• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.63-64
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• 2006

In this paper, multilayer piezoelectric actuator was fabricated in order to develop ultrasonic linear motor. Multilayer actuator showed a high density of 7.78[$g/cm^3$], a large effective electromechanical coupling factor($K_{eff}$) of 0.259, a high mechanical quality factor( Qm ') of 1301, and high capacitance(c) of 19.32[nF]. Curie temperature was $343[^{\circ}C]$.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.418.1-418.1
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• 2016

Atomic layer deposition (ALD)를 이용하여 증착된 aluminum oxide ($Al_2O_3$)는 우수한 패시베이션 특성을 가지고 있다. $Al_2O_3$ 박막은 많은 수소를 가지고 있기 때문에 화학적 패시베이션에 의한 실리콘 표면을 패시베이션 할 수 있다. 또한 $Al_2O_3$는 강한 고정전하를 가져 전계 효과 패시베이션을 할 수 있다. 따라서 $Al_2O_3$ 박막을 태양전지에 적용할 경우 높은 효율을 기대할 수 있다. 실리콘 태양전지를 제작하기 위해 소성공정(> $800^{\circ}C$)은 필수이다. $Al_2O_3$ 박막은 많은 수소를 가지고 있기 때문에 소성공정시 수소가스를 방출하여 $Al_2O_3$ 박막에 블리스터를 형성시킨다. 이 블리스터는 $Al_2O_3/Si$ 계면에서 발생하여 패시베이션 특성을 감소시킨다. 블리스터를 억제하기 위해 수소의 양을 조절할 필요가 있다. 이 실험에서는 plasma-assisted atomic layer deposition (PAALD)으로 $Al_2O_3$를 증착하였다. PAALD의 RF power를 200 W부터 800 W까지 조절하여 $Al_2O_3$ 막에 포함되는 OH의 농도를 조절하였다. $Al_2O_3$ 박막에 포함되는 OH 농도는 X-ray Photoelectron Spectroscopy (XPS)를 이용하여 분석하였다. 열처리공정 후, 화학적 패시베이션에 의한 유효 반송자 수명 (${\tau}_{eff}$) 향상이 나타났다 소성공정 후 블리스터가 형성되지 않는 조건에서 화학적 패시베이션과 전계 효과 패시베이션에 의해 ${\tau}_{eff}$가 증가하였다. 블리스터가 형성되었을 때 기존 논문들과 같이 패시베이션 특성이 감소하였다. 패시베이션 특성의 감소는 블리스터에 의한 화학적 패시베이션의 감소 때문이며 전계 효과 패시베이션은 오히려 증가하였다. 이를 통해 고온에서 열안정성을 갖는 $Al_2O_3$ 박막을 만들었으며 블리스터가 형성되지 않았고 패시베이션 특성이 증가하였다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.11
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• pp.791-803
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• 2001

Mach-Zehnder type traveling-wave Ti：LiNb $O_3$ optical modulators were designed and fabricated. Optimum parameters of optical waveguides were calculated by means of the FDM. Design of CPW traveling-wave electrodes were performed by the FEM in the active region and by the CMM in the input/output section to obtain the conditions of MW effective index and impedance matching. From the measured S parameters, MW characteristics of the traveling-wane electrodes were extracted to be ${\alpha}_m$=0.05426 $\sqrt{f}$, $N_{eff}$=2.2025, and $Z_{c}$=39 ${\Omega}$. The calculated optical response R($\omega$) showed the 3 dB bandwidth of 10 GHz.z..

• Journal of Korean Society of Environmental Engineers
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• v.39 no.9
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• pp.505-512
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• 2017

The adsorption characteristics of Sr ion in aqueous solution was examined using zeolite NaA powder (Z-PA) and pellets (Z-BA). In batch experiment, the adsorption of Sr ions by Z-BA and Z-PA was well expressed by pseudo-second-order kinetic model than psedo-first-order kinetic model. Experimental isotherm results was well fitted to Langmuir isotherm model and the maximum adsorption capacities obtained from Langmuir isotherm model were 233.32 mg/g for Z-PA and 164.60 mg/g for Z-BA, respectively. The continuous experiment results showed that the total Sr ion uptake (q) increased, but the breakthrough time, effluent volume ($V_{eff}$) and total removal (R) of Sr ion decreased with the Sr ion concentration. The breakthrough curves obtained from the experiment was modeled by Thomas model.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.11
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• pp.50-58
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• 2000

A Mach-Zehnder type $Ti:LiNbO_3$ optical modulator with a grooved $SiO_2$ buffer layer, was evaluated in terms of an electrode structure. The finite element method was performed to find out the optinum design parameters of electrodes. characteristic impedance ($Z_o$), MW effective index ($N_{eff}$) and attenuation constant ($a_o$)of fabricated traveling-wave electrodes were measured and compared with those obtained by the simulation expectation. For an optical modulator with 11${\mu}m$thick electrodes and a grooved $SiO_2$ buffer layer, the 3dB bandwidth based on the RF measurement results turned out to be 18GHz.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.3
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• pp.39-45
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• 2016

In this paper, prcess modeling of germanium condensation has been performed and a germanium PMOSFET having nanowire channel implented by the condensation process has been designed and characterized by device simulations. Based on the previous experimental results, our modeling results demonstrate that the ratio of germanium concentration at the silicon germanium-silicon dioxide interface ($C_S$) to that in the bulk region ($C_B$) which are obtainable during the germanium condensation is approximately 4.03 and the effective diffusion coefficient ($D_{eff}$) of germanium atom is $3.16nm^2/s$. Furthermore, a germanium nanowire-channel PMOSFET having the ultra-thin germanium channel on the silicon core that can be fabricated by the germanium condensation has been designed and characterized. As the result, it is confirmed that the proposed device having the coaxial nanowire consisting of silicon core and germanium channel might have superior performances over the device with either all-silicon or all-germanium channel.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.77
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• pp.113-144
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• 2018

This study explores how to prevent the fraudulent export financing and its subsequent export insurance fraud in relation to O/A negotiation. Under the traditional letter of credit(L/C) transactions, the banks, as a negotiation bank, can extend trade financing to the exporters through negotiation of draft and/or shipping documents. Under the O/A transaction scheme, however, bank cannot ascertain existence of trade performance and it is much riskier to extend an advance financing to the exporters before the buyer sends confirmation of debt. In O/A negotiation. some exporters tried to fraud banks by falsifying the shipping documents and the size and gravity of this fraudulent export financing were huge. Therefore, this study examines the banking process in O/A-based trade financing, documents examination process, the negotiation of instruments, treatment of trade financing in export credit guarantee, most importantly, explores what could be the criteria for appropriate treatment of account receivable to insure the safe transfer of account receivable. To maximize the benefit for optimum trade financing, the Bank of Korea established several Trade Finance Rules (refers to "BOK Rules") requiring that commercial banks should maintain optimal credit limits(so called, 'the principle of optimal loan') to extend the trade finance. The K-sure post-shipment credit guarantee programs and short-term export insurance program(EFF)can also facilitate 'the principle of optimal loan' principle.

• Journal of the Korean Magnetics Society
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• v.6 no.4
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• pp.218-224
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• 1996

The magnetic properties and crystallization behaviors of $Fe_{83-x}Al_{x}Nb_{5}B_{12}(X=1~5at%)$ alloys were investigated. The $Fe_{80}Al_{3}Nb_{5}B_{12}$ alloy was developed a very good soft magnetic material with ultra-fine grain structure in Fe-Al-Nb-B system alloys. When 1 at% of Cu was added in Fe-Al-Nb-B alloy, the soft magnetic properties were found to improve significantly through the reduction of the grain size upto about 6~7 nm at $450^{\circ}C$. The magnetic properties of the $Fe_{79}Al_{3}Nb_{5}B_{12}Cu_{1}$ alloy were as follows : ${\mu}_{eff}(1\;kHz)=26,000,\;B_{10}=1.45\;T,\;H_{c}=25\;mOe,\;P_{c}(100\;kHz,\;0.2\;T)=55\;W/kg$, respectively.

• Journal of The Korean Astronomical Society
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• v.46 no.3
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• pp.103-123
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• 2013

Star clusters are superb astrophysical laboratories containing cospatial and coeval samples of stars with similar chemical composition. We initiate the Sejong Open cluster Survey (SOS) - a project dedicated to providing homogeneous photometry of a large number of open clusters in the SAAO Johnson-Cousins' UBV I system. To achieve our main goal, we pay much attention to the observation of standard stars in order to reproduce the SAAO standard system. Many of our targets are relatively small sparse clusters that escaped previous observations. As clusters are considered building blocks of the Galactic disk, their physical properties such as the initial mass function, the pattern of mass segregation, etc. give valuable information on the formation and evolution of the Galactic disk. The spatial distribution of young open clusters will be used to revise the local spiral arm structure of the Galaxy. In addition, the homogeneous data can also be used to test stellar evolutionary theory, especially concerning rare massive stars. In this paper we present the target selection criteria, the observational strategy for accurate photometry, and the adopted calibrations for data analysis such as color-color relations, zero-age main sequence relations, Sp - MV relations, Sp - $T_{eff}$ relations, Sp - color relations, and $T_{eff}$ - BC relations. Finally we provide some data analysis such as the determination of the reddening law, the membership selection criteria, and distance determination.

• Transactions on Electrical and Electronic Materials
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• v.16 no.1
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• pp.10-15
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• 2015

A thin-film transmission line (TFTL) employing a microstrip line/coplanar waveguide (ML/CPW) was fabricated on a silicon substrate for application to a miniaturized on-chip RF component, and the RF characteristics of the device with the proposed structure were investigated. The TFTL employing a ML/CPW composite structure exhibited a shorter wavelength than that of a conventional coplanar waveguide and that of a thin-film microstrip line. When the TFTL with the proposed structure was fabricated to have a length of ${\lambda}/8$, it showed a loss of less than 1.12 dB at up to 30 GHz. The improvement in the periodic capacitance of the TFTL caused for the propagation constant, ${\beta}$, and the effective permittivity, ${\varepsilon}_{eff}$, to have values higher than those of a device with only a conventional coplanar waveguide and a thin film microstrip line. The TFTL with the proposed structure showed a ${\beta}$ of 0.53~2.96 rad/mm and an ${\varepsilon}_{eff}$ of 22.3~25.3 when operating from 5 to 30 GHz. A highly miniaturized impedance transformer was fabricated on a silicon substrate using the proposed TFTL for application to a low-impedance transformation for broadband. The size of the impedance transformer was 0.01 mm2, which is only 1.04% of the size of a transformer fabricated using a conventional coplanar waveguide on a silicon substrate. The impedance transformer showed excellent RF performance for broadband.