Improving reservoir description by using geostatistical and multivariate data analysis techniques     

Henrique Garcia Pereira  António Costa e Silva  Amilcar Soares  Luis Ribeiro  Justino de Carvalho 《Mathematical Geosciences》1990,22(8):879-913

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High-Frequency Response of the Atmospheric Electric Potential Gradient Under Strong and Dry Boundary-Layer Convection     

Ricardo Conceição  Hugo Gonçalves Silva  Alec Bennett  Rui Salgado  Daniele Bortoli  Maria João Costa  Manuel Collares Pereira 《Boundary-Layer Meteorology》2018,166(1):69-81

The spectral response of atmospheric electric potential gradient gives important information about phenomena affecting this gradient at characteristic time scales ranging from years (e.g., solar modulation) to fractions of a second (e.g., turbulence). While long-term time scales have been exhaustively explored, short-term scales have received less attention. At such frequencies, space-charge transport inside the planetary boundary layer becomes a sizeable contribution to the potential gradient variability. For the first time, co-located (Évora, Portugal) measurements of boundary-layer backscatter profiles and the 100-Hz potential gradient are reported. Five campaign days are analyzed, providing evidence for a relation between high-frequency response of the potential gradient and strong dry convection.  相似文献   

Additional Samples: Where They Should Be Located   总被引：2，自引：0，他引：2  

Pilger  G. G.  Costa  J. F. C. L.  Koppe  J. C. 《Natural Resources Research》2001,10(3):197-207

Information for mine planning requires to be close spaced, if compared to the grid used for exploration and resource assessment. The additional samples collected during quasimining usually are located in the same pattern of the original diamond drillholes net but closer spaced. This procedure is not the best in mathematical sense for selecting a location. The impact of an additional information to reduce the uncertainty about the parameter been modeled is not the same everywhere within the deposit. Some locations are more sensitive in reducing the local and global uncertainty than others. This study introduces a methodology to select additional sample locations based on stochastic simulation. The procedure takes into account data variability and their spatial location. Multiple equally probable models representing a geological attribute are generated via geostatistical simulation. These models share basically the same histogram and the same variogram obtained from the original data set. At each block belonging to the model a value is obtained from the n simulations and their combination allows one to access local variability. Variability is measured using an uncertainty index proposed. This index was used to map zones of high variability. A value extracted from a given simulation is added to the original data set from a zone identified as erratic in the previous maps. The process of adding samples and simulation is repeated and the benefit of the additional sample is evaluated. The benefit in terms of uncertainty reduction is measure locally and globally. The procedure showed to be robust and theoretically sound, mapping zones where the additional information is most beneficial. A case study in a coal mine using coal seam thickness illustrates the method.  相似文献   

Old trends and new impulses in Europe's urban affairs     

Allen G. Noble  Frank J. Costa  Ashok K. Dutt 《GeoJournal》1991,24(3):235-235

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Water determination in iron oxyhydroxides and iron ores by Karl Fischer titration     

Camila C. R. F. da Cunha  Geraldo M. da Costa 《Physics and Chemistry of Minerals》2016,43(10):739-748

Protohematite (Fe_2?x/3(OH) _x O_3?x 1 ≤ x < 0.5) and hydrohematite (Fe_2?x/3(OH) _x O_3?x 0.5 ≤ x < 0) are iron-defective phases containing hydroxyl groups in their structures. These species were described in prior studies mainly with the aid of X-ray diffraction and Infrared spectroscopy. The existence of these phases in soils might have influence in redox processes, and they were considered as a possible water reservoir in Martian soils. In this study, we have used for the first time the Karl Fischer titration method to determine the amount of water released after heating several synthetic samples of goethite, hematite and natural iron ores at 105, 400, 600 and 900 °C. It was found that heating at 105 °C did not remove all moisture from the samples, and higher temperatures were necessary to completely remove all the absorbed water. The water contents determined at 400, 600 and 900 °C were found to be the same within the experimental errors, suggesting the inexistence of both protohematite and hydrohematite in the investigated samples. Therefore, the above-mentioned effects of these phases in soils might have to be reevaluated.  相似文献   

The Capilla del Monte pluton,Sierras de Córdoba,Argentina: the easternmost Early Carboniferous magmatism in the pre-Andean SW Gondwana margin     

Juan A. Dahlquist  Robert J. Pankhurst  Carlos W. Rapela  Miguel A. S. Basei  Pablo H. Alasino  Julio Saavedra  Edgardo G. Baldo  Juan A. Murra  Mario da Costa Campos Neto 《International Journal of Earth Sciences》2016,105(5):1287-1305

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Projections of climate change effects on discharge and inundation in the Amazon basin     

Mino Viana Sorribas  Rodrigo C. D. Paiva  John M. Melack  Juan Martin Bravo  Charles Jones  Leila Carvalho  Edward Beighley  Bruce Forsberg  Marcos Heil Costa 《Climatic change》2016,135(3-4):555-568

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Comments on fast pulses in mm-wave bursts     

J. E. R. Costa  P. Kaufmann 《Solar physics》1986,104(1):253-256

The first observation of a solar burst with millisecond time resolution at = 3.3 mm was obtained on 21 May, 1984. The time-scale of the millimetric pulses durations was of about 60 ms. The possible strong correlation between pulsed emission at 3.3 mm and hard X-rays is discussed.Proceedings of the Workshop on Radio Continua during Solar Flares, held at Duino (Trieste), Italy, 27–31 May, 1985.  相似文献   

Use of a tropical bay in southeastern Brazil by juvenile and subadult Micropogonias furnieri (Perciformes, Sciaenidae)     

da Costa  Marcus R; Araujo  Francisco G 《ICES Journal of Marine Science》2003,60(2):268-277

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Impact of trace metals on denitrification in estuarine sediments of the Douro River estuary,Portugal   总被引：1，自引：0，他引：1  

Catarina Magalhães  Joana Costa  Catarina Teixeira  Adriano A. Bordalo 《Marine Chemistry》2007

Denitrification influences the nitrogen budget in estuaries by removing fixed nitrogen from the inorganic pool; rates are dependent on both geological and geographic conditions as well as increasing anthropogenic impacts. In this study the effects of copper (Cu), chromium (Cr), zinc (Zn), cadmium (Cd) and lead (Pb), on the denitrification pathway were evaluated in subtidal and intertidal sediments of the Douro River estuary. Dinitrogen, N₂O and NO₂⁻ production rates were measured in triplicate slurries of field samples under different treatments of metal concentrations. Results demonstrated that similar metal amendments led to different site responses for denitrification, suggesting that variations in sediment properties (metal concentrations, grain size, organic matter content, etc.) and/or differences in denitrifying community tolerance modulate the level of metal toxicity. Denitrifying communities in subtidal muddy sediments were not affected by increasing concentrations of metals. In contrast, intertidal sandy sites revealed high sensitivity to almost all trace metals tested; almost complete inhibition by Cr (95%) and Cu (85%) was observed for 98 and 79 μg per gram of wet sediment respectively, and by Zn (92%) at the highest concentration added (490 μg per gram of wet sediment). Moreover, the addition of trace metals stimulated N₂O and NO₂⁻ accumulation in intertidal sandy (Zn, Cu, Cr and Cd) and muddy sediments (Cu and Zn), demonstrating a pronounced inhibitory effect on specific steps within the denitrification enzymatic system. In summary, the results obtained suggest that, according to the type of estuarine sediment, trace metals cannot only reduce total N removal from an estuary via denitrification but also can enhance the release of N₂O, a powerful greenhouse gas.  相似文献