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  • 1985-1989  (7)
  • 1975-1979
  • 1987  (7)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Computing 38 (1987), S. 341-345 
    ISSN: 1436-5057
    Schlagwort(e): Approximation ; n-dimensional grid
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Es wird ein Verfahren zur Bestimmung einer Translation eines rechtwinkeligen Gitters mit der Eigenschaft, daß eine endliche Punktmenge des ℝN möglichst gut durch Gitterpunkte approximiert wird, angegeben.
    Notizen: Abstract A procedure is given for translating a rectangular grid in such a way that a finite set of points in ℝN is approximated as good as possible by points of the translated grid.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1432-1440
    Schlagwort(e): Intravenous drug abusers ; Acquired immunodeficiency syndrome ; Immunocompetence ; Longitudinal study ; LAV/HTLV-III
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Summary To date, long-term intravenous drug users studied at regional European centers of illicit drug use have had a high number of LAV/HTLV-III infections. Among 200 patients remanded by court or referred from prison to a special clinic in northern Germany for young delinquent drug abusers, 26 (17%) of 157 IV drug abusers were HTLV-III seropositive. With 40% seropositive, female patients showed a significantly higher prevalence of HTLV-III infection than males. The results of longitudinal serological, immunological, and clinical observations over periods of 12 months and 2–3 years indicate that under conditions of continuous medical surveillance, sound preventive counseling, and steady therapeutic care during long-term coeducative residential treatment of drug abusers, neither detectable HTLV-III transmission nor definite progression of HTLV-III induced impairment of immune regulatory functions must ensue.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    ISSN: 1432-0649
    Schlagwort(e): 41.80E ; 52.25 ; 29.15D
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract First results are presented from an experiment scattering laser light from a relativistic electron beam. The 5 cm diameter continuous electron beam of 28 keV kinetic energy and 2.6 A current presents an electron gas of a density of 8×107 cm−3, from which 20 ns pulses of laser light (490 nm) were scattered at a repetition rate of 15 Hz and an average power of 20 mJ per pulse. The Doppler-shifted wavelength of photons backscattered under 180° was analysed with a Fabry-Perot interferometer. This technique provides, for the first time, a non-destructive measurement of the velocity distribution in an electron beam radially resolved in space. The results presented here comprise the direct measurement of the absolute electron energy and the degree of space-charge compensation in the electron beam. The determination of an upper bound of 10−2 for the ratio of longitudinal to transverse electron temperature implies the first direct measurement of a flattened velocity distribution.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Electrical engineering 70 (1987), S. 291-301 
    ISSN: 1432-0487
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik
    Beschreibung / Inhaltsverzeichnis: Contents Calculating transients in power systems it is advantageous to use symmetrical components. The example of the most common three-phase bridge converter shows that also current converters can be described in space phasors. With respect to the characteristics of conducting valves the networks and the conditions of firing and commutation ending are deduced. Numerically calculated results agree with measurements. A parameter study shows the typical space phasor curves of bridge converter currents.
    Notizen: Übersicht Dynamische Netzberechnungen lassen sich vorteilhaft in Drehstrom-Modalkomponenten durchführen. Das Beispiel der meistgebräuchlichen Drehstrom-Brückenschaltung zeigt, daß auch Stromrichter mit Raumzeigern beschrieben werden können. Unter Berücksichtigung der Eigenschaften stromführender Ventile werden die Ersatzschaltpläne sowie die Zünd- und Löschbedingungen in Modalkomponenten hergeleitet. Die Ergebnisse numerischer Berechnungen stimmen mit Messungen überein. Eine Parameterstudie zeigt die für Brückenschaltungen typischen Stromortskurven in Modalkomponenten.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    ISSN: 1432-1319
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Crops grown with flood irrigation on slowly draining clay soils are subject to periods of waterlogging during and after each irrigation. The aim of this experiment was to quantify crop responses to these short-term waterlogging events and to assess the modifying effect of different agronomic practices. Maize was grown in undisturbed (U) and repacked (R) profiles of clay loam soil encased in steel cylinders (0.75 m diameter × 1.4 m deep). Two levels of N (high (HN) 300 kg N ha−1, and low (LN) 150 kg N ha−1) were applied as a split dressing. Three periods of flooding (F) of 72, 72 and 48 h were imposed on half the treatments beginning on days 40, 54 and 68 respectively after sowing. The other irrigation regime (C) kept the profile well watered but avoided surface inundation.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 101 (1987), S. 211-221 
    ISSN: 1573-5036
    Schlagwort(e): aeration ; calcium ; cotton ; flooding ; magnesium ; manganese ; phosphorus ; potassium ; sodium chloride ; waterlogging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract A field experiment was conducted to investigate the effects of intermittent waterlogging on the nutrient status of cotton (Gossypium hirsutum cv. Deltapine 61). The crop was grown in a sloping plot of soil in which a gradient of water-table depth ranging from 0.04m above to 0.60m below the soil surface was established during two periods of waterlogging in mid summer and early autumn. The first waterlogging lasted 8 days; the second lasted 16 days. Dry matter increases were less for severely waterlogged plants than for plants with well-aerated root systems during the first flooding, but the increases were similar during the second. Waterlogging impaired uptake of most nutrients by young plants in the first flooding, but had much less effect on nutrient uptake by older plants in the second. Waterlogging consistently reduced concentrations of P and K in the petioles and laminae of young fully-expanded leaves, and severely waterlogged plants were deficient in these nutrients by the end of the first flooding. Mn did not accumulate to toxic levels in waterlogged plants. During each flooding, waterlogged plants gained in total content of all nutrients studied, but the gains of each nutrient, except for Na, were proportionally smaller than for well-aerated plants. Fluxes of K-, Cl- and HPO4- ions in xylem sap exuded from stumps of detopped plants which had been waterlogged were lower than those from plants with well-aerated root systems. Seed cotton yields and concentrations of nutrients in mature bolls were not affected by the two periods of waterlogging. It is concluded that although intermittent waterlogging induced nutrient stress in cotton plants, especially for P and K in young plants before flowering, they recovered with no detrimental effect upon yield.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 102 (1987), S. 161-170 
    ISSN: 1573-5036
    Schlagwort(e): aeration ; flooding ; Gossypium hirsutum L. ; root zone ; soil oxygen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Surface-irrigated cotton (Gossypium hirsutum L.) grown on slowly draining clay soil is subjected to short-term periods of waterlogging at each irrigation which generally results in reduced productivity. The sequence of above- and below-ground plant responses to transient waterlogging and the role of N availability in modifying the immediate responses were studied. Lysimeters of Marah clay loam (a Natrustalf) were instrumented to monitor soil and plant responses to a 7-day waterlogging event beginning 67 days after sowing. Cotton (‘Deltapine 61’) plants (8 per lysimeter) were grown with two levels of added N (300 kg ha−1 and 30 kg ha−1) and two irrigation treatments (flooded and control). Measured soil-O2 levels decreased rapidly upon surface flooding because water displaced air and root zone respiration consumed O2. The rate of O2 consumption was 2.7 times greater in the high-N treatment than the low-N treatment. This difference was associated with a 1.8 fold difference in numbers of observed roots. Root growth was only slightly affected by flooding. Leaf growth decreased by 28%, foliage temperature increased 2.3% and apparent photosynthesis decreased by 16%. It is suggested that flooding reduced photosynthetic activity within 2 days while other stress symptoms became apparent after about 6 days. Although this stress was reflected in a trend for decreased plant productivity, the effect of flooding on boll dry mass at harvest was not significant at the level of replication used. The single waterlogging did not cause yield reductions comparable to those observed elsewhere when several waterlogging events were imposed.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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