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914.
Generation of wide-swath and high-resolution SAR images from multichannel small spaceborne SAR systems 总被引:9,自引:0,他引:9
Zhenfang Li Hongyang Wang Tao Su Zheng Bao 《Geoscience and Remote Sensing Letters, IEEE》2005,2(1):82-86
Future spaceborne synthetic aperture radar (SAR) systems will be required to produce high-resolution imagery over a wide area of surveillance. However, the minimum antenna area constraint makes it a contradiction to simultaneously obtain both unambiguous wide-area and high azimuth resolution. To overcome this limitation, a technique has been suggested that combines a broad illumination source with multiple receiving channels. Then, the coherent combination of the recorded multichannel signals will allow for the unambiguous SAR mapping of a wide ground area with fine azimuth resolution. This letter first gives an overview of current research work carried out about the generation of wide-swath and high-resolution SAR images from multichannel small spaceborne SAR systems, and then a space-time adaptive processing (STAP) approach combined with conventional SAR imaging algorithms is presented, which could be of help to overcome the existing difficulties in data processing. The main idea of the approach is to use a STAP-based method to properly overcome the aliasing affect caused by the lower pulse repetition frequency and thereby retrieve the unambiguous azimuth wide (full) spectrum signal from the received signal. Following this operation, conventional SAR data processing tools can be applied to fully focus the SAR images. The performance of the approach is also discussed in this letter. The approach has the advantages of simplicity, robustness, and high efficiency. 相似文献
915.
Liping Du Guangchuan Su 《Geoscience and Remote Sensing Letters, IEEE》2005,2(3):247-249
A novel adaptive inverse synthetic aperture radar (ISAR) imaging technique is proposed for targets with nonuniform motion. The proposed algorithm is referred to as the generalized range-Doppler (GRD) ISAR imaging technique and is based on the fractional Fourier transform (FRFT). By utilizing this technique, clear ISAR imaging can be achieved for nonuniformly moving targets without involvement of complex motion compensation. Simulation results have proved that the new algorithm is robust and also computationally efficient as compared with previously reported algorithms such as joint time-frequency (JTF) imaging. 相似文献
916.
通过对童子岩组一段沉积特征分析,并结合天湖山矿区在闽西南凹陷区的空间位置,分析了天湖山矿区童子岩组一段的沉积环境和聚煤规律,划分了童子岩组一段的三个成煤期,这三个成煤期的聚煤作用随着海水进退而改变,煤层的好坏并不随着底板砂岩的厚薄而改变. 相似文献
917.
Geochemistry and origin of the giant Quaternary shallow gas accumulations in the eastern Qaidam Basin, NW China 总被引:1,自引:0,他引:1
Xiongqi Pang Wenzhi Zhao Aiguo Su Shuichang Zhang Maowen Li Yiqi Dang Fengying Xu Ruilian Zhou Daowei Zhang Ziyuan Xu Zhiqiang Guan Jianfa Chen Sumei Li 《Organic Geochemistry》2005,36(12):1636
This study provided an overview of the geological setting and geochemical characteristics of the Pleistocene shallow gas accumulations in the eastern Qaidam Basin, NW China. The five largest gas accumulations discovered in this region have a combined enclosure area of about 87 km2 and 7.9 trillion cubic feet (tcf) of proven gas reserves. The dominance of methane (mostly more than 99.9%) and the δ13C and δD values of methane (−68.51 to −65.00‰ and −227.55 to −221.94‰, respectively) suggest that these gases are biogenic, derived from the degradation of sedimentary organic matter by methanogens under relatively low temperatures (<75 °C). A sufficient supply and adequate preservation of organic matter in the Pleistocene sediments was made possible by the lake basin’s high altitude (2600–3000 m), high water salinity (>15% TDS) and strong stratification. The deposition and extensive lateral occurrence of lacustrine – shoreline sands/silts in beach sand sheets and sand bars provided excellent reservoirs for the biogenic gas generated from adjacent rocks. Effective but dynamic gas seals are provided by a combination of factors, such as the intermittent vertical variation in the sediment lithologies, hydraulic trapping due to the mudstone water saturation, the hydrocarbon gradient created as the result of gas generation from potential caprocks, and the presence of a regional caprock consisting of 400–800 m of muds and evaporites. It appears that the most favorable traps for large gas accumulations occur on structural slopes near the major gas kitchen, and the prolific gas pools are often those large gentle anticlines with little faulting complication. 相似文献
918.
非饱和带中非均质条件下LNAPL运移与分布特性实验研究 总被引:2,自引:3,他引:2
本文通过室内实验建立物理模型,研究非饱和带中层状非均质条件下轻非水相液体LNAPL(Light Non-Aqueous Phase Liquid)运移机制和分布特性。实验结果发现,介质的结构突变面改变了LNAPL的迁移模式。在LNAPL到达干湿界面以后,由于毛细水压力的作用,其入渗速度明显加快。当LNAPL迁移到夹层上界面时,纵向迁移受到阻碍。随着入渗过程的继续,污染物沿着界面产生向右横向迁移;在夹层上界面下部出现“优势流”现象,污染物由集中走向分散,随着分散块的体积不断增大,最终污染物又连接到一起,由分散走向集中;在夹层下界面附近锋面线集中在一起,说明污染物向下的纵向迁移基本停止。另外,介质的局部密实“透镜体”对LNAPL的局部迁移起到“阻滞”作用,并迫使其改变迁移路径。地下水位的变动将使污染物的产生重新分布。当地下水位降低以后,污染物产生明显的向下迁移。 相似文献
919.
920.
介绍了兰州大尖山核试验监测地震台阵的勘址工作,包括本地区的地质背景、气象条件以及中心建筑(CRF)和各子台建筑的的工程地质情况。该台阵投入观测后表明:台阵所在地区的气象、地质条件等观测环境完全满足全面禁止核试验条约组织国际监测系统(CTBTO/MS)勘选台阵的要求。兰州大尖山地震台阵的建成,进一步提高了甘肃省兰州市及周边地区微震活动的监测能力。 相似文献