• Wind and Structures
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• v.14 no.1
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• pp.35-53
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• 2011

Spherical object in wind is a common scenario in daily life and engineering practice. The main challenge in understanding the aerodynamics in turbulent wind lies in the multi-aspect of turbulence. This paper presents a wind tunnel study, which focuses on the role of turbulence integral length scale ${\Lambda}$ on the drag of a sphere. Particular turbulent flow conditions were achieved via the proper combination of wind speed, orifice perforated plate, sphere diameter (D) and distance downstream from the plate. The drag was measured in turbulent flow with $2.2{\times}10^4{\leq}Re{\leq}8{\times}10^4$, $0.043{\leq}{\Lambda}/D{\leq}3.24$, and turbulence intensity Tu up to 6.3%. Our results confirmed the general trends of decreasing drag coefficient and critical Reynolds number with increasing turbulence intensity. More interestingly, the unique role of the relative integral length scale has been revealed. Over the range of conditions studied, an integral length of approximately 65% the sphere diameter is most effective in reducing the drag.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.305-305
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• 2021

XP-SWMM은 EAP-SWMM의 Runoff 기능을 보완하고 2D 해석 기능을 새롭게 추가하여 만든 외산(XP Solutions) 프로그램으로 도시유역 유출량 산정, 우수관거 추적 등과 같은 모의가 가능한 종합 모형이다. 그 중 2차원 분석 기능(2D XP-SWMM)은 연산 결과를 Tu-Flow 모형에 대입한 도시침수 해석모형으로 실무에서 주로 사용되고 있다. 그러나 XP-SWMM은 수량 부분 외에도 수질 부분의 다양한 모형이 통합되어 있어 라이센스 가격이 상당히 높고, 국내 환경에 적합한 모형 수정 등 기술지원을 받기 어렵다는 단점을 갖고 있다. 또한, 실무 활용성이 높은 2차원 분석기능의 경우 모의에 소요되는 시간이 크다는 한계점을 갖고 있다. 2D XP-SWMM 연산의 소요시간이 큰 주요 원인은 계산 시간간격마다 큰 셀수의 행렬 계산을 반복하기 때문이며, 격자를 촘촘하게 설정할수록(행렬의 수가 증가할수록) 수치해석에 소요되는 시간은 기하급수적으로 늘어나게 된다. 2D XP-SWMM 연산은 편미분방정식을 계산하는 모형으로 반복법을 채택하고 있기 때문에 짧은 시간내에 침수해석을 진행해야하는 웹기반 초단기 홍수예경보 시스템 등에 활용하기에는 적합하지 않다. 본 연구에서는 2D XP-SWMM 보다 연산속도를 향상시킨 2차원 도시침수 모형을 개발하였다. 기존 XP-SWMM 중심의 실무 적용성을 유지하고자 XP-SWMM과 동일하게 EPA-SWMM 엔진을 활용하였고 DEM 기반의 지표수 흐름방향 결정 알고리즘을 결합하였다. 본 연구에서 개발한 도시침수 모형 결과를 울산광역시, 청주시 등 도심지에서 발생한 과거 침수피해의 양상과 비교하여 그 타당성을 검증하였다.

• International Journal of Internet, Broadcasting and Communication
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• v.13 no.2
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• pp.267-275
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• 2021

The advent of the "un-tact 2.0 era," described as a "new normal non-face-to-face social relationship," accelerates the transformation of the living paradigm as a fully digital mediated social relationship. The emergence of these new forms of digital behaviors and mediated relationships significantly influences the industry prospect and consumers' individual lives. Advertising has played a decisive role in moving the formation forces of society, creating a dynamic flow of the capitalist system across races and geographical boundaries. Its role will become more fundamental in the physical contactless environment due to the COVID-19 outbreak. Accordingly, advertising has changed and modified its shape and meaning throughout history to adapt to the dynamic external environment. In this article, we illustrated four primary stages of the evolution in the advertising industry from simple advertising to convergence of advertising. Finally, we also identified the challenges of the present advertising industry and the paradigm transformation of "un-tact 2.0" with various related examples.

• Coupled systems mechanics
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• v.11 no.1
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• pp.43-54
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• 2022

In order to analyse the thermal performance of battery systems in electric vehicles complex simulation models with high computational cost are necessary. Using reduced order methods, real-time applicable model can be developed and used for on-board monitoring. In this work a data driven model of the cooling plate as part of the battery system is built and derived from a computational fluid dynamics (CFD) model. The aim of this paper is to create a meta model of the cooling plate that estimates the temperature at the boundary for different heat flow rates, mass flows and inlet temperatures of the cooling fluid. In order to do so, the cooling plate is simulated in a CFD software (ANSYS Fluent ®). A data driven model is built using the design of experiment (DOE) and various approximation methods in Optimus ®. The model can later be combined with a reduced model of the thermal battery system. The assumption and simplification introduced in this paper enable an accurate representation of the cooling plate with a real-time applicable model.

• Journal of the Korean Society of Groundwater Environment
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• v.5 no.4
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• pp.177-191
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• 1998

For various kinds of waters including surface water, shallow groundwater (＜70 m deep) and deep groundwater (500∼810 m deep) from the Pungki area, an integrated study based on hydrochemical, multivariate statistical, thermodynamic, environmental isotopic (tritium, oxygen-hydrogen, carbon and sulfur), and mass-balance approaches was attempted to elucidate the hydrogeochemical and hydrologic characteristics of the groundwater system in the gneiss area. Shallow groundwaters are typified as the 'Ca-HCO$_3$'type with higher concentrations of Ca, Mg, SO$_4$and NO$_3$, whereas deep groundwaters are the 'Na-HCO$_3$'type with elevated concentrations of Na, Ba, Li, H$_2$S, F and Cl and are supersaturated with respect to calcite. The waters in the area are largely classified into two groups: 1) surface waters and most of shallow groundwaters, and 2) deep groundwaters and one sample of shallow groundwater. Seasonal compositional variations are recognized for the former. Multivariate statistical analysis indicates that three factors may explain about 86% of the compositional variations observed in deep groundwaters. These are: 1) plagioclase dissolution and calcite precipitation, 2) sulfate reduction, and 3) acid hydrolysis of hydroxyl-bearing minerals(mainly mica). By combining with results of thermodynamic calculation, four appropriate models of water/ rock interaction, each showing the dissolution of plagioclase, kaolinite and micas and the precipitation of calcite, illite, laumontite, chlorite and smectite, are proposed by mass balance modelling in order to explain the water quality of deep groundwaters. Oxygen-hydrogen isotope data indicate that deep groundwaters were originated from a local meteoric water recharged from distant, topograpically high mountainous region and underwent larger degrees of water/rock interaction during the regional deep circulation, whereas the shallow groundwaters were recharged from nearby, topograpically low region. Tritium data show that the recharge time was the pre-thermonuclear age for deep groundwaters (＜0.2 TU) but the post-thermonuclear age for shallow groundwaters (5.66∼7.79 TU). The $\delta$$\^$34/S values of dissolved sulfate indicate that high amounts of dissolved H$_2$S (up to 3.9 mg/1), a characteristic of deep groundwaters in this area, might be derived from the reduction of sulfate. The $\delta$$\^$13/C values of dissolved carbonates are controlled by not only the dissolution of carbonate minerals by dissolved soil CO$_2$(for shallow groundwaters) but also the reprecipitation of calcite (for deep groundwaters). An integrated model of the origin, flow and chemical evolution for the groundwaters in this area is proposed in this study.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.2
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• pp.87-94
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• 2017

Because the cavitation flow driven by an underwater propeller corrodes the materials around it and generates a high level of noise, it has become an important topic in engineering research. In this study, computational fluid dynamics techniques are applied to simulate cavitation flow, and the noise in the flow is predicted by applying the acoustic analogy to the predicted flow. The predicted results are compared with measurement results and other predictions in terms of surface pressure distribution and the temporal variation in liquid volume fraction. The predicted results are found to be in good agreement with the measured results. The source of the noise attributed to the time rate of change in the liquid volume fraction around the hydrofoil is modeled as a monopole source, and the source of the noise due to unsteady pressure perturbations on the hydrofoil surface is modeled as a dipole source. Then the predicted noise results are analyzed in terms of directivity and SPL spectrum. The noise caused by unsteady pressure perturbations was dominant in the entire frequency range considered in the study.

• YAKHAK HOEJI
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• v.42 no.3
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• pp.302-306
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• 1998

In the previous study we described the antitumor activity of GLB, a protein-polysaccharide fraction of the growing tips of Ganoderma lucidum, against sarcoma 180 solid tu mor in ICR mice. In this study we investigated the stimulatory activity of GLB on macrophages. When analyzed using a flow cytometer, GLB ($100{\mu}g/ml$) was found to increase the phagocytic activity of the BALB/c mouse peritoneal macrophages as well as chicken macrophage BM2CL cells against FITC-labeled C.albicans by 55.2% and 21.2%, respectively. GLB also increased the spreading and the expression of MHC class II molecules of BM2CL cells as well as the mouse peritoneal macrophages. From these results, it is clear that GLB is a strong stimulator to the macrophages.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.2
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• pp.279-289
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• 2017

In this study, a series of conjugate heat transfer (CHT) analyses are conducted for a stage of a fully cooled high-pressure turbine (HPT) at elevated levels of free stream turbulence (Tu = 5% and 25.7%). The goal of the analyses is to investigate the influence of high turbulence intensity on the fluid-thermal characteristics of a nozzle guide vane (NGV). The turbine inlet temperature is defined by considering a typical radial temperature distribution factor (RTDF). The Unsteady Reynolds Average Navier-Stokes (URANS) CHT simulations are carried out using CFX 15.0, a commercial CFD package. The presented CFD modeling approach for high turbulence intensity is verified with the experimental data from two types of NASA C3X NGVs with films. The computation grid is generated for both the fluid and solid domains. The fluid domain grid is created using a tetrahedral grid system with prism layers because of its complex geometry, and the solid domain grid is composed of only tetrahedral elements. The analytical results are compared to understand the effect of turbulence on flow characteristics and metal temperature distributions. The results obtained in this study provide useful insights on the effects of high free stream turbulence and unsteadiness. The results also lead to the proposal of meaningful turbine design guidelines.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.12
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• pp.7451-7457
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• 2013

Background: Understanding and enhancing change capabilities, including Practice Adaptive Reserve (PAR), of Community Health Centers (CHCs) may mitigate cancer-related health disparities. Materials and Methods: Using stratified random sampling, we recruited 232 staff from seven CHCs serving Asian Pacific Islander communities to complete a self-administered survey. We performed multilevel regression analyses to examine PAR composite scores by CHC, position type, and number of years worked at their clinic. Results: The mean PAR score was 0.7 (s.d. 0.14). Higher scores were associated with a greater perceived likelihood that clinic staff would participate in an evidence-based intervention (EBI). Constructs such as communication, clinic flow, sensemaking, change valence, and resource availability were positively associated with EBI implementation or trended toward significance. Conclusions: PAR scores are positively associated with perceived likelihood of clinic staff participation in cancer screening EBI. Future research is needed to determine PAR levels most conducive to implementing change and to developing interventions that enhance Adaptive Reserve.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.352-357
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• 2016

광역상수관은 원수 또는 정수를 자체 수자원확보가 어려운 지자체에 적기에 공급해주는 중요한 역할을 하고 있다. 최근 자연재해에 및 관 노후, 공사 중 사고 등의 원인으로 광역상수관이 파손되는 사례가 발생되었다. 이와 같은 광역상수관의 파손은 상수 보급 수혜지역에 대한 단수피해가 발생될 뿐만 아니라 파손지점에서 상수유량의 분출으로 침수피해를 야기 시킬 수 있게 된다. 본 연구에서는 광역상수관 파손에 따른 파손지역 주변부에서 유량 분출에 의한 침수양상 및 분출지점에 위치하고 있는 지하시설물(지하철 정거장)에 대한 침수피해 영향을 검토하였다. 침수양상 분석 방법은 광역상수관 파손시 분출유량 산정, 지형자료 구축, 표면류 흐름 계산, 침수범람도 작성 순으로 검토를 수행하였다. 광역상수관 파손에 따른 분출유량은 상수관 공급량 $770,000m^3/day$를 기준으로 초당 흐르는 유량(2차원 부정류 흐름 해석)으로 환산하여 유입조건으로 선정하고, 파손위치 및 분출유량에 따른 시나리오를 설정하였다. 광역상수관 파손에 따른 침수양상을 살펴본 결과, 파손 지점의 위치의 지형적 여건에 따라 최대 침수심 및 최대 침수 위치가 상이한 결과가 나타나는 것을 확인할 수 있다. 정거장 주변부 최대 침수심은 0.50m로 정거장 노출부 최소 높이 0.65m(노출부 높이 - 지반고)보다 작은 수치이므로 광역상수관 파손에 따른 분출유량의 정거장 내부 유입은 없는 것으로 분석 되었다.