Influencing Factors of the Rebreak of the Key Rock Block of the Main Roof in the Gob

Geotechnical and Geological Engineering - In view of the phenomenon that upright triangular zone and inverted triangular zone of the collapsed roof appeared alternately in the gob, a mechanical...     

Segmentation algorithm for long time series analysis

Time series analysis is an important issue in the earth science-related engineering applications such as hydrology, meteorology and environmetrics. Inconsistency and nonhomogeneity that might arise in a time series yield segments with different statistical characteristics. In this study, an algorithm based on the first order statistical moment (average) of a time series is developed and applied on five time series with length ranging from 84 items to nearly 1,300. Comparison to the existing segmentation algorithms proves the applicability and usefulness of the proposed algorithm in long hydrometeorological and geophysical time series analysis.     

Assessment of three temperature reconstruction methods in the virtual reality of a climate simulation

The performance of statistical climate reconstruction methods in the pre-instrumental period is uncertain, as they are calibrated in a short instrumental period but applied to much longer reconstructions time spans. Here, the virtual reality created by a climate simulation of the past millennium with the model ECHO-G is used as a test bed of three methods to reconstruct the annual Northern Hemisphere temperature. The methods are Composite plus Scaling, the inverse regression method of Mann et al. (Nature 392:779–787, 1998) and a direct principal-components regression method. The testing methodology is based on the construction of pseudo-proxies derived from the climate model output, the application of each of these methods to pseudo-proxy timeseries, and the comparison of their result with the simulated mean temperature. Different structures of the noise have been used to construct pseudo-proxies, ranging from the simulated grid-point precipitation. Also, one sparse and one denser pseudo-proxy network, co-located with two real networks, have been considered. All three methods underestimate the simulated variations of the Northern Hemisphere temperature, but the Composite plus Scaling method clearly displays a better performance and is robust against the different noise models and network size. The most relevant factor determining the skill of the reconstruction appears to be the network size, whereas the different noise models tend to yield similar results.     

Trace element and REE geochemistry of the Zhewang gold deposit,southeastern Guizhou Province,China

The quartz vein-type gold deposits are widely hosted by the Neoproterozoic （Xiajiang Group） epimeta- morphic clastic rock series in southeastern Guizhou Province, China. The Zhewang gold deposit studied in this paper occurs in the second lithologieal member of the Pinglue Formation of the Xiajiang Group. Trace element geochemis- try of host rocks, quartz veins and arsenopyrite has revealed that ore-forming fluid was enriched in sulphophile ele- ments such as Au, Ag, As, Sb, Pb and Zn, and simultaneously concentrated some magmaphile elements such as W and Mo, which probably provides some evidence for multi-stage mineralization or overprinting of magmatic hydro- therm. Quartz veins and arsenopyrite were characterized by depletion in HFSE and enrichment in LREE. Hf/Sm, Nb/La and Th/La imply that the ore-forming fluid was probably a NaC1-H20 solution system enriched in more C1 than F; Th/U values reflect the strong reducibility of the ore-forming fluid, coincident with the sulfide assemblages. The values of Co/Ni reflect that magmatic fluids may have partly participated in the ore-forming process and Y/Ho values have proved that the ore-forming fluid was associated with metamorphism and exotic hydrotherm which has reformed former quartz veins during late mineralization. The concentrations of REE, Eu anomalies and Ce anomalies of this deposit display that ore-forming elements mainly were derived from host rocks and possibly from a mixed deep source, and the ore-forming fluid was mixed by dominant metamorphic fluid and minor other sources. The physical-chemical conditions of ore-forming fluid changed from the initial stage to the late stage. The metamorphic fluid is responsible for the mineralization. Therefore, the Zhewang gold deposit is classified as a quartz vein-type gold deposit which may have been reformed by magmatic fluids during the late stage.     

模拟CO_2埋藏的煤储层元素迁移实验研究

采用高压超临界CO2地球化学反应器对CO2在煤储层中的地质埋藏进行模拟,利用电感耦合等离子体发射光谱仪(ICP-OES)以及电感耦合等离子体质谱(ICP-MS)分别对淋滤液和煤样中的10种微量元素进行测试,对煤中微量元素在CO2的地质埋藏过程中的迁移进行了实验研究。结果表明:在CO2的地质埋藏过程中对煤的有机组成和无机矿物等均具有改造作用,从而影响到煤中微量元素的赋存和迁移特征,Cr、Zn、Cu等元素迁移能力相对较强,而Co、Ba、V等元素相对较弱;元素迁移能力大小顺序为:CrZnCuNiCdMnCoBaV。     

High pressure equation of state for molten CaCO3 from first principles simulations

Carbonate melts are important active metasomatic agents and efficient transport agents; their thermodynamic properties at high temperatures and pressures are therefore of considerable interest for various geochemica applications. However, due to the extreme challenges in relevant experiments, current knowledge of even the density of carbonate melts is limited. In this study, we provide high quality volumetric data of Ca CO3-melt from firs principles at high temperatures and pressures(up to3,500 K and 60 GPa). The accuracy of these data is demonstrated through comprehensive comparison with available experimental data and a thorough discussion of the predictability of the re-scaling method proposed in this study. Based on the simulations, an equation of state has been established that is critical to relevant highly disputed questions such as the decomposition and solidification boundaries of Ca CO3 melts, the latter of which is briefly discussed in this study with a newly derived ab initio melting curve to high pressures.     

干热退化山地不同类型侵蚀沟生物生态工程治理试验研究

冲沟是生态环境治理和控制泥石流活动的关键地段。结合云南南涧县城后山泥石流生物生态工程治理试验示范研究,总结出由土石混砌与土木筑造结构的生物谷坊,浆筑结构拦坝和谷坊等组成的沟道侵蚀治理方法,并成功地进行了相应的生物坝系建设,筛选出大叶桉,赤桉,马鹿花,台湾相思,马占相思,新叶合欢,夹竹桃等一批适宜干热生境和沟道植被恢复及防护林建设的植物种类,同时采取冲沟与谷坡同时整治,生物治理与调蓄水措施相结合的坡面治理方法。结果表明,这些生物生态工程措施对于防止沟床侵蚀,抑制泥石流活动和护床固坡效果显著。     

Monitoring Large-Scale Tests for Nuclear Waste Disposal

Two large-scale “in situ” demonstration experiments and their instrumentation are described. The first test (FEBEX Experiment) involves the hydration of a compacted bentonite barrier under the combined effect of an inner source of heat and an outer water flow from the confining saturated granite rock. In the second case, the progressive de-saturation of Opalinus clay induced by maintained ventilation of an unlined tunnel is analyzed. The paper shows the performance of different sensors (capacitive cells, psychrometers, TDR’s) and a comparison of fill behaviour with modelling results. The long term performance of some instruments could also be evaluated specially in the case of FEBEX test. Capacitive sensors provide relative humidity data during long transient periods characterised by very large variations of suction within the bentonite.     

中国中世纪暖期温度年代际变化特征及成因分析

利用通用地球系统模式CESM的过去2000年气候模拟试验资料,在与历史气候重建资料、观测/再分析资料及其他模式模拟资料进行对比验证的基础上,分析了中国中世纪暖期（Medieval Warm Period,简称MWP）地表温度年代际变化特征并初步探讨了其成因。结果表明：在公元801~1250年的中国中世纪暖期期间,在年代际尺度上,中国地表温度EOF第一模态的空间分布为全区一致型,并且北部的变率大于南部,最大的变率中心位于中国东北部;EOF第二模态反映出研究区内南北反向的空间分布特征。40°N以北地区温度变化一致;40°N以南青藏高原-云贵高原-东南沿海地区与华北地区呈反相变化,最大的变率中心位于青藏高原东部。中世纪暖期地表温度EOF第一模态主要归因于太阳辐射的影响,火山活动也是影响因子之一;EOF第二模态主要受气候系统内部变率的影响,其他外强迫因子的影响较小。但是,温室气体、土地利用/覆盖两个外强迫因子对气候系统内部变率具有一定的调制作用。在中国,中世纪暖期太阳活动剧烈、火山活动较少,下垫面吸收更多的太阳短波辐射,地表净辐射通量增大,是中世纪暖期形成的主要原因。     

围绕南海问题的信息权力作用过程与机制研究

2010年以来,南海争端呈现扩大化和复杂化的态势,形成环南海周边国家侵占岛礁、域外国家广泛介入的局面,进而推动南海问题日益走向“国际化”。分析南海问题中的国家（地区）间合作与冲突关系,挖掘南海问题“复杂化”的深层原因,这是理解当前南海局势、避免战略误判的重要支撑。文章借助GDELT新闻媒体数据库,提取2013—2021年有关南海问题的事件数据,利用年代约束聚类方法将南海问题划分为矛盾上升期（2013—2018年）和域外介入期（2019年以后）,并利用社会网络分析方法探讨南海问题中的国家（地区）间合作与冲突关系以及背后的信息生产网络。研究发现：1）矛盾上升期,围绕南海问题的合作与冲突主体主要为环南海国家;2）域外介入期,美国、英国、澳大利亚等域外国家结盟合作并围堵中国,中国在与域内国家紧密合作的同时,却成为冲突关系网络的核心,冲突关系复杂、合作关系萎缩与当前人们对南海问题有所缓和的认知形成矛盾,反映信息权力的作用愈发深远;3）信息生产网络中,美、英、澳等国家主导信息制造和加工过程,表明南海问题成为各信息行为体博弈的角力场。