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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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Breaking the Supermassive Black Hole Speed Limit

A new computer simulation helps explain the existence of puzzling supermassive black holes observed in the early universe. The simulation is based on a computer code used to understand the coupling of radiation and certain materials. “Supermassive black holes have a speed limit that governs how fast and how large they can grow,” said Joseph Smidt of the Theoretical Design Division at Los Alamos National Laboratory. “The relatively recent discovery of supermassive black holes in the early development of the universe raised a fundamental question, how did they get so big so fast?” Using computer codes developed at Los Alamos for modeling the interaction of matter and radiation related to the Lab’s stockpile stewardship mission, Smidt and colleagues created a simulation of collapsing stars that resulted in supermassive black holes forming in less time than expected, cosmologically speaking, in the first billion years of the universe.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2019

Experiences from Field Testing for Black Start of a Run-of-the-river Hydropower Plant in Idaho Falls Power Distribution Grid

Idaho Falls Power (IFP) utility has local generation portfolio comprising of 56.3MVA of run-of-the-river (ROR) hydropower that can serve typically 25%-30% of the total load demand. The remaining load is served by importing power from Bonneville Power Administration through two Pacificorp transmission interconnections. In case of emergencies (power disruption or directed load reduction), the capability to island from transmission grid and stably serve critical loads in the IFP distribution grid can be a huge advantage. In this direction, the capability to black start with ROR is an essential requirement, and a challenge due to limited dispatchability and requires re-tuning of hydro-governor and excitation system controls. This paper presents the field experience from the testing done for black start of 8.9 MW ROR hydro plant in the IFP distribution grid using an adjustable load bank in December 2017. The lessons from the successful black start testing is presented along with test results to establish the potential value and requirements to develop black start capability with a ROR hydro plant.

13 HYDRO ENERGY↗
DOE OSTI2023

Investigating Multi-Microgrid Black Start Methods Using Grid-Forming Inverters: Preprint

This paper examines state-of-the-art microgrid (MG) black-start technologies with high IBR penetrations and proposes black-start and interconnection methods for 100% grid-forming (GFM) inverter-based MGs. A multiple-microgrid approach is proposed and compared to the existing methods in a 4-bus, 12-GFM inverter simulation test setup. This investigation involves intelligent synchronization units called "synchrobreakers," which enable the synchronization of multiple MGs based on their terminal measurements. MGs in this setup are held at different loading levels and comprise averaged models of GFM inverters with ideal voltage sources. The results of the black-start techniques are compared, and conclusions are drawn to better prepare MG planners and DSOs for the next-generation GFM inverter-based multi-MG black-start procedures.

black start↗
DOE OSTI2023

Parallel Grid-Forming Inverter-Driven Black Start: Power-Hardware-in-the-Loop Validation: Preprint

With power systems encountering increasing deployment levels of inverter-based resources (IBRs), system restoration using grid-forming (GFM) IBRs has gained attention. Engineered to establish grid voltages in the absence of a stiff grid, black-start-capable GFM IBRs are expected to enhance power system resilience by playing a critical role in bottom-up system restoration. This paper experimentally studies the feasibility of the novel approach through power-hardware-in-the-loop (PHIL) testing and validation with a commercial GFM inverter. The PHIL test setup demonstrates an inverter-driven black start of a 5-MW unbalanced distribution feeder where two GFM inverters collectively black start the feeder: one is a commercial hardware GFM inverter interacting through the PHIL interface, and the other is a software GFM emulated by a real-time simulation with full electromagnetic transient (EMT) models. Both GFM inverters are equipped with negative-sequence voltage control to suppress the voltage imbalance resulting from the unbalanced loading, allowing us to study the dynamic interactions between the GFMs with their control parameters unknown. To evaluate the dynamic behavior of the GFM inverters under the entire black-start process, the EMT model of the distribution system details the transformer and motor dynamics to emulate their inrush and startup behaviors. It abstracts conventional grid-connected inverter dynamics, i.e., grid-following inverters. Oscilloscope measurements of the hardware GFM inverter are also presented for critical steps. Takeaways for further study and field deployment are provided.

grid-forming inverter↗
DOE OSTI2024

Ladder symmetries and Love numbers of Reissner-Nordström black holes

It is well known that asymptotically flat black holes in general relativity have vanishing tidal Love numbers. In the case of Schwarzschild and Kerr black holes, this property has been shown to be a consequence of a hidden structure of ladder symmetries for the perturbations. In this work, we extend the ladder symmetries to non-rotating charged black holes in general relativity. As opposed to previous works in this context, we adopt a more general definition of Love numbers, including quadratic operators that mix gravitational and electromagnetic perturbations in the point-particle effective field theory. We show that the calculation of a subset of those couplings in full general relativity is affected by an ambiguity in the split between source and response, which we resolve through an analytic continuation. As a result, we derive a novel master equation that unifies scalar, electromagnetic and gravitational perturbations around Reissner-Nordström black holes. The equation is hypergeometric and can be obtained from previous formulations via nontrivial field redefinitions, which allow to systematically remove some of the singularities and make the presence of the ladder symmetries more manifest.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Dark radiation and superheavy dark matter from black hole domination

If even a relatively small number of black holes were created in the early universe, they will constitute an increasingly large fraction of the total energy density as space expands. It is thus well-motivated to consider scenarios in which the early universe included an era in which primordial black holes dominated the total energy density. Within this context, we consider Hawking radiation as a mechanism to produce both dark radiation and dark matter. If the early universe included a black hole dominated era, we find that Hawking radiation will produce dark radiation at a level $\Delta N_{\rm eff} \sim 0.03-0.2$ for each light and decoupled species of spin 0, 1/2, or 1. This range is well suited to relax the tension among late and early-time Hubble determinations, and is within the reach of upcoming CMB experiments. The dark matter could additionally originate as Hawking radiation in a black hole dominated early universe, although such dark matter candidates must be very heavy ($m_{\rm DM} >10^{11}$ GeV) if they are to avoid exceeding the measured abundance.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Simple holographic models of black hole evaporation

Several recent papers have shown a close relationship between entanglement wedge reconstruction and the unitarity of black hole evaporation in AdS/CFT. The analysis of these papers however has a rather puzzling feature: all calculations are done using bulk dynamics which are essentially those Hawking used to predict information loss, but applying ideas from entanglement wedge reconstruction seems to suggest a Page curve which is consistent with information conservation. Why should two different calculations in the same model give different answers for the Page curve? In this note we present a new pair of models which clarify this situation. Our first model gives a holographic illustration of unitary black hole evaporation, in which the analogue of the Hawking radiation purifies itself as expected, and this purification is reproduced by the entanglement wedge analysis. Moreover a smooth black hole interior persists until the last stages the evaporation process. Our second model gives an alternative holographic interpretation of the situation where the bulk evolution leads to information loss: unlike in the models proposed so far, this bulk information loss is correctly reproduced by the entanglement wedge analysis. This serves as an illustration that quantum extremal surfaces are in some sense kinematic: the time-dependence of the entropy they compute depends on the choice of bulk dynamics. In both models no bulk quantum corrections need to be considered: classical extremal surfaces are enough to do the job. We argue that our first model is the one which gives the right analogy for what actually happens to evaporating black holes, but we also emphasize that any complete resolution of the information problem will require an understanding of non-perturbative bulk dynamics.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Towards quantum black hole microstates

Abstract We study the cohomology of local BPS operators in$$ \mathcal{N} $$ N = 4 Yang-Mills theory. The finiteNcohomologies consist of the graviton part (subject to the stringy exclusion principle) and the rest which may describe black hole microstates in quantum AdS/CFT. We construct an infinite tower of non-graviton cohomologies in the SU(2) theory and study to what extent they simulate quantum black holes. We find signals for partial no-hair behaviors by showing that certain gravitons are forbidden to dress these cohomologies. This is in qualitative agreement with the perturbative hairs allowed around black holes, which also leads us to a natural setup to construct hairy BPS black holes. The cohomologies are simpler to study in the BMN matrix model truncation of the classical field theory.

Physics↗
DOE OSTI2017

Breastfeeding and Breast Cancer Risk Reduction: Implications for Black Mothers

Breast cancer is the most commonly diagnosed cancer and a leading cause of death from cancer among U.S. women. Studies have suggested that breastfeeding reduces breast cancer risk among parous women, and there is mounting evidence that this association may differ by subtype such that breastfeeding may be more protective of some invasive breast cancer types. The purpose of this review is to discuss breast cancer disparities in the context of breastfeeding and the implications for black mothers. Black women in the U.S. have lower rates of breastfeeding and nearly twice the rates of triple-negative breast cancer (an aggressive subtype) compared with white women. In addition to individual challenges to breastfeeding, black women may also differentially face contextual barriers such as a lack of social and cultural acceptance in their communities, inadequate support from the healthcare community, and unsupportive work environments. More work is needed to improve the social factors and policies that influence breastfeeding rates at a population level. Such efforts should give special consideration to the needs of black mothers to adequately address disparities in breastfeeding among this group and possibly help reduce breast cancer risk. Interventions such as peer counseling, hospital policy changes, breastfeeding-specific clinic appointments, group prenatal education, and enhanced breastfeeding programs have been shown to be effective in communities of color. A comprehensive approach that integrates interventions across multiple levels and settings may be most successful in helping mothers reach their breastfeeding goals and reducing disparities in breastfeeding and potentially breast cancer incidence.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Missing in axion: Where are XENON1T’s big black holes?

We pioneer the black hole mass gap as a powerful new tool for constraining new particles. A new particle that couples to the Standard Model – such as an axion – acts as an additional source of loss in the cores of population-III stars, suppressing mass lost due to winds and quenching the pair-instability. This results in heavier astrophysical black holes. As an example, using stellar simulations we show that the solar axion explanation of the recent XENON1T excess implies astrophysical black holes of ~56M ⊙ , squarely within the black hole mass gap predicted by the Standard Model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Hydrogen incorporation by plasma treatment gives mesoporous black TiO 2 thin films with visible photoelectrochemical water oxidation activity

In this work, we use neutron reflectometry (NR) to investigate the roles of hydrogen in plasma treated hydrogen doped mesoporous black titania thin films in their visible light absorption and enhanced photoactivity for water oxidation. The cubic ordered mesoporous TiO 2 thin films are prepared by a surfactant-templated sol-gel method and are treated with hydrogen plasma, an approach hypothesized to capitalize on the high degree of disorder in the material and the high energy of the plasma species to achieve efficient hydrogen doping. UV-vis absorbance spectra indicate that H 2 plasma treatment makes TiO 2 films black, with broad-spectrum enhancement of visible light absorption, and XPS analysis shows peak for Ti 3+ state in treated films. The presence of hydrogen in black mesoporous titania (H-TiO 2 ) films is confirmed by the scattering length density (SLD) profiles obtained from neutron reflectometry measurements. The H-TiO 2 shows ca. 28 times and 8 times higher photocurrent for photoelectrochemical water oxidation compared to undoped TiO 2 films under UV (365 nm) and blue (455 nm) LED irradiation, respectively. These findings provide the first direct evidence that the dramatic change in visible light absorbance of H-treated black TiO 2 is accompanied by significant hydrogen uptake and not just Ti 3+ generation or surface disordering.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Cold black holes in the Harlow–Hayden approach to firewalls

Firewalls are controversial principally because they seem to imply departures from general relativistic expectations in regions of spacetime where the curvature need not be particularly large. One of the virtues of the Harlow–Hayden approach to the firewall paradox, concerning the time available for decoding of Hawking radiation emanating from charged AdS black holes, is precisely that it operates in the context of cold black holes, which are not strongly curved outside the event horizon. Here we clarify this point. The approach is based on ideas borrowed from applications of the AdS/CFT correspondence to the quark–gluon plasma. Firewalls aside, our work presents a detailed analysis of the thermodynamics and evolution of evaporating charged AdS black holes with flat event horizons. We show that, in one way or another, these black holes are always eventually destroyed in a time which, while long by normal standards, is short relative to the decoding time of Hawking radiation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

An ethanolic extract of black cohosh causes hematological changes but not estrogenic effects in female rodents

Black cohosh rhizome (Actaea racemosa) is used as a remedy for pain and gynecological ailments; modern preparations are commonly sold as ethanolic extracts available as dietary supplements. Black cohosh was nominated to the National Toxicology Program (NTP) for toxicity testing due to its widespread use and lack of safety data. Several commercially available black cohosh extracts (BCE) were characterized by the NTP, and one with chemical composition closest to formulations available to consumers was used for all studies. Female B6C3F1/N mice and Wistar Han rats were given 0, 15 (rats only), 62.5 (mice only), 125, 250, 500, or 1000 mg/kg/day BCE by gavage for 90 days starting at weaning. BCE induced dose-dependent hematological changes consistent with a non-regenerative macrocytic anemia and increased frequencies of peripheral micronucleated red blood cells (RBC) in both species. Effects were more severe in mice, which had decreased RBC counts in all treatment groups and increased micronucleated RBC at doses above 125 mg/kg. Dose-dependent thymus and liver toxicity was observed in rats but not mice. No biologically significant effects were observed in other organs. Puberty was delayed 2.9 days at the highest treatment dose in rats; a similar magnitude delay in mice occurred in the 125 and 250 mg/kg groups but not at the higher doses. An additional uterotrophic assay conducted in mice exposed for 3 days to 0.001, 0.01, 0.1, 1, 10, 100 and 500 mg/kg found no estrogenic or anti-estrogenic activity. These are the first studies to observe adverse effects of BCE in rodents. -- Highlights: ► Mice and rats were dosed with black cohosh extract for 90 days starting at weaning. ► Hematological changes were consistent with a non-regenerative macrocytic anemia. ► Peripheral micronucleated red blood cell frequencies increased. ► Puberty was delayed 2.9 days in rats. ► No estrogenic/anti-estrogenic activity was seen in the uterotrophic assay.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2016

Application of Black Silicon for Nanostructure-Initiator Mass Spectrometry

Nanostructure-initiator mass spectrometry (NIMS) is a matrix-free desorption/ionization technique with high sensitivity for small molecules. Surface preparation has relied on hydrofluoric acid (HF) electrochemical etching which is undesirable given the significant safety controls required in this specialized process. Here in this study, we examine a conventional and widely used process for producing black silicon based on sulfur hexafluoride/oxygen (SF 6 /O 2 ) inductively coupled plasma (ICP) etching at cryogenic temperatures and we find it to be suitable for NIMS. A systematic study varying parameters in the plasma etching process was performed to understand the relationship of black silicon morphology and its sensitivity as a NIMS substrate. The results suggest that a combination of higher silicon temperature and oxygen flow rate gives rise to the formation of black silicon with fine pillar structures, whose aspect ratio are ~8.7 and depth are <1 μm resulting in higher NIMS sensitivity which is attributed to surface restructuring caused by their low melting point upon laser irradiation. Interestingly, we find selectivity of these black silicon substrates to different analytes depending on the etching parameters. Though, the sensitivity of the dry etching process is lower than the traditional "wet" electrochemical etching process, it is suitable for many applications and is prepared using conventional equipment without the use of HF.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Conducting interface in oxide homojunction: Understanding of superior properties in black TiO 2

Black TiO 2 nanoparticles with a crystalline core and amorphous-shell structure exhibit superior optoelectronic properties in comparison with pristine TiO 2 . The fundamental mechanisms underlying these enhancements, however, remain unclear, largely due to the inherent complexities and limitations of powder materials. Here, we fabricate TiO 2 homojunction films consisting of an oxygen-deficient amorphous layer on top of a highly crystalline layer, to simulate the structural/functional configuration of black TiO 2 nanoparticles. Metallic conduction is achieved at the crystalline–amorphous homointerface via electronic interface reconstruction, which we show to be the main reason for the enhanced electron transport of black TiO 2 . As a result, this work not only achieves an unprecedented understanding of black TiO 2 but also provides a new perspective for investigating carrier generation and transport behavior at oxide interfaces, which are of tremendous fundamental and technological interest.

36 MATERIALS SCIENCE↗
DOE OSTI2017

An 800-million-solar-mass black hole in a significantly neutral Universe at a redshift of 7.5

Quasars are the most luminous non-transient objects known and as a result they enable studies of the Universe at the earliest cosmic epochs. Despite extensive efforts, however, the quasar ULAS J1120 + 0641 at redshift z = 7.09 has remained the only one known at z > 7 for more than half a decade. Here we report observations of the quasar ULAS J134208.10 + 092838.61 (hereafter J1342 + 0928) at redshift z = 7.54. This quasar has a bolometric luminosity of 4 × 10 13 times the luminosity of the Sun and a black-hole mass of 8 × 10 8 solar masses. The existence of this supermassive black hole when the Universe was only 690 million years old—just five per cent of its current age—reinforces models of early black-hole growth that allow black holes with initial masses of more than about 104 solar masses or episodic hyper-Eddington accretion. We see strong evidence of absorption of the spectrum of the quasar redwards of the Lyman α emission line (the Gunn–Peterson damping wing), as would be expected if a significant amount (more than 10 per cent) of the hydrogen in the intergalactic medium surrounding J1342 + 0928 is neutral. We derive such a significant fraction of neutral hydrogen, although the exact fraction depends on the modelling. However, even in our most conservative analysis we find a fraction of more than 0.33 (0.11) at 68 per cent (95 per cent) probability, indicating that we are probing well within the reionization epoch of the Universe.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Properties of Disorder-Engineered Black Titanium Dioxide Nanoparticles through Hydrogenation

The recent discovery of ‘‘black’’ TiO2 nanoparticles with visible and infrared absorption has triggered an explosion of interest in the application of TiO2 in a diverse set of solar energy systems; however, what a black TiO2 nanoparticle really is remains a mystery. Here we elucidate more properties and try to understand the inner workings of black TiO2 nanoparticles with hydrogenated disorders in a surface layer surrounding a crystalline core. Contrary to traditional findings, Ti31 here is not responsible for the visible and infrared absorption of black TiO2, while there is evidence of mid-gap states above the valence band maximum due to the hydrogenated, engineered disorders. The hydrogen atoms, on the other hand, can undergo fast diffusion and exchange. The enhanced hydrogen mobility may be explained by the presence of the hydrogenated, disordered surface layer. This unique structure thus may give TiO2, one of the most-studied oxide materials, a renewed potential.

NANOPARTICLES↗
DOE OSTI2014

Synthesis and characterization of black, red and yellow nanoparticles pigments from the iron sand

The aim of this research is to synthesize nanoparticles of black pigment of Magnetite (Fe{sub 3}O{sub 4}), red pigment of hematite (α-Fe{sub 2}O{sub 3}), and yellow pigment of ghoetite (α-FeOOH) from the iron sand. The black pigment of Fe{sub 3}O{sub 4} and the yellow pigment α-FeOOH nanoparticles were synthesized by coprecipitation method with variation of pH. Whereas, the red pigment Fe{sub 2}O{sub 3} was synthesized by sintering Fe{sub 3}O{sub 4} nanoparticles at temperature between 400 °C and 700 7°C for 1 hour. All the pigments has been characterized using X-ray diffraction and SEM. The XRD results shown that the particle size of the black pigmen Fe{sub 3}O{sub 4}, red pigment Fe{sub 3}O{sub 4} and yellow pigment α-FeOOH are around 12, 32, and 30 nm respectively. The particle size of Fe{sub 2}O{sub 3} nanoparticles increase by increasing sintering temperature from 32 nm at 400 °C to 39 nm at 700 °C. For yellow pigment of α-FeOOH, the particle size increase by increasing pH from 30,54 nm at pH 4 to 48,60 nm at pH 7. The SEM results shown that the morphologies of black, yellow and red pigments are aglomarated.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗