负热膨胀材料研究进展

概述负热膨胀材料的发展历程及近年的主要研究成果,介绍负热膨胀的微观机理,分析几种典型负热膨胀材料的特点,展望新型锰氮化物负热膨胀材料的应用前景,探讨负热膨胀材料研究所面临的问题。     

本源微生物驱油数值模拟及应用

为了更好地对本源微生物驱油进行方案设计,很有必要发展本源微生物驱油数值模拟技术.采用室内实验方法,研究了本源微生物采油的机理,引入了微生物因子来描述微生物的特有作用,提出了三维三相本源微生物驱油数学模型,结合具体算例进行了数值求解,比较了不同注水时机对采油的影响.结果表明:该模型所模拟的结果和实际结果较相符,在所模拟的范围内,开始进行本源微生物驱越早越好.该成果对现场应有一定的参考价值和指导意义.     

基于超平面同伦法的平面过约束机构判定

过约束机构的研究涉及到非线性代数方程组的高维解问题,现有的数值法难以确定方程组是否存在高维解,提出超平面同伦法,并基于该方法提出了过约束机构的判定准则.发现了一种平面四回路过约束机构,并运用判定准则对该机构进行验证.通过对该四回路过约束机构的过约束条件分析,构造了一类新的平面过约束机构.     

Fritz London and the scale of quantum mechanisms

Fritz London's seminal idea of “quantum mechanisms of macroscopic scale”, first articulated in 1946, was the unanticipated result of two decades of research, during which London pursued quantum-mechanical explanations of various kinds of systems of particles at different scales. He started at the microphysical scale with the hydrogen molecule, generalized his approach to chemical bonds and intermolecular forces, then turned to macrophysical systems like superconductors and superfluid helium. Along this path, he formulated a set of concepts—the quantum mechanism of exchange, the rigidity of the wave function, the role of quantum statistics in multi-particle systems, the possibility of order in momentum space—that eventually coalesced into a new conception of systems of equal particles. In particular, it was London's clarification of Bose-Einstein condensation that enabled him to formulate the notion of superfluids, and led him to the recognition that quantum mechanics was not, as it was commonly assumed, relevant exclusively as a micromechanics.     

Insights into plastic deformation mechanisms of austenitic steels by coupling generalized stacking fault energy and semi-discrete variational Peierls-Nabarro model

The generalized stacking fault energy (GSFE) is a key parameter to determine the plastic deformation mechanisms of austenitic steels. However, the underlying physics why the GSFE can affect the plastic deformation behaviors remains unclear. In this paper, the plastic deformation mechanisms of austenitic steels with different carbon (C) additions were investigated by coupling the GSFE with the semi-discrete variational Peierls-Nabarro (P–N) model. The internal mechanisms behind the P–N stress and plastic deformation were explained at atomic scale. It is found that the positions and contents of C atoms affect the GSFE of austenite, and thus regulate plastic deformation behaviors of austenitic steels by influencing dislocation core structure. As exemplified that with 4 ​at.%C in austenite, the intrinsic stacking fault energy increases from −433 to −264 mJ/m², and the stacking fault width increases to 6.62b from 4.72b of FCC-Fe with b being the Burgers vector. This corresponds to the plastic deformation mechanism dominated by the ε martensitic transformation with the lattice changing from FCC to HCP. With increasing C contents to 8 ​at.%, the intrinsic stacking fault energy of austenite increases to −9.01 mJ/m², while the stacking fault width decreases to 6.03b. The plastic deformation tends to proceed via the mechanical twinning mode. The present investigation establishes a solid foundation for clarifying the plastic deformation mechanisms of austenitic steels from the perspective of the dislocation core structure.     

齿轮四杆机构停歇位置的动态特性分析

齿轮四杆机构是一种新型的组合机构，具有一阶、二阶瞬时停歇特性－ 通过用有限单元法建立齿轮四杆机构动力学模型，并结合算例模拟计算出其瞬时停歇位置的固有频率和振型－ 图３ ，表２ ，参５－     

盐碱地林木耐盐机制及造林技术研究进展

盐碱地是人工造林的重要潜在资源,而土壤盐胁迫危害是制约林木健康生长的突出问题。揭示林木盐胁迫调控机制,开发盐碱地综合利用技术是实现盐碱地资源化和生态保护的关键。笔者从林木生长发育、光合效率、生理代谢调控及矿质营养等角度,论述了制约盐碱地人工林生产力低下、土壤资源利用效率不足的盐胁迫主要过程。利用林木逆境下进化出的一套以自身生化调控和菌群互作消减为核心的综合耐盐机制,是研发盐碱地造林关键技术的方向,有助于我国盐碱地区人工林高效培育和多目标经营。