Analysis of nitrifying bacterial communities in aerobic biofilm reactors with different DO conditions using molecular techniques

In order to assess the relationship between the dissolved oxygen (DO) concentration and the characteristics of nitrifying bacterial communities in an aerobic biofilm reactor, molecular techniques including denaturing gradient gel electrophoresis (DGGE)/cloning based on PCR targeting 16S rRNA and the amoA gene and fluorescence in situ hybridisation (FISH) were conducted. The D-1, D-2, D-3 and D-4 reactors with different DO concentrations (1, 3, 5 and 7 mg/L, respectively) were set up in the thermostat and acclimated. The optimal DO concentration with stable nitrification efficiency was above 5.0 mg/L. As was shown by the results of DGGE and cloning, the community of ammonia-oxidising bacteria (AOB) and the ratio of Nitrosomonas sp. changed only slightly despite their differing nitrification efficiencies. The results of FISH indicated that higher DO concentrations resulted in an increase in AOB and nitrite-oxidising bacteria (NOB), and a reduction in heterotrophic microorganisms. The INT-dehydrogenase activity (DHA) test demonstrated that the activity of AOB decreased with reductions in the DO concentration. This means that the DO concentration does not influence the community of AOB, but rather the activity of AOB. In the relationship between the attached biomass and the nitrification efficiency, only the active biomass affected the nitrification efficiencies.     

A novel fault-detection technique of high-impedance arcing faults in transmission lines using the wavelet transform

This paper describes a novel fault-detection technique of high-impedance faults (HIFs) in high-voltage transmission lines using the wavelet transform. The wavelet transform (WT) has been successfully applied in many fields. The technique is based on using the absolute sum value of coefficients in multiresolution signal decomposition (MSD) based on the discrete wavelet transform (DWT). A fault indicator and fault criteria are then used to detect the HIF in the transmission line. In order to discriminate between HIF and nonfault transient phenomena, such as capacitor and line switching and arc furnace loads, the concept of duration time (i.e., the transient time period), is presented. On the basis of extensive investigations, optimal mother wavelets for the detection of HIF are chosen. It is shown that the technique developed is robust to fault type, fault inception angle, fault resistance, and fault location. The paper demonstrates a new concept and methodology in HIF in transmission lines. The performance of the proposed technique is tested under a variety of fault conditions on a typical 154-kV Korean transmission-line system.     

Hepatoprotective effect of 2,3-dehydrosilybin on carbon tetrachloride-induced liver injury in rats

The aim of this study was to investigate the protective effect of 2,3-dehydrosilybin (DHS) against carbon tetrachloride (CCl₄)-induced liver injury in rats. Administration of DHS significantly attenuated the levels of serum aspartate aminotransferase, alanine aminotransferase, and liver lipid peroxidation in CCl₄-treated rats. Moreover, we showed that DHS prevented DNA damage and decreased the protein levels of γ-H2AX, which is a specific DNA damage marker, in CCl₄-treated rat livers. DHS also markedly increased the activity of antioxidant enzymes, such as superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase in CCl₄-treated rat livers. Furthermore, we found that DHS significantly inhibited the production of serum nitric oxide as well as the levels of serum IL-6, IFN-γ, and TNF-α in CCl₄-treated rats. Additionally, DHS significantly suppressed iNOS expression on the protein levels in CCl₄-treated rat livers. Collectively, the present study suggests that DHS protects the liver from CCl₄-induced hepatic damage via antioxidant and anti-inflammatory mechanisms.     

Development of cleaning robot system for live-line suspension insulator strings

A new cleaning robot system for suspension insulator strings was developed to prevent a power failure, which can have severe effects on the national industry and economy. Compared with existing cleaning robots using jets of water or water/air, this robot mechanism is superior in insulation as it uses a porcelain-clamping method, and is more useful in mountainous or salt damage areas by adopting a dry cleaning method without water. In addition, in order to increase its cleaning efficiency and to prevent arc generation under live-line conditions, a set of mechanized brush bristles and a voltage-balancing contactor are devised, respectively. Moreover, a manual device for its installation and removal is presented. We confirmed its effectiveness through experiments. Recommended by Editorial Board member Hyoukryeol Choi under the direction of Editor Jae-Bok Song. This work was supported by Electric Power Industry R&D Project performed by Ministry of Commerce, Industry and Energy in Korea. Joon-Young Park received the B.S. degree in Electrical Engineering in 1995, and the M.S. and Ph.D. degrees in Mechanical Engineering from Korea Advanced Institute of Science and Technology (KAIST) in 1997 and 2004, respectively. He is now a Senior Researcher at the Strategic Technology Laboratory in Korea Electric Power Research Institute (KEPRI). His research interests include the robust control of nonlinear systems, the optimum kinematic design of robot manipulators as well as robot systems for the electric power industry. Byung-Hak Cho received the B.S. degree in Electrical Engineering from Hanyang University, Seoul, Korea, in 1982, and the M.S. and Ph.D. degrees in Nuclear Engineering from KAIST, Daejeon, Korea, in 1986 and 1996, respectively. He is now a Chief Researcher at the Strategic Tech-nology Laboratory in KEPRI, Daejeon, Korea. His research interests include robot systems for the electric power industry. Seung-Hyun Byun received the B.S. degree in Electrical Engineering from Yonsei University, Seoul, Korea, in 1992, and the M.S. degree in Electrical Engineering from KAIST, Daejeon, Korea, in 1994. He is now a Senior Researcher at the Power Generation Laboratory in KEPRI, Daejeon, Korea. His research interests include control system design, signal processing and artificial intelligence. Jae-Kyung Lee received the B.S. degree in Electrical Engineering from Kyungpook National University, Daegu, Korea, in 2002, and M.S. the degree in Electrical Engineering from KAIST, Daejeon, Korea, in 2004. He is now a Researcher at the Strategic Technology Laboratory in KEPRI, Daejeon, Korea. His research interests include the development of high-performance robot control and hazardous robot systems.     

Preparation of laminated composite membranes by impregnation of polypropylene with styrene in supercritical CO2 for direct methanol fuel cells

Composite membranes were formed by grafting styrene using supercritical carbon dioxide (scCO_-2) impregnation and polymerization procedures. A polypropylene membrane, styrene monomer, divinylbenzene (DVB), and 2,2′-Azoisobutyronitrile (AIBN) were placed in a reactor, and CO₋₂ was injected into the reactor at 38 ‡C for the scCO₋₂ impregnation process. After impregnation, the polymerization process was carried out at 78 ‡C. The grafted membranes were sulfonated in concentrated sulfuric acid at 95 ‡C. These polypropylene grafted polystyrene sulfonic acid (PP-g-pssa) membranes were characterized by using various methods. The morphology and structure of the PP-g-pssa membranes were analyzed with scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and energy dispersive spectrometer (EDS). The ion conductivity and methanol permeability were also measured. The ion conductivity of the PP-g-pssa membranes was higher and the methanol permeability of the laminated membrane was lower than that of Nafion membranes. The performance of the PP-g-pssa/Nafion laminated membranes was evaluated in a DMFC unit cell at 90 ‡C.     

Inductively coupled plasma etching of Pb(ZrxTi1-x)O3 thin films in Cl2/C2F6/Ar and HBr/Ar plasmas

Pb(Zr_xTi_1-x)O₃ thin films were etched in an inductively coupled plasma by using various etch gases such as Cl₂/Ar, C₂F₆/Ar, Cl₂/C₂F₆/Ar and HBr/Ar. The etch rates and etch profiles for each etch gas were investigated. Fast etch rates were obtained in chlorine-containing etch gases (e.g., Cl₂/Ar and Cl₂/C₂F₆/Ar), and clean and steep etch profiles were achieved in Cl₂/Cv₂F₆/Ar or HBr/Ar gases. The gas mixture of Cl₂ and C₂F₆ was proposed to give a fast etch rate and a steep sidewall angle of etched patterns. The optimum gas mixture of Cl₂C₂F₆/Ar was found by varying the gas ratio of Cl₂ to C₂F₆. On the other hand, HBr/Ar gas as an alternative for etching of the Pb(Zr_xTi_1-x)O₃ films was examined. Cl₂/C₂F₆/Ar and HBr/Ar etch gases were compared with respect to etch rate, etch profile and electrical properties.     

Alignment of electrospun polystyrene with an electric field

Polystyrene (PS) with a concentration of 20% by weight in THF/DMF was electrospun on a flat sheet collector. At a concentration of THF above 75%, blocking at the needle tip caused bead formation. However, a nice fiber mat was obtained with the 75/25 THF/DMF. Moreover, at a traveling distance of 10 and 15 cm and voltages from 10 to 16 kV, the PS fibers exhibited alignment. This alignment was reproducible when voltage stabilizer was connected to the voltage supply. This suggested that the uniformly positive charges arising from external voltage interacted with the aromatic rings on the PS chain, yielding a uniform dipole moment. As a result, during jet traveling, the solvent evaporated and the molecules were oriented and frozen at the ground collector. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Monitoring of bioventing process for diesel-contaminated soil by dehydrogenase activity, microbial counts and the ratio ofn-alkane/isoprenoid

Monitoring parameters were evaluated for a bioventing process that was designed to treat soils contaminated with diesel fuel. Statistical analyses were conducted to evaluate correlations between total petroleum hydrocarbon concentrations in the contaminated soil and physico-chemical parameters of soil such as microbial counts, dehydrogenase activity, andn-alkane/isoprenoid ratio. The correlation coefficients (r²) obtained showed that TPH concentrations in the bioventing system were strongly correlated with dehydrogenase activity (DHA), total heterotrophic bacterial count, and hydrocarbon utilizing bacterial count. Thus, it was concluded that these parameters could useful monitoring parameters for soils contaminated with diesel fuel     

Electrical properties and EMI shielding characteristics of polypyrrole–nylon 6 composite fabrics

Polypyrrole (PPy) was polymerized both chemically and electrochemically in sequence on nylon 6 woven fabrics, giving rise to polypyrrole–nylon 6 composite fabrics (PPy–N) with a high electric conductivity. The stability of the composite prepared by electrochemical polymerization (ECP) on chemical oxidative polymerization (COP) fabric was better than that of the composite prepared solely by the COP process, since the AQSA dopant was able to strongly interact with the PPy main chain and had a large molecular structure. The temperature dependence of the conductivity of the composites was verified over four heating and cooling cycles. The change in conductivity over these four repeated heating and cooling cycles was affected by the interaction between the thermal stability of the dopant and the rearrangement of the PPy main chain. The electromagnetic interference shielding efficiency (EMI SE) values were in the range 5–40 dB and depended on the conductivity and the layer array sequence of the conductive fabric. The composites with a high conductivity represented reflection‐dominant EMI shielding characteristics, which are typical of the EMI shielding characteristics of metals. However, composites with low conductivity showed absorption‐dominant EMI shielding characteristics. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1969–1974, 2003     

Photo patternable porous siloxane thin films using cyclodextrins as template materials

Photo patternable cyclic silsesquioxane (mCSSQ) compositions containing heptakis (2,3,6-tri-O-methyl)-β-cyclodextrin (tCD) as a porogen and photo acid generator (PAG) have been prepared, with the goal of achieving a photo resist free porous low dielectric constant precursor. The composition containing triphenylsulfonium based PAG could effectively create a patterned mCSSQ thin film with a resolution approaching ∼2 μm. The pore size of the mCSSQ film with PAG was smaller than that without PAG. Furthermore, the pore size distribution of the mCSSQ film with PAG was much narrower than that without PAG. This might be attributed to the disturbance effect of the agglomeration of tCD molecules through pre-vitrification of the matrix at the relatively low curing temperature. The mechanical property and dielectric constant of the photo-definable mCSSQ/tCD/PAG film were comparable to those of the mCSSQ/tCD counterpart.