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  • Articles  (761)
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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)
    Journal of Applied Physics 75 (1994), S. 2781-2788 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Argon gas puff experiments on a 3–4 MA generator show that the K-shell x-ray yield is optimized for a 2.5 cm initial diameter and 110 ns implosion time. By varying the driver current, the K-shell yield varies from 13 to 18 kJ following a current to the fourth power scaling. Comparisons of these experimental data to one-dimensional radiation-hydrodynamic simulations with and without enhanced transport coefficients show that the measured K-shell yields exceed those predicted based solely on kinetic energy input.
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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
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 5894-5900 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Heterojunction devices have been fabricated by a low-pressure chemical vapor deposition technique whereby n-type amorphous or microcrystalline silicon films were grown on p-type crystalline silicon substrates. Heterostructures produced under various conditions of thin film deposition were subjected to detailed I-V curve analysis. It is seen that for amorphous-crystalline heterojunctions the current transport is through tunneling in the low bias range and limited by electron-hole recombination in the high bias range. For the microcrystalline-crystalline junctions however, recombination current at the interface dominates the current transport process. Illuminated I-V curves corresponding to films deposited at different substrate temperatures (Ts ) and dopant gas-to-silane ratios (R) show that the high values of the short-circuit current (Isc), open-circuit voltage (Voc ), and fill factor (FF) are achieved at values close to Ts ∼620 °C and R ∼4×10−3 in conformance with dark I-V characteristic data.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 5410-5414 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The specific volumes of Pd40Ni40P20 were measured in the liquid, glass, and crystallized states. It was found that in the molten state, for temperatures below ∼1000 K, the specific volume measurement was successful only if the specimens were properly purified. Such purification could be achieved by fluxing the molten specimen in dehydrated boron oxide. Relaxation effects are observed and they manifested themselves in the variation of the thermal expansion coefficient with the quenching rates of the glassy specimens. The intersection points of the specific volume curves of the liquid (both stable and metastable), glass and crystallized are 573±80 and 492±80 K (extrapolated values), respectively. The former agrees very well with the glass transition temperature 577 K, obtained by the calorimetry method, while the latter implies that the melt, in accord with free volume theory, will have collapsed to the glass before that temperature is reached.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 1091-1101 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of the beam divergence of the input pump laser beams on the nonlinear frequency mixing process in a dielectric medium is discussed. The divergent laser beams have finite angular spreads so that all of the interactions between the two input beams can never satisfy the phase-matching condition exactly. A numerical model is developed to investigate the effects of input beam divergence on conversion efficiency. The angular spread of each of the input beams is represented by a set of plane waves having a distribution of propagation directions. Each of the plane-wave components from one input beam is allowed to interact with all the plane-wave components of the second input beam. This model is applicable to processes such as sum frequency generation, difference frequency generation, and optical parametric amplification. Second-harmonic generations as a special case of sum frequency generation is used as an example in the numerical studies. Results indicate that the conversion efficiency is dependent on the amount of beam divergence, the input intensity, and the length of the nonlinear medium. These parameters must be optimized with respect to one another to maximize the conversion. The optimization is especially critical in high-power systems where high conversion efficiency is sought.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 2151-2151 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: © 1999 American Institute of Physics.
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  • 10
    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.
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