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Two-Temperature Discrete Model For Nonlocal Heat Conduction, Sergey Sobolev

Sergey Sobolev

The two-temperature discrete model for heat conduction in heterogeneous media is proposed. It is shown that the discrete model contains as limiting cases both hyperbolic and parabolic heat conduction equations for propagative and diffusive regimes, respectively. To obtain these limiting cases two different laws of continuum limit have been introduced. The evolution of the two-temperature system comprises three stages with distinct time scales : fast relaxation of each subsystem to local equilibrium, energy exchange between the subsystems and classical hydrodynamics.

Comparison Of Suppression Across Frequencies, Linda M. Thibodeau, Marc A. Fagelson

Marc A. Fagelson

Inclusion Of Charge Correlations In Calculations Of The Energetics And Electronic Structure For Random Substitutional Alloys, Duane D. Johnson, F. J. Pinski

Duane D. Johnson

Currently, the coherent-potential approximation (CPA) implemented via the multiple-scattering theory of Korringa, Kohn, and Rostoker (KKR) gives the best first-principles description of the electronic structure for random substitutional alloys. However, the total energy has an important component of electrostatic energy missing, namely, that arising from the correlation of charges with varying atomic environments. We develop a ‘‘charge-correlated’’ CPA method (cc-CPA) which includes (some) local environmental charge correlations within the KKR-CPA method. We investigate the cc-CPA energetics for several alloys and show that the formation energies are in better agreement with experimental results. These calculations show that the excess charge on …

Solar Cycle And Seasonal Variationsin F Region Electrodynamics At Millstone Hill, M. J. Buonsanto, M. E. Hagan, J. E. Salah, Bela G. Fejer

Bela G. Fejer

Incoherent scatter radar observations of ion drifts taken at Millstone Hill (42.6°N, 288.5°E) during 73 experiments in the period February 1984 to February 1992 are used to construct, for the first time at this station, average quiet-time E×B drift patterns for both solar cycle maximum and minimum, for the summer, winter, and equinox seasons. The daily variation of V⊥N shows a reversal from northward to southward drifts near noon, and a return to northward drifts in the premidnight hours. The weaker southward drift in the afternoon in summer noted by Wand and Evans (1981) is shown to occur only at …

Resistivity Of The High-Temperature Metallic Phase Of Vo2, Werner W. Schulz, Philip B. Allen, Renate M. Wentzcovitch, Paul C. Canfield

Paul C. Canfield

Measurements are reported on the electrical resistivity ρ(T) along the c axis of a single crystal of VO2, from the metal-insulator transition at T=333 K up to 840 K. The temperature dependence is very linear, and a fit to Bloch-Grüneisen theory gives a residual resistivity ρ0=65 μΩ cm and a ratio ρ(840 K)/ρ0=8. With the help of a local-density-approximation band-structure calculation, we further pursue the conventional (Bloch-Boltzmann) interpretation by extracting the electron-phonon coupling constant λ=1.1 and the mean free path l(800 K)=3.3 Å. The short mean free path implies that the conventional interpretation is internally inconsistent. The most likely explanation …

Three-Point Correlation Functions In Uniformly And Randomly Driven Diffusive Systems, K. Hwang, Beate Schmittmann, R. K. P. Zia

Beate Schmittmann

Driven far away from equilibrium by both uniform and random external fields, a system of diffusing particles with short-range attractive forces displays many singular thermodynamic properties. Surprisingly, measuring pair correlations in lattice-gas models with saturation drives, we find little difference between the uniform and random cases, even though the underlying symmetries are quite distinct. Motivated by this puzzle, we study three-point correlations using both field-theoretic and simulation techniques. The continuum theory predicts the following: (a) The three-point function is nonzero only for the uniformly driven system; (b) it is odd under a parity transformation; and (c) there exists an infinite …

Transverse Form Factors Of 117sn, H Baghaei, J Dubach, M B. Frodyma, R S. Hicks, R A. Miskimen, Gerald Alvin Peterson

Gerald Alvin Peterson

Transverse elastic and inelastic form factors for low-lying levels in 117Sn have been measured by 180° electron scattering in the momentum transfer range qeff=1.1–2.4 fm-1. The simple independent-particle model fails to account for these data, predicting form factors that are much too large. In better quantitative agreement with the data are the results of more detailed calculations that allow for configuration mixing of valence nucleons, as well as first-order core polarization. As in the similar case of 205Tl, these calculations successfully predict the presence of a deep diffraction minimum observed in the intermediate q region of the elastic M1 form …

Apparent And True Feature Heights In Force Microscopy, Nancy Burnham

Nancy A. Burnham

In a force microscope, the stiffness of the cantilever beam convolutes with the tip‐sample interaction stiffness to influence the data in a systematic way. The analysis presented here relates the measured feature height to the true feature height in the variable force, constant force, and constant force gradient modes of operation. In this way, one can understand previously published data: the enhanced measured atomic corrugation observed in high resolution force microscopy images, its increase with load, and the improved resolution of lateral force images. The correct interaction stiffness can be obtained for use in surface force and mechanical properties studies. …

Ground-State Magnetization Density Of 89y, J E. Wise, J R. Calarco, J P. Connelly, S A. Fayans, F W. Hersman, J H. Heisenberg, R S. Hicks, W Kim, T E. Milliman, R A. Miskimen, Gerald Alvin Peterson

Gerald Alvin Peterson

Elastic electron scattering cross sections have been measured for 89Y at 180° for 0.72

Measurements Of Transverse Electron Scattering From The Deuteron In The Threshold Region At High Momentum Transfers, M Frodyma, R G. Arnold, D Benton, P E. Bosted, L Clogher, G Dechambrier, A T. Katramatou, J Lambert, A Lung, G G. Petratos, A Rahbar, S E. Rock, Z M. Szalata, B Debebe, R S. Hicks, A Hotta, Gerald Alvin Peterson

Gerald Alvin Peterson

Deuteron electrodisintegration cross sections near 180' have been measured near breakup threshold for the four-momentum transfer squared Q' range 1.21—2.76 (GeV/c) . Evidence for a change of slope in the cross section near Q =1 (GeV/c ) has been obtained. The data are compared to nonrelativistic calculations, which predict a strong influence of meson-exchange currents. The data are also compared to a hybrid quark-hadron model ~ None of these calculations agrees with the data over the entire measured range of Q'. The ratio of inelastic structure functions W, (Q', E„~)/Wz(Q', E„~)is extracted from the present results and previous forward angle …

Measurements Of The Electric And Magnetic Form Factors Of The Neutron From Q2=1.75 To 4.00 (Gev/C)2, A Lung, L M. Stuart, P E. Bosted, L Andivahis, J Alster, R G. Arnold, C C. Chang, F S. Dietrich, W R. Dodge, R Gearhart, J Gomez, K A. Griffioen, R S. Hicks, R A. Miskimen, Gerald Alvin Peterson

Gerald Alvin Peterson

Quasielastic e-d cross sections have been measured at forward and backward angles. Rosenbluth separations were done to obtain RL and RT at Q2=1.75, 2.50, 3.25, and 4.00 (GeV/c)2. The neutron form factors GEn and GMn have been extracted using a nonrelativistic model. The sensitivity to deuteron wave function, relativistic corrections, and models of the inelastic background are reported. The results for GMn are consistent with the dipole form, while GEn is consistent with zero. Comparisons are made to theoretical models based on vector meson dominance, perturbative QCD, and QCD sum rules, as well as constituent quarks.

Burnham, Colton, And Pollock Reply, Nancy Burnham, Rj Colton, Hm Pollock

Nancy A. Burnham

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Tables Of Coincidence Orientations For Ordered Tetragonal L Lo Alloys For A Range Of Axial Ratios, Abha Singh, Alexander H. King

Alexander H. King

In this paper we develop and apply techniques for computation of CSL, DSCL and step-vector data for grain boundaries in tetragonal materials for a range of axial ratios. This has application to L10 alloys including TiA1, which is a candidate for lightweight high-temperature structural applications. Our results are compared with others and found to be more accurate and complete. We provide data for a wider range of axial ratios than those considered by previous workers. We have also derived equivalent quaternions for tetragonal crystals in tetragonal-crystal coordinates and listed conditions for selecting a unique reduced rotation in tetragonal-crystal coordinates so …

A Geometrical Rationalization Of The Special Properties Of The 14° [001] Grain Boundary In Yba2cu3o7−Δ, Alexander H. King, Abha Singh

Alexander H. King

14° [001] tilt grain boundaries in YBa2Cu3O7−δ have been found to exhibit anomalously good superconducting critical currents, associated with magnetic flux pinning, although no special interfacial structure has heretofore been associated with this misorientation. We present an analysis of the geometry of the grain boundary in question and show that it can correspond to a special interface, within the definition of constrained lattice coincidence, which may lead to new understanding of the superconducting behavior of grain boundaries. Our analysis shows that the tetragonal‐to‐orthorhombic phase transformation may have important effects upon grain boundary structure and properties, indicating new approaches to producing …

Doping And Pressure Studies On Ybbipt, A. Lacerda, R. Movshovich, M. F. Hundley, Paul C. Canfield, D. Arms, G. Sparn, J. D. Thompson, Z. Fisk, N. E. Philips, H.-R. Ott

Paul C. Canfield

The compound YbBiPt exhibits an extremely large low‐temperature C/T (γ∼8 J K−2 mol−1/Yb) which, if due solely to a renormalized effective mass, would make this material the heaviest correlated electron system known to date. In the Kondo model, the very large γ corresponds to a small characteristic energy scale that is expected to be pressure dependent. We have studied the effect of chemical pressure on YbBiPt single crystals by heat‐capacity measurements on Y and Lu‐doped samples. We have also made preliminary low‐temperature measurements under hydrostatic pressure of the heat capacity (300 mK≤T≤2 K, up to 8 kbar) and resistance (30 …

F-Region Plasma Drifts Over Arecibo: Solar Cycle, Seasonal And Magnetic Activityeffects, Bela G. Fejer

Bela G. Fejer

We have used Arecibo incoherent scatter measurements from 1981 to 1990 to determine the characteristics of low-latitude F region plasma drifts. The measurements show large day-to-day variability even during magnetically quiet periods. The average poleward/perpendicular plasma drifts do not change significantly with season and solar cycle except in the midnight-morning sector. The zonal drifts show clear solar cycle and seasonal effects. The afternoon-nighttime eastward drifts increase with solar flux; the westward drifts in the early morning-afternoon sector show a large increase from summer to winter but are independent of solar activity. The two perpendicular velocity components also respond differently to …

Nqr Study Of Local Structure And Cooling Rate‐Dependent Superconductivity In La2cuo4+Δ, A. P. Reyes, E. T. Ahrens, P. C. Hammel, J. D. Thompson, Paul C. Canfield, Z. Fisk, R. H. Heffner, J. E. Schirber

Paul C. Canfield

Preliminary results of structural studies in oxygen‐annealed La2CuO4+δ(δ∼0.03) using 139La nuclear quadrupole resonance (NQR) spectroscopy are reported. Superconducting critical temperatures were found to depend on the rate of cooling through a narrow temperature range near 195 K. Analysis of the 139La NQR spectra reveal that lanthanum atoms in the oxygen‐rich metallic region occupy two sites having different local environments. One site has a structural configuration closely related to the stoichiometric oxygen‐poor compound. The second appears only below 200 K and exhibits a large shift and broad distribution of NQR frequency ν Q . Shifts in ν Q in the vicinity …

Timestamp Semantics And Representation., Curtis Dyreson, Richard T. Snodgrass

Curtis Dyreson

Many database Management systems and operating systems provide support for time values. At the physical level time values are known as timestamps. A timestamp has a physical realization and a temporal interpretation. The physical realization is a pattern of bits while the temporal interpretation is the meaning of each bit pattern, that is, the time each pattern represents. All previous proposals defined timestamps in terms of seconds. However, as we show, there are at least seven definitions of this fundamental time unit. We propose a more precise temporal interpretation, the time-line clock, that constructs a time-line by using different well-defined …

Quantam Wave Turbulence, Alejandro Garcia, M. Haeri, S. Putterman, P. Roberts

Alejandro Garcia

The nonlinear quantum kinetic equation for the interaction of sound waves is solved via analytic and numerical techniques. In the classical regime energy cascades to higher frequency (ω) according to the steady-state power law ω-3/2. In the quantum limit, the system prefers a reverse cascade of energy which follows the power law ω-6. Above a critical flux, a new type of spectrum appears which is neither self-similar nor close to equilibrium. This state of nonlinear quantum wave turbulence represents a flow of energy directly from the classical source to the quantum degrees of freedom.

Anomalies For Pedestrians, Br Holstein

Barry R Holstein

The subject of anomalies, i.e., quantum mechanical symmetry breaking, is addressed using only basic quantum mechanics. Examples from different areas of physics are examined

Study Of The Violation Of Parity In Nuclear Beta-Decay Via A Relative Beta-Polarization Measurement With Polarized In-107 Nuclei, N Severijns, R Prieels, M Allet, J Camps, P Demoor, J Deutsch, F Gimenonogues, Br Holstein, Bh King, O Naviliatcuncici, I Pepe, Pa Quin, P Schuurmans, R Siebelink, W Vanderpoorten, J Vanhaverbeke, L Vanneste, J Wouters

Barry R Holstein

No abstract provided.

Solvable Quantum Mechanical Examples Of Broken Supersymmetry, Asim Gangopadhyaya

Asim Gangopadhyaya

Quantum Correlations And 3 Body Decays At A Phi-Factory, Jf Donoghue, Br Holstein, Af Perez

Barry R Holstein

No abstract provided.

Phenomenographic Research And The Measurement Of Understanding: An Investigation Of Students' Conceptions Of Speed, Distance And Time, P Ramsden, Geoff Masters, Andrew Stephanou, E Walsh, E Martin

Prof Geoff Masters AO

No abstract provided.

Physics Students' Understanding Of Relative Speed: A Phenomenographic Study, Eleanor Walsh, Gloria Dall'alba, John Bowden, Elaine Martin, Ference Marton, Geoff Masters, Paul Ramsden, Andrew Stephanou

Prof Geoff Masters AO

It is important that students of physics develop both quantitative and qualitative understanding of physical concepts and principles. Although accuracy and reliability in solving quantitative problems is necessary, a qualitative understanding is required in applying concepts and principles to new problems and in real-life situations. If students are not able to understand what underlies quantitative problem-solving procedures nor interpret the solution in physical terms, it is questionable whether they have developed an adequate understanding of physics. The research reported here is part of a larger phenomenographic study that is concerned with the assessment of physics students' understanding of some basic …

Sliding Mode Control Of The Systems With Uncertain Direction Of Control Vector, Sergey V. Drakunov

Sergey V. Drakunov

No abstract provided.