Experimental study on the deformation and failure mechanism of overburden rock during coal mining using a comprehensive intelligent sensing method

Understanding the spatiotemporal evolution of overburden deformation during coal mining is still a challenge in engineering practice due to the limitation of monitoring techniques. Taking the Yangliu Coal Mine as an example, a similarity model test was designed and conducted to investigate the deformation and failure mechanism of overlying rocks in this study. Distributed fiber optic sensing (DFOS), high-density electrical resistivity tomography (HD-ERT) and close-range photogrammetry (CRP) technologies were used in the test for comprehensive analyses. The combined use of the three methods facilitates the investigation of the spatiotemporal evolution characteristics of overburden deformation, showing that the mining-induced deformation of overburden strata was a dynamic evolution process. This process was accompanied by the formation, propagation, closure and redevelopment of separation cracks. Moreover, the key rock stratum with high strength and high-quality lithology played a crucial role in the whole process of overburden deformation. There were generally three failure modes of overburden rock layers, including bending and tension, overall shearing, and shearing and sliding. Shear failure often leads to overburden falling off in blocks, which poses a serious threat to mining safety. Therefore, real-time and accurate monitoring of overburden deformation is of great significance for the safe mining of underground coal seams.     

Upscaled DEM-CFD model for vibrated fluidized bed based on particle-scale similarities

Simulation based on discrete element method (DEM) coupled with computational fluid dynamics (CFD), coupled DEM-CFD, is a powerful tool for investigating the details of dense particle–fluid interaction problems such as in fluidized beds and pneumatic conveyers. The addition of a mechanical vibration to a system can drastically alter the particle and fluid flows; however, their detailed mechanisms are not well understood. In this study, a DEM-CFD model based on a non-inertial frame of reference is developed to achieve a better understanding of the influence of vibration in a vibrated fluidized bed. Because the high computational cost of DEM-CFD calculations is still a major problem, an upscaled coarse-graining model is also employed. To realize similar behaviors with enlarged model particles, non-dimensional parameters at the particle scale were deduced from the governing equations. The suitability and limitations of the proposed model were examined for a density segregation problem of a binary system. To reduce the computational costs, we show that the ratio between the bed width and model particle size can be reduced to a minimum value of 100; to obtain similar segregation behaviors, the ratio between the bed height and model particle size is considered unchanged.     

融入局部几何特征的流形谱聚类图像分割

为了改善谱聚类图像分割的精准性和时效性,文中提出融入局部几何特征的流形谱聚类图像分割算法.首先,考虑图像数据的流形结构,在数据点的K近邻域内执行局部PCA,得到数据间本征维数的关系.然后,引入流形学习中的局部线性重构技术,通过混合线性分析器得到数据间局部切空间的相似性,结合二者构造含有局部几何特征的相似性矩阵.再利用Nystr m技术逼近待分割图像的特征向量,对构造的k个主特征向量执行谱聚类.最后,在Berkeley数据集上的对比实验验证文中算法的准确性和时效性优势.     

Comparative analysis on similarities and differences of hydrogen energy development in the World's top 4 largest economies: A novel framework

A low-carbon energy transition is permeating many industrialized countries due to the overuse of fossil fuels and the climate change. Some countries stress the hydrogen energy in optimizing their energy structures. This article examines both the markets and the policies of the hydrogen industry in the World's Top 4 largest economies. To make the comparative analysis more logical, a novel conceptual model for energy transition -- the institution-economics-technology-behavior framework -- has been adopted to make a multi-dimensional discussion. The results show that: (1) From the perspective of strategic intention, developing hydrogen energy is conductive to the energy transition. (2) From the horizontal comparison, each country has its own advantages, however, the main driving factors are different. (3) From the vertical comparison, the hydrogen energy development in each country is still in the stage of quantitative change, and the inflection point of qualitative change has not been reached yet.     

Distinguishability of interval type-2 fuzzy sets data by analyzing upper and lower membership functions

In this paper, we deal with the problem of classification of interval type-2 fuzzy sets through evaluating their distinguishability. To this end, we exploit a general matching algorithm to compute their similarity measure. The algorithm is based on the aggregation of two core similarity measures applied independently on the upper and lower membership functions of the given pair of interval type-2 fuzzy sets that are to be compared. Based on the proposed matching procedure, we develop an experimental methodology for evaluating the distinguishability of collections of interval type-2 fuzzy sets. Experimental results on evaluating the proposed methodology are carried out in the context of classification by considering interval type-2 fuzzy sets as patterns of suitable classification problem instances. We show that considering only the upper and lower membership functions of interval type-2 fuzzy sets is sufficient to (i) accurately discriminate between them and (ii) judge and quantify their distinguishability.     

中日韩园林的相似性与独特性

中日韩地理位置相邻,天然地形和地带性气候相近及长期文化交流,形成了有别于西方园林的相似性。又由于自然资源和人文资源的差异而形成各自独特的民族特色。独特性大于相似性。从理念、园林追求的境界、自然山水园布局、园林建筑、置石与掇山、自然式的植物种植方面论述了相似性与独特性。由于地带毗邻且相近,就自然环境而言,滨海、多山、富水、产石,自然资源有相似性。加以文化交流,人文资源也有相似性。自然与人文资源融为一体的园林便有区别于西方园林的东方园林美。但“一方水土养一方人”,各自独特的自然环境和人文资源又造就各自园林的民族特色,自立于世界园林民族之林。     

寻找失落的遗传密码：历史风貌核心区空间修复性设计研究——天津市解放北路街区改造示例

随着越来越多的历史街区及建筑遭受到日益严重的破坏，如何有效地对这些街区进行保护，提出可操作性强的控制指标，已经成为历史街区保护所面临的新课题。本文以天津市解放北路历史风貌核心区为便，采用数理统计和参考控制相结合的方式，探求一种新的研究方法，期望通过这种研究方法寻找量化的参数、准确而又清晰地对这些街区风貌进行控制。     

天津解放北路历史街区的空间分析与虚拟修复

目前,在历史街区的保护建设中常套用现行规划控制指标,但其对于历史街区的空间特性缺乏有效的约束。为此,本文从城市设计的层面进行探索—在概念推导的基础上,运用数理统计比较和图底关系分析等方法,弥补现行规划控制指标的不足,以求较全面地定量分析历史街区的空间属性。     

最小抵抗线对深孔岩石爆破块度的影响

针对最小抵抗线对深孔岩石爆破块度影响的问题,应用相似理论推导深孔岩石爆破中爆破块度与其影响因素的关系,得到小台阶模型下的相似律,并以此为依据进行了现场小台阶模型实验。通过对实验结果的分析,得到最小抵抗线对深孔岩石爆破块度的影响规律：随着抵抗线的增加,爆堆特征块度和均匀指数均增加。将此结论运用于连云港核电扩建山体爆破开挖工程,确定其最小抵抗线范围为3.5~4.5m,爆破后规格石料的成材率相比一期工程提高了23%,达到了预期效果。证明此设计合理,可为同类工程提供参考。