• Journal of Mechanical Science and Technology
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• 제15권12호
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• pp.1711-1727
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• 2001

Heat transfer coefficient were measured and new correlations were developed for two-phase heat transfer in a horizontal pipe for different patterns. Flow patterns were observed in a transparent circular pipe (2.54 cm I. D. and L/D=96) using an air/water mixture. Visual identification of the flow patterns was supplemented with photographic data and the results were plotted on the flow regime map proposed by Taitel and Dukler and agreed quite well with each other. A two-phase heat transfer experimental setup was built for this study and a total of 150 two-phase heat transfer data with different flow patterns were obtained under a uniform wall heat flux boundary condition. For these data, the superficial Reynolds number ranged from 640 to 35,500 for the liquid and from 540 to 21,200 for the gas. Our previously developed robust two-phase heat transfer correlation for a vertical pipe with modified constants predicted the horizontal pipe air-water heat transfer experimental data with good accuracy. Overall the proposed correlations predicted the data with a mean deviation of 1.0% and an rms deviation of 12%.

• 에너지공학
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• 제12권2호
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• pp.74-83
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• 2003

APR1400과 같은 차세대 원자력발전소에서는 원자로 안전성을 증진시키기 위하여 SDVS와 같은 계통을 도입하고 있다. 완전급수상실사고와 같은 경우는 POSRV가 개방되어 수조내 Sparger를 통하여 증기가 방출·응축되게 된다 증기가 응축함에 있어서 설계에서 고려해야 될 사항은 하중과 수조 혼합이며 증기제트 응축의 물리적 현상 이해를 통하여 적절한 대처를 마련할 수 있다. 수조내 Sparger를 통하여 분사되는 증기 응축에 대하여 하중과 수조 혼합 검토에 도움이 될 수 있도록 증기제트 응축의 물리적 현상 이해에 대한 검토와 평가를 수행하였다.

• 동력기계공학회지
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• 제18권3호
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• pp.79-86
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• 2014

Mixed convective vortex flow in the three-dimensional rectangular channel filled with high viscous fluid(Pr=909) is investigated computationally under various operating conditions. The Reynolds number is varied from 0 to $5{\times}10^{-1}$, the Rayleigh number from $10^3$ to $5{\times}10^4$. The three-dimensional governing equations are discretized using the finite volume method. The effects of Reynolds number and Rayleigh number are presented and discussed. From a parametric study, it is found that vortex flow pattern of mixed convection in rectangular channels can be classified into three flow patterns basically, but the new vortex flow structures containing wave rolls are found, which are affected by Rayleigh number and Reynolds number. From this results, we can draw a flow regime map to delineate various vortex flow patterns in the high viscosity fluid mixed convective flow.

• 대한기계학회논문집
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• 제14권5호
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• pp.1290-1299
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• 1990

본 연구에서는 이러한 개념을 확장하여 직경이 26nm와 38nm인 두 개의 수평관 내 기액 2상유동에서 오리피스의 차압교란치의 확률밀도함수, 자기상관함수와 파워 스 펙트럼 밀도함수를 구하여 유동양식에 따른 이 들 통계치의 특성을 구명하였다. 본 연구에서 다룬 유동양식은 기포, 플러그, 슬러그, 성층, 파상, 환상, pseudo-slug 유 동이다. 이 결과 차압교란치의 통계적 해석을 통한 유동양식 판별법이 매우 유용하 다는 사실을 밝혔으며, 또 본 판별법을 관내 압력강하치의 통계적 해석을 통하여 유동 양식을 구분한 타 연구자들의 방법과 비교 분석하였다.

• 한국연소학회지
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• 제5권2호
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• pp.19-27
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• 2000

A turbulent combustion model, based on edge flame dynamics, is discussed in order to predict global extinction of turbulent flames. The model is applicable to the broken flamelet regime of turbulent combustion, in which global extinction of turbulent flame is achieved by gradual expansion of flame holes. The edge flame dynamics is the key mechanism to describe the flame hole expansion or contraction. For flames with Lewis numbers near unity, there is a $Damk{\ddot{o}}hler$ number, namely the crossover $Damk{\ddot{o}}hler$ number, at which edge flame changes its direction of propagation. The parametric region between the quasi-steady extinction condition and the edge-flame crossover condition is a metastable region, in that flames without edge can stay in their burning states while flames with edge have to retract to expand quenching holes. Using the above properties of edge flame, Hartley and Dold proposed a Lagrangian hole dynamics, which allows us to simulate transient variation of quenching holes. In their model, each stoichiometric surface is subjected to a random sequence of scalar dissipation rate compatible to the equilibrium turbulence. Then, each stoichiometric surface will evolve, according to the combustion map, dependent on the scalar dissipation rate and existence of flame edge, If all the burning surfaces are annihilated, the event can be declared as a global extinction. The consequence obtained from the above model also can be used as a subgrid model to determine local extinction occurring in a calculation grid.

• 한국해안해양공학회지
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• 제6권3호
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• pp.290-297
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• 1994

연근해에서의 위성고도계자료의 정확도가 향상됨에 따라 기존에 알려진 Schwiderski의 모형보다 더 정확한 조석모형으로 위성고도계자료에서의 조석성분에 대한 보정을 향상시킬 필요가 있다. 벵갈만은 방글라데시 연안북측에서 발생하는 폭풍해온과 조석의 영향을 현저히 받는 해양특성으로 인해 해양학적 측면에서 관심이 고조되고 있어 초기단계로 벵갈만 전체에 대해 1/4$^{\circ}$ 격자체계의 조석모형을 수립하여 반일주조 (M$_2$, S$_2$, $N_2$, $K_2$)와 일주조 (K$_1$, $O_1$, P$_1$)에 대한 수치모형실험이 이루어졌다. 계산결과들은 기존의 Schwiderski의 조석도 및 관측자료들과의 비교ㆍ검토가 이루어졌다.

• Nuclear Engineering and Technology
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• 제51권5호
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• pp.1231-1240
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• 2019

Unlike land-based nuclear power plants, a marine or floating reactor is affected by external forces due to ocean conditions. These external forces can cause additional accelerations and affect each system and equipment of the marine reactor. Therefore, in designing a marine reactor and evaluating its performance and stability, a thermal hydraulic safety analysis code is necessary to consider the thermal hydrodynamic effects of ship motion. MARS, which is a reactor system analysis code, includes a dynamic motion model that can simulate the thermal-hydraulic phenomena under three-dimensional motion by calculating the body force term included in the momentum equation. In this study, it was verified that the dynamic motion model can simulate fluid motion with reasonable accuracy using conceptual problems. In addition, two modifications were made to the dynamic motion model; first, a user-supplied table to simulate a realistic ship motion was implemented, and second, the flow regime map determination algorithm was improved by calculating the volume inclination information at every time step if the dynamic motion model was activated. With these modifications, MARS could simulate the thermal-hydraulic phenomena under ocean motion more realistically.

• 영어영문학
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• 제54권4호
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• pp.443-459
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• 2008

This paper examines the discourse of masturbation in modern England and aims to re-draw the map of male sexuality related to such issues as nation, empire, family, and economy. It argues that the discourse of masturbation in modern England reflects national anxieties for the future of empire and an economic concern for unproductive sexual behavior, which were the main factors to transform masturbation into "solitary vice." The anxieties about empire and British dominance were constituted as the core of the anti-masturbation discourse on the boys. The imperial destiny was regarded to depend on the protection of the middle- and upper-class boys from the harmful psychological and physiological effects of masturbation represented in Lawrence's "The Rocking-Horse Winner." In the case of a single male, the concern for masturbation is constructed as a concern about economy, family, and human solidarity. As seen in Eliot's Silas Marner, the act of masturbation was condemned as the fulfillment of illegitimate sexual desire outside the familial sphere and a commercial economy, and thus without the possibility of human community. Silas Marner and Meredith's The Ordeal of Richard Feverel show the ways of reconstituting sexual others as normalized subjects: Boys were forced to be asexual through the regime of surveillance; and a single male was required to enroll in a remedial course on familial respectability.

• Nuclear Engineering and Technology
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• 제54권3호
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• pp.826-833
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• 2022

A two-phase natural circulation test using SMART integral test loop (SMART-ITL) was conducted to explore thermo-hydraulic phenomena of two-phase natural circulation in the SMART reactor. Specifically, the test examined the natural circulation in the primary loop under a stepwise coolant inventory loss while keeping the core power constant at 5% of the scaled full power. Based on the test results, three flow regimes were observed: single-phase natural circulation (SPNC), two-phase natural circulation (TPNC), and boiler-condenser natural circulation (BCNC). The flow rate remained steady in the SPNC, slightly increased in the TPNC, and dropped abruptly and maintained in the BCNC. Using a natural circulation flow map, the natural circulation characteristic in the SMART-ITL was compared with those in pressurized water reactor simulators. In the SMART-ITL, a BCNC regime appeared instead of siphon condensation and reflux condensation regimes because of the use of once-through steam generators.

• 환경정책연구
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• 제14권4호
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• pp.3-21
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• 2015

Post-2020 합의를 위해 주요 이슈로 부상하는 MRV(Measurement, Reporting, Verification)에 대한 국제적 상황을 분석하고, 선제적 효과적으로 대응할 수 있는 우리나라 전략을 수립 제시하는 것이 필요한 시점이다. 이에, MRV 체계 대안으로서 1) 이원화(Dual) MRV, 2) 통합(Unified) MRV를 분석 검토하였다. 분석 결과, 국가별 상황 및 능력에 따라 차별화하여 유연성을 부여하는 통합 MRV 체계가 가장 합리적이고, 실현 가능한 대안으로 판단되었다. 통합 MRV 체계 수립을 위해서 첫째, 우리 정부 내부적으로 통합 MRV 체계에 대한 합의, 둘째, 통합 MRV의 수립형태 및 적용 방안에 대해 예측 가능토록 방법과 내용의 구체화, 셋째, 개도국이 납득할 수 있도록 MRV 수준의 다양성 보장 방안에 대한 청사진(유연성에 대한 구체적 계획) 제시, 넷째, 개도국의 MRV 수준 제고를 위해 역량 배양을 위한 구체적 지원 방안 제시, 다섯째, 통합 MRV 도입을 위한 로드맵 개발 제시가 필요하다. 이를 추진하는 과정에서 우리나라는 선진국과 개도국 간 합리적 조정자로서 신기후체제가 합의에 도달하는 데 주도적 역할을 담당해야 한다.