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991.
辽宁兴城地区岩石光谱测试及特征分析 总被引:1,自引:0,他引:1
在辽宁兴城野外实习基地采用ASD光谱仪完成不同岩石样品光谱测试的基础上, 分析了不同类型、不同地质时代的岩浆岩和沉积岩, 及其风化面和新鲜面的光谱曲线特征。兴城野外不同岩浆岩与沉积岩光谱曲线形态相似, 新鲜面和风化面的特征光谱吸收位置相差不大, 但新鲜面的反射率普遍高于风化面的反射率;岩浆岩和沉积岩样品一般在波长为900 nm左右存在铁离子吸收谷;除了在1 400 nm和1 900 nm处有水汽吸收带外, 岩浆岩和沉积岩样品在2 200 nm左右还存在强吸收谷, 而灰岩在2 300 nm左右有比较高的吸收谷, 这也是利用实测光谱进行岩性分类的理论基础。但是, 不同地质年代下的岩石光谱曲线变化并无规律, 更多地与岩石结构、成分和环境因素等相关。这样, 岩石光谱测试及其特征分析可满足研究区岩性识别、矿化蚀变信息提取的需要。 相似文献
992.
993.
以回灌过程中渗透系数衰减模型为基础,推导了不同回扬次数的渗透系数解析表达式;将其应用于Theis公式,获得了考虑渗透系数衰减以及暂时性堵塞率条件下回灌与回扬物理过程中含水层压强的解析表达式,更准确地刻画了回灌与回扬的物理机制。计算结果表明:在连续回灌不回扬过程中,井内灌压增长符合指数曲线特征,而采取回扬措施后,由指数连续上升转变为间断式阶梯上升;回扬次数越多,灌压下降越明显,但灌压变化幅度随回扬次数的递增而减小。根据解析解定义的两种堵塞率的结果,可以实现利用实验判断不同成分回灌水源对含水层堵塞机理的分析,从而达到科学制定回灌水源标准的目的。 相似文献
994.
X. D. Liu S. P. Zhao L. G. Sun H. H. Luo X. B. Yin Z. Q. Xie Y. H. Wang K. X. Liu X. H. Wu X. F. Ding D. P. Fu 《Journal of Paleolimnology》2006,36(3):259-279
From a rare freshwater lake characteristic of alkalescence, named “Cattle Pond”, on the Dongdao Island of South China Sea (16°39′–16°41′ N, 112°43′–112°45′ E), we collected two undisturbed sediment cores that contain seabird droppings. In this paper, we determined the concentration-versus-depth profiles of the geochemical elements in the ornithogenic sediment layers of the two cores, analyzed these profiles by various statistical methods, and studied their geochemical characteristics. The concentration profiles of As, Cd, Cu, Se, Zn, P and S are significantly correlated with each other and with loss on ignition (LOI) at 550°C, the measure for the abundance of organic matter. Similar geochemical characteristics, however, were not observed in the upper sediment layer of the Cattle Pond notably affected by cattle excrements, as well as in the bottom sediment layer compositionally dominated by coral sand and gravel. This shows that these “bio-elements” are mainly derived from seabird feces and their geochemical composition is an important geochemical characteristic of the lacustrine ornithogenic sediments. By Q-mode factor analysis (QFA) on the concentration profiles of these bio-elements, we reconstructed the historical seabird population on Dongdao Island between 1350 and 350 year B.P., and observed significant fluctuations in the calculated population. The fluctuations seem to be related to the change of sea surface temperature (SST) in the Southern China Sea. This study provides new paleoenvironmental information of past seabird population changes in low latitude areas using an indirect geochemical method. 相似文献
995.
Compositions of heavy minerals in Northeastern China sandlands and provenance analysis 总被引:6,自引:0,他引:6
Sand samples deposited since the Last Glacial Maximum (LGM) from the Hulun Buir, Horqin and Otin-dag sandlands were measured for their assemblages of heavy minerals and chemical compositions of detrital garnets and tourmalines. Heavy mineral assemblages of these three sandlands consist mainly of garnet, ilmenite, epidote and minor amphibole and magnetite. Garnets consist mainly of high Mg type-A ones (58% on average), and minor type-B ones. Toumalines are mainly composed of Mg-rich and minor Fe-rich ones. Compared with those of central-southern Mongolia and central Tarim, these three sandlands are derived from the Phanerozoic rocks of the Central Asian Orogenic Belt and the Archean and Paleoprotorozoic basement rocks of the North China Craton. Our results provide direct evidence that the present-day sands may be reworked from LGM ones. Differences of heavy mineral composi-tions occur between the samples of the three sandlands and Taklimakan Desert, indicating that the material of the western arid regions contributes little to the eastern sandlands. 相似文献
996.
广东前汛期异常旱涝的大气环流特征 总被引:1,自引:3,他引:1
用1957~1999年广东省19个代表站4~6月降水资料和500hPa高度场资料,着重分析和讨论了广东省前汛期异常旱、涝年的同期和前期500hPa合成平均场的主要差异,以及前期关键月、关键区的特点,为广东省前汛期异常旱、涝的预测提供判别依据。 相似文献
997.
998.
Hui Yu Xuetong Zhang Tiangang Liang Hongjie Xie Xianwei Wang Qisheng Feng Quangong Chen 《水文研究》2012,26(20):3052-3061
Taking the Northern Xinjiang region as an example, we develop a snow depth model by using the Advanced Microwave Scanning Radiometer‐Earth Observing System (AMSR‐E) horizontal and vertical polarization brightness temperature difference data of 18 and 36 GHz bands and in situ snow depth measurements from 20 climatic stations during the snow seasons November–March) of 2002–2005. This article proposes a method to produce new 5‐day snow cover and snow depth images, using Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) daily snow cover products and AMSR‐E snow water equivalent and daily brightness temperature products. The results indicate that (1) the brightness temperature difference (Tb18h–Tb36h) provides the most accurate and precise prediction of snow depth; (2) the snow, land and overall classification accuracies of the new images are separately 89.2%, 77.7% and 87.2% and are much better than those of AMSR‐E or MODIS products (in all weather conditions) alone; (3) the snow classification accuracy increases as snow depth increases; and (4) snow accuracies for different land cover types vary as 88%, 92.3%, 79.7% and 80.1% for cropland, grassland, shrub, and urban and built‐up, respectively. We conclude that the new 5‐day snow cover–snow depth images can provide both accurate cloud‐free snow cover extent and the snow depth dynamics, which would lay a scientific basis for water management and prevention of snow‐related disasters in this dry and cold pastoral area. After validations of the algorithms over other regions with different snow and climate conditions, this method would also be used for monitoring snow cover and snow depth elsewhere in the world. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
999.
In this paper, we have performed a temporal analysis of single pulses from short (46) and long (51) gamma-ray bursts (GRBs)
to investigate possible differences in their properties. In particular we pay detailed attention to the asymmetry of pulses.
We find that the asymmetry ratio of short GRB pulses clusters around 0.81 and that these pulses are on average more symmetric
than those from long GRBs, which have an average value of 0.47. In addition we note that the pulses in short GRBs display
exponential rises and fast decays (ERFD) in comparison the fast rise exponential decays (FRED) pulses of long GRBs. The asymmetry
ratio does not depend on the full width at half maximum (FWHM) and does not vary with energy channel. Moreover, there is a
general trend for slower pulses to be more asymmetric. Finally, we deduce that the asymmetry could be used to probe the emission
mechanisms of GRBs. 相似文献
1000.
Xingke XU Changwei CHEN Jing SUN Qinglong MENG College of Earth Sciences Jilin University Changchun China 《东北亚地学研究》2007,10(1):25-28
The authors discussed the method of wavelet neural network(WNN) for correlation of base-level cycle.A new vectored method of well log data was proposed.Through the training with the known data set,the WNN can remenber the cycle pattern characteristic of the well log curves.By the trained WNN to identify the cycle pattern in the vectored log data,the ocrrelation process among the well cycles was completed.The application indicates that it is highly efficient and reliable in base-level cycle correlation. 相似文献