A dispersive liquid-liquid microextraction (DLLME) technique was proposed for the enrichment and graphite furnace atomic absorption spectrometric (GFAAS) determination of Cu 2+ in water samples.In this method a mixture of 480 mL acetone (disperser solvent) containing 26 mg S,S-bis(2-aminobenzyl)-dithioglyoxime (BAT) ligand and 20 mL carbon tetrachloride (extraction solvent) was rapidly injected by a syringe into 5 mL aqueous sample containing copper ions (analyte). Thereby, a cloudy solution formed. After centrifugation, the fine droplets containing the extracted copper complex were sedimented at the bottom of the conical test tube. This phase was collected by a microsyring and after dilution by methanol, 20 mL of it was injected into the graphite tube of the instrument for analysis.Effects of some parameters on the extraction, such as extraction and disperser solvent type and volume, extraction time, salt concentration, pH and concentration of the chelating agent were optimized. The response surface method was used for optimization of the effective parameters on the extraction recovery. Under these conditions, an enrichment factor of 312 was obtained. The calibration graph was linear in the rage of 2-50 mg L -1 Cu 2+ with a detection limit of 0.03 mg L -1 and a relative standard deviation (RSD) for five replicate measurements of 3.4% at 20 mg L -1 Cu 2+ . The method was successfully applied to the determination of Cu 2+ in some spring water samples.

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The analysis of stress concentration in geometrically heterogeneous smart structures is of great importance. In this study, by utilizing a recent constitutive model which considered both transformation and plasticity of shape memory alloys (SMAs), the stress concentration factor (SCF) in plates with circular cavities is investigated and the effect of phase transformation, saturation, and plasticity which may occur locally is studied. The results show that the conversion of the austenitic phase to the martensite leads to a reduction in SCF. After saturation of phase transformation at the stress concentration point, the SCF increases until the entire sheet enters the martensite phase. In the example under study, the SCF reaches 5.8 which is greatly higher than the elastic SCF. By entering the plastic region locally, the SCF reduces. Also, the modeling of sheets with more than one cavity has been done. It is concluded that extra hole, as a stress relief method, has a stronger effect on decreasing maximum stress concentration of shape memory alloys (considering transformation and plasticity) compared to purely elastic stress concentration studies.

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