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81.
The on‐line monitoring of batch processes based on principal component analysis (PCA) has been widely studied. Nonetheless, researchers have not paid so much attention to the on‐line application of partial least squares (PLS). In this paper, the influence of several issues in the predictive power of a PLS model for the on‐line estimation of key variables in a batch process is studied. Some of the conclusions can help to better understand the capabilities of the proposals presented for on‐line PCA‐based monitoring. Issues like the convenience of batch‐wise or variable‐wise unfolding, the method for the imputation of future measurements and the use of several sub‐models are addressed. This is the first time that the adaptive hierarchical (or multi‐block) approach is extended to the PLS modelling. Also, the formulation of the so‐called trimmed scores regression (TSR), a powerful imputation method defined for PCA, is extended for its application with PLS modelling. Data from two processes, one simulated and one real, are used to illustrate the results. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
82.
In chemical and biochemical processes, steady‐state models are widely used for process assessment, control and optimisation. In these models, parameter adjustment requires data collected under nearly steady‐state conditions. Several approaches have been developed for steady‐state identification (SSID) in continuous processes, but no attempt has been made to adapt them to the singularities of batch processes. The main aim of this paper is to propose an automated method based on batch‐wise unfolding of the three‐way batch process data followed by a principal component analysis (Unfold‐PCA) in combination with the methodology of Brown and Rhinehart 2 for SSID. A second goal of this paper is to illustrate how by using Unfold‐PCA, process understanding can be gained from the batch‐to‐batch start‐ups and transitions data analysis. The potential of the proposed methodology is illustrated using historical data from a laboratory‐scale sequencing batch reactor (SBR) operated for enhanced biological phosphorus removal (EBPR). The results demonstrate that the proposed approach can be efficiently used to detect when the batches reach the steady‐state condition, to interpret the overall batch‐to‐batch process evolution and also to isolate the causes of changes between batches using contribution plots. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
83.
J. Pérez P.J. Silva C.A. Durante-Rincón J. Primera Ferrer J.R. Fermin 《Journal of magnetism and magnetic materials》2008
Electron paramagnetic resonance (EPR) experiments were made in the diluted magnetic semiconductor CuGa1−xMnxTe2, in the temperature range 70<T<300 K. The samples were synthesized by direct fusion of stoichiometric mixtures of the elements, with Mn composition from x=0.0 to 0.25. The EPR spectra were measured as function of temperature, Mn composition, and field orientation. The temperature variation of the resonance field shows a critical point at about 235 K, and is associated with a transition from the ferromagnetic to the superparamagnetic state. The resonance field was also measured as a function of the field angle, and displays a well-defined uniaxial symmetry. This uniaxial field depends on the Mn concentration and is due to tetragonal distortions induced by Mn2+ at Ga sites, and the demagnetizing effects due to formation of ferromagnetism (FM) Mn-clusters. 相似文献
84.
85.
Blanca G. Beltrán Laura Ferrer Victor Cerdà 《International journal of environmental analytical chemistry》2015,95(11):1054-1065
Lead hydride or plumbane (PbH4) generation was optimised by exploiting a simple flow-injection method coupled to atomic fluorescence spectrometry (HG-AFS), and allowing ultra-trace lead determination. Plumbane was generated through two methods: (1) 5% (v/v) H2O2 was employed as oxidant with 1.5% (m/v) KBH4 as a reducing agent and 1.5% (v/v) HCl solution; (2) with 1.5% (m/v) K3[Fe(CN)6] as an oxidant/sensitiser, 1% (m/v) KBH4 as a reducing agent and 1.5% (v/v) HCl. Variables such as reagent concentrations, flow rates and sample and reagent volumes were tested and critically compared. The best results were obtained with potassium ferricyanide K3[Fe(CN)6], achieving a detection limit of 0.03 μg Pb L?1 and a relative standard deviation (RSD) of 1.1%. The selected method was validated by analysis of certified reference materials such as SRM-2976 (mussel tissue) and BCR-610 (groundwater), with good agreement with the certified values. The developed methodology was successfully applied to different environmental sample matrices, such as rain water, tap water, ground water, spring water and drinking water, and biological samples, i.e., human blood, plasma and serum. 相似文献
86.
Rodríguez-Calvillo Pablo Ferrer Nuria Cabrera José-María 《Journal of Thermal Analysis and Calorimetry》2021,146(3):1393-1403
Journal of Thermal Analysis and Calorimetry - The thermal behavior of two copper alloys, with 0.2 and 0.5 mass % of Mg, was analyzed after severe plastic deformation processing by Equal Channel... 相似文献
87.
88.
Patricia A.M. Williams Evelina G. Ferrer María J. Correa Enrique J. Baran Eduardo E. Castellano Oscar E. Piro 《Journal of chemical crystallography》2004,34(4):285-290
The crystal structure of the complexes [Zn(sac)2(im)2] (1) and [Zn(sac)2(bzim)2]22Et-OHH2O (2) (sac = saccharinate anion; im = imidazole; bzim = benzimidazole; EtOH = ethanol) was determined by single crystal X-ray diffractometry. Complex 1 crystallizes in the monoclinic P2
1/n space group with a = 9.1585(5), b = 16.4409(6), c = 15.0249(5) Å, = 94.079(1)°, and Z = 4, whereas complex 2 belongs to the triclinic space group P1 with a = 10.8500(2), b = 12.4860(2), c = 13.5640(3) Å, = 115,696(1), = 100.086(1), = 102.169(1)°, and Z = 1. In both complexes, the Zn(II) cations are in a slightly distorted tetrahedral ZnN4 environment, coordinated to two saccharinate anions and to two imidazole (1) and to two benzimidazole (2) molecules. The complexes were also characterized by means of infrared spectroscopy and their thermal behavior investigated by means of thermogravimetric and differential thermal analytical techniques. 相似文献
89.
The synthesis of bis- and trisoxazoles via direct arylation is discussed. A variety of aryl groups can be installed at the 2-position of 5-aryl and 5-carboxy-substituted oxazoles under mild conditions using palladium catalysis on water. The direct arylation method can be extended to the synthesis of bis- and trisoxazoles if 2-triisopropylsilyl-4-iodooxazole is used as the electrophile in the arylation. 相似文献
90.
Dr. Arianna Melillo Dr. Antonio Franconetti Prof. Dr. Mercedes Alvaro Prof. Dr. Belen Ferrer Prof. Hermenegildo Garcia 《Chemistry (Weinheim an der Bergstrasse, Germany)》2023,29(1):e202202625
Hydrogenation of multiple bonds are among the most general and important organic reactions. Typical heterogeneous catalysts are based on transition metal nanoparticles, including noble metals. Data are presented here showing that metal nodes of MIL-101(Cr) and UiO-66 in the absence of occluded metal nanoparticles can promote hydrogenation of polarized X=Y double bonds of nitro and carbonyl groups. The catalytic activity is a function of the composition of the metal node and the organic linker. It is proposed that the reaction mechanism is based on the operation of frustrated Lewis acid/base pairs. 相似文献