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  • John Wesley Powell : science and reform in a positive context

    Creator:
    Zernel, John Joseph, 1945-
    Abstract:
    John Wesley Powell worked actively for public land system reform while a director of geographical and geological surveys in the West from 1869 to 1894. Although this has won him acclaim as a conservationist, the basis of Powell's linkage of reform with scientific work is poorly understood. A study of...
    Resource Type:
    Dissertation
    Full Text:
    Department of Geography, Wilbur A. Davis in the Department of Anthropology, and William W. Chilcote in the

  • Seedling recruitment of hairy nightshade and other summer annual weeds in irrigated row crops

    Creator:
    Peachey, Ronald Edward
    Abstract:
    This study evaluated the effects of tillage system, rotational tillage sequences, and winter seed burial depth on weed seedling recruitment in irrigated cropping systems. Notill (NT) planting of vegetable crops reduced emergence of hairy nightshade by 77 to 99% and Powell amaranth emergence from 50 to 87% compared to conventional...
    Resource Type:
    Dissertation
    Full Text:
    simulated NT. Recruitment potential was low in March and April but increased to a maximum in May and June

  • Simulation and field validation of heat and water flow during soil freezing and thawing

    Creator:
    Pikul, Joseph Lawrence
    Abstract:
    Freeze/thaw cycles are numerous in agricultural soils of the Pacific Northwest. Potential loss of soil by erosion is high whenever a soil thaws from the surface creating a saturated soil overlying an impermeable frozen layer. Field studies were conducted to investigate the effect of surface residue on soil freezing. Residue...
    Resource Type:
    Dissertation
    Full Text:
    . Potential loss of soil by erosion is high whenever a soil thaws from the surface creating a saturated soil

  • A general theory of flooding implementing the cuspoid catastrophe

    Creator:
    Lafi, Abd Y.
    Abstract:
    The flooding phenomenon can be defined as the maximum attainable flow condition beyond which the well defined countercurrent flow pattern can no longer exist. Thus the countercurrent flow limit (CCFL) or the flooding limit may be thought of as the flow condition at which the strong interaction between the two...
    Resource Type:
    Dissertation
    Full Text:
    A general theory of flooding implementing the cuspoid

  • Nonlinear control applied to power systems

    Creator:
    Vedam, Rajkumar
    Abstract:
    When large disturbances occur in interconnected power systems, there exists the danger that the power system states may leave an associated region of stability, if timely corrective action is not taken. Open-loop remedial control actions such as field-forcing, line-tripping, switching of series-capacitors, energizing braking resistors, etc., are helpful in reducing...
    Resource Type:
    Dissertation
    Full Text:
    device is used to implement the nonlinear controller in this dissertation. A mathematical model of the