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Results for “Determination and Control”

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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Energy efficiency based control for a cooling system

A method for controlling a cooling system based on a heat dissipation of an electronic module and an ambient air temperature includes determining a combination of individual controls on components of the cooling system that achieve a specific amount of cooling based on a cooling power relationship for the plurality of components, the heat dissipation of the electronic module and the ambient air temperature, and applying the individual controls to the plurality of components.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2022

Energy efficiency based control for a cooling system

A method for controlling a cooling system based on a heat dissipation of an electronic module and an ambient air temperature includes determining a combination of individual controls on components of the cooling system that achieve a specific amount of cooling based on a cooling power relationship for the plurality of components, the heat dissipation of the electronic module and the ambient air temperature, and applying the individual controls to the plurality of components.

Chainer, Timothy J.↗
DOE OSTI2022

Backpack electrofishing does not contribute to external signs of gas bubble trauma in sculpins

Abstract We exposed prickly sculpin Cottus asper and reticulate sculpin Cottus perplexus to electroshock and sham treatments in a controlled laboratory setting to determine if backpack electrofishing contributed to or exacerbated external signs of gas bubble trauma (GBT) in fish exposed to elevated total dissolved gas (TDG) levels. Fish were exposed to 115, 120 and 125% TDG (measured as percent of saturation) for various amounts of time (24–144 h) then subjected to a 5‐s electroshock or sham treatment of no electroshock. Fish were examined to determine the incidence of GBT pre‐ and post‐treatment, and all aspects (i.e., dorsal, ventral, left and right sides) of each fish were photographed. Across all TDG levels in all trials, no sculpin showed any change in GBT incidence following treatment. Analysis of GBT signs evident in photographs of 68 fish found no evidence of change in mean pre‐ and post‐treatment gas bubble sizes in fish in any TDG trial, nor were any new gas bubbles found following treatment. We are aware of no physiological mechanism by which backpack electrofishing can cause GBT in sculpin, and as such, we believe using this gear should not increase GBT incidence rates in sculpin.

Tiffan, Kenneth F.↗
DOE OSTI2023

A wide range experimental and kinetic modeling study of the oxidation of 2,3-dimethyl-2-butene: Part 1

2,3-Dimethyl-2-butene (TME) is a potential fuel additive with high research octane number (RON) and octane sensitivity (S), which can improve internal combustion engine performance and efficiency. However, the combustion characteristics of TME have not been comprehensively investigated. Thus, it is essential to study the combustion characteristics of TME and construct a detailed chemical kinetic model to describe its combustion. In this paper, two high-pressure shock tubes and a constant-volume reactor are used to measure ignition delay times and laminar flame speeds of TME oxidation. Further, the ignition delay times were measured at equivalence ratios of 0.5, 1.0, and 2.0 in “air”, at pressures of 5 and 10 bar, in the temperature range of 950 – 1500 K. Flame speeds of the TME/ “air” mixtures were measured at atmospheric pressure, at a temperature of 325 K, for equivalence ratios ranging from 0.78 to 1.31. Two detailed kinetic mechanisms were constructed independently using different methodologies; the KAUST TME mechanism was constructed based on NUIGMech1.1, and the MIT TME mechanism was built using the Reaction Mechanism Generator (RMG). Both mechanisms were used to simulate the experimental results using Chemkin Pro. In the present work, reaction flux and sensitivity analyses were performed using the KAUST mechanism to determine the critical reactions controlling TME oxidation at the conditions studied.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2020

Design and analysis of optimal pre-cooling in residential buildings

Existing pre-cooling strategies provide a means of shifting or reducing the peak demand and/or energy cost in residential buildings. However, majority of them are rule-based and therefore may not be optimal in terms of cost saving, leaving room for improvement. In this paper, an integer linear programming problem that accounts for the thermal properties of a specific home, HVAC system capacity, utility rate structure, and weather conditions and makes use of a home thermal model is formulated. This problem determines the HVAC on/off control signal that minimizes the 24-h energy cost while maintaining thermal comfort and calculates the corresponding optimal indoor air temperature. The model is constructed using home thermal properties identified via data training in real-time. Through simulation, the energy performance of the proposed optimal pre-cooling strategy is investigated and compared with three rule-based operation strategies from the literature. It is found that the optimal strategy requires the least energy consumption without sacrificing thermal comfort. The superb energy performance of the optimal strategy is attributed to a longer runtime of the HVAC system in cool outdoor air conditions and to the elimination of deadband in HVAC operation, which is required by the rule-based strategies, to allow the indoor air temperature to stay near the thermal comfort upper bound as much as possible. In terms of energy cost, the rule-based operation strategies require 3.52, 1.90, and 2.79, respectively, while the optimal strategy only requires 1.52. These figures represent a saving of 56.82%, 20.00%, and 45.52%, respectively. The results suggest that the optimal strategy is indeed significantly more effective than the existing rule-based operation strategies.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2021

In situ neutron diffraction study of fatigue behavior of CrFeCoNiMo 0.2 high entropy alloy

In situ neutron diffraction measurement was applied to study the low-cycle fatigue behavior of CrFeCoNiMo 0.2 high entropy alloy. A two-step stress-controlled fatigue test with a stress range of 100–460 and 20–500 MPa was employed. The as-cast sample was cycled 129,000 and 61,000 times, respectively, before fracture. The evolution of the lattice strain and peak intensity demonstrates that the main deformation mechanism is dislocation slip, while no evidence of stacking fault was found. A three-stage ratcheting was clearly observed. Under the stress-controlled mode, the experimentally determined dislocation density increases linearly with the ratcheting strain. Here, the increase of the dislocation density results in a decay of the ratcheting strain rate, which stabilizes the structure and is beneficial for fatigue resistance.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Spatial Microbial Respiration Variations in the Hyporheic Zones Within the Columbia River Basin

Abstract While the hyporheic zone (HZ) accounts for a significant portion of whole stream CO 2 concentrations, HZ respiration modeling studies are lacking in quantifying their contributions to the total CO 2 at large watershed/basin scales. Quantifying the contribution of anaerobic respiration is also underappreciated. This study used a carbon‐nitrogen‐coupled river corridor model to quantify HZ aerobic and anaerobic respiration and determined the key factors controlling their spatial variability within the Columbia River Basin (CRB). The modeled respiration patterns showed high spatial variability. Among the nine sub‐basins composing the CRB, the Lower Columbia and the Willamette, which receive higher precipitation, had higher respiration. Medium‐sized rivers (fourth to sixth orders) produced the highest aerobic and anaerobic respiration among reaches of different sizes. At the basin scale, aerobic respiration is dominant, representing approximately 98.7% of the total respiration across the CRB. While most of the reaches were dominant with aerobic respiration, reaches in agricultural land showed a relatively higher anaerobic respiration (18%) ratio. A variable importance analysis showed that hyporheic exchange flux controlled most of the spatial variability of HZ respiration, dominating over other physical variables such as residence time, stream dissolved organic carbon (DOC), nitrate, and dissolved oxygen (DO). The influence of substrate concentration (DOC and DO) is larger in modeling anaerobic respiration than aerobic respiration. Future efforts will focus on improving the estimation of the HZ exchange flux and the implementation of spatially explicit parameterizations for the reactions of interest to reduce model uncertainty.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Heterogenous electromediated depolymerization of highly crystalline polyoxymethylene

Abstract Post-consumer plastic waste in the environment has driven the scientific community to develop deconstruction methods that yield valued substances from these synthetic macromolecules. Electrocatalysis is a well-established method for achieving challenging transformations in small molecule synthesis. Here we present the first electro-chemical depolymerization of polyoxymethylene—a highly crystalline engineering thermoplastic (Delrin®)—into its repolymerizable monomer, formaldehyde/1,3,5-trioxane, under ambient conditions. We investigate this electrochemical deconstruction by employing solvent screening, cyclic voltammetry, divided cell studies, electrolysis with redox mediators, small molecule model studies, and control experiments. Our findings determine that the reaction proceeds via a heterogeneous electro-mediated acid depolymerization mechanism. The bifunctional role of the co-solvent 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) is also revealed. This study demonstrates the potential of electromediated depolymerization serving as an important role in sustainable chemistry by merging the concepts of renewable energy and circular plastic economy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Structural basis for dimerization quality control

Most quality control pathways target misfolded proteins to prevent toxic aggregation and neurodegeneration 1 . Dimerization quality control further improves proteostasis by eliminating complexes of aberrant composition 2 , but how it detects incorrect subunits remains unknown. Here we provide structural insight into target selection by SCF-FBXL17, a dimerization-quality-control E3 ligase that ubiquitylates and helps to degrade inactive heterodimers of BTB proteins while sparing functional homodimers. We find that SCF-FBXL17 disrupts aberrant BTB dimers that fail to stabilize an intermolecular β-sheet around a highly divergent β-strand of the BTB domain. Furthermore, complex dissociation allows SCF-FBXL17 to wrap around a single BTB domain, resulting in robust ubiquitylation. SCF-FBXL17 therefore probes both shape and complementarity of BTB domains, a mechanism that is well suited to establish quality control of complex composition for recurrent interaction modules.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Drying and Analysis of Aluminum (Oxy)hydroxide Films for Dry Storage of Aluminum-Clad Spent Nuclear Fuels

In aluminum-clad spent nuclear fuels, an (oxy)hydroxide layer on the surface of the cladding hosts chemisorbed water formed during reactor and post-discharge exposure to water. Any residual water is susceptible to generating hydrogen via radiolysis, which can be a risk associated with dry fuel storage. Engineering-scale forced helium dehydration (FHD) and vacuum drying tests were conducted on mock-up fuel assemblies that included corroded aluminum surrogate plates to assess the removal of bulk and chemisorbed water. Thermogravimetric analysis was performed on samples of the surrogate plates, both undried control samples used to determine onset temperatures associated with a phase change occurring in the oxide layer and samples from drying tests used to determine the effectiveness of each drying method. Both vacuum drying and FHD processes were capable of removing bulk water. However, FHD was determined to provide additional drying capabilities, including partial removal of chemisorbed water from bayerite due to the higher temperatures during drying. In conclusion, the temperature threshold for partial dehydroxylation of the oxide layer was determined to be around 220°C, meaning any drying methods attempting to remove chemisorbed water must exceed 220°C.

chemisorbed water↗
DOE OSTI2021

Demethylation or Sorption? The Fate of Methylmercury in the Presence of Manganese Dioxide

Manganese oxide (MnO 2 ) amendments to mercury (Hg)-contaminated sediment have been shown to decrease methylmercury (MeHg) concentrations in sediment porewater. In the absence of solid-phase MeHg measurements, it is unclear whether the decreased porewater concentrations are due to inhibition of methylation, adsorption of the MeHg to the MnO 2 , demethylation of MeHg catalyzed by the MnO 2 , or some combination of these mechanisms. We conducted controlled laboratory experiments to determine whether MeHg losses from solution in the presence of amorphous MnO 2 are due to sorption or demethylation. In this work, we quantified MeHg in the dissolved phase and solid phase and found that no demethylation occurred. We used batch and isotherm experiments to determine MeHg sorption efficiency to MnO 2 in a variety of solutions with varying ionic strength and dissolved organic matter (DOM) concentration. Isotherms over an initial concentration range of 5–500 ng/L of MeHg showed no saturation effects. Increasing ionic strength from 0.012 M to 0.1 M produced relatively minor decreases in MeHg sorption. Increasing DOM concentrations from 0.64 to 16.4 mg C/L yielded substantial decreases in MeHg sorption. Under the experimental conditions, MnO2 is a less efficient MeHg sorbent compared to other sorbent materials, such as Thiol-SAMMS®, activated carbon, and biochar.

42 ENGINEERING↗
DOE OSTI2023

A practical approach to determine minimal quantum gate durations using amplitude-bounded quantum controls

Here, we present an iterative scheme to estimate the minimal duration in which a quantum gate can be realized while satisfying hardware constraints on the control pulse amplitudes. The scheme performs a sequence of unconstrained numerical optimal control cycles that each minimize the gate fidelity for a given gate duration alongside an additional penalty term for the control pulse amplitudes. After each cycle, the gate duration is adjusted based on the inverse of the resulting maximum control pulse amplitudes by re-scaling the dynamics to a new duration where control pulses satisfy the amplitude constraints. Those scaled controls then serve as an initial guess for the next unconstrained optimal control cycle, using the adjusted gate duration. We provide multiple numerical examples that each demonstrate fast convergence of the scheme toward a gate duration that is close to the quantum speed limit, given the control pulse amplitude bound. The proposed technique is agnostic to the underlying system and control Hamiltonian models, as well as the target unitary gate operation, making the time-scaling iteration an easy to implement and practically useful scheme for reducing the durations of quantum gate operations.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2024

Investigating the Relative Contribution from Tropical Indo-Pacific SST to Asian Monsoon Precipitation Variability Using LIM

Abstract A critical issue is determining the factors that control the year-to-year variability in precipitation over southern Asia. In this study, we employ a cyclostationary linear inverse model (CS-LIM) to quantify the relative contribution of tropical Pacific and Indian Ocean sea surface temperature anomalies (SSTAs) to the interannual variability of the Asian monsoon, especially Indian summer monsoon rainfall (ISMR). Through a series of CS-LIM experiments, we isolate the impacts of the direct forcing from Pacific SSTAs, Indian Ocean SSTAs, and their interaction on Asian monsoon rainfall variability. Our results reveal distinct patterns of influence with the direct forcing from the Pacific (Indian) Ocean tending to enhance (reduce) the magnitude of precipitation variability, while the Indo-Pacific interaction acts to strongly damp the variability of Asian monsoon precipitation, especially over India. We further investigate these specific impacts on ISMR by analyzing the relationship between tropical Indo-Pacific SSTAs and the leading three empirical orthogonal functions (EOFs) of ISMR. The results from our CS-LIM experiments indicate that the direct forcing from El Niño–Southern Oscillation (ENSO) enhances the variability of the first and third EOFs, while the Indian Ocean SSTA opposes ENSO’s effects, which is consistent with previous studies. Our new results show that the tropical Indo-Pacific interaction strongly damps ISMR variability, which is due to the ENSO-induced Indian Ocean dipole (IOD) opposing the direct impacts from ENSO on ISMR. Additionally, reduced ENSO amplitude and duration associated with the Indo-Pacific interaction may also contribute to the damping effect on ISMR, but this requires further study to understand the relevant mechanisms.

Meteorology & Atmospheric Sciences↗
DOE OSTI2025

Exploring Uncertainty in Moment Estimation for Small Earthquakes in Southern Nevada Using the Coda Envelope Method

Compiling source parameter estimates for small earthquakes is important both for our understanding of earthquake physics and for accurately assessing earthquake hazard. Reliable source parameter estimates are difficult to achieve for small earthquakes, in part due to our inability to accurately model the relevant physical processes at high frequencies. The coda envelope methodology developed by Mayeda and Walter (1996) and Mayeda et al. (2003) can mitigate this concern and estimate the moment of small earthquakes by determining the parameters that control the shape of the S-wave coda envelope while eliminating path effects by minimizing the scatter between seismic stations. Here, we use an open-source implementation of this technique called the Coda Calibration Tool (CCT; Barno, 2017) to calculate CCT-based moment magnitude estimates of small earthquakes (M L 0–3) in the Rock Valley, Nevada, region within the Nevada National Security Site. The Rock Valley data set is of particular interest because it allows us to explore the changes in uncertainties of the coda calibration method with earthquake size and depth. We found that a consistent linear relationship exists between the local magnitude M L and our coda-derived M w estimates for earthquakes as small as M L 0–3, but that current CCT workflows do not accurately characterize very shallow events. We also demonstrate that the epistemic uncertainty in the apparent stress value assumed by the CCT algorithm can influence magnitude estimates of small earthquakes. In conclusion, these results provide valuable insight into the seismicity of this region, and inform future analysis and modeling efforts for nuclear monitoring and seismic hazard.

58 GEOSCIENCES↗
DOE OSTI2023

The application of parallel kinetic simulations to laser and electron transport through plasmas (Final technical report)

This is a final report for the grant entitled, “The application of parallel kinetic simulations to laser and electron transport through plasmas”. The objectives of this grant were to significantly advance the fundamental understanding of the nonlinear optics of plasmas and electron transport in high-energy-density laboratory plasmas (HEDLP), including conditions of relevance to Inertial Fusion Energy (IFE). The ultimate goal was to use the understanding to determine how to fully control laser plasma interactions. The primary research tools were our own kinetic particle-in-cell software, OSIRIS, that includes kinetic physics and can run effectively on leadership class computing facilities. Therefore, one objective was to ensure that OSIRIS in continually improved so that it was more accurate and could effectively utilize state-of-the-art computing facilities. Another objective was to attract and train young researchers into the field of high energy density plasma physics. To meet the research objectives, the funds from this proposal were used to conduct research on stimulated Raman scattering (SRS) and enhance our PIC software OSIRIS. It was found that small normalized magnetic fields can in some cases mitigate SRS and that speckles can mutually interact through SRS. It was also found that it is possible for instabilities drive near quarter critical (e.g., the high frequency hybrid instability-HFHI) can generate light waves that propagate back down a density gradient where they can rescatter into the HFHI at 1/16 of the original quarter critical density.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2026

Measurement of the \bar \nu_\mu- Hydrogen Charged-Current Elastic Cross Section in the NOvA Near Detector

We report a measurement of the total cross-section for muon antineutrino charged-current elastic scattering on hydrogen in the NOvA near detector using $12 \times 10^{20}$ protons-on-target in the NuMI beam, delivered from June 2016 to July 2019. An analysis based on topological and kinematic constraints allows the selection of the largest sample of (anti)neutrino-hydrogen interactions measured to date in the hydrogen-rich target (∼ 11%) of the NOvA detector. Backgrounds from (anti)neutrino interactions on heavier nuclei are determined using dedicated data control samples, significantly reducing the corresponding systematic uncertainties.

Talukdar, Nibir [South Carolina U., Aiken] (ORCID:↗
DOE OSTI2022

Sequential optical response suppression for chemical mixture characterization

The characterization of mixtures of non-interacting, spectroscopically similar quantum components has important applications in chemistry, biology, and materials science. We introduce an approach based on quantum tracking control that allows for determining the relative concentrations of constituents in a quantum mixture, using a single pulse which enhances the distinguishability of components of the mixture and has a length that scales linearly with the number of mixture constituents. To illustrate the method, we consider two very distinct model systems: mixtures of diatomic molecules in the gas phase, as well as solid-state materials composed of a mixture of components. A set of numerical analyses are presented, showing strong performance in both settings.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗