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51.
Yanni Gunnell 《Basin Research》1998,10(3):281-310
This study constitutes a comprehensive attempt to interpret the multistoreyed benchland scenery of the South Indian shield. In South India, two rifted margins (and now competing base levels), a low-elevation margin facing the Bay of Bengal, in existence since ≈130 Ma, and a younger (65 Ma) high-elevation margin facing the Arabian Sea, together with a high-standing backbone of extremely resistant granulitic rocks known as charnockites, have influenced the long-term erosional response to rock uplift and to the eustatic shift of shorelines in a complex way.
Several tiers of flat-lying, denudational topographic surfaces, which are indifferent to stratification, schistosity or foliation and highlighted by a characteristic weathering mantle, are identified and the conditions of their genesis discussed. General definitions and assumptions concerning the evolution of planation surfaces are presented. A major key issue is the nature of crustal uplift in cratonic regions: its relation to global tectonics, its role in the redistribution in time and space of available relief and in the deformation of pre-existing planation surfaces, and its bearing on denudational signals which may be recorded both by isotopic measurement techniques and offshore sedimentary sequences. The proposed denudation chronology considers all these aspects, and the analysis sets out to establish a thread of geodynamic events that can account for the observed morphology. Drainage, weathering and crustal uplift patterns, geological structures and chronostratigraphic data are examined in relation to their possible connections with the migration of drainage divides and surface lowering patterns. The high number of degrees of freedom involved when considering the long-term interplay between gravity-driven and radiation-driven denudation systems is one of the many problems facing this analysis, and is extensively addressed in the discussion. 相似文献
Several tiers of flat-lying, denudational topographic surfaces, which are indifferent to stratification, schistosity or foliation and highlighted by a characteristic weathering mantle, are identified and the conditions of their genesis discussed. General definitions and assumptions concerning the evolution of planation surfaces are presented. A major key issue is the nature of crustal uplift in cratonic regions: its relation to global tectonics, its role in the redistribution in time and space of available relief and in the deformation of pre-existing planation surfaces, and its bearing on denudational signals which may be recorded both by isotopic measurement techniques and offshore sedimentary sequences. The proposed denudation chronology considers all these aspects, and the analysis sets out to establish a thread of geodynamic events that can account for the observed morphology. Drainage, weathering and crustal uplift patterns, geological structures and chronostratigraphic data are examined in relation to their possible connections with the migration of drainage divides and surface lowering patterns. The high number of degrees of freedom involved when considering the long-term interplay between gravity-driven and radiation-driven denudation systems is one of the many problems facing this analysis, and is extensively addressed in the discussion. 相似文献
52.
大气红外吸收带重迭及其处理方法对长波辐射计算的影响 总被引：1，自引：0，他引：1
本文详细地讨论了H_2O,CO_2,O_3,N_2O以及CH_4这五种大气主要红外活性气体的红外吸收带的重迭及其处理方法对长波冷却率及通量计算的影响.结果表明:气体吸收带的重迭对大气红外冷却率具有重要的作用;但在一定的误差范围内,不仅某些气体吸收带的重迭效应很小,可以忽略不计,而且某些重迭光谱区域对整个红外冷却率及通量的贡献亦可不予考虑.另外,本文还定性地讨论了处理重迭带的不同方法对红外辐射计算的影响. 相似文献
53.
Hydrological processes and conditions were quantified for the Mersey River Basin (two basins: one exiting below Mill Falls, and one exiting below George Lake), the Roger's Brook Basin, Moosepit Brook, and for other selected locations at and near Kejimkujik National Park in Nova Scotia, Canada, from 1967 to 1990. Addressed variables included precipitation (rain, snow, fog), air temperature, stream discharge, snowpack accumulations, throughfall, soil and subsoil moisture, soil temperature and soil frost, at a monthly resolution. It was found that monthly per hectare stream discharge was essentially independent of catchment area from <20 km2 to more than 1000 km2. The forest hydrology model ForHyM2 was used to simulate monthly rates of stream discharge, throughfall and snowpack water equivalents for mature forest conditions. These simulations were in good agreement with the historical records once the contributions of fog and mist to the area‐wide water budget were taken into account, each on a monthly basis. The resulting simulations establish a hydrologically consistent, continuous, comprehensive and partially verified record for basin‐wide outcomes for all major hydrological processes and conditions, be these related to stream discharge, soil moisture, soil temperature, snowpack accumulations, soil frost, throughfall, interception and soil percolation. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
54.
目的：探究紫贝止咳颗粒联合阿奇霉素治疗肺炎支原体感染小儿急性支气管炎的疗效和安全性。方法：选取100 例肺炎支原体感染急性支气管炎患儿为研究对象,依照随机数字表法将其分为治疗组和对照组,每组各50 例。对照组单用西药治疗,治疗组在对照组治疗的基础上加用紫贝止咳颗粒治疗,比较2组的临床疗效,发热、咳嗽、咽部充血、肺部啰音消失时间,炎性因子水平［超敏C-反应蛋白（hs-CPR）、γ干扰素（IFN-γ）、降钙素原（PCT）］及不良反应发生情况（肝毒性反应、胃肠道反应、过敏反应）。结果：总有效率治疗组为94.0%（47/50）,高于对照组的76.0%（38/50）,差异有统计学意义（P＜0.05）。治疗组的发热、咳嗽、咽部充血、肺部啰音消失时间均明显短于对照组（P＜0.01）。治疗后,2组患儿hs-CPR、IFN-γ、PCT水平均明显下降,且治疗组降幅大于对照组（均P＜0.05）。不良反应总发生率治疗组为6.0%（3/50）,对照组为4.0%（2/50）,差异无统计学意义（P>0.05）。结论：紫贝止咳颗粒联合阿奇霉素治疗肺炎支原体感染小儿急性支气管炎疗效颇佳,能够有效改善临床症状和体征,降低炎性因子水平,且具有一定安全性。 相似文献
55.
针对宜昌磷矿北部某矿区磷矿矿石性质及可选特性,进行了单一反浮选试验、重液浮沉试验和重介质-反浮选联合工艺扩大试验,并对试验结果进行了综合评价。结果表明,采用重介质-反浮选联合工艺,比较适合该矿开发利用,在分选介质密度2.415g/cm3,磨矿细度-200目(-0.076mm)含量63.70%,原矿P2O5品位20.81%、Mg O含量6.08%时,获得了精矿产率54.69%、P2O5品位30.58%、Mg O含量0.87%,磷回收率80.36%的选矿指标。试验研究结果为该类矿石的合理开发利用提供了参考。 相似文献
56.
Kara L. Webster Jason A. Leach Paul W. Hazlett Robert L. Fleming Erik J. S. Emilson Daniel Houle Kara H. Y. Chan Fariborz Norouzian Amanda S. Cole Jason M. O'Brien Karen E. Smokorowski Stephanie A. Nelson Shelagh D. Yanni 《水文研究》2021,35(4):e14109
The Turkey Lakes Watershed (TLW) study is a federal, interdepartmental study established in 1979 to investigate the effects of acid rain on terrestrial and aquatic ecosystems. The 10.5 km2 watershed, located in the Eastern Temperate Mixed Forest on the Canadian Shield, has been the site of multidisciplinary studies on biogeochemical and ecological processes conducted across plot to catchment scales. The whole-ecosystem investigative approach was adopted from the outset and has allowed research to evolve from its original (and continuing) acidification focus to include investigations on the effects of climate change, forest harvesting and other forest ecosystem perturbations. The extensive scientific and support infrastructure allows for collection of a comprehensive data record essential for understanding long-term environmental trends. Data include atmospheric deposition, meteorology, stream hydrology and chemistry, soil, pore and ground water properties, understory and overstory vegetation, lake and outflow physical and chemical properties, and aquatic macroinvertebrate and fish community composition and abundance. These data have contributed to over 400 published research papers and graduate theses. The watershed has also figured prominently in many continent-wide comparisons advancing fundamental watershed theory. The knowledge gained at TLW has influenced pollutant emission and natural resource management policies provincially, nationally and internationally. 相似文献
57.
高分五号高光谱影像矿物精细识别 总被引：2，自引：2，他引：0
矿物识别是高光谱遥感技术优势之一,已在地质矿产领域取得了显著应用效果。随着光谱分辨率的不断提高,高光谱遥感矿物识别逐渐从识别矿物种类向矿物亚类、矿物成分等精细信息识别发展,且随着应用实践的不断深入,对矿物精细信息的需求也越来越大。而光谱分辨率和矿物识别方法是制约高光谱矿物精细识别的主要因素。高分五号(GF-5)超高的光谱分辨率为矿物精细识别提供了可能。首先在分析总结已有高光谱矿物识别方法优缺性的基础上,提出了综合光谱特征增强匹配度和特征参量的矿物识别方法;其次,选取甘肃柳园和美国Cuprite两个研究较多的地区为研究对象,基于GF-5卫星数据开展了矿物精细识别,在完成矿物种类、亚类识别的基础上,进一步对绢云母成分信息进行了反演;最后,结合上述地区已有机载高光谱数据及填图结果开展对比分析。结果表明:GF-5矿物识别信息分布与机载HyMap、AVIRIS一致性很好,相较机载数据GF-5矿物识别平均正确率优于90%,说明本研究提出的矿物识别方法能够满足GF-5矿物精细识别,可为后续业务化应用提供技术支撑,同时认为超高的光谱分辨率使得GF-5在矿物成分信息识别上更具优势。 相似文献
58.
近1000年来西格陵兰荷尔斯泰因斯堡港生物硅指示的海洋生产力变化 总被引：1，自引：1，他引：0
We analyzed the biogenic silica(BSi) content and produced a diatom-based summer sea-surface temperature(SST) reconstruction for sediment core GC4 from the Holsteinsborg Dyb, West Greenland. Our aim was to reconstruct marine productivity and climatic fluctuations during the last millennium. Increased BSi content and diatom abundance suggest relatively high marine productively during the interval of AD 1000–1400, corresponding in time to the Medieval Warm Period(MWP). The summer SST reconstruction indicates relatively warm conditions during AD 900–1100, followed by cooling after AD 1100. An extended cooling period during AD 1400–1900 is characterized by prolonged low in reconstructed SST and high sea-ice concentration. The BSi values fluctuated during this period, suggesting varying marine productivity during the Little Ice Age(LIA).There is no significant correlation between the BSi content and SST during the last millennium, suggesting that the summer SST has little influence on marine productively in the Holsteinsborg Dyb. A good correspondence between the BSi content and the element Ti counts in core GC4 suggests that silicate-rich meltwater from the Greenland ice sheet was likely responsible for changes in marine productively in the Holsteinsborg Dyb. 相似文献
59.
为深入研究井喷和管道破损等海底事故后溢油在水下环境中的输移扩散过程，文章利用自制的组合式环形水槽（周长9.7 m、宽0.45 m、深1 m），以阿曼原油与消油剂混合物和淡水（含示踪剂）为模拟污染物，初步开展静水和动水环境中海底溢油浮射流的物理模拟实验，并应用基于拉格朗日积分方法的水下溢油浮射流模型进行数值模拟比较分析。研究结果表明:静水环境中，水下溢油浮射流主要沿喷口的垂直中心线向水面输移扩散；非均匀流动水环境中，横流速度越大，浮射流输移轨迹的弯曲程度越明显；数值模拟的浮射流轨迹总体上与实验观测结果符合较好；研究结果可为今后相关物理实验和数值模型的改进研究提供有益参考。 相似文献
60.