Phonon Bottleneck and Auger Recombination Effect on the Perfermance of a Self -assembled Quantum Dot Laser

Silicon - Considering the excited state and the standard rate equations, this study provides a new circuit model for a self-assembled quantum dot laser made by InGaAs/GaAs and investigates the...     

Conventional vs. Temperature-Gradient Transient Liquid Phase Bonding of Stainless Steel 304 Using a Multi-component (Fe–Ni–Mo–B) Filler Metal

Metallurgical and Materials Transactions A - The application of the multi-component Fe-based filler metals (FMs) for transient liquid phase (TLP) bonding of AISI 304 austenitic stainless steel has...     

Comparative Measurements of Plasma Position Using Multipole Moments Method and Analytical Solution of Grad–Shafranov Equation in IR-T1 Tokamak

In this paper we present two methods for determination of plasma position in IR-T1 tokamak: a multipole moments method and analytical solution of equilibrium problem or Grad–Shafranov equation. In the multipole moments method a modified rogowski and saddle coils were designed, constructed, and installed on outer surface of IR-T1 tokamak chamber, then displacement of plasma column were measured from them. To compare the plasma position obtained using this method, analytical solution of Grad–Shafranov equation is also demonstrated on IR-T1 tokamak. Results are in good agreement with each other.     

Comparative evaluation of biocompatibility of dense nanostructured and microstructured Hydroxyapatite/Titania composites

This work deals with the biocompatibility of dense nano- and micro-structured Hydroxyapatite/Titania composites prepared by two step and conventional sintering, respectively. By application of two step sintering, it was shown that the final grain size of HA–15 wt.%TiO₂ is maintained lower than 100 nm while by the application of conventional sintering it reaches higher than 100 nm. Biocompatibility of the dense bulks was evaluated by cell attachment and proliferation experiments. Cell morphology, and viability on each nano- and micro-structured Hydroxyapatite/Titania composites were examined at different time points. The nanostructured HA/Titania dense bulk exhibited higher cell viability than a microstructured one. In addition, the effects of ionic products from nano- and micro-structured bulk dissolution on osteoblasts were studied. The MTT test confirmed that the products from nanostructured HA/Titania dense bulk significantly promoted osteoblast proliferation within a certain concentration range.     

An estimation for velocity and temperature profiles of nanofluids in fully developed turbulent flow conditions

Theoretically convective heat transfer coefficient depends on velocity and temperature profiles. In this work friction factor and convection coefficient are used in order to compare both profiles for nanofluids and base fluids. For this purpose Al₂O₃/water (due to its present vast experimental study) and carbon nanotube/water (manufactured and examined with our group) are selected. The results show that velocity profile of a nanofluid is similar to the velocity profile of its base fluid. It is proposed that the change of temperature profile for nanofluids compared to the base fluids is the only variable responsible for unpredictable convective heat transfer coefficient of nanofluids using available correlations.     

Application of molecularly imprinted hydrogel for the preparation of lactose‐free milk

BACKGROUND: A variety of lactose imprinted hydrogels were prepared and their binding properties were studied in comparison with blank non‐imprinted hydrogel. Methacrylamide and ethylene glycol dimethacrylate were used as functional monomer and cross‐linker, respectively. Dimethylsulfoxide was also applied as polymerisation solvent. RESULTS: Different template/monomer ratios were studied and the optimised imprinted hydrogel (MIP₂), with a lactose/methacrylamide ratio of 1:8, was selected in a rebinding test. In Scatchard analysis of MIP₂‐lactose interactions, the dissociation constant and maximum binding sites were 0.33 mmol L^?1 and 67.76 µmol g^?1 hydrogel, respectively. The selectivity of MIP₂ for lactose in aqueous media was also evaluated in comparison with different mono‐ and disaccharides. The data showed that the affinity of MIP₂ for lactose is significantly higher than other saccharides. The imprinted hydrogel was finally used as a sorbent for separation of lactose from milk. CONCLUSIONS: The results indicated that MIP₂, as an optimised imprinted hydrogel, can effectively bind lactose and decrease its concentration in milk. Copyright © 2012 Society of Chemical Industry     

Effect of Specific Surface Area of a Mechanically Activated Chalcopyrite on Its Rate of Leaching in Sulfuric Acid-Ferric Sulfate Media

The aim of the current study has been to investigate the influence of mechanical activation through intensive milling of a chalcopyrite mineral sample on its BET surface area and the subsequent effect on its leaching reaction rate and mechanism. Leaching kinetics mechanisms of the raw and mechanically activated chalcopyrite in the sulfuric acid-ferric sulfate media have been investigated. Rate-controlling step seems to be the diffusion through the protective product layer, and mechanical activation apparently has no significant effect on the leaching mechanism. An attempt has been made to describe the apparent rate constant as a function of BET specific surface area (S), specific surface energy (σ), and leaching temperature (T). An equation in the form of k = AS ² exp(σ?S/RT) has been developed (A is a constant) and fitted to the experimental data with a fairly good agreement.     

Characterization,microstructure and corrosion behavior of magnesia refractories produced from recycled refractory aggregates

This paper aims to report the results of some investigations carried out in Iranian steel industries to reuse the spent magnesia graphite refractory bricks in the forms of the new shaped and unshaped magnesia refractories. Economical aspects of recycling and minimizing the environmental effects of spent refractories landfills were the basic goals of this research. The spent MgO–C refractory bricks from electric arc (EAF) and ladle (LF) furnaces were analyzed in terms of microstructural and chemical properties. Different samples were prepared from natural sintered magnesia and 10–30 wt.% of recycled aggregates in the forms of magnesia refractory brick and ramming mix and their physical and mechanical properties were evaluated. Also the slag corrosion behavior and microstructural properties of corroded samples were investigated. The results showed that the addition of up to 30 wt.% of recycled aggregates had no negative effects on the properties of magnesia refractories.     

Experimental study on premixed hydrogen/air and hydrogen–methane/air mixtures explosion in 90 degree bend pipeline

Nowadays, hydrogen is being utilized massively in industries as a clean fuel. Displacing of hydrogen due to unique chemical and physical properties has adversely affect on pipeline network, hence increases the potential risk of explosion. This study was carried out to determine the flame propagation of hydrogen/air and hydrogen–methane/air mixtures in pipeline. A 90° pipeline with L/D ratio of 40 was used. Pure hydrogen/air mixture with equivalence ratio, φ = 0.13, 0.17, 0.2, 0.24, 0.27 and 0.30 were used in this work. Different composition of hydrogen–methane–air mixtures were tested in this study i.e. 3%H₂ + 97CH₄, 4%H₂ + 96CH₄, 6%H₂ + 94CH₄ and 8%H₂ + 92CH₄. All mixtures were operated at ambient condition. The results show that bending is the critical part of pipeline and higher concentration of hydrogen can affect on maximum overpressure, flame speed and temperature rise of both pure hydrogen/air and methane-hydrogen/air mixtures.