Publication Search Results

Now showing 1 - 10 of 676

  • (1973) Pilgrim, D. H.; Johnston, P. R.
    A detailed study on the optimisation of the parameter values of the Boughton daily rainfall-runoff model. Optimum values were sought using the Steepest descent, Simplex and Davidson optimising methods. It had been intended to correlate these optimum parameter values with measurable catchment characteristics. Rapid initial reductions in the values of the objective function were readily achieved and the solutions approached apparent optimum points on the response surface. However several of these points were found for each catchment and there were large differences in the parameter values between points. It was found that further improvements in the objective function could usually be achieved by using another of the search techniques or by numerical trials, and in this way, downhill paths on the response surface were found from the apparently optimum points. This work was pursued for one of the catchments until the paths appeared to be converging, but coincidence at a true optimum could not be achieved.. A number of somewhat different sets of parameter values which appeared to lie in a flat "valley" area of the response service were obtained, and these sets gave equally good fits to the observed runoff data. An algebriac analysis of the of the operation of the model and of the effect on the objective function of changes in some individual parameter values led to important findings on some of the problems encountered. It is probable that the findings from the algebriac and numerical analyses would be applicable to the rainfall-runoff models.

  • (1973) Feacham, R
    Study of traditional patterns of water use. Data reported for the Raiapu Enga clan in the Saka Valley near Wapenamanda in the Western Highlands. Regional and environment and culture briefly described. Attitudes to water, including fear of poison,, female contamination. Sources are natural streams, rivers and springs. Rainwater also in the wet season. Pollution status varies from relatively clean to human and porcine faecal material. Water is collected in late afternoons in gourds, bamboos, tins and cooking pots, for which the average return journey takes 12.5 minutes. Each domestic group collects 2.46 liters a day of which 79% is drunk. The rest is used for cooking food (for humans and pigs), drinking for dogs, pigs and chickens, washing utensils, and discarded. Total per capita use is 0.68 litres per day. On average 0.54 litres are drunk daily and, including the water both contained in food and caused by food oxidation. 2.4 litres per day are available to the body. Per capita use decreases with increasing size of domestic group: travel time to source has no association with water use patterns. Major non-domestic uses of water include coffee washing and growing the reed-like plant Kuta from which women's aprons are made.

  • (1973) Jenkins, B. S.
    The mechanism of suspension of a non-buoyant particle in a turbulent flow has been examined from the viewpoint of the history of an individual particle. A program developed to compute trajectories of a non-buoyant particle within a field of eddies. The trajectories indicate that a particle may be suspended indefinitely within an individual eddy of the eddy field or may fall through the eddy field with a fall velocity which differs from the settling velocity of the particle in the quiscent fluid. The quantitative results are specific to the particular conditions examined. In a flow in which the net vertical flow of the fluid is zero, the time averaged fall velocity of a non-buoyant particle may differ from the settling velocity of the particle in the quiescent fluid and may be reduced to zero. In a series of experiments, rates of entrainment of fluids across a density discontinuity between two fluid layers have been measured. In these experiments, the turbulent flow of a fluid layer has been simulated by the motion induced by an oscillating grid. Density discontinuities due to temperature differences, salinity differences and the presence in one layer of suspended particles have been examined. The measured entrainment rates are consistent with the hypothesis that under given conditions the rate of entrainment is dependent upon the molecular diffusitivity of the property causing the the density discontinuity

  • (1974) Fietz, T. R.
    The efficiency of programmable and manual methods of finding the shortest spanning tree of a graph is investigated. Incomplete connecting graphs are the main concern. Computer programs for three methods are included.

  • (1970) Yue, Richard Koon-Yin