• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.359-365
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• 2008

Turbopump test for a 30-ton-thrust liquid rocket engine was carried out using real-propellant. Liquid oxygen, kerosene, cold hydrogen gas were used for the oxidizer pump, the fuel pump, the turbine, respectively. The turbopump was run stably at the design and off-design conditions and the performance requirements were satisfied, which implies that the turbopump development at the engine subsystem level is successfully accomplished in the point of performance validation. This paper presents the results of a test where the turbopump was run for 75 seconds at three operating modes. In terms of performance characteristics of pumps and turbine, the results from turbopump assembly test using real-propellant showed a good agreement with those from the turbopump component tests using simulant working fluid.

• Journal of the Korean Institute of Gas
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• v.5 no.4 s.16
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• pp.8-20
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• 2001

Neoliberalism became a catch word of a post-cold war era. It began to develop in the middle of welfare state crisis in developed countries. It promoted both a unified world market through mutual penetration of national boundaries in International scene and maximization of efficiency through market competition in domestic scene. Privatization of public corporations is a major policy to pursue market efficiency through deregulation. Two reasons are often adduced to support the cause The socio-economic changes diminished the necessity to establish public corporation on the one hand. On the other hand gross inefficiency has been observed in the management of public corporation. 'Government failure' is an apt expression of the inefficiency. In analysing the experiences of privatization of utility industries of some other countries we found a couple of lessons for a Korean case. First, it is doubtful if privatization, that is a change in the form of ownership, is a necessary condition for achieving market efficiency. Because it is possible to operate a mechanism of market competition while maintaining competition among public corporations and with private actors. Second, the patron-agent dilemma is often cited as a major culprit of an inefficient management of public corporations. But it is without saying that the dilemma is also found in the management of private firms. So, the issue is not the privatization per se but to realize responsible management through discipline and incentives.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.1
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• pp.44-49
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• 2013

Hydrogen penetration into a metal leads to damages and mechanical degradations and its content measurement is of importance. For a precise measurement, a sample preparation procedure must be optimized through a series of studies on sample washing and drying. In this study, two-step washing with organic solvents and thermal soaking in inert gas were tried with a rod-shaped, API X65 steel sample. The samples were machined from a steel plate and then washed in acetone and etyl-alcohol for 5 minute each and dried with compressed air. After then, the samples were thermally soaked in a home-made nitrogen gas chamber during 10 minute at different heat gun temperatures from 100 to $400^{\circ}C$ and corresponding temperature range in the soaking chamber was from 77 to $266^{\circ}C$ according to the temperature calibration. Hydrogen residue in the samples was measured with a hot extraction system after each soaking step; hydrogen residue of $0.70{\pm}0.12$ wppm after the thermal soaking at $77^{\circ}C$ decayed with increase of the soaking temperature. By adopting the heat transfer model, decay behavior of the hydrogen residue was fitted into an exponential decay function of the soaking temperature. Saturated value or lower bound of the hydrogen residue was 0.36 wppm and chamber temperature required to lower the hydrogen residue about 95% of the lower bound was $360^{\circ}C$. Furthermore, a thermal desorption spectroscopy was done for the fully soaked samples at $360^{\circ}C$. Weak hydrogen peak was observed for whole temperature range and it means that hydrogen-related contaminants of the sample surface are steadily removed by heating. In addition, a broad peak found around $400^{\circ}C$ means that parts of the hydrogen residue are irreversibly trapped in the steel microstructure.

• Korean Journal of Construction Engineering and Management
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• v.24 no.6
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• pp.24-35
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• 2023

Recently, the Ministry of Land, Infrastructure and Transport presented the '6th Construction Technology Promotion Basic Plan' and 'Smart Construction Revitalization Plan (2022.7.20)'. Off-Site Construction (OSC), which involves construction and production of PC (Precast Concrete) and Modular, etc., has advantages in shortening the construction period, reducing costs, improving quality, reducing construction waste, and reducing safety accidents. However, the construction cost is high compared to the traditional RC construction method, which has hindered its utilization and spread. In this study, OSC utilization was improved. An economic analysis indicator and methodology that can support decision-making in the planning and design stages for multi-unit housing were proposed. The factors used in the economic analysis of OSC (based on the PC method) of apartment houses were reviewed. As for the indicators used in the cost and benefit section, 'Construction Period', 'Disaster Occurrence', 'Waste Generation', and 'Greenhouse gas Emission', which reflect the technical advantages of OSC, were derived. In addition, a scenario analysis was conducted based on actual apartment housing case data for the presented economic analysis indicators and benefit calculation standards. The level of benefit that offsets the difference between the existing RC construction method and the construction cost was reviewed. In future studies, it will be necessary to conduct additional case studies to apply the measurement criteria for detailed indicators and supplement the benefit indicators.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.610-616
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• 2020

Recently, the application of a photocatalyst to road structures is being attempted to solve environmental problems caused by fine particulate matter and automobile exhaust. The purpose of this study was to develop a release agent with GST (low-cost, high-performance photocatalyst produced from wastewater sludge). For this, the method of mixing and dispersing GST with the release agent was used first, and the removal performance of nitrogen oxide (NOx) was then checked. The best performance without a precipitation reaction was achieved using a stabilizing agent at 20 % in an outdoor exposure test for four weeks. The NO and NOx removal rate of the specimen demolded by applying the GST release agent developed in this study showed excellent effects of 200 to 400 % compared to the Plain material. To increase the performance of the GST release agent, it is necessary to improve the dispersibility of GST in the release agent and increase the amount of the nano-sized photocatalyst. In addition, the use of GST release agent in road structures and exposed concrete is expected to increase the NOx removal efficiency.

• Proceedings of KOSOMES biannual meeting
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• 2007.11a
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• pp.97-102
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• 2007

The piggery wastewater is the major source of the water pollution problem in the rural area. The treatment alternatives for piggery wastewater are limited by the characteristics of both high organic and nitrogen(N) content. In order to investigate an efficient N removal system, the thermophilic aerobic digestion process was examined. The experiment was investigated organic and nitrogen removal efficiency at various HRTs and air supply volume. The results of semi-continuous experiment indicated that a higher removal of the soluble portion of COD was achieved with the longer HRTs. However, the inert portion of COD in piggery wastewater was not much changed by thermophilic aerobic digestion. In addition, with the higher HRT of 3 days, up to 79% of NH4-N removal efficiency was achieved. Lower the HRTs, a decrease of NH4-N removal was founds. The gas samples from the lab reactor were analyzed along with the N content in influent and effluent. The N2O formation in our system indicates a novel aerobic deammonification process occurred during the thermophilic aerobic digestion. Both N02 and N03 were not presented in the effluent of thermophilic aerobic digester. With the HRT of 3 days, 36.4% of influent N(or 57.5% removal N) was aerobically converted to N2O gas. The ammonium conversion to N2O gas significantly decrease to 4.5% at low HRT of .05 day..

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.145-149
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• 2004

It is necessary for managing a perfect process for degasing aluminum molten metal according to the increase of a grade of aluminum and its alloy products. There are some methods that have been used to manage a degasing process in recent years, such as an injection method that uses aluminum molten metal powder and chemicals supplier and input method that supplies argon and nitrogen, or chlorine gas by using a gas blow-tube. However, these methods show some problems, and it shows that it is a difficult process to handle. pollution due to the producing a lot of toxic gases like chlorine and fluoride gas. irregular effects, and lowering work efficiency due to the excessive processing time. The problems that are the most fatal are the producing a lot of sludge due to the reaction of aluminum molten metal with chemicals. loss of metals, and decreasing the life of refractory materials. In order to solve these problems. this paper develops a technology that is related to aluminum continuous casting molten metal and monolithic degasing apparatus. A degasing apparatus developed in this study improved the exist ing methods and prevented environmental pollution wi th smokeless. odor less, and harmlessness by using a new method that applies argon and nitrogen gas in which the methods used in the West and Japan are eliminated. The developed method can significantly reduce product faults that are caused by the production of gas and oxidation because it uses a preprocessed molten metal with chemicals. In addition. the amount of the produced sludge can also be reduced by 60-80% maximum compared with the existing methods. Then. it makes it possible to minimize the loss of metals. Moreover. the molten metal processing and settling time is also shortened by comparing it with the existing methods that are applied by using chemicals. In addition, it does much to improve the workers' health, safety and environment because there is no pollution. The improvement of productivity and prevent ion effects of disaster from the results of the development can be summarized as follows. It will contribute to the process rationalization because it does not have any unnecessary processes that the molten metal will be moved to an agitator by using a ladle and returned to process for degasing like the existing process due to the monolithic configuration. There are no floating impurities due to the oxidation caused by the contact with the air as same as the existing process. In addition. it can protect the blending of precipitation impurities. Because it has a monolithic configuration. it can avoid the use of additional energy to compensate the temperature decreasing about 60t that is caused by the moving of molten metal. It is not necessary to invest an extra facilities in order to discharge the gas generated from a degasing process by using an agitator. The working environment can be improved by the hospitable air in the factory because the molten metal is almost not exposed in the interior of the area.

• Journal of Chest Surgery
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• v.32 no.10
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• pp.874-882
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• 1999

배경: 체외순환 후의 부종현상 및 이에 따른 여러 장치의 기능 저하를 방지하기 위하여, 최근에 체외 순환 이탈 후 환자의 혈액을 짧은 시간에 관류하여 여과해 주는 변형 초여과법의 사용이 늘고 있다. 이에 대한 긍정적인 임상결과들의 보고도 있으나, 다른 한편 체외 순환 후 염증반응을 포함한 폐손상의 기전에 혈구 성분의 영향이 보고되고 있는 바, 변형 초여과법의 효과, 특히 폐 조직에 대한 영향을 밝혀 보고자 하였다. 대상 및 방법: 몸무게 15에서 22 Kg(평균 16.5$\pm$0.5)의 16 쌍의 잡견을 이용한 정소성 심장이식, 실험에서, 통상적인 인공심폐기 작동군과 인공심폐기 작동 후 변형 초여과 관류를 시행한 군으로 무작위 구분하였다. 변형초여과법은 체외순환 정지 후에 대동맥관에서 나온 혈류를 Roller pump를 거쳐 Amicon Diafilter 초여과 관에 150 mL/m 정도의 속도로 10~15 분 정도 관류시켜 정맥관을 통하여 우심방에 직접 주입하였다. 혈액 채취 및 폐생검은 심폐기 시작 전과 정지 직후, 그리고 변형초여과 시행 군은 초여과 완료 직후에, 대조군은 심폐기 정지 10~15분 후에 각각 시행하였다. 혈류역학 측정요소는 동맥압, 우심방압, 좌심방압 등이었으며, 혈액 검사 항목은 동맥혈 가스분석, 혈색소 농도, 헤마토크릿, 백혈구 수, 혈소판 수, 혈중 단백 성분, 알부민 성분 등이었다. 폐 생검 조직으로는 냉동 건조법을 이용한 수분 함유량을 측정하였고, 광학 및 전자현미경으로 관찰을 하였다. 결과: 변형 초여과 군에서 혈중 혈색소 농도는 수술전 10.3$\pm$1.7 mg/dL, 심폐기 정지 직후 6.3$\pm$1.7 mg/dL, 초여과 직후는 8.3$\pm$2.8 mg/dL의 변화를(p=0.0078, 0.0117), 혈중 총 단백질의 농도 변화는 4.3$\pm$0.9, 3.1$\pm$1.5, 4.1$\pm$1.6 mg/dL, 혈중 알부민의 농도는 1.9$\pm$0.5, 1.4$\pm$0.7, 1.8$\pm$0.8 mg/dL로서, 각각 초여과법의 시행 전후에 유의한 증가를 가져왔고(p=0.0280, 0.0277), 폐조직의 수분 함유량의 변화는 수술전 75.1$\pm$8.6%, 심폐기 정지 직후 82.8$\pm$6.0%, 초여과 직후 77.88%를 보인 반면, 대조군에서는 각각 74.7$\pm$4.9, 82.1$\pm$5.9, 82.3$\pm$5.1%의 변화를 보였다. 미세 구조의 관찰에서, 폐포의 내포세피의 융합 기저막층과 미토콘드리아에서의 부종은 변형 초여과 후에 급격히 감소하였으나, 미토콘드리아내 크리스티의 파괴성 변화와 막성 파괴 성향이 초여과 후에 심화되게 관찰되었고, 세포질 내 소체의 팽창과 공포화 현상도 심폐기 가동 후 발생하여 초여과 후에 더 심화되게 관찰되었다. 세포질 내 소체의 팽창과 공포화 현상도 심폐기 가동 후 발생하여 초여과 후에 더 심화되게 관찰되었다. 폐조직 내의 백혈구는 심폐기 작동 후에 그 수에 있어서 증가하였으며 백혈구의 괴변, 탈과립 정도도 심폐기 작동 후 및 초여과 후에 증가한 소견을 보였다. 결론: 변형 초여과법은 인공 심폐기 후의 혈색소 농도 및 혈중 단백질 농도의 복원에 효과가 있었으며 변형 초여과 관류후 폐의 미세 조직내에서 부종의 급격한 감소 등을 관찰할 수 있었다.

• Journal of the Korean Magnetics Society
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• v.25 no.4
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• pp.111-116
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• 2015

Practical difficulty in the HDDR (hydrogenation - disproportionation - desorption - recombination) processing of Nd-Fe-B-type alloy is a poor reproducibility of coercivity of the HDDR-treated material. In an attempt to improve the reproducibility of coercivity of the HDDR-treated $Nd_{12.5}Fe_{80.6}B_{6.4}Ga_{0.3}Nb_{0.2}$ alloy, the hydrogen decrepitation was carefully controlled so as to induce more extensive micro-cracks in the particle. Prior to the hydrogenation and disproportionation reaction of HDDR processing, an additional hydrogen degassing was carried out at an elevated temperature of $600^{\circ}C$ under vacuum for the previously hydrogen decrepitated particle. During the additional hydrogen degassing the lattice of hydrogen absorbed $Nd_2Fe_{14}B$ phase was further shrunken, hence more microcracks were introduced in the particle due to its brittle nature. Particles with more micro-cracks had more homogeneous hydrogen absorption and desorption reaction during the HDDR-treatment. The improved reproducibility of coercivity of the HDDR-treated material was attributed to the improved homogeneity of the HDDR reactions due to the presence of more micro-cracks.

• Korean Journal of Construction Engineering and Management
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• v.23 no.6
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• pp.30-42
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• 2022

OSC is a type of supply chain and value chain that spans the entire process of construction production (planning, design, construction, maintenance, etc.). It is a method of producing the final object by manufacturing it in a factory, transporting it to the site, installing and construction. This research as is the construction cost was compared for each case A, which applied the PC method, and case B, which applied the RC method. In the case of applying the PC method (excluding the PC design cost), compared to the case where only the RC method was applied, the frame construction cost per unit quantity (m³) increased by about 70% (50% based on the total RC construction type). Of the total frame construction cost of PC method application, PC accounted for 90.2%, 'PC manufacturing cost' 54.8%, 'PC assembly cost' 28.5%, and 'transportation cost' accounted for 6.89%. Also a decision-making framework that can consider both costs and benefits was established. In the case of benefits, the construction period, defect repair, disaster occurrence, energy efficiency, noise/dust/waste, and greenhouse gas emission indicators reflecting OSC technical advantages were presented. It can contribute to providing a basis for helping decision-making on the introduction of PC apartment houses using OSC.