Miura transformation for the “good” Boussinesq equation

It is well known that each solution of the modified Korteveg–de Vries (mKdV) equation gives rise, via the Miura transformation, to a solution of the Korteveg–de Vries (KdV) equation. In this work, we show that a similar Miura-type transformation exists also for the “good” Boussinesq equation. This transformation maps solutions of a second-order equation to solutions of the fourth-order Boussinesq equation. Just like in the case of mKdV and KdV, the correspondence exists also at the level of the underlying Riemann–Hilbert problems and this is in fact how we construct the new transformation.     

基于中空纤维液相微萃取的大鼠体内大黄素及其代谢物分析

建立了中空纤维液相微萃取(HFLPME)耦合高效液相色谱法(HPLC)用于测定血浆和尿液中大黄素及其代谢物的浓度,比较了中药有效成分大黄素在不同性别大鼠体内的吸收和代谢能力,阐述了大黄素在体内的代谢和转化过程。本实验以聚偏氟乙烯纤维为溶剂载体,正辛醇为萃取溶剂,对血浆和尿液样品进行HFLPME处理,萃取后挥干有机溶剂,用50 μL甲醇溶解,进行HPLC测定。在优化的微萃取条件下,血浆和尿液样品中大黄素及其代谢物标准曲线线性良好(相关系数(r)大于0.9960);检出限为0.1～3.0 μg/L;富集倍数为12.2～26.3;日内、日间精密度(以相对标准偏差(RSD)计)小于11.0%;血浆和尿液中代谢物的平均回收率为97.9%～103%。HFLPME操作简单,富集倍数高,能有效去除生物样品中复杂基体的干扰,适用于复杂样品中微量、痕量成分分析物的分析测定。     

Reversible interpenetration in a metal-organic framework triggered by ligand removal and addition

Caging cages: Crystals of a metal-organic framework, MOF-123 [Zn(7) O(2) (NBD)(5) (DMF)(2) ] have a three-dimensional porous structure in which DMF ligands (see picture, pink) protrude into small channels. Removal of these ligands triggers the transformation of this MOF to the doubly interpenetrating form, MOF-246 [Zn(7) O(2) (NBD)(5) ]. Moreover, addition of DMF into MOF-246 triggers reverse transformation to give MOF-123. NBD=2-nitrobenzene-1,4-dicarboxylate.     

LiTi2(PO4)3/C 复合材料的制备及电化学性能

采用聚乙烯醇(PVA)辅助溶胶-凝胶法合成了具有Na+超离子导体(NASICON)结构的LiTi2(PO4)3/C复合材料.运用X射线衍射(XRD)、扫描电子显微镜(SEM)、充放电测试、循环伏安(CV)、电化学阻抗谱(EIS)等对其结构形貌和电化学性能进行表征.实验结果表明:合成的LiTi2(PO4)3/C具有良好的NASICON结构,首次放电容量为144mAh·g-1.电化学阻抗谱测试结果显示,LiTi2(PO4)3/C复合材料电极在首次嵌锂过程中分别出现了代表固体电解质相界面(SEI)膜及接触阻抗、电荷传递阻抗和相变阻抗的圆弧,并详细分析了它们的变化规律.计算了Li+在LiTi2(PO4)3中嵌入/脱出时的扩散系数,分别为2.40×10-5和1.07×10-5cm2·s-1.     

反应性模板法合成硫化银中空球-银纳米粒子异质结构

以Cu₂S中空球为反应性模板, 通过在水溶液中与银离子的阳离子交换和氧化还原反应制备了大小均匀的Ag₂S中空球-Ag纳米粒子异质结构, 即Ag₂S-Ag异质中空球. 该异质结构中每个Ag₂S中空球的直径约为600 nm, 壁厚约20–30 nm, 其表面均附着一个Ag纳米粒子. 采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射(XRD)和能量色散X射线谱(EDS)对所得Ag₂S-Ag异质中空球的结构和组成进行了表征. 若以CuS中空球为反应性模板, 在相似转化条件下则主要得到不含Ag粒子的Ag₂S中空球. 该结果表明, Cu₂S中的Cu(I)的还原性在Ag₂S-Ag异质中空球的形成中发挥了重要作用. 通过对所制备的Ag₂S-Ag异质中空球进行二次生长, 还可以得到Ag₂S中空球的半球表面均被Ag膜所包覆的Ag₂S-Ag异质中空球.     

有机物单层分散在相关材料制备中的应用

与无机氧化物和盐类在载体表面自发单层分散相类似, 许多有机物也可以在载体表面自发单层分散.有机物在载体表面单层分散行为和分散后的存在状态与有机物分子形状和结构特点及载体表面性质和孔结构有关. 利用有机物在载体表面的单层分散, 可以设计制备具有优异性能的材料. 本文简要综述了近年来这方面研究工作取得的相关进展, 主要介绍了有机物单层分散在碳/氧化物复合物、氧化物和薄壁中孔碳材料的制备和织构调控方面的一些应用实例. 单层分散的有机物热分解后可在载体表面形成均匀的薄碳层, 以无机多孔氧化物为载体可制备出包覆均匀碳薄层的碳/氧化物复合物, 这种碳/氧化物复合物在染料吸附、催化剂载体和光催化方面显现出好的性能. 以溶胶-凝胶法制备氧化物时, 分散的有机物可以隔离溶胶颗粒, 从而制备出高比表面积的氧化物并可对孔容进行调控, 以此方法制备的γ-氧化铝比表面积可达506 m²·g^-1. 在惰性气氛中加热上述碳/氧化物复合物, 碳层可抑制氧化物的相变; 而在氧气中, 碳层燃烧发热会促进相变, 由此可快速制备超细α-氧化铝. 包覆均匀碳薄层的氧化物载体对碳起支撑作用, 在将氧化物溶解去除后, 可便捷制得高比表面积、大孔容、高中孔率的薄壁中孔碳材料, 碳材料的形貌、孔径分布等可通过选用不同织构的氧化物载体进行调控.     

First-principles study of martensitic phase transformation of TiRh alloy

Geometric structures and atomic positions were studied with plane wave pseudo-potential method based on density functional theory for cubic, tetragonal, and monoclinic phases of TiRh alloy. Their phonon dispersion curves were obtained with frozen phonon method at harmonic approximation using density-functional perturbation theory. Our calculations revealed that both B2 and L1₀ phases are thermodynamically unstable. Jahn-Teller effect triggers the occurrence of Bain transformation from cubic to tetragonal phase, and then soft-mode phonon further leads to the transition from tetragonal to monoclinic phase on cooling. The monoclinic phase was predicted to be P2/m space group through atomic vibrational movement along [001] direction of virtual frequency modes of L1₀ phase. The temperature from B2 to L1₀ and then to P2/m were predicted to be about T=1100.53 K and T=324.48 K through free energy calculations with the electronic plus vibrational energy of formation, respectively, which is in good agreement with experimental observations.     

In-situ synchrotron X-ray diffraction study of stress-induced phase transformation in Ti50.1Ni40.8Cu9.1 thin films

Stress-induced martensitic transformation of as-sputtered and post-annealed Ti_50.1Ni_40.8Cu_9.1 thin films was investigated using in-situ synchrotron X-ray diffraction (S-XRD) technique. For the as-deposited film, in-situ S-XRD analysis showed a martensitic transformation from parent phase to martensite during initial loading, followed by reorientation of martensite variants via detwinning. This detwinning process induced a strong 〈0 2 0〉 fiber texture along the loading direction and a strong 〈0 0 2〉 fiber texture perpendicular to the loading direction. For the 650 °C annealed film, there is only elastic deformation, followed by a martensitic transformation during deformation.     

基于可拓变换的商业模式创新研究——以电动汽车商业模式创新为例

商业模式创新是企业本源的创新,是企业一切创新活动的基础和盈利的保障.目前,学术界和实业界对于商业模式创新仍然缺乏有效的方法和工具,在回顾商业模式相关文献的基础上,以电动汽车产业的商业模式创新为例,通过基元理论和可拓变换理论建立了流程化、形式化的商业模式创新方法.研究不仅丰富了商业模式理论,为商业模式创新提供了新的方法,同时对于丰富完善管理可拓工程理论也具有重要的意义.