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At least 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1967

Standards of conduct for NASA special government employees

NASA regulations prescribing standards of conduct for all NASA employees, including special government employees, were approved by the Civil Service Commission on September 19, 1967, and by the Administrator on October 12, 1967, and were published in the Federal Register (32 F.R. 14648-14659) on October 21, 1967. The standards of conduct regulations are issued under Executive Order 11222 of May 11, 1965 (30 F.R. 6469, 3 C.F.R. 1965 Supp.; 5 C.F.R. 735.104), and Chapter 735 of the Federal Personnel Manual. For the convenience of special government employees, those portions of the NASA standards of conduct regulations which are applicable only to special government employees, Part F and Appendixes E, F, and G, are reissued in this handbook. Except for references to 'parts,' 'subparts,' 'sections,' etc., the text is identical to that published in the Federal Register.

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NASA NTRS1924

The Influence of the Form of a Wooden Beam on Its Stiffness and Strength I : Deflection of Beams with Special Reference to Shear Deformations

The purpose of this investigation was to determine to what extent ordinary deflection formulas, which neglect shear deformations, are in error when applied to beams of various sections, and to develop reasonably accurate yet comparatively simple formulas which take into account such deformations. A great many tests were made to determine the amount of shear deformation for beams of various sections tested over many different spans. As the span over which the beam is tested is increased the error introduced by neglecting shear deformations becomes less, and the values obtained by substituting measured deflections in the ordinary formulas approach more nearly the modulus of elasticity in tension and compression. For short spans the error is considerable and increases rapidly as the span is reduced. Two formulas were developed for estimating the magnitude of shear deformations, both of which have been verified by tests. The first assumes the parabolic distribution of shear on a cross section of a beam and, starting with a differential volume, the distortion due to shear is determined by the ordinary methods of summarizing the work. The second assumes that the deflections due to shear in any two beams of the same length, height, and moment of inertia, which are similarly loaded, are proportional to the summations of the shear stresses on their respective vertical sections. Both formulas check experimental results very closely when the calculations are made with great refinement.

Newlin, J A↗
NASA NTRS1975

Thermal diffuse X-ray scattering in simple metals

Calculations are reported for the ionic structure factor and X-ray scattering cross section of sodium (at T=0 K and 90 K) and lithium (both isotopes at T=0 K) within the harmonic approximation. An evaluation of the appropriate displacement- displacement correlation function by the special point method circumvents the need for a multiphonon expansion. In the case of sodium, the structure in the one-phonon scattering was straightforwardly accounted for, and an approximate expansion was obtained for all multiphonon scattering. By treating core and conduction electrons on an equal footing, it is shown that information on the conduction electron system is present in the forward scattering component. In lithium the one-phonon cross section at small angles aids in the determination of the effective electron-ion interaction.

Straus, D. M.↗
DOE OSTI2023

Neutron Leakage Spectra of the EUCLID Experiment [Abstract]

Integral experiments with sub-critical and critical configurations of special nuclear material are performed in support of nuclear data validation and adjustment. Different nuclear data evaluations may have different values for individual cross sections due to uncertainties in (or lack of) differential experiments, but compensating errors in these data sets can lead to the same k eff results for one application while vastly different for another application. One example of this is 239 Pu, where both ENDF/B-VIII.0 and JEFF-3.3 correctly compute k eff of the Jezebel critical assembly, but the individual contributions from each reaction are vastly different. To help resolve this specific case, the Experiments Underpinned by Computational Learning for Improvements in Nuclear Data (EUCLID) project used machine learning to design a set of experiments to help resolve the compensating errors in 239 Pu. A total of six responses were measured during the experimental campaign, which constrain the data in ways that k eff alone cannot and will be used for adjustment of the nuclear data. One of these responses is the neutron leakage spectrum, which recent work has shown to be useful for constraining the prompt fission neutron spectrum and inelastic scattering. The neutron leakage spectra were measured utilizing a 3 in. right cylinder EJ-301D detector. The measured signal in the detector was deconvoluted using spectrum unfolding techniques, which are presented and compared to simulations.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2011

Measuring the lifetime of trapped sleptons using the general purpose LHC detectors

In supergravity where the gravitino is the lightest supersymmetric particle, the next-to-lightest supersymmetric particle decays to the gravitino with a naturally long lifetime (10{sup 4}-10{sup 8} s). However, cosmological constraints favor charged slepton next-to-lightest supersymmetric particles with lifetimes below a year as the natural next-to-lightest supersymmetric particle candidate. For this scenario we report a method to accurately determine the slepton lifetime and supersymmetry cross section from observation of the decays of sleptons trapped in the material comprising the main detector (ATLAS, CMS). A measurement of the lifetime to 5% is possible after 3 yr at nominal luminosity and running conditions. This method is sensitive to the cosmologically preferred stau lifetime of {approx}37 days and does not require the use of ancillary trapping volumes or special LHC experiment initiated beam dump requirements.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Development of 17 N as a time-tagged neutron source for calibration of large antineutrino detectors

Large antineutrino detectors hold the potential for remote nuclear reactor monitoring and discovery, which is of great interest for nonproliferation and treaty verification applications. Correlated-particle calibration sources are especially useful for large-volume designs based on detection of inverse beta-decay events, as the timing information of the coincident particles improves background rejection and event reconstruction. 17 N is a promising calibration source since it emits beta-correlated delayed neutrons and can be produced relatively easily using high-energy neutrons. In this work, we examine the feasibility of 17 N as a time-tagged calibration source for large antineutrino detectors. 17 N was produced using a DT neutron generator from a water sample enriched in 17 O, and the observed production rates were found to be consistent with previous measurements of the 17 O(n,p) 17 N reaction cross-section. As a result, time-tagging of 17 N delayed neutrons is demonstrated via beta-neutron coincidence measurements conducted using a specialized beta detector.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1973

Specification of mesospheric density, pressure, and temperature by extrapolation

A procedure is presented which employs an extrapolation technique to obtain estimates of density, pressure, and temperature up to 90 km from 52 km data. The resulting errors are investigated. The procedure is combined with a special temperature interpolation method around the stratopause to produce such estimates at eight levels between 36 km and 90 km from North American sectional chart data at 5, 2, and 0.4 mb. Fifth charts were processed to obtain mean values and standard deviations at grid points for midseasonal months from 1964 to 1966. The mean values were compared with Groves' model, and internal consistency tests were performed upon the statistics. Through application of the extrapolation procedure, the atmospheric structure of a stratospheric warming event is studied.

Graves, M. E.↗
NASA NTRS1984

Evaluation results of the 700 deg C Chinese strain gages

There is a continuing interest and need for resistance strain gages capable of making static strain measurements on components located in the hot section of gas turbine engines. A paper by Tsen-tai Wu describes the development and evaluation of high temperature gauges fabricated from specially developed Fe-Cr-Al-V-Ti-Y alloy wire. Several of these gages and a quantity of P12-2 ceramic adhesive were purchased for evaluation. Nine members of the aircraft turbine engine community were invited to participate in an evaluation of these gages. Each participant was sent one strain gage, a small amount of ceramic adhesive, instructions for mounting the gage on a test beam, and a set of suggestions for the experiment. Data on gage factor variation with temperature, apparent strain, and drift are discussed.

Hobart, H. F.↗
NASA NTRS1997

Chemical Kinetics and Photochemical Data for Use in Stratospheric Modeling

This is the twelfth in a series of evaluated sets of rate constants and photochemical cross sections compiled by the NASA Panel for Data Evaluation. The primary application of the data is in the modeling of stratospheric processes, with special emphasis on the ozone layer and its possible perturbation by anthropogenic and natural phenomena.

DeMore, W. B.↗
DOE OSTI2026

Semi-inclusive deep-inelastic scattering on a polarized spin-1 target. II. Deuteron and spectator nucleon tagging

We develop the theoretical framework for semi-inclusive deep-inelastic scattering on a polarized spin-1 target and apply it to scattering on the polarized deuteron with spectator nucleon tagging. In Part I (previous article), we present the general form of the semi-inclusive cross section and polarization observables for the spin-1 target. In Part II (this article), we consider deep-inelastic scattering on the polarized deuteron with spectator nucleon tagging as a special case of target fragmentation. Methods of light-front quantization are employed to separate nuclear and hadronic structure in the high-energy process and achieve a composite description. The light-front wave function of the polarized deuteron is obtained from a rotationally covariant three-dimensional wave function in the center-of-mass frame of the proton-neutron system. The tagged structure functions are computed in the impulse approximation. The momentum and spin distribution of the active nucleon are controlled by the deuteron polarization and the detected spectator momentum (𝐷/𝑆 wave ratio). The cross section and spin asymmetries are evaluated for general deuteron polarization (vector and tensor, longitudinal and transverse) as functions of the spectator momentum. Tensor-polarized spin asymmetries of order unity are achieved for spectator momenta of approximately 300 MeV, which select configurations with a large 𝐷 wave. Sum rules for the tagged spin structure functions are derived. The results can be used for simulations of spectator tagging in future polarized fixed-target experiments (Jefferson Lab) or at the Electron-Ion Collider.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Measuring Fiber Orientation of Elliptical Fibers from Optical Microscopy

The orientation of fibers with elliptical cross-sections cannot be estimated using standard optical microscopy analysis methods in which the ratio of the minor-axis to the major-axis and orientation of the major-axis are directly used to determine the fiber spherical coordinates, θ and ϕ . A new method for estimating the orientation of fibers with elliptical cross-sections is presented and validated using both simulations and experiments. Fibers with elliptical cross-sections rather than circular possess a roll degree of freedom, which significantly affects the dimensions of projected cross-sections in viewing planes. The equations of the projected ellipse of an elliptic cylinder onto a viewing plane are determined in terms of typical spherical coordinate system angles, θ and ϕ , the roll angle, α , and the fiber semi-major and semi-minor diameters. Fiber angles are determined by numerical fitting of the developed equations to measured ellipses. An ambiguity in the determined angles is identified, and, in the special case of fiber bundles, a scheme is presented by which the ambiguity can be resolved. Validation experiments showed that the method is quite effective at estimating fiber orientation from micrographs when fiber cross-section dimensions are measured beforehand, and the additional ambiguity is resolved easily in the case of fiber bundles.

Sharp, Nathan D.↗
NASA NTRS1974

The application of space technology to practical problems such as those currently facing the mountain sections of the State of Colorado

Rapid growth in small Colorado mountain communities and dangers posed by development in areas that are potentially dangerous to life and property due to natural processes are studied. Special attention was given to snow avalanche, mudflow, rockfall, landslide and flood, as well as the slow continuous and frequently imperceptible form of soil creep and associated mass movement. Data are also given on the relative reliability of ERTS and Skylab imagery and conventional photography in identifying avalanche paths and run out zones.

Ives, J. D.↗
DOE OSTI2011

High-Quality Cross-Sectioning Method: Examples of Applications in Optimizing Solar Cell Contact Firing

A damage-free polishing method is developed to prepare a high-quality cross-section of a large length of a solar cell. A 1-inch-long sample is diced from the solar cell and embedded in wax using a specially designed chuck. The sample edge is sequentially polished by progressively reducing the grit sizes. The final polishing is done by Chemical Mechanical Polishing (CMP). This polishing procedure produces a highly flat edge, with excellent interfaces between metal contacts and the Si cell. The planarity of the wafer edge makes it possible to perform a variety of analyses of various regions and the interfaces of the cell, using optical microscopy, EDX, scanning electron microscopy (SEM), and conductive AFM (C-AFM). Here, we will discuss some details of the chuck and the polishing procedure, and present some applications for optimizing the contact firing process. This method has an added advantage of delineating the back surface field for optical observation.

14 SOLAR ENERGY↗
NASA NTRS1981

The NASTRAN theoretical manual

Designed to accommodate additions and modifications, this commentary on NASTRAN describes the problem solving capabilities of the program in a narrative fashion and presents developments of the analytical and numerical procedures that underlie the program. Seventeen major sections and numerous subsections cover; the organizational aspects of the program, utility matrix routines, static structural analysis, heat transfer, dynamic structural analysis, computer graphics, special structural modeling techniques, error analysis, interaction between structures and fluids, and aeroelastic analysis.

Source record↗
NASA NTRS1991

Space architecture monograph series. Volume 4: Genesis 2: Advanced lunar outpost

This research and design study investigated advanced lunar habitats for astronauts and mission specialists on the Earth's moon. Design recommendations are based on environmental response to the lunar environment, human habitability (human factors and environmental behavior research), transportability (structural and materials system with least mass), constructability (minimizing extravehicular time), construction dependability and resilience, and suitability for NASA launch research missions in the 21st century. The recommended design uses lunar lava tubes, with construction being a combination of Space Station Freedom derived hard modules and light weight Kevlar laminate inflatable structures. The proposed habitat includes research labs and a biotron, crew quarters and crew support facility, mission control, health maintenance facility, maintenance work areas for psychological retreat, privacy, and comtemplation. Furniture, specialized equipment, and lighting are included in the analysis and design. Drawings include base master plans, construction sequencing, overall architectural configuration, detailed floor plans, sections and axonometrics, with interior perspectives.

Fieber, Joseph P.↗
NASA NTRS1960

Flight Measurement of Wall-Pressure Fluctuations and Boundary-Layer Turbulence

The results are presented for a flight test program using a fighter type jet aircraft flying at pressure altitudes of 10,000, 20,000, and 30,000 feet at Mach numbers from 0.3 to 0.8. Specially designed apparatus was used to measure and record the output of microphones and hot-wire anemometers mounted on the forward-fuselage section and wing of the airplane. Mean-velocity profiles in the boundary layers were obtained from total-pressure measurements. The ratio of the root-mean-square fluctuating wall pressure to the free-stream dynamic pressure is presented as a function of Reynolds number and Mach number. The longitudinal component of the turbulent-velocity fluctuations was measured, and the turbulence-intensity profiles are presented for the wing and forward-fuselage section. In general, the results are in agreement with wind-tunnel measurements which have been-reported in the literature. For example, the variation the square root of p(sup 2)/q times the square root of p(sup 2) is the root mean square of the wall-pressure fluctuation, and q is the free-stream dynamic pressure) with Reynolds number was found to be essentially constant for the forward-fuselage-section boundary layer, while variations at the wing station were probably unduly affected by the microphone diameter (5/8 in.), which was large compared with the boundary-layer thickness.

Mull, Harold R.↗
DOE OSTI2023

Critical Experiments Targeting the Epithermal/Intermediate Cross Sections of Tantalum

Sandia National Laboratories (SNL) and Oak Ridge National Laboratory (ORNL) have collaborated to develop a capability to test the epithermal/intermediate cross sections of materials at the SNL critical experiments facility using the Seven Percent Critical Experiment (7uPCX) fuel. The Sandia Critical Experiments Program provides a specialized facility for performing water moderated and reflected critical experiments with UO 2 fuel rod arrays. The facility offers the ability to modify the core configuration and reactor tank to evaluate various reactor cores for pitch, moderator characteristics, and other criteria. A history of safe operations and flexibility in reactor core configuration has resulted in the completion of nine sets of critical benchmark experiments that have been documented in the International Criticality Safety Benchmark Evaluation Project (ICSBEP) Handbook. The experiment described here is expected to be evaluated for inclusion in the 2024 edition of the ICSBEP Handbook.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗