• Journal of the Korean Electrochemical Society
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• v.6 no.1
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• pp.28-35
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• 2003

A numerical analysis of electrochemical reaction and dynamics of the fluid flow in the channels of a DMFC separator was carried out by using a commercial Computational Fluid Dynamics(CFD) code fluent(ver.6.0). From the simulation work, many valuable informations were obtained in terms of distributions of velocity, pressure, temperature, concentration and current density over the flow field. And it was possible to optimize the flow field structure by using the simulation results. The simulation work using the Cm code was found very helpful in analysing the phenomena occurring in the fuel cell and optimizing the structures of electrodes and flow field.

• Journal of Sensor Science and Technology
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• v.8 no.2
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• pp.202-209
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• 1999

Microstrip line was fabricated on the oxidized porous silicon layer which has nearly electrically and chemically identical properties with thermally oxidized silicon layer. Thick oxidized porous silicon layer of few tenth of micrometers was prepared by thermal oxidation of porous silicon layer on silicon substrate. Multi-step thermal oxidation process was used to obtain high Quality and thick oxidized silicon layer and to release thermal stress. Microstrip line was fabricated on the oxidized porous silicon layer. Its microwave characteristics were measured and the availability for MMIC substrate was investigated.

• Transactions of the Korean hydrogen and new energy society
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• v.13 no.2
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• pp.135-142
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• 2002

본 연구는 Chemical hydride 형태의 수소발생제를 포함한 액체연료를 이용한 신개념의 알칼라인 연료전지의 특성을 분석하였다. Chemical hydride는 연료전지의 수소공급원으로써 사용될 수 있으며, 본 연구팀은 KOH 전해질에 수소발생제인 Sodium Borohydride ($NaBH_4$)를 첨가하여 제조된 액체연료를 알칼라인 연료전지에 공급함으서 상온에서 매운 우수한 전기 화학적 성능결과를 얻을 수 있었다. 이때 음극 찰물질로 $ZrCr_{0.8}Ni_{1.2}$ 수소저장합금이 사용되었으며, 양극은 방수처리된 카본지 위에 분산된 Pt/C 가 사용되었고, air가 latm으로 양극에 공급되었다. 음극에 대한 XRD 분석결과 음극에서의 산화에 의해 Sodium Borohydride ($NaBH_4$)가 분해되어 수소가 발생되며, 연속적으로 액체연료가 주입되어도 전지가 작동하는 것을 확인할 수 있었다. 이때 에너지밀도는 6,000 Ah/kg (for $NaBH_4$ or $KBH_4$)이다.

• Korean Journal of Materials Research
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• v.5 no.6
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• pp.706-714
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• 1995

Silicon oxide thin films were deposited by remote plasma chemical vapor deposition (RPCYD). The effect of the operating variables, such as plasma power, deposition temperature and partial pressure of reactant on the material Properties of the silicon oxide film was investigated. By XPS, it was found out that the film was suboxide (O/Si<2) and small amount of nitrogen due to the plasma excitation was accumulated at the Si/SiO$_2$interface. The amount of dangling bonds at the Si/SiO$_2$interfaces were measured by ESR and the concentration of hydrogen bond was obtained by SIMS and FT-IR. The bond angle distribution(d$\theta$/$\theta$) was shown to be similiar to thermal oxide above 20$0^{\circ}C$ but the etch rate was higher than that of the thermal oxides due to the structural difference and the stress between silicon substrate and silicon oxide film.

• Bulletin of the Korean Chemical Society
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• v.33 no.9
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• pp.2976-2980
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• 2012

Nitrile-forming eliminations from (E)-2,4-$(NO_2)_2C_6H_2CH=NOC_6H_4-2-X-4-NO_2$ (1a-e) promoted by $R_3N$ in MeCN have been studied kinetically. The reactions are second-order and exhibit Br$\ddot{o}$nsted ${\beta}$ = 0.83-1.0 and ${\mid}{\beta}_{lg}{\mid}$ = 0.41-0.46. The results have been interpreted in terms of highly E1cb-like transition state with extensive $C_{\beta}$-H bond cleavage and limited $N_{\alpha}$-OAr bond cleavage. Comparison with existing data reveals that the structure of the transition state changes from E2-central to highly E1cb-like either by the change of the ${\beta}$-aryl group from Ph to 2,4-dinitrophenyl under the same condition or by the base-solvent system variation from $EtO^-$-EtOH to $Et_3N$-MeCN for a given substrate (1a-e).

• Bulletin of the Korean Chemical Society
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• v.23 no.2
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• pp.295-300
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• 2002

The construction of the T-shaped post-column flow cell has been changed to enhance the practicability as a UV-visible absorbance detector for capillary electrophoresis. In this new design, a rectangular cube-shaped inner structure is employed, which completely fits the outer rectangular tubing. This arrangement has greatly facilitated the fabrication of the T-cells. In addition, the volume for the auxiliary flow has been dramatically reduced down to 300 ${\mu}L$, and its volume flow rate is optimized at 4.2 ${\mu}L$/min. The short optical path length in the sheath flows (500 ${\mu}m$ on each side) minimizes background absorption, and thus enhances its performance in low-UV wavelengths. We have optimized the auxiliary flow rate at 50 ${\mu}m$/s, so that migration times are insensitive to the flow rate. This optimization has improved repeatabilities in migration times and peak heights. A double-beam detection scheme using a pair of photodiodes is employed to increase the signal-to-noise ratio.

• Applied Chemistry for Engineering
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• v.9 no.2
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• pp.261-267
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• 1998

We have investigated the stability of macroemulsions of AOT prepared from Winsor systems. The emulsion system was prepared from heptane+aqueous NaCl+AOT. As the concentration of NaCl increases, the stability of the emulsion increases, reaches a maximum, and then decreases. At low salt concentration the creaming occurred due to density difference of oil and aqueous phases. We developed a model for the creaming. Behavior of the emulsions containing low salt could be described very well by the model, however, at high salt concentration the electrostatic repulsion decreased due to screening and droplets started to attract each other and the stability of the emulsion decreased.

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.929-932
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• 2014

We explored interfacial electronic structures in indium tin oxide (ITO)/DNTPD/N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (NPB) layer stack in an OLED to clarify the real role of an aromatic amine-based hole injection layer, DNTPD. A hole injection barrier at the ITO/DNTPD interface is lowered by 0.20 eV but a new hole barrier of 0.36 eV at the DNTPD/NPB is created. The new barrier at the DNTPD/NPB interface and its higher bulk resistance serve as hole retardation, and thus those cause the operation voltage for the ITO/DNTPD/NPB to increase. However, it improves current efficiency through balancing holes and electrons in the emitting layer.

• Korean Chemical Engineering Research
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• v.47 no.3
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• pp.287-291
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• 2009

The heterogeneous decomposition of ammonia on a quartz surface in an inverted, stagnation-point flow reactor was investigated using a measurement reactor and a numerical model of the reactor. In the experiments, 8 mole% of ammonia in nitrogen was used and the temperature of an electric heater was set in the range $300{\sim}900^{\circ}C$ to heat the quartz surface where the decomposition took place. Gas temperatures and ammonia concentrations in the reactor obtained using in situ Raman spectroscopy were analyzed with the numerical model and it was revealed that, depending on the heater temperature, the temperature of the quartz surface was estimated to be in the range $235{\sim}619^{\circ}C$ and the activation energy of the decomposition on the surface was in the range 10.9~15.8 kcal/mol.

• Applied Chemistry for Engineering
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• v.8 no.2
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• pp.246-251
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• 1997

The phase behavior of sucrose monopalmitate/alkanol/water ternary system was investigated. According to compositions of three components ranging from micellar(or inverse micellar) solution up to various lyotropic liquid crystalline(LC) phase, each texture of the separated phases was identified by crossed polarizers equipped with a camera whose stage was connected to a thermostatic circulator. As the carbon atom number in alkanol of the polar oily substance increases, patterns of the various LC phases were also observed hexanol