Results 1 - 10 of 1997
Results 1 - 10 of 1997. Search took: 0.034 seconds
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[en] Six infiltration models, some obtained by reformulating the fitting parameters of the classical Kostiakov (1932) and Philip (1957) equations, were investigated for their ability to describe water infiltration into highly permeable sandy soils from the Nsukka plains of SE Nigeria. The models were Kostiakov, Modified Kostiakov (A), Modified Kostiakov (B), Philip, Modified Philip (A) and Modified Philip (B). Infiltration data were obtained from double ring infiltrometers on field plots established on a Knadic Paleustult (Nkpologu series) to investigate the effects of land use on soil properties and maize yield. The treatments were; (i) tilled-mulched (TM), (ii) tilled-unmulched (TU), (iii) untilled-mulched (UM), (iv) untilled-unmulched (UU) and (v) continuous pasture (CP). Cumulative infiltration was highest on the TM and lowest on the CP plots. All estimated model parameters obtained by the best fit of measured data differed significantly among the treatments. Based on the magnitude of R2 values, the Kostiakov, Modified Kostiakov (A), Philip and Modified Philip (A) models provided best predictions of cumulative infiltration as a function of time. Comparing experimental with model-predicted cumulative infiltration showed, however, that on all treatments the values predicted by the classical Kostiakov, Philip and Modified Philip (A) models deviated most from experimental data. The other models produced values that agreed very well with measured data. Considering the eases of determining the fitting parameters it is proposed that on soils with high infiltration rates, either Modified Kostiakov model (I = Kta + Ict) or Modified Philip model (I St1/2 + Ict), (where I is cumulative infiltration, K, the time coefficient, t, time elapsed, 'a' the time exponent, Ic the equilibrium infiltration rate and S, the soil water sorptivity), be used for routine characterization of the infiltration process. (author). 33 refs, 3 figs 6 tabs
[en] The main objective of this work is was the modeling of flowing of the surface and the solid transport within the watershed of Siliana, in the Tunisian backings, by a model which is a physically specialized KINEROS 2. This model allowed us to decide the process of interception of infiltration, flowing of the surface, and of the erosion in small agricultural or urban watershed. KINEROS2 is applied on a watershed of 1039 m"2 and of a perimeter 183,3 km on 20 years over years of observation. We are described the different steps of making use of this model which are: data preparation parameters estimations, the analyses of the principals' parameters sensibility, model calibration and its validity and the overall estimation of solid transport. The KINEROS2 application necessitates the craving of the watershed in plains and channels, which are reported in succession of the upstream towards the downstream taking into consideration the direction of the flowing of the watercourse, of the geology and of the soil occupation of the watershed. Different parameters are calculated (porosity, peak, morphological parameters of plain and channels) estimated (Manning coefficient, net effective ground conductivity) and measured on a plot (spacing, relief). Model adjusting was done on many numeric criteria, which permit to compare and appreciate stand quality, and of validity between the observed and estimated quantities. The stand of observed and estimated hydro grams was carried out learning in mind the sensibility of parameters K, G and n in the model. The model calibration gave some satisfying results highlighted by the errors that don't exceed 4 pour cent for the flow of the liquid peak and 3 pour cent for the volume of the swelling observed and calculated. For the solid transport, the stand was archived by the variation of parameters that are the most sensible (ch) and (spl). The results will be judged acceptable because the mistake doesn't exceed 1%. Sediment transport estimated by the model by turbidigrammes observed for each storm and it is estimated 14 t / ha / year for the hydrological year 2000/2001, which is close to the observed values (an average of 13.8 t / ha / year).
[en] One is easily inclined to attach particular significance to water ingress accidents in small HTR because of the small volume of the primary circuit. In fact, each 100 kg of steam in the HTR-100 and 200 kg in the HTR-Modul increases the primary circuit pressure by about 1 bar. The release of this pressure rise via the primary circuit relief valve normally is retained in the gas storage (HTR-100) or released filtered (HTR-Modul), but even sequences with direct release do not dominate the very low risk of a small HTR. This was one result of a small-effort PSA carried out by the Institut for both small HTR concepts. Nevertheless water ingress accidents dominate the risk of a small HTR. The main contribution comes from an accident which results in a complete depressurization of the primary circuit via the leak of the steam generator and via the falsely open secondary side, the reason for which is different in both reactor concepts due to the different safety concepts. In the case of the Modul it is CMF of valves in the dump line to close and in the case of the HTR-100 a causal failure of the steamside safety valve after being opened by the false ongoing operation of a feed water pump. The frequency of these accidents were estimated to be in the order of 10-5 to 10-6 per reactor year. Radioactive substances are released only in very small quantities. The main source for the release is the surface contamination of the primary circuit, especially of the steam generator, of which a small part (Cs,Sr) or all (I) can be washed-off by water. In the case of the HTR-100 stripping by steam and graphite corrosion contributes also to the release values, due to the high partial pressure of steam caused by a false after-heat removal with the defective steam generator train at the beginning of the accident. The graphite corrosion itself is insignificant. The release values are so small that even no late fatalities need to be expected, practically. (author)
[en] In this work, we apply and make an evaluation the artificial tritium tagging technique of moisture in many kinds of soils for the determination of rainfall infiltration in unsaturated zone. The purpose of this work is the determination of ground water recharge in order to assist evaluating sites for radioactive waste disposal and water resources. From the experimental results obtained, we can conclude that the use of artificial tritium tagging method is an accurate, useful and probably the best available technique to determine ground water recharge. (author)
[pt]Neste trabalho foi aplicada e avaliada a tecnica de marcacao da umidade do solo com tritio artificial, em varios tipos de solos para a determinacao da infiltracao da precipitacao na zona nao saturada para o calculo da recarga de aquiferos, com a finalidade de auxiliar na avaliacao de locais para disposicao de rejeitos radioativos e em avaliacoes de recursos hidricos. Baseando-se nos resultados obtidos, conclui-se que a tecnica de marcacao da umidade do solo com tritio artificial e uma ferramenta util, precisa e provavelmente a melhor tecnica disponivel para se determinar a recarga de aquiferos. (autor)
[en] Objectives of the study on the maximization of durable years of the underground oil storage facility are as follows - Establishment of the detailed field of study and methodology for the preparation of guideline of operation and maintenance of underground oil storage facility - Preparation of program for the assessment of the impedimental factor of safety such as clogging and seawater intrusion. The study sites are Yeosu, Pyeongtaek, Ulsan underground oil storage facilities which are operated by KNOC, SK gas and E1. Various pending problems of each facilities were summarized and assessed. Long-term program for the maximization of durable years of the underground oil storage facility was prepared based on the results of the assessment of each study sites
[en] Studies have shown that neutron probe method can be used to estimate in situ field capacity of soils. This method was applied to ferrallitic soils on the Kossou lakeside slope. Three access tubes were put along the slope and were monitored during the study. The infiltration rate was higher in top soil layers than in deeper soil layers. Drainage and redistribution results show a juxtaposition of two infiltration kinetics, the first being exponential and the second linear. The extrapolation of the second kinetic (slow) gives, for the first 60 centimeters of soil, field capacities of 154 mm, 184 mm and 163 mm for site T1, T3 and T5 respectively. These differences were especially related to the porosity of the different sites studied
[fr]Des etudes ont montre que la sonde a neutrons peut etre utilisee pour la determination in situ de la capacite au champ des sols. Cette methode a ete appliquee a un sol ferrallitique au bord du lac de Kossou. Trois tubes installes le long de la toposequence ont ete suivis durant cette etude. La vitesse d'infiltration est beaucoup plus elevee en surface qu'en profondeur. Les resultats de drainage et ressuyage donnent une juxtaposition de deux cinetiques d'infiltration, l'une exponentielle, l'autre lineaire. L'extrapolation de la deuxieme cinetique (lente) donne, pour les 60 premiers centimetres du sol des capacites au champ de 154 mm, 184 mm et 163 mm respectivement pour les sites T1, T3 et T5. Ces differences sont notamment liees a la porosite des differents sites etudies
[en] Rainfall-induced landslide is a common geohazard in tropical and humid regions. Capillary barrier system (CBS) is a popular and widely studied mitigating measure for rainfall-induced landslides. However, several previous studies have shown that the performance of the conventional CBS under intense rainfalls has not been particularly convincing. This paper aims to explore the feasibility and effectiveness of a newly proposed system, known as “biomediated capillary barrier system” (B-CBS) in minimizing water infiltration into soil. A one-dimensional soil column was used to investigate the infiltration characteristics of the proposed system. The results showed that the B-CBS of biomediated residual soil overlying original residual soil (Test IV) could effectively control the infiltration into soil by taking advantage of the less-permeable biomediated soil cover. The B-CBS of biomediated residual soil overlying gravelly sand (Test V) and the three-layered B-CBS of fine sand overlying gravelly sand and biomediated residual soil (Test VI) showed the best performance in terms of minimizing the water infiltration. A suction of about 5 kPa still remained in the soil column after 60 min of infiltration from the ponded water on the soil surface.
[en] The extreme floods in northern parts of Pakistan are caused by glacier lake outbursts and Dam-Breaks following landslides, which block river valleys. Geographically glacier dams in mountain rivers and valleys have occurred from the east-western and west-western Karakuram ranges and in the lesser Karakuram range floods which arise from Karakuram precipitation and temperature of various region pose greater problem, as these floods are neither homogeneous nor stationary. These floods arise from various generating mechanisms i. e. generated by melting of snow and glacier and those generated from the monsoon rainfall and dam-breaks following landslide into the river and out burst of glacier lake. The estimation of present and future risk of flooding at sites in northern Pakistan requires an understanding, of the climate, which provides, the generating mechanism of floods. Climates are extremely variable and depend op broad global circulation patterns and local topographic influences. The variables of the climate are studied using available data, with emphasis on temperature and precipitation Spatial Co-relation in northern area stations have been conducted to find Co-relation Co-efficient, using regression analysis. This is spread over intra seasonal and inter station comparison. The time series analysis of the climatic variables has been conducted to examine geographically and statistically the trend in their behaviour. This may be reflected in the hydrological regime of glaciers and rivers and it can cause non linear flood series through changes in any one of the flood generating mechanism. The climate feed-back mechanism has been discussed, which are practically important because they assist seasonal prediction of climate and flow in the Indus. Additionally if climate warming is causing an upward Trend in winter and spring temperature and reduction in snowfall, the effect might be felt more widely over the region. The non-linear changes with elevation and differences between windward and leeward sides indicate the complexity of the rainfall, distribution the region. The study gives monthly seasonal and annual total distribution of meteorological variables between various northern areas station, while discussing each one with its impact and the co-relation with the other over a wider prospective. (author)