Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “effect measure”

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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Continous animal exposure to a mixture of dichloromethane and 1,1,1-trichloroethane

An investigation of the effects of combined exposure of animals to dichloromethane and 1,1,1-trichloroethane was conducted using atmospheric concentrations of each solvent which had individually produced minimal measureable effects on livers. Previously established spacecraft threshold limit values for the individual solvent compounds were studied to determine validity when both were present in an astronaut's breathing environment under continuous exposure conditions. Results show that the combined effect of 90-day continuous exposure of animals to 100 ppm dichloromethane and 1000 ppm 1,1, 1-trichloroethane is no greater than the effect of each alone. While the exposed livers of mice appeared to contain slightly more fat, the degree of increased liver weight and the liver-to-body ratios are slightly lower than those measured for each solvent alone.

Source record↗
NASA NTRS1987

Material growth and characterization for solid state devices

During this period InGaAs and InGaAsP were grown on (100)InP by liquid phase electroepitaxy (LPEE). Results of the epitaxial growth of InGaAs on sputtered quartz masked substrates are presented. The resulting surface morphology can be related to the current density distribution near the edges of a masked pattern. The quaternary InGaAs was grown with compositions corresponding to 1.3 micron and 1.5 micron emission wavelengths. Growth rates were found to be linearly dependent upon current density, and a strong dependence upon composition was noted. These compositions lie in the miscibility gap region of the alloy phase diagram at the 645 C growth temperature. Growths were performed at 685 C to avoid the miscibility gap. Epilayers were characterized by photoluminescence, X-ray diffraction, secondary ion mass spectrometry, and Hall effect measurements. Aluminum oxide was deposited on silicon and InGaAs substrates for the characterization of this material as an insulator in a field effect transistor structure. It was determined that the results did not warrant further work with the deposition from an aluminum isopropoxide source. A metallographic vapor phase epitaxy system installation is nearing completion for use in hybrid III-V semiconductor epilayer growths.

Collis, Ward J.↗
NASA NTRS1988

Numerical and experimental evaluation of a new low-leakage labyrinth seal

The effectiveness of a recently developed leakage model for evaluating new design features of most seals is demonstrated. A preliminary assessment of the present stator groove feature shows that it gives approximately a 20 percent leakage reduction with no shaft speed effects. Also, detailed distributions of predicted streamlines, axial velocity, relative pressure and turbulence energy enhance one's physical insight. In addition, the interesting measured effect of axial position of the rotor/stator pair on leakage rate and stator wall axial pressure distribution is examined.

Rhode, D. L.↗
NASA NTRS1961

Rocket Measurement of a Daytime Electron Density Profile up to 620 Kilometers

On April 27, 1961 at 1502 EST a four-stage research rocket was fired from Wallops Island, Virginia, to measure the ionospheric electron density distribution by means of Seddon's CW propagation technique. This experimental technique is based upon the dispersive Doppler effect measured at two harmonically related frequencies, in this case f = 12.267 Mc and 6f = 73.6 Mc. The electron density profile measured above the peak of the F2 region is representative of a diffusive-equilibrium distribution in an isothermal ionosphere having a temperature of 1640 deg +/- 90 deg K. This result, when compared with satellite and other data, indicates that the upper ionosphere is in thermodynamic equilibrium.

Jackson, J. E.↗
NASA NTRS1975

Jovian protons and electrons - Pioneer 11

The report presented takes into account data from the low energy telescope which were obtained during the passage of Pioneer 11 through the Jovian magnetosphere. The detector system used measures the proton flux in the range from 0.2 to 21.2 MeV in seven energy intervals and the electron flux in the range from 0.1 to 2 MeV in four intervals. The significance of the effects measured in the inner core region of the magnetosphere is discussed and attention is given to the effects of Jovian moons on the particle flux in the planetary environment.

Trainor, J. H.↗
NASA NTRS1993

SATCOM simulator speeds MSS deployment and lowers costs

Mobile satellite systems (MSS) are being proposed and licensed at an accelerating rate. How can the design, manufacture, and performance of these systems be optimized at costs that allow a reasonable return on investment? The answer is the use of system simulation techniques beginning early in the system design and continuing through integration, pre- and post-launch monitoring, and in-orbit monitoring. This paper focuses on using commercially available, validated simulation instruments to deliver accurate, repeatable, and cost effective measurements throughout the life of a typical mobile satellite system. A satellite communications test set is discussed that provides complete parametric test capability with a significant improvement in measurement speed for manufacturing, integration, and pre-launch and in-orbit testing. The test set can simulate actual up and down link traffic conditions to evaluate the effects of system impairments, propagation and multipath on bit error rate (BER), channel capacity and transponder and system load balancing. Using a standard set of commercial instruments to deliver accurate, verifiable measurements anywhere in the world speeds deployment, generates measurement confidence, and lowers total system cost.

Carey, Tim↗
NASA NTRS1983

Effects of Shuttle environment on instrument performance

Examination of the OSTA-1 payload instruments carried in the shuttle bay during the 54.25 hour mission of STS-2 indicates that the shuttle environment has no measurable effect on the Earth-viewing experiments. Operation of the payload shows that flight simulations are essential and experiment replanning practice is needed. Ground control of experiments is desirable since malfunctions of totally automated experiments cannot be fixed in flight. Alarm limits for experiments must be realistic since the crew loses interest after a few alarms. The quality and number of hours of data obtained for each experiment are listed.

Potter, A. E.↗
NASA NTRS1983

Estimation of the average exchanges in momentum and latent heat between the atmosphere and the oceans with Seasat observations

Ocean-surface momentum flux and latent heat flux are determined from Seasat-A data from 1978 and compared with ship observations. Momentum flux was measured using the Seasat-A scatterometer system (SASS) heat flux, with the scanning multichannel MW radiometer (SMMR). Ship measurements were quality selected and averaged to increase their reliability. The fluxes were computed using a bulk parameterization technique. It is found that although SASS effectively measures momentum flux, variations in atmospheric stability and sea-surface temperature cause deviations which are not accounted for by the present data-processing algorithm. The SMMR-latent-heat-flux algorithm, while needing refinement, is shown to given estimations to within 35 W/sq m in its present form, which removes systematic error and uses an empirically determined transfer coefficient.

Liu, W. T.↗
NASA NTRS1990

Mesoscale monitoring of the soil freeze/thaw boundary from orbital microwave radiometry

A technique was developed for mapping the spatial extent of frozen soils from the spectral characteristics of the 10.7 to 37 GHz radiobrightness. Through computational models for the spectral radiobrightness of diurnally heated freesing soils, a distinctive radiobrightness signature was identified for frozen soils, and the signature was cast as a discriminant for unsupervised classification. In addition to large area images, local area spatial averages of radiobrightness were calculated for each radiobrightness channel at 7 meteorologic sites within the test region. Local area averages at the meteorologic sites were used to define the preliminary boundaries in the Freeze Indicator discriminate. Freeze Indicator images based upon Nimbus 7, Scanning Multichannel Microwave Radiometer (SMMR) data effectively map temporal variations in the freeze/thaw pattern for the northern Great Plains at the time scale of days. Diurnal thermal gradients have a small but measurable effect upon the SMMR spectral gradient. Scale-space filtering can be used to improve the spatial resolution of a freeze/thaw classified image.

Dobson, Craig↗
NASA NTRS2011

Bootstrapping Process Improvement Metrics: CMMI Level 4 Process Improvement Metrics in a Level 3 World

The measurement techniques for organizations which have achieved the Software Engineering Institutes CMMI Maturity Levels 4 and 5 are well documented. On the other hand, how to effectively measure when an organization is Maturity Level 3 is less well understood, especially when there is no consistency in tool use and there is extensive tailoring of the organizational software processes. Most organizations fail in their attempts to generate, collect, and analyze standard process improvement metrics under these conditions. But at JPL, NASA's prime center for deep space robotic exploration, we have a long history of proving there is always a solution: It just may not be what you expected. In this paper we describe the wide variety of qualitative and quantitative techniques we have been implementing over the last few years, including the various approaches used to communicate the results to both software technical managers and senior managers.

Hihn, Jairus↗
NASA NTRS2014

Diurnal Variations of Stratospheric Ozone Measured by Ground-Based Microwave Remote Sensing at the Mauna Loa NDACC Site: Measurement Validation and GEOSCCM Model Comparison

There is presently renewed interest in diurnal variations of stratospheric and mesospheric ozone for the purpose of supporting homogenization of records of various ozone measurements that are limited by the technique employed to being made at certain times of day. We have made such measurements for 19 years using a passive microwave remote sensing technique at the Mauna Loa Observatory (MLO) in Hawaii, which is a primary station in the Network for Detection of Atmospheric Composition Change (NDACC). We have recently reprocessed these data with hourly time resolution to study diurnal variations. We inspected differences between pairs of the ozone spectra (e.g., day and night) from which the ozone profiles are derived to determine the extent to which they may be contaminated by diurnally varying systematic instrumental or measurement effects. These are small, and we have reduced them further by selecting data that meet certain criteria that we established. We have calculated differences between profiles measured at different times: morning-night, afternoon-night, and morning-afternoon and have intercompared these with like profiles derived from the Aura Microwave Limb Sounder (Aura-MLS), the Upper Atmosphere Research Satellite Microwave Limb Sounder (UARS-MLS),t he Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES), and Solar Backscatter Ultraviolet version 2 (SBUV2) measurements. Differences between averages of coincident profiles are typically less than 1.5 percent of typical nighttime values over most of the covered altitude range with some exceptions. We calculated averages of ozone values for each hour from the Mauna Loa microwave data, and normalized these to the average for the first hour after midnight for comparison with corresponding values calculated with the Goddard Earth Observing System Chemistry Climate Model (GEOSCCM). We found that the measurements and model output mostly agree to better than 1.5 percent of the midnight value, with one noteworthy exception: The measured morning-night values are significantly (2-3 percent) higher than the modeled ones from 3.2 to 1.8 hPa (approximately 39-43 km), and there is evidence that the measured values are increasing compared to the modeled values before sunrise in this region.

GEOSCCM model comparison↗
NASA NTRS1993

Nulling Hall-Effect Current-Measuring Circuit

Circuit measures electrical current via combination of Hall-effect-sensing and magnetic-field-nulling techniques. Known current generated by feedback circuit adjusted until it causes cancellation or near cancellation of magnetic field produced in toroidal ferrite core by current measured. Remaining magnetic field measured by Hall-effect sensor. Circuit puts out analog signal and digital signal proportional to current measured. Accuracy of measurement does not depend on linearity of sensing components.

Sullender, Craig C.↗
NASA NTRS1978

The effect of helmet loader G-cueing on pilot's simulator performance

A helmet loader has been designed and tested in a differential maneuvering simulator which provides the proper cues without restricting the pilot's movement or requiring cumbersome attachments. An experiment was conducted to determine the effect of the loader on both test pilots and operational F-15 pilots. Both the objective and subjective data from the experiment were used to determine the effect of the helmet provided acceleration cues on the simulator pilot's performance. An analysis of the obtained data indicates that the helmet-loader does have measurable effect on the pilot/simulator system. The effect is mainly seen in the transition portion of the task. The pilots significantly increase their control outputs for pitch which causes a significant increase in aircraft pitch rate.

Ashworth, B. R.↗
NASA NTRS1970

A radiometric method for measuring the insertion loss of radome materials

Radiometer system measures effective noise temperature directed towards sky, with and without radome over antenna horn. Data is then translated into computer format. With additional transmission line insertion loss data from other measurements, computer calculates insertion loss of radome material.

Seidel, B. L.↗
NASA NTRS1972

Status of Langley studies of aerodynamics and interference effects of tandem launch vehicles

Some of the aerodynamic and interference effects measured from wind-tunnel tests of three fully reusable space shuttle configurations at transonic and low-supersonic speeds are presented, and the status is given of an assessment of the analytical approach to date. The three configurations tested were a low-fineness-ratio booster combined in tandem with a delta-wing orbiter, designated the "low-fineness-ratio configuration,' and a phase B shuttle configuration consisting of the delta-wing orbiter and high-fineness-ratio booster, designated the "stage-arrangement configuration,' arranged in tandem and in parallel. The force measurements obtained at a Mach number of 1.5 for the low-fineness-ratio configuration were representative of the transonic and low-supersonic speed ranges where the interference effects are predominant and were used for comparison with values calculated at the same Mach number. This comparison is the basis for a preliminary assessment of the initial application of the analytical approach.

Scallion, W. I.↗
NASA NTRS1980

Autonomous navigation accuracy using simulated horizon sensor and sun sensor observations

A relatively simple autonomous system which would use horizon crossing indicators, a sun sensor, a quartz oscillator, and a microprogrammed computer is discussed. The sensor combination is required only to effectively measure the angle between the centers of the Earth and the Sun. Simulations for a particular orbit indicate that 2 km r.m.s. orbit determination uncertainties may be expected from a system with 0.06 deg measurement uncertainty. A key finding is that knowledge of the satellite orbit plane orientation can be maintained to this level because of the annual motion of the Sun and the predictable effects of Earth oblateness. The basic system described can be updated periodically by transits of the Moon through the IR horizon crossing indicator fields of view.

Pease, G. E.↗
NASA NTRS1996

Properties of Single Crystalline Semiconducting CoSb3

A study of the thermoelectric properties of the skutterudite compound CoSb3 was carried out on single crystals grown by the Bridgman gradient freeze technique. p- and n-type samples were obtained over a wide range of carrier concentration. Undoped As-grown crystals show p-type conductivity while n-type samples were obtained by addition of Te or Pd. Samples were characterized by x-ray diffractometry, electron microprobe analysis, and density measurements. The physical properties of CoSb3 such as linear thermal expansion coefficient, sound velocity, and Debye temperature were also determined and are presented. Seebeck coefficient, electrical resistivity, thermal conductivity, and Hall effect measurements were performed between room temperature and about 900 K. Exceptionally high Hall mobilities were obtained on p-type samples with a maximum room-temperature Hall mobility of 3300 sq cm/V.s at a carrier concentration of 1 x 10(exp 17)/cc. The results of the transport property measurements are discussed and are in agreement with some recent predictions based on band structure calculations. The potential of CoSb3 for thermoelectric applications is evaluated.

Caillat, T.↗