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  • 2
    Publication Date: 2021-05-19
    Description: Southern Africa, broadly defined here as Africa south of the equator, is a region prone to pronounced flood and drought events and significant climate variability on a range of time scales. Some of this variability is thought to be forced remotely via ENSO (e.g., Nicholson and Entekhabi, 1986; Lindesay et al., 1988; Mason and Jury, 1997; Nicholson and Kim, 1997; Reason et al., 2000; Allan et al., 2003) while some is related to variability in the neighbouring Indian and Atlantic Oceans (e.g., Hirst and Hasternrath, 1983; Lough, 1986; Ogallo et al., 1988; Walker, 1990; Mason, 1995; Reason and Mulenga, 1999; Reason, 1999; Behera and Yamagata, 2001; Rouault et al., 2003) or to local land surface processes (Zheng and Eltahir, 1998; Douville et al., 2001). It should be stated at the outset that climate variability over southern Africa is complex with a multitude of forcing factors that interact with each other and wax and wane in their importance through the record. Landman and Mason (1997), Richard et al. (2000), Allan et al. (1996, 2003) amongst others all provide evidence of how the ENSO influence on southern Africa has varied while Mulenga et al. (2003) show that some dry seasons over northern South Africa may be directly related to ENSO whereas others show an influence from the subtropical and midlatitude Atlantic. In this paper, the focus is on possible relationships between the Atlantic Ocean and southern African climate and we begin by considering the annual cycle of SST, winds and moisture fluxes over this region
    Description: Dept. of Oceanography, University of Cape Town, Private Bag, Rondebosch, 7701, South Africa EGS Department, University of Cape Town South African Weather Service, Pretoria, South Africa
    Description: Unpublished
    Keywords: Climate prediction
    Repository Name: AquaDocs
    Type: Theses and Dissertations , Bachelor thesis
    Format: 1609102 bytes
    Format: application/pdf
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  • 3
    Publication Date: 2023-06-08
    Description: Pyroclastic density currents (PDCs) that escape their confining channels are among the most dangerous of volcanic hazards. These unconfined PDCs are capable of inundating inhabited areas that may be unprepared for these hazards, resulting in significant loss of life and damage to infrastructure. Unconfined PDCs can be categorized based on some of their primary dynamic characteristics (e.g., velocity, concentration, dynamic pressure, temperature), which also determine the impacts that they have on humans and infrastructure. Here, we used impact assessments following eruptions at Merapi (Indonesia) in 2010 and Fuego (Guatemala) in 2018 to better understand the dynamics of the PDCs during the eruptions. By analyzing these and similar events, we identified four main categories of unconfined PDC based on their dynamic characteristics: 1. fast overspill flows, 2. slow overspill flows, 3. high-energy surges, and 4. low-energy detached surges (LEDS). How we treat the uncertainty associated with forecasting the inundation area of these PDCs (e.g., in modelling) significantly impacts hazard planning for areas prone to volcanic eruptions. We provide an example of this using hazard modelling of lava dome collapse PDCs from several high-risk volcanoes in Southeast Asia, which show a difference in the projected impacts depending on the overspill buffer with which the PDC is modelled.
    Language: English
    Type: info:eu-repo/semantics/conferenceObject
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Analytical chemistry 28 (1956), S. 858-860 
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 2143-2148 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper we present, results on the growth of in situ doped p-on-n heterojunctions on HgCdTe epilayers grown on (211)B GaAs substrates by molecular-beam epitaxy (MBE). Long wavelength infrared (LWIR) photodiodes made with these grown junctions are of high performance. The n-type MBE HgCdTe/GaAs alloy epilayer in these structures was grown at Ts=185 °C and it was doped with indium (high 1014 cm−3 range) atoms. This epilayer was directly followed by the growth, at Ts=165 °C, of an arsenic-doped (1017–1018 cm−3 ) HgTe/CdTe superlattice structure which was necessary to incorporate the arsenic atoms as acceptors. After the structure was grown, a Hg annealing step was needed to interdiffuse the superlattice and obtain the arsenic-doped p-type HgCdTe layer above the indium-doped layer. LWIR mesa diodes made with this material have 77 K R0A values of 5×103, 81, 8.5, and 1.1 Ω cm2 for cutoff wavelengths of 8.0, 10.2, 10.8, and 13.5 μm, respectively; the 77 K quantum efficiency values for these diodes were greater than 55%. These recent results represent a significant step toward the demonstration of MBE as a viable growth technique for the in situ fabrication of large area LWIR focal plane arrays.
    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 57 (1985), S. 4721-4726 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The isothermal vapor-phase-epitaxial (ISOVPE) growth of device-quality HgCdTe layers on both CdTe and CdTe/Al2O3 substrates has been demonstrated. The material and device properties on both types of substrates have been studied and compared with reported values for HgCdTe grown by other techniques. The as-grown ISOVPE Hg1−xCdxTe (x(approximately-equal-to)0.3) epilayers are always p type with carrier concentrations of ∼5×1015 to 3×1016 cm−3 and mobilities of ∼230–260 cm2/V s at 77 K. The temperature and compositional dependence of electrical properties of ISOVPE Hg1−xCdxTe are somewhat different from those of liquid-phase epitaxy (LPE) and bulk HgCdTe. In particular, the acceptor ionization energy, EA =7 meV, is about half that obtained in midwavelength infrared LPE or bulk HgCdTe, and nearly independent of composition x. The R0A product of a representative photodiode (λc (approximately-equal-to)4.65 μm, 77 K) is 2×106 and 4 Ω cm2 at 77 and 195 K, respectively, with comparable device qualities seen on both CdTe and CdTe/Al2O3 substrates.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The development of an extreme ultraviolet (EUV) interferometer for testing EUV lithography optics operating at a wavelength of 13 nm using the U13U undulator beam line at the National Synchrotron Light Source is presented. The design and implementation of phase-measuring, lateral-shearing interferometry and a knife edge test will be described. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Restoration ecology 2 (1994), S. 0 
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Within an urban park in southern California, the relationship between the structure and floristics of vegetation and the distribution, abundance, and behavior of wildlife was studied in relatively undisturbed areas (San Luis Rey) and in contiguous areas (Guajome Park) in need of restoration. These data were used to develop recommendations for the enhancement of native animal species in the park. The abundance of amphibians and reptiles was highest in native upland scrub and willow (Salix)-riparian vegetation types, and lowest in dry, disturbed sites. Western fence lizards (Sceloporus occidentalis) were the most abundant reptile throughout both study areas. Overall, bullfrogs (Rana catesbiana), an exotic species, were the dominant amphibians; the native Pacific treefrog (Hyla regilla) was rare throughout. At both study areas, the small mammal community was dominated by western harvest mice (Reithrodontomys megalotis) and deer mice (Peromyscus maniculatus) and, to a lesser extent, by brush mice (P. boylii) and exotic house mice (Mus musculus). Negative correlations in abundance existed between house mice and harvest mice, and between house mice abundance and overall small mammal abundance. In riparian sites, cottonwood (Populus fremontii) and various height classes of willow were the dominant factors in the majority of bird abundance–habitat‘correlations and where foraging activities were concentrated. Recommendations for enhancing native animal species include reduction of marsh sedimentation, removal of feral species, and development of connections between the park and nearby natural areas. A corridor of native riparian vegetation (primarily cottonwood-willow) should be developed to replace the existing agricultural fields, thereby linking Guajome with the San Luis Rey River.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 3 (1987), S. 0 
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. Spring wheats are sown in autumn and mature under conditions of spring water deficits in Western Australia. While grain yields are very small (averaging 1.05t ha-1), water-use efficiencies (WUE) of crops grown with good management compare favourably with the rest of Australia at 10 kg grain ha-1 mm-1. Major water loss, calculated at an average 40% of growing-season rainfall, occurs through evaporation from the soil surface, and in some years significant losses also occur through deep drainage on sandy soils. Evaporation losses can be reduced by stubble retention and adding gypsum to improve filtration on structurally unstable, fine-textured soils. More general increases in crop water use occur through all agronomic factors which result in rapid and uniform plant cover as early as possible after break of season. This includes adequate fertilization, weed control and narrow row-width. Wheat crops sown after pasture and grain legumes consistently outyield all-cereal rotations.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The formation chemistry and growth dynamics of thin-film CuInSe2 grown by physical vapor deposition have been considered along the reaction path leading from the CuxSe:CuInSe2 two-phase region to single-phase CuInSe2. The (Cu2Se)β(CuInSe2)1−β (0〈β≤1) mixed-phase precursor is created in a manner consistent with a liquid-phase assisted growth process. At substrate temperatures above 500 °C and in the presence of excess Se, the film structure is columnar through the film thickness with column diameters in the range of 2.0–5.0 μm. Films deposited on glass are described as highly oriented with nearly exclusive (112) crystalline orientation. CuInSe2:CuxSe phase separation is identified and occurs primarily normal to the substrate plane at free surfaces. Single-phase CuInSe2 is created by the conversion of the CuxSe into CuInSe2 upon exposure to In and Se activity. Noninterrupted columnar growth continues at substrate temperatures above 500 °C. The addition of In in excess of that required for conversion produces an In-rich near-surface region with a CuIn3Se5 surface chemistry. A model is developed that describes the growth process. The model provides a vision for the production of thin-film CuInSe2 in industrial scale systems. Photovoltaic devices incorporating Ga with total-area efficiencies of 14.4%–16.4% have been produced by this process and variations on this process. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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