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  • 1
    Electronic Resource
    Electronic Resource
    An efficient parallel algorithm for shortest paths in planar layered digraphs (1995)
    Springer
    Algorithmica 14 (1995), S. 322-339 
    Details
    ISSN: 1432-0541
    Keywords: Parallel algorithms ; Shortest paths ; Planar separators
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Computing shortest paths in a directed graph has received considerable attention in the sequential RAM model of computation. However, developing a polylog-time parallel algorithm that is close to the sequential optimal in terms of the total work done remains an elusive goal. We present a first step in this direction by giving efficient parallel algorithms for shortest paths in planar layered digraphs. We show that these graphs admit special kinds of separators calledone- way separators which allow the paths in the graph to cross it only once. We use these separators to give divide- and -conquer solutions to the problem of finding the shortest paths between any two vertices. We first give a simple algorithm that works in the CREW model and computes the shortest path between any two vertices in ann-node planar layered digraph in timeO(log2 n) usingn/logn processors. We then use results of Aggarwal and Park [1] and Atallah [4] to improve the time bound toO(log2 n) in the CREW model andO(logn log logn) in the CREW model. The processor bounds still remain asn/logn for the CREW model andn/log logn for the CRCW model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294130
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  • 2
    Electronic Resource
    Electronic Resource
    A Fully Dynamic Approximation Scheme for Shortest Paths in Planar Graphs (1998)
    Springer
    Algorithmica 22 (1998), S. 235-249 
    Details
    ISSN: 1432-0541
    Keywords: Key words. Dynamic algorithm, Graph algorithm, Shortest path, Minimum-cost path, Planar graph.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. In this paper we give a fully dynamic approximation scheme for maintaining all-pairs shortest paths in planar networks. Given an error parameter $\epsilon$ such that $0〈\epsilon$ , our algorithm maintains approximate all-pairs shortest paths in an undirected planar graph G with nonnegative edge lengths. The approximate paths are guaranteed to be accurate to within a 1+ $\epsilon$ factor. The time bounds for both query and update for our algorithm is O( \epsilon -1 n 2/3 log 2 n log D) , where n is the number of nodes in G and D is the sum of its edge lengths. The time bound for the queries is worst case, while that for the additions is amortized. Our approximation algorithm is based upon a novel technique for approximately representing all-pairs shortest paths among a selected subset of the nodes by a sparse substitute graph.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00009223
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  • 3
    Electronic Resource
    Electronic Resource
    Photoreflectance and photoluminescence spectroscopy of low-temperature GaAs grown by molecular-beam epitaxy (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 427-432 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoreflectance (PR) and photoluminescence (PL) measurements have been carried out on low-temperature GaAs (LT GaAs) and LT-GaAs/AlGaAs modulation-doped photodetector (MODPD) structures grown by molecular-beam epitaxy. Samples with LT GaAs grown at 350 °C show several PL lines associated with (i) transitions involving two-dimensional electron gas in LT GaAs near the interface, (ii) band-edge transitions in the bulk LT GaAs, and (iii) transitions involving deep level defect complexes in LT GaAs. In addition a PL emission band at 1.65 eV observed in all the MODPD structures is attributed to a crossover transition at the LT-GaAs/AlGaAs interface. PR spectra of these modulation-doped structures show Franz–Keldysh oscillations which are attributed to high electric fields ((approximately-greater-than)105 V/cm) at the LT-GaAs/AlGaAs interface. PR measurements on bare LT-GaAs layers suggest that the E0 transition in LT GaAs is about 20 meV above that of the normal GaAs E0 gap. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360848
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  • 4
    Electronic Resource
    Electronic Resource
    Photoluminescence from modulation doped AlGaAs/ low-temperature molecular beam epitaxy-grown GaAs heterostructures (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1210-1213 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence (PL) results from a novel modulation doped AlGaAs/ low-temperature molecular beam epitaxially-grown-GaAs (LT-GaAs MODFET) heterostructure are reported. A new PL line at 1.65 eV is consistently observed in all the LT-GaAs MODFET structures investigated. A spatially indirect transition from a two-dimensional electron gas at the heterojunction interface to the holes in AlGaAs is believed to be responsible for the observed 1.65 eV PL line. LT-GaAs MODFET structures in which LT-GaAs region is grown at 350 °C show additional lines lying in the band edge region as well as deep inside the band gap region of LT-GaAs. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360359
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  • 5
    Electronic Resource
    Electronic Resource
    Oxidation state and superconducting properties of Y1−xPrxSr2Cu2.85Re0.15O7+δ (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 6884-6887 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Superconductivity exists in orthorhombic Y1−xPrxSr2Cu2.85Re0.15O7+δ up to a critical concentration (xcr) of 0.65. A progressive decrease in Tc occurs as x increases from 0 to 0.65. A further increase in x leads to a tetragonal transformation and as a consequence the Tc vanishes; however, the orthorhombicity of these Sr-based compounds is much lower than that observed for the Ba analog, Y1−xPrxBa2Cu3O7−δ and, hence, the Tc. On the one hand, crystal chemistry correlations indicate that the Pr ion is in trivalent state while on the other hand, the stabilizing cation, viz., Re, is in hexavalent state which accounts for the excess oxygen (〉7.0) in the system. The high xcr value of the Sr series compared to the Ba series (xcr=0.55) is attributed to the much reduced orbital overlap of the trivalent Pr(4f ) state with the Cu(3dx2−y2)–O(2p) conduction band, via hole localization and/or pair breaking, and is not due to the much discussed hole filling by tetravalent Pr. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363758
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  • 6
    Electronic Resource
    Electronic Resource
    Analysis and classification of reaction-driven stationary convective patterns in a porous medium (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 9 (1997), S. 1674-1695 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A two-dimensional model consisting of continuity, momentum, species, and energy balances is considered to analyze the convective patterns that arise due to exothermic reactions occurring in a porous medium. First, the one-dimensional conduction states of the system are classified using singularity theory and the shooting technique. It is observed that there can be either one or three conduction states when the reacting fluid is a gas. Next, we use linear stability analysis to determine the boundary of the parameter values at which the conduction state loses stability leading to convective flows. Pure and mixed-mode convective solutions are then analyzed using local bifurcation theory. The formulas to evaluate the coefficients appearing in the amplitude equations are developed and used to obtain the classification (phase) diagram of the convective flows in the parameter space. The classification is presented in the unique conduction solution region in the presence and absence of mode interactions. The phase diagrams are used to identify the region of parameter values where convection has a detrimental effect on the stability of the system. It is found that the Lewis number (Le), which represents the ratio of thermal to mass diffusivity, has a profound influence on the stability boundaries. For Le〉1, the convective solutions may bifurcate subcritically and introduce an ignition point. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869287
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  • 7
    Electronic Resource
    Electronic Resource
    A low cost remotely operable cutting machine for segmenting metal clad ceramic fuel pellets (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1618-1619 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Cutting of irradiated zircaloy metal clad ceramic fuel pellets requires a special cutting saw that can be remotely operated. The remote operation is essential because of the pyrophoric nature of zircaloy metal and high radiation field associated with the irradiated fuel elements. Conventional saws cannot meet the operational requirements because these are not readily amenable for remote operation and maintenance. Hence we have developed a new laboratory scale cutting saw for cutting radioactive samples remotely. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1147936
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  • 8
    Electronic Resource
    Electronic Resource
    Stabilization of a superconducting TbSr2Cu2.85Re0.15O7+δ compound and the valence state of terbium (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2711-2713 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A single-phase Sr-based Tb-123 phase has been synthesized by chemical stabilization. TbSr2Cu2.85Re0.15O7+δ exhibits superconductivity at Tc,zero=22 K. X-ray diffraction results suggest a relatively small orthorhombicity and neutron diffraction studies indicate an excess oxygen content (≥7.2) in the sample. Tb is present as a trivalent ion in the superconducting phase as derived from x-ray photoelectron spectroscopy. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114301
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  • 9
    Electronic Resource
    Electronic Resource
    Lattice engineered compliant substrate for defect-free heteroepitaxial growth (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 1685-1687 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Presented here is proof-of-principle that a thin single crystal semiconductor film—when twist-wafer bonded to a bulk single crystal substrate (of the same material)—will comply to the lattice constant of a different single crystal semiconductor thick film grown on its surface. In our experiment, a 100 Å film of GaAs was wafer bonded to a GaAs bulk substrate, with a large twist angle between their 〈110〉 directions. The resultant twist boundary ensures high flexibility in the thin film. Dislocation-free films of In0.35Ga0.65P(∼1% strain) were grown with thicknesses of 3000 Å, thirty times the Matthews–Blakeslee critical thickness, on twist-wafer-bonded films of GaAs. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118669
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  • 10
    Electronic Resource
    Electronic Resource
    Band-edge photoluminescence from pseudomorphic Si0.96Sn0.04 alloy (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 3105-3107 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Band-edge related photoluminescence from a strained Si0.96Sn0.04 alloy grown by molecular beam epitaxy on Si(100) substrate has been seen for the first time. We report band-edge related photoluminescence from a compressively strained pseudomorphic Si0.96Sn0.04 alloy. The luminescence observed consisted of two dominant features, a well-resolved band-edge luminescence consisting of a no-phonon and a transverse optical phonon replica, and a deep-level broad luminescence peak around 770 meV. The band-edge feature is attributed to a no-phonon free excitonic recombination in the binary alloy and exhibits a near linear power dependence. We also observe a red shift of the energy gap of Si0.96Sn0.04 alloy with respect to Si, which corresponds to the bulk alloy effect. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.116437
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