• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제23회 추계학술대회 논문집
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• pp.178-183
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• 2004

액체산소 탱크 내에서의 열적 성층화(thermal stratification) 현상은 대기로부터의 열 투입과 탱크 내에서의 극저온 액체의 열적 비평형에 의해 발생된다. 열적 성층화 현상은 벤트 시스템, 탱크 단열. 펌프 설계에 영향을 미치게 되므로 정교한 해석 및 시험적 검증이 필요하다. 본 논문에서는 side-wall에서의 열 투입에 의해 발생되는 경계층 유동을 해석적 방법으로 1차원 모델링하여 시간에 따른 성충화 부피의 증가 및 탱크 내에서의 높이에 따른 온도 분포를 묘사한다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.305-309
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• 2008

본 연구에서는 화염 안정기 형상이 램제트 연소실에서의 단열 막냉각 효율에 미치는 영향에 대하여 실험을 수행하였다. 램제트 연소실 입구의 경사진 확장면의 끝에 화염안정기 형상을 설치하여 세로축 화염안정기에 의해 발생된 난류 유동이 다단 슬롯에 영향을 끼치도록 실험 장치를 구성하였다. 화염 안정기를 설치하였을 경우 화염안정기에 의해 발생된 유동의 높은 전단력과 난류강도로 인해 급격히 주유동과 혼합되어 화염안정기가 설치되지 않은 경우에 비해 전체적으로 냉각 성능이 감소함을 결과를 통해 확인하였다. 또한 각각의 경우 분사율을 높여주면 좀 더 양호한 막냉각 효율을 기대할 수 있었다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.378-385
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• 2012

벤트 혼합기는 혼합기 후류에 존재하는 재순환 영역으로 공기를 유입시켜 연료-공기 혼합을 증대시키는 혼합기이다. Stereoscopic PIV기법을 통해 얻은 3차원 속도, 와류, 난류운동에너지를 토대로 계단형 혼합기를 기본 모델로 하여 벤트 혼합기의 성능을 분석하였다. 벤트 혼합기는 두터운 전단층으로 인해 높은 침투거리를 보였으며, 난류운동에너지는 주로 주유동과 제트유동의 경계면을 따라 분포하였다. 이 난류 영역은 혼합영역 내에서 활발히 물질전달을 일으키며, 혼합 증대를 가져온다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.905-917
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• 2008

Road or Railway construction over soft ground is needed to be considered on secondary consolidation which will be caused differential settlement, lack of transport serviceability, higher maintenance cost. Especially for the railway construction in the second phase of Gyung-Bu or Ho-Nam high speed railway, concrete slab track has been adapted as a safe and cost effective geotechnical solution. In this case controlling the total settlement under the tolerance is essential. And pile supported geogrid reinforced construction method is suggested as a solution for the problem of the traditional method on soft soil treatments. Pile supported geogrid reinforced construction method consists of piles that are designed to transfer the load of the embankment through the compressible soil layer to a firm foundation. The load from the embankment must be effectively transferred to the piles to prevent punching of the piles through the embankment fill creating differential settlement at the surface of the embankment. The arrangement of the piles can create soil arching to carry the load of embankment to the piles. In order to minimize the number of piles geogrid reinforced pile supported construction method is being used on a regular basis. This method consists of one or more layers of geogrid reinforcement placed between the top of the piles and the bottom of the embankment. This paper presents several methods of pile supported geogrid reinforced construction and calculation results from the several methods and comparison of them.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.918-927
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• 2008

The problems associated with constructing high-speed concrete track embankments over soft compressible soil has lead to the development and/or extensive use of many of the ground improvement techniques used today. Drains, surcharge loading, and geosynthetic reinforcement, have all been used to solve the settlement and embankment stability issues associated with construction on soft soils. Geosynthetic-reinforced embankment supporting piles method consist of vertical columns that are designed to transfer the load of the embankment through the soft compressible soil layer to a firm foundation and one or more layers of geosynthetic reinforcement placed between the top of the columns and the bottom of the embankment. In the paper, the evaluations of a seismic performance of geosynthetic-reinforced embankment piles for a ultra soft ground during earthquake were studied. the equivalent linear analysis was performed by SHAKE for soft ground. A seismic performance analysis of Piles was performed by GROUP PILE and PLAXIS for geosynthetic-reinforced embankment piles. Guidelines is required for pile displacement during earthquake. Conclusions of the studies come up with a idea for soil stiffness, conditions of pile cap, pile length and span.

• 설비공학논문집
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• 제16권10호
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• pp.942-951
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• 2004

This paper presents the results of a theoretical study of the effect of radiation during free convective laminar film boiling for methanol/water binary mixtures on an isothermal vertical wall at atmospheric pressure. With the well-known boundary layer theory as a basis, a theoretical model has been formulated into consideration for mass diffusion at liquid phase. The equations are numerically solved by a similarity method to investigate the effects of radiation emissivity on the surface with various parameters such as wall superheat and composition of more volatile component at liquid phase far from the wall. From the results, the distributions of the physical quantifies are investigated in both phases. New correlations are proposed to predict the heat transfer coefficient of binary mixtures. It is shown that the proposed correlations are in good agreement with numerical results and with Bromley's correlation within maximum $11\%$ errors. It is also found that as the wall superheat is increased, radiation effect becomes more important.

• 한국광학회지
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• 제12권5호
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• pp.394-400
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• 2001

다층 박막에서의 빛의 반사와 흡수 및 열전달 방정식을 수치해석적으로 풀어 광기록매체용 다층 박막의 광학적 특성과 열전달 특성을 알아보고 이 두 특성들을 모두 고려하여 광기록에 적합한 레이저의 출력 및 지속시간, 다층 박막 구조 상수를 제시하였다. 그 결과 레이저는 650 nm 파장을 기준으로 출력 18mW, 지속 시간 60 nm가 적당하였으며 박막 구조 상수는 ZnS-SiO$_2$140nm, Ge-Sb-Te 20 nm, ZnS-SiO$_2$20~30nm, Al-alloy 100~150 nm가 적당하였다.

• 상하수도학회지
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• 제33권3호
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• pp.205-213
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• 2019

Batch adsorption tests were performed to evaluate the applicability of adsorption kinetic model by using hydrogel chitosan bead crosslinked with glutaraldehyde (HCB-G) for Cu(II) as cation and/or phosphate as anion. Pseudo first and second order model were applied to determine the sorption kinetic property and intraparticle and Boyd equation were used to predict the diffusion of Cu(II) and phosphate at pore and boundary-layer, respectively. According to the value of theoretical and experimental uptake of Cu(II) and phosphate, pseudo second order is more suitable. On comparison with the value of adsorption rate constant (k), phosphate kinetic was 2-4 times faster than that of Cu(II) at any experimental condition indicating the electrostatic interaction between ${NH_3}^+$ and phosphate is dominated at the presence of single component. However, when Cu(II) and phosphate simultaneously exist, the value of k for phosphate was sharply decreased and then the difference was not significant. Both diffusion models confirmed that the sorption rate was controlled by film mass transfer at the beginning time (t < 3 hr) and pore diffusion at next time section (t > 6 hr).

• 한국재료학회지
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• 제28권12호
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• pp.758-762
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• 2018

The transfer characteristics of zinc tin oxide(ZTO) on silicon dioxide($SiO_2$) thin film transistor generally depend on the electrical properties of gate insulators. $SiO_2$ thin films are prepared with argon gas flow rates of 25 sccm and 30 sccm. The rate of ionization of $SiO_2$(25 sccm) decreases more than that of $SiO_2$(30 sccm), and then the generation of electrons decreases and the conductivity of $SiO_2$(25 sccm) is low. Relatively, the conductivity of $SiO_2$(30 sccm) increases because of the high rate of ionization of argon gases. Therefore, the insulating performance of $SiO_2$(25 sccm) is superior to that of $SiO_2$(30 sccm) because of the high potential barrier of $SiO_2$(25 sccm). The $ZTO/SiO_2$ transistors are prepared to research the $CO_2$ gas sensitivity. The stability of the transistor of $ZTO/SiO_2$(25 sccm) as a high insulator is superior owing to the high potential barrier. It is confirmed that the electrical properties of the insulator in transistor devices is an important factor to detect gases.

• 전기전자학회논문지
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• 제23권3호
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• pp.793-799
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• 2019

본 연구에서는 웨어러블 Fabric(Nylon) + MWCNT 가스센서 내부에서 열확산을 해석하기 위해서 요소해석 프로그램(comsol)을 이용하여 센서 내부에서의 열용량의 확산 과정과 열용량 분포 경도를 확인하였다. 열용량의 확산과정을 해석하기 위해서 가스센서의 구조체에 대하여 이차원으로 모델링을 진행하였으며, 제시된 모델링에 대해서 센서 구성 부분에 대한 특성값을 제시하여 메시 요소법(FEM)을 이용하여 설계된 웨어러블 가스센서에 대해서 열용량이 확산되는 정도와 열용량 경도를 구하기 위해서 지배방정식으로 1계 편미분방정식을 제안하여 해석하였으며, 열속도 전달식을 제안하여 전극층과 가스 검출부의 10[K/mm] 온도 경도를 구하였다.