact within this timeframe. However, certain challenges may limit the production and/or adoption of SAFs in the marketplace, such as competition for feedstocks, production capacity, and high cost. In this case, SAFs would be insufficient to meet the net-zero CO2 emission goals. Therefore, in addition to SAFs, other strategies will be needed to close the gap on emissions produced as a result of SAF shortfalls or to enhance the impact of SAFs on reducing emissions. NASA’s Aeronautics Research Mission Directorate (ARMD) aims to examine these additional pathways to explore how its research may best contribute to the realization of net-zero emissions by 2050. Specifically, this effort considers strategies that can reduce emissions in the aviation sector in combination with the use of SAFs and carbon offsets while still meeting projected passenger demand. The strategies considered are not only feasible but also could be operationally scalable by 2050. The goal of this report is to investigate additional strategies such as alternative flight and ground operations, providing insight into the CO2 emission reduction potential and feasibility of strategy implementation by 2050.

Carbon Emissions↗

DOE OSTI2025

Studies of the influence of heat pipe model and coupling strategy in heat pipe microreactor simulations using Sockeye

This work demonstrates various modeling approaches for thermally coupling heat pipes to a graphite monolithic block in a microreactor context, accounting for the presence of a gap. We show that heat pipe model selection has a significant impact on the transient behavior of a three-dimensional coupled microreactor assembly problem by comparing results obtained using different heat pipe models from the heat pipe code Sockeye. Additionally, we show that the choice of coupling strategy has significant consequences for both accuracy and performance. Furthermore, we found that our heat flux transfer strategy exhibited greater accuracy than our temperature transfer strategy, even when comparing a loose coupling of the heat flux transfer strategy to a tight coupling of the temperature transfer strategy. Although this research uses only theoretical test problems, it provides important insights in modeling thermal fluids phenomena in heat pipe microreactors.

Direwolf↗

DOE OSTI2025

Optimal Control Strategy With Efficiency and Reliability Improvement for Offshore DC Microgrids

Offshore microgrids, due to their remote location and lack of external energy support, face significant challenges in wide-range load operation and maintenance. Consequently, efficiency and reliability are critical concerns for converters in offshore dc microgrids. This article presents an optimal control strategy aimed at enhancing both efficiency and reliability. A normalized nonlinear relationship between power loss and thermal stress of a paralleled converter is first established. Based on this, a dual-objective optimization function with an active weight function as well as a system overall performance index is established. The active weight function dynamically adjusts the control priority based on converter efficiency and switching device thermal stress. Then, the optimal power-sharing strategy is derived by the Lagrange multiplier method with the proposed optimal function. Additionally, to accommodate a wide load range, an optimal selection strategy for operating converter combinations is proposed, requiring only low-bandwidth communication. Experiment verification is given to validate the effectiveness of the proposed control strategy. The experiment results demonstrate that the proposed control strategy can improve the overall performance of offshore microgrids by optimizing efficiency and reliability.

24 POWER TRANSMISSION AND DISTRIBUTION↗

DOE OSTI2025

Business Models for Scaling Demand Flexibility Volume II – Customer relationship management strategies, challenges, and lessons learned from U.S. programs

Load growth at the grid edge is driving increased attention to the distribution system and its ability to enable customer technology adoption in an affordable and timely manner. Key industry stakeholders, including electric utilities and regulators, can benefit from strategies to manage and balance customer needs with infrastructure investments, such as demand flexibility. This report focuses on demand flexibility—the ability to reduce, shift, shed, generate, or modulate loads in response to building and grid needs—to reduce the need for costly grid upgrades by deferring investment needs and increase system reliability by shifting electricity usage during periods of high risk. Specifically, we focus on the emerging characteristics of business models for demand flexibility as a framework to understand how demand flexibility programs generate value. In this report, we focus on demand flexibility program customer relationship management strategies, which provide information on value creation and focus on ensuring customers can navigate programs smoothly. This report discusses the role of customer relationship management strategies in demand flexibility programs, characterizes customer relationship management strategies that can be considered during program design and implementation, identifies existing challenges to customer relationship management strategies, and describes lessons learned. This report is part of a series that includes reports on value propositions, stakeholder ecosystem management, and program life cycle.

24 POWER TRANSMISSION AND DISTRIBUTION↗

DOE OSTI2026

Chasing Gamma-Ray Signals from Binary Neutron Star Coalescences with the Cherenkov Telescope Array: Prospects and Observing Strategies

The detection of gravitational waves (GWs) from a binary neutron star (BNS) merger by Advanced LIGO and Advanced Virgo (GW170817), together with its electromagnetic counterpart, the short gamma-ray burst GRB 170817A, heralded the birth of multimessenger astronomy. The detection of TeV emission from GRBs motivates follow-up observations with the Cherenkov Telescope Array Observatory (CTAO), which is ideal for detecting such signals due to its unprecedented sensitivity, rapid response, and wide-field survey capabilities. The aim of this work is to evaluate GeV–TeV GW follow-up strategies for CTAO using a multistep simulation pipeline and to estimate the expected rate of joint GW–GRB detections during observing run O5. Using a simulated sample of BNS systems with corresponding GW detections, gamma-ray emission is simulated through phenomenological prescriptions based on the observed population of short GRBs, including off-axis jet scenarios. CTAO observations are simulated to account for instrument response, sky tiling strategies, integration times, and varying observing conditions. Strategies with variable and constant integration times are investigated. We find that, via an optimized follow-up strategy, about 5% of simulated GW-associated short GRBs produce GeV–TeV radiation detectable by CTAO. Detectability is strongly influenced by the jet opening angle and viewing angle, suggesting that even rough estimates of the viewing angle in GW alerts could enhance targeting. This framework motivates future follow-ups of GW-detectable events, including neutron star–black hole mergers, and further supports the development of advanced strategies incorporating galaxy distributions and synergies with future detectors such as the Einstein Telescope.

Abe, S. [University of Tokyo] (ORCID:0000000172503↗

DOE OSTI2025

Quantifying the Impact of LSST u -band Survey Strategy on Photometric Redshift Estimation and the Detection of Lyman-break Galaxies

The Vera C. Rubin Observatory will conduct the Legacy Survey of Space and Time (LSST), promising to discover billions of galaxies out to redshift 7, using six photometric bands (ugrizy) spanning the near-ultraviolet to the near-infrared. The exact number of and quality of information about these galaxies will depend on survey depth in these six bands, which in turn depends on the LSST survey strategy, i.e., how often and how long to expose in each band. u-band depth is especially important for photometric redshift (photo-z) estimation and for detection of high-redshift Lyman-break galaxies (LBGs). In this paper, we use a simulated galaxy catalog and an analytic model for the LBG population to study how recent updates and proposed changes to Rubin’s u-band throughput and LSST survey strategy impact photo-z accuracy and LBG detection. We find that proposed variations in u-band strategy have a small impact on photo-z accuracy for z < 1.5 galaxies, but the outlier fraction, scatter, and bias for higher-redshift galaxies vary by up to 50%, depending on the survey strategy considered. The number of u-band dropout LBGs at z ∼ 3 is also highly sensitive to the u-band depth, varying by up to 500%, while the number of griz-band dropouts is only modestly affected. Under the new u-band strategy recommended by the Rubin Survey Cadence Optimization Committee, we predict u-band dropout number densities of 110 deg −2 (3200 deg −2 ) in year 1 (10) of LSST. We discuss the implications of these results for LSST cosmology.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1975

Deterministic optimal maneuver strategy for multi-target missions

This paper presents an optimal strategy for making impulsive correction to a multi-target trajectory by a single maneuver. The concept of an optimal maneuver time is introduced. The choice of suitable weighting functions is explored to enable one to properly translate the subjective desire of mission success into an objective cost function whose minimization yields the optimal strategy. It is shown that a number of strategies previously formulated are derivable from one general expression. A number of other interesting properties of the optimal strategy are described. Numerical results are presented for a typical two-target mission. It is shown that the strategy formulated is optimal. For some perturbations, there exists an optimal maneuver time different from the time of initiation of the perturbation. That is, the physical properties of the trajectory can be exploited to select the optimal time of making a corrective maneuver.

Dwivedi, N. P.↗

NASA NTRS1981

Strategies for weather-dependent data acquisition

A strategy for data acquisition from a very distant spacecraft is presented, when the system performance can be severely degraded by the Earth's weather due to the high microwave frequency being used. When there is no minimum rate to be maintained, the optimum strategy is the greedy strategy, which always transmits at the single rate which maximizes the expected data returned. If there is a minimum data rate, the optimum strategy transmits simultaneously at the minimum or base data rate and at a bonus data rate. A coding system designed for the bandwidth-constrained degraded broadcast channels used. The optimum version of this system can, under realistic assumptions, save on the order of 5 dB over the conservative strategy of just transmitting at a single lower data rate.

Posner, E. C.↗

NASA NTRS1983

Strategies for weather-dependent data acquisition

A strategy for data acquisition from a very distant spacecraft is presented, when the system performance can be severely degraded by the Earth's weather due to the high microwave frequency being used. When there is no minimum rate to be maintained, the optimum strategy is the greedy strategy, which always transmits at the single rate which maximizes the expected data returned. If there is a minimum data rate, tne optimum strategy transmits simultaneously at the minimum or base data rate and at a bonus data rate. A coding system designed for the bandwidth-constrained degraded broadcast channels used. The optimum version of this system can, under realistic assumptions, save on the order of 5 dB over the conservative strategy of just transmitting at a single lower data rate. Previously announced in STAR as N82-11286

Posner, E. C.↗

NASA NTRS1985

The synthesis of primitive 'living' forms - Definitions, goals, strategies and evolution synthesizers

The arbitrariness of the definition of life is discussed in relation to both the archaic biological entities that preceded cells during the Molecular Evolution era, and the hypothetical, primitive, 'living' entities that presumably can be synthesized in the laboratory. Several experimental approaches to the synthesis, detection, and characterization of 'living' entities are discussed. The experimental approaches considered for the synthesis are the constructionist strategy, the whole-environment strategy, and the modular strategy, which is a combination of the first two. The whole-environment strategy is discussed in more detail and the establishment of an Evolution Synthesizer, based on this strategy, is proposed and rationalized. The guidelines for the detection and characterization of populations and processes of 'living' entities include chemical and physical analyses, but are based mainly on the reproductive characterization of these entities. It is expected that the higher the evolutionary level of the 'living' entities, the longer and more difficult it will be to synthesize them, but the easier it will be to detect them.

Lahav, N.↗

NASA NTRS1988

Flight-management strategies for escape from microburst encounters

An effort is underway by NASA, FAA, and industry to reduce the threat of convective microburst wind shear phenomena to aircraft. The goal is to develop and test a candidate set of strategies for recovery from inadvertent microburst encounters during takeoff. Candidate strategies were developed and evaluated using a fast-time simulation consisting of a simple point-mass performance model of a transport-category airplane and an analytical microburst model. The results indicate that the recovery strategy characteristics that best utilize available airplane energy include an initial reduction in pitch attitude to reduce the climb rate, followed by an increase in pitch up to the stick shaker angle of attack. The stick shaker angle of attack should be reached just as the airplane is exiting the microburst. The shallowest angle of climb necessary for obstacle clearance should be used. If the altitude is higher than necessary, an intentional descent to reduce the airspeed deceleration should be used. Of the strategies tested, two flight-path-angle based strategies had the highest recovery altitudes and the least sensitivity to variations in the encounter scenarios.

Hinton, David A.↗

NASA NTRS1990

The Office of Space Science and Applications strategic plan, 1990: A strategy for leadership in space through excellence in space science and applications

A strategic plan for the U.S. space science and applications program during the next 5 to 10 years was developed and published in 1988. Based on the strategies developed by the advisory committees of both the National Academy of Science and NASA, the plan balances major, moderate, and small mission initiatives, the utilization of the Space Station Freedom, and the requirements for a vital research base. The Office of Space Science and Applications (OSSA) strategic plan is constructed around five actions: establish a set of programmatic themes; establish a set of decision rules; establish a set of priorities for missions and programs within each theme; demonstrate that the strategy will yield a viable program; and check the strategy for consistency within resource constraints. The OSSA plan is revised annually. This OSSA 1990 Strategic Plan refines the 1989 Plan and represents OSSA's initial plan for fulfilling its responsibilities in two major national initiatives. The Plan is now built on interrelated, complementary strategies for the core space science and applications program, for the U.S. Global Change Research Program, and for the Space Exploration Initiative. The challenge is to make sure that the current level of activity is sustained through the end of this century and into the next. The 1990 Plan presents OSSA's strategy to do this.

Source record↗

NASA NTRS1995

A hybrid neurocomputing/numerical strategy for nonlinear structural analysis

A hybrid neurocomputing/numerical strategy is presented for geometrically nonlinear analysis of structures. The strategy combines model-free data processing capabilities of computational neural networks with a Pade approximants-based perturbation technique to predict partial information about the nonlinear response of structures. In the hybrid strategy, multilayer feedforward neural networks are used to extend the validity of solutions by using training samples produced by Pade approximations to the Taylor series expansion of the response function. The range of validity of the training samples is taken to be the radius of convergence of Pade approximants and is estimated by setting a tolerance on the diverging approximants. The norm of residual vector of unbalanced forces in a given element is used as a measure to assess the quality of network predictions. To further increase the accuracy and the range of network predictions, additional training data are generated by either applying linear regression to weight matrices or expanding the training data by using predicted coefficients in a Taylor series. The effectiveness of the hybrid strategy is assessed by performing large-deflection analysis of a doubly-curved composite panel with a circular cutout, and postbuckling analyses of stiffened composite panels subjected to an in-plane edge shear load. In all the problems considered, the hybrid strategy is used to predict selective information about the structural response, namely the total strain energy and the maximum displacement components only.

Szewczyk, Z. Peter↗

NASA NTRS1995

Computational strategies for tire monitoring and analysis

Computational strategies are presented for the modeling and analysis of tires in contact with pavement. A procedure is introduced for simple and accurate determination of tire cross-sectional geometric characteristics from a digitally scanned image. Three new strategies for reducing the computational effort in the finite element solution of tire-pavement contact are also presented. These strategies take advantage of the observation that footprint loads do not usually stimulate a significant tire response away from the pavement contact region. The finite element strategies differ in their level of approximation and required amount of computer resources. The effectiveness of the strategies is demonstrated by numerical examples of frictionless and frictional contact of the space shuttle Orbiter nose-gear tire. Both an in-house research code and a commercial finite element code are used in the numerical studies.

Danielson, Kent T.↗

NASA NTRS1996

A Cascade Optimization Strategy for Solution of Difficult Multidisciplinary Design Problems

A research project to comparatively evaluate 10 nonlinear optimization algorithms was recently completed. A conclusion was that no single optimizer could successfully solve all 40 problems in the test bed, even though most optimizers successfully solved at least one-third of the problems. We realized that improved search directions and step lengths, available in the 10 optimizers compared, were not likely to alleviate the convergence difficulties. For the solution of those difficult problems we have devised an alternative approach called cascade optimization strategy. The cascade strategy uses several optimizers, one followed by another in a specified sequence, to solve a problem. A pseudorandom scheme perturbs design variables between the optimizers. The cascade strategy has been tested successfully in the design of supersonic and subsonic aircraft configurations and air-breathing engines for high-speed civil transport applications. These problems could not be successfully solved by an individual optimizer. The cascade optimization strategy, however, generated feasible optimum solutions for both aircraft and engine problems. This paper presents the cascade strategy and solutions to a number of these problems.

Patnaik, Surya N.↗

NASA NTRS1994

Using Induction to Refine Information Retrieval Strategies

Conceptual information retrieval systems use structured document indices, domain knowledge and a set of heuristic retrieval strategies to match user queries with a set of indices describing the document's content. Such retrieval strategies increase the set of relevant documents retrieved (increase recall), but at the expense of returning additional irrelevant documents (decrease precision). Usually in conceptual information retrieval systems this tradeoff is managed by hand and with difficulty. This paper discusses ways of managing this tradeoff by the application of standard induction algorithms to refine the retrieval strategies in an engineering design domain. We gathered examples of query/retrieval pairs during the system's operation using feedback from a user on the retrieved information. We then fed these examples to the induction algorithm and generated decision trees that refine the existing set of retrieval strategies. We found that (1) induction improved the precision on a set of queries generated by another user, without a significant loss in recall, and (2) in an interactive mode, the decision trees pointed out flaws in the retrieval and indexing knowledge and suggested ways to refine the retrieval strategies.

Baudin, Catherine↗