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961.
J. M. Borrego A. Conde V. A. Peña-Rodríguez J. M. Grenèche 《Hyperfine Interactions》2000,131(1-4):67-82
We propose a method to describe accurately Mössbauer spectra recorded on nanocrystalline FINEMET-type alloys by means of two independent components. The validity of the fitting procedure is controlled by comparing hyperfine characteristics of spectra recorded under different experimental configurations. In addition, the reliability of the fitting model is discussed from spectra obtained on nanocrystalline alloys resulting from different annealing treatments, i.e., with different crystalline contents. Such a method allows us to estimate more accurately the crystalline fraction and to refine the values of hyperfine parameters, both their annealing temperature and time dependencies, the hyperfine field distribution characteristic of the intergranular component and the magnetic texture. Finally, their changes versus crystalline fraction provide relevant information to describe the nanocrystallization process occurring during the transformation from the amorphous into the nanocrystalline state in the case of FINEMET alloys. 相似文献
962.
Ying Shi Xiaoli Zhan Zhenhuan Luo Qinghua Zhang Fengqiu Chen 《Journal of polymer science. Part A, Polymer chemistry》2008,46(7):2433-2444
The purpose of this study is to propose a correlation between IR spectra and the urea fraction of waterborne polyurethanes (PUs) to investigate the side reaction, that is, isocyanate–water reaction, during polymerization. This method is based on the decomposition of the spectrum in amide I range, that is, 1600–1800 cm?1, where the bands of interest overlap. Several individual bands present in this region were resolved by employing Fourier self‐deconvolution (FSD) and Gaussian curve‐fitting techniques, and the intensity ratio of urethane's C?O to urea's C?O was determined. To realize some quantitative measurements, a calibration curve was established with some polyurethane‐urea samples, characterized by 1H NMR, which were used as standards. The concentration ratios of urethane groups to urea groups were determined from 1H NMR. A good correlation was evidenced between IR and 1H NMR measurements. Moreover, waterborne PUs were prepared by miniemulsion polymerization of IPDI with diols. From quantitative IR analysis, it was shown that a vinylic monomer, as a solvent of polyaddition, restrained the isocyanate–water reaction, and this side reaction was influenced by the hydrophilicity of the vinylic monomers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2433–2444, 2008 相似文献
963.
In this paper we discuss,an initial-boundary value problem of hyperbolic type with firstderivative with respect to x.The asymptotic solution is constructed and its uniform validityis proved under weader compatibility conditions.Then we develop an exponentially fitteddifference scheme and establish discrete energy inequality.Finally,we prove that thesolution of difference problem uniformly converges to the solution of the original problem. 相似文献
964.
吸附模式识别方法及其应用 总被引:1,自引:0,他引:1
王长发 《高等学校化学学报》1993,14(4):480-482
电活性物质在电极上吸附是十分复杂的,无法用一简单模型描述。不同的吸附模型决定不同的吸附电流方程,因此判别电活性物质的吸附行为服从那种模式具有理论和实际意义,目前,吸附等温模式使用较多的主要有Langmuir等温式、Frumkin等温式和Temkin等温式,通常的识别方法是将实验测定得到的覆盖度θ和电活性物质在溶液中的浓度C代入上述模型方程,并逐一插值计算或拟合回归分析求出最接近的那个模式,以确定该物质的吸附方式。但计算与实验结果有一定差异,且工作量很大。最近张正奇等提出的单纯形-偏差图半定量识别法,具有一定使用价值。本文将介绍一种通用的定量、快速的识别吸附模式法。 相似文献
965.
966.
受钼精矿基体中铜、钼元素的干扰,电感耦合等离子体原子发射光谱法(ICP-OES)无法直接用于磷(213.617nm)的检测。考察了钼和铜谱线对磷(213.617nm)测定的影响,应用ICP-OES多谱拟合(MSF)法消除铜(213.599nm)、钼(213.606nm)的光谱干扰,建立了适合钼精矿中磷的检测方法。对方法的准确度和精密度进行实验,钼精矿中磷的加标回收率为96.2%~103.7%,RSD为2.6%~6.0%。实验证明,多谱拟合(MSF)电感耦合等离子体原子发射光谱法测定钼精矿中磷的方法是一种较为理想的分析方法,适合钼精矿中磷的测量范围为0.0010%~1%。 相似文献
967.
968.
针对惯性约束聚变(ICF)激光等离子体诊断系统应用的需求,提出一种采用非线性相位拟合法设计单透镜代替理想对数轴锥镜的方法。对所要得到的球面透镜与理想对数轴锥镜的相位进行拟合,求解得出所需要的球面透镜参量。设计了用于激光等离子体诊断系统的长焦深透镜,并对透镜的焦深、轴向光场均匀性、横向均匀性、焦斑旁瓣等指标进行分析。数值分析结果表明,长焦深透镜具有与理想对数轴锥镜相同的相位分布,焦深、轴向光场均匀性、横向均匀性、焦斑旁瓣均符合设计要求,验证了非线性相位拟合法的正确性。 相似文献
969.
In this work, we present values for the Mark–Houwink–Sakurada (MHS) and Stockmayer–Fixman (SF) constants for a series of homopolymers of para‐substituted styrenes (4‐X‐styrene; X = OCH3, OCH2CH3, CH3, F, Cl, and Br) in THF at room temperature. The respective values of K (in 10−5 dL/g) and α were: 0.685 and 13.2; 0.662 and 14.1; 0.740 and 8.41; 0.781 and 5.24; 0.726 and 8.95; 0.700 and 7.79. The respective values for Kθ (in 10−4 dL/g) and K' (in 10−7 dL/g) were: 6.01 and 16.1; 6.22 and 9.07; 7.64 and 17.4; 5.59 and 23.7; 6.29 and 17.3; 4.44 and 10.3. These constants were measured using size‐exclusion chromatography with on‐line viscometry. As part of this work, we investigate the applicability of common model fitting procedures to this method of measuring MHS/SF constants and the effect of uncertainties in their estimated values on the accuracy of molecular weight analysis. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2557–2570, 1999 相似文献
970.
The relativistic Gaussian basis set of Hg has been obtained by fitting the numerical relativistic atomic radial wave functions with the adaptive nonlinear least-square algorithm combined with the subset selection method. This fitting procedure and fitted results are presented. From this basis, in a further several-step procedure, we generated a new basis that gave reasonably good results for Hg, HgO, and a Se atom chain, respectively. The original fitted basis did not work, because the resulting overlap matrix was not positive definite. ©1999 John Wiley & Sons, Inc. J Comput Chem 20: 655–664, 1999 相似文献