• Journal of the Korean Society of Industry Convergence
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• 제26권2_2호
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• pp.307-313
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• 2023

This study conducts the flow analysis on the basis of the impeller RPM of water metering valve. The software used for the flow analysis is STAR-CCM+. In terms of the structure of the metering valve, it has an impeller installed inside, and a metering chamber has inlet and outlet holes. The flow analysis on the water metering valve drew the following conclusions: Regarding the flow field in the valve, the impeller had the highest velocity distribution, and complex flow field was generated in the metering chamber. In particular, since the path between the inlet and outlet holes in the metering chamber and the valve body was narrow, there was a section that had flow field interference. The flow rate and flow coefficient distribution according to the impeller RPM were on the linear increase. Given that, it showed the feature of the valve used for water metering on the basis of the impeller RPM.

• Journal of Periodontal and Implant Science
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• 제30권2호
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• pp.471-482
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• 2000

Recent studies have demonstrated that smoking may be one of the most significant risk factors in the development and progression of periodontal disease. Reports have indicated that smoking causes gingival blood flow to be decreased. However, studies on the effects of smoking on gingival blood flow have yielded contradictory results. The purpose of the present study was to determine the effect of smoking on gingival blood flow. One hundred volunteers(fifty non-smokers and fifty smokers) with good general and periodontal health, aged twenties(non-smoker : 22-29 years, mean=25.36, smoker : 23-29 years, mean=26.64) were selected. Laser Doppler flowmetry (floLAB, Moor Instruments Ltd., England) was applied to measure the gingival blood flow of interdental papilla, marginal gingiva, attached gingiva and alveolar mucosa of left and right upper lateral incisors. In smokers, following an overnight abstinence from smoking, gingival blood flow was measured before smoking, immediately after smoking, 1-, 2-, 3-, 4-, 5- and 6- hour after smoking from 9 a.m. to 3:30 p.m. The difference of blood flow in each tissue of non-smokers and that of each measuring time and each tissue of smokers were statistically analyzed by one way ANOVA and Tukey test. And the difference of blood flow between smokers and nonsmokers in each tissue was statistically analyzed by t-test. The results were as follows : 1. Mean blood flow was highest in alveolar mucosa, followed by interdental papilla, attached gingiva and marginal gingiva in both smokers and nonsmokers. There was a statistically significant difference in each tissue(p<0.05) . 2. There was no consistent result between mean blood flow before smoking in smokers and that of nonsmokers in each tissue. 3. There was a statistically significant difference between gingival blood flow at measuring time point and gingival blood flow of smokers in each tissue(p<0.05). The present study suggested that smoking could alter the gingival blood flow, thus might be partly contributed to periodontal destruction.

• Proceedings of the KSME Conference
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2935-2940
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• 2007

To diagnose circulatory diseases in the viewpoint of hemodynamics, we need to get quantitative hemodynamic information of blood flows related with the vascular diseases with high spatial resolution of tens micrometer and high temporal resolution in the order of millisecond. For investigating in-vivo hemodynamic phenomena, a new diagnosing technique combining medical radiography and PIV method was newly proposed and developed. This angiographic PIV technique consists of a medical X-ray tube, an X-ray CCD camera, a shutter module for double pulses of X-ray, and a synchronizer. The feasibility of the angiographic PIV technique was tested and quantitative flow velocity field distribution of a flow inside an opaque conduit was acquired by the developed system. It can be used for measuring flow phenomena of nontransparent fluids inside opaque conduits.

• Journal of Engineering Education Research
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• 제20권4호
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• pp.61-66
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• 2017

Automatic flow control system composed by hardware and software was designed and fabricated to be used as teaching tool of feedback control theory in university experimental class. This system includes hardwares like data acquisition board, flow measuring device, transmitters, and the pneumatic valve, and software like LabView program for the monitoring and control of flow rates. The system was designed as the student can see the control effect of not only set point but also disturbance changes. Also the LabView program was composed for the calculation of controller parameters of both Ziegler-Nichols and Cohen-Coon tuning. The students can apply both tuning constants and compare the control performances. This system will provide the easy way for the students to understand the function and specification of control hardwares, and to raise the programing ability of control software.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.646-651
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• 2002

The flow field around a symmetrical airfoil in a uniform flow under the generation of noise was studied by experiments and numerical simulation. The experiments are conducted by visualizing the surface flow over the airfoil with a shear-sensitive liquid-crystal coating and by measuring the instantaneous velocity field around the trailing edge of the airfoil. The results indicate that the discrete frequency noise is generated when the separated laminar flow reattaches near the trailing edge of the pressure side and the turbulent boundary layer is formed over the suction side of the airfoil near the trailing edge. The periodic behavior of vortex formation was observed around the trailing edge and it persists further downstream in the wake. The frequency of the vortex formation in the wake was consistent with that of the discrete frequency noise.

• Journal of the Korean Society of Industry Convergence
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• 제3권1호
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• pp.29-36
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• 2000

In order to reduce a aerodynamic drag of the rear, body, effects of rear lower end configuration of a vehicles were investigated by measuring the pressure distribution, visual flow phenomena by the use of digital image processing technique. The use of flow visualization in recent years has improved the general understanding of structure of complex flow and has yielded valuable information for analyzing fluid flow. As the results, it was found that the shape of rear lower part vehicles not only effected on the pressure distribution of the rear part of the vehicle but also difference of the flow phenomena.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제5권1호
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• pp.183-191
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• 2001

We develop the new data s]ice representation, called the data value flow graph(VFG), for modeling the information flow oil data slices. Then we define a slice complexity measure by using the existing flow complexity measure in order to measure the complexity of the information flow on VFG. We show relation of the slice complexity on a slice with the slice complexity on a procedure. We also demonstrate the measurement scale factors through a set of atomic modifications and a concatenation operator on VFG.

• Transactions of the Korean Society of Mechanical Engineers B
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• 제26권11호
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• pp.1570-1577
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• 2002

In order to investigate the characteristics of two-phase slug flow, an electromagnetic flowmeter with 240Hz triangular AC excitation was designed and manufactured. The signals and noise from the flowmeter were obtained, and analyzed in comparison with the observations with a high speed CCD camera. The uncertainty of the flowmeter under single-phase flow was $\pm$ 2.24% in real-time. For two-phase slug flow, electromagnetic flowmeter provided real-time simultaneous measurements of the mean film velocity around Taylor bubble and the relative location and the length of the bubble. Besides, it is an easier and cheaper method for measuring mean film velocity than others such as photochromic dye activation method or particle image velocimetry.

• Transactions of the Korean Society of Mechanical Engineers
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• 제9권1호
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• pp.24-30
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• 1985

An experimental work to predict critical flow velocity to give whirling instability on staggered array tube banks model which is located in wind tunnel is presented. The critical flow velocity was obtained by measuring flow induced tube vibration on three tube array models having different pitch to diameter ratio as changing damping ratio and natural frequency of tube model. The obtained experimental results are directly compared with the numbers of other investigators and partly proved the truth of Blevin's new idea to predict critical flow velocity.

• Journal of Advanced Marine Engineering and Technology
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• 제31권8호
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• pp.954-960
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• 2007

The purpose of this paper is to obtain design method of air-distribution system. Air-distribution system is composed of blower, duct, diffusers and measuring equipment. The air-flow rate from each diffuser is not equal. The air-flow rate is calculated with the combined equations which are Bernoulli's equation, continuity equation and minor loss equations. Inlet condition and outlet condition are adapted in each duct system. Then square difference between function of maximum air-flow rate and minimum air-flow rate is used as an object function. Area of diffuser and velocity are established as constraints. To minimize the object function, the optimization method is used. After optimization the design variables are selected under satisfaction of constraints. The air-distribution system is calculated again with the result of optimized design variable. It is shown that the air-distribution system has the equal air-flow rate from diffusers.