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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Towards a 1000 tracks digital tape recorder

As the demand for high data rate (up to 1 Gb/s), high density (down to 1 sq micron/bit) tape recorder increases, the main investigation trend is an improvement of the well known helical scan concept. The drawbacks of this technology are also well known; sophisticated mechanics, head to tape contact, and wear problems. In our fixed head approach, the recorder mechanics is made much more simple, but the complexity is turned towards the integrated magnetic components, which have to record and reproduce hundreds of tracks in parallel. Our multiplexed write inductive head and magneto-optical readout head will be described, and the global system performances evaluated.

Coutellier, J. M.↗
NASA NTRS1993

Ultra-high density recording technologies

The Engineering Research Center in Data Storage Systems at Carnegie Mellon University in cooperation with the National Storage Industry Consortium has selected goals of achieving 10 Gbit/sq in. recording density in magnetic and magneto-optic disk recording and 1 terabyte/cubic in. magnetic tape recording technologies. This talk describes the approaches being taken and the status of research leading to these goals.

Kryder, Mark H.↗
NASA NTRS1990

Application of the inner solar system cratering record to the Earth

The cratering records on the Moon, Mercury, and Mars are studied to provide constraints on: (1) terrestrial conditions prior to about 3.8 Ga, (2) why biology was not extensively established prior to 3.5 Ga, (3) whether impact-induced volcanism can explain some feature of the Cretaceous/Tertiary boundary event, and (4) how common large single-impact events are in the inner solar system. Earth underwent a period of high impact rates and large basin-forming events early in its history, based on the cratering record retained in the Lunar, Mercurian, and Martian highlands. The widespread occurrence of life around 3.5 Ga is linked to the cessation of high impact rates. Impact of a 10-km-diam object into terrestrial oceans could excavate through crustal material and into mantle reservoirs, creating extended basaltic volcanic activity. Scaling laws, coupled with the record retained on Lunar and Martian plains, indicate that between one and seven craters of 90 km diam or greater could have formed on Earth in the past 65 million years.

Barlow, Nadine G.↗
NASA NTRS1920

Design of Recording Wind Tunnel Balances

Given here is a description of the design of a scientific recording wind tunnel balance. It was decided that the most satisfactory arrangement would be a rigid ring completely surrounding the tunnel or wind stream, so that the model could be supported from it by wires or any arrangement of spindles. The forces and moments acting on this ring can then be recorded by suitable weighing apparatus. The methods available for recording forces on the arms are explained. The proposed type of balance will support the model rigidly in a variety of ways, will make a complete test without attention, and will plot the results so that all computations are avoided.

Norton, F H↗
NASA NTRS1994

Instrument Records And Plays Back Acceleration Signals

Small, battery-powered, hand-held instrument feeds power to accelerometer and records time-varying component of output for 15 seconds in analog form. No power needed to maintain content of memory; memory chip removed after recording and stored indefinitely. Recorded signal plays back at any time up to several years later. Principal advantages: compactness, portability, and low cost.

Bozeman, Richard J.↗
NASA NTRS1993

The United States digital recording industry

The recording industry resembles the semiconductor industry in several aspects. Both are large (greater than $60 Billion/year revenues); both are considered critical technologies supporting national objectives; both are experiencing increased competition from foreign suppliers; they recognize significant opportunities for both technological and market growth in the decade to come; and both realize that a key to this future growth lies in alliances among industry, academia, and government. The semiconductor industry has made significant investments in alliances relating to manufacturing technologies (SEMATECH) and to joint long-term technology research centered in universities (SRC). The federal government has provided funding support of these efforts in recognition of the critical roles semiconductor technologies play in national interests. The recording industry is now also forming critical alliances, but has been slower in starting and in gaining broad recognition by government agencies and legislators that the industry needs federal support. Traditionally, the recording industry has been viewed as mature, stable, and, while critical to national interests, able to chart and fund its own course toward future national needs. That perception is fortunately changing.

Simonds, John L.↗
NASA NTRS1994

A comparison of rotary- and stationary-head tape recorders

Digital recording may take advantage of many types of media, but usually a preferred type of drive or transport emerges for each. In magnetic tape recording, two approaches have emerged in which essentially the same medium is tracked in two radically different ways. This paper compares the characteristics of Rotary- and Stationary-Head transports in an attempt to establish which approach might be considered for a given application. The conclusion is that in many cases there is no obvious choice based on recording physics and that often the choice will be made on the experimental knowledge of the designer.

Watkinson, John R.↗
NASA NTRS1994

Approaches to 100 Gbit/sq. in. recording density

A recording density of 10 Gbit/sq. in. is being pursued by a number of companies and universities in the National Storage Industry Consortium. It is widely accepted that this goal will be achieved in the laboratory within a few years. In this paper approaches to achieving 100 Gbit/sq. in. storage densities are considered. A major obstacle to continued scaling of magnetic recording to higher densities is that as the bit size is reduced, the grain size in the magnetic media must be reduced in order that media noise does not become so large that the signal to noise ratio (SNR) degrades sufficiently to make detection impossible. At 100 Gbit/sq. in., the bit size is only 0.006 square micrometers, which, in order to achieve 30 dB SNR, requires a grain size of about 2.5 nm. Such small grains are subject to thermal instability, and the recorded information will degrade over time unless the magnetic anisotropy of the materials used is increased significantly, or the media thickness is made much larger than expected on the basis of scaling today's longitudinal media thickness.

Kryder, Mark H.↗
NASA NTRS1995

Ground-recorded sonic boom signatures of F-18 aircraft formation flight

Two F-18 aircraft were flown, one above the other, in two formations, in order for the shock systems of the two aircraft to merge and propagate to the ground. The first formation had the canopy of the lower F-18 in the inlet shock of the upper F-18 (called inlet-canopy). The flight conditions were Mach 1.22 and an altitude of 23,500 ft. An array of five sonic boom recorders was used on the ground to record the sonic boom signatures. This paper describes the flight test technique and the ground level sonic boom signatures. The tail-canopy formation resulted in two, separated, N-wave signatures. Such signatures probably resulted from aircraft positioning error. The inlet-canopy formation yielded a single modified signature; two recorders measured an approximate flattop signature. Loudness calculations indicated that the single inlet-canopy signatures were quieter than the two, separated tail-canopy signatures. Significant loudness occurs after a sonic boom signature. Such loudness probably comes from the aircraft engines.

Bahm, Catherine M.↗
NASA NTRS1996

Ground-Recorded Sonic Boom Signatures of F-18 Aircraft in Formation Flight

Two F-18 aircraft were flown, one above the other, in two formations, in order for the shock systems of the two aircraft to merge and propagate to the ground. The first formation had the canopy of the lower F-18 in the tail shock of the upper F-18 (called tail-canopy). The second formation had the canopy of the lower F- 18 in the inlet shock of the upper F-18 (called inlet-canopy). The flight conditions were Mach 1.22 and an altitude of 23,500 ft . An array of five sonic boom recorders was used on the ground to record the sonic boom signatures. This paper describes the flight test technique and the ground level sonic boom signatures. The tail-canopy formation resulted in two, separated, N-wave signatures. Such signatures probably resulted from aircraft positioning error. The inlet-canopy formation yielded a single modified signature; two recorders measured an approximate flattop signature. Loudness calculations indicated that the single inlet-canopy signatures were quieter than the two, separated tail-canopy signatures. Significant loudness occurs after a sonic boom signature. Such loudness probably comes from the aircraft engines.

Bahm, Catherine M.↗
NASA NTRS2000

Verification and Improvement of ERS-1/2 Altimeter Geophysical Data Records for Global Change Studies

This Final Technical Report summarizes the research work conducted under NASA's Physical Oceanography Program entitled, Verification And Improvement Of ERS-112 Altimeter Geophysical Data Recorders For Global Change Studies, for the time period from January 1, 2000 through June 30, 2000. This report also provides a summary of the investigation from July 1, 1997 - June 30, 2000. The primary objectives of this investigation include verification and improvement of the ERS-1 and ERS-2 radar altimeter geophysical data records for distribution of the data to the ESA-approved U.S. ERS-1/-2 investigators for global climate change studies. Specifically, the investigation is to verify and improve the ERS geophysical data record products by calibrating the instrument and assessing accuracy for the ERS-1/-2 orbital, geophysical, media, and instrument corrections. The purpose is to ensure that the consistency of constants, standards and algorithms with TOPEX/POSEIDON radar altimeter for global climate change studies such as the monitoring and interpretation of long-term sea level change. This investigation has provided the current best precise orbits, with the radial orbit accuracy for ERS-1 (Phases C-G) and ERS-2 estimated at the 3-5 cm rms level, an 30-fold improvement compared to the 1993 accuracy. We have finalized the production and verification of the value-added ERS-1 mission (Phases A, B, C, D, E, F, and G), in collaboration with JPL PODAAC and the University of Texas. Orbit and data verification and improvement of algorithms led to the best data product available to-date. ERS-2 altimeter data have been improved and we have been active on Envisat (2001 launch) GDR algorithm review and improvement. The data improvement of ERS-1 and ERS-2 led to improvement in the global mean sea surface, marine gravity anomaly and bathymetry models, and a study of Antarctica mass balance, which was published in Science in 1998.

Shum, C. K.↗
NASA NTRS2000

Modern Microbial Ecosystems are a Key to Understanding Our Biosphere's Early Evolution and its Contributions To The Atmosphere and Rock Record

The survival of our early biosphere depended upon efficient coordination anion- diverse microbial populations. Microbial mats exhibit a 3.46-billion-year fossil record, thus they are the oldest known ecosystems. Photosynthetic microbial mats were key because, today, sunlight powers more than 99 percent of global primary productivity. Thus photosynthetic ecosystems have affected the atmosphere profoundly and have created the most pervasive, easily-detected fossils. Photosynthetic biospheres elsewhere will be most detectible via telescopes or spacecraft. As a part of the Astrobiology Institute, our Ames Microbial Ecosystems group examines the roles played by ecological processes in the early evolution of our biosphere, as recorded in geologic fossils and in the macromolecules of living cells: (1) We are defining the microbial mat microenvironment, which was an important milieu for early evolution. (2) We are comparing mats in contrasting environments to discern strategies of adaptation and diversification, traits that were key for long-term survival. (3) We have selected sites that mimic key environmental attributes of early Earth and thereby focus upon evolutionary adaptations to long-term changes in the global environment. (4) Our studies of gas exchange contribute to better estimates of biogenic gases in Earth's early atmosphere. This group therefore directly addresses the question: How have the Earth and its biosphere influenced each other over time Our studies strengthen the systematics for interpreting the microbial fossil record and thereby enhance astrobiological studies of martian samples. Our models of biogenic gas emissions will enhance models of atmospheres that might be detected on inhabited extrasolar planets. This work therefore also addresses the question: How can other biospheres be recogniZed" Our choice of field sites helps us explore Earth's evolving early environment. For example, modern mats that occupy thermal springs and certain freshwater environments experience conditions such as low O2 and sulfate and high inorganic carbon and sulfide levels that resemble those of ancient marine environments. Later in history, both biologically-induced carbonate precipitation and the trapping and binding of suspended grains of carbonate became a dominant mechanism for carbonate deposition. Modern marine carbonate platforms and alkaline offer good examples of microbiologically-induced calcification. Both marine platforms and solar salterns illustrate microbially-driven trapping and binding. We are also exploring the effects of water composition upon the exchange of biogenic gases with the atmosphere.

DesMarais, David J.↗
NASA NTRS2000

Age-of-Air, Tape Recorder, and Vertical Transport Schemes

A numerical-analytic investigation of the impacts of vertical transport schemes on the model simulated age-of-air and the so-called 'tape recorder' will be presented using an idealized 1-D column transport model as well as a more realistic 3-D dynamical model. By comparing to the 'exact' solutions of 'age-of-air' and the 'tape recorder' obtainable in the 1-D setting, useful insight is gained on the impacts of numerical diffusion and dispersion of numerical schemes used in global models. Advantages and disadvantages of Eulerian, semi-Lagrangian, and Lagrangian transport schemes will be discussed. Vertical resolution requirement for numerical schemes as well as observing systems for capturing the fine details of the 'tape recorder' or any upward propagating wave-like structures can potentially be derived from the 1-D analytic model.

Lin, S.-J.↗
NASA NTRS2001

Data Mining of NASA Boeing 737 Flight Data: Frequency Analysis of In-Flight Recorded Data

Data recorded during flights of the NASA Trailblazer Boeing 737 have been analyzed to ascertain the presence of aircraft structural responses from various excitations such as the engine, aerodynamic effects, wind gusts, and control system operations. The NASA Trailblazer Boeing 737 was chosen as a focus of the study because of a large quantity of its flight data records. The goal of this study was to determine if any aircraft structural characteristics could be identified from flight data collected for measuring non-structural phenomena. A number of such data were examined for spatial and frequency correlation as a means of discovering hidden knowledge of the dynamic behavior of the aircraft. Data recorded from on-board dynamic sensors over a range of flight conditions showed consistently appearing frequencies. Those frequencies were attributed to aircraft structural vibrations.

Butterfield, Ansel J.↗
NASA NTRS2004

A Long Data Record (1979-2003) of Stratospheric Ozone Derived from TOMS Cloud Slicing: Comparison with SAGE and Implications for Ozone Recovery

It is generally recognized that Stratospheric Aerosols and Gas Experiment (SAGE) stratospheric ozone data have become a standard long-record reference field for comparison with other stratospheric ozone measurements. This study demonstrates that stratospheric column ozone (SCO) derived from total ozone mapping spectrometer (TOMS) Cloud Slicing may be used to supplement SAGE data as a stand-alone long- record reference field in the tropics extending to middle and high latitudes over the Pacific. Comparisons of SAGE I1 version 6.2 SCO and TOMS version 8 Cloud Slicing SCO for 1984-2003 exhibit remarkable agreement in monthly ensemble means to within 1-3 DU (1 - 1.5% of SCO) despite being independently-calibrated measurements. An important component of our study is to incorporate these column ozone measurements to investigate long-term trends for the period 1979-2003. Our study includes Solar Backscatter Ultraviolet (SBW) version 8 measurements of upper stratospheric column ozone (i.e., zero to 32 hPa column ozone) to characterize seasonal cycles and seasonal trends in this region, as well as the lower stratosphere and troposphere when combined with TOMS SCO and total column ozone. The trend analyses suggest that most ozone reduction in the atmosphere since 1979 in mid-to-high latitudes has occurred in the Lower stratosphere below approx. 25 km. The delineation of upper and lower stratospheric column ozone indicate that trends in the upper stratosphere during the latter half of the 1979-2003 period have reduced to near zero globally, while trends in the lower stratosphere have become larger by approx. 5 DU decade%om the tropics extending to mid-latitudes in both hemispheres. For TCO, the trend analyses suggest moderate increases over the 25-year time record in the extra-tropics of both hemispheres of around 4-6 DU (Northern Hemisphere) and 6-8 DU (Southern Hemisphere).

Ziemke, Jerry R.↗
NASA NTRS2004

Bias Reduction in Short Records of Satellite Soil Moisture

Although surface soil moisture data from different sources (satellite retrievals, ground measurements, and land model integrations of observed meteorological forcing data) have been shown to contain consistent and useful information in their seasonal cycle and anomaly signals, they typically exhibit very different mean values and variability. These biases pose a severe obstacle to exploiting the useful information contained in satellite retrievals through data assimilation. A simple method of bias removal is to match the cumulative distribution functions (cdf) of the satellite and model data. However, accurate cdf estimation typically requires a long record of satellite data. We demonstrate here that by wing spatial sampling with a 2 degree moving window we can obtain local statistics based on a one-year satellite record that are a good approximation to those that would be derived from a much longer time series. This result should increase the usefulness of relatively short satellite data records.

Reichle, Rolf H.↗
NASA NTRS1993

Conventional heart rate variability analysis of ambulatory electrocardiographic recordings fails to predict imminent ventricular fibrillation

OBJECTIVES. The purpose of this report was to study heart rate variability in Holter recordings of patients who experienced ventricular fibrillation during the recording. BACKGROUND. Decreased heart rate variability is recognized as a long-term predictor of overall and arrhythmic death after myocardial infarction. It was therefore postulated that heart rate variability would be lowest when measured immediately before ventricular fibrillation. METHODS. Conventional indexes of heart rate variability were calculated from Holter recordings of 24 patients with structural heart disease who had ventricular fibrillation during monitoring. The control group consisted of 19 patients with coronary artery disease, of comparable age and left ventricular ejection fraction, who had nonsustained ventricular tachycardia but no ventricular fibrillation. RESULTS. Heart rate variability did not differ between the two groups, and no consistent trends in heart rate variability were observed before ventricular fibrillation occurred. CONCLUSIONS. Although conventional heart rate variability is an independent long-term predictor of adverse outcome after myocardial infarction, its clinical utility as a short-term predictor of life-threatening arrhythmias remains to be elucidated.

Non-NASA Center↗
NASA NTRS2005

Origin of the Eumetazoa: testing ecological predictions of molecular clocks against the Proterozoic fossil record

Molecular clocks have the potential to shed light on the timing of early metazoan divergences, but differing algorithms and calibration points yield conspicuously discordant results. We argue here that competing molecular clock hypotheses should be testable in the fossil record, on the principle that fundamentally new grades of animal organization will have ecosystem-wide impacts. Using a set of seven nuclear-encoded protein sequences, we demonstrate the paraphyly of Porifera and calculate sponge/eumetazoan and cnidarian/bilaterian divergence times by using both distance [minimum evolution (ME)] and maximum likelihood (ML) molecular clocks; ME brackets the appearance of Eumetazoa between 634 and 604 Ma, whereas ML suggests it was between 867 and 748 Ma. Significantly, the ME, but not the ML, estimate is coincident with a major regime change in the Proterozoic acritarch record, including: (i) disappearance of low-diversity, evolutionarily static, pre-Ediacaran acanthomorphs; (ii) radiation of the high-diversity, short-lived Doushantuo-Pertatataka microbiota; and (iii) an order-of-magnitude increase in evolutionary turnover rate. We interpret this turnover as a consequence of the novel ecological challenges accompanying the evolution of the eumetazoan nervous system and gut. Thus, the more readily preserved microfossil record provides positive evidence for the absence of pre-Ediacaran eumetazoans and strongly supports the veracity, and therefore more general application, of the ME molecular clock.

NASA Discipline Evolutionary Biology↗