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Tran, Chi Dac,Lee, Jae-Chun,Pandey, Banshi Dhar,Jeong, Jinki,Yoo, Kyoungkeun,Huynh, Trung Hai The Society of Chemical Engineers, Japan 2011 Journal of chemical engineering of Japan Vol.44 No.10
<P>As an alternative using cyanide chemicals for gold extraction, the application of a cyanogenic bacterium <I>viz.</I> <I>Chromobacterium violaceum</I> (<I>C. violaceum</I>) in YP medium has been investigated. The catalytic roles of metal ions such as Na<SUP>+</SUP>, Mg<SUP>2+</SUP>, Fe<SUP>2+</SUP>, and Pb<SUP>2+</SUP>, as well as the effect of Na<SUB>2</SUB>HPO<SUB>4</SUB> nutrient addition on the cyanide generation efficiency of the bacterium in this medium have been elucidated. While MgSO<SUB>4</SUB> and FeSO<SUB>4</SUB> added to the medium were equally effective for cyanide generation, improved efficiency was obtained in the presence of Na<SUB>2</SUB>HPO<SUB>4</SUB> and Pb(NO<SUB>3</SUB>)<SUB>2</SUB>. In order to examine the effectiveness of <I>C. violaceum</I> cultured in YP medium for the generation of cyanide ions, the dissolution of gold and copper from waste mobile phone printed circuit boards (PCBs), a good source of gold and copper in alkaline conditions, was tested at 30°C, for various pH values and metal ion contents. Gold leaching was found to be 11% in 8 d at pH 11.0 in presence of 4.0 × 10<SUP>−3</SUP> mol/L MgSO<SUB>4</SUB>, whereas; copper recovery was high (11.4%) at pH 10.0. Addition of 1.0 × 10<SUP>−2</SUP> mol/L Na<SUB>2</SUB>HPO<SUB>4</SUB> and 3.0 × 10<SUP>−6</SUP> mol/L Pb(NO<SUB>3</SUB>)<SUB>2</SUB> to the YP medium increased copper leaching to 30.3% and 38.1%, respectively, at pH 10.0 in 8 d. However, this effect was not observed for gold leaching.</P>
Dual-band isotropic metamaterial absorber based on near-field interaction in the Ku band
The Linh Pham,Hong Tiep Dinh,Dinh Hai Le,Xuan Khuyen Bui,Son Tung Bui,Hong Luu Dang,Anh Duc Phan,Dac Tuyen Le,Dinh-Lam Vu 한국물리학회 2020 Current Applied Physics Vol.20 No.2
We numerically and experimentally investigate single-band and dual-band isotropic metamaterial absorbers (IMAs) based on metallic disks. By optimizing the diameter of the metallic disks and the thickness of the dielectric substrate, the single-band IMA is observed at 16.2 GHz with absorptivity of 97%. When adding one diskpair to the structure, the dual-band IMA is obtained at 12.8 and 15.5 GHz due to the symmetry breaking. The physical mechanics is explained by near-field coupling effect and equivalent LC circuit model. The measurement results performed in the range 12–18 GHz show a good agreement with simulation and theoretical analysis. Our findings demonstrate a new approach to achieve dual-band and multi-band IMAs.