基于卡尔曼滤波重构GRACE-FO姿态数据

重力卫星姿态数据通过非保守力转换和KBR(K-Band Ranging)天线相位中心改正影响时变重力场模型精度,因此如何获取高精度的姿态数据是原始载荷数据处理的重要研究内容.GRACE-FO(GRACE Follow-On)每颗卫星均安装了三颗星敏感器和一个惯性测量单元(IMU,Inertial Measurement Unit)测量卫星姿态数据.星敏感器对姿态的低频部分敏感,惯性测量单元对姿态的高频部分敏感,融合这两类数据可以获得高精度的姿态数据.为此,本文首先基于扩展Kalman滤波,以四元数和陀螺仪漂移参数为状态变量推导了一种新的姿态Kalman滤波融合算法.然后基于GRACE-FO Level-1A实测数据验证本文提出的姿态Kalman滤波算法是否可行,并分析对反演时变重力场模型精度的影响.对于GRACE-FO星敏感器数据处理而言,融合多个星敏感器数据可以抑制高频部分噪声的精度,特别对于三个星敏感器融合的精度要略高于两个星敏感器融合.对于星敏感器与IMU融合而言,本文解算的姿态数据充分融合了IMU测量的角速度信息,相较于官方机构精度至少提高了3倍,并在0.01～0.1 Hz上噪...     

基于GRACE/GRACE-FO和Swarm卫星研究2002-2020年南极和格陵兰岛冰盖质量时空变化

两极冰盖消融及其质量变化作为全球气候变化的重要指标之一,一直是联合国政府间专门气候委员会IPCC(Intergovernmental Panel on Climate Change)报告的重点关注内容.GRACE(Gravity Recovery and Climate Experiment,2002年4月-2017年...     

1986-2018年广州市建设用地扩张及其影响因素研究

针对快速城市化引起的一系列城市问题,利用扩张速率、等扇分析法、景观扩张指数等方法,分析了广州市19862018年建设用地的时空特征,通过多元回归和地理探测器探索建设用地时序演变和空间分异过程的影响因素及其交互作用,可为城市规划管理中优化城市发展模式和城市可持续发展提供技术支撑.研究结果表明:①1990-2000年是广州市建设用地迅速扩张期,此后有所回落并稳定发展;②建设用地扩张方向呈分阶段分区域进行的特征,主要向东南、西北和东北3个方向扩张;③建设用地扩张呈现蔓延型和填充型为主的扩张模式;④建设用地扩张时序演变过程的主要影响因素包括GDP、人口和地方财政收入;空间演变过程的主要影响因素包括与公路、铁路的距离、DEM,且因子间均为双因子增强关系.     

温度对琼枝麒麟菜生长及色素含量的影响

为进一步提高海南琼枝麒麟菜(Betaphycus gelatinum)产量,本研究主要探讨了温度对琼枝麒麟菜生长及色素含量的影响。结果表明,温度对琼枝麒麟菜生长的影响比较明显,27℃时琼枝麒麟菜生长最快,随着温度的升高或者降低,琼枝麒麟菜生长率均降低,长期低于18℃或者高于36℃会造成琼枝麒麟菜的死亡。在27℃时琼枝麒麟菜含水量最低,干物质积累最快,即光合作用率最大。不同温度下琼枝麒麟菜色素含量与生长率变化趋势基本一致,其藻胆蛋白含量远远大于叶绿素含量。     

Error control of iterative linear solvers for integrated groundwater models

An open problem that arises when using modern iterative linear solvers, such as the preconditioned conjugate gradient method or Generalized Minimum RESidual (GMRES) method, is how to choose the residual tolerance in the linear solver to be consistent with the tolerance on the solution error. This problem is especially acute for integrated groundwater models, which are implicitly coupled to another model, such as surface water models, and resolve both multiple scales of flow and temporal interaction terms, giving rise to linear systems with variable scaling. This article uses the theory of "forward error bound estimation" to explain the correspondence between the residual error in the preconditioned linear system and the solution error. Using examples of linear systems from models developed by the US Geological Survey and the California State Department of Water Resources, we observe that this error bound guides the choice of a practical measure for controlling the error in linear systems. We implemented a preconditioned GMRES algorithm and benchmarked it against the Successive Over-Relaxation (SOR) method, the most widely known iterative solver for nonsymmetric coefficient matrices. With forward error control, GMRES can easily replace the SOR method in legacy groundwater modeling packages, resulting in the overall simulation speedups as large as 7.74×. This research is expected to broadly impact groundwater modelers through the demonstration of a practical and general approach for setting the residual tolerance in line with the solution error tolerance and presentation of GMRES performance benchmarking results.     

ENHANCING THE DECONVOLUTION OF NOISY CHROMATOGRAPHIC DATA BY JANSSON''S METHOD

In previous papers Jansson's method was found to be successful at deconvolving severely overlapped gaschromatographic peaks.In the most recent paper the method was evaluated with respect to quantitativeaceuracy,peak area and retention time repeatability.The problems associated with deconvolving noisydata and some alternatives which can improve the ability of Jansson's method to deconvolve noisy dataare discussed.These alternatives include presmoothing the data with a nine-point,third-order polynomialfilter and data reblurring.This paper will test these methods on peaks with various degrees of resolutionand signal-to-noise ratios.     

卫星姿态误差对GOCE重力梯度精度的影响评估

在地球重力场和海洋环流探测卫星GOCE(Gravity field and Ocean Circulation Explorer)的观测数据中,其主要的观测量重力梯度数据不仅与搭载的6个加速度计的测量值有关,而且还与卫星自身的自转角速度存在着二次函数关系.由于加速度计测量频段的限制,这样就导致了卫星姿态的低频误差混入到...     

Pattern of migration to an industrial area: a case study in Lhokseumawe,Aceh, Sumatera,Indonesia

The author attempts to identify factors influencing decisions to migrate to an industrial area of Sumatra, Indonesia. Reasons for migration, characteristics of migrants, and social assimilation at the place of destination are analyzed using data obtained in a 1978 study of 150 migrants to two subdistricts in Sumatra