SEARCH · Engineering Papers

Results for “Field Procedures”

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.

SourceResearch connectionFrom yearThrough year

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

At least 667 records · Page 37

All sources NASA NTRS DOE OSTI

NASA NTRS1988

Three-dimensional self-adaptive grid method for complex flows

A self-adaptive grid procedure for efficient computation of three-dimensional complex flow fields is described. The method is based on variational principles to minimize the energy of a spring system analogy which redistributes the grid points. Grid control parameters are determined by specifying maximum and minimum grid spacing. Multidirectional adaptation is achieved by splitting the procedure into a sequence of successive applications of a unidirectional adaptation. One-sided, two-directional constraints for orthogonality and smoothness are used to enhance the efficiency of the method. Feasibility of the scheme is demonstrated by application to a multinozzle, afterbody, plume flow field. Application of the algorithm for initial grid generation is illustrated by constructing a three-dimensional grid about a bump-like geometry.

Djomehri, M. Jahed↗

NASA NTRS1988

Three-dimensional self-adaptive grid method for complex flows

Djomehri, M. Jahed↗

DOE OSTI2017

SRF Cavity Testing Using a FPGA Self Excited Loop

This document provides a detailed description of procedures for very-high precision calibration and testing of superconducting RF cavities using digital Low-Level RF (LLRF) electronics based on Field Programmable Gate Arrays (FPGA). The use of a Self-Excited Loop with an innovative procedure for fast turn-on allows the measurement of the forward, reflected and transmitted power from a single port of the directional coupler in front of the cavity, thus eliminating certain measurement errors. Various procedures for measuring the quality factor as a function of cavity fields are described, including a single RF pulse technique. Errors are estimated for the measurements.

43 PARTICLE ACCELERATORS↗

NASA NTRS1991

Field-emitter arrays for vacuum microelectronics

An ongoing program on microfabricated field-emitter arrays has produced a gated field-emitter tip structure with submicrometer dimensions and techniques for fabricating emitter arrays with tip packaging densities of up to 1.5 x 10 exp 7 tips/sq cm. Arrays have been fabricated over areas varying from a few micrometers up to 13 cm in diameter. Very small overall emitter size, materials selection, and rigorous emitter-tip processing procedures have contributed to reducing the potential required for field emission to tens of volts. Emission current densities of up to 100 A/sq cm have been achieved with small arrays of tips, and 100-mA total emission is commonly produced with arrays 1 mm in diameter containing 10,000 tips. Transconductances of 5.0 micro-S per tip have been demonstrated, indicating that 50 S/sq cm should be achievable with tip densities of 10 exp 7 tips/sq cm. Details of the cathode arrays and a variety of performance characteristics are discussed.

Spindt, C. A.↗

NASA NTRS1982

Spatial and spectral simulation of LANDSAT images of agricultural areas

A LANDSAT scene simulation capability was developed to study the effects of small fields and misregistration on LANDSAT-based crop proportion estimation procedures. The simulation employs a pattern of ground polygons each with a crop ID, planting date, and scale factor. Historical greenness/brightness crop development profiles generate the mean signal values for each polygon. Historical within-field covariances add texture to pixels in each polygon. The planting dates and scale factors create between-field/within-crop variation. Between field and crop variation is achieved by the above and crop profile differences. The LANDSAT point spread function is used to add correlation between nearby pixels. The next effect of the point spread function is to blur the image. Mixed pixels and misregistration are also simulated.

Pont, W. F., Jr.↗

NASA NTRS1982

Spatial and spectral simulation of Landsat images of agricultural areas

A Landsat scene simulation capability was developed to study the effects of small fields and misregistration on Landsat-based crop proportion estimation procedures. The simulation employs a pattern of ground polygons each with a crop ID, planting date, and scale factor. Historical greenness/brightness crop development profiles generate the mean signal values for each polygon. Historical within-field covariances add texture to pixels in each polygon. The planting dates and scale factors create between-field/within-crop variation. Between field and crop variation is achieved by the above and crop profile differences. The Landsat point spread function is used to add correlation between nearby pixels. The next effect of the point spread function is to blur the image. Mixed pixels and misregistration are also simulated. Previously announced in STAR as N82-32813

Pont, W. F., Jr.↗

DOE OSTI2018

MAGNETIC HYGIENE CONTROL ON LCLS-II CRYOMODULES FABRICATED AT JLAB

Jefferson Lab (JLab) is in collaboration with Fermi Na-tional Accelerator Laboratory (Fermilab) to build 18 cryomodules to install at the SLAC National Accelerator Laboratory?s tunnel as part of the Linac Coherent Light Source upgrade project (LCLS-II). Each LCLS-II cry-omodule hosts 8 superconducting niobium cavities that adopt the nitrogen doping technique, which aims to en-hance the cavity quality factor Qo to reduce the consumption of liquid helium used to cool down the cavities. It is known that the Qo of niobium cavities is affected by cavity surface magnetic field. Traditionally, magnetic shields made of high magnetic permeability mu-metals are employed as a passive shielding of the ambient magnetic fluxes. During the LCLS-II cryomodule development, magnetic hygiene control that includes magnetic shielding and demagnetization of parts and the whole-machine is implemented. JLab and Fermilab worked closely on developing magnetic hygiene control procedures, identifying relevant tools, investigating causes of magnetization, magnetic field monitoring, etc. This paper focuses on JLab?s experiences with LCLS-II cryomodule magnetic hygiene control during its fabrication.

Cheng, Guangfeng↗

NASA NTRS1991

A Rayleigh-Ritz analysis methodology for cutouts in composite structures

A new Rayleigh-Ritz stress analysis methodology that was developed for composite panels containing cutouts is described. The procedure, which makes use of a general assumed displacement field, accommodates circular and elliptical cutouts in biaxially loaded rectangular composite panels. Symmetric integral padups around the cutout can be included in the analysis. Benchmark results are presented to demonstrate the accuracy of the technique. Strength predictions based on the average stress criterion are generated and compared with experimental data. Finally, the stress analysis methodology is integrated into a design procedure for sizing integral padups around circular cutouts, and a sample problem is solved to illustrate its use.

Russell, Steven G.↗

DOE OSTI2013

One-point remapping of Lagrangian perturbation theory in the mildly non-linear regime of cosmic structure formation

On the smallest scales, three-dimensional large-scale structure surveys contain a wealth of cosmological information which cannot be trivially extracted due to the non-linear dynamical evolution of the density field. Lagrangian perturbation theory (LPT) is widely applied to the generation of mock halo catalogs and data analysis. In this work, we compare topological features of the cosmic web such as voids, sheets, filaments and clusters, in the density fields predicted by LPT and full numerical simulation of gravitational large-scale structure formation. We propose a method designed to improve the correspondence between these density fields, in the mildly non-linear regime. We develop a computationally fast and flexible tool for a variety of cosmological applications. Our method is based on a remapping of the approximately-evolved density field, using information extracted from N-body simulations. The remapping procedure consists of replacing the one-point distribution of the density contrast by one which better accounts for the full gravitational dynamics. As a result, we obtain a physically more pertinent density field on a point-by-point basis, while also improving higher-order statistics predicted by LPT. We quantify the approximation error in the power spectrum and in the bispectrum as a function of scale and redshift. Our remapping procedure improves one-, two- and three-point statistics at scales down to 8 Mpc/h.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS2012

Elastic-Plastic Nonlinear Response of a Space Shuttle External Tank Stringer: Stringer-Feet Imperfections and Assembly - Part 1

Elastic-plastic, large-deflection nonlinear stress analyses are performed for the external hat-shaped stringers (or stiffeners) on the intertank portion of the Space Shuttle s external tank. These stringers are subjected to assembly strains when the stringers are initially installed on an intertank panel. Four different stringer-feet configurations including the baseline flat-feet, the heels-up, the diving-board, and the toes-up configurations are considered. The assembly procedure is analytically simulated for each of these stringer configurations. The location, size, and amplitude of the strain field associated with the stringer assembly are sensitive to the assumed geometry and assembly procedure. The von Mises stress distributions from these simulations indicate that localized plasticity will develop around the first eight fasteners for each stringer-feet configuration examined. However, only the toes-up configuration resulted in high assembly hoop strains.

Knight, Norman F., Jr.↗

DOE OSTI2016

MO-FG-CAMPUS-IeP1-04: Kerma Area Product Calculation for Non-Uniform X-Ray Fields Using a Skin Dose Tracking System

Purpose: The functionality of the Dose-Tracking System (DTS) has been expanded to include the calculation of the Kerma-Area Product (KAP) for non-uniform x-ray fields such as result from the use of compensation filters during fluoroscopic procedures Methods: The DTS calculates skin dose during fluoroscopic interventions and provides a color-coded dose map on a patient-graphic model. The KAP is the integral of air kerma over the x-ray field and is usually measured with a transmission-ionization chamber that intercepts the entire x-ray beam. The DTS has been modified to determine KAP when there are beam non-uniformities that can be modeled. For example, the DTS includes models of the three compensation filters with tapered edges located in the collimator assembly of the Toshiba Infinix fluoroscopic C-Arm and can track their movement. To determine the air kerma after the filters, DTS includes transmission factors for the compensation filters as a function of kVp and beam filtration. A virtual KAP dosimeter is simulated in the DTS by an array of graphic vertices; the air kerma at each vertex is corrected by the field non-uniformity, which in this case is the attenuation factor for those rays which pass through the filter. The products of individual vertex air-kerma values for all vertices within the beam times the effective-area-per-vertex are summed for each x-ray pulse to yield the KAP per pulse and the cumulative KAP for the procedure is then calculated. Results: The KAP values estimated by DTS with the compensation filter inserted into the x-ray field agree within ± 6% with the values displayed on the fluoroscopy unit monitor, which are measured with a transmission chamber. Conclusion: The DTS can account for field non-uniformities such as result from the use of compensation filters in calculating KAP and can obviate the need for a KAP transmission ionization chamber. Partial support from NIH Grant R01-EB002873 and Toshiba Medical Systems Corp.

60 APPLIED LIFE SCIENCES↗

NASA NTRS1986

Determining the general circulation of the ocean - A nonlinear inverse problem

The usual inversion procedures for determining the oceanic circulation take the density field as given. This does not explicitly account for the mismatch between the data (which are typically a single realization of the density field) and the circulation being estimated (which may be a time mean or some other smoothed quantity), but explicit consideration of the uncertainty of the density data renders the problem nonlinear, and new estimation methods have to be used. As an example, a nonlinear inversion is successfully applied here to the simple analytical model of Stommel and Veronis (1981). It is also shown that their linear procedure, if properly used, yields a much better result than they obtained.

Mercier, H.↗

DOE OSTI2023

Improving Nb3Sn Cavity Performance Using Centrifugal Barrel Polishing

Nb3Sn superconducting radiofrequency (SRF) cavities have been an ongoing research topic for many years motivated by the potential for higher accelerating gradients and quality factors compared to niobium SRF cavities. The highest performing Nb3Sn cavities are manufactured using tin vapor-diffusion coating, which creates a Nb3Sn film with a surface roughness of around 100-200 nm. This is thought to be one of the limiting factors for the accelerating gradient of Nb3Sn cavities due to enhancement of magnetic field near sharp surface features. To smooth Nb3Sn SRF cavities, we have developed a mechanical polishing procedure which uses centrifugal barrel polishing to smooth the surface followed by a secondary tin coating step to repair the surface. We show that the accelerating field of a Nb3Sn SRF cavity is improved by applying this procedure. We also investigate the quench mechanism of the polished cavity by utilizing temperature mapping to measure which regions of the cavity e xperience heating during RF operation. We then cut samples from these regions and analyze the film microstructure and chemical composition in 3D using EDS and EBSD measurements together with a focused ion-beam (FIB) tomography technique.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2021

ERDE: The Earth-Field Resonance Detection and Evaluation Devices

Researchers at Los Alamos have developed the Earth-field Resonance Detection and Evaluation devices, or ERDE (German for “Earth”) which brings portable chemical analysis and identification into the field. ERDE uses the Earth’s magnetic field to perform nuclear magnetic resonance measurements without the need for sample preparation, costly cryogens, or calibration procedures, meaning it is extremely user-friendly. In fact, using the Earth’s magnetic field allows detection and identification of chemical species through non-magnetic pipes without sampling, reducing the likelihood of costly biofouling. This innovative new device brings together these outstanding benefits to improve processes in the detection of noxious chemicals in water supplies as well as the identification of toxic materials anywhere. There are two fully-functional ERDE prototypes and efforts are underway to miniaturize the system further for improved portability, increased sensitivity, and expanded capabilities. The Laboratory is seeking qualified licensing or CRADA partners to finalize development of this system.

47 OTHER INSTRUMENTATION↗

DOE OSTI2012

Typical hot water draw patterns based on field data

There is significant variation in hot water use and draw patterns among households. This report describes typical hot water use patterns in single-family residences in North America. We found that daily hot water use is highly variable both among residences and within the same residence. We compared the results of our analysis of the field data to the conditions and draw patterns established in the current U.S. Department of Energy (DOE) test procedure for residential water heaters. The results show a higher number of smaller draws at lower flow rates than used in the test procedure. The data from which the draw patterns were developed were obtained from 12 separate field studies. This report describes the ways in which we managed, cleaned, and analyzed the data and the results of our data analysis. After preparing the data, we used the complete data set to analyze inlet and outlet water temperatures. Then we divided the data into three clusters reflecting house configurations that demonstrated small, medium, or large median daily hot water use. We developed the three clusters partly to reflect efforts of the ASHRAE standard project committee (SPC) 118.2 to revise the test procedure for residential water heaters to incorporate a range of draw patterns. ASHRAE SPC 118.2 has identified the need to separately evaluate at least three, and perhaps as many as five, different water heater capacities. We analyzed the daily hot water use data within each cluster in terms of volume and number of hot water draws. The daily draw patterns in each cluster were characterized using distributions for volume of draws, duration of draws, time since previous draw, and flow rates.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

DOE OSTI2016

Variational projection methods for gradient crystal plasticity using Lie algebras

Summary A computational method is developed for evaluating the plastic strain gradient hardening term within a crystal plasticity formulation. While such gradient terms reproduce the size effects exhibited in experiments, incorporating derivatives of the plastic strain yields a nonlocal constitutive model. Rather than applying mixed methods, we propose an alternative method whereby the plastic deformation gradient is variationally projected from the elemental integration points onto a smoothed nodal field. Crucially, the projection utilizes the mapping between Lie groups and algebras in order to preserve essential physical properties, such as orthogonality of the plastic rotation tensor. Following the projection, the plastic strain field is directly differentiated to yield the Nye tensor. Additionally, an augmentation scheme is introduced within the global Newton iteration loop such that the computed Nye tensor field is fed back into the stress update procedure. Effectively, this method results in a fully implicit evolution of the constitutive model within a traditional displacement‐based formulation. An elemental projection method with explicit time integration of the plastic rotation tensor is compared as a reference. A series of numerical tests are performed for several element types in order to assess the robustness of the method, with emphasis placed upon polycrystalline domains and multi‐axis loading. Copyright © 2016 John Wiley & Sons, Ltd.

Truster, Timothy J.↗

DOE OSTI2018

Novel results for kinklike structures and their connections to quantum mechanics

In this work we use the deformation procedure and explore the route to obtain distinct field theory models that present similar stability potentials. Starting from systems that interact polynomially or hyperbolically, we use a deformation function which allows to construct other theories having the feature of giving rise to the same stability potentials. Such deformation function leads to smooth potentials according to a specific choice of a single parameter. Among the results, one shows that for models with asymmetric topological sectors, the appearance of a new stability potential is also possible.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2015

Al{sub 15}Ge{sub 4}Ni{sub 3}: A new intergrowth structure with Cu{sub 3}Au- and CaF{sub 2}-type building blocks

The new ternary compound Al{sub 15}Ge{sub 4}Ni{sub 3} (τ{sub 2} in the system Al–Ge–Ni) was synthesized in single crystalline form by a special annealing procedure from samples located in the three phase fields [L+Al+τ{sub 2}] and [L+Ge+τ{sub 2}]. The crystal structure of Al{sub 15}Ge{sub 4}Ni{sub 3} was determined by single-crystal X-ray diffraction. The compound crystallizes in a new structure type in space group I4-bar3m, Pearson Symbol cI88, cubic lattice parameter a=11.405(1) Å. Phase diagram investigations indicate stoichiometric composition without considerable homogeneity range; τ{sub 2} melts peritectically at T=444 °C. The crystal structure of Al{sub 15}Ge{sub 4}Ni{sub 3} shows a unique combination of simple Cu{sub 3}Au- and CaF{sub 2}-type building blocks: a three dimensional network of CaF{sub 2}-type units, formed by Ni and Al atoms, is interspaced by clusters (Al{sub 6}Ge{sub 8}) resembling unit cells of the Cu{sub 3}Au-type. Both structural motifs are connected by Al–Ge bonds. The ground state energy of the compound was obtained by DFT calculations and the densities of states were analyzed in detail. In addition, electron density maps were calculated in four different sections through the unit cell using the full potential linearized augmented plane-wave (FLAPW) method. The bonding situation in Al{sub 15}Ge{sub 4}Ni{sub 3} was discussed combining results from electronic calculations with the analysis of the coordination of atoms. - Graphical abstract: The new compound Al{sub 15}Ge{sub 4}Ni{sub 3} shows a unique combination of simple Cu{sub 3}Au- and CaF{sub 2}-type building blocks. - Highlights: • The crystal structure of Al{sub 15}Ge{sub 4}Ni{sub 3} (space group I4-bar3m) was determined. • It shows a unique combination of CaF{sub 2}- and Cu{sub 3}Au-type building blocks. • Electronic (DFT) calculations were performed to gain insight to chemical bonding.

36 MATERIALS SCIENCE↗