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Articles 271 - 295 of 295

Full-Text Articles in Physics

The Nonlinear Coupling Of Electromagnetic Ion Cyclotron And Lower Hybrid Waves In The Ring Current Region: The Magnetic Storm 1–7 May 1998, G. V. Khazanov, E. N. Krivorutsky, K. V. Gamayunov, L. A. Avanov Jan 2004

The Nonlinear Coupling Of Electromagnetic Ion Cyclotron And Lower Hybrid Waves In The Ring Current Region: The Magnetic Storm 1–7 May 1998, G. V. Khazanov, E. N. Krivorutsky, K. V. Gamayunov, L. A. Avanov

Aerospace, Physics, and Space Science Faculty Publications

The excitation of lower hybrid waves (LHWs) is a widely discussed mechanism of interaction between plasma species in space, and is one of the unresolved questions of magnetospheric multi-ion plasmas. In this paper we present the morphology, dynamics, and level of LHWactivity generated by electromagnetic ion cyclotron (EMIC) waves during the 2–7 May 1998 storm period on the global scale. The LHWs were calculated based on a newly developed selfconsistent model (Khazanov et. al., 2002) that couples the system of two kinetic equations: one equation describes the ring current (RC) ion dynamic, and another equation describes the evolution of EMIC …

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Physics First, Marcelo Alonso Dec 2003

Physics First, Marcelo Alonso

Aerospace, Physics, and Space Science Faculty Publications

It is true that now most biology courses begin with the DNA molecule, and many chemistry courses introduce the notion of electronic orbitals in atoms and molecules, topics for which students are not well prepared, since most of them have not taken physics courses. Physics courses in turn relegate to the end some discussion of the structure of matter and electromagnetic interaction, or do not discuss that at all. Thus, students miss the overall picture.

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Tracking Of Moving Objects In Scenery Using Subspace Projection Using Independent Component Analysis, Brian J. Noe, Fredric M. Ham Jan 2001

Tracking Of Moving Objects In Scenery Using Subspace Projection Using Independent Component Analysis, Brian J. Noe, Fredric M. Ham

Aerospace, Physics, and Space Science Faculty Publications

A system is developed for tracking moving objects though natural scenery. A technique is presented for performing change detection on imagery to determine the difference between two images or a sequence of images. Form there an algorithm is presented to detect the presence of a new object and/or the deletion of objects. Then the application of a Variable Structure Interacting Multiple Model tracking filter is presented. The method of performing change detection is based upon the concept of image subspace projection. A set of basis image maps are formed when combined with a mixing matrix can recreate the original image. …

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Automated Alignment By Hybrid Video And 3-D Video Moiré With Both Conventional And Parallel Processing, Barbara Garita, Hector Gutierrez, Ildiko Laszlo, Joel H. Blatt Jan 2001

Automated Alignment By Hybrid Video And 3-D Video Moiré With Both Conventional And Parallel Processing, Barbara Garita, Hector Gutierrez, Ildiko Laszlo, Joel H. Blatt

Aerospace, Physics, and Space Science Faculty Publications

A problem common to automated assembly in manufacturing or in automated docking of spacecraft is angular and lateral alignment of components. A hybrid video system utilizing both conventional imaging and 3-D video moiré has been developed to automatically align a test target with three translational and two rotational degrees of freedom. Alignment was demonstrated via computer controlled translation and rotation stages. The video moiré system is operated in an error map mode, in which a structurally illuminated reference surface is used to chromakey the image of an identical structurally illuminated alignment target. The output is a moiré image generated by …

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How Big Is Our Sun?, Mark Moldwin Feb 2000

How Big Is Our Sun?, Mark Moldwin

Aerospace, Physics, and Space Science Faculty Publications

Putting large numbers into human perspective by using ratios of a known quantity to an unknown quantity is an important scientific skill. An astronomy activity that encourages the use of estimation and helps students get a handle on large numbers is the making of a scale model of Earth and Sun that is relative in both size and distance.

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Enhanced Three-Dimensional Reconstruction Of Surfaces Using Multicolor Gratings, Bernard S. Gilbert, Joel H. Blatt Jan 2000

Enhanced Three-Dimensional Reconstruction Of Surfaces Using Multicolor Gratings, Bernard S. Gilbert, Joel H. Blatt

Aerospace, Physics, and Space Science Faculty Publications

Most optical topolography systems use a single-wavelength laser for projection, using a swept spot, a moving line, or a projected grating. In a typical projected grating system, the gratings are shifted and a series of images is used to recover the 3-D shape of the target. When the series of images is analyzed in the normal phase shift manner, the resulting 2-D phase map typically has phase unwrapping problems due to noise and Nyquist limits. Surfaces with large vertical discontinuities present a problem for phase unwrapping 3-D shape recovery. We look at simultaneously projecting multiple wavelengths onto a surface to …

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Real Time Two Color Variable Resolution Video Moire And Error Map Moire Using A Mach-Zehnder Interferometer, Neville Maycock, August Schutte, Joel H. Blatt Jan 1999

Real Time Two Color Variable Resolution Video Moire And Error Map Moire Using A Mach-Zehnder Interferometer, Neville Maycock, August Schutte, Joel H. Blatt

Aerospace, Physics, and Space Science Faculty Publications

A variable resolution two color video moire system has been built which uses a dual laser illuminated Mach-Zehnder interferometer as the fringe projector. One input of the interferometer is illuminated by a He-Ne laser and the other by an Argon-Ion laser, allowing simultaneous projection of red and green fringes with different spatial frequencies. The dual interferometer outputs are also used, allowing illumination of both the target and reference surfaces. Video cameras view the two surfaces and by mixing the video signals with a chroma-key mix in a video special effects generator, real time moire can be observed. A piezo-electrically driven …

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Mach-Zehnder Interferometer Fringe Projector For Variable Resolution Video Moire, Phillip C. Kalmanson, August Schutte, Chris L. Hart, Joel H. Blatt Jan 1998

Mach-Zehnder Interferometer Fringe Projector For Variable Resolution Video Moire, Phillip C. Kalmanson, August Schutte, Chris L. Hart, Joel H. Blatt

Aerospace, Physics, and Space Science Faculty Publications

A Mach-Zehnder based variable resolution fringe projection system has been built for 3-D video moini machine vision. This system uses the three main advantages of the Mach-Zehnder - 1) There is no optical feedback to the laser source, 2) The interfemmeter can accept two different laser wavelengths simultaneously, and 3) The interferometer produces two orthngonal output beams. The lack of optical feedback makes the Mach-Zehnder especially attractive for use with high power laser diode sources which are sensitive to optical feedback. When the two input ports axe used with two different wavelength lasers, the target can be illuminated by simultaneous …

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Multicolor Fringe Projection System With Enhanced 3-D Reconstruction Of Surfaces, Bernard S. Gilbert, Joel H. Blatt Jan 1998

Multicolor Fringe Projection System With Enhanced 3-D Reconstruction Of Surfaces, Bernard S. Gilbert, Joel H. Blatt

Aerospace, Physics, and Space Science Faculty Publications

Most optical topology systems use a single wavelength laser for projection, using a swept spot, a moving line, or a projected grating. In a typical projected grating system, the gratings are shifted and a series of images are used to recover the 3-D shape of the target. When the series of images is analyzed in the normal phase shift manner, the resulting 2-D phase map typically has phase unwrapping problems due to noise and Nyquist limits. Surfaces with large vertical discontinuities present the biggest problem in 3-D shape recovery. This paper looks at simultaneously projecting multiple wavelengths onto a surface …

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Real Time 3-D Video Moire Inspection System With Enhanced Depth Resolution, Donald W.W. Dawson, Chris L. Hart, Bernard R. Gilbert, Gary L. Wallace, Joel H. Blatt Jan 1997

Real Time 3-D Video Moire Inspection System With Enhanced Depth Resolution, Donald W.W. Dawson, Chris L. Hart, Bernard R. Gilbert, Gary L. Wallace, Joel H. Blatt

Aerospace, Physics, and Space Science Faculty Publications

A variable resolution video machine vision systems has been built which generates twice the number of depth contours for a given grating spacing as a conventional moiré system. This variable resolution system uses a Mach-Zender interferometer to project interference fringes onto a reference surface and onto a target surface. Video images of the two structurally illuminated surfaces are mixed in a video mixer with the resulting output being moiré contours which are the intersections of the two surfaces. If the reference surface is a flat plate, we get equal depth contours of the target surface, and if the reference surface …

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Analysis Of Scanning Tunneling Optical Spectroscopy Applied To Narrow Gap Semiconductors, James D. Patterson, James G. Mantovani Jan 1997

Analysis Of Scanning Tunneling Optical Spectroscopy Applied To Narrow Gap Semiconductors, James D. Patterson, James G. Mantovani

Aerospace, Physics, and Space Science Faculty Publications

Homogeneous II-VI narrow gap semiconducting alloys are of interest because of their use in infrared detectors. These compound semiconductor materials are inherently difficult to grow in bulk due to gravity induced convective flows. A microgravity growth environment has therefore been considered. In order to evaluate the quality of crystals grown in space compared to those grown on the ground, it is necessary to characterize both. One important aspect of this characterization is the study of stoichiometry, x. A characterization scheme using scanning tunneling optical spectroscopy (STOS) involves determining the spectral response of the photoexcited tunneling current for a semiconductor. By …

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Prediction Of Firing Pin Shape And 3d Matching Of Shells And Firing Pins Based On Firing Pin Impressions In Primers, Donald W. Dawson, Chris Hart, Bernard S. Gilbert Iii, Rafael A. Andrade, Joel H. Blatt Jan 1997

Prediction Of Firing Pin Shape And 3d Matching Of Shells And Firing Pins Based On Firing Pin Impressions In Primers, Donald W. Dawson, Chris Hart, Bernard S. Gilbert Iii, Rafael A. Andrade, Joel H. Blatt

Aerospace, Physics, and Space Science Faculty Publications

A variable resolution video machine vision system has been built which will determine the 3-D shape of a firing pin from the dent it has made in the primer of a shell. The system can also compare primer dents in different shells and determine if a 3-D match exists. A real time optical 3-D shape recognition feature allows the operator to align the shells, determine if there is a match, and quantify the quality of the 3-D match. The system uses a laser interferometer to project variable spatial frequency structural illumination on the shells which are viewed by video cameras. …

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Formation Energies And Energy Levels Of Deep Defects In Narrow-Gap Semiconductors, James D. Patterson, Weigang Li Jan 1996

Formation Energies And Energy Levels Of Deep Defects In Narrow-Gap Semiconductors, James D. Patterson, Weigang Li

Aerospace, Physics, and Space Science Faculty Publications

We use a Green's function technique for deep defect energy level calculations in mercury cadmium telluride, mercury zinc telluride, and mercury zinc selenide. The formation energy is calculated from the difference between the total binding energy with an impurity cluster and with a perfect cluster. These alloys are among those that have been experimentally grown in microgravity aboard the Space Shuttle. To evaluate the quality of these crystals, it is necessary to characterize them, and one important aspect of this characterization is the study of deep defects which can limit carrier lifetime. Relaxation effects are calculated with molecular dynamics. The …

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Deep Defects In Narrow-Gap Semiconductors, Weigang Li, James D. Patterson Nov 1994

Deep Defects In Narrow-Gap Semiconductors, Weigang Li, James D. Patterson

Aerospace, Physics, and Space Science Faculty Publications

We use a Green’s-function technique to calculate the position of deep defects in narrow-gap semiconductors. In order to predict chemical trends, we examine the effects of several different chemical elements. Substitutional (including antisite), (ideal) vacancy, and interstitial (self and foreign) deep defects are considered. The compounds considered are mercury cadmium telluride (MCT), mercury zinc telluride (MZT), and mercury zinc selenide (MZS). The effect of relaxation of neighbors is considered for the substitutional and interstitial cases. Relaxation effects can be greater for the interstitial case than for the substitutional one. For all cases we find deep defects in the energy gap …

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Generation Of Surface Shape From Variable-Resolution Video Moire Contours, Joel H. Blatt, Scott C. Cahall, Bernard Gilbert, Jeffrey A. Hooker, Gary L. Wallace Jan 1993

Generation Of Surface Shape From Variable-Resolution Video Moire Contours, Joel H. Blatt, Scott C. Cahall, Bernard Gilbert, Jeffrey A. Hooker, Gary L. Wallace

Aerospace, Physics, and Space Science Faculty Publications

Several methods for generation of three dimensional surface shapes from variable resolution video moire contours are described. In a classical moire system, a physical grating is projected on a target and also used to view the target. The moire contours are generated in the plane of the viewing grating. An unambiguous surface shape can then be computed by processing a set of moire images where the grating, target, or both are moved. By using an interferometer to generate and project variable pitch gratings and video technology to generate the moire contours, a 3-D surface can be scanned at different resolutions …

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Variable-Resolution Video Moire Error Map System For Inspection Of Continuously Manufactured Objects, Joel H. Blatt, Scott C. Cahall, Jeffery A. Hooker Jan 1993

Variable-Resolution Video Moire Error Map System For Inspection Of Continuously Manufactured Objects, Joel H. Blatt, Scott C. Cahall, Jeffery A. Hooker

Aerospace, Physics, and Space Science Faculty Publications

Moire techniques can be a powerful tool to determine deviation of a manufactured shape from a desired shape. In a traditional moire system, distorted gratings on an object are viewed through an undistorted grating. The moire contours that result represent equal depth contours over the entire viewed surface. By generating the moire patterns in video, it is possible to view the distorted gratings on a test object through a set of gratings that has been distorted by a similar but perfect object. The output is then a set of moire contours that corresponds to the differences between the two surfaces. …

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Real-Time Generation Of Intersection Of Surfaces For Welding By Video Moire, Scott Christian Cahall, Jeffery A. Hooker, Joel H. Blatt Jan 1993

Real-Time Generation Of Intersection Of Surfaces For Welding By Video Moire, Scott Christian Cahall, Jeffery A. Hooker, Joel H. Blatt

Aerospace, Physics, and Space Science Faculty Publications

A common problem in fabrication and welding of complex structures is that there is no simple way to determine where to cut one part so that it will fit another part unless both parts designed and built on a CAD/CAM system. Particularly in prototype or retrofit work, cutting and fitting parts for welding is more of an art than a science. We have developed a unique video moire system that generates the intersection contour in near real time with the contour superimposed on a video image of the part, allowing the cut line to be marked while following the contour …

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Detection, Location, And Quantification Of Structural Damage By Neural-Netprocessed Moire Profilometry, Barry G. Grossman, Frank S. Gonzalez, Joel H. Blatt, Jeffery A. Hooker Mar 1992

Detection, Location, And Quantification Of Structural Damage By Neural-Netprocessed Moire Profilometry, Barry G. Grossman, Frank S. Gonzalez, Joel H. Blatt, Jeffery A. Hooker

Electrical Engineering and Computer Science Faculty Publications

The development of efficient high speed techniques to recognize, locate, and quantify damage is vitally important for successful automated inspection systems such as ones used for the inspection of undersea pipelines. Two critical problems must be solved to achieve these goals: the reduction of nonuseful information present in the video image and automatic recognition and quantification of extent and location of damage. Artificial neural network processed moire profilometry appears to be a promising technique to accomplish this. Real time video moire techniques have been developed which clearly distinguish damaged and undamaged areas on structures, thus reducing the amount of extraneous …

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Gaussian Reference Auid And Interpretation Of Quantum Geometrodynamics, Karel V. Kucha, Charles G. Torre Jan 1991

Gaussian Reference Auid And Interpretation Of Quantum Geometrodynamics, Karel V. Kucha, Charles G. Torre

Aerospace, Physics, and Space Science Faculty Publications

The of vacuum geometrodynamics is turned into a Schrödinger equation by imposing the normal Gaussian coordinate conditions with s and then restoring the coordinate invariance of the action by parametrization. This procedure corresponds to coupling the gravitational field to a reference fluid. The source appearing in the Einstein law of gravitation has the structure of a heat-conducting dust. When one imposes only the Gaussian time condition but not the Gaussian frame conditions, the heat flow vanishes and the dust becomes incoherent. The canonical description of the fluid uses the Gaussian coordinates and their conjugate momenta as the fluid variables. The …

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Analytic Variational Method For Hamiltonian Lattice Gauge Theory In 3+ 1 Dimensions, Ming C. Huang, Mohammad W. Katoot Mar 1990

Analytic Variational Method For Hamiltonian Lattice Gauge Theory In 3+ 1 Dimensions, Ming C. Huang, Mohammad W. Katoot

Aerospace, Physics, and Space Science Faculty Publications

We present an analytic d in 3 + 1 dimensions for Hamiltonian lattice gauge theory. This method is based on Batrouni's mean-plaquette method and space integration. The Abelianized Bianchi identities are used and a detailed study of the number of identities that are needed and the validity of this approximation is given. The we use is the product of single-plaquette wave functions. The guage group we consider here is SU(2), but the method is valid for any gauge theory. We apply this method to calculate the 0++ glueball mass, and, in addition, the results of the string tension (scaling is …

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Perturbations Of Gravitational Instantons, Charles G. Torre Jan 1990

Perturbations Of Gravitational Instantons, Charles G. Torre

Aerospace, Physics, and Space Science Faculty Publications

Ashtekar's spinorial formulation of general relativity is used to study perturbations of gravitational instantons corresponding to finite-action solutions of the Euclidean Einstein equations (with a nonzero cosmological constant) possessing an anti-self-dual Weyl curvature tensor. It is shown that, with an appropriate "on-shell" form of infinitesimal gauge transformations, the space of solutions to the can be described in terms of an elliptic complex; the cohomology of the complex defines gauge-inequivalent perturbations. Using this elliptic complex we prove that there are no nontrivial solutions to the linearized instanton equation on conformally anti-self-dual Einstein spaces with a positive cosmological constant. Thus, the space …

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Hamiltonian Formulation Of Induced Gravity In Two Dimensions, Charles G. Torre Oct 1989

Hamiltonian Formulation Of Induced Gravity In Two Dimensions, Charles G. Torre

Aerospace, Physics, and Space Science Faculty Publications

A Hamiltonian formulation of the theory of induced gravity in two dimensions is constructed. This formulation differs from previous efforts in that the formalism is covariant under all relevant transformation groups. In particular, spatial diffeomorphism covariance and/or invariance is manifest throughout; the phase space carries a representation of the Lie algebra of the spacetime diffeomorphism group; the group of conformal isometries is projectively represented on the phase space as a symmetry group. The key ingredient that allows covariance with respect to the above groups is the enlargement of the gravitational phase space by the inclusion of the cotangent bundle over …

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Generation Of Moire Contours With Acousto-Optic Cells, Joel H. Blatt, Huey-Chin Chang Ho, Eddie H. Young Jan 1988

Generation Of Moire Contours With Acousto-Optic Cells, Joel H. Blatt, Huey-Chin Chang Ho, Eddie H. Young

Aerospace, Physics, and Space Science Faculty Publications

Moire contours are seen on a curved surface viewed through a grating when the surface is illuminated with a matched grating. We have been able to replace both the projection and viewing physical gratings with gratings of variable spacing generated in acousto-optic cells, and have been able to observe and record Moire contours. The gratings are generated by amplitude modulating 70 MHz AO cells with a 1 to 10 MHz square wave. The gratings become visible on the curved object by strobing the illuminating laser beam with 50 nsec pulses by means of an AO modulator. Data is given showing …

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Activity Coefficient And The Einstein Relation, Peter T. Landsberg, Albert G. Guy Jul 1983

Activity Coefficient And The Einstein Relation, Peter T. Landsberg, Albert G. Guy

Aerospace, Physics, and Space Science Faculty Publications

A connection between the activity coefficient of current carriers and the Einstein relations is established by two methods, one based on normal semiconductor concepts and one based on irreversible thermodynamics. The connection holds for all densities of states, for Fermi degeneracy, and in the presence of heavy doping.

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Mossbauer Measurements With '"Au In Aua1„Auga„Auin„And Ausb, John O. Thomson, Felix E. Obenshain, Paul G. Huray, John C. Love, John W. Burton Mar 1975

Mossbauer Measurements With '"Au In Aua1„Auga„Auin„And Ausb, John O. Thomson, Felix E. Obenshain, Paul G. Huray, John C. Love, John W. Burton

Aerospace, Physics, and Space Science Faculty Publications

Mossbauer spectra for '"Au in Au metal and the intermetallic compounds AuAl„AuGa„AuIn„and AuSb2 have been obtained for the temperature range 4.2 to 95'K. The isomer shifts for these absorbers with respect to a ' Au in Pt source are —1.223(2) [Au metal], + 2.288(12) [AuSb2], + 3.489(4) [AuIn2], +4.450(11) [AuGa, ], and +.5.967(5) [AuAl, ] in units of mm/sec. The difference in isomer shifts (alloy-Au-metal) may be interpreted in terms of an increasing electron charge density at the Au nucleus in the alloys as compared to that of Au metal. When volume changes for the alloys with respect to the …

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