Development and simulation studies of an unsteady state biofilter model for the treatment of cyclic air emissions of an α‐pinene gas stream

This paper describes the development and simulation of an unsteady state biofilter model used to predict dynamic behaviour of cyclically‐operated biofilters and compares it with experimental results obtained from three, parallel, bench‐scale biofilters treating both periodically fluctuating concentrations and constant concentrations of an α‐pinene‐laden gas stream. The dynamic model, using kinetic parameters estimated from the constant concentration biofilter, was able to predict the performance of cyclic biofilters operating at short cycle periods (ie, in the order of minutes and hours). Steady state kinetic data from a constant concentration biofilter can be used to predict unsteady state biofilter operation. At a 24 h cycle period, the dynamic model compared well with experimental results. For long cycle periods (ie, hours and days), removal efficiency decreased after periods of non‐loading: the longer the period of non‐loading, the poorer the biofilter's performance at the re‐commencement of pollutant loading. At longer time scales the model did not effectively predict transient behaviour, as adsorption and changes in kinetic parameters were not accounted for. Modelling results showed that similar biofiltration performance for the cyclic and constant concentration biofiltration of α‐pinene is expected for biofilters operating solely in the first order kinetics regime. Poorer performance for cyclic biofilters following Monod kinetics spanning the entire kinetics range is expected as the cycle amplitude increases. The most important parameters affecting the performance of a cyclically‐operated biofilter with short cycle periods are: amplitude of cyclic fluctuations, C_{g, max}/C_g, relative value of the half‐saturation constant in the Monod expression, K_s, and effective diffusivity of α‐pinene in the biofilm, D_e. Copyright © 2005 Society of Chemical Industry     

Ultrafast all-optical switching in GaAlAs integrated interferometer in 1.55 mu m spectral region

The first observation is reported of ultrafast all-optical switching in an integrated asymmetric Mach-Zehnder interferometer, using the nonresonant nonlinearity in Ga/sub 0.82/Al/sub 0.18/As below half the bandgap. A relative switching fraction of more than 80% has been achieved using 330 fs pulses at around 1.55 mu m from a coupled-cavity mode-locked colour centre laser.<>     

The prediction of transport parameters in filamentous fermentation broths based on results obtained in pseudoplastic polymer solutions

Transport phenomena studies on single phase “model” fluids are of limited value in biochemical engineering if they cannot be translated to the heterogeneous systems encountered in real fermentation processes. In this paper we discuss the utility of polymer solutions as models of filamentous fermentation broths for evaluation of: pipeline friction factors and impeller power numbers (turbine and helical ribbon). To a first approximation, polymer solutions can serve as suitable models for the prediction of laminar flow pressure drop in pipelines and turbulent power consumption in stirred tanks. However, results obtained on polymer solutions do not directly apply to filamentous fermentation broths for predictions of laminar flow impeller power consumption and the transition point for turbulent flow in stirred tanks. These discrepancies are believed to result from the existence of a time dependent yield stress in filamentous fermentation broths.     

Chromium distribution between liquid iron and molten basic slags

An equilibrium study was made of the distribution of chromium and oxygen between liquid iron, containing less than 1 pct Cr, and simple slags of the CaO(MgO)-SiO₂-FeO-Cr₂O₃ type in the temperature range 1526° to 1734°C The effects of slag oxidation, temperature, and basicity were observed.     

Electronic speckle interferometry, phase-mapping, and nondestructive testing techniques applied to real-time, thermal loading

A digital phase-mapping method has been developed for application in real-time electronic speckle interferometry studies. Its principles and application to a continuously deforming object are described. An efficient digital image-processing algorithm has been developed that permits quantitative interpretation of the resulting phase maps.     

Similarity-based image organization and browsing using multi-resolution self-organizing map

An algorithm is presented in this paper to facilitate the exploration of large image collections based on visual similarities. Starting with an unordered and unannotated set of images, the algorithm first extracts the salient details into feature vectors using both color and gradient information. The feature vectors are then used to train a self-organizing map which maps high-dimensional feature vectors onto a 2D canvas so that images with similar feature vectors are grouped together. When users browse the image collection, an image collage is generated that selects and displays the most pertinent set of images based on which portion of the 2D canvas is currently in view. Flowing from an overview to details is a seamless operation controlled simply by pan and zoom, with representative images selected in a consistent and predictable way. To make organizing larger image collections practical in interactive time, the organization algorithm is designed to run in parallel on graphics processing units. Overall this paper presents an end-to-end solution that facilitates the surfing of image collections in a fresh way.