Mechanical frontiers in shale-gas development

页岩气的开采涉及破裂和收集输运两个关键过程.如何实现2000,m以下、复杂地应力作用下、多相复杂介质组分的页岩层内网状裂纹的形成,同时将孔洞、缝隙中的游离、吸附气体进行高效收集,涉及到诸多的核心力学问题.这一工程过程涵盖了力学前沿研究的诸多领域：介质和裂纹从纳米尺度到千米尺度的空间跨越,游离、吸附气体输运过程中微秒以下的时间尺度事件到历经数年开采的时间尺度跨越,不同尺度上流体固体的相互作用,以及压裂过程中通过监测信息反演内部破坏状态等.针对近年来我们国家页岩气勘探开发工作所取得的成就及后续发展中面临的前沿力学问题,在综合介绍页岩气藏的基本特征和开发技术的基础上,以页岩气开采中的若干力学前沿问题为主线,从页岩力学性质及其表征方法、页岩气藏实验模拟技术、页岩气微观流动机制及流固耦合特征、水力压裂过程数值模拟方法、水力压裂过程微地震监测技术、高效环保的无水压裂技术等6个方面的最新研究进展进行了总结和展望,结合页岩气藏开发的工程实践, 深入探究了其中力学关键问题,以期对从事页岩气领域的开发和研究的从业人员提供理论基础, 同时,该方面的内容对力学学科、尤其是岩土力学领域的科研工作也具有重要指导价值.     

轴向均布载荷下压杆稳定问题的DQ解

叙述了微分求积法(differential quadrature method)的一般方法，研究用微分求积法求解在均布轴向载荷下细长杆的稳定问题．通过Newton-Raphson法求解非线性方程组，以及对问题进行线性假设后求解广义特征值方程，得到了精度很高的后屈曲挠度数值和临界载荷数值．与解析解和其他近似解相比，微分求积法具有较高的精度和简便性．     

一级相变磁制冷材料LaFe_(11.6)Si_(1.4)合金的磁相变特性系统分析

以La Fe11.6Si1.4合金为研究对象,系统分析了该一级相变材料的居里温度(TC)、磁场诱导磁相变的临界磁场(HC)、磁化率(χ)、磁滞、磁熵变(ΔS)、制冷能力(RCP)等磁性特性。结果表明:温度诱导磁相变的居里温度和磁场诱导磁相变的临界磁场均随磁场呈线性增加,ΔTC和ΔH随磁场和温度的变化率的值分别为4.1 K·T-1和0.2 T·K-1。当合金处于纯铁磁态和顺磁态时熵变磁熵变几乎为零,但磁场诱导的磁相变,会导致某一定温度下合金磁熵变有一个突变。但合金最大熵变并不是随磁场的增加而线性增加,当磁场达到一定值后随磁场增加其值基本没有变化。不同模型计算的制冷能力均随磁场的增加而呈线性增加。在两相共存态中,同一温度下两种不同铁磁的磁化率存在差异,即因磁场诱导的铁磁态相与合金中本身的铁磁态相的磁化率存在差异,且前者小于后者,这种物理现象对深入研究温度诱导和磁场诱导磁相变的差异有一定的参考价值。     

The Structure and Optical Properties of the [Au18(SR)14] Nanocluster

Decreasing the core size is one of the best ways to study the evolution from Au^I complexes into Au nanoclusters. Toward this goal, we successfully synthesized the [Au₁₈(SC₆H₁₁)₁₄] nanocluster using the [Au₁₈(SG)₁₄] (SG=L ‐glutathione) nanocluster as the starting material to react with cyclohexylthiol, and determined the X‐ray structure of the cyclohexylthiol‐protected [Au₁₈(C₆H₁₁S)₁₄] nanocluster. The [Au₁₈(SR)₁₄] cluster has a Au₉ bi‐octahedral kernel (or inner core). This Au₉ inner core is built by two octahedral Au₆ cores sharing one triangular face. One transitional gold atom is found in the Au₉ core, which can also be considered as part of the Au₄(SR)₅ staple motif. These findings offer new insight in terms of understanding the evolution from [Au^I(SR)] complexes into Au nanoclusters.     

Static yield stress of ferrofluid-based magnetorheological fluids

In this work, the yield stress of ferrofluid-based magnetorheological fluids (F-MRF) was investigated. The fluids are composed of a ferrofluid as the liquid carrier and micro-sized iron particles as magnetic particles. The physical and magnetorheological properties of the F-MRF have been investigated and compared with a commercial mineral oil-based MR fluid. With the addition of a ferrofluid, the anti-sedimentation property of the commercial MR fluids could be significantly improved. The static yield stress of the F-MRF samples with four different weight fractions (ϕ) of micro-sized iron particles were measured using three different testing modes under various magnetic fields. The effects of weight fraction, magnetic strength, and test mode on the yielding stress have been systematically studied. Finally, a scaling relation, , was proposed for the yield stress modeling of the F-MRF system.     

魔芋的抗病性与叶片中水溶性氨基酸含量的关系

利用反相高效液相色谱法(RP-HPLC)收集了正常花魔芋、软腐病花魔芋、白魔芋和珠芽魔芋叶片的水溶性氨基酸图谱,分析了对 软腐病具有不同抗病性的魔芋品种与多种水溶性氨基酸含量和比例的关系。结果表明:不同抗病性的品种及同一品种的正常魔芋叶片 和病株魔芋叶片中水溶性氨基酸的含量存在显著差别,因而可以以此方法为基础建立指纹图谱库,分析特征峰与魔芋抗病性的关系,为 研究魔芋病害防治技术提供新的思路。     

微波水解-液相色谱-原子荧光光谱法测定硒蛋白中的硒代氨基酸

针对酶解法测定硒代氨基酸操作复杂,时间长,水解不完全且水解产物不稳定等问题,建立一种微波水解-液相色谱-原子荧光光谱仪测定硒蛋白中硒代氨基酸的方法。样品经HCl(6 mol/L)微波水解后,调节pH值至7.5,采用阴离子色谱柱,pH=6.0的(NH_(4))_(2)HPO_(4)(40 mmol/L)溶液为流动相,流速0.6 mL/min,等度洗脱12 min的条件对硒代胱氨酸(SeCys_(2))、甲基-硒代半胱氨酸(MeSeCys)和硒代蛋氨酸(SeMet)进行分离,用原子荧光光谱仪测定其含量。微波水解条件采用星点设计-响应面法进行优化,优选最佳水解条件为:称样量20 mg,水解温度150℃,水解时间40 min。SeCys_(2)、MeSeCys和SeMet均在0~100 ng浓度范围内呈线性关系,相关系数均大于0.999,检出限分别为0.07、0.03和0.14 mg/kg,RSD分别为5.6%、4.6%、3.7%(n=6)。用来测定硒代氨基酸,耗时短,成本低,水解完全,操作简单,水解产物稳定,能够科学评价硒蛋白中硒代氨基酸的组成,对硒蛋白产品的质量控制和溯源提供了科学方法,值得推广应用。     

Cu(i) catalysis for selective condensation/bicycloaromatization of two different arylalkynes: direct and general construction of functionalized C–N axial biaryl compounds

Selective condensation/bicycloaromatization of two different arylalkynes is firstly developed under ligand-free copper(i)-catalysis, which allows the direct synthesis of C–N axial biaryl compounds in high yields with excellent selectivity and functional group tolerance. Due to the critical effects of Cu(i) catalyst and HFIP, many easily occurring undesired reactions are suppressed, and the coupled five–six aromatic rings are constructed via the selective formation of two C(sp²)–N(sp²) bonds and four C(sp²)–C(sp²) bonds. The achievement of moderate enantioselectivity verifies its potential for the simplest asymmetric synthesis of atropoisomeric biaryls. Western blotting demonstrated that the newly developed compounds are promising targets in biology and pharmaceuticals. This unique reaction can construct structurally diverse C–N axial biaryl compounds that have never been reported by other methods, and might be extended to various applications in materials, chemistry, biology, and pharmaceuticals.

Selective condensation/bicycloaromatization of two different arylalkynes is firstly developed under ligand-free copper(i)-catalysis, which allows the direct synthesis of C–N axial biaryl compounds in high yields with excellent selectivity and functional group tolerance.     

Enantiomeric separation of six beta-adrenergic blockers on Chiralpak IB column and identification of chiral recognition mechanisms by molecular docking technique

Enantiomeric separation of six β-adrenergic blockers was systematically studied for the first time on a polysaccharide-based chiral stationary phase, i.e. Chiralpak IB, under the normal-phase mode. The effect of alcohol modifiers, alcohol content and basic additive on enantiomeric separation was evaluated and optimized. Under the optimal conditions, the enantiomers of atenolol, bevantolol, cartelol, esmolol, metoprolol and propranolol were all baseline resolved with resolutions of 1.50, 8.56, 2.05, 2.11, 3.56 and 4.02, respectively. Additionally, molecular docking was tested to explain chiral recognition mechanisms of this set of the drug enantiomers on Chiralpak IB. The details of the various interactions affecting enantiomeric separation were confirmed from the molecular level and the modeling data were in agreement with the chromatographic results concerning the enantioselectivity.     

光电化学水分解中铁酸盐光阴极的制备与改性

由n型半导体光阳极和p型半导体光阴极组成的无偏压光电化学电池通过太阳能可以将水直接转化为高能量密度的氢气,为解决太阳能利用过程中存在的间歇性和储存问题提供了一种潜在的经济有效的解决途径。金属氧化物具有低成本和易制备等优势,相比于发展较成熟的n型光阳极金属氧化物材料,传统的p型光阴极金属氧化物材料由于金属离子易受到光电腐蚀的影响,光电极寿命的提升是个很大的挑战。作为新型的金属氧化物光阴极材料,铁酸盐具有合适的带隙、较好的光稳定性、较正的起始电位以及较低的制备成本,正在成为光电化学电池实际应用中的有力竞争者。本文阐述了光电化学水分解的基本原理与提升光电极性能的一般方法,总结了近年来颇受关注的代表性铁酸盐光阴极材料CuFeO₂、CaFeO₄与LaFeO₃在制备方法、元素掺杂以及表面修饰等方面取得的重要进展,并对铁酸盐光阴极的未来发展趋势做了展望。