Appraisal of soft computing techniques in prediction of total bed material load in tropical rivers     

C K CHANG  H MD AZAMATHULLA  N A ZAKARIA  A AB GHANI 《Journal of Earth System Science》2012,121(1):125-133

This paper evaluates the performance of three soft computing techniques, namely Gene-Expression Programming (GEP) (Zakaria et al 2010), Feed Forward Neural Networks (FFNN) (Ab Ghani et al 2011), and Adaptive Neuro-Fuzzy Inference System (ANFIS) in the prediction of total bed material load for three Malaysian rivers namely Kurau, Langat and Muda. The results of present study are very promising: FFNN (R ² = 0.958, RMSE = 0.0698), ANFIS (R ² = 0.648, RMSE = 6.654), and GEP (R ² = 0.97, RMSE = 0.057), which support the use of these intelligent techniques in the prediction of sediment loads in tropical rivers.  相似文献   

The 2011 submarine volcanic eruption in El Hierro (Canary Islands)   总被引：1，自引：0，他引：1  

Juan Carlos Carracedo  Francisco Pérez Torrado  Alejandro Rodríguez González  Vicente Soler  José Luis Fernández Turiel  Valentin R. Troll  Sebastian Wiesmaier 《Geology Today》2012,28(2):53-58

Forty years after the Teneguía Volcano (La Palma, 1971), a submarine eruption took place off the town of La Restinga, south of El Hierro, the smallest and youngest island of the Canarian Archipelago. Precursors allowed an early detection of the event and its approximate location, suggesting it was submarine. Uncertainties derived from insufficient scientific information available to the authorities during the eruption, leading to disproportionate civil protection measures, which had an impact on the island's economy—based primarily on tourism—while residents experienced extra fear and distress.  相似文献   

Reconstruction of annual winter rainfall since A.D.1579 in central-eastern Spain based on calcite laminated sediment from Lake La Cruz     

Lidia Romero-Viana  Ramon Julià  Martin Schimmel  Antonio Camacho  Eduardo Vicente  M. Rosa Miracle 《Climatic change》2011,107(3-4):343-361

We present the first winter (December to March) rainfall reconstruction based in a novel proxy, the thickness of annual calcite laminations preserved in Lake La Cruz (central–eastern Spain). A previous calibration analysis between laminae thickness and the instrumental data series (1950 to present) indicated a highly significant correlation with winter rainfall. Therefore this study attempts the winter rainfall reconstruction since the onset of laminations (1579 a.d.) by means of the calibration function previously developed. The verification analysis between inferred annual values and earlier instrumental data (1859–1949) confirms the suitability of this novel proxy and the reliability of the series reconstructed. The reconstructed series show the fluctuating character of winter rainfall in the western Mediterranean area; interdecadal dry periods alternated with wetter periods following, in a board sense, the pattern recorded by documentary sources in other regions of the Iberian Peninsula. At present times regional winter rainfall anomalies are highly correlated with the phase of the North Atlantic Oscillation (NAO). However the time series analysis showed the dominance of nonstationary components at high frequencies of the climate signal over the last four centuries suggesting that the connection between winter rainfall and the NAO has not been stable over time and also other modes of variability, not only NAO, may have conditioned winter rainfall variability.  相似文献   

Analysis of extreme temperatures for four sites across Peninsular Spain   总被引：1，自引：1，他引：0  

Dolores Furi��  Vicente Meneu 《Theoretical and Applied Climatology》2011,104(1-2):83-99

Statistical analyses regarding climate studies have often used the average temperature as one of the main variables. However, the tails of the respective distributions are also crucial and have become increasingly considered in recent years. As the Intergovernmental Panel on Climate Change in its fourth assessment report (IPCC 2007) states, ??the type, frequency and intensity of extreme events are expected to change as Earth??s climate changes??. In this paper, the focus is on the statistical behaviour of extreme (maximum and minimum) values of temperature, both in winter and summer. Under the framework of the Extreme Value Theory, the methodology of block maxima is employed. The generalised extreme value distribution, allowing for a linear trend in the location parameter, is fitted to data in order to capture the time tendency in the non-stationary processes. We are able to approximate expected values with a determined probability and to identify time trends of such events. Particularly, an increasing time trend in maximum and minimum temperature is generally detected which could be of great concern to public and private sectors.  相似文献   

Occurrence of perfluorinated compounds in water, sediment and mussels from the Cantabrian Sea (North Spain)   总被引：1，自引：0，他引：1  

Gómez C  Vicente J  Echavarri-Erasun B  Porte C  Lacorte S 《Marine pollution bulletin》2011,62(5):948-955

Perfluorinated compounds (PFCs) have emerged as significant global environmental pollutants with persistent, bioaccumulative and toxic properties. The aim of this study was to determine the occurrence of PFCs in water (wastewater, submarine emissaries and port-waters), sediment and transplanted mussels in estuarine areas of high urban and industrial impact from Northern Spain. Five PFCs of industrial use were studied: perfluorooctanesulfonate, perfluorohexanesulfonate, perfluorobutanesulfonate, perfluorooctanoate acid and perfluorononanoate acid. After selective extraction, samples were analyzed by Ultra Performance Liquid Chromatography coupled to tandem mass spectrometry. ΣPFCs ranged from 0.06 to 10.9 ng/L in water, with higher levels in wastewater treatment plants effluents and port waters than in submarine emissaries. Little accumulation was observed in sediments and mussels with ΣPFCs ranging from 0.01-0.13 ng/g dw and 0.01-0.06 ng/g ww, respectively. Most ubiquitous compounds were PFOS and PFOA. Mass fluxes of PFCs to the Cantabrian Sea are estimated and the impact to the coastal ecosystem is discussed.  相似文献   

Ontogenic shifts in predatory roles involving two invasive species     

Pedro Manuel Anastácio  Emília Pereira Leite  Margarida Ferreira  Luís Vicente  Alexandra Marçal Correia 《Limnologica》2011,41(3):228-234

The red swamp crayfish, Procambarus clarkii, and the eastern mosquitofish, Gambusia holbrooki have been introduced worldwide, but the interactions between these invasive species are not well known. The effects of crayfish presence, crayfish size and water depth on the consumption of G. holbrooki by P. clarkii were analyzed, as were the effects of mosquitofish presence and water depth on the consumption of recently hatched crayfish (RHC) by mosquitofish. To better understand this subject we conducted aquaria and open air mesocosm experiments simulating a rice field section. Aquarium experiments showed that P. clarkii consumes G. holbrooki and that G. holbrooki consumes RHC. Adult crayfish size did not significantly affect the consumption of mosquitofish and water depth had no effect on the consumption of G. holbrooki by P. clarkii and vice versa. In the outdoor mesocosm experiments P. clarkii caused no statistically significant effect on G. holbrooki numbers or biomass when compared with controls without crayfish. In spite of this, the analysis of crayfish stomach contents clearly demonstrated that several G. holbrooki individuals were consumed, indicating that crayfish can profit from the presence of G. holbrooki. Results from our study suggest that in shallow pools there are strong interactions between the two invasive species since adult crayfish predate mosquitofish and mosquitofish predate recently hatched crayfish. Therefore, there are bidirectional trophic interactions between these invasive species which change depending on their relative size. We believe that these interactions should become more relevant in confined areas such as small shallow pools formed during the late summer and autumn.  相似文献   

Impact of subsurface rock fragments on runoff and interrill soil loss from cultivated soils   总被引：1，自引：0，他引：1  

T. Smets  M. López‐Vicente  J. Poesen 《地球表面变化过程与地形》2011,36(14):1929-1937

Field and laboratory studies have indicated that rock fragments in the topsoil may have a large impact on soil properties, soil quality, hydraulic, hydrological and erosion processes. In most studies, the rock fragments investigated still remain visible at the soil surface and only properties of these visible rock fragments are used for predicting runoff and soil loss. However, there are indications that rock fragments completely incorporated in the topsoil could also significantly influence the percolation and water distribution in stony soils and therefore, also infiltration, runoff and soil loss rates. Therefore, in this study interrill laboratory experiments with simulated rainfall for 60 min were conducted to assess the influence of subsurface rock fragments incorporated in a disturbed silt loam soil at different depths below the soil surface (i.e. 0.001, 0.01, 0.05 and 0.10 m), on infiltration, surface runoff and interrill erosion processes for small and large rock fragment sizes (i.e. mean diameter 0.04 and 0.20 m, respectively). Although only small differences in infiltration rate and runoff volume are observed between the soil without rock fragments (control) and the one with subsurface rock fragments, considerable differences in total interrill soil loss are observed between the control treatment and both contrasting rock fragments sizes. This is explained by a rapid increase in soil moisture in the areas above the rock fragments and therefore a decrease in topsoil cohesion compared with the control soil profile. The observed differences in runoff volume and interrill soil loss between the control plots and those with subsurface rock fragments is largest after a cumulative rainfall (P_cum) of 11 mm and progressively decreases with increasing P_cum. The results highlight the impacts and complexity of subsurface rock fragments on the production of runoff volume and soil loss and requires their inclusion in process‐based runoff and erosion models. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献