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991.
用蒙特水罗方法对水气转移反应两种典型机理的寝反应动力学进行了研究。结果表明,Temkin等人的氧化-还原机理中,无论反应物CO和H2O的相对浓度怎样变化,CO2和H2的初始生成速率总是相差很大。 相似文献
992.
With order statistics of the uniform distribution on [0, l], exponential and beta distributions, a stochastic representation
is obtained for the uniform distribution over various domains, where A-type domains are closely associated with reliability
growth analysis, order restricted statistical inference and isotonic regression theory, V-type domains are connected with
the mixture-amount experiments, and T-type domains are well related to mixture experiments. With these stochastic representations,
the corresponding uniform distribution and number-theoretic nets can be generated. This approach seems to be new and is called
order statistics method. Some examples on reliability growth analysis and experimental design are presented.
This work was partially supported by a Hong Kong UGC-RGC grant, the Statistics Research and Consultancy Centre of HK-BU, and
the Chinese Academy of Sciences. 相似文献
993.
994.
固体分层取样方案的最优化设计 总被引:1,自引:0,他引:1
本文首次从理论上探讨了取得量对分层取样误差的影响,提出了总取样量一定时各层的最佳取样量和最小取样方差的计算公式,从而为分层取样的最佳取样方案设计提供了理论依据。 相似文献
995.
Christian Bartels Michael Schaefer Martin Karplus 《Theoretical chemistry accounts》1999,101(1-3):62-66
Adaptive umbrella sampling of the potential energy is used as a search method to determine the structures and thermodynamics
of peptides in solution. It leads to uniform sampling of the potential energy, so as to combine sampling of low-energy conformations
that dominate the properties of the system at room temperature with sampling of high-energy conformations that are important
for transitions between different minima. A modification of the procedure for updating the umbrella potential is introduced
to increase the number of transitions between folded and unfolded conformations. The method does not depend on assumptions
about the geometry of the native state. Two peptides with 12 and 13 residues, respectively, are studied using the CHARMM polar-hydrogen
energy function and the analytical continuum solvent potential for treatment of solvation. In the original adaptive umbrella
sampling simulations of the two peptides, two and six transitions occur between folded and unfolded conformations, respectively,
over a simulation time of 10 ns. The modification increases the number of transitions to 6 and 12, respectively, in the same
simulation time. The precision of estimates of the average effective energy of the system as a function of temperature and
of the contributions to the average effective energy of folded conformations obtained with the adaptive methods is discussed.
Received: 11 July 1998 / Accepted: 22 September 1998 / Published online: 17 December 1998 相似文献
996.
Summary The effects of electron beam irradiation on cork volatile compounds was studied at different doses (25, 100, 1000 kGy). Volatiles
were isolated from cork using the dynamic headspace-sampling technique, then identified by gas chromatography-mass spectrometry
(GC-MS). Similar gas chromatographic profiles were obtained for non-irradiated and irradiated corks. Quantitative differences
induced by the three doses were evaluated by calculating peak areas for each compound identified. The quantitative differences
between non-irradiated corks and those irradiated at 25 kGy were significant for only a few substances, whereas significant
quantitative differences were found in samples irradiated at 100 and 1000 kGy. For these doses, the content of volatile compounds
generally increased, especially that of aliphatic hydrocarbons and carbonyl compounds. The behaviour of radiolytic hydrocarbons
indicates that the mechanisms proposed for their formation in irradiated foods could take place even in cork. 相似文献
997.
998.
The time evolution of adatom and vacancy islands on an Ag(110) surface is studied by using a variable-temperature ultrahigh vacuum scanning tunneling microscope. The islands are created by Ar+ ion sputtering at low temperatures and at very low fluxes (0.004 ML s−1). The area of both kinds of island decreases linearly as a function of time, at least for small islands. The experimental results are compared with kinetic Monte Carlo simulations. 相似文献
999.
光电成像系统混淆效应的定量分析 总被引:3,自引:3,他引:0
光电成像系统由于抽样产生频谱混淆。用矢量分析方法,给出了正弦图像基元的混淆表达式。具体分析了以短形光栅为例的周期目标莫尔条纹式的混淆效应,以及非周期性目标噪 声形式的混淆效应。并分别作了计算机仿真实验。 相似文献
1000.
ALPHA Collaboration Marco Guagnelli Jochen Heitger Rainer Sommer Hartmut Wittig 《Nuclear Physics B》1999,560(1-3):465-481
We explain how masses and matrix elements can be computed in lattice QCD using Schrödinger functional boundary conditions. Numerical results in the quenched approximation demonstrate that good precision can be achieved. For a statistical sample of the same size, our hadron masses have a precision similar to what is achieved with standard methods, but for the computation of matrix elements such as the pseudoscalar decay constant the Schrödinger functional technique turns out to be much more efficient than the known alternatives. 相似文献