The riddles of our galaxy

Paradoxically, it is more difficult to determine the structure of our own Galaxy than that of more remote ones. The difficulty comes from our position inside the system. In addition to this geometrical obstacle there is another: interstellar dust absorbs a large part of the visible light which comes to us from the stars and the atmosphere itself attenuates other wavelengths. Modern developments in spatial and radio astronomy have enabled our Galaxy to be explored extensively. But at the same time, new riddles are being set: our Galaxy is not as well known as might seem at first sight.     

China Catches up in X-ray Astronomy

Five decades ago, the discovery of the X-ray sky opened a new window on the dynamic aspect of our universe, and has since greatly enhanced our understanding of mysterious objects like neutron stars and black holes. China launched its first X-ray telescope in June2017 to map X-ray sources in the Milky Way Galaxy. With a second mission now under development, which will look deeper at extragalactic transients, and a third one waiting for selection, Chinese scientists are striving for a great leap forward from a late comer to world leader in X-ray astronomy.     

Gamma ray astronomy and the COS-B satellite

Gamma photon by gamma photon, throughout almost seven years of perfect operation the European satellite COS-B has produced what amounts to a high-energy chart of the sky: this gives a totally new view of the Milky Way, our Galaxy. COS-B discovered new stars, extraordinarily intense sources of gamma radiation, most of which are invisible at other wavelengths. Are they young pulsars, the remains of supernovae, or evidence of black holes?     

Binary Popldation Synthcsis Study

Binary population synthesis （BPS）, an approach to evolving millions of stars （including binaries） simultaneously, plays a crucial role in our understanding of stellar physics, the structure and evolution of galaxies, and cosmology. We proposed and developed a BPS approach, and used it to investigate the formation of many peculiar stars such as hot subdwarf stars, progenitors of type la supernovae, barium stars, CH stars, planetary nebulae, double white dwarfs, blue stragglers, contact binaries, etc. We also established an evolution population synthesis （EPS） model, the Yunnan Model, which takes into account binary interactions for the first time. We applied our model for the origin of hot subdwarf stars in the study of elliptical galaxies and explained their far-UV radiation.     

Binary Population Synthesis Study

Binary population synthesis(BPS),an approach to evolving millions of stars(including binaries) simultaneously,plays a crucial role in our understanding of stellar physics,the structure and evolution of galaxies,and cosmology.We proposed and developed a BPS approach,and used it to investigate the formation of many peculiar stars such as hot subdwarf stars,progenitors of type la supernovae,barium stars, CH stars,planetary nebulae,double white dwarfs,blue stragglers,contact binaries,etc.We also established an ...     

OAI对象重用与交换

由于现行网络并没有提供标准化的机制来描述复合信息对象边界问题,当它们映射到Web图上,复合对象/组件之间的关系特征会消失,OAI-ORE试图用"命名图"机制来解决这个问题。本文主要介绍OAI-ORE的抽象数据模型,同时对OAI-ORE在数字图书馆的应用进行展望。     

The rise and fall of network stars: Analyzing 2.5 million graphs to reveal how high-degree vertices emerge over time

Trends change rapidly in today’s world, prompting this key question: What is the mechanism behind the emergence of new trends? By representing real-world dynamic systems as complex networks, the emergence of new trends can be symbolized by vertices that “shine.” That is, at a specific time interval in a network’s life, certain vertices become increasingly connected to other vertices. This process creates new high-degree vertices, i.e., network stars. Thus, to study trends, we must look at how networks evolve over time and determine how the stars behave. In our research, we constructed the largest publicly available network evolution dataset to date, which contains 38,000 real-world networks and 2.5 million graphs. Then, we performed the first precise wide-scale analysis of the evolution of networks with various scales. Three primary observations resulted: (a) links are most prevalent among vertices that join a network at a similar time; (b) the rate that new vertices join a network is a central factor in molding a network’s topology; and (c) the emergence of network stars (high-degree vertices) is correlated with fast-growing networks. We applied our learnings to develop a flexible network-generation model based on large-scale, real-world data. This model gives a better understanding of how stars rise and fall within networks, and is applicable to dynamic systems both in nature and society.Multimedia Links▶ Video ▶ Interactive Data Visualization ▶ Data ▶ Code Tutorials     

A usage study of retrieval modalities for video shot retrieval

As an information medium, video offers many possible retrieval and browsing modalities, far more than text, image or audio. Some of these, like searching the text of the spoken dialogue, are well developed, others like keyframe browsing tools are in their infancy, and others not yet technically achievable. For those modalities for browsing and retrieval which we cannot yet achieve we can only speculate as to how useful they will actually be, but we do not know for sure. In our work we have created a system to support multiple modalities for video browsing and retrieval including text search through the spoken dialogue, image matching against shot keyframes and object matching against segmented video objects. For the last of these, automatic segmentation and tracking of video objects is a computationally demanding problem which is not yet solved for generic natural video material, and when it is then it is expected to open up possibilities for user interaction with objects in video, including searching and browsing. In this paper we achieve object segmentation by working in a closed domain of animated cartoons. We describe an interactive user experiment on a medium-sized corpus of video where we were able to measure users’ use of video objects versus other modes of retrieval during multiple-iteration searching. Results of this experiment show that although object searching is used far less than text searching in the first iteration of a user’s search it is a popular and useful search type once an initial set of relevant shots have been found.     

An efficient method for the retrieval of objects by topological relations in spatial database systems

In this paper, we present a new method to improve the performance of query processing in a spatial database. The previous approach can process the retrieval of spatial objects by topological relations using R-tree structures based on minimum bounding rectangles. In our approach, we add internal rectangle to the leaf nodes of the R-tree as additional information for helping objects retrieval. As a result, the number of false hits can be reduced and part of the true hits can be identified at the early stage of searching. The experiments demonstrated that the performance of database systems can be improved because both the number of objects accessed and the number of objects requiring detailed inspection are much less than those in the previous approach.     

北京市水资源短缺风险等级评价与预测

本文利用1979年-2009年的北京市水资源相关数据,采用灰色关联分析方法筛选出主要水资源短缺风险因子;用模糊聚类分析法对水资源系列进行聚类;用灰色系统GM(1,1)法预测2010年-2015年的水资源短缺风险,将结果进行模糊聚类分析.结果表明,降雨量、常住人口、第三产业及生活等其它用水量与北京市水资源短缺的关联度较大.在1999年之前,北京市水资源风险主要处于中等以及较低的等级.1999年之后,北京市的水资源风险基本处于较高的等级.在丰水年条件下,2010年-2015年北京市水资源风险处于较低等级;在平水年处于中等等级;在枯水年和极端枯水年,将处于较高风险甚至高风险等级.2014年后,南水北调工程引水入京将有效缓解水资源短缺状况,使水资源短缺的风险降低一个等级.     

基于多源数据融合的南四湖湿地生态系统服务功能价值评估

随着对湿地生态系统研究的深入,湿地的生态服务价值越来越受到学者的重视。研究以南四湖湿地生态系统为例,通过遥感和地理信息系统软件处理高清影像解译生成的景观数据以及MODIS处理生成的NPP数据,运用市场价值法、碳税法与造林成本法、影子工程法、费用支出法、专家估算法、替代费用法以及生态价值等多种方法对南四湖湿地生态系统物质生产功能、大气调节功能、蓄水功能、调蓄洪水功能、休闲娱乐功能、文化科研功能、养分循环功能以及生物栖息地功能等服务功能价值进行估算。结果表明:①南四湖湿地服务功能价值总和为131亿元,其中调节功能价值最大,达到56.77亿元,其次是支持功能和文化功能,价值量为52.77亿元和15.07亿元,最后是物质生产功能价值为6.39亿元;②虽然人工湿地面积占研究区域总面积的59%以上,其生态服务功能价值总量还不到自然湿地的生态服务功能价值总量的一半。     

多情景模拟下新时代中国耕地保护底线预测

耕地是国家粮食安全的基石,关系到未来中华民族的生存.但究竟需要守住多少耕地才能满足新时代中国粮食需求的底线,一直存在着不同的争论.为此,本文从厘清不同情景下耕地最低保有量需求出发,构建兼顾人口、人均粮食、粮食单产的耕地需求预测模型,模拟完全自给、高度自给、适度自给3种情景的耕地需求量;结合耕地未来可能的变化趋势预测,判...     

命令控制型和市场激励型环境规制对造林面积的影响——来自中国县级层面的准自然实验证据

命令控制型和市场激励型环境规制,孰能更有效地提升造林面积从而更好地保护森林生态环境一直存在争议。本文利用国家重点生态功能区政策这一命令控制型环境规制,和生态转移支付政策这一市场激励型环境规制作为准自然实验,基于2006—2016年1372个县级数据,采用双重差分法识别了这两类环境规制对造林面积影响的因果效应及政策相对有效性。研究结论如下：①与命令控制型环境规制相比,市场激励型环境规制对造林面积的影响更为显著且具有长期效果。表现为国家重点生态功能区政策使造林面积提升了6.7%,但该效应随着时间推移呈现出下降的趋势;生态转移支付政策使造林面积提升了8.2%,且该效应随着时间推移逐步增强。②异质性分析发现,初始造林面积较高和经济发展水平较高的县表现出更高的造林面积提升效应。③进一步的成本收益估算表明,国家重点生态功能区和生态转移支付政策通过提高造林面积带来的环境健康效应分别为5926.11亿元和7256.14亿元,是其减少财政收入所产生的经济成本的2.19和1.92倍。本文结论有助于我国制定长期有效的森林环境规制政策。     

Astronomical fire: Richard Carrington and the solar flare of 1859

An explosion on the Sun in 1859, serendipitously witnessed by amateur astronomer Richard Carrington, plunged telegraphic communications into chaos and bathed two thirds of the Earth's skies in aurorae. Explaining what happened to the Sun and how it could affect Earth, 93 million miles away, helped change the direction of astronomy. From being concerned principally with charting the stars to aid navigation, astronomers became increasingly concerned with what the celestial objects were, how they behaved and how they might affect life on Earth.     

中外再生资源产业发展比较与中国的推进策略

20世纪80年代以来,世界许多国家从可持续发展理念出发,提出了许多新思想,特别在1992年联合国环发大会提出可持续发展道路之后,德国等欧洲国家首先提出了循环经济发展战略,并得到其他发达国家的积极响应.进而再生资源产业被许多国家作为战略性产业而得到迅速发展。近年来,我国再生资源产业发展较快。据统计,2003年我国废旧物资的回收总量已经达到8400×10⁴t,其中七大类废旧物资年回收量突破5500×10⁴t,年回收废旧物资总值约500×10⁸元,2004年我国再生资源主要品种年加工处理量约为2000×10⁴t。但与世界发达国家比较,在废旧物资回收率、回收量、回收总值、回收结构、废弃物的综合利用率、再生产品产量以及产业发展规模等方面还存在较大差距。文章研究分析了我国产业发展中存在的问题,在总结和借鉴发达国家经验的基础上,从加强政府对产业发展的宏观调控和引导、产业管理体制改革、营造产业发展的法规政策环境、构建社会化产业发展体系、调整产业空间布局和组织结构以及建立产业市场体系和技术发展体系等方面提出了加快我国再生资源产业发展的对策,对推进我国循环经济发展,实施可持续发展战略有一定的现实意义。     

科技哲学视域下的象数学

象数学作为易学的一个分支,以象为事物的表征,以数为事物运动变化的规则,构建起一个象数结合的宇宙构成和变化模式,这是感性认识与抽象思维相结合且不断提高的产物。它认为万物皆为阴阳合体,强调天人合一,具有明显的系统性特点,同时也道出了事物变化的动力来源于事物内部的刚柔相推,事物运动变化的趋势是循环变易。这种循环动态观、整体观、重功能观虽有重数的神秘主义特征,把人的思维限制在数与象的范围之内,但长期以来对我国各种自然科学的发展却也具有明显的积极意义。     

高能天体物理学研究与发展

文章将高能天体物理学的内容局限在以下范围:(1)研究的天体限制在黑洞、中子星、超新星遗迹和γ射线暴;(2)研究的手段限制在对X射线和γ射线空间观测。然后描述了高能天体物理学的研究进展和意义,近期国内外发展和我国的未来规划,包括战略目标、有关科学计划和空间项目。最后提出了我国未来相关研究领域发展的策略和措施建议。     

粮食增产背景下松花江区农业水资源承载力优化配置研究

根据全国新增500亿kg粮食生产的规划,松花江区承担粮食增产任务150亿kg。在此粮食增产的背景下,对松花江区的农业水资源承载能力进行评估,计算区域农业水资源能支撑的粮食生产规模是有实际意义的。本文通过构建松花江区的农业水资源最优配置模型,采用单一线性目标函数,约束条件综合考虑了各行业水资源分配、地形地貌、农耕制度、市场调节、区域气候、流域调水、农耕状况及制度等多方面因素,模拟结果显示,松花江区最优能实现粮食产量1 043.57亿kg,其中水稻产量达304.35亿kg,玉米产量为700.92亿kg,农业水资源能够承载预期的生产目标,并且粮食产量还有提升的潜力。模型的优化结果显示,二级区的嫩江区、第二松花江区、松花江干流区和乌苏里江区农业水资源承载力有限,对于其他子区,水资源开发潜力较大,全区优化后灌溉面积增加约250万hm2。模型为区域内水资源调配,区间跨流域调水及优化农业产业结构,推进灌溉节水措施,提供理论支撑。     

北京市湿地生态系统服务功能价值评估

在遥感调查和实地调查的基础上,综合运用资源经济学、生态经济学方法,针对北京大都市的特点建立北京湿地分类体系、生态系统服务功能价值指标体系和评价方法,对2009年北京市湿地生态系统服务功能价值进行了评估。结果表明：2009年北京市湿地生态系统服务功能价值为2137．31亿元,其中经济功能价值为33．99亿元,占总价值的1．59％;社会功能价值为1340．94亿元,占总价值的62．74％;生态功能价值为762．38亿元,占总价值的35．67％,反映了北京湿地生态系统在经济、社会、生态三方面多功能服务于首都经济社会发展和生态城市建设中的地位和作用,可为北京市湿地生态系统保护、恢复和重建决策提供科学依据。