Influence of Stress on Void Ratios of Compacted Crushed Rock Masses in Coal Mine Gobs     

Hu  Shengyong  Han  Dandan  Feng  Guorui  Zhang  Ao  Hao  Guocai  Hu  Lanqing  Zhu  Liping  Li  Bo 《Natural Resources Research》2020,29(2):1361-1373

The transfer and evolution of stress among rock blocks directly change the void ratios of crushed rock masses and affect the flow of methane in coal mine gobs. In this study, a Lagrange framework and a discrete element method, along with the soft-sphere model and EDEM numerical software, were used. The compaction processes of rock blocks with diameters of 0.6, 0.8, and 1.0 m were simulated with the degrees of compression set at 0%, 5%, 10%, 15%, 20%, and 25%. This study examines the influence of stress on void ratios of compacted crushed rock masses in coal mine gobs. The results showed that stress was mainly transmitted downward through strong force chains. As the degree of compression increased, the strong force chains extended downward, which resulted in the stress at the upper rock mass to become significantly higher than that at the lower rock mass. It was determined that under different degrees of compression, the rock mass of coal mine gobs could be divided, from the bottom to the top, into a lower insufficient compression zone (ICZ) and an upper sufficient compression zone (SCZ). From bottom to top, the void ratios in the ICZ sharply decreased and those in the SCZ slowly decreased. Void ratios in the ICZ were 1.2–1.7 times higher than those in the SCZ.

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Geological Control of Fold Structure on Gas Occurrence and Its Implication for Coalbed Gas Outburst: Case Study in the Qinan Coal Mine,Huaibei Coalfield,China     

Zhang  Kaizhong  Wang  Liang  Cheng  Yuanping  Li  Wei  Kan  Jin  Tu  Qingyi  Jiang  Jingyu 《Natural Resources Research》2020,29(2):1375-1395

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3D Mineral Prospectivity Mapping with Random Forests: A Case Study of Tongling,Anhui, China     

Xiang  Jie  Xiao  Keyan  Carranza  Emmanuel John M.  Chen  Jianping  Li  Shi 《Natural Resources Research》2020,29(1):395-414

Natural Resources Research - In the past few decades, a variety of data-driven predictive modeling techniques has led to a dramatic advancement in mineral prospectivity mapping (MPM). The random...  相似文献   

A case study on Landscape Component Niche based on Landscape Pattern Indices: Yanchi,Ningxia Province,China     

XiaoNing Zhang  XueLu Liu  Ghanney Philip  XiaoDan Li  QuanXi Wang  YaNan Xu  TingTing Hui 《寒旱区科学》2020,(1):22-33

Yanchi County is located in the agro-pastoral ecotone and belongs to the ecologically fragile area of Northwest China.It is important to study the evolution of landscape pattern to curb its environmental degradation.In order to intuitively show how the landscape pattern of the study area changes over time,Landsat Thematic Mappers(TM)and Landsat Operational Land Imager(OLI)data of 1991,2000,2010 and 2017 were used.This paper attempts to apply niche theories and methods into landscape ecology,and constructs a niche model of landscape components by using"n-dimentional hypervolume niche theory"and landscape pattern indices.By evaluating the spatial and temporal evolution of niche from the perspective of two-dimensional space to reflect the changes of landscape pattern in the study area over the past 26 years,new theories and methods were introduced for the characterization of landscape pattern.The results indicate that:1)The larger the attribute and dominance value of landscape components,the higher the ecological niche and the stronger the control effect on the overall landscape.2)The ecological niche of each landscape component was significantly different,just as its control effect on the overall landscape.3)The dynamic change of the ecological niche of each landscape component was different,with grassland,unused land and arable land always in a high dominant position,although the ecological niche of construction land and water area was always low.In general,the introduction of niche theory into the landscape ecology provided a new method to study the changes in regional landscape pattern.  相似文献   

Fast genetic mapping in barley: case studies of cuticle mutants using RNA-sequencing     

XiaoFeng Li  Chao Li  Qin Zhou  GuoXiong Chen  PengShan Zhao 《寒旱区科学》2020,12(3):180-188

Barley(Hordeum vulgare L.) is one of the earliest domesticated crop species and ranked as the fourth largest cereal production worldwide. Forward genetic studies in barley have greatly advanced plant genetics during the last century; however, most genes are identified by the conventional mapping method. Array genotyping and exome-capture sequencing have also been successfully used to target the causal mutation in barley populations, but these techniques are not widely adopted because of associated costs and partly due to the huge genome size of barley. This review summarizes three mapping cases of barley cuticle mutants in our laboratory with the help of RNA-sequencing. The causal mutations have been successfully identified for two of them and the target genes are located in the pericentromeric regions. Detailed information on the mapping-by-sequencing, mapping-and-sequencing, and RNA-sequencing assisted linkage mapping are presented and some limitations and challenges on the mapping assisted by RNA sequencing are also discussed. The alternative and elegant methods presented in this review may greatly accelerate forward genetics of barley mapping, especially for laboratories without large funding.  相似文献   

甘南高原乡村社会固有脆弱性及其影响因素   总被引：2，自引：1，他引：1  

李花  赵雪雁  王伟军  李巍 《地理科学》2020,40(5):804-813

开展社会固有脆弱性研究不仅有助于了解区域社会系统的可持续发展状态,更有助于寻求提高社会系统适应能力的恰当策略。通过构建乡村社会固有脆弱性分析框架和评价指标体系,并以甘南高原为研究区,在分析乡村社会固有脆弱性特征的基础上识别了其关键影响因子。结果表明：① 甘南高原乡村社会固有脆弱性呈“梭型”分异,其中,高、中、低脆弱性乡镇分别占18.95%、47.37%、33.68%。② 社会固有脆弱性存在明显的区域差异性,从农区-半农半牧区-牧区、高山峡谷区-山地丘陵区-山原区,社会固有脆弱性趋于增加;同时,随着少数民族聚居度降低、经济发展水平升高,社会固有脆弱性趋于降低。③ 社会固有脆弱性在空间上呈“北高南低”的不均衡分布,敏感性呈“中间高四周低”的集聚分布,适应能力呈相对均衡的“碎片化”分布。④ 气温、生育结构、民族结构、住房安全性、社会弱势群体比重、经济条件、信息可得性和参保比例是影响社会固有脆弱性的关键因子。最后,提出相应的对策建议。  相似文献   

辽宁省春玉米全育期的气候适宜度及年景评估     

曹永强  齐静威  王菲  李玲慧  路洁 《地理科学》2020,40(7):1210-1220

为评价气候变化对玉米生长的影响，以辽宁省为例选取1969—2018年18个气象站点的逐日实测气象数据，利用模糊数学法建立春玉米气候适宜度评估模型，以地理信息技术为依托，探究春玉米气候适宜度的时空特征，并在此基础上进行玉米气候年景的综合评估。结果表明：① 辽宁省春玉米全生育期内日照、温度、降水适宜度波动幅度较大；然而春玉米种植气候适宜度的空间差异性较弱。② 春玉米各生育期气候适宜度由高到低为：出苗期>开花期>成熟期>播种期。全生育期温度适宜度最高，日照适宜度次之，降水适宜度最低。③ 春玉米播种期、出苗期、开花期和成熟期的气候适宜度最高值分别出现在辽阳、葫芦岛、营口和铁岭。④ 春玉米气候年景准确率达64%，表明该评估方法可以较为准确地反映气候年景。近50 a辽宁省春玉米偏好的年景有4个年份（1971、1979、1993、1998年），较差的有1969年（4.98%）及1973年（5.59%）。  相似文献   

大城市近郊农地流转的时空特征及影响因素     

许红梅  郭炎  李志刚  林赛南  李娈琼 《地理科学》2020,40(12):2055-2063

以武汉市蔡甸区为例，结合多源、多时段的村级农地流转数据，采用探索性空间分析和多元线性回归分析方法，揭示大城市近郊农地流转的时空特征及影响因素。研究发现：① 流转规模呈跨越式增长，经历快速增长和短期减速增长两个阶段，流转速度受土地政策影响较大；农地流转的空间分布由随机转向集聚，高高集聚区由主干道沿线转移至以农业为主的平原街镇，低低集聚区由不显著到集中于城镇化水平较高的街镇；② 控制自然、区位、社会经济等因素后，发现流转主体、流转用途对农地流转具有显著影响。建议清楚把握农地流转时空演化特征，合理选择流转主体和流转用途，以优化大城市近郊的人地关系，促进城乡统筹和乡村振兴。  相似文献   

依托乡土资源建构地理问题链教学——以“沙溪河的水循环”为例     

李春军 《地理教学》2020,(7):38-40,37

以学生家乡的河流——沙溪河这一乡土资源为载体,在“自然界的水循环”教学中融入家国情怀、建构地理问题链,实现深度教学的目的。在问题链的建构过程中要依据学情,找准设计落点;围绕问题教学,建构基本框架;基于地理思维,丰富表现形式。  相似文献   

新疆S214公路台特玛湖干涸湖盆段风沙危害及防治     

蔡东旭  李生宇  王海峰  俞祥祥  王世杰  徐新文 《中国沙漠》2020,40(1):1-11

新疆S214（考干-米兰，考米线）公路位于库鲁克塔格沙漠东南缘，穿越台特玛湖干涸湖盆。由于该区气候干旱，风力强劲，沙源丰富，流动沙丘广布且快速移动，风沙危害对公路运输构成严重威胁。通过对风沙环境和风沙危害定位观测和土壤水盐特征系统调查，确定了风沙危害极为严重的公路区段，提出了合理的风沙防护措施及防沙体系结构。结果表明：该区具有明显的单风向风况，主要盛行ENE和NE风，偶有反向风沙活动，起沙风频率、输沙势、输沙率极高，属于高能-大比率风能环境；受土壤水分、盐分含量影响，地表紧实度差异较大，部分地段为极疏松的沙层，部分地段为紧实的盐壳；S214公路风沙危害防护区段为K4+900~K18+200，设计建造的阻-固-输相结合的机械-植物复合防沙体系，防沙效果明显，保障了道路安全运营。这一强风沙、高盐区公路防沙体系建设模式可为类似环境地区工程防沙提供借鉴。  相似文献