GM(1,1)模型初始条件优化及其在GNSS钟差预报中的应用     

谭小容  许江宁  何泓洋  陈丁  梁益丰  吴苗 《大地测量与地球动力学》2022,42(9):919-924

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。  相似文献   

A two-track CDM: improved incentives for sustainable development and offset production     

Asbjørn Torvanger  Manish Kumar Shrivastava  Nimisha Pandey  Silje H. Tørnblad 《Climate Policy》2013,13(4):471-489

The Clean Development Mechanism (CDM) has been criticized in the literature for encouraging a focus on offset production (OP) at the expense of achieving or encouraging sustainable development (SD). It is argued that one explanation for this is that there is no commonly agreed definition of SD and, moreover, the priority of CDM project developers is often to produce cost-effective OP. Many of the proposals to address these drawbacks are not politically feasible. It is argued that the CDM should be split into a two-track mechanism, with one track for offset production and the other for offset production with an emphasis on sustainable development benefits. This would enable the political deadlock to be broken, allow the inclusion of SD benefits in the price mechanism itself, and allow both SD and OP objectives to be simultaneously achieved.

Policy relevance

The CDM has been criticized for failing to achieve its sustainable development objective, for verification problems regarding the mitigation effects of projects’ emissions, for being complex and bureaucratic, and for the very limited participation by the least developed countries. Given the adoption of a second period of the Kyoto Protocol and the discussion of new market mechanisms in the context of negotiating a new global climate agreement to be adopted in 2015, it is time to explore the ways in which the CDM might be reformed. A two-track version of the CDM is proposed, with one track focused on credit (offset) production and the other track focused on sustainable development. This system could improve the incentive for achieving sustainable development, reduce the uncertainty regarding whether real emissions reductions have been achieved, and be attractive to both developing and industrialized countries.  相似文献   

基于EM算法优化相关向量机的BDS-3超快速钟差预报     

胡燕  王德盛  杨玉锋 《大地测量与地球动力学》2021,41(12):1230-1234

提出一种基于EM算法优化相关向量机(RVM)的BDS-3超快速钟差预报算法。首先,利用组合MAD法预处理钟差数据,并进行一次差分计算;然后,利用钟差一次差分数据对RVM模型进行训练,通过EM算法迭代求取模型的超参数;最后,利用优化后的RVM模型进行数据预测,将钟差一次差分预测值还原,得到钟差预报值。采用iGMAS中心提供的实测BDS-3超快速钟差数据进行预报实验,并将本文模型与QP模型、SA模型及iGMAS超快速钟差预报产品(ISU-P)结果进行对比分析。结果表明,对于6 h、12 h和24 h预报,本文模型预报BDS-3卫星钟差数据的平均精度均优于0.61 ns;与ISU-P、QP模型和SA模型相比,本文模型预报24 h时精度分别提升64.1%、50.0%和49.2%。  相似文献   

不同集合的球面矢量Voronoi图生成算法     

童晓冲  贲进  张永生 《测绘学报》2006,35(1):83-89

分析现有球面VORONOI图生成算法的不足,介绍球面不同集合V图的定义,在此基础上提出球面偏置曲线的概念并总结了它的性质,具体分析不同集合在球面上的偏置结果及处理方法,提出基于球面偏置的多集合V图生成算法,通过实验检验算法的正确性与效率,最后得出结论和进一步的研究方向。  相似文献   

一种改进的平方根滤波在卫星钟差实时解算中的应用     

代桃高  李建文  赵静  郭亮亮 《大地测量与地球动力学》2017,37(9):946-950

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%。  相似文献