Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

Missouri University of Science and Technology

Discipline
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 4501 - 4530 of 6056

Full-Text Articles in Physical Sciences and Mathematics

Quantum Transport In The Presence Of Random Traps, John Wm Edwards, Paul Ernest Parris Oct 1989

Quantum Transport In The Presence Of Random Traps, John Wm Edwards, Paul Ernest Parris

Physics Faculty Research & Creative Works

We calculate the asymptotic decay of a quantum particle moving in a d-dimensional medium doped with randomly placed trapping impurities, focusing on contributions from slowly decaying long-wavelength modes centered in large compact regions devoid of traps. By averaging the decay over the statistical distribution associated with these regions we find that the survival probability, P(t) ~exp(-Atd/(d+3)), decays more slowly in any dimension than for diffusive transport.

Go to article

Analysis Of Experimental Nucleation Data For Silver And Sio Using Scaled Nucleation Theory, Barbara N. Hale, Paul R. Kemper, Joseph A. Nuth Oct 1989

Analysis Of Experimental Nucleation Data For Silver And Sio Using Scaled Nucleation Theory, Barbara N. Hale, Paul R. Kemper, Joseph A. Nuth

Physics Faculty Research & Creative Works

The experimental vapor phase nucleation data of Nuth et al., for silver [J. A. Nuth, K. A. Donnelly, B. Donn, and L. U. Lilleleht, J. Chem. Phys. 77, 2639 (1982)] and SiO [J. A. Nuth and B. Donn, J. Chem. Phys. 85, 1116 (1986)] are reanalyzed using a scaled model for homogeneous nucleation [B. N. Hale, Phys. Rev. A 33, 4156 (1986)]. The approximation is made that the vapor pressure at the nucleation site is not diminished significantly from that at the source (crucible). It is found that the data for ln S have a temperature dependence consistent with the …

Go to article

Full Optical Potential For The Electron-Hydrogen Entrance Channel, Igor Bray, Don H. Madison, Ian E. Mccarthy Sep 1989

Full Optical Potential For The Electron-Hydrogen Entrance Channel, Igor Bray, Don H. Madison, Ian E. Mccarthy

Physics Faculty Research & Creative Works

Differential and total elastic and total reaction cross sections are calculated for electron-hydrogen scattering at 30, 100, and 400 eV using an ab initio optical potential that treats bound and continuum nonelastic channels in the distorted-wave Born approximation. Multichannel and partial wave expansions are carried out to numerical convergence. Convergence criteria and quadratures for the continuum-energy integration are chosen for 1% overall accuracy. Results are compared with experiment and less detailed calculations.

Go to article

One-Dimensional Quantum Transport In The Presence Of Traps, Paul Ernest Parris Sep 1989

One-Dimensional Quantum Transport In The Presence Of Traps, Paul Ernest Parris

Physics Faculty Research & Creative Works

A study is made of the survival probability P(t) for a quantum particle moving coherently on an ordered one-dimensional chain containing randomly placed irreversible traps in concentration q. We consider two separate models of the trapping process, focusing on the long-time limit of each. In the first model, intended to describe substitutional traps, the trapping impurities act as disruptive absorbing barriers which prevent further motion along the chain. For this model it is shown that -ln[P(t)]1/4t1/4. The second model is intended to describe interstitial trapping impurities which do not disrupt the transport. It is argued for this case …

Go to article

Resonant Dielectronic And Direct Excitation In Crystal Channels, Sheldon Datz, Charles Randy Vane, Peter F. Dittner, J. P. Giese, J. C. Gomez Del Campo, N. L. Jones, Herbert F. Krause, Philip D. Miller, Michael Schulz, Harald Schone, Thomas M. Rosseel Aug 1989

Resonant Dielectronic And Direct Excitation In Crystal Channels, Sheldon Datz, Charles Randy Vane, Peter F. Dittner, J. P. Giese, J. C. Gomez Del Campo, N. L. Jones, Herbert F. Krause, Philip D. Miller, Michael Schulz, Harald Schone, Thomas M. Rosseel

Physics Faculty Research & Creative Works

We have observed dielectronic and direct excitation of H-like S15+ and Ca19+ and He-like Ti20+ ions in silicon channels caused by collision with weakly bound target electrons which behave as a free-electron gas. As in vacuo, relaxation of the doubly excited states can occur radiatively leading to ions of decreased charge, but in a crystal channel collisional effects can cause double ionization. The effects are seen in both the x-ray yields and charge-state fractions, and, in the case of Ti20+, in charge-state x-ray coincidences.

Go to article

Single And Double-Electron Removal From H− In Energetic Collisions With Multiply-Charged Argon Ions, F. Melchert, W. Debus, M. Liehr, Ronald E. Olson, E. Salzborn Jul 1989

Single And Double-Electron Removal From H− In Energetic Collisions With Multiply-Charged Argon Ions, F. Melchert, W. Debus, M. Liehr, Ronald E. Olson, E. Salzborn

Physics Faculty Research & Creative Works

Absolute cross-sections have been measured and compared to CTMC-calculations for single and double-electron removal from H− in collisions with Arq+ ions (q ≤ 8) at Ec.m. = 50 keV. The single-electron removal cross-sections are found to scale with q1.3, and for the H− + Ar4+ system, this cross-section is found to have a weak energy dependence from 3 keV to 100 keV. A major implication of our measurements is that plasma neutralizers based on multiply charged ions for high-efficiency conversion of intense H− beams into H0 gain little in expected reduced …

Go to article

Automated Translation Of Digital Logic Equations Into Optimized Vhdl Code, John Evan Stark, George Winston Zobrist May 1989

Automated Translation Of Digital Logic Equations Into Optimized Vhdl Code, John Evan Stark, George Winston Zobrist

Computer Science Technical Reports

It was desired to develop an algorithm for the automated translation of finite slate machines from state table form to optimized VHDL form. To do this, algorithms arc needed for reducing the state machine to simplest form, making state assignments, producing minimal logic equations to represent the state machine, and producing VHDL code which describes the intended circuit. Various such algorithms were examined and a prototype program written to perform this translation.

Go to article

Shake-Off Measurements Of Electron-Ion-Scattering Phase Shifts, J. Greg Story, William E. Cooke May 1989

Shake-Off Measurements Of Electron-Ion-Scattering Phase Shifts, J. Greg Story, William E. Cooke

Physics Faculty Research & Creative Works

Continuum electrons are produced in a specific l state with high-energy resolution using shake-off photoionization. This process is well characterized, so that the photoionization signal is an accurate measurement of the difference between the continuum electrons wave-function phase and that produced by a hydrogenic interaction. Measurements are reported showing the phase of a Ba++e- in a d wave, in cases where it is well behaved, and in cases where doubly excited resonances produce rapid phase variations.

Go to article

Long-Range Hopping In Substitutionally Disordered Solids, Paul Ernest Parris May 1989

Long-Range Hopping In Substitutionally Disordered Solids, Paul Ernest Parris

Physics Faculty Research & Creative Works

A theoretical approach for studying charge-carrier and energy diffusion due to long-range hopping in substitutionally disordered solids is presented. Unlike some earlier theories, which invoke a pair approximation to treat back-transfer processes, the current theory makes use of the exact solution to an appropriate single-defect problemone in which long-range jumps into, out of, and between both the defect site and all other active sites in the lattice are explicitly included. From this exact solution a new long-range effective-medium theory is constructed to describe the configurationally averaged transport properties of the disordered system.

Go to article

Spectroscopy Of The 6p3/2Np States Of Barium, J. Greg Story, E. G. Yap, William E. Cooke May 1989

Spectroscopy Of The 6p3/2Np States Of Barium, J. Greg Story, E. G. Yap, William E. Cooke

Physics Faculty Research & Creative Works

The 6p3/2np states of barium have been observed for n values between 14 and 21. The energies, linewidths, and transition strengths have been measured and characterized in terms of one- and two-electron interactions, using a single-configuration approximation.

Go to article

Electron-Electron Interactions In Transfer And Excitation In F⁸⁺ →₂ Collisions, Michael Schulz, J. P. Giese, J. K. Swenson, Sheldon Datz, Peter F. Dittner, Herbert F. Krause, Harald Schone, Charles Randy Vane, Malika Benhenni, Stephen M. Shafroth Apr 1989

Electron-Electron Interactions In Transfer And Excitation In F⁸⁺ →₂ Collisions, Michael Schulz, J. P. Giese, J. K. Swenson, Sheldon Datz, Peter F. Dittner, Herbert F. Krause, Harald Schone, Charles Randy Vane, Malika Benhenni, Stephen M. Shafroth

Physics Faculty Research & Creative Works

We have measured projectile Auger electrons emitted after collisions of H-like F with H2. The cross sections for emission of KLL, KLM, KLN, and KLO Auger electrons show maxima as a function of the projectile energy. One maximum in the KLL emission cross section is due to resonant transfer and excitation. A second maximum in the cross section for KLL emission as well as the maxima in the emission cross section for the higher-n Auger electrons are attributed to a new transfer and excitation process. This involves excitation of a projectile electron by one target electron accompanied by …

Go to article

On The Kelvin Electrostatic Generator, S. Desmet, F. Orban, Fernande Grandjean Apr 1989

On The Kelvin Electrostatic Generator, S. Desmet, F. Orban, Fernande Grandjean

Chemistry Faculty Research & Creative Works

The Kelvin generator is an amazing electrostatic device which poses many questions. The authors report the results of their investigations of this device under various controlled conditions with both nonpolar and polar liquids and a sodium chloride aqueous solution. They have found that the generator works well even if the two liquid streams originate from different electrically insulated reservoirs. In addition they propose a model in which the electric charge results from the separation of the hydrogen and hydroxyl ions as the water droplets form.

Go to article

Condensation Coefficient Measurement For Water In The Umr Cloud Simulation Chamber, Donald E. Hagen, John L. Schmitt, Max B. Trueblood, John C. Carstens, Daniel R. White, Darryl J. Alofs Mar 1989

Condensation Coefficient Measurement For Water In The Umr Cloud Simulation Chamber, Donald E. Hagen, John L. Schmitt, Max B. Trueblood, John C. Carstens, Daniel R. White, Darryl J. Alofs

Physics Faculty Research & Creative Works

A systematic series of condensation coefficient measurements of water have been made using the University of Missouri-Rolla cooled-wall expansion chamber which simulates the thermodynamics of cloud. This coefficient is seen to decrease from a value near unity, at the outset of simulation, to a value in the neighborhood of 0.01 toward the end of a simulation. Final values of this coefficient are sufficiently low as to contribute significantly to the broadening of the drop-size distribution in cloud.

Go to article

One-Dimensional Trapping Kinetics At Zero Temperature, Paul Ernest Parris Mar 1989

One-Dimensional Trapping Kinetics At Zero Temperature, Paul Ernest Parris

Physics Faculty Research & Creative Works

The asymptotic decay of the survival probability is calculated for a quantum particle moving at zero temperature on a one-dimensional tight-binding chain possessing randomly placed irreversible traps of strength γ. The survival probability exhibits a decay, P(t) ~ exp(-At1/4), which is slower than that associated with a diffusing particle.

Go to article

Seismic Signature Of A Swan Hills (Frasnian) Reef Reservoir, Snipe Lake, Alberta, Neil Lennart Anderson, Robert James Sidford Brown, Ronald C. Hinds, L. V. Hills Feb 1989

Seismic Signature Of A Swan Hills (Frasnian) Reef Reservoir, Snipe Lake, Alberta, Neil Lennart Anderson, Robert James Sidford Brown, Ronald C. Hinds, L. V. Hills

Geosciences and Geological and Petroleum Engineering Faculty Research & Creative Works

Swan Hills formation (Frasnian stage) carbonate buildups of the Beaverhill Lake group are generally of low relief and considerable areal extent and are overlain by and encased within the relatively high-velocity shale of the Waterways formation, which thins but does not drape across the reefs. Consistent with this picture, prereef seismic events are not significantly pulled up beneath the reefs nor are postreef events draped across them. Indeed, the seismic images of these reefs are effectively masked by the high-amplitude reflections from the overlying top of the Beaverhill Lake group and underlying Gilwood member and cannot be distinguished from those …

Go to article

Measured Spectra Of The Hygroscopic Fraction Of Atmospheric Aerosol Particles, Darryl J. Alofs, Donald E. Hagen, Max B. Trueblood Feb 1989

Measured Spectra Of The Hygroscopic Fraction Of Atmospheric Aerosol Particles, Darryl J. Alofs, Donald E. Hagen, Max B. Trueblood

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The relation between dry diameter (X0) and critical supersaturation (Sc) for atmospheric submicron aerosol particles is investigated using a long term air sampling program at Rolla, Missouri. The particles are passed through an electrostatic aerosol size classifier, and then through an isothermal haze chamber. Results are reported in terms of an apparent volume fraction of soluble material, εv defined such that for particles composed only of ammonium sulfate and water insoluble compounds, εv is the actual volume fraction of soluble material. The probability distribution of εv is found to be approximately Gaussian in …

Go to article

Elastic Angular Differential Cross Sections For Quasi-One-Electron Collision Systems At Intermediate Energies: (Na⁺, Li⁺)+H And (Mg⁺, Be⁺)+He, Jerry Peacher, E. Redd, Denver G. Seely, Timothy Gay, D. M. Blankenship, John T. Park Feb 1989

Elastic Angular Differential Cross Sections For Quasi-One-Electron Collision Systems At Intermediate Energies: (Na⁺, Li⁺)+H And (Mg⁺, Be⁺)+He, Jerry Peacher, E. Redd, Denver G. Seely, Timothy Gay, D. M. Blankenship, John T. Park

Physics Faculty Research & Creative Works

Measurements of elastic angular differential cross sections have been carried out for four quasi-one-electron collision systems at intermediate energies. Data are presented for Na++H collisions at laboratory energies of 35.94, 51.75, 63.89, and 143.75 keV, for Li++H collisions at energies of 19.44 and 43.75 keV, for Mg++He collisions at energies of 30, 66.7, and 150 keV, and for Be++He collisions at an energy of 56.25 keV. The highest energy in each case corresponds to a projectile velocity of (1/2 a.u. Born and Eikonal calculations, in which we model the projectile ion as …

Go to article

An Improved Exact Graph Coloring Algorithm, Thomas J. Sager, Shi-Jen Lin Jan 1989

An Improved Exact Graph Coloring Algorithm, Thomas J. Sager, Shi-Jen Lin

Computer Science Technical Reports

We present two algorithms for exact graph coloring of the vertex sequential with dynamic reordering of vertices variety. The first, W-DEG, is a straight-forward improvement on Korman’s original algorithm. The second, SWAP2, is a not so straight forward improvement on Korman’s algorithm and appears to offer the best performance of known exact graph coloring algorithms.

Go to article

A Color-Exchange Algorithm For Exact Graph Coloring, Thomas J. Sager, Shi-Jen Lin Jan 1989

A Color-Exchange Algorithm For Exact Graph Coloring, Thomas J. Sager, Shi-Jen Lin

Computer Science Technical Reports

DEXCH, a color-exchange exact graph coloring algorithm is presented. On many classes of graphs, DEXCH can, in the mean, find the chromatic number of a graph considerably faster than the DSATUR algorithm. The improvement over DSATUR stems from the ability to reorganize the subset of colored vertices and to detect in certain instances the existence of a complete subgraph of cardinality equal to the number of colors used in the best coloring found so far. The mean improvement over DSATUR is greatest on high edge-density graphs attaining the value of 42% on random graphs of edge-density 0.7 on 64 vertices.

Go to article

A Pruning Procedure For Exact Graph Coloring, Thomas J. Sager, Shi-Jen Lin Jan 1989

A Pruning Procedure For Exact Graph Coloring, Thomas J. Sager, Shi-Jen Lin

Computer Science Technical Reports

The graph coloring problem can be stated: “Given an undirected graph, using a minimal number of colors, assign each vertex a color so that if two vertices are connected by an edge then they are not assigned the same color.” Graph coloring can be used to solve scheduling problems with constraints of the form: events e and e' can not be scheduled together. Graph coloring is an NP-Complete problem. Generally large problems are solved heuristically, although some of the better heuristic algorithms use an exact graph coloring algorithm to finish coloring a graph after first reducing it heuristically …

Go to article

Robustness & Precision Of Parametric & Distribution-Free Tolerance Limits For Two Lifetime Distributions, Wei Kei Shiue, Lee J. Bain Jan 1989

Robustness & Precision Of Parametric & Distribution-Free Tolerance Limits For Two Lifetime Distributions, Wei Kei Shiue, Lee J. Bain

Mathematics and Statistics Faculty Research & Creative Works

Exact parametric tolerance limits or confidence limits on reliability are not available for the gamma distribution, and it is, difficult to determine approximate methods which are accurate for all parameter values. The precision lost by using the distribution-free tolerance-limit method based on the first order statistic, compared to using an approximate gamma tolerance limit method is studied. The robustness of the approximate gamma tolerance limit when the true model is Weibull and the robustness of a Weibull tolerance limit when the true model is gamma are also studied. The efficiency of the distribution-free method ranges from about 0.60 to 0.90 …

Go to article

Sharp Lower Bounds For A Generalized Jensen Inequality, A. K. Rigler, S. Y. Trimble, R. S. Varga Jan 1989

Sharp Lower Bounds For A Generalized Jensen Inequality, A. K. Rigler, S. Y. Trimble, R. S. Varga

Mathematics and Statistics Faculty Research & Creative Works

No abstract provided.

Go to article

Periodic Points For Homeomorphisms Of Hereditarily Decomposable Chainable Continua, W. T. Ingram Jan 1989

Periodic Points For Homeomorphisms Of Hereditarily Decomposable Chainable Continua, W. T. Ingram

Mathematics and Statistics Faculty Research & Creative Works

In this paper it is shown that homeomorphisms of hereditarily decomposable chainable continua cannot have periodic points whose periods are not powers of two. Examples show that for each power of two there is a hereditarily decomposable chainable continuum and a homeomorphism of it which has a periodic point of period that power of two. © 1989 American Mathematical Society.

Go to article

Graph Coloring Algorithms On Random Graphs, Shi-Jen Lin Jan 1989

Graph Coloring Algorithms On Random Graphs, Shi-Jen Lin

Doctoral Dissertations

"The graph coloring problem, which is to color the vertices of a simple undirected graph with the minimum number of colors such that no adjacent vertices are assigned the same color, arises in a variety of scheduling problems. This dissertation focuses attention on vertex sequential coloring. Two basic approaches, backtracking and branch-and-bound, serve as a foundation for the developed algorithms. The various algorithms have been programmed and applied to random graphs. This dissertation will present several variations of the Korman algorithm, Korw2, Pactual, and Pactmaxw2, which produce exact colorings quicker than the Korman algorithm in the average for some classes …

Go to article

The Directed Steiner Problem On Graphs: A Simulated Annealing Approach, Lawrence Joseph Osborne Jan 1989

The Directed Steiner Problem On Graphs: A Simulated Annealing Approach, Lawrence Joseph Osborne

Doctoral Dissertations

"The well-known Steiner Problem on Graphs is an NP-complete problem for which there are many heuristic and exact algorithms that are deterministic. In this dissertation a new approach to the directed version of this problem is made by applying the ideas of statistical mechanics through the use of the method of simulated annealing. A version of annealing is developed for the Directed Steiner Problem and compared with one of the best general annealing schemes. Then a comparison is made between simulated annealing and the traditional branch and bound technique. The dual ascent algorithm of Richard T. Wong is used to …

Go to article

Electron Removal From Molecular Hydrogen By Fully Stripped Ions At Intermediate Energies, L. Meng, C. O. Reinhold, Ronald E. Olson Jan 1989

Electron Removal From Molecular Hydrogen By Fully Stripped Ions At Intermediate Energies, L. Meng, C. O. Reinhold, Ronald E. Olson

Physics Faculty Research & Creative Works

A classical phase-space model of the hydrogen molecule is presented and applied to the study of the electron-capture and -ionization processes in collisions of fully stripped ions with H2 at intermediate impact energies and charge states from 1 to 10. The model is based on the independent-electron and the impact-parameter approximations. The electron impinging-ion and electron target-nuclei interactions are exactly taken into account. The interaction between the electrons is approximated by model potentials. The calculated total cross sections for production of free electrons and capture of one electron are in good agreement with different experimental data. The ratio between the …

Go to article

Mössbauer Effect Studies Of Nd₂Fe₁₄₋ₓsiₓb And Y₃Fe₁₄₋ₓsiₓb, Oran Allan Pringle, Gary J. Long, G. K. Marasinghe, William Joseph James, Antoni T. Pedziwiatr, W. E. Wallace, Fernande Grandjean Jan 1989

Mössbauer Effect Studies Of Nd₂Fe₁₄₋ₓsiₓb And Y₃Fe₁₄₋ₓsiₓb, Oran Allan Pringle, Gary J. Long, G. K. Marasinghe, William Joseph James, Antoni T. Pedziwiatr, W. E. Wallace, Fernande Grandjean

Physics Faculty Research & Creative Works

No abstract provided.

Go to article

High-Temperature Defect Structure Of Nb-Doped Lacro3, Chikung J. Yu, Harlan U. Anderson, Don M. Sparlin Jan 1989

High-Temperature Defect Structure Of Nb-Doped Lacro3, Chikung J. Yu, Harlan U. Anderson, Don M. Sparlin

Materials Science and Engineering Faculty Research & Creative Works

Electrical conductivity and Seebeck measurements on LaCr0.98Nb0.02CrO3 show that the defect structure of the material is mainly controlled by the extrinsic electrons formed by the Nb donors through the electronic compensation process. The experimental results also indicate that this material conducts electricity via a small polaron mechanism with an electron mobility around 0.004-0.01 cm2/V sec between 1100 and 1300°C. © 1989.

Go to article

Oxidation-Reduction Behavior Of Undoped And Sr-Doped Lamno3 Nonstoichiometry And Defect Structure, J. H. Kuo, Harlan U. Anderson, Don M. Sparlin Jan 1989

Oxidation-Reduction Behavior Of Undoped And Sr-Doped Lamno3 Nonstoichiometry And Defect Structure, J. H. Kuo, Harlan U. Anderson, Don M. Sparlin

Materials Science and Engineering Faculty Research & Creative Works

Undoped and Sr-doped LaMnO3 showed reversible oxidation-reduction behavior. These perovskites can be excess, stoichiometric or deficient in oxygen content depending on the specific conditions. Under very reducing conditions decomposition into new phases occurs. Phase stabilities for these oxides were determined. The results showed that Sr doping caused the LaMnO3 to dissociate at higher oxygen activities than those necessary for undoped LaMnO3. Defect models are proposed to interpret the thermogravimetric results in which metal vacancies are assumed for the oxygen excess condition and oxygen vacancies are assumed for the oxygen deficient condition. Thermodynamic properties were calculated which …

Go to article

Three-Body Interactions In Proton-Helium Angular Scattering, R. Dörner, J. Ullrich, H. Schmidt-Böcking, Ronald E. Olson Jan 1989

Three-Body Interactions In Proton-Helium Angular Scattering, R. Dörner, J. Ullrich, H. Schmidt-Böcking, Ronald E. Olson

Physics Faculty Research & Creative Works

H++He scattering at 0.5 MeV has been investigated using a coincidence technique that completely determines the three-body transverse momentum exchange in single ionization collisions. Three scattering regions could be distinctly recognized that are dominated by proton"helium-nucleus, proton-electron, or electron"helium-nucleus interactions. Calculations and the experimental data show that the coupling between the electronic and nuclear degrees of freedom is required to understand the dynamics for more than 97% of the ionizing collisions. © 1989 The American Physical Society.

Go to article

First Prev Next Last