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  • Nature Publishing Group  (45)
  • American Institute of Physics (AIP)
  • Public Library of Science (PLoS)
  • 11
    Electronic Resource
    Electronic Resource
    Sources of spin-polarized beams (invited) : International conference on ion sources (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 385-388 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Sources producing beams of spin-polarized atoms and ions are now widely used in nuclear physics. Modern systems are increasingly expensive and complex. They provide a variety of species and beam polarizations with intensities often sufficient for experimental needs. The laboratory seeking such a device for its program must evaluate a variety of options and match them to its accelerator, experimental program, and expected resources. The major systems and techniques used are surveyed and criteria dictating the choice of source for particular experimental applications are discussed briefly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141300
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  • 12
    Electronic Resource
    Electronic Resource
    Determining the electric field in [111] strained-layer quantum wells (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 2369-2371 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electric field in a [111] growth-axis strained-layer quantum well embedded in a p-i-n diode is determined by measuring the polarization vector in the quantum well. The polarization is determined from the critical reverse bias necessary to produce zero electric field in the quantum well. The critical reverse bias is obtained from electroreflectance spectra, which have quantum well optical features that exhibit a 180° phase change at flat band. A depletion model of the p-i-n diode with an embedded quantum well is used to relate the electric field in the quantum well to the applied bias and the polarization vector in the well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110478
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  • 13
    Electronic Resource
    Electronic Resource
    An analysis of RNG-based turbulence models for homogeneous shear flow (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 2278-2281 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In a recent paper [Phys. Fluids A 2, 1678 (1990)], the authors compared the performance of a variety of turbulence models including the K-ε model and the second-order closure model derived by Yakhot and Orszag based on renormalization group (RNG) methods. The performance of these RNG models in homogeneous turbulent shear flow was found to be quite poor, apparently due to the value of the constant Cε1 in the modeled dissipation rate equation, which was substantially lower than its traditional value. However, recently a correction has been made in the RNG-based calculation of Cε1. It is shown herein that, with the new value of Cε1, the performance of the RNG K-ε model is substantially improved. On the other hand, while the predictions of the revised RNG second-order closure model are better, some lingering problems still remain that can be remedied by the addition of higher-order terms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.857963
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  • 14
    Electronic Resource
    Electronic Resource
    On testing models for the pressure–strain correlation of turbulence using direct simulations (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2887-2899 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Direct simulations of homogeneous turbulence have, in recent years, come into widespread use for the evaluation of models for the pressure–strain correlation of turbulence. While work in this area has been beneficial, the increasingly common practice of testing the slow and rapid parts of these models separately in uniformly strained turbulent flows is shown in this paper to be unsound. For such flows, the decomposition of models for the total pressure–strain correlation into slow and rapid parts is ambiguous. Consequently, when tested in this manner, misleading conclusions can be drawn about the performance of pressure–strain models. This point is amplified by illustrative calculations of homogeneous shear flow where other pitfalls in the evaluation of models are also uncovered. More meaningful measures for testing the performance of pressure–strain models in uniformly strained turbulent flows are proposed and the implications for turbulence modeling are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858342
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  • 15
    Electronic Resource
    Electronic Resource
    The structure of variable property, compressible mixing layers in binary gas mixtures (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 8 (1996), S. 1945-1953 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present the results of a study of the structure of a parallel compressible mixing layer in a binary mixture of gases. The gases included in this study are hydrogen (H2), helium (He), nitrogen (N2), oxygen (O2), neon (Ne) and argon (Ar). Profiles of the variation of the Lewis and Prandtl numbers across the mixing layer for all 30 combinations of gases are given. It is shown that the Lewis number can vary by as much as a factor of 8 and the Prandtl number by a factor of 2 across the mixing layer. Thus assuming constant values for the Lewis and Prandtl numbers of a binary gas mixture in the shear layer, as is done in many theoretical studies, is a poor approximation. We also present profiles of the velocity, mass fraction, temperature and density for representative binary gas mixtures at zero and supersonic Mach numbers. We show that the shape of these profiles is strongly dependent on which gases are in the mixture as well as on whether the denser gas is in the fast stream or the slow stream. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869103
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  • 16
    Electronic Resource
    Electronic Resource
    The influence of end-plate potential control on magnetohydrodynamic normal modes and stability in mirror machines (1987)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 30 (1987), S. 1564-1566 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By adjusting the electrostatic potential on the end plates of a mirror plasma, the plasma's magnetohydrodynamic (MHD) stability can be altered. Furthermore, the plasma's MHD response to low-frequency modulation of the end plates can be used to pump unwanted ions that collect in a thermal barrier. Here, precise boundary conditions are derived for the MHD equations of motion to model an end plate separated from the plasma by a sheath.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.866219
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  • 17
    Electronic Resource
    Electronic Resource
    Optical and magneto-optical constants of Pr substituted TbFeCo films : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7087-7089 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optimization of tri- or quadrilayer magneto-optic recording media requires knowledge of the optical and/or magneto-optical constants for all of the individual active or passive layers that together comprise the complete disk structure. The optical (n+ik) and first-order magneto-optical (Q1+iQ2) constants for two series (i) (Tb23Fe72.5Co4.5)100−xPrx, (ii) (Tb27Fe65Co8)100−xPrx of Pr substituted TbFeCo films, for which x varies between 0 and 30, have been determined by a combination of ellipsometry and Kerr polarimetry. Ellipsometry has also been used to determine independently the optical constants of the optimized SiN passivation layers developed to protect these samples. Using constants determined experimentally on thick samples, the variation of the polar Kerr rotation and ellipticity as a function of magnetic film thickness has been calculated for light incident from both the air and substrate side of a typical trilayer magneto-optic disk structure in which material from the above series, the magnetic and thermomagnetic properties of which have been previously reported [Carey et al., J. Magn. Magn. Mater. (to be published)], forms the active storage layer. The agreement obtained with measurements demonstrates the self-consistency of the modeling process and the validity of the determined constants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356737
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  • 18
    Electronic Resource
    Electronic Resource
    Compositional dependence of the structural and magnetic properties of PtMnSb films : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7081-7083 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nonstoichiometric, Pt deficient, PtMnSb films have been investigated for evidence of the increase in coercivity suggested by the work of Marinero [Appl. Surf. Sci. 43, 117 (1989)]. Structural, magnetic, and magneto-optic properties of thin PtMnSb films of different compositions annealed in under 30 s using a rapid thermal processing (RTP) system [Carey et al., IEEE Meeting on Current Topics in Applied Magnetism, Keele University, 4 November 1992 (unpublished), Paper 15; J. Magn. Soc. Jpn. 17, 290 (1993)], have been determined. It is shown that the crystalline texture of the films can be controlled by adjustments in composition and RTP time and that Pt deficiency produces increases in coercivity. The production of coercivity does not correlate with the marked changes in texture but appears to be associated with the development of MnSb phases within the PtMnSb microstructure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356735
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  • 19
    Electronic Resource
    Electronic Resource
    Neural network models of potential energy surfaces (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 4129-4137 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Neural networks provide an efficient, general interpolation method for nonlinear functions of several variables. This paper describes the use of feed-forward neural networks to model global properties of potential energy surfaces from information available at a limited number of configurations. As an initial demonstration of the method, several fits are made to data derived from an empirical potential model of CO adsorbed on Ni(111). The data are error-free and geometries are selected from uniform grids of two and three dimensions. The neural network model predicts the potential to within a few hundredths of a kcal/mole at arbitrary geometries. The accuracy and efficiency of the neural network in practical calculations are demonstrated in quantum transition state theory rate calculations for surface diffusion of CO/Ni(111) using a Monte Carlo/path integral method. The network model is much faster to evaluate than the original potential from which it is derived. As a more complex test of the method, the interaction potential of H2 with the Si(100)-2×1 surface is determined as a function of 12 degrees of freedom from energies calculated with the local density functional method at 750 geometries. The training examples are not uniformly spaced and they depend weakly on variables not included in the fit. The neural net model predicts the potential at geometries outside the training set with a mean absolute deviation of 2.1 kcal/mole. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469597
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  • 20
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    Crossover to potential energy landscape dominated dynamics in a model glass-forming liquid (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 9834-9840 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An equilibrated model glass-forming liquid is studied by mapping successive configurations produced by molecular dynamics simulation onto a time series of inherent structures (local minima in the potential energy). Using this "inherent dynamics" approach we find direct numerical evidence for the long held view that below a crossover temperature, Tx, the liquid's dynamics can be separated into (i) vibrations around inherent structures and (ii) transitions between inherent structures [M. Goldstein, J. Chem. Phys. 51, 3728 (1969)], i.e., the dynamics become "dominated" by the potential energy landscape. In agreement with previous proposals, we find that Tx is within the vicinity of the mode-coupling critical temperature Tc. We further find that near Tx, transitions between inherent structures occur via cooperative, stringlike rearrangements of groups of particles moving distances substantially smaller than the average interparticle distance. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481621
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