• Korean Journal of Materials Research
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• v.30 no.11
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• pp.601-608
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• 2020

In this work, Ag₃PO₄/In₂S₃ nanocomposites with low loading of In₂S₃ (5-15 wt %) are fabricated by two step chemical precipitation approach. The microstructure, composition and improved photoelectrochemical properties of the as-prepared composites are studied by X-ray diffraction pattern (XRD), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), photocurrent density, EIS and amperometric i-t curve analysis. It is found that most of In₂S₃ nanoparticles are deposited on the surfaces of Ag₃PO₄. The as-prepared Ag₃PO₄/In₂S₃ composite (10 wt%) is selected and investigated by SEM and TEM, which exhibits special morphology consisting of lager size substrate (Ag₃PO₄), particles and some nanosheets (In₂S₃). The introduction of In₂S₃ is effective at improving the charge separation and transfer efficiency of Ag₃PO₄/In₂S₃, resulting in an enhancement of photoelectric behavior. The origin of the enhanced photoelectrochemical activity of the In₂S₃-modified Ag₃PO₄ may be due to the improved charge separation, photocurrent stability and oriented electrons transport pathways in environment and energy applications.

• KSBB Journal
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• v.15 no.1
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• pp.49-54
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• 2000

Bioluminescence of Photobacterium phosphoreum has been used for the detection of pollutants in the environment. Immobilization method was used to maintain the stability of bioluminescence of P. phosphoreum. The carboxymethylcellulose was investigated to find out whether it was suitable for the immobilization of P. phosphoreum as a matrix without disturbing the bioluminescence emission. A maintenance of bioluminescence was determined from the P. phosphoreum immobilized on the various concentrations of carboxymethylcellulose. A relatively high bioluminescence intensity was shown with immobilized cells on 1%(w/v) carboxymethylcellulose. The effect of carboxymethylcellulose concentrations on the sensitivity of Crcompounds including $Na_{2}CrO_{4}$, $K_{2}CrO_{4}$, $CrO_{3}$, CrK$(SO_4)_{2}$ and $CrCl_{3}$ to the bioluminescence intensity. The calculated $EC_{50}$ showed that the linear relations between such substances and bioluminesence intensity were established.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.12
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• pp.803-808
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• 2014

$Bi_{0.5+x}(Na_{0.78}K_{0.22})_{0.5-3x}TiO_3$ ceramics with an excess $Bi^{3+}$ and a deficiency of $Na^+$ and $K^+$ were synthesized by a conventional solid state reaction method. The structure and morphology of $Bi_{0.5+x}(Na_{0.78}K_{0.22})_{0.5-3x}TiO_3$ ceramics were characterized by X-ray diffraction and field emission scanning electron microscopy. The electric polarization and mechanical strain induced by external electric field, and the temperature dependence of dielectric constant were investigated. These results demonstrated that an ergodic relaxor phase can be induced by controls of the mole ratio of $Bi^{3+}$, $Na^+$ and $K^+$. A phase boundary between non-ergodic and ergodic relaxor phases can be observed at ambient temperature. The ergodic relaxor phase can be transferred to the ferroelectric phase by application of the electric field. The stability of the induced ferroelectric phases strongly depends on the mole ratio of $Bi^{3+}$, $Na^+$ and $K^+$. The maximum strain of 0.31% was observed in $Bi_{0.51}(Na_{0.78}K_{0.22})_{0.47}TiO_3$ ceramics sintered at $1,150^{\circ}C$ for 2 h.

• Membrane Journal
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• v.30 no.6
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• pp.395-408
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• 2020

Polymer electrolyte membrane fuel cells (PEMFCs) have gained much attention as eco-friendly energy conversion devices without emission of environmental pollutant. Polymer electrolyte membrane (PEM) that can transfer proton from anode to cathode and also prevent fuel cross-over has been regarded as a key component of PEMFCs. Although perfluorinated polymer membranes such as Nafion® were already commercialized in PEMFCs, their high cost and toxic byproduct generated by degradation have still limited the wide spread of PEMFCs. To overcome these issues, development of hydrocarbon based PEMs have been studied. Incorporation of cross-linked structure into the hydrocarbon based PEM system has been reported to fabricate the PEMs showing both high proton conductivity and outstanding physicochemical stability. This study focused on the various cross-linking strategies to the preparation of cross-linked PEMs based on hydrocarbon polymers with ion conducting groups for application in PEMFCs.

• Korean Journal of Construction Engineering and Management
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• v.22 no.2
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• pp.53-62
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• 2021

PC component allocation and loading plan can contribute to reductions in carbon dioxide emission and energy use of vehicles and total project costs with increased utilization of vehicle loading space. The study derived 18 considerations that PC construction plant managers and site managers take into account when they plan allocation and loading of PC components. Then, IPA (Importance and Performance Analysis) was performed to assess importance and performance of the 18 considerations. Results show that in the PC component allocation planning, considerations regarding the number of vehicles and existence of yard for storing PC components have not been taken into account well by the managers. In the PC component loading planning, PC component loading direction has not been reflected well by the managers although it is considered important by them. Recently, ill-planning issues of PC component transportation, such as inefficient use of vehicle space and loading with low stability, are frequent due to various types of PC components produced. In this context, if the results of this study are reflected in the development of component allocation and loading planning, vehicle management of PC projects would be more efficient, thereby leading to economic project management.

• Applied Chemistry for Engineering
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• v.32 no.3
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• pp.332-339
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• 2021

Recently, due to concerns about the depletion of fossil fuels and the emission of greenhouse gases, the importance of hydrogen energy technology, which is a clean energy source that does not emit greenhouse gases, is being emphasized. Water electrolysis technology is a green hydrogen technology that obtains hydrogen by electrolyzing water and is attracting attention as one of the ultimate clean future energy resources. In this study, the surface properties of the porous transport layer (PTL), one of the cell components of the proton exchange membrane water electrolysis (PEMWE), were controlled using a sandpaper to reduce overvoltage and increase performance and stability. The surfaces of PTL were sanded using sandpapers of 400, 180, and 100 grit, and then all samples were finally treated with the sandpaper of 1000 grit. The prepared PTL was analyzed for the degree of hydrophilicity by measuring the water contact angle, and the surface shape was observed through SEM analysis. In order to analyze the electrochemical characteristics, I-V performance curves and impedance measurements were conducted.

• The Korean Journal of Nuclear Medicine
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• v.39 no.1
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• pp.44-48
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• 2005

Purpose: Ethylenediamine-tetramethylenephosphonic acid (EDTMP) has widely used chelator for the labeling of bone seeking radiopharmaceuticals complexed with radiometals. $^{153}Sm$ can be produced by the HANARO reactor at the Korea Atomic Energy Research Institute, Taejon, Korea. $^{153}Sm$ has favourable radiation characteristics $T1/2=46.7\;h,\;{\beta}_{max}=0.81\;MeV\;(20%),\;0.71\;MeV\;(49%),\;0.64\;MeV\;(30%)\;and\;{\gamma}=103\;keV\;(30%)$ emission which is suitable for imaging purposes during therapy. We investigated the labeling condition of $^{153}Sm$-EDTMP and imaging of $^{153}Sm$-EDTMP in normal rats. Materials and methods: EDTMP 20 mg was solved in 0.1 mL 2 M NaOH. $^{153}SmCl^3$ was added to EDTMP solution and pH of the reaction mixtures was adjusted to 3 and 12, respectively. Radiochemical purity was determined with paper chromatography. After 30 min. reaction, reaction mixtures were neutralized to pH 7.4, and the stability was estimated upto 120 hrs. Imaging studies of each reaction were perfomed in normal rats (37 MBq/0.1 mL). Results: The labeling yield of $^{153}Sm$-EDTMP was 99%. The stability of pH 8 reaction at 60, 96 and 120 hr was 99%, 95%, 89% and that of pH 12 at 36, 60, 96 and 120 hr was 99%, 95%, 88%, 66%, respectively. The $^{153}Sm$-EDTMP showed constantly higher bone uptake from 2 to 48 hr after injection. Conclusion: $^{153}Sm$-EDTMP, labeled at pH 8 reaction condition, has been stably maintained. Image of $^{153}Sm$-EDTMP at 2, 24, 48 hr after injection, demonstrate that $^{153}Sm$-EDTMP is a good bone seeking radiopharmaceuticals.

• Clean Technology
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• v.25 no.1
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• pp.81-90
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• 2019

A dielectric barrier discharge (DBD) plasma reactor packed with $Ni-CeO_2/{\gamma}-Al_2O_3$ catalyst was used for the dry ($CO_2$) reforming of propane (DRP) to improve the production of syngas (a mixture of $H_2$ and CO) and the catalyst stability. The plasma-catalytic DRP was carried out with either thermally or plasma-reduced $Ni-CeO_2/{\gamma}-Al_2O_3$ catalyst at a $C_3H_8/CO_2$ ratio of 1/3 and a total feed gas flow rate of $300mL\;min^{-1}$. The catalytic activities associated with the DRP were evaluated in the range of $500{\sim}600^{\circ}C$. Following the calcination in ambient air, the ${\gamma}-Al_2O_3$ impregnated with the precursor solution ($Ni(NO_3)_2$ and $Ce(NO_3)_2$) was subjected to reduction in an $H_2/Ar$ atmosphere to prepare $Ni-CeO_2/{\gamma}-Al_2O_3$ catalyst. The characteristics of the catalysts were examined using X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectrometry (EDS), temperature programmed reduction ($H_2-TPR$), temperature programmed desorption ($H_2-TPD$, $CO_2-TPD$), temperature programmed oxidation (TPO), and Raman spectroscopy. The investigation revealed that the plasma-reduced $Ni-CeO_2/{\gamma}-Al_2O_3$ catalyst exhibited superior catalytic activity for the production of syngas, compared to the thermally reduced catalyst. Besides, the plasma-reduced $Ni-CeO_2/{\gamma}-Al_2O_3$ catalyst was found to show long-term catalytic stability with respect to coke resistance that is main concern regarding the DRP process.

• Clean Technology
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• v.29 no.2
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• pp.126-134
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• 2023

Direct catalytic decomposition is a promising method for controlling the emission of nitrous oxide (N₂O) from the semiconductor and display industries. In this study, a γ-Al₂O₃ catalyst was developed to reduce N₂O emissions by a catalytic decomposition reaction. The γ-Al₂O₃ catalyst was prepared by an extrusion method using boehmite powder, and a N₂O decomposition test was performed using a catalyst reactor that was approximately 25.4 mm (1 in) in diameter packed with approximately 5 mm of catalysts. The N₂O decomposition tests were carried out with approximately 1% N₂O at 550 to 750 ℃, an ambient pressure, and a GHSV=1800-2000 h^-1. To confirm the N₂O decomposition properties and the effect of O₂ and steam on the N₂O decomposition, nitrogen, air, and air and steam were used as atmospheric gases. The catalytic decomposition tests showed that the 1% N₂O had almost completely disappeared at 700 ℃ in an N₂ atmosphere. However, air and steam decreased the conversion rate drastically. The long term stability test carried out under an N₂ atmosphere at 700 ℃ for 350 h showed that the N₂O conversion rate remained very stable, confirming no catalytic activity changes. From the results of the N₂O decomposition tests and long-term stability test, it is expected that the prepared γ-Al₂O₃ catalyst can be used to reduce N₂O emissions from several industries including the semiconductor, display, and nitric acid manufacturing industry.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.3
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• pp.187-199
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• 2013

Umbrella arch method (UAM) used for improving the stability of the tunnel ground condition has been widely applied in the tunnel construction projects due to the advantage of obtaining both reinforcement and waterproof. The purpose of this study is to develop the evaluation technique of the integrity of bore-hole in UAM by using a non-destructive test and to evaluate the possibility of being applied to the field. In order to investigate the variations of frequency depending on grouted length, the specimens with different grouted ratios are made in the two constraint conditions (free boundary condition and embedded condition). The hammer impact reflection method in which excitation and reception occur simultaneously at the head of pipe was used. The guided waves generated by hitting a pipe with a hammer were reflected at the tip and returned to the head, and the signals were received by an acoustic emission (AE) sensor installed at the head. For the laboratory experiments, the specimens were prepared with different grouted ratios (25 %, 50 %, 75 %, 100 %). In addition, field tests were performed for the application of the evaluation technique. Fast Fourier transform and wavelet transform were applied to analyze the measured waves. The experimental studies show that grouted ratio has little effects on the velocities of guided waves. Main frequencies of reflected waves tend to decrease with an increase in the grouted length in the time-frequency domain. This study suggests that the non-destructive tests using guided ultrasonic waves be effective to evaluate the bore-hole integrity of the UAM in the field.