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71.
氯化聚乙烯弹性体的固相法合成 总被引:2,自引:0,他引:2
讨论了以固相法合成氯化聚乙烯(CPE)弹性体的过程.实验结果表明,以固相氯化反应所得的CPE,其大分子链上Cl取代基的分布比水相悬浮法更均匀.氯化过程的温度直接影响氯化速度及分子结构,如残留结晶、氯分布等.而聚乙烯颗粒表面与内部的氯化程度取决于氯化速度.大分子链上Cl取代基对邻近基团的氯化起阻碍作用 相似文献
72.
Cellulose acetate (CA) ultrafiltration hollow fibers were spun via the dry-jet wet spinning technique. The effect of the take-up speed on the mechanical properties, morphology, thermal properties, pure water permeation, retention, and surface characterization of hollow fiber membranes were investigated. Both the inner and outer diameters of the hollow fiber decreased with the increase of take-up speed. Macrovoids were observed on the inner surface of the drawn hollow fibers. The d-space decreased with the increase of the take-up speed. The ultimate tensile stress (UTS) increased and the breaking elongation decreased with the increase of take-up speed. The permeation performance was measured. The hydraulic permeability increased and the retention decreased slightly with the increase of the take-up speed. The surface roughness increased with the increase of the take-up speed. The thermal analysis results showed that the endothermic peak shifts to the higher temperature region and coefficient of thermal expansion (CTE) decrease for a higher take-up speed. 相似文献
73.
Summary The quantitative use of high speed capillary electrophoresis (HSCE) is examined by applying high voltages across short capillaries.
Acceptable performance in terms of injection precision and migration times were achieved within 1–2 minute analysis times.
HSCE was used for the novel CE application of dissolution test sample solution analysis. The results generated by HSCE compared
well with those generated using validated on-line UV absorbance measurements. It is concluded that HSCE is a viable alternative
and supplement to standard analytical methods employed in dissolution test analysis. 相似文献
74.
Thermal decomposition of some hydrocarbon and chlorinated hydrocarbon compounds in metal capillary tubes used in an inlet system for high speed gas chromatography has been investigated. The metal tube is cooled to about ?75°C by a flow of cold nitrogen gas in order to focus a vapor sample cryogenically. A capacitive discharge power supply is then used to heat the metal tube resistively in order to revaporize the sample and introduce it to the separation column as a plug 5-10 ms wide. The effects of tube temperature, tube material, sample vapor residence time, and type of carrier gas on thermal cracking are described. Use of a copper-nickel alloy tube resulted in less cracking than either pure platinum or pure nickel. Cracking is more significant with hydrogen as carrier gas than with helium. Cracking also increases with increasing sample residence time in the hot tube. Quantitative sample injection with minimum decomposition can be obtained for a variety of aliphatic and aromatic hydrocarbons and chlorinated hydrocarbon compounds. 相似文献
75.
The partial molar isentropic pressure coefficients at infinite dilution, K
S,2
o
, have been determined for a number of dipeptides in aqueous solution at 25°C. For a series of dipeptides of sequence gly-X, where X is an amino acid with a neutral side chain, the K
S,2
o
values are all more negative than that for diglycine. The results are discussed in terms of the hydration of the side chains. There are significant differences in the K
S,2
o
values for sequence isomeric dipeptides. These differences can be rationalized in terms of the mutual interactions between the side chain and the ionic end groups in the dipeptides. Possible relationships between K
S,2
o
and V
2
o
, the partial molar volume at infinite dilution, were investigated. For the dipeptides of sequence gly-X there is an interesting linear relationship between K
S,2
o
/V
2
o
and V
2
o
. 相似文献
76.
Summary Three aspects with respect to the selection of solvents for static coating of capillary columns, i.e. coating speed, occurrence of bumping and solubility of stationary phases are discussed. Hypotheses are proposed in an attempt to explain the observed facts that mixed solvents result in much higher coating speeds than those obtained from pure solvents, that a proper choice of solvents together with a good and uniform deactivitation of the column inner wall is needed to prevent bumping. Stationary phase solubility vs. solvent composition is also briefly discussed. 相似文献
77.
Helmut Strasser 《Journal of multivariate analysis》1975,5(2):206-226
Let (X, ) be a measurable space, Θ ? an open interval and PΩ ∥ , Ω ? Θ, a family of probability measures fulfilling certain regularity conditions. Let be the maximum likelihood estimate for the sample size n. Let λ be a prior distribution on Θ and let be the posterior distribution for the sample size n given . denotes a loss function fulfilling certain regularity conditions and Tn denotes the Bayes estimate relative to λ and L for the sample size n. It is proved that for every compact K ? Θ there exists cK ≥ 0 such that This theorem improves results of Bickel and Yahav [3], and Ibragimov and Has'minskii [4], as far as the speed of convergence is concerned. 相似文献
78.
高速公路线形设计的质量量化评价模型 总被引:1,自引:0,他引:1
针对道路安全审计中如何量化评价线形的设计质量这一重大技术问题,在分析国内外相关研究及实际调查研究的基础上,构造了高速公路线形设计质量量化评价模型,找出了模型量化评价值与亿车公里事故率之间的内在联系,充分验证了评价模型的适应性和有效性,最后给出了高速公路线形设计质量评价标准. 相似文献
79.
80.