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.     

Nondestructive inspection of delamination in IC packages by high-frequency microwaves

Delamination in IC packages was detected by microwaves. An open-ended coaxial line sensor was employed to couple microwave signals with the package and the package was scanned in two perpendicular directions on a plane parallel to the package. A microwave image was created by measuring the phase of the effective reflection coefficient at the aperture of the coaxial line sensor. A high-frequency microwave was used to obtain a higher spatial resolution. The image obtained from the microwave measurement shows almost the same features as that of a scanning acoustic tomograph. The delamination was detected significantly without a coupling medium. This indicates that microwave imaging is a promising technique for the integrity assessment of IC packages.     

Tangent Stiffness Equations for Laterally Distributed Loaded Members

Tangent stiffness equations for a beam-column, which is subjected to either uniformly or sinusoidally distributed lateral loads, are presented. The equations have been derived by differentiating the slope-deflection equations under axial forces for a member. Thus, the tangent stiffness equations take into consideration axial forces, bowing effect, and laterally distributed loads. As a numerical example, elastic buckling behavior of parallel chord latticed beams with laterally distributed loads is investigated to compare the results obtained from the present method with those from the conventional matrix method in which the distributed loads are considered as a series of concentrated loads at additional intermediate nodes of a member. Furthermore, buckling tests were carried out to confirm the equations derived as well as to clarify the buckling behavior of space frame structures. In conclusion, it can be said that the new equations can provide a good efficient way of estimating the equilibrium paths and buckling loads. They can also lead to a significant savings in core storage and computing time required for the analysis of space frame structures.     

Contamination of silicon surface due to contact with solid polymers

The present research investigates material transfer associated with the contact between polymers and silicon surfaces. Material transfer from a variety of solid polymers (UHMWPE, Teflon, KEL-F, PMMA, Nylon 66, and PEEK) was studied and characterized by optical microscopy, scanning electron microscopy, atomic force microscopy, and by computer image analysis. Experimental results suggest that material transfer is affected by the Hertz contact area. The number of particles and the total particle area increase with an increase in load and a decrease in the Young's modulus. Also, material transfer increases when the contacting surfaces are rougher. Friction appears to be a weak parameter in the material transfer phenomenon. Additionally, hardness is significant only when normal loading is great enough to initiate plastic deformation in the polymer     

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.