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1

Robust aperiodic-disturbance rejection in an uncertain modified repetitive-control system

Zhou L., She J., Li C., Pan C.

International Journal of Applied Mathematics and Computer Science

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2016

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Vol. 26, no. 2

285--295

EN

This paper concerns the problem of designing an EID-based robust output-feedback modified repetitive-control system (ROFMRCS) that provides satisfactory aperiodic-disturbance rejection performance for a class of plants with time-varying structured uncertainties. An equivalent-input-disturbance (EID) estimator is added to the ROFMRCS that estimates the influences of all types of disturbances and compensates them. A continuous-discrete two-dimensional model is built to describe the EID-based ROFMRCS that accurately presents the features of repetitive control, thereby enabling the control and learning actions to be preferentially adjusted. A robust stability condition for the closed-loop system is given in terms of a linear matrix inequality. It yields the parameters of the repetitive controller, the output-feedback controller, and the EID-estimator. Finally, a numerical example demonstrates the validity of the method.

2

A planning model for the chemical integrated system under uncertainty by grey programming approach

Ren J., Tan S., Dong L., Zhou Z., Gao S., Pan C.

Polish Journal of Chemical Technology

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2013

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Vol. 15, nr 2

16--22

EN

A model to optimize the planning of the chemical integrated system comprised by multi-devices and multi-products has been proposed in this paper. With the objective to make more profits, the traditional model for optimizing production planning has been proposed. The price of chemicals, the market demand, and the production capacity have been considered as mutative variables, then an improved model in which some parameters are not constant has been developed and a new method to solve the grey linear programming has been proposed. In the grey programming model, the value of credibility can be suggested by the decision-makers, and the results of the production planning calculated by the model can help them to achieve their desired target. An actual case has been studied by the proposed methodology, and the proposed methodology can be popularized to other cases.

3

Optimization and validation of a method based on derivatization with methylating agent followed by HPLC-DAD for determining dithiocarbamates residues

Zhou L., Xu J., Luan L., Ma J., Gong Y., Qin D., Pan C.

Acta Chromatographica

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2013

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Vol. 25, no. 4

613--625

EN

Dithiocarbamates fungicides (DTCs) are worldwidely used fungicides. Residue analytical methods on DTCs are usually based on headspace gas chromatography, which are not much stable and precise. In this study, a specific, simple and reliable method for determining DTCs fungicides residues was optimized and validated. The DTCs in foods and soils were extracted with an alkaline solution of EDTA and L-cysteine, followed by pH adjusting and methyl derivatization in methyl iodine solution. The organic layer of the reactants was separated, concentrated under vacuum and reconstructed in acetonitrile. DTCs residues were eluted on a C18 column and detected by HPLC-DAD at 272 nm. The S-alkyl derivatives of thiram, mancozeb and propineb were separated at different retention times. At fortified levels of 0.05 mg/kg to 2 mg/kg (residue expressed as CS2, in mg/kg, the same below), it is found that recoveries for DTCs spiked in apple, cucumber, tomato, rice and soil samples ranged from 70.8% to 105.3%, with relative standard deviations (RSD) from 0.6% to 13.7%. Limits of detection (LODs) and quantification (LOQs) ranged from 0.003 to 0.026 mg/kg and from 0.011 to 0.105 mg/kg for various foods and soils. This method was also applied to real sample tests.

4

Hydrophilic-interaction liquid chromatography (HILIC) with dad and mass spectroscopic detection for direct analysis of glyphosate and glufosinate residues and for product quality control

Li X., Xu J., Jiang Y., Chen L, Xu Y., Pan C.

Acta Chromatographica

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2009

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Vol. 21, no. 4

559--576

EN

High-performance liquid chromatography with a hydrophilic-interaction liquid chromatographic (HILIC) column has been successfully used to retain and separate the polar phosphonic herbicides glyphosate and glufosinate. Online electrospray tandem ion-trap mass spectrometric and DAD detection were used. The effects on the separation of mobile phase acetonitrile content, buffer concentration, and flow rate, and of column temperature, were investigated. With UV-visible detection at 195 nm, LOQ were <850 mg kg -1, showing the method is suitable for product quality control of these herbicides alone or in combination. Tandem mass spectrometric conditions were optimized for ion-trap detection. Quantification was by use of selected reaction monitoring transitions m / z 168 → 150 in negative-ion mode for glyphosate and m / z 182 → 136 in positive-ion mode for glufosinate. Limits of detection (LOD; S / N > 3) were 0.20 and 0.16 ng for glyphosate and glufosinate, respectively, and the respective limits of quantification (LOQ; S / N = 10) were 0.02 and 0.05 mg kg -1 . Sample derivatization was not necessary to achieve low detection limits in residue analysis in this study. Recovery from watermelon, spinach, potato, tomato, radish-root, and water fortified with the herbicides ranged from 63.6 to 107.3% and relative standard deviations were <15.3%.

5

New application of mixed C18 -SCX SPE clean-up in gas chromatographic-mass spectrometric determination of six β 2 -agonist residues in pig's liver

Shan J., Pan C., Zhang J., Niu W.

Acta Chromatographica

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2008

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Vol. 20, no. 1

43-57

EN

A new mixed C18-SCX SPE column and gas chromatography-mass spectrometry have been used for determination of six β 2-agonists residues in pig's liver. After hydrolysis, the six β 2-agonists were extracted with 6:4 (v/v) ethyl acetate-isopropanol and then cleaned on a commercial mixed-adsorbent solid-phase extraction column. The eluted solution was analyzed by gas chromatography-mass spectrometry (GC-MS) and quantified by the external standard method. Sample pre-treatment and GC-MS conditions were critically examined. The linear range was 0.005-2.00 mg L-1 and correlation coefficients were 0.9987-1.000. The LOD of mabuterol, clenbuteroland, and salbutamol was 0.2 µg kg -1. Average recoveries of these three compounds from spiked pig's liver ranged from 65.3 to 95.8% and relative standard deviations were between 5.4 and 9.9%. The LOD of cimaterol, bromobuterol, and ractopamine was 0.3 µg kg -1. Average recoveries of these three compounds from spiked pig's liver ranged from 63.8 to 88.1% and relative standard deviations were between 5.0 and 9.7%. These results indicate the method is highly sensitive, simple, inexpensive, and results in good purification. It could also meet requirements for analysis of pig's urine in domestic and import/ export inspection work.

6

Determination of chloramphenicol residues in honey by monolithic column liquid chromatography-mass spectrometry after use of quechers clean-up

Pan C., Zhang A., Chen S., Xu Y., Jiang S.

Acta Chromatographica

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2006

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No. 17

320-327

EN

An HPLC method with a monolithic column and detection by mass spectrometry has been established for determination of chloramphenicol in honey samples previously cleaned by use of a modification of the QuEChERS procedure. Honey samples were dissolved in water containing sodium chloride and extracted with acetonitrile. Further sample clean-up was performed by simple reversed-solid-phase dispersion with primary–secondary amine (PSA) adsorbent. Chloramphenicol (CAP) residues at ppb concentrations were detected by liquid chromatography–mass spectrometry (LC–MS), with electrospray ionization, in negative-ion mode. The mobile phase was methanol–0.2% aqueous ammonium acetate solution, 45:55 (v/v). Under these conditions CAP is eluted after ∼4 min and 8 min from a Merck RP-18e monolithic column and a conventional C18 column, respectively. Recovery at three fortification levels (0.2, 20, and 200 µg kg.1) was in the range 78–93% with RSD from 3.7 to 3.9%. The coefficient of determination, R2, was 0.9995 over a 0.1–100 µg L.1 linear range. Use of this method for determination of CAP in honey resulted in an LCL of 0.20 µg kg.1. The method was validated on the basis of EU decision 2002/657. CCá and CCâ for the honey matrix were 0.002 and 0.006 µg kg.1, so the method was fit for the purpose of monitoring commercial products or checking MRL compliance.