Impact of lightning on organic matter-rich soils: influence of soil grain size and organic matter content on underground fires     

Vittorio Zanon  Fátima Viveiros  Catarina Silva  Ana Rita Hipólito  Teresa Ferreira 《Natural Hazards》2008,45(1):19-31

A detailed study was carried out on a piece of land that had been struck by lightning during the violent rainstorm that raged over the Island of S?o Miguel (Azores Archipelago) in late October 2006. Temperature and gas measurements (CO₂, CO, H₂S and CH₄) were performed in four study trenches, dug in an area of ∼3 m², where an underground fire had been initiated by the impact with a lightning stroke, followed by the emission of a column of gases and smoke. The soil under study was originally a well-pedogenized about 80 cm thick bed, made of volcanic clayey to silty tephra fallouts and contained 5.5–9.7% of organic matter. The underground fire was monitored for one week and revealed a peak release of 404 ppm CO and 3.4% CO₂ originating from a horizon located about 45 cm under the soil surface. Measurements of temperature, performed one week after the impact, indicated a maximum value of 326°C inside the soil, while 516.5°C were measured on the surface of a lava block interred about 20 cm under the surface. Subsequently, a stratigraphic and sedimentologic study proved the role of the grain-size of the soil and of the organic matter content of the different horizons of the impact area, in determining the ratio between anoxic/oxidised combustion conditions and in the progress of the process itself. It was also noticed that combustion was not total all over in the soil bed and that the process had slightly migrated toward SW during the observation period. The combustion process went on for about ten days, in spite of several other violent rainstorms, until it was artificially extinguished through the excavations made to obtain study trenches. This particular circumstance evidenced the potential natural hazard represented by this kind of atmospheric event, especially in a land where the volcanic nature of the soil may easily mislead inexperienced observers and, consequently, delay proper action.  相似文献   

On the assessment of hydrodynamic coefficients of cylinders in heaving     

J. Ramos  C. Guedes Soares 《Ocean Engineering》1997,24(8):743-763

A detailed comparison is made of the common two-dimensional methods for the evaluation of the hydrodynamic coefficients. Special attention was given to the conformal transformation method and the parameters which influence the accuracy of this method are studied. The results were compared with the Frank close-fit method with respect to accuracy and time taken. Finally the correlation between the geometric and hydrodynamic errors is examined and some relations are proposed.  相似文献   

Inertial and hydrodynamic inertial loads on floating units     

Marcelo Ramos Martins   《Ocean Engineering》2007,34(16):2146-2160

The analysis of the dynamic behavior of floating units usually employs a coordinate system with origin in the unit's center of gravity, which significantly simplifies the global mass matrix. Hydrodynamic coefficients are then computed considering the same coordinate system. However, to analyze other conditions of mass distribution and maintain the simplicity of a global mass matrix, it is necessary to determine again the hydrodynamic coefficients, thereby reducing the efficiency of the entire process. Another important point is that the geometries frequently used in floating units are such that the cross-terms of an added mass are relatively unimportant when compared with the main terms, and it is, therefore, common to use only some of them to analyze the unit's dynamic behavior. Recently, however, in the search for production systems suitable for water depths greater than 3000 m, other geometries have been considered in technical and economic feasibility studies. It is possible that for these new geometries all terms of the added mass matrix must be included in the analysis. This paper presents the full development used to determine the complete global mass matrix, the inertial and hydrodynamic inertial loads that make use of the added mass matrices considering any coordinate system and the six degrees of freedom, including all cross-terms.  相似文献   

Some Morphological Aspects and Hydrological Characterization of the Tagus Floods in the Santarém Region, Portugal   总被引：1，自引：0，他引：1  

T. M. Azevêdo  E. Nunes  C. Ramos 《Natural Hazards》2004,31(3):587-601

In Portugal, few studies have been made of the historical floods of the RiverTagus (the longest in the Iberian Peninsula). This fact led to the study of theLower Tagus (Santarém region) using written historical documents,cartographic documents and hydrological data, consisting mainly of waterlevel records. With the support of the historical documents and the analysisof all the maps, it was possible to verify that the human intervention has beenfundamental in the morphological changes of the Tagus' channel. It becameaware that the river changed from a braided to a single channel with alternatebars. From the hydrological data, return periods for the floods were determined,using the Pearson Type 3 distribution. The selection of the most important floods,from 1855 to 1998, enabled to build a ``flood hazard scale' for this region.  相似文献   

Cuyania: An Exotic Block to Gondwana — Introduction     

Graciela I. Vujovich  Luis A.D. Fernandes  Victor A. Ramos 《Gondwana Research》2004,7(4):1005-1007

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Lake sedimentary processes and vegetation changes over the last 45k cal a bp in the uplands of south-eastern Amazonia     

José Tasso Felix Guimarães  Prafulla Kumar Sahoo  Mariana Maha Jana Costa De Figueiredo  Karen da Silva Lopes  Markus Gastauer  Silvio Junio Ramos  Cecilio Frois Caldeira  Pedro Walfir M. Souza-Filho  Luiza Santos Reis  Marcio Sousa Da Silva  Paulo Rogenes Pontes  Renato Oliveira Da Silva Junior  Tarcísio Magevski Rodrigues 《第四纪科学杂志》2021,36(2):255-272

This study addresses paleoclimate influences in a southern Amazonia ecotone based on multiproxy records from lakes of the Carajás region during the last 45k cal a bp. Wet and cool environmental conditions marked the initial deposition in shallow depressions with detrital sediments and high weathering rates until 40k cal a bp. Concomitantly, forest and C3 canga plants, along with cool-adapted taxa, developed; however, short drier episodes enabled expansion of C4 plants and diagenetic formation of siderite. A massive event of siderite formation occurred approximately 30k cal a bp under strong drier conditions. Afterwards, wet and cool environmental conditions returned and persisted until the Last Glacial Maximum (LGM). The LGM was marked by lake-level lowstands and subaerial exposure. The transition from the LGM to the Holocene is marked by the onset of oscillations in temperature and humidity, with an expansion of forest and canga plants. Cool taxa were present for the last time in the Carajás region ~ 9.5–9k cal a bp. After 10k cal a bp , shallow lakes became upland swamps due to natural infilling processes, but the current vegetation types and structures of the plateaus were acquired only after 3k cal a bp under wetter climatic conditions.  相似文献   

Radon in soil anomaly observed at Los Azufres geothermal field,Michoacan: a possible precursor of the 1985 Mexico earthquake (Ms = 8.1)     

N. Segovia  S. de la Cruz-Reyna  M. Mena  E. Ramos  M. Monnin  J. L. Seidel 《Natural Hazards》1989,1(4):319-329

A radon anomaly in a nuclear track detector placed on a fault was detected prior to the destructive (Ms = 8.1) Mexican earthquake of 19 September 1985. The fault is a structural feature of the geothermal field Los Azufres, 260 km NE of the epicentral area. Since no other phenomenon can be found as a possible cause for the radon anomaly, it is proposed that preseismic regional stress perturbations may produce changes in the fluid transport patterns at the fault, suggesting that radon measurements in similar conditions could provide a good precursor in high seismic risk areas.  相似文献   

Proterozoic metavolcanics from western Sierras Pampeanas terrane, Argentina     

G. Vujovich  H. Miller  V.A. Ramos 《Journal of South American Earth Sciences》1994,7(3-4)

A series of medium grade metamorphic rocks of the western sector of the Sierras Pampeanas Terrane in central western Argentina are represented by amphibolites, gneisses and schists derived from sedimentary as well as from igneous rocks. The metavolcanics consist of amphibolites, quartz-K-feldspar-muscovite schists, and hornblende-biotite and biotite-epidote-plagioclase schists. Based on petrographic and geochemical data they are interpreted as originating as basaltic tholeiites, rhyolites and mesosilicic volcanics. The distribution and geochemical behavior are similar to present day western Pacific lavas, mainly those developed on island arcs or heavily attenuated continental crust. Based on these characteristics, an accretionary tectonic model involving a series of island-arc collisions is proposed for the Proterozoic. The complex Proterozoic tectonic history of the western Sierras Pampeanas has been partially obliterated by the emplacement of the Early Paleozoic magmatic arc rocks.  相似文献   

The evaporitic celestite-barite deposits of Neuquen,Argentina   总被引：2，自引：0，他引：2  

M. K. de Brodtkorb  V. Ramos  M. Barbieri  S. Ametrano 《Mineralium Deposita》1982,17(3):423-436

Celestite-barite occurrences of early Cretaceous age were studied in the Extra-Andean region of Neuquén, West central Argentina. The ores are located in a Subandean Mesozoic belt and show a conspicuous stratabound character related to evaporitic facies. The study of the geologic evolution of the sedimentary sequence allows prediction of the temporal and spatial setting of the evaporitic facies. Stratigraphy is the main geologic control for the celestite-barite ores and their areal distribution depends on the structure of the region. Based on the geometry and texture of the mineralization three types of ores have been recognized: 1) celestite beds syngenetic with the evaporitic facies; 2) epigenetic stratabound ores formed by "in situ" mobilization of celestite with stalactite growth and cavity infilling; 3) epigenetic vein-type ores formed by mobilized barium enriched solutions.Lithofacies and isotopic ⁸⁷Sr/⁸⁶Sr analyses together with the geological evidence confirm an evaporitic origin for the celestite beds.  相似文献   

Aquifer development planning to supply a seaside resort: a case study in Goa,India     

J. P. Cárcomo Lobo Ferreira  Maria da Conceição Cunha  A. G. Chachadi  Kai Nagel  Catarina Diamantino  Manuel Mendes Oliveira 《Hydrogeology Journal》2007,15(6):1147-1155

Using the hydrogeological and socio-economic data derived from a European Commission research project on the measurement, monitoring and sustainability of the coastal environment, two optimization models have been applied to satisfy the future water resources needs of the coastal zone of Bardez in Goa, India. The number of tourists visiting Goa since the 1970s has risen considerably, and roughly a third of them go to Bardez taluka, prompting growth in the tourist-related infrastructure in the region. The optimization models are non-linear mixed integer models that have been solved using GAMS/DICOPT++ commercial software. Optimization models were used, firstly, to indicate the most suitable zones for building seaside resorts and wells to supply the tourist industry with an adequate amount of water, and secondly, to indicate the best location for wells to adequately supply pre-existing hotels. The models presented will help to define the optimal locations for the wells and the hydraulic infrastructures needed to satisfy demand at minimum cost, taking into account environmental constraints such as the risk of saline intrusion.

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Résumé A l’aide de données hydrogéologiques et socio-économiques, dérivées d’un projet de recherche de la Commission Européenne sur l’étude, la surveillance et la durabilité de l’environnement c?tier, deux modèles d’optimisation ont été appliqués en vue de satisfaire les besoins futurs en ressources en eau de la zone c?tière de Bardez au Goa en Inde. Le nombre de touristes qui visitent le Goa depuis les années 70 a considérablement augmenté et environ un tiers d’entre eux se rend à Bardez taluka, ce qui encourage la croissance des infrastructures liées au tourisme dans la région. Les modèles d’optimisation sont des modèles non linéaires mixtes en nombres entiers qui ont été résolus en utilisant le logiciel commercial GAMS/DICOPT++. Les modèles d’optimisation ont été utilisés pour indiquer premièrement les zones les plus appropriées pour construire des stations balnéaires et des puits pour approvisionner en quantité d’eau suffisante l’industrie touristique, et deuxièmement pour indiquer la meilleure localisation de puits pour l’alimentation des h?tels préexistants. Les modèles présentés aideront à définir les localisations optimales des puits et des infrastructures hydrauliques nécessaires à la satisfaction de la demande à un co?t minimum, tout en prenant en compte les contraintes environnementales, tel que le risque d’intrusion saline.

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Resumen Se han aplicado dos modelos de optimización en base a datos socio-económicos e hidrogeológicos derivados de un proyecto de investigación de la Comisión Europea sobre medición, monitoreo y sostenibilidad del ambiente costero para satisfacer las necesidades futuras de recursos hídricos de la zona costera de Bardez en Goa, India. El número de turistas que visita Goa desde la década de 1970′s ha subido considerablemente y cerca de un tercio de ellos van a Bardez taluka impulsando el crecimiento en la infraestructura turística de la región. Los modelos de optimización son modelos de números enteros mixtos no-lineales que se han resuelto usando el programa comercial GAMS/DICOPT++. Los modelos de optimización se usaron, primero para indicar las zonas más adecuadas para la construcción de centros de diversión en las márgenes del océano y pozos para abastecer la industria turística con una adecuada cantidad de agua, y segundo, para indicar la mejor localización de pozos para el abastecimiento de hoteles pre-existentes. Los modelos que se presentan ayudarán a definir las localizaciones óptimas para los pozos y las infraestructuras hidráulicas necesarias para satisfacer la demanda al mínimo costo, tomando en consideración restricciones ambientales tal como el riesgo de intrusión salina.

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