• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.2
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• pp.197-204
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• 2012

We explore the evolution of metal plasma generated by high laser irradiances and its effect on the surrounding air by using shadowgraph images after laser pulse termination and X-ray diffraction (XRD) of aluminum plasma ablated by a high-power laser pulse (>1000 mJ/pulse) and oxygen from air. Hence, the formation of laser-supported detonation and combustion processes has been investigated. The essence of this paper is in observing the initiation of chemical reaction between the ablated aluminum plasma and oxygen from air by the high-power laser pulse (>1000 mJ/pulse) and in conducting a quantitative comparison of the chemically reactive laser-initiated waves with the classical detonation of an exploding aluminum (dust) cloud in air. The findings in this work may lead to a new method of initiating detonation from a metal sample in its bulk form without any need to mix nanoparticles with oxygen for initiation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.7
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• pp.1031-1038
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• 2002

The pressure sensitive paint (PSP) has recently received a considerable attention in the fields of aerodynamics and fluid mechanics as a new revolutionary optical technique to measure pressure fields on a body surface. In this study, the feasibility and effectiveness of the PSP pressure field measurement technique have been investigated experimentally. Seven different PSP formulations including two porphyrins(PtOEP and PtTFPP) and four polymers(Polystyrene, cellulous acetate butyrate, GP-197 and Silicon-708) were tested to check the performance and characteristics of each combination. The static calibration of each PSP formulation was carried out in a constant-pressure chamber. The PSP technique was applied to an oblique impinging jet flow to measure variation of pressure field on the impinging plate at on oblique jet angle of ${\theta}=60^{\circ}$. Pressure field images were captured by an 12bit intensified CCD(ICCD, $1K{\times}1K$)camera. As a result, the dynamic response of PSP depends on the oxygen permeability of polymer and the photochemical interaction between luminophore and polymer as well as the reaction of luminophore itself. The reaction of luminophore was changed by employing different polymers. In conclusion, Among 7 PSP formulation tested, the combination of PtTFPP and cellulous acetate butyrate show the best performance. In addition, the detail pressure field of an oblique high-speed impinging jet was measured effectively using the PSP technique.

• Journal of fish pathology
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• v.21 no.1
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• pp.67-79
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• 2008

This study was conducted to find out biological response of bivalves exposed to tributyltin chloride(TBTCl). The results of the study confirmed that TBTCl induce the reduction of oxygen consumption rateand histopathological feature in the gill structure of equilateral venus, Gomphina veneriformis. The experi-mental groups consisted of a control and 3 TBTCl exposure groups (0.4, 0.6 and 0.8 yg TBTCl L') and theexperimental period was 36 weeks. For histological analysis, gill tissues were fixed in Bouin's fluid andthen stained H-E stain, AB-PAS (PH 2.5) reaction and Masson's trichrome stain after having serially sec-tioned the tissue by paraffin method at thickness of 4-6 (an. The oxygen consumption rate was not signifi-cantly different between the control and exposure groups at 4 weeks, but in all exposure groups at 28 weeks,it was significantly different to the control. Gill of G. veneriformis had demibranch that attached two sheetsof lamellae and a lamella was composed of numerous filaments, numbering 25 on average. The frontal fila-ment zone had three types of cilia; frontal, latero-frontal and lateral depending on locations while the lateralcilia were the longest and largest in number. The mucous cells observed in filaments were more abundant in(542c) in AB-PAS (PH 2.5) reaction. Gill exposed to TBTCl was extended hemolymph sinus and increased hemocytes at 4 weeks, and then it showed increases of mucous cells and partially disappearance of frontalcilia. In the group of 0.8 yg TBTCl L' at 12 weeks, hypertrophy of frontal and latero-frontal epithelia wasobserved. Also it observed m decrease of mucous cell containing weekly acid mucosubstance and appearedpartially destruction muscle fiber bundle, In the groups of 0.4 and 0.6 ug TBTCl L' at 36 weeks, it appearedpartially modification of epithelia and in 0.8 us TBTCl L' group, observed filaments that come out chiti-nous rod from disappearance of frontal and latero-frontal epithelia.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.2
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• pp.135-141
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• 2005

Nitric oxide(NO) reduction by methanol was investigated over $La_2O_3$ catalysts in the presence and absence of oxygen. In the absence of $O_2$, $CH_3OH$ reduced NO to both $N_2$ and $N_2O$, with selectivity to $N_2$ formation decreasing from 81-88% at 623K to 47-71% at 723 K. With 1.2% $O_2$ in the feed, the rates were 4-8 times higher, but the selectivity to $N_2$ dropped from 50% at 623 K to 9% at 723 K. The specific activities with $La_2O_3$ for this reaction were higher than those for other reductants; for example, at 773 K with hydrogen a specific activity of $34\;{\mu}mol\;NO/sec{\cdot}m^2$ was obtained whereas that for methanol was $638\;{\mu}mol\;NO/sec{\cdot}m^2$. The Arrhenius plots were linear under differential reaction conditions, and the apparant activation energy was consistantly near 15 kcal/mol with $CH_3OH$. Linear partial pressure dependencies based on a power rate law were obtained and showed a near-zero order in $CH_3OH$ and a near-first order in $H_2$.

• Journal of the Korean Chemical Society
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• v.32 no.6
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• pp.528-535
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• 1988

The rates of oxygen ring formation of $[Mo_2O_3(Ox)_2(OxH)_2(NCS)_2]$ have been investigated spectrophotometric method in binary aqueous mixtures. Temperature was $20^{\circ}C$ to $40^{\circ}C$ and pressure was varied up to 1500 bar. The observed rate constants are increased by hydrogen ion and decreased by thiocyanate. The more increasing of co-solvents dielectric constant, the more stable intermediate is formed. The observed rate constant is given by, $k_{obs}^{-1} = k^{-1} (1 + K^{-1}[H_2O]^{-1}) All activation parameters are positive values. The oxygen ring formation of [Mo_2O_3(Ox)_2(OxH)_2(NCS)_2]$ is believed to be a interchange-dissociative mechanism..

• Bulletin of the Korean Chemical Society
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• v.34 no.4
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• pp.1195-1198
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• 2013

Nickel hexacyanoferrate supported palladium nanoparticles (Pd-NiHCF NPs) were synthesized and studied for oxygen reduction reactions in direct methanol fuel cell. The NiHCF support was readily synthesized by a comixing of $Ni(OCOCH_3)_2$ and equimolar $K_3[Fe(CN)_6]$ solution into DI water under rigorous stirring. After the preparation of NiHCF support, Pd NPs were loaded on NiHCF via L-ascorbic acid reduction method at $80^{\circ}C$. Pd-NiHCF NPs were electrochemically active for oxygen reduction reaction in 0.1 M $HClO_4$ solution. X-ray absorption near edge structure analysis was conducted to measure the white line intensity of Pd-NiHCF to verify the OH adsorption. As a comparison, carbon supported Pd NPs exhibited same white line intensity. This study provides a general synthetic approach to easily load Pd NPs on porous coordination polymers such as NiHCF and can provide further light to load Pd based alloy NPs on NiHCF framework.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.3
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• pp.260-266
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• 2018

To enhance catalyst activity of the palladium (Pd) towards oxygen reduction reaction (ORR), iridium (Ir) and yttrium (Y) were alloyed by polyol method. Due to the low reduction potential of Y, it is hard to reduce Y ion completely by polyol method. In XPS spectra, the binding energy of the Pd is shifted to a lower value, which indicates the d-electron of Pd is filled by the electron from the Y. And other phases of Y are observed by the XPS. Among the catalysts, the $Pd_4IrY_{0.1}/C$ showed the best activity towards ORR, which indicates the metallic Y is effective for improving the catalytic activity. Thus, for further enhancing ORR activity, the novel method for complete reduction of Y is needed.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.4
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• pp.378-385
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• 2014

In this research, we investigate electrical performance and electrochemical properties of graphene supported Pt (Pt/G) and PtM (M = Ni and Y) alloy catalysts (PtM/Gs) that are synthesized by modified polyol method. With the PtM/Gs that are adopted for oxygen reduction reaction (ORR) as cathode of proton exchange membrane fuel cells (PEMFCs), their catalytic activity and ORR performance and electrical performance are estimated and compared with one another. Their particle size, particle distribution and electrochemically active surface (EAS) area are measured by TEM and cyclic voltammetry (CV), respectively. On the other hand, regarding ORR activity and electrical performance of the catalysts, (i) linear sweeping voltammetry by rotating disk electrode and rotating ring-disk electrode and (ii) PEMFC single cell tests are used. The TEM and CV measurements demonstrate particle size and EAS of PtM/Gs are compatible with those of Pt/G. In case of PtNi/G, its half-wave potential, kinetic current density, transferred electron number per oxygen molecule and $H_2O_2$ production % are excellent. Based on data obtained by half-cell test, when PEMFC singlecell tests are carried out, current density measured at 0.6V and maximum power density of the PEMFC single cell employing PtNi/G are better than those employing Pt/G. Conclusively, PtNi/Gs synthesized by modified polyol shows better ORR catalytic activity and PEMFC performance than other catalysts.

• Korean Journal of Materials Research
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• v.28 no.11
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• pp.646-652
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• 2018

During a long-term operation of polymer electrolyte membrane fuel cells(PEMFCs), the fuel cell performance may degrade due to severe agglomeration and dissolution of metal nanoparticles in the cathode. To enhance the electrochemical durability of metal catalysts and to prevent the particle agglomeration in PEMFC operation, this paper proposes a hybrid catalyst structure composed of PtCo alloy nanoparticles encapsulated by porous carbon layers. In the hybrid catalyst structure, the dissolution and migration of PtCo nanoparticles can be effectively prevented by protective carbon shells. In addition, $O_2$ can properly penetrate the porous carbon layers and react on the active Pt surface, which ensures high catalytic activity for the oxygen reduction reaction. Although the hybrid catalyst has a much smaller active surface area due to the carbon encapsulation compared to a commercial Pt catalyst without a carbon layer, it has a much higher specific activity and significantly improved durability than the Pt catalyst. Therefore, it is expected that the designed hybrid catalyst concept will provide an interesting strategy for development of high-performance fuel cell catalysts.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.10
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• pp.1827-1832
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• 2017

To observe the characteristics to be a resistive memory of $V_2O_5$ deposited by oxygen various gas flows and annealed, the hysteresis curves of $V_2O_5$ were analyzed. The good resistive memory was obtained from the electrical characteristics of $V_2O_5$ films with the Schottky contact as a result of electron-hole pair, and the oxygen vacancy generated from the annealing process contributes the high quality of Schottky contact and the formation of resistive memories. The balanced Schottky contacts owing to the oxygen vacancy effect as the result of an ionic reaction were formed at the $V_2O_5$ film annealed at $150^{\circ}C$ and $200^{\circ}C$ and the balanced Schottky contact with negative to positive voltages enhanced the electrical operation with write/erase states according to the forward or reverse bias voltages for the resistive memory behavior due to the oxygen vacancy.