Distribution Characteristics of In Situ Stress Field and Vertical Development Unit Division of CBM in Western Guizhou,China

In situ stress is not only a vital indicator for selecting explorative regions of coalbed methane (CBM), but also a pivotal factor affecting CBM production. The present study explored whether in situ stress affected the development potential of CBM in western Guizhou, China. To this end, we collected injection/falloff well test data and gas content data from 70 coal seams in 28 wells. The study found that from top to bottom, strike slip fault stress fields (<?500 m), normal fault stress fields (500–1000 m) and strike slip fault stress fields (>?1000 m) were successively developed in western Guizhou. The distribution features of vertical permeability in western Guizhou are consistent with the stress fields' transformation location. The coal permeability in the western part in Guizhou presents a tendency of increase followed by decrease as a result of increased burial depth. The vertical development characteristics of coal seam gas content are controlled mainly by reservoir pressure, and the relationship between reservoir pressure and buried depth shows a linear increase. The CBM in western Guizhou is divided vertically into three development potential regions dependent on the characteristics of burial depth, permeability and gas content of coal seams. The most favorable vertical development potential region in western Guizhou is 500–1000 m. This region exhibits high gas content, high permeability and moderate burial depth, which are favorable for the production of CBM. These research results can provide basis for geological selection and engineering implementation of CBM in western Guizhou.

     

金矿资源定量预测的粗糙集方法

矿产信息是各种成矿相关信息的综合体现,为了有效地提取成矿预测综合信息,有必要客观地筛选原始观测信息,突出成矿密切相关的致矿因子。粗糙集不需要数据的附加信息或先验知识,在知识库分类能力不变的前提条件下,删除无关或不重要的属性,能对决策系统进行有效约简。提出基于粗糙集理论进行集成化预测模型研究的新方法,基于粗糙集思想提取与成矿密切相关的特征矿化信息,获取最佳变量组合及区间值,并将其作为参量建立预测模型,结合经典矿床统计预测聚类方法确定代判临界值,及特征分析方法对矿产资源进行定量预测,确立了8个成矿有利单元,与研究区勘查工程资料基本吻合,表明该方法能够有效降噪,简化模型,为靶区预测提供准确的依据。     

Using Multivariate Statistical and Geostatistical Methods to Identify Spatial Variability of Trace Elements in Agricultural Soils in Dongguan City,Guangdong,China

Dongguan (东莞) City, located in the Pearl River Delta, South China, is famous for its rapid industrialization in the past 30 years. A total of 90 topsoil samples have been collected from agricultural fields, including vegetable and orchard soils in the city, and eight heavy metals (As, Cu, Cd,Cr, Hg, Ni, Pb, and Zn) and other items (pH values and organic matter) have been analyzed, to evaluate the influence of anthropie activities on the environmental quality of agricultural soils and to identify the spatial distribution of trace elements and possible sources of trace elements. The elements Hg, Pb, and Cd have accumulated remarkably here, incomparison with the soil background content of elements in Guangdong (广东) Province. Pollution is more serious in the western plain and the central region, which are heavily distributed with industries and rivers. Multivariate and geostatistical methods have been applied to differentiate the influences of natural processes and human activities on the pollution of heavy metals in topsoils in the study area. The results of cluster analysis (CA) and factor analysis (FA) show that Ni, Cr, Cu, Zn, and As are grouped in factor F1,Pb in F2, and Cd and Hg in F3, respectively. The spatial pattern of the three factors may be well demonstrated by geostatistical analysis. It is shown that the first factor could be considered as a natural source controlled by parent rocks. The second factor could be referred to as "industrial and traffic pollution sources". The source of the third factor is mainly controlled by long-term anthropic activities ,ad a consequence of agricultural fossil fuel consumption and atmospheric deposition.     

亚热带城市湖泊与河流CO2气体通量特征及其影响因素

湖泊、河流等内陆水体是连接陆地生态系统和海洋的“长程碳环路”的重要节点,也是温室气体二氧化碳(CO₂)排放源,在调节陆地、海洋间的碳迁移转换中发挥着重要作用。相对于自然水体,城市水体因面积小、水深浅且受监测方法限制,水-气界面碳通量经常被忽略。为探讨我国亚热带城市水体温室气体排放特征,本研究以湖南省长沙市典型城市水体,包括洋湖、西湖、松雅湖、月湖4个湖泊和湘江长沙段为研究对象,分别于2022年4和10月采用光化学反馈-腔增强吸收光谱法(OF-CEAS)和扩散模型法对水-气界面CO₂通量进行对比测定。结果表明,长沙城市湖泊与河流春季为CO₂排放源,秋季为吸收汇,河流水-气界面CO₂通量呈显著季节差异。河湖之间CO₂通量在春季表现为显著差异,秋季差异不显著。CO₂通量与水体溶解氧、水体总氮浓度等呈显著正相关。2种方法的CO₂通量对比测定在湖泊上显著相关,但对河流而言相关性不显著。研究揭示的城市湖泊与河流CO₂气体的排放特征有利于深入探究城市水体碳的迁移转化,可对全面了解全球气候变化过程和河湖湿地温室气体减排和调控提供科学支撑。     

Double-diffusive fluxes of salt and heat in the upper layer of north pacific intermediate water

Almost half of the oceanic water columns exhibit double-diffusion. The importance of double-diffusion in global oceans‘ salt and heat fluxes, water-mass formation and mixing, and circulation is increasingly recognized. However, such an important physical process in the ocean has not been well studied. One of the reasons is the difficulty of parameterizing and quantifying the processes. The paper presented here attempts to quantify the double-diffusive fluxes of salt and heat in the ocean. Previous qualitative analysis by applying the water-mass Turner angle, mTu, to the North Pacific Intermediate Water (NPIW) layer showed a favorable condition for salt-fingering in the upper NPIW due to the overlying warm/salty water above the cold/fresh NPIW core, and a doubly-stable condition in the lower NPIW where potential temperature decreases with depth while salinity increases, inducing double stratification with respect to both potential temperature and salinity. The present study gives a quantitative estimate of double-diffusive fluxes of salt and heat contributed by salt-fingering in the upper NPIW layer.     

北黄海东部坳陷中生界储层特征

北黄海盆地东部坳陷中生界砂岩以细砂-粉砂岩为主,夹少量砂砾岩,岩石学类型以长石砂岩、长石岩屑砂岩为主,储集空间以次生溶蚀孔及裂缝为主,孔喉结构为细小孔隙、细喉-微细喉,属于低孔低渗储层。通过对物性影响因素分析,发现裂缝、沉积相带、成岩作用是控制本区砂岩储层质量的主要因素。     

基于植被盖度和高度的不同退化程度高寒草地地上生物量估算

由于气候变化和不合理的人类活动,20世纪80年代以来青藏高原高寒草地发生严重退化。地上生物量是评价草地退化的直观指标。通常采用植被盖度和高度来估算草地地上生物量,但草地退化后,植被盖度和高度与地上生物量之间的关系是否会发生变化目前还不清楚,这影响着退化草地生物量估算的精度。通过多元回归分析研究了青藏高原中部和东北部高寒草甸、高寒草原在不同退化程度下植被盖度和高度与地上生物量的关系。结果表明：（1）高寒草甸与高寒草原地上生物量整体上及不同退化阶段都没有显著差异（P>0.05）。（2）随着退化程度的加剧植被盖度和高度对地上生物量的影响也发生改变,体现在未退化阶段地上生物量主要受植被高度影响,退化后主要受植被盖度影响。（3）无论是高寒草甸还是高寒草原分退化程度的回归模型估算结果都较不分退化程度模型估算的生物量更接近实测值。我们建议在退化高寒草地研究中采用盖度和高度估算生物量时,根据退化阶段采用不同的估算模型。     

Research of Power Take-off System for “Sharp Eagle Ⅱ” Wave Energy Converter

The "Sharp Eagle" device is a wave energy converter of a hinged double floating body. The wave-absorbing floating body hinges on the semi-submerged floating body structure. Under the action of wave, the wave-absorbing floating body rotates around the hinge point, and the wave energy can be converted into kinetic energy. In this paper, the power take-off system of "Sharp Eagle II" wave energy converter(the second generation of "Sharp Eagle") was studied, which adopts the hydraulic type power take-off system. The 0-1 power generation mode was applied in this system to make the "Sharp Eagle II" operate under various wave conditions. The principle of power generation was introduced in detail, and the power take-off system was simulated. Three groups of different movement period inputs were used to simulate three kinds of wave conditions, and the simulation results were obtained under three different working conditions. In addition, the prototype of "Sharp Eagle II" wave energy converter was tested on land and in real sea conditions. The experimental data have been collected, and the experimental data and simulation results were compared and validated. This work has laid a foundation for the design and application of the following "Sharp Eagle" series of devices.     

M2 Tidal Current Estimation from One-day Observation Data off the Western and Southern Coasts of Korea

Ocean Science Journal - A practical method to estimate the M2 tidal current is proposed based on one-day current observations. In this method, the semi-diurnal constituent, composed of several...     

Experimental study on characteristics of trapping and regulating sediment with an open-type check dam in debris flow hazard mitigation

Beam dams are a highly effective and commonly used open-type check dam in debris-flow hazard mitigation. In this study, dimensional analysis was used to obtain empirical equations for quantitatively determining the sediment-trapping and flow-regulating characteristics of a beam dam. To determine the coefficients of the empirical equations, flume experiments were conducted to simulate the trapping and regulating processes. The flow pattern, trapping, and regulating characteristics were investigated when debris flows passed through a beam dam. Debris-flow bulk density and peak discharge, and sediment-trapping ratios, were measured directly and indirectly. The results showed that three blocking actions occurred, and that blockage-breaking considerably influenced the trapping and regulating performance of the beam dam. The relative opening size and the sediment concentration were the two main factors affecting the performance of the beam dam. The ratio of trapping sediment decreased with relative opening, and increased with sediment concentration as well as reducing ratio of bulk density and reducing ratio of peak discharge. The sediment concentration and relative opening were the leading factors influencing the trapping and regulating sediment of a beam dam, followed by flume gradient. The results showed that the calculated values obtained using empirical equations were in good agreement with the values derived from the experiments, and that the deviation was acceptable. Finally, taking Zechawa Gully as an example, using the empirical equations we designed the opening size of a beam dam aimed to trap sediment and regulate peak discharge of debris flow in the main gully.