• Geomechanics and Engineering
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• 제38권5호
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• pp.497-505
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• 2024

The power plant is a major infrastructure composed of essential machinery such as Turbine Generators (TG), Heat Recovery Steam Generators (HRSG), etc. Particularly, Combined Heat & Power Plants (CHP) are highly efficient power plants that simultaneously produce heat and electricity. Recently, cases have emerged where railway tunnels are being constructed beneath such power plants due to the underground development of urban rail transportation. Therefore, there is a pressing need to assess the impact of vibrations induced by blasting excavation during the construction of railway tunnels beneath the power plant, as well as the vibrations during railway operation, on the major machinery foundations and structures within the power plant. In this study, criteria for evaluating the vibration impact on key vibration-sensitive structures are summarized, and evaluation standards based on international criteria are established. Based on this, the study examines the vibration impact during the blasting excavation method of NATM tunnels beneath the operational power plant. Furthermore, subsequent railway operation, specifically focusing on the impact of train vibrations on Turbine foundations, Pump foundations, and District Heating pipelines using 3D dynamic numerical analysis. The results indicate that vibration values corresponding to up to 97.3% of the evaluation criteria are derived based on the numerical analysis. However, considering the significance of power plant-related structures, additional measures to reduce vibrations are proposed, including further test blasting, alteration of blasting patterns, reducing the charge per delay, or decreasing advance.

• 한국수소및신에너지학회논문집
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• 제35권4호
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• pp.428-436
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• 2024

Liquid hydrogen, which operates in cryogenic environments has a density 800 times greater than gaseous hydrogen, making it advantageous for large-scale storage and transportation. However, continuous evaporation due to external heat intrusion and internal heat generation poses challenges. To mitigate heat conduction, various insulation materials are used. In pipe systems, viscous heating effects from turbulence and viscosity, especially in bends, cause heat generation. This study employs computational fluid dynamics (CFD) to analyze the impact of fluid velocity, pressure drop, inner diameter, and curvature radius of pipe bends on viscous heating. Using liquid nitrogen at 77 K as a working fluid, the CFD results showed that increased velocity and pressure drop along with smaller inner diameter and curvature radius enhanced viscous heating, raising fluid temperature.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2989-2994
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• 2007

Gas hydrates are ice-like crystalline compounds that form under low temperature and elevated pressure conditions. Although hydrate formation can pose serious flow-assurance problems in the gas pipelines or facilities, gas hydrates present a novel means for natural gas storage and transportation with potential applications in a wide variety of areas. An important property of hydrates that makes them attractive for use in gas storage and transportation is their very high gas-to-solid ratio. In addition to the high gas content, gas hydrates are remarkably stable. The main barrier to development of gas hydrate technology is the lack of an effective method to mass produce gas hydrate in solid form. The first objective of this study is investigating the characteristics of gas hydrate formation related to several factors such as pressure, temperature, water-to-storage volume ratio, concentration of SDS, heat transfer and whether stirred or not respectively. And the second objective is clarifying the relation between the formation efficiency and each factor in order to find the proper way or direction to improve the formation performance.

• KIEAE Journal
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• 제13권2호
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• pp.131-139
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• 2013

The aim of this dissertation is establishing internal indicator list for achieving policy goal of Carbon Neutrality Green City. First of all, it started to construct the basic system of planning indicator based on through comprehension of current studies such as advanced researches, government guidelines and green building certifications. And then it was set up final indicator list through inspecting FGI (Focus Group Interview), Verification of suitability, and Analysis of importance). As a result of this research, the planning indicator divided three steps and there were classified four fields in the top-level; Green Land and Ecology, Green Energy, Green Resource and Transportation, Green Living and Institution. According to the data, it deducted four items (ratio of green land, site plan, heat island and management of climate, base of nature ecology) and twelve index in the field of green land and ecology, three item(energy conservation and self-supporting, energy efficiency, new regeneration energy) and twelve index in the field of green energy and regeneration, five items(water resources utilize and circulation, other resource reduction and circulation, public transportation, green transportation plan) and fifteen index. Totally, Planning Indicators of forty nine were deducted. Therefore, there was the result of importance analysis that the indicators of plan and maintain management as the side of space for carbon neutrality were more appreciated than carbon reduction of individual building.

• 한국압력기기공학회 논문집
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• 제19권2호
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• pp.163-170
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• 2023

Since spent nuclear fuel assemblies (SFA) are transported to interim storage or final disposal facility after cooling the decay heat, finite element analysis (FEA) with simplification is widely used to show their integrity against cladding failure to cause dispersal of radioactive material. However, there is a lack of research addressing the comprehensive impact of shape and element simplification on analysis results. In this study, for the optimization of a typical pressurized water reactor SFA, different types of finite element models were generated by changing number of fuel rods, fuel rod element type and assembly length. A series of FEA in use of these different models were conducted under a shock load data obtained from surrogate fuel assembly transportation test. Effects of number of fuel rods, element type and length of assembly were also analyzed, which shows that the element type of fuel rod mainly affected on cladding strain. Finally, an optimal finite element model was determined for other practical application in the future.

• 설비공학논문집
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• 제26권9호
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• pp.434-440
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• 2014

Experiments were performed to verify if performance and characteristic curves obtained from the temperature differential defrosting method, where surface temperature is measured to judge defrosting condition, can be reproduced by the photoelectric technology where defrosting condition is judged by photoelectric sensors. The output voltage of a phototransistor and heating capacity, power consumption, and surface temperature of the outdoor heat exchanger are compared. The results showed that the photoelectric sensors can be used as a defrost control device. On-off control timings in temperature differential defrosting method are in good agreement with those predicted by the high and low threshold output voltages of the photoelectric sensor.

• 한국수소및신에너지학회논문집
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• 제23권5호
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• pp.551-558
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• 2012

Due to high oil prices and global warming problems, researching an alternative energy source and decreasing the energy usage will be the key in the future. Unlike other alternative energy sources, geothermal energy is less dependent on the surrounding environment. Geothermal energy is the ideal energy source for buildings due to the simple and space saving installation. The system is semi permanent once it is installed and this will help reduce the energy usage in controlling the climate in buildings. Geothermal energy does not emit carbon dioxide and other gases that are harmful to the environment. Therefore geothermal energy will be the key in solving high oil prices and a decrease in fossil fuels by applying the geothermal energy system to homes to counter future energy crisis.

• Progress in Superconductivity
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• 제3권1호
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• pp.115-119
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• 2001

For the fabrication of HTS power cable, multifilamentary Bi-2223/Ag tapes have been prepared using the powder-in-tube (PIT) process. After final heat treatment, these tapes have $I_{c}$ value of 43A, and$ J_{c}$ value of $28,000A/\textrm{cm}^2$(77K, 0T). Prototype 1000A class multistrand conductor(length~1m) was fabricated using these tapes(length~300m). This multistrand conductor was impregnated with low-temperature epoxy. The transportation properties of prototype 1000A class multistrand conductor has been evaluated at 77K, and yielding a current capacity up to 1200A.A.A.

• 한국산학기술학회논문지
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• 제17권4호
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• pp.766-771
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• 2016

본 연구에서는 저심도 도시철도시스템 구축시 건설비용의 절감을 위하여 산업부산물인 고로슬래그 미분말과 플라이애쉬로 결합재의 일부를 대체하고, 급냉 전기로 산화슬래그를 잔골재의 대체재료로 사용한 저탄소 친환경 콘크리트와 우수한 조기강도 확보와 양생비용 절감을 위한 마이크로웨이브 발열거푸집으로 제작한 PC BOX의 장기내구성 평가를 수행하였다. 평가결과, 초기강도는 발열양생 조건이 증기양생 조건에 비해 다소 높게 나타났지만 장기재령 강도는 거의 대등한 것으로 나타났다. 또한 화학저항성 및 동결융해 저항성 평가 결과, 재령별 발열 및 증기양생을 통해 제작된 PC BOX의 성능차이는 없는 것으로 나타났으며, 염소이온침투성 평가 결과 역시 발열 및 증기양생 PC BOX 모두 매우 낮은 등급의 수준을 확보하는 것으로 나타났다. 따라서 저탄소 친환경 콘크리트와 발열양생시스템을 적용하여 저심도 철도시스템용 PC BOX를 제작할 경우, 기존 증기양생방법과 대등한 내구성능을 확보할 수 있어 저비용의 저심도 철도시스템 콘크리트 인프라 구축에 기여할 수 있으며, 또한 증기양생 시 사용되는 화석연료의 사용량을 제로화해 이산화탄소 배출 및 환경부하를 저감할 수 있을 것으로 기대된다.

• 한국지구과학회지
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• 제30권6호
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• pp.709-720
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• 2009

보수성 포장재가 지표면 열수지와 중규모 순환장에 미치는 영향을 파악하기 위하여 수치실험과 야외 관측을 실시하였다. 수치실험에 이용된 모형은 LCM(Local Circulation Model)이며, 야외 관측은 대기가 안정되어 날씨가 맑은 2007년 7월 19일 실시되었다. 야외 관측실험에서 보수성 포장재 지표면 온도의 최대치는 1430 LST에서 $41.2^{\circ}C$이고, 보수성 재료가 도포되어 있지 않은 일반 아스팔트보다 $16.1^{\circ}C$ 낮게 관측되었다. 수치실험에서는 증발효율 0.3을 가정한 case BET03에서 관측과 가장 유사한 값을 나타내었다. 이때 현열과 잠열플럭스는 각각 227 와 229 $W/m^2$이다. 수치실험 결과, 보수성 포장재는 낮은 지표면 온도, 혼합고와 관련된 잠열플럭스를 높이는 경향이 나타난다. 보수성 포장재에 의한 잠열플럭스의 불연속은 교외풍과 같은 중규모 순환장의 발달을 강화시키는 역할을 한다.