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Linear model predictive control (MPC) is a widely-used control strategy in chemical processes. Its extension to nonlinear MPC (NMPC) has drawn increasing attention since many process systems are inherently nonlinear. When implementing the NMPC based on a nonlinear predictive model, a nonlinear dynamic optimization problem must be calculated. For the sake of solving this optimization problem efficiently, a latent-variable dynamic optimization approach is proposed. Two kinds of constraint formulations, original variable constraint and Hotelling T2 statistic constraint, are also discussed. The proposed method is illustrated in a pH neutralization process. The results demonstrate that the latent-variable dynamic optimization based the NMPC strategy is efficient and has good control performance.

Certified or reference values for sixty six to sixty seven elements and element oxides are given for geochemical reference materials recently prepared by the Institute of Geophysical and Geochemical Exploration (IGGE), including limestone (GSR-13), granitic gneiss (GSR-14), amphibolite (GSR-15), lake sediment (GSS-9) and stream sediments (GSD-1a, GSD-13, GSD-14). These samples supplement the GSR 1-6, GSD1-8 and GSD 9-12 certified reference materials already prepared and characterized by the IGGE. Cet article donne les concentrations certifiees ou de reference de soixante six a soixante sept elements et oxydes pour des materiaux geochimiques de reference prepares recemment par l'Institut d'Exploration Geophysique et Geochimique de Chine (IGGE), dont un calcaire GSR-13, un gneiss granitique GSR-14, une amphibolite GSR-15, un sediment lacustre GSS-9 et des sediments de riviere GSD-1a, GSD-13 et GSD-14. Ces echantillons completent l'ensemble des materiaux geochimiques de reference GSR 1-6, GSD1-8 and GSD 9-12 deja prepares et caracterises par l'IGGE.

Unlike the situation for other elements, few reference materials certified for the platinum-group elements are currently available. Therefore, the GPt1-7 series of PGE geochemical CRMs, prepared by the IGGE, represent an important addition and comprise a range of matrix types, including a soil, stream sediment, Mg-rich ultramafic rock, Fe-rich ultramafic rock, platinoid ore depleted in Cu, Ni and Fe, and a chromitite. The concentration of PGE in these samples ranges over 4-5 orders of magnitude and the samples were shown to have good homogeneity as assessed by a variance test. Analytical methods based on different principles were used in sample certification, including several fire assay and wet chemical procedures used for decomposition and preconcentration. Certified values for the elements Pt, Pd, Os, Ru, Ir, Rh and Au were determined by AAS, catalytic colourimetry (COL), catalytic polarography (POL), atomic emission spectrometry (AES), ICP-MS and NAA. Recently, the GPt1-7 samples were approved as national primary CRMs by the State Bureau of Technical Supervision of China. A la difference d'autres elements, bien peu de materiaux de reference a valeurs certifies existent dans le cas des elements du groupe du platine. En consequence, l'ensemble de materiaux de reference certifies GPt1-7 prepares par l'IGGE est un apport important, car il comprend des materiaux a matrices variees: un sol, un sediment de riviere, des peridotites riches en magnesium ou en fer, un minerai de platinoides appauvri en Cu, Ni et Fe et une chromitite. Les concentrations en PGE de ces materiaux setalent sur cinq ordres de grandeur et les echantillons sont bien homogenes, comme le demontre un test de variance. Differentes methodes analytiques ont ete utilisees pour la certification, incluant plusieurs preconcentrations par fusion et des procedures de chimie humide classiques pour la mise en solution et la preconcentration. Les valeurs certifiees pour les elements Pt, Pd, Os, Ru, Ir, Rh, Au ont ete determinees par AAS, colorimetrie catalytique (COL), polarographie catalytique (POL), spectrometrie d'emission (AES), ICP-MS et activation neutronique (NAA). Recemment, les echantillons GPt1-7 ont ete reconnus comme materiaux primaires de reference nationale par le Bureau d'Etat de la Supervision Technique de Chine.

Eleven gold geochemical reference samples, GAu 8–18, have been prepared by the Institute of Geophysical and Geochemical Exploration, People's Republic of China. The concentration range of gold in these samples is from 0.5 ng/g to 10 μg/g. Fifteen Chinese Institutes, experienced in gold analysis of geological samples, have participated in the certification procedure using seven reliable analytical methods.