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151.
152.
D. Moret‐Fernández J. Vicente B. Latorre F. Lera C. Castañeda M. V. López J. Herrero 《水文研究》2012,26(2):246-254
The water retention curve (θ(ψ)), which defines the relationship between soil volumetric water content (θ) and matric potential (ψ), is of paramount importance in characterizing the hydraulic behaviour of soils. However, few methods are so far available for estimating θ(ψ) in undisturbed soil samples. We present a new design of TDR‐pressure cell (TDR‐Cell) for estimating θ(ψ) in undisturbed soil samples. The TDR‐Cell consists of a 50‐mm‐long and 50‐mm internal diameter stainless steel cylinder (which constitutes the outer frame of a coaxial line) attached to a porous ceramic disc and closed at the ends with two aluminium lids. A 49‐mm‐long and 3‐mm‐diameter stainless steel rod, which runs longitudinally through the centre of the cylinder, constitutes the inner rod of a coaxial TDR probe. The TDR‐Cell was used to determine the θ(ψ) curves of a packed sand and seven undisturbed soil samples from three profiles of agricultural soils. These θ(ψ) curves were subsequently compared to those obtained from the corresponding 2‐mm sieved soils using the pressure plate method. Measurements of bulk electrical conductivity, σa, as a function of the water content, σa(θ), of the undisturbed soil samples were also performed. An excellent correlation (R2 = 0·988) was found between the θ values measured by TDR on the different undisturbed soils and the corresponding θ obtained from the soil gravimetric water content. A typical bimodal θ(ψ) function was found for most of the undisturbed soil samples. Comparison between the θ(ψ) curves measured with the TDR‐Cell and those obtained from the 2‐mm sieved soils showed that the pressure plate method overestimates θ at low ψ values. The σa(θ) relationship was well described by a simple power expression (R2 > 0·95), in which the power factor, defined as tortuosity, ranged between 1·18 and 3·75. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
153.
Vicente de P. Rodrigues da Silva Adelgicio F. Belo Filho Vijay P. Singh Rafaela S. Rodrigues Almeida Bernardo B. da Silva Inajá F. de Sousa 《水文科学杂志》2017,62(7):1029-1038
Using the Shannon entropy, the space–time variability of rainfall and streamflow was assessed for daily rainfall and streamflow data for a 10-year period from 189 stations in the northeastern region of Brazil. Mean values of marginal entropy were computed for all observation stations and entropy maps were then constructed for delineating annual and seasonal characteristics of rainfall and streamflow. The Mann-Kendall test was used to evaluate the long-term trend in marginal entropy as well as relative entropy for two sample stations. The marginal entropy values of rainfall and streamflow were higher for locations and periods with the highest amounts of rainfall. The entropy values were higher where rainfall was higher. This was because the probability distributions of rainfall and the resulting streamflow were more uniform and less skewed. The Shannon entropy produced spatial patterns which led to a better understanding of rainfall and streamflow characteristics throughout the northeastern region of Brazil. The total relative entropy indicated that rainfall and streamflow carried the same information content at annual and rainy season time scales. 相似文献
154.
Hellen Kezia Silva Almada Divino Vicente Silvério Marcia Nunes Macedo Leonardo Maracahipes-Santos Elizabete Carolina Pinheiro Zaratim Karina Pinheiro Zaratim 《水文科学杂志》2019,64(5):620-632
Water quality in streams is determined by several factors, including geology, topography, climate, and anthropogenic changes. This study aimed to assess the effects of watershed physical, morphology, and precipitation seasonality on the water quality of two streams that supply drinking water to rural settlements and urban areas in the Cerrado-Amazonia transition region. We monitored 16 physico-chemical attributes of water at six different sample locations over three years (2013–2016). Our results indicate that eight of these physico-chemical attributes did not meet the standards for safe drinking water established by Brazilian legislation. Precipitation seasonality, degradation of riparian zones, stream length, and watershed slope were the most important predictors of impaired water quality. Our results highlight the importance of restoring and conserving riparian forests in order to maintain drinking water quality. 相似文献
155.
Maia M. Moreira N. Vicente S. Mirão J. Noronha F. Nogueira P. 《Geology of Ore Deposits》2020,62(6):508-534
Geology of Ore Deposits - The Mociços Cu-deposit is part of a cluster of ancient copper mines in the Sousel-Barrancos metallogenic belt in the Ossa-Morena Zone at the SW Iberia. The orebodies... 相似文献
156.
R. O. Vicente 《Astronomische Nachrichten》1984,305(1):31-32
The campaigns of the programme of international cooperation, called MERIT, for the determination of the earth rotation parameters are reviewed, especially about the difficulties to infer results about polar motion from such short intervals of observations. It is pointed out the need to employ the same models and standards in order to facilitate the comparison of data obtained by classical and modern techniques. 相似文献
157.
This paper describes methods for combining independent observations of polar motion into a single time series, and applies these methods to satellite laser ranging, Doppler, and astrometric polar motion data taken over the period 1981--1983. The polar motion data are treated as complex valued time series, yielding one estimate of the noise level for each series, rather than a separate estimate for X and Y components. Estimates of the noise level which take advantage of the existence of simultaneous observations are preferred. Linear combination of the data may be performed in both the time and the frequency domain, and examples of each are present. The results of analyzing three years of observations show little difference between the Allan and conventional variance. Present day Doppler determinations do not show marked improvement compared to classical astrometric results. Thus, the astrometric observations are still useful. 相似文献
158.
159.
Giorgio Rivalenti Maurizio Mazzucchelli Vicente A.V. Girardi Riccardo Vannucci M. Adelaide Barbieri Alberto Zanetti Steve L. Goldstein 《Contributions to Mineralogy and Petrology》2000,138(4):308-325
Spinel–peridotite facies mantle xenoliths in Cenozoic alkali basalts of the Pico Cabuji volcano (Rio Grande do Norte State,
Northeast Brazil) and the adjacent South Atlantic oceanic island of Fernando de Noronha are studied for: (1) the information
they provide on the composition of the lithospheric component in the erupted basalt geochemistry, and (2) to check the effects
of the Fernando de Noronha plume track on the mantle lithosphere. Xenoliths from Pico Cabuji are protogranular lherzolites
and porphyroclastic harzburgites recording average equilibrium temperatures of 825 ± 116 and 1248 ± 19 °C, respectively. Pressure
in the porphyroclastic xenoliths ranges from 1.9 to 2.7 GPa (Ca-in-olivine geobarometer). Both groups show major element chemical
variation trends in whole-rock and Ti and HREE (Er, Yb) variations in clinopyroxene consistent with fractional melting and
basalt extraction. REE (rare earth element) profiles of clinopyroxenes vary from LREE (La, Ce) enriched (spoon shaped) to
LREE depleted in the protogranular group, whereas they are slightly convex upward in most porphyroclastic clinopyroxenes.
HFSE (Ti and Zr) negative anomalies are in general modest in the clinopyroxenes of both groups. Xenoliths from Fernando de
Noronha have textural variations similar to those of Pico Cabuji. Protogranular and porphyroclastic samples have similar temperature
(1035 ± 80 °C) and the pressure is 1–1.9 and 2.3 GPa, respectively. Whole-rock chemical variation trends overlap and extend
further than those of Pico Cabuji. The trace element profiles of the clinopyroxenes of the porphyroclastic xenoliths are enriched
in La up to 30 × PM and are smoothly fractionated from LREE to HREE, with deep, negative, Zr and Ti anomalies. The geochemical
heterogeneities of the xenoliths from both localities are interpreted in terms of reactive porous percolation. The porphyroclastic
xenoliths from Pico Cabuji represent the lower part of a mantle column (the head of a mantle diapir, at the transition conductive–adiabatic
mantle), where OIB infiltration triggers melting, and the protogranular xenoliths the top of the mantle column, chromatographically
enriched by percolation at a low melt/rock ratio. This interpretation may also apply for Fernando de Noronha, but the different
geochemical signature recorded by the clinopyroxenes requires a different composition of the infiltrated melt. Nd and Sr isotopes
of the Pico Cabuji porphyroclastic clinopyroxenes (143Nd/144Nd= 0.51339–0.51255, 87Sr/86Sr=0.70275–0.70319) and of Fernando de Noronha (143Nd/144Nd=0.51323–0.51285, 87Sr/86Sr=0.70323–0.70465) plot on distinct arrays originating from a similar, isotopically depleted composition and trending to
low Nd–low Sr (EMI) and low Nd–high Sr (EMII), respectively. Correlation of the isotope variation with geochemical parameters
indicates that the isotopic variation was induced by the metasomatic component, of EMI type at Pico Cabuji and of EMII type
at Fernando de Noronha. These different components enriched a lithosphere isotopically similar to DMM (depleted MORB mantle)
at both localities. At Fernando de Noronha, the isotopic signature of the metasomatic component is similar to that of the
∼ 8 Ma old lavas of the Remedios Formation, suggesting that this is the age of metasomatism. At Pico Cabuji, the mantle xenoliths
do not record the high 87Sr/86Sr component present in the basalts. We speculate that the EMII component derives from a lithospheric reservoir, which was
not thermally affected during mantle metasomatism at Pico Cabuji, but was mobilized by the hotspot thermal influence at Fernando
de Noronha. This interpretation provides a plausible explanation for the presence of distinct metasomatic components at the
two localities, which would be difficult to reconcile with their genetic relationship with the same plume.
Received: 12 June 1999 / Accepted: 13 December 1999 相似文献
160.
Nota sobre la profundidad hipocentral del sismo del apenino toscano-romañol de 11 de febrero de 1939
Ing. Vicente Inglada 《Pure and Applied Geophysics》1948,12(5-6):181-188
Resumen En la presente Nota se determina por el método deKöveslighèty, valiéndose de fórmulas especiales y una variante que simplifica el cálculo extraordinariamente, la profundidad del sismo del Apenino toscano-romañol de 11 de febrero de 1939. Se obtiene para ella el valorh=6871 metros, que está en muy buen acuerdo con los dos de 7 y 10 km, obtenidos por el Prof.P. Caloi, valiéndose de los sismogramas registrados en las Estaciones próximas. Al final se hecen algunas consideraciones acerca de las ventajas, que, en ciertos casos, ofrece dicho metodo.Esta Nota va dedicada, como prueba de gran consideración y afecto, a nuestro querido amigo e ilustre Sismólogo Dr.G. Agamennone, con ocasión del homenaje que se le tributa en su 90° aniversario. 相似文献