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961.
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963.
白云鄂博矿区北部韧性剪切带特征及其构造意义 总被引:1,自引:0,他引:1
在白云鄂博主矿北西约6.5km处的查干楚鲁一带,有一条近东西向延伸的断层带,前人在该带中部识别出了蛇绿岩混杂堆积。本文作者在蛇绿岩东部的大理岩质糜棱岩中发现鞘褶皱、拉伸线理及旋转碎斑系等变形构造,在大理岩周围发现石英岩型宏观压力影构造,在变质石英砂岩中识别出褶劈理以及方解石脉等相关构造,在这条东西向断裂带北边发现典型的黄铁矿型压力影。根据上述特征判断,查干楚鲁一带为一条近东西向延伸的韧性剪切带,同时具有NEE—SWW向逆左旋走滑的特征。该带揭示出蒙古洋板块与华北板块在晚古生代汇聚拼合的基本格局。 相似文献
964.
Interpreting the physical dynamics of ancient environments requires an understanding of how current‐generated sedimentary structures, such as ripples and dunes, are created. Traditional interpretations of these structures are based on experimental flume studies of unconsolidated quartz sand, in which stepwise increases in flow velocity yield a suite of sedimentary structures analogous to those found in the rock record. Yet cyanobacteria, which were excluded from these studies, are pervasive in wet sandy environments and secrete sufficient extracellular polysaccharides to inhibit grain movement and markedly change the conditions under which sedimentary structures form. Here, the results of flume experiments using cyanobacteria‐inoculated quartz sand are reported which demonstrate that microbes strongly influence the behaviour of unconsolidated sand. In medium sand, thin (ca 0·1 to 0·5 mm thick) microbial communities growing at the sediment–water interface can nearly double the flow velocity required to produce the traditional sequence of ripple→dune→plane‐bed lamination bedforms. In some cases, these thin film‐like microbial communities can inhibit the growth of ripples or dunes entirely, and instead bed shear stresses result in flip‐over and rip‐up structures. Thicker (ca≥1 mm thick) microbial mats mediate terracing of erosional edges; they also, foster transport of multi‐grain aggregates and yield a bedform progression consisting of flip‐overs→roll‐ups→rip‐ups of bound sand. 相似文献
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967.
Response surface methodology (RSM) and artificial neural networks (ANNs) based on a multivariate central composite design (CCD) were applied to model and optimize the photocatalytic degradation of N,N‐diethyl‐m‐toluamide (DEET). The individual and interaction effects of three main operating factors (mass of TiO2, initial DEET concentration, and irradiation intensity) on process efficiency were estimated, proving their important effect on % DEET removal. Among the independent variables, TiO2 concentration displayed the highest effect on DEET degradation followed by initial DEET concentration and UV intensity. The optimization and prediction capabilities of ANNs and RSM were compared on the basis of root mean squared error, mean absolute error, absolute average deviation, and correlation coefficient values. Results proved the usefulness and capability of the experimental design strategy for successful investigation and modeling of the photocatalytic process. Moreover, the selected ANN gave better estimation capabilities throughout the range of variables than RSM. Based on the models and the related experimental conditions, the optimal values of each parameter were determined. Under optimum conditions, DEET and total organic carbon (TOC) followed pseudo‐first order kinetics. Nearly complete degradation of DEET took place within 15 min whereas high TOC removal percentages (>85%) was achieved after 90 min irradiation time. 相似文献
968.
Jennifer Saleem Arrigo 《The Professional geographer》2013,65(3):364-378
Water quality studies seeking to identify modes or processes of river systems often use targeted, research-designed, high-frequency data, whereas most water quality data today are collected for monitoring and reporting requirements are of low frequency and are collected through cooperative and volunteer programs. There exists in this situation an information gap between the science of understanding river system dynamics and the collection of data in most of these systems. Using data collected by volunteers in the Neponset Watershed (Massachusetts, U.S.), we demonstrate that multivariate analysis is a viable option for enhancing the use and information of spatially distributed, long-term monitoring data sets common in the United States. Additionally, the geographic, environmental, and time line information inherent in these community-maintained data leads to a more complete picture of river and stream dynamics. Principal component analyses of three distinct reaches with different channel characteristics and surrounding environments demonstrate differences in dominant modes, with undeveloped stretches driven by seasonal processes, and other stretches exhibiting organic or nutrient sources. This type of information can bridge gaps from problem identification or monitoring to a more complete understanding of river system processes influencing water quality, thereby leading to better stewardship of resources. 相似文献
969.
Work,Home, and Market: The Social Transformation of Housing Space in Guangzhou,China 总被引:1,自引:0,他引:1
《Urban geography》2013,34(4):434-452
Principal components analysis of small-area data provided by China's 2000 Population Census shows that major new economic and social forces largely shape the spatial composition of housing in Guangzhou. This is generally manifested in a series of concentric rings: the old urban core, the middle zone of reform housing, and the outer ring of new commodity housing. In addition, urban villages punctuate the metropolitan landscape. Corresponding analysis of sociodemographic attributes depict a metropolis in transition, with market elements and choice-based housing decisions beginning to impinge on the urban fabric. However, the deeply entrenched socialist institutions established during the early years of the People's Republic ensure the continuing dominance of the workplace and occupational attributes as factors structuring China's metropolitan space. 相似文献
970.
《自然地理学》2013,34(1):76-96
Regions based on seasonal precipitation variability for Hawaii are determined using a principal components analysis applied to 124 stations for the period 1971-2000. Nine regions are delineated and are consistent with known precipitation patterns; leeward and windward stations are in separate regions on all islands. Within each region, the relationship between precipitation and the El Niño-Southern Oscillation (ENSO) is examined using a correlation analysis with the Southern Oscillation Index (SOI), and the Niño 3.4 and Niño 1+2 indices. Precipitation is most frequently correlated with ENSO in the different regions using SOI and Niño 3.4. Using several nonparametric statistical tests, it is determined that while average precipitation received in Hawaii during El Niño events is significantly different from average precipitation (1971-2000) and from precipitation received during La Niña events, the relationship between precipitation and individual ENSO events within regions is rarely significant. Finally, during El Niño or La Niña events, average precipitation receipt across the regions co-varies during winter and summer under concurrent conditions and a one-season lag. Synoptic patterns are examined and indicate a deviation from average conditions during ENSO events that affects subsidence and precipitation patterns. 相似文献