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1992

Faculty Publications

Articles 1 - 25 of 25

Full-Text Articles in Physical Sciences and Mathematics

Intermediate Mass Fragment Emission As A Probe Of Nuclear Dynamics, D. R. Bowman, C. M. Mader, Graham F. Peaslee, W. Bauer, N. Carlin, R. T. De Souza, C. K. Gelbke, W. G. Gong, Y. D. Kim, M. A. Lisa, W. G. Lynch, L. Phair, M. B. Tsang, C. Williams, N. Colonna, K. Hanold, M. A. Mcmahan, G. J. Wozniak, L. G. Moretto, W. A. Friedman Nov 1992

Intermediate Mass Fragment Emission As A Probe Of Nuclear Dynamics, D. R. Bowman, C. M. Mader, Graham F. Peaslee, W. Bauer, N. Carlin, R. T. De Souza, C. K. Gelbke, W. G. Gong, Y. D. Kim, M. A. Lisa, W. G. Lynch, L. Phair, M. B. Tsang, C. Williams, N. Colonna, K. Hanold, M. A. Mcmahan, G. J. Wozniak, L. G. Moretto, W. A. Friedman

Faculty Publications

Element distributions and fragment multiplicity distributions have been measured for E/A=50 MeV Xe129+12C, Al27, V51, Cunat, Y89, and Au197 reactions using a low threshold 4π detector. Both distributions show a strong correlation with the detected charged particle multiplicity and a large degree of target independence. The measured distributions are compared with hybrid model calculations which incorporate important dynamical aspects in both the preequilibrium and statistical emission phases. Results of these calculations are in reasonable agreement with the data. However, uncertainties with regard to the compressibility of nuclear matter remain due to uncertainties in the coupling of the two models.

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Linear Theory Of Non-Neutral Plasma Equilibrium In A Tilted Magnetic Field, Ross L. Spencer, Grant W. Hart Nov 1992

Linear Theory Of Non-Neutral Plasma Equilibrium In A Tilted Magnetic Field, Ross L. Spencer, Grant W. Hart

Faculty Publications

A linear perturbation expansion has been found that allows the rapid and accurate calculation of the response of a non-neutral plasma to a tilted magnetic field. The results of the calculation have been found to agree with previous three-dimensional equilibrium calculations, and also to agree with Keinigs' [Phys. Fluids 24, 860 (1981)] calculation of zero-frequency resonances caused by magnetic field errors. This expansion also allows the perturbed velocity to be calculated. It is speculated that this perturbed flow may be related to the enhanced radial transport in a non-neutral plasma with a tilted magnetic field.

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Labeling Graphs With A Condition At Distance 2, Jerrold R. Griggs, Roger K. Yeh Nov 1992

Labeling Graphs With A Condition At Distance 2, Jerrold R. Griggs, Roger K. Yeh

Faculty Publications

No abstract provided.

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Use Of Raman Spectroscopy In Characterizing Soft X-Ray Multilayers: Tools In Understanding Structure And Interfaces, Ming Cai, Qi Wang, David D. Allred, Larry V. Knight, Dorian M. Hatch, A. Reyes-Mena, Guizhong Zhang Oct 1992

Use Of Raman Spectroscopy In Characterizing Soft X-Ray Multilayers: Tools In Understanding Structure And Interfaces, Ming Cai, Qi Wang, David D. Allred, Larry V. Knight, Dorian M. Hatch, A. Reyes-Mena, Guizhong Zhang

Faculty Publications

Our group is studying the structure and interfaces of soft x-ray multilayers by various techniques including x-ray diffraction and Raman spectroscopy. Raman spectroscopy is particularly useful since it is sensitive to the identity of individual bonds and thus can potentially characterize the abruptness of interfaces in multilayers. Blocking interfacial mixing is very important in achieving and maintaining high reflectivity. We report our studies of the as-deposited and postannealed structure of Mo/Si and W/C multilayers. The Mo/Si system is probably the most widely studied multilayer currently because of its potential applications for soft x-ray projection lithography for the range of 13 …

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Impact Parameter Filters For 36ar + 197au Collisions At E/A = 50, 80 And 110 Mev, L. Phair, D. R. Bowman, C. K. Gelbke, W. G. Gong, Y. D. Kim, M. A. Lisa, W. G. Lynch, Graham F. Peaslee, R. T. De Souza, M. B. Tsang, F. Zhu Oct 1992

Impact Parameter Filters For 36ar + 197au Collisions At E/A = 50, 80 And 110 Mev, L. Phair, D. R. Bowman, C. K. Gelbke, W. G. Gong, Y. D. Kim, M. A. Lisa, W. G. Lynch, Graham F. Peaslee, R. T. De Souza, M. B. Tsang, F. Zhu

Faculty Publications

Collisions between 36Ar projectiles and 197Au target nuclei at have been studied with the MSU Miniball, a 4π phoswich array with a low detection threshold. Various impact-parameter filters, based upon total charged-particle multiplicity, transverse energy, midrapidity charge and multiplicity of emitted hydrogen nuclei, are compared and cross-correlated. The relative selectivity of each prescription for small impact-parameter collisions is evaluated by assessing the suppression of fast-particle emission at forward angles.

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Adaptive Boundary Detection Using “Live-Wire” Two-Dimensional Dynamic Programming, William A. Barrett, Bryan S. Morse, Eric N. Mortensen, Jayaram Udupa Oct 1992

Adaptive Boundary Detection Using “Live-Wire” Two-Dimensional Dynamic Programming, William A. Barrett, Bryan S. Morse, Eric N. Mortensen, Jayaram Udupa

Faculty Publications

An adaptive boundary detection algorithm that uses two-dimensional dynamic programming is presented. The algorithm is less constrained than previous one-dimensional dynamic programming algorithms and allows the user to interactively determine the mathematically optimal boundary between a user-selected seed point and any other dynamically selected "free” point in the image. Interactive movement of the free point by the cursor causes the boundary to behave like a “live wire” as it adapts to the new minimum cost path between the seed point and the currently selected free point. The algorithm can also be adapted or customized to learn boundary-defining features for a …

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Fluctuations In Multifragment Decays, L. Phair, M. A. Lisa, D. R. Bowman, C. K. Gelbke, W. G. Gong, Y. D. Kim, W. G. Lynch, Graham F. Peaslee, H. Schulz, R. T. De Souza, M. B. Tsang, F. Zhu Sep 1992

Fluctuations In Multifragment Decays, L. Phair, M. A. Lisa, D. R. Bowman, C. K. Gelbke, W. G. Gong, Y. D. Kim, W. G. Lynch, Graham F. Peaslee, H. Schulz, R. T. De Souza, M. B. Tsang, F. Zhu

Faculty Publications

An analysis of charged particle distributions is performed to search for large fluctuations and signals of intermittency in reactions at E/A=35–110 MeV. When the effects of impact-parameter averaging are reduced by appropriate cuts on the total transverse energy, charged particle multiplicity distributions narrower than Poisson distributions are observed. Such distributions are inconsistent with intermittency signals of non-trivial origin.

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Drying Of Beulah-Zap Lignite, Karl S. Vorres, David L. Wertz, Vivak Malhotra, Yuhong Dang, J.T. Joseph, Ronald Fisher Sep 1992

Drying Of Beulah-Zap Lignite, Karl S. Vorres, David L. Wertz, Vivak Malhotra, Yuhong Dang, J.T. Joseph, Ronald Fisher

Faculty Publications

Lignite dried in a stream of dry nitrogen at moderate temperatures (20-80-degrees-C) loses water in two distinguishable modes. The first mode represents about 80-85% of the loss of moisture. The second represents the other 15-20% lost under these conditions. The rate follows a unimolecular mechanism (like radioactive decay) for each mode. The activation energy for the first mode is close to the heat of vaporization of water. The rate is dependent upon the gas flow around the sample and the weight (or thickness) of the sample. Work at Amoco Oil Company indicated that the oil yield was higher for the …

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Approximation By Interval Bezier Curves, Thomas W. Sederberg, Rida T. Farouki Sep 1992

Approximation By Interval Bezier Curves, Thomas W. Sederberg, Rida T. Farouki

Faculty Publications

The interval Bezier curve, which, unlike other curve and surface approximation schemes, can transfer a complete description of approximation errors between diverse CAD/CAM systems that impose fundamentally incompatible constraints on their canonical representation schemes, is described. Interval arithmetic, which offers an essentially infallible way to monitor error propagation in numerical algorithms that use floating-point arithmetic is reviewed. Affine maps, the computations of which are key operations in the de Casteljau subdivision and degree-elevation algorithms for Bezier curves, the floating-point error propagation in such computations, approximation by interval polynomials, and approximation by interval Bezier curves are discussed.

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Species Of The Cretaceous Tree Fern Tempskya From Utah, William D. Tidwell, Naomi Hebbert Sep 1992

Species Of The Cretaceous Tree Fern Tempskya From Utah, William D. Tidwell, Naomi Hebbert

Faculty Publications

Nine species of the permineralized stems of Tempskya were investigated from the Lower Cretaceous Cedar Mountain and Burro Canyon Formations, and the lower Upper Cretaceous Dakota Formation in central and southeastern Utah. Tempskya jonesii, T. stichkae, and T. readii are new and are differentiated on the basis of the radial orientation of their dorsiventral stems, their internodal lengths, the lack of sclerenchyma in the inner cortex of T. jonesii, the three nearly continuous zones of sclerenchyma in the inner cortex off T. stichkae, and the completely sclerotic inner cortex of T. readii. Specimens of T. jonesii and T. minor were …

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Multifragment Emission In 36ar + 197au And 129xe + 197au Collisions: Percolation Model, L. Phair, W. Bauer, D. R. Bowman, N. Carlin, R. T. De Souza, C. K. Gelbke, W. G. Gong, Y. D. Kim, M. A. Lisa, W. G. Lynch, Graham F. Peaslee, M. B. Tsang, C. Williams, F. Zhu, N. Colonna, K. Hanold, M. A. Mcmahan, G. J. Wozniak, L. G. Moretto Jul 1992

Multifragment Emission In 36ar + 197au And 129xe + 197au Collisions: Percolation Model, L. Phair, W. Bauer, D. R. Bowman, N. Carlin, R. T. De Souza, C. K. Gelbke, W. G. Gong, Y. D. Kim, M. A. Lisa, W. G. Lynch, Graham F. Peaslee, M. B. Tsang, C. Williams, F. Zhu, N. Colonna, K. Hanold, M. A. Mcmahan, G. J. Wozniak, L. G. Moretto

Faculty Publications

Relative abundances of intermediate mass fragments and light particles measured for 36Ar+197Au collisions at lie within the range of percolation model predictions, but for129Xe+197Au collisions at , the percolation model predicts too small admixtures of intermediate mass fragments among the emitted charged particles.

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Recoil Effects And Cp Violation In Neutron Scattering, Vladimir Gudkov Jul 1992

Recoil Effects And Cp Violation In Neutron Scattering, Vladimir Gudkov

Faculty Publications

The problem of the imitation of CP violation in neutron scattering is discussed. The thermal motion of nuclei cannot contribute to symmetry-violating effects. The influence of the nuclear depolarization due to neutron scattering is estimated.

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Viscoelastic Properties Of A Liquid-Crystalline Monomer And Its Dimer, Gregory A. Dilisi, Charles Rosenblatt, Anselm C. Griffin, Uma Hari Apr 1992

Viscoelastic Properties Of A Liquid-Crystalline Monomer And Its Dimer, Gregory A. Dilisi, Charles Rosenblatt, Anselm C. Griffin, Uma Hari

Faculty Publications

Quasielastic-light-scattering measurements are reported for a dialkoxyphenylbenzoate monomer and its dimer in their respective nematic phases. The splay and twist elastic moduli of the dimer are found to be nearly independent of molecular length. The dimer's bend modulus, however, shows an anomalous increase with decreasing temperature well below the nematic-isotropic phase transition. Monomer viscosities are consistent with typical literature values, although γ1/ηsplay and ηbend seem to be larger than expected for the dimer, where γ1 is the twist viscosity. The results are discussed in terms of viscoelastic properties of semiflexible rods. The elastic properties in …

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Pressure Dependence Of The Thermal Conductivity Of Pyrophyllite To 40 Kbar, Wei Chen, Daniel L. Decker Mar 1992

Pressure Dependence Of The Thermal Conductivity Of Pyrophyllite To 40 Kbar, Wei Chen, Daniel L. Decker

Faculty Publications

A mathematical model for calculating the temperature distribution as a function of power delivered to a line source and the thermal conductivity of the surrounding medium in the pressure cell of a cubic-anvil press was derived. The model will handle anisotropic thermal conductivities. A simple sample assembly consisting of a line source and two or three thermocouple junctions is described. A comparison of measured to calculated temperatures yields the thermal conductivity. Thermal conductivity measurements were made on natural pyrophyllite and baked pyrophyllite to 40 kbar. For the natural pyrophyllite the thermal conductivity parallel to the bedding plane at room temperature …

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Solid-State Nmr Characterization Of Organics In Cement, Michael A. Janusa Jan 1992

Solid-State Nmr Characterization Of Organics In Cement, Michael A. Janusa

Faculty Publications

Solid-state magic angle spinning nuclear magnetic resonance (MAS NMR) has been applied to cement samples containing water-soluble organics, ethylene glycol, phenol, p­bromophenol and p-chlorophenol. Cement matrix development has been followed by 29Si and27Al NMR, which shows the organics, particularly ethylene glycol, to be promoters of silicate polymerization despite the fact that they reduce the compressive strength of the pastes. 13C NMR shows that phenol is completely ionized in cement pastes, but with substituted phenols in the presence of extra added metal salts, ionization is not always complete. 2H NMR on d5 …

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Slip Length In A Dilute Gas, Alejandro Garcia, D. Morris, L. Hannon Jan 1992

Slip Length In A Dilute Gas, Alejandro Garcia, D. Morris, L. Hannon

Faculty Publications

We study the phenomenon of slip length using molecular dynamics and direct simulation Monte Carlo simulations of a dilute gas. Our work extends the range of Knudsen numbers that have been previously studied. In a recent paper, Bhattacharya and Lie [Phys. Rev. 43, 761 (1991)] suggest a logarithmic dependence of slip length on Knudsen number. By a simple redefinition of the mean free path, we obtain good agreement between simulation results and Maxwell theory for slip length. The anomalies seen by Bhattacharya and Lie appear to be due to their definition of the mean free path.

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Stable Isotope Analysis Using Tunable Diode Laser Spectroscopy, Todd B. Sauke, J. F. Becker, M. Loewenstein Jan 1992

Stable Isotope Analysis Using Tunable Diode Laser Spectroscopy, Todd B. Sauke, J. F. Becker, M. Loewenstein

Faculty Publications

Measurements of ratios of stable isotopes are used in such diverse fields as petroleum prospecting, medical diagnostics, and planetary exploration. The narrow emission linewidth available from tunable diode lasers permits high-resolution infrared absorption measurements of closely spaced isotopic rovibrational lines. Our dual beam spectrometer uses the sweep integration technique in a spectral region where adjacent spectral lines are of approximately equal absorbance at the expected isotopic abundances. The experimental results reported here indicate that isotopic ratios of carbon in carbon dioxide can be measured to an accuracy of better than 0.4%. This laser spectroscopic spectrometric technique offers an alternative to …

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A Modular Array To Detect Complex Fragments Produced In Intermediate-Energy Reverse-Kinematics Reactions, W. L. Kehoe, A. C. Mignerey, A. Moroni, I. Iori, Graham F. Peaslee, N. Colonna, K. Hanold, K. Hanold, D. R. Bowman, L. G. Moretto, M. A. Mcmahan, J. T. Walton, G. J. Wozniak Jan 1992

A Modular Array To Detect Complex Fragments Produced In Intermediate-Energy Reverse-Kinematics Reactions, W. L. Kehoe, A. C. Mignerey, A. Moroni, I. Iori, Graham F. Peaslee, N. Colonna, K. Hanold, K. Hanold, D. R. Bowman, L. G. Moretto, M. A. Mcmahan, J. T. Walton, G. J. Wozniak

Faculty Publications

A segmented silicon-silicon-plastic array was constructed for studying complex fragment production in heavy-ion reactions with incident energies of 35–100 MeV/u. The array was designed: (1) to measure the energy, position and charge of fragments with 1≤Z≤Zproj; (2) to have high efficiency for detecting fragments produced in reverse-kinematics reactions; (3) to detect events with two or more fragments; and (4) to have a flexible configuration. Each array telescope consists of a 300 μm Si detector, a 5 mm Si(Li) detector and a 7.6 cm plastic scintillator. The elements of the telescope are held by interconnecting modular packages which allow the telescopes …

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Real And Virtual Images Using A Classroom Hologram, Dale W. Olson Jan 1992

Real And Virtual Images Using A Classroom Hologram, Dale W. Olson

Faculty Publications

No abstract provided.

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A Family Of Complexes Associated To An Almost Alternating Map, With Applications To Residual Intersections, Andrew R. Kustin, Bernd Ulrich Jan 1992

A Family Of Complexes Associated To An Almost Alternating Map, With Applications To Residual Intersections, Andrew R. Kustin, Bernd Ulrich

Faculty Publications

No abstract provided.

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Removal Of Mercury From Waste Water: Large-Scale Performance Of An Ion Exchange Process, James A. Ritter, J. P. Bibler Jan 1992

Removal Of Mercury From Waste Water: Large-Scale Performance Of An Ion Exchange Process, James A. Ritter, J. P. Bibler

Faculty Publications

Duolite™ GT-73 ion exchange resin routinely reduces the mercury content of a waste water stream to less than the permitted level of 10 ppb. Effluent concentrations from the ion exchange facility (IEF) are consistently between 1 to 5 ppb, even though the feed contains a varying concentration of mercury (0.2 to 70 ppm). Two operational problems have been encountered at that facility, however. Firstly, the stated capacity of the resin for mercury was not being achieved. The abnormally low capacity was traced to analytical laboratory waste which was intermittently treated by the resin. That waste contained hydrochloric acid, stannous chloride, …

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Characterizations Of Antimony Tri‐Sulfide Chemically Deposited With Silicotungstic Acid, O. Savadogo, K. C. Mandal Jan 1992

Characterizations Of Antimony Tri‐Sulfide Chemically Deposited With Silicotungstic Acid, O. Savadogo, K. C. Mandal

Faculty Publications

No abstract provided.

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Characterization Of As-Prepared And Annealed W/C Multilayer Thin Films, David D. Allred, Qi Wang, Jesus González-Hernández, B. S. Chao, D. A. Pawlik Jan 1992

Characterization Of As-Prepared And Annealed W/C Multilayer Thin Films, David D. Allred, Qi Wang, Jesus González-Hernández, B. S. Chao, D. A. Pawlik

Faculty Publications

Tungsten/carbon (W/C) multilayer thin films were prepared by dc magnetron sputtering. All samples consisted of 30 layer pairs with a nominal d-spacing varying from 2.5 to 14 nm, the W layer thickness was kept at 2 nm in all samples. The W/C multilayers were subjected to isochronal anneals in a quartz tube furnace at the temperature range from 500 to 950 °C under a flow of high purity Ar gas. X-ray diffraction, Raman scattering, and Auger depth profile were used to characterize the structure of the as-prepared and annealed multilayer films. Both the W and C layers appear to be …

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X-Ray Diode Using A Silicon Field Emission Photocathode, W. I. Karian, Larry V. Knight, David D. Allred, A. Reyes-Mena Jan 1992

X-Ray Diode Using A Silicon Field Emission Photocathode, W. I. Karian, Larry V. Knight, David D. Allred, A. Reyes-Mena

Faculty Publications

We have produced arrays of 10,000 sharp p-type silicon points using an etch plus oxidation method. The points were used as electron emitters. No high vacuum cesiation or high temperature cleaning was needed to observe the electron emission. These are seen to be photosensitive sources of electrons at 200 K and 300 K. They were also used to produce AlKα x-rays. This constitutes the first use of etched, point arrays for generating electrons for x-ray sources.

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Manufacturing Of Atomically Sharp Silicon Tips And Their Use As Photocathodes, W. I. Karian, Larry V. Knight, David D. Allred, A. Reyes-Mena Jan 1992

Manufacturing Of Atomically Sharp Silicon Tips And Their Use As Photocathodes, W. I. Karian, Larry V. Knight, David D. Allred, A. Reyes-Mena

Faculty Publications

The discovery and understanding of the photoelectric effect led to the study of photoemissive materials fall into two major categories: classical photoemitters and negative-electron-affinity (NEA) materials. Classical photoemitters usually involve an alkali metal, a group-V element such as phosphorus, silver, and/or oxygen. An example is the Ag-O-Cs (S1) photoemitter. NEA photocathodes consist of a photoconductive single crystal semiconductor covered with a thin layer of cesium and oxygen. This layer lowers the work function of the photocathode. A dipole layer is formed at the surface, and band bending occurs. This lowers the effective work function. An example is the GaAs(CsO) photocathode …

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