Search NASA⌕ Search

SEARCH · Search NASA

Results for “calculation method”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,549 records · Page 86
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Weighted Mobility

Engineering semiconductor devices requires an understanding of charge carrier mobility. Typically, mobilities are estimated using Hall effect and electrical resistivity meausrements, which are are routinely performed at room temperature and below, in materials with mobilities greater than 1 cm 2 V -1 s -1 . With the availability of combined Seebeck coefficient and electrical resistivity measurement systems, it is now easy to measure the weighted mobility (electron mobility weighted by the density of electronic states). A simple method to calculate the weighted mobility from Seebeck coefficient and electrical resistivity measurements is introduced, which gives good results at room temperature and above, and for mobilities as low as 10 -3 cm 2 V -1 s -1 , <!--FIGURE--> μ w = 331 c m 2 V s ( m Ω c m ρ ) ( T 300 K ) - 3 / 2 [ e x p [ | S | k B / e - 2 ] 1 + exp [ - 5 ( | S | k B / e - 1 ) ] + 3 π 2 | S | k B / e 1 + exp [ 5 ( | S | k B / e - 1 ) ] ] In this paper, μ w is the weighted mobility, ρ is the electrical resistivity measured in mΩ cm, T is the absolute temperature in K, S is the Seebeck coefficient, and k B /e = 86.3 µV K -1 . Weighted mobility analysis can elucidate the electronic structure and scattering mechanisms in materials and is particularly helpful in understanding and optimizing thermoelectric systems.

36 MATERIALS SCIENCE↗
DOE OSTI2021

NanoSIP: NanoSIMS Applications for Microbial Biology

High-resolution imaging with secondary ion mass spectrometry (nanoSIMS) has become a standard method in systems biology and environmental biogeochemistry and is broadly used to decipher ecophysiological traits of environmental microorganisms, metabolic processes in plant and animal tissues, and cross-kingdom symbioses. When combined with stable isotope-labeling—an approach we refer to as nanoSIP—nanoSIMS imaging offers a distinctive means to quantify net assimilation rates and stoichiometry of individual cell-sized particles in both low- and high-complexity environments. While the majority of nanoSIP studies in environmental and microbial biology have focused on nitrogen and carbon metabolism (using 15 N and 13 C tracers), multiple advances have pushed the capabilities of this approach in the past decade. The development of a high-brightness oxygen ion source has enabled high-resolution metal analyses that are easier to perform, allowing quantification of metal distribution in cells and environmental particles. New preparation methods, tools for automated data extraction from large data sets, and analytical approaches that push the limits of sensitivity and spatial resolution have allowed for more robust characterization of populations ranging from marine archaea to fungi and viruses. Further, NanoSIMS studies continue to be enhanced by correlation with orthogonal imaging and ‘omics approaches; when linked to molecular visualization methods, such as in situ hybridization and antibody labeling, these techniques enable in situ function to be linked to microbial identity and gene expression. Here we present an updated description of the primary materials, methods, and calculations used for nanoSIP, with an emphasis on recent advances in nanoSIMS applications, key methodological steps, and potential pitfalls.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2020

Renormalization and matching for the Collins-Soper kernel from lattice QCD

The Collins-Soper kernel, which governs the energy evolution of transverse- momentum dependent parton distribution functions (TMDPDFs), is required to accurately predict Drell-Yan like processes at small transverse momentum, and is a key ingredient for extracting TMDPDFs from experiment. Earlier we proposed a method to calculate this kernel from ratios of the so-called quasi-TMDPDFs determined with lattice QCD, which are defined as hadronic matrix elements of staple-shaped Euclidean Wilson line operators. Here we provide the one-loop renormalization of these operators in a regularization-independent momentum subtraction (RI'/MOM) scheme, as well as the conversion factor from the RI'/MOM-renormalized quasi-TMDPDF to the \( \overline{\mathrm{MS}} \) scheme. We also propose a procedure for calculating the Collins-Soper kernel directly from position space correlators, which simplifies the lattice determination.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

A generalized Selberg zeta function for flat space cosmologies

Flat space cosmologies (FSCs) are time dependent solutions of three-dimensional (3D) gravity with a vanishing cosmological constant. They can be constructed from a discrete quotient of empty 3D flat spacetime and are also called shifted-boost orbifolds. Using this quotient structure, we build a new and generalized Selberg zeta function for FSCs, and show that it is directly related to the scalar 1-loop partition function. We then propose an extension of this formalism applicable to more general quotient manifolds $\mathcal{M}$/ℤ, based on representation theory of fields propagating on this background. Our prescription constitutes a novel and expedient method for calculating regularized 1-loop determinants, without resorting to the heat kernel. We compute quasinormal modes in the FSC using the zeroes of a Selberg zeta function, and match them to known results.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Two splits, three ways: advances in double splitting quenches

In this work we introduce a method for calculating holographic duals of BCFTs with more than two boundaries. We apply it to calculating the dynamics of entanglement entropy in a 1+1d CFT that is instantaneously split into multiple segments and calculate the entanglement entropy as a function of time for the case of two splits, showing that our approach reproduces earlier results for the double split case. Our manuscript lays the groundwork for future calculations of the entanglement entropy for more than two splits and systems at nonzero temperature.

AdS-CFT correspondence↗
DOE OSTI2021

Analytic techniques for solving the transport equations in electroweak baryogenesis

We develop an efficient method for solving transport equations, particularly in the context of electroweak baryogenesis. It provides fully-analytical results under mild approximations and can also test semi-analytical results, which are applicable in more general cases. Key elements of our method include the reduction of the second-order differential equations to first order, representing the set of coupled equations as a block matrix of the particle densities and their derivatives, identification of zero modes, and block decomposition of the matrix. We apply our method to calculate the baryon asymmetry of the Universe (BAU) in a Standard Model effective field theory framework of complex Yukawa couplings to determine the sensitivity of the resulting BAU to modifications of various model parameters and rates, and to estimate the effect of the commonly-used thin-wall approximation.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

An integrated approach to derive relative permeability from capillary pressure

Surface tension affects all aspects of fluid flow in porous media. Through measurements of surface tension interaction under multiphase conditions, a relative permeability curve can be determined. Relative permeability is a numerical description of the interaction between two or more fluids and the porous media. It is a critical parameter for various tools that characterize subsurface multiphase flow systems, such as numerical simulation for carbon sequestration, oil and gas development, and groundwater contamination remediation. Therefore, it is critical to get a good statistical distribution of relative permeability in the porous media under study. Empirical formula for determining relative permeability from capillary pressure are already well established but do not provide the needed flexibility that is required to match laboratory-derived relative permeability curves. By expanding the existing methods for calculating relative permeability from capillary pressure data, it is possible to create both two and three-phase relative permeability curves. Mercury intrusion capillary pressure (MICP) data from the Morrow 'B' Sandstone coupled with interfacial tension and contact angle measurements were used to create a suite of relative permeability curves. Furthermore, these curves were then calibrated to a small sample of existing laboratory curves to elucidate common fitting parameters for the formation that were then used to create relative permeability curves from MICP data that does not have an associated laboratory-measured relative permeability curve.

58 GEOSCIENCES↗
DOE OSTI2018

Analysis of Transient Recovery Voltage at the Terminals of Breakers Using Current-Limiting Reactors

Current-limiting reactors (CLR) are known to have a significant effect on transition processes during short circuits (SC) leading to excesses beyond the permissible values of the transient recovery voltage (TRV) at the terminals of breakers for short-circuit currents, which in turn can lead to failure of the breakers. It is shown that the traditional (generally accepted) method for calculating transient recovery voltages based on using a circuit with the reactor replaced by lumped parameters is not suitable for magnetized CLR, and in the case of uncontrolled CLR can yield erroneous results. It is argued that there is a need to account for the distribution of the winding parameters of current-limiting reactors in calculations of the TRV at the contacts of breakers as they interrupt short circuits and relevant analytic expressions are derived.

42 ENGINEERING↗
DOE OSTI2019

Strength of Reinforced Concrete Structures of Hydroelectric Power Plants and Nuclear Power Plants

The reinforced concrete structures of hydroelectric power plants and nuclear power plants differ from civil structures by their massive nature, including high cross-sections, low reinforcement percentage, and the presence of block seams. A decrease in the safety of these structures results when these features are not taken into account. Methods of calculation that take these features into account are proposed.

42 ENGINEERING↗
DOE OSTI2019

To the Calculations of Scattering Amplitudes in Diffraction Problems for Elongated Bodies of Revolution

This paper is a complement to the article “Scattering amplitudes in a neighborhood of limit rays in short-wave diffraction by elongated bodies of revolution”. It contains discussions of some points of the article, which worth of more detailed considerations, such as the influence of the integration limits on the computation result of scattering amplitudes and the estimation of permissible values of scattering angle intervals as functions of parameters of the problems.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2019

Analyzing honeycomb photonic crystal waveguides by Dirichlet-to-Neumann maps

As an analog to graphene, honeycomb photonic crystals (PhCs) have attracted a great deal of interest in recent years. The additional degrees of freedom in a honeycomb PhC are useful in designing and optimizing waveguides, can be used to control the symmetry of the system and to realize novel optical devices. In this paper, we present an efficient numerical method for analyzing two-dimensional honeycomb PhC waveguides. Our method is based on a special supercell that covers one period of the honeycomb PhC waveguide and the so-called Dirichlet-to-Neumann map of the supercell. The method gives rise to a linear eigenvalue value problem with relatively small matrices, and it is validated by comparing with previous works. As an application of the method, we calculate edge modes for a few different PhCs. For a honeycomb PhC with dielectric rods in air, we found an edge mode at the zigzag edge, without using special modified rods at the edge. For a honeycomb PhC with air holes, we found a new edge mode when the PhC is bounded by a perfectly electric conductor.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

An elementary optical logic circuit for quantum computing: a review

The classical computing has already done wonders with computation, however limitations on speed and security of transmitted information is endorsing novel computation techniques. Quantum computing is expected to resolve complex problems especially for unachievable speed with best possible secure communication. The logic gates for two Quantum bits (qubits) are one of the most important part of information processing in Quantum computing. Although photons are the best candidates for the processing of qubit but they need lots of nonlinear coupling to perform logic operations. Recent developments in the field of integrated optics showing promising signs for the development of Quantum networks and Quantum computation. In this article we have reviewed the technology of handling polarization encoded Qubit to perform logic operations and interconnections of logic circuits.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Generation of spiraling Bessel beams from dark/antidark Gaussian beams diffracted by a curved fork-shaped hologram

In this paper, we present a theoretical study on the generation of spiraling Bessel beams by illuminating a curved fork-shaped hologram (CFH) by spatially coherent dark/antidark Gaussian beams. The amplitude expression of the generated spiraling Bessel beam is obtained by using the framework of the Fresnel diffraction approach and by means of the stationary phase method. Numerical calculations show that upon propagating, the longitudinal intensity of the generated field reaches a threshold maximum value at a distance z{sub max}. It is demonstrated that z{sub max} increases with the increasing of the topological charge p and the order m. The result corresponding to the incident Gaussian beam diffracted by CFH is obtained as a particular case of this study.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Influence of Aluminum-Carbon Composite Pellets on FeO Reduction and Iron Recovery from Electric Arc Furnace Slag

We investigated the effect of Al-C composite pellets (ACCP) on the reduction behavior of FeO in electric arc furnace (EAF) slag and the iron recovery at different n{sub Al}/(n{sub Al} + n{sub C}) at 1823 K (1550 °C). A carbothermic reaction was the dominant process at n{sub Al}/(n{sub Al} + n{sub C}) < 0.4, whereas aluminothermic reduction was the major process at n{sub Al}/(n{sub Al} + n{sub C}) > 0.6; these observations are based on the final content of FeO and Al{sub 2}O{sub 3} in the molten slag. The aluminum and carbon present in the ACCP competitively affected the reaction stoichiometry (i.e., the material balance) between the production of CO + Al{sub 2}O{sub 3} and the consumption of FeO. Iron recovery increased up to a yield of approx. 90 pct as the n{sub Al}/(n{sub Al} + n{sub C}) ratio increased. Because Al in the ACCP readily reacts to reduce FeO in the molten slag, iron recovery is proportional to the n{sub Al}/(n{sub Al} + n{sub C}) ratio. The precipitation of solid compounds in the slag phase, such as monoxide ([Mg,Fe]·O) and spinel (MgO·Al{sub 2}O{sub 3}), occurred during FeO reduction; this was experimentally confirmed as well as by thermochemical computation. Furthermore, we proposed a schematic reaction mechanism in the present study.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Sensitivity of Viscosity on Molten Ti Infusion into a B{sub 4}C-Packed Bed at the Microscale

The effect of the surface tension–viscosity dissipation driving liquid Ti flow into a B{sub 4}C packed bed was analyzed at 1941 K and 2573 K. The model consisted of randomized size distributions of pores (1 to 10 µm) mimicking a packed bed to determine the depth of infusion. Statistical uncertainty was determined as a function of viscosity and pore geometry. The computations were performed with our in-house software, which incorporates a directed acyclic graph and modified nodal analysis algorithms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

RFB Side Effects - Shunt Currents

The various models related to fluid flow, electrochemistry and shunt current, and their interactions are reviewed, and gaps identified in the development of flow battery holistic models. In a flow battery stack, the cells are electrically connected through the manifolds via the electrolyte. This results in shunt current through the electrolyte, which is a source of loss in the battery stack. This issue is examined in depth with a mathematical method of calculating shunt current distribution, the associated losses, and strategies to mitigate shunt current losses, along with the trade-offs.

Crawford, Aladsair J.↗
DOE OSTI2021

Hybrid machine learning/physics-based approach for predicting oxide glass-forming ability

Predicting the liquid compositions that will vitrify at experimentally accessible quench rates remains one of the grand challenges in the field of condensed matter physics. This glass-forming ability can be quantified as the critical quench rate needed to suppress crystallization. Knowledge of this critical quench rate also informs which glass composition could be used for new applications. There have been several physical and empirical models presented in the literature to predict the critical quench rate/glass forming ability. These models range from those theoretically derived to those quantified only through experimental characterization. In this work, we instead propose a new method to calculate the critical quench rate using the recently developed toy landscape model combined with machine learning. The toy landscape model accesses the underlying physics that control the vitrification behavior by directly simulating the liquid thermodynamics and kinetics. In conclusion, the results are discussed in terms of industrial impact, physical insights, and how the glass science community can develop improved predictions of glass-forming ability.

Crystallization↗