非线性Schringer方程的一个新的守恒差分格式

本文对非线性Ｓｃｈｒｏｄｉｎｇｅｒ方程提出了一种新的带参数的守恒差分格式,并证明了该格式的收敛性与稳定性,通过数值计算获得如下结论,本文提出的差分格式在取适当的参数后,精度上比Ｚｈａｎｇ Ｆｅｉ等人（１９９５）的格式有较大幅度的提高．     

非线性Schr(o)dinger方程初边值问题的守恒数值格式

该文对非线性Schr(o)dinger方程提出了一种新的守恒差分格式,并证明了该格式的收敛性与稳定性,通过数值计算获得如下结论,提出的差分格式在取适当的参数后,精度上好于文[7]中的格式.     

带五次项的非线性Schrdinger方程的守恒数值格式

本文对一类带五次项的非线性Ｓｃｈｒｄｉｎｇｅｒ方程提出了一种守恒差分格式,并证明了该格式的收敛性和稳定性．数值实验结果表明,该格式在计算这类非线性Ｓｃｈｒｄｉｎｇｅｒ方程时是可靠的．     

量子信息讲座 第五讲 量子克隆与量子复制

量子态不可克隆体现了量子力学的固有特性,它是量子信息科学的重要基础之一．文章简要介绍了量子不可克隆定理的物理内容以及量子复制机的基本原理,通过幺正坍缩过程我们构造了一种概率量子克隆机,并论证所有线性无关的量子态都可以被概率量子克隆机克隆     

棒球棒动力学分析

通过建立有限元模型, 寻找棒球的击球最佳点与棒球棒固有频率、模态振型之间的联系. 假定棒球棒模型采用的是线弹性材料, 并且边界条件为两端自由, 这与实际是相符合的. 接着讨论了给球棒``软木化'(在球棒头部掏出一个圆柱空腔, 在里面塞入软木或橡胶, 然后盖上木帽) , 或者采用金属球棒都能增加``最佳点'的效果. 最后又通过实验验证了该模型的正确性.     

Local detrended fluctuation analysis for spectral red-edge parameters extraction

Nowadays, spectrum technology makes it possible to nondestructively monitor crop and provide real-time diagnostic advice. Spectral red-edge parameters are important detection target for the growth of rapeseed. In this work, we propose a new method to acquire the rapeseed’s spectral red-edge parameters based on local detrended fluctuation analysis (L-DFA). In practice, by using the L-DFA, local Hurst exponent of the spectrum is calculated firstly. And then, six traditional red-edge parameter extraction methods, namely maximum first derivative method, adjusted linear extrapolation method, linear four-point interpolation method, inverted Gaussian method, Lagrangian interpolation method, and polynomial fitting interpolation, are employed to act on the estimated local Hurst exponent, and thus four red-edge parameters, i.e., red-edge position, red-edge amplitude, and left and right red-edge area, are obtained. In our experiments, by using the above four local Hurst exponent-based red-edge parameters as argument, a prediction model is developed to forecast the SPAD values (soil and plant analyzer development, often used as a parameter to indicate the chlorophyll content) for the five rapeseed’s growth periods based on random decision forest method. The results show that the local Hurst exponent-based red-edge feature can produce better model effect than the original spectrum-based one for the all phenological periods. Significance test for the four kinds of plant patterns shows that there is huge difference of the proposed four-dimensional red-edge features between the transplant and direct plant in the whole process of rapeseed’s growth. The differences between the other three groups of plant factors (two planting densities, two fertilizer types, and two weed controls) are not significant in certain specific growth periods of rapeseed. These findings provide a basis for studying difference of rapeseed yield and oil differences between different planting patterns.     

Morphology-Reserved Synthesis of Discrete Nanosheets of CuO@SAPO-34 and Pore Mouth Catalysis for One-Pot Oxidation of Cyclohexane

Discrete nanosheets of silicon-doped AlPO₄ molecular sieves (SAPO-34) with a thickness of ≈7 nm have been prepared through morphology-reserved synthesis with a lamellar aluminum phosphate as precursor. Cages of the nanosheets are in situ incorporated with copper oxide clusters. The CuO@SAPO-34 nanosheets exhibit a large external surface area with a high number of (010) channel pores on the surface. Due to the thin morphology, copper oxide clusters occupy the outmost cages with a probability >50 %. The distinctive configuration facilitates a new concept of pore mouth catalysis, i.e., reactant molecules larger than the pores cannot enter the interior of the molecular sieves but can interact with the CuO clusters at “the mouth” of the pore. In heterogeneous catalysis, CuO@SAPO-34 nanosheets have shown top performance in one-pot oxidation of cyclohexane to adipic acid by O₂, a key compound for the manufacture of nylon-66, which is so far produced using non-green nitric acid oxidation.     

Isoreticular Linker Substitution in Conductive Metal–Organic Frameworks with Through-Space Transport Pathways

The extension of reticular chemistry concepts to electrically conductive three-dimensional metal–organic frameworks (MOFs) has been challenging, particularly for cases in which strong interactions between electroactive linkers create the charge transport pathways. Here, we report the successful replacement of tetrathiafulvalene (TTF) with a nickel glyoximate core in a family of isostructural conductive MOFs with Mn²⁺, Zn²⁺, and Cd²⁺. Different coordination environments of the framework metals lead to variations in the linker stacking geometries and optical properties. Single-crystal conductivity data are consistent with charge transport along the linker stacking direction, with conductivity values only slightly lower than those reported for the analogous TTF materials. These results serve as a case study demonstrating how reticular chemistry design principles can be extended to conductive frameworks with significant intermolecular contacts.     

The application of the extremum principles for a Bingham solid

Summary An extension of the extremum principle concerned with statically admissible stress fields for boundary value problems of an incompressible rigid visco-plastic (Bingham) solid is derived. This extension is an inequality that gives a lower bound for the rate of work of the unknown surface tractions in certain visco-plastic boundary value problems. Lower bounds are obtained for the torque required to twist a prismatic visco-plastic bar of square crossection and these lower bounds are presented along with upper bounds obtained from an inequality that was derived in a previous paper¹).Nomenclature k yield stress in pure shear - coefficient of viscosity - _ij stress tensor referred to rectangular cartesian axes Ox _i - s _ij stress deviator tensor - T _i surface traction - J (1/2s _ij s _ij )^1/2 - v _i velocity vector - _ij = rate of deformation tensor - n _i outward unit normal to surface - I (2 _{ij ij} )^1/2 - [v] magnitude of a velocity discontinuity in flow of a rigid perfectly plastic solid - S surface - V volume - S _t part of surface upon which T _i is prescribed - S _v part of surface upon which v _i is prescribed - S _d surface of velocity discontinuity in flow of a rigid plastic solid - x, y, z rectangular cartesian coordinates - u, v, w velocity components in the x, y and z directions respectively - rate of twist per unit length - T torque     

特种氧化铝负载氧化钛作为异丙醇还原肉桂醛的高性能催化剂

肉桂醇在香料、香精以及医药等诸多高端领域有着重要应用,常通过肉桂醛加氢法制备.由于热力学上肉桂醛中C=C–C=O官能团的C=C双键加氢比C=O双键更有优势,因此不管是从学术角度还是工业生产角度来看,高选择性还原C=O基团都是一项极具挑战的任务.肉桂醛加氢反应的副产物苯丙醛以及苯丙醇的生成不仅导致肉桂醇收率降低,而且大大增加分离纯化成本,因此设计并制备出有利于C=O官能团高选择性氢化的高效催化剂具有重要意义.Meer-wein-Ponndorf-Verley(MPV)反应以异丙醇为氢供体,是一种可选择加氢C=C–C=O中C=O官能团的反应.目前用于MPV还原的催化剂(均相或多相)在实际应用中通常选择性不高,使得目标产物得率低且分离成本高.本文报道了负载于一种特殊氧化铝表面的氧化钛催化剂(记为TiOx/γ-Al2O3-nt),其催化肉桂醛经MPV还原为肉桂醇的催化性能优异,表征结果发现该特殊氧化铝可导致表面氧化钛呈较高比例的低价钛物种高度分散状态,从而成为一种高效的肉桂醛MPV还原催化剂.TEM结果表明,这种特殊氧化铝和普通氧化铝在形貌上有很大差别,具有比较规整的一维纳米粒子形貌.综合XRD,TEM,Raman以及H/D同位素交换表征结果,可得到氧化钛高度分散在氧化铝表面的结论.原位XPS结果表明,Ti-Ox/γ-Al2O3-nt催化剂表面具有较高浓度的Ti(III)物种,而以普通氧化铝为载体的催化剂TiOx/γ-Al2O3-c在相同的还原条件下其表面Ti(Ⅲ)物种浓度较低,这种差异的来源是具有规整形貌的一维纳米氧化铝提供了更加均匀的表面位点使得表面高度分散的氧化钛容易被还原为低价态.NH3-TPD结果表明,TiOx/γ-Al2O3-nt催化剂具有高的L酸酸量.肉桂醛MPV还原反应结果显示,表面负载氧化钛的特殊氧化铝(TiOx/γ-Al2O3-nt)是一种非常高效的催化剂,具有很高的目标产物肉桂醇的选择性,几乎观察不到副产物的生成,多次套用实验结果也证实该催化剂具有良好的稳定性.该催化剂的高性能可归纳为以下两个方面的原因:一方面,L酸是MPV还原反应的活性中心,该催化剂具有高的L酸酸量,因此转化率高;另一方面,其表面较高浓度的Ti(III)物种可以使肉桂醛以垂直吸附模式(吸附终端为C=O)在催化剂表面吸附,这种吸附模式可以高选择性地还原为目标产物肉桂醇,因此同时具有很高的选择性.