卫星钟差预报的小波神经网络算法研究   总被引：3，自引：3，他引：0  

王宇谱  吕志平  陈正生  崔阳 《测绘学报》2013,42(3)

卫星导航系统中星载原子钟的钟差预报在优化导航电文中的钟差参数、满足实时动态精密单点定位的需求和提供卫星自主导航所需的先验信息方面具有重要的作用.根据星载原子钟钟差的特点,提出一种基于一次差方法的小波神经网络钟差预报算法:首先对钟差相邻历元间作一次差后的差值进行建模,根据时间序列预报一次差的值,然后再将预报的一次差还原,得到钟差预报值.该方法使得预报钟差的小波神经网络不但模型结构简单,而且预报精度高.最后,通过算例将本文所建模型与常用的二次多项式模型和灰色模型进行对比,结果表明:一次差方法可以使给定结构的小波神经网络的钟差预报精度得到显著提高,而且所建模型的预报效果优于两种常规模型.  相似文献   

鄂尔多斯南部地区早古生代主动大陆边缘演化特征   总被引：3，自引：0，他引：3  

钱锋  艾永峰 《地球科学与环境学报》2002,24(1):18-21

中—晚奥陶世期间 ,鄂尔多斯南部地区为古秦岭洋北侧具沟、弧、盆体系的主动大陆边缘。在此背景下 ,有序地发育了可分别用镶边碳酸盐陆棚模式及重力流模式概括的弧后盆地与残留海盆地沉积类型 ;构造轮廓为向洋呈阶状断落和块状错移结构特征的基本格局。晚奥陶世末 ,华北板块与扬子板块的陆 -陆碰撞作用结束了主动大陆边缘构造阶段  相似文献   

GPS���ջ��������о�   总被引：2，自引：2，他引：0  

杨剑  王泽民  王贵文  柳景斌  孟泱 《大地测量与地球动力学》2007,27(3):123-127

??????GPS???????????????????GPS???????????????????????????????????GPS?????λ??????α??????????????,?????????????λ??????????????????????????????????????????????????GPS?????????????λ???????????????GPS?????????????в??????????κθ????????????????????????????????????????????λ??????????????С?  相似文献   

上海天文台原子频标研究50年   总被引：1，自引：0，他引：1  

翟造成 《中国科学院上海天文台年刊》2007,(1):142-150

中国科学院上海天文台1958年开始原子频标的研究，先后研制成功氨分子钟和各种类型的氢原子钟，并实现主动型氢钟的商品化生产。迄今为止，已经研制生产主动型氢钟60多台，广泛用于科学技术各领域。该文简单介绍了上海天文台原子频标的发展、性能指标的改进和氢钟的应用概况，并对今后的发展前景进行了展望。  相似文献   

Bookkeeping rather than climate policy making: national mitigation strategies in Western Europe     

Juan Casado-Asensio 《Climate Policy》2016,16(1):88-108

Climate change mitigation is a wicked problem that cuts horizontally across sectors and vertically across levels of government. To address it effectively, governments around the world, in particular in the EU, have developed several generations of multi-sectoral national mitigation strategies (NMS) since the early 1990s. Although NMS became the main effort to systematically coordinate mitigation policies, few works have studied them comparatively so far. The present article fills this gap by analysing how the EU-15 group of countries operationalized climate protection through NMS. First, we introduce the three roles policy strategies usually aim to fulfil: besides being policy documents they also represent governance processes (supposed to coordinate sectoral implementation), and capacity-building efforts. Empirically, we then explore the rationale, origins and prevalence of NMS. Subsequently, we characterize them as policy documents (with regards to their contents and structures) and as governance processes that address capacity building only implicitly. Based on existing assessments we finally review some performance indications of NMS. We find that in particular second- and third-generation NMS aimed to take their governance function seriously but resembled ‘lacklustre bookkeeping' of emissions, targets and mitigation options. Instead of approximating NMS towards their obviously overcharging governance function, we suggest to recalibrate them towards their communication and capacity-building function in a way that goes beyond bookkeeping.

Policy relevance

The present article shows that NMS fail to effectively govern climate change mitigation across a broad range of sectoral policy domains. Since most European countries have adopted not one but up to three generations of NMS since the 1990s, this finding is highly relevant for them – and for all others aiming to adopt similarly broad strategies. Instead of piling one strategy on top of another irrespective of their implementation, and instead of abolishing mitigation strategies altogether, we recommend recalibrating them towards what they can realistically accomplish: effective communication and capacity building so that NMS can advance from lacklustre bookkeeping to actively promoting a government-wide climate change mitigation vision. The article can help governments to realise that renewing integrated strategies such as NMS without overhauling them comes close to flogging a dead horse.  相似文献   

Energy research within the UNFCCC: a proposal to guard against ongoing climate-deadlock†     

Barry W. Brook  Kingsley Edney  Rafaela Hillerbrand  Rasmus Karlsson 《Climate Policy》2016,16(6):803-813

We propose that an international ‘Low-Emissions Technology Commitment’ should be incorporated into the United Nations Framework Convention on Climate Change (UNFCCC) negotiation process in order to promote innovation that will enable deep decarbonization. The goal is to accelerate research, development, and demonstration of safe, scalable, and affordable low-emissions energy technologies. Such a commitment should be based on three elements. First, it should operate within existing UNFCCC negotiations so as to encourage developed states to offer directed funding for energy research as part of their national contributions. Second, pledges should be binding, verifiable, and coordinated within an international energy-research plan. Third, expert scientific networks and participating governments should collaborate to design a coordinated global research and technology-demonstration strategy and oversee national research efforts. To this end an Intergovernmental Panel on Low-Emissions Technology Research might be established. This proposal offers some insurance against the risk that the political impasse in international negotiations cannot be overcome. The higher costs associated with low-emissions alternatives to fossil fuels currently creates significant economic and political resistance to their widespread adoption. To breach this impasse, a mechanism supporting accelerated energy research is needed that seeks to reduce future abatement costs, share experience and ‘learning-by-doing’ in first-of-a-kind demonstrations, and thus facilitate future widespread deployments. These actions will also assist in addressing inequalities in energy access.

Policy relevance

Over the past decade, global fossil-fuel use and associated carbon emissions have risen steadily, despite the majority of nations agreeing, in principle, to work to limit global warming to less than 2?°C above pre-industrial conditions (IPCC, 2014 IPCC. (2014). Climate change 2014: Mitigation of climate change. In O. Edenhofer, R. Pichs-Madruga, Y. Sokona, E. Farahani, S. Kadner, K. Seyboth, … J. C. Minx (Eds.), Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (pp. 1–1415). Cambridge and New York, NY: Cambridge University Press. Retrieved from http://mitigation2014.org/report [Google Scholar]). Accelerated research, development, and demonstration of low-emissions technologies will be required for successful and economically efficient decarbonization of the global economy, but how can the current deadlock be broken? The UNFCCC does not contain adequate mechanisms to promote increased investment in research, so climate-governance institutions are not capturing the gains that could be achieved through a globally coordinated approach. Here, we outline reform proposals that would enhance both the economic effectiveness of global abatement efforts and the political feasibility of accelerated innovation.  相似文献   

顾及钟差变化率的GPS卫星钟差预报法     

王甫红  夏博洋  龚学文 《测绘学报》2016,45(12):1387-1395

提出了一种基于钟差变化率拟合建模的卫星钟差预报方法。以附加周期项的线性或二次多项式作为基础模型对钟差变化率序列进行拟合,最优估计卫星钟差的趋势项系数,然后直接使用精密定轨得到的相应时刻的卫星钟差计算预报初始时刻的基准项系数,来建立卫星钟差的预报模型。以IGS发布的快速星历(IGR)的卫星钟差为试验数据,对GPS星座中各种型号的所有卫星钟差进行预报。结果表明:本文方法3、6、12与24h的预报精度分别可达0.43、0.58、0.90与1.47ns,相比于传统的基于钟差拟合的预报方法,精度分别提高69.3%、61.8%、50.5%与37.2%;与IGS发布的超快速星历(IGU)的预报钟差相比,钟差精度分别提高15.7%、23.7%、27.4%与34.4%。  相似文献   

iGMAS GNSS钟差产品综合与评估     

陈康慷  徐天河  杨玉国  蔡洪亮  陈国 《测绘学报》2016,45(Z2):46-53

高精度卫星导航定位离不开精密钟差改正信息,钟差产品综合与评估是产品综合与服务中心(ISC)的重要任务之一。本文首先介绍了ISC钟差产品综合策略和抗差估计方法,重点阐述了非线性系统误差处理、钟差参考基准统一及残余线性偏差补偿;然后,对比逐历元对准方法和"三步"校准法两种不同综合产品的精度和稳定性,并对iGMAS近两年的钟差产品进行了评估和详细分析;最后,为验证综合产品的精度和一致性,采用5个测站的静态数据进行了PPP测试。计算结果表明:综合钟差的RMS最优且稳定,可作为评估分析中心产品精度的参考解。此外,综合产品北斗单系统静态PPP的结果优于多数分析中心,位置精度在4cm以内。  相似文献   

估计北斗卫星钟差频间偏差的一种方法     

李浩军  李博峰  王解先  徐天河 《测绘学报》2016,45(2):140-146

针对北斗频间卫星钟差偏差现有估计方法的不足,提出一种估计方法。该方法不仅顾及频间卫星钟差偏差的变化部分也顾及了其常数部分。采用10个观测站数据,验证了本文提出的算法,分析了北斗频间卫星钟差偏差的特性。在短期内,北斗频间卫星钟差偏差常数部分具有稳定性。对采用新算法计算得到的北斗频间卫星钟差偏差进行了模型化,结果表明,每颗卫星对应的频间钟差偏差可以利用10个参数予以高精度表示,对应精度可以达到厘米级。当采用第1天的模型参数进行第2天频间卫星钟差偏差值计算时,可实现厘米级结果。基于北斗频间卫星钟差偏差的稳定性与可模型化性,提出了高精度北斗卫星钟差服务策略,为我国高精度北斗卫星钟差服务提供参考。  相似文献   

SSA+FBPF方法及其在北斗卫星钟差周期项提取中的应用     

肖胜红  王国成  涂弋 《测绘学报》2016,45(Z2):172-178

针对奇异谱分析(singular spectrum analysis,SSA)方法在重建准周期项时容易存在频率混叠的现象,傅里叶带通滤波器(fourier band pass filtering,FBPF)提取准周期项时,边界值极易受到残留的趋势项的影响而导致其不够精确,本文提出了一种SSA与FBPF相结合的方法(SSA+FBPF),即先利用SSA方法对信号进行分层选组重建,再对重建信号进行傅里叶带通滤波。仿真试验结果表明在信噪比(SNR)为0.017的情况下,SSA+FBPF方法重建周期信号精度比SSA方法提高了35%,比FBPF方法提高了26%,这说明该方法不仅抑制趋势项对边界值的影响,而且具有良好抗噪声干扰的能力。将SSA+FBPF方法用于重建北斗卫星PC06和PC07的24h周期项,发现北斗卫星钟PC06和PC07周期项幅值均存在明显变化。  相似文献