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Full-Text Articles in Physics

Photoemission Study Of Ce-Catalyzed Oxidation Of W(110) And W(111), C. Gu, C. G. Olson, David W. Lynch Oct 1993

Photoemission Study Of Ce-Catalyzed Oxidation Of W(110) And W(111), C. Gu, C. G. Olson, David W. Lynch

Physics and Astronomy Publications

Different catalytic oxidation effects of Ce on W(110) and W(111) were observed with photo- emission spectroscopy. On Ce-covered W(110), the top W layer is quickly oxidized to a surface monoxide at room temperature. Oxidation is almost halted after the completion of one monolayer of WO. On Ce/W(111), instead of WO, WO3 grows on the surface under the same conditions. The monolayer suboxide formation found on Ce/W(110) and Ce/Ta(110) (as reported earlier) is a direct consequence of the most densely packed structure of the bcc (110) surfaces. The more effective oxidation promotion ...


Observation Of Non-Isotropic Auger Angular Distribution In The C(1s) Shape Resonance Of Co, Oliver Hemmers, Franz Heiser, J. Eiben, R. Wehlitz, U. Becker Aug 1993

Observation Of Non-Isotropic Auger Angular Distribution In The C(1s) Shape Resonance Of Co, Oliver Hemmers, Franz Heiser, J. Eiben, R. Wehlitz, U. Becker

Environmental Studies Faculty Publications

Angle-resolved high-resolution C(KVV) Auger spectra of CO were taken in the vicinity of the C(1s) σ* shape resonance. These spectra show clear evidence for the theoretically predicted anisotropic K-shell Auger emission in molecules. Complementary results from angle-resolved photoion spectroscopy show that the small size of the observed effect is, besides the varying intrinsic anisotropy of the Auger decay, also due to a smaller anisotropy in the primary absorption process than originally predicted but in good agreement with more recent calculations. Contrary to this, satellite Auger transitions show unexpectedly large anisotropies.


Orientational Phase Transition In Na_{X}C_{60} (1, T. Yildirim, J. E. Fischer, A. B. Harris, Peter W. Stephens, Dengfa Liu, Laurent Brard, Robert M. Strongin, Amos B. Smith Iii Aug 1993

Orientational Phase Transition In Na_{X}C_{60} (1, T. Yildirim, J. E. Fischer, A. B. Harris, Peter W. Stephens, Dengfa Liu, Laurent Brard, Robert M. Strongin, Amos B. Smith Iii

Chemistry Faculty Publications and Presentations

X-ray diffraction and calorimetry data on cubic NaxC60(1<x60, e.g., Tm(x=1.3)=325 K. The ordered phases are the same as in pure C60: simple cubic, space group Pa3¯, but the orientations in the disordered phase are more restricted. We explain how Na stabilizes the ordered phase to rather high T, while K and Rb do not, in terms of Coulomb interactions between C60 molecules and and Na ions which we calculate from the local charge density of C60.


Design And Construction Of A Lithium Vapor Oven, Corey A. Leon Jul 1993

Design And Construction Of A Lithium Vapor Oven, Corey A. Leon

Honors Theses

A lithium vapor oven to be used as a source of lithium target atoms in atomic collision experiments was designed and constructed. The oven was installed in the beamline of the Van de Graaff accelerator at Western Michigan University. Test results indicated the oven produced a diffuse cloud of evaporated lithium instead of the intended concentrated jet spray. Recommendations concerning the design are made for future efforts.


Interatomic Forces And Atomic Structure Of Grain Boundaries In Copper-Bismuth Alloys, Min Yan, Mojmír Šob, David E. Luzzi, Vaclav Vitek, Graeme J. Ackland, M. Methfessel, C. O. Rodriguez Mar 1993

Interatomic Forces And Atomic Structure Of Grain Boundaries In Copper-Bismuth Alloys, Min Yan, Mojmír Šob, David E. Luzzi, Vaclav Vitek, Graeme J. Ackland, M. Methfessel, C. O. Rodriguez

Departmental Papers (MSE)

The many-body empirical potentials that describe atomic interactions in the copper-bismuth system were constructed using both experimental data and physical quantities obtained by ab initio full-potential linear muffin-tin orbital calculations for a metastable Cu3Bi compound. These potentials were then used to calculate the structure of a grain boundary in copper containing bismuth, which was at the same time studied by high-resolution electron microscopy (HREM). Excellent agreement between the calculated and observed structures is shown by comparing a through-focal series of observed and calculated images. This agreement validates the constructed potentials, which can be used with a high confidence ...


Multiplet-Changing Auger Transitions In Valence Double Photoionization, U. Becker, Oliver Hemmers, B. Langer, I. Lee, A. Menzel, R. Wehlitz, M. Ya Amusia Feb 1993

Multiplet-Changing Auger Transitions In Valence Double Photoionization, U. Becker, Oliver Hemmers, B. Langer, I. Lee, A. Menzel, R. Wehlitz, M. Ya Amusia

Environmental Studies Faculty Publications

The decay of valence satellite states in neon above the first double-ionization threshold has been studied experimentally and theoretically. Special emphasis was given to differentiate between two decay modes: valence Auger and valence-multiplet Auger decay. It is shown that the latter process is predominant in the low kinetic energy part of the spectrum. The main structures of this low-energy Auger spectrum could be designated by help of calculated transition energies and decay rates.


Measurement Of The Casimir-Polder Force, C. I. Sukenik, M. G. Boshier, S. Cho, V. Sandoghdar, E. A. Hinds Feb 1993

Measurement Of The Casimir-Polder Force, C. I. Sukenik, M. G. Boshier, S. Cho, V. Sandoghdar, E. A. Hinds

Physics Faculty Publications

The authors have studied the deflection of ground-state sodium atoms passing through a micron-sized parallel-plate cavity by measuring the intensity of a sodium atomic beam transmitted through the cavity as a function of cavity plate separation. This experiment provides clear evidence for the existence of the Casimir-Polder force, which is due to modification of the ground-state Lamb shift in the confined space of a cavity. The results confirm the magnitude of the force and the distance dependence predicted by quantum electrodynamics.


Application Of Diffracto Sight Ot The Nondestructive Inspection Of Aircraft Structures, Jerzy Komorowski, Ronald W. Gould, David L. Simpson, Omer Hageniers Jan 1993

Application Of Diffracto Sight Ot The Nondestructive Inspection Of Aircraft Structures, Jerzy Komorowski, Ronald W. Gould, David L. Simpson, Omer Hageniers

Review of Progress in Quantitative Nondestructive Evaluation

The D Sight optical set up was first assembled nearly ten years ago at Diffracto Ltd. It has received several patents, the first of which was in the United States [1]. Since the mid 1980’s, D Sight has been successfully applied to surface quality inspections, particularly in the automotive and plastics industries. Recently, Komorowski et al. [2–5] have shown several potential applications of D Sight in the field of nondestructive inspection of aircraft structures. The technique has been shown to be particularly effective in locating nonvisible impact damage on large surfaces of aircraft structures built from composite materials ...


High-Speed Time-Resolved Holography For Imaging Transient Events, Michael Ehrlich, James W. Wagner Jan 1993

High-Speed Time-Resolved Holography For Imaging Transient Events, Michael Ehrlich, James W. Wagner

Review of Progress in Quantitative Nondestructive Evaluation

A time-resolved holographic system was developed to study detonation dynamics in dispersed solid particulate explosives. This required a system capable of recording a rapid sequence of exposures during the approximate 1/µs lifetime of the detonation event.


Solid Rocket Motor Nde Using Nuclear Magnetic Resonance, Lowell Burnett, Dale R. Mckay, Erik M. Magnuson, E. J. Vanderheiden Jan 1993

Solid Rocket Motor Nde Using Nuclear Magnetic Resonance, Lowell Burnett, Dale R. Mckay, Erik M. Magnuson, E. J. Vanderheiden

Review of Progress in Quantitative Nondestructive Evaluation

Solid rocket motors (SRMs) are complex integrated structures. An integral part of an SRM is the adhesive liner, which is used to bond the propellant to the insulator covering the inner surface of the case. In order to ensure SRM performance and reliability, the adhesive liner must be properly cured, of the specified thickness, and free of contamination. The goal of this study is to demonstrate the feasibility of a nuclear magnetic resonance (NMR) method to ensure that these conditions are met.


Nuclear Quadrupole Resonance As A Non-Destructive Testing Tool, George Williams, Z. M. Saleh, P. Hari Jan 1993

Nuclear Quadrupole Resonance As A Non-Destructive Testing Tool, George Williams, Z. M. Saleh, P. Hari

Review of Progress in Quantitative Nondestructive Evaluation

Nuclear pure quadrupole resonance (NQR) is a resonance technique that provides distinctly different information from that provided by nuclear magnetic resonance (NMR). In NMR the splitting of the energy levels, and therefore the frequency observed, occurs because of the interaction of the nuclear magnetic moment with an external magnetic field. Information about the system under study comes from perturbations on this magnetic interaction. These perturbations lead to a broadening of the line, or to relaxation effects on the interchange of energy between the spins and the lattice, and among the spins. In NQR the primary interaction is between the electric ...


General Automated Flaw Detection Scheme For Nde X-Ray Images, Karl Ulmer, John P. Basart Jan 1993

General Automated Flaw Detection Scheme For Nde X-Ray Images, Karl Ulmer, John P. Basart

Review of Progress in Quantitative Nondestructive Evaluation

This paper presents an approach to automated flaw detection (AFD) in an arbitrary X-ray image. The intensities in the digitized radiographic image are modeled as piecewise-smooth surface functions corrupted by noise and flaws. It has been observed that radiographs generated for NDE purposes containing flaws also have a combination of three unwanted features; background trends, geometrical structures, and noise. These features inhibit the performance of automated flaw detection algorithms. The proposed general processing scheme reduces the unwanted features in such a way that candidate flaws within the image can be identified. The proposed scheme is robust and is applicable to ...


X-Ray Computed Tomography For Geometry Acquisition, R. Bossi, A. Crews, G. Georgeson, J. Nelson, J. Shrader Jan 1993

X-Ray Computed Tomography For Geometry Acquisition, R. Bossi, A. Crews, G. Georgeson, J. Nelson, J. Shrader

Review of Progress in Quantitative Nondestructive Evaluation

X-ray computed tomography (CT) uses penetrating radiation measurements from many angles about an object to reconstruct cross sectional images of the object interior [1–2]. The images are two dimensional maps of the X-ray linear attenuation coefficient for small volume elements in the object defined by the effective X-ray beam size. The CT images provide quantitative measures of component feature dimensions and density as related to the linear X-ray attenuation of the material under study.


Computed Tomography Applications In Turbine Engine Overhaul, Ward Rummel, Mark Davis, Rodolfo Garcia Jan 1993

Computed Tomography Applications In Turbine Engine Overhaul, Ward Rummel, Mark Davis, Rodolfo Garcia

Review of Progress in Quantitative Nondestructive Evaluation

The United States Air Force has an initiative for technology development and implementation in design, production, acceptance and maintenance overhaul operations. As a part of this initiative, an x-ray computed tomography capability was acquired for use in the support of aircraft structures and gas turbine engine overhaul applications at Kelly Air Force Base, Texas. Implementation of the technology into the Kelly work flow has required acquisition of the knowledge and skills required to use the system, and re-analysis of work functions to assess added capability, measurement precision, reliability and productivity. At the same time, the nature of the data / information ...


Development And Application Of Local 3-D Ct Reconstruction Software For Imaging Critical Regions In Large Ceramic Turbine Rotors, E. Sivers, D. L. Holloway, W. A. Ellingson, J. Ling Jan 1993

Development And Application Of Local 3-D Ct Reconstruction Software For Imaging Critical Regions In Large Ceramic Turbine Rotors, E. Sivers, D. L. Holloway, W. A. Ellingson, J. Ling

Review of Progress in Quantitative Nondestructive Evaluation

Current 3-D X-ray CT imaging technology is limited in some cases by the size and sensitivity of the X-ray detector. This limitation can be overcome to some degree by the use of region-of-interest (ROI) reconstruction software when only part of a larger object need be examined. However, images produced from ROI data often exhibit severe density shading if they are reconstructed by unaltered 3-D X-ray CT algorithms (called Global methods here). These density artifacts can be so severe that low-contrast features are hidden. Time-consuming methods introduced previously to remedy these artifacts require specialized processing to replace or approximate the missing ...


Electronic Holography And Shearography Nde For Inspection Of Modern Materials And Structures, J. Clarady, M. Summers Jan 1993

Electronic Holography And Shearography Nde For Inspection Of Modern Materials And Structures, J. Clarady, M. Summers

Review of Progress in Quantitative Nondestructive Evaluation

Coherent optical techniques such as holography, shearography, and ESPI have been available for inspection applications for years. However, they are still not well known or widely used. In fact, they have sometimes been described as “a solution looking for a problem” and like so many new technologies, they may have been somewhat oversold. These optical NDE methods do, however, offer some impressive advantages over more conventional inspection techniques for the right applications. It is the intent of this paper to provide some basic information on how two of these optical methods, holography and shearography, work discuss capabilities and limitations of ...


Beam Profile Reflectometry: A New Technique For Thin Film Measurements, J. Fanton, J. Opsal, D. L. Willenborg, S. M. Kelso, Allan Rosencwaig Jan 1993

Beam Profile Reflectometry: A New Technique For Thin Film Measurements, J. Fanton, J. Opsal, D. L. Willenborg, S. M. Kelso, Allan Rosencwaig

Review of Progress in Quantitative Nondestructive Evaluation

In the manufacture of semiconductor devices, it is of critical importance to know the thickness and material properties of various dielectric and semiconducting thin films. Although there are many techniques for measuring these films, the most commonly used are reflection spectrophotometry [1,2] and ellipsometry [3]. In the former method, the normal- incidence reflectivity is measured as a function of wavelength. The shape of the reflectivity spectrum is then analyzed using the Fresnel equations to determine the thickness of the film. In some cases, the refractive index can also be determined provided that the dispersion of the optical constants are ...


Electronic Shearography: Current Capabilities, Potential Limitations, And Future Possibilities For Industrial Nondestructive Inspection, John Deaton Jr., Robert S. Rogowski Jan 1993

Electronic Shearography: Current Capabilities, Potential Limitations, And Future Possibilities For Industrial Nondestructive Inspection, John Deaton Jr., Robert S. Rogowski

Review of Progress in Quantitative Nondestructive Evaluation

Image-shearing speckle pattern interferometry, more commonly referred to as ‘shearography’, is a full-field, laser-based interferometric technique first developed for applications in experimental mechanics [1,2]. Shearography is sensitive to derivatives of the out-of-plane surface displacement of a body under load, as opposed to other full-field methods such as holographic interferometry and conventional speckle pattern interferometry, which typically contour the surface displacement directly [3]. The early shearography experiments used high-resolution photographic film to record images of the laser speckle patterns. In contrast to traditional film-based techniques, electronic shearography uses an electronic camera for image recording [4]. This technology, commercially available for ...


Quantitative Analysis Of A Class Of Subsurface Cracks Using Shearography And Finite Element Modeling, Leland Melvin, Brooks A. Childers, James P. Fulton Jan 1993

Quantitative Analysis Of A Class Of Subsurface Cracks Using Shearography And Finite Element Modeling, Leland Melvin, Brooks A. Childers, James P. Fulton

Review of Progress in Quantitative Nondestructive Evaluation

The application of a full field non-contacting measurement system for nondestructively evaluating (NDE) subsurface flaws in structures has been conducted using Electronic Shearography. Shearography has primarily been used as a qualitative tool for locating areas of stress concentration caused by anomalies in materials[1–4]. NASA has been applying optical techniques such as these to NDE inspection of aircraft lap joint integrity, composite material defects, and pressure vessel quality assurance. This paper examines a special class of defects manufactured in thin metal panels and serves as a testbed for interpreting the displacement gradients produced on a simple well-characterized sample with ...


Laser Shearographic Testing Of Foam Insulation On Cryogenic Fuel Tanks, Douglas Burleigh, James E. Engel, David R. Kuhns Jan 1993

Laser Shearographic Testing Of Foam Insulation On Cryogenic Fuel Tanks, Douglas Burleigh, James E. Engel, David R. Kuhns

Review of Progress in Quantitative Nondestructive Evaluation

The Centaur is a high-energy rocket used as a second stage to the Atlas launch vehicle. The Centaur is cryogenically fueled, using liquid hydrogen and liquid oxygen, and requires insulation to prevent fuel boiloff prior to launch. The original insulation system used on Centaur is a set of fiberglass honeycomb panels, which are jettisoned after launch. These panels are still used on the Atlas I version of Atlas/Centaur.


Shearography With Syncrhonized Pressure Stressing, Tom Chatters, Bruno Pouet, Sridhar Krishnaswamy Jan 1993

Shearography With Syncrhonized Pressure Stressing, Tom Chatters, Bruno Pouet, Sridhar Krishnaswamy

Review of Progress in Quantitative Nondestructive Evaluation

Non-destructive evaluation (NDE) techniques of optical video-based speckle interferometry are gaining importance as inspection tools, particularly by the aerospace industry [1,2]. An optical technique such as shearography is attractive to the NDE community largely because of its non-contacting nature, full-field measurement and fast inspection results. However, in order for this optical interferometric method to become widely used as an NDE tool, this technique must be made to be robust enough to operate in noisy environments typically found in industry settings. In this paper, we address these issues for the case of detection of disbonds using shearography in conjunction with ...


Practical Estimates Of The Errors Associated With The Governing Shearography Equation, John Fulton, M. Namkung, L. D. Melvin Jan 1993

Practical Estimates Of The Errors Associated With The Governing Shearography Equation, John Fulton, M. Namkung, L. D. Melvin

Review of Progress in Quantitative Nondestructive Evaluation

In a series of papers Hung[1–3] pioneered the development of shearography, an optical NDE technique that detects gradients of surface displacements. Its utility for qualitative flaw characterization has been demonstrated, and while there is a need for using shearography in NDE for quantitative analysis, a large amount of the research[2–7] has concentrated on the qualitative evaluation of structures and materials. The purpose of this paper is to begin building upon a foundation for the newly emerging quantitative shearography[8].


Noise Reduction Techniques For Electronic Speckle Interferometry, Bruno Pouet, Sridhar Krishnaswamy Jan 1993

Noise Reduction Techniques For Electronic Speckle Interferometry, Bruno Pouet, Sridhar Krishnaswamy

Review of Progress in Quantitative Nondestructive Evaluation

Video-based speckle interferometric methods such as electronic speckle pattern interferometry (ESPI) allow us to measure full-field surface deformation of a diffuse object. In this paper we show, in a first step, that the susceptibility of ESPI to noise can be substantially reduced [1] by synchronizing the optical interferometer and the object stressing system with the CCD image acquisition and processing system, and by performing what amounts to a repetitive sequence of rapid ESPI tests. In this manner, a stable fringe pattern can be obtained as long as the ambient noise is of sufficiently lower frequency than the video acquisition rate ...


Transcatter X-Ray Technique For The Inspection Of Insulated, Oil-Carrying Pipelines, P.-S. Ong, W. L. Anderson, B. D. Cook, R. Subramanyan Jan 1993

Transcatter X-Ray Technique For The Inspection Of Insulated, Oil-Carrying Pipelines, P.-S. Ong, W. L. Anderson, B. D. Cook, R. Subramanyan

Review of Progress in Quantitative Nondestructive Evaluation

Pipelines are subjected to corrosion and require periodic inspection. These pipes are generally covered with an insulating material, that is contained within a metal jacket. The removal of the insulating material is costly, and can hazardous if asbestos is the material being removed. Because a large number of pipes need to be inspected, a cost effective technique for the characterization of corrosion under insulation is desirable.


Wall-Thickness Measurement From Two Dimensional Radiographs, W. Graeme Jr., J. F. Singer, R. Mayer Jan 1993

Wall-Thickness Measurement From Two Dimensional Radiographs, W. Graeme Jr., J. F. Singer, R. Mayer

Review of Progress in Quantitative Nondestructive Evaluation

Radiographic film has been used for many years in NDE as a means to detect thickness variations in parts. The part thickness information is captured as varying shades of grey on the film. Radiographic film can be an extremely sensitive detector capable of detecting small variations in part thickness as thousands of shades of greys.


"Vision" Approach Of Calibration Methods For Radiographic Systems, Christophe Icord, Philippe Rizo, Pascal Sire Jan 1993

"Vision" Approach Of Calibration Methods For Radiographic Systems, Christophe Icord, Philippe Rizo, Pascal Sire

Review of Progress in Quantitative Nondestructive Evaluation

The geometric calibration of radiographic systems cannot be avoided in image reconstruction problems in stereoradiography, X-ray or SPECT tomography. This operation performed usually before the object examination, provides the relative positions of the different parts of the system (object, source, detector). The source-detector geometry is then described by intrinsic parameters, and the scanning motion by extrinsic ones.


Optical Probing Of Spherical Resonance Applied To Surface Defect Inspection, Chung-Kao Hsieh, B. T. Khuri-Yakub Jan 1993

Optical Probing Of Spherical Resonance Applied To Surface Defect Inspection, Chung-Kao Hsieh, B. T. Khuri-Yakub

Review of Progress in Quantitative Nondestructive Evaluation

Ceramic materials keep high strength under high temperature and nonlubricative environments. Ceramic bearing balls are more commonly used now to replace steel bearing balls to sustain high loads under such hostile environments. However, because ceramics are brittle, surface defects of ceramic bearing balls can cause total mechanical failure of the whole mechanism. In this paper, we shall discuss a quick, efficient, and accurate method for performing nondestructive testing of spherical objects. Currently, there are several techniques being used to inspect spherical objects. Here, we introduce a new noncontacting technique, the optical probing technique of spherical resonance. This technique has great ...


Development Of A Neutron Radiography Simulation Model, Troy Groth, Joseph Nahum Gray Jan 1993

Development Of A Neutron Radiography Simulation Model, Troy Groth, Joseph Nahum Gray

Review of Progress in Quantitative Nondestructive Evaluation

Measurement models of NDE techniques have been developed with the purpose of proving the capabilities of NDE techniques for finding flaws. The models take NDE parameters such as ultrasonic frequency, probe diameter, and angle of incidence, and predict the response from the flaw. Models are also a part of quantitative NDE, i.e., the ability to size and characterize flaws and or materials.


Experiments With Double Microwave Apertures, John Basart, Zhong Zhang Jan 1993

Experiments With Double Microwave Apertures, John Basart, Zhong Zhang

Review of Progress in Quantitative Nondestructive Evaluation

One of the significant characterizations of microwave imaging is the spatial resolution. The relative long wavelength of microwaves as compared to ultrasonic waves and x-rays necessarily means that aperture arrays (real-time or synthetic) are required for high-resolution microwave imaging. Certain limitations on resolution apply regardless of how the array is realized. Types of antenna arrays fall into two broad categories: Phased arrays which are usually operated in real time by scanning a beam past an object, and aperture synthesis in which data are collected with one or more antennas and later processed to produce an image. In NDE we are ...


Application Of The X-Ray Measurement Model To Image Processing Of X-Ray Radiographs, E. Siwek, Joseph Nahum Gray Jan 1993

Application Of The X-Ray Measurement Model To Image Processing Of X-Ray Radiographs, E. Siwek, Joseph Nahum Gray

Review of Progress in Quantitative Nondestructive Evaluation

A computational model has been developed at which simulates the film response to the interaction of x-rays with a sample[1,2]. By using a CAD model as a virtual part, film densities of the radiograph are predicted. The number of photons which reach the film is based on the thickness of the part, part geometry, and the material absorption coefficient. Also taken into consideration are the x-ray beam characteristics, film properties, and the experimental configuration. The model generated images can vary in size and resolution, depending on the user chosen parameters. Noise is calculated using a Gaussian noise distribution ...