| 1. |
- Bobba, A. G., et al.
(författare)
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Application of a watershed runoff model to north-east pond river, Newfoundland: To study water balance and hydrological characteristics owing to atmospheric change
- 1997
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Ingår i: Hydrological Processes. - 1099-1085. ; 11:12, s. 1573-1593
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Tidskriftsartikel (refereegranskat)abstract
- The hydrological sensitivities to long-term climate change of a watershed in Eastern Canada were analysed using a deterministic watershed runoff model developed to simulate watershed acidification. This model was modified to study atmospheric change effects in the watershed. Water balance modelling techniques, modified for assessing climate effects, were developed and tested for a watershed using atmospheric change scenarios from both state of the art general circulation models and a series of hypothetical scenarios. The model computed daily surface, inter- and groundwater hows from the watershed. The moisture, infiltration and recharge rate are also computed in the soil reservoirs. The thirty years of simulated data can be used to evaluate the effects of climatic change on soil moisture, recharge rate and surface and subsurface flow systems. The interaction between surface and subsurface water is discussed in relation to climate change. These hydrological results raise the possibility of major environmental and socioeconomic difficulties and have significant implications for future water resource planning and management. (C) 1997 John Wiley & Sons, Ltd.
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| 2. |
- Bobba, A. G., et al.
(författare)
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Application of first-order and Monte Carlo analysis in watershed water quality models
- 1996
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Ingår i: Water Resources Management. - 0920-4741. ; 10:3, s. 219-240
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Tidskriftsartikel (refereegranskat)abstract
- Functional analysis and Monte Carlo simulation were used to quantify uncertainties in model simulation of pollution behaviour and effects. The first-order part of the functional analysis method provides a measure of uncertainties in dependent variables in terms of uncertainties in independent variables. The procedure is based on first-order terms in the Taylor series expansion of the dependent variable about its mean value with respect to one or more independent variables. The major assumption is that all independent and dependent variables are the second moment variables (SMV), which means that the behaviour of any SMV is completely described by its mean and standard deviation. The mathematical simplicity of the procedure allows application by simple input-output models. Consequently, it has been applied to many environmental simulators, e.g. hydrological models, stream water quality models, lake water quality models and ground water pollution models. The Monte Carlo simulation method uses a large number of repeated trials or simulations with the values for stochastic inputs or uncertain variables selected at random from their assumed parent probability distributions to establish an expected range of model uncertainty.
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| 3. |
- Bobba, A. G., et al.
(författare)
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Computer program (shock) to predict acid shocks in watersheds using stochastic analysis
- 1996
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Ingår i: Computers & Geosciences. - : Elsevier BV. - 1873-7803 .- 0098-3004. ; 22:4, s. 399-408
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Tidskriftsartikel (refereegranskat)abstract
- High hydrogen ion concentrations of runoff events were analyzed in terms of the probability distributions of frequency, duration, magnitude, and time of occurrence. Simple stochastic models were applied to the probability distributions of the annual frequency of high hydrogen ion concentration flows and their magnitudes. A consideration of the statistical properties of the given stochastic variables led to the development of a technique with which higher hydrogen flow events exceeding any higher level of interest may be investigated without resorting to reanalysis of the historical data. The proposed methodology was applied to the daily hydrogen ion concentration flow records of Mersey River Watershed, N.S., Canada, which is affected by acid precipitation. Copyright (C) 1996 Elsevier Science Ltd
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| 4. |
- Krishna, G. R., et al.
(författare)
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Role of Pt content in the microstructural development and oxidation performance of Pt-aluminide coatings produced using a high-activity aluminizing process
- 1998
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Ingår i: Materials Science and Engineering A. ; 251:1-2, s. 40-47
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Tidskriftsartikel (refereegranskat)abstract
- The present study highlights the effect of Pt content on the microstructure of Pt-aluminide coatings produced using a single-step high-activity aluminizing process. The amount of Pt in the coating was varied by changing the thickness of the initial electroplated Pt layer between 1 and 15 μm. The aluminium uptake from the pack was found to be almost the same for all the coatings produced using a Pt layer of thickness 2.5 μm and above, with a somewhat lower uptake for the coating corresponding to a 1 μm thick Pt layer. The coating microstructure, which consisted of an outer two-phase (PtAl2 in a matrix of NiAl) layer, an intermediate NiAl layer and an interdiffusion layer, was also found to be independent of the Pt layer thickness when it was in the range 2.5-10 μm. In the case of the 1 μm Pt layer, however, the whole of the Pt remained in solid solution in the NiAl phase. For a Pt layer thickness exceeding 10 μm, on the other hand, a continuous surface layer of PtAl2 phase was observed. The above mentioned influence of the thickness of the Pt plated layer on the microstructure of the Pt-aluminide coatings observed in the present investigation could be explained in terms of the Pt concentration in the diffusion layer resulting from the interdiffusion between the Pt layer and the superalloy substrate during the pre-aluminizing diffusion treatment. Cyclic oxidation tests on these Pt-aluminide coatings reveal that the presence of Pt in aluminide coatings, in general, enhances oxidation resistance. However, in order to fully realize the beneficial effects of Pt on oxidation behaviour, a certain minimum Pt content in the coating was found to be necessary.
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