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Articles 1  30 of 35
FullText Articles in Physics
Reflectance Spectra And Dielectric Functions For Ag In The Region Of Interband Transitions, G. Leveque, C. G. Olson, David W. Lynch
Reflectance Spectra And Dielectric Functions For Ag In The Region Of Interband Transitions, G. Leveque, C. G. Olson, David W. Lynch
Physics and Astronomy Publications
New measurements have been made of the reflectances of single crystals of Ag and of Ag films in the (3.530)eV range. The data were analyzed with the KramersKronig method and the resultant dielectric functions were compared with those in the literature and with recent calculations. We find all structures previously seen, and a new weak peak at 11.5 eV. Our magnitudes for ε2 are in considerably better agreement with those of the calculated spectra than are those in the literature. Secondderivative spectra of the absorption coefficient have been calculated and compared with previously measured thermotransmission spectra, showing ...
Thermoreflectance Investigation Of The Antiferromagnetic And Paramagnetic Phases Of Cr, E. Colavita, A. Franciosi, David W. Lynch, G. Paolucci, R. Rosei
Thermoreflectance Investigation Of The Antiferromagnetic And Paramagnetic Phases Of Cr, E. Colavita, A. Franciosi, David W. Lynch, G. Paolucci, R. Rosei
Physics and Astronomy Publications
Thermoreflectance measurements have been performed on Cr single crystals at several temperatures above and below the Néel temperature. We observe dramatic changes induced by the magnetic phase transition. In contrast, static optical data fail to show appreciable differences in the (0.55.0)eV photonenergy range. Magnetic ordering gives rise to the disappearance of transitions involving specific regions of the Fermi surface. New criticalpoint absorptions appear at the boundaries of the new Brillouin zone in antiferromagnetic Cr. Most of the observed experimental features have been identified by comparison with recent bandstructure calculations.
Scattering Theory In Arrangement Channel Quantum Mechanics, James W. Evans, D. K. Hoffman, D. J. Kouri
Scattering Theory In Arrangement Channel Quantum Mechanics, James W. Evans, D. K. Hoffman, D. J. Kouri
Physics and Astronomy Publications
The time‐independent scattering theory associated with the non‐self‐adjoint matrix Hamiltonians H of arrangement channel quantum mechanics is presented in detail first using the 3‐particle case as an example. A key feature is the biorthogonality of a suitably constructed set of scattering eigenvectors and duals. Channel space Möller operators, S‐ and T‐matrices are defined and a variety of properties investigated including the way multichannel unitarity is embedded into the theory. Some remarks on the time‐dependent theory are also made. A detailed discussion of channel space density matrix scattering theory(of interest, e.g., in reactive ...
Thermoacoustic Nde Imaging Induced By Deeply Penetrating Radiation, Theodore Bowen, Richard L. Nasoni, Alburt E. Pifer
Thermoacoustic Nde Imaging Induced By Deeply Penetrating Radiation, Theodore Bowen, Richard L. Nasoni, Alburt E. Pifer
Review of Progress in Quantitative Nondestructive Evaluation
Although the use of thermoacoustic emission in ultrasonic nondestructive testing and in medical imaging has been discussed by Van Gutfeld, 1 among others, its application is principally confined to the use of laser beams and surface or thinlayer emissions. In this paper we propose a more general thermoacoustic method of nondestructive material testing in which deeply penetrating radiation generates thermoacoustic signals thoughout the volume of a material. These ideas are the outgrowth of early work by one of the authors, T. Bowen, in the use of thermoacoustic emissions in cosmic ray detection2 and experimental checks have been carried out in ...
Quantitative Measurement And Imaging Of Metal Fatigue, William J. Baxter
Quantitative Measurement And Imaging Of Metal Fatigue, William J. Baxter
Review of Progress in Quantitative Nondestructive Evaluation
A simple electrochemical technique is described, which images and quantitatively measures the distribution and severity of fatigue damage in aluminum alloys. The technique is based upon (i) the creation of microcracks in a surface anodic oxide film during fatigue of the underlying metal, and (ii) the detection of these microcracks by contacting the surface with a gel electrode. When a voltage pulse is applied, current passes through the fatigue—induced microcracks in the oxide film, and an image of the sites of current flow is retained in the surface of the gel. The capabilities of the technique are illustrated by ...
Geological Fracture Mapping Using Electromagnetic Geotomography, A. L. Ramirez, F. J. Deadrick, R. J. Lytle
Geological Fracture Mapping Using Electromagnetic Geotomography, A. L. Ramirez, F. J. Deadrick, R. J. Lytle
Review of Progress in Quantitative Nondestructive Evaluation
This article describes the evaluation of a new geophysical technique used to map fractures between boreholes: electromagnetic geotomography used in conjunction with salt water tracers. An experiment has been performed in a granitic rock mass. Geotomographic images have been generated and compared with borehole geophysical data: neutron logs, acoustic velocity logs, caliper logs and acoustic televiewer records. Comparisons between the images and the geophysical logs indicate that clusters of fractures were detected but single fractures were not.
Fiber Optics For A Damage Assessment System For Fiber Reinforced Plastic Composite Structures, Roger M. Crane, Aleksander B. Macander, James Gagorik
Fiber Optics For A Damage Assessment System For Fiber Reinforced Plastic Composite Structures, Roger M. Crane, Aleksander B. Macander, James Gagorik
Review of Progress in Quantitative Nondestructive Evaluation
There are a limited number of nondestructive evaluation techniques available for field inspection of large composite structures and practically no viable techniques for inservice inspection. With this in mind, an innovative Damage Assessment System is proposed which is based on a concept of using an optical fiber mesh, implanted into the body of a fiber reinforced composite structure. Such a mesh would become an integral part of the structure during the course of its fabrication. The selection of the mesh fibers would be predicated on their strain to failure characteristics and strain compatibility with the base, composite reinforcing fibers. This ...
Nondestructive Evaluation Of The Thermal Cycling Effects On Graphite/Aluminum Precursor Wire, Albert L. Bertram, James H. Prout, Robert W. Reed
Nondestructive Evaluation Of The Thermal Cycling Effects On Graphite/Aluminum Precursor Wire, Albert L. Bertram, James H. Prout, Robert W. Reed
Review of Progress in Quantitative Nondestructive Evaluation
The objective of the work was to nondestructively examine the effects of thermal cycling on properties (e.g., torsional velocity and electrical resistance) of graphite/aluminum (Gr/A1) precursor wire. Precursor wires were periodically heated at selected temperatures for various periods of time; the exact heating period being dependent on the test temperature. Wires were tested in the asreceived condition and after each thermal excursion. Changes occurred in both the torsional velocity and the resistance; although at different rates and to different extents. Subsequent longitudinal velocity tests run on the heat treated sections of the wires showed little if any ...
Quantitative Attenuation And Velocity Measurements In Metal Matrix Precursor Wires, Robert W. Reed
Quantitative Attenuation And Velocity Measurements In Metal Matrix Precursor Wires, Robert W. Reed
Review of Progress in Quantitative Nondestructive Evaluation
The nondestructive evaluation of metal matrix composite precursor wires is being pursued by measurements of the attenuation and velocity of both torsional and longitudinal ultrasonic pulses propagating along the wire axis. The sound waves are generated by noncontacting electromagnetic transducers. Continuous scans of the attenuation and velocity are made along wires of any length by use of a fourtransducer arrangement. The attenuation and velocity have been related to physical wire properties which are important for nondestructive evaluation and characterization.
Measurements Of Ultrasonic Scattering From NearSurface Flaws, David K. Hsu, T. A. Gray, R. Bruce Thompson
Measurements Of Ultrasonic Scattering From NearSurface Flaws, David K. Hsu, T. A. Gray, R. Bruce Thompson
Review of Progress in Quantitative Nondestructive Evaluation
In ultrasonic NDE measurements the detection of subsurface flaws is of practical importance, especially flaws too far from the surface to be detected by eddy current methods and yet close enough to the surface for the flawsurface interaction to be important. In this paper we report experimental results of ultrasonic scattering measurements of subsurface flaws in the presence of a fluidsolid interface and compare these results with theoretical calculations of subsurface flaw scattering. Comparison of the absolute value of the scattering amplitude in terms of frequency, flawtosurface distance, ultrasonic mode and scattering angle will be made for an oblate spheroidal ...
The Maximum Entropy Formulation Of Inverse Problems Of Nde, R. M. Bevensee
The Maximum Entropy Formulation Of Inverse Problems Of Nde, R. M. Bevensee
Review of Progress in Quantitative Nondestructive Evaluation
This paper introduces the Maximum Entropy method of resolving underdetermined objects (flaws or inclusions) by a physicists’ brand of nonlinear processing of the image data. We survey three areas of research: (1) synthetic aperture imaging to resolve three dimensional flaws, with the aid of selective back projection, (2) scattering from anomalies according to the inhomogeneous Fredholm integral equation of the second kind, and (3) ultrasonic flaw characterization by the boundary integral equation method. A simple example is offered to illustrate the potential resolving power of the ME method for problems in area (2). We present some criteria for effective ME ...
The Inverse Born Approximation: Exact Determination Of Shape Of Convex Voids, James H. Rose, Jon L. Opsal
The Inverse Born Approximation: Exact Determination Of Shape Of Convex Voids, James H. Rose, Jon L. Opsal
Review of Progress in Quantitative Nondestructive Evaluation
The Inverse Born Approximation (IBA) to the elastic wave inverse scattering problem is known to give highly accurate results for the shape of complex voids. In this paper we present an argument demonstrating that the IBA is, in fact, exact for determining the size, shape and orientation of a wide class of these scatterers given infinite bandwidth and unlimited aperture information. Essentially, our argument demonstrates how the IBA algorithm picks out the singular contribution to the impulse response function and correctly relates it to the shape of the scatterer. Some specific examples will be used to illustrate the more intuitive ...
Noncontacting Measurement Of Surface Acoustic Waves, R. L. Jungerman, J. E. Bowers, B. T. KhuriYakub, G. S. Kino
Noncontacting Measurement Of Surface Acoustic Waves, R. L. Jungerman, J. E. Bowers, B. T. KhuriYakub, G. S. Kino
Review of Progress in Quantitative Nondestructive Evaluation
A new sensor is presented for detecting surface acoustic waves. The sensor constructed, using single mode fiber components, is small and rugged and has better sensitivity (.0003 Å) than has been reported for other SAW sensors. Optical reflection changes encountered while scanning surfaces can be divided out, making the probe applicable to rough samples of practical interest. Normal surface displacements near a defect (100 μm deep crack) have been measured in both long and short wavelength acoustic regimes.
Ultrasonic Nondestructive Evaluation Using Laser Transducers, Michael J. Rudd
Ultrasonic Nondestructive Evaluation Using Laser Transducers, Michael J. Rudd
Review of Progress in Quantitative Nondestructive Evaluation
A program is described which employs lasers for ultrasonic NDE. A highpower laser is used to generate a brief sound pulse in the test specimen. A second lowpower laser then measures the response of the specimen to that sound pulse.
The response of the specimen is measured by a “Laser Vibrometer.” This is a novel type of heterodyne interferometer which focuses a HeliumNeon laser beam onto the surface of the specimen and measures its displacement. Displacements as small as 2×1012 meters on a 0.15 sec averaging time can be detected and also displacements of 1.5×l09 meters ...
Nondestructive Evaluation With Beamforming Transducer Arrays, M. Simaan
Nondestructive Evaluation With Beamforming Transducer Arrays, M. Simaan
Review of Progress in Quantitative Nondestructive Evaluation
If a nondestructive evaluation system is designed to detect the presence or absence of a flaw in a material, typically one transducer may be sufficient. If, however, a characterization of the flaw is desired, then an array of transducers is in most cases required. Besides the capability of two and three dimensional imaging, array data has the advantages of increased resolution, improved signaltonoise ratio after preprocessing and sharper focusing.
In any NDE system, the acquisition of data is only one step towards the final objective of flaw characterization. The other step is that of processing the data in order to ...
Thermoelastic Structures For High Density Ultrasonic Energy, R. J. Von Gutfeld, D. R. Vigliotti, C. S. Oh, W. R. Scott
Thermoelastic Structures For High Density Ultrasonic Energy, R. J. Von Gutfeld, D. R. Vigliotti, C. S. Oh, W. R. Scott
Review of Progress in Quantitative Nondestructive Evaluation
The use of lasers to generate thermoelastic waves has received considerable attention since the publication of the theoretical work of White.1 The author derives equations for the propagation of longitudinal elastic waves produced by surface heating of a semiinfinite medium with harmonic thermal (laser) excitation. The importance of the boundary conditions in determining the magnitude of the resulting elastic waves is described. Two conditions are imposed and the resulting amplitudes derived: (1) Laser absorption at x = 0 with elastic amplitude u=0 at x = 0 for all times t ≥ 0 (perfectly clamped or constrained surface) and (2) for the ...
Ultrasonic Transducer Standards, N. Jayasundere, Leonard J. Bond
Ultrasonic Transducer Standards, N. Jayasundere, Leonard J. Bond
Review of Progress in Quantitative Nondestructive Evaluation
The piezoelectric transducer is the electromechanical conversion element in NDE. Existing transducers of this type are found to impose limits on the improvement in system performance and, at present, there is a lack of standards as required for calibration procedures. Physical “standards” based on equivalent circuits have been produced which model individual transducers, single transducers in pulseecho mode and twotransducer configurations. The performance of these “standards” is shown to be in good agreement with that given by real transducers, and subject to less variability.
Ultrasonic 3D Reconstruction Of Inclusions In Solids Using The Inverse Born Algorithm, David K. Hsu, James H. Rose, Donald O. Thompson
Ultrasonic 3D Reconstruction Of Inclusions In Solids Using The Inverse Born Algorithm, David K. Hsu, James H. Rose, Donald O. Thompson
Review of Progress in Quantitative Nondestructive Evaluation
Considerable progress has been made in recent years in the development of signal processing algorithms for use in ultrasonic nondestructive evaluation which yield the size, shape, and orientation of a flaw. This kind of flaw information is necessary in order that failure predictions of materials and components can be made from nondestructive tests. The signal processing algorithms that have been developed for ultrasonics are based upon both direct and inverse approximate solutions to the elastic wave scattering problem, and cover various ranges of the parameter ka where k=2π/λ is the wave number of the ultrasound and a is ...
Evaluation Of Photoacoustic Microscopy Fatigue Crack Detection, K. R. Grice, L. D. Favro, P. K. Kuo, R. L. Thomas
Evaluation Of Photoacoustic Microscopy Fatigue Crack Detection, K. R. Grice, L. D. Favro, P. K. Kuo, R. L. Thomas
Review of Progress in Quantitative Nondestructive Evaluation
The purpose of this paper is to evaluate the technique of scanning photoacoustic microscopy (SPAM) for the detection of fatigue cracks in metal alloys, and to describe an experimental arrangement for SPAM measurements on the inner surface of a cylindrical bolt hole. The experimental technique is based upon the physical mechanism of thermal wave imaging and has been described in detail at previous1, 2 Reviews of Progress in Quantitative NDE and elsewhere.3 In this paper we will also present some results of theoretical calculations for thermal wave scattering from closed, slanted cracks which intersect the surface of an opaque ...
High Resolution Arma Model Reconstruction For Nde Ultrasonic Imaging, YohHan Pao, Victor Chen, Ahmed ElSherbini
High Resolution Arma Model Reconstruction For Nde Ultrasonic Imaging, YohHan Pao, Victor Chen, Ahmed ElSherbini
Review of Progress in Quantitative Nondestructive Evaluation
Ultrasonic imaging is of use in a number of important areas, including nondestructive testing and medicine. The field has grown considerably in the past ten years and remains an active and growing area of research. For nondestructive evaluation of materials (NDE), the aim is to provide means for obtaining estimates of the size, shape and orientation of flaws in sufficiently a quantitative manner so that failure of mechanical structural parts can be predicted.1,2 As an imaging technique, ultrasonic imaging is appropriate whenever the medium considered is opaque to other sources of radiation, such as optical radiation. It is ...
A Miniature Optical Acoustic Emission Transducer, D. C. Emmony, M. W. Godfrey, R. G. White
A Miniature Optical Acoustic Emission Transducer, D. C. Emmony, M. W. Godfrey, R. G. White
Review of Progress in Quantitative Nondestructive Evaluation
The optical transduction of acoustic emission signals offers many advantages over piezoelectric devices. These include high bandwidth, no modification to the signal as well as providing contactless measurement. The major difficulties associated with optical devices are stability against low frequency vibrations and the generally complex nature of an optical interferometer. This paper describes the attempts to miniaturize a Michelson interferometer while at the same time overcoming some of the stability problems associated with these devices.
Active stability of an interferometric transducer with dimensions of ∿ 5cm (2″) cube has been achieved over 8 fringes of red light at 100Hz and 4 ...
Elastic Wave Scattering From Rough Surfaces And Cracks, S. Ayter, Bert A. Auld
Elastic Wave Scattering From Rough Surfaces And Cracks, S. Ayter, Bert A. Auld
Review of Progress in Quantitative Nondestructive Evaluation
The scattering from rough surfaces and cracks in the high frequency regime is analyzed via a scattering formula based on the reciprocity relation. Scattering from the smooth cracks is investigated first to rederive the “flash point” concept by Fourier transform methods. Based on this analysis, an inversion procedure is proposed for obtaining the characteristic function of the crack, which, for the case of rough cracks, gives information about the roughness as well as the dimensions and shape of the crack. The theory is applicable to both 2D and 3D scattering problems, as well as surface wave scattering from surface breaking ...
Elastic Wave Inversion Transformation, F. CohenTenoudji, G. Quentin, B. R. Tittmann
Elastic Wave Inversion Transformation, F. CohenTenoudji, G. Quentin, B. R. Tittmann
Review of Progress in Quantitative Nondestructive Evaluation
This paper presents results of a study on an inversion transformation ℐA for backscattering of ultrasonic waves from an obstacle embedded in a solid. For a rigid sphere the resulting function A(t) is derived which is related to the crosssectional area intercepted at any given time by a transverse plane moving across the obstacle in the same direction as the incident wave. The maximum value of A(t) is the total backscattering cross section. From this study emerges a proposed inversion algorithm for cavities. The use of the inversion algorithm is demonstrated for “exact” theoretical data obtained from Opsal ...
The Automation Of The Born Inversion For Ultrasonic Flaw Sizing, K. A. Marsh, J. M. Richardson, R. C. Addison, R. K. Elsley
The Automation Of The Born Inversion For Ultrasonic Flaw Sizing, K. A. Marsh, J. M. Richardson, R. C. Addison, R. K. Elsley
Review of Progress in Quantitative Nondestructive Evaluation
The Born approximation has been widely employed as a basis for determining flaw sizes using individual pulseecho waveforms together with the assumption of an ellipsoidal flaw geometry. A major difficulty in implementing such algorithms has been the determination of the time delay corresponding to the flaw centroid. However, both the time delay calculation and the flaw size determination itself can be performed in an optimal fashion using statistical estimation techniques with an appropriate error model. We will discuss the application of these techniques to an automated flawsizing algorithm requiring a minimum of operator input, and will compare the results obtained ...
Estimation Of The Boundary Of An Inclusion Of Known Material From Scattering Data, John M. Richardson
Estimation Of The Boundary Of An Inclusion Of Known Material From Scattering Data, John M. Richardson
Review of Progress in Quantitative Nondestructive Evaluation
A computationally tractable inversion algorithm has been developed for the case of the scattering of longitudinal elastic waves from an inclusion. It is assumed that the material properties of the inclusion are known a priori but that the boundary geometry is unknown — in fact the boundary could belong to two or more separate inclusions. It is further assumed that the material properties of the inclusion are sufficiently close to those of the host that the Born approximation can be employed.
Existence And Uniqueness Of Bound‐State Eigenvectors For Some Channel Coupling Hamiltonians, James W. Evans
Existence And Uniqueness Of Bound‐State Eigenvectors For Some Channel Coupling Hamiltonians, James W. Evans
Physics and Astronomy Publications
For the three‐particle, two‐cluster, 2×2 channel coupling Hamiltonians used, e.g., in H+2 and He bound‐state calculations, we demonstrate that typically there exist unique eigenvectors for all bound states. This result also holds, with some technical assumptions on the potentials, for the corresponding 3×3 case provided there are no spurious eigenvectors with bound‐state eigenvalues. The proofs use the analogous results for the corresponding Faddeev‐type Hamiltonians together with spurious multiplier relationships.
The Reactive Quantum Boltzmann Equations: A Derivation From An Arrangement Channel Space Representation And Bbgky Hierarchy, James W. Evans, D. K. Hoffman, D. J. Kouri
The Reactive Quantum Boltzmann Equations: A Derivation From An Arrangement Channel Space Representation And Bbgky Hierarchy, James W. Evans, D. K. Hoffman, D. J. Kouri
Physics and Astronomy Publications
A rigorous derivation of the reactive quantum Boltzmann equations is presented for systems where breakup and recombination are excluded. The use of an arrangement channel space representation allows an exact decomposition of the N particle density matrix into components for different chemical compositions and an exact definition of reduced species density matrices (as opposed, e.g., to standard projection operator techniques). This necessitates the use of the combinatorially complex arrangement channel BBGKY hierarchy which, however, avoids the need for the usual heuristic specification of collision terms. Another advantage is that scattering equations generated for the reactive and nonreactive many body ...
Irreversible Reaction On A Polymer Chain With Range Two Cooperative Effects, James W. Evans, D. R. Burgess
Irreversible Reaction On A Polymer Chain With Range Two Cooperative Effects, James W. Evans, D. R. Burgess
Physics and Astronomy Publications
We consider the kinetics of an irreversible reaction at the sites of an infinite, uniform, 1D polymer chain with first and second nearest neighbor (nn) cooperative effects. The special cases with just nn cooperative effects, and with nn blocking and general second nn cooperative effects have previously been solved exactly. For the latter case, we present several new results for highly autoinhibitory and autocatalytic rates. The general problem cannot be solved exactly but we apply the techniques of the preceding paper, which for this process exploit a shielding property of quadruples of unreacted sites, to obtain approximate solutions. Various ...
Irreversible Random And Cooperative Processes On Lattices: Exact And Approximate Hierarchy Truncation And Solution, James W. Evans, D. R. Burgess, D. K. Hoffman
Irreversible Random And Cooperative Processes On Lattices: Exact And Approximate Hierarchy Truncation And Solution, James W. Evans, D. R. Burgess, D. K. Hoffman
Physics and Astronomy Publications
Hierarchial rate equations are presented for processes where events occur irreversibly and, in general, cooperatively ‘‘filling’’ the sites of a lattice (the hierarchy is infinite for an infinite lattice). We comment on the hierarchial connectivity structure and a shielding property of empty sites. Hierachy truncation techniques are developed based on these. We consider, in detail, two irreversible processes on infinite, uniform lattices with nearest neighbor cooperative effects, modeling: (i) reaction at the sites of a 1D polymer chain; and (ii) chemisorption onto the sites of a 2D square lattice. Our truncation procedure recovers previously obtained exact results for ...
Nonstrange Baryon Properties From OneGluon Exchange And Linear Confinement Between Quarks , Mark Linden Kiefer
Nonstrange Baryon Properties From OneGluon Exchange And Linear Confinement Between Quarks , Mark Linden Kiefer
Retrospective Theses and Dissertations
We present a model of the quark structure of nonstrange baryons. We use quasiquarks whose masses are roughly 1/3 the proton mass and which interact via onegluon exchange and linear confining twobody potentials. The model is semirelativistic in that the quark kinetic energies and the onegluon exchange potential include the lowest order, nonrelativistic terms plus the first order relativistic corrections. The three quark Hamiltonian is diagonalized in a harmonic oscillator basis using all states up to 6(omega) of excitation energy. The basis states have the center of mass motion explicitly factored out and are overall antisymmetric in the ...