On-line evolutionary optimization of an industrial fed-batch yeast fermentation process

This paper presents two genetic algorithms based on optimization methods to maximize biomass concentration, and to minimize ethanol formation. The objective function is maximized according to the values of feed flow rate, using genetic search approaches. Five case studies were carried out for different initial conditions, which strongly influence the optimal profiles of feed flow rate for the fermentation process. The ethanol and glucose disturbance effects were examined to stress the effectiveness of proposed approaches. The proposed genetic approaches were implemented for an industrial scale baker's yeast fermentor which produces Saccharomyces cerevisiae known as baker's yeast. The results show that optimal feed flow rate was obtained in a satisfactory and successful way for fed-batch fermentation process.     

Neural network modeling of arc spot welding

This study presents neural network (NN) for the prediction of ultimate capacity of arc spot welding. The proposed NN model is based on experimental results. The ultimate capacity of arc spot welding is modeled in terms of weld strength, average welding thickness and diameter. The results of the proposed NN model are later compared with results of existing codes and are found to more accurate. Moreover, the proposed NN model is presented in explicit form as a mathematical function. Parametric studies are also carried out to analyze the effect of each variable. The proposed NN model is a unified formulation valid for governing shear failures.     

Production of a dry sausage from African catfish (Clarias gariepinus, Burchell, 1822): microbial, chemical and sensory evaluations

Production of a dry sausage from African catfish and determination of its microbial, chemical and sensory properties during a 70‐day storage at both 4 and 22 °C were prompted. pH of the samples at 4 and 22 °C did not significantly change during the storage (P > 0.05). Moisture content of the samples was 74%, and reduced to 45% at 4 °C and to 22% at 22 °C. Protein content of the samples was 20.71%, and increased to 42.5% at 4 °C and to 57.99% at 22 °C. Total lipid content was 4.5%, and increased to 10.98% at 4 °C and to 15.68% at 22 °C (P < 0.05). Microbial analyses showed that there was a significant reduction in total aerobic mesophilic and psychrotrophilic bacteria, total mould and yeast, total lactic acid bacteria, total Enterobacteriaceae and Staphylococcus aureus counts at both 4 and 22 °C (P < 0.05). Samples stored at 4 °C had significantly higher sensory ratings than that of the samples stored at 22 °C (P < 0.05).     

Modeling and design optimization of asynchronous flexible assembly systems with statistical process control and repair

This article presents the implementation of hybrid procedures involving the use of analytical performance evaluation techniques, discrete event simulation, and Monte Carlo optimization methods for the stochastic design optimization of asynchronous flexible assembly systems (AFASs) with statistical process control (SPC) and repair loops. AFASs are extremely complex and difficult to analyze in that such systems are subject to starvation and blocking effects, random jam occurrences at workstations, and splitting and merging of the assembly flow due to repair loops. Hence, an integrated approach simultaneously analyzing the interactions between product quality and optimal/near optimal system design is pursued. In the analytical analysis stage, a model based on GI/G/1 queueing network theory is used. In the Monte Carlo optimization stage, two alternative stochastic optimization approaches, namely, heuristic versions of stochastic quasigradient and simulated annealing algorithms, are implemented and compared in terms of their capabilities of solving complex AFAS design problems. The hybrid procedures presented appear to perform reasonably well in designing AFASs to reach a target production rate.     

Cost optimization of mixed feeds with the particle swarm optimization method

In this study, the best mixed feed was prepared by using the algorithm of particle swarm optimization (PSO) and by taking into account the breeding type and method of the poultries and various farm animals (cattle, sheep, rabbit), their needs, ages, and feeding costs and optimizing them all. Results obtained through PSO were compared through linear programming and real-coded genetic algorithm. According to the results that were obtained, PSO produces more rapid, more stable, and optimum values.     

The effect of thawing methods on the quality of eels (Anguilla anguilla)

Physical (colour), chemical (pH, total volatile basic nitrogen (TVB-N), thiobarbituric acid values (TBA)) and microbiological (total aerobic mesophylic bacteria, salmonella, coliform, yeast and mould counts) analyses were carried out on thawed European eel (Anguilla anguilla). Different thawing treatments were used (in a refrigerator, in water, in air at ambient temperature and in a microwave oven). The results obtained were compared statistically with those of fresh fish. pH, TBA and a^∗ values of thawed samples usually decreased significantly (P < 0.05) when compared to the fresh control. Salmonella was not detected in any of the samples. Coliform and mould counts of fresh control and thawed samples were <1 CFU/g. Total aerobic mesophylic bacteria count of all thawed fish decreased. However, the yeast count of the refrigerator–thawed samples increased. The lowest total aerobic mesophylic bacteria and yeast counts were determined in water–thawed samples. Water thawing is therefore suitable for frozen eel.     

Counterion-coupled gemini (Cocogem) surfactants based on dodecylisopropylol amine and dicarboxylic acids: synthesis,characterization and evaluation as biocide against SRB

New cocogem surfactants were synthesized by interaction of dodecylisopropylol amine with dicarboxylic (oxalic, succinic, adipic, sebacic, tartaric, maleic, fumaric, isophthalic) acids. By tensiometric method, the surface activity of aqueous solutions of the synthesized cocogem surfactants at the border with air was studied and, by conductometric method, the specific electrical conductivity of these solutions was determined. The degree of counterion binding (β), critical micelle concentration (CMC), effectiveness of surface tension reduction (π_CMC), surface excess concentration (Γ_max), area per molecule at the interface (A_min), changes of Gibbs free energies of adsorption (ΔG_ad) and micellization (ΔG_mic) have been calculated. The character of change of the colloidal-chemical indices depending on spacer-group nature and length has been clarified. So, with an elongation of the spacer group and when passing from cis-form to trans-form, the value of CMC decreases. The obtained cocogem surfactants exhibit a considerable bactericidal effectiveness against sulfate-reducing bacteria. The bactericide properties of the cocogem surfactants containing in the spacer chain a saturated hydrocarbon fragment and benzene ring are stronger than for the others.     

Adsorption rate and protective effect of tributyl(cyclohexyl)ammonium chloride inhibitor on the acidic corrosion of steel

The inhibition of corrosion of a steel surface by an inhibitor, tributyl(cyclohexyl)ammonium chloride (TBCA), was investigated by gravimetric and electrochemical polarization measurements in various aqueous solutions of HCl and H₂SO₄ acids. It is known that the most extensive corrosive destruction proceeds during the initial stage of contact between the metallic surface and the aggressive surroundings. The change from H₂SO₄ to HCl considerably decreases the time for formation of an adsorption layer. The high adsorption of the surface‐active cationic TBCA on the steel electrode surface can be explained by the specific adsorption of Cl^? anions increasing the negative charge on the electrode surface. It was observed that the value of the polarizing current can be increased from time to time by addition of more TBCA inhibitor. This fact can be explained by the low stability of the film‐forming layer on the steel. A similar decrease of the protective effect was also observed in HCl solution. The inhibitor provides at least a slowing of the corrosion process (τ = 21 min). It was found that an increase in H₂SO₄ concentration from 1.0 to 0.2 N did not change the protective action of the inhibitor and had rather high values (θ = 283 ma/h, ψ = 84%, and τ = 14 min at [I] = 3.5 × 10^?4 mol/L). It was shown that the attraction constant has a negative value (A = ?1.5 and K_a = 22.3) for the inhibitor, which relates to a high value for the adsorption ability of TBCA in HCl solution and therefore with the intermolecular repulsive force between adsorption molecules having similar charges. The protective action of TBCA increases with an increase in temperature, which is correlated with the chemical nature of its adsorption on the steel surface.