多波束测深海底混响仿真研究

海底混响是海洋混响的重要组成部分,采用模拟仿真进行验证分析,是仿真技术的一项重要应用。采用单元散射模型,研究在单发射阵元下,分布在同一直线上多个接收阵元接收的海底回波,忽略声波传播的相位起伏,只考虑振幅起伏,将传播损失、声吸收系数、海底反射损失、海底沉积层密度等参数带入海底混响仿真数学模型,仿真海底混响,使其更加接近海底的实际情况。     

基于相对风险模型的土地利用变化生态风险定量评价——以石羊河流域为例

土地利用是否合理是推进国民经济发展的关键,也是生态环境变化的风向标。通过理论研究和实地调研,构建了土地利用生态风险定量评价体系,借助相对风险模型（RRM）对石羊河流域的生态风险及其影响因素进行研究。结果表明：（1）在划分的3个评价单元中,中部绿洲生态保护区在土地利用中面临的生态风险最大,北部盆地防沙治沙区次之,南部山地水源涵养区生态风险最小;（2）在3大风险单元的6类不同风险源中,工程建设对石羊河流域的生态风险影响最大,其次是作物种植和畜牧养殖,且在自然环境相对较好的区域表现得尤为明显。     

Spatial difference and mechanisms of influence of geo-economy in the border areas of China

Border areas are both important territorial security barriers and portals to the outside world. Considering the complicated geopolitical environment of China’s inland borders, analysis of the current status and mechanisms of influence of geo-economy in border areas is of great significance. Namely, this analysis is important towards leveraging traditional advantages to accelerate China’s development in border and minority areas. Based on a comprehensive analysis, our study constructed a framework to analyze the geo-economy in border areas, and also introduced three indexes: local economy, export-oriented economy and local development. In addition, our study systematically described geo-economic evolution in the border areas of China. We also analyzed the mechanism of geo-economic spatial differentiation in these border areas by using geographical detectors. Our results indicated that the level of geo-economic influence in border areas has grown steadily with significant spatial differentiation. The absolute geo-economic dominance of Northeast China gradually declines over time. Areas with geo-economic advantages are highly dispersed, showing a spatial polarization pattern with several polar nuclei including Mudanjiang city (Northeast China), Baotou city (Inner Mongolia), Bortala Mongol Autonomous Prefecture (Xinjiang), Dehong Dai and Jingpo Autonomous Prefecture and the city of Chongzuo (Yunnan-Guangxi area). Geo-economics in border area is mainly influenced by national policies, the development level of neighboring countries, as well as the desire of these countries to cooperate with China in bilateral trade. Favorable policies, traffic, cultural proximity and other factors also impact the geo-economics of border areas significantly. The Inner Mongolia and Tibet areas are mainly influenced by neighboring countries, while Northeast China and Xinjiang are mainly affected by Chinese policies; the Yunnan-Guangxi area is influenced by a combination of these factors. At the end of the study, we provide our recommendations for developing policies that further geo-economic advantages in complex geopolitical environments and in areas with varied development.     

Automatic mapping of lunar landforms using DEM-derived geomorphometric parameters

Developing approaches to automate the analysis of the massive amounts of data sent back from the Moon will generate significant benefits for the field of lunar geomorphology. In this paper, we outline an automated method for mapping lunar landforms that is based on digital terrain analysis. An iterative self-organizing (ISO) cluster unsupervised classification enables the automatic mapping of landforms via a series of input raster bands that utilize six geomorphometric parameters. These parameters divide landforms into a number of spatially extended, topographically homogeneous segments that exhibit similar terrain attributes and neighborhood properties. To illustrate the applicability of our approach, we apply it to three representative test sites on the Moon, automatically presenting our results as a thematic landform map. We also quantitatively evaluated this approach using a series of confusion matrices, achieving overall accuracies as high as 83.34% and Kappa coefficients (K) as high as 0.77. An immediate version of our algorithm can also be applied for automatically mapping large-scale lunar landforms and for the quantitative comparison of lunar surface morphologies.     

A simplified analytical model for run-out prediction of flow slides in municipal solid waste landfills

Flow slides in municipal solid waste (MSW) landfills are common geoenvironmental issues in the urban environment and can pose a serious threat to the surrounding population and infrastructure. Prediction of the maximum run-out distance of flow slides in MSW landfills is therefore an essential part of hazard and risk assessment in engineering design. Based on the framework for simple analysis originally developed by Hungr (1995), we propose a simplified analytical model for calculating dam breaks in a plastic fluid along a single inclined base. In the proposed model, a quarter-elliptical shape is used to describe the approximate configuration of the flow slide. Following this step, the physical laws relating to the conservation of mass and energy are used to calculate the potential flow. Of additional note is a boundary condition in mathematics relating to this simplified analytical model, which is also reported in this study. Taking the obvious mobility characteristics of the MSW at point of failure into consideration, a three-phase simplified model along double inclined bases has been further developed for run-out prediction of the flow slide in MSW landfill. The proposed three-phase model is then applied to estimate the maximum run-out distance of two typical flow failures of landfills located in Sarajevo and Bandung, which demonstrate the capability of the proposed simplified analytical model for use in hazard assessments of landfills.     

Geochronological data of igneous and metamorphic rocks from the Xing’an-Mongolia Orogenic Belt of the eastern Central Asian Orogenic Belt: implications for the final closure of the Paleo-Asian Ocean

International Journal of Earth Sciences - In order to better constrain the evolution of the Xing’an-Mongolia Orogenic Belt and the resulting closure of the Paleo-Asian Ocean, we conducted an...     

内蒙古突泉县牤牛海地区超镁铁质岩地球化学及源区特征

内蒙古突泉县牤牛海地区发育超镁铁质岩,主要岩石类型为蛇纹石化橄榄岩、辉石橄榄岩、异剥辉石橄榄岩和蛇纹岩,局部蛇纹岩中可见显微鬣刺假象结构,包括蛇纹石呈假像的柱状中空骸晶结构、鱼骨状或羽状结构。岩石化学具有高镁(w(MgO)为33.63%~39.44%)、铬(2 200×10~(-6)~17 200×10~(-6))、镍(1 900×10~(-6)~3 000×10~(-6)),高CaO/Al_2O_3(0.56~39.01,平均为7.05),低钛(w(TiO_2)为0.01%~0.02%)、低铝(w(Al2O3)为0.03%~0.36%)、低碱(w(K_2O+Na_2O)为0.03%~0.65%)特征,类似科马提岩;Mg#值(平均为87)与纯橄榄岩(86)接近;稀土元素(w(∑REE)为0.32×10~(-6)~2.79×10~(-6))明显低于大洋脊含量,轻稀土富集(LREE/HREE为2.80~16.68),Eu正异常明显(δEu为0.59~4.84);微量元素富集大离子亲石元素(LILE)Rb、Ba、Sr,亏损高场强元素(HFSE)Nb、P等。说明超镁铁质岩石岩浆源自亏损软流圈地幔,并受到俯冲流体交代作用,形成于岛弧环境。牤牛海超镁铁质岩与西部包括突泉围场、好老鹿场、超日海乌拉、梅劳特乌拉、苏尼特左旗二道井一带超镁铁质岩共同构成一条近东西向展布的超镁铁质岩(蛇绿岩)带,通过地质建造分析,认为该构造带可能为华北板块与西伯利亚板块最终缝合带。     

全球前寒武—寒武系含油气盆地石油地质特征及成藏主控因素

前寒武—寒武系油气作为我国中西部含油气盆地未来油气勘探的重要接替领域,近年来受到广泛关注。本文以阿曼和东西伯利亚盆地为例,阐述全球典型前寒武—寒武系古老含油气盆地石油地质特征及成藏主控因素,为国内前寒武—寒武系油气勘探取得进一步突破提供参考。阿曼和东西伯利亚盆地烃源岩主要发育在盆地初始裂陷作用区,受埋深及地温梯度控制,在志留纪或泥盆纪之前就已大量生油;储集层岩性以砂岩为主,分布面积广,受表生风化淋滤、胶结物溶蚀及构造裂缝改造等后期作用影响,可形成优质区域性储层;优质的区域性盖层是前寒武—寒武系古老油气藏得以保存的关键性因素,盆地膏盐岩累计厚度都超过1 000m。塔里木盆地寒武系盐下深层含油气层系,同国外古老含油气盆地相比,同样具有多套高丰度优质烃源岩生烃、厚层区域性膏盐岩封堵及长距离运移、多层系成藏特征,具有良好的油气勘探潜力。     

Greenhouse gases abatement by catalytic dry reforming of methane to syngas over samarium oxide-supported cobalt catalyst

Anthropogenic activities often result in the emissions of methane (CH₄) and carbon dioxide (CO₂) which are the principal components of greenhouse gases. The mitigation of these gases to avert further occurrence of global warming has attracted a lot of research interest. In this study, the potential of greenhouse gases abatement via catalytic CO₂ (dry) reforming of methane to syngas over samarium oxide-supported cobalt (20 wt% Co/80 wt% Sm₂O₃) catalyst was investigated. The 20 wt% Co/80 wt% Sm₂O₃ material was synthesized via wet impregnation method and characterized using different instrument techniques. The methane dry reforming reaction, as well as its kinetics over the catalyst, was studied in a stainless steel fixed-bed continuous flow reactor at feed (CH₄:CO₂) ratios range of 0.1–1.0, temperature range of 923–1023 K and gas hourly space velocity (GHSV) of 30,000 h^?1. The 20 wt% Co/80 wt% Sm₂O₃ catalyst showed promising catalytic activity evident from the highest CH₄ and CO₂ conversion of ~71 and ~74% as well as the highest hydrogen (H₂) and carbon monoxide (CO) yield of ~62 and ~73%, respectively. Moreover, the methane dry reforming over the 20 wt% Co/80 wt% Sm₂O₃ catalyst produces H₂/CO ratio close to unity hence suitable for use as a chemical intermediate for synthesis of oxygenated fuels. The kinetic data obtained from the methane dry reforming were fitted to power law model. Apparent activation energies of 88.62, 80.12, 108.12 and 100.91 kJ mol^?1 were obtained for CH₄, CO₂, H₂ and CO, respectively. The characterization of the spent 20 wt% Co/80 wt% Sm₂O₃ catalyst after 4 h of time-on-stream has confirmed the presence of amorphous carbon which can easily be gasified.     

Numerical simulation on excavation-induced damage of rock under quasi-static unloading and dynamic disturbance

During the excavation of underground opening, the rock may experience a complex loading path that includes the highly confined compression before excavation, unloading of confining stress and further disturbance of dynamic loading after excavation. By using Rock Failure Process Analysis for Dynamics (RFPA-Dynamics), the failure of rock sequentially subjected to this complex loading path is numerically simulated, in order to examine the rock failure mechanism induced by excavation. The RFPA-Dynamics is firstly used to reproduce the failure of rock under confined compression, followed by unloading of confining pressure, and it is validated against with the existing experimental observation. Then, the failure characteristics of rock specimen sequentially subjected to the quasi-static triaxial loading, unloading of confining pressure and dynamic disturbance are numerically simulated, where the effect of magnitude of axial loading and confining pressure, and duration and amplitude of the dynamic disturbance on the final failure patterns of rock are examined. The numerical results indicate that the arc-shaped spalling damage zone is prone to develop with the increase in the axial pressure and lateral pressure coefficient. As for the effect of dynamic disturbance, the contribution of duration and amplitude of dynamic disturbance on the energy input are similar, where the area of damage zone increases with the energy input into the rock specimen. In this regard, the area of the damage zone is influenced by both the magnitude of in situ stress and waveform of dynamic disturbance. This study denotes that it is of great significance to trace the complex loading path induced by excavation in order to capture the rock failure mechanism induced by underground excavation.