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21.
DEEB MARJI KHAMIS ABBAS 《Journal of inclusion phenomena and macrocyclic chemistry》1997,27(4):269-277
The effect of 18-crown-6 and kryptofix (2,2,1) on the oxidation of triethylamine byaqueous ferricyanide ion has been studied at pH 4, 7, and 9.The macrocycle retarded the normal oxidation process at all pH values,the effect depending on the macrocyclic ligand concentration Kryptofix (2,2,1) had a greater effect than 18-crown-6 at all pHvalues in this study. For 18-crown-6, retardation decreases in the order pH 9 > 4 > 7 while forkryptofix it follows the order pH 9 > 7 > 4. 相似文献
22.
A model of two interacting (chemically different) linear polymer chains is solved exactly using the real-space renormalization
group transformation on a family of Sierpinski gasket type fractals and on a truncated 4-simplex lattice. The members of the
family of the Sierpinski gasket-type fractals are characterized by an integer scale factorb which runs from 2 to ∞. The Hausdorff dimensiond
F of these fractals tends to 2 from below asb → ∞. We calculate the contact exponenty for the transition from the State of segregation to a State in which the two chains are entangled forb = 2-5. Using arguments based on the finite-size scaling theory, we show that forb→∞, y = 2 - v(b) d
F, wherev is the end-toend distance exponent of a chain. For a truncated 4-simplex lattice it is shown that the system of two chains
either remains in a State in which these chains are intermingled in such a way that they cannot be told apart, in the sense
that the chemical difference between the polymer chains completely drop out of the thermodynamics of the system, or in a State
in which they are either zipped or entangled. We show the region of existence of these different phases separated by tricritical
lines. The value of the contact exponenty is calculated at the tricritical points. 相似文献
23.
Two Convergence Problems for Monotone Sequences 总被引:1,自引:0,他引:1
Eight measures of rate of convergence of monotone sequences of real numbers have been proposed and discussed in a paper by Beyer, Ebanks, and Qualls (Acta Appl. Math. 20 (1990), 267–284). These rates arose in discussions of dynamical systems. In the comparisons of these rates, two problems remained. A complete answer is given to one of the problems and a partial answer is given to the other problem. 相似文献
24.
This research extends previous work with dynamic models to manage groundwater quality by using the consumptive nitrate use rate instead of the nitrate application rate. The analysis indicates that misspecification results in overestimation of economic benefits, and supra-optimum nitrogen fertilizer application rates and groundwater nitrate stocks at a steady state. 相似文献
25.
本文提出用一种新的时间离散化方法对汽车拖拉机的转向机构进行优化设计.该离散化方法是按被实现函数变化率的大小划分时间单元,在被实现函数变化率较大的区域,分点较密;在率化率较小的区域,分点较稀.笔者还分别用等间距的时间离散化及切比雪夫时间离散化方法,对同一机构使用同一种优化方法进行了优化设计,并将三种计算结果进行了比较.结果表明,笔者提出的方法,没有增加计算工作量,而能提高计算精度. 相似文献
26.
建立了铸件成品率的数学模型,以实现铸件成品率的微机管理.该系统具有统计、分析、判断、优化等各项功能,满足了生产现场对铸件成本的控制. 相似文献
27.
对高浓度的再生丝素水溶液(15%~37%)在不同剪切速率下(1000s-1和2000s-1)的构象变化进行了研究,对剪切前后的溶液进行了DSC和Raman对比测试。发现经过剪切,丝素溶液更客易发生从无规线团或α-螺旋向β-折叠构象的转变,且转变的程度随所受剪切速率的增加而提高。而且当丝素浓度低于27%时对剪切不敏感;超过30%时则对剪切敏感。 相似文献
28.
Ben-Yuan Gu Yao Lu Tzong-Jer Yang 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(4):493-502
We present numerical investigations of the transmission properties of electrons in a normal quantum wire tangentially attached
to a superconductor ring threaded by magnetic flux. A point scatterer with a δ -function potential is placed at node to model
scattering effect. We find that the transmission characteristics of electrons in this structure strongly depend on the normal
or superconducting state of the ring. The transmission probability as a function of the energy of incident electrons, in the
case of a superconductor ring threaded by one quantum magnetic flux, emerges one deep dip, imposed upon the first broad bump
in spectrum. This intrinsic conductance dip originates from the superconductor state of the ring. When increasing the magnetic
flux from one quantum magnetic flux to two, the spectrum shifts toward higher energy region in the whole. This conductance
dip accordingly shifts and appears in the second bump. In the presence of a point-scatterer at the node, the spectrum is substantially
modified. Based on the condition of the formation of the standing wave functions in the ring and the broken of the time-reserve
symmetry of Schr?dinger equation after switching magnetic flux, the characteristics of transmission of electrons in this structure
can be well understood.
Received 6 November 2001 相似文献
29.
In this note, we study convergence rates in the law of large numbers for independent and identically distributed random variables under sublinear expectations. We obtain a strong L^p-convergence version and a strongly quasi sure convergence version of the law of large numbers. 相似文献
30.
可提前还款的定期贷款是隐含着期权的利率衍生物,本文建立CIR利率模型下可提前还款的定期贷款的数学模型,通过离散偏微分方程,建立了模型的计算方法,讨论了随机利率对提前还贷的影响. 相似文献