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Glria da Silva Cezar Paula Lucia Ferrucio da Rocha Angela Buarque Ariovaldo da Costa 《Journal of Applied Geophysics》2001,47(3-4)
The application of the ground penetrating radar (GPR) at two archaeological sites, Serrano and Morro Grande, situated in Araruama County, Rio de Janeiro, Brazil, aids the study of a prehistoric indigenous culture, associated with the “Tupinambá” that inhabited the region during prehistoric times.The archaeological remains of the study area are mainly characterized by pottery artifacts for several uses, including funerary urns, which were buried within layers of sand and clay. Several profiles were acquired using a RAMAC system, with a 200 and 400 MHz frequency antennae. At the Serrano site, the profiles were acquired around some partially exposed pottery shards, due to sand exploitation. The resultant profiles provided a response model to guide the interpretation of new profiles acquired at other sites in the area, which present similar characteristics.The results showed the great importance of the dielectric permittivity contrast which exists between the targets and the host media, in order for possibly significant features to be identified in radar data. 相似文献
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This study shows that the use of uniaxial recordings maintains the linear dependence of the low frequency displacements, with first polarities included, on the moment tensor components, and thus can be easily incorporated in the evaluation of failure mechanism using a moment tensor approach. Synthetic data analysis demonstrates that the errors in the orientation of the principal strain axes of the mechanism solution can be reliably evaluated using a linear error propagation approximation for up to 30% variance in the amplitude data. Case studies at the Kidd Mine indicate that the general characteristics of the mechanism solution are well retrieved, regardless of the type of data used, as relatively small disorientation angles of 15–20° are found between the solutions derived from rotated triaxial data and those from unrotated triaxial data used as uniaxial data, and of 25–30° between the solutions based on rotated triaxial data and those on independent uniaxial data. 相似文献
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Willow species(Salix fragilis L.and S.alba L.) are important elements of cold desert agroforestry systems in the Lahaul valley,northwestern Himalaya.Their ability to grow through shoot-cuttings plantations under extreme and xeric climatic conditions of cold deserts,makes them ecologically suited and socially accepted for forestry programmes.Willow species in cold deserts may combat desertification and can thrive well in these areas as compared to any other species.Salix fragilis L.and S.alba L.are under cultivation in the Lahaul valley.However,S.fragilis is widely cultivated under the agroforestry and plantation forestry systems.In the Lahaul valley,willow species are used as subsistence resources and for socio-religious purposes.The present study was carried out to examine the vegetation analysis,density,diversity and distribution of willow species,present status and potential willow plantation sites and uses.The results of present study revealed that a higher species density was recorded at middle altitude villages(Jahlma-3,000 m asl and Hinsa-2,700 m asl),except,a higher density of S.fragilis was at Khoksar(3,200 m asl) in plantation forestry on south-facing slopes.In forests,S.fragilis was planted mainly along the water channels,resulted a low density.The shrubby willow species occurred naturally in the entire Lahaul valley up to an altitude of 3,850 m asl.81% of households felt the scarcity of willow trees,whereas,19% of households were satisfied with the willow trees they owned.The majority of willow species were planted in middle altitudes on privately owned irrigated lands.It was rated most potential prospective willow planting site by the farmers.Small size of land-holdings was one of the main constraints for establishing a large number of willow plantations.Commercial aspects of willow species need to be investigated to encourage the farmers to plant more willows further. 相似文献
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The juniper species Juniperus polycarpos C. Koch, J. indica Bertol. and J. communis L. var. saxatilis (Pallas) are important elements of the forest vegetation in Lahaul valley in the north-western Himalaya. Their ability to grow under the barren and xeric conditions of cold deserts makes them particularly suited for afforestation programmes under these ecological conditions. In the Lahaul valley, juniper species are used as subsistence resources and for religious purposes. Excessive removal of juniper wood and leaves by the local population, overgrazing, habitat fragmentation and low regeneration potential are the main obstacles to conservation of juniper forests in this region. The present study was carried out to assess density, basal area and importance value index (IVI) of the local vegetation as well as uses and amounts of juniper wood and leaves removed from the local forests. Pressure on relict juniper forests due to grazing animals and intensive removal of wood and leaves by the local population was found to be greater at an altitude above 3,000 m. The results of the study demonstrated that the different juniper species were adapted to specific altitude ranges. A higher species density was recorded at lower altitude except for J. indica which was only present at high altitude (>3,200 m) on south-facing slopes. Density, basal area and IVI of J. polycarpos were higher at Hinsa (2,700 m) than at Jahlma (3,000 m). The rapid loss of vegetation due to overuse and habitat degradation has made the conservation of juniper forests an important priority in the Lahaul valley. J. polycarpos at lower altitude and J. indica at higher altitude are ecologically the more suitable species for the successful implementation of conservation programmes. The support of rehabilitation programmes by regional authorities is essential for the reestablishment of the local juniper forests. 相似文献
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The retrieval of Snow Water Equivalent (SWE) from remote sensing satellites continues to be a very challenging problem. In this paper, we evaluate the accuracy of a new SWE product derived from the blending of a passive microwave SWE product based on the Advanced Microwave Sounding Unit (AMSU) with a multi‐sensor snow cover extent product based on the Interactive Multi‐sensor Snow and Ice Mapping System (IMS). The microwave measurements have the ability to penetrate the snow pack, and thus, the retrieval of SWE is best accomplished using the AMSU. On the other hand, the IMS maps snow cover more reliably due to the use of multiple satellite and ground observations. The evolution of global snow cover from the blended, the AMSU and the IMS products was examined during the 2006 snow season. Despite the overall good inter‐product agreement, it was shown that the retrievals of snow cover extent in the blended product are improved when using IMS, with implications for improved microwave retrievals of SWE. In a separate investigation, the skill of the microwave SWE product was also examined for its ability to correctly estimate SWE globally and regionally. Qualitative evaluation of global SWE retrievals suggested dependence on land surface temperature: the lower the temperature, the higher the SWE retrieved. This temperature bias was attributed in part to temperature effects on those snow properties that impact microwave response. Therefore, algorithm modifications are needed with more dynamical adjustments to account for changing snow cover. Quantitative evaluation over Slovakia in central Europe, for a limited period in 2006, showed reasonably good performance for SWE less than 100 mm. Sensitivity to deeper snow decreased significantly. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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Julio Cezar Mendes Ciro Alexandre vila Ronaldo Mello Pereira Mnica P.L. Heilbron Candido A.V. Moura 《Gondwana Research》2006,9(3):326-336
In the central segment of the Ribeira belt, southeast Brazil, several foliated porphyritic granitic bodies intrude high-grade migmatitic gneisses of the Andrelândia and Juiz de Fora domains and Embú Complex. Results of geological, geochemical and geochronological investigations of the Maromba, Pedra Selada, Serra do Lagarto and Funil porphyritic I-type granites provide profound similarities, except for the distinct geochemical behavior of the Funil Granite, perhaps related to a different crustal source. These granitoids show similar structural, textural and mineralogical features. Pb-evaporation of single zircons provided ages of 586 ± 6, 579.6 ± 6.3, 586.3 ± 4.8 and 584 ± 5 Ma for the granites, respectively, coincident with the syn-collision I episode of the central Ribeira belt. The intrusion of I-type porphyritic granitoids coeval with the main collisional event has not often been reported in the geological literature. The most common syn-collisional granitic magmatism has normally an S-type signature or even a slightly peraluminous I-type character. However, the occurrence of coeval I- and S-type syn-tectonic granites along the central Ribeira belt, as observed in the investigated area and discussed in this paper is noteworthy. 相似文献