基于探地雷达解译的喀斯特坡地表层岩溶带空间分布特征研究

表层岩溶带作为喀斯特关键带区别于其他区域地球关键带的近地表岩土结构标志层,对于水分和养分下渗、赋存、滞留、植被水分养分利用等方面具有重要作用,是岩石-土壤-植被系统中生物地球化学过程最为活跃的关键地带。描述和认识表层岩溶带对认知喀斯特关键带结构信息、研究水土物质循环过程、揭示表层与地下水资源利用规律等方面具有十分重要的理论和现实意义。本文利用探地雷达技术,探测黔中高原黔西县东南部喀斯特坡地,共计测线35条,测点799个,提取表层岩溶带发育厚度并分析空间分布特征,得到以下结论：喀斯特高原峰丛地貌区表层岩溶带发育较好,发育厚度集中在2~8m之间,最深可达18.8m。表层岩溶带发育空间分布异质性强,坡地表层岩溶带厚度发育异质性变化强于坝地。地面物质组成和表层岩溶带发育厚度关系密切,坡地石质化比例提高,表层岩溶带发育较深,地面物质组成可作为高原型喀斯特坡地反映表层岩溶带发育程度的综合代用性指标。本次研究还指示了喀斯特坡地土地石质化是表层岩溶带地质历史时期不断溶蚀发育演化、土壤地质历史持续漏失的结果。表层岩溶带的发育为水土漏失提供了空间基础,水土漏失也进一步加剧了岩土界面的水岩反应过程,促进了表层岩溶带的进一步发育以及地表土体下沉、基岩裸露、土地石质化景观的出现。

     

Revisiting pulsar velocities using Gaia Data Release 2

Precise measurements of neutron star(NS) velocities provide critical clues in regard to the supernova physics and evolution of binary systems. Based on Gaia Data Release 2(DR2), we selected a sample of 24 young( 3 Myr) pulsars with precise parallax measurements and measured the velocity of their local standard of rest(LSR) and the velocity dispersion among their respective local stellar groups. The median velocity difference between thus calculated LSRs and the Galactic rotation model is ～ 7.6 km s~(-1),small compared to the typical velocity dispersion of ～ 27.5 km s~(-1). For pulsars off the Galactic plane,such differences grow significantly to as large as ～ 40 km s~(-1). More importantly, the velocity dispersion of stars in the local group of low-velocity pulsars can be comparable to their transverse velocities, suggesting that the intrinsic velocities of NS progenitors should be taken into account when we consider their natal kicks and binary evolution. We also examined the double NS system J0737-3039 A/B, and measured its transverse velocity to be 26_(-13)~(+18) km s~(-1) assuming nearby Gaia sources are representative of their birth environment. This work demonstrated the feasibility and importance of using Gaia data to study the velocity of individual systems and velocity distribution of NSs.     

雄安新区雾迷山组岩溶热储特征与有利区

为了深化对雄安新区中深层地热资源的规模化开发利用,以露头、岩心、薄片、钻井资料与地震测线解释成果为基础,分析雄安新区中元古界蓟县系雾迷山组热储岩石学和储集空间特征,研究了雾迷山组热储沉积相模式、岩相古地理和孔隙度、渗透率分布特征;结合构造演化和热储成岩作用类型,分析雾迷山组热储岩溶发育期次、岩溶作用、岩溶古地貌分布特征,针对岩溶主要发育层,厘清控制因素,明确雄安新区雾迷山组岩溶热储特征;综合上述特征,结合雄安新区地温梯度、断裂分布及水动力等因素,优选出该区雾迷山组岩溶热储有利勘探靶区。研究结果表明：雄安新区蓟县系雾迷山组热储有利岩性主要为叠层石白云岩、藻凝块白云岩、颗粒白云岩,藻云坪微相、滩微相易发育各类溶蚀作用,云坪易发育裂缝,储集空间类型为孔隙、溶洞和裂缝3大系统。岩溶作用类型可分为同生—准同生岩溶、表生岩溶和埋藏岩溶,自雾迷山组沉积后主要发育于芹峪期、印支期和燕山期的表生岩溶和晚喜山期的埋藏溶蚀,对雾迷山组储层有着建设性作用,燕山—早喜马拉雅期对岩溶热储的形成演化起决定作用;同期主要伴随3期高角度裂缝发育,这些高角度缝增加了储集空间与输导体系,促进期后的相关溶蚀作用;裂缝在白云岩中最发育, 灰质云岩次之,泥质云岩最不发育。孔隙度和渗透率区域上分布有3个高值区。岩溶古地貌在印支期前北低南高,在印支期及以后,地貌北高南低,北部岩溶作用强烈,南部次高地也发育岩溶带。溶蚀相为最有利的成岩相区,溶蚀—泥质充填相为较有利的成岩相区。研究区雾迷山组岩溶储集层分布主要受岩性（包括组分、结构、厚度）、成岩相带、构造（包括断裂、裂缝、不整合面）和古地貌等方面因素的控制,地热勘探最有利靶区位于大王镇西部及南部、容城—八于、雄县—赵北口镇西部、大营镇、高深1井—高阳等区带。     

The Potential Vertical Distribution of Bigeye Tuna ( Thunnus obesus ) and Its Influence on the Spatial Distribution of CPUEs in the Tropical Atlantic Ocean

Understanding the potential vertical distribution of bigeye tuna(Thunnus obesus) is necessary to understand the catch rate fluctuations and the stock assessment of bigeye tuna. To characterize the potential vertical distribution of this fish while foraging and determine the influences of the distribution on longline efficiency in the tropical Atlantic Ocean, the catch per unit effort(CPUE) data were compiled from the International Commission for the Conservation of Atlantic Tunas and the Argo buoy data were downloaded from the Argo data center. The raw Argo buoy data were processed by data mining methods. The CPUE was standardized by support vector machine before analysis. We assumed the depths with the upper and lower limits of the optimum water temperatures of 15℃ and 9℃ as the preferred swimming depth, while the lower limit of the temperature(12℃) associated with the highest hooking rate as the preferred foraging depth(D12) of bigeye tuna during the daytime in the Atlantic Ocean. The preferred swimming depth and foraging depth range in the daytime were assessed by plotting the isobath based on Argo buoy data. The preferred swimming depth and vertical structure of the water column were identified to investigate the spatial effects on the CPUE by using a generalized additive model(GAM). The empirical cumulative distribution function was used to assess the relationship between the spatial distribution of CPUE and the depth of 12℃ isolines and thermocline. The results indicate that 1) the preferred swimming depth of bigeye tuna in the tropical Atlantic is from 100 m to 400 m and displays spatial variation; 2) the preferred foraging depth of bigeye tuna is between 190 and 300 m and below the thermocline; 3) the number of CPUEs peaks at a relative depth of 30 –50 m(difference between the 12℃ isolines and the lower boundary of the thermocline); and 4) most CPUEs are within the lower depth boundary of the thermocline levels(LDBT) which is from 160 m to 230 m. GAM analysis indicates that the general relationship between the nominal CPUE and LDBT is characterized by a dome shape and peaks at approximately 190 m. The oceanographic features influence the habitat of tropical pelagic fish and fisheries. Argo buoy data can be an important tool to describe the habitat of oceanic fish. Our results provide new insights into how oceanographic features influence the habitat of tropical pelagic fish and fisheries and how fisheries exploit these fish using a new tool(Argo profile data).     

The Large-Scale, Decelerating X-ray Jets from the Microquasar Xte J1550−564: Evidence for External Shocks Caused by the Jet-Ism Interaction?

Large-scale, decelerating, relativistic X-ray jets from microquasar XTE J1550−564 has been recently discovered with Chandra by Corbel et al. (2002). We find that the dynamical evolution of the approaching jet at the late time is consistent with the well-known Sedov evolutionary phase R∝ t ^2/5. A trans-relativistic external shock dynamic model by analogy with the evolution of gamma-ray burst remnants, is shown to be able to fit the proper-motion data of the approaching jet reasonably well. The inferred interstellar medium density around the source is well below the canonical value n _ISM∼1 cm⁻³. The rapidly fading X-ray emission can be interpreted as synchrotron radiation from the non-thermal electrons in the adiabatically expanding ejecta. These electrons were accelerated by the reverse shock (moving back into the ejecta) which becomes important when the inertia of the swept external matter leads to an appreciable slowing down of the original ejecta.     

甘南毕家山铅锌矿床地质特征与成因

该矿床由两种类型矿化组成:(1)与所谓“微石英岩”密切共生的成层碎屑矿;(2)层状矿下伏石灰岩顶部的网脉矿。矿石硫化物在同位素组成上与围岩中的黄铁矿显然不同,其δ~(34)S值( 15至 18)表明可能是海水来源的,由海水硫酸离子在较高温度下无机还原而成。矿石中的碳酸盐矿物以较低的δ~(13)C和较高的δ~(18)O值不同于围岩石灰岩,前者表明可能有深成碳参加,后者表明成矿流体可能在较高温度下与硅酸盐岩石达到了同位素平衡。氧化硅的δ~(18)O值很重,落入海相燧石的变化范围。区域内没有火山活动的确切证据,以海水来源为主的成矿流体可能是沿分开不同地层小区的区域性断裂循环并被加热的。     

The Origin of the Element Eu in Extremely Metal-poor Halo Stars

The fast neutron capture process (the r-process) occurs in the neutron-rich circumstance. However its concrete physical environment is not very clear. With recent progress in observations, many extremely metal-poor halo stars have been discovered. They have two characteristics: one is the overabundance of fast neutron elements with the relative abundance consistent with that of the sun; the other is that fast neutron element contents in stars at the same metal abundance have a very large dispersion. This provides a particular way to study the origin of the r-process. Simulation was used to study the galaxy's evolution process and the resulting dispersion of fast neutron nuclide contents in stars. The model of galaxy evolution obtained in this way not only contains spontaneous star formation in the gas region, but also includes the star formation excited by the supernova explosion. It is shown from our results that the supernovae at the low mass end should be the place producing the fast neutron nuclides. In addition, it is also shown that the non-uniformity of the galaxy evolution caused by the supernova explosion is not enough to explain the observed dispersion of fast neutron element contents in halo stars. This problem should be further studied.     

Effect of particle shape of glass beads on the strength and deformation of cemented sands

Acta Geotechnica - Few studies have focused on the influence of particle shape on the mechanical properties of cemented sand. To address this lack of information, this study investigated the...     

An empirical ensemble rainfall nowcasting model using multi-scaled analogues

Natural Hazards - Short-term rainfall prediction with high spatial and temporal resolution is of great importance to rainfall-triggered natural hazards such as landslide, flood, and debris flow. An...     

基于土地利用方式的巢湖流域氮排放情景模拟

土地利用方式及其转移对区域氮素迁移和水体氮负荷产生重要影响,但量化自然发展、耕地保护和生态保护等多情景下土地利用方式氮排放时空变化特征,揭示流域水体氮负荷对土地利用变化的响应机制仍面临挑战。本研究以巢湖流域为研究区,通过遥感解译多时相土地利用类型数据,借助PLUS和InVEST模型探索不同情景下氮排放对各土地利用类型变化的响应机制。结果表明:(1)2000—2020年期间,巢湖流域建设用地面积的增加(626.14 km²)主要占据的是耕地(减少了775.64 km²),城市化建设成为土地利用方式变化的主要驱动力;(2)PLUS模型多情景预测结果显示:2020—2030年间土地利用变化特征与2000—2020年基本保持一致,但各用地间的转换频率降低;(3)经InVEST模拟,耕地面积缩减而导致氮排放的减少量(340.17 t)大于建设用地等面积增加带来的氮排放增加量(170.11 t),使2000—2020年间巢湖流域土地利用所排放的总氮量呈降低趋势,由2000年的4768.04 t降至2020年的4597.98 t;(4)不同情景下,2030年各土地利用方式的氮排放量较2020年均呈降低趋势。其中,生态保护情景既有效地保障了巢湖流域生态功能又展现出较好的氮减排效果(113.36 t);鉴于此,建议流域管理部门应通过合理规划各用地类型的发展,严格控制建设用地对林草地、水域等生态用地的侵占,以期削减流域水体氮负荷、缓解氮素治理压力。