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  • 2000-2004  (95)
  • 1995-1999  (90)
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  • 1
    ISSN: 1573-4889
    Keywords: modeling ; numerical techniques ; finite-difference methods ; diffusion ; moving boundary problem ; steam oxidation ; Zircaloy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Numerical solutions of the oxygen-diffusion problem arising in the oxidation of metals at high temperatures are complicated by the change in density as the oxide is formed and the occurrence of moving boundaries separating the different phases. The former complication is resolved by a transformation of the dependent variable and the coordinate, which reduces the problem to a form identical to one without density change. The latter complication is dealt with by demonstrating an analogy with the Stefan problem in heat transfer with phase change in the enthalpy formulation, for which abundant numerical works exist. A finite-difference code is written to solve the resulting equations. It is successfully applied to simulate an oxidation experiment of Zircaloy by steam at 1600°C.
    Type of Medium: Electronic Resource
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  • 2
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    In:  Zoologische Verhandelingen vol. 327, pp. 61-74
    Publication Date: 2024-01-12
    Description: The megapode hatchling receives no care or guidance from its parents and so must be able to survive by itself. This raises some basic questions about the innate abilities of megapode hatchlings, including the possibility of predator recognition. Experiments were conducted to investigate the visual predator recognition abilities of the hatchlings of the Australian brush-turkey Alectura lathami J.E. Gray, 1831. Two separate methods involving video images and actual stimuli were used. There were no significant differences between the behaviours observed before compared to after the presentation of each stimulus, whether it was predator or non-predator, moving or non-moving. The hatchlings did not respond with any escape or avoidance behaviours when presented with predator stimuli. Although there are a number of potential explanations for these results, it is most likely that the responses observed were genuine, indicating that brush-turkey hatchlings do not instinctively flee in response to the visual presence or movement of a predator. In the wild, they may adopt the strategy of freezing, as do hatchlings of the malleefowl Leipoa ocellata Gould, 1840. However, high mortality rates indicate this strategy is not very successful and their survival to sub-adult stage may be largely dependent on chance.
    Keywords: Megapodiidae ; megapode ; Australian brush-turkey ; Alectura lathami ; predator recognition ; anti-predator behaviour
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 71 (2000), S. 666-668 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A conventional zero-dimensional (uniform plasma parameters with no spatial variations) fluid model will provide a good match with an experimental electron cyclotron resonance ion source (ECRIS) charge-state distribution (CSD) if provided with a judicious set of user inputs. However, this arbitrarily chosen set of inputs is not necessarily unique. To be truly predictive, an ECRIS model should rely on experimental parameters as inputs. A multi-species model for an ECRIS plasma using experimental parameters as inputs is under development. The model eliminates electron temperature as a user input by employing a 2 V(v,θ) Fokker–Planck code with an ECR heating term to calculate the non-Maxwellian anisotropic electron distribution function. Further arbitrary user inputs are eliminated in favor of controlled parameters by bounce averaging the Fokker–Planck coefficients for a one-dimensional (1D)/2 V axial model. The neutral gas modeling has been extended to 1D using axially coupled particle balance equations. The improved model is able to reproduce experimental Faraday cup (CSDA) from the Argonne National Laboratory's ECR-II. Further elimination of arbitrary inputs is expected when the ion model is extended to 1D. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6826-6833 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Interdiffusion in InGaAs/InP quantum wells has been studied using magneto-optical transmission spectroscopy. The effects of dopants in the substrates and quantum wells, overgrowth and annealing processes have been investigated, providing useful information on the interdiffusion effects in typical growth and fabrication processes. The blue shift effect which is often observed in multiple quantum well (MQW) structures subjected to heat treatment, is attributed to a dominant group V interdiffusion which can be suppressed by high defect densities in the substrate. The presence of Zn-dopants in an overgrown layer on top of the MQW structures causes a counteractive redshift effect after long annealing times due to group III diffusion, but in situ Zn- or S-dopants produce no observable shift in transition energies due to interdiffusion. This is attributed to enhanced group III interdiffusion induced by Zn diffusion into the MQWs. We conclude that there are very different interdiffusion mechanisms for group III and group V elements and support the recent suggestion of vacancy-related group V interdiffusion in contrast to the interstitialcy mechanism for the group III interdiffusion. © 1996 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 4294-4296 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report experimental results on monolithic stable-resonator semiconductor lasers. Curved end mirrors defining a near-concentric stable resonator were fabricated on wide-stripe GaAs/AlGaAs GRINSCH-SQW lasers using reactive-ion-etching. These lasers oscillate in close to the expected lowest-order Gaussian stable-resonator modes at threshold, evolving into a coherent superposition of higher-order modes as the pump current is increased up to two to three times threshold. At higher pump currents nonlinear defocusing effects cause the resonators to become geometrically unstable so that the lateral modes are determined by both the resonator geometry and the saturated gain and index profile. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Sustained stabilization of the n=1 kink mode by plasma rotation at beta approaching twice the stability limit calculated without a wall has been achieved in DIII-D by a combination of error field reduction and sufficient rotation drive. Previous experiments have transiently exceeded the no-wall beta limit. However, demonstration of sustained rotational stabilization has remained elusive because the rotation has been found to decay whenever the plasma is wall stabilized. Recent theory [Boozer, Phys. Rev. Lett. 86, 5059 (2001)] predicts a resonant response to error fields in a plasma approaching marginal stability to a low-n kink mode. Enhancement of magnetic nonaxisymmetry in the plasma leads to strong damping of the toroidal rotation, precisely in the high-beta regime where it is needed for stabilization. This resonant response, or "error field amplification" is demonstrated in DIII-D experiments: applied n=1 radial fields cause enhanced plasma response and strong rotation damping at beta above the no wall limit but have little effect at lower beta. The discovery of an error field amplification has led to sustained operation above the no-wall limit through improved magnetic field symmetrization using an external coil set. The required symmetrization is determined both by optimizing the external currents with respect to the plasma rotation and by use of feedback to detect and minimize the plasma response to nonaxisymmetric fields as beta increases. Ideal stability analysis and rotation braking experiments at different beta values show that beta is maintained 50% higher than the no wall stability limit for durations greater than 1 s, and approaches beta twice the no-wall limit in several cases, with steady-state rotation levels. The results suggest that improved magnetic-field symmetry could allow plasmas to be maintained well above no-wall beta limit for as long as sufficient torque is provided. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 3711-3713 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ferroelectric SrBi2Ta2O9 thin films have been deposited on the Bi4Ti3O12 buffered Pt/Ti/SiO2/Si substrates using the metalorganic decomposition technique at annealing temperatures ranging from 600 to 750 °C. No pyrochlore phase was found in the SrBi2Ta2O9 thin films although the Bi2Ti2O7 phase appeared in the Bi4Ti3O12 buffer layers. A SrBi2Ta2O9 film with (200) predominant orientation was formed at 650 °C. The effects of the Bi4Ti3O12 buffer layer and post-annealing temperature on the structure, surface morphology, and electrical properties of SrBi2Ta2O9 thin films were analyzed. © 1999 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 1628-1630 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have obtained an analytic solution for the stress distribution under a thin film edge in isotropic substrates of finite thickness and of infinite extent in the other two directions. Far from the film edge on the side without the film, all stress components are zero and far from the film edge under the film, the stress distribution is in accordance with that given by the bimetallic strip theory. To demonstrate the validity of this solution, the experimental infrared photoelastic stress fringe pattern obtained by a dark-field plane polariscope in a Si substrate under an oxide film edge was successfully reproduced using this solution. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 249-251 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nickel disilicide (NiSi2) layers were synthesized by nickel ion implantation into silicon substrates using a metal vapor vacuum-arc ion source. The electrical transport properties were studied before and after annealing using sheet resistivity and Hall effect measurements from 30 to 400 K, and the results showed surprising features very different from those generally reported NiSi2 layers. The temperature dependence of sheet resistivity Rs(T) and Hall mobility μH(T) in the as-implanted samples showed peculiar peak and valley features varying from sample to sample, depending on the preparation conditions. However, after annealing, the differences between samples seemed to have diminished in that they all showed similar shapes in both the Rs(T) and the μH(T) curves. A two-band model was proposed to explain the observed electrical transport properties. © 2002 American Institute of Physics.
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 1221-1223 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: SrBi2Ta2O9 (SBT) ferroelectric thin films were prepared by metalorganic decomposition on Pt/Ti/SiO2/Si substrates at annealing temperatures ranging from 600 to 750 °C. The SBT thin films were annealed layer by layer during the spin-coating process using a rapid thermal annealing (RTA) furnace. The relative intensity of (200) peak in x-ray diffraction increased with the increase of the annealing temperature. A (200)-predominant film can be formed at 700 and 750 °C. For the film annealed by RTA furnace at 650 °C, the remanent polarization (2Pr) and coercive field (2Ec) were 19.8 μC/cm2 and 116 kV/cm, respectively. © 1999 American Institute of Physics.
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