• 방송공학회논문지
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• 제19권3호
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• pp.405-414
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• 2014

HEVC는 재귀적 쿼드 트리 구조를 갖는 CU를 부호화에 적용함으로써 높은 부호화 효율을 얻었다. 그러나 이러한 재귀적 쿼드 트리 구조는 HEVC의 부호화 복잡도를 매우 증가시키는 결과를 가져왔다. 본 논문에서는 이러한 재귀적 쿼드 트리 구조 안에서 빠른 CU 결정이 가능한 알고리즘을 제안한다. 제안하는 알고리즘은 CTU 부호화가 이루어지기 전에 미리 초기 CU 크기를 예측하고, CU 부호화 과정에서 CBF와 PU 모드 예측 비용을 이용한 조건을 확인하여 고속 CU 결정이 이루어지도록 한다. 또한 인터 PU 모드 예측과정에서 얻은 CBF값들을 이용하여 인트라 모드 예측 생략이 가능하다. 실험결과, 제안한 알고리즘의 조건에 포함된 가중치값에 따라 최대 평균 49.91%, 37.97%의 부호화 시간 감소 효과를 얻을 수 있었다.

• 대한기계학회논문집B
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• 제20권5호
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• pp.1689-1699
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• 1996

A study on the transitional boundary layer with arbitrary pressure gradient under various upstream conditions is very important for engineering applications like the performance predictions of the turbomachineries under various and strong disturbances. Experimental data on the transitional boundary layer for real cascades of the turbomachinery are rare because of difficulties in boundary layer experiments. Flow on NACA0012 airfoil is more similar to the real case than that on the flat plate with which many researches are done. The data of the transitional flow on the airfoil could be used to verify or to develop a turbulence model for numerical simulations. The experiment was performed with two cases of Reynolds number at a=0$^{0}$ and one case of Reynolds number at a=5$^{0}$ . The measured data are the transition length and the wall shear stresses. These two characteristic values are measured within 25%~90% of the airfoil chord by Computation Preston tube Method(CPM) proposed by Nitsche et al.(1983). At a=0$^{0}$ , transition occured at 70% and 55% of chord length when R $e_{c}$=6*10$^{5}$ and 8* 10$^{5}$ , respectively. It started when R {\theta}=500 regardless of R $e_{c}$, and ended when R {\theta}=750, and 850 respectively. The transition length was 15~20% of the chord length. At a=5$^{0}$ (R $e_{c}$=6*10$^{5}$ ), boundary layer on the pressure side does not undergo transition, but on the suction side transition occured at .chi.$_{c}$/c=0.16 and ended at .chi.$_{c}$/c=0.22.c//c=0.22./c=0.22.c//c=0.22.

• 대한기계학회논문집B
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• 제20권9호
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• pp.2944-2952
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• 1996

In this paper the CSCM type upwind flux difference splitting Navier-Stokes method has been applied to study the ARL-SL19 transoni $c^ersonic compressor cascade flow. First, the general characteristics of baseline cascade flow were analyzed. At freestream Mach n.1.612 and exit/inlet pressure ratio 2.15, the results from current laminar flow were compared well in suction surface with the experiment; however, not well in pressure surface. Second, numerical study of the transoni $c^ersonic compressor cascade flow demonstrated the effectiveness of a passive control by the various size cavities. A cavity under the shock foot point at the suction surface of the blades was used as a passive control. The passive control of shock-boundary layer interaction by a cavity reduced total pressure losses. The effect of cavity length and depth was studied. The total pressure loss was reduced by about 10% and the isentropic efficiency was improved slightly. The effect of cavity depth in current study(d/l = 0.05, 0.02) was not found strong. Further adequate turbulence modeling and TVD schemes would help to capture the shock more accurately and increase the effectiveness of the current shock-boundary layer interaction study using upwind flux difference splitting computational methods.thods.

• Journal of Mechanical Science and Technology
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• 제17권9호
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• pp.1349-1357
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• 2003

This paper deals with verification of the theoretical model for dynamic behavior of Pipeline Inspection Gauge (PIG) traveling through high pressure natural gas pipeline. The dynamic behavior of the PIG depends on the differential pressure across its body. This differential pressure is generated by injected gas flow behind the tail of the PIG and expelled gas flow in front of its nose. To analyze the dynamic behavior characteristics such as gas flow in pipeline, and the PIG position and velocity, not only the mathematical models are derived, but also the theoretical models must be certified by actual pigging experiment. But there is not any found results of research on the experimental certification for dynamic behavior of the PIG. The reason is why the fabrication of the PIG as well as, a field application are very difficult. In this research, the effectiveness of the introduced solution using the method of characteristics (MOC) was certified through field application. In-line inspection tool, 30" geometry PIG, was fabricated and actual pigging was carried out at the pipeline segment in Korea Gas Corporation (KOGAS) high pressure system, Incheon LT (LNG Terminal) -Namdong GS (Governor Station) line. Pigging is fulfilled successfully. Comparison of simulation results with experimental results show that the derived mathematical models and the proposed computational schemes are effective for predicting the position and velocity of the PIG with a given operational conditions of pipeline.

• 한국기계가공학회지
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• 제19권4호
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• pp.58-64
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• 2020

Large-scale flooding due to extreme weather and typhoons causes heavy damage. This is especially true in urban areas where accumulated debris prevents the smooth drainage of rainwater in sewage facilities such as rain gutters installed near roads. In this study, to improve the drainage performance and effectively remove foreign substances by applying the dust screen used in rivers, the rain gutter with Coanda effect was simulated and compared with the experiment. The simulation was performed by setting the parameters to the fillet radius R₁ and R₂ at the top of the screen filter, the fillet radius R₃ at the bottom of the screen filter, and the height H of the gap W from the bottom. W is the gap at the backside of screen filter which is applied to stimulate the Coanda effect. According to the simulation results, the highest drain performance was 87.99% derived from R₁= 30mm, R₂= 5mm, R₃= 85mm, H= 75mm, and W= 2mm. The error rate of simulation results refer to the 4.89%~7.36% compared to the experimental results. In the future, by considering the slope according to the installation environment, the simulation results can be applied to the actual roadside to help prevent flood damage.

• 컴퓨터교육학회논문지
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• 제20권4호
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• pp.47-57
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• 2017

본 연구는 중학생을 대상으로 컴퓨팅 사고력 기반의 창의적 문제해결(이하 CT-CPS) 수업모형을 통해 설계한 소프트웨어 수업을 적용하여, 인지적, 정의적 영역에서의 효과성을 분석하기 위하여 수행하였다. 이러한 연구의 목적을 달성하기 위해 본 연구자는 이론적 배경 탐색을 통해 인지적 정의적 활동을 수행할 수 있도록 CT-CPS 수업모형 기반의 소프트웨어 수업을 설계하였다. 이후 이를 중학교 소프트웨어 수업에 적용하고, 수업의 전, 후에 3가지 검사를 실시하였다. 연구 결과 3가지 검사의 인지적, 정의적 영역에 해당하는 대부분의 요소에서 통계적으로 유의한 향상이 관찰되었고, 중학생의 소프트웨어 수업에서 CT-CPS 수업모형의 인지적, 정의적 영역에서의 효과성 검증과 시사점을 논할 수 있었다.

• 인터넷정보학회논문지
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• 제13권5호
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• pp.9-19
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• 2012

디지털 콘텐츠에서 HCI로 활용되는 가상 인간은 얼굴 표정과 신체자세와 같은 모달을 이용하여 다양한 감정을 표현하지만 비언어적 다중모달의 조합에 대한 연구는 많지 않다. 감정을 표현하는 가상 인간을 제작하려면 계산 엔진 모델은 얼굴 표정과 신체자세와 같은 비언어적 모달의 조합이 사용자에 의해 어떻게 인식되는지를 고려해야 하기 때문에 본 연구는 가상 인간의 감정 표현 디자인에 필요한 비언어적 다중모달의 영향을 분석하여 제시한다. 먼저 가상 인간에 대한 다중모달 별 감정 인식을 평가하여 다른 모달간의 상대적 영향성을 분석하였다. 그리고 일치하는 얼굴과 자세 모달을 통해 기본 감정 및 정서가와 활성화 인식에 대한 영향을 평가하며 감정이 불일치하는 다중모달을 통해 일상생활에서 빈번하게 드러나는 중첩된 감정의 인식 정도를 관측하였다. 실험 결과, 가상 인간의 얼굴과 신체자세의 표정이 일치하면 감정 인식이 용이하며, 얼굴 표정으로 감정 카테고리를 판별하지만 감정의 활성화 차원 판단에는 자세 모달리티가 선호됨을 확인하였다. 본 연구 결과는 감정을 드러내는 가상 인간의 행동 동기화 및 애니메이션 엔진 시스템 구현에 활용할 수 있다.

• 한국정밀공학회지
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• 제28권8호
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• pp.975-983
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• 2011

A microfin on a heated surface and its effects of the heat transfer has been investigated. The thickness of the fin is about 8 micrometer to allow the flexible up-down motion of the fin. Two-way complete FSI (Fluid-Structure Interaction) method has been applied for the analysis. Firstly, the deformation of a microfin due to the pulsating flow is evaluated using structure analysis. The flow and temperature patterns are predicted by CFD (Computational Fluid Dynamics) method. At each time step, using the pressure force and temperature distribution from CFD, the deformation of the wing is evaluated by FEM. Also in order to estimate the resonance probability, the natural frequency of the wing structure is calculated by modal analysis. The proposed numerical procedure was validated through experiment using a single fin. Through this work, we show that the increase of 40% in heat transfer capacity using the microfin has been compared with that of flat plate case.

• Wind and Structures
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• 제24권1호
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• pp.1-24
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• 2017

Wind environment in urban residential areas is an important index to consider when evaluating the living environment. However, due to the complexity of the flow field in residential areas, it is difficult to specify the correct inflow boundary conditions in the large eddy simulation (LES). In this paper, the weighted amplitude wave superposition (WAWS) is adopted to simulate the fluctuating velocity data, which satisfies the desired target wind field. The fluctuating velocity data are given to the inlet boundary of the LES by developing an UDF script, which is implemented into the FLUENT. Then, two numerical models - the empty numerical wind tunnel model and the numerical wind tunnel model with spires and roughness elements are established based on the wind tunnel experiment to verify the present method. Finally, the turbulence generation approach presented in this paper is used to carry out a numerical simulation on the wind environment in an urban residential area in Lisbon. The computational results are compared with the wind tunnel experimental data, showing that the numerical results in the LES have a good agreement with the experimental results, and the simulated flow field with the inlet fluctuations can generate a reasonable turbulent wind field. It also shows that strong wind velocities and turbulent kinetic energy occur at the passageways, which may affect the comfort of people in the residential neighborhood, and the small wind velocities and vortexes appear at the leeward corners of buildings, which may affect the spreading of the pollutants.

• 대한기계학회논문집A
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• 제24권9호
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• pp.2159-2166
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• 2000

Recently, high performance machining center requires special type of sealing mechanism that prevent a leakage of oil jet or oil mist lubrication system. Sealing of oil-air mixture plays important r oles to have an enhanced lubrication for performance machining center. Current work emphasizes on investigations of the air jet effect on the protective collar type labyrinth seal. To improve sealing capabilities of conventional labyrinth seals, air jet is injected against the leakage flow. In this study, an adapted model is introduced to improve sealing capability of conventional non-contact type seals. It has a combined geometry of a protective collar type and an air jet type. Both of a numerical analysis by CFD (Computational Fluid Dynamics) and experimental measurements are carried out to verify sealing improvement. The sealing effects of the leakage clearance and the air jet magnitude aic studied in various parameters. Gas or liquid has been used as a working fluid for most of nori-contact types seals including the labyrinth seal. However, it is more reasonable to regard two-phase flows because oil mist or oil jet are used for high performance spindle's lubrication. In this study, working fluid is regarded as two phases that are mixed flow of oil and air phase. Both of turbulence and compressible flow model are also introduced in a CFD analysis to represent an isentropic process. Estimation of non-leaking property is determined by amount of pressure drop in the leakage path. Results of pressure drop in the experiment match reasonably to those of the simulation by introducing a flow coefficient. Effect of the sealing improvement is explained as decreasing of leakage clearance by air jetting. Thus, sealing effect is improved by amount of air jetting even though clearance becomes larger