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Margot Bennink Marcel A. Croon Brigitte Kroon Jeroen K. Vermunt 《Advances in Data Analysis and Classification》2016,10(2):139-154
An existing micro–macro method for a single individual-level variable is extended to the multivariate situation by presenting two multilevel latent class models in which multiple discrete individual-level variables are used to explain a group-level outcome. As in the univariate case, the individual-level data are summarized at the group-level by constructing a discrete latent variable at the group level and this group-level latent variable is used as a predictor for the group-level outcome. In the first extension, that is referred to as the Direct model, the multiple individual-level variables are directly used as indicators for the group-level latent variable. In the second extension, referred to as the Indirect model, the multiple individual-level variables are used to construct an individual-level latent variable that is used as an indicator for the group-level latent variable. This implies that the individual-level variables are used indirectly at the group-level. The within- and between components of the (co)varn the individual-level variables are independent in the Direct model, but dependent in the Indirect model. Both models are discussed and illustrated with an empirical data example. 相似文献
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Ia Torelm Lars-B?rje Croon Kurt Kolar Torbj?rn Schr?der 《Fresenius' Journal of Analytical Chemistry》1990,338(4):435-437
Summary Reference materials for carrying out in-house quality assurance by food laboratories that analyse macronutrients have to date been inadequate. The freeze-dried, very specialized, materials that exist on the market are not always comparable with ordinary food products analysed at those laboratories.A homogeneous, fresh, canned meat material was produced by an ordinary cannery. The total amount of material (pork, nitrite salt and water) was 1700 kg. During production, the fat content was continuously analysed in the different sub-batches and combinations are made accordingly. The material was packed in tin cans containing 200 g, and tested for homogeneity. The shelf life is, by experience, at least five years. A large number of authorized public and industry laboratories participated in the certification procedure. For each constituent different types of standard analytical methods were used. The material is offered for sale together with a certificate, giving mean values for moisture, ash, fat, nitrogen, sodium, sodium chloride and hydroxyproline content. The uncertainty is given as standard deviations including the analytical error and the variations between laboratories, methods and units. 相似文献
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Bruno Cortese Timothy Noel Mart H. J. M. de Croon Simon Schulze Elias Klemm Volker Hessel 《大分子反应工程》2012,6(12):507-515
This paper explains the reasons behind the very low polydispersity index (PDI) obtained in living anionic polymerizations in microstructured reactors. From the results, it can be explained that a narrow molecular weight distribution can be obtained due to the presence of a highly segregated flow behavior, even in microflow conditions, provided that the mean residence time is high enough. This paper investigates the feasibility of a living anionic polymerization reaction under micro‐fluidic conditions. This is accomplished using a multiphysics model that accounts for the changes in viscosity and diffusivity. These properties descend with the increase in weight of the polymer, and could not be un‐coupled from hydrodynamics and mass transfer. The results of the model are used to understand the reasons behind the very low PDI that can be experimentally obtained in microflow conditions. This leads to the conclusion that the increased viscosity almost “suppresses” the diffusion of the monomer, even at the very short characteristic lengths of a micro‐device. These conditions generate a fully segregated flow that yields an almost monodisperse polymer regardless of the effective residence time distribution encountered in the reactor.
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