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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.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Equations for the kinetic modeling of supersonically flowing electrically excited lasers

The equations for the kinetic modeling of a supersonically flowing electrically excited laser system are presented. The work focuses on the use of diatomic gases, in particular carbon monoxide mixtures. The equations presented include the vibrational rate equation which describes the vibrational population distribution, the electron, ion and electronic level rate equations, the gasdynamic equations for an ionized gas in the presence of an applied electric field, and the free electron Boltzmann equation including flow and gradient coupling terms. The model developed accounts for vibration-vibration collisions, vibration-translation collisions, electron-molecule inelastic excitation and superelastic de-excitation collisions, charge particle collisions, ionization and three body recombination collisions, elastic collisions, and radiative decay, all of which take place in such a system. A simplified form of the free electron Boltzmann equation is developed and discussed with emphasis placed on its coupling with the supersonic flow. A brief description of a possible solution procedure for the set of coupled equations is then discussed.

Lind, R. C.↗
NASA NTRS2001

Method and apparatus for guiding ablative therapy of abnormal biological electrical excitation

This invention involves method and apparatus for guiding ablative therapy of abnormal biological electrical excitation. In particular, it is designed for treatment of cardiac arrhythmias. In the method of this invention electrical signals are acquired from passive electrodes, and an inverse dipole method is used to identify the site of origin of an arrhytmia. The location of the tip of the ablation catheter is similarly localized from signals acquired from the passive electrodes while electrical energy is delivered to the tip of the catheter. The catheter tip is then guided to the site of origin of the arrhythmia, and ablative radio frequency energy is delivered to its tip to ablate the site.

Armoundas, Antonis A.↗
NASA NTRS1996

Propagation of Electrical Excitation in a Ring of Cardiac Cells: A Computer Simulation Study

The propagation of electrical excitation in a ring of cells described by the Noble, Beeler-Reuter (BR), Luo-Rudy I (LR I), and third-order simplified (TOS) mathematical models is studied using computer simulation. For each of the models it is shown that after transition from steady-state circulation to quasi-periodicity achieved by shortening the ring length (RL), the action potential duration (APD) restitution curve becomes a double-valued function and is located below the original ( that of an isolated cell) APD restitution curve. The distributions of APD and diastolic interval (DI) along a ring for the entire range of RL corresponding to quasi-periodic oscillations remain periodic with the period slightly different from two RLs. The 'S' shape of the original APD restitution curve determines the appearance of the second steady-state circulation region for short RLs. For all the models and the wide variety of their original APD restitution curves, no transition from quasi-periodicity to chaos was observed.

Kogan, B. Y.↗
NASA NTRS1989

Electric quadrupole excitations in relativistic nucleus-nucleus collisions

Calculations are presented for electric quadrupole excitations in relativistic nucleus-nucleus collisions. The theoretical results are compared to an extensive data set and it is found that electric quadrupole effects provide substantial corrections to cross sections, especially for heavier nuclei.

Norbury, John W.↗
NASA NTRS1990

Electric quadrupole excitations in relativistic nucleus-nucleus collisions

Calculations are presented for electric quadrupole excitations in relativistic nucleus-nucleus collisions. The theoretical results are compared to an extensive data set and it is found that electric quadrupole effects provide substantial corrections to cross sections, especially for heavier nuclei.

NASA Discipline Radiation Health↗
NASA NTRS1977

Longitudinal variations of very-low-frequency chorus activity in the magnetosphere - Evidence of excitation by electrical power transmission lines

The distribution of VLF chorus in the high-altitude magnetosphere as detected by the Ogo 3 satellite was investigated. Chorus occurrence frequency over 4,668 samples of 5 min of broadband data was computed for Northern Hemisphere bins of 10 deg by 10 deg in dipole invariant latitude and longitude. Peaks in activity were noted over Alaska, the eastern U.S. and Canada, western Europe, and western Siberia, and were shown not to be the result of biased sampling. It is suggested that power line radiation of only about 1 W or less at a given harmonic frequency may be sufficient to stimulate the observed chorus activity and that such power levels can be expected in industrial areas or from large distribution networks. Preliminary results show that chorus starting frequencies are highly correlated with 60 Hz harmonics in the American sector and with 50 Hz harmonics in the European sector.

Luette, J. P.↗
NASA NTRS2013

Application of electrical stimulation for functional tissue engineering in vitro and in vivo

The present invention provides new methods for the in vitro preparation of bioartificial tissue equivalents and their enhanced integration after implantation in vivo. These methods include submitting a tissue construct to a biomimetic electrical stimulation during cultivation in vitro to improve its structural and functional properties, and/or in vivo, after implantation of the construct, to enhance its integration with host tissue and increase cell survival and functionality. The inventive methods are particularly useful for the production of bioartificial equivalents and/or the repair and replacement of native tissues that contain electrically excitable cells and are subject to electrical stimulation in vivo, such as, for example, cardiac muscle tissue, striated skeletal muscle tissue, smooth muscle tissue, bone, vasculature, and nerve tissue.

Radisic, Milica↗
NASA NTRS1979

Nuclear-pumped CO2 laser

The He-3 (n,p)T reaction was examined as an energy source for a CO2 laser. For this purpose He-3 was added to a functioning CO2 electrically excited laser. Initially the laser was run electrically with 12 torr total pressure. The gas mixture was 1:1:8, CO2:N2:He. At zero reactor power, the laser was tested in place next to the core of the Georgia Tech. Research Reactor. After verification of laser action He-3 was added to the system. The He-3 partial pressures of 10 torr, 50 torr, and 300 torr were added in three separate reactor runs. Reactor power ranged from zero to 5 million watts, which corresponds to a peak flux of 10 to the 14th power/sq cm. At reactor powers greater than 10 kW, gain of up to 30 percent was shown. However, indications are this may be due to gamma excitation rather than caused by the He-3 (n,p)T reaction. These results do agree with the data of past CO2 nuclear pumped laser experiments.

Rowe, M.↗
NASA NTRS1976

Electromyographic analysis of skeletal muscle changes arising from 9 days of weightlessness in the Apollo-Soyuz space mission

Both integration and frequency analyses of the electromyograms from voluntary contractions were performed in one crewman of the Apollo-Soyuz Test Project mission. Of particular interest were changes in excitability, electrical efficiency, and fatigability. As a result of 9 days of weightlessness, muscle excitability was shown to increase; muscle electrical efficiency was found to decrease in calf muscles and to increase in arm muscles; and fatigability was found to increase significantly, as shown by spectral power shifts into lower frequencies. It was concluded from this study that skeletal muscles are affected by the disuse of weightlessness early in the period of weightlessness, antigravity muscles seem most affected by weightlessness, and exercise may abrogate the weightlessness effect. It was further concluded that electromyography is a sensitive tool for measuring spaceflight muscle effects.

Lafevers, E. V.↗
NASA NTRS1998

1.54 micron Emission from Erbium implanted GaN for Photonic Applications

The development of efficient and compact light sources operating at 1.54 micron is of enormous importance for the advancement of new optical communication systems. Erbium (1%) doped fiber amplifiers (EDFA's) or semiconductor lasers are currently being employed as near infrared light sources. Both devices, however, have inherent limitations due to their mode of operation. EDFA's employ an elaborate optical pumping scheme, whereas diode lasers have a strongly temperature dependent lasing wavelength. Novel light emitters based on erbium doped III-V semiconductors could overcome these limitations. Er doped semiconductors combine the convenience of electrical excitation with the excellent luminescence properties of Er(3+) ions. Electrically pumped, compact, and temperature stable optoelectronic devices are envisioned from this new class of luminescent materials. In this paper we discuss the potential of Er doped GaN for optoelectronic applications based on temperature dependent photoluminescence excitation studies.

Thaik, Myo↗
NASA NTRS2010

Method and apparatus for the guided ablative therapy of fast ventricular arrhythmia

Method and apparatus for guiding ablative therapy of abnormal biological electrical excitation. The excitation from the previous excitatory wave is significant at the beginning of the next excitation. In particular, it is designed for treatment of fast cardiac arrhythmias. Electrical signals are acquired from recording electrodes, and an inverse dipole method is used to identify the site of origin of an arrhythmia. The location of the tip of an ablation catheter is similarly localized from signals acquired from the recording electrodes while electrical pacing energy is delivered to the tip of the catheter close to or in contact with the cardiac tissue. The catheter tip is then guided to the site of origin of the arrhythmia, and ablative radio frequency energy is delivered to its tip to ablate the site.

Cohen, Richard J.↗
NASA NTRS1992

Method and apparatus for minimizing multiple degree of freedom vibration transmission between two regions of a structure

Arrays of actuators are affixed to structural elements to impede the transmission of vibrational energy. A single pair is used to provide control of bending and extensional waves and two pairs are used to control torsional motion. The arrays are applied to a wide variety of structural elements such as a beam structure that is part of a larger framework that may or may not support a rigid or non-rigid skin. Electrical excitation is applied to the actuators that generate forces on the structure. These electrical inputs may be adjusted in their amplitude and phase by a controller in communication with appropriate vibrational wave sensors to impede the flow of vibrational power in all of the above mentioned wave forms beyond the actuator location. Additional sensor elements can be used to monitor the performance and adjust the electrical inputs to maximize the attenuation of vibrational energy.

Silcox, Richard J.↗
NASA NTRS1971

Nuclear pumping of lasers.

Summary of the theoretical and experimental work dealing with nuclear lasers that has been completed during the last year (1971), and review of some new work which may help to establish the direction research in this field may take in the future. So far, the most successful experiments have been carried out utilizing nuclear enhancement of electrically excited CO2 lasers. The goal of attaining lasing in gases utilizing nuclear pumping without an applied electric field is much more difficult to achieve but is being pursued. No experimental or theoretical work has been undertaken thus far in the study of the class of lasers where high-energy particles are produced internally in high-temperature multiple ionized plasmas. Some new approaches to high-power nuclear lasers are suggested.

Russell, G. R.↗
NASA NTRS2007

Tachometers Derived From a Brushless DC Motor

The upper part of the figure illustrates the major functional blocks of a direction-sensitive analog tachometer circuit based on the use of an unexcited two-phase brushless dc motor as a rotation transducer. The primary advantages of this circuit over many older tachometer circuits include the following: Its output inherently varies linearly with the rate of rotation of the shaft. Unlike some tachometer circuits that rely on differentiation of voltages with respect to time, this circuit relies on integration, which results in signals that are less noisy. There is no need for an additional shaft-angle sensor, nor is there any need to supply electrical excitation to a shaft-angle sensor. There is no need for mechanical brushes (which tend to act as sources of electrical noise). The underlying concept and electrical design are relatively simple. This circuit processes the back-electromagnetic force (back-emf) outputs of the two motor phases into a voltage directly proportional to the instantaneous rate (sign magnitude) of rotation of the shaft. The processing in this circuit effects a straightforward combination of mathematical operations leading to a final operation based on the well-known trigonometric identity (sin x)2 + (cos x)2 = 1 for any value of x. The principle of operation of this circuit is closely related to that of the tachometer circuit described in Tachometer Derived From Brushless Shaft-Angle Resolver (MFS-28845), NASA Tech Briefs, Vol. 19, No. 3 (March 1995), page 39. However, the present circuit is simpler in some respects because there is no need for sinusoidal excitation of shaftangle- resolver windings.

Howard, David E.↗