Adsorption of Cr(VI) from aqueous solution by hydrous zirconium oxide

A type of ZrO₂·nH₂O was synthesized and its Cr(VI) removal potential was investigated in this study. The kinetic study, adsorption isotherm, pH effect, thermodynamic study and desorption were examined in batch experiments. The kinetic process was described by a pseudo-second-order rate model very well. The Cr(VI) adsorption tended to increase with a decrease of pH. The adsorption data fitted well to the Langmuir model. The adsorption capacity increased from 61 to 66 mg g^?1 when the temperature was increased from 298 to 338 K. The positive values of both ΔH° and ΔS° suggest an endothermic reaction and increase in randomness at the solid–liquid interface during the adsorption. ΔG° values obtained were negative indicating a spontaneous adsorption process. The effective desorption of Cr(VI) on ZrO₂·nH₂O could be achieved using distilled water at pH 12.     

An evaluation of the creep properties of two Al-Si alloys produced by rapid solidification processing

Tensile creep tests were conducted on two Al-Si alloys produced by rapid solidification: an Al-Si-Ni-Cr alloy and an Al-Si-Cu-Fe alloy, designated alloys A and B, respectively. The creep curves of these two alloys in the temperature range from 493 to 573 K were markedly different, with alloy A exhibiting a normal creep curve with a very short tertiary region and alloy B exhibiting an extended tertiary stage associated with strain localization. The minimum creep rates varied, with the applied stress raised to exponents of ∼9.0 and ∼8.5 for the two alloys, respectively. The hardness of alloy B decreased with time during the creep testing, but there was little or no change in the hardness of alloy A. These differences in the creep and hardness characteristics are attributed to the evolution of precipitates within the two alloys during creep testing. A detailed analysis shows that, over the temperature range examined experimentally, alloy A exhibits a creep strength that is superior to conventional Al-based alloys and comparable to, or even higher than, some SiC-reinforced Al composites.     

Preparation and characterization of thermoplastic polymers from hydroxyalkyl methacrylates

Soluble polymers have been produced from technical-grade 2-hydroxyethyl methacrylate (HEMA) and hydroxypropyl methacrylate (HPHA) using a combination of vacuum distillation and solvent extractions to purify the monomers prior to solution polymerization. These extractions, particularly of HEMA with hexane and corn oil, were found to reduce the level of ethylene glycol dimethacrylate to < 1%, according to gas chromatographic analysis. Homopolymers of HEMA and HPMA and copolymers of HEMA with methyl methacrylate were prepared with a wide range of molecular weights and characterized by viscometry in dimethyl formamide, infrared spectroscopy including deuterium exchange experiments, and high resolution proton and carbon nuclear magnetic resonance (NMR) spectroscopy. The latter was used to determine copolymer composition and tacticity distribution.     

Precipitation effects during hot deformation of a copper alloy

Hot compression tests were performed on a previously solution-treated Cu-3Ni-lSi-O.8Cr-O.1 Mg alloy below the solvus temperature. The effects of precipitation occurring during hot deformation and the accompanying flow stresses were analyzed on the basis of microstructural evolution using optical, scanning, and transmission electron microscopy, and microhardness measurements. It was found that the hardening stage was followed by strain-induced localized Ni₂Si-precipitate coarsening at the temperature related to the most effective dynamic precipi-tation. Intensive coarsening of precipitates began at grain boundaries. Very fine Ni₂Si precip-itates were transformed into elongated particles at grain boundaries, producing flow localization, softening, and finally sample fracture. Formerly Graduate Student, Academy of Mining and Metallurgy, Cracow, Poland     

High temperature distillation process with sea water feed decalcification pretreatment

The performance ratio of a desalination plant can be increased to reach 16–18 by coupling it with a decalcification pretreatment by ion exchange of the sea-water make-up, so making MSF comparable with RO from energetic point of view. A new strong cationic resin DECAL has been tailored; its main features are high selectivity towards the calcium ion and low concentration of the regenerating brine. These characteristics make it compatible with the normal operating range of multiflash plants and very suitable for the above service, when compared with other resins.The optimum coupling conditions of the whole plant, as has been pointed out, lie between 140°C and 150 °C for the top brine temperature and 2 to 2.5 for the brine concentration factor. In these conditions it is possible to operate with sea water-resin bed ratio higher than 20.     

Energy dissipation efficiency in aluminum dependent on monotonic flow curves and dynamic recovery

In the hot working of Al, the flow curves are usually monotonic, reaching saturation at a lower strain ε_s and stress σ_s as temperature rises and strain rate declines. Microstructural examination confirms that the dislocation density rises to a steady-state level through formation of an equiaxed subgrain substructure with constant dimension that is larger for lower stress. The energy dis-sipation efficiency estimated by dynamic materials modeling for flow curves of the above type is the result of dynamic recovery, not of dynamic recrystallization, which is characterized by flow curves with a peak and marked softening to a steady-state regime. Formerly with Concordia University     

Evaluating an augmented reality interface for sailing navigation: a comparative study with a immersive virtual reality simulator

Sailing navigation is an activity that requires acquiring and processing information from the surrounding environment. The advancement of technology has enabled sailboats to have an increasing number of onboard sensors that make sailing more user-friendly. However, data provided by these sensors are still visualized on 2D digital displays that imitate traditional analog interfaces. Although these displays are strategically placed on the sailboat, the user needs to divert attention from the primary navigation task to look at them, thus spending a significant amount of cognitive resources. AR-based technologies have the potential to overcome these limitations by displaying information registered in the real environment, but there are no studies in the literature for validating the effectiveness of this technology in the field of sailing. Thus, we designed a head-mounted display AR-based interface to assist users in monitoring wind data to avoid user diversion from the primary task of sailing. We conducted a user study involving 45 participants in an Immersive Virtual Reality simulated environment. We collected objective and subjective measures to compare the AR-based interface with a traditional data visualization system. The AR-based interface outperformed the traditional data visualization system regarding reaction time, cognitive load, system usability, and user experience.