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Selected Works

1988

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Articles 1 - 30 of 42

Full-Text Articles in Physical Sciences and Mathematics

Effects Of Surfaces On Dynamic Percolation, H. K. Janssen, B. Schaub, Beate Schmittmann Dec 1988

Effects Of Surfaces On Dynamic Percolation, H. K. Janssen, B. Schaub, Beate Schmittmann

Beate Schmittmann

The general epidemic process, which is a stochastic multiparticle process belonging to the universality class of dynamic percolation, is studied in a semi-infinite geometry. Critical exponents characterizing the fractal properties are calculated to O(ε) (ε=6-d, where d is the spatial dimension) with use of renormalization-group techniques.

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Modified Broyden’S Method For Accelerating Convergence In Self-Consistent Calculations, Duane D. Johnson Dec 1988

Modified Broyden’S Method For Accelerating Convergence In Self-Consistent Calculations, Duane D. Johnson

Duane D. Johnson

A modification to Broyden’s method for obtaining stable and computationally efficient convergence in self-consistent calculations is developed and discussed. The method incorporates the advantages of two schemes proposed by Srivastava and by Vanderbilt and Louie without any increase in complexity. Its improvement over their methods is discussed. The present method is compared with two other widely used convergence methods, simple mixing and Anderson’s method, for the case of the disordered binary alloy Ni0.35Fe0.65 on the verge of a magnetic instability and is shown to be much improved in stability and rate of convergence.

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Potential Energy Surfaces For The Reaction Si (Silicon) + H2o (Water), Shogo Sakai, Mark S. Gordon, Kenneth D. Jordan Dec 1988

Potential Energy Surfaces For The Reaction Si (Silicon) + H2o (Water), Shogo Sakai, Mark S. Gordon, Kenneth D. Jordan

Mark S. Gordon

The potential energy surfaces for the reactions of silicon atom (ID and 3P) with the water molecule were calculated by ab initio self-consistent field (SCF) methods. The transition states for the insertion of silicon atom into the D--H bond of water were also calculated by the multiconfigurational SCF method. It is found that the crossing point of the singlet and triplet surfaces along the insertion reaction paths is near the transition state for the triplet rearrangement from the Si:OH2 complex to HSiOH. The potential energy surfaces for the 1,2-hydrogen migration HSiOH- H2Si0 in the singlet and triplet states and the …

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Polymer Science In Romania I: "Petru Poni" Institute Of Macromolecular Chemistry, Iasi, Romania, Otto Vogl, Cristofor I. Simionescu, Ioan I. Negulescu Dec 1988

Polymer Science In Romania I: "Petru Poni" Institute Of Macromolecular Chemistry, Iasi, Romania, Otto Vogl, Cristofor I. Simionescu, Ioan I. Negulescu

Otto Vogl

No abstract provided.

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U.S.-Japan Seminar: "Synthesis, Properties And Reactions Of Specialty Polymers", Otto Vogl, Hiroshi Sumitomo Dec 1988

U.S.-Japan Seminar: "Synthesis, Properties And Reactions Of Specialty Polymers", Otto Vogl, Hiroshi Sumitomo

Otto Vogl

No abstract provided.

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31st International Congress Of Pure And Applied Chemistry, Sofia, Bulgaria,1987, Otto Vogl, Ivan Shopov, Ivan Panayotov Nov 1988

31st International Congress Of Pure And Applied Chemistry, Sofia, Bulgaria,1987, Otto Vogl, Ivan Shopov, Ivan Panayotov

Otto Vogl

No abstract provided.

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Polymer Science In Czechoslovakia Ii: Universities In The Czech Socialist Republic, Otto Vogl, Jaroslav Kralicek, Miroslav Schatz, Petr Vondracek Nov 1988

Polymer Science In Czechoslovakia Ii: Universities In The Czech Socialist Republic, Otto Vogl, Jaroslav Kralicek, Miroslav Schatz, Petr Vondracek

Otto Vogl

No abstract provided.

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Relative Energies Of Silaethylene And Methylsilylene, Roger S. Grev, Gustavo E. Scuseria, Andrew C. Scheiner, Henry F. Schaefer Iii, Mark S. Gordon Oct 1988

Relative Energies Of Silaethylene And Methylsilylene, Roger S. Grev, Gustavo E. Scuseria, Andrew C. Scheiner, Henry F. Schaefer Iii, Mark S. Gordon

Mark S. Gordon

The energy difference between silaethylene (H2Si=CH2) and methylsilylene (SiHMe) has been determined with ab initio quantum chemical techniques. Large basis sets and a variety of methods for the inclusion of electron correlation effects have been employed. In direct contrast to the recent theoretical and experimental results of Shin, Irikura, Beauchamp, and Goddard, which suggested silaethylene was 10 kcaljmol more stable than methylsilylene, we find the energy difference to be nearer 4 kcal/mol.

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Slip, Twinning, And Fracture At A Grain Boundary In The L12 Ordered Structure—Aς = 9 Tilt Boundary, Alexander H. King, M. H. Yoo Oct 1988

Slip, Twinning, And Fracture At A Grain Boundary In The L12 Ordered Structure—Aς = 9 Tilt Boundary, Alexander H. King, M. H. Yoo

Alexander H. King

The role of interaction between slip dislocations and a Σ = 9 tilt boundary in localized microplastic deformation, cleavage, or intergranular fracture in the Li2 ordered structure has been analyzed by using the anisotropic elasticity theory of dislocations and fracture. Screw superpartials cross slip easily at the boundary onto the (1$\overline 1$1) and the (001) planes at low and high temperatures, respectively. Transmission of primary slip dislocations onto the conjugate slip system occurs with a certain degree of difficulty, which is eased by localized disordering. When the transmission is impeded, cleavage fracture on the ($\overline 1$11) plane is predicted to …

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Iupac “Macro 87” In Merseburg (Gdr) Linking Tradition And Future In Polymer Science, Otto Vogl, Burkart Philipp Oct 1988

Iupac “Macro 87” In Merseburg (Gdr) Linking Tradition And Future In Polymer Science, Otto Vogl, Burkart Philipp

Otto Vogl

No abstract provided.

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Gas-Phase And Computational Studies Of Pentacoordinate Silicon, Robert Damrauer, Larry W. Burggraf, Larry P. Davis, Mark S. Gordon Sep 1988

Gas-Phase And Computational Studies Of Pentacoordinate Silicon, Robert Damrauer, Larry W. Burggraf, Larry P. Davis, Mark S. Gordon

Mark S. Gordon

We have demonstrated that a wide variety of pentacoordinate silicon anions (siliconates) should be stable and can be prepared by combining the predictive powers of MNDO and ab initio computational methods and the flowing afterglow (FA) experimental technique. MNDO has been used to compute the anion affinities of 91 siliconates; all but five of these are predicted to be stable with respect to the loss of an anion. Twenty-four siliconates, most of them previously unreported, have been prepared and studied in the FA. The MNDO predictions were, in general, consistent with the experimental results and with trends previously reported by …

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A Comprehensive Method To Characterize Mixed Conduction Electrolytes, Michael P. Setter, J. Bruce Wagner Jr. Aug 1988

A Comprehensive Method To Characterize Mixed Conduction Electrolytes, Michael P. Setter, J. Bruce Wagner Jr.

Michael P. Setter

Determination of the electrical characteristics of an electrolyte is vitally important to the design of battery materials and sensors. A wide variety of parameters are available from both dc and ac measurements. Through the use of computer control and a custom multiplexor, we can perform dc polarization and ac impedance measurements on a sample, without replacing electrodes.

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Bulking Control With Ozonation In A Nutrient Removal Activated Sludge System, Johannes Van Leeuwen Jul 1988

Bulking Control With Ozonation In A Nutrient Removal Activated Sludge System, Johannes Van Leeuwen

Johannes van Leeuwen

The control of sludge bulking by ozonation was studied on four parallel pilot-scale (100 l/d) biological nutrient removal systems. Bulking was caused by filamentous organisms which typically occur in nutrient removal systems, i.e. Type 0092, Tpye 0041 and Microthrix parvicella. Continuous dosing of ozone, at 1; 2 and 4g O3/kg mixed liquor suspended solids (MLSS).d resulted in a diluted sludge volume index of about 50 ml/g less than the unozonated control. Ozonation was more effective in the sludge cycle than directly into the aeration basin. Nitrification-denitrification was not affected, not even at dosages of 30 g O3/kg MLSS.d. Biological phosphate …

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Remarks On A Semilinear Elliptic Equation On Rn, Yi Li Jul 1988

Remarks On A Semilinear Elliptic Equation On Rn, Yi Li

Yi Li

No abstract provided.

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Analysis Of The Convergence History Of Fluid Flow Through Nozzles With Shocks, Mohammad Saleem, A Cheer, M Hafez, T Pulliam Jul 1988

Analysis Of The Convergence History Of Fluid Flow Through Nozzles With Shocks, Mohammad Saleem, A Cheer, M Hafez, T Pulliam

Mohammad Saleem

"Convergence of iterative methods for the solution of the steady quasi-one-dimensional nozzle problem with shocks is considered. The finite-difference algorithms obtained from implicit schemes are used to approximate both the Euler and Navier-Stokes Equations. These algorithms are investigated for stability and convergence characteristics. The numerical methods are broken down into their matrix-vector components and then analyzed by examining a subset of the eigensystem using a method based on the Arnoldi process. The eigenvalues obtained by this method are accurate to within 5 digits for the largest ones and to within 2 digits for the ones smaller in magnitude compared the …

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Theoretical Studies Of Silabicyclobutanes And Silacyclobutenes, Cnsi4-Nh6 (N = 0-4), Jerry A. Boatz, Mark S. Gordon Jun 1988

Theoretical Studies Of Silabicyclobutanes And Silacyclobutenes, Cnsi4-Nh6 (N = 0-4), Jerry A. Boatz, Mark S. Gordon

Mark S. Gordon

The geometries of the silicon-substituted bicyclobutanes and cyclobutenes c.Si4-.H6 are predicted by using the 3-21G(d) basis set and SCF wave functions. Strain energies and heats of formation are predicted by using MP2/6-31G(d) energies in conjunction with the appropriate homodesmic reactions. Bent bond lengths are calculated by tracing the path of maximum electron density connecting two nuclei, with the 6-31 G(2d) basis set at the 3-21 G(d) structures.

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Potentially Aromatic Metallocycles, Kim K. Baldridge, Mark S. Gordon Jun 1988

Potentially Aromatic Metallocycles, Kim K. Baldridge, Mark S. Gordon

Mark S. Gordon

Ab initio molecular orbital theory is used to characterize a series of metal-substituted benzene and cyclopentadiene structures, with the heteroatom taken from the block in the periodic table bounded by groups IV-VI and periods 2-5. Structures are predicted with the 3-21G* basis set and SCF wave functions. The calculated bond lengths and bond angles are in general within 0.04 A and 2°, respectively, of the available experimental values. As a measure of the de localization stabilization, !::.£and t::..H0 values for the appropriate bond separation and superhomodesmic reactions are calculated with 3-21 G* Hartree-Fock energies for these compounds and some smaller …

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Theoretical Study Of The Decomposition Of Five-Coordinate Silicon Anions, Larry P. David, Larry W. Burggraf, Mark S. Gordon May 1988

Theoretical Study Of The Decomposition Of Five-Coordinate Silicon Anions, Larry P. David, Larry W. Burggraf, Mark S. Gordon

Mark S. Gordon

We have performed a theoretical study of the decomposition of the five-coordinate silicon anions (siliconates) H3(CH3)SiOH- and (CH3) 4SiOH-. These ions can be formed from hydroxide ion attack on methylsilane or tetramethylsilane, respectively. Both MNDO and ab initio calculations show that removal of methane from the five-coordinate structure is likely, via a transfer of the proton from the OH group to an adjacent methyl substituent. This process we term anionic dissociative proton transfer, because the transition state is one in which the methyl group being removed is almost completely dissociated to methide ion before the proton transfer takes place. This …

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Two Discrete Forms Of The Jordan Curve Theorem, Lawrence N. Stout Mar 1988

Two Discrete Forms Of The Jordan Curve Theorem, Lawrence N. Stout

Lawrence N. Stout

The Jordan curve theorem is one of those frustrating results in topology: it is intuitively clear but quite hard to prove. In this note we will look at two discrete analogs of the Jordan curve theorem that are easy to prove by an induction argument coupled with some geometric intuition. One of the surprises is that when we discretize the plane we get two Jordan curve theorems rather than one, a consequence of the interplay between two natural products in the category of graphs. Topology in this context has been studied by Farmer in [2]. To state the discrete versions, …

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Toeplitz Systems Associated With The Product Of A Formal Laurent Series And A Laurent Polynomial, William F. Trench Mar 1988

Toeplitz Systems Associated With The Product Of A Formal Laurent Series And A Laurent Polynomial, William F. Trench

William F. Trench

No abstract provided.

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Numerical Solution Of The Eigenvalue Problem For Symmetric Rationally Generated Toeplitz Matrices, William F. Trench Mar 1988

Numerical Solution Of The Eigenvalue Problem For Symmetric Rationally Generated Toeplitz Matrices, William F. Trench

William F. Trench

No abstract provided.

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Algorithms And Accuracy Requirements For Computing Reaction Paths By The Method Of Steepest Descent, Bruce C. Garrett, Michael J. Redmon, Rozeanne Steckler, Donald G. Truhlar, Kim K. Baldridge, David Bartol, Michael W. Schmidt, Mark S. Gordon Mar 1988

Algorithms And Accuracy Requirements For Computing Reaction Paths By The Method Of Steepest Descent, Bruce C. Garrett, Michael J. Redmon, Rozeanne Steckler, Donald G. Truhlar, Kim K. Baldridge, David Bartol, Michael W. Schmidt, Mark S. Gordon

Mark S. Gordon

We present several algorithms for computing minimum energy reaction paths by the method of steepest descents of the potential energy and for interpolating reaction-path potentials. The algorithms are suited for use with global analytic potential surfaces or ab initio calculations of energies and gradients. The efficiencies of the various algorithms are demonstrated and compared by applications to several test cases.

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Asymptotic Integration Of A Perturbed Constant Coefficient Differential Equation Under Mild Integral Smallness Conditions, William F. Trench Feb 1988

Asymptotic Integration Of A Perturbed Constant Coefficient Differential Equation Under Mild Integral Smallness Conditions, William F. Trench

William F. Trench

No abstract provided.

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Mixed Sublinear, Superlinear, And Singular Systems Of Functional Differential Equations, William Trench Jan 1988

Mixed Sublinear, Superlinear, And Singular Systems Of Functional Differential Equations, William Trench

William F. Trench

No abstract provided.

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Numerical Simulations Of Narrow Planetary Rings: An Animation, Robert A. Kolvoord, J A. Burns Jan 1988

Numerical Simulations Of Narrow Planetary Rings: An Animation, Robert A. Kolvoord, J A. Burns

Robert A Kolvoord

No abstract provided.

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Microcomputer In An Introductory College Astronomy Laboratory: A Software Development Project, D D. Meisel, K F. Kinsey, Charles H. Recchia Jan 1988

Microcomputer In An Introductory College Astronomy Laboratory: A Software Development Project, D D. Meisel, K F. Kinsey, Charles H. Recchia

Charles H Recchia

No abstract provided.

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The Magical Computer, David Morgan Lochhead Jan 1988

The Magical Computer, David Morgan Lochhead

Dr. David Morgan Lochhead

David Lochhead's speech: "Two years ago, I had the privilege of giving the opening address at the first CAMCON. I opened that address by posing the question "Does God love Computers?" Today I would like to start with a related question. What makes computers loveable? "

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Prediction Of Fracture In Patients With Acute Musculoskeletal Ankle Trauma, Paula Diehr Jan 1988

Prediction Of Fracture In Patients With Acute Musculoskeletal Ankle Trauma, Paula Diehr

Paula Diehr

X-rays taken for ankle trauma contribute significantly to the cost of health care in this country. In an attempt to find clinical correlates of ankle fracture 36 detailed historical and physical examination variables were collected from 587 consecutive patients with ankle trauma, and ankle x-rays were taken of all patients. The association of each variable with the final diagnosis of fracture, rupture, or sprain was tested; 21 variables were significant predictors of fracture (vs. sprain and rupture) and 15 were not significantly associated with final diagnosis. The variables were used in a linear discriminant analysis to develop a rule which …

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Effects Of Chemical And Magnetic Disorder In Fe0.50mn0.50, Duane D. Johnson, F. J. Pinski, G. M. Stocks Jan 1988

Effects Of Chemical And Magnetic Disorder In Fe0.50mn0.50, Duane D. Johnson, F. J. Pinski, G. M. Stocks

Duane D. Johnson

We present the results of first‐principles calculations of the total energy and spin‐polarized electronic structure of disordered fcc Fe0.50Mn0.50. These self‐consistent calculations were performed using the Korringa–Kohn–Rostoker method and the coherent‐potential approximation (KKR‐CPA), using the local‐spin‐density approximation to treat exchange and correlation. We use a lattice constant of a=6.80 a.u.; information about stability can be inferred from calculated pressure and energy. The moments on the Fe and Mn sites are large but antiparallel to each other, resulting in a small net magnetization. A comparison of the electronic structure is made for fcc Fe, Mn, and FeMn in both the ferromagnetic …

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Substituted Silabenzenes, Kim K. Baldridge, Mark S. Gordon Jan 1988

Substituted Silabenzenes, Kim K. Baldridge, Mark S. Gordon

Mark S. Gordon

Ab initio calculations have been carried out on a group of substituted monosilabenzenes. Twelve different substituents are considered (Cl, F, SH, OH, PH2, NH2, CH3, SiH3, N02, CN, OCH3, COOH), each placed in the four unique positions on the ring. The relative energies and stabilities, aromaticities (as measured by bond separation reactions), electron density distributions, and dipole moments of these compounds are considered and discussed with the aid of density difference plots.

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