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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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We use a sample of ~340 low surface brightness (LSB) disk galaxies with measured redshifts in combination with the Center for Astrophysics redshift survey to test the hypothesis that LSB galaxies have a deficit of nearby companion galaxies compared to high surface brightness (HSB) disk galaxies.
A variety of evidence suggests that at least 50% of low-mass stars are surrounded by disks of the gas and dust similar to the nebula that surrounded the Sun, before the formation of the planets. The properties of these disks may bear strongly on the way in which planetary systems form and evolve.
By 2025, it is estimated that installed data storage in the US will be 2.2 Zettabytes, generating about 50 million units of end-of-life hard-disk drives (HDDs) per year. The circular economy tackles waste issues by maximizing value retention in the economy, for instance, through reuse and recycling. However, the reuse of hard disk drives is hindered by the lack of trust organizations have toward other means of data removal than physically destroying HDDs. Here, an agent-based approach explores how organizations’ decisions to adopt other data removal means affect HDDs circularity. The model applies the theory of planned behaviour to model the decisions of HDDs end-users. Results demonstrate that the attitude (which is affected by trust) of end-users toward data-wiping technologies acts as a barrier to reuse. Moreover, social pressure can play a significant role as organizations that adopt CE behaviours can set an example for others.
We investigate the disk partition function for the open string. This is a subtle problem because of the presence of a residual gauge group PSL(2, R) on the worldsheet even after fixing the conformal gauge. It naively has infinite volume and leads to a vanishing answer. We use different methods that all demonstrate that PSL(2, R) effectively behaves like a group with finite negative volume in the path integral, which leads to a simple prescription for the computation of the disk partition function. We apply our findings to give a simple rederivation of the D-brane tensions.
Abstract As Setti and Woltjer noted back in 1973, one can use quasars to construct the Hubble diagram; however, the actual application of the idea was not that straightforward. It took years to implement the proposition successfully. Most ways to employ quasars for cosmology now require an advanced understanding of their structure, step by step. We briefly review this progress, with unavoidable personal biases, and concentrate on bright unobscured sources. We will mention the problem of the gas flow character close to the innermost stable circular orbit near the black hole, as discussed five decades ago. This problem later led to the development of the slim disk scenario and is recently revived in the context of Magnetically Arrested Disks (MAD) and Standard and Normal Evolution (SANE) models. We also discuss the hot or warm corona issue, which is still under debate and complicates the analysis of X-ray reflection. We present the scenario of the formation of the low ionization part of the Broad Line Region as a failed wind powered by radiation pressure acting on dust (Failed Radiatively Driven Dusty Outflow – FRADO). Next, we examine the cosmological constraints currently achievable with quasars, primarily concentrating on light echo methods (continuum time delays and spectral-line time delays to the continuum) that are (or should be) incorporating the progress mentioned above. Finally, we briefly discuss prospects in this lively subject area.
Throughout this work, large amplitude magnetization dynamics in elliptical permalloy nano-disks are studied via simulation of the Landau-Lifshitz equation. When the external magnetic field is applied in the plane of the disk two low-lying resonant modes exist. The higher frequency mode corresponds to the Kittel-like uniform ferromagnetic resonance mode and is consistent with previous experimental observations. The second mode with the lower frequency, termed the "cap mode", is localized near the two ends of the ellipse. At certain fields the ratio of the frequencies of these modes is equal to two or three and here one can efficiently generate the Kittel mode as the 2nd or 3rd harmonic of the "cap mode" when the magnitude of the input microwave field is of order 0.1 Oe, which can easily be achieved in practice. The nonlinear responses depend strongly on the equilibrium, field-dep-endent, behavior of the magnetization which is non-uniform and displays features not captured by the Stoner-Wohlfarth model for an ellipsoid.
Here, this study introduces an airfoil-based refinement technique to enhance the Actuator Disk Model (ADM) for improved wind turbine aerodynamic load prediction and structural simulation in conjunction with Large Eddy Simulations of the wind flow. While ADM offers higher computational efficiency than the more detailed but resource-intensive Actuator Line Model (ALM), it traditionally lacks the resolution needed to capture the localized blade forces accurately. To address this limitation, we introduce a refinement technique that uses airfoil-specific data and employs interpolation-based grid point refinement, achieving ALM-comparable accuracy while preserving ADM's efficiency. Unlike conventional ADM that provides only rotor-disk averaged forces, our synthetic method tracks transient aerodynamic load variations over multiple blade revolutions, allowing us to calculate the distributions of maximum and minimum loads during typical cycles. Applied to the NREL 5 MW reference turbine, our enhanced ADM accurately predicts key aerodynamic parameters (angle of attack, axial velocity, lift, drag, axial and tangential forces along the blades) as well as structural responses (blade tip deflection, maximum stress, and stress concentration). Our results show that the tip deflection ranges from 2.33m (3.69 % of blade length) to 4.28m (6.79 %), with maximum stress concentration occurring near the blade root. This research demonstrates that a refined synthetic ADM approach can serve as a computationally efficient alternative for both aerodynamic analysis and structural simulation of wind turbine blades subjected to realistic wind fields.
Abstract We present fitting formulae for the dynamical ejecta properties and remnant disk masses from the largest to date sample of numerical relativity simulations. The considered data include some of the latest simulations with microphysical nuclear equations of state (EOS) and neutrino transport as well as other results with polytropic EOS available in the literature. Our analysis indicates that the broad features of the dynamical ejecta and disk properties can be captured by fitting expressions, that depend on mass ratio and reduced tidal parameter. The comparative analysis of literature data shows that microphysics and neutrino absorption have a significant impact on the dynamical ejecta properties. Microphysical nuclear EOS lead to average velocities smaller than polytropic EOS, while including neutrino absorption results in larger average ejecta masses and electron fractions. Hence, microphysics and neutrino transport are necessary to obtain quantitative models of the ejecta in terms of the binary parameters.
There is irresistible observational evidence that binary systems of compact objects with at least one neutron star are progenitors of short gamma-ray bursts, as well as a production site for r -process elements, at least when some matter is ejected by the merger and an accretion disk is formed. Here, the recent observations of gravitational waves in conjunction with electromagnetic counterparts fuel the need for models predicting the outcome of a given merger and the properties of the associated matter outflows as a function of the initial parameters of the binary. In this manuscript, we provide updated fitting formulas that estimate the disk mass for double neutron star binaries and ejecta masses for black hole–neutron star and double neutron star binaries, fitted to the results of numerical simulations. Our proposed fitting formulas improve on existing models by aiming for analytical simplicity, by covering a larger region of parameter space, and by accounting for regions of parameter space not covered by numerical simulations but with physically manifest merger outcomes.
Under the influence of oscillatory shear, a monolayer of frictional granular disks exhibits two dynamical phase transitions: a transition from an initially disordered state to an ordered crystalline state and a dynamic active-absorbing phase transition. Although there is no reason a priori for these to be at the same critical point, they are. Also, the transitions may also be characterized by the disk trajectories, which are nontrivial loops breaking time-reversal invariance.
Understanding the current response at an electrode from suspended solid particles in an electrolyte is crucial for developing materials to be used in semi-solid electrodes for energy storage applications. Here, an analytical model is proposed to predict and understand the current response from non-disintegrable solid particles at a rotating disk electrode. The current is shown to be limited by a combination of ion diffusion within the solid particle and the mean residence time of the particle at the rotating disk electrode. This results in a relationship between current and angular frequency of I ∝ ω 3 / 4 , instead of the classical I ∝ ω 1 / 2 predicted by Levich theory. Specifically, the current response of Li 4 Ti 5 O 12 (LTO) microparticles suspended in a non-aqueous electrolyte of lithium hexafluorophosphate (LiPF 6 ) in ethylene carbonate: diethyl carbonate (EC:DEC) was determined experimentally and compared favorably with predictions from the proposed analytical model using fitting parameters consistent with the experimental conditions.
Aldehydes are selectively oxidized to carboxylates on group 11 metals at low potentials (<0.4 V vs. RHE) in alkaline media. This process can occur by a pathway that generates H 2 gas from the aldehyde, known as electro-oxidative dehydrogenation (EOD) or anodic hydrogen production. The EOD process occurs with transfer of only one electron per aldehyde, whereas typical oxidation with discharge of hydrogen to form water is a two-electron process. Here, we study the catalytic activity and selectivity toward H 2 of Au, Ag, and Cu electrodes using benzaldehyde with rotating disk and ring-disk electrode (RDE/RRDE) techniques. The average number of electrons per benzaldehyde molecule obtained via H 2 detection by RRDE agrees with that obtained via Koutecký-Levich analysis conducted at various rotation rates. We find that Au and Ag have much higher H 2 and benzoate formation rates than Cu, but that Cu can perform the reaction at about 0.2 V lower overpotentials. On all three materials, benzaldehyde oxidation has high selectivity to anodic H 2 (one-electron pathway) below ∼0.5 V vs. RHE, but, with increasing potential, the selectivity shifts to H-oxidation forming water (two-electron pathway).
A novel type of Yb:YAG transparent ceramic thin disk laser amplifier is demonstrated, based on fabricating a composite gain element with a paraboloidal interface between gain and no-gain regions and employing side-pumping of the thin disk. The pump-induced gain and the impact of amplified spontaneous emission on the achievable inversion are reported.
99 Mo production with linear accelerators can be achieved via the bremsstrahlung photonuclear reaction 100 Mo(γ,n) 99 Mo or the neutron capture reaction 98 Mo(n,γ) 99 Mo. For commercial producers, maximum recovery of enriched 98 Mo and 100 Mo target material is critical for sustaining an economic production cycle. During the peroxide dissolution of Mo metal disks and subsequent conversion to K 2 MoO 4 , several grams of Mo can be lost during filtration from solution when several hundred grams of sintered Mo disks are processed. This investigation shows that 5–8 g Mo is routinely retained on the filter units, but it can be almost fully recovered using aqueous washes. Washing can be done immediately and incorporated into the dissolution procedure, or it can occur several months after the initial filtration process to decrease processing time.
Histograms of mass of a given ratio of electron to baryon number in winds from a post-merger disk for four disks of different masses. This ratio determines how many elements heavier than iron, if any, are produced by a black hole-neutron star merger event. Analysis performed by PhD student Sanjana Curtis (NCSU, now graduated) on Capulin in collaboration with her advisor, Carla Frohlich, and LANL staff Jonah Miller.
Magnetic Field in the azimuthal (orbital) direction in an accretion disk formed after the in-spiral and merger of two neutron stars. Color is magnetic field strength (in code units). X-axis is time in seconds and y-axis is dimensionless height in the disk, in units of scale height. The characteristic butterfly pattern indicates onset of the magnetohydrodynamic dynamo and the magnetorotational instability. Simulations performed by graduate student Kelsey Lund working with LANL scientists Jonah Miller and Matt Mumpower and PhD advisor Gail McLaughlin at North Carolina State University
We simulate a black hole accretion disk system with full-transport general relativistic neutrino radiation magnetohydrodynamics for 1.2 s. This system is likely to form after the merger of two compact objects and is thought to be a robust site of r-process nucleosynthesis. We consider the case of a black hole accretion disk arising from the merger of two neutron stars. Our simulation time coincides with the nucleosynthesis timescale of the r-process (~1 s). Because these simulations are time-consuming, it is common practice to run for a “short” duration of approximately 0.1–0.3 s. We analyze the nucleosynthetic outflow from this system and compare the results of stopping at 0.12 and 1.2 s. We find that the addition of mass ejected in the longer simulation as well as more favorable thermodynamic conditions from emergent viscous ejecta greatly impacts the nucleosynthetic outcome. We quantify the error in nucleosynthetic outcomes between short and long cuts.
In this poster, we first provide motivation for why rare earth elements as rare earth permanent magnets (REPM) are increasing in demand. We then highlight some of the recent work that has been done by several national labs (National Renewable Energy Laboratory (NREL), Environmental Protection Agency (EPA), Critical Minerals Institute (CMI)) on recycling rare earth elements from end-of-life hard disk drives (EOL). Then, we mention our long-term plan to design a feedstock agnostic process to recover rare earth elements as rare earth oxides from many different EOL products at once. Next, we discuss how we quantified the rare earth elements available for recycling from EOL hard disk drives from consumer desktops and laptops. We then discuss how we used superstructure optimization to design the optimal pathway. The proposed superstructure was modeled as a MILP optimization problem, selecting the net present value as the objective function. Costing data from the literature was used to inform this model whenever possible. However, due to the novelty of this research area, data were often unavailable, thus requiring the generation of flowsheets implemented in Aspen Plus.