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DOE OSTI2013

xsapr (i0)

The X-band Scanning ARM Precipitation Radar (X-SAPR) is an X-band dual-polarization Doppler weather radar. The X-SAPR operates in a simultaneous transmit and receive (STAR) mode, meaning that the transmit signal is split so that power is transmitted on both horizontal and vertical polarizations at the same time. The X-SAPR transmitter is a 200 kW (peak power) magnetron. The receiver is based upon the Vaisala RVP-900 and runs Vaisala’s IRIS software. In addition to the first three Doppler moments (reflectivity, radial velocity, and spectra width), the X-SAPR also provides differential reflectivity, correlation coefficient, and specific differential phases. The dual-polarization variables enable estimates of rainfall rates and identification of precipitation types. At the Southern Great Plains site, three X-SAPRs surround the Central Facility, allowing the use of multi-Doppler velocity retrievals to estimate wind fields.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2026

X-Band Scanning ARM Precipitation Radar, CF/Radial Formatted, Quality Controlled

xsaprcfrqc↗

DOE OSTI2015

Spatially extended and high-velocity dispersion molecular component in spiral galaxies: Single-dish versus interferometric observations

Recent studies of the molecular medium in nearby galaxies have provided mounting evidence that the molecular gas can exist in two phases: one that is clumpy and organized as molecular clouds and another one that is more diffuse. This last component has a higher velocity dispersion than the clumpy one. In order to investigate these two molecular components further, we compare the fluxes and line widths of CO in NGC 4736 and NGC 5055, two nearby spiral galaxies for which high-quality interferometric as well as single-dish data sets are available. Our analysis leads to two main results: (1) employing three different methods, we determine the flux recovery of the interferometer as compared to the single-dish to be within a range of 35%–74% for NGC 4736 and 81%–92% for NGC 5055, and (2) when focusing on high (S/N ≥ 5) lines of sight (LOSs), the single-dish line widths are larger by ∼(40 ± 20)% than the ones derived from interferometric data, which is in agreement with stacking all LOSs. These results point to a molecular gas component that is distributed over spatial scales larger than 30″(∼1 kpc), and is therefore filtered out by the interferometer. The available observations do not allow us to distinguish between a truly diffuse gas morphology and a uniform distribution of small clouds that are separated by less than the synthesized beam size (∼3″ or ∼100 pc), as they would both be invisible for the interferometer. This high velocity dispersion component has a dispersion similar to what is found in the atomic medium, as traced through observations of the H i line.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2014

Initial phase zone for phase locking to the resonance, using “main condition” of phase stability in DC-biased single-sided multipactor

In the present work, the concept of accurate phase stability is employed to study a DC-biased single-sided multipactor. A “main condition” of phase stability was introduced in our previous studies of two-sided multipactors [M. Mostajeran, J. Instrum. 8, P04024 (2013); M. Mostajeran and M. Lamehi Rachti, Nucl. Instrum. Methods Phys. Res. A 615, 1–5 (2010)]. Using the same condition and assuming zero initial velocity for the secondary electrons, a regime of multipactors outside the resonance zones is found. The theoretical results are then verified by numerical simulation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2013

DIAGNOSTICS OF AGN-DRIVEN MOLECULAR OUTFLOWS IN ULIRGs FROM HERSCHEL-PACS OBSERVATIONS OF OH AT 119 μm

We report on our observations of the 79 and 119 μm doublet transitions of OH for 24 local (z < 0.262) ULIRGs observed with Herschel-PACS as part of the Herschel ULIRG Survey (HERUS). Some OH 119 μm profiles display a clear P-Cygni shape and therefore imply outflowing OH gas, while other profiles are predominantly in absorption or are completely in emission. We find that the relative strength of the OH emission component decreases as the silicate absorption increases. This result locates the OH outflows inside the obscured nuclei. The maximum outflow velocities for our sources range from less than 100 to ∼2000 km s{sup –1}, with 15/24 (10/24) sources showing OH absorption at velocities exceeding 700 km s{sup –1} (1000 km s{sup –1}). Three sources show maximum OH outflow velocities exceeding that of Mrk231. Since outflow velocities above 500-700 km s{sup –1} are thought to require an active galactic nucleus (AGN) to drive them, about two-thirds of our ULIRG sample may host AGN-driven molecular outflows. This finding is supported by the correlation we find between the maximum OH outflow velocity and the IR-derived bolometric AGN luminosity. No such correlation is found with the IR-derived star formation rate. The highest outflow velocities are found among sources that are still deeply embedded. We speculate that the molecular outflows in these sources may be in an early phase of disrupting the nuclear dust veil before these sources evolve into less-obscured AGNs. Four of our sources show high-velocity wings in their [C II] fine-structure line profiles, implying neutral gas outflow masses of at least (2-4.5) × 10{sup 8} M{sub ☉}.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2014

Self-sustained turbulence without dynamical forcing: A two-dimensional study of a bistable interstellar medium

In this paper, the nonlinear evolution of a bistable interstellar medium is investigated using two-dimensional simulations with a realistic cooling rate, thermal conduction, and physical viscosity. The calculations are performed using periodic boundary conditions without any external dynamical forcing. As the initial condition, a spatially uniform unstable gas under thermal equilibrium is considered. At the initial stage, the unstable gas quickly segregates into two phases: cold neutral medium (CNM) and warm neutral medium (WNM). Then, self-sustained turbulence with velocity dispersion of 0.1-0.2 km s{sup –1} is observed in which the CNM moves around in the WNM. We find that the interfacial medium (IFM) between the CNM and WNM plays an important role in sustaining the turbulence. The self-sustaining mechanism can be divided into two steps. First, thermal conduction drives fast flows streaming into concave CNM surfaces toward the WNM. The kinetic energy of the fast flows in the IFM is incorporated into that of the CNM through the phase transition. Second, turbulence inside the CNM deforms interfaces and forms other concave CNM surfaces, leading to fast flows in the IFM. This drives the first step again and a cycle is established by which turbulent motions are self-sustained.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2014

Theoretical model for plasma expansion generated by hypervelocity impact

The hypervelocity impact experiments of spherical LY12 aluminum projectile diameter of 6.4 mm on LY12 aluminum target thickness of 23 mm have been conducted using a two-stage light gas gun. The impact velocity of the projectile is 5.2, 5.7, and 6.3 km/s, respectively. The experimental results show that the plasma phase transition appears under the current experiment conditions, and the plasma expansion consists of accumulation, equilibrium, and attenuation. The plasma characteristic parameters decrease as the plasma expands outward and are proportional with the third power of the impact velocity, i.e., (T{sub e}, n{sub e}) ∝ v{sub p}{sup 3}. Based on the experimental results, a theoretical model on the plasma expansion is developed and the theoretical results are consistent with the experimental data.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2016

Elastic anisotropy and electronic properties of Si{sub 3}N{sub 4} under pressures

First principles calculations are performed to systematically investigate the electronic structures, elastic, anisotropic and electronic properties of the monoclinic, tetragonal and orthorhombic structures of Si{sub 3}N{sub 4} under pressure. Anisotropy studies show that three Si{sub 3}N{sub 4} phases exhibit a large anisotropy. Furthermore, using the HSE06 hybrid functional, the monoclinic, tetragonal and orthorhombic phases are found to be wide band-gap semiconductors. The pressure induced band gap direct-indirect transition is found for monoclinic Si{sub 3}N{sub 4}. The elastic modulus, compressional and shear wave velocities as well as Debye temperatures as a function of pressure in three Si{sub 3}N{sub 4} phases are also investigated in detail.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2011

What Controls the Phase Diagram and Superconductivity in Ru-Substituted BaFe 2 As 2 ?

Not Available

Dhaka, R. S.↗

DOE OSTI2015

Vertical structure and physical processes of the Madden-Julian Oscillation: Biases and uncertainties at short range

We present an analysis of diabatic heating and moistening processes from 12 to 36 h lead time forecasts from 12 Global Circulation Models as part of the “Vertical structure and physical processes of the Madden-Julian Oscillation (MJO)” project. A lead time of 12–36 h is chosen to constrain the large-scale dynamics and thermodynamics to be close to observations while avoiding being too close to the initial spin-up of the models as they adjust to being driven from the Years of Tropical Convection (YOTC) analysis. A comparison of the vertical velocity and rainfall with the observations and YOTC analysis suggests that the phases of convection associated with the MJO are constrained in most models at this lead time although the rainfall in the suppressed phase is typically overestimated. Although the large-scale dynamics is reasonably constrained, moistening and heating profiles have large intermodel spread. In particular, there are large spreads in convective heating and moistening at midlevels during the transition to active convection. Radiative heating and cloud parameters have the largest relative spread across models at upper levels during the active phase. A detailed analysis of time step behavior shows that some models show strong intermittency in rainfall and differences in the precipitation and dynamics relationship between models. In conclusion, the wealth of model outputs archived during this project is a very valuable resource for model developers beyond the study of the MJO. Additionally, the findings of this study can inform the design of process model experiments, and inform the priorities for field experiments and future observing systems.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2016

On the evolution of elastic properties during laboratory stick‐slip experiments spanning the transition from slow slip to dynamic rupture

Abstract The physical mechanisms governing slow earthquakes remain unknown, as does the relationship between slow and regular earthquakes. To investigate the mechanism(s) of slow earthquakes and related quasi‐dynamic modes of fault slip we performed laboratory experiments on simulated fault gouge in the double direct shear configuration. We reproduced the full spectrum of slip behavior, from slow to fast stick slip, by altering the elastic stiffness of the loading apparatus ( k ) to match the critical rheologic stiffness of fault gouge ( k c ). Our experiments show an evolution from stable sliding, when k > k c , to quasi‐dynamic transients when k ~ k c , to dynamic instabilities when k < k c . To evaluate the microphysical processes of fault weakening we monitored variations of elastic properties. We find systematic changes in P wave velocity ( V p ) for laboratory seismic cycles. During the coseismic stress drop, seismic velocity drops abruptly, consistent with observations on natural faults. In the preparatory phase preceding failure, we find that accelerated fault creep causes a V p reduction for the complete spectrum of slip behaviors. Our results suggest that the mechanics of slow and fast ruptures share key features and that they can occur on same faults, depending on frictional properties. In agreement with seismic surveys on tectonic faults our data show that their state of stress can be monitored by V p changes during the seismic cycle. The observed reduction in V p during the earthquake preparatory phase suggests that if similar mechanisms are confirmed in nature high‐resolution monitoring of fault zone properties may be a promising avenue for reliable detection of earthquake precursors.

Tinti, E.↗

DOE OSTI2022

Assessing free tropospheric quasi-equilibrium for different GCM resolutions using a cloud-resolving model simulation of tropical convection

Abstract This study examines the free-tropospheric quasi-equilibrium at different global climate model (GCM) resolutions using the simulation of tropical convection by a cloud-resolving model during the Tropical Western Pacific International Cloud Experiment. The simulated dynamic and thermodynamic fields within the model domain are averaged over subdomains of different sizes equivalent to different GCM resolutions. These coarse-grained fields are then used to compute CAPE and its change with time, and their relationships with simulated convection. Results show that CAPE change with time is controlled predominantly by variations of thermodynamic properties in the planetary boundary layer for all subdomain sizes ranging from 64 to 4 km. Lag correlation analysis shows that CAPE generation by the free-tropospheric dynamical advection (dCAPE ls ) leads convective precipitation but is in phase with convective mass flux at 600 mb and 500 mb vertical velocity for all subdomain sizes. However, the correlation coefficients and regression slopes decrease as the subdomain size decreases for subdomain sizes smaller than 16 km. This is probably due to increased randomness of convection and more scale-dependence of the relationships when the subdomain size reaches the grey zone. By examining the sensitivity of the relationships of convection with dCAPE ls to temporal scales in different subdomain size, it shows that the quasi-equilibrium between dCAPE ls and convection holds well for timescales of 30 min or longer at all subdomain sizes. These results suggest that the free tropospheric quasi-equilibrium assumption may still be useable even for GCM resolutions in the grey zone.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2019

Investigation of Compatibility Between M-Cr-Al-X Thermal Spray Coatings and Third Generation γ-TiAl Alloys

In this work, the physical and chemical compatibility of cast Ti-Al-Nb-Cr-Zr and Ti-Al-Nb-Cr-Zr-B-La alloys was investigated with oxidation-resistant M-Cr-Al-X thermal spray coatings. Ti and Al are main alloy elements to form γ-TiAl and α{sub 2}-Ti{sub 3}Al phases. To obtain coatings, we used air plasma spray and high-velocity oxygen fuel equipment. Four commercially available M-Cr-Al-X powders, including Ta-containing, were used as starting materials. Our investigation of compatibility between M-Cr-Al-X thermal spray coatings and γ-TiAl alloys consists of isothermal annealing in air muffle furnace during 100 h at 920 °C, followed by samples investigation. Oxidation products formed at coatings surface were studied by XRD analysis with Rietveld refinement. Interdiffusion between coatings and alloys was studied by means of cross-sectional SEM with EDX analysis. Plots were made to show concentration of each main element at the end of experiments. Samples were subjected to dynamic mechanical thermal analysis in order to determine the effect of high-temperature exposure on complex elastic modulus. Finally, burner rig cycling test was performed to estimate the thermal shock resistance of M-Cr-Al-X coatings.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Adiabatic quantum decoherence in many non-interacting subsystems induced by the coupling with a common boson bath

Highlights: • System–environment quantum correlation: a main solid state NMR decoherence channel. • Non-separable system–environment model yields realistic spin decoherence rates. • New open quantum system approach explains irreversible decay of refocused NMR echoes. • Adiabatic quantum decoherence is inherently irreversible and eigen-selective. This work addresses adiabatic quantum decoherence of many-body spin systems coupled with a boson field in the framework of open quantum systems theory. We generalize the traditional spin-boson model by considering a system–environment interaction Hamiltonian that represents a partition of non-interacting subsystems and highlights the collective correlation that appears exclusively due to the coupling with a common environment. Remarkably, this simple, exactly solvable model encompasses relevant aspects of a many-body open quantum system and features the subtle quantum effects that arise when the size scales up to a macroscopic level. We derive an analytical expression for the time dependence of the density matrix elements (in the preferred basis) without assuming coarse-graining. The resulting decoherence function is eigen-selective and is a complex exponential whose exponent has a real part that introduces a decay similar to that in the spin-boson model. On the contrary, the imaginary part depends on the quantum numbers and geometry of the whole partition and does not reflect the system temperature. Motivated by decoherence in solid-state NMR, and in search of realistic numerical estimations, we apply the theoretical results to a partition of dipole-coupled spin pairs in contact with a common phonon bath, using typical parameters of hydrated salts. The proposal allows estimating the decoherence time scale in terms of the system physical constants: sound velocity and eigenvalue distribution width. As a significant novelty, the decoherence function phase depends on the eigenvalue distribution throughout the sample. It plays the leading role, overshadowing the mechanism associated with the bath thermal state. Finally, we apply the formalism to describe decoherence in the “magic echo” NMR reversal experiment. We find that the system–environment correlation explains the origin of irreversibility, and both the decoherence rate value and its dependence on the dipolar frequency, are remarkably similar to the experiment.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2021

Experimental study of flash boiling spray with isooctane, hexane, ethanol and their binary mixtures

The main goal of this study is to understand the effect of fuel properties on flash boiling sprays using multi-hole injectors. Macroscopic characteristics were investigated using Diffused Backlight Imaging (DBI) and quantified with liquid penetration length and spray angles. Phase Doppler Anemometry (PDA) was applied to measure the droplet size and velocity. Behaviors of spray with three single-component fuels (isooctane, hexane, ethanol) under different ambient pressures (100 kPa, 80 kPa, 50 kPa, 22 kPa) as well as their binary mixtures under different blend ratios (10%, 30%, 85%) were reported and analyzed. The results showed that adding ethanol or hexane to isooctane could both promote flash boiling by increasing the overall vapor pressure thus superheated degree. Under mixing ratios of 10% and 30%, sprays with ethanol blends showed more severe flash boiling comparing with sprays with hexane blends. Shorter liquid penetration and better liquid dispersion have been observed. Comparing with isooctane spray, the droplet size continuously decreased with increasing hexane content due to enhanced breakup and faster vaporization. Sprays with ethanol mixtures showed a different trend. Noticeable droplet size reduction has been observed for spray with 10% ethanol content. However, droplet size did not further decrease with higher blend ratios regardless of higher flash boiling intensity. Such observations indicate severe vaporization inhibition caused by the high latent heat of vaporization of ethanol. For sprays with all test fuels, collapsing occurred when the pressure ratio of ambient pressure to saturation pressure (Rp) dropped below 0.3.

03 NATURAL GAS↗

DOE OSTI2022

Ultrasonic nondestructive diagnosis of lithium-ion batteries with multiple frequencies

Accurately estimating the state of charge (SoC) in battery management systems (BMSs) requires the measurement of numerous parameters and advanced algorithms. This work studies multifrequency ultrasonic waves to estimate the SoC of Li-ion batteries by sensing the material changes during charge/discharge. A pouch-type LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC622) graphite battery cell is designed and fabricated with a capacity of 2.4 Ah. Different ultrasonic testing setups are explored to determine the optimal testing parameters for the battery. An ultrasonic monitoring system is developed to monitor the battery during charge/discharge at 750 kHz, 1 MHz, and 1.5 MHz. Signal processing algorithms are proposed for extracting three ultrasonic features—amplitude, wave velocity, and attenuation. In a three-cycle test, the amplitude histories do not show clear correlations with the SoC. The wave velocities of all three frequencies have an approximately linear relationship with the SoC, which can be used for SoC estimation. Hysteresis behavior is observed for the wave velocity in terms of a larger slope in the discharge process and velocity drop after a close charge/discharge cycle. The wave attenuation is able to capture the material phase transitions during charge/discharge.

25 ENERGY STORAGE↗

DOE OSTI2020

Modal dynamics of high-frequency transverse combustion instabilities

This paper investigates the modal dynamics of self-excited high frequency transverse instabilities in a multi-nozzle, swirl-stabilized can combustor. It utilizes results from multiple pressure sensors to decompose the disturbance into clockwise (CW) and counter-clockwise (CCW) waves, enabling a reconstruction of the pressure amplitude, phase, anti-nodal line location, and spin ratio. While these types of decompositions have been demonstrated on small scale combustors, particularly annular combustors, this is the first study to analyze these results for a high power, multi-nozzle can combustor. Its particular focus is in characterizing the system evolution in phase space and the nature of the system attractors under linearly unstable conditions; results are presented in spin ratio-phase difference space, so that limit cycle oscillations appear as fixed points. Results are shown for conditions where three different attractors dominate (standing, CW, and CCW) but are taken for very long time periods (~50,000 cycles) so that the system's interaction with these attractors can be observed. For the standing mode-dominated case, the phase portrait shows spiral trajectories converging to a single fixed point. For the spinning mode dominated cases, however, multiple fixed points and saddle points were observed, and the trajectories showed a more complicated structure. It was also shown that even though the CW mode is dominant, this mode intermittently switches to standing or CCW modes for short period. These results suggest that the strength of each attractor depends on test conditions and that random noise stochastically perturbs the system so that large regions of the phase space are explored. Lastly, one interesting observation is that the angular velocity of the anti-nodal line linearly varies with the spin ratio under standing-mode dominant conditions.

42 ENGINEERING↗

DOE OSTI2022

Stability of a Mixed–Valence Hydrous Iron–Rich Oxide: Implications for Water Storage and Dynamics in the Deep Lower Mantle

Incorporation of water into mantle compositions can have significant effects on the phase relations in the systems. Here, we synthesized an iron-rich hexagonal hydrous phase (referred to as "HH1-phase") under the high pressure-temperature (P-T) conditions of the deep lower mantle and determined the crystal structure of the HH1-phase at 79 GPa using the multigrain crystallography method. The chemical formula obtained was Fe 12.76 O 18 H x (x ~ to 4.5) in the Fe-O-H system. To demonstrate the role of HH1-phase for water storage in multicomponent systems relevant to mantle compositions, we investigated the stability of HH1-phase in both MgO-rich pyrolitic and SiO 2 -rich basaltic compositions. Our results indicate that the HH1-phase serves as major water storage in a pyrolitic composition, whereas the Al-rich CaCl 2 -type δ-phase and SiO 2 phase are major water storage phases in a SiO 2 -rich basaltic composition. Incorporation of considerable amounts of SiO 2 , MgO, and Al 2 O 3 into the HH1-phase expands its stability field from 98 GPa in the Fe-Al-O-H system to at least 108 GPa (corresponding to similar to 2,400 km depth) in the Mg-Si-Al-Fe-O-H system. Plumes of hot upwelling rock rooted at the base of the lower mantle have been proposed as a possible origin of hotspot volcanoes. The hydrous Fe-rich HH1-phase, if included into the material of upwelling plumes, will decompose on its rising to the upper part of the lower mantle and release water. Our results should provide constraints on water storage in the deep lower mantle and have implications for deep mantle dynamics.

58 GEOSCIENCES↗