• Korean Chemical Engineering Research
• /
• v.49 no.6
• /
• pp.775-780
• /
• 2011

5-cell DMFC stack was fabricated and operated with the load of 4 A for 4000 hrs. After 4000 hrs operation peak power density of the stack reduced by 27.3%. Two of the five cells did now show performance degradation, the performance of other two was reduced by 40% and the performance of the other decreased by 60%. The amount of performance degradation of each cell by long-term operation did not correlate with the position in the stack. Platinum particle size in the anode catalyst layer of the MEA with the strongest degradation increased and the increase was severer on the position of methanol inlet than on the position of methanol outlet. However, platinum particle size in the cathode catalyst layers did not changed for all the MEA'. Ruthenium crossover from the anode catalyst layer to the cathode catalyst layer through the membrane was observed after 4,000 hrs operation by SEM-EDX and it occurred for all MEA' regardless of the degree of performance degradation. Atomic ratio of ruthenium to platinum in the cathode catalyst layer was the highest in the MEA with the strongest performance degradation.

• Korean Chemical Engineering Research
• /
• v.57 no.1
• /
• pp.17-21
• /
• 2019

The redox flow battery (RFB) is a large-capacity energy storage equipment, and the vanadium redox flow cell is a typical RFB, but VRFB is expensive. Iron-chrome RFBs are economical because they use low-cost active materials, but their low performance is an urgent problem. One of the reasons for the low performance is the crossover of the active materials. In this study, the sulfonated Poly (ether ether ketone) (sPEEK) membrane, which is a hydrocarbon membrane, was used instead of the fluorine membrane to reduce the crossover of the active materials. The chromium ion permeability of the sPEEK membrane was $1.8{\times}10^{-6}cm^2/min$, which was about 1/33 of that of the Nafion membrane. Thus, it was shown that the use of the sPEEK membrane instead of the fluorine membrane could solve the high active material crossover problem. The activation energy of iron diffusion through the sPEEK membrane was 24.9 kJ/mol, which was about 66% of Nafion membrane. And that the e-PTFE support in the polymer membrane reduces the active material crossover through Iron-Chrome Redox Flow Battery (ICRFB).

• Applied Chemistry for Engineering
• /
• v.33 no.2
• /
• pp.126-132
• /
• 2022

Alkaline fuel cells using liquid fuels such as hydrazine and ammonia are gaining great attention as a clean and renewable energy solution possibly owing to advantages such as excellent energy density, simple structure, compact size in fuel container, and ease of storage and transportation. However, common shortcomings including cathode flooding, fuel crossover, side yield reactions, and fuel security and toxicity are still challenging issues. Real time monitoring of fuel concentrations integrated into a fuel cell device can help improving fuel cell performance via predicting any loss of fuels used at a cathode for efficient energy production. There have been extensive research efforts made on developing real-time sensing platforms for hydrazine and ammonia. Among these, recent advancements in electrochemical sensors offering high sensitivity and selectivity, easy fabrication, and fast monitoring capability for analysis of hydrazine and ammonia concentrations will be introduced. In particular, research trend on the integration of metallic and metal oxide nanoparticles and also their hybrids with carbon-based nanomaterials into electrochemical sensing platforms for improvement in sensitivity and selectivity will be highlighted.

• Journal of the Korean Society of Radiology
• /
• v.7 no.1
• /
• pp.25-30
• /
• 2013

In this work, we investigate the statistical properties of gamma exposure rates using well-known analysis methods, such as Autocorrelation Function Analysis(ACF), Rescaled Range Analysis(R/S Analysis), and Detrended Fluctuation Analysis(DFA). Especially, DFA is an important method to reliably detect long-range correlations in non-stationary time series. Our data are measured by Gangneung regional radiation monitoring station over the period of 1998 to 2011. First, we find a crossover indicating two different governing regimes in fluctuations of gamma exposure rates. Within a year, they show a strong long-ranged memory while this property vanishes over the range of time period longer than one year. Second, our finding is very securely supported by a variety of analysis tools. Those tools yield many relevant exponents which satisfies the well known relation between them.

• Korean journal of communication and information
• /
• v.57
• /
• pp.227-249
• /
• 2012

In the media convergence era, contents industry is raising core area in the government level. This study explores directions of development policy of national contents industry. So this study performs depth interview with 10 experts and investigates delphi research with 30 experts who are specialists in digital convergence area. Following the depth interview, there are three categories in the convergence contents - technical area, human resource area, and political area. The result shows that there is discordance between importance and present status each area. This finding suggests that there is political delay in the convergence media industry. In conclusion, it is necessary to look over the current limits and inspect defects. This study implicates further directions of national contents industry.

• Journal of the Korean Society of Costume
• /
• v.60 no.9
• /
• pp.1-15
• /
• 2010

Fashion designer Jean Paul Gaultier incorporated his own boundless and unique artistic Into his design of dance costumes, presenting an unobstructed imaginary world that was filled with freedom, which is no less than one would expect from the one-time enfant t${\'{e}}$rrible of Paris fashion. This creativity of Gaultier was made possible only through the fantastic partnership he formed with the French modern dancer, R${\'{e}}$gine Chopinot. Gaultier and Chopinot shared a deep-rooted sympathy that enabled their own artistic worlds to fully mingle and cross over, resulting in a doubled synergy of their talent and their fame. This study analyzed 11 dancing costumes created through the collaborated efforts of those two enfants t${\'{e}}$rribles, one from the fashion industry and the other from the world of dance. The following are the results of my analysis. Gaultier's dance costumes served as a artistic venue for experimenting with a number of creative inspirations lurking in his mind, which were sometimes expressed in pr${\^{e}}$t-${\`{a}}$-porter collections. Instead of the decorative and expressive features of conventional dance costumes, his was the revival of the dancer's persona as a human being, ablaze with individuality and uniqueness. He pointed out that there is no good in the distorted turturro's fixed point of view, and the great joy of an opposing way of thinking that overturned the established. Leotard material was used as a second skin by transforming it into various styles and delivering his message. In addition, obscene and sexual expressions were delivered in a direct narrative. His eccentric ideas provided entertainment while showing his oppositional way of thinking. In the dance, the effect of the costumes was doubled by the use of cumbersome and exaggerated accessories, which is generally forbidden in modern dance.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.11B
• /
• pp.673-684
• /
• 2007

In this paper, we introduce an FARNS (Flooding algorithm with Adaptive Retransmission Nodes Selection). It is an efficient cross layer-based flooding technique to solve broadcast storm problem that is produced by simple flooding of nodes in wireless sensor network. FARNS can decrease waste of unnecessary energy by preventing retransmission action of whole network node by deciding retransmission candidate nodes that are selected by identification in MAC and distance with neighborhood node through received signal strength information in PHY. In simulation part, we show the results that FARNS has excellent performance than the other flooding schemes in terms of broadcast forwarding ratio, broadcast delivery ratio, number of redundancy packets and overhead. And FARNS can adjust of node ratio for retransmission operation, it can solve broadcast storm problem as well as meet the requirements of various network environments.

• Journal of Broadcast Engineering
• /
• v.13 no.2
• /
• pp.245-250
• /
• 2008

Efficient service discovery mechanism is a crucial feature for the usability of a wireless ad-hoc network. A wireless ad-hoc network is a temporal network formed by a collection of wireless mobile nodes without the aid of any existing network infrastructure or centralized administration. We propose an efficient service discovery mechanism using non-disjoint multi-path routing protocol for a wireless ad-hoc network. Our scheme has advantages of not only multi-path routing protocol but also cross-layer service discovery. By simulation, we showed that faster route recovery is possible by maintaining multiple routing paths in each node, and the route maintenance overhead can be reduced by limiting the number of multiple routing paths and by maintaining link/node non-disjoint multi-path.

• Applied Chemistry for Engineering
• /
• v.30 no.4
• /
• pp.389-398
• /
• 2019

Hydrogen energy is not only a solution to climate change problems caused by the use of fossil fuels, but also as an alternative source for the industrial power generation and automotive fuel. Among hydrogen production methods, electrolysis of water is considered to be one of the most efficient and practical methods. Compared to that of the fossil fuel production method, the method of producing hydrogen directly from water has no emission of methane and carbon dioxide, which are regarded as global environmental pollutants. In this paper, the alkaline water electrolysis (AWE) and polymer electrolyte membrane water electrolysis (PEMWE), which are one of the hydrogen production methods, were discussed. Recent research trends of hydrocarbon electrolyte membranes and the crossover phenomenon of electrolyte membranes were also described.

• Korean Journal of Applied Biomechanics
• /
• v.12 no.2
• /
• pp.345-359
• /
• 2002

The purpose of the study was to provide the fundamental data to instruct athletes through the analysis athletes' movement in javelin. Three athletes in the level of national representative were participated in this study. The study analyzed kinematic variables(lead foot and releasing javelin) through 3-D analysis and obtained the following results. 1. During withdrawal, it is important to maintain of running horizontal velocity. 2. It was showed that throng average height was $84{\pm}3.3%$ and javelin adequative degree, Among the athletes, $S_2$ who had the best record was released the javelin with the fast velocity, but throw the javelin with the less releasing velocity. 3. $S_2$ released after lead foot were completely landed and therefore it is no problem in a kinematic aspect. However, $S_1$ angle was too small. it caused increase of release velocity to be prevented. 4. $S_2$ showing the best result indicated shorter in duration time. Generally, the shorter duration time in release phase showed the longer release distance. Especially $S_1$ and $S_3$ showing the worse result indicated the longer duration time in preparatory phase, causing the breakup of force. Therefore to improve the record, it should be decreased the duration time in preparatory phase. 5. Compared with $S_1$ and $S_3$, $S_2$ showing the best record indicated the higher velocity in center of mass, trunk, upper arm, lower arm and hand That is the higher velocity of upper arm at release leaded the better velocity transfer from upper arm to following lower arm and hand, these action should be considered to be helpful of better record. According to the above conclusion, when the athletic leaders cauch athletes, they should focus on maintaining knee angle, upper body and hip angle in a previous stage of release and throwing angle, throwing height, throwing velocity in a release stage.