• International Journal of Fluid Machinery and Systems
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• 제9권2호
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• pp.169-174
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• 2016

A cross-flow wind turbine has a high torque coefficient at a low tip speed ratio. Therefore, it is a good candidate for use as a self-starting turbine. Furthermore, it has low noise and excellent stability; therefore, it has attracted attention from the viewpoint of applications as a small wind turbine for an urban district. However, its maximum power coefficient is extremely low (10 %) as compared to that of other small wind turbines. In order to improve the performance and flow condition of the cross-flow rotor, the symmetrical casing with a nozzle and a diffuser are proposed and the experimental research with the symmetrical casing is conducted. The maximum power coefficient is obtained as $C_{pmax}=0.17$ in the case with the casing and $C_{pmax}=0.098$ in the case without the casing. In the present study, the power characteristics of the cross-flow rotor and those of the symmetrical casing with the nozzle and diffuser are investigated. Then, the performance and internal flow patterns of the cross-flow wind turbine with the symmetrical casings are clarified. After that, the effect of the side boards set on the symmetrical casing is discussed on the basis of the analysis results.

• 환경영향평가
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• 제21권3호
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• pp.339-352
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• 2012

Total maximum daily load have been implemented and indicated that nonpoint discharge coeffients in flow duration curve were 0.50 of Normal flow duration ($Q_{185}$) and 0.15 of low flow duration($Q_{275}$). By using SWAT, nonpoint discharge coefficients are studied with the conditions of the instream flow and the rainfall in two study areas. The nonpoint discharge coefficient average of BOD and TP for normal flows duration in 3 years are 0.32~0.36 and 0.28~0.31. For the low flow duration, the nonpoint discharge coefficient avergae of BOD and TP were 0.10~0.12 and 0.10~0.11. These are lower than the coefficients of total maximum load regulation. There are big differences between one of regulation and one of SWAT for the normal flow duration. With the consideration of rainfall condition, the nonpoint discharge coefficient of flood flow duration are influenced on the amount of rainfalls. However, the nonpoint discharge coefficients of normal flow duration and low flow duration are not effected by the rainfall condition. Since the spatial distribution and geomorphological characteristics could be considered with SWAT, the estimation of nonpoint discharge coefficient in watershed model is better method than the use of the recommended number in the regulation.

• International Journal of Fluid Machinery and Systems
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• 제2권2호
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• pp.127-135
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• 2009

A conventional centrifugal pump causes a drastic deterioration of air-water two-phase flow performances even at an air-water two-phase flow condition of inlet void fraction less than 10% in the range of relatively low water flow rate. Then we have developed a two-phase flow centrifugal pump which consists of a tandem arrangement of double rotating cascades and blades of outer cascade have higher outlet angle more than $90^{\circ}$. In design of the two-phase flow pump for various sized and operating conditions, similarity relations of geometric dimensions to hydraulic performances is very useful. The similarity relations of rotational speed, impeller diameter and blade height are investigated for the developed impeller in the present paper. As the results, the similarity law of rotational speed and impeller diameter is clarified experimentally even in two-phase flow condition. In addition, influences of blade height on air-water two-phase flow performances indicate a little difference from the similarity relations.

• 동의생리병리학회지
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• 제21권1호
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• pp.54-61
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• 2007

The study was designed to investigate the effects of Mixture of Yukgunja-tang and Bambusae Caulis in Liquamen (YTBCL) on the change of regional cerebral blood flow (rCBF) and mean arterial blood pressure (MABP) in rats, and further to determine the mechanism of action of YTBCL. The results in rats were as follows ; YTBCL 25 ${\mu}l$ significantly decreased rCBF and MABP compared with basal condition. YTBCL 100 ${\mu}l$ significantly increased rCBF compared with basal condition, but decreased MABP compared with basal condition. YTBCL 50 ${\mu}l$ significantly increased rCBF compared with basal condition, but MABP was somewhat decreased compared with basal condition. The VTBCL 50 ${\mu}l$-induced increase in rCBF was significantly inhibited by pretreatment with methylene blue (10 ${\mu}g$/kg, i.p.), an inhibitor of guanylate cyclase and indomethacin (1 mg/kg, i.p.), an inhibitor of cyclooxygenase. The YTBCL 50 ${\mu}l$-induced decreased MABP significantly increased by pretreatment with methylene blue but was inhibited by indomethacin. This results were suggested that the mechanism of YTBCL was mediated Dy guanylate cyclase.

• 조명전기설비학회논문지
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• 제29권7호
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• pp.28-37
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• 2015

Owing to the variability of large-scaled wind power system, the development of wind farm management technologies and related compensation methods have been receiving attention. To provide an accurate and reliable output power, certain wind farm adopts a specified management system including a wind prediction model and grid expectation solutions for considering grid condition. Those technologies are focused on improving the reliability and stability issues of wind farms, which can affect not only nearby system devices but also a voltage condition of utility grid. Therefore, to adapt the develop management system, an expectation process about voltage condition of Point of Common Coupling should be integrated in operating system for responding system requirements in real-time basis. This paper introduce a grid imposing method for a real-time based wind farm management system. The expected power can be transferred to the power flow section and the required quantity about reactive power can be calculated through the proposed system. For the verification process, the gauss-seidel method is introduced in the Matlab/Simulink for analysing power flow condition. The entire simulation process was designed to interwork with PSCAD for verifying real power system condition.

• 품질경영학회지
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• 제42권3호
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• pp.325-338
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• 2014

Purpose: The purpose of this study was to explain de-painting phenomenon of KUH-1 tail blade and to propose useful solution of it by test. The proposed solution was evaluated by real flight, and then it applied to mass product to improve the paint qual ity of KUH-1 tail blade. Methods: This study investigated an adhesive ability of primer following surface sanding condition. The cross cut and scratch test were conducted to evaluate the adhesive strength. And the water flow test was designed to simulate a real flight condition under rain. Through water flow test, an optimal condition of tail blade to prevent a de-painting phenomenon was deduced. Finally, the improvement method was evaluated by real flight under rain. Results: The results of this study are as follows; The sequential polishing was most excellent method in primer painting quality. The results of test including cross cut, scratch and water flow showed that MIL-DTL-53039 paint with epoxy primer has excellent adhesive ability. To proof the effect of improvement, a real flight during a rain condition was conducted. Finally, the comparison between original and improved configuration was conducted. Conclusion: The painting quality of KUH-1 tail blade was improved through deriving an optimal painting condition. In detail, a condition of optimal sanding and a sort of primer and paint was showed. Finally, the reliability of tail blade was guaranteed through improving the quality of painting.

• 한국기계가공학회지
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• 제7권3호
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• pp.25-29
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• 2008

In this paper, we design internal space in plunger-type low pressure vacuum injection molding machine from numerical study. And we study characteristic of viscoelastic flow for searching injection molding condition. Then the flow analysis was performed using the CAE S/W. The result shows optimal value of nozzle and hole in injection chamber. And we investigated qualitatively relationship between injection pressure and injection mass flow with variable shear rate

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 추계학술발표회논문집(1)
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• pp.403-408
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• 1996

The subchannel analysis was performed to verify the behavior of hot channel characteristics and obtain the information to support the core thermal-hydraulic behavior at post-trip steam line break with low flow condition. During this postulated accident, buoyancy-induced cross flow occurs, and the coupled nuclear and thermal-hydraulic interactions become important. The code predictions with TORC are in good agreement with the test data. Under such conditions, the mass flow increase in the hot channel by buoyancy-induced cross flow depends on the parameter $GR^{*}\;/\;Re^2$, and buoyancy effect becomes more noticeable as $GR^{*}\;/\;Re^2$ increases.

• International Journal of Fluid Machinery and Systems
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• 제2권3호
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• pp.206-214
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• 2009

Alternate blade cavitation, rotating cavitation and cavitation surge in rocket turbopump inducers were simulated by a three dimensional commercial CFD code. In order to clarify the cause of cavitation instabilities, the velocity disturbance caused by cavitation was obtained by subtracting the velocity vector under non-cavitating condition from that under cavitating condition. It was found that there exists a disturbance flow towards the trailing edge of the tip cavity. This flow has an axial flow component towards downstream which reduces the incidence angle to the next blade. It was found that all of the cavitation instabilities start to occur when this flow starts to interact with the leading edge of the next blade. The existence of the disturbance flow was validated by experiments.

• 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.