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排序方式: 共有221条查询结果,搜索用时 31 毫秒
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Conventional seismic data processing methods based on post‐stack time migration have been playing an important role in coal exploration for decades. However, post‐stack time migration processing often results in low‐quality images in complex geological environments. In order to obtain high‐quality images, we present a strategy that applies the Kirchhoff prestack time migration (PSTM) method to coal seismic data. In this paper, we describe the implementation of Kirchhoff PSTM to a 3D coal seam. Meanwhile we derive the workflow of 3D Kirchhoff PSTM processing based on coal seismic data. The processing sequence of 3D Kirchhoff PSTM includes two major steps: 1) the estimation of the 3D root‐mean‐square (RMS) velocity field; 2) Kirchhoff prestack time migration processing. During the construction of a 3D velocity model, dip moveout velocity is served as an initial migration velocity field. We combine 3D Kirchhoff PSTM with the continuous adjustment of a 3D RMS velocity field by the criteria of flattened common reflection point gathers. In comparison with post‐stack time migration, the application of 3D Kirchhoff PSTM to coal seismic data produces better images of the coal seam reflections. 相似文献
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104.
Liying Wang Ming Ye J. Fernando Rios Raoul Fernandes Paul Z. Lee Richard W. Hicks 《Environmental Earth Sciences》2013,70(4):1911-1926
Nitrate, as a commonly identified groundwater and surface water pollutant, poses serious threats to human health and the environment. One important source of nitrate in the environment is due to wastewater treatment using Onsite Sewage Treatment and Disposal Systems (OSTDS) (a.k.a., septic systems). To facilitate water resources and environmental management, an ArcGIS-Based Nitrate Load Estimation Toolkit (ArcNLET) is developed to simulate nitrate transport and estimate nitrate load from septic systems and collocated fertilizer applications in groundwater to surface water bodies. It is a screening tool based on a simplified conceptual model of groundwater flow and nitrate transport. It is used in this study to estimate nitrate load from thousands of septic systems to surface water bodies in two neighborhoods located in Jacksonville, FL, USA, where nitrate due to septic systems is believed to be one of the reasons of nutrient enrichment and an isotope study indicates that denitrification is significant. A global sensitivity analysis is performed to identify critical parameters for model calibration, and the most critical parameter is the first-order decay coefficient used to simulate the denitrification process. Hydraulic conductivities at different soil zones have different levels of influence on simulated nitrate concentrations at different locations. By manually adjusting model parameters, simulated shapes of water table and nitrate concentration agree reasonably with average field observations, suggesting that ArcNLET is able to simulate spatial variability of field observations. Estimated nitrate loads exhibit spatial variability, which is useful to facilitate decisions on the conversion of OSTDS into sewers in certain areas for reducing nitrate load from septic systems to surface water bodies. 相似文献
105.
We studied the effect of pH(pH 5, 6, 7 and 8) on the hatching percentage, survival and reproduction of Artemia strains in Bohai Bay salt ponds. Strains included parthenogenetic Artemia from Bohai Bay(BHB), Artemia franciscana from San Francisco Bay, and A. franciscana artifi cially produced in salt ponds in Vietnam. The latter was included as a potential inoculum for biological management of salt ponds. The hatching percentage of cysts after 24 h and the survival rate of the tested Artemia strains were signifi cantly reduced when exposed to a culture medium at pH 5 for 18 d( P 0.05). The tolerance of Artemia to 48 h acid exposure varied with developmental stage, increasing in the following order: juvenile, nauplii, pre-adult, with maximum tolerance in adults. All strains of Artemia tested could not reproduce at pH 5. At pH levels from pH 6–8, a higher pH generally resulted in a shorter brood interval and enhanced ovoviviparity. Hence, we suggest that brine acidifi cation has a negative impact on Artemia populations in the Bohai Bay saltworks. Inoculation of Artemia with either local parthenogenetic Artemia or exotic A. franciscana should be feasible at pH 7–8. 相似文献
106.
Halophilic archaea comprise the majority of microorganisms found in hypersaline environments. C50 carotenoids accumulated in archaea cells are considered potential biotechnological products and possess a number of biological functions. Ten red colordes were isolated from brine water in a saltem crystaltizer pond of the Hangu Saltworks, China. 16S rRNA gene sequence analysis showed that the colonies belonged to the extremely halophilic archaea genera Halobacterium and Halorubrum. Two representative strains, Halobacterium strain SP-2 and Halorubrum strain SP-4, were selected for further study on the phenotypic characteristics and effects of salinity and pH on accumulation and composition of pigments in their cells. The archaeal strains were isolated and grown in a culture medium prepared by dissolving yeast extract (10 g/L) and acid-hydrolyzed casein (7.5 g/L) into brine water obtained from a I.ocal salt pond. Their optimum salinity and pH for growth were 250 and 7, respectively, although pigment accumulation (OD490/ mL broth) was highest at pH 8. In addition, at 150-300 salinity, increasing salinity resulted in decreasing pigment accumulation. Analysis of the UV-Vis spectrum, TLC and HLPC chromatograms showed that C50 carotenoid bacterioruberin is the major pigment in both strains. 相似文献
107.
相对于我国各行业抗震规范反应谱下降段呈现的多样性,欧美规范谱基于理想化反应谱模型,其长周期下降段的规定形式统一,且由第二特征周期TD确定.基于理想化反应谱模型,TD的确定与位移谱形态、"结构所需周期范围"等概念相关.基于我国区划图研究中大量采用NGA数据库的地震动记录及以地震动峰值加速度分区值表达地震强度的现状,以理想... 相似文献
108.
轨道站点是城市轨道交通基本线网系统中的关键节点,科学的轨道站点分类,对了解城市功能分区及评价轨道交通基础设施建设情况具有重要意义。轨道交通站点时间序列客观记录了所观测的站点在各个时刻点的重要信息,研究其时间序列聚类,是认识和理解轨道交通站点时间序列形成本质的重要手段,也是挖掘轨道交通站点时间序列中隐含的有较高价值规律知识的重要方法。本文以北京IC卡轨道站点刷卡数据为研究对象,提出了描述轨道站点的4个数据集,即工作日进站数据集(WB)、工作日出站数据集(WA)、休息日进站数据集(RB)和休息日出站数据集(RA);并首次引入时间序列分析方法(符号集合近似(SAX)方法)对4个数据集进行聚类分析,实现了高维数据的有效降维和轨道站点之间的相似性度量。采用层次聚类方法并根据聚类有效性DB指数确定将195个站点分为8类更为合理。通过分析每类站点的日客流特征和空间位置分布情况,为轨道交通站点规划设计和管理服务提供一定的客观参考依据。 相似文献
109.
基于景观孤岛化分析的传统地域文化景观保护模式——以江苏苏州市甪直镇为例 总被引:1,自引:0,他引:1
在城镇化、现代化和商业化快速发展的今天,传统文化景观的破碎化已成为传统地域文化景观的重要空间特征和现象,破碎化直接催生了传统文化景观空间的孤岛化现象,直接影响着传统地域文化景观的整体性,成为传统文化景观整体性保护的重要障碍。本文以苏州市甪直镇为例,在分析区域特征及对当地居民进行问卷调查的基础上,通过构造孤岛化评价指数,评价甪直古镇传统文化景观的格局的综合特征和景观孤岛化现象、特征及形成过程。在传统文化景观孤岛化评价的基础上,通过确定保护圈层、构建文化景观遗产廊道和景观生态网络格局,实现传统文化景观空间的拓展、连接和传统文化景观与缓冲空间的有机复合,成为传统地域文化景观区域性整体保护的空间模式。 相似文献
110.
目前径流变化相关研究较少涉及径流的不同组分。利用湖南省澧水流域4个水文站点长序列观测资料,不仅分析了2007-2011年相对于1985年以前径流总量及其历时曲线的变化,也分析了地表径流和基流及其历时曲线的变化。与1985年以前比,流域年降雨量保持不变,最显著的变化为森林覆盖率的增加和大量水库的修建。这些人类活动没有造成年径流总量、年基流量和年地表径流量的显著变化,但在日时间尺度上对径流过程产生了重要影响。地表径流和地下径流对人类活动存在差异性响应,2007年以后地表径流在洪峰期流量变小而其他时段变大,而地下径流汇水受人类活动影响较小,基流流量除枯水期外与1985年以前基本一致。本文所揭示的规律可能在中国南方具有一定的代表性。 相似文献