On-line characterization of single bubbles in multiphase reactors

ECCE 7 - 7th European Congress of Chemical Engineering, CHISA 2010 - 19th International Congress of Chemical and Process Engineering (CD-ROM of Full Texts)This paper presents an on-line method to identify automatically the single bubbles (isolated bubbles without influence of surrounded bubbles) in multiphase reactors. Based on image analysis technique (IA), the method combines the information given by IA with the Discriminant factorial analysis leading to results that allow the identification of single bubbles and the study of bubble population complexity. By this way, it is possible to characterize the single bubbles on different conditions and to understand their influence on mass transfer. Agreement between automated and manual classification, measured in terms of a performance index, is 90% on average. Further, it describes the application of such methodology to the study of the influence of bubble characteristics (size, shape, bubble population complexity, etc) on the individual parameters of volumetric liquid side mass transfer coefficient, kLa. The experiments were done at different temperatures (25-35ºC) and superficial gas velocities (up to 14 mm/s) in a bubble column.info:eu-repo/semantics/publishedVersio

Effect of viscosity of a liquid membrane containing oleyl alcohol on the pertraction of butyric acid

Solvent formulation is important in the optimization of the mass-transfer through supported liquid membranes (SLM) in pertraction and membrane extraction. Oleyl alcohol (OA) is frequently used as the solvent or diluent in the extraction of carboxylic acids. A disadvantage of OA is its relatively high viscosity of 28.32 mPa s at 25°C. This can be decreased by the application of a less viscous OA diluent, e.g. dodecane. The relationship between the ratio of the distribution coefficient of butyric acid (BA), D F, and the viscosity of OA-dodecane solvents, µ, as extraction and transport characteristics, and the overall mass-transfer coefficient, K p, through SLMs was analyzed. Dependence of the D F/µ ratio on the OA concentration showed a maximum at the OA concentration of 15 mass % to 30 mass %. The OA concentration dependence of K p for SLMs exhibited also a maximum at about 30 mass % and 20 mass % of OA at the BA concentration driving force of 0.12 kmol m−3 and 0.3 kmol m−3, respectively. Shifting of the maximum in K p dependences towards lower OA concentrations by increasing the BA concentration driving force is in agreement with the D F/µ ratio dependence. Using pure OA as the solvent or diluent is not preferable and a mixture of a low viscosity diluent with the OA concentration below 40 mass % should be used. The presented results show the potential of the D F/µ ratio in the screening and formulation of solvents in extraction and SLM optimization.Support of the Slovak grant agency VEGA No. 1-1184-11 is acknowledged

Enhancement of oxygen mass transfer in pneumatical bioreactors using n-dodecane as oxygen-vector

In biotechnology, oxygen mass transfer is a key parameter involved in the design and operation of bioreactors and it can be analyzed by means of the oxygen mass transfer coefficient (kLa). Due to the fact that oxygen has a very low solubility in an aqueous media (8–10 ppm at 20°C), actively growing cells can consume all the dissolved oxygen very fast, therefore, it has to be supplied continuously into the broths. In conventionally aerated bioreactors, low oxygen solubility combined with slow oxygen transfer rates often results in reduced growth and culture productivity. Due to their higher oxygen solubility, non-toxicity to microbes, antifoaming action, oxygen-vectors addition is one of the most effective methods to improve oxygen mass transfer rate in aerobic fermentations. The aim of this study was to investigate the use of n-dodecane as oxygen-vector in bubble column and air-lift bioreactors, under different working conditions (air superficial velocity, volumetric fraction of the organic phase, medium temperature). The results show that volumetric fraction of oxygen-vector (φ) has a great influence on kLa; in the presence of low volumetric fraction (φ=0.005 (v/v)), the oxygen mass transfer coefficient’s value in bubble column bioreactor was increased by almost 100% at 35°C and for φ=0.02 (v/v) by 5% at 25°C, while in air-lift bioreactor, at 25°C and φ=0.005 (v/v), the kLa value was enhanced by approximately 50%.his paper was supported by the project PERFORM-ERA "Postdoctoral Performance for Integration in the European Research Area" (ID-57649), financed by the European Social Fund and the Romanian Government

Fractal Patch Antenna based on Crystal Photonic applied to Intelligent Transportation Systems in the 40 GHz Millimeter Waveband

5G (and beyond) has very high bandwidth, short latency, better quality of service, and the right amount of capacity. Technological breakthroughs in mobile communication systems user equipments operating in the millimeter wavebands imply a high gain to compensate the effect of path loss. In this work, a novel photonic crystal-based microstrip patch antenna array with high gain is designed to be used in the next generation intelligent transportation ssytems, e.g., V2X, and other exciting applications. The Photonic Band Gap (PBG) structure and Finite Element Method were considered. By using the High Frequency Structure Simulation (HFSS) software, a fractal microstrip patch antenna operating in the U-band of the electromagnetic spectrum is conceived and modeled on a two-dimensional photonic crystal. The use of the PBG structure improves the antenna’s gain and bandwidth, while the antenna’s fractal form decreases its size and improves its input impedance. The operational frequency range is 41.72-45.12 GHz with a resonant band centered at 43.26 GHz. The proposed antenna is comprised of a 0.45 mm thick copper ground plane, a 0.9 mm thick FR-4 epoxy substrate with a relative transmittance of 4.4, and a 0.45 mm thick copper antenna patch. The achieved frequency band gain is 8.95 dBi.This work was supported by FCT/MCTES through national funds and when applicable co-funded EU funds under the project UIDB/50008/2020. It was also supported by COST CA20120 INTERACT and TeamUp5G. TeamUp5G project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie project number 813391.info:eu-repo/semantics/acceptedVersio

Surface-ATRP of PEGMA onto polydimethyl siloxane for biomedical applications

Silicone rubber (poly(dimethyl siloxane; PDMS)), is extensively used for biomedical implants due to its low toxicity, flexible processing techniques, long-term endurance and good blood compatibility. However, the presence of low molecular weight organic molecules and catalyst residues that cause host systemic inflammatory reactions. The hydrophobic nature of PDMS also allows microbial adhesion followed by infection. Hydrophilic PDMS surfaces would be of great value in inhibiting biofilm formation thus prolonging the lifetime of the implants. This could be obtained by surface-initiated atom transfer radical polymerization (ATRP). The robustness and versatility of ATRP allow the preparation of functional bioactive surfaces, including antifouling, antibacterial, stimuliresponsive, biomolecule-coupled and micropatterned surfaces.[1-3] We aim at establishing the experimental conditions allowing the surface-grafting of polyethylene glycol methacrylate (PEGMA) by surface attaching an initiator (1- trichlorosilyl-2-(chloromethylphenyl)ethane) onto PDMS (Sylgard ® 184). Here, cooper is being used as a metal catalyst and 2,2'-Bipyridine as a ligant. Polymerizations are being assayed in aqueous media. The native smooth and transparent surface of the PDMS could be preserved following polymerization (as confirmed by SEM). FTIR-ATR also showed the presence of PEGMA polymer chains. By contact angle measurement, a change in the surface hydrophobicity was observed, the values changing from 114º to 60º, following 30h polymerization. Work is in progress to optimize the modification of PDMS by PEGMA surface-ATRP. This implies following up the polymer chain growth kinetics, surface characterization by XPS, FTIR-ATR, SEM and contact angle measurements. Static and dynamic microbial adhesion, as well as biocompatibility studies are also envisaged

Impact of the propagation model on the capacity in small‐cell networks: comparison between the UHF/SHF and the millimetre wavebands

This work shows how both frequency and the election of path loss model affect estimated spectral efficiency. Six different frequency bands are considered, ranging from 2.6 GHz in the Ultra High Frequency (UHF) band to 73 GHz in the millimetre wave bands (mmWaves), using both single-slope and two-slope path-loss models. We start by comparing four ur ban path loss models for UHF: the urban/vehicular and pedestrian test environment from the ITU-R M. 1255 Report, which includes the two-slope urban micro line-of-sight (LoS) and NLoS, from the ITU-R 2135 Report. Then, we consider mmWaves taking into con26 sideration the modified Friis propagation model, followed by an analysis of the through put for the 2.6, 3.5, 28, 38, 60 and 73 GHz frequency bands. We have found that the signal to-interference-plus-noise ratio, as estimated with the more realistic two-slope model, is lower for devices that are within the break-point of the transmitter, which is a small dis tance in the UHF/SHF band. As a result, spectral efficiency is higher with mmWaves than with UHF/SHF spectrum when cell radius is under 40 meters but not when cells are larger. Consequently, mmWaves spectrum will be more valuable as cells get small. We also find that capacity as estimated with the two-slope model is considerably smaller than one would obtain with the one-slope model when cells are small but there is little difference in the models when cells are larger. Thus, as cells get smaller, the use of one slope models may underestimate the number of cells that must be deployed.info:eu-repo/semantics/acceptedVersio

Continuous-flow precipitation of hydroxyapatite at 37 °C in a meso oscillatory flow reactor

Continuous-flow precipitation of hydroxyapatite (HAp) was investigated in a meso oscillatory flow reactor (meso- OFR) and in a scaled-up meso-OFR, obtained by associating in series eight vertical meso-ORFs. Experiments were carried out under near-physiological conditions of temperature and pH, using fixed frequency ( f = 0.83 Hz) and amplitude (x0 = 4.5 mm), and varying the residence time from 0.4 to 6.7 min. It has been shown that the mean particle size and the aggregation degree of the prepared HAp particles decrease with decreasing residence time. HAp nanoparticles with a mean size (d50) of 77 nm, narrow size distribution, and uniform morphology were obtained at the lowest residence times, τ = 0.4 and 3.3 min in the meso-OFR and the scaled-up meso-OFR, respectively. These results show the capability of the meso-OFR and the scaled-up meso-OFR for continuous production of uniform HAp nanoparticles, while also confirming the possibility of OFR scale-up by in series association of individual OFRs

Process intensification of gas-liquid flows with a novel constricted oscillatory-meso tube

GLD-8 - 8th International Conference on Gas-Liquid and Gas-Liquid-Solid Reactor EngineeringA novel constricted meso-tube (4.4. mm internal diameter) operated with oscillatory flow mixing has recently demonstrated enhanced volumetric mass transfer coefficients ( kLa) for continuous gas-liquid flows. Values of kLa up to 0.16 s-1 were obtained with a very low air-inflow rate (QG = 0.28 ml min-1) for the continuous running of a liquid phase (QL = 1.58 ml min-1), while in the presence of fluid oscillations. This is a one-order of magnitude improvement in the O2 transfer efficiencies in comparison with those values typically found for the most common-aerated reactors (e.g. stirred tank reactor, bubbles column, air-lift reactor). The design of novel multiphase, scaled-down reactors based on this novel tube’s geometry allows the intensification of gas-liquid flow processes through reducing the required processing volumes and the improved performance in terms of mixing, residence times and mass transfer. As a correct design does require a full understanding of the mass transfer processes, the different contributions of the mass transfer coefficient and the gas-liquid interfacial area in the global kLa enhancement were explored and herein reportedinfo:eu-repo/semantics/publishedVersio

A mathematical study of a bistable nematic liquid crystal device

Electronic version of an article published as Mathematical Models and Methods in Applied Sciences Vol. 17, No. 12 (2007). p. 2009–2034. Article DOI No: 10.1142/S0218202507002546. Copyright World Scientific Publishing Company http://www.worldscientific.com/We consider a model of a bistable nematic liquid crystal device based on the Ericksen– Leslie theory. The resulting mathematical object is a parabolic PDE with nonlinear dynamic boundary conditions. We analyze well-posedness of the problem and global existence of solutions using the theory developed by Amann. Furthermore, using phaseplane methods, we give an exhaustive description of the steady state solutions and hence of the switching capabilities of the device.peerreviewe

Die Optimierung von Poly(Dimethylsiloxan) für biomedizinische Anwendungen durch oberflächeninitiierte Atom-Transferradikal-Polymerisation

Project BIOSURFA ref. PTDC/SAU-BEB/73498/200