岩石矿物组份质量转移的模糊聚类定量计算

本文根据岩石矿物组份质量分数值的定和特性 ,提出定量计算组份质量转移的新方法。该方法运用模糊动态聚类分析技术 ,通过计算复原定和差并判定差值类型 ,辅以相应的判别参数 ,逐步从中筛选出真恒量组份 ,再利用真恒量组份定值系数 ,计算出变组岩石矿物各组份的真实质量分数值和转移量值。笔者将该方法称为真恒量组份定值法 (TCF法 )。     

Spatial and temporal variations in bank erosion on sand‐bed streams in the seasonally wet tropics of northern Australia

Bank erosion rates and processes across a range of spatial scales are poorly understood in most environments, especially in the seasonally wet tropics of northern Australia where sediment yields are among global minima. A total of 177 erosion pins was installed at 45 sites on four sand‐bed streams (Tributaries North and Central, East Tributary and Ngarradj) in the Ngarradj catchment in the Alligator Rivers Region. Bank erosion was measured for up to 3·5 years (start of 1998/99 wet season to end of 2001/02 wet season) at three spatial scales, namely a discontinuous gully (0·6 km²) that was initiated by erosion of a grass swale between 1975 and 1981, a small continuous channel (2·5 km²) on an alluvial fan that was formed by incision of a formerly discontinuous channel between 1964 and 1978, and three medium‐sized, continuous channels (8·5–43·6 km²) with riparian vegetation. The bank erosion measurements during a period of average to above‐average rainfall established that substantial bank erosion occurred during the wet season on the two smaller channels by rapid lateral migration (Tributary Central) and by erosion of gully sidewalls due to a combination of within‐gully flows and overland flow plunging over the sidewalls (Tributary North). Minor bank erosion also occurred during the dry season by faunal activity, by desiccation and loss of cohesion of the sandy bank sediments and by dry flow processes. The larger channels with riparian vegetation (East Tributary and Ngarradj) did not generate significant amounts of sediment by bank erosion. Deposition (i.e. negative pin values) was locally significant at all scales. Bank profile form and channel planform exert a strong control on erosion rates during the wet season but not during the dry season. Copyright © 2006 Commonwealth Government of Australia.     

Residual strength of slip zones of large landslides in the Three Gorges area, China

Slip zones of the large landslides in the Three Gorges area are commonly composed of fine-grained soils with substantial amount of coarse-grained particles, particularly gravel-sized particles. In this study, residual strength of the soils from slip zones of these landslides were examined in relation to their index properties based on a survey of 170 landslides. It was found that laboratory-determined residual friction angle using gravel-free fraction of the disturbed soils from the slip zones was closely related to clay content, liquid limit and plasticity index. On the other hand, in-situ residual friction angle of these soils (i.e. including gravel fraction) showed very weak correlations with clay content and Atterberg limits, but was largely dependent on gravel and fines (clays + silts) contents, increasing with gravels and decreasing with fines, and displayed strong linear correlation with the ratio of gravel to fines contents. These observations indicate that among the index properties, clay content and Atterberg limits can be used to estimate residual strength of the soils finer than 2 mm, but they are not appropriate evaluate the residual strength of the soils containing considerable amount of gravel-sized particles. For the latter, particle size distribution (particularly the ratio of gravel to fines contents) appears to be a useful index. Additionally, it was found that there was no identifiable correlation between relative abundance of individual major clay minerals and residual friction angles of both gravel-free fraction of disturbed and in-situ soils, suggesting that influence of clay minerals on residual strength of these soils can not be simply evaluated based on their abundance.     

The appraisal of seven economic zones in China

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Evaluation ofCitrullus colocynthis, a desert plant native in Israel, as a potential source of edible oil

Citrulus colocynthis(wild gourd) is a desert plant of the Cucurbitaceae, naturally adapted to arid environments. It was known in biblical times as a source of seed oil and its fruits were used as an efficient laxative. Accessions were collected in Israel and evaluated as a potential oil seed crop adapted to arid zones. It was found that its oil composition is similar to safflower oil, with a total of 80-85% unsaturated fatty acids. A potential yield of oil of 250-400 l ha⁻¹was calculated. The best yield was obtained during the first 4 weeks of the 10-week maturation period. Yield potential should be estimated under desert conditions in order to evaluate the plant's economic future as a crop suitable for an arid environment.     

Methodological problems of intercultural comparisons of retail environments

The internationalising activities of retailers have tended to precede the theoretical contributions of academics. This is particularly the case for the cultural context within which retail internationalisation takes place. Following an examination of the growth of international retailing activity, the article reviews generic difficulties in studying inter-cultural differences before considering the specific steps which retail practitioners have taken to understand the comparative characteristics of retail and consumer markets through the growth of geodemographic and lifestyle analysis. Finally, we relate one of the most significant integrative intercultural theoretical instruments to the case of retail internationalisation within Western Europe. We find that significant insights into retailer behaviour and strategy can be gained from an understanding of the culturally-specific characteristics of the activity. This revised version was published online in July 2006 with corrections to the Cover Date.     

Mantle heat flow and geotherms for major tectonic units in central Europe

The results of seismic measurements along the deep seismic sounding profile VII and terrestrial heat flow measurements used for construction of heat generation models for the crust in the Paleozoic Platform region, the Sudetic Mountains (Variscan Internides) and the European Precambrian Platform show considerable differences in mantle heat flow and temperatures. At the base of the crust variations from 440–510°C in the models of Precambrian Platform to 700–820°C for the Paleozoic Platform and the Variscan Internides (Sudets) are found. These differences are associated with considerable mantle heat flow variations.The calculated models show mantle heat flow of about 8.4–12.6 mW m^–2 for the Precambrian Platform and 31 mW m^–2 to 40.2 mW m^–2 for Paleozoic orogenic areas. The heat flow contribution originating from crustal radioactivity is almost the same for the different tectonic units (from 33.5 mW m^–2 to 37.6 mW m^–2). Considerable physical differences in the lower crust and upper mantle between the Precambrian Platform and the adjacent areas, produced by lateral temperature variations, could be expected. On the basis of carbon ratio data it can be concluded that the Carboniferous paleogeothermal gradient was much lower in the Precambrian Platform area than in the Paleozoic Platform region.     

Atmospheric noble gases in volcanic glasses from the southern Lau Basin: origin from the subducting slab?

Noble gas concentrations and isotopic compositions have been determined for four submarine volcanic glasses from the Valu Fa Ridge (VFR) in the southern Lau Basin. The samples are the least differentiated ones from this area, and they display enrichments in fluid-mobile elements similar to the nearby island arc. ³He/⁴He ratios are slightly below average MORB (6.8–7.8 times atmospheric), whereas Ne, Ar, Kr, and Xe have isotopic compositions very similar to air. Together with previously published data from the Valu Fa Ridge and other spreading segments in the Lau Basin, our data show a systematic latitudinal variation of increasing Ne, Ar, Kr, and Xe abundances from north to south as well as Ne and Ar isotopic compositions changing from MORB-like to atmosphere-like in the same direction. Moreover, isotopic compositions and noble gas abundances of the lavas correlate strongly with Ba/Nb ratios and H₂O concentrations. Based on these observations and mass balance arguments, we propose that the atmospheric noble gases come from the subducting oceanic crust and are not due to shallow contamination with air dissolved in seawater or assimilation of old crust. Our data suggest that the noble gases released from the subducting slab are atmospheric and thus contain little or no solar He and Ne. In addition to the fact that ratios of He to heavy noble gases are small in aged ocean crust, He has possibly fractionated from the other noble gases due to its higher diffusivity, and thus He transport from the subducting slab into the mantle wedge is probably insignificant. We propose that the ³He/⁴He ratios lower than MORB observed in the VFR lavas result from radiogenic ingrowth of He in a highly depleted, and hence degassed, mantle wedge after the enrichment of U and Th released from the downgoing slab.     

Marine conservation challenges in an era of economic crisis and geopolitical instability: The case of the Mediterranean Sea

In the Mediterranean Sea, socio-economic drivers may accelerate the process of exclusive economic zone (EEZ) declarations. Despite the challenges, the EEZ declarations may provide important opportunities for leveraging change to national policy towards the development of large-scale conservation of marine ecosystems and biodiversity in this zone. Using the Mediterranean Sea as a case study, we aim to highlight a set of best practices that will maximize the potential for the development of large-scale marine conservation initiatives. These include a range of approaches, such as using surrogates to fill the many biodiversity data gaps in the region, further the development of consistent and open access databases, and the utilization of technological developments to improve monitoring, research and surveillance of less accessible and under-explored marine areas. The integration of Mediterranean-wide and local conservation efforts, the facilitation of transboundary collaboration, and the establishment of regional funds for conservation will further enhance opportunities for marine conservation in this region.