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排序方式: 共有174条查询结果,搜索用时 15 毫秒
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S. V. Semikolenov K. A. Dubkov E. V. Starokon' D. E. Babushkin G. I. Panov 《Russian Chemical Bulletin》2005,54(4):948-956
The kinetics and mechanism of noncatalytic liquid-phase oxidation of but-1-ene and but-2-ene with nitrous oxide in a benzene
solution in the temperature range from 180 to 240°C were studied. Oxidation proceeds via the 1,3-dipolar cycloaddition mechanism to form carbonyl compounds. Both of these reactions occur with close rates and activation
energies and have the first orders with respect to the alkene and N2O. A considerable fraction (39%) of but-1-ene involved in oxidation undergoes cleavage at the double bond yielding propanal
and an equivalent amount of methylene, the latter producing ethylcyclopropane and cycloheptatriene. The oxidation of but-2-ene
proceeds with a minimum bond cleavage and affords methyl ethyl ketone with 84% selectivity. Regularities of the oxidation
of terminal and internal alkenes C2—C8 with nitrous oxide were analyzed using the previously published data.
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Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 925–933, April, 2005. 相似文献
3.
P. V. Pavlov I. V. Babushkin N. A. Loiko N. N. Rosanov S. V. Fedorov 《Radiophysics and Quantum Electronics》2004,47(10-11):898-904
We consider spatial dissipative solitons arising in the system of two nonlinear thin films which interact resonantly with light. Symmetric and nonsymmetric solitons and methods of their exciting and switching are studied. 相似文献
4.
Richard P. Kent IV 《Geometriae Dedicata》2004,106(1):145-159
We answer a question of J. Anderson's by producing infinitely many commensurability classes of fibered hyperbolic 3-manifolds whose fundamental groups contain subgroups that are locally free and not free. These manifolds are obtained by performing 0–surgery on a collection of knots with the same properties. 相似文献
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In a study of the reaction system MAO/(C5H5)2ZrMe2, the size of the ion pair [(C5H5)2Zr(mu-Me)2AlMe2]+ [Me-MAO]- was determined by pulsed field-gradient NMR of its cationic moiety. A mean effective hydrodynamic radius of 12.2-12.5 A, determined from diffusion rates in benzene solution at different zirconocene and MAO concentrations, indicates that the ion pair remains associated even at the lowest concentrations studied. At elevated concentrations, aggregation to ion quadruples or higher aggregates is indicated by an apparent size increase and by shifts of the C5H5 and Me 1H NMR signals. The equilibrium constant for the reaction [(C5H5)2ZrMe+...Me-MAO-] + 1/2Al2Me6 right harpoon over left harpoon [(C5H5)2Zr(mu-Me)2AlMe2]+ [Me-MAO]- changes at different Al/Zr ratios; this indicates that MAO contains various species that produce Me-MAO- anions with different Lewis basicities. The volume of the Me-MAO- anion suggests that it contains 150-200 Al atoms. 相似文献
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Enrique Castillo Rosa Eva Pruneda MÓnica Esquivel IV 《International Journal of Mathematical Education in Science & Technology》2013,44(2):209-232
The paper presents a method for generating random linear programming problems with a previously selected type of solution. The user can choose a problem whose solution is unbounded, bounded for minima, maxima or both, unique or multiple, with given structure, at wish. Initially, the feasible solution of the LPP is generated as the sum of a linear space, a cone, and a polytope, depending on the desired properties of the solution. With the aim of obtaining a simple set of constraints, the generators of these three structures are selected as random vectors with integer simple components, the range of which can be given. Next, an objective function that satisfies the required conditions, i.e. leads to a solution of the desired type, is obtained. The generating algorithms have been implemented in Mathematica and some illustrative examples are given to clarify the generation process. With this tool, a LPP can be generated, according to the instructor requirements, where this is a human or an expert system. They can control student progress and generate a sequence of problems covering all possible cases, in steps of increasing difficulty. Combining this tool with another (also produced by the same authors) that solves the problems and explains the whole process, step by step, a computer aided module for learning LPP, which is completely autonomous, can be easily obtained. 相似文献
9.
Abstract The electrical resistivity temperature dependence of S has been studied in the diamond anvil cell (DAC) of the “rounded cone-plane” type. The pressure is about 50 GPa. The experimental data analysis shows the polymerization between 380–410 K. The electrical resistivity temperature dependence is distorted by a number of maxima, some of them being shifted along the temperature axis towards the lower temperature and disappear with increasing transport current. 相似文献
10.
R. M. Arkhipov D. O. Zhiguleva A. V. Pakhomov M. V. Arkhipov I. Babushkin N. N. Rosanov 《Optics and Spectroscopy》2018,124(4):536-540
The possibility of generation of quasi-unipolar extremely short pulses (with a duration of several periods of field oscillations) is theoretically analyzed for the excitation of a circular, nonlinear, and resonant medium with a light spot. The light spot rotates along a circle with a velocity that exceeds the speed of light in vacuum, while particles of the medium are distributed uniformly along the circle. It is shown that, by introducing a delay in the form of a phase plate into the system, one can control the shape, the duration, and the amplitude of generated pulses. 相似文献