• 한국전산유체공학회:학술대회논문집
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• 2007.10a
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• pp.272-276
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• 2007

In this paper, we researched a parametric study in flow control system using louver with numerical method. Generally, for the large fans with constant rotational speed, the louver can be used to control the flow rate. The opening and closing of louver can make a some change of flow properties generated by a large fan. To develope the relation between the opening angle of louver and flow rate(or pressure difference), we simulated the flow past the modelled louver installed in a virtual wind tunnel. For the various angles, the mean flow properties are investigated and parameterized with a given boundary condition. The research result can be used directly to design the flow control system of large constant-speed fans, which are often applied to petrolic refinery system.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.6
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• pp.60-67
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• 2002

A precise measurement of field test was performed to estimate the thermal performance of the forced convection electric air heater by experiment. Air temperature, flow rate and electrical power input were measured with the related measurement sensors, and acquisition methods for the measured data were studied to estimate the thermal performance of the tested air heater effectively. To determine the mean air temperature at the flow cross-section, measuring positions were chosen by considering the flow velocity profile and the equally divided cross-sectional area. From the experimental results, thermal efficiency was obtained accurately as an indication of the tested heating system performance.

• The Journal of Internal Korean Medicine
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• v.21 no.5
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• pp.805-811
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• 2000

Objectives : To determine the effects on blood flow of vertebrobasal vascular system in cerebral infarction, Methods : We altered 33 normal patients and 12 patients who were diagnosed cerebral infarction on Rt. middle cerebral artery(MCA) region and 8 patients who were diagnosed cerebral infarction on Lt, MCA region, and measured the mean velocity, systolic to diastolic rate(SD rate), asymmetrical index(A/I) by TCD. Results : The mean velocity of posterior cerebral artery(PCA), vertebral artery was increased in same direction as infarcted site and the mean velocity of basal artery was more increased than control, and the SD rate of PCA, vertebral artery, basal artery was larger than control. The A/l of PCA, vertebral artery was revealed that mean velocity of vertebrobasal vascular system is increase the same direction as infarcted area. Conclusion : TCD examination within 7 days(acute stage) after stroke can help to predict the infarcted direction.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.1
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• pp.74-81
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• 2016

The aim of this study was to find the initial design value of turbine blade for electrical type turbocompound system generating 10 kW. Turbocompound is one of the waste heat recovery system applying to internal combustion engine to recover exhaust gas energy that was about 30 % of total input energy. To design the turbine blade, 1-D mean line flow model was used. Exhaust gas temperature, pressure, flow rate and turbine rotating speed was fixed as primary boundary conditions. The velocity triangles was defined and used to determine the rotor inlet radius and width, the rotor outlet radius at shroud and radius at hub, the rotor flow angles and the number of blades.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.4
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• pp.407-416
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• 2007

Fuel spray nozzle has a critical effect on combustion characteristics. Mass flow rate and SMD(sauter mean diameter) were selected as design variables by using the experiment data of various types of duplex fuel nozzles for the swirl atomizers. The sensitivity of each design variable on the mass flow rate and SMD was analyzed and the uniformity of mass flow rate was investigated through the shape optimization of duel-orifice-type swirl atomizers. The design variables that have a little effect on the optimum design were excluded using the DOE(design of experiments) method, which enabled the optimization of sensitive design variables on mass flow rate and limit tolerance. The SMD of the research spray nozzle that was used in this study was found to be most similar to that of the calculation results using the Jasuja's SMD relationship. This study showed the specific characteristics of duel orifice type swirl atomizers and the optimization of these kinds of nozzle. This study provided the optimization design of mass flow rate and its allowable tolerance.

• Journal of the Korean Society of Visualization
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• v.15 no.3
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• pp.14-19
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• 2017

Increase of blood viscosity significantly changes the flow resistance and wall shear stress which are related with cardiovascular diseases. For measurement of blood viscosity, microfluidic method has proposed by monitoring pressure between sample and reference flows in the downstream of a microchannel with two inlets. However, it is difficult to apply this method to unknown flow conditions. To measure blood viscosity under unknown flow conditions, a microfluidic method based on micro particle image velocimetry(PIV) is proposed in this study. Flow rate in the microchannel was estimated by assuming velocity profiles represent mean value along channel depth. To demonstrate the measurement accuracy of flow rate, the flow rates measured at the upstream and downstream of a T-shaped microchannel were compared with injection flow rate. The present results indicate that blood viscosity could be reasonably estimated according to shear rate by measuring the interfacial width and flow rate of blood flow. This method would be useful for understanding the effects of hemorheological features on the cardiovascular diseases.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.8 no.1
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• pp.27-32
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• 1997

Recently, many people suffering from voice color change visit otolaryngologist. There is no specific data which can be evaluated objectively for voice color change in korean. In aerodynamic study, maximum phonation time, mean air flow rate, phonatory flow volume and subglottal pressure were tested by using Aerophone II voice function analyzer in korean. 112 male and 122 female aged from 10 to 69 years were randomly selected. Maximum phonation time was 20.8${\pm}$6.4sec in male and 17.2${\pm}$4.1sec in female. Mean air flow rate was 167.1${\pm}$61.4ml/sec. in male and 129.6${\pm}$49.3ml/sec in female. Phonatory flow volume was 3184.5${\pm}$646.0ml in male and 2122.1${\pm}$670.5ml in female. Subglottal pressure was 4.1${\pm}$1.8 cmH2O in male and 3.5${\pm}$1.4cm $H_2O$ in female. There was no statistically significant difference among age groups in all above results.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.9 no.2
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• pp.109-114
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• 1998

Background and Objectives : Aerodynamic investigation is valuable information about the efficiency of the larynx in translating air pressure to acoustic signal. The normal data of the Korean has been reported, but there is no basic data of professional western classical singers who have learned how to control the flow of expiratory air for singing. The purpose of this study was to investigate the normal aerodynamic data of korean professional western classical singers and compare this with that of the Korean Materials and Methods : 50 Korean western classical singers were studied. Expiratory lung pressure combined with measurements of the mean air flow rate, voice frequency and intensity were measured with the aerodynamic test using airway interruption method. These data were compared with normal data of untrained normal adults. Results and Conclusions : The voice frequency and the voice intensity were increased in the western classic singers, but the mean air flow rate and the expiratory air pressure of the classical singers were within the same range of the untrained normal adults. This result means that western classical singers can change the loudness and pitch with a little increased or decreasing the mean air flow and the expiratory air pressure.

• Journal of Chest Surgery
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• v.24 no.12
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• pp.1167-1172
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• 1991

Since March 1988 we have performed 133 arteriovenous fistulae for hemodialysis in 121 patients with chronic renal failure. Of the 133 cases of arteriovenous fistulae, follow-up evaluation was possible for 80 cases which performed in 69 patients. The relation between blood flow and patency rate and duration of arteriovenous fistula was examined. The overall 6 - 12 - 18 -, and 24 - month patency rates of arteriovenous fistulae were 82%, 64%a, 62%, and 57%, respectively. The maximum blood flow was 150 ~ 350ml /min[mean 217.1$\pm$44.27]. The patency duration was evaluated in patients divided into three groups owing to maximum blood flow through the fistulae. The range of maximum blood flow was 150 ~ 200ml /min for group A, 200 ~ 250ml /min for group B, and above 250ml /min for group C. The mean duration of the patency was 10.7$\pm$7.60 months in group A, 14.9$\pm$9.82 months in group B, and 21.6$\pm$11.16 months in group C[p<0 05]. With increased maximum blood flow, the duration of the patency was longer in group A than group B and C [r=0.39, p<0. 05]. The maintenance blood flow was 100 ~ 250ml /min[mean 179.2$\pm$37.26 ml/min]. When the maintenance blood flow was above 200ml /min, long-term patency rate was higher than the group below 200ml /min[r=0.48, p<0.01]. In the same range of blood flow, patency duration of the patients with using their own blood vessels were longer than the patients with using vascular graft for A-V fistula. We concluded that the patency of the arteriovenous fistulae was closely correlated with the blood flow through the fistulae.

• Journal of Oral Medicine and Pain
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• v.26 no.4
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• pp.331-343
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• 2001

Advances in medical procedures and utilization of medication have resulted in expanding aged population, which leads to increased aged patients with salivary hypofunction and its associated symptoms in dental clinic. The purpose of this study was to investigate clinical characteristics of patients with dry mouth and its correlation with their salivary flow rate. Forty dry mouth patients (7 males, 33 females, mean age 42.0 years) whose flow rate of unstimulated whole saliva was less than 0.15 ml/min were included and their gender- and age-matched controls (7 males, 33 females, mean age 42.9 years) who did not report any complaints, suggestive of salivary gland dysfunction and had the flow rate of greater than 0.20 ml/min were included for comparison. The salivary flow rate was measured in both unstimulated and stimulated conditions. Dry mouth-related clinical information including history, dry mouth associated symptoms, exacerbating and relieving factors, drugs, systemic diseases, and family history was investigated using questionnaires. The differences in distribution of patients and control subjects to each question and their relation to the salivary flow rate were analyzed and we came to following conclusions. 1. There were statistically significant differences in the distribution of patients and controls to the following questions: the period and frequency of suffering from dry mouth; severity of dry feeling during a meal; severity of discomfort during swallowing; necessity of sipping liquids during swallowing dry foods, severity of discomfort in usual life due to dry feeling; self-assessment of residual salivary volume; taking medications. 2. The patients had more stress-related medical histories including indigestion, insomnia, and gastritis compared with controls. The patients took many kinds of medications to control their systemic diseases. 3. There were statistically significant differences in the salivary flow rate between different groups of patients to following questions: severity of dry feeling during a meal; severity of discomfort during swallowing; necessity of sipping liquids during swallowing dry foods. The difference was more significant in the case of stimulated salivary flow rate rather than unstimulated one. 4. The salivary flow rate of patients taking medications was significantly less than that of patients who did not take medications. The difference was more significant in the case of stimulated salivary flow rate rather than unstimulated one.