断层岩柱瓦斯超前突出机理数值模拟及防护厚度

针对矿井巷道掘进面前方遭遇含瓦斯断层时,安全岩柱内的沉积界面将会遭受气体损伤作用的问题,通过ABAQUS软件的二次开发,基于流-固耦合理论和T-P损伤演化准则的cohesive单元,对豫西大平煤矿21轨道下山一次大型瓦斯突出事故进行数值模拟。计算结果表明：由于受巷道开挖所产生的二次应力与断层带瓦斯压力的共同作用,前方岩柱内两个沉积界面将优先产生损伤软化现象。随着巷道向断层带的推进,气体的侵蚀作用不断加强,沉积界面的损伤急剧增加并向掘进面延伸。当掘进面距离前方断层分别为19,17,15 m时,上层面相应产生6.2,9.7,13.4 m长的损伤裂隙;下层面相应延伸距离较短,仅产生4.1,4.6,4.8 m长的损伤裂隙。与此同时,上层面瓦斯急剧渗透扩展,在掘进面前方1-2 m处开始出现3.5 MPa的孔隙气压升高带。由此可见,界面差异性强的上层面相对较弱的下层面容易损伤,而且损伤后的沉积界面优先产生相应的渗流扩散现象。当损伤沉积界面最终贯通掘进面与断层面之间的岩柱,即裂隙损伤长度达到极限岩柱安全厚度时,瓦斯将突破岩体阻抗并产生冲击地压。

郭维森和中国当代楚辞学研究

早在1960年,中华书局出版的郭维森先生的楚辞研究力著《屈原》便在海内外产生了较大影响。在新时期,郭先生的楚辞研究更是呈现出立体的多维观照、纵向的由表及里、横向的渗透扩展等时代特点。他的工作几乎涉及到了楚辞研究的各主要方面,为维护楚辞学研究严肃性和科学性做出了贡献。郭先生的研究工作还涉及了美学、民俗学、比较文学、文化学等等,往往通过多学科的交叉研究,拓宽了原有研究领域和视野,弘扬了民族文化精华,推动了精神文明建设。

Simulation of thermal and sodium expansion stress in aluminum reduction cells

Two finite element(FE) models were built up for analysis of stress field in the lining of aluminum electrolysis cells.Distribution of sodium concentration in cathode carbon blocks was calculated by one FE model of a cathode block.Thermal stress field was calculated by the other slice model of the cell at the end of the heating-up.Then stresses coupling thermal and sodium expansion were considered after 30 d start-up.The results indicate that sodium penetrates to the bottom of the cathode block after 30 d start-up.The semi-graphitic carbon block has the largest stress at the thermal stage.After 30 d start-up the anthracitic carbon has the greatest sodium expansion stress and the graphitized carbon has the lowest sodium expansion stress.Sodium penetration can cause larger deformation and stress in the cathode carbon block than thermal expansion.

Ultrasonic vibrations and coal permeability: Laboratory experimental investigations and numerical simulations

Ultrasonic vibrations in coal lead to cavitation bubble oscillation, growth, shrinkage, and collapse, and the strong vibration of cavitation bubbles not only makes coal pores break and cracks propagate, but plays an important role in enhancing the permeability of coal. In this paper, the influence of ultrasonic cavitation on coal and the effects of the sonic waves on crack generation, propagation, connection, as well as the effect of cracks on the coal permeability, are studied. The experimental results show that cracks in coal are generated even connected rapidly after ultrasonic cavitation. Under the effect of ultrasonic cavitation,the permeability increases between 30% and 60%, and the number of cracks in coal also significantly increased. Numerical experiments show that the effective sound pressure is beneficial to fracture propagation and connection, and it is closely related to the permeability. Moreover, the numerical simulations and physical experiments provide a guide for the coal permeability improvement.

高技术产业化的特征

1.群体化。高技术的产生与发展,不像以往的技术革命那样,是由比较单一的技术发展起来的,而是采用群体的形式在短短的十几年内涌现出来,是现代高技术与传统技术以及高技术内部相互作用的结果,并导致了新的高技术领域的延伸和发展。高技术体系的层次表明了高技术产业的群体化特征。随着时间推移,高技术产业群体将不断扩大。

试论高职教育中“两课”教学的培养目标及实施步骤

高职教育是要培养学生具有“适应职业变化的这种关键能力” ,而这正是“两课”教育的重要培养目标。实现高职教育中“两课”教学培养目标的实施步骤是 :第一阶段进行基础理论教育 ,第二阶段进行扩展渗透教育 ,第三阶段延伸强化教育。

浅谈拓展阅读的实效性

在课堂上进行有效拓展阅读,不仅可以利用资源来化解教学的重点、难点,还可以有效地培养学生的阅读能力、理解能力和自主学习的能力,使自主、探究、合作的学习方式真正落实到实处;进行拓展阅读,可以让学生通过资源更好地了解课文的相关知识,从而使拓展阅读资源成为学习课文的基石,在帮助学生深入理解、领悟课文主题及教学目标要求方面起到了关键性的作用。