A simple approach to quantifying the noise–ENSO interaction. Part II: the role of coupling between the warm pool and equatorial zonal wind anomalies
Not provided.
Meteorology & Atmospheric Sciences↗
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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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Evaluating a Simple Fracturing Criterion for a Hydraulic Fracture Crossing Stress and Stiffness Contrasts
Hydraulic fracture height containment is a critical issue in the development of unconventional reservoirs. The extent of fracture height growth depends on a variety of factors, particularly stress and stiffness contrasts between adjacent layers. Accurate simulation of fracture growth and containment requires a reliable fracturing criterion. The virtual crack closure technique (VCCT) is a widely used method for computing energy release rate. However, it is based on the assumption that a small crack extension does not significantly alter the state of the crack tip, which is generally not the case when a fracture crosses strong stress and/or stiffness contrasts. In this work, we assess the applicability and accuracy of a modified virtual crack closure technique (MVCCT) for a fluid-driven fracture in breaking through interfaces with significant stress and/or stiffness contrasts, through comparisons with analytical and reference numerical solutions. Here, the results show that significant error could occur when the fracture tip is very near or at stress/stiffness interfaces. However, this error is localized to the interface and proves to be inconsequential to the predicted penetration depth into the rock layer beyond the interface. Finally, this study validates the applicability of MVCCT in 3D hydraulic fracturing simulation in strongly heterogeneous rock formations.
36 MATERIALS SCIENCE↗
A simple method for simulating wind profiles in the boundary layer of tropical cyclones
A method to simulate characteristics of wind speed in the boundary layer of tropical cyclones in an idealized manner is developed and evaluated. The method can be used in a single-column modelling set-up with a planetary boundary-layer parametrization, or within large-eddy simulations (LES). The key step is to include terms in the horizontal velocity equations representing advection and centrifugal acceleration in tropical cyclones that occurs on scales larger than the domain size. Compared to other recently developed methods, which require two input parameters (a reference wind speed, and radius from the centre of a tropical cyclone) this new method also requires a third input parameter: the radial gradient of reference wind speed. With the new method, simulated wind profiles are similar to composite profiles from dropsonde observations; in contrast, a classic Ekman-type method tends to overpredict inflow-layer depth and magnitude, and two recently developed methods for tropical cyclone environments tend to overpredict near-surface wind speed. When used in LES, the new technique produces vertical profiles of total turbulent stress and estimated eddy viscosity that are similar to values determined from low-level aircraft flights in tropical cyclones. Lastly, temporal spectra from LES produce an inertial subrange for frequencies ≳0.1 Hz, but only when the horizontal grid spacing ≲20 m.
17 WIND ENERGY↗
A Simple Approach for the Synthesis of Cellulose Nanofiber Reinforced Chitosan/PVP Bio Nanocomposite Film for Packaging
The development of chitosan-based food packaging film has been increasing due to its wider availability, biodegradability, low-cost, and renewability. The purpose of this study was to develop cellulose nanofibers (CNFs) reinforced Chitosan/PVP(CHP) green bio nanocomposite film by solvent casting method with enhanced barrier and mechanical property. CNFs of dimension 9–11 nm and 100–200 nm were extracted from jute fibers by directly treating it with HNO{sub 3}–NaNO{sub 2} mixture. Bio nanocomposite films were synthesized with various concentrations of CNFs and evaluated using SEM, TGA/DTG and XRD to analyze the morphology, thermal behavior and crystallinity of bio nanocomposite films. SEM analysis revealed the uniform dispersion of CNFs in CHP matrix. Thermal stability of prepared bio nanocomposite films was improved with the loading of 5 wt% of cellulose nanofibers. ATR(FT-IR) spectra shows physical interaction between all the components of bio nanocomposite film. The bio nanocomposite films were also characterized for physical property like thickness, mechanical testing and barrier properties. The addition of CNFs significantly enhanced the mechanical property of bio nanocomposite films. Furthermore, water and oxygen transmission rate of bio nanocomposite film decreased with the increase in CNFs concentration. Overall the performed studies confirmed, the use of CNFs in polymer matrix makes it possible to produce a flexible, transparent, thermally stable bio nanocomposite film with enhanced mechanical and barrier properties for food packaging applications.
36 MATERIALS SCIENCE↗
Morphology-Tuneable Synthesis and Magnetic Performances of CeO{sub 2} Hollow Nanospheres Fabricated by a Simple Template-Free Hydrothermal Method
The large-scale uniform CeO{sub 2} hollow nanospheres with a diameter of about 200–300 nm were fabricated by a facile template-free hydrothermal method using Ce(NO{sub 3}){sub 3} ⋅6H{sub 2}O as cerium source, NH{sub 4}HCO{sub 3} as precipitator, and ethanediamine as surfactant. X-ray diffraction (XRD), X-ray photoelectron spectrum (XPS), and Raman spectrum showed that the CeO{sub 2} hollow nanospheres with no crystalline impurity phase have a cubic fluorite structure, and many Ce{sup 3+} ions and oxygen vacancies exist in its surface. The magnetic measurements show that the CeO{sub 2} hollow nanospheres have excellent room temperature ferromagnetism while its precursors exhibit paramagnetism The dominating influences on RTFM may be assigned to the morphology and size of obtained CeO{sub 2} samples.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
On Derived Equivalence of Algebras of Semidihedral Type with Two Simple Modules
The Hochschild cohomology groups of degrees not exceeding 3 are computed for algebras of semidihedral type that form the family SD(2B){sub 1} (from the famous K. Erdmann’s classification). In the calculation, the beforehand construction of the initial part of the minimal projective bimodule resolution is used for algebras from the family under discussion. The obtained results imply that the algebras from the families SD(2B){sub 1} and SD(2B){sub 2} with the same parameters in defining relations are not derived equivalent.
97 MATHEMATICS AND COMPUTING↗
Vector Bundles on P{sup 1}{sub ℤ} with Simple Jumps
Vector bundles of rank 2 on the projective line over ℤ are considered. It is assumed that such a bundle E is trivial on a generic fiber, and its restriction to any special fiber is isomorphic either to O{sup 2} or to O(−1)⊕O(1). Under these assumptions it is proved that an exact sequence of the form 0→O(−2) → E →O(2) → 0 exists.
97 MATHEMATICS AND COMPUTING↗
Vector Bundles on P{sup 1}{sub ℤ} with Generic Fiber O ⊕ O(1) and Simple Jumps
Vector bundles on the projective line over a Dedekind domain A are studied. In the case where A is a principal ideal domain, a complete classification is obtained for rank 2 vector bundles with generic fiber O ⊕ O(1) and special fibers isomorphic either to O ⊕ O(1) or to O(−1) ⊕ O(2).
97 MATHEMATICS AND COMPUTING↗
A simple way to integrate distributed storage into a wholesale electricity market
Abstract Current plans to decarbonize the electric supply system imply that the generation from wind and solar sources will grow substantially. This growth will increase the uncertainty of system operations due to the inherent variability of these renewable sources, and as a result, more reserve capacity will be required to provide the ramping (flexibility) needed for reliable operations. This paper assumes that all of the increased uncertainty comes from wind farms on the grid, and it shows how distributed storage managed locally by aggregators can provide the ramping needed without introducing a separate market for flexibility. This can be accomplished when the aggregators minimize the expected daily cost of the energy purchased from the grid for their customers by submitting optimal bids into the wholesale market with high and low price thresholds for discharging and charging the storage. This model is illustrated using a stochastic multi-period security constrained optimal power flow together with realistic data for a reduction of the network in the Northeast Power Coordinating Council region of the United States. The results show that the bidding strategy for distributed storage provides ramping to the grid just as effectively as storage managed by a system operator.
Lamadrid, Alberto J.↗
Preventing Wetting Between Liquid Copper and Solid Steel: A Simple Extraction Technique
Copper contamination of end-of-life steel scrap is the main barrier to high-quality recycling. Preferential melting of copper from solid steel scrap is a potential extraction technique, which could be integrated into conventional scrap re-melting with little additional energy. However, previous investigations show removal of liquid copper is limited by its adherence to solid scrap. Preventing wetting between liquid copper and steel is essential to enable separation. The carbon content of steel, initial surface oxidation, and applied coatings effect wetting behavior, but have not been systematically studied. In this study, the individual and combined effects of these parameters on wetting behavior in an inert gaseous environment are observed with a heating microscope. Carbon content appears to be the most significant factor: blistering of the oxide scale on medium-carbon steels causes liquid copper to flow rapidly between the oxide and steel substrate. Liquid copper exhibited a stable droplet on low-carbon steel, regardless of the initial level of oxidation. The tested coatings did not consistently improve nonwetting behavior, but impaired the connection between the scale and steel substrate. This study confirms the potential of the preferential melting technique, but further investigation is needed to determine the most robust process conditions to handle diverse, fragmented scrap at an industrial scale.
36 MATERIALS SCIENCE↗
Right ventricular perfusion: Do we need additional evidence or just a simple methodology?
No abstract prepared.
62 RADIOLOGY AND NUCLEAR MEDICINE↗
A Simple Method for Improving the Spatial Resolution in Infrared Laser Ablation Mass Spectrometry Imaging
In mass spectrometry imaging of tissues, the size of structures that can be distinguished is determined by the spatial resolution of the imaging technique. Here, the spatial resolution of IR laser ablation is markedly improved by increasing the distance between the laser and the focusing lens. As the distance between the laser and the lens is increased from 1 to 18 m, the ablation spot size decreases from 440 to 44 μm. This way, only the collimated center of the divergent laser beam is directed on the focusing lens, which results in better focusing of the beam. Part of the laser energy is lost at longer distance, but this is compensated by focusing of the radiation to a smaller area on the sample surface. The long distance can also be achieved by a set of mirrors, between which the radiation travels before it is directed to the focusing lens and the sample. This method for improving the spatial resolution can be utilized in mass spectrometry imaging of tissues by techniques that utilize IR laser ablation, such as laser ablation electrospray ionization, laser ablation atmospheric pressure photoionization, and matrix-assisted laser desorption electrospray ionization. .
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Atmospheric Solid Analysis Probe Coupled to Ion Mobility Spectrometry-Mass Spectrometry, a Fast and Simple Method for Polyalphaolefin Characterization
Polyalphaolefins (PAOs) are polymers produced from linear alpha olefins through catalytic oligomerization processes. The PAOs are known as synthetic high-performance base stock fluids used to improve the efficiency of many other synthetic products. In this study, we report the direct characterization of PAOs using atmospheric solid analysis probe (ASAP) coupled with ion mobility spectrometry-mass spectrometry (IMS-MS). We studied different PAOs grades exhibiting low- and high-viscosity index. Specific adjustments of the ASAP source parameters permitted the monitoring of ionization processes as three mechanisms could occur for these compounds: hydride abstraction, nitrogen addition, and/or the formation of [M−2H]{sup +•} ions. Several series of fragment ions were obtained, which allowed the identification of the alpha olefin used to synthesize the PAO. The use of the ion mobility separation dimension provides information on isomeric species. In addition, the drift time versus m/z plots permitted rapid comparison between PAO samples and to evidence their complexity. These 2D plots appear as fingerprints of PAO samples. To conclude, the resort to ASAP-IMS-MS provides a rapid characterization of the PAO samples in a direct analysis approach, without any sample preparation. .
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
On differential singular perturbation problems: a simple variational approach
An alternative approach for the analysis and the numerical approximation of singular perturbation problems, using a variational framework, is presented. It is based on the natural idea of minimizing the residual of the differential equation measured in the L{sup 2} norm. By this strategy, the approximation is based in the solution of a set of linear problems giving the descent step directions of the problem. This is the main advantage of our approach, since we can use stable and convergent methods for linear problems (without assuming the knowledge of good initial guesses used in the approximation of the associated non-linear systems necessary in Newton-type methods). Remember that for this type of problems, we should use implicit methods. We prove that our procedure can never get stuck in local minima, and the error decreases until getting to the original solution independent of the perturbation parameter. Finally, we include some numerical examples.
97 MATHEMATICS AND COMPUTING↗
Convection and Climate: What Have We Learned from Simple Models and Simplified Settings?
Not provided.
Meteorology & Atmospheric Sciences↗