• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.7
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• pp.38-45
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• 2020

A magnetically levitating capsule train, which runs inside the sub-vacuum tube, can reach ultra-fast speeds by dramatically reducing the aerodynamic drag and friction. The capsule train uses the superconductor electrodynamic suspension (SC-EDS) method for levitation. The SC-EDS method has advantages, such as a large levitation gap and free of gap control, which could reduce the infra-construction cost. On the other hand, disadvantages, such as the large variation of the levitation-guidance gap and small damping characteristics in levitation-guidance force, could degrade the running stability and ride comfort of the capsule train. In this study, a dynamic analytical model of a capsule train based on the SC-EDS was developed to analyze the running dynamic characteristics. First, as important factors in the capsule train dynamics, the levitation and guidance stiffness in the SC-EDS system were derived, which depend non-linearly on the velocity and gap variation. A 3D dynamic analysis model for capsule trains was developed based on the derived stiffness. Through the developed model, the effects of the different running speeds on the ride comfort were analyzed. The effects of a disturbance from infrastructure, such as the curve radius, tube sag, and connection joint difference, on the running stability of the capsule train, were also analyzed.

• Journal of the Korea Concrete Institute
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• v.19 no.2
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• pp.189-197
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• 2007

Concrete tunnel lining must be designed to having the fireproof performance because the lining are sometimes exposed to very high temperature due to traffic accident. Such fire temperature may cause explosion of concrete, or collapse of tunnel structure. The purpose of this study is to obtain the fundamental fireproof behavior of fire resistance-engineered cementitious composites(FR-ECC) under fire temperature in order to use the fire protection material in tunnel lining system. The present study conducted the experiment to simulate fire temperature by employing 2 types of FR-ECC and investigated experimentally the explosion and cracks in heated surface of these FR-ECC. Employed temperature curve were hydro carbon(HC, ECl) criterion, which are severe in various criterion of fire temperature. The numerical analysis is carried out the nonlinear transient heat flow analysis and verified against the experimental data. The complex features of behavior in fire conditions, such as thermal expansion, plasticity, cracking or crushing, and material properties changing with temperature are considered. By the use of analytical model, the concrete tunnel subjected to fire loads were analyzed and discussed. With comparison of current concrete materials and FR-ECC, the experimental and analytical results of FR-ECC shows the better fire resistance performance than the other.

• Journal of IKEEE
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• v.22 no.2
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• pp.495-498
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• 2018

In this paper, we propose an DAP system for dose evaluation of medical and industrial X-ray generator. Based on the DAP measurement technique using the Ion-Chamber, the proposed system can clearly measure the exposure radiation dose generated by the diagnostic X-ray apparatus. The hardware part of the DAP measures the amount of charge in the air that is captured by an X-ray. The high-speed processing algorithm part for cumulative radiation dose measurement through microcurrent measures the amount of charge captured by X-ray at a low implementation cost (power) with no input loss. The wired/wireless transmission/reception protocol part synchronized with the operation of the X-ray generator improves communication speed. The PC-based control program part for interlocking and aging measures the amount of X-ray generated in real time and enables measurement graphs and numerical value monitoring through PC GUI. As a result of evaluating the performance of the proposed system in an accredited testing laboratory, the measured values using DAP increased linearly in each energy band (30, 60, 100, 150 kV). In addition, since the standard deviation of the measured value at the point of 4 division was ${\pm}1.25%$, it was confirmed that the DAP showed uniform measurements regardless of location. It was confirmed that the normal operation was not less than ${\pm}4.2%$ of the international standard.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.2
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• pp.161-168
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• 2011

The heating, ventilating, air conditioning (HVAC) system is a very important part of an automotive vehicle: it controls the microclimate inside the passenger's compartment and removes the frost or mist that is produced in cold/rainy weather. In this study, the numerical analysis of the defrost duct in an HVAC system and the de-icing pattern is carried out using commercial CFX-code. The mass flow distribution and flow structure at the outlet of the defrost duct satisfied the duct design specification. For analyzing the de-icing pattern, additional grid generation of solid domain of ice and glass is pre-defined for conductive heat transfer. The flow structure near the windshield, streakline, and temperature fields clearly indicate that the de-icing capacity of the given defrost duct configuration is excellent and that it can be operated in a stable manner. In this paper, the unsteady changes in temperature, water volume fraction, and static enthalpy at four monitoring points are discussed.

• Clean Technology
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• v.23 no.4
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• pp.345-356
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• 2017

The composting is a biological process that converts organic matter into useful resources such as fertilizers. It is a continuous transition of microbial communities to adapt changes in organic matter and environmental conditions (carbonation rate, temperature, humidity, oxygen supply, pH, etc.). Most of the composting plants are located in the proximity of the residential areas. It is a general scenario where government authorities receive complaints from the local residents due to release of odor from the composting, and has become a social problem in Korea. Identification of dominant microorganisms, understanding change in microbial communities and augmentation of specific microorganism for composting is vital to enhance the efficiency of composting, quality of the compost produced, and reduction of odor. In this paper, we suggest the optimum operation conditions and methods for compost depot to reduce odor generation. The selection of the appropriate microorganisms and their rapid increase in population are effective to promote composting. The optimal growth conditions of bacteria such as aeration (oxygen), temperature, and humidity were standardized to maximize composting through microbial degradation. The use of porous minerals and moisture control has significantly improved odor removal. Recent technologies to reduce odor from the composting environment and improved composting processes are also presented.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2006.05a
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• pp.412-419
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• 2006

An Experimental study was conducted on $CO_{2}$ recycle combustion heating system using pure oxygen instead of conventional air as an oxidant, which is thereby producing a flue gas of mostly $CO_{2}$ and water vapor($H_{2}O$ and water vapor($H_{2}O$) and resulting in higher $CO_{2}$ concentration. The advantages of the system are not only the ability to control high temperatures characteristic of oxygen combustion with recycling $CO_{2}$ but also the possibility to reduce NOx emission in the flue gas. A small scale industrial reheating furnace simulator and specially designed variable flame burner were used to characterize the $CO_{2}$ recycle oxy-fuel combustion, such as the variations of furnace pressure, temperature and composition in the flue gas during recycle. It was found that $CO_{2}$ concentration in the flue gas was about 80% without $CO_{2}$recycle. The furnace temperature and pressure and pressure were decreased due to recycle and the NOx emission was also reduced to maintain under 100ppm.

• Journal of Bio-Environment Control
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• v.14 no.3
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• pp.218-231
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• 2005

This paper reviews the engineering approach needed to support humans during their long-term missions in space. This approach includes closed plant production systems under microgravity or low pressure, mass recycling, air revitalization, water purification, waste management, elimination of trace contaminants, lighting, and nutrient delivery systems in controlled ecological life support system (CELSS). Requirements of crops f3r space use are high production, edibility, digestibility, many culinary uses, capability of automation, short stems, and high transpiration. Low pressure on Mars is considered to be a major obstacle for the design of greenhouses fer crop production. However interest in Mars inflatable greenhouse applicable to planetary surface has increased. Structure, internal pressure, material, method of lighting, and shielding are principal design parameters for the inflatable greenhouse. The inflatable greenhouse operating at low pressure can reduce the structural mass and atmosphere leakage rate. Plants growing at reduced pressure show an increasing transpiration rates and a high water loss. Vapor pressure increases as moisture is added to the air through transpiration or evaporation from leaks in the hydroponic system. Fluctuations in vapor pressure will significantly influence total pressure in a closed system. Thus hydroponic systems should be as tight as possible to reduce the quantity of water that evaporates from leaks. And the environmental control system to maintain high relative humidity at low pressure should be developed. The essence of technologies associated with CELSS can support human lift even at extremely harsh conditions such as in deserts, polar regions, and under the ocean on Earth as well as in space.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.318-318
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• 2011

자연수를 가압(4~5기압)하면서 물과 공기의 비를 4:1~3:1로 혼합하면 수체 내 초미세기포(Diameter $3{\sim}10{\mu}m$)가 발생하는데 이를 산소용해수라 하며 수질정화시설 또는 양식장 등에 널리 사용되고 있다. 산소용해수의 특징은 기포의 비표면적이 넓고 10시간 이상 포화 농도를 유지하여 수체에 잔류하는 시간이 길기 때문에, 일반 산기석을 활용한 포기나 순산소 용해 등의 타 방법과 구별된다. 산소용해수의 산소전달효율은 기존 방법과 큰 차이를 보이기 때문에 실제 적용시에는 대상수를 이용하여 산소전달계수($K_{L}a$)를 사전에 산정할 필요가 있다. 본 연구에서는 한국건설기술 연구원의 안동 수자원 환경실험센터 내 실외형 콘크리트 사각반응수조에 산소용해장치 및 확산장치를 결합한 일체형 시스템을 적용시켜 2010년 9월~2011년 1월의 5개월간 결과를 분석, 본 장치의 $K_{L}a$를 산정 후 수질정화의 활용 면에서 검토하였다. $K_{L}a$의 산정에는 다양한 방법이 이용되나 용존 산소 농도의 제어에 한계가 있는 실외 대형실험장에 적합한 Lewis and Whitman의 Two-film 이론에 근거한 정상포기법을 적용하였다. 체적 $80m^3$의 수조 내에서 현장 유지용수를 대상으로 실험한 결과 산소전달계수는 $0.324\pm0.050$/min, 포화농도는 8.64 mg $O_2$/L, 도달시간은 11 /min이 산정되었으며, 이는 기존 산기석 포기의 산소전달계수 범위인 $0.105\pm0.019$ /min보다 약 3.1배 높은 결과를 보였다. 또한, 확산장치의 수류 순환 방향 및 정도를 검토하기 위하여 실험수조에서 1m단위로 격자를 구성한 후 초음파 유속계로 실측한 결과 0.0~2.5 m/s 의 평면적 유속범위를 도출하였다. 그리고 전체 순환을 고려했을 때 용존산소는 약 8시간 후 8.64 mg $O_2$/L 값에 도달하여 안정화 되었으며, 강한 수류순환과 산소용해수에 의해 하상에 존재하는 퇴적물들의 이송 및 산화촉진을 유도하였다. 이를 근거로 실험수조의 체적과 기준 가동시간인 8시간을 적용시켰을 때, 실험구 수질은 대조구와 비교하여 COD, T-N, T-P가 모두 25~35% 개선되었다. 이 결과는 여과공정 없이 단순 순환만을 고려한 물리적 수질정화 방법의 단독 활용 가능성을 나타내며, 기존 연구에서 나타난 SOD (Sediment oxygen demand) 저감 능력을 감안할 때 향후 폐쇄성 수역의 수질관리에도 효율적으로 활용할 수 있음을 시사한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.9
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• pp.643-651
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• 2020

A capsule train runs inside a sub-vacuum tube and can reach very high speed due to the low air resistance. A capsule train uses a superconducting electrodynamic suspension (SC-EDS) method for levitation, which allows for a large levitation gap and does not require gap control. However, SC-EDS has inherent characteristics such as the large gap variation and a small damping effect in the levitation force, which can degrade the running stability and ride comfort. To overcome this, a stability improvement device should be designed and applied based on dynamic analysis. In this study, a 1/10 small-scale testbed was developed to replicate the dynamic characteristics of a capsule train and investigate the performance of stability improvement devices. The testbed is composed of a 6-degree-of-freedom Stewart platform for the realization of bogie motion, a secondary suspension with a running stabilization device, and a carbody. Based on the dynamic similarity law proposed by Jaschinski, the small-scale testbed was manufactured, and a bogie motion algorithm was applied with the consideration of guideway irregularity and levitation stiffness. The experimental results from the testbed were compared with simulation results to investigate the performance of the testbed.

• Korean Journal of Environmental Agriculture
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• v.35 no.1
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• pp.46-54
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• 2016

BACKGROUND: The tobacco whitefly(Bemisia tabaci Gennadius) and western flower thrips(Frankliniella occidentalis Pergande) seriously damaged to several greenhouse crops and transmitted plant viruses such as the Tomato Yellow Leaf Curl Virus(TYLCV) and Tomato Spotted Wilt Virus(TSWV). Objective of this study was to elucidate exclusion effects of insect screen nets by various hole sizes and colors for control of the two insect pests in controlled environments such as a closed plant production system.METHODS AND RESULTS: The exclusion effects to various hole sizes of three other colors with 30 individuals of two insect pests was evaluated. B. tabaci was not showed not difference to different colors and sizes. F. occidentalis showed that 0.2 mm black screen was the most effective exclusion than other colors of 0.6 and 0.8 mm.CONCLUSION: The two insects were different reponses to various hole sizes of white and other color screen nets. It was proved that the 0.4 mm white screen net used in this experimental condition was suitable for exclusion of B. tabaci and 0.2 mm black forF. occidentalis.