Early-fusion based pulsar identification with smart under-sampling

The discovery of pulsars is of great significance in the field of physics and astronomy.As the astronomical equipment produces a large number of pulsar data,an ...     

两河口水电站右坝肩边坡的氡异常特征

通过对岩体的氡气测试,得到不同高程氡气脉冲值的硐深变化曲线,分析岩体卸荷强度和方式与其氡异常的相关性。岩体卸荷强度愈高,高氡异常值越高,异常深度范围越大,异常特征越明显。边坡集中卸荷拉裂部位、断层及错动带高氡异常,但边坡深部某些顺层断层或错动带异常特征不明显。结果显示卸荷强度和方式与氡气异常特征密切相关。     

鄂尔多斯盆地南部晚三叠世沉降与沉积中心研究

从古地貌恢复的角度出发,依据残留厚度和补偿厚度印模法原理,恢复了鄂尔多斯盆地晚三叠世早期古地层厚度,从而确定了沉降中心;选取粒度矩法平均值这一参数,对同井位同层位的粒度值求平均值,将所得值投放平面图,获得粒度均值平面等值线图,湖盆中细粒碎屑物质的聚集区反映了古水流的汇合区,指示沉积中心。研究结果表明,鄂尔多斯盆地晚三叠世早期沉降中心位于马家滩-白豹-宜君一线,西南部镇原-崇信一线存在局部沉降区,盆地的地层厚度变化较大,说明晚三叠世差异沉降作用明显;而沉积中心主要位于正宁-合水-姬塬-吴起-志丹-太白-黄陵-黄龙一线围成的区域,由西北向东南延展,并以北西-南东为轴向两侧迁移,长10至长7沉积期湖岸线的变化,反映了受构造沉降速率控制,湖盆的沉积中心不断扩大,长7沉积期湖盆面积最大。     

A STUDY OF RAPID DECAY TYPHOONS IN OFFSHORE WATERS OF CHINA

On the basis of NCEP/NCAR reanalysis data and yearbooks of CMA tropical cyclones, statistical analysis is performed for 1949—2013 offshore typhoons subjected to rapid decay(RD). This analysis indicates that RD typhoons are small-probability events, making up about 2.2% of the total offshore typhoons during this period. The RD events experience a decadal variation, mostly in the 1960 s and 1970 s(maximal in the 1970 s), rapidly decrease in the 1980 s and 1990 s and quickly increase from 2000. Also, RD typhoons show remarkable seasonal differences: they arise mainly in April and July-December, with the prime stage being in October-November. The offshore RD typhoons occur mostly in the South China Sea(SCS) and to a lesser extent in the East China Sea(ECS); however, none are observed over the Huang Sea and Bo Sea.Composite analysis and dynamic diagnosis of the RD typhoon-related large-scale circulations are performed.Physical quantities of the composite analysis consist of 500-h Pa height and temperature fields, vapor transfer, vertical wind shear(VWS), density of core convection(DCC), and high-level jet and upper-air outflow of the typhoon. The results suggest that(1) at the 500-h Pa height field, the typhoon is ahead of a westerly trough and under the effects of its passing trough;(2) at the temperature field, the typhoon is ahead of a temperature trough, with an invading cold tongue present;(3) at the vapor transfer field, water transfer into the RD typhoon is cut off; and(4) at higher levels, the related jet weakens and the outbreak of convection becomes attenuated in the typhoon core. In addition, VWS bears a relation to the RD typhoon; in particular, strong VWS favors RD occurrence.The differences in RD events between the SCS and ECS show that for the RD, the VWS of the ECS environmental winds is markedly stronger in comparison with its SCS counterpart. The cold advection invading into the typhoons is more intense in the SCS than in the ECS, and the low-level vapor transfer and high-level outflow are weaker in the SCS RD typhoons.Data analysis shows that sea surface temperature(SST), VWS, and DCC can be employed as efficient factors to predict RD occurrence. With appropriate SST, VWS, and DCC, a warning of RD occurrence can be given 36, 30-36,and 30 h, respectively, in advance. These values suggest that atmospheric SST responses lag. Owing to this time lag,the prediction of RD typhoons is possible.     

基于矩谐分析的航空重力向下延拓

提出基于矩谐分析的航空重力向下延拓方法,以重力扰动作为基本观测值,给出基于矩谐分析的向下延拓模型和算法。利用EGM2008重力位模型设计模拟数值试验,对比研究矩谐分析、直接法和基于广义岭估计的逆泊松积分法,分别采用这3种方法将飞行高度处含高斯白噪声的2.5′×2.5′重力扰动向下延拓至大地水准面,与真实值作外部检验。数值比较结果表明:矩谐分析在延拓精度、稳定性和边界效应等方面都要优于直接法和基于广义岭估计的逆泊松积分法,能取得良好的向下延拓效果。     

Mapping hourly dynamics of urban population using trajectories reconstructed from mobile phone records

Understanding the spatiotemporal dynamics of urban population is crucial for addressing a wide range of urban planning and management issues. Aggregated geospatial big data have been widely used to quantitatively estimate population distribution at fine spatial scales over a given time period. However, it is still a challenge to estimate population density at a fine temporal resolution over a large geographical space, mainly due to the temporal asynchrony of population movement and the challenges to acquiring a complete individual movement record. In this article, we propose a method to estimate hourly population density by examining the time‐series individual trajectories, which were reconstructed from call detail records using BP neural networks. We first used BP neural networks to predict the positions of mobile phone users at an hourly interval and then estimated the hourly population density using log‐linear regression at the cell tower level. The estimated population density is linearly correlated with population census data at the sub‐district level. Trajectory clustering results show five distinct diurnal dynamic patterns of population movement in the study area, revealing spatially explicit characteristics of the diurnal commuting flows, though the driving forces of the flows need further investigation.     

土层厚度对紫色土坡地生产力的影响

通过紫色土坡地土层厚度的调查与不同土层厚度的小区对比试验,研究紫色土薄层坡地的生产力特性. 结果表明,约73%的紫色土坡耕地土层厚度为20-60 cm.土层厚度是紫色土生产力的基本限制条件.土层越薄, 作物株高、生物量和产量愈低,生产力愈低;土层越厚,生物量、产量愈高,生产力愈高,土层厚度的影响在玉米季尤 为突出,20 cm、40 cm小区夏玉米产量仅为60 cm小区的50%、74%,为80 cm小区的28%、40%,100 cm小区的23%、34%.当土壤厚度超过60 cm,小麦、玉米的株高、生物量及根重差异不显著,而土壤蓄水可抵御紫色丘陵区连续20 d的夏旱,因此,可初步判定60 cm土层为紫色土生产力临界土层.60cm以上厚度的紫色土可维持基本稳定的生产力水平.     

华北克拉通中生代伸展构造研究的几个问题及其在岩石圈减薄研究中的意义

总结了华北克拉通及周边以变质核杂岩和穹隆为代表的伸展构造研究的进展和存在的问题,提出了值得进一步研究的几个重要问题及其在华北克拉通破坏和岩石圈减薄研究中的意义。以变质核杂岩和穹隆为窗口,开展推覆向伸展的转化机制、区域性伸展运动学特征、剪切应变类型、伸展构造发育的时间和过程的研究,有助于深入探讨增厚地壳向伸展减薄转化的起因和过程,确定减薄的区域运动学方式及时限,查明伸展构造变形对地壳及岩石圈减薄的贡献。这方面的研究将提升华北伸展构造研究的水平,有助于查明岩石圈减薄的地壳响应,为探讨华北克拉通破坏和减薄的时限、机制、模式及深部动力学问题提供直接的构造证据。     

瞬变电磁虚拟波场的三维曲面延拓成像

根据瞬变电磁场扩散方程与波动方程间存在的数学对应形式,将已知瞬变电磁场数据转换为虚拟波场数据,在此基础上,提出了用克希霍夫积分法将所转换的波场从地面向地下反向延拓的方法.在延拓的数值计算中,为提高计算效率,采用三维边界元技术,把边界积分分解为诸三角单元积分的积分之和, 建立了曲面延拓方程式;通过地面测点的波场值,求出地下某一点的波场值,实现了地表为曲面的向下延拓成像计算.通过对理论模型计算和实际资料处理,证明了该方法可以增强瞬变电磁法识别地下电性分界面的能力,使瞬变电磁法对地下目标体的三维精细探测成为可能.