EUV resonance fluorescence of the c′4→X (0,v″) and b′→X (1,v″) transitions of N2

Extreme ultraviolet (EUV) resonance fluorescence of the (0,v″) bands of the c′₄¹Σ_u⁺→X¹Σ_g⁺ and the (1,v″) bands of the b′ ¹Σ_u⁺→X¹Σ_g⁺ transitions of N₂ has been observed by photon excitation of N₂ in the vicinity of 95.8 nm. The integrated fluorescence intensities of the c′₄→X (0,v″) emission become saturated at N₂ pressures higher than ∼0.16 mTorr. The emission features in the spectral region between 105 and 130 nm become progressively significant as the N₂ pressure is increased. The (1,v″) progression for v″ up to 11 of the b′→X transition and two progressions of the Lyman-Birge-Hopfield (LBH) system have been identified. The multiple scattering processes apparently cause significant reduction in the c′₄→X (0,0) emission rates. The present results may be useful in the explanation of the weak c′₄→X (0,0) fluorescence as well as the significant c′₄→X (0,v″) features in the dayglow of the Earth observed by the Far Ultraviolet Spectroscopic Explorer.     

The Emission Heights of Transition Region Lines in an Equatorial Coronal Hole and the Surrounding Quiet Sun

Using the correlation between the radiance or Doppler velocity and the extrapolated magnetic field, we determined the emission heights of a set of solar transition region lines in an equatorial coronal hole and in the surrounding quiet Sun region. We found that for all of the six lower-transition-region lines, the emission height is about 4-5 Mm in the equatorial coronal hole, and around 2 Mm in the quiet Sun region. This result confirms the previous findings that plasma with different temperature can coexist at the same layer of transition region. In the quiet Sun region, the emission height of the upper-transition-region line Ne viii is almost the same that of the lower-transition-region line, but in the coronal hole, it is twice as high. This difference reveals that the outflow of Ne Ⅷ is a signature of solar wind in the coronal hole and is just a mass supply to the large loops in the quiet Sun.     

青藏高原抬升加热气候效应研究的新进展

对近4年来关于青藏高原加热影响气候的研究进行回顾.首先介绍利用位涡方程和热力适应理论,揭示;夏季高原上空低层气旋式及高层反气旋式环流结构稳定维持的动力学机理.结果表明高原加热作用造成的低层正涡源是低层气旋式环流得以稳定维持的重要原因.而边界层摩擦产生的负位涡是平衡正位涡的主要因素.高原加热还在高原上空形成负位涡,它影响着盛夏的大气环流,是青藏高原上空强大而稳定的反气旋环流得以维持的重要因素.在春夏过渡季节青藏高原非绝热加热对大气环流季节变化以及亚洲季风爆发的影响力方面,进一步确认了感热加热在过渡季节早期(5月中旬以前)环:流演变中的重要作用.青藏高原非绝热加热的时间演变引起了海陆热力差异对比的变化,使副热带高压带首先在孟加拉湾东部断裂,亚洲季风因而在孟加拉湾爆发.结果还表明,用纬向风垂直差异的时空分布能更准确地表示季节变化的区域差异.在青藏高原非绝热加热与北半球环流系统年际变化的联系方面,发现夏季青藏高原的加热强(弱)的年份,高原感热加热气泵(SHAP)高(低)效工作,使高原加热对周边地区低层暖湿空气的抽吸效应和对高层大气向周边地区的排放作用加强(减弱),高原及邻近地区的上升运动,下层辐合和上层辐散均增强(减弱),从而影响着高原和周边地区的环流以及亚洲季风区大尺度环流系统.而且高原的加热强迫还能够激发产生一支沿亚欧大陆东部海岸向东北方向传播的Rossby波列,其频散效应可影响到更远的东太平洋以至北美地区的大气环流.研究还表明,盛夏的南亚高压存在"青藏高压型"和"伊朗高压型"的双模态,它们与高原加热状态有关,且显著地与亚洲季风区的气候分布密切联系.     

1949年以来中国耕地功能变化

耕地功能变化具有明显的阶段性。日本、韩国、美国及欧洲发达国家耕地功能已普遍转型。中国农业发展及土地利用需求变化与以上国家颇为相似。那么,目前中国耕地功能变化是否也在发生转型？对此,在构建耕地功能变化分析框架与度量方法的基础上,分析1949年以来中国耕地功能变化过程。结果表明,中国耕地功能总体上于2006 年开始转型,转型前后耕地功能供需协调与供需错位、供给滞后、形态扭曲并存。在综合考虑以上发达国家经验与中国耕地功能变化过程的基础上,尝试提出耕地多功能管理建议。此外,从耕地功能变化研究框架出发探讨了土地利用转型的研究路径。     

Mechanism for the formation of the January 2013 heavy haze pollution episode over central and eastern China

In January 2013,a long-lasting episode of severe haze occurred in central and eastern China,and it attracted attention from all sectors of society.The process and evolution of haze pollution episodes were observed by the"Forming Mechanism and Control Strategies of Haze in China"group using an intensive aerosol and trace gases campaign that simultaneously obtained data at 11 ground-based observing sites in the CARE-China network.The characteristics and formation mechanism of haze pollution episodes were discussed.Five haze pollution episodes were identified in the Beijing-Tianjin-Hebei(Jing-Jin-Ji)area;the two most severe episodes occurred during 9–15 January and 25–31 January.During these two haze pollution episodes,the maximum hourly PM2.5mass concentrations in Beijing were 680 and 530μg m 3,respectively.The process and evolution of haze pollution episodes in other major cities in the Jing-Jin-Ji area,such as Shijiazhuang and Tianjin were almost the same as those observed in Beijing.The external cause of the severe haze episodes was the unusual atmospheric circulation,the depression of strong cold air activities and the very unfavorable dispersion due to geographical and meteorological conditions.However,the internal cause was the quick secondary transformation of primary gaseous pollutants to secondary aerosols,which contributed to the"explosive growth"and"sustained growth"of PM2.5.Particularly,the abnormally high amount of nitric oxide(NOx)in the haze episodes,produced by fossil fuel combustion and vehicle emissions,played a direct or indirect role in the quick secondary transformation of coal-burning sulphur dioxide(SO2)to sulphate aerosols.Furthermore,gaseous pollutants were transformed into secondary aerosols through heterogeneous reactions on the surface of fine particles,which can change the particle’s size and chemical composition.Consequently,the proportion of secondary inorganic ions,such as sulphate and nitrate,gradually increased,which enhances particle hygroscopicity and thereby accelerating formation of the haze pollution.     

The crustal structures of the central Longmenshan along and its margins as related to the seismotectonics of the 2008 Wenchuan Earthquake

In 2010, a 500-km-long wide-angle reflection/refraction seismic profile was completed, running northwest from the central Sichuan Basin. This profile orthogonally crosses the meizoseismal area of great Wenchuan earthquake of 12 May 2008, which occurred in the central part of the Longmenshan. The profile also passes through the northwestern Sichuan Plateau, along which a new deep seismic sounding observation system was set up that was much improved over previous datasets and enabled abundant observations to be recorded. Seismic wave phase records that reflect the structural characteristics of different tectonic blocks, especially the complicated phase features associated with the Wenchuan earthquake, were calculated and analyzed in detail. A 2D crustal P-wave velocity model for the orogenic belt in the central Longmenshan and its margins was determined, and crustal structure differences between the stable Sichuan Basin and the thickened northwestern Sichuan Plateau were characterized. Lithological variations within the upper and lower crust in the interior of the plateau, especially a great velocity decrease and plastic rheological properties associated with strong lithologic weakening in lower crust, were detected. From west to east in the lower crust beneath the orogenic belt lying between the Sichuan Basin and the northwestern Sichuan Plateau, a giant shovel-like upwelling is observed that dips gently in the lower part and at higher angles in the upper part; this is inferred to be related to the fault systems in the central Longmenshan. An upwelling in the upper-middle crust along the eastern margin of the orogenic belt is associated with steeply dipping thrusts that strongly uplift the upper crust and crystalline basement beneath a central fault system in the Longmenshan. The data, combined with an understanding of the regional tectonic stress field and previous geological results, enable a discussion of basin-and-range coupling, orogenic tectonics, the crustal fault system, and the seismogenic tectonic environment of the central Longmenshan along the eastern margin of the Qinghai-Tibet Plateau.     

The microfacies and sedimentary responses to the mass extinction during the Permian-Triassic transition at Yangou Section,Jiangxi Province,South China

A Permian-Triassic (P-Tr) boundary section of continuous carbonate facies, which well recorded the biotic and environmental processes through the great P-Tr transition in the shallow non-microbialite carbonate facies, has been studied in Yangou, Leping County, Jiangxi Province. The P-Tr sequence is well correlated with the Meishan section according to the conodont biostratigraphy and the excursion of carbon isotopes. A series of high-resolution thin-sections from the P-Tr boundary carbonate rocks at the Yangou section are studied to explore the interrelation between environmental change and biological evolution during the transitional time. Six microfacies have been identified based upon the observation of the thin-sections under a microscope on the grains and matrix and their interrelation. Combined with the data of fossils and carbon isotopes, Microfacies 4 (MF-4), coated-grain-bearing foraminifer oolitic sparitic limestone, and Microfacies 6 (MF-6), dark shelly micritic limestone, should be the different responses to the two episodes of mass extinction and environmental events that can be correlated throughout South China and even over the world. The oolitic limestone of MF-4 is the first finding from the latest Permian strata in South China and it might be a proxy of an unusual environmental condition of high pCO₂, low sulfate concentration and of microbial blooming in the aftermath of the latest Permian mass extinction. The micritic limestone of MF-6 containing rich micro-gastropods and ostracods probably represents the blooming event of disaster taxa in the earliest Triassic environment. The microfacies analysis at the Yangou section can well reveal the episodic process of the biological evolution and environmental change in the shallow non-microbialite carbonate facies throughout the great P-Tr transition, thus the Yangou section becomes an important complement to the Meishan section.     

匿名集序列规则与转移概率矩阵的空间预测和实验

随着位置服务（Location Based Service,LBS）的广泛应用,隐私保护成为LBS进一步深入发展亟待解决的问题,时空K-匿名成为一个主流方向。LBS应用服务器存储用户执行连续查询生成的历史匿名数据集,分析大时空尺度历史的匿名数据集,空间预测可以实现LBS应用的个性化服务。本文提出了一种融合概率统计与数据挖掘2种典型技术——马尔科夫链与序列规则,对匿名数据集中包含的特定空间区域进行预测的方法。方法包括4个过程：（1）分析序列规则、马尔科夫过程进行预测的特点;（2）以匿名数据集序列规则的均一化置信度为初始转移概率,构建n步转移概率矩阵;（3）设计以n步转移概率矩阵进行概略空间预测的方法,以及改进的指定精确路径的空间预测方法;（4）实验验证方法的性能。结果证明,该方法具有模型结构建立速度快、精确空间预测概率与真实概率的近似度可灵活调节等优点,具有可用性。     

一种面向海量浮动车数据的地图匹配方法

浮动车数据已广泛应用于交通监管、智能出行、城市规划等领域,地图匹配是浮动车数据关键技术之一,保障匹配算法精度的同时提高匹配效率,是面向海量浮动车数据地图匹配方法的难点。本文提出一种基于HMM（Hidden Markov Model）的地图匹配模型,相对传统模型尝试了多个方面的改进：在发射概率计算中引入航向角变量,并探讨了该变量对模型精度的影响;以格网对路网进行划分,构建哈希索引,实现候选路段快速查找;采用路径无权距离替代路径实际距离,并对路网进行预处理,根据浮动车有限时间内的活动范围构建路段转移矩阵,实现路段转移概率快速计算,以减小路径匹配算法时间复杂度。将模型应用于北京出租车轨迹数据匹配结果表明,对于采样时间间隔在1~120 s的浮动车数据模型切实可行。在满足匹配精度应用需求的前提下,模型效率有了较大幅度提升,能有效应用于海量浮动车数据地图匹配。     

扎龙湿地景观动态变化特征

扎龙湿地近35年来湿地景观发生了巨大的变化,本文定义了一套基于TM影像的适用于描述湿地景观变化的湿地分类系统,利用景观转换系数分析以5年为周期的时间尺度上湿地的转换幅度的变化,统计和分析了湿地从1979-2013期间景观转换系数的动态变化特征,总结了扎龙湿地景观动态变化主要为四类景观动态类型：A-小幅度规则型稳定景观,B-中幅度不规则型变化景观,C-幅度渐弱规则型稳定景观,D-大幅度不规则型变化景观。研究表明：扎龙湿地1979-2013年期间,湿地景观在前10年向湿生景观转换,但是转换的幅度越来越小;后20年,湿地转向干旱趋势。在不同的景观动态类型中A类小幅度规则型稳定景观所占面积最大,为973.60 km²,接近湿地面积的二分之一,主要集中在核心区和外围稳定的农田部分;D类大幅度不规则型变化景观面积最少,为311.92 km²,主要分布于人类干扰强烈的区域。