David Scholefield

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A refinement calculus for the development of real-time systems is presented. The calculus is based upon a wide-spectrum language called TAM (the Temporal Agent Model), within which both functional and timing properties can be expressed in either abstract or concrete terms. A specification oriented semantics for the language is given. Program development is(More)
Re-packed soil columns of the Crediton series were sown with white clover or perennial ryegrass, with nitrate managed according to organic and conventional farming regimes respectively. Visual observations revealed a rapid enhancement in soil structure beneath white clover compared to ryegrass and unplanted soil. Enhanced structural differentiation beneath(More)
The Temporal Agent Model (TAM) is a wide-spectrum development language for rea~-time systems. In TAM, limited resources axe modelled by deriving release times and absolute deadlines from weakest pre-condition predicate transformers. In this paper the language syntax and semantics are described along with a number of examples. 1 I n t r o d u c t i o n The(More)
Because of current environmental legislation in European grass-based farming, there is a need to develop tools that can link nitrogen (N) production with losses to the environment. A mass balance empirical model (NCYCLE) is proposed to fulfil this role. This study describes the principles and stages to develop a mass balance N cycle model for Irish(More)
Several long-term sets of hourly nitrate concentration data were obtained through deployment of a nitrate sensor in an upper reach of the River Taw, a small moorland-fed river in the South West of the UK. Examination of the data obtained during periods of low flow and the absence of rainfall in the catchment revealed the presence of marked diurnal cycles,(More)
Organic farming practice prohibits the use of triple superphosphate (TSP) as a source of phosphorus. As basic slag is not now generally available, interest is focused on the relative value of ground rock phosphate (GRP). A comparison of TSP and Gafsa GRP was made during 1988–92 as to their ability to increase DM production under cutting from newly sown(More)
Sustainable catchment management requires increased levels of integration between groups of natural and social scientists, land and water users, land and water managers, planners and policy makers across spatial scales. Multiple policy drivers, covering urban and rural communities and their relationships with land and water use, have resulted in the need(More)