• International Journal of Naval Architecture and Ocean Engineering
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• 제8권3호
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• pp.219-227
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• 2016

Numerical simulation based on the Reynolds Averaged Naviere-Stokes (RANS) Computational Fluid Dynamics (CFD) method had been carried out with the commercial code ANSYS CFX. The structured grid and SST $k-{\omega}$ turbulence model had been adopted. The impact of non-condensable gas (NCG) on cavitation performance had been introduced into the Schnerr and Sauer cavitation model. The numerical investigation of cavitating flow of marine propeller E779A was carried out with different advance ratios and cavitation numbers to verify the numerical simulation method. Tip clearance effects on the performance of pumpjet propulsor had been investigated. Results showed that the structure and characteristics of the tip leakage vortex and the efficiency of the propulsor dropped more sharply with the increase of the tip clearance size. Furthermore, the numerical simulation of tip clearance cavitation of pumpjet propulsor had been presented with different rotational speed and tip clearance size. The mechanism of tip clearance cavitation causing a further loss of the efficiency had been studied. The influence of rotational speed and tip clearance size on tip clearance cavitation had been investigated.

• Bulletin of the Korean Chemical Society
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• 제19권5호
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• pp.501-503
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• 1998

In this work, we applied the 1D $11^B$ nutation NMR method for the analysis of the local structural environments in powdered borosilicates $(SiO_2-B_2O_3)$. Spin dynamics during a rf irradiation for spin I=3/2 was analytically calculated with a density ma trix formalism. Spectral simulation programs were written in MATLAB on a PC. Two borosilicates prepared by the sol-gel process at different stabilization temperature were used for the 1D $11^B$ nutation NMR experiment. The $11^B$ NMR parameters, quadrupole coupling constants $(e^2qQ/h)$ and asymmetry parameters (η), for each borosilicate were extracted from the nonlinear least-squares fitting. The effects of heat treatments on the local structures of boron sites in borosilicates were discussed.

• Wind and Structures
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• 제28권3호
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• pp.141-153
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• 2019

In this study, we have focused on commonly used 14 different small wind turbine airfoils (A18, BW3, Clark Y, E387, FX77, NACA 2414, RG 15, S822, S823, S6062, S7012, SD6060, SD7032, SD7062). The main purpose of the study is to determine the lift, drag and lift/drag coefficients of these airfoils with numerical analysis and to verify 2 best airfoil's results with experimental analysis. Airfoils were determined from past studies on small wind turbines. Numerical analyzes of the airfoils were done with Ansys Fluent fluid dynamics program. Experimental analyzes were done at wind tunnel in Erciyes University, Turkey. Lift and drag coefficients of these airfoils were determined for 50,000-100,000-200,000 Reynolds numbers.

• 한국산학기술학회논문지
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• 제13권8호
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• pp.3792-3799
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• 2012

본 연구에서는 전산유체역학(CFD)을 이용하여 산업체에 널리 적용되고 있는 충격기류형 탈진시스템의 탈진 특성을 규명하고, 그 성능을 향상시키기 위해 탈진부 유니트(unit) 형상을 개조한 경우의 탈진 성능을 비교하였다. 탈진부 각 형상별로 탈진 공기량과 기류 분포, 유입속도 분포 등을 검토한 결과, 블로우 튜브에 노즐을 설치한 경우(Case 3)와 벤츄리에 이중 유입관을 설치한 경우(Case4, 5)가 현재 현장에서 널리 적용되고 있는 구조(Case 1)에 비해 탈진 공기량의 증폭 효과 및 기류 폭의 확장 현상이 우수한 것으로 예측되었다. 선정된 Case-5를 상용 백필터의 사양(직경 150 mm)에 적용하기 위해 벤츄리 제원을 결정한 결과, 내측 유입관의 직경 50 mm, 외측 유입관의 직경 90 mm의 제원을 적용하면 탈진 공기량을 최대로 유지할 수 있을 것으로 판단된다.

• 벤처창업연구
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• 제14권1호
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• pp.167-185
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• 2019

대부분의 G20 국가에서 향후 수십 년 동안 의료 지출이 급격하게 성장할 것으로 예상하고 있듯이, 고연령 인구와 만성질환자의 증가로 인해 전 세계적으로 의료비 부담은 지속적으로 늘어나고 있으며 의료서비스의 지속적인 질 개선도 해결해야 할 과제로 대두되고 있다. 그러나 헬스케어와 IT 융합의 급변하는 기술 환경 하에서 이런 변화를 제대로 인식하지 못하고 적절한 대비를 하지 않는데서 그 문제가 더 커질 수 있다. 패러다임 변화와 의료 분야 문제 증대 상황에서 기술적, 제도적, 사업적 측면에서의 복합적인 대응이 절실히 필요하다. 핵심은 의료분야에 IT를 융합한 사업에 적합한 비즈니스모델의 도출이라 할 수 있다. 4차 산업혁명시대의 도래와 함께 사물인터넷 등의 신기술이 e헬스케어에 적용되면서 새로운 비즈니스모델의 필요성이 대두 되었다. 기존 인터넷 시대의 e헬스케어에서는 전통적인 조직 기반 (Firm-centric) 비즈니스모델이 되었으나 사물인터넷 시대에는 사물인터넷의 역동성 (Dynamics) 및 복잡성 (Complex)의 특성으로 인하여 단위 조직 (Firm-Centric)보다는 비즈니스생태계 (Business Ecosystem)기반의 접근이 필요하다. 본 논문에서는 사물인터넷 등 이머징 기술 (Emerging Technology)기반의 e헬스케어의 비즈니스생태계에 대한 연구 결과로 e헬스케어 비즈니스생태계의 3-레이어 (Layer) 구조에 기반한 생태계의 주요 발전 인자를 분석 제시한다. 3-레이어 비즈니스생태계는 (1) 인프라 스트럭처 레이어 (Infrastructure Layer), (2) 특성 레이어 (Characteristics Layer) 및 (3) 이해당사자 레이어 (Stakeholder Layer)로 정의하여 분석하였다. e헬스케어 비즈니스생태계의 주요 발전 인자측면에서는 (1) i헬스케어 개념의 도입, (2) 비즈니스생태계의 확장, (3) 비즈니스생태계 변화 프로세스 혁신, (4) 비즈니스생태계 리더쉽 혁신의 4가지 인자를 제안한다.

• 한국시스템다이내믹스연구
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• 제12권3호
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• pp.47-66
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• 2011

South Korea has achieved remarkable social and economic development together with the process of democratization over the past 20 years. In the democratic process in South Korea, ordinary people have actively participated in conventional political activities such as elections. But recently, one of the salient phenomena is that the public have been showing political apathy associated with a light poll. Especially, the most serious concern in the political environment of South Korea is that young voters (e.g., 20-30s) have serious political apathy leading to low voter turnout. Regarding this concern, many political scientists argued that this political phenomenon is not only the case in South Korea, insisting that many consolidated democratic countries such as European countries and the US have the same problems. However, South Korea has contained different factors (e.g., historical, culture, social, and political differences) leading to political apathy and light poll. Unfortunately, no one has clearly explain the phenomenon. In fact, in order for scholars to understand and explain these concerns, they should carefully look at the phenomenon with diverse perspectives and approaches. The main purpose of this paper is to explain why the digital generation has political apathy and are reluctant to participate in political activities such as voting. Using causal loop analysis which is based on systematic thinking, we not only analyzed the pattern of the digital generation' political participation with regard to diverse perspectives, but also attempted to draw new political implications from the analysis. Based on our analysis, we tried to suggest some implications for political stability and development in South Korea in the future.

• 한국농공학회논문집
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• 제51권6호
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• pp.53-62
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• 2009

The EFDC (Environmental Fluid Dynamics Code), a numerical model for simulating three-dimensional (3D) flow, transport, and biogeochemical processes in surface water systems including rivers, reservoirs, and estuaries, was applied to assess the effect of sea water and fresh water exchange rates ($Q_e$) on the mixing characteristics of a conservative pollutant (tracer) induced from upstreams and salinity in Saemangeum Lake, Korea. The lake has been closed by a 33 km estuary embankment since last April of 2006, and now seawater enters the lake partially through two sluice gates (Sinsi and Garyuk), which is driving the changes of hydrodynamic and water quality properties of the lake. The EFDC was constructed and calibrated with surveyed bathymetry data and field data including water level, temperature, and salinity in 2008. The model showed good agreement with the field data and adequately replicated the spatial and temporal variations of the variables. The validated model was applied to simulated the tracer and salinity with two different gate operation scenarios: RUN-1 and RUN-2. RUN-1 is the case of real operation condition ($Q_e=25,000,000\;m^3$) of 2008, while RUN-2 assumed full open of Sinsi gate to increase $Q_e$ by $120,000,000\;m^3$. Statistical analysis of the simulation results indicate that mixing characteristics of pollutants from upstream can be significantly affected by the amount of $Q_e$.

• 한국운동역학회지
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• 제33권4호
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• pp.175-184
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• 2023

Objective: The purpose of this study is to investigate the effects of human motion and javelin kinematics during the energy transfer in javelin throwing on records, and to provide evidence-based training insights for athletes and coaches to enhance records. Method: Three javelin throw athletes (age: 22.67 ± 0.58 years, height: 178.33 ± 7.37 cm, weight: 83.67 ± 1.15 kg) were recruited for this study. Each athlete attempted ten maximum record trials, and the kinematic data from each performance were analyzed to determine their influence on the records. The Theia3d Markerless system was used for motion analysis. Results: Key factors were modeled and identified at each moment. In E1, main variables were COM Y (𝛽 8.162, p<.05) and COM velocity Z (𝛽 -72.489, p<.05); in E2, COM X (𝛽 -17.604, p<.05); in E3, COM X (𝛽 -18.606, p<.05), COM velocity Y (𝛽 38.694, p<.05), and COM velocity X (𝛽 66.323, p<.05). For the javelin throw dynamics in E3, key determinants were Attitude angle and Javelin velocity in the Y-axis. Conclusion: The study reveals that controlled vertical movement, center of mass management during braking, and enhanced pelvic rotation significantly improve javelin throw performance. These kinematic strategies are critical for record enhancement in javelin throwing.

• Journal of Ginseng Research
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• 제37권4호
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• pp.413-424
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• 2013

Korean Red Ginseng extract (KRGE) is a traditional herbal medicine utilized to prevent endothelium dysfunction in the cardiovascular system; however, its underlying mechanism has not been clearly elucidated. We here examined the pharmacological effect and molecular mechanism of KRGE on apoptosis of human umbilical vein endothelial cells (HUVECs) in a serum-deprived apoptosis model. KRGE protected HUVECs from serum-deprived apoptosis by inhibiting mitochondrial cytochrome c release and caspase-9/-3 activation. This protective effect was significantly higher than that of American ginseng extract. KRGE treatment increased antiapoptotic Bcl-2 and Bcl-$X_L$ protein expression and Akt-dependent Bad phosphorylation. Moreover, KRGE prevented serum deprivation-induced subcellular redistribution of these proteins between the mitochondrion and the cytosol, resulting in suppression of mitochondrial cytochrome c release. In addition, KRGE increased nitric oxide (NO) production via Akt-dependent activation of endothelial NO synthase (eNOS), as well as inhibited caspase-9/-3 activities. These increases were reversed by co-treatment of cells with inhibitors of eNOS and phosphoinositide 3-kinase (PI3K) and pre-incubation of cell lysates in dithiothreitol, indicating KRGE induces NO-mediated caspase modification. Indeed, KRGE inhibited caspase-3 activity via S-nitrosylation. These findings suggest that KRGE prevents serum deprivation-induced HUVEC apoptosis via increased Bcl-2 and Bcl-$X_L$ protein expression, PI3K/Akt-dependent Bad phosphorylation, and eNOS/NO-mediated S-nitrosylation of caspases. The cytoprotective property of KRGE may be valuable for developing new pharmaceutical means that limit endothelial cell death induced during the pathogenesis of vascular diseases.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1207-1212
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• 2004

A model for the phonon dispersion relationship for cubic zinc sulfide structure, for example SiC, is developed in terms of two unknown force constants. Born model that incorporates bond bending and bond stretching, is used for the force constants. The force constants are determined by fitting to experimental data. Using only the nearest-neighbor coupling results in $6{\times}6$ sized dynamic matrix. The eigenvalues of dynamics matrix for each wavenumber in 3-D ${\kappa}$ space correspond to frequencies, 3 for optical phonon and 3 for acoustic phonon, which is so-called dispersion relation (${\kappa}$-${\omega}$). The density of state is determined by counting the states for each frequency bin, and the properties such as specific heat and thermal conductivity can be obtained. The specific heat is estimated on this model and compared with experiment and other models, i.e. Debye model, Einstein model and combined Debye-Einstein model. In spite of the simple bond potential model, reasonable agreements are found.