天文地球动力学中的相对论效应

天文地球动力学利用空间与地面观测手段 ,监测和研究地球整体与各圈层的物质运动以及它们间的相互作用 ,这都离不开广义相对论涉及的时间与空间。随着空间对地观测精度的提高 ,为了充分利用高精度观测提供的信息 ,在天文地球动力学的研究中必须考虑相对论效应。所涉及的相对论效应包括 :( 1 )相对论参考系的建立 ,( 2 )在恰当的参考系中对观测者和被观测对象的相对论运动方程 (平动和自转 )的描述 ,( 3 )观测者和被观测对象间的电磁信号传播 ,( 4 )依赖于坐标选择的结果与具有物理意义的可观测量间的转换 ,( 5)某些基本概念与定义在广义相对论框架下的重新确认。本文对天文地球动力学中的这些相对论效应作了简要的评述。     

On the observability of radiation forces acting on near-Earth asteroids

We consider the perturbations on near-earth asteroid orbits due to various forces stemming from solar radiation. We find that the existence of precise radar astrometric observations at multiple apparitions, spanning periods on the order of 10 years, allows the detection of such forces on bodies as large as kilometer across. Indeed, the perturbations are so substantial that certain of the forces can be essential to fit an orbit to the observations. In particular, we show that the recoil force of thermal radiation from the asteroid, known as the Yarkovsky effect, is the most important of these unmodeled perturbations. We also show that the effect of reflected light can be important if even moderate albedo variations are present, while moderate changes in oblateness appear to have a far smaller effect. An unexpected result is that the Poynting–Robertson effect, typically only considered for submillimeter dust particles, could be observable on smaller asteroids with high eccentricity, such as 1566 Icarus. Finally, we also study the possibility of improving the orbit uncertainty through well-timed optical observations which might help in better detection of these nongravitational perturbations.     

成都城市热岛效应研究

木文通过成都城市气温的水平测量及多点低层探空测量的资料,分析了在不同条件下的热岛强度、中心位置及垂直方向上的伸展高度等变化规律、在考虑到热岛强度非周期性变化时,建立了适用于成都城市的热岛强度△Tμ-γ的回归计算公式。     

粤港澳大湾区科技基础设施的空间集聚与区域发展效应

为探究科技基础设施的空间分布特征和区域发展效应,论文以粤港澳大湾区688个科技基础设施为研究对象,以56个县区为基本研究单元,采用平均最近邻距离法分析粤港澳大湾区科技基础设施的空间集聚性与空间差异格局。基于地理探测器从经济水平、居住收入、住房价格、人口学历结构4个方面分析粤港澳大湾区科技基础设施的区域发展效应。结果表明：① 粤港澳大湾区科技基础设施呈现高度的空间集聚性分布,主要集中在广州核心区、深圳南山区和香港南部地区,在县区尺度上具有显著的空间差异和空间极化现象;② 粤港澳大湾区科技基础设施分布对人口学历结构、经济水平、住房价格的空间格局具有显著的正向影响,显示出区域发展效应;③ 不同性质科技基础设施的区域发展效应有所差别,基础研究类科技基础设施对人口学历结构的影响强度最高,应用类科技基础设施对经济水平的影响最为明显。该研究可为粤港澳大湾区创新地理的学术研究提供案例补充,也为粤港澳大湾区科技基础设施的合理布局和优化配置提供决策支撑,具有学术意义和现实价值。     

Research progress on behaviors and environmental effects of mercury in the cryosphere of the Tibetan Plateau:a critical review

The behavior and fates of environmental pollutants within the cryosphere and the associated environmental impacts are of increasing concerns in the context of global warming.The Tibetan Plateau(TP),also known as the"Third Pole",represents one of the most important cryospheric regions in the world.Mercury(Hg)is recognized as a global pollutant.Here,we summarize the current knowledge of Hg concentration levels,pools and spatio-temporal distribution in cryospheric environments(e.g.,glacier,permafrost),and its transfer and potential cycle in the TP cryospheric region.Transboundary transport of anthropogenic Hg from the surrounding heavily-polluted regions,such as South and Southeast Asia,provides significant sources of atmospheric Hg depositions onto the TP cryosphere.We concluded that the melting of the cryosphere on the TP represents an increasing source of Hg and brings a risk to the TP environment.In addition,global warming acts as an important catalyst accelerating the release of legacy Hg from the melting cryosphere,adversely impacting ecosystems and biological health.Furthermore,we emphasize on the remaining gaps and proposed issues needed to be addressed in future work,including enhancing our knowledge on some key release pathways and the related environmental effects of Hg in the cryospheric region,integrated observation and consideration of Hg distribution,migration and cycle processes at a key region,and uses of Hg isotopic technical and Hg models to improve the understanding of Hg cycling in the TP cryospheric region.     

Land consolidation and eco-environmental sustainability in Loess Plateau: A study of Baota district,Shaanxi province,China

Journal of Geographical Sciences - Eco-environmental sustainability is the basis for sustainable development in ecologically fragile areas. Land consolidation plays an important role in...     

Site-specific prediction of West Nile virus mosquito abundance in Greater Toronto Area using generalized linear mixed models

Mosquito surveillance programs provide a primary means of understanding mosquito vector population dynamics for the risk assessment of human exposure to West Nile virus (WNv). The lack of spatial coverage and missing observations in mosquito surveillance data often challenge our efforts to predict this vector-borne disease and implement control measures. We developed a WNv mosquito abundance prediction model in which local meteorological and environmental data were synthesized with entomological data in a generalized linear mixed modeling framework. The discrete nature of mosquito surveillance data is accommodated by a Poisson distributional assumption, and the site-specific random effects of the generalized linear mixed model (GLMM) capture any fluctuation unexplained by a general trend. The proposed Poisson GLMMs efficiently account for the nested structure of mosquito surveillance data and incorporate the temporal correlation between observations obtained at each trap by a first-order autoregressive model. In the case study, Bayesian inference of the proposed models is illustrated using a subset of mosquito surveillance data in the Greater Toronto Area. The relevance of the proposed GLMM tailored to WNv mosquito surveillance data is highlighted by the comparison of model performance in the presence of inevitable but quantifiable uncertainties.     

问题教学法在控制测量教学中的实践探索

介绍采用问题教学法的必然性,以控制测量学中精密水准测量授课为例,给出了问题教学法的教学方案、教学效果和教学体会。