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41.
In this paper a new and very simple method was developed for the simultaneous determination of binary and ternary mixtures, without prior separation steps. This method is based on the mean centering of ratio spectra. The mathematical explanation of the procedure is illustrated. After modeling procedure, the method has been successfully applied to the simultaneous analysis of binary mixtures of mefnamic acid and paracetamol and ternary mixtures of acetylsalysilic acid, ascorbic acid and paracetamol. The analytical characteristics of the method such as detection limit, accuracy, precision, relative standard deviation (R.S.D.) and relative standard error (R.S.E.) was calculated. The results showed that the proposed method is simple, rapid, accurate and precise method for analysis of binary and ternary mixtures. 相似文献
42.
恒压-恒流充电容量比值法测定石墨电极中的锂离子扩散系数 总被引:4,自引:0,他引:4
通过球形扩散模型推导了恒压-恒流充电容量比(简称RPG)与石墨电极中锂离子固相扩散系数的关系,给出了一种测量锂离子在石墨负极中固相扩散系数的新方法即RPG法.理论结果表明固相扩散系数D与RPG值q,颗粒半径R和恒流充电时间tG有关.当q ≤ 0.5时,其关系式可通过最小方差线性化拟合为D=R2/(15.36qtG) (q ≤ 0.5).实验结果表明,RPG法具有非常好的重现性,不同恒流充电电流和时间下测得1.5 V(vs Li/Li+)的锂离子固相扩散系数值均在1.060×10-10 cm2•s-1左右.采用RPG法对石墨电极在1.0~2.5 V(vs Li/Li+)高电压区的锂离子固相扩散系数进行了测试,结果表明在1.0~2.5 V的高电压区,随着电压的升高,D值从4.292×10-10 cm2•s-1减小到1.219×10-11 cm2•s-1. 相似文献
43.
Macroreticular cation exchangers can be prepared by polymerizing sulfonated phenols with formaldehyde under acidic conditions. The resins are highly porous with large surface areas. Their properties compare well with those based on styrene and divinylbenzene copolymers. 相似文献
44.
《高分子科学杂志,A辑:纯化学与应用化学》2013,50(6):573-590
To investigate the effects of solvent type and temperature on the interpolymer complexation via hydrogen bonding, a study was made on the complex system of poly(acrylic acid) (PAA) and poly(ethylene oxide) (PEO) in two kinds of solvent systems, pure water and water-MeOH (30 wt%) mixed solvent, at various temperatures using the Ubbelohde viscometer, pH-meter, and UV spectrophotometer. The repeating unit mole ratio at the most optimum complexation as confirmed by the reduced viscosity measurement was shifted from [PEO]/[PAA] ≈ 1.25:1 to 1.5:1 by the addition of methanol to water. From the UV measurement, the deviation from the “isosbestic point” (where the absorbance of the solution remains constant) has presented another evidence for the solvent effect on complexation. In addition, the analysis of the changes in thermodynamic properties upon complexation as well as the fraction of carboxyls associated with PEO oxygens and the complex stability constant as estimated by potentiometric titration at several temperatures reveals that the complex formation in mixed solvent became more unfavorable compared to that in pure solvent at high temperatures above 30°C. This could be explained by considering that in water the hydrophobic interaction as well as the hydrogen bonding may greatly contribute to the stabilization of the polymer complex formed, while in water-methanol the main stabilizing force would be the hydrogen bonding alone. 相似文献
45.
The asymptotic performance ratio of an on-line algorithm for uniform parallel machine scheduling with release dates 总被引:1,自引:0,他引:1
Jobs arriving over time must be non-preemptively processed on one of m parallel machines, each running at its own speed, so as to minimize a weighted sum of the job completion times. In this on-line
environment, the processing requirement and weight of a job are not known before the job arrives. The Weighted Shortest Processing
Requirement (WSPR) heuristic is a simple extension of the well known WSPT heuristic, which is optimal for the single machine
problem without release dates. According to WSPR, whenever a machine completes a job, the next job assigned to it is the one
with the least ratio of processing requirement to weight among all jobs available for processing at this point in time. We
analyze the performance of this heuristic and prove that its asymptotic competitive ratio is one for all instances with bounded job processing requirements and weights. This implies that the WSPR algorithm generates a
solution whose relative error approaches zero as the number of jobs increases. Our proof does not require any probabilistic
assumption on the job parameters and relies extensively on properties of optimal solutions to a single machine relaxation
of the problem.
Research supported in part by ONR Contracts N00014-90-J-1649 and N00014-95-1-0232, NSF Contracts DDM-9322828, DMI-9732795,
DMI-0085683 and DMI-0245352, NUS Academic Research Grant R314-000-046-112, and a research grant from the Natural Sciences
and Research Council of Canada (NSERC). 相似文献
46.
We consider the inference on quantiles, Q
y
(β), with jackknife techniques, in finite populations of a variable, Y, using the quantile information on an auxiliary variable, X. Jackknife techniques are applied to estimate quantiles and the behaviour of these estimators is analyzed. Their properties
are studied for simple random sampling. We also examine the confidence intervals obtained with jackknife variances. 相似文献
47.
48.
G. López Lagomasino I.A. Rocha 《Journal of Mathematical Analysis and Applications》2010,372(2):390-401
For any pair of compact intervals of the real line Δ1, Δ2, with Δ1∩Δ2=∅, we obtain two probability measures μ1, τ1, supported on Δ1 and Δ2 respectively, such that the Nikishin system N(μ1,τ1) has a sequence of monic multiple orthogonal polynomials which satisfy a four term recurrence relation with constant coefficients of period 2. The measures are obtained from the functions which give the ratio asymptotic of multiple orthogonal polynomials with respect to an arbitrary Nikishin system N(σ1,σ2) on Δ1, Δ2, such that a.e. on Δi, i=1,2. The role of μ1, τ1 is symmetric in the sense that the same construction is possible on Δ2, Δ1, with N(τ1,μ1). 相似文献
49.
Feng Qi Senlin Guo Shou-Xin Chen 《Journal of Computational and Applied Mathematics》2008,220(1-2):111-118
In the paper, a new upper bound in the second Kershaw's double inequality involving ratio of gamma functions is established, and, as generalizations of the second Kershaw's double inequality, the divided differences of the psi and polygamma functions are bounded. 相似文献
50.
双重傅里叶变换滤波二阶比光谱导数分光光度法同时测定苯酚、邻苯二酚及对苯二酚 总被引:4,自引:0,他引:4
本文针对三组分混合体系分析提出了双重傅里叶变换滤波二阶比光谱导数分光光度法。对所测的吸收光谱用较大滤波窗口先后进行两次滤波 ;利用两次对混合体系光谱和单组分光谱比光谱求导使某两个组分对混合体系比光谱导数的贡献为零 ,而剩余组分的比光谱导数与其浓度成正比。对双重傅里叶变换滤波效果、实验参数的优化作了研究。用此方法对苯酚、邻苯二酚及对苯二酚含量为 0 0 1 0 0 9~ 0 0 5 3 2 5mg·mL- 1 的混合溶液进行测定 ,所得结果的相对误差为 0 0 7%~ 5 4%。 相似文献