3,751 research outputs found
Effect of TiO2 nanoparticles on fouling mitigation of ultrafiltration membranes for activated sludge filtration
No full textMembrane bioreactors (MBRs) have been widely used as advanced wastewater treatment process in recent years. However, MBR system has a membrane fouling problem, which makes the system less competitive. Thus there have been great efforts for fouling mitigation. In this study, two types of TiO2 immobilized ultrafiltration membranes (TiO2 entrapped and deposited membranes) were prepared and applied to activated sludge filtration in order to evaluate their fouling mitigation effect. Membrane performances were changed by addition of TiO2 nanoparticles to the casting solution. TiO2 entrapped membrane showed lower flux decline compared to that of neat polymeric membrane. Fouling mitigation effect increased with nanoparticle content, but it reached limit content above which fouling mitigation did not increase. Regardless of polymeric materials, membrane fouling was mitigated by TiO2 immobilization. TiO2 deposited membrane showed greater fouling mitigation effect compared to that of TiO2 entrapped membrane, since larger amount of nanoparticle was located on membrane surface. It can be concluded that TiO2 immobilized membranes are simple and powerful alternative for fouling mitigation in MBR application. (C) 2004 Published by Elsevier B.V.
Interpretation of fouling characteristics of ultrafiltration membranes during the filtration of membrane bioreactor mixed liquor
No full textIn this study, ultrafiltration (UF) membranes with various pore sizes were prepared by the phase inversion method, and their fouling characteristics were investigated with membrane bioreactor (MBR) mixed liquor. MBR sludge was fractionated into three parts, suspended solids, colloids and solutes, and their individual contributions to membrane fouling were quantified in order to asses the mechanisms by which fouling occurs. Cake layer formation on the membrane surface constituted the main fouling mechanism and the incidence of irreversible fouling was so small as to be negligible. The degree of fouling correlated very strongly with membrane permeability. This implies that hydrodynamic conditions are important factors affecting membrane fouling. The fouling contribution of each sludge fraction appeared to depend on particle size, as both permeation drag and back transport velocity are particle size-related functions. Solutes played a significant role in the initiation of cake layer formation, because they were deposited onto the membrane surface and pore wall immediately upon initial filtration, but were dislodged only in small amounts by cross flow. Suspended solids were consistently deposited onto the membrane surface, until flux reached a steady state and colloids exhibited characteristics commensurate with an intermediated state between solutes and suspended solids. Suspended A solids were, in fact, found to be the main contributor to the fouling process. However, the relative contribution of each of the sludge fractions to membrane fouling varied with the permeability of the membrane, and also with the hydrodynamic condition. (c) 2005 Elsevier B.V. All rights reserved.
Preparation of TiO2 self-assembled polymeric nanocomposite membranes and examination of their fouling mitigation effects in a membrane bioreactor system
No full textIn this study, we investigated the ability of TiO2 self-assembled nanocomposite membranes to mitigate fouling effects during the filtration of membrane bioreactor (MBR) mixed liquor. Our results showed that membrane fouling was significantly reduced by the immobilization of TiO2 nanoparticles on the surface of these membranes. The fouling mitigation effect increased with increasing amounts of TiO2 nanoparticles and the initial sharp flux decline observed for neat polymeric membranes was alleviated by TiO2 immobilization. Adsorbed foulants on the surface of nanocomposite membranes were more readily dislodged by shear force than those on neat polymeric membranes due to the increased hydrophilicity of the membrane. Accordingly, the amount and the rate of membrane fouling decreased in the nanocomposite membranes. (c) 2005 Elsevier B.V. All rights reserved.
Improvement of inter-layer motion prediction in scalable video coding
No full textIn this letter, we propose an enhanced method for interlayer motion prediction in scalable video coding (SVC). For inter-layer motion prediction, the use of refined motion data in the Fine Granular Scalability (FGS) layer is proposed instead of the conventional use of motion data in the base quality layer to reduce the inter-layer redundancy efficiently. Experimental results show that the proposed method enhances coding efficiency without increasing the computational complexity of the decoder.The authors would especially like to thank Dong Soo Lee for his contributions to this study
Preparation and characterization of fouling-resistant TiO2 self-assembled nanocomposite membranes
No full textIn this study, fouling-resistant nanocomposite membranes were prepared via electrostatic self-assembly between TiO2 nanoparticles and sulfonic acid groups on the membrane surface. Sulfonated polyethersulfone (SPES) was prepared by heterogeneous sulfonation with chlorosulfonic acid, and a TiO2 nanoparticle solution was prepared from the controlled hydrolysis of titanium tetraisopropoxide. Then, the SPES ultrafiltration membranes, which were prepared by the phase inversion method, were dipped in the TiO2 nanoparticle solution, thereby producing the TiO2/polymer nanocomposite membranes. The fouling mitigation property of the nanocomposite membrane was examined using membrane bioreactor (MBR) sludge, which contains a great number of various foulants. The results showed that the amount and rate of membrane fouling decreased in the nanocomposite membranes compared to the polymeric membranes. (c) 2006 Elsevier B.V. All rights reserved.
Influence of sludge retention time on membrane fouling and bioactivities in membrane bioreactor system
No full textSludge retention time (SRT) can produce significant effects on biomass properties in a membrane bioreactor (MBR) system. In this study, the membrane separation process was coupled to a sequencing batch reactor (SBR), which is one of the biological nutrient removal (BNR) processes, and the influence of SRT on membrane fouling and biological activity was investigated. Membrane fouling increased with SRT since sludge particles were more severely deposited on the membrane surface at longer SRT. Regardless of SRT change, COD removal efficiency was high and stable (over 92%) throughout the experiment. Nitrogen removal efficiency also attained a high treatment level. However, it was not proportioned to SRT increase and rather decreased at the longest SRT. Phosphorus removal decreased at prolonged SRT since excess sludge was reduced. Biological activity such as specific oxygen uptake rate (SOUR), specific nitrification rate (SNR), and specific denitrification rate (SDNR) did not increase with SRT but decreased at prolonged SRT. (c) 2004 Elsevier Ltd. All rights reserved.
Intelligent broadcasting system and services for personalized semantic contents consumption
No full textCurrently, digital broadcasting tends to personalize the TV watching environment by offering services that can adapt to viewer preferences. In this paper, an intelligent broadcasting system for enhanced personalized-services, based on the semantics of broadcasting contents, is proposed. To implement the system, the MPEG-7 and TV-Anytime Forum (TVAF), as well as agent technology, are employed. For content-level services, real-time content filtering, personalized video skimming, and content-based retrieval using audio characteristic are implemented. To verify the usefulness of the proposed system, we demonstrate it with a test-bed on which content-level personalized services are implemented(1). (c) 2005 Elsevier Ltd. All rights reserved.We would like to thank Mr Sungtak Kim, Mr Jun Ho Cho,
and Mr Mun Jo Kim who participated in this project
Semantic event detection in structured video using hybrid HMM/SVM
No full textIn this paper, we propose a new semantic event detection algorithm in structured video. A hybrid method that combines HMM with SVM to detect semantic events in video is proposed. The proposed detection method has some advantages that it is suitable to the temporal structure of event thanks to Hidden Markov Models (HMM) and guarantees high classification accuracy thanks to Support Vector Machines (SVM). The performance of the proposed method is compared with that of HMM based method, which shows the performance increase in both recall and precision of semantic event detection
Synthesis optimization and charge carrier transfer mechanism in LiLuSiO<sub>4</sub>:Ce, Tm storage phosphor
No full textLiLuSiO4:Ce and LiLuSiO4:Ce, Tm show very efficient charge carrier storage properties upon beta irradiation after samples have received treatment in vacuum. They outperform the commercial storage phosphor BaFBr(I):Eu2+ in many aspects. The influence of the synthesis conditions, Ce and Tm concentration, nonstoichiometry and codoping with Ca, Hf, Al and Ge are reported. Based on the results of the synthesis optimization, thermoluminescence (TL) emission and TL excitation spectra a mechanism of charge carrier transfer, storage, and recombination during irradiation and thermal or optical readout is proposed.Accepted Author ManuscriptRST/Fundamental Aspects of Materials and EnergyRST/Luminescence Material
Multiple region-of-interest support in scalable video coding
No full textIn this letter, we propose a new functionality to scalable video coding (SVC), that is, the support of multiple region of interests (ROIs) for heterogeneous display resolution. The main objective of SVC is to provide temporal spatial, and quality scalability of an encoded bitstream. The ROI is an area that is semantically important to a particular user especially users with heterogeneous display resolutions. Less transmission bandwidth is needed compared to when the entire region is transmitted/decoded and then sub-sampled or cropped. To support multiple ROIs in SVC, we adopt flexible macroblock ordering (FMO), a tool defined in H.264, and based on it, we propose a way to encode and, independently, decode ROIs. The proposed method is implemented on the joint scalable video model (JSVM) and its functionality verified
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