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151.
The generalized T2 chart (GT‐chart), which is composed of the T2 statistic based on a small number of principal components and the remaining components, is a popular alternative to the traditional Hotelling's T2 control chart. However, the application of the GT‐chart to high‐dimensional data, which are now ubiquitous, encounters difficulties from high dimensionality similar to other multivariate procedures. The sample principal components and their eigenvalues do not consistently estimate the population values, and the GT‐chart relying on them is also inconsistent in estimating the control limits. In this paper, we investigate the effects of high dimensionality on the GT‐chart and then propose a corrected GT‐chart using the recent results of random matrix theory for the spiked covariance model. We numerically show that the corrected GT‐chart exhibits superior performance compared to the existing methods, including the GT‐chart and Hotelling's T2 control chart, under various high‐dimensional cases. Finally, we apply the proposed corrected GT‐chart to monitor chemical processes introduced in the literature. 相似文献
152.
混水平部分因析设计在各类试验中有广泛应用.纯净效应准则是用于选取最优部分因析设计的重要准则之一.本文考虑含有一个八水平因子、一个四水平因子和若干二水平因子的8×4×2~n混水平设计,给出了分辨度为Ⅲ和Ⅳ的该类混水平设计包含纯净两因子交互作用成分最大数的上界和下界.下界通过构造特定设计而得到. 相似文献
153.
Viscoelastic behavior, phase morphology and flow conditions relationships in polymer/rubber blends have been investigated. The importance of such correlations is illustrated on polymethylmethacrylate (PMMA)/rubber blends subjected to different flow conditions both under small and large deformations. In small-amplitude oscillatory shear (the morphology does not change during the flow) the elastic modulus G of the concentrated blends shows a secondary plateau, G
p
, in the low frequency region. This solid-like behavior appears for rubber particle contents beyond the percolation threshold concentration (15%). Morphological observations revealed that for concentrations higher than 15%, the particles are dispersed in a three-dimensional network-type structure.In capillary flow it was found that the network-type structure was destroyed and replaced by an alignment of particles in the flow direction. This morphological modification resulted in a decrease in both viscosity and post-extrusion swell of the blends. Morphological observations revealed that the ordered structure in the flow direction was concentrated only in the skin region of the extrudate, where the shear stress is higher than the secondary plateau, G
p
. A simple kinetic mechanism is proposed to explain the observed morphology.Similarly, steady shear measurements performed in the cone-and-plate geometry revealed alignment of particles in the flow direction for shear stress values higher than Gp.Presented in part at the Symposium Recent Developments in Structured Continua Montréal (Canada) 26–28 May 1993 and at the 45th Canadian Chemical Engineering Conference, Quebec, October 15–18 (1995) 相似文献
154.
Addition of a viscoelastic material based on silanols cured by boron oxide was used to delay sharkskin and stick–slip instabilities
in extrusion of linear low-density polyethylene (LLDPE). Delay of flow instabilities to rates of extrusion 25–35 times higher
than without additive and about 40% less extrusion pressure at the same throughput are achieved by the use of this material
as an additive (∼0.1%) to LLDPE or as a coating of the extrusion die. Mechanical properties of the lubricant were changed
by small variations of composition to investigate the impact of elasticity on lubrication and sharkskin delay. Both lubrication
and sharkskin delay were considerably improved when more elastic lubricants were used while the chemical composition of the
lubricants was nearly the same. Filling the lubricants with powders of metal oxides or especially particulates having plate-like
particles (kaolin, mica, BN) helped to delay the flow instabilities further to even higher throughputs. Together with experimental
results, we present a tentative explanation for the importance of elasticity of polymer processing aids in the delay of sharkskin
and the stabilization of slip.
This paper was presented at Annual European Rheology Conference (AERC) held in Hersonisos, Crete, Greece, April 27–29, 2006. 相似文献
155.
In this work, melt spinning experiments were tentatively used for the determination of the elongational viscosity of polymer
melts at different levels of tensile strain and strain rate. The materials examined were two high-density polyethylene grades
for blow moulding with similar number-average molecular mass but different polydispersity index. The data from melt spinning
tests were compared with transient extensional viscosity data obtained by uniform isothermal tensile tests, performed by means
of an extensional rheometer, as well as with those produced by converging flow tests (Cogswell model). The results showed
that for high strain and strain rate levels, the melt spinning experiments provide elongational viscosity data quite close
to the transient extensional viscosity values obtained from the tensile tests. 相似文献
156.
Necking in non-isothermal high-speed melt spinning is treated as a problem of sensitivity to external disturbances at both ends of the spin-line. Necessary conditions for existence of necking are formulated in terms of the corresponding increments of velocities, forces, viscosities, etc. It is shown that necking may be present in the high-inertia range for a rather small viscosity variation. Small inertia effects require higher values of the radial viscosity gradients. 相似文献
157.
Amine Kassouf Maria El Rakwe Hanna Chebib Violette Ducruet Douglas N. Rutledge Jacqueline Maalouly 《Analytica chimica acta》2014
Olive oil is one of the most valued sources of fats in the Mediterranean diet. Its storage was generally done using glass or metallic packaging materials. Nowadays, plastic packaging has gained worldwide spread for the storage of olive oil. However, plastics are not inert and interaction phenomena may occur between packaging materials and olive oil. In this study, extra virgin olive oil samples were submitted to accelerated interaction conditions, in contact with polypropylene (PP) and polylactide (PLA) plastic packaging materials. 3D-front-face fluorescence spectroscopy, being a simple, fast and non destructive analytical technique, was used to study this interaction. Independent components analysis (ICA) was used to analyze raw 3D-front-face fluorescence spectra of olive oil. ICA was able to highlight a probable effect of a migration of substances with antioxidant activity. The signals extracted by ICA corresponded to natural olive oil fluorophores (tocopherols and polyphenols) as well as newly formed ones which were tentatively identified as fluorescent oxidation products. Based on the extracted fluorescent signals, olive oil in contact with plastics had slower aging rates in comparison with reference oils. Peroxide and free acidity values validated the results obtained by ICA, related to olive oil oxidation rates. Sorbed olive oil in plastic was also quantified given that this sorption could induce a swelling of the polymer thus promoting migration. 相似文献
158.
Surjeet Verma Shiv Kumar Santosh Kumar Srivastava Mahendra P. Darokar 《中国化学会会志》2014,61(10):1121-1126
A new clionasterol glucoside, clionasterol‐[(1'→3α)‐O‐β‐D]‐glucopyranoside ( 1 ), a new acylated clionasterol glucoside, clionasterol‐[6'‐O‐acyl‐(1'→3β)‐O‐b‐D]‐glucopyranoside ( 2 ) and clionasterol ( 3 ) were isolated from the aerial parts of Oplismenus burmannii. The nature and length of fatty acid acyl chains in 2 was identified by alkaline methanolysis of compound 2 . The aglycone fraction on GC‐MS analysis showed three peaks in GC at tR 49.86 (82.1%), 51.13 (13.3%) and 56.53 (4.6%) min, which were characterized as arachidic acid methyl ester ( a ) oleic acid methyl ester ( b ) and 12‐methyltetradecanoic acid methyl ester ( c ) respectively. Thus 2 was characterized as a mixture of three new compounds, clionasterol‐[6'‐O‐eicosanoyl‐(1'→3β)‐O‐β‐D]‐glucopyranoside ( 2a ), clionasterol‐[6'‐O‐(8Z)‐octa‐deca‐9‐enoyl‐(1'→3β)‐O‐β‐D]‐glucopyranoside ( 2b ) and clionasterol‐[6'‐O‐(12‐methyltetradecanoyl)‐(1'→3β)‐O‐β‐D]‐glucopyranoside ( 2c ). 相似文献
159.
Giulio Peruginelli 《代数通讯》2015,43(1):197-211
We describe an algorithm to compute the different factorizations of a given image primitive integer-valued polynomial f(X) = g(X)/d ∈ ?[X], where g ∈ ?[X] and d ∈ ? is square-free, assuming that the factorizations of g(X) in ?[X] and d in ? are known. We translate this problem into a combinatorial one. 相似文献
160.
提出了高效液相色谱法同时测定复方草珊瑚含片中原儿荼酸、3-羟基-4-甲氧基苯甲酸、异嗪皮啶和迷迭香酸的含量。样品经甲醇超声提取,用Waters Sun Fire ODS色谱柱(4.6 mm×150mm,5μm)分离,以不同比例混合的乙腈和磷酸-水(0.1+99.9)溶液为流动相进行梯度洗脱,流量0.8mL·min~(-1),在294 nm波长处用紫外检测器检测。在优化的色谱条件下,4种活性成分可完全分离。原儿茶酸、3-羟基-4-甲氧基苯甲酸、异嗪皮啶和迷迭香酸的线性范围分别为2.508~50.16,18.40~368.0,6.375~127.5,41.04~820.8ng;平均回收率分别为92.8%,93.1%,91.9%,99.6%;相对标准偏差(n=6)均不大于5.0%。 相似文献