• Archives of Pharmacal Research
• /
• v.21 no.3
• /
• pp.291-297
• /
• 1998

Cop protein has been overexpressed in Escherichia coli using a T7 RNA polymerase system. Purification to apparent homogeneity was achieved by the sequential chromatography on ion exchange, affinity chromatography, and reverse phase high performance liquid chromatography system. The molecular weight of the purified Cop was estimated as 6.1 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). But the molecular mass of the native state Cop was shown to be 19 kDa by an analytical high performance size exclusion chromatography, suggesting a trimer-like structure in 50 mM Tris-HCI buffer (pH 7.5) containing 100 mM NaCl. Cop protein Was calculated to contain $39.1% {\alpha}-helix, 16.8% {\beta}-sheet$, 17.4% turn, and 26.8% random structure. The DNA binding property of Cop protein expressed in E. coli Was preserved during the expression and purification process. The isoelectric point of Cop was determined to be 9.0. The results of amino acid composition analysis and N-terminal amino acid sequencing of Cop showed that it has the same amino acid composition and N-terminal amino acid sequence as those deduced from its DNA sequence analysis, except for the partial removal of N-terminal methionine residue by methionyl-aminopeptidase in E. coli.

• Membrane and Water Treatment
• /
• v.8 no.5
• /
• pp.437-448
• /
• 2017

A high quality Na-X zeolite membrane was synthesized on a seeded ${\alpha}-alumina$ disc by the secondary growth method. Structural characterization was done by X-ray spectroscopy, FT-IR spectroscopy, SEM and AFM imaging. The performance evaluation of the membrane was firstly tested in separation of glucose/water solutions by pervaporation process. There was obtained a separation factor $182.7{\pm}8.8$, while the flux through the membrane was $3.6{\pm}0.3kg\;m^{-2}\;h^{-1}$. The zeolite membrane was then used for desalination of aqueous solutions consisting of $Na^+$, $Ca^{2+}$, $Cs^+$ and $Sr^{2+}$ because of the importance of these ions in water and wastewater treatments. The effects of some parameters such as temperature and solution concentration on the desalination process were studied for investigating of diffusion/adsorption mechanism in membrane separation. Finally, high water fluxes ranged from 2 up to $9kg\;m^{-2}\;h^{-1}$ were obtained and the rejection factors were resulted more than 95% for $Na^+$ and $Ca^{2+}$ and near to 99% for $Cs^+$ and $Sr^{2+}$. Based on the results, fluxes were significantly improved due to convenient passage of water molecules from large pores of NaX, while the fouling was declining dramatically. Based on the results, NaX zeolite can efficiently use for the removal of different cations from wastewaters.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.14 no.1
• /
• pp.8-16
• /
• 2006

The research was conducted to characterize of Rh-Pd-Pt TWC with a double-layer washcoat for gasoline vehicle. The physical characteristics on surface of catalyst were inspected by BET, SEM and TEM. The characteristics of catalytic reaction were examined by the TPD/TPR and CO-pulse chemisorption. The catalyst $6Hx(0.35\times11\times3)$ showed superior conversion performance after hydrothermal aging process, which was due to small difference of the surface area between. the fresh and the aged catalyst. The CO-chemisorption and surface area were superior in the 600 cpsi catalyst than other catalysts, this catalyst also shown the higher conversion efficiency of the exhaust emissions. From the TPR test, the conversion performance of the aged catalyst was decreased by the agglomeration and sintering of the PM and metal oxides. From the TPD result, it was found that the NO chemisorption was happed on the bottom-layer washcoat with Pd, and the NO chemisorption was re-happened on the upper-layer washcoat with Pt and Rh in the desorption process.

• Korean Membrane Journal
• /
• v.10 no.1
• /
• pp.46-52
• /
• 2008

Optimization of ionomer solution was conducted in order to improve the performance of MEAs in PEMPC. The interface between membrane and electrodes in MEAs is crucial region determining fuel cell performance as well as ORR reaction at cathode. Through the modification of Nafion ionomer content at the interface between membrane and electrodes, an optimal content was obtained with Nafion 115 membranes. Two times higher current density was obtained with the outer Nafion sprayed MEA compared with the non-sprayed one. In addition, the symmetrical impedance spectroscopy mode (SM) exhibited that the resistances of membrane area, proton hydration, and charge transfer decreased as the outer Nafion is sprayed. From the polarization curves and SM, the highest current density and the lowest resistance was obtained at the outer ionomer content of $0.15\;mg\;cm^{-2}$.

• Journal of Institute of Control, Robotics and Systems
• /
• v.16 no.7
• /
• pp.711-719
• /
• 2010

Heliostat, as a concentrator reflecting the incident solar energy to the receiver located at the tower, is the most important system in the tower-type solar thermal power plant, since it determines the efficiency and performance of solar thermal plower plant. Thus, a good sun tracking ability as well as its good optical property are required. In this paper, we propose a method to compensate the heliostat sun tracking error. We first model the sun tracking error, which could be measured using BCS (Beam Characterization System), by multilayered neural network. Then the extended Kalman filter was employed to train the neural network. Finally the model is used to compensate the sun tracking errors. Simulated result shows that the method proposed in this paper improve the heliostat sun tracking performance dramatically. It also shows that the training of neural network by the extended Kalman filter provides faster convergence property, more accurate estimation and higher measurement noise rejection ability compared with the other training methods like gradient descent method.

• Journal of the Korean Society for Precision Engineering
• /
• v.29 no.2
• /
• pp.208-213
• /
• 2012

In this study, the mechanical joint performance of the V-Insert clamp applied to automobile exhaust pipes was evaluated through the experimental investigation of its axial load capacity. The axial load of the V-Insert clamp was also determined by using theoretical equations presented by Shoghi and compared with the experimental results. As results of the theoretical prediction, the axial load of the V-Insert clamp tended to increase along with smaller angle of the V-Insert segment and the lower friction coefficient between the V-Insert segment and exhaust pipes. The experimental results under tightening effects were similar to the theoretical results and the axial load of the V-Insert clamp presented maximum values in the range of all torques at distance of 2mm between each exhaust pipes. The experimental results under loading effects were similar to the theoretical results in the range of lower torques but deviated from the theoretical results in the range of higher torques. These results would be beneficial to improve the joint and sealing performance of the V-Insert clamp.

• Membrane and Water Treatment
• /
• v.8 no.4
• /
• pp.323-336
• /
• 2017

The main challenge in many applications of acetic acid is acid dehydration and its recovery from wastewater streams. Therefore, the performance of polyamide thin film composite is evaluated to separate acetic acid from water. To reach this goal, the formation of polyamide layer on polysulfone support membrane was investigated via interfacial polymerization (IP) of meta-phenylenediamine (MPD) in water with trimesoyl chloride (TMC) in hexane. Also, the effect of synthesis conditions, such as concentration of monomers and curing temperature on separation of acetic acid from water were investigated by reverse osmosis process. Moreover, the separation mechanism was discussed. The solute permeation was carried out under applied pressure of 5 bar at $25^{\circ}C$. Surface properties of TFC membrane were characterized by ATR-FTIR, SEM and AFM. The performance test indicated that 3.5 wt% of MPD, 0.35 wt% of TMC and curing temperature of $75^{\circ}C$ are the optimum conditions. Moreover, the permeate flux was $4.3{\frac{L}{m^2\;h}}$ and acetic acid rejection was about 43% at these conditions.

• Membrane and Water Treatment
• /
• v.6 no.4
• /
• pp.309-321
• /
• 2015

We report in this study the synthesis of mixed matrix reverse osmosis membranes by interfacial polymerization (IP) of thin film nanocomposite (TFNC) on porous polysulfone supports (PS). This paper investigates the synthesis of ZnO nanoparticles (NPs) using the sol-gel processing technique and evaluates the performance of mixed matrix membranes reached by these aerogel NPs. Aqueous m-phenyl diamine (MPD) and organic trimesoyl chloride (TMC)-NPs mixture solutions were used in the IP process. The reaction of MPD and TMC at the interface of PS substrates resulted in the formation of the thin film composite (TFC). NPs of ZnO with a size of about 25 nm were used for the fabrication of the TFNC membranes. These membranes were characterized and evaluated in comparison with neat TFC ones. Their performances were evaluated based on the water permeability and salt rejection. Experimental results indicated that the NPs improved membrane performance under optimal concentration of NPs. By changing the content of the filler, better hydrophilicity was obtained; the contact angle was decreased from $74^{\circ}$ to $32^{\circ}$. Also, the permeate water flux was increased from 26 to 49 L/m2.h when the content of NPs is 0.1 (wt.%) with the maintaining of lower salt passage of 1%.

• Journal of Hydrogen and New Energy
• /
• v.32 no.5
• /
• pp.401-409
• /
• 2021

The combination of different concentrations of ZnSO₄ in acidic solution as electrolyte in Zn-air batteries was investigated by Zn symmetrical cell test, half-cell and full cell tests. Using 1 M ZnSO₄ + 0.05 M H₂SO₄ as electrolyte and MnO₂ as air cathode catalyst with Zn foil anode, this combination had a satisfactory performance with balance of electrochemical activity and stability. Its electrochemical activity was matched to or even better than the PtRu catalyst in different current density. And its cycle life was improved (more than 100 cycles stable) by suppressing the growth of zinc dendrites on anode obviously. This electrolyte overcame the shortcomings of alkaline electrolyte that are easy to react with CO₂ in the air, severely growth of Zn dendrites caused by uneven plating/stripping of Zn.

• Nuclear Engineering and Technology
• /
• v.51 no.7
• /
• pp.1784-1790
• /
• 2019

Accurate and consistent characterization of defects in steam generator tubes (SGT) in nuclear power plants is one of the key issues in the field of nondestructive testing since the large number of signals to be analyzed in a time-limited in-service inspection causes a serious problem in practice. This paper presents an effective approach to this difficult task of automated classification of motorized rotating pancake coil (MRPC) eddy current flaw acquired from tube specimens with deliberated defects using deep neural networks (DNN). This approach consists of five steps, namely, the data acquisition using the MRPC probe in the tube, the signal preprocessing to make data more suitable for training DNN, the data augmentation for boosting a training performance, the training of DNN, and finally demonstration of the trained DNN for discriminating the axial and circumferential defects. The high performance obtained in this study shows that DNN is useful for classification of defects in tubes from the MRPC eddy current signals even though the number of signals is very large.