SEARCH · Engineering Papers
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.
Cardiac R wave detector obtains the systolic contraction signal of the human heart and uses it as a reference signal for the heart-assist pump cycle. It processes the electrocardiac signal /QRS wave complex/ of the natural heart in a sequence of operations which essentially elimates all components from the input signal except the R wave.
Radiation at IR wavelengths from circumstellar grains surrounding R CrB has been observed for approximately three years. Variations of flux with time have been larger at a wavelength of 3.5 microns than at 11 microns. Observations at IR and visual wavelengths of R CrB are presented in a graph. Another graph shows the change in the shape of the excess radiaton between two observations spaced by a period of about one year.
An electronic circuit that automatically changes its sensitivity was developed for detecting the bioelectric signal resulting from activation of the heart's ventricles. Regulation of sensitivity was accomplished with two feedback channels that maintain the sensitivity level between an upper and a lower limit. These limits are proportional to the R-wave amplitude. Tests on an experimental circuit demonstrated a capability to reject unwanted signal noise, illustrated difficulties encountered without sensitivity control, and presented closed loop transients which occurred for step changes in R-wave amplitude.
A new R = 1/2 K = 32 quick-look-in code is described and compared to the R = 1/2 K = 32 Massey-Costello code now used in some NASA systems. The new code, has the optimum distance profile property. This new code is shown, by comparison of Fano sequential decoding performance on a simulated Gaussian noise channel, to be computationally superior to the Massey-Costello code. The new code is also shown to be superior to the Massey-Costello code according to several analytical code criteria.
Seven appendices related to a previous report on the economic impact of NASA R and D spending were presented. They dealt with: (1) theoretical and empirical development of aggregate production functions, (2) the calculation of the time series for the rate of technological progress, (3) the calculation of the industry mix variable, (4) the estimation of distributed lags, (5) the estimation of the equations for gamma, (6) a ten-year forecast of the U.S. economy, (7) simulations of the macroeconomic model for increases in NASA R and D spending of $1.0, $.0.5, and 0.1 billions.
The emission line of the forbidden coronal transition of Fe XIII at 10,747 A has been detected in data from a spectral survey at R Aquarii. Strong emission lines of He I at 10,830 A and P gamma have been identified; a line at 11,013 A may be He I 3(1)S-6(1)P. It is suggested that the observed iron line is produced by a corona surrounding R Aquarii inter alia. The corona may be the source of the radio emission reported by Gregory and Seaquist (1974).
The study on which this paper is based, known as RECAT (Study of Cost Benefit Tradeoffs for Reducing the Energy Consumption of the Commercial Air Transportation System), was sponsored by NASA to establish a basis for assigning priorities in its aircraft fuel-conservation R&D program. The study involved coordinated efforts by four independent contractors to conceive and quantify fuel-conserving technology alternatives, transform these alternatives into viable R&D options, and simulate each option in a general model of the U.S. domestic air transportation system. This paper deals primarily with the latter phase and concentrates on the results of the study, as revealed not only by estimated fuel usage but also by other impacts of the technology options, such as demand growth, operator economics, and fleet composition. However, while the paper focuses on results, the basic assumptions and technology inputs are documented, and a general description of the modeling approach is provided to demonstrate the level of detail considered in the analysis.
Simulated orbiter direct approaches during long duration exposure facility (LDEF) retrieval operations reveal that the resultant orbiter jet plume fields can significantly disturb LDEF. An alternate approach technique which utilizes orbital mechanics forces in lieu of jets to brake the final orbiter/LDEF relative motion during the final approach, is described. Topics discussed include: rendezvous operations from the terminal phase initiation burn through braking at some standoff distance from LDEF, pilot and copilot activities, the cockpit instrumentation employed, and a convenient coordinate frame for studying the relative motion between two orbiting bodies. The basic equations of motion for operating on the LDEF radius vector are introduced. Practical considerations of implementing an R-bar approach, namely, orbiter/LDEF relative state uncertainties and orbiter control system limitations are explored. A possible R-bar approach strategy is developed and demonstrated.
My analysis of new discoveries by McCulloch and Wasserburg of Ba and Nd isotopic anomalies in inclusions of the Allende meteorite argues that (1) these anomalies contain special extinct radioactivities resulting from radioactive decay within grains formed in and ejected from the supernova interior, (2) the inclusions studied are fused assemblies of interstellar grains that were never totally vaporized, and (3) theoretical separation into r and s abundances suggests that fluctuations between r and s components has occurred during the accumulation processes. These points lend support to a new chemical picture of the early solar system that I have developed, although many interpretations remain possible. Measurements of the neutron-capture cross sections of Nd isotopes are urgently needed to experimentally validate these conclusions.
The research and technology base program was examined to determine those tasks which either enabled or enhanced a theme and should be incorporated into that theme, and to identify new and promising R&T candidates which should be incorporated into the R&T base to meet essential long range space technology goals not addressed by the various themes. Candidates in the ongoing tasks category generally reflect the reorientation or pursuit of an ongoing RTOP on specific theme objectives, primarily involving the development and ground testing of new technology components and systems. Thirty-eight recommended candidate tasks are listed.
Using the finite field transform and continued fractions, a simplified algorithm for decoding Reed-Solomon (R-S) codes is developed to correct erasures caused by other codes as well as errors over the finite field GF (q(m), where q is a prime and m is an integer. Such an R-S decoder can be faster and simpler than a decoder that uses more conventional methods.
An analysis of the International Ultraviolet Explorer spectra of the R CrB-type variables R CrB, RY Sgr, XX Cam, and MV Sgr suggests that: (1) it should be possible to construct useful models for the atmospheres of these hydrogen deficient, carbon rich stars if present standards of metallic line blanketing are used; and (2) the observed wavelength dependence of the circumstellar extinction is primarily due to circumstellar grains.
Observations of the variable star R Aquarii from 1928 to the present are examined to conclude that the star is a binary system with a jet. The orbital period of the objects is estimated at 22 yr, and a supercritical mass transfer that occurs once every 44 yr is suggested as a mechanism to explain deep minima observed on two occasions that many years apart. Calculations presented for the critical accretion rate of the two Miras indicated that one of the objects possesses a substantially stronger gravitational field than the other and features a large accretion disk. Oriental astronomical records from 930 AD are cited as evidence that a nova occurred in the vicinity of R Aquarii at that time. The system is noted to be the closest jet thus far observed, and the accretion disk may be visible with the Space Telescope.
It is shown that a natural consequence of the binary pulsar's evolution is a neutron star collision. Such a collision is expected to eject neutron-rich matter of an r-process character. Taking reasonable estimates for the number of such events over the history of the galaxy, it may be that they account for all of the r-process nuclei.
The high resolution ultraviolet spectra of the 4.4-day period binary R Arae, observed in 1980 with the International Ultraviolet Explorer, show that its continuum flux level varied outside the eclipse by more than a factor of two in ten days, and by over 50 percent within the same orbital cycle. The flux level varied nonmonotonically at different wavelengths. The resonance lines of Mg II and Si IV exhibited shortward-shifted absorption components near phase 0.4, indicating the presence of a gas stream toward the observer at a velocity of some -450 to -500 km/s. The observations of R Arae with the Einstein satellite show it to be an X-ray source.
The eclipsing binary system R Arae = HD 149730 is a relatively bright southern system with an orbital period of about 4.4 days. It is a single-lined spectroscopic binary. The spectral class of the primary component is B9 Vp. The system was included in a study of mass flow and evolution in close binary systems using the International Ultraviolet Explorer satellite (IUE). Four spectra in the wavelength range from 1150 to 1900 A were obtained with the far-ultraviolet SWP camera, and six spectra in the range from 1900 to 3200 range were obtained with the mid-ultraviolet LWR camera. The close binary R Arae exhibits very unusual ultraviolet spectra. It appears that no other close binary system, observed with any of the orbiting satellites, shows outside-eclipse ultraviolet continuum flux variations of this nature.
The steady flow approximation to the r-process has been used to evaluate the validity of the waiting point assumption (that, for a given charge number Z, neutron captures become balanced by neutron photodisintegrations) under a variety of conditions. The criterion for the accuracy of the approximation for any set of nuclei with the same value of Z is that the ratio of the total rate of neutron photodisintegration in those nuclei to the total rate of neutron captures should be close to unity. No set of conditions involving neutron production by helium thermonuclear reactions (at temperatures up to 10 to the 9th K) could be found for which the waiting point approximation is useful for all values of Z, and it is recommended that all such r-process calculations not use this approximation. At higher temperatures, such as those characteristic of explosive carbon burning (2 x 10 to the 9th K), the waiting point approximation is much better.
JHK infrared photometry shows that R asteroids have two distinct infrared color domains. Most R asteroids have JHK and visual colors and albedos that fall amongst those observed for S asteroids, but a small subset is clearly different. These are designated as a new A class of asteroids.