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排序方式: 共有259条查询结果,搜索用时 281 毫秒
1.
Transport in Porous Media - Based on microfocus X-ray computed tomography analyses, the relationship between the characteristics of pore structure and fluid flow behavior was investigated through... 相似文献
2.
As a highly strained small molecule, [1.1.1]propellane has been widely used in various synthetic transformations owing to the exceptional reactivity of the central bond between the two bridgehead carbons. Utilizing strain-release approaches, the rapid development of strategies for the construction of bicyclo[1.1.1]pentane (BCP) and cyclobutane derivatives using [1.1.1]propellane as the starting material has been witnessed in the past few years. In this review, we highlight the most recent advances in this field. Accordingly, the reactivity of [1.1.1]propellane can be divided into three pathways, including radical, anionic and transition metal-catalyzed pathways under appropriate conditions. 相似文献
3.
4.
The effects of the Gaussian white noise excitation on structural safety due to erosion of safe basin in Duffing oscillator
with double potential wells are studied in the present paper. By employing the well-developed stochastic Melnikov condition
and Monte–Carlo method, various eroded basins are simulated in deterministic and stochastic cases of the system, and the ratio
of safe initial points (RSIP) is presented in some given limited domain defined by the system’s Hamiltonian for various parameters
or first-passage times. It is shown that structural safety control becomes more difficult when the noise excitation is imposed
on the system, and the fractal basin boundary may also appear when the system is excited by Gaussian white noise only. From
the RSIP results in given limited domain, sudden discontinuous descents in RSIP curves may occur when the system is excited
by harmonic or stochastic forces, which are different from the customary continuous ones in view of the first-passage problems.
In addition, it is interesting to find that RSIP values can even increase with increasing driving amplitude of the external
harmonic excitation when the Gaussian white noise is also present in the system.
The project supported by the National Natural Science Foundation of China (10302025 and 10672140).
The English text was polished by Yunming Chen. 相似文献
5.
Sheng Xia Shan Yin Shimin Tao Yanhui Shi Liangce Rong Xianyong Wei Zhimin Zong 《Research on Chemical Intermediates》2012,38(9):2435-2442
One-pot, multicomponent reaction for the synthesis of novel substituted pyrimidine derivatives: 4-amino-5-carbonitrile-2-nitroaminopyrimidine from aromatic aldehydes, 1-nitroguanidine, and malononitrile under ethanol is described. Because of containing many active functional groups, such as amino, cyan and nitro, these products are important intermediate of organic synthesis. The advantages of this procedure include the short reaction time, mild reaction conditions, and excellent yields. 相似文献
6.
Shimin Zhang 《Colloid Journal》2011,73(4):467-477
Interaction between two double layers for the Na3PO4 type electrolytes at y
0 > y
d
> 0 were investigated with the aid of λ parameter methods and the accurate numeral results were given. The maximum of the
interaction energies between two double layers for Av+ Bv- A_{v_ + } B_{v_ - } type electrolytes at y
0 > y
d
> 0 is independent of y
0, but increases with y
d
. The interaction energies between two double layers for NaCl, CaCl2, FeCl3, Na2SO4 and Na3PO4 type electrolytes at y
0 = 5 and y
d
= 2 were compared. If the negative or positive ions for Av+ Bv- A_{v_ + } B_{v_ - } type electrolytes have the same charge number, the maximum of their interaction energies increases with the charge number
of the ions of opposite charge. If the negative or positive ions of the electrolytes have different charge numbers, the relative
heights of the maxima of their interaction energies are indefinite. For the in pairs conjugate type electrolytes like CaCl2 and Na2SO4 or FeCl3 and Na3PO4, the larger the charge number of the negative ions of the electrolytes is, the higher the maximum of their interaction energies
is. The results for Na3PO4 type electrolytes at y
0 > y
d
> 0 can also be applied to FeCl3 type electrolytes at y
0 > y
d
> 0. 相似文献
7.
The interaction between two similar plane double-layers for K4Fe(CN)6 type asymmetric electrolytes was investigated with the aid of λ parameter method. The interaction energies for the system
at positive surface potential were expanded in a power series. This formula covers with the bounds of all potential (y
0 ≤ 20). The accurate numeral results and V′ − ζ
d
curves were given for y
0 ≤ 20. When y
0 ≥ 2, V′ hardly changes with y
0. The interaction energies between two similar plane parallel double layers for the different type electrolytes at y
0 = 1 were compared. The present results are also fit for Th(NO3)4 type electrolytes at negative surface potential. 相似文献
8.
Shimin Guo Liquan Mei 《Physics letters. A》2011,375(3):309-313
In this Letter, by introducing He's polynomials in the correct functional, we propose a new fractional variational iteration method to solve nonlinear time-fractional partial differential equations involving Jumarie's modified Riemann-Liouville derivative. Several examples have been solved to illustrate the proposed method is quite effective and convenient for solving kinds of nonlinear fractional order problems. 相似文献
9.
10.
合成抗病毒母体三羟基核苷的新方法 总被引:1,自引:0,他引:1
三羟基核苷因其具有良好的抗病毒性能及作为核酸代谢作用的抑制剂而受到人们的关注.文献报道的合成方法[1~3]因反应需避光,温度控制要求严格,中间体二醛不稳定[4],给操作带来困难.产物不易纯化,一般局限于使用离子交换色谱法[5],而按此方法得到的无环核... 相似文献