Poleward shift and intensified variability of Kuroshio-Oyashio extension and North Pacific Transition Zone under climate change
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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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Development of Technological Equipment for RBMK Service-Life Extension
This article is devoted to the solution of the now urgent problem of the aging of the RBMK-1000 graphite stack (bending of the graphite columns as a result of cracking of the graphite blocks under the action of temperature and exposure to radiation). The successful work performed by a group of specialists from the Diakont Company Group on restoring the service-life characteristics of the first two power-generating units at the Leningradskaya NPP is considered as an example. Laying bare the crux of the main stages and particulars of the technological process, considerable attention is given to the principle of operation, technical possibilities, and rigging of unique equipment produced by the Diakont. The development of a complete rigging complex for restoring the service-life characteristics of the reactor plant is given together with a detailed description of the operating principles of each type of equipment.
22 GENERAL STUDIES OF NUCLEAR REACTORS↗
Sensitivity of Turbine-Height Wind Speeds to Parameters in the Planetary Boundary-Layer Parametrization Used in the Weather Research and Forecasting Model: Extension to Wintertime Conditions
This work extends the model sensitivity analysis of Yang et al. (Boundary-Layer Meteorology, 2017, Vol. 162, 117-142) to include results for February 2011, in addition to May of the same year. We investigated the sensitivity of simulated hub-height wind speeds to the selection of 26 parameters applied in the Mellor-Yamada-Nakanishi-Niino (MYNN) planetary boundary-layer parameterization in the Weather Research and Forecasting (WRF) model, including parameters used to represent the dissipation of turbulence kinetic energy (TKE), Prandtl number (Pr), and turbulence length scales. Differences in the sensitivity of the ensemble of simulated wind speed to the various parameters can largely be explained by changes in the static stability. The largest monthly differences were found during the day, while the sensitivity to many of the parameters during the night were similar regardless of the month. This finding is consistent with an increased frequency of day-time stable conditions in February compared to May. The spatial variability of the sensitivity to TKE dissipation, Pr, and k can also be attributed to variability in the static stability across the domain at any point in time.
parametrization schemes, Parametric sensitivity, P↗
Preparation of Low-Density Microcellular Foams from Recycled PET Modified by Solid State Polymerization and Chain Extension
Recycled polyethylene-terephthalate (RPET) bottle regrinds were physically foamed after two types of industrially feasible molecular weight increasing processes. Intrinsic viscosity (IV) of initial waste (0.71 dL/g) increased both after reactive extrusion carried out using a multifunctional epoxy-based chain extender (0.74 dL/g) and after solid state polycondensation (SSP) (0.78 dL/g), while capillary rheometry revealed higher degree of branching in the chain extended PET material. Despite the relatively low IV values (below 0.80 dL/g), physical foaming, a mild and cost-efficient way, was successful in both cases, uniform microcellular foam structures with void fractions ranging between 75 and 83% were achieved. During the experiments morphology change in the materials was tracked by differential scanning calorimetry (DSC) besides recording IV values. The IV drop during foaming was between 0.03 and 0.10 depending on the pre-processing technology. Structure of foams produced from the two different modified RPET materials was compared with each other based on scanning electron microscopic imaging of cryogenic fracture surfaces. The average cell diameters were measured to be 213 and 360 µm in the case of chain extended and SSP-modified materials, respectively.
36 MATERIALS SCIENCE↗
Extension of the Concept of Invariance and Statistically Weakly Invariant Sets of Controllable Systems
We continue the study of statistically invariant and statistically weakly invariant sets with respect to controllable systems and differential inclusions launched by Prof. E. L. Tonkov. We examine properties of such statistical characteristics as the lower freq{sub *}(𝜑) and upper freq{sup *}(𝜑) relative frequencies of hitting a solution 𝜑(t) of a differential inclusion in a prescribed set. We obtain estimates and conditions of coincidence of these characteristics for functions whose difference tends to zero at infinity. We also present conditions of statistically weak invariance of a given set of a relatively controllable system.
97 MATHEMATICS AND COMPUTING↗
SCIP-Jack—a solver for STP and variants with parallelization extensions
The Steiner tree problem in graphs is a classical problem that commonly arises in practical applications as one of many variants. While often a strong relationship between different Steiner tree problem variants can be observed, solution approaches employed so far have been prevalently problem-specific. In contrast, this paper introduces a general-purpose solver that can be used to solve both the classical Steiner tree problem and many of its variants without modification. This versatility is achieved by transforming various problem variants into a general form and solving them by using a state-of-the-art MIP-framework. The result is a high-performance solver that can be employed in massively parallel environments and is capable of solving previously unsolved instances.
90C10↗
Quantum Chemical Mass Spectrometry: Verification and Extension of the Mobile Proton Model for Histidine
The quantum chemical mass spectrometry for materials science (QCMS{sup 2}) method is used to verify the proposed mechanism for proton transfer – the Mobile Proton Model (MPM) – by histidine for ten XHS tripeptides, based on quantum chemical calculations at the DFT/B3LYP/6-311+G* level of theory. The fragmentations of the different intermediate structures in the MPM mechanism are studied within the QCMS{sup 2} framework, and the energetics of the proposed mechanism itself and those of the fragmentations of the intermediate structures are compared, leading to the computational confirmation of the MPM. In addition, the calculations suggest that the mechanism should be extended from considering only the formation of five-membered ring intermediates to include larger-ring intermediates. .
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Unconventional lignin monomers—Extension of the lignin paradigm
Lignin is largely produced by the oxidative radical coupling of the three monolignols, pcoumaryl, coniferyl, and sinapyl alcohols, which form the p-hydroxyphenyl, guaiacyl, and syringyl lignin units in the lignin polymer. However, it is increasingly appreciated that other “unconventional” phenolic compounds can also behave as lignin monomers participating in oxidative radical reactions during the lignification process and being also integrated into the lignin polymer in some plants. Various phenolic compounds have been found incorporated into the lignin, including phenolic compounds derived from the monolignol biosynthetic pathway (e.g., monolignol ester conjugates, caffeyl and 5-hydroxyconiferyl alcohols, hydroxycinnamaldehydes, among others). More fascinating still was the discovery in some plants of a series of phenolic compounds arising from other polyphenolic biosynthetic pathways, including flavonoids (tricin, dihydrotricin, naringenin, naringenin chalcone), hydroxystilbenes (resveratrol, piceatannol, and isorhapontigenin, and their O-glucosylated counterparts piceid, astringin, and isorhapontin), and ferulic acid amides (feruloyltyramine, and diferuloylputrescine), that are integrated into the lignin polymer. All of these discoveries indicate that the lignin structure is far more complex than previously thought, that the definition of lignin should not be restricted to a polymer derived solely from the three traditional monolignols, and that other unconventional lignin monomers must be considered, thus expanding the established definition of lignin. Here, the overriding factor remains, however, that lignification, the process of polymerization to the lignin polymer, allows this compositional flexibility because it is a simple chemical process.
59 BASIC BIOLOGICAL SCIENCES↗
Extensive nanoprecipitate morphology transformation in a nanostructured ferritic alloy due to extreme thermomechanical processing
Nano-oxide precipitates in a modern nanostructured ferritic alloy were investigated after extreme thermomechanical processing into a thin-walled tube geometry. It was found that the morphology of the precipitates changed from spherical to rod-shaped, with some increasing to aspect ratios of up to 9, despite the precipitate volume fraction (0.3%) and number density (> 10 23 m -3 ) of precipitates remaining unchanged. High-resolution electron microscopy showed that the precipitates likely remained coherent with the Fe-matrix, while atom probe tomography confirmed that the precipitate compositions remained unaffected by the transformation. The morphological change was attributed to the shearable nature of the (Y,Ti,O)-rich precipitates, indicating they should be considered as “soft” obstacles to dislocation motion. The elongation was most pronounced in larger (>5 nm) precipitates, which may be caused by preferential dissolution of the smallest (1–3 nm) precipitates followed by the competition between re-precipitation and solute diffusion to larger precipitates during recovery heat treatments.
36 MATERIALS SCIENCE↗
A Geometric Volume of Fluid-Based Multiphase Flow Solver Extension to the Reacting Flow Solver, PeleLM
A new algorithm is presented to simulate multiphase flows with surface tension in a pathway for spray combustion simulation. The algorithm combines capabilities from two open-source packages, including the interface reconstruction library (IRL), a library of computational geometry routines to enable the volume of fluid (VOF) method, and PeleLM, a solver for the reacting Navier-Stokes equations. Additionally, surface tension is implemented using the continuum surface force (CSF) model with an improved height function technique in the volume fraction field. Spurious errors in volume fraction arising from our combined strategy are corrected through a topology-based method that improves both numerical stability and accuracy. Multiple validation simulations are conducted, including (i) translations and rotations of Zalesak's disk, (ii) a stationary circular droplet with surface tension, (iii) an oscillating elliptical droplet, and (iv) three-dimensional deformation of a spherical droplet. Results indicate that the combined scheme retains the favorable properties of each of the component algorithms.
42 ENGINEERING↗
An extension of Darcy’s law incorporating dynamic length scales
We propose a physics-based, macroscale formulation of multiphase porous-media flows that both honors the validity of Darcy’s law in steady or near-steady flows and accommodates the effects of heterogeneities and nonlinearities in unsteady flows. The new formulation recognizes that parameters characterizing the system operate at different length-scales. In particular, the use of Darcy’s law, predicated on the assumption of near-steady flows, requires dynamic length scales, owing to the possibility of rapid fluctuations in rock properties and fluid saturations attributable to heterogeneity and nonlinearity. We accommodate these dynamic length-scales through dynamic spatial averaging. The length and position of the averaging window are characterized by the length of the mixing zone and the direction of propagation of information in the transport process. Here, we validate the proposed formulation by comparing highly accurate,two dimensional numerical solutions against core-scale displacement experiments. The proposed paradigm is consistent with the classical multiphase Darcy formulation, in the sense that the latter also represents the results of an averaging approach.
42 ENGINEERING↗
Extension of SCALE/Sampler’s sensitivity analysis
Nuclear data are a major source of uncertainties in reactor physics calculations. The propagation of nuclear data uncertainties to important system responses is instrumental when determining appropriate safety margins in reactor safety analyses. It is also important to understand the major contributors to the observed uncertainties to make recommendations for further measurements and evaluations and aid in the understanding of the studied system. The SCALE code system allows for nuclear data uncertainty analysis based on the random sampling approach as implemented in SCALE’s Sampler sequence. Sampler was recently extended by a sensitivity analysis in terms of the calculation of two correlation-based sensitivity indices. This analysis allows for the identification of the top contributing nuclear reactions to any analyzed output uncertainty. This paper presents the sensitivity indices, along with their interpretation and limitations. It demonstrates the application in an eigenvalue and decay heat analysis for a boiling water reactor fuel assembly.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Extension of the discrete generalized multigroup method using SPH factors
The discrete generalized multigroup (DGM) method provides a way to treat the energy dependence of neutron transport similarly to the standard multigroup approximation. However, DGM uses an orthogonal basis to retain the energy dependence in higher-order terms. Using correction factors similar to traditional Superhomogénéisation (SPH) factors, the DGM method may be extended to produce cross sections that are homogenized over both space and energy. Additionally, since some fine-group energy dependence is retained, the resulting homogenized cross sections are more problem-independent than cross sections homogenized by SPH factors alone. In particular, a 44-group set of cross sections is collapsed to approximately a 1% error in the pincell fission densities for a test problem using three DOF per coarse energy group.
22 GENERAL STUDIES OF NUCLEAR REACTORS↗
Scattering amplitudes for multi-indexed extensions of solvable potentials
New solvable one-dimensional quantum mechanical scattering problems are presented. They are obtained from known solvable potentials by multiple Darboux transformations in terms of virtual and pseudo virtual wavefunctions. The same method applied to confining potentials, e.g. Pöschl–Teller and the radial oscillator potentials, has generated the multi-indexed Jacobi and Laguerre polynomials. Simple multi-indexed formulas are derived for the transmission and reflection amplitudes of several solvable potentials. -- Highlights: •Scattering amplitudes calculated for infinitely many new solvable potentials. •New scattering potentials obtained by deforming six known solvable potentials. •Multiple Darboux transformations in terms of (pseudo) virtual states employed. •Scattering amplitudes checked to obey the shape invariance relation. •Errors in scattering amplitudes of some undeformed potentials in the literature corrected.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Phenomenology of SUGRA extensions of the Starobinsky model
We analyze BI-extended model in a complete form and compare the predictions with that of Starobinsky model. Under the parameter constraints in Planck 2018, we find that the dynamics of the whole inflation process described by BI-extended and Starobinsky models are nearly the same, even though there are some differences in the regions out of inflation. We also find the scales of parameters in BI-extended model and inflaton values at the first horizon crossing required to implement inflation. The changes of (n{sub s},r) fingerprints of BI-extended model and that of evolutions of inflaton field due to the variations of relevant parameters are also investigated.
79 ASTRONOMY AND ASTROPHYSICS↗
Extensive remodeling of the photosynthetic apparatus alters energy transfer among photosynthetic complexes when cyanobacteria acclimate to far-red light
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59 BASIC BIOLOGICAL SCIENCES↗