• Transactions of the Korean hydrogen and new energy society
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• v.23 no.1
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• pp.8-18
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• 2012

This paper presents a three-dimensional, transient cold-start polymer electrolyte fuel cell (PEFC) model to numerically evaluate the effects of membrane electrode assembly (MEA) design and cell location in a PEFC stack on PEFC cold start behaviors. The cold-start simulations show that the end cell experiences significant heat loss to the sub-freezing ambient and thus finally cold-start failure due to considerable ice filling in the cathode catalyst layer. On the other hand, the middle cells in the stack successfully start from $-30^{\circ}C$ sub-freezing temperature due to rapid cell temperature rise owing to the efficient use of waste heat generated during the cold-start. In addition, the simulation results clearly indicate that the cathode catalyst layer (CL) composition and thickness have an substantial influence on PEFC cold-start behaviors while membrane thickness has limited effect mainly due to inefficient water absorption and transport capability at subzero temperatures.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.199-201
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• 2002

Cancer therapy using high-energy $^{12}$ C ions is successfully under way at HIMAC, Japan. An alternative beam to $^{12}$ C is $^{11}$ C ions. The merit of $^{11}$ C over $^{12}$ C is its capability for monitoring spatial distribution of the irradiated $^{11}$ C by observing the $\beta$$^{+}$ decay with a good position resolution. One of the several problems to be solved before its use for therapy is the amount of nuclear interaction that deteriorates the dose concentration owing to the Bragg curve. Utilizing the dedicated secondary beam course for R&D studies at HIMAC, we measured the total energy loss of $^{11}$ C ions in a scintillator block that simulates the soft tissue in human bodies. In addition to the total absorption $^{11}$ C peak, non-negligible bump-shaped contribution is observed in the energy spectrum. The origin of the bump contribution can be nuclear interaction of the incident $^{11}$ C ions with hydrogen and carbon atoms. Further studies to reduce the ambiguity in dose distribution are mentioned.

• Archives of Reconstructive Microsurgery
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• v.9 no.1
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• pp.44-48
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• 2000

The advent of free bone flaps has made successful replacement of extensive areas of bone loss in the upper and lower extremities. The microvascular free bone flaps have faster healing without bony absorption or atrophy and can heal in the hostile environment of scarred bed or infection. Since the fibula free flap introduced by Taylor and colleague in 1975, it has been used extensively for skeletal reconstruction of extremities. In 1988, the folded vascularized fibula free flap was first described as a technique to reconstruct significant long bone defect of upper and lower extremities. During the same time, the fibular free flap has evolved to become most preferred choice of mandibular reconstruction. Up to present day, few reports have been made on the fibular free flap used for reconstruction of injured hand containing metacarpal bone and soft tissue defect. We present here our new and unique experiences with vascularized fibular osteocutaneous free flap as useful and satisfactory one for reconstruction of hand with composite defects.

• Computers and Concrete
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• v.21 no.1
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• pp.87-94
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• 2018

This paper presents the results of an experimental study to investigate the influences of high temperatures on the mechanical properties of concrete containing recycled fine aggregate. A total of 150 concrete prisms ($100{\times}100{\times}300mm$) and 150 concrete cubes ($100{\times}100{\times}100mm$) are cast and heated under five different temperatures ($20^{\circ}C$, $200^{\circ}C$, $400^{\circ}C$, $600^{\circ}C$, $800^{\circ}C$) for test. The results show that the mass loss, compressive strength, elastic modulus, splitting tensile strength of concrete specimens containing recycled fine aggregate decline significantly as the temperature rise. At the same temperature, the compressive strength, splitting tensile strength, elastic modulus of concrete specimens containing recycled coarse aggregate and recycled fine aggregate (RHC) is lower than that of concrete specimens containing natural coarse aggregate and recycled fine aggregate (RFC). The shape of stress-strain curves of concrete specimens at different temperatures is different, and the shape of that become flatter as the temperature rises. Normal concrete has better energy absorption capacity than concrete containing recycled fine aggregate.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.619-624
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• 2000

Design of experiments based on Taguchi's orthogonal array is utilized for exploring the design space and for building response surface models of insulator and isolator database in order to facilitate the effective solution of multi-objective optimization commonly occurred in NVH problems. Response surface models, called engineering database of design space, provide an efficient means to rapidly model the trade-off among many conflicting NVH goals in automotive. In the design of insulator and isolator in automotive interior part, it is important not only to construct effective matrices of NVH but also to build up engineering database of current products. The experimental design especially based on orthogonal array and the nonlinear optimization algorithms are successfully used together to obtain the optimal design of insulator and isolator. The $2^{nd}$ order response surface models of absorption coefficient and insertion loss are constructed by using modified Taguchi's $L_{12}2^13^7$ orthogonal array and successfully used in optimal design of insulator and isolator.

• The Korean Journal of Ceramics
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• v.4 no.3
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• pp.260-267
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• 1998

A homogeneous and stoichimetric fine powder of the ferroelectric $Pb_[0.97}La_{0.02}(Zr_{0.64}Sn_{0.25}Ti_{0.11})O_3$ (PLZST) has been prepared by the hydroxide coprecipitation method. Studies on the crystallization behavior of precursor as a function of temperature by X-ray powder diffraction and transmission electron microscopy technique were consistent with the formation of the pyrochlore phase from amorphous, initially at low temperatures around 500~$550^{\circ}C$. Further heat treatment up to $750^{\circ}C$ resulted in development of the perovskite phase with no significant pyrochlore crystallite growth. At intermediate temperatures the precursor yields a fine mixture of pyrochlore and perovskite phases. When the pyrochlore phase was heat teated in air, slight weight increase was observed in the temperature range of 300~$700^{\circ}C$, which is thought to be caused from oxygen absorption. In argon atmosphere, weight increase was not observed. On the other hand, weight loss began to occur near $700^{\circ}C$, with giving off mostly CO2 gas. This implies that the pyrochlore phase seems to be crystallorgraphycally and thermodynamically metastable. An apparent activation energy of 53.9 ㎉/mol was estimated for the pyrochlore-perovskite phase transformation.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.673-675
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• 2015

This paper presents a design of a high speed 2-phase 6/5 switched reluctance motor (SRM) for an air-blower application. This type of motor is suitable for the applications that require high speed and only one directional rotation as air-blower. The desired air-blower is unidirectional application, and requires a wide positive torque region without torque dead-zone. In order to get a wide positive torque region without torque dead-zone during phase commutation, asymmetric inductance characteristic with non-uniform air-gap is considered. The proposed motor can be operated at any rotor position. The proposed 6/5 SRM uses short flux path technique that achieved by means of winding configuration and lamination geometry. The purpose of short flux path is to reduce the core loss and the absorption MMF in the stator. The proposed 2-phase 6/5 SRM is verified by finite element method (FEM) analysis and Matlab-Simulink. In order to verify the design, a prototype of the proposed motor was manufactured for practical system.

• BMB Reports
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• v.31 no.2
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• pp.144-148
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• 1998

A bifunctional catalase-peroxidase, designated catalase-2, of a UV resistant Deinococcus radiophilus was purified to electrophoretic homogeneity by both chromatographic and electrophoretic methods. Its molecular weight was 310 kDa and composed of a tetramer of 80 kDa subunits. The catalase-2 exerted its optimal activity at $30^{\circ}C$ and around pH 9. Its $K_m$ value for $H_{2}0_{2} $ was about 10 mM. It showed the typical ferric heme spectrum with maximum absorption at 403 nm which shifted to 419 nm in the presence of cyanide. The ratio of A40i' A2S0 was 0.48. Fifty percent inhibition of the enzyme activity was observed at $4.6{\times}10^{-6}$, $7.7{\times}10^{-6}$, and $3.0{\times}10^{-6}$ M of NaCN, $NaN_3$, and $NH_{2}OH$, respectively. The enzyme was thermostable and not sensitive to 3-amino-1,2,4-triazole. Treatment of the enzyme with ethanol-chloroform caused a partial loss (30%) of its activity. The catalase-2 was distinct from the Deinococcal bifunctional catalase-3 in a number of properties, particularly in its molecular structure and substrate affinity.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.04a
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• pp.760-765
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• 2013

Eco-friendly material applied to building would be one of the materials which is must developed for global environmental conservation and reduction of carbon dioxide. For development of eco-friendly material, a cellulose sound-absorbing material has been developed with waste paper through adjustment of various mix proportions. The developed cellulose sound-absorbing material has been tested for its acoustic properties such as acoustic absorptivity and dynamic elastic modulus. The absorptivity was evaluated by developing six samples and using impedance tube and reverberation chamber. As a result of the evaluation, 0.64(NRC) was secured in absorptivity and $4.7MN/m^3$ was indicated in dynamic elastic modulus. Also, for practical use of developed sound-absorbing material as inner heartwood in drywall, comparison test of sound reduction index was performed with existing glass wool sound-absorbing material and constructed drywall of gybsum board. The results have shown 55dB(Rw) of sound reduction index in glass-wool wall and 46dB(Rw) in cellulose.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1995.04a
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• pp.75-75
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• 1995

Succinic semialdehyde reductase, one of key enzyme of GABA shunt in CNS, is inactivated by o-phthalaldehyde, The inactivation followed pseudo first-order kinetics, and the second-order rate constant for the inactivation process was 28 M$\^$-1/s$\^$-1/ at pH 7.4 and 25$^{\circ}C$. The absorption spectrum(λ$\_$max/=377nm), fluorescence exitation(λ$\_$max/=340nm) and fluorescence emission spectra (λ$\_$max/=409nm) were consistent with the formation of an isoindole derivative in the catalytic site between a cysteine and a lysine residues about 3${\AA}$ apart. The substrate, succinic semialdehyde, did not protect the enzymatic activity against inactivation, whereas the coenzyme, NADPH, protected against o-phthalaldehyde induced inactivation of the enzyme. About 1 isoindole group per moi of the enzyme was formed following complete loss of the enzymatic activity. These results suggest that the amino acid residues of the enzyme participating in reaction with o-phthalaldehyde more likely residues at or near the coenzyme binding site.