• Transactions of the Korean hydrogen and new energy society
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• v.26 no.2
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• pp.170-178
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• 2015

In this study, we carry out a study on how to improve performance of vanadium redox flow battery (VRFB) through promoting reaction rate of rate determining vanadium reaction ($[VO]^{2+}/[VO_2]^+$). In order to do that, three different carbons like Vulcan (XC-72), CMK3 and MSU-F-C are adopted as the catalysts, while their catalytic activity and reaction reversibility are evaluated using half-cell tests. Their topological images are also measured by TEM. For estimation of the VRFB performance, multiple charge-discharge curves of VRFBs including the catalysts are measured by single cell tests. As a result of that, MSU-F-C shows relatively excellent catalytic activity and reaction reversibility as well as large surface area compared to those of Vulcan (XC-72) and CMK3. Also, in terms of the performance of VRFBs including the catalysts, VRFB including MSU-F-C indicates (i) low charging/discharging overpotentials and low internal resistance, (ii) high charge/discharge capacities and (iii) high energy efficiency. These VRFB performance data are well agreed with results on catalytic activity and reaction reversibility. The reason that MSU-F-C induces superior VRFB performances is attributed to (i) its large surface area and (ii) its hydrophilic surface functional groups that mainly consist of hydroxyl bonds that are supposed to play active surface site role for facilitaing $[VO]^{2+}/[VO_2]^+$ redox reaction. Based on the above results, it is found that adoption of MSU-F-C as catalyst for VRFB results in improvement in VRFB performance by promoting the languid $[VO]^{2+}/[VO_2]^+$ redox reaction.

• Journal of Adhesion and Interface
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• v.22 no.1
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• pp.1-7
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• 2021

The importance of high capacity energy storage devices has recently emerged for stable power supply through renewable energy generation. From this point of view, the Na-air battery (NAB), which is a next-generation secondary battery, is receiving huge attention because it can realize a high capacity through abundant and inexpensive raw materials. In this study, activated carbon-based catalysts for hybrid type Na-air batteries were prepared and their characteristics were compared and analysed. In particular, from the viewpoint of resource recycling, activated carbon (Orange-C) was prepared using discarded orange peel, and performance was compared with Vulcan carbon, which is widely used. In addition, a Pt/C catalyst (homemade-Pt/C, HM-Pt/C) was synthesized using a modified polyol method to check whether the prepared activated carbon can be used as a supported catalyst, and a commercial Pt/C catalyst (Commercial Pt/C) and electrochemical performance were compared. The prepared Orange-C exhibited a typical H3 type BET isotherm, which is evidence that micropore and mesopore exist. In addition, in the case of HM-Pt/C, it was confirmed through TEM analysis that Pt particles were evenly distributed on the activated carbon supported catalyst. In particular, the HM-Pt/C-based NAB showed the smallest voltage gap (0.224V) and good voltage efficiency (92.34%) in the 1st galvanostatic charge-discharge test. In addition, the cycle performance test conducted for 20 cycles showed the most stable performance.

• KIPS Transactions on Software and Data Engineering
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• v.2 no.6
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• pp.377-382
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• 2013

A convergence software development methodology based on product line engineering provides an architecture model for application development and it also provides workflow as a behavior specification of control component development to develop transaction centric application. To effect a change on software development based on product line engineering it has to be supported by a tool. But almost workflow modeling tools dose not support product line engineering concept. So we need new workflow modeling tool to support the convergence software development methodology. In this paper, we introduce a toolset for workflow modeling that consists of eclipse plug-in applications and open source tool and describe the relationships of tools through example.

• Journal of Environmental Science International
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• v.26 no.6
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• pp.729-739
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• 2017

The Weather Research and Forecasting (WRF) model and Vegetation Photosynthesis and Respiration Model (VPRM) were coupled to simulate atmospheric $CO_2$ concentrations. The performance of the WRF-VPRM to simulate regional scale $CO_2$ concentration was estimated over coastal basin areas. Either Hestia 2011(HST) or Vulcan 2002(VUL) anthropogenic $CO_2$ emission data were used in two numerical experiments for the study regions. Simulated meteorological variables were validated with ground and background $CO_2$ measurement data, and the results show that the model captured temporal variations of $CO_2$ concentration on a daily basis. $CO_2$ directional analysis revealed that the dominant $CO_2$ emission sources are located S and SW. The simulated Net Ecosystem Exchange (NEE) agreed relatively well with measured $CO_2$ fluxes at each vegetation class site, showing approximately 40% at max improvement at shrub areas.

• Journal of the military operations research society of Korea
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• v.1 no.1
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• pp.111-129
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• 1975

U.S. Air Force Regulation 80-1 defines that a weapon system is composed of equipments, skills, and techniques, the composite of which ferns an instrument of combat. The complete weapon system includes all related facilities, equipments, materials, services, and personnels required for the operation of the system, so that the instrument of combat can be considered as a self-sufficient unit of striking power in its intended operational environment. Effectiveness of a weapon system can be expressed as a function of its liability, reliability and performance capability. Among these attributes which influence the weapon effectiveness, performance capability is considered to be the most critical factor for many weapon systems. In order to illustrate the application of the methodology of performance capability, a specific ease study on the effectiveness of Vulcan anti-air craft gun system is presented with special emphasis on hitting probability on moving targets, effects of artificial rounds dispersion, and several principles related to the deployment of the system. This thesis includes the thorough survey of the possibility of calculating the absolute value of hitting probability on moving targets, indicates that the effects of artificial rounds dispersion increase the value of probability only when the total number of rounds fired within fire range exceeds a certain critical number, and suggests that concentrated guns deployment is better than scattered deployment in order to obtain higher probability and lower average amount of rounds if it is assumed that the effects of counter-attack from enemy threats are not serious.

• Ocean and Polar Research
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• v.25 no.spc3
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• pp.373-384
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• 2003

When pile foundation is constructed by dynamic method, it is desirable to perform monitoring of drivability with pile penetration. Dynamic pile monitoring yields information regarding driving hammer, cushion, pile and soil behaviour that can be used to confirm the assumptions of wave equation analysis. In this study, dynamic monitoring of the steel pipe pile was performed with Pile Driving Analyser (PDA). The PDA utilizes the wave propagation theory to compute numerous variables which describe the conditions of the hammer-pile-soil system in real-time and following each hammer impact. This approach allows immediate field verification of hammer performance, driving efficiency, and estimation of pile bearing capacity. A series of PDA test were performed at the Ieodo Ocean Research Station (IORS) located in southeast of Marado, a southernmost small island south of Jeju Island. The drilling core sediments of Ieodo subsoil are composed of mud and sand, showing lamination and wavy or lenticular bedding, which were often bioturbated. This paper summarizes the results of PDA tests which were applied in measurement and estimation of large diameter open ended steel pipe pile driven by steam hammer, Vulcan-560 and MRBS-4600, at the marine sediments.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.4
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• pp.826-831
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• 2007

Analytic solutions for pile driving system with and without suspension were presented and influences of suspension on the driving system were discussed. According to the results of analysis, magnitude of amplitude of vibratory pile driver with suspension increases as the mass of the suspension increases and soil dampening decreases. As a results of comparing power of vibratory pile driver with suspension with that of design criterion, power versus soil dampening reaches a peak value and then declines. The maximum power increases with mass ratio and the power is always below that of the Vulcan design criterion.

• Korean Journal of Materials Research
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• v.25 no.3
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• pp.113-118
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• 2015

To improve the methanol electro-oxidation in direct methanol fuel cells(DMFCs), Pt electrocatalysts embedded on porous carbon nanofibers(CNFs) were synthesized by electrospinning followed by a reduction method. To fabricate the porous CNFs, we prepared three types of porous CNFs using three different amount of a styrene-co-acrylonitrile(SAN) polymer: 0.2 wt%, 0.5 wt%, and 1 wt%, respectively. A SAN polymer, which provides vacant spaces in porous CNFs, was decomposed and burn out during the carbonization. The structure and morphology of the samples were examined using field emission scanning electron microscopy and transmission electron microscopy and their surface area were measured using the Brunauer-Emmett-Teller(BET). The crystallinities and chemical compositions of the samples were examined using X-ray diffraction and X-ray photoelectron spectroscopy. The electrochemical properties on the methanol electro-oxidation were characterized using cyclic voltammetry and chronoamperometry. Pt electrocatalysts embedded on porous CNFs containing 0.5 wt% SAN polymer exhibited the improved methanol oxidation and electrocatalytic stability compared to Pt/conventional CNFs and commercial Pt/C(40 wt% Pt on Vulcan carbon, E-TEK).

• Carbon letters
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• v.6 no.1
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• pp.41-46
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• 2005

Plasma carbon blacks of 20~30 nm diameter were synthesized by direct decomposition of natural gas using a hybrid plasma torch system with 50 kW direct current and 4 MHz of radio frequency. The insulating rector which inside diameter of 400 mm and length of 1500 mm, respectively was kept at 300~$400^{\circ}C$ during the preparation. The ultimate analysis of plasma carbon blacks reveals that the raw plasma carbon blacks contains a large quantity of volatile which is mainly consist of hydrogen. Therefore devolatilization of raw plasma carbon blacks were carried out at $900^{\circ}C$ for one hour under nitrogen atmosphere. The devolatilization leads to the decrease in electrical resistivity and surface oxygen functional groups of plasma carbon black significantly. In order to investigate the plasma carbon as a catalyst support, devolatilized plasma black at $900^{\circ}C$ (DPB) supported PtAu catalyst was synthesized by sodium boronhydride reduction method. Electrochemical measurements and direct formic acid fuel cell test indicated that catalytic activity of DPB supported PtAu catalyst for formic acid oxidation was similar to that of Vulcan XC-72 of commercial carbon black supported one.

• The Journal of the Korea Contents Association
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• v.21 no.5
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• pp.499-507
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• 2021

This study compares the educational effect using real equipment, virtual reality, and video to improve the educational and training effect of the army and verifies which method of education is excellent. The Army has made a lot of efforts to realize the actual training environment, however, it is increasingly difficult to provide the actual training environment because of 1) restrictions on securing training sites and urbanization, 2) deepening conflicts with the people, and 3) difficulties in acquiring defense budget. To resolve these issues, the use of virtual reality(VR) has the advantage to experience actual battlefield indirectly and could save budget by training in a virtual battlefield environment. In particular, in the case of dangerous or expensive weapons systems, is further required. Hence this paper studies how effective virtual reality is compared to the actual weapons system. virtual reality(VR) education is less effective than actual equipment education, but it is higher than video education. Based on this research result, it will be used as a basic data for the analysis of educational effects based in virtual reality(VR).