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  • 1995-1999  (3)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Journal of applied electrochemistry 27 (1997), S. 1143-1148 
    ISSN: 1572-8838
    Schlagwort(e): Voidage ; electrolyser ; conductivity cell ; 20-segment electrode
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract Vertical electrolysers with parallel-plate electrodes and with a narrow interelectrode gap or with narrow gaps between the membrane and each of the electrodes are used industrially to produce gases. Conductivity measurements were carried out with a small conductivity cell built within one compartment of the cell and just above the top of the working electrode. KOH solutions were used as electrolytes and gas bubbles were evolved at a 20-segment electrode. The effect of various parameters, including current passed through the 20-segments electrode, flow rate of liquid, temperature and nature of gas evolved, was studied. From the normalized conductivity measured, the gas voidage ε was obtained. It was found that for a bubbly flow the gas voidage just above the gas-evolving electrode is given by the relation: ε/(εmax − ε) = 1.4 Qg/Ql where εmax is the maximum voidage for gas bubbles in a solution; εmax=0.69 for oxygen as well as hydrogen in a concentrated and a dilute KOH solution at different liquid flow rates. Qg is the volumetric flow rate of gas saturated with water vapour and Ql is the volumetric flow rate of liquid. This relation can be used to calculate the voidage distribution in the bulk solution of the cell compartment with a gas-evolving electrode.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    ISSN: 1573-5117
    Schlagwort(e): Lake Tanganyika ; limnology ; upwelling ; internal waves ; patchiness
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Ten variables were measured at least twice per month at three locations of Lake Tanganyika (East Africa) over one year (1993–94). Upwelling was observed in the south of the lake during the dry, windy season from May to September. Stratification was variable in strength but always present in the north. The lake showed a marked tilting of the epilimnion during the dry season (0-20 m in the South, 60–70 m in the North). This period was followed by oscillations of water masses towards an equilibrium when the strong winds from the south east ceased. Conductivity and pH fluctuations indicated dampened oscillations, particularly at the ends of the lake. Movements of the epilimnion toward an equilibrium position generated and/or re-inforced internal waves. These waves were inferred from fluctuations of chemical and physical characteristics of the lake. The concentrations of inorganic P and N commonly fluctuated by a factor of 3 or more in the epilimnion. The period of long-period internal waves was estimated to be ca. 28–33 days. Turbidity changes suggested pulse production caused by internal waves linked to non-random patchiness in nutrients and organisms. Turbulence resulting from highly dynamic physical events also induce random-patchiness in water composition. The lake water generally showed oligotrophic characteristics near the surface but had high concentrations of nutrients in deep water. The results showed that the trophic state of Lake Tanganyika, like that of the oceans, seems to depend largely on regeneration processes. The annual limnological cycle in Lake Tanganyika appears closely linked to the climatic conditions.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Hydrobiologia 407 (1999), S. 1-24 
    ISSN: 1573-5117
    Schlagwort(e): L. Tanganyika ; management ; responsible fisheries ; sustainable development
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Lake Tanganyika hosts one of the largest inland fisheries in Africa and is a significant source of food and livelihood to millions dwelling inside and outside of its basin. The lake and its environs support a wide array of subsistence and commercial activity as well as a remarkable assemblage of tropical flora and fauna, including highly diverse populations of endemic fish. This paper describes efforts undertaken through the FAO/FINNIDA Lake Tanganyika Research Project (LTR) to investigate the lake's production and potential and to advise on modalities for the optimal management of its resources, in order to serve present and future human welfare and conservation needs. Specifically, the paper essays to: (a) provide background on the scope and content of LTR Project work; (b) situate project research and methodologies in terms of contemporary developments in fisheries management theory and application; (c) identify and characterise, with reference to research outcomes generated through the project's Scientific Sampling Programme, socio-economic investigations and legal-institutional studies, major development and management challenges that confront fisheries resource users, administrators, planners, and policy makers; and finally, (d) consider various policy options appropriate to conditions of ecosystem uncertainty, plural stakeholder interests and complex interactions between fishing and non-fishing sectors of the wider economy. It is argued that the Lake Tanganyika situation defies diagnosis and prescription according to conventional ‘stock assessment driven’ management thinking. The lake instead presents a compelling case for the application of multi-disciplinary management approaches, involving strong levels of community participation.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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