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  • 2010-2014  (105)
  • 1990-1994  (69)
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  • 1
    Electronic Resource
    Electronic Resource
    n-CdSe/p-ZnTe based wide band-gap light emitters: Numerical simulation and design (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 4660-4668 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The only II-VI/II-VI wide band-gap heterojunction to provide both good lattice match and p- and n-type dopability is CdSe/ZnTe. We have carried out numerical simulations of several light emitter designs incorporating CdSe, ZnTe, and Mg alloys. In the simulations, Poisson's equation is solved in conjunction with the hole and electron current and continuity equations. Radiative and nonradiative recombination in bulk material and at interfaces are included in the model. Simulation results show that an n-CdSe/p-ZnTe heterostructure is unfavorable for efficient wide band-gap light emission due to recombination in the CdSe and at the CdSe/ZnTe interface. An n-CdSe/MgxCd1−xSe/p-ZnTe heterostructure significantly reduces interfacial recombination and facilitates electron injection into the p-ZnTe layer. The addition of a MgyZn1−yTe electron confining layer further improves the efficiency of light emission. Finally, an n-CdSe/MgxCd1−xSe/MgyZn1−yTe/p-ZnTe design allows tunability of the wavelength of light emission from green into the blue wavelength regime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352761
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  • 2
    Electronic Resource
    Electronic Resource
    Stable single mode hybrid laser with high power and narrow linewidth (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 2634-2636 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe hybrid lasers combining a semiconductor gain section and fiber cavity with integrated chirped Bragg reflector. These devices have produced output powers of 27.5 mW in a narrow linewidth (400 KHz) stable single longitudinal mode. The use of a chirped reflector to stabilize the single mode output, and correct grating orientation are described. The laser output has a side-mode suppression ratio of over 55 dB at 27.5 mW output, and relative intensity noise (RIN) below 160 dB/Hz.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111475
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  • 3
    Electronic Resource
    Electronic Resource
    X-ray photoelectron spectroscopy measurement of valence-band offsets for Mg-based semiconductor compounds (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 3455-3457 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have used x-ray photoelectron spectroscopy to measure the valence-band offsets for the lattice matched MgSe/Cd0.54Zn0.46Se and MgTe/Cd0.88Zn0.12Te heterojunctions grown by molecular beam epitaxy. By measuring core level to valence-band maxima and core level to core level binding energy separations, we obtain values of 0.56±0.07 eV and 0.43±0.11 eV for the valence-band offsets of MgSe/Cd0.54Zn0.46Se and MgTe/Cd0.88Zn0.12Te, respectively. Both of these values deviate from the common anion rule, as may be expected given the unoccupied cation d orbitals in Mg. Application of our results to the design of current II-VI wide band-gap light emitters is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111239
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  • 4
    Electronic Resource
    Electronic Resource
    Proposal and verification of a new visible light emitter based on wide band gap II-VI semiconductors (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 1962-1964 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We propose a new device structure for obtaining visible light emission from wide band gap semiconductors. This heterojunction structure avoids ohmic contacting problems by using only the doping types which tend to occur naturally in II-VI semiconductors, while using a novel injection scheme to obtain efficient minority carrier injection into the wider band gap semiconductor. To verify this proposal we have fabricated green light emitting structures using n-CdSe and p-ZnTe regions separated by a graded MgxCd1−xSe injection region. Room temperature electroluminescence spectra from these devices demonstrate the effectiveness of the injection scheme, while the current-voltage characteristics show the merits of avoiding difficult ohmic contacts. We further show how the structure can be extended to blue wavelengths and beyond by opening up the band gap of the ZnTe recombination region with a MgyZn1−yTe alloy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108353
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of current profile shape on second region access in high-beta tokamak plasmas (1990)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 973-977 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of current density distribution in tokamak plasmas is examined on the access to the second stability regime of high-n ballooning modes. The main factor in determining access to the second stability regime is to lower shear sufficiently on each flux surface. This is achieved by broadening the current profile. A general method of finding equilibria with access to the second region of stability is presented. The value of on-axis safety factor q0 is found not to be a good measure of the type of profile required for second region access.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859243
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  • 6
    Electronic Resource
    Electronic Resource
    Magnetohydrodynamic stability studies of supershot plasmas (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 3267-3275 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Slowly growing magnetohydrodynamic (MHD) instabilities are usually detected experimentally in supershot plasmas in the Tokamak Fusion Test Reactor [in Plasma Physics and Controlled Nuclear Fusion Research 1986, Kyoto (International Atomic Energy Agency, Vienna, 1987), Vol. 1, p. 75] (TFTR). These instabilities, when they occur, result in deterioration of the confinement and limit the attainable β. Using initial profile data from transport analysis of specific high β supershot plasmas, the predictions of the single fluid, linear MHD stability model are studied and compared with the experimental observations. It is shown that, in the highest β plasmas achieved, the pressure gradients in the interior are such that the absence of the 1/1 mode is difficult to reconcile with the single fluid MHD model if the safety factor, q〈1. On the assumption that q exceeds unity everywhere, it is found that supershot plasmas are predicted to be unstable or near marginal to small toroidal mode number, pressure-driven instabilities of the ballooning variety. When finite plasma resistivity is included in the analysis the range of parameters over which these instabilities are excited is significantly extended.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860663
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  • 7
    Electronic Resource
    Electronic Resource
    Ion cyclotron range of frequencies stabilization of sawteeth on Tokamak Fusion Test Reactor (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 2155-2164 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Results obtained from experiments utilizing high-power ion cyclotron range of frequencies (ICRF) heating to stabilize sawtooth oscillations on Tokamak Fusion Test Reactor (TFTR) [Hawryluk et al., Plasma Phys. Controlled Fusion 33, 1509 (1991)] are reviewed. The key observations include existence of a minimum ICRF power required to achieve stabilization, a dependence of the stabilization threshold on the relative size of the ICRF power deposition profile to the q=1 volume, and a peaking of the equilibrium pressure and current profiles during sawtooth-free phases of the discharges. In addition, preliminary measurements of the poloidal magnetic field profile indicate that q on axis decreases to a value of 0.55±0.15 after a sawtooth-stabilized period of ∼0.5 sec has transpired. The results are discussed in the context of theory, which suggests that the fast ions produced by the ICRF heating suppress sawteeth by stabilizing the m=1 magnetohydrodynamic (MHD) instabilities believed to be the trigger for the sawtooth oscillations. Though qualitative agreement is found between the observations and the theory, further refinement of the theory coupled with more accurate measurements of experimental profiles will be required in order to complete quantitative comparisons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860484
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  • 8
    Electronic Resource
    Electronic Resource
    4-Thiazolidinones, Potent Antioxidants, as Antiinflammatory Agents (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 696 (1993), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1993.tb17182.x
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of Li/MgO methane coupling catalyst on alonized steel reactors (1992)
    Springer
    Catalysis letters 13 (1992), S. 157-174 
    Details
    ISSN: 1572-879X
    Keywords: Alonized ; coupling ; lithium ; stainless steel ; corrosion ; methane ; reactor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Alonized 316 stainless steel reactors were used in life tests of a Li/MgO methane coupling catalyst. Severe corrosion of the portion of the reactor in contact with the catalyst bed was observed. Loss of physical integrity and chemical passivity resulted from layer formations of differing elemental compositions from the bulk metal. Chromium was leached from the stainless steel alloy and deposited on the catalyst. There were no adverse changes in those portions of the reactor not in direct contact with the catalyst. These results demonstrate that Alonized 316 stainless steel is unsuitable for use in methane coupling service with this lithium-containing catalyst.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00770988
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  • 10
    Electronic Resource
    Electronic Resource
    Microstructure and properties of polyester/urethane acrylate thermosetting blends, and their use as composite matrices (1993)
    Springer
    Journal of materials science 28 (1993), S. 3116-3124 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Thermosetting blends of a rigid polyester (PE) and a poly(urethane acrylate) elastomer (UA) have been investigated over a wide range of compositions in the cast condition, and in use as matrices of unidirectional glass-fibre composites. Transmission electron microscopy showed that blends in the composition range 20%–60% UA have a two-phase structure, probably with a phase inversion from PE-rich to UA-rich matrix between 40% and 50% UA. It was found that the observed variation in Young's modulus with blend composition could be represented by a simple geometrical model based on series/parallel combination of phases with a regular dispersion. This analysis provided supporting evidence for the proposed phase structures of the blends. Further evidence as to the phase structures was the rapid decline in indentation hardness and in temperature of distortion under load which occurred between 40% and 50% UA. Blends with up to 15% UA were found to have higher tensile strength, and slightly higher failure strain, than the unblended polyester. For composites with PE-rich matrices, the transverse Young's modulus exceeded that of the matrix in bulk, and it was found that the relationship could be expressed approximately by a version of the series/parallel model referred to above. Transverse tensile strengths of the composites were, in all cases, lower than the bulk matrix strength. To account for the observed relationship, a modified version of the Cooper and Kelly model for transverse strength is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00354718
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