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최서원,백영호,김두연,강호철,Choe, Seo-Won,Baek, Yeong-Ho,Kim, Du-Yeon,Gang, Ho-Cheol 대한기계학회 1997 大韓機械學會論文集B Vol.21 No.1
Heat-transfer enhancement is seeked through modifications of fin surface. Real life plate-fin heat exchangers have complex three-dimensional geometries. Fins can have arrays of dimples and are attached to rows of penetrating tubes. To isolate the effect of surface modification, we model the real flow by a two-dimensional channel flow with a dimple on one side. The flow is analysed by solving the incompressible Navier-Stokes equation by a finite volume method on a generalized boundary-fitted coordinate. Results show a trapped vortex inside the dimple for all cases computed. Local maximum of Nusselt number occurs near the downstream end of the dimple, due to such a vortex. Location of the vortex does not change with respect to the wall temperature change, but moved downstream when Reynolds number increases. This, together with the results that in all cases vortex core is somewhat downstream of the dimple center, suggests that the mean flow above continuously feeds the kinetic energy to the recirculating flow. Heat transfer enhancement and pressure losses are studied through analysing the relevant dimensionless parameters like, Nusselt number and friction factor. In all cases computed, dimpled channel flow experiences less pressure loss than two-dimensional Poiseuille flow.
압축성 전단층 불안정성의 critical layer 해석
崔瑞源 弘益大學校 科學技術硏究所 1994 科學技術硏究論文集 Vol.4 No.-
Instability of compressible free shear layer is studied by analysing spatial evolution of a pair of oblique waves whose amplitude growth is dictated by critical layer nonlinearity. The resulting amplitude equation has a downstream singularity in all cases for inviscid compressible shear layers, and the amplitude grows exponentially as the waves approach the singularity. The analysis is more relevant to experimental findings than the incompressible one1) because the oblique modes grow faster than the two-dimensional modes in linear regime10).
3세대 K-Pop 아이돌의 전략 분석: EXO, 트와이스, 방탄소년단을 중심으로
최서원,임성준 경성대학교 산업개발연구소 2019 산업혁신연구 Vol.35 No.4
Currently, K-Pop is expanding its influence around the world based on SNS, and has become the representative content of the Korean Wave. For example, the BTS syndrome has occurred even in the US market, which was formerly perceived as a wasteland of K-Pop. Further, in Japan, where unfriendly atmospheres for Korean Wave prevailed, a K-pop craze begins to be detected. At the heart of this K-pop craze is the third-generation idols. This study examines the characteristics and changing history of idol singers in Korea for each generation. Especially, this study focuses on strategies of the third generation K-Pop idols. Specifically, EXO, Twice, and BTS are selected as the idol groups representing the third generation, and their strategies are analyzed to explore commonalities and differences. We find out that EXO, Twice, and BTS are using 'glocalization', 'pre-marketing before debut', 'simultaneous growth strategy at home and abroad', 'storytelling', and 'active utilization of SNS' strategies. It can be seen that the third-generation idols implement more advanced strategies than those implemented by the first and second-generation idols in the past. Although the strategies of these three groups have some commonalities, there are also differentiated features. This suggests that K-Pop may be able to evolve and prosper in various ways overcoming the problem of standardization of contents due to indiscriminate self-reproduction that was often blamed in the past. 현재 K-Pop은 SNS를 기반으로 전세계에 영향력을 확대시키며 한류 대표 콘텐츠로 자리매김하였다. K-Pop의 불모지로 인식되던 미국시장에서 BTS 신드롬이 일어났으며, 한류에 대해 경계 분위기가 상존하던 일본에서도 기존과는 다른 분위기의 K-Pop 열풍이 감지되고 있다. 이러한 K-Pop 열풍의 중심에는 3세대 아이돌이 있다. 이에 본 연구는 한국의 세대별 아이돌 가수의특성과 변천사를 고찰하고, 특히 2세대 아이돌의 침체와 SNS의 일반화로 인해 변화하고 있는K-Pop의 발전흐름 속에서 새로이 부상(浮上)하고 있는 3세대 아이돌에 집중하며 이들의 전략적특성을 살펴보고자 하였다. 구체적으로 본 연구에서는 3세대를 대표하는 아이돌그룹으로 EXO, 트와이스, 방탄소년단을 연구대상으로 선정하고 이들의 전략을 분석하여 공통점과 차별성을 탐구하였다. 3세대 아이돌의 특징을 바탕으로 EXO, 트와이스, 방탄소년단의 전략을 분석한 결과, 이들이 ‘글로벌 현지화 전략', '데뷔 전 사전 마케팅', '국내외 동시성장 전략’, ‘스토리텔링 전략’ 을 SNS를 기반으로 실시한다는 것을 알 수 있었다. 이전 1 2세대 아이돌의 전략에 관한 논의와견주어 볼 때, 이들의 전략은 보다 진화된 전략임을 알 수 있었다. 이 세 그룹의 전략에서는 대체적인 공통점을 찾을 수 있었지만 동시에 각 그룹만의 차별화 된 특징도 존재했다. 이는K-Pop이 과거 비난받았던 무분별한 자기복제에 따른 콘텐츠의 획일화의 문제를 뛰어넘어 다양한 방식으로 진화하며 지속할 수 있는 가능성을 시사하는 것으로 볼 수 있다.
崔瑞源 弘益大學校 科學技術硏究所 1996 科學技術硏究論文集 Vol.7 No.1
Exterior ballistics of a typical high-speed projectile is studied through a flow-visualization experiment and a compressible Navier-Stokes computation. Experiment produced a schlieren photograph that adequately shows the characteristic features of this complex flow, namely two kinds of oblique cone shocks and turbulent wake developing into the downstream. A hybrid scheme of finite volume-element method is used to simulate the compressible Navier-Stokes solution on an unstructured mesh. Osher's approximate Riemann solver is used for the convection term and Galerkin method is used for the viscous term. Fourth-order Runge-Kutta method is used for time-stepping. A two-layer k-ε turbulence model is used to simulate the turbulent wakes accurately. Axi-symmetric flow and two-dimensional flow with an angle of attack have been computed. 2-D calculation shows that effect of angle of attack is not severe. Axi-symmetric results of the computation agrees well with the flow visualization.