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  • Blackwell Publishing Ltd  (2)
  • Wiley-Blackwell  (2)
  • American Geophysical Union (AGU)
  • American Association of Petroleum Geologists (AAPG)
  • 1995-1999  (4)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 28 (1997), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Accumulation of nutrients in the sediment under a tilapia cage farm (2.8–4.4% C, 0.26–0.49% N and 0.04–0.26% P) seemed to follow a seasonal pattern, with highest concentrations prior to winter water turnover. However, in April 1994 (and for P also in April 1992) the surface sediment contained significantly higher nutrient concentrations compared to controls. Generally, significantly higher pore water concentrations were found under the cages compared to controls. However, only in April 1992 were these concentrations of the same magnitude as those found in temperate studies. The average flux of particulate material under the cages, 20–49 g m−2 per day, was up to 22 times greater compared to controls. Carbon accumulated only in April 1994, implying rapid decomposition. This was supported by a 4–25-fold higher outward flux of ammonium and phosphate from the farm sediment but sediment O2 consumption was only 29–40% higher compared to control sites. It was concluded that intensive fish farming in the tropics can generate similar eutrophication effects that are observed in temperate regions. However, the results also indicated that a tropical lake system may be able to process local deposition of organic wastes better than a temperate one, suggesting that microbial decomposition may be a rapid and prominent process.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 28 (1997), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: We review estimates of the spatial ecosystem support required to run a typical semi-intensive shrimp farm in a coastal mangrove area in Carribean Colombia, and to produce food inputs and process wastes for large-scale industrially managed tilapia cage culture and small-scale, semi-intensive tilapia pond farming in Lake Kariba, Zimbabwe. The tilapia farming is discussed in relation to the pelagic kapenta, Limnothrissa miodon (Boulenger), fishery and to inshore fisheries in the Lake.The results show that a semi-intensive shrimp farm needs a spatial ecosystem support—the ecological footprint—35 to 190 times the surface area of the pond, mainly mangrove area. Based on the analysis, we conclude that shrimp farming in Colombia is already utilizing close to the full support capacity of its coastal environment. In intensive tilapia cage farming, the ecological footprint for feed production is 10 000 times larger than the area of the cages. In contrast, a tilapia pond farm maintained on offals from fisheries, agriculture and households depends very little on external ecosystem areas. As long as there is a direct market for human consumption of all kapenta caught in the Lake, fish cage farming based on fish meal from kapenta would be doubtful from ethical, ecological as well as resource management points of view, even if it was economically feasible.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 148-158 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Rules are presented for the startup of an adiabatic tubular reactor, based on a qualitative analysis of the dynamic behavior of continuously-operated vapor- and liquid-phase processes. The relationships between the process dynamics, operating criteria, and operating constraints are investigated, since a reactor startup cannot be isolated from an entire plant startup. Composition control of the process material is critical to speed up plant startup operations and to minimize the amount of offgrade materials. The initial reactor conditions are normally critical for a successful startup. For process conditioning, a plant should have an operating mode at which the reactor can be included in a recycle loop together with its feed system and downstream process section. Experimental data of an adiabatic tubular reactor startup and thermal runaway demonstrate some operational problems when such an intermediate operating stage is missing. The derived rules are applied to an industrial, highly heat-integrated reactor section, and the resulting startup strategy is summarized in an elementary-step diagram.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 503-515 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The safeguarding methodology of chemical plants is usually based on controlling the instantaneous values of process state variables within a certain operating window, the process being brought to shutdown when operating constraints are exceeded. This method does not necessarily prevent chemical reactors suffering from a runaway during dynamic operations because (a) excessive amounts of unreacted chemicals can still accumulate in the process, and (b) no means are provided to the operating personnel to identify hazardous process deviations. A model-based startup and safeguarding procedure is developed for an industrial adiabatic tubular reactor to improve process safety during startup. The trajectories of manipulated variables are calculated by minimizing the amount of one of the main reactants in the reactor effuent. It is concluded that proper control of the initial reactor temperature profile is critical for a safe startup while the impact of other manipulated variables is relatively smaller than that of the initial reactor temperature profile.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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