Microstructure and mechanical properties of aluminum alloy 1421 after ECAP and warm rolling

The process of equichannel angular pressing (ECAP) is studied with the aim of fabricating large-size preforms with a diameter of 40 mm and a length of 160 mm from alloy 1421 to be used for forming sheets by subsequent warm rolling. Special features of the microstructure and optimum modes of superplasticity and mechanical properties of sheets with ultrafine-grain (UFG) structure are considered. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 45–48, March, 2007.     

Effect of osmotic dehydration on the drying kinetics and quality of cashew apple

The effect of different osmotic pretreatments on cashew apple drying kinetics and product quality were investigated. The osmotic pretreatment was carried out in an incubator at constant temperature and agitation. The drying process was conducted in a fixed bed dryer at different temperatures and constant air velocity. Experimental data were fitted successfully using the Page and the two‐term exponential models for dried fresh and pretreated fruit, respectively. It was found that drying rates of osmosed fruits decreased owing to the presence of infused solutes. Evaluation of the final product was performed by means of ascorbic acid content, water activity and sensorial test. The osmotic pretreated samples showed the highest vitamin C losses and the lowest water activity. The samples pretreated in sucrose solution had the highest acceptance.     

Preparation of amino-functionalized silica for copper removal from an aqueous solution

In the present research, amino-functionalized silica materials were synthesized to develop absorbents for removing copper (II) ions from water. Three kinds of silica with various BET surface areas and pore volumes (331.4 m²/g, 460.1 m²/g, 717.7 m²/g and 1.38 cm³/g, 1.06 cm³/g, 0.57 cm³/g, respectively) were used to determine an optimum material. 3-Aminopropyltrimethoxysilane (3-APTMS) and N-[3-(trimethoxysilyl)propyl]-ethylenediamine (MSDA) are two amino-functional moieties grafted onto silica surfaces. A maximum copper absorption of 33.45 mg/g was confirmed using the amino-functionalized material at an initial 3-APTMS concentration of 2.52 mmol/g. Silica with a BET surface of 331 m²/g and a pore volume of 1.38 cm³/g demonstrated a good copper absorption capacity. Interference species such as pH, NH₃ and EDTA were also studied in this work.     

The Development of Rating Curve Considering Variance Function Using Pseudo-likelihood Estimation Method

This paper employs a new estimation method for estimating stage–discharge rating curve parameters. In typical practical applications, the original non-linear rating curve is transformed into a simple linear regression model by log-transforming the measurement without examining the effect of heteroscedasticity of residuals. Therefore, the model with pseudo-likelihood estimation is developed in this study to deal with heteroscedasticity of residuals in the original non-linear model. The parameters of rating curves and variance functions of errors are simultaneously estimated by the pseudo-likelihood estimation (P-LE) method. Also simulated annealing, a sort of global optimization techniques, is adapted to minimize the log likelihood of the weighted residuals. At first, the developed P-LE model was applied to a hypothetical site where stage–discharge data were generated by incorporating various errors for statistical test. Also, the limit of stages for segmentation is estimated in the process of P-LE using the Heaviside function. For the validation of effects of the developed P-LE model, the results of the conventional log-transformed linear regression (LT-LR) model and the P-LE model are estimated and compared. After statistical simulation, the developed P-LE model is then applied to the real data sets from six gauge stations in the Geum River basin. It can be suggested that this new estimation method is applied to real river sites to successfully determine the weights taking into account error distributions from observed discharge data.     

The Effect of Extruded Orange Pulp on Enzymatic Hydrolysis of Starch and Glucose Retardation Index

Orange pulp was extruded using a Brabender laboratory single screw extruder (20:1 L/D). The independent variables evaluated were barrel temperature (83, 100, 125, 150, and 167 °C), feed moisture content (22, 25, 30, 35, and 38/100 g), and screw speed (126, 140, 160, 180, and 194 rpm). The apparent density and apparent viscosity values of the extruded orange pulp increased during extrusion, while the oil absorption index decreased, in comparison with the values for raw orange pulp. In vitro studies showed that at the end of the incubation time, 90.68% of the starch was hydrolyzed in the control sample, while only 77.82% and 69.40% pulp of the starch experienced hydrolysis in the presence of raw fiber and extruded orange pulp, respectively. Extruded orange pulp showed a higher glucose retradation index (16.04–25.92%) after 30 min of dialysis and after 60 min (11.66% and 18.33%) than raw orange pulp (8.33%). These results indicated that glucose could be bound with compacted fiber matrices and inhibit alpha-amylase activity. These mechanisms may create a definite benefit by decreasing the rate of glucose absorption and eventually lowering the concentration of postprandial serum glucose. The potential hypoglycemic effects of extruded orange pulp suggest that orange pulp is a good and abundant dietary fiber resource that could be of great benefit in controlling glucose levels in the blood. It could also be added to high-fiber foods as a low-calorie bulk ingredient to reduce the calorie level.     

Abnormal Failure Behavior of Sn-3.5Ag Solder Bumps Under Excessive Electric Current Stressing Conditions

Abnormal failure behavior of flip chip Sn-3.5Ag solder bumps with a Cu underbump metallurgy under excessive electric current stressing conditions is investigated with regard to electromigration lifetime characteristics and damage evolution morphologies. Abnormal behavior such as abrupt changes in the slope of the resistance versus stressing time curve correlate well with the changes in mean time to failure and the standard deviation with respect to␣the resistance increase ratio, which seems to be strongly related to highly␣accelerated electromigration test conditions of 120°C to 160°C and 3 × 10⁴ A/cm² to 4.6 × 10⁴ A/cm². This is closely related to changes in the damage evolution mechanism with time, even though the activation energy for electrical failure is primarily controlled by Cu diffusion through Cu-Sn intermetallic compound layers.