Experimental research on influence mechanism of loading rates on rock pressure stimulated currents

The study of pressure stimulated current(PSC)changes of rocks is significant to monitor dynamic disasters in mines and rock masses.The existing studies focus on change laws and mechanism of currents generated under the loading of rocks.An electrical and mechanics test system was established in this paper to explore the impacts of loading rates on PSCs.The results indicated that PSC curves of different rocks had different change laws under low/high loading rates.When the loading rate was relatively low,PSC curves firstly changed gently and then increased exponentially.Under high loading rates,PSC curves experienced the rapid increase stage,gentle increase stage and sudden change stage.The compressive strength could greatly affect the peak PSC in case of rock failure.The loading rate was a key factor in average PSC.Under low loading rates,the variations of PSCs conformed to the damage charge model of fracture mechanics,while they did not at the fracture moment.Under high loading rates,the PSCs at low stress didn’t fit the model due to the stress impact effects.The experimental results could provide theoretical basis for the influence of loading rates on PSCs.

Synthesis,Microstructure,and Property of Cr_2AlC

Cr2AlC is an unusual layered ternary ceramic that combines the merits of both metals and ceramics. The salient properties of Cr2AlC are strongly related to its bonding characteristics and microstructures. Synthesis, microstructure, and property of Cr2AlC are reviewed in this paper. First, theoretical calculations and physical properties are introduced. Then, the processing of Cr2AlC ceramic in both bulk form and thin films and their basic mechanical properties are summarized. Atomic-scale characterizations of Cr2AlC, as well as the microstructural relationships among Cr2AlC, AlCr5, and AlCr2 were achieved using a series of transmission electron microscopy （TEM） techniques. Moreover, high-temperature oxidation and hot corrosion behaviors of Cr2AlC were investigated by means of thermogravimetric analysis, X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and TEM. Mechanism of the excellent high-temperature corrosion resistance of Cr2AlC is discussed based on systematic microstructural analyses. Finally, concise conclusions are drawn.

TEM Investigations on Layered Ternary Ceramics

Layered ternary ceramics represent a new class of solids that combine the merits of both metals and ceramics.These unique properties are strongly related to their layered crystal structures and microstructures. The combination of atomic-resolution Z-contrast scanning transmission electron microscopy （STEM） and transmission electron microscopy （TEM）, selected area electron diffraction （SAED）, convergent beam electron diffraction （CBED） represents a powerful method to link microstructures of materials to macroscopic properties, allowing layered ternary ceramics to be investigated in an unprecedented detail. Vicrostructural information obtained using TEM is useful in understanding the formation mechanism, layered stacking characteristics, and defect structures for layered ternary ceramics down to atomic-scale level; and thus provides insight into understanding the ＂Processing-Structure-Property＂ relationship of layered ternary ceramics. Transmission electron microscopic characterizations of layered ternary ceramics in Ti-Si-C, Ti-Al-C, Cr-Al-C, Zr-Al-C, Ta-Al-C and Ti-Al-N systems are reviewed.

Survey on Fertility of Tea Garden Soil in Meizhou Region

Survey on fertility of tea garden soil in Meizhou region indicates that tea garden soil has strong acidity; organic matter content remains at medium level; there is a severe lack of available content of nitrogen(N),phosphorus(P) and potassium(K); available calcium(Ca) and magnesium(Mg) content is also insufficient; available sulfur(S) is abundant. In the management of tea cultivation,it is recommended to supplement organic fertilizer,balance the application of NPK fertilizer,and adequately alleviate shortage of Ca and Mg element,to guarantee high and stable yield of tea.

社会信任与审计意见购买

社会信任作为非正式制度,在社会发展的历程中不可或缺。就审计而言,社会信任对审计意见购买行为是否具有显著影响及如何影响,尚缺乏相关研究。本文以A股非金融类上市公司2010~2018年数据及中国综合社会调查(Chinese general social survey,CGSS)数据为样本,研究社会信任是否对审计意见购买产生影响。实证结果显示,社会信任水平增加了审计意见购买行为发生的可能性。进一步看,法治水平和盈余管理削弱了社会信任与审计意见购买之间的正向关系,分析师跟踪则使两者关系弱化。我们从多角度进行了稳健性检验,结论依然成立。本文拓展了社会信任对上市公司行为影响的研究,丰富了审计意见购买行为影响因素的研究文献,也可为监管层决策提供相关的理论参考和现实指导意义。