Comparison of Coupled-Potentials and Field-Based Finite-Volume Techniques for Modeling of Borehole EM Tools     

Novo  M.S. da Silva  L.C. Teixeira  F.L. 《Geoscience and Remote Sensing Letters, IEEE》2008,5(2):209-211

In this letter, we compare two finite-volume (FV) techniques, viz., the field-based formulation and the coupled vector-scalar potentials formulation, for the modeling of borehole electromagnetic tools in 3-D earth formations. Eccentric boreholes, anisotropic dipping beds, and high-contrast multilayered earth formations are considered. We compare the two FV formulations in terms of accuracy, convergence rate, and CPU time. Although these two formulations yield similar accuracy in the examples considered, their efficiencies in terms of convergence rate and CPU time depends on the scenario.  相似文献   

Isotopic and thermochronologic evidence of extremely cold lithosphere associated with a slab flattening in the Central Andes of Argentina          下载免费PDF全文

Gilda Collo  Federico M. Dávila  Wilson Teixeira  Julieta C. Nóbile  Lucy G. Sant′ Anna  Andrew Carter 《Basin Research》2017,29(1):16-40

We present mineralogic, isotopic and thermochronologic analyses on psammopelitic and tuffaceous levels from the Bermejo and Vinchina basins – both foreland depocentres of the Central Andes of Argentina – that define a low‐temperature regime for the crust akin to a slab shallowing and flattening process. The contents of illite in illite/smectite interstratified (I/S) show a progressive illitization into the deeper parts of both basins. The distribution of I/S is compatible with theoretical simulations and predicted heat flow values of ca. 26 mW m^?2 in the 8–3.4 Ma interval for the Vinchina Basin and ca. 42 mW m^?2 since 9 Ma for the Bermejo Basin. The latter shows heat flow values that are comparable to those reported by magnetotelluric analysis (36–40 mW m^?2) in agreement with previously published heat flow calculations along the modern Andean foreland. The Rb–Sr isochrones in psammopelites (<2 μm fractions) show ages between 125 and 165 Ma, whereas the K–Ar ages decrease as the grain size is smaller (136–224 Ma for 1–2 μm, 112–159 Ma for 0.2–1 μm, 76–116 Ma for <0.2 μ and 39.3–42 Ma for <0.1 μm). These ages are significantly older than the sedimentation in the basins (ca. 16 Ma for the Vinchina Basin; U–Pb age), and can be explained by the presence of a significant amount of detrital components, mainly illite, even in the finer fractions. The preservation of detrital ages is consistent with the shallow diagenesis related to a low‐temperature regime, proposed here for the basins. Younger K–Ar ages (21.3–12 Ma) were obtained for a basal tuffaceous level. Clay mineralogy and R0 ordering in the deepest part of the Vinchina Basin, together with the evolution model of I/S with depth, suggest that the burial temperatures would have not exceeded ca. 100°C in agreement with (U–Th)/He analyses performed on apatite extracted from two tuffaceous units. Thermal indicators from both studied basins confirm the existence of a low‐temperature regime during flat subduction.  相似文献   

If Quebec Goes . . . The ‘Exodus' Impact?     

Lucia Lo  Carlos Teixeira 《The Professional geographer》1998,50(4):481-498

In this paper, we explore migration aspects of the 1995 Quebec Sovereignty Referendum with data from a survey administered to non-francophones in Montreal two weeks prior to the Referendum. While the Quebec sovereignty issue has been around for some time and earlier exodus from the province, particularly among anglophones, is largely regarded as “forced” in some way, this study neither confirms the 1995 Sovereignty Referendum as a paramount factor in explaining outmigration from Quebec nor points to a real reluctance to leave Montreal. The decision to move is influenced by the interplay of a multitude of factors. The political influence is only an added factor to longstanding economic decline and cultural clash. Moreover, if there is any impulsion, the degree varies among different cultural and socioeconomic groups.  相似文献   

Hybrid modeling in meteorological applications: Anatomy of a $ 200 million freeze     

E. R. Reiter  L. Teixeira  R. -J. Shen  J. D. Martsolf  P. D. Spyke  C. Townsend 《Meteorology and Atmospheric Physics》1998,67(1-4):239-248

Summary Unbeknownst to many fruit and vegetable producers a killer frost sneaked down the Florida peninsula during the night of January 18 to 19, 1997. According to news reports in left in its wake approximately $ 200 million in damage to crops and tress, much of which could have been avoided with available abatement technology. A lot of finger pointing followed between victims and agencies trying to fix the blame on an identifiable culprit. The recent privatization of some of the National Weather Service's former responsibilities added fuel to the fire. Without touching these politically hot potatoes the present paper gives a brief account of observational facts and then describes the results from an inexpensive, PC-based, operational forecasting system. That system has been described earlier (Reiter, 1991; Teixeira and Reiter, 1995; Reiter et al., 1998). The advantage of a hybrid system in which the user can interact with, and modify, the forecast on the fly is demonstrated.With 7 Figures and 9 Color PlatesThis paper, albeit dealing with a different season, is dedicated to the memory of Herbert Riehl who often used Florida as a base for his hurricane field research.  相似文献   

Tropical twilight HeI 10830 emission     

N.R. Teixeira  P.D. Angreji  Y. Sahai  B.A. Tinsley  A.B. Christensen 《Planetary and Space Science》1975,23(10):1425-1430

A further year's observation of twilight Hel 10830 Å emission made in Brazil confirms the trend of seasonal variation found earlier. The 10830 intensities taken with concurrent ionosonde data are discussed in the context of recent model calculations of the emission rates. An increase with K_P is attributable to changing production and loss rates of He 2³S with changing thermospheric temperature. The morning intensities being greater than those of the evening can be due to several effects, an important one of which appears to be the much greater loss rate of photoelectron energy to ambient electrons in the evening, arising from the very high evening electron concentrations at the Appleton Anomaly ionization crests.  相似文献   

Hybrid modeling in meteorological applications. Part II: An operational system     

L. Teixeira  E. R. Reiter 《Meteorology and Atmospheric Physics》1995,55(3-4):135-149

Summary In this paper a real-time, operational weather prediction system is described which is based on the concepts of hybrid modeling, combining numerical forecasting techniques with user-interactive, graphics based post-processing tools. The system consists of 5 major components: an automated data reception and decoding module which receives raw surface and radiosonde observational data via a satellite communication link; a geographic information module structured for meterological applications; a numerical prediction module running in a fully automated mode; a display module for meteorological charts; a user-interactive GUI (graphical user interface) module whose database structure permits interaction between, and display as well as manipulation of, terrain and weather characteristics. The whole system is PC-based. Its major current applications are in support of winter highway maintenance operations. The system can easily be customized for other applications.With 15 Figures  相似文献   

Power spectrum analysis of the time-series of annual mean surface air temperatures     

R. P. Kane  N. R. Teixeira 《Climatic change》1990,17(1):121-130

Maximum Entropy Spectral Analysis of the annual mean surface temperature series for land masses and sea in the northern and southern hemispheres indicated long-term linear warming trends of (0.12 to 0.56) °C/century with superposed significant periods in the ranges T = 5–6 yr, 10–11 yr, 15 yr, 20 yr, 28–32 yr, and 55–80 yr. Extrapolation in future indicated for 2000–2030 a departure of (+0.4 °C) above the 1950–70 level. However, for the 1980s, the observed values are above the expected level, probably indicating large greenhouse effects due to human intervention. In that case, our predictions would be underestimates.  相似文献   

Diurnal and seasonal variations of the oh (8, 3) airglow band and its correlation with OI 5577 Å     

H. Takahashi  Y. Sahai  B.R. Clemesha  P.P. Batista  N.R. Teixeira 《Planetary and Space Science》1977,25(6):541-547

In this paper the results of OH (8,3) emission intensity and rotational temperature measurements made in the Brazilian sector (23°S) from 1972 to 1974 are presented. Diurnal variations of both the parameters are found to fall into distinct classes, showing significant seasonal effects. A correlative study with the OI 5577 Å emission measured simultaneously is also presented. It is shown that both the phase and amplitude of the major part of the mean nocturnal intensity variations of the two emissions can be explained by the density and temperature perturbations caused by the solar semidiurnal tide. The OH emission is found to increase slightly during magnetic disturbances.  相似文献   

U–Pb and Sm–Nd geochronology of amphibolites from the Curaçá Belt, São Francisco Craton, Brazil: Tectonic implications     

Luiz Jos Homem D'el-Rey Silva  Elton Luiz Dantas  Joo Batista Guimares Teixeira  Jorge Henrique Laux  Maria da Glria da Silva 《Gondwana Research》2007,12(4):454-467

The Curaçá terrane is part of the Itabuna–Salvador–Curaçá (I–S–C) Paleoproterozoic orogen in the São Francisco craton, northeastern Brazil, and comprises supracrustal rocks, gneisses of their probable basement, amphibolites, and mafic-ultramafic Cu-bearing bodies (including the Caraíba Cu-Mine), all affected by D₁-D₃ deformation events associated to M₁-M₃ metamorphism under high-T granulite and amphibolite facies, and assisted by G₁-G₃ tonalitic-granodioritic-granitic intrusions. U–Pb and Sm–Nd Thermal Ionization Mass Spectrometry (TIMS) isotopic data from amphibolite, tonalite, and granite, sampled in a well-known outcrop, indicate partial reset and heterogeneous modification of the original isotopic systems, attributable to deformation and metamorphism. The ages obtained from these systems agree with each other, and also with other previously published U–Pb data, and imply that 2.6 Ga is the crystallization age of the protolith of the amphibolite. Together with key structural relationships, they also indicate a 2.08–2.05 Ga interval for M₃ metamorphism, and make even a less precise age (2.2–2.3 Ga) acceptable, as it suggests contamination in the amphibolite with material in a syn-D₂ tonalite crystallized 2248 ± 36 Ma ago. The new data demonstrate the existence of Neoarchean fragments of both oceanic and continental crusts and constrain the Archean-Paleoproterozoic development of the Curaçá belt, the I–S–C orogen, and the São Francisco craton.  相似文献   

Introduction: immigrants and transnational experiences in world cities   总被引：1，自引：0，他引：1  

Wei Li  Carlos Teixeira 《GeoJournal》2007,68(2-3):93-102

Today, in the early 21st century, goods, information, services, financial capital and human beings are flowing across national borders at an ever-accelerating rate. In this context, transnationalism has become a key paradigm in the study of international migration and urbanism. This theme issue on “Immigrants and transnational experiences in world cities” explores these new trends in contemporary international migration, with respect to transnational communities and geographies, in articles grouped according to four themes: international migration and world cities; highly-skilled and low-skilled immigrants; economic impacts; and immigrant experiences in world cities.  相似文献