• Electrical & Electronic Materials
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• v.10 no.2
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• pp.134-140
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• 1997

PbTiO$_{3}$-PbZrO$_{3}$-Pb(Ni$_{1}$3/Nb $_{2}$3/O$_{3}$)(PZT-PNN) thin films were prepared from corresponding metal organics partially stabilized with diethanolamine by the sol-gel spin coating method. Each mol rates of PT:PZ:PNN solutions were #1(50:40:10), #2(50:30:20), #3(45:35:20) and #4(40:40:20), respectively. The spin-coated PZT-PNN films were sintered at the temperature from 500.deg. C to 600.deg. C for crystallization. The P-E hysteresis curve was drawn by Sawyer-Tower circuit with PZT-PNN film. The coercive field and the remanent polarization of #4(40:40:20 mol%) PZT-PNN film were 28.8 kV/cm and 18.3 .mu.C/cm$^{2}$, respectively. Their dielectric constants were shown between 128 and 1120, and became maximum value in MPB(40:40:20 mol%). The leakage currents of PZT-PNN films were about 9.4x 10$^{-8}$ A/cm$^{2}$, and the breakdown voltages were about 0.14 and 1.1 MV/cm. The Curie point of #3(45:35:20 mol%, sintered at 600.deg. C) film was 330.deg. C.

• Journal of the Korean Ceramic Society
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• v.39 no.1
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• pp.92-98
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• 2002

To investigate the electrode structural effect on the ferroelectric electron emission, the electric field distribution in a 2-dimensional structure was calculated as a function of upper electrode diameter, and the switching charge density and emission charge were measured simultaneously. The simulation of the electric field distribution showed that an asymmetric electrode structure could cause a stray field on the bare surface of the ferroelectric cathode near the edge of upper electrode. The distance of stray field from the electrode edge increased with increasing ferroelectric thickness, but it did not depend on the upper electrode diameter. The switching charge density increased more on the cathode with smaller upper electrode diameter. This was attributed to the stray field on the bare ferroelectric surface near the electrode edge, because the stray field for the asymmetric ferroelectric cathode enhanced polarization switching near the electrode edge. From the switching charge density, the distance of stray field from the electrode edge was calculated as about 11-14${\mu}{\textrm}{m}$. The threshold voltage of electron emission was 61-68 kV/cm, which was almost 3 times lager than the coercive voltage. The threshold voltage was not determined just by coercive voltage, but by strength and distance of the stray-field, which largely depended on the geometrical structure of ferroelectric cathode.

• Journal of the Korea Organic Resources Recycling Association
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• v.18 no.1
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• pp.57-65
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• 2010

Two types of microbial fuel cells(MFC) were continuously operated using synthetic wastewater. One was conventional two-chambered MFC using proton exchange membrane(PEM-MFC), the other was upflow type membraneless MFC(ML-MFC). Graphite felt was used as a anode in PEM-MFC. In membraneless MFC, two MFCs were operated using porous RVC(reticulated vitreous carbon) as a anode. Graphite felt was used as a cathode in all experiments. In experiment of PEM-MFC, the COD removal rate based on the surface area of anode was about $3.0g/m^2{\cdot}d$ regardless of organic loading rate. And the coulombic efficiency amounted to 22.4~23.4%. The acetic acid used as a fuel was transferred through PEM from the anodic chamber to cathodic chamber. The COD removal rate in ML-MFC were $9.3{\sim}10.1g/m^2{\cdot}d$, which indicated the characteristics of anode had no significant effects on COD removal. Coulombic efficiency were 3.6~3.7 % in both cases of ML-MFC experiments, which were relatively small. It was also observed that the microbial growth in cathodic chamber had an adverse effects on the electricity generation in membraneless MFC.

• Journal of the Korean Electrochemical Society
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• v.10 no.1
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• pp.7-13
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• 2007

We synthesized and investigated $La_{0.75}Sr_{0.25}FeO_3$ by Glycine Nitrate Process(GNP) method used as cathode materials for SOFC(solid oxide fuel cell). Optimized amount of glycine is 3.17 mol. ICP elemental composition analysis indicated that the stoichiometry of the synthesized powders have nearly nominal values. SEM images and XRD patterns reveal that the synthesized powder has uniform size distribution and high degree of crystallinity. The sample powders were isostatically pressed to form a pellet. The green body was sintered at $1200^{\circ}C$ and the relative density of the sintered specimens were measured by Archimedes mettled. We measured electrochemical performance of LSF by AC impedance spectroscopy. Resistance of LSF shows lower value than that of LSM throughout all temperature region. The anode-supported solid oxide fuel cell showed a performance of $342mW/cm^2(0.7V,\;488mA/cm^2)$ at $750^{\circ}C$. The electrochemical characteristics of the single cell were examined by at impedance method.

• The Journal of Engineering Geology
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• v.12 no.4
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• pp.405-419
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• 2002

Fracture roughness of rock specimens is observed by a new confocal laser scanning microscope (CLSM; Olympus OLS1100). The wave length of laser is 488 nm, and the laser scanning is managed by a light polarization method using two galvano-meter scanner mirrors. The function of laser reflection auto-focusing enables us to measure line data fast and precisely. The system improves resolution in the light axis (namely z) direction because of the confocal optics. Using the CLSM, it is Possible to measure a specimen of the size up to $10{\;}{\times}{\;}10{\;}cm$ which is fixed on a specially designed stage. A sampling is managed in a spacing $2.5{\;}\mu\textrm{m}$ along x and y directions. The highest measurement resolution of z direction is $10{\;}\mu\textrm{m}$, which is more accurate than other methods. Core specimens of coarse and fine grained granite are provided. Fractures are artificially maneuvered by a Brazilian test method. Measurements are performed along three scan lines on each fracture surface. The measured data are represented as 2-D and 3-D digital images showing detailed features of roughness. Line profiles of the coarse granites represent more frequent change of undulation than those of the fine granite. Spectral analyses by the fast Fourier transform (FFT) are performed to characterize the roughness data quantitatively and to identify influential frequency of roughness. The FFT results suggest that a specimen loaded by large and low frequency energy tends to have high values of undulation change and large wave length of fracture roughness.

• BMB Reports
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• v.47 no.2
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• pp.115-120
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• 2014

In this study, we show that Mycobacterium avium subsp. paratuberculosis MAP1305 induces the maturation of bone marrow-derived dendritic cells (BMDCs), a representative antigen presenting cell (APC). MAP1305 protein induces DC maturation and the production of pro-inflammatory cytokines (Interleukin (IL)-6), tumor necrosis factor (TNF)-${\alpha}$, and IL-$1{\beta}$) through Toll like receptor-4 (TLR-4) signaling by directly binding with TLR4. MAP1305 activates the phosphorylation of MAPKs, such as ERK, p38MAPK, and JNK, which is essential for DC maturation. Furthermore, MAP1305-treated DCs transform naive T cells to polarized $CD4^+$ and $CD8^+$ T cells, thus indicating a key role for this protein in the Th1 polarization of the resulting immune response. Taken together, M. avium subsp. paratuberculosis MAP1305 is important for the regulation of innate immune response through DC-mediated proliferation of $CD4^+$ and $CD8^+$ T cells.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.04a
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• pp.191-194
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• 2000

In this study, we have investigated the photoinduced birefringence(PB), ${\Delta}n$ in chalcogenide $As_{40}Ge_{10}Se_{15}S_{35}$ thin film with a He-Ne Laser at 633nm as In this study, we have investigated the photoinduced birefringence(PB), ${\Delta}n$ in chalcogenide $As_{40}Ge_{10}Se_{15}S_{35}$ thin film with a He-Ne Laser at 633nm as a pumping beam and a semiconductor laser at 780nm as a probing beam. The PB for the variable thickness of thin films was investigated. The thickness of the thin films is about $0.4{\mu}m$, $0.92{\mu}m$, $1.4{\mu}m$, $2.0{\mu}m$, respectively. The experimental result of PB in chalcogenide thin films was represented higher PB in the thickness of thin film, $0.92{\mu}m$. It was meant to represent higher PB in the thickness of the film that was made closely the optimal thickness, $0.96{\mu}m$. The optimal thickness of thin film, $0.96{\mu}m$ was calculated by the penetration depth of the pumping light Also, the PB in thickness of $0.92{\mu}m$ was obtained almost two times higher 0.15 than other thickness of thin films.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.313-316
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• 2002

비철금속 습식 제련용 고효율 장수명의 양극을 개발하기 위해서 산소 과전압이 낮은 $MnO_{2}$를 촉매로 사용하여 반도체 산화물계의 산소선택성 전극을 제조하고 산화물 coating층의 미세구조와 전기화학적 특성을 분석하였다. PVDF : $MnO_{2}$의 함량비플 1 : 1 에서 1 : 40까지 정량적으로 변화시켰고， 용제의 점도에 지배적인 영향을 미치는 DMF의 함량을 각각의 고정된 PVDF : $MnO_{2}$의 함량비에서 변화시켜 용제를 제조하였으며 4% $HNO_{3}$ 용액에 세척된 Pb전극을 1.5 mm/sec 의 속도로 5회 dipping 하였다. PVDF : $MnO_{2}$ = 1 : 6인 경우 PVDF의 양이 증가하고 DMF의 양이 감소할수록 피막층이 두꺼워지고 PVDF : DMF = 4 : 96인 경우 pb 전극의 피막층이 얇기 때문에 박리현상이 일어났으며 이는 산화물 용제의 낮은 점도 때문인 것으로 판단된다. 또한 PVDF : DMF = 10 : 90의 경우는 5회 dipping 하여 약 $150{\mu}m$의 피막층을 형성하였다. PVDF : Mn02의 함량비가 1:1에서 1:6 까지는 DMF의 함량에 무관하게 전극 특성이 나타나지 않았지만 $MnO_{2}$의 양이 상대적으로 증가하면 cycle 이 증가하더라도 거의 일정한 전류 값을 갖고$MnO_2$와 PVDF의 비가 20:1 이상의 조성에서는 균일한 CV 특성을 나타냈다 이는 $MnO_{2}$가 효과적으로 촉매 작용을 한 것으로 판단되며 anodic polarization에 의한 산소 발생 과전압도 약 1.4V 정도로 감소되었다.

• Journal of Electrochemical Science and Technology
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• v.12 no.2
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• pp.246-256
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• 2021

Mo,Cu-doped CeO₂ (CMCuO) nanopowders were synthesized by the nitrate-fuel combustion method aiming to improve the electrical and electrochemical properties of its Mo-doped CeO₂ (CMO) parent by the addition of copper. An electrical conductivity of ca. 1.22·10^-2 S cm^-1 was measured in air at 800℃ for CMCuO, which is nearly 10 times higher than that reported for CMO. This increase was associated with the inclusion of copper into the crystal lattice of ceria and the presence of Cu and Cu₂O as secondary phases in the CMCuO structure, which also could explain the increase in the charge transfer activities of the CMCuO based anode for the hydrogen and carbon monoxide electro-oxidation processes compared to the CMO based anode. A maximum power density of ca. 120 mW cm^-2 was measured using a CMCuO based anode in a solid oxide fuel cell (SOFC) with YSZ electrolyte and LSM-YSZ cathode operating at 800℃ with humidified syngas as fuel, which is comparable to the power output reported for other SOFCs with anodes containing copper. An increase in the area specific resistance of the SOFC was observed after ca. 10 hours of operation under cycling open circuit voltage and polarization conditions, which was attributed to the anode delamination caused by the reduction of the Cu₂O secondary phase contained in its microstructure. Therefore, the addition of a more electroactive phase for hydrogen oxidation is suggested to confer long-term stability to the CMCuO based anode.

• Restorative Dentistry and Endodontics
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• v.22 no.1
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• pp.1-33
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• 1997

The objective of this study was to analyze the in vitro and in vivo corrosion products of low and high copper amalgams. The four different types of amalgam alloy used in this study were Fine cut, Caulk spherical, Dispersalloy, and Tytin. After each amalgam alloy and Hg were triturated according to the directions of the manufacturer by means of the mechanical amalgamator(Amalgam mixer. Shinhung Co. Korea), the triturated mass was inserted into a cylindrical metal mold which was 12mm in diameter and 10mm in height. The mass was condensed by 150Kg/cm compressive force. The specimen was removed from the mold and aged at room temperature for about seven days. The standard surface preparation was routinely carried out by emery paper polishing under running water. In vitro amalgam specimens were potentiostatically polarized ten times in a normal saline solution at $37^{\circ}C$(potentiostat : HA-301. Hukuto Denko Corp. Japan). Each specimen was subjected to anodic polarization scan within the potential range -1700mV to+400mV(SCE). After corrosion tests, anodic polarization curves and corrosion potentials were obtained. The amount of component elements dissolved from amalgams into solution was measured three times by ICP AES(Inductive Coupled Plasma Atomic Emission Spectrometry: Plasma 40. Perkim Elmer Co. U.S.A.). The four different types of amalgam were filled in occlusal and buccal class I cavities of four human 3rd molars. After about five years the restorations were carefully removed after tooth extraction to preserve the structural details including the deteriorated margins. The occlusal surface, amalgam-tooth interface and the fractured surface of in vivo amalgam corrosion products were analyzed. In vivo and in vitro amalgam specimens were examined and analyzed metallographically by SEM(Scanning Electron Microscope: JSM 840. Jeol Co. Japan) and EDAX(Energy Dispersive Micro X-ray Analyser: JSM 840. Jeol Co. Japan). 1. The following results are obtained from in vitro corrosion tests. 1) Corrosion potentials of all amalgams became more noble after ten times passing through the in vitro corrosion test compared to first time. 2) After times through the test, released Cu concentration in saline solution was almost equal but highest in Fine cut. Ag and Hg ion concentration was highest in Caulk spherical and Sn was highest in Dispersalloy. 3) Analyses of surface corrosion products in vitro reveal the following results. a)The corroded surface of Caulk spherical has Na-Sn-Cl containing clusters of $5{\mu}m$ needle-like crystals and oval shapes of Sn-Cl phase, polyhedral Sn oxide phase. b)In Fine cut, there appeared to be a large Sn containing phase, surrounded by many Cu-Sn phases of $1{\mu}m$ granular shapes. c)Dispersalloy was covered by a thick reticular layer which contained Zn-Cl phase. d)In Tytin, a very thin, corroded layer had formed with irregularly growing Sn-Cl phases that looked like a stack of plates. 2. The following results are obtained by an analysis of in vivo amalgam corrosion products. 1) Occlusal surfaces of all amalgams were covered by thick amorphous layers containing Ca-P elements which were abraded by occlusal force. 2) In tooth-amalgam interface, Ca-P containing products were examined in all amalgams but were most clearly seen in low copper amalgams. 3) Sn oxide appeared as a polyhedral shape in internal space in Caulk spherical and Fine cut. 4) Apical pyramidal shaped Sn oxide and curved plate-like Sn-Cl phases resulted in Dispersalloy. 5) In Tytin, Sn oxide and Sn hydroxide were not seen but polyhedral Ag-Hg phase crystal appeared in internal space which assumed a ${\beta}_l$ phase.