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181.
182.
黄永明 《科技导报(北京)》2007,25(21):11-11
"直接法"测定蛋白质晶体结构新方法我国科学家近年来在发展"直接法"测定蛋白质晶体结构的研究方面,提出了一种处理单对同晶型置换数据的新方法。 相似文献
183.
本文探讨了目前高职高专院校以大学英语四、六级考试,作为三年制英语专业学生终结性评估标准的必要性,通过对该考试改革趋势的分析,浅析其对学生听力和口语表达能力教学的指导作用。 相似文献
184.
185.
Theoretical analysis of the acoustical characteristics of suspended micro-perforated panel absorbers
SHENGShengwo SONGYongmin WANGJiqing 《声学学报:英文版》2005,24(3):234-241
Sound absorption characteristics of suspended micro-perforated panel absorbers were investigated theoretically. The method of half thickness model of such panel absorber with quadripole analysis was used for predicting its acoustic performance. The analysis results show that the predictions agree well with the measurements of absorption in the reverberation chamber. The factors affecting the absorption characteristics for such absorbers were discussed, and some rules as design guidelines were given. 相似文献
186.
An analytical model for fractal dimension of tortuous streamtubes in porous media is derived. The proposed fractal dimension for tortuous streamtubes in porous media is expressed as a function of porosity and scale, and there is no empirical constant in the proposed expression. The model predictions for the fractal dimension of tortuous streamtubes in porous media are in good agreement with those by the box-counting method and with the observations of other researchers. 相似文献
187.
The chaotic Property of the Bak-Sneppen model is studied from the local Lyapunov exponent in the same way as for dynamical nonlinear systems.Similar behaviour is found for the one- and two-dimensional Bak-Sneppen models.The Lyapunov exponents for the two cases have the same order of magnitude and both decrease at early evolution but show a slow increasing saturation at late evolution. 相似文献
188.
189.
We study the spectral characteristics theoretically and experimentally in the Fraunhofer diffraction pattern formed by the diffraction of a spatially coherent, polychromatic light through a slit. It is found that the spectrum in some diffraction directions close to the singular direction is redshifted, compared to the spectrum of the incident polychromatic light, and blueshifted in other directions, and splits into two lines at the singular direction. We show that the experimental results are consistent with the theoretical expectations. 相似文献
190.
Monte Carlo (MC) simulations are used to simulate the voltage profile and the ionic conductivity s of Li ions in LixMn2O4 and its dependence on the lithium concentration x. The open circuit potential shows clearly the two plateaus in the charge/discharge curve, which agrees well with the experimental results. The two plateaus become more and more steep when the temperature is increased. The simulated ionic conductivity shows an M-shaped curve in the plot of ionic conductivity cr versus x when the simulation temperature is low. Interestingly,the minimum valley, which lies at the middle single-phase area near x=0.5, disappears gradually when the temperature increases to 453K. 相似文献