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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS2002

Tracking the harmonic response of magnetically-soft sensors for wireless temperature, stress, and corrosive monitoring

This paper describes the application of magnetically-soft ribbon-like sensors for measurement of temperature and stress, as well as corrosive monitoring, based upon changes in the amplitudes of the higher-order harmonics generated by the sensors in response to a magnetic interrogation signal. The sensors operate independently of mass loading, and so can be placed or rigidly embedded inside nonmetallic, opaque structures such as concrete or plastic. The passive harmonic-based sensor is remotely monitored through a single coplanar interrogation and detection coil. Effects due to the relative location of the sensor are eliminated by tracking harmonic amplitude ratios, thereby, enabling wide area monitoring. The wireless, passive, mass loading independent nature of the described sensor platform makes it ideally suited for long-term structural monitoring applications, such as measurement of temperature and stress inside concrete structures. A theoretical model is presented to explain the origin and behavior of the higher-order harmonics in response to temperature and stress. c2002 Elsevier Science B.V. All rights reserved.

Non-NASA Center↗
NASA NTRS2016

Method of Mapping Anomalies in Homogenous Material

An electrical conductor and antenna are positioned in a fixed relationship to one another. Relative lateral movement is generated between the electrical conductor and a homogenous material while maintaining the electrical conductor at a fixed distance from the homogenous material. The antenna supplies a time-varying magnetic field that causes the electrical conductor to resonate and generate harmonic electric and magnetic field responses. Disruptions in at least one of the electric and magnetic field responses during this lateral movement are indicative of a lateral location of a subsurface anomaly. Next, relative out-of-plane movement is generated between the electrical conductor and the homogenous material in the vicinity of the anomaly's lateral location. Disruptions in at least one of the electric and magnetic field responses during this out-of-plane movement are indicative of a depth location of the subsurface anomaly. A recording of the disruptions provides a mapping of the anomaly.

Woodard, Stanley E.↗
NASA NTRS1995

Integrated back to back barrier-N-N(+) varactor diode tripler using a split-waveguide block

The back-to-back barrier-N-N(+) (bbBNN) varactor is a nonlinear device being developed for frequency multiplier applications above 100 GHz. Its symmetrical C-V characteristic, low series resistance, freedom from external bias and suitability to planarization make it an ideal choice for high frequency, low power, odd harmonic generation. In this paper, the performance of a 220-GHz waveguide tripler using, for the first time, a planar GaAs bbBNN device integrated on a quartz microstrip circuit is presented. A new split-waveguide block design has been employed to provide the proper embedding impedances to the device at the input and third harmonic output frequencies. A flange-to-flange tripling efficiency of 7% has been obtained at 220 GHz with an output power in excess of 700 mu W. This is believed to be the highest conversion efficiency yet reported for a tripler with an integrated device at this frequency. Theoretical calculations indicate that substantial improvement is possible with modest changes to the device and circuit parameters.

QUARTZ MICROSTRIP CIRCUITS↗
NASA NTRS2012

Envelope Solitons in Acoustically Dispersive Vitreous Silica

Acoustic radiation-induced static strains, displacements, and stresses are manifested as rectified or dc waveforms linked to the energy density of an acoustic wave or vibrational mode via the mode nonlinearity parameter of the material. An analytical model is developed for acoustically dispersive media that predicts the evolution of the energy density of an initial waveform into a series of energy solitons that generates a corresponding series of radiation-induced static strains (envelope solitons). The evolutionary characteristics of the envelope solitons are confirmed experimentally in Suprasil W1 vitreous silica. The value (-11.9 plus or minus 1.43) for the nonlinearity parameter, determined from displacement measurements of the envelope solitons via a capacitive transducer, is in good agreement with the value (-11.6 plus or minus 1.16) obtained independently from acoustic harmonic generation measurements. The agreement provides strong, quantitative evidence for the validity of the model.

Cantrell, John H.↗
NASA NTRS2014

Wireless Open-Circuit In-Plane Strain and Displacement Sensor Requiring No Electrical Connections

A wireless in-plane strain and displacement sensor includes an electrical conductor fixedly coupled to a substrate subject to strain conditions. The electrical conductor is shaped between its ends for storage of an electric field and a magnetic field, and remains electrically unconnected to define an unconnected open-circuit having inductance and capacitance. In the presence of a time-varying magnetic field, the electrical conductor so-shaped resonates to generate harmonic electric and magnetic field responses. The sensor also includes at least one electrically unconnected electrode having an end and a free portion extending from the end thereof. The end of each electrode is fixedly coupled to the substrate and the free portion thereof remains unencumbered and spaced apart from a portion of the electrical conductor so-shaped. More specifically, at least some of the free portion is disposed at a location lying within the magnetic field response generated by the electrical conductor. A motion guidance structure is slidingly engaged with each electrode's free portion in order to maintain each free portion parallel to the electrical conductor so-shaped.

Woodard, Stanley E.↗
NASA NTRS2000

Nondestructive Determination of Bond Strength

Although many nondestructive techniques have been applied to detect disbonds in adhesive joints, no absolutely reliable nondestructive method has been developed to detect poor adhesion and evaluate the strength of bonded joints prior to the present work which used nonlinear ultrasonic methods to investigate adhesive bond cure conditions. Previously, a variety of linear and nonlinear ultrasonic methods with water coupling had been used to study aluminum-adhesive-aluminum laminates, prepared under different adhesive curing conditions, for possible bond strength determination. Therefore, in the course of this research effort, a variety of finite-amplitude experimental methods which could possibly differentiate various cure conditions were investigated, including normal and oblique incidence approaches based on nonlinear harmonic generation as well as several non-collinear two-wave interaction approaches. Test samples were mechanically scanned in various ways with respect to the focus of a transmitting transducer operated at several variable excitation frequencies and excitation levels. Even when powerful sample-related resonances were exploited by means of a frequency scanning approach, it was very difficult to isolate the nonlinear characteristics of adhesive bonds. However, a multi-frequency multi-power approach was quite successful and reliable. Ultrasonic tone burst signals at increasing power levels, over a wide frequency range, were transmitted through each bond specimen to determine its excitation dependent nonlinear harmonic resonance behavior. Relative amplitude changes were observed particularly in the higher harmonic spectral data and analyzed using a local displacement and strain analysis in the linear approximation. Two analysis approaches of the excitation-dependent data at specific resonances were found to be quite promising. One of these approaches may represent a very robust algorithm for classifying an adhesive bond as being properly cured or not. Another approach, in addition to differentiation between various cure conditions, may even provide information with respect to the bond strength. Several technical papers were published during the course of this research and a summary is presented in the Ph.D. dissertation of Tobias P. Berndt, a graduate student financially supported by this NASA Grant.

Source record↗
NASA NTRS1969

Fluorescent photography of spray droplets using a laser light source

Monochromatic laser emission transformed by a fluorescent process into droplet emission over a wavelength band provides high light intensities for obtaining adequate time resolution to stop droplet motion in photographic spray studies. Experiments showed that the Q-switched laser-optical harmonic generator combination produced sharp, well-exposed droplet images.

Groeneweg, J.↗
NASA NTRS1971

Microwave device investigations

Several tasks were active during this report period: (1) noise modulation in avalanche-diode devices; (2) schottky-barrier microwave devices; (3) intermodulation products in IMPATT diode amplifiers; (4) harmonic generation using Read-diode varactors; and (5) fabrication of GaAs Schottky-barrier IMPATT diodes.

Haddad, G. I.↗
NASA NTRS1973

Ankylosis-stabilized oscillator

One feature of this mechanism is reduction of self-modulation, a source of harmonic generation. Since amplitude of oscillation is large, cutoff frequency is varied in proportion to the amplitude and frequency of oscillation. While one transistor is experiencing a positive alteration, the other is experiencing a negative alteration. Net effect is reduction in self-modulation.

Kleinberg, L. L.↗
NASA NTRS1972

NASA automatic system for computer program documentation, volume 2

The DYNASOR 2 program is used for the dynamic nonlinear analysis of shells of revolution. The equations of motion of the shell are solved using Houbolt's numerical procedure. The displacements and stress resultants are determined for both symmetrical and asymmetrical loading conditions. Asymmetrical dynamic buckling can be investigated. Solutions can be obtained for highly nonlinear problems utilizing as many as five of the harmonics generated by SAMMSOR program. A restart capability allows the user to restart the program at a specified time. For Vol. 1, see N73-22129.

Simmons, D. B.↗
NASA NTRS1974

Fractional harmonics in a plasma

Theoretical study of plasma nonlinearity effects that cannot be described by modified linear theory, such, for example, as those effects that arise only when a source of disturbances in a plasma reaches a certain threshold amplitude. In particular, the possibility of fractional harmonic generation, independently of the requirements of the plasma wave decay, is investigated.

Lewak, G. J.↗
NASA NTRS1976

Demonstration of the frequency offset errors introduced by an incorrect setting of the Zeeman/magnetic field adjustment on the cesium beam frequency standard

The fine frequency setting of a cesium beam frequency standard is accomplished by adjusting the C field control with the appropriate Zeeman frequency applied to the harmonic generator. A novice operator in the field, even when using the correct Zeeman frequency input, may mistakenly set the C field to any one of seven major Beam I peaks (fingers) represented by the Ramsey curve. This can result in frequency offset errors of as much as 2.5 parts in ten to the tenth. The effects of maladjustment are demonstrated and suggestions are discussed on how to avoid the subtle traps associated with C field adjustments.

Kaufmann, D. C.↗
NASA NTRS1976

Waves in active and passive periodic structures - A review

The theory and recent applications of waves in periodic structures are reviewed. Both the Floquet and coupled waves approach are analyzed in some detail. The theoretical part of the paper includes wave propagation in unbounded and bounded active or passive periodic media, wave scattering from periodic boundaries, source radiation (dipole, Cerenkov, transition, and Smith-Purcell) in periodic media, and pulse transmission through a periodic slab. The applications part covers the recent development in a variety of fields: distributed feedback oscillators, filters, mode converters, couplers, second-harmonic generators, deflectors, modulators, and transducers in the fields of integrated optics and integrated surface acoustics. Work on insect compound eyes, mechanical structures, ocean waves, pulse compressions, temperature waves, and cholesteric liquid crystals, and particles interaction with crystals is briefly reviewed, especially in the case of zeolite crystals and superlattices. Recent advances in fabrication techniques for very fine gratings are also covered.

Elachi, C.↗
NASA NTRS1980

Fundamental emission in three type III solar bursts

Three particularly clear type III bursts have been observed with a satellite instrument (Helios 2). The results show that, in the range 25-200 kHz, both fundamental and harmonic generation are present.

Kellogg, P. J.↗
NASA NTRS1980

Generalized Grueneisen tensor from solid nonlinearity parameters

Anharmonic effects in solids are often described in terms of generalized Grueneisen parameters which measure the strain dependence of the lattice vibrational frequencies. The relationship between these parameters and the solid nonlinearity parameters measured directly in ultrasonic harmonic generation experiments is derived using an approach valid for normal-mode elastic wave propagation in any crystalline direction. The resulting generalized Grueneisen parameters are purely isentropic in contrast to the Brugger-Grueneisen parameters which are of a mixed thermodynamic state. Experimental data comparing the isentropic generalized Grueneisen parameters and the Brugger-Grueneisen parameters are presented.

Cantrell, J. H., Jr.↗