基于双谱滤波的综合脉冲星时算法研究          下载免费PDF全文

周庆勇  魏子卿  张华  刘思伟  孙鹏飞  张奋  姜坤  刘晓刚  李奎 《天文学报》2021,62(2):19-95

毫秒脉冲星的自转频率非常稳定,提供了一种独立的基于遥远自然天体并能持续数百万乃至数十亿年的时间基准,具有稳定性强、运行时间长、服务范围广等特点.为了减弱毫秒脉冲星计时观测中各种高斯噪声对脉冲星时的影响,研究了一种基于双谱滤波的综合脉冲星时构建算法,处理分析了国际脉冲星计时阵(International Pul-sar Timing Array,IPTA)最新发布的4颗毫秒脉冲星(PSR J0437-4715、J0613-0200、J1713+0747和J1909-3744)的观测数据,分析了不同时间尺度综合脉冲星时的稳定性,并与构成国际原子时(International Atomic Time,TAI)的4家授时单位原子钟稳定性进行了比较.结果表明:双谱滤波算法能够较好地抑制观测噪声,提高综合脉冲星时的稳定性.相比于经典加权算法,综合脉冲星时1 yr、10 yr稳定度从7.77×10^-14、8.56×10^-16分别提高到1.50×10^-14、3.50×10^-16,单脉冲星时稳定性的提升也类似.同时发现,综合脉冲星时稳定性在5 yr及以上时间尺度上优于原子钟稳定性,可用于改善当前原子时的长期稳定性.  相似文献   

The Natural Resource Management Planning Portal: Perspectives for NRM Planning and Reporting     

Birgita D. Hansen  Peter G. Dahlhaus  Robert G. Milne  Andrew D. MacLeod  Chris Pitfield 《社会与自然资源》2019,32(6):709-719

Natural Resource Management (NRM) is often conducted as a partnership between government and citizens. In Australia, government agencies formulate policy and fund implementation that may be delivered on-ground by community groups (such as Landcare). Since the late 1980s, over AUS$8b of Commonwealth investment has been made in NRM. However, quantitative evidence of environmental improvements is lacking. The NRM Planning Portal has been developed to (1) provide an online spatial information system for sharing Landcare and agency data; and (2) to facilitate NRM priority setting at local and regional planning scales. While the project successfully federates Landcare NRM activity data, challenges included (1) unstructured, non-standardized data, meaning that quantitative reporting against strategic objectives is not currently possible, and (2) a lack of common understanding about the value proposition for adopting the portal approach. Demonstrating the benefit of technology adoption is a key lesson for digital NRM planning.  相似文献   

基于混合聚类的岩体结构面优势分组方法     

许扬  张文  符锐  聂振邦  兰志广  陈怀玉  单博 《世界地质》2020,39(1):113-120

提出一种基于凝聚层次法和模糊C均值法的混合聚类法,用于对岩体结构面的优势组划分。该方法将结构面投放到在单位球面上,并使用欧式距离作为极点的相似性度量准则。先剔除结构面数据中的孤值产状,然后用凝聚层次法得到初步聚类结果,并将其作为FCM法的初始聚类中心,最后用FCM法划分优势组。通对人工生成产状样本的分组,验证了该法的正确性。将该方法应用于大藤峡坝址区实测的结构面数据的划分。在实测数据中寻找到两个孤值产状,成功将大藤峡D1y^1-3地层岩体结构面划分为两组,得到了符合实际的分组结果。  相似文献   

Water quality data for Fall Creek,New York,USA: 1972–1995     

David R. Bouldin  Niamh O'Leary 《水文研究》2021,35(1):e13968

The 33 086 ha mixed land use Fall Creek watershed in upstate New York is part of the Great Lakes drainage system. Results from more than 3500 water samples are available in a data set that compiles flow data and measurements of various water quality analytes collected between 1972 and 1995 in all seasons and under all flow regimes in Fall Creek and its tributaries. Data is freely accessible at https://ecommons.cornell.edu/handle/1813/8148 and includes measurements of suspended solids, pH, alkalinity, calcium, magnesium, potassium, sodium, chloride, nitrate nitrogen (NO3-N), sulphate sulphur (SO4-S), phosphorus (P) fractions molybdate reactive P (MRP) and total dissolved P (TDP), percent P in sediment, and ammonium nitrogen (NH4-N). Methods, sub-watershed areas, and coordinates for sampling sites are also included. The work represented in this data set has made important scientific contributions to understanding of hydrological and biogeochemical processes that influence loading in mixed use watersheds and that have an impact on algal productivity in receiving water bodies. In addition, the work has been foundational for important regulatory and management decisions in the region.  相似文献   

鄂尔多斯盆地南缘黄陵地区煤铀兼探钻孔数据集成与三维地质模型构建          下载免费PDF全文

张云  张天福  孙立新  程银行  张祺  王少轶  程先钰  周小希 《中国地质》2020,47(S1):231-240

鄂尔多斯盆地南缘黄陵地区铀成矿前景良好。中国地质调查局在该地区组织实施了含铀岩系三维地质调查工作，以寻找可地浸砂岩型铀矿找矿靶区为目标，采用“煤铀兼探”、“油铀兼探”的新思路，对煤田钻孔资料进行“二次开发利用”，开展勘查选区研究，完成了354口煤田钻孔（其中筛选出潜在砂岩型铀矿（化）孔49口）和21口铀矿验证钻孔（其中工业矿（化）孔16口）的数据采集建库，在此基础上建立了专题成果图集及三维地质模型。该数据库主要由含铀岩系地层厚度等值线图、砂体厚度等值线图、顶底板埋深等值线图、含砂率等值线图、放射性异常等值线图等专题成果图集和三维地质结构模型组成，为铀矿勘探开发提供了有利支撑和服务作用。  相似文献   

Fully coupled elastoplastic hydro-mechanical analysis of unsaturated porous media using a meshfree method     

Omid Ghaffaripour  Golnaz A. Esgandani  Arman Khoshghalb  Babak Shahbodaghkhan 《国际地质力学数值与分析法杂志》2019,43(11):1919-1955

This paper presents the first application of an advanced meshfree method, ie, the edge-based smoothed point interpolation method (ESPIM), in simulation of the coupled hydro-mechanical behaviour of unsaturated porous media. In the proposed technique, the problem domain is spatially discretised using a triangular background mesh, and the polynomial point interpolation method combined with a simple node selection scheme is adopted for creating nodal shape functions. Smoothing domains are formed on top of the background mesh, and a constant smoothed strain, created by applying the smoothing operation over the smoothing domains, is assigned to each smoothing domain. The deformation and flow models are developed based on the equilibrium equation of the mixture, and linear momentum and mass balance equations of the fluid phases, respectively. The effective stress approach is followed to account for the coupling between the flow and deformation models. Further coupling among the phases is captured through a hysteretic soil water retention model that evolves with changes in void ratio. An advanced elastoplastic constitutive model within the context of the bounding surface plasticity theory is employed for predicting the nonlinear behaviour of soil skeleton. Time discretisation is performed by adopting a three-point discretisation method with growing time steps to avoid temporal instabilities. A modified Newton-Raphson framework is designed for dealing with nonlinearities of the discretised system of equations. The performance of the numerical model is examined through a number of numerical examples. The state-of-the-art computational scheme developed is useful for simulation of geotechnical engineering problems involving unsaturated soils.  相似文献   

南极中山站全天信息采集系统     

王宇  辛玉新  姜鹏  杨勇  伦宝利  王传军  余晓光  常亮  范玉峰 《天文研究与技术》2021,(2):272-282

南极高原拥有独特的天文观测优势,为了对南极中山站夜天文观测条件进行实测研究,中国科学院云南天文台专门研制了一套具有耐低温、自动除雪除霜等适应南极气候特征的全自动全天信息采集系统,该系统可以提供实时的全天云量、天光背景和全天图像,并将信息推送到网页实时显示。介绍了系统的研制及为适应南极气候进行的耐低温实验,统计分析了中山站2016~2017年的全天信息数据,结果显示,中山站2016和2017年的可观测时间为772.21 h和437.38 h,可观测夜数为93 d和51 d,天光背景最大真实值为22.05 Mag/arcsec 2,年平均气温为-10.6℃,最高气温19.1℃,最低气温为-44℃,2016年平均相对湿度为55.2%。  相似文献   

基于灯光数据的京津冀城市多标度异速分析     

龙玉清  陈彦光 《地理科学进展》2019,38(1):88-100

城镇体系的时空演化是一个复杂的动力学过程,具有无尺度性,其特征可以采用异速标度指数定量描述。论文以京津冀为例,基于1992—2013年夜间灯光数据的校正结果,提取城镇夜间灯光信息,采用多标度异速分析方法,分析京津冀城镇体系的相对发展特征及其空间分异格局。研究发现：①京津冀大城市的增长空间局限日益显著。虽然大城市如京津唐的绝对发展水平高,但接近环境承载量的极限,22 a间增长快速的是大城市交接地带的小城市(如三河、迁安、廊坊等)。②相对增长速度快的城市从东北到西南呈现带状分布——政府选择发展的“雄安新区”就在这个轴带上。由此可以得出两个结论：其一,京津冀城市演化的趋势相对均衡化,空间结构异质性逐步减弱,整个城镇体系的发展趋于相对平衡状态;其二,大、小城市“两极”贯通或许是增强城镇体系功能的有效途径。京津冀的空间格局优化不能仅仅考虑主要的、规模大的中心城市,而应该基于等级结构协调整个城镇网络体系。  相似文献   

自然资源一体化政务服务系统及数据融合建设——以南京为例     

陈波  崔蓓  丁鑫 《测绘通报》2020,(12):75-78

自然资源部制定的信息化建设总体方案中，要求构建“互联网+自然资源政务服务”应用体系，实现“服务事项标准统一、整体联动、业务协同，自然资源政务服务和共享开放能力全面提高”。一体化政务服务系统作为政务服务应用体系的重点建设内容，也是落实自然资源管理“两统一”职责的重要支撑，如何整合各类数据资源、发挥系统作用，成为亟待研究的问题。本文在分析自然资源业务管理需求后，提出了一体化政务服务系统及数据融合的建设思路。  相似文献   

基于圆柱多段拟合的隧道中轴线提取方法研究     

荆海峰  李广云  王力  杨文锋 《大地测量与地球动力学》2018,38(2):211-215

提出基于圆柱多段拟合的隧道中轴线提取方法。首先对隧道点云数据进行预处理，并将点云按隧道走向分成不同区段；然后对各区段依据轴线与表面点云法线垂直关系，提取精度较低的中轴线；最后对各区段利用圆柱多段拟合，提取精度较高的中轴线。实验表明，隧道中轴线的提取在一定的采样区间具有较高的稳定性，对直线和弯曲的圆形隧道有良好的适用性，算法可靠，精度较高。  相似文献