国产磁通门磁力仪稳定性分析

国产磁通门磁力仪(GM-3磁通门磁力仪)在全国各地磁台站推广应用,两年来,该仪器在武汉地震台工作比较稳定。本文对该仪器的基线值进行了多层线性回归分析。结果表明仪器性能比较稳定。     

月球交会对接VLBI差分时延研究

中国探月3期任务中,月球交会对接技术是任务成功的重要保障.利用嫦娥3号(CE03)绕月飞行的VLBI (Very Long Baseline Interferometry)时延数据,模拟仿真绕月交会对接过程中,同波束VLBI观测模式下,差分群时延的变化情况.仿真结果显示,在远程导引段,轨道器和上升组合体轨道距离保持100 km,持续半小时,差分群时延很好地反映了两者的轨道信息,可以用于定轨定位;自主控制段,上升组合体靠近轨道器,在轨道距离从5 km减小到20 m过程中,上升组合体加速追赶轨道器时,差分群时延快速趋近于0,上升组合体减速远离轨道器时,差分群时延绝对值快速变大.最后,利用嫦娥3号奔月段同时发射两个DOR (Differential One-Ranging)信号的VLBI时延数据,计算差分相时延,初步展示了月球交会对接过程中同波束VLBI差分相时延的误差情况.     

内点最大化与冗余点控制的无人机遥感图像配准

利用小型无人机进行遥感图像配准在自然灾害损害评估、环境监测和目标检测与追踪等领域发挥着至关重要的作用,但小型无人机的图像采集过程容易受风速/风向、复杂地形、电池容量、飞行姿态、飞行高度等自然或人为因素的影响。这些问题通常会导致捕捉到的场景重叠率低与图像非刚性畸变,在特征点提取过程中产生大量冗余点,增加了图像配准的难度。本文提出一种基于特征点的小型无人机图像配准方法,该方法的核心思想是在配准过程中识别冗余点,同时最大化可用内点数量。所识别的冗余点当作控制点,用于控制网格代图像的运动。最后通过最大化内点和合理移动控制点来恢复图像变换。本文使用50对小型无人机图像进行特征匹配和图像配准的实验,其中平均配准精度可达80.38%,并且本文方法在所有的情况下都优于5种当前流行算法。     

一种基于北斗三频的改进CIR算法

北斗卫星导航系统能全星座播发3个频率的观测值,有利于载波相位模糊度的解算。本文以传统的CIR方法为基础,分析了其在短基线和长基线计算时的优点和限制。针对于电离层延迟的影响,经典的CIR难以实现长基线模糊度固定的问题,本文提出了一种附有约束条件的适用于长基线的改进CIR算法,利用北斗三频数据对算法性能进行了验证。实验表明:提出的新算法能够提高长基线宽巷模糊度的固定成功率,并且能够很大程度上缩小窄巷模糊度的搜索空间,使其估值的波动能够在4周以内。     

张家口—渤海地震带中小地震应力降分布特征

采用河北测震台网资料,分析了张家口—渤海地震带2008—2018年1220条ML≥2.0地震的应力降.结果表明,应力降可能与应力有关,并且随震级的增加而出现不同尺度的变化,该区域应力降优势分布为0.70—3.00 MPa.     

广西苍梧贺街-夏郢断裂遥感影像和小震分布

采用遥感影像解译、小震精定位等方法,结合野外地震地质调查,分析了贺街-夏郢断裂附近的遥感影像特征和小震分布特征,并据此将贺街-夏郢断裂从南到北分为南段(夏郢镇毓秀-石桥镇新塘)、中段(石桥镇新塘-步头镇白石口)、北段(步头镇白石口以北).结果显示,贺街-夏郢断裂中段卫星影像上线性特征明显,控制石桥-沙头盆地的发育,局部...     

GPS在鞍山市城区地壳形变监测中的应用

GPS作为全球卫星定位系统已经成功地应用于军事、交通、大地测量、地壳形变监测等方面。本文所要研究的是将GPS技术应用于地壳形变监测中所采取的测量方法及精度分析。     

一种手工进行航线设计的算法

航线设计是每次飞行的基础,在航空摄影测量中,它占有重要的地位和作用。航线设计的好坏将直接影响航拍成果的质量,所以在进行每次航拍飞行之前都要对测区内的航线进行设计,以保证航飞的顺利进行。     

Vulnerable groups and preliminary insights into intersecting categories of identity in Laamu Atoll,Maldives

The notion of vulnerability has acquired a significant role in discussions around reducing risk and identifying vulnerable groups, which is particularly important for targeting risk‐reducing policy and practice. Through ten semi‐structured interviews with 24 stakeholders, this study collected local perceptions on the following groups considered most vulnerable in Laamu Atoll, Maldives: youth and children, women, the elderly, people with disabilities, displaced persons and migrants, and farmers. In doing this, the significance of intersecting categories of identity for understanding vulnerability emerged and was explored; an approach that is often absent or scarcely applied in studies that identify vulnerable groups in the Maldives and elsewhere. Intersections between location, youth and gender or disability, as well as gender and marital status emerged as relevant for the Laamu Atoll context. Although this study acknowledges the incompleteness of its intersectional analysis, these findings provide important preliminary insights into the role of intersectionality in shaping vulnerability experience. To enhance scholarship on vulnerability, future studies could further explore intersectionality in Laamu Atoll and the Maldives using this study as a base and also improve its practical applicability for policy and practice.     

Spatio-temporal variability of small fishes related with environmental factors in a typical domestic tap water lake,Eastern China

The knowledge of prey small ?sh stock, distribution and abundance is necessary to guide stocking of piscivorous ?sh for the biomanipulation in domestic tap water lakes. This study describes the current status of small ?sh community in Kuilei Lake(China), and examines the spatial and seasonal variations of the community in relation to key environmental factors. Based on submerged macrophyte cover and water depth, the lake was divided into ?ve major habitats:(1) macrophyte covered shallow habitat of water depth< 2.00 m,(2) uncovered or less-covered shallow habitat(2.00 m–3.50 m),(3) uncovered medium shallow habitat(3.50 m–5.00 m),(4) uncovered medium deep habitat(5.00 m–6.50 m) and(5) uncovered deep habitat(6.50 m–8.50 m). The abundance and composition of small ?sh were monitored by benthic fykenet sampling from April 2013 to January 2014. A total of 2881 individuals belonging to 5 families and 21 species were collected. Based on their abundance(accounted for 88.96% of the total) and occurrence(more than 33.33%), Acheilognathus chankaensis, Acheilognathus macropterus, Microphysogobio microstomus,Pseudorasbora parva and Rhinogobius giurinus were recognized as dominant small ?sh species. The results of correlation analysis identi?ed that species richness( Sr), Shannon-Wiener diversity index( H′)and Margalef′s richness index( D) were signi?cantly negatively correlated with water depth, but positively correlated with biomass of submerged macrophytes.Redundancy analysis(RDA) revealed that the spatial distributions of most small ?shes were negatively associated with water depth. The details of these ?ndings are bene?cial to understanding the adaptation of the small ?shes in degraded environments, and to developing suitable biomanipulation strategies for the management of ?sh resources and water quality in the lakes along the lower reach of the Changjiang(Yangtze) River basin.