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Atomic Insight into the W-Doping Effect on Carrier Dynamics and Photoelectrochemical Properties of BiVO[subscript 4] Photoanodes
Abstract not provided
Relationships Between Mesoscale Convective System Properties and Midlevel Dynamic Perturbations
Abstract Past studies implicate dynamic anomalies operating on subsynoptic scales as a possible initiation source of summertime (July–August) mesoscale convective systems (MCSs) in the central United States during northwesterly flow regimes. To improve our understanding of warm season MCSs occurring over a variety of flow regimes, we track midlevel (600 hPa) vorticity perturbations (“MPs”) as 2D objects comprising wavelengths of 500–2,500 km over the central US from May–August of 2004–2021. We perform statistical analysis of relationships between metrics of MP objects (e.g., duration, size, intensity, and origin) and high‐resolution MCS precipitation characteristics (e.g., duration, total rainfall, rain coverage area, and motion) that occur while collocated with or in the absence of MPs to discern predictive capability of background dynamic features on storm precipitation potential. Although the majority of MPs collocated with MCS initiation occur during July–August, a significant number (40%) occur between May and June. Northwesterly flow MPs comprise a relative minority of our events, suggesting that MPs can affect MCSs across a variety of warm season flow regimes. MPs affecting MCSs initiated primarily over the high plains near the central Rockies. Only approximately 20% of tracked MCS initiation events were collocated with MPs, but these storms produced ∼25% greater lifetime rainfall and coverage area, and ∼29% more stratiform rain than non‐MP‐induced MCSs. In general, larger and more vigorous MPs resulted in more hydrologically impactful MCSs. The most directly attributable benefit to MCS initiation was from MP‐enhanced background vertical motion and thermodynamic instability (e.g., increased CAPE).
Injectable Silica–Permanganate Gel as a Slow-Release MnO 4 - Source for Groundwater Remediation. Rheological Properties and Release Dynamics
Injectable slow-release permanganate gel (ISRPG), formed by mixing KMnO 4 solution with fumed silica powder, may have a potential application in remediating chlorinated solvent plumes in groundwater. A series of batch, column, and flow cell experiments has been completed to test the gel behavior under a variety of conditions. The experiments have provided information on ISRPG rheology, permanganate (MnO 4 - ) release dynamics and distribution, and trichloroethene (TCE) degradation by ISRPG-released oxidant. The gel possesses remarkable shear thinning characteristics, resulting in a relative low viscosity during mixing, and facilitating its subsurface injection and distribution. Batch tests revealed that MnO 4 - was diffused out from ISRPG into water while the gel did not dissolve or disperse into water but maintained its initial shape. Column experiments showed that MnO 4 - release from ISRPG lasted considerably longer than the release from aqueous solution. TCE degradation by ISRPG-released MnO 4 - was much more effective than that when MnO 4 - was delivered using aqueous solution injection. In two-dimensional flow cell experiments, it was demonstrated that ISRPG slowly released a long-lasting low concentration MnO 4 - plume sufficient for remediation and sustainable in an aquifer for a long period of time.
Modification of vortex dynamics and transport properties of transitional axisymmetric jets using zero-net-mass-flux actuation
We study the near field of a zero-net-mass-flux (ZNMF) actuated round jet using direct numerical simulations. The Reynolds number of the jet Re{sub D} = 2000 and three ZNMF actuators are used, evenly distributed over a circle, and directed towards the main jet. The actuators are triggered in phase, and have a relatively low momentum coefficient of C{sub μ} = 0.0049 each. We study four different control frequencies with Strouhal numbers ranging from St{sub D} = 0.165 to St{sub D} = 1.32; next to that, also two uncontrolled baseline cases are included in the study. We find that this type of ZNMF actuation leads to strong deformations of the near-field jet region that are very similar to those observed for non-circular jets. At the end of the jet's potential core (x/D = 5), the jet-column cross section is deformed into a hexagram-like geometry that results from strong modifications of the vortex structures. Two mechanisms lead to these modifications, i.e., (i) self-deformation of the jet's primary vortex rings started by distortions in their azimuthal curvature by the actuation, and (ii) production of side jets by the development and subsequent detachment of secondary streamwise vortex pairs. Further downstream (x/D = 10), the jet transforms into a triangular pattern, as the sharp corner regions of the hexagram entrain fluid and spread. We further investigate the global characteristics of the actuated jets. In particular when using the jet preferred frequency, i.e., St{sub D} = 0.33, parameters such as entrainment, centerline decay rate, and mean turbulent kinetic energy are significantly increased. Furthermore, high frequency actuation, i.e., St{sub D} = 1.32, is found to suppress the mechanisms leading to large scale structure growth and turbulent kinetic energy production. The simulations further include a passive scalar equation, and passive scalar mixing is also quantified and visualized.
Effect of gas properties on the dynamics of the electrical slope asymmetry effect in capacitive plasmas: comparison of Ar, H 2 and CF 4
Tailored voltage excitation waveforms provide an efficient control of the ion energy (through the electrical asymmetry effect) in capacitive plasmas by varying the 'amplitude' asymmetry of the waveform. In this work, the effect of a 'slope' asymmetry of the waveform is investigated by using sawtooth-like waveforms, through which the sheath dynamic can be manipulated. A remarkably different discharge dynamic is found for Ar, H 2 , and CF 4 gases, which is explained by the different dominant electron heating mechanisms and plasma chemistries. In comparison to Argon we find that the electrical asymmetry can even be reversed by using an electronegative gas such as CF 4 . Phase resolved optical emission spectroscopy measurements, probing the spatiotemporal distribution of the excitation rate show excellent agreement with the results of particle-in-cell simulations, confirming the high degree of correlation between the excitation rates with the dominant heating mechanisms in the various gases. It is shown that, depending on the gas used, sawtooth-like voltage waveforms may cause a strong asymmetry.
Dynamical versus equilibrium properties of the QCD phase transition: A holographic perspective
Not Available
Effect of mechanical boundary conditions on the dynamic and static properties of a strongly anisotropic ferromagnet
The spectra of coupled magnetoelastic waves in a semi-infinite strongly anisotropic easy-plane ferromagnet with a rigidly fixed face are analyzed for two variants of fixation (in the basal plane and perpendicularly to it). The phase states of the system are determined. Differences in the phase diagrams and elementary excitation spectra depending on the choice of the sample fixation plane are considered. When rotational invariance is taken into account, the nonreciprocity effect for the velocities of sound in a crystal appears. It is shown that the velocity of sound in the sample considerably depends on the symmetry of the imposed mechanical boundary conditions. The phase diagrams of the system under investigation are presented.
Dynamic and nonlinear properties of epitaxial quantum dot lasers on silicon for isolator-free integration
Not Available
In-situ Nondestructive Evaluation of In-flight Particle Dynamics and Intrinsic Properties for Directed Energy Deposition
The objective of this exploratory project is to determine the feasibility of using laser diffraction, structured light 3D scanning, and x-ray diffraction for in-situ assessment and inspection of metal directed energy deposition (DED) that is applied to repair components such as engine parts in remanufacturing. During this project, we have successfully published or submitted at least one journal article for each subtask that we identified. One of our conference paper and presentation has won “best paper award” from Manufacturing & Design Division in the Institute of Industrial and Systems Engineers (IISE) Annual Conference 2021. Through this seed grant, we successfully validated the concepts and proved the three in-situ monitoring techniques work well to predict some defects generation during direct energy deposition. We submitted follow-up proposals to continue work on this topic.
Comparison of numerical calculations and measured space-time resolved plasma properties of a dynamical theta pinch.
Dense high-temperature plasma produced by 30- kjoule theta pinch examined by IR maser-excited coupled resonator system
Comparison of numerical calculations and measured space-time resolved plasma properties of a dynamical theta pinch.
Dense high temperature plasma produced by 30- kjoule theta pinch examined by IR maser-excited coupled resonator system
Observer properties for understanding dynamical displays: Capacities, limitations, and defaults
People's ability to extract relevant information while viewing ongoing events is discussed in terms of human capabilities, limitations, and defaults. A taxonomy of event complexity is developed which predicts which dynamical events people can and cannot construe. This taxonomy is related to the distinction drawn in classical mechanics between particle and extended body motions. People's commonsense understandings of simple mechanical systems are impacted little by formal training, but rather reflect heuristical simplifications that focus on a single dimension of perceived dynamical relevance.
Structural, dynamical and electronic properties of CaCuO2
The scalar relativistic version of an accurate first principles full potential self-consistent linearized muffin tin orbital (LMTO) method has been employed for describing the physical properties of the parent system of the high-T(sub c) oxide superconductors, i.e., CaCuO2. The presently employed modified version of the LMTO method is quite fast and goes beyond the usual LMTO ASA method in the sense that it permits a completely general shape of the potential and the charge density. Also, in contrast to LMTO ASA, the present method is also capable of treating distorted lattice structures accurately. The calculated values of the lattice parameters of pure CaCuO2 lie within 3% of the experimentally measured values for the Sr-doped system Ca(0.86)Sr(0.14)CuO(2). The computed electronic structures and the density of states is quite similar to those of the other oxide superconductors, except of their three- dimensional character because of the presence of strong coupling between the closely spaced CuO2 layers. The van Hove singularity peak appears slightly below the Fermi level and a small concentration of oxygenation /or/ substitutional doping may pin it at the Fermi level. The calculated frequencies for some symmetric frozen phonons for undoped CaCuO2 are quite near to the measured data for the Sr-doped CaCuO2.
The Dynamical and Microphysical Properties of Wet Season Convection in Darwin as a Function of Wet Season Regime
No abstract available