Fatih Külahcı

Artificial neural network model for earthquake prediction with radon monitoring

Apart from the linear monitoring studies concerning the relationship between radon and earthquake, an artificial neural networks (ANNs) model approach is presented starting out from non-linear changes of the eight different parameters during the earthquake occurrence. A three-layer Levenberg-Marquardt feedforward learning algorithm is used to model the earthquake prediction process in the East Anatolian Fault System (EAFS). The proposed ANN system employs individual training strategy with fixed-weight and supervised models leading to estimations. The average relative error between the magnitudes of the earthquakes acquired by ANN and measured data is about 2.3%. The relative error between the test and earthquake data varies between 0% and 12%. In addition, the factor analysis was applied on all data and the model output values to see the statistical variation. The total variance of 80.18% was explained with four factors by this analysis. Consequently, it can be concluded that ANN approach is a potential alternative to other models with complex mathematical operations.

Iso-radioactivity curves of the water of the Hazar Lake, Elazig, Turkey

Alpha and beta radioactivity concentrations have been determined in the Hazar Lake (East of Turkey) surface, middle and bottom water. The total alpha-radioactivity concentration in the surface, middle and bottom levels varies from 0.32 to 2.52 Bq/l, from 0.21 to 2.70 Bq/l and from 0.12 to 0.96 Bq/l, respectively. The beta-radioactivity concentration in the surface, middle and bottom water levels varies from 0.01 to 0.16 Bq/l, from 0.01 to 0.27 Bq/l and from 0.03 to 0.23 Bq/l, respectively. The iso-radioactivity curves were drawn from the obtained data during 1998–2001.

Spatio-temporal modeling of 210Pb transportation in lake environments

Radioactive particle movement analysis in any environment gives valuable information about the effects of the concerned environment on the particle and the transportation phenomenon. In this study, the spatio-temporal point cumulative semivariogram (STPCSV) approach is proposed for the analysis of the spatio-temporal changes in the radioactive particle movement within a surface water body. This methodology is applied to the (210)Pb radioactive isotope measurements at 44 stations, which are determined beforehand in order to characterize the Keban Dam water environment on the Euphrates River in the southeastern part of Turkey. It considers the contributions coming from all the stations and provides information about the spatio-temporal behavior of (210)Pb in the water environment. After having identified the radii of influences at each station it is possible to draw maps for further interpretations. In order to see holistically the spatial changes of the radioisotope after 1st, 3rd and 5th hours, the radius of influence maps are prepared and interpreted accordingly.

Potential utilization of the absolute point cumulative semivariogram technique for the evaluation of distribution coefficient.

The classical solid/liquid distribution coefficient, K(d), for radionuclides in water-sediment systems is dependent on many parameters such as flow, geology, pH, acidity, alkalinity, total hardness, radioactivity concentration, etc. in a region. Considerations of all these effects require a regional analysis with an effective methodology, which has been based on the concept of the cumulative semivariogram concept in this paper. Although classical K(d) calculations are punctual and cannot represent regional pattern, in this paper a regional calculation methodology is suggested through the use of Absolute Point Cumulative SemiVariogram (APCSV) technique. The application of the methodology is presented for (137)Cs and (90)Sr measurements at a set of points in Keban Dam reservoir, Turkey.

Risk assessment of distribution coefficient from 137Cs measurements

Classically distribution coefficient is defined as the ratio of solid total element concentration to surface water total concentration. This coefficient is obtained from the ion measurements in the Keban Dam, Turkey, which supplies water for domestic, irrigation and hydroelectric energy generation purposes. The measurements of 137Cs are carried out in 40 different sites and the general risk formulation and application is achieved for the distribution coefficient. The models are of exponential type and the spatial independence of the data is considered. Various charts are prepared for a set of risk levels as 5%, 10%, 20%, 25%, and 50%.

A suggestion to radiological hazards characterization of 226 Ra, 232 Th, 40 K and 137 Cs: spatial distribution modelling

Spatial distribution modelling has been proposed to characterize the radiological hazards associated with concentration of natural 226Ra, 232Th, 40K and artificial 137Cs radionuclides in the nature. These elements have been determined for the sediment samples of the Bafa Lake with the aim of radiation hazard evaluation via a high purity germanium detector gamma spectrometry. Their activity concentrations in sediments are in the ranges of 29.87 ± 2.2-72.56 ± 11 Bq kg- 1 dry weight (dw), 31.57 ± 3.5-66.48 ± 8.3 Bq kg- 1 (dw), 332.01 ± 12-1092.37 ± 21 and 0.65 ± 0.04-3.96 ± 0.78 Bq kg- 1 (dw), respectively. In order to determine the radiological hazard associated with the radioactivity in the samples, the external terrestrial gamma dose rate in air, annual effective dose rate, the radium equivalent activity and the external hazard index are calculated and compared with the data from literature. Moreover, the spatial modelling distributions are obtained visually for radiological hazards characterization of these elements, which are very dangerous in terms of radiological and environmental pollution in the nature. These visual distributions give meaningful information for future researches on the migration of radionuclides in the environment.

Chaotic Behavior of Soil Radon Gas and Applications

The soil 222Rn concentration non-linear patterns are investigated by the application of various chaos methodologies based on 70 272 measurement data from the East Anatolian Fault Zone, which is one of the world’s most active faults. Among these methodologies are Lyapunov exponent, surrogate data, rescaled range (R/S) analysis, Fourier spectrum, phase space reconstruction, mutual information, false nearest neighbors, and correlation dimension. The results indicate that the nonlinear dynamical approach is convenient for characterization and prediction of the 222Rn concentration dynamics, which are in turn usually used as an earthquake precursor. Behaviour of 222Rn gas is important in earthquake prediction researches.

Spatiotemporal modeling and simulation of chernobyl radioactive fallout in northern Turkey

In this study, the Chernobyl radioactive fallouts are described through the spatio-temporal point cumulative semivariogram (STPCSV) method, which is used to identify spatial and temporal regionalized changes in 134Cs and 137Cs concentrations. The application of the methodology is presented for the Black Sea Region, which is the most affected area from the Chernobyl radioactive fallouts in Turkey. After detailed explanation of the methodology hourly simulation maps are prepared for 134Cs and 137Cs spreads over the area. Each one of these maps provides valuable information about the spatial variability of the concentrations concerned. The STPCSV helps to identify the exhibition of heterogenic structure of radioactive concentration in the study area.

The Statistical Analysis of the Radioactivity Concentration of the Water Data in Malatya City, Turkey

Abstract The natural radioactivity data of 306 water samples, which were obtained from various 51 sampling points of Malatya that is the eastern city of Turkey, was studied by applying the factor and cluster statistical analysis to interpretation and determination of the general radioactivity in the city. The obtained data from the statistical analysis were evaluated according to the geological formation of the state. The varimax factor rotation was applied to the data. Two factors were extracted from the radioactivity of the water supplies, tap water, and water depots data, which account for about 95.52% of the total variance. Factor 1 and factor 2 explained 48.5% and 47% of the variance, respectively.

Hazar Gölü’ndeki Radyoaktif Seviyelerin Belirlenmesi için Uyarlamalı Sinirsel-Bulanık Çıkarım Sistemi (ANFIS) ile Modellenmesi

Bu calismada, bir Adaptif Sinirsel Bulanik Cikarim Sistemi (ANFIS) modeli Hazar Golu (Turkiye) sularinin alfa radyoaktivitesinin belirlenmesi ve onun bilinmeyen degerlerinin ongorulmesi icin onerilmistir. Model parametreleri olarak pH, toplam sertlik (TH), derinlik, elektriksel iletkenlik (EC) ve gol suyunun toplam alfa radyoaktivitesi belirlenmistir. ANFIS modeli bes tabakali yapi icin geri-yayilim algoritmasi kullanilarak gerceklestirilmistir. Teorik ve deneysel (ANFIS) tahmin sonuclari arasindaki ortalama rolatif hata 0.7043% dir. Test verileriyle radyoaktivite verileri arasindaki rolatif hata 0.06% ve 14% arasinda degismistir. Ek olarak, ANFIS modelinin gecerliligi regresyon modeli ile de test edilmistir. ANFIS modeli istatistiksel olarak regresyon modelinden daha guvenilir sonuclar vermistir.