• Transactions of the Korean hydrogen and new energy society
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• v.23 no.1
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• pp.83-92
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• 2012

Syngas combustion characteristics of mass produced oxygen carrier particle (OCN706-1100) were investigated in a pressurized fluidized bed reactor using simulated syngas and air as reactants for reduction and oxidation, respectively. The oxygen carrier showed high fuel conversion, high $CO_2$ selectivity, and low CO concentration at reduction conditions and no NO emission at oxidation conditions. Moreover, OCN706-1100 particle showed good regeneration ability during successive reduction-oxidation cyclic tests up to the 10th cycle. Fuel conversion and $CO_2$ selectivity decreased and CO emission increased as temperature increased. These results can be explained by trend of calculated equilibrium CO concentration with temperature. However, fuel conversion and $CO_2$ selectivity increased and CO emission decreased as pressure and gas residence time increased.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.2
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• pp.173-182
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• 2012

Effects of temperature, pressure, and gas residence time on methane combustion characteristics of mass produced oxygen carrier particle (OCN706-1100) were investigated in a pressurized fluidized bed reactor using methane and air as reactants for reduction and oxidation, respectively. The oxygen carrier showed high fuel conversion, high $CO_2$ selectivity, and low CO concentration at reduction condition and very low NO emission at oxidation condition. Moreover OCN706-1100 particle showed good regeneration ability during successive reduction-oxidation cyclic tests up to the 10th cycle. Fuel conversion and $CO_2$ selectivity decreased and CO emission increased as temperature increased. These results can be explained by trend of calculated equilibrium CO concentration. However, $CO_2$ selectivity increased as pressure increased and fuel conversion increased as gas residence time increased.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.5
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• pp.581-588
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• 2016

To compare reduction reactivity of oxygen carrier particles, $CH_4$ combustion characteristics were measured and investigated in a bubbling fluidized bed reactor with increasing $CH_4$ concentration from 10 to 100 %. Among five oxygen carriers (OC-1, OC-2, SDN70, C14, C28), OC-1, OC-2, SDN70 particles were selected as better oxygen carriers from the viewpoints of fuel conversion and $CO_2$ selectivity. However, some oxygen carriers showed lower fuel conversion and $CO_2$ selectivity even though they have high oxygen transfer capacity. Therefore, we could conclude that not only TGA tests to measure the oxygen transfer capacity but also fluidized bed tests to analyze exhaust gas concentration should be performed to select better oxygen carrier without misunderstanding of carriers reactivity.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.5
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• pp.589-596
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• 2016

Effects of pressure, temperature, gas velocity, and fuel flow rate on reduction of three oxygen carriers, SDN70, OC-1, OC-2, were measured and investigated in a pressurized bubbling fluidized bed reactor. Among three oxygen carriers OC-2 was selected as the best oxygen carrier in view of fuel conversion and $CO_2$ selectivity. However, all oxygen carriers showed good reactivity even at high pressure conditions. SDN70 particle showed maximum reactivity at $900^{\circ}C$ and low reactivity at $950^{\circ}C$. However, reactivity decay of OC-1 and OC-2 particles at high temperature condition was negligible. The fuel conversion and the $CO_2$ selectivity slightly decreased as the gas velocity increased, whereas they are slightly increased as the fuel concentration increased.

• KEPCO Journal on Electric Power and Energy
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• v.5 no.1
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• pp.33-38
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• 2019

Thermal power generation accounts for the highest percentage of domestic power generation, among which coal-fired boiler generation accounts for the highest percentage. Coal boilers generate harmful substances and fine dust during coal combustion and have a serious effect on air pollution. So, fluidized-bed boilers have been introduced as eco-friendly coal boilers. It uses a fluid medium which affect the combustion temperature of coal. Because of it fluidized-bed boilers emit less pollutants than original one. Water-wall tubes play an important role in this fluidized bed boiler. Due to the fluid medium, the wall damage is more severe than the existing boiler. However, there is no quantitative maintenance technique in Korea yet. Remote field eddy current testing is a non-destructive evaluation technique that is often used for inspection of inner and outer wall of tube. it can inspect with non-contact and high speed. However, it is an inspection that proceeds from inside the pipe, and the water-wall tube is not able to enter the interior. In this study, we designed and simulated an external remote field eddy current sensor suitable for water-wall tube of a fluidized - bed boiler using simulations. By obtaining a signal similar to the existing remote field eddy current test, the criteria for the external remote field eddy current sensor design can be presented.

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.451-464
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• 2008

Three-phase inverse fluidized bed has been widely adopted with its increasing demand in the fields of bioreactor, fermentation process, wastewater treatment process, absorption and adsorption processes, where the fluidized or suspended particles are small or lower density comparing with that of continuous liquid phase, since the particles are frequently substrate, contacting medium or catalyst carrier. However, there has been little attention on the three-phase inverse fluidized beds even on the hydrodynamics. Needless to say, the information on the hydrodynamics and transport phenomena such as heat and mass transfer in the inverse fluidized beds has been essential for the operation, design and scale-up of various reactors and processes which are employing the three-phase inverse beds. In the present article, thus, the information on the three-phase inverse fluidized beds has been summarized and reorganized to suggest a pre-requisite knowledge for the field work in a sense of engineering point of view. The article is composed of three parts; hydrodynamics, heat and mass transfer characteristics of three-phase inverse fluidized beds. Effects of operating variables on the phase holdup, bubble properties and particle fluctuating frequency and dispersion were discussed in the section of hydrodynamics; effects of operating variables on the heat transfer coefficient and on the heat transfer model were discussed in the section of heat transfer characteristics ; and in the section of mass transfer characteristics, effects of operating variables on the liquid axial dispersion and volumetric liquid phase mass transfer coefficient were examined. In each section, correlations to predict the hydrodynamic characteristics such as minimum fluidization velocity, phase holdup, bubble properties and particle fluctuating frequency and dispersion and heat and mass transfer coefficients were suggested. And finally suggestions have been made for the future study for the application of three-phase inverse fluidized bed in several available fields to meet the increasing demands of this system.

• Journal of the Korean Institute of Landscape Architecture
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• v.43 no.2
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• pp.30-39
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• 2015

The English Landscape garden and picturesque aesthetics, which was in fashion during the 18th to early 19th century in England, has been accused of making people see the actual garden in terms of a static landscape painting without a synesthetic engagement in nature. As new optic devices such as diorama, panorama, photography, and cinematography were invented, ways of seeing nature transitioned from a perspective vision to a panoramic, that is, modern one. This study intends to uncover signs of this kind of modern vision in the picturesque aesthetics and visual representation of landscape gardener Humphry Repton. German garden theorist Christian Cay Lorenz Hirschfeld contended that the English landscape garden was a new style of designing landscape that followed the principle of the serpentine line, which produced movement in sightlines; thus, he considered garden art as a superior art form among all other genres. The signs of visual motion appear in Repton's sketches of "Red Books". Firstly, he designed systemic routes in his clients' properties by considering different types of movements between walks and drives. Secondly, he often used the visual effects of panoramic views for his sketches in order to allow his clients to experience the human visual field. Lastly, he constructed sequences of sketches in order to provide his clients with an illusion of movement; in other words, Repton's sketches functioned as potential visual media to produce the duration of time in a visual experience. Thus, the garden aesthetics of the time reflected the contemporary visual culture, that is to say, a panoramic vision pertaining to visual motion.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2002.10a
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• pp.104-112
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• 2002

최근 도심지 지하철내 누유로 인한 악취·화재의 위험이 대중매체를 통해 보도되어 사회적 문제로 대두되고 있으며, 개정된 토양환경보전법 및 지하수법에 따라 주유소오염에 대한 정화기준이 강화되고 있어 도심지 주유소와 인접한 천층부 지하철터널의 누유대책 마련이 절실히 요구되고 있다. 도심지 지하철터널의 누유대책을 서울시 지하철 00공구 설계사례를 통해 먼저 지하수 유동분석에 의한 지하수위 검토와 오염자 추적에 의한 누유확산 범위를 파악하고, 두 번째로 누유감지센서에 의한 누유조기경보, 유량계 및 수질센서에 의한 수질data화의 수질 및 유량자동모니터링 시스템을 구축하며, 마지막으로 Oil-Stop 맨홀에 의한 누유분리 차단대책을 제안하고자 한다.

• Journal of Korea Multimedia Society
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• v.22 no.11
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• pp.1259-1268
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• 2019

Recently, Communication media have been developed for the underwater communication in underwater environments where the underwater communication failures occur frequently. Although the underwater communication by one medium is not stable due to the influence of the underwater environment, the use of various communication media can complement each other and so this makes the underwater communication more stable. For this reason, this paper proposes approaches to the design and implementation of integrated MAC for complementing individual unstable underwater communications. In addition this paper presents the comparison and analysis on each of the proposed approaches so to be able to provide guidelines to designers and implementers of integrated MAC.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.10a
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• pp.249-253
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• 1995

본 연구에서는 잠재적 응용성이 큰 ER유체와 압전필름을 액튜에이터로 하는 하이브리드형 지능구조물을 제안한 후 능동 진동제어를 실시하였다. 먼저 중공(hollow)의 샌드위치 형태 복합재료(glass/epoxy)보에 ER유체와 압전필름을 각각 삽입과 접착을 하여 하이브리드형 지능구조물을 제작하였다. 그리고 각 매체의 액튜에이팅 특성을 고려하여, ER유체 액튜에이터(ERFA)는 전장부하 함수로 도출되는 구조물의 주파수응답을 특징으로 하였고, 압전필름 액튜에이터(PFA)는 신경 슬라이딩 모드 제어기 (neuro sliding mode controller : NSC)를 적용하였다. 이 두 액튜에이터가 동시에 작동하는 능동 진동제어계를 실험적으로 구현한 후 과도응답과 강제 응답에 대한 진동제어 성능을 단일 액튜에이터 작동시와 비교 고찰하여 제시된 하이브리드 액튜에이팅의 효과를 입증하였다.