基于混沌加权一阶局域法的IGS超快星历钟差预报

为提高IGS超快星历钟差预报产品的精度,针对卫星钟差数据具有确定项和随机项成分的特点,在采用多项式模型对钟差确定项建模的基础上,提出采用混沌加权一阶局域法对钟差随机项进行建模预报。仿真结果表明,采用混沌加权一阶局域法的预报精度优于超快星历钟差预报产品。     

实时时钟芯片x1226使用设计与功能实现

本文介绍了一种高性能时钟芯片x1226的功能,技术参数,阐述了该时钟芯片的工作原理、主要功能;并介绍了此芯片的应用电路、软件流程和代码。     

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一种改进的平方根滤波在卫星钟差实时解算中的应用

目前普遍采用卡尔曼滤波方法来实现非差法卫星钟差的实时解算。平方根滤波可以增强数值计算的稳定性,避免滤波发散,但矩阵的求逆会耗费较长的计算时间;序贯算法可以避免对矩阵直接求逆,能提升计算效率。综合两种算法的优点,提出一种基于序贯算法的平方根滤波器,并应用于卫星钟差的实时解算,得到的卫星钟差精度优于0.2 ns,且计算时长缩短40%。     

我国发射射电卫星的作用及关键技术研究

论述了我国发射射电卫星对于天文学和射电天文方法的发展、我国月球及深空探测计划、大地测量和天文地球动力学的研究和发展等方面的意义;根据VLBI卫星的技术和应用特点,分析了射电望远镜及相关设施的技术要求和指标,比较全面地分析和总结了VLBI卫星及相关设施的关键技术和方法。     

灰色系统模型在卫星钟差预报中的应用

分析了二次多项式模型在卫星钟差长期预报中的缺陷，依据灰色系统理论和卫星钟差的变化规律，以较少的观测样本建立了预报卫星钟差的灰色预测模型，并将其与二次多项式预测模型进行分析比较。计算结果表明，两者的短期预报精度基本相当，而灰色系统模型的长期预报精度要明显地优于二次多项式模型，更适合于实际应用。     

GM(1,1)模型初始条件优化及其在GNSS钟差预报中的应用

针对现有改进GM(1,1)模型在导航卫星钟差预报中性能无明显提升的问题,提出通过优化初始条件来提高钟差预报精度的方法。首先构建初始条件未知的GM(1,1)预报模型,然后采用原始序列的最新分量求解初始条件,最后利用该模型对IGS提供的精密钟差数据进行预报实验。结果表明,将初始条件优化后的GM(1,1)模型用于钟差预报切实可行,且预报精度比传统GM(1,1)模型有较大提高。     

Molecular insights into the circadian clock in marine diatoms

The circadian clock is a fundamental endogenous mechanism of adaptation that coordinates the physiology and behavior of most organisms with diel variations in the external environment to maintain temporal homeostasis. Diatoms are the major primary producers in the ocean. However, little is known about the circadian clock in marine diatoms compared with other organisms. Here, we investigated circadian clock genes, their expression patterns, and responses to environmental stimuli such as light, nitrogen and phosphorus in two marine diatoms, Skeletonema costatum and Phaeodactylum tricornutum, using a combination of qRT-PCR and bioinformatic analysis. We identified 17 and 18 circadian clock genes in P. tricornutum and S. costatum, respectively. Despite significant evolutionary differences, these genes were similar to those of the higher plant Arabidopsis. We also established a molecular model for the marine diatom circadian clock comprising an input pathway, core oscillator, output pathway, and valve effector. Notably, the expression patterns of core clock genes (circadian clock associated 1 (CCA1), late elongated hypocotyl (LHY) and timing of cab 1 (TOC1)) in both species differed from those of terrestrial plants. Furthermore, the expression of these genes was influenced by variations in ambient light, nitrogen and phosphorus availability. Although marine diatoms and higher plants share common circadian clock components, their clock genes have diverged throughout evolution, likely as a result of adapting to contrasting environments.     

BDS-3钟差改正数实时预报方法

在远海精密动态定位研究中,BDS-3卫星钟差改正信息的质量对定位结果具有直接影响。在传输实时改正信息时,为了同时兼顾效率及成本,岸基用户端通常会将实时信息压缩后传输至远海用户端。针对数据压缩问题,本文提出了利用钟差改正数预报模型进行数据压缩,同时分析钟差改正数的结构特征,并将其分解为总体趋势序列与随机波动序列,分别构建预报模型。结果表明,DSC模型在20 min的预报区间内较DLP模型提升了6%,较DLP模型提升了9%。     

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