Biaxial Q-shearing of 27Al 3QMAS NMR spectra: Insight into the structural disorder of framework aluminosilicates

In this contribution, we present the application potentiality of biaxial Q-shearing of ²⁷Al 3QMAS NMR spectra in the analysis of structural defects of aluminium units in aluminosilicates. This study demonstrates that the combination of various shearing transformations of the recorded ²⁷Al 3QMAS NMR spectra enables an understanding of the broadening processes of the correlation signals of disordered framework aluminosilicates, for which a wide distribution of ²⁷Al MAS NMR chemical shifts and quadrupolar parameters (i.e., second-order quadrupolar splitting and quadrupole-induced chemical shifts) can be expected. By combining the suitably selected shearing transformation procedures, the mechanisms of the formation of local defects in aluminosilicate frameworks, including Al/Si substitution effects in the next-nearest neighbouring T-sites, variations in bond angles, and/or variations in the physicochemical nature of charge-balancing counter-ions, can be identified. The proposed procedure has been extensively tested on a range of model aluminosilicate materials (kyanite, γ-alumina, metakaolin, analcime, chabazite, natrolite, phillipsite, mordenite, zeolite A, and zeolite Y).     

用于板料成形反向模拟的特殊应力更新算法

提出了一种改进的反向模拟法,以最终构型为研究对象,采用Euler坐标系,基于虚功原理获得有限元列式. 改进的反向模拟法采用了一种基于塑性流动理论的本构方程,可以充分考虑应变历史对塑性变形的影响. 为了避免流动理论应力更新算法过程中关于未知量\Delta\lambda 的非线性方程的求解,引入等效应力思想,无需Newton-Raphson迭代直接计算未知量\Delta \lambda . 盒形件的拉深实例中,传统的基于塑性形变本构方程的反向模拟法和改进的基于塑性流动本构方程的反向模拟法计算结果,分别与基于增量有限元法的正向数值模拟求解器LS-DYNA计算结果进行对比. 通过获得的坯料轮廓、成形极限图、等效应变分布、计算效率等的比较,验证了所提出的基于塑性流动理论本构模型的应力更新算法的有效性.      

上海世博会气象馆平均风压数值模拟研究

采用数值模拟方法对上海世博会气象馆进行了平均风压数值模拟,比较了4种较适合于结构风工程的RNG k-ε,SST-k-ω,SSG-RSM和BSL-RSM湍流物理模型,包括体型系数、表面合力、合力矩及湍动能结果,同时结合风流动特性分析了其规律性和差别的原因,并得到SST-k-ω,BSL-RSM与SSG-RSM模型各有优势,而RNG k-ε模型稍差的结论.最后研究了有无干扰情况下的场馆表面平均风压系数,分析了风干扰的原因.     

方向数据密度函数核估计的重对数律

本文讨论方向数据密度函数核估计的逐点收敛速度问题,在较为温和的条件下建立了该核估计的重对数律并给出了它的逐点最优收敛速度.     

Planning and coordination of production and distribution facilities for multiple commodities

We study an integrated logistics model for locating production and distribution facilities in a multi-echelon environment. Designing such logistics systems requires two essential decisions, one strategic (e.g., where to locate plants and warehouses) and the other operational (distribution strategy from plants to customer outlets through warehouses). The distribution strategy is influenced by the product mix at each plant, the shipments of raw material from vendors to manufacturing plants and the distribution of finished products from the plants to the different customer zones through a set of warehouses. First we provide a mixed integer programming formulation to the integrated model. Then, we present an efficient heuristic solution procedure that utilizes the solution generated from a Lagrangian relaxation of the problem. We use this heuristic procedure to evaluate the performance of the model with respect to solution quality and algorithm performance. Results of extensive tests on the solution procedure indicate that the solution method is both efficient and effective. Finally a `real-world' example is solved to explore the implications of the model.     

手性联苯类化合物的制备

手性联苯化合物在有机合成和天然产物化学中都有相当重要的地位,本文论述了近年来得到手性联苯类化合物的一些方法。     

二氢卟吩P6醚类衍生物的合成

以蚕沙糊状叶绿素经酸碱降解制得的二氢卟吩P6三甲酯(2)为关键中间体,设计合成了9个二氢卟吩P6醚类衍生物3a～3e和4b～4e,用UV、IR、^1H、NMR、FAB-MS和元素分析确证了它们的结构。     

Two new coordination host frameworks for the inclusion of 4-amino-benzophenone guest molecules

The synthesis and structural characterization of novel organometallic coordination polymers are reported. The reaction of Cd(NO₃)₂ and 4,4′-bipy in CH₃OH/H₂O gave a 2D coordination network formulated as {[Cd(4,4′-bpy)₂·(H₂O)₂](NO₃)₂·4H₂O}¹⁰, which was used to capture an organic guest species (4-amino-benezopheone, C₁₃H₁₁NO (3)) to obtain {[Cd(4,4′-bpy)₂(NO₃)(H₂O)]·NO₃·(C₁₃H₁₁NO)₂} (1). Using L (L=4,4′-trimethylenedipyridine) instead of 4,4′-bipy, {[Cd(L)₂(H₂O)₂]·2H₂O·2NO₃·C₁₃H₁₁NO} (2) was synthesized, which has an interesting configuration.     

In situ measurement of cake thickness distribution by a photointerrupt sensor

An in situ optical method was developed to determine the thickness of the cake layer by using a low-cost photointerrupt sensor. The effects of slurry concentration, agitating speed (i.e. slurry transport velocity), background light and color of slurry on the accuracy of measurement were examined to verify the validity of this method. The accuracy of the thickness measurements was confirmed using uniform sized PMMA spheres. Experimental results show that the developed technique is useful for cake thickness ranging from 10 μm to 5 mm and yields a vertical resolution as high as 10 μm in the same order as that of gamma-ray absorption and NMR micro-imaging methods. This method has benefits of inexpensive, easy installation and a comparable accuracy compared with gamma-ray absorption, NMR micro-imaging and CATSCAN techniques. The developed method was then applied to measure the time course of cake layer thickness variation on the membrane surface during cross-flow micro-filtration of a PMMA suspension. Results of measurements show that the dynamic surface shape is not at all flat during a course of CFMF.     

纳米α-Fe~2O~3的XANES研究

选择纳米α-Fe~2O~3体系,运用X射线近边吸收谱(XANES)技术对纳米材料进行分析。结果表明,三种尺寸的纳米α-Fe~2O~3样品(颗粒尺寸分别是3nm,10nm和55nm)与粗颗粒商品的氧K边XANES谱的不同之处在于,纳米样品出现了一个新的吸收B峰。研究揭示,该峰可能是纳米α-Fe~2O~3中晶界部分氧的2p-4sp杂化所产生的一个新电子跃迁末态造成的。进一步的研究表明,随着纳米α-Fe~2O~3的粒子尺寸减小,氧的2p轨道和铁的3d轨道杂化增加,主要体现在2p-e~g杂化程度加剧,使得纳米颗粒中铁周围的氧配位八面体畸变程度加强。最后,通过对3nm样品在研磨和不研磨两种制样方式获得的氧K边XANES谱分析,证实纳米粒子体系中存在特殊的协同作用力。