Generation of wide-swath and high-resolution SAR images from multichannel small spaceborne SAR systems

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.     

Adaptive inverse synthetic aperture radar imaging for nonuniformly moving targets

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.     

近30年乌鲁木齐地区自然植被净第一性生产力变化分析

利用周广胜、张新时提出的自然植被净第一性生产力模型，估算分析了乌鲁木齐地区近30年自然植被净第一性生产力（NPP）的时空变化。结果表明，除后峡地区的NPP呈递减趋势外，其它各地的NPP总体上呈递增趋势；中山带的NPP最高，亚高山、高寒、低山和山前荒漠地带依次降低；气候变暖除对高寒地带的自然植被的NPP有一定的正效应外，对其它地区的NPP均产生较明显的负效应；年降水量的增加对提高自然植被净第一性生产力具有积极作用。     

武都数字化流体资料对岷县Ms5.2地震的前兆异常反映

在2003年11月13日岷县Ms5.2级地震前,武都数字化流体资料出现了明显的前兆短临异常变化.深部水温在震前10天出现了高值变化,浅部水温震前几天出现大幅度升高,变化幅度达1℃;气氡资料也出现了明显的趋势及短临变化.     

云南建水-蒙自一带冲沟走滑断错及其意义

云南建水-蒙自一带位于川滇菱形块体向SE145°平移的前锋,受其影响,该地区的蒙自东山断裂、田山断裂和黑泥地断裂等表现出一定程度的晚第四纪活动性,跨过断裂的冲沟被走滑断错。攀枝花以东的蒙自东山断裂右旋错断冲沟和其间的山脊约40m,并在山前洪积扇上形成偏离上游约30m的废弃古河道,古河道中堆积物的年龄为44kaBP,断裂右旋滑动速率约为0.7mma。大红地北一条冲沟在跨过田山断裂时发生右旋拐弯。冲沟在山前形成了年龄分别为31kaBP和39kaBP的2级洪积阶地,呈现出年轻阶地位错量大于老阶地的反常现象。田山断裂的平均右旋滑动速率约0.9mma。发育于黑泥地断裂南侧的多条冲沟在流过断裂时发生一致性的右旋位错,其中一条冲沟位错量达14m,断裂的右旋滑动速率为0.4mma。这一地区自30～40kaBP开始发生了一次明显的构造运动,表现为这一时代的洪积扇上的地貌过程由加积转变为切割,并被断裂错断。断裂的走滑速率明显低于小江断裂带、曲江断裂带和石屏-建水断裂带等。川滇菱形地块向SSE方向的平移及其构造活动不仅仅局限在小江断裂带以西的地块内部,而是引起了外围地块上的断裂活动,但断裂活动强度不及内部断裂的13。冲沟对走滑断错的响应分为3种类型,分别为同步弯曲型、加剧弯曲型和不对称谷地型,其中加剧弯曲型的地貌过程较为复杂。每种类型都记录了断裂的走滑活动,在估算断错量和滑动速率时应甄别不同的响应类型,以免人为的“加大”或“减小”甚至“忽略”断裂的活动幅度。     

荥经-马边-盐津逆冲构造带断裂运动组合及地震分段特征

逆冲构造带的分段性研究是评价该类发震构造地震危险性的基础工作。荥经-马边-盐津逆冲构造带是青藏高原东南边缘重要的NW向强震构造带,该构造带以逆冲错动为主要活动形式,其组合形式与逆冲强度存在南北差异。通过NE向横向断裂的构造地貌分析,发现横向断裂以右旋走滑活动为主,兼有倾滑活动。根据其与纵向断裂的交接关系,将横向断裂概括为横向分割断裂、横向撕裂断裂和横向转换断裂3种类型,讨论了3类横向断裂在逆冲构造带分段中所起的不同作用,进而将荥经-马边-盐津逆冲构造带分为独立的3段,并分析了各段的地震活动特征。研究表明,荥经-马边-盐津逆冲构造带以横向断裂为标志的3分段特点,既体现了段与段之间断裂活动强度、地震破裂强度与步调的差异,又体现了段内地震破裂步调的一致性,表明横向断裂在一定程度上控制了逆冲构造带的破裂分段,只是横向断裂的类型不同,其所起的作用也不同     

福建天湖山煤矿区童子岩组一段沉积环境与聚煤规律

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.     

Geochemistry and origin of the giant Quaternary shallow gas accumulations in the eastern Qaidam Basin, NW China

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.     

非饱和带中非均质条件下LNAPL运移与分布特性实验研究

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。     

大比例尺城乡一体化土地调查综合技术的研究

本研究项目根据国家法规、规程和规定,以江阴市”数字国土”工程为研究对象,依靠3S现代测绘高新技术手段,对江阴市城镇1∶500、农村1∶1000进行地籍、地形和土地利用现状调查技术研究,建立城乡一体化地籍管理信息系统和基础地理信息系统,探索城乡一体化建设和维护更新等管理模式。