排序方式: 共有49条查询结果,搜索用时 609 毫秒
11.
本文对钙钛矿型氧化物的制备方法及其用于固体氧化物燃料电池(SOCFs)和金属-空气电池中的最新进展进行了较为全面的综述。制备钙钛矿型氧化物的方法有很多,包括盐分解法、固相法、共沉淀法、溶胶-凝胶法、水热法、反微乳法和模板法等。不同的制备方法可以得到各种形貌的钙钛矿型氧化物,如纳米立方体、纳米管、纳米棒、纳米片、纳米纤维和介孔结构。本文总结了这些制备方法的优点、缺点以及其适用的范围。作为一种重要的功能材料,钙钛矿型氧化物广泛应用于电极材料中。在SOCF中,重点介绍了阴极、阳极和电解质的研究现状,从电极材料的设计出发,比较了它们用于不同电极材料时的稳定性、电导率以及电催化活性,指出不足之处;在空气电极中,主要讨论了影响钙钛矿型氧化物氧的析出/还原催化活性和稳定性的因素。最后对钙钛矿型氧化物今后研究的方向和应用前景进行了预测。 相似文献
12.
We develop a locally conservative Eulerian–Lagrangian finite volume scheme with the weighted essentially non-oscillatory property (EL–WENO) in one-space dimension. This method has the advantages of both WENO and Eulerian–Lagrangian schemes. It is formally high-order accurate in space (we present the fifth order version) and essentially non-oscillatory. Moreover, it is free of a CFL time step stability restriction and has small time truncation error. The scheme requires a new integral-based WENO reconstruction to handle trace-back integration. A Strang splitting algorithm is presented for higher-dimensional problems, using both the new integral-based and pointwise-based WENO reconstructions. We show formally that it maintains the fifth order accuracy. It is also locally mass conservative. Numerical results are provided to illustrate the performance of the scheme and verify its formal accuracy. 相似文献
13.
Total Syntheses of Crinipellins Enabled by Cobalt‐Mediated and Palladium‐Catalyzed Intramolecular Pauson–Khand Reactions
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Zhihui Huang Dr. Jun Huang Yongzheng Qu Weibin Zhang Prof. Dr. Jianxian Gong Prof. Dr. Zhen Yang 《Angewandte Chemie (International ed. in English)》2018,57(28):8744-8748
Efficient total syntheses of the naturally occurring, potent antibiotic compounds (?)‐crinipellin A and (?)‐crinipellin B are described. The key advanced intermediate, a fully functionalized tetraquinane core, was constructed by a novel thiourea/palladium‐catalyzed Pauson–Khand reaction. This intermediate can serve as a common intermediate for the collective total synthesis of other members of the crinipellin family. 相似文献
14.
Yuan Zhengqiu Dai Wei Zhang Shenghong Wang Fengxin Jian Jian Zeng Jianxian Zhou Hu 《Cellulose (London, England)》2022,29(6):3059-3077
Cellulose - Lignocellulosic biomass is the most abundant renewable carbon resource on earth, for which many efforts have been made to convert it using various chemocatalytic processes.... 相似文献
15.
A mesh condition is developed for linear finite element approximations of anisotropic diffusion–convection–reaction problems to satisfy a discrete maximum principle. Loosely speaking, the condition requires that the mesh be simplicial and \(\mathcal {O}(\Vert \varvec{b}\Vert _\infty h + \Vert c\Vert _\infty h^2)\) -nonobtuse when the dihedral angles are measured in the metric specified by the inverse of the diffusion matrix, where \(h\) denotes the mesh size and \(\varvec{b}\) and \(c\) are the coefficients of the convection and reaction terms. In two dimensions, the condition can be replaced by a weaker mesh condition (an \(\mathcal {O}(\Vert \varvec{b}\Vert _\infty h + \Vert c\Vert _\infty h^2)\) perturbation of a generalized Delaunay condition). These results include many existing mesh conditions as special cases. Numerical results are presented to verify the theoretical findings. 相似文献
16.
Concise Stereoselective Synthesis of Oxaspirocycles with 1‐Tosyl‐1,2,3‐triazoles: Application to the Total Syntheses of (±)‐Tuberostemospiroline and (±)‐Stemona‐lactam R
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Junkai Fu Hongjuan Shen Yuanyuan Chang Prof. Dr. Chuangchuang Li Dr. Jianxian Gong Prof. Dr. Zhen Yang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(40):12881-12888
A 4‐substituted‐1‐tosyl‐1,2,3‐triazole‐based stereoselective synthesis of structurally diverse oxaspirocycles is reported. The synthesis involves Rh‐catalyzed loss of nitrogen from 4‐substituted‐1‐tosyl‐1,2,3‐triazoles, Grignard reaction, and a ring‐closing metathesis reaction as key steps. By employing readily available and stable 4‐substituted‐1‐tosyl‐1,2,3‐triazoles as surrogates of diazo compounds and nitrogen sources, two types of oxaspirocycles were obtained. The latter compounds, which contain adjacent nitrogen stereocenters, could serve as the core structures of many natural products. This chemistry has been successfully applied to the total syntheses of (±)‐tuberostemospiroline and (±)‐stemona‐lactam R. 相似文献
17.
Fuzhuo Li Qian Tu Sijia Chen Lei Zhu Prof. Dr. Yu Lan Prof. Dr. Jianxian Gong Prof. Dr. Zhen Yang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(21):5938-5942
The first enantiospecific synthesis of hispidanin A ( 4 ), a dimeric diterpenoid from the rhizomes of Isodon hispida, was achieved with a longest linear sequence of 12 steps in 6.5 % overall yield. A key component is the use of the abundant and naturally occurring diterpenoids (+)-sclareolide and (+)-sclareol as starting materials, which enables the gram-scale preparation of the key intermediates totarane ( 1 ) and s-trans-12E,14-labdadien-20,8β-olide ( 2 ). Subsequently a thermal or an erbium-catalyzed intermolecular Diels–Alder reaction of totarane ( 1 ) with labdadienolide ( 2 ) provide convergent and rapid access to the natural product hispidanin A ( 4 ). The synthetic studies have offered significant impetus for the efficient construction of these architecturally complex natural products. 相似文献
18.
In this paper, a class of high-order central Hermite WENO (HWENO) schemes based on finite volume framework and staggered meshes is proposed for directly solving one- and two-dimensional Hamilton-Jacobi (HJ) equations. The methods involve the Lax-Wendroff type discretizations or the natural continuous extension of Runge-Kutta methods in time. This work can be regarded as an extension of central HWENO schemes for hyperbolic conservation laws (Tao et al. J. Comput. Phys. 318, 222–251, 2016) which combine the central scheme and the HWENO spatial reconstructions and therefore carry many features of both schemes. Generally, it is not straightforward to design a finite volume scheme to directly solve HJ equations and a key ingredient for directly solving such equations is the reconstruction of numerical Hamiltonians to guarantee the stability of methods. Benefited from the central strategy, our methods require no numerical Hamiltonians. Meanwhile, the zeroth-order and the first-order moments of the solution are involved in the spatial HWENO reconstructions which is more compact compared with WENO schemes. The reconstructions are implemented through a dimension-by-dimension strategy when the spatial dimension is higher than one. A collection of one- and two- dimensional numerical examples is performed to validate high resolution and robustness of the methods in approximating the solutions of HJ equations, which involve linear, nonlinear, smooth, non-smooth, convex or non-convex Hamiltonians. 相似文献
19.
Dr. Jun Huang Yueqing Gu Kai Guo Lei Zhu Prof. Dr. Yu Lan Prof. Dr. Jianxian Gong Prof. Dr. Zhen Yang 《Angewandte Chemie (International ed. in English)》2017,56(27):7890-7894
Homodimericin A is a remarkable fungal metabolite. This highly oxygenated racemic unsaturated polyketide poses a significant synthetic challenge owing to its sterically demanding central cagelike core containing eight contiguous stereogenic centers (including three quaternary stereocenters) and several carbonyl functionalities. On the basis of its proposed biogenetic synthesis, we designed a total synthesis of homodimericin A that proceeds in seven steps and features a double Michael reaction, an intramolecular Diels–Alder reaction, and an ene reaction. 相似文献
20.
In [35, 36], we presented an $h$-adaptive Runge-Kutta
discontinuous Galerkin method using troubled-cell indicators for
solving hyperbolic conservation laws. A tree data structure (binary
tree in one dimension and quadtree in two dimensions) is used to aid
storage and neighbor finding. Mesh adaptation is achieved by
refining the troubled cells and coarsening the untroubled
"children". Extensive numerical tests indicate that the proposed $h$-adaptive method is capable of saving the computational cost and
enhancing the resolution near the discontinuities. In this paper, we
apply this $h$-adaptive method to solve Hamilton-Jacobi equations,
with an objective of enhancing the resolution near the
discontinuities of the solution derivatives. One- and
two-dimensional numerical examples are shown to illustrate the
capability of the method. 相似文献