岩土材料的两种经典本构模型之分析比较

文章选取了岩土材料的两种经典本构模型,通过详细的介绍与比较,从本质上分析其各自的优缺点,从而对这两种本构模型做了比较,以便为以后工程实践中提供一些参考和借鉴。     

应力作用下高分子材料的老化行为研究

从微观角度综述了应力影响高分子材料老化性能的现象,提出了应力引发材料老化的特殊性,并分析了其产生的原因,总结了应力引发材料老化的机理,讨论了应力与其他因素相结合对材料老化的影响,展望了其研究方向。     

胶东牟乳成矿带金青顶矿床构造叠加晕研究

金青顶金矿床是牟平—乳山金成矿带最大的石英脉型金矿床,矿脉严格受构造控制,已探明储量为32 t,平均品位为6.44×10^-6。为探讨金青顶金矿床深部成矿潜力,本文在分析矿区成矿地质条件及矿床地质特征的基础上,对金青顶金矿床II号主矿体开展了构造叠加晕研究。结果表明：金青顶金矿床II号矿体的前缘晕特征指示元素组合为As、Sb、Hg,近矿特征指示元素组合为Au、Ag、Cu、Pb、Zn,尾晕特征指示元素组合为Bi、Mo、Co。II号矿体特征指示元素的分带序列由上至下为Sb→Cu、Ni→Au→Sn→W→Hg→As、Co→Ag→Zn→Pb、Mo→Bi,结合地球化学参数确定了II号矿体在-195 m、-435 m和-945 m中段深部存在金成矿作用叠加,并据此建立了II号矿体的构造叠加晕理想模型。综合矿脉品位等值线图、数据统计学分析、元素轴向分带序列、地球化学参数变化规律、构造叠加晕成矿模式以及井下地质现象观察分析,显示出金青顶金矿床II号矿体向深部的延伸较差,说明在深部存在矿体的可能性不是很大。因此,今后在本区开展找矿工作时,应重点关注矿区内的空白区及矿床外围。     

Impact of Fluid Flow Shear Stress on Osteoblast Differentiation and Cross-Talk with Articular Chondrocytes

Bone cells, in particular osteoblasts, are capable of communication with each other during bone growth and homeostasis. More recently it has become clear that they also communicate with other cell-types; including chondrocytes in articular cartilage. One way that this process is facilitated is by interstitial fluid movement within the pericellular and extracellular matrices. This stimulus is also an important mechanical signal in skeletal tissues, and is known to generate shear stresses at the micron-scale (known as fluid flow shear stresses (FFSS)). The primary aim of this study was to develop and characterize an in vitro bone–cartilage crosstalk system, to examine the effect of FFSS on these cell types. Specifically, we evaluated the response of osteoblasts and chondrocytes to FFSS and the effect of FFSS-induced soluble factors from the former, on the latter. This system will ultimately be used to help us understand the role of subchondral bone damage in articular cartilage degeneration. We also carried out a comparison of responses between cell lines and primary murine cells in this work. Our findings demonstrate that primary cells produce a more reliable and reproducible response to FFSS. Furthermore we found that at lower magnitudes , direct FFSS produces anabolic responses in both chondrocytes and osteoblasts, whereas higher levels produce more catabolic responses. Finally we show that exposure to osteoblast-derived factors in conditioned media experiments produced similarly catabolic changes in primary chondrocytes.     

Physapruin A Enhances DNA Damage and Inhibits DNA Repair to Suppress Oral Cancer Cell Proliferation

The selective antiproliferation to oral cancer cells of Physalis peruviana-derived physapruin A (PHA) is rarely reported. Either drug-induced apoptosis and DNA damage or DNA repair suppression may effectively inhibit cancer cell proliferation. This study examined the selective antiproliferation ability of PHA and explored detailed mechanisms of apoptosis, DNA damage, and repair. During an ATP assay, PHA provided high cytotoxicity to two oral cancer cell lines (CAL 27 and Ca9-22) but no cytotoxicity to two non-malignant oral cells (HGF-1 and SG). This selective antiproliferation of PHA was associated with the selective generation of reactive oxygen species (ROS) in oral cancer cells rather than in non-malignant oral cells, as detected by flow cytometry. Moreover, PHA induced other oxidative stresses in oral cancer cells, such as mitochondrial superoxide generation and mitochondrial membrane potential depletion. PHA also demonstrated selective apoptosis in oral cancer cells rather than non-malignant cells in annexin V/7-aminoactinmycin D and caspase 3/7 activity assays. In flow cytometry and immunofluorescence assays, PHA induced γH2AX expressions and increased the γH2AX foci number of DNA damages in oral cancer cells. In contrast, the mRNA expressions for DNA repair signaling, including homologous recombination (HR) and non-homologous end joining (NHEJ)-associated genes, were inhibited by PHA in oral cancer cells. Moreover, the PHA-induced changes were alleviated by the oxidative stress inhibitor N-acetylcysteine. Therefore, PHA generates selective antiproliferation, oxidative stress, and apoptosis associated with DNA damage induction and DNA repair suppression in oral cancer cells.     

上覆煤柱影响下工作面应力场分布变化规律

为了研究近距离煤层群下行开采过程中,下煤层工作面受到上覆煤柱影响形成高应力区后,导致顶板垮落、冲击地压、煤壁片帮、瓦斯爆炸等煤矿灾害的发生问题,本文运用FLAC3D软件,分别对厚度为1m、2m、3m、5m的上覆煤柱作用下位煤层开采前及开采过程中顶板应力分布动态变化规律进行数值模拟与分析.研究表明:①在下煤层未开采前,上...     

水平井分段体积压裂复杂裂缝形成机制研究现状与发展趋势

水平井分段体积压裂是油气储层中复杂裂缝网络形成的重要技术之一,准确了解复杂裂缝网络形成机制、预测复杂裂缝网络形态对非常规油气资源高效开发具有重要意义,同时也是水力压裂设计优化的理论基础。围绕非常规储层复杂裂缝形成机制,国内外学者根据"应力阴影"效应对水力裂缝同步扩展、水力压裂顺序对多裂缝动态延伸影响、层理面对水力裂缝纵向扩展遮挡效应和天然裂缝与水力裂缝交互动态等方面,分别建立了相应的水力压裂模型,并从数值模拟角度对其进行了定性分析。通过总结国内外研究现状,并从模型建立假设条件、数值模拟模型思想和模型局限性3方面对现有模型进行了剖析,并对未来研究方向提出了建议,研究结果可对未来水力压裂复杂裂缝形成机制研究提供借鉴。     

煤储层等效有效应力系数变化规律实验研究

煤储层进入饱和气体单相流后,储层有效应力系数的变化规律是正确评估储层渗透性的关键。本文采集不同变质程度的煤岩样品,对不同外界荷载和孔隙压力条件下煤储层的等效有效应力系数进行了研究,结果表明：在孔隙压力一定的条件下,外界荷载对煤储层等效有效应力系数具有负效应,随外界荷载加载,煤储层等效有效应力系数减小,且外界荷载越大负作用越强;在外界荷载一定条件下,随孔隙压力增加,煤储层等效有效应力系数增大,孔隙压力对煤储层等效有效应力系数具有正效应;相对于中阶煤和高阶煤储层,低阶煤储层由于孔隙类型多样,孔隙尺度大,储层的等效有效应力系数在外界荷载和孔隙压力耦合作用下影响程度相对较小。由于煤储层等效有效应力系数在不同外界荷载和孔隙压力下差异较大,煤储层进入饱和气体单相流后,在不考虑解吸收缩效应条件下,煤储层的有效应力变化并非等同于储层孔隙压力的变化,而与煤阶类型、地应力高低和孔隙压力大小密切相关,原位高地应力条件下,由于煤储层的等效有效应力系数较小,随孔隙压力降低,煤储层有效应力变化相对微弱。     

基于流固耦合的柱面气膜密封支撑结构性能研究

利用流固耦合分析方法,研究一种波箔结构柔性支撑柱面气膜密封,探讨气膜厚度、浮环与转子的偏心率以及柔性支撑结构的泊松比、弹性模量、波箔数量等参数对支撑结构等效应力及变形量的影响。结果表明:柔性支承结构满足柱面气膜密封的正常运作,不会造成因为气膜刚度过大而使得浮环与波箔发生破坏性变形,并且变形量远小于波箔高度;柔性支撑的等效应力和变形量随平均气膜厚度的增大而减小,随偏心率的增加而增大,随支撑材料泊松比的增大而增大;弹性模量的增加并不影响柔性支撑结构的等效应力,但是会使变形量减小;增加波箔数量,柔性支撑的等效应力略有减小,变形量显著减小。     

弹药步进应力寿命试验数据处理

弹药的步进应力加速寿命试验数据处理的关键是异常数据的处理和弹药长贮寿命分布参数的估计.针对这两个问题,人们提出了许多相关解决办法,但迄今为止,尚没有一种通用的、行之有效的方法.为此,尝试依据贝叶斯理论对试验中可能出现的数据异常进行预处理,并利用鲍维尔法先求取各级加速应力下的样品分布参数的似然估计,再结合加速方程得到常应力下弹药的贮存寿命分布参数.最后,通过实例说明了方法的可行性.