Physical Sciences and Mathematics Commons^™

Relaxation Time Of The Order Parameter In A High-Temperature Superconductor, G.L. Eesley, J. Heremans, M.S. Meyer, G.L. Doll, Sy_Hwang Liou

Sy-Hwang Liou Publications

We present femtosecond time-resolved measurements on the high-T_c superconductor Tl₂Ba₂Ca₂Cu₃O₁₀. At temperatures below T_c, we observe a relaxation process which is distinct from the equilibration of hot carriers in the normal state. Our results demonstrate an increasing relaxation rate as the superconducting gap opens. This is consistent with the behavior of conventional metallic superconductors.

Power Law Exponents For A Spreading Front And Growing Interface In An Irreversible Wetting, Evan Willett, Ras B. Pandey

Faculty Publications

Using computer simulations, the power-law behavior of the interface growth of a spreading fluid is studied in a two-dimensional lattice model. The interface width exponent ν and the dynamical exponent k for the evolution of the front are consistent with their dynamical scaling relation. The magnitude of these exponents seems to depend upon the nature of the substrate and the concentration of the carriers of the wetting fluid.

Uniform Stationary-Phase Methods For Energy Spectra Resulting From Collisions In A Complex Potential: Penning And Associative Ionization Of He*(2³S)+He*(23s), Ronald James Bieniek, M. W. Muller, M. Movre

Physics Faculty Research & Creative Works

Heavy-particle collisions involving strong electronic coupling can be conveniently described by using a complex (optical) potential in the entrance channel. Uniform JWKB stationary-phase techniques are used to evaluate T-matrix elements for transitions where an electron is ejected. The semi-analytic expressions for the resulting electron energy spectra are no more difficult to implement than corresponding ones for totally real potentials. Numerical results are reported for Penning and associative ionization from sub thermal He*(23S)+He*(23S) collisions. These are in excellent agreement with fully quantal, complex-potential computations. The stationary-phase expressions for T-matrix elements and differential cross sections are employed to elucidate the rapid and …

Projectile- And Target-Charge Dependent Effects In Ionizing Collisions Of H ⁺ And He 2+ With He, Ne And Ar Atoms, Timothy James Gay, M. W. Gealy, M. E. Rudd

Physics Faculty Research & Creative Works

The spectra of electrons emitted in collisions between H + and He 2+ projectiles and He, Ne and Ar targets at energies of 50 and 100 keV amu -1 have been studied. The data are in qualitative agreement with results of Irby el al., but are in disagreement with measurements of Bernardi et al. It is shown that the observed electron spectra have a dependence on both target-ion and projectile effective charge that can be understood qualitatively in terms of 'saddle-point' ionization. Several issues relevant to saddle-point ionization are discussed. © 1990 IOP Publishing Ltd.

Laser Cvd And Plasma Cvd Of Cro2 Films And Cobalt Doped Cro2 Films Using Organometallic Precursors, Peter A. Dowben, Marshall Onellion

Peter Dowben Publications

Chromium dioxide is deposited as a ferromagnetic layer onto selected portions of a substrate or over the entire substrate. Chromium hexacarbonyl vapor is introduced into a vacuum deposition chamber at e.g. 10 milliTorr and oxygen is introduced at e.g. 15 to 100 milliTorr. A UV laser beam is focused onto the substrate to form the CrO₂ layer photolytically. The CrO₂ layer can also be deposited by RF plasma deposition. This technique can also be employed for depositing MoC₂, WC₂, Mo_2φ3, MoO₂ or WO₂. Magnetic recording or memory devices are …

In Situ Infrared Evidence For The Electrochemical Incorporation Of Hydrogen Into Si And Ge, K. C. Mandal, F. Ozanam, J.-N. Chazalviel

Faculty Publications

No abstract provided.

Beryllium-7 And Lead-210 In The Atmosphere And Surface Snow Over The Greenland Ice Sheet In The Summer Of 1989, Jack E. Dibb

Earth Sciences

The concentrations of ⁷Be and ²¹⁰Pb were measured in surface air and fresh and aging snow samples from Summit (72°20′N, 38°45′W) and Dye 3 (65°10′N, 44°45′W) Greenland, during June and July 1989. The aerosol concentrations of these radionuclides showed rapid variations at both sites, but were nearly twice as high, on average, at Summit. Concentrations in the 16 fresh snowfall events that were sampled also showed wide variability, but the averages were the same at the two sites. The apparent difference in air-snow fractionation and the lack of coherence in the concentration in air time series between the …

A Tight Upper Bound On The Benefits Of Replication And Consistency Control Protocols, Donald B. Johnson, Larry Raab

Computer Science Technical Reports

We present an upper bound on the performance provided by a protocol guaranteeing mutually exclusive access to a replicated resource in a network subject to component failure and subsequent partitioning. The bound is presented in terms of the performance of a single resource in the same network. The bound is tight and is the first such bound known to us. Since mutual exclusion is one of the requirements for maintaining the consistency of a database object, this bound provides an upper limit on the availability provided by any database consistency control protocol, including those employing dynamic data relocation and replication. …

The Relationship Of The Virtual Orbitals Of Self-Consistent-Field Theory To Temporary Negative Ions In Electron Scattering From Molecules, Donghai Chen, Gordon A. Gallup

Gordon Gallup Publications

The theory given here shows how certain of the virtual orbitals of self-consistent field (SCF) theory provide a natural ingredient for constructing basis functions to study the shape resonances associated with temporary molecular ions. We give specific calculations of resonant behavior in H₂, N₂, ethylene, cyclopropene, and cyclobutene. In addition, we show how the theory can rationalize the relationship between Koopmans' theorem values of the energy of a resonance and the experimental values. The Journal of Chemical Physics is copyrighted by The American Institute of Physics.

Array Reshaping -- A Mechanism For Optimizing Array Storage On Parallel Architecture, Ko-Yang Wang

Department of Computer Science Technical Reports

No abstract provided.

Heuristic Guided Pre-Optimized Algorithm Substitution For Parallel Computers, Ko-Yang Wang

Department of Computer Science Technical Reports

No abstract provided.

Notes On Sufficient Conditions For A Graph To Be Hamiltonian, Michael Joseph Paul, Carmen Baytan Shershin, Anthony Connors Shershin

School of Computing and Information Sciences

The first part of this paper deals with an extension of Dirac's Theorem to directed graphs. It is related to a result often referred to as the Ghouila-Houri Theorem. Here we show that the requirement of being strongly connected in the hypothesis of the Ghouila-Houri Theorem is redundant.

The Second part of the paper shows that a condition on the number of edges for a graph to be hamiltonian implies Ore's condition on the degrees of the vertices.

The Duke Internet Programming Contest, Owen Astrachan, Vivek Khera, David Kotz

Dartmouth Scholarship

On the evening of October 23, 1990, electronic mail messages started to pour into the computers at the Duke University Computer Science Department. Teams of programmers from all over the world were registering to compete in the first global (as far as the authors are aware) programming contest to be held on the Internet. During the three hour competition, modeled after the annual ACM scholastic programming contest, 60 teams from 37 institutions in 5 countries attempted to solve a set of six programming problems using C or Pascal. Their solutions were sent by electronic mail to Duke, where their programs …

Models And Algorithms For Co-Scheduling Compute-Intensive Tasks On A Network Of Workstations, Mikhail J. Atallah, Christina Lock, Dan C. Marinescu, Howard J. Seigel, Thomas L. Casavant

Department of Computer Science Technical Reports

No abstract provided.

Voronoi Diagrams In A River, Kokichi Sugihara

Department of Computer Science Technical Reports

No abstract provided.

Implementing Expert System Rule Conditions By Neural Networks, Henry Tirri

Department of Computer Science Technical Reports

No abstract provided.

Brep-Index: A Multi-Dimensional Space Partitioning Tree, George Vanĕček

Department of Computer Science Technical Reports

No abstract provided.

Polymer Science In Hungary, Part Iii. The Industrial Research Institutes And Their Factories, Otto Vogl, Gyula Hardy, Sandor Doubravsky, Margit Iring, Ferenc Tudos

Emeritus Faculty Author Gallery

No abstract provided.

73. Professor Cristofor I. Simionescu On His 70th Birthday, Otto Vogl, Ioan I. Negulescu

Emeritus Faculty Author Gallery

No abstract provided.

Organic And Polymeric Nonlinear Optical Materials, Otto Vogl, Donald R. Ulrich

Emeritus Faculty Author Gallery

No abstract provided.

A Report On Black-Tailed Prairie Dogs In Nebraska-- Their Biology, Behavior, Ecology, Management, And Responses To A Visual Barrier Fence, Nancy S. Foster

School of Natural Resources: Dissertations, Theses, and Student Research

I examined the effects of a visual barrier fence, which had a see-through visibility of 600/0, on the foraging, vigilance, and aggressive behaviors of adult female black-tailed prairie dogs from June through August 1990 in central Nebraska. I also examined changes in their home ranges and use of an area in response to this fence. Prairie dogs prefer an open view of their surroundings. Therefore, I expected animals near a visual barrier to spend more time in vigilance and aggression, and less time foraging. Adult female prairie dogs exposed to the visual barrier devoted more time to foraging and less …

A Nonstandard Delta Function, Todor D. Todorov

Mathematics

We prove that the Dirac delta distribution has a kernel in the class of the pointwise nonstandard functions.

Nitrate Concentrations Of Ground Water Benton County, Arkansas, Charles R. Smith, Kenneth F. Steele

Technical Reports

No abstract provided.

Nitrate Concentrations Of Ground Water Northern Madison County, Arkansas, Andrew Y. Austin, Kenneth F. Steele

Technical Reports

The presence of an extensive network of solution channels in the fractured carbonate bedrock and a thin permeable regolith in northwest Arkansas makes aquifers in this region susceptible to contamination. Because of these conditions, there is concern about nitrate contamination of the ground water from land applied animal wastes, commercial fertilizers, rural septic systems and municipal sewage systems. In response to these concerns a survey was conducted of the nitrate concentration in rural water wells in the carbonate aquifers of a 420 mi2 area of northern Madison county during "wet" and "dry" seasons in 1990. Information from well owners, drilling …

Long Term Management Measures For The Cockburn Sound Restricted Entry Fisheries., P. Millington

Fisheries management papers

The objective of this management plan is to introduce rules which will ensure there is a real reduction in professional fishing units and fishing effort in the medium to long term. This reduction should enable a small professional fishery to co-exist with the recreational sector, supply fresh fish to the metropolitan area, ensuring there is no proliferation of "shamateur fishing" and providing a supply of recreational angling bait.

Characterization Of Matrix Variate Normal Distributions, A.K. Gupta, T. Varga

Mathematical Sciences Technical Reports (MSTR)

In this paper, it is shown that two random matrices have a joint matrix variate distribution if conditioning each one on the other the resulting distributions satisfy certain conditions. A general result involving more than two matrices is also proved.

Magnetism Of Rare-Earth–Transition-Metal Nanoscale Multilayers. Ii. Theoretical Analysis Of Magnetization And Perpendicular Magnetic Anisotropy, Z.S. Shan, David J. Sellmyer, Sitaram Jaswal, Y.J. Wang, J.X. Shen

David Sellmyer Publications

Systematic studies of rare-earth–transition-metal amorphous compositionally modulated films (CMF) permit the development of a detailed model for understanding the magnetization and perpendicular magnetic anisotropy and their distributions along the film normal. It is shown that the single-ion anisotropy of rare-earth ions with orbital angular momentum is the major contributor to the perpendicular anisotropy for this class of CMF. The calculated results agree well with the experimental data for Dy/Co and Tb/Fe CMF when the individual layer thicknesses are small enough (<10 Å); these films have structures which can be characterized as compositionally modulated amorphous alloys.

Magnetism Of Rare-Earth–Transition-Metal Nanoscale Multilayers. I. Experiments On Dy/Co, Dy/Fe, And Tb/Fe, Z.S. Shan, David J. Sellmyer

David Sellmyer Publications

Experimental investigations of magnetic and structural properties for rare-earth–transition-metal (RE-TM) compositionally modulated films (CMF) are presented in this paper. In particular, A^RE/B^TM including A^RE=Dy and Tb and B^TM=Fe, Co, and Ni, are studied. The layer thickness and temperature dependence of magnetic properties, which can be interpreted in terms of the antiferromagnetic coupling of RE and TM moments and their atomic distributions, are reported. These A^RE/B^TM CMF with nanoscale layer thicknesses exhibit perpendicular magnetic anisotropy (PMA) and the range of the layer thickness required for PMA is determined. The …

Lake Mead Nutrient Enhancement Project, Peter D. Vaux, Larry J. Paulson, Nevada Department Of Wildlife, National Oceanic And Atmospheric Administration

Publications (WR)

The Lake Mead Fertilization Project is a research program designed to investigate the potential for using large-scale artificial fertilization to enhance the game fisheries of this reservoir through an increase in the population of threadfin shad, the system's primary forage species. A substantial decline in the population of largemouth bass, together with poor condition of adult striped bass, are the two major issues affecting the Lake Mead game fisheries. Both issues have been hypothesized to be a result of an inadequate amount of forage in the reservoir. Previous studies have in turn suggested that a major factor limiting the shad …

Resource Law Notes Newsletter, No. 21, Dec. 1990, University Of Colorado Boulder. Natural Resources Law Center

Resource Law Notes: The Newsletter of the Natural Resources Law Center (1984-2002)

No abstract provided.