Fault detection, identification and diagnosis using CUSUM based PCA

In this paper, a cumulative sum based statistical monitoring scheme is used to monitor a particular set of the Tennessee Eastman Process (TEP) faults that could not be properly detected or diagnosed with other fault detection and diagnosis methodologies previously reported.T² and Q statistics based on the cumulative sums of all available measurements were successful in observing these three faults. For the purpose of fault isolation, contribution plots were found to be inadequate when similar variable responses are associated with different faults. Fault historical data is then used in combination with the proposed CUSUM based PCA model to unambiguously characterize the different fault signatures. The proposed CUSUM based PCA was successful in detecting, identifying and diagnosing both individual as well as simultaneous occurrences of these faults.     

Unimpaired highly extensible tough chemically crosslinked hydrogel after experiencing freeze/thaw and boiling processes

A highly extensible, tough, chemically crosslinked double-network (DN) hydrogel was synthesized from acrylamide. Three samples of this hydrogel were swelled using different solutions. One swelled in water, one in an aqueous glycerol solution, and one in an aqueous sodium chloride solution. The freezing points of the hydrogel samples were determined using differential scanning calorimetry (DSC). Then, the samples underwent controlled freeze–thaw cycles, and their mechanical behavior under loading-unloading-reloading large-strain tensile deformation were analyzed. The results of these mechanical tests indicated that all the data points for deformation cycles coincided, despite the large water content of the samples. This means that no mechanical damage occurred during the deformation process. The results of hydrogel samples boiled in these solutions also showed no damage. Thus, it can be concluded that the tough chemically crosslinked DN hydrogel does not damage under large-strain tensile deformations even after experiencing harsh environmental conditions, such as freeze/thaw or boiling processes, which makes it a great candidate for applications that involve large temperature variations. The resistance of the DN hydrogel to damage is attributed to the specific molecular architecture of this hydrogel, in that the building block of this material is a loosely crosslinked polymeric network.     

Effect of canned tuna fish processing steps on lead and cadmium contents of Iranian tuna fish

The contents of Pb and Cd in two species of Iranian tuna fish (yellowfin and skipjack), which were caught from the Persian Gulf and Oman Sea, and the effects of canning processing steps on their contents were assessed by electrothermal atomic absorption spectrometry. The results revealed that the levels of lead and cadmium throughout the processing steps in yellowfin were in range of 0.154 ± 0.019–0.441 ± 0.025 μg/g and 0.029 ± 0.002–0.084 ± 0.0005 μg/g, respectively. Pb and Cd concentrations from received fish to final product in skipjack were found to be in range of 0.072 ± 0.031–0.218 ± 0.031 μg/g and 0.016 ± 0.001–0.062 ± 0.002 μg/g, respectively. The limit of detection for lead and cadmium were 0.058 μg/g (11.6022 μg/l) and 0.0007 μg/g (0.1485 μg/l), respectively. Results from paired sample t-test analysis showed that defrosting, cooking, and sterilisation by autoclave would reduce the contents of lead and cadmium, considerably.     

A Simple Route to Fabricate Percolated Perpendicular Magnetic Recording Media

A simple approach is proposed for fabrication of percolated perpendicular media (PPM). Nano pore array with pore diameter of 12-15 nm and different pore densities has been prepared by anodizing aluminum on silicon wafers. The pore density increases from 3.2times10¹⁰ cm^-2 to 11.0times10¹⁰ cm^-2 with the decrease in anodizing voltage from 30 to 10 V. Then, Pt (7 nm)/{Co (0.5 nm)/Pt (2) nm}₅ multilayers are deposited onto this porous anodized alumina (AAO) by sputtering. The pore size is reduced to 10-12 nm after deposition of magnetic layers. The Co/Pt multilayers on AAO exhibit perpendicular magnetic anisotropy, squareness ratios of unity, and negative nucleation fields. The perpendicular coercivity increases linearly with the increase in pore density due to the pinning effect imposed by the pores, which is consistent with theoretical calculation for PPM     

Adsorption of Cu(II) ions from aqueous solutions using ion exchange resins with different functional groups

The extraction of heavy metals from industrial effluents using efficient adsorbents is crucial for wastewater treatment and beneficial for metal recycling. In this study, the removal of Cu(II) from an acidic solution by commercial resins Dowex G-26 and Puromet™ MTS9570 was investigated. The influences of contact time, solution concentration, pH, temperature, and a resin dosage on the adsorption process were studied with batch technique. The optimum adsorption conditions were obtained at a concentration of 1100 mg/L Cu, contact time of 30 min, pH 3.5, and resin dosage of 0.025 g/ml for the removal of 99.9% and 90% of copper ions by G-26 and MTS9570, respectively. The experimental data of copper adsorption were analyzed using the Langmuir, Freundlich, and Temkin isotherm models. The highest metal uptakes of 41.67 and 37.70 mg/g were observed for Dowex G-26 and MTS9570, respectively. It was found that both resins had higher adsorption capacities than the substances reported in the literature. The adsorption kinetic studies showed that the copper adsorption process could be better described by the pseudo-second order model. Adsorption occurs spontaneously under endothermic conditions, which indicates the endothermic nature of the process.     

Activated nitriles in heterocyclic synthesis: A Novel Synthesis of Pyrimidine Derivatives

The reaction of 3-amino-2,4-diethoxycarbonylcrotononitrile with cinnamonitrile derivatives afforded the pyrimidines 5a--d and not the pyridines 4 as expected from literature. Similarly pyrimidines 5e--h were produced when 3-amino-2,4-dicyanocrotononitrile was treated with the same reagent. The structure was established based on MS and high resolution ¹H-n.m.r. spectroscopy.