广西箭猪坡矿床首次发现的石英脉型锡矿体特征及 锡石微量元素地球化学意义

箭猪坡矿床是丹池成矿带南端的一个以铅锌锑为主的矿床，随着2012-2014年在箭猪坡矿床钻孔中石英脉型锡矿体的首次发现，打开了箭猪坡矿床新的找矿空间。新发现的锡矿体矿石矿物组合类型主要为锡石+闪锌矿+脆硫锑铅矿+黄铁矿+石英及锡石+脆硫锑铅矿+石英+方解石。箭猪坡矿床锡石呈自形-半自形粒状，锡石粒径多在0.1～0.2mm，少数0.02～0.05mm，分布在含硫化物的石英脉裂隙中。物相分析显示箭猪坡矿床锡主要赋存在锡石中，锡石物相占83.33%～100%。阴极发光（CL）图像显示箭猪坡矿床中的锡石经历了两期结晶作用：早期锡石（Ⅰ）和晚期锡石(Ⅱ），早期锡石CL荧光亮度较小，呈暗灰色至黑色；晚期CL荧光亮度较大，呈白色至浅灰色。锡石单矿物SnO2含量91.623%～96.288%，平均94.03%，杂质主要有Fe、W、In等，其中FeO含量0.02%～0.52%，WO3含量多在0.02～1.34%，In2O3含量在0.476%～0.954%，Sn与FeO、In2O3呈负相关，锡石中FeO、WO3、Ta2O5、Nb2O5、MnO含量指示箭猪坡锡形成于中低-中温热液环境，成矿热液来源于高度分异演化的花岗质岩浆。通过与大厂矿田西矿带上部脉状锡矿体的类比分析，具有相似的成矿条件及矿物组合，推测所揭露到的脉状锡矿（化）体相当于西矿带上部脉状锡矿（化）体，而下部的网脉状、似层状锡矿体尚未揭露到，由此预测箭猪坡矿床深部找矿空间及找矿潜力大。     

水平裂缝对坚硬顶板失稳破断的影响规律研究

为了研究水力压裂形成水平裂缝后坚硬顶板的失稳破断规律,基于材料力学和关键层相关理论,结合数值模拟,对含水平裂缝坚硬顶板的变形破坏特征和失稳破断机制进行了研究。结果表明:当坚硬顶板存在水平贯穿裂缝时,无论上位与下位岩层是否发生同步运动,坚硬顶板的破断步距均小于其初始极限跨距。存在水平贯穿裂缝的坚硬顶板及其上覆岩层,会形成拉压复合破坏区,更易于发生失稳破坏。坚硬顶板块体咬合点区域的拉压复合破坏作用是造成块体局部失稳、回转加剧和整体破断的主要原因。     

Propagation and termination of an internal crack in continuously cast austenitic stainless steel analyzed by ∑ values and the Schmid factor

The formation mechanism of an internal crack was clarified from the viewpoint of the crystallography and thermal expansion. An inverse pole figure map obtained by EBSD pattern showed that the crack propagated along the grain boundaries having high ∑ values within the columnar zone. After the crack initiation, these positions were considered to undergo cracking followed by propagation toward the equiaxed side. Near the termination position, the grains ahead of crack propagation had a Schmid factor higher than 0.45 consuming elastic strain energy. Thermal expansion measurements showed that the grain with (0 0 1) orientation had the largest expansion while that with (0 1 1) the smallest. The grain boundaries neighboring the combination of (0 0 1) and (0 1 1) grains had the largest thermal stress. Therefore, thermal stress contributed to the initiation of cracking. It was thus proposed to enlarge the equiaxed zone to prevent cracking by discontinuing the crack propagation.     

Age-dependent size effect and fracture characteristics of ultra-high performance concrete

This paper presents an investigation of the age-dependent size effect and fracture characteristics of ultra-high performance concrete (UHPC). The study is based on a unique set of experimental data connecting aging tests for two curing protocols of one size and size effect tests of one age. Both aging and size effect studies are performed on notched three-point bending tests. Experimental data are augmented by state-of-the-art simulations employing a recently developed discrete early-age computational framework. The framework is constructed by coupling a hygro-thermo-chemical (HTC) model and the Lattice Discrete Particle Model (LDPM) through a set of aging functions. The HTC component allows taking into account variable curing conditions and predicts the maturity of concrete. The mechanical component, LDPM, simulates the failure behavior of concrete at the length scale of major heterogeneities. After careful calibration and validation, the mesoscale HTC-LDPM model is uniquely posed to perform predictive simulations. The ultimate flexural strengths from experiments and simulations are analyzed by the cohesive size effect curves (CSEC) method, and the classical size effect law (SEL). The fracture energies obtained by LDPM, CSEC, SEL, and cohesive crack analyses are compared, and an aging formulation for fracture properties is proposed. Based on experiments, simulations, and size-effect analyses, the age-dependence of size effect and the robustness of analytical-size effect methods are evaluated.     

Shear crack growth in brittle materials modeled by constrained Cosserat elasticity

The propagation of in-plane shear cracks is investigated in brittle microstructured materials modeled by the constrained Cosserat elasticity. This theory introduces characteristic material lengths in order to describe the scale effects that emerge from the underlying microstructure and has proved to be very effective for modeling complex microstructured materials. An exact solution is obtained based on integral transforms and the Wiener-Hopf technique. Numerical results are presented illustrating the dependence of the stress intensity factor and the energy release rate upon the loading profile, the propagation velocity, and the characteristic material lengths of Cosserat elasticity. It is shown that depending on the Cosserat microstructural lengths the limiting crack propagation velocity can be significantly lower than the classical Rayleigh limit. Moreover, strengthening effects are observed when the characteristic material lengths become comparable to the geometrical lengths of the problem, a behavior that has been experimentally verified in fracture of ceramics.     

基于四元数理论的 ２ Ｕ ＰＳ-Ｐ Ｕ并联机构位置反解

介 绍 了 四 元 数 在 描 述 刚 体 位 置 和 方 位 中 的 应 用 ，并 简 要 描 述 了 ２ Ｕ ＰＳ-Ｐ Ｕ并 联 机 构 ，接 着 给 出 了利 用 四 元 数 计 算 ２ Ｕ ＰＳ-Ｐ Ｕ并 联 机 构 的 位 置 反 解 的 推 导 过 程 ，得 到 了 ２ Ｕ ＰＳ-Ｐ Ｕ并 联 机 构 的 位 置 反 解 公 式 ，最后 结 合Ｍ ＡＴ Ｌ Ａ Ｂ和 Ｓｏｌｉｄ Ｗ ｏｒｋｓ Ｍ ｏｔｉｏｎ 进 行 仿 真 分 析 ，仿 真 结 果 验 证 了 该 位 置 反 解 方 法 的 正 确 性 和 有 效 性 。     

Solution combustion synthesis of cerium oxide nanoparticles as corrosion inhibitor

In this study, combustion synthesis of cerium oxide nanoparticles was reported using cerium nitrate hexahydrate as starting material as well as urea, glycine, glucose, and citric acid as fuels. The influence of fuel type on structure, microstructure, band gap, and corrosion inhibition was investigated. X-ray diffraction (XRD) patterns and scanning electron microscopy micrographs showed that CeO₂ nanoparticles with different morphologies were obtained depending on the fuel type. Microstructural changes from unreacted gel to sponge-like morphologies were resulted by varying the fuel type from urea, glycine, and glucose to citric acid. In addition to Ce–O bonds, Fourier transform infrared analysis showed carbon bonds of carbonaceous compositions from incomplete combustion which were declined during combustion reaction. Furthermore, corrosion analyses showed that samples synthesized using urea fuel released the most Ce⁺⁴ ions and could have better protection than other samples.     

协同二酰亚胺催化剂制备氢化丁腈橡胶（英文）

采用维生素C、对苯二酚和茶多酚协同二酰亚胺对丁腈橡胶(NBR)分子链双键进行加氢,有效解决了NBR乳液二酰亚胺原位加氢过程中加氢程度低、凝胶含量高的问题。结果表明,采用维生素C、对苯二酚和茶多酚协同还原剂制备的氢化NBR(HNBR)的加氢程度明显提高,说明协同还原剂可参与双键加氢反应并起促进作用。与此同时,在NBR乳液加氢体系中引入协同还原剂有效降低了产物的凝胶含量。维生素C、对苯二酚和茶多酚均呈现一定的还原性和水溶性,可较好地溶解在NBR胶乳体系中,有效消除胶乳体系中的自由基,避免自由基之间的交联产生凝胶。HNBR经协同还原剂加氢后,热稳定性及低温柔韧性均有提高。     

带延迟索赔和随机收入的离散风险模型的Gerber-Shiu分析（英）

破产理论是保险数学中的重要问题，它可以为保险公司决策者提供一个非常有用的早期风险预警手段．本文研究了一个带潜在延迟索赔和随机保费收入的复合二项风险模型．利用矩母函数的技巧，得到了 Gerber-Shiu 期望折罚函数的递推公式．特别地，还得到了贴现因子为 1 的特殊情形下的 Gerber-Shiu 期望折罚函数的解析表达式．最后还得到了实际应用中的一些重要的破产特征量，包括破产概率，破产时赤字的密度函数，破产前盈余与破产时赤字的联合密度函数，以及导致破产的索赔密度函数等．