• 치과방사선
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• 제26권2호
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• pp.65-73
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• 1996

The purpose of this study was to evaluate the clinical and computed tomographic features of 7 cases of maxillofacial gunshot injuries in the suicidal patients visited the emergency room, Capital Armed Forces General Hospital. The obtained results were as follows : 1. The gunshot wounds were directed from submental area to dorsum of nose(3 cases), frontal area(1 case), orbit(1 case), infraorbital area (1 case), and lateral to nasal wing(l case). The shape of inlet in gunshot wounds were round (diameter: l-3cm) and that of outlet were oval shape(size : inlet

• 한국유체기계학회 논문집
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• 제18권1호
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• pp.20-28
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• 2015

The pump-turbine impeller is the key component of pumped storage power plant. Current design methods of pump-turbine impeller are private and protected from public viewing. Generally, the design proceeds in two steps: the initial hydraulic design and optimization design to achieve a balanced performance between pump mode and turbine mode. In this study, the 3D inverse design method is used for the initial hydraulic impeller design. However, due to the special demand of high performance in both pump and reverse mode, the design method is insufficient. This study is carried out by modifying the geometrical parameters of the blade which have great influence and need special consideration in obtaining the high performance on the both modes, such as blade shape type at low pressure side (inlet of pump mode, outlet of turbine mode) and the blade lean at blade high pressure side (outlet of pump mode, inlet of turbine mode). The influence of the geometrical parameters on the performance characteristic is evaluated by CFD analysis which presents the efficiency and internal flow results. After these investigations of the geometrical parameters, the criteria of designing pump-turbine impeller blade low and high sides shape is achieved.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2002년도 제24회 KOSCO SYMPOSIUM 논문집
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• pp.85-94
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• 2002

Computational flow dynamics(CFD) has been frequently applied to the waste incinerators to understand the flow performance for various design and operating parameters. Though it needs many simplifications and complicated flow models, the reasonability of its results is not fully evaluated. For example, the inlet condition is calculated from an arbitrarily assumed properties of combustion gas release from the waste bed, since the combustion in the bed is difficult to be predicted. In this study, the computational modeling and calculation procedures of CFD for the grate type waste incinerator were evaluated using comparative simulations. Though the assumption method on the generation of the combustion gas directly affected the temperature and gas species concentrations, the overall flow pattern was dominated by the secondary air jets. The gaseous reaction could be included by assuming the release of the products of incomplete combusion from the bed. However, the reaction effficiency cannot not be directly evaluated from the species concentration, since it is not possible to simulate the actual co-existence of fuel rich or oxygen rich puffs over the bed. In predicting the turbulence, the higher order model, such as Reynolds stress model, gave difference shape of local recirculation zones, but similar results was acquired from the standard $k-{\varepsilon}$ model. Introducing radiation model was required for accurate temperature prediction, but it also caused heat imbalance due to the fixed temperature of the inlet, i.e. the waste bed. Thus, the computational modeling procedures on incinerators and the analysis of the predicted results should be progressed carefully. Though not validated experimentally, current simulation method is capable of comparative evaluation on the flow-related parameters such as the furnace shape and secondary air injection using identical inlet conditions. Quantitative analysis using measures of the residence time and mixing is essential to compare the flow performance efficiently.

• Journal of Biosystems Engineering
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• 제42권1호
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• pp.1-11
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• 2017

Purpose: Methods: Three-dimensional CFD modeling was conducted to analyze the flow structure and discharge flow rate corresponding to the variation in the geometry of the flow channel in a microtube. Additionally, experiments were carried out, and the discharge flow rate was measured at various inlet pressures and inclination angles of the microtube. Results: The quantitative data of velocity distribution and discharge flow rate were obtained. As the width and length of the microtip increased, the discharge flow rate decreased significantly because of the increase in the loss of pressure along the microtube. As the depth of the microtip increased, the flow rate also increased because of the reduction in the flow resistance. However, in this analysis, the variation in the angle of the microtip did not influence the flow rate. From the experimental results, it was observed that the flow rate increased linearly with the increase in the inlet pressure, and the effects of the inclination angle were not clearly observed in those test cases. The values of the flow rate obtained from the experiments were significantly lower than that obtained from the CFD analysis. This is because of the distortion of the shape of the flow path inside the microtube during the fabrication process. The distortion of the flow path might decrease the flow cross-sectional area, and it would increase the flow resistance inside the microtube. The variation in the flow rate corresponding to the variation in the inlet pressure showed similar trends. Conclusions: Therefore, the results of the numerical analysis obtained from this study can be efficiently utilized for optimizing the shape of the microtip inside a microtube.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.546-550
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• 2008

In this study, 3-dimensional Computational Fluid Dynamics (CFD) analysis was induced to simulate air flow and particle motion in the axial flow cyclone separator. The commercialized CFD code FLUENT was used to visualize pressure drop and particle collection efficiency inside the cyclone. We simulated 4 cyclone models with different shape of vane, such as turning angle or shape of cross section. For the air flow simulation, we calculated the flow field using standard ${\kappa}-{\varepsilon}$ turbulence viscous model. Each model was simulated with different inlet or outlet boundary conditions. Our major concern for the flow filed simulation was pressure drop across the cyclone. For the particle trajectory simulation, we adopted Euler-Lagrangian approach to track particle motion from inlet to outlet of the cyclone. Particle collection efficiencies of various conditions are calculated by number based collection efficiency. The result showed that the rotation angle of the vane plays major roll to the pressure drop. But the smaller rotation angle of vane causes particle collection efficiency difference with different inlet position.

• 한국농공학회지
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• 제42권1호
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• pp.73-82
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• 2000

Large quantitive of polllutants are washed into reservoirs during storm events. These polllutants contribute to eutrophication, such as algal blooms and fish kills. This study was conducted for the purpose of assessing the pollutant removal possibilities of sedimentation pool formed by deep dredging of a reservoir inlet. Water quality data were collected in the Masan reservoir, whose inlet has been dredged deep like sedimentation pool. The average concentration of chemical oxygen demand(COD) , toatal nitrogen(T-N) and total phosphrous(T-P) in the deep dredged area were 8.7 ~20.5mg/ι (T-N), 0.17~0.84mg/ι(T-P), which were 4.9%(COD), 29.0%(T-N) and 44.8%(T-P) higher than those of middle part of the reservior. The texture of sediment in the dredged area was silty loam, while that of the middle part was sandy clay loam. Organic matter contents, T-N and T-P of the bottom soil in the dredge area showed higher values than the middle part of the reservoirs. From these results, it was considered thedeep dredged area in the inlet of reservoir might play a key role to settle pollutant particulate. Based on the result of water quality analysis, deep dredging of the reservoir inlet could be assessed to reduce T-N and T-P of the reservoir about 6.5% , 8.3%, respectively. However, the effect of the sedimentation pool would be raised if the settled particles were taken into account in assessing water quality improvement for the reservoir. Accordingly, dredging of a reservoir inlet to make a shape of sedimentation pool is recommended for water quality improvement of reservoir in the stage of dredging plan.

• 한국대기환경학회지
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• 제18권5호
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• pp.401-410
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• 2002

Concerns for energy conservation, environmental pollution, and the fact that organic wastes account for a major portion of our waste materials, have created the interest of biogas, which usually contains about 60 to 70 percent methane, 30 to 40 percent carbon dioxide, and other gases, including ammonia, hydrogen sulfide, mercaptans and other noxious gases. Cyclone combustors are used for homing a wide range of fuels such as low calorific value gas, waste water, sludge. coal, etc. The 3-dimensional swirling flow, combustion and emission in a tangential inlet cyclone incinerator under different inlet conditions are simulated using a standard k-s turbulence model and ESCRS (Extended Simple Chemically-Reacting System) model. The commercial code Phoenics Ver.3.4 was used for the present work. The main parameters considered in this work are inlet velocity and air to fuel ratio. The results showed that the change of operating conditions had an influence on the shape and size of recirculation zones, mixture fraction and axial velocity which are important factors for combustion efficiency and emission behavior. The application of this kind of computer program seams to be promising as a potential tool for the optimum design of a cyclone combustor with low emission.

• 한국기계가공학회지
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• 제15권6호
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• pp.35-40
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• 2016

In this study, the thermal and fluid dynamic characteristics for the coating process of large-sized water pipes was studied by heating the inside of a pipe directly with a gas burner. Heat and flow analyses were performed on large pipes with various inlet shapes. Using large pipes for coating was shown to be the proper shape for heating large pipes uniformly. This type has a screw with a diameter of 200 mm installed at the inlet to provide a rotational motion to the heating air. The rotational motion resulted in a uniform temperature distribution that ranged from $289.1^{\circ}C$ to $352.1^{\circ}C$ The optimized geometric configuration of the inlet of the pipe successfully and uniformly enhanced the thermal characteristics of the devised temperature limit.

• 수산해양기술연구
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• 제51권4호
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• pp.545-552
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• 2015

The main object of this study is to investigate the collection characteristics of an electro-static multi-staged impaction system, experimentally. The experiment is carried out to analyze the characteristics of pressure drop and collection efficiency for the present system with the experimental parameters such as the inlet velocity, stage number, applied voltage and shape of discharge electrode, etc. In results, the pressure drop is shown below $148mmH_2O$ lower than that of the conventional bag filter at inlet velocity 3.46 m/s and 5 stage. For 5 stage, the collection efficiencies are to be 97.4, 99.0% with the applied voltage 0 kV at the inlet velocity 2.07, 3.46 m/s, while 98.4, 99.9% with 40 kV of a sharp edge discharge electrode. Additionally, the present system is to be considered as an effective compact system for a removal of particulate pollutants from marine diesel engines due to much higher collection efficiency and appropriate pressure drop.

• 대한기계학회논문집B
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• 제38권2호
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• pp.115-120
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• 2014

자동차용 터보차저 압축기의 성능 개선을 위해 원주방향의 볼류트 입구 높이들이 수정되었고 디퓨저를 포함한 볼류트에 대한 유동장이 상용 소프트웨어를 사용하여 조사되었다. 기본적으로 잘 설계된 볼류트는 높은 압력회복계수와 낮은 전압력손실계수를 보여주어야 한다. 본 연구에서는 동일한 단면형상과 설단면각(Tongue Angle)을 가지나 원주방향으로는 서로 다른 볼류트 입구 높이를 갖는 두 경우의 원형단면 볼류트가 선정되었다. 하나는 $90^{\circ}$ 원주방향에서는 단면 중앙으로 유입되나 이후의 원주방향에서는 볼류트 단면 최하단부들을 잇는 접선과 동일한 높이를 유지하면서 점진적으로 하단부로 유입되는 볼류트 형상이다(케이스 1 볼류트). 다른 하나는 설단면에서는 접선방향으로 유입되도록 모든 원주방향에 대하여 입구 높이를 2 mm 낮춘 형상이다(케이스 2 볼류트). 해석결과, 케이스 2 볼류트가 케이스 1 볼류트보다 높은 압력회복계수로 인한 높은 전압력비와 낮은 전압력손실계수로 인한 높은 등엔트로피 효율을 보여주었다.