PILOT PLANT STUDIES AND MODELLING OF A SEMI-BATCH POLYESTERIFICATION PROCESS

A novel unsaturated polyester formulation was developed recently in our laboratories. The polyester resin, which was designed as a green-house glazing material, exhibited excellent optical properties and superior resistance to weathering conditions. This study describes the scale-up procedure followed in preparing the resin in a 200 L pilot plant reactor starting from its preparation in a 1 L reactor. The paper analyzes the major variables affecting the polyesterification process and presents a semi-empirical model capable of predicting the pilot plant kinetic data from laboratory reactor data. The model is based on a recently developed third order kinetic equation for the reaction of non-stoichiometric amounts of hydroxyl and carboxylic groups. The model quantifies the effects of reaction temperature and inert gas flow rate on reaction rate and provides a basis for the polyesterification process scale-up. The reaction temperature dependence is assumed Arrhenius, whereas the gas flow rate dependence is empirically determined as a function of the molar ratio of reactants to inert gas. Application of the model to commercial sized reactors will be highlighted.     

Dynamic Performance of Ozonation Treatment for Nonionic Surfactants (Polyoxyethylene Alkyl Ether) in a Bubble Column Reactor

The ozonation of a nonionic surfactant, Sannonic SS-90 (polyoxyethylene alkyl ether), which is one of polyoxyethylene nonionic surfactants, in water has been investigated using a bubble column. The effects of initial nonionic surfactant concentration, ozone gas flow rate, inlet ozone concentration in the gas-phase, liquid-phase temperature and hydrogen peroxide dose on decomposition of Sannonic SS-90 were systematically examined. The decomposition rate of Sannonic SS-90 decreased with the increase in the initial surfactant concentration and increased with increasing ozone flow rate and temperature. It was found that the rate of Sannonic SS-90 mineralization was weakly dependent on the gas-phase inlet ozone concentration in the range of the gas-phase inlet ozone concentration in this study. The oxidation rate increased with increasing concentration of H₂O₂, reached a maximum value and then decreased with further increasing of H₂O₂ concentration. The dynamic performance of the ozonation in a semi-batch bubble column was simulated using a mathematical model based on a tanks-in-series model. Reasonable agreement between the present experimental data and the simulated results was found.     

Flurbiprofen-loaded niosomes-in-gel system improves the ocular bioavailability of flurbiprofen in the aqueous humor

The present work aimed to prolong the contact time of flurbiprofen (FBP) in the ocular tissue to improve the drug anti-inflammatory activity. Different niosome systems were fabricated adopting thin-film hydration technique and using the nonionic surfactant Span 60. The morphology of the prepared niosomes was characterized by scanning electron microscopy (SEM). Physical characterization by differential scanning calorimetry, X-ray powder diffraction and Fourier transform infrared spectroscopy were conducted for the optimized formula (F5) that was selected on the basis of percent entrapment efficiency, vesicular size and total lipid content. F5 was formulated as 1% w/w Carpobol 934 gel. Pharmacokinetic parameters of FBP were investigated following ocular administration of F5-loaded gel system, F5 niosome dispersion or the corresponding FBP ocular drops to albino rabbits dispersion. Anti-inflamatory effect of F5-loaded carbopol gel was investigated by histopathological examination of the corneal tissue before and after the treatment of inflamed rabbit eye with the system. Results showed that cholesterol content, surfactant type. and total lipid contents had an apparent impact on the vesicle size of the formulated niosomes. Physical characterization revealed reduced drug crystallinity and incidence of interaction with other niosome contents. F5-loaded gel showed higher C_max, area under the curve (AUC_0–12), and thus higher ocular bioavailability than those of the corresponding FBP ocular solution. F5-loaded gel showed a promising rapid anti-inflammatory effect in the inflamed rabbit eye. These findings will eradicate the necessity for frequent ocular drug instillation and thus, improve patient compliance.     

Variable Selection‐based Multivariate Cumulative Sum Control Chart

High‐dimensional applications pose a significant challenge to the capability of conventional statistical process control techniques in detecting abnormal changes in process parameters. These techniques fail to recognize out‐of‐control signals and locate the root causes of faults especially when small shifts occur in high‐dimensional variables under the sparsity assumption of process mean changes. In this paper, we propose a variable selection‐based multivariate cumulative sum (VS‐MCUSUM) chart for enhancing sensitivity to out‐of‐control conditions in high‐dimensional processes. While other existing charts with variable selection techniques tend to show weak performances in detecting small shifts in process parameters due to the misidentification of the ‘faulty’ parameters, the proposed chart performs well for small process shifts in identifying the parameters. The performance of the VS‐MCUSUM chart under different combinations of design parameters is compared with the conventional MCUSUM and the VS‐multivariate exponentially weighted moving average control charts. Finally, a case study is presented as a real‐life example to illustrate the operational procedures of the proposed chart. Both the simulation and numerical studies show the superior performance of the proposed chart in detecting mean shift in multivariate processes. Copyright © 2016 John Wiley & Sons, Ltd.     

Evaluating order acceptance policies for divergent production systems with co-production

The impacts of using different order acceptance policies in manufacturing sectors are usually well known and documented in the literature. However, for industries facing divergent processes with co-production (i.e. several products produced at the same time from a common raw material), the evaluation, comparison and selection of policies are not trivial tasks. This paper proposes a framework to enable this evaluation. Using a simulation model that integrates a custom-built ERP, we compare and evaluate different order acceptance policies in various market conditions. Experiments are carried out using a case from the forest products industry. Results illustrate how and when different market conditions related to divergent/co-production industries may call for available-to-promise (ATP), capable-to-promise (CTP), and other known strategies. Especially, we show that advanced order acceptance policies like CTP may generate a better income for certain types of market and, conversely to typical manufacturing industries, ATP performs better than other strategies for a specific demand patterns.     

Comparison study of silicon carbide coatings produced at different deposition conditions with use of high temperature nanoindentation

The elastic modulus and hardness of different silicon carbide (SiC) coatings in tristructural-isotropic (TRISO) fuel particles were measured by in situ high temperature nanoindentation up to 500 °C. Three samples fabricated by different research institutions were compared. Due to varied fabrication parameters the samples exhibited different grain sizes and one contained some visible porosity. However, irrespective of the microstructural features in each case the hardness was found to be very similar in the three coatings around 35 GPa at room temperature. Compared with the significantly coarser grained bulk CVD SiC, the drop in hardness with temperature was less pronounced for TRISO particles, suggesting that the presence of grain boundaries impeded plastic deformation. The elastic modulus differed for the three TRISO coatings with room temperature values ranging from 340 to 400 GPa. With increasing measurement temperature the elastic modulus showed a continuous decrease.     

A New Approach for Nonlinear Multivariable Fed-Batch Bioprocess Trajectory Tracking Control

This paper proposes a new control law based on linear algebra. This technique allows nonlinear path tracking in multivariable and complex systems. This new methodology consists in finding the control action to make the system follow predefined concentration profiles solving a system of linear equations. The controller parameters are selected with a Monte Carlo algorithm so as to minimize a previously defined cost index. The control scheme is applied to a fed-batch penicillin production process. Different tests are shown to prove the controller effectiveness, such as adding parametric uncertainty, perturbations in the control action and in the initial conditions. Moreover, a comparison with other controllers from the literature is made, showing the better performance of the present approach.     

Adequacy of the daily TMPA 3B42 high-resolution satellite precipitation product for monitoring hydrometeorological hazards in the Southeast Sahel of Africa

Rural hamlets in the Southeast Sahel, because of their pastoral setting and dependence on local agricultural production, are particularly vulnerable to flash flooding, loss of soil and the inundation of arable land caused by sudden storm events. High resolution satellite precipitation estimates (SPEs) could prove essential for detecting, monitoring, predicting and mitigating the effects of such hydrometeorological extremes. The focus of this report is on assessing – in the context of the needs of the local community ? the effectiveness of what has become the gold standard for such applications in Africa and elsewhere since 1998: Tropical Rainfall Monitoring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA) program’s 0.25° × 0.25°, daily 3B42 Version 7 satellite-gauge merged product. The scientific community now has almost 20 years of TMPA data that will likely play a significant role well into the future for retrospective studies in conjunction with the next generation (post-2014) Global Precipitation Mission (GPM) products. To assess the 3B42 product for the purposes of this report, we employ a pixel-to-point comparison of 3B42 daily time series with synchronous gauge data at four well-separated gauge sites. While others have found notable agreement between 3B42 and gauge observations aggregated over large areas and seasonal to annual time periods, it is a different matter downscaling to daily values at local sites, where we find a disturbing number of ‘false alarms’ and ‘missed events’. More than 90% of the total annual rainfall estimated by the 3B42 is contributed by daily events that are misaligned in time or intensity with gauge events. This largely concurs with the findings of our prior reports based on CPC-RFE2 0.1° × 0.1° daily values. Thus, users might be cautious in using the TMPA 3B42, CPC-RFE2 or, by inference, any SPE, as deterministic metrics for detecting and monitoring short term (i.e. ≤ 1 day), extreme storm events in this area of the Sahel.