Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Curves”

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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Hubble Space Telescope Observations of GW170817: Complete Light Curves and the Properties of the Galaxy Merger of NGC 4993

We present the complete set of Hubble Space Telescope imaging of the binary neutron star merger GW170817 and its optical counterpart AT 2017gfo. Including deep template imaging in F814W, F110W, F140W, and F160W at 3.4 yr post-merger, we reanalyze the full light curve of AT 2017gfo across 12 bands from 5 to 1273 rest-frame days after merger. We obtain four new detections of the short γ-ray burst 170817A afterglow from 109 to 170 rest-frame days post-merger. These detections are consistent with the previously observed β = -0.6 spectral index in the afterglow light curve with no evidence for spectral evolution. We also analyze our limits in the context of kilonova afterglow or IR dust echo emission but find that our limits are not constraining for these models. We use the new data to construct deep optical and IR stacks, reaching limits of M = -6.3 to -4.6 mag, to analyze the local environment around AT 2017gfo and low surface brightness features in its host galaxy NGC 4993. We rule out the presence of any globular cluster at the position of AT 2017gfo to 2.3 × 10$^{4}$L$_{⊙}$, including those with the reddest V - H colors. Finally, we analyze the substructure of NGC 4993 in deep residual imaging and find shell features that extend up to 71."8 (14.2 kpc) from NGC 4993. The shells have a cumulative stellar mass of 6.3 × 10$^{8}$M$_{⊙}$, roughly 2% of NGC 4993, and mass-weighted ages of >3 Gyr. We conclude that it was unlikely that the GW170817 progenitor system formed in the galaxy merger.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Connecting the Light Curves of Type IIP Supernovae to the Properties of Their Progenitors

Abstract Observations of core-collapse supernovae (CCSNe) reveal a wealth of information about the dynamics of the supernova ejecta and its composition but very little direct information about the progenitor. Constraining properties of the progenitor and the explosion requires coupling the observations with a theoretical model of the explosion. Here we begin with the CCSN simulations of Couch et al., which use a nonparametric treatment of the neutrino transport while also accounting for turbulence and convection. In this work we use the SuperNova Explosion Code to evolve the CCSN hydrodynamics to later times and compute bolometric light curves. Focusing on Type IIP SNe (SNe IIP), we then (1) directly compare the theoretical STIR explosions to observations and (2) assess how properties of the progenitor’s core can be estimated from optical photometry in the plateau phase alone. First, the distribution of plateau luminosities ( L 50 ) and ejecta velocities achieved by our simulations is similar to the observed distributions. Second, we fit our models to the light curves and velocity evolution of some well-observed SNe. Third, we recover well-known correlations, as well as the difficulty of connecting any one SN property to zero-age main-sequence mass. Finally, we show that there is a usable, linear correlation between iron core mass and L 50 such that optical photometry alone of SNe IIP can give us insights into the cores of massive stars. Illustrating this by application to a few SNe, we find iron core masses of 1.3–1.5 M ⊙ with typical errors of 0.05 M ⊙ . Data are publicly available online on Zenodo: doi: 10.5281/zenodo.6631964 .

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Photometry of Outer Solar System Objects from the Dark Energy Survey. I. Photometric Methods, Light-curve Distributions, and Trans-Neptunian Binaries

We report the methods of and initial scientific inferences from the extraction of precision photometric information for the >800 trans-Neptunian objects (TNOs) discovered in the images of the Dark Energy Survey (DES). Scene-modeling photometry is used to obtain shot-noise-limited flux measures for each exposure of each TNO, with background sources subtracted. Comparison of double-source fits to the pixel data with single-source fits are used to identify and characterize two binary TNO systems. A Markov Chain Monte Carlo method samples the joint likelihood of the intrinsic colors of each source as well as the amplitude of its flux variation, given the time series of multiband flux measurements and their uncertainties. A catalog of these colors and light-curve amplitudes A is included with this publication. We show how to assign a likelihood to the distribution q(A) of light-curve amplitudes in any subpopulation. Using this method, we find decisive evidence (i.e., evidence ratio <0.01) that cold classical (CC) TNOs with absolute magnitude 6 < H$_{r}$ < 8.2 are more variable than the hot classical (HC) population of the same H$_{r}$, reinforcing theories that the former form in situ and the latter arise from a different physical population. Resonant and scattering TNOs in this H$_{r}$ range have variability consistent with either the HCs or CCs. DES TNOs with H$_{r}$ < 6 are seen to be decisively less variable than higher-H$_{r}$ members of any dynamical group, as expected. More surprising is that detached TNOs are decisively less variable than scattering TNOs, which requires them to have distinct source regions or some subsequent differential processing.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

HarDWR - Cumulative Water Rights Curves

A dataset within the Harmonized Database of Western U.S. Water Rights (HarDWR). For a detailed description of the database, please see the meta-record v2.0. Changelog v2.0 - Recalculated based on Harmonized Water Rights Records v2.0 sourced from WestDAAT - Added "Unspecified" was a water source category, and files associated with this category v1.01 - Updated the names of each file with an ID number less than 3 digits to include leading 0s v1.0 - Initial public release Description This product an updated version of the database used as input to the WBM model (Grogan et al. in review; Grogan et al. 2022), and is the result of the step creating cumulative water rights curves described in Lisk et al. (2024). This database contains 2,667 individual .csv files, three for each Water Management Area (WMA) in the 11-state region. File Naming WMA_[###]_[X]W.csv, where [###] is the unique identifier for each WMA, and [X] is either "S" for surface water rights, "G" for groundwater rights, or "U" for unspecified. Column headers in each file: Year: the priority date year CUML: the total cumulative water rights allocated up to this priority date year (ft3s-1) Irrigation: The percent of cumulative water rights allocated to the Irrigation category up to this priority date year (%) Domestic: The percent of cumulative water rights allocated to the Domestic category up to this priority date year (%) Livestock: The percent of cumulative water rights allocated to the Livestock category up to this priority date year (%) Fish: The percent of cumulative water rights allocated to the Fish category up to this priority date year (%) Industrial: The percent of cumulative water rights allocated to the Industrial category up to this priority date year (%) Environmental: The percent of cumulative water rights allocated to the Environmental category up to this priority date year (%) Other: The percent of cumulative water rights allocated to the Other category up to this priority date year (%) In addition to the database files, there is a companion .csv file, called stateWMAs_ID.csv. The main purpose of this file is to provide the means of translating between the [###] unique identifier and the various other id of the WMA the file is attached to. This translation file has five columns, which are: basinNum: The official state given alpha-numeric identifier of the WMA basinName: the state provided English name of the area, where applicable state: the state name uniID: a unique identifier we created by concatenating the state name, and underscore, and the state numerical ID ID: a unique numeric identifier we created as a requirement for the files to be used within WBM (Grogan et al. in review) For those whom may be interested in exploring our code more in depth, we are also making available an internal data file for convenience. The file is in .RData format and contains everything described above as well as some minor additional objects used within the code calculating the cumulative curves. For completeness, here is a detailed description of the various objects which can be found within the .RData file: states: A character vector containing the state names for those states in the study region. More importantly, the index of the state name is also the index in which that state's data can be found in the various following list objects. For example, if California is the second index in this object, the data for California will also be in the second index for each accompanying list. wmasRightsPersGrd: A list of nested lists of data frames. Each state has one entry in the top level list and consist of a list with one data frame per WMA. The data frames in this object are the same as the above described .csv files, specifically for groundwater. wmasRightsPersSur: A list of nested lists of data frames. Each state has one entry in the top level list and consist of a list with one data frame per WMA. The data frames in this object are the same as the above described .csv files, specifically for surface water. wmasRightsPersUnsp: A list of nested lists of data frames. Each state has one entry in the top level list and consist of a list with one data frame per WMA. The data frames in this object are the same as the above described .csv files, specifically for water from an unspecified source. wmasRightsTotsGrd: A list of nested lists of data frames. Each state has one entry in the top level list and consist of a list with one data frame per WMA. The values in the data frames of this object would be the equivalent to multiplying the CUML column by the sector percentage columns to create the sector total ft3s-1, specifically for groundwater. This object is provided for convenience to check out original total values, if desired. wmasRightsTotsSur: A list of nested lists of data frames. Each state has one entry in the top level list and consist of a list with one data frame per WMA. The values in the data frames of this object would be the equivalent to multiplying the CUML column by the sector percentage columns to create the sector total ft3s-1, specifically for surface water. This object is provided for convenience to check out original total values, if desired. wmasRightsTotsUnsp: A list of nested lists of data frames. Each state has one entry in the top level list and consist of a list with one data frame per WMA. The values in the data frames of this object would be the equivalent to multiplying the CUML column by the sector percentage columns to create the sector total ft3s-1, specifically for water from an unspecified source. This object is provided for convenience to check out original total values, if desired. wmaIDByState: A list of data frames which contain the by state allocation by WMA matrix. There is a matrix for each state in a different data frame within the object.

Economics↗
NASA NTRS1970

Digital-voltage curve generator

Curve generator capable of producing precisely repeatable curve for any single-valued function of voltage versus time uses digital approach, implemented by means of clocked feedback shift register, large scale integrated circuit diode matrix comprising about 12,000 diodes, counter, and digital-to-analog converter.

Perlman, M.↗
NASA NTRS1971

On propagation of long waves in curved ducts

Long acoustic wave propagation in curved ducts and junctions between straight and curved ducts utilizing Bessel functions for steady and decaying fields of motion

Rostafinski, W.↗
NASA NTRS1972

Curve crossing for low energy elastic scattering of He (plus) by Ne

The perturbation seen in the experimental differential elastic scattering cross section for the 40 eV He(+) + Ne system was attributed to a single crossing of two intermolecular potential energy curves. A new theoretical treatment of the curve crossing problem, that of Delos and Thorson, is employed to obtain the crossing probabilities and phases associated with the crossing. These are determined by utilizing ab initio potentials involved in the crossing and are further used in a partial wave calculation of the cross section, which is compared with our experiment. The origin of the oscillatory structure observed in the differential cross section is discussed in semiclassical terms by defining the problem in terms of two pseudo-deflection functions. A rainbow effect is shown to be related to a particular feature (a maximum rather than a minimum) of these deflection functions.

Bobbio, S. M.↗
NASA NTRS1972

Investigation of forming curved ablative panels from flat panels for space shuttle

The purpose of this study was to determine the feasibility of reforming flat ablative panels to a curved configuration. The study indicated that if the panels could be shaped to a radius of 2.54 m (100 in.) then 88.7% of the surface area of the orbiter could be covered, and that if they could be shaped to a radius of 3.81 m (150 in.) then 77.2% of the surface could be covered. Two basic approaches were followed to determine the best method for forming the flat panels to a curved shape. The first was to determine if partially cured panels could be formed, allowing the forming heat cycle to complete the curing of the ablator. The second method was to form fully cured flat panels into the desired curvature through a secondary heat cycle. Measurements made on the panels during storage indicated that they continued to straighten out over time. This was attributed to residual stresses locked into the panels that had not been fully relaxed by the heat cycle.

Chandler, H. H.↗
NASA NTRS1972

Use of the Hough transformation to detect lines and curves in pictures.

Hough (1962) has proposed an interesting and computationally efficient procedure for detecting lines in pictures. It is pointed out that the use of angle-radius rather than slope-intercept parameters simplifies the computation further. Two alternative interpretations of Hough's method are presented. The transform approach considered can be extended to arbitrary curves. A convenient parameterization for the family of curves of interest has to be selected. It is important to have a small number of parameters since the accumulator implementation requires quantization of the entire parameter space.

Duda, R. O.↗
NASA NTRS1972

An analytical investigation of the impingement jets on curved deflectors

Numerical solutions are obtained for the cases of straight circular jets impinging on axisymmetric curved surfaces and plane jets impinging symmetrically on two-dimensional curved surfaces. These geometries are representative of some types of thrust reversers for transport aircraft. The solutions are based on the assumptions of incompressible and potential flow. The velocity field, pressure distribution at the deflector surface and reverser effectiveness are predicted for deflector turning angles of 15 to 75 deg, deflector width to jet diameter ratios of 1.5 to 2.0, and ratios of deflector clearance to jet diameter of 1.0 to 3.0. Reverser effectiveness is found to be a maximum for a ratio of deflector clearance to jet diameter of about 2.0. The effect of back pressuring due to the presence of the deflector is predicted. Experimental verification of the theoretical predictions is obtained. A compressible solution obtained for a limited number of cases indicates that the incompressible solution is satisfactory for jet exit Mach numbers less than 0.8.

Schnurr, N. M.↗
NASA NTRS1973

Propagation of waves of acoustic frequencies in curved ducts

The propagation of waves of acoustic frequencies in curved ducts is studied for the first four modes. The analysis makes use of Bessel functions to construct curves of wave number in the duct versus imposed wave number. The results apply to ducts of arbitrary width and arbitrary radii of curvature. The characteristics of motion in a bend are compared with propagation of waves in a straight duct, and important differences in the behavior of waves are noted.

Rostafinski, W.↗
NASA NTRS1973

A fixed-base simulation study of two STOL aircraft flying curved, descending instrument approach paths

A real-time, fixed-base simulation study has been conducted to determine the curved, descending approach paths (within passenger-comfort limits) that would be acceptable to pilots, the flight-director-system logic requirements for curved-flight-path guidance, and the paths which can be flown within proposed microwave landing system (MLS) coverage angles. Two STOL aircraft configurations were used in the study. Generally, no differences in the results between the two STOL configurations were found. The investigation showed that paths with a 1828.8 meter turn radius and a 1828.8 meter final-approach distance were acceptable without winds and with winds up to at least 15 knots for airspeeds from 75 to 100 knots. The altitude at roll-out from the final turn determined which final-approach distances were acceptable. Pilots preferred to have an initial straight leg of about 1 n. mi. after MLS guidance acquisition before turn intercept. The size of the azimuth coverage angle necessary to meet passenger and pilot criteria depends on the size of the turn angle: plus or minus 60 deg was adequate to cover all paths execpt ones with a 180 deg turn.

Benner, M. S.↗
NASA NTRS1972

On propagation of long waves in curved ducts.

A two-dimensional detailed study of the behavior of long waves in curved ducts and in junctions between straight and curved ducts will be given. The mathematical treatment of the problem utilizes the method of separation variables. Solutions and expressions for principal mode of the wave are obtained by using the linearized equation of motion solved for its characteristic values. The unavoidable approximations in the numerical solutions of the cylindrical functions are due to use of series expansion of Bessel functions and from restrictions necessary to solve infinite matrices.

Rostafinski, W.↗
NASA NTRS1972

An analytical investigation of the impingement of jets on curved deflectors.

Numerical solutions are obtained for the cases of straight circular jets impinging on axisymmetric curved surfaces, and plane jets impinging symmetrically on two-dimensional curved surfaces. These geometries are representative of some types of thrust reversers for transport aircraft. The solutions are based on the assumptions of incompressible and potential flow. The velocity field, pressure distribution at the deflector surface, and reverser effectiveness are predicted for deflector turning angles of 15 to 75 deg, deflector width to jet diameter ratios of 1.5-2.0, and ratios of deflector clearance to jet diameter of 1.0-3.0. Reverser effectiveness is found to be a maximum for a ratio of deflector clearance to jet diameter of about 2.0. The effect of back pressuring resulting from the presence of the deflector is predicted.

Schnurr, N. M.↗
NASA NTRS1973

Curve crossing for low-energy elastic scattering of He/+/ by Ne.

The perturbation seen in the experimental differential elastic-scattering cross section for the 40-eV He/+/ + Ne system has been attributed to a single crossing of two intermolecular potential-energy curves. A new theoretical treatment of the curve-crossing problem, namely, that of Delos and Thorson, is employed to obtain the crossing probabilities and phases associated with the crossing. These are determined by utilizing ab initio potentials involved in the crossing and are further used in a partial-wave calculation of the cross section, which is compared with our experiment. The origin of the oscillatory structure observed in the differential cross section is discussed in semiclassical terms by defining the problem in terms of two pseudo-deflection-functions. A rainbow effect is shown to be related to a particular feature (a maximum rather than a minimum) of these deflection functions.

Bobbio, S. M.↗
NASA NTRS1973

The 3.5 micron light curves of long period variable stars

Infrared observations at an effective wavelength of 3.5 microns of a selected group of long period variable (LPV) stars are presented. Mira type and semiregular stars of M, S, and C spectral classifications were monitored throughout the full cycle of variability. Although the variable infrared radiation does not exactly repeat in intensity or time, the regularity is sufficient to produce mean 3.5 micron light curves. The 3.5 micron maximum radiation lags the visual maximum by about one-seventh of a cycle, while the minimum 3.5 micron intensity occurs nearly one-half cycle after infrared maximum. In some stars, there are inflections or humps on the ascending portion of the 3.5 micron light curve which may also be seen in the visual variations.

Strecker, D. W.↗