Numerical simulation of the wire‐pinning process in PET film casting: Steady‐state results

Poly(ethylene terephthalate) (PET) film casting involves melt flow through a slot die, across a small span, and onto a fast moving quench drum. In the “wire‐pinning” casting process, a thin electrified wire close to the line of contact with the drum creates a strong pinning force that delays air entrainment to higher line speeds. Nonuniform wetting of the die lips by the extruded melt is thought to be responsible for the formation of streaks, a defect in the machine direction. A finite element model of the film casting process with wire pinning was developed to assist in understanding what causes significant wetting of the lips and whether this can be avoided by electrostatic pinning. The solution of the governing equations provide the location of the static and dynamic contact lines, thus finding the wetting and pinning points in the process. The simulations investigate the sensitivity of the static wetting line locations on the die lands to the imposed values of static contact angle and die‐lip gap. It was found that while the contact angle has a small effect on the extent of die‐lip wetting within the parameter ranges examined, there is a considerable chance that the feed slot surfaces can be dewetted. This seems to be the greatest danger for causing streaks rather than excessive wetting of the die lands. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Ethylene epoxidation on Ag catalysts supported on non-porous, microporous and mesoporous silicates

The ethylene epoxidation activity of Ag catalysts supported on non-porous SiO₂, microporous silicalite zeolite and mesoporous MCM-41 and HMS silicates was investigated in the present study in comparison to conventional low surface area -Al₂O₃ based catalysts. The MCM-41 and HMS based catalysts exhibited similar ethylene conversion activity and ethylene oxide (EO) selectivity with the SiO₂ and -Al₂O₃ based catalysts at relatively lower temperatures (up to 230 °C), whereas their activity and selectivity decreased significantly at higher temperatures (≥300 °C). The silicalite based catalyst was highly active for a wide temperature range, similar to the SiO₂ and -Al₂O₃ based catalysts, but it was the less selective amongst all catalysts tested. High loadings of Ag particles (up to ca. 40 wt.%) with medium crystallites size (20–55 nm) could be achieved on the mesoporous materials resulting in very active epoxidation catalysts. The HMS-type silicate with the 3D network of wormhole-like framework mesopores (with average diameter of 3.5 nm), in combination with a high-textural (interparticle) porosity, appeared to be the most promising mesoporous support.     

Welfare Improvisation from the Receiving Waters of Urban Wastewater Systems in the Context of the Water Framework Directive

The compliance of wastewater authorities with the Water Framework Directive (WFD, 2000/60/EC) although may highly contribute to a “good” ecological status in aquatic ecosystems, is alleged to require disproportionally high costs in relevance to the anticipated benefits. This is mainly due to the limited yet research in the assessment of the economic welfare derived by the compliance with the WFD. In this light, the direct and indirect economic benefits emerged by the attaining of WFD are investigated. The wastewater treatment plant of Athens (Greece) is demonstrated as a comprehensive pilot case.     

Trinocular Stereo: A Real-Time Algorithm and its Evaluation

In telepresence applications each user is immersed in a rendered 3D-world composed from representations transmitted from remote sites. The challenge is to compute dense range data at high frame rates, since participants cannot easily communicate if the processing cycle or network latencies are long. Moreover, errors in new stereoscopic views of the remote 3D-world should be hardly perceptible. To achieve the required speed and accuracy, we use trinocular stereo, a matching algorithm based on the sum of modified normalized cross-correlations, and subpixel disparity interpolation. To increase speed we use Intel IPL functions in the pre-processing steps of background subtraction and image rectification as well as a four-processor parallelization. To evaluate our system we have developed a test-bed which provides a set of registered dense ground-truth laser data and image data from multiple views.     

Removal of toxic metal ions from aqueous systems by biosorptive flotation

Biosorptive flotation was used as a combined operation for the simultaneous abstraction of nickel, copper and zinc ions from aqueous streams. Laboratory‐scale batch experiments, as well as pilot‐scale continuous experiments, have been conducted. Grape stalks, a by‐product of the winery industry, were used as sorbent material. The experimental procedure consisted of two consecutive stages: (i) biosorption, and (ii) flotation. The possibility of reusing biomass, after appropriate elution, was also examined. The main parameters examined were biomass concentration, particle size of sorbent, surfactant concentration, pH and flocculation. Flotation removals, following laboratory‐scale experiments, were found to be in the order of 100, 85 and 70% for copper, zinc and nickel, respectively. In pilot‐scale experiments, biomass sorption capacities were determined as 25 for copper, 81 for zinc and 7 µmol dm^?3 for nickel. The order of biomass affinity regarding the studied metals was Cu > Zn > Ni. Short retention time and high effectiveness suggest that biosorptive flotation is a promising treatment process for the removal of toxic metals from contaminated aqueous solutions. © 2002 Society of Chemical Industry