• Proceedings of the KIEE Conference
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• 2007.11a
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• pp.192-193
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• 2007

A hollow cathode which has extremely stable discharge characteristic has been developed. This is composed of the two separated lanthanum hexaboride ($LaB_6$) of a disk type in the tube as the electron emitters. The way of design is of great advantage to extend the surface discharge area of the $LaB_6$, which is also useful for optimal fixing of the $LaB_6$. The hollow cathode is capable of producing 30 kW (100 V, 300 A) of power continuously.

• Journal of the Korean Vacuum Society
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• v.12 no.1
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• pp.64-69
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• 2003

Using a high fewer electron beam gun (max. power 20 kW), Gadolinium (Gd, atomic number 64) metal was melted and the temperature distribution of melted surface was measured. With proper optical filters and the adjustment of aperture of lens, the radiation of melted surface was received by a ccd camera and its signal transferred to a computer. The real time monitoring of melted surface with a variation of electron beam Power was Possible and stable operation of electron beam was achieved. It was found that the max. temperature measured by a ccd camera with an assumption of blackbody radiation of melted Gd surface and adaption of Planet's law was above 100~$200^{\circ}C$ compared to that measured by a pyrometer in the same e-beam power.

• Macromolecular Research
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• v.15 no.6
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• pp.533-540
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• 2007

We designed and successfully synthesized UV curable, functional acrylate monomers having a polarizing group, i.e., an electron-withdrawing and/or electron-donating group for the optical materials of high refractive index. Optical polymer films made from the functional methacrylate monomers were achieved with photo crosslinking under UV illumination. A monomer having amino and cyano groups (Dimer-CN) exhibited the highest refractive index ($n_{TE}$=1.595 at 850nm) among the studied methacrylate derivatives, due to the large polarizability of the dipolar monomer structures with electron-donating and withdrawing groups. By controlling the compositions of the functional acrylate monomer of copolymers, the refractive indices of the polymers were readily adjusted within a wide range of 1.498-1.595. The copolymers showed a high glass transition temperature $(T_g)$ and good thermal stability, which are desirable for optical applications. $T_g$ and $T_{10%}$ (10%-weight loss occurred) of the copolymers ranged from $120-140^{\circ}C$ and from $329-387^{\circ}C$, respectively.

• Journal of the Korean Electrochemical Society
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• v.10 no.3
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• pp.229-232
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• 2007

An amperometric immunosensor for the determination of rabbit IgG is proposed. The immunoassay utilizes a screen-printed carbon electrode on which osmium redox polymer is electrodeposited. This immunoassay detects 0.1 ng/ml of rabbit IgG, which is ${\sim}10^2$ fold higher than the most sensitive enzyme amplified amperometric immunoassay. The assay utilizes a screen-printed carbon electrode which was pre-coated by a co-electrodeposited film of an electron conducting redox hydrogel and a rabbit IgG. The rabbit IgG in the electron conducting film conjugates captures, when present, the anti-rabbit IgG. The captured anti-rabbit-IgG is labeled with horseradish peroxidase (HRP) which catalyzes the two-electron reduction of $H_2O_2$ to water. Because the redox hydrogel electrically connects HRP reaction centers to the electrode, completion of the sandwich converts the film from non-electrocatalytic to electro-catalytic for the reduction of $H_2O_2$ to $H_2O$ when the electrode is poised at 200 mV vs. Ag/AgCl.

• BMB Reports
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• v.29 no.1
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• pp.58-62
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• 1996

The structural changes in the electron donor side of the PSII reaction center have been monitored since heat treatment ($45^{\circ}C$ for 5 min) of thylakoids is known to decrease the oxygen evolving activity. In heat-treated spinach chloroplast thylakoids, the inhibitory effect of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) on the electron transport activity of the PSII reaction center from diphenyl carbazide to dichlorophenolindophenol became reduced approximately 3.8 times and [$^{14}C$]-labeled DCMU binding on the D1 polypeptide decreased to 25~30% that of intact thylakoid membranes, implying that the conformational changes of the DCMU binding pocket, residing on the D1 polypeptide, occur by heat treatment. The accessibility of trypsin to the $NH_2$-terminus of the cytochrome b-559 ${\alpha}$-subunit, assayed with Western blot using an antibody generated against the synthetic peptide (Arg-68 to Arg-80) of the COOH-terminal domain, was also increased, indicating that heat-treatment caused changes in the structural environments near the stromal side of the cytochrome b-559 ${\alpha}$-subunit, allowing trypsin more easily to cleave the $NH_2$-terminal domain. Therefore, the structural changes in the electron donor side of the PSII reaction center complexes could be one of the reasons why the oxygen evolving activity of the heat-treated thylakoid membranes decreased.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.74-74
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• 1999

TEM(투과전자현미경, Transmission Electron Microscop)은 결정재료뿐 아니라 비정질 재료까지도 원자단위의 구조를 연구하는데 매우 유용한 도구이다. 특히 200kV의 가속전압 투과전자현미경에 FEG(Field Emission Gun) 전자총이 장착되기 시작하면서 TEM은 비정질 구조 연구에 하나의 핵심적인 도구로서의 역할이 크게 기대되는 장비가 되었다. 본 연구에서는 TEM의 microanalysis accessary인 EELS(Electron Energy Loss Spectroscopy)technique을 주로 이용하던 기존의 방법대신 고 분해능(HRTEM(High Resolution Transmission Electron Microscopy)의 image로부터 비정질 정량묘사의 유일한 도구인 원자분포함수(RDF(Radial Distribution Function))로의 Reconstruction을 Simulation을 이용하여 시도하였다. 비정질 HRTEM image의 정량분석을 통하여 이 분야에서의 TEM의 한계를 이해하기 위하여 몇 모델을 제시하고 사용하였다. 또한 비정질 구조를 정량적으로 묘사하는 도구인 원자분포함수를 알아보고 비정질재료를 보다 물리적으로 모델링하기 위하여 가능한 모델 제시 후 첫 단계로서 HRTEM image에서 원자분포함수를 이끌어내기 위한 모델링을 수행하고 비정질 게르마늄(a-Ge) film에 대하여 실제로 적용하여 보았다. 마지막으로 실험적인 접근으로 200kV FE-TEm (poingt resolution 0.14nm) 으로 비정질 Ge의 image를 solw Scan CCD를 이용한 Elastic image를 Through Focus로 얻었으며 수치적인 정량비교를 역격자 공간에서 출발한 가장 물리적인 구조 모델을 이용하여 수행하였다. 모든 정량비교는 image의 Fourier 변환인 Diffractogram으로 하였다. 결론적으로, 많은 복잡한 수치 처리과정을 거쳐야 하지만 HRTEM의 image로부터 구조에 대한 정보(RDF)는 명확하게 얻을 수 있었다.

• Journal of the Korean Vacuum Society
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• v.12 no.4
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• pp.228-234
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• 2003

The velocity of gadolinium(Gd) atomic vapor vaporized by an electron beam was measured by a microbalance. The velocity of about 900 ㎧ was obtained at an evaporation surface temperature of 2400-2500 K. The measured value was approximately 100 ㎧ faster than the maximum velocity of an ideal monatomic gas in an adiabatic expansion. This phenomenon can be explained that the internal energy of Gd atoms populated in higher excited levels at the high temperature should be convened to kinetic energy during adiabatic expansion. The calculated velocity agrees with the measured one when 100 excited energy levels are included in an enthalpy term for the velocity calculation. The characteristics of vapor flow as a function of heated surface temperature are also reported.

• Proceedings of the Botanical Society of Korea Conference
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• 1999.08a
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• pp.83-90
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• 1999

Electron crystallography of two-dimensional crystalsand electron cryo-microscopy is becoming an established method for determining the structure and function of a variety of membrane proteins that are providing difficult to crystallize in three dimension. In this study this technique has been used to investigate the structure of a ~160 kDa reaction centre sub-core complex of photosystem II. Photosystem II is a photosynthetic membrane protein consisting of more than 25 subunits. It uses solar energy to split water releasing molecular oxygen into the atmosphere and creates electrochemical potential across the thylakoid membrane, which is eventually utilized to generate ATP and NADPH. Images were taken using Philips CM200 field emission gun electron microscope with an acceleration voltage of 200kW at liquid nitrogen temperature. In total, 79 images recorded dat tilt angles ranging from 0 to 67 degree yielded amplitudes and phases for a three-dimensional map with an in-plant resolution of 6$\AA$ and 11.4$\AA$ in the third dimension shows at least 23 transmembrane helices resolved in a monomeric complex, of which 18 were able to be assigned to the D1, D2, CP47 , and cytochrome b559 alfa beta-subunits with their associated pigments that ae active in electron transport (Rhee, 1998, Ph.D.thesis). The D1/D2 heterodimer is located in the central position within the complex and its helical scalffold is remarkably similar to that of the reaction centres not only in purple bacteria but also in plant photosystem I (PSI) , indicating a common evoluationary origin of all types of reaction centre in photosynthetic organism known today 9RHee et al. 1998). The structural homology is now extended to the inner antenna subunit, ascribed to CP47 in our map, where the 6 transmembrane helices show a striking structural similarity to the corresponding helices of the PSI reaction centre proteins. The overall arrangement of the chlorophylls in the D1 /D2 heterodimer, and in particular the distance between the central pair, is ocnsistent with the weak exciton coupling of P680 that distinguishes this reaction centre from bacterial counterpart. The map in most progress towards high resolution structure will be presented and discussed.

• Journal of the Mineralogical Society of Korea
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• v.22 no.4
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• pp.407-415
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• 2009

The change of the nitrogen-related centers and the color change of electron beam irradiated type Ia natural diamonds were studied. The irradiation of diamond with high-energy electron beam creates lattice defects which are neutral single vacancy $V^0$. It increased with increasing electron dose density. The B aggregation seems to produce vacancies more easily than the A aggregation, because diamonds with more B aggregation have more platelets, which are sufficient breakable size by electron beam. Greenish blue color of irradiated diamond is changed to darker with increasing electron dose density. GR1 centers with a zero-phonon line at 741 nm and phonon sidebands make transmit visible light at 530 nm and it moves to 500 nm with higher intensity of GR1 centers.

• Applied Chemistry for Engineering
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• v.25 no.5
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• pp.463-467
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• 2014

In this paper, the thermal behaviors of expanded graphite(EG)/erythritol composites with different contents of EG were studied. The surface and structure properties of the composites were determined by using scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD), respectively. The thermal properties were investigated by differential scanning calorimetry (DSC) and thermal conductivity (TC). As experimental results, the thermal conductivity of the composites increased with increasing the EG content. However, the latent heat was somewhat decreased in the presence of EG. We could concluded that EG was highly promising materials for improving the heat transfer enhancement and energy storage capacity of phase change materials (PCMs).