• 동의생리병리학회지
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• 제20권6호
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• pp.1477-1484
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• 2006

This experimental study was designed to investigate the effects of Acanthopanax sessiliflorus $S_{EEM}$ extracts following gamma-ray irradiation on the change of weight, the serum total cholesterol, HDL-cholesterol, LDL-cholesterol, triglyceride, free fatty acid, total lipid, phospholipid level in obese mice induced by high fat diet, and the change of regional cerebral blood flow (rCBF) and blood pressure (BP) in normal rats. Experimental materials were as follows ; 10AS was the bark powder of Acanthopanax sessiliflorus $S_{EEM}$ stems which was exposed in 10 kGy electron beam, 10AS was the bark powder of Acanthopanax sessiliflorus $S_{EEM}$ roots which was exposed in 10 kGy electron beam, 100S was the bark powder of Acanthopanax sessiliflorus $S_{EEM}$ stems which was exposed in 100 kGy electron beam, Experimental groups were as follows ; Normal group was fed with normal diet and administered with distilled water during 5 weeks, Control group was fed with high fat diet and administered with distilled water during 5 weeks, Sample A group was fed with high fat diet and administered with 10AS of 300 mg/kg/mouse/day during 5 weeks, Sample B group was fed with high fat diet and administered with 10AR of 300 mg/kg/mouse/day during 5 weeks, Sample C group was fed with high fat diet and administered with 100AS of 300 mg/kg/mouse/day during 5 weeks. The results were as follows ; Sample A group, Sample B group and Sample C group were significantly decreased body weight and the serum LDL-cholesterol, triglyceride, total lipid level in comparison with Control group. Sample A group, Sample B group and Sample C group were significantly increased the serum HDL-cholesterol level in comparison with Control group. Sample B group and Sample C group were significantly decreased the serum total cholesterol, free fatty acid and phospholipid level in comparison with Control group. This results were suggested that all experimental materials were able to be used for the obesity. 10AS did not changed rCBF and MABP in a dose-dependent manner. 10AR significantly increased rCBR in a dose-dependent manner, and BP did not change in a dose-dependent manner. 100AS decreased rCBF and BP in a dose-dependent manner. This results were suggested that 10 AR significantly increased rCBF by dilating pial arterial diameter. According to above results, the authors suggested that 10AR was able to be used for the obesity and ischemic disease.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.800-804
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• 2005

Load flow and short circuit fault transients of a power distribution system with wind turbines as dispersed generation units is presented. Usage of renewable energies such as wind is already a small part of total installed power system in medium and low voltage networks. In this paper, a radial power distribution system with wind turbines is simulated using DIgSILENT PowerFactory software for their influence on load flow and short circuit fault transients. Short fault occurring in dispersed generation systems causes some problems for the system and costumers such as fault level increase or the problems of sudden fluctuations in the current, voltage, power and torque of the double fed induction machine utilized in the wind turbines which have been studied and investigated.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.980-985
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• 2003

The present study addresses a computational work to investigate the influence of a turbulent wake flow on the pressure recovery of a subsonic diffuser. The turbulent wake is generated by a cylinder with a small diameter, which is installed at the inlet of a 2-dimensional diffuser. Computation are applied to three-dimensional steady Navier-Stokes equations. The fully implicit finite volume scheme is used to discretize the governing equations. The computational results are qualitatively well compared to the experimental results. The results show that the pressure recovery of the subsonic diffuser is dependent on the diameter and location of cylinder. It is found that a certain diameter and location of the cylinder to generate the turbulent wake give a better pressure recovery, compared with no cylinder flow.

• 한국IT서비스학회지
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• 제6권3호
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• pp.163-177
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• 2007

This research is the concept of a game addiction absorbed in the game based on the review and analysis of factors that affect the characteristics of game addiction, it is appropriate to extract the purpose of factors. Game addiction factor is composed of a total of 32 questions, and a total of 356 people, to collect data through surveys. Factor analysis of the collected data to the target as a result of physical and mental problems, loss of control, tolerance, and avoidance of real world consists of three sub-factors. Factors that affect flow of tolerance and loss of control, and avoid the real world, including two sub-factors that could determine. Diagnostic game addiction factor in the reliability coefficients (Cronbach alpha) is a robust .966 aspects in the event. The game addiction scale score of 90-game addiction by category 'regular user', 90 points and 114 between the terms 'potentially dangerous user' and 13 percent of the overall. Finally, more than 115 points in the 'high-risk user' has been classified as 5% of the overall distribution of the notice that. Such factors extract game is a game addict, addicted users of the game and tend to properly evaluate and navigate game addiction-related problems early in the game addiction and found it could be used properly.

• Environmental Engineering Research
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• 제24권4호
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• pp.582-590
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• 2019

Currently, the waterfront facility was constructed in New Songdo City, South Korea. It has the various water leisure areas and especially an artificial urban canal with filtered seawater by re-circulating flow system. However, due to excessive amount of nutrients from seawater combined with complicated geometry, it is highly vulnerable to deterioration of water quality. In this study, flow characteristics and pollutant transport were analyzed with comprehensive numerical models, MIKE 3 FM and ECO-lab. Based on these numerical results, notable sampling points were selected for field measurements and comparison between modeling and measured results were conducted. In addition, the integrated water quality evaluation index, Water Quality Index was applied to analyze various water quality issues. We also set up scenarios to control the two kinds of water quality factors, dissolved oxygen (DO), and total phosphorus (TP). As a result, the effect of 20% reduction of TP was less than 10% and it was almost ineffective for a year but it was reduced by up to 40% in case of scenario which DO is increased by 20%. Therefore, it was recommended to control the DO concentration, usually by applying re-aeration facility, rather than TP in artificial urban canal with seawater.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제26회 춘계학술대회논문집
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• pp.306-309
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• 2006

슬롯을 이용한 충격파와 난류 경계층의 간섭유동의 피동제어에 관한 연구가 이루어졌다. 슬롯의 다양한 형상 변화가 간섭유동에 미치는 영향이 관찰되었으며, 이를 위하여 간섭유동 후방에서 피토/벽압력 분포 및 쉴리렌, 오일막 간섭 줄무늬 형상과 같은 유동가시화 정보 등이 얻어졌다. 특정한 슬롯적용의 경우, 충격파를 통한 전압손실의 감소가 관찰되었으나 경계층의 두께는 두꺼워지는 것으로 나타났다.

• 상하수도학회지
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• 제30권6호
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• pp.645-652
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• 2016

A membrane module including grid was designed and introduced to MBR (membrane bio-reactor) for the purpose of better control of membrane fouling. It could be anticipated that the grid enhances the shear force of fluid-air mixture into the membrane surface by even-distributing the fluid-air to the membrane module. As MLSS concentration, packing density which is expressed in the ratio of the housing and the cross-sectional area of membrane fibers ($A_m/A_t$) and air-flow rate were changed, membrane foulings were checked by monitoring fouling resistances. The total fouling resistance ($R_c+R_f$) without grid installation (i.e., control) was $2.13{\times}10^{12}m^{-1}$, whereas it was reduced to $1.69{\times}10^{12}m^{-1}$ after the grid was installed. Regardless of the grid installation, the $R_c+R_f$ increased as the packing density increased from 0.09 to 0.28, however, the increment of resistance for the grid installation was less than that of the control. Increase in the air flow rate did not always guarantee the reduction of fouling resistance, indicating that the higher air flow rate can partially de-flocculate the activated sludge flocs, which led to severer membrane fouling. Consequently, installation of grids inside the housing have brought a beneficial effect on membrane fouling and optimum air flow rate is important to keep the membrane lowering fouling.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 후기학술대회논문집
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• pp.230-231
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• 2005

As environmental problems are important, automotive industries are developing various techniques to prevent air pollution. One of these is Positive Crankcase Ventilation (PCV) system. It removes blowby gas which includes about 30% hydrocarbon of total generated quantity. In this system, a PCV valve is attached in a manifold suction tube to control the flow rate of blowby gas which generates differently according to various operating conditions of an automotive engine. As this valve is very important, designers are feeling to design it because of both small size and high velocity. For this reason, we numerically investigated to understand both spool dynamic motion and internal fluid flow characteristics. As the results, spool dynamic characteristics, i.e. displacement, velocity, acting force, increase in direct proportion to the magnitude of differential pressure and indicate periodic oscillating motions. And, the velocity at the orifice region decreases according to the increase of differential pressure because of energy loss which is caused by the sudden decrease of flow area at the orifice region and the increase of flow volume in the front of spool head. Finally, the mass flow rate at the outlet decreases with the increase of spool displacement. We expect that PCV valve designers can easily understand fluid flow inside a PCV valve with our visual information for their help.

• Journal of Electrical Engineering and Technology
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• 제8권4호
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• pp.872-878
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• 2013

In industrial control systems, flow measurement is a very important issue. It is frequently needed to calculate how much total fluid or gas flows through a cross-section. Flow volume measurement tools use simple sampling or rectangle methods. Actually, flow volume measurement process is an integration process. For this reason, measurement systems using instantaneous sampling technique cause considerably high errors. In order to make more accurate flow measurement, numerical integration methods should be used. Literally, for numerical integration method, Rectangular, Trapezoidal, Simpson, Romberg and Gaussian Quadrature methods are suggested. Among these methods, trapezoidal rule method is quite easy to calculate and is notably more accurate and contains no restrictive conditions. Therefore, it is especially convenient for the portable flow volume measurement systems. In this study, the volume measurement of air which is flowing through a cross-section is achieved by using PLC ladder diagram. The measurements are done using two different approaches. Trapezoidal rule method is proposed to measure the flow sensor signal to minimize measurement errors due to the classical sampling method as a different approach. It is concluded that the trapezoidal rule method is more effective than the classical sampling.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.159-160
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• 2002

New S-shaped aeroelastic mesoflaps are utilized to control normal shock/boundary-layer interactions. New generation of the mesoflaps is designed f3r a better rigidness and a good flow uniformity across the ulteractions. ,Major advantages of the mesoflap system can be a better total pressure recovery downstream of the interactions due to the lambda shock structure over the flap system, and a rehabilitation of the thickened boundary layer due to bleeding through a cavity underneath the flap system. Skin friction has been measured downstream of the interactions, using the laser interferometer skin friction (LISF) meter, which optically detects the rate of thinning of an oil film applied to the test surface. Various flap-thicknesses of the S-shaped mesoflap arrays are tested, and the results are compared to the solid-wall reference case. Overall, not much difference in the level of skin friction is noticed for the S-shaped flap arrays of various thicknesses, and its level is lower than the skin friction downstream of the solid-wall interaction