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  • American Institute of Physics (AIP)
  • Cambridge University Press
  • 2010-2014  (2)
  • 2000-2004  (4)
  • 1975-1979
  • 1
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 3434-3436 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A way of analyzing the data in a variable stripe length method gain experiment is presented. We confirm that the stripe length dependence of the gain in In0.02Ga0.98N/In0.16Ga0.84N multiple quantum wells is caused by the change of the chemical potential along the excited stripe due to the interaction of the carrier and photon densities, and the gain threshold density is estimated. A trial function assuming a Lorentzian line shape for the stripe length dependence of the gain is compared with the edge emission intensity as a function of the stripe length. This is found to fit very well with our data, even beyond the saturation region. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 1097-1099 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present spectrally resolved and time-integrated four-wave mixing measurements at coherent dynamics of bound excitons in a high-quality GaN epilayer. Coherent excitation, with co-circular polarized light, of the neutral donor-bound excitons (D 0X) and A excitons (XA) results in quantum beats, corresponding to the energy splitting between D 0X and XA. The temperature-dependent dephasing rate is used to deduce the strength of the D 0X-acoustic–phonon interaction via the homogeneous linewidth. © 2001 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 3577-3579 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present intensity noise studies of a self-organized InAs/GaAs quantum-dot laser. The noise power measured for the full emission spectrum was found to be smaller than that for separate longitudinal mode groups. This noise cancellation indicates that the intensity fluctuations of the mode groups were anticorrelated, with typical values of the normalized correlation coefficient of around −0.50. This surprisingly high value is not consistent with the model of the quantum-dot laser as an inhomogeneous ensemble of independent microlasers. © 2001 American Institute of Physics.
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  • 4
    Publication Date: 2002-04-09
    Description: Laboratory experiments were performed in which an intrusive gravity current was observed using shadowgraph and particle tracking methods. The intrusion was generated in a two-layer fluid with a sharp interface by mixing the fluid behind a vertical lock gate and then suddenly withdrawing the gate from the tank. The purpose of the experiments was to determine the structure of the velocity field inside the intrusion and the stability characteristics of the interface. Soon after the removal of the lock gate, the front of the intrusive gravity current travelled at a constant speed close to the value predicted by theory for an energy-conserving gravity current. The observed structure of the flow inside the intrusion can be divided into three regions. At the front of the intrusion there is an energy-conserving head region in which the fluid velocity is nearly uniform with speed equal to the front speed. This is followed by a dissipative wake region in which large billows are present with their associated mixing and in which the fluid velocity is observed to be non-uniform and have a maximum speed approximately 50% greater than the front speed. Behind the wake region is a tail region in which there is very little mixing and the velocity field is nearly uniform with a speed slightly faster than the front speed.
    Print ISSN: 0022-1120
    Electronic ISSN: 1469-7645
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 5
    Publication Date: 2010-01-21
    Description: SUMMARYThe Mediterranean region is experiencing unrelenting land-use pressure, largely driven by population growth. Long-term cropping system trials can guide crop and soil management options that are biophysically and economically sustainable. Thus, an extensive cereal-based rotation trial (1983–98) was established in northern Syria, to assess various two-course rotations with durum wheat (Triticum turgidum Desf.). The alternative rotations were: continuous wheat, fallow, chickpea (Cicer arietinum), lentil (Lens culinaris), medic (Medicago spp.), vetch (Vicia sativa) and watermelon (Citrullus vulgaris) as a summer crop. Ancillary treatments were: nitrogen (N) fertilizer application to the cereal phase (0, 30, 60 and 90 kg N/ha) and variable stubble grazing management (zero or stubble retention, moderate and heavy grazing). Both phases of the rotation trial occurred each year. The soil is a fine clay, thermic Calcixerollic Xerochrept. Seasonal rainfall was the dominant factor in influencing overall yields. Rotations significantly influenced yields, being highest for fallow (2·43 t/ha), followed by watermelon (similar to fallow), vetch, lentil, medic and chickpea, and least for continuous wheat (1·08 t/ha). Overall, yields increased consistently with added N, but responses varied with the rotation. The various stubble grazing regimes had little or no effect on either grain or straw yields. While the trial confirmed the value of fallow and the drawbacks of continuous cereal cropping, it also showed that replacing either practice with chickpea or lentil, or vetch for animal feed, was potentially a viable option. Given favourable economics, legume-based rotations for food and forage could contribute to sustainable cropping throughout the Mediterranean region.
    Print ISSN: 0021-8596
    Electronic ISSN: 1469-5146
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 6
    Publication Date: 2013-01-01
    Description: Sea-ice thicknesses observed in Canadian coastal waters with helicopter-borne electromagnetic–laser sensors show large interannual variability caused by atmospheric fluctuations in two years for two areas where surveys were repeated, one in the Amundsen Gulf of the Canadian Beaufort Sea and one over the Labrador Shelf. For the Amundsen Gulf, the bimodal ice thickness peaks shifted by 40 cm to thinner thicknesses for the warmer winter of 2008 compared with 2004. The thinner ice in 2008 can be explained partially by reduced thermodynamic ice growth during the warmer winter of 2008. In addition, winds from the east were more persistent throughout the winter of 2008, increasing ice export from the Amundsen Gulf and thereby creating open-water areas where new ice growth in late winter produced the thinner ice classes. For the Labrador Shelf, the mean ice thicknesses of the warmer winter of 2011 (0.71 m) were much less than those of the near-normal winter of 2009 (1.60 m). Again the difference can be explained by the fact that along the entire Labrador Shelf the winter of 2011 was much warmer, reducing ice growth and resulting in thinner ice locally and thinner ice being transported into the survey region from northern latitudes. In addition, northwesterly winds occurred less frequently during the winter of 2011, reducing the transport of relatively thicker ice into the survey area from northern latitudes.
    Print ISSN: 0260-3055
    Electronic ISSN: 1727-5644
    Topics: Geography , Geosciences
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