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  • Springer  (19)
  • American Physical Society  (15)
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  • 1991  (34)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    International journal of biometeorology 35 (1991), S. 67-70 
    ISSN: 1432-1254
    Schlagwort(e): Air ions ; Corona current ; Radiogauge ; Potato drying
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geographie , Physik
    Notizen: Abstract Space charge (air ions) produced by single corona electrodes was used to enhance drying rates from fresh slabs of potato. The drying path was traced by a beta-ray gauge which provided both sensitivity and reproducibility to the measurements of drying time. The rate of evaporation was increased 2.2 to 3.0 times when subjected to fluxes of 3.02×1012 positive ions alone or in combination with 7.31×1012 negative air ions/cm2 per s compared to that from an air-drying control slab. Electric wind caused by an ionic drag force seems to be the principal driving force for the observed enhancement in drying rates.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Acta mechanica 87 (1991), S. 123-133 
    ISSN: 1619-6937
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Summary A new integral equation concerning the thin airfoil problem is proposed. In this equation, the unknown function represents vorticity along the thin airfoil, and the right hand term of the equation is chosen as the stream function in two-dimensional potential flow. The equation has a logarithm kernel with a weaker singularity than the known one [1]. After solution of the integral equation, i.e. after determination of vorticity, the lift forces and moment actjing on the thin airfoil can be calculated immediately, as it follows from the Blasius's formulae. Several numerical examples are given.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 130 (1991), S. 231-241 
    ISSN: 1573-5036
    Schlagwort(e): cotton ; iron uptake ; peanuts ; plant iron nutrition ; pseudobactin ; Pseudomonas putida ; redox potential ; siderophore ; sorghum ; sunflower
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Iron uptake from ferrated (59Fe) pseudobactin (PSB), a Pseudomonas putida siderophore, by various plant species was studied in nutrient solution culture under short term (10 h) and long term (3 weeks) conditions. In the short term experiments, 59Fe uptake rate from 59FePSB by dicots (peanuts, cotton and sunflower) was relatively low when compared with 59Fe uptake rate from 59FeEDDHA. Iron uptake rate from 59FePSB was pH and concentration dependent, as was the Fe uptake rate from 59FeEDDHA. The rate was about 10 times lower than that of Fe uptake from the synthetic chelate. Results were similar for long term experiments. Monocots (sorghum) in short term experiments exhibited significantly higher uptake rate of Fe from FePSB than from FeEDDHA. In long term experiments, FePSB was less efficient than FeEDDHA as an Fe source for sorghum at pH 6, but the same levels of leaf chlorophyll concentration were obtained at pH 7.3. Fe uptake rates by dicots from the siderophore and FeEDDHA were found to correlate with Fe reduction rates and reduction potentials (E0) of both chelates. Therefore, it is suggested that the reduction mechanism governs the Fe uptake process from PSB by dicots. Further studies will be conducted to determine the role of pH in Fe aquisition from PSB by monocots.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 130 (1991), S. 35-43 
    ISSN: 1573-5036
    Schlagwort(e): enrichment ; farmyard manure ; iron ; manganese ; peat ; poultry manure ; zinc
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Earlier studies have shown that some naturally occuring organic materials can be used as an Fe source for plants. The aim of this research was to study enrichment procedures that would result in complex formation in common, low cost organic materials and to determine the maximum attainable Fe enrichment levels. Three organic materials-farmyard manure (FYM), poultry manure (PM) and Huleh Valley peat (PE) were studied for their characteristics as Fe, Mn and Zn carriers for plant uptake. Various enrichment procedures were investigated. These studies have shown that the enrichment level depends on the metal, pH and the water soluble fraction (WSF) of the organic materials. Maximum enrichment levels (at pH=3.5) were measured after the excess of inorganic salts was removed by leaching. These levels were 5.8–6.6% for Fe, 3.0–3.4% for Mn and 6.0–6.3% for Zn. An infrared spectrum of the Fe enriched WSF showed that most of the ligands in the complex formed are polysaccharides or polysaccharide-like compounds.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Plant and soil 130 (1991), S. 45-50 
    ISSN: 1573-5036
    Schlagwort(e): enrichment ; farmyard manure ; iron ; peat ; poultry manure ; transport
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Iron transport in soils amended with Fe-enriched farmyard manure (FYM), poultry manure (PM) and Huleh Valley peat (Peat) was studied in saturated soil columns under constant water flow rate. The Fe concentration in the effluent varied with the type of the organic material, water soluble fraction (WSF) concentrations and the susceptibility of the WSF to chemical and microbial degradation. Incubation of soils treated with the enriched organic materials significantly enhanced the levels of leachable Fe complexes in the case of the FYM and PM treatments which were easily subjected to biodegradation, whereas incubation of a soil with Fe-enriched peat resulted in minor effects. Under a simulated drip irrigation regime (5 irrigation cycles during 104 days), DTPA extractable Fe concentration increased to a depth of 45 cm and to a horizontal distance of 30 cm from a point source of Fe enriched organic matter. The Fe movement in the soil was attributed to mass-flow of water-soluble complexes which are partially present in the original organic material and partially formed by degradation processes.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Transport in porous media 6 (1991), S. 667-702 
    ISSN: 1573-1634
    Schlagwort(e): Modified method of characteristics ; time-splitting ; in situ biorestoration ; adsorption ; contaminant transport
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Technik allgemein
    Notizen: Abstract A convergent numerical method for modeling in situ biorestoration of contaminated groundwater is outlined. This method treats systems of transport-biodegradation equations by operator splitting in time. Transport is approximated by a finite element modified method of characteristics. The biodegradation terms are split from the transport terms and treated as a system of ordinary differential equations. Numerical results for vertical cross-sectional flow are presented. The effects of variable hydraulic conductivity and variable linear adsorption are studied.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Experimental mechanics 31 (1991), S. 144-149 
    ISSN: 1741-2765
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract A new method of measuring the normal and sliding loads associated with multiple-point contact is introduced. A multiple-point contact is modeled with a steel die with a profile that simulates a rough surface. A very large scale factor is used in modeling this surface. The steel die is placed in contact with a photoelastic model of a half plane and is subjected to a normal load. This normal load is partitioned over the multiple points of contact producing an isochromatic fringe pattern that describes the stress distribution in the local neighborhood of the contact points. A sliding load is then imposed on the model which destroys the symmetry of this fringe pattern. The fringe data in this pattern are sufficient to determine the local loadsP i andQ i and the local coefficient of frictionf i =Q i /P i at each contact point. An overdeterministic method is introduced which gives the solution forP i ,Q i andf i using many data points taken from the isochromatic pattern in the local neighborhood of the contacts.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Reaction kinetics and catalysis letters 43 (1991), S. 439-446 
    ISSN: 1588-2837
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Beschreibung / Inhaltsverzeichnis: Abstract Каталитическое гидродесульфурирование играет важную роль в превращениях серосодержащих остаточных нефтей. Обычно для этого процесса используют кобальтмолибдатные катализаторы. Для приготовления алюмоземного носителя использовали технику высаждения при постоянном pH. Такой материал обладает весьма узким распределением пор по размерам со средним диаметром пор около 8 нм. Он также обладает большой поверхностной площадью и объемом пор и поэтому может служить носителем катализаторов CoMo ВДС. Результаты ТПД аммиака свидетельствуют о том, что этот катализатор обладает повышенной поверхностной кислотностью по сравнению с обычными катализаторами, которая повышает способность к крекингу катализатора. Результаты ВДС свидетельствуют о том, что образцы, приготовленные высаждением, более активны и стабильны, чем обычные катализаторы, по-крайней мере в первые 72 часа. Эти результаты приписывают уникальной структуре пор и высокой поверхностной кислотности.
    Notizen: Abstract Catalytic hydrodesulfurization plays an important role in the conversion of sulfur laden residual oils. Cobalt molybdate catalysts are more commonly used for this process. In the present study, a precipitation technique at constant pH value was used to prepare alumina support. This material has very narrow pore size distribution centered around the pore diameter of about 8 nm. It also has a large surface area and pore volume and, therefore, can be used as a support for CoMo RDS catalysts. The results of temperature-programmed desorption of ammonia indicated that this catalyst has higher surface acidity than the conventional catalysts. The high surface acidity could enhance the cracking ability of the catalyst. The RDS reaction results showed that the samples prepared by precipitation are more active and more stable than the conventional catalysts, at least in the first 72 h. The results can be attributed to its unique pore structure and high surface acidity.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    International journal of fracture 48 (1991), S. R75 
    ISSN: 1573-2673
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    International journal of fracture 49 (1991), S. R39 
    ISSN: 1573-2673
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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