Application of Doehlert experimental design for the optimization of cadmium biosorption in an aqueous solution by marine yeast biomass of Yarrowia lipolytica

A cadmium biosorption process was optimized by varying three independent variables pH (4.5–7.5), initial cadmium ion concentration (10–30 mg L^?1), and Yarrowia lipolytica dosage (3–5 g L^?1) by using a Doehlert experimental design (DD) involving response surface methodology (RSM). For the maximum biosorption of cadmium ion in an aqueous solution by Y. lipolytica, a total of fifteen experimental runs were set and the experimental data fitted to the empirical second-order polynomial model of a suitable degree. The analysis of variance of the quadratic model demonstrates that the model was highly significant. Three-dimensional plots demonstrate relationships between the cadmium ion uptake with the paired variables (when other variable was kept at its optimal level), describing the behavior of biosorption system in a batch process. The model showed that cadmium uptake in aqueous solution was affected by all the three variables studied. The optimum values of the variables were found to be 6.43, 17.56 mg L^?1 and 3.63 g L^?1 for pH, initial cadmium ion concentration and biomass dosage, respectively, at a contact time of 40 min. At these optimal conditions, the maximum percentage biosorption of cadmium was predicted to be 48.89. The experimental values were in good agreement with predicted values and the correlation coefficient was found to be 0.9985. It showed that both monolayer adsorption and intra-particle diffusion mechanisms were effective in the cadmium biosorption process. Therefore, it is apparent that the DD involving RSM not only gives valuable information on interactions between the variables but also leads to identification of feasible optimum values of the studied variables.     

Optimization of removal of lead from bearing-lead anode slime

An optimization process is conducted by the Taguchi experimental design method for removal of lead from decopperized anode slime in aqueous Na₂CO₃/HNO₃ media. The effects of parameters such as reaction temperature, Na₂CO₃ concentration, solid–liquid ratio and reaction period on the conversion are studied. It is seen that the most important parameters affecting the conversion of lead sulphate to lead carbonate are solid–liquid ratio and reaction period. The optimum conversion conditions for process are found to be solid–liquid ratio of 0.05 g/mL, reaction period of 600 s, reaction temperature of 50 °C and Na₂CO₃ concentration of 2 M. Under optimal conditions, the experimental results put out that the conversion of lead sulphate at the 95% confidence level can be 97%, approximately.     

High-energy X-ray computed tomography of the progression of the solidification front in pure aluminum

An X-ray computed tomography (CT) system was developed for monitoring the solidification front in metal casting. The X-ray source was a 6 MeV linear accelerator (linac) emitting photons in 5 μs pulses at a rate of 180 Hz. The source intensity was 300 R/min at 1 m. The X-ray beam was collimated in a 30 deg fan shape with a 10-mm height. A detector array comprising 128 elements was located 845 mm from the source. Pure aluminum in a clay-graphite crucible (178-mm o.d., 146-mm i.d.) was melted in a resistance heater furnace, and a cooling tube at the center of the crucible solidified the molten aluminum to simulate the casting process. A solidification front formed around the tube and progressed outward over an hour until the aluminum was completely solidified. X-ray attenuation measurements were taken every minute during this time. Density images were later reconstructed from these measurements using CT. From these images, the progression of the solidification front was determined with a planar resolution of 1.3 mm and a sensitivity of 3.7 pct. The density maps agree with expected values and correlate well with temperature measurements obtained independently by thermocouples.     

Characterization of diffraction patterns directly from in-line holograms with the fractional Fourier transform

We show that the fractional Fourier transform is a suitable mechanism with which to analyze the diffraction patterns produced by a one-dimensional object because its intensity distribution is partially described by a linear chirp function. The three-dimensional location and the diameter of a fiber can be determined, provided that the optimal fractional order is selected. The effect of compaction of the intensity distribution in the fractional Fourier domain is discussed. A few experimental results are presented.     

Performance evaluation of metaheuristic search techniques in the optimum design of real size pin jointed structures

In recent years a number of metaheuristic search techniques have been widely used in developing structural optimization algorithms. Amongst these techniques are genetic algorithms, simulated annealing, evolution strategies, particle swarm optimizer, tabu search, ant colony optimization and harmony search. The primary goal of this paper is to objectively evaluate the performance of abovementioned seven techniques in optimum design of pin jointed structures. First, a verification of the algorithms used to implement the techniques is carried out using a benchmark problem from the literature. Next, the techniques compiled in an unbiased coding platform are evaluated and compared in terms of their solution accuracies as well as convergence rates and reliabilities using four real size design examples formulated according to the design limitations imposed by ASD-AISC (Allowable Stress Design Code of American Institute of Steel Institution). The results reveal that simulated annealing and evolution strategies are the most powerful techniques, and harmony search and simple genetic algorithm methods can be characterized by slow convergence rates and unreliable search performance in large-scale problems.     

Simplified NDE of multiple cracks by means of the potential drop technique

A method is developed for the simplified evaluation of multiple cracks, based on the d.c. potential drop technique. A subregion containing cracks is considered. The distribution of the potential drop for the cracks except for end cracks in the subregion is measured and calculated numerically by assuming a value for the depths of the end cracks and by assuming any value for the depths of other cracks. Modifying the depths of the other cracks is repeated until the difference between measured and calculated potential drops is minimized, where the depths of the end cracks are fixed. Evaluation of the centre crack in the subregion is made for different assumed depths of the end cracks. To make the evaluation independent of the depths of the end cracks, a subregion is extended to increase successively the number of cracks considered. Multiple cracks are sized well enough by this method.     

Microstructural investigation of ceria-zirconia solid solution with oxygen vacancies

The microstructural change in CeO2-ZrO2 solid solution (Ce2Zr2O7 + x; 0 < or = x < or = 1) with an ordered arrangement of Ce and Zr associated with the absorption/release of oxygen was observed by transmission electron microscopy (TEM). The oxidation of Ce2Zr2O7 was observed in TEM by electron diffraction analysis. The change in the electron diffraction pattern shows that Ce2Zr2O7 was easily oxidized in the TEM and that the oxidation was completed, giving an intermediate phase Ce2Zr2O7.5. Three different lattice images corresponding to x = 0, 0.5 and 1.0 were observed in high-resolution photographs of Ce2Zr2O7 + x. This difference in contrast image may be used for determining the local amount of oxygen absorbed.     

In situ HREM observation of nucleation and growth of nanotwins beneath the solid-liquid interface in Si

Nucleation and growth of nanotwins in Si grown from Al-Si liquid have been observed directly using an in situ heating experiment in a high-resolution transmission electron microscope. Nanotwins are nucleated at the triple point between a vacuum and the solid-liquid interface. When two parallel twins, the mirror planes of which are separated slightly, encounter each other, very complicated atomic arrangements are formed. The structure of the perturbed region is discussed tentatively in terms of the high-pressure phases in Si.     

A new ultrasonic angle-beam technique for sensitive evaluation of closed cracks

This paper is on the ultrasonic nondestructive evaluation of smaller cracks in the size range of 1–7 mm. Sensitive evaluation of the crack that was originally present or that developed during operation is imperative for assessing the integrity of structural components. In order to develop a method for the enhancement of sensitivity of ultrasonic evaluation of closed cracks, the principle of a new angle-beam approach is proposed, where the use of an oblique longitudinal wave with a small angle of incidence upon the specimen surface is emphasized. The crack treated exists nearly vertically on the back surface of the specimen. In contrast with the normally incident wave beam, the effect of angular incidence on the ultrasonic response due to a crack is investigated in an attempt to predict the optimum angle of evaluation. The sensitive feature of the present angle-beam technique is discussed in light of comparison made with the usual methods of normal incidence and large-angle beam technique. Ultrasonic measurements performed on the closed fatigue-cracked specimens show that the method offers bright prospects for the sensitive evaluation of small, closed cracks.     

Antioxidant activity of medicinal plant extracts in cookies

The antioxidant activity of ethanolic extracts of parsley, buckthorn, mint, caraway, and their mixture "Vitalplant" was evaluated, and the potential of "Vitalplant" mixture extract to retard the process of lipid oxidation in cookies was tested. The antioxidant activity was estimated by 2 direct (ESR) and 4 indirect (spectrophotometric) tests and correlated with the total phenolic and flavonoid content. The potential of "Vitalplant" mixture extract to retard the process of lipid oxidation in cookies was measured by thiobarbituric acid (TBA)-reactive-substances assay (TBARS) and DPPH˙ (1,1-diphenyl-2-picryl-hydrazyl) test. Significantly different (P < 0.05) amounts of total phenolics were found among extracts in the following order: mint > buckthorn > "Vitalplant" > parsley > caraway. Total flavonoid content varied from 0.510% (parsley) to 2.05% ("Vitalplant"). A statistically significant correlation was found between IC(50) values on DPPH˙ and total flavonoid content of the samples (r=- 0.94, P < 0.05) and between IC(50) values on DPPH˙ and IC(50) values on O(2) (·-) scavenging activity (r= 0.89, P < 0.05). A correlation between reducing activity and total phenolic content was found to be positive and statistically significant (r= 0.94, P < 0.05). "Vitalplant" mixture exhibited a relatively high antioxidant activity in most of the tests, which can be explained by synergistic effects of the ingredients of which it is composed. Finally, "Vitalplant" extract addition (2%, 4%, and 6%) improved antioxidant activity and oxidative stability of the cookies in dose-dependent manner. PRACTICAL APPLICATION: Supplementation of cookies with a mixture of Petroselini fructus, Frangulae cortex, Mentha piperitae folium, Carvi fructus can retard the process of lipid oxidation and elevate antioxidant activity of the final product.