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121.
L. S. Ettre 《Chromatographia》1979,12(7):509-515
Summary The selection of the average linear carrier gas velocity in the analysis of a multicomponent mixture under isothermal and programmed-temperature conditions is discussed. It is shown that one shouls always select a velocity which is at least equal but preferably higher than the optimum average gas velocity of the earliest peak at the initial column temperature.These symbols essentially correspond to those specified by the British Standard [6], ASTM [7] and IUPAC [8] GC nomenclastures. 相似文献
122.
本文对多元线性回归模型定义了AP统计量和距离影响函数;将它们分解为两项之积,指出强影响点、异常点、高杠杆点间的内在联系;讨论了上述三种点的探查方法.最后,给出与距离影响函数有关的一个定理. 相似文献
123.
该文研究了协方差阵扰动和数据删除对最佳线性无偏估计(BLUE)的影响问题, 给出了在约束条件下一般线性模型与在约束条件下Gauss-Markov模型及在约束条件下数据删除模型中回归参数β的BLUE之间的关系式. 作者还定义了度量影响大小的广义Cook距离DV并给出了DV的两个计算公式. 相似文献
124.
《Journal of computational and graphical statistics》2013,22(2):370-387
This article proposes a new approach to the robust estimation of a mixed autoregressive and moving average (ARMA) model. It is based on the indirect inference method that originally was proposed for models with an intractable likelihood function. The estimation algorithm proposed is based on an auxiliary autoregressive representation whose parameters are first estimated on the observed time series and then on data simulated from the ARMA model. To simulate data the parameters of the ARMA model have to be set. By varying these we can minimize a distance between the simulation-based and the observation-based auxiliary estimate. The argument of the minimum yields then an estimator for the parameterization of the ARMA model. This simulation-based estimation procedure inherits the properties of the auxiliary model estimator. For instance, robustness is achieved with GM estimators. An essential feature of the introduced estimator, compared to existing robust estimators for ARMA models, is its theoretical tractability that allows us to show consistency and asymptotic normality. Moreover, it is possible to characterize the influence function and the breakdown point of the estimator. In a small sample Monte Carlo study it is found that the new estimator performs fairly well when compared with existing procedures. Furthermore, with two real examples, we also compare the proposed inferential method with two different approaches based on outliers detection. 相似文献
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126.
Influence of mechanical activation on the graft copolymerization of sugarcane bagasse and acrylic acid 总被引:2,自引:0,他引:2
Zuqiang Huang Xingtang Liang Huayu Hu Li Gao Yongjun Chen Zhangfa Tong 《Polymer Degradation and Stability》2009,94(10):1737-1745
Sugarcane bagasse (SCB) was mechanically activated by home-made high efficiency stirring mill. Graft copolymers (SCB-g-PAA) of SCB with different mechanical activation times (tM) and acrylic acid (AA) have been synthesized by using ammonium persulfate/sodium sulfite redox pair as an initiator in aqueous solution. The effect of tM on the graft co-polymerization was evaluated by grafting ratio (GR) and grafting efficiency (GE). In addition, scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were used to characterize the granular morphology, functional groups, crystal structure and thermal properties of the product. It was found that the mechanical activation could split fiber bundles and decrease significantly the crystallinity. SCB degraded after the mechanical activation (MA) and its thermal stability declined. Moreover, the graft copolymerization was enhanced obviously by MA processing. And GR and GE increased with the increase of activation time. 相似文献
127.
Summary The regularities of the retention of polymethyl- and monoalkylbenzenes on a nonpolar adsorbent (silanized silica gel) with a polar eluent (23 isopropanol-water) have been studied. In contrast to the retention of the same compounds on a polar adsorbent (silica gel with hydroxylated surface) and with a nonpolar eluent (hexane) polymethylbenzenes are retained on silanized silica gel for a shorter time than the corresponding monoalkylbenzene isomers. The retention order of tert.-, sec.- and n-butylbenzenes is the reverse of that observed on silica gel having a hydroxylated surface. The retention order of xylenes, trimethyl- and tetramethylbenzenes is also the reverse of their retention order on silica gel having a hydroxylated surface. All the mixtures of the corresponding homologues and isomers have been separated. 相似文献
128.
129.
本文考虑了强磁场对碰撞过程的影响,用Bogoliubov方程来讨论强磁场中等离子体的输运过程。当分布函数随空间的变化比较缓慢、在Debye屏蔽距离内等离子体的密度、温度的变化可以忽略时,得到了计算强磁场中等离子体输运过程的一般方法。最后计算了沿磁场方向的电导率,电导率随磁场的增加而增加。在温度10~6K,电子密度10~(12)cm~(-3),磁场强度约为9T时,考虑磁场对碰撞影响所计算出的电导率,要比忽略磁场对碰撞影响所得结果大22.3%。 相似文献
130.