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排序方式: 共有138条查询结果,搜索用时 328 毫秒
101.
The Monitoring Network of the Vancouver 2010 Olympics 总被引:1,自引:0,他引:1
Paul Joe Bill Scott Chris Doyle George Isaac Ismail Gultepe Douglas Forsyth Stewart Cober Edwin Campos Ivan Heckman Norman Donaldson David Hudak Roy Rasmussen Paul Kucera Ron Stewart Julie M. Thériault Teresa Fisico Kristen L. Rasmussen Hannah Carmichael Alex Laplante Monika Bailey Faisal Boudala 《Pure and Applied Geophysics》2014,171(1-2):25-58
102.
Marcel?Antonio?Arcari?BassaniEmail author Jo?o?Felipe?Coimbra?Leite?Costa Waleska?Campos?Guaglianoni Ricardo?Hundelshaussen?Rubio 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(3):785-797
In this paper we compare two estimation methods to deal with samples of different support: (1) the indirect approach using accumulation and (2) kriging with samples of different support. These two methods were tested in a simple example. The estimates of the two methods were compared against a benchmark scenario. The benchmark consisted of kriging using a complete set of samples on the same support. The effects of the nugget effect, variogram range and type on the weight of long samples, the estimate, and the error variance were assessed. Kriging with samples of different support led to lower error variance and to estimates closer to the estimates of the benchmark scenario. Furthermore, in the case of spatially continuous attributes (low nugget effect), the indirect approach assigns greater weight to long samples than kriging with samples of different support. A cross validation study comparing the two methods with a database from a bauxite deposit was performed. The results of the cross validation study showed that kriging with samples of different support resulted in more precise estimates. 相似文献
103.
Marquis Henrique Campos de Oliveira Nilza Maria dos Reis Castro Olavo Correa Pedrollo 《水文科学杂志》2017,62(13):2120-2138
Soil water content (SWC) is an important factor in transfer processes between soil and air, contributing to water and energy balances, and quantifying it remains a challenge. This study uses artificial neural networks (ANNs) to analyse spatial and temporal variation of SWC in a Brazilian watershed, based on climate information, soil physical properties and topographic variables. Thirty eight input variables were tested in 200 models. The outputs were compared with 650 gravimetric moisture measurements collected at 26 points (25 field studies). The results show that it is possible to estimate SWC efficiently (Nash-Sutcliffe statistic, NS = 0.77) using topographic data, soil physical properties and rainfall. If only climate information is considered, modelling is less efficient (NS = 0.28). Using many variables does not necessarily improve performance. Alternatively, SWC can be estimated by simplified models using rainfall and topographic maps information, although the performance is less good (NS = 0.65). 相似文献
104.
Vnia Freitas Joana F.M.F. Cardoso Sílvia Santos Joana Campos Jan Drent Sofia Saraiva Johannes IJ. Witte Sebastiaan A.L.M. Kooijman Henk W. Van der Veer 《Journal of Sea Research》2009,62(2-3):75
Required assimilated energy to support observed growth was reconstructed for four common bivalve species (Mya arenaria, Cerastoderma edule, Mytilus edulis and Macoma balthica) from various Northeast Atlantic coastal areas, along the species distributional range. The approach applied was based on the Dynamic Energy Budget (DEB) theory whereby observed growth patterns in the field, in combination with prevailing temperatures, were used to reconstruct the average food intake experienced in the field scaled to the maximum possible. For all species, results suggest food limitation over the range of locations. In general, reconstructed food intake indicated better conditions for C. edule compared to the other species, while M. edulis presented the lowest food conditions in all the areas. Despite the indications for a latitudinal trend in primary production, no clear pattern or relationship between reconstructed food conditions and latitude was observed suggesting that any trend may be overruled by local conditions. 相似文献
105.
Rmi Coltat Yannick Branquet Pierre Gautier Hector Campos Rodriguez Marc Poujol Ewan Pelleter Sean McClenaghan Gianreto Manatschal Philippe Boulvais 《地学学报》2019,31(6):549-561
Mid‐Ocean Ridges host various types of hydrothermal systems including high‐T black‐smokers found in ultramafic rocks exhumed along slow spreading ridges. These systems are mostly described in two dimensions as their exposure on the present‐day seafloor lacks the vertical dimension. One way to understand these systems at depth is to study their fossilized equivalents preserved on‐land. Such observation can be done in the Platta nappe, Switzerland, where a Jurassic‐aged mineralized system is exposed in 3D. Serpentinites host a Cu‐Fe‐Ni‐Co‐Zn‐rich mineralization made of sulphides, magnetite and Fe‐Ca‐silicates either replacing serpentinites or within stockwork. Fe‐Ca‐silicates, abundant at the deepest levels, vanish in the mineralization close to the palaeo‐detachment. Fluids were channelized along mafic dykes and sills acting as preferential drains. Warm carbonation (~130°C) is the latest hydrothermal record. We propose that this system is an analog to the root zone of present‐day serpentinite‐hosted hydrothermal systems such as those found along the Mid‐Atlantic Ridge. 相似文献
106.
Life spans and thermal evolution of hydrothermal systems are of fundamental metallogenic importance. We were able to establish
the chronology and cooling history of the Zaldívar porphyry copper deposit (Northern Chile) by applying a combination of different
isotopic dating methods in minerals with different closure temperatures, including 40Ar/39Ar geochronology and zircon fission track thermochronology, together with fluid inclusion thermometry and previous published
U–Pb zircon geochronology. The hydrothermal mineralization in the Zaldívar deposit is genetically related to the Llamo Porphyry
unit. Samples of igneous biotites from this intrusion yielded 40Ar/39Ar plateau ages between 35.5 ± 0.7 and 37.7 ± 0.4 Ma defining a weighted average of 36.6 ± 0.5 Ma (2σ). In contrast, one sample from the Zaldívar porphyry, one from the andesites, and two from the Llamo porphyry yielded considerably
younger fission track ages of approximately 29 Ma with a weighted mean for all ages of 29.1 ± 1.7 Ma (2σ). Thermal and compositional constraints for the hydrothermal system in the Zaldívar deposit from fluid inclusions thermometry
show that at least three fluid types broadly characterize two main hydrothermal episodes during the evolution of the deposit.
The main mineralization and alteration event is characterized by high temperature (above 320°C) hypersaline fluids (salinity
between 30 and 56 wt.% NaCl equivalents) coexisting with low-density gas-rich inclusions (salinity less than 17 wt.% NaCl
equivalents) that homogenizing into the gas phase at temperatures above 350°C. The second episode corresponds to a low-temperature
event which is characterized by liquid-rich fluid inclusions that homogenize into the liquid phase at temperatures ranging
from 200°C to 300°C with salinities lower than 10 wt.% NaCl equivalents. The 40Ar/39Ar data (36.6 ± 0.5 Ma, weighted average) obtained from igneous biotites represent the minimum age for the last high-temperature
(above 300°C) hydrothermal pulse. When compared with previously published U–Pb ages (38.7 ± 1.3 Ma) in zircons from the Llamo
porphyry, a close temporal relationship between crystallization of the parental intrusion and the thermal collapse of the
last high-temperature hydrothermal event is evident. Cooling took place from approximately 800°C (crystallization of the intrusive
complex defined by zircon U–Pb ages) to below 300 ± 50°C (biotite 40Ar/39Ar closure temperature) within approximately 1.5 m.y. Because the thermal annealing of fission tracks in zircons occurs at
temperatures of 240 ± 30°, the zircon fission track (ZFT) ages of 29.1 ± 1.7 Ma (2σ) mark the end of the thermal activity in the Zaldívar area, specifically the time when the whole area cooled below this temperature,
well after the collapse of the main hydrothermal event in the Zaldívar porphyry copper deposit. This cooling age roughly coincides
with the age defined for the emplacement of dacitic dikes at 31 ± 2.8 Ma (2σ) (published K–Ar whole rock), 5 km south of the Zaldívar deposit, in the Escondida area. This late magmatic pulse probably
is responsible for high heat flow in the Zaldívar deposit as late as 29 Ma. There is no evidence that the low temperature
hydrothermal pulse recognized by fluid inclusion studies is related to this thermal event. The zircon fission track cooling
ages are interpreted to be related to the time lag required for complete relaxation of the perturbation of the isotherms in
the geothermal field imposed by the intrusion of magmatic bodies, with or without any association with low temperature hydrothermal
activity. 相似文献
107.
Leandro Z.S. Campos Marcelo M.F. Saba Osmar Pinto Jr. Maurício G. Ballarotti 《Atmospheric Research》2009,91(2-4):416-424
This work analyses the waveshapes of continuing currents and parameters of M-components in positive cloud-to-ground (CG) flashes through high-speed GPS synchronized videos. The dataset is composed of only long continuing currents (with duration longer than 40 ms) and was selected from more than 800 flashes recorded in São José dos Campos (45.864°W, 23.215°S) and Uruguaiana (29.806°W, 57.005°S) in Southeast and South of Brazil, respectively, during 2003 to 2007 summers. The videos are compared with data obtained by the Brazilian Lightning Location System (BrasilDAT) in order to determine the polarity of each flash and select only positive cases. There are only two studies of waveshapes of continuing currents in the literature. One is based on direct current measurements of triggered lightning, in which four different types of waveshapes were observed; and the other is based on measurements of luminosity variations in high-speed videos of CG negative lightning, in which besides the four types above mentioned two additional types were observed. The present work is an extension of the latter, using the same method but now applied to obtain the waveshapes of positive CG lightning. As far as the authors know, this is the first report on M-components in positive continuing currents. We also have used the luminosity-versus-time graphs to observe their occurrence and measure some parameters (duration, elapsed time and time between two successive M-components), whose statistics are presented and compared in detail to the data for negative flashes. We have plotted a histogram of the M-components elapsed time over the total duration of the continuing current for positive flashes, which presented an exponential decay (correlation coefficient: 0.83), similar to what has been observed for negative flashes. 相似文献
108.
Myriam Andrea Rada Torres Vincenzo Costanzo-Álvarez Milagrosa Aldana Nery Suárez Corina Campos Maria Magdalena Mackowiak-Antczak María Carmela Brandt 《Studia Geophysica et Geodaetica》2011,55(4):717-736
Rock magnetic, petrographic and dielectric analyses were carried out, in a number of archeological ceramic potsherds, in order
to characterize the different manufacturing techniques used by Prehistoric Venezuelan Amerindian potters. Samples were excavated
in 7 Venezuelan islands and ascribed to distinct cultural groups on purely stylistic grounds (i.e. Valencioide, Ocumaroide,
Dabajuroide and Unknown). Mean coercivity values were determined through a direct signal analyses (DSA) applied to isothermal
remanent magnetization (IRM) acquisition curves. Logarithmic plots of these mean coercivities are the best quantitative means
to classify diverse ceramics. The mean coercivity values seem to group the samples according to the manufacturing development.
These values also seem to discriminate the samples provenance, indeed, this plot displays a good grouping of data for samples
presumably manufactured by the same culture but excavated at different locations. Thermomagnetic cycles supply helpful information
about original ceramic firing conditions. The irreversibility parameter (IP) for thermomagnetic curves (heating and cooling),
serves as an indicator of the amount of organic matter burnt during original pottery firing. The IP for a number of pottery
samples from Venezuelan islands and mainland, with ages ranging between 300 BC to 1500 AD, might suggest a possible increasing
trend in time towards the complete reversibility line of IP = 0. Most samples, independently of age and cultural group, have
IP values that suggest that most open fires, used by primitive Venezuelan Amerindian potters, had enough ventilation and oxidizing
atmospheres. A scatter plot of maximum current depolarization temperatures versus natural remanent magnetization (NRM) suggests
a complex non-linear relationship between these two parameters most likely due to the fact that both, dielectric and rock
magnetic data, are linked to pore-related features. 相似文献
109.
Ricardo Varela Miguel A. S. Basei Pablo D. Gonz��lez Ana M. Sato Maximiliano Naipauer Mario Campos Neto Carlos A. Cingolani Vinicius T. Meira 《International Journal of Earth Sciences》2011,100(2-3):243-272
A comprehensive review of the geological, geochronological, and isotopic features of the Mesoproterozoic Grenvillian terranes attached to the southwest of the Río de la Plata craton in Early Paleozoic times is presented in this paper. They are grouped into the northern (sierras de Umango, Maz and del Espinal and surroundings), central (Sierra de Pie de Palo, southern Precordillera and Frontal Cordillera), and southern (San Rafael and Las Matras Blocks) segments. The Mesoproterozoic basement consists mainly of arc related, intermediate to acidic and mafic?Cultramafic rocks of 1,244?C1,027?Ma, with juvenile, Laurentian affinity. Exception to it is the Maz Group, with a protracted history and reworked character. They are affected by 846?C570?Ma, extensional magmatism in the northern and central segments, which represents the Neoproterozoic breakup of the Rodinia supercontinent. Successive passive margin sedimentation is registered in Late Neoproterozoic (~640?C580?Ma) and Cambro-Ordovician (~550?C470?Ma) times. The southern segment is noted for the younger sedimentation alone, and for showing the exclusive primary unconformable relationship between the Mesoproterozoic basement and Early Ordovician cover. The effects of Early Paleozoic Famatinian orogeny, associated with the collisions of Cuyania and Chilenia terranes, are recorded as main phase (480?C450?Ma), late phase (440?C420?Ma), and Chanic phase (400?C360?Ma). Among them, the tectonothermal climax is the Ordovician main phase, to which klippe and nappe structures typical of collisional orogens are related in the northern and central segments. Preliminary data allow us to suggest a set of paired metamorphic belts, with an outboard high-P/T belt, and an inboard Barrowian P/T belt. 相似文献
110.
Sílvia Santos Pieternella C. Luttikhuizen Joana Campos Carlo H.R. Heip Henk W. van der Veer 《Journal of Sea Research》2011,66(3):238-247
The bivalve Scrobicularia plana is an important species of shallow water benthic communities with a wide geographic distribution but also with a general patchy pattern, i.e. irregular in occurrence and in density. This review aims to determine the processes responsible for the species' spatial distribution pattern based on the available information on S. plana. Although several pre- and post-settlement processes are believed to influence spatial patterns of marine invertebrates, the general patchy distribution of S. plana seems to be determined by the existence of specific environmental conditions during settlement. Factors such as temperature, salinity, sediment type, hydrographic conditions and predation affect settlement and spat survival and not one but a combination of factors seems to explain the species distribution pattern. Future work should focus on determining the scale of patchiness, using hierarchical sampling, as well as the connectivity between populations by analysing the population genetic structure. 相似文献