• Journal of computational fluids engineering
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• v.16 no.4
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• pp.64-71
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• 2011

Cerebral aneurysm mostly occurs at a bifurcation of the circle of Willis. When the cerebral aneurysm is ruptured, a disease like subarachnoid hemorrhage and stroke is caused and this can be even deadly for patients. Generally it is known that causes of the intracranial aneurysm are a congenital deformity of the artery and pressure or shear stress from the blood flow. A blood flow pattern and the geometry of the blood vessel are important factors for the aneurysm formation. Research for several hemodynamic indices has been performed and these indices can be used for the prediction of aneurysm initiation and rupture. Therefore, the numerical analysis was performed for hemodynamic characteristics of the blood flow through the cerebral artery applying the various bifurcation angle and flow rate ratio. We analyze the flow characteristics using indices from the results of the numerical simulation. In addition, to investigate the flow pattern in the aneurysm according to the bifurcation angle and the flow rate ratio, we performed the numerical simulation on the supposition that the aneurysm occurs.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.407-408
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• 2006

Passenger safety is one of the most important considerations in the purchase of an automobile. A curtain-type air bag is increasingly adapted in deluxe cars for protecting passengers from the danger of side clash. Inflator housing is a main part of the curtain-type air bag system for supplying high-pressure gases to pump up the air bag-curtain. Although the inflator housing is fundamental in designing a curtain-type air bag system, flow information on the inflator housing is very limited. In this study, we measured instantaneous velocity fields of a high-speed flow ejecting from the inflator housing using a dynamic PIV system. From the velocity field data measured at a high frame-rate, we evaluated the variation of the mass flow rate with time. From the instantaneous velocity fields of flow ejecting from the airbag inflator housing in the initial stage, we can see a flow pattern of broken shock wave front and its downward propagation. The flow ejecting from the inflator housing was found to have large velocity fluctuations and the maximum velocity was about 700m/s. The velocity of high-speed flow was decreased rapidly and the duration of high-speed flow over 400m/s was maintained only to 30ms. After 100ms, there was no perceptible flow.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.4
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• pp.511-517
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• 2003

An experiment is conducted to investigate the effect of air and water mass flow rates on cooling characteristics of mist impinging jet on a flat plate. The air mass flow rate ranges from 0.0 to 3.0 g/s, and water mass flow rates from 5.0 to 20.0 g/s. An air-atomizing nozzle is used fur the purpose of controlling air and water mass flow rates. The test section is designed distinctively from previous works to obtain local heat transfer coefficient distributions. Heat transfer characteristics of the mist impinging jet are explained with the aid of flow visualization. Surface temperature and heat transfer coefficient distributions become more uniform as air mass flow rate increases. The water flow rate provides substantial contribution to enhancement of cooling performance. On the other hand, The air mass flow rate weakly influences the averaged heat transfer rate when the water mass flow rate is low, but the averaged heat transfer rate Increases remarkably with the air mass flow rate in case of the high water mass flow rate.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.161-168
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• 2011

Cerebral aneurysm mostly occurs at a bifurcation of the circle of Willis. When the cerebral aneurysm is ruptured a disease like subarachnoid hemorrhage and stroke is caused and this can be even deadly for patients. Generally it is known that causes of the intracranial aneurysm are a congenital deformity of the artery and pressure or shear stress from the blood flow. A blood flow pattern and the geometry of the blood vessel are important factors for the aneurysm formation. Research for several hemodynamic indices has been performed and these indices can be used for the prediction of aneurysm initiation and rupture. Therefore, the numerical analysis was performed for hemodynamic characteristics of the blood flow through the cerebral artery applying the various bifurcation angle and flow rate ratio. We analyze the flow characteristics using indices from the results of the numerical simulation. In addition, to investigate the flow pattern in the aneurysm according to the bifurcation angle and the flow rate ratio, we performed the numerical simulation on the supposition that the aneurysm occurs.

• International Journal of Automotive Technology
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• v.8 no.5
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• pp.575-581
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• 2007

As current and future automobile emission regulations become more stringent, the research on flow distribution for an exhaust manifold and close-coupled catalyst(CCC) has become an interesting and remarkable subjects. The design of a CCC and exhaust manifold is a formidable task due to the complexity of the flow distribution caused by the pulsating flows from piston motion and engine combustion. Transient flow at the exhaust manifold can be analyzed with various computational fluid dynamics(CFD) tools. However, the results of such simulations must be verified with appropriate experimental data from real engine operating condition. In this study, an experimental approach was performed to investigate the flow distribution of exhaust gases for conventional cast types and stainless steel bending types of a four-cylinder engine. The pressure distribution of each exhaust sub-component was measured using a simulated dynamic flow bench and five-hole pitot probe. Moreover, using the results of the pitot tube measurement at the exit of the CCC, the flow distribution for two types of manifolds(cast type and bending type) was compared in terms of flow uniformity. Based on these experimental techniques, this study can be highly applicable to the design and optimization of exhaust for the better use of catalytic converters to meet the PZEV emission regulation.

• Journal of Wetlands Research
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• v.10 no.3
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• pp.57-68
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• 2008

For improving water quality and hish habitat environment the targeted instream flows added to the field measurement of low flow at each reach along Wonju Cheon are calculated by depth, velocity, and the present lower channel width with considering the landscape, aquatic environment, and natural ecological function. Target instream flow increasing ranged from $0.03m^3/s$ of upstream to $0.90m^3/s$ of downstream according to the proposed depths of 0.10m to 0.30m and velocity of 0.2m/s. The methods for target instream flow increasing are base flow increasing by watershed management, non polluted discharge inflow from valley and combined sewer by sewerage system modification, and discharges from upstream reservoirs and detention basins near-by stream. The possible increasing flow rates are $0.19m^3/s$ to $3.42m^3/s$ which are 1.4 to 2.5 times of low flow to be measured which are the equivalent targeted instream flows along Wonju Cheon. The BOD-based water quality improvement are analyzed by QUAL2E. The habitat suitability indices by PHABSIM of Zacco temmincki as target species at middle stream of Wonju Cheon improve significantly by low flow increasing, which is very important to improve water quality and fish habitat.

• Journal of The Korean Society of Integrative Medicine
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• v.11 no.3
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• pp.219-226
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• 2023

Purpose : The purpose of this study was to compare changes of salivary flow rate, salivary buffering capacity, and S. mutans after using a mouthwash containing essential oil or probiotics widely used as oral lactic acid bacteria in the oral environment. Methods : Fifty-three healthy adults aged 20 years or older voluntarily participated in this study after they were informed of the purpose of this study. Subjects were divided into a group treated with probiotics (L. reuteri) and a group treated with mouthwash containing essential oil. To evaluate changes in the oral environment, salivary flow rate, salivary buffering capacity, and S. mutans test were performed at baseline and 4 weeks later. Unstimulated and stimulated salivary flow samples were collected for 5 minutes and results were recorded in ml per minute. Salivary buffering capacity was divided into scores of 1 (low), 2 (moderate) and 3 (high) according to the color of the strip. The amount of S. mutans was classified as scores of 0, 1, 2, and 3 according to the decision table. Data collected in this study were analyzed at the 95 % significance level using the SPSS Version 23.0 program. Results : Both the unstimulated salivary flow rate and the stimulated salivary flow rate increased statistically after the intervention compared to those before intervention in the probiotics group. However, there was no statistically significant difference between the probiotics group and the mouthwash group. Salivary buffering capacity and S. mutans results showed no statistically significant differences between the probiotics group and the mouthwash group either. The salivary buffering capacity and the salivary flow rate showed a positive correlation. Conclusion : To improve the oral environment, such as salivary flow rate and salivary buffering capacity, an optimal product can be selected in consideration of individual preference and cost-effectiveness.

• Journal of Korean Neurosurgical Society
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• v.67 no.2
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• pp.158-165
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• 2024

Objective : Superficial temporal artery (STA)-middle cerebral artery (MCA) anastomosis is conducted for flow augmentation. In this study, we measured the STA cut flow of a Korean population and evaluated the relationship between STA cut flow and long-term patency of the bypass. Methods : A retrospective study was conducted. Intraoperative measurement of STA flow was conducted using a microvascular flow meter on patients who underwent STA-MCA. After cutting the distal end, the STA flow rate was measured with no resistance and recorded. After finishing anastomosis, STA flow was measured and recorded. The cut flow index was calculated by dividing post anastomosis flow by cut flow in intracranial atherosclerotic stenosis patients. Results : The median STA cut flow was 35.0 mL/min and the post anastomosis flow was 24.0 mL/min. The cut flow of STA decreased with aging (p=0.027) and increased with diameter (p=0.004). The cut flow showed no correlation with history of hypertension or diabetes mellitus (p=0.713 and p=0.786), but did correlate a positively with history of hyperlipidemia (p=0.004). There were no statistical differences in cut flow, STA diameter, and post anastomosis flow between the frontal and parietal branches (p=0.081, p=0.853, and p=0.990, respectively). Conclusion : The median STA cut flow of a Korean population was 35 mL/min. Upon reviewing previous articles, it appears that there are differences in the STA cut flow between Western and Asian patients.

• Nuclear Engineering and Technology
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• v.55 no.11
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• pp.3973-3982
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• 2023

As for two-phase flow in rectangular channels, the flow regimes especially like churn-turbulent and annular flow are significant for the physical problem like Countercurrent Flow Limitation (CCFL). In this study, the rectangular channels with cross-sections of 4 × 66 mm, 6 × 66 mm, 8 × 66 mm are adopted to investigate the flow regimes of air-water vertical upward two phase flow under adiabatic condition. The gas and liquid superficial velocities are 0 ≤ j_g ≤ 20m/s and 0.25 ≤ j_f ≤ 3m/s respectively which covering bubbly to annular flow. The flow regimes are identified by random forest algorithm and the flow regime maps are obtained. As the results, the transitional void fraction from slug to churn turbulent flow fluctuate from 0.47 to 0.58 which is significantly affected by the dimensional size of channel and flow rate. Besides, the void fraction at transitional points from churn-turbulent (slug) to annular flow are 0.66-0.67, which are independent with the gap size. Furthermore, a new criteria of slug to churn-turbulent flow is established in this study. In addition, by introducing the interfacial force model, the criteria of churn-turbulent (slug) flow to annular flow is verified.

• Journal of the Korea Construction Safety Engineering Association
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• s.41
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• pp.80-87
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• 2007

The purpose of this paper is to investigate the removal efficiency of fine dusts as the configuration condition of machinery and equipments in Clean Room and to analyze the flowing behaviors of fine dusts as the layout of Clean Room. The layout of the Clean Room was classified into side layout type, 2 center line type and center concentration type layout, and the flow rates used in this research were 0.22m/s, 0.44m/s and0.80m/s. Dust removal efficiency as layout change was decreased 37% for side layout type, 31% for 2 centerline type and 20% for center concentration type layout at the flow rate of 0.22m/s, compared with the state without machinery and equipments in Clean Room. The efficiency was decreased 42% for side layout type,22% for 2 center line type and 8% for center concentration type layout at the flow rate of 0.44m/s, and decreased 20% for side layout type, 18% for 2 center line type and 10% for center concentration type layout at the flow rate of 0.80m/s. According to the result of dust removal behavior, $0.3\mum$, $1\mum$and $3\mum$dust except for $5\mum$showed the higher change of the behavior in side layout type than in center concentration type layout due to the change of air flow. It was confirmed that removal behavior depends on the layout of machinery and equipments as the dust size decreases.