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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 569-573 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The wavelength of semiconductor lasers generally increases with increased output power due to changes in laser gain with current and temperature. Time-resolved studies of the optical spectrum during the write-pulse train clearly depicted the quasirandom mode hopping that occurred. In optically dispersive systems, the wavelength shifts caused significant write-spot displacements down at the recording surface and affected mark lengths. Thermal modeling studies successfully duplicated the salient features of this effect and provided explanations for some of the experimental observations.
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  • 2
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Measured length variations of laser written marks in rare earth–transition metal (RE-TM) optical data storage media were found to be a strong function of test conditions. In particular, the mark length standard deviation was found to be inversely proportional to the difference between the threshold and bias power levels. Differences in mark length variabilities of various RE-TM compositions written with the same bias power were found to be attributable to their differing marking thresholds.
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  • 3
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This communication provides a detailed examination of the morphology of thin films of CuInSe2 prepared by chemical spray pyrolysis on borosilicate glass, molybdenum-coated glass, and CdS substrates. The latter two are used in thin-film heterojunction solar cells of CuInSe2/CdS in the backwall and reverse backwall (RBW) configurations, respectively, and hence are of great technological interest. The pseudoepitaxial growth of CIS on CdS and its low deposition temperature (250 °C) which inhibits interdiffusion suggest that one should prepare CuInSe2/CdS solar cells in the RBW configuration.
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 1825-1828 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The bifurcated structure of the water dimer has been the subject of considerable uncertainty with respect to its vibrational characterization. We have considered this question at the self-consistent-field (SCF) level of theory using finite basis sets that allow a close approach to the Hartree–Fock limit. As one approaches the Hartree–Fock limit, the bifurcated structure is predicted to be a true transition state, with one imaginary vibrational frequency, ω12(B2)∼200i cm−1.
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  • 5
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High levels of ab initio molecular orbital theory were used to examine rearrangement processes in the water dimer corresponding to the interchange of various hydrogen atoms. Our most reliable calculations involve MP4/6-311+G(2df,2p) energy evaluations at MP2/6-311+G(d,p) optimized structures. The lowest energy rearrangement pathway corresponds to the interchange of hydrogen atoms of the acceptor molecule within the Cs water dimer structure (1). This proceeds via a transition structure of C1 symmetry (2) and requires an energy of 0.59 kcal mol−1. The interchange of donor and acceptor molecules can be achieved via a transition structure with Ci symmetry (4) and requires an energy of 0.87 kcal mol−1. Finally, the interchange of hydrogen atoms of the donor molecule, via a C2v transition structure (9), requires 1.88 kcal mol−1. The rearrangements via 2 and 4 lead to complete scrambling of hydrogen atoms within the individual H2O moieties at a cost of 0.87 kcal mol−1; the transition structure 9 is not necessary for this process. The implications of these results with regard to the interpretation of spectroscopic data on the water dimer will be of interest.
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 3612-3616 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new united-atom force field is proposed for α-olefins. The proposed force field is used to study vapor–liquid equilibria for pure components and binary mixtures. Results of phase equilibria simulations are found to be in good agreement with available experimental data. © 2001 American Institute of Physics.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 2008-2013 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Studies of direct numerical simulations of incompressible, homogeneous, and inhomogeneous turbulence indicate that, in regions of high kinetic energy dissipation rate, the geometry of the local velocity gradient field has a universal character. The velocity gradient tensor satisfies the nonlinear evolution equation (dAij/dt)+AikAkj−1/3 (AmnAnm)δij=Hij where Aij=∂ui/∂xj and the tensor Hij contains terms involving the action of cross derivatives of the pressure field and viscous diffusion of Aij. The restricted Euler equation corresponding to Hij=0 can be solved in closed form [Cantwell, Phys. Fluids A 4, 782 (1992)] and the solution has the property that, for any initial condition, Aij(t) evolves to an asymptotic state of the form Aij(t)(approximately-equal-to)Kij[R(t)]1/3 where R(t) is a function which becomes singular in a finite time and Kij is a constant matrix. A number of the universal features of fine-scale motions observed in direct numerical simulations are reproduced by Kij.In the simulation studies the first invariant of Aij is zero by incompressibility. The second and third invariants, Q and R, are determined at every grid point in the flow and the entire data set is cross-plotted to search for significant features in the space of tensor invariants. Such features can then be associated with corresponding local flow structures in physical space. When a variety of incompressible simulations are studied, scatter plots of Q vs R reveal that a fairly significant fraction of the data lies in the lower right quadrant. This is consistent with behavior predicted by the restricted Euler solution. However, the bulk of the data lies more or less uniformly distributed in a slightly elliptical region about the origin. In a direct numerical simulation of a plane, time-developing, mixing layer a small fraction of the data collects along a very pronounced, nearly straight, ridgeline extending into the upper left quadrant. This data can be traced to regions with local vorticity much larger than the local strain lying within streamwise rib vortices which connect adjacent spanwise rollers in the mixing layer simulation. Neither the predominant tendency for Q and R to lie near the origin nor the possibility for Q and R to lie far from the origin in the upper left quadrant are predicted by the restricted Euler solution. The purpose of this paper is to show that, by relaxing the assumption Hij=0 while retaining a model of dAij/dt motivated by the asymptotic form of the restricted Euler solution, one can begin to account for these features of the (Q,R) scatter plots. The results suggest that the velocity gradient tensor in three-dimensional flow tends to evolve toward an attractor in the space of tensor invariants. A significant feature of the model is that, although Hij≠0, singular behavior of Aij(t) can still occur along specific paths in the (Q,R) plane corresponding to zero values of the discriminant of Hij.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 12 (2000), S. 1005-1015 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The equilibria and stability of fixed contact line dual liquid bridges are considered. The dual liquid bridges considered consist of two fixed length single bridges joined by an open channel so that both bridges are in pressure equilibrium. The system is simplified by requiring all bounds to be of equal radius, and also by neglecting gravity or other applied forces. The dual liquid bridge is found to be generally more stable than a single bridge of equal length in the fixed pressure case, but less stable in the fixed volume case. The maximum length of dual liquid bridge in the fixed pressure case is double that for a single bridge, 7.4547 times the radius. In the fixed volume case, a rupture of the stability envelope leads to ranges of boundary conditions for which there are no stable dual liquid bridges of any volume. One exception to fixed volume destabilization is the cylindrical dual bridge. The maximum length attainable for a cylinder is 8.9868 times the radius, which not coincidentally is also the secondary stability limit for a single fixed volume cylinder (beyond the classical limit of 2π times the radius). The results suggest that any application which pumps fluid through a series of cylindrical liquid bridges would be most favorable using a dual liquid bridge with pressure-constrained pumping. © 2000 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 12 (2000), S. 996-1004 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Attempts to stabilize the fixed contact line cylindrical liquid bridge have generally implicitly assumed that it was related to stable equilibria in a continuous manner. An examination of the branch structure of equilibria demonstrates that for longer liquid bridges, the cylinder becomes separate from normally stable equilibria and hence likely cannot be stabilized by a continuous perturbation. All axisymmetric equilibria for a fixed contact line liquid bridge of fixed moderate length in the absence of applied forces (zero gravity, no spin) are found to lie on a single semi-infinite bridged double helix. This helix breaks repeatedly as the length of the liquid bridge is increased, separating the stable truncated sphere state from the generally desirable cylindrical state. This structural change appears to explain why several approaches to stabilization of long cylindrical liquid bridges beyond the classical Plateau–Rayleigh limit have been largely unsuccessful over the past few decades. The first breakage of the helix, when liquid bridge length equals 9.0973 times radius, corresponds roughly to the maximum length of cylindrical liquid bridge achieved experimentally via a perturbative applied force (using acoustic radiation pressure). An examination of the deformations of the helix under gravity reveals that for moderate length liquid bridges at small Bond number, all axisymmetric equilibria lie on a single unbroken branch which forms a single (unbridged) semi-infinite double helix. Combined effects of gravity and length are investigated as well, resulting in multiple disconnected loops of equilibria. © 2000 American Institute of Physics.
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  • 10
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ions of the terrestrial magnetosheath are typically observed to have bi-Maxwellian velocity distributions with T⊥(approximately-greater-than)T(parallel), where ⊥ and (parallel) denote directions perpendicular and parallel to the background magnetic field. Observations of the highly compressed magnetosheath have demonstrated an inverse correlation between the proton temperature anisotropy and the proton parallel β. Hybrid computer simulations have shown that wave–particle scattering by the proton cyclotron anisotropy instability can yield similar correlations between these two parameters. Although these correlations are due to nonlinear plasma processes, they correspond to a threshold of this instability that can be determined from linear Vlasov theory. This proton anisotropy/β correlation represents a limited closure relation for anisotropic magnetohydrodynamic plasma models.
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