• 한국전산유체공학회지
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• 제13권1호
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• pp.35-40
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• 2008

Generally flight vehicles have many cavities such as wheel wells, bomb bays and windows on their external surfaces and the flow around these cavities makes separation, vortex, shock and expansion waves, reattachment and other complex flow phenomenon. The flow around the cavity makes abnormal and three-dimensional noise and vibration even thought the aspect ratio (L/D) is small. The cavity giving large effects to the flow might make large noise, cause structural damage or breakage, harm the aerodynamic performance and stability, or damage the sensitive devices. In this study, numerical analysis was performed for cavity flows by the unsteady compressible three dimensional Reynolds-Averaged Navier-Stokes (RANS) equations with Wilcox's $\kappa-\omega$ turbulence model. The MPI(Message Passing Interface) parallelized code was used for calculations by PC-cluster. The cavity has the aspect ratios of 2.5, 3.5 and 4.5 with the W/D ratio of 2 for three-dimensional cavities. The Sound Pressure Level (SPL) analysis was done with FFT to check the dominant frequency of the cavity flow. The dominant frequencies were analyzed and compared with the results of Rossiter's formula and Ahuja& Mendoza's experimental datum.

• 항공우주시스템공학회지
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• 제12권5호
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• pp.40-47
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• 2018

초음속 수축-확대 사각 노즐 내 강한 유동 박리를 동반한 초음속 유동에 적합한 난류 모델과 압축성 보정 모델을 평가하였다. 난류 모델로는 Yang과 Shih의 Low-Re $k-{\varepsilon}$ 모델, Menter의 $k-{\omega}$ SST모델, Wilcox의 $k-{\omega}$ 모델을 평가하였다. 압축성 효과를 보다 정확하게 예측하기 위하여 각각의 난류 모델에 Sarkar와 Wilcox의 압축성 보정 모델을 적용하였다. 각 난류 모델과 압축성 보정 모델의 결과는 실험 데이터와 비교하여 분석을 하였다. 난류 모델에 따라 충격파의 위치와 압력 회복률이 다르게 나타났으나 압축성 보정을 통해 더욱 개선된 결과를 얻었다.

• Journal of Mechanical Science and Technology
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• 제18권1호
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• pp.153-166
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• 2004

This paper presents a comparative study of a fully coupled, upwind, compressible Navier-Stokes code with three two-equation models and the Baldwin-Lomax algebraic model in predicting transonic/supersonic flow. The k-$\varepsilon$ turbulence model of Abe performed well in predicting the pressure distributions and the velocity profiles near the flow separation over the axisymmetric bump, even though there were some discrepancies with the experimental data in the shear-stress distributions. Additionally, it is noted that this model has y$\^$*/ in damping functions instead of y$\^$＋/. The turbulence model of Abe and Wilcox showed better agreements in skin friction coefficient distribution with the experimental data than the other models did for a supersonic compression ramp problem. Wilcox's model seems to be more reliable than the other models in terms of numerical stability. The two-equation models revealed that the redevelopment of the boundary layer was somewhat slow downstream of the reattachment portion.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2007년도 춘계 학술대회논문집
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• pp.45-49
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• 2007

Asymmetric force and vibration caused by separation flow at high angle of attack affect the stability of supersonic missile. As a preliminary study we verified the effect of turbulence model through general 3-D slender body for the supersonic flow at high angle of attack. ${\kappa}-{\omega}$ Wilcox model, ${\kappa}-{\omega}$ Wilcox-Durbin+ model, ${\kappa}-{\omega}$ shear-stress transport model, and Spalart-Allmaras one equation model are used. Grid sensitivity test was performed with three different grid system. results show that all models are in good agreement with the experimental data.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2000년도 추계 학술대회논문집
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• pp.15-24
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• 2000

The transient response of an airfoil to a rapidly deploying spoiler is numerically investigated using the turbulent compressible Navier-Stokes equations in two dimensions. Algebraic Baldwin-Lomax model, Wilcox $\kappa-\omega$ model, and SST $\kappa-\omega$ turbulence model are used to calculate the unsteady separated flow due to the rapid spoiler deployment. The spoiler motion relative to a stationary airfoil is treated by an overset grid hounded by a Dynamic Domain-Dividing Line which has been devised by the authors. The adverse effects of the spoiler influenced by the spoiler location and the hinge gap are expounded. The numerical results are in reasonably good agreement with the existing experimental data.

• 대한화학회지
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• 제40권10호
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• pp.674-677
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• 1996

• Asian-Australasian Journal of Animal Sciences
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• 제4권2호
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• pp.111-120
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• 1991

A study was conducted to determine the macromineral status of grazing cattle in three climatic regions of the province of South Sulawesi, Indonesia. Soil, forage, blood and rib bone samples were collected within the Western, Central and Eastern regions, respectively, in February-March and August-September of 1987. Calcium and magnesium were not deficient in soil samples. For forages, calcium and phosphorus were deficient for all regions and forage sodium was deficient except for the western region in the dry season. Crude protein was deficient during the dry season. The overall percentage of deficient plasma phosphorus samples was 17 or 23% for the wet and dry seasons, respectively. Based on these analyses, macrominerals most likely deficient in both seasons were phosphorus and calcium in all regions, in addition to sodium in the Central and Eastern regions.

• Asian-Australasian Journal of Animal Sciences
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• 제4권2호
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• pp.121-130
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• 1991

Research was conducted to determine the micromineral status of grazing cattle in three climatic regions of the province of South Sulawesi, Indonesia. Soil, forage, blood and liver samples were collected within the Western, Central and Eastern regions in February-March and August-September of 1987. Forages were deficient in copper, selenium and zinc. Serum copper was deficient in all regions but zinc was deficient more in the dry season. Liver copper was deficient in all regions and both seasons except in the central region in the rainy season. Based on the analyses, microminerals most likely deficient in both the rainy and dry seasons for each region were as follows: Western-copper, selenium and zinc; Central-manganese and copper; Eastern-selenium, copper and zinc. Some degree of molybdenum excess was found in the Eastern region.

• 한국콘텐츠학회논문지
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• 제14권12호
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• pp.835-844
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• 2014

본 연구는 노인요양시설에서 노인에게 전인적 돌봄을 제공하는 요양보호사의 노인의 성에 대한 긍정적 태도와 지식을 가지고 적절하게 대응할 수 있도록 하기 위해 요양보호사를 위한 노인 성교육 프로그램을 개발하고 노인 성교육 프로그램이 요양보호사의 성에 대한 지식, 태도 및 대처에 미치는 효과를 검증하고자 하였다. 본 연구의 노인 성교육 프로그램은 4주 프로그램으로 주 1회 120분씩 총 4회 실시하였다. 2012년 9월 10일부터 10월 10일까지 H지역의 H노인요양시설에서 요양보호사 실험군 19명과 S지역의 S노인요양시설 요양보호사 대조군 18명 총 37명을 대상으로 프로그램 실시 전 후 사전 사후조사를 실시하였다. 수집된 자료는 SPSS/PC WIN 18.0 프로그램을 이용하여 실수와 백분율, 평균과 표준편차, Shapiro-Wilk test, Fisher의 정확한 검증, Paired t-test, Indepent Samples t-test, Wilcox signed rank test, Mann-Whitney test로 분석하였다. 연구 결과 성교육프로그램을 받은 요양보호사는 교육을 받지 않은 요양보호사에 비해 성교육프로그램을 적용한 후 성에 대한 지식은 증가하였으나, 태도와 대처는 유의한 변화가 나타나지 않았다. 따라서 노인요양시설 요양보호사의 개방적인 성태도와 효율적인 대처를 위해서는 대상자의 특성을 고려한 장기적이고 구체적인 교육프로그램의 개발이 필요하다고 하겠다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 학술대회
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• pp.297-301
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• 2008

The flight vehicles have cavities such as wheel wells and bomb bays. The flow around a cavity is characterized as unsteady flow because of the formation and dissipation of vortices due to the interaction between the freestream shear layer and cavity internal flow, the generation of shock and expansion waves. Resonance phenomena can damage the structures around the cavity and negatively affect aerodynamic performance and stability. The flow field is observed to oscillate in the "shear layer mode" with low aspect ratio. In the present study, numerical analysis was performed for cavity flows by the unsteady compressible three dimensional Reynolds-Averaged Navier-Stokes (RANS) equations with Wilcox's $\kappa$-$\omega$ turbulence model. The flow field is observed to oscillate in the shear layer mode" with large aspect ratio. Based on the SPL(Sound Pressure Level) analysis of the pressure variation at the cavity trailing edge, the dominant frequency was analyzed and compared with the results of Rossiter's formul. The aero-acoustic wave analyzed with CPD(Correlation of Pressure Distribution).