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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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Wellbore corrosion and failure assessment for CO2 EOR and storage: Two case studies in the Weyburn field
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Formation of AlF x Gaseous Phases during High Temperature Etching: A Reactive Force Field Based Molecular Dynamics Study
Not provided.
Catalysis in Extreme Field Environments: A Case Study of Strongly Ionized SiO 2 Nanoparticle Surfaces
Not Available
Theoretical study of phosphorene tunneling field effect transistors
In this work, device performances of tunneling field effect transistors (TFETs) based on phosphorene are explored via self-consistent atomistic quantum transport simulations. Phosphorene is an ultra-thin two-dimensional (2-D) material with a direct band gap suitable for TFETs applications. Our simulation shows that phosphorene TFETs exhibit subthreshold slope below 60 mV/dec and a wide range of on-current depending on the transport direction due to highly anisotropic band structures of phosphorene. By benchmarking with monolayer MoTe{sub 2} TFETs, we predict that phosphorene TFETs oriented in the small effective mass direction can yield much larger on-current at the same on-current/off-current ratio than monolayer MoTe{sub 2} TFETs. It is also observed that a gate underlap structure is required for scaling down phosphorene TFETs in the small effective mass direction to suppress the source-to-drain direct tunneling leakage current.
An experimental study to investigate magnetic field and winding force-dependent contact resistance of NI REBCO coil
Abstract This paper reports the magnetic field and winding force-dependent contact resistance, also known as characteristic resistance, of no-insulation (NI) REBCO coil. Three NI coils were wound with different winding forces ( < 1 kgf, 3 kgf, and 5 kgf) using the same REBCO-coated conductor, and they were tested at 4.2 K in a background field of 0, 5, 10, and 14 T. The contact resistance of each coil is measured at each field. As a result of the measurements, we draw two conclusions. First, a quadratic function for magnetic field intensity reasonably reproduces the measurement results of each NI test coil’s magnetic field-dependent contact resistance, where the practical fit function’s coefficients are determined depending on the winding force. Second, the contact resistance of each coil is partially inconsistent with the magnetoresistance of the electroplated material, i.e. copper, of the REBCO-coated conductor. This paper will present the measurement results in detail, discuss them with Kohler’s rule, and formulate the contact resistance using winding force and magnetic field terms.
Neutron spectroscopic study of crystalline electric field excitations in stoichiometric and lightly stuffed Yb 2 Ti 2 O 7
Time-of-flight neutron spectroscopy has been used to determine the crystalline electric field Hamiltonian, eigenvalues and eigenvectors appropriate to the J=7/2 Yb 3+ ion in the candidate quantum spin ice pyrochlore magnet Yb 2 Ti 2 O 7 . The precise ground state of this exotic, geometrically frustrated magnet is known to be sensitive to weak disorder associated with the growth of single crystals from the melt. Such materials display weak “stuffing,” wherein a small proportion, approximately 2%, of the nonmagnetic Ti 4+ sites are occupied by excess Yb 3+ . We have carried out neutron spectroscopic measurements on a stoichiometric powder sample of Yb 2 Ti 2 O 7 , as well as a crushed single crystal with weak stuffing and an approximate composition of Yb 2+x Ti 2–x O 7+y with x = 0.046. All samples display three crystalline electric field transitions out of the ground state, and the ground state doublet itself is identified as primarily composed of m J = ±1/2, as expected. However, stuffing at low temperatures in Yb 2+x Ti 2–x O 7+y induces a similar finite crystalline electric field lifetime as is induced in stoichiometric Yb 2 Ti 2 O 7 by elevated temperature. In conclusion, an extended strain field exists about each local “stuffed” site, which produces a distribution of random crystalline electric field environments in the lightly stuffed Yb 2+x Ti 2–x O 7+y , in addition to producing a small fraction of Yb ions in defective environments with grossly different crystalline electric field eigenvalues and eigenvectors.
Optical Time Reversal from Time-Dependent Epsilon-Near-Zero Media
Materials with a spatially uniform but temporally varying optical response have applications ranging from magnetic field-free optical isolators to fundamental studies of quantum field theories. However, these effects typically become relevant only for time variations oscillating at optical frequencies, thus presenting a significant hurdle that severely limits the realization of such conditions. Here we present a thin-film material with a permittivity that pulsates (uniformly in space) at optical frequencies and realizes a time-reversing medium of the form originally proposed by Pendry [Science 322, 71 (2008)]. We use an optically pumped, 500 nm thick film of epsilon-near-zero (ENZ) material based on Al-doped zinc oxide. An incident probe beam is both negatively refracted and time reversed through a reflected phase-conjugated beam. As a result of the high nonlinearity and the refractive index that is close to zero, the ENZ film leads to time reversed beams (simultaneous negative refraction and phase conjugation) with near-unit efficiency and greater-than-unit internal conversion efficiency. The ENZ platform therefore presents the time-reversal features required, e.g., for efficient subwavelength imaging, all-optical isolators and fundamental quantum field theory studies.
Full strain tensor measurements with X-ray diffraction and strain field mapping: a simulation study
Abstract not provided
Data for Impact of Non-Irrigation on 1G and 2G Bioethanol Potential of Oilcane Feedstock: A Field to Fuel Pipeline Study
This study evaluates the bioethanol potential in response to irrigation (IR) and non-irrigation (NIR) of oilcane (OC) during a seasonal drought prior harvest. The juice was extracted through mechanical pressing of stems and fermented by Ethanol Red® yeast to produce first-generation bioethanol. Hydrothermal pretreatment followed by enzymatic hydrolysis of bagasse was performed to produce monomeric sugars from structural carbohydrates. The hydrolysates were fermented with engineered yeast for second-generation bioethanol production. The irrigated oilcane juice (276.3 ± 8.9 g/L) constitutes higher sugar concentrations than non-irrigated oilcane juice (236.5 ± 2.2 g/L). The enzymatic hydrolysis of IR-OC and NIR-OC pretreated bagasse yielded similar concentrations of 247.5 ± 2.22 and 249.7 ± 4.98 g/L fermentable sugars. Industry-relevant bioethanol titers of ≥99 g/L and ≥75 g/L were achieved from juice and hydrolysates, respectively. Therefore, the non-irrigation regime did not impact the 1G and 2G bioethanol titers. However, the overall bioethanol yield can be lower due to the reduction of stem yield (8 %) per hectare.
Time Resolved Optical Studies on The Plasmonic Field Enhancement of Bacteriorhodopsin Proton Photo-current: Final Technical Report Covering Aug 31, 2015–Aug 31, 2016
Our research continues to focus on the effects of plasmonic nanoparticles on organic and inorganic light-harvesting materials. Recent work has focused on the synthesis of stabilized gold nanoparticles to enhance the efficiency of dye-sensitized solar cells (DSSCs). Two major concerns in dye sensitized solar cells (DSSCs) are efficient light absorption and charge collection. Charge collection typically suffers because transport of electrons through the mesoporous TiO 2 substrate is slow. Thus, one obvious way to improve charge collection is to reduce the thickness of the TiO 2 . Alternatively, a form of TiO 2 with fewer grain boundaries, such as nanotubes, could be used in place of sintered nanospheres. Unfortunately, both of these solutions end up reducing the amount of surface area available to adsorb dye molecules. This directly reduces the percentage of photons absorbed. This problem could be avoided if dye molecules with larger absorption were designed; although synthetic chemists seem to be pushing the limits of what is achievable. Plasmonic nanoparticles offer an alternative way to boost light absorption. It is well known that plasmonic nanoparticles can enhance the local electric field of resonant frequencies of light. If this were in the same spectral region as the dye’s absorption band it would increase the percentage of absorbed photons. One concern is that if the nanoparticles are too close to the dye molecules they can quench the excited state. To avoid this problem, we prepared gold nanoparticles with a silica shell. This limited the amount of quenching while still permitting some enhancement of absorption. Unfortunately, we ran into some serious issues. The iodide based electrolyte etched the gold nanoparticles, completely dissolving them within a few hours. The silica shell should have provided protection but there were pinholes through which iodide could diffuse. Increasing the thickness of the silica to over 10 nm prevented etching but also limited any photon absorption enhancement.
Search for Low-Mass Dark Matter wtih SuperCDMS Soudan and Study of Shorted Electric Field Configurations in CDMS Detectors
The area of dark matter is one of the most interesting and exciting topics in physics today. Existing at the intersection of particle physics and astrophysics, the existence of a new dark matter particle can be used to explain many astrophysical and cosmological observations, as well as to reconcile outstanding issues in the standard model of particle physics. Experiments such as SuperCDMS are built to detect dark matter in the lab by looking for low-energy nuclear recoils produced by collisions between dark matter particles and atoms in terrestrial detectors. SuperCDMS Soudan is particularly well-suited to follow up on possible hints of low-mass dark matter seen by other recent experiments because of its low thresholds and excellent background discrimination. Analyzing SuperCDMS Soudan data to look for low-mass dark matter comes with particular challenges because of the low signal-to-noise very near threshold. However, with a detailed background model developed by scaling high-energy events down into the low-energy signal region, SuperCDMS Soudan produced worldleading limits on the existence of low-mass dark matter. In addition, a few SuperCDMS Soudan detectors experienced cold hardware problems that can affect the data collected. Of particular interest is one detector considered for the low-mass WIMP search that has one of its charge electrodes shorted to chassis ground. Three events were observed in this detector upon unblinding the SuperCDMS Soudan low-energy data, even though <1 event was expected based on pre-unblinding calulations. However, the data collected by the shorted detector may have been compromised since an electrode shorted to ground will modify the electric field in the detector. The SuperCDMS Detector Monte Carlo (DMC) provides an excellent way to model the effects of the modified electric field, so a new model of the expected backgrounds in the low-mass WIMP search is developed using the DMC to try to explain how the short may have affected the data collected. This thesis is organized as follows: Chapter 1 gives a broad introduction to dark matter, discussing the astrophysical and cosmological evidence for its existence, listing several possible particle physics candidates, and outlining several experimental strategies to look for dark matter. Chapter 2 is an overview of CDMS detector technology and the experimental setup at the Soudan Underground Laboratory, with a focus on how data coming out of Soudan is analyzed. Chapter 3 presents results from a search for low-mass dark matter at SuperCDMS Soudan and discusses the interpretation of the results. Chapter 4 contains follow-up work that uses the CDMS Detector Monte Carlo (DMC) to understand the possible systematics associated with a detector that had one of its charge electrodes shorted to ground. This chapter represents the first time the DMC has been used to inform ongoing CDMS analysis. Chapter 5 takes a brief detour into the world of effective field theory (EFT), examining the consequences of an expanded set of possible WIMP-nucleon interactions in the EFT framework. Finally, Chapter 6 wraps up the material of the previous chapters and discusses how the research presented in this thesis can be applied as CDMS moves toward SuperCDMS SNOLAB.
Treatability Study Pilot Test Operation Field Photos
Photos in each group are in chronological order as captured: Group I Tank Platform Setup, November 14, 2017; Group II Tank Setup, November 15, 2017; Group III Aboveground Injestion System (AIS) Setup, November 20, 2017; Group IV Chemical Mixing, November 21, 2017; Group V KB-1 Bacteria Injection, November 27, 2017; Group VI Miscellaneous.
Electrically Detected Magnetic Resonance Study of High-Field Stress Induced Si/SiO 2 Interface Defects.
It is widely accepted that the breakdown of Si0 2 gate dielectrics is caused by the buildup of stress-induced defects over time. Although several physical mechanisms have been proposed for the generation of these defects, very little direct experimental evidence as to the chemical and physical identity of these defects has been generated in the literature thus far. Here, we present electrically detected magnetic resonance (EDMR) measurements obtained via spin-dependent recombination currents at the interface of high-field stressed Si/Si0 2 metal-oxide-semiconductor field effect transistors (MOSFETs).
Electrically Detected Magnetic Resonance Study of High-Field Stress Induced Si/SiO 2 Interface Defects [Slides]
We have measured the DCIV EDMR response before and after high field gate stressing in Si/Si0 2 MOSFETs. The g-value and orientation dependence of the stress induced EDMR response indicate that it is dominated by some combination of Pbo and Pb1 interface defects.
Fundamental Study of High Electric Field Surface Flashover in Vacuum.
Abstract not provided.
Theoretical study of zero-field electron work function of metal immersed in gas- direct application to cesium thermionic diode
Electron work function of metal immersed in gas for cesium thermionic diode application
A Study of the Velocity Field in m 82 and Its Bearing on Explosive Phenomena in that Galaxy
Velocity field in M 82 and relation to explosive phenomena in galaxy