MSFN reliability - A summary of theory and results
Mean time between failure and confidence limits for unified S-band system of Manned Space Flight Network based on reliability and performance data from unmanned Apollo flights
Kalil, F.↗
SEARCH · Engineering Papers
Results for “confidence limits”
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.
Reliability testing and demonstration session 3-B
Statistical method in reliability tests including confidence limits for normal, lognormal, and binomial functions
Lalli, V.↗
Acceptance sampling for the normal distribution - Standard deviation unknown but assumed constant
Standard deviation estimates causing operating characteristic curves to be random variables in quality control acceptance sampling plans and methods for computing confidence limits
Sidik, S. M.↗
Performance of silicon solar cell assemblies
Solar cell assembly current-voltage characteristics, thermal-optical properties, and power performance were determined. Solar cell cover glass thermal radiation, optical properties, confidence limits, and temperature intensity effects on maximum power were discussed.
Ross, R. G., Jr.↗
Supporting data package for TR 32-1541, effects of storage temperatures on silicon solar cell contacts
A series of summary curves is presented for cells having various contact systems, depicting the effects of temperature exposure as a function of time on the electrical and mechanical characteristics. Each curve represents the results obtained from a minimum of 32 and a maximum of 1104 individual data inputs and includes the 95% confidence limits associated with each time-temperature combination for which measurements were obtained. The curves are useful for detailed analysis and comparison of the behavior of the contact system as a function of the environmental conditions studied.
Berman, P. A.↗
The Viking project safety program
The safety requirements and the management of these requirements for the Viking Project are given. Potential hazards are identified and ways of reducing or providing a sound confidence limit are analyzed.
Donald H. Ward↗
Micro-organism distribution sampling for bioassays
Purpose of sampling distribution is to characterize sample-to-sample variation so statistical tests may be applied, to estimate error due to sampling (confidence limits) and to evaluate observed differences between samples. Distribution could be used for bioassays taken in hospitals, breweries, food-processing plants, and pharmaceutical plants.
Nelson, B. A.↗
Mathematical estimation of the level of microbial contamination on spacecraft surfaces by volumetric air sampling
Microbiological sampling methods presently used for enumeration of microorganisms on spacecraft surfaces require contact with easily damaged components. Estimation of viable particles on surfaces using air sampling methods in conjunction with a mathematical model would be desirable. Parameters necessary for the mathematical model are the effect of angled surfaces on viable particle collection and the number of viable cells per viable particle. Deposition of viable particles on angled surfaces closely followed a cosine function, and the number of viable cells per viable particle was consistent with a Poisson distribution. Other parameters considered by the mathematical model included deposition rate and fractional removal per unit time. A close nonlinear correlation between volumetric air sampling and airborne fallout on surfaces was established with all fallout data points falling within the 95% confidence limits as determined by the mathematical model.
Oxborrow, G. S.↗
Assessment of NDE reliability data
Twenty sets of relevant nondestructive test (NDT) reliability data were identified, collected, compiled, and categorized. A criterion for the selection of data for statistical analysis considerations was formulated, and a model to grade the quality and validity of the data sets was developed. Data input formats, which record the pertinent parameters of the defect/specimen and inspection procedures, were formulated for each NDE method. A comprehensive computer program was written and debugged to calculate the probability of flaw detection at several confidence limits by the binomial distribution. This program also selects the desired data sets for pooling and tests the statistical pooling criteria before calculating the composite detection reliability. An example of the calculated reliability of crack detection in bolt holes by an automatic eddy current method is presented.
Yee, B. G. W.↗
Studies of cluster X-ray sources, energy spectra for the Perseus, Virgo, and Coma clusters
Final Uhuru X-ray differential-energy spectra are presented for the Perseus, Virgo, and Coma clusters. Power-law and isothermal bremsstrahlung model spectra with low-energy cutoffs are given, and the energy-dependent Gaunt factor is calculated for the bremsstrahlung. The spectra, which are best fits to the Uhuru data between 2 and 10 keV, are compared with previous observations of these sources in the energy range from 0.1 to 100 keV. The problem of parameter estimation is discussed, error bars with 68% confidence are given for the independently determined slope and cutoff parameters, and the 68% confidence limits are plotted for the fitted spectral functions. The data for Perseus above 20 keV marginally favor the bremsstrahlung fit, those for Virgo between 0.25 and 1.0 keV clearly favor that curve, and those for Coma indicate a low-energy turnover or cutoff. Implications of such a cutoff are briefly discussed.
Kellogg, E.↗
Interim analysis of long time creep behavior of columbium C-103 alloy
Analysis of 16 long time creep tests on columbium C-103 alloy (Cb-10Hf-1Ti-0.7Zr) indicates that the calculated stresses to give 1 percent creep strain in 100,000 hours at 1,255 K (1800 F) are 7.93 and 8.96 MPa (1,150 and 1,300 psi) for fine grained and course grained materials, respectively. The apparent activation energy and stress dependence for creep of this alloy are approximately 315 KJ/gmol (75,300 cal/gmol) and 2.51, respectively, based on Dorn-Sherby types of relations. However, the 90 percent confidence limits on these values are wide because of the limited data currently available.
Klopp, W. D.↗
An X-ray determination of the orbital elements of 3U 0900-40
The orbital elements of the 3U 0900-40 binary system were determined by measuring the variations in the arrival times of the 283-second X-ray pulses. The best-fit values of the system parameters and their 95% confidence limits are listed.
Mcclintock, J.↗
Refractivities of H2, He, O2, CO, and Kr for 168-288 nm wavelength range
Precision measurements of the refractivities of H2, He, O2, CO, and Kr were made in the wavelength range 168-288 nm. By using a 1.2-m-long test cell and by keeping the test gas at accurately determined conditions near atmospheric pressure and room temperature, accuracies (90% confidence limit) were achieved for the absolute refractivities that ranged from plus or minus 0.1% to plus or minus 1.0% depending upon the gas and wavelength range. For a given gas, the ratio of refractivities at any two wavelengths has a smaller uncertainty. For H2, CO, and O2, results are for wavelengths shorter than those of previous measurements and, for He and Kr, the uncertainties are less than those of other measurements. For He refractivities agree with the theoretical ones, but in the case of H2 results are about 1% larger than the theoretical values. At the upper end of the wavelength range studied, the data are in agreement with previous measurements on H2, CO, and Kr. For O2 results indicate that the hitherto available data are too large by amounts ranging from 0.8% to 10%.
Smith, P. L.↗
Flash photolysis resonance fluorescence investigation of the reaction of Cl/2P/ atoms with ClONO2
Rate constants for the removal of Cl(2P) atoms by homogeneous gas phase reaction with ClONO2 were measured using the flash photolysis resonance fluorescence technique at 224, 250, and 273 K. The values obtained have been used to derive the above Arrhenius equation. The uncertainties expressed are 95% confidence limits obtained using the statistical standard deviation of the individual rate constants plus a 15% additional estimated uncertainty attributed to difficulties in chlorine nitrate concentration measurements. The results indicate that destruction of chlorine nitrate by reaction with chlorine atoms is perhaps the least important of the atmospheric reactive channels, and is at least three orders of magnitude slower than calculated photodissociation rates at all stratospheric altitudes.
Kurylo, M. J.↗
Reliability of nondestructive evaluation data
Program calculates probability of defects at selected confidence levels from nondestructive evaluation data. It provides alternate method of grouping sample data to obtain reasonable value for lower confidence limit with small sample size.
Couchman, J. C.↗
Statistical considerations in design of spacelab experiments
After making an analysis of experimental error sources, statistical models were developed for the design and analysis of potential Space Shuttle experiments. Guidelines for statistical significance and/or confidence limits of expected results were also included. The models were then tested out on the following proposed Space Shuttle biomedical experiments: (1) bone density by computer tomography; (2) basal metabolism; and (3) total body water. Analysis of those results and therefore of the models proved inconclusive due to the lack of previous research data and statistical values. However, the models were seen as possible guides to making some predictions and decisions.
Robinson, J.↗
Performance characteristics of the electrochemical concentration cell ozonesonde
A large number of electrochemical concentration cell (ECC) ozonesondes were calibrated in relation to a UV photometric absorption ozone instrument prior to using the ozonesondes in atmospheric soundings. The two methods of measuring ozone were in reasonable agreement on the average, but there was considerable variation from one ozonesonde to another. Averaging the individual linear regressions gives an ECC ozone concentration equal to 0 + or - 8 nbar plus (0.96 + or - 0.10) times the concentration determined with the UV instrument, where uncertainties represent 90% confidence limits. Applying individual calibration corrections to atmospheric sounding data reduced the mean difference between Dobson spectrophotometric measurements of total ozone overburdens and corresponding values obtained from ozonesonde data from -8.5 + or - 8.2 to -1.4 + or - 7.3% for a series of measurements carried out in 1977. Corresponding uncorrected and corrected differences averaged 3.2 + or - 9.7 and 1.9 + or - 10.6%, respectively, for soundings carried out in 1976.
Torres, A. L.↗
Submilliarcsecond astrometry via VLBI. I - Relative position of the radio sources 3C 345 and NRAO 512
The relative position and relative proper motion of the radio sources 3C 345 and NRAO 512 are estimated from four sets of VLBI observations spread out over the period from October 1971 to May 1974. The use of phase-connection techniques yields the separation, in 1950.0 coordinates, of the centers of brightness of the compact components of the two sources. An upper bound of 0.0005 arcsec/yr is placed on the relative proper motion (70% estimated confidence limits). Bounds that can be placed on the distances to the two sources are considered, prospects for improvement in the determination of relative position and proper motion of these sources are discussed, and other possible applications of the basic technique are described.
Shapiro, I. I.↗