Sample records for olade
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NASA Astrophysics Data System (ADS)
Kopka, Piotr; Wawrzynczak, Anna; Borysiewicz, Mieczyslaw
2016-11-01
In this paper the Bayesian methodology, known as Approximate Bayesian Computation (ABC), is applied to the problem of the atmospheric contamination source identification. The algorithm input data are on-line arriving concentrations of the released substance registered by the distributed sensors network. This paper presents the Sequential ABC algorithm in detail and tests its efficiency in estimation of probabilistic distributions of atmospheric release parameters of a mobile contamination source. The developed algorithms are tested using the data from Over-Land Atmospheric Diffusion (OLAD) field tracer experiment. The paper demonstrates estimation of seven parameters characterizing the contamination source, i.e.: contamination source starting position (x,y), the direction of the motion of the source (d), its velocity (v), release rate (q), start time of release (ts) and its duration (td). The online-arriving new concentrations dynamically update the probability distributions of search parameters. The atmospheric dispersion Second-order Closure Integrated PUFF (SCIPUFF) Model is used as the forward model to predict the concentrations at the sensors locations.
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NASA Astrophysics Data System (ADS)
Kopka, P.; Wawrzynczak, A.; Borysiewicz, M.
2015-09-01
In many areas of application, a central problem is a solution to the inverse problem, especially estimation of the unknown model parameters to model the underlying dynamics of a physical system precisely. In this situation, the Bayesian inference is a powerful tool to combine observed data with prior knowledge to gain the probability distribution of searched parameters. We have applied the modern methodology named Sequential Approximate Bayesian Computation (S-ABC) to the problem of tracing the atmospheric contaminant source. The ABC is technique commonly used in the Bayesian analysis of complex models and dynamic system. Sequential methods can significantly increase the efficiency of the ABC. In the presented algorithm, the input data are the on-line arriving concentrations of released substance registered by distributed sensor network from OVER-LAND ATMOSPHERIC DISPERSION (OLAD) experiment. The algorithm output are the probability distributions of a contamination source parameters i.e. its particular location, release rate, speed and direction of the movement, start time and duration. The stochastic approach presented in this paper is completely general and can be used in other fields where the parameters of the model bet fitted to the observable data should be found.
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NASA Astrophysics Data System (ADS)
Ajayi, C. O.; Ajakaiye, D. E.
1981-12-01
The origin of the Benue trough has been a controversial subject. Previous workers in the area have evolved several theories ranging from a rift, with or without plate tectonic concepts (King, 1950; Wright, 1968, 1970; Burke et al., 1970; Grant, 1971; Olade, 1975) to a geosyncline (Lees, 1952) and a combination of both (Cratchley and Jones, 1965; Offodile, 1976) to explain the origin of the trough. One of the aims of the gravity survey, carried out in the middle Benue and discussed in this paper, was to attempt to resolve some of the problems associated with the origin of the trough as proposed by previous workers and in so doing to explain the geological peculiarities associated with the trough. Interpretations of the gravity data along two north—south profiles in the survey area indicated the existence of a rift, of normal width (about 40 km) buried under the Cretaceous cover and located between the central axis (ridge) of the trough and the northern boundary of the trough. The gravity minimum which occurs south of the central axis of the trough, was also ascribed to another rift. Thus the Benue trough is considered to consist of two parallel rifts separated by the axial ridge which partly explains the abnormal width of the trough. The interpreted models also indicate a low-angle thrust fault, with a small displacement, which may be related to the folding of the sediments in the trough and also to the asymmetry of the trough. Furthermore, the gravity data suggest that oceanic crust might not have reached the ground surface in the Benue trough, as in the Red Sea, before rifting ceased.
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NASA Astrophysics Data System (ADS)
Kovács, Gábor; Raveloson, Andrea; Székely, Balázs; Timár, Gábor
2013-04-01
The northern scarp of the Pinka flat - situated in the western part of the Pannonian Basin - is largely characterized by landslides and gullies. This area is a transition zone between the uplifting Eastern Alps and the subsiding Little Hungarian Plain. The interaction of the juxtaposed units results in neotectonically induced features, such as unstable slopes, gullies and landslides. These mass movements represented economical and social hazard in the 20th century. Earlier studies of this area (eg. Kecskés, 1968; Szilágyi, 1989) concentrated on regional scale, but the real nature of mass movements is still unclear. Therefore our goal was to study the landslides on smaller scales. This contribution presents an individual landslide (in the vicinity of Olad, outskirt of Szombathely) that has been examined in detail, using different geophysical and geomorphological methods. Field surveys and geomorphological measurements have been achieved several times (from 2006) to have a better view on the role of geomorphology in the formation of the landslide. Fixed points were deployed inside the landslide as well as near to it to quantify movements of surface over time. The structure of the slope was studied using shallow boreholes and vertical electrical sounding (VES) measurements. Furthermore Electrical Resistivity Tomography (ERT) was used along several transverse and longitudinal profiles to complement these studies with two dimensional electrical resistivity sections. Results from the last 6 years show that the evolution of the landslide seems to be triggered by the weather conditions of the Alpine foothills and the northern scarp of Pinka flat, though the origin of the landslide is neotectonic. Geophysical results show that the sliding mass is situated on a clayey layer. The main cause of mass movement seems to be the slope-parallel layering of the clayey and sandy sediment, though recent time human influence played an important role as well. This research was financed by the Hungarian National Scientific Fund (OTKA NK83400). KECSKÉS T. 1968. A szombathelyi dombcsúszás. Vasi Szemle 22. 4. pp. 557-566 SZILÁGYI E. 1980. Vas megye felszínmozgásainak katasztere. Földr. Ért. 38 1-2. pp. 33-54