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  • 1
    Electronic Resource
    Electronic Resource
    Early bifurcation in rotating fluid flow with free surface studied by axisymmetric numerical simulations (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 8 (1996), S. 3057-3062 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Simulations of a fluid rotating inside a partially open cylindrical cavity, performed by numerical solution of the unsteady axisymmetric Navier–Stokes equations, are presented. The configuration consists of a cylindrical vessel holding the fluid, which is entrained into motion by a rotating lid. This one is a coaxial disk in contact with the fluid surface but without covering it entirely. The study focuses on the occurrence of time-dependent flow, more specifically, the first transition to unsteadiness, by considering cavity cases with different amounts of free surface, for a fixed aspect ratio. By following the time evolution of a few arbitrarily chosen dynamical variables as a function of the Reynolds number, the location of this first Hopf bifurcation is obtained for a collection of cavity cases. Results show a rather strong influence of the free surface both on the onset of the unsteadiness and on the dynamical features of the flow. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.869079
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  • 2
    Electronic Resource
    Electronic Resource
    Low-dimensional representations of early transition in rotating fluid flow (1993)
    Springer
    Theoretical and computational fluid dynamics 5 (1993), S. 259-267 
    Details
    ISSN: 1432-2250
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Low-dimensional representations of the axisymmetric Navier-Stokes equations are generated by a Galerkin projection. Proper orthogonal decomposition (POD) techniques based on snapshots generated from a finite-difference algorithm are used. The Reynolds number range is extended by adding displacement vectors to the Galerkin basis. For the fluid flow enclosed in a cylindrical vessel with rotating end cover, the first transition from steady to oscillatory motion is detected as a supercritical Hopf bifurcation. Comparison with the full numerical solution of the Navier-Stokes equations as well as experimental results show excellent agreement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00271422
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of growth conditions on the value of crisphead lettuce (1994)
    Springer
    Plant foods for human nutrition 46 (1994), S. 1-11 
    Details
    ISSN: 1573-9104
    Keywords: Chemical composition ; Cultivar ; Harvest data ; Lactuca sativa L. ; Lettuce ; Nitrate ; Nitrogen ; Plant age ; Tipburn ; Quality ; Vitamin C
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The marketable and nutritional quality of crisphead lettuce as affected by nitrogen supply, cultivar, and plant age at harvest was investigated in six plantings during 1989 and 1990. The optimum yield of marketable heads was obtained at a total nitrogen supply of 150 kg N per ha although only small differences were observed to the yield at 100 and 200 kg total N per ha. The total nitrogen supply included the amount of mineral nitrogen within the rhizosphere. The incidence of dry tipburn in older leaves was clearly decreased by an increased nitrogen supply, especially at late planting. The content of nitrate was increased and the content of dry matter and vitamin C decreased with increased nitrogen supply. The vitamin C content was higher for the cultivar ‘Marius’ than for ‘Saladin’. As plants got older, the nutritional quality of crisphead lettuce decreased because the content of nutrients, especially vitamin C, decreased with increased plant age at harvest.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01088455
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  • 4
    Electronic Resource
    Electronic Resource
    Influence on growth conditions on the value of crisphead lettuce (1994)
    Springer
    Plant foods for human nutrition 46 (1994), S. 13-18 
    Details
    ISSN: 1573-9104
    Keywords: Cold storage ; Ice bank cooling ; Lactuca sativa L. ; Lettuce ; Nitrogen supply ; Plant age ; Weight losses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Storage of crisphead lettuce was carried out at 1°C in an ordinary cold storage room and in an ice bank cooling system. The plants were grown at three plantings at 50, 100, 150 and 200 kg total nitrogen supply per hectare and harvested at two or three different plant ages. The cultivars used were ‘Marius’ and ‘Saladin’. The aim of the experiment was to prolong the storage and to reduce the losses. After 14 days of storage the greatest total weight losses were found at the mid-season planting whereas the least total weight loss was found at the late planting. Ice bank cooling at all plantings reduced the total weight loss in comparison to the cold storage. The effect of nitrogen and cultivar was low. The total weight loss defined as loss due to transpiration and trimming was neither related to the head weight nor the surface area of the heads. A reduced loss with increasing plant age was not a question of increased transpiration due to surface to volume ratio changes, but may be related to other factors. A lower average total weight loss was found in the ice bank cooling system compared to the cold storage. The explanation of this might be the existence of a high relative humidity in the ice bank storage. To reduce the total weight loss harvest must take place at the right plant age. No definite growth stage was defined here, but the plants must have reached marketable quality as the young plants are more susceptible to weight loss during storage. It seems likely that some unknown internal factors in the plant were involved in reduction of the total weight loss.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01088456
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of growth conditions on the value of crisphead lettuce (1994)
    Springer
    Plant foods for human nutrition 46 (1994), S. 255-265 
    Details
    ISSN: 1573-9104
    Keywords: Crisphead lettuce ; Digestible energy ; Fiber level ; Growth conditions ; Protein quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Crisphead lettuce was cultivated under different growth conditions. Sixteen batches differed in time of planting (early and late), total nitrogen supply (200 kg N/ha, 150 kg N/ha, 100 kg N/ha, 50 kg N/ha) and time of harvest (early and late). Based on chemical analysis and balance studies on rats the nutritive value of each 16 batches was determined. The protein content increased progressively from 16.00 to 19.88% with fertilization level. This increase in protein caused a significant drop in essential amino acids (g/16 g N) demonstrating a lower biological value of this protein. Early planting or early harvest resulted in a higher protein content than in lettuce of late planting or late harvest. Total dietary fibre content was approximately 25% of DM — and this value was not much influenced by the different growth conditions. Soluble dietary fibre was approximately 20–25% of total dietary fibre. Due to the high fibre content, energy digestibility was relatively low. The contents of Cd and Pb were below what is considered as ‘acceptable’ levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01088998
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  • 6
    Electronic Resource
    Electronic Resource
    Influence of growth conditions on the value of crisphead lettuce (1995)
    Springer
    Plant foods for human nutrition 47 (1995), S. 157-162 
    Details
    ISSN: 1573-9104
    Keywords: Lactuca sativa ; Lettuce ; Cold storage ; Ice bank cooling ; Internal quality ; Nitrogen supply ; Dry matter ; Vitamin C ; Glucose ; Fructose ; Nitrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Crisphead lettuce (Lactuca sativa L. varcapitata cvs.Marius andSaladin) were grown with a nitrogen supply from 50 to 200 kg N/hectare. Heads were stored for one or two weeks at 1 °C in cold storage or ice bank cooling. Samples were taken for measurement of dry matter, sugars, vitamin C and nitrate. The content of dry matter, sugars (glucose, fructose) and vitamin C decreased with increasing level of nitrogen, and the content of nitrate increased. Except for nitrate the contents of the other quality attributes decreased at all nitrogen supply levels during storage. No differences were found between the storage systems, and beside fructose no significant differences were found between the two cultivars. The content of dry matter, vitamin C, and nitrate decreased from the outer to the inner head fraction, while the content of sugars increased. Trimming decreased the content of dry matter, vitamin C and nitrate and increased the content of sugars. To obtain heads from storage with a relatively high content of dry matter, sugars and vitamin C, and a relatively low content of nitrate the nitrogen supply must be as low as possible. Except for nitrate where no distinct results were found in this experiment it must also be recommended to store the heads as short time as possible. Possibly the cv.Saladin has some advantage quality attributes after storage compared with the cv.Marius.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01089265
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  • 7
    Electronic Resource
    Electronic Resource
    High-order axisymmetric Navier-Stokes code: Description and evaluation of boundary conditions (1989)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 9 (1989), S. 1517-1537 
    Details
    ISSN: 0271-2091
    Keywords: Navier-Stokes equations ; Boundary conditions ; Higher order finite difference method ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A description is given of a high-order solution algorithm for the solution of the unsteady axisymmetric Navier-Stokes equations. The method consists of a combination of fourth-order and second-order accurate finite difference schemes, where the approximated equations are solved by an alternating direction implicit (ADI) method. Special attention is paid to the boundary conditions. Results are compared with measurements for the cases of rotating flow within a closed cylinder (rotating driven cavity), developing axial flow in a stationary pipe and developing flow in a rotating pipe.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650091207
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