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Selected Works

1996

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Articles 1 - 26 of 26

Full-Text Articles in Physics

Coarsening And Persistence In The Voter Model, E. Ben-Naim, L. Frachebourg, P.L. Krapivsky Dec 1996

Coarsening And Persistence In The Voter Model, E. Ben-Naim, L. Frachebourg, P.L. Krapivsky

Eli Ben-Naim

No abstract provided.


Auroral Electrojet Irregularity Theory And Experiment: A Criticalreview Of Present Understanding And Future Directions, J. D. Sahr, Bela G. Fejer Dec 1996

Auroral Electrojet Irregularity Theory And Experiment: A Criticalreview Of Present Understanding And Future Directions, J. D. Sahr, Bela G. Fejer

Bela G. Fejer

We review the experimental observations of meter scale plasma irregularities in the auroral E region and the status of their theoretical understanding. Most of the experimental data is derived from VHF radar scatter experiments, but sounding rockets also provide crucial information not obtainable from radars. Linear theories correctly predict the altitude of occurence, strong magnetic aspect sensitivity, marginal instability, and typical phase velocities. Subsequent nonlinear theories have been developed to account for other observed features but with less satisfying application. Further understanding of auroral electrojet irregularities is impeded by precision limitations of existing instruments, by radar data which may seem …


Frozen Disorder In A Driven System, Beate Schmittmann, K. E. Bassler Oct 1996

Frozen Disorder In A Driven System, Beate Schmittmann, K. E. Bassler

Beate Schmittmann

We investigate the effects of quenched disorder on the universal properties of a randomly driven Ising lattice gas. The Hamiltonian fixed point of the pure system becomes unstable in the presence of a quenched local bias, giving rise to a new fixed point which controls a novel universality class. We determine the associated scaling forms of correlation and response functions, quoting critical exponents to two-loop order in an expansion around the upper critical dimension dc=5.


Observationsof Inner-Plasmasphere Irregularities With A Satellite Beacon Interferometer Array, A. R. Jacobsen, G. Hogeveen, R. C. Carlos, G. Wu, Bela G. Fejer, M. C. Kelley Sep 1996

Observationsof Inner-Plasmasphere Irregularities With A Satellite Beacon Interferometer Array, A. R. Jacobsen, G. Hogeveen, R. C. Carlos, G. Wu, Bela G. Fejer, M. C. Kelley

Bela G. Fejer

A radio-interferometer array illuminated by 136-MHz beacons of several geosynchronous satellites has been used to study small (≥ 1013 m−2) transient disturbances in the total electron content along the lines of sight to the satellites. High-frequency (ƒ> 3 mHz) electron content oscillations are persistently observed, particularly during night and particularly during geomagnetically disturbed periods. The oscillations move across the array plane at speeds in the range 200–2000 m/s, with propagation azimuths that are strongly peaked in lobes toward the western half-plane. Detailed analysis of this azimuth behavior, involving comparison between observations on various satellite positions, indicates compellingly that the phase …


Phase Transitions In Driven Bilayer Systems: A Monte Carlo Study, C. C. Hill, R. K. P. Zia, Beate Schmittmann Jul 1996

Phase Transitions In Driven Bilayer Systems: A Monte Carlo Study, C. C. Hill, R. K. P. Zia, Beate Schmittmann

Beate Schmittmann

We investigate the phase diagram of a system with two layers of an Ising lattice gas at half filling. In addition to the usual intralayer nearest neighbor attractive interaction, there is an interlayer potential J. Under equilibrium conditions, the phase diagram is symmetric under J→−J, though the ground states are different. The effects of imposing a uniform external drive, studied by simulation techniques, are dramatic. The mechanisms responsible for such behavior are discussed.


Incoherent Scatter Radar, Ionosonde,And Satellite Measurements Of Equatorial F Region Vertical Plasma Drifts In The Evening Sector, Bela G. Fejer, E. R. De Paula, L. Scherliess, I. S. Batista Jul 1996

Incoherent Scatter Radar, Ionosonde,And Satellite Measurements Of Equatorial F Region Vertical Plasma Drifts In The Evening Sector, Bela G. Fejer, E. R. De Paula, L. Scherliess, I. S. Batista

Bela G. Fejer

Studies of equatorial F region evening vertical plasma drifts using different measurement techniques have produced conflicting results. We examine the relationship of incoherent scatter radar and ionosonde drift observations over the Peruvian equatorial region, and AE-E satellite drifts for different geophysical conditions. Our data show that there is large day-to-day variability on the ratios of radar and ionosonde drifts, but on the average the measurements from these two techniques are in fair agreement during low and moderate solar flux conditions. For high solar activity, however, the Jicamarca evening drifts during equinox and December solstice are significantly larger than the ionosonde …


The Spectral Function Of Random Resistor Networks, Anthony Day, M. Thorpe Jun 1996

The Spectral Function Of Random Resistor Networks, Anthony Day, M. Thorpe

Anthony Roy Day

The effective complex conductivity [...] of a two-component material can be conveniently expressed as an integral transformation of a spectral function. The spectral function depends only on the geometry of the material, and can be used to calculate [...] for any particular choice of component conductivities. This is a very useful feature if the component conductivities can be varied (by changing the temperature or frequency, for example) at a fixed geometry. We present a derivation of the spectral function that identifies it as a density of states. We have made direct numerical calculations of the spectral function of two-dimensional random …


Построение Редуцированного Физического Гамильтониана Для Сферически-Симметричной Гравитации, Николай Заркевич Jun 1996

Построение Редуцированного Физического Гамильтониана Для Сферически-Симметричной Гравитации, Николай Заркевич

Nikolai A. Zarkevich

No abstract provided.


Electronic Origins Of Ordering In Multicomponent Metallic Alloys: Application To The Cu-Ni-Zn System, J. D. Althoff, Duane D. Johnson, F. J. Pinski, J. B. Staunton Apr 1996

Electronic Origins Of Ordering In Multicomponent Metallic Alloys: Application To The Cu-Ni-Zn System, J. D. Althoff, Duane D. Johnson, F. J. Pinski, J. B. Staunton

Duane D. Johnson

We investigate the ordering tendencies of the fcc Cu-Ni-Zn system using a recently developed first-principles, density-functional-based theory of atomic short-range order (ASRO) in disordered substitutional alloys of an arbitrary number of components. We find for the binary alloys a variety of effects which should lead to competition in the ternaries: commensurate ordering (Ni-Zn), long-period ordering (Cu-rich Cu-Zn), and clustering (Cu-Ni), in agreement with experiment. We calculate the ASRO of various disordered ternary alloys (as described by the Warren-Cowley pair-correlation function) and discuss its relationship to the electronic structure of the binary and ternary disordered alloys. We find [100]-type ASRO over …


Η Production In Peripheral Heavy-Ion Collisions, Alec Schramm, Daniel Reeves Mar 1996

Η Production In Peripheral Heavy-Ion Collisions, Alec Schramm, Daniel Reeves

Alec J Schramm

We estimate the impact parameter dependence of the production cross section for ηc and ηb mesons in peripheral heavy-ion collisions. Total and elastic γγ cross sections are calculated in an equivalent photon approximation.


Scanning Local‐Acceleration Microscopy, Nancy Burnham, A. Kulik, G. Gremaud, P. Gallo, F. Oulevey Feb 1996

Scanning Local‐Acceleration Microscopy, Nancy Burnham, A. Kulik, G. Gremaud, P. Gallo, F. Oulevey

Nancy A. Burnham

By adapting a scanning force microscope to operate at frequencies above the highest tip–sample resonance, the sensitivity of the microscope to materials’ properties is greatly enhanced. The cantilever’s behavior in response to high‐frequency excitation from a transducer underneath the sample is fundamentally different than to its low‐frequency response. In this article, the motivations, instrumentation, theory, and first results for this technique are described.


Non-Traditional Techniques In Teaching Science For General Students, Gary Lewis, Ben Golden, Gail Schiffer, Diane Willey Feb 1996

Non-Traditional Techniques In Teaching Science For General Students, Gary Lewis, Ben Golden, Gail Schiffer, Diane Willey

Gary C. Lewis

No abstract provided.


Materials’ Properties Measurements: Choosing The Optimal Scanning Probe Microscope Configuration, Nancy Burnham, G Gremaud, A Kulik, P Gallo, F Oulevey Feb 1996

Materials’ Properties Measurements: Choosing The Optimal Scanning Probe Microscope Configuration, Nancy Burnham, G Gremaud, A Kulik, P Gallo, F Oulevey

Nancy A. Burnham

Rheological models are used to represent different scanning probe microscope configurations. The solutions for their static and dynamic behavior are found and used to analyze which scanning probe microscope configuration is best for a given application. We find that modulating the sample at high frequencies results in the best microscope behavior for measuring the stiffness of rigid materials, and that by modulating the tip at low frequencies and detecting the motion of the tip itself (not its position relative to the tip holder) should be best for studying compliant materials in liquids.


Error In The Calculation Of Synchronized Spontaneous Otoacoustic Emission Frequencies Measured With The Ilo88 System, Jacek Smurzynski, Rudolf Probst Jan 1996

Error In The Calculation Of Synchronized Spontaneous Otoacoustic Emission Frequencies Measured With The Ilo88 System, Jacek Smurzynski, Rudolf Probst

Jacek Smurzynski

No abstract provided.


Nonlinear Deformed Su(2) Algebras Involving Two Deforming Function, Andrei Ludu Jan 1996

Nonlinear Deformed Su(2) Algebras Involving Two Deforming Function, Andrei Ludu

Andrei Ludu

No abstract provided.


Gaussian Phase Approximation For Evaluating The Decay Of Nmr Spin Echoes, Charles Recchia, K Gorny, C Pennington Jan 1996

Gaussian Phase Approximation For Evaluating The Decay Of Nmr Spin Echoes, Charles Recchia, K Gorny, C Pennington

Charles H Recchia

No abstract provided.


Effects Of Local Non-Equilibrium Solute Diffusion On Rapid Solidification Of Alloys, Sergey Sobolev Jan 1996

Effects Of Local Non-Equilibrium Solute Diffusion On Rapid Solidification Of Alloys, Sergey Sobolev

Sergey Sobolev

A conceptual foundation for the study of local non-equilibrium solute diffusion under rapid solidifica- tion conditions is proposed. The model takes into account the relaxation to local equilibrium of the solute flux and incorporates two diffusion speeds, VDb, the bulk liquid diffusion speed, and VDi, the interface diffusive speed, as the most important parameters governing the solute concentration in the liquid phase and solute partitioning. The analysis of the model predicts complete solute trapping and the transition to a purely thermally controlled solidification, which occur abruptly when the interface velocity V equals the bulk liquid diffusion speed VDb. The abrupt …


The Local-Nonequilibrium Temperature Field Around The Melting And Crystallization Front Induced By Picosecond Pulsed Laser Irradiation, Sergey Sobolev Jan 1996

The Local-Nonequilibrium Temperature Field Around The Melting And Crystallization Front Induced By Picosecond Pulsed Laser Irradiation, Sergey Sobolev

Sergey Sobolev

The local-nonequilibrium model for heat transport around melting and crystallization zone induced by ultrafast laser irradiation is considered. The model predicts strong overheating during melting of the material near the interface. Moreover, the local-nonequilibrium effects lead to an interface temperature gradient steeper than expected from the classical heat flow calculations. Possible modification of the kinetics of melting to include the relaxation effects is also discussed.


Applications Of Extended Thermodynamics ...Part Iii., Sergey Sobolev Jan 1996

Applications Of Extended Thermodynamics ...Part Iii., Sergey Sobolev

Sergey Sobolev

No abstract provided.


Synthesis And Characterization Of A New Class Of Μ3-Oh-Bridged Trimers That Contain Octahedrally Coordinated Divalent Metal Ions Bridged By Three Acetate Ligands And A Unique Catecholate Ligand. Solid State Molecular Structures Of The [(Py)5mii3(Oac)3(Μ3-Oh)((Cat)] Complexes (M = Mn(Ii), Fe(Ii), Co(Ii), Ni(Ii)), R.A. Reynolds, Edward Yu, W.R. Dunham, D. Coucouvanis Jan 1996

Synthesis And Characterization Of A New Class Of Μ3-Oh-Bridged Trimers That Contain Octahedrally Coordinated Divalent Metal Ions Bridged By Three Acetate Ligands And A Unique Catecholate Ligand. Solid State Molecular Structures Of The [(Py)5mii3(Oac)3(Μ3-Oh)((Cat)] Complexes (M = Mn(Ii), Fe(Ii), Co(Ii), Ni(Ii)), R.A. Reynolds, Edward Yu, W.R. Dunham, D. Coucouvanis

Edward Yu

The synthesis and structural characterization of a new class of “basic” trinuclear acetate clusters with solely divalent metal ions and a central μ3-OH ligand are reported. These molecules with the [(py)5MII3(OAc)3(μ3-OH)(cat)] stoichiometry (M = Mn, Fe, Co, Ni) are X-ray isomorphous and isostructural and contain octahedrally coordinated metal ions. The core consists of an antiferromagnetically coupled M3 unit with the metals arranged in the corners of an isosceles triangle. Two of the M−M distances vary between 2.98 and 3.16 Å, and the longer M−M distance is observed between 3.65 and 3.76 Å. As expected from the relative ionic radius lengths, …


A Simple Model For Nonequilibrium Fluctuations In A Fluid, Alejandro Garcia, F. Baras, M. Malek Mansour Jan 1996

A Simple Model For Nonequilibrium Fluctuations In A Fluid, Alejandro Garcia, F. Baras, M. Malek Mansour

Alejandro Garcia

Presents a train model that shows the long-range spatial correlations of fluctuations in nonequilibrium fluid systems. Illustration of model through analysis of flat-car trains running on parallel tracks; Simulation of train model in computers; Theoretical analysis for fluctuations in the train model; Relationship between train model and the fluctuating hydrodynamic theory of fluids.


Answer To Question #26. Electromagnetic Field Momentum, Br Holstein Dec 1995

Answer To Question #26. Electromagnetic Field Momentum, Br Holstein

Barry R Holstein

No abstract provided.


Understanding Alpha Decay, Br Holstein Dec 1995

Understanding Alpha Decay, Br Holstein

Barry R Holstein

The subject of alpha decay is an important part of a course in modern physics, as it provides a clear experimental manifestation of the phenomenon of barrier penetration. The traditional approach, based on Gamow's complex eigenvalue method, raises a number of questions which can be answered by employing the older but less well-known procedure of summing over scattering states. Additional insights are gained by examination of the alpha decay system via more contemporary path integral based techniques.


Su(1,1) Algebraic Description Of One-Dimensional Potentials Within The R-Matrix Theory, Andrei Ludu Dec 1995

Su(1,1) Algebraic Description Of One-Dimensional Potentials Within The R-Matrix Theory, Andrei Ludu

Andrei Ludu

No abstract provided.


Interface Roughening In A Hydrodynamic Lattice-Gas Model With Surfactant, Francis W. Starr, S. T. Harrington, B. M. Boghosian, H. E. Stanley Dec 1995

Interface Roughening In A Hydrodynamic Lattice-Gas Model With Surfactant, Francis W. Starr, S. T. Harrington, B. M. Boghosian, H. E. Stanley

Francis Starr

No abstract provided.


Generalization Kdv Equation For Fluid Dynamics And Quantum Algebras, Andrei Ludu Dec 1995

Generalization Kdv Equation For Fluid Dynamics And Quantum Algebras, Andrei Ludu

Andrei Ludu

No abstract provided.