• Journal of the Korean Society of Safety
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• v.34 no.1
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• pp.14-20
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• 2019

This paper presents a safety assessment based approach for the safe operation for PCS(Power Conditioning System) of photovoltaic and energy storage systems, applying FTA. The approach established top events as power outage and a failure likely to cause the largest damage among the potential risks of PCS. Then the Minimal Cut Set (MCS) and the importance of basic events were analyzed for implementing risk assessment. To cope with the objects, the components and their functions of PCS were categorized. To calculate the MCS frequency based on IEEE J Photovolt 2013, IEEE Std. 493-2007 and RAC (EPRD, NPRD), the failure rate and failure mode were produced regarding the basic events. In order to analyze the top event of failure and power outage, it was assumed that failures occurred in DC breaker, AC breaker, SMPS, DC filter, Inverter, CT, PT, DSP board, HMI, AC reactor, MC and EMI filter and Fault Tree was drawn. It is expected that the MCS and the importance of basic event resulting from this study will help find and remove the causes of failure and power outage in PCS for efficient safety management.

• Composites Research
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• v.37 no.4
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• pp.296-300
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• 2024

The rational synthesis of efficient transitional metal phosphides (TMPs) could revolutionize green hydrogen production via water splitting. Hydrogen, with the highest energy density among fuels, stands out as an excellent alternative to address environmental issues and ensure sustainable future energy generation. However, the limited availability of state-of-the-art electrocatalysts like Pt/C and RuO₂, used for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, necessitates the development of cost-effective and non-noble electrocatalysts for green hydrogen production. In this context, we present a novel heterointerface-modulated heterostructure design comprising ultrathin nanosheets of a 3D Co₂P/VP heterostructure on a conductive nickel foam substrate. This heterostructure demonstrates remarkably low overpotentials of 96 mV for HER and 237 mV for OER at 10 mA cm^-2. The material's robust electrochemical kinetics are further evidenced by low Tafel slopes of 68.28 mV dec^-1 and 116.54 mV dec^-1, respectively.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1034-1035
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• 2015

Watertight 25.8 kV/600 A/12.5 kA fault current limiters (FCLs) have successfully installed in five areas (Incheon, Seoul, Gyeong-gi, Daejeon, Suwon) on KEPCO power distribution line for the purpose of commercial demonstrations. The fault current limiting operation of this FCL, which includes functions of sensing, commutation, and reduction of fault currents, is perfectly completed within 1 cycle immediately after fault occurs. The performance of FCL was verified by short circuit test, impedance test, insulation test, temperature-rise test, and control test, etc at PT&T in LS industrial systems, which is the official certification institute in Korea. In 2013, and also the FCL field test was performed in order to test the protection coordination between conventional relays and FCL, on the 1.5 kA and 5.0 kA faults, which were made by connecting the Artificial Fault Generator (AFG) to the distribution line in test grid at KEPCO Power Testing Center. The next step of this project is to check the FCL conditions caused by real external environment, and acquire the various data from five regions installed with FCL. In this paper, we intend to explain the FCL specifications and performance characteristics, and check the expected effect by application of FCL to power distribution line based on the power system analysis of an application site.

• KSBB Journal
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• v.27 no.6
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• pp.375-380
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• 2012

We previously reported that Ultra nattokinase$^{(R)}$ showed high fibrinolytic activity and revealed antithrombotic effect in rat blood plasma based on its ability to suppress collagen-induced platelet aggregation. This research was carried out to verify the clot lysing activity and blood flow enhancing effects of Ultra nattokinase$^{(R)}$ via monitoring and comparing the antithrombotic effects in rat artery between oral administration of Ultra nattokinase$^{(R)}$ and maltodextrin. SD rats were fed with 1.11 mg/kg of Ultra nattokinase$^{(R)}$ for 4 weeks. The effect on arterial thrombosis was then evaluated using an antithrombotic model after induction by $FeCl_3$. Detected fibrinolytic activity was proportional to the content of Ultra nattokinase$^{(R)}$ and statistical extents of the antithrombotic activity was enhanced strongly twice rather than control group. The PT and the aPTT, however, showed only a small difference between two groups. The results suggest that Ultra nattokinase$^{(R)}$ can effectively treat thromboembolism and enhance blood flow, and that Ultra nattokinase$^{(R)}$ can also prevent venous occlusion by aiding clot lysis.

• Clean Technology
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• v.21 no.2
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• pp.117-123
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• 2015

This inquiry was conducted to develop DeNOx catalyst for LNT. In order to develop appropriate catalysts, four catalysts, which do not use PGM (Platinum Group Metal), were carefully selected : Al/Co/Mn, Al/Co/Ni/Mn, Al/Co/Mn/Ca, Al/Co/Ni mixed metal oxides during preliminary experiments. Also, XRD, EDS, SEM, BET and TPD tests were carried as well to evaluate both physicochemical properties of such four catalysts. As a result of the experiment, four catalysts were composed of spinel-shaped crystals and had more than enough pore volume and size to have oxidation-reduction reaction of NOx gases. Additionally, through TPD test, all four types of catalysts were proved to possibly have an oxidation-reduction acid site and NO oxidation activities similar to commercial catalysts. Based on the results above, if we have further change in the composition components and active ingredients according to the catalysts that were chosen in this investigation, then we are more welcomed to expect to have an enhanced DeNox catalyst for LNT.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.288-294
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• 2009

Various polymer electrolyte membrane fuel cell (PEMFC) startup procedures were tested to explore possible techniques for reducing performance decay and improving durability during repeated startup-shutdown cycles. The effects of applying a dummy load, which prevents cell reversal by consuming the air at the cathode, on the degradation of a membrane electrode assembly (MEA) were investigated via single cell experiments. The electrochemical results showed that application of a dummy load during the startup procedure significantly reduced the performance decay, the decrease in the electrochemically active surface area (EAS), and the increase in the charge transfer resistance ($R_{ct}$), which resulted in a dramatic improvement in durability. After 1200 startup-shutdown cycles, post-mortem analyses were carried out to investigate the degradation mechanisms via various physicochemical methods including FESEM, an on-line $CO_2$ analysis, EPMA, XRD, FETEM, SAED, FTIR. After 1200 startup-shutdown cycles, severe Pt particle sintering/agglomeration/dissolution and carbon corrosion were observed at the cathode catalyst layer when starting up a PEMFC without a dummy load, which significantly contributed to a loss of Pt surface area, and thus to cell performance degradation. However, applying a dummy load during the startup procedure remarkably mitigated such severe degradations, and should be used to increase the durability of MEAs in PEMFCs. Our results suggest that starting up PEMFCs while applying a dummy load is an effective method for mitigating performance degradation caused by reverse current under a repetition of unprotected startup cycles.

• Journal of Hydrogen and New Energy
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• v.19 no.1
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• pp.71-76
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• 2008

CuFeOx/$Al_2O_3$ catalysts are developed for the use in sulfuric acid decomposition which is a subcycle in thermochemical iodine-sulfur cycle to split water into hydrogen and oxygen. Both Cu and Fe components are co-precipitated with Al component to enhance distribution of active components. Developed catalysts are improved in the capability of sulfuric acid decomposition and endurance under highly acidic environment compared to commercial catalysts such as Pt/$Al_2O_3$ and $2CuO{\cdot}Cr_2O_3$. Developed CuFeAlOx catalysts exhibited higher sulfuric acid decomposition ability than $2CuO{\cdot}Cr_2O_3$ and longer endurance trends than Pt/$Al_2O_3$ maintaining comparable performance, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11B
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• pp.689-697
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• 2005

The IETF has created the v6ops Working Group to assist IPv6 transition and propose technical solutions to achieve it. But it's quite problem which security consideration for a stage of IPv4/IPv6 transition and co-existence. There are new security problem threat that it caused by the characteristics of heterogeneity. In this paper, we describe IPv6 transition mechanisms and analyze security problem for IPv6 transition mechanism. also we propose security consideration and new security mechanism. We analyzed DoS and DRDoS in 6to4 environment and presented a address sanity check as a solution. We also showed an attack of address exhaustion in address allocation server. To solve this problem, we proposed challenge-response mechanism in DSTM.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.3
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• pp.138-145
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• 2011

Diesel particulate filter (DPF) systems are being used to reduce the particulate matter emission of diesel vehicles. The DPF should be regenerated after certain driving hours or distance to eliminate soot in the filter. The most widely used method is active regeneration with oxygen at $550{\sim}650^{\circ}C$. Syngas (synthetic gas) can be used to lower the regeneration temperature of Catalyzed DPF (CDPF). The syngas is formed by fuel reforming process of CPOx (Catalytic Partial Oxidation) at specific engine condition (1500rpm, 2bar) using 1wt.% $Rh/CeO_2-ZrO_2$ catalyst. The oxidation characteristics of PM with syngas supplied to filter were studied using partial flow system that can control temperature and flow rate independently. The filter is coated with washcoat loading of $25g/ft^3$ $Pt/Al_2O_3-CeO_2$, and multi-channel CDPF (MC-CDPF) was used. The filter regeneration experiments were performed to investigate the effect of syngas exothermic reaction on soot oxidation in the filter. For this purpose, before oxidation experiment, PM was collected about 8g/L to the filter at engine condition of 1500rpm, bmep 8bar and flow temperature of $200^{\circ}C$ Various conditions of temperature and concentration of syngas were used for the tests. Regeneration of filter started at 2% $H_2$ and CO concentration respectively and inlet temperature of $260^{\circ}C$. Filter Regeneration occurs more actively as the syngas concentration becomes higher.

• Journal of the Korean Electrochemical Society
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• v.23 no.4
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• pp.90-96
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• 2020

Polymer electrolyte membrane fuel cells, which convert the chemical reaction energy of hydrogen into electric power directly, are a type of eco-friendly power for future vehicles. Due to the sluggish oxygen reduction reaction and costly Pt catalyst in the cathode, the research related to the replacement of Pt-based catalysts has been vitally carried out. In this case, however, the performance is significantly different from each other and a variety of factors have existed. In this review paper, we rearrange and summarize relevant papers published within 5 years approximately. The selection of precursors, synthesis method, and co-catalyst are represented as a core factor, while the necessity of research for the further enhancement of activity may be raised. It can be anticipated to contribute to the replacement of precious metal catalysts in the various fields of study. The final objective of the future research is depicted in detail.