Propylene Polymerization Reactor Control and Estimation Using a Particle Filter and Neural Network

Polymeric materials are present in various industrial sectors and in daily life, presenting advantages such as low cost and durability. Several processes for manufacturing have been developed. To achieve safety and operational goals measurement methods for proper process monitoring and effective control are needed. However, in real polymer plants, measuring devices are subject to uncertainties and are not always available. Hence, this paper proposes a virtual sensor scheme based on a particle filter and artificial neural network (ANN) that is applied to a simulated polymerization reactor. This scheme reduces uncertainties and enables the observation of latent variables. The ANN is also used for predicting the final properties of the polymer. The goal is to provide controllers with more complete and improved information. The results show that the virtual sensor scheme improves the process control, providing accurate estimates and action times that are consistent with industrial sampling intervals, which highlights its potential for practical applications.

     

Gas diffusion sequential injection system for the spectrophotometric determination of free chlorine with o-dianisidine

A gas diffusion sequential injection system for spectrophotometric determination of free chlorine is described. The detection is based in the colorimetric reaction between free chlorine and a low toxicity reagent o-dianisidine. A gas diffusion unit is used to isolate free chlorine from the sample in order to avoid possible interferences. This feature results from the conversion of free chlorine to molecular chlorine (gaseous) with sample acidification. With minor changes in the operating conditions, two different dynamic ranges were obtained enhancing the application both to water samples and bleaches. The results obtained with the developed system were compared to the reference method, iodometric titration and proved not to be statistically different. A detection limit of 0.6 mg ClO⁻/L was achieved. Repeatability was evaluated from 10 consecutive determinations being the results better than 2%. The two dynamic ranges presented different determination rates: 15 h⁻¹ for 0.6-4.8 mg ClO⁻/L (water samples) and 30 h⁻¹ for 0.047-0.188 g ClO⁻/L (bleaches).     

Spectroscopic studies on copper(II)triphenylarsine oxide square planar complexes

Electronic and ESR spectra of the complexes [Cu(II)(tpa_so)₄][Cu(I)Cl₂]₂,[Cu(tpa_so)₄](NO₃)₂ and [Cu(tpa_so)₄](ClO     

Development of flow injection potentiometric methods for the off-line and on-line determination of fluoride to monitor the biodegradation of a monofluorophenol in two bioreactors

Water treatment has become a source of concern as new pollutants and higher volumes of waste water must be treated. Emerging biological approaches, namely the use of bioreactors, for cleaning processes have been introduced. The use of bioreactors requires the development of efficient monitoring tools, preferably with real-time measurements. In this work, a couple of flow injection systems were developed and optimized for the potentiometric determination of fluoride to monitor a rotating biological contactor (RBC) bioreactor and a sequencing batch reactor (SBR) with off-line and on-line sampling. Both the RBC and the SBR bioreactors were set up for the biodegradation of the halogenated organic compound 2-fluorophenol and, as fluoride was a degradation byproduct, the process was monitored by following up its concentration.The described flow injection potentiometric methods enabled the fluoride determination within the required quantification range 0.10-100 mM. The possible interferences from the growth medium were minimized in-line. The determination rate was 78 h⁻¹ for the off-line monitoring of RBC and 50⁻¹ h for the on-line monitoring of the SBR, with a sample consumption of 0.500 mL and 0.133 mL per determination, respectively. Furthermore, the overall reagent consumption was quite low. The accuracy of the system was evaluated by comparison with a batch procedure. The SBR efficiency was monitored both on-line by the flow system and off-line by HPLC, for comparison purposes.     

Behavioral multi-criteria decision analysis: the TODIM method with criteria interactions

In this paper a multi-criteria decision aiding model is developed through the use of the Choquet integral. The proposed model is an extension of the TODIM method, which is based on nonlinear Cumulative Prospect Theory. The paper starts by reviewing the first steps of behavioral decision theory. A presentation of the TODIM method follows. The basic concepts of the Choquet integral as related to multi-criteria decision aiding are reviewed. It is also shown how the measures of dominance of the TODIM method can be rewritten through the application of the Choquet integral. From the ordering of decision criteria the fuzzy measures of criteria interactions are computed, which leads to the ranking of alternatives. A case study on the forecasting of property values for rent in a Brazilian city illustrates the proposed model. Results obtained from the use of the Choquet integral are then compared against a previously made usage of the TODIM method. It is concluded that significant advantages exist derived from the use of the Choquet integral. The paper closes with recommendations for future research.     

Treatment of PVC using an alternative low energy ion bombardment procedure

In many applications, polymers have progressively substituted traditional materials such as ceramics, glasses, and metals. Nevertheless, the use of polymeric materials is still limited by their surface properties. Frequently, selective modifications are necessary to suit the surface to a given application. Amongst the most common treatments, plasma immersion ion implantation (PIII) has attracted the attention of many researchers owing to its versatility and practicality. This method, however, requires a power supply to provide high voltage (tens of kV) negative pulses, with a controlled duty cycle, width and frequency. Owing to this, the implementation of PIII on the industrial scale can become economically inviable. In this work, an alternative plasma treatment that enables low energy ion bombardment without the need of a high voltage pulse generator is presented. To evaluate the efficiency of the treatment of polymers, polyvinylchloride, PVC, specimens were exposed to 5 Pa argon plasmas for 3600 s, at excitation powers, P, of between 10 and 125 W. Through contact angle and atomic force microscopy data, the influence of P on the wettability, surface free energy and roughness of the samples was studied. Surface chemical composition was measured by X-ray photoelectron spectroscopy, XPS. To evaluate the effect of aging under atmospheric conditions, contact angle and XPS measurements were performed one and 1334 days after the treatment. The plasma potential and ion density around the driven electrode were determined from Langmuir probe measurements while the self-bias potential was derived with the aid of an oscilloscope. From these data it was possible to estimate the mean energy of ions bombarding the PVC surface. Chlorine, carbon and oxygen contamination were detected on the surface of the as-received PVC. Upon exposure to the plasma, the proportion of chlorine was observed to decrease while that of oxygen increased. Consequently, the wettability and surface energy increased after the treatment but such modifications were not stable after aging: the contact angle increased for all the samples, modifying the initially hydrophilic surface into a highly hydrophobic one. Consistently, the surface composition also changed after aging: there was carbon enrichment due to further losses of oxygen and chlorine. Another relevant factor for the elevation of θ was the change in morphology induced by the treatment. At greater powers, the uniform matrix of the PVC was transformed into a columnar structure containing randomly distributed sharp pillars. Interpretation of such results is proposed in terms of the total energy deposited in the solid by ionic collisions.     

Using error bounds to compare aggregated generalized transportation models

A comparative study of aggregation error bounds for the generalized transportation problem is presented. A priori and a posteriori error bounds were derived and a computational study was performed to (a) test the correlation between the a priori, the a posteriori, and the actual error and (b) quantify the difference of the error bounds from the actual error. Based on the results we conclude that calculating the a priori error bound can be considered as a useful strategy to select the appropriate aggregation level. The a posteriori error bound provides a good quantitative measure of the actual error.     

A survey on inborn errors of metabolism in 323 neonates from the state of Rio de Janeiro, Brazil

Inborn errors of metabolism (IEM) are a relevant cause of morbidity and death among children, and neonates in particular. However, little is known about the prevalence of these disorders in Brazilian newborns. Our laboratory of IEM (LABEIM) at the Department of Biochemistry, Institute of Chemistry, Federal University of Rio de Janeiro (UFRJ), has been working on the diagnosis of IEM since 1988. Out of 3,300 patients (90% children), screened and evaluated from 1989 to 2,000 because of a high clinical suspicion of having an IEM, 323 (9.8%) were neonates. Patients came from different regions of the state of Rio de Janeiro, in which lives approximately 8.5% of the total Brazilian population. Chemical tests, various chromatographic techniques and enzyme assays were performed in urine, plasma and in some cases, cerebrospinal fluid (CSF). This study describes our laboratory and the experience with the 323 investigated neonates, among which 28 cases (8.7%) of IEM were identified and 18 (5.6%), strongly suspected. All these cases were related mainly to the metabolism of amino acids, organic acids, lysosomal enzymes and carbohydrates. Furthermore, data on population, community and health services are presented.     

Sequential injection system for the spectrophotometric determination of reducing sugars in wines

A sequential injection system for the spectrophotometric determination of reducing sugars in wines is described. The methodology is based on the formation of a coloured complex produced by the reaction of copper (I) with 2,9-dimethyl-1,10-phenanthroline (neocuproine), after reduction of copper (II) to copper (I) by reducing sugars. In the present SI system, a dialysis unit was incorporated not only to allow the sample dilution, but also to minimise the interference of some coloured compounds. In this way, direct sample introduction into the system was possible, without any previous treatment of the wine samples. The proposed method can be applied to the determination of reducing sugars in two concentration ranges: from 2 to 25 g l(-1) (table wines) and from 20 to 140 g l(-1) (Port wines). To perform determinations in these two ranges, the manifold configuration remained the same; just a few operational parameters were changed in the controlling software. A sampling-rate of 14-18 samples per hour was obtained with good repeatability for ten consecutive injections of wine samples (relative standard deviations (RSD) <2.1%). The results obtained from 19 wine samples were comparable to those obtained by the reference method.