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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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Validation on Aggregate Flexibility from Residential Air Conditioning Systems for Building-to-Grid Integration
To facilitate the integration of buildings to the power grid, battery-equivalent models have been proposed to characterize and quantify aggregate flexibility from building loads. An analytical method has been proposed to construct such a flexibility model for thermostatically controlled loads. Since this analytical method is derived from a simplified representation of building thermal dynamics, it is necessary to evaluate the resulting flexibility model in a more realistic context. This paper focuses on the validation of this analytical method for estimating aggregate flexibility from residential air conditioning (ACs) systems. A high-fidelity model is first developed to mimic thermal behaviors of a residential AC system through a co-simulation between Modelica and EnergyPlus. A population of virtual residential AC systems is then generated by randomizing parameters of the high-fidelity model. Finally, an aggregate flexibility model is constructed for the residential AC population using the analytical method and validated using results from simulation of the high-fidelity model. It is found that the flexibility estimated using the analytical method is with reasonable accuracy, but can be improved by explicitly incorporating heat gains into the method.
Conception of an integrated flowsheet for rare earth elements recovery from coal coarse refuse
Not provided.
The effect of low dose ionizing radiation on homeostasis and functional integrity in an organotypic human skin model
Not Available
Structural integrity--Searching the key factor to suppress the voltage fade of Li-rich layered cathode materials through 3D X-ray imaging and spectroscopy techniques
Li-rich layered materials are important cathode compounds used in commercial lithium ion batteries, which, however, suffers from some drawbacks including the so-called voltage fade upon electrochemical cycling. Here, our study employs novel transmission X-ray microscopy to investigate the electrochemical reaction induced morphological and chemical changes in the Li-rich Li 2 Ru 0.5 Mn 0.5 O 3 cathode particles at the meso to nano scale. We performed combined X-ray spectroscopy, diffraction and microscopy experiments to systematically study this cathode material's evolution upon cycling as well as to establish a comprehensive understanding of the structural origin of capacity fade through 2D and 3D fine length scale morphology and heterogeneity change of this material. This work suggests that atomic manipulation (e.g. doping, substitution etc.) or nano engineering (e.g. nano-sizing, heterogeneous structure) are important strategies to mitigate the internal strain and defects induced by extensive lithium insertion/extraction. It also shows that maintaining the structural integrity is the key in designing and synthesizing lithium-rich layered materials with better cycle stability.
Biojet fuels and emissions mitigation in aviation: An integrated assessment modeling analysis
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Tensor Network Path Integral Study of Dynamics in B850 LH2 Ring with Atomistically Derived Vibrations
The recently introduced multisite tensor network path integral (MS-TNPI) allows simulation of extended quantum systems coupled to dissipative media. We use MS-TNPI to simulate the exciton transport and the absorption spectrum of a B850 bacteriochlorophyll (BChl) ring. The MS-TNPI network is extended to account for the ring topology of the B850 system. Accurate molecular-dynamics-based description of the molecular vibrations and the protein scaffold is incorporated through the framework of Feynman–Vernon influence functional. To relate the present work with the excitonic picture, an exploration of the absorption spectrum is done by simulating it using approximate and topologically consistent transition dipole moment vectors. Comparison of these numerically exact MS-TNPI absorption spectra are shown with second-order cumulant approximations. Finally, the effect of temperature on both the exact and the approximate spectra is also explored.
Integrated Reference Electrodes in Anion-Exchange-Membrane Electrolyzers: Impact of Stainless-Steel Gas-Diffusion Layers and Internal Mechanical Pressure
Alkaline-membrane electrolyzers operating in pure water might provide scalable low-cost H 2 production but currently lag in performance and durability compared to commercial technologies. Typically, membrane–electrode assemblies (MEAs) are optimized in electrolyzers by changing one parameter at a time and assessing the resulting system performance via two-electrode polarization and impedance measurements. These approaches are limited in their ability to assign performance changes and durability to specific electrodes or processes. We integrate a reference electrode with the MEA to separate anode and cathode responses in both polarization and impedance measurements. Here we illustrate the power of the approach by showing how the fiber diameter of stainless-steel gas-diffusion layers (GDLs) affects performance solely at the anode, while changing the thickness of the cathode GDL simultaneously affects the performance of the anode and cathode due to changes in internal pressure from mechanical compression. This finding was obscured in conventional two-electrode measurements. The work thus guides both high-performance alkaline-membrane water-electrolyzer development and illustrates a useful strategy to study structure–activity relationships in the MEA.
Hyperexpandable, self-healing macromolecular crystals with integrated polymer networks
Formation of condensed matter typically involves a trade-off between structural order and flexibility. As the extent and directionality of interactions between atomic or molecular components increase, materials generally become more ordered but less compliant and vice versa. Yet, high levels of structural order and flexibility need not necessarily be mutually exclusive: there are many biological (e.g., microtubules, flagella, viruses) and synthetic assemblies (e.g., dynamic molecular crystals and frameworks) that can undergo considerable structural transformations without losing their crystalline order and possess remarkable mechanical properties with utility in diverse applications such as selective sorption, separation, sensing, and mechanoactuation. Ultimately, however, the extent of structural changes by such flexible crystals and their elasticity are constrained by the necessity to maintain a continuous network of bonding interactions between the constituents of the lattice. Consequently, even the most dynamic porous materials tend to be brittle and isolated as microcrystalline powders,14 and flexible organic/inorganic molecular crystals cannot expand without fracturing. Owing to their rigidity, crystalline materials rarely display self-healing behavior. Here we report that macromolecular ferritin crystals with integrated hydrogel polymers can isotropically expand to 180% of their original dimensions and >500% of their original volume while retaining periodic order and faceted Wulff morphologies. Even after the separation of neighboring ferritin molecules by 50 Å upon lattice expansion, specific molecular contacts between them can be reformed upon lattice contraction, resulting in the recovery of atomic-level periodicity and the highest resolution ferritin structure reported. Dynamic bonding interactions between the hydrogel network and the ferritin molecules endow the crystals with the ability to resist fragmentation and self-heal efficiently, while the chemical tailorability of the ferritin molecules enables the creation of chemically and mechanically differentiated domains within single crystals.
Integrated three-dimensional photonic nanostructures for achieving near-unity solar absorption and superhydrophobicity
In this paper, we proposed and realized 3D photonic nanostructures consisting of ultra-thin graded index antireflective coatings (ARCs) and woodpile photonic crystals. The use of the integrated ARC and photonic crystal structure can achieve broadband, broad-angle near unity solar absorption. The amorphous silicon based photonic nanostructure experimentally shows an average absorption of ∼95% for λ = 400–620 nm over a wide angular acceptance of θ = 0°–60°. Theoretical studies show that a Gallium Arsenide (GaAs) based structure can achieve an average absorption of >95% for λ = 400–870 nm. Furthermore, the use of the slanted SiO{sub 2} nanorod ARC surface layer by glancing angle deposition exhibits Cassie-Baxter state wetting, and superhydrophobic surface is obtained with highest water contact angle θ{sub CB} ∼ 153°. These properties are fundamentally important for achieving maximum solar absorption and surface self-cleaning in thin film solar cell applications.
Invited Article: A novel calibration method for the JET real-time far infrared polarimeter and integration of polarimetry-based line-integrated density measurements for machine protection of a fusion plant
In this paper, we present the work in the implementation of a new calibration for the JET real-time polarimeter based on the complex amplitude ratio technique and a new self-validation mechanism of data. This allowed easy integration of the polarimetry measurements into the JET plasma density control (gas feedback control) and as well as machine protection systems (neutral beam injection heating safety interlocks). The new addition was used successfully during 2014 JET Campaign and is envisaged that will operate routinely from 2015 campaign onwards in any plasma condition (including ITER relevant scenarios). This mode of operation elevated the importance of the polarimetry as a diagnostic tool in the view of future fusion experiments.
Measurement and models of bent KAP(001) crystal integrated reflectivity and resolution (invited)
The Advanced Light Source beamline-9.3.1 x-rays are used to calibrate the rocking curve of bent potassium acid phthalate (KAP) crystals in the 2.3-4.5 keV photon-energy range. Crystals are bent on a cylindrically convex substrate with a radius of curvature ranging from 2 to 9 in. and also including the flat case to observe the effect of bending on the KAP spectrometric properties. As the bending radius increases, the crystal reflectivity converges to the mosaic crystal response. The X-ray Oriented Programs (XOP) multi-lamellar model of bent crystals is used to model the rocking curve of these crystals and the calibration data confirm that a single model is adequate to reproduce simultaneously all measured integrated reflectivities and rocking-curve FWHM for multiple radii of curvature in both 1st and 2nd order of diffraction.
Tuning metal-insulator behavior in LaTiO 3 /SrTiO 3 heterostructures integrated directly on Si(100) through control of atomic layer thickness
Abstract not provided