• 한국지반환경공학회 논문집
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• 제22권12호
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• pp.71-77
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• 2021

국내의 공용 중인 도로의 연장의 증가와 함께 유지보수 비용 및 교통혼잡비용도 함께 증가하고 있는 추세이다. 도로의 유지보수 비용 및 소요시간의 단축을 위하여 기존에 지속가능한 장수명 모듈러 도로시스템이 제안되었다. 본 연구에서는 제안된 시스템의 하부구조인 맞춤형 지지모듈의 설계 및 성능평가를 수행하였다. 하중을 결정하고 형태가 다른 2가지의 맞춤형(Cross-Beam 형태) 지지모듈을 설계, 제작하였다. 제작한 맞춤형 지지모듈을 시공하고 성능이 더 우수한 형태의 지지모듈 선정을 위하여 정하중재하 시험을 진행하였다. 하중재하 시험 결과 두가지 형태의 맞춤형 지지모듈에서 측정된 최대 토압은약 158kPa 차이가 났으며, 최대 침하량은 약 0.032mm의 차이가 나타났다. 이러한 결과를 바탕으로 하부곡선형 Cross-Beam 형태의 맞춤형 지지모듈의 성능이 더 우수한 것으로 판단된다.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1999년도 PROCEEDINGS OF 99 INTERNATIONAL CONFERENCE OF THE KACG AND 6TH KOREA·JAPAN EMG SYMPOSIUM (ELECTRONIC MATERIALS GROWTH SYMPOSIUM), HANYANG UNIVERSITY, SEOUL, 06월 09일 JUNE 1999
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• pp.419-431
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• 1999

InP, III-V binary compound semiconductor, single crystal was grown by VGF (vertical gradient freeze) method using quartz ampoule and its electrical optical properties were investigated. Phosphorous powders were put in the bottom of quartz ampoule and Indium metal changed in conical quartz crucible hat was attached at the upper side position inside the quartz ampoule. It was vacuous under the pressure of 10-5 Torr and sealed up. In metal in the quartz crucible was melted at 1070$^{\circ}C$ and phophorous sublimated at 450$^{\circ}C$, there after it was diffused in In melt and so InP composition was formed. By cooling the InP composition melt (2$^{\circ}C$∼5$^{\circ}C$/hr of cooling rate) in range of 1070$^{\circ}C$∼900$^{\circ}C$, InP crystal was grown. the grown InP single crystals were investigated by X-ray analysis and polarized optical microscopy. Electrical properties of them were measured by Van der Pauw method. At the cooling rate of 2$^{\circ}C$/hr, its direction was (111), quality of the ingot ws better upper side of the ingot than lower. It was found that the InP crystals were n-type semiconductor and the carrier concentration, electron mobility and relative resistivity were 1015∼1016/㎤, 2x103∼3x104$\textrm{cm}^2$/Vsec and 2x10-1∼2x10-3Ωcm in the range of 150K∼300K, respectively.

• Nuclear Engineering and Technology
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• 제55권8호
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• pp.2997-3009
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• 2023

The Passive containment Air-cooling System (PAS) can effectively remove the decay heat of the modular small nuclear reactor after an accident. The details of natural convection around the dome, which is a key part of PAS, were investigated numerically in the present study. The thermal dynamics around the dome were studied through the temperature, pressure and velocity contours and the streamlines. Additionally, the formation of the buoyant plume at the top of the dome was investigated. The results show that with the increase of Ra, the lift-off point moves toward the bottom of the dome, and the eddy under the buoyant plume grows larger gradually, which enhances the heat transfer. And the heat transfer along the dome surface with different truncation angles was investigated. As the angle increases, the heat transfer coefficient becomes stronger as well. Consequently, a newly developed heat transfer correlation considering the influence of truncation angle for the dome is proposed based on the simulated results. This study could provide a better understanding of natural convection around the dome of PAS and the proposed correlation could also offer more predictive value in the improvement of nuclear safety.

• Nuclear Engineering and Technology
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• 제55권8호
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• pp.3017-3029
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• 2023

In the late in-vessel phase of a nuclear reactor severe accident, the internal heat transfer and crust evolution during the debris bed melting process have important effects on the thermal load distribution along the vessel wall, and further affect the reactor pressure vessel (RPV) failure mode and the state of melt during leakage. This study coupled the phase change model and large eddy simulation to investigate the variations of the temperature, melt liquid fraction, crust and heat flux distributions during the debris bed melting process in the hypothetical severe accident of HPR1000. The results indicated that the heat flow towards the vessel wall and upper surface were similar at the beginning stage of debris melting, but the upward heat flow increased significantly as the development of the molten pool. The maximum heat flux towards the vessel wall reached 0.4 MW/m². The thickness of lower crust decreased as the debris melting. It was much thicker at the bottom region with the azimuthal angle below 20° and decreased rapidly at the azimuthal angle around 20-50°. The maximum and minimum thicknesses were 2 and 90 mm, respectively. By contrast, the distribution of upper crust was uniform and reached stable state much earlier than the lower crust, with the thickness of about 10 mm. Moreover, the sensitivity analysis of initial condition indicated that as the decrease of time interval from reactor scram to debris bed dried-out, the maximum debris temperature and melt fraction became larger, the lower crust thickness became thinner, but the upper crust had no significant change. The sensitivity analysis of in-vessel retention (IVR) strategies indicated that the passive and active external reactor vessel cooling (ERVC) had little effect on the internal heat transfer and crust evolution. In the case not considering the internal reactor vessel cooling (IRVC), the upper crust was not obvious.

• 한국수소및신에너지학회논문집
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• 제34권4호
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• pp.350-357
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• 2023

In this study, the experimental investigation and theoretical analysis were conducted to verify the cooling capacity of the cryocooler used for pre-cooling of hydrogen gas. The effect of the flow rate on a copper pipe attached to the bottom of the cryocooler, which has a coil shape in a hydrogen line, was investigated. Temperature sensors were strategically placed at various positions on the cryocooler to analyze the temperature variations with respect to the flow rate. In this study, the thermal properties of hydrogen for the pressure and temperature were utilized using REFPROP to analyze the cooling capacity of the cryocooler. Based on the experimental results derived from this study, the cooling capacity of the cryocooler for pre-cooling hydrogen gas was considered by calculating the cooling temperature according to the flow rate through theoretical analysis.

• 한국의류학회지
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• 제46권4호
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• pp.657-671
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• 2022

This study aims to develop three dimensional (3D) yoga knee protectors that provide excellent wearing comfort. Three types of pads were modeled using 3D human data: two types of 3.0-cm-wide pads separated into top and bottom with thicknesses of 0.1 cm (TPU-1: A) and 0.2 cm (TPU-2: B); and one type with three 0.2-cm-thick separated panels (TPU-S: C). Based on these models, five knee protectors were developed using 3D patterning and 3D printing. Types A, B, and C were integrated with 0.6-cm neoprene pads. Type D was fabricated with a donut-shaped 0.6-cm neoprene pad inserted, while Type E consisted of two discrete 0.6-cm neoprene pads embedded in the protector's upper and lower sides. Wearing comfort was evaluated in terms of fit, pressure, and cushioning while in a standing and kneeling position and while in motion. The findings suggest that the fabricated knee protectors were evaluated as comfortable to the individuals with knee pain, rather than those without knee pain. The individuals with knee pain preferred the soft pads made of neoprene positioned around the knee (NEO-S: E), while those without knee pain favored the cushioned pads with a pattern structure maintained by thin 3D-printed pads (TPU-1: A).

• 자원환경지질
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• 제57권1호
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• pp.25-39
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• 2024

The Téra manganese deposit represents the most significant manganese mineralization discovered in Niger up today. The main host rocks of this ore are gondites, which are a garnet and quartz rich metamorphic rocks. The supergene weathering developed an alteration profile on these gondites. This study aims to identify the mineralogical composition of gondites and associated rocks, in order to highlight the origine of rocks and the manganese enrichment. The methodological approach adopted involved a field study followed by polarizing microscopic analysis using transmitted and reflected lights. Additionally, quantitative X-ray diffraction (XRD) analysis was performed to assess the manganese ore minerals present in the gondite and associated rocks, including mica schists, amphibolites, and quartzites. The petrographic study revealed a paragenesis characterized by the presence of kyanite, staurolites, garnets and plagioclases that are generally poikiloblasts with quartz and opaque minerals inclusions, emphasizing the internal schistosity which is planar, helicitic or microfolded. These features indicate a prograde metamorphism until high-pressure amphibolite facies conditions. These conditions are followed by greenschist facies conditions marked by calcite, epidote, muscovite, chlorite and muscovite assemblage which emphasizes the vertical tectonics. Depending on the alteration process, the manganese ore exhibit a granular texture at the bottom of the gondite hills, transitioning to a colloform texture towards the top, passing through the epigenization and replacement texture. The XRD analysis further revealed that the studied rocks originated from a volcano-sedimentary complex, characterized by alternating marly, arenaceous and pelitic sequences associated with submarine exhalations.

• 생물환경조절학회지
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• 제21권3호
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• pp.163-169
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• 2012

관비재배 및 수경재배시 비료를 녹일 때 소요되는 시간과 노동력을 절감하고, 작업의 안전성 확보와 자동화를 가능하게 할 수 있는 장치의 개발을 위해 본 실험을 실시하였다. 실험은 세 종류로 수행되었다. 먼저, 효과적인 비료용해 방법을 구명하기 위해 수중펌프를 양액 통 속에 두고 양액 통의 입구에 삼베포를 깐 거름망을 설치하여 물을 스프레이하여 비료를 녹이는 방법(Spray), 수중프로펠러를 이용하는 방법(Propeller), 수중펌프를 양액 통 속에 넣어 물의 흐름을 만들어 주는 방법(Submerged), 에어컴프레서를 이용하여 양액 통 속에 공기흐름을 만들어 비료를 용해하는 방법(Airflow) 등 4개의 처리를 두고 실험하였다. Spray 처리에서 가장 시간이 짧게 소요되는 것으로 조사되었으나 농가가 실제로 적용하는데 어려움이 있어서, Spray 처리 다음으로 비료를 녹이는 시간이 짧고, 노동력을 절감할 수 있으며 양액제조 과정을 자동화 하는 것이 용이할 것으로 사료되는 Airflow 처리를 선택하였다. 두 번째 실험에서는 Airflow 처리에서 사용한 재질과 분지관수를 개선한 6지관 및 8지관 장치를 제작하여 비교 실험했는데, 6지관 장치가 비료용해시간이 짧고, 양액탱크의 입구 크기에 관계없이 사용이 가능하며, 제작이 용이하여 가장 효과적인 장치로 판단되었다. 세 번째 실험에서는 개발된 6지관 장치를 이용하여 비료를 용해하는데 소요되는 시간을 조사하여 경제성을 분석하였는데, 농가에서 수중펌프를 이용하여 비료를 용해하는 방법보다 시간은 1/8배 절약할 수 있으며 경제성이 큰 것으로 나타났다. 아울러 $KNO_3$, $Ca(NO_3)_2{\cdot}4H_2O$, Fe-EDTA 등의 용해특성을 조사했다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.131.1-131.1
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• 2010

This study was conducted for engineering optimization for the gasification process which is the key factor for success of Taean IGCC gasification plant which has been driven forward under the government support in order to expand to supply new and renewable energy and diminish the burden of the responsibility for the reduction of the green house gas emission. The gasification process consists of coal milling and drying, pressurization and feeding, gasification, quenching and HP syngas cooling, slag removal system, dry flyash removal system, wet scrubbing system, and primary water treatment system. The configuration optimization is essential for the high efficiency and the cost saving. For this purpose, it was designed to have syngas cooler to recover the sensible heat as much as possible from the hot syngas produced from the gasifier which is the dry-feeding and entrained bed slagging type and also applied with the oxygen combustion and the first stage cylindrical upward gas flow. The pressure condition inside of the gasifier is around 40~45Mpg and the temperature condition is up to $1500{\sim}1700^{\circ}C$. It was designed for about 70% out of fly ash to be drained out throughout the quenching water in the bottom part of the gasifier as a type of molten slag flowing down on the membrane wall and finally become a byproduct over the slag removal system. The flyash removal system to capture solid particulates is applied with HPHT ceramic candle filter to stand up against the high pressure and temperature. When it comes to the residual tiny particles after the flyash removal system, wet scurbbing system is applied to finally clean up the solids. The washed-up syngas through the wet scrubber will keep around $130{\sim}135^{\circ}C$, 40~42Mpg and 250 ppmv of hydrochloric acid(HCl) and hydrofluoric acid(HF) at maximum and it is turned over to the gas treatment system for removing toxic gases out of the syngas to comply with the conditions requested from the gas turbine. The result of this study will be utilized to the detailed engineering, procurement and manufacturing of equipments, and construction for the Taean IGCC plant and furthermore it is the baseline technology applicable for the poly-generation such as coal gasification(SNG) and liquefaction(CTL) to reinforce national energy security and create new business models.

• 농업과학연구
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• 제23권1호
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• pp.25-38
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• 1996

연약지반상에 시공되는 용 배수로 굴착사면의 안정문제를 구명하기 위하여 굴착사면의 경사에 따른 지반의 거동을 한계평형법 및 유한요소법에 의하여 해석하고 실제 현장실험과 비교 분석한 결과 다음과 같은 결론을 얻었다. 1. 수로에서 수위를 급강하시켰을 때 과잉공극수압의 영향으로 균열이 발생하였고, 그 이후에 공극수압의 감소는 완만하게 나타났다. 2. 연직굴착시는 굴착폭이 클수록 균열의 폭도 커지고, 굴착깊이가 깊어지면서 진행성 파괴형태를 나타냈다. 3. 연약지반에서 소규모의 굴착공사를 할 때 최소안전율은 굴착사면의 경사(1:1, 1:1.5, 1:2)보다는 점착력(1.0, 1.5, 2.0, 2.5, $3.0t/m^2$)에 더 큰 영향을 받는 것으로 나타났다. 4. 굴착이 진행되면서 소성영역이 발달하는 상부사면에서는 침하가 발생하였으며, 굴착저면에서는 히빙현상이 나타났다. 5. 최대전단응력은 저부지반으로 갈수록 크게 나타났으며, 이와같은 현상은 인장영역을 발생시켜서 국부적인 파괴 가능성을 증가시킴을 알 수 있었다. 6. 최대전단변형은 굴착깊이에 따라 증가하며, 굴착저면에서 가장 큰값을 나타내고 굴착사면의 중앙저부에 집중되는 분포형태를 나타냈다.