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41.
Nicola Nocilla Aldo Evangelista Anna Scotto di Santolo 《Rock Mechanics and Rock Engineering》2009,42(5):815-833
In recent years, rock fall phenomena in Italy have received considerable attention for risk mitigation through in situ observations
and experimental data. This paper reports the study conducted at Camaldoli Hill, in the urban area of Naples, and at Monte
Pellegrino, Palermo, Italy. The rocks involved are volcanic Neapolitan yellow tuff (NYT) in the former area and dolomitic
limestone in the latter. Both rocks, even though with different strength characteristics, have shown a significant tendency
towards rock fragmentation during run out. This behavior was first investigated by comparing the volumes of removable blocks
on the cliff faces (V
0) and fallen blocks on the slopes (V
f). It was assumed that the ratio V
f/V
0 decreases with the distance (x
f) from the detachment area by an empirical law, which depends on a coefficient α, correlated with the geotechnical properties of the materials involved in the rock fall. Finally, this law was validated
by observation of well-documented natural rock falls (Palermo) and by in situ full-scale tests (Naples). From the engineering
perspective, consideration of fragmentation processes in rock fall modeling provides a means for designing low-cost mitigation
measures. 相似文献
42.
Lin-gun Liu C.-C. Lin Y. J. Yung T. P. Mernagh T. Irifune 《Physics and Chemistry of Minerals》2009,36(3):143-149
K-lingunite is a high-pressure modification of K-feldspar that possesses the tetragonal hollandite structure. Variations of
the Raman spectra of K-lingunite were studied up to ~31.5 GPa at room temperature, and in the range 79–823 K at atmospheric
pressure. The Raman frequencies of all bands were observed to increase with increasing pressure, and decrease with increasing
temperature for K-lingunite. This behavior is in line with those observed for most of other materials. New sharp Raman bands
appear at pressures greater than 13–15 GPa, suggesting a phase transition in K-lingunite with increasing pressure. The transition
is reversible when pressure was released. The appearance of these new Raman bands may correspond to the phase transition revealed
earlier at around 20 GPa by X-ray diffraction studies. Instead of transforming back to its stable minerals, such as orthoclase,
microcline or sanidine, K-lingunite became amorphous in the temperature range 803–823 K at atmospheric pressure. 相似文献
43.
Shovan Lal Chattoraj Santanu Banerjee P. K. Saraswati 《Journal of the Geological Society of India》2009,73(4):567-574
Glauconitic minerals are considered as one of the valuable input parameters in sequence stratigraphic analysis of a basin.
In the present study glauconitic minerals are reported from subtidal green shale facies in the lower part of the Late Paleocene-Early
Eocene Naredi Formation of western Kutch. On the basis of the foraminiferal assemblage the glauconite bearing beds are interpreted
to have formed in a mid shelf depositional settings of an unstable marine conditions. XRD studies confirm the glauconite mineralogy
of the green pellets and provide an estimation of glauconite maturity. Textural attributes of the glauconites confirm their
derivation by different degrees of alteration of precursor feldspar grains. Because of the authigenic origin and autochthonous
nature, these glauconites hold promise for understanding sequence stratigraphy of the Palaeogene succession of the western
Kutch. 相似文献
44.
45.
It is generally accepted that the compositions and properties of soil organic matter (SOM) are influenced by many factors. In order to reveal the effects of soil texture on characteristics and dynamics of SOM and its sub-fraction, humic acid (HA), along two soil profiles, a yellow soil profile and a purplish soil profile, under the same climate and vegetation conditions were determined. Results indicate that the decomposition and humification degrees of SOM and HA of the purplish soils are higher than those of the corresponding yellow soils indicated by A/O–A ratios of HAs, TOCs and HA yields of bulk soil samples, nevertheless, the development degree of the purplish soil is lower than that of the yellow soil. The variations of E4/E6 ratios of HAs along the soil profiles indicate the overall molecular sizes of HAs decreased downward along the soil profiles. A/O–A ratios of HAs decreased downward along both the soil profiles indicate that humification processes decrease downward along both the soil profiles. Leaching of SOM shows significant effects on the distribution and characteristics of HAs in the yellow soil profile but the purplish soil profile, which is consistent with the higher hydrophobicity of HAs in purplish soils, shows that the distribution characteristics of SOM along the soil profiles are a complex result of the combination of soil texture and characteristics of SOM itself. The remarkably different sand contents are concluded tentatively as one of reasons to the different distributions and dynamics of HAs along the soil profiles, however, to profoundly understand the evolution and transport of SOM along soil profiles needs more researches. 相似文献
46.
47.
去除EOS/MODIS 1B数据中"弯弓"效应的方法 总被引:8,自引:7,他引:8
分析了中分辨率成像光谱仪EOS/MODIS的扫描方式,在此基础上研究了EOS/MODIS1B数据集“弯弓”效应的成因。对EOS/MODIS1B数据02级产品HDF文件的格式进行了探讨,并以250m分辨率资料为例,在2002年7月13日10时的MODIS资料中选取鄱阳湖以北部分地区,读取其数据进行插值、Lambert投影、重采样等处理,从而消除了影响资料使用的“弯弓”效应,同时也完成了对EOS/MODIS数据的几何校正,取得了一定的效果,为EOS/MODIS遥感资料在今后得以广泛应用作了有益的尝试。 相似文献
48.
49.
Characteristics of dry-wet abrupt alternation events in the middle and lower reaches of the Yangtze River Basin and the relationship with ENSO 总被引:1,自引:0,他引:1
During recent decades, more frequent flood-drought alternations have been seen in China as a result of global climate change and intensive human activities, which have significant implications on water and food security. To better identify the characteristics of flood-drought alternations, we proposed a modified dry-wet abrupt alternation index (DWAAI) and applied the new method in the middle and lower reaches of the Yangtze River Basin (YRB-ML) to analyze the long-term spatio-temporal characteristics of dry-wet abrupt alternation (DWAA) events based on the daily precipitation observations at 75 rainfall stations in summer from 1960 to 2015. We found that the DWAA events have been spreading in the study area with higher frequency and intensity since 1960. In particular, the DWAA events mainly occurred in May and June in the northwest of the YRB-ML, including Hanjiang River Basin, the middle reaches of the YRB, north of Dongting Lake and northwest of Poyang Lake. In addition, we also analyzed the impact of El Niño Southern Oscillation (ENSO) on DWAA events in the YRB-ML. The results showed that around 41.04% of DWAA events occurred during the declining stages of La Niña or within the subsequent 8 months after La Niña, which implies that La Niña events could be predictive signals of DWAA events. Besides, significant negative correlations have been found between the modified DWAAI values of all the rainfall stations and the sea surface temperature anomalies in the Nino3.4 region within the 6 months prior to the DWAA events, particularly for the Poyang Lake watershed and the middle reaches of the YRB. This study has significant implications on the flood and drought control and water resources management in the YRB-ML under the challenge of future climate change. 相似文献
50.
中国东部植被NDVI对气温和降水的时空响应(英文) 总被引:4,自引:4,他引:4
Temporal and spatial response characteristics of vegetation NDVI to the variation of temperature and precipitation in the whole year,spring,summer and autumn was analyzed from April 1998 to March 2008 based on the SPOT VGT-NDVI data and daily temperature and precipitation data from 205 meteorological stations in eastern China.The results indicate that as a whole,the response of vegetation NDVI to the variation of temperature is more pronounced than that of precipitation in eastern China.Vegetation NDVI maxi... 相似文献