Numerical analysis of stability for mined-out area in multi-field coupling

There were differences between real boundary and blast hole controlling boundary of irregular mined-out area in underground metal mines. There were errors in numerical analysis of stability for goaf, if it was analyzed as regular 3D mined-out area and the influence of coupling stress-seepage-disturbance was not considered adequately. Taking a lead zinc mine as the background, the model was built by the coupling of Surpac and Midas-Gts based on the goaf model precisely measured by CMS.According to seepage stress fundamental equations based on the equivalent continuum mechanical and the theory about equivalent load of dynamic disturbance in deep-hole blasting, the stability of mined-out area under multi-field coupling of stress-seepage-dynamic disturbance was numerically analyzed. The results show that it is more consistent between the numerical analysis model based on the real model of irregular 3D shape goaf and the real situation, which could faithfully reappear the change rule of stress–strain about the surrounding rock under synthetic action of blasting dynamic loading and the seepage pressure. The mined-out area multi-field coupling formed by blasting excavation is stable. Based on combination of the advantages of the CMS,Surpac and Midas-Gts, and fully consideration of the effects of multi-field coupling, the accurate and effective way could be provided for numerical analysis of stability for mined-out area.

Numerical simulation for influence of excavation and blasting vibration on stability of mined-out area

Dynamic analysis steps and general flow of fast lagrangian analysis of continua in 3 dimensions(FLAC3D) were discussed. Numerical simulation for influence of excavation and blasting vibration on stability of mined-out area was carried out with FLAC3D. The whole analytical process was divided into two steps, including the static analysis and the dynamic analysis which were used to simulate the influence of excavation process and blasting vibration respectively. The results show that the shape of right upper boundary is extremely irregular after excavation, and stress concentration occurs at many places and higher tensile stress appears. The maximum tensile stress is higher than the tensile strength of rock mass, and surrounding rock of right roof will be damaged with tension fracture. The maximum displacement of surrounding rock is 4.75 mm after excavation. However, the maximum displacement increases to 5.47 mm after the blasting dynamic load is applied. And the covering area of plastic zones expands obviously, especially at the foot of right upper slope. The analytical results are in basic accordance with the observed results on the whole. Damage and disturbance on surrounding rock to some degree are caused by excavation, while blasting dynamic load increases the possibility of occurrence of dynamic instability and destruction further. So the effective supporting and vibration reducing measures should be taken during mining.

Instability identification on large scale underground mined-out area in the metal mine based on the improved FRBFNN

To identify the instability on large scale underground mined-out area in the metal mine effectively,the parameters of radial basis function were determined through clustering method and the improved fuzzy radial basis function neural network(FRBFNN)model of instability identification model about large scale underground mined-out area in the metal mine was built.The improved FRBFNN model was trained and tested.The results show that the improved FRBFNN model has high training accuracy and generalization ability.Parameters such as pillar area ratio,filling level and the value of rock quality designation have strong influence on instability of large scale underground mined-out area.Correctness of analysis about the improved FRBFNN model was proved by the practical application results about instability discrimination of surrounding rock in large-scale underground mined-out area of a metal mine in south China.

Quantitative analysis of biotechnical reinforcement for a steep slope consisting of composite coal-gangue-soil medium adjacent to a mined-out area

The engineering and geological characteristics of a steep slope consisting of coal gangue, rock and soil medium in Huating coal mine have been comprehensively investigated. Owing to humid weather, heavy rainfall, vegetation and porous characteristics of the soil and rock mass, the steep slope will be destabilized and induce mud-rock flow or derive hazard easily. Firstly, based on the classical slope reinforcement theory, some regularity between the shear and displacement in the destabilized zone of the slope with or without root strength contribution is presented. Then, based on the experimental and statistical analysis of root strength, hydrological characteristics and stability status, etc., some possible biotechnical techniques for reinforcement of the steep slope have been suggested. These methods are important for quantitative analysis of destabilization of the slope and design of the biotechnical reinforcement.

Time function of surface subsidence based on Harris model in mined-out area

The surface subsidence is a common environmental hazard in mined-out area. Based on careful analysis of the regularity of surface subsidence in mined-out area, we proposed a new time function based on Harris curve model in consideration of the shortage of current surface subsidence time functions. By analyzing the characteristics of the new time function, we found that it could meet the dynamic process, the velocity change process and the acceleration change process during surface subsidence. Then its rationality had been verified through project cases. The results show that the proposed time function model can give a good reflection of the regularity of surface subsidence in mined-out area and can accurately predict surface subsidence. And the prediction data of the model are a little greater than measured data on condition of proper measured data quantity, which is safety in the engineering. This model provides a new method for the analysis of surface subsidence in mined-out area and reference for future prediction, and it is valuable to engineering application.

气候变化下菟丝子属3种植物在中国的潜在地理分布

菟丝子属(Cuscuta)植物因茎全寄生的特点全属均被列为检疫植物,探究菟丝子属植物在中国潜在空间分布特点对其防治有重要作用。本研究选取杯花菟丝子(C.cupulata)、原野菟丝子(C.campestris)、单柱菟丝子(C.monogyna)3种菟丝子属植物为研究对象,结合其已有地理分布记录932条、野外考察记录144条和20个环境变量,应用最大熵模型和Arc GIS,预测其在当前和未来(2041—2060年、2061—2080年)SSP2-4.5温室气体排放浓度场景下的潜在适生区分布,并将当前气候情景下菟丝子属3种植物的适生区与土地利用数据进行叠加分析。结果表明:(1)受试者工作特征曲线下的面积(AUC)均大于0.9,预测精度较高。(2)影响菟丝子属3种植物适生区分布的主要环境因子存在差异,但均是气候因子占主导,地形因子的贡献率相对较小。(3)当前气候情景下杯花菟丝子与单柱菟丝子适生区多分布于我国北方,而原野菟丝子适生区除了在北方有分布外亦在东南沿海有大面积覆盖,并且未来3种菟丝子属植物均表现出向我国北部扩张的趋势。(4)当前时期菟丝子属3种植物的适生区大部分土地已经被开发利用。

基于数值模拟高强度开采条件下天然气井受力及水平变形特征研究

针对煤-天然气同采区煤层高强度开采引起的覆岩移动变形导致气井失稳问题,基于小保当二号煤矿地质、开采技术条件及现场实测数据,通过数值模拟研究了超长超宽工作面高强度开采条件下,气井套管-水泥环组合体的剪切受力及水平变形特征,分析得到了沿套管轴向易发生变形的位置及岩层分布特征对气井稳定性的影响。结果表明,关键层以上至地表范围内覆岩以拉伸变形为主,关键层及下伏相邻岩层以剪切变形为主。倾向上132204-132206工作面多重采动影响下气井套管最大剪应力为208.5 MPa,为许用剪切强度255 MPa的81.76%,最大水平位移为87.3 mm。沿132205工作面走向留设180 m宽气井保护煤柱,工作面自二次切眼推进250 m后,套管达到最大剪应力169.5 MPa,为许用剪切强度的66.5%,最大水平位移为83.1 mm,留设180 m宽保护煤柱能够保障气井的完整性。研究结果对于合理确定小保当二号煤矿井田内其他气井保护煤柱尺寸、预防井筒失效、实现煤-天然气资源协同开发具有重要价值和意义。

跃层结构上下重叠区域模板支架搭设施工技术

在工程实践中,跃层结构的施工普遍会涉及部分上下重叠区域梁板模板支撑、混凝土浇筑的工况。在这种工况下,传统的现浇钢筋混凝土结构梁板施工工艺往往难以同时兼顾技术性与经济性。立足于甘肃庆阳金融中心商业综合体项目工程实例,应用一种约束构件,为模架立杆提供一条稳定的传力路线,保证局部两层模架搭设及使用过程中的安全性。以一种较为简便的机构,实现同时浇筑上下重叠区域楼板的混凝土。不仅满足了工程对安全、质量的要求,而且兼顾了项目进度及成本控制的需求。

大运河遗产区空间叠压下的乡镇发展困境与路径研究——以淮安市马头镇为例

随着乡村振兴战略的深入实施和国家对文化遗产价值的高度重视,加强大运河保护与乡镇地区发展的协同,对于促进历史文化传承和大运河沿线地区的可持续发展具有重要意义。清口枢纽作为大运河重要的文化遗产区,与马头镇存在特殊的空间叠压关系,并对其社会经济发展与空间格局塑造产生深刻影响。基于此展开研究,剖析清口枢纽保护利用与马头镇发展建设的关系脉络,揭示遗产区赋能马头镇发展的同时所引发的现实困境,针对性提出“空间解绑”的建设思路,并结合规划实践,提出坚守保护底线、传承文化价值、重塑空间格局、打造产业模式,构建清口枢纽与马头镇共兴共荣的路径,以期为此类乡镇地区发展建设提供借鉴。

Diversity analysis of soil dematiaceous hyphomycetes from the Yellow River source area:Ⅰ

Twenty-four soil samples of eight ecosystem-types around the Yellow River source area were investigated for the number and specific composition of soil dematiaceous hyphomycetes by dilution plate technique. And then the co-relationship between genus species of soil dematiaceous hyphomycetes and ecosystem-types was analyzed. The results show that the amount and species distribution of soil dematiaceous hyphomycetes had an obvious variability in different ecosystem-types, and that the dominant genus species varied in the eight ecosystem-types studied, with Cladosporium being the dominant genus in seven of the eight ecosystem-types except wetland. The index of species diversity varied in different ecosystem-types. The niche breadth analysis showed that Cladosporium had the highest niche breadth and distributed in all ecosystem-types, while the genera with a narrow niche breadth distributed only in a few ecosystem-types. The results of niche overlap index analysis indicated that Stachybotrys and Torula, Doratomyces and Scolecobasidium, Cladosporium and Chrysosporium had a higher niche overlap, whereas Arthrinium and Gliomastix, Phialophora and Doratomyces, Oidiodendron and Ulocladium had no niche overlap.

Spatial Pattern and Development of Protected Areas in the North-south Transitional Zone of China

The north-south transitional zone in China mainly consists of the Qinling-Daba Mountains. It is the most important West-East geo-ecological space in China, containing protected areas vital for biodiversity conservation and ecological security of China. The protection and rational development of its natural habitat is of great significance to China’s ecological security and integration of protected areas based on mountain forest ecosystems on a global scale. In this study, five important types of protected areas in the transitional zone were selected, and their spatial patterns were analysed. Spatial analysis methods, such as kernel density estimation and accessibility analysis, were employed for both point and areal data, and focused on four aspects: land use scale, shift in the centre of gravity, spatial agglomeration, and accessibility. In addition, policy background and evolution of spatial and temporal characteristics of the protected area system in the transitional zone from 1963 to 2017 were also examined. We analysed the characteristics and geographical significance of the West-east corridor using the spatial pattern of the protected area system from the perspective of ecological and economic spaces. We focused on spatial shape, type intersection, and key areas to analyse the spatial overlap of the protected areas. Protected area establishment was divided into three stages: initial(1956–1980), rapid development(1981–2013), and national park transformation(2014–present). These stages reflected the change in the concept of ‘simple protection—sustainable use—integration and upgrade’ for protected areas of China. The spatial centre of gravity of the protection zone system was located in the west Qinling-Daba Mountains, and its high-density core exhibited a relatively stable N-shaped structure composed of four gathering areas. Affected by factors such as geographic environment and socio-economic development density, the average access time for protected areas was high(1.56 h);wetland parks and scenic areas are located closer to the city centre. As the West-east corridor in the transitional zone extends from west to east, there is a clear spatial dislocation between the development of protected areas and the intensity of human activities. During development, differentiated goal orientation should be adopted based on the idea of zoning and classified governance. With the advancement of the construction of protected areas, the spatial overlap of protected areas in the transition zone has become more prominent. At present, the spatially overlapped protected areas in the transitional zone remain prominent, with inclusion overlap being the most common, and forest parks exhibiting the highest probability of overlap with other protected areas, we should focus on in the integration process of the corridor-type ecological space based on the mountain forest ecosystem.

Partially Overlapping Channel Assignment Using Bonded and Non-Bonded Channels in IEEE 802.11n WLAN

Nowadays,wireless local area network(WLAN)has become prevalent Internet access due to its low-cost gadgets,flexible coverage and hasslefree simple wireless installation.WLAN facilitates wireless Internet services to users with mobile devices like smart phones,tablets,and laptops through deployment of multiple access points(APs)in a network field.Every AP operates on a frequency band called channel.Popular wireless standard such as IEEE 802.11n has a limited number of channels where frequency spectrum of adjacent channels overlaps partially with each other.In a crowded environment,users may experience poor Internet services due to channel collision i.e.,interference from surrounding APs that affects the performance of the WLAN system.Therefore,it becomes a challenge to maintain expected performance in a crowded environment.A mathematical model of throughput considering interferences from surrounding APs can play an important role to set up a WLAN system properly.While set up,assignment of channels considering interference can maximize network performance.In this paper,we investigate the signal propagation of APs under interference of partially overlapping channels for both bonded and non-bonded channels.Then,a throughput estimation model is proposed using difference of operating channels and received signal strength indicator(RSSI).Then,a channel assignment algorithm is introduced using proposed throughput estimation model.Finally,the efficiency of the proposal is verified by numerical experiments using simulator.The results show that the proposal selects the best channel combination of bonded and non-bonded channels that maximize the performance.

淮北矿区多种类型植被地上生物量反演研究

生物量是植被碳的重要组成部分,对于评估矿山生态环境修复效果至关重要。在淮北矿业闸河矿区,生态破坏与修复并存,地表植被类型丰富多样,有林木、草本和农作物等。在这种多植被类型交叉覆盖的地区,传统的单一物种生物量模型难以应用。为准确反演该区域综合植被的生物量,以sentinel卫星数据为基础,利用植被指数和波段运算方法构建的光谱指数作为特征数据集,通过不同特征和模型的组合构建该区域生物量反演模型。在特征选择阶段,利用随机森林和相关性分析两种方法对特征进行综合评价,最终筛选出关键的5个光谱指数(增强植被指数、归一化差分水体指数、改进的归一化差分水体指数、Sentinel-2红边位置、陆地叶绿素指数)以及5个基于波段运算的自建光谱特征(1/B1、1/B2、1/B7、B1/B2、B5/B6)。基于这些筛选出的特征,设计了5种不同的特征组合方案,并结合传统方程回归和机器学习模型,在林地和综合植被数据上分别构建了生物量反演模型。研究结果表明,相较于传统回归模型,机器学习模型在生物量反演领域具有更高的精度。基于波段运算的自建光谱特征可以提高机器学习模型生物量反演的精度,其中支持向量回归(SVR)模型结合自建光谱特征与原始波段得到的反演结果精度最高,模型验证集的决定系数R^(2)为0.74,均方根误差为8.14kg·m^(-2)。将SVR模型应用于研究区进行生物量反演,得到的结果与当地植被分布特征高度一致。本研究成果不仅为矿区生态修复评价提供了数据支撑,而且为类似生态系统的后续研究提供了借鉴和经验。

模型低晃动的无标识增强现实系统

基于视觉SLAM的无标识增强现实,提出了一种优化的无标识增强现实方法。在平面拟合前增加了基于点云重叠率的点云拼接模块,使得连续帧拟合平面过渡更为平滑;平面拟合阶段在主成分分析法的基础上结合自适应阈值的RANSAC算法,剔除点云数据中的异常值和粗差,以提高平面拟合精度。测试结果表明该方法具有更高的拟合精度和稳定性。

一种基于证据多视角的模糊C-means聚类算法

针对传统多视角聚类算法难以准确识别噪声和有效划分类间重叠区域样本的问题,提出一种基于证据多视角的模糊C均值(evidential multi-view fuzzy C-means,EMVFCM)聚类算法。首先,在证据推理框架下,研究一种改进的模糊C-means多视角聚类算法,通过优化改进的目标函数获得待测样本属于单类和噪声的信任值,从而识别出噪声数据。然后,由于重叠区域的样本不能被准确地划分类别,所以将其划分到相对应的复合类,这不仅能够表征数据样本类别的不精确性,还能降低错误分类的风险。最后,通过人工数据集和UCI数据集验证本文算法的性能并与相关算法对比。实验结果表明,本文算法较传统多视角聚类算法能更有效地处理数据中的噪声和重叠样本难以准确划分的问题。

南太行自然保护地空间分布格局及交叉重叠关系研究

以南太行地区5种类型99处国家级和省级自然保护地为研究对象,运用最邻近点指数、地理集中指数和核密度分析法并借助GIS的空间分析功能,对南太行自然保护地的空间分布特征以及交叉重叠情况进行定性和定量分析。结果表明,南太行自然保护地森林公园的数量最多,自然保护区面积最大,长治市内的保护地分布数量最多,整体呈集聚的空间分布类型;其保护地按照密度值可分为3档,大多为点状分布,高密度区主要呈带状和团块状分布在南太行东部地带及部分南部地区;99处保护地中存在27处交叉重叠,风景名胜区交地质公园是最多的重叠类型。

基于树冠重叠面积的天然混交林林木竞争指数

构建基于树冠重叠面积和林木混交关系的竞争指数,探究天然混交林林分及主要树种竞争的表达方法,并以甘肃省小陇山林区锐齿槲栎天然混交林为研究对象,采用胸径、树高、冠幅、距离等信息的2期调查数据,对新构建的基于树冠重叠面积的天然混交林林木竞争(CIM)指数进行验证,并选取Spearman系数,对CIM竞争指数和传统竞争指数进行相关性分析。结果表明,采用树冠投影重叠和考虑树高关系确定竞争木的方法能有效避免竞争木多选或漏选;CIM1、CIM2、CIM3能够表达出混交林竞争压力变化,表现出竞争压力越大林木蓄积生长量越小的趋势,将树种混交因子引入竞争指数能够提高蓄积生长量与竞争指数的相关性,更加客观的描述林分中竞争状况。竞争指数与蓄积生长量相关性由大到小排序为CIM2>CIM3>CIM1>Bella竞争指数(CIO)>简单竞争指数(CI)>CIO_(2)>CIO1,表明竞争指数CIM2对混交林竞争表达更具参考意义。林分中主要树种锐齿槲栎由于相邻木中同树种相邻木增加,导致竞争压力增大。天然混交林中树种组成复杂多样,林木分布不均匀,在竞争指数中引入树种混交因子能够较为真实的反映林木竞争状况。

我国“交叠式”家校社课后体育服务机制构建与实践路径

运用文献资料、逻辑分析等方法,发现我国家校社推进课后体育服务的“分离式”困境表现为:家校社协同意识不强、家校社协同供给缺乏、家校社有效沟通不足、家校社协同管理不到位。以交叠影响域理论为基础,构建我国“交叠式”家校社课后体育服务机制,提出我国“交叠式”家校社课后体育服务机制的实践路径:营造协同氛围,达成体育育人目标共识;协调三方资源,强化课后体育服务育人成效;健全沟通机制,促进家校社深度融合;搭建智慧平台,优化课后体育服务管理。

基于叠覆朵体模式的厚层三角洲前缘砂体精细刻画——以大庆油田杏六中区PⅠ油层组为例

为了厘清大庆油田杏六中区PⅠ油层组厚层三角洲前缘砂体的内部结构特征,为剩余油开发提供地质支撑,文中针对按照水下分流河道模式无法精细刻画目标砂体的问题,引入叠覆朵体模式,提出六步剖析法,依据密井网资料,对目标砂体的内部结构进行了精细刻画。结果表明:1)按照叠覆朵体模式,能够较清楚地刻画目标砂体的内部结构特征。2)运用六步剖析法(即确定标志层,划分等时地层单元;进行底拉平处理,认识等时地层单元内砂体的内部结构特征;识别较大的沉积界面,区分并追踪复合朵体;在复合朵体内识别单朵体,刻画其分布;分析朵体间接触关系,确定朵体间连通性;结合生产动态资料,验证剖析结果的正确性),对目标砂体的刻画结果打破了三角洲前缘砂体呈层状结构的传统认识。3)目标砂体内部可以以进积、退积特征划分为一系列的沉积复合朵体和单朵体。按照叠覆朵体模式,运用六步剖析法对砂体内部结构的刻画结果,避免了传统的基于相带的砂体结构剖析法中跨沉积时间单元所造成的对砂体内部结构认识的偏差,为剩余油分析提供了可靠的依据。

不同低密度衰减区分级慢性阻塞性肺疾病急性加重期和哮喘-慢性阻塞性肺疾病重叠患者临床特征分析

背景慢性阻塞性肺疾病(COPD)是异质性疾病,哮喘-COPD重叠(ACO)同时具有哮喘和COPD相关临床特征,部分患者无法配合行肺功能检查,难以判断气流受限程度。目的比较COPD急性加重期(AECOPD)及ACO患者不同低密度衰减区(LAA)分级的临床资料,分析第1秒用力呼气容积占预计值百分比(FEV_(1)%pred)与LAA分级的关联性,为肺功能检查受限患者提供参考指标。方法收集2020年3月—2022年5月在河北医科大学第二医院呼吸与危重症医学科住院的AECOPD及ACO患者的临床资料,LAA≥2级归为肺气肿型,LAA<2级归为支气管炎型,共分为4组:(1)支气管炎型AECOPD组(84例):LAA 0级33例和LAA 1级51例;(2)肺气肿型AECOPD组(150例):LAA 2级55例、LAA 3级63例和LAA 4级32例;(3)支气管炎型ACO组(59例):LAA 0级26例和LAA 1级33例;(4)肺气肿型ACO组(47例):LAA 2级21例、LAA 3级17例和LAA 4级9例。比较AECOPD和ACO患者各组及组内不同LAA分级患者的临床特点。ACO患者及AECOPD患者的FEV_(1)%pred影响因素采用多重线性回归分析。结果与支气管炎型AECOPD组比,肺气肿型AECOPD组BMI、氧合指数(PaO_(2)/FiO_(2))、FEV_(1)%pred更低,吸烟量、男性、吸烟比例更高(P<0.05)。支气管炎型AECOPD组:与LAA 0级组比,LAA 1级患者BMI、FEV_(1)%pred、PaO_(2)/FiO_(2)、血清白蛋白(ALB)更低,外周血中性粒细胞/淋巴细胞比值(NLR)、超敏C反应蛋白(hs-CRP)、纤维蛋白原降解产物(FDP)、白介素(IL)-6更高(P<0.05)。肺气肿型AECOPD组:与LAA4级患者相比,LAA3级患者年龄、BMI、FEV_(1)%pred更高,LAA2级患者BMI、FEV_(1)%pred更高,住院天数更短;LAA 3级患者NLR、hs-CRP、FEV_(1)%pred高于LAA 2级(P<0.05)。与支气管炎型ACO组相比,肺气肿型ACO组年龄、吸烟量、男性比例、吸烟比例更高,BMI、FEV_(1)%pred更低(P<0.05)。支气管炎型ACO组:与LAA 1级患者相比,LAA 0级患者应用全身激素、激素总量更高,FEV_(1)%pred更低(P<0.05)。肺气肿型ACO组:LAA 4级组FEV_(1)%pred低于LAA3级和LAA2级,LAA3级患者FEV_(1)%pred低于LAA2级(P<0.05)。多重线性回归分析结果显示,AECOPD和ACO患者LAA分级与FEV_(1)%pred呈负相关(P<0.05)。结论在AECOPD和ACO患者中,LAA分级不同,临床特征不同。ACO患者LAA 1级比LAA 0级对激素更不敏感。LAA分级与FEV_(1)%pred呈负相关,LAA分级可以为肺功能检查受限的AECOPD和ACO患者在评估气流受限程度方面提供参考。