CCD联合平差方法及其初步实例检验

在常规照相天体测量工作中 ,对暗天体的定位是采用逐级定标星过渡的方法实现的。由于星表系统差和局部差的存在 ,最终定位结果可能包含难以把握的误差积累。在CCD小视场观测情况下时常难以找到足够数量的定标星。鉴于此 ,推导了CCD观测联合平差方法的严格矢量表达式 ,以期通过共同星的过渡 ,实现大天区统一平差。原理上此方法可实现相对于河外天体的定位 ,以削弱星表系统差和局部差对定位结果的影响。讨论了CCD联合平差方法实现中的问题 ,包括底片常数模型选择、切点位置改正、共同星的较差改正和法方程解算方法等 ,并分析了具体的处理措施。用实例初步检验了CCD联合平差方法的效果 ,表明通过对多张CCD观测的联合平差 ,可以削弱单张CCD观测参考星数目过少、单张CCD观测参考星分布不均、个别参考星存在位置偏差和局部区域参考星存在系统性位置偏差等不利因素对归算结果的影响 ,进而达到扩大视场和提高归算精度的目的     

The 550-au Mission: a critical discussion

We have studied the science rationale, goals and requirements for a mission aimed at using the gravitational lensing from the Sun as a way of achieving high angular resolution and high signal amplification. We find that such a mission concept is compromised by several practical problems. Most severe are the effects due to the plasma in the solar atmosphere which cause refraction and scattering of the propagating rays. These effects either limit the frequencies that can be observed to those above ∼1 THz, or they move the optical point outwards beyond the vacuum value of ≥550 au. (Thus for observing frequency of 300 GHz the optical point is moved outwards to ∼ 680 au.) Density fluctuations in the inner solar atmosphere will further cause random pathlength differences for different rays. The corrections for the radiation from the Sun itself will also be a major challenge at any wavelength used, but could be mitigated with coronographic techniques. Given reasonable constraints on the spacecraft (particularly in terms of size and propulsion), source selection as well as severe navigational constraints further add to the difficulties for a potential mission. Nevertheless, unbiased surveys of small-scale structure on the sky at short wavelengths might be the most promising application of such a mission.     

Simulations of 3D DC borehole resistivity measurements with a goal-oriented <Emphasis Type="Italic">hp</Emphasis> finite-element method. Part II: through-casing resistivity instruments

We simulate direct current (DC) borehole resistivity measurements acquired in steel-cased deviated wells for the assessment of rock formation properties. The assumed data acquisition configuration considers one current (emitter) and three voltage (collector) electrodes that are utilized to measure the second difference of the electric potential along the well trajectory. We assume a homogeneous, 1.27-cm-thick steel casing with resistivity equal to 10^− 5 Ω· m. Simulations are performed with two different numerical methodologies. The first one is based on transferring two-dimensional (2D) axisymmetric optimal grids to a three-dimensional (3D) simulation software. The second one automatically produces optimal 3D grids yielded by a 3D self-adaptive goal-oriented algorithm. Both methodologies utilize high-order finite elements (FE) that are specially well-suited for problems with high-contrast coefficients and rapid spatial variations of the electric field, as it occurs in simulations that involve steel-cased wells. The method based on transferring 2D-optimal grids is efficient in terms of CPU time (few seconds per logging position). Unfortunately, it may produce inaccurate 3D simulations in deviated wells, even though the error remains below 1% for the axisymmetric (vertical) well. The method based on optimal 3D grids, although less efficient in terms of CPU time (few hours per logging position), produces more accurate results that are validated by a built-in a posteriori error estimator. This paper provides the first existing simulations of through-casing resistivity measurements in deviated wells. Simulated resistivity measurements indicate that, for a 30° deviated well, measurements in conductive layers 0.01 Ω· m) are similar to those obtained in vertical wells. However, in resistive layers (10,000 Ω· m), we observe 100% larger readings in the 30° deviated well. This difference becomes 3,000% for the case of a 60° deviated well. For this highly-deviated well, readings corresponding to the conductive formation layer are about 30% smaller in magnitude than those in a vertical well. Shoulder effects significantly vary in deviated wells.     

基于遥感和GIS的选址策略研究与实现

以某地新建化工厂选址为例,详细介绍了基于遥感和GIS的工程项目选址建模方法。该方法通过遥感获得地物的空间属性和类别特征,通过GIS的缓冲区分析、再分类、栅格叠加、归组、面积计算等空间分析与统计方法实现满足多个条件的目标区块的提取。作为选址模型的具体实现,以遥感和GIS分析软件为依托,规划出了某地适宜兴建化工厂的区块,实施了化工厂选址的遥感和GIS辅助决策。     

RESEARCH OF THE INHOMOGENEITY TEST OF CLIMATOLOGICAL DATA SERIES IN CHINA*

Some achievements on the inhomogeneity test of climatological data series and some correlative conclusions were described,from which we concluded that it was very necessary to test the homogeneity of the Chinese climatological data series.Many techniques on this field developed by foreign experts are suitable for Chinese climatological series,and the main factors for the inhomogeneity of the Chinese climatological data are the relocation of stations and the change of instruments.     

International and national climate policies for aviation: a review

Aviation constitutes about 2.5% of all energy-related CO₂ emissions and in addition there are non-CO₂ effects. In 2016, the ICAO decided to implement a Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) and in 2017 the EU decided on faster emission reductions in its Emissions Trading System (EU ETS), which since 2012 includes the aviation sector. The effects of these policies on the expected development of air travel emissions from 2017 to 2030 have been analyzed. For the sample country Sweden, the analysis shows that when emissions reductions in other sectors are attributed to the aviation sector as a result of the EU ETS and CORSIA, carbon emissions are expected to reduce by ?0.8% per year (however if non-CO₂ emissions are included in the analysis, then emissions will increase). This is much less than what is needed to achieve the 2°C target. Our analysis of potential national aviation policy instruments shows that there are legally feasible options that could mitigate emissions in addition to the EU ETS and CORSIA. Distance-based air passenger taxes are common among EU Member States and through increased ticket prices these taxes can reduce demand for air travel and thus reduce emissions. Tax on jet fuel is an option for domestic aviation and for international aviation if bilateral agreements are concluded. A quota obligation for biofuels is a third option.

Key policy insights

• Existing international climate policies for aviation will not deliver any major emission reductions.

• Policymakers who want to significantly push the aviation sector to contribute to meeting the 2°C target need to work towards putting in place tougher international policy instruments in the long term, and simultaneously implement temporary national policy instruments in the near-term.

• Distance-based air passenger taxes, carbon taxes on jet fuel and quota obligations for biofuels are available national policy options; if they are gradually increased, and harmonized with other countries, they can help to significantly reduce emissions.

     

地电阻率供电回路故障检测板的研制与使用

地电阻率仪器在工作中容易出现无电流、电流不稳等故障现象,不易排查维修.通过对仪器工作原理和供电回路过程进行研究,发现供电回路中间仪器的内部或外部各接头接触不良是造成上述现象的主要因素.根据存在的问题,洛阳地震台研制出供电回路故障检测板.该检测板可利用其继电器上LED灯的工作状态和动作时序,快速查找、排除相关供电回路故障...     

1983—2017年宁夏盐池县生态治理政策的类型与变化——基于政策工具视角

政策工具是政府实施政策的手段。结合盐池县1983-2017年出台的生态治理政策,运用内容分析法,从政策工具视角,对盐池县生态治理政策的类型与变化进行了分析,并深入探讨其原因。结果表明:强制型和混合型政策工具占主导地位,其中,规制、直接提供、信息与劝诫、补贴与奖励4种工具使用频率最高,自愿型工具的使用还很缺乏。政策工具的运用受到中央政策的显著影响。以后应当开发更多可利用的政策工具,并对不同政策工具进行优化组合。通过本研究可深入了解生态脆弱区地方政府生态政策的政策工具使用情况,为生态脆弱区生态保护的政策工具选择与优化组合提供参考。     

海底观测网发展现状及趋势研究

文中详细研究了当前世界上最典型的海底观测网的建设发展规模、形式、设备类型以及我国海底观测网的发展现状,并对国内外海底观测网的发展趋势进行总结。对日本、加拿大、美国及欧洲的海底观测网进行了设备级研究,对我国台湾地区、东海、南海的海底观测网现状进行了研究,并讨论了国外先进观测网对我国的海底观测网建设的借鉴意义。文中总结出海底观测网发展的整体趋势为:单节点网络加速验证新型设备及传感器的水下能力;区域尺度网络用于加速多学科发展并提升灾害预警能力;而浮标平台网络作为补充,铺设在远海区域以降低阶段建设成本。