一次冬季冰雹的双偏振多普勒天气雷达回波分析

为研究双偏振雷达资料在冬季冰雹监测预警中的应用,利用厦门S波段双偏振雷达资料,分析了2016年12月21日福建漳州冰雹的回波特征。发现在降雹过程中,最强回波达69 dBZ,三体散射回波径向长度达16 km,旁瓣回波切向宽达20 km,低层的钩状回波与入流缺口明显;冰雹区的差分反射率因子Z_(dr)和差分相位常数K_(dp)数值小,冰水混合区的相关系数ρ_(hv)较低。分析表明:此冰雹个例并非典型的超级单体,但存在超级单体的部分偏振回波特征,回波前侧下沉气流存在Z_(dr)弧,可延伸到中层,在入流缺口和后侧下沉气流处,Z_(dr)柱和K_(dp)柱成对出现,中层存在CC的低值环。     

文本特征提取的研究进展

文本理解是人工智能的一个重要分支,其技术推动了人与计算机之间在自然语言上的有效交互.为了让计算机准确地理解和感知文本数据,文本特征提取是最为基础和关键的步骤之一.基于此,本文介绍文本特征提取研究的发展历史,以及近年来主流特征提取的方法,并对未来的研究方向进行展望.首先,介绍语义最底层的词级表示;接着,总结在词级表示基础上衍生出的句级表示上的研究进展;随后,介绍比词级表示和句级表示更高层的篇分析;最后,通过文本特征提取的一个典型应用——问答系统的介绍,阐述文本特征提取的最新方法和技术在问答系统上的应用,并对未来的研究方向做了展望.     

山东省胶南市七宝山铅矿区地质矿产特征综合研究

胶南七宝山位于胶东半岛东部地区,区域上属于胶南-威海造山带.山东省地质调查院在此开展普查工作,并通过激电测深、土壤测量、钻孔取芯,以及化学和光谱等分析方法,得出铅矿矿体赋存于断裂构造中,属岩浆热液充填型.矿体主要呈脉状、凸镜状,宽1～3 m,长70～200 m,主要矿体走向近南北,多倾向东.矿石有用化学成分主要为Pb、Ag、CaF2、Cu,Pb含量一般为1.36%～3.96%(平均3.11%),矿体平均厚度3.13m.     

天津市地面沉降的特征及其危害

天津是我国北方地面沉降最严重的城市之一,40余年的持续沉降不仅直接造成对安全高程、市政基础设施、房屋等建筑物的破坏,而且还通过安全高程的损失加剧了其他自然灾害的发生,使社会经济遭受严重损失.正确认识天津市地面沉降的特点及其危害,有利于控沉部门制定科学而有效的地面沉降减灾防灾政策和措施.基于对地面沉降所造成的危害分析和阐述,认为不合理开发地下流体资源是导致天津市地面沉降的主要原因,并提出相应预防和治理地面沉降的对策.     

Submarine canyons on the north of Chiwei Island:influenced by recent extension of the southern Okinawa Trough

Based on new multibeam bathymetric data and about 300 km long single seismic profiles, three topographic units were identified： the canyons, fractural valley and submarine terrace on the north of Chiwei Island where is a structural transition zone between the southern trough and the middle trough. The Chiwei Canyon and the North Chiwei Canyon are two of the largest canyons in the East China Sea （ECS） slope. Topographic features and architectures of them are described. The study shows that both of them are originated along faults. The evolution and spatial distribution of topographic units in the study area are controlled mainly by three groups of faults which were formed and reactive in the recent extensional phase of Okinawa Trough. The Chiwei Canyon was initia- ted during the middle Pleistocene and guided by F4 that is a N--S trending fault on the slope and F1, a large NW--SE trending fault on the trough. The pathway migration from the remnant channel to the present one of Chiwei Canyon is the result of uplift of tilted fault block that is coupled to the recent extension movements of the southern trough. The submarine terrace is detached from the ECS slope by the NEE -trending fault. The North Chiwei Canyon, developing during the late Pleistocene, is guided by FS, a N-S trending fault, diverted and blocked by the submarine terrace.     

Rural settlement spatial patterns and effects: Road traffic accessibility and geographic factors in Guangdong Province,China

Journal of Geographical Sciences - Based on land use classification data of remote sensing images, using kernel density, the minimal cumulative resistance model of road traffic accessibility, and a...     

Strain analysis of a seismically imaged mass‐transport complex,offshore Uruguay

Strain style, magnitude and distribution within mass‐transport complexes (MTCs) are important for understanding the process evolution of submarine mass flows and for estimating their runout distances. Structural restoration and quantification of strain in gravitationally driven passive margins have been shown to approximately balance between updip extensional and downdip contractional domains; such an exercise has not yet been attempted for MTCs. We here interpret and structurally restore a shallowly buried (c. 1,500 mbsf) and well‐imaged MTC, offshore Uruguay using a high‐resolution (12.5 m vertical and 15 × 12.5 m horizontal resolution) three‐dimensional seismic‐reflection survey. This allows us to characterise and quantify vertical and lateral strain distribution within the deposit. Detailed seismic mapping and attribute analysis shows that the MTC is characterised by a complicated array of kinematic indicators, which vary spatially in style and concentration. Seismic‐attribute extractions reveal several previously undocumented fabrics preserved in the MTC, including internal shearing in the form of sub‐orthogonal shear zones, and fold‐thrust systems within the basal shear zone beneath rafted‐blocks. These features suggest multiple transport directions and phases of flow during emplacement. The MTC is characterised by a broadly tripartite strain distribution, with extensional (e.g. normal faults), translational and contractional (e.g. folds and thrusts) domains, along with a radial frontally emergent zone. We also show how strain is preferentially concentrated around intra‐MTC rafted‐blocks due to their kinematic interactions with the underlying basal shear zone. Overall, and even when volume loss within the frontally emergent zone is included, a strain difference between extension (1.6–1.9 km) and contraction (6.7–7.3 km) is calculated. We attribute this to a combination of distributed, sub‐seismic, ‘cryptic’ strain, likely related to de‐watering, grain‐scale deformation and related changes in bulk sediment volume. This work has implications for assessing MTCs strain distribution and provides a practical approach for evaluating structural interpretations within such deposits.     

南沙群岛珊瑚礁砾洲地貌特征

通过对南沙群岛永暑礁、西门礁和安达礁3个砾洲的现场调查,基于理论最低潮面和平均海面分别计算了砾洲的可能分布范围和平均出露范围,获得了砾洲的地形地貌特征。3个砾洲均为向西北凸出的弧形,呈北东-南西向展布。永暑礁和西门礁砾洲周边地势较高,中部相对低洼,分布有多条砾脊,边缘向海侧主砾脊高度最大,内部多条较低的次砾脊相交于主砾脊并汇聚于砾洲东部;安达礁砾洲则中部凸起地势较高,周边较低,无多重砾脊分布。推断砾洲的发育由最初珊瑚枝块堆积于中部形成凸起,逐渐向北东和南西两侧以砾脊形式扩展,最终形成砾洲由内向外的洼地-砾脊-砾滩的地貌分带模式。砾洲的地形地貌特征表明,南沙群岛砾洲的发育主要受北东-南西向水动力条件季节性交替的控制,反映了南海海区盛行季风的影响。南沙群岛珊瑚礁砾洲的地貌特征为深入研究南海珊瑚礁灰沙岛地貌发育演化及动力机制提供了基础数据。     

大面积水深异常检测的条件变化自编码算法

针对大面积海底地形数据缺失或异常的复杂及多变性特点,结合条件变分自编码器(CVAE)与深度卷积生成对抗网络(DCGAN),构建了条件变分自编码生成对抗网络(CVAE-GAN)大面积海底伪地形的检测与剔除方法。本文方法利用条件变分自编码算法改变原有的样本分布,通过对训练样本的学习重新构建样本之间的分布规律,有效提高了高维到低维映射的稳定性;结合生成对抗网络,提高了整体算法的稳健性,最终得到较优的检测与剔除结果。采用水深格网数据进行试验,并与中值滤波法、趋势面滤波法进行比较。结果表明,本文方法在精度、稳定性及噪声稳健性方面有所提高,验证了本文方法在海底地形数据处理上具有可行性。