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91.
The economic development of the Rio Colca region and related infrastructure endangers the environment of the deepest canyon worldwide. The unique values of the Colca Valley and Canyon and its tributary Valley of the Volcanoes are summarised. They include a magnificent, deep section of the orogenic belt 100 km long, different geological formations, active faults, a variety of fold structures, young volcanoes, hot springs, geysers, several ecological zones and the largest condor habitat in the Andes. Based on the observed land use, development and regional planning, the threats and conflict areas are outlined. Studies performed by the Polish Scientific Expedition to Peru since 2003 add greatly to the knowledge of geology, landscape and pioneering biota development of the area and its importance to the world heritage of nature. They are aimed to give scientific background to the project of the Canyon Colca and Valley of the Volcanoes National Park. The article gives the proposed limits of the park and its buffer zones, categories of protection zones compatible with the SINANPE system of Peru and suggestions on tourist accessibility. The strict protection zone should cover the most inaccessible part of the area where human economic activity practically does not exist. Traditional farming and animal husbandry, wildlife, cultural tourism and some forms of adventure tourism will be allowed in the zone of special usage. The new park would strengthen the relatively poor system of the protected areas in the Arequipa Department, increase tourist attractiveness and determine constraints for sustained regional development. The expected actions of the park authority and local governments are specified. 相似文献
92.
Comparison between rocking analysis and kinematic analysis for the dynamic out‐of‐plane behavior of masonry walls 下载免费PDF全文
This paper provides a contribution to the rocking analysis of masonry walls by making a comparison with the kinematic analysis suggested by the Italian code. It is shown that the latter approach is generally over‐conservative and therefore potentially inappropriate for historic buildings, where rehabilitation can be expensive and can affect their cultural value. The equation of motion given by the Housner formulation, corresponding to the movement of a rigid block, is here modified to account for different boundary conditions at different heights of the wall. These boundary conditions or horizontal restraints can represent vaults, transverse walls, or retrofitting devices such as steel tie‐rods. A systemic analysis of walls having different dimensions and slenderness is performed, and the results from the Italian code and rocking analysis are compared. Finally, the improvement in the response offered by retrofitting devices is discussed in terms of reduction of amplitude ratio. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
93.
A model for pushover analysis of confined masonry structures: implementation and validation 总被引:1,自引:0,他引:1
Confined masonry (CM) is a typical building technique in Latin American countries. This technique, due to its simplicity of construction and similarity with traditional practices of reinforced concrete building, presents a potential of use in European regions with moderate-to-high seismicity. However, most of the procedures for seismic design in codes for Latin America are force-based, which appears to be inadequate due to the high dissipative response observed for CM. This paper presents a simplified numerical-analytical approach to model CM structures using pushover analysis, aiming to apply performance-based design procedures. First, a data mining process is performed on a database of experimental results collected from lateral tests on CM walls to adjust prediction models for the wall shear strength and to determine the input relevance through a sensitivity analysis. Then, an analytical model of CM structures for pushover analysis is proposed with basis on a wide-column approach that employs an adaptive shear load-displacement constitutive relation. The proposed method is compared with a discrete element model that represents explicitly the confinements-masonry interaction, against the experimental results obtained in a quasi-static test of a full-scale tridimensional CM structure. The accuracy of the predictions from both methods is very satisfactory, allowing to capture the base shear-displacement envelope and also the damage patterns of the structure, thus, demonstrating the ability of the methods to be used in performance-based seismic assessment and design of CM buildings. 相似文献
94.
Morphologic and sedimentologic patterns of active aeolian dune‐fields on the east coast of Maranhão,northeast Brazil 下载免费PDF全文
The eastern portion of the Maranhão coast is characterized by large active dune‐fields located in a tropical setting. This article combines the analysis of dune‐field morphologic patterns with the classical analysis of grain size and heavy minerals to study the sedimentary dynamics of the active aeolian system in this region. Based on the heavy mineral analysis, the main sedimentary suppliers feeding the system are the westward alongshore drift bringing sand from the coast east of the Parnaíba River mouth and the river itself. The absence of well‐defined variation patterns of the two morphometric parameters studied, dune spacing and crest length, reflects complex sedimentary dynamics and transport pathways, inside the aeolian system, despite the unidirectional wind. During the wet season, the interdune plains are flooded and the system is intensely reworked by intermittent drainages. During the dry season, the deposits formed by the drainages and interdune lakes become temporary internal sedimentary sources for the system. Due to this combined aeolian‐fluvial transport, the sediment source area has a planar geometry, with contributions from the beach and interdune plains, and not linear as expected in a typical case of source only in the beach. The areal limits of the dune‐fields is the main boundary condition controlling the dune‐field patterns, as dune spacing and crest length, by changing the sedimentary inflow–outflow balance and interactions between migration dunes. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
95.
96.
Jian-Wei Li Paulo Vasconcelos Wei Zhang Xiao-Dong Deng Nurdan Duzgoren-Aydin Dai-Rong Yan Jian-Qiang Zhang Ming-An Hu 《Mineralium Deposita》2007,42(4):361-383
Supergene Mn-oxide deposits are widely distributed in Guangxi, Guangdong, Yunnan, and Hunan Provinces, South China, accounting
for 18% of the total Mn reserves in the country. Direct dating of supergene Mn enrichment, however, is lacking. In this paper,
we present high-resolution 40Ar/39Ar ages of Mn oxides from the Xinrong Mn deposit, western Guangdong, to place numerical constraints on the timing and duration
of supergene Mn enrichment. A total of ten cryptomelane samples, spanning a vertical extent of 67 m, were dated using the
40Ar/39Ar laser incremental heating technique, with seven samples yielding well-defined plateau or pseudo-plateau ages ranging from
23.48 ± 0.91 to 2.06 ± 0.05 Ma (2σ). One sample yields a staircase spectrum that does not reach a plateau; the spectrum, however, indicates the presence of
two or more generations of Mn oxides in the sample, whose ages are best estimated at 22.34 ± 0.31 and 10.2 ± 0.86 Ma, respectively.
The remaining two samples gave meaningless or uninterpretable results due to significant 39Ar recoil and contamination by old phases. The 40Ar/39Ar data thus reveal a protracted history of weathering and supergene Mn enrichment that started at least in the end of the
Oligocene or beginning of Miocene and extending into the latest Pliocene. Staircase-apparent age spectra, resulting from banded
or botryoidal samples, yield an average growth rate of Mn oxides at 0.6–0.7 × 10−3 mm kyr−1. The values indicate that a 1-mm grain of Mn oxides may host minerals precipitated during a time span of ca. 1.5 m.y., and
accumulation of Mn oxides to form economic deposits under weathering environments may take millions of years. The distribution
of weathering ages shows that the oldest Mn oxides occur on the top of the profile, whereas the youngest minerals are found
at the bottom, suggesting downward propagation of weathering fronts. However, two samples located at the intermediate depths
of the profile yield ages comparable with those occurring at the highest elevations. Such a complexity of age distribution
is interpreted in terms of preferential penetration of Mn-rich weathering solutions along more permeable fault zones, or as
a result of multi stages of dissolution and re-precipitation of Mn oxides. A synthesis of geochronological and geological
data suggests that formation of the Xinrong deposit was a consequence of a combination of favorable lithological, climatic,
and structural conditions. Because the climatic and structural conditions are similar among the provinces of South China during
the Cenozoic, the geochronological results obtained at Xinrong may also have implications for the timing of supergene Mn enrichment
throughout South China. 相似文献
97.
Igor Bogunovic Darija Bilandzija Zeljko Andabaka Domagoj Stupic Jesús Rodrigo Comino Marija Cacic Luka Brezinscak Edi Maletic Paulo Pereira 《Arabian Journal of Geosciences》2017,10(15):340
The use of machinery in vineyards is increasing soil compaction and erosion. However, there is a lack of information about the impacts of different management practices on soil conditions of vineyards. Therefore, the aim of this study was to assess soil compaction in Croatian vineyards under four different management systems: no-tillage (NT) system, conventional tillage (CT), yearly inversed grass covered (INV-GC) and tillage managed (INV-T) treatments. Four key top-soil (0–20 cm) parameters were assessed in the different land uses: bulk density (BD), penetration resistance (PR), soil water content (SWC) and carbon dioxide (CO2) fluxes. Tractor traffic increased the BD and PR in all treatments, with exception of CT treatment, as consequence of tillage. SWC showed higher values in INV-GC treatment during the dry period; meanwhile, it was similar during the wet season in every management type. Lower CO2 fluxes were found in INV-GC and NT than in the CT and INV-T treatments. 相似文献
98.
Paulo Cesar da Costa Gomes 《GeoJournal》2004,60(4):339-344
We are concerned here with the notion of space as a primary condition for building social relations. From this stand, we have
created two analytical matrixes that can help us characterize two modes: that of ‘being-there-in-space’ and that of ‘being-of-the-space’;
the nomospace and the genospace. While the nomospace is characterized by ‘cold’ connotations, which are ideally defined as a result of a logical option, the genospace is mainly characterized by emotional or ‘warm’ connotations, which originate from a feeling of shared nature and common destiny.
We believe that these matrixes could help us to identify the meanings of some behaviours and, therefore, make us more capable
of interpreting many dynamics that occur in modern societies. The importance of geography is justified by the existing relationship
between these behaviours and their proper spatial form.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
99.
Paulo Cesar Abreu César S. B. Costa Carlos Bemvenuti Clarisse Odebrecht Wilhelm Graneli Alexandre M. Anesio 《Estuaries and Coasts》2006,29(2):277-285
Stable isotopes ratios (δ13C and δ15N) were measured in primary producers and consumers of two bays with contrasting eutrophic conditions in the Patos Lagoon
estuary, southern Brazil: the Justino bay, a more pristine ecosystem, and the Mangueira bay, a heavily polluted region that
receives the Rio Grande city sewage and effluencts of several industries. δ13C values of organisms collected in both subsystems were not different, but δ15N values had significant statistical differences, ca. 3.5‰ higher in the Mangueira bay. It is likely that primary producers
and consumers in this subsystem are greatly influenced by higher nitrogen input due to domestic and industrial sewages. The
stable isotope analysis also corroborated several trophic interactions previously established by gut content analysis, and
due to its higher sensitivity, it was possible to better determine the contributions of different primary producers and detrital
fractions to the consumers' diets. It was confirmed that plant detritus represents the main food source for most organisms.
The stable isotope analysis also demonstrated that detritivorous benthic organisms in the same habitat have distinct diet
compositions, with differential consumption of C3 and C4 plants. This technique showed that some consumers that eat detritus
do not have in their stable isotopic signature any relationship with that of plants. It is likely that these consumers assimilate
their carbon and nitrogen from other sources like microalgae or microorganisms that colonize decaying plants. 相似文献
100.
The pattern of commercial spaces in a city has never been the consequence of chance. Retailers have always searched for the ‘best location’, but the notion of what exactly constitutes the ‘best location’ has changed over the decades. It is no longer a question of being close-to-market. It depends on an amount of social, economic and even morphological aspects of urban life, not to mention intrinsic aspects of the retail sector itself, namely new types of stores, products and purchase and payment options. Consequently, the methods retailers have employed to determine ‘best location’ have also evolved, and today increasingly complex mathematical and geospatial models are in use. It should then be safe to assume that commercial geography has changed and therefore, commercial hierarchies need to be re-invented, or at least challenged. A current trend in the literature is revealing more than ever the influence of commerce in the spatial and morphological re-configuration of cities. Thus, the understanding of modern retail patterns may be a key issue in interpreting and regulating the processes of urban, social and economic development. Using as test-beds four Portuguese medium-sized cities, commercial and morphological data was collected, analysed and compared, applying spatial analysis techniques. Similar patterns were found between the four cities, which led to the proposal of two geospatial commercial distribution models, one for the city-centre and one for the suburbia. These models shed a new light on the structure of Portuguese medium-size cities, and may well be valid in other medium and small towns across Europe. 相似文献